From: DJ Delorie Date: Fri, 1 Jun 2001 16:51:18 +0000 (-0400) Subject: c-tree.texi, [...]: Move to doc subdirectory. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=95e30ecc774ffb60a9222e042c04cd452fcbdcc0;p=gcc.git c-tree.texi, [...]: Move to doc subdirectory. * c-tree.texi, contrib.texi, cpp.texi, cppinternals.texi, extend.texi, fdl.texi, gcov.texi, invoke.texi, md.texi, objc.texi, rtl.texi, tm.texi, texinfo.tex: Move to doc subdirectory. * install.texi: Move to doc/install-old.texi. * gcc.texi: Move to doc, refer to install-old.texi. * Makefile.in: Reflect move of docs to doc/. * f/Make-lang.in: Ditto. * java/Make-lang.in: Ditto. * doc/.cvsignore: New. From-SVN: r42779 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 90fcd9831bb..08c85787acb 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,15 @@ +2001-06-01 DJ Delorie + + * c-tree.texi, contrib.texi, cpp.texi, cppinternals.texi, + extend.texi, fdl.texi, gcov.texi, invoke.texi, md.texi, objc.texi, + rtl.texi, tm.texi, texinfo.tex: Move to doc subdirectory. + * install.texi: Move to doc/install-old.texi. + * gcc.texi: Move to doc, refer to install-old.texi. + * Makefile.in: Reflect move of docs to doc/. + * f/Make-lang.in: Ditto. + * java/Make-lang.in: Ditto. + * doc/.cvsignore: New. + 2001-05-31 Jan van Male * invoke.texi: use two spaces between command options, eliminate diff --git a/gcc/Makefile.in b/gcc/Makefile.in index 12e26e3f6fa..0c94050020b 100644 --- a/gcc/Makefile.in +++ b/gcc/Makefile.in @@ -2187,61 +2187,63 @@ stmp-fixproto: fixhdr.ready fixproto stmp-int-hdrs # # Remake the info files. +docdir = $(srcdir)/doc + doc: $(BUILD_INFO) gccbug -info: $(srcdir)/cpp.info $(srcdir)/gcc.info lang.info $(srcdir)/cppinternals.info +info: $(docdir)/cpp.info $(docdir)/gcc.info lang.info $(docdir)/cppinternals.info -$(srcdir)/cpp.info: $(srcdir)/cpp.texi - cd $(srcdir) && $(MAKEINFO) $(MAKEINFOFLAGS) -o cpp.info cpp.texi +$(docdir)/cpp.info: $(docdir)/cpp.texi + cd $(srcdir) && $(MAKEINFO) $(MAKEINFOFLAGS) -I doc -o doc/cpp.info doc/cpp.texi -$(srcdir)/gcc.info: $(srcdir)/gcc.texi $(srcdir)/extend.texi $(srcdir)/install.texi \ - $(srcdir)/invoke.texi $(srcdir)/md.texi $(srcdir)/c-tree.texi \ - $(srcdir)/rtl.texi $(srcdir)/tm.texi $(srcdir)/gcov.texi \ - $(srcdir)/contrib.texi $(srcdir)/objc.texi $(srcdir)/fdl.texi - cd $(srcdir) && $(MAKEINFO) $(MAKEINFOFLAGS) -o gcc.info gcc.texi +$(docdir)/gcc.info: $(docdir)/gcc.texi $(docdir)/extend.texi $(docdir)/install.texi \ + $(docdir)/invoke.texi $(docdir)/md.texi $(docdir)/c-tree.texi \ + $(docdir)/rtl.texi $(docdir)/tm.texi $(docdir)/gcov.texi \ + $(docdir)/contrib.texi $(docdir)/objc.texi $(docdir)/fdl.texi + cd $(srcdir) && $(MAKEINFO) $(MAKEINFOFLAGS) -I doc -o doc/gcc.info doc/gcc.texi -$(srcdir)/cppinternals.info: $(srcdir)/cppinternals.texi - cd $(srcdir) && $(MAKEINFO) $(MAKEINFOFLAGS) -o cppinternals.info \ - cppinternals.texi +$(docdir)/cppinternals.info: $(docdir)/cppinternals.texi + cd $(srcdir) && $(MAKEINFO) $(MAKEINFOFLAGS) -I doc -o doc/cppinternals.info \ + doc/cppinternals.texi dvi: gcc.dvi cpp.dvi lang.dvi cppinternals.dvi # This works with GNU Make's default rule. -cpp.dvi: $(srcdir)/cpp.texi - $(TEXI2DVI) -I $(srcdir) $(srcdir)/cpp.texi - -gcc.dvi: $(srcdir)/gcc.texi $(srcdir)/extend.texi $(srcdir)/install.texi \ - $(srcdir)/invoke.texi $(srcdir)/md.texi $(srcdir)/c-tree.texi \ - $(srcdir)/rtl.texi $(srcdir)/tm.texi $(srcdir)/gcov.texi \ - $(srcdir)/contrib.texi $(srcdir)/objc.texi $(srcdir)/fdl.texi - $(TEXI2DVI) -I $(srcdir) $(srcdir)/gcc.texi - -cppinternals.dvi: $(srcdir)/cppinternals.texi - $(TEXI2DVI) -I $(srcdir) $(srcdir)/cppinternals.texi - -generated-manpages: $(srcdir)/gcov.1 $(srcdir)/cpp.1 $(srcdir)/gcc.1 - -$(srcdir)/gcov.1: $(srcdir)/gcov.texi - $(STAMP) $(srcdir)/gcov.1 - -$(TEXI2POD) < $(srcdir)/gcov.texi > gcov.pod - -($(POD2MAN) gcov.pod > $(srcdir)/gcov.1.T$$$$ && \ - mv -f $(srcdir)/gcov.1.T$$$$ $(srcdir)/gcov.1) || \ - (rm -f $(srcdir)/gcov.1.T$$$$ && exit 1) +cpp.dvi: $(docdir)/cpp.texi + $(TEXI2DVI) -I $(docdir) $(docdir)/cpp.texi + +gcc.dvi: $(docdir)/gcc.texi $(docdir)/extend.texi $(docdir)/install.texi \ + $(docdir)/invoke.texi $(docdir)/md.texi $(docdir)/c-tree.texi \ + $(docdir)/rtl.texi $(docdir)/tm.texi $(docdir)/gcov.texi \ + $(docdir)/contrib.texi $(docdir)/objc.texi $(docdir)/fdl.texi + $(TEXI2DVI) -I $(docdir) $(docdir)/gcc.texi + +cppinternals.dvi: $(docdir)/cppinternals.texi + $(TEXI2DVI) -I $(docdir) $(docdir)/cppinternals.texi + +generated-manpages: $(docdir)/gcov.1 $(docdir)/cpp.1 $(docdir)/gcc.1 + +$(docdir)/gcov.1: $(docdir)/gcov.texi + $(STAMP) $(docdir)/gcov.1 + -$(TEXI2POD) < $(docdir)/gcov.texi > gcov.pod + -($(POD2MAN) gcov.pod > $(docdir)/gcov.1.T$$$$ && \ + mv -f $(docdir)/gcov.1.T$$$$ $(docdir)/gcov.1) || \ + (rm -f $(docdir)/gcov.1.T$$$$ && exit 1) -rm -f gcov.pod -$(srcdir)/cpp.1: $(srcdir)/cpp.texi - $(STAMP) $(srcdir)/cpp.1 - -$(TEXI2POD) < $(srcdir)/cpp.texi > cpp.pod - -($(POD2MAN) cpp.pod > $(srcdir)/cpp.1.T$$$$ && \ - mv -f $(srcdir)/cpp.1.T$$$$ $(srcdir)/cpp.1) || \ - (rm -f $(srcdir)/cpp.1.T$$$$ && exit 1) +$(docdir)/cpp.1: $(docdir)/cpp.texi + $(STAMP) $(docdir)/cpp.1 + -$(TEXI2POD) < $(docdir)/cpp.texi > cpp.pod + -($(POD2MAN) cpp.pod > $(docdir)/cpp.1.T$$$$ && \ + mv -f $(docdir)/cpp.1.T$$$$ $(docdir)/cpp.1) || \ + (rm -f $(docdir)/cpp.1.T$$$$ && exit 1) -rm -f cpp.pod -$(srcdir)/gcc.1: $(srcdir)/invoke.texi - $(STAMP) $(srcdir)/gcc.1 - -$(TEXI2POD) < $(srcdir)/invoke.texi > gcc.pod - -($(POD2MAN) gcc.pod > $(srcdir)/gcc.1.T$$$$ && \ - mv -f $(srcdir)/gcc.1.T$$$$ $(srcdir)/gcc.1) || \ - (rm -f $(srcdir)/gcc.1.T$$$$ && exit 1) +$(docdir)/gcc.1: $(docdir)/invoke.texi + $(STAMP) $(docdir)/gcc.1 + -$(TEXI2POD) < $(docdir)/invoke.texi > gcc.pod + -($(POD2MAN) gcc.pod > $(docdir)/gcc.1.T$$$$ && \ + mv -f $(docdir)/gcc.1.T$$$$ $(docdir)/gcc.1) || \ + (rm -f $(docdir)/gcc.1.T$$$$ && exit 1) -rm -f gcc.pod # @@ -2370,9 +2372,9 @@ maintainer-clean: -rm -f c-parse.y c-parse.c c-parse.output TAGS -rm -f cpp.??s cpp.*aux -rm -f gcc.??s gcc.*aux - -rm -f $(srcdir)/cpp.info* $(srcdir)/gcc.info* - -rm -f $(srcdir)/cppinternals.info* - -rm -f $(srcdir)/gcov.1 $(srcdir)/cpp.1 $(srcdir)/gcc.1 + -rm -f $(docdir)/cpp.info* $(docdir)/gcc.info* + -rm -f $(docdir)/cppinternals.info* + -rm -f $(docdir)/gcov.1 $(docdir)/cpp.1 $(docdir)/gcc.1 # # Entry points `install' and `uninstall'. # Also use `install-collect2' to install collect2 when the config files don't. @@ -2543,9 +2545,9 @@ install-driver: installdirs xgcc$(exeext) install-info: doc installdirs lang.install-info -rm -f $(infodir)/cpp.info* $(infodir)/gcc.info* -rm -f $(infodir)/cppinternals.info* - if [ -f $(srcdir)/gcc.info ]; then \ - for f in $(srcdir)/cpp.info* $(srcdir)/gcc.info* \ - $(srcdir)/cppinternals.info*; do \ + if [ -f $(docdir)/gcc.info ]; then \ + for f in $(docdir)/cpp.info* $(docdir)/gcc.info* \ + $(docdir)/cppinternals.info*; do \ realfile=`echo $$f | sed -e 's|.*/\([^/]*\)$$|\1|'`; \ $(INSTALL_DATA) $$f $(infodir)/$$realfile; \ done; \ @@ -2566,18 +2568,18 @@ install-info: doc installdirs lang.install-info install-man: installdirs $(GENERATED_MANPAGES) lang.install-man -if [ -f gcc-cross$(exeext) ] ; then \ rm -f $(man1dir)/$(GCC_CROSS_NAME)$(manext); \ - $(INSTALL_DATA) $(srcdir)/gcc.1 $(man1dir)/$(GCC_CROSS_NAME)$(manext); \ + $(INSTALL_DATA) $(docdir)/gcc.1 $(man1dir)/$(GCC_CROSS_NAME)$(manext); \ chmod a-x $(man1dir)/$(GCC_CROSS_NAME)$(manext); \ else \ rm -f $(man1dir)/$(GCC_INSTALL_NAME)$(manext); \ - $(INSTALL_DATA) $(srcdir)/gcc.1 $(man1dir)/$(GCC_INSTALL_NAME)$(manext); \ + $(INSTALL_DATA) $(docdir)/gcc.1 $(man1dir)/$(GCC_INSTALL_NAME)$(manext); \ chmod a-x $(man1dir)/$(GCC_INSTALL_NAME)$(manext); \ fi -rm -f $(man1dir)/cpp$(manext) - -$(INSTALL_DATA) $(srcdir)/cpp.1 $(man1dir)/cpp$(manext) + -$(INSTALL_DATA) $(docdir)/cpp.1 $(man1dir)/cpp$(manext) -chmod a-x $(man1dir)/cpp$(manext) -rm -f $(man1dir)/gcov$(manext) - -$(INSTALL_DATA) $(srcdir)/gcov.1 $(man1dir)/gcov$(manext) + -$(INSTALL_DATA) $(docdir)/gcov.1 $(man1dir)/gcov$(manext) -chmod a-x $(man1dir)/gcov$(manext) # Install the library. diff --git a/gcc/c-tree.texi b/gcc/c-tree.texi deleted file mode 100644 index ad9cb94f051..00000000000 --- a/gcc/c-tree.texi +++ /dev/null @@ -1,2232 +0,0 @@ -@c Copyright (c) 1999, 2000, 2001 Free Software Foundation, Inc. -@c Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@c --------------------------------------------------------------------- -@c Trees -@c --------------------------------------------------------------------- - -@node Trees -@chapter Trees: The intermediate representation used by the C and C++ front-ends -@cindex Trees -@cindex C/C++ Internal Representation - -This chapter documents the internal representation used by GCC and C++ to -represent C and C++ source programs. When presented with a C or C++ -source program, GCC parses the program, performs semantic analysis -(including the generation of error messages), and then produces the -internal representation described here. This representation contains a -complete representation for the entire translation unit provided as -input to the front-end. This representation is then typically processed -by a code-generator in order to produce machine code, but could also be -used in the creation of source browsers, intelligent editors, automatic -documentation generators, interpreters, and any other programs needing -the ability to process C or C++ code. - -This chapter explains the internal representation. In particular, it -documents the internal representation for C and C++ source -constructs, and the macros, functions, and variables that can be used to -access these constructs. The C++ representation which is largely a superset -of the representation used in the C front-end. There is only one -construct used in C that does not appear in the C++ front-end and that -is the GNU ``nested function'' extension. Many of the macros documented -here do not apply in C because the corresponding language constructs do -not appear in C. - -If you are developing a ``back-end'', be it is a code-generator or some -other tool, that uses this representation, you may occasionally find -that you need to ask questions not easily answered by the functions and -macros available here. If that situation occurs, it is quite likely -that GCC already supports the functionality you desire, but that the -interface is simply not documented here. In that case, you should ask -the GCC maintainers (via mail to @email{gcc@@gcc.gnu.org}) about -documenting the functionality you require. Similarly, if you find -yourself writing functions that do not deal directly with your back-end, -but instead might be useful to other people using the GCC front-end, you -should submit your patches for inclusion in GCC. - -@menu -* Deficiencies:: Topics net yet covered in this document. -* Tree overview:: All about @code{tree}s. -* Types:: Fundamental and aggregate types. -* Scopes:: Namespaces and classes. -* Functions:: Overloading, function bodies, and linkage. -* Declarations:: Type declarations and variables. -* Expression trees:: From @code{typeid} to @code{throw}. -@end menu - -@c --------------------------------------------------------------------- -@c Deficiencies -@c --------------------------------------------------------------------- - -@node Deficiencies -@section Deficiencies - -There are many places in which this document is incomplet and incorrekt. -It is, as of yet, only @emph{preliminary} documentation. - -@c --------------------------------------------------------------------- -@c Overview -@c --------------------------------------------------------------------- - -@node Tree overview -@section Overview -@cindex tree -@findex TREE_CODE - -The central data structure used by the internal representation is the -@code{tree}. These nodes, while all of the C type @code{tree}, are of -many varieties. A @code{tree} is a pointer type, but the object to -which it points may be of a variety of types. From this point forward, -we will refer to trees in ordinary type, rather than in @code{this -font}, except when talking about the actual C type @code{tree}. - -You can tell what kind of node a particular tree is by using the -@code{TREE_CODE} macro. Many, many macros take a trees as input and -return trees as output. However, most macros require a certain kinds of -tree node as input. In other words, there is a type-system for trees, -but it is not reflected in the C type-system. - -For safety, it is useful to configure G++ with @code{--enable-checking}. -Although this results in a significant performance penalty (since all -tree types are checked at run-time), and is therefore inappropriate in a -release version, it is extremely helpful during the development process. - -Many macros behave as predicates. Many, although not all, of these -predicates end in @samp{_P}. Do not rely on the result type of these -macros being of any particular type. You may, however, rely on the fact -that the type can be compared to @code{0}, so that statements like -@example -if (TEST_P (t) && !TEST_P (y)) - x = 1; -@end example -@noindent -and -@example -int i = (TEST_P (t) != 0); -@end example -@noindent -are legal. Macros that return @code{int} values now may be changed to -return @code{tree} values, or other pointers in the future. Even those -that continue to return @code{int} may return multiple non-zero codes -where previously they returned only zero and one. Therefore, you should -not write code like -@example -if (TEST_P (t) == 1) -@end example -@noindent -as this code is not guaranteed to work correctly in the future. - -You should not take the address of values returned by the macros or -functions described here. In particular, no guarantee is given that the -values are lvalues. - -In general, the names of macros are all in uppercase, while the names of -functions are entirely in lower case. There are rare exceptions to this -rule. You should assume that any macro or function whose name is made -up entirely of uppercase letters may evaluate its arguments more than -once. You may assume that a macro or function whose name is made up -entirely of lowercase letters will evaluate its arguments only once. - -The @code{error_mark_node} is a special tree. Its tree code is -@code{ERROR_MARK}, but since there is only ever one node with that code, -the usual practice is to compare the tree against -@code{error_mark_node}. (This test is just a test for pointer -equality.) If an error has occurred during front-end processing the -flag @code{errorcount} will be set. If the front-end has encountered -code it cannot handle, it will issue a message to the user and set -@code{sorrycount}. When these flags are set, any macro or function -which normally returns a tree of a particular kind may instead return -the @code{error_mark_node}. Thus, if you intend to do any processing of -erroneous code, you must be prepared to deal with the -@code{error_mark_node}. - -Occasionally, a particular tree slot (like an operand to an expression, -or a particular field in a declaration) will be referred to as -``reserved for the back-end.'' These slots are used to store RTL when -the tree is converted to RTL for use by the GCC back-end. However, if -that process is not taking place (e.g., if the front-end is being hooked -up to an intelligent editor), then those slots may be used by the -back-end presently in use. - -If you encounter situations that do not match this documentation, such -as tree nodes of types not mentioned here, or macros documented to -return entities of a particular kind that instead return entities of -some different kind, you have found a bug, either in the front-end or in -the documentation. Please report these bugs as you would any other -bug. - -@menu -* Macros and Functions::Macros and functions that can be used with all trees. -* Identifiers:: The names of things. -* Containers:: Lists and vectors. -@end menu - -@c --------------------------------------------------------------------- -@c Trees -@c --------------------------------------------------------------------- - -@node Macros and Functions -@subsection Trees -@cindex tree - -This section is not here yet. - -@c --------------------------------------------------------------------- -@c Identifiers -@c --------------------------------------------------------------------- - -@node Identifiers -@subsection Identifiers -@cindex identifier -@cindex name -@tindex IDENTIFIER_NODE - -An @code{IDENTIFIER_NODE} represents a slightly more general concept -that the standard C or C++ concept of identifier. In particular, an -@code{IDENTIFIER_NODE} may contain a @samp{$}, or other extraordinary -characters. - -There are never two distinct @code{IDENTIFIER_NODE}s representing the -same identifier. Therefore, you may use pointer equality to compare -@code{IDENTIFIER_NODE}s, rather than using a routine like @code{strcmp}. - -You can use the following macros to access identifiers: -@ftable @code -@item IDENTIFIER_POINTER -The string represented by the identifier, represented as a -@code{char*}. This string is always @code{NUL}-terminated, and contains -no embedded @code{NUL} characters. - -@item IDENTIFIER_LENGTH -The length of the string returned by @code{IDENTIFIER_POINTER}, not -including the trailing @code{NUL}. This value of -@code{IDENTIFIER_LENGTH (x)} is always the same as @code{strlen -(IDENTIFIER_POINTER (x))}. - -@item IDENTIFIER_OPNAME_P -This predicate holds if the identifier represents the name of an -overloaded operator. In this case, you should not depend on the -contents of either the @code{IDENTIFIER_POINTER} or the -@code{IDENTIFIER_LENGTH}. - -@item IDENTIFIER_TYPENAME_P -This predicate holds if the identifier represents the name of a -user-defined conversion operator. In this case, the @code{TREE_TYPE} of -the @code{IDENTIFIER_NODE} holds the type to which the conversion -operator converts. - -@end ftable - -@c --------------------------------------------------------------------- -@c Containers -@c --------------------------------------------------------------------- - -@node Containers -@subsection Containers -@cindex container -@cindex list -@cindex vector -@tindex TREE_LIST -@tindex TREE_VEC -@findex TREE_PURPOSE -@findex TREE_VALUE -@findex TREE_VEC_LENGTH -@findex TREE_VEC_ELT - -Two common container data structures can be represented directly with -tree nodes. A @code{TREE_LIST} is a singly linked list containing two -trees per node. These are the @code{TREE_PURPOSE} and @code{TREE_VALUE} -of each node. (Often, the @code{TREE_PURPOSE} contains some kind of -tag, or additional information, while the @code{TREE_VALUE} contains the -majority of the payload. In other cases, the @code{TREE_PURPOSE} is -simply @code{NULL_TREE}, while in still others both the -@code{TREE_PURPOSE} and @code{TREE_VALUE} are of equal stature.) Given -one @code{TREE_LIST} node, the next node is found by following the -@code{TREE_CHAIN}. If the @code{TREE_CHAIN} is @code{NULL_TREE}, then -you have reached the end of the list. - -A @code{TREE_VEC} is a simple vector. The @code{TREE_VEC_LENGTH} is an -integer (not a tree) giving the number of nodes in the vector. The -nodes themselves are accessed using the @code{TREE_VEC_ELT} macro, which -takes two arguments. The first is the @code{TREE_VEC} in question; the -second is an integer indicating which element in the vector is desired. -The elements are indexed from zero. - -@c --------------------------------------------------------------------- -@c Types -@c --------------------------------------------------------------------- - -@node Types -@section Types -@cindex type -@cindex pointer -@cindex reference -@cindex fundamental type -@cindex array -@tindex VOID_TYPE -@tindex INTEGER_TYPE -@tindex TYPE_MIN_VALUE -@tindex TYPE_MAX_VALUE -@tindex REAL_TYPE -@tindex COMPLEX_TYPE -@tindex ENUMERAL_TYPE -@tindex BOOLEAN_TYPE -@tindex POINTER_TYPE -@tindex REFERENCE_TYPE -@tindex FUNCTION_TYPE -@tindex METHOD_TYPE -@tindex ARRAY_TYPE -@tindex RECORD_TYPE -@tindex UNION_TYPE -@tindex UNKNOWN_TYPE -@tindex OFFSET_TYPE -@tindex TYPENAME_TYPE -@tindex TYPEOF_TYPE -@findex CP_TYPE_QUALS -@findex TYPE_UNQUALIFIED -@findex TYPE_QUAL_CONST -@findex TYPE_QUAL_VOLATILE -@findex TYPE_QUAL_RESTRICT -@findex TYPE_MAIN_VARIANT -@cindex qualified type -@findex TYPE_SIZE -@findex TYPE_ALIGN -@findex TYPE_PRECISION -@findex TYPE_ARG_TYPES -@findex TYPE_METHOD_BASETYPE -@findex TYPE_PTRMEM_P -@findex TYPE_OFFSET_BASETYPE -@findex TREE_TYPE -@findex TYPE_CONTEXT -@findex TYPE_NAME -@findex TYPENAME_TYPE_FULLNAME -@findex TYPE_FIELDS -@findex TYPE_PTROBV_P - -All types have corresponding tree nodes. However, you should not assume -that there is exactly one tree node corresponding to each type. There -are often several nodes each of which correspond to the same type. - -For the most part, different kinds of types have different tree codes. -(For example, pointer types use a @code{POINTER_TYPE} code while arrays -use an @code{ARRAY_TYPE} code.) However, pointers to member functions -use the @code{RECORD_TYPE} code. Therefore, when writing a -@code{switch} statement that depends on the code associated with a -particular type, you should take care to handle pointers to member -functions under the @code{RECORD_TYPE} case label. - -In C++, an array type is not qualified; rather the type of the array -elements is qualified. This situation is reflected in the intermediate -representation. The macros described here will always examine the -qualification of the underlying element type when applied to an array -type. (If the element type is itself an array, then the recursion -continues until a non-array type is found, and the qualification of this -type is examined.) So, for example, @code{CP_TYPE_CONST_P} will hold of -the type @code{const int ()[7]}, denoting an array of seven @code{int}s. - -The following functions and macros deal with cv-qualification of types: -@ftable @code -@item CP_TYPE_QUALS -This macro returns the set of type qualifiers applied to this type. -This value is @code{TYPE_UNQUALIFIED} if no qualifiers have been -applied. The @code{TYPE_QUAL_CONST} bit is set if the type is -@code{const}-qualified. The @code{TYPE_QUAL_VOLATILE} bit is set if the -type is @code{volatile}-qualified. The @code{TYPE_QUAL_RESTRICT} bit is -set if the type is @code{restrict}-qualified. - -@item CP_TYPE_CONST_P -This macro holds if the type is @code{const}-qualified. - -@item CP_TYPE_VOLATILE_P -This macro holds if the type is @code{volatile}-qualified. - -@item CP_TYPE_RESTRICT_P -This macro holds if the type is @code{restrict}-qualified. - -@item CP_TYPE_CONST_NON_VOLATILE_P -This predicate holds for a type that is @code{const}-qualified, but -@emph{not} @code{volatile}-qualified; other cv-qualifiers are ignored as -well: only the @code{const}-ness is tested. - -@item TYPE_MAIN_VARIANT -This macro returns the unqualified version of a type. It may be applied -to an unqualified type, but it is not always the identity function in -that case. -@end ftable - -A few other macros and functions are usable with all types: -@ftable @code -@item TYPE_SIZE -The number of bits required to represent the type, represented as an -@code{INTEGER_CST}. For an incomplete type, @code{TYPE_SIZE} will be -@code{NULL_TREE}. - -@item TYPE_ALIGN -The alignment of the type, in bits, represented as an @code{int}. - -@item TYPE_NAME -This macro returns a declaration (in the form of a @code{TYPE_DECL}) for -the type. (Note this macro does @emph{not} return a -@code{IDENTIFIER_NODE}, as you might expect, given its name!) You can -look at the @code{DECL_NAME} of the @code{TYPE_DECL} to obtain the -actual name of the type. The @code{TYPE_NAME} will be @code{NULL_TREE} -for a type that is not a builtin type, the result of a typedef, or a -named class type. - -@item CP_INTEGRAL_TYPE -This predicate holds if the type is an integral type. Notice that in -C++, enumerations are @emph{not} integral types. - -@item ARITHMETIC_TYPE_P -This predicate holds if the type is an integral type (in the C++ sense) -or a floating point type. - -@item CLASS_TYPE_P -This predicate holds for a class-type. - -@item TYPE_BUILT_IN -This predicate holds for a builtin type. - -@item TYPE_PTRMEM_P -This predicate holds if the type is a pointer to data member. - -@item TYPE_PTR_P -This predicate holds if the type is a pointer type, and the pointee is -not a data member. - -@item TYPE_PTRFN_P -This predicate holds for a pointer to function type. - -@item TYPE_PTROB_P -This predicate holds for a pointer to object type. Note however that it -does not hold for the generic pointer to object type @code{void *}. You -may use @code{TYPE_PTROBV_P} to test for a pointer to object type as -well as @code{void *}. - -@item same_type_p -This predicate takes two types as input, and holds if they are the same -type. For example, if one type is a @code{typedef} for the other, or -both are @code{typedef}s for the same type. This predicate also holds if -the two trees given as input are simply copies of one another; i.e., -there is no difference between them at the source level, but, for -whatever reason, a duplicate has been made in the representation. You -should never use @code{==} (pointer equality) to compare types; always -use @code{same_type_p} instead. -@end ftable - -Detailed below are the various kinds of types, and the macros that can -be used to access them. Although other kinds of types are used -elsewhere in G++, the types described here are the only ones that you -will encounter while examining the intermediate representation. - -@table @code -@item VOID_TYPE -Used to represent the @code{void} type. - -@item INTEGER_TYPE -Used to represent the various integral types, including @code{char}, -@code{short}, @code{int}, @code{long}, and @code{long long}. This code -is not used for enumeration types, nor for the @code{bool} type. Note -that GCC's @code{CHAR_TYPE} node is @emph{not} used to represent -@code{char}. The @code{TYPE_PRECISION} is the number of bits used in -the representation, represented as an @code{unsigned int}. (Note that -in the general case this is not the same value as @code{TYPE_SIZE}; -suppose that there were a 24-bit integer type, but that alignment -requirements for the ABI required 32-bit alignment. Then, -@code{TYPE_SIZE} would be an @code{INTEGER_CST} for 32, while -@code{TYPE_PRECISION} would be 24.) The integer type is unsigned if -@code{TREE_UNSIGNED} holds; otherwise, it is signed. - -The @code{TYPE_MIN_VALUE} is an @code{INTEGER_CST} for the smallest -integer that may be represented by this type. Similarly, the -@code{TYPE_MAX_VALUE} is an @code{INTEGER_CST} for the largest integer -that may be represented by this type. - -@item REAL_TYPE -Used to represent the @code{float}, @code{double}, and @code{long -double} types. The number of bits in the floating-point representation -is given by @code{TYPE_PRECISION}, as in the @code{INTEGER_TYPE} case. - -@item COMPLEX_TYPE -Used to represent GCC builtin @code{__complex__} data types. The -@code{TREE_TYPE} is the type of the real and imaginary parts. - -@item ENUMERAL_TYPE -Used to represent an enumeration type. The @code{TYPE_PRECISION} gives -(as an @code{int}), the number of bits used to represent the type. If -there are no negative enumeration constants, @code{TREE_UNSIGNED} will -hold. The minimum and maximum enumeration constants may be obtained -with @code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE}, respectively; each -of these macros returns an @code{INTEGER_CST}. - -The actual enumeration constants themselves may be obtained by looking -at the @code{TYPE_VALUES}. This macro will return a @code{TREE_LIST}, -containing the constants. The @code{TREE_PURPOSE} of each node will be -an @code{IDENTIFIER_NODE} giving the name of the constant; the -@code{TREE_VALUE} will be an @code{INTEGER_CST} giving the value -assigned to that constant. These constants will appear in the order in -which they were declared. The @code{TREE_TYPE} of each of these -constants will be the type of enumeration type itself. - -@item BOOLEAN_TYPE -Used to represent the @code{bool} type. - -@item POINTER_TYPE -Used to represent pointer types, and pointer to data member types. The -@code{TREE_TYPE} gives the type to which this type points. If the type -is a pointer to data member type, then @code{TYPE_PTRMEM_P} will hold. -For a pointer to data member type of the form @samp{T X::*}, -@code{TYPE_PTRMEM_CLASS_TYPE} will be the type @code{X}, while -@code{TYPE_PTRMEM_POINTED_TO_TYPE} will be the type @code{T}. - -@item REFERENCE_TYPE -Used to represent reference types. The @code{TREE_TYPE} gives the type -to which this type refers. - -@item FUNCTION_TYPE -Used to represent the type of non-member functions and of static member -functions. The @code{TREE_TYPE} gives the return type of the function. -The @code{TYPE_ARG_TYPES} are a @code{TREE_LIST} of the argument types. -The @code{TREE_VALUE} of each node in this list is the type of the -corresponding argument; the @code{TREE_PURPOSE} is an expression for the -default argument value, if any. If the last node in the list is -@code{void_list_node} (a @code{TREE_LIST} node whose @code{TREE_VALUE} -is the @code{void_type_node}), then functions of this type do not take -variable arguments. Otherwise, they do take a variable number of -arguments. - -Note that in C (but not in C++) a function declared like @code{void f()} -is an unprototyped function taking a variable number of arguments; the -@code{TYPE_ARG_TYPES} of such a function will be NULL. - -@item METHOD_TYPE -Used to represent the type of a non-static member function. Like a -@code{FUNCTION_TYPE}, the return type is given by the @code{TREE_TYPE}. -The type of @code{*this}, i.e., the class of which functions of this -type are a member, is given by the @code{TYPE_METHOD_BASETYPE}. The -@code{TYPE_ARG_TYPES} is the parameter list, as for a -@code{FUNCTION_TYPE}, and includes the @code{this} argument. - -@item ARRAY_TYPE -Used to represent array types. The @code{TREE_TYPE} gives the type of -the elements in the array. If the array-bound is present in the type, -the @code{TYPE_DOMAIN} is an @code{INTEGER_TYPE} whose -@code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE} will be the lower and -upper bounds of the array, respectively. The @code{TYPE_MIN_VALUE} will -always be an @code{INTEGER_CST} for zero, while the -@code{TYPE_MAX_VALUE} will be one less than the number of elements in -the array, i.e., the highest value which may be used to index an element -in the array. - -@item RECORD_TYPE -Used to represent @code{struct} and @code{class} types, as well as -pointers to member functions. If @code{TYPE_PTRMEMFUNC_P} holds, then -this type is a pointer-to-member type. In that case, the -@code{TYPE_PTRMEMFUNC_FN_TYPE} is a @code{POINTER_TYPE} pointing to a -@code{METHOD_TYPE}. The @code{METHOD_TYPE} is the type of a function -pointed to by the pointer-to-member function. If -@code{TYPE_PTRMEMFUNC_P} does not hold, this type is a class type. For -more information, see @pxref{Classes}. - -@item UNKNOWN_TYPE -This node is used to represent a type the knowledge of which is -insufficient for a sound processing. - -@item OFFSET_TYPE -This node is used to represent a data member; for example a -pointer-to-data-member is represented by a @code{POINTER_TYPE} whose -@code{TREE_TYPE} is an @code{OFFSET_TYPE}. For a data member @code{X::m} -the @code{TYPE_OFFSET_BASETYPE} is @code{X} and the @code{TREE_TYPE} is -the type of @code{m}. - -@item TYPENAME_TYPE -Used to represent a construct of the form @code{typename T::A}. The -@code{TYPE_CONTEXT} is @code{T}; the @code{TYPE_NAME} is an -@code{IDENTIFIER_NODE} for @code{A}. If the type is specified via a -template-id, then @code{TYPENAME_TYPE_FULLNAME} yields a -@code{TEMPLATE_ID_EXPR}. The @code{TREE_TYPE} is non-@code{NULL} if the -node is implicitly generated in support for the implicit typename -extension; in which case the @code{TREE_TYPE} is a type node for the -base-class. - -@item TYPEOF_TYPE -Used to represent the @code{__typeof__} extension. The -@code{TYPE_FIELDS} is the expression the type of which is being -represented. - -@item UNION_TYPE -Used to represent @code{union} types. For more information, @pxref{Classes}. -@end table - -There are variables whose values represent some of the basic types. -These include: -@table @code -@item void_type_node -A node for @code{void}. - -@item integer_type_node -A node for @code{int}. - -@item unsigned_type_node. -A node for @code{unsigned int}. - -@item char_type_node. -A node for @code{char}. -@end table -@noindent -It may sometimes be useful to compare one of these variables with a type -in hand, using @code{same_type_p}. - -@c --------------------------------------------------------------------- -@c Scopes -@c --------------------------------------------------------------------- - -@node Scopes -@section Scopes -@cindex namespace, class, scope - -The root of the entire intermediate representation is the variable -@code{global_namespace}. This is the namespace specified with @code{::} -in C++ source code. All other namespaces, types, variables, functions, -and so forth can be found starting with this namespace. - -Besides namespaces, the other high-level scoping construct in C++ is the -class. (Throughout this manual the term @dfn{class} is used to mean the -types referred to in the ANSI/ISO C++ Standard as classes; these include -types defined with the @code{class}, @code{struct}, and @code{union} -keywords.) - -@menu -* Namespaces:: Member functions, types, etc. -* Classes:: Members, bases, friends, etc. -@end menu - -@c --------------------------------------------------------------------- -@c Namespaces -@c --------------------------------------------------------------------- - -@node Namespaces -@subsection Namespaces -@cindex namespace -@tindex NAMESPACE_DECL - -A namespace is represented by a @code{NAMESPACE_DECL} node. - -However, except for the fact that it is distinguished as the root of the -representation, the global namespace is no different from any other -namespace. Thus, in what follows, we describe namespaces generally, -rather than the global namespace in particular. - -The @code{::std} namespace, however, @emph{is} special, unless -@code{flag_honor_std} is set. This variable is set by the use -@samp{-fhonor-std} (or an option that implies it, like -@samp{-fnew-abi}), when invoking G++. When @code{flag_honor_std} is -set, the @code{std} namespace is just like any other namespace. When -@code{flag_honor_std} is not set, however, the @code{::std} namespace is -treated as a synonym for the global namespace, thereby allowing users to -write code that will work with compilers that put the standard library -in the @code{::std} namespace, even though the library supplied with G++ -does not do so, as of GCC 2.95. The @code{std} namespace is represented -by the variable @code{std_node}. Although @code{std_node} is a -@code{NAMESPACE_DECL}, it does not have all the fields required of a -real namespace, and the macros and functions described here do not work, -in general. It is safest simply to ignore @code{std_node} should you -encounter it while examining the internal representation. In -particular, you will encounter @code{std_node} while looking at the -members of the global namespace. Just skip it without attempting to -examine its members. - -The following macros and functions can be used on a @code{NAMESPACE_DECL}: - -@ftable @code -@item DECL_NAME -This macro is used to obtain the @code{IDENTIFIER_NODE} corresponding to -the unqualified name of the name of the namespace (@pxref{Identifiers}). -The name of the global namespace is @samp{::}, even though in C++ the -global namespace is unnamed. However, you should use comparison with -@code{global_namespace}, rather than @code{DECL_NAME} to determine -whether or not a namespaces is the global one. An unnamed namespace -will have a @code{DECL_NAME} equal to @code{anonymous_namespace_name}. -Within a single translation unit, all unnamed namespaces will have the -same name. - -@item DECL_CONTEXT -This macro returns the enclosing namespace. The @code{DECL_CONTEXT} for -the @code{global_namespace} is @code{NULL_TREE}. - -@item DECL_NAMESPACE_ALIAS -If this declaration is for a namespace alias, then -@code{DECL_NAMESPACE_ALIAS} is the namespace for which this one is an -alias. - -Do not attempt to use @code{cp_namespace_decls} for a namespace which is -an alias. Instead, follow @code{DECL_NAMESPACE_ALIAS} links until you -reach an ordinary, non-alias, namespace, and call -@code{cp_namespace_decls} there. - -@item DECL_NAMESPACE_STD_P -This predicate holds if the namespace is the special @code{::std} -namespace. - -@item cp_namespace_decls -This function will return the declarations contained in the namespace, -including types, overloaded functions, other namespaces, and so forth. -If there are no declarations, this function will return -@code{NULL_TREE}. The declarations are connected through their -@code{TREE_CHAIN} fields. - -Although most entries on this list will be declarations, -@code{TREE_LIST} nodes may also appear. In this case, the -@code{TREE_VALUE} will be an @code{OVERLOAD}. The value of the -@code{TREE_PURPOSE} is unspecified; back-ends should ignore this value. -As with the other kinds of declarations returned by -@code{cp_namespace_decls}, the @code{TREE_CHAIN} will point to the next -declaration in this list. - -For more information on the kinds of declarations that can occur on this -list, @xref{Declarations}. Some declarations will not appear on this -list. In particular, no @code{FIELD_DECL}, @code{LABEL_DECL}, or -@code{PARM_DECL} nodes will appear here. - -This function cannot be used with namespaces that have -@code{DECL_NAMESPACE_ALIAS} set. - -@end ftable - -@c --------------------------------------------------------------------- -@c Classes -@c --------------------------------------------------------------------- - -@node Classes -@subsection Classes -@cindex class -@tindex RECORD_TYPE -@tindex UNION_TYPE -@findex CLASSTYPE_DECLARED_CLASS -@findex TYPE_BINFO -@findex BINFO_TYPE -@findex TREE_VIA_PUBLIC -@findex TREE_VIA_PROTECTED -@findex TREE_VIA_PRIVATE -@findex TYPE_FIELDS -@findex TYPE_VFIELD -@findex TYPE_METHODS - -A class type is represented by either a @code{RECORD_TYPE} or a -@code{UNION_TYPE}. A class declared with the @code{union} tag is -represented by a @code{UNION_TYPE}, while classes declared with either -the @code{struct} or the @code{class} tag are represented by -@code{RECORD_TYPE}s. You can use the @code{CLASSTYPE_DECLARED_CLASS} -macro to discern whether or not a particular type is a @code{class} as -opposed to a @code{struct}. This macro will be true only for classes -declared with the @code{class} tag. - -Almost all non-function members are available on the @code{TYPE_FIELDS} -list. Given one member, the next can be found by following the -@code{TREE_CHAIN}. You should not depend in any way on the order in -which fields appear on this list. All nodes on this list will be -@samp{DECL} nodes. A @code{FIELD_DECL} is used to represent a non-static -data member, a @code{VAR_DECL} is used to represent a static data -member, and a @code{TYPE_DECL} is used to represent a type. Note that -the @code{CONST_DECL} for an enumeration constant will appear on this -list, if the enumeration type was declared in the class. (Of course, -the @code{TYPE_DECL} for the enumeration type will appear here as well.) -There are no entries for base classes on this list. In particular, -there is no @code{FIELD_DECL} for the ``base-class portion'' of an -object. - -The @code{TYPE_VFIELD} is a compiler-generated field used to point to -virtual function tables. It may or may not appear on the -@code{TYPE_FIELDS} list. However, back-ends should handle the -@code{TYPE_VFIELD} just like all the entries on the @code{TYPE_FIELDS} -list. - -The function members are available on the @code{TYPE_METHODS} list. -Again, subsequent members are found by following the @code{TREE_CHAIN} -field. If a function is overloaded, each of the overloaded functions -appears; no @code{OVERLOAD} nodes appear on the @code{TYPE_METHODS} -list. Implicitly declared functions (including default constructors, -copy constructors, assignment operators, and destructors) will appear on -this list as well. - -Every class has an associated @dfn{binfo}, which can be obtained with -@code{TYPE_BINFO}. Binfos are used to represent base-classes. The -binfo given by @code{TYPE_BINFO} is the degenerate case, whereby every -class is considered to be its own base-class. The base classes for a -particular binfo can be obtained with @code{BINFO_BASETYPES}. These -base-classes are themselves binfos. The class type associated with a -binfo is given by @code{BINFO_TYPE}. It is always the case that -@code{BINFO_TYPE (TYPE_BINFO (x))} is the same type as @code{x}, up to -qualifiers. However, it is not always the case that @code{TYPE_BINFO -(BINFO_TYPE (y))} is always the same binfo as @code{y}. The reason is -that if @code{y} is a binfo representing a base-class @code{B} of a -derived class @code{D}, then @code{BINFO_TYPE (y)} will be @code{B}, and -@code{TYPE_INFO (BINFO_TYPE (y))} will be @code{B} as its own -base-class, rather than as a base-class of @code{D}. - -The @code{BINFO_BASETYPES} is a @code{TREE_VEC} (@pxref{Containers}). -Base types appear in left-to-right order in this vector. You can tell -whether or @code{public}, @code{protected}, or @code{private} -inheritance was used by using the @code{TREE_VIA_PUBLIC}, -@code{TREE_VIA_PROTECTED}, and @code{TREE_VIA_PRIVATE} macros. Each of -these macros takes a @code{BINFO} and is true if and only if the -indicated kind of inheritance was used. If @code{TREE_VIA_VIRTUAL} -holds of a binfo, then its @code{BINFO_TYPE} was inherited from -virtually. - -FIXME: Talk about @code{TYPE_NONCOPIED_PARTS}. - -The following macros can be used on a tree node representing a class-type. - -@ftable @code -@item LOCAL_CLASS_P -This predicate holds if the class is local class @emph{i.e.} declared -inside a function body. - -@item TYPE_POLYMORPHIC_P -This predicate holds if the class has at least one virtual function -(declared or inherited). - -@item TYPE_HAS_DEFAULT_CONSTRUCTOR -This predicate holds whenever its argument represents a class-type with -default constructor. - -@item CLASSTYPE_HAS_MUTABLE -@item TYPE_HAS_MUTABLE_P -These predicates hold for a class-type having a mutable data member. - -@item CLASSTYPE_NON_POD_P -This predicate holds only for class-types that are not PODs. - -@item TYPE_HAS_NEW_OPERATOR -This predicate holds for a class-type that defines -@code{operator new}. - -@item TYPE_HAS_ARRAY_NEW_OPERATOR -This predicate holds for a class-type for which -@code{operator new[]} is defined. - -@item TYPE_OVERLOADS_CALL_EXPR -This predicate holds for class-type for which the function call -@code{operator()} is overloaded. - -@item TYPE_OVERLOADS_ARRAY_REF -This predicate holds for a class-type that overloads -@code{operator[]} - -@item TYPE_OVERLOADS_ARROW -This predicate holds for a class-type for which @code{operator->} is -overloaded. - -@end ftable - -@c --------------------------------------------------------------------- -@c Declarations -@c --------------------------------------------------------------------- - -@node Declarations -@section Declarations -@cindex declaration -@cindex variable -@cindex type declaration -@tindex LABEL_DECL -@tindex CONST_DECL -@tindex TYPE_DECL -@tindex VAR_DECL -@tindex PARM_DECL -@tindex FIELD_DECL -@tindex NAMESPACE_DECL -@tindex RESULT_DECL -@tindex TEMPLATE_DECL -@tindex THUNK_DECL -@tindex USING_DECL -@findex THUNK_DELTA -@findex DECL_INITIAL -@findex DECL_SIZE -@findex DECL_ALIGN -@findex DECL_EXTERNAL - -This section covers the various kinds of declarations that appear in the -internal representation, except for declarations of functions -(represented by @code{FUNCTION_DECL} nodes), which are described in -@ref{Functions}. - -Some macros can be used with any kind of declaration. These include: -@ftable @code -@item DECL_NAME -This macro returns an @code{IDENTIFIER_NODE} giving the name of the -entity. - -@item TREE_TYPE -This macro returns the type of the entity declared. - -@item DECL_SOURCE_FILE -This macro returns the name of the file in which the entity was -declared, as a @code{char*}. For an entity declared implicitly by the -compiler (like @code{__builtin_memcpy}), this will be the string -@code{""}. - -@item DECL_SOURCE_LINE -This macro returns the line number at which the entity was declared, as -an @code{int}. - -@item DECL_ARTIFICIAL -This predicate holds if the declaration was implicitly generated by the -compiler. For example, this predicate will hold of an implicitly -declared member function, or of the @code{TYPE_DECL} implicitly -generated for a class type. Recall that in C++ code like: -@example -struct S @{@}; -@end example -@noindent -is roughly equivalent to C code like: -@example -struct S @{@}; -typedef struct S S; -@end example -The implicitly generated @code{typedef} declaration is represented by a -@code{TYPE_DECL} for which @code{DECL_ARTIFICIAL} holds. - -@item DECL_NAMESPACE_SCOPE_P -This predicate holds if the entity was declared at a namespace scope. - -@item DECL_CLASS_SCOPE_P -This predicate holds if the entity was declared at a class scope. - -@item DECL_FUNCTION_SCOPE_P -This predicate holds if the entity was declared inside a function -body. - -@end ftable - -The various kinds of declarations include: -@table @code -@item LABEL_DECL -These nodes are used to represent labels in function bodies. For more -information, see @ref{Functions}. These nodes only appear in block -scopes. - -@item CONST_DECL -These nodes are used to represent enumeration constants. The value of -the constant is given by @code{DECL_INITIAL} which will be an -@code{INTEGER_CST} with the same type as the @code{TREE_TYPE} of the -@code{CONST_DECL}, i.e., an @code{ENUMERAL_TYPE}. - -@item RESULT_DECL -These nodes represent the value returned by a function. When a value is -assigned to a @code{RESULT_DECL}, that indicates that the value should -be returned, via bitwise copy, by the function. You can use -@code{DECL_SIZE} and @code{DECL_ALIGN} on a @code{RESULT_DECL}, just as -with a @code{VAR_DECL}. - -@item TYPE_DECL -These nodes represent @code{typedef} declarations. The @code{TREE_TYPE} -is the type declared to have the name given by @code{DECL_NAME}. In -some cases, there is no associated name. - -@item VAR_DECL -These nodes represent variables with namespace or block scope, as well -as static data members. The @code{DECL_SIZE} and @code{DECL_ALIGN} are -analogous to @code{TYPE_SIZE} and @code{TYPE_ALIGN}. For a declaration, -you should always use the @code{DECL_SIZE} and @code{DECL_ALIGN} rather -than the @code{TYPE_SIZE} and @code{TYPE_ALIGN} given by the -@code{TREE_TYPE}, since special attributes may have been applied to the -variable to give it a particular size and alignment. You may use the -predicates @code{DECL_THIS_STATIC} or @code{DECL_THIS_EXTERN} to test -whether the storage class specifiers @code{static} or @code{extern} were -used to declare a variable. - -If this variable is initialized (but does not require a constructor), -the @code{DECL_INITIAL} will be an expression for the initializer. The -initializer should be evaluated, and a bitwise copy into the variable -performed. If the @code{DECL_INITIAL} is the @code{error_mark_node}, -there is an initializer, but it is given by an explicit statement later -in the code; no bitwise copy is required. - -GCC provides an extension that allows either automatic variables, or -global variables, to be placed in particular registers. This extension -is being used for a particular @code{VAR_DECL} if @code{DECL_REGISTER} -holds for the @code{VAR_DECL}, and if @code{DECL_ASSEMBLER_NAME} is not -equal to @code{DECL_NAME}. In that case, @code{DECL_ASSEMBLER_NAME} is -the name of the register into which the variable will be placed. - -@item PARM_DECL -Used to represent a parameter to a function. Treat these nodes -similarly to @code{VAR_DECL} nodes. These nodes only appear in the -@code{DECL_ARGUMENTS} for a @code{FUNCTION_DECL}. - -The @code{DECL_ARG_TYPE} for a @code{PARM_DECL} is the type that will -actually be used when a value is passed to this function. It may be a -wider type than the @code{TREE_TYPE} of the parameter; for example, the -ordinary type might be @code{short} while the @code{DECL_ARG_TYPE} is -@code{int}. - -@item FIELD_DECL -These nodes represent non-static data members. The @code{DECL_SIZE} and -@code{DECL_ALIGN} behave as for @code{VAR_DECL} nodes. The -@code{DECL_FIELD_BITPOS} gives the first bit used for this field, as an -@code{INTEGER_CST}. These values are indexed from zero, where zero -indicates the first bit in the object. - -If @code{DECL_C_BIT_FIELD} holds, this field is a bitfield. - -@item NAMESPACE_DECL -@xref{Namespaces}. - -@item TEMPLATE_DECL - -These nodes are used to represent class, function, and variable (static -data member) templates. The @code{DECL_TEMPLATE_SPECIALIZATIONS} are a -@code{TREE_LIST}. The @code{TREE_VALUE} of each node in the lst is a -@code{TEMPLATE_DECL}s or @code{FUNCTION_DECL}s representing -specializations (including instantiations) of this template. Back-ends -can safely ignore @code{TEMPLATE_DECL}s, but should examine -@code{FUNCTION_DECL} nodes on the specializations list just as they -would ordinary @code{FUNCTION_DECL} nodes. - -For a class template, the @code{DECL_TEMPLATE_INSTANTIATIONS} list -contains the instantiations. The @code{TREE_VALUE} of each node is an -instantiation of the class. The @code{DECL_TEMPLATE_SPECIALIZATIONS} -contains partial specializations of the class. - -@item USING_DECL - -Back-ends can safely ignore these nodes. - -@end table - -@c --------------------------------------------------------------------- -@c Functions -@c --------------------------------------------------------------------- - -@node Functions -@section Functions -@cindex function -@tindex FUNCTION_DECL -@tindex OVERLOAD -@findex OVL_CURRENT -@findex OVL_NEXT - -A function is represented by a @code{FUNCTION_DECL} node. A set of -overloaded functions is sometimes represented by a @code{OVERLOAD} node. - -An @code{OVERLOAD} node is not a declaration, so none of the -@samp{DECL_} macros should be used on an @code{OVERLOAD}. An -@code{OVERLOAD} node is similar to a @code{TREE_LIST}. Use -@code{OVL_CURRENT} to get the function associated with an -@code{OVERLOAD} node; use @code{OVL_NEXT} to get the next -@code{OVERLOAD} node in the list of overloaded functions. The macros -@code{OVL_CURRENT} and @code{OVL_NEXT} are actually polymorphic; you can -use them to work with @code{FUNCTION_DECL} nodes as well as with -overloads. In the case of a @code{FUNCTION_DECL}, @code{OVL_CURRENT} -will always return the function itself, and @code{OVL_NEXT} will always -be @code{NULL_TREE}. - -To determine the scope of a function, you can use the -@code{DECL_REAL_CONTEXT} macro. This macro will return the class -(either a @code{RECORD_TYPE} or a @code{UNION_TYPE}) or namespace (a -@code{NAMESPACE_DECL}) of which the function is a member. For a virtual -function, this macro returns the class in which the function was -actually defined, not the base class in which the virtual declaration -occurred. If a friend function is defined in a class scope, the -@code{DECL_CLASS_CONTEXT} macro can be used to determine the class in -which it was defined. For example, in -@example -class C @{ friend void f() @{@} @}; -@end example -the @code{DECL_REAL_CONTEXT} for @code{f} will be the -@code{global_namespace}, but the @code{DECL_CLASS_CONTEXT} will be the -@code{RECORD_TYPE} for @code{C}. - -The @code{DECL_REAL_CONTEXT} and @code{DECL_CLASS_CONTEXT} are not -available in C; instead you should simply use @code{DECL_CONTEXT}. In C, -the @code{DECL_CONTEXT} for a function maybe another function. This -representation indicates that the GNU nested function extension is in -use. For details on the semantics of nested functions, see the GCC -Manual. The nested function can refer to local variables in its -containing function. Such references are not explicitly marked in the -tree structure; back-ends must look at the @code{DECL_CONTEXT} for the -referenced @code{VAR_DECL}. If the @code{DECL_CONTEXT} for the -referenced @code{VAR_DECL} is not the same as the function currently -being processed, and neither @code{DECL_EXTERNAL} nor @code{DECL_STATIC} -hold, then the reference is to a local variable in a containing -function, and the back-end must take appropriate action. - -@menu -* Function Basics:: Function names, linkage, and so forth. -* Function Bodies:: The statements that make up a function body. -@end menu - -@c --------------------------------------------------------------------- -@c Function Basics -@c --------------------------------------------------------------------- - -@node Function Basics -@subsection Function Basics -@cindex constructor -@cindex destructor -@cindex copy constructor -@cindex assignment operator -@cindex linkage -@findex DECL_NAME -@findex DECL_ASSEMBLER_NAME -@findex TREE_PUBLIC -@findex DECL_LINKONCE_P -@findex DECL_FUNCTION_MEMBER_P -@findex DECL_CONSTRUCTOR_P -@findex DECL_DESTRUCTOR_P -@findex DECL_OVERLOADED_OPERATOR_P -@findex DECL_CONV_FN_P -@findex DECL_ARTIFICIAL -@findex DECL_GLOBAL_CTOR_P -@findex DECL_GLOBAL_DTOR_P -@findex GLOBAL_INIT_PRIORITY - -The following macros and functions can be used on a @code{FUNCTION_DECL}: -@ftable @code -@item DECL_MAIN_P -This predicate holds for a function that is the program entry point -@code{::code}. - -@item DECL_NAME -This macro returns the unqualified name of the function, as an -@code{IDENTIFIER_NODE}. For an instantiation of a function template, -the @code{DECL_NAME} is the unqualified name of the template, not -something like @code{f}. The value of @code{DECL_NAME} is -undefined when used on a constructor, destructor, overloaded operator, -or type-conversion operator, or any function that is implicitly -generated by the compiler. See below for macros that can be used to -distinguish these cases. - -@item DECL_ASSEMBLER_NAME -This macro returns the mangled name of the function, also an -@code{IDENTIFIER_NODE}. This name does not contain leading underscores -on systems that prefix all identifiers with underscores. The mangled -name is computed in the same way on all platforms; if special processing -is required to deal with the object file format used on a particular -platform, it is the responsibility of the back-end to perform those -modifications. (Of course, the back-end should not modify -@code{DECL_ASSEMBLER_NAME} itself.) - -@item DECL_EXTERNAL -This predicate holds if the function is undefined. - -@item TREE_PUBLIC -This predicate holds if the function has external linkage. - -@item DECL_LOCAL_FUNCTION_P -This predicate holds if the function was declared at block scope, even -though it has a global scope. - -@item DECL_ANTICIPATED -This predicate holds if the function is a built-in function but its -prototype is not yet explicitly declared. - -@item DECL_EXTERN_C_FUNCTION_P -This predicate holds if the function is declared as an -`@code{extern "C"}' function. - -@item DECL_LINKONCE_P -This macro holds if multiple copies of this function may be emitted in -various translation units. It is the responsibility of the linker to -merge the various copies. Template instantiations are the most common -example of functions for which @code{DECL_LINKONCE_P} holds; G++ -instantiates needed templates in all translation units which require them, -and then relies on the linker to remove duplicate instantiations. - -FIXME: This macro is not yet implemented. - -@item DECL_FUNCTION_MEMBER_P -This macro holds if the function is a member of a class, rather than a -member of a namespace. - -@item DECL_STATIC_FUNCTION_P -This predicate holds if the function a static member function. - -@item DECL_NONSTATIC_MEMBER_FUNCTION_P -This macro holds for a non-static member function. - -@item DECL_CONST_MEMFUNC_P -This predicate holds for a @code{const}-member function. - -@item DECL_VOLATILE_MEMFUNC_P -This predicate holds for a @code{volatile}-member function. - -@item DECL_CONSTRUCTOR_P -This macro holds if the function is a constructor. - -@item DECL_NONCONVERTING_P -This predicate holds if the constructor is a non-converting constructor. - -@item DECL_COMPLETE_CONSTRUCTOR_P -This predicate holds for a function which is a constructor for an object -of a complete type. - -@item DECL_BASE_CONSTRUCTOR_P -This predicate holds for a function which is a constructor for a base -class sub-object. - -@item DECL_COPY_CONSTRUCTOR_P -This predicate holds for a function which is a copy-constructor. - -@item DECL_DESTRUCTOR_P -This macro holds if the function is a destructor. - -@item DECL_COMPLETE_DESTRUCTOR_P -This predicate holds if the function is the destructor for an object a -complete type. - -@item DECL_OVERLOADED_OPERATOR_P -This macro holds if the function is an overloaded operator. - -@item DECL_CONV_FN_P -This macro holds if the function is a type-conversion operator. - -@item DECL_GLOBAL_CTOR_P -This predicate holds if the function is a file-scope initialization -function. - -@item DECL_GLOBAL_DTOR_P -This predicate holds if the function is a file-scope finalization -function. - -@item DECL_THUNK_P -This predicate holds if the function is a thunk. - -These functions represent stub code that adjusts the @code{this} pointer -and then jumps to another function. When the jumped-to function -returns, control is transferred directly to the caller, without -returning to the thunk. The first parameter to the thunk is always the -@code{this} pointer; the thunk should add @code{THUNK_DELTA} to this -value. (The @code{THUNK_DELTA} is an @code{int}, not an -@code{INTEGER_CST}.) - -Then, if @code{THUNK_VCALL_OFFSET} (an @code{INTEGER_CST}) is non-zero -the adjusted @code{this} pointer must be adjusted again. The complete -calculation is given by the following pseudo-code: - -@example -this += THUNK_DELTA -if (THUNK_VCALL_OFFSET) - this += (*((ptrdiff_t **) this))[THUNK_VCALL_OFFSET] -@end example - -Finally, the thunk should jump to the location given -by @code{DECL_INITIAL}; this will always be an expression for the -address of a function. - -@item DECL_NON_THUNK_FUNCTION_P -This predicate holds if the function is @emph{not} a thunk function. - -@item GLOBAL_INIT_PRIORITY -If either @code{DECL_GLOBAL_CTOR_P} or @code{DECL_GLOBAL_DTOR_P} holds, -then this gives the initialization priority for the function. The -linker will arrange that all functions for which -@code{DECL_GLOBAL_CTOR_P} holds are run in increasing order of priority -before @code{main} is called. When the program exits, all functions for -which @code{DECL_GLOBAL_DTOR_P} holds are run in the reverse order. - -@item DECL_ARTIFICIAL -This macro holds if the function was implicitly generated by the -compiler, rather than explicitly declared. In addition to implicitly -generated class member functions, this macro holds for the special -functions created to implement static initialization and destruction, to -compute run-time type information, and so forth. - -@item DECL_ARGUMENTS -This macro returns the @code{PARM_DECL} for the first argument to the -function. Subsequent @code{PARM_DECL} nodes can be obtained by -following the @code{TREE_CHAIN} links. - -@item DECL_RESULT -This macro returns the @code{RESULT_DECL} for the function. - -@item TREE_TYPE -This macro returns the @code{FUNCTION_TYPE} or @code{METHOD_TYPE} for -the function. - -@item TYPE_RAISES_EXCEPTIONS -This macro returns the list of exceptions that a (member-)function can -raise. The returned list, if non @code{NULL}, is comprised of nodes -whose @code{TREE_VALUE} represents a type. - -@item TYPE_NOTHROW_P -This predicate holds when the exception-specification of its arguments -if of the form `@code{()}'. - -@item DECL_ARRAY_DELETE_OPERATOR_P -This predicate holds if the function an overloaded -@code{operator delete[]}. - -@end ftable - -@c --------------------------------------------------------------------- -@c Function Bodies -@c --------------------------------------------------------------------- - -@node Function Bodies -@subsection Function Bodies -@cindex function body -@cindex statements -@tindex ASM_STMT -@findex ASM_STRING -@findex ASM_CV_QUAL -@findex ASM_INPUTS -@findex ASM_OUTPUTS -@findex ASM_CLOBBERS -@tindex BREAK_STMT -@tindex CLEANUP_STMT -@findex CLEANUP_DECL -@findex CLEANUP_EXPR -@tindex COMPOUND_STMT -@findex COMPOUND_BODY -@tindex CONTINUE_STMT -@tindex DECL_STMT -@findex DECL_STMT_DECL -@tindex DO_STMT -@findex DO_BODY -@findex DO_COND -@tindex EMPTY_CLASS_EXPR -@tindex EXPR_STMT -@findex EXPR_STMT_EXPR -@tindex FOR_STMT -@findex FOR_INIT_STMT -@findex FOR_COND -@findex FOR_EXPR -@findex FOR_BODY -@tindex GOTO_STMT -@findex GOTO_DESTINATION -@tindex HANDLER -@tindex IF_STMT -@findex IF_COND -@findex THEN_CLAUSE -@findex ELSE_CLAUSE -@tindex LABEL_STMT -@tindex LABEL_STMT_LABEL -@tindex RETURN_INIT -@tindex RETURN_STMT -@findex RETURN_EXPR -@tindex SCOPE_STMT -@findex SCOPE_BEGIN_P -@findex SCOPE_END_P -@findex SCOPE_NULLIFIED_P -@tindex SUBOBJECT -@findex SUBOBJECT_CLEANUP -@tindex SWITCH_STMT -@findex SWITCH_COND -@findex SWITCH_BODY -@tindex TRY_BLOCK -@findex TRY_STMTS -@findex TRY_HANDLERS -@findex HANDLER_PARMS -@findex HANDLER_BODY -@findex USING_STMT -@tindex WHILE_STMT -@findex WHILE_BODY -@findex WHILE_COND - -A function that has a definition in the current translation unit will -have a non-NULL @code{DECL_INITIAL}. However, back-ends should not make -use of the particular value given by @code{DECL_INITIAL}. - -The @code{DECL_SAVED_TREE} macro will give the complete body of the -function. This node will usually be a @code{COMPOUND_STMT} representing -the outermost block of the function, but it may also be a -@code{TRY_BLOCK}, a @code{RETURN_INIT}, or any other valid statement. - -@subsubsection Statements - -There are tree nodes corresponding to all of the source-level statement -constructs. These are enumerated here, together with a list of the -various macros that can be used to obtain information about them. There -are a few macros that can be used with all statements: - -@ftable @code -@item STMT_LINENO -This macro returns the line number for the statement. If the statement -spans multiple lines, this value will be the number of the first line on -which the statement occurs. Although we mention @code{CASE_LABEL} below -as if it were a statement, they do not allow the use of -@code{STMT_LINENO}. There is no way to obtain the line number for a -@code{CASE_LABEL}. - -Statements do not contain information about -the file from which they came; that information is implicit in the -@code{FUNCTION_DECL} from which the statements originate. - -@item STMT_IS_FULL_EXPR_P -In C++, statements normally constitute ``full expressions''; temporaries -created during a statement are destroyed when the statement is complete. -However, G++ sometimes represents expressions by statements; these -statements will not have @code{STMT_IS_FULL_EXPR_P} set. Temporaries -created during such statements should be destroyed when the innermost -enclosing statement with @code{STMT_IS_FULL_EXPR_P} set is exited. - -@end ftable - -Here is the list of the various statement nodes, and the macros used to -access them. This documentation describes the use of these nodes in -non-template functions (including instantiations of template functions). -In template functions, the same nodes are used, but sometimes in -slightly different ways. - -Many of the statements have substatements. For example, a @code{while} -loop will have a body, which is itself a statement. If the substatement -is @code{NULL_TREE}, it is considered equivalent to a statement -consisting of a single @code{;}, i.e., an expression statement in which -the expression has been omitted. A substatement may in fact be a list -of statements, connected via their @code{TREE_CHAIN}s. So, you should -always process the statement tree by looping over substatements, like -this: -@example -void process_stmt (stmt) - tree stmt; -@{ - while (stmt) - @{ - switch (TREE_CODE (stmt)) - @{ - case IF_STMT: - process_stmt (THEN_CLAUSE (stmt)); - /* More processing here. */ - break; - - ... - @} - - stmt = TREE_CHAIN (stmt); - @} -@} -@end example -In other words, while the @code{then} clause of an @code{if} statement -in C++ can be only one statement (although that one statement may be a -compound statement), the intermediate representation will sometimes use -several statements chained together. - -@table @code -@item ASM_STMT - -Used to represent an inline assembly statement. For an inline assembly -statement like: -@example -asm ("mov x, y"); -@end example -The @code{ASM_STRING} macro will return a @code{STRING_CST} node for -@code{"mov x, y"}. If the original statement made use of the -extended-assembly syntax, then @code{ASM_OUTPUTS}, -@code{ASM_INPUTS}, and @code{ASM_CLOBBERS} will be the outputs, inputs, -and clobbers for the statement, represented as @code{STRING_CST} nodes. -The extended-assembly syntax looks like: -@example -asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); -@end example -The first string is the @code{ASM_STRING}, containing the instruction -template. The next two strings are the output and inputs, respectively; -this statement has no clobbers. As this example indicates, ``plain'' -assembly statements are merely a special case of extended assembly -statements; they have no cv-qualifiers, outputs, inputs, or clobbers. -All of the strings will be @code{NUL}-terminated, and will contain no -embedded @code{NUL}-characters. - -If the assembly statement is declared @code{volatile}, or if the -statement was not an extended assembly statement, and is therefore -implicitly volatile, then the predicate @code{ASM_VOLATILE_P} will hold -of the @code{ASM_STMT}. - -@item BREAK_STMT - -Used to represent a @code{break} statement. There are no additional -fields. - -@item CASE_LABEL - -Use to represent a @code{case} label, range of @code{case} labels, or a -@code{default} label. If @code{CASE_LOW} is NULL_TREE, then this is a a -@code{default} label. Otherwise, if @code{CASE_HIGH} is NULL_TREE, then -this is an ordinary @code{case} label. In this case, @code{CASE_LOW} is -an expression giving the value of the label. Both @code{CASE_LOW} and -@code{CASE_HIGH} are @code{INTEGER_CST} nodes. These values will have -the same type as the condition expression in the switch statement. - -Otherwise, if both @code{CASE_LOW} and @code{CASE_HIGH} are defined, the -statement is a range of case labels. Such statements originate with the -extension that allows users to write things of the form: -@example -case 2 ... 5: -@end example -The first value will be @code{CASE_LOW}, while the second will be -@code{CASE_HIGH}. - -@item CLEANUP_STMT - -Used to represent an action that should take place upon exit from the -enclosing scope. Typically, these actions are calls to destructors for -local objects, but back-ends cannot rely on this fact. If these nodes -are in fact representing such destructors, @code{CLEANUP_DECL} will be -the @code{VAR_DECL} destroyed. Otherwise, @code{CLEANUP_DECL} will be -@code{NULL_TREE}. In any case, the @code{CLEANUP_EXPR} is the -expression to execute. The cleanups executed on exit from a scope -should be run in the reverse order of the order in which the associated -@code{CLEANUP_STMT}s were encountered. - -@item COMPOUND_STMT - -Used to represent a brace-enclosed block. The first substatement is -given by @code{COMPOUND_BODY}. Subsequent substatements are found by -following the @code{TREE_CHAIN} link from one substatement to the next. - -@item CONTINUE_STMT - -Used to represent a @code{continue} statement. There are no additional -fields. - -@item CTOR_STMT - -Used to mark the beginning (if @code{CTOR_BEGIN_P} holds) or end (if -@code{CTOR_END_P} holds of the main body of a constructor. See also -@code{SUBOBJECT} for more information on how to use these nodes. - -@item DECL_STMT - -Used to represent a local declaration. The @code{DECL_STMT_DECL} macro -can be used to obtain the entity declared. This declaration may be a -@code{LABEL_DECL}, indicating that the label declared is a local label. -(As an extension, GCC allows the declaration of labels with scope.) In -C, this declaration may be a @code{FUNCTION_DECL}, indicating the -use of the GCC nested function extension. For more information, -@pxref{Functions}. - -@item DO_STMT - -Used to represent a @code{do} loop. The body of the loop is given by -@code{DO_BODY} while the termination condition for the loop is given by -@code{DO_COND}. The condition for a @code{do}-statement is always an -expression. - -@item EMPTY_CLASS_EXPR - -Used to represent a temporary object of a class with no data whose -address is never taken. (All such objects are interchangeable.) The -@code{TREE_TYPE} represents the type of the object. - -@item EXPR_STMT - -Used to represent an expression statement. Use @code{EXPR_STMT_EXPR} to -obtain the expression. - -@item FOR_STMT - -Used to represent a @code{for} statement. The @code{FOR_INIT_STMT} is -the initialization statement for the loop. The @code{FOR_COND} is the -termination condition. The @code{FOR_EXPR} is the expression executed -right before the @code{FOR_COND} on each loop iteration; often, this -expression increments a counter. The body of the loop is given by -@code{FOR_BODY}. Note that @code{FOR_INIT_STMT} and @code{FOR_BODY} -return statements, while @code{FOR_COND} and @code{FOR_EXPR} return -expressions. - -@item GOTO_STMT - -Used to represent a @code{goto} statement. The @code{GOTO_DESTINATION} -will usually be a @code{LABEL_DECL}. However, if the ``computed -goto'' extension has been used, the @code{GOTO_DESTINATION} will be an -arbitrary expression indicating the destination. This expression will -always have pointer type. - -@item HANDLER - -Used to represent a C++ @code{catch} block. The @code{HANDLER_TYPE} -is the type of exception that will be caught by this handler; it is -equal (by pointer equality) to @code{CATCH_ALL_TYPE} if this handler -is for all types. @code{HANDLER_PARMS} is the @code{DECL_STMT} for -the catch parameter, and @code{HANDLER_BODY} is the -@code{COMPOUND_STMT} for the block itself. - -@item IF_STMT - -Used to represent an @code{if} statement. The @code{IF_COND} is the -expression. - -If the condition is a @code{TREE_LIST}, then the @code{TREE_PURPOSE} is -a statement (usually a @code{DECL_STMT}). Each time the coondition is -evaluated, the statement should be executed. Then, the -@code{TREE_VALUE} should be used as the conditional expression itself. -This representation is used to handle C++ code like this: - -@example -if (int i = 7) ... -@end example - -where there is a new local variable (or variables) declared within the -condition. - -The @code{THEN_CLAUSE} represents the statement given by the @code{then} -condition, while the @code{ELSE_CLAUSE} represents the statement given -by the @code{else} condition. - -@item LABEL_STMT - -Used to represent a label. The @code{LABEL_DECL} declared by this -statement can be obtained with the @code{LABEL_STMT_LABEL} macro. The -@code{IDENTIFIER_NODE} giving the name of the label can be obtained from -the @code{LABEL_DECL} with @code{DECL_NAME}. - -@item RETURN_INIT - -If the function uses the G++ ``named return value'' extension, meaning -that the function has been defined like: -@example -S f(int) return s @{...@} -@end example -then there will be a @code{RETURN_INIT}. There is never a named -returned value for a constructor. The first argument to the -@code{RETURN_INIT} is the name of the object returned; the second -argument is the initializer for the object. The object is initialized -when the @code{RETURN_INIT} is encountered. The object referred to is -the actual object returned; this extension is a manual way of doing the -``return-value optimization.'' Therefore, the object must actually be -constructed in the place where the object will be returned. - -@item RETURN_STMT - -Used to represent a @code{return} statement. The @code{RETURN_EXPR} is -the expression returned; it will be @code{NULL_TREE} if the statement -was just -@example -return; -@end example - -@item SCOPE_STMT - -A scope-statement represents the beginning or end of a scope. If -@code{SCOPE_BEGIN_P} holds, this statement represents the beginning of a -scope; if @code{SCOPE_END_P} holds this statement represents the end of -a scope. On exit from a scope, all cleanups from @code{CLEANUP_STMT}s -occurring in the scope must be run, in reverse order to the order in -which they were encountered. If @code{SCOPE_NULLIFIED_P} or -@code{SCOPE_NO_CLEANUPS_P} holds of the scope, back-ends should behave -as if the @code{SCOPE_STMT} were not present at all. - -@item SUBOBJECT - -In a constructor, these nodes are used to mark the point at which a -subobject of @code{this} is fully constructed. If, after this point, an -exception is thrown before a @code{CTOR_STMT} with @code{CTOR_END_P} set -is encountered, the @code{SUBOBJECT_CLEANUP} must be executed. The -cleanups must be executed in the reverse order in which they appear. - -@item SWITCH_STMT - -Used to represent a @code{switch} statement. The @code{SWITCH_COND} is -the expression on which the switch is occurring. See the documentation -for an @code{IF_STMT} for more information on the representation used -for the condition. The @code{SWITCH_BODY} is the body of the switch -statement. - -@item TRY_BLOCK -Used to represent a @code{try} block. The body of the try block is -given by @code{TRY_STMTS}. Each of the catch blocks is a @code{HANDLER} -node. The first handler is given by @code{TRY_HANDLERS}. Subsequent -handlers are obtained by following the @code{TREE_CHAIN} link from one -handler to the next. The body of the handler is given by -@code{HANDLER_BODY}. - -If @code{CLEANUP_P} holds of the @code{TRY_BLOCK}, then the -@code{TRY_HANDLERS} will not be a @code{HANDLER} node. Instead, it will -be an expression that should be executed if an exception is thrown in -the try block. It must rethrow the exception after executing that code. -And, if an exception is thrown while the expression is executing, -@code{terminate} must be called. - -@item USING_STMT -Used to represent a @code{using} directive. The namespace is given by -@code{USING_STMT_NAMESPACE}, which will be a NAMESPACE_DECL. This node -is needed inside template functions, to implement using directives -during instantiation. - -@item WHILE_STMT - -Used to represent a @code{while} loop. The @code{WHILE_COND} is the -termination condition for the loop. See the documentation for an -@code{IF_STMT} for more information on the representation used for the -condition. - -The @code{WHILE_BODY} is the body of the loop. - -@end table - -@c --------------------------------------------------------------------- -@c Expressions -@c --------------------------------------------------------------------- - -@node Expression trees -@section Expressions -@cindex expression -@findex TREE_OPERAND -@tindex INTEGER_CST -@findex TREE_INT_CST_HIGH -@findex TREE_INT_CST_LOW -@findex tree_int_cst_lt -@findex tree_int_cst_equal -@tindex REAL_CST -@tindex COMPLEX_CST -@tindex STRING_CST -@findex TREE_STRING_LENGTH -@findex TREE_STRING_POINTER -@tindex PTRMEM_CST -@findex PTRMEM_CST_CLASS -@findex PTRMEM_CST_MEMBER -@tindex VAR_DECL -@tindex NEGATE_EXPR -@tindex BIT_NOT_EXPR -@tindex TRUTH_NOT_EXPR -@tindex ADDR_EXPR -@tindex INDIRECT_REF -@tindex FIX_TRUNC_EXPR -@tindex FLOAT_EXPR -@tindex COMPLEX_EXPR -@tindex CONJ_EXPR -@tindex REALPART_EXPR -@tindex IMAGPART_EXPR -@tindex NOP_EXPR -@tindex CONVERT_EXPR -@tindex THROW_EXPR -@tindex LSHIFT_EXPR -@tindex RSHIFT_EXPR -@tindex BIT_IOR_EXPR -@tindex BIT_XOR_EXPR -@tindex BIT_AND_EXPR -@tindex TRUTH_ANDIF_EXPR -@tindex TRUTH_ORIF_EXPR -@tindex TRUTH_AND_EXPR -@tindex TRUTH_OR_EXPR -@tindex TRUTH_XOR_EXPR -@tindex PLUS_EXPR -@tindex MINUS_EXPR -@tindex MULT_EXPR -@tindex TRUNC_DIV_EXPR -@tindex TRUNC_MOD_EXPR -@tindex RDIV_EXPR -@tindex LT_EXPR -@tindex LE_EXPR -@tindex GT_EXPR -@tindex GE_EXPR -@tindex EQ_EXPR -@tindex NE_EXPR -@tindex INIT_EXPR -@tindex MODIFY_EXPR -@tindex COMPONENT_REF -@tindex COMPOUND_EXPR -@tindex COND_EXPR -@tindex CALL_EXPR -@tindex CONSTRUCTOR -@tindex STMT_EXPR -@tindex BIND_EXPR -@tindex LOOP_EXPR -@tindex EXIT_EXPR -@tindex CLEANUP_POINT_EXPR -@tindex ARRAY_REF - -The internal representation for expressions is for the most part quite -straightforward. However, there are a few facts that one must bear in -mind. In particular, the expression ``tree'' is actually a directed -acyclic graph. (For example there may be many references to the integer -constant zero throughout the source program; many of these will be -represented by the same expression node.) You should not rely on -certain kinds of node being shared, nor should rely on certain kinds of -nodes being unshared. - -The following macros can be used with all expression nodes: - -@ftable @code -@item TREE_TYPE -Returns the type of the expression. This value may not be precisely the -same type that would be given the expression in the original program. -@end ftable - -In what follows, some nodes that one might expect to always have type -@code{bool} are documented to have either integral or boolean type. At -some point in the future, the C front-end may also make use of this same -intermediate representation, and at this point these nodes will -certainly have integral type. The previous sentence is not meant to -imply that the C++ front-end does not or will not give these nodes -integral type. - -Below, we list the various kinds of expression nodes. Except where -noted otherwise, the operands to an expression are accessed using the -@code{TREE_OPERAND} macro. For example, to access the first operand to -a binary plus expression @code{expr}, use: - -@example -TREE_OPERAND (expr, 0) -@end example -@noindent -As this example indicates, the operands are zero-indexed. - -The table below begins with constants, moves on to unary expressions, -then proceeds to binary expressions, and concludes with various other -kinds of expressions: - -@table @code -@item INTEGER_CST -These nodes represent integer constants. Note that the type of these -constants is obtained with @code{TREE_TYPE}; they are not always of type -@code{int}. In particular, @code{char} constants are represented with -@code{INTEGER_CST} nodes. The value of the integer constant @code{e} is -given by @example -((TREE_INT_CST_HIGH (e) << HOST_BITS_PER_WIDE_INT) -+ TREE_INST_CST_LOW (e)) -@end example -@noindent -HOST_BITS_PER_WIDE_INT is at least thirty-two on all platforms. Both -@code{TREE_INT_CST_HIGH} and @code{TREE_INT_CST_LOW} return a -@code{HOST_WIDE_INT}. The value of an @code{INTEGER_CST} is interpreted -as a signed or unsigned quantity depending on the type of the constant. -In general, the expression given above will overflow, so it should not -be used to calculate the value of the constant. - -The variable @code{integer_zero_node} is a integer constant with value -zero. Similarly, @code{integer_one_node} is an integer constant with -value one. The @code{size_zero_node} and @code{size_one_node} variables -are analogous, but have type @code{size_t} rather than @code{int}. - -The function @code{tree_int_cst_lt} is a predicate which holds if its -first argument is less than its second. Both constants are assumed to -have the same signedness (i.e., either both should be signed or both -should be unsigned.) The full width of the constant is used when doing -the comparison; the usual rules about promotions and conversions are -ignored. Similarly, @code{tree_int_cst_equal} holds if the two -constants are equal. The @code{tree_int_cst_sgn} function returns the -sign of a constant. The value is @code{1}, @code{0}, or @code{-1} -according on whether the constant is greater than, equal to, or less -than zero. Again, the signedness of the constant's type is taken into -account; an unsigned constant is never less than zero, no matter what -its bit-pattern. - -@item REAL_CST - -FIXME: Talk about how to obtain representations of this constant, do -comparisons, and so forth. - -@item COMPLEX_CST -These nodes are used to represent complex number constants, that is a -@code{__complex__} whose parts are constant nodes. The -@code{TREE_REALPART} and @code{TREE_IMAGPART} return the real and the -imaginary parts respectively. - -@item STRING_CST -These nodes represent string-constants. The @code{TREE_STRING_LENGTH} -returns the length of the string, as an @code{int}. The -@code{TREE_STRING_POINTER} is a @code{char*} containing the string -itself. The string may not be @code{NUL}-terminated, and it may contain -embedded @code{NUL} characters. Therefore, the -@code{TREE_STRING_LENGTH} includes the trailing @code{NUL} if it is -present. - -For wide string constants, the @code{TREE_STRING_LENGTH} is the number -of wide characters in the string, and the @code{TREE_STRING_POINTER} -points to an array of the bytes of the string, as represented on the -target system (that is, as integers in the target endianness). Wide and -non-wide string constants are distinguished only by the @code{TREE_TYPE} -of the @code{STRING_CST}. - -FIXME: The formats of string constants are not well-defined when the -target system bytes are not the same width as host system bytes. - -@item PTRMEM_CST -These nodes are used to represent pointer-to-member constants. The -@code{PTRMEM_CST_CLASS} is the class type (either a @code{RECORD_TYPE} -or @code{UNION_TYPE} within which the pointer points), and the -@code{PTRMEM_CST_MEMBER} is the declaration for the pointed to object. -Note that the @code{DECL_CONTEXT} for the @code{PTRMEM_CST_MEMBER} is in -general different from from the @code{PTRMEM_CST_CLASS}. For example, -given: -@example -struct B @{ int i; @}; -struct D : public B @{@}; -int D::*dp = &D::i; -@end example -@noindent -The @code{PTRMEM_CST_CLASS} for @code{&D::i} is @code{D}, even though -the @code{DECL_CONTEXT} for the @code{PTRMEM_CST_MEMBER} is @code{B}, -since @code{B::i} is a member of @code{B}, not @code{D}. - -@item VAR_DECL - -These nodes represent variables, including static data members. For -more information, @pxref{Declarations}. - -@item NEGATE_EXPR -These nodes represent unary negation of the single operand, for both -integer and floating-point types. The type of negation can be -determined by looking at the type of the expression. - -@item BIT_NOT_EXPR -These nodes represent bitwise complement, and will always have integral -type. The only operand is the value to be complemented. - -@item TRUTH_NOT_EXPR -These nodes represent logical negation, and will always have integral -(or boolean) type. The operand is the value being negated. - -@item PREDECREMENT_EXPR -@itemx PREINCREMENT_EXPR -@itemx POSTDECREMENT_EXPR -@itemx POSTINCREMENT_EXPR -These nodes represent increment and decrement expressions. The value of -the single operand is computed, and the operand incremented or -decremented. In the case of @code{PREDECREMENT_EXPR} and -@code{PREINCREMENT_EXPR}, the value of the expression is the value -resulting after the increment or decrement; in the case of -@code{POSTDECREMENT_EXPR} and @code{POSTINCREMENT_EXPR} is the value -before the increment or decrement occurs. The type of the operand, like -that of the result, will be either integral, boolean, or floating-point. - -@item ADDR_EXPR -These nodes are used to represent the address of an object. (These -expressions will always have pointer or reference type.) The operand may -be another expression, or it may be a declaration. - -As an extension, GCC allows users to take the address of a label. In -this case, the operand of the @code{ADDR_EXPR} will be a -@code{LABEL_DECL}. The type of such an expression is @code{void*}. - -If the object addressed is not an lvalue, a temporary is created, and -the address of the temporary is used. - -@item INDIRECT_REF -These nodes are used to represent the object pointed to by a pointer. -The operand is the pointer being dereferenced; it will always have -pointer or reference type. - -@item FIX_TRUNC_EXPR -These nodes represent conversion of a floating-point value to an -integer. The single operand will have a floating-point type, while the -the complete expression will have an integral (or boolean) type. The -operand is rounded towards zero. - -@item FLOAT_EXPR -These nodes represent conversion of an integral (or boolean) value to a -floating-point value. The single operand will have integral type, while -the complete expression will have a floating-point type. - -FIXME: How is the operand supposed to be rounded? Is this dependent on --mieee? - -@item COMPLEX_EXPR -These nodes are used to represent complex numbers constructed from two -expressions of the same (integer or real) type. The first operand is the -real part and the second operand is the imaginary part. - -@item CONJ_EXPR -These nodes represent the conjugate of their operand. - -@item REALPART_EXPR -@item IMAGPART_EXPR -These nodes represent respectively the real and the imaginary parts -of complex numbers (their sole argument). - -@item NON_LVALUE_EXPR -These nodes indicate that their one and only operand is not an lvalue. -A back-end can treat these identically to the single operand. - -@item NOP_EXPR -These nodes are used to represent conversions that do not require any -code-generation. For example, conversion of a @code{char*} to an -@code{int*} does not require any code be generated; such a conversion is -represented by a @code{NOP_EXPR}. The single operand is the expression -to be converted. The conversion from a pointer to a reference is also -represented with a @code{NOP_EXPR}. - -@item CONVERT_EXPR -These nodes are similar to @code{NOP_EXPR}s, but are used in those -situations where code may need to be generated. For example, if an -@code{int*} is converted to an @code{int} code may need to be generated -on some platforms. These nodes are never used for C++-specific -conversions, like conversions between pointers to different classes in -an inheritance hierarchy. Any adjustments that need to be made in such -cases are always indicated explicitly. Similarly, a user-defined -conversion is never represented by a @code{CONVERT_EXPR}; instead, the -function calls are made explicit. - -@item THROW_EXPR -These nodes represent @code{throw} expressions. The single operand is -an expression for the code that should be executed to throw the -exception. However, there is one implicit action not represented in -that expression; namely the call to @code{__throw}. This function takes -no arguments. If @code{setjmp}/@code{longjmp} exceptions are used, the -function @code{__sjthrow} is called instead. The normal GCC back-end -uses the function @code{emit_throw} to generate this code; you can -examine this function to see what needs to be done. - -@item LSHIFT_EXPR -@itemx RSHIFT_EXPR -These nodes represent left and right shifts, respectively. The first -operand is the value to shift; it will always be of integral type. The -second operand is an expression for the number of bits by which to -shift. Right shift should be treated as arithmetic, i.e., the -high-order bits should be zero-filled when the expression has unsigned -type and filled with the sign bit when the expression has signed type. - -@item BIT_IOR_EXPR -@itemx BIT_XOR_EXPR -@itemx BIT_AND_EXPR -These nodes represent bitwise inclusive or, bitwise exclusive or, and -bitwise and, respectively. Both operands will always have integral -type. - -@item TRUTH_ANDIF_EXPR -@itemx TRUTH_ORIF_EXPR -These nodes represent logical and and logical or, respectively. These -operators are not strict; i.e., the second operand is evaluated only if -the value of the expression is not determined by evaluation of the first -operand. The type of the operands, and the result type, is always of -boolean or integral type. - -@item TRUTH_AND_EXPR -@itemx TRUTH_OR_EXPR -@itemx TRUTH_XOR_EXPR -These nodes represent logical and, logical or, and logical exclusive or. -They are strict; both arguments are always evaluated. There are no -corresponding operators in C or C++, but the front-end will sometimes -generate these expressions anyhow, if it can tell that strictness does -not matter. - -@itemx PLUS_EXPR -@itemx MINUS_EXPR -@itemx MULT_EXPR -@itemx TRUNC_DIV_EXPR -@itemx TRUNC_MOD_EXPR -@itemx RDIV_EXPR -These nodes represent various binary arithmetic operations. -Respectively, these operations are addition, subtraction (of the second -operand from the first), multiplication, integer division, integer -remainder, and floating-point division. The operands to the first three -of these may have either integral or floating type, but there will never -be case in which one operand is of floating type and the other is of -integral type. - -The result of a @code{TRUNC_DIV_EXPR} is always rounded towards zero. -The @code{TRUNC_MOD_EXPR} of two operands @code{a} and @code{b} is -always @code{a - a/b} where the division is as if computed by a -@code{TRUNC_DIV_EXPR}. - -@item ARRAY_REF -These nodes represent array accesses. The first operand is the array; -the second is the index. To calculate the address of the memory -accessed, you must scale the index by the size of the type of the array -elements. - -@item EXACT_DIV_EXPR -Document. - -@item LT_EXPR -@itemx LE_EXPR -@itemx GT_EXPR -@itemx GE_EXPR -@itemx EQ_EXPR -@itemx NE_EXPR - -These nodes represent the less than, less than or equal to, greater -than, greater than or equal to, equal, and not equal comparison -operators. The first and second operand with either be both of integral -type or both of floating type. The result type of these expressions -will always be of integral or boolean type. - -@item MODIFY_EXPR -These nodes represent assignment. The left-hand side is the first -operand; the right-hand side is the second operand. The left-hand side -will be a @code{VAR_DECL}, @code{INDIRECT_REF}, @code{COMPONENT_REF}, or -other lvalue. - -These nodes are used to represent not only assignment with @samp{=} but -also compount assignments (like @samp{+=}), by reduction to @samp{=} -assignment. In other words, the representation for @samp{i += 3} looks -just like that for @samp{i = i + 3}. - -@item INIT_EXPR -These nodes are just like @code{MODIFY_EXPR}, but are used only when a -variable is initialized, rather than assigned to subsequently. - -@item COMPONENT_REF -These nodes represent non-static data member accesses. The first -operand is the object (rather than a pointer to it); the second operand -is the @code{FIELD_DECL} for the data member. - -@item COMPOUND_EXPR -These nodes represent comma-expressions. The first operand is an -expression whose value is computed and thrown away prior to the -evaluation of the second operand. The value of the entire expression is -the value of the second operand. - -@item COND_EXPR -These nodes represent @code{?:} expressions. The first operand -is of boolean or integral type. If it evaluates to a non-zero value, -the second operand should be evaluated, and returned as the value of the -expression. Otherwise, the third operand is evaluated, and returned as -the value of the expression. As a GNU extension, the middle operand of -the @code{?:} operator may be omitted in the source, like this: - -@example -x ? : 3 -@end example -@noindent -which is equivalent to - -@example -x ? x : 3 -@end example - -@noindent -assuming that @code{x} is an expression without side-effects. However, -in the case that the first operation causes side effects, the -side-effects occur only once. Consumers of the internal representation -do not need to worry about this oddity; the second operand will be -always be present in the internal representation. - -@item CALL_EXPR -These nodes are used to represent calls to functions, including -non-static member functions. The first operand is a pointer to the -function to call; it is always an expression whose type is a -@code{POINTER_TYPE}. The second argument is a @code{TREE_LIST}. The -arguments to the call appear left-to-right in the list. The -@code{TREE_VALUE} of each list node contains the expression -corresponding to that argument. (The value of @code{TREE_PURPOSE} for -these nodes is unspecified, and should be ignored.) For non-static -member functions, there will be an operand corresponding to the -@code{this} pointer. There will always be expressions corresponding to -all of the arguments, even if the function is declared with default -arguments and some arguments are not explicitly provided at the call -sites. - -@item STMT_EXPR -These nodes are used to represent GCC's statement-expression extension. -The statement-expression extension allows code like this: -@example -int f() @{ return (@{ int j; j = 3; j + 7; @}); @} -@end example -In other words, an sequence of statements may occur where a single -expression would normally appear. The @code{STMT_EXPR} node represents -such an expression. The @code{STMT_EXPR_STMT} gives the statement -contained in the expression; this is always a @code{COMPOUND_STMT}. The -value of the expression is the value of the last sub-statement in the -@code{COMPOUND_STMT}. More precisely, the value is the value computed -by the last @code{EXPR_STMT} in the outermost scope of the -@code{COMPOUND_STMT}. For example, in: -@example -(@{ 3; @}) -@end example -the value is @code{3} while in: -@example -(@{ if (x) @{ 3; @} @}) -@end example -(represented by a nested @code{COMPOUND_STMT}), there is no value. If -the @code{STMT_EXPR} does not yield a value, it's type will be -@code{void}. - -@item BIND_EXPR -These nodes represent local blocks. The first operand is a list of -temporary variables, connected via their @code{TREE_CHAIN} field. These -will never require cleanups. The scope of these variables is just the -body of the @code{BIND_EXPR}. The body of the @code{BIND_EXPR} is the -second operand. - -@item LOOP_EXPR -These nodes represent ``infinite'' loops. The @code{LOOP_EXPR_BODY} -represents the body of the loop. It should be executed forever, unless -an @code{EXIT_EXPR} is encountered. - -@item EXIT_EXPR -These nodes represent conditional exits from the nearest enclosing -@code{LOOP_EXPR}. The single operand is the condition; if it is -non-zero, then the loop should be exited. An @code{EXIT_EXPR} will only -appear within a @code{LOOP_EXPR}. - -@item CLEANUP_POINT_EXPR -These nodes represent full-expressions. The single operand is an -expression to evaluate. Any destructor calls engendered by the creation -of temporaries during the evaluation of that expression should be -performed immediately after the expression is evaluated. - -@item CONSTRUCTOR -These nodes represent the brace-enclosed initializers for a structure or -array. The first operand is reserved for use by the back-end. The -second operand is a @code{TREE_LIST}. If the @code{TREE_TYPE} of the -@code{CONSTRUCTOR} is a @code{RECORD_TYPE} or @code{UNION_TYPE}, then -the @code{TREE_PURPOSE} of each node in the @code{TREE_LIST} will be a -@code{FIELD_DECL} and the @code{TREE_VALUE} of each node will be the -expression used to initialize that field. You should not depend on the -fields appearing in any particular order, nor should you assume that all -fields will be represented. Unrepresented fields may be assigned any -value. - -If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is an -@code{ARRAY_TYPE}, then the @code{TREE_PURPOSE} of each element in the -@code{TREE_LIST} will be an @code{INTEGER_CST}. This constant indicates -which element of the array (indexed from zero) is being assigned to; -again, the @code{TREE_VALUE} is the corresponding initializer. If the -@code{TREE_PURPOSE} is @code{NULL_TREE}, then the initializer is for the -next available array element. - -Conceptually, before any initialization is done, the entire area of -storage is initialized to zero. - -@item SAVE_EXPR - -A @code{SAVE_EXPR} represents an expression (possibly involving -side-effects) that is used more than once. The side-effects should -occur only the first time the expression is evaluated. Subsequent uses -should just reuse the computed value. The first operand to the -@code{SAVE_EXPR} is the expression to evaluate. The side-effects should -be executed where the @code{SAVE_EXPR} is first encountered in a -depth-first preorder traversal of the expression tree. - -@item TARGET_EXPR -A @code{TARGET_EXPR} represents a temporary object. The first operand -is a @code{VAR_DECL} for the temporary variable. The second operand is -the initializer for the temporary. The initializer is evaluated, and -copied (bitwise) into the temporary. - -Often, a @code{TARGET_EXPR} occurs on the right-hand side of an -assignment, or as the second operand to a comma-expression which is -itself the right-hand side of an assignment, etc. In this case, we say -that the @code{TARGET_EXPR} is ``normal''; otherwise, we say it is -``orphaned''. For a normal @code{TARGET_EXPR} the temporary variable -should be treated as an alias for the left-hand side of the assignment, -rather than as a new temporary variable. - -The third operand to the @code{TARGET_EXPR}, if present, is a -cleanup-expression (i.e., destructor call) for the temporary. If this -expression is orphaned, then this expression must be executed when the -statement containing this expression is complete. These cleanups must -always be executed in the order opposite to that in which they were -encountered. Note that if a temporary is created on one branch of a -conditional operator (i.e., in the second or third operand to a -@code{COND_EXPR}), the cleanup must be run only if that branch is -actually executed. - -See @code{STMT_IS_FULL_EXPR_P} for more information about running these -cleanups. - -@item AGGR_INIT_EXPR -An @code{AGGR_INIT_EXPR} represents the initialization as the return -value of a function call, or as the result of a constructor. An -@code{AGGR_INIT_EXPR} will only appear as the second operand of a -@code{TARGET_EXPR}. The first operand to the @code{AGGR_INIT_EXPR} is -the address of a function to call, just as in a @code{CALL_EXPR}. The -second operand are the arguments to pass that function, as a -@code{TREE_LIST}, again in a manner similar to that of a -@code{CALL_EXPR}. The value of the expression is that returned by the -function. - -If @code{AGGR_INIT_VIA_CTOR_P} holds of the @code{AGGR_INIT_EXPR}, then -the initialization is via a constructor call. The address of the third -operand of the @code{AGGR_INIT_EXPR}, which is always a @code{VAR_DECL}, -is taken, and this value replaces the first argument in the argument -list. In this case, the value of the expression is the @code{VAR_DECL} -given by the third operand to the @code{AGGR_INIT_EXPR}; constructors do -not return a value. - -@end table diff --git a/gcc/contrib.texi b/gcc/contrib.texi deleted file mode 100644 index 7b4db8da804..00000000000 --- a/gcc/contrib.texi +++ /dev/null @@ -1,690 +0,0 @@ -The GCC project would like to thank its many contributors. Without them the -project would not have been nearly as successful as it has been. Any omissions -in this list are accidental. Feel free to contact -@email{law@@redhat.com} if you have been left out -or some of your contributions are not listed. Please keep this list in -alphabetical order. - -@itemize @bullet - -@item -Analog Devices helped implement the support for complex data types -and iterators. - -@item -James van Artsdalen wrote the code that makes efficient use of -the Intel 80387 register stack. - -@item -Alasdair Baird for various bugfixes. - -@item -Gerald Baumgartner added the signature extension to the C++ front-end. - -@item -Neil Booth for various work on cpplib. - -@item -Per Bothner for his direction via the steering committee and various -improvements to our infrastructure for supporting new languages. Chill -and Java front end implementations. Initial implementations of -cpplib, fix-header, config.guess, libio, and past C++ library -(libg++) maintainer. - -@item -Devon Bowen helped port GCC to the Tahoe. - -@item -Don Bowman for mips-vxworks contributions. - -@item -Dave Brolley for work on cpplib and Chill. - -@item -Robert Brown implemented the support for Encore 32000 systems. - -@item -Christian Bruel for improvements to local store elimination. - -@item -Herman A.J. ten Brugge for various fixes. - -@item -Joe Buck for his direction via the steering committee. - -@item -Craig Burley for leadership of the Fortran effort. - -@item -John Carr for his alias work, SPARC hacking, infrastructure improvements, -previous contributions to the steering committee, loop optimizations, etc. - -@item -Steve Chamberlain wrote the support for the Hitachi SH and H8 processors -and the PicoJava processor. - -@item -Scott Christley for his ObjC contributions. - -@item -Branko Cibej for more warning contributions. - -@item -Nick Clifton for arm, mcore, fr30, v850, m32r work, --help, and other random -hacking. - -@item -Ralf Corsepius for SH testing and minor bugfixing. - -@item -Stan Cox for care and feeding of the x86 port and lots of behind -the scenes hacking. - -@item -Alex Crain provided changes for the 3b1. - -@item -Ian Dall for major improvements to the NS32k port. - -@item -Dario Dariol contributed the four varieties of sample programs -that print a copy of their source. - -@item -Ulrich Drepper for his work on the C++ runtime libraries, glibc, - testing of GCC using glibc, ISO C99 support, CFG dumping support, etc. - -@item -Richard Earnshaw for his ongoing work with the ARM. - -@item -David Edelsohn for his direction via the steering committee, -ongoing work with the RS6000/PowerPC port, and help cleaning up Haifa -loop changes. - -@item -Mark Elbrecht for various DJGPP improvements. - -@item -Ben Elliston for his work to move the Objective-C runtime into its -own subdirectory and for his work on autoconf. - -@item -Paul Eggert for random hacking all over gcc. - -@item -Marc Espie for OpenBSD support. - -@item -Doug Evans for much of the global optimization framework, arc, m32r, -and SPARC work. - -@item -Fred Fish for BeOS support and Ada fixes. - -@item -Peter Gerwinski for various bugfixes and the Pascal front end. - -@item -Anthony Green for his -Os contributions and Java front end work. - -@item -Kaveh Ghazi for his direction via the steering committee and -amazing work to make -W -Wall useful. - -@item -Judy Goldberg for c++ contributions. - -@item -Torbjorn Granlund for various fixes and the c-torture testsuite, -multiply- and divide-by-constant optimization, improved long long -support, improved leaf function register allocation, and his direction -via the steering committee. - -@item -Michael K. Gschwind contributed the port to the PDP-11. - -@item -Ron Guilmette implemented the @code{protoize} and @code{unprotoize} -tools, the support for Dwarf symbolic debugging information, and much of -the support for System V Release 4. He has also worked heavily on the -Intel 386 and 860 support. - -@item -Bruno Haible for improvements in the runtime overhead for EH, new -warnings and assorted bugfixes. - -@item -Andrew Haley for his Java work. - -@item -Chris Hanson assisted in making GCC work on HP-UX for the 9000 series 300. - -@item -Michael Hayes for various thankless work he's done trying to get -the c30/c40 ports functional. Lots of loop and unroll improvements and -fixes. - -@item -Kate Hedstrom for staking the g77 folks with an initial testsuite. - -@item -Richard Henderson for his ongoing SPARC and alpha work, loop opts, and -generally fixing lots of old problems we've ignored for years, flow -rewrite and lots of stuff I've forgotten. - -@item -Nobuyuki Hikichi of Software Research Associates, Tokyo, contributed -the support for the Sony NEWS machine. - -@item -Manfred Hollstein for his ongoing work to keep the m88k alive, lots -of testing an bugfixing, particularly of our configury code. - -@item -Steve Holmgren for MachTen patches. - -@item -Jan Hubicka for his x86 port improvements. - -@item -Christian Iseli for various bugfixes. - -@item -Kamil Iskra for general m68k hacking. - -@item -Lee Iverson for random fixes and mips testing. - -@item -Andreas Jaeger for various fixes to the MIPS port - -@item -Jakub Jelinek for his SPARC work and sibling call optimizations. - -@item -J. Kean Johnston for OpenServer support. - -@item -Klaus Kaempf for his ongoing work to make alpha-vms a viable target. - -@item -David Kashtan of SRI adapted GCC to VMS. - -@item -Richard Kenner of the New York University Ultracomputer Research -Laboratory wrote the machine descriptions for the AMD 29000, the DEC -Alpha, the IBM RT PC, and the IBM RS/6000 as well as the support for -instruction attributes. He also made changes to better support RISC -processors including changes to common subexpression elimination, -strength reduction, function calling sequence handling, and condition -code support, in addition to generalizing the code for frame pointer -elimination and delay slot scheduling. Richard Kenner was also the -head maintainer of GCC for several years. - -@item -Robin Kirkham for cpu32 support. - -@item -Mark Klein for PA improvements. - -@item -Geoffrey Keating for his ongoing work to make the PPC work for Linux. - -@item -Brendan Kehoe for his ongoing work with g++. - -@item -Oliver M. Kellogg of Deutsche Aerospace contributed the port to the -MIL-STD-1750A. - -@item -Mumit Khan for various contributions to the cygwin and mingw32 ports and -maintaining binary releases for Windows hosts. - -@item -Thomas Koenig for various bugfixes. - -@item -Bruce Korb for the new and improved fixincludes code. - -@item -Benjamin Kosnik for his g++ work. - -@item -Ted Lemon wrote parts of the RTL reader and printer. - -@item -Charles LaBrec contributed the support for the Integrated Solutions -68020 system. - -@item -Jeff Law for his direction via the steering committee, coordinating the -entire egcs project and GCC 2.95, rolling out snapshots and releases, -handling merges from GCC2, reviewing tons of patches that might have -fallen through the cracks else, and random but extensive hacking. - -@item -Marc Lehmann for his direction via the steering committee and helping -with analysis and improvements of x86 performance. - -@item -Kriang Lerdsuwanakij for improvements to demangler and various c++ fixes. - -@item -Warren Levy major work on libgjc (Java Runtime Library) and random -work on the Java front-end. - -@item -Alain Lichnewsky ported GCC to the Mips cpu. - -@item -Robert Lipe for OpenServer support, new testsuites, testing, etc. - -@item -Weiwen Liu for testing and various bugfixes. - -@item -Martin von Löwis for internal consistency checking infrastructure, -and various C++ improvements including namespace support. - -@item -Dave Love for his ongoing work with the Fortran front end and -runtime libraries. - -@item -H.J. Lu for his previous contributions to the steering committee, many x86 -bug reports, prototype patches, and keeping the Linux ports working. - -@item -Andrew MacLeod for his ongoing work in building a real EH system, -various code generation improvements, work on the global optimizer, etc. - -@item -Bob Manson for his behind the scenes work on dejagnu. - -@item -Vladimir Makarov for hacking some ugly i960 problems, PowerPC -hacking improvements to compile-time performance and overall knowledge -and direction in the area of instruction scheduling. - -@item -Greg McGary for random fixes and (someday) bounded pointers. - -@item -Michael Meissner for LRS framework, ia32, m32r, v850, m88k, MIPS powerpc, haifa, -ECOFF debug support, and other assorted hacking. - -@item -Jason Merrill for his direction via the steering committee and leading -the g++ effort. - -@item -Jason Molenda for major help in the care and feeding of all the services -on the gcc.gnu.org (formerly egcs.cygnus.com) machine -- mail, web -services, ftp services, etc etc. - -@item -David Mosberger-Tang for various Alpha improvements. - -@item -Stephen Moshier contributed the floating point emulator that assists in -cross-compilation and permits support for floating point numbers wider -than 64 bits and for ISO C99 support. - -@item -Bill Moyer for his behind the scenes work on various issues. - -@item -David Miller for his direction via the steering committee, lots of -SPARC work, improvements in jump.c and interfacing with the Linux kernel -developers. - -@item -Gary Miller ported GCC to Charles River Data Systems machines. - -@item -Mark Mitchell for his direction via the steering committee, mountains -of C++ work, load/store hoisting out of loops and alias analysis -improvements, ISO "restrict" support. - -@item -Alan Modra for various Linux bits and testing. - -@item -Toon Moene for his direction via the steering committee, Fortran -maintainance, and his ongoing work to make us make Fortran run fast. - -@item -Catherine Moore for fixing various ugly problems we have sent her -way, including the haifa bug which was killing the Alpha & PowerPC Linux -kernels. - -@item -Philippe De Muyter for his work on the m68k port. - -@item -Joseph Myers for his work on the PDP-11 port, format checking and ISO -C99 support. - -@item -Nathan Myers for his work on libstdc++-v3. - -@item -NeXT, Inc.@: donated the front end that supports the Objective C -language. - -@item -Hans-Peter Nilsson for improvements to the search engine -setup, various documentation fixes and other small fixes. - -@item -Geoff Noer for this work on getting cygwin native builds working. - -@item -Alexandre Oliva for various build infrastructure improvements, scripts and -amazing testing work. - -@item -Rainer Orth for random MIPS work, including improvements to our o32 -ABI support, improvements to dejagnu's MIPS support, etc. - -@item -Melissa O'Neill for various NeXT fixes. - -@item -Paul Petersen wrote the machine description for the Alliant FX/8. - -@item -Alexandre Petit-Bianco for his Java work. - -@item -Matthias Pfaller for major improvements to the NS32k port. - -@item -Gerald Pfeifer his direction via the steering committee, maintenance of -the web pages and pointing out lots of problems we need to solve. - -@item -Ovidiu Predescu for his work on the ObjC front end and runtime libraries. - -@item -Ken Raeburn for various improvements to checker, mips ports and various -cleanups in the compiler. - -@item -David Reese of Sun Microsystems contributed to the Solaris on PowerPC -port. -@item -Gabriel Dos Reis for contributions and maintenance of libstdc++-v3, -including valarray implementation and limits support. - -@item -Joern Rennecke for maintaining the sh port, loop, regmove & reload -hacking. - -@item -Gavin Romig-Koch for lots of behind the scenes MIPS work. - -@item -Ken Rose for fixes to our delay slot filling code. - -@item -Paul Rubin wrote most of the preprocessor. - -@item -Andreas Schwab for his work on the m68k port. - -@item -Graham Stott. for various infrastructure improvements. - -@item -Juha Sarlin for improvements to the H8 code generator. - -@item -Greg Satz assisted in making GCC work on HP-UX for the 9000 series 300. - -@item -Peter Schauer wrote the code to allow debugging to work on the Alpha. - -@item -William Schelter did most of the work on the Intel 80386 support. - -@item -Bernd Schmidt for various code generation improvements and major -work in the reload pass. - -@item -Franz Sirl for his ongoing work with making the PPC port stable -for linux. - -@item -Joel Sherrill for his direction via the steering committee, RTEMS -contributions and RTEMS testing. - -@item -Nathan Sidwell for many C++ fixes/improvements. - -@item -Jeffrey Siegal for helping RMS with the original design of GCC, some -code which handles the parse tree and RTL data structures, constant -folding and help with the original VAX & m68k ports. - -@item -Andrey Slepuhin for assorted AIX hacking. - -@item -Randy Smith finished the Sun FPA support. - -@item -Christopher Smith did the port for Convex machines. - -@item -Scott Snyder for various fixes. - -@item -Richard Stallman, for writing the original gcc and launching the GNU project. - -@item -Jan Stein of the Chalmers Computer Society provided support for -Genix, as well as part of the 32000 machine description. - -@item -Nigel Stephens for various mips16 related fixes/improvements. - -@item -Jonathan Stone wrote the machine description for the Pyramid computer. - -@item -Mike Stump for his Elxsi port, g++ contributions over the years and more -recently his vxworks contributions - -@item -Shigeya Suzuki for this fixes for the bsdi platforms. - -@item -Ian Lance Taylor for his mips16 work, general configury hacking, -fixincludes, etc. - -@item -Holger Teutsch provided the support for the Clipper cpu. - -@item -Michael Tiemann for random bugfixes the first instruction scheduler, -initial C++ support, function integration, NS32k, sparc and M88k -machine description work, delay slot scheduling. - -@item -Gary Thomas for his ongoing work to make the PPC work for Linux. - -@item -Philipp Thomas for random bugfixes throughout the compiler - -@item -Kresten Krab Thorup wrote the run time support for the Objective C -language. - -@item -Teemu Torma for thread safe exception handling support. - -@item -Leonard Tower wrote parts of the parser, RTL generator, and RTL -definitions, and of the Vax machine description. - -@item -Tom Tromey for internationalization support and his Java work. - -@item -Lassi Tuura for improvements to config.guess to determine HP processor -types. - -@item -Todd Vierling for contributions for NetBSD ports. - -@item -Krister Walfridsson for random bugfixes. - -@item -John Wehle for various improvements for the x86 code generator, -related infrastructure improvements to help x86 code generation, -value range propagation and other work, WE32k port. - -@item -Dale Wiles helped port GCC to the Tahoe. - -@item -Zack Weinberg for major work on cpplib and various other bugfixes. - -@item -Jim Wilson for his direction via the steering committee, tackling hard -problems in various places that nobody else wanted to work on, strength -reduction and other loop optimizations. - -@item -Carlo Wood for various fixes. - -@item -Tom Wood for work on the m88k port. - -@item -Masanobu Yuhara of Fujitsu Laboratories implemented the machine -description for the Tron architecture (specifically, the Gmicro). - -@item -Kevin Zachmann helped ported GCC to the Tahoe. - -@end itemize - - -We'd also like to thank the folks who have contributed time and energy in -testing GCC: - -@itemize @bullet -@item -David Billinghurst - -@item -Horst von Brand - -@item -Rodney Brown - -@item -Joe Buck - -@item -Craig Burley - -@item -Ulrich Drepper - -@item -David Edelsohn - -@item -Kaveh Ghazi - -@item -Yung Shing Gene - -@item -Richard Henderson - -@item -Manfred Hollstein - -@item -Kate Hedstrom - -@item -Kamil Iskra - -@item -Christian Joensson - -@item -Jeff Law - -@item -Robert Lipe - -@item -Dave Love - -@item -Damon Love - -@item -H.J. Lu - -@item -Mumit Khan - -@item -Matthias Klose - -@item -Martin Knoblauch - -@item -Toon Moene - -@item -David Miller - -@item -Matthias Mueller - -@item -Alexandre Oliva - -@item -Richard Polton - -@item -David Rees - -@item -Peter Schmid - -@item -David Schuler - -@item -Vin Shelton - -@item -Franz Sirl - -@item -Mike Stump - -@item -Carlo Wood - -@item -And many others -@end itemize - -And finally we'd like to thank everyone who uses the compiler, submits bug -reports and generally reminds us why we're doing this work in the first place. diff --git a/gcc/cpp.1 b/gcc/cpp.1 deleted file mode 100644 index f3e227e6b05..00000000000 --- a/gcc/cpp.1 +++ /dev/null @@ -1,764 +0,0 @@ -.\" Automatically generated by Pod::Man version 1.1 -.\" Mon Feb 19 19:32:17 2001 -.\" -.\" Standard preamble: -.\" ====================================================================== -.de Sh \" Subsection heading -.br -.if t .Sp -.ne 5 -.PP -\fB\\$1\fR -.PP -.. -.de Sp \" Vertical space (when we can't use .PP) -.if t .sp .5v -.if n .sp -.. -.de Ip \" List item -.br -.ie \\n(.$>=3 .ne \\$3 -.el .ne 3 -.IP "\\$1" \\$2 -.. -.de Vb \" Begin verbatim text -.ft CW -.nf -.ne \\$1 -.. -.de Ve \" End verbatim text -.ft R - -.fi -.. -.\" Set up some character translations and predefined strings. \*(-- will -.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left -.\" double quote, and \*(R" will give a right double quote. | will give a -.\" real vertical bar. \*(C+ will give a nicer C++. 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For macro processing of other files, you are -strongly encouraged to use alternatives like M4, which will likely give -you better results and avoid many problems. For example, normally the C -preprocessor does not preserve arbitrary whitespace verbatim, but -instead replaces each sequence with a single space. -.PP -For use on C-like source files, the C preprocessor provides four -separate facilities that you can use as you see fit: -.Ip "\(bu" 4 -Inclusion of header files. These are files of declarations that can be -substituted into your program. -.Ip "\(bu" 4 -Macro expansion. You can define \fImacros\fR, which are abbreviations -for arbitrary fragments of C code, and then the C preprocessor will -replace the macros with their definitions throughout the program. -.Ip "\(bu" 4 -Conditional compilation. Using special preprocessing directives, you -can include or exclude parts of the program according to various -conditions. -.Ip "\(bu" 4 -Line control. If you use a program to combine or rearrange source files -into an intermediate file which is then compiled, you can use line -control to inform the compiler of where each source line originally came -from. -.PP -C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C -preprocessor, which provides a small superset of the features of \s-1ISO\s0 -Standard C. -.PP -In its default mode, the \s-1GNU\s0 C preprocessor does not do a few things -required by the standard. These are features which are rarely, if ever, -used, and may cause surprising changes to the meaning of a program which -does not expect them. To get strict \s-1ISO\s0 Standard C, you should use the -\&\fB\-std=c89\fR or \fB\-std=c99\fR options, depending on which version -of the standard you want. To get all the mandatory diagnostics, you -must also use \fB\-pedantic\fR. -.SH "OPTIONS" -.IX Header "OPTIONS" -The C preprocessor expects two file names as arguments, \fIinfile\fR and -\&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any -other files it specifies with \fB#include\fR. All the output generated -by the combined input files is written in \fIoutfile\fR. -.PP -Either \fIinfile\fR or \fIoutfile\fR may be \fB-\fR, which as -\&\fIinfile\fR means to read from standard input and as \fIoutfile\fR -means to write to standard output. Also, if either file is omitted, it -means the same as if \fB-\fR had been specified for that file. -.PP -Here is a table of command options accepted by the C preprocessor. -These options can also be given when compiling a C program; they are -passed along automatically to the preprocessor when it is invoked by the -compiler. -.Ip "\fB\-P\fR" 4 -.IX Item "-P" -Inhibit generation of \fB#\fR\-lines with line-number information in the -output from the preprocessor. This might be useful when running the -preprocessor on something that is not C code and will be sent to a -program which might be confused by the \fB#\fR\-lines. -.Ip "\fB\-C\fR" 4 -.IX Item "-C" -Do not discard comments. All comments are passed through to the output -file, except for comments in processed directives, which are deleted -along with the directive. Comments appearing in the expansion list of a -macro will be preserved, and appear in place wherever the macro is -invoked. -.Sp -You should be prepared for side effects when using \fB\-C\fR; it causes -the preprocessor to treat comments as tokens in their own right. For -example, macro redefinitions that were trivial when comments were -replaced by a single space might become significant when comments are -retained. Also, comments appearing at the start of what would be a -directive line have the effect of turning that line into an ordinary -source line, since the first token on the line is no longer a \fB#\fR. -.Ip "\fB\-traditional\fR" 4 -.IX Item "-traditional" -Try to imitate the behavior of old-fashioned C, as opposed to \s-1ISO\s0 C. -.RS 4 -.Ip "\(bu" 4 -Traditional macro expansion pays no attention to single-quote or -double-quote characters; macro argument symbols are replaced by the -argument values even when they appear within apparent string or -character constants. -.Ip "\(bu" 4 -Traditionally, it is permissible for a macro expansion to end in the -middle of a string or character constant. The constant continues into -the text surrounding the macro call. -.Ip "\(bu" 4 -However, traditionally the end of the line terminates a string or -character constant, with no error. -.Ip "\(bu" 4 -In traditional C, a comment is equivalent to no text at all. (In \s-1ISO\s0 -C, a comment counts as whitespace.) -.Ip "\(bu" 4 -Traditional C does not have the concept of a ``preprocessing number''. -It considers \fB1.0e+4\fR to be three tokens: \fB1.0e\fR, \fB+\fR, -and \fB4\fR. -.Ip "\(bu" 4 -A macro is not suppressed within its own definition, in traditional C. -Thus, any macro that is used recursively inevitably causes an error. -.Ip "\(bu" 4 -The character \fB#\fR has no special meaning within a macro definition -in traditional C. -.Ip "\(bu" 4 -In traditional C, the text at the end of a macro expansion can run -together with the text after the macro call, to produce a single token. -(This is impossible in \s-1ISO\s0 C.) -.Ip "\(bu" 4 -None of the \s-1GNU\s0 extensions to the preprocessor are available in -\&\fB\-traditional\fR mode. -.RE -.RS 4 -.Sp -Use the \fB\-traditional\fR option when preprocessing Fortran code, so -that single-quotes and double-quotes within Fortran comment lines (which -are generally not recognized as such by the preprocessor) do not cause -diagnostics about unterminated character or string constants. -.Sp -However, this option does not prevent diagnostics about unterminated -comments when a C-style comment appears to start, but not end, within -Fortran-style commentary. -.Sp -So, the following Fortran comment lines are accepted with -\&\fB\-traditional\fR: -.Sp -.Vb 3 -\& C This isn't an unterminated character constant -\& C Neither is "20000000000, an octal constant -\& C in some dialects of Fortran -.Ve -However, this type of comment line will likely produce a diagnostic, or -at least unexpected output from the preprocessor, due to the -unterminated comment: -.Sp -.Vb 2 -\& C Some Fortran compilers accept /* as starting -\& C an inline comment. -.Ve -Note that \f(CW\*(C`g77\*(C'\fR automatically supplies the \fB\-traditional\fR -option when it invokes the preprocessor. However, a future version of -\&\f(CW\*(C`g77\*(C'\fR might use a different, more-Fortran-aware preprocessor in -place of \f(CW\*(C`cpp\*(C'\fR. -.RE -.Ip "\fB\-trigraphs\fR" 4 -.IX Item "-trigraphs" -Process \s-1ISO\s0 standard trigraph sequences. These are three-character -sequences, all starting with \fB??\fR, that are defined by \s-1ISO\s0 C to -stand for single characters. For example, \fB??/\fR stands for -\&\fB\e\fR, so \fB'??/n'\fR is a character constant for a newline. By -default, \s-1GCC\s0 ignores trigraphs, but in standard-conforming modes it -converts them. See the \fB\-std\fR option. -.Sp -The nine trigraph sequences are -.RS 4 -.Ip "\fB??(\fR" 4 -.IX Item "??(" --> \fB[\fR -.Ip "\fB??)\fR" 4 -.IX Item "??)" --> \fB]\fR -.Ip "\fB??<\fR" 4 -.IX Item "??<" --> \fB{\fR -.Ip "\fB??>\fR" 4 -.IX Item "??>" --> \fB}\fR -.Ip "\fB??=\fR" 4 -.IX Item "??=" --> \fB#\fR -.Ip "\fB??/\fR" 4 -.IX Item "??/" --> \fB\e\fR -.Ip "\fB??'\fR" 4 -.IX Item "??'" --> \fB^\fR -.Ip "\fB??!\fR" 4 -.IX Item "??!" --> \fB|\fR -.Ip "\fB??-\fR" 4 -.IX Item "??-" --> \fB~\fR -.RE -.RS 4 -.Sp -Trigraph support is not popular, so many compilers do not implement it -properly. Portable code should not rely on trigraphs being either -converted or ignored. -.RE -.Ip "\fB\-pedantic\fR" 4 -.IX Item "-pedantic" -Issue warnings required by the \s-1ISO\s0 C standard in certain cases such -as when text other than a comment follows \fB#else\fR or \fB#endif\fR. -.Ip "\fB\-pedantic-errors\fR" 4 -.IX Item "-pedantic-errors" -Like \fB\-pedantic\fR, except that errors are produced rather than -warnings. -.Ip "\fB\-Wcomment\fR" 4 -.IX Item "-Wcomment" -.PD 0 -.Ip "\fB\-Wcomments\fR" 4 -.IX Item "-Wcomments" -.PD -(Both forms have the same effect). -Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR -comment, or whenever a backslash-newline appears in a \fB//\fR comment. -.Ip "\fB\-Wtrigraphs\fR" 4 -.IX Item "-Wtrigraphs" -Warn if any trigraphs are encountered. This option used to take effect -only if \fB\-trigraphs\fR was also specified, but now works -independently. Warnings are not given for trigraphs within comments, as -we feel this is obnoxious. -.Ip "\fB\-Wwhite-space\fR" 4 -.IX Item "-Wwhite-space" -Warn about possible white space confusion, e.g. white space between a -backslash and a newline. -.Ip "\fB\-Wall\fR" 4 -.IX Item "-Wall" -Requests \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR, and \fB\-Wwhite-space\fR -(but not \fB\-Wtraditional\fR or \fB\-Wundef\fR). -.Ip "\fB\-Wtraditional\fR" 4 -.IX Item "-Wtraditional" -Warn about certain constructs that behave differently in traditional and -\&\s-1ISO\s0 C. -.RS 4 -.Ip "\(bu" 4 -Macro parameters that appear within string literals in the macro body. -In traditional C macro replacement takes place within string literals, -but does not in \s-1ISO\s0 C. -.Ip "\(bu" 4 -In traditional C, some preprocessor directives did not exist. -Traditional preprocessors would only consider a line to be a directive -if the \fB#\fR appeared in column 1 on the line. Therefore -\&\fB\-Wtraditional\fR warns about directives that traditional C -understands but would ignore because the \fB#\fR does not appear as the -first character on the line. It also suggests you hide directives like -\&\fB#pragma\fR not understood by traditional C by indenting them. Some -traditional implementations would not recognise \fB#elif\fR, so it -suggests avoiding it altogether. -.Ip "\(bu" 4 -A function-like macro that appears without arguments. -.Ip "\(bu" 4 -The unary plus operator. -.Ip "\(bu" 4 -The `U' integer constant suffix. (Traditonal C does support the `L' -suffix on integer constants.) Note, these suffixes appear in macros -defined in the system headers of most modern systems, e.g. the _MIN/_MAX -macros in limits.h. Use of these macros can lead to spurious warnings -as they do not necessarily reflect whether the code in question is any -less portable to traditional C given that suitable backup definitions -are provided. -.RE -.RS 4 -.RE -.Ip "\fB\-Wundef\fR" 4 -.IX Item "-Wundef" -Warn if an undefined identifier is evaluated in an \fB#if\fR directive. -.Ip "\fB\-I\fR \fIdirectory\fR" 4 -.IX Item "-I directory" -Add the directory \fIdirectory\fR to the head of the list of -directories to be searched for header files. -This can be used to override a system header file, substituting your -own version, since these directories are searched before the system -header file directories. If you use more than one \fB\-I\fR option, -the directories are scanned in left-to-right order; the standard -system directories come after. -.Ip "\fB\-I-\fR" 4 -.IX Item "-I-" -Any directories specified with \fB\-I\fR options before the \fB\-I-\fR -option are searched only for the case of \fB#include "\fR\fIfile\fR\fB"\fR; -they are not searched for \fB#include <\fR\fIfile\fR\fB>\fR. -.Sp -If additional directories are specified with \fB\-I\fR options after -the \fB\-I-\fR, these directories are searched for all \fB#include\fR -directives. -.Sp -In addition, the \fB\-I-\fR option inhibits the use of the current -directory as the first search directory for \fB#include "\fR\fIfile\fR\fB"\fR. -Therefore, the current directory is searched only if it is requested -explicitly with \fB\-I.\fR. Specifying both \fB\-I-\fR and \fB\-I.\fR -allows you to control precisely which directories are searched before -the current one and which are searched after. -.Ip "\fB\-nostdinc\fR" 4 -.IX Item "-nostdinc" -Do not search the standard system directories for header files. -Only the directories you have specified with \fB\-I\fR options -(and the current directory, if appropriate) are searched. -.Sp -By using both \fB\-nostdinc\fR and \fB\-I-\fR, you can limit the include-file -search path to only those directories you specify explicitly. -.Ip "\fB\-nostdinc++\fR" 4 -.IX Item "-nostdinc++" -Do not search for header files in the \*(C+\-specific standard directories, -but do still search the other standard directories. (This option is -used when building the \*(C+ library.) -.Ip "\fB\-remap\fR" 4 -.IX Item "-remap" -When searching for a header file in a directory, remap file names if a -file named \fIheader.gcc\fR exists in that directory. This can be used -to work around limitations of file systems with file name restrictions. -The \fIheader.gcc\fR file should contain a series of lines with two -tokens on each line: the first token is the name to map, and the second -token is the actual name to use. -.Ip "\fB\-D\fR \fIname\fR" 4 -.IX Item "-D name" -Predefine \fIname\fR as a macro, with definition \fB1\fR. -.Ip "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4 -.IX Item "-D name=definition" -Predefine \fIname\fR as a macro, with definition \fIdefinition\fR. -There are no restrictions on the contents of \fIdefinition\fR, but if -you are invoking the preprocessor from a shell or shell-like program you -may need to use the shell's quoting syntax to protect characters such as -spaces that have a meaning in the shell syntax. If you use more than -one \fB\-D\fR for the same \fIname\fR, the rightmost definition takes -effect. -.Sp -Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in -order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the -order in which they are written. -.Ip "\fB\-U\fR \fIname\fR" 4 -.IX Item "-U name" -Do not predefine \fIname\fR. -.Sp -Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in -order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the -order in which they are written. -.Ip "\fB\-undef\fR" 4 -.IX Item "-undef" -Do not predefine any nonstandard macros. -.Ip "\fB\-gcc\fR" 4 -.IX Item "-gcc" -Define the macros \fI_\|_GNUC_\|_\fR, \fI_\|_GNUC_MINOR_\|_\fR and -\&\fI_\|_GNUC_PATCHLEVEL_\|_\fR. These are defined automatically when you use -\&\fBgcc \-E\fR; you can turn them off in that case with \fB\-no-gcc\fR. -.Ip "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4 -.IX Item "-A predicate=answer" -Make an assertion with the predicate \fIpredicate\fR and answer -\&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR -\&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because -it does not use shell special characters. -.Ip "\fB\-A -\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4 -.IX Item "-A -predicate=answer" -Disable an assertion with the predicate \fIpredicate\fR and answer -\&\fIanswer\fR. Specifying no predicate, by \fB\-A-\fR or \fB\-A -\fR, -disables all predefined assertions and all assertions preceding it on -the command line; and also undefines all predefined macros and all -macros preceding it on the command line. -.Ip "\fB\-dM\fR" 4 -.IX Item "-dM" -Instead of outputting the result of preprocessing, output a list of -\&\fB#define\fR directives for all the macros defined during the -execution of the preprocessor, including predefined macros. This gives -you a way of finding out what is predefined in your version of the -preprocessor; assuming you have no file \fBfoo.h\fR, the command -.Sp -.Vb 1 -\& touch foo.h; cpp -dM foo.h -.Ve -will show the values of any predefined macros. -.Ip "\fB\-dD\fR" 4 -.IX Item "-dD" -Like \fB\-dM\fR except in two respects: it does \fInot\fR include the -predefined macros, and it outputs \fIboth\fR the \fB#define\fR -directives and the result of preprocessing. Both kinds of output go to -the standard output file. -.Ip "\fB\-dN\fR" 4 -.IX Item "-dN" -Like \fB\-dD\fR, but emit only the macro names, not their expansions. -.Ip "\fB\-dI\fR" 4 -.IX Item "-dI" -Output \fB#include\fR directives in addition to the result of -preprocessing. -.Ip "\fB\-M\fR" 4 -.IX Item "-M" -Instead of outputting the result of preprocessing, output a rule -suitable for \f(CW\*(C`make\*(C'\fR describing the dependencies of the main source -file. The preprocessor outputs one \f(CW\*(C`make\*(C'\fR rule containing the -object file name for that source file, a colon, and the names of all the -included files, including those coming from \fB\-include\fR or -\&\fB\-imacros\fR command line options. Unless specified explicitly (with -\&\fB\-MT\fR or \fB\-MQ\fR), the object file name consists of the basename -of the source file with any suffix replaced with object file suffix. -If there are many included files -then the rule is split into several lines using \fB\e\fR\-newline. -.Ip "\fB\-MM\fR" 4 -.IX Item "-MM" -Like \fB\-M\fR, but mention only the files included with \fB#include -"\fR\fIfile\fR\fB"\fR or with \fB\-include\fR or \fB\-imacros\fR command line -options. System header files included with \fB#include <\fR\fIfile\fR\fB>\fR -are omitted. -.Ip "\fB\-MF\fR \fIfile\fR" 4 -.IX Item "-MF file" -When used with \fB\-M\fR or \fB\-MM\fR, specifies a file to write the -dependencies to. This allows the preprocessor to write the preprocessed -file to stdout normally. If no \fB\-MF\fR switch is given, \s-1CPP\s0 sends -the rules to stdout and suppresses normal preprocessed output. -.Ip "\fB\-MG\fR" 4 -.IX Item "-MG" -When used with \fB\-M\fR or \fB\-MM\fR, \fB\-MG\fR says to treat missing -header files as generated files and assume they live in the same -directory as the source file. It suppresses preprocessed output, as a -missing header file is ordinarily an error. -.Sp -This feature is used in automatic updating of makefiles. -.Ip "\fB\-MP\fR" 4 -.IX Item "-MP" -This option instructs \s-1CPP\s0 to add a phony target for each dependency -other than the main file, causing each to depend on nothing. These -dummy rules work around errors \f(CW\*(C`make\*(C'\fR gives if you remove header -files without updating the \f(CW\*(C`Makefile\*(C'\fR to match. -.Sp -This is typical output:\- -.Sp -.Vb 1 -\& /tmp/test.o: /tmp/test.c /tmp/test.h -.Ve -.Vb 1 -\& /tmp/test.h: -.Ve -.Ip "\fB\-MQ\fR \fItarget\fR" 4 -.IX Item "-MQ target" -.PD 0 -.Ip "\fB\-MT\fR \fItarget\fR" 4 -.IX Item "-MT target" -.PD -By default \s-1CPP\s0 uses the main file name, including any path, and appends -the object suffix, normally ``.o'', to it to obtain the name of the -target for dependency generation. With \fB\-MT\fR you can specify a -target yourself, overriding the default one. -.Sp -If you want multiple targets, you can specify them as a single argument -to \fB\-MT\fR, or use multiple \fB\-MT\fR options. -.Sp -The targets you specify are output in the order they appear on the -command line. \fB\-MQ\fR is identical to \fB\-MT\fR, except that the -target name is quoted for Make, but with \fB\-MT\fR it isn't. For -example, \-MT '$(objpfx)foo.o' gives -.Sp -.Vb 1 -\& $(objpfx)foo.o: /tmp/foo.c -.Ve -but \-MQ '$(objpfx)foo.o' gives -.Sp -.Vb 1 -\& $$(objpfx)foo.o: /tmp/foo.c -.Ve -The default target is automatically quoted, as if it were given with -\&\fB\-MQ\fR. -.Ip "\fB\-H\fR" 4 -.IX Item "-H" -Print the name of each header file used, in addition to other normal -activities. -.Ip "\fB\-imacros\fR \fIfile\fR" 4 -.IX Item "-imacros file" -Process \fIfile\fR as input, discarding the resulting output, before -processing the regular input file. Because the output generated from -\&\fIfile\fR is discarded, the only effect of \fB\-imacros\fR \fIfile\fR -is to make the macros defined in \fIfile\fR available for use in the -main input. -.Ip "\fB\-include\fR \fIfile\fR" 4 -.IX Item "-include file" -Process \fIfile\fR as input, and include all the resulting output, -before processing the regular input file. -.Ip "\fB\-idirafter\fR \fIdir\fR" 4 -.IX Item "-idirafter dir" -Add the directory \fIdir\fR to the second include path. The directories -on the second include path are searched when a header file is not found -in any of the directories in the main include path (the one that -\&\fB\-I\fR adds to). -.Ip "\fB\-iprefix\fR \fIprefix\fR" 4 -.IX Item "-iprefix prefix" -Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR -options. If the prefix represents a directory, you should include the -final \fB/\fR. -.Ip "\fB\-iwithprefix\fR \fIdir\fR" 4 -.IX Item "-iwithprefix dir" -Add a directory to the second include path. The directory's name is -made by concatenating \fIprefix\fR and \fIdir\fR, where \fIprefix\fR was -specified previously with \fB\-iprefix\fR. -.Ip "\fB\-isystem\fR \fIdir\fR" 4 -.IX Item "-isystem dir" -Add a directory to the beginning of the second include path, marking it -as a system directory, so that it gets the same special treatment as -is applied to the standard system directories. -.Ip "\fB\-x c\fR" 4 -.IX Item "-x c" -.PD 0 -.Ip "\fB\-x c++\fR" 4 -.IX Item "-x c++" -.Ip "\fB\-x objective-c\fR" 4 -.IX Item "-x objective-c" -.Ip "\fB\-x assembler-with-cpp\fR" 4 -.IX Item "-x assembler-with-cpp" -.PD -Specify the source language: C, \*(C+, Objective-C, or assembly. This has -nothing to do with standards conformance or extensions; it merely -selects which base syntax to expect. If you give none of these options, -cpp will deduce the language from the extension of the source file: -\&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common -extensions for \*(C+ and assembly are also recognized. If cpp does not -recognize the extension, it will treat the file as C; this is the most -generic mode. -.Sp -\&\fBNote:\fR Previous versions of cpp accepted a \fB\-lang\fR option -which selected both the language and the standards conformance level. -This option has been removed, because it conflicts with the \fB\-l\fR -option. -.Ip "\fB\-std=\fR\fIstandard\fR" 4 -.IX Item "-std=standard" -.PD 0 -.Ip "\fB\-ansi\fR" 4 -.IX Item "-ansi" -.PD -Specify the standard to which the code should conform. Currently cpp -only knows about the standards for C; other language standards will be -added in the future. -.Sp -\&\fIstandard\fR -may be one of: -.RS 4 -.if n .Ip "\f(CW""iso9899:1990""\fR" 4 -.el .Ip "\f(CWiso9899:1990\fR" 4 -.IX Item "iso9899:1990" -.PD 0 -.if n .Ip "\f(CW""c89""\fR" 4 -.el .Ip "\f(CWc89\fR" 4 -.IX Item "c89" -.PD -The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for -this version of the standard. -.Sp -The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR. -.if n .Ip "\f(CW""iso9899:199409""\fR" 4 -.el .Ip "\f(CWiso9899:199409\fR" 4 -.IX Item "iso9899:199409" -The 1990 C standard, as amended in 1994. -.if n .Ip "\f(CW""iso9899:1999""\fR" 4 -.el .Ip "\f(CWiso9899:1999\fR" 4 -.IX Item "iso9899:1999" -.PD 0 -.if n .Ip "\f(CW""c99""\fR" 4 -.el .Ip "\f(CWc99\fR" 4 -.IX Item "c99" -.if n .Ip "\f(CW""iso9899:199x""\fR" 4 -.el .Ip "\f(CWiso9899:199x\fR" 4 -.IX Item "iso9899:199x" -.if n .Ip "\f(CW""c9x""\fR" 4 -.el .Ip "\f(CWc9x\fR" 4 -.IX Item "c9x" -.PD -The revised \s-1ISO\s0 C standard, published in December 1999. Before -publication, this was known as C9X. -.if n .Ip "\f(CW""gnu89""\fR" 4 -.el .Ip "\f(CWgnu89\fR" 4 -.IX Item "gnu89" -The 1990 C standard plus \s-1GNU\s0 extensions. This is the default. -.if n .Ip "\f(CW""gnu99""\fR" 4 -.el .Ip "\f(CWgnu99\fR" 4 -.IX Item "gnu99" -.PD 0 -.if n .Ip "\f(CW""gnu9x""\fR" 4 -.el .Ip "\f(CWgnu9x\fR" 4 -.IX Item "gnu9x" -.PD -The 1999 C standard plus \s-1GNU\s0 extensions. -.RE -.RS 4 -.RE -.Ip "\fB\-ftabstop=NUMBER\fR" 4 -.IX Item "-ftabstop=NUMBER" -Set the distance between tab stops. This helps the preprocessor -report correct column numbers in warnings or errors, even if tabs appear -on the line. Values less than 1 or greater than 100 are ignored. The -default is 8. -.Ip "\fB\-$\fR" 4 -.IX Item "-$" -Forbid the use of \fB$\fR in identifiers. The C standard allows -implementations to define extra characters that can appear in -identifiers. By default the \s-1GNU\s0 C preprocessor permits \fB$\fR, a -common extension. -.SH "SEE ALSO" -.IX Header "SEE ALSO" -\&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and -\&\fIbinutils\fR. -.SH "COPYRIGHT" -.IX Header "COPYRIGHT" -Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, -1997, 1998, 1999, 2000, 2001 -Free Software Foundation, Inc. -.PP -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. -.PP -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that -the entire resulting derived work is distributed under the terms of a -permission notice identical to this one. -.PP -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. diff --git a/gcc/cpp.texi b/gcc/cpp.texi deleted file mode 100644 index ef689feaa7b..00000000000 --- a/gcc/cpp.texi +++ /dev/null @@ -1,3734 +0,0 @@ -\input texinfo -@setfilename cpp.info -@settitle The C Preprocessor - -@ifinfo -@dircategory Programming -@direntry -* Cpp: (cpp). The GNU C preprocessor. -@end direntry -@end ifinfo - -@c @smallbook -@c @cropmarks -@c @finalout -@setchapternewpage odd -@ifinfo -This file documents the GNU C Preprocessor. - -Copyright 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, -1999, 2000, 2001 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -@ignore -Permission is granted to process this file through Tex and print the -results, provided the printed document carries copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). - -@end ignore -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that -the entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. -@end ifinfo - -@titlepage -@c @finalout -@title The C Preprocessor -@subtitle Last revised January 2001 -@subtitle for GCC version 3 -@author Richard M. Stallman -@page -@vskip 2pc -This booklet is eventually intended to form the first chapter of a GNU -C Language manual. - -@vskip 0pt plus 1filll -@c man begin COPYRIGHT -Copyright @copyright{} 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, -1997, 1998, 1999, 2000, 2001 -Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that -the entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. -@c man end -@end titlepage -@page - -@node Top, Global Actions,, (DIR) -@chapter The C Preprocessor -@c man begin DESCRIPTION - -The C preprocessor is a @dfn{macro processor} that is used automatically -by the C compiler to transform your program before actual compilation. -It is called a macro processor because it allows you to define -@dfn{macros}, which are brief abbreviations for longer constructs. - -The C preprocessor is intended only for macro processing of C, C++ and -Objective C source files. For macro processing of other files, you are -strongly encouraged to use alternatives like M4, which will likely give -you better results and avoid many problems. For example, normally the C -preprocessor does not preserve arbitrary whitespace verbatim, but -instead replaces each sequence with a single space. - -For use on C-like source files, the C preprocessor provides four -separate facilities that you can use as you see fit: - -@itemize @bullet -@item -Inclusion of header files. These are files of declarations that can be -substituted into your program. - -@item -Macro expansion. You can define @dfn{macros}, which are abbreviations -for arbitrary fragments of C code, and then the C preprocessor will -replace the macros with their definitions throughout the program. - -@item -Conditional compilation. Using special preprocessing directives, you -can include or exclude parts of the program according to various -conditions. - -@item -Line control. If you use a program to combine or rearrange source files -into an intermediate file which is then compiled, you can use line -control to inform the compiler of where each source line originally came -from. -@end itemize - -C preprocessors vary in some details. This manual discusses the GNU C -preprocessor, which provides a small superset of the features of ISO -Standard C@. - -In its default mode, the GNU C preprocessor does not do a few things -required by the standard. These are features which are rarely, if ever, -used, and may cause surprising changes to the meaning of a program which -does not expect them. To get strict ISO Standard C, you should use the -@samp{-std=c89} or @samp{-std=c99} options, depending on which version -of the standard you want. To get all the mandatory diagnostics, you -must also use @samp{-pedantic}. @xref{Invocation}. - -@c man end - -@menu -* Global Actions:: Actions made uniformly on all input files. -* Directives:: General syntax of preprocessing directives. -* Header Files:: How and why to use header files. -* Macros:: How and why to use macros. -* Conditionals:: How and why to use conditionals. -* Assertions:: How and why to use assertions. -* Line Control:: Use of line control when you combine source files. -* Other Directives:: Miscellaneous preprocessing directives. -* Output:: Format of output from the C preprocessor. -* Implementation:: Implementation limits and behavior. -* Unreliable Features:: Undefined behavior and deprecated features. -* Invocation:: How to invoke the preprocessor; command options. -* Concept Index:: Index of concepts and terms. -* Index:: Index of directives, predefined macros and options. -@end menu - -@node Global Actions, Directives, Top, Top -@section Transformations Made Globally -@cindex ASCII NUL handling - -Most C preprocessor features are inactive unless you give specific -directives to request their use. (Preprocessing directives are lines -starting with a @samp{#} token, possibly preceded by whitespace; -@pxref{Directives}). However, there are four transformations that the -preprocessor always makes on all the input it receives, even in the -absence of directives. These are, in order: - -@enumerate -@item -Trigraphs, if enabled, are replaced with the character they represent. - -@item -Backslash-newline sequences are deleted, no matter where. This -feature allows you to break long lines for cosmetic purposes without -changing their meaning. - -Recently, the non-traditional preprocessor has relaxed its treatment of -escaped newlines. Previously, the newline had to immediately follow a -backslash. The current implementation allows whitespace in the form of -spaces, horizontal and vertical tabs, and form feeds between the -backslash and the subsequent newline. The preprocessor issues a -warning, but treats it as a valid escaped newline and combines the two -lines to form a single logical line. This works within comments and -tokens, as well as between tokens. Comments are @emph{not} treated as -whitespace for the purposes of this relaxation, since they have not yet -been replaced with spaces. - -@item -All comments are replaced with single spaces. - -@item -Predefined macro names are replaced with their expansions -(@pxref{Predefined}). -@end enumerate - -For end-of-line indicators, any of \n, \r\n, \n\r and \r are recognised, -and treated as ending a single line. As a result, if you mix these in a -single file you might get incorrect line numbering, because the -preprocessor would interpret the two-character versions as ending just -one line. Previous implementations would only handle UNIX-style \n -correctly, so DOS-style \r\n would need to be passed through a filter -first. - -The first three transformations are done @emph{before} all other parsing -and before preprocessing directives are recognized. Thus, for example, -you can split a line mechanically with backslash-newline anywhere -(except within trigraphs since they are replaced first; see below). - -@example -/* -*/ # /* -*/ defi\ -ne FO\ -O 10\ -20 -@end example - -@noindent -is equivalent into @samp{#define FOO 1020}. - -There is no way to prevent a backslash at the end of a line from being -interpreted as a backslash-newline. For example, - -@example -"foo\\ -bar" -@end example - -is equivalent to @code{"foo\bar"}, not to @code{"foo\\bar"}. To avoid -having to worry about this, do not use the deprecated GNU extension -which permits multi-line strings. Instead, use string literal -concatenation: - -@example - "foo\\" - "bar" -@end example - -Your program will be more portable this way, too. - -There are a few things to note about the above four transformations. - -@itemize @bullet -@item -Comments and predefined macro names (or any macro names, for that -matter) are not recognized inside the argument of an @samp{#include} -directive, when it is delimited with quotes or with @samp{<} and -@samp{>}. - -@item -Comments and predefined macro names are never recognized within a -character or string constant. - -@item -ISO ``trigraphs'' are converted before backslash-newlines are deleted. -If you write what looks like a trigraph with a backslash-newline inside, -the backslash-newline is deleted as usual, but it is too late to -recognize the trigraph. - -This is relevant only if you use the @samp{-trigraphs} option to enable -trigraph processing. @xref{Invocation}. -@end itemize - -The preprocessor handles null characters embedded in the input file -depending upon the context in which the null appears. Note that here we -are referring not to the two-character escape sequence "\0", but to the -single character ASCII NUL. - -There are three different contexts in which a null character may -appear: - -@itemize @bullet -@item -Within comments. Here, null characters are silently ignored. - -@item -Within a string or character constant. Here the preprocessor emits a -warning, but preserves the null character and passes it through to the -output file or compiler front-end. - -@item -In any other context, the preprocessor issues a warning, and discards -the null character. The preprocessor treats it like whitespace, -combining it with any surrounding whitespace to become a single -whitespace block. Representing the null character by "^@@", this means -that code like - -@example -#define X^@@1 -@end example - -is equivalent to - -@example -#define X 1 -@end example - -and X is defined with replacement text "1". -@end itemize - -@node Directives, Header Files, Global Actions, Top -@section Preprocessing Directives - -@cindex preprocessing directives -@cindex directives -Most preprocessor features are active only if you use preprocessing -directives to request their use. - -Preprocessing directives are lines in your program that start with -@samp{#}. Whitespace is allowed before and after the @samp{#}. The -@samp{#} is followed by an identifier that is the @dfn{directive name}. -For example, @samp{#define} is the directive that defines a macro. - -Since the @samp{#} must be the first token on the line, it cannot come -from a macro expansion if you wish it to begin a directive. Also, the -directive name is not macro expanded. Thus, if @samp{foo} is defined as -a macro expanding to @samp{define}, that does not make @samp{#foo} a -valid preprocessing directive. - -The set of valid directive names is fixed. Programs cannot define new -preprocessing directives. - -Some directive names require arguments; these make up the rest of the -directive line and must be separated from the directive name by -whitespace. For example, @samp{#define} must be followed by a macro -name and the intended expansion of the macro. @xref{Object-like -Macros}. - -A preprocessing directive cannot cover more than one line. It may be -logically extended with backslash-newline, but that has no effect on its -meaning. Comments containing newlines can also divide the directive -into multiple lines, but a comment is replaced by a single space before -the directive is interpreted. - -@node Header Files, Macros, Directives, Top -@section Header Files - -@cindex header file -A header file is a file containing C declarations and macro definitions -(@pxref{Macros}) to be shared between several source files. You request -the use of a header file in your program with the C preprocessing -directive @samp{#include}. - -@menu -* Header Uses:: What header files are used for. -* Include Syntax:: How to write @samp{#include} directives. -* Include Operation:: What @samp{#include} does. -* Once-Only:: Preventing multiple inclusion of one header file. -* Inheritance:: Including one header file in another header file. -* System Headers:: Special treatment for some header files. -@end menu - -@node Header Uses, Include Syntax, Header Files, Header Files -@subsection Uses of Header Files - -Header files serve two kinds of purposes. - -@itemize @bullet -@item -@cindex system header files -System header files declare the interfaces to parts of the operating -system. You include them in your program to supply the definitions and -declarations you need to invoke system calls and libraries. - -@item -Your own header files contain declarations for interfaces between the -source files of your program. Each time you have a group of related -declarations and macro definitions all or most of which are needed in -several different source files, it is a good idea to create a header -file for them. -@end itemize - -Including a header file produces the same results in C compilation as -copying the header file into each source file that needs it. Such -copying would be time-consuming and error-prone. With a header file, -the related declarations appear in only one place. If they need to be -changed, they can be changed in one place, and programs that include the -header file will automatically use the new version when next recompiled. -The header file eliminates the labor of finding and changing all the -copies as well as the risk that a failure to find one copy will result -in inconsistencies within a program. - -The usual convention is to give header files names that end with -@file{.h}. Avoid unusual characters in header file names, as they -reduce portability. - -@node Include Syntax, Include Operation, Header Uses, Header Files -@subsection The @samp{#include} Directive - -@findex #include -Both user and system header files are included using the preprocessing -directive @samp{#include}. It has three variants: - -@table @code -@item #include <@var{file}> -This variant is used for system header files. It searches for a file -named @var{file} in a list of directories specified by you, then in a -standard list of system directories. You specify directories to search -for header files with the command option @samp{-I} (@pxref{Invocation}). -The option @samp{-nostdinc} inhibits searching the standard system -directories; in this case only the directories you specify are searched. - -The first @samp{>} character terminates the file name. The file name -may contain a @samp{<} character. - -@item #include "@var{file}" -This variant is used for header files of your own program. It searches -for a file named @var{file} first in the current directory, then in the -same directories used for system header files. The current directory is -the directory of the current input file. It is tried first because it -is presumed to be the location of the files that the current input file -refers to. (If the @samp{-I-} option is used, the special treatment of -the current directory is inhibited. @xref{Invocation}.) - -The first @samp{"} character terminates the file name. - -In both these variants, the argument behaves like a string constant in -that comments are not recognized, and macro names are not expanded. -Thus, in @samp{#include } the @samp{/*} does not start a comment -and the directive specifies inclusion of a system header file named -@file{x/*y}. - -However, in either variant, if backslashes occur within @var{file}, they -are considered ordinary text characters, not escape characters. None of -the character escape sequences appropriate to string constants in C are -processed. Thus, @samp{#include "x\n\\y"} specifies a filename -containing three backslashes. - -@item #include @var{anything else} -@cindex computed @samp{#include} -This variant is called a @dfn{computed #include}. Any @samp{#include} -directive whose argument does not fit the above two forms is a computed -include. The text @var{anything else} is checked for macro calls, which -are expanded (@pxref{Macros}). When this is done, the result must match -one of the above two variants --- in particular, the expansion must form -a string literal token, or a sequence of tokens surrounded by angle -braces. @xref{Implementation}. - -This feature allows you to define a macro which controls the file name -to be used at a later point in the program. One application of this is -to allow a site-specific configuration file for your program to specify -the names of the system include files to be used. This can help in -porting the program to various operating systems in which the necessary -system header files are found in different places. -@end table - -@node Include Operation, Once-Only, Include Syntax, Header Files -@subsection How @samp{#include} Works - -The @samp{#include} directive works by directing the C preprocessor to -scan the specified file as input before continuing with the rest of the -current file. The output from the preprocessor contains the output -already generated, followed by the output resulting from the included -file, followed by the output that comes from the text after the -@samp{#include} directive. For example, given a header file -@file{header.h} as follows, - -@example -char *test (); -@end example - -@noindent -and a main program called @file{program.c} that uses the header file, -like this, - -@example -int x; -#include "header.h" - -main () -@{ - printf (test ()); -@} -@end example - -@noindent -the output generated by the C preprocessor for @file{program.c} as input -would be - -@example -int x; -char *test (); - -main () -@{ - printf (test ()); -@} -@end example - -Included files are not limited to declarations and macro definitions; -those are merely the typical uses. Any fragment of a C program can be -included from another file. The include file could even contain the -beginning of a statement that is concluded in the containing file, or -the end of a statement that was started in the including file. However, -a comment or a string or character constant may not start in the -included file and finish in the including file. An unterminated -comment, string constant or character constant in an included file is -considered to end (with an error message) at the end of the file. - -It is possible for a header file to begin or end a syntactic unit such -as a function definition, but that would be very confusing, so don't do -it. - -The line following the @samp{#include} directive is always treated as a -separate line by the C preprocessor, even if the included file lacks a -final newline. - -@node Once-Only, Inheritance, Include Operation, Header Files -@subsection Once-Only Include Files -@cindex repeated inclusion -@cindex including just once - -Very often, one header file includes another. It can easily result that -a certain header file is included more than once. This may lead to -errors, if the header file defines structure types or typedefs, and is -certainly wasteful. Therefore, we often wish to prevent multiple -inclusion of a header file. - -The standard way to do this is to enclose the entire real contents of the -file in a conditional, like this: - -@example -#ifndef FILE_FOO_SEEN -#define FILE_FOO_SEEN - -@var{the entire file} - -#endif /* FILE_FOO_SEEN */ -@end example - -The macro @code{FILE_FOO_SEEN} indicates that the file has been included -once already. In a user header file, the macro name should not begin -with @samp{_}. In a system header file, this name should begin with -@samp{__} to avoid conflicts with user programs. In any kind of header -file, the macro name should contain the name of the file and some -additional text, to avoid conflicts with other header files. - -The GNU C preprocessor is programmed to notice when a header file uses -this particular construct and handle it efficiently. If a header file -is contained entirely in a @samp{#ifndef} conditional, modulo whitespace -and comments, then it remembers that fact. If a subsequent -@samp{#include} specifies the same file, and the macro in the -@samp{#ifndef} is already defined, then the directive is skipped without -processing the specified file at all. - -@findex #import -In the Objective C language, there is a variant of @samp{#include} -called @samp{#import} which includes a file, but does so at most once. -If you use @samp{#import} @emph{instead of} @samp{#include}, then you -don't need the conditionals inside the header file to prevent multiple -execution of the contents. - -@samp{#import} is obsolete because it is not a well designed feature. -It requires the users of a header file --- the applications programmers ---- to know that a certain header file should only be included once. It -is much better for the header file's implementor to write the file so -that users don't need to know this. Using @samp{#ifndef} accomplishes -this goal. - -@node Inheritance, System Headers, Once-Only, Header Files -@subsection Inheritance and Header Files -@cindex inheritance -@cindex overriding a header file - -@dfn{Inheritance} is what happens when one object or file derives some -of its contents by virtual copying from another object or file. In -the case of C header files, inheritance means that one header file -includes another header file and then replaces or adds something. - -If the inheriting header file and the base header file have different -names, then inheritance is straightforward: simply write @samp{#include -"@var{base}"} in the inheriting file. - -Sometimes it is necessary to give the inheriting file the same name as -the base file. This is less straightforward. - -For example, suppose an application program uses the system header -@file{sys/signal.h}, but the version of @file{/usr/include/sys/signal.h} -on a particular system doesn't do what the application program expects. -It might be convenient to define a ``local'' version, perhaps under the -name @file{/usr/local/include/sys/signal.h}, to override or add to the -one supplied by the system. - -You can do this by compiling with the option @samp{-I.}, and writing a -file @file{sys/signal.h} that does what the application program expects. -Making this file include the standard @file{sys/signal.h} is not so easy ---- writing @samp{#include } in that file doesn't work, -because it includes your own version of the file, not the standard -system version. Used in that file itself, this leads to an infinite -recursion and a fatal error in compilation. - -@samp{#include } would find the proper file, -but that is not clean, since it makes an assumption about where the -system header file is found. This is bad for maintenance, since it -means that any change in where the system's header files are kept -requires a change somewhere else. - -@findex #include_next -The clean way to solve this problem is to use -@samp{#include_next}, which means, ``Include the @emph{next} file with -this name.'' This directive works like @samp{#include} except in -searching for the specified file: it starts searching the list of header -file directories @emph{after} the directory in which the current file -was found. - -Suppose you specify @samp{-I /usr/local/include}, and the list of -directories to search also includes @file{/usr/include}; and suppose -both directories contain @file{sys/signal.h}. Ordinary @samp{#include -} finds the file under @file{/usr/local/include}. If that -file contains @samp{#include_next }, it starts searching -after that directory, and finds the file in @file{/usr/include}. - -@samp{#include_next} is a GCC extension and should not be used in -programs intended to be portable to other compilers. - -@node System Headers,, Inheritance, Header Files -@subsection System Headers -@cindex system header files - -The header files declaring interfaces to the operating system and -runtime libraries often cannot be written in strictly conforming C. -Therefore, GNU C gives code found in @dfn{system headers} special -treatment. Certain categories of warnings are suppressed, notably those -enabled by @samp{-pedantic}. - -Normally, only the headers found in specific directories are considered -system headers. The set of these directories is determined when GCC is -compiled. There are, however, two ways to add to the set. - -@findex -isystem -The @samp{-isystem} command line option adds its argument to the list of -directories to search for headers, just like @samp{-I}. In addition, -any headers found in that directory will be considered system headers. -Note that unlike @samp{-I}, you must put a space between @samp{-isystem} -and its argument. - -All directories named by @samp{-isystem} are searched @strong{after} all -directories named by @samp{-I}, no matter what their order was on the -command line. If the same directory is named by both @samp{-I} and -@samp{-isystem}, @samp{-I} wins; it is as if the @samp{-isystem} option -had never been specified at all. - -@findex #pragma GCC system_header -There is also a directive, @samp{#pragma GCC system_header}, which tells -GCC to consider the rest of the current include file a system header, no -matter where it was found. Code that comes before the @samp{#pragma} in -the file will not be affected. - -@samp{#pragma GCC system_header} has no effect in the primary source file. - -@node Macros, Conditionals, Header Files, Top -@section Macros - -A macro is a sort of abbreviation which you can define once and then -use later. There are many complicated features associated with macros -in the C preprocessor. - -@menu -* Object-like Macros:: Macros that always expand the same way. -* Function-like Macros:: Macros that accept arguments that are substituted - into the macro expansion. -* Macro Varargs:: Macros with variable number of arguments. -* Predefined:: Predefined macros that are always available. -* Stringification:: Macro arguments converted into string constants. -* Concatenation:: Building tokens from parts taken from macro arguments. -* Undefining:: Cancelling a macro's definition. -* Redefining:: Changing a macro's definition. -* Poisoning:: Ensuring a macro is never defined or used. -* Macro Pitfalls:: Macros can confuse the unwary. Here we explain - several common problems and strange features. -@end menu - -@node Object-like Macros, Function-like Macros, Macros, Macros -@subsection Object-like Macros -@cindex object-like macro -@cindex manifest constant - -An @dfn{object-like macro} is a kind of abbreviation. It is a name -which stands for a fragment of code. Some people refer to these as -@dfn{manifest constants}. - -Before you can use a macro, you must @dfn{define} it explicitly with the -@samp{#define} directive. @samp{#define} is followed by the name of the -macro and then the token sequence it should be an abbreviation for, -which is variously referred to as the macro's @dfn{body}, -@dfn{expansion} or @dfn{replacement list}. For example, - -@example -#define BUFFER_SIZE 1020 -@end example - -@noindent -defines a macro named @samp{BUFFER_SIZE} as an abbreviation for the -token @samp{1020}. If somewhere after this @samp{#define} directive -there comes a C statement of the form - -@example -foo = (char *) xmalloc (BUFFER_SIZE); -@end example - -@noindent -then the C preprocessor will recognize and @dfn{expand} the macro -@samp{BUFFER_SIZE}, resulting in - -@example -foo = (char *) xmalloc (1020); -@end example - -The use of all upper case for macro names is a standard convention. -Programs are easier to read when it is possible to tell at a glance -which names are macros. - -Normally, a macro definition can only span a single logical line, like -all C preprocessing directives. Comments within a macro definition may -contain newlines, which make no difference since each comment is -replaced by a space regardless of its contents. - -Apart from this, there is no restriction on what can go in a macro body -provided it decomposes into valid preprocessing tokens. In particular, -parentheses need not balance, and the body need not resemble valid C -code. (If it does not, you may get error messages from the C -compiler when you use the macro.) - -The C preprocessor scans your program sequentially, so macro definitions -take effect at the place you write them. Therefore, the following input -to the C preprocessor - -@example -foo = X; -#define X 4 -bar = X; -@end example - -@noindent -produces as output - -@example -foo = X; - -bar = 4; -@end example - -When the preprocessor expands a macro name, the macro's expansion -replaces the macro invocation, and the result is re-scanned for more -macros to expand. For example, after - -@example -#define BUFSIZE 1020 -#define TABLESIZE BUFSIZE -@end example - -@noindent -the name @samp{TABLESIZE} when used in the program would go through two -stages of expansion, resulting ultimately in @samp{1020}. - -This is not the same as defining @samp{TABLESIZE} to be @samp{1020}. -The @samp{#define} for @samp{TABLESIZE} uses exactly the expansion you -specify --- in this case, @samp{BUFSIZE} --- and does not check to see -whether it too contains macro names. Only when you @emph{use} -@samp{TABLESIZE} is the result of its expansion scanned for more macro -names. @xref{Cascaded Macros}. - -@node Function-like Macros, Macro Varargs, Object-like Macros, Macros -@subsection Macros with Arguments -@cindex macros with argument -@cindex arguments in macro definitions -@cindex function-like macro - -An object-like macro is always replaced by exactly the same tokens each -time it is used. Macros can be made more flexible by taking -@dfn{arguments}. Arguments are fragments of code that you supply each -time the macro is used. These fragments are included in the expansion -of the macro according to the directions in the macro definition. A -macro that accepts arguments is called a @dfn{function-like macro} -because the syntax for using it looks like a function call. - -@findex #define -To define a macro that uses arguments, you write a @samp{#define} -directive with a list of @dfn{parameters} in parentheses after the name -of the macro. The parameters must be valid C identifiers, separated by -commas and optionally whitespace. The @samp{(} must follow the macro -name immediately, with no space in between. If you leave a space, you -instead define an object-like macro whose expansion begins with a -@samp{(}, and often leads to confusing errors at compile time. - -As an example, here is a macro that computes the minimum of two numeric -values, as it is defined in many C programs: - -@example -#define min(X, Y) ((X) < (Y) ? (X) : (Y)) -@end example - -@noindent -(This is not the best way to define a ``minimum'' macro in GNU C@. -@xref{Side Effects}, for more information.) - -To invoke a function-like macro, you write the name of the macro -followed by a list of @dfn{arguments} in parentheses, separated by -commas. The invocation of the macro need not be restricted to a single -logical line - it can cross as many lines in the source file as you -wish. The number of arguments you give must match the number of -parameters in the macro definition; empty arguments are fine. Examples -of use of the macro @samp{min} include @samp{min (1, 2)} and @samp{min -(x + 28, *p)}. - -The expansion text of the macro depends on the arguments you use. Each -macro parameter is replaced throughout the macro expansion with the -tokens of the corresponding argument. Leading and trailing argument -whitespace is dropped, and all whitespace between the tokens of an -argument is reduced to a single space. Using the same macro @samp{min} -defined above, @samp{min (1, 2)} expands into - -@example -((1) < (2) ? (1) : (2)) -@end example - -@noindent -where @samp{1} has been substituted for @samp{X} and @samp{2} for @samp{Y}. - -Likewise, @samp{min (x + 28, *p)} expands into - -@example -((x + 28) < (*p) ? (x + 28) : (*p)) -@end example - -Parentheses within each argument must balance; a comma within such -parentheses does not end the argument. However, there is no requirement -for square brackets or braces to balance, and they do not prevent a -comma from separating arguments. Thus, - -@example -macro (array[x = y, x + 1]) -@end example - -@noindent -passes two arguments to @code{macro}: @samp{array[x = y} and @samp{x + -1]}. If you want to supply @samp{array[x = y, x + 1]} as an argument, -you must write it as @samp{array[(x = y, x + 1)]}, which is equivalent C -code. - -After the arguments have been substituted into the macro body, the -resulting expansion replaces the macro invocation, and re-scanned for -more macro calls. Therefore even arguments can contain calls to other -macros, either with or without arguments, and even to the same macro. -For example, @samp{min (min (a, b), c)} expands into this text: - -@example -((((a) < (b) ? (a) : (b))) < (c) - ? (((a) < (b) ? (a) : (b))) - : (c)) -@end example - -@noindent -(Line breaks shown here for clarity would not actually be generated.) - -@cindex empty macro arguments -If a macro @code{foo} takes one argument, and you want to supply an -empty argument, simply supply no preprocessing tokens. Since whitespace -does not form a preprocessing token, it is optional. For example, -@samp{foo ()}, @samp{foo ( )} and @samp{bar (, arg2)}. - -Previous GNU preprocessor implementations and documentation were -incorrect on this point, insisting that a function-like macro that takes -a single argument be passed a space if an empty argument was required. - -If you use a macro name followed by something other than a @samp{(} -(after ignoring any whitespace that might follow), it does not form an -invocation of the macro, and the preprocessor does not change what you -have written. Therefore, it is possible for the same identifier to be a -variable or function in your program as well as a macro, and you can -choose in each instance whether to refer to the macro (if an actual -argument list follows) or the variable or function (if an argument list -does not follow). For example, - -@example -#define foo(X) X -foo bar foo(baz) -@end example - -expands to @samp{foo bar baz}. Such dual use of one name could be -confusing and should be avoided except when the two meanings are -effectively synonymous: that is, when the name is both a macro and a -function and the two have similar effects. You can think of the name -simply as a function; use of the name for purposes other than calling it -(such as, to take the address) will refer to the function, while calls -will expand the macro and generate better but equivalent code. - -For example, you can use a function named @samp{min} in the same source -file that defines the macro. If you write @samp{&min} with no argument -list, you refer to the function. If you write @samp{min (x, bb)}, with -an argument list, the macro is expanded. If you write @samp{(min) (a, -bb)}, where the name @samp{min} is not followed by an open-parenthesis, -the macro is not expanded, so you wind up with a call to the function -@samp{min}. - -In the definition of a macro with arguments, the list of argument names -must follow the macro name immediately with no space in between. If -there is a space after the macro name, the macro is defined as taking no -arguments, and all the rest of the line is taken to be the expansion. -The reason for this is that it is often useful to define a macro that -takes no arguments and whose definition begins with an identifier in -parentheses. This rule makes it possible for you to do either this: - -@example -#define FOO(x) - 1 / (x) -@end example - -@noindent -(which defines @samp{FOO} to take an argument and expand into minus the -reciprocal of that argument) or this: - -@example -#define BAR (x) - 1 / (x) -@end example - -@noindent -(which defines @samp{BAR} to take no argument and always expand into -@samp{(x) - 1 / (x)}). - -Note that the @emph{uses} of a macro with arguments can have spaces -before the left parenthesis; it's the @emph{definition} where it matters -whether there is a space. - -@node Macro Varargs, Predefined, Function-like Macros, Macros -@subsection Macros with Variable Numbers of Arguments -@cindex variable number of arguments -@cindex macro with variable arguments -@cindex rest argument (in macro) - -In the ISO C standard of 1999, a macro can be declared to accept a -variable number of arguments much as a function can. The syntax for -defining the macro is similar to that of a function. Here is an -example: - -@example -#define eprintf(...) fprintf (stderr, __VA_ARGS__) -@end example - -Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of -such a macro, it represents the zero or more tokens until the closing -parenthesis that ends the invocation, including any commas. This set of -tokens replaces the identifier @code{__VA_ARGS__} in the macro body -wherever it appears. Thus, we have this expansion: - -@example -eprintf ("%s:%d: ", input_file_name, line_number) -@expansion{} -fprintf (stderr, "%s:%d: " , input_file_name, line_number) -@end example - -Within a @samp{#define} directive, ISO C mandates that the only place -the identifier @code{__VA_ARGS__} can appear is in the replacement list -of a variable-argument macro. It may not be used as a macro name, macro -argument name, or within a different type of macro. It may also be -forbidden in open text; the standard is ambiguous. We recommend you -avoid using it except for its defined purpose. - -If your macro is complicated, you may want a more descriptive name for -the variable argument than @code{__VA_ARGS__}. GNU cpp permits this, as -an extension. You may write an argument name immediately before the -@samp{@dots{}}; that name is used for the variable argument. The -@code{eprintf} macro above could be written - -@example -#define eprintf(args...) fprintf (stderr, args) -@end example - -@noindent -using this extension. You cannot use @code{__VA_ARGS__} and this -extension in the same macro. - -We might instead have defined eprintf as follows: - -@example -#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__) -@end example - -This formulation looks more descriptive, but cannot be used as flexibly. -There is no way to produce expanded output of - -@example -fprintf (stderr, "success!\n") -@end example - -@noindent -because, in standard C, you are not allowed to leave the variable -argument out entirely, and passing an empty argument for the variable -arguments will not do what you want. Writing - -@example -eprintf ("success!\n", ) -@end example - -@noindent -produces - -@example -fprintf (stderr, "success!\n",) -@end example - -@noindent -where the extra comma originates from the replacement list and not from -the arguments to eprintf. - -There is another extension in the GNU C preprocessor which deals with -this difficulty. First, you are allowed to leave the variable argument -out entirely: - -@example -eprintf ("success!\n") -@end example - -Second, the @samp{##} token paste operator has a special meaning when -placed between a comma and a variable argument. If you write - -@example -#define eprintf(format, ...) fprintf (stderr, format, ##__VA_ARGS__) -@end example - -and the variable argument is left out when the @samp{eprintf} macro is -used, then the comma before the @samp{##} will be deleted. This does -@emph{not} happen if you pass an empty argument, nor does it happen if -the token preceding @samp{##} is anything other than a comma. - -Previous versions of the preprocessor implemented this extension much -more generally. We have restricted it in order to minimize the -difference from the C standard. @xref{Unreliable Features}. - -@node Predefined, Stringification, Macro Varargs, Macros -@subsection Predefined Macros - -@cindex predefined macros -Several object-like macros are predefined; you use them without -supplying their definitions. They fall into two classes: standard -macros and system-specific macros. - -@menu -* Standard Predefined:: Standard predefined macros. -* Nonstandard Predefined:: Nonstandard predefined macros. -@end menu - -@node Standard Predefined, Nonstandard Predefined, Predefined, Predefined -@subsubsection Standard Predefined Macros -@cindex standard predefined macros - -The standard predefined macros are available with the same meanings -regardless of the machine or operating system on which you are using GNU -C@. Their names all start and end with double underscores. Those -preceding @code{__GNUC__} in this table are standardized by ISO C; the -rest are GNU C extensions. - -@table @code -@item __FILE__ -@findex __FILE__ -This macro expands to the name of the current input file, in the form of -a C string constant. The precise name returned is the one that was -specified in @samp{#include} or as the input file name argument. For -example, @samp{"/usr/local/include/myheader.h"} is a possible expansion -of this macro. - -@item __LINE__ -@findex __LINE__ -This macro expands to the current input line number, in the form of a -decimal integer constant. While we call it a predefined macro, it's -a pretty strange macro, since its ``definition'' changes with each -new line of source code. - -This and @samp{__FILE__} are useful in generating an error message to -report an inconsistency detected by the program; the message can state -the source line at which the inconsistency was detected. For example, - -@smallexample -fprintf (stderr, "Internal error: " - "negative string length " - "%d at %s, line %d.", - length, __FILE__, __LINE__); -@end smallexample - -A @samp{#include} directive changes the expansions of @samp{__FILE__} -and @samp{__LINE__} to correspond to the included file. At the end of -that file, when processing resumes on the input file that contained -the @samp{#include} directive, the expansions of @samp{__FILE__} and -@samp{__LINE__} revert to the values they had before the -@samp{#include} (but @samp{__LINE__} is then incremented by one as -processing moves to the line after the @samp{#include}). - -The expansions of both @samp{__FILE__} and @samp{__LINE__} are altered -if a @samp{#line} directive is used. @xref{Line Control}. - -@item __DATE__ -@findex __DATE__ -This macro expands to a string constant that describes the date on -which the preprocessor is being run. The string constant contains -eleven characters and looks like @w{@samp{"Feb 1 1996"}}. -@c After reformatting the above, check that the date remains `Feb 1 1996', -@c all on one line, with two spaces between the `Feb' and the `1'. - -@item __TIME__ -@findex __TIME__ -This macro expands to a string constant that describes the time at -which the preprocessor is being run. The string constant contains -eight characters and looks like @samp{"23:59:01"}. - -@item __STDC__ -@findex __STDC__ -This macro expands to the constant 1, to signify that this is ISO -Standard C@. (Whether that is actually true depends on what C compiler -will operate on the output from the preprocessor.) - -On some hosts, system include files use a different convention, where -@samp{__STDC__} is normally 0, but is 1 if the user specifies strict -conformance to the C Standard. The preprocessor follows the host -convention when processing system include files, but when processing -user files it follows the usual GNU C convention. - -This macro is not defined if the @samp{-traditional} option is used. - -@item __STDC_VERSION__ -@findex __STDC_VERSION__ -This macro expands to the C Standard's version number, a long integer -constant of the form @samp{@var{yyyy}@var{mm}L} where @var{yyyy} and -@var{mm} are the year and month of the Standard version. This signifies -which version of the C Standard the preprocessor conforms to. Like -@samp{__STDC__}, whether this version number is accurate for the entire -implementation depends on what C compiler will operate on the output -from the preprocessor. - -This macro is not defined if the @samp{-traditional} option is used. - -@item __GNUC__ -@findex __GNUC__ -This macro is defined if and only if this is GNU C@. This macro is -defined only when the entire GNU C compiler is in use; if you invoke the -preprocessor directly, @samp{__GNUC__} is undefined. The value -identifies the major version number of GNU CC (@samp{1} for GNU CC -version 1, which is now obsolete, and @samp{2} for version 2). - -@item __GNUC_MINOR__ -@findex __GNUC_MINOR__ -The macro contains the minor version number of the compiler. This can -be used to work around differences between different releases of the -compiler (for example, if GCC 2.6.x is known to support a feature, you -can test for @code{__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 6)}). - -@item __GNUC_PATCHLEVEL__ -@findex __GNUC_PATCHLEVEL__ -This macro contains the patch level of the compiler. This can be -used to work around differences between different patch level releases -of the compiler (for example, if GCC 2.6.2 is known to contain a bug, -whereas GCC 2.6.3 contains a fix, and you have code which can workaround -the problem depending on whether the bug is fixed or not, you can test for -@code{__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ > 6) || -(__GNUC__ == 2 && __GNUC_MINOR__ == 6 && __GNUC_PATCHLEVEL__ >= 3)}). - -@item __GNUG__ -@findex __GNUG__ -The GNU C compiler defines this when the compilation language is -C++; use @samp{__GNUG__} to distinguish between GNU C and GNU -C++. - -@item __cplusplus -@findex __cplusplus -The ISO standard for C++ requires predefining this variable. You can -use @samp{__cplusplus} to test whether a header is compiled by a C -compiler or a C++ compiler. The compiler currently uses a value of -@samp{1}, instead of the value @samp{199711L}, which would indicate full -conformance with the standard. - -@item __STRICT_ANSI__ -@findex __STRICT_ANSI__ -GNU C defines this macro if and only if the @option{-ansi} switch, or a -@option{-std} switch specifying strict conformance to some version of ISO C, -was specified when GNU C was invoked. Its definition is the null string. -This macro exists primarily to direct certain GNU header files not to -define certain traditional Unix constructs which are incompatible with -ISO C@. - -@item __BASE_FILE__ -@findex __BASE_FILE__ -This macro expands to the name of the main input file, in the form -of a C string constant. This is the source file that was specified -on the command line of the preprocessor or C compiler. - -@item __INCLUDE_LEVEL__ -@findex __INCLUDE_LEVEL_ -This macro expands to a decimal integer constant that represents the -depth of nesting in include files. The value of this macro is -incremented on every @samp{#include} directive and decremented at the -end of every included file. It starts out at 0, it's value within the -base file specified on the command line. - -@item __VERSION__ -@findex __VERSION__ -This macro expands to a string constant which describes the version -number of GNU C@. The string is normally a sequence of decimal numbers -separated by periods, such as @samp{"2.6.0"}. - -@item __OPTIMIZE__ -@findex __OPTIMIZE__ -GNU CC defines this macro in optimizing compilations. It causes certain -GNU header files to define alternative macro definitions for some system -library functions. You should not refer to or test the definition of -this macro unless you make very sure that programs will execute with the -same effect regardless. - -@item __OPTIMIZE_SIZE__ -@findex __OPTIMIZE_SIZE__ -GNU CC defines this macro when optimizing for size with @samp{-Os}. It -causes certain GNU header files to define alternative macro definitions -for some system library functions. You should not refer to or test the -definition of this macro unless you make very sure that programs will -execute with the same effect regardless. - -@item __NO_INLINE__ -@findex __NO_INLINE__ -GNU CC defines this macro if it will not attempt to inline functions -with @samp{inline} keyword (either when not optimizing or when inlining -has been explicitely forbidden through @samp{-fno-inline}). It causes -certain GNU header files to define alternative macro definitions for some -system library functions. You should not refer to or test the definition -of this macro unless you make very sure that programs will execute with -the same effect regardless. - -@item __CHAR_UNSIGNED__ -@findex __CHAR_UNSIGNED__ -GNU C defines this macro if and only if the data type @code{char} is -unsigned on the target machine. It exists to cause the standard header -file @file{limits.h} to work correctly. You should not refer to this -macro yourself; instead, refer to the standard macros defined in -@file{limits.h}. The preprocessor uses this macro to determine whether -or not to sign-extend large character constants written in octal; see -@ref{#if Directive,,The @samp{#if} Directive}. - -@item __REGISTER_PREFIX__ -@findex __REGISTER_PREFIX__ -This macro expands to a string (not a string constant) describing the -prefix applied to CPU registers in assembler code. You can use it to -write assembler code that is usable in multiple environments. For -example, in the @samp{m68k-aout} environment it expands to the null -string, but in the @samp{m68k-coff} environment it expands to the string -@samp{%}. - -@item __USER_LABEL_PREFIX__ -@findex __USER_LABEL_PREFIX__ -Similar to @code{__REGISTER_PREFIX__}, but describes the prefix applied -to user generated labels in assembler code. For example, in the -@samp{m68k-aout} environment it expands to the string @samp{_}, but in -the @samp{m68k-coff} environment it expands to the null string. This -does not work with the @samp{-mno-underscores} option that the i386 -OSF/rose and m88k targets provide nor with the @samp{-mcall*} options of -the rs6000 System V Release 4 target. -@end table - -@node Nonstandard Predefined,, Standard Predefined, Predefined -@subsubsection Nonstandard Predefined Macros - -The C preprocessor normally has several predefined macros that vary -between machines because their purpose is to indicate what type of -system and machine is in use. This manual, being for all systems and -machines, cannot tell you exactly what their names are; instead, we -offer a list of some typical ones. You can use @samp{cpp -dM} to see -the values of predefined macros; see @ref{Invocation}. - -Some nonstandard predefined macros describe the operating system in use, -with more or less specificity. For example, - -@table @code -@item unix -@findex unix -@samp{unix} is normally predefined on all Unix systems. - -@item BSD -@findex BSD -@samp{BSD} is predefined on recent versions of Berkeley Unix -(perhaps only in version 4.3). -@end table - -Other nonstandard predefined macros describe the kind of CPU, with more or -less specificity. For example, - -@table @code -@item vax -@findex vax -@samp{vax} is predefined on Vax computers. - -@item mc68000 -@findex mc68000 -@samp{mc68000} is predefined on most computers whose CPU is a Motorola -68000, 68010 or 68020. - -@item m68k -@findex m68k -@samp{m68k} is also predefined on most computers whose CPU is a 68000, -68010 or 68020; however, some makers use @samp{mc68000} and some use -@samp{m68k}. Some predefine both names. What happens in GNU C -depends on the system you are using it on. - -@item M68020 -@findex M68020 -@samp{M68020} has been observed to be predefined on some systems that -use 68020 CPUs --- in addition to @samp{mc68000} and @samp{m68k}, which -are less specific. - -@item _AM29K -@findex _AM29K -@itemx _AM29000 -@findex _AM29000 -Both @samp{_AM29K} and @samp{_AM29000} are predefined for the AMD 29000 -CPU family. - -@item ns32000 -@findex ns32000 -@samp{ns32000} is predefined on computers which use the National -Semiconductor 32000 series CPU. -@end table - -Yet other nonstandard predefined macros describe the manufacturer of -the system. For example, - -@table @code -@item sun -@findex sun -@samp{sun} is predefined on all models of Sun computers. - -@item pyr -@findex pyr -@samp{pyr} is predefined on all models of Pyramid computers. - -@item sequent -@findex sequent -@samp{sequent} is predefined on all models of Sequent computers. -@end table - -These predefined symbols are not only nonstandard, they are contrary to the -ISO standard because their names do not start with underscores. -Therefore, the option @samp{-ansi} inhibits the definition of these -symbols. - -This tends to make @samp{-ansi} useless, since many programs depend on -the customary nonstandard predefined symbols. Even system header files -check them and will generate incorrect declarations if they do not find -the names that are expected. You might think that the header files -supplied for the Uglix computer would not need to test what machine they -are running on, because they can simply assume it is the Uglix; but -often they do, and they do so using the customary names. As a result, -very few C programs will compile with @samp{-ansi}. We intend to avoid -such problems on the GNU system. - -What, then, should you do in an ISO C program to test the type of machine -it will run on? - -GNU C offers a parallel series of symbols for this purpose, whose names -are made from the customary ones by adding @samp{__} at the beginning -and end. Thus, the symbol @code{__vax__} would be available on a Vax, -and so on. - -The set of nonstandard predefined names in the GNU C preprocessor is -controlled (when @code{cpp} is itself compiled) by the macro -@samp{CPP_PREDEFINES}, which should be a string containing @samp{-D} -options, separated by spaces. For example, on the Sun 3, we use the -following definition: - -@example -#define CPP_PREDEFINES "-Dmc68000 -Dsun -Dunix -Dm68k" -@end example - -@noindent -This macro is usually specified in @file{tm.h}. - -@node Stringification, Concatenation, Predefined, Macros -@subsection Stringification - -@cindex stringification -@dfn{Stringification} means turning a sequence of preprocessing tokens -into a string literal. For example, stringifying @samp{foo (z)} results -in @samp{"foo (z)"}. - -In the C preprocessor, stringification is possible when macro arguments -are substituted during macro expansion. When a parameter appears -preceded by a @samp{#} token in the replacement list of a function-like -macro, it indicates that both tokens should be replaced with the -stringification of the corresponding argument during expansion. The -same argument may be substituted in other places in the definition -without stringification if the argument name appears in those places -with no preceding @samp{#}. - -Here is an example of a macro definition that uses stringification: - -@smallexample -@group -#define WARN_IF(EXP) \ -do @{ if (EXP) \ - fprintf (stderr, "Warning: " #EXP "\n"); @} \ -while (0) -@end group -@end smallexample - -@noindent -Here the argument for @samp{EXP} is substituted once, as-is, into the -@samp{if} statement, and once, stringified, into the argument to -@samp{fprintf}. The @samp{do} and @samp{while (0)} are a kludge to make -it possible to write @samp{WARN_IF (@var{arg});}, which the resemblance -of @samp{WARN_IF} to a function would make C programmers want to do; see -@ref{Swallow Semicolon}. - -The stringification feature is limited to transforming the tokens of a -macro argument into a string constant: there is no way to combine the -argument with surrounding text and stringify it all together. The -example above shows how an equivalent result can be obtained in ISO -Standard C, using the fact that adjacent string constants are -concatenated by the C compiler to form a single string constant. The -preprocessor stringifies the actual value of @samp{EXP} into a separate -string constant, resulting in text like - -@smallexample -@group -do @{ if (x == 0) \ - fprintf (stderr, "Warning: " "x == 0" "\n"); @} \ -while (0) -@end group -@end smallexample - -@noindent -but the compiler then sees three consecutive string constants and -concatenates them into one, producing effectively - -@smallexample -do @{ if (x == 0) \ - fprintf (stderr, "Warning: x == 0\n"); @} \ -while (0) -@end smallexample - -Stringification in C involves more than putting double-quote characters -around the fragment. The preprocessor backslash-escapes the surrounding -quotes of string literals, and all backslashes within string and -character constants, in order to get a valid C string constant with the -proper contents. Thus, stringifying @samp{p = "foo\n";} results in -@samp{"p = \"foo\\n\";"}. However, backslashes that are not inside -string or character constants are not duplicated: @samp{\n} by itself -stringifies to @samp{"\n"}. - -Whitespace (including comments) in the text being stringified is handled -according to precise rules. All leading and trailing whitespace is -ignored. Any sequence of whitespace in the middle of the text is -converted to a single space in the stringified result. - -@node Concatenation, Undefining, Stringification, Macros -@subsection Concatenation -@cindex concatenation -@cindex @samp{##} -@dfn{Concatenation} means joining two strings into one. In the context -of macro expansion, concatenation refers to joining two preprocessing -tokens to form one. In particular, a token of a macro argument can be -concatenated with another argument's token or with fixed text to produce -a longer name. The longer name might be the name of a function, -variable, type, or a C keyword; it might even be the name of another -macro, in which case it will be expanded. - -When you define a function-like or object-like macro, you request -concatenation with the special operator @samp{##} in the macro's -replacement list. When the macro is called, any arguments are -substituted without performing macro expansion, every @samp{##} operator -is deleted, and the two tokens on either side of it are concatenated to -form a single token. - -Consider a C program that interprets named commands. There probably needs -to be a table of commands, perhaps an array of structures declared as -follows: - -@example -struct command -@{ - char *name; - void (*function) (); -@}; - -struct command commands[] = -@{ - @{ "quit", quit_command@}, - @{ "help", help_command@}, - @dots{} -@}; -@end example - -It would be cleaner not to have to give each command name twice, once in -the string constant and once in the function name. A macro which takes the -name of a command as an argument can make this unnecessary. The string -constant can be created with stringification, and the function name by -concatenating the argument with @samp{_command}. Here is how it is done: - -@example -#define COMMAND(NAME) @{ #NAME, NAME ## _command @} - -struct command commands[] = -@{ - COMMAND (quit), - COMMAND (help), - @dots{} -@}; -@end example - -The usual case of concatenation is concatenating two names (or a name -and a number) into a longer name. This isn't the only valid case. -It is also possible to concatenate two numbers (or a number and a name, -such as @samp{1.5} and @samp{e3}) into a number. Also, multi-character -operators such as @samp{+=} can be formed by concatenation. However, -two tokens that don't together form a valid token cannot be -concatenated. For example, concatenation of @samp{x} on one side and -@samp{+} on the other is not meaningful because those two tokens do not -form a valid preprocessing token when concatenated. UNDEFINED - -Keep in mind that the C preprocessor converts comments to whitespace -before macros are even considered. Therefore, you cannot create a -comment by concatenating @samp{/} and @samp{*}: the @samp{/*} sequence -that starts a comment is not a token, but rather the beginning of a -comment. You can freely use comments next to @samp{##} in a macro -definition, or in arguments that will be concatenated, because the -comments will be converted to spaces at first sight, and concatenation -operates on tokens and so ignores whitespace. - -@node Undefining, Redefining, Concatenation, Macros -@subsection Undefining Macros - -@cindex undefining macros -To @dfn{undefine} a macro means to cancel its definition. This is done -with the @samp{#undef} directive. @samp{#undef} is followed by the macro -name to be undefined. - -Like definition, undefinition occurs at a specific point in the source -file, and it applies starting from that point. The name ceases to be a -macro name, and from that point on it is treated by the preprocessor as -if it had never been a macro name. - -For example, - -@example -#define FOO 4 -x = FOO; -#undef FOO -x = FOO; -@end example - -@noindent -expands into - -@example -x = 4; - -x = FOO; -@end example - -@noindent -In this example, @samp{FOO} had better be a variable or function as well -as (temporarily) a macro, in order for the result of the expansion to be -valid C code. - -The same form of @samp{#undef} directive will cancel definitions with -arguments or definitions that don't expect arguments. The @samp{#undef} -directive has no effect when used on a name not currently defined as a -macro. - -@node Redefining, Poisoning, Undefining, Macros -@subsection Redefining Macros - -@cindex redefining macros -@dfn{Redefining} a macro means defining (with @samp{#define}) a name that -is already defined as a macro. - -A redefinition is trivial if the new definition is transparently -identical to the old one. You probably wouldn't deliberately write a -trivial redefinition, but they can happen automatically when a header -file is included more than once (@pxref{Header Files}), so they are -accepted silently and without effect. - -Nontrivial redefinition is considered likely to be an error, so it -provokes a warning message from the preprocessor. However, sometimes it -is useful to change the definition of a macro in mid-compilation. You -can inhibit the warning by undefining the macro with @samp{#undef} -before the second definition. - -In order for a redefinition to be trivial, the parameter names must -match and be in the same order, and the new replacement list must -exactly match the one already in effect, with two possible exceptions: - -@itemize @bullet -@item -Whitespace may be added or deleted at the beginning or the end of the -replacement list. In a sense this is vacuous, since strictly such -whitespace doesn't form part of the macro's expansion. - -@item -Between tokens in the expansion, any two forms of whitespace are -considered equivalent. In particular, whitespace may not be eliminated -entirely, nor may it be added where there previously wasn't any. -@end itemize - -Recall that a comment counts as whitespace. - -As a particular case of the above, you may not redefine an object-like -macro as a function-like macro, and vice-versa. - -@node Poisoning, Macro Pitfalls, Redefining, Macros -@subsection Poisoning Macros -@cindex poisoning macros -@findex #pragma GCC poison - -Sometimes, there is an identifier that you want to remove completely -from your program, and make sure that it never creeps back in. To -enforce this, the @samp{#pragma GCC poison} directive can be used. -@samp{#pragma GCC poison} is followed by a list of identifiers to -poison, and takes effect for the rest of the source. You cannot -@samp{#undef} a poisoned identifier or test to see if it's defined with -@samp{#ifdef}. - -For example, - -@example -#pragma GCC poison printf sprintf fprintf -sprintf(some_string, "hello"); -@end example - -@noindent -will produce an error. - -Note, if the poisoned identifier appears through the result of macro -expansion it @emph{won't} cause an error. So if you poison an -identifier you need not worry about system headers defining macros that -use it. - -For example, - -@example -#define strrchr rindex -#pragma GCC poison rindex -strrchr(some_string, 'h'); -@end example - -@noindent -will not produce an error. - -@node Macro Pitfalls,, Poisoning, Macros -@subsection Pitfalls and Subtleties of Macros -@cindex problems with macros -@cindex pitfalls of macros - -In this section we describe some special rules that apply to macros and -macro expansion, and point out certain cases in which the rules have -counterintuitive consequences that you must watch out for. - -@menu -* Misnesting:: Macros can contain unmatched parentheses. -* Macro Parentheses:: Why apparently superfluous parentheses - may be necessary to avoid incorrect grouping. -* Swallow Semicolon:: Macros that look like functions - but expand into compound statements. -* Side Effects:: Unsafe macros that cause trouble when - arguments contain side effects. -* Self-Reference:: Macros whose definitions use the macros' own names. -* Argument Prescan:: Arguments are checked for macro calls before they - are substituted. -* Cascaded Macros:: Macros whose definitions use other macros. -* Newlines in Args:: Sometimes line numbers get confused. -@end menu - -@node Misnesting, Macro Parentheses, Macro Pitfalls, Macro Pitfalls -@subsubsection Improperly Nested Constructs - -Recall that when a macro is called with arguments, the arguments are -substituted into the macro body and the result is checked, together with -the rest of the input file, for more macro calls. - -It is possible to piece together a macro call coming partially from the -macro body and partially from the arguments. For example, - -@example -#define double(x) (2*(x)) -#define call_with_1(x) x(1) -@end example - -@noindent -would expand @samp{call_with_1 (double)} into @samp{(2*(1))}. - -Macro definitions do not have to have balanced parentheses. By writing -an unbalanced open parenthesis in a macro body, it is possible to create -a macro call that begins inside the macro body but ends outside of it. -For example, - -@example -#define strange(file) fprintf (file, "%s %d", -@dots{} -strange(stderr) p, 35) -@end example - -@noindent -This bizarre example expands to @samp{fprintf (stderr, "%s %d", p, 35)}! - -@node Macro Parentheses, Swallow Semicolon, Misnesting, Macro Pitfalls -@subsubsection Unintended Grouping of Arithmetic -@cindex parentheses in macro bodies - -You may have noticed that in most of the macro definition examples shown -above, each occurrence of a macro argument name had parentheses around -it. In addition, another pair of parentheses usually surround the -entire macro definition. Here is why it is best to write macros that -way. - -Suppose you define a macro as follows, - -@example -#define ceil_div(x, y) (x + y - 1) / y -@end example - -@noindent -whose purpose is to divide, rounding up. (One use for this operation is -to compute how many @samp{int} objects are needed to hold a certain -number of @samp{char} objects.) Then suppose it is used as follows: - -@example -a = ceil_div (b & c, sizeof (int)); -@end example - -@noindent -This expands into - -@example -a = (b & c + sizeof (int) - 1) / sizeof (int); -@end example - -@noindent -which does not do what is intended. The operator-precedence rules of -C make it equivalent to this: - -@example -a = (b & (c + sizeof (int) - 1)) / sizeof (int); -@end example - -@noindent -What we want is this: - -@example -a = ((b & c) + sizeof (int) - 1)) / sizeof (int); -@end example - -@noindent -Defining the macro as - -@example -#define ceil_div(x, y) ((x) + (y) - 1) / (y) -@end example - -@noindent -provides the desired result. - -Unintended grouping can result in another way. Consider @samp{sizeof -ceil_div(1, 2)}. That has the appearance of a C expression that would -compute the size of the type of @samp{ceil_div (1, 2)}, but in fact it -means something very different. Here is what it expands to: - -@example -sizeof ((1) + (2) - 1) / (2) -@end example - -@noindent -This would take the size of an integer and divide it by two. The -precedence rules have put the division outside the @samp{sizeof} when it -was intended to be inside. - -Parentheses around the entire macro definition can prevent such -problems. Here, then, is the recommended way to define @samp{ceil_div}: - -@example -#define ceil_div(x, y) (((x) + (y) - 1) / (y)) -@end example - -@node Swallow Semicolon, Side Effects, Macro Parentheses, Macro Pitfalls -@subsubsection Swallowing the Semicolon - -@cindex semicolons (after macro calls) -Often it is desirable to define a macro that expands into a compound -statement. Consider, for example, the following macro, that advances a -pointer (the argument @samp{p} says where to find it) across whitespace -characters: - -@example -#define SKIP_SPACES(p, limit) \ -@{ register char *lim = (limit); \ - while (p != lim) @{ \ - if (*p++ != ' ') @{ \ - p--; break; @}@}@} -@end example - -@noindent -Here backslash-newline is used to split the macro definition, which must -be a single logical line, so that it resembles the way such C code would -be laid out if not part of a macro definition. - -A call to this macro might be @samp{SKIP_SPACES (p, lim)}. Strictly -speaking, the call expands to a compound statement, which is a complete -statement with no need for a semicolon to end it. However, since it -looks like a function call, it minimizes confusion if you can use it -like a function call, writing a semicolon afterward, as in -@samp{SKIP_SPACES (p, lim);} - -This can cause trouble before @samp{else} statements, because the -semicolon is actually a null statement. Suppose you write - -@example -if (*p != 0) - SKIP_SPACES (p, lim); -else @dots{} -@end example - -@noindent -The presence of two statements --- the compound statement and a null -statement --- in between the @samp{if} condition and the @samp{else} -makes invalid C code. - -The definition of the macro @samp{SKIP_SPACES} can be altered to solve -this problem, using a @samp{do @dots{} while} statement. Here is how: - -@example -#define SKIP_SPACES(p, limit) \ -do @{ register char *lim = (limit); \ - while (p != lim) @{ \ - if (*p++ != ' ') @{ \ - p--; break; @}@}@} \ -while (0) -@end example - -Now @samp{SKIP_SPACES (p, lim);} expands into - -@example -do @{@dots{}@} while (0); -@end example - -@noindent -which is one statement. - -@node Side Effects, Self-Reference, Swallow Semicolon, Macro Pitfalls -@subsubsection Duplication of Side Effects - -@cindex side effects (in macro arguments) -@cindex unsafe macros -Many C programs define a macro @samp{min}, for ``minimum'', like this: - -@example -#define min(X, Y) ((X) < (Y) ? (X) : (Y)) -@end example - -When you use this macro with an argument containing a side effect, -as shown here, - -@example -next = min (x + y, foo (z)); -@end example - -@noindent -it expands as follows: - -@example -next = ((x + y) < (foo (z)) ? (x + y) : (foo (z))); -@end example - -@noindent -where @samp{x + y} has been substituted for @samp{X} and @samp{foo (z)} -for @samp{Y}. - -The function @samp{foo} is used only once in the statement as it appears -in the program, but the expression @samp{foo (z)} has been substituted -twice into the macro expansion. As a result, @samp{foo} might be called -two times when the statement is executed. If it has side effects or if -it takes a long time to compute, the results might not be what you -intended. We say that @samp{min} is an @dfn{unsafe} macro. - -The best solution to this problem is to define @samp{min} in a way that -computes the value of @samp{foo (z)} only once. The C language offers -no standard way to do this, but it can be done with GNU C extensions as -follows: - -@example -#define min(X, Y) \ -(@{ typeof (X) __x = (X), __y = (Y); \ - (__x < __y) ? __x : __y; @}) -@end example - -If you do not wish to use GNU C extensions, the only solution is to be -careful when @emph{using} the macro @samp{min}. For example, you can -calculate the value of @samp{foo (z)}, save it in a variable, and use -that variable in @samp{min}: - -@example -#define min(X, Y) ((X) < (Y) ? (X) : (Y)) -@dots{} -@{ - int tem = foo (z); - next = min (x + y, tem); -@} -@end example - -@noindent -(where we assume that @samp{foo} returns type @samp{int}). - -@node Self-Reference, Argument Prescan, Side Effects, Macro Pitfalls -@subsubsection Self-Referential Macros - -@cindex self-reference -A @dfn{self-referential} macro is one whose name appears in its -definition. A special feature of ISO Standard C is that the -self-reference is not considered a macro call. It is passed into the -preprocessor output unchanged. - -Let's consider an example: - -@example -#define foo (4 + foo) -@end example - -@noindent -where @samp{foo} is also a variable in your program. - -Following the ordinary rules, each reference to @samp{foo} will expand -into @samp{(4 + foo)}; then this will be rescanned and will expand into -@samp{(4 + (4 + foo))}; and so on until it causes a fatal error (memory -full) in the preprocessor. - -However, the special rule about self-reference cuts this process short -after one step, at @samp{(4 + foo)}. Therefore, this macro definition -has the possibly useful effect of causing the program to add 4 to the -value of @samp{foo} wherever @samp{foo} is referred to. - -In most cases, it is a bad idea to take advantage of this feature. A -person reading the program who sees that @samp{foo} is a variable will -not expect that it is a macro as well. The reader will come across the -identifier @samp{foo} in the program and think its value should be that -of the variable @samp{foo}, whereas in fact the value is four greater. - -The special rule for self-reference applies also to @dfn{indirect} -self-reference. This is the case where a macro @var{x} expands to use a -macro @samp{y}, and the expansion of @samp{y} refers to the macro -@samp{x}. The resulting reference to @samp{x} comes indirectly from the -expansion of @samp{x}, so it is a self-reference and is not further -expanded. Thus, after - -@example -#define x (4 + y) -#define y (2 * x) -@end example - -@noindent -@samp{x} would expand into @samp{(4 + (2 * x))}. Clear? - -Suppose @samp{y} is used elsewhere, not from the definition of @samp{x}. -Then the use of @samp{x} in the expansion of @samp{y} is not a -self-reference because @samp{x} is not ``in progress''. So it does -expand. However, the expansion of @samp{x} contains a reference to -@samp{y}, and that is an indirect self-reference now because @samp{y} is -``in progress''. The result is that @samp{y} expands to @samp{(2 * (4 + -y))}. - -This behavior is specified by the ISO C standard, so you may need to -understand it. - -@node Argument Prescan, Cascaded Macros, Self-Reference, Macro Pitfalls -@subsubsection Separate Expansion of Macro Arguments -@cindex expansion of arguments -@cindex macro argument expansion -@cindex prescan of macro arguments - -We have explained that the expansion of a macro, including the substituted -arguments, is re-scanned for macro calls to be expanded. - -What really happens is more subtle: first each argument is scanned -separately for macro calls. Then the resulting tokens are substituted -into the macro body to produce the macro expansion, and the macro -expansion is scanned again for macros to expand. - -The result is that the arguments are scanned @emph{twice} to expand -macro calls in them. - -Most of the time, this has no effect. If the argument contained any -macro calls, they are expanded during the first scan. The result -therefore contains no macro calls, so the second scan does not change -it. If the argument were substituted as given, with no prescan, the -single remaining scan would find the same macro calls and produce the -same results. - -You might expect the double scan to change the results when a -self-referential macro is used in an argument of another macro -(@pxref{Self-Reference}): the self-referential macro would be expanded -once in the first scan, and a second time in the second scan. However, -this is not what happens. The self-references that do not expand in the -first scan are marked so that they will not expand in the second scan -either. - -The prescan is not done when an argument is stringified or concatenated. -Thus, - -@example -#define str(s) #s -#define foo 4 -str (foo) -@end example - -@noindent -expands to @samp{"foo"}. Once more, prescan has been prevented from -having any noticeable effect. - -More precisely, stringification and concatenation use the argument -tokens as given without initially scanning for macros. The same -argument would be used in expanded form if it is substituted elsewhere -without stringification or concatenation. - -@example -#define str(s) #s lose(s) -#define foo 4 -str (foo) -@end example - -expands to @samp{"foo" lose(4)}. - -You might now ask, ``Why mention the prescan, if it makes no difference? -And why not skip it and make the preprocessor faster?'' The answer is -that the prescan does make a difference in three special cases: - -@itemize @bullet -@item -Nested calls to a macro. - -@item -Macros that call other macros that stringify or concatenate. - -@item -Macros whose expansions contain unshielded commas. -@end itemize - -We say that @dfn{nested} calls to a macro occur when a macro's argument -contains a call to that very macro. For example, if @samp{f} is a macro -that expects one argument, @samp{f (f (1))} is a nested pair of calls to -@samp{f}. The desired expansion is made by expanding @samp{f (1)} and -substituting that into the definition of @samp{f}. The prescan causes -the expected result to happen. Without the prescan, @samp{f (1)} itself -would be substituted as an argument, and the inner use of @samp{f} would -appear during the main scan as an indirect self-reference and would not -be expanded. Here, the prescan cancels an undesirable side effect (in -the medical, not computational, sense of the term) of the special rule -for self-referential macros. - -Prescan causes trouble in certain other cases of nested macro calls. -Here is an example: - -@example -#define foo a,b -#define bar(x) lose(x) -#define lose(x) (1 + (x)) - -bar(foo) -@end example - -@noindent -We would like @samp{bar(foo)} to turn into @samp{(1 + (foo))}, which -would then turn into @samp{(1 + (a,b))}. Instead, @samp{bar(foo)} -expands into @samp{lose(a,b)}, and you get an error because @code{lose} -requires a single argument. In this case, the problem is easily solved -by the same parentheses that ought to be used to prevent misnesting of -arithmetic operations: - -@example -#define foo (a,b) -#define bar(x) lose((x)) -@end example - -The problem is more serious when the operands of the macro are not -expressions; for example, when they are statements. Then parentheses -are unacceptable because they would make for invalid C code: - -@example -#define foo @{ int a, b; @dots{} @} -@end example - -@noindent -In GNU C you can shield the commas using the @samp{(@{@dots{}@})} -construct which turns a compound statement into an expression: - -@example -#define foo (@{ int a, b; @dots{} @}) -@end example - -Or you can rewrite the macro definition to avoid such commas: - -@example -#define foo @{ int a; int b; @dots{} @} -@end example - -There is also one case where prescan is useful. It is possible to use -prescan to expand an argument and then stringify it --- if you use two -levels of macros. Let's add a new macro @samp{xstr} to the example -shown above: - -@example -#define xstr(s) str(s) -#define str(s) #s -#define foo 4 -xstr (foo) -@end example - -This expands into @samp{"4"}, not @samp{"foo"}. The reason for the -difference is that the argument of @samp{xstr} is expanded at prescan -(because @samp{xstr} does not specify stringification or concatenation -of the argument). The result of prescan then forms the argument for -@samp{str}. @samp{str} uses its argument without prescan because it -performs stringification; but it cannot prevent or undo the prescanning -already done by @samp{xstr}. - -@node Cascaded Macros, Newlines in Args, Argument Prescan, Macro Pitfalls -@subsubsection Cascaded Use of Macros - -@cindex cascaded macros -@cindex macro body uses macro -A @dfn{cascade} of macros is when one macro's body contains a reference -to another macro. This is very common practice. For example, - -@example -#define BUFSIZE 1020 -#define TABLESIZE BUFSIZE -@end example - -This is not at all the same as defining @samp{TABLESIZE} to be -@samp{1020}. The @samp{#define} for @samp{TABLESIZE} uses exactly the -body you specify --- in this case, @samp{BUFSIZE} --- and does not check -to see whether it too is the name of a macro. - -It's only when you @emph{use} @samp{TABLESIZE} that the result of its -expansion is checked for more macro names. - -This makes a difference if you change the definition of @samp{BUFSIZE} -at some point in the source file. @samp{TABLESIZE}, defined as shown, -will always expand using the definition of @samp{BUFSIZE} that is -currently in effect: - -@example -#define BUFSIZE 1020 -#define TABLESIZE BUFSIZE -#undef BUFSIZE -#define BUFSIZE 37 -@end example - -@noindent -Now @samp{TABLESIZE} expands (in two stages) to @samp{37}. (The -@samp{#undef} is to prevent any warning about the nontrivial -redefinition of @code{BUFSIZE}.) - -@node Newlines in Args,, Cascaded Macros, Macro Pitfalls -@subsection Newlines in Macro Arguments -@cindex newlines in macro arguments - -The invocation of a function-like macro can extend over many logical -lines. The ISO C standard requires that newlines within a macro -invocation be treated as ordinary whitespace. This means that when the -expansion of a function-like macro replaces its invocation, it appears -on the same line as the macro name did. Thus line numbers emitted by -the compiler or debugger refer to the line the invocation started on, -which might be different to the line containing the argument causing the -problem. - -Here is an example illustrating this: - -@example -#define ignore_second_arg(a,b,c) a; c - -ignore_second_arg (foo (), - ignored (), - syntax error); -@end example - -@noindent -The syntax error triggered by the tokens @samp{syntax error} results in -an error message citing line three --- the line of ignore_second_arg --- -even though the problematic code comes from line five. - -@node Conditionals, Assertions, Macros, Top -@section Conditionals - -@cindex conditionals -In a macro processor, a @dfn{conditional} is a directive that allows a -part of the program to be ignored during compilation, on some -conditions. In the C preprocessor, a conditional can test either an -arithmetic expression or whether a name is defined as a macro. - -A conditional in the C preprocessor resembles in some ways an @samp{if} -statement in C, but it is important to understand the difference between -them. The condition in an @samp{if} statement is tested during the -execution of your program. Its purpose is to allow your program to -behave differently from run to run, depending on the data it is -operating on. The condition in a preprocessing conditional directive is -tested when your program is compiled. Its purpose is to allow different -code to be included in the program depending on the situation at the -time of compilation. - -@menu -* Uses: Conditional Uses. What conditionals are for. -* Syntax: Conditional Syntax. How conditionals are written. -* Deletion: Deleted Code. Making code into a comment. -* Macros: Conditionals-Macros. Why conditionals are used with macros. -* Errors: #error Directive. Detecting inconsistent compilation parameters. -@end menu - -@node Conditional Uses -@subsection Why Conditionals are Used - -Generally there are three kinds of reason to use a conditional. - -@itemize @bullet -@item -A program may need to use different code depending on the machine or -operating system it is to run on. In some cases the code for one -operating system may be erroneous on another operating system; for -example, it might refer to library routines that do not exist on the -other system. When this happens, it is not enough to avoid executing -the invalid code: merely having it in the program makes it impossible to -link the program and run it. With a preprocessing conditional, the -offending code can be effectively excised from the program when it is -not valid. - -@item -You may want to be able to compile the same source file into two -different programs. Sometimes the difference between the programs is -that one makes frequent time-consuming consistency checks on its -intermediate data, or prints the values of those data for debugging, -while the other does not. - -@item -A conditional whose condition is always false is a good way to exclude -code from the program but keep it as a sort of comment for future -reference. -@end itemize - -Most simple programs that are intended to run on only one machine will -not need to use preprocessing conditionals. - -@node Conditional Syntax -@subsection Syntax of Conditionals - -@findex #if -A conditional in the C preprocessor begins with a @dfn{conditional -directive}: @samp{#if}, @samp{#ifdef} or @samp{#ifndef}. -@xref{Conditionals-Macros}, for information on @samp{#ifdef} and -@samp{#ifndef}; only @samp{#if} is explained here. - -@menu -* If: #if Directive. Basic conditionals using @samp{#if} and @samp{#endif}. -* Else: #else Directive. Including some text if the condition fails. -* Elif: #elif Directive. Testing several alternative possibilities. -@end menu - -@node #if Directive -@subsubsection The @samp{#if} Directive - -The @samp{#if} directive in its simplest form consists of - -@example -#if @var{expression} -@var{controlled text} -#endif /* @var{expression} */ -@end example - -The comment following the @samp{#endif} is not required, but it is a -good practice because it helps people match the @samp{#endif} to the -corresponding @samp{#if}. Such comments should always be used, except -in short conditionals that are not nested. In fact, you can put -anything at all after the @samp{#endif} and it will be ignored by the -GNU C preprocessor, but only comments are acceptable in ISO Standard C@. - -@var{expression} is a C expression of integer type, subject to stringent -restrictions. It may contain - -@itemize @bullet -@item -Integer constants, which are all regarded as @code{long} or -@code{unsigned long}. - -@item -Character constants, which are interpreted according to the character -set and conventions of the machine and operating system on which the -preprocessor is running. The GNU C preprocessor uses the C data type -@samp{char} for these character constants; therefore, whether some -character codes are negative is determined by the C compiler used to -compile the preprocessor. If it treats @samp{char} as signed, then -character codes large enough to set the sign bit will be considered -negative; otherwise, no character code is considered negative. - -@item -Arithmetic operators for addition, subtraction, multiplication, -division, bitwise operations, shifts, comparisons, and logical -operations (@samp{&&} and @samp{||}). The latter two obey the usual -short-circuiting rules of standard C. - -@item -Identifiers that are not macros, which are all treated as zero(!). - -@item -Macro calls. All macro calls in the expression are expanded before -actual computation of the expression's value begins. -@end itemize - -Note that @samp{sizeof} operators and @code{enum}-type values are not -allowed. @code{enum}-type values, like all other identifiers that are -not taken as macro calls and expanded, are treated as zero. - -The @var{controlled text} inside of a conditional can include -preprocessing directives. Then the directives inside the conditional -are obeyed only if that branch of the conditional succeeds. The text -can also contain other conditional groups. However, the @samp{#if} and -@samp{#endif} directives must balance. - -@node #else Directive -@subsubsection The @samp{#else} Directive - -@findex #else -The @samp{#else} directive can be added to a conditional to provide -alternative text to be used if the condition is false. This is what -it looks like: - -@example -#if @var{expression} -@var{text-if-true} -#else /* Not @var{expression} */ -@var{text-if-false} -#endif /* Not @var{expression} */ -@end example - -If @var{expression} is nonzero, and thus the @var{text-if-true} is -active, then @samp{#else} acts like a failing conditional and the -@var{text-if-false} is ignored. Conversely, if the @samp{#if} -conditional fails, the @var{text-if-false} is considered included. - -@node #elif Directive -@subsubsection The @samp{#elif} Directive - -@findex #elif -One common case of nested conditionals is used to check for more than two -possible alternatives. For example, you might have - -@example -#if X == 1 -@dots{} -#else /* X != 1 */ -#if X == 2 -@dots{} -#else /* X != 2 */ -@dots{} -#endif /* X != 2 */ -#endif /* X != 1 */ -@end example - -Another conditional directive, @samp{#elif}, allows this to be -abbreviated as follows: - -@example -#if X == 1 -@dots{} -#elif X == 2 -@dots{} -#else /* X != 2 and X != 1*/ -@dots{} -#endif /* X != 2 and X != 1*/ -@end example - -@samp{#elif} stands for ``else if''. Like @samp{#else}, it goes in the -middle of a @samp{#if}-@samp{#endif} pair and subdivides it; it does not -require a matching @samp{#endif} of its own. Like @samp{#if}, the -@samp{#elif} directive includes an expression to be tested. - -The text following the @samp{#elif} is processed only if the original -@samp{#if}-condition failed and the @samp{#elif} condition succeeds. -More than one @samp{#elif} can go in the same @samp{#if}-@samp{#endif} -group. Then the text after each @samp{#elif} is processed only if the -@samp{#elif} condition succeeds after the original @samp{#if} and any -previous @samp{#elif} directives within it have failed. @samp{#else} is -equivalent to @samp{#elif 1}, and @samp{#else} is allowed after any -number of @samp{#elif} directives, but @samp{#elif} may not follow -@samp{#else}. - -@node Deleted Code -@subsection Keeping Deleted Code for Future Reference -@cindex commenting out code - -If you replace or delete a part of the program but want to keep the old -code around as a comment for future reference, the easy way to do this -is to put @samp{#if 0} before it and @samp{#endif} after it. This is -better than using comment delimiters @samp{/*} and @samp{*/} since those -won't work if the code already contains comments (C comments do not -nest). - -This works even if the code being turned off contains conditionals, but -they must be entire conditionals (balanced @samp{#if} and @samp{#endif}). - -Conversely, do not use @samp{#if 0} for comments which are not C code. -Use the comment delimiters @samp{/*} and @samp{*/} instead. The -interior of @samp{#if 0} must consist of complete tokens; in particular, -single-quote characters must balance. Comments often contain unbalanced -single-quote characters (known in English as apostrophes). These -confuse @samp{#if 0}. They do not confuse @samp{/*}. - -@node Conditionals-Macros -@subsection Conditionals and Macros - -Conditionals are useful in connection with macros or assertions, because -those are the only ways that an expression's value can vary from one -compilation to another. A @samp{#if} directive whose expression uses no -macros or assertions is equivalent to @samp{#if 1} or @samp{#if 0}; you -might as well determine which one, by computing the value of the -expression yourself, and then simplify the program. - -For example, here is a conditional that tests the expression -@samp{BUFSIZE == 1020}, where @samp{BUFSIZE} must be a macro. - -@example -#if BUFSIZE == 1020 - printf ("Large buffers!\n"); -#endif /* BUFSIZE is large */ -@end example - -(Programmers often wish they could test the size of a variable or data -type in @samp{#if}, but this does not work. The preprocessor does not -understand @code{sizeof}, or typedef names, or even the type keywords -such as @code{int}.) - -@findex defined -The special operator @samp{defined} is used in @samp{#if} and -@samp{#elif} expressions to test whether a certain name is defined as a -macro. Either @samp{defined @var{name}} or @samp{defined (@var{name})} -is an expression whose value is 1 if @var{name} is defined as macro at -the current point in the program, and 0 otherwise. To the -@samp{defined} operator it makes no difference what the definition of -the macro is; all that matters is whether there is a definition. Thus, -for example,@refill - -@example -#if defined (vax) || defined (ns16000) -@end example - -@noindent -would succeed if either of the names @samp{vax} and @samp{ns16000} is -defined as a macro. You can test the same condition using assertions -(@pxref{Assertions}), like this: - -@example -#if #cpu (vax) || #cpu (ns16000) -@end example - -If a macro is defined and later undefined with @samp{#undef}, subsequent -use of the @samp{defined} operator returns 0, because the name is no -longer defined. If the macro is defined again with another -@samp{#define}, @samp{defined} will recommence returning 1. - -If the @samp{defined} operator appears as a result of a macro expansion, -the C standard says the behavior is undefined. GNU cpp treats it as a -genuine @samp{defined} operator and evaluates it normally. It will warn -wherever your code uses this feature if you use the command-line option -@samp{-pedantic}, since other compilers may handle it differently. - -@findex #ifdef -@findex #ifndef -Conditionals that test whether a single macro is defined are very common, -so there are two special short conditional directives for this case. - -@table @code -@item #ifdef @var{name} -is equivalent to @samp{#if defined (@var{name})}. - -@item #ifndef @var{name} -is equivalent to @samp{#if ! defined (@var{name})}. -@end table - -Macro definitions can vary between compilations for several reasons. - -@itemize @bullet -@item -Some macros are predefined on each kind of machine. For example, on a -Vax, the name @samp{vax} is a predefined macro. On other machines, it -would not be defined. - -@item -Many more macros are defined by system header files. Different systems -and machines define different macros, or give them different values. It -is useful to test these macros with conditionals to avoid using a system -feature on a machine where it is not implemented. - -@item -Macros are a common way of allowing users to customize a program for -different machines or applications. For example, the macro -@samp{BUFSIZE} might be defined in a configuration file for your program -that is included as a header file in each source file. You would use -@samp{BUFSIZE} in a preprocessing conditional in order to generate -different code depending on the chosen configuration. - -@item -Macros can be defined or undefined with @samp{-D} and @samp{-U} command -options when you compile the program. You can arrange to compile the -same source file into two different programs by choosing a macro name to -specify which program you want, writing conditionals to test whether or -how this macro is defined, and then controlling the state of the macro -with compiler command options. @xref{Invocation}. -@end itemize - -@ifinfo -Assertions are usually predefined, but can be defined with preprocessor -directives or command-line options. -@end ifinfo - -@node #error Directive -@subsection The @samp{#error} and @samp{#warning} Directives - -@findex #error -The directive @samp{#error} causes the preprocessor to report a fatal -error. The tokens forming the rest of the line following @samp{#error} -are used as the error message, and not macro-expanded. Internal -whitespace sequences are each replaced with a single space. The line -must consist of complete tokens. - -You would use @samp{#error} inside of a conditional that detects a -combination of parameters which you know the program does not properly -support. For example, if you know that the program will not run -properly on a Vax, you might write - -@smallexample -@group -#ifdef __vax__ -#error "Won't work on Vaxen. See comments at get_last_object." -#endif -@end group -@end smallexample - -@noindent -@xref{Nonstandard Predefined}, for why this works. - -If you have several configuration parameters that must be set up by -the installation in a consistent way, you can use conditionals to detect -an inconsistency and report it with @samp{#error}. For example, - -@smallexample -#if HASH_TABLE_SIZE % 2 == 0 || HASH_TABLE_SIZE % 3 == 0 \ - || HASH_TABLE_SIZE % 5 == 0 -#error HASH_TABLE_SIZE should not be divisible by a small prime -#endif -@end smallexample - -@findex #warning -The directive @samp{#warning} is like the directive @samp{#error}, but -causes the preprocessor to issue a warning and continue preprocessing. -The tokens following @samp{#warning} are used as the warning message, -and not macro-expanded. - -You might use @samp{#warning} in obsolete header files, with a message -directing the user to the header file which should be used instead. - -@node Assertions, Line Control, Conditionals, Top -@section Assertions -@cindex assertions -@dfn{Assertions} are a more systematic alternative to macros in writing -conditionals to test what sort of computer or system the compiled -program will run on. Assertions are usually predefined, but you can -define them with preprocessing directives or command-line options. - -@cindex predicates -The macros traditionally used to describe the type of target are not -classified in any way according to which question they answer; they may -indicate a hardware architecture, a particular hardware model, an -operating system, a particular version of an operating system, or -specific configuration options. These are jumbled together in a single -namespace. In contrast, each assertion consists of a named question and -an answer. The question is usually called the @dfn{predicate}. An -assertion looks like this: - -@example -#@var{predicate} (@var{answer}) -@end example - -@noindent -You must use a properly formed identifier for @var{predicate}. The -value of @var{answer} can be any sequence of words; all characters are -significant except for leading and trailing whitespace, and differences -in internal whitespace sequences are ignored. (This is similar to the -rules governing macro redefinition.) Thus, @samp{x + y} is different -from @samp{x+y} but equivalent to @samp{ x + y }. @samp{)} is not -allowed in an answer. - -@cindex testing predicates -Here is a conditional to test whether the answer @var{answer} is asserted -for the predicate @var{predicate}: - -@example -#if #@var{predicate} (@var{answer}) -@end example - -@noindent -There may be more than one answer asserted for a given predicate. If -you omit the answer, you can test whether @emph{any} answer is asserted -for @var{predicate}: - -@example -#if #@var{predicate} -@end example - -@findex #system -@findex #machine -@findex #cpu -Most of the time, the assertions you test will be predefined assertions. -GNU C provides three predefined predicates: @code{system}, @code{cpu}, -and @code{machine}. @code{system} is for assertions about the type of -software, @code{cpu} describes the type of computer architecture, and -@code{machine} gives more information about the computer. For example, -on a GNU system, the following assertions would be true: - -@example -#system (gnu) -#system (mach) -#system (mach 3) -#system (mach 3.@var{subversion}) -#system (hurd) -#system (hurd @var{version}) -@end example - -@noindent -and perhaps others. The alternatives with -more or less version information let you ask more or less detailed -questions about the type of system software. - -On a Unix system, you would find @code{#system (unix)} and perhaps one of: -@code{#system (aix)}, @code{#system (bsd)}, @code{#system (hpux)}, -@code{#system (lynx)}, @code{#system (mach)}, @code{#system (posix)}, -@code{#system (svr3)}, @code{#system (svr4)}, or @code{#system (xpg4)} -with possible version numbers following. - -Other values for @code{system} are @code{#system (mvs)} -and @code{#system (vms)}. - -@strong{Portability note:} Many Unix C compilers provide only one answer -for the @code{system} assertion: @code{#system (unix)}, if they support -assertions at all. This is less than useful. - -An assertion with a multi-word answer is completely different from several -assertions with individual single-word answers. For example, the presence -of @code{system (mach 3.0)} does not mean that @code{system (3.0)} is true. -It also does not directly imply @code{system (mach)}, but in GNU C, that -last will normally be asserted as well. - -The current list of possible assertion values for @code{cpu} is: -@code{#cpu (a29k)}, @code{#cpu (alpha)}, @code{#cpu (arm)}, @code{#cpu -(clipper)}, @code{#cpu (convex)}, @code{#cpu (elxsi)}, @code{#cpu -(tron)}, @code{#cpu (h8300)}, @code{#cpu (i370)}, @code{#cpu (i386)}, -@code{#cpu (i860)}, @code{#cpu (i960)}, @code{#cpu (m68k)}, @code{#cpu -(m88k)}, @code{#cpu (mips)}, @code{#cpu (ns32k)}, @code{#cpu (hppa)}, -@code{#cpu (pyr)}, @code{#cpu (ibm032)}, @code{#cpu (rs6000)}, -@code{#cpu (sh)}, @code{#cpu (sparc)}, @code{#cpu (spur)}, @code{#cpu -(tahoe)}, @code{#cpu (vax)}, @code{#cpu (we32000)}. - -@findex #assert -You can create assertions within a C program using @samp{#assert}, like -this: - -@example -#assert @var{predicate} (@var{answer}) -@end example - -@noindent -(Note the absence of a @samp{#} before @var{predicate}.) - -@cindex unassert -@cindex assertions, undoing -@cindex retracting assertions -@findex #unassert -Each time you do this, you assert a new true answer for @var{predicate}. -Asserting one answer does not invalidate previously asserted answers; -they all remain true. The only way to remove an answer is with -@samp{#unassert}. @samp{#unassert} has the same syntax as -@samp{#assert}. You can also remove all answers to a @var{predicate} -like this: - -@example -#unassert @var{predicate} -@end example - -You can also add or cancel assertions using command options -when you run @code{gcc} or @code{cpp}. @xref{Invocation}. - -@node Line Control, Other Directives, Assertions, Top -@section Combining Source Files - -@cindex line control -One of the jobs of the C preprocessor is to inform the C compiler of where -each line of C code came from: which source file and which line number. - -C code can come from multiple source files if you use @samp{#include}; -both @samp{#include} and the use of conditionals and macros can cause -the line number of a line in the preprocessor output to be different -from the line's number in the original source file. You will appreciate -the value of making both the C compiler (in error messages) and symbolic -debuggers such as GDB use the line numbers in your source file. - -The C preprocessor builds on this feature by offering a directive by -which you can control the feature explicitly. This is useful when a -file for input to the C preprocessor is the output from another program -such as the @code{bison} parser generator, which operates on another -file that is the true source file. Parts of the output from -@code{bison} are generated from scratch, other parts come from a -standard parser file. The rest are copied nearly verbatim from the -source file, but their line numbers in the @code{bison} output are not -the same as their original line numbers. Naturally you would like -compiler error messages and symbolic debuggers to know the original -source file and line number of each line in the @code{bison} input. - -@findex #line -@code{bison} arranges this by writing @samp{#line} directives into the output -file. @samp{#line} is a directive that specifies the original line number -and source file name for subsequent input in the current preprocessor input -file. @samp{#line} has three variants: - -@table @code -@item #line @var{linenum} -Here @var{linenum} is a decimal integer constant. This specifies that -the line number of the following line of input, in its original source file, -was @var{linenum}. - -@item #line @var{linenum} @var{filename} -Here @var{linenum} is a decimal integer constant and @var{filename} is a -string constant. This specifies that the following line of input came -originally from source file @var{filename} and its line number there was -@var{linenum}. Keep in mind that @var{filename} is not just a file -name; it is surrounded by double-quote characters so that it looks like -a string constant. - -@item #line @var{anything else} -@var{anything else} is checked for macro calls, which are expanded. -The result should be a decimal integer constant followed optionally -by a string constant, as described above. -@end table - -@samp{#line} directives alter the results of the @samp{__FILE__} and -@samp{__LINE__} predefined macros from that point on. @xref{Standard -Predefined}. - -The output of the preprocessor (which is the input for the rest of the -compiler) contains directives that look much like @samp{#line} -directives. They start with just @samp{#} instead of @samp{#line}, but -this is followed by a line number and file name as in @samp{#line}. -@xref{Output}. - -@node Other Directives, Output, Line Control, Top -@section Miscellaneous Preprocessing Directives - -This section describes some additional, rarely used, preprocessing -directives. - -@findex #pragma -@findex #pragma GCC - -The ISO standard specifies that the effect of the @samp{#pragma} -directive is implementation-defined. The GNU C preprocessor recognizes -some pragmas, and passes unrecognized ones through to the preprocessor -output, so they are available to the compilation pass. - -In line with the C99 standard, which introduces a STDC namespace for C99 -pragmas, the preprocessor introduces a GCC namespace for GCC pragmas. -Supported GCC preprocessor pragmas are of the form @samp{#pragma GCC -...}. For backwards compatibility previously supported pragmas are also -recognized without the @samp{GCC} prefix, however that use is -deprecated. Pragmas that are already deprecated are not recognized with -a @samp{GCC} prefix. - -@findex #pragma GCC dependency -The @samp{#pragma GCC dependency} allows you to check the relative dates -of the current file and another file. If the other file is more recent -than the current file, a warning is issued. This is useful if the -include file is derived from the other file, and should be regenerated. -The other file is searched for using the normal include search path. -Optional trailing text can be used to give more information in the -warning message. - -@smallexample -#pragma GCC dependency "parse.y" -#pragma GCC dependency "/usr/include/time.h" rerun /path/to/fixincludes -@end smallexample - -@findex _Pragma -The C99 standard also introduces the @samp{_Pragma} operator. The -syntax is @code{_Pragma (string-literal)}, where @samp{string-literal} -can be either a normal or wide-character string literal. It is -destringized, by replacing all @samp{\\} with a single @samp{\} and all -@samp{\"} with a @samp{"}. The result is then processed as if it had -appeared as the right hand side of a @samp{#pragma} directive. For -example, - -@smallexample -_Pragma ("GCC dependency \"parse.y\"") -@end smallexample - -@noindent has the same effect as @samp{#pragma GCC dependency -"parse.y"}. The same effect could be achieved using macros, for example - -@smallexample -#define DO_PRAGMA(x) _Pragma (#x) -DO_PRAGMA (GCC dependency "parse.y") -@end smallexample - -The standard is unclear on where a @samp{_Pragma} operator can appear. -The preprocessor accepts it even within a preprocessing conditional -directive like @samp{#if}. To be safe, you are probably best keeping it -out of directives other than @samp{#define}, and putting it on a line of -its own. - -@findex #ident -The @samp{#ident} directive is supported for compatibility with certain -other systems. It is followed by a line of text. On some systems, the -text is copied into a special place in the object file; on most systems, -the text is ignored and this directive has no effect. Typically -@samp{#ident} is only used in header files supplied with those systems -where it is meaningful. - -@cindex null directive -The @dfn{null directive} consists of a @samp{#} followed by a newline, -with only whitespace (including comments) in between. A null directive -is understood as a preprocessing directive but has no effect on the -preprocessor output. The primary significance of the existence of the -null directive is that an input line consisting of just a @samp{#} will -produce no output, rather than a line of output containing just a -@samp{#}. Supposedly some old C programs contain such lines. - -@node Output, Implementation, Other Directives, Top -@section C Preprocessor Output - -@cindex output format -The output from the C preprocessor looks much like the input, except -that all preprocessing directive lines have been replaced with blank -lines and all comments with spaces. - -The ISO standard specifies that it is implementation defined whether a -preprocessor preserves whitespace between tokens, or replaces it with -e.g. a single space. In the GNU C preprocessor, whitespace between -tokens is collapsed to become a single space, with the exception that -the first token on a non-directive line is preceded with sufficient -spaces that it appears in the same column in the preprocessed output -that it appeared in in the original source file. This is so the output -is easy to read. @xref{Unreliable Features}. - -Source file name and line number information is conveyed by lines -of the form - -@example -# @var{linenum} @var{filename} @var{flags} -@end example - -@noindent -which are inserted as needed into the output (but never within a string -or character constant), and in place of long sequences of empty lines. -Such a line means that the following line originated in file -@var{filename} at line @var{linenum}. - -After the file name comes zero or more flags, which are @samp{1}, -@samp{2}, @samp{3}, or @samp{4}. If there are multiple flags, spaces -separate them. Here is what the flags mean: - -@table @samp -@item 1 -This indicates the start of a new file. -@item 2 -This indicates returning to a file (after having included another file). -@item 3 -This indicates that the following text comes from a system header file, -so certain warnings should be suppressed. -@item 4 -This indicates that the following text should be treated as C@. -@c maybe cross reference NO_IMPLICIT_EXTERN_C -@end table - -@node Implementation, Unreliable Features, Output, Top -@section Implementation-defined Behavior and Implementation Limits -@cindex implementation limits -@cindex implementation-defined behavior - -The ISO C standard mandates that implementations document various -aspects of preprocessor behavior. You should try to avoid undue -reliance on behaviour described here, as it is possible that it will -change subtly in future implementations. - -@itemize @bullet - -@item The mapping of physical source file multi-byte characters to the -execution character set. - -Currently, GNU cpp only supports character sets that are strict supersets -of ASCII, and performs no translation of characters. - -@item Non-empty sequences of whitespace characters. - -Each whitespace sequence is not preserved, but collapsed to a single -space. For aesthetic reasons, the first token on each non-directive -line of output is preceded with sufficient spaces that it appears in the -same column as it did in the original source file. - -@item The numeric value of character constants in preprocessor expressions. - -The preprocessor and compiler interpret character constants in the same -way; escape sequences such as @code{\a} are given the values they would -have on the target machine. - -Multi-character character constants are interpreted a character at a -time, shifting the previous result left by the number of bits per -character on the host, and adding the new character. For example, 'ab' -on an 8-bit host would be interpreted as 'a' * 256 + 'b'. If there are -more characters in the constant than can fit in the widest native -integer type on the host, usually a @samp{long}, the excess characters -are ignored and a diagnostic is given. - -@item Source file inclusion. - -For a discussion on how the preprocessor locates header files, -@pxref{Include Operation}. - -@item Interpretation of the filename resulting from a macro-expanded -@samp{#include} directive. - -If the macro expands to a string literal, the @samp{#include} directive -is processed as if the string had been specified directly. Otherwise, -the macro must expand to a token stream beginning with a @samp{<} token -and including a @samp{>} token. In this case, the tokens between the -@samp{<} and the first @samp{>} are combined to form the filename to be -included. Any whitespace between tokens is reduced to a single space; -then any space after the initial @samp{<} is retained, but a trailing -space before the closing @samp{>} is ignored. - -In either case, if any excess tokens remain, an error occurs and the -directive is not processed. - -@item Treatment of a @samp{#pragma} directive that after macro-expansion -results in a standard pragma. - -The pragma is processed as if it were a normal standard pragma. - -@end itemize - -The following documents internal limits of GNU cpp. - -@itemize @bullet - -@item Nesting levels of @samp{#include} files. - -We impose an arbitrary limit of 200 levels, to avoid runaway recursion. -The standard requires at least 15 levels. - -@item Nesting levels of conditional inclusion. - -The C standard mandates this be at least 63. The GNU C preprocessor -is limited only by available memory. - -@item Levels of parenthesised expressions within a full expression. - -The C standard requires this to be at least 63. In preprocessor -conditional expressions it is limited only by available memory. - -@item Significant initial characters in an identifier or macro name. - -The preprocessor treats all characters as significant. The C standard -requires only that the first 63 be significant. - -@item Number of macros simultaneously defined in a single translation unit. - -The standard requires at least 4095 be possible; GNU cpp is limited only -by available memory. - -@item Number of parameters in a macro definition and arguments in a macro call. - -We allow USHRT_MAX, which is normally 65,535, and above the minimum of -127 required by the standard. - -@item Number of characters on a logical source line. - -The C standard requires a minimum of 4096 be permitted. GNU cpp places -no limits on this, but you may get incorrect column numbers reported in -diagnostics for lines longer than 65,535 characters. - -@end itemize - -@node Unreliable Features, Invocation, Implementation, Top -@section Undefined Behavior and Deprecated Features -@cindex undefined behavior -@cindex deprecated features - -This section details GNU C preprocessor behavior that is subject to -change or deprecated. You are @emph{strongly advised} to write your -software so it does not rely on anything described here; future versions -of the preprocessor may subtly change such behavior or even remove the -feature altogether. - -Preservation of the form of whitespace between tokens is unlikely to -change from current behavior (@ref{Output}), but you are advised not -to rely on it. - -The following are undocumented and subject to change:- - -@itemize @bullet - -@item Precedence of ## operators with respect to each other - -Whether a sequence of ## operators is evaluated left-to-right, -right-to-left or indeed in a consistent direction at all is not -specified. An example of where this might matter is pasting the -arguments @samp{1}, @samp{e} and @samp{-2}. This would be fine for -left-to-right pasting, but right-to-left pasting would produce an -invalid token @samp{e-2}. It is possible to guarantee precedence by -suitable use of nested macros. - -@item Precedence of # operator with respect to the ## operator - -Which of these two operators is evaluated first is not specified. - -@end itemize - -The following features are in flux and should not be used in portable -code: - -@itemize @bullet - -@item Optional argument when invoking rest argument macros - -As an extension, GCC permits you to omit the variable arguments entirely -when you use a variable argument macro. This works whether or not you -give the variable argument a name. For example, the two macro -invocations in the example below expand to the same thing: - -@smallexample -#define debug(format, ...) printf (format, __VA_ARGS__) -debug("string"); /* Not permitted by C standard. */ -debug("string",); /* OK. */ -@end smallexample - -This extension will be preserved, but the special behavior of @samp{##} -in this context has changed in the past and may change again in the -future. - -@item ## swallowing preceding text in rest argument macros - -Formerly, in a macro expansion, if @samp{##} appeared before a variable -arguments parameter, and the set of tokens specified for that argument in -the macro invocation was empty, previous versions of the GNU C -preprocessor would back up and remove the preceding sequence of -non-whitespace characters (@strong{not} the preceding token). This -extension is in direct conflict with the 1999 C standard and has been -drastically pared back. - -In the current version of the preprocessor, if @samp{##} appears between -a comma and a variable arguments parameter, and the variable argument is -omitted entirely, the comma will be removed from the expansion. If the -variable argument is empty, or the token before @samp{##} is not a -comma, then @samp{##} behaves as a normal token paste. - -Portable code should avoid this extension at all costs. - -@end itemize - -The following features are deprecated and will likely be removed at some -point in the future:- - -@itemize @bullet - -@item Attempting to paste two tokens which together do not form a valid -preprocessing token - -The preprocessor currently warns about this and outputs the two tokens -adjacently, which is probably the behavior the programmer intends. It -may not work in future, though. - -Most of the time, when you get this warning, you will find that @samp{##} -is being used superstitiously, to guard against whitespace appearing -between two tokens. It is almost always safe to delete the @samp{##}. - -@findex #pragma once -@item #pragma once - -This pragma was once used to tell the preprocessor that it need not -include a file more than once. It is now obsolete and should not be -used at all. - -@item #pragma poison - -This pragma has been superseded by @samp{#pragma GCC poison}. -@xref{Poisoning}. - -@item Multi-line string literals - -The preprocessor currently allows raw newlines in string literals. This -extension is deprecated and will be removed in a future version of GCC. -The preprocessor already forbids such string literals in all directives -apart from #define. - -Instead, make use of ISO C concatenation of adjacent string literals, or -use @samp{\n} followed by an escaped newline. - -@item Preprocessing things which are not C - -The C preprocessor is intended to be used only with C, C++, and -Objective C source code. In the past, it has been abused as a general -text processor. It will choke on input which is not lexically valid C; -for example, apostrophes will be interpreted as the beginning of -character constants, and cause errors. Also, you cannot rely on it -preserving characteristics of the input which are not significant to -C-family languages. For instance, if a Makefile is preprocessed, all -the hard tabs will be lost, and the Makefile will not work. - -Having said that, you can often get away with using cpp on things which -are not C. Other Algol-ish programming languages are often safe -(Pascal, Ada, ...) and so is assembly, with caution. @samp{-traditional} -mode is much more permissive, and can safely be used with e.g. Fortran. -Many of the problems go away if you write C or C++ style comments -instead of native language comments, and if you avoid elaborate macros. - -Wherever possible, you should use a preprocessor geared to the language -you are writing in. Modern versions of the GNU assembler have macro -facilities. Most high level programming languages have their own -conditional compilation and inclusion mechanism. If all else fails, -try a true general text processor, such as @xref{Top, M4, , m4, GNU `m4'}. - -@end itemize - -@node Invocation, Concept Index, Unreliable Features, Top -@section Invoking the C Preprocessor -@cindex invocation of the preprocessor - -Most often when you use the C preprocessor you will not have to invoke it -explicitly: the C compiler will do so automatically. However, the -preprocessor is sometimes useful on its own. - -@ignore -@c man begin SYNOPSIS -cpp [@samp{-P}] [@samp{-C}] [@samp{-gcc}] [@samp{-traditional}] - [@samp{-undef}] [@samp{-trigraphs}] [@samp{-pedantic}] - [@samp{-W}@var{warn}...] [@samp{-I}@var{dir}...] - [@samp{-D}@var{macro}[=@var{defn}]...] [@samp{-U}@var{macro}] - [@samp{-A}@var{predicate}(@var{answer})] - [@samp{-M}|@samp{-MM}][@samp{-MG}][@samp{-MF}@var{filename}] - [@samp{-MP}][@samp{-MQ}@var{target}...][@samp{-MT}@var{target}...] - [@samp{-x} @var{language}] [@samp{-std=}@var{standard}] - @var{infile} @var{outfile} - -Only the most useful options are listed here; see below for the remainder. -@c man end -@c man begin SEEALSO -gcc(1), as(1), ld(1), and the Info entries for @file{cpp}, @file{gcc}, and -@file{binutils}. -@c man end -@end ignore - -@c man begin OPTIONS -The C preprocessor expects two file names as arguments, @var{infile} and -@var{outfile}. The preprocessor reads @var{infile} together with any -other files it specifies with @samp{#include}. All the output generated -by the combined input files is written in @var{outfile}. - -Either @var{infile} or @var{outfile} may be @samp{-}, which as -@var{infile} means to read from standard input and as @var{outfile} -means to write to standard output. Also, if either file is omitted, it -means the same as if @samp{-} had been specified for that file. - -@cindex options -Here is a table of command options accepted by the C preprocessor. -These options can also be given when compiling a C program; they are -passed along automatically to the preprocessor when it is invoked by the -compiler. - -@table @samp -@item -P -@findex -P -Inhibit generation of @samp{#}-lines with line-number information in the -output from the preprocessor. This might be useful when running the -preprocessor on something that is not C code and will be sent to a -program which might be confused by the @samp{#}-lines. @xref{Output}. - -@item -C -@findex -C -Do not discard comments. All comments are passed through to the output -file, except for comments in processed directives, which are deleted -along with the directive. Comments appearing in the expansion list of a -macro will be preserved, and appear in place wherever the macro is -invoked. - -You should be prepared for side effects when using @samp{-C}; it causes -the preprocessor to treat comments as tokens in their own right. For -example, macro redefinitions that were trivial when comments were -replaced by a single space might become significant when comments are -retained. Also, comments appearing at the start of what would be a -directive line have the effect of turning that line into an ordinary -source line, since the first token on the line is no longer a @samp{#}. - -@item -traditional -@findex -traditional -Try to imitate the behavior of old-fashioned C, as opposed to ISO C@. - -@itemize @bullet -@item -Traditional macro expansion pays no attention to single-quote or -double-quote characters; macro argument symbols are replaced by the -argument values even when they appear within apparent string or -character constants. - -@item -Traditionally, it is permissible for a macro expansion to end in the -middle of a string or character constant. The constant continues into -the text surrounding the macro call. - -@item -However, traditionally the end of the line terminates a string or -character constant, with no error. - -@item -In traditional C, a comment is equivalent to no text at all. (In ISO -C, a comment counts as whitespace.) - -@item -Traditional C does not have the concept of a ``preprocessing number''. -It considers @samp{1.0e+4} to be three tokens: @samp{1.0e}, @samp{+}, -and @samp{4}. - -@item -A macro is not suppressed within its own definition, in traditional C@. -Thus, any macro that is used recursively inevitably causes an error. - -@item -The character @samp{#} has no special meaning within a macro definition -in traditional C@. - -@item -In traditional C, the text at the end of a macro expansion can run -together with the text after the macro call, to produce a single token. -(This is impossible in ISO C@.) - -@item -None of the GNU extensions to the preprocessor are available in -@samp{-traditional} mode. - -@end itemize - -@cindex Fortran -@cindex unterminated -Use the @samp{-traditional} option when preprocessing Fortran code, so -that single-quotes and double-quotes within Fortran comment lines (which -are generally not recognized as such by the preprocessor) do not cause -diagnostics about unterminated character or string constants. - -However, this option does not prevent diagnostics about unterminated -comments when a C-style comment appears to start, but not end, within -Fortran-style commentary. - -So, the following Fortran comment lines are accepted with -@samp{-traditional}: - -@smallexample -C This isn't an unterminated character constant -C Neither is "20000000000, an octal constant -C in some dialects of Fortran -@end smallexample - -However, this type of comment line will likely produce a diagnostic, or -at least unexpected output from the preprocessor, due to the -unterminated comment: - -@smallexample -C Some Fortran compilers accept /* as starting -C an inline comment. -@end smallexample - -@cindex g77 -Note that @code{g77} automatically supplies the @samp{-traditional} -option when it invokes the preprocessor. However, a future version of -@code{g77} might use a different, more-Fortran-aware preprocessor in -place of @code{cpp}. - -@item -trigraphs -@findex -trigraphs -Process ISO standard trigraph sequences. These are three-character -sequences, all starting with @samp{??}, that are defined by ISO C to -stand for single characters. For example, @samp{??/} stands for -@samp{\}, so @samp{'??/n'} is a character constant for a newline. By -default, GCC ignores trigraphs, but in standard-conforming modes it -converts them. See the @samp{-std} option. - -The nine trigraph sequences are -@table @samp -@item ??( --> @samp{[} - -@item ??) --> @samp{]} - -@item ??< --> @samp{@{} - -@item ??> --> @samp{@}} - -@item ??= --> @samp{#} - -@item ??/ --> @samp{\} - -@item ??' --> @samp{^} - -@item ??! --> @samp{|} - -@item ??- --> @samp{~} - -@end table - -Trigraph support is not popular, so many compilers do not implement it -properly. Portable code should not rely on trigraphs being either -converted or ignored. - -@item -pedantic -@findex -pedantic -Issue warnings required by the ISO C standard in certain cases such -as when text other than a comment follows @samp{#else} or @samp{#endif}. - -@item -pedantic-errors -@findex -pedantic-errors -Like @samp{-pedantic}, except that errors are produced rather than -warnings. - -@item -Wcomment -@findex -Wcomment -@itemx -Wcomments -(Both forms have the same effect). -Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*} -comment, or whenever a backslash-newline appears in a @samp{//} comment. - -@item -Wtrigraphs -@findex -Wtrigraphs -Warn if any trigraphs are encountered. This option used to take effect -only if @samp{-trigraphs} was also specified, but now works -independently. Warnings are not given for trigraphs within comments, as -we feel this is obnoxious. - -@item -Wall -@findex -Wall -Requests @samp{-Wcomment} and @samp{-Wtrigraphs} (but not -@samp{-Wtraditional} or @samp{-Wundef}). - -@item -Wtraditional -@findex -Wtraditional -Warn about certain constructs that behave differently in traditional and -ISO C@. Also warn about ISO C constructs that have no traditional C -equivalent, and/or problematic constructs which should be avoided. - -@itemize @bullet -@item -Macro parameters that appear within string literals in the macro body. -In traditional C macro replacement takes place within string literals, -but does not in ISO C. - -@item -In traditional C, some preprocessor directives did not exist. -Traditional preprocessors would only consider a line to be a directive -if the @samp{#} appeared in column 1 on the line. Therefore -@samp{-Wtraditional} warns about directives that traditional C -understands but would ignore because the @samp{#} does not appear as the -first character on the line. It also suggests you hide directives like -@samp{#pragma} not understood by traditional C by indenting them. Some -traditional implementations would not recognise @samp{#elif}, so it -suggests avoiding it altogether. - -@item -A function-like macro that appears without arguments. - -@item -The unary plus operator. - -@item -The `U' integer constant suffix. (Traditonal C does support the `L' -suffix on integer constants.) Note, these suffixes appear in macros -defined in the system headers of most modern systems, e.g. the _MIN/_MAX -macros in limits.h. Use of these macros in user code might normally -lead to spurious warnings, however gcc's integrated preprocessor has -enough context to avoid warning in these cases. -@end itemize - -@item -Wundef -@findex -Wundef -Warn if an undefined identifier is evaluated in an @samp{#if} directive. - -@item -I @var{directory} -@findex -I -Add the directory @var{directory} to the head of the list of -directories to be searched for header files (@pxref{Include Syntax}). -This can be used to override a system header file, substituting your -own version, since these directories are searched before the system -header file directories. If you use more than one @samp{-I} option, -the directories are scanned in left-to-right order; the standard -system directories come after. - -@item -I- -Any directories specified with @samp{-I} options before the @samp{-I-} -option are searched only for the case of @samp{#include "@var{file}"}; -they are not searched for @samp{#include <@var{file}>}. - -If additional directories are specified with @samp{-I} options after -the @samp{-I-}, these directories are searched for all @samp{#include} -directives. - -In addition, the @samp{-I-} option inhibits the use of the current -directory as the first search directory for @samp{#include "@var{file}"}. -Therefore, the current directory is searched only if it is requested -explicitly with @samp{-I.}. Specifying both @samp{-I-} and @samp{-I.} -allows you to control precisely which directories are searched before -the current one and which are searched after. - -@item -nostdinc -@findex -nostdinc -Do not search the standard system directories for header files. -Only the directories you have specified with @samp{-I} options -(and the current directory, if appropriate) are searched. - -By using both @samp{-nostdinc} and @samp{-I-}, you can limit the include-file -search path to only those directories you specify explicitly. - -@item -nostdinc++ -@findex -nostdinc++ -Do not search for header files in the C++-specific standard directories, -but do still search the other standard directories. (This option is -used when building the C++ library.) - -@item -remap -@findex -remap -When searching for a header file in a directory, remap file names if a -file named @file{header.gcc} exists in that directory. This can be used -to work around limitations of file systems with file name restrictions. -The @file{header.gcc} file should contain a series of lines with two -tokens on each line: the first token is the name to map, and the second -token is the actual name to use. - -@item -D @var{name} -@findex -D -Predefine @var{name} as a macro, with definition @samp{1}. - -@item -D @var{name}=@var{definition} -Predefine @var{name} as a macro, with definition @var{definition}. -There are no restrictions on the contents of @var{definition}, but if -you are invoking the preprocessor from a shell or shell-like program you -may need to use the shell's quoting syntax to protect characters such as -spaces that have a meaning in the shell syntax. If you use more than -one @samp{-D} for the same @var{name}, the rightmost definition takes -effect. - -Any @samp{-D} and @samp{-U} options on the command line are processed in -order, and always before @samp{-imacros @var{file}}, regardless of the -order in which they are written. - -@item -U @var{name} -@findex -U -Do not predefine @var{name}. - -Any @samp{-D} and @samp{-U} options on the command line are processed in -order, and always before @samp{-imacros @var{file}}, regardless of the -order in which they are written. - -@item -undef -@findex -undef -Do not predefine any nonstandard macros. - -@item -gcc -@findex -gcc -Define the macros @var{__GNUC__}, @var{__GNUC_MINOR__} and -@var{__GNUC_PATCHLEVEL__}. These are defined automatically when you use -@samp{gcc -E}; you can turn them off in that case with @samp{-no-gcc}. - -@item -A @var{predicate}=@var{answer} -@findex -A -Make an assertion with the predicate @var{predicate} and answer -@var{answer}. This form is preferred to the older form @samp{-A -@var{predicate}(@var{answer})}, which is still supported, because -it does not use shell special characters. @xref{Assertions}. - -@item -A -@var{predicate}=@var{answer} -Disable an assertion with the predicate @var{predicate} and answer -@var{answer}. Specifying no predicate, by @samp{-A-} or @samp{-A -}, -disables all predefined assertions and all assertions preceding it on -the command line; and also undefines all predefined macros and all -macros preceding it on the command line. - -@item -dM -@findex -dM -Instead of outputting the result of preprocessing, output a list of -@samp{#define} directives for all the macros defined during the -execution of the preprocessor, including predefined macros. This gives -you a way of finding out what is predefined in your version of the -preprocessor; assuming you have no file @samp{foo.h}, the command - -@example -touch foo.h; cpp -dM foo.h -@end example - -@noindent -will show the values of any predefined macros. - -@item -dD -@findex -dD -Like @samp{-dM} except in two respects: it does @emph{not} include the -predefined macros, and it outputs @emph{both} the @samp{#define} -directives and the result of preprocessing. Both kinds of output go to -the standard output file. - -@item -dN -@findex -dN -Like @samp{-dD}, but emit only the macro names, not their expansions. - -@item -dI -@findex -dI -Output @samp{#include} directives in addition to the result of -preprocessing. - -@item -M -@findex -M -Instead of outputting the result of preprocessing, output a rule -suitable for @code{make} describing the dependencies of the main source -file. The preprocessor outputs one @code{make} rule containing the -object file name for that source file, a colon, and the names of all the -included files, including those coming from @samp{-include} or -@samp{-imacros} command line options. Unless specified explicitly (with -@samp{-MT} or @samp{-MQ}), the object file name consists of the basename -of the source file with any suffix replaced with object file suffix. -If there are many included files -then the rule is split into several lines using @samp{\}-newline. - -@item -MM -@findex -MM -Like @samp{-M}, but mention only the files included with @samp{#include -"@var{file}"} or with @samp{-include} or @samp{-imacros} command line -options. System header files included with @samp{#include <@var{file}>} -are omitted. - -@item -MF @var{file} -@findex -MF -When used with @samp{-M} or @samp{-MM}, specifies a file to write the -dependencies to. This allows the preprocessor to write the preprocessed -file to stdout normally. If no @samp{-MF} switch is given, CPP sends -the rules to stdout and suppresses normal preprocessed output. - -@item -MG -@findex -MG -When used with @samp{-M} or @samp{-MM}, @samp{-MG} says to treat missing -header files as generated files and assume they live in the same -directory as the source file. It suppresses preprocessed output, as a -missing header file is ordinarily an error. - -This feature is used in automatic updating of makefiles. - -@item -MP -@findex -MP -This option instructs CPP to add a phony target for each dependency -other than the main file, causing each to depend on nothing. These -dummy rules work around errors @code{make} gives if you remove header -files without updating the @code{Makefile} to match. - -This is typical output:- - -@smallexample -/tmp/test.o: /tmp/test.c /tmp/test.h - -/tmp/test.h: -@end smallexample - -@item -MQ @var{target} -@item -MT @var{target} -@findex -MQ -@findex -MT -By default CPP uses the main file name, including any path, and appends -the object suffix, normally ``.o'', to it to obtain the name of the -target for dependency generation. With @samp{-MT} you can specify a -target yourself, overriding the default one. - -If you want multiple targets, you can specify them as a single argument -to @samp{-MT}, or use multiple @samp{-MT} options. - -The targets you specify are output in the order they appear on the -command line. @samp{-MQ} is identical to @samp{-MT}, except that the -target name is quoted for Make, but with @samp{-MT} it isn't. For -example, -MT '$(objpfx)foo.o' gives - -@smallexample -$(objpfx)foo.o: /tmp/foo.c -@end smallexample - -but -MQ '$(objpfx)foo.o' gives - -@smallexample -$$(objpfx)foo.o: /tmp/foo.c -@end smallexample - -The default target is automatically quoted, as if it were given with -@samp{-MQ}. - -@item -H -@findex -H -Print the name of each header file used, in addition to other normal -activities. - -@item -imacros @var{file} -@findex -imacros -Process @var{file} as input and discard the resulting output. - -This has all the effects of @code{#include "file"} appearing on the -first line of the main source file, such as generating dependencies and -being listed with the @samp{-H} option, except that no output is -generated, and that the first directory searched for @var{file} is the -preprocessor's working directory @emph{instead of} the directory -containing the main source file. If not found there, it is searched for -in the remainder of the @code{#include "..."} search chain as normal. - -Because the output is discarded, the main effect of @samp{-imacros -@var{file}} is to make the macros defined in @var{file} available for -use in the main input. - -@item -include @var{file} -@findex -include -Process @var{file} as input, and include all the resulting output. - -This has all the effects of @code{#include "file"} appearing on the -first line of the main source file, such as generating dependencies and -being listed with the @samp{-H} option, except that the first directory -searched for @var{file} is the preprocessor's working directory -@emph{instead of} the directory containing the main source file. If not -found there, it is searched for in the remainder of the @code{#include -"..."} search chain as normal. - -@item -idirafter @var{dir} -@findex -idirafter -@cindex second include path -Add the directory @var{dir} to the second include path, marking it as a -system directory. The directories on the second include path are searched -when a header file is not found in any of the directories in the main -include path (the one that @samp{-I} adds to). - -@item -iprefix @var{prefix} -@findex -iprefix -Specify @var{prefix} as the prefix for subsequent @samp{-iwithprefix} -options. If the prefix represents a directory, you should include the -final @samp{/}. - -@item -iwithprefix @var{dir} -@findex -iwithprefix -Add a directory to the second include path, marking it as a system -directory. The directory's name is made by concatenating @var{prefix} -and @var{dir}, where @var{prefix} was specified previously with -@samp{-iprefix}. - -@item -isystem @var{dir} -@findex -isystem -Add a directory to the beginning of the second include path, marking it -as a system directory, so that it gets the same special treatment as -is applied to the standard system directories. @xref{System Headers}. - -@item -x c -@itemx -x c++ -@itemx -x objective-c -@itemx -x assembler-with-cpp -@findex -x c -@findex -x objective-c -@findex -x assembler-with-cpp -Specify the source language: C, C++, Objective-C, or assembly. This has -nothing to do with standards conformance or extensions; it merely -selects which base syntax to expect. If you give none of these options, -cpp will deduce the language from the extension of the source file: -@samp{.c}, @samp{.cc}, @samp{.m}, or @samp{.S}. Some other common -extensions for C++ and assembly are also recognized. If cpp does not -recognize the extension, it will treat the file as C; this is the most -generic mode. - -@strong{Note:} Previous versions of cpp accepted a @samp{-lang} option -which selected both the language and the standards conformance level. -This option has been removed, because it conflicts with the @samp{-l} -option. - -@item -std=@var{standard} -@itemx -ansi -@findex -std -@findex -ansi -Specify the standard to which the code should conform. Currently cpp -only knows about the standards for C; other language standards will be -added in the future. - -@var{standard} -may be one of: -@table @code -@item iso9899:1990 -@itemx c89 -The ISO C standard from 1990. @samp{c89} is the customary shorthand for -this version of the standard. - -The @samp{-ansi} option is equivalent to @samp{-std=c89}. - -@item iso9899:199409 -The 1990 C standard, as amended in 1994. - -@item iso9899:1999 -@itemx c99 -@itemx iso9899:199x -@itemx c9x -The revised ISO C standard, published in December 1999. Before -publication, this was known as C9X. - -@item gnu89 -The 1990 C standard plus GNU extensions. This is the default. - -@item gnu99 -@itemx gnu9x -The 1999 C standard plus GNU extensions. -@end table - -@item -ftabstop=NUMBER -@findex -ftabstop -Set the distance between tab stops. This helps the preprocessor -report correct column numbers in warnings or errors, even if tabs appear -on the line. Values less than 1 or greater than 100 are ignored. The -default is 8. - -@item -$ -@findex -$ -Forbid the use of @samp{$} in identifiers. The C standard allows -implementations to define extra characters that can appear in -identifiers. By default the GNU C preprocessor permits @samp{$}, a -common extension. -@end table -@c man end - -@node Concept Index, Index, Invocation, Top -@unnumbered Concept Index -@printindex cp - -@node Index,, Concept Index, Top -@unnumbered Index of Directives, Macros and Options -@printindex fn - -@contents -@bye diff --git a/gcc/cppinternals.texi b/gcc/cppinternals.texi deleted file mode 100644 index 2a038cb259e..00000000000 --- a/gcc/cppinternals.texi +++ /dev/null @@ -1,430 +0,0 @@ -\input texinfo -@setfilename cppinternals.info -@settitle The GNU C Preprocessor Internals - -@ifinfo -@dircategory Programming -@direntry -* Cpplib: (cppinternals). Cpplib internals. -@end direntry -@end ifinfo - -@c @smallbook -@c @cropmarks -@c @finalout -@setchapternewpage odd -@ifinfo -This file documents the internals of the GNU C Preprocessor. - -Copyright 2000, 2001 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -@ignore -Permission is granted to process this file through Tex and print the -results, provided the printed document carries copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). - -@end ignore -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that -the entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. -@end ifinfo - -@titlepage -@c @finalout -@title Cpplib Internals -@subtitle Last revised Jan 2001 -@subtitle for GCC version 3.0 -@author Neil Booth -@page -@vskip 0pt plus 1filll -@c man begin COPYRIGHT -Copyright @copyright{} 2000, 2001 -Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that -the entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions. -@c man end -@end titlepage -@page - -@node Top, Conventions,, (DIR) -@chapter Cpplib - the core of the GNU C Preprocessor - -The GNU C preprocessor in GCC 3.0 has been completely rewritten. It is -now implemented as a library, cpplib, so it can be easily shared between -a stand-alone preprocessor, and a preprocessor integrated with the C, -C++ and Objective C front ends. It is also available for use by other -programs, though this is not recommended as its exposed interface has -not yet reached a point of reasonable stability. - -This library has been written to be re-entrant, so that it can be used -to preprocess many files simultaneously if necessary. It has also been -written with the preprocessing token as the fundamental unit; the -preprocessor in previous versions of GCC would operate on text strings -as the fundamental unit. - -This brief manual documents some of the internals of cpplib, and a few -tricky issues encountered. It also describes certain behaviour we would -like to preserve, such as the format and spacing of its output. - -Identifiers, macro expansion, hash nodes, lexing. - -@menu -* Conventions:: Conventions used in the code. -* Lexer:: The combined C, C++ and Objective C Lexer. -* Whitespace:: Input and output newlines and whitespace. -* Hash Nodes:: All identifiers are hashed. -* Macro Expansion:: Macro expansion algorithm. -* Files:: File handling. -* Index:: Index. -@end menu - -@node Conventions, Lexer, Top, Top -@unnumbered Conventions -@cindex interface -@cindex header files - -cpplib has two interfaces - one is exposed internally only, and the -other is for both internal and external use. - -The convention is that functions and types that are exposed to multiple -files internally are prefixed with @samp{_cpp_}, and are to be found in -the file @samp{cpphash.h}. Functions and types exposed to external -clients are in @samp{cpplib.h}, and prefixed with @samp{cpp_}. For -historical reasons this is no longer quite true, but we should strive to -stick to it. - -We are striving to reduce the information exposed in cpplib.h to the -bare minimum necessary, and then to keep it there. This makes clear -exactly what external clients are entitled to assume, and allows us to -change internals in the future without worrying whether library clients -are perhaps relying on some kind of undocumented implementation-specific -behaviour. - -@node Lexer, Whitespace, Conventions, Top -@unnumbered The Lexer -@cindex lexer -@cindex tokens - -The lexer is contained in the file @samp{cpplex.c}. We want to have a -lexer that is single-pass, for efficiency reasons. We would also like -the lexer to only step forwards through the input files, and not step -back. This will make future changes to support different character -sets, in particular state or shift-dependent ones, much easier. - -This file also contains all information needed to spell a token, i.e. to -output it either in a diagnostic or to a preprocessed output file. This -information is not exported, but made available to clients through such -functions as @samp{cpp_spell_token} and @samp{cpp_token_len}. - -The most painful aspect of lexing ISO-standard C and C++ is handling -trigraphs and backlash-escaped newlines. Trigraphs are processed before -any interpretation of the meaning of a character is made, and unfortunately -there is a trigraph representation for a backslash, so it is possible for -the trigraph @samp{??/} to introduce an escaped newline. - -Escaped newlines are tedious because theoretically they can occur -anywhere - between the @samp{+} and @samp{=} of the @samp{+=} token, -within the characters of an identifier, and even between the @samp{*} -and @samp{/} that terminates a comment. Moreover, you cannot be sure -there is just one - there might be an arbitrarily long sequence of them. - -So the routine @samp{parse_identifier}, that lexes an identifier, cannot -assume that it can scan forwards until the first non-identifier -character and be done with it, because this could be the @samp{\} -introducing an escaped newline, or the @samp{?} introducing the trigraph -sequence that represents the @samp{\} of an escaped newline. Similarly -for the routine that handles numbers, @samp{parse_number}. If these -routines stumble upon a @samp{?} or @samp{\}, they call -@samp{skip_escaped_newlines} to skip over any potential escaped newlines -before checking whether they can finish. - -Similarly code in the main body of @samp{_cpp_lex_token} cannot simply -check for a @samp{=} after a @samp{+} character to determine whether it -has a @samp{+=} token; it needs to be prepared for an escaped newline of -some sort. These cases use the function @samp{get_effective_char}, -which returns the first character after any intervening newlines. - -The lexer needs to keep track of the correct column position, -including counting tabs as specified by the @samp{-ftabstop=} option. -This should be done even within comments; C-style comments can appear in -the middle of a line, and we want to report diagnostics in the correct -position for text appearing after the end of the comment. - -Some identifiers, such as @samp{__VA_ARGS__} and poisoned identifiers, -may be invalid and require a diagnostic. However, if they appear in a -macro expansion we don't want to complain with each use of the macro. -It is therefore best to catch them during the lexing stage, in -@samp{parse_identifier}. In both cases, whether a diagnostic is needed -or not is dependent upon lexer state. For example, we don't want to -issue a diagnostic for re-poisoning a poisoned identifier, or for using -@samp{__VA_ARGS__} in the expansion of a variable-argument macro. -Therefore @samp{parse_identifier} makes use of flags to determine -whether a diagnostic is appropriate. Since we change state on a -per-token basis, and don't lex whole lines at a time, this is not a -problem. - -Another place where state flags are used to change behaviour is whilst -parsing header names. Normally, a @samp{<} would be lexed as a single -token. After a @code{#include} directive, though, it should be lexed -as a single token as far as the nearest @samp{>} character. Note that -we don't allow the terminators of header names to be escaped; the first -@samp{"} or @samp{>} terminates the header name. - -Interpretation of some character sequences depends upon whether we are -lexing C, C++ or Objective C, and on the revision of the standard in -force. For example, @samp{::} is a single token in C++, but two -separate @samp{:} tokens, and almost certainly a syntax error, in C. -Such cases are handled in the main function @samp{_cpp_lex_token}, based -upon the flags set in the @samp{cpp_options} structure. - -Note we have almost, but not quite, achieved the goal of not stepping -backwards in the input stream. Currently @samp{skip_escaped_newlines} -does step back, though with care it should be possible to adjust it so -that this does not happen. For example, one tricky issue is if we meet -a trigraph, but the command line option @samp{-trigraphs} is not in -force but @samp{-Wtrigraphs} is, we need to warn about it but then -buffer it and continue to treat it as 3 separate characters. - -@node Whitespace, Hash Nodes, Lexer, Top -@unnumbered Whitespace -@cindex whitespace -@cindex newlines -@cindex escaped newlines -@cindex paste avoidance -@cindex line numbers - -The lexer has been written to treat each of @samp{\r}, @samp{\n}, -@samp{\r\n} and @samp{\n\r} as a single new line indicator. This allows -it to transparently preprocess MS-DOS, Macintosh and Unix files without -their needing to pass through a special filter beforehand. - -We also decided to treat a backslash, either @samp{\} or the trigraph -@samp{??/}, separated from one of the above newline indicators by -non-comment whitespace only, as intending to escape the newline. It -tends to be a typing mistake, and cannot reasonably be mistaken for -anything else in any of the C-family grammars. Since handling it this -way is not strictly conforming to the ISO standard, the library issues a -warning wherever it encounters it. - -Handling newlines like this is made simpler by doing it in one place -only. The function @samp{handle_newline} takes care of all newline -characters, and @samp{skip_escaped_newlines} takes care of arbitrarily -long sequences of escaped newlines, deferring to @samp{handle_newline} -to handle the newlines themselves. - -Another whitespace issue only concerns the stand-alone preprocessor: we -want to guarantee that re-reading the preprocessed output results in an -identical token stream. Without taking special measures, this might not -be the case because of macro substitution. We could simply insert a -space between adjacent tokens, but ideally we would like to keep this to -a minimum, both for aesthetic reasons and because it causes problems for -people who still try to abuse the preprocessor for things like Fortran -source and Makefiles. - -The token structure contains a flags byte, and two flags are of interest -here: @samp{PREV_WHITE} and @samp{AVOID_LPASTE}. @samp{PREV_WHITE} -indicates that the token was preceded by whitespace; if this is the case -we need not worry about it incorrectly pasting with its predecessor. -The @samp{AVOID_LPASTE} flag is set by the macro expansion routines, and -indicates that paste avoidance by insertion of a space to the left of -the token may be necessary. Recursively, the first token of a macro -substitution, the first token after a macro substitution, the first -token of a substituted argument, and the first token after a substituted -argument are all flagged @samp{AVOID_LPASTE} by the macro expander. - -If a token flagged in this way does not have a @samp{PREV_WHITE} flag, -and the routine @var{cpp_avoid_paste} determines that it might be -misinterpreted by the lexer if a space is not inserted between it and -the immediately preceding token, then stand-alone CPP's output routines -will insert a space between them. To avoid excessive spacing, -@var{cpp_avoid_paste} tries hard to only request a space if one is -likely to be necessary, but for reasons of efficiency it is slightly -conservative and might recommend a space where one is not strictly -needed. - -Finally, the preprocessor takes great care to ensure it keeps track of -both the position of a token in the source file, for diagnostic -purposes, and where it should appear in the output file, because using -CPP for other languages like assembler requires this. The two positions -may differ for the following reasons: - -@itemize @bullet -@item -Escaped newlines are deleted, so lines spliced in this way are joined to -form a single logical line. - -@item -A macro expansion replaces the tokens that form its invocation, but any -newlines appearing in the macro's arguments are interpreted as a single -space, with the result that the macro's replacement appears in full on -the same line that the macro name appeared in the source file. This is -particularly important for stringification of arguments - newlines -embedded in the arguments must appear in the string as spaces. -@end itemize - -The source file location is maintained in the @var{lineno} member of the -@var{cpp_buffer} structure, and the column number inferred from the -current position in the buffer relative to the @var{line_base} buffer -variable, which is updated with every newline whether escaped or not. - -TODO: Finish this. - -@node Hash Nodes, Macro Expansion, Whitespace, Top -@unnumbered Hash Nodes -@cindex hash table -@cindex identifiers -@cindex macros -@cindex assertions -@cindex named operators - -When cpplib encounters an "identifier", it generates a hash code for it -and stores it in the hash table. By "identifier" we mean tokens with -type @samp{CPP_NAME}; this includes identifiers in the usual C sense, as -well as keywords, directive names, macro names and so on. For example, -all of "pragma", "int", "foo" and "__GNUC__" are identifiers and hashed -when lexed. - -Each node in the hash table contain various information about the -identifier it represents. For example, its length and type. At any one -time, each identifier falls into exactly one of three categories: - -@itemize @bullet -@item Macros - -These have been declared to be macros, either on the command line or -with @code{#define}. A few, such as @samp{__TIME__} are builtins -entered in the hash table during initialisation. The hash node for a -normal macro points to a structure with more information about the -macro, such as whether it is function-like, how many arguments it takes, -and its expansion. Builtin macros are flagged as special, and instead -contain an enum indicating which of the various builtin macros it is. - -@item Assertions - -Assertions are in a separate namespace to macros. To enforce this, cpp -actually prepends a @code{#} character before hashing and entering it in -the hash table. An assertion's node points to a chain of answers to -that assertion. - -@item Void - -Everything else falls into this category - an identifier that is not -currently a macro, or a macro that has since been undefined with -@code{#undef}. - -When preprocessing C++, this category also includes the named operators, -such as @samp{xor}. In expressions these behave like the operators they -represent, but in contexts where the spelling of a token matters they -are spelt differently. This spelling distinction is relevant when they -are operands of the stringizing and pasting macro operators @code{#} and -@code{##}. Named operator hash nodes are flagged, both to catch the -spelling distinction and to prevent them from being defined as macros. -@end itemize - -The same identifiers share the same hash node. Since each identifier -token, after lexing, contains a pointer to its hash node, this is used -to provide rapid lookup of various information. For example, when -parsing a @code{#define} statement, CPP flags each argument's identifier -hash node with the index of that argument. This makes duplicated -argument checking an O(1) operation for each argument. Similarly, for -each identifier in the macro's expansion, lookup to see if it is an -argument, and which argument it is, is also an O(1) operation. Further, -each directive name, such as @samp{endif}, has an associated directive -enum stored in its hash node, so that directive lookup is also O(1). - -@node Macro Expansion, Files, Hash Nodes, Top -@unnumbered Macro Expansion Algorithm - -@node Files, Index, Macro Expansion, Top -@unnumbered File Handling -@cindex files - -Fairly obviously, the file handling code of cpplib resides in the file -@samp{cppfiles.c}. It takes care of the details of file searching, -opening, reading and caching, for both the main source file and all the -headers it recursively includes. - -The basic strategy is to minimize the number of system calls. On many -systems, the basic @code{open ()} and @code{fstat ()} system calls can -be quite expensive. For every @code{#include}-d file, we need to try -all the directories in the search path until we find a match. Some -projects, such as glibc, pass twenty or thirty include paths on the -command line, so this can rapidly become time consuming. - -For a header file we have not encountered before we have little choice -but to do this. However, it is often the case that the same headers are -repeatedly included, and in these cases we try to avoid repeating the -filesystem queries whilst searching for the correct file. - -For each file we try to open, we store the constructed path in a splay -tree. This path first undergoes simplification by the function -@code{_cpp_simplify_pathname}. For example, -@samp{/usr/include/bits/../foo.h} is simplified to -@samp{/usr/include/foo.h} before we enter it in the splay tree and try -to @code{open ()} the file. CPP will then find subsequent uses of -@samp{foo.h}, even as @samp{/usr/include/foo.h}, in the splay tree and -save system calls. - -Further, it is likely the file contents have also been cached, saving a -@code{read ()} system call. We don't bother caching the contents of -header files that are re-inclusion protected, and whose re-inclusion -macro is defined when we leave the header file for the first time. If -the host supports it, we try to map suitably large files into memory, -rather than reading them in directly. - -The include paths are internally stored on a null-terminated -singly-linked list, starting with the @code{"header.h"} directory search -chain, which then links into the @code{} directory chain. - -Files included with the @code{} syntax start the lookup directly -in the second half of this chain. However, files included with the -@code{"foo.h"} syntax start at the beginning of the chain, but with one -extra directory prepended. This is the directory of the current file; -the one containing the @code{#include} directive. Prepending this -directory on a per-file basis is handled by the function -@code{search_from}. - -Note that a header included with a directory component, such as -@code{#include "mydir/foo.h"} and opened as -@samp{/usr/local/include/mydir/foo.h}, will have the complete path minus -the basename @samp{foo.h} as the current directory. - -Enough information is stored in the splay tree that CPP can immediately -tell whether it can skip the header file because of the multiple include -optimisation, whether the file didn't exist or couldn't be opened for -some reason, or whether the header was flagged not to be re-used, as it -is with the obsolete @code{#import} directive. - -For the benefit of MS-DOS filesystems with an 8.3 filename limitation, -CPP offers the ability to treat various include file names as aliases -for the real header files with shorter names. The map from one to the -other is found in a special file called @samp{header.gcc}, stored in the -command line (or system) include directories to which the mapping -applies. This may be higher up the directory tree than the full path to -the file minus the base name. - -@node Index,, Files, Top -@unnumbered Index -@printindex cp - -@contents -@bye diff --git a/gcc/doc/.cvsignore b/gcc/doc/.cvsignore new file mode 100644 index 00000000000..26fdfb2454c --- /dev/null +++ b/gcc/doc/.cvsignore @@ -0,0 +1,3 @@ +gcc.info* +cpp.info* +cppinternals.info* diff --git a/gcc/doc/c-tree.texi b/gcc/doc/c-tree.texi new file mode 100644 index 00000000000..ad9cb94f051 --- /dev/null +++ b/gcc/doc/c-tree.texi @@ -0,0 +1,2232 @@ +@c Copyright (c) 1999, 2000, 2001 Free Software Foundation, Inc. +@c Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@c --------------------------------------------------------------------- +@c Trees +@c --------------------------------------------------------------------- + +@node Trees +@chapter Trees: The intermediate representation used by the C and C++ front-ends +@cindex Trees +@cindex C/C++ Internal Representation + +This chapter documents the internal representation used by GCC and C++ to +represent C and C++ source programs. When presented with a C or C++ +source program, GCC parses the program, performs semantic analysis +(including the generation of error messages), and then produces the +internal representation described here. This representation contains a +complete representation for the entire translation unit provided as +input to the front-end. This representation is then typically processed +by a code-generator in order to produce machine code, but could also be +used in the creation of source browsers, intelligent editors, automatic +documentation generators, interpreters, and any other programs needing +the ability to process C or C++ code. + +This chapter explains the internal representation. In particular, it +documents the internal representation for C and C++ source +constructs, and the macros, functions, and variables that can be used to +access these constructs. The C++ representation which is largely a superset +of the representation used in the C front-end. There is only one +construct used in C that does not appear in the C++ front-end and that +is the GNU ``nested function'' extension. Many of the macros documented +here do not apply in C because the corresponding language constructs do +not appear in C. + +If you are developing a ``back-end'', be it is a code-generator or some +other tool, that uses this representation, you may occasionally find +that you need to ask questions not easily answered by the functions and +macros available here. If that situation occurs, it is quite likely +that GCC already supports the functionality you desire, but that the +interface is simply not documented here. In that case, you should ask +the GCC maintainers (via mail to @email{gcc@@gcc.gnu.org}) about +documenting the functionality you require. Similarly, if you find +yourself writing functions that do not deal directly with your back-end, +but instead might be useful to other people using the GCC front-end, you +should submit your patches for inclusion in GCC. + +@menu +* Deficiencies:: Topics net yet covered in this document. +* Tree overview:: All about @code{tree}s. +* Types:: Fundamental and aggregate types. +* Scopes:: Namespaces and classes. +* Functions:: Overloading, function bodies, and linkage. +* Declarations:: Type declarations and variables. +* Expression trees:: From @code{typeid} to @code{throw}. +@end menu + +@c --------------------------------------------------------------------- +@c Deficiencies +@c --------------------------------------------------------------------- + +@node Deficiencies +@section Deficiencies + +There are many places in which this document is incomplet and incorrekt. +It is, as of yet, only @emph{preliminary} documentation. + +@c --------------------------------------------------------------------- +@c Overview +@c --------------------------------------------------------------------- + +@node Tree overview +@section Overview +@cindex tree +@findex TREE_CODE + +The central data structure used by the internal representation is the +@code{tree}. These nodes, while all of the C type @code{tree}, are of +many varieties. A @code{tree} is a pointer type, but the object to +which it points may be of a variety of types. From this point forward, +we will refer to trees in ordinary type, rather than in @code{this +font}, except when talking about the actual C type @code{tree}. + +You can tell what kind of node a particular tree is by using the +@code{TREE_CODE} macro. Many, many macros take a trees as input and +return trees as output. However, most macros require a certain kinds of +tree node as input. In other words, there is a type-system for trees, +but it is not reflected in the C type-system. + +For safety, it is useful to configure G++ with @code{--enable-checking}. +Although this results in a significant performance penalty (since all +tree types are checked at run-time), and is therefore inappropriate in a +release version, it is extremely helpful during the development process. + +Many macros behave as predicates. Many, although not all, of these +predicates end in @samp{_P}. Do not rely on the result type of these +macros being of any particular type. You may, however, rely on the fact +that the type can be compared to @code{0}, so that statements like +@example +if (TEST_P (t) && !TEST_P (y)) + x = 1; +@end example +@noindent +and +@example +int i = (TEST_P (t) != 0); +@end example +@noindent +are legal. Macros that return @code{int} values now may be changed to +return @code{tree} values, or other pointers in the future. Even those +that continue to return @code{int} may return multiple non-zero codes +where previously they returned only zero and one. Therefore, you should +not write code like +@example +if (TEST_P (t) == 1) +@end example +@noindent +as this code is not guaranteed to work correctly in the future. + +You should not take the address of values returned by the macros or +functions described here. In particular, no guarantee is given that the +values are lvalues. + +In general, the names of macros are all in uppercase, while the names of +functions are entirely in lower case. There are rare exceptions to this +rule. You should assume that any macro or function whose name is made +up entirely of uppercase letters may evaluate its arguments more than +once. You may assume that a macro or function whose name is made up +entirely of lowercase letters will evaluate its arguments only once. + +The @code{error_mark_node} is a special tree. Its tree code is +@code{ERROR_MARK}, but since there is only ever one node with that code, +the usual practice is to compare the tree against +@code{error_mark_node}. (This test is just a test for pointer +equality.) If an error has occurred during front-end processing the +flag @code{errorcount} will be set. If the front-end has encountered +code it cannot handle, it will issue a message to the user and set +@code{sorrycount}. When these flags are set, any macro or function +which normally returns a tree of a particular kind may instead return +the @code{error_mark_node}. Thus, if you intend to do any processing of +erroneous code, you must be prepared to deal with the +@code{error_mark_node}. + +Occasionally, a particular tree slot (like an operand to an expression, +or a particular field in a declaration) will be referred to as +``reserved for the back-end.'' These slots are used to store RTL when +the tree is converted to RTL for use by the GCC back-end. However, if +that process is not taking place (e.g., if the front-end is being hooked +up to an intelligent editor), then those slots may be used by the +back-end presently in use. + +If you encounter situations that do not match this documentation, such +as tree nodes of types not mentioned here, or macros documented to +return entities of a particular kind that instead return entities of +some different kind, you have found a bug, either in the front-end or in +the documentation. Please report these bugs as you would any other +bug. + +@menu +* Macros and Functions::Macros and functions that can be used with all trees. +* Identifiers:: The names of things. +* Containers:: Lists and vectors. +@end menu + +@c --------------------------------------------------------------------- +@c Trees +@c --------------------------------------------------------------------- + +@node Macros and Functions +@subsection Trees +@cindex tree + +This section is not here yet. + +@c --------------------------------------------------------------------- +@c Identifiers +@c --------------------------------------------------------------------- + +@node Identifiers +@subsection Identifiers +@cindex identifier +@cindex name +@tindex IDENTIFIER_NODE + +An @code{IDENTIFIER_NODE} represents a slightly more general concept +that the standard C or C++ concept of identifier. In particular, an +@code{IDENTIFIER_NODE} may contain a @samp{$}, or other extraordinary +characters. + +There are never two distinct @code{IDENTIFIER_NODE}s representing the +same identifier. Therefore, you may use pointer equality to compare +@code{IDENTIFIER_NODE}s, rather than using a routine like @code{strcmp}. + +You can use the following macros to access identifiers: +@ftable @code +@item IDENTIFIER_POINTER +The string represented by the identifier, represented as a +@code{char*}. This string is always @code{NUL}-terminated, and contains +no embedded @code{NUL} characters. + +@item IDENTIFIER_LENGTH +The length of the string returned by @code{IDENTIFIER_POINTER}, not +including the trailing @code{NUL}. This value of +@code{IDENTIFIER_LENGTH (x)} is always the same as @code{strlen +(IDENTIFIER_POINTER (x))}. + +@item IDENTIFIER_OPNAME_P +This predicate holds if the identifier represents the name of an +overloaded operator. In this case, you should not depend on the +contents of either the @code{IDENTIFIER_POINTER} or the +@code{IDENTIFIER_LENGTH}. + +@item IDENTIFIER_TYPENAME_P +This predicate holds if the identifier represents the name of a +user-defined conversion operator. In this case, the @code{TREE_TYPE} of +the @code{IDENTIFIER_NODE} holds the type to which the conversion +operator converts. + +@end ftable + +@c --------------------------------------------------------------------- +@c Containers +@c --------------------------------------------------------------------- + +@node Containers +@subsection Containers +@cindex container +@cindex list +@cindex vector +@tindex TREE_LIST +@tindex TREE_VEC +@findex TREE_PURPOSE +@findex TREE_VALUE +@findex TREE_VEC_LENGTH +@findex TREE_VEC_ELT + +Two common container data structures can be represented directly with +tree nodes. A @code{TREE_LIST} is a singly linked list containing two +trees per node. These are the @code{TREE_PURPOSE} and @code{TREE_VALUE} +of each node. (Often, the @code{TREE_PURPOSE} contains some kind of +tag, or additional information, while the @code{TREE_VALUE} contains the +majority of the payload. In other cases, the @code{TREE_PURPOSE} is +simply @code{NULL_TREE}, while in still others both the +@code{TREE_PURPOSE} and @code{TREE_VALUE} are of equal stature.) Given +one @code{TREE_LIST} node, the next node is found by following the +@code{TREE_CHAIN}. If the @code{TREE_CHAIN} is @code{NULL_TREE}, then +you have reached the end of the list. + +A @code{TREE_VEC} is a simple vector. The @code{TREE_VEC_LENGTH} is an +integer (not a tree) giving the number of nodes in the vector. The +nodes themselves are accessed using the @code{TREE_VEC_ELT} macro, which +takes two arguments. The first is the @code{TREE_VEC} in question; the +second is an integer indicating which element in the vector is desired. +The elements are indexed from zero. + +@c --------------------------------------------------------------------- +@c Types +@c --------------------------------------------------------------------- + +@node Types +@section Types +@cindex type +@cindex pointer +@cindex reference +@cindex fundamental type +@cindex array +@tindex VOID_TYPE +@tindex INTEGER_TYPE +@tindex TYPE_MIN_VALUE +@tindex TYPE_MAX_VALUE +@tindex REAL_TYPE +@tindex COMPLEX_TYPE +@tindex ENUMERAL_TYPE +@tindex BOOLEAN_TYPE +@tindex POINTER_TYPE +@tindex REFERENCE_TYPE +@tindex FUNCTION_TYPE +@tindex METHOD_TYPE +@tindex ARRAY_TYPE +@tindex RECORD_TYPE +@tindex UNION_TYPE +@tindex UNKNOWN_TYPE +@tindex OFFSET_TYPE +@tindex TYPENAME_TYPE +@tindex TYPEOF_TYPE +@findex CP_TYPE_QUALS +@findex TYPE_UNQUALIFIED +@findex TYPE_QUAL_CONST +@findex TYPE_QUAL_VOLATILE +@findex TYPE_QUAL_RESTRICT +@findex TYPE_MAIN_VARIANT +@cindex qualified type +@findex TYPE_SIZE +@findex TYPE_ALIGN +@findex TYPE_PRECISION +@findex TYPE_ARG_TYPES +@findex TYPE_METHOD_BASETYPE +@findex TYPE_PTRMEM_P +@findex TYPE_OFFSET_BASETYPE +@findex TREE_TYPE +@findex TYPE_CONTEXT +@findex TYPE_NAME +@findex TYPENAME_TYPE_FULLNAME +@findex TYPE_FIELDS +@findex TYPE_PTROBV_P + +All types have corresponding tree nodes. However, you should not assume +that there is exactly one tree node corresponding to each type. There +are often several nodes each of which correspond to the same type. + +For the most part, different kinds of types have different tree codes. +(For example, pointer types use a @code{POINTER_TYPE} code while arrays +use an @code{ARRAY_TYPE} code.) However, pointers to member functions +use the @code{RECORD_TYPE} code. Therefore, when writing a +@code{switch} statement that depends on the code associated with a +particular type, you should take care to handle pointers to member +functions under the @code{RECORD_TYPE} case label. + +In C++, an array type is not qualified; rather the type of the array +elements is qualified. This situation is reflected in the intermediate +representation. The macros described here will always examine the +qualification of the underlying element type when applied to an array +type. (If the element type is itself an array, then the recursion +continues until a non-array type is found, and the qualification of this +type is examined.) So, for example, @code{CP_TYPE_CONST_P} will hold of +the type @code{const int ()[7]}, denoting an array of seven @code{int}s. + +The following functions and macros deal with cv-qualification of types: +@ftable @code +@item CP_TYPE_QUALS +This macro returns the set of type qualifiers applied to this type. +This value is @code{TYPE_UNQUALIFIED} if no qualifiers have been +applied. The @code{TYPE_QUAL_CONST} bit is set if the type is +@code{const}-qualified. The @code{TYPE_QUAL_VOLATILE} bit is set if the +type is @code{volatile}-qualified. The @code{TYPE_QUAL_RESTRICT} bit is +set if the type is @code{restrict}-qualified. + +@item CP_TYPE_CONST_P +This macro holds if the type is @code{const}-qualified. + +@item CP_TYPE_VOLATILE_P +This macro holds if the type is @code{volatile}-qualified. + +@item CP_TYPE_RESTRICT_P +This macro holds if the type is @code{restrict}-qualified. + +@item CP_TYPE_CONST_NON_VOLATILE_P +This predicate holds for a type that is @code{const}-qualified, but +@emph{not} @code{volatile}-qualified; other cv-qualifiers are ignored as +well: only the @code{const}-ness is tested. + +@item TYPE_MAIN_VARIANT +This macro returns the unqualified version of a type. It may be applied +to an unqualified type, but it is not always the identity function in +that case. +@end ftable + +A few other macros and functions are usable with all types: +@ftable @code +@item TYPE_SIZE +The number of bits required to represent the type, represented as an +@code{INTEGER_CST}. For an incomplete type, @code{TYPE_SIZE} will be +@code{NULL_TREE}. + +@item TYPE_ALIGN +The alignment of the type, in bits, represented as an @code{int}. + +@item TYPE_NAME +This macro returns a declaration (in the form of a @code{TYPE_DECL}) for +the type. (Note this macro does @emph{not} return a +@code{IDENTIFIER_NODE}, as you might expect, given its name!) You can +look at the @code{DECL_NAME} of the @code{TYPE_DECL} to obtain the +actual name of the type. The @code{TYPE_NAME} will be @code{NULL_TREE} +for a type that is not a builtin type, the result of a typedef, or a +named class type. + +@item CP_INTEGRAL_TYPE +This predicate holds if the type is an integral type. Notice that in +C++, enumerations are @emph{not} integral types. + +@item ARITHMETIC_TYPE_P +This predicate holds if the type is an integral type (in the C++ sense) +or a floating point type. + +@item CLASS_TYPE_P +This predicate holds for a class-type. + +@item TYPE_BUILT_IN +This predicate holds for a builtin type. + +@item TYPE_PTRMEM_P +This predicate holds if the type is a pointer to data member. + +@item TYPE_PTR_P +This predicate holds if the type is a pointer type, and the pointee is +not a data member. + +@item TYPE_PTRFN_P +This predicate holds for a pointer to function type. + +@item TYPE_PTROB_P +This predicate holds for a pointer to object type. Note however that it +does not hold for the generic pointer to object type @code{void *}. You +may use @code{TYPE_PTROBV_P} to test for a pointer to object type as +well as @code{void *}. + +@item same_type_p +This predicate takes two types as input, and holds if they are the same +type. For example, if one type is a @code{typedef} for the other, or +both are @code{typedef}s for the same type. This predicate also holds if +the two trees given as input are simply copies of one another; i.e., +there is no difference between them at the source level, but, for +whatever reason, a duplicate has been made in the representation. You +should never use @code{==} (pointer equality) to compare types; always +use @code{same_type_p} instead. +@end ftable + +Detailed below are the various kinds of types, and the macros that can +be used to access them. Although other kinds of types are used +elsewhere in G++, the types described here are the only ones that you +will encounter while examining the intermediate representation. + +@table @code +@item VOID_TYPE +Used to represent the @code{void} type. + +@item INTEGER_TYPE +Used to represent the various integral types, including @code{char}, +@code{short}, @code{int}, @code{long}, and @code{long long}. This code +is not used for enumeration types, nor for the @code{bool} type. Note +that GCC's @code{CHAR_TYPE} node is @emph{not} used to represent +@code{char}. The @code{TYPE_PRECISION} is the number of bits used in +the representation, represented as an @code{unsigned int}. (Note that +in the general case this is not the same value as @code{TYPE_SIZE}; +suppose that there were a 24-bit integer type, but that alignment +requirements for the ABI required 32-bit alignment. Then, +@code{TYPE_SIZE} would be an @code{INTEGER_CST} for 32, while +@code{TYPE_PRECISION} would be 24.) The integer type is unsigned if +@code{TREE_UNSIGNED} holds; otherwise, it is signed. + +The @code{TYPE_MIN_VALUE} is an @code{INTEGER_CST} for the smallest +integer that may be represented by this type. Similarly, the +@code{TYPE_MAX_VALUE} is an @code{INTEGER_CST} for the largest integer +that may be represented by this type. + +@item REAL_TYPE +Used to represent the @code{float}, @code{double}, and @code{long +double} types. The number of bits in the floating-point representation +is given by @code{TYPE_PRECISION}, as in the @code{INTEGER_TYPE} case. + +@item COMPLEX_TYPE +Used to represent GCC builtin @code{__complex__} data types. The +@code{TREE_TYPE} is the type of the real and imaginary parts. + +@item ENUMERAL_TYPE +Used to represent an enumeration type. The @code{TYPE_PRECISION} gives +(as an @code{int}), the number of bits used to represent the type. If +there are no negative enumeration constants, @code{TREE_UNSIGNED} will +hold. The minimum and maximum enumeration constants may be obtained +with @code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE}, respectively; each +of these macros returns an @code{INTEGER_CST}. + +The actual enumeration constants themselves may be obtained by looking +at the @code{TYPE_VALUES}. This macro will return a @code{TREE_LIST}, +containing the constants. The @code{TREE_PURPOSE} of each node will be +an @code{IDENTIFIER_NODE} giving the name of the constant; the +@code{TREE_VALUE} will be an @code{INTEGER_CST} giving the value +assigned to that constant. These constants will appear in the order in +which they were declared. The @code{TREE_TYPE} of each of these +constants will be the type of enumeration type itself. + +@item BOOLEAN_TYPE +Used to represent the @code{bool} type. + +@item POINTER_TYPE +Used to represent pointer types, and pointer to data member types. The +@code{TREE_TYPE} gives the type to which this type points. If the type +is a pointer to data member type, then @code{TYPE_PTRMEM_P} will hold. +For a pointer to data member type of the form @samp{T X::*}, +@code{TYPE_PTRMEM_CLASS_TYPE} will be the type @code{X}, while +@code{TYPE_PTRMEM_POINTED_TO_TYPE} will be the type @code{T}. + +@item REFERENCE_TYPE +Used to represent reference types. The @code{TREE_TYPE} gives the type +to which this type refers. + +@item FUNCTION_TYPE +Used to represent the type of non-member functions and of static member +functions. The @code{TREE_TYPE} gives the return type of the function. +The @code{TYPE_ARG_TYPES} are a @code{TREE_LIST} of the argument types. +The @code{TREE_VALUE} of each node in this list is the type of the +corresponding argument; the @code{TREE_PURPOSE} is an expression for the +default argument value, if any. If the last node in the list is +@code{void_list_node} (a @code{TREE_LIST} node whose @code{TREE_VALUE} +is the @code{void_type_node}), then functions of this type do not take +variable arguments. Otherwise, they do take a variable number of +arguments. + +Note that in C (but not in C++) a function declared like @code{void f()} +is an unprototyped function taking a variable number of arguments; the +@code{TYPE_ARG_TYPES} of such a function will be NULL. + +@item METHOD_TYPE +Used to represent the type of a non-static member function. Like a +@code{FUNCTION_TYPE}, the return type is given by the @code{TREE_TYPE}. +The type of @code{*this}, i.e., the class of which functions of this +type are a member, is given by the @code{TYPE_METHOD_BASETYPE}. The +@code{TYPE_ARG_TYPES} is the parameter list, as for a +@code{FUNCTION_TYPE}, and includes the @code{this} argument. + +@item ARRAY_TYPE +Used to represent array types. The @code{TREE_TYPE} gives the type of +the elements in the array. If the array-bound is present in the type, +the @code{TYPE_DOMAIN} is an @code{INTEGER_TYPE} whose +@code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE} will be the lower and +upper bounds of the array, respectively. The @code{TYPE_MIN_VALUE} will +always be an @code{INTEGER_CST} for zero, while the +@code{TYPE_MAX_VALUE} will be one less than the number of elements in +the array, i.e., the highest value which may be used to index an element +in the array. + +@item RECORD_TYPE +Used to represent @code{struct} and @code{class} types, as well as +pointers to member functions. If @code{TYPE_PTRMEMFUNC_P} holds, then +this type is a pointer-to-member type. In that case, the +@code{TYPE_PTRMEMFUNC_FN_TYPE} is a @code{POINTER_TYPE} pointing to a +@code{METHOD_TYPE}. The @code{METHOD_TYPE} is the type of a function +pointed to by the pointer-to-member function. If +@code{TYPE_PTRMEMFUNC_P} does not hold, this type is a class type. For +more information, see @pxref{Classes}. + +@item UNKNOWN_TYPE +This node is used to represent a type the knowledge of which is +insufficient for a sound processing. + +@item OFFSET_TYPE +This node is used to represent a data member; for example a +pointer-to-data-member is represented by a @code{POINTER_TYPE} whose +@code{TREE_TYPE} is an @code{OFFSET_TYPE}. For a data member @code{X::m} +the @code{TYPE_OFFSET_BASETYPE} is @code{X} and the @code{TREE_TYPE} is +the type of @code{m}. + +@item TYPENAME_TYPE +Used to represent a construct of the form @code{typename T::A}. The +@code{TYPE_CONTEXT} is @code{T}; the @code{TYPE_NAME} is an +@code{IDENTIFIER_NODE} for @code{A}. If the type is specified via a +template-id, then @code{TYPENAME_TYPE_FULLNAME} yields a +@code{TEMPLATE_ID_EXPR}. The @code{TREE_TYPE} is non-@code{NULL} if the +node is implicitly generated in support for the implicit typename +extension; in which case the @code{TREE_TYPE} is a type node for the +base-class. + +@item TYPEOF_TYPE +Used to represent the @code{__typeof__} extension. The +@code{TYPE_FIELDS} is the expression the type of which is being +represented. + +@item UNION_TYPE +Used to represent @code{union} types. For more information, @pxref{Classes}. +@end table + +There are variables whose values represent some of the basic types. +These include: +@table @code +@item void_type_node +A node for @code{void}. + +@item integer_type_node +A node for @code{int}. + +@item unsigned_type_node. +A node for @code{unsigned int}. + +@item char_type_node. +A node for @code{char}. +@end table +@noindent +It may sometimes be useful to compare one of these variables with a type +in hand, using @code{same_type_p}. + +@c --------------------------------------------------------------------- +@c Scopes +@c --------------------------------------------------------------------- + +@node Scopes +@section Scopes +@cindex namespace, class, scope + +The root of the entire intermediate representation is the variable +@code{global_namespace}. This is the namespace specified with @code{::} +in C++ source code. All other namespaces, types, variables, functions, +and so forth can be found starting with this namespace. + +Besides namespaces, the other high-level scoping construct in C++ is the +class. (Throughout this manual the term @dfn{class} is used to mean the +types referred to in the ANSI/ISO C++ Standard as classes; these include +types defined with the @code{class}, @code{struct}, and @code{union} +keywords.) + +@menu +* Namespaces:: Member functions, types, etc. +* Classes:: Members, bases, friends, etc. +@end menu + +@c --------------------------------------------------------------------- +@c Namespaces +@c --------------------------------------------------------------------- + +@node Namespaces +@subsection Namespaces +@cindex namespace +@tindex NAMESPACE_DECL + +A namespace is represented by a @code{NAMESPACE_DECL} node. + +However, except for the fact that it is distinguished as the root of the +representation, the global namespace is no different from any other +namespace. Thus, in what follows, we describe namespaces generally, +rather than the global namespace in particular. + +The @code{::std} namespace, however, @emph{is} special, unless +@code{flag_honor_std} is set. This variable is set by the use +@samp{-fhonor-std} (or an option that implies it, like +@samp{-fnew-abi}), when invoking G++. When @code{flag_honor_std} is +set, the @code{std} namespace is just like any other namespace. When +@code{flag_honor_std} is not set, however, the @code{::std} namespace is +treated as a synonym for the global namespace, thereby allowing users to +write code that will work with compilers that put the standard library +in the @code{::std} namespace, even though the library supplied with G++ +does not do so, as of GCC 2.95. The @code{std} namespace is represented +by the variable @code{std_node}. Although @code{std_node} is a +@code{NAMESPACE_DECL}, it does not have all the fields required of a +real namespace, and the macros and functions described here do not work, +in general. It is safest simply to ignore @code{std_node} should you +encounter it while examining the internal representation. In +particular, you will encounter @code{std_node} while looking at the +members of the global namespace. Just skip it without attempting to +examine its members. + +The following macros and functions can be used on a @code{NAMESPACE_DECL}: + +@ftable @code +@item DECL_NAME +This macro is used to obtain the @code{IDENTIFIER_NODE} corresponding to +the unqualified name of the name of the namespace (@pxref{Identifiers}). +The name of the global namespace is @samp{::}, even though in C++ the +global namespace is unnamed. However, you should use comparison with +@code{global_namespace}, rather than @code{DECL_NAME} to determine +whether or not a namespaces is the global one. An unnamed namespace +will have a @code{DECL_NAME} equal to @code{anonymous_namespace_name}. +Within a single translation unit, all unnamed namespaces will have the +same name. + +@item DECL_CONTEXT +This macro returns the enclosing namespace. The @code{DECL_CONTEXT} for +the @code{global_namespace} is @code{NULL_TREE}. + +@item DECL_NAMESPACE_ALIAS +If this declaration is for a namespace alias, then +@code{DECL_NAMESPACE_ALIAS} is the namespace for which this one is an +alias. + +Do not attempt to use @code{cp_namespace_decls} for a namespace which is +an alias. Instead, follow @code{DECL_NAMESPACE_ALIAS} links until you +reach an ordinary, non-alias, namespace, and call +@code{cp_namespace_decls} there. + +@item DECL_NAMESPACE_STD_P +This predicate holds if the namespace is the special @code{::std} +namespace. + +@item cp_namespace_decls +This function will return the declarations contained in the namespace, +including types, overloaded functions, other namespaces, and so forth. +If there are no declarations, this function will return +@code{NULL_TREE}. The declarations are connected through their +@code{TREE_CHAIN} fields. + +Although most entries on this list will be declarations, +@code{TREE_LIST} nodes may also appear. In this case, the +@code{TREE_VALUE} will be an @code{OVERLOAD}. The value of the +@code{TREE_PURPOSE} is unspecified; back-ends should ignore this value. +As with the other kinds of declarations returned by +@code{cp_namespace_decls}, the @code{TREE_CHAIN} will point to the next +declaration in this list. + +For more information on the kinds of declarations that can occur on this +list, @xref{Declarations}. Some declarations will not appear on this +list. In particular, no @code{FIELD_DECL}, @code{LABEL_DECL}, or +@code{PARM_DECL} nodes will appear here. + +This function cannot be used with namespaces that have +@code{DECL_NAMESPACE_ALIAS} set. + +@end ftable + +@c --------------------------------------------------------------------- +@c Classes +@c --------------------------------------------------------------------- + +@node Classes +@subsection Classes +@cindex class +@tindex RECORD_TYPE +@tindex UNION_TYPE +@findex CLASSTYPE_DECLARED_CLASS +@findex TYPE_BINFO +@findex BINFO_TYPE +@findex TREE_VIA_PUBLIC +@findex TREE_VIA_PROTECTED +@findex TREE_VIA_PRIVATE +@findex TYPE_FIELDS +@findex TYPE_VFIELD +@findex TYPE_METHODS + +A class type is represented by either a @code{RECORD_TYPE} or a +@code{UNION_TYPE}. A class declared with the @code{union} tag is +represented by a @code{UNION_TYPE}, while classes declared with either +the @code{struct} or the @code{class} tag are represented by +@code{RECORD_TYPE}s. You can use the @code{CLASSTYPE_DECLARED_CLASS} +macro to discern whether or not a particular type is a @code{class} as +opposed to a @code{struct}. This macro will be true only for classes +declared with the @code{class} tag. + +Almost all non-function members are available on the @code{TYPE_FIELDS} +list. Given one member, the next can be found by following the +@code{TREE_CHAIN}. You should not depend in any way on the order in +which fields appear on this list. All nodes on this list will be +@samp{DECL} nodes. A @code{FIELD_DECL} is used to represent a non-static +data member, a @code{VAR_DECL} is used to represent a static data +member, and a @code{TYPE_DECL} is used to represent a type. Note that +the @code{CONST_DECL} for an enumeration constant will appear on this +list, if the enumeration type was declared in the class. (Of course, +the @code{TYPE_DECL} for the enumeration type will appear here as well.) +There are no entries for base classes on this list. In particular, +there is no @code{FIELD_DECL} for the ``base-class portion'' of an +object. + +The @code{TYPE_VFIELD} is a compiler-generated field used to point to +virtual function tables. It may or may not appear on the +@code{TYPE_FIELDS} list. However, back-ends should handle the +@code{TYPE_VFIELD} just like all the entries on the @code{TYPE_FIELDS} +list. + +The function members are available on the @code{TYPE_METHODS} list. +Again, subsequent members are found by following the @code{TREE_CHAIN} +field. If a function is overloaded, each of the overloaded functions +appears; no @code{OVERLOAD} nodes appear on the @code{TYPE_METHODS} +list. Implicitly declared functions (including default constructors, +copy constructors, assignment operators, and destructors) will appear on +this list as well. + +Every class has an associated @dfn{binfo}, which can be obtained with +@code{TYPE_BINFO}. Binfos are used to represent base-classes. The +binfo given by @code{TYPE_BINFO} is the degenerate case, whereby every +class is considered to be its own base-class. The base classes for a +particular binfo can be obtained with @code{BINFO_BASETYPES}. These +base-classes are themselves binfos. The class type associated with a +binfo is given by @code{BINFO_TYPE}. It is always the case that +@code{BINFO_TYPE (TYPE_BINFO (x))} is the same type as @code{x}, up to +qualifiers. However, it is not always the case that @code{TYPE_BINFO +(BINFO_TYPE (y))} is always the same binfo as @code{y}. The reason is +that if @code{y} is a binfo representing a base-class @code{B} of a +derived class @code{D}, then @code{BINFO_TYPE (y)} will be @code{B}, and +@code{TYPE_INFO (BINFO_TYPE (y))} will be @code{B} as its own +base-class, rather than as a base-class of @code{D}. + +The @code{BINFO_BASETYPES} is a @code{TREE_VEC} (@pxref{Containers}). +Base types appear in left-to-right order in this vector. You can tell +whether or @code{public}, @code{protected}, or @code{private} +inheritance was used by using the @code{TREE_VIA_PUBLIC}, +@code{TREE_VIA_PROTECTED}, and @code{TREE_VIA_PRIVATE} macros. Each of +these macros takes a @code{BINFO} and is true if and only if the +indicated kind of inheritance was used. If @code{TREE_VIA_VIRTUAL} +holds of a binfo, then its @code{BINFO_TYPE} was inherited from +virtually. + +FIXME: Talk about @code{TYPE_NONCOPIED_PARTS}. + +The following macros can be used on a tree node representing a class-type. + +@ftable @code +@item LOCAL_CLASS_P +This predicate holds if the class is local class @emph{i.e.} declared +inside a function body. + +@item TYPE_POLYMORPHIC_P +This predicate holds if the class has at least one virtual function +(declared or inherited). + +@item TYPE_HAS_DEFAULT_CONSTRUCTOR +This predicate holds whenever its argument represents a class-type with +default constructor. + +@item CLASSTYPE_HAS_MUTABLE +@item TYPE_HAS_MUTABLE_P +These predicates hold for a class-type having a mutable data member. + +@item CLASSTYPE_NON_POD_P +This predicate holds only for class-types that are not PODs. + +@item TYPE_HAS_NEW_OPERATOR +This predicate holds for a class-type that defines +@code{operator new}. + +@item TYPE_HAS_ARRAY_NEW_OPERATOR +This predicate holds for a class-type for which +@code{operator new[]} is defined. + +@item TYPE_OVERLOADS_CALL_EXPR +This predicate holds for class-type for which the function call +@code{operator()} is overloaded. + +@item TYPE_OVERLOADS_ARRAY_REF +This predicate holds for a class-type that overloads +@code{operator[]} + +@item TYPE_OVERLOADS_ARROW +This predicate holds for a class-type for which @code{operator->} is +overloaded. + +@end ftable + +@c --------------------------------------------------------------------- +@c Declarations +@c --------------------------------------------------------------------- + +@node Declarations +@section Declarations +@cindex declaration +@cindex variable +@cindex type declaration +@tindex LABEL_DECL +@tindex CONST_DECL +@tindex TYPE_DECL +@tindex VAR_DECL +@tindex PARM_DECL +@tindex FIELD_DECL +@tindex NAMESPACE_DECL +@tindex RESULT_DECL +@tindex TEMPLATE_DECL +@tindex THUNK_DECL +@tindex USING_DECL +@findex THUNK_DELTA +@findex DECL_INITIAL +@findex DECL_SIZE +@findex DECL_ALIGN +@findex DECL_EXTERNAL + +This section covers the various kinds of declarations that appear in the +internal representation, except for declarations of functions +(represented by @code{FUNCTION_DECL} nodes), which are described in +@ref{Functions}. + +Some macros can be used with any kind of declaration. These include: +@ftable @code +@item DECL_NAME +This macro returns an @code{IDENTIFIER_NODE} giving the name of the +entity. + +@item TREE_TYPE +This macro returns the type of the entity declared. + +@item DECL_SOURCE_FILE +This macro returns the name of the file in which the entity was +declared, as a @code{char*}. For an entity declared implicitly by the +compiler (like @code{__builtin_memcpy}), this will be the string +@code{""}. + +@item DECL_SOURCE_LINE +This macro returns the line number at which the entity was declared, as +an @code{int}. + +@item DECL_ARTIFICIAL +This predicate holds if the declaration was implicitly generated by the +compiler. For example, this predicate will hold of an implicitly +declared member function, or of the @code{TYPE_DECL} implicitly +generated for a class type. Recall that in C++ code like: +@example +struct S @{@}; +@end example +@noindent +is roughly equivalent to C code like: +@example +struct S @{@}; +typedef struct S S; +@end example +The implicitly generated @code{typedef} declaration is represented by a +@code{TYPE_DECL} for which @code{DECL_ARTIFICIAL} holds. + +@item DECL_NAMESPACE_SCOPE_P +This predicate holds if the entity was declared at a namespace scope. + +@item DECL_CLASS_SCOPE_P +This predicate holds if the entity was declared at a class scope. + +@item DECL_FUNCTION_SCOPE_P +This predicate holds if the entity was declared inside a function +body. + +@end ftable + +The various kinds of declarations include: +@table @code +@item LABEL_DECL +These nodes are used to represent labels in function bodies. For more +information, see @ref{Functions}. These nodes only appear in block +scopes. + +@item CONST_DECL +These nodes are used to represent enumeration constants. The value of +the constant is given by @code{DECL_INITIAL} which will be an +@code{INTEGER_CST} with the same type as the @code{TREE_TYPE} of the +@code{CONST_DECL}, i.e., an @code{ENUMERAL_TYPE}. + +@item RESULT_DECL +These nodes represent the value returned by a function. When a value is +assigned to a @code{RESULT_DECL}, that indicates that the value should +be returned, via bitwise copy, by the function. You can use +@code{DECL_SIZE} and @code{DECL_ALIGN} on a @code{RESULT_DECL}, just as +with a @code{VAR_DECL}. + +@item TYPE_DECL +These nodes represent @code{typedef} declarations. The @code{TREE_TYPE} +is the type declared to have the name given by @code{DECL_NAME}. In +some cases, there is no associated name. + +@item VAR_DECL +These nodes represent variables with namespace or block scope, as well +as static data members. The @code{DECL_SIZE} and @code{DECL_ALIGN} are +analogous to @code{TYPE_SIZE} and @code{TYPE_ALIGN}. For a declaration, +you should always use the @code{DECL_SIZE} and @code{DECL_ALIGN} rather +than the @code{TYPE_SIZE} and @code{TYPE_ALIGN} given by the +@code{TREE_TYPE}, since special attributes may have been applied to the +variable to give it a particular size and alignment. You may use the +predicates @code{DECL_THIS_STATIC} or @code{DECL_THIS_EXTERN} to test +whether the storage class specifiers @code{static} or @code{extern} were +used to declare a variable. + +If this variable is initialized (but does not require a constructor), +the @code{DECL_INITIAL} will be an expression for the initializer. The +initializer should be evaluated, and a bitwise copy into the variable +performed. If the @code{DECL_INITIAL} is the @code{error_mark_node}, +there is an initializer, but it is given by an explicit statement later +in the code; no bitwise copy is required. + +GCC provides an extension that allows either automatic variables, or +global variables, to be placed in particular registers. This extension +is being used for a particular @code{VAR_DECL} if @code{DECL_REGISTER} +holds for the @code{VAR_DECL}, and if @code{DECL_ASSEMBLER_NAME} is not +equal to @code{DECL_NAME}. In that case, @code{DECL_ASSEMBLER_NAME} is +the name of the register into which the variable will be placed. + +@item PARM_DECL +Used to represent a parameter to a function. Treat these nodes +similarly to @code{VAR_DECL} nodes. These nodes only appear in the +@code{DECL_ARGUMENTS} for a @code{FUNCTION_DECL}. + +The @code{DECL_ARG_TYPE} for a @code{PARM_DECL} is the type that will +actually be used when a value is passed to this function. It may be a +wider type than the @code{TREE_TYPE} of the parameter; for example, the +ordinary type might be @code{short} while the @code{DECL_ARG_TYPE} is +@code{int}. + +@item FIELD_DECL +These nodes represent non-static data members. The @code{DECL_SIZE} and +@code{DECL_ALIGN} behave as for @code{VAR_DECL} nodes. The +@code{DECL_FIELD_BITPOS} gives the first bit used for this field, as an +@code{INTEGER_CST}. These values are indexed from zero, where zero +indicates the first bit in the object. + +If @code{DECL_C_BIT_FIELD} holds, this field is a bitfield. + +@item NAMESPACE_DECL +@xref{Namespaces}. + +@item TEMPLATE_DECL + +These nodes are used to represent class, function, and variable (static +data member) templates. The @code{DECL_TEMPLATE_SPECIALIZATIONS} are a +@code{TREE_LIST}. The @code{TREE_VALUE} of each node in the lst is a +@code{TEMPLATE_DECL}s or @code{FUNCTION_DECL}s representing +specializations (including instantiations) of this template. Back-ends +can safely ignore @code{TEMPLATE_DECL}s, but should examine +@code{FUNCTION_DECL} nodes on the specializations list just as they +would ordinary @code{FUNCTION_DECL} nodes. + +For a class template, the @code{DECL_TEMPLATE_INSTANTIATIONS} list +contains the instantiations. The @code{TREE_VALUE} of each node is an +instantiation of the class. The @code{DECL_TEMPLATE_SPECIALIZATIONS} +contains partial specializations of the class. + +@item USING_DECL + +Back-ends can safely ignore these nodes. + +@end table + +@c --------------------------------------------------------------------- +@c Functions +@c --------------------------------------------------------------------- + +@node Functions +@section Functions +@cindex function +@tindex FUNCTION_DECL +@tindex OVERLOAD +@findex OVL_CURRENT +@findex OVL_NEXT + +A function is represented by a @code{FUNCTION_DECL} node. A set of +overloaded functions is sometimes represented by a @code{OVERLOAD} node. + +An @code{OVERLOAD} node is not a declaration, so none of the +@samp{DECL_} macros should be used on an @code{OVERLOAD}. An +@code{OVERLOAD} node is similar to a @code{TREE_LIST}. Use +@code{OVL_CURRENT} to get the function associated with an +@code{OVERLOAD} node; use @code{OVL_NEXT} to get the next +@code{OVERLOAD} node in the list of overloaded functions. The macros +@code{OVL_CURRENT} and @code{OVL_NEXT} are actually polymorphic; you can +use them to work with @code{FUNCTION_DECL} nodes as well as with +overloads. In the case of a @code{FUNCTION_DECL}, @code{OVL_CURRENT} +will always return the function itself, and @code{OVL_NEXT} will always +be @code{NULL_TREE}. + +To determine the scope of a function, you can use the +@code{DECL_REAL_CONTEXT} macro. This macro will return the class +(either a @code{RECORD_TYPE} or a @code{UNION_TYPE}) or namespace (a +@code{NAMESPACE_DECL}) of which the function is a member. For a virtual +function, this macro returns the class in which the function was +actually defined, not the base class in which the virtual declaration +occurred. If a friend function is defined in a class scope, the +@code{DECL_CLASS_CONTEXT} macro can be used to determine the class in +which it was defined. For example, in +@example +class C @{ friend void f() @{@} @}; +@end example +the @code{DECL_REAL_CONTEXT} for @code{f} will be the +@code{global_namespace}, but the @code{DECL_CLASS_CONTEXT} will be the +@code{RECORD_TYPE} for @code{C}. + +The @code{DECL_REAL_CONTEXT} and @code{DECL_CLASS_CONTEXT} are not +available in C; instead you should simply use @code{DECL_CONTEXT}. In C, +the @code{DECL_CONTEXT} for a function maybe another function. This +representation indicates that the GNU nested function extension is in +use. For details on the semantics of nested functions, see the GCC +Manual. The nested function can refer to local variables in its +containing function. Such references are not explicitly marked in the +tree structure; back-ends must look at the @code{DECL_CONTEXT} for the +referenced @code{VAR_DECL}. If the @code{DECL_CONTEXT} for the +referenced @code{VAR_DECL} is not the same as the function currently +being processed, and neither @code{DECL_EXTERNAL} nor @code{DECL_STATIC} +hold, then the reference is to a local variable in a containing +function, and the back-end must take appropriate action. + +@menu +* Function Basics:: Function names, linkage, and so forth. +* Function Bodies:: The statements that make up a function body. +@end menu + +@c --------------------------------------------------------------------- +@c Function Basics +@c --------------------------------------------------------------------- + +@node Function Basics +@subsection Function Basics +@cindex constructor +@cindex destructor +@cindex copy constructor +@cindex assignment operator +@cindex linkage +@findex DECL_NAME +@findex DECL_ASSEMBLER_NAME +@findex TREE_PUBLIC +@findex DECL_LINKONCE_P +@findex DECL_FUNCTION_MEMBER_P +@findex DECL_CONSTRUCTOR_P +@findex DECL_DESTRUCTOR_P +@findex DECL_OVERLOADED_OPERATOR_P +@findex DECL_CONV_FN_P +@findex DECL_ARTIFICIAL +@findex DECL_GLOBAL_CTOR_P +@findex DECL_GLOBAL_DTOR_P +@findex GLOBAL_INIT_PRIORITY + +The following macros and functions can be used on a @code{FUNCTION_DECL}: +@ftable @code +@item DECL_MAIN_P +This predicate holds for a function that is the program entry point +@code{::code}. + +@item DECL_NAME +This macro returns the unqualified name of the function, as an +@code{IDENTIFIER_NODE}. For an instantiation of a function template, +the @code{DECL_NAME} is the unqualified name of the template, not +something like @code{f}. The value of @code{DECL_NAME} is +undefined when used on a constructor, destructor, overloaded operator, +or type-conversion operator, or any function that is implicitly +generated by the compiler. See below for macros that can be used to +distinguish these cases. + +@item DECL_ASSEMBLER_NAME +This macro returns the mangled name of the function, also an +@code{IDENTIFIER_NODE}. This name does not contain leading underscores +on systems that prefix all identifiers with underscores. The mangled +name is computed in the same way on all platforms; if special processing +is required to deal with the object file format used on a particular +platform, it is the responsibility of the back-end to perform those +modifications. (Of course, the back-end should not modify +@code{DECL_ASSEMBLER_NAME} itself.) + +@item DECL_EXTERNAL +This predicate holds if the function is undefined. + +@item TREE_PUBLIC +This predicate holds if the function has external linkage. + +@item DECL_LOCAL_FUNCTION_P +This predicate holds if the function was declared at block scope, even +though it has a global scope. + +@item DECL_ANTICIPATED +This predicate holds if the function is a built-in function but its +prototype is not yet explicitly declared. + +@item DECL_EXTERN_C_FUNCTION_P +This predicate holds if the function is declared as an +`@code{extern "C"}' function. + +@item DECL_LINKONCE_P +This macro holds if multiple copies of this function may be emitted in +various translation units. It is the responsibility of the linker to +merge the various copies. Template instantiations are the most common +example of functions for which @code{DECL_LINKONCE_P} holds; G++ +instantiates needed templates in all translation units which require them, +and then relies on the linker to remove duplicate instantiations. + +FIXME: This macro is not yet implemented. + +@item DECL_FUNCTION_MEMBER_P +This macro holds if the function is a member of a class, rather than a +member of a namespace. + +@item DECL_STATIC_FUNCTION_P +This predicate holds if the function a static member function. + +@item DECL_NONSTATIC_MEMBER_FUNCTION_P +This macro holds for a non-static member function. + +@item DECL_CONST_MEMFUNC_P +This predicate holds for a @code{const}-member function. + +@item DECL_VOLATILE_MEMFUNC_P +This predicate holds for a @code{volatile}-member function. + +@item DECL_CONSTRUCTOR_P +This macro holds if the function is a constructor. + +@item DECL_NONCONVERTING_P +This predicate holds if the constructor is a non-converting constructor. + +@item DECL_COMPLETE_CONSTRUCTOR_P +This predicate holds for a function which is a constructor for an object +of a complete type. + +@item DECL_BASE_CONSTRUCTOR_P +This predicate holds for a function which is a constructor for a base +class sub-object. + +@item DECL_COPY_CONSTRUCTOR_P +This predicate holds for a function which is a copy-constructor. + +@item DECL_DESTRUCTOR_P +This macro holds if the function is a destructor. + +@item DECL_COMPLETE_DESTRUCTOR_P +This predicate holds if the function is the destructor for an object a +complete type. + +@item DECL_OVERLOADED_OPERATOR_P +This macro holds if the function is an overloaded operator. + +@item DECL_CONV_FN_P +This macro holds if the function is a type-conversion operator. + +@item DECL_GLOBAL_CTOR_P +This predicate holds if the function is a file-scope initialization +function. + +@item DECL_GLOBAL_DTOR_P +This predicate holds if the function is a file-scope finalization +function. + +@item DECL_THUNK_P +This predicate holds if the function is a thunk. + +These functions represent stub code that adjusts the @code{this} pointer +and then jumps to another function. When the jumped-to function +returns, control is transferred directly to the caller, without +returning to the thunk. The first parameter to the thunk is always the +@code{this} pointer; the thunk should add @code{THUNK_DELTA} to this +value. (The @code{THUNK_DELTA} is an @code{int}, not an +@code{INTEGER_CST}.) + +Then, if @code{THUNK_VCALL_OFFSET} (an @code{INTEGER_CST}) is non-zero +the adjusted @code{this} pointer must be adjusted again. The complete +calculation is given by the following pseudo-code: + +@example +this += THUNK_DELTA +if (THUNK_VCALL_OFFSET) + this += (*((ptrdiff_t **) this))[THUNK_VCALL_OFFSET] +@end example + +Finally, the thunk should jump to the location given +by @code{DECL_INITIAL}; this will always be an expression for the +address of a function. + +@item DECL_NON_THUNK_FUNCTION_P +This predicate holds if the function is @emph{not} a thunk function. + +@item GLOBAL_INIT_PRIORITY +If either @code{DECL_GLOBAL_CTOR_P} or @code{DECL_GLOBAL_DTOR_P} holds, +then this gives the initialization priority for the function. The +linker will arrange that all functions for which +@code{DECL_GLOBAL_CTOR_P} holds are run in increasing order of priority +before @code{main} is called. When the program exits, all functions for +which @code{DECL_GLOBAL_DTOR_P} holds are run in the reverse order. + +@item DECL_ARTIFICIAL +This macro holds if the function was implicitly generated by the +compiler, rather than explicitly declared. In addition to implicitly +generated class member functions, this macro holds for the special +functions created to implement static initialization and destruction, to +compute run-time type information, and so forth. + +@item DECL_ARGUMENTS +This macro returns the @code{PARM_DECL} for the first argument to the +function. Subsequent @code{PARM_DECL} nodes can be obtained by +following the @code{TREE_CHAIN} links. + +@item DECL_RESULT +This macro returns the @code{RESULT_DECL} for the function. + +@item TREE_TYPE +This macro returns the @code{FUNCTION_TYPE} or @code{METHOD_TYPE} for +the function. + +@item TYPE_RAISES_EXCEPTIONS +This macro returns the list of exceptions that a (member-)function can +raise. The returned list, if non @code{NULL}, is comprised of nodes +whose @code{TREE_VALUE} represents a type. + +@item TYPE_NOTHROW_P +This predicate holds when the exception-specification of its arguments +if of the form `@code{()}'. + +@item DECL_ARRAY_DELETE_OPERATOR_P +This predicate holds if the function an overloaded +@code{operator delete[]}. + +@end ftable + +@c --------------------------------------------------------------------- +@c Function Bodies +@c --------------------------------------------------------------------- + +@node Function Bodies +@subsection Function Bodies +@cindex function body +@cindex statements +@tindex ASM_STMT +@findex ASM_STRING +@findex ASM_CV_QUAL +@findex ASM_INPUTS +@findex ASM_OUTPUTS +@findex ASM_CLOBBERS +@tindex BREAK_STMT +@tindex CLEANUP_STMT +@findex CLEANUP_DECL +@findex CLEANUP_EXPR +@tindex COMPOUND_STMT +@findex COMPOUND_BODY +@tindex CONTINUE_STMT +@tindex DECL_STMT +@findex DECL_STMT_DECL +@tindex DO_STMT +@findex DO_BODY +@findex DO_COND +@tindex EMPTY_CLASS_EXPR +@tindex EXPR_STMT +@findex EXPR_STMT_EXPR +@tindex FOR_STMT +@findex FOR_INIT_STMT +@findex FOR_COND +@findex FOR_EXPR +@findex FOR_BODY +@tindex GOTO_STMT +@findex GOTO_DESTINATION +@tindex HANDLER +@tindex IF_STMT +@findex IF_COND +@findex THEN_CLAUSE +@findex ELSE_CLAUSE +@tindex LABEL_STMT +@tindex LABEL_STMT_LABEL +@tindex RETURN_INIT +@tindex RETURN_STMT +@findex RETURN_EXPR +@tindex SCOPE_STMT +@findex SCOPE_BEGIN_P +@findex SCOPE_END_P +@findex SCOPE_NULLIFIED_P +@tindex SUBOBJECT +@findex SUBOBJECT_CLEANUP +@tindex SWITCH_STMT +@findex SWITCH_COND +@findex SWITCH_BODY +@tindex TRY_BLOCK +@findex TRY_STMTS +@findex TRY_HANDLERS +@findex HANDLER_PARMS +@findex HANDLER_BODY +@findex USING_STMT +@tindex WHILE_STMT +@findex WHILE_BODY +@findex WHILE_COND + +A function that has a definition in the current translation unit will +have a non-NULL @code{DECL_INITIAL}. However, back-ends should not make +use of the particular value given by @code{DECL_INITIAL}. + +The @code{DECL_SAVED_TREE} macro will give the complete body of the +function. This node will usually be a @code{COMPOUND_STMT} representing +the outermost block of the function, but it may also be a +@code{TRY_BLOCK}, a @code{RETURN_INIT}, or any other valid statement. + +@subsubsection Statements + +There are tree nodes corresponding to all of the source-level statement +constructs. These are enumerated here, together with a list of the +various macros that can be used to obtain information about them. There +are a few macros that can be used with all statements: + +@ftable @code +@item STMT_LINENO +This macro returns the line number for the statement. If the statement +spans multiple lines, this value will be the number of the first line on +which the statement occurs. Although we mention @code{CASE_LABEL} below +as if it were a statement, they do not allow the use of +@code{STMT_LINENO}. There is no way to obtain the line number for a +@code{CASE_LABEL}. + +Statements do not contain information about +the file from which they came; that information is implicit in the +@code{FUNCTION_DECL} from which the statements originate. + +@item STMT_IS_FULL_EXPR_P +In C++, statements normally constitute ``full expressions''; temporaries +created during a statement are destroyed when the statement is complete. +However, G++ sometimes represents expressions by statements; these +statements will not have @code{STMT_IS_FULL_EXPR_P} set. Temporaries +created during such statements should be destroyed when the innermost +enclosing statement with @code{STMT_IS_FULL_EXPR_P} set is exited. + +@end ftable + +Here is the list of the various statement nodes, and the macros used to +access them. This documentation describes the use of these nodes in +non-template functions (including instantiations of template functions). +In template functions, the same nodes are used, but sometimes in +slightly different ways. + +Many of the statements have substatements. For example, a @code{while} +loop will have a body, which is itself a statement. If the substatement +is @code{NULL_TREE}, it is considered equivalent to a statement +consisting of a single @code{;}, i.e., an expression statement in which +the expression has been omitted. A substatement may in fact be a list +of statements, connected via their @code{TREE_CHAIN}s. So, you should +always process the statement tree by looping over substatements, like +this: +@example +void process_stmt (stmt) + tree stmt; +@{ + while (stmt) + @{ + switch (TREE_CODE (stmt)) + @{ + case IF_STMT: + process_stmt (THEN_CLAUSE (stmt)); + /* More processing here. */ + break; + + ... + @} + + stmt = TREE_CHAIN (stmt); + @} +@} +@end example +In other words, while the @code{then} clause of an @code{if} statement +in C++ can be only one statement (although that one statement may be a +compound statement), the intermediate representation will sometimes use +several statements chained together. + +@table @code +@item ASM_STMT + +Used to represent an inline assembly statement. For an inline assembly +statement like: +@example +asm ("mov x, y"); +@end example +The @code{ASM_STRING} macro will return a @code{STRING_CST} node for +@code{"mov x, y"}. If the original statement made use of the +extended-assembly syntax, then @code{ASM_OUTPUTS}, +@code{ASM_INPUTS}, and @code{ASM_CLOBBERS} will be the outputs, inputs, +and clobbers for the statement, represented as @code{STRING_CST} nodes. +The extended-assembly syntax looks like: +@example +asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); +@end example +The first string is the @code{ASM_STRING}, containing the instruction +template. The next two strings are the output and inputs, respectively; +this statement has no clobbers. As this example indicates, ``plain'' +assembly statements are merely a special case of extended assembly +statements; they have no cv-qualifiers, outputs, inputs, or clobbers. +All of the strings will be @code{NUL}-terminated, and will contain no +embedded @code{NUL}-characters. + +If the assembly statement is declared @code{volatile}, or if the +statement was not an extended assembly statement, and is therefore +implicitly volatile, then the predicate @code{ASM_VOLATILE_P} will hold +of the @code{ASM_STMT}. + +@item BREAK_STMT + +Used to represent a @code{break} statement. There are no additional +fields. + +@item CASE_LABEL + +Use to represent a @code{case} label, range of @code{case} labels, or a +@code{default} label. If @code{CASE_LOW} is NULL_TREE, then this is a a +@code{default} label. Otherwise, if @code{CASE_HIGH} is NULL_TREE, then +this is an ordinary @code{case} label. In this case, @code{CASE_LOW} is +an expression giving the value of the label. Both @code{CASE_LOW} and +@code{CASE_HIGH} are @code{INTEGER_CST} nodes. These values will have +the same type as the condition expression in the switch statement. + +Otherwise, if both @code{CASE_LOW} and @code{CASE_HIGH} are defined, the +statement is a range of case labels. Such statements originate with the +extension that allows users to write things of the form: +@example +case 2 ... 5: +@end example +The first value will be @code{CASE_LOW}, while the second will be +@code{CASE_HIGH}. + +@item CLEANUP_STMT + +Used to represent an action that should take place upon exit from the +enclosing scope. Typically, these actions are calls to destructors for +local objects, but back-ends cannot rely on this fact. If these nodes +are in fact representing such destructors, @code{CLEANUP_DECL} will be +the @code{VAR_DECL} destroyed. Otherwise, @code{CLEANUP_DECL} will be +@code{NULL_TREE}. In any case, the @code{CLEANUP_EXPR} is the +expression to execute. The cleanups executed on exit from a scope +should be run in the reverse order of the order in which the associated +@code{CLEANUP_STMT}s were encountered. + +@item COMPOUND_STMT + +Used to represent a brace-enclosed block. The first substatement is +given by @code{COMPOUND_BODY}. Subsequent substatements are found by +following the @code{TREE_CHAIN} link from one substatement to the next. + +@item CONTINUE_STMT + +Used to represent a @code{continue} statement. There are no additional +fields. + +@item CTOR_STMT + +Used to mark the beginning (if @code{CTOR_BEGIN_P} holds) or end (if +@code{CTOR_END_P} holds of the main body of a constructor. See also +@code{SUBOBJECT} for more information on how to use these nodes. + +@item DECL_STMT + +Used to represent a local declaration. The @code{DECL_STMT_DECL} macro +can be used to obtain the entity declared. This declaration may be a +@code{LABEL_DECL}, indicating that the label declared is a local label. +(As an extension, GCC allows the declaration of labels with scope.) In +C, this declaration may be a @code{FUNCTION_DECL}, indicating the +use of the GCC nested function extension. For more information, +@pxref{Functions}. + +@item DO_STMT + +Used to represent a @code{do} loop. The body of the loop is given by +@code{DO_BODY} while the termination condition for the loop is given by +@code{DO_COND}. The condition for a @code{do}-statement is always an +expression. + +@item EMPTY_CLASS_EXPR + +Used to represent a temporary object of a class with no data whose +address is never taken. (All such objects are interchangeable.) The +@code{TREE_TYPE} represents the type of the object. + +@item EXPR_STMT + +Used to represent an expression statement. Use @code{EXPR_STMT_EXPR} to +obtain the expression. + +@item FOR_STMT + +Used to represent a @code{for} statement. The @code{FOR_INIT_STMT} is +the initialization statement for the loop. The @code{FOR_COND} is the +termination condition. The @code{FOR_EXPR} is the expression executed +right before the @code{FOR_COND} on each loop iteration; often, this +expression increments a counter. The body of the loop is given by +@code{FOR_BODY}. Note that @code{FOR_INIT_STMT} and @code{FOR_BODY} +return statements, while @code{FOR_COND} and @code{FOR_EXPR} return +expressions. + +@item GOTO_STMT + +Used to represent a @code{goto} statement. The @code{GOTO_DESTINATION} +will usually be a @code{LABEL_DECL}. However, if the ``computed +goto'' extension has been used, the @code{GOTO_DESTINATION} will be an +arbitrary expression indicating the destination. This expression will +always have pointer type. + +@item HANDLER + +Used to represent a C++ @code{catch} block. The @code{HANDLER_TYPE} +is the type of exception that will be caught by this handler; it is +equal (by pointer equality) to @code{CATCH_ALL_TYPE} if this handler +is for all types. @code{HANDLER_PARMS} is the @code{DECL_STMT} for +the catch parameter, and @code{HANDLER_BODY} is the +@code{COMPOUND_STMT} for the block itself. + +@item IF_STMT + +Used to represent an @code{if} statement. The @code{IF_COND} is the +expression. + +If the condition is a @code{TREE_LIST}, then the @code{TREE_PURPOSE} is +a statement (usually a @code{DECL_STMT}). Each time the coondition is +evaluated, the statement should be executed. Then, the +@code{TREE_VALUE} should be used as the conditional expression itself. +This representation is used to handle C++ code like this: + +@example +if (int i = 7) ... +@end example + +where there is a new local variable (or variables) declared within the +condition. + +The @code{THEN_CLAUSE} represents the statement given by the @code{then} +condition, while the @code{ELSE_CLAUSE} represents the statement given +by the @code{else} condition. + +@item LABEL_STMT + +Used to represent a label. The @code{LABEL_DECL} declared by this +statement can be obtained with the @code{LABEL_STMT_LABEL} macro. The +@code{IDENTIFIER_NODE} giving the name of the label can be obtained from +the @code{LABEL_DECL} with @code{DECL_NAME}. + +@item RETURN_INIT + +If the function uses the G++ ``named return value'' extension, meaning +that the function has been defined like: +@example +S f(int) return s @{...@} +@end example +then there will be a @code{RETURN_INIT}. There is never a named +returned value for a constructor. The first argument to the +@code{RETURN_INIT} is the name of the object returned; the second +argument is the initializer for the object. The object is initialized +when the @code{RETURN_INIT} is encountered. The object referred to is +the actual object returned; this extension is a manual way of doing the +``return-value optimization.'' Therefore, the object must actually be +constructed in the place where the object will be returned. + +@item RETURN_STMT + +Used to represent a @code{return} statement. The @code{RETURN_EXPR} is +the expression returned; it will be @code{NULL_TREE} if the statement +was just +@example +return; +@end example + +@item SCOPE_STMT + +A scope-statement represents the beginning or end of a scope. If +@code{SCOPE_BEGIN_P} holds, this statement represents the beginning of a +scope; if @code{SCOPE_END_P} holds this statement represents the end of +a scope. On exit from a scope, all cleanups from @code{CLEANUP_STMT}s +occurring in the scope must be run, in reverse order to the order in +which they were encountered. If @code{SCOPE_NULLIFIED_P} or +@code{SCOPE_NO_CLEANUPS_P} holds of the scope, back-ends should behave +as if the @code{SCOPE_STMT} were not present at all. + +@item SUBOBJECT + +In a constructor, these nodes are used to mark the point at which a +subobject of @code{this} is fully constructed. If, after this point, an +exception is thrown before a @code{CTOR_STMT} with @code{CTOR_END_P} set +is encountered, the @code{SUBOBJECT_CLEANUP} must be executed. The +cleanups must be executed in the reverse order in which they appear. + +@item SWITCH_STMT + +Used to represent a @code{switch} statement. The @code{SWITCH_COND} is +the expression on which the switch is occurring. See the documentation +for an @code{IF_STMT} for more information on the representation used +for the condition. The @code{SWITCH_BODY} is the body of the switch +statement. + +@item TRY_BLOCK +Used to represent a @code{try} block. The body of the try block is +given by @code{TRY_STMTS}. Each of the catch blocks is a @code{HANDLER} +node. The first handler is given by @code{TRY_HANDLERS}. Subsequent +handlers are obtained by following the @code{TREE_CHAIN} link from one +handler to the next. The body of the handler is given by +@code{HANDLER_BODY}. + +If @code{CLEANUP_P} holds of the @code{TRY_BLOCK}, then the +@code{TRY_HANDLERS} will not be a @code{HANDLER} node. Instead, it will +be an expression that should be executed if an exception is thrown in +the try block. It must rethrow the exception after executing that code. +And, if an exception is thrown while the expression is executing, +@code{terminate} must be called. + +@item USING_STMT +Used to represent a @code{using} directive. The namespace is given by +@code{USING_STMT_NAMESPACE}, which will be a NAMESPACE_DECL. This node +is needed inside template functions, to implement using directives +during instantiation. + +@item WHILE_STMT + +Used to represent a @code{while} loop. The @code{WHILE_COND} is the +termination condition for the loop. See the documentation for an +@code{IF_STMT} for more information on the representation used for the +condition. + +The @code{WHILE_BODY} is the body of the loop. + +@end table + +@c --------------------------------------------------------------------- +@c Expressions +@c --------------------------------------------------------------------- + +@node Expression trees +@section Expressions +@cindex expression +@findex TREE_OPERAND +@tindex INTEGER_CST +@findex TREE_INT_CST_HIGH +@findex TREE_INT_CST_LOW +@findex tree_int_cst_lt +@findex tree_int_cst_equal +@tindex REAL_CST +@tindex COMPLEX_CST +@tindex STRING_CST +@findex TREE_STRING_LENGTH +@findex TREE_STRING_POINTER +@tindex PTRMEM_CST +@findex PTRMEM_CST_CLASS +@findex PTRMEM_CST_MEMBER +@tindex VAR_DECL +@tindex NEGATE_EXPR +@tindex BIT_NOT_EXPR +@tindex TRUTH_NOT_EXPR +@tindex ADDR_EXPR +@tindex INDIRECT_REF +@tindex FIX_TRUNC_EXPR +@tindex FLOAT_EXPR +@tindex COMPLEX_EXPR +@tindex CONJ_EXPR +@tindex REALPART_EXPR +@tindex IMAGPART_EXPR +@tindex NOP_EXPR +@tindex CONVERT_EXPR +@tindex THROW_EXPR +@tindex LSHIFT_EXPR +@tindex RSHIFT_EXPR +@tindex BIT_IOR_EXPR +@tindex BIT_XOR_EXPR +@tindex BIT_AND_EXPR +@tindex TRUTH_ANDIF_EXPR +@tindex TRUTH_ORIF_EXPR +@tindex TRUTH_AND_EXPR +@tindex TRUTH_OR_EXPR +@tindex TRUTH_XOR_EXPR +@tindex PLUS_EXPR +@tindex MINUS_EXPR +@tindex MULT_EXPR +@tindex TRUNC_DIV_EXPR +@tindex TRUNC_MOD_EXPR +@tindex RDIV_EXPR +@tindex LT_EXPR +@tindex LE_EXPR +@tindex GT_EXPR +@tindex GE_EXPR +@tindex EQ_EXPR +@tindex NE_EXPR +@tindex INIT_EXPR +@tindex MODIFY_EXPR +@tindex COMPONENT_REF +@tindex COMPOUND_EXPR +@tindex COND_EXPR +@tindex CALL_EXPR +@tindex CONSTRUCTOR +@tindex STMT_EXPR +@tindex BIND_EXPR +@tindex LOOP_EXPR +@tindex EXIT_EXPR +@tindex CLEANUP_POINT_EXPR +@tindex ARRAY_REF + +The internal representation for expressions is for the most part quite +straightforward. However, there are a few facts that one must bear in +mind. In particular, the expression ``tree'' is actually a directed +acyclic graph. (For example there may be many references to the integer +constant zero throughout the source program; many of these will be +represented by the same expression node.) You should not rely on +certain kinds of node being shared, nor should rely on certain kinds of +nodes being unshared. + +The following macros can be used with all expression nodes: + +@ftable @code +@item TREE_TYPE +Returns the type of the expression. This value may not be precisely the +same type that would be given the expression in the original program. +@end ftable + +In what follows, some nodes that one might expect to always have type +@code{bool} are documented to have either integral or boolean type. At +some point in the future, the C front-end may also make use of this same +intermediate representation, and at this point these nodes will +certainly have integral type. The previous sentence is not meant to +imply that the C++ front-end does not or will not give these nodes +integral type. + +Below, we list the various kinds of expression nodes. Except where +noted otherwise, the operands to an expression are accessed using the +@code{TREE_OPERAND} macro. For example, to access the first operand to +a binary plus expression @code{expr}, use: + +@example +TREE_OPERAND (expr, 0) +@end example +@noindent +As this example indicates, the operands are zero-indexed. + +The table below begins with constants, moves on to unary expressions, +then proceeds to binary expressions, and concludes with various other +kinds of expressions: + +@table @code +@item INTEGER_CST +These nodes represent integer constants. Note that the type of these +constants is obtained with @code{TREE_TYPE}; they are not always of type +@code{int}. In particular, @code{char} constants are represented with +@code{INTEGER_CST} nodes. The value of the integer constant @code{e} is +given by @example +((TREE_INT_CST_HIGH (e) << HOST_BITS_PER_WIDE_INT) ++ TREE_INST_CST_LOW (e)) +@end example +@noindent +HOST_BITS_PER_WIDE_INT is at least thirty-two on all platforms. Both +@code{TREE_INT_CST_HIGH} and @code{TREE_INT_CST_LOW} return a +@code{HOST_WIDE_INT}. The value of an @code{INTEGER_CST} is interpreted +as a signed or unsigned quantity depending on the type of the constant. +In general, the expression given above will overflow, so it should not +be used to calculate the value of the constant. + +The variable @code{integer_zero_node} is a integer constant with value +zero. Similarly, @code{integer_one_node} is an integer constant with +value one. The @code{size_zero_node} and @code{size_one_node} variables +are analogous, but have type @code{size_t} rather than @code{int}. + +The function @code{tree_int_cst_lt} is a predicate which holds if its +first argument is less than its second. Both constants are assumed to +have the same signedness (i.e., either both should be signed or both +should be unsigned.) The full width of the constant is used when doing +the comparison; the usual rules about promotions and conversions are +ignored. Similarly, @code{tree_int_cst_equal} holds if the two +constants are equal. The @code{tree_int_cst_sgn} function returns the +sign of a constant. The value is @code{1}, @code{0}, or @code{-1} +according on whether the constant is greater than, equal to, or less +than zero. Again, the signedness of the constant's type is taken into +account; an unsigned constant is never less than zero, no matter what +its bit-pattern. + +@item REAL_CST + +FIXME: Talk about how to obtain representations of this constant, do +comparisons, and so forth. + +@item COMPLEX_CST +These nodes are used to represent complex number constants, that is a +@code{__complex__} whose parts are constant nodes. The +@code{TREE_REALPART} and @code{TREE_IMAGPART} return the real and the +imaginary parts respectively. + +@item STRING_CST +These nodes represent string-constants. The @code{TREE_STRING_LENGTH} +returns the length of the string, as an @code{int}. The +@code{TREE_STRING_POINTER} is a @code{char*} containing the string +itself. The string may not be @code{NUL}-terminated, and it may contain +embedded @code{NUL} characters. Therefore, the +@code{TREE_STRING_LENGTH} includes the trailing @code{NUL} if it is +present. + +For wide string constants, the @code{TREE_STRING_LENGTH} is the number +of wide characters in the string, and the @code{TREE_STRING_POINTER} +points to an array of the bytes of the string, as represented on the +target system (that is, as integers in the target endianness). Wide and +non-wide string constants are distinguished only by the @code{TREE_TYPE} +of the @code{STRING_CST}. + +FIXME: The formats of string constants are not well-defined when the +target system bytes are not the same width as host system bytes. + +@item PTRMEM_CST +These nodes are used to represent pointer-to-member constants. The +@code{PTRMEM_CST_CLASS} is the class type (either a @code{RECORD_TYPE} +or @code{UNION_TYPE} within which the pointer points), and the +@code{PTRMEM_CST_MEMBER} is the declaration for the pointed to object. +Note that the @code{DECL_CONTEXT} for the @code{PTRMEM_CST_MEMBER} is in +general different from from the @code{PTRMEM_CST_CLASS}. For example, +given: +@example +struct B @{ int i; @}; +struct D : public B @{@}; +int D::*dp = &D::i; +@end example +@noindent +The @code{PTRMEM_CST_CLASS} for @code{&D::i} is @code{D}, even though +the @code{DECL_CONTEXT} for the @code{PTRMEM_CST_MEMBER} is @code{B}, +since @code{B::i} is a member of @code{B}, not @code{D}. + +@item VAR_DECL + +These nodes represent variables, including static data members. For +more information, @pxref{Declarations}. + +@item NEGATE_EXPR +These nodes represent unary negation of the single operand, for both +integer and floating-point types. The type of negation can be +determined by looking at the type of the expression. + +@item BIT_NOT_EXPR +These nodes represent bitwise complement, and will always have integral +type. The only operand is the value to be complemented. + +@item TRUTH_NOT_EXPR +These nodes represent logical negation, and will always have integral +(or boolean) type. The operand is the value being negated. + +@item PREDECREMENT_EXPR +@itemx PREINCREMENT_EXPR +@itemx POSTDECREMENT_EXPR +@itemx POSTINCREMENT_EXPR +These nodes represent increment and decrement expressions. The value of +the single operand is computed, and the operand incremented or +decremented. In the case of @code{PREDECREMENT_EXPR} and +@code{PREINCREMENT_EXPR}, the value of the expression is the value +resulting after the increment or decrement; in the case of +@code{POSTDECREMENT_EXPR} and @code{POSTINCREMENT_EXPR} is the value +before the increment or decrement occurs. The type of the operand, like +that of the result, will be either integral, boolean, or floating-point. + +@item ADDR_EXPR +These nodes are used to represent the address of an object. (These +expressions will always have pointer or reference type.) The operand may +be another expression, or it may be a declaration. + +As an extension, GCC allows users to take the address of a label. In +this case, the operand of the @code{ADDR_EXPR} will be a +@code{LABEL_DECL}. The type of such an expression is @code{void*}. + +If the object addressed is not an lvalue, a temporary is created, and +the address of the temporary is used. + +@item INDIRECT_REF +These nodes are used to represent the object pointed to by a pointer. +The operand is the pointer being dereferenced; it will always have +pointer or reference type. + +@item FIX_TRUNC_EXPR +These nodes represent conversion of a floating-point value to an +integer. The single operand will have a floating-point type, while the +the complete expression will have an integral (or boolean) type. The +operand is rounded towards zero. + +@item FLOAT_EXPR +These nodes represent conversion of an integral (or boolean) value to a +floating-point value. The single operand will have integral type, while +the complete expression will have a floating-point type. + +FIXME: How is the operand supposed to be rounded? Is this dependent on +-mieee? + +@item COMPLEX_EXPR +These nodes are used to represent complex numbers constructed from two +expressions of the same (integer or real) type. The first operand is the +real part and the second operand is the imaginary part. + +@item CONJ_EXPR +These nodes represent the conjugate of their operand. + +@item REALPART_EXPR +@item IMAGPART_EXPR +These nodes represent respectively the real and the imaginary parts +of complex numbers (their sole argument). + +@item NON_LVALUE_EXPR +These nodes indicate that their one and only operand is not an lvalue. +A back-end can treat these identically to the single operand. + +@item NOP_EXPR +These nodes are used to represent conversions that do not require any +code-generation. For example, conversion of a @code{char*} to an +@code{int*} does not require any code be generated; such a conversion is +represented by a @code{NOP_EXPR}. The single operand is the expression +to be converted. The conversion from a pointer to a reference is also +represented with a @code{NOP_EXPR}. + +@item CONVERT_EXPR +These nodes are similar to @code{NOP_EXPR}s, but are used in those +situations where code may need to be generated. For example, if an +@code{int*} is converted to an @code{int} code may need to be generated +on some platforms. These nodes are never used for C++-specific +conversions, like conversions between pointers to different classes in +an inheritance hierarchy. Any adjustments that need to be made in such +cases are always indicated explicitly. Similarly, a user-defined +conversion is never represented by a @code{CONVERT_EXPR}; instead, the +function calls are made explicit. + +@item THROW_EXPR +These nodes represent @code{throw} expressions. The single operand is +an expression for the code that should be executed to throw the +exception. However, there is one implicit action not represented in +that expression; namely the call to @code{__throw}. This function takes +no arguments. If @code{setjmp}/@code{longjmp} exceptions are used, the +function @code{__sjthrow} is called instead. The normal GCC back-end +uses the function @code{emit_throw} to generate this code; you can +examine this function to see what needs to be done. + +@item LSHIFT_EXPR +@itemx RSHIFT_EXPR +These nodes represent left and right shifts, respectively. The first +operand is the value to shift; it will always be of integral type. The +second operand is an expression for the number of bits by which to +shift. Right shift should be treated as arithmetic, i.e., the +high-order bits should be zero-filled when the expression has unsigned +type and filled with the sign bit when the expression has signed type. + +@item BIT_IOR_EXPR +@itemx BIT_XOR_EXPR +@itemx BIT_AND_EXPR +These nodes represent bitwise inclusive or, bitwise exclusive or, and +bitwise and, respectively. Both operands will always have integral +type. + +@item TRUTH_ANDIF_EXPR +@itemx TRUTH_ORIF_EXPR +These nodes represent logical and and logical or, respectively. These +operators are not strict; i.e., the second operand is evaluated only if +the value of the expression is not determined by evaluation of the first +operand. The type of the operands, and the result type, is always of +boolean or integral type. + +@item TRUTH_AND_EXPR +@itemx TRUTH_OR_EXPR +@itemx TRUTH_XOR_EXPR +These nodes represent logical and, logical or, and logical exclusive or. +They are strict; both arguments are always evaluated. There are no +corresponding operators in C or C++, but the front-end will sometimes +generate these expressions anyhow, if it can tell that strictness does +not matter. + +@itemx PLUS_EXPR +@itemx MINUS_EXPR +@itemx MULT_EXPR +@itemx TRUNC_DIV_EXPR +@itemx TRUNC_MOD_EXPR +@itemx RDIV_EXPR +These nodes represent various binary arithmetic operations. +Respectively, these operations are addition, subtraction (of the second +operand from the first), multiplication, integer division, integer +remainder, and floating-point division. The operands to the first three +of these may have either integral or floating type, but there will never +be case in which one operand is of floating type and the other is of +integral type. + +The result of a @code{TRUNC_DIV_EXPR} is always rounded towards zero. +The @code{TRUNC_MOD_EXPR} of two operands @code{a} and @code{b} is +always @code{a - a/b} where the division is as if computed by a +@code{TRUNC_DIV_EXPR}. + +@item ARRAY_REF +These nodes represent array accesses. The first operand is the array; +the second is the index. To calculate the address of the memory +accessed, you must scale the index by the size of the type of the array +elements. + +@item EXACT_DIV_EXPR +Document. + +@item LT_EXPR +@itemx LE_EXPR +@itemx GT_EXPR +@itemx GE_EXPR +@itemx EQ_EXPR +@itemx NE_EXPR + +These nodes represent the less than, less than or equal to, greater +than, greater than or equal to, equal, and not equal comparison +operators. The first and second operand with either be both of integral +type or both of floating type. The result type of these expressions +will always be of integral or boolean type. + +@item MODIFY_EXPR +These nodes represent assignment. The left-hand side is the first +operand; the right-hand side is the second operand. The left-hand side +will be a @code{VAR_DECL}, @code{INDIRECT_REF}, @code{COMPONENT_REF}, or +other lvalue. + +These nodes are used to represent not only assignment with @samp{=} but +also compount assignments (like @samp{+=}), by reduction to @samp{=} +assignment. In other words, the representation for @samp{i += 3} looks +just like that for @samp{i = i + 3}. + +@item INIT_EXPR +These nodes are just like @code{MODIFY_EXPR}, but are used only when a +variable is initialized, rather than assigned to subsequently. + +@item COMPONENT_REF +These nodes represent non-static data member accesses. The first +operand is the object (rather than a pointer to it); the second operand +is the @code{FIELD_DECL} for the data member. + +@item COMPOUND_EXPR +These nodes represent comma-expressions. The first operand is an +expression whose value is computed and thrown away prior to the +evaluation of the second operand. The value of the entire expression is +the value of the second operand. + +@item COND_EXPR +These nodes represent @code{?:} expressions. The first operand +is of boolean or integral type. If it evaluates to a non-zero value, +the second operand should be evaluated, and returned as the value of the +expression. Otherwise, the third operand is evaluated, and returned as +the value of the expression. As a GNU extension, the middle operand of +the @code{?:} operator may be omitted in the source, like this: + +@example +x ? : 3 +@end example +@noindent +which is equivalent to + +@example +x ? x : 3 +@end example + +@noindent +assuming that @code{x} is an expression without side-effects. However, +in the case that the first operation causes side effects, the +side-effects occur only once. Consumers of the internal representation +do not need to worry about this oddity; the second operand will be +always be present in the internal representation. + +@item CALL_EXPR +These nodes are used to represent calls to functions, including +non-static member functions. The first operand is a pointer to the +function to call; it is always an expression whose type is a +@code{POINTER_TYPE}. The second argument is a @code{TREE_LIST}. The +arguments to the call appear left-to-right in the list. The +@code{TREE_VALUE} of each list node contains the expression +corresponding to that argument. (The value of @code{TREE_PURPOSE} for +these nodes is unspecified, and should be ignored.) For non-static +member functions, there will be an operand corresponding to the +@code{this} pointer. There will always be expressions corresponding to +all of the arguments, even if the function is declared with default +arguments and some arguments are not explicitly provided at the call +sites. + +@item STMT_EXPR +These nodes are used to represent GCC's statement-expression extension. +The statement-expression extension allows code like this: +@example +int f() @{ return (@{ int j; j = 3; j + 7; @}); @} +@end example +In other words, an sequence of statements may occur where a single +expression would normally appear. The @code{STMT_EXPR} node represents +such an expression. The @code{STMT_EXPR_STMT} gives the statement +contained in the expression; this is always a @code{COMPOUND_STMT}. The +value of the expression is the value of the last sub-statement in the +@code{COMPOUND_STMT}. More precisely, the value is the value computed +by the last @code{EXPR_STMT} in the outermost scope of the +@code{COMPOUND_STMT}. For example, in: +@example +(@{ 3; @}) +@end example +the value is @code{3} while in: +@example +(@{ if (x) @{ 3; @} @}) +@end example +(represented by a nested @code{COMPOUND_STMT}), there is no value. If +the @code{STMT_EXPR} does not yield a value, it's type will be +@code{void}. + +@item BIND_EXPR +These nodes represent local blocks. The first operand is a list of +temporary variables, connected via their @code{TREE_CHAIN} field. These +will never require cleanups. The scope of these variables is just the +body of the @code{BIND_EXPR}. The body of the @code{BIND_EXPR} is the +second operand. + +@item LOOP_EXPR +These nodes represent ``infinite'' loops. The @code{LOOP_EXPR_BODY} +represents the body of the loop. It should be executed forever, unless +an @code{EXIT_EXPR} is encountered. + +@item EXIT_EXPR +These nodes represent conditional exits from the nearest enclosing +@code{LOOP_EXPR}. The single operand is the condition; if it is +non-zero, then the loop should be exited. An @code{EXIT_EXPR} will only +appear within a @code{LOOP_EXPR}. + +@item CLEANUP_POINT_EXPR +These nodes represent full-expressions. The single operand is an +expression to evaluate. Any destructor calls engendered by the creation +of temporaries during the evaluation of that expression should be +performed immediately after the expression is evaluated. + +@item CONSTRUCTOR +These nodes represent the brace-enclosed initializers for a structure or +array. The first operand is reserved for use by the back-end. The +second operand is a @code{TREE_LIST}. If the @code{TREE_TYPE} of the +@code{CONSTRUCTOR} is a @code{RECORD_TYPE} or @code{UNION_TYPE}, then +the @code{TREE_PURPOSE} of each node in the @code{TREE_LIST} will be a +@code{FIELD_DECL} and the @code{TREE_VALUE} of each node will be the +expression used to initialize that field. You should not depend on the +fields appearing in any particular order, nor should you assume that all +fields will be represented. Unrepresented fields may be assigned any +value. + +If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is an +@code{ARRAY_TYPE}, then the @code{TREE_PURPOSE} of each element in the +@code{TREE_LIST} will be an @code{INTEGER_CST}. This constant indicates +which element of the array (indexed from zero) is being assigned to; +again, the @code{TREE_VALUE} is the corresponding initializer. If the +@code{TREE_PURPOSE} is @code{NULL_TREE}, then the initializer is for the +next available array element. + +Conceptually, before any initialization is done, the entire area of +storage is initialized to zero. + +@item SAVE_EXPR + +A @code{SAVE_EXPR} represents an expression (possibly involving +side-effects) that is used more than once. The side-effects should +occur only the first time the expression is evaluated. Subsequent uses +should just reuse the computed value. The first operand to the +@code{SAVE_EXPR} is the expression to evaluate. The side-effects should +be executed where the @code{SAVE_EXPR} is first encountered in a +depth-first preorder traversal of the expression tree. + +@item TARGET_EXPR +A @code{TARGET_EXPR} represents a temporary object. The first operand +is a @code{VAR_DECL} for the temporary variable. The second operand is +the initializer for the temporary. The initializer is evaluated, and +copied (bitwise) into the temporary. + +Often, a @code{TARGET_EXPR} occurs on the right-hand side of an +assignment, or as the second operand to a comma-expression which is +itself the right-hand side of an assignment, etc. In this case, we say +that the @code{TARGET_EXPR} is ``normal''; otherwise, we say it is +``orphaned''. For a normal @code{TARGET_EXPR} the temporary variable +should be treated as an alias for the left-hand side of the assignment, +rather than as a new temporary variable. + +The third operand to the @code{TARGET_EXPR}, if present, is a +cleanup-expression (i.e., destructor call) for the temporary. If this +expression is orphaned, then this expression must be executed when the +statement containing this expression is complete. These cleanups must +always be executed in the order opposite to that in which they were +encountered. Note that if a temporary is created on one branch of a +conditional operator (i.e., in the second or third operand to a +@code{COND_EXPR}), the cleanup must be run only if that branch is +actually executed. + +See @code{STMT_IS_FULL_EXPR_P} for more information about running these +cleanups. + +@item AGGR_INIT_EXPR +An @code{AGGR_INIT_EXPR} represents the initialization as the return +value of a function call, or as the result of a constructor. An +@code{AGGR_INIT_EXPR} will only appear as the second operand of a +@code{TARGET_EXPR}. The first operand to the @code{AGGR_INIT_EXPR} is +the address of a function to call, just as in a @code{CALL_EXPR}. The +second operand are the arguments to pass that function, as a +@code{TREE_LIST}, again in a manner similar to that of a +@code{CALL_EXPR}. The value of the expression is that returned by the +function. + +If @code{AGGR_INIT_VIA_CTOR_P} holds of the @code{AGGR_INIT_EXPR}, then +the initialization is via a constructor call. The address of the third +operand of the @code{AGGR_INIT_EXPR}, which is always a @code{VAR_DECL}, +is taken, and this value replaces the first argument in the argument +list. In this case, the value of the expression is the @code{VAR_DECL} +given by the third operand to the @code{AGGR_INIT_EXPR}; constructors do +not return a value. + +@end table diff --git a/gcc/doc/contrib.texi b/gcc/doc/contrib.texi new file mode 100644 index 00000000000..7b4db8da804 --- /dev/null +++ b/gcc/doc/contrib.texi @@ -0,0 +1,690 @@ +The GCC project would like to thank its many contributors. Without them the +project would not have been nearly as successful as it has been. Any omissions +in this list are accidental. Feel free to contact +@email{law@@redhat.com} if you have been left out +or some of your contributions are not listed. Please keep this list in +alphabetical order. + +@itemize @bullet + +@item +Analog Devices helped implement the support for complex data types +and iterators. + +@item +James van Artsdalen wrote the code that makes efficient use of +the Intel 80387 register stack. + +@item +Alasdair Baird for various bugfixes. + +@item +Gerald Baumgartner added the signature extension to the C++ front-end. + +@item +Neil Booth for various work on cpplib. + +@item +Per Bothner for his direction via the steering committee and various +improvements to our infrastructure for supporting new languages. Chill +and Java front end implementations. Initial implementations of +cpplib, fix-header, config.guess, libio, and past C++ library +(libg++) maintainer. + +@item +Devon Bowen helped port GCC to the Tahoe. + +@item +Don Bowman for mips-vxworks contributions. + +@item +Dave Brolley for work on cpplib and Chill. + +@item +Robert Brown implemented the support for Encore 32000 systems. + +@item +Christian Bruel for improvements to local store elimination. + +@item +Herman A.J. ten Brugge for various fixes. + +@item +Joe Buck for his direction via the steering committee. + +@item +Craig Burley for leadership of the Fortran effort. + +@item +John Carr for his alias work, SPARC hacking, infrastructure improvements, +previous contributions to the steering committee, loop optimizations, etc. + +@item +Steve Chamberlain wrote the support for the Hitachi SH and H8 processors +and the PicoJava processor. + +@item +Scott Christley for his ObjC contributions. + +@item +Branko Cibej for more warning contributions. + +@item +Nick Clifton for arm, mcore, fr30, v850, m32r work, --help, and other random +hacking. + +@item +Ralf Corsepius for SH testing and minor bugfixing. + +@item +Stan Cox for care and feeding of the x86 port and lots of behind +the scenes hacking. + +@item +Alex Crain provided changes for the 3b1. + +@item +Ian Dall for major improvements to the NS32k port. + +@item +Dario Dariol contributed the four varieties of sample programs +that print a copy of their source. + +@item +Ulrich Drepper for his work on the C++ runtime libraries, glibc, + testing of GCC using glibc, ISO C99 support, CFG dumping support, etc. + +@item +Richard Earnshaw for his ongoing work with the ARM. + +@item +David Edelsohn for his direction via the steering committee, +ongoing work with the RS6000/PowerPC port, and help cleaning up Haifa +loop changes. + +@item +Mark Elbrecht for various DJGPP improvements. + +@item +Ben Elliston for his work to move the Objective-C runtime into its +own subdirectory and for his work on autoconf. + +@item +Paul Eggert for random hacking all over gcc. + +@item +Marc Espie for OpenBSD support. + +@item +Doug Evans for much of the global optimization framework, arc, m32r, +and SPARC work. + +@item +Fred Fish for BeOS support and Ada fixes. + +@item +Peter Gerwinski for various bugfixes and the Pascal front end. + +@item +Anthony Green for his -Os contributions and Java front end work. + +@item +Kaveh Ghazi for his direction via the steering committee and +amazing work to make -W -Wall useful. + +@item +Judy Goldberg for c++ contributions. + +@item +Torbjorn Granlund for various fixes and the c-torture testsuite, +multiply- and divide-by-constant optimization, improved long long +support, improved leaf function register allocation, and his direction +via the steering committee. + +@item +Michael K. Gschwind contributed the port to the PDP-11. + +@item +Ron Guilmette implemented the @code{protoize} and @code{unprotoize} +tools, the support for Dwarf symbolic debugging information, and much of +the support for System V Release 4. He has also worked heavily on the +Intel 386 and 860 support. + +@item +Bruno Haible for improvements in the runtime overhead for EH, new +warnings and assorted bugfixes. + +@item +Andrew Haley for his Java work. + +@item +Chris Hanson assisted in making GCC work on HP-UX for the 9000 series 300. + +@item +Michael Hayes for various thankless work he's done trying to get +the c30/c40 ports functional. Lots of loop and unroll improvements and +fixes. + +@item +Kate Hedstrom for staking the g77 folks with an initial testsuite. + +@item +Richard Henderson for his ongoing SPARC and alpha work, loop opts, and +generally fixing lots of old problems we've ignored for years, flow +rewrite and lots of stuff I've forgotten. + +@item +Nobuyuki Hikichi of Software Research Associates, Tokyo, contributed +the support for the Sony NEWS machine. + +@item +Manfred Hollstein for his ongoing work to keep the m88k alive, lots +of testing an bugfixing, particularly of our configury code. + +@item +Steve Holmgren for MachTen patches. + +@item +Jan Hubicka for his x86 port improvements. + +@item +Christian Iseli for various bugfixes. + +@item +Kamil Iskra for general m68k hacking. + +@item +Lee Iverson for random fixes and mips testing. + +@item +Andreas Jaeger for various fixes to the MIPS port + +@item +Jakub Jelinek for his SPARC work and sibling call optimizations. + +@item +J. Kean Johnston for OpenServer support. + +@item +Klaus Kaempf for his ongoing work to make alpha-vms a viable target. + +@item +David Kashtan of SRI adapted GCC to VMS. + +@item +Richard Kenner of the New York University Ultracomputer Research +Laboratory wrote the machine descriptions for the AMD 29000, the DEC +Alpha, the IBM RT PC, and the IBM RS/6000 as well as the support for +instruction attributes. He also made changes to better support RISC +processors including changes to common subexpression elimination, +strength reduction, function calling sequence handling, and condition +code support, in addition to generalizing the code for frame pointer +elimination and delay slot scheduling. Richard Kenner was also the +head maintainer of GCC for several years. + +@item +Robin Kirkham for cpu32 support. + +@item +Mark Klein for PA improvements. + +@item +Geoffrey Keating for his ongoing work to make the PPC work for Linux. + +@item +Brendan Kehoe for his ongoing work with g++. + +@item +Oliver M. Kellogg of Deutsche Aerospace contributed the port to the +MIL-STD-1750A. + +@item +Mumit Khan for various contributions to the cygwin and mingw32 ports and +maintaining binary releases for Windows hosts. + +@item +Thomas Koenig for various bugfixes. + +@item +Bruce Korb for the new and improved fixincludes code. + +@item +Benjamin Kosnik for his g++ work. + +@item +Ted Lemon wrote parts of the RTL reader and printer. + +@item +Charles LaBrec contributed the support for the Integrated Solutions +68020 system. + +@item +Jeff Law for his direction via the steering committee, coordinating the +entire egcs project and GCC 2.95, rolling out snapshots and releases, +handling merges from GCC2, reviewing tons of patches that might have +fallen through the cracks else, and random but extensive hacking. + +@item +Marc Lehmann for his direction via the steering committee and helping +with analysis and improvements of x86 performance. + +@item +Kriang Lerdsuwanakij for improvements to demangler and various c++ fixes. + +@item +Warren Levy major work on libgjc (Java Runtime Library) and random +work on the Java front-end. + +@item +Alain Lichnewsky ported GCC to the Mips cpu. + +@item +Robert Lipe for OpenServer support, new testsuites, testing, etc. + +@item +Weiwen Liu for testing and various bugfixes. + +@item +Martin von Löwis for internal consistency checking infrastructure, +and various C++ improvements including namespace support. + +@item +Dave Love for his ongoing work with the Fortran front end and +runtime libraries. + +@item +H.J. Lu for his previous contributions to the steering committee, many x86 +bug reports, prototype patches, and keeping the Linux ports working. + +@item +Andrew MacLeod for his ongoing work in building a real EH system, +various code generation improvements, work on the global optimizer, etc. + +@item +Bob Manson for his behind the scenes work on dejagnu. + +@item +Vladimir Makarov for hacking some ugly i960 problems, PowerPC +hacking improvements to compile-time performance and overall knowledge +and direction in the area of instruction scheduling. + +@item +Greg McGary for random fixes and (someday) bounded pointers. + +@item +Michael Meissner for LRS framework, ia32, m32r, v850, m88k, MIPS powerpc, haifa, +ECOFF debug support, and other assorted hacking. + +@item +Jason Merrill for his direction via the steering committee and leading +the g++ effort. + +@item +Jason Molenda for major help in the care and feeding of all the services +on the gcc.gnu.org (formerly egcs.cygnus.com) machine -- mail, web +services, ftp services, etc etc. + +@item +David Mosberger-Tang for various Alpha improvements. + +@item +Stephen Moshier contributed the floating point emulator that assists in +cross-compilation and permits support for floating point numbers wider +than 64 bits and for ISO C99 support. + +@item +Bill Moyer for his behind the scenes work on various issues. + +@item +David Miller for his direction via the steering committee, lots of +SPARC work, improvements in jump.c and interfacing with the Linux kernel +developers. + +@item +Gary Miller ported GCC to Charles River Data Systems machines. + +@item +Mark Mitchell for his direction via the steering committee, mountains +of C++ work, load/store hoisting out of loops and alias analysis +improvements, ISO "restrict" support. + +@item +Alan Modra for various Linux bits and testing. + +@item +Toon Moene for his direction via the steering committee, Fortran +maintainance, and his ongoing work to make us make Fortran run fast. + +@item +Catherine Moore for fixing various ugly problems we have sent her +way, including the haifa bug which was killing the Alpha & PowerPC Linux +kernels. + +@item +Philippe De Muyter for his work on the m68k port. + +@item +Joseph Myers for his work on the PDP-11 port, format checking and ISO +C99 support. + +@item +Nathan Myers for his work on libstdc++-v3. + +@item +NeXT, Inc.@: donated the front end that supports the Objective C +language. + +@item +Hans-Peter Nilsson for improvements to the search engine +setup, various documentation fixes and other small fixes. + +@item +Geoff Noer for this work on getting cygwin native builds working. + +@item +Alexandre Oliva for various build infrastructure improvements, scripts and +amazing testing work. + +@item +Rainer Orth for random MIPS work, including improvements to our o32 +ABI support, improvements to dejagnu's MIPS support, etc. + +@item +Melissa O'Neill for various NeXT fixes. + +@item +Paul Petersen wrote the machine description for the Alliant FX/8. + +@item +Alexandre Petit-Bianco for his Java work. + +@item +Matthias Pfaller for major improvements to the NS32k port. + +@item +Gerald Pfeifer his direction via the steering committee, maintenance of +the web pages and pointing out lots of problems we need to solve. + +@item +Ovidiu Predescu for his work on the ObjC front end and runtime libraries. + +@item +Ken Raeburn for various improvements to checker, mips ports and various +cleanups in the compiler. + +@item +David Reese of Sun Microsystems contributed to the Solaris on PowerPC +port. +@item +Gabriel Dos Reis for contributions and maintenance of libstdc++-v3, +including valarray implementation and limits support. + +@item +Joern Rennecke for maintaining the sh port, loop, regmove & reload +hacking. + +@item +Gavin Romig-Koch for lots of behind the scenes MIPS work. + +@item +Ken Rose for fixes to our delay slot filling code. + +@item +Paul Rubin wrote most of the preprocessor. + +@item +Andreas Schwab for his work on the m68k port. + +@item +Graham Stott. for various infrastructure improvements. + +@item +Juha Sarlin for improvements to the H8 code generator. + +@item +Greg Satz assisted in making GCC work on HP-UX for the 9000 series 300. + +@item +Peter Schauer wrote the code to allow debugging to work on the Alpha. + +@item +William Schelter did most of the work on the Intel 80386 support. + +@item +Bernd Schmidt for various code generation improvements and major +work in the reload pass. + +@item +Franz Sirl for his ongoing work with making the PPC port stable +for linux. + +@item +Joel Sherrill for his direction via the steering committee, RTEMS +contributions and RTEMS testing. + +@item +Nathan Sidwell for many C++ fixes/improvements. + +@item +Jeffrey Siegal for helping RMS with the original design of GCC, some +code which handles the parse tree and RTL data structures, constant +folding and help with the original VAX & m68k ports. + +@item +Andrey Slepuhin for assorted AIX hacking. + +@item +Randy Smith finished the Sun FPA support. + +@item +Christopher Smith did the port for Convex machines. + +@item +Scott Snyder for various fixes. + +@item +Richard Stallman, for writing the original gcc and launching the GNU project. + +@item +Jan Stein of the Chalmers Computer Society provided support for +Genix, as well as part of the 32000 machine description. + +@item +Nigel Stephens for various mips16 related fixes/improvements. + +@item +Jonathan Stone wrote the machine description for the Pyramid computer. + +@item +Mike Stump for his Elxsi port, g++ contributions over the years and more +recently his vxworks contributions + +@item +Shigeya Suzuki for this fixes for the bsdi platforms. + +@item +Ian Lance Taylor for his mips16 work, general configury hacking, +fixincludes, etc. + +@item +Holger Teutsch provided the support for the Clipper cpu. + +@item +Michael Tiemann for random bugfixes the first instruction scheduler, +initial C++ support, function integration, NS32k, sparc and M88k +machine description work, delay slot scheduling. + +@item +Gary Thomas for his ongoing work to make the PPC work for Linux. + +@item +Philipp Thomas for random bugfixes throughout the compiler + +@item +Kresten Krab Thorup wrote the run time support for the Objective C +language. + +@item +Teemu Torma for thread safe exception handling support. + +@item +Leonard Tower wrote parts of the parser, RTL generator, and RTL +definitions, and of the Vax machine description. + +@item +Tom Tromey for internationalization support and his Java work. + +@item +Lassi Tuura for improvements to config.guess to determine HP processor +types. + +@item +Todd Vierling for contributions for NetBSD ports. + +@item +Krister Walfridsson for random bugfixes. + +@item +John Wehle for various improvements for the x86 code generator, +related infrastructure improvements to help x86 code generation, +value range propagation and other work, WE32k port. + +@item +Dale Wiles helped port GCC to the Tahoe. + +@item +Zack Weinberg for major work on cpplib and various other bugfixes. + +@item +Jim Wilson for his direction via the steering committee, tackling hard +problems in various places that nobody else wanted to work on, strength +reduction and other loop optimizations. + +@item +Carlo Wood for various fixes. + +@item +Tom Wood for work on the m88k port. + +@item +Masanobu Yuhara of Fujitsu Laboratories implemented the machine +description for the Tron architecture (specifically, the Gmicro). + +@item +Kevin Zachmann helped ported GCC to the Tahoe. + +@end itemize + + +We'd also like to thank the folks who have contributed time and energy in +testing GCC: + +@itemize @bullet +@item +David Billinghurst + +@item +Horst von Brand + +@item +Rodney Brown + +@item +Joe Buck + +@item +Craig Burley + +@item +Ulrich Drepper + +@item +David Edelsohn + +@item +Kaveh Ghazi + +@item +Yung Shing Gene + +@item +Richard Henderson + +@item +Manfred Hollstein + +@item +Kate Hedstrom + +@item +Kamil Iskra + +@item +Christian Joensson + +@item +Jeff Law + +@item +Robert Lipe + +@item +Dave Love + +@item +Damon Love + +@item +H.J. Lu + +@item +Mumit Khan + +@item +Matthias Klose + +@item +Martin Knoblauch + +@item +Toon Moene + +@item +David Miller + +@item +Matthias Mueller + +@item +Alexandre Oliva + +@item +Richard Polton + +@item +David Rees + +@item +Peter Schmid + +@item +David Schuler + +@item +Vin Shelton + +@item +Franz Sirl + +@item +Mike Stump + +@item +Carlo Wood + +@item +And many others +@end itemize + +And finally we'd like to thank everyone who uses the compiler, submits bug +reports and generally reminds us why we're doing this work in the first place. diff --git a/gcc/doc/cpp.1 b/gcc/doc/cpp.1 new file mode 100644 index 00000000000..f3e227e6b05 --- /dev/null +++ b/gcc/doc/cpp.1 @@ -0,0 +1,764 @@ +.\" Automatically generated by Pod::Man version 1.1 +.\" Mon Feb 19 19:32:17 2001 +.\" +.\" Standard preamble: +.\" ====================================================================== +.de Sh \" Subsection heading +.br +.if t .Sp +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Ip \" List item +.br +.ie \\n(.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R + +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. | will give a +.\" real vertical bar. \*(C+ will give a nicer C++. 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For macro processing of other files, you are +strongly encouraged to use alternatives like M4, which will likely give +you better results and avoid many problems. For example, normally the C +preprocessor does not preserve arbitrary whitespace verbatim, but +instead replaces each sequence with a single space. +.PP +For use on C-like source files, the C preprocessor provides four +separate facilities that you can use as you see fit: +.Ip "\(bu" 4 +Inclusion of header files. These are files of declarations that can be +substituted into your program. +.Ip "\(bu" 4 +Macro expansion. You can define \fImacros\fR, which are abbreviations +for arbitrary fragments of C code, and then the C preprocessor will +replace the macros with their definitions throughout the program. +.Ip "\(bu" 4 +Conditional compilation. Using special preprocessing directives, you +can include or exclude parts of the program according to various +conditions. +.Ip "\(bu" 4 +Line control. If you use a program to combine or rearrange source files +into an intermediate file which is then compiled, you can use line +control to inform the compiler of where each source line originally came +from. +.PP +C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C +preprocessor, which provides a small superset of the features of \s-1ISO\s0 +Standard C. +.PP +In its default mode, the \s-1GNU\s0 C preprocessor does not do a few things +required by the standard. These are features which are rarely, if ever, +used, and may cause surprising changes to the meaning of a program which +does not expect them. To get strict \s-1ISO\s0 Standard C, you should use the +\&\fB\-std=c89\fR or \fB\-std=c99\fR options, depending on which version +of the standard you want. To get all the mandatory diagnostics, you +must also use \fB\-pedantic\fR. +.SH "OPTIONS" +.IX Header "OPTIONS" +The C preprocessor expects two file names as arguments, \fIinfile\fR and +\&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any +other files it specifies with \fB#include\fR. All the output generated +by the combined input files is written in \fIoutfile\fR. +.PP +Either \fIinfile\fR or \fIoutfile\fR may be \fB-\fR, which as +\&\fIinfile\fR means to read from standard input and as \fIoutfile\fR +means to write to standard output. Also, if either file is omitted, it +means the same as if \fB-\fR had been specified for that file. +.PP +Here is a table of command options accepted by the C preprocessor. +These options can also be given when compiling a C program; they are +passed along automatically to the preprocessor when it is invoked by the +compiler. +.Ip "\fB\-P\fR" 4 +.IX Item "-P" +Inhibit generation of \fB#\fR\-lines with line-number information in the +output from the preprocessor. This might be useful when running the +preprocessor on something that is not C code and will be sent to a +program which might be confused by the \fB#\fR\-lines. +.Ip "\fB\-C\fR" 4 +.IX Item "-C" +Do not discard comments. All comments are passed through to the output +file, except for comments in processed directives, which are deleted +along with the directive. Comments appearing in the expansion list of a +macro will be preserved, and appear in place wherever the macro is +invoked. +.Sp +You should be prepared for side effects when using \fB\-C\fR; it causes +the preprocessor to treat comments as tokens in their own right. For +example, macro redefinitions that were trivial when comments were +replaced by a single space might become significant when comments are +retained. Also, comments appearing at the start of what would be a +directive line have the effect of turning that line into an ordinary +source line, since the first token on the line is no longer a \fB#\fR. +.Ip "\fB\-traditional\fR" 4 +.IX Item "-traditional" +Try to imitate the behavior of old-fashioned C, as opposed to \s-1ISO\s0 C. +.RS 4 +.Ip "\(bu" 4 +Traditional macro expansion pays no attention to single-quote or +double-quote characters; macro argument symbols are replaced by the +argument values even when they appear within apparent string or +character constants. +.Ip "\(bu" 4 +Traditionally, it is permissible for a macro expansion to end in the +middle of a string or character constant. The constant continues into +the text surrounding the macro call. +.Ip "\(bu" 4 +However, traditionally the end of the line terminates a string or +character constant, with no error. +.Ip "\(bu" 4 +In traditional C, a comment is equivalent to no text at all. (In \s-1ISO\s0 +C, a comment counts as whitespace.) +.Ip "\(bu" 4 +Traditional C does not have the concept of a ``preprocessing number''. +It considers \fB1.0e+4\fR to be three tokens: \fB1.0e\fR, \fB+\fR, +and \fB4\fR. +.Ip "\(bu" 4 +A macro is not suppressed within its own definition, in traditional C. +Thus, any macro that is used recursively inevitably causes an error. +.Ip "\(bu" 4 +The character \fB#\fR has no special meaning within a macro definition +in traditional C. +.Ip "\(bu" 4 +In traditional C, the text at the end of a macro expansion can run +together with the text after the macro call, to produce a single token. +(This is impossible in \s-1ISO\s0 C.) +.Ip "\(bu" 4 +None of the \s-1GNU\s0 extensions to the preprocessor are available in +\&\fB\-traditional\fR mode. +.RE +.RS 4 +.Sp +Use the \fB\-traditional\fR option when preprocessing Fortran code, so +that single-quotes and double-quotes within Fortran comment lines (which +are generally not recognized as such by the preprocessor) do not cause +diagnostics about unterminated character or string constants. +.Sp +However, this option does not prevent diagnostics about unterminated +comments when a C-style comment appears to start, but not end, within +Fortran-style commentary. +.Sp +So, the following Fortran comment lines are accepted with +\&\fB\-traditional\fR: +.Sp +.Vb 3 +\& C This isn't an unterminated character constant +\& C Neither is "20000000000, an octal constant +\& C in some dialects of Fortran +.Ve +However, this type of comment line will likely produce a diagnostic, or +at least unexpected output from the preprocessor, due to the +unterminated comment: +.Sp +.Vb 2 +\& C Some Fortran compilers accept /* as starting +\& C an inline comment. +.Ve +Note that \f(CW\*(C`g77\*(C'\fR automatically supplies the \fB\-traditional\fR +option when it invokes the preprocessor. However, a future version of +\&\f(CW\*(C`g77\*(C'\fR might use a different, more-Fortran-aware preprocessor in +place of \f(CW\*(C`cpp\*(C'\fR. +.RE +.Ip "\fB\-trigraphs\fR" 4 +.IX Item "-trigraphs" +Process \s-1ISO\s0 standard trigraph sequences. These are three-character +sequences, all starting with \fB??\fR, that are defined by \s-1ISO\s0 C to +stand for single characters. For example, \fB??/\fR stands for +\&\fB\e\fR, so \fB'??/n'\fR is a character constant for a newline. By +default, \s-1GCC\s0 ignores trigraphs, but in standard-conforming modes it +converts them. See the \fB\-std\fR option. +.Sp +The nine trigraph sequences are +.RS 4 +.Ip "\fB??(\fR" 4 +.IX Item "??(" +-> \fB[\fR +.Ip "\fB??)\fR" 4 +.IX Item "??)" +-> \fB]\fR +.Ip "\fB??<\fR" 4 +.IX Item "??<" +-> \fB{\fR +.Ip "\fB??>\fR" 4 +.IX Item "??>" +-> \fB}\fR +.Ip "\fB??=\fR" 4 +.IX Item "??=" +-> \fB#\fR +.Ip "\fB??/\fR" 4 +.IX Item "??/" +-> \fB\e\fR +.Ip "\fB??'\fR" 4 +.IX Item "??'" +-> \fB^\fR +.Ip "\fB??!\fR" 4 +.IX Item "??!" +-> \fB|\fR +.Ip "\fB??-\fR" 4 +.IX Item "??-" +-> \fB~\fR +.RE +.RS 4 +.Sp +Trigraph support is not popular, so many compilers do not implement it +properly. Portable code should not rely on trigraphs being either +converted or ignored. +.RE +.Ip "\fB\-pedantic\fR" 4 +.IX Item "-pedantic" +Issue warnings required by the \s-1ISO\s0 C standard in certain cases such +as when text other than a comment follows \fB#else\fR or \fB#endif\fR. +.Ip "\fB\-pedantic-errors\fR" 4 +.IX Item "-pedantic-errors" +Like \fB\-pedantic\fR, except that errors are produced rather than +warnings. +.Ip "\fB\-Wcomment\fR" 4 +.IX Item "-Wcomment" +.PD 0 +.Ip "\fB\-Wcomments\fR" 4 +.IX Item "-Wcomments" +.PD +(Both forms have the same effect). +Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR +comment, or whenever a backslash-newline appears in a \fB//\fR comment. +.Ip "\fB\-Wtrigraphs\fR" 4 +.IX Item "-Wtrigraphs" +Warn if any trigraphs are encountered. This option used to take effect +only if \fB\-trigraphs\fR was also specified, but now works +independently. Warnings are not given for trigraphs within comments, as +we feel this is obnoxious. +.Ip "\fB\-Wwhite-space\fR" 4 +.IX Item "-Wwhite-space" +Warn about possible white space confusion, e.g. white space between a +backslash and a newline. +.Ip "\fB\-Wall\fR" 4 +.IX Item "-Wall" +Requests \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR, and \fB\-Wwhite-space\fR +(but not \fB\-Wtraditional\fR or \fB\-Wundef\fR). +.Ip "\fB\-Wtraditional\fR" 4 +.IX Item "-Wtraditional" +Warn about certain constructs that behave differently in traditional and +\&\s-1ISO\s0 C. +.RS 4 +.Ip "\(bu" 4 +Macro parameters that appear within string literals in the macro body. +In traditional C macro replacement takes place within string literals, +but does not in \s-1ISO\s0 C. +.Ip "\(bu" 4 +In traditional C, some preprocessor directives did not exist. +Traditional preprocessors would only consider a line to be a directive +if the \fB#\fR appeared in column 1 on the line. Therefore +\&\fB\-Wtraditional\fR warns about directives that traditional C +understands but would ignore because the \fB#\fR does not appear as the +first character on the line. It also suggests you hide directives like +\&\fB#pragma\fR not understood by traditional C by indenting them. Some +traditional implementations would not recognise \fB#elif\fR, so it +suggests avoiding it altogether. +.Ip "\(bu" 4 +A function-like macro that appears without arguments. +.Ip "\(bu" 4 +The unary plus operator. +.Ip "\(bu" 4 +The `U' integer constant suffix. (Traditonal C does support the `L' +suffix on integer constants.) Note, these suffixes appear in macros +defined in the system headers of most modern systems, e.g. the _MIN/_MAX +macros in limits.h. Use of these macros can lead to spurious warnings +as they do not necessarily reflect whether the code in question is any +less portable to traditional C given that suitable backup definitions +are provided. +.RE +.RS 4 +.RE +.Ip "\fB\-Wundef\fR" 4 +.IX Item "-Wundef" +Warn if an undefined identifier is evaluated in an \fB#if\fR directive. +.Ip "\fB\-I\fR \fIdirectory\fR" 4 +.IX Item "-I directory" +Add the directory \fIdirectory\fR to the head of the list of +directories to be searched for header files. +This can be used to override a system header file, substituting your +own version, since these directories are searched before the system +header file directories. If you use more than one \fB\-I\fR option, +the directories are scanned in left-to-right order; the standard +system directories come after. +.Ip "\fB\-I-\fR" 4 +.IX Item "-I-" +Any directories specified with \fB\-I\fR options before the \fB\-I-\fR +option are searched only for the case of \fB#include "\fR\fIfile\fR\fB"\fR; +they are not searched for \fB#include <\fR\fIfile\fR\fB>\fR. +.Sp +If additional directories are specified with \fB\-I\fR options after +the \fB\-I-\fR, these directories are searched for all \fB#include\fR +directives. +.Sp +In addition, the \fB\-I-\fR option inhibits the use of the current +directory as the first search directory for \fB#include "\fR\fIfile\fR\fB"\fR. +Therefore, the current directory is searched only if it is requested +explicitly with \fB\-I.\fR. Specifying both \fB\-I-\fR and \fB\-I.\fR +allows you to control precisely which directories are searched before +the current one and which are searched after. +.Ip "\fB\-nostdinc\fR" 4 +.IX Item "-nostdinc" +Do not search the standard system directories for header files. +Only the directories you have specified with \fB\-I\fR options +(and the current directory, if appropriate) are searched. +.Sp +By using both \fB\-nostdinc\fR and \fB\-I-\fR, you can limit the include-file +search path to only those directories you specify explicitly. +.Ip "\fB\-nostdinc++\fR" 4 +.IX Item "-nostdinc++" +Do not search for header files in the \*(C+\-specific standard directories, +but do still search the other standard directories. (This option is +used when building the \*(C+ library.) +.Ip "\fB\-remap\fR" 4 +.IX Item "-remap" +When searching for a header file in a directory, remap file names if a +file named \fIheader.gcc\fR exists in that directory. This can be used +to work around limitations of file systems with file name restrictions. +The \fIheader.gcc\fR file should contain a series of lines with two +tokens on each line: the first token is the name to map, and the second +token is the actual name to use. +.Ip "\fB\-D\fR \fIname\fR" 4 +.IX Item "-D name" +Predefine \fIname\fR as a macro, with definition \fB1\fR. +.Ip "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4 +.IX Item "-D name=definition" +Predefine \fIname\fR as a macro, with definition \fIdefinition\fR. +There are no restrictions on the contents of \fIdefinition\fR, but if +you are invoking the preprocessor from a shell or shell-like program you +may need to use the shell's quoting syntax to protect characters such as +spaces that have a meaning in the shell syntax. If you use more than +one \fB\-D\fR for the same \fIname\fR, the rightmost definition takes +effect. +.Sp +Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in +order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the +order in which they are written. +.Ip "\fB\-U\fR \fIname\fR" 4 +.IX Item "-U name" +Do not predefine \fIname\fR. +.Sp +Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in +order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the +order in which they are written. +.Ip "\fB\-undef\fR" 4 +.IX Item "-undef" +Do not predefine any nonstandard macros. +.Ip "\fB\-gcc\fR" 4 +.IX Item "-gcc" +Define the macros \fI_\|_GNUC_\|_\fR, \fI_\|_GNUC_MINOR_\|_\fR and +\&\fI_\|_GNUC_PATCHLEVEL_\|_\fR. These are defined automatically when you use +\&\fBgcc \-E\fR; you can turn them off in that case with \fB\-no-gcc\fR. +.Ip "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4 +.IX Item "-A predicate=answer" +Make an assertion with the predicate \fIpredicate\fR and answer +\&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR +\&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because +it does not use shell special characters. +.Ip "\fB\-A -\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4 +.IX Item "-A -predicate=answer" +Disable an assertion with the predicate \fIpredicate\fR and answer +\&\fIanswer\fR. Specifying no predicate, by \fB\-A-\fR or \fB\-A -\fR, +disables all predefined assertions and all assertions preceding it on +the command line; and also undefines all predefined macros and all +macros preceding it on the command line. +.Ip "\fB\-dM\fR" 4 +.IX Item "-dM" +Instead of outputting the result of preprocessing, output a list of +\&\fB#define\fR directives for all the macros defined during the +execution of the preprocessor, including predefined macros. This gives +you a way of finding out what is predefined in your version of the +preprocessor; assuming you have no file \fBfoo.h\fR, the command +.Sp +.Vb 1 +\& touch foo.h; cpp -dM foo.h +.Ve +will show the values of any predefined macros. +.Ip "\fB\-dD\fR" 4 +.IX Item "-dD" +Like \fB\-dM\fR except in two respects: it does \fInot\fR include the +predefined macros, and it outputs \fIboth\fR the \fB#define\fR +directives and the result of preprocessing. Both kinds of output go to +the standard output file. +.Ip "\fB\-dN\fR" 4 +.IX Item "-dN" +Like \fB\-dD\fR, but emit only the macro names, not their expansions. +.Ip "\fB\-dI\fR" 4 +.IX Item "-dI" +Output \fB#include\fR directives in addition to the result of +preprocessing. +.Ip "\fB\-M\fR" 4 +.IX Item "-M" +Instead of outputting the result of preprocessing, output a rule +suitable for \f(CW\*(C`make\*(C'\fR describing the dependencies of the main source +file. The preprocessor outputs one \f(CW\*(C`make\*(C'\fR rule containing the +object file name for that source file, a colon, and the names of all the +included files, including those coming from \fB\-include\fR or +\&\fB\-imacros\fR command line options. Unless specified explicitly (with +\&\fB\-MT\fR or \fB\-MQ\fR), the object file name consists of the basename +of the source file with any suffix replaced with object file suffix. +If there are many included files +then the rule is split into several lines using \fB\e\fR\-newline. +.Ip "\fB\-MM\fR" 4 +.IX Item "-MM" +Like \fB\-M\fR, but mention only the files included with \fB#include +"\fR\fIfile\fR\fB"\fR or with \fB\-include\fR or \fB\-imacros\fR command line +options. System header files included with \fB#include <\fR\fIfile\fR\fB>\fR +are omitted. +.Ip "\fB\-MF\fR \fIfile\fR" 4 +.IX Item "-MF file" +When used with \fB\-M\fR or \fB\-MM\fR, specifies a file to write the +dependencies to. This allows the preprocessor to write the preprocessed +file to stdout normally. If no \fB\-MF\fR switch is given, \s-1CPP\s0 sends +the rules to stdout and suppresses normal preprocessed output. +.Ip "\fB\-MG\fR" 4 +.IX Item "-MG" +When used with \fB\-M\fR or \fB\-MM\fR, \fB\-MG\fR says to treat missing +header files as generated files and assume they live in the same +directory as the source file. It suppresses preprocessed output, as a +missing header file is ordinarily an error. +.Sp +This feature is used in automatic updating of makefiles. +.Ip "\fB\-MP\fR" 4 +.IX Item "-MP" +This option instructs \s-1CPP\s0 to add a phony target for each dependency +other than the main file, causing each to depend on nothing. These +dummy rules work around errors \f(CW\*(C`make\*(C'\fR gives if you remove header +files without updating the \f(CW\*(C`Makefile\*(C'\fR to match. +.Sp +This is typical output:\- +.Sp +.Vb 1 +\& /tmp/test.o: /tmp/test.c /tmp/test.h +.Ve +.Vb 1 +\& /tmp/test.h: +.Ve +.Ip "\fB\-MQ\fR \fItarget\fR" 4 +.IX Item "-MQ target" +.PD 0 +.Ip "\fB\-MT\fR \fItarget\fR" 4 +.IX Item "-MT target" +.PD +By default \s-1CPP\s0 uses the main file name, including any path, and appends +the object suffix, normally ``.o'', to it to obtain the name of the +target for dependency generation. With \fB\-MT\fR you can specify a +target yourself, overriding the default one. +.Sp +If you want multiple targets, you can specify them as a single argument +to \fB\-MT\fR, or use multiple \fB\-MT\fR options. +.Sp +The targets you specify are output in the order they appear on the +command line. \fB\-MQ\fR is identical to \fB\-MT\fR, except that the +target name is quoted for Make, but with \fB\-MT\fR it isn't. For +example, \-MT '$(objpfx)foo.o' gives +.Sp +.Vb 1 +\& $(objpfx)foo.o: /tmp/foo.c +.Ve +but \-MQ '$(objpfx)foo.o' gives +.Sp +.Vb 1 +\& $$(objpfx)foo.o: /tmp/foo.c +.Ve +The default target is automatically quoted, as if it were given with +\&\fB\-MQ\fR. +.Ip "\fB\-H\fR" 4 +.IX Item "-H" +Print the name of each header file used, in addition to other normal +activities. +.Ip "\fB\-imacros\fR \fIfile\fR" 4 +.IX Item "-imacros file" +Process \fIfile\fR as input, discarding the resulting output, before +processing the regular input file. Because the output generated from +\&\fIfile\fR is discarded, the only effect of \fB\-imacros\fR \fIfile\fR +is to make the macros defined in \fIfile\fR available for use in the +main input. +.Ip "\fB\-include\fR \fIfile\fR" 4 +.IX Item "-include file" +Process \fIfile\fR as input, and include all the resulting output, +before processing the regular input file. +.Ip "\fB\-idirafter\fR \fIdir\fR" 4 +.IX Item "-idirafter dir" +Add the directory \fIdir\fR to the second include path. The directories +on the second include path are searched when a header file is not found +in any of the directories in the main include path (the one that +\&\fB\-I\fR adds to). +.Ip "\fB\-iprefix\fR \fIprefix\fR" 4 +.IX Item "-iprefix prefix" +Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR +options. If the prefix represents a directory, you should include the +final \fB/\fR. +.Ip "\fB\-iwithprefix\fR \fIdir\fR" 4 +.IX Item "-iwithprefix dir" +Add a directory to the second include path. The directory's name is +made by concatenating \fIprefix\fR and \fIdir\fR, where \fIprefix\fR was +specified previously with \fB\-iprefix\fR. +.Ip "\fB\-isystem\fR \fIdir\fR" 4 +.IX Item "-isystem dir" +Add a directory to the beginning of the second include path, marking it +as a system directory, so that it gets the same special treatment as +is applied to the standard system directories. +.Ip "\fB\-x c\fR" 4 +.IX Item "-x c" +.PD 0 +.Ip "\fB\-x c++\fR" 4 +.IX Item "-x c++" +.Ip "\fB\-x objective-c\fR" 4 +.IX Item "-x objective-c" +.Ip "\fB\-x assembler-with-cpp\fR" 4 +.IX Item "-x assembler-with-cpp" +.PD +Specify the source language: C, \*(C+, Objective-C, or assembly. This has +nothing to do with standards conformance or extensions; it merely +selects which base syntax to expect. If you give none of these options, +cpp will deduce the language from the extension of the source file: +\&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common +extensions for \*(C+ and assembly are also recognized. If cpp does not +recognize the extension, it will treat the file as C; this is the most +generic mode. +.Sp +\&\fBNote:\fR Previous versions of cpp accepted a \fB\-lang\fR option +which selected both the language and the standards conformance level. +This option has been removed, because it conflicts with the \fB\-l\fR +option. +.Ip "\fB\-std=\fR\fIstandard\fR" 4 +.IX Item "-std=standard" +.PD 0 +.Ip "\fB\-ansi\fR" 4 +.IX Item "-ansi" +.PD +Specify the standard to which the code should conform. Currently cpp +only knows about the standards for C; other language standards will be +added in the future. +.Sp +\&\fIstandard\fR +may be one of: +.RS 4 +.if n .Ip "\f(CW""iso9899:1990""\fR" 4 +.el .Ip "\f(CWiso9899:1990\fR" 4 +.IX Item "iso9899:1990" +.PD 0 +.if n .Ip "\f(CW""c89""\fR" 4 +.el .Ip "\f(CWc89\fR" 4 +.IX Item "c89" +.PD +The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for +this version of the standard. +.Sp +The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR. +.if n .Ip "\f(CW""iso9899:199409""\fR" 4 +.el .Ip "\f(CWiso9899:199409\fR" 4 +.IX Item "iso9899:199409" +The 1990 C standard, as amended in 1994. +.if n .Ip "\f(CW""iso9899:1999""\fR" 4 +.el .Ip "\f(CWiso9899:1999\fR" 4 +.IX Item "iso9899:1999" +.PD 0 +.if n .Ip "\f(CW""c99""\fR" 4 +.el .Ip "\f(CWc99\fR" 4 +.IX Item "c99" +.if n .Ip "\f(CW""iso9899:199x""\fR" 4 +.el .Ip "\f(CWiso9899:199x\fR" 4 +.IX Item "iso9899:199x" +.if n .Ip "\f(CW""c9x""\fR" 4 +.el .Ip "\f(CWc9x\fR" 4 +.IX Item "c9x" +.PD +The revised \s-1ISO\s0 C standard, published in December 1999. Before +publication, this was known as C9X. +.if n .Ip "\f(CW""gnu89""\fR" 4 +.el .Ip "\f(CWgnu89\fR" 4 +.IX Item "gnu89" +The 1990 C standard plus \s-1GNU\s0 extensions. This is the default. +.if n .Ip "\f(CW""gnu99""\fR" 4 +.el .Ip "\f(CWgnu99\fR" 4 +.IX Item "gnu99" +.PD 0 +.if n .Ip "\f(CW""gnu9x""\fR" 4 +.el .Ip "\f(CWgnu9x\fR" 4 +.IX Item "gnu9x" +.PD +The 1999 C standard plus \s-1GNU\s0 extensions. +.RE +.RS 4 +.RE +.Ip "\fB\-ftabstop=NUMBER\fR" 4 +.IX Item "-ftabstop=NUMBER" +Set the distance between tab stops. This helps the preprocessor +report correct column numbers in warnings or errors, even if tabs appear +on the line. Values less than 1 or greater than 100 are ignored. The +default is 8. +.Ip "\fB\-$\fR" 4 +.IX Item "-$" +Forbid the use of \fB$\fR in identifiers. The C standard allows +implementations to define extra characters that can appear in +identifiers. By default the \s-1GNU\s0 C preprocessor permits \fB$\fR, a +common extension. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and +\&\fIbinutils\fR. +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, +1997, 1998, 1999, 2000, 2001 +Free Software Foundation, Inc. +.PP +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. +.PP +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. +.PP +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions. diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi new file mode 100644 index 00000000000..ef689feaa7b --- /dev/null +++ b/gcc/doc/cpp.texi @@ -0,0 +1,3734 @@ +\input texinfo +@setfilename cpp.info +@settitle The C Preprocessor + +@ifinfo +@dircategory Programming +@direntry +* Cpp: (cpp). The GNU C preprocessor. +@end direntry +@end ifinfo + +@c @smallbook +@c @cropmarks +@c @finalout +@setchapternewpage odd +@ifinfo +This file documents the GNU C Preprocessor. + +Copyright 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, +1999, 2000, 2001 Free Software Foundation, Inc. + +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. + +@ignore +Permission is granted to process this file through Tex and print the +results, provided the printed document carries copying permission +notice identical to this one except for the removal of this paragraph +(this paragraph not being relevant to the printed manual). + +@end ignore +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions. +@end ifinfo + +@titlepage +@c @finalout +@title The C Preprocessor +@subtitle Last revised January 2001 +@subtitle for GCC version 3 +@author Richard M. Stallman +@page +@vskip 2pc +This booklet is eventually intended to form the first chapter of a GNU +C Language manual. + +@vskip 0pt plus 1filll +@c man begin COPYRIGHT +Copyright @copyright{} 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, +1997, 1998, 1999, 2000, 2001 +Free Software Foundation, Inc. + +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. + +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions. +@c man end +@end titlepage +@page + +@node Top, Global Actions,, (DIR) +@chapter The C Preprocessor +@c man begin DESCRIPTION + +The C preprocessor is a @dfn{macro processor} that is used automatically +by the C compiler to transform your program before actual compilation. +It is called a macro processor because it allows you to define +@dfn{macros}, which are brief abbreviations for longer constructs. + +The C preprocessor is intended only for macro processing of C, C++ and +Objective C source files. For macro processing of other files, you are +strongly encouraged to use alternatives like M4, which will likely give +you better results and avoid many problems. For example, normally the C +preprocessor does not preserve arbitrary whitespace verbatim, but +instead replaces each sequence with a single space. + +For use on C-like source files, the C preprocessor provides four +separate facilities that you can use as you see fit: + +@itemize @bullet +@item +Inclusion of header files. These are files of declarations that can be +substituted into your program. + +@item +Macro expansion. You can define @dfn{macros}, which are abbreviations +for arbitrary fragments of C code, and then the C preprocessor will +replace the macros with their definitions throughout the program. + +@item +Conditional compilation. Using special preprocessing directives, you +can include or exclude parts of the program according to various +conditions. + +@item +Line control. If you use a program to combine or rearrange source files +into an intermediate file which is then compiled, you can use line +control to inform the compiler of where each source line originally came +from. +@end itemize + +C preprocessors vary in some details. This manual discusses the GNU C +preprocessor, which provides a small superset of the features of ISO +Standard C@. + +In its default mode, the GNU C preprocessor does not do a few things +required by the standard. These are features which are rarely, if ever, +used, and may cause surprising changes to the meaning of a program which +does not expect them. To get strict ISO Standard C, you should use the +@samp{-std=c89} or @samp{-std=c99} options, depending on which version +of the standard you want. To get all the mandatory diagnostics, you +must also use @samp{-pedantic}. @xref{Invocation}. + +@c man end + +@menu +* Global Actions:: Actions made uniformly on all input files. +* Directives:: General syntax of preprocessing directives. +* Header Files:: How and why to use header files. +* Macros:: How and why to use macros. +* Conditionals:: How and why to use conditionals. +* Assertions:: How and why to use assertions. +* Line Control:: Use of line control when you combine source files. +* Other Directives:: Miscellaneous preprocessing directives. +* Output:: Format of output from the C preprocessor. +* Implementation:: Implementation limits and behavior. +* Unreliable Features:: Undefined behavior and deprecated features. +* Invocation:: How to invoke the preprocessor; command options. +* Concept Index:: Index of concepts and terms. +* Index:: Index of directives, predefined macros and options. +@end menu + +@node Global Actions, Directives, Top, Top +@section Transformations Made Globally +@cindex ASCII NUL handling + +Most C preprocessor features are inactive unless you give specific +directives to request their use. (Preprocessing directives are lines +starting with a @samp{#} token, possibly preceded by whitespace; +@pxref{Directives}). However, there are four transformations that the +preprocessor always makes on all the input it receives, even in the +absence of directives. These are, in order: + +@enumerate +@item +Trigraphs, if enabled, are replaced with the character they represent. + +@item +Backslash-newline sequences are deleted, no matter where. This +feature allows you to break long lines for cosmetic purposes without +changing their meaning. + +Recently, the non-traditional preprocessor has relaxed its treatment of +escaped newlines. Previously, the newline had to immediately follow a +backslash. The current implementation allows whitespace in the form of +spaces, horizontal and vertical tabs, and form feeds between the +backslash and the subsequent newline. The preprocessor issues a +warning, but treats it as a valid escaped newline and combines the two +lines to form a single logical line. This works within comments and +tokens, as well as between tokens. Comments are @emph{not} treated as +whitespace for the purposes of this relaxation, since they have not yet +been replaced with spaces. + +@item +All comments are replaced with single spaces. + +@item +Predefined macro names are replaced with their expansions +(@pxref{Predefined}). +@end enumerate + +For end-of-line indicators, any of \n, \r\n, \n\r and \r are recognised, +and treated as ending a single line. As a result, if you mix these in a +single file you might get incorrect line numbering, because the +preprocessor would interpret the two-character versions as ending just +one line. Previous implementations would only handle UNIX-style \n +correctly, so DOS-style \r\n would need to be passed through a filter +first. + +The first three transformations are done @emph{before} all other parsing +and before preprocessing directives are recognized. Thus, for example, +you can split a line mechanically with backslash-newline anywhere +(except within trigraphs since they are replaced first; see below). + +@example +/* +*/ # /* +*/ defi\ +ne FO\ +O 10\ +20 +@end example + +@noindent +is equivalent into @samp{#define FOO 1020}. + +There is no way to prevent a backslash at the end of a line from being +interpreted as a backslash-newline. For example, + +@example +"foo\\ +bar" +@end example + +is equivalent to @code{"foo\bar"}, not to @code{"foo\\bar"}. To avoid +having to worry about this, do not use the deprecated GNU extension +which permits multi-line strings. Instead, use string literal +concatenation: + +@example + "foo\\" + "bar" +@end example + +Your program will be more portable this way, too. + +There are a few things to note about the above four transformations. + +@itemize @bullet +@item +Comments and predefined macro names (or any macro names, for that +matter) are not recognized inside the argument of an @samp{#include} +directive, when it is delimited with quotes or with @samp{<} and +@samp{>}. + +@item +Comments and predefined macro names are never recognized within a +character or string constant. + +@item +ISO ``trigraphs'' are converted before backslash-newlines are deleted. +If you write what looks like a trigraph with a backslash-newline inside, +the backslash-newline is deleted as usual, but it is too late to +recognize the trigraph. + +This is relevant only if you use the @samp{-trigraphs} option to enable +trigraph processing. @xref{Invocation}. +@end itemize + +The preprocessor handles null characters embedded in the input file +depending upon the context in which the null appears. Note that here we +are referring not to the two-character escape sequence "\0", but to the +single character ASCII NUL. + +There are three different contexts in which a null character may +appear: + +@itemize @bullet +@item +Within comments. Here, null characters are silently ignored. + +@item +Within a string or character constant. Here the preprocessor emits a +warning, but preserves the null character and passes it through to the +output file or compiler front-end. + +@item +In any other context, the preprocessor issues a warning, and discards +the null character. The preprocessor treats it like whitespace, +combining it with any surrounding whitespace to become a single +whitespace block. Representing the null character by "^@@", this means +that code like + +@example +#define X^@@1 +@end example + +is equivalent to + +@example +#define X 1 +@end example + +and X is defined with replacement text "1". +@end itemize + +@node Directives, Header Files, Global Actions, Top +@section Preprocessing Directives + +@cindex preprocessing directives +@cindex directives +Most preprocessor features are active only if you use preprocessing +directives to request their use. + +Preprocessing directives are lines in your program that start with +@samp{#}. Whitespace is allowed before and after the @samp{#}. The +@samp{#} is followed by an identifier that is the @dfn{directive name}. +For example, @samp{#define} is the directive that defines a macro. + +Since the @samp{#} must be the first token on the line, it cannot come +from a macro expansion if you wish it to begin a directive. Also, the +directive name is not macro expanded. Thus, if @samp{foo} is defined as +a macro expanding to @samp{define}, that does not make @samp{#foo} a +valid preprocessing directive. + +The set of valid directive names is fixed. Programs cannot define new +preprocessing directives. + +Some directive names require arguments; these make up the rest of the +directive line and must be separated from the directive name by +whitespace. For example, @samp{#define} must be followed by a macro +name and the intended expansion of the macro. @xref{Object-like +Macros}. + +A preprocessing directive cannot cover more than one line. It may be +logically extended with backslash-newline, but that has no effect on its +meaning. Comments containing newlines can also divide the directive +into multiple lines, but a comment is replaced by a single space before +the directive is interpreted. + +@node Header Files, Macros, Directives, Top +@section Header Files + +@cindex header file +A header file is a file containing C declarations and macro definitions +(@pxref{Macros}) to be shared between several source files. You request +the use of a header file in your program with the C preprocessing +directive @samp{#include}. + +@menu +* Header Uses:: What header files are used for. +* Include Syntax:: How to write @samp{#include} directives. +* Include Operation:: What @samp{#include} does. +* Once-Only:: Preventing multiple inclusion of one header file. +* Inheritance:: Including one header file in another header file. +* System Headers:: Special treatment for some header files. +@end menu + +@node Header Uses, Include Syntax, Header Files, Header Files +@subsection Uses of Header Files + +Header files serve two kinds of purposes. + +@itemize @bullet +@item +@cindex system header files +System header files declare the interfaces to parts of the operating +system. You include them in your program to supply the definitions and +declarations you need to invoke system calls and libraries. + +@item +Your own header files contain declarations for interfaces between the +source files of your program. Each time you have a group of related +declarations and macro definitions all or most of which are needed in +several different source files, it is a good idea to create a header +file for them. +@end itemize + +Including a header file produces the same results in C compilation as +copying the header file into each source file that needs it. Such +copying would be time-consuming and error-prone. With a header file, +the related declarations appear in only one place. If they need to be +changed, they can be changed in one place, and programs that include the +header file will automatically use the new version when next recompiled. +The header file eliminates the labor of finding and changing all the +copies as well as the risk that a failure to find one copy will result +in inconsistencies within a program. + +The usual convention is to give header files names that end with +@file{.h}. Avoid unusual characters in header file names, as they +reduce portability. + +@node Include Syntax, Include Operation, Header Uses, Header Files +@subsection The @samp{#include} Directive + +@findex #include +Both user and system header files are included using the preprocessing +directive @samp{#include}. It has three variants: + +@table @code +@item #include <@var{file}> +This variant is used for system header files. It searches for a file +named @var{file} in a list of directories specified by you, then in a +standard list of system directories. You specify directories to search +for header files with the command option @samp{-I} (@pxref{Invocation}). +The option @samp{-nostdinc} inhibits searching the standard system +directories; in this case only the directories you specify are searched. + +The first @samp{>} character terminates the file name. The file name +may contain a @samp{<} character. + +@item #include "@var{file}" +This variant is used for header files of your own program. It searches +for a file named @var{file} first in the current directory, then in the +same directories used for system header files. The current directory is +the directory of the current input file. It is tried first because it +is presumed to be the location of the files that the current input file +refers to. (If the @samp{-I-} option is used, the special treatment of +the current directory is inhibited. @xref{Invocation}.) + +The first @samp{"} character terminates the file name. + +In both these variants, the argument behaves like a string constant in +that comments are not recognized, and macro names are not expanded. +Thus, in @samp{#include } the @samp{/*} does not start a comment +and the directive specifies inclusion of a system header file named +@file{x/*y}. + +However, in either variant, if backslashes occur within @var{file}, they +are considered ordinary text characters, not escape characters. None of +the character escape sequences appropriate to string constants in C are +processed. Thus, @samp{#include "x\n\\y"} specifies a filename +containing three backslashes. + +@item #include @var{anything else} +@cindex computed @samp{#include} +This variant is called a @dfn{computed #include}. Any @samp{#include} +directive whose argument does not fit the above two forms is a computed +include. The text @var{anything else} is checked for macro calls, which +are expanded (@pxref{Macros}). When this is done, the result must match +one of the above two variants --- in particular, the expansion must form +a string literal token, or a sequence of tokens surrounded by angle +braces. @xref{Implementation}. + +This feature allows you to define a macro which controls the file name +to be used at a later point in the program. One application of this is +to allow a site-specific configuration file for your program to specify +the names of the system include files to be used. This can help in +porting the program to various operating systems in which the necessary +system header files are found in different places. +@end table + +@node Include Operation, Once-Only, Include Syntax, Header Files +@subsection How @samp{#include} Works + +The @samp{#include} directive works by directing the C preprocessor to +scan the specified file as input before continuing with the rest of the +current file. The output from the preprocessor contains the output +already generated, followed by the output resulting from the included +file, followed by the output that comes from the text after the +@samp{#include} directive. For example, given a header file +@file{header.h} as follows, + +@example +char *test (); +@end example + +@noindent +and a main program called @file{program.c} that uses the header file, +like this, + +@example +int x; +#include "header.h" + +main () +@{ + printf (test ()); +@} +@end example + +@noindent +the output generated by the C preprocessor for @file{program.c} as input +would be + +@example +int x; +char *test (); + +main () +@{ + printf (test ()); +@} +@end example + +Included files are not limited to declarations and macro definitions; +those are merely the typical uses. Any fragment of a C program can be +included from another file. The include file could even contain the +beginning of a statement that is concluded in the containing file, or +the end of a statement that was started in the including file. However, +a comment or a string or character constant may not start in the +included file and finish in the including file. An unterminated +comment, string constant or character constant in an included file is +considered to end (with an error message) at the end of the file. + +It is possible for a header file to begin or end a syntactic unit such +as a function definition, but that would be very confusing, so don't do +it. + +The line following the @samp{#include} directive is always treated as a +separate line by the C preprocessor, even if the included file lacks a +final newline. + +@node Once-Only, Inheritance, Include Operation, Header Files +@subsection Once-Only Include Files +@cindex repeated inclusion +@cindex including just once + +Very often, one header file includes another. It can easily result that +a certain header file is included more than once. This may lead to +errors, if the header file defines structure types or typedefs, and is +certainly wasteful. Therefore, we often wish to prevent multiple +inclusion of a header file. + +The standard way to do this is to enclose the entire real contents of the +file in a conditional, like this: + +@example +#ifndef FILE_FOO_SEEN +#define FILE_FOO_SEEN + +@var{the entire file} + +#endif /* FILE_FOO_SEEN */ +@end example + +The macro @code{FILE_FOO_SEEN} indicates that the file has been included +once already. In a user header file, the macro name should not begin +with @samp{_}. In a system header file, this name should begin with +@samp{__} to avoid conflicts with user programs. In any kind of header +file, the macro name should contain the name of the file and some +additional text, to avoid conflicts with other header files. + +The GNU C preprocessor is programmed to notice when a header file uses +this particular construct and handle it efficiently. If a header file +is contained entirely in a @samp{#ifndef} conditional, modulo whitespace +and comments, then it remembers that fact. If a subsequent +@samp{#include} specifies the same file, and the macro in the +@samp{#ifndef} is already defined, then the directive is skipped without +processing the specified file at all. + +@findex #import +In the Objective C language, there is a variant of @samp{#include} +called @samp{#import} which includes a file, but does so at most once. +If you use @samp{#import} @emph{instead of} @samp{#include}, then you +don't need the conditionals inside the header file to prevent multiple +execution of the contents. + +@samp{#import} is obsolete because it is not a well designed feature. +It requires the users of a header file --- the applications programmers +--- to know that a certain header file should only be included once. It +is much better for the header file's implementor to write the file so +that users don't need to know this. Using @samp{#ifndef} accomplishes +this goal. + +@node Inheritance, System Headers, Once-Only, Header Files +@subsection Inheritance and Header Files +@cindex inheritance +@cindex overriding a header file + +@dfn{Inheritance} is what happens when one object or file derives some +of its contents by virtual copying from another object or file. In +the case of C header files, inheritance means that one header file +includes another header file and then replaces or adds something. + +If the inheriting header file and the base header file have different +names, then inheritance is straightforward: simply write @samp{#include +"@var{base}"} in the inheriting file. + +Sometimes it is necessary to give the inheriting file the same name as +the base file. This is less straightforward. + +For example, suppose an application program uses the system header +@file{sys/signal.h}, but the version of @file{/usr/include/sys/signal.h} +on a particular system doesn't do what the application program expects. +It might be convenient to define a ``local'' version, perhaps under the +name @file{/usr/local/include/sys/signal.h}, to override or add to the +one supplied by the system. + +You can do this by compiling with the option @samp{-I.}, and writing a +file @file{sys/signal.h} that does what the application program expects. +Making this file include the standard @file{sys/signal.h} is not so easy +--- writing @samp{#include } in that file doesn't work, +because it includes your own version of the file, not the standard +system version. Used in that file itself, this leads to an infinite +recursion and a fatal error in compilation. + +@samp{#include } would find the proper file, +but that is not clean, since it makes an assumption about where the +system header file is found. This is bad for maintenance, since it +means that any change in where the system's header files are kept +requires a change somewhere else. + +@findex #include_next +The clean way to solve this problem is to use +@samp{#include_next}, which means, ``Include the @emph{next} file with +this name.'' This directive works like @samp{#include} except in +searching for the specified file: it starts searching the list of header +file directories @emph{after} the directory in which the current file +was found. + +Suppose you specify @samp{-I /usr/local/include}, and the list of +directories to search also includes @file{/usr/include}; and suppose +both directories contain @file{sys/signal.h}. Ordinary @samp{#include +} finds the file under @file{/usr/local/include}. If that +file contains @samp{#include_next }, it starts searching +after that directory, and finds the file in @file{/usr/include}. + +@samp{#include_next} is a GCC extension and should not be used in +programs intended to be portable to other compilers. + +@node System Headers,, Inheritance, Header Files +@subsection System Headers +@cindex system header files + +The header files declaring interfaces to the operating system and +runtime libraries often cannot be written in strictly conforming C. +Therefore, GNU C gives code found in @dfn{system headers} special +treatment. Certain categories of warnings are suppressed, notably those +enabled by @samp{-pedantic}. + +Normally, only the headers found in specific directories are considered +system headers. The set of these directories is determined when GCC is +compiled. There are, however, two ways to add to the set. + +@findex -isystem +The @samp{-isystem} command line option adds its argument to the list of +directories to search for headers, just like @samp{-I}. In addition, +any headers found in that directory will be considered system headers. +Note that unlike @samp{-I}, you must put a space between @samp{-isystem} +and its argument. + +All directories named by @samp{-isystem} are searched @strong{after} all +directories named by @samp{-I}, no matter what their order was on the +command line. If the same directory is named by both @samp{-I} and +@samp{-isystem}, @samp{-I} wins; it is as if the @samp{-isystem} option +had never been specified at all. + +@findex #pragma GCC system_header +There is also a directive, @samp{#pragma GCC system_header}, which tells +GCC to consider the rest of the current include file a system header, no +matter where it was found. Code that comes before the @samp{#pragma} in +the file will not be affected. + +@samp{#pragma GCC system_header} has no effect in the primary source file. + +@node Macros, Conditionals, Header Files, Top +@section Macros + +A macro is a sort of abbreviation which you can define once and then +use later. There are many complicated features associated with macros +in the C preprocessor. + +@menu +* Object-like Macros:: Macros that always expand the same way. +* Function-like Macros:: Macros that accept arguments that are substituted + into the macro expansion. +* Macro Varargs:: Macros with variable number of arguments. +* Predefined:: Predefined macros that are always available. +* Stringification:: Macro arguments converted into string constants. +* Concatenation:: Building tokens from parts taken from macro arguments. +* Undefining:: Cancelling a macro's definition. +* Redefining:: Changing a macro's definition. +* Poisoning:: Ensuring a macro is never defined or used. +* Macro Pitfalls:: Macros can confuse the unwary. Here we explain + several common problems and strange features. +@end menu + +@node Object-like Macros, Function-like Macros, Macros, Macros +@subsection Object-like Macros +@cindex object-like macro +@cindex manifest constant + +An @dfn{object-like macro} is a kind of abbreviation. It is a name +which stands for a fragment of code. Some people refer to these as +@dfn{manifest constants}. + +Before you can use a macro, you must @dfn{define} it explicitly with the +@samp{#define} directive. @samp{#define} is followed by the name of the +macro and then the token sequence it should be an abbreviation for, +which is variously referred to as the macro's @dfn{body}, +@dfn{expansion} or @dfn{replacement list}. For example, + +@example +#define BUFFER_SIZE 1020 +@end example + +@noindent +defines a macro named @samp{BUFFER_SIZE} as an abbreviation for the +token @samp{1020}. If somewhere after this @samp{#define} directive +there comes a C statement of the form + +@example +foo = (char *) xmalloc (BUFFER_SIZE); +@end example + +@noindent +then the C preprocessor will recognize and @dfn{expand} the macro +@samp{BUFFER_SIZE}, resulting in + +@example +foo = (char *) xmalloc (1020); +@end example + +The use of all upper case for macro names is a standard convention. +Programs are easier to read when it is possible to tell at a glance +which names are macros. + +Normally, a macro definition can only span a single logical line, like +all C preprocessing directives. Comments within a macro definition may +contain newlines, which make no difference since each comment is +replaced by a space regardless of its contents. + +Apart from this, there is no restriction on what can go in a macro body +provided it decomposes into valid preprocessing tokens. In particular, +parentheses need not balance, and the body need not resemble valid C +code. (If it does not, you may get error messages from the C +compiler when you use the macro.) + +The C preprocessor scans your program sequentially, so macro definitions +take effect at the place you write them. Therefore, the following input +to the C preprocessor + +@example +foo = X; +#define X 4 +bar = X; +@end example + +@noindent +produces as output + +@example +foo = X; + +bar = 4; +@end example + +When the preprocessor expands a macro name, the macro's expansion +replaces the macro invocation, and the result is re-scanned for more +macros to expand. For example, after + +@example +#define BUFSIZE 1020 +#define TABLESIZE BUFSIZE +@end example + +@noindent +the name @samp{TABLESIZE} when used in the program would go through two +stages of expansion, resulting ultimately in @samp{1020}. + +This is not the same as defining @samp{TABLESIZE} to be @samp{1020}. +The @samp{#define} for @samp{TABLESIZE} uses exactly the expansion you +specify --- in this case, @samp{BUFSIZE} --- and does not check to see +whether it too contains macro names. Only when you @emph{use} +@samp{TABLESIZE} is the result of its expansion scanned for more macro +names. @xref{Cascaded Macros}. + +@node Function-like Macros, Macro Varargs, Object-like Macros, Macros +@subsection Macros with Arguments +@cindex macros with argument +@cindex arguments in macro definitions +@cindex function-like macro + +An object-like macro is always replaced by exactly the same tokens each +time it is used. Macros can be made more flexible by taking +@dfn{arguments}. Arguments are fragments of code that you supply each +time the macro is used. These fragments are included in the expansion +of the macro according to the directions in the macro definition. A +macro that accepts arguments is called a @dfn{function-like macro} +because the syntax for using it looks like a function call. + +@findex #define +To define a macro that uses arguments, you write a @samp{#define} +directive with a list of @dfn{parameters} in parentheses after the name +of the macro. The parameters must be valid C identifiers, separated by +commas and optionally whitespace. The @samp{(} must follow the macro +name immediately, with no space in between. If you leave a space, you +instead define an object-like macro whose expansion begins with a +@samp{(}, and often leads to confusing errors at compile time. + +As an example, here is a macro that computes the minimum of two numeric +values, as it is defined in many C programs: + +@example +#define min(X, Y) ((X) < (Y) ? (X) : (Y)) +@end example + +@noindent +(This is not the best way to define a ``minimum'' macro in GNU C@. +@xref{Side Effects}, for more information.) + +To invoke a function-like macro, you write the name of the macro +followed by a list of @dfn{arguments} in parentheses, separated by +commas. The invocation of the macro need not be restricted to a single +logical line - it can cross as many lines in the source file as you +wish. The number of arguments you give must match the number of +parameters in the macro definition; empty arguments are fine. Examples +of use of the macro @samp{min} include @samp{min (1, 2)} and @samp{min +(x + 28, *p)}. + +The expansion text of the macro depends on the arguments you use. Each +macro parameter is replaced throughout the macro expansion with the +tokens of the corresponding argument. Leading and trailing argument +whitespace is dropped, and all whitespace between the tokens of an +argument is reduced to a single space. Using the same macro @samp{min} +defined above, @samp{min (1, 2)} expands into + +@example +((1) < (2) ? (1) : (2)) +@end example + +@noindent +where @samp{1} has been substituted for @samp{X} and @samp{2} for @samp{Y}. + +Likewise, @samp{min (x + 28, *p)} expands into + +@example +((x + 28) < (*p) ? (x + 28) : (*p)) +@end example + +Parentheses within each argument must balance; a comma within such +parentheses does not end the argument. However, there is no requirement +for square brackets or braces to balance, and they do not prevent a +comma from separating arguments. Thus, + +@example +macro (array[x = y, x + 1]) +@end example + +@noindent +passes two arguments to @code{macro}: @samp{array[x = y} and @samp{x + +1]}. If you want to supply @samp{array[x = y, x + 1]} as an argument, +you must write it as @samp{array[(x = y, x + 1)]}, which is equivalent C +code. + +After the arguments have been substituted into the macro body, the +resulting expansion replaces the macro invocation, and re-scanned for +more macro calls. Therefore even arguments can contain calls to other +macros, either with or without arguments, and even to the same macro. +For example, @samp{min (min (a, b), c)} expands into this text: + +@example +((((a) < (b) ? (a) : (b))) < (c) + ? (((a) < (b) ? (a) : (b))) + : (c)) +@end example + +@noindent +(Line breaks shown here for clarity would not actually be generated.) + +@cindex empty macro arguments +If a macro @code{foo} takes one argument, and you want to supply an +empty argument, simply supply no preprocessing tokens. Since whitespace +does not form a preprocessing token, it is optional. For example, +@samp{foo ()}, @samp{foo ( )} and @samp{bar (, arg2)}. + +Previous GNU preprocessor implementations and documentation were +incorrect on this point, insisting that a function-like macro that takes +a single argument be passed a space if an empty argument was required. + +If you use a macro name followed by something other than a @samp{(} +(after ignoring any whitespace that might follow), it does not form an +invocation of the macro, and the preprocessor does not change what you +have written. Therefore, it is possible for the same identifier to be a +variable or function in your program as well as a macro, and you can +choose in each instance whether to refer to the macro (if an actual +argument list follows) or the variable or function (if an argument list +does not follow). For example, + +@example +#define foo(X) X +foo bar foo(baz) +@end example + +expands to @samp{foo bar baz}. Such dual use of one name could be +confusing and should be avoided except when the two meanings are +effectively synonymous: that is, when the name is both a macro and a +function and the two have similar effects. You can think of the name +simply as a function; use of the name for purposes other than calling it +(such as, to take the address) will refer to the function, while calls +will expand the macro and generate better but equivalent code. + +For example, you can use a function named @samp{min} in the same source +file that defines the macro. If you write @samp{&min} with no argument +list, you refer to the function. If you write @samp{min (x, bb)}, with +an argument list, the macro is expanded. If you write @samp{(min) (a, +bb)}, where the name @samp{min} is not followed by an open-parenthesis, +the macro is not expanded, so you wind up with a call to the function +@samp{min}. + +In the definition of a macro with arguments, the list of argument names +must follow the macro name immediately with no space in between. If +there is a space after the macro name, the macro is defined as taking no +arguments, and all the rest of the line is taken to be the expansion. +The reason for this is that it is often useful to define a macro that +takes no arguments and whose definition begins with an identifier in +parentheses. This rule makes it possible for you to do either this: + +@example +#define FOO(x) - 1 / (x) +@end example + +@noindent +(which defines @samp{FOO} to take an argument and expand into minus the +reciprocal of that argument) or this: + +@example +#define BAR (x) - 1 / (x) +@end example + +@noindent +(which defines @samp{BAR} to take no argument and always expand into +@samp{(x) - 1 / (x)}). + +Note that the @emph{uses} of a macro with arguments can have spaces +before the left parenthesis; it's the @emph{definition} where it matters +whether there is a space. + +@node Macro Varargs, Predefined, Function-like Macros, Macros +@subsection Macros with Variable Numbers of Arguments +@cindex variable number of arguments +@cindex macro with variable arguments +@cindex rest argument (in macro) + +In the ISO C standard of 1999, a macro can be declared to accept a +variable number of arguments much as a function can. The syntax for +defining the macro is similar to that of a function. Here is an +example: + +@example +#define eprintf(...) fprintf (stderr, __VA_ARGS__) +@end example + +Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of +such a macro, it represents the zero or more tokens until the closing +parenthesis that ends the invocation, including any commas. This set of +tokens replaces the identifier @code{__VA_ARGS__} in the macro body +wherever it appears. Thus, we have this expansion: + +@example +eprintf ("%s:%d: ", input_file_name, line_number) +@expansion{} +fprintf (stderr, "%s:%d: " , input_file_name, line_number) +@end example + +Within a @samp{#define} directive, ISO C mandates that the only place +the identifier @code{__VA_ARGS__} can appear is in the replacement list +of a variable-argument macro. It may not be used as a macro name, macro +argument name, or within a different type of macro. It may also be +forbidden in open text; the standard is ambiguous. We recommend you +avoid using it except for its defined purpose. + +If your macro is complicated, you may want a more descriptive name for +the variable argument than @code{__VA_ARGS__}. GNU cpp permits this, as +an extension. You may write an argument name immediately before the +@samp{@dots{}}; that name is used for the variable argument. The +@code{eprintf} macro above could be written + +@example +#define eprintf(args...) fprintf (stderr, args) +@end example + +@noindent +using this extension. You cannot use @code{__VA_ARGS__} and this +extension in the same macro. + +We might instead have defined eprintf as follows: + +@example +#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__) +@end example + +This formulation looks more descriptive, but cannot be used as flexibly. +There is no way to produce expanded output of + +@example +fprintf (stderr, "success!\n") +@end example + +@noindent +because, in standard C, you are not allowed to leave the variable +argument out entirely, and passing an empty argument for the variable +arguments will not do what you want. Writing + +@example +eprintf ("success!\n", ) +@end example + +@noindent +produces + +@example +fprintf (stderr, "success!\n",) +@end example + +@noindent +where the extra comma originates from the replacement list and not from +the arguments to eprintf. + +There is another extension in the GNU C preprocessor which deals with +this difficulty. First, you are allowed to leave the variable argument +out entirely: + +@example +eprintf ("success!\n") +@end example + +Second, the @samp{##} token paste operator has a special meaning when +placed between a comma and a variable argument. If you write + +@example +#define eprintf(format, ...) fprintf (stderr, format, ##__VA_ARGS__) +@end example + +and the variable argument is left out when the @samp{eprintf} macro is +used, then the comma before the @samp{##} will be deleted. This does +@emph{not} happen if you pass an empty argument, nor does it happen if +the token preceding @samp{##} is anything other than a comma. + +Previous versions of the preprocessor implemented this extension much +more generally. We have restricted it in order to minimize the +difference from the C standard. @xref{Unreliable Features}. + +@node Predefined, Stringification, Macro Varargs, Macros +@subsection Predefined Macros + +@cindex predefined macros +Several object-like macros are predefined; you use them without +supplying their definitions. They fall into two classes: standard +macros and system-specific macros. + +@menu +* Standard Predefined:: Standard predefined macros. +* Nonstandard Predefined:: Nonstandard predefined macros. +@end menu + +@node Standard Predefined, Nonstandard Predefined, Predefined, Predefined +@subsubsection Standard Predefined Macros +@cindex standard predefined macros + +The standard predefined macros are available with the same meanings +regardless of the machine or operating system on which you are using GNU +C@. Their names all start and end with double underscores. Those +preceding @code{__GNUC__} in this table are standardized by ISO C; the +rest are GNU C extensions. + +@table @code +@item __FILE__ +@findex __FILE__ +This macro expands to the name of the current input file, in the form of +a C string constant. The precise name returned is the one that was +specified in @samp{#include} or as the input file name argument. For +example, @samp{"/usr/local/include/myheader.h"} is a possible expansion +of this macro. + +@item __LINE__ +@findex __LINE__ +This macro expands to the current input line number, in the form of a +decimal integer constant. While we call it a predefined macro, it's +a pretty strange macro, since its ``definition'' changes with each +new line of source code. + +This and @samp{__FILE__} are useful in generating an error message to +report an inconsistency detected by the program; the message can state +the source line at which the inconsistency was detected. For example, + +@smallexample +fprintf (stderr, "Internal error: " + "negative string length " + "%d at %s, line %d.", + length, __FILE__, __LINE__); +@end smallexample + +A @samp{#include} directive changes the expansions of @samp{__FILE__} +and @samp{__LINE__} to correspond to the included file. At the end of +that file, when processing resumes on the input file that contained +the @samp{#include} directive, the expansions of @samp{__FILE__} and +@samp{__LINE__} revert to the values they had before the +@samp{#include} (but @samp{__LINE__} is then incremented by one as +processing moves to the line after the @samp{#include}). + +The expansions of both @samp{__FILE__} and @samp{__LINE__} are altered +if a @samp{#line} directive is used. @xref{Line Control}. + +@item __DATE__ +@findex __DATE__ +This macro expands to a string constant that describes the date on +which the preprocessor is being run. The string constant contains +eleven characters and looks like @w{@samp{"Feb 1 1996"}}. +@c After reformatting the above, check that the date remains `Feb 1 1996', +@c all on one line, with two spaces between the `Feb' and the `1'. + +@item __TIME__ +@findex __TIME__ +This macro expands to a string constant that describes the time at +which the preprocessor is being run. The string constant contains +eight characters and looks like @samp{"23:59:01"}. + +@item __STDC__ +@findex __STDC__ +This macro expands to the constant 1, to signify that this is ISO +Standard C@. (Whether that is actually true depends on what C compiler +will operate on the output from the preprocessor.) + +On some hosts, system include files use a different convention, where +@samp{__STDC__} is normally 0, but is 1 if the user specifies strict +conformance to the C Standard. The preprocessor follows the host +convention when processing system include files, but when processing +user files it follows the usual GNU C convention. + +This macro is not defined if the @samp{-traditional} option is used. + +@item __STDC_VERSION__ +@findex __STDC_VERSION__ +This macro expands to the C Standard's version number, a long integer +constant of the form @samp{@var{yyyy}@var{mm}L} where @var{yyyy} and +@var{mm} are the year and month of the Standard version. This signifies +which version of the C Standard the preprocessor conforms to. Like +@samp{__STDC__}, whether this version number is accurate for the entire +implementation depends on what C compiler will operate on the output +from the preprocessor. + +This macro is not defined if the @samp{-traditional} option is used. + +@item __GNUC__ +@findex __GNUC__ +This macro is defined if and only if this is GNU C@. This macro is +defined only when the entire GNU C compiler is in use; if you invoke the +preprocessor directly, @samp{__GNUC__} is undefined. The value +identifies the major version number of GNU CC (@samp{1} for GNU CC +version 1, which is now obsolete, and @samp{2} for version 2). + +@item __GNUC_MINOR__ +@findex __GNUC_MINOR__ +The macro contains the minor version number of the compiler. This can +be used to work around differences between different releases of the +compiler (for example, if GCC 2.6.x is known to support a feature, you +can test for @code{__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 6)}). + +@item __GNUC_PATCHLEVEL__ +@findex __GNUC_PATCHLEVEL__ +This macro contains the patch level of the compiler. This can be +used to work around differences between different patch level releases +of the compiler (for example, if GCC 2.6.2 is known to contain a bug, +whereas GCC 2.6.3 contains a fix, and you have code which can workaround +the problem depending on whether the bug is fixed or not, you can test for +@code{__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ > 6) || +(__GNUC__ == 2 && __GNUC_MINOR__ == 6 && __GNUC_PATCHLEVEL__ >= 3)}). + +@item __GNUG__ +@findex __GNUG__ +The GNU C compiler defines this when the compilation language is +C++; use @samp{__GNUG__} to distinguish between GNU C and GNU +C++. + +@item __cplusplus +@findex __cplusplus +The ISO standard for C++ requires predefining this variable. You can +use @samp{__cplusplus} to test whether a header is compiled by a C +compiler or a C++ compiler. The compiler currently uses a value of +@samp{1}, instead of the value @samp{199711L}, which would indicate full +conformance with the standard. + +@item __STRICT_ANSI__ +@findex __STRICT_ANSI__ +GNU C defines this macro if and only if the @option{-ansi} switch, or a +@option{-std} switch specifying strict conformance to some version of ISO C, +was specified when GNU C was invoked. Its definition is the null string. +This macro exists primarily to direct certain GNU header files not to +define certain traditional Unix constructs which are incompatible with +ISO C@. + +@item __BASE_FILE__ +@findex __BASE_FILE__ +This macro expands to the name of the main input file, in the form +of a C string constant. This is the source file that was specified +on the command line of the preprocessor or C compiler. + +@item __INCLUDE_LEVEL__ +@findex __INCLUDE_LEVEL_ +This macro expands to a decimal integer constant that represents the +depth of nesting in include files. The value of this macro is +incremented on every @samp{#include} directive and decremented at the +end of every included file. It starts out at 0, it's value within the +base file specified on the command line. + +@item __VERSION__ +@findex __VERSION__ +This macro expands to a string constant which describes the version +number of GNU C@. The string is normally a sequence of decimal numbers +separated by periods, such as @samp{"2.6.0"}. + +@item __OPTIMIZE__ +@findex __OPTIMIZE__ +GNU CC defines this macro in optimizing compilations. It causes certain +GNU header files to define alternative macro definitions for some system +library functions. You should not refer to or test the definition of +this macro unless you make very sure that programs will execute with the +same effect regardless. + +@item __OPTIMIZE_SIZE__ +@findex __OPTIMIZE_SIZE__ +GNU CC defines this macro when optimizing for size with @samp{-Os}. It +causes certain GNU header files to define alternative macro definitions +for some system library functions. You should not refer to or test the +definition of this macro unless you make very sure that programs will +execute with the same effect regardless. + +@item __NO_INLINE__ +@findex __NO_INLINE__ +GNU CC defines this macro if it will not attempt to inline functions +with @samp{inline} keyword (either when not optimizing or when inlining +has been explicitely forbidden through @samp{-fno-inline}). It causes +certain GNU header files to define alternative macro definitions for some +system library functions. You should not refer to or test the definition +of this macro unless you make very sure that programs will execute with +the same effect regardless. + +@item __CHAR_UNSIGNED__ +@findex __CHAR_UNSIGNED__ +GNU C defines this macro if and only if the data type @code{char} is +unsigned on the target machine. It exists to cause the standard header +file @file{limits.h} to work correctly. You should not refer to this +macro yourself; instead, refer to the standard macros defined in +@file{limits.h}. The preprocessor uses this macro to determine whether +or not to sign-extend large character constants written in octal; see +@ref{#if Directive,,The @samp{#if} Directive}. + +@item __REGISTER_PREFIX__ +@findex __REGISTER_PREFIX__ +This macro expands to a string (not a string constant) describing the +prefix applied to CPU registers in assembler code. You can use it to +write assembler code that is usable in multiple environments. For +example, in the @samp{m68k-aout} environment it expands to the null +string, but in the @samp{m68k-coff} environment it expands to the string +@samp{%}. + +@item __USER_LABEL_PREFIX__ +@findex __USER_LABEL_PREFIX__ +Similar to @code{__REGISTER_PREFIX__}, but describes the prefix applied +to user generated labels in assembler code. For example, in the +@samp{m68k-aout} environment it expands to the string @samp{_}, but in +the @samp{m68k-coff} environment it expands to the null string. This +does not work with the @samp{-mno-underscores} option that the i386 +OSF/rose and m88k targets provide nor with the @samp{-mcall*} options of +the rs6000 System V Release 4 target. +@end table + +@node Nonstandard Predefined,, Standard Predefined, Predefined +@subsubsection Nonstandard Predefined Macros + +The C preprocessor normally has several predefined macros that vary +between machines because their purpose is to indicate what type of +system and machine is in use. This manual, being for all systems and +machines, cannot tell you exactly what their names are; instead, we +offer a list of some typical ones. You can use @samp{cpp -dM} to see +the values of predefined macros; see @ref{Invocation}. + +Some nonstandard predefined macros describe the operating system in use, +with more or less specificity. For example, + +@table @code +@item unix +@findex unix +@samp{unix} is normally predefined on all Unix systems. + +@item BSD +@findex BSD +@samp{BSD} is predefined on recent versions of Berkeley Unix +(perhaps only in version 4.3). +@end table + +Other nonstandard predefined macros describe the kind of CPU, with more or +less specificity. For example, + +@table @code +@item vax +@findex vax +@samp{vax} is predefined on Vax computers. + +@item mc68000 +@findex mc68000 +@samp{mc68000} is predefined on most computers whose CPU is a Motorola +68000, 68010 or 68020. + +@item m68k +@findex m68k +@samp{m68k} is also predefined on most computers whose CPU is a 68000, +68010 or 68020; however, some makers use @samp{mc68000} and some use +@samp{m68k}. Some predefine both names. What happens in GNU C +depends on the system you are using it on. + +@item M68020 +@findex M68020 +@samp{M68020} has been observed to be predefined on some systems that +use 68020 CPUs --- in addition to @samp{mc68000} and @samp{m68k}, which +are less specific. + +@item _AM29K +@findex _AM29K +@itemx _AM29000 +@findex _AM29000 +Both @samp{_AM29K} and @samp{_AM29000} are predefined for the AMD 29000 +CPU family. + +@item ns32000 +@findex ns32000 +@samp{ns32000} is predefined on computers which use the National +Semiconductor 32000 series CPU. +@end table + +Yet other nonstandard predefined macros describe the manufacturer of +the system. For example, + +@table @code +@item sun +@findex sun +@samp{sun} is predefined on all models of Sun computers. + +@item pyr +@findex pyr +@samp{pyr} is predefined on all models of Pyramid computers. + +@item sequent +@findex sequent +@samp{sequent} is predefined on all models of Sequent computers. +@end table + +These predefined symbols are not only nonstandard, they are contrary to the +ISO standard because their names do not start with underscores. +Therefore, the option @samp{-ansi} inhibits the definition of these +symbols. + +This tends to make @samp{-ansi} useless, since many programs depend on +the customary nonstandard predefined symbols. Even system header files +check them and will generate incorrect declarations if they do not find +the names that are expected. You might think that the header files +supplied for the Uglix computer would not need to test what machine they +are running on, because they can simply assume it is the Uglix; but +often they do, and they do so using the customary names. As a result, +very few C programs will compile with @samp{-ansi}. We intend to avoid +such problems on the GNU system. + +What, then, should you do in an ISO C program to test the type of machine +it will run on? + +GNU C offers a parallel series of symbols for this purpose, whose names +are made from the customary ones by adding @samp{__} at the beginning +and end. Thus, the symbol @code{__vax__} would be available on a Vax, +and so on. + +The set of nonstandard predefined names in the GNU C preprocessor is +controlled (when @code{cpp} is itself compiled) by the macro +@samp{CPP_PREDEFINES}, which should be a string containing @samp{-D} +options, separated by spaces. For example, on the Sun 3, we use the +following definition: + +@example +#define CPP_PREDEFINES "-Dmc68000 -Dsun -Dunix -Dm68k" +@end example + +@noindent +This macro is usually specified in @file{tm.h}. + +@node Stringification, Concatenation, Predefined, Macros +@subsection Stringification + +@cindex stringification +@dfn{Stringification} means turning a sequence of preprocessing tokens +into a string literal. For example, stringifying @samp{foo (z)} results +in @samp{"foo (z)"}. + +In the C preprocessor, stringification is possible when macro arguments +are substituted during macro expansion. When a parameter appears +preceded by a @samp{#} token in the replacement list of a function-like +macro, it indicates that both tokens should be replaced with the +stringification of the corresponding argument during expansion. The +same argument may be substituted in other places in the definition +without stringification if the argument name appears in those places +with no preceding @samp{#}. + +Here is an example of a macro definition that uses stringification: + +@smallexample +@group +#define WARN_IF(EXP) \ +do @{ if (EXP) \ + fprintf (stderr, "Warning: " #EXP "\n"); @} \ +while (0) +@end group +@end smallexample + +@noindent +Here the argument for @samp{EXP} is substituted once, as-is, into the +@samp{if} statement, and once, stringified, into the argument to +@samp{fprintf}. The @samp{do} and @samp{while (0)} are a kludge to make +it possible to write @samp{WARN_IF (@var{arg});}, which the resemblance +of @samp{WARN_IF} to a function would make C programmers want to do; see +@ref{Swallow Semicolon}. + +The stringification feature is limited to transforming the tokens of a +macro argument into a string constant: there is no way to combine the +argument with surrounding text and stringify it all together. The +example above shows how an equivalent result can be obtained in ISO +Standard C, using the fact that adjacent string constants are +concatenated by the C compiler to form a single string constant. The +preprocessor stringifies the actual value of @samp{EXP} into a separate +string constant, resulting in text like + +@smallexample +@group +do @{ if (x == 0) \ + fprintf (stderr, "Warning: " "x == 0" "\n"); @} \ +while (0) +@end group +@end smallexample + +@noindent +but the compiler then sees three consecutive string constants and +concatenates them into one, producing effectively + +@smallexample +do @{ if (x == 0) \ + fprintf (stderr, "Warning: x == 0\n"); @} \ +while (0) +@end smallexample + +Stringification in C involves more than putting double-quote characters +around the fragment. The preprocessor backslash-escapes the surrounding +quotes of string literals, and all backslashes within string and +character constants, in order to get a valid C string constant with the +proper contents. Thus, stringifying @samp{p = "foo\n";} results in +@samp{"p = \"foo\\n\";"}. However, backslashes that are not inside +string or character constants are not duplicated: @samp{\n} by itself +stringifies to @samp{"\n"}. + +Whitespace (including comments) in the text being stringified is handled +according to precise rules. All leading and trailing whitespace is +ignored. Any sequence of whitespace in the middle of the text is +converted to a single space in the stringified result. + +@node Concatenation, Undefining, Stringification, Macros +@subsection Concatenation +@cindex concatenation +@cindex @samp{##} +@dfn{Concatenation} means joining two strings into one. In the context +of macro expansion, concatenation refers to joining two preprocessing +tokens to form one. In particular, a token of a macro argument can be +concatenated with another argument's token or with fixed text to produce +a longer name. The longer name might be the name of a function, +variable, type, or a C keyword; it might even be the name of another +macro, in which case it will be expanded. + +When you define a function-like or object-like macro, you request +concatenation with the special operator @samp{##} in the macro's +replacement list. When the macro is called, any arguments are +substituted without performing macro expansion, every @samp{##} operator +is deleted, and the two tokens on either side of it are concatenated to +form a single token. + +Consider a C program that interprets named commands. There probably needs +to be a table of commands, perhaps an array of structures declared as +follows: + +@example +struct command +@{ + char *name; + void (*function) (); +@}; + +struct command commands[] = +@{ + @{ "quit", quit_command@}, + @{ "help", help_command@}, + @dots{} +@}; +@end example + +It would be cleaner not to have to give each command name twice, once in +the string constant and once in the function name. A macro which takes the +name of a command as an argument can make this unnecessary. The string +constant can be created with stringification, and the function name by +concatenating the argument with @samp{_command}. Here is how it is done: + +@example +#define COMMAND(NAME) @{ #NAME, NAME ## _command @} + +struct command commands[] = +@{ + COMMAND (quit), + COMMAND (help), + @dots{} +@}; +@end example + +The usual case of concatenation is concatenating two names (or a name +and a number) into a longer name. This isn't the only valid case. +It is also possible to concatenate two numbers (or a number and a name, +such as @samp{1.5} and @samp{e3}) into a number. Also, multi-character +operators such as @samp{+=} can be formed by concatenation. However, +two tokens that don't together form a valid token cannot be +concatenated. For example, concatenation of @samp{x} on one side and +@samp{+} on the other is not meaningful because those two tokens do not +form a valid preprocessing token when concatenated. UNDEFINED + +Keep in mind that the C preprocessor converts comments to whitespace +before macros are even considered. Therefore, you cannot create a +comment by concatenating @samp{/} and @samp{*}: the @samp{/*} sequence +that starts a comment is not a token, but rather the beginning of a +comment. You can freely use comments next to @samp{##} in a macro +definition, or in arguments that will be concatenated, because the +comments will be converted to spaces at first sight, and concatenation +operates on tokens and so ignores whitespace. + +@node Undefining, Redefining, Concatenation, Macros +@subsection Undefining Macros + +@cindex undefining macros +To @dfn{undefine} a macro means to cancel its definition. This is done +with the @samp{#undef} directive. @samp{#undef} is followed by the macro +name to be undefined. + +Like definition, undefinition occurs at a specific point in the source +file, and it applies starting from that point. The name ceases to be a +macro name, and from that point on it is treated by the preprocessor as +if it had never been a macro name. + +For example, + +@example +#define FOO 4 +x = FOO; +#undef FOO +x = FOO; +@end example + +@noindent +expands into + +@example +x = 4; + +x = FOO; +@end example + +@noindent +In this example, @samp{FOO} had better be a variable or function as well +as (temporarily) a macro, in order for the result of the expansion to be +valid C code. + +The same form of @samp{#undef} directive will cancel definitions with +arguments or definitions that don't expect arguments. The @samp{#undef} +directive has no effect when used on a name not currently defined as a +macro. + +@node Redefining, Poisoning, Undefining, Macros +@subsection Redefining Macros + +@cindex redefining macros +@dfn{Redefining} a macro means defining (with @samp{#define}) a name that +is already defined as a macro. + +A redefinition is trivial if the new definition is transparently +identical to the old one. You probably wouldn't deliberately write a +trivial redefinition, but they can happen automatically when a header +file is included more than once (@pxref{Header Files}), so they are +accepted silently and without effect. + +Nontrivial redefinition is considered likely to be an error, so it +provokes a warning message from the preprocessor. However, sometimes it +is useful to change the definition of a macro in mid-compilation. You +can inhibit the warning by undefining the macro with @samp{#undef} +before the second definition. + +In order for a redefinition to be trivial, the parameter names must +match and be in the same order, and the new replacement list must +exactly match the one already in effect, with two possible exceptions: + +@itemize @bullet +@item +Whitespace may be added or deleted at the beginning or the end of the +replacement list. In a sense this is vacuous, since strictly such +whitespace doesn't form part of the macro's expansion. + +@item +Between tokens in the expansion, any two forms of whitespace are +considered equivalent. In particular, whitespace may not be eliminated +entirely, nor may it be added where there previously wasn't any. +@end itemize + +Recall that a comment counts as whitespace. + +As a particular case of the above, you may not redefine an object-like +macro as a function-like macro, and vice-versa. + +@node Poisoning, Macro Pitfalls, Redefining, Macros +@subsection Poisoning Macros +@cindex poisoning macros +@findex #pragma GCC poison + +Sometimes, there is an identifier that you want to remove completely +from your program, and make sure that it never creeps back in. To +enforce this, the @samp{#pragma GCC poison} directive can be used. +@samp{#pragma GCC poison} is followed by a list of identifiers to +poison, and takes effect for the rest of the source. You cannot +@samp{#undef} a poisoned identifier or test to see if it's defined with +@samp{#ifdef}. + +For example, + +@example +#pragma GCC poison printf sprintf fprintf +sprintf(some_string, "hello"); +@end example + +@noindent +will produce an error. + +Note, if the poisoned identifier appears through the result of macro +expansion it @emph{won't} cause an error. So if you poison an +identifier you need not worry about system headers defining macros that +use it. + +For example, + +@example +#define strrchr rindex +#pragma GCC poison rindex +strrchr(some_string, 'h'); +@end example + +@noindent +will not produce an error. + +@node Macro Pitfalls,, Poisoning, Macros +@subsection Pitfalls and Subtleties of Macros +@cindex problems with macros +@cindex pitfalls of macros + +In this section we describe some special rules that apply to macros and +macro expansion, and point out certain cases in which the rules have +counterintuitive consequences that you must watch out for. + +@menu +* Misnesting:: Macros can contain unmatched parentheses. +* Macro Parentheses:: Why apparently superfluous parentheses + may be necessary to avoid incorrect grouping. +* Swallow Semicolon:: Macros that look like functions + but expand into compound statements. +* Side Effects:: Unsafe macros that cause trouble when + arguments contain side effects. +* Self-Reference:: Macros whose definitions use the macros' own names. +* Argument Prescan:: Arguments are checked for macro calls before they + are substituted. +* Cascaded Macros:: Macros whose definitions use other macros. +* Newlines in Args:: Sometimes line numbers get confused. +@end menu + +@node Misnesting, Macro Parentheses, Macro Pitfalls, Macro Pitfalls +@subsubsection Improperly Nested Constructs + +Recall that when a macro is called with arguments, the arguments are +substituted into the macro body and the result is checked, together with +the rest of the input file, for more macro calls. + +It is possible to piece together a macro call coming partially from the +macro body and partially from the arguments. For example, + +@example +#define double(x) (2*(x)) +#define call_with_1(x) x(1) +@end example + +@noindent +would expand @samp{call_with_1 (double)} into @samp{(2*(1))}. + +Macro definitions do not have to have balanced parentheses. By writing +an unbalanced open parenthesis in a macro body, it is possible to create +a macro call that begins inside the macro body but ends outside of it. +For example, + +@example +#define strange(file) fprintf (file, "%s %d", +@dots{} +strange(stderr) p, 35) +@end example + +@noindent +This bizarre example expands to @samp{fprintf (stderr, "%s %d", p, 35)}! + +@node Macro Parentheses, Swallow Semicolon, Misnesting, Macro Pitfalls +@subsubsection Unintended Grouping of Arithmetic +@cindex parentheses in macro bodies + +You may have noticed that in most of the macro definition examples shown +above, each occurrence of a macro argument name had parentheses around +it. In addition, another pair of parentheses usually surround the +entire macro definition. Here is why it is best to write macros that +way. + +Suppose you define a macro as follows, + +@example +#define ceil_div(x, y) (x + y - 1) / y +@end example + +@noindent +whose purpose is to divide, rounding up. (One use for this operation is +to compute how many @samp{int} objects are needed to hold a certain +number of @samp{char} objects.) Then suppose it is used as follows: + +@example +a = ceil_div (b & c, sizeof (int)); +@end example + +@noindent +This expands into + +@example +a = (b & c + sizeof (int) - 1) / sizeof (int); +@end example + +@noindent +which does not do what is intended. The operator-precedence rules of +C make it equivalent to this: + +@example +a = (b & (c + sizeof (int) - 1)) / sizeof (int); +@end example + +@noindent +What we want is this: + +@example +a = ((b & c) + sizeof (int) - 1)) / sizeof (int); +@end example + +@noindent +Defining the macro as + +@example +#define ceil_div(x, y) ((x) + (y) - 1) / (y) +@end example + +@noindent +provides the desired result. + +Unintended grouping can result in another way. Consider @samp{sizeof +ceil_div(1, 2)}. That has the appearance of a C expression that would +compute the size of the type of @samp{ceil_div (1, 2)}, but in fact it +means something very different. Here is what it expands to: + +@example +sizeof ((1) + (2) - 1) / (2) +@end example + +@noindent +This would take the size of an integer and divide it by two. The +precedence rules have put the division outside the @samp{sizeof} when it +was intended to be inside. + +Parentheses around the entire macro definition can prevent such +problems. Here, then, is the recommended way to define @samp{ceil_div}: + +@example +#define ceil_div(x, y) (((x) + (y) - 1) / (y)) +@end example + +@node Swallow Semicolon, Side Effects, Macro Parentheses, Macro Pitfalls +@subsubsection Swallowing the Semicolon + +@cindex semicolons (after macro calls) +Often it is desirable to define a macro that expands into a compound +statement. Consider, for example, the following macro, that advances a +pointer (the argument @samp{p} says where to find it) across whitespace +characters: + +@example +#define SKIP_SPACES(p, limit) \ +@{ register char *lim = (limit); \ + while (p != lim) @{ \ + if (*p++ != ' ') @{ \ + p--; break; @}@}@} +@end example + +@noindent +Here backslash-newline is used to split the macro definition, which must +be a single logical line, so that it resembles the way such C code would +be laid out if not part of a macro definition. + +A call to this macro might be @samp{SKIP_SPACES (p, lim)}. Strictly +speaking, the call expands to a compound statement, which is a complete +statement with no need for a semicolon to end it. However, since it +looks like a function call, it minimizes confusion if you can use it +like a function call, writing a semicolon afterward, as in +@samp{SKIP_SPACES (p, lim);} + +This can cause trouble before @samp{else} statements, because the +semicolon is actually a null statement. Suppose you write + +@example +if (*p != 0) + SKIP_SPACES (p, lim); +else @dots{} +@end example + +@noindent +The presence of two statements --- the compound statement and a null +statement --- in between the @samp{if} condition and the @samp{else} +makes invalid C code. + +The definition of the macro @samp{SKIP_SPACES} can be altered to solve +this problem, using a @samp{do @dots{} while} statement. Here is how: + +@example +#define SKIP_SPACES(p, limit) \ +do @{ register char *lim = (limit); \ + while (p != lim) @{ \ + if (*p++ != ' ') @{ \ + p--; break; @}@}@} \ +while (0) +@end example + +Now @samp{SKIP_SPACES (p, lim);} expands into + +@example +do @{@dots{}@} while (0); +@end example + +@noindent +which is one statement. + +@node Side Effects, Self-Reference, Swallow Semicolon, Macro Pitfalls +@subsubsection Duplication of Side Effects + +@cindex side effects (in macro arguments) +@cindex unsafe macros +Many C programs define a macro @samp{min}, for ``minimum'', like this: + +@example +#define min(X, Y) ((X) < (Y) ? (X) : (Y)) +@end example + +When you use this macro with an argument containing a side effect, +as shown here, + +@example +next = min (x + y, foo (z)); +@end example + +@noindent +it expands as follows: + +@example +next = ((x + y) < (foo (z)) ? (x + y) : (foo (z))); +@end example + +@noindent +where @samp{x + y} has been substituted for @samp{X} and @samp{foo (z)} +for @samp{Y}. + +The function @samp{foo} is used only once in the statement as it appears +in the program, but the expression @samp{foo (z)} has been substituted +twice into the macro expansion. As a result, @samp{foo} might be called +two times when the statement is executed. If it has side effects or if +it takes a long time to compute, the results might not be what you +intended. We say that @samp{min} is an @dfn{unsafe} macro. + +The best solution to this problem is to define @samp{min} in a way that +computes the value of @samp{foo (z)} only once. The C language offers +no standard way to do this, but it can be done with GNU C extensions as +follows: + +@example +#define min(X, Y) \ +(@{ typeof (X) __x = (X), __y = (Y); \ + (__x < __y) ? __x : __y; @}) +@end example + +If you do not wish to use GNU C extensions, the only solution is to be +careful when @emph{using} the macro @samp{min}. For example, you can +calculate the value of @samp{foo (z)}, save it in a variable, and use +that variable in @samp{min}: + +@example +#define min(X, Y) ((X) < (Y) ? (X) : (Y)) +@dots{} +@{ + int tem = foo (z); + next = min (x + y, tem); +@} +@end example + +@noindent +(where we assume that @samp{foo} returns type @samp{int}). + +@node Self-Reference, Argument Prescan, Side Effects, Macro Pitfalls +@subsubsection Self-Referential Macros + +@cindex self-reference +A @dfn{self-referential} macro is one whose name appears in its +definition. A special feature of ISO Standard C is that the +self-reference is not considered a macro call. It is passed into the +preprocessor output unchanged. + +Let's consider an example: + +@example +#define foo (4 + foo) +@end example + +@noindent +where @samp{foo} is also a variable in your program. + +Following the ordinary rules, each reference to @samp{foo} will expand +into @samp{(4 + foo)}; then this will be rescanned and will expand into +@samp{(4 + (4 + foo))}; and so on until it causes a fatal error (memory +full) in the preprocessor. + +However, the special rule about self-reference cuts this process short +after one step, at @samp{(4 + foo)}. Therefore, this macro definition +has the possibly useful effect of causing the program to add 4 to the +value of @samp{foo} wherever @samp{foo} is referred to. + +In most cases, it is a bad idea to take advantage of this feature. A +person reading the program who sees that @samp{foo} is a variable will +not expect that it is a macro as well. The reader will come across the +identifier @samp{foo} in the program and think its value should be that +of the variable @samp{foo}, whereas in fact the value is four greater. + +The special rule for self-reference applies also to @dfn{indirect} +self-reference. This is the case where a macro @var{x} expands to use a +macro @samp{y}, and the expansion of @samp{y} refers to the macro +@samp{x}. The resulting reference to @samp{x} comes indirectly from the +expansion of @samp{x}, so it is a self-reference and is not further +expanded. Thus, after + +@example +#define x (4 + y) +#define y (2 * x) +@end example + +@noindent +@samp{x} would expand into @samp{(4 + (2 * x))}. Clear? + +Suppose @samp{y} is used elsewhere, not from the definition of @samp{x}. +Then the use of @samp{x} in the expansion of @samp{y} is not a +self-reference because @samp{x} is not ``in progress''. So it does +expand. However, the expansion of @samp{x} contains a reference to +@samp{y}, and that is an indirect self-reference now because @samp{y} is +``in progress''. The result is that @samp{y} expands to @samp{(2 * (4 + +y))}. + +This behavior is specified by the ISO C standard, so you may need to +understand it. + +@node Argument Prescan, Cascaded Macros, Self-Reference, Macro Pitfalls +@subsubsection Separate Expansion of Macro Arguments +@cindex expansion of arguments +@cindex macro argument expansion +@cindex prescan of macro arguments + +We have explained that the expansion of a macro, including the substituted +arguments, is re-scanned for macro calls to be expanded. + +What really happens is more subtle: first each argument is scanned +separately for macro calls. Then the resulting tokens are substituted +into the macro body to produce the macro expansion, and the macro +expansion is scanned again for macros to expand. + +The result is that the arguments are scanned @emph{twice} to expand +macro calls in them. + +Most of the time, this has no effect. If the argument contained any +macro calls, they are expanded during the first scan. The result +therefore contains no macro calls, so the second scan does not change +it. If the argument were substituted as given, with no prescan, the +single remaining scan would find the same macro calls and produce the +same results. + +You might expect the double scan to change the results when a +self-referential macro is used in an argument of another macro +(@pxref{Self-Reference}): the self-referential macro would be expanded +once in the first scan, and a second time in the second scan. However, +this is not what happens. The self-references that do not expand in the +first scan are marked so that they will not expand in the second scan +either. + +The prescan is not done when an argument is stringified or concatenated. +Thus, + +@example +#define str(s) #s +#define foo 4 +str (foo) +@end example + +@noindent +expands to @samp{"foo"}. Once more, prescan has been prevented from +having any noticeable effect. + +More precisely, stringification and concatenation use the argument +tokens as given without initially scanning for macros. The same +argument would be used in expanded form if it is substituted elsewhere +without stringification or concatenation. + +@example +#define str(s) #s lose(s) +#define foo 4 +str (foo) +@end example + +expands to @samp{"foo" lose(4)}. + +You might now ask, ``Why mention the prescan, if it makes no difference? +And why not skip it and make the preprocessor faster?'' The answer is +that the prescan does make a difference in three special cases: + +@itemize @bullet +@item +Nested calls to a macro. + +@item +Macros that call other macros that stringify or concatenate. + +@item +Macros whose expansions contain unshielded commas. +@end itemize + +We say that @dfn{nested} calls to a macro occur when a macro's argument +contains a call to that very macro. For example, if @samp{f} is a macro +that expects one argument, @samp{f (f (1))} is a nested pair of calls to +@samp{f}. The desired expansion is made by expanding @samp{f (1)} and +substituting that into the definition of @samp{f}. The prescan causes +the expected result to happen. Without the prescan, @samp{f (1)} itself +would be substituted as an argument, and the inner use of @samp{f} would +appear during the main scan as an indirect self-reference and would not +be expanded. Here, the prescan cancels an undesirable side effect (in +the medical, not computational, sense of the term) of the special rule +for self-referential macros. + +Prescan causes trouble in certain other cases of nested macro calls. +Here is an example: + +@example +#define foo a,b +#define bar(x) lose(x) +#define lose(x) (1 + (x)) + +bar(foo) +@end example + +@noindent +We would like @samp{bar(foo)} to turn into @samp{(1 + (foo))}, which +would then turn into @samp{(1 + (a,b))}. Instead, @samp{bar(foo)} +expands into @samp{lose(a,b)}, and you get an error because @code{lose} +requires a single argument. In this case, the problem is easily solved +by the same parentheses that ought to be used to prevent misnesting of +arithmetic operations: + +@example +#define foo (a,b) +#define bar(x) lose((x)) +@end example + +The problem is more serious when the operands of the macro are not +expressions; for example, when they are statements. Then parentheses +are unacceptable because they would make for invalid C code: + +@example +#define foo @{ int a, b; @dots{} @} +@end example + +@noindent +In GNU C you can shield the commas using the @samp{(@{@dots{}@})} +construct which turns a compound statement into an expression: + +@example +#define foo (@{ int a, b; @dots{} @}) +@end example + +Or you can rewrite the macro definition to avoid such commas: + +@example +#define foo @{ int a; int b; @dots{} @} +@end example + +There is also one case where prescan is useful. It is possible to use +prescan to expand an argument and then stringify it --- if you use two +levels of macros. Let's add a new macro @samp{xstr} to the example +shown above: + +@example +#define xstr(s) str(s) +#define str(s) #s +#define foo 4 +xstr (foo) +@end example + +This expands into @samp{"4"}, not @samp{"foo"}. The reason for the +difference is that the argument of @samp{xstr} is expanded at prescan +(because @samp{xstr} does not specify stringification or concatenation +of the argument). The result of prescan then forms the argument for +@samp{str}. @samp{str} uses its argument without prescan because it +performs stringification; but it cannot prevent or undo the prescanning +already done by @samp{xstr}. + +@node Cascaded Macros, Newlines in Args, Argument Prescan, Macro Pitfalls +@subsubsection Cascaded Use of Macros + +@cindex cascaded macros +@cindex macro body uses macro +A @dfn{cascade} of macros is when one macro's body contains a reference +to another macro. This is very common practice. For example, + +@example +#define BUFSIZE 1020 +#define TABLESIZE BUFSIZE +@end example + +This is not at all the same as defining @samp{TABLESIZE} to be +@samp{1020}. The @samp{#define} for @samp{TABLESIZE} uses exactly the +body you specify --- in this case, @samp{BUFSIZE} --- and does not check +to see whether it too is the name of a macro. + +It's only when you @emph{use} @samp{TABLESIZE} that the result of its +expansion is checked for more macro names. + +This makes a difference if you change the definition of @samp{BUFSIZE} +at some point in the source file. @samp{TABLESIZE}, defined as shown, +will always expand using the definition of @samp{BUFSIZE} that is +currently in effect: + +@example +#define BUFSIZE 1020 +#define TABLESIZE BUFSIZE +#undef BUFSIZE +#define BUFSIZE 37 +@end example + +@noindent +Now @samp{TABLESIZE} expands (in two stages) to @samp{37}. (The +@samp{#undef} is to prevent any warning about the nontrivial +redefinition of @code{BUFSIZE}.) + +@node Newlines in Args,, Cascaded Macros, Macro Pitfalls +@subsection Newlines in Macro Arguments +@cindex newlines in macro arguments + +The invocation of a function-like macro can extend over many logical +lines. The ISO C standard requires that newlines within a macro +invocation be treated as ordinary whitespace. This means that when the +expansion of a function-like macro replaces its invocation, it appears +on the same line as the macro name did. Thus line numbers emitted by +the compiler or debugger refer to the line the invocation started on, +which might be different to the line containing the argument causing the +problem. + +Here is an example illustrating this: + +@example +#define ignore_second_arg(a,b,c) a; c + +ignore_second_arg (foo (), + ignored (), + syntax error); +@end example + +@noindent +The syntax error triggered by the tokens @samp{syntax error} results in +an error message citing line three --- the line of ignore_second_arg --- +even though the problematic code comes from line five. + +@node Conditionals, Assertions, Macros, Top +@section Conditionals + +@cindex conditionals +In a macro processor, a @dfn{conditional} is a directive that allows a +part of the program to be ignored during compilation, on some +conditions. In the C preprocessor, a conditional can test either an +arithmetic expression or whether a name is defined as a macro. + +A conditional in the C preprocessor resembles in some ways an @samp{if} +statement in C, but it is important to understand the difference between +them. The condition in an @samp{if} statement is tested during the +execution of your program. Its purpose is to allow your program to +behave differently from run to run, depending on the data it is +operating on. The condition in a preprocessing conditional directive is +tested when your program is compiled. Its purpose is to allow different +code to be included in the program depending on the situation at the +time of compilation. + +@menu +* Uses: Conditional Uses. What conditionals are for. +* Syntax: Conditional Syntax. How conditionals are written. +* Deletion: Deleted Code. Making code into a comment. +* Macros: Conditionals-Macros. Why conditionals are used with macros. +* Errors: #error Directive. Detecting inconsistent compilation parameters. +@end menu + +@node Conditional Uses +@subsection Why Conditionals are Used + +Generally there are three kinds of reason to use a conditional. + +@itemize @bullet +@item +A program may need to use different code depending on the machine or +operating system it is to run on. In some cases the code for one +operating system may be erroneous on another operating system; for +example, it might refer to library routines that do not exist on the +other system. When this happens, it is not enough to avoid executing +the invalid code: merely having it in the program makes it impossible to +link the program and run it. With a preprocessing conditional, the +offending code can be effectively excised from the program when it is +not valid. + +@item +You may want to be able to compile the same source file into two +different programs. Sometimes the difference between the programs is +that one makes frequent time-consuming consistency checks on its +intermediate data, or prints the values of those data for debugging, +while the other does not. + +@item +A conditional whose condition is always false is a good way to exclude +code from the program but keep it as a sort of comment for future +reference. +@end itemize + +Most simple programs that are intended to run on only one machine will +not need to use preprocessing conditionals. + +@node Conditional Syntax +@subsection Syntax of Conditionals + +@findex #if +A conditional in the C preprocessor begins with a @dfn{conditional +directive}: @samp{#if}, @samp{#ifdef} or @samp{#ifndef}. +@xref{Conditionals-Macros}, for information on @samp{#ifdef} and +@samp{#ifndef}; only @samp{#if} is explained here. + +@menu +* If: #if Directive. Basic conditionals using @samp{#if} and @samp{#endif}. +* Else: #else Directive. Including some text if the condition fails. +* Elif: #elif Directive. Testing several alternative possibilities. +@end menu + +@node #if Directive +@subsubsection The @samp{#if} Directive + +The @samp{#if} directive in its simplest form consists of + +@example +#if @var{expression} +@var{controlled text} +#endif /* @var{expression} */ +@end example + +The comment following the @samp{#endif} is not required, but it is a +good practice because it helps people match the @samp{#endif} to the +corresponding @samp{#if}. Such comments should always be used, except +in short conditionals that are not nested. In fact, you can put +anything at all after the @samp{#endif} and it will be ignored by the +GNU C preprocessor, but only comments are acceptable in ISO Standard C@. + +@var{expression} is a C expression of integer type, subject to stringent +restrictions. It may contain + +@itemize @bullet +@item +Integer constants, which are all regarded as @code{long} or +@code{unsigned long}. + +@item +Character constants, which are interpreted according to the character +set and conventions of the machine and operating system on which the +preprocessor is running. The GNU C preprocessor uses the C data type +@samp{char} for these character constants; therefore, whether some +character codes are negative is determined by the C compiler used to +compile the preprocessor. If it treats @samp{char} as signed, then +character codes large enough to set the sign bit will be considered +negative; otherwise, no character code is considered negative. + +@item +Arithmetic operators for addition, subtraction, multiplication, +division, bitwise operations, shifts, comparisons, and logical +operations (@samp{&&} and @samp{||}). The latter two obey the usual +short-circuiting rules of standard C. + +@item +Identifiers that are not macros, which are all treated as zero(!). + +@item +Macro calls. All macro calls in the expression are expanded before +actual computation of the expression's value begins. +@end itemize + +Note that @samp{sizeof} operators and @code{enum}-type values are not +allowed. @code{enum}-type values, like all other identifiers that are +not taken as macro calls and expanded, are treated as zero. + +The @var{controlled text} inside of a conditional can include +preprocessing directives. Then the directives inside the conditional +are obeyed only if that branch of the conditional succeeds. The text +can also contain other conditional groups. However, the @samp{#if} and +@samp{#endif} directives must balance. + +@node #else Directive +@subsubsection The @samp{#else} Directive + +@findex #else +The @samp{#else} directive can be added to a conditional to provide +alternative text to be used if the condition is false. This is what +it looks like: + +@example +#if @var{expression} +@var{text-if-true} +#else /* Not @var{expression} */ +@var{text-if-false} +#endif /* Not @var{expression} */ +@end example + +If @var{expression} is nonzero, and thus the @var{text-if-true} is +active, then @samp{#else} acts like a failing conditional and the +@var{text-if-false} is ignored. Conversely, if the @samp{#if} +conditional fails, the @var{text-if-false} is considered included. + +@node #elif Directive +@subsubsection The @samp{#elif} Directive + +@findex #elif +One common case of nested conditionals is used to check for more than two +possible alternatives. For example, you might have + +@example +#if X == 1 +@dots{} +#else /* X != 1 */ +#if X == 2 +@dots{} +#else /* X != 2 */ +@dots{} +#endif /* X != 2 */ +#endif /* X != 1 */ +@end example + +Another conditional directive, @samp{#elif}, allows this to be +abbreviated as follows: + +@example +#if X == 1 +@dots{} +#elif X == 2 +@dots{} +#else /* X != 2 and X != 1*/ +@dots{} +#endif /* X != 2 and X != 1*/ +@end example + +@samp{#elif} stands for ``else if''. Like @samp{#else}, it goes in the +middle of a @samp{#if}-@samp{#endif} pair and subdivides it; it does not +require a matching @samp{#endif} of its own. Like @samp{#if}, the +@samp{#elif} directive includes an expression to be tested. + +The text following the @samp{#elif} is processed only if the original +@samp{#if}-condition failed and the @samp{#elif} condition succeeds. +More than one @samp{#elif} can go in the same @samp{#if}-@samp{#endif} +group. Then the text after each @samp{#elif} is processed only if the +@samp{#elif} condition succeeds after the original @samp{#if} and any +previous @samp{#elif} directives within it have failed. @samp{#else} is +equivalent to @samp{#elif 1}, and @samp{#else} is allowed after any +number of @samp{#elif} directives, but @samp{#elif} may not follow +@samp{#else}. + +@node Deleted Code +@subsection Keeping Deleted Code for Future Reference +@cindex commenting out code + +If you replace or delete a part of the program but want to keep the old +code around as a comment for future reference, the easy way to do this +is to put @samp{#if 0} before it and @samp{#endif} after it. This is +better than using comment delimiters @samp{/*} and @samp{*/} since those +won't work if the code already contains comments (C comments do not +nest). + +This works even if the code being turned off contains conditionals, but +they must be entire conditionals (balanced @samp{#if} and @samp{#endif}). + +Conversely, do not use @samp{#if 0} for comments which are not C code. +Use the comment delimiters @samp{/*} and @samp{*/} instead. The +interior of @samp{#if 0} must consist of complete tokens; in particular, +single-quote characters must balance. Comments often contain unbalanced +single-quote characters (known in English as apostrophes). These +confuse @samp{#if 0}. They do not confuse @samp{/*}. + +@node Conditionals-Macros +@subsection Conditionals and Macros + +Conditionals are useful in connection with macros or assertions, because +those are the only ways that an expression's value can vary from one +compilation to another. A @samp{#if} directive whose expression uses no +macros or assertions is equivalent to @samp{#if 1} or @samp{#if 0}; you +might as well determine which one, by computing the value of the +expression yourself, and then simplify the program. + +For example, here is a conditional that tests the expression +@samp{BUFSIZE == 1020}, where @samp{BUFSIZE} must be a macro. + +@example +#if BUFSIZE == 1020 + printf ("Large buffers!\n"); +#endif /* BUFSIZE is large */ +@end example + +(Programmers often wish they could test the size of a variable or data +type in @samp{#if}, but this does not work. The preprocessor does not +understand @code{sizeof}, or typedef names, or even the type keywords +such as @code{int}.) + +@findex defined +The special operator @samp{defined} is used in @samp{#if} and +@samp{#elif} expressions to test whether a certain name is defined as a +macro. Either @samp{defined @var{name}} or @samp{defined (@var{name})} +is an expression whose value is 1 if @var{name} is defined as macro at +the current point in the program, and 0 otherwise. To the +@samp{defined} operator it makes no difference what the definition of +the macro is; all that matters is whether there is a definition. Thus, +for example,@refill + +@example +#if defined (vax) || defined (ns16000) +@end example + +@noindent +would succeed if either of the names @samp{vax} and @samp{ns16000} is +defined as a macro. You can test the same condition using assertions +(@pxref{Assertions}), like this: + +@example +#if #cpu (vax) || #cpu (ns16000) +@end example + +If a macro is defined and later undefined with @samp{#undef}, subsequent +use of the @samp{defined} operator returns 0, because the name is no +longer defined. If the macro is defined again with another +@samp{#define}, @samp{defined} will recommence returning 1. + +If the @samp{defined} operator appears as a result of a macro expansion, +the C standard says the behavior is undefined. GNU cpp treats it as a +genuine @samp{defined} operator and evaluates it normally. It will warn +wherever your code uses this feature if you use the command-line option +@samp{-pedantic}, since other compilers may handle it differently. + +@findex #ifdef +@findex #ifndef +Conditionals that test whether a single macro is defined are very common, +so there are two special short conditional directives for this case. + +@table @code +@item #ifdef @var{name} +is equivalent to @samp{#if defined (@var{name})}. + +@item #ifndef @var{name} +is equivalent to @samp{#if ! defined (@var{name})}. +@end table + +Macro definitions can vary between compilations for several reasons. + +@itemize @bullet +@item +Some macros are predefined on each kind of machine. For example, on a +Vax, the name @samp{vax} is a predefined macro. On other machines, it +would not be defined. + +@item +Many more macros are defined by system header files. Different systems +and machines define different macros, or give them different values. It +is useful to test these macros with conditionals to avoid using a system +feature on a machine where it is not implemented. + +@item +Macros are a common way of allowing users to customize a program for +different machines or applications. For example, the macro +@samp{BUFSIZE} might be defined in a configuration file for your program +that is included as a header file in each source file. You would use +@samp{BUFSIZE} in a preprocessing conditional in order to generate +different code depending on the chosen configuration. + +@item +Macros can be defined or undefined with @samp{-D} and @samp{-U} command +options when you compile the program. You can arrange to compile the +same source file into two different programs by choosing a macro name to +specify which program you want, writing conditionals to test whether or +how this macro is defined, and then controlling the state of the macro +with compiler command options. @xref{Invocation}. +@end itemize + +@ifinfo +Assertions are usually predefined, but can be defined with preprocessor +directives or command-line options. +@end ifinfo + +@node #error Directive +@subsection The @samp{#error} and @samp{#warning} Directives + +@findex #error +The directive @samp{#error} causes the preprocessor to report a fatal +error. The tokens forming the rest of the line following @samp{#error} +are used as the error message, and not macro-expanded. Internal +whitespace sequences are each replaced with a single space. The line +must consist of complete tokens. + +You would use @samp{#error} inside of a conditional that detects a +combination of parameters which you know the program does not properly +support. For example, if you know that the program will not run +properly on a Vax, you might write + +@smallexample +@group +#ifdef __vax__ +#error "Won't work on Vaxen. See comments at get_last_object." +#endif +@end group +@end smallexample + +@noindent +@xref{Nonstandard Predefined}, for why this works. + +If you have several configuration parameters that must be set up by +the installation in a consistent way, you can use conditionals to detect +an inconsistency and report it with @samp{#error}. For example, + +@smallexample +#if HASH_TABLE_SIZE % 2 == 0 || HASH_TABLE_SIZE % 3 == 0 \ + || HASH_TABLE_SIZE % 5 == 0 +#error HASH_TABLE_SIZE should not be divisible by a small prime +#endif +@end smallexample + +@findex #warning +The directive @samp{#warning} is like the directive @samp{#error}, but +causes the preprocessor to issue a warning and continue preprocessing. +The tokens following @samp{#warning} are used as the warning message, +and not macro-expanded. + +You might use @samp{#warning} in obsolete header files, with a message +directing the user to the header file which should be used instead. + +@node Assertions, Line Control, Conditionals, Top +@section Assertions +@cindex assertions +@dfn{Assertions} are a more systematic alternative to macros in writing +conditionals to test what sort of computer or system the compiled +program will run on. Assertions are usually predefined, but you can +define them with preprocessing directives or command-line options. + +@cindex predicates +The macros traditionally used to describe the type of target are not +classified in any way according to which question they answer; they may +indicate a hardware architecture, a particular hardware model, an +operating system, a particular version of an operating system, or +specific configuration options. These are jumbled together in a single +namespace. In contrast, each assertion consists of a named question and +an answer. The question is usually called the @dfn{predicate}. An +assertion looks like this: + +@example +#@var{predicate} (@var{answer}) +@end example + +@noindent +You must use a properly formed identifier for @var{predicate}. The +value of @var{answer} can be any sequence of words; all characters are +significant except for leading and trailing whitespace, and differences +in internal whitespace sequences are ignored. (This is similar to the +rules governing macro redefinition.) Thus, @samp{x + y} is different +from @samp{x+y} but equivalent to @samp{ x + y }. @samp{)} is not +allowed in an answer. + +@cindex testing predicates +Here is a conditional to test whether the answer @var{answer} is asserted +for the predicate @var{predicate}: + +@example +#if #@var{predicate} (@var{answer}) +@end example + +@noindent +There may be more than one answer asserted for a given predicate. If +you omit the answer, you can test whether @emph{any} answer is asserted +for @var{predicate}: + +@example +#if #@var{predicate} +@end example + +@findex #system +@findex #machine +@findex #cpu +Most of the time, the assertions you test will be predefined assertions. +GNU C provides three predefined predicates: @code{system}, @code{cpu}, +and @code{machine}. @code{system} is for assertions about the type of +software, @code{cpu} describes the type of computer architecture, and +@code{machine} gives more information about the computer. For example, +on a GNU system, the following assertions would be true: + +@example +#system (gnu) +#system (mach) +#system (mach 3) +#system (mach 3.@var{subversion}) +#system (hurd) +#system (hurd @var{version}) +@end example + +@noindent +and perhaps others. The alternatives with +more or less version information let you ask more or less detailed +questions about the type of system software. + +On a Unix system, you would find @code{#system (unix)} and perhaps one of: +@code{#system (aix)}, @code{#system (bsd)}, @code{#system (hpux)}, +@code{#system (lynx)}, @code{#system (mach)}, @code{#system (posix)}, +@code{#system (svr3)}, @code{#system (svr4)}, or @code{#system (xpg4)} +with possible version numbers following. + +Other values for @code{system} are @code{#system (mvs)} +and @code{#system (vms)}. + +@strong{Portability note:} Many Unix C compilers provide only one answer +for the @code{system} assertion: @code{#system (unix)}, if they support +assertions at all. This is less than useful. + +An assertion with a multi-word answer is completely different from several +assertions with individual single-word answers. For example, the presence +of @code{system (mach 3.0)} does not mean that @code{system (3.0)} is true. +It also does not directly imply @code{system (mach)}, but in GNU C, that +last will normally be asserted as well. + +The current list of possible assertion values for @code{cpu} is: +@code{#cpu (a29k)}, @code{#cpu (alpha)}, @code{#cpu (arm)}, @code{#cpu +(clipper)}, @code{#cpu (convex)}, @code{#cpu (elxsi)}, @code{#cpu +(tron)}, @code{#cpu (h8300)}, @code{#cpu (i370)}, @code{#cpu (i386)}, +@code{#cpu (i860)}, @code{#cpu (i960)}, @code{#cpu (m68k)}, @code{#cpu +(m88k)}, @code{#cpu (mips)}, @code{#cpu (ns32k)}, @code{#cpu (hppa)}, +@code{#cpu (pyr)}, @code{#cpu (ibm032)}, @code{#cpu (rs6000)}, +@code{#cpu (sh)}, @code{#cpu (sparc)}, @code{#cpu (spur)}, @code{#cpu +(tahoe)}, @code{#cpu (vax)}, @code{#cpu (we32000)}. + +@findex #assert +You can create assertions within a C program using @samp{#assert}, like +this: + +@example +#assert @var{predicate} (@var{answer}) +@end example + +@noindent +(Note the absence of a @samp{#} before @var{predicate}.) + +@cindex unassert +@cindex assertions, undoing +@cindex retracting assertions +@findex #unassert +Each time you do this, you assert a new true answer for @var{predicate}. +Asserting one answer does not invalidate previously asserted answers; +they all remain true. The only way to remove an answer is with +@samp{#unassert}. @samp{#unassert} has the same syntax as +@samp{#assert}. You can also remove all answers to a @var{predicate} +like this: + +@example +#unassert @var{predicate} +@end example + +You can also add or cancel assertions using command options +when you run @code{gcc} or @code{cpp}. @xref{Invocation}. + +@node Line Control, Other Directives, Assertions, Top +@section Combining Source Files + +@cindex line control +One of the jobs of the C preprocessor is to inform the C compiler of where +each line of C code came from: which source file and which line number. + +C code can come from multiple source files if you use @samp{#include}; +both @samp{#include} and the use of conditionals and macros can cause +the line number of a line in the preprocessor output to be different +from the line's number in the original source file. You will appreciate +the value of making both the C compiler (in error messages) and symbolic +debuggers such as GDB use the line numbers in your source file. + +The C preprocessor builds on this feature by offering a directive by +which you can control the feature explicitly. This is useful when a +file for input to the C preprocessor is the output from another program +such as the @code{bison} parser generator, which operates on another +file that is the true source file. Parts of the output from +@code{bison} are generated from scratch, other parts come from a +standard parser file. The rest are copied nearly verbatim from the +source file, but their line numbers in the @code{bison} output are not +the same as their original line numbers. Naturally you would like +compiler error messages and symbolic debuggers to know the original +source file and line number of each line in the @code{bison} input. + +@findex #line +@code{bison} arranges this by writing @samp{#line} directives into the output +file. @samp{#line} is a directive that specifies the original line number +and source file name for subsequent input in the current preprocessor input +file. @samp{#line} has three variants: + +@table @code +@item #line @var{linenum} +Here @var{linenum} is a decimal integer constant. This specifies that +the line number of the following line of input, in its original source file, +was @var{linenum}. + +@item #line @var{linenum} @var{filename} +Here @var{linenum} is a decimal integer constant and @var{filename} is a +string constant. This specifies that the following line of input came +originally from source file @var{filename} and its line number there was +@var{linenum}. Keep in mind that @var{filename} is not just a file +name; it is surrounded by double-quote characters so that it looks like +a string constant. + +@item #line @var{anything else} +@var{anything else} is checked for macro calls, which are expanded. +The result should be a decimal integer constant followed optionally +by a string constant, as described above. +@end table + +@samp{#line} directives alter the results of the @samp{__FILE__} and +@samp{__LINE__} predefined macros from that point on. @xref{Standard +Predefined}. + +The output of the preprocessor (which is the input for the rest of the +compiler) contains directives that look much like @samp{#line} +directives. They start with just @samp{#} instead of @samp{#line}, but +this is followed by a line number and file name as in @samp{#line}. +@xref{Output}. + +@node Other Directives, Output, Line Control, Top +@section Miscellaneous Preprocessing Directives + +This section describes some additional, rarely used, preprocessing +directives. + +@findex #pragma +@findex #pragma GCC + +The ISO standard specifies that the effect of the @samp{#pragma} +directive is implementation-defined. The GNU C preprocessor recognizes +some pragmas, and passes unrecognized ones through to the preprocessor +output, so they are available to the compilation pass. + +In line with the C99 standard, which introduces a STDC namespace for C99 +pragmas, the preprocessor introduces a GCC namespace for GCC pragmas. +Supported GCC preprocessor pragmas are of the form @samp{#pragma GCC +...}. For backwards compatibility previously supported pragmas are also +recognized without the @samp{GCC} prefix, however that use is +deprecated. Pragmas that are already deprecated are not recognized with +a @samp{GCC} prefix. + +@findex #pragma GCC dependency +The @samp{#pragma GCC dependency} allows you to check the relative dates +of the current file and another file. If the other file is more recent +than the current file, a warning is issued. This is useful if the +include file is derived from the other file, and should be regenerated. +The other file is searched for using the normal include search path. +Optional trailing text can be used to give more information in the +warning message. + +@smallexample +#pragma GCC dependency "parse.y" +#pragma GCC dependency "/usr/include/time.h" rerun /path/to/fixincludes +@end smallexample + +@findex _Pragma +The C99 standard also introduces the @samp{_Pragma} operator. The +syntax is @code{_Pragma (string-literal)}, where @samp{string-literal} +can be either a normal or wide-character string literal. It is +destringized, by replacing all @samp{\\} with a single @samp{\} and all +@samp{\"} with a @samp{"}. The result is then processed as if it had +appeared as the right hand side of a @samp{#pragma} directive. For +example, + +@smallexample +_Pragma ("GCC dependency \"parse.y\"") +@end smallexample + +@noindent has the same effect as @samp{#pragma GCC dependency +"parse.y"}. The same effect could be achieved using macros, for example + +@smallexample +#define DO_PRAGMA(x) _Pragma (#x) +DO_PRAGMA (GCC dependency "parse.y") +@end smallexample + +The standard is unclear on where a @samp{_Pragma} operator can appear. +The preprocessor accepts it even within a preprocessing conditional +directive like @samp{#if}. To be safe, you are probably best keeping it +out of directives other than @samp{#define}, and putting it on a line of +its own. + +@findex #ident +The @samp{#ident} directive is supported for compatibility with certain +other systems. It is followed by a line of text. On some systems, the +text is copied into a special place in the object file; on most systems, +the text is ignored and this directive has no effect. Typically +@samp{#ident} is only used in header files supplied with those systems +where it is meaningful. + +@cindex null directive +The @dfn{null directive} consists of a @samp{#} followed by a newline, +with only whitespace (including comments) in between. A null directive +is understood as a preprocessing directive but has no effect on the +preprocessor output. The primary significance of the existence of the +null directive is that an input line consisting of just a @samp{#} will +produce no output, rather than a line of output containing just a +@samp{#}. Supposedly some old C programs contain such lines. + +@node Output, Implementation, Other Directives, Top +@section C Preprocessor Output + +@cindex output format +The output from the C preprocessor looks much like the input, except +that all preprocessing directive lines have been replaced with blank +lines and all comments with spaces. + +The ISO standard specifies that it is implementation defined whether a +preprocessor preserves whitespace between tokens, or replaces it with +e.g. a single space. In the GNU C preprocessor, whitespace between +tokens is collapsed to become a single space, with the exception that +the first token on a non-directive line is preceded with sufficient +spaces that it appears in the same column in the preprocessed output +that it appeared in in the original source file. This is so the output +is easy to read. @xref{Unreliable Features}. + +Source file name and line number information is conveyed by lines +of the form + +@example +# @var{linenum} @var{filename} @var{flags} +@end example + +@noindent +which are inserted as needed into the output (but never within a string +or character constant), and in place of long sequences of empty lines. +Such a line means that the following line originated in file +@var{filename} at line @var{linenum}. + +After the file name comes zero or more flags, which are @samp{1}, +@samp{2}, @samp{3}, or @samp{4}. If there are multiple flags, spaces +separate them. Here is what the flags mean: + +@table @samp +@item 1 +This indicates the start of a new file. +@item 2 +This indicates returning to a file (after having included another file). +@item 3 +This indicates that the following text comes from a system header file, +so certain warnings should be suppressed. +@item 4 +This indicates that the following text should be treated as C@. +@c maybe cross reference NO_IMPLICIT_EXTERN_C +@end table + +@node Implementation, Unreliable Features, Output, Top +@section Implementation-defined Behavior and Implementation Limits +@cindex implementation limits +@cindex implementation-defined behavior + +The ISO C standard mandates that implementations document various +aspects of preprocessor behavior. You should try to avoid undue +reliance on behaviour described here, as it is possible that it will +change subtly in future implementations. + +@itemize @bullet + +@item The mapping of physical source file multi-byte characters to the +execution character set. + +Currently, GNU cpp only supports character sets that are strict supersets +of ASCII, and performs no translation of characters. + +@item Non-empty sequences of whitespace characters. + +Each whitespace sequence is not preserved, but collapsed to a single +space. For aesthetic reasons, the first token on each non-directive +line of output is preceded with sufficient spaces that it appears in the +same column as it did in the original source file. + +@item The numeric value of character constants in preprocessor expressions. + +The preprocessor and compiler interpret character constants in the same +way; escape sequences such as @code{\a} are given the values they would +have on the target machine. + +Multi-character character constants are interpreted a character at a +time, shifting the previous result left by the number of bits per +character on the host, and adding the new character. For example, 'ab' +on an 8-bit host would be interpreted as 'a' * 256 + 'b'. If there are +more characters in the constant than can fit in the widest native +integer type on the host, usually a @samp{long}, the excess characters +are ignored and a diagnostic is given. + +@item Source file inclusion. + +For a discussion on how the preprocessor locates header files, +@pxref{Include Operation}. + +@item Interpretation of the filename resulting from a macro-expanded +@samp{#include} directive. + +If the macro expands to a string literal, the @samp{#include} directive +is processed as if the string had been specified directly. Otherwise, +the macro must expand to a token stream beginning with a @samp{<} token +and including a @samp{>} token. In this case, the tokens between the +@samp{<} and the first @samp{>} are combined to form the filename to be +included. Any whitespace between tokens is reduced to a single space; +then any space after the initial @samp{<} is retained, but a trailing +space before the closing @samp{>} is ignored. + +In either case, if any excess tokens remain, an error occurs and the +directive is not processed. + +@item Treatment of a @samp{#pragma} directive that after macro-expansion +results in a standard pragma. + +The pragma is processed as if it were a normal standard pragma. + +@end itemize + +The following documents internal limits of GNU cpp. + +@itemize @bullet + +@item Nesting levels of @samp{#include} files. + +We impose an arbitrary limit of 200 levels, to avoid runaway recursion. +The standard requires at least 15 levels. + +@item Nesting levels of conditional inclusion. + +The C standard mandates this be at least 63. The GNU C preprocessor +is limited only by available memory. + +@item Levels of parenthesised expressions within a full expression. + +The C standard requires this to be at least 63. In preprocessor +conditional expressions it is limited only by available memory. + +@item Significant initial characters in an identifier or macro name. + +The preprocessor treats all characters as significant. The C standard +requires only that the first 63 be significant. + +@item Number of macros simultaneously defined in a single translation unit. + +The standard requires at least 4095 be possible; GNU cpp is limited only +by available memory. + +@item Number of parameters in a macro definition and arguments in a macro call. + +We allow USHRT_MAX, which is normally 65,535, and above the minimum of +127 required by the standard. + +@item Number of characters on a logical source line. + +The C standard requires a minimum of 4096 be permitted. GNU cpp places +no limits on this, but you may get incorrect column numbers reported in +diagnostics for lines longer than 65,535 characters. + +@end itemize + +@node Unreliable Features, Invocation, Implementation, Top +@section Undefined Behavior and Deprecated Features +@cindex undefined behavior +@cindex deprecated features + +This section details GNU C preprocessor behavior that is subject to +change or deprecated. You are @emph{strongly advised} to write your +software so it does not rely on anything described here; future versions +of the preprocessor may subtly change such behavior or even remove the +feature altogether. + +Preservation of the form of whitespace between tokens is unlikely to +change from current behavior (@ref{Output}), but you are advised not +to rely on it. + +The following are undocumented and subject to change:- + +@itemize @bullet + +@item Precedence of ## operators with respect to each other + +Whether a sequence of ## operators is evaluated left-to-right, +right-to-left or indeed in a consistent direction at all is not +specified. An example of where this might matter is pasting the +arguments @samp{1}, @samp{e} and @samp{-2}. This would be fine for +left-to-right pasting, but right-to-left pasting would produce an +invalid token @samp{e-2}. It is possible to guarantee precedence by +suitable use of nested macros. + +@item Precedence of # operator with respect to the ## operator + +Which of these two operators is evaluated first is not specified. + +@end itemize + +The following features are in flux and should not be used in portable +code: + +@itemize @bullet + +@item Optional argument when invoking rest argument macros + +As an extension, GCC permits you to omit the variable arguments entirely +when you use a variable argument macro. This works whether or not you +give the variable argument a name. For example, the two macro +invocations in the example below expand to the same thing: + +@smallexample +#define debug(format, ...) printf (format, __VA_ARGS__) +debug("string"); /* Not permitted by C standard. */ +debug("string",); /* OK. */ +@end smallexample + +This extension will be preserved, but the special behavior of @samp{##} +in this context has changed in the past and may change again in the +future. + +@item ## swallowing preceding text in rest argument macros + +Formerly, in a macro expansion, if @samp{##} appeared before a variable +arguments parameter, and the set of tokens specified for that argument in +the macro invocation was empty, previous versions of the GNU C +preprocessor would back up and remove the preceding sequence of +non-whitespace characters (@strong{not} the preceding token). This +extension is in direct conflict with the 1999 C standard and has been +drastically pared back. + +In the current version of the preprocessor, if @samp{##} appears between +a comma and a variable arguments parameter, and the variable argument is +omitted entirely, the comma will be removed from the expansion. If the +variable argument is empty, or the token before @samp{##} is not a +comma, then @samp{##} behaves as a normal token paste. + +Portable code should avoid this extension at all costs. + +@end itemize + +The following features are deprecated and will likely be removed at some +point in the future:- + +@itemize @bullet + +@item Attempting to paste two tokens which together do not form a valid +preprocessing token + +The preprocessor currently warns about this and outputs the two tokens +adjacently, which is probably the behavior the programmer intends. It +may not work in future, though. + +Most of the time, when you get this warning, you will find that @samp{##} +is being used superstitiously, to guard against whitespace appearing +between two tokens. It is almost always safe to delete the @samp{##}. + +@findex #pragma once +@item #pragma once + +This pragma was once used to tell the preprocessor that it need not +include a file more than once. It is now obsolete and should not be +used at all. + +@item #pragma poison + +This pragma has been superseded by @samp{#pragma GCC poison}. +@xref{Poisoning}. + +@item Multi-line string literals + +The preprocessor currently allows raw newlines in string literals. This +extension is deprecated and will be removed in a future version of GCC. +The preprocessor already forbids such string literals in all directives +apart from #define. + +Instead, make use of ISO C concatenation of adjacent string literals, or +use @samp{\n} followed by an escaped newline. + +@item Preprocessing things which are not C + +The C preprocessor is intended to be used only with C, C++, and +Objective C source code. In the past, it has been abused as a general +text processor. It will choke on input which is not lexically valid C; +for example, apostrophes will be interpreted as the beginning of +character constants, and cause errors. Also, you cannot rely on it +preserving characteristics of the input which are not significant to +C-family languages. For instance, if a Makefile is preprocessed, all +the hard tabs will be lost, and the Makefile will not work. + +Having said that, you can often get away with using cpp on things which +are not C. Other Algol-ish programming languages are often safe +(Pascal, Ada, ...) and so is assembly, with caution. @samp{-traditional} +mode is much more permissive, and can safely be used with e.g. Fortran. +Many of the problems go away if you write C or C++ style comments +instead of native language comments, and if you avoid elaborate macros. + +Wherever possible, you should use a preprocessor geared to the language +you are writing in. Modern versions of the GNU assembler have macro +facilities. Most high level programming languages have their own +conditional compilation and inclusion mechanism. If all else fails, +try a true general text processor, such as @xref{Top, M4, , m4, GNU `m4'}. + +@end itemize + +@node Invocation, Concept Index, Unreliable Features, Top +@section Invoking the C Preprocessor +@cindex invocation of the preprocessor + +Most often when you use the C preprocessor you will not have to invoke it +explicitly: the C compiler will do so automatically. However, the +preprocessor is sometimes useful on its own. + +@ignore +@c man begin SYNOPSIS +cpp [@samp{-P}] [@samp{-C}] [@samp{-gcc}] [@samp{-traditional}] + [@samp{-undef}] [@samp{-trigraphs}] [@samp{-pedantic}] + [@samp{-W}@var{warn}...] [@samp{-I}@var{dir}...] + [@samp{-D}@var{macro}[=@var{defn}]...] [@samp{-U}@var{macro}] + [@samp{-A}@var{predicate}(@var{answer})] + [@samp{-M}|@samp{-MM}][@samp{-MG}][@samp{-MF}@var{filename}] + [@samp{-MP}][@samp{-MQ}@var{target}...][@samp{-MT}@var{target}...] + [@samp{-x} @var{language}] [@samp{-std=}@var{standard}] + @var{infile} @var{outfile} + +Only the most useful options are listed here; see below for the remainder. +@c man end +@c man begin SEEALSO +gcc(1), as(1), ld(1), and the Info entries for @file{cpp}, @file{gcc}, and +@file{binutils}. +@c man end +@end ignore + +@c man begin OPTIONS +The C preprocessor expects two file names as arguments, @var{infile} and +@var{outfile}. The preprocessor reads @var{infile} together with any +other files it specifies with @samp{#include}. All the output generated +by the combined input files is written in @var{outfile}. + +Either @var{infile} or @var{outfile} may be @samp{-}, which as +@var{infile} means to read from standard input and as @var{outfile} +means to write to standard output. Also, if either file is omitted, it +means the same as if @samp{-} had been specified for that file. + +@cindex options +Here is a table of command options accepted by the C preprocessor. +These options can also be given when compiling a C program; they are +passed along automatically to the preprocessor when it is invoked by the +compiler. + +@table @samp +@item -P +@findex -P +Inhibit generation of @samp{#}-lines with line-number information in the +output from the preprocessor. This might be useful when running the +preprocessor on something that is not C code and will be sent to a +program which might be confused by the @samp{#}-lines. @xref{Output}. + +@item -C +@findex -C +Do not discard comments. All comments are passed through to the output +file, except for comments in processed directives, which are deleted +along with the directive. Comments appearing in the expansion list of a +macro will be preserved, and appear in place wherever the macro is +invoked. + +You should be prepared for side effects when using @samp{-C}; it causes +the preprocessor to treat comments as tokens in their own right. For +example, macro redefinitions that were trivial when comments were +replaced by a single space might become significant when comments are +retained. Also, comments appearing at the start of what would be a +directive line have the effect of turning that line into an ordinary +source line, since the first token on the line is no longer a @samp{#}. + +@item -traditional +@findex -traditional +Try to imitate the behavior of old-fashioned C, as opposed to ISO C@. + +@itemize @bullet +@item +Traditional macro expansion pays no attention to single-quote or +double-quote characters; macro argument symbols are replaced by the +argument values even when they appear within apparent string or +character constants. + +@item +Traditionally, it is permissible for a macro expansion to end in the +middle of a string or character constant. The constant continues into +the text surrounding the macro call. + +@item +However, traditionally the end of the line terminates a string or +character constant, with no error. + +@item +In traditional C, a comment is equivalent to no text at all. (In ISO +C, a comment counts as whitespace.) + +@item +Traditional C does not have the concept of a ``preprocessing number''. +It considers @samp{1.0e+4} to be three tokens: @samp{1.0e}, @samp{+}, +and @samp{4}. + +@item +A macro is not suppressed within its own definition, in traditional C@. +Thus, any macro that is used recursively inevitably causes an error. + +@item +The character @samp{#} has no special meaning within a macro definition +in traditional C@. + +@item +In traditional C, the text at the end of a macro expansion can run +together with the text after the macro call, to produce a single token. +(This is impossible in ISO C@.) + +@item +None of the GNU extensions to the preprocessor are available in +@samp{-traditional} mode. + +@end itemize + +@cindex Fortran +@cindex unterminated +Use the @samp{-traditional} option when preprocessing Fortran code, so +that single-quotes and double-quotes within Fortran comment lines (which +are generally not recognized as such by the preprocessor) do not cause +diagnostics about unterminated character or string constants. + +However, this option does not prevent diagnostics about unterminated +comments when a C-style comment appears to start, but not end, within +Fortran-style commentary. + +So, the following Fortran comment lines are accepted with +@samp{-traditional}: + +@smallexample +C This isn't an unterminated character constant +C Neither is "20000000000, an octal constant +C in some dialects of Fortran +@end smallexample + +However, this type of comment line will likely produce a diagnostic, or +at least unexpected output from the preprocessor, due to the +unterminated comment: + +@smallexample +C Some Fortran compilers accept /* as starting +C an inline comment. +@end smallexample + +@cindex g77 +Note that @code{g77} automatically supplies the @samp{-traditional} +option when it invokes the preprocessor. However, a future version of +@code{g77} might use a different, more-Fortran-aware preprocessor in +place of @code{cpp}. + +@item -trigraphs +@findex -trigraphs +Process ISO standard trigraph sequences. These are three-character +sequences, all starting with @samp{??}, that are defined by ISO C to +stand for single characters. For example, @samp{??/} stands for +@samp{\}, so @samp{'??/n'} is a character constant for a newline. By +default, GCC ignores trigraphs, but in standard-conforming modes it +converts them. See the @samp{-std} option. + +The nine trigraph sequences are +@table @samp +@item ??( +-> @samp{[} + +@item ??) +-> @samp{]} + +@item ??< +-> @samp{@{} + +@item ??> +-> @samp{@}} + +@item ??= +-> @samp{#} + +@item ??/ +-> @samp{\} + +@item ??' +-> @samp{^} + +@item ??! +-> @samp{|} + +@item ??- +-> @samp{~} + +@end table + +Trigraph support is not popular, so many compilers do not implement it +properly. Portable code should not rely on trigraphs being either +converted or ignored. + +@item -pedantic +@findex -pedantic +Issue warnings required by the ISO C standard in certain cases such +as when text other than a comment follows @samp{#else} or @samp{#endif}. + +@item -pedantic-errors +@findex -pedantic-errors +Like @samp{-pedantic}, except that errors are produced rather than +warnings. + +@item -Wcomment +@findex -Wcomment +@itemx -Wcomments +(Both forms have the same effect). +Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*} +comment, or whenever a backslash-newline appears in a @samp{//} comment. + +@item -Wtrigraphs +@findex -Wtrigraphs +Warn if any trigraphs are encountered. This option used to take effect +only if @samp{-trigraphs} was also specified, but now works +independently. Warnings are not given for trigraphs within comments, as +we feel this is obnoxious. + +@item -Wall +@findex -Wall +Requests @samp{-Wcomment} and @samp{-Wtrigraphs} (but not +@samp{-Wtraditional} or @samp{-Wundef}). + +@item -Wtraditional +@findex -Wtraditional +Warn about certain constructs that behave differently in traditional and +ISO C@. Also warn about ISO C constructs that have no traditional C +equivalent, and/or problematic constructs which should be avoided. + +@itemize @bullet +@item +Macro parameters that appear within string literals in the macro body. +In traditional C macro replacement takes place within string literals, +but does not in ISO C. + +@item +In traditional C, some preprocessor directives did not exist. +Traditional preprocessors would only consider a line to be a directive +if the @samp{#} appeared in column 1 on the line. Therefore +@samp{-Wtraditional} warns about directives that traditional C +understands but would ignore because the @samp{#} does not appear as the +first character on the line. It also suggests you hide directives like +@samp{#pragma} not understood by traditional C by indenting them. Some +traditional implementations would not recognise @samp{#elif}, so it +suggests avoiding it altogether. + +@item +A function-like macro that appears without arguments. + +@item +The unary plus operator. + +@item +The `U' integer constant suffix. (Traditonal C does support the `L' +suffix on integer constants.) Note, these suffixes appear in macros +defined in the system headers of most modern systems, e.g. the _MIN/_MAX +macros in limits.h. Use of these macros in user code might normally +lead to spurious warnings, however gcc's integrated preprocessor has +enough context to avoid warning in these cases. +@end itemize + +@item -Wundef +@findex -Wundef +Warn if an undefined identifier is evaluated in an @samp{#if} directive. + +@item -I @var{directory} +@findex -I +Add the directory @var{directory} to the head of the list of +directories to be searched for header files (@pxref{Include Syntax}). +This can be used to override a system header file, substituting your +own version, since these directories are searched before the system +header file directories. If you use more than one @samp{-I} option, +the directories are scanned in left-to-right order; the standard +system directories come after. + +@item -I- +Any directories specified with @samp{-I} options before the @samp{-I-} +option are searched only for the case of @samp{#include "@var{file}"}; +they are not searched for @samp{#include <@var{file}>}. + +If additional directories are specified with @samp{-I} options after +the @samp{-I-}, these directories are searched for all @samp{#include} +directives. + +In addition, the @samp{-I-} option inhibits the use of the current +directory as the first search directory for @samp{#include "@var{file}"}. +Therefore, the current directory is searched only if it is requested +explicitly with @samp{-I.}. Specifying both @samp{-I-} and @samp{-I.} +allows you to control precisely which directories are searched before +the current one and which are searched after. + +@item -nostdinc +@findex -nostdinc +Do not search the standard system directories for header files. +Only the directories you have specified with @samp{-I} options +(and the current directory, if appropriate) are searched. + +By using both @samp{-nostdinc} and @samp{-I-}, you can limit the include-file +search path to only those directories you specify explicitly. + +@item -nostdinc++ +@findex -nostdinc++ +Do not search for header files in the C++-specific standard directories, +but do still search the other standard directories. (This option is +used when building the C++ library.) + +@item -remap +@findex -remap +When searching for a header file in a directory, remap file names if a +file named @file{header.gcc} exists in that directory. This can be used +to work around limitations of file systems with file name restrictions. +The @file{header.gcc} file should contain a series of lines with two +tokens on each line: the first token is the name to map, and the second +token is the actual name to use. + +@item -D @var{name} +@findex -D +Predefine @var{name} as a macro, with definition @samp{1}. + +@item -D @var{name}=@var{definition} +Predefine @var{name} as a macro, with definition @var{definition}. +There are no restrictions on the contents of @var{definition}, but if +you are invoking the preprocessor from a shell or shell-like program you +may need to use the shell's quoting syntax to protect characters such as +spaces that have a meaning in the shell syntax. If you use more than +one @samp{-D} for the same @var{name}, the rightmost definition takes +effect. + +Any @samp{-D} and @samp{-U} options on the command line are processed in +order, and always before @samp{-imacros @var{file}}, regardless of the +order in which they are written. + +@item -U @var{name} +@findex -U +Do not predefine @var{name}. + +Any @samp{-D} and @samp{-U} options on the command line are processed in +order, and always before @samp{-imacros @var{file}}, regardless of the +order in which they are written. + +@item -undef +@findex -undef +Do not predefine any nonstandard macros. + +@item -gcc +@findex -gcc +Define the macros @var{__GNUC__}, @var{__GNUC_MINOR__} and +@var{__GNUC_PATCHLEVEL__}. These are defined automatically when you use +@samp{gcc -E}; you can turn them off in that case with @samp{-no-gcc}. + +@item -A @var{predicate}=@var{answer} +@findex -A +Make an assertion with the predicate @var{predicate} and answer +@var{answer}. This form is preferred to the older form @samp{-A +@var{predicate}(@var{answer})}, which is still supported, because +it does not use shell special characters. @xref{Assertions}. + +@item -A -@var{predicate}=@var{answer} +Disable an assertion with the predicate @var{predicate} and answer +@var{answer}. Specifying no predicate, by @samp{-A-} or @samp{-A -}, +disables all predefined assertions and all assertions preceding it on +the command line; and also undefines all predefined macros and all +macros preceding it on the command line. + +@item -dM +@findex -dM +Instead of outputting the result of preprocessing, output a list of +@samp{#define} directives for all the macros defined during the +execution of the preprocessor, including predefined macros. This gives +you a way of finding out what is predefined in your version of the +preprocessor; assuming you have no file @samp{foo.h}, the command + +@example +touch foo.h; cpp -dM foo.h +@end example + +@noindent +will show the values of any predefined macros. + +@item -dD +@findex -dD +Like @samp{-dM} except in two respects: it does @emph{not} include the +predefined macros, and it outputs @emph{both} the @samp{#define} +directives and the result of preprocessing. Both kinds of output go to +the standard output file. + +@item -dN +@findex -dN +Like @samp{-dD}, but emit only the macro names, not their expansions. + +@item -dI +@findex -dI +Output @samp{#include} directives in addition to the result of +preprocessing. + +@item -M +@findex -M +Instead of outputting the result of preprocessing, output a rule +suitable for @code{make} describing the dependencies of the main source +file. The preprocessor outputs one @code{make} rule containing the +object file name for that source file, a colon, and the names of all the +included files, including those coming from @samp{-include} or +@samp{-imacros} command line options. Unless specified explicitly (with +@samp{-MT} or @samp{-MQ}), the object file name consists of the basename +of the source file with any suffix replaced with object file suffix. +If there are many included files +then the rule is split into several lines using @samp{\}-newline. + +@item -MM +@findex -MM +Like @samp{-M}, but mention only the files included with @samp{#include +"@var{file}"} or with @samp{-include} or @samp{-imacros} command line +options. System header files included with @samp{#include <@var{file}>} +are omitted. + +@item -MF @var{file} +@findex -MF +When used with @samp{-M} or @samp{-MM}, specifies a file to write the +dependencies to. This allows the preprocessor to write the preprocessed +file to stdout normally. If no @samp{-MF} switch is given, CPP sends +the rules to stdout and suppresses normal preprocessed output. + +@item -MG +@findex -MG +When used with @samp{-M} or @samp{-MM}, @samp{-MG} says to treat missing +header files as generated files and assume they live in the same +directory as the source file. It suppresses preprocessed output, as a +missing header file is ordinarily an error. + +This feature is used in automatic updating of makefiles. + +@item -MP +@findex -MP +This option instructs CPP to add a phony target for each dependency +other than the main file, causing each to depend on nothing. These +dummy rules work around errors @code{make} gives if you remove header +files without updating the @code{Makefile} to match. + +This is typical output:- + +@smallexample +/tmp/test.o: /tmp/test.c /tmp/test.h + +/tmp/test.h: +@end smallexample + +@item -MQ @var{target} +@item -MT @var{target} +@findex -MQ +@findex -MT +By default CPP uses the main file name, including any path, and appends +the object suffix, normally ``.o'', to it to obtain the name of the +target for dependency generation. With @samp{-MT} you can specify a +target yourself, overriding the default one. + +If you want multiple targets, you can specify them as a single argument +to @samp{-MT}, or use multiple @samp{-MT} options. + +The targets you specify are output in the order they appear on the +command line. @samp{-MQ} is identical to @samp{-MT}, except that the +target name is quoted for Make, but with @samp{-MT} it isn't. For +example, -MT '$(objpfx)foo.o' gives + +@smallexample +$(objpfx)foo.o: /tmp/foo.c +@end smallexample + +but -MQ '$(objpfx)foo.o' gives + +@smallexample +$$(objpfx)foo.o: /tmp/foo.c +@end smallexample + +The default target is automatically quoted, as if it were given with +@samp{-MQ}. + +@item -H +@findex -H +Print the name of each header file used, in addition to other normal +activities. + +@item -imacros @var{file} +@findex -imacros +Process @var{file} as input and discard the resulting output. + +This has all the effects of @code{#include "file"} appearing on the +first line of the main source file, such as generating dependencies and +being listed with the @samp{-H} option, except that no output is +generated, and that the first directory searched for @var{file} is the +preprocessor's working directory @emph{instead of} the directory +containing the main source file. If not found there, it is searched for +in the remainder of the @code{#include "..."} search chain as normal. + +Because the output is discarded, the main effect of @samp{-imacros +@var{file}} is to make the macros defined in @var{file} available for +use in the main input. + +@item -include @var{file} +@findex -include +Process @var{file} as input, and include all the resulting output. + +This has all the effects of @code{#include "file"} appearing on the +first line of the main source file, such as generating dependencies and +being listed with the @samp{-H} option, except that the first directory +searched for @var{file} is the preprocessor's working directory +@emph{instead of} the directory containing the main source file. If not +found there, it is searched for in the remainder of the @code{#include +"..."} search chain as normal. + +@item -idirafter @var{dir} +@findex -idirafter +@cindex second include path +Add the directory @var{dir} to the second include path, marking it as a +system directory. The directories on the second include path are searched +when a header file is not found in any of the directories in the main +include path (the one that @samp{-I} adds to). + +@item -iprefix @var{prefix} +@findex -iprefix +Specify @var{prefix} as the prefix for subsequent @samp{-iwithprefix} +options. If the prefix represents a directory, you should include the +final @samp{/}. + +@item -iwithprefix @var{dir} +@findex -iwithprefix +Add a directory to the second include path, marking it as a system +directory. The directory's name is made by concatenating @var{prefix} +and @var{dir}, where @var{prefix} was specified previously with +@samp{-iprefix}. + +@item -isystem @var{dir} +@findex -isystem +Add a directory to the beginning of the second include path, marking it +as a system directory, so that it gets the same special treatment as +is applied to the standard system directories. @xref{System Headers}. + +@item -x c +@itemx -x c++ +@itemx -x objective-c +@itemx -x assembler-with-cpp +@findex -x c +@findex -x objective-c +@findex -x assembler-with-cpp +Specify the source language: C, C++, Objective-C, or assembly. This has +nothing to do with standards conformance or extensions; it merely +selects which base syntax to expect. If you give none of these options, +cpp will deduce the language from the extension of the source file: +@samp{.c}, @samp{.cc}, @samp{.m}, or @samp{.S}. Some other common +extensions for C++ and assembly are also recognized. If cpp does not +recognize the extension, it will treat the file as C; this is the most +generic mode. + +@strong{Note:} Previous versions of cpp accepted a @samp{-lang} option +which selected both the language and the standards conformance level. +This option has been removed, because it conflicts with the @samp{-l} +option. + +@item -std=@var{standard} +@itemx -ansi +@findex -std +@findex -ansi +Specify the standard to which the code should conform. Currently cpp +only knows about the standards for C; other language standards will be +added in the future. + +@var{standard} +may be one of: +@table @code +@item iso9899:1990 +@itemx c89 +The ISO C standard from 1990. @samp{c89} is the customary shorthand for +this version of the standard. + +The @samp{-ansi} option is equivalent to @samp{-std=c89}. + +@item iso9899:199409 +The 1990 C standard, as amended in 1994. + +@item iso9899:1999 +@itemx c99 +@itemx iso9899:199x +@itemx c9x +The revised ISO C standard, published in December 1999. Before +publication, this was known as C9X. + +@item gnu89 +The 1990 C standard plus GNU extensions. This is the default. + +@item gnu99 +@itemx gnu9x +The 1999 C standard plus GNU extensions. +@end table + +@item -ftabstop=NUMBER +@findex -ftabstop +Set the distance between tab stops. This helps the preprocessor +report correct column numbers in warnings or errors, even if tabs appear +on the line. Values less than 1 or greater than 100 are ignored. The +default is 8. + +@item -$ +@findex -$ +Forbid the use of @samp{$} in identifiers. The C standard allows +implementations to define extra characters that can appear in +identifiers. By default the GNU C preprocessor permits @samp{$}, a +common extension. +@end table +@c man end + +@node Concept Index, Index, Invocation, Top +@unnumbered Concept Index +@printindex cp + +@node Index,, Concept Index, Top +@unnumbered Index of Directives, Macros and Options +@printindex fn + +@contents +@bye diff --git a/gcc/doc/cppinternals.texi b/gcc/doc/cppinternals.texi new file mode 100644 index 00000000000..2a038cb259e --- /dev/null +++ b/gcc/doc/cppinternals.texi @@ -0,0 +1,430 @@ +\input texinfo +@setfilename cppinternals.info +@settitle The GNU C Preprocessor Internals + +@ifinfo +@dircategory Programming +@direntry +* Cpplib: (cppinternals). Cpplib internals. +@end direntry +@end ifinfo + +@c @smallbook +@c @cropmarks +@c @finalout +@setchapternewpage odd +@ifinfo +This file documents the internals of the GNU C Preprocessor. + +Copyright 2000, 2001 Free Software Foundation, Inc. + +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. + +@ignore +Permission is granted to process this file through Tex and print the +results, provided the printed document carries copying permission +notice identical to this one except for the removal of this paragraph +(this paragraph not being relevant to the printed manual). + +@end ignore +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions. +@end ifinfo + +@titlepage +@c @finalout +@title Cpplib Internals +@subtitle Last revised Jan 2001 +@subtitle for GCC version 3.0 +@author Neil Booth +@page +@vskip 0pt plus 1filll +@c man begin COPYRIGHT +Copyright @copyright{} 2000, 2001 +Free Software Foundation, Inc. + +Permission is granted to make and distribute verbatim copies of +this manual provided the copyright notice and this permission notice +are preserved on all copies. + +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions. +@c man end +@end titlepage +@page + +@node Top, Conventions,, (DIR) +@chapter Cpplib - the core of the GNU C Preprocessor + +The GNU C preprocessor in GCC 3.0 has been completely rewritten. It is +now implemented as a library, cpplib, so it can be easily shared between +a stand-alone preprocessor, and a preprocessor integrated with the C, +C++ and Objective C front ends. It is also available for use by other +programs, though this is not recommended as its exposed interface has +not yet reached a point of reasonable stability. + +This library has been written to be re-entrant, so that it can be used +to preprocess many files simultaneously if necessary. It has also been +written with the preprocessing token as the fundamental unit; the +preprocessor in previous versions of GCC would operate on text strings +as the fundamental unit. + +This brief manual documents some of the internals of cpplib, and a few +tricky issues encountered. It also describes certain behaviour we would +like to preserve, such as the format and spacing of its output. + +Identifiers, macro expansion, hash nodes, lexing. + +@menu +* Conventions:: Conventions used in the code. +* Lexer:: The combined C, C++ and Objective C Lexer. +* Whitespace:: Input and output newlines and whitespace. +* Hash Nodes:: All identifiers are hashed. +* Macro Expansion:: Macro expansion algorithm. +* Files:: File handling. +* Index:: Index. +@end menu + +@node Conventions, Lexer, Top, Top +@unnumbered Conventions +@cindex interface +@cindex header files + +cpplib has two interfaces - one is exposed internally only, and the +other is for both internal and external use. + +The convention is that functions and types that are exposed to multiple +files internally are prefixed with @samp{_cpp_}, and are to be found in +the file @samp{cpphash.h}. Functions and types exposed to external +clients are in @samp{cpplib.h}, and prefixed with @samp{cpp_}. For +historical reasons this is no longer quite true, but we should strive to +stick to it. + +We are striving to reduce the information exposed in cpplib.h to the +bare minimum necessary, and then to keep it there. This makes clear +exactly what external clients are entitled to assume, and allows us to +change internals in the future without worrying whether library clients +are perhaps relying on some kind of undocumented implementation-specific +behaviour. + +@node Lexer, Whitespace, Conventions, Top +@unnumbered The Lexer +@cindex lexer +@cindex tokens + +The lexer is contained in the file @samp{cpplex.c}. We want to have a +lexer that is single-pass, for efficiency reasons. We would also like +the lexer to only step forwards through the input files, and not step +back. This will make future changes to support different character +sets, in particular state or shift-dependent ones, much easier. + +This file also contains all information needed to spell a token, i.e. to +output it either in a diagnostic or to a preprocessed output file. This +information is not exported, but made available to clients through such +functions as @samp{cpp_spell_token} and @samp{cpp_token_len}. + +The most painful aspect of lexing ISO-standard C and C++ is handling +trigraphs and backlash-escaped newlines. Trigraphs are processed before +any interpretation of the meaning of a character is made, and unfortunately +there is a trigraph representation for a backslash, so it is possible for +the trigraph @samp{??/} to introduce an escaped newline. + +Escaped newlines are tedious because theoretically they can occur +anywhere - between the @samp{+} and @samp{=} of the @samp{+=} token, +within the characters of an identifier, and even between the @samp{*} +and @samp{/} that terminates a comment. Moreover, you cannot be sure +there is just one - there might be an arbitrarily long sequence of them. + +So the routine @samp{parse_identifier}, that lexes an identifier, cannot +assume that it can scan forwards until the first non-identifier +character and be done with it, because this could be the @samp{\} +introducing an escaped newline, or the @samp{?} introducing the trigraph +sequence that represents the @samp{\} of an escaped newline. Similarly +for the routine that handles numbers, @samp{parse_number}. If these +routines stumble upon a @samp{?} or @samp{\}, they call +@samp{skip_escaped_newlines} to skip over any potential escaped newlines +before checking whether they can finish. + +Similarly code in the main body of @samp{_cpp_lex_token} cannot simply +check for a @samp{=} after a @samp{+} character to determine whether it +has a @samp{+=} token; it needs to be prepared for an escaped newline of +some sort. These cases use the function @samp{get_effective_char}, +which returns the first character after any intervening newlines. + +The lexer needs to keep track of the correct column position, +including counting tabs as specified by the @samp{-ftabstop=} option. +This should be done even within comments; C-style comments can appear in +the middle of a line, and we want to report diagnostics in the correct +position for text appearing after the end of the comment. + +Some identifiers, such as @samp{__VA_ARGS__} and poisoned identifiers, +may be invalid and require a diagnostic. However, if they appear in a +macro expansion we don't want to complain with each use of the macro. +It is therefore best to catch them during the lexing stage, in +@samp{parse_identifier}. In both cases, whether a diagnostic is needed +or not is dependent upon lexer state. For example, we don't want to +issue a diagnostic for re-poisoning a poisoned identifier, or for using +@samp{__VA_ARGS__} in the expansion of a variable-argument macro. +Therefore @samp{parse_identifier} makes use of flags to determine +whether a diagnostic is appropriate. Since we change state on a +per-token basis, and don't lex whole lines at a time, this is not a +problem. + +Another place where state flags are used to change behaviour is whilst +parsing header names. Normally, a @samp{<} would be lexed as a single +token. After a @code{#include} directive, though, it should be lexed +as a single token as far as the nearest @samp{>} character. Note that +we don't allow the terminators of header names to be escaped; the first +@samp{"} or @samp{>} terminates the header name. + +Interpretation of some character sequences depends upon whether we are +lexing C, C++ or Objective C, and on the revision of the standard in +force. For example, @samp{::} is a single token in C++, but two +separate @samp{:} tokens, and almost certainly a syntax error, in C. +Such cases are handled in the main function @samp{_cpp_lex_token}, based +upon the flags set in the @samp{cpp_options} structure. + +Note we have almost, but not quite, achieved the goal of not stepping +backwards in the input stream. Currently @samp{skip_escaped_newlines} +does step back, though with care it should be possible to adjust it so +that this does not happen. For example, one tricky issue is if we meet +a trigraph, but the command line option @samp{-trigraphs} is not in +force but @samp{-Wtrigraphs} is, we need to warn about it but then +buffer it and continue to treat it as 3 separate characters. + +@node Whitespace, Hash Nodes, Lexer, Top +@unnumbered Whitespace +@cindex whitespace +@cindex newlines +@cindex escaped newlines +@cindex paste avoidance +@cindex line numbers + +The lexer has been written to treat each of @samp{\r}, @samp{\n}, +@samp{\r\n} and @samp{\n\r} as a single new line indicator. This allows +it to transparently preprocess MS-DOS, Macintosh and Unix files without +their needing to pass through a special filter beforehand. + +We also decided to treat a backslash, either @samp{\} or the trigraph +@samp{??/}, separated from one of the above newline indicators by +non-comment whitespace only, as intending to escape the newline. It +tends to be a typing mistake, and cannot reasonably be mistaken for +anything else in any of the C-family grammars. Since handling it this +way is not strictly conforming to the ISO standard, the library issues a +warning wherever it encounters it. + +Handling newlines like this is made simpler by doing it in one place +only. The function @samp{handle_newline} takes care of all newline +characters, and @samp{skip_escaped_newlines} takes care of arbitrarily +long sequences of escaped newlines, deferring to @samp{handle_newline} +to handle the newlines themselves. + +Another whitespace issue only concerns the stand-alone preprocessor: we +want to guarantee that re-reading the preprocessed output results in an +identical token stream. Without taking special measures, this might not +be the case because of macro substitution. We could simply insert a +space between adjacent tokens, but ideally we would like to keep this to +a minimum, both for aesthetic reasons and because it causes problems for +people who still try to abuse the preprocessor for things like Fortran +source and Makefiles. + +The token structure contains a flags byte, and two flags are of interest +here: @samp{PREV_WHITE} and @samp{AVOID_LPASTE}. @samp{PREV_WHITE} +indicates that the token was preceded by whitespace; if this is the case +we need not worry about it incorrectly pasting with its predecessor. +The @samp{AVOID_LPASTE} flag is set by the macro expansion routines, and +indicates that paste avoidance by insertion of a space to the left of +the token may be necessary. Recursively, the first token of a macro +substitution, the first token after a macro substitution, the first +token of a substituted argument, and the first token after a substituted +argument are all flagged @samp{AVOID_LPASTE} by the macro expander. + +If a token flagged in this way does not have a @samp{PREV_WHITE} flag, +and the routine @var{cpp_avoid_paste} determines that it might be +misinterpreted by the lexer if a space is not inserted between it and +the immediately preceding token, then stand-alone CPP's output routines +will insert a space between them. To avoid excessive spacing, +@var{cpp_avoid_paste} tries hard to only request a space if one is +likely to be necessary, but for reasons of efficiency it is slightly +conservative and might recommend a space where one is not strictly +needed. + +Finally, the preprocessor takes great care to ensure it keeps track of +both the position of a token in the source file, for diagnostic +purposes, and where it should appear in the output file, because using +CPP for other languages like assembler requires this. The two positions +may differ for the following reasons: + +@itemize @bullet +@item +Escaped newlines are deleted, so lines spliced in this way are joined to +form a single logical line. + +@item +A macro expansion replaces the tokens that form its invocation, but any +newlines appearing in the macro's arguments are interpreted as a single +space, with the result that the macro's replacement appears in full on +the same line that the macro name appeared in the source file. This is +particularly important for stringification of arguments - newlines +embedded in the arguments must appear in the string as spaces. +@end itemize + +The source file location is maintained in the @var{lineno} member of the +@var{cpp_buffer} structure, and the column number inferred from the +current position in the buffer relative to the @var{line_base} buffer +variable, which is updated with every newline whether escaped or not. + +TODO: Finish this. + +@node Hash Nodes, Macro Expansion, Whitespace, Top +@unnumbered Hash Nodes +@cindex hash table +@cindex identifiers +@cindex macros +@cindex assertions +@cindex named operators + +When cpplib encounters an "identifier", it generates a hash code for it +and stores it in the hash table. By "identifier" we mean tokens with +type @samp{CPP_NAME}; this includes identifiers in the usual C sense, as +well as keywords, directive names, macro names and so on. For example, +all of "pragma", "int", "foo" and "__GNUC__" are identifiers and hashed +when lexed. + +Each node in the hash table contain various information about the +identifier it represents. For example, its length and type. At any one +time, each identifier falls into exactly one of three categories: + +@itemize @bullet +@item Macros + +These have been declared to be macros, either on the command line or +with @code{#define}. A few, such as @samp{__TIME__} are builtins +entered in the hash table during initialisation. The hash node for a +normal macro points to a structure with more information about the +macro, such as whether it is function-like, how many arguments it takes, +and its expansion. Builtin macros are flagged as special, and instead +contain an enum indicating which of the various builtin macros it is. + +@item Assertions + +Assertions are in a separate namespace to macros. To enforce this, cpp +actually prepends a @code{#} character before hashing and entering it in +the hash table. An assertion's node points to a chain of answers to +that assertion. + +@item Void + +Everything else falls into this category - an identifier that is not +currently a macro, or a macro that has since been undefined with +@code{#undef}. + +When preprocessing C++, this category also includes the named operators, +such as @samp{xor}. In expressions these behave like the operators they +represent, but in contexts where the spelling of a token matters they +are spelt differently. This spelling distinction is relevant when they +are operands of the stringizing and pasting macro operators @code{#} and +@code{##}. Named operator hash nodes are flagged, both to catch the +spelling distinction and to prevent them from being defined as macros. +@end itemize + +The same identifiers share the same hash node. Since each identifier +token, after lexing, contains a pointer to its hash node, this is used +to provide rapid lookup of various information. For example, when +parsing a @code{#define} statement, CPP flags each argument's identifier +hash node with the index of that argument. This makes duplicated +argument checking an O(1) operation for each argument. Similarly, for +each identifier in the macro's expansion, lookup to see if it is an +argument, and which argument it is, is also an O(1) operation. Further, +each directive name, such as @samp{endif}, has an associated directive +enum stored in its hash node, so that directive lookup is also O(1). + +@node Macro Expansion, Files, Hash Nodes, Top +@unnumbered Macro Expansion Algorithm + +@node Files, Index, Macro Expansion, Top +@unnumbered File Handling +@cindex files + +Fairly obviously, the file handling code of cpplib resides in the file +@samp{cppfiles.c}. It takes care of the details of file searching, +opening, reading and caching, for both the main source file and all the +headers it recursively includes. + +The basic strategy is to minimize the number of system calls. On many +systems, the basic @code{open ()} and @code{fstat ()} system calls can +be quite expensive. For every @code{#include}-d file, we need to try +all the directories in the search path until we find a match. Some +projects, such as glibc, pass twenty or thirty include paths on the +command line, so this can rapidly become time consuming. + +For a header file we have not encountered before we have little choice +but to do this. However, it is often the case that the same headers are +repeatedly included, and in these cases we try to avoid repeating the +filesystem queries whilst searching for the correct file. + +For each file we try to open, we store the constructed path in a splay +tree. This path first undergoes simplification by the function +@code{_cpp_simplify_pathname}. For example, +@samp{/usr/include/bits/../foo.h} is simplified to +@samp{/usr/include/foo.h} before we enter it in the splay tree and try +to @code{open ()} the file. CPP will then find subsequent uses of +@samp{foo.h}, even as @samp{/usr/include/foo.h}, in the splay tree and +save system calls. + +Further, it is likely the file contents have also been cached, saving a +@code{read ()} system call. We don't bother caching the contents of +header files that are re-inclusion protected, and whose re-inclusion +macro is defined when we leave the header file for the first time. If +the host supports it, we try to map suitably large files into memory, +rather than reading them in directly. + +The include paths are internally stored on a null-terminated +singly-linked list, starting with the @code{"header.h"} directory search +chain, which then links into the @code{} directory chain. + +Files included with the @code{} syntax start the lookup directly +in the second half of this chain. However, files included with the +@code{"foo.h"} syntax start at the beginning of the chain, but with one +extra directory prepended. This is the directory of the current file; +the one containing the @code{#include} directive. Prepending this +directory on a per-file basis is handled by the function +@code{search_from}. + +Note that a header included with a directory component, such as +@code{#include "mydir/foo.h"} and opened as +@samp{/usr/local/include/mydir/foo.h}, will have the complete path minus +the basename @samp{foo.h} as the current directory. + +Enough information is stored in the splay tree that CPP can immediately +tell whether it can skip the header file because of the multiple include +optimisation, whether the file didn't exist or couldn't be opened for +some reason, or whether the header was flagged not to be re-used, as it +is with the obsolete @code{#import} directive. + +For the benefit of MS-DOS filesystems with an 8.3 filename limitation, +CPP offers the ability to treat various include file names as aliases +for the real header files with shorter names. The map from one to the +other is found in a special file called @samp{header.gcc}, stored in the +command line (or system) include directories to which the mapping +applies. This may be higher up the directory tree than the full path to +the file minus the base name. + +@node Index,, Files, Top +@unnumbered Index +@printindex cp + +@contents +@bye diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi new file mode 100644 index 00000000000..7e45b61e00a --- /dev/null +++ b/gcc/doc/extend.texi @@ -0,0 +1,4637 @@ +@c Copyright (C) 1988,1989,1992,1993,1994,1996,1998,1999,2000,2001 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@node C Extensions +@chapter Extensions to the C Language Family +@cindex extensions, C language +@cindex C language extensions + +GNU C provides several language features not found in ISO standard C. +(The @samp{-pedantic} option directs GNU CC to print a warning message if +any of these features is used.) To test for the availability of these +features in conditional compilation, check for a predefined macro +@code{__GNUC__}, which is always defined under GNU CC. + +These extensions are available in C and Objective C. Most of them are +also available in C++. @xref{C++ Extensions,,Extensions to the +C++ Language}, for extensions that apply @emph{only} to C++. + +Some features that are in ISO C99 but not C89 or C++ are also, as +extensions, accepted by GCC in C89 mode and in C++. + +@c The only difference between the two versions of this menu is that the +@c version for clear INTERNALS has an extra node, "Constraints" (which +@c appears in a separate chapter in the other version of the manual). +@ifset INTERNALS +@menu +* Statement Exprs:: Putting statements and declarations inside expressions. +* Local Labels:: Labels local to a statement-expression. +* Labels as Values:: Getting pointers to labels, and computed gotos. +* Nested Functions:: As in Algol and Pascal, lexical scoping of functions. +* Constructing Calls:: Dispatching a call to another function. +* Naming Types:: Giving a name to the type of some expression. +* Typeof:: @code{typeof}: referring to the type of an expression. +* Lvalues:: Using @samp{?:}, @samp{,} and casts in lvalues. +* Conditionals:: Omitting the middle operand of a @samp{?:} expression. +* Long Long:: Double-word integers---@code{long long int}. +* Complex:: Data types for complex numbers. +* Hex Floats:: Hexadecimal floating-point constants. +* Zero Length:: Zero-length arrays. +* Variable Length:: Arrays whose length is computed at run time. +* Variadic Macros:: Macros with a variable number of arguments. +* Escaped Newlines:: Slightly looser rules for escaped newlines. +* Multi-line Strings:: String literals with embedded newlines. +* Subscripting:: Any array can be subscripted, even if not an lvalue. +* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers. +* Initializers:: Non-constant initializers. +* Compound Literals:: Compound literals give structures, unions + or arrays as values. +* Designated Inits:: Labeling elements of initializers. +* Cast to Union:: Casting to union type from any member of the union. +* Case Ranges:: `case 1 ... 9' and such. +* Mixed Declarations:: Mixing declarations and code. +* Function Attributes:: Declaring that functions have no side effects, + or that they can never return. +* Attribute Syntax:: Formal syntax for attributes. +* Function Prototypes:: Prototype declarations and old-style definitions. +* C++ Comments:: C++ comments are recognized. +* Dollar Signs:: Dollar sign is allowed in identifiers. +* Character Escapes:: @samp{\e} stands for the character @key{ESC}. +* Variable Attributes:: Specifying attributes of variables. +* Type Attributes:: Specifying attributes of types. +* Alignment:: Inquiring about the alignment of a type or variable. +* Inline:: Defining inline functions (as fast as macros). +* Extended Asm:: Assembler instructions with C expressions as operands. + (With them you can define ``built-in'' functions.) +* Asm Labels:: Specifying the assembler name to use for a C symbol. +* Explicit Reg Vars:: Defining variables residing in specified registers. +* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files. +* Incomplete Enums:: @code{enum foo;}, with details to follow. +* Function Names:: Printable strings which are the name of the current + function. +* Return Address:: Getting the return or frame address of a function. +* Other Builtins:: Other built-in functions. +@end menu +@end ifset +@ifclear INTERNALS +@menu +* Statement Exprs:: Putting statements and declarations inside expressions. +* Local Labels:: Labels local to a statement-expression. +* Labels as Values:: Getting pointers to labels, and computed gotos. +* Nested Functions:: As in Algol and Pascal, lexical scoping of functions. +* Constructing Calls:: Dispatching a call to another function. +* Naming Types:: Giving a name to the type of some expression. +* Typeof:: @code{typeof}: referring to the type of an expression. +* Lvalues:: Using @samp{?:}, @samp{,} and casts in lvalues. +* Conditionals:: Omitting the middle operand of a @samp{?:} expression. +* Long Long:: Double-word integers---@code{long long int}. +* Complex:: Data types for complex numbers. +* Hex Floats:: Hexadecimal floating-point constants. +* Zero Length:: Zero-length arrays. +* Variable Length:: Arrays whose length is computed at run time. +* Variadic Macros:: Macros with a variable number of arguments. +* Escaped Newlines:: Slightly looser rules for escaped newlines. +* Multi-line Strings:: String literals with embedded newlines. +* Subscripting:: Any array can be subscripted, even if not an lvalue. +* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers. +* Initializers:: Non-constant initializers. +* Compound Literals:: Compound literals give structures, unions + or arrays as values. +* Designated Inits:: Labeling elements of initializers. +* Cast to Union:: Casting to union type from any member of the union. +* Case Ranges:: `case 1 ... 9' and such. +* Mixed Declarations:: Mixing declarations and code. +* Function Attributes:: Declaring that functions have no side effects, + or that they can never return. +* Attribute Syntax:: Formal syntax for attributes. +* Function Prototypes:: Prototype declarations and old-style definitions. +* C++ Comments:: C++ comments are recognized. +* Dollar Signs:: Dollar sign is allowed in identifiers. +* Character Escapes:: @samp{\e} stands for the character @key{ESC}. +* Variable Attributes:: Specifying attributes of variables. +* Type Attributes:: Specifying attributes of types. +* Alignment:: Inquiring about the alignment of a type or variable. +* Inline:: Defining inline functions (as fast as macros). +* Extended Asm:: Assembler instructions with C expressions as operands. + (With them you can define ``built-in'' functions.) +* Constraints:: Constraints for asm operands +* Asm Labels:: Specifying the assembler name to use for a C symbol. +* Explicit Reg Vars:: Defining variables residing in specified registers. +* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files. +* Incomplete Enums:: @code{enum foo;}, with details to follow. +* Function Names:: Printable strings which are the name of the current + function. +* Return Address:: Getting the return or frame address of a function. +* Other Builtins:: Other built-in functions. +@end menu +@end ifclear + +@node Statement Exprs +@section Statements and Declarations in Expressions +@cindex statements inside expressions +@cindex declarations inside expressions +@cindex expressions containing statements +@cindex macros, statements in expressions + +@c the above section title wrapped and causes an underfull hbox.. i +@c changed it from "within" to "in". --mew 4feb93 + +A compound statement enclosed in parentheses may appear as an expression +in GNU C. This allows you to use loops, switches, and local variables +within an expression. + +Recall that a compound statement is a sequence of statements surrounded +by braces; in this construct, parentheses go around the braces. For +example: + +@example +(@{ int y = foo (); int z; + if (y > 0) z = y; + else z = - y; + z; @}) +@end example + +@noindent +is a valid (though slightly more complex than necessary) expression +for the absolute value of @code{foo ()}. + +The last thing in the compound statement should be an expression +followed by a semicolon; the value of this subexpression serves as the +value of the entire construct. (If you use some other kind of statement +last within the braces, the construct has type @code{void}, and thus +effectively no value.) + +This feature is especially useful in making macro definitions ``safe'' (so +that they evaluate each operand exactly once). For example, the +``maximum'' function is commonly defined as a macro in standard C as +follows: + +@example +#define max(a,b) ((a) > (b) ? (a) : (b)) +@end example + +@noindent +@cindex side effects, macro argument +But this definition computes either @var{a} or @var{b} twice, with bad +results if the operand has side effects. In GNU C, if you know the +type of the operands (here let's assume @code{int}), you can define +the macro safely as follows: + +@example +#define maxint(a,b) \ + (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @}) +@end example + +Embedded statements are not allowed in constant expressions, such as +the value of an enumeration constant, the width of a bit field, or +the initial value of a static variable. + +If you don't know the type of the operand, you can still do this, but you +must use @code{typeof} (@pxref{Typeof}) or type naming (@pxref{Naming +Types}). + +Statement expressions are not supported fully in G++, and their fate +there is unclear. (It is possible that they will become fully supported +at some point, or that they will be deprecated, or that the bugs that +are present will continue to exist indefinitely.) Presently, statement +expressions do not work well as default arguments. + +In addition, there are semantic issues with statement-expressions in +C++. If you try to use statement-expressions instead of inline +functions in C++, you may be surprised at the way object destruction is +handled. For example: + +@example +#define foo(a) (@{int b = (a); b + 3; @}) +@end example + +@noindent +does not work the same way as: + +@example +inline int foo(int a) @{ int b = a; return b + 3; @} +@end example + +@noindent +In particular, if the expression passed into @code{foo} involves the +creation of temporaries, the destructors for those temporaries will be +run earlier in the case of the macro than in the case of the function. + +These considerations mean that it is probably a bad idea to use +statement-expressions of this form in header files that are designed to +work with C++. (Note that some versions of the GNU C Library contained +header files using statement-expression that lead to precisely this +bug.) + +@node Local Labels +@section Locally Declared Labels +@cindex local labels +@cindex macros, local labels + +Each statement expression is a scope in which @dfn{local labels} can be +declared. A local label is simply an identifier; you can jump to it +with an ordinary @code{goto} statement, but only from within the +statement expression it belongs to. + +A local label declaration looks like this: + +@example +__label__ @var{label}; +@end example + +@noindent +or + +@example +__label__ @var{label1}, @var{label2}, @dots{}; +@end example + +Local label declarations must come at the beginning of the statement +expression, right after the @samp{(@{}, before any ordinary +declarations. + +The label declaration defines the label @emph{name}, but does not define +the label itself. You must do this in the usual way, with +@code{@var{label}:}, within the statements of the statement expression. + +The local label feature is useful because statement expressions are +often used in macros. If the macro contains nested loops, a @code{goto} +can be useful for breaking out of them. However, an ordinary label +whose scope is the whole function cannot be used: if the macro can be +expanded several times in one function, the label will be multiply +defined in that function. A local label avoids this problem. For +example: + +@example +#define SEARCH(array, target) \ +(@{ \ + __label__ found; \ + typeof (target) _SEARCH_target = (target); \ + typeof (*(array)) *_SEARCH_array = (array); \ + int i, j; \ + int value; \ + for (i = 0; i < max; i++) \ + for (j = 0; j < max; j++) \ + if (_SEARCH_array[i][j] == _SEARCH_target) \ + @{ value = i; goto found; @} \ + value = -1; \ + found: \ + value; \ +@}) +@end example + +@node Labels as Values +@section Labels as Values +@cindex labels as values +@cindex computed gotos +@cindex goto with computed label +@cindex address of a label + +You can get the address of a label defined in the current function +(or a containing function) with the unary operator @samp{&&}. The +value has type @code{void *}. This value is a constant and can be used +wherever a constant of that type is valid. For example: + +@example +void *ptr; +@dots{} +ptr = &&foo; +@end example + +To use these values, you need to be able to jump to one. This is done +with the computed goto statement@footnote{The analogous feature in +Fortran is called an assigned goto, but that name seems inappropriate in +C, where one can do more than simply store label addresses in label +variables.}, @code{goto *@var{exp};}. For example, + +@example +goto *ptr; +@end example + +@noindent +Any expression of type @code{void *} is allowed. + +One way of using these constants is in initializing a static array that +will serve as a jump table: + +@example +static void *array[] = @{ &&foo, &&bar, &&hack @}; +@end example + +Then you can select a label with indexing, like this: + +@example +goto *array[i]; +@end example + +@noindent +Note that this does not check whether the subscript is in bounds---array +indexing in C never does that. + +Such an array of label values serves a purpose much like that of the +@code{switch} statement. The @code{switch} statement is cleaner, so +use that rather than an array unless the problem does not fit a +@code{switch} statement very well. + +Another use of label values is in an interpreter for threaded code. +The labels within the interpreter function can be stored in the +threaded code for super-fast dispatching. + +You may not use this mechanism to jump to code in a different function. +If you do that, totally unpredictable things will happen. The best way to +avoid this is to store the label address only in automatic variables and +never pass it as an argument. + +An alternate way to write the above example is + +@example +static const int array[] = @{ &&foo - &&foo, &&bar - &&foo, + &&hack - &&foo @}; +goto *(&&foo + array[i]); +@end example + +@noindent +This is more friendly to code living in shared libraries, as it reduces +the number of dynamic relocations that are needed, and by consequence, +allows the data to be read-only. + +@node Nested Functions +@section Nested Functions +@cindex nested functions +@cindex downward funargs +@cindex thunks + +A @dfn{nested function} is a function defined inside another function. +(Nested functions are not supported for GNU C++.) The nested function's +name is local to the block where it is defined. For example, here we +define a nested function named @code{square}, and call it twice: + +@example +@group +foo (double a, double b) +@{ + double square (double z) @{ return z * z; @} + + return square (a) + square (b); +@} +@end group +@end example + +The nested function can access all the variables of the containing +function that are visible at the point of its definition. This is +called @dfn{lexical scoping}. For example, here we show a nested +function which uses an inherited variable named @code{offset}: + +@example +bar (int *array, int offset, int size) +@{ + int access (int *array, int index) + @{ return array[index + offset]; @} + int i; + @dots{} + for (i = 0; i < size; i++) + @dots{} access (array, i) @dots{} +@} +@end example + +Nested function definitions are permitted within functions in the places +where variable definitions are allowed; that is, in any block, before +the first statement in the block. + +It is possible to call the nested function from outside the scope of its +name by storing its address or passing the address to another function: + +@example +hack (int *array, int size) +@{ + void store (int index, int value) + @{ array[index] = value; @} + + intermediate (store, size); +@} +@end example + +Here, the function @code{intermediate} receives the address of +@code{store} as an argument. If @code{intermediate} calls @code{store}, +the arguments given to @code{store} are used to store into @code{array}. +But this technique works only so long as the containing function +(@code{hack}, in this example) does not exit. + +If you try to call the nested function through its address after the +containing function has exited, all hell will break loose. If you try +to call it after a containing scope level has exited, and if it refers +to some of the variables that are no longer in scope, you may be lucky, +but it's not wise to take the risk. If, however, the nested function +does not refer to anything that has gone out of scope, you should be +safe. + +GNU CC implements taking the address of a nested function using a +technique called @dfn{trampolines}. A paper describing them is +available as @uref{http://people.debian.org/~karlheg/Usenix88-lexic.pdf}. + +A nested function can jump to a label inherited from a containing +function, provided the label was explicitly declared in the containing +function (@pxref{Local Labels}). Such a jump returns instantly to the +containing function, exiting the nested function which did the +@code{goto} and any intermediate functions as well. Here is an example: + +@example +@group +bar (int *array, int offset, int size) +@{ + __label__ failure; + int access (int *array, int index) + @{ + if (index > size) + goto failure; + return array[index + offset]; + @} + int i; + @dots{} + for (i = 0; i < size; i++) + @dots{} access (array, i) @dots{} + @dots{} + return 0; + + /* @r{Control comes here from @code{access} + if it detects an error.} */ + failure: + return -1; +@} +@end group +@end example + +A nested function always has internal linkage. Declaring one with +@code{extern} is erroneous. If you need to declare the nested function +before its definition, use @code{auto} (which is otherwise meaningless +for function declarations). + +@example +bar (int *array, int offset, int size) +@{ + __label__ failure; + auto int access (int *, int); + @dots{} + int access (int *array, int index) + @{ + if (index > size) + goto failure; + return array[index + offset]; + @} + @dots{} +@} +@end example + +@node Constructing Calls +@section Constructing Function Calls +@cindex constructing calls +@cindex forwarding calls + +Using the built-in functions described below, you can record +the arguments a function received, and call another function +with the same arguments, without knowing the number or types +of the arguments. + +You can also record the return value of that function call, +and later return that value, without knowing what data type +the function tried to return (as long as your caller expects +that data type). + +@table @code +@findex __builtin_apply_args +@item __builtin_apply_args () +This built-in function returns a pointer of type @code{void *} to data +describing how to perform a call with the same arguments as were passed +to the current function. + +The function saves the arg pointer register, structure value address, +and all registers that might be used to pass arguments to a function +into a block of memory allocated on the stack. Then it returns the +address of that block. + +@findex __builtin_apply +@item __builtin_apply (@var{function}, @var{arguments}, @var{size}) +This built-in function invokes @var{function} (type @code{void (*)()}) +with a copy of the parameters described by @var{arguments} (type +@code{void *}) and @var{size} (type @code{int}). + +The value of @var{arguments} should be the value returned by +@code{__builtin_apply_args}. The argument @var{size} specifies the size +of the stack argument data, in bytes. + +This function returns a pointer of type @code{void *} to data describing +how to return whatever value was returned by @var{function}. The data +is saved in a block of memory allocated on the stack. + +It is not always simple to compute the proper value for @var{size}. The +value is used by @code{__builtin_apply} to compute the amount of data +that should be pushed on the stack and copied from the incoming argument +area. + +@findex __builtin_return +@item __builtin_return (@var{result}) +This built-in function returns the value described by @var{result} from +the containing function. You should specify, for @var{result}, a value +returned by @code{__builtin_apply}. +@end table + +@node Naming Types +@section Naming an Expression's Type +@cindex naming types + +You can give a name to the type of an expression using a @code{typedef} +declaration with an initializer. Here is how to define @var{name} as a +type name for the type of @var{exp}: + +@example +typedef @var{name} = @var{exp}; +@end example + +This is useful in conjunction with the statements-within-expressions +feature. Here is how the two together can be used to define a safe +``maximum'' macro that operates on any arithmetic type: + +@example +#define max(a,b) \ + (@{typedef _ta = (a), _tb = (b); \ + _ta _a = (a); _tb _b = (b); \ + _a > _b ? _a : _b; @}) +@end example + +@cindex underscores in variables in macros +@cindex @samp{_} in variables in macros +@cindex local variables in macros +@cindex variables, local, in macros +@cindex macros, local variables in + +The reason for using names that start with underscores for the local +variables is to avoid conflicts with variable names that occur within the +expressions that are substituted for @code{a} and @code{b}. Eventually we +hope to design a new form of declaration syntax that allows you to declare +variables whose scopes start only after their initializers; this will be a +more reliable way to prevent such conflicts. + +@node Typeof +@section Referring to a Type with @code{typeof} +@findex typeof +@findex sizeof +@cindex macros, types of arguments + +Another way to refer to the type of an expression is with @code{typeof}. +The syntax of using of this keyword looks like @code{sizeof}, but the +construct acts semantically like a type name defined with @code{typedef}. + +There are two ways of writing the argument to @code{typeof}: with an +expression or with a type. Here is an example with an expression: + +@example +typeof (x[0](1)) +@end example + +@noindent +This assumes that @code{x} is an array of pointers to functions; +the type described is that of the values of the functions. + +Here is an example with a typename as the argument: + +@example +typeof (int *) +@end example + +@noindent +Here the type described is that of pointers to @code{int}. + +If you are writing a header file that must work when included in ISO C +programs, write @code{__typeof__} instead of @code{typeof}. +@xref{Alternate Keywords}. + +A @code{typeof}-construct can be used anywhere a typedef name could be +used. For example, you can use it in a declaration, in a cast, or inside +of @code{sizeof} or @code{typeof}. + +@itemize @bullet +@item +This declares @code{y} with the type of what @code{x} points to. + +@example +typeof (*x) y; +@end example + +@item +This declares @code{y} as an array of such values. + +@example +typeof (*x) y[4]; +@end example + +@item +This declares @code{y} as an array of pointers to characters: + +@example +typeof (typeof (char *)[4]) y; +@end example + +@noindent +It is equivalent to the following traditional C declaration: + +@example +char *y[4]; +@end example + +To see the meaning of the declaration using @code{typeof}, and why it +might be a useful way to write, let's rewrite it with these macros: + +@example +#define pointer(T) typeof(T *) +#define array(T, N) typeof(T [N]) +@end example + +@noindent +Now the declaration can be rewritten this way: + +@example +array (pointer (char), 4) y; +@end example + +@noindent +Thus, @code{array (pointer (char), 4)} is the type of arrays of 4 +pointers to @code{char}. +@end itemize + +@node Lvalues +@section Generalized Lvalues +@cindex compound expressions as lvalues +@cindex expressions, compound, as lvalues +@cindex conditional expressions as lvalues +@cindex expressions, conditional, as lvalues +@cindex casts as lvalues +@cindex generalized lvalues +@cindex lvalues, generalized +@cindex extensions, @code{?:} +@cindex @code{?:} extensions +Compound expressions, conditional expressions and casts are allowed as +lvalues provided their operands are lvalues. This means that you can take +their addresses or store values into them. + +Standard C++ allows compound expressions and conditional expressions as +lvalues, and permits casts to reference type, so use of this extension +is deprecated for C++ code. + +For example, a compound expression can be assigned, provided the last +expression in the sequence is an lvalue. These two expressions are +equivalent: + +@example +(a, b) += 5 +a, (b += 5) +@end example + +Similarly, the address of the compound expression can be taken. These two +expressions are equivalent: + +@example +&(a, b) +a, &b +@end example + +A conditional expression is a valid lvalue if its type is not void and the +true and false branches are both valid lvalues. For example, these two +expressions are equivalent: + +@example +(a ? b : c) = 5 +(a ? b = 5 : (c = 5)) +@end example + +A cast is a valid lvalue if its operand is an lvalue. A simple +assignment whose left-hand side is a cast works by converting the +right-hand side first to the specified type, then to the type of the +inner left-hand side expression. After this is stored, the value is +converted back to the specified type to become the value of the +assignment. Thus, if @code{a} has type @code{char *}, the following two +expressions are equivalent: + +@example +(int)a = 5 +(int)(a = (char *)(int)5) +@end example + +An assignment-with-arithmetic operation such as @samp{+=} applied to a cast +performs the arithmetic using the type resulting from the cast, and then +continues as in the previous case. Therefore, these two expressions are +equivalent: + +@example +(int)a += 5 +(int)(a = (char *)(int) ((int)a + 5)) +@end example + +You cannot take the address of an lvalue cast, because the use of its +address would not work out coherently. Suppose that @code{&(int)f} were +permitted, where @code{f} has type @code{float}. Then the following +statement would try to store an integer bit-pattern where a floating +point number belongs: + +@example +*&(int)f = 1; +@end example + +This is quite different from what @code{(int)f = 1} would do---that +would convert 1 to floating point and store it. Rather than cause this +inconsistency, we think it is better to prohibit use of @samp{&} on a cast. + +If you really do want an @code{int *} pointer with the address of +@code{f}, you can simply write @code{(int *)&f}. + +@node Conditionals +@section Conditionals with Omitted Operands +@cindex conditional expressions, extensions +@cindex omitted middle-operands +@cindex middle-operands, omitted +@cindex extensions, @code{?:} +@cindex @code{?:} extensions + +The middle operand in a conditional expression may be omitted. Then +if the first operand is nonzero, its value is the value of the conditional +expression. + +Therefore, the expression + +@example +x ? : y +@end example + +@noindent +has the value of @code{x} if that is nonzero; otherwise, the value of +@code{y}. + +This example is perfectly equivalent to + +@example +x ? x : y +@end example + +@cindex side effect in ?: +@cindex ?: side effect +@noindent +In this simple case, the ability to omit the middle operand is not +especially useful. When it becomes useful is when the first operand does, +or may (if it is a macro argument), contain a side effect. Then repeating +the operand in the middle would perform the side effect twice. Omitting +the middle operand uses the value already computed without the undesirable +effects of recomputing it. + +@node Long Long +@section Double-Word Integers +@cindex @code{long long} data types +@cindex double-word arithmetic +@cindex multiprecision arithmetic +@cindex @code{LL} integer suffix +@cindex @code{ULL} integer suffix + +ISO C99 supports data types for integers that are at least 64 bits wide, +and as an extension GCC supports them in C89 mode and in C++. +Simply write @code{long long int} for a signed integer, or +@code{unsigned long long int} for an unsigned integer. To make an +integer constant of type @code{long long int}, add the suffix @code{LL} +to the integer. To make an integer constant of type @code{unsigned long +long int}, add the suffix @code{ULL} to the integer. + +You can use these types in arithmetic like any other integer types. +Addition, subtraction, and bitwise boolean operations on these types +are open-coded on all types of machines. Multiplication is open-coded +if the machine supports fullword-to-doubleword a widening multiply +instruction. Division and shifts are open-coded only on machines that +provide special support. The operations that are not open-coded use +special library routines that come with GNU CC. + +There may be pitfalls when you use @code{long long} types for function +arguments, unless you declare function prototypes. If a function +expects type @code{int} for its argument, and you pass a value of type +@code{long long int}, confusion will result because the caller and the +subroutine will disagree about the number of bytes for the argument. +Likewise, if the function expects @code{long long int} and you pass +@code{int}. The best way to avoid such problems is to use prototypes. + +@node Complex +@section Complex Numbers +@cindex complex numbers +@cindex @code{_Complex} keyword +@cindex @code{__complex__} keyword + +ISO C99 supports complex floating data types, and as an extension GCC +supports them in C89 mode and in C++, and supports complex integer data +types which are not part of ISO C99. You can declare complex types +using the keyword @code{_Complex}. As an extension, the older GNU +keyword @code{__complex__} is also supported. + +For example, @samp{_Complex double x;} declares @code{x} as a +variable whose real part and imaginary part are both of type +@code{double}. @samp{_Complex short int y;} declares @code{y} to +have real and imaginary parts of type @code{short int}; this is not +likely to be useful, but it shows that the set of complex types is +complete. + +To write a constant with a complex data type, use the suffix @samp{i} or +@samp{j} (either one; they are equivalent). For example, @code{2.5fi} +has type @code{_Complex float} and @code{3i} has type +@code{_Complex int}. Such a constant always has a pure imaginary +value, but you can form any complex value you like by adding one to a +real constant. This is a GNU extension; if you have an ISO C99 +conforming C library (such as GNU libc), and want to construct complex +constants of floating type, you should include @code{} and +use the macros @code{I} or @code{_Complex_I} instead. + +@cindex @code{__real__} keyword +@cindex @code{__imag__} keyword +To extract the real part of a complex-valued expression @var{exp}, write +@code{__real__ @var{exp}}. Likewise, use @code{__imag__} to +extract the imaginary part. This is a GNU extension; for values of +floating type, you should use the ISO C99 functions @code{crealf}, +@code{creal}, @code{creall}, @code{cimagf}, @code{cimag} and +@code{cimagl}, declared in @code{} and also provided as +builtin functions by GCC. + +@cindex complex conjugation +The operator @samp{~} performs complex conjugation when used on a value +with a complex type. This is a GNU extension; for values of +floating type, you should use the ISO C99 functions @code{conjf}, +@code{conj} and @code{conjl}, declared in @code{} and also +provided as builtin functions by GCC. + +GNU CC can allocate complex automatic variables in a noncontiguous +fashion; it's even possible for the real part to be in a register while +the imaginary part is on the stack (or vice-versa). None of the +supported debugging info formats has a way to represent noncontiguous +allocation like this, so GNU CC describes a noncontiguous complex +variable as if it were two separate variables of noncomplex type. +If the variable's actual name is @code{foo}, the two fictitious +variables are named @code{foo$real} and @code{foo$imag}. You can +examine and set these two fictitious variables with your debugger. + +A future version of GDB will know how to recognize such pairs and treat +them as a single variable with a complex type. + +@node Hex Floats +@section Hex Floats +@cindex hex floats + +ISO C99 supports floating-point numbers written not only in the usual +decimal notation, such as @code{1.55e1}, but also numbers such as +@code{0x1.fp3} written in hexadecimal format. As a GNU extension, GCC +supports this in C89 mode (except in some cases when strictly +conforming) and in C++. In that format the +@code{0x} hex introducer and the @code{p} or @code{P} exponent field are +mandatory. The exponent is a decimal number that indicates the power of +2 by which the significant part will be multiplied. Thus @code{0x1.f} is +1 15/16, @code{p3} multiplies it by 8, and the value of @code{0x1.fp3} +is the same as @code{1.55e1}. + +Unlike for floating-point numbers in the decimal notation the exponent +is always required in the hexadecimal notation. Otherwise the compiler +would not be able to resolve the ambiguity of, e.g., @code{0x1.f}. This +could mean @code{1.0f} or @code{1.9375} since @code{f} is also the +extension for floating-point constants of type @code{float}. + +@node Zero Length +@section Arrays of Length Zero +@cindex arrays of length zero +@cindex zero-length arrays +@cindex length-zero arrays +@cindex flexible array members + +Zero-length arrays are allowed in GNU C. They are very useful as the +last element of a structure which is really a header for a variable-length +object: + +@example +struct line @{ + int length; + char contents[0]; +@}; + +struct line *thisline = (struct line *) + malloc (sizeof (struct line) + this_length); +thisline->length = this_length; +@end example + +In ISO C89, you would have to give @code{contents} a length of 1, which +means either you waste space or complicate the argument to @code{malloc}. + +In ISO C99, you would use a @dfn{flexible array member}, which is +slightly different in syntax and semantics: + +@itemize @bullet +@item +Flexible array members are written as @code{contents[]} without +the @code{0}. + +@item +Flexible array members have incomplete type, and so the @code{sizeof} +operator may not be applied. As a quirk of the original implementation +of zero-length arrays, @code{sizeof} evaluates to zero. + +@item +Flexible array members may only appear as the last member of a +@code{struct} that is otherwise non-empty. GCC currently allows +zero-length arrays anywhere. You may encounter problems, however, +defining structures containing only a zero-length array. Such usage +is deprecated, and we recommend using zero-length arrays only in +places in which flexible array members would be allowed. +@end itemize + +GCC versions before 3.0 allowed zero-length arrays to be statically +initialized. In addition to those cases that were useful, it also +allowed initializations in situations that would corrupt later data. +Non-empty initialization of zero-length arrays is now deprecated. + +Instead GCC allows static initialization of flexible array members. +This is equivalent to defining a new structure containing the original +structure followed by an array of sufficient size to contain the data. +I.e. in the following, @code{f1} is constructed as if it were declared +like @code{f2}. + +@example +struct f1 @{ + int x; int y[]; +@} f1 = @{ 1, @{ 2, 3, 4 @} @}; + +struct f2 @{ + struct f1 f1; int data[3]; +@} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @}; +@end example + +@noindent +The convenience of this extension is that @code{f1} has the desired +type, eliminating the need to consistently refer to @code{f2.f1}. + +This has symmetry with normal static arrays, in that an array of +unknown size is also written with @code{[]}. + +Of course, this extension only makes sense if the extra data comes at +the end of a top-level object, as otherwise we would be overwriting +data at subsequent offsets. To avoid undue complication and confusion +with initialization of deeply nested arrays, we simply disallow any +non-empty initialization except when the structure is the top-level +object. For example: + +@example +struct foo @{ int x; int y[]; @}; +struct bar @{ struct foo z; @}; + +struct foo a = @{ 1, @{ 2, 3, 4 @} @}; // Legal. +struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // Illegal. +struct bar c = @{ @{ 1, @{ @} @} @}; // Legal. +struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @}; // Illegal. +@end example + +@node Variable Length +@section Arrays of Variable Length +@cindex variable-length arrays +@cindex arrays of variable length +@cindex VLAs + +Variable-length automatic arrays are allowed in ISO C99, and as an +extension GCC accepts them in C89 mode and in C++. (However, GCC's +implementation of variable-length arrays does not yet conform in detail +to the ISO C99 standard.) These arrays are +declared like any other automatic arrays, but with a length that is not +a constant expression. The storage is allocated at the point of +declaration and deallocated when the brace-level is exited. For +example: + +@example +FILE * +concat_fopen (char *s1, char *s2, char *mode) +@{ + char str[strlen (s1) + strlen (s2) + 1]; + strcpy (str, s1); + strcat (str, s2); + return fopen (str, mode); +@} +@end example + +@cindex scope of a variable length array +@cindex variable-length array scope +@cindex deallocating variable length arrays +Jumping or breaking out of the scope of the array name deallocates the +storage. Jumping into the scope is not allowed; you get an error +message for it. + +@cindex @code{alloca} vs variable-length arrays +You can use the function @code{alloca} to get an effect much like +variable-length arrays. The function @code{alloca} is available in +many other C implementations (but not in all). On the other hand, +variable-length arrays are more elegant. + +There are other differences between these two methods. Space allocated +with @code{alloca} exists until the containing @emph{function} returns. +The space for a variable-length array is deallocated as soon as the array +name's scope ends. (If you use both variable-length arrays and +@code{alloca} in the same function, deallocation of a variable-length array +will also deallocate anything more recently allocated with @code{alloca}.) + +You can also use variable-length arrays as arguments to functions: + +@example +struct entry +tester (int len, char data[len][len]) +@{ + @dots{} +@} +@end example + +The length of an array is computed once when the storage is allocated +and is remembered for the scope of the array in case you access it with +@code{sizeof}. + +If you want to pass the array first and the length afterward, you can +use a forward declaration in the parameter list---another GNU extension. + +@example +struct entry +tester (int len; char data[len][len], int len) +@{ + @dots{} +@} +@end example + +@cindex parameter forward declaration +The @samp{int len} before the semicolon is a @dfn{parameter forward +declaration}, and it serves the purpose of making the name @code{len} +known when the declaration of @code{data} is parsed. + +You can write any number of such parameter forward declarations in the +parameter list. They can be separated by commas or semicolons, but the +last one must end with a semicolon, which is followed by the ``real'' +parameter declarations. Each forward declaration must match a ``real'' +declaration in parameter name and data type. ISO C99 does not support +parameter forward declarations. + +@node Variadic Macros +@section Macros with a Variable Number of Arguments. +@cindex variable number of arguments +@cindex macro with variable arguments +@cindex rest argument (in macro) +@cindex variadic macros + +In the ISO C standard of 1999, a macro can be declared to accept a +variable number of arguments much as a function can. The syntax for +defining the macro is similar to that of a function. Here is an +example: + +@example +#define debug(format, ...) fprintf (stderr, format, __VA_ARGS__) +@end example + +Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of +such a macro, it represents the zero or more tokens until the closing +parenthesis that ends the invocation, including any commas. This set of +tokens replaces the identifier @code{__VA_ARGS__} in the macro body +wherever it appears. See the CPP manual for more information. + +GCC has long supported variadic macros, and used a different syntax that +allowed you to give a name to the variable arguments just like any other +argument. Here is an example: + +@example +#define debug(format, args...) fprintf (stderr, format, args) +@end example + +This is in all ways equivalent to the ISO C example above, but arguably +more readable and descriptive. + +GNU CPP has two further variadic macro extensions, and permits them to +be used with either of the above forms of macro definition. + +In standard C, you are not allowed to leave the variable argument out +entirely; but you are allowed to pass an empty argument. For example, +this invocation is invalid in ISO C, because there is no comma after +the string: + +@example +debug ("A message") +@end example + +GNU CPP permits you to completely omit the variable arguments in this +way. In the above examples, the compiler would complain, though since +the expansion of the macro still has the extra comma after the format +string. + +To help solve this problem, CPP behaves specially for variable arguments +used with the token paste operator, @samp{##}. If instead you write + +@example +#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__) +@end example + +and if the variable arguments are omitted or empty, the @samp{##} +operator causes the preprocessor to remove the comma before it. If you +do provide some variable arguments in your macro invocation, GNU CPP +does not complain about the paste operation and instead places the +variable arguments after the comma. Just like any other pasted macro +argument, these arguments are not macro expanded. + +@node Escaped Newlines +@section Slightly Looser Rules for Escaped Newlines +@cindex escaped newlines +@cindex newlines (escaped) + +Recently, the non-traditional preprocessor has relaxed its treatment of +escaped newlines. Previously, the newline had to immediately follow a +backslash. The current implementation allows whitespace in the form of +spaces, horizontal and vertical tabs, and form feeds between the +backslash and the subsequent newline. The preprocessor issues a +warning, but treats it as a valid escaped newline and combines the two +lines to form a single logical line. This works within comments and +tokens, including multi-line strings, as well as between tokens. +Comments are @emph{not} treated as whitespace for the purposes of this +relaxation, since they have not yet been replaced with spaces. + +@node Multi-line Strings +@section String Literals with Embedded Newlines +@cindex multi-line string literals + +As an extension, GNU CPP permits string literals to cross multiple lines +without escaping the embedded newlines. Each embedded newline is +replaced with a single @samp{\n} character in the resulting string +literal, regardless of what form the newline took originally. + +CPP currently allows such strings in directives as well (other than the +@samp{#include} family). This is deprecated and will eventually be +removed. + +@node Subscripting +@section Non-Lvalue Arrays May Have Subscripts +@cindex subscripting +@cindex arrays, non-lvalue + +@cindex subscripting and function values +Subscripting is allowed on arrays that are not lvalues, even though the +unary @samp{&} operator is not. (In ISO C99, both are allowed (though +the array may not be used after the next sequence point), but this ISO +C99 feature is not yet fully supported in GCC.) For example, +this is valid in GNU C though not valid in C89: + +@example +@group +struct foo @{int a[4];@}; + +struct foo f(); + +bar (int index) +@{ + return f().a[index]; +@} +@end group +@end example + +@node Pointer Arith +@section Arithmetic on @code{void}- and Function-Pointers +@cindex void pointers, arithmetic +@cindex void, size of pointer to +@cindex function pointers, arithmetic +@cindex function, size of pointer to + +In GNU C, addition and subtraction operations are supported on pointers to +@code{void} and on pointers to functions. This is done by treating the +size of a @code{void} or of a function as 1. + +A consequence of this is that @code{sizeof} is also allowed on @code{void} +and on function types, and returns 1. + +The option @samp{-Wpointer-arith} requests a warning if these extensions +are used. + +@node Initializers +@section Non-Constant Initializers +@cindex initializers, non-constant +@cindex non-constant initializers + +As in standard C++ and ISO C99, the elements of an aggregate initializer for an +automatic variable are not required to be constant expressions in GNU C. +Here is an example of an initializer with run-time varying elements: + +@example +foo (float f, float g) +@{ + float beat_freqs[2] = @{ f-g, f+g @}; + @dots{} +@} +@end example + +@node Compound Literals +@section Compound Literals +@cindex constructor expressions +@cindex initializations in expressions +@cindex structures, constructor expression +@cindex expressions, constructor +@cindex compound literals +@c The GNU C name for what C99 calls compound literals was "constructor expressions". + +ISO C99 supports compound literals. A compound literal looks like +a cast containing an initializer. Its value is an object of the +type specified in the cast, containing the elements specified in +the initializer. (GCC does not yet implement the full ISO C99 semantics +for compound literals.) As an extension, GCC supports compound literals +in C89 mode and in C++. + +Usually, the specified type is a structure. Assume that +@code{struct foo} and @code{structure} are declared as shown: + +@example +struct foo @{int a; char b[2];@} structure; +@end example + +@noindent +Here is an example of constructing a @code{struct foo} with a compound literal: + +@example +structure = ((struct foo) @{x + y, 'a', 0@}); +@end example + +@noindent +This is equivalent to writing the following: + +@example +@{ + struct foo temp = @{x + y, 'a', 0@}; + structure = temp; +@} +@end example + +You can also construct an array. If all the elements of the compound literal +are (made up of) simple constant expressions, suitable for use in +initializers, then the compound literal is an lvalue and can be coerced to a +pointer to its first element, as shown here: + +@example +char **foo = (char *[]) @{ "x", "y", "z" @}; +@end example + +Array compound literals whose elements are not simple constants are +not very useful, because the compound literal is not an lvalue; ISO C99 +specifies that it is, being a temporary object with automatic storage +duration associated with the enclosing block, but GCC does not yet +implement this. There are currently only two valid ways to use it with +GCC: to subscript it, or initialize +an array variable with it. The former is probably slower than a +@code{switch} statement, while the latter does the same thing an +ordinary C initializer would do. Here is an example of +subscripting an array compound literal: + +@example +output = ((int[]) @{ 2, x, 28 @}) [input]; +@end example + +Compound literals for scalar types and union types are is +also allowed, but then the compound literal is equivalent +to a cast. + +@node Designated Inits +@section Designated Initializers +@cindex initializers with labeled elements +@cindex labeled elements in initializers +@cindex case labels in initializers +@cindex designated initializers + +Standard C89 requires the elements of an initializer to appear in a fixed +order, the same as the order of the elements in the array or structure +being initialized. + +In ISO C99 you can give the elements in any order, specifying the array +indices or structure field names they apply to, and GNU C allows this as +an extension in C89 mode as well. This extension is not +implemented in GNU C++. + +To specify an array index, write +@samp{[@var{index}] =} before the element value. For example, + +@example +int a[6] = @{ [4] = 29, [2] = 15 @}; +@end example + +@noindent +is equivalent to + +@example +int a[6] = @{ 0, 0, 15, 0, 29, 0 @}; +@end example + +@noindent +The index values must be constant expressions, even if the array being +initialized is automatic. + +An alternative syntax for this which has been obsolete since GCC 2.5 but +GCC still accepts is to write @samp{[@var{index}]} before the element +value, with no @samp{=}. + +To initialize a range of elements to the same value, write +@samp{[@var{first} ... @var{last}] = @var{value}}. This is a GNU +extension. For example, + +@example +int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @}; +@end example + +@noindent +If the value in it has side-effects, the side-effects will happen only once, +not for each initialized field by the range initializer. + +@noindent +Note that the length of the array is the highest value specified +plus one. + +In a structure initializer, specify the name of a field to initialize +with @samp{.@var{fieldname} =} before the element value. For example, +given the following structure, + +@example +struct point @{ int x, y; @}; +@end example + +@noindent +the following initialization + +@example +struct point p = @{ .y = yvalue, .x = xvalue @}; +@end example + +@noindent +is equivalent to + +@example +struct point p = @{ xvalue, yvalue @}; +@end example + +Another syntax which has the same meaning, obsolete since GCC 2.5, is +@samp{@var{fieldname}:}, as shown here: + +@example +struct point p = @{ y: yvalue, x: xvalue @}; +@end example + +@cindex designators +The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a +@dfn{designator}. You can also use a designator (or the obsolete colon +syntax) when initializing a union, to specify which element of the union +should be used. For example, + +@example +union foo @{ int i; double d; @}; + +union foo f = @{ .d = 4 @}; +@end example + +@noindent +will convert 4 to a @code{double} to store it in the union using +the second element. By contrast, casting 4 to type @code{union foo} +would store it into the union as the integer @code{i}, since it is +an integer. (@xref{Cast to Union}.) + +You can combine this technique of naming elements with ordinary C +initialization of successive elements. Each initializer element that +does not have a designator applies to the next consecutive element of the +array or structure. For example, + +@example +int a[6] = @{ [1] = v1, v2, [4] = v4 @}; +@end example + +@noindent +is equivalent to + +@example +int a[6] = @{ 0, v1, v2, 0, v4, 0 @}; +@end example + +Labeling the elements of an array initializer is especially useful +when the indices are characters or belong to an @code{enum} type. +For example: + +@example +int whitespace[256] + = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1, + ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @}; +@end example + +@cindex designator lists +You can also write a series of @samp{.@var{fieldname}} and +@samp{[@var{index}]} designators before an @samp{=} to specify a +nested subobject to initialize; the list is taken relative to the +subobject corresponding to the closest surrounding brace pair. For +example, with the @samp{struct point} declaration above: + +@example +struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @}; +@end example + +@noindent +If the same field is initialized multiple times, it will have value from +the last initialization. If any such overridden initialization has +side-effect, it is unspecified whether the side-effect happens or not. +Currently, gcc will discard them and issue a warning. + +@node Case Ranges +@section Case Ranges +@cindex case ranges +@cindex ranges in case statements + +You can specify a range of consecutive values in a single @code{case} label, +like this: + +@example +case @var{low} ... @var{high}: +@end example + +@noindent +This has the same effect as the proper number of individual @code{case} +labels, one for each integer value from @var{low} to @var{high}, inclusive. + +This feature is especially useful for ranges of ASCII character codes: + +@example +case 'A' ... 'Z': +@end example + +@strong{Be careful:} Write spaces around the @code{...}, for otherwise +it may be parsed wrong when you use it with integer values. For example, +write this: + +@example +case 1 ... 5: +@end example + +@noindent +rather than this: + +@example +case 1...5: +@end example + +@node Cast to Union +@section Cast to a Union Type +@cindex cast to a union +@cindex union, casting to a + +A cast to union type is similar to other casts, except that the type +specified is a union type. You can specify the type either with +@code{union @var{tag}} or with a typedef name. A cast to union is actually +a constructor though, not a cast, and hence does not yield an lvalue like +normal casts. (@xref{Compound Literals}.) + +The types that may be cast to the union type are those of the members +of the union. Thus, given the following union and variables: + +@example +union foo @{ int i; double d; @}; +int x; +double y; +@end example + +@noindent +both @code{x} and @code{y} can be cast to type @code{union} foo. + +Using the cast as the right-hand side of an assignment to a variable of +union type is equivalent to storing in a member of the union: + +@example +union foo u; +@dots{} +u = (union foo) x @equiv{} u.i = x +u = (union foo) y @equiv{} u.d = y +@end example + +You can also use the union cast as a function argument: + +@example +void hack (union foo); +@dots{} +hack ((union foo) x); +@end example + +@node Mixed Declarations +@section Mixed Declarations and Code +@cindex mixed declarations and code +@cindex declarations, mixed with code +@cindex code, mixed with declarations + +ISO C99 and ISO C++ allow declarations and code to be freely mixed +within compound statements. As an extension, GCC also allows this in +C89 mode. For example, you could do: + +@example +int i; +@dots{} +i++; +int j = i + 2; +@end example + +Each identifier is visible from where it is declared until the end of +the enclosing block. + +@node Function Attributes +@section Declaring Attributes of Functions +@cindex function attributes +@cindex declaring attributes of functions +@cindex functions that never return +@cindex functions that have no side effects +@cindex functions in arbitrary sections +@cindex functions that behave like malloc +@cindex @code{volatile} applied to function +@cindex @code{const} applied to function +@cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments +@cindex functions that are passed arguments in registers on the 386 +@cindex functions that pop the argument stack on the 386 +@cindex functions that do not pop the argument stack on the 386 + +In GNU C, you declare certain things about functions called in your program +which help the compiler optimize function calls and check your code more +carefully. + +The keyword @code{__attribute__} allows you to specify special +attributes when making a declaration. This keyword is followed by an +attribute specification inside double parentheses. Fourteen attributes, +@code{noreturn}, @code{pure}, @code{const}, @code{format}, +@code{format_arg}, @code{no_instrument_function}, @code{section}, +@code{constructor}, @code{destructor}, @code{unused}, @code{weak}, +@code{malloc}, @code{alias} and @code{no_check_memory_usage} are +currently defined for functions. Several other attributes are defined +for functions on particular target systems. Other attributes, including +@code{section} are supported for variables declarations (@pxref{Variable +Attributes}) and for types (@pxref{Type Attributes}). + +You may also specify attributes with @samp{__} preceding and following +each keyword. This allows you to use them in header files without +being concerned about a possible macro of the same name. For example, +you may use @code{__noreturn__} instead of @code{noreturn}. + +@xref{Attribute Syntax}, for details of the exact syntax for using +attributes. + +@table @code +@cindex @code{noreturn} function attribute +@item noreturn +A few standard library functions, such as @code{abort} and @code{exit}, +cannot return. GNU CC knows this automatically. Some programs define +their own functions that never return. You can declare them +@code{noreturn} to tell the compiler this fact. For example, + +@smallexample +void fatal () __attribute__ ((noreturn)); + +void +fatal (@dots{}) +@{ + @dots{} /* @r{Print error message.} */ @dots{} + exit (1); +@} +@end smallexample + +The @code{noreturn} keyword tells the compiler to assume that +@code{fatal} cannot return. It can then optimize without regard to what +would happen if @code{fatal} ever did return. This makes slightly +better code. More importantly, it helps avoid spurious warnings of +uninitialized variables. + +Do not assume that registers saved by the calling function are +restored before calling the @code{noreturn} function. + +It does not make sense for a @code{noreturn} function to have a return +type other than @code{void}. + +The attribute @code{noreturn} is not implemented in GNU C versions +earlier than 2.5. An alternative way to declare that a function does +not return, which works in the current version and in some older +versions, is as follows: + +@smallexample +typedef void voidfn (); + +volatile voidfn fatal; +@end smallexample + +@cindex @code{pure} function attribute +@item pure +Many functions have no effects except the return value and their +return value depends only on the parameters and/or global variables. +Such a function can be subject +to common subexpression elimination and loop optimization just as an +arithmetic operator would be. These functions should be declared +with the attribute @code{pure}. For example, + +@smallexample +int square (int) __attribute__ ((pure)); +@end smallexample + +@noindent +says that the hypothetical function @code{square} is safe to call +fewer times than the program says. + +Some of common examples of pure functions are @code{strlen} or @code{memcmp}. +Interesting non-pure functions are functions with infinite loops or those +depending on volatile memory or other system resource, that may change between +two consecutive calls (such as @code{feof} in a multithreading environment). + +The attribute @code{pure} is not implemented in GNU C versions earlier +than 2.96. +@cindex @code{const} function attribute +@item const +Many functions do not examine any values except their arguments, and +have no effects except the return value. Basically this is just slightly +more strict class than the "pure" attribute above, since function is not +allowed to read global memory. + +@cindex pointer arguments +Note that a function that has pointer arguments and examines the data +pointed to must @emph{not} be declared @code{const}. Likewise, a +function that calls a non-@code{const} function usually must not be +@code{const}. It does not make sense for a @code{const} function to +return @code{void}. + +The attribute @code{const} is not implemented in GNU C versions earlier +than 2.5. An alternative way to declare that a function has no side +effects, which works in the current version and in some older versions, +is as follows: + +@smallexample +typedef int intfn (); + +extern const intfn square; +@end smallexample + +This approach does not work in GNU C++ from 2.6.0 on, since the language +specifies that the @samp{const} must be attached to the return value. + + +@item format (@var{archetype}, @var{string-index}, @var{first-to-check}) +@cindex @code{format} function attribute +The @code{format} attribute specifies that a function takes @code{printf}, +@code{scanf}, @code{strftime} or @code{strfmon} style arguments which +should be type-checked against a format string. For example, the +declaration: + +@smallexample +extern int +my_printf (void *my_object, const char *my_format, ...) + __attribute__ ((format (printf, 2, 3))); +@end smallexample + +@noindent +causes the compiler to check the arguments in calls to @code{my_printf} +for consistency with the @code{printf} style format string argument +@code{my_format}. + +The parameter @var{archetype} determines how the format string is +interpreted, and should be @code{printf}, @code{scanf}, @code{strftime} +or @code{strfmon}. (You can also use @code{__printf__}, +@code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.) The +parameter @var{string-index} specifies which argument is the format +string argument (starting from 1), while @var{first-to-check} is the +number of the first argument to check against the format string. For +functions where the arguments are not available to be checked (such as +@code{vprintf}), specify the third parameter as zero. In this case the +compiler only checks the format string for consistency. For +@code{strftime} formats, the third parameter is required to be zero. + +In the example above, the format string (@code{my_format}) is the second +argument of the function @code{my_print}, and the arguments to check +start with the third argument, so the correct parameters for the format +attribute are 2 and 3. + +The @code{format} attribute allows you to identify your own functions +which take format strings as arguments, so that GNU CC can check the +calls to these functions for errors. The compiler always (unless +@samp{-ffreestanding} is used) checks formats +for the standard library functions @code{printf}, @code{fprintf}, +@code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime}, +@code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such +warnings are requested (using @samp{-Wformat}), so there is no need to +modify the header file @file{stdio.h}. In C99 mode, the functions +@code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and +@code{vsscanf} are also checked. Except in strictly conforming C +standard modes, the X/Open function @code{strfmon} is also checked. +@xref{C Dialect Options,,Options Controlling C Dialect}. + +@item format_arg (@var{string-index}) +@cindex @code{format_arg} function attribute +The @code{format_arg} attribute specifies that a function takes a format +string for a @code{printf}, @code{scanf}, @code{strftime} or +@code{strfmon} style function and modifies it (for example, to translate +it into another language), so the result can be passed to a +@code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style +function (with the remaining arguments to the format function the same +as they would have been for the unmodified string). For example, the +declaration: + +@smallexample +extern char * +my_dgettext (char *my_domain, const char *my_format) + __attribute__ ((format_arg (2))); +@end smallexample + +@noindent +causes the compiler to check the arguments in calls to a @code{printf}, +@code{scanf}, @code{strftime} or @code{strfmon} type function, whose +format string argument is a call to the @code{my_dgettext} function, for +consistency with the format string argument @code{my_format}. If the +@code{format_arg} attribute had not been specified, all the compiler +could tell in such calls to format functions would be that the format +string argument is not constant; this would generate a warning when +@code{-Wformat-nonliteral} is used, but the calls could not be checked +without the attribute. + +The parameter @var{string-index} specifies which argument is the format +string argument (starting from 1). + +The @code{format-arg} attribute allows you to identify your own +functions which modify format strings, so that GNU CC can check the +calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} +type function whose operands are a call to one of your own function. +The compiler always treats @code{gettext}, @code{dgettext}, and +@code{dcgettext} in this manner except when strict ISO C support is +requested by @samp{-ansi} or an appropriate @samp{-std} option, or +@samp{-ffreestanding} is used. @xref{C Dialect Options,,Options +Controlling C Dialect}. + +@item no_instrument_function +@cindex @code{no_instrument_function} function attribute +If @samp{-finstrument-functions} is given, profiling function calls will +be generated at entry and exit of most user-compiled functions. +Functions with this attribute will not be so instrumented. + +@item section ("section-name") +@cindex @code{section} function attribute +Normally, the compiler places the code it generates in the @code{text} section. +Sometimes, however, you need additional sections, or you need certain +particular functions to appear in special sections. The @code{section} +attribute specifies that a function lives in a particular section. +For example, the declaration: + +@smallexample +extern void foobar (void) __attribute__ ((section ("bar"))); +@end smallexample + +@noindent +puts the function @code{foobar} in the @code{bar} section. + +Some file formats do not support arbitrary sections so the @code{section} +attribute is not available on all platforms. +If you need to map the entire contents of a module to a particular +section, consider using the facilities of the linker instead. + +@item constructor +@itemx destructor +@cindex @code{constructor} function attribute +@cindex @code{destructor} function attribute +The @code{constructor} attribute causes the function to be called +automatically before execution enters @code{main ()}. Similarly, the +@code{destructor} attribute causes the function to be called +automatically after @code{main ()} has completed or @code{exit ()} has +been called. Functions with these attributes are useful for +initializing data that will be used implicitly during the execution of +the program. + +These attributes are not currently implemented for Objective C. + +@item unused +This attribute, attached to a function, means that the function is meant +to be possibly unused. GNU CC will not produce a warning for this +function. GNU C++ does not currently support this attribute as +definitions without parameters are valid in C++. + +@item weak +@cindex @code{weak} attribute +The @code{weak} attribute causes the declaration to be emitted as a weak +symbol rather than a global. This is primarily useful in defining +library functions which can be overridden in user code, though it can +also be used with non-function declarations. Weak symbols are supported +for ELF targets, and also for a.out targets when using the GNU assembler +and linker. + +@item malloc +@cindex @code{malloc} attribute +The @code{malloc} attribute is used to tell the compiler that a function +may be treated as if it were the malloc function. The compiler assumes +that calls to malloc result in a pointers that cannot alias anything. +This will often improve optimization. + +@item alias ("target") +@cindex @code{alias} attribute +The @code{alias} attribute causes the declaration to be emitted as an +alias for another symbol, which must be specified. For instance, + +@smallexample +void __f () @{ /* do something */; @} +void f () __attribute__ ((weak, alias ("__f"))); +@end smallexample + +declares @samp{f} to be a weak alias for @samp{__f}. In C++, the +mangled name for the target must be used. + +Not all target machines support this attribute. + +@item no_check_memory_usage +@cindex @code{no_check_memory_usage} function attribute +The @code{no_check_memory_usage} attribute causes GNU CC to omit checks +of memory references when it generates code for that function. Normally +if you specify @samp{-fcheck-memory-usage} (see @pxref{Code Gen +Options}), GNU CC generates calls to support routines before most memory +accesses to permit support code to record usage and detect uses of +uninitialized or unallocated storage. Since GNU CC cannot handle +@code{asm} statements properly they are not allowed in such functions. +If you declare a function with this attribute, GNU CC will not generate +memory checking code for that function, permitting the use of @code{asm} +statements without having to compile that function with different +options. This also allows you to write support routines of your own if +you wish, without getting infinite recursion if they get compiled with +@code{-fcheck-memory-usage}. + +@item regparm (@var{number}) +@cindex functions that are passed arguments in registers on the 386 +On the Intel 386, the @code{regparm} attribute causes the compiler to +pass up to @var{number} integer arguments in registers @var{EAX}, +@var{EDX}, and @var{ECX} instead of on the stack. Functions that take a +variable number of arguments will continue to be passed all of their +arguments on the stack. + +@item stdcall +@cindex functions that pop the argument stack on the 386 +On the Intel 386, the @code{stdcall} attribute causes the compiler to +assume that the called function will pop off the stack space used to +pass arguments, unless it takes a variable number of arguments. + +The PowerPC compiler for Windows NT currently ignores the @code{stdcall} +attribute. + +@item cdecl +@cindex functions that do pop the argument stack on the 386 +On the Intel 386, the @code{cdecl} attribute causes the compiler to +assume that the calling function will pop off the stack space used to +pass arguments. This is +useful to override the effects of the @samp{-mrtd} switch. + +The PowerPC compiler for Windows NT currently ignores the @code{cdecl} +attribute. + +@item longcall +@cindex functions called via pointer on the RS/6000 and PowerPC +On the RS/6000 and PowerPC, the @code{longcall} attribute causes the +compiler to always call the function via a pointer, so that functions +which reside further than 64 megabytes (67,108,864 bytes) from the +current location can be called. + +@item long_call/short_call +@cindex indirect calls on ARM +This attribute allows to specify how to call a particular function on +ARM. Both attributes override the @code{-mlong-calls} (@pxref{ARM Options}) +command line switch and @code{#pragma long_calls} settings. The +@code{long_call} attribute causes the compiler to always call the +function by first loading its address into a register and then using the +contents of that register. The @code{short_call} attribute always places +the offset to the function from the call site into the @samp{BL} +instruction directly. + +@item dllimport +@cindex functions which are imported from a dll on PowerPC Windows NT +On the PowerPC running Windows NT, the @code{dllimport} attribute causes +the compiler to call the function via a global pointer to the function +pointer that is set up by the Windows NT dll library. The pointer name +is formed by combining @code{__imp_} and the function name. + +@item dllexport +@cindex functions which are exported from a dll on PowerPC Windows NT +On the PowerPC running Windows NT, the @code{dllexport} attribute causes +the compiler to provide a global pointer to the function pointer, so +that it can be called with the @code{dllimport} attribute. The pointer +name is formed by combining @code{__imp_} and the function name. + +@item exception (@var{except-func} [, @var{except-arg}]) +@cindex functions which specify exception handling on PowerPC Windows NT +On the PowerPC running Windows NT, the @code{exception} attribute causes +the compiler to modify the structured exception table entry it emits for +the declared function. The string or identifier @var{except-func} is +placed in the third entry of the structured exception table. It +represents a function, which is called by the exception handling +mechanism if an exception occurs. If it was specified, the string or +identifier @var{except-arg} is placed in the fourth entry of the +structured exception table. + +@item function_vector +@cindex calling functions through the function vector on the H8/300 processors +Use this option on the H8/300 and H8/300H to indicate that the specified +function should be called through the function vector. Calling a +function through the function vector will reduce code size, however; +the function vector has a limited size (maximum 128 entries on the H8/300 +and 64 entries on the H8/300H) and shares space with the interrupt vector. + +You must use GAS and GLD from GNU binutils version 2.7 or later for +this option to work correctly. + +@item interrupt_handler +@cindex interrupt handler functions on the H8/300 processors +Use this option on the H8/300 and H8/300H to indicate that the specified +function is an interrupt handler. The compiler will generate function +entry and exit sequences suitable for use in an interrupt handler when this +attribute is present. + +@item interrupt +@cindex interrupt handler functions +Use this option on the ARM, AVR and M32R/D ports to indicate that the +specified function is an interrupt handler. The compiler will generate +function entry and exit sequences suitable for use in an interrupt +handler when this attribute is present. + +Note, interrupt handlers for the H8/300 and H8/300H processors can be +specified via the @code{interrupt_handler} attribute. + +Note, on the AVR interrupts will be enabled inside the function. + +Note, for the ARM you can specify the kind of interrupt to be handled by +adding an optional parameter to the interrupt attribute like this: + +@smallexample +void f () __attribute__ ((interrupt ("IRQ"))); +@end smallexample + +Permissible values for this parameter are: IRQ, FIQ, SWI, ABORT and UNDEF. + +@item eightbit_data +@cindex eight bit data on the H8/300 and H8/300H +Use this option on the H8/300 and H8/300H to indicate that the specified +variable should be placed into the eight bit data section. +The compiler will generate more efficient code for certain operations +on data in the eight bit data area. Note the eight bit data area is limited to +256 bytes of data. + +You must use GAS and GLD from GNU binutils version 2.7 or later for +this option to work correctly. + +@item tiny_data +@cindex tiny data section on the H8/300H +Use this option on the H8/300H to indicate that the specified +variable should be placed into the tiny data section. +The compiler will generate more efficient code for loads and stores +on data in the tiny data section. Note the tiny data area is limited to +slightly under 32kbytes of data. + +@item signal +@cindex signal handler functions on the AVR processors +Use this option on the AVR to indicate that the specified +function is an signal handler. The compiler will generate function +entry and exit sequences suitable for use in an signal handler when this +attribute is present. Interrupts will be disabled inside function. + +@item naked +@cindex function without a prologue/epilogue code +Use this option on the ARM or AVR ports to indicate that the specified +function do not need prologue/epilogue sequences generated by the +compiler. It is up to the programmer to provide these sequences. + +@item model (@var{model-name}) +@cindex function addressability on the M32R/D +Use this attribute on the M32R/D to set the addressability of an object, +and the code generated for a function. +The identifier @var{model-name} is one of @code{small}, @code{medium}, +or @code{large}, representing each of the code models. + +Small model objects live in the lower 16MB of memory (so that their +addresses can be loaded with the @code{ld24} instruction), and are +callable with the @code{bl} instruction. + +Medium model objects may live anywhere in the 32-bit address space (the +compiler will generate @code{seth/add3} instructions to load their addresses), +and are callable with the @code{bl} instruction. + +Large model objects may live anywhere in the 32-bit address space (the +compiler will generate @code{seth/add3} instructions to load their addresses), +and may not be reachable with the @code{bl} instruction (the compiler will +generate the much slower @code{seth/add3/jl} instruction sequence). + +@end table + +You can specify multiple attributes in a declaration by separating them +by commas within the double parentheses or by immediately following an +attribute declaration with another attribute declaration. + +@cindex @code{#pragma}, reason for not using +@cindex pragma, reason for not using +Some people object to the @code{__attribute__} feature, suggesting that +ISO C's @code{#pragma} should be used instead. At the time +@code{__attribute__} was designed, there were two reasons for not doing +this. + +@enumerate +@item +It is impossible to generate @code{#pragma} commands from a macro. + +@item +There is no telling what the same @code{#pragma} might mean in another +compiler. +@end enumerate + +These two reasons applied to almost any application that might have been +proposed for @code{#pragma}. It was basically a mistake to use +@code{#pragma} for @emph{anything}. + +The ISO C99 standard includes @code{_Pragma}, which now allows pragmas +to be generated from macros. In addition, a @code{#pragma GCC} +namespace is now in use for GCC-specific pragmas. However, it has been +found convenient to use @code{__attribute__} to achieve a natural +attachment of attributes to their corresponding declarations, whereas +@code{#pragma GCC} is of use for constructs that do not naturally form +part of the grammar. @xref{Other Directives,,Miscellaneous +Preprocessing Directives, cpp, The C Preprocessor}. + +@node Attribute Syntax +@section Attribute Syntax +@cindex attribute syntax + +This section describes the syntax with which @code{__attribute__} may be +used, and the constructs to which attribute specifiers bind, for the C +language. Some details may vary for C++ and Objective C. Because of +infelicities in the grammar for attributes, some forms described here +may not be successfully parsed in all cases. + +@xref{Function Attributes}, for details of the semantics of attributes +applying to functions. @xref{Variable Attributes}, for details of the +semantics of attributes applying to variables. @xref{Type Attributes}, +for details of the semantics of attributes applying to structure, union +and enumerated types. + +An @dfn{attribute specifier} is of the form +@code{__attribute__ ((@var{attribute-list}))}. An @dfn{attribute list} +is a possibly empty comma-separated sequence of @dfn{attributes}, where +each attribute is one of the following: + +@itemize @bullet +@item +Empty. Empty attributes are ignored. + +@item +A word (which may be an identifier such as @code{unused}, or a reserved +word such as @code{const}). + +@item +A word, followed by, in parentheses, parameters for the attribute. +These parameters take one of the following forms: + +@itemize @bullet +@item +An identifier. For example, @code{mode} attributes use this form. + +@item +An identifier followed by a comma and a non-empty comma-separated list +of expressions. For example, @code{format} attributes use this form. + +@item +A possibly empty comma-separated list of expressions. For example, +@code{format_arg} attributes use this form with the list being a single +integer constant expression, and @code{alias} attributes use this form +with the list being a single string constant. +@end itemize +@end itemize + +An @dfn{attribute specifier list} is a sequence of one or more attribute +specifiers, not separated by any other tokens. + +An attribute specifier list may appear after the colon following a +label, other than a @code{case} or @code{default} label. The only +attribute it makes sense to use after a label is @code{unused}. This +feature is intended for code generated by programs which contains labels +that may be unused but which is compiled with @option{-Wall}. It would +not normally be appropriate to use in it human-written code, though it +could be useful in cases where the code that jumps to the label is +contained within an @code{#ifdef} conditional. + +An attribute specifier list may appear as part of a @code{struct}, +@code{union} or @code{enum} specifier. It may go either immediately +after the @code{struct}, @code{union} or @code{enum} keyword, or after +the closing brace. It is ignored if the content of the structure, union +or enumerated type is not defined in the specifier in which the +attribute specifier list is used---that is, in usages such as +@code{struct __attribute__((foo)) bar} with no following opening brace. +Where attribute specifiers follow the closing brace, they are considered +to relate to the structure, union or enumerated type defined, not to any +enclosing declaration the type specifier appears in, and the type +defined is not complete until after the attribute specifiers. +@c Otherwise, there would be the following problems: a shift/reduce +@c conflict between attributes binding the the struct/union/enum and +@c binding to the list of specifiers/qualifiers; and "aligned" +@c attributes could use sizeof for the structure, but the size could be +@c changed later by "packed" attributes. + +Otherwise, an attribute specifier appears as part of a declaration, +counting declarations of unnamed parameters and type names, and relates +to that declaration (which may be nested in another declaration, for +example in the case of a parameter declaration). In future, attribute +specifiers in some places may however apply to a particular declarator +within a declaration instead; these cases are noted below. Where an +attribute specifier is applied to a parameter declared as a function or +an array, it should apply to the function or array rather than the +pointer to which the parameter is implicitly converted, but this is not +yet correctly implemented. + +Any list of specifiers and qualifiers at the start of a declaration may +contain attribute specifiers, whether or not such a list may in that +context contain storage class specifiers. (Some attributes, however, +are essentially in the nature of storage class specifiers, and only make +sense where storage class specifiers may be used; for example, +@code{section}.) There is one necessary limitation to this syntax: the +first old-style parameter declaration in a function definition cannot +begin with an attribute specifier, because such an attribute applies to +the function instead by syntax described below (which, however, is not +yet implemented in this case). In some other cases, attribute +specifiers are permitted by this grammar but not yet supported by the +compiler. All attribute specifiers in this place relate to the +declaration as a whole. In the obsolencent usage where a type of +@code{int} is implied by the absence of type specifiers, such a list of +specifiers and qualifiers may be an attribute specifier list with no +other specifiers or qualifiers. + +An attribute specifier list may appear immediately before a declarator +(other than the first) in a comma-separated list of declarators in a +declaration of more than one identifier using a single list of +specifiers and qualifiers. At present, such attribute specifiers apply +not only to the identifier before whose declarator they appear, but to +all subsequent identifiers declared in that declaration, but in future +they may apply only to that single identifier. For example, in +@code{__attribute__((noreturn)) void d0 (void), +__attribute__((format(printf, 1, 2))) d1 (const char *, ...), d2 +(void)}, the @code{noreturn} attribute applies to all the functions +declared; the @code{format} attribute should only apply to @code{d1}, +but at present applies to @code{d2} as well (and so causes an error). + +An attribute specifier list may appear immediately before the comma, +@code{=} or semicolon terminating the declaration of an identifier other +than a function definition. At present, such attribute specifiers apply +to the declared object or function, but in future they may attach to the +outermost adjacent declarator. In simple cases there is no difference, +but, for example, in @code{void (****f)(void) +__attribute__((noreturn));}, at present the @code{noreturn} attribute +applies to @code{f}, which causes a warning since @code{f} is not a +function, but in future it may apply to the function @code{****f}. The +precise semantics of what attributes in such cases will apply to are not +yet specified. Where an assembler name for an object or function is +specified (@pxref{Asm Labels}), at present the attribute must follow the +@code{asm} specification; in future, attributes before the @code{asm} +specification may apply to the adjacent declarator, and those after it +to the declared object or function. + +An attribute specifier list may, in future, be permitted to appear after +the declarator in a function definition (before any old-style parameter +declarations or the function body). + +Attribute specifiers may be mixed with type qualifiers appearing inside +the @code{[]} of a parameter array declarator, in the C99 construct by +which such qualifiers are applied to the pointer to which the array is +implicitly converted. Such attribute specifiers apply to the pointer, +not to the array, but at present this is not implemented and they are +ignored. + +An attribute specifier list may appear at the start of a nested +declarator. At present, there are some limitations in this usage: the +attributes apply to the identifer declared, and to all subsequent +identifiers declared in that declaration (if it includes a +comma-separated list of declarators), rather than to a specific +declarator. When attribute specifiers follow the @code{*} of a pointer +declarator, they must presently follow any type qualifiers present, and +cannot be mixed with them. The following describes intended future +semantics which make this syntax more useful only. It will make the +most sense if you are familiar with the formal specification of +declarators in the ISO C standard. + +Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T +D1}, where @code{T} contains declaration specifiers that specify a type +@var{Type} (such as @code{int}) and @code{D1} is a declarator that +contains an identifier @var{ident}. The type specified for @var{ident} +for derived declarators whose type does not include an attribute +specifier is as in the ISO C standard. + +If @code{D1} has the form @code{( @var{attribute-specifier-list} D )}, +and the declaration @code{T D} specifies the type +``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then +@code{T D1} specifies the type ``@var{derived-declarator-type-list} +@var{attribute-specifier-list} @var{Type}'' for @var{ident}. + +If @code{D1} has the form @code{* +@var{type-qualifier-and-attribute-specifier-list} D}, and the +declaration @code{T D} specifies the type +``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then +@code{T D1} specifies the type ``@var{derived-declarator-type-list} +@var{type-qualifier-and-attribute-specifier-list} @var{Type}'' for +@var{ident}. + +For example, @code{void (__attribute__((noreturn)) ****f)();} specifies +the type ``pointer to pointer to pointer to pointer to non-returning +function returning @code{void}''. As another example, @code{char +*__attribute__((aligned(8))) *f;} specifies the type ``pointer to +8-byte-aligned pointer to @code{char}''. Note again that this describes +intended future semantics, not current implementation. + +@node Function Prototypes +@section Prototypes and Old-Style Function Definitions +@cindex function prototype declarations +@cindex old-style function definitions +@cindex promotion of formal parameters + +GNU C extends ISO C to allow a function prototype to override a later +old-style non-prototype definition. Consider the following example: + +@example +/* @r{Use prototypes unless the compiler is old-fashioned.} */ +#ifdef __STDC__ +#define P(x) x +#else +#define P(x) () +#endif + +/* @r{Prototype function declaration.} */ +int isroot P((uid_t)); + +/* @r{Old-style function definition.} */ +int +isroot (x) /* ??? lossage here ??? */ + uid_t x; +@{ + return x == 0; +@} +@end example + +Suppose the type @code{uid_t} happens to be @code{short}. ISO C does +not allow this example, because subword arguments in old-style +non-prototype definitions are promoted. Therefore in this example the +function definition's argument is really an @code{int}, which does not +match the prototype argument type of @code{short}. + +This restriction of ISO C makes it hard to write code that is portable +to traditional C compilers, because the programmer does not know +whether the @code{uid_t} type is @code{short}, @code{int}, or +@code{long}. Therefore, in cases like these GNU C allows a prototype +to override a later old-style definition. More precisely, in GNU C, a +function prototype argument type overrides the argument type specified +by a later old-style definition if the former type is the same as the +latter type before promotion. Thus in GNU C the above example is +equivalent to the following: + +@example +int isroot (uid_t); + +int +isroot (uid_t x) +@{ + return x == 0; +@} +@end example + +GNU C++ does not support old-style function definitions, so this +extension is irrelevant. + +@node C++ Comments +@section C++ Style Comments +@cindex // +@cindex C++ comments +@cindex comments, C++ style + +In GNU C, you may use C++ style comments, which start with @samp{//} and +continue until the end of the line. Many other C implementations allow +such comments, and they are likely to be in a future C standard. +However, C++ style comments are not recognized if you specify +@w{@samp{-ansi}}, a @option{-std} option specifying a version of ISO C +before C99, or @w{@samp{-traditional}}, since they are incompatible +with traditional constructs like @code{dividend//*comment*/divisor}. + +@node Dollar Signs +@section Dollar Signs in Identifier Names +@cindex $ +@cindex dollar signs in identifier names +@cindex identifier names, dollar signs in + +In GNU C, you may normally use dollar signs in identifier names. +This is because many traditional C implementations allow such identifiers. +However, dollar signs in identifiers are not supported on a few target +machines, typically because the target assembler does not allow them. + +@node Character Escapes +@section The Character @key{ESC} in Constants + +You can use the sequence @samp{\e} in a string or character constant to +stand for the ASCII character @key{ESC}. + +@node Alignment +@section Inquiring on Alignment of Types or Variables +@cindex alignment +@cindex type alignment +@cindex variable alignment + +The keyword @code{__alignof__} allows you to inquire about how an object +is aligned, or the minimum alignment usually required by a type. Its +syntax is just like @code{sizeof}. + +For example, if the target machine requires a @code{double} value to be +aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8. +This is true on many RISC machines. On more traditional machine +designs, @code{__alignof__ (double)} is 4 or even 2. + +Some machines never actually require alignment; they allow reference to any +data type even at an odd addresses. For these machines, @code{__alignof__} +reports the @emph{recommended} alignment of a type. + +When the operand of @code{__alignof__} is an lvalue rather than a type, the +value is the largest alignment that the lvalue is known to have. It may +have this alignment as a result of its data type, or because it is part of +a structure and inherits alignment from that structure. For example, after +this declaration: + +@example +struct foo @{ int x; char y; @} foo1; +@end example + +@noindent +the value of @code{__alignof__ (foo1.y)} is probably 2 or 4, the same as +@code{__alignof__ (int)}, even though the data type of @code{foo1.y} +does not itself demand any alignment.@refill + +It is an error to ask for the alignment of an incomplete type. + +A related feature which lets you specify the alignment of an object is +@code{__attribute__ ((aligned (@var{alignment})))}; see the following +section. + +@node Variable Attributes +@section Specifying Attributes of Variables +@cindex attribute of variables +@cindex variable attributes + +The keyword @code{__attribute__} allows you to specify special +attributes of variables or structure fields. This keyword is followed +by an attribute specification inside double parentheses. Eight +attributes are currently defined for variables: @code{aligned}, +@code{mode}, @code{nocommon}, @code{packed}, @code{section}, +@code{transparent_union}, @code{unused}, and @code{weak}. Some other +attributes are defined for variables on particular target systems. Other +attributes are available for functions (@pxref{Function Attributes}) and +for types (@pxref{Type Attributes}). Other front-ends might define more +attributes (@pxref{C++ Extensions,,Extensions to the C++ Language}). + +You may also specify attributes with @samp{__} preceding and following +each keyword. This allows you to use them in header files without +being concerned about a possible macro of the same name. For example, +you may use @code{__aligned__} instead of @code{aligned}. + +@xref{Attribute Syntax}, for details of the exact syntax for using +attributes. + +@table @code +@cindex @code{aligned} attribute +@item aligned (@var{alignment}) +This attribute specifies a minimum alignment for the variable or +structure field, measured in bytes. For example, the declaration: + +@smallexample +int x __attribute__ ((aligned (16))) = 0; +@end smallexample + +@noindent +causes the compiler to allocate the global variable @code{x} on a +16-byte boundary. On a 68040, this could be used in conjunction with +an @code{asm} expression to access the @code{move16} instruction which +requires 16-byte aligned operands. + +You can also specify the alignment of structure fields. For example, to +create a double-word aligned @code{int} pair, you could write: + +@smallexample +struct foo @{ int x[2] __attribute__ ((aligned (8))); @}; +@end smallexample + +@noindent +This is an alternative to creating a union with a @code{double} member +that forces the union to be double-word aligned. + +It is not possible to specify the alignment of functions; the alignment +of functions is determined by the machine's requirements and cannot be +changed. You cannot specify alignment for a typedef name because such a +name is just an alias, not a distinct type. + +As in the preceding examples, you can explicitly specify the alignment +(in bytes) that you wish the compiler to use for a given variable or +structure field. Alternatively, you can leave out the alignment factor +and just ask the compiler to align a variable or field to the maximum +useful alignment for the target machine you are compiling for. For +example, you could write: + +@smallexample +short array[3] __attribute__ ((aligned)); +@end smallexample + +Whenever you leave out the alignment factor in an @code{aligned} attribute +specification, the compiler automatically sets the alignment for the declared +variable or field to the largest alignment which is ever used for any data +type on the target machine you are compiling for. Doing this can often make +copy operations more efficient, because the compiler can use whatever +instructions copy the biggest chunks of memory when performing copies to +or from the variables or fields that you have aligned this way. + +The @code{aligned} attribute can only increase the alignment; but you +can decrease it by specifying @code{packed} as well. See below. + +Note that the effectiveness of @code{aligned} attributes may be limited +by inherent limitations in your linker. On many systems, the linker is +only able to arrange for variables to be aligned up to a certain maximum +alignment. (For some linkers, the maximum supported alignment may +be very very small.) If your linker is only able to align variables +up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} +in an @code{__attribute__} will still only provide you with 8 byte +alignment. See your linker documentation for further information. + +@item mode (@var{mode}) +@cindex @code{mode} attribute +This attribute specifies the data type for the declaration---whichever +type corresponds to the mode @var{mode}. This in effect lets you +request an integer or floating point type according to its width. + +You may also specify a mode of @samp{byte} or @samp{__byte__} to +indicate the mode corresponding to a one-byte integer, @samp{word} or +@samp{__word__} for the mode of a one-word integer, and @samp{pointer} +or @samp{__pointer__} for the mode used to represent pointers. + +@item nocommon +@cindex @code{nocommon} attribute +This attribute specifies requests GNU CC not to place a variable +``common'' but instead to allocate space for it directly. If you +specify the @samp{-fno-common} flag, GNU CC will do this for all +variables. + +Specifying the @code{nocommon} attribute for a variable provides an +initialization of zeros. A variable may only be initialized in one +source file. + +@item packed +@cindex @code{packed} attribute +The @code{packed} attribute specifies that a variable or structure field +should have the smallest possible alignment---one byte for a variable, +and one bit for a field, unless you specify a larger value with the +@code{aligned} attribute. + +Here is a structure in which the field @code{x} is packed, so that it +immediately follows @code{a}: + +@example +struct foo +@{ + char a; + int x[2] __attribute__ ((packed)); +@}; +@end example + +@item section ("section-name") +@cindex @code{section} variable attribute +Normally, the compiler places the objects it generates in sections like +@code{data} and @code{bss}. Sometimes, however, you need additional sections, +or you need certain particular variables to appear in special sections, +for example to map to special hardware. The @code{section} +attribute specifies that a variable (or function) lives in a particular +section. For example, this small program uses several specific section names: + +@smallexample +struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @}; +struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @}; +char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @}; +int init_data __attribute__ ((section ("INITDATA"))) = 0; + +main() +@{ + /* Initialize stack pointer */ + init_sp (stack + sizeof (stack)); + + /* Initialize initialized data */ + memcpy (&init_data, &data, &edata - &data); + + /* Turn on the serial ports */ + init_duart (&a); + init_duart (&b); +@} +@end smallexample + +@noindent +Use the @code{section} attribute with an @emph{initialized} definition +of a @emph{global} variable, as shown in the example. GNU CC issues +a warning and otherwise ignores the @code{section} attribute in +uninitialized variable declarations. + +You may only use the @code{section} attribute with a fully initialized +global definition because of the way linkers work. The linker requires +each object be defined once, with the exception that uninitialized +variables tentatively go in the @code{common} (or @code{bss}) section +and can be multiply "defined". You can force a variable to be +initialized with the @samp{-fno-common} flag or the @code{nocommon} +attribute. + +Some file formats do not support arbitrary sections so the @code{section} +attribute is not available on all platforms. +If you need to map the entire contents of a module to a particular +section, consider using the facilities of the linker instead. + +@item shared +@cindex @code{shared} variable attribute +On Windows NT, in addition to putting variable definitions in a named +section, the section can also be shared among all running copies of an +executable or DLL. For example, this small program defines shared data +by putting it in a named section "shared" and marking the section +shareable: + +@smallexample +int foo __attribute__((section ("shared"), shared)) = 0; + +int +main() +@{ + /* Read and write foo. All running + copies see the same value. */ + return 0; +@} +@end smallexample + +@noindent +You may only use the @code{shared} attribute along with @code{section} +attribute with a fully initialized global definition because of the way +linkers work. See @code{section} attribute for more information. + +The @code{shared} attribute is only available on Windows NT. + +@item transparent_union +This attribute, attached to a function parameter which is a union, means +that the corresponding argument may have the type of any union member, +but the argument is passed as if its type were that of the first union +member. For more details see @xref{Type Attributes}. You can also use +this attribute on a @code{typedef} for a union data type; then it +applies to all function parameters with that type. + +@item unused +This attribute, attached to a variable, means that the variable is meant +to be possibly unused. GNU CC will not produce a warning for this +variable. + +@item weak +The @code{weak} attribute is described in @xref{Function Attributes}. + +@item model (@var{model-name}) +@cindex variable addressability on the M32R/D +Use this attribute on the M32R/D to set the addressability of an object. +The identifier @var{model-name} is one of @code{small}, @code{medium}, +or @code{large}, representing each of the code models. + +Small model objects live in the lower 16MB of memory (so that their +addresses can be loaded with the @code{ld24} instruction). + +Medium and large model objects may live anywhere in the 32-bit address space +(the compiler will generate @code{seth/add3} instructions to load their +addresses). + +@end table + +To specify multiple attributes, separate them by commas within the +double parentheses: for example, @samp{__attribute__ ((aligned (16), +packed))}. + +@node Type Attributes +@section Specifying Attributes of Types +@cindex attribute of types +@cindex type attributes + +The keyword @code{__attribute__} allows you to specify special +attributes of @code{struct} and @code{union} types when you define such +types. This keyword is followed by an attribute specification inside +double parentheses. Four attributes are currently defined for types: +@code{aligned}, @code{packed}, @code{transparent_union}, and @code{unused}. +Other attributes are defined for functions (@pxref{Function Attributes}) and +for variables (@pxref{Variable Attributes}). + +You may also specify any one of these attributes with @samp{__} +preceding and following its keyword. This allows you to use these +attributes in header files without being concerned about a possible +macro of the same name. For example, you may use @code{__aligned__} +instead of @code{aligned}. + +You may specify the @code{aligned} and @code{transparent_union} +attributes either in a @code{typedef} declaration or just past the +closing curly brace of a complete enum, struct or union type +@emph{definition} and the @code{packed} attribute only past the closing +brace of a definition. + +You may also specify attributes between the enum, struct or union +tag and the name of the type rather than after the closing brace. + +@xref{Attribute Syntax}, for details of the exact syntax for using +attributes. + +@table @code +@cindex @code{aligned} attribute +@item aligned (@var{alignment}) +This attribute specifies a minimum alignment (in bytes) for variables +of the specified type. For example, the declarations: + +@smallexample +struct S @{ short f[3]; @} __attribute__ ((aligned (8))); +typedef int more_aligned_int __attribute__ ((aligned (8))); +@end smallexample + +@noindent +force the compiler to insure (as far as it can) that each variable whose +type is @code{struct S} or @code{more_aligned_int} will be allocated and +aligned @emph{at least} on a 8-byte boundary. On a Sparc, having all +variables of type @code{struct S} aligned to 8-byte boundaries allows +the compiler to use the @code{ldd} and @code{std} (doubleword load and +store) instructions when copying one variable of type @code{struct S} to +another, thus improving run-time efficiency. + +Note that the alignment of any given @code{struct} or @code{union} type +is required by the ISO C standard to be at least a perfect multiple of +the lowest common multiple of the alignments of all of the members of +the @code{struct} or @code{union} in question. This means that you @emph{can} +effectively adjust the alignment of a @code{struct} or @code{union} +type by attaching an @code{aligned} attribute to any one of the members +of such a type, but the notation illustrated in the example above is a +more obvious, intuitive, and readable way to request the compiler to +adjust the alignment of an entire @code{struct} or @code{union} type. + +As in the preceding example, you can explicitly specify the alignment +(in bytes) that you wish the compiler to use for a given @code{struct} +or @code{union} type. Alternatively, you can leave out the alignment factor +and just ask the compiler to align a type to the maximum +useful alignment for the target machine you are compiling for. For +example, you could write: + +@smallexample +struct S @{ short f[3]; @} __attribute__ ((aligned)); +@end smallexample + +Whenever you leave out the alignment factor in an @code{aligned} +attribute specification, the compiler automatically sets the alignment +for the type to the largest alignment which is ever used for any data +type on the target machine you are compiling for. Doing this can often +make copy operations more efficient, because the compiler can use +whatever instructions copy the biggest chunks of memory when performing +copies to or from the variables which have types that you have aligned +this way. + +In the example above, if the size of each @code{short} is 2 bytes, then +the size of the entire @code{struct S} type is 6 bytes. The smallest +power of two which is greater than or equal to that is 8, so the +compiler sets the alignment for the entire @code{struct S} type to 8 +bytes. + +Note that although you can ask the compiler to select a time-efficient +alignment for a given type and then declare only individual stand-alone +objects of that type, the compiler's ability to select a time-efficient +alignment is primarily useful only when you plan to create arrays of +variables having the relevant (efficiently aligned) type. If you +declare or use arrays of variables of an efficiently-aligned type, then +it is likely that your program will also be doing pointer arithmetic (or +subscripting, which amounts to the same thing) on pointers to the +relevant type, and the code that the compiler generates for these +pointer arithmetic operations will often be more efficient for +efficiently-aligned types than for other types. + +The @code{aligned} attribute can only increase the alignment; but you +can decrease it by specifying @code{packed} as well. See below. + +Note that the effectiveness of @code{aligned} attributes may be limited +by inherent limitations in your linker. On many systems, the linker is +only able to arrange for variables to be aligned up to a certain maximum +alignment. (For some linkers, the maximum supported alignment may +be very very small.) If your linker is only able to align variables +up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} +in an @code{__attribute__} will still only provide you with 8 byte +alignment. See your linker documentation for further information. + +@item packed +This attribute, attached to an @code{enum}, @code{struct}, or +@code{union} type definition, specified that the minimum required memory +be used to represent the type. + +Specifying this attribute for @code{struct} and @code{union} types is +equivalent to specifying the @code{packed} attribute on each of the +structure or union members. Specifying the @samp{-fshort-enums} +flag on the line is equivalent to specifying the @code{packed} +attribute on all @code{enum} definitions. + +You may only specify this attribute after a closing curly brace on an +@code{enum} definition, not in a @code{typedef} declaration, unless that +declaration also contains the definition of the @code{enum}. + +@item transparent_union +This attribute, attached to a @code{union} type definition, indicates +that any function parameter having that union type causes calls to that +function to be treated in a special way. + +First, the argument corresponding to a transparent union type can be of +any type in the union; no cast is required. Also, if the union contains +a pointer type, the corresponding argument can be a null pointer +constant or a void pointer expression; and if the union contains a void +pointer type, the corresponding argument can be any pointer expression. +If the union member type is a pointer, qualifiers like @code{const} on +the referenced type must be respected, just as with normal pointer +conversions. + +Second, the argument is passed to the function using the calling +conventions of first member of the transparent union, not the calling +conventions of the union itself. All members of the union must have the +same machine representation; this is necessary for this argument passing +to work properly. + +Transparent unions are designed for library functions that have multiple +interfaces for compatibility reasons. For example, suppose the +@code{wait} function must accept either a value of type @code{int *} to +comply with Posix, or a value of type @code{union wait *} to comply with +the 4.1BSD interface. If @code{wait}'s parameter were @code{void *}, +@code{wait} would accept both kinds of arguments, but it would also +accept any other pointer type and this would make argument type checking +less useful. Instead, @code{} might define the interface +as follows: + +@smallexample +typedef union + @{ + int *__ip; + union wait *__up; + @} wait_status_ptr_t __attribute__ ((__transparent_union__)); + +pid_t wait (wait_status_ptr_t); +@end smallexample + +This interface allows either @code{int *} or @code{union wait *} +arguments to be passed, using the @code{int *} calling convention. +The program can call @code{wait} with arguments of either type: + +@example +int w1 () @{ int w; return wait (&w); @} +int w2 () @{ union wait w; return wait (&w); @} +@end example + +With this interface, @code{wait}'s implementation might look like this: + +@example +pid_t wait (wait_status_ptr_t p) +@{ + return waitpid (-1, p.__ip, 0); +@} +@end example + +@item unused +When attached to a type (including a @code{union} or a @code{struct}), +this attribute means that variables of that type are meant to appear +possibly unused. GNU CC will not produce a warning for any variables of +that type, even if the variable appears to do nothing. This is often +the case with lock or thread classes, which are usually defined and then +not referenced, but contain constructors and destructors that have +nontrivial bookkeeping functions. + +@end table + +To specify multiple attributes, separate them by commas within the +double parentheses: for example, @samp{__attribute__ ((aligned (16), +packed))}. + +@node Inline +@section An Inline Function is As Fast As a Macro +@cindex inline functions +@cindex integrating function code +@cindex open coding +@cindex macros, inline alternative + +By declaring a function @code{inline}, you can direct GNU CC to +integrate that function's code into the code for its callers. This +makes execution faster by eliminating the function-call overhead; in +addition, if any of the actual argument values are constant, their known +values may permit simplifications at compile time so that not all of the +inline function's code needs to be included. The effect on code size is +less predictable; object code may be larger or smaller with function +inlining, depending on the particular case. Inlining of functions is an +optimization and it really ``works'' only in optimizing compilation. If +you don't use @samp{-O}, no function is really inline. + +Inline functions are included in the ISO C99 standard, but there are +currently substantial differences between what GCC implements and what +the ISO C99 standard requires. + +To declare a function inline, use the @code{inline} keyword in its +declaration, like this: + +@example +inline int +inc (int *a) +@{ + (*a)++; +@} +@end example + +(If you are writing a header file to be included in ISO C programs, write +@code{__inline__} instead of @code{inline}. @xref{Alternate Keywords}.) +You can also make all ``simple enough'' functions inline with the option +@samp{-finline-functions}. + +Note that certain usages in a function definition can make it unsuitable +for inline substitution. Among these usages are: use of varargs, use of +alloca, use of variable sized data types (@pxref{Variable Length}), +use of computed goto (@pxref{Labels as Values}), use of nonlocal goto, +and nested functions (@pxref{Nested Functions}). Using @samp{-Winline} +will warn when a function marked @code{inline} could not be substituted, +and will give the reason for the failure. + +Note that in C and Objective C, unlike C++, the @code{inline} keyword +does not affect the linkage of the function. + +@cindex automatic @code{inline} for C++ member fns +@cindex @code{inline} automatic for C++ member fns +@cindex member fns, automatically @code{inline} +@cindex C++ member fns, automatically @code{inline} +GNU CC automatically inlines member functions defined within the class +body of C++ programs even if they are not explicitly declared +@code{inline}. (You can override this with @samp{-fno-default-inline}; +@pxref{C++ Dialect Options,,Options Controlling C++ Dialect}.) + +@cindex inline functions, omission of +When a function is both inline and @code{static}, if all calls to the +function are integrated into the caller, and the function's address is +never used, then the function's own assembler code is never referenced. +In this case, GNU CC does not actually output assembler code for the +function, unless you specify the option @samp{-fkeep-inline-functions}. +Some calls cannot be integrated for various reasons (in particular, +calls that precede the function's definition cannot be integrated, and +neither can recursive calls within the definition). If there is a +nonintegrated call, then the function is compiled to assembler code as +usual. The function must also be compiled as usual if the program +refers to its address, because that can't be inlined. + +@cindex non-static inline function +When an inline function is not @code{static}, then the compiler must assume +that there may be calls from other source files; since a global symbol can +be defined only once in any program, the function must not be defined in +the other source files, so the calls therein cannot be integrated. +Therefore, a non-@code{static} inline function is always compiled on its +own in the usual fashion. + +If you specify both @code{inline} and @code{extern} in the function +definition, then the definition is used only for inlining. In no case +is the function compiled on its own, not even if you refer to its +address explicitly. Such an address becomes an external reference, as +if you had only declared the function, and had not defined it. + +This combination of @code{inline} and @code{extern} has almost the +effect of a macro. The way to use it is to put a function definition in +a header file with these keywords, and put another copy of the +definition (lacking @code{inline} and @code{extern}) in a library file. +The definition in the header file will cause most calls to the function +to be inlined. If any uses of the function remain, they will refer to +the single copy in the library. + +For future compatibility with when GCC implements ISO C99 semantics for +inline functions, it is best to use @code{static inline} only. (The +existing semantics will remain available when @option{-std=gnu89} is +specified, but eventually the default will be @option{-std=gnu99} and +that will implement the C99 semantics, though it does not do so yet.) + +GNU C does not inline any functions when not optimizing. It is not +clear whether it is better to inline or not, in this case, but we found +that a correct implementation when not optimizing was difficult. So we +did the easy thing, and turned it off. + +@node Extended Asm +@section Assembler Instructions with C Expression Operands +@cindex extended @code{asm} +@cindex @code{asm} expressions +@cindex assembler instructions +@cindex registers + +In an assembler instruction using @code{asm}, you can specify the +operands of the instruction using C expressions. This means you need not +guess which registers or memory locations will contain the data you want +to use. + +You must specify an assembler instruction template much like what +appears in a machine description, plus an operand constraint string for +each operand. + +For example, here is how to use the 68881's @code{fsinx} instruction: + +@example +asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); +@end example + +@noindent +Here @code{angle} is the C expression for the input operand while +@code{result} is that of the output operand. Each has @samp{"f"} as its +operand constraint, saying that a floating point register is required. +The @samp{=} in @samp{=f} indicates that the operand is an output; all +output operands' constraints must use @samp{=}. The constraints use the +same language used in the machine description (@pxref{Constraints}). + +Each operand is described by an operand-constraint string followed by +the C expression in parentheses. A colon separates the assembler +template from the first output operand and another separates the last +output operand from the first input, if any. Commas separate the +operands within each group. The total number of operands is limited to +ten or to the maximum number of operands in any instruction pattern in +the machine description, whichever is greater. + +If there are no output operands but there are input operands, you must +place two consecutive colons surrounding the place where the output +operands would go. + +Output operand expressions must be lvalues; the compiler can check this. +The input operands need not be lvalues. The compiler cannot check +whether the operands have data types that are reasonable for the +instruction being executed. It does not parse the assembler instruction +template and does not know what it means or even whether it is valid +assembler input. The extended @code{asm} feature is most often used for +machine instructions the compiler itself does not know exist. If +the output expression cannot be directly addressed (for example, it is a +bit field), your constraint must allow a register. In that case, GNU CC +will use the register as the output of the @code{asm}, and then store +that register into the output. + +The ordinary output operands must be write-only; GNU CC will assume that +the values in these operands before the instruction are dead and need +not be generated. Extended asm supports input-output or read-write +operands. Use the constraint character @samp{+} to indicate such an +operand and list it with the output operands. + +When the constraints for the read-write operand (or the operand in which +only some of the bits are to be changed) allows a register, you may, as +an alternative, logically split its function into two separate operands, +one input operand and one write-only output operand. The connection +between them is expressed by constraints which say they need to be in +the same location when the instruction executes. You can use the same C +expression for both operands, or different expressions. For example, +here we write the (fictitious) @samp{combine} instruction with +@code{bar} as its read-only source operand and @code{foo} as its +read-write destination: + +@example +asm ("combine %2,%0" : "=r" (foo) : "0" (foo), "g" (bar)); +@end example + +@noindent +The constraint @samp{"0"} for operand 1 says that it must occupy the +same location as operand 0. A digit in constraint is allowed only in an +input operand and it must refer to an output operand. + +Only a digit in the constraint can guarantee that one operand will be in +the same place as another. The mere fact that @code{foo} is the value +of both operands is not enough to guarantee that they will be in the +same place in the generated assembler code. The following would not +work reliably: + +@example +asm ("combine %2,%0" : "=r" (foo) : "r" (foo), "g" (bar)); +@end example + +Various optimizations or reloading could cause operands 0 and 1 to be in +different registers; GNU CC knows no reason not to do so. For example, the +compiler might find a copy of the value of @code{foo} in one register and +use it for operand 1, but generate the output operand 0 in a different +register (copying it afterward to @code{foo}'s own address). Of course, +since the register for operand 1 is not even mentioned in the assembler +code, the result will not work, but GNU CC can't tell that. + +Some instructions clobber specific hard registers. To describe this, +write a third colon after the input operands, followed by the names of +the clobbered hard registers (given as strings). Here is a realistic +example for the VAX: + +@example +asm volatile ("movc3 %0,%1,%2" + : /* no outputs */ + : "g" (from), "g" (to), "g" (count) + : "r0", "r1", "r2", "r3", "r4", "r5"); +@end example + +You may not write a clobber description in a way that overlaps with an +input or output operand. For example, you may not have an operand +describing a register class with one member if you mention that register +in the clobber list. There is no way for you to specify that an input +operand is modified without also specifying it as an output +operand. Note that if all the output operands you specify are for this +purpose (and hence unused), you will then also need to specify +@code{volatile} for the @code{asm} construct, as described below, to +prevent GNU CC from deleting the @code{asm} statement as unused. + +If you refer to a particular hardware register from the assembler code, +you will probably have to list the register after the third colon to +tell the compiler the register's value is modified. In some assemblers, +the register names begin with @samp{%}; to produce one @samp{%} in the +assembler code, you must write @samp{%%} in the input. + +If your assembler instruction can alter the condition code register, add +@samp{cc} to the list of clobbered registers. GNU CC on some machines +represents the condition codes as a specific hardware register; +@samp{cc} serves to name this register. On other machines, the +condition code is handled differently, and specifying @samp{cc} has no +effect. But it is valid no matter what the machine. + +If your assembler instruction modifies memory in an unpredictable +fashion, add @samp{memory} to the list of clobbered registers. This +will cause GNU CC to not keep memory values cached in registers across +the assembler instruction. You will also want to add the +@code{volatile} keyword if the memory affected is not listed in the +inputs or outputs of the @code{asm}, as the @samp{memory} clobber does +not count as a side-effect of the @code{asm}. + +You can put multiple assembler instructions together in a single +@code{asm} template, separated by the characters normally used in assembly +code for the system. A combination that works in most places is a newline +to break the line, plus a tab character to move to the instruction field +(written as @samp{\n\t}). Sometimes semicolons can be used, if the +assembler allows semicolons as a line-breaking character. Note that some +assembler dialects use semicolons to start a comment. +The input operands are guaranteed not to use any of the clobbered +registers, and neither will the output operands' addresses, so you can +read and write the clobbered registers as many times as you like. Here +is an example of multiple instructions in a template; it assumes the +subroutine @code{_foo} accepts arguments in registers 9 and 10: + +@example +asm ("movl %0,r9\n\tmovl %1,r10\n\tcall _foo" + : /* no outputs */ + : "g" (from), "g" (to) + : "r9", "r10"); +@end example + +Unless an output operand has the @samp{&} constraint modifier, GNU CC +may allocate it in the same register as an unrelated input operand, on +the assumption the inputs are consumed before the outputs are produced. +This assumption may be false if the assembler code actually consists of +more than one instruction. In such a case, use @samp{&} for each output +operand that may not overlap an input. @xref{Modifiers}. + +If you want to test the condition code produced by an assembler +instruction, you must include a branch and a label in the @code{asm} +construct, as follows: + +@example +asm ("clr %0\n\tfrob %1\n\tbeq 0f\n\tmov #1,%0\n0:" + : "g" (result) + : "g" (input)); +@end example + +@noindent +This assumes your assembler supports local labels, as the GNU assembler +and most Unix assemblers do. + +Speaking of labels, jumps from one @code{asm} to another are not +supported. The compiler's optimizers do not know about these jumps, and +therefore they cannot take account of them when deciding how to +optimize. + +@cindex macros containing @code{asm} +Usually the most convenient way to use these @code{asm} instructions is to +encapsulate them in macros that look like functions. For example, + +@example +#define sin(x) \ +(@{ double __value, __arg = (x); \ + asm ("fsinx %1,%0": "=f" (__value): "f" (__arg)); \ + __value; @}) +@end example + +@noindent +Here the variable @code{__arg} is used to make sure that the instruction +operates on a proper @code{double} value, and to accept only those +arguments @code{x} which can convert automatically to a @code{double}. + +Another way to make sure the instruction operates on the correct data +type is to use a cast in the @code{asm}. This is different from using a +variable @code{__arg} in that it converts more different types. For +example, if the desired type were @code{int}, casting the argument to +@code{int} would accept a pointer with no complaint, while assigning the +argument to an @code{int} variable named @code{__arg} would warn about +using a pointer unless the caller explicitly casts it. + +If an @code{asm} has output operands, GNU CC assumes for optimization +purposes the instruction has no side effects except to change the output +operands. This does not mean instructions with a side effect cannot be +used, but you must be careful, because the compiler may eliminate them +if the output operands aren't used, or move them out of loops, or +replace two with one if they constitute a common subexpression. Also, +if your instruction does have a side effect on a variable that otherwise +appears not to change, the old value of the variable may be reused later +if it happens to be found in a register. + +You can prevent an @code{asm} instruction from being deleted, moved +significantly, or combined, by writing the keyword @code{volatile} after +the @code{asm}. For example: + +@example +#define get_and_set_priority(new) \ +(@{ int __old; \ + asm volatile ("get_and_set_priority %0, %1" \ + : "=g" (__old) : "g" (new)); \ + __old; @}) +@end example + +@noindent +If you write an @code{asm} instruction with no outputs, GNU CC will know +the instruction has side-effects and will not delete the instruction or +move it outside of loops. + +The @code{volatile} keyword indicates that the instruction has +important side-effects. GCC will not delete a volatile @code{asm} if +it is reachable. (The instruction can still be deleted if GCC can +prove that control-flow will never reach the location of the +instruction.) In addition, GCC will not reschedule instructions +across a volatile @code{asm} instruction. For example: + +@example +*(volatile int *)addr = foo; +asm volatile ("eieio" : : ); +@end example + +@noindent +Assume @code{addr} contains the address of a memory mapped device +register. The PowerPC @code{eieio} instruction (Enforce In-order +Execution of I/O) tells the cpu to make sure that the store to that +device register happens before it issues any other I/O. + +Note that even a volatile @code{asm} instruction can be moved in ways +that appear insignificant to the compiler, such as across jump +instructions. You can't expect a sequence of volatile @code{asm} +instructions to remain perfectly consecutive. If you want consecutive +output, use a single @code{asm}. Also, GCC will perform some +optimizations across a volatile @code{asm} instruction; GCC does not +``forget everything'' when it encounters a volatile @code{asm} +instruction the way some other compilers do. + +An @code{asm} instruction without any operands or clobbers (an ``old +style'' @code{asm}) will be treated identically to a volatile +@code{asm} instruction. + +It is a natural idea to look for a way to give access to the condition +code left by the assembler instruction. However, when we attempted to +implement this, we found no way to make it work reliably. The problem +is that output operands might need reloading, which would result in +additional following ``store'' instructions. On most machines, these +instructions would alter the condition code before there was time to +test it. This problem doesn't arise for ordinary ``test'' and +``compare'' instructions because they don't have any output operands. + +For reasons similar to those described above, it is not possible to give +an assembler instruction access to the condition code left by previous +instructions. + +If you are writing a header file that should be includable in ISO C +programs, write @code{__asm__} instead of @code{asm}. @xref{Alternate +Keywords}. + +@subsection i386 floating point asm operands + +There are several rules on the usage of stack-like regs in +asm_operands insns. These rules apply only to the operands that are +stack-like regs: + +@enumerate +@item +Given a set of input regs that die in an asm_operands, it is +necessary to know which are implicitly popped by the asm, and +which must be explicitly popped by gcc. + +An input reg that is implicitly popped by the asm must be +explicitly clobbered, unless it is constrained to match an +output operand. + +@item +For any input reg that is implicitly popped by an asm, it is +necessary to know how to adjust the stack to compensate for the pop. +If any non-popped input is closer to the top of the reg-stack than +the implicitly popped reg, it would not be possible to know what the +stack looked like --- it's not clear how the rest of the stack ``slides +up''. + +All implicitly popped input regs must be closer to the top of +the reg-stack than any input that is not implicitly popped. + +It is possible that if an input dies in an insn, reload might +use the input reg for an output reload. Consider this example: + +@example +asm ("foo" : "=t" (a) : "f" (b)); +@end example + +This asm says that input B is not popped by the asm, and that +the asm pushes a result onto the reg-stack, ie, the stack is one +deeper after the asm than it was before. But, it is possible that +reload will think that it can use the same reg for both the input and +the output, if input B dies in this insn. + +If any input operand uses the @code{f} constraint, all output reg +constraints must use the @code{&} earlyclobber. + +The asm above would be written as + +@example +asm ("foo" : "=&t" (a) : "f" (b)); +@end example + +@item +Some operands need to be in particular places on the stack. All +output operands fall in this category --- there is no other way to +know which regs the outputs appear in unless the user indicates +this in the constraints. + +Output operands must specifically indicate which reg an output +appears in after an asm. @code{=f} is not allowed: the operand +constraints must select a class with a single reg. + +@item +Output operands may not be ``inserted'' between existing stack regs. +Since no 387 opcode uses a read/write operand, all output operands +are dead before the asm_operands, and are pushed by the asm_operands. +It makes no sense to push anywhere but the top of the reg-stack. + +Output operands must start at the top of the reg-stack: output +operands may not ``skip'' a reg. + +@item +Some asm statements may need extra stack space for internal +calculations. This can be guaranteed by clobbering stack registers +unrelated to the inputs and outputs. + +@end enumerate + +Here are a couple of reasonable asms to want to write. This asm +takes one input, which is internally popped, and produces two outputs. + +@example +asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp)); +@end example + +This asm takes two inputs, which are popped by the @code{fyl2xp1} opcode, +and replaces them with one output. The user must code the @code{st(1)} +clobber for reg-stack.c to know that @code{fyl2xp1} pops both inputs. + +@example +asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)"); +@end example + +@ifclear INTERNALS +@c Show the details on constraints if they do not appear elsewhere in +@c the manual +@include md.texi +@end ifclear + +@node Asm Labels +@section Controlling Names Used in Assembler Code +@cindex assembler names for identifiers +@cindex names used in assembler code +@cindex identifiers, names in assembler code + +You can specify the name to be used in the assembler code for a C +function or variable by writing the @code{asm} (or @code{__asm__}) +keyword after the declarator as follows: + +@example +int foo asm ("myfoo") = 2; +@end example + +@noindent +This specifies that the name to be used for the variable @code{foo} in +the assembler code should be @samp{myfoo} rather than the usual +@samp{_foo}. + +On systems where an underscore is normally prepended to the name of a C +function or variable, this feature allows you to define names for the +linker that do not start with an underscore. + +It does not make sense to use this feature with a non-static local +variable since such variables do not have assembler names. If you are +trying to put the variable in a particular register, see @ref{Explicit +Reg Vars}. GCC presently accepts such code with a warning, but will +probably be changed to issue an error, rather than a warning, in the +future. + +You cannot use @code{asm} in this way in a function @emph{definition}; but +you can get the same effect by writing a declaration for the function +before its definition and putting @code{asm} there, like this: + +@example +extern func () asm ("FUNC"); + +func (x, y) + int x, y; +@dots{} +@end example + +It is up to you to make sure that the assembler names you choose do not +conflict with any other assembler symbols. Also, you must not use a +register name; that would produce completely invalid assembler code. GNU +CC does not as yet have the ability to store static variables in registers. +Perhaps that will be added. + +@node Explicit Reg Vars +@section Variables in Specified Registers +@cindex explicit register variables +@cindex variables in specified registers +@cindex specified registers +@cindex registers, global allocation + +GNU C allows you to put a few global variables into specified hardware +registers. You can also specify the register in which an ordinary +register variable should be allocated. + +@itemize @bullet +@item +Global register variables reserve registers throughout the program. +This may be useful in programs such as programming language +interpreters which have a couple of global variables that are accessed +very often. + +@item +Local register variables in specific registers do not reserve the +registers. The compiler's data flow analysis is capable of determining +where the specified registers contain live values, and where they are +available for other uses. Stores into local register variables may be deleted +when they appear to be dead according to dataflow analysis. References +to local register variables may be deleted or moved or simplified. + +These local variables are sometimes convenient for use with the extended +@code{asm} feature (@pxref{Extended Asm}), if you want to write one +output of the assembler instruction directly into a particular register. +(This will work provided the register you specify fits the constraints +specified for that operand in the @code{asm}.) +@end itemize + +@menu +* Global Reg Vars:: +* Local Reg Vars:: +@end menu + +@node Global Reg Vars +@subsection Defining Global Register Variables +@cindex global register variables +@cindex registers, global variables in + +You can define a global register variable in GNU C like this: + +@example +register int *foo asm ("a5"); +@end example + +@noindent +Here @code{a5} is the name of the register which should be used. Choose a +register which is normally saved and restored by function calls on your +machine, so that library routines will not clobber it. + +Naturally the register name is cpu-dependent, so you would need to +conditionalize your program according to cpu type. The register +@code{a5} would be a good choice on a 68000 for a variable of pointer +type. On machines with register windows, be sure to choose a ``global'' +register that is not affected magically by the function call mechanism. + +In addition, operating systems on one type of cpu may differ in how they +name the registers; then you would need additional conditionals. For +example, some 68000 operating systems call this register @code{%a5}. + +Eventually there may be a way of asking the compiler to choose a register +automatically, but first we need to figure out how it should choose and +how to enable you to guide the choice. No solution is evident. + +Defining a global register variable in a certain register reserves that +register entirely for this use, at least within the current compilation. +The register will not be allocated for any other purpose in the functions +in the current compilation. The register will not be saved and restored by +these functions. Stores into this register are never deleted even if they +would appear to be dead, but references may be deleted or moved or +simplified. + +It is not safe to access the global register variables from signal +handlers, or from more than one thread of control, because the system +library routines may temporarily use the register for other things (unless +you recompile them specially for the task at hand). + +@cindex @code{qsort}, and global register variables +It is not safe for one function that uses a global register variable to +call another such function @code{foo} by way of a third function +@code{lose} that was compiled without knowledge of this variable (i.e. in a +different source file in which the variable wasn't declared). This is +because @code{lose} might save the register and put some other value there. +For example, you can't expect a global register variable to be available in +the comparison-function that you pass to @code{qsort}, since @code{qsort} +might have put something else in that register. (If you are prepared to +recompile @code{qsort} with the same global register variable, you can +solve this problem.) + +If you want to recompile @code{qsort} or other source files which do not +actually use your global register variable, so that they will not use that +register for any other purpose, then it suffices to specify the compiler +option @samp{-ffixed-@var{reg}}. You need not actually add a global +register declaration to their source code. + +A function which can alter the value of a global register variable cannot +safely be called from a function compiled without this variable, because it +could clobber the value the caller expects to find there on return. +Therefore, the function which is the entry point into the part of the +program that uses the global register variable must explicitly save and +restore the value which belongs to its caller. + +@cindex register variable after @code{longjmp} +@cindex global register after @code{longjmp} +@cindex value after @code{longjmp} +@findex longjmp +@findex setjmp +On most machines, @code{longjmp} will restore to each global register +variable the value it had at the time of the @code{setjmp}. On some +machines, however, @code{longjmp} will not change the value of global +register variables. To be portable, the function that called @code{setjmp} +should make other arrangements to save the values of the global register +variables, and to restore them in a @code{longjmp}. This way, the same +thing will happen regardless of what @code{longjmp} does. + +All global register variable declarations must precede all function +definitions. If such a declaration could appear after function +definitions, the declaration would be too late to prevent the register from +being used for other purposes in the preceding functions. + +Global register variables may not have initial values, because an +executable file has no means to supply initial contents for a register. + +On the Sparc, there are reports that g3 @dots{} g7 are suitable +registers, but certain library functions, such as @code{getwd}, as well +as the subroutines for division and remainder, modify g3 and g4. g1 and +g2 are local temporaries. + +On the 68000, a2 @dots{} a5 should be suitable, as should d2 @dots{} d7. +Of course, it will not do to use more than a few of those. + +@node Local Reg Vars +@subsection Specifying Registers for Local Variables +@cindex local variables, specifying registers +@cindex specifying registers for local variables +@cindex registers for local variables + +You can define a local register variable with a specified register +like this: + +@example +register int *foo asm ("a5"); +@end example + +@noindent +Here @code{a5} is the name of the register which should be used. Note +that this is the same syntax used for defining global register +variables, but for a local variable it would appear within a function. + +Naturally the register name is cpu-dependent, but this is not a +problem, since specific registers are most often useful with explicit +assembler instructions (@pxref{Extended Asm}). Both of these things +generally require that you conditionalize your program according to +cpu type. + +In addition, operating systems on one type of cpu may differ in how they +name the registers; then you would need additional conditionals. For +example, some 68000 operating systems call this register @code{%a5}. + +Defining such a register variable does not reserve the register; it +remains available for other uses in places where flow control determines +the variable's value is not live. However, these registers are made +unavailable for use in the reload pass; excessive use of this feature +leaves the compiler too few available registers to compile certain +functions. + +This option does not guarantee that GNU CC will generate code that has +this variable in the register you specify at all times. You may not +code an explicit reference to this register in an @code{asm} statement +and assume it will always refer to this variable. + +Stores into local register variables may be deleted when they appear to be dead +according to dataflow analysis. References to local register variables may +be deleted or moved or simplified. + +@node Alternate Keywords +@section Alternate Keywords +@cindex alternate keywords +@cindex keywords, alternate + +The option @option{-traditional} disables certain keywords; +@option{-ansi} and the various @option{-std} options disable certain +others. This causes trouble when you want to use GNU C extensions, or +ISO C features, in a general-purpose header file that should be usable +by all programs, including ISO C programs and traditional ones. The +keywords @code{asm}, @code{typeof} and @code{inline} cannot be used +since they won't work in a program compiled with @option{-ansi} +(although @code{inline} can be used in a program compiled with +@option{-std=c99}), while the keywords @code{const}, @code{volatile}, +@code{signed}, @code{typeof} and @code{inline} won't work in a program +compiled with @option{-traditional}. The ISO C99 keyword +@code{restrict} is only available when @option{-std=gnu99} (which will +eventually be the default) or @option{-std=c99} (or the equivalent +@option{-std=iso9899:1999}) is used.@refill + +The way to solve these problems is to put @samp{__} at the beginning and +end of each problematical keyword. For example, use @code{__asm__} +instead of @code{asm}, @code{__const__} instead of @code{const}, and +@code{__inline__} instead of @code{inline}. + +Other C compilers won't accept these alternative keywords; if you want to +compile with another compiler, you can define the alternate keywords as +macros to replace them with the customary keywords. It looks like this: + +@example +#ifndef __GNUC__ +#define __asm__ asm +#endif +@end example + +@findex __extension__ +@samp{-pedantic} and other options cause warnings for many GNU C extensions. +You can +prevent such warnings within one expression by writing +@code{__extension__} before the expression. @code{__extension__} has no +effect aside from this. + +@node Incomplete Enums +@section Incomplete @code{enum} Types + +You can define an @code{enum} tag without specifying its possible values. +This results in an incomplete type, much like what you get if you write +@code{struct foo} without describing the elements. A later declaration +which does specify the possible values completes the type. + +You can't allocate variables or storage using the type while it is +incomplete. However, you can work with pointers to that type. + +This extension may not be very useful, but it makes the handling of +@code{enum} more consistent with the way @code{struct} and @code{union} +are handled. + +This extension is not supported by GNU C++. + +@node Function Names +@section Function Names as Strings +@cindex @code{__FUNCTION__} identifier +@cindex @code{__PRETTY_FUNCTION__} identifier +@cindex @code{__func__} identifier + +GNU CC predefines two magic identifiers to hold the name of the current +function. The identifier @code{__FUNCTION__} holds the name of the function +as it appears in the source. The identifier @code{__PRETTY_FUNCTION__} +holds the name of the function pretty printed in a language specific +fashion. + +These names are always the same in a C function, but in a C++ function +they may be different. For example, this program: + +@smallexample +extern "C" @{ +extern int printf (char *, ...); +@} + +class a @{ + public: + sub (int i) + @{ + printf ("__FUNCTION__ = %s\n", __FUNCTION__); + printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__); + @} +@}; + +int +main (void) +@{ + a ax; + ax.sub (0); + return 0; +@} +@end smallexample + +@noindent +gives this output: + +@smallexample +__FUNCTION__ = sub +__PRETTY_FUNCTION__ = int a::sub (int) +@end smallexample + +The compiler automagically replaces the identifiers with a string +literal containing the appropriate name. Thus, they are neither +preprocessor macros, like @code{__FILE__} and @code{__LINE__}, nor +variables. This means that they catenate with other string literals, and +that they can be used to initialize char arrays. For example + +@smallexample +char here[] = "Function " __FUNCTION__ " in " __FILE__; +@end smallexample + +On the other hand, @samp{#ifdef __FUNCTION__} does not have any special +meaning inside a function, since the preprocessor does not do anything +special with the identifier @code{__FUNCTION__}. + +GNU CC also supports the magic word @code{__func__}, defined by the +ISO standard C99: + +@display +The identifier @code{__func__} is implicitly declared by the translator +as if, immediately following the opening brace of each function +definition, the declaration + +@smallexample +static const char __func__[] = "function-name"; +@end smallexample + +appeared, where function-name is the name of the lexically-enclosing +function. This name is the unadorned name of the function. +@end display + +By this definition, @code{__func__} is a variable, not a string literal. +In particular, @code{__func__} does not catenate with other string +literals. + +In @code{C++}, @code{__FUNCTION__} and @code{__PRETTY_FUNCTION__} are +variables, declared in the same way as @code{__func__}. + +@node Return Address +@section Getting the Return or Frame Address of a Function + +These functions may be used to get information about the callers of a +function. + +@table @code +@findex __builtin_return_address +@item __builtin_return_address (@var{level}) +This function returns the return address of the current function, or of +one of its callers. The @var{level} argument is number of frames to +scan up the call stack. A value of @code{0} yields the return address +of the current function, a value of @code{1} yields the return address +of the caller of the current function, and so forth. + +The @var{level} argument must be a constant integer. + +On some machines it may be impossible to determine the return address of +any function other than the current one; in such cases, or when the top +of the stack has been reached, this function will return @code{0}. + +This function should only be used with a non-zero argument for debugging +purposes. + +@findex __builtin_frame_address +@item __builtin_frame_address (@var{level}) +This function is similar to @code{__builtin_return_address}, but it +returns the address of the function frame rather than the return address +of the function. Calling @code{__builtin_frame_address} with a value of +@code{0} yields the frame address of the current function, a value of +@code{1} yields the frame address of the caller of the current function, +and so forth. + +The frame is the area on the stack which holds local variables and saved +registers. The frame address is normally the address of the first word +pushed on to the stack by the function. However, the exact definition +depends upon the processor and the calling convention. If the processor +has a dedicated frame pointer register, and the function has a frame, +then @code{__builtin_frame_address} will return the value of the frame +pointer register. + +The caveats that apply to @code{__builtin_return_address} apply to this +function as well. +@end table + +@node Other Builtins +@section Other built-in functions provided by GNU CC +@cindex builtin functions +@findex __builtin_isgreater +@findex __builtin_isgreaterequal +@findex __builtin_isless +@findex __builtin_islessequal +@findex __builtin_islessgreater +@findex __builtin_isunordered +@findex abort +@findex abs +@findex alloca +@findex bcmp +@findex bzero +@findex cimag +@findex cimagf +@findex cimagl +@findex conj +@findex conjf +@findex conjl +@findex cos +@findex cosf +@findex cosl +@findex creal +@findex crealf +@findex creall +@findex exit +@findex _exit +@findex _Exit +@findex fabs +@findex fabsf +@findex fabsl +@findex ffs +@findex fprintf +@findex fputs +@findex imaxabs +@findex index +@findex labs +@findex llabs +@findex memcmp +@findex memcpy +@findex memset +@findex printf +@findex rindex +@findex sin +@findex sinf +@findex sinl +@findex sqrt +@findex sqrtf +@findex sqrtl +@findex strcat +@findex strchr +@findex strcmp +@findex strcpy +@findex strcspn +@findex strlen +@findex strncat +@findex strncmp +@findex strncpy +@findex strpbrk +@findex strrchr +@findex strspn +@findex strstr + +GNU CC provides a large number of built-in functions other than the ones +mentioned above. Some of these are for internal use in the processing +of exceptions or variable-length argument lists and will not be +documented here because they may change from time to time; we do not +recommend general use of these functions. + +The remaining functions are provided for optimization purposes. + +GNU CC includes builtin versions of many of the functions in the +standard C library. The versions prefixed with @code{__builtin_} will +always be treated as having the same meaning as the C library function +even if you specify the @samp{-fno-builtin} (@pxref{C Dialect Options}) +option. Many of these functions are only optimized in certain cases; if +not optimized in a particular case, a call to the library function will +be emitted. + +The functions @code{abort}, @code{exit}, @code{_Exit} and @code{_exit} +are recognized and presumed not to return, but otherwise are not built +in. @code{_exit} is not recognized in strict ISO C mode (@samp{-ansi}, +@samp{-std=c89} or @samp{-std=c99}). @code{_Exit} is not recognized in +strict C89 mode (@samp{-ansi} or @samp{-std=c89}). + +Outside strict ISO C mode, the functions @code{alloca}, @code{bcmp}, +@code{bzero}, @code{index}, @code{rindex} and @code{ffs} may be handled +as builtins. Corresponding versions @code{__builtin_alloca}, +@code{__builtin_bcmp}, @code{__builtin_bzero}, @code{__builtin_index}, +@code{__builtin_rindex} and @code{__builtin_ffs} are also recognized in +strict ISO C mode. + +The ISO C99 functions @code{conj}, @code{conjf}, @code{conjl}, +@code{creal}, @code{crealf}, @code{creall}, @code{cimag}, @code{cimagf}, +@code{cimagl}, @code{llabs} and @code{imaxabs} are handled as builtins +except in strict ISO C89 mode. There are also builtin versions of the ISO C99 +functions @code{cosf}, @code{cosl}, @code{fabsf}, @code{fabsl}, +@code{sinf}, @code{sinl}, @code{sqrtf}, and @code{sqrtl}, that are +recognized in any mode since ISO C89 reserves these names for the +purpose to which ISO C99 puts them. All these functions have +corresponding versions prefixed with @code{__builtin_}. + +The following ISO C89 functions are recognized as builtins unless +@samp{-fno-builtin} is specified: @code{abs}, @code{cos}, @code{fabs}, +@code{fprintf}, @code{fputs}, @code{labs}, @code{memcmp}, @code{memcpy}, +@code{memset}, @code{printf}, @code{sin}, @code{sqrt}, @code{strcat}, +@code{strchr}, @code{strcmp}, @code{strcpy}, @code{strcspn}, +@code{strlen}, @code{strncat}, @code{strncmp}, @code{strncpy}, +@code{strpbrk}, @code{strrchr}, @code{strspn}, and @code{strstr}. All +of these functions have corresponding versions prefixed with +@code{__builtin_}, except that the version for @code{sqrt} is called +@code{__builtin_fsqrt}. + +GNU CC provides builtin versions of the ISO C99 floating point +comparison macros (that avoid raising exceptions for unordered +operands): @code{__builtin_isgreater}, @code{__builtin_isgreaterequal}, +@code{__builtin_isless}, @code{__builtin_islessequal}, +@code{__builtin_islessgreater}, and @code{__builtin_isunordered}. + + +@table @code +@findex __builtin_constant_p +@item __builtin_constant_p (@var{exp}) +You can use the builtin function @code{__builtin_constant_p} to +determine if a value is known to be constant at compile-time and hence +that GNU CC can perform constant-folding on expressions involving that +value. The argument of the function is the value to test. The function +returns the integer 1 if the argument is known to be a compile-time +constant and 0 if it is not known to be a compile-time constant. A +return of 0 does not indicate that the value is @emph{not} a constant, +but merely that GNU CC cannot prove it is a constant with the specified +value of the @samp{-O} option. + +You would typically use this function in an embedded application where +memory was a critical resource. If you have some complex calculation, +you may want it to be folded if it involves constants, but need to call +a function if it does not. For example: + +@smallexample +#define Scale_Value(X) \ + (__builtin_constant_p (X) \ + ? ((X) * SCALE + OFFSET) : Scale (X)) +@end smallexample + +You may use this builtin function in either a macro or an inline +function. However, if you use it in an inlined function and pass an +argument of the function as the argument to the builtin, GNU CC will +never return 1 when you call the inline function with a string constant +or compound literal (@pxref{Compound Literals}) and will not return 1 +when you pass a constant numeric value to the inline function unless you +specify the @samp{-O} option. + +@findex __builtin_expect +@item __builtin_expect(@var{exp}, @var{c}) +You may use @code{__builtin_expect} to provide the compiler with +branch prediction information. In general, you should prefer to +use actual profile feedback for this (@samp{-fprofile-arcs}), as +programmers are notoriously bad at predicting how their programs +actually perform. However, there are applications in which this +data is hard to collect. + +The return value is the value of @var{exp}, which should be an +integral expression. The value of @var{c} must be a compile-time +constant. The semantics of the builtin are that it is expected +that @var{exp} == @var{c}. For example: + +@smallexample +if (__builtin_expect (x, 0)) + foo (); +@end smallexample + +@noindent +would indicate that we do not expect to call @code{foo}, since +we expect @code{x} to be zero. Since you are limited to integral +expressions for @var{exp}, you should use constructions such as + +@smallexample +if (__builtin_expect (ptr != NULL, 1)) + error (); +@end smallexample + +@noindent +when testing pointer or floating-point values. +@end table + +@node C++ Extensions +@chapter Extensions to the C++ Language +@cindex extensions, C++ language +@cindex C++ language extensions + +The GNU compiler provides these extensions to the C++ language (and you +can also use most of the C language extensions in your C++ programs). If you +want to write code that checks whether these features are available, you can +test for the GNU compiler the same way as for C programs: check for a +predefined macro @code{__GNUC__}. You can also use @code{__GNUG__} to +test specifically for GNU C++ (@pxref{Standard Predefined,,Standard +Predefined Macros,cpp.info,The C Preprocessor}). + +@menu +* Min and Max:: C++ Minimum and maximum operators. +* Volatiles:: What constitutes an access to a volatile object. +* Restricted Pointers:: C99 restricted pointers and references. +* Vague Linkage:: Where G++ puts inlines, vtables and such. +* C++ Interface:: You can use a single C++ header file for both + declarations and definitions. +* Template Instantiation:: Methods for ensuring that exactly one copy of + each needed template instantiation is emitted. +* Bound member functions:: You can extract a function pointer to the + method denoted by a @samp{->*} or @samp{.*} expression. +* C++ Attributes:: Variable, function, and type attributes for C++ only. +* Java Exceptions:: Tweaking exception handling to work with Java. +* Deprecated Features:: Things might disappear from g++. +* Backwards Compatibility:: Compatibilities with earlier definitions of C++. +@end menu + +@node Min and Max +@section Minimum and Maximum Operators in C++ + +It is very convenient to have operators which return the ``minimum'' or the +``maximum'' of two arguments. In GNU C++ (but not in GNU C), + +@table @code +@item @var{a} ? @var{b} +@findex >? +@cindex maximum operator +is the @dfn{maximum}, returning the larger of the numeric values @var{a} +and @var{b}. +@end table + +These operations are not primitive in ordinary C++, since you can +use a macro to return the minimum of two things in C++, as in the +following example. + +@example +#define MIN(X,Y) ((X) < (Y) ? : (X) : (Y)) +@end example + +@noindent +You might then use @w{@samp{int min = MIN (i, j);}} to set @var{min} to +the minimum value of variables @var{i} and @var{j}. + +However, side effects in @code{X} or @code{Y} may cause unintended +behavior. For example, @code{MIN (i++, j++)} will fail, incrementing +the smaller counter twice. A GNU C extension allows you to write safe +macros that avoid this kind of problem (@pxref{Naming Types,,Naming an +Expression's Type}). However, writing @code{MIN} and @code{MAX} as +macros also forces you to use function-call notation for a +fundamental arithmetic operation. Using GNU C++ extensions, you can +write @w{@samp{int min = i ?} are built into the compiler, they properly +handle expressions with side-effects; @w{@samp{int min = i++ ; +volatile int *src = ; +*dst = *src; +@end example + +@noindent +will cause a read of the volatile object pointed to by @var{src} and stores the +value into the volatile object pointed to by @var{dst}. There is no +guarantee that these reads and writes are atomic, especially for objects +larger than @code{int}. + +Less obvious expressions are where something which looks like an access +is used in a void context. An example would be, + +@example +volatile int *src = ; +*src; +@end example + +With C, such expressions are rvalues, and as rvalues cause a read of +the object, gcc interprets this as a read of the volatile being pointed +to. The C++ standard specifies that such expressions do not undergo +lvalue to rvalue conversion, and that the type of the dereferenced +object may be incomplete. The C++ standard does not specify explicitly +that it is this lvalue to rvalue conversion which is responsible for +causing an access. However, there is reason to believe that it is, +because otherwise certain simple expressions become undefined. However, +because it would surprise most programmers, g++ treats dereferencing a +pointer to volatile object of complete type in a void context as a read +of the object. When the object has incomplete type, g++ issues a +warning. + +@example +struct S; +struct T @{int m;@}; +volatile S *ptr1 = ; +volatile T *ptr2 = ; +*ptr1; +*ptr2; +@end example + +In this example, a warning is issued for @code{*ptr1}, and @code{*ptr2} +causes a read of the object pointed to. If you wish to force an error on +the first case, you must force a conversion to rvalue with, for instance +a static cast, @code{static_cast(*ptr1)}. + +When using a reference to volatile, g++ does not treat equivalent +expressions as accesses to volatiles, but instead issues a warning that +no volatile is accessed. The rationale for this is that otherwise it +becomes difficult to determine where volatile access occur, and not +possible to ignore the return value from functions returning volatile +references. Again, if you wish to force a read, cast the reference to +an rvalue. + +@node Restricted Pointers +@section Restricting Pointer Aliasing +@cindex restricted pointers +@cindex restricted references +@cindex restricted this pointer + +As with gcc, g++ understands the C99 feature of restricted pointers, +specified with the @code{__restrict__}, or @code{__restrict} type +qualifier. Because you cannot compile C++ by specifying the -std=c99 +language flag, @code{restrict} is not a keyword in C++. + +In addition to allowing restricted pointers, you can specify restricted +references, which indicate that the reference is not aliased in the local +context. + +@example +void fn (int *__restrict__ rptr, int &__restrict__ rref) +@{ + @dots{} +@} +@end example + +@noindent +In the body of @code{fn}, @var{rptr} points to an unaliased integer and +@var{rref} refers to a (different) unaliased integer. + +You may also specify whether a member function's @var{this} pointer is +unaliased by using @code{__restrict__} as a member function qualifier. + +@example +void T::fn () __restrict__ +@{ + @dots{} +@} +@end example + +@noindent +Within the body of @code{T::fn}, @var{this} will have the effective +definition @code{T *__restrict__ const this}. Notice that the +interpretation of a @code{__restrict__} member function qualifier is +different to that of @code{const} or @code{volatile} qualifier, in that it +is applied to the pointer rather than the object. This is consistent with +other compilers which implement restricted pointers. + +As with all outermost parameter qualifiers, @code{__restrict__} is +ignored in function definition matching. This means you only need to +specify @code{__restrict__} in a function definition, rather than +in a function prototype as well. + +@node Vague Linkage +@section Vague Linkage +@cindex vague linkage + +There are several constructs in C++ which require space in the object +file but are not clearly tied to a single translation unit. We say that +these constructs have ``vague linkage''. Typically such constructs are +emitted wherever they are needed, though sometimes we can be more +clever. + +@table @asis +@item Inline Functions +Inline functions are typically defined in a header file which can be +included in many different compilations. Hopefully they can usually be +inlined, but sometimes an out-of-line copy is necessary, if the address +of the function is taken or if inlining fails. In general, we emit an +out-of-line copy in all translation units where one is needed. As an +exception, we only emit inline virtual functions with the vtable, since +it will always require a copy. + +Local static variables and string constants used in an inline function +are also considered to have vague linkage, since they must be shared +between all inlined and out-of-line instances of the function. + +@item VTables +@cindex vtable +C++ virtual functions are implemented in most compilers using a lookup +table, known as a vtable. The vtable contains pointers to the virtual +functions provided by a class, and each object of the class contains a +pointer to its vtable (or vtables, in some multiple-inheritance +situations). If the class declares any non-inline, non-pure virtual +functions, the first one is chosen as the ``key method'' for the class, +and the vtable is only emitted in the translation unit where the key +method is defined. + +@emph{Note:} If the chosen key method is later defined as inline, the +vtable will still be emitted in every translation unit which defines it. +Make sure that any inline virtuals are declared inline in the class +body, even if they are not defined there. + +@item type_info objects +@cindex type_info +@cindex RTTI +C++ requires information about types to be written out in order to +implement @samp{dynamic_cast}, @samp{typeid} and exception handling. +For polymorphic classes (classes with virtual functions), the type_info +object is written out along with the vtable so that @samp{dynamic_cast} +can determine the dynamic type of a class object at runtime. For all +other types, we write out the type_info object when it is used: when +applying @samp{typeid} to an expression, throwing an object, or +referring to a type in a catch clause or exception specification. + +@item Template Instantiations +Most everything in this section also applies to template instantiations, +but there are other options as well. +@xref{Template Instantiation,,Where's the Template?}. + +@end table + +When used with GNU ld version 2.8 or later on an ELF system such as +Linux/GNU or Solaris 2, or on Microsoft Windows, duplicate copies of +these constructs will be discarded at link time. This is known as +COMDAT support. + +On targets that don't support COMDAT, but do support weak symbols, GCC +will use them. This way one copy will override all the others, but +the unused copies will still take up space in the executable. + +For targets which do not support either COMDAT or weak symbols, +most entities with vague linkage will be emitted as local symbols to +avoid duplicate definition errors from the linker. This will not happen +for local statics in inlines, however, as having multiple copies will +almost certainly break things. + +@xref{C++ Interface,,Declarations and Definitions in One Header}, for +another way to control placement of these constructs. + +@node C++ Interface +@section Declarations and Definitions in One Header + +@cindex interface and implementation headers, C++ +@cindex C++ interface and implementation headers +C++ object definitions can be quite complex. In principle, your source +code will need two kinds of things for each object that you use across +more than one source file. First, you need an @dfn{interface} +specification, describing its structure with type declarations and +function prototypes. Second, you need the @dfn{implementation} itself. +It can be tedious to maintain a separate interface description in a +header file, in parallel to the actual implementation. It is also +dangerous, since separate interface and implementation definitions may +not remain parallel. + +@cindex pragmas, interface and implementation +With GNU C++, you can use a single header file for both purposes. + +@quotation +@emph{Warning:} The mechanism to specify this is in transition. For the +nonce, you must use one of two @code{#pragma} commands; in a future +release of GNU C++, an alternative mechanism will make these +@code{#pragma} commands unnecessary. +@end quotation + +The header file contains the full definitions, but is marked with +@samp{#pragma interface} in the source code. This allows the compiler +to use the header file only as an interface specification when ordinary +source files incorporate it with @code{#include}. In the single source +file where the full implementation belongs, you can use either a naming +convention or @samp{#pragma implementation} to indicate this alternate +use of the header file. + +@table @code +@item #pragma interface +@itemx #pragma interface "@var{subdir}/@var{objects}.h" +@kindex #pragma interface +Use this directive in @emph{header files} that define object classes, to save +space in most of the object files that use those classes. Normally, +local copies of certain information (backup copies of inline member +functions, debugging information, and the internal tables that implement +virtual functions) must be kept in each object file that includes class +definitions. You can use this pragma to avoid such duplication. When a +header file containing @samp{#pragma interface} is included in a +compilation, this auxiliary information will not be generated (unless +the main input source file itself uses @samp{#pragma implementation}). +Instead, the object files will contain references to be resolved at link +time. + +The second form of this directive is useful for the case where you have +multiple headers with the same name in different directories. If you +use this form, you must specify the same string to @samp{#pragma +implementation}. + +@item #pragma implementation +@itemx #pragma implementation "@var{objects}.h" +@kindex #pragma implementation +Use this pragma in a @emph{main input file}, when you want full output from +included header files to be generated (and made globally visible). The +included header file, in turn, should use @samp{#pragma interface}. +Backup copies of inline member functions, debugging information, and the +internal tables used to implement virtual functions are all generated in +implementation files. + +@cindex implied @code{#pragma implementation} +@cindex @code{#pragma implementation}, implied +@cindex naming convention, implementation headers +If you use @samp{#pragma implementation} with no argument, it applies to +an include file with the same basename@footnote{A file's @dfn{basename} +was the name stripped of all leading path information and of trailing +suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source +file. For example, in @file{allclass.cc}, giving just +@samp{#pragma implementation} +by itself is equivalent to @samp{#pragma implementation "allclass.h"}. + +In versions of GNU C++ prior to 2.6.0 @file{allclass.h} was treated as +an implementation file whenever you would include it from +@file{allclass.cc} even if you never specified @samp{#pragma +implementation}. This was deemed to be more trouble than it was worth, +however, and disabled. + +If you use an explicit @samp{#pragma implementation}, it must appear in +your source file @emph{before} you include the affected header files. + +Use the string argument if you want a single implementation file to +include code from multiple header files. (You must also use +@samp{#include} to include the header file; @samp{#pragma +implementation} only specifies how to use the file---it doesn't actually +include it.) + +There is no way to split up the contents of a single header file into +multiple implementation files. +@end table + +@cindex inlining and C++ pragmas +@cindex C++ pragmas, effect on inlining +@cindex pragmas in C++, effect on inlining +@samp{#pragma implementation} and @samp{#pragma interface} also have an +effect on function inlining. + +If you define a class in a header file marked with @samp{#pragma +interface}, the effect on a function defined in that class is similar to +an explicit @code{extern} declaration---the compiler emits no code at +all to define an independent version of the function. Its definition +is used only for inlining with its callers. + +Conversely, when you include the same header file in a main source file +that declares it as @samp{#pragma implementation}, the compiler emits +code for the function itself; this defines a version of the function +that can be found via pointers (or by callers compiled without +inlining). If all calls to the function can be inlined, you can avoid +emitting the function by compiling with @samp{-fno-implement-inlines}. +If any calls were not inlined, you will get linker errors. + +@node Template Instantiation +@section Where's the Template? + +@cindex template instantiation + +C++ templates are the first language feature to require more +intelligence from the environment than one usually finds on a UNIX +system. Somehow the compiler and linker have to make sure that each +template instance occurs exactly once in the executable if it is needed, +and not at all otherwise. There are two basic approaches to this +problem, which I will refer to as the Borland model and the Cfront model. + +@table @asis +@item Borland model +Borland C++ solved the template instantiation problem by adding the code +equivalent of common blocks to their linker; the compiler emits template +instances in each translation unit that uses them, and the linker +collapses them together. The advantage of this model is that the linker +only has to consider the object files themselves; there is no external +complexity to worry about. This disadvantage is that compilation time +is increased because the template code is being compiled repeatedly. +Code written for this model tends to include definitions of all +templates in the header file, since they must be seen to be +instantiated. + +@item Cfront model +The AT&T C++ translator, Cfront, solved the template instantiation +problem by creating the notion of a template repository, an +automatically maintained place where template instances are stored. A +more modern version of the repository works as follows: As individual +object files are built, the compiler places any template definitions and +instantiations encountered in the repository. At link time, the link +wrapper adds in the objects in the repository and compiles any needed +instances that were not previously emitted. The advantages of this +model are more optimal compilation speed and the ability to use the +system linker; to implement the Borland model a compiler vendor also +needs to replace the linker. The disadvantages are vastly increased +complexity, and thus potential for error; for some code this can be +just as transparent, but in practice it can been very difficult to build +multiple programs in one directory and one program in multiple +directories. Code written for this model tends to separate definitions +of non-inline member templates into a separate file, which should be +compiled separately. +@end table + +When used with GNU ld version 2.8 or later on an ELF system such as +Linux/GNU or Solaris 2, or on Microsoft Windows, g++ supports the +Borland model. On other systems, g++ implements neither automatic +model. + +A future version of g++ will support a hybrid model whereby the compiler +will emit any instantiations for which the template definition is +included in the compile, and store template definitions and +instantiation context information into the object file for the rest. +The link wrapper will extract that information as necessary and invoke +the compiler to produce the remaining instantiations. The linker will +then combine duplicate instantiations. + +In the mean time, you have the following options for dealing with +template instantiations: + +@enumerate +@item +Compile your template-using code with @samp{-frepo}. The compiler will +generate files with the extension @samp{.rpo} listing all of the +template instantiations used in the corresponding object files which +could be instantiated there; the link wrapper, @samp{collect2}, will +then update the @samp{.rpo} files to tell the compiler where to place +those instantiations and rebuild any affected object files. The +link-time overhead is negligible after the first pass, as the compiler +will continue to place the instantiations in the same files. + +This is your best option for application code written for the Borland +model, as it will just work. Code written for the Cfront model will +need to be modified so that the template definitions are available at +one or more points of instantiation; usually this is as simple as adding +@code{#include } to the end of each template header. + +For library code, if you want the library to provide all of the template +instantiations it needs, just try to link all of its object files +together; the link will fail, but cause the instantiations to be +generated as a side effect. Be warned, however, that this may cause +conflicts if multiple libraries try to provide the same instantiations. +For greater control, use explicit instantiation as described in the next +option. + +@item +Compile your code with @samp{-fno-implicit-templates} to disable the +implicit generation of template instances, and explicitly instantiate +all the ones you use. This approach requires more knowledge of exactly +which instances you need than do the others, but it's less +mysterious and allows greater control. You can scatter the explicit +instantiations throughout your program, perhaps putting them in the +translation units where the instances are used or the translation units +that define the templates themselves; you can put all of the explicit +instantiations you need into one big file; or you can create small files +like + +@example +#include "Foo.h" +#include "Foo.cc" + +template class Foo; +template ostream& operator << + (ostream&, const Foo&); +@end example + +for each of the instances you need, and create a template instantiation +library from those. + +If you are using Cfront-model code, you can probably get away with not +using @samp{-fno-implicit-templates} when compiling files that don't +@samp{#include} the member template definitions. + +If you use one big file to do the instantiations, you may want to +compile it without @samp{-fno-implicit-templates} so you get all of the +instances required by your explicit instantiations (but not by any +other files) without having to specify them as well. + +g++ has extended the template instantiation syntax outlined in the +Working Paper to allow forward declaration of explicit instantiations +(with @code{extern}), instantiation of the compiler support data for a +template class (i.e. the vtable) without instantiating any of its +members (with @code{inline}), and instantiation of only the static data +members of a template class, without the support data or member +functions (with (@code{static}): + +@example +extern template int max (int, int); +inline template class Foo; +static template class Foo; +@end example + +@item +Do nothing. Pretend g++ does implement automatic instantiation +management. Code written for the Borland model will work fine, but +each translation unit will contain instances of each of the templates it +uses. In a large program, this can lead to an unacceptable amount of code +duplication. + +@item +Add @samp{#pragma interface} to all files containing template +definitions. For each of these files, add @samp{#pragma implementation +"@var{filename}"} to the top of some @samp{.C} file which +@samp{#include}s it. Then compile everything with +@samp{-fexternal-templates}. The templates will then only be expanded +in the translation unit which implements them (i.e. has a @samp{#pragma +implementation} line for the file where they live); all other files will +use external references. If you're lucky, everything should work +properly. If you get undefined symbol errors, you need to make sure +that each template instance which is used in the program is used in the +file which implements that template. If you don't have any use for a +particular instance in that file, you can just instantiate it +explicitly, using the syntax from the latest C++ working paper: + +@example +template class A; +template ostream& operator << (ostream&, const A&); +@end example + +This strategy will work with code written for either model. If you are +using code written for the Cfront model, the file containing a class +template and the file containing its member templates should be +implemented in the same translation unit. + +A slight variation on this approach is to instead use the flag +@samp{-falt-external-templates}; this flag causes template +instances to be emitted in the translation unit that implements the +header where they are first instantiated, rather than the one which +implements the file where the templates are defined. This header must +be the same in all translation units, or things are likely to break. + +@xref{C++ Interface,,Declarations and Definitions in One Header}, for +more discussion of these pragmas. +@end enumerate + +@node Bound member functions +@section Extracting the function pointer from a bound pointer to member function + +@cindex pmf +@cindex pointer to member function +@cindex bound pointer to member function + +In C++, pointer to member functions (PMFs) are implemented using a wide +pointer of sorts to handle all the possible call mechanisms; the PMF +needs to store information about how to adjust the @samp{this} pointer, +and if the function pointed to is virtual, where to find the vtable, and +where in the vtable to look for the member function. If you are using +PMFs in an inner loop, you should really reconsider that decision. If +that is not an option, you can extract the pointer to the function that +would be called for a given object/PMF pair and call it directly inside +the inner loop, to save a bit of time. + +Note that you will still be paying the penalty for the call through a +function pointer; on most modern architectures, such a call defeats the +branch prediction features of the CPU. This is also true of normal +virtual function calls. + +The syntax for this extension is + +@example +extern A a; +extern int (A::*fp)(); +typedef int (*fptr)(A *); + +fptr p = (fptr)(a.*fp); +@end example + +For PMF constants (i.e. expressions of the form @samp{&Klasse::Member}), +no object is needed to obtain the address of the function. They can be +converted to function pointers directly: + +@example +fptr p1 = (fptr)(&A::foo); +@end example + +You must specify @samp{-Wno-pmf-conversions} to use this extension. + +@node C++ Attributes +@section C++-Specific Variable, Function, and Type Attributes + +Some attributes only make sense for C++ programs. + +@table @code +@item init_priority (@var{priority}) +@cindex init_priority attribute + + +In Standard C++, objects defined at namespace scope are guaranteed to be +initialized in an order in strict accordance with that of their definitions +@emph{in a given translation unit}. No guarantee is made for initializations +across translation units. However, GNU C++ allows users to control the +order of initialization of objects defined at namespace scope with the +@code{init_priority} attribute by specifying a relative @var{priority}, +a constant integral expression currently bounded between 101 and 65535 +inclusive. Lower numbers indicate a higher priority. + +In the following example, @code{A} would normally be created before +@code{B}, but the @code{init_priority} attribute has reversed that order: + +@example +Some_Class A __attribute__ ((init_priority (2000))); +Some_Class B __attribute__ ((init_priority (543))); +@end example + +@noindent +Note that the particular values of @var{priority} do not matter; only their +relative ordering. + +@item java_interface +@cindex java_interface attribute + +This type attribute informs C++ that the class is a Java interface. It may +only be applied to classes declared within an @code{extern "Java"} block. +Calls to methods declared in this interface will be dispatched using GCJ's +interface table mechanism, instead of regular virtual table dispatch. + +@end table + +@node Java Exceptions +@section Java Exceptions + +The Java language uses a slightly different exception handling model +from C++. Normally, GNU C++ will automatically detect when you are +writing C++ code that uses Java exceptions, and handle them +appropriately. However, if C++ code only needs to execute destructors +when Java exceptions are thrown through it, GCC will guess incorrectly. +Sample problematic code: + +@example + struct S @{ ~S(); @}; + extern void bar(); // is implemented in Java and may throw exceptions + void foo() + @{ + S s; + bar(); + @} +@end example + +@noindent +The usual effect of an incorrect guess is a link failure, complaining of +a missing routine called @samp{__gxx_personality_v0}. + +You can inform the compiler that Java exceptions are to be used in a +translation unit, irrespective of what it might think, by writing +@samp{@w{#pragma GCC java_exceptions}} at the head of the file. This +@samp{#pragma} must appear before any functions that throw or catch +exceptions, or run destructors when exceptions are thrown through them. + +You cannot mix Java and C++ exceptions in the same translation unit. It +is believed to be safe to throw a C++ exception from one file through +another file compiled for the for the Java exception model, or vice +versa, but there may be bugs in this area. + +@node Deprecated Features +@section Deprecated Features + +In the past, the GNU C++ compiler was extended to experiment with new +features, at a time when the C++ language was still evolving. Now that +the C++ standard is complete, some of those features are superseded by +superior alternatives. Using the old features might cause a warning in +some cases that the feature will be dropped in the future. In other +cases, the feature might be gone already. + +While the list below is not exhaustive, it documents some of the options +that are now deprecated: + +@table @code +@item -fexternal-templates +@itemx -falt-external-templates +These are two of the many ways for g++ to implement template +instantiation. @xref{Template Instantiation}. The C++ standard clearly +defines how template definitions have to be organized across +implementation units. g++ has an implicit instantiation mechanism that +should work just fine for standard-conforming code. + +@item -fstrict-prototype +@itemx -fno-strict-prototype +Previously it was possible to use an empty prototype parameter list to +indicate an unspecified number of parameters (like C), rather than no +parameters, as C++ demands. This feature has been removed, except where +it is required for backwards compatibility @xref{Backwards Compatibility}. +@end table + +The named return value extension has been deprecated, and will be +removed from g++ at some point. + +The use of initializer lists with new expressions has been deprecated, +and will be removed from g++ at some point. + +@node Backwards Compatibility +@section Backwards Compatibility +@cindex Backwards Compatibility +@cindex ARM [Annotated C++ Reference Manual] + +Now that there is a definitive ISO standard C++, g++ has a specification +to adhere to. The C++ language evolved over time, and features that +used to be acceptable in previous drafts of the standard, such as the ARM +[Annotated C++ Reference Manual], are no longer accepted. In order to allow +compilation of C++ written to such drafts, g++ contains some backwards +compatibilities. @emph{All such backwards compatibility features are +liable to disappear in future versions of g++.} They should be considered +deprecated @xref{Deprecated Features}. + +@table @code +@item For scope +If a variable is declared at for scope, it used to remain in scope until +the end of the scope which contained the for statement (rather than just +within the for scope). g++ retains this, but issues a warning, if such a +variable is accessed outside the for scope. + +@item implicit C language +Old C system header files did not contain an @code{extern "C" @{...@}} +scope to set the language. On such systems, all header files are +implicitly scoped inside a C language scope. Also, an empty prototype +@code{()} will be treated as an unspecified number of arguments, rather +than no arguments, as C++ demands. +@end table diff --git a/gcc/doc/fdl.texi b/gcc/doc/fdl.texi new file mode 100644 index 00000000000..db691df61ed --- /dev/null +++ b/gcc/doc/fdl.texi @@ -0,0 +1,403 @@ + +@node GNU Free Documentation License +@unnumbered GNU Free Documentation License + +@cindex FDL, GNU Free Documentation License +@center Version 1.1, March 2000 + +@display +Copyright @copyright{} 2000 Free Software Foundation, Inc. +59 Temple Place, Suite 330, Boston, MA 02111-1307, USA + +Everyone is permitted to copy and distribute verbatim copies +of this license document, but changing it is not allowed. +@end display + +@enumerate 0 +@item +PREAMBLE + +The purpose of this License is to make a manual, textbook, or other +written document @dfn{free} in the sense of freedom: to assure everyone +the effective freedom to copy and redistribute it, with or without +modifying it, either commercially or noncommercially. Secondarily, +this License preserves for the author and publisher a way to get +credit for their work, while not being considered responsible for +modifications made by others. + +This License is a kind of ``copyleft'', which means that derivative +works of the document must themselves be free in the same sense. It +complements the GNU General Public License, which is a copyleft +license designed for free software. + +We have designed this License in order to use it for manuals for free +software, because free software needs free documentation: a free +program should come with manuals providing the same freedoms that the +software does. But this License is not limited to software manuals; +it can be used for any textual work, regardless of subject matter or +whether it is published as a printed book. We recommend this License +principally for works whose purpose is instruction or reference. + +@item +APPLICABILITY AND DEFINITIONS + +This License applies to any manual or other work that contains a +notice placed by the copyright holder saying it can be distributed +under the terms of this License. The ``Document'', below, refers to any +such manual or work. Any member of the public is a licensee, and is +addressed as ``you''. + +A ``Modified Version'' of the Document means any work containing the +Document or a portion of it, either copied verbatim, or with +modifications and/or translated into another language. + +A ``Secondary Section'' is a named appendix or a front-matter section of +the Document that deals exclusively with the relationship of the +publishers or authors of the Document to the Document's overall subject +(or to related matters) and contains nothing that could fall directly +within that overall subject. (For example, if the Document is in part a +textbook of mathematics, a Secondary Section may not explain any +mathematics.) The relationship could be a matter of historical +connection with the subject or with related matters, or of legal, +commercial, philosophical, ethical or political position regarding +them. + +The ``Invariant Sections'' are certain Secondary Sections whose titles +are designated, as being those of Invariant Sections, in the notice +that says that the Document is released under this License. + +The ``Cover Texts'' are certain short passages of text that are listed, +as Front-Cover Texts or Back-Cover Texts, in the notice that says that +the Document is released under this License. + +A ``Transparent'' copy of the Document means a machine-readable copy, +represented in a format whose specification is available to the +general public, whose contents can be viewed and edited directly and +straightforwardly with generic text editors or (for images composed of +pixels) generic paint programs or (for drawings) some widely available +drawing editor, and that is suitable for input to text formatters or +for automatic translation to a variety of formats suitable for input +to text formatters. A copy made in an otherwise Transparent file +format whose markup has been designed to thwart or discourage +subsequent modification by readers is not Transparent. A copy that is +not ``Transparent'' is called ``Opaque''. + +Examples of suitable formats for Transparent copies include plain +@sc{ascii} without markup, Texinfo input format, La@TeX{} input format, +@acronym{SGML} or @acronym{XML} using a publicly available +@acronym{DTD}, and standard-conforming simple @acronym{HTML} designed +for human modification. 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For works in +formats which do not have any title page as such, ``Title Page'' means +the text near the most prominent appearance of the work's title, +preceding the beginning of the body of the text. + +@item +VERBATIM COPYING + +You may copy and distribute the Document in any medium, either +commercially or noncommercially, provided that this License, the +copyright notices, and the license notice saying this License applies +to the Document are reproduced in all copies, and that you add no other +conditions whatsoever to those of this License. You may not use +technical measures to obstruct or control the reading or further +copying of the copies you make or distribute. However, you may accept +compensation in exchange for copies. If you distribute a large enough +number of copies you must also follow the conditions in section 3. + +You may also lend copies, under the same conditions stated above, and +you may publicly display copies. + +@item +COPYING IN QUANTITY + +If you publish printed copies of the Document numbering more than 100, +and the Document's license notice requires Cover Texts, you must enclose +the copies in covers that carry, clearly and legibly, all these Cover +Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on +the back cover. Both covers must also clearly and legibly identify +you as the publisher of these copies. The front cover must present +the full title with all words of the title equally prominent and +visible. 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In addition, you must do these things in the Modified Version: + +@enumerate A +@item +Use in the Title Page (and on the covers, if any) a title distinct +from that of the Document, and from those of previous versions +(which should, if there were any, be listed in the History section +of the Document). You may use the same title as a previous version +if the original publisher of that version gives permission. + +@item +List on the Title Page, as authors, one or more persons or entities +responsible for authorship of the modifications in the Modified +Version, together with at least five of the principal authors of the +Document (all of its principal authors, if it has less than five). + +@item +State on the Title page the name of the publisher of the +Modified Version, as the publisher. + +@item +Preserve all the copyright notices of the Document. + +@item +Add an appropriate copyright notice for your modifications +adjacent to the other copyright notices. + +@item +Include, immediately after the copyright notices, a license notice +giving the public permission to use the Modified Version under the +terms of this License, in the form shown in the Addendum below. + +@item +Preserve in that license notice the full lists of Invariant Sections +and required Cover Texts given in the Document's license notice. + +@item +Include an unaltered copy of this License. + +@item +Preserve the section entitled ``History'', and its title, and add to +it an item stating at least the title, year, new authors, and +publisher of the Modified Version as given on the Title Page. If +there is no section entitled ``History'' in the Document, create one +stating the title, year, authors, and publisher of the Document as +given on its Title Page, then add an item describing the Modified +Version as stated in the previous sentence. + +@item +Preserve the network location, if any, given in the Document for +public access to a Transparent copy of the Document, and likewise +the network locations given in the Document for previous versions +it was based on. These may be placed in the ``History'' section. +You may omit a network location for a work that was published at +least four years before the Document itself, or if the original +publisher of the version it refers to gives permission. + +@item +In any section entitled ``Acknowledgments'' or ``Dedications'', +preserve the section's title, and preserve in the section all the +substance and tone of each of the contributor acknowledgments +and/or dedications given therein. + +@item +Preserve all the Invariant Sections of the Document, +unaltered in their text and in their titles. Section numbers +or the equivalent are not considered part of the section titles. + +@item +Delete any section entitled ``Endorsements''. Such a section +may not be included in the Modified Version. + +@item +Do not retitle any existing section as ``Endorsements'' +or to conflict in title with any Invariant Section. +@end enumerate + +If the Modified Version includes new front-matter sections or +appendices that qualify as Secondary Sections and contain no material +copied from the Document, you may at your option designate some or all +of these sections as invariant. To do this, add their titles to the +list of Invariant Sections in the Modified Version's license notice. +These titles must be distinct from any other section titles. + +You may add a section entitled ``Endorsements'', provided it contains +nothing but endorsements of your Modified Version by various +parties---for example, statements of peer review or that the text has +been approved by an organization as the authoritative definition of a +standard. + +You may add a passage of up to five words as a Front-Cover Text, and a +passage of up to 25 words as a Back-Cover Text, to the end of the list +of Cover Texts in the Modified Version. Only one passage of +Front-Cover Text and one of Back-Cover Text may be added by (or +through arrangements made by) any one entity. If the Document already +includes a cover text for the same cover, previously added by you or +by arrangement made by the same entity you are acting on behalf of, +you may not add another; but you may replace the old one, on explicit +permission from the previous publisher that added the old one. + +The author(s) and publisher(s) of the Document do not by this License +give permission to use their names for publicity for or to assert or +imply endorsement of any Modified Version. + +@item +COMBINING DOCUMENTS + +You may combine the Document with other documents released under this +License, under the terms defined in section 4 above for modified +versions, provided that you include in the combination all of the +Invariant Sections of all of the original documents, unmodified, and +list them all as Invariant Sections of your combined work in its +license notice. + +The combined work need only contain one copy of this License, and +multiple identical Invariant Sections may be replaced with a single +copy. If there are multiple Invariant Sections with the same name but +different contents, make the title of each such section unique by +adding at the end of it, in parentheses, the name of the original +author or publisher of that section if known, or else a unique number. +Make the same adjustment to the section titles in the list of +Invariant Sections in the license notice of the combined work. + +In the combination, you must combine any sections entitled ``History'' +in the various original documents, forming one section entitled +``History''; likewise combine any sections entitled ``Acknowledgments'', +and any sections entitled ``Dedications''. You must delete all sections +entitled ``Endorsements.'' + +@item +COLLECTIONS OF DOCUMENTS + +You may make a collection consisting of the Document and other documents +released under this License, and replace the individual copies of this +License in the various documents with a single copy that is included in +the collection, provided that you follow the rules of this License for +verbatim copying of each of the documents in all other respects. + +You may extract a single document from such a collection, and distribute +it individually under this License, provided you insert a copy of this +License into the extracted document, and follow this License in all +other respects regarding verbatim copying of that document. + +@item +AGGREGATION WITH INDEPENDENT WORKS + +A compilation of the Document or its derivatives with other separate +and independent documents or works, in or on a volume of a storage or +distribution medium, does not as a whole count as a Modified Version +of the Document, provided no compilation copyright is claimed for the +compilation. Such a compilation is called an ``aggregate'', and this +License does not apply to the other self-contained works thus compiled +with the Document, on account of their being thus compiled, if they +are not themselves derivative works of the Document. + +If the Cover Text requirement of section 3 is applicable to these +copies of the Document, then if the Document is less than one quarter +of the entire aggregate, the Document's Cover Texts may be placed on +covers that surround only the Document within the aggregate. +Otherwise they must appear on covers around the whole aggregate. + +@item +TRANSLATION + +Translation is considered a kind of modification, so you may +distribute translations of the Document under the terms of section 4. +Replacing Invariant Sections with translations requires special +permission from their copyright holders, but you may include +translations of some or all Invariant Sections in addition to the +original versions of these Invariant Sections. You may include a +translation of this License provided that you also include the +original English version of this License. In case of a disagreement +between the translation and the original English version of this +License, the original English version will prevail. + +@item +TERMINATION + +You may not copy, modify, sublicense, or distribute the Document except +as expressly provided for under this License. Any other attempt to +copy, modify, sublicense or distribute the Document is void, and will +automatically terminate your rights under this License. However, +parties who have received copies, or rights, from you under this +License will not have their licenses terminated so long as such +parties remain in full compliance. + +@item +FUTURE REVISIONS OF THIS LICENSE + +The Free Software Foundation may publish new, revised versions +of the GNU Free Documentation License from time to time. Such new +versions will be similar in spirit to the present version, but may +differ in detail to address new problems or concerns. See +@uref{http://www.gnu.org/copyleft/}. + +Each version of the License is given a distinguishing version number. +If the Document specifies that a particular numbered version of this +License ``or any later version'' applies to it, you have the option of +following the terms and conditions either of that specified version or +of any later version that has been published (not as a draft) by the +Free Software Foundation. If the Document does not specify a version +number of this License, you may choose any version ever published (not +as a draft) by the Free Software Foundation. +@end enumerate + +@page +@unnumberedsec ADDENDUM: How to use this License for your documents + +To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and +license notices just after the title page: + +@smallexample +@group + Copyright (C) @var{year} @var{your name}. + Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.1 + or any later version published by the Free Software Foundation; + with the Invariant Sections being @var{list their titles}, with the + Front-Cover Texts being @var{list}, and with the Back-Cover Texts being @var{list}. + A copy of the license is included in the section entitled ``GNU + Free Documentation License''. +@end group +@end smallexample + +If you have no Invariant Sections, write ``with no Invariant Sections'' +instead of saying which ones are invariant. If you have no +Front-Cover Texts, write ``no Front-Cover Texts'' instead of +``Front-Cover Texts being @var{list}''; likewise for Back-Cover Texts. + +If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, +to permit their use in free software. + +@c Local Variables: +@c ispell-local-pdict: "ispell-dict" +@c End: + diff --git a/gcc/doc/gcc.1 b/gcc/doc/gcc.1 new file mode 100644 index 00000000000..98fbab9b659 --- /dev/null +++ b/gcc/doc/gcc.1 @@ -0,0 +1,8046 @@ +.\" Automatically generated by Pod::Man version 1.15 +.\" Sun May 20 12:45:49 2001 +.\" +.\" Standard preamble: +.\" ====================================================================== +.de Sh \" Subsection heading +.br +.if t .Sp +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Ip \" List item +.br +.ie \\n(.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R + +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. | will give a +.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used +.\" to do unbreakable dashes and therefore won't be available. \*(C` and +.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<> +.tr \(*W-|\(bv\*(Tr +.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' +.ie n \{\ +. ds -- \(*W- +. ds PI pi +. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch +. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch +. ds L" "" +. ds R" "" +. ds C` "" +. ds C' "" +'br\} +.el\{\ +. ds -- \|\(em\| +. ds PI \(*p +. ds L" `` +. ds R" '' +'br\} +.\" +.\" If the F register is turned on, we'll generate index entries on stderr +.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and +.\" index entries marked with X<> in POD. Of course, you'll have to process +.\" the output yourself in some meaningful fashion. +.if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. nr % 0 +. rr F +.\} +.\" +.\" For nroff, turn off justification. 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The ``overall options'' allow you to stop this +process at an intermediate stage. For example, the \fB\-c\fR option +says not to run the linker. Then the output consists of object files +output by the assembler. +.PP +Other options are passed on to one stage of processing. Some options +control the preprocessor and others the compiler itself. Yet other +options control the assembler and linker; most of these are not +documented here, since you rarely need to use any of them. +.PP +Most of the command line options that you can use with \s-1GCC\s0 are useful +for C programs; when an option is only useful with another language +(usually \*(C+), the explanation says so explicitly. If the description +for a particular option does not mention a source language, you can use +that option with all supported languages. +.PP +The \fBgcc\fR program accepts options and file names as operands. Many +options have multi-letter names; therefore multiple single-letter options +may \fInot\fR be grouped: \fB\-dr\fR is very different from \fB\-d\ \-r\fR. +.PP +You can mix options and other arguments. For the most part, the order +you use doesn't matter. Order does matter when you use several options +of the same kind; for example, if you specify \fB\-L\fR more than once, +the directories are searched in the order specified. +.PP +Many options have long names starting with \fB\-f\fR or with +\&\fB\-W\fR\-\-\-for example, \fB\-fforce-mem\fR, +\&\fB\-fstrength-reduce\fR, \fB\-Wformat\fR and so on. Most of +these have both positive and negative forms; the negative form of +\&\fB\-ffoo\fR would be \fB\-fno-foo\fR. This manual documents +only one of these two forms, whichever one is not the default. +.SH "OPTIONS" +.IX Header "OPTIONS" +.Sh "Option Summary" +.IX Subsection "Option Summary" +Here is a summary of all the options, grouped by type. Explanations are +in the following sections. +.Ip "\fIOverall Options\fR" 4 +.IX Item "Overall Options" +\&\fB\-c \-S \-E \-o\fR \fIfile\fR \fB\-pipe \-pass-exit-codes \-x\fR \fIlanguage\fR +\&\fB\-v \-\-target-help \-\-help\fR +.Ip "\fIC Language Options\fR" 4 +.IX Item "C Language Options" +\&\fB\-ansi \-std=\fR\fIstandard\fR \fB\-fno-asm \-fno-builtin +\&\-fhosted \-ffreestanding +\&\-trigraphs \-traditional \-traditional-cpp +\&\-fallow-single-precision \-fcond-mismatch +\&\-fsigned-bitfields \-fsigned-char +\&\-funsigned-bitfields \-funsigned-char +\&\-fwritable-strings \-fshort-wchar\fR +.Ip "\fI\*(C+ Language Options\fR" 4 +.IX Item " Language Options" +\&\fB\-fno-access-control \-fcheck-new \-fconserve-space +\&\-fdollars-in-identifiers \-fno-elide-constructors +\&\-fno-enforce-eh-specs \-fexternal-templates +\&\-falt-external-templates +\&\-ffor-scope \-fno-for-scope \-fno-gnu-keywords \-fhonor-std +\&\-fhuge-objects \-fno-implicit-templates +\&\-fno-implicit-inline-templates +\&\-fno-implement-inlines \-fms-extensions +\&\-fno-operator-names +\&\-fno-optional-diags \-fpermissive +\&\-frepo \-fno-rtti \-ftemplate-depth-\fR\fIn\fR +\&\fB\-fuse-cxa-atexit \-fvtable-thunks \-nostdinc++ +\&\-fno-default-inline \-Wctor-dtor-privacy +\&\-Wnon-virtual-dtor \-Wreorder +\&\-Weffc++ \-Wno-deprecated +\&\-Wno-non-template-friend \-Wold-style-cast +\&\-Woverloaded-virtual \-Wno-pmf-conversions +\&\-Wsign-promo \-Wsynth\fR +.Ip "\fIObjective-C Language Options\fR" 4 +.IX Item "Objective-C Language Options" +\&\fB\-fconstant-string-class=\fR\fIclass name\fR +\&\fB\-fgnu-runtime \-fnext-runtime \-gen-decls +\&\-Wno-protocol \-Wselector\fR +.Ip "\fILanguage Independent Options\fR" 4 +.IX Item "Language Independent Options" +\&\fB\-fmessage-length=\fR\fIn\fR +\&\fB\-fdiagnostics-show-location=\fR[\fBonce\fR|\fBevery-line\fR] +.Ip "\fIWarning Options\fR" 4 +.IX Item "Warning Options" +\&\fB\-fsyntax-only \-pedantic \-pedantic-errors +\&\-w \-W \-Wall \-Waggregate-return +\&\-Wcast-align \-Wcast-qual \-Wchar-subscripts \-Wcomment +\&\-Wconversion \-Wdisabled-optimization \-Werror +\&\-Wfloat-equal \-Wformat \-Wformat=2 +\&\-Wformat-nonliteral \-Wformat-security +\&\-Wid-clash-\fR\fIlen\fR \fB\-Wimplicit \-Wimplicit-int +\&\-Wimplicit-function-declaration +\&\-Werror-implicit-function-declaration +\&\-Wimport \-Winline +\&\-Wlarger-than-\fR\fIlen\fR \fB\-Wlong-long +\&\-Wmain \-Wmissing-braces \-Wmissing-declarations +\&\-Wmissing-format-attribute \-Wmissing-noreturn +\&\-Wmultichar \-Wno-format-extra-args \-Wno-format-y2k +\&\-Wno-import \-Wpacked \-Wpadded +\&\-Wparentheses \-Wpointer-arith \-Wredundant-decls +\&\-Wreturn-type \-Wsequence-point \-Wshadow +\&\-Wsign-compare \-Wswitch \-Wsystem-headers +\&\-Wtrigraphs \-Wundef \-Wuninitialized +\&\-Wunknown-pragmas \-Wunreachable-code +\&\-Wunused \-Wunused-function \-Wunused-label \-Wunused-parameter +\&\-Wunused-value \-Wunused-variable \-Wwrite-strings\fR +.Ip "\fIC-only Warning Options\fR" 4 +.IX Item "C-only Warning Options" +\&\fB\-Wbad-function-cast \-Wmissing-prototypes \-Wnested-externs +\&\-Wstrict-prototypes \-Wtraditional\fR +.Ip "\fIDebugging Options\fR" 4 +.IX Item "Debugging Options" +\&\fB\-a \-ax \-d\fR\fIletters\fR \fB\-dumpspecs \-dumpmachine \-dumpversion +\&\-fdump-unnumbered \-fdump-translation-unit=\fR\fIfile\fR +\&\fB\-fdump-class-layout=\fR\fIfile\fR \fB\-fmem-report \-fpretend-float +\&\-fprofile-arcs \-ftest-coverage \-ftime-report +\&\-g \-g\fR\fIlevel\fR \fB\-gcoff \-gdwarf \-gdwarf-1 \-gdwarf-1+ \-gdwarf-2 +\&\-ggdb \-gstabs \-gstabs+ \-gxcoff \-gxcoff+ +\&\-p \-pg \-print-file-name=\fR\fIlibrary\fR \fB\-print-libgcc-file-name +\&\-print-prog-name=\fR\fIprogram\fR \fB\-print-search-dirs \-Q +\&\-save-temps \-time\fR +.Ip "\fIOptimization Options\fR" 4 +.IX Item "Optimization Options" +\&\fB\-falign-functions=\fR\fIn\fR \fB\-falign-jumps=\fR\fIn\fR +\&\fB\-falign-labels=\fR\fIn\fR \fB\-falign-loops=\fR\fIn\fR +\&\fB\-fbranch-probabilities \-fcaller-saves +\&\-fcse-follow-jumps \-fcse-skip-blocks \-fdata-sections \-fdce +\&\-fdelayed-branch \-fdelete-null-pointer-checks +\&\-fexpensive-optimizations \-ffast-math \-ffloat-store +\&\-fforce-addr \-fforce-mem \-ffunction-sections \-fgcse \-fgcse-lm \-fgcse-sm +\&\-finline-functions \-finline-limit=\fR\fIn\fR \fB\-fkeep-inline-functions +\&\-fkeep-static-consts \-fmove-all-movables +\&\-fno-default-inline \-fno-defer-pop +\&\-fno-function-cse \-fno-guess-branch-probability +\&\-fno-inline \-fno-math-errno \-fno-peephole +\&\-funsafe-math-optimizations \-fno-trapping-math +\&\-fomit-frame-pointer \-foptimize-register-move +\&\-foptimize-sibling-calls \-freduce-all-givs +\&\-fregmove \-frename-registers +\&\-frerun-cse-after-loop \-frerun-loop-opt +\&\-fschedule-insns \-fschedule-insns2 +\&\-fsingle-precision-constant \-fssa +\&\-fstrength-reduce \-fstrict-aliasing \-fthread-jumps \-ftrapv +\&\-funroll-all-loops \-funroll-loops +\&\-\-param\fR \fIname\fR\fB=\fR\fIvalue\fR +\&\fB\-O \-O0 \-O1 \-O2 \-O3 \-Os\fR +.Ip "\fIPreprocessor Options\fR" 4 +.IX Item "Preprocessor Options" +\&\fB\-$ \-A\fR\fIquestion\fR\fB=\fR\fIanswer\fR \fB\-A-\fR\fIquestion\fR[\fB=\fR\fIanswer\fR] +\&\fB\-C \-dD \-dI \-dM \-dN +\&\-D\fR\fImacro\fR[\fB=\fR\fIdefn\fR] \fB\-E \-H +\&\-idirafter\fR \fIdir\fR +\&\fB\-include\fR \fIfile\fR \fB\-imacros\fR \fIfile\fR +\&\fB\-iprefix\fR \fIfile\fR \fB\-iwithprefix\fR \fIdir\fR +\&\fB\-iwithprefixbefore\fR \fIdir\fR \fB\-isystem\fR \fIdir\fR \fB\-isystem-c++\fR \fIdir\fR +\&\fB\-M \-MM \-MF \-MG \-MP \-MQ \-MT \-nostdinc \-P \-remap +\&\-trigraphs \-undef \-U\fR\fImacro\fR \fB\-Wp,\fR\fIoption\fR +.Ip "\fIAssembler Option\fR" 4 +.IX Item "Assembler Option" +\&\fB\-Wa,\fR\fIoption\fR +.Ip "\fILinker Options\fR" 4 +.IX Item "Linker Options" +\&\fB +\&\fR\fIobject-file-name\fR \fB\-l\fR\fIlibrary\fR +\&\fB\-nostartfiles \-nodefaultlibs \-nostdlib +\&\-s \-static \-static-libgcc \-shared \-shared-libgcc \-symbolic +\&\-Wl,\fR\fIoption\fR \fB\-Xlinker\fR \fIoption\fR +\&\fB\-u\fR \fIsymbol\fR +.Ip "\fIDirectory Options\fR" 4 +.IX Item "Directory Options" +\&\fB\-B\fR\fIprefix\fR \fB\-I\fR\fIdir\fR \fB\-I- \-L\fR\fIdir\fR \fB\-specs=\fR\fIfile\fR +.Ip "\fITarget Options\fR" 4 +.IX Item "Target Options" +\&\fB\-b\fR \fImachine\fR \fB\-V\fR \fIversion\fR +.Ip "\fIMachine Dependent Options\fR" 4 +.IX Item "Machine Dependent Options" +\&\fIM680x0 Options\fR +.Sp +\&\fB\-m68000 \-m68020 \-m68020\-40 \-m68020\-60 \-m68030 \-m68040 +\&\-m68060 \-mcpu32 \-m5200 \-m68881 \-mbitfield \-mc68000 \-mc68020 +\&\-mfpa \-mnobitfield \-mrtd \-mshort \-msoft-float \-mpcrel +\&\-malign-int \-mstrict-align\fR +.Sp +\&\fIM68hc1x Options\fR +.Sp +\&\fB\-m6811 \-m6812 \-m68hc11 \-m68hc12 +\&\-mauto-incdec \-mshort \-msoft-reg-count=\fR\fIcount\fR +.Sp +\&\fI\s-1VAX\s0 Options\fR +.Sp +\&\fB\-mg \-mgnu \-munix\fR +.Sp +\&\fI\s-1SPARC\s0 Options\fR +.Sp +\&\fB\-mcpu=\fR\fIcpu type\fR +\&\fB\-mtune=\fR\fIcpu type\fR +\&\fB\-mcmodel=\fR\fIcode model\fR +\&\fB\-m32 \-m64 +\&\-mapp-regs \-mbroken-saverestore \-mcypress +\&\-mepilogue \-mfaster-structs \-mflat +\&\-mfpu \-mhard-float \-mhard-quad-float +\&\-mimpure-text \-mlive-g0 \-mno-app-regs +\&\-mno-epilogue \-mno-faster-structs \-mno-flat \-mno-fpu +\&\-mno-impure-text \-mno-stack-bias \-mno-unaligned-doubles +\&\-msoft-float \-msoft-quad-float \-msparclite \-mstack-bias +\&\-msupersparc \-munaligned-doubles \-mv8\fR +.Sp +\&\fIConvex Options\fR +.Sp +\&\fB\-mc1 \-mc2 \-mc32 \-mc34 \-mc38 +\&\-margcount \-mnoargcount +\&\-mlong32 \-mlong64 +\&\-mvolatile-cache \-mvolatile-nocache\fR +.Sp +\&\fI\s-1AMD29K\s0 Options\fR +.Sp +\&\fB\-m29000 \-m29050 \-mbw \-mnbw \-mdw \-mndw +\&\-mlarge \-mnormal \-msmall +\&\-mkernel-registers \-mno-reuse-arg-regs +\&\-mno-stack-check \-mno-storem-bug +\&\-mreuse-arg-regs \-msoft-float \-mstack-check +\&\-mstorem-bug \-muser-registers\fR +.Sp +\&\fI\s-1ARM\s0 Options\fR +.Sp +\&\fB\-mapcs-frame \-mno-apcs-frame +\&\-mapcs-26 \-mapcs-32 +\&\-mapcs-stack-check \-mno-apcs-stack-check +\&\-mapcs-float \-mno-apcs-float +\&\-mapcs-reentrant \-mno-apcs-reentrant +\&\-msched-prolog \-mno-sched-prolog +\&\-mlittle-endian \-mbig-endian \-mwords-little-endian +\&\-malignment-traps \-mno-alignment-traps +\&\-msoft-float \-mhard-float \-mfpe +\&\-mthumb-interwork \-mno-thumb-interwork +\&\-mcpu= \-march= \-mfpe= +\&\-mstructure-size-boundary= +\&\-mbsd \-mxopen \-mno-symrename +\&\-mabort-on-noreturn +\&\-mlong-calls \-mno-long-calls +\&\-mnop-fun-dllimport \-mno-nop-fun-dllimport +\&\-msingle-pic-base \-mno-single-pic-base +\&\-mpic-register=\fR +.Sp +\&\fIThumb Options\fR +.Sp +\&\fB\-mtpcs-frame \-mno-tpcs-frame +\&\-mtpcs-leaf-frame \-mno-tpcs-leaf-frame +\&\-mlittle-endian \-mbig-endian +\&\-mthumb-interwork \-mno-thumb-interwork +\&\-mstructure-size-boundary= +\&\-mnop-fun-dllimport \-mno-nop-fun-dllimport +\&\-mcallee-super-interworking \-mno-callee-super-interworking +\&\-mcaller-super-interworking \-mno-caller-super-interworking +\&\-msingle-pic-base \-mno-single-pic-base +\&\-mpic-register=\fR +.Sp +\&\fI\s-1MN10200\s0 Options\fR +.Sp +\&\fB\-mrelax\fR +.Sp +\&\fI\s-1MN10300\s0 Options\fR +.Sp +\&\fB\-mmult-bug +\&\-mno-mult-bug +\&\-mam33 +\&\-mno-am33 +\&\-mrelax\fR +.Sp +\&\fIM32R/D Options\fR +.Sp +\&\fB\-mcode-model=\fR\fImodel type\fR \fB\-msdata=\fR\fIsdata type\fR +\&\fB\-G\fR \fInum\fR +.Sp +\&\fIM88K Options\fR +.Sp +\&\fB\-m88000 \-m88100 \-m88110 \-mbig-pic +\&\-mcheck-zero-division \-mhandle-large-shift +\&\-midentify-revision \-mno-check-zero-division +\&\-mno-ocs-debug-info \-mno-ocs-frame-position +\&\-mno-optimize-arg-area \-mno-serialize-volatile +\&\-mno-underscores \-mocs-debug-info +\&\-mocs-frame-position \-moptimize-arg-area +\&\-mserialize-volatile \-mshort-data-\fR\fInum\fR \fB\-msvr3 +\&\-msvr4 \-mtrap-large-shift \-muse-div-instruction +\&\-mversion-03.00 \-mwarn-passed-structs\fR +.Sp +\&\fI\s-1RS/6000\s0 and PowerPC Options\fR +.Sp +\&\fB\-mcpu=\fR\fIcpu type\fR +\&\fB\-mtune=\fR\fIcpu type\fR +\&\fB\-mpower \-mno-power \-mpower2 \-mno-power2 +\&\-mpowerpc \-mpowerpc64 \-mno-powerpc +\&\-mpowerpc-gpopt \-mno-powerpc-gpopt +\&\-mpowerpc-gfxopt \-mno-powerpc-gfxopt +\&\-mnew-mnemonics \-mold-mnemonics +\&\-mfull-toc \-mminimal-toc \-mno-fop-in-toc \-mno-sum-in-toc +\&\-m64 \-m32 \-mxl-call \-mno-xl-call \-mthreads \-mpe +\&\-msoft-float \-mhard-float \-mmultiple \-mno-multiple +\&\-mstring \-mno-string \-mupdate \-mno-update +\&\-mfused-madd \-mno-fused-madd \-mbit-align \-mno-bit-align +\&\-mstrict-align \-mno-strict-align \-mrelocatable +\&\-mno-relocatable \-mrelocatable-lib \-mno-relocatable-lib +\&\-mtoc \-mno-toc \-mlittle \-mlittle-endian \-mbig \-mbig-endian +\&\-mcall-aix \-mcall-sysv \-mprototype \-mno-prototype +\&\-msim \-mmvme \-mads \-myellowknife \-memb \-msdata +\&\-msdata=\fR\fIopt\fR \fB\-mvxworks \-G\fR \fInum\fR +.Sp +\&\fI\s-1RT\s0 Options\fR +.Sp +\&\fB\-mcall-lib-mul \-mfp-arg-in-fpregs \-mfp-arg-in-gregs +\&\-mfull-fp-blocks \-mhc-struct-return \-min-line-mul +\&\-mminimum-fp-blocks \-mnohc-struct-return\fR +.Sp +\&\fI\s-1MIPS\s0 Options\fR +.Sp +\&\fB\-mabicalls \-mcpu=\fR\fIcpu type\fR +\&\fB\-membedded-data \-muninit-const-in-rodata +\&\-membedded-pic \-mfp32 \-mfp64 \-mgas \-mgp32 \-mgp64 +\&\-mgpopt \-mhalf-pic \-mhard-float \-mint64 \-mips1 +\&\-mips2 \-mips3 \-mips4 \-mlong64 \-mlong32 \-mlong-calls \-mmemcpy +\&\-mmips-as \-mmips-tfile \-mno-abicalls +\&\-mno-embedded-data \-mno-uninit-const-in-rodata \-mno-embedded-pic +\&\-mno-gpopt \-mno-long-calls +\&\-mno-memcpy \-mno-mips-tfile \-mno-rnames \-mno-stats +\&\-mrnames \-msoft-float +\&\-m4650 \-msingle-float \-mmad +\&\-mstats \-EL \-EB \-G\fR \fInum\fR \fB\-nocpp +\&\-mabi=32 \-mabi=n32 \-mabi=64 \-mabi=eabi +\&\-mfix7000 \-mno-crt0\fR +.Sp +\&\fIi386 Options\fR +.Sp +\&\fB\-mcpu=\fR\fIcpu type\fR \fB\-march=\fR\fIcpu type\fR +\&\fB\-mintel-syntax \-mieee-fp \-mno-fancy-math-387 +\&\-mno-fp-ret-in-387 \-msoft-float \-msvr3\-shlib +\&\-mno-wide-multiply \-mrtd \-malign-double +\&\-mpreferred-stack-boundary=\fR\fInum\fR +\&\fB\-mthreads \-mno-align-stringops \-minline-all-stringops +\&\-mpush-args \-maccumulate-outgoing-args \-m128bit-long-double +\&\-m96bit-long-double \-mregparm=\fR\fInum\fR \fB\-momit-leaf-frame-pointer\fR +.Sp +\&\fI\s-1HPPA\s0 Options\fR +.Sp +\&\fB\-march=\fR\fIarchitecture type\fR +\&\fB\-mbig-switch \-mdisable-fpregs \-mdisable-indexing +\&\-mfast-indirect-calls \-mgas \-mjump-in-delay +\&\-mlong-load-store \-mno-big-switch \-mno-disable-fpregs +\&\-mno-disable-indexing \-mno-fast-indirect-calls \-mno-gas +\&\-mno-jump-in-delay \-mno-long-load-store +\&\-mno-portable-runtime \-mno-soft-float +\&\-mno-space-regs \-msoft-float \-mpa-risc-1\-0 +\&\-mpa-risc-1\-1 \-mpa-risc-2\-0 \-mportable-runtime +\&\-mschedule=\fR\fIcpu type\fR \fB\-mspace-regs\fR +.Sp +\&\fIIntel 960 Options\fR +.Sp +\&\fB\-m\fR\fIcpu type\fR \fB\-masm-compat \-mclean-linkage +\&\-mcode-align \-mcomplex-addr \-mleaf-procedures +\&\-mic-compat \-mic2.0\-compat \-mic3.0\-compat +\&\-mintel-asm \-mno-clean-linkage \-mno-code-align +\&\-mno-complex-addr \-mno-leaf-procedures +\&\-mno-old-align \-mno-strict-align \-mno-tail-call +\&\-mnumerics \-mold-align \-msoft-float \-mstrict-align +\&\-mtail-call\fR +.Sp +\&\fI\s-1DEC\s0 Alpha Options\fR +.Sp +\&\fB\-mfp-regs \-mno-fp-regs \-mno-soft-float \-msoft-float +\&\-malpha-as \-mgas +\&\-mieee \-mieee-with-inexact \-mieee-conformant +\&\-mfp-trap-mode=\fR\fImode\fR \fB\-mfp-rounding-mode=\fR\fImode\fR +\&\fB\-mtrap-precision=\fR\fImode\fR \fB\-mbuild-constants +\&\-mcpu=\fR\fIcpu type\fR +\&\fB\-mbwx \-mno-bwx \-mcix \-mno-cix \-mmax \-mno-max +\&\-mmemory-latency=\fR\fItime\fR +.Sp +\&\fIClipper Options\fR +.Sp +\&\fB\-mc300 \-mc400\fR +.Sp +\&\fIH8/300 Options\fR +.Sp +\&\fB\-mrelax \-mh \-ms \-mint32 \-malign-300\fR +.Sp +\&\fI\s-1SH\s0 Options\fR +.Sp +\&\fB\-m1 \-m2 \-m3 \-m3e +\&\-m4\-nofpu \-m4\-single-only \-m4\-single \-m4 +\&\-mb \-ml \-mdalign \-mrelax +\&\-mbigtable \-mfmovd \-mhitachi \-mnomacsave +\&\-misize \-mpadstruct \-mspace +\&\-mprefergot +\&\-musermode\fR +.Sp +\&\fISystem V Options\fR +.Sp +\&\fB\-Qy \-Qn \-YP,\fR\fIpaths\fR \fB\-Ym,\fR\fIdir\fR +.Sp +\&\fI\s-1ARC\s0 Options\fR +.Sp +\&\fB\-EB \-EL +\&\-mmangle-cpu \-mcpu=\fR\fIcpu\fR \fB\-mtext=\fR\fItext section\fR +\&\fB\-mdata=\fR\fIdata section\fR \fB\-mrodata=\fR\fIreadonly data section\fR +.Sp +\&\fITMS320C3x/C4x Options\fR +.Sp +\&\fB\-mcpu=\fR\fIcpu\fR \fB\-mbig \-msmall \-mregparm \-mmemparm +\&\-mfast-fix \-mmpyi \-mbk \-mti \-mdp-isr-reload +\&\-mrpts=\fR\fIcount\fR \fB\-mrptb \-mdb \-mloop-unsigned +\&\-mparallel-insns \-mparallel-mpy \-mpreserve-float\fR +.Sp +\&\fIV850 Options\fR +.Sp +\&\fB\-mlong-calls \-mno-long-calls \-mep \-mno-ep +\&\-mprolog-function \-mno-prolog-function \-mspace +\&\-mtda=\fR\fIn\fR \fB\-msda=\fR\fIn\fR \fB\-mzda=\fR\fIn\fR +\&\fB\-mv850 \-mbig-switch\fR +.Sp +\&\fI\s-1NS32K\s0 Options\fR +.Sp +\&\fB\-m32032 \-m32332 \-m32532 \-m32081 \-m32381 \-mmult-add \-mnomult-add +\&\-msoft-float \-mrtd \-mnortd \-mregparam \-mnoregparam \-msb \-mnosb +\&\-mbitfield \-mnobitfield \-mhimem \-mnohimem\fR +.Sp +\&\fI\s-1AVR\s0 Options\fR +.Sp +\&\fB\-mmcu=\fR\fImcu\fR \fB\-msize \-minit-stack=\fR\fIn\fR \fB\-mno-interrupts +\&\-mcall-prologues \-mno-tablejump \-mtiny-stack\fR +.Sp +\&\fIMCore Options\fR +.Sp +\&\fB\-mhardlit \-mno-hardlit \-mdiv \-mno-div \-mrelax-immediates +\&\-mno-relax-immediates \-mwide-bitfields \-mno-wide-bitfields +\&\-m4byte-functions \-mno-4byte-functions \-mcallgraph-data +\&\-mno-callgraph-data \-mslow-bytes \-mno-slow-bytes \-mno-lsim +\&\-mlittle-endian \-mbig-endian \-m210 \-m340 \-mstack-increment\fR +.Sp +\&\fI\s-1IA-64\s0 Options\fR +.Sp +\&\fB\-mbig-endian \-mlittle-endian \-mgnu-as \-mgnu-ld \-mno-pic +\&\-mvolatile-asm-stop \-mb-step \-mregister-names \-mno-sdata +\&\-mconstant-gp \-mauto-pic \-minline-divide-min-latency +\&\-minline-divide-max-throughput \-mno-dwarf2\-asm +\&\-mfixed-range=\fR\fIregister range\fR +.Ip "\fICode Generation Options\fR" 4 +.IX Item "Code Generation Options" +\&\fB\-fcall-saved-\fR\fIreg\fR \fB\-fcall-used-\fR\fIreg\fR +\&\fB\-fexceptions \-funwind-tables \-ffixed-\fR\fIreg\fR +\&\fB\-finhibit-size-directive \-finstrument-functions +\&\-fcheck-memory-usage \-fprefix-function-name +\&\-fno-common \-fno-ident \-fno-gnu-linker +\&\-fpcc-struct-return \-fpic \-fPIC +\&\-freg-struct-return \-fshared-data \-fshort-enums +\&\-fshort-double \-fvolatile \-fvolatile-global \-fvolatile-static +\&\-fverbose-asm \-fpack-struct \-fstack-check +\&\-fstack-limit-register=\fR\fIreg\fR \fB\-fstack-limit-symbol=\fR\fIsym\fR +\&\fB\-fargument-alias \-fargument-noalias +\&\-fargument-noalias-global +\&\-fleading-underscore\fR +.Sh "Options Controlling the Kind of Output" +.IX Subsection "Options Controlling the Kind of Output" +Compilation can involve up to four stages: preprocessing, compilation +proper, assembly and linking, always in that order. The first three +stages apply to an individual source file, and end by producing an +object file; linking combines all the object files (those newly +compiled, and those specified as input) into an executable file. +.PP +For any given input file, the file name suffix determines what kind of +compilation is done: +.Ip "\fIfile\fR\fB.c\fR" 4 +.IX Item "file.c" +C source code which must be preprocessed. +.Ip "\fIfile\fR\fB.i\fR" 4 +.IX Item "file.i" +C source code which should not be preprocessed. +.Ip "\fIfile\fR\fB.ii\fR" 4 +.IX Item "file.ii" +\&\*(C+ source code which should not be preprocessed. +.Ip "\fIfile\fR\fB.m\fR" 4 +.IX Item "file.m" +Objective-C source code. Note that you must link with the library +\&\fIlibobjc.a\fR to make an Objective-C program work. +.Ip "\fIfile\fR\fB.mi\fR" 4 +.IX Item "file.mi" +Objective-C source code which should not be preprocessed. +.Ip "\fIfile\fR\fB.h\fR" 4 +.IX Item "file.h" +C header file (not to be compiled or linked). +.Ip "\fIfile\fR\fB.cc\fR" 4 +.IX Item "file.cc" +.PD 0 +.Ip "\fIfile\fR\fB.cp\fR" 4 +.IX Item "file.cp" +.Ip "\fIfile\fR\fB.cxx\fR" 4 +.IX Item "file.cxx" +.Ip "\fIfile\fR\fB.cpp\fR" 4 +.IX Item "file.cpp" +.Ip "\fIfile\fR\fB.c++\fR" 4 +.IX Item "file.c++" +.Ip "\fIfile\fR\fB.C\fR" 4 +.IX Item "file.C" +.PD +\&\*(C+ source code which must be preprocessed. Note that in \fB.cxx\fR, +the last two letters must both be literally \fBx\fR. Likewise, +\&\fB.C\fR refers to a literal capital C. +.Ip "\fIfile\fR\fB.f\fR" 4 +.IX Item "file.f" +.PD 0 +.Ip "\fIfile\fR\fB.for\fR" 4 +.IX Item "file.for" +.Ip "\fIfile\fR\fB.FOR\fR" 4 +.IX Item "file.FOR" +.PD +Fortran source code which should not be preprocessed. +.Ip "\fIfile\fR\fB.F\fR" 4 +.IX Item "file.F" +.PD 0 +.Ip "\fIfile\fR\fB.fpp\fR" 4 +.IX Item "file.fpp" +.Ip "\fIfile\fR\fB.FPP\fR" 4 +.IX Item "file.FPP" +.PD +Fortran source code which must be preprocessed (with the traditional +preprocessor). +.Ip "\fIfile\fR\fB.r\fR" 4 +.IX Item "file.r" +Fortran source code which must be preprocessed with a \s-1RATFOR\s0 +preprocessor (not included with \s-1GCC\s0). +.Ip "\fIfile\fR\fB.ch\fR" 4 +.IX Item "file.ch" +.PD 0 +.Ip "\fIfile\fR\fB.chi\fR" 4 +.IX Item "file.chi" +.PD +\&\s-1CHILL\s0 source code (preprocessed with the traditional preprocessor). +.Ip "\fIfile\fR\fB.s\fR" 4 +.IX Item "file.s" +Assembler code. +.Ip "\fIfile\fR\fB.S\fR" 4 +.IX Item "file.S" +Assembler code which must be preprocessed. +.Ip "\fIother\fR" 4 +.IX Item "other" +An object file to be fed straight into linking. +Any file name with no recognized suffix is treated this way. +.PP +You can specify the input language explicitly with the \fB\-x\fR option: +.Ip "\fB\-x\fR \fIlanguage\fR" 4 +.IX Item "-x language" +Specify explicitly the \fIlanguage\fR for the following input files +(rather than letting the compiler choose a default based on the file +name suffix). This option applies to all following input files until +the next \fB\-x\fR option. Possible values for \fIlanguage\fR are: +.Sp +.Vb 6 +\& c c-header cpp-output +\& c++ c++-cpp-output +\& objective-c objc-cpp-output +\& assembler assembler-with-cpp +\& f77 f77-cpp-input ratfor +\& java chill +.Ve +.Ip "\fB\-x none\fR" 4 +.IX Item "-x none" +Turn off any specification of a language, so that subsequent files are +handled according to their file name suffixes (as they are if \fB\-x\fR +has not been used at all). +.Ip "\fB\-pass-exit-codes\fR" 4 +.IX Item "-pass-exit-codes" +Normally the \fBgcc\fR program will exit with the code of 1 if any +phase of the compiler returns a non-success return code. If you specify +\&\fB\-pass-exit-codes\fR, the \fBgcc\fR program will instead return with +numerically highest error produced by any phase that returned an error +indication. +.PP +If you only want some of the stages of compilation, you can use +\&\fB\-x\fR (or filename suffixes) to tell \fBgcc\fR where to start, and +one of the options \fB\-c\fR, \fB\-S\fR, or \fB\-E\fR to say where +\&\fBgcc\fR is to stop. Note that some combinations (for example, +\&\fB\-x cpp-output \-E\fR) instruct \fBgcc\fR to do nothing at all. +.Ip "\fB\-c\fR" 4 +.IX Item "-c" +Compile or assemble the source files, but do not link. The linking +stage simply is not done. The ultimate output is in the form of an +object file for each source file. +.Sp +By default, the object file name for a source file is made by replacing +the suffix \fB.c\fR, \fB.i\fR, \fB.s\fR, etc., with \fB.o\fR. +.Sp +Unrecognized input files, not requiring compilation or assembly, are +ignored. +.Ip "\fB\-S\fR" 4 +.IX Item "-S" +Stop after the stage of compilation proper; do not assemble. The output +is in the form of an assembler code file for each non-assembler input +file specified. +.Sp +By default, the assembler file name for a source file is made by +replacing the suffix \fB.c\fR, \fB.i\fR, etc., with \fB.s\fR. +.Sp +Input files that don't require compilation are ignored. +.Ip "\fB\-E\fR" 4 +.IX Item "-E" +Stop after the preprocessing stage; do not run the compiler proper. The +output is in the form of preprocessed source code, which is sent to the +standard output. +.Sp +Input files which don't require preprocessing are ignored. +.Ip "\fB\-o\fR \fIfile\fR" 4 +.IX Item "-o file" +Place output in file \fIfile\fR. This applies regardless to whatever +sort of output is being produced, whether it be an executable file, +an object file, an assembler file or preprocessed C code. +.Sp +Since only one output file can be specified, it does not make sense to +use \fB\-o\fR when compiling more than one input file, unless you are +producing an executable file as output. +.Sp +If \fB\-o\fR is not specified, the default is to put an executable file +in \fIa.out\fR, the object file for \fI\fIsource\fI.\fIsuffix\fI\fR in +\&\fI\fIsource\fI.o\fR, its assembler file in \fI\fIsource\fI.s\fR, and +all preprocessed C source on standard output. +.Ip "\fB\-v\fR" 4 +.IX Item "-v" +Print (on standard error output) the commands executed to run the stages +of compilation. Also print the version number of the compiler driver +program and of the preprocessor and the compiler proper. +.Ip "\fB\-pipe\fR" 4 +.IX Item "-pipe" +Use pipes rather than temporary files for communication between the +various stages of compilation. This fails to work on some systems where +the assembler is unable to read from a pipe; but the \s-1GNU\s0 assembler has +no trouble. +.Ip "\fB\*(--help\fR" 4 +.IX Item "help" +Print (on the standard output) a description of the command line options +understood by \fBgcc\fR. If the \fB\-v\fR option is also specified +then \fB\*(--help\fR will also be passed on to the various processes +invoked by \fBgcc\fR, so that they can display the command line options +they accept. If the \fB\-W\fR option is also specified then command +line options which have no documentation associated with them will also +be displayed. +.Ip "\fB\*(--target-help\fR" 4 +.IX Item "target-help" +Print (on the standard output) a description of target specific command +line options for each tool. +.Sh "Compiling \*(C+ Programs" +.IX Subsection "Compiling Programs" +\&\*(C+ source files conventionally use one of the suffixes \fB.C\fR, +\&\fB.cc\fR, \fB.cpp\fR, \fB.c++\fR, \fB.cp\fR, or \fB.cxx\fR; +preprocessed \*(C+ files use the suffix \fB.ii\fR. \s-1GCC\s0 recognizes +files with these names and compiles them as \*(C+ programs even if you +call the compiler the same way as for compiling C programs (usually with +the name \fBgcc\fR). +.PP +However, \*(C+ programs often require class libraries as well as a +compiler that understands the \*(C+ language\-\-\-and under some +circumstances, you might want to compile programs from standard input, +or otherwise without a suffix that flags them as \*(C+ programs. +\&\fBg++\fR is a program that calls \s-1GCC\s0 with the default language +set to \*(C+, and automatically specifies linking against the \*(C+ +library. On many systems, \fBg++\fR is also +installed with the name \fBc++\fR. +.PP +When you compile \*(C+ programs, you may specify many of the same +command-line options that you use for compiling programs in any +language; or command-line options meaningful for C and related +languages; or options that are meaningful only for \*(C+ programs. +.Sh "Options Controlling C Dialect" +.IX Subsection "Options Controlling C Dialect" +The following options control the dialect of C (or languages derived +from C, such as \*(C+ and Objective C) that the compiler accepts: +.Ip "\fB\-ansi\fR" 4 +.IX Item "-ansi" +In C mode, support all \s-1ISO\s0 C89 programs. In \*(C+ mode, +remove \s-1GNU\s0 extensions that conflict with \s-1ISO\s0 \*(C+. +.Sp +This turns off certain features of \s-1GCC\s0 that are incompatible with \s-1ISO\s0 +C (when compiling C code), or of standard \*(C+ (when compiling \*(C+ code), +such as the \f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`typeof\*(C'\fR keywords, and +predefined macros such as \f(CW\*(C`unix\*(C'\fR and \f(CW\*(C`vax\*(C'\fR that identify the +type of system you are using. It also enables the undesirable and +rarely used \s-1ISO\s0 trigraph feature. For the C compiler, +it disables recognition of \*(C+ style \fB//\fR comments as well as +the \f(CW\*(C`inline\*(C'\fR keyword. +.Sp +The alternate keywords \f(CW\*(C`_\|_asm_\|_\*(C'\fR, \f(CW\*(C`_\|_extension_\|_\*(C'\fR, +\&\f(CW\*(C`_\|_inline_\|_\*(C'\fR and \f(CW\*(C`_\|_typeof_\|_\*(C'\fR continue to work despite +\&\fB\-ansi\fR. You would not want to use them in an \s-1ISO\s0 C program, of +course, but it is useful to put them in header files that might be included +in compilations done with \fB\-ansi\fR. Alternate predefined macros +such as \f(CW\*(C`_\|_unix_\|_\*(C'\fR and \f(CW\*(C`_\|_vax_\|_\*(C'\fR are also available, with or +without \fB\-ansi\fR. +.Sp +The \fB\-ansi\fR option does not cause non-ISO programs to be +rejected gratuitously. For that, \fB\-pedantic\fR is required in +addition to \fB\-ansi\fR. +.Sp +The macro \f(CW\*(C`_\|_STRICT_ANSI_\|_\*(C'\fR is predefined when the \fB\-ansi\fR +option is used. Some header files may notice this macro and refrain +from declaring certain functions or defining certain macros that the +\&\s-1ISO\s0 standard doesn't call for; this is to avoid interfering with any +programs that might use these names for other things. +.Sp +Functions which would normally be builtin but do not have semantics +defined by \s-1ISO\s0 C (such as \f(CW\*(C`alloca\*(C'\fR and \f(CW\*(C`ffs\*(C'\fR) are not builtin +functions with \fB\-ansi\fR is used. +.Ip "\fB\-std=\fR" 4 +.IX Item "-std=" +Determine the language standard. A value for this option must be provided; +possible values are +.RS 4 +.Ip "\fBiso9899:1990\fR" 4 +.IX Item "iso9899:1990" +Same as \fB\-ansi\fR +.Ip "\fBiso9899:199409\fR" 4 +.IX Item "iso9899:199409" +\&\s-1ISO\s0 C as modified in amend. 1 +.Ip "\fBiso9899:1999\fR" 4 +.IX Item "iso9899:1999" +\&\s-1ISO\s0 C99. Note that this standard is not yet fully supported; see +<\fBhttp://gcc.gnu.org/c99status.html\fR> for more information. +.Ip "\fBc89\fR" 4 +.IX Item "c89" +same as \fB\-std=iso9899:1990\fR +.Ip "\fBc99\fR" 4 +.IX Item "c99" +same as \fB\-std=iso9899:1999\fR +.Ip "\fBgnu89\fR" 4 +.IX Item "gnu89" +default, iso9899:1990 + gnu extensions +.Ip "\fBgnu99\fR" 4 +.IX Item "gnu99" +iso9899:1999 + gnu extensions +.Ip "\fBiso9899:199x\fR" 4 +.IX Item "iso9899:199x" +same as \fB\-std=iso9899:1999\fR, deprecated +.Ip "\fBc9x\fR" 4 +.IX Item "c9x" +same as \fB\-std=iso9899:1999\fR, deprecated +.Ip "\fBgnu9x\fR" 4 +.IX Item "gnu9x" +same as \fB\-std=gnu99\fR, deprecated +.RE +.RS 4 +.Sp +Even when this option is not specified, you can still use some of the +features of newer standards in so far as they do not conflict with +previous C standards. For example, you may use \f(CW\*(C`_\|_restrict_\|_\*(C'\fR even +when \fB\-std=c99\fR is not specified. +.Sp +The \fB\-std\fR options specifying some version of \s-1ISO\s0 C have the same +effects as \fB\-ansi\fR, except that features that were not in \s-1ISO\s0 C89 +but are in the specified version (for example, \fB//\fR comments and +the \f(CW\*(C`inline\*(C'\fR keyword in \s-1ISO\s0 C99) are not disabled. +.RE +.Ip "\fB\-fno-asm\fR" 4 +.IX Item "-fno-asm" +Do not recognize \f(CW\*(C`asm\*(C'\fR, \f(CW\*(C`inline\*(C'\fR or \f(CW\*(C`typeof\*(C'\fR as a +keyword, so that code can use these words as identifiers. You can use +the keywords \f(CW\*(C`_\|_asm_\|_\*(C'\fR, \f(CW\*(C`_\|_inline_\|_\*(C'\fR and \f(CW\*(C`_\|_typeof_\|_\*(C'\fR +instead. \fB\-ansi\fR implies \fB\-fno-asm\fR. +.Sp +In \*(C+, this switch only affects the \f(CW\*(C`typeof\*(C'\fR keyword, since +\&\f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`inline\*(C'\fR are standard keywords. You may want to +use the \fB\-fno-gnu-keywords\fR flag instead, which has the same +effect. In C99 mode (\fB\-std=c99\fR or \fB\-std=gnu99\fR), this +switch only affects the \f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`typeof\*(C'\fR keywords, since +\&\f(CW\*(C`inline\*(C'\fR is a standard keyword in \s-1ISO\s0 C99. +.Ip "\fB\-fno-builtin\fR" 4 +.IX Item "-fno-builtin" +Don't recognize builtin functions that do not begin with +\&\fB_\|_builtin_\fR as prefix. +.Sp +\&\s-1GCC\s0 normally generates special code to handle certain builtin functions +more efficiently; for instance, calls to \f(CW\*(C`alloca\*(C'\fR may become single +instructions that adjust the stack directly, and calls to \f(CW\*(C`memcpy\*(C'\fR +may become inline copy loops. The resulting code is often both smaller +and faster, but since the function calls no longer appear as such, you +cannot set a breakpoint on those calls, nor can you change the behavior +of the functions by linking with a different library. +.Ip "\fB\-fhosted\fR" 4 +.IX Item "-fhosted" +Assert that compilation takes place in a hosted environment. This implies +\&\fB\-fbuiltin\fR. A hosted environment is one in which the +entire standard library is available, and in which \f(CW\*(C`main\*(C'\fR has a return +type of \f(CW\*(C`int\*(C'\fR. Examples are nearly everything except a kernel. +This is equivalent to \fB\-fno-freestanding\fR. +.Ip "\fB\-ffreestanding\fR" 4 +.IX Item "-ffreestanding" +Assert that compilation takes place in a freestanding environment. This +implies \fB\-fno-builtin\fR. A freestanding environment +is one in which the standard library may not exist, and program startup may +not necessarily be at \f(CW\*(C`main\*(C'\fR. The most obvious example is an \s-1OS\s0 kernel. +This is equivalent to \fB\-fno-hosted\fR. +.Ip "\fB\-trigraphs\fR" 4 +.IX Item "-trigraphs" +Support \s-1ISO\s0 C trigraphs. You don't want to know about this +brain-damage. The \fB\-ansi\fR option (and \fB\-std\fR options for +strict \s-1ISO\s0 C conformance) implies \fB\-trigraphs\fR. +.Ip "\fB\-traditional\fR" 4 +.IX Item "-traditional" +Attempt to support some aspects of traditional C compilers. +Specifically: +.RS 4 +.Ip "\(bu" 4 +All \f(CW\*(C`extern\*(C'\fR declarations take effect globally even if they +are written inside of a function definition. This includes implicit +declarations of functions. +.Ip "\(bu" 4 +The newer keywords \f(CW\*(C`typeof\*(C'\fR, \f(CW\*(C`inline\*(C'\fR, \f(CW\*(C`signed\*(C'\fR, \f(CW\*(C`const\*(C'\fR +and \f(CW\*(C`volatile\*(C'\fR are not recognized. (You can still use the +alternative keywords such as \f(CW\*(C`_\|_typeof_\|_\*(C'\fR, \f(CW\*(C`_\|_inline_\|_\*(C'\fR, and +so on.) +.Ip "\(bu" 4 +Comparisons between pointers and integers are always allowed. +.Ip "\(bu" 4 +Integer types \f(CW\*(C`unsigned short\*(C'\fR and \f(CW\*(C`unsigned char\*(C'\fR promote +to \f(CW\*(C`unsigned int\*(C'\fR. +.Ip "\(bu" 4 +Out-of-range floating point literals are not an error. +.Ip "\(bu" 4 +Certain constructs which \s-1ISO\s0 regards as a single invalid preprocessing +number, such as \fB0xe-0xd\fR, are treated as expressions instead. +.Ip "\(bu" 4 +String ``constants'' are not necessarily constant; they are stored in +writable space, and identical looking constants are allocated +separately. (This is the same as the effect of +\&\fB\-fwritable-strings\fR.) +.Ip "\(bu" 4 +All automatic variables not declared \f(CW\*(C`register\*(C'\fR are preserved by +\&\f(CW\*(C`longjmp\*(C'\fR. Ordinarily, \s-1GNU\s0 C follows \s-1ISO\s0 C: automatic variables +not declared \f(CW\*(C`volatile\*(C'\fR may be clobbered. +.Ip "\(bu" 4 +The character escape sequences \fB\ex\fR and \fB\ea\fR evaluate as the +literal characters \fBx\fR and \fBa\fR respectively. Without +\&\fB\-traditional\fR, \fB\ex\fR is a prefix for the hexadecimal +representation of a character, and \fB\ea\fR produces a bell. +.RE +.RS 4 +.Sp +You may wish to use \fB\-fno-builtin\fR as well as \fB\-traditional\fR +if your program uses names that are normally \s-1GNU\s0 C builtin functions for +other purposes of its own. +.Sp +You cannot use \fB\-traditional\fR if you include any header files that +rely on \s-1ISO\s0 C features. Some vendors are starting to ship systems with +\&\s-1ISO\s0 C header files and you cannot use \fB\-traditional\fR on such +systems to compile files that include any system headers. +.Sp +The \fB\-traditional\fR option also enables \fB\-traditional-cpp\fR, +which is described next. +.RE +.Ip "\fB\-traditional-cpp\fR" 4 +.IX Item "-traditional-cpp" +Attempt to support some aspects of traditional C preprocessors. +Specifically: +.RS 4 +.Ip "\(bu" 4 +Comments convert to nothing at all, rather than to a space. This allows +traditional token concatenation. +.Ip "\(bu" 4 +In a preprocessing directive, the \fB#\fR symbol must appear as the first +character of a line. +.Ip "\(bu" 4 +Macro arguments are recognized within string constants in a macro +definition (and their values are stringified, though without additional +quote marks, when they appear in such a context). The preprocessor +always considers a string constant to end at a newline. +.Ip "\(bu" 4 +The predefined macro \f(CW\*(C`_\|_STDC_\|_\*(C'\fR is not defined when you use +\&\fB\-traditional\fR, but \f(CW\*(C`_\|_GNUC_\|_\*(C'\fR is (since the \s-1GNU\s0 extensions +which \f(CW\*(C`_\|_GNUC_\|_\*(C'\fR indicates are not affected by +\&\fB\-traditional\fR). If you need to write header files that work +differently depending on whether \fB\-traditional\fR is in use, by +testing both of these predefined macros you can distinguish four +situations: \s-1GNU\s0 C, traditional \s-1GNU\s0 C, other \s-1ISO\s0 C compilers, and other +old C compilers. The predefined macro \f(CW\*(C`_\|_STDC_VERSION_\|_\*(C'\fR is also +not defined when you use \fB\-traditional\fR. +.Ip "\(bu" 4 +The preprocessor considers a string constant to end at a newline (unless +the newline is escaped with \fB\e\fR). (Without \fB\-traditional\fR, +string constants can contain the newline character as typed.) +.RE +.RS 4 +.RE +.Ip "\fB\-fcond-mismatch\fR" 4 +.IX Item "-fcond-mismatch" +Allow conditional expressions with mismatched types in the second and +third arguments. The value of such an expression is void. This option +is not supported for \*(C+. +.Ip "\fB\-funsigned-char\fR" 4 +.IX Item "-funsigned-char" +Let the type \f(CW\*(C`char\*(C'\fR be unsigned, like \f(CW\*(C`unsigned char\*(C'\fR. +.Sp +Each kind of machine has a default for what \f(CW\*(C`char\*(C'\fR should +be. It is either like \f(CW\*(C`unsigned char\*(C'\fR by default or like +\&\f(CW\*(C`signed char\*(C'\fR by default. +.Sp +Ideally, a portable program should always use \f(CW\*(C`signed char\*(C'\fR or +\&\f(CW\*(C`unsigned char\*(C'\fR when it depends on the signedness of an object. +But many programs have been written to use plain \f(CW\*(C`char\*(C'\fR and +expect it to be signed, or expect it to be unsigned, depending on the +machines they were written for. This option, and its inverse, let you +make such a program work with the opposite default. +.Sp +The type \f(CW\*(C`char\*(C'\fR is always a distinct type from each of +\&\f(CW\*(C`signed char\*(C'\fR or \f(CW\*(C`unsigned char\*(C'\fR, even though its behavior +is always just like one of those two. +.Ip "\fB\-fsigned-char\fR" 4 +.IX Item "-fsigned-char" +Let the type \f(CW\*(C`char\*(C'\fR be signed, like \f(CW\*(C`signed char\*(C'\fR. +.Sp +Note that this is equivalent to \fB\-fno-unsigned-char\fR, which is +the negative form of \fB\-funsigned-char\fR. Likewise, the option +\&\fB\-fno-signed-char\fR is equivalent to \fB\-funsigned-char\fR. +.Sp +You may wish to use \fB\-fno-builtin\fR as well as \fB\-traditional\fR +if your program uses names that are normally \s-1GNU\s0 C builtin functions for +other purposes of its own. +.Sp +You cannot use \fB\-traditional\fR if you include any header files that +rely on \s-1ISO\s0 C features. Some vendors are starting to ship systems with +\&\s-1ISO\s0 C header files and you cannot use \fB\-traditional\fR on such +systems to compile files that include any system headers. +.Ip "\fB\-fsigned-bitfields\fR" 4 +.IX Item "-fsigned-bitfields" +.PD 0 +.Ip "\fB\-funsigned-bitfields\fR" 4 +.IX Item "-funsigned-bitfields" +.Ip "\fB\-fno-signed-bitfields\fR" 4 +.IX Item "-fno-signed-bitfields" +.Ip "\fB\-fno-unsigned-bitfields\fR" 4 +.IX Item "-fno-unsigned-bitfields" +.PD +These options control whether a bitfield is signed or unsigned, when the +declaration does not use either \f(CW\*(C`signed\*(C'\fR or \f(CW\*(C`unsigned\*(C'\fR. By +default, such a bitfield is signed, because this is consistent: the +basic integer types such as \f(CW\*(C`int\*(C'\fR are signed types. +.Sp +However, when \fB\-traditional\fR is used, bitfields are all unsigned +no matter what. +.Ip "\fB\-fwritable-strings\fR" 4 +.IX Item "-fwritable-strings" +Store string constants in the writable data segment and don't uniquize +them. This is for compatibility with old programs which assume they can +write into string constants. The option \fB\-traditional\fR also has +this effect. +.Sp +Writing into string constants is a very bad idea; ``constants'' should +be constant. +.Ip "\fB\-fallow-single-precision\fR" 4 +.IX Item "-fallow-single-precision" +Do not promote single precision math operations to double precision, +even when compiling with \fB\-traditional\fR. +.Sp +Traditional K&R C promotes all floating point operations to double +precision, regardless of the sizes of the operands. On the +architecture for which you are compiling, single precision may be faster +than double precision. If you must use \fB\-traditional\fR, but want +to use single precision operations when the operands are single +precision, use this option. This option has no effect when compiling +with \s-1ISO\s0 or \s-1GNU\s0 C conventions (the default). +.Ip "\fB\-fshort-wchar\fR" 4 +.IX Item "-fshort-wchar" +Override the underlying type for \fBwchar_t\fR to be \fBshort +unsigned int\fR instead of the default for the target. This option is +useful for building programs to run under \s-1WINE\s0. +.Sh "Options Controlling \*(C+ Dialect" +.IX Subsection "Options Controlling Dialect" +This section describes the command-line options that are only meaningful +for \*(C+ programs; but you can also use most of the \s-1GNU\s0 compiler options +regardless of what language your program is in. For example, you +might compile a file \f(CW\*(C`firstClass.C\*(C'\fR like this: +.PP +.Vb 1 +\& g++ -g -frepo -O -c firstClass.C +.Ve +In this example, only \fB\-frepo\fR is an option meant +only for \*(C+ programs; you can use the other options with any +language supported by \s-1GCC\s0. +.PP +Here is a list of options that are \fIonly\fR for compiling \*(C+ programs: +.Ip "\fB\-fno-access-control\fR" 4 +.IX Item "-fno-access-control" +Turn off all access checking. This switch is mainly useful for working +around bugs in the access control code. +.Ip "\fB\-fcheck-new\fR" 4 +.IX Item "-fcheck-new" +Check that the pointer returned by \f(CW\*(C`operator new\*(C'\fR is non-null +before attempting to modify the storage allocated. The current Working +Paper requires that \f(CW\*(C`operator new\*(C'\fR never return a null pointer, so +this check is normally unnecessary. +.Sp +An alternative to using this option is to specify that your +\&\f(CW\*(C`operator new\*(C'\fR does not throw any exceptions; if you declare it +\&\fB\f(BIthrow()\fB\fR, g++ will check the return value. See also \fBnew +(nothrow)\fR. +.Ip "\fB\-fconserve-space\fR" 4 +.IX Item "-fconserve-space" +Put uninitialized or runtime-initialized global variables into the +common segment, as C does. This saves space in the executable at the +cost of not diagnosing duplicate definitions. If you compile with this +flag and your program mysteriously crashes after \f(CW\*(C`main()\*(C'\fR has +completed, you may have an object that is being destroyed twice because +two definitions were merged. +.Sp +This option is no longer useful on most targets, now that support has +been added for putting variables into \s-1BSS\s0 without making them common. +.Ip "\fB\-fno-const-strings\fR" 4 +.IX Item "-fno-const-strings" +Give string constants type \f(CW\*(C`char *\*(C'\fR instead of type \f(CW\*(C`const +char *\*(C'\fR. By default, G++ uses type \f(CW\*(C`const char *\*(C'\fR as required by +the standard. Even if you use \fB\-fno-const-strings\fR, you cannot +actually modify the value of a string constant, unless you also use +\&\fB\-fwritable-strings\fR. +.Sp +This option might be removed in a future release of G++. For maximum +portability, you should structure your code so that it works with +string constants that have type \f(CW\*(C`const char *\*(C'\fR. +.Ip "\fB\-fdollars-in-identifiers\fR" 4 +.IX Item "-fdollars-in-identifiers" +Accept \fB$\fR in identifiers. You can also explicitly prohibit use of +\&\fB$\fR with the option \fB\-fno-dollars-in-identifiers\fR. (\s-1GNU\s0 C allows +\&\fB$\fR by default on most target systems, but there are a few exceptions.) +Traditional C allowed the character \fB$\fR to form part of +identifiers. However, \s-1ISO\s0 C and \*(C+ forbid \fB$\fR in identifiers. +.Ip "\fB\-fno-elide-constructors\fR" 4 +.IX Item "-fno-elide-constructors" +The \*(C+ standard allows an implementation to omit creating a temporary +which is only used to initialize another object of the same type. +Specifying this option disables that optimization, and forces g++ to +call the copy constructor in all cases. +.Ip "\fB\-fno-enforce-eh-specs\fR" 4 +.IX Item "-fno-enforce-eh-specs" +Don't check for violation of exception specifications at runtime. This +option violates the \*(C+ standard, but may be useful for reducing code +size in production builds, much like defining \fB\s-1NDEBUG\s0\fR. The compiler +will still optimize based on the exception specifications. +.Ip "\fB\-fexternal-templates\fR" 4 +.IX Item "-fexternal-templates" +Cause template instantiations to obey \fB#pragma interface\fR and +\&\fBimplementation\fR; template instances are emitted or not according +to the location of the template definition. +.Sp +This option is deprecated. +.Ip "\fB\-falt-external-templates\fR" 4 +.IX Item "-falt-external-templates" +Similar to \-fexternal-templates, but template instances are emitted or +not according to the place where they are first instantiated. +.Sp +This option is deprecated. +.Ip "\fB\-ffor-scope\fR" 4 +.IX Item "-ffor-scope" +.PD 0 +.Ip "\fB\-fno-for-scope\fR" 4 +.IX Item "-fno-for-scope" +.PD +If \-ffor-scope is specified, the scope of variables declared in +a \fIfor-init-statement\fR is limited to the \fBfor\fR loop itself, +as specified by the \*(C+ standard. +If \-fno-for-scope is specified, the scope of variables declared in +a \fIfor-init-statement\fR extends to the end of the enclosing scope, +as was the case in old versions of gcc, and other (traditional) +implementations of \*(C+. +.Sp +The default if neither flag is given to follow the standard, +but to allow and give a warning for old-style code that would +otherwise be invalid, or have different behavior. +.Ip "\fB\-fno-gnu-keywords\fR" 4 +.IX Item "-fno-gnu-keywords" +Do not recognize \f(CW\*(C`typeof\*(C'\fR as a keyword, so that code can use this +word as an identifier. You can use the keyword \f(CW\*(C`_\|_typeof_\|_\*(C'\fR instead. +\&\fB\-ansi\fR implies \fB\-fno-gnu-keywords\fR. +.Ip "\fB\-fhonor-std\fR" 4 +.IX Item "-fhonor-std" +Treat the \f(CW\*(C`namespace std\*(C'\fR as a namespace, instead of ignoring +it. For compatibility with earlier versions of g++, the compiler will, +by default, ignore \f(CW\*(C`namespace\-declarations\*(C'\fR, +\&\f(CW\*(C`using\-declarations\*(C'\fR, \f(CW\*(C`using\-directives\*(C'\fR, and +\&\f(CW\*(C`namespace\-names\*(C'\fR, if they involve \f(CW\*(C`std\*(C'\fR. +.Ip "\fB\-fhuge-objects\fR" 4 +.IX Item "-fhuge-objects" +Support virtual function calls for objects that exceed the size +representable by a \fBshort int\fR. Users should not use this flag by +default; if you need to use it, the compiler will tell you so. +.Sp +This flag is not useful when compiling with \-fvtable-thunks. +.Sp +Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding +libgcc\fR must be built with the same setting of this option. +.Ip "\fB\-fno-implicit-templates\fR" 4 +.IX Item "-fno-implicit-templates" +Never emit code for non-inline templates which are instantiated +implicitly (i.e. by use); only emit code for explicit instantiations. +.Ip "\fB\-fno-implicit-inline-templates\fR" 4 +.IX Item "-fno-implicit-inline-templates" +Don't emit code for implicit instantiations of inline templates, either. +The default is to handle inlines differently so that compiles with and +without optimization will need the same set of explicit instantiations. +.Ip "\fB\-fno-implement-inlines\fR" 4 +.IX Item "-fno-implement-inlines" +To save space, do not emit out-of-line copies of inline functions +controlled by \fB#pragma implementation\fR. This will cause linker +errors if these functions are not inlined everywhere they are called. +.Ip "\fB\-fms-extensions\fR" 4 +.IX Item "-fms-extensions" +Disable pedantic warnings about constructs used in \s-1MFC\s0, such as implicit +int and getting a pointer to member function via non-standard syntax. +.Ip "\fB\-fno-nonansi-builtins\fR" 4 +.IX Item "-fno-nonansi-builtins" +Disable builtin declarations of functions that are not mandated by +\&\s-1ANSI/ISO\s0 C. These include \f(CW\*(C`ffs\*(C'\fR, \f(CW\*(C`alloca\*(C'\fR, \f(CW\*(C`_exit\*(C'\fR, +\&\f(CW\*(C`index\*(C'\fR, \f(CW\*(C`bzero\*(C'\fR, \f(CW\*(C`conjf\*(C'\fR, and other related functions. +.Ip "\fB\-fno-operator-names\fR" 4 +.IX Item "-fno-operator-names" +Do not treat the operator name keywords \f(CW\*(C`and\*(C'\fR, \f(CW\*(C`bitand\*(C'\fR, +\&\f(CW\*(C`bitor\*(C'\fR, \f(CW\*(C`compl\*(C'\fR, \f(CW\*(C`not\*(C'\fR, \f(CW\*(C`or\*(C'\fR and \f(CW\*(C`xor\*(C'\fR as +synonyms as keywords. +.Ip "\fB\-fno-optional-diags\fR" 4 +.IX Item "-fno-optional-diags" +Disable diagnostics that the standard says a compiler does not need to +issue. Currently, the only such diagnostic issued by g++ is the one for +a name having multiple meanings within a class. +.Ip "\fB\-fpermissive\fR" 4 +.IX Item "-fpermissive" +Downgrade messages about nonconformant code from errors to warnings. By +default, g++ effectively sets \fB\-pedantic-errors\fR without +\&\fB\-pedantic\fR; this option reverses that. This behavior and this +option are superseded by \fB\-pedantic\fR, which works as it does for \s-1GNU\s0 C. +.Ip "\fB\-frepo\fR" 4 +.IX Item "-frepo" +Enable automatic template instantiation. This option also implies +\&\fB\-fno-implicit-templates\fR. +.Ip "\fB\-fno-rtti\fR" 4 +.IX Item "-fno-rtti" +Disable generation of information about every class with virtual +functions for use by the \*(C+ runtime type identification features +(\fBdynamic_cast\fR and \fBtypeid\fR). If you don't use those parts +of the language, you can save some space by using this flag. Note that +exception handling uses the same information, but it will generate it as +needed. +.Ip "\fB\-fstats\fR" 4 +.IX Item "-fstats" +Emit statistics about front-end processing at the end of the compilation. +This information is generally only useful to the G++ development team. +.Ip "\fB\-ftemplate-depth-\fR\fIn\fR" 4 +.IX Item "-ftemplate-depth-n" +Set the maximum instantiation depth for template classes to \fIn\fR. +A limit on the template instantiation depth is needed to detect +endless recursions during template class instantiation. \s-1ANSI/ISO\s0 \*(C+ +conforming programs must not rely on a maximum depth greater than 17. +.Ip "\fB\-fuse-cxa-atexit\fR" 4 +.IX Item "-fuse-cxa-atexit" +Register destructors for objects with static storage duration with the +\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR function rather than the \f(CW\*(C`atexit\*(C'\fR function. +This option is required for fully standards-compliant handling of static +destructors, but will only work if your C library supports +\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR. +.Ip "\fB\-fvtable-thunks\fR" 4 +.IX Item "-fvtable-thunks" +Use \fBthunks\fR to implement the virtual function dispatch table +(\fBvtable\fR). The traditional (cfront-style) approach to +implementing vtables was to store a pointer to the function and two +offsets for adjusting the \fBthis\fR pointer at the call site. Newer +implementations store a single pointer to a \fBthunk\fR function which +does any necessary adjustment and then calls the target function. +.Sp +This option also enables a heuristic for controlling emission of +vtables; if a class has any non-inline virtual functions, the vtable +will be emitted in the translation unit containing the first one of +those. +.Sp +Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding +libgcc.a\fR must be built with the same setting of this option. +.Ip "\fB\-fno-weak\fR" 4 +.IX Item "-fno-weak" +Do not use weak symbol support, even if it is provied by the linker. +By default, G++ will use weak symbols if they are available. This +option exists only for testing, and should not be used by end-users; +it will result in inferior code and has no benefits. This option may +be removed in a future release of G++. +.Ip "\fB\-nostdinc++\fR" 4 +.IX Item "-nostdinc++" +Do not search for header files in the standard directories specific to +\&\*(C+, but do still search the other standard directories. (This option +is used when building the \*(C+ library.) +.PP +In addition, these optimization, warning, and code generation options +have meanings only for \*(C+ programs: +.Ip "\fB\-fno-default-inline\fR" 4 +.IX Item "-fno-default-inline" +Do not assume \fBinline\fR for functions defined inside a class scope. + Note that these +functions will have linkage like inline functions; they just won't be +inlined by default. +.Ip "\fB\-Wctor-dtor-privacy (\*(C+ only)\fR" 4 +.IX Item "-Wctor-dtor-privacy ( only)" +Warn when a class seems unusable, because all the constructors or +destructors in a class are private and the class has no friends or +public static member functions. +.Ip "\fB\-Wnon-virtual-dtor (\*(C+ only)\fR" 4 +.IX Item "-Wnon-virtual-dtor ( only)" +Warn when a class declares a non-virtual destructor that should probably +be virtual, because it looks like the class will be used polymorphically. +.Ip "\fB\-Wreorder (\*(C+ only)\fR" 4 +.IX Item "-Wreorder ( only)" +Warn when the order of member initializers given in the code does not +match the order in which they must be executed. For instance: +.Sp +.Vb 5 +\& struct A { +\& int i; +\& int j; +\& A(): j (0), i (1) { } +\& }; +.Ve +Here the compiler will warn that the member initializers for \fBi\fR +and \fBj\fR will be rearranged to match the declaration order of the +members. +.PP +The following \fB\-W...\fR options are not affected by \fB\-Wall\fR. +.Ip "\fB\-Weffc++ (\*(C+ only)\fR" 4 +.IX Item "-Weffc++ ( only)" +Warn about violations of various style guidelines from Scott Meyers' +\&\fIEffective \*(C+\fR books. If you use this option, you should be aware +that the standard library headers do not obey all of these guidelines; +you can use \fBgrep \-v\fR to filter out those warnings. +.Ip "\fB\-Wno-deprecated (\*(C+ only)\fR" 4 +.IX Item "-Wno-deprecated ( only)" +Do not warn about usage of deprecated features. +.Ip "\fB\-Wno-non-template-friend (\*(C+ only)\fR" 4 +.IX Item "-Wno-non-template-friend ( only)" +Disable warnings when non-templatized friend functions are declared +within a template. With the advent of explicit template specification +support in g++, if the name of the friend is an unqualified-id (ie, +\&\fBfriend foo(int)\fR), the \*(C+ language specification demands that the +friend declare or define an ordinary, nontemplate function. (Section +14.5.3). Before g++ implemented explicit specification, unqualified-ids +could be interpreted as a particular specialization of a templatized +function. Because this non-conforming behavior is no longer the default +behavior for g++, \fB\-Wnon-template-friend\fR allows the compiler to +check existing code for potential trouble spots, and is on by default. +This new compiler behavior can be turned off with +\&\fB\-Wno-non-template-friend\fR which keeps the conformant compiler code +but disables the helpful warning. +.Ip "\fB\-Wold-style-cast (\*(C+ only)\fR" 4 +.IX Item "-Wold-style-cast ( only)" +Warn if an old-style (C-style) cast is used within a \*(C+ program. The +new-style casts (\fBstatic_cast\fR, \fBreinterpret_cast\fR, and +\&\fBconst_cast\fR) are less vulnerable to unintended effects. +.Ip "\fB\-Woverloaded-virtual (\*(C+ only)\fR" 4 +.IX Item "-Woverloaded-virtual ( only)" +Warn when a function declaration hides virtual functions from a +base class. For example, in: +.Sp +.Vb 3 +\& struct A { +\& virtual void f(); +\& }; +.Ve +.Vb 3 +\& struct B: public A { +\& void f(int); +\& }; +.Ve +the \f(CW\*(C`A\*(C'\fR class version of \f(CW\*(C`f\*(C'\fR is hidden in \f(CW\*(C`B\*(C'\fR, and code +like this: +.Sp +.Vb 2 +\& B* b; +\& b->f(); +.Ve +will fail to compile. +.Ip "\fB\-Wno-pmf-conversions (\*(C+ only)\fR" 4 +.IX Item "-Wno-pmf-conversions ( only)" +Disable the diagnostic for converting a bound pointer to member function +to a plain pointer. +.Ip "\fB\-Wsign-promo (\*(C+ only)\fR" 4 +.IX Item "-Wsign-promo ( only)" +Warn when overload resolution chooses a promotion from unsigned or +enumeral type to a signed type over a conversion to an unsigned type of +the same size. Previous versions of g++ would try to preserve +unsignedness, but the standard mandates the current behavior. +.Ip "\fB\-Wsynth (\*(C+ only)\fR" 4 +.IX Item "-Wsynth ( only)" +Warn when g++'s synthesis behavior does not match that of cfront. For +instance: +.Sp +.Vb 4 +\& struct A { +\& operator int (); +\& A& operator = (int); +\& }; +.Ve +.Vb 5 +\& main () +\& { +\& A a,b; +\& a = b; +\& } +.Ve +In this example, g++ will synthesize a default \fBA& operator = +(const A&);\fR, while cfront will use the user-defined \fBoperator =\fR. +.Sh "Options Controlling Objective-C Dialect" +.IX Subsection "Options Controlling Objective-C Dialect" +This section describes the command-line options that are only meaningful +for Objective-C programs; but you can also use most of the \s-1GNU\s0 compiler +options regardless of what language your program is in. For example, +you might compile a file \f(CW\*(C`some_class.m\*(C'\fR like this: +.PP +.Vb 1 +\& gcc -g -fgnu-runtime -O -c some_class.m +.Ve +In this example, only \fB\-fgnu-runtime\fR is an option meant only for +Objective-C programs; you can use the other options with any language +supported by \s-1GCC\s0. +.PP +Here is a list of options that are \fIonly\fR for compiling Objective-C +programs: +.Ip "\fB\-fconstant-string-class=\fR\fIclass name\fR" 4 +.IX Item "-fconstant-string-class=class name" +Use \fIclass name\fR as the name of the class to instantiate for each +literal string specified with the syntax \f(CW\*(C`@"..."\*(C'\fR. The default +class name is \f(CW\*(C`NXConstantString\*(C'\fR. +.Ip "\fB\-fgnu-runtime\fR" 4 +.IX Item "-fgnu-runtime" +Generate object code compatible with the standard \s-1GNU\s0 Objective-C +runtime. This is the default for most types of systems. +.Ip "\fB\-fnext-runtime\fR" 4 +.IX Item "-fnext-runtime" +Generate output compatible with the NeXT runtime. This is the default +for NeXT-based systems, including Darwin and Mac \s-1OS\s0 X. +.Ip "\fB\-gen-decls\fR" 4 +.IX Item "-gen-decls" +Dump interface declarations for all classes seen in the source file to a +file named \fI\fIsourcename\fI.decl\fR. +.Ip "\fB\-Wno-protocol\fR" 4 +.IX Item "-Wno-protocol" +Do not warn if methods required by a protocol are not implemented +in the class adopting it. +.Ip "\fB\-Wselector\fR" 4 +.IX Item "-Wselector" +Warn if a selector has multiple methods of different types defined. +.Sh "Options to Control Diagnostic Messages Formatting" +.IX Subsection "Options to Control Diagnostic Messages Formatting" +Traditionally, diagnostic messages have been formatted irrespective of +the output device's aspect (e.g. its width, ...). The options described +below can be used to control the diagnostic messages formatting +algorithm, e.g. how many characters per line, how often source location +information should be reported. Right now, only the \*(C+ front-end can +honor these options. However it is expected, in the near future, that +the remaining front-ends would be able to digest them correctly. +.Ip "\fB\-fmessage-length=\fR\fIn\fR" 4 +.IX Item "-fmessage-length=n" +Try to format error messages so that they fit on lines of about \fIn\fR +characters. The default is 72 characters for g++ and 0 for the rest of +the front-ends supported by \s-1GCC\s0. If \fIn\fR is zero, then no +line-wrapping will be done; each error message will appear on a single +line. +.Ip "\fB\-fdiagnostics-show-location=once\fR" 4 +.IX Item "-fdiagnostics-show-location=once" +Only meaningful in line-wrapping mode. Instructs the diagnostic messages +reporter to emit \fIonce\fR source location information; that is, in +case the message is too long to fit on a single physical line and has to +be wrapped, the source location won't be emitted (as prefix) again, +over and over, in subsequent continuation lines. This is the default +behaviour. +.Ip "\fB\-fdiagnostics-show-location=every-line\fR" 4 +.IX Item "-fdiagnostics-show-location=every-line" +Only meaningful in line-wrapping mode. Instructs the diagnostic +messages reporter to emit the same source location information (as +prefix) for physical lines that result from the process of breaking a +a message which is too long to fit on a single line. +.Sh "Options to Request or Suppress Warnings" +.IX Subsection "Options to Request or Suppress Warnings" +Warnings are diagnostic messages that report constructions which +are not inherently erroneous but which are risky or suggest there +may have been an error. +.PP +You can request many specific warnings with options beginning \fB\-W\fR, +for example \fB\-Wimplicit\fR to request warnings on implicit +declarations. Each of these specific warning options also has a +negative form beginning \fB\-Wno-\fR to turn off warnings; +for example, \fB\-Wno-implicit\fR. This manual lists only one of the +two forms, whichever is not the default. +.PP +These options control the amount and kinds of warnings produced by \s-1GCC:\s0 +.Ip "\fB\-fsyntax-only\fR" 4 +.IX Item "-fsyntax-only" +Check the code for syntax errors, but don't do anything beyond that. +.Ip "\fB\-pedantic\fR" 4 +.IX Item "-pedantic" +Issue all the warnings demanded by strict \s-1ISO\s0 C and \s-1ISO\s0 \*(C+; +reject all programs that use forbidden extensions, and some other +programs that do not follow \s-1ISO\s0 C and \s-1ISO\s0 \*(C+. For \s-1ISO\s0 C, follows the +version of the \s-1ISO\s0 C standard specified by any \fB\-std\fR option used. +.Sp +Valid \s-1ISO\s0 C and \s-1ISO\s0 \*(C+ programs should compile properly with or without +this option (though a rare few will require \fB\-ansi\fR or a +\&\fB\-std\fR option specifying the required version of \s-1ISO\s0 C). However, +without this option, certain \s-1GNU\s0 extensions and traditional C and \*(C+ +features are supported as well. With this option, they are rejected. +.Sp +\&\fB\-pedantic\fR does not cause warning messages for use of the +alternate keywords whose names begin and end with \fB_\|_\fR. Pedantic +warnings are also disabled in the expression that follows +\&\f(CW\*(C`_\|_extension_\|_\*(C'\fR. However, only system header files should use +these escape routes; application programs should avoid them. +.Sp +Some users try to use \fB\-pedantic\fR to check programs for strict \s-1ISO\s0 +C conformance. They soon find that it does not do quite what they want: +it finds some non-ISO practices, but not all\-\-\-only those for which +\&\s-1ISO\s0 C \fIrequires\fR a diagnostic, and some others for which +diagnostics have been added. +.Sp +A feature to report any failure to conform to \s-1ISO\s0 C might be useful in +some instances, but would require considerable additional work and would +be quite different from \fB\-pedantic\fR. We don't have plans to +support such a feature in the near future. +.Sp +Where the standard specified with \fB\-std\fR represents a \s-1GNU\s0 +extended dialect of C, such as \fBgnu89\fR or \fBgnu99\fR, there is a +corresponding \fIbase standard\fR, the version of \s-1ISO\s0 C on which the \s-1GNU\s0 +extended dialect is based. Warnings from \fB\-pedantic\fR are given +where they are required by the base standard. (It would not make sense +for such warnings to be given only for features not in the specified \s-1GNU\s0 +C dialect, since by definition the \s-1GNU\s0 dialects of C include all +features the compiler supports with the given option, and there would be +nothing to warn about.) +.Ip "\fB\-pedantic-errors\fR" 4 +.IX Item "-pedantic-errors" +Like \fB\-pedantic\fR, except that errors are produced rather than +warnings. +.Ip "\fB\-w\fR" 4 +.IX Item "-w" +Inhibit all warning messages. +.Ip "\fB\-Wno-import\fR" 4 +.IX Item "-Wno-import" +Inhibit warning messages about the use of \fB#import\fR. +.Ip "\fB\-Wchar-subscripts\fR" 4 +.IX Item "-Wchar-subscripts" +Warn if an array subscript has type \f(CW\*(C`char\*(C'\fR. This is a common cause +of error, as programmers often forget that this type is signed on some +machines. +.Ip "\fB\-Wcomment\fR" 4 +.IX Item "-Wcomment" +Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR +comment, or whenever a Backslash-Newline appears in a \fB//\fR comment. +.Ip "\fB\-Wformat\fR" 4 +.IX Item "-Wformat" +Check calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR, etc., to make sure that +the arguments supplied have types appropriate to the format string +specified, and that the conversions specified in the format string make +sense. This includes standard functions, and others specified by format +attributes, in the \f(CW\*(C`printf\*(C'\fR, +\&\f(CW\*(C`scanf\*(C'\fR, \f(CW\*(C`strftime\*(C'\fR and \f(CW\*(C`strfmon\*(C'\fR (an X/Open extension, +not in the C standard) families. +.Sp +The formats are checked against the format features supported by \s-1GNU\s0 +libc version 2.2. These include all \s-1ISO\s0 C89 and C99 features, as well +as features from the Single Unix Specification and some \s-1BSD\s0 and \s-1GNU\s0 +extensions. Other library implementations may not support all these +features; \s-1GCC\s0 does not support warning about features that go beyond a +particular library's limitations. However, if \fB\-pedantic\fR is used +with \fB\-Wformat\fR, warnings will be given about format features not +in the selected standard version (but not for \f(CW\*(C`strfmon\*(C'\fR formats, +since those are not in any version of the C standard). +.Sp +\&\fB\-Wformat\fR is included in \fB\-Wall\fR. For more control over some +aspects of format checking, the options \fB\-Wno-format-y2k\fR, +\&\fB\-Wno-format-extra-args\fR, \fB\-Wformat-nonliteral\fR, +\&\fB\-Wformat-security\fR and \fB\-Wformat=2\fR are available, but are +not included in \fB\-Wall\fR. +.Ip "\fB\-Wno-format-y2k\fR" 4 +.IX Item "-Wno-format-y2k" +If \fB\-Wformat\fR is specified, do not warn about \f(CW\*(C`strftime\*(C'\fR +formats which may yield only a two-digit year. +.Ip "\fB\-Wno-format-extra-args\fR" 4 +.IX Item "-Wno-format-extra-args" +If \fB\-Wformat\fR is specified, do not warn about excess arguments to a +\&\f(CW\*(C`printf\*(C'\fR or \f(CW\*(C`scanf\*(C'\fR format function. The C standard specifies +that such arguments are ignored. +.Ip "\fB\-Wformat-nonliteral\fR" 4 +.IX Item "-Wformat-nonliteral" +If \fB\-Wformat\fR is specified, also warn if the format string is not a +string literal and so cannot be checked, unless the format function +takes its format arguments as a \f(CW\*(C`va_list\*(C'\fR. +.Ip "\fB\-Wformat-security\fR" 4 +.IX Item "-Wformat-security" +If \fB\-Wformat\fR is specified, also warn about uses of format +functions that represent possible security problems. At present, this +warns about calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR functions where the +format string is not a string literal and there are no format arguments, +as in \f(CW\*(C`printf (foo);\*(C'\fR. This may be a security hole if the format +string came from untrusted input and contains \fB%n\fR. (This is +currently a subset of what \fB\-Wformat-nonliteral\fR warns about, but +in future warnings may be added to \fB\-Wformat-security\fR that are not +included in \fB\-Wformat-nonliteral\fR.) +.Ip "\fB\-Wformat=2\fR" 4 +.IX Item "-Wformat=2" +Enable \fB\-Wformat\fR plus format checks not included in +\&\fB\-Wformat\fR. Currently equivalent to \fB\-Wformat +\&\-Wformat-nonliteral \-Wformat-security\fR. +.Ip "\fB\-Wimplicit-int\fR" 4 +.IX Item "-Wimplicit-int" +Warn when a declaration does not specify a type. +.Ip "\fB\-Wimplicit-function-declaration\fR" 4 +.IX Item "-Wimplicit-function-declaration" +.PD 0 +.Ip "\fB\-Werror-implicit-function-declaration\fR" 4 +.IX Item "-Werror-implicit-function-declaration" +.PD +Give a warning (or error) whenever a function is used before being +declared. +.Ip "\fB\-Wimplicit\fR" 4 +.IX Item "-Wimplicit" +Same as \fB\-Wimplicit-int\fR and \fB\-Wimplicit-function-\fR\fBdeclaration\fR. +.Ip "\fB\-Wmain\fR" 4 +.IX Item "-Wmain" +Warn if the type of \fBmain\fR is suspicious. \fBmain\fR should be a +function with external linkage, returning int, taking either zero +arguments, two, or three arguments of appropriate types. +.Ip "\fB\-Wmissing-braces\fR" 4 +.IX Item "-Wmissing-braces" +Warn if an aggregate or union initializer is not fully bracketed. In +the following example, the initializer for \fBa\fR is not fully +bracketed, but that for \fBb\fR is fully bracketed. +.Sp +.Vb 2 +\& int a[2][2] = { 0, 1, 2, 3 }; +\& int b[2][2] = { { 0, 1 }, { 2, 3 } }; +.Ve +.Ip "\fB\-Wmultichar\fR" 4 +.IX Item "-Wmultichar" +Warn if a multicharacter constant (\fB'\s-1FOOF\s0'\fR) is used. Usually they +indicate a typo in the user's code, as they have implementation-defined +values, and should not be used in portable code. +.Ip "\fB\-Wparentheses\fR" 4 +.IX Item "-Wparentheses" +Warn if parentheses are omitted in certain contexts, such +as when there is an assignment in a context where a truth value +is expected, or when operators are nested whose precedence people +often get confused about. +.Sp +Also warn about constructions where there may be confusion to which +\&\f(CW\*(C`if\*(C'\fR statement an \f(CW\*(C`else\*(C'\fR branch belongs. Here is an example of +such a case: +.Sp +.Vb 7 +\& { +\& if (a) +\& if (b) +\& foo (); +\& else +\& bar (); +\& } +.Ve +In C, every \f(CW\*(C`else\*(C'\fR branch belongs to the innermost possible \f(CW\*(C`if\*(C'\fR +statement, which in this example is \f(CW\*(C`if (b)\*(C'\fR. This is often not +what the programmer expected, as illustrated in the above example by +indentation the programmer chose. When there is the potential for this +confusion, \s-1GNU\s0 C will issue a warning when this flag is specified. +To eliminate the warning, add explicit braces around the innermost +\&\f(CW\*(C`if\*(C'\fR statement so there is no way the \f(CW\*(C`else\*(C'\fR could belong to +the enclosing \f(CW\*(C`if\*(C'\fR. The resulting code would look like this: +.Sp +.Vb 9 +\& { +\& if (a) +\& { +\& if (b) +\& foo (); +\& else +\& bar (); +\& } +\& } +.Ve +.Ip "\fB\-Wsequence-point\fR" 4 +.IX Item "-Wsequence-point" +Warn about code that may have undefined semantics because of violations +of sequence point rules in the C standard. +.Sp +The C standard defines the order in which expressions in a C program are +evaluated in terms of \fIsequence points\fR, which represent a partial +ordering between the execution of parts of the program: those executed +before the sequence point, and those executed after it. These occur +after the evaluation of a full expression (one which is not part of a +larger expression), after the evaluation of the first operand of a +\&\f(CW\*(C`&&\*(C'\fR, \f(CW\*(C`||\*(C'\fR, \f(CW\*(C`? :\*(C'\fR or \f(CW\*(C`,\*(C'\fR (comma) operator, before a +function is called (but after the evaluation of its arguments and the +expression denoting the called function), and in certain other places. +Other than as expressed by the sequence point rules, the order of +evaluation of subexpressions of an expression is not specified. All +these rules describe only a partial order rather than a total order, +since, for example, if two functions are called within one expression +with no sequence point between them, the order in which the functions +are called is not specified. However, the standards committee have +ruled that function calls do not overlap. +.Sp +It is not specified when between sequence points modifications to the +values of objects take effect. Programs whose behavior depends on this +have undefined behavior; the C standard specifies that ``Between the +previous and next sequence point an object shall have its stored value +modified at most once by the evaluation of an expression. Furthermore, +the prior value shall be read only to determine the value to be +stored.''. If a program breaks these rules, the results on any +particular implementation are entirely unpredictable. +.Sp +Examples of code with undefined behavior are \f(CW\*(C`a = a++;\*(C'\fR, \f(CW\*(C`a[n] += b[n++]\*(C'\fR and \f(CW\*(C`a[i++] = i;\*(C'\fR. Some more complicated cases are not +diagnosed by this option, and it may give an occasional false positive +result, but in general it has been found fairly effective at detecting +this sort of problem in programs. +.Sp +The present implementation of this option only works for C programs. A +future implementation may also work for \*(C+ programs. +.Sp +There is some controversy over the precise meaning of the sequence point +rules in subtle cases. Alternative formal definitions may be found in +Clive Feather's ``Annex S'' +<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n925.htm\fR> and in +Michael Norrish's thesis +<\fBhttp://www.cl.cam.ac.uk/users/mn200/PhD/thesis-report.ps.gz\fR>. +Other discussions are by Raymond Mak +<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n926.htm\fR> and +D. Hugh Redelmeier +<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n927.htm\fR>. +.Ip "\fB\-Wreturn-type\fR" 4 +.IX Item "-Wreturn-type" +Warn whenever a function is defined with a return-type that defaults to +\&\f(CW\*(C`int\*(C'\fR. Also warn about any \f(CW\*(C`return\*(C'\fR statement with no +return-value in a function whose return-type is not \f(CW\*(C`void\*(C'\fR. +.Sp +For \*(C+, a function without return type always produces a diagnostic +message, even when \fB\-Wno-return-type\fR is specified. The only +exceptions are \fBmain\fR and functions defined in system headers. +.Ip "\fB\-Wswitch\fR" 4 +.IX Item "-Wswitch" +Warn whenever a \f(CW\*(C`switch\*(C'\fR statement has an index of enumeral type +and lacks a \f(CW\*(C`case\*(C'\fR for one or more of the named codes of that +enumeration. (The presence of a \f(CW\*(C`default\*(C'\fR label prevents this +warning.) \f(CW\*(C`case\*(C'\fR labels outside the enumeration range also +provoke warnings when this option is used. +.Ip "\fB\-Wtrigraphs\fR" 4 +.IX Item "-Wtrigraphs" +Warn if any trigraphs are encountered that might change the meaning of +the program (trigraphs within comments are not warned about). +.Ip "\fB\-Wunused-function\fR" 4 +.IX Item "-Wunused-function" +Warn whenever a static function is declared but not defined or a +non\e-inline static function is unused. +.Ip "\fB\-Wunused-label\fR" 4 +.IX Item "-Wunused-label" +Warn whenever a label is declared but not used. +.Sp +To suppress this warning use the \fBunused\fR attribute. +.Ip "\fB\-Wunused-parameter\fR" 4 +.IX Item "-Wunused-parameter" +Warn whenever a function parameter is unused aside from its declaration. +.Sp +To suppress this warning use the \fBunused\fR attribute. +.Ip "\fB\-Wunused-variable\fR" 4 +.IX Item "-Wunused-variable" +Warn whenever a local variable or non-constant static variable is unused +aside from its declaration +.Sp +To suppress this warning use the \fBunused\fR attribute. +.Ip "\fB\-Wunused-value\fR" 4 +.IX Item "-Wunused-value" +Warn whenever a statement computes a result that is explicitly not used. +.Sp +To suppress this warning cast the expression to \fBvoid\fR. +.Ip "\fB\-Wunused\fR" 4 +.IX Item "-Wunused" +All all the above \fB\-Wunused\fR options combined. +.Sp +In order to get a warning about an unused function parameter, you must +either specify \fB\-W \-Wunused\fR or separately specify +\&\fB\-Wunused-parameter\fR. +.Ip "\fB\-Wuninitialized\fR" 4 +.IX Item "-Wuninitialized" +Warn if an automatic variable is used without first being initialized or +if a variable may be clobbered by a \f(CW\*(C`setjmp\*(C'\fR call. +.Sp +These warnings are possible only in optimizing compilation, +because they require data flow information that is computed only +when optimizing. If you don't specify \fB\-O\fR, you simply won't +get these warnings. +.Sp +These warnings occur only for variables that are candidates for +register allocation. Therefore, they do not occur for a variable that +is declared \f(CW\*(C`volatile\*(C'\fR, or whose address is taken, or whose size +is other than 1, 2, 4 or 8 bytes. Also, they do not occur for +structures, unions or arrays, even when they are in registers. +.Sp +Note that there may be no warning about a variable that is used only +to compute a value that itself is never used, because such +computations may be deleted by data flow analysis before the warnings +are printed. +.Sp +These warnings are made optional because \s-1GCC\s0 is not smart +enough to see all the reasons why the code might be correct +despite appearing to have an error. Here is one example of how +this can happen: +.Sp +.Vb 12 +\& { +\& int x; +\& switch (y) +\& { +\& case 1: x = 1; +\& break; +\& case 2: x = 4; +\& break; +\& case 3: x = 5; +\& } +\& foo (x); +\& } +.Ve +If the value of \f(CW\*(C`y\*(C'\fR is always 1, 2 or 3, then \f(CW\*(C`x\*(C'\fR is +always initialized, but \s-1GCC\s0 doesn't know this. Here is +another common case: +.Sp +.Vb 6 +\& { +\& int save_y; +\& if (change_y) save_y = y, y = new_y; +\& ... +\& if (change_y) y = save_y; +\& } +.Ve +This has no bug because \f(CW\*(C`save_y\*(C'\fR is used only if it is set. +.Sp +This option also warns when a non-volatile automatic variable might be +changed by a call to \f(CW\*(C`longjmp\*(C'\fR. These warnings as well are possible +only in optimizing compilation. +.Sp +The compiler sees only the calls to \f(CW\*(C`setjmp\*(C'\fR. It cannot know +where \f(CW\*(C`longjmp\*(C'\fR will be called; in fact, a signal handler could +call it at any point in the code. As a result, you may get a warning +even when there is in fact no problem because \f(CW\*(C`longjmp\*(C'\fR cannot +in fact be called at the place which would cause a problem. +.Sp +Some spurious warnings can be avoided if you declare all the functions +you use that never return as \f(CW\*(C`noreturn\*(C'\fR. +.Ip "\fB\-Wreorder (\*(C+ only)\fR" 4 +.IX Item "-Wreorder ( only)" +Warn when the order of member initializers given in the code does not +match the order in which they must be executed. For instance: +.Ip "\fB\-Wunknown-pragmas\fR" 4 +.IX Item "-Wunknown-pragmas" +Warn when a #pragma directive is encountered which is not understood by +\&\s-1GCC\s0. If this command line option is used, warnings will even be issued +for unknown pragmas in system header files. This is not the case if +the warnings were only enabled by the \fB\-Wall\fR command line option. +.Ip "\fB\-Wall\fR" 4 +.IX Item "-Wall" +All of the above \fB\-W\fR options combined. This enables all the +warnings about constructions that some users consider questionable, and +that are easy to avoid (or modify to prevent the warning), even in +conjunction with macros. +.Ip "\fB\-Wsystem-headers\fR" 4 +.IX Item "-Wsystem-headers" +Print warning messages for constructs found in system header files. +Warnings from system headers are normally suppressed, on the assumption +that they usually do not indicate real problems and would only make the +compiler output harder to read. Using this command line option tells +\&\s-1GCC\s0 to emit warnings from system headers as if they occurred in user +code. However, note that using \fB\-Wall\fR in conjunction with this +option will \fInot\fR warn about unknown pragmas in system +headers\-\-\-for that, \fB\-Wunknown-pragmas\fR must also be used. +.PP +The following \fB\-W...\fR options are not implied by \fB\-Wall\fR. +Some of them warn about constructions that users generally do not +consider questionable, but which occasionally you might wish to check +for; others warn about constructions that are necessary or hard to avoid +in some cases, and there is no simple way to modify the code to suppress +the warning. +.Ip "\fB\-W\fR" 4 +.IX Item "-W" +Print extra warning messages for these events: +.RS 4 +.Ip "\(bu" 4 +A function can return either with or without a value. (Falling +off the end of the function body is considered returning without +a value.) For example, this function would evoke such a +warning: +.Sp +.Vb 5 +\& foo (a) +\& { +\& if (a > 0) +\& return a; +\& } +.Ve +.Ip "\(bu" 4 +An expression-statement or the left-hand side of a comma expression +contains no side effects. +To suppress the warning, cast the unused expression to void. +For example, an expression such as \fBx[i,j]\fR will cause a warning, +but \fBx[(void)i,j]\fR will not. +.Ip "\(bu" 4 +An unsigned value is compared against zero with \fB<\fR or \fB<=\fR. +.Ip "\(bu" 4 +A comparison like \fBx<=y<=z\fR appears; this is equivalent to +\&\fB(x<=y ? 1 : 0) <= z\fR, which is a different interpretation from +that of ordinary mathematical notation. +.Ip "\(bu" 4 +Storage-class specifiers like \f(CW\*(C`static\*(C'\fR are not the first things in +a declaration. According to the C Standard, this usage is obsolescent. +.Ip "\(bu" 4 +The return type of a function has a type qualifier such as \f(CW\*(C`const\*(C'\fR. +Such a type qualifier has no effect, since the value returned by a +function is not an lvalue. (But don't warn about the \s-1GNU\s0 extension of +\&\f(CW\*(C`volatile void\*(C'\fR return types. That extension will be warned about +if \fB\-pedantic\fR is specified.) +.Ip "\(bu" 4 +If \fB\-Wall\fR or \fB\-Wunused\fR is also specified, warn about unused +arguments. +.Ip "\(bu" 4 +A comparison between signed and unsigned values could produce an +incorrect result when the signed value is converted to unsigned. +(But don't warn if \fB\-Wno-sign-compare\fR is also specified.) +.Ip "\(bu" 4 +An aggregate has a partly bracketed initializer. +For example, the following code would evoke such a warning, +because braces are missing around the initializer for \f(CW\*(C`x.h\*(C'\fR: +.Sp +.Vb 3 +\& struct s { int f, g; }; +\& struct t { struct s h; int i; }; +\& struct t x = { 1, 2, 3 }; +.Ve +.Ip "\(bu" 4 +An aggregate has an initializer which does not initialize all members. +For example, the following code would cause such a warning, because +\&\f(CW\*(C`x.h\*(C'\fR would be implicitly initialized to zero: +.Sp +.Vb 2 +\& struct s { int f, g, h; }; +\& struct s x = { 3, 4 }; +.Ve +.RE +.RS 4 +.RE +.Ip "\fB\-Wfloat-equal\fR" 4 +.IX Item "-Wfloat-equal" +Warn if floating point values are used in equality comparisons. +.Sp +The idea behind this is that sometimes it is convenient (for the +programmer) to consider floating-point values as approximations to +infinitely precise real numbers. If you are doing this, then you need +to compute (by analysing the code, or in some other way) the maximum or +likely maximum error that the computation introduces, and allow for it +when performing comparisons (and when producing output, but that's a +different problem). In particular, instead of testing for equality, you +would check to see whether the two values have ranges that overlap; and +this is done with the relational operators, so equality comparisons are +probably mistaken. +.Ip "\fB\-Wtraditional (C only)\fR" 4 +.IX Item "-Wtraditional (C only)" +Warn about certain constructs that behave differently in traditional and +\&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C +equivalent, and/or problematic constructs which should be avoided. +.RS 4 +.Ip "\(bu" 4 +Macro parameters that appear within string literals in the macro body. +In traditional C macro replacement takes place within string literals, +but does not in \s-1ISO\s0 C. +.Ip "\(bu" 4 +In traditional C, some preprocessor directives did not exist. +Traditional preprocessors would only consider a line to be a directive +if the \fB#\fR appeared in column 1 on the line. Therefore +\&\fB\-Wtraditional\fR warns about directives that traditional C +understands but would ignore because the \fB#\fR does not appear as the +first character on the line. It also suggests you hide directives like +\&\fB#pragma\fR not understood by traditional C by indenting them. Some +traditional implementations would not recognise \fB#elif\fR, so it +suggests avoiding it altogether. +.Ip "\(bu" 4 +A function-like macro that appears without arguments. +.Ip "\(bu" 4 +The unary plus operator. +.Ip "\(bu" 4 +The `U' integer constant suffix, or the `F' or `L' floating point +constant suffixes. (Traditonal C does support the `L' suffix on integer +constants.) Note, these suffixes appear in macros defined in the system +headers of most modern systems, e.g. the _MIN/_MAX macros in limits.h. +Use of these macros in user code might normally lead to spurious +warnings, however gcc's integrated preprocessor has enough context to +avoid warning in these cases. +.Ip "\(bu" 4 +A function declared external in one block and then used after the end of +the block. +.Ip "\(bu" 4 +A \f(CW\*(C`switch\*(C'\fR statement has an operand of type \f(CW\*(C`long\*(C'\fR. +.Ip "\(bu" 4 +A non-\f(CW\*(C`static\*(C'\fR function declaration follows a \f(CW\*(C`static\*(C'\fR one. +This construct is not accepted by some traditional C compilers. +.Ip "\(bu" 4 +The \s-1ISO\s0 type of an integer constant has a different width or +signedness from its traditional type. This warning is only issued if +the base of the constant is ten. I.e. hexadecimal or octal values, which +typically represent bit patterns, are not warned about. +.Ip "\(bu" 4 +Usage of \s-1ISO\s0 string concatenation is detected. +.Ip "\(bu" 4 +Initialization of automatic aggregates. +.Ip "\(bu" 4 +Identifier conflicts with labels. Traditional C lacks a separate +namespace for labels. +.Ip "\(bu" 4 +Initialization of unions. If the initializer is zero, the warning is +omitted. This is done under the assumption that the zero initializer in +user code appears conditioned on e.g. \f(CW\*(C`_\|_STDC_\|_\*(C'\fR to avoid missing +initializer warnings and relies on default initialization to zero in the +traditional C case. +.Ip "\(bu" 4 +Conversions by prototypes between fixed/floating point values and vice +versa. The absence of these prototypes when compiling with traditional +C would cause serious problems. This is a subset of the possible +conversion warnings, for the full set use \fB\-Wconversion\fR. +.RE +.RS 4 +.RE +.Ip "\fB\-Wundef\fR" 4 +.IX Item "-Wundef" +Warn if an undefined identifier is evaluated in an \fB#if\fR directive. +.Ip "\fB\-Wshadow\fR" 4 +.IX Item "-Wshadow" +Warn whenever a local variable shadows another local variable, parameter or +global variable or whenever a built-in function is shadowed. +.Ip "\fB\-Wid-clash-\fR\fIlen\fR" 4 +.IX Item "-Wid-clash-len" +Warn whenever two distinct identifiers match in the first \fIlen\fR +characters. This may help you prepare a program that will compile +with certain obsolete, brain-damaged compilers. +.Ip "\fB\-Wlarger-than-\fR\fIlen\fR" 4 +.IX Item "-Wlarger-than-len" +Warn whenever an object of larger than \fIlen\fR bytes is defined. +.Ip "\fB\-Wpointer-arith\fR" 4 +.IX Item "-Wpointer-arith" +Warn about anything that depends on the ``size of'' a function type or +of \f(CW\*(C`void\*(C'\fR. \s-1GNU\s0 C assigns these types a size of 1, for +convenience in calculations with \f(CW\*(C`void *\*(C'\fR pointers and pointers +to functions. +.Ip "\fB\-Wbad-function-cast (C only)\fR" 4 +.IX Item "-Wbad-function-cast (C only)" +Warn whenever a function call is cast to a non-matching type. +For example, warn if \f(CW\*(C`int malloc()\*(C'\fR is cast to \f(CW\*(C`anything *\*(C'\fR. +.Ip "\fB\-Wcast-qual\fR" 4 +.IX Item "-Wcast-qual" +Warn whenever a pointer is cast so as to remove a type qualifier from +the target type. For example, warn if a \f(CW\*(C`const char *\*(C'\fR is cast +to an ordinary \f(CW\*(C`char *\*(C'\fR. +.Ip "\fB\-Wcast-align\fR" 4 +.IX Item "-Wcast-align" +Warn whenever a pointer is cast such that the required alignment of the +target is increased. For example, warn if a \f(CW\*(C`char *\*(C'\fR is cast to +an \f(CW\*(C`int *\*(C'\fR on machines where integers can only be accessed at +two- or four-byte boundaries. +.Ip "\fB\-Wwrite-strings\fR" 4 +.IX Item "-Wwrite-strings" +Give string constants the type \f(CW\*(C`const char[\f(CIlength\f(CW]\*(C'\fR so that +copying the address of one into a non-\f(CW\*(C`const\*(C'\fR \f(CW\*(C`char *\*(C'\fR +pointer will get a warning. These warnings will help you find at +compile time code that can try to write into a string constant, but +only if you have been very careful about using \f(CW\*(C`const\*(C'\fR in +declarations and prototypes. Otherwise, it will just be a nuisance; +this is why we did not make \fB\-Wall\fR request these warnings. +.Ip "\fB\-Wconversion\fR" 4 +.IX Item "-Wconversion" +Warn if a prototype causes a type conversion that is different from what +would happen to the same argument in the absence of a prototype. This +includes conversions of fixed point to floating and vice versa, and +conversions changing the width or signedness of a fixed point argument +except when the same as the default promotion. +.Sp +Also, warn if a negative integer constant expression is implicitly +converted to an unsigned type. For example, warn about the assignment +\&\f(CW\*(C`x = \-1\*(C'\fR if \f(CW\*(C`x\*(C'\fR is unsigned. But do not warn about explicit +casts like \f(CW\*(C`(unsigned) \-1\*(C'\fR. +.Ip "\fB\-Wsign-compare\fR" 4 +.IX Item "-Wsign-compare" +Warn when a comparison between signed and unsigned values could produce +an incorrect result when the signed value is converted to unsigned. +This warning is also enabled by \fB\-W\fR; to get the other warnings +of \fB\-W\fR without this warning, use \fB\-W \-Wno-sign-compare\fR. +.Ip "\fB\-Waggregate-return\fR" 4 +.IX Item "-Waggregate-return" +Warn if any functions that return structures or unions are defined or +called. (In languages where you can return an array, this also elicits +a warning.) +.Ip "\fB\-Wstrict-prototypes (C only)\fR" 4 +.IX Item "-Wstrict-prototypes (C only)" +Warn if a function is declared or defined without specifying the +argument types. (An old-style function definition is permitted without +a warning if preceded by a declaration which specifies the argument +types.) +.Ip "\fB\-Wmissing-prototypes (C only)\fR" 4 +.IX Item "-Wmissing-prototypes (C only)" +Warn if a global function is defined without a previous prototype +declaration. This warning is issued even if the definition itself +provides a prototype. The aim is to detect global functions that fail +to be declared in header files. +.Ip "\fB\-Wmissing-declarations\fR" 4 +.IX Item "-Wmissing-declarations" +Warn if a global function is defined without a previous declaration. +Do so even if the definition itself provides a prototype. +Use this option to detect global functions that are not declared in +header files. +.Ip "\fB\-Wmissing-noreturn\fR" 4 +.IX Item "-Wmissing-noreturn" +Warn about functions which might be candidates for attribute \f(CW\*(C`noreturn\*(C'\fR. +Note these are only possible candidates, not absolute ones. Care should +be taken to manually verify functions actually do not ever return before +adding the \f(CW\*(C`noreturn\*(C'\fR attribute, otherwise subtle code generation +bugs could be introduced. You will not get a warning for \f(CW\*(C`main\*(C'\fR in +hosted C environments. +.Ip "\fB\-Wmissing-format-attribute\fR" 4 +.IX Item "-Wmissing-format-attribute" +If \fB\-Wformat\fR is enabled, also warn about functions which might be +candidates for \f(CW\*(C`format\*(C'\fR attributes. Note these are only possible +candidates, not absolute ones. \s-1GCC\s0 will guess that \f(CW\*(C`format\*(C'\fR +attributes might be appropriate for any function that calls a function +like \f(CW\*(C`vprintf\*(C'\fR or \f(CW\*(C`vscanf\*(C'\fR, but this might not always be the +case, and some functions for which \f(CW\*(C`format\*(C'\fR attributes are +appropriate may not be detected. This option has no effect unless +\&\fB\-Wformat\fR is enabled (possibly by \fB\-Wall\fR). +.Ip "\fB\-Wpacked\fR" 4 +.IX Item "-Wpacked" +Warn if a structure is given the packed attribute, but the packed +attribute has no effect on the layout or size of the structure. +Such structures may be mis-aligned for little benefit. For +instance, in this code, the variable \f(CW\*(C`f.x\*(C'\fR in \f(CW\*(C`struct bar\*(C'\fR +will be misaligned even though \f(CW\*(C`struct bar\*(C'\fR does not itself +have the packed attribute: +.Sp +.Vb 8 +\& struct foo { +\& int x; +\& char a, b, c, d; +\& } __attribute__((packed)); +\& struct bar { +\& char z; +\& struct foo f; +\& }; +.Ve +.Ip "\fB\-Wpadded\fR" 4 +.IX Item "-Wpadded" +Warn if padding is included in a structure, either to align an element +of the structure or to align the whole structure. Sometimes when this +happens it is possible to rearrange the fields of the structure to +reduce the padding and so make the structure smaller. +.Ip "\fB\-Wredundant-decls\fR" 4 +.IX Item "-Wredundant-decls" +Warn if anything is declared more than once in the same scope, even in +cases where multiple declaration is valid and changes nothing. +.Ip "\fB\-Wnested-externs (C only)\fR" 4 +.IX Item "-Wnested-externs (C only)" +Warn if an \f(CW\*(C`extern\*(C'\fR declaration is encountered within a function. +.Ip "\fB\-Wunreachable-code\fR" 4 +.IX Item "-Wunreachable-code" +Warn if the compiler detects that code will never be executed. +.Sp +This option is intended to warn when the compiler detects that at +least a whole line of source code will never be executed, because +some condition is never satisfied or because it is after a +procedure that never returns. +.Sp +It is possible for this option to produce a warning even though there +are circumstances under which part of the affected line can be executed, +so care should be taken when removing apparently-unreachable code. +.Sp +For instance, when a function is inlined, a warning may mean that the +line is unreachable in only one inlined copy of the function. +.Sp +This option is not made part of \fB\-Wall\fR because in a debugging +version of a program there is often substantial code which checks +correct functioning of the program and is, hopefully, unreachable +because the program does work. Another common use of unreachable +code is to provide behaviour which is selectable at compile-time. +.Ip "\fB\-Winline\fR" 4 +.IX Item "-Winline" +Warn if a function can not be inlined and it was declared as inline. +.Ip "\fB\-Wlong-long\fR" 4 +.IX Item "-Wlong-long" +Warn if \fBlong long\fR type is used. This is default. To inhibit +the warning messages, use \fB\-Wno-long-long\fR. Flags +\&\fB\-Wlong-long\fR and \fB\-Wno-long-long\fR are taken into account +only when \fB\-pedantic\fR flag is used. +.Ip "\fB\-Wdisabled-optimization\fR" 4 +.IX Item "-Wdisabled-optimization" +Warn if a requested optimization pass is disabled. This warning does +not generally indicate that there is anything wrong with your code; it +merely indicates that \s-1GCC\s0's optimizers were unable to handle the code +effectively. Often, the problem is that your code is too big or too +complex; \s-1GCC\s0 will refuse to optimize programs when the optimization +itself is likely to take inordinate amounts of time. +.Ip "\fB\-Werror\fR" 4 +.IX Item "-Werror" +Make all warnings into errors. +.Sh "Options for Debugging Your Program or \s-1GCC\s0" +.IX Subsection "Options for Debugging Your Program or GCC" +\&\s-1GCC\s0 has various special options that are used for debugging +either your program or \s-1GCC:\s0 +.Ip "\fB\-g\fR" 4 +.IX Item "-g" +Produce debugging information in the operating system's native format +(stabs, \s-1COFF\s0, \s-1XCOFF\s0, or \s-1DWARF\s0). \s-1GDB\s0 can work with this debugging +information. +.Sp +On most systems that use stabs format, \fB\-g\fR enables use of extra +debugging information that only \s-1GDB\s0 can use; this extra information +makes debugging work better in \s-1GDB\s0 but will probably make other debuggers +crash or +refuse to read the program. If you want to control for certain whether +to generate the extra information, use \fB\-gstabs+\fR, \fB\-gstabs\fR, +\&\fB\-gxcoff+\fR, \fB\-gxcoff\fR, \fB\-gdwarf-1+\fR, or \fB\-gdwarf-1\fR +(see below). +.Sp +Unlike most other C compilers, \s-1GCC\s0 allows you to use \fB\-g\fR with +\&\fB\-O\fR. The shortcuts taken by optimized code may occasionally +produce surprising results: some variables you declared may not exist +at all; flow of control may briefly move where you did not expect it; +some statements may not be executed because they compute constant +results or their values were already at hand; some statements may +execute in different places because they were moved out of loops. +.Sp +Nevertheless it proves possible to debug optimized output. This makes +it reasonable to use the optimizer for programs that might have bugs. +.Sp +The following options are useful when \s-1GCC\s0 is generated with the +capability for more than one debugging format. +.Ip "\fB\-ggdb\fR" 4 +.IX Item "-ggdb" +Produce debugging information for use by \s-1GDB\s0. This means to use the +most expressive format available (\s-1DWARF\s0 2, stabs, or the native format +if neither of those are supported), including \s-1GDB\s0 extensions if at all +possible. +.Ip "\fB\-gstabs\fR" 4 +.IX Item "-gstabs" +Produce debugging information in stabs format (if that is supported), +without \s-1GDB\s0 extensions. This is the format used by \s-1DBX\s0 on most \s-1BSD\s0 +systems. On \s-1MIPS\s0, Alpha and System V Release 4 systems this option +produces stabs debugging output which is not understood by \s-1DBX\s0 or \s-1SDB\s0. +On System V Release 4 systems this option requires the \s-1GNU\s0 assembler. +.Ip "\fB\-gstabs+\fR" 4 +.IX Item "-gstabs+" +Produce debugging information in stabs format (if that is supported), +using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger (\s-1GDB\s0). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program. +.Ip "\fB\-gcoff\fR" 4 +.IX Item "-gcoff" +Produce debugging information in \s-1COFF\s0 format (if that is supported). +This is the format used by \s-1SDB\s0 on most System V systems prior to +System V Release 4. +.Ip "\fB\-gxcoff\fR" 4 +.IX Item "-gxcoff" +Produce debugging information in \s-1XCOFF\s0 format (if that is supported). +This is the format used by the \s-1DBX\s0 debugger on \s-1IBM\s0 \s-1RS/6000\s0 systems. +.Ip "\fB\-gxcoff+\fR" 4 +.IX Item "-gxcoff+" +Produce debugging information in \s-1XCOFF\s0 format (if that is supported), +using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger (\s-1GDB\s0). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program, and may cause assemblers other than the \s-1GNU\s0 +assembler (\s-1GAS\s0) to fail with an error. +.Ip "\fB\-gdwarf\fR" 4 +.IX Item "-gdwarf" +Produce debugging information in \s-1DWARF\s0 version 1 format (if that is +supported). This is the format used by \s-1SDB\s0 on most System V Release 4 +systems. +.Ip "\fB\-gdwarf+\fR" 4 +.IX Item "-gdwarf+" +Produce debugging information in \s-1DWARF\s0 version 1 format (if that is +supported), using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger +(\s-1GDB\s0). The use of these extensions is likely to make other debuggers +crash or refuse to read the program. +.Ip "\fB\-gdwarf-2\fR" 4 +.IX Item "-gdwarf-2" +Produce debugging information in \s-1DWARF\s0 version 2 format (if that is +supported). This is the format used by \s-1DBX\s0 on \s-1IRIX\s0 6. +.Ip "\fB\-g\fR\fIlevel\fR" 4 +.IX Item "-glevel" +.PD 0 +.Ip "\fB\-ggdb\fR\fIlevel\fR" 4 +.IX Item "-ggdblevel" +.Ip "\fB\-gstabs\fR\fIlevel\fR" 4 +.IX Item "-gstabslevel" +.Ip "\fB\-gcoff\fR\fIlevel\fR" 4 +.IX Item "-gcofflevel" +.Ip "\fB\-gxcoff\fR\fIlevel\fR" 4 +.IX Item "-gxcofflevel" +.Ip "\fB\-gdwarf\fR\fIlevel\fR" 4 +.IX Item "-gdwarflevel" +.Ip "\fB\-gdwarf-2\fR\fIlevel\fR" 4 +.IX Item "-gdwarf-2level" +.PD +Request debugging information and also use \fIlevel\fR to specify how +much information. The default level is 2. +.Sp +Level 1 produces minimal information, enough for making backtraces in +parts of the program that you don't plan to debug. This includes +descriptions of functions and external variables, but no information +about local variables and no line numbers. +.Sp +Level 3 includes extra information, such as all the macro definitions +present in the program. Some debuggers support macro expansion when +you use \fB\-g3\fR. +.Ip "\fB\-p\fR" 4 +.IX Item "-p" +Generate extra code to write profile information suitable for the +analysis program \f(CW\*(C`prof\*(C'\fR. You must use this option when compiling +the source files you want data about, and you must also use it when +linking. +.Ip "\fB\-pg\fR" 4 +.IX Item "-pg" +Generate extra code to write profile information suitable for the +analysis program \f(CW\*(C`gprof\*(C'\fR. You must use this option when compiling +the source files you want data about, and you must also use it when +linking. +.Ip "\fB\-a\fR" 4 +.IX Item "-a" +Generate extra code to write profile information for basic blocks, which will +record the number of times each basic block is executed, the basic block start +address, and the function name containing the basic block. If \fB\-g\fR is +used, the line number and filename of the start of the basic block will also be +recorded. If not overridden by the machine description, the default action is +to append to the text file \fIbb.out\fR. +.Sp +This data could be analyzed by a program like \f(CW\*(C`tcov\*(C'\fR. Note, +however, that the format of the data is not what \f(CW\*(C`tcov\*(C'\fR expects. +Eventually \s-1GNU\s0 \f(CW\*(C`gprof\*(C'\fR should be extended to process this data. +.Ip "\fB\-Q\fR" 4 +.IX Item "-Q" +Makes the compiler print out each function name as it is compiled, and +print some statistics about each pass when it finishes. +.Ip "\fB\-ftime-report\fR" 4 +.IX Item "-ftime-report" +Makes the compiler print some statistics about the time consumed by each +pass when it finishes. +.Ip "\fB\-fmem-report\fR" 4 +.IX Item "-fmem-report" +Makes the compiler print some statistics about permanent memory +allocation when it finishes. +.Ip "\fB\-ax\fR" 4 +.IX Item "-ax" +Generate extra code to profile basic blocks. Your executable will +produce output that is a superset of that produced when \fB\-a\fR is +used. Additional output is the source and target address of the basic +blocks where a jump takes place, the number of times a jump is executed, +and (optionally) the complete sequence of basic blocks being executed. +The output is appended to file \fIbb.out\fR. +.Sp +You can examine different profiling aspects without recompilation. Your +executable will read a list of function names from file \fIbb.in\fR. +Profiling starts when a function on the list is entered and stops when +that invocation is exited. To exclude a function from profiling, prefix +its name with `\-'. If a function name is not unique, you can +disambiguate it by writing it in the form +\&\fB/path/filename.d:functionname\fR. Your executable will write the +available paths and filenames in file \fIbb.out\fR. +.Sp +Several function names have a special meaning: +.RS 4 +.if n .Ip "\f(CW""""_\|_bb_jumps_\|_""""\fR" 4 +.el .Ip "\f(CW_\|_bb_jumps_\|_\fR" 4 +.IX Item "__bb_jumps__" +Write source, target and frequency of jumps to file \fIbb.out\fR. +.if n .Ip "\f(CW""""_\|_bb_hidecall_\|_""""\fR" 4 +.el .Ip "\f(CW_\|_bb_hidecall_\|_\fR" 4 +.IX Item "__bb_hidecall__" +Exclude function calls from frequency count. +.if n .Ip "\f(CW""""_\|_bb_showret_\|_""""\fR" 4 +.el .Ip "\f(CW_\|_bb_showret_\|_\fR" 4 +.IX Item "__bb_showret__" +Include function returns in frequency count. +.if n .Ip "\f(CW""""_\|_bb_trace_\|_""""\fR" 4 +.el .Ip "\f(CW_\|_bb_trace_\|_\fR" 4 +.IX Item "__bb_trace__" +Write the sequence of basic blocks executed to file \fIbbtrace.gz\fR. +The file will be compressed using the program \fBgzip\fR, which must +exist in your \fB\s-1PATH\s0\fR. On systems without the \fBpopen\fR +function, the file will be named \fIbbtrace\fR and will not be +compressed. \fBProfiling for even a few seconds on these systems +will produce a very large file.\fR Note: \f(CW\*(C`_\|_bb_hidecall_\|_\*(C'\fR and +\&\f(CW\*(C`_\|_bb_showret_\|_\*(C'\fR will not affect the sequence written to +\&\fIbbtrace.gz\fR. +.RE +.RS 4 +.Sp +Here's a short example using different profiling parameters +in file \fIbb.in\fR. Assume function \f(CW\*(C`foo\*(C'\fR consists of basic blocks +1 and 2 and is called twice from block 3 of function \f(CW\*(C`main\*(C'\fR. After +the calls, block 3 transfers control to block 4 of \f(CW\*(C`main\*(C'\fR. +.Sp +With \f(CW\*(C`_\|_bb_trace_\|_\*(C'\fR and \f(CW\*(C`main\*(C'\fR contained in file \fIbb.in\fR, +the following sequence of blocks is written to file \fIbbtrace.gz\fR: +0 3 1 2 1 2 4. The return from block 2 to block 3 is not shown, because +the return is to a point inside the block and not to the top. The +block address 0 always indicates, that control is transferred +to the trace from somewhere outside the observed functions. With +\&\fB\-foo\fR added to \fIbb.in\fR, the blocks of function +\&\f(CW\*(C`foo\*(C'\fR are removed from the trace, so only 0 3 4 remains. +.Sp +With \f(CW\*(C`_\|_bb_jumps_\|_\*(C'\fR and \f(CW\*(C`main\*(C'\fR contained in file \fIbb.in\fR, +jump frequencies will be written to file \fIbb.out\fR. The +frequencies are obtained by constructing a trace of blocks +and incrementing a counter for every neighbouring pair of blocks +in the trace. The trace 0 3 1 2 1 2 4 displays the following +frequencies: +.Sp +.Vb 5 +\& Jump from block 0x0 to block 0x3 executed 1 time(s) +\& Jump from block 0x3 to block 0x1 executed 1 time(s) +\& Jump from block 0x1 to block 0x2 executed 2 time(s) +\& Jump from block 0x2 to block 0x1 executed 1 time(s) +\& Jump from block 0x2 to block 0x4 executed 1 time(s) +.Ve +With \f(CW\*(C`_\|_bb_hidecall_\|_\*(C'\fR, control transfer due to call instructions +is removed from the trace, that is the trace is cut into three parts: 0 +3 4, 0 1 2 and 0 1 2. With \f(CW\*(C`_\|_bb_showret_\|_\*(C'\fR, control transfer due +to return instructions is added to the trace. The trace becomes: 0 3 1 +2 3 1 2 3 4. Note, that this trace is not the same, as the sequence +written to \fIbbtrace.gz\fR. It is solely used for counting jump +frequencies. +.RE +.Ip "\fB\-fprofile-arcs\fR" 4 +.IX Item "-fprofile-arcs" +Instrument \fIarcs\fR during compilation. For each function of your +program, \s-1GCC\s0 creates a program flow graph, then finds a spanning tree +for the graph. Only arcs that are not on the spanning tree have to be +instrumented: the compiler adds code to count the number of times that these +arcs are executed. When an arc is the only exit or only entrance to a +block, the instrumentation code can be added to the block; otherwise, a +new basic block must be created to hold the instrumentation code. +.Sp +Since not every arc in the program must be instrumented, programs +compiled with this option run faster than programs compiled with +\&\fB\-a\fR, which adds instrumentation code to every basic block in the +program. The tradeoff: since \f(CW\*(C`gcov\*(C'\fR does not have +execution counts for all branches, it must start with the execution +counts for the instrumented branches, and then iterate over the program +flow graph until the entire graph has been solved. Hence, \f(CW\*(C`gcov\*(C'\fR +runs a little more slowly than a program which uses information from +\&\fB\-a\fR. +.Sp +\&\fB\-fprofile-arcs\fR also makes it possible to estimate branch +probabilities, and to calculate basic block execution counts. In +general, basic block execution counts do not give enough information to +estimate all branch probabilities. When the compiled program exits, it +saves the arc execution counts to a file called +\&\fI\fIsourcename\fI.da\fR. Use the compiler option +\&\fB\-fbranch-probabilities\fR when recompiling, to optimize using estimated +branch probabilities. +.Ip "\fB\-ftest-coverage\fR" 4 +.IX Item "-ftest-coverage" +Create data files for the \f(CW\*(C`gcov\*(C'\fR code-coverage utility. +The data file names begin with the name of your source file: +.RS 4 +.Ip "\fIsourcename\fR\fB.bb\fR" 4 +.IX Item "sourcename.bb" +A mapping from basic blocks to line numbers, which \f(CW\*(C`gcov\*(C'\fR uses to +associate basic block execution counts with line numbers. +.Ip "\fIsourcename\fR\fB.bbg\fR" 4 +.IX Item "sourcename.bbg" +A list of all arcs in the program flow graph. This allows \f(CW\*(C`gcov\*(C'\fR +to reconstruct the program flow graph, so that it can compute all basic +block and arc execution counts from the information in the +\&\f(CW\*(C`\f(CIsourcename\f(CW.da\*(C'\fR file (this last file is the output from +\&\fB\-fprofile-arcs\fR). +.RE +.RS 4 +.RE +.Ip "\fB\-d\fR\fIletters\fR" 4 +.IX Item "-dletters" +Says to make debugging dumps during compilation at times specified by +\&\fIletters\fR. This is used for debugging the compiler. The file names +for most of the dumps are made by appending a pass number and a word to +the source file name (e.g. \fIfoo.c.00.rtl\fR or \fIfoo.c.01.sibling\fR). +Here are the possible letters for use in \fIletters\fR, and their meanings: +.RS 4 +.Ip "\fBA\fR" 4 +.IX Item "A" +Annotate the assembler output with miscellaneous debugging information. +.Ip "\fBb\fR" 4 +.IX Item "b" +Dump after computing branch probabilities, to \fI\fIfile\fI.11.bp\fR. +.Ip "\fBB\fR" 4 +.IX Item "B" +Dump after block reordering, to \fI\fIfile\fI.26.bbro\fR. +.Ip "\fBc\fR" 4 +.IX Item "c" +Dump after instruction combination, to the file \fI\fIfile\fI.14.combine\fR. +.Ip "\fBC\fR" 4 +.IX Item "C" +Dump after the first if conversion, to the file \fI\fIfile\fI.15.ce\fR. +.Ip "\fBd\fR" 4 +.IX Item "d" +Dump after delayed branch scheduling, to \fI\fIfile\fI.29.dbr\fR. +.Ip "\fBD\fR" 4 +.IX Item "D" +Dump all macro definitions, at the end of preprocessing, in addition to +normal output. +.Ip "\fBe\fR" 4 +.IX Item "e" +Dump after \s-1SSA\s0 optimizations, to \fI\fIfile\fI.05.ssa\fR and +\&\fI\fIfile\fI.06.ussa\fR. +.Ip "\fBE\fR" 4 +.IX Item "E" +Dump after the second if conversion, to \fI\fIfile\fI.24.ce2\fR. +.Ip "\fBf\fR" 4 +.IX Item "f" +Dump after life analysis, to \fI\fIfile\fI.13.life\fR. +.Ip "\fBF\fR" 4 +.IX Item "F" +Dump after purging \f(CW\*(C`ADDRESSOF\*(C'\fR codes, to \fI\fIfile\fI.04.addressof\fR. +.Ip "\fBg\fR" 4 +.IX Item "g" +Dump after global register allocation, to \fI\fIfile\fI.19.greg\fR. +.Ip "\fBo\fR" 4 +.IX Item "o" +Dump after post-reload \s-1CSE\s0 and other optimizations, to \fI\fIfile\fI.20.postreload\fR. +.Ip "\fBG\fR" 4 +.IX Item "G" +Dump after \s-1GCSE\s0, to \fI\fIfile\fI.08.gcse\fR. +.Ip "\fBi\fR" 4 +.IX Item "i" +Dump after sibling call optimizations, to \fI\fIfile\fI.01.sibling\fR. +.Ip "\fBj\fR" 4 +.IX Item "j" +Dump after the first jump optimization, to \fI\fIfile\fI.02.jump\fR. +.Ip "\fBJ\fR" 4 +.IX Item "J" +Dump after the last jump optimization, to \fI\fIfile\fI.27.jump2\fR. +.Ip "\fBk\fR" 4 +.IX Item "k" +Dump after conversion from registers to stack, to \fI\fIfile\fI.29.stack\fR. +.Ip "\fBl\fR" 4 +.IX Item "l" +Dump after local register allocation, to \fI\fIfile\fI.18.lreg\fR. +.Ip "\fBL\fR" 4 +.IX Item "L" +Dump after loop optimization, to \fI\fIfile\fI.09.loop\fR. +.Ip "\fBM\fR" 4 +.IX Item "M" +Dump after performing the machine dependent reorganisation pass, to +\&\fI\fIfile\fI.28.mach\fR. +.Ip "\fBn\fR" 4 +.IX Item "n" +Dump after register renumbering, to \fI\fIfile\fI.23.rnreg\fR. +.Ip "\fBN\fR" 4 +.IX Item "N" +Dump after the register move pass, to \fI\fIfile\fI.16.regmove\fR. +.Ip "\fBr\fR" 4 +.IX Item "r" +Dump after \s-1RTL\s0 generation, to \fI\fIfile\fI.00.rtl\fR. +.Ip "\fBR\fR" 4 +.IX Item "R" +Dump after the second instruction scheduling pass, to +\&\fI\fIfile\fI.25.sched2\fR. +.Ip "\fBs\fR" 4 +.IX Item "s" +Dump after \s-1CSE\s0 (including the jump optimization that sometimes follows +\&\s-1CSE\s0), to \fI\fIfile\fI.03.cse\fR. +.Ip "\fBS\fR" 4 +.IX Item "S" +Dump after the first instruction scheduling pass, to +\&\fI\fIfile\fI.17.sched\fR. +.Ip "\fBt\fR" 4 +.IX Item "t" +Dump after the second \s-1CSE\s0 pass (including the jump optimization that +sometimes follows \s-1CSE\s0), to \fI\fIfile\fI.10.cse2\fR. +.Ip "\fBw\fR" 4 +.IX Item "w" +Dump after the second flow pass, to \fI\fIfile\fI.21.flow2\fR. +.Ip "\fBX\fR" 4 +.IX Item "X" +Dump after dead code elimination, to \fI\fIfile\fI.06.dce\fR. +.Ip "\fBz\fR" 4 +.IX Item "z" +Dump after the peephole pass, to \fI\fIfile\fI.22.peephole2\fR. +.Ip "\fBa\fR" 4 +.IX Item "a" +Produce all the dumps listed above. +.Ip "\fBm\fR" 4 +.IX Item "m" +Print statistics on memory usage, at the end of the run, to +standard error. +.Ip "\fBp\fR" 4 +.IX Item "p" +Annotate the assembler output with a comment indicating which +pattern and alternative was used. The length of each instruction is +also printed. +.Ip "\fBP\fR" 4 +.IX Item "P" +Dump the \s-1RTL\s0 in the assembler output as a comment before each instruction. +Also turns on \fB\-dp\fR annotation. +.Ip "\fBv\fR" 4 +.IX Item "v" +For each of the other indicated dump files (except for +\&\fI\fIfile\fI.00.rtl\fR), dump a representation of the control flow graph +suitable for viewing with \s-1VCG\s0 to \fI\fIfile\fI.\fIpass\fI.vcg\fR. +.Ip "\fBx\fR" 4 +.IX Item "x" +Just generate \s-1RTL\s0 for a function instead of compiling it. Usually used +with \fBr\fR. +.Ip "\fBy\fR" 4 +.IX Item "y" +Dump debugging information during parsing, to standard error. +.RE +.RS 4 +.RE +.Ip "\fB\-fdump-unnumbered\fR" 4 +.IX Item "-fdump-unnumbered" +When doing debugging dumps (see \-d option above), suppress instruction +numbers and line number note output. This makes it more feasible to +use diff on debugging dumps for compiler invocations with different +options, in particular with and without \-g. +.Ip "\fB\-fdump-translation-unit=\fR\fIfile\fR \fB(C and \*(C+ only)\fR" 4 +.IX Item "-fdump-translation-unit=file (C and only)" +Dump a representation of the tree structure for the entire translation +unit to \fIfile\fR. +.Ip "\fB\-fdump-class_layout=\fR\fIfile\fR \fB(\*(C+ only)\fR" 4 +.IX Item "-fdump-class_layout=file ( only)" +.PD 0 +.Ip "\fB\-fdump-class_layout (\*(C+ only)\fR" 4 +.IX Item "-fdump-class_layout ( only)" +.PD +Dump a representation of each class's heirarchy to \fIfile\fR, or +\&\f(CW\*(C`stderr\*(C'\fR if not specified. +.Ip "\fB\-fpretend-float\fR" 4 +.IX Item "-fpretend-float" +When running a cross-compiler, pretend that the target machine uses the +same floating point format as the host machine. This causes incorrect +output of the actual floating constants, but the actual instruction +sequence will probably be the same as \s-1GCC\s0 would make when running on +the target machine. +.Ip "\fB\-save-temps\fR" 4 +.IX Item "-save-temps" +Store the usual ``temporary'' intermediate files permanently; place them +in the current directory and name them based on the source file. Thus, +compiling \fIfoo.c\fR with \fB\-c \-save-temps\fR would produce files +\&\fIfoo.i\fR and \fIfoo.s\fR, as well as \fIfoo.o\fR. This creates a +preprocessed \fIfoo.i\fR output file even though the compiler now +normally uses an integrated preprocessor. +.Ip "\fB\-time\fR" 4 +.IX Item "-time" +Report the \s-1CPU\s0 time taken by each subprocess in the compilation +sequence. For C source files, this is the compiler proper and assembler +(plus the linker if linking is done). The output looks like this: +.Sp +.Vb 2 +\& # cc1 0.12 0.01 +\& # as 0.00 0.01 +.Ve +The first number on each line is the ``user time,'' that is time spent +executing the program itself. The second number is ``system time,'' +time spent executing operating system routines on behalf of the program. +Both numbers are in seconds. +.Ip "\fB\-print-file-name=\fR\fIlibrary\fR" 4 +.IX Item "-print-file-name=library" +Print the full absolute name of the library file \fIlibrary\fR that +would be used when linking\-\-\-and don't do anything else. With this +option, \s-1GCC\s0 does not compile or link anything; it just prints the +file name. +.Ip "\fB\-print-prog-name=\fR\fIprogram\fR" 4 +.IX Item "-print-prog-name=program" +Like \fB\-print-file-name\fR, but searches for a program such as \fBcpp\fR. +.Ip "\fB\-print-libgcc-file-name\fR" 4 +.IX Item "-print-libgcc-file-name" +Same as \fB\-print-file-name=libgcc.a\fR. +.Sp +This is useful when you use \fB\-nostdlib\fR or \fB\-nodefaultlibs\fR +but you do want to link with \fIlibgcc.a\fR. You can do +.Sp +.Vb 1 +\& gcc -nostdlib I... `gcc -print-libgcc-file-name` +.Ve +.Ip "\fB\-print-search-dirs\fR" 4 +.IX Item "-print-search-dirs" +Print the name of the configured installation directory and a list of +program and library directories gcc will search\-\-\-and don't do anything else. +.Sp +This is useful when gcc prints the error message +\&\fBinstallation problem, cannot exec cpp0: No such file or directory\fR. +To resolve this you either need to put \fIcpp0\fR and the other compiler +components where gcc expects to find them, or you can set the environment +variable \fB\s-1GCC_EXEC_PREFIX\s0\fR to the directory where you installed them. +Don't forget the trailing '/'. +.Ip "\fB\-dumpmachine\fR" 4 +.IX Item "-dumpmachine" +Print the compiler's target machine (for example, +\&\fBi686\-pc-linux-gnu\fR)\-\-\-and don't do anything else. +.Ip "\fB\-dumpversion\fR" 4 +.IX Item "-dumpversion" +Print the compiler version (for example, \fB3.0\fR)\-\-\-and don't do +anything else. +.Ip "\fB\-dumpspecs\fR" 4 +.IX Item "-dumpspecs" +Print the compiler's built-in specs\-\-\-and don't do anything else. (This +is used when \s-1GCC\s0 itself is being built.) +.Sh "Options That Control Optimization" +.IX Subsection "Options That Control Optimization" +These options control various sorts of optimizations: +.Ip "\fB\-O\fR" 4 +.IX Item "-O" +.PD 0 +.Ip "\fB\-O1\fR" 4 +.IX Item "-O1" +.PD +Optimize. Optimizing compilation takes somewhat more time, and a lot +more memory for a large function. +.Sp +Without \fB\-O\fR, the compiler's goal is to reduce the cost of +compilation and to make debugging produce the expected results. +Statements are independent: if you stop the program with a breakpoint +between statements, you can then assign a new value to any variable or +change the program counter to any other statement in the function and +get exactly the results you would expect from the source code. +.Sp +Without \fB\-O\fR, the compiler only allocates variables declared +\&\f(CW\*(C`register\*(C'\fR in registers. The resulting compiled code is a little +worse than produced by \s-1PCC\s0 without \fB\-O\fR. +.Sp +With \fB\-O\fR, the compiler tries to reduce code size and execution +time. +.Sp +When you specify \fB\-O\fR, the compiler turns on \fB\-fthread-jumps\fR +and \fB\-fdefer-pop\fR on all machines. The compiler turns on +\&\fB\-fdelayed-branch\fR on machines that have delay slots, and +\&\fB\-fomit-frame-pointer\fR on machines that can support debugging even +without a frame pointer. On some machines the compiler also turns +on other flags. +.Ip "\fB\-O2\fR" 4 +.IX Item "-O2" +Optimize even more. \s-1GCC\s0 performs nearly all supported optimizations +that do not involve a space-speed tradeoff. The compiler does not +perform loop unrolling or function inlining when you specify \fB\-O2\fR. +As compared to \fB\-O\fR, this option increases both compilation time +and the performance of the generated code. +.Sp +\&\fB\-O2\fR turns on all optional optimizations except for loop unrolling, +function inlining, and register renaming. It also turns on the +\&\fB\-fforce-mem\fR option on all machines and frame pointer elimination +on machines where doing so does not interfere with debugging. +.Ip "\fB\-O3\fR" 4 +.IX Item "-O3" +Optimize yet more. \fB\-O3\fR turns on all optimizations specified by +\&\fB\-O2\fR and also turns on the \fB\-finline-functions\fR and +\&\fB\-frename-registers\fR options. +.Ip "\fB\-O0\fR" 4 +.IX Item "-O0" +Do not optimize. +.Ip "\fB\-Os\fR" 4 +.IX Item "-Os" +Optimize for size. \fB\-Os\fR enables all \fB\-O2\fR optimizations that +do not typically increase code size. It also performs further +optimizations designed to reduce code size. +.Sp +If you use multiple \fB\-O\fR options, with or without level numbers, +the last such option is the one that is effective. +.PP +Options of the form \fB\-f\fR\fIflag\fR specify machine-independent +flags. Most flags have both positive and negative forms; the negative +form of \fB\-ffoo\fR would be \fB\-fno-foo\fR. In the table below, +only one of the forms is listed\-\-\-the one which is not the default. +You can figure out the other form by either removing \fBno-\fR or +adding it. +.Ip "\fB\-ffloat-store\fR" 4 +.IX Item "-ffloat-store" +Do not store floating point variables in registers, and inhibit other +options that might change whether a floating point value is taken from a +register or memory. +.Sp +This option prevents undesirable excess precision on machines such as +the 68000 where the floating registers (of the 68881) keep more +precision than a \f(CW\*(C`double\*(C'\fR is supposed to have. Similarly for the +x86 architecture. For most programs, the excess precision does only +good, but a few programs rely on the precise definition of \s-1IEEE\s0 floating +point. Use \fB\-ffloat-store\fR for such programs, after modifying +them to store all pertinent intermediate computations into variables. +.Ip "\fB\-fno-default-inline\fR" 4 +.IX Item "-fno-default-inline" +Do not make member functions inline by default merely because they are +defined inside the class scope (\*(C+ only). Otherwise, when you specify +\&\fB\-O\fR, member functions defined inside class scope are compiled +inline by default; i.e., you don't need to add \fBinline\fR in front of +the member function name. +.Ip "\fB\-fno-defer-pop\fR" 4 +.IX Item "-fno-defer-pop" +Always pop the arguments to each function call as soon as that function +returns. For machines which must pop arguments after a function call, +the compiler normally lets arguments accumulate on the stack for several +function calls and pops them all at once. +.Ip "\fB\-fforce-mem\fR" 4 +.IX Item "-fforce-mem" +Force memory operands to be copied into registers before doing +arithmetic on them. This produces better code by making all memory +references potential common subexpressions. When they are not common +subexpressions, instruction combination should eliminate the separate +register-load. The \fB\-O2\fR option turns on this option. +.Ip "\fB\-fforce-addr\fR" 4 +.IX Item "-fforce-addr" +Force memory address constants to be copied into registers before +doing arithmetic on them. This may produce better code just as +\&\fB\-fforce-mem\fR may. +.Ip "\fB\-fomit-frame-pointer\fR" 4 +.IX Item "-fomit-frame-pointer" +Don't keep the frame pointer in a register for functions that +don't need one. This avoids the instructions to save, set up and +restore frame pointers; it also makes an extra register available +in many functions. \fBIt also makes debugging impossible on +some machines.\fR +.Sp +On some machines, such as the Vax, this flag has no effect, because +the standard calling sequence automatically handles the frame pointer +and nothing is saved by pretending it doesn't exist. The +machine-description macro \f(CW\*(C`FRAME_POINTER_REQUIRED\*(C'\fR controls +whether a target machine supports this flag. +.Ip "\fB\-foptimize-sibling-calls\fR" 4 +.IX Item "-foptimize-sibling-calls" +Optimize sibling and tail recursive calls. +.Ip "\fB\-ftrapv\fR" 4 +.IX Item "-ftrapv" +This option generates traps for signed overflow on addition, subtraction, +multiplication operations. +.Ip "\fB\-fno-inline\fR" 4 +.IX Item "-fno-inline" +Don't pay attention to the \f(CW\*(C`inline\*(C'\fR keyword. Normally this option +is used to keep the compiler from expanding any functions inline. +Note that if you are not optimizing, no functions can be expanded inline. +.Ip "\fB\-finline-functions\fR" 4 +.IX Item "-finline-functions" +Integrate all simple functions into their callers. The compiler +heuristically decides which functions are simple enough to be worth +integrating in this way. +.Sp +If all calls to a given function are integrated, and the function is +declared \f(CW\*(C`static\*(C'\fR, then the function is normally not output as +assembler code in its own right. +.Ip "\fB\-finline-limit=\fR\fIn\fR" 4 +.IX Item "-finline-limit=n" +By default, gcc limits the size of functions that can be inlined. This flag +allows the control of this limit for functions that are explicitly marked as +inline (ie marked with the inline keyword or defined within the class +definition in c++). \fIn\fR is the size of functions that can be inlined in +number of pseudo instructions (not counting parameter handling). The default +value of n is 10000. Increasing this value can result in more inlined code at +the cost of compilation time and memory consumption. Decreasing usually makes +the compilation faster and less code will be inlined (which presumably +means slower programs). This option is particularly useful for programs that +use inlining heavily such as those based on recursive templates with c++. +.Sp +\&\fINote:\fR pseudo instruction represents, in this particular context, an +abstract measurement of function's size. In no way, it represents a count +of assembly instructions and as such its exact meaning might change from one +release to an another. +.Ip "\fB\-fkeep-inline-functions\fR" 4 +.IX Item "-fkeep-inline-functions" +Even if all calls to a given function are integrated, and the function +is declared \f(CW\*(C`static\*(C'\fR, nevertheless output a separate run-time +callable version of the function. This switch does not affect +\&\f(CW\*(C`extern inline\*(C'\fR functions. +.Ip "\fB\-fkeep-static-consts\fR" 4 +.IX Item "-fkeep-static-consts" +Emit variables declared \f(CW\*(C`static const\*(C'\fR when optimization isn't turned +on, even if the variables aren't referenced. +.Sp +\&\s-1GCC\s0 enables this option by default. If you want to force the compiler to +check if the variable was referenced, regardless of whether or not +optimization is turned on, use the \fB\-fno-keep-static-consts\fR option. +.Ip "\fB\-fno-function-cse\fR" 4 +.IX Item "-fno-function-cse" +Do not put function addresses in registers; make each instruction that +calls a constant function contain the function's address explicitly. +.Sp +This option results in less efficient code, but some strange hacks +that alter the assembler output may be confused by the optimizations +performed when this option is not used. +.Ip "\fB\-ffast-math\fR" 4 +.IX Item "-ffast-math" +Sets \fB\-fno-math-errno\fR, \fB\-funsafe-math-optimizations\fR, +and \fB\-fno-trapping-math\fR. +.Sp +This option causes the preprocessor macro _\|_FAST_MATH_\|_ to be defined. +.Sp +This option should never be turned on by any \fB\-O\fR option since +it can result in incorrect output for programs which depend on +an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for +math functions. +.Ip "\fB\-fno-math-errno\fR" 4 +.IX Item "-fno-math-errno" +Do not set \s-1ERRNO\s0 after calling math functions that are executed +with a single instruction, e.g., sqrt. A program that relies on +\&\s-1IEEE\s0 exceptions for math error handling may want to use this flag +for speed while maintaining \s-1IEEE\s0 arithmetic compatibility. +.Sp +This option should never be turned on by any \fB\-O\fR option since +it can result in incorrect output for programs which depend on +an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for +math functions. +.Sp +The default is \fB\-fmath-errno\fR. The \fB\-ffast-math\fR option +sets \fB\-fno-math-errno\fR. +.Ip "\fB\-funsafe-math-optimizations\fR" 4 +.IX Item "-funsafe-math-optimizations" +Allow optimizations for floating-point arithmetic that (a) assume +that arguments and results are valid and (b) may violate \s-1IEEE\s0 or +\&\s-1ANSI\s0 standards. +.Sp +This option should never be turned on by any \fB\-O\fR option since +it can result in incorrect output for programs which depend on +an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for +math functions. +.Sp +The default is \fB\-fno-unsafe-math-optimizations\fR. The +\&\fB\-ffast-math\fR option sets \fB\-funsafe-math-optimizations\fR. +.Ip "\fB\-fno-trapping-math\fR" 4 +.IX Item "-fno-trapping-math" +Compile code assuming that floating-point operations cannot generate +user-visible traps. Setting this option may allow faster code +if one relies on ``non-stop'' \s-1IEEE\s0 arithmetic, for example. +.Sp +This option should never be turned on by any \fB\-O\fR option since +it can result in incorrect output for programs which depend on +an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for +math functions. +.Sp +The default is \fB\-ftrapping-math\fR. The \fB\-ffast-math\fR +option sets \fB\-fno-trapping-math\fR. +.PP +The following options control specific optimizations. The \fB\-O2\fR +option turns on all of these optimizations except \fB\-funroll-loops\fR +and \fB\-funroll-all-loops\fR. On most machines, the \fB\-O\fR option +turns on the \fB\-fthread-jumps\fR and \fB\-fdelayed-branch\fR options, +but specific machines may handle it differently. +.PP +You can use the following flags in the rare cases when ``fine-tuning'' +of optimizations to be performed is desired. +.Ip "\fB\-fstrength-reduce\fR" 4 +.IX Item "-fstrength-reduce" +Perform the optimizations of loop strength reduction and +elimination of iteration variables. +.Ip "\fB\-fthread-jumps\fR" 4 +.IX Item "-fthread-jumps" +Perform optimizations where we check to see if a jump branches to a +location where another comparison subsumed by the first is found. If +so, the first branch is redirected to either the destination of the +second branch or a point immediately following it, depending on whether +the condition is known to be true or false. +.Ip "\fB\-fcse-follow-jumps\fR" 4 +.IX Item "-fcse-follow-jumps" +In common subexpression elimination, scan through jump instructions +when the target of the jump is not reached by any other path. For +example, when \s-1CSE\s0 encounters an \f(CW\*(C`if\*(C'\fR statement with an +\&\f(CW\*(C`else\*(C'\fR clause, \s-1CSE\s0 will follow the jump when the condition +tested is false. +.Ip "\fB\-fcse-skip-blocks\fR" 4 +.IX Item "-fcse-skip-blocks" +This is similar to \fB\-fcse-follow-jumps\fR, but causes \s-1CSE\s0 to +follow jumps which conditionally skip over blocks. When \s-1CSE\s0 +encounters a simple \f(CW\*(C`if\*(C'\fR statement with no else clause, +\&\fB\-fcse-skip-blocks\fR causes \s-1CSE\s0 to follow the jump around the +body of the \f(CW\*(C`if\*(C'\fR. +.Ip "\fB\-frerun-cse-after-loop\fR" 4 +.IX Item "-frerun-cse-after-loop" +Re-run common subexpression elimination after loop optimizations has been +performed. +.Ip "\fB\-frerun-loop-opt\fR" 4 +.IX Item "-frerun-loop-opt" +Run the loop optimizer twice. +.Ip "\fB\-fgcse\fR" 4 +.IX Item "-fgcse" +Perform a global common subexpression elimination pass. +This pass also performs global constant and copy propagation. +.Ip "\fB\-fgcse-lm\fR" 4 +.IX Item "-fgcse-lm" +When \-fgcse-lm is enabled, global common subexpression elimination will +attempt to move loads which are only killed by stores into themselves. This +allows a loop containing a load/store sequence to be changed to a load outside +the loop, and a copy/store within the loop. +.Ip "\fB\-fgcse-sm\fR" 4 +.IX Item "-fgcse-sm" +When \-fgcse-sm is enabled, A store motion pass is run after global common +subexpression elimination. This pass will attempt to move stores out of loops. +When used in conjunction with \-fgcse-lm, loops containing a load/store sequence +can be changed to a load before the loop and a store after the loop. +.Ip "\fB\-fdelete-null-pointer-checks\fR" 4 +.IX Item "-fdelete-null-pointer-checks" +Use global dataflow analysis to identify and eliminate useless null +pointer checks. Programs which rely on \s-1NULL\s0 pointer dereferences \fInot\fR +halting the program may not work properly with this option. Use +\&\-fno-delete-null-pointer-checks to disable this optimizing for programs +which depend on that behavior. +.Ip "\fB\-fexpensive-optimizations\fR" 4 +.IX Item "-fexpensive-optimizations" +Perform a number of minor optimizations that are relatively expensive. +.Ip "\fB\-foptimize-register-move\fR" 4 +.IX Item "-foptimize-register-move" +.PD 0 +.Ip "\fB\-fregmove\fR" 4 +.IX Item "-fregmove" +.PD +Attempt to reassign register numbers in move instructions and as +operands of other simple instructions in order to maximize the amount of +register tying. This is especially helpful on machines with two-operand +instructions. \s-1GCC\s0 enables this optimization by default with \fB\-O2\fR +or higher. +.Sp +Note \fB\-fregmove\fR and \fB\-foptimize-register-move\fR are the same +optimization. +.Ip "\fB\-fdelayed-branch\fR" 4 +.IX Item "-fdelayed-branch" +If supported for the target machine, attempt to reorder instructions +to exploit instruction slots available after delayed branch +instructions. +.Ip "\fB\-fschedule-insns\fR" 4 +.IX Item "-fschedule-insns" +If supported for the target machine, attempt to reorder instructions to +eliminate execution stalls due to required data being unavailable. This +helps machines that have slow floating point or memory load instructions +by allowing other instructions to be issued until the result of the load +or floating point instruction is required. +.Ip "\fB\-fschedule-insns2\fR" 4 +.IX Item "-fschedule-insns2" +Similar to \fB\-fschedule-insns\fR, but requests an additional pass of +instruction scheduling after register allocation has been done. This is +especially useful on machines with a relatively small number of +registers and where memory load instructions take more than one cycle. +.Ip "\fB\-ffunction-sections\fR" 4 +.IX Item "-ffunction-sections" +.PD 0 +.Ip "\fB\-fdata-sections\fR" 4 +.IX Item "-fdata-sections" +.PD +Place each function or data item into its own section in the output +file if the target supports arbitrary sections. The name of the +function or the name of the data item determines the section's name +in the output file. +.Sp +Use these options on systems where the linker can perform optimizations +to improve locality of reference in the instruction space. \s-1HPPA\s0 +processors running \s-1HP-UX\s0 and Sparc processors running Solaris 2 have +linkers with such optimizations. Other systems using the \s-1ELF\s0 object format +as well as \s-1AIX\s0 may have these optimizations in the future. +.Sp +Only use these options when there are significant benefits from doing +so. When you specify these options, the assembler and linker will +create larger object and executable files and will also be slower. +You will not be able to use \f(CW\*(C`gprof\*(C'\fR on all systems if you +specify this option and you may have problems with debugging if +you specify both this option and \fB\-g\fR. +.Ip "\fB\-fcaller-saves\fR" 4 +.IX Item "-fcaller-saves" +Enable values to be allocated in registers that will be clobbered by +function calls, by emitting extra instructions to save and restore the +registers around such calls. Such allocation is done only when it +seems to result in better code than would otherwise be produced. +.Sp +This option is always enabled by default on certain machines, usually +those which have no call-preserved registers to use instead. +.Sp +For all machines, optimization level 2 and higher enables this flag by +default. +.Ip "\fB\-funroll-loops\fR" 4 +.IX Item "-funroll-loops" +Perform the optimization of loop unrolling. This is only done for loops +whose number of iterations can be determined at compile time or run time. +\&\fB\-funroll-loops\fR implies both \fB\-fstrength-reduce\fR and +\&\fB\-frerun-cse-after-loop\fR. +.Ip "\fB\-funroll-all-loops\fR" 4 +.IX Item "-funroll-all-loops" +Perform the optimization of loop unrolling. This is done for all loops +and usually makes programs run more slowly. \fB\-funroll-all-loops\fR +implies \fB\-fstrength-reduce\fR as well as \fB\-frerun-cse-after-loop\fR. +.Ip "\fB\-fmove-all-movables\fR" 4 +.IX Item "-fmove-all-movables" +Forces all invariant computations in loops to be moved +outside the loop. +.Ip "\fB\-freduce-all-givs\fR" 4 +.IX Item "-freduce-all-givs" +Forces all general-induction variables in loops to be +strength-reduced. +.Sp +\&\fINote:\fR When compiling programs written in Fortran, +\&\fB\-fmove-all-movables\fR and \fB\-freduce-all-givs\fR are enabled +by default when you use the optimizer. +.Sp +These options may generate better or worse code; results are highly +dependent on the structure of loops within the source code. +.Sp +These two options are intended to be removed someday, once +they have helped determine the efficacy of various +approaches to improving loop optimizations. +.Sp +Please let us (<\fBgcc@gcc.gnu.org\fR> and <\fBfortran@gnu.org\fR>) +know how use of these options affects +the performance of your production code. +We're very interested in code that runs \fIslower\fR +when these options are \fIenabled\fR. +.Ip "\fB\-fno-peephole\fR" 4 +.IX Item "-fno-peephole" +Disable any machine-specific peephole optimizations. +.Ip "\fB\-fbranch-probabilities\fR" 4 +.IX Item "-fbranch-probabilities" +After running a program compiled with \fB\-fprofile-arcs\fR, you can compile it a second time using +\&\fB\-fbranch-probabilities\fR, to improve optimizations based on +guessing the path a branch might take. +.Ip "\fB\-fno-guess-branch-probability\fR" 4 +.IX Item "-fno-guess-branch-probability" +Sometimes gcc will opt to guess branch probabilities when none are +available from either profile directed feedback (\fB\-fprofile-arcs\fR) +or \fB_\|_builtin_expect\fR. In a hard real-time system, people don't +want different runs of the compiler to produce code that has different +behavior; minimizing non-determinism is of paramount import. This +switch allows users to reduce non-determinism, possibly at the expense +of inferior optimization. +.Ip "\fB\-fstrict-aliasing\fR" 4 +.IX Item "-fstrict-aliasing" +Allows the compiler to assume the strictest aliasing rules applicable to +the language being compiled. For C (and \*(C+), this activates +optimizations based on the type of expressions. In particular, an +object of one type is assumed never to reside at the same address as an +object of a different type, unless the types are almost the same. For +example, an \f(CW\*(C`unsigned int\*(C'\fR can alias an \f(CW\*(C`int\*(C'\fR, but not a +\&\f(CW\*(C`void*\*(C'\fR or a \f(CW\*(C`double\*(C'\fR. A character type may alias any other +type. +.Sp +Pay special attention to code like this: +.Sp +.Vb 4 +\& union a_union { +\& int i; +\& double d; +\& }; +.Ve +.Vb 5 +\& int f() { +\& a_union t; +\& t.d = 3.0; +\& return t.i; +\& } +.Ve +The practice of reading from a different union member than the one most +recently written to (called ``type-punning'') is common. Even with +\&\fB\-fstrict-aliasing\fR, type-punning is allowed, provided the memory +is accessed through the union type. So, the code above will work as +expected. However, this code might not: +.Sp +.Vb 7 +\& int f() { +\& a_union t; +\& int* ip; +\& t.d = 3.0; +\& ip = &t.i; +\& return *ip; +\& } +.Ve +.Ip "\fB\-falign-functions\fR" 4 +.IX Item "-falign-functions" +.PD 0 +.Ip "\fB\-falign-functions=\fR\fIn\fR" 4 +.IX Item "-falign-functions=n" +.PD +Align the start of functions to the next power-of-two greater than +\&\fIn\fR, skipping up to \fIn\fR bytes. For instance, +\&\fB\-falign-functions=32\fR aligns functions to the next 32\-byte +boundary, but \fB\-falign-functions=24\fR would align to the next +32\-byte boundary only if this can be done by skipping 23 bytes or less. +.Sp +\&\fB\-fno-align-functions\fR and \fB\-falign-functions=1\fR are +equivalent and mean that functions will not be aligned. +.Sp +Some assemblers only support this flag when \fIn\fR is a power of two; +in that case, it is rounded up. +.Sp +If \fIn\fR is not specified, use a machine-dependent default. +.Ip "\fB\-falign-labels\fR" 4 +.IX Item "-falign-labels" +.PD 0 +.Ip "\fB\-falign-labels=\fR\fIn\fR" 4 +.IX Item "-falign-labels=n" +.PD +Align all branch targets to a power-of-two boundary, skipping up to +\&\fIn\fR bytes like \fB\-falign-functions\fR. This option can easily +make code slower, because it must insert dummy operations for when the +branch target is reached in the usual flow of the code. +.Sp +If \fB\-falign-loops\fR or \fB\-falign-jumps\fR are applicable and +are greater than this value, then their values are used instead. +.Sp +If \fIn\fR is not specified, use a machine-dependent default which is +very likely to be \fB1\fR, meaning no alignment. +.Ip "\fB\-falign-loops\fR" 4 +.IX Item "-falign-loops" +.PD 0 +.Ip "\fB\-falign-loops=\fR\fIn\fR" 4 +.IX Item "-falign-loops=n" +.PD +Align loops to a power-of-two boundary, skipping up to \fIn\fR bytes +like \fB\-falign-functions\fR. The hope is that the loop will be +executed many times, which will make up for any execution of the dummy +operations. +.Sp +If \fIn\fR is not specified, use a machine-dependent default. +.Ip "\fB\-falign-jumps\fR" 4 +.IX Item "-falign-jumps" +.PD 0 +.Ip "\fB\-falign-jumps=\fR\fIn\fR" 4 +.IX Item "-falign-jumps=n" +.PD +Align branch targets to a power-of-two boundary, for branch targets +where the targets can only be reached by jumping, skipping up to \fIn\fR +bytes like \fB\-falign-functions\fR. In this case, no dummy operations +need be executed. +.Sp +If \fIn\fR is not specified, use a machine-dependent default. +.Ip "\fB\-fssa\fR" 4 +.IX Item "-fssa" +Perform optimizations in static single assignment form. Each function's +flow graph is translated into \s-1SSA\s0 form, optimizations are performed, and +the flow graph is translated back from \s-1SSA\s0 form. User's should not +specify this option, since it is not yet ready for production use. +.Ip "\fB\-fdce\fR" 4 +.IX Item "-fdce" +Perform dead-code elimination in \s-1SSA\s0 form. Requires \fB\-fssa\fR. Like +\&\fB\-fssa\fR, this is an experimental feature. +.Ip "\fB\-fsingle-precision-constant\fR" 4 +.IX Item "-fsingle-precision-constant" +Treat floating point constant as single precision constant instead of +implicitly converting it to double precision constant. +.Ip "\fB\-frename-registers\fR" 4 +.IX Item "-frename-registers" +Attempt to avoid false dependancies in scheduled code by making use +of registers left over after register allocation. This optimization +will most benefit processors with lots of registers. It can, however, +make debugging impossible, since variables will no longer stay in +a ``home register''. +.Ip "\fB\*(--param\fR \fIname\fR\fB=\fR\fIvalue\fR" 4 +.IX Item "param name=value" +In some places, \s-1GCC\s0 uses various constants to control the amount of +optimization that is done. For example, \s-1GCC\s0 will not inline functions +that contain more that a certain number of instructions. You can +control some of these constants on the command-line using the +\&\fB\*(--param\fR option. +.Sp +In each case, the \fIvalue\fR is a integer. The allowable choices for +\&\fIname\fR are given in the following table: +.RS 4 +.Ip "\fBmax-delay-slot-insn-search\fR" 4 +.IX Item "max-delay-slot-insn-search" +The maximum number of instructions to consider when looking for an +instruction to fill a delay slot. If more than this arbitrary number of +instructions is searched, the time savings from filling the delay slot +will be minimal so stop searching. Increasing values mean more +aggressive optimization, making the compile time increase with probably +small improvement in executable run time. +.Ip "\fBmax-delay-slot-live-search\fR" 4 +.IX Item "max-delay-slot-live-search" +When trying to fill delay slots, the maximum number of instructions to +consider when searching for a block with valid live register +information. Increasing this arbitrarily chosen value means more +aggressive optimization, increasing the compile time. This parameter +should be removed when the delay slot code is rewritten to maintain the +control-flow graph. +.Ip "\fBmax-gcse-memory\fR" 4 +.IX Item "max-gcse-memory" +The approximate maximum amount of memory that will be allocated in +order to perform the global common subexpression elimination +optimization. If more memory than specified is required, the +optimization will not be done. +.Ip "\fBmax-inline-insns\fR" 4 +.IX Item "max-inline-insns" +If an function contains more than this many instructions, it +will not be inlined. This option is precisely equivalent to +\&\fB\-finline-limit\fR. +.RE +.RS 4 +.RE +.Sh "Options Controlling the Preprocessor" +.IX Subsection "Options Controlling the Preprocessor" +These options control the C preprocessor, which is run on each C source +file before actual compilation. +.PP +If you use the \fB\-E\fR option, nothing is done except preprocessing. +Some of these options make sense only together with \fB\-E\fR because +they cause the preprocessor output to be unsuitable for actual +compilation. +.Ip "\fB\-include\fR \fIfile\fR" 4 +.IX Item "-include file" +Process \fIfile\fR as input before processing the regular input file. +In effect, the contents of \fIfile\fR are compiled first. Any \fB\-D\fR +and \fB\-U\fR options on the command line are always processed before +\&\fB\-include\fR \fIfile\fR, regardless of the order in which they are +written. All the \fB\-include\fR and \fB\-imacros\fR options are +processed in the order in which they are written. +.Ip "\fB\-imacros\fR \fIfile\fR" 4 +.IX Item "-imacros file" +Process \fIfile\fR as input, discarding the resulting output, before +processing the regular input file. Because the output generated from +\&\fIfile\fR is discarded, the only effect of \fB\-imacros\fR \fIfile\fR +is to make the macros defined in \fIfile\fR available for use in the +main input. All the \fB\-include\fR and \fB\-imacros\fR options are +processed in the order in which they are written. +.Ip "\fB\-idirafter\fR \fIdir\fR" 4 +.IX Item "-idirafter dir" +Add the directory \fIdir\fR to the second include path. The directories +on the second include path are searched when a header file is not found +in any of the directories in the main include path (the one that +\&\fB\-I\fR adds to). +.Ip "\fB\-iprefix\fR \fIprefix\fR" 4 +.IX Item "-iprefix prefix" +Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR +options. +.Ip "\fB\-iwithprefix\fR \fIdir\fR" 4 +.IX Item "-iwithprefix dir" +Add a directory to the second include path. The directory's name is +made by concatenating \fIprefix\fR and \fIdir\fR, where \fIprefix\fR was +specified previously with \fB\-iprefix\fR. If you have not specified a +prefix yet, the directory containing the installed passes of the +compiler is used as the default. +.Ip "\fB\-iwithprefixbefore\fR \fIdir\fR" 4 +.IX Item "-iwithprefixbefore dir" +Add a directory to the main include path. The directory's name is made +by concatenating \fIprefix\fR and \fIdir\fR, as in the case of +\&\fB\-iwithprefix\fR. +.Ip "\fB\-isystem\fR \fIdir\fR" 4 +.IX Item "-isystem dir" +Add a directory to the beginning of the second include path, marking it +as a system directory, so that it gets the same special treatment as +is applied to the standard system directories. +.Ip "\fB\-nostdinc\fR" 4 +.IX Item "-nostdinc" +Do not search the standard system directories for header files. Only +the directories you have specified with \fB\-I\fR options (and the +current directory, if appropriate) are searched. +.Sp +By using both \fB\-nostdinc\fR and \fB\-I-\fR, you can limit the include-file +search path to only those directories you specify explicitly. +.Ip "\fB\-remap\fR" 4 +.IX Item "-remap" +When searching for a header file in a directory, remap file names if a +file named \fIheader.gcc\fR exists in that directory. This can be used +to work around limitations of file systems with file name restrictions. +The \fIheader.gcc\fR file should contain a series of lines with two +tokens on each line: the first token is the name to map, and the second +token is the actual name to use. +.Ip "\fB\-undef\fR" 4 +.IX Item "-undef" +Do not predefine any nonstandard macros. (Including architecture flags). +.Ip "\fB\-E\fR" 4 +.IX Item "-E" +Run only the C preprocessor. Preprocess all the C source files +specified and output the results to standard output or to the +specified output file. +.Ip "\fB\-C\fR" 4 +.IX Item "-C" +Tell the preprocessor not to discard comments. Used with the +\&\fB\-E\fR option. +.Ip "\fB\-P\fR" 4 +.IX Item "-P" +Tell the preprocessor not to generate \fB#line\fR directives. +Used with the \fB\-E\fR option. +.Ip "\fB\-M\fR" 4 +.IX Item "-M" +Instead of outputting the result of preprocessing, output a rule +suitable for \f(CW\*(C`make\*(C'\fR describing the dependencies of the main source +file. The preprocessor outputs one \f(CW\*(C`make\*(C'\fR rule containing the +object file name for that source file, a colon, and the names of all the +included files. Unless overridden explicitly, the object file name +consists of the basename of the source file with any suffix replaced with +object file suffix. If there are many included files then the +rule is split into several lines using \fB\e\fR\-newline. +.Sp +\&\fB\-M\fR implies \fB\-E\fR. +.Ip "\fB\-MM\fR" 4 +.IX Item "-MM" +Like \fB\-M\fR, but mention only the files included with \fB#include +"\fR\fIfile\fR\fB"\fR. System header files included with \fB#include +<\fR\fIfile\fR\fB>\fR are omitted. +.Ip "\fB\-MD\fR" 4 +.IX Item "-MD" +Like \fB\-M\fR but the dependency information is written to a file +rather than stdout. \f(CW\*(C`gcc\*(C'\fR will use the same file name and +directory as the object file, but with the suffix \*(L".d\*(R" instead. +.Sp +This is in addition to compiling the main file as specified \-\-\- +\&\fB\-MD\fR does not inhibit ordinary compilation the way \fB\-M\fR does, +unless you also specify \fB\-MG\fR. +.Sp +With Mach, you can use the utility \f(CW\*(C`md\*(C'\fR to merge multiple +dependency files into a single dependency file suitable for using with +the \fBmake\fR command. +.Ip "\fB\-MMD\fR" 4 +.IX Item "-MMD" +Like \fB\-MD\fR except mention only user header files, not system +\&\-header files. +.Ip "\fB\-MF\fR \fIfile\fR" 4 +.IX Item "-MF file" +When used with \fB\-M\fR or \fB\-MM\fR, specifies a file to write the +dependencies to. This allows the preprocessor to write the preprocessed +file to stdout normally. If no \fB\-MF\fR switch is given, \s-1CPP\s0 sends +the rules to stdout and suppresses normal preprocessed output. +.Sp +Another way to specify output of a \f(CW\*(C`make\*(C'\fR rule is by setting +the environment variable \fB\s-1DEPENDENCIES_OUTPUT\s0\fR. +.Ip "\fB\-MG\fR" 4 +.IX Item "-MG" +When used with \fB\-M\fR or \fB\-MM\fR, \fB\-MG\fR says to treat missing +header files as generated files and assume they live in the same +directory as the source file. It suppresses preprocessed output, as a +missing header file is ordinarily an error. +.Sp +This feature is used in automatic updating of makefiles. +.Ip "\fB\-MP\fR" 4 +.IX Item "-MP" +This option instructs \s-1CPP\s0 to add a phony target for each dependency +other than the main file, causing each to depend on nothing. These +dummy rules work around errors \f(CW\*(C`make\*(C'\fR gives if you remove header +files without updating the \f(CW\*(C`Makefile\*(C'\fR to match. +.Sp +This is typical output:\- +.Sp +.Vb 1 +\& /tmp/test.o: /tmp/test.c /tmp/test.h +.Ve +.Vb 1 +\& /tmp/test.h: +.Ve +.Ip "\fB\-MQ\fR \fItarget\fR" 4 +.IX Item "-MQ target" +.PD 0 +.Ip "\fB\-MT\fR \fItarget\fR" 4 +.IX Item "-MT target" +.PD +By default \s-1CPP\s0 uses the main file name, including any path, and appends +the object suffix, normally ``.o'', to it to obtain the name of the +target for dependency generation. With \fB\-MT\fR you can specify a +target yourself, overriding the default one. +.Sp +If you want multiple targets, you can specify them as a single argument +to \fB\-MT\fR, or use multiple \fB\-MT\fR options. +.Sp +The targets you specify are output in the order they appear on the +command line. \fB\-MQ\fR is identical to \fB\-MT\fR, except that the +target name is quoted for Make, but with \fB\-MT\fR it isn't. For +example, \-MT '$(objpfx)foo.o' gives +.Sp +.Vb 1 +\& $(objpfx)foo.o: /tmp/foo.c +.Ve +but \-MQ '$(objpfx)foo.o' gives +.Sp +.Vb 1 +\& $$(objpfx)foo.o: /tmp/foo.c +.Ve +The default target is automatically quoted, as if it were given with +\&\fB\-MQ\fR. +.Ip "\fB\-H\fR" 4 +.IX Item "-H" +Print the name of each header file used, in addition to other normal +activities. +.Ip "\fB\-A\fR\fIquestion\fR\fB(\fR\fIanswer\fR\fB)\fR" 4 +.IX Item "-Aquestion(answer)" +Assert the answer \fIanswer\fR for \fIquestion\fR, in case it is tested +with a preprocessing conditional such as \fB#if +#\fR\fIquestion\fR\fB(\fR\fIanswer\fR\fB)\fR. \fB\-A-\fR disables the standard +assertions that normally describe the target machine. +.Ip "\fB\-D\fR\fImacro\fR" 4 +.IX Item "-Dmacro" +Define macro \fImacro\fR with the string \fB1\fR as its definition. +.Ip "\fB\-D\fR\fImacro\fR\fB=\fR\fIdefn\fR" 4 +.IX Item "-Dmacro=defn" +Define macro \fImacro\fR as \fIdefn\fR. All instances of \fB\-D\fR on +the command line are processed before any \fB\-U\fR options. +.Sp +Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in +order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the +order in which they are written. +.Ip "\fB\-U\fR\fImacro\fR" 4 +.IX Item "-Umacro" +Undefine macro \fImacro\fR. \fB\-U\fR options are evaluated after all +\&\fB\-D\fR options, but before any \fB\-include\fR and \fB\-imacros\fR +options. +.Sp +Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in +order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the +order in which they are written. +.Ip "\fB\-dM\fR" 4 +.IX Item "-dM" +Tell the preprocessor to output only a list of the macro definitions +that are in effect at the end of preprocessing. Used with the \fB\-E\fR +option. +.Ip "\fB\-dD\fR" 4 +.IX Item "-dD" +Tell the preprocessing to pass all macro definitions into the output, in +their proper sequence in the rest of the output. +.Ip "\fB\-dN\fR" 4 +.IX Item "-dN" +Like \fB\-dD\fR except that the macro arguments and contents are omitted. +Only \fB#define\fR \fIname\fR is included in the output. +.Ip "\fB\-dI\fR" 4 +.IX Item "-dI" +Output \fB#include\fR directives in addition to the result of +preprocessing. +.Ip "\fB\-trigraphs\fR" 4 +.IX Item "-trigraphs" +Process \s-1ISO\s0 standard trigraph sequences. These are three-character +sequences, all starting with \fB??\fR, that are defined by \s-1ISO\s0 C to +stand for single characters. For example, \fB??/\fR stands for +\&\fB\e\fR, so \fB'??/n'\fR is a character constant for a newline. By +default, \s-1GCC\s0 ignores trigraphs, but in standard-conforming modes it +converts them. See the \fB\-std\fR and \fB\-ansi\fR options. +.Sp +The nine trigraph sequences are +.RS 4 +.Ip "\fB??(\fR" 4 +.IX Item "??(" +-> \fB[\fR +.Ip "\fB??)\fR" 4 +.IX Item "??)" +-> \fB]\fR +.Ip "\fB??<\fR" 4 +.IX Item "??<" +-> \fB{\fR +.Ip "\fB??>\fR" 4 +.IX Item "??>" +-> \fB}\fR +.Ip "\fB??=\fR" 4 +.IX Item "??=" +-> \fB#\fR +.Ip "\fB??/\fR" 4 +.IX Item "??/" +-> \fB\e\fR +.Ip "\fB??'\fR" 4 +.IX Item "??'" +-> \fB^\fR +.Ip "\fB??!\fR" 4 +.IX Item "??!" +-> \fB|\fR +.Ip "\fB??-\fR" 4 +.IX Item "??-" +-> \fB~\fR +.RE +.RS 4 +.Sp +Trigraph support is not popular, so many compilers do not implement it +properly. Portable code should not rely on trigraphs being either +converted or ignored. +.RE +.Ip "\fB\-Wp,\fR\fIoption\fR" 4 +.IX Item "-Wp,option" +Pass \fIoption\fR as an option to the preprocessor. If \fIoption\fR +contains commas, it is split into multiple options at the commas. +.Sh "Passing Options to the Assembler" +.IX Subsection "Passing Options to the Assembler" +You can pass options to the assembler. +.Ip "\fB\-Wa,\fR\fIoption\fR" 4 +.IX Item "-Wa,option" +Pass \fIoption\fR as an option to the assembler. If \fIoption\fR +contains commas, it is split into multiple options at the commas. +.Sh "Options for Linking" +.IX Subsection "Options for Linking" +These options come into play when the compiler links object files into +an executable output file. They are meaningless if the compiler is +not doing a link step. +.Ip "\fIobject-file-name\fR" 4 +.IX Item "object-file-name" +A file name that does not end in a special recognized suffix is +considered to name an object file or library. (Object files are +distinguished from libraries by the linker according to the file +contents.) If linking is done, these object files are used as input +to the linker. +.Ip "\fB\-c\fR" 4 +.IX Item "-c" +.PD 0 +.Ip "\fB\-S\fR" 4 +.IX Item "-S" +.Ip "\fB\-E\fR" 4 +.IX Item "-E" +.PD +If any of these options is used, then the linker is not run, and +object file names should not be used as arguments. +.Ip "\fB\-l\fR\fIlibrary\fR" 4 +.IX Item "-llibrary" +.PD 0 +.Ip "\fB\-l\fR \fIlibrary\fR" 4 +.IX Item "-l library" +.PD +Search the library named \fIlibrary\fR when linking. (The second +alternative with the library as a separate argument is only for +\&\s-1POSIX\s0 compliance and is not recommended.) +.Sp +It makes a difference where in the command you write this option; the +linker searches and processes libraries and object files in the order they +are specified. Thus, \fBfoo.o \-lz bar.o\fR searches library \fBz\fR +after file \fIfoo.o\fR but before \fIbar.o\fR. If \fIbar.o\fR refers +to functions in \fBz\fR, those functions may not be loaded. +.Sp +The linker searches a standard list of directories for the library, +which is actually a file named \fIlib\fIlibrary\fI.a\fR. The linker +then uses this file as if it had been specified precisely by name. +.Sp +The directories searched include several standard system directories +plus any that you specify with \fB\-L\fR. +.Sp +Normally the files found this way are library files\-\-\-archive files +whose members are object files. The linker handles an archive file by +scanning through it for members which define symbols that have so far +been referenced but not defined. But if the file that is found is an +ordinary object file, it is linked in the usual fashion. The only +difference between using an \fB\-l\fR option and specifying a file name +is that \fB\-l\fR surrounds \fIlibrary\fR with \fBlib\fR and \fB.a\fR +and searches several directories. +.Ip "\fB\-lobjc\fR" 4 +.IX Item "-lobjc" +You need this special case of the \fB\-l\fR option in order to +link an Objective C program. +.Ip "\fB\-nostartfiles\fR" 4 +.IX Item "-nostartfiles" +Do not use the standard system startup files when linking. +The standard system libraries are used normally, unless \fB\-nostdlib\fR +or \fB\-nodefaultlibs\fR is used. +.Ip "\fB\-nodefaultlibs\fR" 4 +.IX Item "-nodefaultlibs" +Do not use the standard system libraries when linking. +Only the libraries you specify will be passed to the linker. +The standard startup files are used normally, unless \fB\-nostartfiles\fR +is used. The compiler may generate calls to memcmp, memset, and memcpy +for System V (and \s-1ISO\s0 C) environments or to bcopy and bzero for +\&\s-1BSD\s0 environments. These entries are usually resolved by entries in +libc. These entry points should be supplied through some other +mechanism when this option is specified. +.Ip "\fB\-nostdlib\fR" 4 +.IX Item "-nostdlib" +Do not use the standard system startup files or libraries when linking. +No startup files and only the libraries you specify will be passed to +the linker. The compiler may generate calls to memcmp, memset, and memcpy +for System V (and \s-1ISO\s0 C) environments or to bcopy and bzero for +\&\s-1BSD\s0 environments. These entries are usually resolved by entries in +libc. These entry points should be supplied through some other +mechanism when this option is specified. +.Sp +One of the standard libraries bypassed by \fB\-nostdlib\fR and +\&\fB\-nodefaultlibs\fR is \fIlibgcc.a\fR, a library of internal subroutines +that \s-1GCC\s0 uses to overcome shortcomings of particular machines, or special +needs for some languages. +.Sp +In most cases, you need \fIlibgcc.a\fR even when you want to avoid +other standard libraries. In other words, when you specify \fB\-nostdlib\fR +or \fB\-nodefaultlibs\fR you should usually specify \fB\-lgcc\fR as well. +This ensures that you have no unresolved references to internal \s-1GCC\s0 +library subroutines. (For example, \fB_\|_main\fR, used to ensure \*(C+ +constructors will be called.) +.Ip "\fB\-s\fR" 4 +.IX Item "-s" +Remove all symbol table and relocation information from the executable. +.Ip "\fB\-static\fR" 4 +.IX Item "-static" +On systems that support dynamic linking, this prevents linking with the shared +libraries. On other systems, this option has no effect. +.Ip "\fB\-shared\fR" 4 +.IX Item "-shared" +Produce a shared object which can then be linked with other objects to +form an executable. Not all systems support this option. For predictable +results, you must also specify the same set of options that were used to +generate code (\fB\-fpic\fR, \fB\-fPIC\fR, or model suboptions) +when you specify this option.[1] +.Ip "\fB\-shared-libgcc\fR" 4 +.IX Item "-shared-libgcc" +.PD 0 +.Ip "\fB\-static-libgcc\fR" 4 +.IX Item "-static-libgcc" +.PD +On systems that provide \fIlibgcc\fR as a shared library, these options +force the use of either the shared or static version respectively. +If no shared version of \fIlibgcc\fR was built when the compiler was +configured, these options have no effect. +.Sp +There are several situations in which an application should use the +shared \fIlibgcc\fR instead of the static version. The most common +of these is when the application wishes to throw and catch exceptions +across different shared libraries. In that case, each of the libraries +as well as the application itself should use the shared \fIlibgcc\fR. +.Sp +Therefore, whenever you specify the \fB\-shared\fR option, the \s-1GCC\s0 +driver automatically adds \fB\-shared-libgcc\fR, unless you explicitly +specify \fB\-static-libgcc\fR. The G++ driver automatically adds +\&\fB\-shared-libgcc\fR when you build a main executable as well because +for \*(C+ programs that is typically the right thing to do. +(Exception-handling will not work reliably otherwise.) +.Sp +However, when linking a main executable written in C, you must +explicitly say \fB\-shared-libgcc\fR if you want to use the shared +\&\fIlibgcc\fR. +.Ip "\fB\-symbolic\fR" 4 +.IX Item "-symbolic" +Bind references to global symbols when building a shared object. Warn +about any unresolved references (unless overridden by the link editor +option \fB\-Xlinker \-z \-Xlinker defs\fR). Only a few systems support +this option. +.Ip "\fB\-Xlinker\fR \fIoption\fR" 4 +.IX Item "-Xlinker option" +Pass \fIoption\fR as an option to the linker. You can use this to +supply system-specific linker options which \s-1GCC\s0 does not know how to +recognize. +.Sp +If you want to pass an option that takes an argument, you must use +\&\fB\-Xlinker\fR twice, once for the option and once for the argument. +For example, to pass \fB\-assert definitions\fR, you must write +\&\fB\-Xlinker \-assert \-Xlinker definitions\fR. It does not work to write +\&\fB\-Xlinker \*(L"\-assert definitions\*(R"\fR, because this passes the entire +string as a single argument, which is not what the linker expects. +.Ip "\fB\-Wl,\fR\fIoption\fR" 4 +.IX Item "-Wl,option" +Pass \fIoption\fR as an option to the linker. If \fIoption\fR contains +commas, it is split into multiple options at the commas. +.Ip "\fB\-u\fR \fIsymbol\fR" 4 +.IX Item "-u symbol" +Pretend the symbol \fIsymbol\fR is undefined, to force linking of +library modules to define it. You can use \fB\-u\fR multiple times with +different symbols to force loading of additional library modules. +.Sh "Options for Directory Search" +.IX Subsection "Options for Directory Search" +These options specify directories to search for header files, for +libraries and for parts of the compiler: +.Ip "\fB\-I\fR\fIdir\fR" 4 +.IX Item "-Idir" +Add the directory \fIdir\fR to the head of the list of directories to be +searched for header files. This can be used to override a system header +file, substituting your own version, since these directories are +searched before the system header file directories. However, you should +not use this option to add directories that contain vendor-supplied +system header files (use \fB\-isystem\fR for that). If you use more than +one \fB\-I\fR option, the directories are scanned in left-to-right +order; the standard system directories come after. +.Ip "\fB\-I-\fR" 4 +.IX Item "-I-" +Any directories you specify with \fB\-I\fR options before the \fB\-I-\fR +option are searched only for the case of \fB#include "\fR\fIfile\fR\fB"\fR; +they are not searched for \fB#include <\fR\fIfile\fR\fB>\fR. +.Sp +If additional directories are specified with \fB\-I\fR options after +the \fB\-I-\fR, these directories are searched for all \fB#include\fR +directives. (Ordinarily \fIall\fR \fB\-I\fR directories are used +this way.) +.Sp +In addition, the \fB\-I-\fR option inhibits the use of the current +directory (where the current input file came from) as the first search +directory for \fB#include "\fR\fIfile\fR\fB"\fR. There is no way to +override this effect of \fB\-I-\fR. With \fB\-I.\fR you can specify +searching the directory which was current when the compiler was +invoked. That is not exactly the same as what the preprocessor does +by default, but it is often satisfactory. +.Sp +\&\fB\-I-\fR does not inhibit the use of the standard system directories +for header files. Thus, \fB\-I-\fR and \fB\-nostdinc\fR are +independent. +.Ip "\fB\-L\fR\fIdir\fR" 4 +.IX Item "-Ldir" +Add directory \fIdir\fR to the list of directories to be searched +for \fB\-l\fR. +.Ip "\fB\-B\fR\fIprefix\fR" 4 +.IX Item "-Bprefix" +This option specifies where to find the executables, libraries, +include files, and data files of the compiler itself. +.Sp +The compiler driver program runs one or more of the subprograms +\&\fIcpp\fR, \fIcc1\fR, \fIas\fR and \fIld\fR. It tries +\&\fIprefix\fR as a prefix for each program it tries to run, both with and +without \fImachine\fR\fB/\fR\fIversion\fR\fB/\fR. +.Sp +For each subprogram to be run, the compiler driver first tries the +\&\fB\-B\fR prefix, if any. If that name is not found, or if \fB\-B\fR +was not specified, the driver tries two standard prefixes, which are +\&\fI/usr/lib/gcc/\fR and \fI/usr/local/lib/gcc-lib/\fR. If neither of +those results in a file name that is found, the unmodified program +name is searched for using the directories specified in your +\&\fB\s-1PATH\s0\fR environment variable. +.Sp +\&\fB\-B\fR prefixes that effectively specify directory names also apply +to libraries in the linker, because the compiler translates these +options into \fB\-L\fR options for the linker. They also apply to +includes files in the preprocessor, because the compiler translates these +options into \fB\-isystem\fR options for the preprocessor. In this case, +the compiler appends \fBinclude\fR to the prefix. +.Sp +The run-time support file \fIlibgcc.a\fR can also be searched for using +the \fB\-B\fR prefix, if needed. If it is not found there, the two +standard prefixes above are tried, and that is all. The file is left +out of the link if it is not found by those means. +.Sp +Another way to specify a prefix much like the \fB\-B\fR prefix is to use +the environment variable \fB\s-1GCC_EXEC_PREFIX\s0\fR. +.Ip "\fB\-specs=\fR\fIfile\fR" 4 +.IX Item "-specs=file" +Process \fIfile\fR after the compiler reads in the standard \fIspecs\fR +file, in order to override the defaults that the \fIgcc\fR driver +program uses when determining what switches to pass to \fIcc1\fR, +\&\fIcc1plus\fR, \fIas\fR, \fIld\fR, etc. More than one +\&\fB\-specs=\fR\fIfile\fR can be specified on the command line, and they +are processed in order, from left to right. +.Sh "Specifying Target Machine and Compiler Version" +.IX Subsection "Specifying Target Machine and Compiler Version" +By default, \s-1GCC\s0 compiles code for the same type of machine that you +are using. However, it can also be installed as a cross-compiler, to +compile for some other type of machine. In fact, several different +configurations of \s-1GCC\s0, for different target machines, can be +installed side by side. Then you specify which one to use with the +\&\fB\-b\fR option. +.PP +In addition, older and newer versions of \s-1GCC\s0 can be installed side +by side. One of them (probably the newest) will be the default, but +you may sometimes wish to use another. +.Ip "\fB\-b\fR \fImachine\fR" 4 +.IX Item "-b machine" +The argument \fImachine\fR specifies the target machine for compilation. +This is useful when you have installed \s-1GCC\s0 as a cross-compiler. +.Sp +The value to use for \fImachine\fR is the same as was specified as the +machine type when configuring \s-1GCC\s0 as a cross-compiler. For +example, if a cross-compiler was configured with \fBconfigure +i386v\fR, meaning to compile for an 80386 running System V, then you +would specify \fB\-b i386v\fR to run that cross compiler. +.Sp +When you do not specify \fB\-b\fR, it normally means to compile for +the same type of machine that you are using. +.Ip "\fB\-V\fR \fIversion\fR" 4 +.IX Item "-V version" +The argument \fIversion\fR specifies which version of \s-1GCC\s0 to run. +This is useful when multiple versions are installed. For example, +\&\fIversion\fR might be \fB2.0\fR, meaning to run \s-1GCC\s0 version 2.0. +.Sp +The default version, when you do not specify \fB\-V\fR, is the last +version of \s-1GCC\s0 that you installed. +.PP +The \fB\-b\fR and \fB\-V\fR options actually work by controlling part of +the file name used for the executable files and libraries used for +compilation. A given version of \s-1GCC\s0, for a given target machine, is +normally kept in the directory \fI/usr/local/lib/gcc-lib/\fImachine\fI/\fIversion\fI\fR. +.PP +Thus, sites can customize the effect of \fB\-b\fR or \fB\-V\fR either by +changing the names of these directories or adding alternate names (or +symbolic links). If in directory \fI/usr/local/lib/gcc-lib/\fR the +file \fI80386\fR is a link to the file \fIi386v\fR, then \fB\-b +80386\fR becomes an alias for \fB\-b i386v\fR. +.PP +In one respect, the \fB\-b\fR or \fB\-V\fR do not completely change +to a different compiler: the top-level driver program \fBgcc\fR +that you originally invoked continues to run and invoke the other +executables (preprocessor, compiler per se, assembler and linker) +that do the real work. However, since no real work is done in the +driver program, it usually does not matter that the driver program +in use is not the one for the specified target. It is common for the +interface to the other executables to change incompatibly between +compiler versions, so unless the version specified is very close to that +of the driver (for example, \fB\-V 3.0\fR with a driver program from \s-1GCC\s0 +version 3.0.1), use of \fB\-V\fR may not work; for example, using +\&\fB\-V 2.95.2\fR will not work with a driver program from \s-1GCC\s0 3.0. +.PP +The only way that the driver program depends on the target machine is +in the parsing and handling of special machine-specific options. +However, this is controlled by a file which is found, along with the +other executables, in the directory for the specified version and +target machine. As a result, a single installed driver program adapts +to any specified target machine, and sufficiently similar compiler +versions. +.PP +The driver program executable does control one significant thing, +however: the default version and target machine. Therefore, you can +install different instances of the driver program, compiled for +different targets or versions, under different names. +.PP +For example, if the driver for version 2.0 is installed as \fBogcc\fR +and that for version 2.1 is installed as \fBgcc\fR, then the command +\&\fBgcc\fR will use version 2.1 by default, while \fBogcc\fR will use +2.0 by default. However, you can choose either version with either +command with the \fB\-V\fR option. +.Sh "Hardware Models and Configurations" +.IX Subsection "Hardware Models and Configurations" +Earlier we discussed the standard option \fB\-b\fR which chooses among +different installed compilers for completely different target +machines, such as Vax vs. 68000 vs. 80386. +.PP +In addition, each of these target machine types can have its own +special options, starting with \fB\-m\fR, to choose among various +hardware models or configurations\-\-\-for example, 68010 vs 68020, +floating coprocessor or none. A single installed version of the +compiler can compile for any model or configuration, according to the +options specified. +.PP +Some configurations of the compiler also support additional special +options, usually for compatibility with other compilers on the same +platform. +.PP +.I "M680x0 Options" +.IX Subsection "M680x0 Options" +.PP +These are the \fB\-m\fR options defined for the 68000 series. The default +values for these options depends on which style of 68000 was selected when +the compiler was configured; the defaults for the most common choices are +given below. +.Ip "\fB\-m68000\fR" 4 +.IX Item "-m68000" +.PD 0 +.Ip "\fB\-mc68000\fR" 4 +.IX Item "-mc68000" +.PD +Generate output for a 68000. This is the default +when the compiler is configured for 68000\-based systems. +.Sp +Use this option for microcontrollers with a 68000 or \s-1EC000\s0 core, +including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. +.Ip "\fB\-m68020\fR" 4 +.IX Item "-m68020" +.PD 0 +.Ip "\fB\-mc68020\fR" 4 +.IX Item "-mc68020" +.PD +Generate output for a 68020. This is the default +when the compiler is configured for 68020\-based systems. +.Ip "\fB\-m68881\fR" 4 +.IX Item "-m68881" +Generate output containing 68881 instructions for floating point. +This is the default for most 68020 systems unless \fB\-nfp\fR was +specified when the compiler was configured. +.Ip "\fB\-m68030\fR" 4 +.IX Item "-m68030" +Generate output for a 68030. This is the default when the compiler is +configured for 68030\-based systems. +.Ip "\fB\-m68040\fR" 4 +.IX Item "-m68040" +Generate output for a 68040. This is the default when the compiler is +configured for 68040\-based systems. +.Sp +This option inhibits the use of 68881/68882 instructions that have to be +emulated by software on the 68040. Use this option if your 68040 does not +have code to emulate those instructions. +.Ip "\fB\-m68060\fR" 4 +.IX Item "-m68060" +Generate output for a 68060. This is the default when the compiler is +configured for 68060\-based systems. +.Sp +This option inhibits the use of 68020 and 68881/68882 instructions that +have to be emulated by software on the 68060. Use this option if your 68060 +does not have code to emulate those instructions. +.Ip "\fB\-mcpu32\fR" 4 +.IX Item "-mcpu32" +Generate output for a \s-1CPU32\s0. This is the default +when the compiler is configured for CPU32\-based systems. +.Sp +Use this option for microcontrollers with a +\&\s-1CPU32\s0 or \s-1CPU32+\s0 core, including the 68330, 68331, 68332, 68333, 68334, +68336, 68340, 68341, 68349 and 68360. +.Ip "\fB\-m5200\fR" 4 +.IX Item "-m5200" +Generate output for a 520X \*(L"coldfire\*(R" family cpu. This is the default +when the compiler is configured for 520X-based systems. +.Sp +Use this option for microcontroller with a 5200 core, including +the \s-1MCF5202\s0, \s-1MCF5203\s0, \s-1MCF5204\s0 and \s-1MCF5202\s0. +.Ip "\fB\-m68020\-40\fR" 4 +.IX Item "-m68020-40" +Generate output for a 68040, without using any of the new instructions. +This results in code which can run relatively efficiently on either a +68020/68881 or a 68030 or a 68040. The generated code does use the +68881 instructions that are emulated on the 68040. +.Ip "\fB\-m68020\-60\fR" 4 +.IX Item "-m68020-60" +Generate output for a 68060, without using any of the new instructions. +This results in code which can run relatively efficiently on either a +68020/68881 or a 68030 or a 68040. The generated code does use the +68881 instructions that are emulated on the 68060. +.Ip "\fB\-mfpa\fR" 4 +.IX Item "-mfpa" +Generate output containing Sun \s-1FPA\s0 instructions for floating point. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not available for all m68k +targets. Normally the facilities of the machine's usual C compiler are +used, but this can't be done directly in cross-compilation. You must +make your own arrangements to provide suitable library functions for +cross-compilation. The embedded targets \fBm68k-*\-aout\fR and +\&\fBm68k-*\-coff\fR do provide software floating point support. +.Ip "\fB\-mshort\fR" 4 +.IX Item "-mshort" +Consider type \f(CW\*(C`int\*(C'\fR to be 16 bits wide, like \f(CW\*(C`short int\*(C'\fR. +.Ip "\fB\-mnobitfield\fR" 4 +.IX Item "-mnobitfield" +Do not use the bit-field instructions. The \fB\-m68000\fR, \fB\-mcpu32\fR +and \fB\-m5200\fR options imply \fB\-mnobitfield\fR. +.Ip "\fB\-mbitfield\fR" 4 +.IX Item "-mbitfield" +Do use the bit-field instructions. The \fB\-m68020\fR option implies +\&\fB\-mbitfield\fR. This is the default if you use a configuration +designed for a 68020. +.Ip "\fB\-mrtd\fR" 4 +.IX Item "-mrtd" +Use a different function-calling convention, in which functions +that take a fixed number of arguments return with the \f(CW\*(C`rtd\*(C'\fR +instruction, which pops their arguments while returning. This +saves one instruction in the caller since there is no need to pop +the arguments there. +.Sp +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. +.Sp +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR); +otherwise incorrect code will be generated for calls to those +functions. +.Sp +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) +.Sp +The \f(CW\*(C`rtd\*(C'\fR instruction is supported by the 68010, 68020, 68030, +68040, 68060 and \s-1CPU32\s0 processors, but not by the 68000 or 5200. +.Ip "\fB\-malign-int\fR" 4 +.IX Item "-malign-int" +.PD 0 +.Ip "\fB\-mno-align-int\fR" 4 +.IX Item "-mno-align-int" +.PD +Control whether \s-1GCC\s0 aligns \f(CW\*(C`int\*(C'\fR, \f(CW\*(C`long\*(C'\fR, \f(CW\*(C`long long\*(C'\fR, +\&\f(CW\*(C`float\*(C'\fR, \f(CW\*(C`double\*(C'\fR, and \f(CW\*(C`long double\*(C'\fR variables on a 32\-bit +boundary (\fB\-malign-int\fR) or a 16\-bit boundary (\fB\-mno-align-int\fR). +Aligning variables on 32\-bit boundaries produces code that runs somewhat +faster on processors with 32\-bit busses at the expense of more memory. +.Sp +\&\fBWarning:\fR if you use the \fB\-malign-int\fR switch, \s-1GCC\s0 will +align structures containing the above types differently than +most published application binary interface specifications for the m68k. +.Ip "\fB\-mpcrel\fR" 4 +.IX Item "-mpcrel" +Use the pc-relative addressing mode of the 68000 directly, instead of +using a global offset table. At present, this option implies \-fpic, +allowing at most a 16\-bit offset for pc-relative addressing. \-fPIC is +not presently supported with \-mpcrel, though this could be supported for +68020 and higher processors. +.Ip "\fB\-mno-strict-align\fR" 4 +.IX Item "-mno-strict-align" +.PD 0 +.Ip "\fB\-mstrict-align\fR" 4 +.IX Item "-mstrict-align" +.PD +Do not (do) assume that unaligned memory references will be handled by +the system. +.PP +.I "M68hc1x Options" +.IX Subsection "M68hc1x Options" +.PP +These are the \fB\-m\fR options defined for the 68hc11 and 68hc12 +microcontrollers. The default values for these options depends on +which style of microcontroller was selected when the compiler was configured; +the defaults for the most common choices are given below. +.Ip "\fB\-m6811\fR" 4 +.IX Item "-m6811" +.PD 0 +.Ip "\fB\-m68hc11\fR" 4 +.IX Item "-m68hc11" +.PD +Generate output for a 68HC11. This is the default +when the compiler is configured for 68HC11\-based systems. +.Ip "\fB\-m6812\fR" 4 +.IX Item "-m6812" +.PD 0 +.Ip "\fB\-m68hc12\fR" 4 +.IX Item "-m68hc12" +.PD +Generate output for a 68HC12. This is the default +when the compiler is configured for 68HC12\-based systems. +.Ip "\fB\-mauto-incdec\fR" 4 +.IX Item "-mauto-incdec" +Enable the use of 68HC12 pre and post auto-increment and auto-decrement +addressing modes. +.Ip "\fB\-mshort\fR" 4 +.IX Item "-mshort" +Consider type \f(CW\*(C`int\*(C'\fR to be 16 bits wide, like \f(CW\*(C`short int\*(C'\fR. +.Ip "\fB\-msoft-reg-count=\fR\fIcount\fR" 4 +.IX Item "-msoft-reg-count=count" +Specify the number of pseudo-soft registers which are used for the +code generation. The maximum number is 32. Using more pseudo-soft +register may or may not result in better code depending on the program. +The default is 4 for 68HC11 and 2 for 68HC12. +.PP +.I "\s-1VAX\s0 Options" +.IX Subsection "VAX Options" +.PP +These \fB\-m\fR options are defined for the Vax: +.Ip "\fB\-munix\fR" 4 +.IX Item "-munix" +Do not output certain jump instructions (\f(CW\*(C`aobleq\*(C'\fR and so on) +that the Unix assembler for the Vax cannot handle across long +ranges. +.Ip "\fB\-mgnu\fR" 4 +.IX Item "-mgnu" +Do output those jump instructions, on the assumption that you +will assemble with the \s-1GNU\s0 assembler. +.Ip "\fB\-mg\fR" 4 +.IX Item "-mg" +Output code for g-format floating point numbers instead of d-format. +.PP +.I "\s-1SPARC\s0 Options" +.IX Subsection "SPARC Options" +.PP +These \fB\-m\fR switches are supported on the \s-1SPARC:\s0 +.Ip "\fB\-mno-app-regs\fR" 4 +.IX Item "-mno-app-regs" +.PD 0 +.Ip "\fB\-mapp-regs\fR" 4 +.IX Item "-mapp-regs" +.PD +Specify \fB\-mapp-regs\fR to generate output using the global registers +2 through 4, which the \s-1SPARC\s0 \s-1SVR4\s0 \s-1ABI\s0 reserves for applications. This +is the default. +.Sp +To be fully \s-1SVR4\s0 \s-1ABI\s0 compliant at the cost of some performance loss, +specify \fB\-mno-app-regs\fR. You should compile libraries and system +software with this option. +.Ip "\fB\-mfpu\fR" 4 +.IX Item "-mfpu" +.PD 0 +.Ip "\fB\-mhard-float\fR" 4 +.IX Item "-mhard-float" +.PD +Generate output containing floating point instructions. This is the +default. +.Ip "\fB\-mno-fpu\fR" 4 +.IX Item "-mno-fpu" +.PD 0 +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +.PD +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not available for all \s-1SPARC\s0 +targets. Normally the facilities of the machine's usual C compiler are +used, but this cannot be done directly in cross-compilation. You must make +your own arrangements to provide suitable library functions for +cross-compilation. The embedded targets \fBsparc-*\-aout\fR and +\&\fBsparclite-*\-*\fR do provide software floating point support. +.Sp +\&\fB\-msoft-float\fR changes the calling convention in the output file; +therefore, it is only useful if you compile \fIall\fR of a program with +this option. In particular, you need to compile \fIlibgcc.a\fR, the +library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for +this to work. +.Ip "\fB\-mhard-quad-float\fR" 4 +.IX Item "-mhard-quad-float" +Generate output containing quad-word (long double) floating point +instructions. +.Ip "\fB\-msoft-quad-float\fR" 4 +.IX Item "-msoft-quad-float" +Generate output containing library calls for quad-word (long double) +floating point instructions. The functions called are those specified +in the \s-1SPARC\s0 \s-1ABI\s0. This is the default. +.Sp +As of this writing, there are no sparc implementations that have hardware +support for the quad-word floating point instructions. They all invoke +a trap handler for one of these instructions, and then the trap handler +emulates the effect of the instruction. Because of the trap handler overhead, +this is much slower than calling the \s-1ABI\s0 library routines. Thus the +\&\fB\-msoft-quad-float\fR option is the default. +.Ip "\fB\-mno-epilogue\fR" 4 +.IX Item "-mno-epilogue" +.PD 0 +.Ip "\fB\-mepilogue\fR" 4 +.IX Item "-mepilogue" +.PD +With \fB\-mepilogue\fR (the default), the compiler always emits code for +function exit at the end of each function. Any function exit in +the middle of the function (such as a return statement in C) will +generate a jump to the exit code at the end of the function. +.Sp +With \fB\-mno-epilogue\fR, the compiler tries to emit exit code inline +at every function exit. +.Ip "\fB\-mno-flat\fR" 4 +.IX Item "-mno-flat" +.PD 0 +.Ip "\fB\-mflat\fR" 4 +.IX Item "-mflat" +.PD +With \fB\-mflat\fR, the compiler does not generate save/restore instructions +and will use a \*(L"flat\*(R" or single register window calling convention. +This model uses \f(CW%i7\fR as the frame pointer and is compatible with the normal +register window model. Code from either may be intermixed. +The local registers and the input registers (0\-5) are still treated as +\&\*(L"call saved\*(R" registers and will be saved on the stack as necessary. +.Sp +With \fB\-mno-flat\fR (the default), the compiler emits save/restore +instructions (except for leaf functions) and is the normal mode of operation. +.Ip "\fB\-mno-unaligned-doubles\fR" 4 +.IX Item "-mno-unaligned-doubles" +.PD 0 +.Ip "\fB\-munaligned-doubles\fR" 4 +.IX Item "-munaligned-doubles" +.PD +Assume that doubles have 8 byte alignment. This is the default. +.Sp +With \fB\-munaligned-doubles\fR, \s-1GCC\s0 assumes that doubles have 8 byte +alignment only if they are contained in another type, or if they have an +absolute address. Otherwise, it assumes they have 4 byte alignment. +Specifying this option avoids some rare compatibility problems with code +generated by other compilers. It is not the default because it results +in a performance loss, especially for floating point code. +.Ip "\fB\-mno-faster-structs\fR" 4 +.IX Item "-mno-faster-structs" +.PD 0 +.Ip "\fB\-mfaster-structs\fR" 4 +.IX Item "-mfaster-structs" +.PD +With \fB\-mfaster-structs\fR, the compiler assumes that structures +should have 8 byte alignment. This enables the use of pairs of +\&\f(CW\*(C`ldd\*(C'\fR and \f(CW\*(C`std\*(C'\fR instructions for copies in structure +assignment, in place of twice as many \f(CW\*(C`ld\*(C'\fR and \f(CW\*(C`st\*(C'\fR pairs. +However, the use of this changed alignment directly violates the Sparc +\&\s-1ABI\s0. Thus, it's intended only for use on targets where the developer +acknowledges that their resulting code will not be directly in line with +the rules of the \s-1ABI\s0. +.Ip "\fB\-mv8\fR" 4 +.IX Item "-mv8" +.PD 0 +.Ip "\fB\-msparclite\fR" 4 +.IX Item "-msparclite" +.PD +These two options select variations on the \s-1SPARC\s0 architecture. +.Sp +By default (unless specifically configured for the Fujitsu SPARClite), +\&\s-1GCC\s0 generates code for the v7 variant of the \s-1SPARC\s0 architecture. +.Sp +\&\fB\-mv8\fR will give you \s-1SPARC\s0 v8 code. The only difference from v7 +code is that the compiler emits the integer multiply and integer +divide instructions which exist in \s-1SPARC\s0 v8 but not in \s-1SPARC\s0 v7. +.Sp +\&\fB\-msparclite\fR will give you SPARClite code. This adds the integer +multiply, integer divide step and scan (\f(CW\*(C`ffs\*(C'\fR) instructions which +exist in SPARClite but not in \s-1SPARC\s0 v7. +.Sp +These options are deprecated and will be deleted in a future \s-1GCC\s0 release. +They have been replaced with \fB\-mcpu=xxx\fR. +.Ip "\fB\-mcypress\fR" 4 +.IX Item "-mcypress" +.PD 0 +.Ip "\fB\-msupersparc\fR" 4 +.IX Item "-msupersparc" +.PD +These two options select the processor for which the code is optimised. +.Sp +With \fB\-mcypress\fR (the default), the compiler optimizes code for the +Cypress \s-1CY7C602\s0 chip, as used in the SparcStation/SparcServer 3xx series. +This is also appropriate for the older SparcStation 1, 2, \s-1IPX\s0 etc. +.Sp +With \fB\-msupersparc\fR the compiler optimizes code for the SuperSparc cpu, as +used in the SparcStation 10, 1000 and 2000 series. This flag also enables use +of the full \s-1SPARC\s0 v8 instruction set. +.Sp +These options are deprecated and will be deleted in a future \s-1GCC\s0 release. +They have been replaced with \fB\-mcpu=xxx\fR. +.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 +.IX Item "-mcpu=cpu_type" +Set the instruction set, register set, and instruction scheduling parameters +for machine type \fIcpu_type\fR. Supported values for \fIcpu_type\fR are +\&\fBv7\fR, \fBcypress\fR, \fBv8\fR, \fBsupersparc\fR, \fBsparclite\fR, +\&\fBhypersparc\fR, \fBsparclite86x\fR, \fBf930\fR, \fBf934\fR, +\&\fBsparclet\fR, \fBtsc701\fR, \fBv9\fR, and \fBultrasparc\fR. +.Sp +Default instruction scheduling parameters are used for values that select +an architecture and not an implementation. These are \fBv7\fR, \fBv8\fR, +\&\fBsparclite\fR, \fBsparclet\fR, \fBv9\fR. +.Sp +Here is a list of each supported architecture and their supported +implementations. +.Sp +.Vb 5 +\& v7: cypress +\& v8: supersparc, hypersparc +\& sparclite: f930, f934, sparclite86x +\& sparclet: tsc701 +\& v9: ultrasparc +.Ve +.Ip "\fB\-mtune=\fR\fIcpu_type\fR" 4 +.IX Item "-mtune=cpu_type" +Set the instruction scheduling parameters for machine type +\&\fIcpu_type\fR, but do not set the instruction set or register set that the +option \fB\-mcpu=\fR\fIcpu_type\fR would. +.Sp +The same values for \fB\-mcpu=\fR\fIcpu_type\fR are used for +\&\fB\-mtune=\fR\fIcpu_type\fR, though the only useful values are those that +select a particular cpu implementation: \fBcypress\fR, \fBsupersparc\fR, +\&\fBhypersparc\fR, \fBf930\fR, \fBf934\fR, \fBsparclite86x\fR, +\&\fBtsc701\fR, \fBultrasparc\fR. +.PP +These \fB\-m\fR switches are supported in addition to the above +on the \s-1SPARCLET\s0 processor. +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +Generate code for a processor running in little-endian mode. +.Ip "\fB\-mlive-g0\fR" 4 +.IX Item "-mlive-g0" +Treat register \f(CW\*(C`%g0\*(C'\fR as a normal register. +\&\s-1GCC\s0 will continue to clobber it as necessary but will not assume +it always reads as 0. +.Ip "\fB\-mbroken-saverestore\fR" 4 +.IX Item "-mbroken-saverestore" +Generate code that does not use non-trivial forms of the \f(CW\*(C`save\*(C'\fR and +\&\f(CW\*(C`restore\*(C'\fR instructions. Early versions of the \s-1SPARCLET\s0 processor do +not correctly handle \f(CW\*(C`save\*(C'\fR and \f(CW\*(C`restore\*(C'\fR instructions used with +arguments. They correctly handle them used without arguments. A \f(CW\*(C`save\*(C'\fR +instruction used without arguments increments the current window pointer +but does not allocate a new stack frame. It is assumed that the window +overflow trap handler will properly handle this case as will interrupt +handlers. +.PP +These \fB\-m\fR switches are supported in addition to the above +on \s-1SPARC\s0 V9 processors in 64\-bit environments. +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +Generate code for a processor running in little-endian mode. +.Ip "\fB\-m32\fR" 4 +.IX Item "-m32" +.PD 0 +.Ip "\fB\-m64\fR" 4 +.IX Item "-m64" +.PD +Generate code for a 32\-bit or 64\-bit environment. +The 32\-bit environment sets int, long and pointer to 32 bits. +The 64\-bit environment sets int to 32 bits and long and pointer +to 64 bits. +.Ip "\fB\-mcmodel=medlow\fR" 4 +.IX Item "-mcmodel=medlow" +Generate code for the Medium/Low code model: the program must be linked +in the low 32 bits of the address space. Pointers are 64 bits. +Programs can be statically or dynamically linked. +.Ip "\fB\-mcmodel=medmid\fR" 4 +.IX Item "-mcmodel=medmid" +Generate code for the Medium/Middle code model: the program must be linked +in the low 44 bits of the address space, the text segment must be less than +2G bytes, and data segment must be within 2G of the text segment. +Pointers are 64 bits. +.Ip "\fB\-mcmodel=medany\fR" 4 +.IX Item "-mcmodel=medany" +Generate code for the Medium/Anywhere code model: the program may be linked +anywhere in the address space, the text segment must be less than +2G bytes, and data segment must be within 2G of the text segment. +Pointers are 64 bits. +.Ip "\fB\-mcmodel=embmedany\fR" 4 +.IX Item "-mcmodel=embmedany" +Generate code for the Medium/Anywhere code model for embedded systems: +assume a 32\-bit text and a 32\-bit data segment, both starting anywhere +(determined at link time). Register \f(CW%g4\fR points to the base of the +data segment. Pointers are still 64 bits. +Programs are statically linked, \s-1PIC\s0 is not supported. +.Ip "\fB\-mstack-bias\fR" 4 +.IX Item "-mstack-bias" +.PD 0 +.Ip "\fB\-mno-stack-bias\fR" 4 +.IX Item "-mno-stack-bias" +.PD +With \fB\-mstack-bias\fR, \s-1GCC\s0 assumes that the stack pointer, and +frame pointer if present, are offset by \-2047 which must be added back +when making stack frame references. +Otherwise, assume no such offset is present. +.PP +.I "Convex Options" +.IX Subsection "Convex Options" +.PP +These \fB\-m\fR options are defined for Convex: +.Ip "\fB\-mc1\fR" 4 +.IX Item "-mc1" +Generate output for C1. The code will run on any Convex machine. +The preprocessor symbol \f(CW\*(C`_\|_convex_\|_c1_\|_\*(C'\fR is defined. +.Ip "\fB\-mc2\fR" 4 +.IX Item "-mc2" +Generate output for C2. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C2. +The preprocessor symbol \f(CW\*(C`_\|_convex_c2_\|_\*(C'\fR is defined. +.Ip "\fB\-mc32\fR" 4 +.IX Item "-mc32" +Generate output for C32xx. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C32. +The preprocessor symbol \f(CW\*(C`_\|_convex_c32_\|_\*(C'\fR is defined. +.Ip "\fB\-mc34\fR" 4 +.IX Item "-mc34" +Generate output for C34xx. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C34. +The preprocessor symbol \f(CW\*(C`_\|_convex_c34_\|_\*(C'\fR is defined. +.Ip "\fB\-mc38\fR" 4 +.IX Item "-mc38" +Generate output for C38xx. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C38. +The preprocessor symbol \f(CW\*(C`_\|_convex_c38_\|_\*(C'\fR is defined. +.Ip "\fB\-margcount\fR" 4 +.IX Item "-margcount" +Generate code which puts an argument count in the word preceding each +argument list. This is compatible with regular \s-1CC\s0, and a few programs +may need the argument count word. \s-1GDB\s0 and other source-level debuggers +do not need it; this info is in the symbol table. +.Ip "\fB\-mnoargcount\fR" 4 +.IX Item "-mnoargcount" +Omit the argument count word. This is the default. +.Ip "\fB\-mvolatile-cache\fR" 4 +.IX Item "-mvolatile-cache" +Allow volatile references to be cached. This is the default. +.Ip "\fB\-mvolatile-nocache\fR" 4 +.IX Item "-mvolatile-nocache" +Volatile references bypass the data cache, going all the way to memory. +This is only needed for multi-processor code that does not use standard +synchronization instructions. Making non-volatile references to volatile +locations will not necessarily work. +.Ip "\fB\-mlong32\fR" 4 +.IX Item "-mlong32" +Type long is 32 bits, the same as type int. This is the default. +.Ip "\fB\-mlong64\fR" 4 +.IX Item "-mlong64" +Type long is 64 bits, the same as type long long. This option is useless, +because no library support exists for it. +.PP +.I "\s-1AMD29K\s0 Options" +.IX Subsection "AMD29K Options" +.PP +These \fB\-m\fR options are defined for the \s-1AMD\s0 Am29000: +.Ip "\fB\-mdw\fR" 4 +.IX Item "-mdw" +Generate code that assumes the \f(CW\*(C`DW\*(C'\fR bit is set, i.e., that byte and +halfword operations are directly supported by the hardware. This is the +default. +.Ip "\fB\-mndw\fR" 4 +.IX Item "-mndw" +Generate code that assumes the \f(CW\*(C`DW\*(C'\fR bit is not set. +.Ip "\fB\-mbw\fR" 4 +.IX Item "-mbw" +Generate code that assumes the system supports byte and halfword write +operations. This is the default. +.Ip "\fB\-mnbw\fR" 4 +.IX Item "-mnbw" +Generate code that assumes the systems does not support byte and +halfword write operations. \fB\-mnbw\fR implies \fB\-mndw\fR. +.Ip "\fB\-msmall\fR" 4 +.IX Item "-msmall" +Use a small memory model that assumes that all function addresses are +either within a single 256 \s-1KB\s0 segment or at an absolute address of less +than 256k. This allows the \f(CW\*(C`call\*(C'\fR instruction to be used instead +of a \f(CW\*(C`const\*(C'\fR, \f(CW\*(C`consth\*(C'\fR, \f(CW\*(C`calli\*(C'\fR sequence. +.Ip "\fB\-mnormal\fR" 4 +.IX Item "-mnormal" +Use the normal memory model: Generate \f(CW\*(C`call\*(C'\fR instructions only when +calling functions in the same file and \f(CW\*(C`calli\*(C'\fR instructions +otherwise. This works if each file occupies less than 256 \s-1KB\s0 but allows +the entire executable to be larger than 256 \s-1KB\s0. This is the default. +.Ip "\fB\-mlarge\fR" 4 +.IX Item "-mlarge" +Always use \f(CW\*(C`calli\*(C'\fR instructions. Specify this option if you expect +a single file to compile into more than 256 \s-1KB\s0 of code. +.Ip "\fB\-m29050\fR" 4 +.IX Item "-m29050" +Generate code for the Am29050. +.Ip "\fB\-m29000\fR" 4 +.IX Item "-m29000" +Generate code for the Am29000. This is the default. +.Ip "\fB\-mkernel-registers\fR" 4 +.IX Item "-mkernel-registers" +Generate references to registers \f(CW\*(C`gr64\-gr95\*(C'\fR instead of to +registers \f(CW\*(C`gr96\-gr127\*(C'\fR. This option can be used when compiling +kernel code that wants a set of global registers disjoint from that used +by user-mode code. +.Sp +Note that when this option is used, register names in \fB\-f\fR flags +must use the normal, user-mode, names. +.Ip "\fB\-muser-registers\fR" 4 +.IX Item "-muser-registers" +Use the normal set of global registers, \f(CW\*(C`gr96\-gr127\*(C'\fR. This is the +default. +.Ip "\fB\-mstack-check\fR" 4 +.IX Item "-mstack-check" +.PD 0 +.Ip "\fB\-mno-stack-check\fR" 4 +.IX Item "-mno-stack-check" +.PD +Insert (or do not insert) a call to \f(CW\*(C`_\|_msp_check\*(C'\fR after each stack +adjustment. This is often used for kernel code. +.Ip "\fB\-mstorem-bug\fR" 4 +.IX Item "-mstorem-bug" +.PD 0 +.Ip "\fB\-mno-storem-bug\fR" 4 +.IX Item "-mno-storem-bug" +.PD +\&\fB\-mstorem-bug\fR handles 29k processors which cannot handle the +separation of a mtsrim insn and a storem instruction (most 29000 chips +to date, but not the 29050). +.Ip "\fB\-mno-reuse-arg-regs\fR" 4 +.IX Item "-mno-reuse-arg-regs" +.PD 0 +.Ip "\fB\-mreuse-arg-regs\fR" 4 +.IX Item "-mreuse-arg-regs" +.PD +\&\fB\-mno-reuse-arg-regs\fR tells the compiler to only use incoming argument +registers for copying out arguments. This helps detect calling a function +with fewer arguments than it was declared with. +.Ip "\fB\-mno-impure-text\fR" 4 +.IX Item "-mno-impure-text" +.PD 0 +.Ip "\fB\-mimpure-text\fR" 4 +.IX Item "-mimpure-text" +.PD +\&\fB\-mimpure-text\fR, used in addition to \fB\-shared\fR, tells the compiler to +not pass \fB\-assert pure-text\fR to the linker when linking a shared object. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. +.Ip "\fB\-mno-multm\fR" 4 +.IX Item "-mno-multm" +Do not generate multm or multmu instructions. This is useful for some embedded +systems which do not have trap handlers for these instructions. +.PP +.I "\s-1ARM\s0 Options" +.IX Subsection "ARM Options" +.PP +These \fB\-m\fR options are defined for Advanced \s-1RISC\s0 Machines (\s-1ARM\s0) +architectures: +.Ip "\fB\-mapcs-frame\fR" 4 +.IX Item "-mapcs-frame" +Generate a stack frame that is compliant with the \s-1ARM\s0 Procedure Call +Standard for all functions, even if this is not strictly necessary for +correct execution of the code. Specifying \fB\-fomit-frame-pointer\fR +with this option will cause the stack frames not to be generated for +leaf functions. The default is \fB\-mno-apcs-frame\fR. +.Ip "\fB\-mapcs\fR" 4 +.IX Item "-mapcs" +This is a synonym for \fB\-mapcs-frame\fR. +.Ip "\fB\-mapcs-26\fR" 4 +.IX Item "-mapcs-26" +Generate code for a processor running with a 26\-bit program counter, +and conforming to the function calling standards for the \s-1APCS\s0 26\-bit +option. This option replaces the \fB\-m2\fR and \fB\-m3\fR options +of previous releases of the compiler. +.Ip "\fB\-mapcs-32\fR" 4 +.IX Item "-mapcs-32" +Generate code for a processor running with a 32\-bit program counter, +and conforming to the function calling standards for the \s-1APCS\s0 32\-bit +option. This option replaces the \fB\-m6\fR option of previous releases +of the compiler. +.Ip "\fB\-mapcs-stack-check\fR" 4 +.IX Item "-mapcs-stack-check" +Generate code to check the amount of stack space available upon entry to +every function (that actually uses some stack space). If there is +insufficient space available then either the function +\&\fB_\|_rt_stkovf_split_small\fR or \fB_\|_rt_stkovf_split_big\fR will be +called, depending upon the amount of stack space required. The run time +system is required to provide these functions. The default is +\&\fB\-mno-apcs-stack-check\fR, since this produces smaller code. +.Ip "\fB\-mapcs-float\fR" 4 +.IX Item "-mapcs-float" +Pass floating point arguments using the float point registers. This is +one of the variants of the \s-1APCS\s0. This option is recommended if the +target hardware has a floating point unit or if a lot of floating point +arithmetic is going to be performed by the code. The default is +\&\fB\-mno-apcs-float\fR, since integer only code is slightly increased in +size if \fB\-mapcs-float\fR is used. +.Ip "\fB\-mapcs-reentrant\fR" 4 +.IX Item "-mapcs-reentrant" +Generate reentrant, position independent code. This is the equivalent +to specifying the \fB\-fpic\fR option. The default is +\&\fB\-mno-apcs-reentrant\fR. +.Ip "\fB\-mthumb-interwork\fR" 4 +.IX Item "-mthumb-interwork" +Generate code which supports calling between the \s-1ARM\s0 and \s-1THUMB\s0 +instruction sets. Without this option the two instruction sets cannot +be reliably used inside one program. The default is +\&\fB\-mno-thumb-interwork\fR, since slightly larger code is generated +when \fB\-mthumb-interwork\fR is specified. +.Ip "\fB\-mno-sched-prolog\fR" 4 +.IX Item "-mno-sched-prolog" +Prevent the reordering of instructions in the function prolog, or the +merging of those instruction with the instructions in the function's +body. This means that all functions will start with a recognizable set +of instructions (or in fact one of a choice from a small set of +different function prologues), and this information can be used to +locate the start if functions inside an executable piece of code. The +default is \fB\-msched-prolog\fR. +.Ip "\fB\-mhard-float\fR" 4 +.IX Item "-mhard-float" +Generate output containing floating point instructions. This is the +default. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not available for all \s-1ARM\s0 +targets. Normally the facilities of the machine's usual C compiler are +used, but this cannot be done directly in cross-compilation. You must make +your own arrangements to provide suitable library functions for +cross-compilation. +.Sp +\&\fB\-msoft-float\fR changes the calling convention in the output file; +therefore, it is only useful if you compile \fIall\fR of a program with +this option. In particular, you need to compile \fIlibgcc.a\fR, the +library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for +this to work. +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +Generate code for a processor running in little-endian mode. This is +the default for all standard configurations. +.Ip "\fB\-mbig-endian\fR" 4 +.IX Item "-mbig-endian" +Generate code for a processor running in big-endian mode; the default is +to compile code for a little-endian processor. +.Ip "\fB\-mwords-little-endian\fR" 4 +.IX Item "-mwords-little-endian" +This option only applies when generating code for big-endian processors. +Generate code for a little-endian word order but a big-endian byte +order. That is, a byte order of the form \fB32107654\fR. Note: this +option should only be used if you require compatibility with code for +big-endian \s-1ARM\s0 processors generated by versions of the compiler prior to +2.8. +.Ip "\fB\-malignment-traps\fR" 4 +.IX Item "-malignment-traps" +Generate code that will not trap if the \s-1MMU\s0 has alignment traps enabled. +On \s-1ARM\s0 architectures prior to ARMv4, there were no instructions to +access half-word objects stored in memory. However, when reading from +memory a feature of the \s-1ARM\s0 architecture allows a word load to be used, +even if the address is unaligned, and the processor core will rotate the +data as it is being loaded. This option tells the compiler that such +misaligned accesses will cause a \s-1MMU\s0 trap and that it should instead +synthesise the access as a series of byte accesses. The compiler can +still use word accesses to load half-word data if it knows that the +address is aligned to a word boundary. +.Sp +This option is ignored when compiling for \s-1ARM\s0 architecture 4 or later, +since these processors have instructions to directly access half-word +objects in memory. +.Ip "\fB\-mno-alignment-traps\fR" 4 +.IX Item "-mno-alignment-traps" +Generate code that assumes that the \s-1MMU\s0 will not trap unaligned +accesses. This produces better code when the target instruction set +does not have half-word memory operations (implementations prior to +ARMv4). +.Sp +Note that you cannot use this option to access unaligned word objects, +since the processor will only fetch one 32\-bit aligned object from +memory. +.Sp +The default setting for most targets is \-mno-alignment-traps, since +this produces better code when there are no half-word memory +instructions available. +.Ip "\fB\-mshort-load-bytes\fR" 4 +.IX Item "-mshort-load-bytes" +This is a deprecated alias for \fB\-malignment-traps\fR. +.Ip "\fB\-mno-short-load-bytes\fR" 4 +.IX Item "-mno-short-load-bytes" +This is a deprecated alias for \fB\-mno-alignment-traps\fR. +.Ip "\fB\-mshort-load-words\fR" 4 +.IX Item "-mshort-load-words" +This is a deprecated alias for \fB\-mno-alignment-traps\fR. +.Ip "\fB\-mno-short-load-words\fR" 4 +.IX Item "-mno-short-load-words" +This is a deprecated alias for \fB\-malignment-traps\fR. +.Ip "\fB\-mbsd\fR" 4 +.IX Item "-mbsd" +This option only applies to \s-1RISC\s0 iX. Emulate the native BSD-mode +compiler. This is the default if \fB\-ansi\fR is not specified. +.Ip "\fB\-mxopen\fR" 4 +.IX Item "-mxopen" +This option only applies to \s-1RISC\s0 iX. Emulate the native X/Open-mode +compiler. +.Ip "\fB\-mno-symrename\fR" 4 +.IX Item "-mno-symrename" +This option only applies to \s-1RISC\s0 iX. Do not run the assembler +post-processor, \fBsymrename\fR, after code has been assembled. +Normally it is necessary to modify some of the standard symbols in +preparation for linking with the \s-1RISC\s0 iX C library; this option +suppresses this pass. The post-processor is never run when the +compiler is built for cross-compilation. +.Ip "\fB\-mcpu=\fR" 4 +.IX Item "-mcpu=" +This specifies the name of the target \s-1ARM\s0 processor. \s-1GCC\s0 uses this name +to determine what kind of instructions it can use when generating +assembly code. Permissible names are: arm2, arm250, arm3, arm6, arm60, +arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, +arm70, arm700, arm700i, arm710, arm710c, arm7100, arm7500, arm7500fe, +arm7tdmi, arm8, strongarm, strongarm110, strongarm1100, arm8, arm810, +arm9, arm920, arm920t, arm9tdmi. +.Ip "\fB\-mtune=\fR" 4 +.IX Item "-mtune=" +This option is very similar to the \fB\-mcpu=\fR option, except that +instead of specifying the actual target processor type, and hence +restricting which instructions can be used, it specifies that \s-1GCC\s0 should +tune the performance of the code as if the target were of the type +specified in this option, but still choosing the instructions that it +will generate based on the cpu specified by a \fB\-mcpu=\fR option. +For some arm implementations better performance can be obtained by using +this option. +.Ip "\fB\-march=\fR" 4 +.IX Item "-march=" +This specifies the name of the target \s-1ARM\s0 architecture. \s-1GCC\s0 uses this +name to determine what kind of instructions it can use when generating +assembly code. This option can be used in conjunction with or instead +of the \fB\-mcpu=\fR option. Permissible names are: armv2, armv2a, +armv3, armv3m, armv4, armv4t, armv5. +.Ip "\fB\-mfpe=\fR" 4 +.IX Item "-mfpe=" +.PD 0 +.Ip "\fB\-mfp=\fR" 4 +.IX Item "-mfp=" +.PD +This specifies the version of the floating point emulation available on +the target. Permissible values are 2 and 3. \fB\-mfp=\fR is a synonym +for \fB\-mfpe=\fR to support older versions of \s-1GCC\s0. +.Ip "\fB\-mstructure-size-boundary=\fR" 4 +.IX Item "-mstructure-size-boundary=" +The size of all structures and unions will be rounded up to a multiple +of the number of bits set by this option. Permissible values are 8 and +32. The default value varies for different toolchains. For the \s-1COFF\s0 +targeted toolchain the default value is 8. Specifying the larger number +can produce faster, more efficient code, but can also increase the size +of the program. The two values are potentially incompatible. Code +compiled with one value cannot necessarily expect to work with code or +libraries compiled with the other value, if they exchange information +using structures or unions. Programmers are encouraged to use the 32 +value as future versions of the toolchain may default to this value. +.Ip "\fB\-mabort-on-noreturn\fR" 4 +.IX Item "-mabort-on-noreturn" +Generate a call to the function abort at the end of a noreturn function. +It will be executed if the function tries to return. +.Ip "\fB\-mlong-calls\fR" 4 +.IX Item "-mlong-calls" +.PD 0 +.Ip "\fB\-mno-long-calls\fR" 4 +.IX Item "-mno-long-calls" +.PD +Tells the compiler to perform function calls by first loading the +address of the function into a register and then performing a subroutine +call on this register. This switch is needed if the target function +will lie outside of the 64 megabyte addressing range of the offset based +version of subroutine call instruction. +.Sp +Even if this switch is enabled, not all function calls will be turned +into long calls. The heuristic is that static functions, functions +which have the \fBshort-call\fR attribute, functions that are inside +the scope of a \fB#pragma no_long_calls\fR directive and functions whose +definitions have already been compiled within the current compilation +unit, will not be turned into long calls. The exception to this rule is +that weak function definitions, functions with the \fBlong-call\fR +attribute or the \fBsection\fR attribute, and functions that are within +the scope of a \fB#pragma long_calls\fR directive, will always be +turned into long calls. +.Sp +This feature is not enabled by default. Specifying +\&\fB\*(--no-long-calls\fR will restore the default behaviour, as will +placing the function calls within the scope of a \fB#pragma +long_calls_off\fR directive. Note these switches have no effect on how +the compiler generates code to handle function calls via function +pointers. +.Ip "\fB\-mnop-fun-dllimport\fR" 4 +.IX Item "-mnop-fun-dllimport" +Disable the support for the \fIdllimport\fR attribute. +.Ip "\fB\-msingle-pic-base\fR" 4 +.IX Item "-msingle-pic-base" +Treat the register used for \s-1PIC\s0 addressing as read-only, rather than +loading it in the prologue for each function. The run-time system is +responsible for initialising this register with an appropriate value +before execution begins. +.Ip "\fB\-mpic-register=\fR" 4 +.IX Item "-mpic-register=" +Specify the register to be used for \s-1PIC\s0 addressing. The default is R10 +unless stack-checking is enabled, when R9 is used. +.PP +.I "Thumb Options" +.IX Subsection "Thumb Options" +.Ip "\fB\-mthumb-interwork\fR" 4 +.IX Item "-mthumb-interwork" +Generate code which supports calling between the \s-1THUMB\s0 and \s-1ARM\s0 +instruction sets. Without this option the two instruction sets cannot +be reliably used inside one program. The default is +\&\fB\-mno-thumb-interwork\fR, since slightly smaller code is generated +with this option. +.Ip "\fB\-mtpcs-frame\fR" 4 +.IX Item "-mtpcs-frame" +Generate a stack frame that is compliant with the Thumb Procedure Call +Standard for all non-leaf functions. (A leaf function is one that does +not call any other functions). The default is \fB\-mno-apcs-frame\fR. +.Ip "\fB\-mtpcs-leaf-frame\fR" 4 +.IX Item "-mtpcs-leaf-frame" +Generate a stack frame that is compliant with the Thumb Procedure Call +Standard for all leaf functions. (A leaf function is one that does +not call any other functions). The default is \fB\-mno-apcs-leaf-frame\fR. +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +Generate code for a processor running in little-endian mode. This is +the default for all standard configurations. +.Ip "\fB\-mbig-endian\fR" 4 +.IX Item "-mbig-endian" +Generate code for a processor running in big-endian mode. +.Ip "\fB\-mstructure-size-boundary=\fR" 4 +.IX Item "-mstructure-size-boundary=" +The size of all structures and unions will be rounded up to a multiple +of the number of bits set by this option. Permissible values are 8 and +32. The default value varies for different toolchains. For the \s-1COFF\s0 +targeted toolchain the default value is 8. Specifying the larger number +can produced faster, more efficient code, but can also increase the size +of the program. The two values are potentially incompatible. Code +compiled with one value cannot necessarily expect to work with code or +libraries compiled with the other value, if they exchange information +using structures or unions. Programmers are encouraged to use the 32 +value as future versions of the toolchain may default to this value. +.Ip "\fB\-mnop-fun-dllimport\fR" 4 +.IX Item "-mnop-fun-dllimport" +Disable the support for the \fIdllimport\fR attribute. +.Ip "\fB\-mcallee-super-interworking\fR" 4 +.IX Item "-mcallee-super-interworking" +Gives all externally visible functions in the file being compiled an \s-1ARM\s0 +instruction set header which switches to Thumb mode before executing the +rest of the function. This allows these functions to be called from +non-interworking code. +.Ip "\fB\-mcaller-super-interworking\fR" 4 +.IX Item "-mcaller-super-interworking" +Allows calls via function pointers (including virtual functions) to +execute correctly regardless of whether the target code has been +compiled for interworking or not. There is a small overhead in the cost +of executing a function pointer if this option is enabled. +.Ip "\fB\-msingle-pic-base\fR" 4 +.IX Item "-msingle-pic-base" +Treat the register used for \s-1PIC\s0 addressing as read-only, rather than +loading it in the prologue for each function. The run-time system is +responsible for initialising this register with an appropriate value +before execution begins. +.Ip "\fB\-mpic-register=\fR" 4 +.IX Item "-mpic-register=" +Specify the register to be used for \s-1PIC\s0 addressing. The default is R10. +.PP +.I "\s-1MN10200\s0 Options" +.IX Subsection "MN10200 Options" +.PP +These \fB\-m\fR options are defined for Matsushita \s-1MN10200\s0 architectures: +.Ip "\fB\-mrelax\fR" 4 +.IX Item "-mrelax" +Indicate to the linker that it should perform a relaxation optimization pass +to shorten branches, calls and absolute memory addresses. This option only +has an effect when used on the command line for the final link step. +.Sp +This option makes symbolic debugging impossible. +.PP +.I "\s-1MN10300\s0 Options" +.IX Subsection "MN10300 Options" +.PP +These \fB\-m\fR options are defined for Matsushita \s-1MN10300\s0 architectures: +.Ip "\fB\-mmult-bug\fR" 4 +.IX Item "-mmult-bug" +Generate code to avoid bugs in the multiply instructions for the \s-1MN10300\s0 +processors. This is the default. +.Ip "\fB\-mno-mult-bug\fR" 4 +.IX Item "-mno-mult-bug" +Do not generate code to avoid bugs in the multiply instructions for the +\&\s-1MN10300\s0 processors. +.Ip "\fB\-mam33\fR" 4 +.IX Item "-mam33" +Generate code which uses features specific to the \s-1AM33\s0 processor. +.Ip "\fB\-mno-am33\fR" 4 +.IX Item "-mno-am33" +Do not generate code which uses features specific to the \s-1AM33\s0 processor. This +is the default. +.Ip "\fB\-mrelax\fR" 4 +.IX Item "-mrelax" +Indicate to the linker that it should perform a relaxation optimization pass +to shorten branches, calls and absolute memory addresses. This option only +has an effect when used on the command line for the final link step. +.Sp +This option makes symbolic debugging impossible. +.PP +.I "M32R/D Options" +.IX Subsection "M32R/D Options" +.PP +These \fB\-m\fR options are defined for Mitsubishi M32R/D architectures: +.Ip "\fB\-mcode-model=small\fR" 4 +.IX Item "-mcode-model=small" +Assume all objects live in the lower 16MB of memory (so that their addresses +can be loaded with the \f(CW\*(C`ld24\*(C'\fR instruction), and assume all subroutines +are reachable with the \f(CW\*(C`bl\*(C'\fR instruction. +This is the default. +.Sp +The addressability of a particular object can be set with the +\&\f(CW\*(C`model\*(C'\fR attribute. +.Ip "\fB\-mcode-model=medium\fR" 4 +.IX Item "-mcode-model=medium" +Assume objects may be anywhere in the 32\-bit address space (the compiler +will generate \f(CW\*(C`seth/add3\*(C'\fR instructions to load their addresses), and +assume all subroutines are reachable with the \f(CW\*(C`bl\*(C'\fR instruction. +.Ip "\fB\-mcode-model=large\fR" 4 +.IX Item "-mcode-model=large" +Assume objects may be anywhere in the 32\-bit address space (the compiler +will generate \f(CW\*(C`seth/add3\*(C'\fR instructions to load their addresses), and +assume subroutines may not be reachable with the \f(CW\*(C`bl\*(C'\fR instruction +(the compiler will generate the much slower \f(CW\*(C`seth/add3/jl\*(C'\fR +instruction sequence). +.Ip "\fB\-msdata=none\fR" 4 +.IX Item "-msdata=none" +Disable use of the small data area. Variables will be put into +one of \fB.data\fR, \fBbss\fR, or \fB.rodata\fR (unless the +\&\f(CW\*(C`section\*(C'\fR attribute has been specified). +This is the default. +.Sp +The small data area consists of sections \fB.sdata\fR and \fB.sbss\fR. +Objects may be explicitly put in the small data area with the +\&\f(CW\*(C`section\*(C'\fR attribute using one of these sections. +.Ip "\fB\-msdata=sdata\fR" 4 +.IX Item "-msdata=sdata" +Put small global and static data in the small data area, but do not +generate special code to reference them. +.Ip "\fB\-msdata=use\fR" 4 +.IX Item "-msdata=use" +Put small global and static data in the small data area, and generate +special instructions to reference them. +.Ip "\fB\-G\fR \fInum\fR" 4 +.IX Item "-G num" +Put global and static objects less than or equal to \fInum\fR bytes +into the small data or bss sections instead of the normal data or bss +sections. The default value of \fInum\fR is 8. +The \fB\-msdata\fR option must be set to one of \fBsdata\fR or \fBuse\fR +for this option to have any effect. +.Sp +All modules should be compiled with the same \fB\-G\fR \fInum\fR value. +Compiling with different values of \fInum\fR may or may not work; if it +doesn't the linker will give an error message \- incorrect code will not be +generated. +.PP +.I "M88K Options" +.IX Subsection "M88K Options" +.PP +These \fB\-m\fR options are defined for Motorola 88k architectures: +.Ip "\fB\-m88000\fR" 4 +.IX Item "-m88000" +Generate code that works well on both the m88100 and the +m88110. +.Ip "\fB\-m88100\fR" 4 +.IX Item "-m88100" +Generate code that works best for the m88100, but that also +runs on the m88110. +.Ip "\fB\-m88110\fR" 4 +.IX Item "-m88110" +Generate code that works best for the m88110, and may not run +on the m88100. +.Ip "\fB\-mbig-pic\fR" 4 +.IX Item "-mbig-pic" +Obsolete option to be removed from the next revision. +Use \fB\-fPIC\fR. +.Ip "\fB\-midentify-revision\fR" 4 +.IX Item "-midentify-revision" +Include an \f(CW\*(C`ident\*(C'\fR directive in the assembler output recording the +source file name, compiler name and version, timestamp, and compilation +flags used. +.Ip "\fB\-mno-underscores\fR" 4 +.IX Item "-mno-underscores" +In assembler output, emit symbol names without adding an underscore +character at the beginning of each name. The default is to use an +underscore as prefix on each name. +.Ip "\fB\-mocs-debug-info\fR" 4 +.IX Item "-mocs-debug-info" +.PD 0 +.Ip "\fB\-mno-ocs-debug-info\fR" 4 +.IX Item "-mno-ocs-debug-info" +.PD +Include (or omit) additional debugging information (about registers used +in each stack frame) as specified in the 88open Object Compatibility +Standard, ``\s-1OCS\s0''. This extra information allows debugging of code that +has had the frame pointer eliminated. The default for \s-1DG/UX\s0, SVr4, and +Delta 88 SVr3.2 is to include this information; other 88k configurations +omit this information by default. +.Ip "\fB\-mocs-frame-position\fR" 4 +.IX Item "-mocs-frame-position" +When emitting \s-1COFF\s0 debugging information for automatic variables and +parameters stored on the stack, use the offset from the canonical frame +address, which is the stack pointer (register 31) on entry to the +function. The \s-1DG/UX\s0, SVr4, Delta88 SVr3.2, and \s-1BCS\s0 configurations use +\&\fB\-mocs-frame-position\fR; other 88k configurations have the default +\&\fB\-mno-ocs-frame-position\fR. +.Ip "\fB\-mno-ocs-frame-position\fR" 4 +.IX Item "-mno-ocs-frame-position" +When emitting \s-1COFF\s0 debugging information for automatic variables and +parameters stored on the stack, use the offset from the frame pointer +register (register 30). When this option is in effect, the frame +pointer is not eliminated when debugging information is selected by the +\&\-g switch. +.Ip "\fB\-moptimize-arg-area\fR" 4 +.IX Item "-moptimize-arg-area" +.PD 0 +.Ip "\fB\-mno-optimize-arg-area\fR" 4 +.IX Item "-mno-optimize-arg-area" +.PD +Control how function arguments are stored in stack frames. +\&\fB\-moptimize-arg-area\fR saves space by optimizing them, but this +conflicts with the 88open specifications. The opposite alternative, +\&\fB\-mno-optimize-arg-area\fR, agrees with 88open standards. By default +\&\s-1GCC\s0 does not optimize the argument area. +.Ip "\fB\-mshort-data-\fR\fInum\fR" 4 +.IX Item "-mshort-data-num" +Generate smaller data references by making them relative to \f(CW\*(C`r0\*(C'\fR, +which allows loading a value using a single instruction (rather than the +usual two). You control which data references are affected by +specifying \fInum\fR with this option. For example, if you specify +\&\fB\-mshort-data-512\fR, then the data references affected are those +involving displacements of less than 512 bytes. +\&\fB\-mshort-data-\fR\fInum\fR is not effective for \fInum\fR greater +than 64k. +.Ip "\fB\-mserialize-volatile\fR" 4 +.IX Item "-mserialize-volatile" +.PD 0 +.Ip "\fB\-mno-serialize-volatile\fR" 4 +.IX Item "-mno-serialize-volatile" +.PD +Do, or don't, generate code to guarantee sequential consistency +of volatile memory references. By default, consistency is +guaranteed. +.Sp +The order of memory references made by the \s-1MC88110\s0 processor does +not always match the order of the instructions requesting those +references. In particular, a load instruction may execute before +a preceding store instruction. Such reordering violates +sequential consistency of volatile memory references, when there +are multiple processors. When consistency must be guaranteed, +\&\s-1GNU\s0 C generates special instructions, as needed, to force +execution in the proper order. +.Sp +The \s-1MC88100\s0 processor does not reorder memory references and so +always provides sequential consistency. However, by default, \s-1GNU\s0 +C generates the special instructions to guarantee consistency +even when you use \fB\-m88100\fR, so that the code may be run on an +\&\s-1MC88110\s0 processor. If you intend to run your code only on the +\&\s-1MC88100\s0 processor, you may use \fB\-mno-serialize-volatile\fR. +.Sp +The extra code generated to guarantee consistency may affect the +performance of your application. If you know that you can safely +forgo this guarantee, you may use \fB\-mno-serialize-volatile\fR. +.Ip "\fB\-msvr4\fR" 4 +.IX Item "-msvr4" +.PD 0 +.Ip "\fB\-msvr3\fR" 4 +.IX Item "-msvr3" +.PD +Turn on (\fB\-msvr4\fR) or off (\fB\-msvr3\fR) compiler extensions +related to System V release 4 (SVr4). This controls the following: +.RS 4 +.Ip "1." 4 +Which variant of the assembler syntax to emit. +.Ip "2." 4 +\&\fB\-msvr4\fR makes the C preprocessor recognize \fB#pragma weak\fR +that is used on System V release 4. +.Ip "3." 4 +\&\fB\-msvr4\fR makes \s-1GCC\s0 issue additional declaration directives used in +SVr4. +.RE +.RS 4 +.Sp +\&\fB\-msvr4\fR is the default for the m88k-motorola-sysv4 and +m88k-dg-dgux m88k configurations. \fB\-msvr3\fR is the default for all +other m88k configurations. +.RE +.Ip "\fB\-mversion-03.00\fR" 4 +.IX Item "-mversion-03.00" +This option is obsolete, and is ignored. +.Ip "\fB\-mno-check-zero-division\fR" 4 +.IX Item "-mno-check-zero-division" +.PD 0 +.Ip "\fB\-mcheck-zero-division\fR" 4 +.IX Item "-mcheck-zero-division" +.PD +Do, or don't, generate code to guarantee that integer division by +zero will be detected. By default, detection is guaranteed. +.Sp +Some models of the \s-1MC88100\s0 processor fail to trap upon integer +division by zero under certain conditions. By default, when +compiling code that might be run on such a processor, \s-1GNU\s0 C +generates code that explicitly checks for zero-valued divisors +and traps with exception number 503 when one is detected. Use of +mno-check-zero-division suppresses such checking for code +generated to run on an \s-1MC88100\s0 processor. +.Sp +\&\s-1GNU\s0 C assumes that the \s-1MC88110\s0 processor correctly detects all +instances of integer division by zero. When \fB\-m88110\fR is +specified, both \fB\-mcheck-zero-division\fR and +\&\fB\-mno-check-zero-division\fR are ignored, and no explicit checks for +zero-valued divisors are generated. +.Ip "\fB\-muse-div-instruction\fR" 4 +.IX Item "-muse-div-instruction" +Use the div instruction for signed integer division on the +\&\s-1MC88100\s0 processor. By default, the div instruction is not used. +.Sp +On the \s-1MC88100\s0 processor the signed integer division instruction +div) traps to the operating system on a negative operand. The +operating system transparently completes the operation, but at a +large cost in execution time. By default, when compiling code +that might be run on an \s-1MC88100\s0 processor, \s-1GNU\s0 C emulates signed +integer division using the unsigned integer division instruction +divu), thereby avoiding the large penalty of a trap to the +operating system. Such emulation has its own, smaller, execution +cost in both time and space. To the extent that your code's +important signed integer division operations are performed on two +nonnegative operands, it may be desirable to use the div +instruction directly. +.Sp +On the \s-1MC88110\s0 processor the div instruction (also known as the +divs instruction) processes negative operands without trapping to +the operating system. When \fB\-m88110\fR is specified, +\&\fB\-muse-div-instruction\fR is ignored, and the div instruction is used +for signed integer division. +.Sp +Note that the result of dividing \s-1INT_MIN\s0 by \-1 is undefined. In +particular, the behavior of such a division with and without +\&\fB\-muse-div-instruction\fR may differ. +.Ip "\fB\-mtrap-large-shift\fR" 4 +.IX Item "-mtrap-large-shift" +.PD 0 +.Ip "\fB\-mhandle-large-shift\fR" 4 +.IX Item "-mhandle-large-shift" +.PD +Include code to detect bit-shifts of more than 31 bits; respectively, +trap such shifts or emit code to handle them properly. By default \s-1GCC\s0 +makes no special provision for large bit shifts. +.Ip "\fB\-mwarn-passed-structs\fR" 4 +.IX Item "-mwarn-passed-structs" +Warn when a function passes a struct as an argument or result. +Structure-passing conventions have changed during the evolution of the C +language, and are often the source of portability problems. By default, +\&\s-1GCC\s0 issues no such warning. +.PP +.I "\s-1IBM\s0 \s-1RS/6000\s0 and PowerPC Options" +.IX Subsection "IBM RS/6000 and PowerPC Options" +.PP +These \fB\-m\fR options are defined for the \s-1IBM\s0 \s-1RS/6000\s0 and PowerPC: +.Ip "\fB\-mpower\fR" 4 +.IX Item "-mpower" +.PD 0 +.Ip "\fB\-mno-power\fR" 4 +.IX Item "-mno-power" +.Ip "\fB\-mpower2\fR" 4 +.IX Item "-mpower2" +.Ip "\fB\-mno-power2\fR" 4 +.IX Item "-mno-power2" +.Ip "\fB\-mpowerpc\fR" 4 +.IX Item "-mpowerpc" +.Ip "\fB\-mno-powerpc\fR" 4 +.IX Item "-mno-powerpc" +.Ip "\fB\-mpowerpc-gpopt\fR" 4 +.IX Item "-mpowerpc-gpopt" +.Ip "\fB\-mno-powerpc-gpopt\fR" 4 +.IX Item "-mno-powerpc-gpopt" +.Ip "\fB\-mpowerpc-gfxopt\fR" 4 +.IX Item "-mpowerpc-gfxopt" +.Ip "\fB\-mno-powerpc-gfxopt\fR" 4 +.IX Item "-mno-powerpc-gfxopt" +.Ip "\fB\-mpowerpc64\fR" 4 +.IX Item "-mpowerpc64" +.Ip "\fB\-mno-powerpc64\fR" 4 +.IX Item "-mno-powerpc64" +.PD +\&\s-1GCC\s0 supports two related instruction set architectures for the +\&\s-1RS/6000\s0 and PowerPC. The \fI\s-1POWER\s0\fR instruction set are those +instructions supported by the \fBrios\fR chip set used in the original +\&\s-1RS/6000\s0 systems and the \fIPowerPC\fR instruction set is the +architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and +the \s-1IBM\s0 4xx microprocessors. +.Sp +Neither architecture is a subset of the other. However there is a +large common subset of instructions supported by both. An \s-1MQ\s0 +register is included in processors supporting the \s-1POWER\s0 architecture. +.Sp +You use these options to specify which instructions are available on the +processor you are using. The default value of these options is +determined when configuring \s-1GCC\s0. Specifying the +\&\fB\-mcpu=\fR\fIcpu_type\fR overrides the specification of these +options. We recommend you use the \fB\-mcpu=\fR\fIcpu_type\fR option +rather than the options listed above. +.Sp +The \fB\-mpower\fR option allows \s-1GCC\s0 to generate instructions that +are found only in the \s-1POWER\s0 architecture and to use the \s-1MQ\s0 register. +Specifying \fB\-mpower2\fR implies \fB\-power\fR and also allows \s-1GCC\s0 +to generate instructions that are present in the \s-1POWER2\s0 architecture but +not the original \s-1POWER\s0 architecture. +.Sp +The \fB\-mpowerpc\fR option allows \s-1GCC\s0 to generate instructions that +are found only in the 32\-bit subset of the PowerPC architecture. +Specifying \fB\-mpowerpc-gpopt\fR implies \fB\-mpowerpc\fR and also allows +\&\s-1GCC\s0 to use the optional PowerPC architecture instructions in the +General Purpose group, including floating-point square root. Specifying +\&\fB\-mpowerpc-gfxopt\fR implies \fB\-mpowerpc\fR and also allows \s-1GCC\s0 to +use the optional PowerPC architecture instructions in the Graphics +group, including floating-point select. +.Sp +The \fB\-mpowerpc64\fR option allows \s-1GCC\s0 to generate the additional +64\-bit instructions that are found in the full PowerPC64 architecture +and to treat GPRs as 64\-bit, doubleword quantities. \s-1GCC\s0 defaults to +\&\fB\-mno-powerpc64\fR. +.Sp +If you specify both \fB\-mno-power\fR and \fB\-mno-powerpc\fR, \s-1GCC\s0 +will use only the instructions in the common subset of both +architectures plus some special \s-1AIX\s0 common-mode calls, and will not use +the \s-1MQ\s0 register. Specifying both \fB\-mpower\fR and \fB\-mpowerpc\fR +permits \s-1GCC\s0 to use any instruction from either architecture and to +allow use of the \s-1MQ\s0 register; specify this for the Motorola \s-1MPC601\s0. +.Ip "\fB\-mnew-mnemonics\fR" 4 +.IX Item "-mnew-mnemonics" +.PD 0 +.Ip "\fB\-mold-mnemonics\fR" 4 +.IX Item "-mold-mnemonics" +.PD +Select which mnemonics to use in the generated assembler code. +\&\fB\-mnew-mnemonics\fR requests output that uses the assembler mnemonics +defined for the PowerPC architecture, while \fB\-mold-mnemonics\fR +requests the assembler mnemonics defined for the \s-1POWER\s0 architecture. +Instructions defined in only one architecture have only one mnemonic; +\&\s-1GCC\s0 uses that mnemonic irrespective of which of these options is +specified. +.Sp +\&\s-1GCC\s0 defaults to the mnemonics appropriate for the architecture in +use. Specifying \fB\-mcpu=\fR\fIcpu_type\fR sometimes overrides the +value of these option. Unless you are building a cross-compiler, you +should normally not specify either \fB\-mnew-mnemonics\fR or +\&\fB\-mold-mnemonics\fR, but should instead accept the default. +.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 +.IX Item "-mcpu=cpu_type" +Set architecture type, register usage, choice of mnemonics, and +instruction scheduling parameters for machine type \fIcpu_type\fR. +Supported values for \fIcpu_type\fR are \fBrios\fR, \fBrios1\fR, +\&\fBrsc\fR, \fBrios2\fR, \fBrs64a\fR, \fB601\fR, \fB602\fR, +\&\fB603\fR, \fB603e\fR, \fB604\fR, \fB604e\fR, \fB620\fR, +\&\fB630\fR, \fB740\fR, \fB750\fR, \fBpower\fR, \fBpower2\fR, +\&\fBpowerpc\fR, \fB403\fR, \fB505\fR, \fB801\fR, \fB821\fR, +\&\fB823\fR, and \fB860\fR and \fBcommon\fR. \fB\-mcpu=power\fR, +\&\fB\-mcpu=power2\fR, \fB\-mcpu=powerpc\fR, and \fB\-mcpu=powerpc64\fR +specify generic \s-1POWER\s0, \s-1POWER2\s0, pure 32\-bit PowerPC (i.e., not \s-1MPC601\s0), +and 64\-bit PowerPC architecture machine types, with an appropriate, +generic processor model assumed for scheduling purposes. +.Sp +Specifying any of the following options: +\&\fB\-mcpu=rios1\fR, \fB\-mcpu=rios2\fR, \fB\-mcpu=rsc\fR, +\&\fB\-mcpu=power\fR, or \fB\-mcpu=power2\fR +enables the \fB\-mpower\fR option and disables the \fB\-mpowerpc\fR option; +\&\fB\-mcpu=601\fR enables both the \fB\-mpower\fR and \fB\-mpowerpc\fR options. +All of \fB\-mcpu=rs64a\fR, \fB\-mcpu=602\fR, \fB\-mcpu=603\fR, +\&\fB\-mcpu=603e\fR, \fB\-mcpu=604\fR, \fB\-mcpu=620\fR, \fB\-mcpu=630\fR, +\&\fB\-mcpu=740\fR, and \fB\-mcpu=750\fR +enable the \fB\-mpowerpc\fR option and disable the \fB\-mpower\fR option. +Exactly similarly, all of \fB\-mcpu=403\fR, +\&\fB\-mcpu=505\fR, \fB\-mcpu=821\fR, \fB\-mcpu=860\fR and \fB\-mcpu=powerpc\fR +enable the \fB\-mpowerpc\fR option and disable the \fB\-mpower\fR option. +\&\fB\-mcpu=common\fR disables both the +\&\fB\-mpower\fR and \fB\-mpowerpc\fR options. +.Sp +\&\s-1AIX\s0 versions 4 or greater selects \fB\-mcpu=common\fR by default, so +that code will operate on all members of the \s-1RS/6000\s0 \s-1POWER\s0 and PowerPC +families. In that case, \s-1GCC\s0 will use only the instructions in the +common subset of both architectures plus some special \s-1AIX\s0 common-mode +calls, and will not use the \s-1MQ\s0 register. \s-1GCC\s0 assumes a generic +processor model for scheduling purposes. +.Sp +Specifying any of the options \fB\-mcpu=rios1\fR, \fB\-mcpu=rios2\fR, +\&\fB\-mcpu=rsc\fR, \fB\-mcpu=power\fR, or \fB\-mcpu=power2\fR also +disables the \fBnew-mnemonics\fR option. Specifying \fB\-mcpu=601\fR, +\&\fB\-mcpu=602\fR, \fB\-mcpu=603\fR, \fB\-mcpu=603e\fR, \fB\-mcpu=604\fR, +\&\fB\-mcpu=620\fR, \fB\-mcpu=630\fR, \fB\-mcpu=403\fR, \fB\-mcpu=505\fR, +\&\fB\-mcpu=821\fR, \fB\-mcpu=860\fR or \fB\-mcpu=powerpc\fR also enables +the \fBnew-mnemonics\fR option. +.Sp +Specifying \fB\-mcpu=403\fR, \fB\-mcpu=821\fR, or \fB\-mcpu=860\fR also +enables the \fB\-msoft-float\fR option. +.Ip "\fB\-mtune=\fR\fIcpu_type\fR" 4 +.IX Item "-mtune=cpu_type" +Set the instruction scheduling parameters for machine type +\&\fIcpu_type\fR, but do not set the architecture type, register usage, +choice of mnemonics like \fB\-mcpu=\fR\fIcpu_type\fR would. The same +values for \fIcpu_type\fR are used for \fB\-mtune=\fR\fIcpu_type\fR as +for \fB\-mcpu=\fR\fIcpu_type\fR. The \fB\-mtune=\fR\fIcpu_type\fR +option overrides the \fB\-mcpu=\fR\fIcpu_type\fR option in terms of +instruction scheduling parameters. +.Ip "\fB\-mfull-toc\fR" 4 +.IX Item "-mfull-toc" +.PD 0 +.Ip "\fB\-mno-fp-in-toc\fR" 4 +.IX Item "-mno-fp-in-toc" +.Ip "\fB\-mno-sum-in-toc\fR" 4 +.IX Item "-mno-sum-in-toc" +.Ip "\fB\-mminimal-toc\fR" 4 +.IX Item "-mminimal-toc" +.PD +Modify generation of the \s-1TOC\s0 (Table Of Contents), which is created for +every executable file. The \fB\-mfull-toc\fR option is selected by +default. In that case, \s-1GCC\s0 will allocate at least one \s-1TOC\s0 entry for +each unique non-automatic variable reference in your program. \s-1GCC\s0 +will also place floating-point constants in the \s-1TOC\s0. However, only +16,384 entries are available in the \s-1TOC\s0. +.Sp +If you receive a linker error message that saying you have overflowed +the available \s-1TOC\s0 space, you can reduce the amount of \s-1TOC\s0 space used +with the \fB\-mno-fp-in-toc\fR and \fB\-mno-sum-in-toc\fR options. +\&\fB\-mno-fp-in-toc\fR prevents \s-1GCC\s0 from putting floating-point +constants in the \s-1TOC\s0 and \fB\-mno-sum-in-toc\fR forces \s-1GCC\s0 to +generate code to calculate the sum of an address and a constant at +run-time instead of putting that sum into the \s-1TOC\s0. You may specify one +or both of these options. Each causes \s-1GCC\s0 to produce very slightly +slower and larger code at the expense of conserving \s-1TOC\s0 space. +.Sp +If you still run out of space in the \s-1TOC\s0 even when you specify both of +these options, specify \fB\-mminimal-toc\fR instead. This option causes +\&\s-1GCC\s0 to make only one \s-1TOC\s0 entry for every file. When you specify this +option, \s-1GCC\s0 will produce code that is slower and larger but which +uses extremely little \s-1TOC\s0 space. You may wish to use this option +only on files that contain less frequently executed code. +.Ip "\fB\-maix64\fR" 4 +.IX Item "-maix64" +.PD 0 +.Ip "\fB\-maix32\fR" 4 +.IX Item "-maix32" +.PD +Enable 64\-bit \s-1AIX\s0 \s-1ABI\s0 and calling convention: 64\-bit pointers, 64\-bit +\&\f(CW\*(C`long\*(C'\fR type, and the infrastructure needed to support them. +Specifying \fB\-maix64\fR implies \fB\-mpowerpc64\fR and +\&\fB\-mpowerpc\fR, while \fB\-maix32\fR disables the 64\-bit \s-1ABI\s0 and +implies \fB\-mno-powerpc64\fR. \s-1GCC\s0 defaults to \fB\-maix32\fR. +.Ip "\fB\-mxl-call\fR" 4 +.IX Item "-mxl-call" +.PD 0 +.Ip "\fB\-mno-xl-call\fR" 4 +.IX Item "-mno-xl-call" +.PD +On \s-1AIX\s0, pass floating-point arguments to prototyped functions beyond the +register save area (\s-1RSA\s0) on the stack in addition to argument FPRs. The +\&\s-1AIX\s0 calling convention was extended but not initially documented to +handle an obscure K&R C case of calling a function that takes the +address of its arguments with fewer arguments than declared. \s-1AIX\s0 \s-1XL\s0 +compilers access floating point arguments which do not fit in the +\&\s-1RSA\s0 from the stack when a subroutine is compiled without +optimization. Because always storing floating-point arguments on the +stack is inefficient and rarely needed, this option is not enabled by +default and only is necessary when calling subroutines compiled by \s-1AIX\s0 +\&\s-1XL\s0 compilers without optimization. +.Ip "\fB\-mthreads\fR" 4 +.IX Item "-mthreads" +Support \fI\s-1AIX\s0 Threads\fR. Link an application written to use +\&\fIpthreads\fR with special libraries and startup code to enable the +application to run. +.Ip "\fB\-mpe\fR" 4 +.IX Item "-mpe" +Support \fI\s-1IBM\s0 \s-1RS/6000\s0 \s-1SP\s0\fR \fIParallel Environment\fR (\s-1PE\s0). Link an +application written to use message passing with special startup code to +enable the application to run. The system must have \s-1PE\s0 installed in the +standard location (\fI/usr/lpp/ppe.poe/\fR), or the \fIspecs\fR file +must be overridden with the \fB\-specs=\fR option to specify the +appropriate directory location. The Parallel Environment does not +support threads, so the \fB\-mpe\fR option and the \fB\-mthreads\fR +option are incompatible. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +.PD 0 +.Ip "\fB\-mhard-float\fR" 4 +.IX Item "-mhard-float" +.PD +Generate code that does not use (uses) the floating-point register set. +Software floating point emulation is provided if you use the +\&\fB\-msoft-float\fR option, and pass the option to \s-1GCC\s0 when linking. +.Ip "\fB\-mmultiple\fR" 4 +.IX Item "-mmultiple" +.PD 0 +.Ip "\fB\-mno-multiple\fR" 4 +.IX Item "-mno-multiple" +.PD +Generate code that uses (does not use) the load multiple word +instructions and the store multiple word instructions. These +instructions are generated by default on \s-1POWER\s0 systems, and not +generated on PowerPC systems. Do not use \fB\-mmultiple\fR on little +endian PowerPC systems, since those instructions do not work when the +processor is in little endian mode. The exceptions are \s-1PPC740\s0 and +\&\s-1PPC750\s0 which permit the instructions usage in little endian mode. +.Ip "\fB\-mstring\fR" 4 +.IX Item "-mstring" +.PD 0 +.Ip "\fB\-mno-string\fR" 4 +.IX Item "-mno-string" +.PD +Generate code that uses (does not use) the load string instructions +and the store string word instructions to save multiple registers and +do small block moves. These instructions are generated by default on +\&\s-1POWER\s0 systems, and not generated on PowerPC systems. Do not use +\&\fB\-mstring\fR on little endian PowerPC systems, since those +instructions do not work when the processor is in little endian mode. +The exceptions are \s-1PPC740\s0 and \s-1PPC750\s0 which permit the instructions +usage in little endian mode. +.Ip "\fB\-mupdate\fR" 4 +.IX Item "-mupdate" +.PD 0 +.Ip "\fB\-mno-update\fR" 4 +.IX Item "-mno-update" +.PD +Generate code that uses (does not use) the load or store instructions +that update the base register to the address of the calculated memory +location. These instructions are generated by default. If you use +\&\fB\-mno-update\fR, there is a small window between the time that the +stack pointer is updated and the address of the previous frame is +stored, which means code that walks the stack frame across interrupts or +signals may get corrupted data. +.Ip "\fB\-mfused-madd\fR" 4 +.IX Item "-mfused-madd" +.PD 0 +.Ip "\fB\-mno-fused-madd\fR" 4 +.IX Item "-mno-fused-madd" +.PD +Generate code that uses (does not use) the floating point multiply and +accumulate instructions. These instructions are generated by default if +hardware floating is used. +.Ip "\fB\-mno-bit-align\fR" 4 +.IX Item "-mno-bit-align" +.PD 0 +.Ip "\fB\-mbit-align\fR" 4 +.IX Item "-mbit-align" +.PD +On System V.4 and embedded PowerPC systems do not (do) force structures +and unions that contain bit fields to be aligned to the base type of the +bit field. +.Sp +For example, by default a structure containing nothing but 8 +\&\f(CW\*(C`unsigned\*(C'\fR bitfields of length 1 would be aligned to a 4 byte +boundary and have a size of 4 bytes. By using \fB\-mno-bit-align\fR, +the structure would be aligned to a 1 byte boundary and be one byte in +size. +.Ip "\fB\-mno-strict-align\fR" 4 +.IX Item "-mno-strict-align" +.PD 0 +.Ip "\fB\-mstrict-align\fR" 4 +.IX Item "-mstrict-align" +.PD +On System V.4 and embedded PowerPC systems do not (do) assume that +unaligned memory references will be handled by the system. +.Ip "\fB\-mrelocatable\fR" 4 +.IX Item "-mrelocatable" +.PD 0 +.Ip "\fB\-mno-relocatable\fR" 4 +.IX Item "-mno-relocatable" +.PD +On embedded PowerPC systems generate code that allows (does not allow) +the program to be relocated to a different address at runtime. If you +use \fB\-mrelocatable\fR on any module, all objects linked together must +be compiled with \fB\-mrelocatable\fR or \fB\-mrelocatable-lib\fR. +.Ip "\fB\-mrelocatable-lib\fR" 4 +.IX Item "-mrelocatable-lib" +.PD 0 +.Ip "\fB\-mno-relocatable-lib\fR" 4 +.IX Item "-mno-relocatable-lib" +.PD +On embedded PowerPC systems generate code that allows (does not allow) +the program to be relocated to a different address at runtime. Modules +compiled with \fB\-mrelocatable-lib\fR can be linked with either modules +compiled without \fB\-mrelocatable\fR and \fB\-mrelocatable-lib\fR or +with modules compiled with the \fB\-mrelocatable\fR options. +.Ip "\fB\-mno-toc\fR" 4 +.IX Item "-mno-toc" +.PD 0 +.Ip "\fB\-mtoc\fR" 4 +.IX Item "-mtoc" +.PD +On System V.4 and embedded PowerPC systems do not (do) assume that +register 2 contains a pointer to a global area pointing to the addresses +used in the program. +.Ip "\fB\-mlittle\fR" 4 +.IX Item "-mlittle" +.PD 0 +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +.PD +On System V.4 and embedded PowerPC systems compile code for the +processor in little endian mode. The \fB\-mlittle-endian\fR option is +the same as \fB\-mlittle\fR. +.Ip "\fB\-mbig\fR" 4 +.IX Item "-mbig" +.PD 0 +.Ip "\fB\-mbig-endian\fR" 4 +.IX Item "-mbig-endian" +.PD +On System V.4 and embedded PowerPC systems compile code for the +processor in big endian mode. The \fB\-mbig-endian\fR option is +the same as \fB\-mbig\fR. +.Ip "\fB\-mcall-sysv\fR" 4 +.IX Item "-mcall-sysv" +On System V.4 and embedded PowerPC systems compile code using calling +conventions that adheres to the March 1995 draft of the System V +Application Binary Interface, PowerPC processor supplement. This is the +default unless you configured \s-1GCC\s0 using \fBpowerpc-*\-eabiaix\fR. +.Ip "\fB\-mcall-sysv-eabi\fR" 4 +.IX Item "-mcall-sysv-eabi" +Specify both \fB\-mcall-sysv\fR and \fB\-meabi\fR options. +.Ip "\fB\-mcall-sysv-noeabi\fR" 4 +.IX Item "-mcall-sysv-noeabi" +Specify both \fB\-mcall-sysv\fR and \fB\-mno-eabi\fR options. +.Ip "\fB\-mcall-aix\fR" 4 +.IX Item "-mcall-aix" +On System V.4 and embedded PowerPC systems compile code using calling +conventions that are similar to those used on \s-1AIX\s0. This is the +default if you configured \s-1GCC\s0 using \fBpowerpc-*\-eabiaix\fR. +.Ip "\fB\-mcall-solaris\fR" 4 +.IX Item "-mcall-solaris" +On System V.4 and embedded PowerPC systems compile code for the Solaris +operating system. +.Ip "\fB\-mcall-linux\fR" 4 +.IX Item "-mcall-linux" +On System V.4 and embedded PowerPC systems compile code for the +Linux-based \s-1GNU\s0 system. +.Ip "\fB\-mprototype\fR" 4 +.IX Item "-mprototype" +.PD 0 +.Ip "\fB\-mno-prototype\fR" 4 +.IX Item "-mno-prototype" +.PD +On System V.4 and embedded PowerPC systems assume that all calls to +variable argument functions are properly prototyped. Otherwise, the +compiler must insert an instruction before every non prototyped call to +set or clear bit 6 of the condition code register (\fI\s-1CR\s0\fR) to +indicate whether floating point values were passed in the floating point +registers in case the function takes a variable arguments. With +\&\fB\-mprototype\fR, only calls to prototyped variable argument functions +will set or clear the bit. +.Ip "\fB\-msim\fR" 4 +.IX Item "-msim" +On embedded PowerPC systems, assume that the startup module is called +\&\fIsim-crt0.o\fR and that the standard C libraries are \fIlibsim.a\fR and +\&\fIlibc.a\fR. This is the default for \fBpowerpc-*\-eabisim\fR. +configurations. +.Ip "\fB\-mmvme\fR" 4 +.IX Item "-mmvme" +On embedded PowerPC systems, assume that the startup module is called +\&\fIcrt0.o\fR and the standard C libraries are \fIlibmvme.a\fR and +\&\fIlibc.a\fR. +.Ip "\fB\-mads\fR" 4 +.IX Item "-mads" +On embedded PowerPC systems, assume that the startup module is called +\&\fIcrt0.o\fR and the standard C libraries are \fIlibads.a\fR and +\&\fIlibc.a\fR. +.Ip "\fB\-myellowknife\fR" 4 +.IX Item "-myellowknife" +On embedded PowerPC systems, assume that the startup module is called +\&\fIcrt0.o\fR and the standard C libraries are \fIlibyk.a\fR and +\&\fIlibc.a\fR. +.Ip "\fB\-mvxworks\fR" 4 +.IX Item "-mvxworks" +On System V.4 and embedded PowerPC systems, specify that you are +compiling for a VxWorks system. +.Ip "\fB\-memb\fR" 4 +.IX Item "-memb" +On embedded PowerPC systems, set the \fI\s-1PPC_EMB\s0\fR bit in the \s-1ELF\s0 flags +header to indicate that \fBeabi\fR extended relocations are used. +.Ip "\fB\-meabi\fR" 4 +.IX Item "-meabi" +.PD 0 +.Ip "\fB\-mno-eabi\fR" 4 +.IX Item "-mno-eabi" +.PD +On System V.4 and embedded PowerPC systems do (do not) adhere to the +Embedded Applications Binary Interface (eabi) which is a set of +modifications to the System V.4 specifications. Selecting \fB\-meabi\fR +means that the stack is aligned to an 8 byte boundary, a function +\&\f(CW\*(C`_\|_eabi\*(C'\fR is called to from \f(CW\*(C`main\*(C'\fR to set up the eabi +environment, and the \fB\-msdata\fR option can use both \f(CW\*(C`r2\*(C'\fR and +\&\f(CW\*(C`r13\*(C'\fR to point to two separate small data areas. Selecting +\&\fB\-mno-eabi\fR means that the stack is aligned to a 16 byte boundary, +do not call an initialization function from \f(CW\*(C`main\*(C'\fR, and the +\&\fB\-msdata\fR option will only use \f(CW\*(C`r13\*(C'\fR to point to a single +small data area. The \fB\-meabi\fR option is on by default if you +configured \s-1GCC\s0 using one of the \fBpowerpc*\-*\-eabi*\fR options. +.Ip "\fB\-msdata=eabi\fR" 4 +.IX Item "-msdata=eabi" +On System V.4 and embedded PowerPC systems, put small initialized +\&\f(CW\*(C`const\*(C'\fR global and static data in the \fB.sdata2\fR section, which +is pointed to by register \f(CW\*(C`r2\*(C'\fR. Put small initialized +non-\f(CW\*(C`const\*(C'\fR global and static data in the \fB.sdata\fR section, +which is pointed to by register \f(CW\*(C`r13\*(C'\fR. Put small uninitialized +global and static data in the \fB.sbss\fR section, which is adjacent to +the \fB.sdata\fR section. The \fB\-msdata=eabi\fR option is +incompatible with the \fB\-mrelocatable\fR option. The +\&\fB\-msdata=eabi\fR option also sets the \fB\-memb\fR option. +.Ip "\fB\-msdata=sysv\fR" 4 +.IX Item "-msdata=sysv" +On System V.4 and embedded PowerPC systems, put small global and static +data in the \fB.sdata\fR section, which is pointed to by register +\&\f(CW\*(C`r13\*(C'\fR. Put small uninitialized global and static data in the +\&\fB.sbss\fR section, which is adjacent to the \fB.sdata\fR section. +The \fB\-msdata=sysv\fR option is incompatible with the +\&\fB\-mrelocatable\fR option. +.Ip "\fB\-msdata=default\fR" 4 +.IX Item "-msdata=default" +.PD 0 +.Ip "\fB\-msdata\fR" 4 +.IX Item "-msdata" +.PD +On System V.4 and embedded PowerPC systems, if \fB\-meabi\fR is used, +compile code the same as \fB\-msdata=eabi\fR, otherwise compile code the +same as \fB\-msdata=sysv\fR. +.Ip "\fB\-msdata-data\fR" 4 +.IX Item "-msdata-data" +On System V.4 and embedded PowerPC systems, put small global and static +data in the \fB.sdata\fR section. Put small uninitialized global and +static data in the \fB.sbss\fR section. Do not use register \f(CW\*(C`r13\*(C'\fR +to address small data however. This is the default behavior unless +other \fB\-msdata\fR options are used. +.Ip "\fB\-msdata=none\fR" 4 +.IX Item "-msdata=none" +.PD 0 +.Ip "\fB\-mno-sdata\fR" 4 +.IX Item "-mno-sdata" +.PD +On embedded PowerPC systems, put all initialized global and static data +in the \fB.data\fR section, and all uninitialized data in the +\&\fB.bss\fR section. +.Ip "\fB\-G\fR \fInum\fR" 4 +.IX Item "-G num" +On embedded PowerPC systems, put global and static items less than or +equal to \fInum\fR bytes into the small data or bss sections instead of +the normal data or bss section. By default, \fInum\fR is 8. The +\&\fB\-G\fR \fInum\fR switch is also passed to the linker. +All modules should be compiled with the same \fB\-G\fR \fInum\fR value. +.Ip "\fB\-mregnames\fR" 4 +.IX Item "-mregnames" +.PD 0 +.Ip "\fB\-mno-regnames\fR" 4 +.IX Item "-mno-regnames" +.PD +On System V.4 and embedded PowerPC systems do (do not) emit register +names in the assembly language output using symbolic forms. +.PP +.I "\s-1IBM\s0 \s-1RT\s0 Options" +.IX Subsection "IBM RT Options" +.PP +These \fB\-m\fR options are defined for the \s-1IBM\s0 \s-1RT\s0 \s-1PC:\s0 +.Ip "\fB\-min-line-mul\fR" 4 +.IX Item "-min-line-mul" +Use an in-line code sequence for integer multiplies. This is the +default. +.Ip "\fB\-mcall-lib-mul\fR" 4 +.IX Item "-mcall-lib-mul" +Call \f(CW\*(C`lmul$$\*(C'\fR for integer multiples. +.Ip "\fB\-mfull-fp-blocks\fR" 4 +.IX Item "-mfull-fp-blocks" +Generate full-size floating point data blocks, including the minimum +amount of scratch space recommended by \s-1IBM\s0. This is the default. +.Ip "\fB\-mminimum-fp-blocks\fR" 4 +.IX Item "-mminimum-fp-blocks" +Do not include extra scratch space in floating point data blocks. This +results in smaller code, but slower execution, since scratch space must +be allocated dynamically. +.Ip "\fB\-mfp-arg-in-fpregs\fR" 4 +.IX Item "-mfp-arg-in-fpregs" +Use a calling sequence incompatible with the \s-1IBM\s0 calling convention in +which floating point arguments are passed in floating point registers. +Note that \f(CW\*(C`varargs.h\*(C'\fR and \f(CW\*(C`stdargs.h\*(C'\fR will not work with +floating point operands if this option is specified. +.Ip "\fB\-mfp-arg-in-gregs\fR" 4 +.IX Item "-mfp-arg-in-gregs" +Use the normal calling convention for floating point arguments. This is +the default. +.Ip "\fB\-mhc-struct-return\fR" 4 +.IX Item "-mhc-struct-return" +Return structures of more than one word in memory, rather than in a +register. This provides compatibility with the MetaWare HighC (hc) +compiler. Use the option \fB\-fpcc-struct-return\fR for compatibility +with the Portable C Compiler (pcc). +.Ip "\fB\-mnohc-struct-return\fR" 4 +.IX Item "-mnohc-struct-return" +Return some structures of more than one word in registers, when +convenient. This is the default. For compatibility with the +IBM-supplied compilers, use the option \fB\-fpcc-struct-return\fR or the +option \fB\-mhc-struct-return\fR. +.PP +.I "\s-1MIPS\s0 Options" +.IX Subsection "MIPS Options" +.PP +These \fB\-m\fR options are defined for the \s-1MIPS\s0 family of computers: +.Ip "\fB\-mcpu=\fR\fIcpu type\fR" 4 +.IX Item "-mcpu=cpu type" +Assume the defaults for the machine type \fIcpu type\fR when scheduling +instructions. The choices for \fIcpu type\fR are \fBr2000\fR, \fBr3000\fR, +\&\fBr3900\fR, \fBr4000\fR, \fBr4100\fR, \fBr4300\fR, \fBr4400\fR, +\&\fBr4600\fR, \fBr4650\fR, \fBr5000\fR, \fBr6000\fR, \fBr8000\fR, +and \fBorion\fR. Additionally, the \fBr2000\fR, \fBr3000\fR, +\&\fBr4000\fR, \fBr5000\fR, and \fBr6000\fR can be abbreviated as +\&\fBr2k\fR (or \fBr2K\fR), \fBr3k\fR, etc. While picking a specific +\&\fIcpu type\fR will schedule things appropriately for that particular +chip, the compiler will not generate any code that does not meet level 1 +of the \s-1MIPS\s0 \s-1ISA\s0 (instruction set architecture) without a \fB\-mipsX\fR +or \fB\-mabi\fR switch being used. +.Ip "\fB\-mips1\fR" 4 +.IX Item "-mips1" +Issue instructions from level 1 of the \s-1MIPS\s0 \s-1ISA\s0. This is the default. +\&\fBr3000\fR is the default \fIcpu type\fR at this \s-1ISA\s0 level. +.Ip "\fB\-mips2\fR" 4 +.IX Item "-mips2" +Issue instructions from level 2 of the \s-1MIPS\s0 \s-1ISA\s0 (branch likely, square +root instructions). \fBr6000\fR is the default \fIcpu type\fR at this +\&\s-1ISA\s0 level. +.Ip "\fB\-mips3\fR" 4 +.IX Item "-mips3" +Issue instructions from level 3 of the \s-1MIPS\s0 \s-1ISA\s0 (64\-bit instructions). +\&\fBr4000\fR is the default \fIcpu type\fR at this \s-1ISA\s0 level. +.Ip "\fB\-mips4\fR" 4 +.IX Item "-mips4" +Issue instructions from level 4 of the \s-1MIPS\s0 \s-1ISA\s0 (conditional move, +prefetch, enhanced \s-1FPU\s0 instructions). \fBr8000\fR is the default +\&\fIcpu type\fR at this \s-1ISA\s0 level. +.Ip "\fB\-mfp32\fR" 4 +.IX Item "-mfp32" +Assume that 32 32\-bit floating point registers are available. This is +the default. +.Ip "\fB\-mfp64\fR" 4 +.IX Item "-mfp64" +Assume that 32 64\-bit floating point registers are available. This is +the default when the \fB\-mips3\fR option is used. +.Ip "\fB\-mgp32\fR" 4 +.IX Item "-mgp32" +Assume that 32 32\-bit general purpose registers are available. This is +the default. +.Ip "\fB\-mgp64\fR" 4 +.IX Item "-mgp64" +Assume that 32 64\-bit general purpose registers are available. This is +the default when the \fB\-mips3\fR option is used. +.Ip "\fB\-mint64\fR" 4 +.IX Item "-mint64" +Force int and long types to be 64 bits wide. See \fB\-mlong32\fR for an +explanation of the default, and the width of pointers. +.Ip "\fB\-mlong64\fR" 4 +.IX Item "-mlong64" +Force long types to be 64 bits wide. See \fB\-mlong32\fR for an +explanation of the default, and the width of pointers. +.Ip "\fB\-mlong32\fR" 4 +.IX Item "-mlong32" +Force long, int, and pointer types to be 32 bits wide. +.Sp +If none of \fB\-mlong32\fR, \fB\-mlong64\fR, or \fB\-mint64\fR are set, +the size of ints, longs, and pointers depends on the \s-1ABI\s0 and \s-1ISA\s0 chosen. +For \fB\-mabi=32\fR, and \fB\-mabi=n32\fR, ints and longs are 32 bits +wide. For \fB\-mabi=64\fR, ints are 32 bits, and longs are 64 bits wide. +For \fB\-mabi=eabi\fR and either \fB\-mips1\fR or \fB\-mips2\fR, ints +and longs are 32 bits wide. For \fB\-mabi=eabi\fR and higher ISAs, ints +are 32 bits, and longs are 64 bits wide. The width of pointer types is +the smaller of the width of longs or the width of general purpose +registers (which in turn depends on the \s-1ISA\s0). +.Ip "\fB\-mabi=32\fR" 4 +.IX Item "-mabi=32" +.PD 0 +.Ip "\fB\-mabi=o64\fR" 4 +.IX Item "-mabi=o64" +.Ip "\fB\-mabi=n32\fR" 4 +.IX Item "-mabi=n32" +.Ip "\fB\-mabi=64\fR" 4 +.IX Item "-mabi=64" +.Ip "\fB\-mabi=eabi\fR" 4 +.IX Item "-mabi=eabi" +.PD +Generate code for the indicated \s-1ABI\s0. The default instruction level is +\&\fB\-mips1\fR for \fB32\fR, \fB\-mips3\fR for \fBn32\fR, and +\&\fB\-mips4\fR otherwise. Conversely, with \fB\-mips1\fR or +\&\fB\-mips2\fR, the default \s-1ABI\s0 is \fB32\fR; otherwise, the default \s-1ABI\s0 +is \fB64\fR. +.Ip "\fB\-mmips-as\fR" 4 +.IX Item "-mmips-as" +Generate code for the \s-1MIPS\s0 assembler, and invoke \fImips-tfile\fR to +add normal debug information. This is the default for all +platforms except for the \s-1OSF/1\s0 reference platform, using the OSF/rose +object format. If the either of the \fB\-gstabs\fR or \fB\-gstabs+\fR +switches are used, the \fImips-tfile\fR program will encapsulate the +stabs within \s-1MIPS\s0 \s-1ECOFF\s0. +.Ip "\fB\-mgas\fR" 4 +.IX Item "-mgas" +Generate code for the \s-1GNU\s0 assembler. This is the default on the \s-1OSF/1\s0 +reference platform, using the OSF/rose object format. Also, this is +the default if the configure option \fB\*(--with-gnu-as\fR is used. +.Ip "\fB\-msplit-addresses\fR" 4 +.IX Item "-msplit-addresses" +.PD 0 +.Ip "\fB\-mno-split-addresses\fR" 4 +.IX Item "-mno-split-addresses" +.PD +Generate code to load the high and low parts of address constants separately. +This allows \f(CW\*(C`gcc\*(C'\fR to optimize away redundant loads of the high order +bits of addresses. This optimization requires \s-1GNU\s0 as and \s-1GNU\s0 ld. +This optimization is enabled by default for some embedded targets where +\&\s-1GNU\s0 as and \s-1GNU\s0 ld are standard. +.Ip "\fB\-mrnames\fR" 4 +.IX Item "-mrnames" +.PD 0 +.Ip "\fB\-mno-rnames\fR" 4 +.IX Item "-mno-rnames" +.PD +The \fB\-mrnames\fR switch says to output code using the \s-1MIPS\s0 software +names for the registers, instead of the hardware names (ie, \fIa0\fR +instead of \fI$4\fR). The only known assembler that supports this option +is the Algorithmics assembler. +.Ip "\fB\-mgpopt\fR" 4 +.IX Item "-mgpopt" +.PD 0 +.Ip "\fB\-mno-gpopt\fR" 4 +.IX Item "-mno-gpopt" +.PD +The \fB\-mgpopt\fR switch says to write all of the data declarations +before the instructions in the text section, this allows the \s-1MIPS\s0 +assembler to generate one word memory references instead of using two +words for short global or static data items. This is on by default if +optimization is selected. +.Ip "\fB\-mstats\fR" 4 +.IX Item "-mstats" +.PD 0 +.Ip "\fB\-mno-stats\fR" 4 +.IX Item "-mno-stats" +.PD +For each non-inline function processed, the \fB\-mstats\fR switch +causes the compiler to emit one line to the standard error file to +print statistics about the program (number of registers saved, stack +size, etc.). +.Ip "\fB\-mmemcpy\fR" 4 +.IX Item "-mmemcpy" +.PD 0 +.Ip "\fB\-mno-memcpy\fR" 4 +.IX Item "-mno-memcpy" +.PD +The \fB\-mmemcpy\fR switch makes all block moves call the appropriate +string function (\fBmemcpy\fR or \fBbcopy\fR) instead of possibly +generating inline code. +.Ip "\fB\-mmips-tfile\fR" 4 +.IX Item "-mmips-tfile" +.PD 0 +.Ip "\fB\-mno-mips-tfile\fR" 4 +.IX Item "-mno-mips-tfile" +.PD +The \fB\-mno-mips-tfile\fR switch causes the compiler not +postprocess the object file with the \fImips-tfile\fR program, +after the \s-1MIPS\s0 assembler has generated it to add debug support. If +\&\fImips-tfile\fR is not run, then no local variables will be +available to the debugger. In addition, \fIstage2\fR and +\&\fIstage3\fR objects will have the temporary file names passed to the +assembler embedded in the object file, which means the objects will +not compare the same. The \fB\-mno-mips-tfile\fR switch should only +be used when there are bugs in the \fImips-tfile\fR program that +prevents compilation. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. +.Ip "\fB\-mhard-float\fR" 4 +.IX Item "-mhard-float" +Generate output containing floating point instructions. This is the +default if you use the unmodified sources. +.Ip "\fB\-mabicalls\fR" 4 +.IX Item "-mabicalls" +.PD 0 +.Ip "\fB\-mno-abicalls\fR" 4 +.IX Item "-mno-abicalls" +.PD +Emit (or do not emit) the pseudo operations \fB.abicalls\fR, +\&\fB.cpload\fR, and \fB.cprestore\fR that some System V.4 ports use for +position independent code. +.Ip "\fB\-mlong-calls\fR" 4 +.IX Item "-mlong-calls" +.PD 0 +.Ip "\fB\-mno-long-calls\fR" 4 +.IX Item "-mno-long-calls" +.PD +Do all calls with the \fB\s-1JALR\s0\fR instruction, which requires +loading up a function's address into a register before the call. +You need to use this switch, if you call outside of the current +512 megabyte segment to functions that are not through pointers. +.Ip "\fB\-mhalf-pic\fR" 4 +.IX Item "-mhalf-pic" +.PD 0 +.Ip "\fB\-mno-half-pic\fR" 4 +.IX Item "-mno-half-pic" +.PD +Put pointers to extern references into the data section and load them +up, rather than put the references in the text section. +.Ip "\fB\-membedded-pic\fR" 4 +.IX Item "-membedded-pic" +.PD 0 +.Ip "\fB\-mno-embedded-pic\fR" 4 +.IX Item "-mno-embedded-pic" +.PD +Generate \s-1PIC\s0 code suitable for some embedded systems. All calls are +made using \s-1PC\s0 relative address, and all data is addressed using the \f(CW$gp\fR +register. No more than 65536 bytes of global data may be used. This +requires \s-1GNU\s0 as and \s-1GNU\s0 ld which do most of the work. This currently +only works on targets which use \s-1ECOFF\s0; it does not work with \s-1ELF\s0. +.Ip "\fB\-membedded-data\fR" 4 +.IX Item "-membedded-data" +.PD 0 +.Ip "\fB\-mno-embedded-data\fR" 4 +.IX Item "-mno-embedded-data" +.PD +Allocate variables to the read-only data section first if possible, then +next in the small data section if possible, otherwise in data. This gives +slightly slower code than the default, but reduces the amount of \s-1RAM\s0 required +when executing, and thus may be preferred for some embedded systems. +.Ip "\fB\-muninit-const-in-rodata\fR" 4 +.IX Item "-muninit-const-in-rodata" +.PD 0 +.Ip "\fB\-mno-uninit-const-in-rodata\fR" 4 +.IX Item "-mno-uninit-const-in-rodata" +.PD +When used together with \-membedded-data, it will always store uninitialized +const variables in the read-only data section. +.Ip "\fB\-msingle-float\fR" 4 +.IX Item "-msingle-float" +.PD 0 +.Ip "\fB\-mdouble-float\fR" 4 +.IX Item "-mdouble-float" +.PD +The \fB\-msingle-float\fR switch tells gcc to assume that the floating +point coprocessor only supports single precision operations, as on the +\&\fBr4650\fR chip. The \fB\-mdouble-float\fR switch permits gcc to use +double precision operations. This is the default. +.Ip "\fB\-mmad\fR" 4 +.IX Item "-mmad" +.PD 0 +.Ip "\fB\-mno-mad\fR" 4 +.IX Item "-mno-mad" +.PD +Permit use of the \fBmad\fR, \fBmadu\fR and \fBmul\fR instructions, +as on the \fBr4650\fR chip. +.Ip "\fB\-m4650\fR" 4 +.IX Item "-m4650" +Turns on \fB\-msingle-float\fR, \fB\-mmad\fR, and, at least for now, +\&\fB\-mcpu=r4650\fR. +.Ip "\fB\-mips16\fR" 4 +.IX Item "-mips16" +.PD 0 +.Ip "\fB\-mno-mips16\fR" 4 +.IX Item "-mno-mips16" +.PD +Enable 16\-bit instructions. +.Ip "\fB\-mentry\fR" 4 +.IX Item "-mentry" +Use the entry and exit pseudo ops. This option can only be used with +\&\fB\-mips16\fR. +.Ip "\fB\-EL\fR" 4 +.IX Item "-EL" +Compile code for the processor in little endian mode. +The requisite libraries are assumed to exist. +.Ip "\fB\-EB\fR" 4 +.IX Item "-EB" +Compile code for the processor in big endian mode. +The requisite libraries are assumed to exist. +.Ip "\fB\-G\fR \fInum\fR" 4 +.IX Item "-G num" +Put global and static items less than or equal to \fInum\fR bytes into +the small data or bss sections instead of the normal data or bss +section. This allows the assembler to emit one word memory reference +instructions based on the global pointer (\fIgp\fR or \fI$28\fR), +instead of the normal two words used. By default, \fInum\fR is 8 when +the \s-1MIPS\s0 assembler is used, and 0 when the \s-1GNU\s0 assembler is used. The +\&\fB\-G\fR \fInum\fR switch is also passed to the assembler and linker. +All modules should be compiled with the same \fB\-G\fR \fInum\fR +value. +.Ip "\fB\-nocpp\fR" 4 +.IX Item "-nocpp" +Tell the \s-1MIPS\s0 assembler to not run its preprocessor over user +assembler files (with a \fB.s\fR suffix) when assembling them. +.Ip "\fB\-mfix7000\fR" 4 +.IX Item "-mfix7000" +Pass an option to gas which will cause nops to be inserted if +the read of the destination register of an mfhi or mflo instruction +occurs in the following two instructions. +.Ip "\fB\-no-crt0\fR" 4 +.IX Item "-no-crt0" +Do not include the default crt0. +.PP +.I "Intel 386 Options" +.IX Subsection "Intel 386 Options" +.PP +These \fB\-m\fR options are defined for the i386 family of computers: +.Ip "\fB\-mcpu=\fR\fIcpu type\fR" 4 +.IX Item "-mcpu=cpu type" +Assume the defaults for the machine type \fIcpu type\fR when scheduling +instructions. The choices for \fIcpu type\fR are \fBi386\fR, +\&\fBi486\fR, \fBi586\fR, \fBi686\fR, \fBpentium\fR, +\&\fBpentiumpro\fR, \fBpentium4\fR, \fBk6\fR, and \fBathlon\fR +.Sp +While picking a specific \fIcpu type\fR will schedule things appropriately +for that particular chip, the compiler will not generate any code that +does not run on the i386 without the \fB\-march=\fR\fIcpu type\fR option +being used. \fBi586\fR is equivalent to \fBpentium\fR and \fBi686\fR +is equivalent to \fBpentiumpro\fR. \fBk6\fR and \fBathlon\fR are the +\&\s-1AMD\s0 chips as opposed to the Intel ones. +.Ip "\fB\-march=\fR\fIcpu type\fR" 4 +.IX Item "-march=cpu type" +Generate instructions for the machine type \fIcpu type\fR. The choices +for \fIcpu type\fR are the same as for \fB\-mcpu\fR. Moreover, +specifying \fB\-march=\fR\fIcpu type\fR implies \fB\-mcpu=\fR\fIcpu type\fR. +.Ip "\fB\-m386\fR" 4 +.IX Item "-m386" +.PD 0 +.Ip "\fB\-m486\fR" 4 +.IX Item "-m486" +.Ip "\fB\-mpentium\fR" 4 +.IX Item "-mpentium" +.Ip "\fB\-mpentiumpro\fR" 4 +.IX Item "-mpentiumpro" +.PD +Synonyms for \-mcpu=i386, \-mcpu=i486, \-mcpu=pentium, and \-mcpu=pentiumpro +respectively. These synonyms are deprecated. +.Ip "\fB\-mintel-syntax\fR" 4 +.IX Item "-mintel-syntax" +Emit assembly using Intel syntax opcodes instead of \s-1AT&T\s0 syntax. +.Ip "\fB\-mieee-fp\fR" 4 +.IX Item "-mieee-fp" +.PD 0 +.Ip "\fB\-mno-ieee-fp\fR" 4 +.IX Item "-mno-ieee-fp" +.PD +Control whether or not the compiler uses \s-1IEEE\s0 floating point +comparisons. These handle correctly the case where the result of a +comparison is unordered. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. +.Sp +On machines where a function returns floating point results in the 80387 +register stack, some floating point opcodes may be emitted even if +\&\fB\-msoft-float\fR is used. +.Ip "\fB\-mno-fp-ret-in-387\fR" 4 +.IX Item "-mno-fp-ret-in-387" +Do not use the \s-1FPU\s0 registers for return values of functions. +.Sp +The usual calling convention has functions return values of types +\&\f(CW\*(C`float\*(C'\fR and \f(CW\*(C`double\*(C'\fR in an \s-1FPU\s0 register, even if there +is no \s-1FPU\s0. The idea is that the operating system should emulate +an \s-1FPU\s0. +.Sp +The option \fB\-mno-fp-ret-in-387\fR causes such values to be returned +in ordinary \s-1CPU\s0 registers instead. +.Ip "\fB\-mno-fancy-math-387\fR" 4 +.IX Item "-mno-fancy-math-387" +Some 387 emulators do not support the \f(CW\*(C`sin\*(C'\fR, \f(CW\*(C`cos\*(C'\fR and +\&\f(CW\*(C`sqrt\*(C'\fR instructions for the 387. Specify this option to avoid +generating those instructions. This option is the default on FreeBSD. +As of revision 2.6.1, these instructions are not generated unless you +also use the \fB\-funsafe-math-optimizations\fR switch. +.Ip "\fB\-malign-double\fR" 4 +.IX Item "-malign-double" +.PD 0 +.Ip "\fB\-mno-align-double\fR" 4 +.IX Item "-mno-align-double" +.PD +Control whether \s-1GCC\s0 aligns \f(CW\*(C`double\*(C'\fR, \f(CW\*(C`long double\*(C'\fR, and +\&\f(CW\*(C`long long\*(C'\fR variables on a two word boundary or a one word +boundary. Aligning \f(CW\*(C`double\*(C'\fR variables on a two word boundary will +produce code that runs somewhat faster on a \fBPentium\fR at the +expense of more memory. +.Ip "\fB\-m128bit-long-double\fR" 4 +.IX Item "-m128bit-long-double" +.PD 0 +.Ip "\fB\-m128bit-long-double\fR" 4 +.IX Item "-m128bit-long-double" +.PD +Control the size of \f(CW\*(C`long double\*(C'\fR type. i386 application binary interface +specify the size to be 12 bytes, while modern architectures (Pentium and newer) +preffer \f(CW\*(C`long double\*(C'\fR aligned to 8 or 16 byte boundary. This is +impossible to reach with 12 byte long doubles in the array accesses. +.Sp +\&\fBWarning:\fR if you use the \fB\-m128bit-long-double\fR switch, the +structures and arrays containing \f(CW\*(C`long double\*(C'\fR will change their size as +well as function calling convention for function taking \f(CW\*(C`long double\*(C'\fR +will be modified. +.Ip "\fB\-m96bit-long-double\fR" 4 +.IX Item "-m96bit-long-double" +.PD 0 +.Ip "\fB\-m96bit-long-double\fR" 4 +.IX Item "-m96bit-long-double" +.PD +Set the size of \f(CW\*(C`long double\*(C'\fR to 96 bits as required by the i386 +application binary interface. This is the default. +.Ip "\fB\-msvr3\-shlib\fR" 4 +.IX Item "-msvr3-shlib" +.PD 0 +.Ip "\fB\-mno-svr3\-shlib\fR" 4 +.IX Item "-mno-svr3-shlib" +.PD +Control whether \s-1GCC\s0 places uninitialized locals into \f(CW\*(C`bss\*(C'\fR or +\&\f(CW\*(C`data\*(C'\fR. \fB\-msvr3\-shlib\fR places these locals into \f(CW\*(C`bss\*(C'\fR. +These options are meaningful only on System V Release 3. +.Ip "\fB\-mno-wide-multiply\fR" 4 +.IX Item "-mno-wide-multiply" +.PD 0 +.Ip "\fB\-mwide-multiply\fR" 4 +.IX Item "-mwide-multiply" +.PD +Control whether \s-1GCC\s0 uses the \f(CW\*(C`mul\*(C'\fR and \f(CW\*(C`imul\*(C'\fR that produce +64\-bit results in \f(CW\*(C`eax:edx\*(C'\fR from 32\-bit operands to do \f(CW\*(C`long +long\*(C'\fR multiplies and 32\-bit division by constants. +.Ip "\fB\-mrtd\fR" 4 +.IX Item "-mrtd" +Use a different function-calling convention, in which functions that +take a fixed number of arguments return with the \f(CW\*(C`ret\*(C'\fR \fInum\fR +instruction, which pops their arguments while returning. This saves one +instruction in the caller since there is no need to pop the arguments +there. +.Sp +You can specify that an individual function is called with this calling +sequence with the function attribute \fBstdcall\fR. You can also +override the \fB\-mrtd\fR option by using the function attribute +\&\fBcdecl\fR. +.Sp +\&\fBWarning:\fR this calling convention is incompatible with the one +normally used on Unix, so you cannot use it if you need to call +libraries compiled with the Unix compiler. +.Sp +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR); +otherwise incorrect code will be generated for calls to those +functions. +.Sp +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) +.Ip "\fB\-mregparm=\fR\fInum\fR" 4 +.IX Item "-mregparm=num" +Control how many registers are used to pass integer arguments. By +default, no registers are used to pass arguments, and at most 3 +registers can be used. You can control this behavior for a specific +function by using the function attribute \fBregparm\fR. +.Sp +\&\fBWarning:\fR if you use this switch, and +\&\fInum\fR is nonzero, then you must build all modules with the same +value, including any libraries. This includes the system libraries and +startup modules. +.Ip "\fB\-mpreferred-stack-boundary=\fR\fInum\fR" 4 +.IX Item "-mpreferred-stack-boundary=num" +Attempt to keep the stack boundary aligned to a 2 raised to \fInum\fR +byte boundary. If \fB\-mpreferred-stack-boundary\fR is not specified, +the default is 4 (16 bytes or 128 bits). +.Sp +The stack is required to be aligned on a 4 byte boundary. On Pentium +and PentiumPro, \f(CW\*(C`double\*(C'\fR and \f(CW\*(C`long double\*(C'\fR values should be +aligned to an 8 byte boundary (see \fB\-malign-double\fR) or suffer +significant run time performance penalties. On Pentium \s-1III\s0, the +Streaming \s-1SIMD\s0 Extension (\s-1SSE\s0) data type \f(CW\*(C`_\|_m128\*(C'\fR suffers similar +penalties if it is not 16 byte aligned. +.Sp +To ensure proper alignment of this values on the stack, the stack boundary +must be as aligned as that required by any value stored on the stack. +Further, every function must be generated such that it keeps the stack +aligned. Thus calling a function compiled with a higher preferred +stack boundary from a function compiled with a lower preferred stack +boundary will most likely misalign the stack. It is recommended that +libraries that use callbacks always use the default setting. +.Sp +This extra alignment does consume extra stack space. Code that is sensitive +to stack space usage, such as embedded systems and operating system kernels, +may want to reduce the preferred alignment to +\&\fB\-mpreferred-stack-boundary=2\fR. +.Ip "\fB\-mpush-args\fR" 4 +.IX Item "-mpush-args" +Use \s-1PUSH\s0 operations to store outgoing parameters. This method is shorter +and usually equally fast as method using \s-1SUB/MOV\s0 operations and is enabled +by default. In some cases disabling it may improve performance because of +improved scheduling and reduced dependencies. +.Ip "\fB\-maccumulate-outgoing-args\fR" 4 +.IX Item "-maccumulate-outgoing-args" +If enabled, the maximum amount of space required for outgoing arguments will be +computed in the function prologue. This in faster on most modern CPUs +because of reduced dependencies, improved scheduling and reduced stack usage +when preferred stack boundary is not equal to 2. The drawback is a notable +increase in code size. This switch implies \-mno-push-args. +.Ip "\fB\-mthreads\fR" 4 +.IX Item "-mthreads" +Support thread-safe exception handling on \fBMingw32\fR. Code that relies +on thread-safe exception handling must compile and link all code with the +\&\fB\-mthreads\fR option. When compiling, \fB\-mthreads\fR defines +\&\fB\-D_MT\fR; when linking, it links in a special thread helper library +\&\fB\-lmingwthrd\fR which cleans up per thread exception handling data. +.Ip "\fB\-mno-align-stringops\fR" 4 +.IX Item "-mno-align-stringops" +Do not align destination of inlined string operations. This switch reduces +code size and improves performance in case the destination is already aligned, +but gcc don't know about it. +.Ip "\fB\-minline-all-stringops\fR" 4 +.IX Item "-minline-all-stringops" +By default \s-1GCC\s0 inlines string operations only when destination is known to be +aligned at least to 4 byte boundary. This enables more inlining, increase code +size, but may improve performance of code that depends on fast memcpy, strlen +and memset for short lengths. +.Ip "\fB\-momit-leaf-frame-pointer\fR" 4 +.IX Item "-momit-leaf-frame-pointer" +Don't keep the frame pointer in a register for leaf functions. This +avoids the instructions to save, set up and restore frame pointers and +makes an extra register available in leaf functions. The option +\&\fB\-fomit-frame-pointer\fR removes the frame pointer for all functions +which might make debugging harder. +.PP +.I "\s-1HPPA\s0 Options" +.IX Subsection "HPPA Options" +.PP +These \fB\-m\fR options are defined for the \s-1HPPA\s0 family of computers: +.Ip "\fB\-march=\fR\fIarchitecture type\fR" 4 +.IX Item "-march=architecture type" +Generate code for the specified architecture. The choices for +\&\fIarchitecture type\fR are \fB1.0\fR for \s-1PA\s0 1.0, \fB1.1\fR for \s-1PA\s0 +1.1, and \fB2.0\fR for \s-1PA\s0 2.0 processors. Refer to +\&\fI/usr/lib/sched.models\fR on an \s-1HP-UX\s0 system to determine the proper +architecture option for your machine. Code compiled for lower numbered +architectures will run on higher numbered architectures, but not the +other way around. +.Sp +\&\s-1PA\s0 2.0 support currently requires gas snapshot 19990413 or later. The +next release of binutils (current is 2.9.1) will probably contain \s-1PA\s0 2.0 +support. +.Ip "\fB\-mpa-risc-1\-0\fR" 4 +.IX Item "-mpa-risc-1-0" +.PD 0 +.Ip "\fB\-mpa-risc-1\-1\fR" 4 +.IX Item "-mpa-risc-1-1" +.Ip "\fB\-mpa-risc-2\-0\fR" 4 +.IX Item "-mpa-risc-2-0" +.PD +Synonyms for \-march=1.0, \-march=1.1, and \-march=2.0 respectively. +.Ip "\fB\-mbig-switch\fR" 4 +.IX Item "-mbig-switch" +Generate code suitable for big switch tables. Use this option only if +the assembler/linker complain about out of range branches within a switch +table. +.Ip "\fB\-mjump-in-delay\fR" 4 +.IX Item "-mjump-in-delay" +Fill delay slots of function calls with unconditional jump instructions +by modifying the return pointer for the function call to be the target +of the conditional jump. +.Ip "\fB\-mdisable-fpregs\fR" 4 +.IX Item "-mdisable-fpregs" +Prevent floating point registers from being used in any manner. This is +necessary for compiling kernels which perform lazy context switching of +floating point registers. If you use this option and attempt to perform +floating point operations, the compiler will abort. +.Ip "\fB\-mdisable-indexing\fR" 4 +.IX Item "-mdisable-indexing" +Prevent the compiler from using indexing address modes. This avoids some +rather obscure problems when compiling \s-1MIG\s0 generated code under \s-1MACH\s0. +.Ip "\fB\-mno-space-regs\fR" 4 +.IX Item "-mno-space-regs" +Generate code that assumes the target has no space registers. This allows +\&\s-1GCC\s0 to generate faster indirect calls and use unscaled index address modes. +.Sp +Such code is suitable for level 0 \s-1PA\s0 systems and kernels. +.Ip "\fB\-mfast-indirect-calls\fR" 4 +.IX Item "-mfast-indirect-calls" +Generate code that assumes calls never cross space boundaries. This +allows \s-1GCC\s0 to emit code which performs faster indirect calls. +.Sp +This option will not work in the presence of shared libraries or nested +functions. +.Ip "\fB\-mlong-load-store\fR" 4 +.IX Item "-mlong-load-store" +Generate 3\-instruction load and store sequences as sometimes required by +the \s-1HP-UX\s0 10 linker. This is equivalent to the \fB+k\fR option to +the \s-1HP\s0 compilers. +.Ip "\fB\-mportable-runtime\fR" 4 +.IX Item "-mportable-runtime" +Use the portable calling conventions proposed by \s-1HP\s0 for \s-1ELF\s0 systems. +.Ip "\fB\-mgas\fR" 4 +.IX Item "-mgas" +Enable the use of assembler directives only \s-1GAS\s0 understands. +.Ip "\fB\-mschedule=\fR\fIcpu type\fR" 4 +.IX Item "-mschedule=cpu type" +Schedule code according to the constraints for the machine type +\&\fIcpu type\fR. The choices for \fIcpu type\fR are \fB700\fR +\&\fB7100\fR, \fB7100LC\fR, \fB7200\fR, and \fB8000\fR. Refer to +\&\fI/usr/lib/sched.models\fR on an \s-1HP-UX\s0 system to determine the +proper scheduling option for your machine. +.Ip "\fB\-mlinker-opt\fR" 4 +.IX Item "-mlinker-opt" +Enable the optimization pass in the \s-1HPUX\s0 linker. Note this makes symbolic +debugging impossible. It also triggers a bug in the \s-1HPUX\s0 8 and \s-1HPUX\s0 9 linkers +in which they give bogus error messages when linking some programs. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries are not available for all \s-1HPPA\s0 +targets. Normally the facilities of the machine's usual C compiler are +used, but this cannot be done directly in cross-compilation. You must make +your own arrangements to provide suitable library functions for +cross-compilation. The embedded target \fBhppa1.1\-*\-pro\fR +does provide software floating point support. +.Sp +\&\fB\-msoft-float\fR changes the calling convention in the output file; +therefore, it is only useful if you compile \fIall\fR of a program with +this option. In particular, you need to compile \fIlibgcc.a\fR, the +library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for +this to work. +.PP +.I "Intel 960 Options" +.IX Subsection "Intel 960 Options" +.PP +These \fB\-m\fR options are defined for the Intel 960 implementations: +.Ip "\fB\-m\fR\fIcpu type\fR" 4 +.IX Item "-mcpu type" +Assume the defaults for the machine type \fIcpu type\fR for some of +the other options, including instruction scheduling, floating point +support, and addressing modes. The choices for \fIcpu type\fR are +\&\fBka\fR, \fBkb\fR, \fBmc\fR, \fBca\fR, \fBcf\fR, +\&\fBsa\fR, and \fBsb\fR. +The default is +\&\fBkb\fR. +.Ip "\fB\-mnumerics\fR" 4 +.IX Item "-mnumerics" +.PD 0 +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +.PD +The \fB\-mnumerics\fR option indicates that the processor does support +floating-point instructions. The \fB\-msoft-float\fR option indicates +that floating-point support should not be assumed. +.Ip "\fB\-mleaf-procedures\fR" 4 +.IX Item "-mleaf-procedures" +.PD 0 +.Ip "\fB\-mno-leaf-procedures\fR" 4 +.IX Item "-mno-leaf-procedures" +.PD +Do (or do not) attempt to alter leaf procedures to be callable with the +\&\f(CW\*(C`bal\*(C'\fR instruction as well as \f(CW\*(C`call\*(C'\fR. This will result in more +efficient code for explicit calls when the \f(CW\*(C`bal\*(C'\fR instruction can be +substituted by the assembler or linker, but less efficient code in other +cases, such as calls via function pointers, or using a linker that doesn't +support this optimization. +.Ip "\fB\-mtail-call\fR" 4 +.IX Item "-mtail-call" +.PD 0 +.Ip "\fB\-mno-tail-call\fR" 4 +.IX Item "-mno-tail-call" +.PD +Do (or do not) make additional attempts (beyond those of the +machine-independent portions of the compiler) to optimize tail-recursive +calls into branches. You may not want to do this because the detection of +cases where this is not valid is not totally complete. The default is +\&\fB\-mno-tail-call\fR. +.Ip "\fB\-mcomplex-addr\fR" 4 +.IX Item "-mcomplex-addr" +.PD 0 +.Ip "\fB\-mno-complex-addr\fR" 4 +.IX Item "-mno-complex-addr" +.PD +Assume (or do not assume) that the use of a complex addressing mode is a +win on this implementation of the i960. Complex addressing modes may not +be worthwhile on the K-series, but they definitely are on the C-series. +The default is currently \fB\-mcomplex-addr\fR for all processors except +the \s-1CB\s0 and \s-1CC\s0. +.Ip "\fB\-mcode-align\fR" 4 +.IX Item "-mcode-align" +.PD 0 +.Ip "\fB\-mno-code-align\fR" 4 +.IX Item "-mno-code-align" +.PD +Align code to 8\-byte boundaries for faster fetching (or don't bother). +Currently turned on by default for C-series implementations only. +.Ip "\fB\-mic-compat\fR" 4 +.IX Item "-mic-compat" +.PD 0 +.Ip "\fB\-mic2.0\-compat\fR" 4 +.IX Item "-mic2.0-compat" +.Ip "\fB\-mic3.0\-compat\fR" 4 +.IX Item "-mic3.0-compat" +.PD +Enable compatibility with iC960 v2.0 or v3.0. +.Ip "\fB\-masm-compat\fR" 4 +.IX Item "-masm-compat" +.PD 0 +.Ip "\fB\-mintel-asm\fR" 4 +.IX Item "-mintel-asm" +.PD +Enable compatibility with the iC960 assembler. +.Ip "\fB\-mstrict-align\fR" 4 +.IX Item "-mstrict-align" +.PD 0 +.Ip "\fB\-mno-strict-align\fR" 4 +.IX Item "-mno-strict-align" +.PD +Do not permit (do permit) unaligned accesses. +.Ip "\fB\-mold-align\fR" 4 +.IX Item "-mold-align" +Enable structure-alignment compatibility with Intel's gcc release version +1.3 (based on gcc 1.37). This option implies \fB\-mstrict-align\fR. +.Ip "\fB\-mlong-double-64\fR" 4 +.IX Item "-mlong-double-64" +Implement type \fBlong double\fR as 64\-bit floating point numbers. +Without the option \fBlong double\fR is implemented by 80\-bit +floating point numbers. The only reason we have it because there is +no 128\-bit \fBlong double\fR support in \fBfp-bit.c\fR yet. So it +is only useful for people using soft-float targets. Otherwise, we +should recommend against use of it. +.PP +.I "\s-1DEC\s0 Alpha Options" +.IX Subsection "DEC Alpha Options" +.PP +These \fB\-m\fR options are defined for the \s-1DEC\s0 Alpha implementations: +.Ip "\fB\-mno-soft-float\fR" 4 +.IX Item "-mno-soft-float" +.PD 0 +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +.PD +Use (do not use) the hardware floating-point instructions for +floating-point operations. When \fB\-msoft-float\fR is specified, +functions in \fIlibgcc.a\fR will be used to perform floating-point +operations. Unless they are replaced by routines that emulate the +floating-point operations, or compiled in such a way as to call such +emulations routines, these routines will issue floating-point +operations. If you are compiling for an Alpha without floating-point +operations, you must ensure that the library is built so as not to call +them. +.Sp +Note that Alpha implementations without floating-point operations are +required to have floating-point registers. +.Ip "\fB\-mfp-reg\fR" 4 +.IX Item "-mfp-reg" +.PD 0 +.Ip "\fB\-mno-fp-regs\fR" 4 +.IX Item "-mno-fp-regs" +.PD +Generate code that uses (does not use) the floating-point register set. +\&\fB\-mno-fp-regs\fR implies \fB\-msoft-float\fR. If the floating-point +register set is not used, floating point operands are passed in integer +registers as if they were integers and floating-point results are passed +in \f(CW$0\fR instead of \f(CW$f0\fR. This is a non-standard calling sequence, so any +function with a floating-point argument or return value called by code +compiled with \fB\-mno-fp-regs\fR must also be compiled with that +option. +.Sp +A typical use of this option is building a kernel that does not use, +and hence need not save and restore, any floating-point registers. +.Ip "\fB\-mieee\fR" 4 +.IX Item "-mieee" +The Alpha architecture implements floating-point hardware optimized for +maximum performance. It is mostly compliant with the \s-1IEEE\s0 floating +point standard. However, for full compliance, software assistance is +required. This option generates code fully \s-1IEEE\s0 compliant code +\&\fIexcept\fR that the \fIinexact flag\fR is not maintained (see below). +If this option is turned on, the \s-1CPP\s0 macro \f(CW\*(C`_IEEE_FP\*(C'\fR is defined +during compilation. The option is a shorthand for: \fB\-D_IEEE_FP +\&\-mfp-trap-mode=su \-mtrap-precision=i \-mieee-conformant\fR. The resulting +code is less efficient but is able to correctly support denormalized +numbers and exceptional \s-1IEEE\s0 values such as not-a-number and plus/minus +infinity. Other Alpha compilers call this option +\&\fB\-ieee_with_no_inexact\fR. +.Ip "\fB\-mieee-with-inexact\fR" 4 +.IX Item "-mieee-with-inexact" +This is like \fB\-mieee\fR except the generated code also maintains the +\&\s-1IEEE\s0 \fIinexact flag\fR. Turning on this option causes the generated +code to implement fully-compliant \s-1IEEE\s0 math. The option is a shorthand +for \fB\-D_IEEE_FP \-D_IEEE_FP_INEXACT\fR plus the three following: +\&\fB\-mieee-conformant\fR, +\&\fB\-mfp-trap-mode=sui\fR, +and \fB\-mtrap-precision=i\fR. +On some Alpha implementations the resulting code may execute +significantly slower than the code generated by default. Since there +is very little code that depends on the \fIinexact flag\fR, you should +normally not specify this option. Other Alpha compilers call this +option \fB\-ieee_with_inexact\fR. +.Ip "\fB\-mfp-trap-mode=\fR\fItrap mode\fR" 4 +.IX Item "-mfp-trap-mode=trap mode" +This option controls what floating-point related traps are enabled. +Other Alpha compilers call this option \fB\-fptm\fR \fItrap mode\fR. +The trap mode can be set to one of four values: +.RS 4 +.Ip "\fBn\fR" 4 +.IX Item "n" +This is the default (normal) setting. The only traps that are enabled +are the ones that cannot be disabled in software (e.g., division by zero +trap). +.Ip "\fBu\fR" 4 +.IX Item "u" +In addition to the traps enabled by \fBn\fR, underflow traps are enabled +as well. +.Ip "\fBsu\fR" 4 +.IX Item "su" +Like \fBsu\fR, but the instructions are marked to be safe for software +completion (see Alpha architecture manual for details). +.Ip "\fBsui\fR" 4 +.IX Item "sui" +Like \fBsu\fR, but inexact traps are enabled as well. +.RE +.RS 4 +.RE +.Ip "\fB\-mfp-rounding-mode=\fR\fIrounding mode\fR" 4 +.IX Item "-mfp-rounding-mode=rounding mode" +Selects the \s-1IEEE\s0 rounding mode. Other Alpha compilers call this option +\&\fB\-fprm\fR \fIrounding mode\fR. The \fIrounding mode\fR can be one +of: +.RS 4 +.Ip "\fBn\fR" 4 +.IX Item "n" +Normal \s-1IEEE\s0 rounding mode. Floating point numbers are rounded towards +the nearest machine number or towards the even machine number in case +of a tie. +.Ip "\fBm\fR" 4 +.IX Item "m" +Round towards minus infinity. +.Ip "\fBc\fR" 4 +.IX Item "c" +Chopped rounding mode. Floating point numbers are rounded towards zero. +.Ip "\fBd\fR" 4 +.IX Item "d" +Dynamic rounding mode. A field in the floating point control register +(\fIfpcr\fR, see Alpha architecture reference manual) controls the +rounding mode in effect. The C library initializes this register for +rounding towards plus infinity. Thus, unless your program modifies the +\&\fIfpcr\fR, \fBd\fR corresponds to round towards plus infinity. +.RE +.RS 4 +.RE +.Ip "\fB\-mtrap-precision=\fR\fItrap precision\fR" 4 +.IX Item "-mtrap-precision=trap precision" +In the Alpha architecture, floating point traps are imprecise. This +means without software assistance it is impossible to recover from a +floating trap and program execution normally needs to be terminated. +\&\s-1GCC\s0 can generate code that can assist operating system trap handlers +in determining the exact location that caused a floating point trap. +Depending on the requirements of an application, different levels of +precisions can be selected: +.RS 4 +.Ip "\fBp\fR" 4 +.IX Item "p" +Program precision. This option is the default and means a trap handler +can only identify which program caused a floating point exception. +.Ip "\fBf\fR" 4 +.IX Item "f" +Function precision. The trap handler can determine the function that +caused a floating point exception. +.Ip "\fBi\fR" 4 +.IX Item "i" +Instruction precision. The trap handler can determine the exact +instruction that caused a floating point exception. +.RE +.RS 4 +.Sp +Other Alpha compilers provide the equivalent options called +\&\fB\-scope_safe\fR and \fB\-resumption_safe\fR. +.RE +.Ip "\fB\-mieee-conformant\fR" 4 +.IX Item "-mieee-conformant" +This option marks the generated code as \s-1IEEE\s0 conformant. You must not +use this option unless you also specify \fB\-mtrap-precision=i\fR and either +\&\fB\-mfp-trap-mode=su\fR or \fB\-mfp-trap-mode=sui\fR. Its only effect +is to emit the line \fB.eflag 48\fR in the function prologue of the +generated assembly file. Under \s-1DEC\s0 Unix, this has the effect that +IEEE-conformant math library routines will be linked in. +.Ip "\fB\-mbuild-constants\fR" 4 +.IX Item "-mbuild-constants" +Normally \s-1GCC\s0 examines a 32\- or 64\-bit integer constant to +see if it can construct it from smaller constants in two or three +instructions. If it cannot, it will output the constant as a literal and +generate code to load it from the data segment at runtime. +.Sp +Use this option to require \s-1GCC\s0 to construct \fIall\fR integer constants +using code, even if it takes more instructions (the maximum is six). +.Sp +You would typically use this option to build a shared library dynamic +loader. Itself a shared library, it must relocate itself in memory +before it can find the variables and constants in its own data segment. +.Ip "\fB\-malpha-as\fR" 4 +.IX Item "-malpha-as" +.PD 0 +.Ip "\fB\-mgas\fR" 4 +.IX Item "-mgas" +.PD +Select whether to generate code to be assembled by the vendor-supplied +assembler (\fB\-malpha-as\fR) or by the \s-1GNU\s0 assembler \fB\-mgas\fR. +.Ip "\fB\-mbwx\fR" 4 +.IX Item "-mbwx" +.PD 0 +.Ip "\fB\-mno-bwx\fR" 4 +.IX Item "-mno-bwx" +.Ip "\fB\-mcix\fR" 4 +.IX Item "-mcix" +.Ip "\fB\-mno-cix\fR" 4 +.IX Item "-mno-cix" +.Ip "\fB\-mmax\fR" 4 +.IX Item "-mmax" +.Ip "\fB\-mno-max\fR" 4 +.IX Item "-mno-max" +.PD +Indicate whether \s-1GCC\s0 should generate code to use the optional \s-1BWX\s0, +\&\s-1CIX\s0, and \s-1MAX\s0 instruction sets. The default is to use the instruction sets +supported by the \s-1CPU\s0 type specified via \fB\-mcpu=\fR option or that +of the \s-1CPU\s0 on which \s-1GCC\s0 was built if none was specified. +.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 +.IX Item "-mcpu=cpu_type" +Set the instruction set, register set, and instruction scheduling +parameters for machine type \fIcpu_type\fR. You can specify either the +\&\fB\s-1EV\s0\fR style name or the corresponding chip number. \s-1GCC\s0 +supports scheduling parameters for the \s-1EV4\s0 and \s-1EV5\s0 family of processors +and will choose the default values for the instruction set from +the processor you specify. If you do not specify a processor type, +\&\s-1GCC\s0 will default to the processor on which the compiler was built. +.Sp +Supported values for \fIcpu_type\fR are +.RS 4 +.Ip "\fBev4\fR" 4 +.IX Item "ev4" +.PD 0 +.Ip "\fB21064\fR" 4 +.IX Item "21064" +.PD +Schedules as an \s-1EV4\s0 and has no instruction set extensions. +.Ip "\fBev5\fR" 4 +.IX Item "ev5" +.PD 0 +.Ip "\fB21164\fR" 4 +.IX Item "21164" +.PD +Schedules as an \s-1EV5\s0 and has no instruction set extensions. +.Ip "\fBev56\fR" 4 +.IX Item "ev56" +.PD 0 +.Ip "\fB21164a\fR" 4 +.IX Item "21164a" +.PD +Schedules as an \s-1EV5\s0 and supports the \s-1BWX\s0 extension. +.Ip "\fBpca56\fR" 4 +.IX Item "pca56" +.PD 0 +.Ip "\fB21164pc\fR" 4 +.IX Item "21164pc" +.Ip "\fB21164PC\fR" 4 +.IX Item "21164PC" +.PD +Schedules as an \s-1EV5\s0 and supports the \s-1BWX\s0 and \s-1MAX\s0 extensions. +.Ip "\fBev6\fR" 4 +.IX Item "ev6" +.PD 0 +.Ip "\fB21264\fR" 4 +.IX Item "21264" +.PD +Schedules as an \s-1EV5\s0 (until Digital releases the scheduling parameters +for the \s-1EV6\s0) and supports the \s-1BWX\s0, \s-1CIX\s0, and \s-1MAX\s0 extensions. +.RE +.RS 4 +.RE +.Ip "\fB\-mmemory-latency=\fR\fItime\fR" 4 +.IX Item "-mmemory-latency=time" +Sets the latency the scheduler should assume for typical memory +references as seen by the application. This number is highly +dependent on the memory access patterns used by the application +and the size of the external cache on the machine. +.Sp +Valid options for \fItime\fR are +.RS 4 +.Ip "\fInumber\fR" 4 +.IX Item "number" +A decimal number representing clock cycles. +.Ip "\fBL1\fR" 4 +.IX Item "L1" +.PD 0 +.Ip "\fBL2\fR" 4 +.IX Item "L2" +.Ip "\fBL3\fR" 4 +.IX Item "L3" +.Ip "\fBmain\fR" 4 +.IX Item "main" +.PD +The compiler contains estimates of the number of clock cycles for +``typical'' \s-1EV4\s0 & \s-1EV5\s0 hardware for the Level 1, 2 & 3 caches +(also called Dcache, Scache, and Bcache), as well as to main memory. +Note that L3 is only valid for \s-1EV5\s0. +.RE +.RS 4 +.RE +.PP +.I "Clipper Options" +.IX Subsection "Clipper Options" +.PP +These \fB\-m\fR options are defined for the Clipper implementations: +.Ip "\fB\-mc300\fR" 4 +.IX Item "-mc300" +Produce code for a C300 Clipper processor. This is the default. +.Ip "\fB\-mc400\fR" 4 +.IX Item "-mc400" +Produce code for a C400 Clipper processor i.e. use floating point +registers f8..f15. +.PP +.I "H8/300 Options" +.IX Subsection "H8/300 Options" +.PP +These \fB\-m\fR options are defined for the H8/300 implementations: +.Ip "\fB\-mrelax\fR" 4 +.IX Item "-mrelax" +Shorten some address references at link time, when possible; uses the +linker option \fB\-relax\fR. +.Ip "\fB\-mh\fR" 4 +.IX Item "-mh" +Generate code for the H8/300H. +.Ip "\fB\-ms\fR" 4 +.IX Item "-ms" +Generate code for the H8/S. +.Ip "\fB\-ms2600\fR" 4 +.IX Item "-ms2600" +Generate code for the H8/S2600. This switch must be used with \-ms. +.Ip "\fB\-mint32\fR" 4 +.IX Item "-mint32" +Make \f(CW\*(C`int\*(C'\fR data 32 bits by default. +.Ip "\fB\-malign-300\fR" 4 +.IX Item "-malign-300" +On the H8/300H and H8/S, use the same alignment rules as for the H8/300. +The default for the H8/300H and H8/S is to align longs and floats on 4 +byte boundaries. +\&\fB\-malign-300\fR causes them to be aligned on 2 byte boundaries. +This option has no effect on the H8/300. +.PP +.I "\s-1SH\s0 Options" +.IX Subsection "SH Options" +.PP +These \fB\-m\fR options are defined for the \s-1SH\s0 implementations: +.Ip "\fB\-m1\fR" 4 +.IX Item "-m1" +Generate code for the \s-1SH1\s0. +.Ip "\fB\-m2\fR" 4 +.IX Item "-m2" +Generate code for the \s-1SH2\s0. +.Ip "\fB\-m3\fR" 4 +.IX Item "-m3" +Generate code for the \s-1SH3\s0. +.Ip "\fB\-m3e\fR" 4 +.IX Item "-m3e" +Generate code for the SH3e. +.Ip "\fB\-m4\-nofpu\fR" 4 +.IX Item "-m4-nofpu" +Generate code for the \s-1SH4\s0 without a floating-point unit. +.Ip "\fB\-m4\-single-only\fR" 4 +.IX Item "-m4-single-only" +Generate code for the \s-1SH4\s0 with a floating-point unit that only +supports single-precision arithmentic. +.Ip "\fB\-m4\-single\fR" 4 +.IX Item "-m4-single" +Generate code for the \s-1SH4\s0 assuming the floating-point unit is in +single-precision mode by default. +.Ip "\fB\-m4\fR" 4 +.IX Item "-m4" +Generate code for the \s-1SH4\s0. +.Ip "\fB\-mb\fR" 4 +.IX Item "-mb" +Compile code for the processor in big endian mode. +.Ip "\fB\-ml\fR" 4 +.IX Item "-ml" +Compile code for the processor in little endian mode. +.Ip "\fB\-mdalign\fR" 4 +.IX Item "-mdalign" +Align doubles at 64\-bit boundaries. Note that this changes the calling +conventions, and thus some functions from the standard C library will +not work unless you recompile it first with \-mdalign. +.Ip "\fB\-mrelax\fR" 4 +.IX Item "-mrelax" +Shorten some address references at link time, when possible; uses the +linker option \fB\-relax\fR. +.Ip "\fB\-mbigtable\fR" 4 +.IX Item "-mbigtable" +Use 32\-bit offsets in \f(CW\*(C`switch\*(C'\fR tables. The default is to use +16\-bit offsets. +.Ip "\fB\-mfmovd\fR" 4 +.IX Item "-mfmovd" +Enable the use of the instruction \f(CW\*(C`fmovd\*(C'\fR. +.Ip "\fB\-mhitachi\fR" 4 +.IX Item "-mhitachi" +Comply with the calling conventions defined by Hitachi. +.Ip "\fB\-mnomacsave\fR" 4 +.IX Item "-mnomacsave" +Mark the \f(CW\*(C`MAC\*(C'\fR register as call-clobbered, even if +\&\fB\-mhitachi\fR is given. +.Ip "\fB\-misize\fR" 4 +.IX Item "-misize" +Dump instruction size and location in the assembly code. +.Ip "\fB\-mpadstruct\fR" 4 +.IX Item "-mpadstruct" +This option is deprecated. It pads structures to multiple of 4 bytes, +which is incompatible with the \s-1SH\s0 \s-1ABI\s0. +.Ip "\fB\-mspace\fR" 4 +.IX Item "-mspace" +Optimize for space instead of speed. Implied by \fB\-Os\fR. +.Ip "\fB\-mprefergot\fR" 4 +.IX Item "-mprefergot" +When generating position-independent code, emit function calls using +the Global Offset Table instead of the Procedure Linkage Table. +.Ip "\fB\-musermode\fR" 4 +.IX Item "-musermode" +Generate a library function call to invalidate instruction cache +entries, after fixing up a trampoline. This library function call +doesn't assume it can write to the whole memory address space. This +is the default when the target is \f(CW\*(C`sh\-*\-linux*\*(C'\fR. +.PP +.I "Options for System V" +.IX Subsection "Options for System V" +.PP +These additional options are available on System V Release 4 for +compatibility with other compilers on those systems: +.Ip "\fB\-G\fR" 4 +.IX Item "-G" +Create a shared object. +It is recommended that \fB\-symbolic\fR or \fB\-shared\fR be used instead. +.Ip "\fB\-Qy\fR" 4 +.IX Item "-Qy" +Identify the versions of each tool used by the compiler, in a +\&\f(CW\*(C`.ident\*(C'\fR assembler directive in the output. +.Ip "\fB\-Qn\fR" 4 +.IX Item "-Qn" +Refrain from adding \f(CW\*(C`.ident\*(C'\fR directives to the output file (this is +the default). +.Ip "\fB\-YP,\fR\fIdirs\fR" 4 +.IX Item "-YP,dirs" +Search the directories \fIdirs\fR, and no others, for libraries +specified with \fB\-l\fR. +.Ip "\fB\-Ym,\fR\fIdir\fR" 4 +.IX Item "-Ym,dir" +Look in the directory \fIdir\fR to find the M4 preprocessor. +The assembler uses this option. +.PP +.I "TMS320C3x/C4x Options" +.IX Subsection "TMS320C3x/C4x Options" +.PP +These \fB\-m\fR options are defined for TMS320C3x/C4x implementations: +.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 +.IX Item "-mcpu=cpu_type" +Set the instruction set, register set, and instruction scheduling +parameters for machine type \fIcpu_type\fR. Supported values for +\&\fIcpu_type\fR are \fBc30\fR, \fBc31\fR, \fBc32\fR, \fBc40\fR, and +\&\fBc44\fR. The default is \fBc40\fR to generate code for the +\&\s-1TMS320C40\s0. +.Ip "\fB\-mbig-memory\fR" 4 +.IX Item "-mbig-memory" +.PD 0 +.Ip "\fB\-mbig\fR" 4 +.IX Item "-mbig" +.Ip "\fB\-msmall-memory\fR" 4 +.IX Item "-msmall-memory" +.Ip "\fB\-msmall\fR" 4 +.IX Item "-msmall" +.PD +Generates code for the big or small memory model. The small memory +model assumed that all data fits into one 64K word page. At run-time +the data page (\s-1DP\s0) register must be set to point to the 64K page +containing the .bss and .data program sections. The big memory model is +the default and requires reloading of the \s-1DP\s0 register for every direct +memory access. +.Ip "\fB\-mbk\fR" 4 +.IX Item "-mbk" +.PD 0 +.Ip "\fB\-mno-bk\fR" 4 +.IX Item "-mno-bk" +.PD +Allow (disallow) allocation of general integer operands into the block +count register \s-1BK\s0. +.Ip "\fB\-mdb\fR" 4 +.IX Item "-mdb" +.PD 0 +.Ip "\fB\-mno-db\fR" 4 +.IX Item "-mno-db" +.PD +Enable (disable) generation of code using decrement and branch, +\&\fIDBcond\fR\|(D), instructions. This is enabled by default for the C4x. To be +on the safe side, this is disabled for the C3x, since the maximum +iteration count on the C3x is 2^23 + 1 (but who iterates loops more than +2^23 times on the C3x?). Note that \s-1GCC\s0 will try to reverse a loop so +that it can utilise the decrement and branch instruction, but will give +up if there is more than one memory reference in the loop. Thus a loop +where the loop counter is decremented can generate slightly more +efficient code, in cases where the \s-1RPTB\s0 instruction cannot be utilised. +.Ip "\fB\-mdp-isr-reload\fR" 4 +.IX Item "-mdp-isr-reload" +.PD 0 +.Ip "\fB\-mparanoid\fR" 4 +.IX Item "-mparanoid" +.PD +Force the \s-1DP\s0 register to be saved on entry to an interrupt service +routine (\s-1ISR\s0), reloaded to point to the data section, and restored on +exit from the \s-1ISR\s0. This should not be required unless someone has +violated the small memory model by modifying the \s-1DP\s0 register, say within +an object library. +.Ip "\fB\-mmpyi\fR" 4 +.IX Item "-mmpyi" +.PD 0 +.Ip "\fB\-mno-mpyi\fR" 4 +.IX Item "-mno-mpyi" +.PD +For the C3x use the 24\-bit \s-1MPYI\s0 instruction for integer multiplies +instead of a library call to guarantee 32\-bit results. Note that if one +of the operands is a constant, then the multiplication will be performed +using shifts and adds. If the \-mmpyi option is not specified for the C3x, +then squaring operations are performed inline instead of a library call. +.Ip "\fB\-mfast-fix\fR" 4 +.IX Item "-mfast-fix" +.PD 0 +.Ip "\fB\-mno-fast-fix\fR" 4 +.IX Item "-mno-fast-fix" +.PD +The C3x/C4x \s-1FIX\s0 instruction to convert a floating point value to an +integer value chooses the nearest integer less than or equal to the +floating point value rather than to the nearest integer. Thus if the +floating point number is negative, the result will be incorrectly +truncated an additional code is necessary to detect and correct this +case. This option can be used to disable generation of the additional +code required to correct the result. +.Ip "\fB\-mrptb\fR" 4 +.IX Item "-mrptb" +.PD 0 +.Ip "\fB\-mno-rptb\fR" 4 +.IX Item "-mno-rptb" +.PD +Enable (disable) generation of repeat block sequences using the \s-1RPTB\s0 +instruction for zero overhead looping. The \s-1RPTB\s0 construct is only used +for innermost loops that do not call functions or jump across the loop +boundaries. There is no advantage having nested \s-1RPTB\s0 loops due to the +overhead required to save and restore the \s-1RC\s0, \s-1RS\s0, and \s-1RE\s0 registers. +This is enabled by default with \-O2. +.Ip "\fB\-mrpts=\fR\fIcount\fR" 4 +.IX Item "-mrpts=count" +.PD 0 +.Ip "\fB\-mno-rpts\fR" 4 +.IX Item "-mno-rpts" +.PD +Enable (disable) the use of the single instruction repeat instruction +\&\s-1RPTS\s0. If a repeat block contains a single instruction, and the loop +count can be guaranteed to be less than the value \fIcount\fR, \s-1GCC\s0 will +emit a \s-1RPTS\s0 instruction instead of a \s-1RPTB\s0. If no value is specified, +then a \s-1RPTS\s0 will be emitted even if the loop count cannot be determined +at compile time. Note that the repeated instruction following \s-1RPTS\s0 does +not have to be reloaded from memory each iteration, thus freeing up the +\&\s-1CPU\s0 buses for operands. However, since interrupts are blocked by this +instruction, it is disabled by default. +.Ip "\fB\-mloop-unsigned\fR" 4 +.IX Item "-mloop-unsigned" +.PD 0 +.Ip "\fB\-mno-loop-unsigned\fR" 4 +.IX Item "-mno-loop-unsigned" +.PD +The maximum iteration count when using \s-1RPTS\s0 and \s-1RPTB\s0 (and \s-1DB\s0 on the C40) +is 2^31 + 1 since these instructions test if the iteration count is +negative to terminate the loop. If the iteration count is unsigned +there is a possibility than the 2^31 + 1 maximum iteration count may be +exceeded. This switch allows an unsigned iteration count. +.Ip "\fB\-mti\fR" 4 +.IX Item "-mti" +Try to emit an assembler syntax that the \s-1TI\s0 assembler (asm30) is happy +with. This also enforces compatibility with the \s-1API\s0 employed by the \s-1TI\s0 +C3x C compiler. For example, long doubles are passed as structures +rather than in floating point registers. +.Ip "\fB\-mregparm\fR" 4 +.IX Item "-mregparm" +.PD 0 +.Ip "\fB\-mmemparm\fR" 4 +.IX Item "-mmemparm" +.PD +Generate code that uses registers (stack) for passing arguments to functions. +By default, arguments are passed in registers where possible rather +than by pushing arguments on to the stack. +.Ip "\fB\-mparallel-insns\fR" 4 +.IX Item "-mparallel-insns" +.PD 0 +.Ip "\fB\-mno-parallel-insns\fR" 4 +.IX Item "-mno-parallel-insns" +.PD +Allow the generation of parallel instructions. This is enabled by +default with \-O2. +.Ip "\fB\-mparallel-mpy\fR" 4 +.IX Item "-mparallel-mpy" +.PD 0 +.Ip "\fB\-mno-parallel-mpy\fR" 4 +.IX Item "-mno-parallel-mpy" +.PD +Allow the generation of MPY||ADD and MPY||SUB parallel instructions, +provided \-mparallel-insns is also specified. These instructions have +tight register constraints which can pessimize the code generation +of large functions. +.PP +.I "V850 Options" +.IX Subsection "V850 Options" +.PP +These \fB\-m\fR options are defined for V850 implementations: +.Ip "\fB\-mlong-calls\fR" 4 +.IX Item "-mlong-calls" +.PD 0 +.Ip "\fB\-mno-long-calls\fR" 4 +.IX Item "-mno-long-calls" +.PD +Treat all calls as being far away (near). If calls are assumed to be +far away, the compiler will always load the functions address up into a +register, and call indirect through the pointer. +.Ip "\fB\-mno-ep\fR" 4 +.IX Item "-mno-ep" +.PD 0 +.Ip "\fB\-mep\fR" 4 +.IX Item "-mep" +.PD +Do not optimize (do optimize) basic blocks that use the same index +pointer 4 or more times to copy pointer into the \f(CW\*(C`ep\*(C'\fR register, and +use the shorter \f(CW\*(C`sld\*(C'\fR and \f(CW\*(C`sst\*(C'\fR instructions. The \fB\-mep\fR +option is on by default if you optimize. +.Ip "\fB\-mno-prolog-function\fR" 4 +.IX Item "-mno-prolog-function" +.PD 0 +.Ip "\fB\-mprolog-function\fR" 4 +.IX Item "-mprolog-function" +.PD +Do not use (do use) external functions to save and restore registers at +the prolog and epilog of a function. The external functions are slower, +but use less code space if more than one function saves the same number +of registers. The \fB\-mprolog-function\fR option is on by default if +you optimize. +.Ip "\fB\-mspace\fR" 4 +.IX Item "-mspace" +Try to make the code as small as possible. At present, this just turns +on the \fB\-mep\fR and \fB\-mprolog-function\fR options. +.Ip "\fB\-mtda=\fR\fIn\fR" 4 +.IX Item "-mtda=n" +Put static or global variables whose size is \fIn\fR bytes or less into +the tiny data area that register \f(CW\*(C`ep\*(C'\fR points to. The tiny data +area can hold up to 256 bytes in total (128 bytes for byte references). +.Ip "\fB\-msda=\fR\fIn\fR" 4 +.IX Item "-msda=n" +Put static or global variables whose size is \fIn\fR bytes or less into +the small data area that register \f(CW\*(C`gp\*(C'\fR points to. The small data +area can hold up to 64 kilobytes. +.Ip "\fB\-mzda=\fR\fIn\fR" 4 +.IX Item "-mzda=n" +Put static or global variables whose size is \fIn\fR bytes or less into +the first 32 kilobytes of memory. +.Ip "\fB\-mv850\fR" 4 +.IX Item "-mv850" +Specify that the target processor is the V850. +.Ip "\fB\-mbig-switch\fR" 4 +.IX Item "-mbig-switch" +Generate code suitable for big switch tables. Use this option only if +the assembler/linker complain about out of range branches within a switch +table. +.PP +.I "\s-1ARC\s0 Options" +.IX Subsection "ARC Options" +.PP +These options are defined for \s-1ARC\s0 implementations: +.Ip "\fB\-EL\fR" 4 +.IX Item "-EL" +Compile code for little endian mode. This is the default. +.Ip "\fB\-EB\fR" 4 +.IX Item "-EB" +Compile code for big endian mode. +.Ip "\fB\-mmangle-cpu\fR" 4 +.IX Item "-mmangle-cpu" +Prepend the name of the cpu to all public symbol names. +In multiple-processor systems, there are many \s-1ARC\s0 variants with different +instruction and register set characteristics. This flag prevents code +compiled for one cpu to be linked with code compiled for another. +No facility exists for handling variants that are \*(L"almost identical\*(R". +This is an all or nothing option. +.Ip "\fB\-mcpu=\fR\fIcpu\fR" 4 +.IX Item "-mcpu=cpu" +Compile code for \s-1ARC\s0 variant \fIcpu\fR. +Which variants are supported depend on the configuration. +All variants support \fB\-mcpu=base\fR, this is the default. +.Ip "\fB\-mtext=\fR\fItext section\fR" 4 +.IX Item "-mtext=text section" +.PD 0 +.Ip "\fB\-mdata=\fR\fIdata section\fR" 4 +.IX Item "-mdata=data section" +.Ip "\fB\-mrodata=\fR\fIreadonly data section\fR" 4 +.IX Item "-mrodata=readonly data section" +.PD +Put functions, data, and readonly data in \fItext section\fR, +\&\fIdata section\fR, and \fIreadonly data section\fR respectively +by default. This can be overridden with the \f(CW\*(C`section\*(C'\fR attribute. +.PP +.I "\s-1NS32K\s0 Options" +.IX Subsection "NS32K Options" +.PP +These are the \fB\-m\fR options defined for the 32000 series. The default +values for these options depends on which style of 32000 was selected when +the compiler was configured; the defaults for the most common choices are +given below. +.Ip "\fB\-m32032\fR" 4 +.IX Item "-m32032" +.PD 0 +.Ip "\fB\-m32032\fR" 4 +.IX Item "-m32032" +.PD +Generate output for a 32032. This is the default +when the compiler is configured for 32032 and 32016 based systems. +.Ip "\fB\-m32332\fR" 4 +.IX Item "-m32332" +.PD 0 +.Ip "\fB\-m32332\fR" 4 +.IX Item "-m32332" +.PD +Generate output for a 32332. This is the default +when the compiler is configured for 32332\-based systems. +.Ip "\fB\-m32532\fR" 4 +.IX Item "-m32532" +.PD 0 +.Ip "\fB\-m32532\fR" 4 +.IX Item "-m32532" +.PD +Generate output for a 32532. This is the default +when the compiler is configured for 32532\-based systems. +.Ip "\fB\-m32081\fR" 4 +.IX Item "-m32081" +Generate output containing 32081 instructions for floating point. +This is the default for all systems. +.Ip "\fB\-m32381\fR" 4 +.IX Item "-m32381" +Generate output containing 32381 instructions for floating point. This +also implies \fB\-m32081\fR. The 32381 is only compatible with the 32332 +and 32532 cpus. This is the default for the pc532\-netbsd configuration. +.Ip "\fB\-mmulti-add\fR" 4 +.IX Item "-mmulti-add" +Try and generate multiply-add floating point instructions \f(CW\*(C`polyF\*(C'\fR +and \f(CW\*(C`dotF\*(C'\fR. This option is only available if the \fB\-m32381\fR +option is in effect. Using these instructions requires changes to to +register allocation which generally has a negative impact on +performance. This option should only be enabled when compiling code +particularly likely to make heavy use of multiply-add instructions. +.Ip "\fB\-mnomulti-add\fR" 4 +.IX Item "-mnomulti-add" +Do not try and generate multiply-add floating point instructions +\&\f(CW\*(C`polyF\*(C'\fR and \f(CW\*(C`dotF\*(C'\fR. This is the default on all platforms. +.Ip "\fB\-msoft-float\fR" 4 +.IX Item "-msoft-float" +Generate output containing library calls for floating point. +\&\fBWarning:\fR the requisite libraries may not be available. +.Ip "\fB\-mnobitfield\fR" 4 +.IX Item "-mnobitfield" +Do not use the bit-field instructions. On some machines it is faster to +use shifting and masking operations. This is the default for the pc532. +.Ip "\fB\-mbitfield\fR" 4 +.IX Item "-mbitfield" +Do use the bit-field instructions. This is the default for all platforms +except the pc532. +.Ip "\fB\-mrtd\fR" 4 +.IX Item "-mrtd" +Use a different function-calling convention, in which functions +that take a fixed number of arguments return pop their +arguments on return with the \f(CW\*(C`ret\*(C'\fR instruction. +.Sp +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. +.Sp +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR); +otherwise incorrect code will be generated for calls to those +functions. +.Sp +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) +.Sp +This option takes its name from the 680x0 \f(CW\*(C`rtd\*(C'\fR instruction. +.Ip "\fB\-mregparam\fR" 4 +.IX Item "-mregparam" +Use a different function-calling convention where the first two arguments +are passed in registers. +.Sp +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. +.Ip "\fB\-mnoregparam\fR" 4 +.IX Item "-mnoregparam" +Do not pass any arguments in registers. This is the default for all +targets. +.Ip "\fB\-msb\fR" 4 +.IX Item "-msb" +It is \s-1OK\s0 to use the sb as an index register which is always loaded with +zero. This is the default for the pc532\-netbsd target. +.Ip "\fB\-mnosb\fR" 4 +.IX Item "-mnosb" +The sb register is not available for use or has not been initialized to +zero by the run time system. This is the default for all targets except +the pc532\-netbsd. It is also implied whenever \fB\-mhimem\fR or +\&\fB\-fpic\fR is set. +.Ip "\fB\-mhimem\fR" 4 +.IX Item "-mhimem" +Many ns32000 series addressing modes use displacements of up to 512MB. +If an address is above 512MB then displacements from zero can not be used. +This option causes code to be generated which can be loaded above 512MB. +This may be useful for operating systems or \s-1ROM\s0 code. +.Ip "\fB\-mnohimem\fR" 4 +.IX Item "-mnohimem" +Assume code will be loaded in the first 512MB of virtual address space. +This is the default for all platforms. +.PP +.I "\s-1AVR\s0 Options" +.IX Subsection "AVR Options" +.PP +These options are defined for \s-1AVR\s0 implementations: +.Ip "\fB\-mmcu=\fR\fImcu\fR" 4 +.IX Item "-mmcu=mcu" +Specify \s-1ATMEL\s0 \s-1AVR\s0 instruction set or \s-1MCU\s0 type. +.Sp +Instruction set avr1 is for the minimal \s-1AVR\s0 core, not supported by the C +compiler, only for assembler programs (\s-1MCU\s0 types: at90s1200, attiny10, +attiny11, attiny12, attiny15, attiny28). +.Sp +Instruction set avr2 (default) is for the classic \s-1AVR\s0 core with up to +8K program memory space (\s-1MCU\s0 types: at90s2313, at90s2323, attiny22, +at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, +at90c8534, at90s8535). +.Sp +Instruction set avr3 is for the classic \s-1AVR\s0 core with up to 128K program +memory space (\s-1MCU\s0 types: atmega103, atmega603). +.Sp +Instruction set avr4 is for the enhanced \s-1AVR\s0 core with up to 8K program +memory space (\s-1MCU\s0 types: atmega83, atmega85). +.Sp +Instruction set avr5 is for the enhanced \s-1AVR\s0 core with up to 128K program +memory space (\s-1MCU\s0 types: atmega161, atmega163, atmega32, at94k). +.Ip "\fB\-msize\fR" 4 +.IX Item "-msize" +Output instruction sizes to the asm file. +.Ip "\fB\-minit-stack=\fR\fIN\fR" 4 +.IX Item "-minit-stack=N" +Specify the initial stack address, which may be a symbol or numeric value, +_\|_stack is the default. +.Ip "\fB\-mno-interrupts\fR" 4 +.IX Item "-mno-interrupts" +Generated code is not compatible with hardware interrupts. +Code size will be smaller. +.Ip "\fB\-mcall-prologues\fR" 4 +.IX Item "-mcall-prologues" +Functions prologues/epilogues expanded as call to appropriate +subroutines. Code size will be smaller. +.Ip "\fB\-mno-tablejump\fR" 4 +.IX Item "-mno-tablejump" +Do not generate tablejump insns which sometimes increase code size. +.Ip "\fB\-mtiny-stack\fR" 4 +.IX Item "-mtiny-stack" +Change only the low 8 bits of the stack pointer. +.PP +.I "MCore Options" +.IX Subsection "MCore Options" +.PP +These are the \fB\-m\fR options defined for the Motorola M*Core +processors. +.Ip "\fB\-mhardlit\fR" 4 +.IX Item "-mhardlit" +.PD 0 +.Ip "\fB\-mhardlit\fR" 4 +.IX Item "-mhardlit" +.Ip "\fB\-mno-hardlit\fR" 4 +.IX Item "-mno-hardlit" +.PD +Inline constants into the code stream if it can be done in two +instructions or less. +.Ip "\fB\-mdiv\fR" 4 +.IX Item "-mdiv" +.PD 0 +.Ip "\fB\-mdiv\fR" 4 +.IX Item "-mdiv" +.Ip "\fB\-mno-div\fR" 4 +.IX Item "-mno-div" +.PD +Use the divide instruction. (Enabled by default). +.Ip "\fB\-mrelax-immediate\fR" 4 +.IX Item "-mrelax-immediate" +.PD 0 +.Ip "\fB\-mrelax-immediate\fR" 4 +.IX Item "-mrelax-immediate" +.Ip "\fB\-mno-relax-immediate\fR" 4 +.IX Item "-mno-relax-immediate" +.PD +Allow arbitrary sized immediates in bit operations. +.Ip "\fB\-mwide-bitfields\fR" 4 +.IX Item "-mwide-bitfields" +.PD 0 +.Ip "\fB\-mwide-bitfields\fR" 4 +.IX Item "-mwide-bitfields" +.Ip "\fB\-mno-wide-bitfields\fR" 4 +.IX Item "-mno-wide-bitfields" +.PD +Always treat bitfields as int-sized. +.Ip "\fB\-m4byte-functions\fR" 4 +.IX Item "-m4byte-functions" +.PD 0 +.Ip "\fB\-m4byte-functions\fR" 4 +.IX Item "-m4byte-functions" +.Ip "\fB\-mno-4byte-functions\fR" 4 +.IX Item "-mno-4byte-functions" +.PD +Force all functions to be aligned to a four byte boundary. +.Ip "\fB\-mcallgraph-data\fR" 4 +.IX Item "-mcallgraph-data" +.PD 0 +.Ip "\fB\-mcallgraph-data\fR" 4 +.IX Item "-mcallgraph-data" +.Ip "\fB\-mno-callgraph-data\fR" 4 +.IX Item "-mno-callgraph-data" +.PD +Emit callgraph information. +.Ip "\fB\-mslow-bytes\fR" 4 +.IX Item "-mslow-bytes" +.PD 0 +.Ip "\fB\-mslow-bytes\fR" 4 +.IX Item "-mslow-bytes" +.Ip "\fB\-mno-slow-bytes\fR" 4 +.IX Item "-mno-slow-bytes" +.PD +Prefer word access when reading byte quantities. +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +.PD 0 +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +.Ip "\fB\-mbig-endian\fR" 4 +.IX Item "-mbig-endian" +.PD +Generate code for a little endian target. +.Ip "\fB\-m210\fR" 4 +.IX Item "-m210" +.PD 0 +.Ip "\fB\-m210\fR" 4 +.IX Item "-m210" +.Ip "\fB\-m340\fR" 4 +.IX Item "-m340" +.PD +Generate code for the 210 processor. +.PP +.I "\s-1IA-64\s0 Options" +.IX Subsection "IA-64 Options" +.PP +These are the \fB\-m\fR options defined for the Intel \s-1IA-64\s0 architecture. +.Ip "\fB\-mbig-endian\fR" 4 +.IX Item "-mbig-endian" +Generate code for a big endian target. This is the default for \s-1HPUX\s0. +.Ip "\fB\-mlittle-endian\fR" 4 +.IX Item "-mlittle-endian" +Generate code for a little endian target. This is the default for \s-1AIX5\s0 +and Linux. +.Ip "\fB\-mgnu-as\fR" 4 +.IX Item "-mgnu-as" +.PD 0 +.Ip "\fB\-mno-gnu-as\fR" 4 +.IX Item "-mno-gnu-as" +.PD +Generate (or don't) code for the \s-1GNU\s0 assembler. This is the default. +.Ip "\fB\-mgnu-ld\fR" 4 +.IX Item "-mgnu-ld" +.PD 0 +.Ip "\fB\-mno-gnu-ld\fR" 4 +.IX Item "-mno-gnu-ld" +.PD +Generate (or don't) code for the \s-1GNU\s0 linker. This is the default. +.Ip "\fB\-mno-pic\fR" 4 +.IX Item "-mno-pic" +Generate code that does not use a global pointer register. The result +is not position independent code, and violates the \s-1IA-64\s0 \s-1ABI\s0. +.Ip "\fB\-mvolatile-asm-stop\fR" 4 +.IX Item "-mvolatile-asm-stop" +.PD 0 +.Ip "\fB\-mno-volatile-asm-stop\fR" 4 +.IX Item "-mno-volatile-asm-stop" +.PD +Generate (or don't) a stop bit immediately before and after volatile asm +statements. +.Ip "\fB\-mb-step\fR" 4 +.IX Item "-mb-step" +Generate code that works around Itanium B step errata. +.Ip "\fB\-mregister-names\fR" 4 +.IX Item "-mregister-names" +.PD 0 +.Ip "\fB\-mno-register-names\fR" 4 +.IX Item "-mno-register-names" +.PD +Generate (or don't) \fBin\fR, \fBloc\fR, and \fBout\fR register names for +the stacked registers. This may make assembler output more readable. +.Ip "\fB\-mno-sdata\fR" 4 +.IX Item "-mno-sdata" +.PD 0 +.Ip "\fB\-msdata\fR" 4 +.IX Item "-msdata" +.PD +Disable (or enable) optimizations that use the small data section. This may +be useful for working around optimizer bugs. +.Ip "\fB\-mconstant-gp\fR" 4 +.IX Item "-mconstant-gp" +Generate code that uses a single constant global pointer value. This is +useful when compiling kernel code. +.Ip "\fB\-mauto-pic\fR" 4 +.IX Item "-mauto-pic" +Generate code that is self-relocatable. This implies \fB\-mconstant-gp\fR. +This is useful when compiling firmware code. +.Ip "\fB\-minline-divide-min-latency\fR" 4 +.IX Item "-minline-divide-min-latency" +Generate code for inline divides using the minimum latency algorithm. +.Ip "\fB\-minline-divide-max-throughput\fR" 4 +.IX Item "-minline-divide-max-throughput" +Generate code for inline divides using the maximum throughput algorithm. +.Ip "\fB\-mno-dwarf2\-asm\fR" 4 +.IX Item "-mno-dwarf2-asm" +.PD 0 +.Ip "\fB\-mdwarf2\-asm\fR" 4 +.IX Item "-mdwarf2-asm" +.PD +Don't (or do) generate assembler code for the \s-1DWARF2\s0 line number debugging +info. This may be useful when not using the \s-1GNU\s0 assembler. +.Ip "\fB\-mfixed-range=\fR\fIregister range\fR" 4 +.IX Item "-mfixed-range=register range" +Generate code treating the given register range as fixed registers. +A fixed register is one that the register allocator can not use. This is +useful when compiling kernel code. A register range is specified as +two registers separated by a dash. Multiple register ranges can be +specified separated by a comma. +.PP +.I "D30V Options" +.IX Subsection "D30V Options" +.PP +These \fB\-m\fR options are defined for D30V implementations: +.Ip "\fB\-mextmem\fR" 4 +.IX Item "-mextmem" +Link the \fB.text\fR, \fB.data\fR, \fB.bss\fR, \fB.strings\fR, +\&\fB.rodata\fR, \fB.rodata1\fR, \fB.data1\fR sections into external +memory, which starts at location \f(CW\*(C`0x80000000\*(C'\fR. +.Ip "\fB\-mextmemory\fR" 4 +.IX Item "-mextmemory" +Same as the \fB\-mextmem\fR switch. +.Ip "\fB\-monchip\fR" 4 +.IX Item "-monchip" +Link the \fB.text\fR section into onchip text memory, which starts at +location \f(CW\*(C`0x0\*(C'\fR. Also link \fB.data\fR, \fB.bss\fR, +\&\fB.strings\fR, \fB.rodata\fR, \fB.rodata1\fR, \fB.data1\fR sections +into onchip data memory, which starts at location \f(CW\*(C`0x20000000\*(C'\fR. +.Ip "\fB\-mno-asm-optimize\fR" 4 +.IX Item "-mno-asm-optimize" +.PD 0 +.Ip "\fB\-masm-optimize\fR" 4 +.IX Item "-masm-optimize" +.PD +Disable (enable) passing \fB\-O\fR to the assembler when optimizing. +The assembler uses the \fB\-O\fR option to automatically parallelize +adjacent short instructions where possible. +.Ip "\fB\-mbranch-cost=\fR\fIn\fR" 4 +.IX Item "-mbranch-cost=n" +Increase the internal costs of branches to \fIn\fR. Higher costs means +that the compiler will issue more instructions to avoid doing a branch. +The default is 2. +.Ip "\fB\-mcond-exec=\fR\fIn\fR" 4 +.IX Item "-mcond-exec=n" +Specify the maximum number of conditionally executed instructions that +replace a branch. The default is 4. +.Sh "Options for Code Generation Conventions" +.IX Subsection "Options for Code Generation Conventions" +These machine-independent options control the interface conventions +used in code generation. +.PP +Most of them have both positive and negative forms; the negative form +of \fB\-ffoo\fR would be \fB\-fno-foo\fR. In the table below, only +one of the forms is listed\-\-\-the one which is not the default. You +can figure out the other form by either removing \fBno-\fR or adding +it. +.Ip "\fB\-fexceptions\fR" 4 +.IX Item "-fexceptions" +Enable exception handling. Generates extra code needed to propagate +exceptions. For some targets, this implies \s-1GNU\s0 \s-1CC\s0 will generate frame +unwind information for all functions, which can produce significant data +size overhead, although it does not affect execution. If you do not +specify this option, \s-1GNU\s0 \s-1CC\s0 will enable it by default for languages like +\&\*(C+ which normally require exception handling, and disable itfor +languages like C that do not normally require it. However, you may need +to enable this option when compiling C code that needs to interoperate +properly with exception handlers written in \*(C+. You may also wish to +disable this option if you are compiling older \*(C+ programs that don't +use exception handling. +.Ip "\fB\-funwind-tables\fR" 4 +.IX Item "-funwind-tables" +Similar to \fB\-fexceptions\fR, except that it will just generate any needed +static data, but will not affect the generated code in any other way. +You will normally not enable this option; instead, a language processor +that needs this handling would enable it on your behalf. +.Ip "\fB\-fpcc-struct-return\fR" 4 +.IX Item "-fpcc-struct-return" +Return ``short'' \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR values in memory like +longer ones, rather than in registers. This convention is less +efficient, but it has the advantage of allowing intercallability between +GCC-compiled files and files compiled with other compilers. +.Sp +The precise convention for returning structures in memory depends +on the target configuration macros. +.Sp +Short structures and unions are those whose size and alignment match +that of some integer type. +.Ip "\fB\-freg-struct-return\fR" 4 +.IX Item "-freg-struct-return" +Use the convention that \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR values are +returned in registers when possible. This is more efficient for small +structures than \fB\-fpcc-struct-return\fR. +.Sp +If you specify neither \fB\-fpcc-struct-return\fR nor its contrary +\&\fB\-freg-struct-return\fR, \s-1GCC\s0 defaults to whichever convention is +standard for the target. If there is no standard convention, \s-1GCC\s0 +defaults to \fB\-fpcc-struct-return\fR, except on targets where \s-1GCC\s0 +is the principal compiler. In those cases, we can choose the standard, +and we chose the more efficient register return alternative. +.Ip "\fB\-fshort-enums\fR" 4 +.IX Item "-fshort-enums" +Allocate to an \f(CW\*(C`enum\*(C'\fR type only as many bytes as it needs for the +declared range of possible values. Specifically, the \f(CW\*(C`enum\*(C'\fR type +will be equivalent to the smallest integer type which has enough room. +.Ip "\fB\-fshort-double\fR" 4 +.IX Item "-fshort-double" +Use the same size for \f(CW\*(C`double\*(C'\fR as for \f(CW\*(C`float\*(C'\fR. +.Ip "\fB\-fshared-data\fR" 4 +.IX Item "-fshared-data" +Requests that the data and non-\f(CW\*(C`const\*(C'\fR variables of this +compilation be shared data rather than private data. The distinction +makes sense only on certain operating systems, where shared data is +shared between processes running the same program, while private data +exists in one copy per process. +.Ip "\fB\-fno-common\fR" 4 +.IX Item "-fno-common" +Allocate even uninitialized global variables in the data section of the +object file, rather than generating them as common blocks. This has the +effect that if the same variable is declared (without \f(CW\*(C`extern\*(C'\fR) in +two different compilations, you will get an error when you link them. +The only reason this might be useful is if you wish to verify that the +program will work on other systems which always work this way. +.Ip "\fB\-fno-ident\fR" 4 +.IX Item "-fno-ident" +Ignore the \fB#ident\fR directive. +.Ip "\fB\-fno-gnu-linker\fR" 4 +.IX Item "-fno-gnu-linker" +Do not output global initializations (such as \*(C+ constructors and +destructors) in the form used by the \s-1GNU\s0 linker (on systems where the \s-1GNU\s0 +linker is the standard method of handling them). Use this option when +you want to use a non-GNU linker, which also requires using the +\&\fBcollect2\fR program to make sure the system linker includes +constructors and destructors. (\fBcollect2\fR is included in the \s-1GCC\s0 +distribution.) For systems which \fImust\fR use \fBcollect2\fR, the +compiler driver \fBgcc\fR is configured to do this automatically. +.Ip "\fB\-finhibit-size-directive\fR" 4 +.IX Item "-finhibit-size-directive" +Don't output a \f(CW\*(C`.size\*(C'\fR assembler directive, or anything else that +would cause trouble if the function is split in the middle, and the +two halves are placed at locations far apart in memory. This option is +used when compiling \fIcrtstuff.c\fR; you should not need to use it +for anything else. +.Ip "\fB\-fverbose-asm\fR" 4 +.IX Item "-fverbose-asm" +Put extra commentary information in the generated assembly code to +make it more readable. This option is generally only of use to those +who actually need to read the generated assembly code (perhaps while +debugging the compiler itself). +.Sp +\&\fB\-fno-verbose-asm\fR, the default, causes the +extra information to be omitted and is useful when comparing two assembler +files. +.Ip "\fB\-fvolatile\fR" 4 +.IX Item "-fvolatile" +Consider all memory references through pointers to be volatile. +.Ip "\fB\-fvolatile-global\fR" 4 +.IX Item "-fvolatile-global" +Consider all memory references to extern and global data items to +be volatile. \s-1GCC\s0 does not consider static data items to be volatile +because of this switch. +.Ip "\fB\-fvolatile-static\fR" 4 +.IX Item "-fvolatile-static" +Consider all memory references to static data to be volatile. +.Ip "\fB\-fpic\fR" 4 +.IX Item "-fpic" +Generate position-independent code (\s-1PIC\s0) suitable for use in a shared +library, if supported for the target machine. Such code accesses all +constant addresses through a global offset table (\s-1GOT\s0). The dynamic +loader resolves the \s-1GOT\s0 entries when the program starts (the dynamic +loader is not part of \s-1GCC\s0; it is part of the operating system). If +the \s-1GOT\s0 size for the linked executable exceeds a machine-specific +maximum size, you get an error message from the linker indicating that +\&\fB\-fpic\fR does not work; in that case, recompile with \fB\-fPIC\fR +instead. (These maximums are 16k on the m88k, 8k on the Sparc, and 32k +on the m68k and \s-1RS/6000\s0. The 386 has no such limit.) +.Sp +Position-independent code requires special support, and therefore works +only on certain machines. For the 386, \s-1GCC\s0 supports \s-1PIC\s0 for System V +but not for the Sun 386i. Code generated for the \s-1IBM\s0 \s-1RS/6000\s0 is always +position-independent. +.Ip "\fB\-fPIC\fR" 4 +.IX Item "-fPIC" +If supported for the target machine, emit position-independent code, +suitable for dynamic linking and avoiding any limit on the size of the +global offset table. This option makes a difference on the m68k, m88k, +and the Sparc. +.Sp +Position-independent code requires special support, and therefore works +only on certain machines. +.Ip "\fB\-ffixed-\fR\fIreg\fR" 4 +.IX Item "-ffixed-reg" +Treat the register named \fIreg\fR as a fixed register; generated code +should never refer to it (except perhaps as a stack pointer, frame +pointer or in some other fixed role). +.Sp +\&\fIreg\fR must be the name of a register. The register names accepted +are machine-specific and are defined in the \f(CW\*(C`REGISTER_NAMES\*(C'\fR +macro in the machine description macro file. +.Sp +This flag does not have a negative form, because it specifies a +three-way choice. +.Ip "\fB\-fcall-used-\fR\fIreg\fR" 4 +.IX Item "-fcall-used-reg" +Treat the register named \fIreg\fR as an allocable register that is +clobbered by function calls. It may be allocated for temporaries or +variables that do not live across a call. Functions compiled this way +will not save and restore the register \fIreg\fR. +.Sp +It is an error to used this flag with the frame pointer or stack pointer. +Use of this flag for other registers that have fixed pervasive roles in +the machine's execution model will produce disastrous results. +.Sp +This flag does not have a negative form, because it specifies a +three-way choice. +.Ip "\fB\-fcall-saved-\fR\fIreg\fR" 4 +.IX Item "-fcall-saved-reg" +Treat the register named \fIreg\fR as an allocable register saved by +functions. It may be allocated even for temporaries or variables that +live across a call. Functions compiled this way will save and restore +the register \fIreg\fR if they use it. +.Sp +It is an error to used this flag with the frame pointer or stack pointer. +Use of this flag for other registers that have fixed pervasive roles in +the machine's execution model will produce disastrous results. +.Sp +A different sort of disaster will result from the use of this flag for +a register in which function values may be returned. +.Sp +This flag does not have a negative form, because it specifies a +three-way choice. +.Ip "\fB\-fpack-struct\fR" 4 +.IX Item "-fpack-struct" +Pack all structure members together without holes. Usually you would +not want to use this option, since it makes the code suboptimal, and +the offsets of structure members won't agree with system libraries. +.Ip "\fB\-fcheck-memory-usage\fR" 4 +.IX Item "-fcheck-memory-usage" +Generate extra code to check each memory access. \s-1GCC\s0 will generate +code that is suitable for a detector of bad memory accesses such as +\&\fIChecker\fR. +.Sp +Normally, you should compile all, or none, of your code with this option. +.Sp +If you do mix code compiled with and without this option, +you must ensure that all code that has side effects +and that is called by code compiled with this option +is, itself, compiled with this option. +If you do not, you might get erroneous messages from the detector. +.Sp +If you use functions from a library that have side-effects (such as +\&\f(CW\*(C`read\*(C'\fR), you might not be able to recompile the library and +specify this option. In that case, you can enable the +\&\fB\-fprefix-function-name\fR option, which requests \s-1GCC\s0 to encapsulate +your code and make other functions look as if they were compiled with +\&\fB\-fcheck-memory-usage\fR. This is done by calling ``stubs'', +which are provided by the detector. If you cannot find or build +stubs for every function you call, you might have to specify +\&\fB\-fcheck-memory-usage\fR without \fB\-fprefix-function-name\fR. +.Sp +If you specify this option, you can not use the \f(CW\*(C`asm\*(C'\fR or +\&\f(CW\*(C`_\|_asm_\|_\*(C'\fR keywords in functions with memory checking enabled. \s-1GNU\s0 +\&\s-1CC\s0 cannot understand what the \f(CW\*(C`asm\*(C'\fR statement may do, and therefore +cannot generate the appropriate code, so it will reject it. However, if +you specify the function attribute \f(CW\*(C`no_check_memory_usage\*(C'\fR, \s-1GNU\s0 \s-1CC\s0 will disable memory checking within a +function; you may use \f(CW\*(C`asm\*(C'\fR statements inside such functions. You +may have an inline expansion of a non-checked function within a checked +function; in that case \s-1GNU\s0 \s-1CC\s0 will not generate checks for the inlined +function's memory accesses. +.Sp +If you move your \f(CW\*(C`asm\*(C'\fR statements to non-checked inline functions +and they do access memory, you can add calls to the support code in your +inline function, to indicate any reads, writes, or copies being done. +These calls would be similar to those done in the stubs described above. +.Ip "\fB\-fprefix-function-name\fR" 4 +.IX Item "-fprefix-function-name" +Request \s-1GCC\s0 to add a prefix to the symbols generated for function names. +\&\s-1GCC\s0 adds a prefix to the names of functions defined as well as +functions called. Code compiled with this option and code compiled +without the option can't be linked together, unless stubs are used. +.Sp +If you compile the following code with \fB\-fprefix-function-name\fR +.Sp +.Vb 6 +\& extern void bar (int); +\& void +\& foo (int a) +\& { +\& return bar (a + 5); +\& } +.Ve +\&\s-1GCC\s0 will compile the code as if it was written: +.Sp +.Vb 6 +\& extern void prefix_bar (int); +\& void +\& prefix_foo (int a) +\& { +\& return prefix_bar (a + 5); +\& } +.Ve +This option is designed to be used with \fB\-fcheck-memory-usage\fR. +.Ip "\fB\-finstrument-functions\fR" 4 +.IX Item "-finstrument-functions" +Generate instrumentation calls for entry and exit to functions. Just +after function entry and just before function exit, the following +profiling functions will be called with the address of the current +function and its call site. (On some platforms, +\&\f(CW\*(C`_\|_builtin_return_address\*(C'\fR does not work beyond the current +function, so the call site information may not be available to the +profiling functions otherwise.) +.Sp +.Vb 2 +\& void __cyg_profile_func_enter (void *this_fn, void *call_site); +\& void __cyg_profile_func_exit (void *this_fn, void *call_site); +.Ve +The first argument is the address of the start of the current function, +which may be looked up exactly in the symbol table. +.Sp +This instrumentation is also done for functions expanded inline in other +functions. The profiling calls will indicate where, conceptually, the +inline function is entered and exited. This means that addressable +versions of such functions must be available. If all your uses of a +function are expanded inline, this may mean an additional expansion of +code size. If you use \fBextern inline\fR in your C code, an +addressable version of such functions must be provided. (This is +normally the case anyways, but if you get lucky and the optimizer always +expands the functions inline, you might have gotten away without +providing static copies.) +.Sp +A function may be given the attribute \f(CW\*(C`no_instrument_function\*(C'\fR, in +which case this instrumentation will not be done. This can be used, for +example, for the profiling functions listed above, high-priority +interrupt routines, and any functions from which the profiling functions +cannot safely be called (perhaps signal handlers, if the profiling +routines generate output or allocate memory). +.Ip "\fB\-fstack-check\fR" 4 +.IX Item "-fstack-check" +Generate code to verify that you do not go beyond the boundary of the +stack. You should specify this flag if you are running in an +environment with multiple threads, but only rarely need to specify it in +a single-threaded environment since stack overflow is automatically +detected on nearly all systems if there is only one stack. +.Sp +Note that this switch does not actually cause checking to be done; the +operating system must do that. The switch causes generation of code +to ensure that the operating system sees the stack being extended. +.Ip "\fB\-fstack-limit-register=\fR\fIreg\fR" 4 +.IX Item "-fstack-limit-register=reg" +.PD 0 +.Ip "\fB\-fstack-limit-symbol=\fR\fIsym\fR" 4 +.IX Item "-fstack-limit-symbol=sym" +.Ip "\fB\-fno-stack-limit\fR" 4 +.IX Item "-fno-stack-limit" +.PD +Generate code to ensure that the stack does not grow beyond a certain value, +either the value of a register or the address of a symbol. If the stack +would grow beyond the value, a signal is raised. For most targets, +the signal is raised before the stack overruns the boundary, so +it is possible to catch the signal without taking special precautions. +.Sp +For instance, if the stack starts at address \fB0x80000000\fR and grows +downwards you can use the flags +\&\fB\-fstack-limit-symbol=_\|_stack_limit\fR +\&\fB\-Wl,\-\-defsym,_\|_stack_limit=0x7ffe0000\fR which will enforce a stack +limit of 128K. +.Ip "\fB\-fargument-alias\fR" 4 +.IX Item "-fargument-alias" +.PD 0 +.Ip "\fB\-fargument-noalias\fR" 4 +.IX Item "-fargument-noalias" +.Ip "\fB\-fargument-noalias-global\fR" 4 +.IX Item "-fargument-noalias-global" +.PD +Specify the possible relationships among parameters and between +parameters and global data. +.Sp +\&\fB\-fargument-alias\fR specifies that arguments (parameters) may +alias each other and may alias global storage. +\&\fB\-fargument-noalias\fR specifies that arguments do not alias +each other, but may alias global storage. +\&\fB\-fargument-noalias-global\fR specifies that arguments do not +alias each other and do not alias global storage. +.Sp +Each language will automatically use whatever option is required by +the language standard. You should not need to use these options yourself. +.Ip "\fB\-fleading-underscore\fR" 4 +.IX Item "-fleading-underscore" +This option and its counterpart, \-fno-leading-underscore, forcibly +change the way C symbols are represented in the object file. One use +is to help link with legacy assembly code. +.Sp +Be warned that you should know what you are doing when invoking this +option, and that not all targets provide complete support for it. +.SH "ENVIRONMENT" +.IX Header "ENVIRONMENT" +This section describes several environment variables that affect how \s-1GCC\s0 +operates. Some of them work by specifying directories or prefixes to use +when searching for various kinds of files. Some are used to specify other +aspects of the compilation environment. +.PP +Note that you can also specify places to search using options such as +\&\fB\-B\fR, \fB\-I\fR and \fB\-L\fR. These +take precedence over places specified using environment variables, which +in turn take precedence over those specified by the configuration of \s-1GCC\s0. +.Ip "\fB\s-1LANG\s0\fR" 4 +.IX Item "LANG" +.PD 0 +.Ip "\fB\s-1LC_CTYPE\s0\fR" 4 +.IX Item "LC_CTYPE" +.Ip "\fB\s-1LC_MESSAGES\s0\fR" 4 +.IX Item "LC_MESSAGES" +.Ip "\fB\s-1LC_ALL\s0\fR" 4 +.IX Item "LC_ALL" +.PD +These environment variables control the way that \s-1GCC\s0 uses +localization information that allow \s-1GCC\s0 to work with different +national conventions. \s-1GCC\s0 inspects the locale categories +\&\fB\s-1LC_CTYPE\s0\fR and \fB\s-1LC_MESSAGES\s0\fR if it has been configured to do +so. These locale categories can be set to any value supported by your +installation. A typical value is \fBen_UK\fR for English in the United +Kingdom. +.Sp +The \fB\s-1LC_CTYPE\s0\fR environment variable specifies character +classification. \s-1GCC\s0 uses it to determine the character boundaries in +a string; this is needed for some multibyte encodings that contain quote +and escape characters that would otherwise be interpreted as a string +end or escape. +.Sp +The \fB\s-1LC_MESSAGES\s0\fR environment variable specifies the language to +use in diagnostic messages. +.Sp +If the \fB\s-1LC_ALL\s0\fR environment variable is set, it overrides the value +of \fB\s-1LC_CTYPE\s0\fR and \fB\s-1LC_MESSAGES\s0\fR; otherwise, \fB\s-1LC_CTYPE\s0\fR +and \fB\s-1LC_MESSAGES\s0\fR default to the value of the \fB\s-1LANG\s0\fR +environment variable. If none of these variables are set, \s-1GCC\s0 +defaults to traditional C English behavior. +.Ip "\fB\s-1TMPDIR\s0\fR" 4 +.IX Item "TMPDIR" +If \fB\s-1TMPDIR\s0\fR is set, it specifies the directory to use for temporary +files. \s-1GCC\s0 uses temporary files to hold the output of one stage of +compilation which is to be used as input to the next stage: for example, +the output of the preprocessor, which is the input to the compiler +proper. +.Ip "\fB\s-1GCC_EXEC_PREFIX\s0\fR" 4 +.IX Item "GCC_EXEC_PREFIX" +If \fB\s-1GCC_EXEC_PREFIX\s0\fR is set, it specifies a prefix to use in the +names of the subprograms executed by the compiler. No slash is added +when this prefix is combined with the name of a subprogram, but you can +specify a prefix that ends with a slash if you wish. +.Sp +If \fB\s-1GCC_EXEC_PREFIX\s0\fR is not set, \s-1GNU\s0 \s-1CC\s0 will attempt to figure out +an appropriate prefix to use based on the pathname it was invoked with. +.Sp +If \s-1GCC\s0 cannot find the subprogram using the specified prefix, it +tries looking in the usual places for the subprogram. +.Sp +The default value of \fB\s-1GCC_EXEC_PREFIX\s0\fR is +\&\fI\fIprefix\fI/lib/gcc-lib/\fR where \fIprefix\fR is the value +of \f(CW\*(C`prefix\*(C'\fR when you ran the \fIconfigure\fR script. +.Sp +Other prefixes specified with \fB\-B\fR take precedence over this prefix. +.Sp +This prefix is also used for finding files such as \fIcrt0.o\fR that are +used for linking. +.Sp +In addition, the prefix is used in an unusual way in finding the +directories to search for header files. For each of the standard +directories whose name normally begins with \fB/usr/local/lib/gcc-lib\fR +(more precisely, with the value of \fB\s-1GCC_INCLUDE_DIR\s0\fR), \s-1GCC\s0 tries +replacing that beginning with the specified prefix to produce an +alternate directory name. Thus, with \fB\-Bfoo/\fR, \s-1GCC\s0 will search +\&\fIfoo/bar\fR where it would normally search \fI/usr/local/lib/bar\fR. +These alternate directories are searched first; the standard directories +come next. +.Ip "\fB\s-1COMPILER_PATH\s0\fR" 4 +.IX Item "COMPILER_PATH" +The value of \fB\s-1COMPILER_PATH\s0\fR is a colon-separated list of +directories, much like \fB\s-1PATH\s0\fR. \s-1GCC\s0 tries the directories thus +specified when searching for subprograms, if it can't find the +subprograms using \fB\s-1GCC_EXEC_PREFIX\s0\fR. +.Ip "\fB\s-1LIBRARY_PATH\s0\fR" 4 +.IX Item "LIBRARY_PATH" +The value of \fB\s-1LIBRARY_PATH\s0\fR is a colon-separated list of +directories, much like \fB\s-1PATH\s0\fR. When configured as a native compiler, +\&\s-1GCC\s0 tries the directories thus specified when searching for special +linker files, if it can't find them using \fB\s-1GCC_EXEC_PREFIX\s0\fR. Linking +using \s-1GCC\s0 also uses these directories when searching for ordinary +libraries for the \fB\-l\fR option (but directories specified with +\&\fB\-L\fR come first). +.Ip "\fBC_INCLUDE_PATH\fR" 4 +.IX Item "C_INCLUDE_PATH" +.PD 0 +.Ip "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4 +.IX Item "CPLUS_INCLUDE_PATH" +.Ip "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4 +.IX Item "OBJC_INCLUDE_PATH" +.PD +These environment variables pertain to particular languages. Each +variable's value is a colon-separated list of directories, much like +\&\fB\s-1PATH\s0\fR. When \s-1GCC\s0 searches for header files, it tries the +directories listed in the variable for the language you are using, after +the directories specified with \fB\-I\fR but before the standard header +file directories. +.Ip "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4 +.IX Item "DEPENDENCIES_OUTPUT" +If this variable is set, its value specifies how to output dependencies +for Make based on the header files processed by the compiler. This +output looks much like the output from the \fB\-M\fR option, but it goes to a separate file, and is +in addition to the usual results of compilation. +.Sp +The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in +which case the Make rules are written to that file, guessing the target +name from the source file name. Or the value can have the form +\&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to +file \fIfile\fR using \fItarget\fR as the target name. +.Ip "\fB\s-1LANG\s0\fR" 4 +.IX Item "LANG" +This variable is used to pass locale information to the compiler. One way in +which this information is used is to determine the character set to be used +when character literals, string literals and comments are parsed in C and \*(C+. +When the compiler is configured to allow multibyte characters, +the following values for \fB\s-1LANG\s0\fR are recognized: +.RS 4 +.Ip "\fBC-JIS\fR" 4 +.IX Item "C-JIS" +Recognize \s-1JIS\s0 characters. +.Ip "\fBC-SJIS\fR" 4 +.IX Item "C-SJIS" +Recognize \s-1SJIS\s0 characters. +.Ip "\fBC-EUCJP\fR" 4 +.IX Item "C-EUCJP" +Recognize \s-1EUCJP\s0 characters. +.RE +.RS 4 +.Sp +If \fB\s-1LANG\s0\fR is not defined, or if it has some other value, then the +compiler will use mblen and mbtowc as defined by the default locale to +recognize and translate multibyte characters. +.RE +.SH "BUGS" +.IX Header "BUGS" +For instructions on reporting bugs, see +<\fBhttp://gcc.gnu.org/bugs.html\fR>. Use of the \fBgccbug\fR +script to report bugs is recommended. +.SH "FOOTNOTES" +.IX Header "FOOTNOTES" +.Ip "1." 4 +On some systems, \fBgcc \-shared\fR +needs to build supplementary stub code for constructors to work. On +multi-libbed systems, \fBgcc \-shared\fR must select the correct support +libraries to link against. Failing to supply the correct flags may lead +to subtle defects. Supplying them in cases where they are not necessary +is innocuous. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fIcpp\fR\|(1), \fIgcov\fR\|(1), \fIg77\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), \fIgdb\fR\|(1), \fIadb\fR\|(1), \fIdbx\fR\|(1), \fIsdb\fR\|(1) +and the Info entries for \fIgcc\fR, \fIcpp\fR, \fIg77\fR, \fIas\fR, +\&\fIld\fR, \fIbinutils\fR and \fIgdb\fR. +.SH "AUTHOR" +.IX Header "AUTHOR" +See the Info entry for \fIgcc\fR, or +<\fBhttp://gcc.gnu.org/thanks.html\fR>, for contributors to \s-1GCC\s0. +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, +1998, 1999, 2000, 2001 Free Software Foundation, Inc. +.PP +Permission is granted to make and distribute verbatim copies of this +manual provided the copyright notice and this permission notice are +preserved on all copies. +.PP +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that the +entire resulting derived work is distributed under the terms of a +permission notice identical to this one. +.PP +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions, +except that this permission notice may be included in translations +approved by the Free Software Foundation instead of in the original +English. diff --git a/gcc/doc/gcc.texi b/gcc/doc/gcc.texi new file mode 100644 index 00000000000..fe570e8a0a5 --- /dev/null +++ b/gcc/doc/gcc.texi @@ -0,0 +1,4793 @@ +\input texinfo @c -*-texinfo-*- +@c %**start of header +@setfilename gcc.info +@c @setfilename usegcc.info +@c @setfilename portgcc.info +@c To produce the full manual, use the "gcc.info" setfilename, and +@c make sure the following do NOT begin with '@c' (and the @clear lines DO) +@set INTERNALS +@set USING +@c To produce a user-only manual, use the "usegcc.info" setfilename, and +@c make sure the following does NOT begin with '@c': +@c @clear INTERNALS +@c To produce a porter-only manual, use the "portgcc.info" setfilename, +@c and make sure the following does NOT begin with '@c': +@c @clear USING + +@c (For FSF printing, turn on smallbook, comment out finalout below; +@c that is all that is needed.) + +@c 6/27/96 FSF DO wants smallbook fmt for 1st bound edition. +@c @smallbook + +@c i also commented out the finalout command, so if there *are* any +@c overfulls, you'll (hopefully) see the rectangle in the right hand +@c margin. -mew 15june93 +@c @finalout + +@c NOTE: checks/things to do: +@c +@c -have bob do a search in all seven files for "mew" (ideally --mew, +@c but i may have forgotten the occasional "--"..). +@c Just checked... all have `--'! Bob 22Jul96 +@c Use this to search: grep -n '\-\-mew' *.texi +@c -item/itemx, text after all (sub/sub)section titles, etc.. +@c -consider putting the lists of options on pp 17--> etc in columns or +@c some such. +@c -spellcheck +@c -continuity of phrasing; ie, bit-field vs bitfield in rtl.texi +@c -overfulls. do a search for "mew" in the files, and you will see +@c overfulls that i noted but could not deal with. +@c -have to add text: beginning of chapter 8 + +@c +@c anything else? --mew 10feb93 + +@macro gcctabopt{body} +@code{\body\} +@end macro +@macro gccoptlist{body} +@smallexample +\body\ +@end smallexample +@end macro +@c Makeinfo handles the above macro OK, TeX needs manual line breaks; +@c they get lost at some point in handling the macro. But if @macro is +@c used here rather than @alias, it produces double line breaks. +@iftex +@alias gol = * +@end iftex +@ifnottex +@macro gol +@end macro +@end ifnottex + +@ifset INTERNALS +@ifset USING +@settitle Using and Porting the GNU Compiler Collection (GCC) +@end ifset +@end ifset +@c seems reasonable to assume at least one of INTERNALS or USING is set... +@ifclear INTERNALS +@settitle Using the GNU Compiler Collection +@end ifclear +@ifclear USING +@settitle Porting the GNU Compiler Collection +@end ifclear + +@syncodeindex fn cp +@syncodeindex vr cp +@syncodeindex ky cp +@syncodeindex pg cp +@syncodeindex tp cp + +@c %**end of header + +@c Use with @@smallbook. + +@c Cause even numbered pages to be printed on the left hand side of +@c the page and odd numbered pages to be printed on the right hand +@c side of the page. Using this, you can print on both sides of a +@c sheet of paper and have the text on the same part of the sheet. + +@c The text on right hand pages is pushed towards the right hand +@c margin and the text on left hand pages is pushed toward the left +@c hand margin. +@c (To provide the reverse effect, set bindingoffset to -0.75in.) + +@c @tex +@c \global\bindingoffset=0.75in +@c \global\normaloffset =0.75in +@c @end tex + +@ifnottex +@dircategory Programming +@direntry +* gcc: (gcc). The GNU Compiler Collection. +@end direntry +@ifset INTERNALS +@ifset USING +This file documents the use and the internals of the GNU compiler. +@end ifset +@end ifset +@ifclear USING +This file documents the internals of the GNU compiler. +@end ifclear +@ifclear INTERNALS +This file documents the use of the GNU compiler. +@end ifclear +@sp 1 +Published by the Free Software Foundation@* +59 Temple Place - Suite 330@* +Boston, MA 02111-1307 USA +@sp 1 +@c When you update the list of years below, search for copyright{} and +@c update the other copy too. +Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, +1999, 2000, 2001 Free Software Foundation, Inc. +@sp 1 +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.1 or +any later version published by the Free Software Foundation; with the +Invariant Sections being ``GNU General Public License'' and ``Funding +Free Software'', the Front-Cover texts being (a) (see below), and with +the Back-Cover Texts being (b) (see below). A copy of the license is +included in the section entitled ``GNU Free Documentation License''. + +(a) The FSF's Front-Cover Text is: + + A GNU Manual + +(b) The FSF's Back-Cover Text is: + + You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. +@end ifnottex + +@setchapternewpage odd +@c @finalout +@titlepage +@ifset INTERNALS +@ifset USING +@center @titlefont{Using and Porting the GNU Compiler Collection} + +@end ifset +@end ifset +@ifclear INTERNALS +@title Using the GNU Compiler Collection +@end ifclear +@ifclear USING +@title Porting the GNU Compiler Collection +@end ifclear +@sp 2 +@center Richard M. Stallman +@sp 3 +@center Last updated 9 May 2001 +@sp 1 +@c The version number appears five times more in this file. + +@center for gcc-3.1 +@page +@vskip 0pt plus 1filll +Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1998, +1999, 2000, 2001 Free Software Foundation, Inc. +@sp 2 +For GCC Version 3.1@* +@sp 1 +Published by the Free Software Foundation @* +59 Temple Place - Suite 330@* +Boston, MA 02111-1307, USA@* +Last printed April, 1998.@* +Printed copies are available for $50 each.@* +ISBN 1-882114-37-X +@sp 1 +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.1 or +any later version published by the Free Software Foundation; with the +Invariant Sections being ``GNU General Public License'', the Front-Cover +texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +``GNU Free Documentation License''. + +(a) The FSF's Front-Cover Text is: + + A GNU Manual + +(b) The FSF's Back-Cover Text is: + + You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. +@end titlepage +@page + +@node Top, G++ and GCC,, (DIR) +@top Introduction +@cindex introduction + +@ifset INTERNALS +@ifset USING +This manual documents how to run, install and port the GNU +compiler, as well as its new features and incompatibilities, and how to +report bugs. It corresponds to GCC version 3.1. +@end ifset +@end ifset + +@ifclear INTERNALS +This manual documents how to run and install the GNU compiler, +as well as its new features and incompatibilities, and how to report +bugs. It corresponds to GCC version 3.1. +@end ifclear +@ifclear USING +This manual documents how to port the GNU compiler, +as well as its new features and incompatibilities, and how to report +bugs. It corresponds to GCC version 3.1. +@end ifclear + +@menu +@ifset USING +* G++ and GCC:: You can compile C or C++ programs. +* Standards:: Language standards supported by GCC. +* Invoking GCC:: Command options supported by @samp{gcc}. +* Installation:: How to configure, compile and install GCC. +* C Extensions:: GNU extensions to the C language family. +* C++ Extensions:: GNU extensions to the C++ language. +* Objective C:: GNU Objective-C runtime features. +* Gcov:: gcov: a GCC test coverage program. +* Trouble:: If you have trouble installing GCC. +* Bugs:: How, why and where to report bugs. +* Service:: How to find suppliers of support for GCC. +* Contributing:: How to contribute to testing and developing GCC. +* VMS:: Using GCC on VMS. +* Makefile:: List of Makefile targets. +@end ifset +@ifset INTERNALS +* Portability:: Goals of GCC's portability features. +* Interface:: Function-call interface of GCC output. +* Passes:: Order of passes, what they do, and what each file is for. +* Trees:: The source representation used by the C and C++ front-ends. +* RTL:: The intermediate representation that most passes work on. +* Machine Desc:: How to write machine description instruction patterns. +* Target Macros:: How to write the machine description C macros. +* Config:: Writing the @file{xm-@var{machine}.h} file. +* Fragments:: Writing the @file{t-@var{target}} and @file{x-@var{host}} files. +@end ifset + +* Funding:: How to help assure funding for free software. +* GNU/Linux:: Linux and the GNU Project + +* Copying:: GNU General Public License says + how you can copy and share GCC. +* GNU Free Documentation License:: How you can copy and share this manual. +* Contributors:: People who have contributed to GCC. + +* Index:: Index of concepts and symbol names. +@end menu + +@ifset USING +@node G++ and GCC +@chapter Compile C, C++, Objective C, Fortran, Java or CHILL + +@cindex Objective C +Several versions of the compiler (C, C++, Objective C, Fortran, Java +and CHILL) are integrated; this is why we use the name +``GNU Compiler Collection''. GCC can compile programs written in any of these +languages. The Fortran, CHILL, and Java compilers are described in +separate manuals. + +@cindex GCC +``GCC'' is a common shorthand term for the GNU Compiler Collection. This is both +the most general name for the compiler, and the name used when the +emphasis is on compiling C programs (as the abbreviation formerly +stood for ``GNU C Compiler''). + +@cindex C++ +@cindex G++ +When referring to C++ compilation, it is usual to call the compiler +``G++''. Since there is only one compiler, it is also accurate to call +it ``GCC'' no matter what the language context; however, the term +``G++'' is more useful when the emphasis is on compiling C++ programs. + +We use the name ``GCC'' to refer to the compilation system as a +whole, and more specifically to the language-independent part of the +compiler. For example, we refer to the optimization options as +affecting the behavior of ``GCC'' or sometimes just ``the compiler''. + +Front ends for other languages, such as Ada 95 and Pascal exist but +have not yet been integrated into GCC. These front-ends, like that for C++, +are built in subdirectories of GCC and link to it. The result is an +integrated compiler that can compile programs written in C, C++, +Objective C, or any of the languages for which you have installed front +ends. + +In this manual, we only discuss the options for the C, Objective-C, and +C++ compilers and those of the GCC core. Consult the documentation +of the other front ends for the options to use when compiling programs +written in other languages. + +@cindex compiler compared to C++ preprocessor +@cindex intermediate C version, nonexistent +@cindex C intermediate output, nonexistent +G++ is a @emph{compiler}, not merely a preprocessor. G++ builds object +code directly from your C++ program source. There is no intermediate C +version of the program. (By contrast, for example, some other +implementations use a program that generates a C program from your C++ +source.) Avoiding an intermediate C representation of the program means +that you get better object code, and better debugging information. The +GNU debugger, GDB, works with this information in the object code to +give you comprehensive C++ source-level editing capabilities +(@pxref{C,,C and C++,gdb.info, Debugging with GDB}). + +@c FIXME! Someone who knows something about Objective C ought to put in +@c a paragraph or two about it here, and move the index entry down when +@c there is more to point to than the general mention in the 1st par. + +@node Standards +@chapter Language Standards Supported by GCC +@cindex C standard +@cindex C standards +@cindex ANSI C standard +@cindex ANSI C +@cindex ANSI C89 +@cindex C89 +@cindex ANSI X3.159-1989 +@cindex X3.159-1989 +@cindex ISO C standard +@cindex ISO C +@cindex ISO C89 +@cindex ISO C90 +@cindex ISO/IEC 9899 +@cindex ISO 9899 +@cindex C90 +@cindex ISO C94 +@cindex C94 +@cindex ISO C95 +@cindex C95 +@cindex ISO C99 +@cindex C99 +@cindex ISO C9X +@cindex C9X +@cindex Technical Corrigenda +@cindex TC1 +@cindex Technical Corrigendum 1 +@cindex TC2 +@cindex Technical Corrigendum 2 +@cindex AMD1 +@cindex freestanding implementation +@cindex freestanding environment +@cindex hosted implementation +@cindex hosted environment +@findex __STDC_HOSTED__ + +For each language compiled by GCC for which there is a standard, GCC +attempts to follow one or more versions of that standard, possibly +with some exceptions, and possibly with some extensions. + +GCC supports three versions of the C standard, although support for +the most recent version is not yet complete. + +The original ANSI C standard (X3.159-1989) was ratified in 1989 and +published in 1990. This standard was ratified as an ISO standard +(ISO/IEC 9899:1990) later in 1990. There were no technical +differences between these publications, although the sections of the +ANSI standard were renumbered and became clauses in the ISO standard. +This standard, in both its forms, is commonly known as @dfn{C89}, or +occasionally as @dfn{C90}, from the dates of ratification. The ANSI +standard, but not the ISO standard, also came with a Rationale +document. To select this standard in GCC, use one of the options +@samp{-ansi}, @samp{-std=c89} or @samp{-std=iso9899:1990}; to obtain +all the diagnostics required by the standard, you should also specify +@samp{-pedantic} (or @samp{-pedantic-errors} if you want them to be +errors rather than warnings). @xref{C Dialect Options,,Options +Controlling C Dialect}. + +Errors in the 1990 ISO C standard were corrected in two Technical +Corrigenda published in 1994 and 1996. GCC does not support the +uncorrected version. + +An amendment to the 1990 standard was published in 1995. This +amendment added digraphs and @code{__STDC_VERSION__} to the language, +but otherwise concerned the library. This amendment is commonly known +as @dfn{AMD1}; the amended standard is sometimes known as @dfn{C94} or +@dfn{C95}. To select this standard in GCC, use the option +@samp{-std=iso9899:199409} (with, as for other standard versions, +@samp{-pedantic} to receive all required diagnostics). + +A new edition of the ISO C standard was published in 1999 as ISO/IEC +9899:1999, and is commonly known as @dfn{C99}. GCC has incomplete +support for this standard version; see +@uref{http://gcc.gnu.org/c99status.html} for details. To select this +standard, use @samp{-std=c99} or @samp{-std=iso9899:1999}. (While in +development, drafts of this standard version were referred to as +@dfn{C9X}.) + +GCC also has some limited support for traditional (pre-ISO) C with the +@samp{-traditional} option. This support may be of use for compiling +some very old programs that have not been updated to ISO C, but should +not be used for new programs. It will not work with some modern C +libraries such as the GNU C library. + +By default, GCC provides some extensions to the C language that on +rare occasions conflict with the C standard. @xref{C +Extensions,,Extensions to the C Language Family}. Use of the +@samp{-std} options listed above will disable these extensions where +they conflict with the C standard version selected. You may also +select an extended version of the C language explicitly with +@samp{-std=gnu89} (for C89 with GNU extensions) or @samp{-std=gnu99} +(for C99 with GNU extensions). The default, if no C language dialect +options are given, is @samp{-std=gnu89}; this will change to +@samp{-std=gnu99} in some future release when the C99 support is +complete. Some features that are part of the C99 standard are +accepted as extensions in C89 mode. + +The ISO C standard defines (in clause 4) two classes of conforming +implementation. A @dfn{conforming hosted implementation} supports the +whole standard including all the library facilities; a @dfn{conforming +freestanding implementation} is only required to provide certain +library facilities: those in @code{}, @code{}, +@code{}, and @code{}; since AMD1, also those in +@code{}; and in C99, also those in @code{} and +@code{}. In addition, complex types, added in C99, are not +required for freestanding implementations. The standard also defines +two environments for programs, a @dfn{freestanding environment}, +required of all implementations and which may not have library +facilities beyond those required of freestanding implementations, +where the handling of program startup and termination are +implementation-defined, and a @dfn{hosted environment}, which is not +required, in which all the library facilities are provided and startup +is through a function @code{int main (void)} or @code{int main (int, +char *[])}. An OS kernel would be a freestanding environment; a +program using the facilities of an operating system would normally be +in a hosted implementation. + +GNU CC aims towards being usable as a conforming freestanding +implementation, or as the compiler for a conforming hosted +implementation. By default, it will act as the compiler for a hosted +implementation, defining @code{__STDC_HOSTED__} as @code{1} and +presuming that when the names of ISO C functions are used, they have +the semantics defined in the standard. To make it act as a conforming +freestanding implementation for a freestanding environment, use the +option @samp{-ffreestanding}; it will then define +@code{__STDC_HOSTED__} to @code{0} and not make assumptions about the +meanings of function names from the standard library. To build an OS +kernel, you may well still need to make your own arrangements for +linking and startup. @xref{C Dialect Options,,Options Controlling C +Dialect}. + +GNU CC does not provide the library facilities required only of hosted +implementations, nor yet all the facilities required by C99 of +freestanding implementations; to use the facilities of a hosted +environment, you will need to find them elsewhere (for example, in the +GNU C library). @xref{Standard Libraries,,Standard Libraries}. + +For references to Technical Corrigenda, Rationale documents and +information concerning the history of C that is available online, see +@uref{http://gcc.gnu.org/readings.html} + +@c FIXME: details of C++ standard. + +There is no formal written standard for Objective-C. The most +authoritative manual is ``Object-Oriented Programming and the +Objective-C Language'', available at a number of web sites; +@uref{http://developer.apple.com/techpubs/macosx/Cocoa/ObjectiveC} has a +recent version, while @uref{http://www.toodarkpark.org/computers/objc/} +is an older example. @uref{http://www.gnustep.org} includes useful +information as well. + +@xref{Language,,The GNU Fortran Language, g77, Using and Porting GNU +Fortran}, for details of the Fortran language supported by GCC. + +@xref{Compatibility,,Compatibility with the Java Platform, gcj, GNU gcj}, +for details of compatibility between @code{gcj} and the Java Platform. + +@xref{References,,Language Definition References, chill, GNU Chill}, +for details of the CHILL standard. + +@include invoke.texi + +@include install-old.texi + +@include extend.texi + +@include objc.texi + +@include gcov.texi + +@node Trouble +@chapter Known Causes of Trouble with GCC +@cindex bugs, known +@cindex installation trouble +@cindex known causes of trouble + +This section describes known problems that affect users of GCC. Most +of these are not GCC bugs per se---if they were, we would fix them. +But the result for a user may be like the result of a bug. + +Some of these problems are due to bugs in other software, some are +missing features that are too much work to add, and some are places +where people's opinions differ as to what is best. + +@menu +* Actual Bugs:: Bugs we will fix later. +* Installation Problems:: Problems that manifest when you install GCC. +* Cross-Compiler Problems:: Common problems of cross compiling with GCC. +* Interoperation:: Problems using GCC with other compilers, + and with certain linkers, assemblers and debuggers. +* External Bugs:: Problems compiling certain programs. +* Incompatibilities:: GCC is incompatible with traditional C. +* Fixed Headers:: GNU C uses corrected versions of system header files. + This is necessary, but doesn't always work smoothly. +* Standard Libraries:: GNU C uses the system C library, which might not be + compliant with the ISO C standard. +* Disappointments:: Regrettable things we can't change, but not quite bugs. +* C++ Misunderstandings:: Common misunderstandings with GNU C++. +* Protoize Caveats:: Things to watch out for when using @code{protoize}. +* Non-bugs:: Things we think are right, but some others disagree. +* Warnings and Errors:: Which problems in your code get warnings, + and which get errors. +@end menu + +@node Actual Bugs +@section Actual Bugs We Haven't Fixed Yet + +@itemize @bullet +@item +The @code{fixincludes} script interacts badly with automounters; if the +directory of system header files is automounted, it tends to be +unmounted while @code{fixincludes} is running. This would seem to be a +bug in the automounter. We don't know any good way to work around it. + +@item +The @code{fixproto} script will sometimes add prototypes for the +@code{sigsetjmp} and @code{siglongjmp} functions that reference the +@code{jmp_buf} type before that type is defined. To work around this, +edit the offending file and place the typedef in front of the +prototypes. + +@item +When @samp{-pedantic-errors} is specified, GCC will incorrectly give +an error message when a function name is specified in an expression +involving the comma operator. +@end itemize + +@node Installation Problems +@section Installation Problems + +This is a list of problems (and some apparent problems which don't +really mean anything is wrong) that show up during installation of GNU +CC. + +@itemize @bullet +@item +On certain systems, defining certain environment variables such as +@code{CC} can interfere with the functioning of @code{make}. + +@item +If you encounter seemingly strange errors when trying to build the +compiler in a directory other than the source directory, it could be +because you have previously configured the compiler in the source +directory. Make sure you have done all the necessary preparations. +@xref{Other Dir}. + +@item +If you build GCC on a BSD system using a directory stored in a System +V file system, problems may occur in running @code{fixincludes} if the +System V file system doesn't support symbolic links. These problems +result in a failure to fix the declaration of @code{size_t} in +@file{sys/types.h}. If you find that @code{size_t} is a signed type and +that type mismatches occur, this could be the cause. + +The solution is not to use such a directory for building GCC. + +@item +Some commands executed when making the compiler may fail (return a +non-zero status) and be ignored by @code{make}. These failures, which +are often due to files that were not found, are expected, and can safely +be ignored. + +@item +It is normal to have warnings in compiling certain files about +unreachable code and about enumeration type clashes. These files' names +begin with @samp{insn-}. Also, @file{real.c} may get some warnings that +you can ignore. + +@item +Sometimes @code{make} recompiles parts of the compiler when installing +the compiler. In one case, this was traced down to a bug in +@code{make}. Either ignore the problem or switch to GNU Make. + +@item +On GNU/Linux SLS 1.01, there is a problem with @file{libc.a}: it does not +contain the obstack functions. However, GCC assumes that the obstack +functions are in @file{libc.a} when it is the GNU C library. To work +around this problem, change the @code{__GNU_LIBRARY__} conditional +around line 31 to @samp{#if 1}. + +@item +On SCO systems, when compiling GCC with the system's compiler, +do not use @samp{-O}. Some versions of the system's compiler miscompile +GCC with @samp{-O}. + +@cindex @code{genflags}, crash on Sun 4 +@item +Sometimes on a Sun 4 you may observe a crash in the program +@code{genflags} or @code{genoutput} while building GCC. This is said to +be due to a bug in @code{sh}. You can probably get around it by running +@code{genflags} or @code{genoutput} manually and then retrying the +@code{make}. + +@item +On Solaris 2, executables of GCC version 2.0.2 are commonly +available, but they have a bug that shows up when compiling current +versions of GCC: undefined symbol errors occur during assembly if you +use @samp{-g}. + +The solution is to compile the current version of GCC without +@samp{-g}. That makes a working compiler which you can use to recompile +with @samp{-g}. + +@item +Solaris 2 comes with a number of optional OS packages. Some of these +packages are needed to use GCC fully. If you did not install all +optional packages when installing Solaris, you will need to verify that +the packages that GCC needs are installed. + +To check whether an optional package is installed, use +the @code{pkginfo} command. To add an optional package, use the +@code{pkgadd} command. For further details, see the Solaris +documentation. + +For Solaris 2.0 and 2.1, GCC needs six packages: @samp{SUNWarc}, +@samp{SUNWbtool}, @samp{SUNWesu}, @samp{SUNWhea}, @samp{SUNWlibm}, and +@samp{SUNWtoo}. + +For Solaris 2.2, GCC needs an additional seventh package: @samp{SUNWsprot}. + +@item +On Solaris 2, trying to use the linker and other tools in +@file{/usr/ucb} to install GCC has been observed to cause trouble. +For example, the linker may hang indefinitely. The fix is to remove +@file{/usr/ucb} from your @code{PATH}. + +@item +If you use the 1.31 version of the MIPS assembler (such as was shipped +with Ultrix 3.1), you will need to use the -fno-delayed-branch switch +when optimizing floating point code. Otherwise, the assembler will +complain when the GCC compiler fills a branch delay slot with a +floating point instruction, such as @code{add.d}. + +@item +If on a MIPS system you get an error message saying ``does not have gp +sections for all it's [sic] sectons [sic]'', don't worry about it. This +happens whenever you use GAS with the MIPS linker, but there is not +really anything wrong, and it is okay to use the output file. You can +stop such warnings by installing the GNU linker. + +It would be nice to extend GAS to produce the gp tables, but they are +optional, and there should not be a warning about their absence. + +@item +Users have reported some problems with version 2.0 of the MIPS +compiler tools that were shipped with Ultrix 4.1. Version 2.10 +which came with Ultrix 4.2 seems to work fine. + +Users have also reported some problems with version 2.20 of the +MIPS compiler tools that were shipped with RISC/os 4.x. The earlier +version 2.11 seems to work fine. + +@item +Some versions of the MIPS linker will issue an assertion failure +when linking code that uses @code{alloca} against shared +libraries on RISC-OS 5.0, and DEC's OSF/1 systems. This is a bug +in the linker, that is supposed to be fixed in future revisions. +To protect against this, GCC passes @samp{-non_shared} to the +linker unless you pass an explicit @samp{-shared} or +@samp{-call_shared} switch. + +@item +On System V release 3, you may get this error message +while linking: + +@smallexample +ld fatal: failed to write symbol name @var{something} + in strings table for file @var{whatever} +@end smallexample + +This probably indicates that the disk is full or your ULIMIT won't allow +the file to be as large as it needs to be. + +This problem can also result because the kernel parameter @code{MAXUMEM} +is too small. If so, you must regenerate the kernel and make the value +much larger. The default value is reported to be 1024; a value of 32768 +is said to work. Smaller values may also work. + +@item +On System V, if you get an error like this, + +@example +/usr/local/lib/bison.simple: In function `yyparse': +/usr/local/lib/bison.simple:625: virtual memory exhausted +@end example + +@noindent +that too indicates a problem with disk space, ULIMIT, or @code{MAXUMEM}. + +@item +Current GCC versions probably do not work on version 2 of the NeXT +operating system. + +@item +On NeXTStep 3.0, the Objective C compiler does not work, due, +apparently, to a kernel bug that it happens to trigger. This problem +does not happen on 3.1. + +@item +On the Tower models 4@var{n}0 and 6@var{n}0, by default a process is not +allowed to have more than one megabyte of memory. GCC cannot compile +itself (or many other programs) with @samp{-O} in that much memory. + +To solve this problem, reconfigure the kernel adding the following line +to the configuration file: + +@smallexample +MAXUMEM = 4096 +@end smallexample + +@item +On HP 9000 series 300 or 400 running HP-UX release 8.0, there is a bug +in the assembler that must be fixed before GCC can be built. This +bug manifests itself during the first stage of compilation, while +building @file{libgcc2.a}: + +@smallexample +_floatdisf +cc1: warning: `-g' option not supported on this version of GCC +cc1: warning: `-g1' option not supported on this version of GCC +./xgcc: Internal compiler error: program as got fatal signal 11 +@end smallexample + +A patched version of the assembler is available as the file +@uref{ftp://altdorf.ai.mit.edu/archive/cph/hpux-8.0-assembler}. If you +have HP software support, the patch can also be obtained directly from +HP, as described in the following note: + +@quotation +This is the patched assembler, to patch SR#1653-010439, where the +assembler aborts on floating point constants. + +The bug is not really in the assembler, but in the shared library +version of the function ``cvtnum(3c)''. The bug on ``cvtnum(3c)'' is +SR#4701-078451. Anyway, the attached assembler uses the archive +library version of ``cvtnum(3c)'' and thus does not exhibit the bug. +@end quotation + +This patch is also known as PHCO_4484. + +@item +On HP-UX version 8.05, but not on 8.07 or more recent versions, +the @code{fixproto} shell script triggers a bug in the system shell. +If you encounter this problem, upgrade your operating system or +use BASH (the GNU shell) to run @code{fixproto}. + +@item +There may be similar problems on System V Release 3.1 on 386 systems. + +@item +On the Intel Paragon (an i860 machine), if you are using operating +system version 1.0, you will get warnings or errors about redefinition +of @code{va_arg} when you build GCC. + +If this happens, then you need to link most programs with the library +@file{iclib.a}. You must also modify @file{stdio.h} as follows: before +the lines + +@example +#if defined(__i860__) && !defined(_VA_LIST) +#include +@end example + +@noindent +insert the line + +@example +#if __PGC__ +@end example + +@noindent +and after the lines + +@example +extern int vprintf(const char *, va_list ); +extern int vsprintf(char *, const char *, va_list ); +#endif +@end example + +@noindent +insert the line + +@example +#endif /* __PGC__ */ +@end example + +These problems don't exist in operating system version 1.1. + +@item +On the Altos 3068, programs compiled with GCC won't work unless you +fix a kernel bug. This happens using system versions V.2.2 1.0gT1 and +V.2.2 1.0e and perhaps later versions as well. See the file +@file{README.ALTOS}. + +@item +You will get several sorts of compilation and linking errors on the +we32k if you don't follow the special instructions. @xref{Configurations}. + +@item +A bug in the HP-UX 8.05 (and earlier) shell will cause the fixproto +program to report an error of the form: + +@example +./fixproto: sh internal 1K buffer overflow +@end example + +To fix this, change the first line of the fixproto script to look like: + +@example +#!/bin/ksh +@end example +@end itemize + +@node Cross-Compiler Problems +@section Cross-Compiler Problems + +You may run into problems with cross compilation on certain machines, +for several reasons. + +@itemize @bullet +@item +Cross compilation can run into trouble for certain machines because +some target machines' assemblers require floating point numbers to be +written as @emph{integer} constants in certain contexts. + +The compiler writes these integer constants by examining the floating +point value as an integer and printing that integer, because this is +simple to write and independent of the details of the floating point +representation. But this does not work if the compiler is running on +a different machine with an incompatible floating point format, or +even a different byte-ordering. + +In addition, correct constant folding of floating point values +requires representing them in the target machine's format. +(The C standard does not quite require this, but in practice +it is the only way to win.) + +It is now possible to overcome these problems by defining macros such +as @code{REAL_VALUE_TYPE}. But doing so is a substantial amount of +work for each target machine. +@ifset INTERNALS +@xref{Cross-compilation}. +@end ifset +@ifclear INTERNALS +@xref{Cross-compilation,,Cross Compilation and Floating Point Format, +gcc.info, Using and Porting GCC}. +@end ifclear + +@item +At present, the program @file{mips-tfile} which adds debug +support to object files on MIPS systems does not work in a cross +compile environment. +@end itemize + +@node Interoperation +@section Interoperation + +This section lists various difficulties encountered in using GNU C or +GNU C++ together with other compilers or with the assemblers, linkers, +libraries and debuggers on certain systems. + +@itemize @bullet +@item +Objective C does not work on the RS/6000. + +@item +GNU C++ does not do name mangling in the same way as other C++ +compilers. This means that object files compiled with one compiler +cannot be used with another. + +This effect is intentional, to protect you from more subtle problems. +Compilers differ as to many internal details of C++ implementation, +including: how class instances are laid out, how multiple inheritance is +implemented, and how virtual function calls are handled. If the name +encoding were made the same, your programs would link against libraries +provided from other compilers---but the programs would then crash when +run. Incompatible libraries are then detected at link time, rather than +at run time. + +@item +Older GDB versions sometimes fail to read the output of GCC version +2. If you have trouble, get GDB version 4.4 or later. + +@item +@cindex DBX +DBX rejects some files produced by GCC, though it accepts similar +constructs in output from PCC. Until someone can supply a coherent +description of what is valid DBX input and what is not, there is +nothing I can do about these problems. You are on your own. + +@item +The GNU assembler (GAS) does not support PIC. To generate PIC code, you +must use some other assembler, such as @file{/bin/as}. + +@item +On some BSD systems, including some versions of Ultrix, use of profiling +causes static variable destructors (currently used only in C++) not to +be run. + +@item +Use of @samp{-I/usr/include} may cause trouble. + +Many systems come with header files that won't work with GCC unless +corrected by @code{fixincludes}. The corrected header files go in a new +directory; GCC searches this directory before @file{/usr/include}. +If you use @samp{-I/usr/include}, this tells GCC to search +@file{/usr/include} earlier on, before the corrected headers. The +result is that you get the uncorrected header files. + +Instead, you should use these options (when compiling C programs): + +@smallexample +-I/usr/local/lib/gcc-lib/@var{target}/@var{version}/include -I/usr/include +@end smallexample + +For C++ programs, GCC also uses a special directory that defines C++ +interfaces to standard C subroutines. This directory is meant to be +searched @emph{before} other standard include directories, so that it +takes precedence. If you are compiling C++ programs and specifying +include directories explicitly, use this option first, then the two +options above: + +@example +-I/usr/local/lib/g++-include +@end example + +@ignore +@cindex @code{vfork}, for the Sun-4 +@item +There is a bug in @code{vfork} on the Sun-4 which causes the registers +of the child process to clobber those of the parent. Because of this, +programs that call @code{vfork} are likely to lose when compiled +optimized with GCC when the child code alters registers which contain +C variables in the parent. This affects variables which are live in the +parent across the call to @code{vfork}. + +If you encounter this, you can work around the problem by declaring +variables @code{volatile} in the function that calls @code{vfork}, until +the problem goes away, or by not declaring them @code{register} and not +using @samp{-O} for those source files. +@end ignore + +@item +On some SGI systems, when you use @samp{-lgl_s} as an option, +it gets translated magically to @samp{-lgl_s -lX11_s -lc_s}. +Naturally, this does not happen when you use GCC. +You must specify all three options explicitly. + +@item +On a Sparc, GCC aligns all values of type @code{double} on an 8-byte +boundary, and it expects every @code{double} to be so aligned. The Sun +compiler usually gives @code{double} values 8-byte alignment, with one +exception: function arguments of type @code{double} may not be aligned. + +As a result, if a function compiled with Sun CC takes the address of an +argument of type @code{double} and passes this pointer of type +@code{double *} to a function compiled with GCC, dereferencing the +pointer may cause a fatal signal. + +One way to solve this problem is to compile your entire program with GNU +CC. Another solution is to modify the function that is compiled with +Sun CC to copy the argument into a local variable; local variables +are always properly aligned. A third solution is to modify the function +that uses the pointer to dereference it via the following function +@code{access_double} instead of directly with @samp{*}: + +@smallexample +inline double +access_double (double *unaligned_ptr) +@{ + union d2i @{ double d; int i[2]; @}; + + union d2i *p = (union d2i *) unaligned_ptr; + union d2i u; + + u.i[0] = p->i[0]; + u.i[1] = p->i[1]; + + return u.d; +@} +@end smallexample + +@noindent +Storing into the pointer can be done likewise with the same union. + +@item +On Solaris, the @code{malloc} function in the @file{libmalloc.a} library +may allocate memory that is only 4 byte aligned. Since GCC on the +Sparc assumes that doubles are 8 byte aligned, this may result in a +fatal signal if doubles are stored in memory allocated by the +@file{libmalloc.a} library. + +The solution is to not use the @file{libmalloc.a} library. Use instead +@code{malloc} and related functions from @file{libc.a}; they do not have +this problem. + +@item +Sun forgot to include a static version of @file{libdl.a} with some +versions of SunOS (mainly 4.1). This results in undefined symbols when +linking static binaries (that is, if you use @samp{-static}). If you +see undefined symbols @code{_dlclose}, @code{_dlsym} or @code{_dlopen} +when linking, compile and link against the file +@file{mit/util/misc/dlsym.c} from the MIT version of X windows. + +@item +The 128-bit long double format that the Sparc port supports currently +works by using the architecturally defined quad-word floating point +instructions. Since there is no hardware that supports these +instructions they must be emulated by the operating system. Long +doubles do not work in Sun OS versions 4.0.3 and earlier, because the +kernel emulator uses an obsolete and incompatible format. Long doubles +do not work in Sun OS version 4.1.1 due to a problem in a Sun library. +Long doubles do work on Sun OS versions 4.1.2 and higher, but GCC +does not enable them by default. Long doubles appear to work in Sun OS +5.x (Solaris 2.x). + +@item +On HP-UX version 9.01 on the HP PA, the HP compiler @code{cc} does not +compile GCC correctly. We do not yet know why. However, GCC +compiled on earlier HP-UX versions works properly on HP-UX 9.01 and can +compile itself properly on 9.01. + +@item +On the HP PA machine, ADB sometimes fails to work on functions compiled +with GCC. Specifically, it fails to work on functions that use +@code{alloca} or variable-size arrays. This is because GCC doesn't +generate HP-UX unwind descriptors for such functions. It may even be +impossible to generate them. + +@item +Debugging (@samp{-g}) is not supported on the HP PA machine, unless you use +the preliminary GNU tools (@pxref{Installation}). + +@item +Taking the address of a label may generate errors from the HP-UX +PA assembler. GAS for the PA does not have this problem. + +@item +Using floating point parameters for indirect calls to static functions +will not work when using the HP assembler. There simply is no way for GCC +to specify what registers hold arguments for static functions when using +the HP assembler. GAS for the PA does not have this problem. + +@item +In extremely rare cases involving some very large functions you may +receive errors from the HP linker complaining about an out of bounds +unconditional branch offset. This used to occur more often in previous +versions of GCC, but is now exceptionally rare. If you should run +into it, you can work around by making your function smaller. + +@item +GCC compiled code sometimes emits warnings from the HP-UX assembler of +the form: + +@smallexample +(warning) Use of GR3 when + frame >= 8192 may cause conflict. +@end smallexample + +These warnings are harmless and can be safely ignored. + +@item +The current version of the assembler (@file{/bin/as}) for the RS/6000 +has certain problems that prevent the @samp{-g} option in GCC from +working. Note that @file{Makefile.in} uses @samp{-g} by default when +compiling @file{libgcc2.c}. + +IBM has produced a fixed version of the assembler. The upgraded +assembler unfortunately was not included in any of the AIX 3.2 update +PTF releases (3.2.2, 3.2.3, or 3.2.3e). Users of AIX 3.1 should request +PTF U403044 from IBM and users of AIX 3.2 should request PTF U416277. +See the file @file{README.RS6000} for more details on these updates. + +You can test for the presence of a fixed assembler by using the +command + +@smallexample +as -u < /dev/null +@end smallexample + +@noindent +If the command exits normally, the assembler fix already is installed. +If the assembler complains that "-u" is an unknown flag, you need to +order the fix. + +@item +On the IBM RS/6000, compiling code of the form + +@smallexample +extern int foo; + +@dots{} foo @dots{} + +static int foo; +@end smallexample + +@noindent +will cause the linker to report an undefined symbol @code{foo}. +Although this behavior differs from most other systems, it is not a +bug because redefining an @code{extern} variable as @code{static} +is undefined in ISO C. + +@item +AIX on the RS/6000 provides support (NLS) for environments outside of +the United States. Compilers and assemblers use NLS to support +locale-specific representations of various objects including +floating-point numbers ("." vs "," for separating decimal fractions). +There have been problems reported where the library linked with GCC does +not produce the same floating-point formats that the assembler accepts. +If you have this problem, set the LANG environment variable to "C" or +"En_US". + +@item +Even if you specify @samp{-fdollars-in-identifiers}, +you cannot successfully use @samp{$} in identifiers on the RS/6000 due +to a restriction in the IBM assembler. GAS supports these +identifiers. + +@item +On the RS/6000, XLC version 1.3.0.0 will miscompile @file{jump.c}. XLC +version 1.3.0.1 or later fixes this problem. You can obtain XLC-1.3.0.2 +by requesting PTF 421749 from IBM. + +@item +There is an assembler bug in versions of DG/UX prior to 5.4.2.01 that +occurs when the @samp{fldcr} instruction is used. GCC uses +@samp{fldcr} on the 88100 to serialize volatile memory references. Use +the option @samp{-mno-serialize-volatile} if your version of the +assembler has this bug. + +@item +On VMS, GAS versions 1.38.1 and earlier may cause spurious warning +messages from the linker. These warning messages complain of mismatched +psect attributes. You can ignore them. @xref{VMS Install}. + +@item +On NewsOS version 3, if you include both of the files @file{stddef.h} +and @file{sys/types.h}, you get an error because there are two typedefs +of @code{size_t}. You should change @file{sys/types.h} by adding these +lines around the definition of @code{size_t}: + +@smallexample +#ifndef _SIZE_T +#define _SIZE_T +@var{actual typedef here} +#endif +@end smallexample + +@cindex Alliant +@item +On the Alliant, the system's own convention for returning structures +and unions is unusual, and is not compatible with GCC no matter +what options are used. + +@cindex RT PC +@cindex IBM RT PC +@item +On the IBM RT PC, the MetaWare HighC compiler (hc) uses a different +convention for structure and union returning. Use the option +@samp{-mhc-struct-return} to tell GCC to use a convention compatible +with it. + +@cindex Vax calling convention +@cindex Ultrix calling convention +@item +On Ultrix, the Fortran compiler expects registers 2 through 5 to be saved +by function calls. However, the C compiler uses conventions compatible +with BSD Unix: registers 2 through 5 may be clobbered by function calls. + +GCC uses the same convention as the Ultrix C compiler. You can use +these options to produce code compatible with the Fortran compiler: + +@smallexample +-fcall-saved-r2 -fcall-saved-r3 -fcall-saved-r4 -fcall-saved-r5 +@end smallexample + +@item +On the WE32k, you may find that programs compiled with GCC do not +work with the standard shared C library. You may need to link with +the ordinary C compiler. If you do so, you must specify the following +options: + +@smallexample +-L/usr/local/lib/gcc-lib/we32k-att-sysv/2.8.1 -lgcc -lc_s +@end smallexample + +The first specifies where to find the library @file{libgcc.a} +specified with the @samp{-lgcc} option. + +GCC does linking by invoking @code{ld}, just as @code{cc} does, and +there is no reason why it @emph{should} matter which compilation program +you use to invoke @code{ld}. If someone tracks this problem down, +it can probably be fixed easily. + +@item +On the Alpha, you may get assembler errors about invalid syntax as a +result of floating point constants. This is due to a bug in the C +library functions @code{ecvt}, @code{fcvt} and @code{gcvt}. Given valid +floating point numbers, they sometimes print @samp{NaN}. + +@item +On Irix 4.0.5F (and perhaps in some other versions), an assembler bug +sometimes reorders instructions incorrectly when optimization is turned +on. If you think this may be happening to you, try using the GNU +assembler; GAS version 2.1 supports ECOFF on Irix. + +Or use the @samp{-noasmopt} option when you compile GCC with itself, +and then again when you compile your program. (This is a temporary +kludge to turn off assembler optimization on Irix.) If this proves to +be what you need, edit the assembler spec in the file @file{specs} so +that it unconditionally passes @samp{-O0} to the assembler, and never +passes @samp{-O2} or @samp{-O3}. +@end itemize + +@node External Bugs +@section Problems Compiling Certain Programs + +@c prevent bad page break with this line +Certain programs have problems compiling. + +@itemize @bullet +@item +Parse errors may occur compiling X11 on a Decstation running Ultrix 4.2 +because of problems in DEC's versions of the X11 header files +@file{X11/Xlib.h} and @file{X11/Xutil.h}. People recommend adding +@samp{-I/usr/include/mit} to use the MIT versions of the header files, +using the @samp{-traditional} switch to turn off ISO C, or fixing the +header files by adding this: + +@example +#ifdef __STDC__ +#define NeedFunctionPrototypes 0 +#endif +@end example + +@item +On various 386 Unix systems derived from System V, including SCO, ISC, +and ESIX, you may get error messages about running out of virtual memory +while compiling certain programs. + +You can prevent this problem by linking GCC with the GNU malloc +(which thus replaces the malloc that comes with the system). GNU malloc +is available as a separate package, and also in the file +@file{src/gmalloc.c} in the GNU Emacs 19 distribution. + +If you have installed GNU malloc as a separate library package, use this +option when you relink GCC: + +@example +MALLOC=/usr/local/lib/libgmalloc.a +@end example + +Alternatively, if you have compiled @file{gmalloc.c} from Emacs 19, copy +the object file to @file{gmalloc.o} and use this option when you relink +GCC: + +@example +MALLOC=gmalloc.o +@end example +@end itemize + +@node Incompatibilities +@section Incompatibilities of GCC +@cindex incompatibilities of GCC + +There are several noteworthy incompatibilities between GNU C and K&R +(non-ISO) versions of C. The @samp{-traditional} option +eliminates many of these incompatibilities, @emph{but not all}, by +telling GNU C to behave like a K&R C compiler. + +@itemize @bullet +@cindex string constants +@cindex read-only strings +@cindex shared strings +@item +GCC normally makes string constants read-only. If several +identical-looking string constants are used, GCC stores only one +copy of the string. + +@cindex @code{mktemp}, and constant strings +One consequence is that you cannot call @code{mktemp} with a string +constant argument. The function @code{mktemp} always alters the +string its argument points to. + +@cindex @code{sscanf}, and constant strings +@cindex @code{fscanf}, and constant strings +@cindex @code{scanf}, and constant strings +Another consequence is that @code{sscanf} does not work on some systems +when passed a string constant as its format control string or input. +This is because @code{sscanf} incorrectly tries to write into the string +constant. Likewise @code{fscanf} and @code{scanf}. + +The best solution to these problems is to change the program to use +@code{char}-array variables with initialization strings for these +purposes instead of string constants. But if this is not possible, +you can use the @samp{-fwritable-strings} flag, which directs GCC +to handle string constants the same way most C compilers do. +@samp{-traditional} also has this effect, among others. + +@item +@code{-2147483648} is positive. + +This is because 2147483648 cannot fit in the type @code{int}, so +(following the ISO C rules) its data type is @code{unsigned long int}. +Negating this value yields 2147483648 again. + +@item +GCC does not substitute macro arguments when they appear inside of +string constants. For example, the following macro in GCC + +@example +#define foo(a) "a" +@end example + +@noindent +will produce output @code{"a"} regardless of what the argument @var{a} is. + +The @samp{-traditional} option directs GCC to handle such cases +(among others) in the old-fashioned (non-ISO) fashion. + +@cindex @code{setjmp} incompatibilities +@cindex @code{longjmp} incompatibilities +@item +When you use @code{setjmp} and @code{longjmp}, the only automatic +variables guaranteed to remain valid are those declared +@code{volatile}. This is a consequence of automatic register +allocation. Consider this function: + +@example +jmp_buf j; + +foo () +@{ + int a, b; + + a = fun1 (); + if (setjmp (j)) + return a; + + a = fun2 (); + /* @r{@code{longjmp (j)} may occur in @code{fun3}.} */ + return a + fun3 (); +@} +@end example + +Here @code{a} may or may not be restored to its first value when the +@code{longjmp} occurs. If @code{a} is allocated in a register, then +its first value is restored; otherwise, it keeps the last value stored +in it. + +If you use the @samp{-W} option with the @samp{-O} option, you will +get a warning when GCC thinks such a problem might be possible. + +The @samp{-traditional} option directs GNU C to put variables in +the stack by default, rather than in registers, in functions that +call @code{setjmp}. This results in the behavior found in +traditional C compilers. + +@item +Programs that use preprocessing directives in the middle of macro +arguments do not work with GCC. For example, a program like this +will not work: + +@example +foobar ( +#define luser + hack) +@end example + +ISO C does not permit such a construct. It would make sense to support +it when @samp{-traditional} is used, but it is too much work to +implement. + +@item +K&R compilers allow comments to cross over an inclusion boundary (i.e. +started in an include file and ended in the including file). I think +this would be quite ugly and can't imagine it could be needed. + +@cindex external declaration scope +@cindex scope of external declarations +@cindex declaration scope +@item +Declarations of external variables and functions within a block apply +only to the block containing the declaration. In other words, they +have the same scope as any other declaration in the same place. + +In some other C compilers, a @code{extern} declaration affects all the +rest of the file even if it happens within a block. + +The @samp{-traditional} option directs GNU C to treat all @code{extern} +declarations as global, like traditional compilers. + +@item +In traditional C, you can combine @code{long}, etc., with a typedef name, +as shown here: + +@example +typedef int foo; +typedef long foo bar; +@end example + +In ISO C, this is not allowed: @code{long} and other type modifiers +require an explicit @code{int}. Because this criterion is expressed +by Bison grammar rules rather than C code, the @samp{-traditional} +flag cannot alter it. + +@cindex typedef names as function parameters +@item +PCC allows typedef names to be used as function parameters. The +difficulty described immediately above applies here too. + +@item +When in @samp{-traditional} mode, GCC allows the following erroneous +pair of declarations to appear together in a given scope: + +@example +typedef int foo; +typedef foo foo; +@end example + +@item +GCC treats all characters of identifiers as significant, even when in +@samp{-traditional} mode. According to K&R-1 (2.2), ``No more than the +first eight characters are significant, although more may be used.''. +Also according to K&R-1 (2.2), ``An identifier is a sequence of letters +and digits; the first character must be a letter. The underscore _ +counts as a letter.'', but GCC also allows dollar signs in identifiers. + +@cindex whitespace +@item +PCC allows whitespace in the middle of compound assignment operators +such as @samp{+=}. GCC, following the ISO standard, does not +allow this. The difficulty described immediately above applies here +too. + +@cindex apostrophes +@cindex ' +@item +GCC complains about unterminated character constants inside of +preprocessing conditionals that fail. Some programs have English +comments enclosed in conditionals that are guaranteed to fail; if these +comments contain apostrophes, GCC will probably report an error. For +example, this code would produce an error: + +@example +#if 0 +You can't expect this to work. +#endif +@end example + +The best solution to such a problem is to put the text into an actual +C comment delimited by @samp{/*@dots{}*/}. However, +@samp{-traditional} suppresses these error messages. + +@item +Many user programs contain the declaration @samp{long time ();}. In the +past, the system header files on many systems did not actually declare +@code{time}, so it did not matter what type your program declared it to +return. But in systems with ISO C headers, @code{time} is declared to +return @code{time_t}, and if that is not the same as @code{long}, then +@samp{long time ();} is erroneous. + +The solution is to change your program to use appropriate system headers +(@code{} on systems with ISO C headers) and not to declare +@code{time} if the system header files declare it, or failing that to +use @code{time_t} as the return type of @code{time}. + +@cindex @code{float} as function value type +@item +When compiling functions that return @code{float}, PCC converts it to +a double. GCC actually returns a @code{float}. If you are concerned +with PCC compatibility, you should declare your functions to return +@code{double}; you might as well say what you mean. + +@cindex structures +@cindex unions +@item +When compiling functions that return structures or unions, GCC +output code normally uses a method different from that used on most +versions of Unix. As a result, code compiled with GCC cannot call +a structure-returning function compiled with PCC, and vice versa. + +The method used by GCC is as follows: a structure or union which is +1, 2, 4 or 8 bytes long is returned like a scalar. A structure or union +with any other size is stored into an address supplied by the caller +(usually in a special, fixed register, but on some machines it is passed +on the stack). The machine-description macros @code{STRUCT_VALUE} and +@code{STRUCT_INCOMING_VALUE} tell GCC where to pass this address. + +By contrast, PCC on most target machines returns structures and unions +of any size by copying the data into an area of static storage, and then +returning the address of that storage as if it were a pointer value. +The caller must copy the data from that memory area to the place where +the value is wanted. GCC does not use this method because it is +slower and nonreentrant. + +On some newer machines, PCC uses a reentrant convention for all +structure and union returning. GCC on most of these machines uses a +compatible convention when returning structures and unions in memory, +but still returns small structures and unions in registers. + +You can tell GCC to use a compatible convention for all structure and +union returning with the option @samp{-fpcc-struct-return}. + +@cindex preprocessing tokens +@cindex preprocessing numbers +@item +GNU C complains about program fragments such as @samp{0x74ae-0x4000} +which appear to be two hexadecimal constants separated by the minus +operator. Actually, this string is a single @dfn{preprocessing token}. +Each such token must correspond to one token in C. Since this does not, +GNU C prints an error message. Although it may appear obvious that what +is meant is an operator and two values, the ISO C standard specifically +requires that this be treated as erroneous. + +A @dfn{preprocessing token} is a @dfn{preprocessing number} if it +begins with a digit and is followed by letters, underscores, digits, +periods and @samp{e+}, @samp{e-}, @samp{E+}, @samp{E-}, @samp{p+}, +@samp{p-}, @samp{P+}, or @samp{P-} character sequences. (In strict C89 +mode, the sequences @samp{p+}, @samp{p-}, @samp{P+} and @samp{P-} cannot +appear in preprocessing numbers.) + +To make the above program fragment valid, place whitespace in front of +the minus sign. This whitespace will end the preprocessing number. +@end itemize + +@node Fixed Headers +@section Fixed Header Files + +GCC needs to install corrected versions of some system header files. +This is because most target systems have some header files that won't +work with GCC unless they are changed. Some have bugs, some are +incompatible with ISO C, and some depend on special features of other +compilers. + +Installing GCC automatically creates and installs the fixed header +files, by running a program called @code{fixincludes} (or for certain +targets an alternative such as @code{fixinc.svr4}). Normally, you +don't need to pay attention to this. But there are cases where it +doesn't do the right thing automatically. + +@itemize @bullet +@item +If you update the system's header files, such as by installing a new +system version, the fixed header files of GCC are not automatically +updated. The easiest way to update them is to reinstall GCC. (If +you want to be clever, look in the makefile and you can find a +shortcut.) + +@item +On some systems, in particular SunOS 4, header file directories contain +machine-specific symbolic links in certain places. This makes it +possible to share most of the header files among hosts running the +same version of SunOS 4 on different machine models. + +The programs that fix the header files do not understand this special +way of using symbolic links; therefore, the directory of fixed header +files is good only for the machine model used to build it. + +In SunOS 4, only programs that look inside the kernel will notice the +difference between machine models. Therefore, for most purposes, you +need not be concerned about this. + +It is possible to make separate sets of fixed header files for the +different machine models, and arrange a structure of symbolic links so +as to use the proper set, but you'll have to do this by hand. + +@item +On Lynxos, GCC by default does not fix the header files. This is +because bugs in the shell cause the @code{fixincludes} script to fail. + +This means you will encounter problems due to bugs in the system header +files. It may be no comfort that they aren't GCC's fault, but it +does mean that there's nothing for us to do about them. +@end itemize + +@node Standard Libraries +@section Standard Libraries + +GCC by itself attempts to be a conforming freestanding implementation. +@xref{Standards,,Language Standards Supported by GCC}, for details of +what this means. Beyond the library facilities required of such an +implementation, the rest of the C library is supplied by the vendor of +the operating system. If that C library doesn't conform to the C +standards, then your programs might get warnings (especially when using +@samp{-Wall}) that you don't expect. + +For example, the @code{sprintf} function on SunOS 4.1.3 returns +@code{char *} while the C standard says that @code{sprintf} returns an +@code{int}. The @code{fixincludes} program could make the prototype for +this function match the Standard, but that would be wrong, since the +function will still return @code{char *}. + +If you need a Standard compliant library, then you need to find one, as +GCC does not provide one. The GNU C library (called @code{glibc}) +provides ISO C, POSIX, BSD, SystemV and X/Open compatibility for +GNU/Linux and HURD-based GNU systems; no recent version of it supports +other systems, though some very old versions did. Version 2.2 of the +GNU C library includes nearly complete C99 support. You could also ask +your operating system vendor if newer libraries are available. + +@node Disappointments +@section Disappointments and Misunderstandings + +These problems are perhaps regrettable, but we don't know any practical +way around them. + +@itemize @bullet +@item +Certain local variables aren't recognized by debuggers when you compile +with optimization. + +This occurs because sometimes GCC optimizes the variable out of +existence. There is no way to tell the debugger how to compute the +value such a variable ``would have had'', and it is not clear that would +be desirable anyway. So GCC simply does not mention the eliminated +variable when it writes debugging information. + +You have to expect a certain amount of disagreement between the +executable and your source code, when you use optimization. + +@cindex conflicting types +@cindex scope of declaration +@item +Users often think it is a bug when GCC reports an error for code +like this: + +@example +int foo (struct mumble *); + +struct mumble @{ @dots{} @}; + +int foo (struct mumble *x) +@{ @dots{} @} +@end example + +This code really is erroneous, because the scope of @code{struct +mumble} in the prototype is limited to the argument list containing it. +It does not refer to the @code{struct mumble} defined with file scope +immediately below---they are two unrelated types with similar names in +different scopes. + +But in the definition of @code{foo}, the file-scope type is used +because that is available to be inherited. Thus, the definition and +the prototype do not match, and you get an error. + +This behavior may seem silly, but it's what the ISO standard specifies. +It is easy enough for you to make your code work by moving the +definition of @code{struct mumble} above the prototype. It's not worth +being incompatible with ISO C just to avoid an error for the example +shown above. + +@item +Accesses to bitfields even in volatile objects works by accessing larger +objects, such as a byte or a word. You cannot rely on what size of +object is accessed in order to read or write the bitfield; it may even +vary for a given bitfield according to the precise usage. + +If you care about controlling the amount of memory that is accessed, use +volatile but do not use bitfields. + +@item +GCC comes with shell scripts to fix certain known problems in system +header files. They install corrected copies of various header files in +a special directory where only GCC will normally look for them. The +scripts adapt to various systems by searching all the system header +files for the problem cases that we know about. + +If new system header files are installed, nothing automatically arranges +to update the corrected header files. You will have to reinstall GCC +to fix the new header files. More specifically, go to the build +directory and delete the files @file{stmp-fixinc} and +@file{stmp-headers}, and the subdirectory @code{include}; then do +@samp{make install} again. + +@item +@cindex floating point precision +On 68000 and x86 systems, for instance, you can get paradoxical results +if you test the precise values of floating point numbers. For example, +you can find that a floating point value which is not a NaN is not equal +to itself. This results from the fact that the floating point registers +hold a few more bits of precision than fit in a @code{double} in memory. +Compiled code moves values between memory and floating point registers +at its convenience, and moving them into memory truncates them. + +You can partially avoid this problem by using the @samp{-ffloat-store} +option (@pxref{Optimize Options}). + +@item +On the MIPS, variable argument functions using @file{varargs.h} +cannot have a floating point value for the first argument. The +reason for this is that in the absence of a prototype in scope, +if the first argument is a floating point, it is passed in a +floating point register, rather than an integer register. + +If the code is rewritten to use the ISO standard @file{stdarg.h} +method of variable arguments, and the prototype is in scope at +the time of the call, everything will work fine. + +@item +On the H8/300 and H8/300H, variable argument functions must be +implemented using the ISO standard @file{stdarg.h} method of +variable arguments. Furthermore, calls to functions using @file{stdarg.h} +variable arguments must have a prototype for the called function +in scope at the time of the call. +@end itemize + +@node C++ Misunderstandings +@section Common Misunderstandings with GNU C++ + +@cindex misunderstandings in C++ +@cindex surprises in C++ +@cindex C++ misunderstandings +C++ is a complex language and an evolving one, and its standard +definition (the ISO C++ standard) was only recently completed. As a +result, your C++ compiler may occasionally surprise you, even when its +behavior is correct. This section discusses some areas that frequently +give rise to questions of this sort. + +@menu +* Static Definitions:: Static member declarations are not definitions +* Temporaries:: Temporaries may vanish before you expect +* Copy Assignment:: Copy Assignment operators copy virtual bases twice +@end menu + +@node Static Definitions +@subsection Declare @emph{and} Define Static Members + +@cindex C++ static data, declaring and defining +@cindex static data in C++, declaring and defining +@cindex declaring static data in C++ +@cindex defining static data in C++ +When a class has static data members, it is not enough to @emph{declare} +the static member; you must also @emph{define} it. For example: + +@example +class Foo +@{ + @dots{} + void method(); + static int bar; +@}; +@end example + +This declaration only establishes that the class @code{Foo} has an +@code{int} named @code{Foo::bar}, and a member function named +@code{Foo::method}. But you still need to define @emph{both} +@code{method} and @code{bar} elsewhere. According to the ISO +standard, you must supply an initializer in one (and only one) source +file, such as: + +@example +int Foo::bar = 0; +@end example + +Other C++ compilers may not correctly implement the standard behavior. +As a result, when you switch to @code{g++} from one of these compilers, +you may discover that a program that appeared to work correctly in fact +does not conform to the standard: @code{g++} reports as undefined +symbols any static data members that lack definitions. + +@node Temporaries +@subsection Temporaries May Vanish Before You Expect + +@cindex temporaries, lifetime of +@cindex portions of temporary objects, pointers to +It is dangerous to use pointers or references to @emph{portions} of a +temporary object. The compiler may very well delete the object before +you expect it to, leaving a pointer to garbage. The most common place +where this problem crops up is in classes like string classes, +especially ones that define a conversion function to type @code{char *} +or @code{const char *} -- which is one reason why the standard +@code{string} class requires you to call the @code{c_str} member +function. However, any class that returns a pointer to some internal +structure is potentially subject to this problem. + +For example, a program may use a function @code{strfunc} that returns +@code{string} objects, and another function @code{charfunc} that +operates on pointers to @code{char}: + +@example +string strfunc (); +void charfunc (const char *); + +void +f () +@{ + const char *p = strfunc().c_str(); + ... + charfunc (p); + ... + charfunc (p); +@} +@end example + +@noindent +In this situation, it may seem reasonable to save a pointer to the C +string returned by the @code{c_str} member function and use that rather +than call @code{c_str} repeatedly. However, the temporary string +created by the call to @code{strfunc} is destroyed after @code{p} is +initialized, at which point @code{p} is left pointing to freed memory. + +Code like this may run successfully under some other compilers, +particularly obsolete cfront-based compilers that delete temporaries +along with normal local variables. However, the GNU C++ behavior is +standard-conforming, so if your program depends on late destruction of +temporaries it is not portable. + +The safe way to write such code is to give the temporary a name, which +forces it to remain until the end of the scope of the name. For +example: + +@example +string& tmp = strfunc (); +charfunc (tmp.c_str ()); +@end example + +@node Copy Assignment +@subsection Implicit Copy-Assignment for Virtual Bases + +When a base class is virtual, only one subobject of the base class +belongs to each full object. Also, the constructors and destructors are +invoked only once, and called from the most-derived class. However, such +objects behave unspecified when being assigned. For example: + +@example +struct Base@{ + char *name; + Base(char *n) : name(strdup(n))@{@} + Base& operator= (const Base& other)@{ + free (name); + name = strdup (other.name); + @} +@}; + +struct A:virtual Base@{ + int val; + A():Base("A")@{@} +@}; + +struct B:virtual Base@{ + int bval; + B():Base("B")@{@} +@}; + +struct Derived:public A, public B@{ + Derived():Base("Derived")@{@} +@}; + +void func(Derived &d1, Derived &d2) +@{ + d1 = d2; +@} +@end example + +The C++ standard specifies that @samp{Base::Base} is only called once +when constructing or copy-constructing a Derived object. It is +unspecified whether @samp{Base::operator=} is called more than once when +the implicit copy-assignment for Derived objects is invoked (as it is +inside @samp{func} in the example). + +g++ implements the "intuitive" algorithm for copy-assignment: assign all +direct bases, then assign all members. In that algorithm, the virtual +base subobject can be encountered many times. In the example, copying +proceeds in the following order: @samp{val}, @samp{name} (via +@code{strdup}), @samp{bval}, and @samp{name} again. + +If application code relies on copy-assignment, a user-defined +copy-assignment operator removes any uncertainties. With such an +operator, the application can define whether and how the virtual base +subobject is assigned. + +@node Protoize Caveats +@section Caveats of using @code{protoize} + +The conversion programs @code{protoize} and @code{unprotoize} can +sometimes change a source file in a way that won't work unless you +rearrange it. + +@itemize @bullet +@item +@code{protoize} can insert references to a type name or type tag before +the definition, or in a file where they are not defined. + +If this happens, compiler error messages should show you where the new +references are, so fixing the file by hand is straightforward. + +@item +There are some C constructs which @code{protoize} cannot figure out. +For example, it can't determine argument types for declaring a +pointer-to-function variable; this you must do by hand. @code{protoize} +inserts a comment containing @samp{???} each time it finds such a +variable; so you can find all such variables by searching for this +string. ISO C does not require declaring the argument types of +pointer-to-function types. + +@item +Using @code{unprotoize} can easily introduce bugs. If the program +relied on prototypes to bring about conversion of arguments, these +conversions will not take place in the program without prototypes. +One case in which you can be sure @code{unprotoize} is safe is when +you are removing prototypes that were made with @code{protoize}; if +the program worked before without any prototypes, it will work again +without them. + +You can find all the places where this problem might occur by compiling +the program with the @samp{-Wconversion} option. It prints a warning +whenever an argument is converted. + +@item +Both conversion programs can be confused if there are macro calls in and +around the text to be converted. In other words, the standard syntax +for a declaration or definition must not result from expanding a macro. +This problem is inherent in the design of C and cannot be fixed. If +only a few functions have confusing macro calls, you can easily convert +them manually. + +@item +@code{protoize} cannot get the argument types for a function whose +definition was not actually compiled due to preprocessing conditionals. +When this happens, @code{protoize} changes nothing in regard to such +a function. @code{protoize} tries to detect such instances and warn +about them. + +You can generally work around this problem by using @code{protoize} step +by step, each time specifying a different set of @samp{-D} options for +compilation, until all of the functions have been converted. There is +no automatic way to verify that you have got them all, however. + +@item +Confusion may result if there is an occasion to convert a function +declaration or definition in a region of source code where there is more +than one formal parameter list present. Thus, attempts to convert code +containing multiple (conditionally compiled) versions of a single +function header (in the same vicinity) may not produce the desired (or +expected) results. + +If you plan on converting source files which contain such code, it is +recommended that you first make sure that each conditionally compiled +region of source code which contains an alternative function header also +contains at least one additional follower token (past the final right +parenthesis of the function header). This should circumvent the +problem. + +@item +@code{unprotoize} can become confused when trying to convert a function +definition or declaration which contains a declaration for a +pointer-to-function formal argument which has the same name as the +function being defined or declared. We recommend you avoid such choices +of formal parameter names. + +@item +You might also want to correct some of the indentation by hand and break +long lines. (The conversion programs don't write lines longer than +eighty characters in any case.) +@end itemize + +@node Non-bugs +@section Certain Changes We Don't Want to Make + +This section lists changes that people frequently request, but which +we do not make because we think GCC is better without them. + +@itemize @bullet +@item +Checking the number and type of arguments to a function which has an +old-fashioned definition and no prototype. + +Such a feature would work only occasionally---only for calls that appear +in the same file as the called function, following the definition. The +only way to check all calls reliably is to add a prototype for the +function. But adding a prototype eliminates the motivation for this +feature. So the feature is not worthwhile. + +@item +Warning about using an expression whose type is signed as a shift count. + +Shift count operands are probably signed more often than unsigned. +Warning about this would cause far more annoyance than good. + +@item +Warning about assigning a signed value to an unsigned variable. + +Such assignments must be very common; warning about them would cause +more annoyance than good. + +@item +Warning when a non-void function value is ignored. + +Coming as I do from a Lisp background, I balk at the idea that there is +something dangerous about discarding a value. There are functions that +return values which some callers may find useful; it makes no sense to +clutter the program with a cast to @code{void} whenever the value isn't +useful. + +@item +Making @samp{-fshort-enums} the default. + +This would cause storage layout to be incompatible with most other C +compilers. And it doesn't seem very important, given that you can get +the same result in other ways. The case where it matters most is when +the enumeration-valued object is inside a structure, and in that case +you can specify a field width explicitly. + +@item +Making bitfields unsigned by default on particular machines where ``the +ABI standard'' says to do so. + +The ISO C standard leaves it up to the implementation whether a bitfield +declared plain @code{int} is signed or not. This in effect creates two +alternative dialects of C. + +The GNU C compiler supports both dialects; you can specify the signed +dialect with @samp{-fsigned-bitfields} and the unsigned dialect with +@samp{-funsigned-bitfields}. However, this leaves open the question of +which dialect to use by default. + +Currently, the preferred dialect makes plain bitfields signed, because +this is simplest. Since @code{int} is the same as @code{signed int} in +every other context, it is cleanest for them to be the same in bitfields +as well. + +Some computer manufacturers have published Application Binary Interface +standards which specify that plain bitfields should be unsigned. It is +a mistake, however, to say anything about this issue in an ABI. This is +because the handling of plain bitfields distinguishes two dialects of C. +Both dialects are meaningful on every type of machine. Whether a +particular object file was compiled using signed bitfields or unsigned +is of no concern to other object files, even if they access the same +bitfields in the same data structures. + +A given program is written in one or the other of these two dialects. +The program stands a chance to work on most any machine if it is +compiled with the proper dialect. It is unlikely to work at all if +compiled with the wrong dialect. + +Many users appreciate the GNU C compiler because it provides an +environment that is uniform across machines. These users would be +inconvenienced if the compiler treated plain bitfields differently on +certain machines. + +Occasionally users write programs intended only for a particular machine +type. On these occasions, the users would benefit if the GNU C compiler +were to support by default the same dialect as the other compilers on +that machine. But such applications are rare. And users writing a +program to run on more than one type of machine cannot possibly benefit +from this kind of compatibility. + +This is why GCC does and will treat plain bitfields in the same +fashion on all types of machines (by default). + +There are some arguments for making bitfields unsigned by default on all +machines. If, for example, this becomes a universal de facto standard, +it would make sense for GCC to go along with it. This is something +to be considered in the future. + +(Of course, users strongly concerned about portability should indicate +explicitly in each bitfield whether it is signed or not. In this way, +they write programs which have the same meaning in both C dialects.) + +@item +Undefining @code{__STDC__} when @samp{-ansi} is not used. + +Currently, GCC defines @code{__STDC__} as long as you don't use +@samp{-traditional}. This provides good results in practice. + +Programmers normally use conditionals on @code{__STDC__} to ask whether +it is safe to use certain features of ISO C, such as function +prototypes or ISO token concatenation. Since plain @samp{gcc} supports +all the features of ISO C, the correct answer to these questions is +``yes''. + +Some users try to use @code{__STDC__} to check for the availability of +certain library facilities. This is actually incorrect usage in an ISO +C program, because the ISO C standard says that a conforming +freestanding implementation should define @code{__STDC__} even though it +does not have the library facilities. @samp{gcc -ansi -pedantic} is a +conforming freestanding implementation, and it is therefore required to +define @code{__STDC__}, even though it does not come with an ISO C +library. + +Sometimes people say that defining @code{__STDC__} in a compiler that +does not completely conform to the ISO C standard somehow violates the +standard. This is illogical. The standard is a standard for compilers +that claim to support ISO C, such as @samp{gcc -ansi}---not for other +compilers such as plain @samp{gcc}. Whatever the ISO C standard says +is relevant to the design of plain @samp{gcc} without @samp{-ansi} only +for pragmatic reasons, not as a requirement. + +GCC normally defines @code{__STDC__} to be 1, and in addition +defines @code{__STRICT_ANSI__} if you specify the @option{-ansi} option, +or a @option{-std} option for strict conformance to some version of ISO C. +On some hosts, system include files use a different convention, where +@code{__STDC__} is normally 0, but is 1 if the user specifies strict +conformance to the C Standard. GCC follows the host convention when +processing system include files, but when processing user files it follows +the usual GNU C convention. + +@item +Undefining @code{__STDC__} in C++. + +Programs written to compile with C++-to-C translators get the +value of @code{__STDC__} that goes with the C compiler that is +subsequently used. These programs must test @code{__STDC__} +to determine what kind of C preprocessor that compiler uses: +whether they should concatenate tokens in the ISO C fashion +or in the traditional fashion. + +These programs work properly with GNU C++ if @code{__STDC__} is defined. +They would not work otherwise. + +In addition, many header files are written to provide prototypes in ISO +C but not in traditional C. Many of these header files can work without +change in C++ provided @code{__STDC__} is defined. If @code{__STDC__} +is not defined, they will all fail, and will all need to be changed to +test explicitly for C++ as well. + +@item +Deleting ``empty'' loops. + +Historically, GCC has not deleted ``empty'' loops under the +assumption that the most likely reason you would put one in a program is +to have a delay, so deleting them will not make real programs run any +faster. + +However, the rationale here is that optimization of a nonempty loop +cannot produce an empty one, which holds for C but is not always the +case for C++. + +Moreover, with @samp{-funroll-loops} small ``empty'' loops are already +removed, so the current behavior is both sub-optimal and inconsistent +and will change in the future. + +@item +Making side effects happen in the same order as in some other compiler. + +@cindex side effects, order of evaluation +@cindex order of evaluation, side effects +It is never safe to depend on the order of evaluation of side effects. +For example, a function call like this may very well behave differently +from one compiler to another: + +@example +void func (int, int); + +int i = 2; +func (i++, i++); +@end example + +There is no guarantee (in either the C or the C++ standard language +definitions) that the increments will be evaluated in any particular +order. Either increment might happen first. @code{func} might get the +arguments @samp{2, 3}, or it might get @samp{3, 2}, or even @samp{2, 2}. + +@item +Not allowing structures with volatile fields in registers. + +Strictly speaking, there is no prohibition in the ISO C standard +against allowing structures with volatile fields in registers, but +it does not seem to make any sense and is probably not what you wanted +to do. So the compiler will give an error message in this case. + +@item +Making certain warnings into errors by default. + +Some ISO C testsuites report failure when the compiler does not produce +an error message for a certain program. + +ISO C requires a ``diagnostic'' message for certain kinds of invalid +programs, but a warning is defined by GCC to count as a diagnostic. If +GCC produces a warning but not an error, that is correct ISO C support. +If test suites call this ``failure'', they should be run with the GCC +option @samp{-pedantic-errors}, which will turn these warnings into +errors. + +@end itemize + +@node Warnings and Errors +@section Warning Messages and Error Messages + +@cindex error messages +@cindex warnings vs errors +@cindex messages, warning and error +The GNU compiler can produce two kinds of diagnostics: errors and +warnings. Each kind has a different purpose: + +@itemize @w{} +@item +@emph{Errors} report problems that make it impossible to compile your +program. GCC reports errors with the source file name and line +number where the problem is apparent. + +@item +@emph{Warnings} report other unusual conditions in your code that +@emph{may} indicate a problem, although compilation can (and does) +proceed. Warning messages also report the source file name and line +number, but include the text @samp{warning:} to distinguish them +from error messages. +@end itemize + +Warnings may indicate danger points where you should check to make sure +that your program really does what you intend; or the use of obsolete +features; or the use of nonstandard features of GNU C or C++. Many +warnings are issued only if you ask for them, with one of the @samp{-W} +options (for instance, @samp{-Wall} requests a variety of useful +warnings). + +GCC always tries to compile your program if possible; it never +gratuitously rejects a program whose meaning is clear merely because +(for instance) it fails to conform to a standard. In some cases, +however, the C and C++ standards specify that certain extensions are +forbidden, and a diagnostic @emph{must} be issued by a conforming +compiler. The @samp{-pedantic} option tells GCC to issue warnings in +such cases; @samp{-pedantic-errors} says to make them errors instead. +This does not mean that @emph{all} non-ISO constructs get warnings +or errors. + +@xref{Warning Options,,Options to Request or Suppress Warnings}, for +more detail on these and related command-line options. + +@node Bugs +@chapter Reporting Bugs +@cindex bugs +@cindex reporting bugs + +Your bug reports play an essential role in making GCC reliable. + +When you encounter a problem, the first thing to do is to see if it is +already known. @xref{Trouble}. If it isn't known, then you should +report the problem. + +Reporting a bug may help you by bringing a solution to your problem, or +it may not. (If it does not, look in the service directory; see +@ref{Service}.) In any case, the principal function of a bug report is +to help the entire community by making the next version of GCC work +better. Bug reports are your contribution to the maintenance of GCC. + +Since the maintainers are very overloaded, we cannot respond to every +bug report. However, if the bug has not been fixed, we are likely to +send you a patch and ask you to tell us whether it works. + +In order for a bug report to serve its purpose, you must include the +information that makes for fixing the bug. + +@menu +* Criteria: Bug Criteria. Have you really found a bug? +* Where: Bug Lists. Where to send your bug report. +* Reporting: Bug Reporting. How to report a bug effectively. +* GNATS: gccbug. You can use a bug reporting tool. +* Patches: Sending Patches. How to send a patch for GCC. +* Known: Trouble. Known problems. +* Help: Service. Where to ask for help. +@end menu + +@node Bug Criteria,Bug Lists,,Bugs +@section Have You Found a Bug? +@cindex bug criteria + +If you are not sure whether you have found a bug, here are some guidelines: + +@itemize @bullet +@cindex fatal signal +@cindex core dump +@item +If the compiler gets a fatal signal, for any input whatever, that is a +compiler bug. Reliable compilers never crash. + +@cindex invalid assembly code +@cindex assembly code, invalid +@item +If the compiler produces invalid assembly code, for any input whatever +(except an @code{asm} statement), that is a compiler bug, unless the +compiler reports errors (not just warnings) which would ordinarily +prevent the assembler from being run. + +@cindex undefined behavior +@cindex undefined function value +@cindex increment operators +@item +If the compiler produces valid assembly code that does not correctly +execute the input source code, that is a compiler bug. + +However, you must double-check to make sure, because you may have run +into an incompatibility between GNU C and traditional C +(@pxref{Incompatibilities}). These incompatibilities might be considered +bugs, but they are inescapable consequences of valuable features. + +Or you may have a program whose behavior is undefined, which happened +by chance to give the desired results with another C or C++ compiler. + +For example, in many nonoptimizing compilers, you can write @samp{x;} +at the end of a function instead of @samp{return x;}, with the same +results. But the value of the function is undefined if @code{return} +is omitted; it is not a bug when GCC produces different results. + +Problems often result from expressions with two increment operators, +as in @code{f (*p++, *p++)}. Your previous compiler might have +interpreted that expression the way you intended; GCC might +interpret it another way. Neither compiler is wrong. The bug is +in your code. + +After you have localized the error to a single source line, it should +be easy to check for these things. If your program is correct and +well defined, you have found a compiler bug. + +@item +If the compiler produces an error message for valid input, that is a +compiler bug. + +@cindex invalid input +@item +If the compiler does not produce an error message for invalid input, +that is a compiler bug. However, you should note that your idea of +``invalid input'' might be my idea of ``an extension'' or ``support +for traditional practice''. + +@item +If you are an experienced user of one of the languages GCC supports, your +suggestions for improvement of GCC are welcome in any case. +@end itemize + +@node Bug Lists,Bug Reporting,Bug Criteria,Bugs +@section Where to Report Bugs +@cindex bug report mailing lists +@kindex gcc-bugs@@gcc.gnu.org or bug-gcc@@gnu.org +Send bug reports for the GNU Compiler Collection to +@email{gcc-bugs@@gcc.gnu.org}. In accordance with the GNU-wide +convention, in which bug reports for tool ``foo'' are sent +to @samp{bug-foo@@gnu.org}, the address @email{bug-gcc@@gnu.org} +may also be used; it will forward to the address given above. + +Please read @uref{http://gcc.gnu.org/bugs.html} for additional and/or +more up-to-date bug reporting instructions before you post a bug report. + +@node Bug Reporting,gccbug,Bug Lists,Bugs +@section How to Report Bugs +@cindex compiler bugs, reporting + +The fundamental principle of reporting bugs usefully is this: +@strong{report all the facts}. If you are not sure whether to state a +fact or leave it out, state it! + +Often people omit facts because they think they know what causes the +problem and they conclude that some details don't matter. Thus, you might +assume that the name of the variable you use in an example does not matter. +Well, probably it doesn't, but one cannot be sure. Perhaps the bug is a +stray memory reference which happens to fetch from the location where that +name is stored in memory; perhaps, if the name were different, the contents +of that location would fool the compiler into doing the right thing despite +the bug. Play it safe and give a specific, complete example. That is the +easiest thing for you to do, and the most helpful. + +Keep in mind that the purpose of a bug report is to enable someone to +fix the bug if it is not known. It isn't very important what happens if +the bug is already known. Therefore, always write your bug reports on +the assumption that the bug is not known. + +Sometimes people give a few sketchy facts and ask, ``Does this ring a +bell?'' This cannot help us fix a bug, so it is basically useless. We +respond by asking for enough details to enable us to investigate. +You might as well expedite matters by sending them to begin with. + +Try to make your bug report self-contained. If we have to ask you for +more information, it is best if you include all the previous information +in your response, as well as the information that was missing. + +Please report each bug in a separate message. This makes it easier for +us to track which bugs have been fixed and to forward your bugs reports +to the appropriate maintainer. + +To enable someone to investigate the bug, you should include all these +things: + +@itemize @bullet +@item +The version of GCC. You can get this by running it with the +@samp{-v} option. + +Without this, we won't know whether there is any point in looking for +the bug in the current version of GCC. + +@item +A complete input file that will reproduce the bug. If the bug is in the +C preprocessor, send a source file and any header files that it +requires. If the bug is in the compiler proper (@file{cc1}), send the +preprocessor output generated by adding @samp{-save-temps} to the +compilation command (@pxref{Debugging Options}). When you do this, use +the same @samp{-I}, @samp{-D} or @samp{-U} options that you used in +actual compilation. Then send the @var{input}.i or @var{input}.ii files +generated. + +A single statement is not enough of an example. In order to compile it, +it must be embedded in a complete file of compiler input; and the bug +might depend on the details of how this is done. + +Without a real example one can compile, all anyone can do about your bug +report is wish you luck. It would be futile to try to guess how to +provoke the bug. For example, bugs in register allocation and reloading +frequently depend on every little detail of the function they happen in. + +Even if the input file that fails comes from a GNU program, you should +still send the complete test case. Don't ask the GCC maintainers to +do the extra work of obtaining the program in question---they are all +overworked as it is. Also, the problem may depend on what is in the +header files on your system; it is unreliable for the GCC maintainers +to try the problem with the header files available to them. By sending +CPP output, you can eliminate this source of uncertainty and save us +a certain percentage of wild goose chases. + +@item +The command arguments you gave GCC to compile that example +and observe the bug. For example, did you use @samp{-O}? To guarantee +you won't omit something important, list all the options. + +If we were to try to guess the arguments, we would probably guess wrong +and then we would not encounter the bug. + +@item +The type of machine you are using, and the operating system name and +version number. + +@item +The operands you gave to the @code{configure} command when you installed +the compiler. + +@item +A complete list of any modifications you have made to the compiler +source. (We don't promise to investigate the bug unless it happens in +an unmodified compiler. But if you've made modifications and don't tell +us, then you are sending us on a wild goose chase.) + +Be precise about these changes. A description in English is not +enough---send a context diff for them. + +Adding files of your own (such as a machine description for a machine we +don't support) is a modification of the compiler source. + +@item +Details of any other deviations from the standard procedure for installing +GCC. + +@item +A description of what behavior you observe that you believe is +incorrect. For example, ``The compiler gets a fatal signal,'' or, +``The assembler instruction at line 208 in the output is incorrect.'' + +Of course, if the bug is that the compiler gets a fatal signal, then one +can't miss it. But if the bug is incorrect output, the maintainer might +not notice unless it is glaringly wrong. None of us has time to study +all the assembler code from a 50-line C program just on the chance that +one instruction might be wrong. We need @emph{you} to do this part! + +Even if the problem you experience is a fatal signal, you should still +say so explicitly. Suppose something strange is going on, such as, your +copy of the compiler is out of synch, or you have encountered a bug in +the C library on your system. (This has happened!) Your copy might +crash and the copy here would not. If you @i{said} to expect a crash, +then when the compiler here fails to crash, we would know that the bug +was not happening. If you don't say to expect a crash, then we would +not know whether the bug was happening. We would not be able to draw +any conclusion from our observations. + +If the problem is a diagnostic when compiling GCC with some other +compiler, say whether it is a warning or an error. + +Often the observed symptom is incorrect output when your program is run. +Sad to say, this is not enough information unless the program is short +and simple. None of us has time to study a large program to figure out +how it would work if compiled correctly, much less which line of it was +compiled wrong. So you will have to do that. Tell us which source line +it is, and what incorrect result happens when that line is executed. A +person who understands the program can find this as easily as finding a +bug in the program itself. + +@item +If you send examples of assembler code output from GCC, +please use @samp{-g} when you make them. The debugging information +includes source line numbers which are essential for correlating the +output with the input. + +@item +If you wish to mention something in the GCC source, refer to it by +context, not by line number. + +The line numbers in the development sources don't match those in your +sources. Your line numbers would convey no useful information to the +maintainers. + +@item +Additional information from a debugger might enable someone to find a +problem on a machine which he does not have available. However, you +need to think when you collect this information if you want it to have +any chance of being useful. + +@cindex backtrace for bug reports +For example, many people send just a backtrace, but that is never +useful by itself. A simple backtrace with arguments conveys little +about GCC because the compiler is largely data-driven; the same +functions are called over and over for different RTL insns, doing +different things depending on the details of the insn. + +Most of the arguments listed in the backtrace are useless because they +are pointers to RTL list structure. The numeric values of the +pointers, which the debugger prints in the backtrace, have no +significance whatever; all that matters is the contents of the objects +they point to (and most of the contents are other such pointers). + +In addition, most compiler passes consist of one or more loops that +scan the RTL insn sequence. The most vital piece of information about +such a loop---which insn it has reached---is usually in a local variable, +not in an argument. + +@findex debug_rtx +What you need to provide in addition to a backtrace are the values of +the local variables for several stack frames up. When a local +variable or an argument is an RTX, first print its value and then use +the GDB command @code{pr} to print the RTL expression that it points +to. (If GDB doesn't run on your machine, use your debugger to call +the function @code{debug_rtx} with the RTX as an argument.) In +general, whenever a variable is a pointer, its value is no use +without the data it points to. +@end itemize + +Here are some things that are not necessary: + +@itemize @bullet +@item +A description of the envelope of the bug. + +Often people who encounter a bug spend a lot of time investigating +which changes to the input file will make the bug go away and which +changes will not affect it. + +This is often time consuming and not very useful, because the way we +will find the bug is by running a single example under the debugger with +breakpoints, not by pure deduction from a series of examples. You might +as well save your time for something else. + +Of course, if you can find a simpler example to report @emph{instead} of +the original one, that is a convenience. Errors in the output will be +easier to spot, running under the debugger will take less time, etc. +Most GCC bugs involve just one function, so the most straightforward +way to simplify an example is to delete all the function definitions +except the one where the bug occurs. Those earlier in the file may be +replaced by external declarations if the crucial function depends on +them. (Exception: inline functions may affect compilation of functions +defined later in the file.) + +However, simplification is not vital; if you don't want to do this, +report the bug anyway and send the entire test case you used. + +@item +In particular, some people insert conditionals @samp{#ifdef BUG} around +a statement which, if removed, makes the bug not happen. These are just +clutter; we won't pay any attention to them anyway. Besides, you should +send us cpp output, and that can't have conditionals. + +@item +A patch for the bug. + +A patch for the bug is useful if it is a good one. But don't omit the +necessary information, such as the test case, on the assumption that a +patch is all we need. We might see problems with your patch and decide +to fix the problem another way, or we might not understand it at all. + +Sometimes with a program as complicated as GCC it is very hard to +construct an example that will make the program follow a certain path +through the code. If you don't send the example, we won't be able to +construct one, so we won't be able to verify that the bug is fixed. + +And if we can't understand what bug you are trying to fix, or why your +patch should be an improvement, we won't install it. A test case will +help us to understand. + +@xref{Sending Patches}, for guidelines on how to make it easy for us to +understand and install your patches. + +@item +A guess about what the bug is or what it depends on. + +Such guesses are usually wrong. Even I can't guess right about such +things without first using the debugger to find the facts. + +@item +A core dump file. + +We have no way of examining a core dump for your type of machine +unless we have an identical system---and if we do have one, +we should be able to reproduce the crash ourselves. +@end itemize + +@node gccbug,Sending Patches, Bug Reporting, Bugs +@section The gccbug script +@cindex gccbug script + +To simplify creation of bug reports, and to allow better tracking of +reports, we use the GNATS bug tracking system. Part of that system is +the @code{gccbug} script. This is a Unix shell script, so you need a +shell to run it. It is normally installed in the same directory where +@code{gcc} is installed. + +The gccbug script is derived from send-pr, @pxref{using +send-pr,,Creating new Problem Reports,send-pr,Reporting Problems}. When +invoked, it starts a text editor so you can fill out the various fields +of the report. When the you quit the editor, the report is automatically +send to the bug reporting address. + +A number of fields in this bug report form are specific to GCC, and are +explained at @uref{http://gcc.gnu.org/gnats.html}. + +@node Sending Patches,, gccbug, Bugs +@section Sending Patches for GCC + +If you would like to write bug fixes or improvements for the GNU C +compiler, that is very helpful. Send suggested fixes to the patches +mailing list, @email{gcc-patches@@gcc.gnu.org}. + +Please follow these guidelines so we can study your patches efficiently. +If you don't follow these guidelines, your information might still be +useful, but using it will take extra work. Maintaining GNU C is a lot +of work in the best of circumstances, and we can't keep up unless you do +your best to help. + +@itemize @bullet +@item +Send an explanation with your changes of what problem they fix or what +improvement they bring about. For a bug fix, just include a copy of the +bug report, and explain why the change fixes the bug. + +(Referring to a bug report is not as good as including it, because then +we will have to look it up, and we have probably already deleted it if +we've already fixed the bug.) + +@item +Always include a proper bug report for the problem you think you have +fixed. We need to convince ourselves that the change is right before +installing it. Even if it is right, we might have trouble judging it if +we don't have a way to reproduce the problem. + +@item +Include all the comments that are appropriate to help people reading the +source in the future understand why this change was needed. + +@item +Don't mix together changes made for different reasons. +Send them @emph{individually}. + +If you make two changes for separate reasons, then we might not want to +install them both. We might want to install just one. If you send them +all jumbled together in a single set of diffs, we have to do extra work +to disentangle them---to figure out which parts of the change serve +which purpose. If we don't have time for this, we might have to ignore +your changes entirely. + +If you send each change as soon as you have written it, with its own +explanation, then the two changes never get tangled up, and we can +consider each one properly without any extra work to disentangle them. + +Ideally, each change you send should be impossible to subdivide into +parts that we might want to consider separately, because each of its +parts gets its motivation from the other parts. + +@item +Send each change as soon as that change is finished. Sometimes people +think they are helping us by accumulating many changes to send them all +together. As explained above, this is absolutely the worst thing you +could do. + +Since you should send each change separately, you might as well send it +right away. That gives us the option of installing it immediately if it +is important. + +@item +Use @samp{diff -c} to make your diffs. Diffs without context are hard +for us to install reliably. More than that, they make it hard for us to +study the diffs to decide whether we want to install them. Unidiff +format is better than contextless diffs, but not as easy to read as +@samp{-c} format. + +If you have GNU diff, use @samp{diff -cp}, which shows the name of the +function that each change occurs in. + +@item +Write the change log entries for your changes. We get lots of changes, +and we don't have time to do all the change log writing ourselves. + +Read the @file{ChangeLog} file to see what sorts of information to put +in, and to learn the style that we use. The purpose of the change log +is to show people where to find what was changed. So you need to be +specific about what functions you changed; in large functions, it's +often helpful to indicate where within the function the change was. + +On the other hand, once you have shown people where to find the change, +you need not explain its purpose. Thus, if you add a new function, all +you need to say about it is that it is new. If you feel that the +purpose needs explaining, it probably does---but the explanation will be +much more useful if you put it in comments in the code. + +If you would like your name to appear in the header line for who made +the change, send us the header line. + +@item +When you write the fix, keep in mind that we can't install a change that +would break other systems. + +People often suggest fixing a problem by changing machine-independent +files such as @file{toplev.c} to do something special that a particular +system needs. Sometimes it is totally obvious that such changes would +break GCC for almost all users. We can't possibly make a change like +that. At best it might tell us how to write another patch that would +solve the problem acceptably. + +Sometimes people send fixes that @emph{might} be an improvement in +general---but it is hard to be sure of this. It's hard to install +such changes because we have to study them very carefully. Of course, +a good explanation of the reasoning by which you concluded the change +was correct can help convince us. + +The safest changes are changes to the configuration files for a +particular machine. These are safe because they can't create new bugs +on other machines. + +Please help us keep up with the workload by designing the patch in a +form that is good to install. +@end itemize + +@node Service +@chapter How To Get Help with GCC + +If you need help installing, using or changing GCC, there are two +ways to find it: + +@itemize @bullet +@item +Send a message to a suitable network mailing list. First try +@email{gcc-help@@gcc.gnu.org} (for help installing or using GCC), and if +that brings no response, try @email{gcc@@gcc.gnu.org}. For help +changing GCC, ask @email{gcc@@gcc.gnu.org}. If you think you have found +a bug in GCC, please report it following the instructions at +@pxref{Bug Reporting}. + +@item +Look in the service directory for someone who might help you for a fee. +The service directory is found at +@uref{http://www.gnu.org/prep/service.html}. +@end itemize + +@c For further information, see +@c @uref{http://gcc.gnu.org/cgi-bin/fom.cgi?file=12}. +@c FIXME: this URL may be too volatile, this FAQ entry needs to move to +@c the regular web pages before we can uncomment the reference. + +@node Contributing +@chapter Contributing to GCC Development + +If you would like to help pretest GCC releases to assure they work well, +our current development sources are available by CVS (see +@uref{http://gcc.gnu.org/cvs.html}). Source and binary snapshots are +also available for FTP; see @uref{http://gcc.gnu.org/snapshots.html}. + +If you would like to work on improvements to GCC, please read +@uref{http://gcc.gnu.org/contribute.html} and +@uref{http://gcc.gnu.org/contributewhy.html} for information on how to +make useful contributions and avoid duplication of effort. Suggested +projects are listed at @uref{http://gcc.gnu.org/projects/}. + +@node VMS +@chapter Using GCC on VMS + +@c prevent bad page break with this line +Here is how to use GCC on VMS. + +@menu +* Include Files and VMS:: Where the preprocessor looks for the include files. +* Global Declarations:: How to do globaldef, globalref and globalvalue with + GCC. +* VMS Misc:: Misc information. +@end menu + +@node Include Files and VMS +@section Include Files and VMS + +@cindex include files and VMS +@cindex VMS and include files +@cindex header files and VMS +Due to the differences between the filesystems of Unix and VMS, GCC +attempts to translate file names in @samp{#include} into names that VMS +will understand. The basic strategy is to prepend a prefix to the +specification of the include file, convert the whole filename to a VMS +filename, and then try to open the file. GCC tries various prefixes +one by one until one of them succeeds: + +@enumerate +@item +The first prefix is the @samp{GNU_CC_INCLUDE:} logical name: this is +where GNU C header files are traditionally stored. If you wish to store +header files in non-standard locations, then you can assign the logical +@samp{GNU_CC_INCLUDE} to be a search list, where each element of the +list is suitable for use with a rooted logical. + +@item +The next prefix tried is @samp{SYS$SYSROOT:[SYSLIB.]}. This is where +VAX-C header files are traditionally stored. + +@item +If the include file specification by itself is a valid VMS filename, the +preprocessor then uses this name with no prefix in an attempt to open +the include file. + +@item +If the file specification is not a valid VMS filename (i.e. does not +contain a device or a directory specifier, and contains a @samp{/} +character), the preprocessor tries to convert it from Unix syntax to +VMS syntax. + +Conversion works like this: the first directory name becomes a device, +and the rest of the directories are converted into VMS-format directory +names. For example, the name @file{X11/foobar.h} is +translated to @file{X11:[000000]foobar.h} or @file{X11:foobar.h}, +whichever one can be opened. This strategy allows you to assign a +logical name to point to the actual location of the header files. + +@item +If none of these strategies succeeds, the @samp{#include} fails. +@end enumerate + +Include directives of the form: + +@example +#include foobar +@end example + +@noindent +are a common source of incompatibility between VAX-C and GCC. VAX-C +treats this much like a standard @code{#include } directive. +That is incompatible with the ISO C behavior implemented by GCC: to +expand the name @code{foobar} as a macro. Macro expansion should +eventually yield one of the two standard formats for @code{#include}: + +@example +#include "@var{file}" +#include <@var{file}> +@end example + +If you have this problem, the best solution is to modify the source to +convert the @code{#include} directives to one of the two standard forms. +That will work with either compiler. If you want a quick and dirty fix, +define the file names as macros with the proper expansion, like this: + +@example +#define stdio +@end example + +@noindent +This will work, as long as the name doesn't conflict with anything else +in the program. + +Another source of incompatibility is that VAX-C assumes that: + +@example +#include "foobar" +@end example + +@noindent +is actually asking for the file @file{foobar.h}. GCC does not +make this assumption, and instead takes what you ask for literally; +it tries to read the file @file{foobar}. The best way to avoid this +problem is to always specify the desired file extension in your include +directives. + +GCC for VMS is distributed with a set of include files that is +sufficient to compile most general purpose programs. Even though the +GCC distribution does not contain header files to define constants +and structures for some VMS system-specific functions, there is no +reason why you cannot use GCC with any of these functions. You first +may have to generate or create header files, either by using the public +domain utility @code{UNSDL} (which can be found on a DECUS tape), or by +extracting the relevant modules from one of the system macro libraries, +and using an editor to construct a C header file. + +A @code{#include} file name cannot contain a DECNET node name. The +preprocessor reports an I/O error if you attempt to use a node name, +whether explicitly, or implicitly via a logical name. + +@node Global Declarations +@section Global Declarations and VMS + +@findex GLOBALREF +@findex GLOBALDEF +@findex GLOBALVALUEDEF +@findex GLOBALVALUEREF +GCC does not provide the @code{globalref}, @code{globaldef} and +@code{globalvalue} keywords of VAX-C. You can get the same effect with +an obscure feature of GAS, the GNU assembler. (This requires GAS +version 1.39 or later.) The following macros allow you to use this +feature in a fairly natural way: + +@smallexample +#ifdef __GNUC__ +#define GLOBALREF(TYPE,NAME) \ + TYPE NAME \ + asm ("_$$PsectAttributes_GLOBALSYMBOL$$" #NAME) +#define GLOBALDEF(TYPE,NAME,VALUE) \ + TYPE NAME \ + asm ("_$$PsectAttributes_GLOBALSYMBOL$$" #NAME) \ + = VALUE +#define GLOBALVALUEREF(TYPE,NAME) \ + const TYPE NAME[1] \ + asm ("_$$PsectAttributes_GLOBALVALUE$$" #NAME) +#define GLOBALVALUEDEF(TYPE,NAME,VALUE) \ + const TYPE NAME[1] \ + asm ("_$$PsectAttributes_GLOBALVALUE$$" #NAME) \ + = @{VALUE@} +#else +#define GLOBALREF(TYPE,NAME) \ + globalref TYPE NAME +#define GLOBALDEF(TYPE,NAME,VALUE) \ + globaldef TYPE NAME = VALUE +#define GLOBALVALUEDEF(TYPE,NAME,VALUE) \ + globalvalue TYPE NAME = VALUE +#define GLOBALVALUEREF(TYPE,NAME) \ + globalvalue TYPE NAME +#endif +@end smallexample + +@noindent +(The @code{_$$PsectAttributes_GLOBALSYMBOL} prefix at the start of the +name is removed by the assembler, after it has modified the attributes +of the symbol). These macros are provided in the VMS binaries +distribution in a header file @file{GNU_HACKS.H}. An example of the +usage is: + +@example +GLOBALREF (int, ijk); +GLOBALDEF (int, jkl, 0); +@end example + +The macros @code{GLOBALREF} and @code{GLOBALDEF} cannot be used +straightforwardly for arrays, since there is no way to insert the array +dimension into the declaration at the right place. However, you can +declare an array with these macros if you first define a typedef for the +array type, like this: + +@example +typedef int intvector[10]; +GLOBALREF (intvector, foo); +@end example + +Array and structure initializers will also break the macros; you can +define the initializer to be a macro of its own, or you can expand the +@code{GLOBALDEF} macro by hand. You may find a case where you wish to +use the @code{GLOBALDEF} macro with a large array, but you are not +interested in explicitly initializing each element of the array. In +such cases you can use an initializer like: @code{@{0,@}}, which will +initialize the entire array to @code{0}. + +A shortcoming of this implementation is that a variable declared with +@code{GLOBALVALUEREF} or @code{GLOBALVALUEDEF} is always an array. For +example, the declaration: + +@example +GLOBALVALUEREF(int, ijk); +@end example + +@noindent +declares the variable @code{ijk} as an array of type @code{int [1]}. +This is done because a globalvalue is actually a constant; its ``value'' +is what the linker would normally consider an address. That is not how +an integer value works in C, but it is how an array works. So treating +the symbol as an array name gives consistent results---with the +exception that the value seems to have the wrong type. @strong{Don't +try to access an element of the array.} It doesn't have any elements. +The array ``address'' may not be the address of actual storage. + +The fact that the symbol is an array may lead to warnings where the +variable is used. Insert type casts to avoid the warnings. Here is an +example; it takes advantage of the ISO C feature allowing macros that +expand to use the same name as the macro itself. + +@example +GLOBALVALUEREF (int, ss$_normal); +GLOBALVALUEDEF (int, xyzzy,123); +#ifdef __GNUC__ +#define ss$_normal ((int) ss$_normal) +#define xyzzy ((int) xyzzy) +#endif +@end example + +Don't use @code{globaldef} or @code{globalref} with a variable whose +type is an enumeration type; this is not implemented. Instead, make the +variable an integer, and use a @code{globalvaluedef} for each of the +enumeration values. An example of this would be: + +@example +#ifdef __GNUC__ +GLOBALDEF (int, color, 0); +GLOBALVALUEDEF (int, RED, 0); +GLOBALVALUEDEF (int, BLUE, 1); +GLOBALVALUEDEF (int, GREEN, 3); +#else +enum globaldef color @{RED, BLUE, GREEN = 3@}; +#endif +@end example + +@node VMS Misc +@section Other VMS Issues + +@cindex exit status and VMS +@cindex return value of @code{main} +@cindex @code{main} and the exit status +GCC automatically arranges for @code{main} to return 1 by default if +you fail to specify an explicit return value. This will be interpreted +by VMS as a status code indicating a normal successful completion. +Version 1 of GCC did not provide this default. + +GCC on VMS works only with the GNU assembler, GAS. You need version +1.37 or later of GAS in order to produce value debugging information for +the VMS debugger. Use the ordinary VMS linker with the object files +produced by GAS. + +@cindex shared VMS run time system +@cindex @file{VAXCRTL} +Under previous versions of GCC, the generated code would occasionally +give strange results when linked to the sharable @file{VAXCRTL} library. +Now this should work. + +A caveat for use of @code{const} global variables: the @code{const} +modifier must be specified in every external declaration of the variable +in all of the source files that use that variable. Otherwise the linker +will issue warnings about conflicting attributes for the variable. Your +program will still work despite the warnings, but the variable will be +placed in writable storage. + +@cindex name augmentation +@cindex case sensitivity and VMS +@cindex VMS and case sensitivity +Although the VMS linker does distinguish between upper and lower case +letters in global symbols, most VMS compilers convert all such symbols +into upper case and most run-time library routines also have upper case +names. To be able to reliably call such routines, GCC (by means of +the assembler GAS) converts global symbols into upper case like other +VMS compilers. However, since the usual practice in C is to distinguish +case, GCC (via GAS) tries to preserve usual C behavior by augmenting +each name that is not all lower case. This means truncating the name +to at most 23 characters and then adding more characters at the end +which encode the case pattern of those 23. Names which contain at +least one dollar sign are an exception; they are converted directly into +upper case without augmentation. + +Name augmentation yields bad results for programs that use precompiled +libraries (such as Xlib) which were generated by another compiler. You +can use the compiler option @samp{/NOCASE_HACK} to inhibit augmentation; +it makes external C functions and variables case-independent as is usual +on VMS. Alternatively, you could write all references to the functions +and variables in such libraries using lower case; this will work on VMS, +but is not portable to other systems. The compiler option @samp{/NAMES} +also provides control over global name handling. + +Function and variable names are handled somewhat differently with GNU +C++. The GNU C++ compiler performs @dfn{name mangling} on function +names, which means that it adds information to the function name to +describe the data types of the arguments that the function takes. One +result of this is that the name of a function can become very long. +Since the VMS linker only recognizes the first 31 characters in a name, +special action is taken to ensure that each function and variable has a +unique name that can be represented in 31 characters. + +If the name (plus a name augmentation, if required) is less than 32 +characters in length, then no special action is performed. If the name +is longer than 31 characters, the assembler (GAS) will generate a +hash string based upon the function name, truncate the function name to +23 characters, and append the hash string to the truncated name. If the +@samp{/VERBOSE} compiler option is used, the assembler will print both +the full and truncated names of each symbol that is truncated. + +The @samp{/NOCASE_HACK} compiler option should not be used when you are +compiling programs that use libg++. libg++ has several instances of +objects (i.e. @code{Filebuf} and @code{filebuf}) which become +indistinguishable in a case-insensitive environment. This leads to +cases where you need to inhibit augmentation selectively (if you were +using libg++ and Xlib in the same program, for example). There is no +special feature for doing this, but you can get the result by defining a +macro for each mixed case symbol for which you wish to inhibit +augmentation. The macro should expand into the lower case equivalent of +itself. For example: + +@example +#define StuDlyCapS studlycaps +@end example + +These macro definitions can be placed in a header file to minimize the +number of changes to your source code. + +@node Makefile +@chapter Makefile Targets +@cindex makefile targets +@cindex targets, makefile + +@table @code +@item all +This is the default target. Depending on what your build/host/target +configuration is, it coordinates all the things that need to be built. + +@item doc +Produce info-formatted documentation. Also, @code{make dvi} is +available for DVI-formatted documentation, and @code{make +generated-manpages} to generate man pages. + +@item mostlyclean +Delete the files made while building the compiler. + +@item clean +That, and all the other files built by @code{make all}. + +@item distclean +That, and all the files created by @code{configure}. + +@item extraclean +That, and any temporary or intermediate files, like emacs backup files. + +@item maintainer-clean +Distclean plus any file that can be generated from other files. Note +that additional tools may be required beyond what is normally needed to +build gcc. + +@item install +Installs gcc. + +@item uninstall +Deletes installed files. + +@item check +Run the testsuite. This creates a @file{testsuite} subdirectory that +has various @file{.sum} and @file{.log} files containing the results of +the testing. You can run subsets with, for example, @code{make check-gcc}. +You can specify specific tests by setting RUNTESTFLAGS to be the name +of the @file{.exp} file, optionally followed by (for some tests) an equals +and a file wildcard, like: + +@example +make check-gcc RUNTESTFLAGS="execute.exp=19980413-*" +@end example + +Note that running the testsuite may require additional tools be +installed, such as TCL or dejagnu. + +@item bootstrap +Builds gcc three times - once with the native compiler, once with the +native-built compiler it just built, and once with the compiler it built +the second time. In theory, the last two should produce the same +results, which @code{make compare} can check. Each step of this process +is called a "stage", and the results of each stage N (N=1..3) are copied +to a subdirectory @file{stageN/}. + +@item bootstrap-lean +Like @code{bootstrap}, except that the various stages are removed once +they're no longer needed. This saves disk space. + +@item bubblestrap +Once bootstrapped, this incrementally rebuilds each of the three stages, +one at a time. It does this by "bubbling" the stages up from their +stubdirectories, rebuilding them, and copying them back to their +subdirectories. This will allow you to, for example, quickly rebuild a +bootstrapped compiler after changing the sources, without having to do a +full bootstrap. + +@item quickstrap +Rebuilds the most recently built stage. Since each stage requires +special invocation, using this target means you don't have to keep track +of which stage you're on or what invocation that stage needs. + +@item cleanstrap +Removed everything (@code{make clean}) and rebuilds (@code{make bootstrap}). + +@item stageN (N=1..4) +For each stage, moves the appropriate files to the stageN subdirectory. + +@item unstageN (N=1..4) +Undoes the corresponding @code{stageN}. + +@item restageN (N=1..4) +Undoes the corresponding @code{stageN} and rebuilds it with the +appropriate flags. + +@item compare +Compares the results of stages 2 and 3. This ensures that the compiler +is running properly, since it should produce the same object files +regardless of how it itself was compiled. + +@end table + +@end ifset + +@ifset INTERNALS +@node Portability +@chapter GCC and Portability +@cindex portability +@cindex GCC and portability + +The main goal of GCC was to make a good, fast compiler for machines in +the class that the GNU system aims to run on: 32-bit machines that address +8-bit bytes and have several general registers. Elegance, theoretical +power and simplicity are only secondary. + +GCC gets most of the information about the target machine from a machine +description which gives an algebraic formula for each of the machine's +instructions. This is a very clean way to describe the target. But when +the compiler needs information that is difficult to express in this +fashion, I have not hesitated to define an ad-hoc parameter to the machine +description. The purpose of portability is to reduce the total work needed +on the compiler; it was not of interest for its own sake. + +@cindex endianness +@cindex autoincrement addressing, availability +@findex abort +GCC does not contain machine dependent code, but it does contain code +that depends on machine parameters such as endianness (whether the most +significant byte has the highest or lowest address of the bytes in a word) +and the availability of autoincrement addressing. In the RTL-generation +pass, it is often necessary to have multiple strategies for generating code +for a particular kind of syntax tree, strategies that are usable for different +combinations of parameters. Often I have not tried to address all possible +cases, but only the common ones or only the ones that I have encountered. +As a result, a new target may require additional strategies. You will know +if this happens because the compiler will call @code{abort}. Fortunately, +the new strategies can be added in a machine-independent fashion, and will +affect only the target machines that need them. +@end ifset + +@ifset INTERNALS +@node Interface +@chapter Interfacing to GCC Output +@cindex interfacing to GCC output +@cindex run-time conventions +@cindex function call conventions +@cindex conventions, run-time + +GCC is normally configured to use the same function calling convention +normally in use on the target system. This is done with the +machine-description macros described (@pxref{Target Macros}). + +@cindex unions, returning +@cindex structures, returning +@cindex returning structures and unions +However, returning of structure and union values is done differently on +some target machines. As a result, functions compiled with PCC +returning such types cannot be called from code compiled with GCC, +and vice versa. This does not cause trouble often because few Unix +library routines return structures or unions. + +GCC code returns structures and unions that are 1, 2, 4 or 8 bytes +long in the same registers used for @code{int} or @code{double} return +values. (GCC typically allocates variables of such types in +registers also.) Structures and unions of other sizes are returned by +storing them into an address passed by the caller (usually in a +register). The machine-description macros @code{STRUCT_VALUE} and +@code{STRUCT_INCOMING_VALUE} tell GCC where to pass this address. + +By contrast, PCC on most target machines returns structures and unions +of any size by copying the data into an area of static storage, and then +returning the address of that storage as if it were a pointer value. +The caller must copy the data from that memory area to the place where +the value is wanted. This is slower than the method used by GCC, and +fails to be reentrant. + +On some target machines, such as RISC machines and the 80386, the +standard system convention is to pass to the subroutine the address of +where to return the value. On these machines, GCC has been +configured to be compatible with the standard compiler, when this method +is used. It may not be compatible for structures of 1, 2, 4 or 8 bytes. + +@cindex argument passing +@cindex passing arguments +GCC uses the system's standard convention for passing arguments. On +some machines, the first few arguments are passed in registers; in +others, all are passed on the stack. It would be possible to use +registers for argument passing on any machine, and this would probably +result in a significant speedup. But the result would be complete +incompatibility with code that follows the standard convention. So this +change is practical only if you are switching to GCC as the sole C +compiler for the system. We may implement register argument passing on +certain machines once we have a complete GNU system so that we can +compile the libraries with GCC. + +On some machines (particularly the Sparc), certain types of arguments +are passed ``by invisible reference''. This means that the value is +stored in memory, and the address of the memory location is passed to +the subroutine. + +@cindex @code{longjmp} and automatic variables +If you use @code{longjmp}, beware of automatic variables. ISO C says that +automatic variables that are not declared @code{volatile} have undefined +values after a @code{longjmp}. And this is all GCC promises to do, +because it is very difficult to restore register variables correctly, and +one of GCC's features is that it can put variables in registers without +your asking it to. + +If you want a variable to be unaltered by @code{longjmp}, and you don't +want to write @code{volatile} because old C compilers don't accept it, +just take the address of the variable. If a variable's address is ever +taken, even if just to compute it and ignore it, then the variable cannot +go in a register: + +@example +@{ + int careful; + &careful; + @dots{} +@} +@end example + +@cindex arithmetic libraries +@cindex math libraries +Code compiled with GCC may call certain library routines. Most of +them handle arithmetic for which there are no instructions. This +includes multiply and divide on some machines, and floating point +operations on any machine for which floating point support is disabled +with @samp{-msoft-float}. Some standard parts of the C library, such as +@code{bcopy} or @code{memcpy}, are also called automatically. The usual +function call interface is used for calling the library routines. + +Some of these routines can be defined in mostly machine-independent C; +they appear in @file{libgcc2.c}. Others must be hand-written in +assembly language for each processor. Wherever they are defined, they +are compiled into the support library, @file{libgcc.a}, which is +automatically searched when you link programs with GCC. +@end ifset + +@ifset INTERNALS +@node Passes +@chapter Passes and Files of the Compiler +@cindex passes and files of the compiler +@cindex files and passes of the compiler +@cindex compiler passes and files + +@cindex top level of compiler +The overall control structure of the compiler is in @file{toplev.c}. This +file is responsible for initialization, decoding arguments, opening and +closing files, and sequencing the passes. + +@cindex parsing pass +The parsing pass is invoked only once, to parse the entire input. The RTL +intermediate code for a function is generated as the function is parsed, a +statement at a time. Each statement is read in as a syntax tree and then +converted to RTL; then the storage for the tree for the statement is +reclaimed. Storage for types (and the expressions for their sizes), +declarations, and a representation of the binding contours and how they nest, +remain until the function is finished being compiled; these are all needed +to output the debugging information. + +@findex rest_of_compilation +@findex rest_of_decl_compilation +Each time the parsing pass reads a complete function definition or +top-level declaration, it calls either the function +@code{rest_of_compilation}, or the function +@code{rest_of_decl_compilation} in @file{toplev.c}, which are +responsible for all further processing necessary, ending with output of +the assembler language. All other compiler passes run, in sequence, +within @code{rest_of_compilation}. When that function returns from +compiling a function definition, the storage used for that function +definition's compilation is entirely freed, unless it is an inline +function +@ifset USING +(@pxref{Inline,,An Inline Function is As Fast As a Macro}). +@end ifset +@ifclear USING +(@pxref{Inline,,An Inline Function is As Fast As a Macro,gcc.texi,Using GCC}). +@end ifclear + +Here is a list of all the passes of the compiler and their source files. +Also included is a description of where debugging dumps can be requested +with @samp{-d} options. + +@itemize @bullet +@item +Parsing. This pass reads the entire text of a function definition, +constructing partial syntax trees. This and RTL generation are no longer +truly separate passes (formerly they were), but it is easier to think +of them as separate. + +The tree representation does not entirely follow C syntax, because it is +intended to support other languages as well. + +Language-specific data type analysis is also done in this pass, and every +tree node that represents an expression has a data type attached. +Variables are represented as declaration nodes. + +@cindex constant folding +@cindex arithmetic simplifications +@cindex simplifications, arithmetic +Constant folding and some arithmetic simplifications are also done +during this pass. + +The language-independent source files for parsing are +@file{stor-layout.c}, @file{fold-const.c}, and @file{tree.c}. +There are also header files @file{tree.h} and @file{tree.def} +which define the format of the tree representation.@refill + +@c Avoiding overfull is tricky here. +The source files to parse C are +@file{c-parse.in}, +@file{c-decl.c}, +@file{c-typeck.c}, +@file{c-aux-info.c}, +@file{c-convert.c}, +and @file{c-lang.c} +along with header files +@file{c-lex.h}, and +@file{c-tree.h}. + +The source files for parsing C++ are in @file{cp/}. +They are @file{parse.y}, +@file{class.c},@* +@file{cvt.c}, @file{decl.c}, @file{decl2.c}, +@file{except.c},@* +@file{expr.c}, @file{init.c}, @file{lex.c}, +@file{method.c}, @file{ptree.c},@* +@file{search.c}, @file{tree.c}, +@file{typeck2.c}, and +@file{typeck.c}, along with header files @file{cp-tree.def}, +@file{cp-tree.h}, and @file{decl.h}. + +The special source files for parsing Objective C are in @file{objc/}. +They are @file{objc-parse.y}, @file{objc-act.c}, @file{objc-tree.def}, and +@file{objc-act.h}. Certain C-specific files are used for this as +well. + +The file @file{c-common.c} is also used for all of the above languages. + +@cindex RTL generation +@item +RTL generation. This is the conversion of syntax tree into RTL code. +It is actually done statement-by-statement during parsing, but for +most purposes it can be thought of as a separate pass. + +@cindex target-parameter-dependent code +This is where the bulk of target-parameter-dependent code is found, +since often it is necessary for strategies to apply only when certain +standard kinds of instructions are available. The purpose of named +instruction patterns is to provide this information to the RTL +generation pass. + +@cindex tail recursion optimization +Optimization is done in this pass for @code{if}-conditions that are +comparisons, boolean operations or conditional expressions. Tail +recursion is detected at this time also. Decisions are made about how +best to arrange loops and how to output @code{switch} statements. + +@c Avoiding overfull is tricky here. +The source files for RTL generation include +@file{stmt.c}, +@file{calls.c}, +@file{expr.c}, +@file{explow.c}, +@file{expmed.c}, +@file{function.c}, +@file{optabs.c} +and @file{emit-rtl.c}. +Also, the file +@file{insn-emit.c}, generated from the machine description by the +program @code{genemit}, is used in this pass. The header file +@file{expr.h} is used for communication within this pass.@refill + +@findex genflags +@findex gencodes +The header files @file{insn-flags.h} and @file{insn-codes.h}, +generated from the machine description by the programs @code{genflags} +and @code{gencodes}, tell this pass which standard names are available +for use and which patterns correspond to them.@refill + +Aside from debugging information output, none of the following passes +refers to the tree structure representation of the function (only +part of which is saved). + +@cindex inline, automatic +The decision of whether the function can and should be expanded inline +in its subsequent callers is made at the end of rtl generation. The +function must meet certain criteria, currently related to the size of +the function and the types and number of parameters it has. Note that +this function may contain loops, recursive calls to itself +(tail-recursive functions can be inlined!), gotos, in short, all +constructs supported by GCC. The file @file{integrate.c} contains +the code to save a function's rtl for later inlining and to inline that +rtl when the function is called. The header file @file{integrate.h} +is also used for this purpose. + +The option @samp{-dr} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.rtl} to +the input file name. + +@cindex jump optimization +@cindex unreachable code +@cindex dead code +@item +Jump optimization. This pass simplifies jumps to the following +instruction, jumps across jumps, and jumps to jumps. It deletes +unreferenced labels and unreachable code, except that unreachable code +that contains a loop is not recognized as unreachable in this pass. +(Such loops are deleted later in the basic block analysis.) It also +converts some code originally written with jumps into sequences of +instructions that directly set values from the results of comparisons, +if the machine has such instructions. + +Jump optimization is performed two or three times. The first time is +immediately following RTL generation. The second time is after CSE, +but only if CSE says repeated jump optimization is needed. The +last time is right before the final pass. That time, cross-jumping +and deletion of no-op move instructions are done together with the +optimizations described above. + +The source file of this pass is @file{jump.c}. + +The option @samp{-dj} causes a debugging dump of the RTL code after +this pass is run for the first time. This dump file's name is made by +appending @samp{.jump} to the input file name. + +@cindex register use analysis +@item +Register scan. This pass finds the first and last use of each +register, as a guide for common subexpression elimination. Its source +is in @file{regclass.c}. + +@cindex jump threading +@item +Jump threading. This pass detects a condition jump that branches to an +identical or inverse test. Such jumps can be @samp{threaded} through +the second conditional test. The source code for this pass is in +@file{jump.c}. This optimization is only performed if +@samp{-fthread-jumps} is enabled. + +@cindex common subexpression elimination +@cindex constant propagation +@item +Common subexpression elimination. This pass also does constant +propagation. Its source file is @file{cse.c}. If constant +propagation causes conditional jumps to become unconditional or to +become no-ops, jump optimization is run again when CSE is finished. + +The option @samp{-ds} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.cse} to +the input file name. + +@cindex global common subexpression elimination +@cindex constant propagation +@cindex copy propagation +@item +Global common subexpression elimination. This pass performs GCSE +using Morel-Renvoise Partial Redundancy Elimination, with the exception +that it does not try to move invariants out of loops - that is left to +the loop optimization pass. This pass also performs global constant +and copy propagation. + +The source file for this pass is gcse.c. + +The option @samp{-dG} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.gcse} to +the input file name. + +@cindex loop optimization +@cindex code motion +@cindex strength-reduction +@item +Loop optimization. This pass moves constant expressions out of loops, +and optionally does strength-reduction and loop unrolling as well. +Its source files are @file{loop.c} and @file{unroll.c}, plus the header +@file{loop.h} used for communication between them. Loop unrolling uses +some functions in @file{integrate.c} and the header @file{integrate.h}. + +The option @samp{-dL} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.loop} to +the input file name. + +@item +If @samp{-frerun-cse-after-loop} was enabled, a second common +subexpression elimination pass is performed after the loop optimization +pass. Jump threading is also done again at this time if it was specified. + +The option @samp{-dt} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.cse2} to +the input file name. + +@cindex data flow analysis +@cindex analysis, data flow +@cindex basic blocks +@item +Data flow analysis (@file{flow.c}). This pass divides the program +into basic blocks (and in the process deletes unreachable loops); then +it computes which pseudo-registers are live at each point in the +program, and makes the first instruction that uses a value point at +the instruction that computed the value. + +@cindex autoincrement/decrement analysis +This pass also deletes computations whose results are never used, and +combines memory references with add or subtract instructions to make +autoincrement or autodecrement addressing. + +The option @samp{-df} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.flow} to +the input file name. If stupid register allocation is in use, this +dump file reflects the full results of such allocation. + +@cindex instruction combination +@item +Instruction combination (@file{combine.c}). This pass attempts to +combine groups of two or three instructions that are related by data +flow into single instructions. It combines the RTL expressions for +the instructions by substitution, simplifies the result using algebra, +and then attempts to match the result against the machine description. + +The option @samp{-dc} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.combine} +to the input file name. + +@cindex register movement +@item +Register movement (@file{regmove.c}). This pass looks for cases where +matching constraints would force an instruction to need a reload, and +this reload would be a register to register move. It then attempts +to change the registers used by the instruction to avoid the move +instruction. + +The option @samp{-dN} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.regmove} +to the input file name. + +@cindex instruction scheduling +@cindex scheduling, instruction +@item +Instruction scheduling (@file{sched.c}). This pass looks for +instructions whose output will not be available by the time that it is +used in subsequent instructions. (Memory loads and floating point +instructions often have this behavior on RISC machines). It re-orders +instructions within a basic block to try to separate the definition and +use of items that otherwise would cause pipeline stalls. + +Instruction scheduling is performed twice. The first time is immediately +after instruction combination and the second is immediately after reload. + +The option @samp{-dS} causes a debugging dump of the RTL code after this +pass is run for the first time. The dump file's name is made by +appending @samp{.sched} to the input file name. + +@cindex register class preference pass +@item +Register class preferencing. The RTL code is scanned to find out +which register class is best for each pseudo register. The source +file is @file{regclass.c}. + +@cindex register allocation +@cindex local register allocation +@item +Local register allocation (@file{local-alloc.c}). This pass allocates +hard registers to pseudo registers that are used only within one basic +block. Because the basic block is linear, it can use fast and +powerful techniques to do a very good job. + +The option @samp{-dl} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.lreg} to +the input file name. + +@cindex global register allocation +@item +Global register allocation (@file{global.c}). This pass +allocates hard registers for the remaining pseudo registers (those +whose life spans are not contained in one basic block). + +@cindex reloading +@item +Reloading. This pass renumbers pseudo registers with the hardware +registers numbers they were allocated. Pseudo registers that did not +get hard registers are replaced with stack slots. Then it finds +instructions that are invalid because a value has failed to end up in +a register, or has ended up in a register of the wrong kind. It fixes +up these instructions by reloading the problematical values +temporarily into registers. Additional instructions are generated to +do the copying. + +The reload pass also optionally eliminates the frame pointer and inserts +instructions to save and restore call-clobbered registers around calls. + +Source files are @file{reload.c} and @file{reload1.c}, plus the header +@file{reload.h} used for communication between them. + +The option @samp{-dg} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.greg} to +the input file name. + +@cindex instruction scheduling +@cindex scheduling, instruction +@item +Instruction scheduling is repeated here to try to avoid pipeline stalls +due to memory loads generated for spilled pseudo registers. + +The option @samp{-dR} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.sched2} +to the input file name. + +@cindex cross-jumping +@cindex no-op move instructions +@item +Jump optimization is repeated, this time including cross-jumping +and deletion of no-op move instructions. + +The option @samp{-dJ} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.jump2} +to the input file name. + +@cindex delayed branch scheduling +@cindex scheduling, delayed branch +@item +Delayed branch scheduling. This optional pass attempts to find +instructions that can go into the delay slots of other instructions, +usually jumps and calls. The source file name is @file{reorg.c}. + +The option @samp{-dd} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.dbr} +to the input file name. + +@cindex branch shortening +@item +Branch shortening. On many RISC machines, branch instructions have a +limited range. Thus, longer sequences of instructions must be used for +long branches. In this pass, the compiler figures out what how far each +instruction will be from each other instruction, and therefore whether +the usual instructions, or the longer sequences, must be used for each +branch. + +@cindex register-to-stack conversion +@item +Conversion from usage of some hard registers to usage of a register +stack may be done at this point. Currently, this is supported only +for the floating-point registers of the Intel 80387 coprocessor. The +source file name is @file{reg-stack.c}. + +The options @samp{-dk} causes a debugging dump of the RTL code after +this pass. This dump file's name is made by appending @samp{.stack} +to the input file name. + +@cindex final pass +@cindex peephole optimization +@item +Final. This pass outputs the assembler code for the function. It is +also responsible for identifying spurious test and compare +instructions. Machine-specific peephole optimizations are performed +at the same time. The function entry and exit sequences are generated +directly as assembler code in this pass; they never exist as RTL. + +The source files are @file{final.c} plus @file{insn-output.c}; the +latter is generated automatically from the machine description by the +tool @file{genoutput}. The header file @file{conditions.h} is used +for communication between these files. + +@cindex debugging information generation +@item +Debugging information output. This is run after final because it must +output the stack slot offsets for pseudo registers that did not get +hard registers. Source files are @file{dbxout.c} for DBX symbol table +format, @file{sdbout.c} for SDB symbol table format, and +@file{dwarfout.c} for DWARF symbol table format. +@end itemize + +Some additional files are used by all or many passes: + +@itemize @bullet +@item +Every pass uses @file{machmode.def} and @file{machmode.h} which define +the machine modes. + +@item +Several passes use @file{real.h}, which defines the default +representation of floating point constants and how to operate on them. + +@item +All the passes that work with RTL use the header files @file{rtl.h} +and @file{rtl.def}, and subroutines in file @file{rtl.c}. The tools +@code{gen*} also use these files to read and work with the machine +description RTL. + +@findex genconfig +@item +Several passes refer to the header file @file{insn-config.h} which +contains a few parameters (C macro definitions) generated +automatically from the machine description RTL by the tool +@code{genconfig}. + +@cindex instruction recognizer +@item +Several passes use the instruction recognizer, which consists of +@file{recog.c} and @file{recog.h}, plus the files @file{insn-recog.c} +and @file{insn-extract.c} that are generated automatically from the +machine description by the tools @file{genrecog} and +@file{genextract}.@refill + +@item +Several passes use the header files @file{regs.h} which defines the +information recorded about pseudo register usage, and @file{basic-block.h} +which defines the information recorded about basic blocks. + +@item +@file{hard-reg-set.h} defines the type @code{HARD_REG_SET}, a bit-vector +with a bit for each hard register, and some macros to manipulate it. +This type is just @code{int} if the machine has few enough hard registers; +otherwise it is an array of @code{int} and some of the macros expand +into loops. + +@item +Several passes use instruction attributes. A definition of the +attributes defined for a particular machine is in file +@file{insn-attr.h}, which is generated from the machine description by +the program @file{genattr}. The file @file{insn-attrtab.c} contains +subroutines to obtain the attribute values for insns. It is generated +from the machine description by the program @file{genattrtab}.@refill +@end itemize +@end ifset + +@ifset INTERNALS +@include c-tree.texi +@include rtl.texi +@include md.texi +@include tm.texi +@end ifset + +@ifset INTERNALS +@node Config +@chapter The Configuration File +@cindex configuration file +@cindex @file{xm-@var{machine}.h} + +The configuration file @file{xm-@var{machine}.h} contains macro +definitions that describe the machine and system on which the compiler +is running, unlike the definitions in @file{@var{machine}.h}, which +describe the machine for which the compiler is producing output. Most +of the values in @file{xm-@var{machine}.h} are actually the same on all +machines that GCC runs on, so large parts of all configuration files +are identical. But there are some macros that vary: + +@table @code +@findex USG +@item USG +Define this macro if the host system is System V. + +@findex VMS +@item VMS +Define this macro if the host system is VMS. + +@findex FATAL_EXIT_CODE +@item FATAL_EXIT_CODE +A C expression for the status code to be returned when the compiler +exits after serious errors. The default is the system-provided macro +@samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that +macro. Define this macro only if these defaults are incorrect. + +@findex SUCCESS_EXIT_CODE +@item SUCCESS_EXIT_CODE +A C expression for the status code to be returned when the compiler +exits without serious errors. (Warnings are not serious errors.) The +default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if +the system doesn't define that macro. Define this macro only if these +defaults are incorrect. + +@findex HOST_WORDS_BIG_ENDIAN +@item HOST_WORDS_BIG_ENDIAN +Defined if the host machine stores words of multi-word values in +big-endian order. (GCC does not depend on the host byte ordering +within a word.) + +@findex HOST_FLOAT_WORDS_BIG_ENDIAN +@item HOST_FLOAT_WORDS_BIG_ENDIAN +Define this macro to be 1 if the host machine stores @code{DFmode}, +@code{XFmode} or @code{TFmode} floating point numbers in memory with the +word containing the sign bit at the lowest address; otherwise, define it +to be zero. + +This macro need not be defined if the ordering is the same as for +multi-word integers. + +@findex HOST_FLOAT_FORMAT +@item HOST_FLOAT_FORMAT +A numeric code distinguishing the floating point format for the host +machine. See @code{TARGET_FLOAT_FORMAT} in @ref{Storage Layout} for the +alternatives and default. + +@findex HOST_BITS_PER_CHAR +@item HOST_BITS_PER_CHAR +A C expression for the number of bits in @code{char} on the host +machine. + +@findex HOST_BITS_PER_SHORT +@item HOST_BITS_PER_SHORT +A C expression for the number of bits in @code{short} on the host +machine. + +@findex HOST_BITS_PER_INT +@item HOST_BITS_PER_INT +A C expression for the number of bits in @code{int} on the host +machine. + +@findex HOST_BITS_PER_LONG +@item HOST_BITS_PER_LONG +A C expression for the number of bits in @code{long} on the host +machine. + +@findex ONLY_INT_FIELDS +@item ONLY_INT_FIELDS +Define this macro to indicate that the host compiler only supports +@code{int} bit fields, rather than other integral types, including +@code{enum}, as do most C compilers. + +@findex OBSTACK_CHUNK_SIZE +@item OBSTACK_CHUNK_SIZE +A C expression for the size of ordinary obstack chunks. +If you don't define this, a usually-reasonable default is used. + +@findex OBSTACK_CHUNK_ALLOC +@item OBSTACK_CHUNK_ALLOC +The function used to allocate obstack chunks. +If you don't define this, @code{xmalloc} is used. + +@findex OBSTACK_CHUNK_FREE +@item OBSTACK_CHUNK_FREE +The function used to free obstack chunks. +If you don't define this, @code{free} is used. + +@findex USE_C_ALLOCA +@item USE_C_ALLOCA +Define this macro to indicate that the compiler is running with the +@code{alloca} implemented in C. This version of @code{alloca} can be +found in the file @file{alloca.c}; to use it, you must also alter the +@file{Makefile} variable @code{ALLOCA}. (This is done automatically +for the systems on which we know it is needed.) + +If you do define this macro, you should probably do it as follows: + +@example +#ifndef __GNUC__ +#define USE_C_ALLOCA +#else +#define alloca __builtin_alloca +#endif +@end example + +@noindent +so that when the compiler is compiled with GCC it uses the more +efficient built-in @code{alloca} function. + +@item FUNCTION_CONVERSION_BUG +@findex FUNCTION_CONVERSION_BUG +Define this macro to indicate that the host compiler does not properly +handle converting a function value to a pointer-to-function when it is +used in an expression. + +@findex MULTIBYTE_CHARS +@item MULTIBYTE_CHARS +Define this macro to enable support for multibyte characters in the +input to GCC. This requires that the host system support the ISO C +library functions for converting multibyte characters to wide +characters. + +@findex POSIX +@item POSIX +Define this if your system is POSIX.1 compliant. + +@findex PATH_SEPARATOR +@item PATH_SEPARATOR +Define this macro to be a C character constant representing the +character used to separate components in paths. The default value is +the colon character + +@findex DIR_SEPARATOR +@item DIR_SEPARATOR +If your system uses some character other than slash to separate +directory names within a file specification, define this macro to be a C +character constant specifying that character. When GCC displays file +names, the character you specify will be used. GCC will test for +both slash and the character you specify when parsing filenames. + +@findex TARGET_OBJECT_SUFFIX +@item TARGET_OBJECT_SUFFIX +Define this macro to be a C string representing the suffix for object +files on your target machine. If you do not define this macro, GCC will +use @samp{.o} as the suffix for object files. + +@findex TARGET_EXECUTABLE_SUFFIX +@item TARGET_EXECUTABLE_SUFFIX +Define this macro to be a C string representing the suffix to be +automatically added to executable files on your target machine. If you +do not define this macro, GCC will use the null string as the suffix for +executable files. + +@findex HOST_OBJECT_SUFFIX +@item HOST_OBJECT_SUFFIX +Define this macro to be a C string representing the suffix for object +files on your host machine (@samp{xm-*.h}). If you do not define this +macro, GCC will use @samp{.o} as the suffix for object files. + +@findex HOST_EXECUTABLE_SUFFIX +@item HOST_EXECUTABLE_SUFFIX +Define this macro to be a C string representing the suffix for +executable files on your host machine (@samp{xm-*.h}). If you do not +define this macro, GCC will use the null string as the suffix for +executable files. + +@findex HOST_BIT_BUCKET +@item HOST_BIT_BUCKET +The name of a file or file-like object on the host system which acts as +a ``bit bucket''. If you do not define this macro, GCC will use +@samp{/dev/null} as the bit bucket. If the target does not support a +bit bucket, this should be defined to the null string, or some other +illegal filename. If the bit bucket is not writable, GCC will use a +temporary file instead. + +@findex COLLECT_EXPORT_LIST +@item COLLECT_EXPORT_LIST +If defined, @code{collect2} will scan the individual object files +specified on its command line and create an export list for the linker. +Define this macro for systems like AIX, where the linker discards +object files that are not referenced from @code{main} and uses export +lists. + +@findex COLLECT2_HOST_INITIALIZATION +@item COLLECT2_HOST_INITIALIZATION +If defined, a C statement (sans semicolon) that performs host-dependent +initialization when @code{collect2} is being initialized. + +@findex GCC_DRIVER_HOST_INITIALIZATION +@item GCC_DRIVER_HOST_INITIALIZATION +If defined, a C statement (sans semicolon) that performs host-dependent +initialization when a compilation driver is being initialized. + +@findex UPDATE_PATH_HOST_CANONICALIZE +@item UPDATE_PATH_HOST_CANONICALIZE (@var{path}, @var{key}) +If defined, a C statement (sans semicolon) that performs host-dependent +canonicalization when a path used in a compilation driver or preprocessor is +canonicalized. @var{path} is the path to be canonicalized, and @var{key} is +a translation prefix when its value isn't @code{NULL}. If the C statement +does canonicalize @var{path}, the new path should be returned. +@end table + +@findex bzero +@findex bcmp +In addition, configuration files for system V define @code{bcopy}, +@code{bzero} and @code{bcmp} as aliases. Some files define @code{alloca} +as a macro when compiled with GCC, in order to take advantage of the +benefit of GCC's built-in @code{alloca}. + +@node Fragments +@chapter Makefile Fragments +@cindex makefile fragment + +When you configure GCC using the @file{configure} script +(@pxref{Installation}), it will construct the file @file{Makefile} from +the template file @file{Makefile.in}. When it does this, it will +incorporate makefile fragment files from the @file{config} directory, +named @file{t-@var{target}} and @file{x-@var{host}}. If these files do +not exist, it means nothing needs to be added for a given target or +host. + +@menu +* Target Fragment:: Writing the @file{t-@var{target}} file. +* Host Fragment:: Writing the @file{x-@var{host}} file. +@end menu + +@node Target Fragment +@section The Target Makefile Fragment +@cindex target makefile fragment +@cindex @file{t-@var{target}} + +The target makefile fragment, @file{t-@var{target}}, defines special +target dependent variables and targets used in the @file{Makefile}: + +@table @code +@findex LIBGCC2_CFLAGS +@item LIBGCC2_CFLAGS +Compiler flags to use when compiling @file{libgcc2.c}. + +@findex LIB2FUNCS_EXTRA +@item LIB2FUNCS_EXTRA +A list of source file names to be compiled or assembled and inserted +into @file{libgcc.a}. + +@findex Floating Point Emulation +@item Floating Point Emulation +To have GCC include software floating point libraries in @file{libgcc.a} +define @code{FPBIT} and @code{DPBIT} along with a few rules as follows: +@smallexample +# We want fine grained libraries, so use the new code +# to build the floating point emulation libraries. +FPBIT = fp-bit.c +DPBIT = dp-bit.c + + +fp-bit.c: $(srcdir)/config/fp-bit.c + echo '#define FLOAT' > fp-bit.c + cat $(srcdir)/config/fp-bit.c >> fp-bit.c + +dp-bit.c: $(srcdir)/config/fp-bit.c + cat $(srcdir)/config/fp-bit.c > dp-bit.c +@end smallexample + +You may need to provide additional #defines at the beginning of @file{fp-bit.c} +and @file{dp-bit.c} to control target endianness and other options. + + +@findex CRTSTUFF_T_CFLAGS +@item CRTSTUFF_T_CFLAGS +Special flags used when compiling @file{crtstuff.c}. +@xref{Initialization}. + +@findex CRTSTUFF_T_CFLAGS_S +@item CRTSTUFF_T_CFLAGS_S +Special flags used when compiling @file{crtstuff.c} for shared +linking. Used if you use @file{crtbeginS.o} and @file{crtendS.o} +in @code{EXTRA-PARTS}. +@xref{Initialization}. + +@findex MULTILIB_OPTIONS +@item MULTILIB_OPTIONS +For some targets, invoking GCC in different ways produces objects +that can not be linked together. For example, for some targets GCC +produces both big and little endian code. For these targets, you must +arrange for multiple versions of @file{libgcc.a} to be compiled, one for +each set of incompatible options. When GCC invokes the linker, it +arranges to link in the right version of @file{libgcc.a}, based on +the command line options used. + +The @code{MULTILIB_OPTIONS} macro lists the set of options for which +special versions of @file{libgcc.a} must be built. Write options that +are mutually incompatible side by side, separated by a slash. Write +options that may be used together separated by a space. The build +procedure will build all combinations of compatible options. + +For example, if you set @code{MULTILIB_OPTIONS} to @samp{m68000/m68020 +msoft-float}, @file{Makefile} will build special versions of +@file{libgcc.a} using the following sets of options: @samp{-m68000}, +@samp{-m68020}, @samp{-msoft-float}, @samp{-m68000 -msoft-float}, and +@samp{-m68020 -msoft-float}. + +@findex MULTILIB_DIRNAMES +@item MULTILIB_DIRNAMES +If @code{MULTILIB_OPTIONS} is used, this variable specifies the +directory names that should be used to hold the various libraries. +Write one element in @code{MULTILIB_DIRNAMES} for each element in +@code{MULTILIB_OPTIONS}. If @code{MULTILIB_DIRNAMES} is not used, the +default value will be @code{MULTILIB_OPTIONS}, with all slashes treated +as spaces. + +For example, if @code{MULTILIB_OPTIONS} is set to @samp{m68000/m68020 +msoft-float}, then the default value of @code{MULTILIB_DIRNAMES} is +@samp{m68000 m68020 msoft-float}. You may specify a different value if +you desire a different set of directory names. + +@findex MULTILIB_MATCHES +@item MULTILIB_MATCHES +Sometimes the same option may be written in two different ways. If an +option is listed in @code{MULTILIB_OPTIONS}, GCC needs to know about +any synonyms. In that case, set @code{MULTILIB_MATCHES} to a list of +items of the form @samp{option=option} to describe all relevant +synonyms. For example, @samp{m68000=mc68000 m68020=mc68020}. + +@findex MULTILIB_EXCEPTIONS +@item MULTILIB_EXCEPTIONS +Sometimes when there are multiple sets of @code{MULTILIB_OPTIONS} being +specified, there are combinations that should not be built. In that +case, set @code{MULTILIB_EXCEPTIONS} to be all of the switch exceptions +in shell case syntax that should not be built. + +For example, in the PowerPC embedded ABI support, it is not desirable +to build libraries compiled with the @samp{-mcall-aix} option +and either of the @samp{-fleading-underscore} or @samp{-mlittle} options +at the same time. Therefore @code{MULTILIB_EXCEPTIONS} is set to +@code{*mcall-aix/*fleading-underscore* *mlittle/*mcall-aix*}. + +@findex MULTILIB_EXTRA_OPTS +@item MULTILIB_EXTRA_OPTS +Sometimes it is desirable that when building multiple versions of +@file{libgcc.a} certain options should always be passed on to the +compiler. In that case, set @code{MULTILIB_EXTRA_OPTS} to be the list +of options to be used for all builds. +@end table + +@node Host Fragment +@section The Host Makefile Fragment +@cindex host makefile fragment +@cindex @file{x-@var{host}} + +The host makefile fragment, @file{x-@var{host}}, defines special host +dependent variables and targets used in the @file{Makefile}: + +@table @code +@findex CC +@item CC +The compiler to use when building the first stage. + +@findex INSTALL +@item INSTALL +The install program to use. +@end table +@end ifset + +@node Funding +@unnumbered Funding Free Software + +If you want to have more free software a few years from now, it makes +sense for you to help encourage people to contribute funds for its +development. The most effective approach known is to encourage +commercial redistributors to donate. + +Users of free software systems can boost the pace of development by +encouraging for-a-fee distributors to donate part of their selling price +to free software developers---the Free Software Foundation, and others. + +The way to convince distributors to do this is to demand it and expect +it from them. So when you compare distributors, judge them partly by +how much they give to free software development. Show distributors +they must compete to be the one who gives the most. + +To make this approach work, you must insist on numbers that you can +compare, such as, ``We will donate ten dollars to the Frobnitz project +for each disk sold.'' Don't be satisfied with a vague promise, such as +``A portion of the profits are donated,'' since it doesn't give a basis +for comparison. + +Even a precise fraction ``of the profits from this disk'' is not very +meaningful, since creative accounting and unrelated business decisions +can greatly alter what fraction of the sales price counts as profit. +If the price you pay is $50, ten percent of the profit is probably +less than a dollar; it might be a few cents, or nothing at all. + +Some redistributors do development work themselves. This is useful too; +but to keep everyone honest, you need to inquire how much they do, and +what kind. Some kinds of development make much more long-term +difference than others. For example, maintaining a separate version of +a program contributes very little; maintaining the standard version of a +program for the whole community contributes much. Easy new ports +contribute little, since someone else would surely do them; difficult +ports such as adding a new CPU to the GNU Compiler Collection contribute more; +major new features or packages contribute the most. + +By establishing the idea that supporting further development is ``the +proper thing to do'' when distributing free software for a fee, we can +assure a steady flow of resources into making more free software. + +@display +Copyright (C) 1994 Free Software Foundation, Inc. +Verbatim copying and redistribution of this section is permitted +without royalty; alteration is not permitted. +@end display + +@node GNU/Linux +@unnumbered Linux and the GNU Project + +Many computer users run a modified version of the GNU system every +day, without realizing it. Through a peculiar turn of events, the +version of GNU which is widely used today is more often known as +``Linux'', and many users are not aware of the extent of its +connection with the GNU Project. + +There really is a Linux; it is a kernel, and these people are using +it. But you can't use a kernel by itself; a kernel is useful only as +part of a whole system. The system in which Linux is typically used +is a modified variant of the GNU system---in other words, a Linux-based +GNU system. + +Many users are not fully aware of the distinction between the kernel, +which is Linux, and the whole system, which they also call ``Linux''. +The ambiguous use of the name doesn't promote understanding. + +Programmers generally know that Linux is a kernel. But since they +have generally heard the whole system called ``Linux'' as well, they +often envisage a history which fits that name. For example, many +believe that once Linus Torvalds finished writing the kernel, his +friends looked around for other free software, and for no particular +reason most everything necessary to make a Unix-like system was +already available. + +What they found was no accident---it was the GNU system. The available +free software added up to a complete system because the GNU Project +had been working since 1984 to make one. The GNU Manifesto +had set forth the goal of developing a free Unix-like system, called +GNU. By the time Linux was written, the system was almost finished. + +Most free software projects have the goal of developing a particular +program for a particular job. For example, Linus Torvalds set out to +write a Unix-like kernel (Linux); Donald Knuth set out to write a text +formatter (TeX); Bob Scheifler set out to develop a window system (X +Windows). It's natural to measure the contribution of this kind of +project by specific programs that came from the project. + +If we tried to measure the GNU Project's contribution in this way, +what would we conclude? One CD-ROM vendor found that in their ``Linux +distribution'', GNU software was the largest single contingent, around +28% of the total source code, and this included some of the essential +major components without which there could be no system. Linux itself +was about 3%. So if you were going to pick a name for the system +based on who wrote the programs in the system, the most appropriate +single choice would be ``GNU''. + +But we don't think that is the right way to consider the question. +The GNU Project was not, is not, a project to develop specific +software packages. It was not a project to develop a C compiler, +although we did. It was not a project to develop a text editor, +although we developed one. The GNU Project's aim was to develop +@emph{a complete free Unix-like system}. + +Many people have made major contributions to the free software in the +system, and they all deserve credit. But the reason it is @emph{a +system}---and not just a collection of useful programs---is because the +GNU Project set out to make it one. We wrote the programs that were +needed to make a @emph{complete} free system. We wrote essential but +unexciting major components, such as the assembler and linker, because +you can't have a system without them. A complete system needs more +than just programming tools, so we wrote other components as well, +such as the Bourne Again SHell, the PostScript interpreter +Ghostscript, and the GNU C library. + +By the early 90s we had put together the whole system aside from the +kernel (and we were also working on a kernel, the GNU Hurd, which runs +on top of Mach). Developing this kernel has been a lot harder than we +expected, and we are still working on finishing it. + +Fortunately, you don't have to wait for it, because Linux is working +now. When Linus Torvalds wrote Linux, he filled the last major gap. +People could then put Linux together with the GNU system to make a +complete free system: a Linux-based GNU system (or GNU/Linux system, +for short). + +Putting them together sounds simple, but it was not a trivial job. +The GNU C library (called glibc for short) needed substantial changes. +Integrating a complete system as a distribution that would work ``out +of the box'' was a big job, too. It required addressing the issue of +how to install and boot the system---a problem we had not tackled, +because we hadn't yet reached that point. The people who developed +the various system distributions made a substantial contribution. + +The GNU Project supports GNU/Linux systems as well as @emph{the} +GNU system---even with funds. We funded the rewriting of the +Linux-related extensions to the GNU C library, so that now they are +well integrated, and the newest GNU/Linux systems use the current +library release with no changes. We also funded an early stage of the +development of Debian GNU/Linux. + +We use Linux-based GNU systems today for most of our work, and we hope +you use them too. But please don't confuse the public by using the +name ``Linux'' ambiguously. Linux is the kernel, one of the essential +major components of the system. The system as a whole is more or less +the GNU system. + +@node Copying +@unnumbered GNU GENERAL PUBLIC LICENSE +@center Version 2, June 1991 + +@display +Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. +59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + +Everyone is permitted to copy and distribute verbatim copies +of this license document, but changing it is not allowed. +@end display + +@unnumberedsec Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. By contrast, the GNU General Public +License is intended to guarantee your freedom to share and change free +software---to make sure the software is free for all its users. This +General Public License applies to most of the Free Software +Foundation's software and to any other program whose authors commit to +using it. (Some other Free Software Foundation software is covered by +the GNU Library General Public License instead.) You can apply it to +your programs, too. + + When we speak of free software, we are referring to freedom, not +price. Our General Public Licenses are designed to make sure that you +have the freedom to distribute copies of free software (and charge for +this service if you wish), that you receive source code or can get it +if you want it, that you can change the software or use pieces of it +in new free programs; and that you know you can do these things. + + To protect your rights, we need to make restrictions that forbid +anyone to deny you these rights or to ask you to surrender the rights. +These restrictions translate to certain responsibilities for you if you +distribute copies of the software, or if you modify it. + + For example, if you distribute copies of such a program, whether +gratis or for a fee, you must give the recipients all the rights that +you have. You must make sure that they, too, receive or can get the +source code. And you must show them these terms so they know their +rights. + + We protect your rights with two steps: (1) copyright the software, and +(2) offer you this license which gives you legal permission to copy, +distribute and/or modify the software. + + Also, for each author's protection and ours, we want to make certain +that everyone understands that there is no warranty for this free +software. If the software is modified by someone else and passed on, we +want its recipients to know that what they have is not the original, so +that any problems introduced by others will not reflect on the original +authors' reputations. + + Finally, any free program is threatened constantly by software +patents. We wish to avoid the danger that redistributors of a free +program will individually obtain patent licenses, in effect making the +program proprietary. To prevent this, we have made it clear that any +patent must be licensed for everyone's free use or not licensed at all. + + The precise terms and conditions for copying, distribution and +modification follow. + +@iftex +@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION +@end iftex +@ifnottex +@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION +@end ifnottex + +@enumerate 0 +@item +This License applies to any program or other work which contains +a notice placed by the copyright holder saying it may be distributed +under the terms of this General Public License. The ``Program'', below, +refers to any such program or work, and a ``work based on the Program'' +means either the Program or any derivative work under copyright law: +that is to say, a work containing the Program or a portion of it, +either verbatim or with modifications and/or translated into another +language. (Hereinafter, translation is included without limitation in +the term ``modification''.) Each licensee is addressed as ``you''. + +Activities other than copying, distribution and modification are not +covered by this License; they are outside its scope. The act of +running the Program is not restricted, and the output from the Program +is covered only if its contents constitute a work based on the +Program (independent of having been made by running the Program). +Whether that is true depends on what the Program does. + +@item +You may copy and distribute verbatim copies of the Program's +source code as you receive it, in any medium, provided that you +conspicuously and appropriately publish on each copy an appropriate +copyright notice and disclaimer of warranty; keep intact all the +notices that refer to this License and to the absence of any warranty; +and give any other recipients of the Program a copy of this License +along with the Program. + +You may charge a fee for the physical act of transferring a copy, and +you may at your option offer warranty protection in exchange for a fee. + +@item +You may modify your copy or copies of the Program or any portion +of it, thus forming a work based on the Program, and copy and +distribute such modifications or work under the terms of Section 1 +above, provided that you also meet all of these conditions: + +@enumerate a +@item +You must cause the modified files to carry prominent notices +stating that you changed the files and the date of any change. + +@item +You must cause any work that you distribute or publish, that in +whole or in part contains or is derived from the Program or any +part thereof, to be licensed as a whole at no charge to all third +parties under the terms of this License. + +@item +If the modified program normally reads commands interactively +when run, you must cause it, when started running for such +interactive use in the most ordinary way, to print or display an +announcement including an appropriate copyright notice and a +notice that there is no warranty (or else, saying that you provide +a warranty) and that users may redistribute the program under +these conditions, and telling the user how to view a copy of this +License. (Exception: if the Program itself is interactive but +does not normally print such an announcement, your work based on +the Program is not required to print an announcement.) +@end enumerate + +These requirements apply to the modified work as a whole. If +identifiable sections of that work are not derived from the Program, +and can be reasonably considered independent and separate works in +themselves, then this License, and its terms, do not apply to those +sections when you distribute them as separate works. But when you +distribute the same sections as part of a whole which is a work based +on the Program, the distribution of the whole must be on the terms of +this License, whose permissions for other licensees extend to the +entire whole, and thus to each and every part regardless of who wrote it. + +Thus, it is not the intent of this section to claim rights or contest +your rights to work written entirely by you; rather, the intent is to +exercise the right to control the distribution of derivative or +collective works based on the Program. + +In addition, mere aggregation of another work not based on the Program +with the Program (or with a work based on the Program) on a volume of +a storage or distribution medium does not bring the other work under +the scope of this License. + +@item +You may copy and distribute the Program (or a work based on it, +under Section 2) in object code or executable form under the terms of +Sections 1 and 2 above provided that you also do one of the following: + +@enumerate a +@item +Accompany it with the complete corresponding machine-readable +source code, which must be distributed under the terms of Sections +1 and 2 above on a medium customarily used for software interchange; or, + +@item +Accompany it with a written offer, valid for at least three +years, to give any third party, for a charge no more than your +cost of physically performing source distribution, a complete +machine-readable copy of the corresponding source code, to be +distributed under the terms of Sections 1 and 2 above on a medium +customarily used for software interchange; or, + +@item +Accompany it with the information you received as to the offer +to distribute corresponding source code. (This alternative is +allowed only for noncommercial distribution and only if you +received the program in object code or executable form with such +an offer, in accord with Subsection b above.) +@end enumerate + +The source code for a work means the preferred form of the work for +making modifications to it. For an executable work, complete source +code means all the source code for all modules it contains, plus any +associated interface definition files, plus the scripts used to +control compilation and installation of the executable. However, as a +special exception, the source code distributed need not include +anything that is normally distributed (in either source or binary +form) with the major components (compiler, kernel, and so on) of the +operating system on which the executable runs, unless that component +itself accompanies the executable. + +If distribution of executable or object code is made by offering +access to copy from a designated place, then offering equivalent +access to copy the source code from the same place counts as +distribution of the source code, even though third parties are not +compelled to copy the source along with the object code. + +@item +You may not copy, modify, sublicense, or distribute the Program +except as expressly provided under this License. Any attempt +otherwise to copy, modify, sublicense or distribute the Program is +void, and will automatically terminate your rights under this License. +However, parties who have received copies, or rights, from you under +this License will not have their licenses terminated so long as such +parties remain in full compliance. + +@item +You are not required to accept this License, since you have not +signed it. However, nothing else grants you permission to modify or +distribute the Program or its derivative works. These actions are +prohibited by law if you do not accept this License. Therefore, by +modifying or distributing the Program (or any work based on the +Program), you indicate your acceptance of this License to do so, and +all its terms and conditions for copying, distributing or modifying +the Program or works based on it. + +@item +Each time you redistribute the Program (or any work based on the +Program), the recipient automatically receives a license from the +original licensor to copy, distribute or modify the Program subject to +these terms and conditions. You may not impose any further +restrictions on the recipients' exercise of the rights granted herein. +You are not responsible for enforcing compliance by third parties to +this License. + +@item +If, as a consequence of a court judgment or allegation of patent +infringement or for any other reason (not limited to patent issues), +conditions are imposed on you (whether by court order, agreement or +otherwise) that contradict the conditions of this License, they do not +excuse you from the conditions of this License. If you cannot +distribute so as to satisfy simultaneously your obligations under this +License and any other pertinent obligations, then as a consequence you +may not distribute the Program at all. For example, if a patent +license would not permit royalty-free redistribution of the Program by +all those who receive copies directly or indirectly through you, then +the only way you could satisfy both it and this License would be to +refrain entirely from distribution of the Program. + +If any portion of this section is held invalid or unenforceable under +any particular circumstance, the balance of the section is intended to +apply and the section as a whole is intended to apply in other +circumstances. + +It is not the purpose of this section to induce you to infringe any +patents or other property right claims or to contest validity of any +such claims; this section has the sole purpose of protecting the +integrity of the free software distribution system, which is +implemented by public license practices. Many people have made +generous contributions to the wide range of software distributed +through that system in reliance on consistent application of that +system; it is up to the author/donor to decide if he or she is willing +to distribute software through any other system and a licensee cannot +impose that choice. + +This section is intended to make thoroughly clear what is believed to +be a consequence of the rest of this License. + +@item +If the distribution and/or use of the Program is restricted in +certain countries either by patents or by copyrighted interfaces, the +original copyright holder who places the Program under this License +may add an explicit geographical distribution limitation excluding +those countries, so that distribution is permitted only in or among +countries not thus excluded. In such case, this License incorporates +the limitation as if written in the body of this License. + +@item +The Free Software Foundation may publish revised and/or new versions +of the General Public License from time to time. Such new versions will +be similar in spirit to the present version, but may differ in detail to +address new problems or concerns. + +Each version is given a distinguishing version number. If the Program +specifies a version number of this License which applies to it and ``any +later version'', you have the option of following the terms and conditions +either of that version or of any later version published by the Free +Software Foundation. If the Program does not specify a version number of +this License, you may choose any version ever published by the Free Software +Foundation. + +@item +If you wish to incorporate parts of the Program into other free +programs whose distribution conditions are different, write to the author +to ask for permission. For software which is copyrighted by the Free +Software Foundation, write to the Free Software Foundation; we sometimes +make exceptions for this. Our decision will be guided by the two goals +of preserving the free status of all derivatives of our free software and +of promoting the sharing and reuse of software generally. + +@iftex +@heading NO WARRANTY +@end iftex +@ifnottex +@center NO WARRANTY +@end ifnottex + +@item +BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY +FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN +OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES +PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED +OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF +MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS +TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE +PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, +REPAIR OR CORRECTION. + +@item +IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING +WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR +REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, +INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING +OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED +TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY +YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER +PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE +POSSIBILITY OF SUCH DAMAGES. +@end enumerate + +@iftex +@heading END OF TERMS AND CONDITIONS +@end iftex +@ifnottex +@center END OF TERMS AND CONDITIONS +@end ifnottex + +@page +@unnumberedsec How to Apply These Terms to Your New Programs + + If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these terms. + + To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +convey the exclusion of warranty; and each file should have at least +the ``copyright'' line and a pointer to where the full notice is found. + +@smallexample +@var{one line to give the program's name and a brief idea of what it does.} +Copyright (C) @var{yyyy} @var{name of author} + +This program is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2 of the License, or +(at your option) any later version. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with this program; if not, write to the Free Software +Foundation, Inc., 59 Temple Place - Suite 330, +Boston, MA 02111-1307, USA. +@end smallexample + +Also add information on how to contact you by electronic and paper mail. + +If the program is interactive, make it output a short notice like this +when it starts in an interactive mode: + +@smallexample +Gnomovision version 69, Copyright (C) @var{yyyy} @var{name of author} +Gnomovision comes with ABSOLUTELY NO WARRANTY; for details +type `show w'. +This is free software, and you are welcome to redistribute it +under certain conditions; type `show c' for details. +@end smallexample + +The hypothetical commands @samp{show w} and @samp{show c} should show +the appropriate parts of the General Public License. Of course, the +commands you use may be called something other than @samp{show w} and +@samp{show c}; they could even be mouse-clicks or menu items---whatever +suits your program. + +You should also get your employer (if you work as a programmer) or your +school, if any, to sign a ``copyright disclaimer'' for the program, if +necessary. Here is a sample; alter the names: + +@smallexample +Yoyodyne, Inc., hereby disclaims all copyright interest in the program +`Gnomovision' (which makes passes at compilers) written by James Hacker. + +@var{signature of Ty Coon}, 1 April 1989 +Ty Coon, President of Vice +@end smallexample + +This General Public License does not permit incorporating your program into +proprietary programs. If your program is a subroutine library, you may +consider it more useful to permit linking proprietary applications with the +library. If this is what you want to do, use the GNU Library General +Public License instead of this License. + +@c --------------------------------------------------------------------- +@c GFDL +@c --------------------------------------------------------------------- + +@include fdl.texi + +@node Contributors +@unnumbered Contributors to GCC +@cindex contributors +@include contrib.texi + +@c --------------------------------------------------------------------- +@c Node Index +@c --------------------------------------------------------------------- + +@node Index +@unnumbered Index + +@printindex cp + +@c --------------------------------------------------------------------- +@c Epilogue +@c --------------------------------------------------------------------- + +@summarycontents +@contents +@bye diff --git a/gcc/doc/gcov.1 b/gcc/doc/gcov.1 new file mode 100644 index 00000000000..633d7546384 --- /dev/null +++ b/gcc/doc/gcov.1 @@ -0,0 +1,414 @@ +.\" Automatically generated by Pod::Man version 1.1 +.\" Mon Feb 19 19:31:56 2001 +.\" +.\" Standard preamble: +.\" ====================================================================== +.de Sh \" Subsection heading +.br +.if t .Sp +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Ip \" List item +.br +.ie \\n(.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R + +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. | will give a +.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used +.\" to do unbreakable dashes and therefore won't be available. \*(C` and +.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<> +.tr \(*W-|\(bv\*(Tr +.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' +.ie n \{\ +. ds -- \(*W- +. ds PI pi +. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch +. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch +. ds L" "" +. ds R" "" +. ds C` "" +. ds C' "" +'br\} +.el\{\ +. ds -- \|\(em\| +. ds PI \(*p +. ds L" `` +. ds R" '' +'br\} +.\" +.\" If the F register is turned on, we'll generate index entries on stderr +.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and +.\" index entries marked with X<> in POD. Of course, you'll have to process +.\" the output yourself in some meaningful fashion. +.if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. nr % 0 +. rr F +.\} +.\" +.\" For nroff, turn off justification. 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No user-serviceable parts. +.bd B 3 +. \" fudge factors for nroff and troff +.if n \{\ +. ds #H 0 +. ds #V .8m +. ds #F .3m +. ds #[ \f1 +. ds #] \fP +.\} +.if t \{\ +. ds #H ((1u-(\\\\n(.fu%2u))*.13m) +. ds #V .6m +. ds #F 0 +. ds #[ \& +. ds #] \& +.\} +. \" simple accents for nroff and troff +.if n \{\ +. ds ' \& +. ds ` \& +. ds ^ \& +. ds , \& +. ds ~ ~ +. ds / +.\} +.if t \{\ +. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" +. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' +. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' +. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' +. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' +. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' +.\} +. \" troff and (daisy-wheel) nroff accents +.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' +.ds 8 \h'\*(#H'\(*b\h'-\*(#H' +.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] +.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' +.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' +.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] +.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] +.ds ae a\h'-(\w'a'u*4/10)'e +.ds Ae A\h'-(\w'A'u*4/10)'E +. \" corrections for vroff +.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' +.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' +. \" for low resolution devices (crt and lpr) +.if \n(.H>23 .if \n(.V>19 \ +\{\ +. ds : e +. ds 8 ss +. ds o a +. ds d- d\h'-1'\(ga +. ds D- D\h'-1'\(hy +. ds th \o'bp' +. ds Th \o'LP' +. ds ae ae +. ds Ae AE +.\} +.rm #[ #] #H #V #F C +.\" ====================================================================== +.\" +.IX Title "GCOV 1" +.TH GCOV 1 "gcc-3.1" "2001-02-19" "GNU" +.UC +.SH "NAME" +gcov \- coverage testing tool +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +gcov [\fB\-b\fR] [\fB\-c\fR] [\fB\-v\fR] [\fB\-n\fR] [\fB\-l\fR] [\fB\-f\fR] [\fB\-o\fR \fIdirectory\fR] \fIsourcefile\fR +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +\&\f(CW\*(C`gcov\*(C'\fR is a test coverage program. Use it in concert with \s-1GNU\s0 +\&\s-1CC\s0 to analyze your programs to help create more efficient, faster +running code. You can use \f(CW\*(C`gcov\*(C'\fR as a profiling tool to help +discover where your optimization efforts will best affect your code. You +can also use \f(CW\*(C`gcov\*(C'\fR along with the other profiling tool, +\&\f(CW\*(C`gprof\*(C'\fR, to assess which parts of your code use the greatest amount +of computing time. +.PP +Profiling tools help you analyze your code's performance. Using a +profiler such as \f(CW\*(C`gcov\*(C'\fR or \f(CW\*(C`gprof\*(C'\fR, you can find out some +basic performance statistics, such as: +.Ip "\(bu" 4 +how often each line of code executes +.Ip "\(bu" 4 +what lines of code are actually executed +.Ip "\(bu" 4 +how much computing time each section of code uses +.PP +Once you know these things about how your code works when compiled, you +can look at each module to see which modules should be optimized. +\&\f(CW\*(C`gcov\*(C'\fR helps you determine where to work on optimization. +.PP +Software developers also use coverage testing in concert with +testsuites, to make sure software is actually good enough for a release. +Testsuites can verify that a program works as expected; a coverage +program tests to see how much of the program is exercised by the +testsuite. Developers can then determine what kinds of test cases need +to be added to the testsuites to create both better testing and a better +final product. +.PP +You should compile your code without optimization if you plan to use +\&\f(CW\*(C`gcov\*(C'\fR because the optimization, by combining some lines of code +into one function, may not give you as much information as you need to +look for `hot spots' where the code is using a great deal of computer +time. Likewise, because \f(CW\*(C`gcov\*(C'\fR accumulates statistics by line (at +the lowest resolution), it works best with a programming style that +places only one statement on each line. If you use complicated macros +that expand to loops or to other control structures, the statistics are +less helpful\-\-\-they only report on the line where the macro call +appears. If your complex macros behave like functions, you can replace +them with inline functions to solve this problem. +.PP +\&\f(CW\*(C`gcov\*(C'\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which +indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR +has executed. You can use these logfiles along with \f(CW\*(C`gprof\*(C'\fR to aid +in fine-tuning the performance of your programs. \f(CW\*(C`gprof\*(C'\fR gives +timing information you can use along with the information you get from +\&\f(CW\*(C`gcov\*(C'\fR. +.PP +\&\f(CW\*(C`gcov\*(C'\fR works only on code compiled with \s-1GNU\s0 \s-1CC\s0. It is not +compatible with any other profiling or test coverage mechanism. +.SH "OPTIONS" +.IX Header "OPTIONS" +.if n .Ip "\f(CW""\-b""\fR" 4 +.el .Ip "\f(CW\-b\fR" 4 +.IX Item "-b" +Write branch frequencies to the output file, and write branch summary +info to the standard output. This option allows you to see how often +each branch in your program was taken. +.if n .Ip "\f(CW""\-c""\fR" 4 +.el .Ip "\f(CW\-c\fR" 4 +.IX Item "-c" +Write branch frequencies as the number of branches taken, rather than +the percentage of branches taken. +.if n .Ip "\f(CW""\-v""\fR" 4 +.el .Ip "\f(CW\-v\fR" 4 +.IX Item "-v" +Display the \f(CW\*(C`gcov\*(C'\fR version number (on the standard error stream). +.if n .Ip "\f(CW""\-n""\fR" 4 +.el .Ip "\f(CW\-n\fR" 4 +.IX Item "-n" +Do not create the \f(CW\*(C`gcov\*(C'\fR output file. +.if n .Ip "\f(CW""\-l""\fR" 4 +.el .Ip "\f(CW\-l\fR" 4 +.IX Item "-l" +Create long file names for included source files. For example, if the +header file \fBx.h\fR contains code, and was included in the file +\&\fBa.c\fR, then running \f(CW\*(C`gcov\*(C'\fR on the file \fBa.c\fR will produce +an output file called \fBa.c.x.h.gcov\fR instead of \fBx.h.gcov\fR. +This can be useful if \fBx.h\fR is included in multiple source files. +.if n .Ip "\f(CW""\-f""\fR" 4 +.el .Ip "\f(CW\-f\fR" 4 +.IX Item "-f" +Output summaries for each function in addition to the file level summary. +.if n .Ip "\f(CW""\-o""\fR" 4 +.el .Ip "\f(CW\-o\fR" 4 +.IX Item "-o" +The directory where the object files live. Gcov will search for \f(CW\*(C`.bb\*(C'\fR, +\&\f(CW\*(C`.bbg\*(C'\fR, and \f(CW\*(C`.da\*(C'\fR files in this directory. +.PP +When using \f(CW\*(C`gcov\*(C'\fR, you must first compile your program with two +special \s-1GNU\s0 \s-1CC\s0 options: \fB\-fprofile-arcs \-ftest-coverage\fR. +This tells the compiler to generate additional information needed by +gcov (basically a flow graph of the program) and also includes +additional code in the object files for generating the extra profiling +information needed by gcov. These additional files are placed in the +directory where the source code is located. +.PP +Running the program will cause profile output to be generated. For each +source file compiled with \-fprofile-arcs, an accompanying \f(CW\*(C`.da\*(C'\fR +file will be placed in the source directory. +.PP +Running \f(CW\*(C`gcov\*(C'\fR with your program's source file names as arguments +will now produce a listing of the code along with frequency of execution +for each line. For example, if your program is called \fBtmp.c\fR, this +is what you see when you use the basic \f(CW\*(C`gcov\*(C'\fR facility: +.PP +.Vb 5 +\& $ gcc -fprofile-arcs -ftest-coverage tmp.c +\& $ a.out +\& $ gcov tmp.c +\& 87.50% of 8 source lines executed in file tmp.c +\& Creating tmp.c.gcov. +.Ve +The file \fItmp.c.gcov\fR contains output from \f(CW\*(C`gcov\*(C'\fR. +Here is a sample: +.PP +.Vb 3 +\& main() +\& { +\& 1 int i, total; +.Ve +.Vb 1 +\& 1 total = 0; +.Ve +.Vb 2 +\& 11 for (i = 0; i < 10; i++) +\& 10 total += i; +.Ve +.Vb 5 +\& 1 if (total != 45) +\& ###### printf ("Failure\en"); +\& else +\& 1 printf ("Success\en"); +\& 1 } +.Ve +When you use the \fB\-b\fR option, your output looks like this: +.PP +.Vb 6 +\& $ gcov -b tmp.c +\& 87.50% of 8 source lines executed in file tmp.c +\& 80.00% of 5 branches executed in file tmp.c +\& 80.00% of 5 branches taken at least once in file tmp.c +\& 50.00% of 2 calls executed in file tmp.c +\& Creating tmp.c.gcov. +.Ve +Here is a sample of a resulting \fItmp.c.gcov\fR file: +.PP +.Vb 3 +\& main() +\& { +\& 1 int i, total; +.Ve +.Vb 1 +\& 1 total = 0; +.Ve +.Vb 5 +\& 11 for (i = 0; i < 10; i++) +\& branch 0 taken = 91% +\& branch 1 taken = 100% +\& branch 2 taken = 100% +\& 10 total += i; +.Ve +.Vb 9 +\& 1 if (total != 45) +\& branch 0 taken = 100% +\& ###### printf ("Failure\en"); +\& call 0 never executed +\& branch 1 never executed +\& else +\& 1 printf ("Success\en"); +\& call 0 returns = 100% +\& 1 } +.Ve +For each basic block, a line is printed after the last line of the basic +block describing the branch or call that ends the basic block. There can +be multiple branches and calls listed for a single source line if there +are multiple basic blocks that end on that line. In this case, the +branches and calls are each given a number. There is no simple way to map +these branches and calls back to source constructs. In general, though, +the lowest numbered branch or call will correspond to the leftmost construct +on the source line. +.PP +For a branch, if it was executed at least once, then a percentage +indicating the number of times the branch was taken divided by the +number of times the branch was executed will be printed. Otherwise, the +message ``never executed'' is printed. +.PP +For a call, if it was executed at least once, then a percentage +indicating the number of times the call returned divided by the number +of times the call was executed will be printed. This will usually be +100%, but may be less for functions call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR, +and thus may not return every time they are called. +.PP +The execution counts are cumulative. If the example program were +executed again without removing the \f(CW\*(C`.da\*(C'\fR file, the count for the +number of times each line in the source was executed would be added to +the results of the previous \fIrun\fR\|(s). This is potentially useful in +several ways. For example, it could be used to accumulate data over a +number of program runs as part of a test verification suite, or to +provide more accurate long-term information over a large number of +program runs. +.PP +The data in the \f(CW\*(C`.da\*(C'\fR files is saved immediately before the program +exits. For each source file compiled with \-fprofile-arcs, the profiling +code first attempts to read in an existing \f(CW\*(C`.da\*(C'\fR file; if the file +doesn't match the executable (differing number of basic block counts) it +will ignore the contents of the file. It then adds in the new execution +counts and finally writes the data to the file. +.if n .Sh "Using \f(CW""gcov""\fP with \s-1GCC\s0 Optimization" +.el .Sh "Using \f(CWgcov\fP with \s-1GCC\s0 Optimization" +.IX Subsection "Using gcov with GCC Optimization" +If you plan to use \f(CW\*(C`gcov\*(C'\fR to help optimize your code, you must +first compile your program with two special \s-1GNU\s0 \s-1CC\s0 options: +\&\fB\-fprofile-arcs \-ftest-coverage\fR. Aside from that, you can use any +other \s-1GNU\s0 \s-1CC\s0 options; but if you want to prove that every single line +in your program was executed, you should not compile with optimization +at the same time. On some machines the optimizer can eliminate some +simple code lines by combining them with other lines. For example, code +like this: +.PP +.Vb 4 +\& if (a != b) +\& c = 1; +\& else +\& c = 0; +.Ve +can be compiled into one instruction on some machines. In this case, +there is no way for \f(CW\*(C`gcov\*(C'\fR to calculate separate execution counts +for each line because there isn't separate code for each line. Hence +the \f(CW\*(C`gcov\*(C'\fR output looks like this if you compiled the program with +optimization: +.PP +.Vb 4 +\& 100 if (a != b) +\& 100 c = 1; +\& 100 else +\& 100 c = 0; +.Ve +The output shows that this block of code, combined by optimization, +executed 100 times. In one sense this result is correct, because there +was only one instruction representing all four of these lines. However, +the output does not indicate how many times the result was 0 and how +many times the result was 1. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fIgcc\fR\|(1) and the Info entry for \fIgcc\fR. +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright (c) 1996, 1997, 1999, 2000 Free Software Foundation, Inc. +.PP +Permission is granted to make and distribute verbatim copies of this +manual provided the copyright notice and this permission notice are +preserved on all copies. +.PP +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that the +entire resulting derived work is distributed under the terms of a +permission notice identical to this one. +.PP +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions, +except that this permission notice may be included in translations +approved by the Free Software Foundation instead of in the original +English. diff --git a/gcc/doc/gcov.texi b/gcc/doc/gcov.texi new file mode 100644 index 00000000000..5fc46d297a5 --- /dev/null +++ b/gcc/doc/gcov.texi @@ -0,0 +1,386 @@ +@c Copyright (C) 1996, 1997, 1999, 2000 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@ignore +@c man begin COPYRIGHT +Copyright @copyright{} 1996, 1997, 1999, 2000 Free Software Foundation, Inc. + +Permission is granted to make and distribute verbatim copies of this +manual provided the copyright notice and this permission notice are +preserved on all copies. + +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that the +entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions, +except that this permission notice may be included in translations +approved by the Free Software Foundation instead of in the original +English. +@c man end +@c Set file name and title for the man page. +@setfilename gcov +@settitle coverage testing tool +@end ignore + +@node Gcov +@chapter @code{gcov}: a Test Coverage Program + +@code{gcov} is a tool you can use in conjunction with @sc{gnu} CC to +test code coverage in your programs. + +This chapter describes version 1.5 of @code{gcov}. + +@menu +* Gcov Intro:: Introduction to gcov. +* Invoking Gcov:: How to use gcov. +* Gcov and Optimization:: Using gcov with GCC optimization. +* Gcov Data Files:: The files used by gcov. +@end menu + +@node Gcov Intro +@section Introduction to @code{gcov} +@c man begin DESCRIPTION + +@code{gcov} is a test coverage program. Use it in concert with @sc{gnu} +CC to analyze your programs to help create more efficient, faster +running code. You can use @code{gcov} as a profiling tool to help +discover where your optimization efforts will best affect your code. You +can also use @code{gcov} along with the other profiling tool, +@code{gprof}, to assess which parts of your code use the greatest amount +of computing time. + +Profiling tools help you analyze your code's performance. Using a +profiler such as @code{gcov} or @code{gprof}, you can find out some +basic performance statistics, such as: + +@itemize @bullet +@item +how often each line of code executes + +@item +what lines of code are actually executed + +@item +how much computing time each section of code uses +@end itemize + +Once you know these things about how your code works when compiled, you +can look at each module to see which modules should be optimized. +@code{gcov} helps you determine where to work on optimization. + +Software developers also use coverage testing in concert with +testsuites, to make sure software is actually good enough for a release. +Testsuites can verify that a program works as expected; a coverage +program tests to see how much of the program is exercised by the +testsuite. Developers can then determine what kinds of test cases need +to be added to the testsuites to create both better testing and a better +final product. + +You should compile your code without optimization if you plan to use +@code{gcov} because the optimization, by combining some lines of code +into one function, may not give you as much information as you need to +look for `hot spots' where the code is using a great deal of computer +time. Likewise, because @code{gcov} accumulates statistics by line (at +the lowest resolution), it works best with a programming style that +places only one statement on each line. If you use complicated macros +that expand to loops or to other control structures, the statistics are +less helpful---they only report on the line where the macro call +appears. If your complex macros behave like functions, you can replace +them with inline functions to solve this problem. + +@code{gcov} creates a logfile called @file{@var{sourcefile}.gcov} which +indicates how many times each line of a source file @file{@var{sourcefile}.c} +has executed. You can use these logfiles along with @code{gprof} to aid +in fine-tuning the performance of your programs. @code{gprof} gives +timing information you can use along with the information you get from +@code{gcov}. + +@code{gcov} works only on code compiled with @sc{gnu} CC. It is not +compatible with any other profiling or test coverage mechanism. + +@c man end + +@node Invoking Gcov +@section Invoking gcov + +@smallexample +gcov [-b] [-c] [-v] [-n] [-l] [-f] [-o directory] @var{sourcefile} +@end smallexample + +@ignore +@c man begin SYNOPSIS +gcov [@samp{-b}] [@samp{-c}] [@samp{-v}] [@samp{-n}] [@samp{-l}] [@samp{-f}] [@samp{-o} @var{directory}] @var{sourcefile} +@c man end +@c man begin SEEALSO +gcc(1) and the Info entry for @file{gcc}. +@c man end +@end ignore + +@c man begin OPTIONS +@table @code +@item -b +Write branch frequencies to the output file, and write branch summary +info to the standard output. This option allows you to see how often +each branch in your program was taken. + +@item -c +Write branch frequencies as the number of branches taken, rather than +the percentage of branches taken. + +@item -v +Display the @code{gcov} version number (on the standard error stream). + +@item -n +Do not create the @code{gcov} output file. + +@item -l +Create long file names for included source files. For example, if the +header file @samp{x.h} contains code, and was included in the file +@samp{a.c}, then running @code{gcov} on the file @samp{a.c} will produce +an output file called @samp{a.c.x.h.gcov} instead of @samp{x.h.gcov}. +This can be useful if @samp{x.h} is included in multiple source files. + +@item -f +Output summaries for each function in addition to the file level summary. + +@item -o +The directory where the object files live. Gcov will search for @code{.bb}, +@code{.bbg}, and @code{.da} files in this directory. +@end table + +@need 3000 +When using @code{gcov}, you must first compile your program with two +special @sc{gnu} CC options: @samp{-fprofile-arcs -ftest-coverage}. +This tells the compiler to generate additional information needed by +gcov (basically a flow graph of the program) and also includes +additional code in the object files for generating the extra profiling +information needed by gcov. These additional files are placed in the +directory where the source code is located. + +Running the program will cause profile output to be generated. For each +source file compiled with -fprofile-arcs, an accompanying @code{.da} +file will be placed in the source directory. + +Running @code{gcov} with your program's source file names as arguments +will now produce a listing of the code along with frequency of execution +for each line. For example, if your program is called @samp{tmp.c}, this +is what you see when you use the basic @code{gcov} facility: + +@smallexample +$ gcc -fprofile-arcs -ftest-coverage tmp.c +$ a.out +$ gcov tmp.c + 87.50% of 8 source lines executed in file tmp.c +Creating tmp.c.gcov. +@end smallexample + +The file @file{tmp.c.gcov} contains output from @code{gcov}. +Here is a sample: + +@smallexample + main() + @{ + 1 int i, total; + + 1 total = 0; + + 11 for (i = 0; i < 10; i++) + 10 total += i; + + 1 if (total != 45) + ###### printf ("Failure\n"); + else + 1 printf ("Success\n"); + 1 @} +@end smallexample + +@need 450 +When you use the @samp{-b} option, your output looks like this: + +@smallexample +$ gcov -b tmp.c + 87.50% of 8 source lines executed in file tmp.c + 80.00% of 5 branches executed in file tmp.c + 80.00% of 5 branches taken at least once in file tmp.c + 50.00% of 2 calls executed in file tmp.c +Creating tmp.c.gcov. +@end smallexample + +Here is a sample of a resulting @file{tmp.c.gcov} file: + +@smallexample + main() + @{ + 1 int i, total; + + 1 total = 0; + + 11 for (i = 0; i < 10; i++) +branch 0 taken = 91% +branch 1 taken = 100% +branch 2 taken = 100% + 10 total += i; + + 1 if (total != 45) +branch 0 taken = 100% + ###### printf ("Failure\n"); +call 0 never executed +branch 1 never executed + else + 1 printf ("Success\n"); +call 0 returns = 100% + 1 @} +@end smallexample + +For each basic block, a line is printed after the last line of the basic +block describing the branch or call that ends the basic block. There can +be multiple branches and calls listed for a single source line if there +are multiple basic blocks that end on that line. In this case, the +branches and calls are each given a number. There is no simple way to map +these branches and calls back to source constructs. In general, though, +the lowest numbered branch or call will correspond to the leftmost construct +on the source line. + +For a branch, if it was executed at least once, then a percentage +indicating the number of times the branch was taken divided by the +number of times the branch was executed will be printed. Otherwise, the +message ``never executed'' is printed. + +For a call, if it was executed at least once, then a percentage +indicating the number of times the call returned divided by the number +of times the call was executed will be printed. This will usually be +100%, but may be less for functions call @code{exit} or @code{longjmp}, +and thus may not return every time they are called. + +The execution counts are cumulative. If the example program were +executed again without removing the @code{.da} file, the count for the +number of times each line in the source was executed would be added to +the results of the previous run(s). This is potentially useful in +several ways. For example, it could be used to accumulate data over a +number of program runs as part of a test verification suite, or to +provide more accurate long-term information over a large number of +program runs. + +The data in the @code{.da} files is saved immediately before the program +exits. For each source file compiled with -fprofile-arcs, the profiling +code first attempts to read in an existing @code{.da} file; if the file +doesn't match the executable (differing number of basic block counts) it +will ignore the contents of the file. It then adds in the new execution +counts and finally writes the data to the file. + +@node Gcov and Optimization +@section Using @code{gcov} with GCC Optimization + +If you plan to use @code{gcov} to help optimize your code, you must +first compile your program with two special @sc{gnu} CC options: +@samp{-fprofile-arcs -ftest-coverage}. Aside from that, you can use any +other @sc{gnu} CC options; but if you want to prove that every single line +in your program was executed, you should not compile with optimization +at the same time. On some machines the optimizer can eliminate some +simple code lines by combining them with other lines. For example, code +like this: + +@smallexample +if (a != b) + c = 1; +else + c = 0; +@end smallexample + +@noindent +can be compiled into one instruction on some machines. In this case, +there is no way for @code{gcov} to calculate separate execution counts +for each line because there isn't separate code for each line. Hence +the @code{gcov} output looks like this if you compiled the program with +optimization: + +@smallexample + 100 if (a != b) + 100 c = 1; + 100 else + 100 c = 0; +@end smallexample + +The output shows that this block of code, combined by optimization, +executed 100 times. In one sense this result is correct, because there +was only one instruction representing all four of these lines. However, +the output does not indicate how many times the result was 0 and how +many times the result was 1. +@c man end + +@node Gcov Data Files +@section Brief description of @code{gcov} data files + +@code{gcov} uses three files for doing profiling. The names of these +files are derived from the original @emph{source} file by substituting +the file suffix with either @code{.bb}, @code{.bbg}, or @code{.da}. All +of these files are placed in the same directory as the source file, and +contain data stored in a platform-independent method. + +The @code{.bb} and @code{.bbg} files are generated when the source file +is compiled with the @sc{gnu} CC @samp{-ftest-coverage} option. The +@code{.bb} file contains a list of source files (including headers), +functions within those files, and line numbers corresponding to each +basic block in the source file. + +The @code{.bb} file format consists of several lists of 4-byte integers +which correspond to the line numbers of each basic block in the +file. Each list is terminated by a line number of 0. A line number of -1 +is used to designate that the source file name (padded to a 4-byte +boundary and followed by another -1) follows. In addition, a line number +of -2 is used to designate that the name of a function (also padded to a +4-byte boundary and followed by a -2) follows. + +The @code{.bbg} file is used to reconstruct the program flow graph for +the source file. It contains a list of the program flow arcs (possible +branches taken from one basic block to another) for each function which, +in combination with the @code{.bb} file, enables gcov to reconstruct the +program flow. + +In the @code{.bbg} file, the format is: +@smallexample + number of basic blocks for function #0 (4-byte number) + total number of arcs for function #0 (4-byte number) + count of arcs in basic block #0 (4-byte number) + destination basic block of arc #0 (4-byte number) + flag bits (4-byte number) + destination basic block of arc #1 (4-byte number) + flag bits (4-byte number) + ... + destination basic block of arc #N (4-byte number) + flag bits (4-byte number) + count of arcs in basic block #1 (4-byte number) + destination basic block of arc #0 (4-byte number) + flag bits (4-byte number) + ... +@end smallexample + +A -1 (stored as a 4-byte number) is used to separate each function's +list of basic blocks, and to verify that the file has been read +correctly. + +The @code{.da} file is generated when a program containing object files +built with the @sc{gnu} CC @samp{-fprofile-arcs} option is executed. A +separate @code{.da} file is created for each source file compiled with +this option, and the name of the @code{.da} file is stored as an +absolute pathname in the resulting object file. This path name is +derived from the source file name by substituting a @code{.da} suffix. + +The format of the @code{.da} file is fairly simple. The first 8-byte +number is the number of counts in the file, followed by the counts +(stored as 8-byte numbers). Each count corresponds to the number of +times each arc in the program is executed. The counts are cumulative; +each time the program is executed, it attempts to combine the existing +@code{.da} files with the new counts for this invocation of the +program. It ignores the contents of any @code{.da} files whose number of +arcs doesn't correspond to the current program, and merely overwrites +them instead. + +All three of these files use the functions in @code{gcov-io.h} to store +integers; the functions in this header provide a machine-independent +mechanism for storing and retrieving data from a stream. + diff --git a/gcc/doc/install-old.texi b/gcc/doc/install-old.texi new file mode 100644 index 00000000000..be00cd49cc7 --- /dev/null +++ b/gcc/doc/install-old.texi @@ -0,0 +1,2102 @@ +@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@c The text of this file appears in the file INSTALL +@c in the GCC distribution, as well as in the GCC manual. + +Note most of this information is out of date and superseded by the +online GCC install procedures @uref{http://gcc.gnu.org/install/}. It is +provided for historical reference only. + +@ifclear INSTALLONLY +@node Installation +@chapter Installing GNU CC +@end ifclear +@cindex installing GNU CC + +@menu +* Configuration Files:: Files created by running @code{configure}. +* Configurations:: Configurations Supported by GNU CC. +* Other Dir:: Compiling in a separate directory (not where the source is). +* Cross-Compiler:: Building and installing a cross-compiler. +* VMS Install:: See below for installation on VMS. +* Collect2:: How @code{collect2} works; how it finds @code{ld}. +* Header Dirs:: Understanding the standard header file directories. +@end menu + +Here is the procedure for installing GNU CC on a GNU or Unix system. +See @ref{VMS Install}, for VMS systems. In this section we assume you +compile in the same directory that contains the source files; see +@ref{Other Dir}, to find out how to compile in a separate directory on +Unix systems. + +You cannot install GNU C by itself on MSDOS; it will not compile under +any MSDOS compiler except itself. You need to get the complete +compilation package DJGPP, which includes binaries as well as sources, +and includes all the necessary compilation tools and libraries. + +@enumerate +@item +If you have built GNU CC previously in the same directory for a +different target machine, do @samp{make distclean} to delete all files +that might be invalid. One of the files this deletes is +@file{Makefile}; if @samp{make distclean} complains that @file{Makefile} +does not exist, it probably means that the directory is already suitably +clean. + +@item +On a System V release 4 system, make sure @file{/usr/bin} precedes +@file{/usr/ucb} in @code{PATH}. The @code{cc} command in +@file{/usr/ucb} uses libraries which have bugs. + +@cindex Bison parser generator +@cindex parser generator, Bison +@item +Make sure the Bison parser generator is installed. (This is unnecessary +if the Bison output file @file{c-parse.c} is more recent than +@file{c-parse.y},and you do not plan to change the @samp{.y} file.) + +Bison versions older than Sept 8, 1988 will produce incorrect output +for @file{c-parse.c}. + +@item +If you have chosen a configuration for GNU CC which requires other GNU +tools (such as GAS or the GNU linker) instead of the standard system +tools, install the required tools in the build directory under the names +@file{as}, @file{ld} or whatever is appropriate. This will enable the +compiler to find the proper tools for compilation of the program +@file{enquire}. + +Alternatively, you can do subsequent compilation using a value of the +@code{PATH} environment variable such that the necessary GNU tools come +before the standard system tools. + +@item +Specify the host, build and target machine configurations. You do this +when you run the @file{configure} script. + +The @dfn{build} machine is the system which you are using, the +@dfn{host} machine is the system where you want to run the resulting +compiler (normally the build machine), and the @dfn{target} machine is +the system for which you want the compiler to generate code. + +If you are building a compiler to produce code for the machine it runs +on (a native compiler), you normally do not need to specify any operands +to @file{configure}; it will try to guess the type of machine you are on +and use that as the build, host and target machines. So you don't need +to specify a configuration when building a native compiler unless +@file{configure} cannot figure out what your configuration is or guesses +wrong. + +In those cases, specify the build machine's @dfn{configuration name} +with the @samp{--host} option; the host and target will default to be +the same as the host machine. (If you are building a cross-compiler, +see @ref{Cross-Compiler}.) + +Here is an example: + +@smallexample +./configure --host=sparc-sun-sunos4.1 +@end smallexample + +A configuration name may be canonical or it may be more or less +abbreviated. + +A canonical configuration name has three parts, separated by dashes. +It looks like this: @samp{@var{cpu}-@var{company}-@var{system}}. +(The three parts may themselves contain dashes; @file{configure} +can figure out which dashes serve which purpose.) For example, +@samp{m68k-sun-sunos4.1} specifies a Sun 3. + +You can also replace parts of the configuration by nicknames or aliases. +For example, @samp{sun3} stands for @samp{m68k-sun}, so +@samp{sun3-sunos4.1} is another way to specify a Sun 3. + +You can specify a version number after any of the system types, and some +of the CPU types. In most cases, the version is irrelevant, and will be +ignored. So you might as well specify the version if you know it. + +See @ref{Configurations}, for a list of supported configuration names and +notes on many of the configurations. You should check the notes in that +section before proceeding any further with the installation of GNU CC. + +@item +When running @code{configure}, you may also need to specify certain +additional options that describe variant hardware and software +configurations. These are @samp{--with-gnu-as}, @samp{--with-gnu-ld}, +@samp{--with-stabs} and @samp{--nfp}. + +@table @samp +@item --with-gnu-as +If you will use GNU CC with the GNU assembler (GAS), you should declare +this by using the @samp{--with-gnu-as} option when you run +@file{configure}. + +Using this option does not install GAS. It only modifies the output of +GNU CC to work with GAS. Building and installing GAS is up to you. + +Conversely, if you @emph{do not} wish to use GAS and do not specify +@samp{--with-gnu-as} when building GNU CC, it is up to you to make sure +that GAS is not installed. GNU CC searches for a program named +@code{as} in various directories; if the program it finds is GAS, then +it runs GAS. If you are not sure where GNU CC finds the assembler it is +using, try specifying @samp{-v} when you run it. + +The systems where it makes a difference whether you use GAS are@* +@samp{hppa1.0-@var{any}-@var{any}}, @samp{hppa1.1-@var{any}-@var{any}}, +@samp{i386-@var{any}-sysv}, @samp{i386-@var{any}-isc},@* +@samp{i860-@var{any}-bsd}, @samp{m68k-bull-sysv},@* +@samp{m68k-hp-hpux}, @samp{m68k-sony-bsd},@* +@samp{m68k-altos-sysv}, @samp{m68000-hp-hpux},@* +@samp{m68000-att-sysv}, @samp{@var{any}-lynx-lynxos}, +and @samp{mips-@var{any}}). +On any other system, @samp{--with-gnu-as} has no effect. + +On the systems listed above (except for the HP-PA, for ISC on the +386, and for @samp{mips-sgi-irix5.*}), if you use GAS, you should also +use the GNU linker (and specify @samp{--with-gnu-ld}). + +@item --with-gnu-ld +Specify the option @samp{--with-gnu-ld} if you plan to use the GNU +linker with GNU CC. + +This option does not cause the GNU linker to be installed; it just +modifies the behavior of GNU CC to work with the GNU linker. +@c Specifically, it inhibits the installation of @code{collect2}, a program +@c which otherwise serves as a front-end for the system's linker on most +@c configurations. + +@item --with-stabs +On MIPS based systems and on Alphas, you must specify whether you want +GNU CC to create the normal ECOFF debugging format, or to use BSD-style +stabs passed through the ECOFF symbol table. The normal ECOFF debug +format cannot fully handle languages other than C. BSD stabs format can +handle other languages, but it only works with the GNU debugger GDB. + +Normally, GNU CC uses the ECOFF debugging format by default; if you +prefer BSD stabs, specify @samp{--with-stabs} when you configure GNU +CC. + +No matter which default you choose when you configure GNU CC, the user +can use the @samp{-gcoff} and @samp{-gstabs+} options to specify explicitly +the debug format for a particular compilation. + +@samp{--with-stabs} is meaningful on the ISC system on the 386, also, if +@samp{--with-gas} is used. It selects use of stabs debugging +information embedded in COFF output. This kind of debugging information +supports C++ well; ordinary COFF debugging information does not. + +@samp{--with-stabs} is also meaningful on 386 systems running SVR4. It +selects use of stabs debugging information embedded in ELF output. The +C++ compiler currently (2.6.0) does not support the DWARF debugging +information normally used on 386 SVR4 platforms; stabs provide a +workable alternative. This requires gas and gdb, as the normal SVR4 +tools can not generate or interpret stabs. + +@item --nfp +On certain systems, you must specify whether the machine has a floating +point unit. These systems include @samp{m68k-sun-sunos@var{n}} and +@samp{m68k-isi-bsd}. On any other system, @samp{--nfp} currently has no +effect, though perhaps there are other systems where it could usefully +make a difference. + +@cindex Haifa scheduler +@cindex scheduler, experimental +@item --enable-haifa +@itemx --disable-haifa +Use @samp{--enable-haifa} to enable use of an experimental instruction +scheduler (from IBM Haifa). This may or may not produce better code. +Some targets on which it is known to be a win enable it by default; use +@samp{--disable-haifa} to disable it in these cases. @code{configure} +will print out whether the Haifa scheduler is enabled when it is run. + +@cindex Objective C threads +@cindex threads, Objective C +@item --enable-threads=@var{type} +Certain systems, notably Linux-based GNU systems, can't be relied on to +supply a threads facility for the Objective C runtime and so will +default to single-threaded runtime. They may, however, have a library +threads implementation available, in which case threads can be enabled +with this option by supplying a suitable @var{type}, probably +@samp{posix}. The possibilities for @var{type} are @samp{single}, +@samp{posix}, @samp{win32}, @samp{solaris}, @samp{irix} and @samp{mach}. + +@cindex Internal Compiler Checking +@item --enable-checking +When you specify this option, the compiler is built to perform checking +of tree node types when referencing fields of that node. This does not +change the generated code, but adds error checking within the compiler. +This will slow down the compiler and may only work properly if you +are building the compiler with GNU C. + +@cindex Native Language Support +@cindex NLS +@item --enable-nls +@itemx --disable-nls +The @samp{--enable-nls} option enables Native Language Support (NLS), +which lets GCC output diagnostics in languages other than American +English. Native Language Support is enabled by default if not doing a +canadian cross build. The @samp{--disable-nls} option disables NLS. + +@cindex @code{gettext} +@item --with-included-gettext +If NLS is enbled, the @samp{--with-included-gettext} option causes the build +procedure to prefer its copy of GNU @code{gettext}. This is the default. If +you want the GCC build procedure to prefer the host's @code{gettext} +libraries, use @samp{--without-included-gettext}. + +@cindex @code{catgets} +@item --with-catgets +If NLS is enabled, and if the host lacks @code{gettext} but has the +inferior @code{catgets} interface, the GCC build procedure normally +ignores @code{catgets} and instead uses GCC's copy of the GNU +@code{gettext} library. The @samp{--with-catgets} option causes the +build procedure to use the host's @code{catgets} in this situation. + +@cindex @code{maintainer-mode} +@item --enable-maintainer-mode +The build rules that regenerate the GCC master message catalog +@code{gcc.pot} are normally disabled. This is because it can only be rebuilt +if the complete source tree is present. If you have changed the sources and +want to rebuild the catalog, configuring with +@samp{--enable-maintainer-mode} will enable this. Note that you need a +special version of the @code{gettext} tools to do so. + +@cindex Windows32 Registry support +@item --enable-win32-registry +@itemx --enable-win32-registry=@var{KEY} +@itemx --disable-win32-registry +The @samp{--enable-win32-registry} option enables Windows-hosted GCC +to look up installations paths in the registry using the following key: + +@smallexample +@code{HKEY_LOCAL_MACHINE\SOFTWARE\Free Software Foundation\} +@end smallexample + + defaults to GCC version number, and can be overridden by the +@code{--enable-win32-registry=KEY} option. Vendors and distributors +who use custom installers are encouraged to provide a different key, +perhaps one comprised of vendor name and GCC version number, to +avoid conflict with existing installations. This feature is enabled +by default, and can be disabled by @code{--disable-win32-registry} +option. This option has no effect on the other hosts. +@end table + +@item +In certain cases, you should specify certain other options when you run +@code{configure}. + +@itemize @bullet +@item +The standard directory for installing GNU CC is @file{/usr/local/lib}. +If you want to install its files somewhere else, specify +@samp{--prefix=@var{dir}} when you run @file{configure}. Here @var{dir} +is a directory name to use instead of @file{/usr/local} for all purposes +with one exception: the directory @file{/usr/local/include} is searched +for header files no matter where you install the compiler. To override +this name, use the @code{--with-local-prefix} option below. The directory +you specify need not exist, but its parent directory must exist. + +@item +Specify @samp{--with-local-prefix=@var{dir}} if you want the compiler to +search directory @file{@var{dir}/include} for locally installed header +files @emph{instead} of @file{/usr/local/include}. + +You should specify @samp{--with-local-prefix} @strong{only} if your site has +a different convention (not @file{/usr/local}) for where to put +site-specific files. + +The default value for @samp{--with-local-prefix} is @file{/usr/local} +regardless of the value of @samp{--prefix}. Specifying @samp{--prefix} +has no effect on which directory GNU CC searches for local header files. +This may seem counterintuitive, but actually it is logical. + +The purpose of @samp{--prefix} is to specify where to @emph{install GNU +CC}. The local header files in @file{/usr/local/include}---if you put +any in that directory---are not part of GNU CC. They are part of other +programs---perhaps many others. (GNU CC installs its own header files +in another directory which is based on the @samp{--prefix} value.) + +@strong{Do not} specify @file{/usr} as the @samp{--with-local-prefix}! The +directory you use for @samp{--with-local-prefix} @strong{must not} contain +any of the system's standard header files. If it did contain them, +certain programs would be miscompiled (including GNU Emacs, on certain +targets), because this would override and nullify the header file +corrections made by the @code{fixincludes} script. + +Indications are that people who use this option use it based on +mistaken ideas of what it is for. People use it as if it specified +where to install part of GNU CC. Perhaps they make this assumption +because installing GNU CC creates the directory. +@end itemize + +@item +Build the compiler. Just type @samp{make LANGUAGES=c} in the compiler +directory. + +@samp{LANGUAGES=c} specifies that only the C compiler should be +compiled. The makefile normally builds compilers for all the supported +languages; currently, C, C++, Objective C, Java, FORTRAN, and CHILL. +However, C is the only language that is sure to work when you build with +other non-GNU C compilers. In addition, building anything but C at this +stage is a waste of time. + +In general, you can specify the languages to build by typing the +argument @samp{LANGUAGES="@var{list}"}, where @var{list} is one or more +words from the list @samp{c}, @samp{c++}, @samp{objective-c}, +@samp{java}, @samp{f77}, and @samp{CHILL}. If you have any additional +GNU compilers as subdirectories of the GNU CC source directory, you may +also specify their names in this list. + +Ignore any warnings you may see about ``statement not reached'' in +@file{insn-emit.c}; they are normal. Also, warnings about ``unknown +escape sequence'' are normal in @file{genopinit.c} and perhaps some +other files. Likewise, you should ignore warnings about ``constant is +so large that it is unsigned'' in @file{insn-emit.c} and +@file{insn-recog.c}, and a warning about a comparison always being zero +in @file{enquire.o}. Any other compilation errors may represent bugs in +the port to your machine or operating system, and +@ifclear INSTALLONLY +should be investigated and reported (@pxref{Bugs}). +@end ifclear +@ifset INSTALLONLY +should be investigated and reported. +@end ifset + +Some compilers fail to compile GNU CC because they have bugs or +limitations. For example, the Microsoft compiler is said to run out of +macro space. Some Ultrix compilers run out of expression space; then +you need to break up the statement where the problem happens. + +@item +If you are building a cross-compiler, stop here. @xref{Cross-Compiler}. + +@cindex stage1 +@item +Move the first-stage object files and executables into a subdirectory +with this command: + +@smallexample +make stage1 +@end smallexample + +The files are moved into a subdirectory named @file{stage1}. +Once installation is complete, you may wish to delete these files +with @code{rm -r stage1}. + +@item +If you have chosen a configuration for GNU CC which requires other GNU +tools (such as GAS or the GNU linker) instead of the standard system +tools, install the required tools in the @file{stage1} subdirectory +under the names @file{as}, @file{ld} or whatever is appropriate. This +will enable the stage 1 compiler to find the proper tools in the +following stage. + +Alternatively, you can do subsequent compilation using a value of the +@code{PATH} environment variable such that the necessary GNU tools come +before the standard system tools. + +@item +Recompile the compiler with itself, with this command: + +@smallexample +make CC="stage1/xgcc -Bstage1/" CFLAGS="-g -O2" +@end smallexample + +This is called making the stage 2 compiler. + +The command shown above builds compilers for all the supported +languages. If you don't want them all, you can specify the languages to +build by typing the argument @samp{LANGUAGES="@var{list}"}. @var{list} +should contain one or more words from the list @samp{c}, @samp{c++}, +@samp{objective-c}, and @samp{proto}. Separate the words with spaces. +@samp{proto} stands for the programs @code{protoize} and +@code{unprotoize}; they are not a separate language, but you use +@code{LANGUAGES} to enable or disable their installation. + +If you are going to build the stage 3 compiler, then you might want to +build only the C language in stage 2. + +Once you have built the stage 2 compiler, if you are short of disk +space, you can delete the subdirectory @file{stage1}. + +On a 68000 or 68020 system lacking floating point hardware, +unless you have selected a @file{tm.h} file that expects by default +that there is no such hardware, do this instead: + +@smallexample +make CC="stage1/xgcc -Bstage1/" CFLAGS="-g -O2 -msoft-float" +@end smallexample + +@item +If you wish to test the compiler by compiling it with itself one more +time, install any other necessary GNU tools (such as GAS or the GNU +linker) in the @file{stage2} subdirectory as you did in the +@file{stage1} subdirectory, then do this: + +@smallexample +make stage2 +make CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O2" +@end smallexample + +@noindent +This is called making the stage 3 compiler. Aside from the @samp{-B} +option, the compiler options should be the same as when you made the +stage 2 compiler. But the @code{LANGUAGES} option need not be the +same. The command shown above builds compilers for all the supported +languages; if you don't want them all, you can specify the languages to +build by typing the argument @samp{LANGUAGES="@var{list}"}, as described +above. + +If you do not have to install any additional GNU tools, you may use the +command + +@smallexample +make bootstrap LANGUAGES=@var{language-list} BOOT_CFLAGS=@var{option-list} +@end smallexample + +@noindent +instead of making @file{stage1}, @file{stage2}, and performing +the two compiler builds. + +@item +Compare the latest object files with the stage 2 object files---they +ought to be identical, aside from time stamps (if any). + +On some systems, meaningful comparison of object files is impossible; +they always appear ``different.'' This is currently true on Solaris and +some systems that use ELF object file format. On some versions of Irix +on SGI machines and DEC Unix (OSF/1) on Alpha systems, you will not be +able to compare the files without specifying @file{-save-temps}; see the +description of individual systems above to see if you get comparison +failures. You may have similar problems on other systems. + +Use this command to compare the files: + +@smallexample +make compare +@end smallexample + +This will mention any object files that differ between stage 2 and stage +3. Any difference, no matter how innocuous, indicates that the stage 2 +compiler has compiled GNU CC incorrectly, and is therefore a potentially +@ifclear INSTALLONLY +serious bug which you should investigate and report (@pxref{Bugs}). +@end ifclear +@ifset INSTALLONLY +serious bug which you should investigate and report. +@end ifset + +If your system does not put time stamps in the object files, then this +is a faster way to compare them (using the Bourne shell): + +@smallexample +for file in *.o; do +cmp $file stage2/$file +done +@end smallexample + +If you have built the compiler with the @samp{-mno-mips-tfile} option on +MIPS machines, you will not be able to compare the files. + +@item +Install the compiler driver, the compiler's passes and run-time support +with @samp{make install}. Use the same value for @code{CC}, +@code{CFLAGS} and @code{LANGUAGES} that you used when compiling the +files that are being installed. One reason this is necessary is that +some versions of Make have bugs and recompile files gratuitously when +you do this step. If you use the same variable values, those files will +be recompiled properly. + +For example, if you have built the stage 2 compiler, you can use the +following command: + +@smallexample +make install CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O" LANGUAGES="@var{list}" +@end smallexample + +@noindent +This copies the files @file{cc1}, @file{cpp} and @file{libgcc.a} to +files @file{cc1}, @file{cpp} and @file{libgcc.a} in the directory +@file{/usr/local/lib/gcc-lib/@var{target}/@var{version}}, which is where +the compiler driver program looks for them. Here @var{target} is the +canonicalized form of target machine type specified when you ran +@file{configure}, and @var{version} is the version number of GNU CC. +This naming scheme permits various versions and/or cross-compilers to +coexist. It also copies the executables for compilers for other +languages (e.g., @file{cc1plus} for C++) to the same directory. + +This also copies the driver program @file{xgcc} into +@file{/usr/local/bin/gcc}, so that it appears in typical execution +search paths. It also copies @file{gcc.1} into +@file{/usr/local/man/man1} and info pages into @file{/usr/local/info}. + +On some systems, this command causes recompilation of some files. This +is usually due to bugs in @code{make}. You should either ignore this +problem, or use GNU Make. + +(It is usually better to install GNU CC executables from stage 2 or 3, +since they usually run faster than the ones compiled with some other +compiler.) + +@item +GNU CC includes a runtime library for Objective-C because it is an +integral part of the language. You can find the files associated with +the library in the subdirectory @file{objc}. The GNU Objective-C +Runtime Library requires header files for the target's C library in +order to be compiled,and also requires the header files for the target's +thread library if you want thread support. @xref{Cross Headers, +Cross-Compilers and Header Files, Cross-Compilers and Header Files}, for +discussion about header files issues for cross-compilation. + +When you run @file{configure}, it picks the appropriate Objective-C +thread implementation file for the target platform. In some situations, +you may wish to choose a different back-end as some platforms support +multiple thread implementations or you may wish to disable thread +support completely. You do this by specifying a value for the +@var{OBJC_THREAD_FILE} makefile variable on the command line when you +run make, for example: + +@smallexample +make CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O2" OBJC_THREAD_FILE=thr-single +@end smallexample + +@noindent +Below is a list of the currently available back-ends. + +@itemize @bullet +@item thr-single +Disable thread support, should work for all platforms. +@item thr-decosf1 +DEC OSF/1 thread support. +@item thr-irix +SGI IRIX thread support. +@item thr-mach +Generic MACH thread support, known to work on NEXTSTEP. +@item thr-os2 +IBM OS/2 thread support. +@item thr-posix +Generix POSIX thread support. +@item thr-pthreads +PCThreads on Linux-based GNU systems. +@item thr-solaris +SUN Solaris thread support. +@item thr-win32 +Microsoft Win32 API thread support. +@end itemize +@end enumerate + +@node Configuration Files +@section Files Created by @code{configure} + +Here we spell out what files will be set up by @code{configure}. Normally +you need not be concerned with these files. + +@itemize @bullet +@item +@ifset INTERNALS +A file named @file{config.h} is created that contains a @samp{#include} +of the top-level config file for the machine you will run the compiler +on (@pxref{Config}). This file is responsible for defining information +about the host machine. It includes @file{tm.h}. +@end ifset +@ifclear INTERNALS +A file named @file{config.h} is created that contains a @samp{#include} +of the top-level config file for the machine you will run the compiler +on (@pxref{Config,,The Configuration File, gcc.info, Using and Porting +GCC}). This file is responsible for defining information about the host +machine. It includes @file{tm.h}. +@end ifclear + +The top-level config file is located in the subdirectory @file{config}. +Its name is always @file{xm-@var{something}.h}; usually +@file{xm-@var{machine}.h}, but there are some exceptions. + +If your system does not support symbolic links, you might want to +set up @file{config.h} to contain a @samp{#include} command which +refers to the appropriate file. + +@item +A file named @file{tconfig.h} is created which includes the top-level config +file for your target machine. This is used for compiling certain +programs to run on that machine. + +@item +A file named @file{tm.h} is created which includes the +machine-description macro file for your target machine. It should be in +the subdirectory @file{config} and its name is often +@file{@var{machine}.h}. + +@item +The command file @file{configure} also constructs the file +@file{Makefile} by adding some text to the template file +@file{Makefile.in}. The additional text comes from files in the +@file{config} directory, named @file{t-@var{target}} and +@file{x-@var{host}}. If these files do not exist, it means nothing +needs to be added for a given target or host. +@end itemize + +@node Configurations +@section Configurations Supported by GNU CC +@cindex configurations supported by GNU CC + +Here are the possible CPU types: + +@quotation +@c gmicro, fx80, spur and tahoe omitted since they don't work. +1750a, a29k, alpha, arm, avr, c@var{n}, clipper, dsp16xx, elxsi, fr30, h8300, +hppa1.0, hppa1.1, i370, i386, i486, i586, i686, i786, i860, i960, m32r, +m68000, m68k, m6811, m6812, m88k, mcore, mips, mipsel, mips64, mips64el, +mn10200, mn10300, ns32k, pdp11, powerpc, powerpcle, romp, rs6000, sh, sparc, +sparclite, sparc64, v850, vax, we32k. +@end quotation + +Here are the recognized company names. As you can see, customary +abbreviations are used rather than the longer official names. + +@c What should be done about merlin, tek*, dolphin? +@quotation +acorn, alliant, altos, apollo, apple, att, bull, +cbm, convergent, convex, crds, dec, dg, dolphin, +elxsi, encore, harris, hitachi, hp, ibm, intergraph, isi, +mips, motorola, ncr, next, ns, omron, plexus, +sequent, sgi, sony, sun, tti, unicom, wrs. +@end quotation + +The company name is meaningful only to disambiguate when the rest of +the information supplied is insufficient. You can omit it, writing +just @samp{@var{cpu}-@var{system}}, if it is not needed. For example, +@samp{vax-ultrix4.2} is equivalent to @samp{vax-dec-ultrix4.2}. + +Here is a list of system types: + +@quotation +386bsd, aix, acis, amigaos, aos, aout, aux, bosx, bsd, clix, coff, ctix, cxux, +dgux, dynix, ebmon, ecoff, elf, esix, freebsd, hms, genix, gnu, linux, +linux-gnu, hiux, hpux, iris, irix, isc, luna, lynxos, mach, minix, msdos, mvs, +netbsd, newsos, nindy, ns, osf, osfrose, ptx, riscix, riscos, rtu, sco, sim, +solaris, sunos, sym, sysv, udi, ultrix, unicos, uniplus, unos, vms, vsta, +vxworks, winnt, xenix. +@end quotation + +@noindent +You can omit the system type; then @file{configure} guesses the +operating system from the CPU and company. + +You can add a version number to the system type; this may or may not +make a difference. For example, you can write @samp{bsd4.3} or +@samp{bsd4.4} to distinguish versions of BSD. In practice, the version +number is most needed for @samp{sysv3} and @samp{sysv4}, which are often +treated differently. + +@samp{linux-gnu} is the canonical name for the GNU/Linux target; however +GNU CC will also accept @samp{linux}. The version of the kernel in use is +not relevant on these systems. A suffix such as @samp{libc1} or @samp{aout} +distinguishes major versions of the C library; all of the suffixed versions +are obsolete. + +If you specify an impossible combination such as @samp{i860-dg-vms}, +then you may get an error message from @file{configure}, or it may +ignore part of the information and do the best it can with the rest. +@file{configure} always prints the canonical name for the alternative +that it used. GNU CC does not support all possible alternatives. + +Often a particular model of machine has a name. Many machine names are +recognized as aliases for CPU/company combinations. Thus, the machine +name @samp{sun3}, mentioned above, is an alias for @samp{m68k-sun}. +Sometimes we accept a company name as a machine name, when the name is +popularly used for a particular machine. Here is a table of the known +machine names: + +@quotation +3300, 3b1, 3b@var{n}, 7300, altos3068, altos, +apollo68, att-7300, balance, +convex-c@var{n}, crds, decstation-3100, +decstation, delta, encore, +fx2800, gmicro, hp7@var{nn}, hp8@var{nn}, +hp9k2@var{nn}, hp9k3@var{nn}, hp9k7@var{nn}, +hp9k8@var{nn}, iris4d, iris, isi68, +m3230, magnum, merlin, miniframe, +mmax, news-3600, news800, news, next, +pbd, pc532, pmax, powerpc, powerpcle, ps2, risc-news, +rtpc, sun2, sun386i, sun386, sun3, +sun4, symmetry, tower-32, tower. +@end quotation + +@noindent +Remember that a machine name specifies both the cpu type and the company +name. +If you want to install your own homemade configuration files, you can +use @samp{local} as the company name to access them. If you use +configuration @samp{@var{cpu}-local}, the configuration name +without the cpu prefix +is used to form the configuration file names. + +Thus, if you specify @samp{m68k-local}, configuration uses +files @file{m68k.md}, @file{local.h}, @file{m68k.c}, +@file{xm-local.h}, @file{t-local}, and @file{x-local}, all in the +directory @file{config/m68k}. + +Here is a list of configurations that have special treatment or special +things you must know: + +@table @samp +@item 1750a-*-* +MIL-STD-1750A processors. + +The MIL-STD-1750A cross configuration produces output for +@code{as1750}, an assembler/linker available under the GNU Public +License for the 1750A. @code{as1750} can be obtained at +@uref{ftp://ftp.fta-berlin.de/pub/crossgcc/1750gals/}. +A similarly licensed simulator for +the 1750A is available from same address. + +You should ignore a fatal error during the building of libgcc (libgcc is +not yet implemented for the 1750A.) + +The @code{as1750} assembler requires the file @file{ms1750.inc}, which is +found in the directory @file{config/1750a}. + +GNU CC produced the same sections as the Fairchild F9450 C Compiler, +namely: + +@table @code +@item Normal +The program code section. + +@item Static +The read/write (RAM) data section. + +@item Konst +The read-only (ROM) constants section. + +@item Init +Initialization section (code to copy KREL to SREL). +@end table + +The smallest addressable unit is 16 bits (BITS_PER_UNIT is 16). This +means that type `char' is represented with a 16-bit word per character. +The 1750A's "Load/Store Upper/Lower Byte" instructions are not used by +GNU CC. + +@item alpha-*-osf1 +Systems using processors that implement the DEC Alpha architecture and +are running the DEC Unix (OSF/1) operating system, for example the DEC +Alpha AXP systems.CC.) + +GNU CC writes a @samp{.verstamp} directive to the assembler output file +unless it is built as a cross-compiler. It gets the version to use from +the system header file @file{/usr/include/stamp.h}. If you install a +new version of DEC Unix, you should rebuild GCC to pick up the new version +stamp. + +Note that since the Alpha is a 64-bit architecture, cross-compilers from +32-bit machines will not generate code as efficient as that generated +when the compiler is running on a 64-bit machine because many +optimizations that depend on being able to represent a word on the +target in an integral value on the host cannot be performed. Building +cross-compilers on the Alpha for 32-bit machines has only been tested in +a few cases and may not work properly. + +@code{make compare} may fail on old versions of DEC Unix unless you add +@samp{-save-temps} to @code{CFLAGS}. On these systems, the name of the +assembler input file is stored in the object file, and that makes +comparison fail if it differs between the @code{stage1} and +@code{stage2} compilations. The option @samp{-save-temps} forces a +fixed name to be used for the assembler input file, instead of a +randomly chosen name in @file{/tmp}. Do not add @samp{-save-temps} +unless the comparisons fail without that option. If you add +@samp{-save-temps}, you will have to manually delete the @samp{.i} and +@samp{.s} files after each series of compilations. + +GNU CC now supports both the native (ECOFF) debugging format used by DBX +and GDB and an encapsulated STABS format for use only with GDB. See the +discussion of the @samp{--with-stabs} option of @file{configure} above +for more information on these formats and how to select them. + +There is a bug in DEC's assembler that produces incorrect line numbers +for ECOFF format when the @samp{.align} directive is used. To work +around this problem, GNU CC will not emit such alignment directives +while writing ECOFF format debugging information even if optimization is +being performed. Unfortunately, this has the very undesirable +side-effect that code addresses when @samp{-O} is specified are +different depending on whether or not @samp{-g} is also specified. + +To avoid this behavior, specify @samp{-gstabs+} and use GDB instead of +DBX. DEC is now aware of this problem with the assembler and hopes to +provide a fix shortly. + +@item arc-*-elf +Argonaut ARC processor. +This configuration is intended for embedded systems. + +@item arm-*-aout +Advanced RISC Machines ARM-family processors. These are often used in +embedded applications. There are no standard Unix configurations. +This configuration corresponds to the basic instruction sequences and will +produce @file{a.out} format object modules. + +You may need to make a variant of the file @file{arm.h} for your particular +configuration. + +@item arm-*-elf +This configuration is intended for embedded systems. + +@item arm-*-linux*aout +Any of the ARM-family processors running the Linux-based GNU system with +the @file{a.out} binary format. This is an obsolete configuration. + +@item arm-*-linux +@itemx arm-*-linux-gnu +@itemx arm-*-linux*oldld +Any of the ARM-family processors running the Linux-based GNU system with +the @file{ELF} binary format. You must use version 2.9.1.0.22 or later +of the GNU/Linux binutils, which you can download from +@uref{ftp://ftp.varesearch.com/pub/support/hjl/binutils/}. + +These two configurations differ only in the required version of GNU +binutils. For binutils 2.9.1.0.x, use @samp{arm-*-linux-gnuoldld}. For +newer versions of binutils, use @samp{arm-*-linux-gnu}. + +@item arm-*-riscix +The ARM2 or ARM3 processor running RISC iX, Acorn's port of BSD Unix. +If you are running a version of RISC iX prior to 1.2 then you must +specify the version number during configuration. Note that the +assembler shipped with RISC iX does not support stabs debugging +information; a new version of the assembler, with stabs support +included, is now available from Acorn and via ftp +@uref{ftp://ftp.acorn.com/pub/riscix/as+xterm.tar.Z}. To enable stabs +debugging, pass @samp{--with-gnu-as} to configure. + +You will need to install GNU @file{sed} before you can run configure. + +@item a29k +AMD Am29k-family processors. These are normally used in embedded +applications. There are no standard Unix configurations. +This configuration +corresponds to AMD's standard calling sequence and binary interface +and is compatible with other 29k tools. + +You may need to make a variant of the file @file{a29k.h} for your +particular configuration. + +@item a29k-*-bsd +AMD Am29050 used in a system running a variant of BSD Unix. + +@item avr +ATMEL AVR-family micro controllers. These are used in embedded +applications. There are no standard Unix configurations. +@xref{AVR Options}, for the list of supported MCU types. + +@item decstation-* +MIPS-based DECstations can support three different personalities: +Ultrix, DEC OSF/1, and OSF/rose. (Alpha-based DECstation products have +a configuration name beginning with @samp{alpha-dec}.) To configure GCC +for these platforms use the following configurations: + +@table @samp +@item decstation-ultrix +Ultrix configuration. + +@item decstation-osf1 +Dec's version of OSF/1. + +@item decstation-osfrose +Open Software Foundation reference port of OSF/1 which uses the +OSF/rose object file format instead of ECOFF. Normally, you +would not select this configuration. +@end table + +The MIPS C compiler needs to be told to increase its table size +for switch statements with the @samp{-Wf,-XNg1500} option in +order to compile @file{cp/parse.c}. If you use the @samp{-O2} +optimization option, you also need to use @samp{-Olimit 3000}. +Both of these options are automatically generated in the +@file{Makefile} that the shell script @file{configure} builds. +If you override the @code{CC} make variable and use the MIPS +compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. + +@item elxsi-elxsi-bsd +The Elxsi's C compiler has known limitations that prevent it from +compiling GNU C. Please contact @email{mrs@@cygnus.com} for more details. + +@item dsp16xx +A port to the AT&T DSP1610 family of processors. + +@ignore +@item fx80 +Alliant FX/8 computer. Note that the standard installed C compiler in +Concentrix 5.0 has a bug which prevent it from compiling GNU CC +correctly. You can patch the compiler bug as follows: + +@smallexample +cp /bin/pcc ./pcc +adb -w ./pcc - << EOF +15f6?w 6610 +EOF +@end smallexample + +Then you must use the @samp{-ip12} option when compiling GNU CC +with the patched compiler, as shown here: + +@smallexample +make CC="./pcc -ip12" CFLAGS=-w +@end smallexample + +Note also that Alliant's version of DBX does not manage to work with the +output from GNU CC. +@end ignore + +@item h8300-*-* +Hitachi H8/300 series of processors. + +The calling convention and structure layout has changed in release 2.6. +All code must be recompiled. The calling convention now passes the +first three arguments in function calls in registers. Structures are no +longer a multiple of 2 bytes. + +@item i370-*-* +This port is very preliminary and has many known bugs. We hope to +have a higher-quality port for this machine soon. + +@item i386-*-linux*oldld +Use this configuration to generate @file{a.out} binaries on Linux-based +GNU systems if you do not have gas/binutils version 2.5.2 or later +installed. This is an obsolete configuration. + +@item i386-*-linux*aout +Use this configuration to generate @file{a.out} binaries on Linux-based +GNU systems. This configuration is being superseded. You must use +gas/binutils version 2.5.2 or later. + +@item i386-*-linux +@itemx i386-*-linux-gnu +Use this configuration to generate ELF binaries on Linux-based GNU +systems. You must use gas/binutils version 2.5.2 or later. + +@item i386-*-sco +Compilation with RCC is recommended. Also, it may be a good idea to +link with GNU malloc instead of the malloc that comes with the system. + +@item i386-*-sco3.2v4 +Use this configuration for SCO release 3.2 version 4. + +@item i386-*-sco3.2v5* +Use this for the SCO OpenServer Release 5 family of operating systems. + +@item i386-*-isc +It may be a good idea to link with GNU malloc instead of the malloc that +comes with the system. + +In ISC version 4.1, @file{sed} core dumps when building +@file{deduced.h}. Use the version of @file{sed} from version 4.0. + +@item i386-*-esix +It may be good idea to link with GNU malloc instead of the malloc that +comes with the system. + +@item i386-ibm-aix +You need to use GAS version 2.1 or later, and LD from +GNU binutils version 2.2 or later. + +@item i386-sequent-bsd +Go to the Berkeley universe before compiling. + +@item i386-sequent-ptx1* +@itemx i386-sequent-ptx2* +You must install GNU @file{sed} before running @file{configure}. + +@item *-lynx-lynxos +LynxOS 2.2 and earlier comes with GNU CC 1.x already installed as +@file{/bin/gcc}. You should compile with this instead of @file{/bin/cc}. +You can tell GNU CC to use the GNU assembler and linker, by specifying +@samp{--with-gnu-as --with-gnu-ld} when configuring. These will produce +COFF format object files and executables; otherwise GNU CC will use the +installed tools, which produce @file{a.out} format executables. + +@item m32r-*-elf +Mitsubishi M32R processor. +This configuration is intended for embedded systems. + +@item m68000-hp-bsd +HP 9000 series 200 running BSD. Note that the C compiler that comes +with this system cannot compile GNU CC; contact @email{law@@cygnus.com} +to get binaries of GNU CC for bootstrapping. + +@item m68k-altos +Altos 3068. You must use the GNU assembler, linker and debugger. +Also, you must fix a kernel bug. Details in the file @file{README.ALTOS}. + +@item m68k-apple-aux +Apple Macintosh running A/UX. +You may configure GCC to use either the system assembler and +linker or the GNU assembler and linker. You should use the GNU configuration +if you can, especially if you also want to use GNU C++. You enabled +that configuration with + the @samp{--with-gnu-as} and @samp{--with-gnu-ld} +options to @code{configure}. + +Note the C compiler that comes +with this system cannot compile GNU CC. You can find binaries of GNU CC +for bootstrapping on @code{jagubox.gsfc.nasa.gov}. +You will also a patched version of @file{/bin/ld} there that +raises some of the arbitrary limits found in the original. + +@item m68k-att-sysv +AT&T 3b1, a.k.a. 7300 PC. This version of GNU CC cannot +be compiled with the system C compiler, which is too buggy. +You will need to get a previous version of GCC and use it to +bootstrap. Binaries are available from the OSU-CIS archive, at +@uref{ftp://archive.cis.ohio-state.edu/pub/att7300/}. + +@item m68k-bull-sysv +Bull DPX/2 series 200 and 300 with BOS-2.00.45 up to BOS-2.01. GNU CC works +either with native assembler or GNU assembler. You can use +GNU assembler with native coff generation by providing @samp{--with-gnu-as} to +the configure script or use GNU assembler with dbx-in-coff encapsulation +by providing @samp{--with-gnu-as --stabs}. For any problem with native +assembler or for availability of the DPX/2 port of GAS, contact +@email{F.Pierresteguy@@frcl.bull.fr}. + +@item m68k-crds-unox +Use @samp{configure unos} for building on Unos. + +The Unos assembler is named @code{casm} instead of @code{as}. For some +strange reason linking @file{/bin/as} to @file{/bin/casm} changes the +behavior, and does not work. So, when installing GNU CC, you should +install the following script as @file{as} in the subdirectory where +the passes of GCC are installed: + +@example +#!/bin/sh +casm $* +@end example + +The default Unos library is named @file{libunos.a} instead of +@file{libc.a}. To allow GNU CC to function, either change all +references to @samp{-lc} in @file{gcc.c} to @samp{-lunos} or link +@file{/lib/libc.a} to @file{/lib/libunos.a}. + +@cindex @code{alloca}, for Unos +When compiling GNU CC with the standard compiler, to overcome bugs in +the support of @code{alloca}, do not use @samp{-O} when making stage 2. +Then use the stage 2 compiler with @samp{-O} to make the stage 3 +compiler. This compiler will have the same characteristics as the usual +stage 2 compiler on other systems. Use it to make a stage 4 compiler +and compare that with stage 3 to verify proper compilation. + +(Perhaps simply defining @code{ALLOCA} in @file{x-crds} as described in +the comments there will make the above paragraph superfluous. Please +inform us of whether this works.) + +Unos uses memory segmentation instead of demand paging, so you will need +a lot of memory. 5 Mb is barely enough if no other tasks are running. +If linking @file{cc1} fails, try putting the object files into a library +and linking from that library. + +@item m68k-hp-hpux +HP 9000 series 300 or 400 running HP-UX. HP-UX version 8.0 has a bug in +the assembler that prevents compilation of GNU CC. To fix it, get patch +PHCO_4484 from HP. + +In addition, if you wish to use gas @samp{--with-gnu-as} you must use +gas version 2.1 or later, and you must use the GNU linker version 2.1 or +later. Earlier versions of gas relied upon a program which converted the +gas output into the native HP-UX format, but that program has not been +kept up to date. gdb does not understand that native HP-UX format, so +you must use gas if you wish to use gdb. + +@item m68k-sun +Sun 3. We do not provide a configuration file to use the Sun FPA by +default, because programs that establish signal handlers for floating +point traps inherently cannot work with the FPA. + +@item m6811-elf +Motorola 68HC11 family micro controllers. These are used in embedded +applications. There are no standard Unix configurations. + +@item m6812-elf +Motorola 68HC12 family micro controllers. These are used in embedded +applications. There are no standard Unix configurations. + +@item m88k-*-svr3 +Motorola m88k running the AT&T/Unisoft/Motorola V.3 reference port. +These systems tend to use the Green Hills C, revision 1.8.5, as the +standard C compiler. There are apparently bugs in this compiler that +result in object files differences between stage 2 and stage 3. If this +happens, make the stage 4 compiler and compare it to the stage 3 +compiler. If the stage 3 and stage 4 object files are identical, this +suggests you encountered a problem with the standard C compiler; the +stage 3 and 4 compilers may be usable. + +It is best, however, to use an older version of GNU CC for bootstrapping +if you have one. + +@item m88k-*-dgux +Motorola m88k running DG/UX. To build 88open BCS native or cross +compilers on DG/UX, specify the configuration name as +@samp{m88k-*-dguxbcs} and build in the 88open BCS software development +environment. To build ELF native or cross compilers on DG/UX, specify +@samp{m88k-*-dgux} and build in the DG/UX ELF development environment. +You set the software development environment by issuing +@samp{sde-target} command and specifying either @samp{m88kbcs} or +@samp{m88kdguxelf} as the operand. + +If you do not specify a configuration name, @file{configure} guesses the +configuration based on the current software development environment. + +@item m88k-tektronix-sysv3 +Tektronix XD88 running UTekV 3.2e. Do not turn on +optimization while building stage1 if you bootstrap with +the buggy Green Hills compiler. Also, The bundled LAI +System V NFS is buggy so if you build in an NFS mounted +directory, start from a fresh reboot, or avoid NFS all together. +Otherwise you may have trouble getting clean comparisons +between stages. + +@item mips-mips-bsd +MIPS machines running the MIPS operating system in BSD mode. It's +possible that some old versions of the system lack the functions +@code{memcpy}, @code{memmove}, @code{memcmp}, and @code{memset}. If your +system lacks these, you must remove or undo the definition of +@code{TARGET_MEM_FUNCTIONS} in @file{mips-bsd.h}. + +The MIPS C compiler needs to be told to increase its table size +for switch statements with the @samp{-Wf,-XNg1500} option in +order to compile @file{cp/parse.c}. If you use the @samp{-O2} +optimization option, you also need to use @samp{-Olimit 3000}. +Both of these options are automatically generated in the +@file{Makefile} that the shell script @file{configure} builds. +If you override the @code{CC} make variable and use the MIPS +compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. + +@item mips-mips-riscos* +The MIPS C compiler needs to be told to increase its table size +for switch statements with the @samp{-Wf,-XNg1500} option in +order to compile @file{cp/parse.c}. If you use the @samp{-O2} +optimization option, you also need to use @samp{-Olimit 3000}. +Both of these options are automatically generated in the +@file{Makefile} that the shell script @file{configure} builds. +If you override the @code{CC} make variable and use the MIPS +compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. + +MIPS computers running RISC-OS can support four different +personalities: default, BSD 4.3, System V.3, and System V.4 +(older versions of RISC-OS don't support V.4). To configure GCC +for these platforms use the following configurations: + +@table @samp +@item mips-mips-riscos@code{rev} +Default configuration for RISC-OS, revision @code{rev}. + +@item mips-mips-riscos@code{rev}bsd +BSD 4.3 configuration for RISC-OS, revision @code{rev}. + +@item mips-mips-riscos@code{rev}sysv4 +System V.4 configuration for RISC-OS, revision @code{rev}. + +@item mips-mips-riscos@code{rev}sysv +System V.3 configuration for RISC-OS, revision @code{rev}. +@end table + +The revision @code{rev} mentioned above is the revision of +RISC-OS to use. You must reconfigure GCC when going from a +RISC-OS revision 4 to RISC-OS revision 5. This has the effect of +avoiding a linker +@ifclear INSTALLONLY +bug (see @ref{Installation Problems}, for more details). +@end ifclear +@ifset INSTALLONLY +bug. +@end ifset + +@item mips-sgi-* +In order to compile GCC on an SGI running IRIX 4, the "c.hdr.lib" +option must be installed from the CD-ROM supplied from Silicon Graphics. +This is found on the 2nd CD in release 4.0.1. + +In order to compile GCC on an SGI running IRIX 5, the "compiler_dev.hdr" +subsystem must be installed from the IDO CD-ROM supplied by Silicon +Graphics. + +@code{make compare} may fail on version 5 of IRIX unless you add +@samp{-save-temps} to @code{CFLAGS}. On these systems, the name of the +assembler input file is stored in the object file, and that makes +comparison fail if it differs between the @code{stage1} and +@code{stage2} compilations. The option @samp{-save-temps} forces a +fixed name to be used for the assembler input file, instead of a +randomly chosen name in @file{/tmp}. Do not add @samp{-save-temps} +unless the comparisons fail without that option. If you do you +@samp{-save-temps}, you will have to manually delete the @samp{.i} and +@samp{.s} files after each series of compilations. + +The MIPS C compiler needs to be told to increase its table size +for switch statements with the @samp{-Wf,-XNg1500} option in +order to compile @file{cp/parse.c}. If you use the @samp{-O2} +optimization option, you also need to use @samp{-Olimit 3000}. +Both of these options are automatically generated in the +@file{Makefile} that the shell script @file{configure} builds. +If you override the @code{CC} make variable and use the MIPS +compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. + +On Irix version 4.0.5F, and perhaps on some other versions as well, +there is an assembler bug that reorders instructions incorrectly. To +work around it, specify the target configuration +@samp{mips-sgi-irix4loser}. This configuration inhibits assembler +optimization. + +In a compiler configured with target @samp{mips-sgi-irix4}, you can turn +off assembler optimization by using the @samp{-noasmopt} option. This +compiler option passes the option @samp{-O0} to the assembler, to +inhibit reordering. + +The @samp{-noasmopt} option can be useful for testing whether a problem +is due to erroneous assembler reordering. Even if a problem does not go +away with @samp{-noasmopt}, it may still be due to assembler +reordering---perhaps GNU CC itself was miscompiled as a result. + +To enable debugging under Irix 5, you must use GNU as 2.5 or later, +and use the @samp{--with-gnu-as} configure option when configuring gcc. +GNU as is distributed as part of the binutils package. + +@item mips-sony-sysv +Sony MIPS NEWS. This works in NEWSOS 5.0.1, but not in 5.0.2 (which +uses ELF instead of COFF). Support for 5.0.2 will probably be provided +soon by volunteers. In particular, the linker does not like the +code generated by GCC when shared libraries are linked in. + +@item ns32k-encore +Encore ns32000 system. Encore systems are supported only under BSD. + +@item ns32k-*-genix +National Semiconductor ns32000 system. Genix has bugs in @code{alloca} +and @code{malloc}; you must get the compiled versions of these from GNU +Emacs. + +@item ns32k-sequent +Go to the Berkeley universe before compiling. + +@item ns32k-utek +UTEK ns32000 system (``merlin''). The C compiler that comes with this +system cannot compile GNU CC; contact @samp{tektronix!reed!mason} to get +binaries of GNU CC for bootstrapping. + +@item romp-*-aos +@itemx romp-*-mach +The only operating systems supported for the IBM RT PC are AOS and +MACH. GNU CC does not support AIX running on the RT. We recommend you +compile GNU CC with an earlier version of itself; if you compile GNU CC +with @code{hc}, the Metaware compiler, it will work, but you will get +mismatches between the stage 2 and stage 3 compilers in various files. +These errors are minor differences in some floating-point constants and +can be safely ignored; the stage 3 compiler is correct. + +@item rs6000-*-aix +@itemx powerpc-*-aix +Various early versions of each release of the IBM XLC compiler will not +bootstrap GNU CC. Symptoms include differences between the stage2 and +stage3 object files, and errors when compiling @file{libgcc.a} or +@file{enquire}. Known problematic releases include: xlc-1.2.1.8, +xlc-1.3.0.0 (distributed with AIX 3.2.5), and xlc-1.3.0.19. Both +xlc-1.2.1.28 and xlc-1.3.0.24 (PTF 432238) are known to produce working +versions of GNU CC, but most other recent releases correctly bootstrap +GNU CC. + +Release 4.3.0 of AIX and ones prior to AIX 3.2.4 include a version of +the IBM assembler which does not accept debugging directives: assembler +updates are available as PTFs. Also, if you are using AIX 3.2.5 or +greater and the GNU assembler, you must have a version modified after +October 16th, 1995 in order for the GNU C compiler to build. See the +file @file{README.RS6000} for more details on any of these problems. + +GNU CC does not yet support the 64-bit PowerPC instructions. + +Objective C does not work on this architecture because it makes assumptions +that are incompatible with the calling conventions. + +AIX on the RS/6000 provides support (NLS) for environments outside of +the United States. Compilers and assemblers use NLS to support +locale-specific representations of various objects including +floating-point numbers ("." vs "," for separating decimal fractions). +There have been problems reported where the library linked with GNU CC +does not produce the same floating-point formats that the assembler +accepts. If you have this problem, set the LANG environment variable to +"C" or "En_US". + +Due to changes in the way that GNU CC invokes the binder (linker) for AIX +4.1, you may now receive warnings of duplicate symbols from the link step +that were not reported before. The assembly files generated by GNU CC for +AIX have always included multiple symbol definitions for certain global +variable and function declarations in the original program. The warnings +should not prevent the linker from producing a correct library or runnable +executable. + +By default, AIX 4.1 produces code that can be used on either Power or +PowerPC processors. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpc-*-elf +@itemx powerpc-*-sysv4 +PowerPC system in big endian mode, running System V.4. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpc-*-linux +@itemx powerpc-*-linux-gnu +PowerPC system in big endian mode, running the Linux-based GNU system. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpc-*-eabiaix +Embedded PowerPC system in big endian mode with -mcall-aix selected as +the default. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpc-*-eabisim +Embedded PowerPC system in big endian mode for use in running under the +PSIM simulator. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpc-*-eabi +Embedded PowerPC system in big endian mode. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpcle-*-elf +@itemx powerpcle-*-sysv4 +PowerPC system in little endian mode, running System V.4. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpcle-*-eabisim +Embedded PowerPC system in little endian mode for use in running under +the PSIM simulator. + +@itemx powerpcle-*-eabi +Embedded PowerPC system in little endian mode. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item powerpcle-*-winnt +@itemx powerpcle-*-pe +PowerPC system in little endian mode running Windows NT. + +You can specify a default version for the @samp{-mcpu=}@var{cpu_type} +switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. + +@item vax-dec-ultrix +Don't try compiling with Vax C (@code{vcc}). It produces incorrect code +in some cases (for example, when @code{alloca} is used). + +Meanwhile, compiling @file{cp/parse.c} with pcc does not work because of +an internal table size limitation in that compiler. To avoid this +problem, compile just the GNU C compiler first, and use it to recompile +building all the languages that you want to run. + +@item vax-dec-vms +See @ref{VMS Install}, for details on how to install GNU CC on VMS. + +@item we32k-*-* +These computers are also known as the 3b2, 3b5, 3b20 and other similar +names. (However, the 3b1 is actually a 68000; see +@ref{Configurations}.) + +Don't use @samp{-g} when compiling with the system's compiler. The +system's linker seems to be unable to handle such a large program with +debugging information. + +The system's compiler runs out of capacity when compiling @file{stmt.c} +in GNU CC. You can work around this by building @file{cpp} in GNU CC +first, then use that instead of the system's preprocessor with the +system's C compiler to compile @file{stmt.c}. Here is how: + +@smallexample +mv /lib/cpp /lib/cpp.att +cp cpp /lib/cpp.gnu +echo '/lib/cpp.gnu -traditional $@{1+"$@@"@}' > /lib/cpp +chmod +x /lib/cpp +@end smallexample + +The system's compiler produces bad code for some of the GNU CC +optimization files. So you must build the stage 2 compiler without +optimization. Then build a stage 3 compiler with optimization. +That executable should work. Here are the necessary commands: + +@smallexample +make LANGUAGES=c CC=stage1/xgcc CFLAGS="-Bstage1/ -g" +make stage2 +make CC=stage2/xgcc CFLAGS="-Bstage2/ -g -O" +@end smallexample + +You may need to raise the ULIMIT setting to build a C++ compiler, +as the file @file{cc1plus} is larger than one megabyte. +@end table + +@node Other Dir +@section Compilation in a Separate Directory +@cindex other directory, compilation in +@cindex compilation in a separate directory +@cindex separate directory, compilation in + +If you wish to build the object files and executables in a directory +other than the one containing the source files, here is what you must +do differently: + +@enumerate +@item +Make sure you have a version of Make that supports the @code{VPATH} +feature. (GNU Make supports it, as do Make versions on most BSD +systems.) + +@item +If you have ever run @file{configure} in the source directory, you must undo +the configuration. Do this by running: + +@example +make distclean +@end example + +@item +Go to the directory in which you want to build the compiler before +running @file{configure}: + +@example +mkdir gcc-sun3 +cd gcc-sun3 +@end example + +On systems that do not support symbolic links, this directory must be +on the same file system as the source code directory. + +@item +Specify where to find @file{configure} when you run it: + +@example +../gcc/configure @dots{} +@end example + +This also tells @code{configure} where to find the compiler sources; +@code{configure} takes the directory from the file name that was used to +invoke it. But if you want to be sure, you can specify the source +directory with the @samp{--srcdir} option, like this: + +@example +../gcc/configure --srcdir=../gcc @var{other options} +@end example + +The directory you specify with @samp{--srcdir} need not be the same +as the one that @code{configure} is found in. +@end enumerate + +Now, you can run @code{make} in that directory. You need not repeat the +configuration steps shown above, when ordinary source files change. You +must, however, run @code{configure} again when the configuration files +change, if your system does not support symbolic links. + +@node Cross-Compiler +@section Building and Installing a Cross-Compiler +@cindex cross-compiler, installation + +GNU CC can function as a cross-compiler for many machines, but not all. + +@itemize @bullet +@item +Cross-compilers for the Mips as target using the Mips assembler +currently do not work, because the auxiliary programs +@file{mips-tdump.c} and @file{mips-tfile.c} can't be compiled on +anything but a Mips. It does work to cross compile for a Mips +if you use the GNU assembler and linker. + +@item +Cross-compilers between machines with different floating point formats +have not all been made to work. GNU CC now has a floating point +emulator with which these can work, but each target machine description +needs to be updated to take advantage of it. + +@item +Cross-compilation between machines of different word sizes is +somewhat problematic and sometimes does not work. +@end itemize + +Since GNU CC generates assembler code, you probably need a +cross-assembler that GNU CC can run, in order to produce object files. +If you want to link on other than the target machine, you need a +cross-linker as well. You also need header files and libraries suitable +for the target machine that you can install on the host machine. + +@menu +* Steps of Cross:: Using a cross-compiler involves several steps + that may be carried out on different machines. +* Configure Cross:: Configuring a cross-compiler. +* Tools and Libraries:: Where to put the linker and assembler, and the C library. +* Cross Headers:: Finding and installing header files + for a cross-compiler. +* Build Cross:: Actually compiling the cross-compiler. +@end menu + +@node Steps of Cross +@subsection Steps of Cross-Compilation + +To compile and run a program using a cross-compiler involves several +steps: + +@itemize @bullet +@item +Run the cross-compiler on the host machine to produce assembler files +for the target machine. This requires header files for the target +machine. + +@item +Assemble the files produced by the cross-compiler. You can do this +either with an assembler on the target machine, or with a +cross-assembler on the host machine. + +@item +Link those files to make an executable. You can do this either with a +linker on the target machine, or with a cross-linker on the host +machine. Whichever machine you use, you need libraries and certain +startup files (typically @file{crt@dots{}.o}) for the target machine. +@end itemize + +It is most convenient to do all of these steps on the same host machine, +since then you can do it all with a single invocation of GNU CC. This +requires a suitable cross-assembler and cross-linker. For some targets, +the GNU assembler and linker are available. + +@node Configure Cross +@subsection Configuring a Cross-Compiler + +To build GNU CC as a cross-compiler, you start out by running +@file{configure}. Use the @samp{--target=@var{target}} to specify the +target type. If @file{configure} was unable to correctly identify the +system you are running on, also specify the @samp{--build=@var{build}} +option. For example, here is how to configure for a cross-compiler that +produces code for an HP 68030 system running BSD on a system that +@file{configure} can correctly identify: + +@smallexample +./configure --target=m68k-hp-bsd4.3 +@end smallexample + +@node Tools and Libraries +@subsection Tools and Libraries for a Cross-Compiler + +If you have a cross-assembler and cross-linker available, you should +install them now. Put them in the directory +@file{/usr/local/@var{target}/bin}. Here is a table of the tools +you should put in this directory: + +@table @file +@item as +This should be the cross-assembler. + +@item ld +This should be the cross-linker. + +@item ar +This should be the cross-archiver: a program which can manipulate +archive files (linker libraries) in the target machine's format. + +@item ranlib +This should be a program to construct a symbol table in an archive file. +@end table + +The installation of GNU CC will find these programs in that directory, +and copy or link them to the proper place to for the cross-compiler to +find them when run later. + +The easiest way to provide these files is to build the Binutils package +and GAS. Configure them with the same @samp{--host} and @samp{--target} +options that you use for configuring GNU CC, then build and install +them. They install their executables automatically into the proper +directory. Alas, they do not support all the targets that GNU CC +supports. + +If you want to install libraries to use with the cross-compiler, such as +a standard C library, put them in the directory +@file{/usr/local/@var{target}/lib}; installation of GNU CC copies +all the files in that subdirectory into the proper place for GNU CC to +find them and link with them. Here's an example of copying some +libraries from a target machine: + +@example +ftp @var{target-machine} +lcd /usr/local/@var{target}/lib +cd /lib +get libc.a +cd /usr/lib +get libg.a +get libm.a +quit +@end example + +@noindent +The precise set of libraries you'll need, and their locations on +the target machine, vary depending on its operating system. + +@cindex start files +Many targets require ``start files'' such as @file{crt0.o} and +@file{crtn.o} which are linked into each executable; these too should be +placed in @file{/usr/local/@var{target}/lib}. There may be several +alternatives for @file{crt0.o}, for use with profiling or other +compilation options. Check your target's definition of +@code{STARTFILE_SPEC} to find out what start files it uses. +Here's an example of copying these files from a target machine: + +@example +ftp @var{target-machine} +lcd /usr/local/@var{target}/lib +prompt +cd /lib +mget *crt*.o +cd /usr/lib +mget *crt*.o +quit +@end example + +@node Cross Headers +@subsection Cross-Compilers and Header Files + +If you are cross-compiling a standalone program or a program for an +embedded system, then you may not need any header files except the few +that are part of GNU CC (and those of your program). However, if you +intend to link your program with a standard C library such as +@file{libc.a}, then you probably need to compile with the header files +that go with the library you use. + +The GNU C compiler does not come with these files, because (1) they are +system-specific, and (2) they belong in a C library, not in a compiler. + +If the GNU C library supports your target machine, then you can get the +header files from there (assuming you actually use the GNU library when +you link your program). + +If your target machine comes with a C compiler, it probably comes with +suitable header files also. If you make these files accessible from the host +machine, the cross-compiler can use them also. + +Otherwise, you're on your own in finding header files to use when +cross-compiling. + +When you have found suitable header files, put them in the directory +@file{/usr/local/@var{target}/include}, before building the cross +compiler. Then installation will run fixincludes properly and install +the corrected versions of the header files where the compiler will use +them. + +Provide the header files before you build the cross-compiler, because +the build stage actually runs the cross-compiler to produce parts of +@file{libgcc.a}. (These are the parts that @emph{can} be compiled with +GNU CC.) Some of them need suitable header files. + +Here's an example showing how to copy the header files from a target +machine. On the target machine, do this: + +@example +(cd /usr/include; tar cf - .) > tarfile +@end example + +Then, on the host machine, do this: + +@example +ftp @var{target-machine} +lcd /usr/local/@var{target}/include +get tarfile +quit +tar xf tarfile +@end example + +@node Build Cross +@subsection Actually Building the Cross-Compiler + +Now you can proceed just as for compiling a single-machine compiler +through the step of building stage 1. + +If your target is exotic, you may need to provide the header file +@file{float.h}.One way to do this is to compile @file{enquire} and run +it on your target machine. The job of @file{enquire} is to run on the +target machine and figure out by experiment the nature of its floating +point representation. @file{enquire} records its findings in the header +file @file{float.h}. If you can't produce this file by running +@file{enquire} on the target machine, then you will need to come up with +a suitable @file{float.h} in some other way (or else, avoid using it in +your programs). + +Do not try to build stage 2 for a cross-compiler. It doesn't work to +rebuild GNU CC as a cross-compiler using the cross-compiler, because +that would produce a program that runs on the target machine, not on the +host. For example, if you compile a 386-to-68030 cross-compiler with +itself, the result will not be right either for the 386 (because it was +compiled into 68030 code) or for the 68030 (because it was configured +for a 386 as the host). If you want to compile GNU CC into 68030 code, +whether you compile it on a 68030 or with a cross-compiler on a 386, you +must specify a 68030 as the host when you configure it. + +To install the cross-compiler, use @samp{make install}, as usual. + +@node VMS Install +@section Installing GNU CC on VMS +@cindex VMS installation +@cindex installing GNU CC on VMS + +The VMS version of GNU CC is distributed in a backup saveset containing +both source code and precompiled binaries. + +To install the @file{gcc} command so you can use the compiler easily, in +the same manner as you use the VMS C compiler, you must install the VMS CLD +file for GNU CC as follows: + +@enumerate +@item +Define the VMS logical names @samp{GNU_CC} and @samp{GNU_CC_INCLUDE} +to point to the directories where the GNU CC executables +(@file{gcc-cpp.exe}, @file{gcc-cc1.exe}, etc.) and the C include files are +kept respectively. This should be done with the commands:@refill + +@smallexample +$ assign /system /translation=concealed - + disk:[gcc.] gnu_cc +$ assign /system /translation=concealed - + disk:[gcc.include.] gnu_cc_include +@end smallexample + +@noindent +with the appropriate disk and directory names. These commands can be +placed in your system startup file so they will be executed whenever +the machine is rebooted. You may, if you choose, do this via the +@file{GCC_INSTALL.COM} script in the @file{[GCC]} directory. + +@item +Install the @file{GCC} command with the command line: + +@smallexample +$ set command /table=sys$common:[syslib]dcltables - + /output=sys$common:[syslib]dcltables gnu_cc:[000000]gcc +$ install replace sys$common:[syslib]dcltables +@end smallexample + +@item +To install the help file, do the following: + +@smallexample +$ library/help sys$library:helplib.hlb gcc.hlp +@end smallexample + +@noindent +Now you can invoke the compiler with a command like @samp{gcc /verbose +file.c}, which is equivalent to the command @samp{gcc -v -c file.c} in +Unix. +@end enumerate + +If you wish to use GNU C++ you must first install GNU CC, and then +perform the following steps: + +@enumerate +@item +Define the VMS logical name @samp{GNU_GXX_INCLUDE} to point to the +directory where the preprocessor will search for the C++ header files. +This can be done with the command:@refill + +@smallexample +$ assign /system /translation=concealed - + disk:[gcc.gxx_include.] gnu_gxx_include +@end smallexample + +@noindent +with the appropriate disk and directory name. If you are going to be +using a C++ runtime library, this is where its install procedure will install +its header files. + +@item +Obtain the file @file{gcc-cc1plus.exe}, and place this in the same +directory that @file{gcc-cc1.exe} is kept. + +The GNU C++ compiler can be invoked with a command like @samp{gcc /plus +/verbose file.cc}, which is equivalent to the command @samp{g++ -v -c +file.cc} in Unix. +@end enumerate + +We try to put corresponding binaries and sources on the VMS distribution +tape. But sometimes the binaries will be from an older version than the +sources, because we don't always have time to update them. (Use the +@samp{/version} option to determine the version number of the binaries and +compare it with the source file @file{version.c} to tell whether this is +so.) In this case, you should use the binaries you get to recompile the +sources. If you must recompile, here is how: + +@enumerate +@item +Execute the command procedure @file{vmsconfig.com} to set up the files +@file{tm.h}, @file{config.h}, @file{aux-output.c}, and @file{md.}, and +to create files @file{tconfig.h} and @file{hconfig.h}. This procedure +also creates several linker option files used by @file{make-cc1.com} and +a data file used by @file{make-l2.com}.@refill + +@smallexample +$ @@vmsconfig.com +@end smallexample + +@item +Setup the logical names and command tables as defined above. In +addition, define the VMS logical name @samp{GNU_BISON} to point at the +to the directories where the Bison executable is kept. This should be +done with the command:@refill + +@smallexample +$ assign /system /translation=concealed - + disk:[bison.] gnu_bison +@end smallexample + +You may, if you choose, use the @file{INSTALL_BISON.COM} script in the +@file{[BISON]} directory. + +@item +Install the @samp{BISON} command with the command line:@refill + +@smallexample +$ set command /table=sys$common:[syslib]dcltables - + /output=sys$common:[syslib]dcltables - + gnu_bison:[000000]bison +$ install replace sys$common:[syslib]dcltables +@end smallexample + +@item +Type @samp{@@make-gcc} to recompile everything (alternatively, submit +the file @file{make-gcc.com} to a batch queue). If you wish to build +the GNU C++ compiler as well as the GNU CC compiler, you must first edit +@file{make-gcc.com} and follow the instructions that appear in the +comments.@refill + +@item +In order to use GCC, you need a library of functions which GCC compiled code +will call to perform certain tasks, and these functions are defined in the +file @file{libgcc2.c}. To compile this you should use the command procedure +@file{make-l2.com}, which will generate the library @file{libgcc2.olb}. +@file{libgcc2.olb} should be built using the compiler built from +the same distribution that @file{libgcc2.c} came from, and +@file{make-gcc.com} will automatically do all of this for you. + +To install the library, use the following commands:@refill + +@smallexample +$ library gnu_cc:[000000]gcclib/delete=(new,eprintf) +$ library gnu_cc:[000000]gcclib/delete=L_* +$ library libgcc2/extract=*/output=libgcc2.obj +$ library gnu_cc:[000000]gcclib libgcc2.obj +@end smallexample + +The first command simply removes old modules that will be replaced with +modules from @file{libgcc2} under different module names. The modules +@code{new} and @code{eprintf} may not actually be present in your +@file{gcclib.olb}---if the VMS librarian complains about those modules +not being present, simply ignore the message and continue on with the +next command. The second command removes the modules that came from the +previous version of the library @file{libgcc2.c}. + +Whenever you update the compiler on your system, you should also update the +library with the above procedure. + +@item +You may wish to build GCC in such a way that no files are written to the +directory where the source files reside. An example would be the when +the source files are on a read-only disk. In these cases, execute the +following DCL commands (substituting your actual path names): + +@smallexample +$ assign dua0:[gcc.build_dir.]/translation=concealed, - + dua1:[gcc.source_dir.]/translation=concealed gcc_build +$ set default gcc_build:[000000] +@end smallexample + +@noindent +where the directory @file{dua1:[gcc.source_dir]} contains the source +code, and the directory @file{dua0:[gcc.build_dir]} is meant to contain +all of the generated object files and executables. Once you have done +this, you can proceed building GCC as described above. (Keep in mind +that @file{gcc_build} is a rooted logical name, and thus the device +names in each element of the search list must be an actual physical +device name rather than another rooted logical name). + +@item +@strong{If you are building GNU CC with a previous version of GNU CC, +you also should check to see that you have the newest version of the +assembler}. In particular, GNU CC version 2 treats global constant +variables slightly differently from GNU CC version 1, and GAS version +1.38.1 does not have the patches required to work with GCC version 2. +If you use GAS 1.38.1, then @code{extern const} variables will not have +the read-only bit set, and the linker will generate warning messages +about mismatched psect attributes for these variables. These warning +messages are merely a nuisance, and can safely be ignored. + +If you are compiling with a version of GNU CC older than 1.33, specify +@samp{/DEFINE=("inline=")} as an option in all the compilations. This +requires editing all the @code{gcc} commands in @file{make-cc1.com}. +(The older versions had problems supporting @code{inline}.) Once you +have a working 1.33 or newer GNU CC, you can change this file back. + +@item +If you want to build GNU CC with the VAX C compiler, you will need to +make minor changes in @file{make-cccp.com} and @file{make-cc1.com} +to choose alternate definitions of @code{CC}, @code{CFLAGS}, and +@code{LIBS}. See comments in those files. However, you must +also have a working version of the GNU assembler (GNU as, aka GAS) as +it is used as the back-end for GNU CC to produce binary object modules +and is not included in the GNU CC sources. GAS is also needed to +compile @file{libgcc2} in order to build @file{gcclib} (see above); +@file{make-l2.com} expects to be able to find it operational in +@file{gnu_cc:[000000]gnu-as.exe}. + +To use GNU CC on VMS, you need the VMS driver programs +@file{gcc.exe}, @file{gcc.com}, and @file{gcc.cld}. They are +distributed with the VMS binaries (@file{gcc-vms}) rather than the +GNU CC sources. GAS is also included in @file{gcc-vms}, as is Bison. + +Once you have successfully built GNU CC with VAX C, you should use the +resulting compiler to rebuild itself. Before doing this, be sure to +restore the @code{CC}, @code{CFLAGS}, and @code{LIBS} definitions in +@file{make-cccp.com} and @file{make-cc1.com}. The second generation +compiler will be able to take advantage of many optimizations that must +be suppressed when building with other compilers. +@end enumerate + +Under previous versions of GNU CC, the generated code would occasionally +give strange results when linked with the sharable @file{VAXCRTL} library. +Now this should work. + +Even with this version, however, GNU CC itself should not be linked with +the sharable @file{VAXCRTL}. The version of @code{qsort} in +@file{VAXCRTL} has a bug (known to be present in VMS versions V4.6 +through V5.5) which causes the compiler to fail. + +The executables are generated by @file{make-cc1.com} and +@file{make-cccp.com} use the object library version of @file{VAXCRTL} in +order to make use of the @code{qsort} routine in @file{gcclib.olb}. If +you wish to link the compiler executables with the shareable image +version of @file{VAXCRTL}, you should edit the file @file{tm.h} (created +by @file{vmsconfig.com}) to define the macro @code{QSORT_WORKAROUND}. + +@code{QSORT_WORKAROUND} is always defined when GNU CC is compiled with +VAX C, to avoid a problem in case @file{gcclib.olb} is not yet +available. + +@node Collect2 +@section @code{collect2} + +GNU CC uses a utility called @code{collect2} on nearly all systems to arrange +to call various initialization functions at start time. + +The program @code{collect2} works by linking the program once and +looking through the linker output file for symbols with particular names +indicating they are constructor functions. If it finds any, it +creates a new temporary @samp{.c} file containing a table of them, +compiles it, and links the program a second time including that file. + +@findex __main +@cindex constructors, automatic calls +The actual calls to the constructors are carried out by a subroutine +called @code{__main}, which is called (automatically) at the beginning +of the body of @code{main} (provided @code{main} was compiled with GNU +CC). Calling @code{__main} is necessary, even when compiling C code, to +allow linking C and C++ object code together. (If you use +@samp{-nostdlib}, you get an unresolved reference to @code{__main}, +since it's defined in the standard GCC library. Include @samp{-lgcc} at +the end of your compiler command line to resolve this reference.) + +The program @code{collect2} is installed as @code{ld} in the directory +where the passes of the compiler are installed. When @code{collect2} +needs to find the @emph{real} @code{ld}, it tries the following file +names: + +@itemize @bullet +@item +@file{real-ld} in the directories listed in the compiler's search +directories. + +@item +@file{real-ld} in the directories listed in the environment variable +@code{PATH}. + +@item +The file specified in the @code{REAL_LD_FILE_NAME} configuration macro, +if specified. + +@item +@file{ld} in the compiler's search directories, except that +@code{collect2} will not execute itself recursively. + +@item +@file{ld} in @code{PATH}. +@end itemize + +``The compiler's search directories'' means all the directories where +@code{gcc} searches for passes of the compiler. This includes +directories that you specify with @samp{-B}. + +Cross-compilers search a little differently: + +@itemize @bullet +@item +@file{real-ld} in the compiler's search directories. + +@item +@file{@var{target}-real-ld} in @code{PATH}. + +@item +The file specified in the @code{REAL_LD_FILE_NAME} configuration macro, +if specified. + +@item +@file{ld} in the compiler's search directories. + +@item +@file{@var{target}-ld} in @code{PATH}. +@end itemize + +@code{collect2} explicitly avoids running @code{ld} using the file name +under which @code{collect2} itself was invoked. In fact, it remembers +up a list of such names---in case one copy of @code{collect2} finds +another copy (or version) of @code{collect2} installed as @code{ld} in a +second place in the search path. + +@code{collect2} searches for the utilities @code{nm} and @code{strip} +using the same algorithm as above for @code{ld}. + +@node Header Dirs +@section Standard Header File Directories + +@code{GCC_INCLUDE_DIR} means the same thing for native and cross. It is +where GNU CC stores its private include files, and also where GNU CC +stores the fixed include files. A cross compiled GNU CC runs +@code{fixincludes} on the header files in @file{$(tooldir)/include}. +(If the cross compilation header files need to be fixed, they must be +installed before GNU CC is built. If the cross compilation header files +are already suitable for ISO C and GNU CC, nothing special need be +done). + +@code{GPLUSPLUS_INCLUDE_DIR} means the same thing for native and cross. It +is where @code{g++} looks first for header files. The C++ library +installs only target independent header files in that directory. + +@code{LOCAL_INCLUDE_DIR} is used only for a native compiler. It is +normally @file{/usr/local/include}. GNU CC searches this directory so +that users can install header files in @file{/usr/local/include}. + +@code{CROSS_INCLUDE_DIR} is used only for a cross compiler. GNU CC +doesn't install anything there. + +@code{TOOL_INCLUDE_DIR} is used for both native and cross compilers. It +is the place for other packages to install header files that GNU CC will +use. For a cross-compiler, this is the equivalent of +@file{/usr/include}. When you build a cross-compiler, +@code{fixincludes} processes any header files in this directory. diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi new file mode 100644 index 00000000000..2fab624fa94 --- /dev/null +++ b/gcc/doc/invoke.texi @@ -0,0 +1,8722 @@ +@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, +@c 2000, 2001 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@ignore +@c man begin COPYRIGHT +Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, +1998, 1999, 2000, 2001 Free Software Foundation, Inc. + +Permission is granted to make and distribute verbatim copies of this +manual provided the copyright notice and this permission notice are +preserved on all copies. + +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that the +entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions, +except that this permission notice may be included in translations +approved by the Free Software Foundation instead of in the original +English. +@c man end +@c Set file name and title for the man page. +@setfilename gcc +@settitle GNU project C and C++ compiler +@c man begin SYNOPSIS +gcc [@samp{-c}|@samp{-S}|@samp{-E}] [@samp{-std=}@var{standard}] + [@samp{-g}] [@samp{-pg}] [@samp{-O}@var{level}] + [@samp{-W}@var{warn}...] [@samp{-pedantic}] + [@samp{-I}@var{dir}...] [@samp{-L}@var{dir}...] + [@samp{-D}@var{macro}[=@var{defn}]...] [@samp{-U}@var{macro}] + [@samp{-f}@var{option}...] [@samp{-m}@var{machine-option}...] + [@samp{-o} @var{outfile}] @var{infile}... + +Only the most useful options are listed here; see below for the +remainder. @samp{g++} accepts mostly the same options as @samp{gcc}. +@c man end +@c man begin SEEALSO +cpp(1), gcov(1), g77(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1) +and the Info entries for @file{gcc}, @file{cpp}, @file{g77}, @file{as}, +@file{ld}, @file{binutils} and @file{gdb}. +@c man end +@c man begin BUGS +For instructions on reporting bugs, see +@w{@uref{http://gcc.gnu.org/bugs.html}}. Use of the @command{gccbug} +script to report bugs is recommended. +@c man end +@c man begin AUTHOR +See the Info entry for @file{gcc}, or +@w{@uref{http://gcc.gnu.org/thanks.html}}, for contributors to GCC. +@c man end +@end ignore + +@node Invoking GCC +@chapter GCC Command Options +@cindex GCC command options +@cindex command options +@cindex options, GCC command + +@c man begin DESCRIPTION + +When you invoke GCC, it normally does preprocessing, compilation, +assembly and linking. The ``overall options'' allow you to stop this +process at an intermediate stage. For example, the @samp{-c} option +says not to run the linker. Then the output consists of object files +output by the assembler. + +Other options are passed on to one stage of processing. Some options +control the preprocessor and others the compiler itself. Yet other +options control the assembler and linker; most of these are not +documented here, since you rarely need to use any of them. + +@cindex C compilation options +Most of the command line options that you can use with GCC are useful +for C programs; when an option is only useful with another language +(usually C++), the explanation says so explicitly. If the description +for a particular option does not mention a source language, you can use +that option with all supported languages. + +@cindex C++ compilation options +@xref{Invoking G++,,Compiling C++ Programs}, for a summary of special +options for compiling C++ programs. + +@cindex grouping options +@cindex options, grouping +The @command{gcc} program accepts options and file names as operands. Many +options have multi-letter names; therefore multiple single-letter options +may @emph{not} be grouped: @samp{-dr} is very different from @w{@samp{-d +-r}}. + +@cindex order of options +@cindex options, order +You can mix options and other arguments. For the most part, the order +you use doesn't matter. Order does matter when you use several options +of the same kind; for example, if you specify @samp{-L} more than once, +the directories are searched in the order specified. + +Many options have long names starting with @samp{-f} or with +@samp{-W}---for example, @samp{-fforce-mem}, +@samp{-fstrength-reduce}, @samp{-Wformat} and so on. Most of +these have both positive and negative forms; the negative form of +@samp{-ffoo} would be @samp{-fno-foo}. This manual documents +only one of these two forms, whichever one is not the default. + +@c man end + +@menu +* Option Summary:: Brief list of all options, without explanations. +* Overall Options:: Controlling the kind of output: + an executable, object files, assembler files, + or preprocessed source. +* Invoking G++:: Compiling C++ programs. +* C Dialect Options:: Controlling the variant of C language compiled. +* C++ Dialect Options:: Variations on C++. +* Objective-C Dialect Options:: Variations on Objective-C. +* Language Independent Options:: Controlling how diagnostics should be + formatted. +* Warning Options:: How picky should the compiler be? +* Debugging Options:: Symbol tables, measurements, and debugging dumps. +* Optimize Options:: How much optimization? +* Preprocessor Options:: Controlling header files and macro definitions. + Also, getting dependency information for Make. +* Assembler Options:: Passing options to the assembler. +* Link Options:: Specifying libraries and so on. +* Directory Options:: Where to find header files and libraries. + Where to find the compiler executable files. +* Spec Files:: How to pass switches to sub-processes. +* Target Options:: Running a cross-compiler, or an old version of GCC. +* Submodel Options:: Specifying minor hardware or convention variations, + such as 68010 vs 68020. +* Code Gen Options:: Specifying conventions for function calls, data layout + and register usage. +* Environment Variables:: Env vars that affect GCC. +* Running Protoize:: Automatically adding or removing function prototypes. +@end menu + +@c man begin OPTIONS + +@node Option Summary +@section Option Summary + +Here is a summary of all the options, grouped by type. Explanations are +in the following sections. + +@table @emph +@item Overall Options +@xref{Overall Options,,Options Controlling the Kind of Output}. +@gccoptlist{ +-c -S -E -o @var{file} -pipe -pass-exit-codes -x @var{language} @gol +-v --target-help --help} + +@item C Language Options +@xref{C Dialect Options,,Options Controlling C Dialect}. +@gccoptlist{ +-ansi -std=@var{standard} -fno-asm -fno-builtin @gol +-fhosted -ffreestanding @gol +-trigraphs -traditional -traditional-cpp @gol +-fallow-single-precision -fcond-mismatch @gol +-fsigned-bitfields -fsigned-char @gol +-funsigned-bitfields -funsigned-char @gol +-fwritable-strings -fshort-wchar} + +@item C++ Language Options +@xref{C++ Dialect Options,,Options Controlling C++ Dialect}. +@gccoptlist{ +-fno-access-control -fcheck-new -fconserve-space @gol +-fno-const-strings -fdollars-in-identifiers @gol +-fno-elide-constructors @gol +-fno-enforce-eh-specs -fexternal-templates @gol +-falt-external-templates @gol +-ffor-scope -fno-for-scope -fno-gnu-keywords -fhonor-std @gol +-fno-implicit-templates @gol +-fno-implicit-inline-templates @gol +-fno-implement-inlines -fms-extensions @gol +-fno-nonansi-builtins -fno-operator-names @gol +-fno-optional-diags -fpermissive @gol +-frepo -fno-rtti -fstats -ftemplate-depth-@var{n} @gol +-fuse-cxa-atexit -fvtable-gc -fno-weak -nostdinc++ @gol +-fno-default-inline -Wctor-dtor-privacy @gol +-Wnon-virtual-dtor -Wreorder @gol +-Weffc++ -Wno-deprecated @gol +-Wno-non-template-friend -Wold-style-cast @gol +-Woverloaded-virtual -Wno-pmf-conversions @gol +-Wsign-promo -Wsynth} + +@item Objective-C Language Options +@xref{Objective-C Dialect Options,,Options Controlling Objective-C Dialect}. +@gccoptlist{ +-fconstant-string-class=@var{class name} @gol +-fgnu-runtime -fnext-runtime -gen-decls @gol +-Wno-protocol -Wselector} + +@item Language Independent Options +@xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}. +@gccoptlist{ +-fmessage-length=@var{n} @gol +-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}} + +@item Warning Options +@xref{Warning Options,,Options to Request or Suppress Warnings}. +@gccoptlist{ +-fsyntax-only -pedantic -pedantic-errors @gol +-w -W -Wall -Waggregate-return @gol +-Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol +-Wconversion -Wdisabled-optimization -Werror @gol +-Wfloat-equal -Wformat -Wformat=2 @gol +-Wformat-nonliteral -Wformat-security @gol +-Wimplicit -Wimplicit-int @gol +-Wimplicit-function-declaration @gol +-Werror-implicit-function-declaration @gol +-Wimport -Winline @gol +-Wlarger-than-@var{len} -Wlong-long @gol +-Wmain -Wmissing-braces -Wmissing-declarations @gol +-Wmissing-format-attribute -Wmissing-noreturn @gol +-Wmultichar -Wno-format-extra-args -Wno-format-y2k @gol +-Wno-import -Wpacked -Wpadded @gol +-Wparentheses -Wpointer-arith -Wredundant-decls @gol +-Wreturn-type -Wsequence-point -Wshadow @gol +-Wsign-compare -Wswitch -Wsystem-headers @gol +-Wtrigraphs -Wundef -Wuninitialized @gol +-Wunknown-pragmas -Wunreachable-code @gol +-Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol +-Wunused-value -Wunused-variable -Wwrite-strings} + +@item C-only Warning Options +@gccoptlist{ +-Wbad-function-cast -Wmissing-prototypes -Wnested-externs @gol +-Wstrict-prototypes -Wtraditional} + +@item Debugging Options +@xref{Debugging Options,,Options for Debugging Your Program or GCC}. +@gccoptlist{ +-a -ax -d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol +-fdump-unnumbered -fdump-translation-unit=@var{file} @gol +-fdump-class-layout=@var{file} -fmem-report -fpretend-float @gol +-fprofile-arcs -ftest-coverage -ftime-report @gol +-g -g@var{level} -gcoff -gdwarf -gdwarf-1 -gdwarf-1+ -gdwarf-2 @gol +-ggdb -gstabs -gstabs+ -gxcoff -gxcoff+ @gol +-p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol +-print-prog-name=@var{program} -print-search-dirs -Q @gol +-save-temps -time} + +@item Optimization Options +@xref{Optimize Options,,Options that Control Optimization}. +@gccoptlist{ +-falign-functions=@var{n} -falign-jumps=@var{n} @gol +-falign-labels=@var{n} -falign-loops=@var{n} @gol +-fbranch-probabilities -fcaller-saves @gol +-fcse-follow-jumps -fcse-skip-blocks -fdata-sections -fdce @gol +-fdelayed-branch -fdelete-null-pointer-checks @gol +-fexpensive-optimizations -ffast-math -ffloat-store @gol +-fforce-addr -fforce-mem -ffunction-sections @gol +-fgcse -fgcse-lm -fgcse-sm @gol +-finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol +-fkeep-static-consts -fmove-all-movables @gol +-fno-default-inline -fno-defer-pop @gol +-fno-function-cse -fno-guess-branch-probability @gol +-fno-inline -fno-math-errno -fno-peephole @gol +-funsafe-math-optimizations -fno-trapping-math @gol +-fomit-frame-pointer -foptimize-register-move @gol +-foptimize-sibling-calls -freduce-all-givs @gol +-fregmove -frename-registers @gol +-frerun-cse-after-loop -frerun-loop-opt @gol +-fschedule-insns -fschedule-insns2 @gol +-fsingle-precision-constant -fssa @gol +-fstrength-reduce -fstrict-aliasing -fthread-jumps -ftrapv @gol +-funroll-all-loops -funroll-loops @gol +--param @var{name}=@var{value} +-O -O0 -O1 -O2 -O3 -Os} + +@item Preprocessor Options +@xref{Preprocessor Options,,Options Controlling the Preprocessor}. +@gccoptlist{ +-$ -A@var{question}=@var{answer} -A-@var{question}@r{[}=@var{answer}@r{]} @gol +-C -dD -dI -dM -dN @gol +-D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol +-idirafter @var{dir} @gol +-include @var{file} -imacros @var{file} @gol +-iprefix @var{file} -iwithprefix @var{dir} @gol +-iwithprefixbefore @var{dir} -isystem @var{dir} @gol +-M -MM -MF -MG -MP -MQ -MT -nostdinc -P -remap @gol +-trigraphs -undef -U@var{macro} -Wp\,@var{option}} + +@item Assembler Option +@xref{Assembler Options,,Passing Options to the Assembler}. +@gccoptlist{ +-Wa\,@var{option}} + +@item Linker Options +@xref{Link Options,,Options for Linking}. +@gccoptlist{ +@var{object-file-name} -l@var{library} @gol +-nostartfiles -nodefaultlibs -nostdlib @gol +-s -static -static-libgcc -shared -shared-libgcc -symbolic @gol +-Wl\,@var{option} -Xlinker @var{option} @gol +-u @var{symbol}} + +@item Directory Options +@xref{Directory Options,,Options for Directory Search}. +@gccoptlist{ +-B@var{prefix} -I@var{dir} -I- -L@var{dir} -specs=@var{file}} + +@item Target Options +@c I wrote this xref this way to avoid overfull hbox. -- rms +@xref{Target Options}. +@gccoptlist{ +-b @var{machine} -V @var{version}} + +@item Machine Dependent Options +@xref{Submodel Options,,Hardware Models and Configurations}. +@emph{M680x0 Options} +@gccoptlist{ +-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol +-m68060 -mcpu32 -m5200 -m68881 -mbitfield -mc68000 -mc68020 @gol +-mfpa -mnobitfield -mrtd -mshort -msoft-float -mpcrel @gol +-malign-int -mstrict-align} + +@emph{M68hc1x Options} +@gccoptlist{ +-m6811 -m6812 -m68hc11 -m68hc12 @gol +-mauto-incdec -mshort -msoft-reg-count=@var{count}} + +@emph{VAX Options} +@gccoptlist{ +-mg -mgnu -munix} + +@emph{SPARC Options} +@gccoptlist{ +-mcpu=@var{cpu type} @gol +-mtune=@var{cpu type} @gol +-mcmodel=@var{code model} @gol +-m32 -m64 @gol +-mapp-regs -mbroken-saverestore -mcypress @gol +-mepilogue -mfaster-structs -mflat @gol +-mfpu -mhard-float -mhard-quad-float @gol +-mimpure-text -mlive-g0 -mno-app-regs @gol +-mno-epilogue -mno-faster-structs -mno-flat -mno-fpu @gol +-mno-impure-text -mno-stack-bias -mno-unaligned-doubles @gol +-msoft-float -msoft-quad-float -msparclite -mstack-bias @gol +-msupersparc -munaligned-doubles -mv8} + +@emph{Convex Options} +@gccoptlist{ +-mc1 -mc2 -mc32 -mc34 -mc38 @gol +-margcount -mnoargcount @gol +-mlong32 -mlong64 @gol +-mvolatile-cache -mvolatile-nocache} + +@emph{AMD29K Options} +@gccoptlist{ +-m29000 -m29050 -mbw -mnbw -mdw -mndw @gol +-mlarge -mnormal -msmall @gol +-mkernel-registers -mno-reuse-arg-regs @gol +-mno-stack-check -mno-storem-bug @gol +-mreuse-arg-regs -msoft-float -mstack-check @gol +-mstorem-bug -muser-registers} + +@emph{ARM Options} +@gccoptlist{ +-mapcs-frame -mno-apcs-frame @gol +-mapcs-26 -mapcs-32 @gol +-mapcs-stack-check -mno-apcs-stack-check @gol +-mapcs-float -mno-apcs-float @gol +-mapcs-reentrant -mno-apcs-reentrant @gol +-msched-prolog -mno-sched-prolog @gol +-mlittle-endian -mbig-endian -mwords-little-endian @gol +-malignment-traps -mno-alignment-traps @gol +-msoft-float -mhard-float -mfpe @gol +-mthumb-interwork -mno-thumb-interwork @gol +-mcpu=@var{name} -march=@var{name} -mfpe=@var{name} @gol +-mstructure-size-boundary=@var{n} @gol +-mbsd -mxopen -mno-symrename @gol +-mabort-on-noreturn @gol +-mlong-calls -mno-long-calls @gol +-msingle-pic-base -mno-single-pic-base @gol +-mpic-register=@var{reg} @gol +-mnop-fun-dllimport @gol +-mpoke-function-name @gol +-mthumb -marm @gol +-mtpcs-frame -mtpcs-leaf-frame @gol +-mcaller-super-interworking -mcallee-super-interworking } + +@emph{MN10200 Options} +@gccoptlist{ +-mrelax} + +@emph{MN10300 Options} +@gccoptlist{ +-mmult-bug @gol +-mno-mult-bug @gol +-mam33 @gol +-mno-am33 @gol +-mrelax} + +@emph{M32R/D Options} +@gccoptlist{ +-mcode-model=@var{model type} -msdata=@var{sdata type} @gol +-G @var{num}} + +@emph{M88K Options} +@gccoptlist{ +-m88000 -m88100 -m88110 -mbig-pic @gol +-mcheck-zero-division -mhandle-large-shift @gol +-midentify-revision -mno-check-zero-division @gol +-mno-ocs-debug-info -mno-ocs-frame-position @gol +-mno-optimize-arg-area -mno-serialize-volatile @gol +-mno-underscores -mocs-debug-info @gol +-mocs-frame-position -moptimize-arg-area @gol +-mserialize-volatile -mshort-data-@var{num} -msvr3 @gol +-msvr4 -mtrap-large-shift -muse-div-instruction @gol +-mversion-03.00 -mwarn-passed-structs} + +@emph{RS/6000 and PowerPC Options} +@gccoptlist{ +-mcpu=@var{cpu type} @gol +-mtune=@var{cpu type} @gol +-mpower -mno-power -mpower2 -mno-power2 @gol +-mpowerpc -mpowerpc64 -mno-powerpc @gol +-mpowerpc-gpopt -mno-powerpc-gpopt @gol +-mpowerpc-gfxopt -mno-powerpc-gfxopt @gol +-mnew-mnemonics -mold-mnemonics @gol +-mfull-toc -mminimal-toc -mno-fop-in-toc -mno-sum-in-toc @gol +-m64 -m32 -mxl-call -mno-xl-call -mthreads -mpe @gol +-msoft-float -mhard-float -mmultiple -mno-multiple @gol +-mstring -mno-string -mupdate -mno-update @gol +-mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol +-mstrict-align -mno-strict-align -mrelocatable @gol +-mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol +-mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol +-mcall-aix -mcall-sysv -mprototype -mno-prototype @gol +-msim -mmvme -mads -myellowknife -memb -msdata @gol +-msdata=@var{opt} -mvxworks -G @var{num}} + +@emph{RT Options} +@gccoptlist{ +-mcall-lib-mul -mfp-arg-in-fpregs -mfp-arg-in-gregs @gol +-mfull-fp-blocks -mhc-struct-return -min-line-mul @gol +-mminimum-fp-blocks -mnohc-struct-return} + +@emph{MIPS Options} +@gccoptlist{ +-mabicalls -mcpu=@var{cpu type} @gol +-membedded-data -muninit-const-in-rodata @gol +-membedded-pic -mfp32 -mfp64 -mgas -mgp32 -mgp64 @gol +-mgpopt -mhalf-pic -mhard-float -mint64 -mips1 @gol +-mips2 -mips3 -mips4 -mlong64 -mlong32 -mlong-calls -mmemcpy @gol +-mmips-as -mmips-tfile -mno-abicalls @gol +-mno-embedded-data -mno-uninit-const-in-rodata @gol +-mno-embedded-pic -mno-gpopt -mno-long-calls @gol +-mno-memcpy -mno-mips-tfile -mno-rnames -mno-stats @gol +-mrnames -msoft-float @gol +-m4650 -msingle-float -mmad @gol +-mstats -EL -EB -G @var{num} -nocpp @gol +-mabi=32 -mabi=n32 -mabi=64 -mabi=eabi @gol +-mfix7000 -mno-crt0} + +@emph{i386 Options} +@gccoptlist{ +-mcpu=@var{cpu type} -march=@var{cpu type} @gol +-mintel-syntax -mieee-fp -mno-fancy-math-387 @gol +-mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol +-mno-wide-multiply -mrtd -malign-double @gol +-mpreferred-stack-boundary=@var{num} @gol +-mthreads -mno-align-stringops -minline-all-stringops @gol +-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol +-m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer} + +@emph{HPPA Options} +@gccoptlist{ +-march=@var{architecture type} @gol +-mbig-switch -mdisable-fpregs -mdisable-indexing @gol +-mfast-indirect-calls -mgas -mjump-in-delay @gol +-mlong-load-store -mno-big-switch -mno-disable-fpregs @gol +-mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol +-mno-jump-in-delay -mno-long-load-store @gol +-mno-portable-runtime -mno-soft-float @gol +-mno-space-regs -msoft-float -mpa-risc-1-0 @gol +-mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol +-mschedule=@var{cpu type} -mspace-regs} + +@emph{Intel 960 Options} +@gccoptlist{ +-m@var{cpu type} -masm-compat -mclean-linkage @gol +-mcode-align -mcomplex-addr -mleaf-procedures @gol +-mic-compat -mic2.0-compat -mic3.0-compat @gol +-mintel-asm -mno-clean-linkage -mno-code-align @gol +-mno-complex-addr -mno-leaf-procedures @gol +-mno-old-align -mno-strict-align -mno-tail-call @gol +-mnumerics -mold-align -msoft-float -mstrict-align @gol +-mtail-call} + +@emph{DEC Alpha Options} +@gccoptlist{ +-mfp-regs -mno-fp-regs -mno-soft-float -msoft-float @gol +-malpha-as -mgas @gol +-mieee -mieee-with-inexact -mieee-conformant @gol +-mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol +-mtrap-precision=@var{mode} -mbuild-constants @gol +-mcpu=@var{cpu type} @gol +-mbwx -mno-bwx -mcix -mno-cix -mmax -mno-max @gol +-mmemory-latency=@var{time}} + +@emph{Clipper Options} +@gccoptlist{ +-mc300 -mc400} + +@emph{H8/300 Options} +@gccoptlist{ +-mrelax -mh -ms -mint32 -malign-300} + +@emph{SH Options} +@gccoptlist{ +-m1 -m2 -m3 -m3e @gol +-m4-nofpu -m4-single-only -m4-single -m4 @gol +-mb -ml -mdalign -mrelax @gol +-mbigtable -mfmovd -mhitachi -mnomacsave @gol +-misize -mpadstruct -mspace @gol +-mprefergot +-musermode} + +@emph{System V Options} +@gccoptlist{ +-Qy -Qn -YP\,@var{paths} -Ym\,@var{dir}} + +@emph{ARC Options} +@gccoptlist{ +-EB -EL @gol +-mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text section} @gol +-mdata=@var{data section} -mrodata=@var{readonly data section}} + +@emph{TMS320C3x/C4x Options} +@gccoptlist{ +-mcpu=@var{cpu} -mbig -msmall -mregparm -mmemparm @gol +-mfast-fix -mmpyi -mbk -mti -mdp-isr-reload @gol +-mrpts=@var{count} -mrptb -mdb -mloop-unsigned @gol +-mparallel-insns -mparallel-mpy -mpreserve-float} + +@emph{V850 Options} +@gccoptlist{ +-mlong-calls -mno-long-calls -mep -mno-ep @gol +-mprolog-function -mno-prolog-function -mspace @gol +-mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol +-mv850 -mbig-switch} + +@emph{NS32K Options} +@gccoptlist{ +-m32032 -m32332 -m32532 -m32081 -m32381 @gol +-mmult-add -mnomult-add -msoft-float -mrtd -mnortd @gol +-mregparam -mnoregparam -msb -mnosb @gol +-mbitfield -mnobitfield -mhimem -mnohimem} + +@emph{AVR Options} +@gccoptlist{ +-mmcu=@var{mcu} -msize -minit-stack=@var{n} -mno-interrupts @gol +-mcall-prologues -mno-tablejump -mtiny-stack} + +@emph{MCore Options} +@gccoptlist{ +-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol +-mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol +-m4byte-functions -mno-4byte-functions -mcallgraph-data @gol +-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol +-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment} + +@emph{IA-64 Options} +@gccoptlist{ +-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol +-mvolatile-asm-stop -mb-step -mregister-names -mno-sdata @gol +-mconstant-gp -mauto-pic -minline-divide-min-latency @gol +-minline-divide-max-throughput -mno-dwarf2-asm @gol +-mfixed-range=@var{register range}} + +@item Code Generation Options +@xref{Code Gen Options,,Options for Code Generation Conventions}. +@gccoptlist{ +-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol +-fexceptions -funwind-tables -ffixed-@var{reg} @gol +-finhibit-size-directive -finstrument-functions @gol +-fcheck-memory-usage -fprefix-function-name @gol +-fno-common -fno-ident -fno-gnu-linker @gol +-fpcc-struct-return -fpic -fPIC @gol +-freg-struct-return -fshared-data -fshort-enums @gol +-fshort-double -fvolatile @gol +-fvolatile-global -fvolatile-static @gol +-fverbose-asm -fpack-struct -fstack-check @gol +-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol +-fargument-alias -fargument-noalias @gol +-fargument-noalias-global -fleading-underscore} +@end table + +@menu +* Overall Options:: Controlling the kind of output: + an executable, object files, assembler files, + or preprocessed source. +* C Dialect Options:: Controlling the variant of C language compiled. +* C++ Dialect Options:: Variations on C++. +* Objective-C Dialect Options:: Variations on Objective-C. +* Language Independent Options:: Controlling how diagnostics should be + formatted. +* Warning Options:: How picky should the compiler be? +* Debugging Options:: Symbol tables, measurements, and debugging dumps. +* Optimize Options:: How much optimization? +* Preprocessor Options:: Controlling header files and macro definitions. + Also, getting dependency information for Make. +* Assembler Options:: Passing options to the assembler. +* Link Options:: Specifying libraries and so on. +* Directory Options:: Where to find header files and libraries. + Where to find the compiler executable files. +* Spec Files:: How to pass switches to sub-processes. +* Target Options:: Running a cross-compiler, or an old version of GCC. +@end menu + +@node Overall Options +@section Options Controlling the Kind of Output + +Compilation can involve up to four stages: preprocessing, compilation +proper, assembly and linking, always in that order. The first three +stages apply to an individual source file, and end by producing an +object file; linking combines all the object files (those newly +compiled, and those specified as input) into an executable file. + +@cindex file name suffix +For any given input file, the file name suffix determines what kind of +compilation is done: + +@table @gcctabopt +@item @var{file}.c +C source code which must be preprocessed. + +@item @var{file}.i +C source code which should not be preprocessed. + +@item @var{file}.ii +C++ source code which should not be preprocessed. + +@item @var{file}.m +Objective-C source code. Note that you must link with the library +@file{libobjc.a} to make an Objective-C program work. + +@item @var{file}.mi +Objective-C source code which should not be preprocessed. + +@item @var{file}.h +C header file (not to be compiled or linked). + +@item @var{file}.cc +@itemx @var{file}.cp +@itemx @var{file}.cxx +@itemx @var{file}.cpp +@itemx @var{file}.c++ +@itemx @var{file}.C +C++ source code which must be preprocessed. Note that in @samp{.cxx}, +the last two letters must both be literally @samp{x}. Likewise, +@samp{.C} refers to a literal capital C. + +@item @var{file}.f +@itemx @var{file}.for +@itemx @var{file}.FOR +Fortran source code which should not be preprocessed. + +@item @var{file}.F +@itemx @var{file}.fpp +@itemx @var{file}.FPP +Fortran source code which must be preprocessed (with the traditional +preprocessor). + +@item @var{file}.r +Fortran source code which must be preprocessed with a RATFOR +preprocessor (not included with GCC). + +@xref{Overall Options,,Options Controlling the Kind of Output, g77, +Using and Porting GNU Fortran}, for more details of the handling of +Fortran input files. + +@c FIXME: Descriptions of Java file types. +@c @var{file}.java +@c @var{file}.class +@c @var{file}.zip +@c @var{file}.jar + +@c GCC also knows about some suffixes for languages not yet included: +@c Ada: +@c @var{file}.ads +@c @var{file}.adb +@c @var{file}.ada +@c Pascal: +@c @var{file}.p +@c @var{file}.pas + +@item @var{file}.ch +@itemx @var{file}.chi +CHILL source code (preprocessed with the traditional preprocessor). + +@item @var{file}.s +Assembler code. + +@item @var{file}.S +Assembler code which must be preprocessed. + +@item @var{other} +An object file to be fed straight into linking. +Any file name with no recognized suffix is treated this way. +@end table + +You can specify the input language explicitly with the @samp{-x} option: + +@table @gcctabopt +@item -x @var{language} +Specify explicitly the @var{language} for the following input files +(rather than letting the compiler choose a default based on the file +name suffix). This option applies to all following input files until +the next @samp{-x} option. Possible values for @var{language} are: +@example +c c-header cpp-output +c++ c++-cpp-output +objective-c objc-cpp-output +assembler assembler-with-cpp +f77 f77-cpp-input ratfor +java chill +@end example +@c Also f77-version, for internal use only. + +@item -x none +Turn off any specification of a language, so that subsequent files are +handled according to their file name suffixes (as they are if @samp{-x} +has not been used at all). + +@item -pass-exit-codes +Normally the @command{gcc} program will exit with the code of 1 if any +phase of the compiler returns a non-success return code. If you specify +@samp{-pass-exit-codes}, the @command{gcc} program will instead return with +numerically highest error produced by any phase that returned an error +indication. +@end table + +If you only want some of the stages of compilation, you can use +@samp{-x} (or filename suffixes) to tell @command{gcc} where to start, and +one of the options @samp{-c}, @samp{-S}, or @samp{-E} to say where +@command{gcc} is to stop. Note that some combinations (for example, +@samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all. + +@table @gcctabopt +@item -c +Compile or assemble the source files, but do not link. The linking +stage simply is not done. The ultimate output is in the form of an +object file for each source file. + +By default, the object file name for a source file is made by replacing +the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}. + +Unrecognized input files, not requiring compilation or assembly, are +ignored. + +@item -S +Stop after the stage of compilation proper; do not assemble. The output +is in the form of an assembler code file for each non-assembler input +file specified. + +By default, the assembler file name for a source file is made by +replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}. + +Input files that don't require compilation are ignored. + +@item -E +Stop after the preprocessing stage; do not run the compiler proper. The +output is in the form of preprocessed source code, which is sent to the +standard output. + +Input files which don't require preprocessing are ignored. + +@cindex output file option +@item -o @var{file} +Place output in file @var{file}. This applies regardless to whatever +sort of output is being produced, whether it be an executable file, +an object file, an assembler file or preprocessed C code. + +Since only one output file can be specified, it does not make sense to +use @samp{-o} when compiling more than one input file, unless you are +producing an executable file as output. + +If @samp{-o} is not specified, the default is to put an executable file +in @file{a.out}, the object file for @file{@var{source}.@var{suffix}} in +@file{@var{source}.o}, its assembler file in @file{@var{source}.s}, and +all preprocessed C source on standard output.@refill + +@item -v +Print (on standard error output) the commands executed to run the stages +of compilation. Also print the version number of the compiler driver +program and of the preprocessor and the compiler proper. + +@item -pipe +Use pipes rather than temporary files for communication between the +various stages of compilation. This fails to work on some systems where +the assembler is unable to read from a pipe; but the GNU assembler has +no trouble. + +@item --help +Print (on the standard output) a description of the command line options +understood by @command{gcc}. If the @option{-v} option is also specified +then @option{--help} will also be passed on to the various processes +invoked by @command{gcc}, so that they can display the command line options +they accept. If the @option{-W} option is also specified then command +line options which have no documentation associated with them will also +be displayed. + +@item --target-help +Print (on the standard output) a description of target specific command +line options for each tool. +@end table + +@node Invoking G++ +@section Compiling C++ Programs + +@cindex suffixes for C++ source +@cindex C++ source file suffixes +C++ source files conventionally use one of the suffixes @samp{.C}, +@samp{.cc}, @samp{.cpp}, @samp{.c++}, @samp{.cp}, or @samp{.cxx}; +preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes +files with these names and compiles them as C++ programs even if you +call the compiler the same way as for compiling C programs (usually with +the name @command{gcc}). + +@findex g++ +@findex c++ +However, C++ programs often require class libraries as well as a +compiler that understands the C++ language---and under some +circumstances, you might want to compile programs from standard input, +or otherwise without a suffix that flags them as C++ programs. +@command{g++} is a program that calls GCC with the default language +set to C++, and automatically specifies linking against the C++ +library. On many systems, @command{g++} is also +installed with the name @command{c++}. + +@cindex invoking @command{g++} +When you compile C++ programs, you may specify many of the same +command-line options that you use for compiling programs in any +language; or command-line options meaningful for C and related +languages; or options that are meaningful only for C++ programs. +@xref{C Dialect Options,,Options Controlling C Dialect}, for +explanations of options for languages related to C. +@xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for +explanations of options that are meaningful only for C++ programs. + +@node C Dialect Options +@section Options Controlling C Dialect +@cindex dialect options +@cindex language dialect options +@cindex options, dialect + +The following options control the dialect of C (or languages derived +from C, such as C++ and Objective C) that the compiler accepts: + +@table @gcctabopt +@cindex ANSI support +@cindex ISO support +@item -ansi +In C mode, support all ISO C89 programs. In C++ mode, +remove GNU extensions that conflict with ISO C++. + +This turns off certain features of GCC that are incompatible with ISO +C (when compiling C code), or of standard C++ (when compiling C++ code), +such as the @code{asm} and @code{typeof} keywords, and +predefined macros such as @code{unix} and @code{vax} that identify the +type of system you are using. It also enables the undesirable and +rarely used ISO trigraph feature. For the C compiler, +it disables recognition of C++ style @samp{//} comments as well as +the @code{inline} keyword. + +The alternate keywords @code{__asm__}, @code{__extension__}, +@code{__inline__} and @code{__typeof__} continue to work despite +@samp{-ansi}. You would not want to use them in an ISO C program, of +course, but it is useful to put them in header files that might be included +in compilations done with @samp{-ansi}. Alternate predefined macros +such as @code{__unix__} and @code{__vax__} are also available, with or +without @samp{-ansi}. + +The @samp{-ansi} option does not cause non-ISO programs to be +rejected gratuitously. For that, @samp{-pedantic} is required in +addition to @samp{-ansi}. @xref{Warning Options}. + +The macro @code{__STRICT_ANSI__} is predefined when the @samp{-ansi} +option is used. Some header files may notice this macro and refrain +from declaring certain functions or defining certain macros that the +ISO standard doesn't call for; this is to avoid interfering with any +programs that might use these names for other things. + +Functions which would normally be builtin but do not have semantics +defined by ISO C (such as @code{alloca} and @code{ffs}) are not builtin +functions with @samp{-ansi} is used. @xref{Other Builtins,,Other +built-in functions provided by GNU CC}, for details of the functions +affected. + +@item -std= +Determine the language standard. A value for this option must be provided; +possible values are + +@table @samp +@item iso9899:1990 +Same as @option{-ansi} + +@item iso9899:199409 +ISO C as modified in amend. 1 + +@item iso9899:1999 +ISO C99. Note that this standard is not yet fully supported; see +@w{@uref{http://gcc.gnu.org/c99status.html}} for more information. + +@item c89 +same as @option{-std=iso9899:1990} + +@item c99 +same as @option{-std=iso9899:1999} + +@item gnu89 +default, iso9899:1990 + gnu extensions + +@item gnu99 +iso9899:1999 + gnu extensions + +@item iso9899:199x +same as @option{-std=iso9899:1999}, deprecated + +@item c9x +same as @option{-std=iso9899:1999}, deprecated + +@item gnu9x +same as @option{-std=gnu99}, deprecated + +@end table + +Even when this option is not specified, you can still use some of the +features of newer standards in so far as they do not conflict with +previous C standards. For example, you may use @code{__restrict__} even +when @option{-std=c99} is not specified. + +The @option{-std} options specifying some version of ISO C have the same +effects as @option{-ansi}, except that features that were not in ISO C89 +but are in the specified version (for example, @samp{//} comments and +the @code{inline} keyword in ISO C99) are not disabled. + +@xref{Standards,,Language Standards Supported by GCC}, for details of +these standard versions. + +@item -fno-asm +Do not recognize @code{asm}, @code{inline} or @code{typeof} as a +keyword, so that code can use these words as identifiers. You can use +the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__} +instead. @samp{-ansi} implies @samp{-fno-asm}. + +In C++, this switch only affects the @code{typeof} keyword, since +@code{asm} and @code{inline} are standard keywords. You may want to +use the @samp{-fno-gnu-keywords} flag instead, which has the same +effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this +switch only affects the @code{asm} and @code{typeof} keywords, since +@code{inline} is a standard keyword in ISO C99. + +@item -fno-builtin +@cindex builtin functions +Don't recognize builtin functions that do not begin with +@samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in +functions provided by GNU CC}, for details of the functions affected, +including those which are not builtin functions when @option{-ansi} or +@option{-std} options for strict ISO C conformance are used because they +do not have an ISO standard meaning. + +GCC normally generates special code to handle certain builtin functions +more efficiently; for instance, calls to @code{alloca} may become single +instructions that adjust the stack directly, and calls to @code{memcpy} +may become inline copy loops. The resulting code is often both smaller +and faster, but since the function calls no longer appear as such, you +cannot set a breakpoint on those calls, nor can you change the behavior +of the functions by linking with a different library. + +In C++, @samp{-fno-builtin} is always in effect. The @samp{-fbuiltin} +option has no effect. Therefore, in C++, the only way to get the +optimization benefits of builtin functions is to call the function +using the @samp{__builtin_} prefix. The GNU C++ Standard Library uses +builtin functions to implement many functions (like +@code{std::strchr}), so that you automatically get efficient code. + +@item -fhosted +@cindex hosted environment + +Assert that compilation takes place in a hosted environment. This implies +@samp{-fbuiltin}. A hosted environment is one in which the +entire standard library is available, and in which @code{main} has a return +type of @code{int}. Examples are nearly everything except a kernel. +This is equivalent to @samp{-fno-freestanding}. + +@item -ffreestanding +@cindex hosted environment + +Assert that compilation takes place in a freestanding environment. This +implies @samp{-fno-builtin}. A freestanding environment +is one in which the standard library may not exist, and program startup may +not necessarily be at @code{main}. The most obvious example is an OS kernel. +This is equivalent to @samp{-fno-hosted}. + +@xref{Standards,,Language Standards Supported by GCC}, for details of +freestanding and hosted environments. + +@item -trigraphs +Support ISO C trigraphs. You don't want to know about this +brain-damage. The @option{-ansi} option (and @option{-std} options for +strict ISO C conformance) implies @option{-trigraphs}. + +@cindex traditional C language +@cindex C language, traditional +@item -traditional +Attempt to support some aspects of traditional C compilers. +Specifically: + +@itemize @bullet +@item +All @code{extern} declarations take effect globally even if they +are written inside of a function definition. This includes implicit +declarations of functions. + +@item +The newer keywords @code{typeof}, @code{inline}, @code{signed}, @code{const} +and @code{volatile} are not recognized. (You can still use the +alternative keywords such as @code{__typeof__}, @code{__inline__}, and +so on.) + +@item +Comparisons between pointers and integers are always allowed. + +@item +Integer types @code{unsigned short} and @code{unsigned char} promote +to @code{unsigned int}. + +@item +Out-of-range floating point literals are not an error. + +@item +Certain constructs which ISO regards as a single invalid preprocessing +number, such as @samp{0xe-0xd}, are treated as expressions instead. + +@item +String ``constants'' are not necessarily constant; they are stored in +writable space, and identical looking constants are allocated +separately. (This is the same as the effect of +@samp{-fwritable-strings}.) + +@cindex @code{longjmp} and automatic variables +@item +All automatic variables not declared @code{register} are preserved by +@code{longjmp}. Ordinarily, GNU C follows ISO C: automatic variables +not declared @code{volatile} may be clobbered. + +@item +@kindex \x +@kindex \a +@cindex escape sequences, traditional +The character escape sequences @samp{\x} and @samp{\a} evaluate as the +literal characters @samp{x} and @samp{a} respectively. Without +@w{@samp{-traditional}}, @samp{\x} is a prefix for the hexadecimal +representation of a character, and @samp{\a} produces a bell. +@end itemize + +You may wish to use @samp{-fno-builtin} as well as @samp{-traditional} +if your program uses names that are normally GNU C builtin functions for +other purposes of its own. + +You cannot use @samp{-traditional} if you include any header files that +rely on ISO C features. Some vendors are starting to ship systems with +ISO C header files and you cannot use @samp{-traditional} on such +systems to compile files that include any system headers. + +The @samp{-traditional} option also enables @samp{-traditional-cpp}, +which is described next. + +@item -traditional-cpp +Attempt to support some aspects of traditional C preprocessors. +Specifically: + +@itemize @bullet +@item +Comments convert to nothing at all, rather than to a space. This allows +traditional token concatenation. + +@item +In a preprocessing directive, the @samp{#} symbol must appear as the first +character of a line. + +@item +Macro arguments are recognized within string constants in a macro +definition (and their values are stringified, though without additional +quote marks, when they appear in such a context). The preprocessor +always considers a string constant to end at a newline. + +@item +@cindex detecting @w{@samp{-traditional}} +The predefined macro @code{__STDC__} is not defined when you use +@samp{-traditional}, but @code{__GNUC__} is (since the GNU extensions +which @code{__GNUC__} indicates are not affected by +@samp{-traditional}). If you need to write header files that work +differently depending on whether @samp{-traditional} is in use, by +testing both of these predefined macros you can distinguish four +situations: GNU C, traditional GNU C, other ISO C compilers, and other +old C compilers. The predefined macro @code{__STDC_VERSION__} is also +not defined when you use @samp{-traditional}. @xref{Standard +Predefined,,Standard Predefined Macros,cpp.info,The C Preprocessor}, +for more discussion of these and other predefined macros. + +@item +@cindex string constants vs newline +@cindex newline vs string constants +The preprocessor considers a string constant to end at a newline (unless +the newline is escaped with @samp{\}). (Without @w{@samp{-traditional}}, +string constants can contain the newline character as typed.) +@end itemize + +@item -fcond-mismatch +Allow conditional expressions with mismatched types in the second and +third arguments. The value of such an expression is void. This option +is not supported for C++. + +@item -funsigned-char +Let the type @code{char} be unsigned, like @code{unsigned char}. + +Each kind of machine has a default for what @code{char} should +be. It is either like @code{unsigned char} by default or like +@code{signed char} by default. + +Ideally, a portable program should always use @code{signed char} or +@code{unsigned char} when it depends on the signedness of an object. +But many programs have been written to use plain @code{char} and +expect it to be signed, or expect it to be unsigned, depending on the +machines they were written for. This option, and its inverse, let you +make such a program work with the opposite default. + +The type @code{char} is always a distinct type from each of +@code{signed char} or @code{unsigned char}, even though its behavior +is always just like one of those two. + +@item -fsigned-char +Let the type @code{char} be signed, like @code{signed char}. + +Note that this is equivalent to @samp{-fno-unsigned-char}, which is +the negative form of @samp{-funsigned-char}. Likewise, the option +@samp{-fno-signed-char} is equivalent to @samp{-funsigned-char}. + +You may wish to use @samp{-fno-builtin} as well as @samp{-traditional} +if your program uses names that are normally GNU C builtin functions for +other purposes of its own. + +You cannot use @samp{-traditional} if you include any header files that +rely on ISO C features. Some vendors are starting to ship systems with +ISO C header files and you cannot use @samp{-traditional} on such +systems to compile files that include any system headers. + +@item -fsigned-bitfields +@itemx -funsigned-bitfields +@itemx -fno-signed-bitfields +@itemx -fno-unsigned-bitfields +These options control whether a bitfield is signed or unsigned, when the +declaration does not use either @code{signed} or @code{unsigned}. By +default, such a bitfield is signed, because this is consistent: the +basic integer types such as @code{int} are signed types. + +However, when @samp{-traditional} is used, bitfields are all unsigned +no matter what. + +@item -fwritable-strings +Store string constants in the writable data segment and don't uniquize +them. This is for compatibility with old programs which assume they can +write into string constants. The option @samp{-traditional} also has +this effect. + +Writing into string constants is a very bad idea; ``constants'' should +be constant. + +@item -fallow-single-precision +Do not promote single precision math operations to double precision, +even when compiling with @samp{-traditional}. + +Traditional K&R C promotes all floating point operations to double +precision, regardless of the sizes of the operands. On the +architecture for which you are compiling, single precision may be faster +than double precision. If you must use @samp{-traditional}, but want +to use single precision operations when the operands are single +precision, use this option. This option has no effect when compiling +with ISO or GNU C conventions (the default). + +@item -fshort-wchar +Override the underlying type for @samp{wchar_t} to be @samp{short +unsigned int} instead of the default for the target. This option is +useful for building programs to run under WINE. +@end table + +@node C++ Dialect Options +@section Options Controlling C++ Dialect + +@cindex compiler options, C++ +@cindex C++ options, command line +@cindex options, C++ +This section describes the command-line options that are only meaningful +for C++ programs; but you can also use most of the GNU compiler options +regardless of what language your program is in. For example, you +might compile a file @code{firstClass.C} like this: + +@example +g++ -g -frepo -O -c firstClass.C +@end example + +@noindent +In this example, only @samp{-frepo} is an option meant +only for C++ programs; you can use the other options with any +language supported by GCC. + +Here is a list of options that are @emph{only} for compiling C++ programs: + +@table @gcctabopt +@item -fno-access-control +Turn off all access checking. This switch is mainly useful for working +around bugs in the access control code. + +@item -fcheck-new +Check that the pointer returned by @code{operator new} is non-null +before attempting to modify the storage allocated. The current Working +Paper requires that @code{operator new} never return a null pointer, so +this check is normally unnecessary. + +An alternative to using this option is to specify that your +@code{operator new} does not throw any exceptions; if you declare it +@samp{throw()}, g++ will check the return value. See also @samp{new +(nothrow)}. + +@item -fconserve-space +Put uninitialized or runtime-initialized global variables into the +common segment, as C does. This saves space in the executable at the +cost of not diagnosing duplicate definitions. If you compile with this +flag and your program mysteriously crashes after @code{main()} has +completed, you may have an object that is being destroyed twice because +two definitions were merged. + +This option is no longer useful on most targets, now that support has +been added for putting variables into BSS without making them common. + +@item -fno-const-strings +Give string constants type @code{char *} instead of type @code{const +char *}. By default, G++ uses type @code{const char *} as required by +the standard. Even if you use @samp{-fno-const-strings}, you cannot +actually modify the value of a string constant, unless you also use +@samp{-fwritable-strings}. + +This option might be removed in a future release of G++. For maximum +portability, you should structure your code so that it works with +string constants that have type @code{const char *}. + +@item -fdollars-in-identifiers +Accept @samp{$} in identifiers. You can also explicitly prohibit use of +@samp{$} with the option @samp{-fno-dollars-in-identifiers}. (GNU C allows +@samp{$} by default on most target systems, but there are a few exceptions.) +Traditional C allowed the character @samp{$} to form part of +identifiers. However, ISO C and C++ forbid @samp{$} in identifiers. + +@item -fno-elide-constructors +The C++ standard allows an implementation to omit creating a temporary +which is only used to initialize another object of the same type. +Specifying this option disables that optimization, and forces g++ to +call the copy constructor in all cases. + +@item -fno-enforce-eh-specs +Don't check for violation of exception specifications at runtime. This +option violates the C++ standard, but may be useful for reducing code +size in production builds, much like defining @samp{NDEBUG}. The compiler +will still optimize based on the exception specifications. + +@item -fexternal-templates +Cause template instantiations to obey @samp{#pragma interface} and +@samp{implementation}; template instances are emitted or not according +to the location of the template definition. @xref{Template +Instantiation}, for more information. + +This option is deprecated. + +@item -falt-external-templates +Similar to -fexternal-templates, but template instances are emitted or +not according to the place where they are first instantiated. +@xref{Template Instantiation}, for more information. + +This option is deprecated. + +@item -ffor-scope +@itemx -fno-for-scope +If -ffor-scope is specified, the scope of variables declared in +a @i{for-init-statement} is limited to the @samp{for} loop itself, +as specified by the C++ standard. +If -fno-for-scope is specified, the scope of variables declared in +a @i{for-init-statement} extends to the end of the enclosing scope, +as was the case in old versions of gcc, and other (traditional) +implementations of C++. + +The default if neither flag is given to follow the standard, +but to allow and give a warning for old-style code that would +otherwise be invalid, or have different behavior. + +@item -fno-gnu-keywords +Do not recognize @code{typeof} as a keyword, so that code can use this +word as an identifier. You can use the keyword @code{__typeof__} instead. +@samp{-ansi} implies @samp{-fno-gnu-keywords}. + +@item -fhonor-std +Treat the @code{namespace std} as a namespace, instead of ignoring +it. For compatibility with earlier versions of g++, the compiler will, +by default, ignore @code{namespace-declarations}, +@code{using-declarations}, @code{using-directives}, and +@code{namespace-names}, if they involve @code{std}. + +@item -fno-implicit-templates +Never emit code for non-inline templates which are instantiated +implicitly (i.e. by use); only emit code for explicit instantiations. +@xref{Template Instantiation}, for more information. + +@item -fno-implicit-inline-templates +Don't emit code for implicit instantiations of inline templates, either. +The default is to handle inlines differently so that compiles with and +without optimization will need the same set of explicit instantiations. + +@item -fno-implement-inlines +To save space, do not emit out-of-line copies of inline functions +controlled by @samp{#pragma implementation}. This will cause linker +errors if these functions are not inlined everywhere they are called. + +@item -fms-extensions +Disable pedantic warnings about constructs used in MFC, such as implicit +int and getting a pointer to member function via non-standard syntax. + +@item -fno-nonansi-builtins +Disable builtin declarations of functions that are not mandated by +ANSI/ISO C. These include @code{ffs}, @code{alloca}, @code{_exit}, +@code{index}, @code{bzero}, @code{conjf}, and other related functions. + +@item -fno-operator-names +Do not treat the operator name keywords @code{and}, @code{bitand}, +@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as +synonyms as keywords. + +@item -fno-optional-diags +Disable diagnostics that the standard says a compiler does not need to +issue. Currently, the only such diagnostic issued by g++ is the one for +a name having multiple meanings within a class. + +@item -fpermissive +Downgrade messages about nonconformant code from errors to warnings. By +default, g++ effectively sets @samp{-pedantic-errors} without +@samp{-pedantic}; this option reverses that. This behavior and this +option are superseded by @samp{-pedantic}, which works as it does for GNU C. + +@item -frepo +Enable automatic template instantiation. This option also implies +@samp{-fno-implicit-templates}. @xref{Template Instantiation}, for more +information. + +@item -fno-rtti +Disable generation of information about every class with virtual +functions for use by the C++ runtime type identification features +(@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts +of the language, you can save some space by using this flag. Note that +exception handling uses the same information, but it will generate it as +needed. + +@item -fstats +Emit statistics about front-end processing at the end of the compilation. +This information is generally only useful to the G++ development team. + +@item -ftemplate-depth-@var{n} +Set the maximum instantiation depth for template classes to @var{n}. +A limit on the template instantiation depth is needed to detect +endless recursions during template class instantiation. ANSI/ISO C++ +conforming programs must not rely on a maximum depth greater than 17. + +@item -fuse-cxa-atexit +Register destructors for objects with static storage duration with the +@code{__cxa_atexit} function rather than the @code{atexit} function. +This option is required for fully standards-compliant handling of static +destructors, but will only work if your C library supports +@code{__cxa_atexit}. + +@item -fvtable-gc +Emit special relocations for vtables and virtual function references +so that the linker can identify unused virtual functions and zero out +vtable slots that refer to them. This is most useful with +@samp{-ffunction-sections} and @samp{-Wl,--gc-sections}, in order to +also discard the functions themselves. + +This optimization requires GNU as and GNU ld. Not all systems support +this option. @samp{-Wl,--gc-sections} is ignored without @samp{-static}. + +@item -fno-weak +Do not use weak symbol support, even if it is provided by the linker. +By default, G++ will use weak symbols if they are available. This +option exists only for testing, and should not be used by end-users; +it will result in inferior code and has no benefits. This option may +be removed in a future release of G++. + +@item -nostdinc++ +Do not search for header files in the standard directories specific to +C++, but do still search the other standard directories. (This option +is used when building the C++ library.) +@end table + +In addition, these optimization, warning, and code generation options +have meanings only for C++ programs: + +@table @gcctabopt +@item -fno-default-inline +Do not assume @samp{inline} for functions defined inside a class scope. +@xref{Optimize Options,,Options That Control Optimization}. Note that these +functions will have linkage like inline functions; they just won't be +inlined by default. + +@item -Wctor-dtor-privacy (C++ only) +Warn when a class seems unusable, because all the constructors or +destructors in a class are private and the class has no friends or +public static member functions. + +@item -Wnon-virtual-dtor (C++ only) +Warn when a class declares a non-virtual destructor that should probably +be virtual, because it looks like the class will be used polymorphically. + +@item -Wreorder (C++ only) +@cindex reordering, warning +@cindex warning for reordering of member initializers +Warn when the order of member initializers given in the code does not +match the order in which they must be executed. For instance: + +@smallexample +struct A @{ + int i; + int j; + A(): j (0), i (1) @{ @} +@}; +@end smallexample + +Here the compiler will warn that the member initializers for @samp{i} +and @samp{j} will be rearranged to match the declaration order of the +members. +@end table + +The following @samp{-W@dots{}} options are not affected by @samp{-Wall}. + +@table @gcctabopt +@item -Weffc++ (C++ only) +Warn about violations of various style guidelines from Scott Meyers' +@cite{Effective C++} books. If you use this option, you should be aware +that the standard library headers do not obey all of these guidelines; +you can use @samp{grep -v} to filter out those warnings. + +@item -Wno-deprecated (C++ only) +Do not warn about usage of deprecated features. @xref{Deprecated Features}. + +@item -Wno-non-template-friend (C++ only) +Disable warnings when non-templatized friend functions are declared +within a template. With the advent of explicit template specification +support in g++, if the name of the friend is an unqualified-id (ie, +@samp{friend foo(int)}), the C++ language specification demands that the +friend declare or define an ordinary, nontemplate function. (Section +14.5.3). Before g++ implemented explicit specification, unqualified-ids +could be interpreted as a particular specialization of a templatized +function. Because this non-conforming behavior is no longer the default +behavior for g++, @samp{-Wnon-template-friend} allows the compiler to +check existing code for potential trouble spots, and is on by default. +This new compiler behavior can be turned off with +@samp{-Wno-non-template-friend} which keeps the conformant compiler code +but disables the helpful warning. + +@item -Wold-style-cast (C++ only) +Warn if an old-style (C-style) cast is used within a C++ program. The +new-style casts (@samp{static_cast}, @samp{reinterpret_cast}, and +@samp{const_cast}) are less vulnerable to unintended effects, and much +easier to grep for. + +@item -Woverloaded-virtual (C++ only) +@cindex overloaded virtual fn, warning +@cindex warning for overloaded virtual fn +Warn when a function declaration hides virtual functions from a +base class. For example, in: + +@smallexample +struct A @{ + virtual void f(); +@}; + +struct B: public A @{ + void f(int); +@}; +@end smallexample + +the @code{A} class version of @code{f} is hidden in @code{B}, and code +like this: + +@smallexample +B* b; +b->f(); +@end smallexample + +will fail to compile. + +@item -Wno-pmf-conversions (C++ only) +Disable the diagnostic for converting a bound pointer to member function +to a plain pointer. + +@item -Wsign-promo (C++ only) +Warn when overload resolution chooses a promotion from unsigned or +enumeral type to a signed type over a conversion to an unsigned type of +the same size. Previous versions of g++ would try to preserve +unsignedness, but the standard mandates the current behavior. + +@item -Wsynth (C++ only) +@cindex warning for synthesized methods +@cindex synthesized methods, warning +Warn when g++'s synthesis behavior does not match that of cfront. For +instance: + +@smallexample +struct A @{ + operator int (); + A& operator = (int); +@}; + +main () +@{ + A a,b; + a = b; +@} +@end smallexample + +In this example, g++ will synthesize a default @samp{A& operator = +(const A&);}, while cfront will use the user-defined @samp{operator =}. +@end table + +@node Objective-C Dialect Options +@section Options Controlling Objective-C Dialect + +@cindex compiler options, Objective-C +@cindex Objective-C options, command line +@cindex options, Objective-C +This section describes the command-line options that are only meaningful +for Objective-C programs; but you can also use most of the GNU compiler +options regardless of what language your program is in. For example, +you might compile a file @code{some_class.m} like this: + +@example +gcc -g -fgnu-runtime -O -c some_class.m +@end example + +@noindent +In this example, only @samp{-fgnu-runtime} is an option meant only for +Objective-C programs; you can use the other options with any language +supported by GCC. + +Here is a list of options that are @emph{only} for compiling Objective-C +programs: + +@table @gcctabopt +@item -fconstant-string-class=@var{class name} +Use @var{class name} as the name of the class to instantiate for each +literal string specified with the syntax @code{@@"..."}. The default +class name is @code{NXConstantString}. + +@item -fgnu-runtime +Generate object code compatible with the standard GNU Objective-C +runtime. This is the default for most types of systems. + +@item -fnext-runtime +Generate output compatible with the NeXT runtime. This is the default +for NeXT-based systems, including Darwin and Mac OS X. + +@item -gen-decls +Dump interface declarations for all classes seen in the source file to a +file named @file{@var{sourcename}.decl}. + +@item -Wno-protocol +Do not warn if methods required by a protocol are not implemented +in the class adopting it. + +@item -Wselector +Warn if a selector has multiple methods of different types defined. + +@c not documented because only avail via -Wp +@c @item -print-objc-runtime-info + +@end table + +@node Language Independent Options +@section Options to Control Diagnostic Messages Formatting +@cindex options to control diagnostics formatting +@cindex diagnostic messages +@cindex message formatting + +Traditionally, diagnostic messages have been formatted irrespective of +the output device's aspect (e.g. its width, ...). The options described +below can be used to control the diagnostic messages formatting +algorithm, e.g. how many characters per line, how often source location +information should be reported. Right now, only the C++ front-end can +honor these options. However it is expected, in the near future, that +the remaining front-ends would be able to digest them correctly. + +@table @gcctabopt +@item -fmessage-length=@var{n} +Try to format error messages so that they fit on lines of about @var{n} +characters. The default is 72 characters for g++ and 0 for the rest of +the front-ends supported by GCC. If @var{n} is zero, then no +line-wrapping will be done; each error message will appear on a single +line. + +@item -fdiagnostics-show-location=once +Only meaningful in line-wrapping mode. Instructs the diagnostic messages +reporter to emit @emph{once} source location information; that is, in +case the message is too long to fit on a single physical line and has to +be wrapped, the source location won't be emitted (as prefix) again, +over and over, in subsequent continuation lines. This is the default +behaviour. + +@item -fdiagnostics-show-location=every-line +Only meaningful in line-wrapping mode. Instructs the diagnostic +messages reporter to emit the same source location information (as +prefix) for physical lines that result from the process of breaking a +a message which is too long to fit on a single line. + +@end table + +@node Warning Options +@section Options to Request or Suppress Warnings +@cindex options to control warnings +@cindex warning messages +@cindex messages, warning +@cindex suppressing warnings + +Warnings are diagnostic messages that report constructions which +are not inherently erroneous but which are risky or suggest there +may have been an error. + +You can request many specific warnings with options beginning @samp{-W}, +for example @samp{-Wimplicit} to request warnings on implicit +declarations. Each of these specific warning options also has a +negative form beginning @samp{-Wno-} to turn off warnings; +for example, @samp{-Wno-implicit}. This manual lists only one of the +two forms, whichever is not the default. + +These options control the amount and kinds of warnings produced by GCC: + +@table @gcctabopt +@cindex syntax checking +@item -fsyntax-only +Check the code for syntax errors, but don't do anything beyond that. + +@item -pedantic +Issue all the warnings demanded by strict ISO C and ISO C++; +reject all programs that use forbidden extensions, and some other +programs that do not follow ISO C and ISO C++. For ISO C, follows the +version of the ISO C standard specified by any @samp{-std} option used. + +Valid ISO C and ISO C++ programs should compile properly with or without +this option (though a rare few will require @option{-ansi} or a +@option{-std} option specifying the required version of ISO C). However, +without this option, certain GNU extensions and traditional C and C++ +features are supported as well. With this option, they are rejected. + +@samp{-pedantic} does not cause warning messages for use of the +alternate keywords whose names begin and end with @samp{__}. Pedantic +warnings are also disabled in the expression that follows +@code{__extension__}. However, only system header files should use +these escape routes; application programs should avoid them. +@xref{Alternate Keywords}. + +Some users try to use @samp{-pedantic} to check programs for strict ISO +C conformance. They soon find that it does not do quite what they want: +it finds some non-ISO practices, but not all---only those for which +ISO C @emph{requires} a diagnostic, and some others for which +diagnostics have been added. + +A feature to report any failure to conform to ISO C might be useful in +some instances, but would require considerable additional work and would +be quite different from @samp{-pedantic}. We don't have plans to +support such a feature in the near future. + +Where the standard specified with @option{-std} represents a GNU +extended dialect of C, such as @samp{gnu89} or @samp{gnu99}, there is a +corresponding @dfn{base standard}, the version of ISO C on which the GNU +extended dialect is based. Warnings from @option{-pedantic} are given +where they are required by the base standard. (It would not make sense +for such warnings to be given only for features not in the specified GNU +C dialect, since by definition the GNU dialects of C include all +features the compiler supports with the given option, and there would be +nothing to warn about.) + +@item -pedantic-errors +Like @samp{-pedantic}, except that errors are produced rather than +warnings. + +@item -w +Inhibit all warning messages. + +@item -Wno-import +Inhibit warning messages about the use of @samp{#import}. + +@item -Wchar-subscripts +Warn if an array subscript has type @code{char}. This is a common cause +of error, as programmers often forget that this type is signed on some +machines. + +@item -Wcomment +Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*} +comment, or whenever a Backslash-Newline appears in a @samp{//} comment. + +@item -Wformat +Check calls to @code{printf} and @code{scanf}, etc., to make sure that +the arguments supplied have types appropriate to the format string +specified, and that the conversions specified in the format string make +sense. This includes standard functions, and others specified by format +attributes (@pxref{Function Attributes}), in the @code{printf}, +@code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension, +not in the C standard) families. + +The formats are checked against the format features supported by GNU +libc version 2.2. These include all ISO C89 and C99 features, as well +as features from the Single Unix Specification and some BSD and GNU +extensions. Other library implementations may not support all these +features; GCC does not support warning about features that go beyond a +particular library's limitations. However, if @samp{-pedantic} is used +with @samp{-Wformat}, warnings will be given about format features not +in the selected standard version (but not for @code{strfmon} formats, +since those are not in any version of the C standard). @xref{C Dialect +Options,,Options Controlling C Dialect}. + +@samp{-Wformat} is included in @samp{-Wall}. For more control over some +aspects of format checking, the options @samp{-Wno-format-y2k}, +@samp{-Wno-format-extra-args}, @samp{-Wformat-nonliteral}, +@samp{-Wformat-security} and @samp{-Wformat=2} are available, but are +not included in @samp{-Wall}. + +@item -Wno-format-y2k +If @samp{-Wformat} is specified, do not warn about @code{strftime} +formats which may yield only a two-digit year. + +@item -Wno-format-extra-args +If @samp{-Wformat} is specified, do not warn about excess arguments to a +@code{printf} or @code{scanf} format function. The C standard specifies +that such arguments are ignored. + +@item -Wformat-nonliteral +If @samp{-Wformat} is specified, also warn if the format string is not a +string literal and so cannot be checked, unless the format function +takes its format arguments as a @code{va_list}. + +@item -Wformat-security +If @samp{-Wformat} is specified, also warn about uses of format +functions that represent possible security problems. At present, this +warns about calls to @code{printf} and @code{scanf} functions where the +format string is not a string literal and there are no format arguments, +as in @code{printf (foo);}. This may be a security hole if the format +string came from untrusted input and contains @samp{%n}. (This is +currently a subset of what @samp{-Wformat-nonliteral} warns about, but +in future warnings may be added to @samp{-Wformat-security} that are not +included in @samp{-Wformat-nonliteral}.) + +@item -Wformat=2 +Enable @samp{-Wformat} plus format checks not included in +@samp{-Wformat}. Currently equivalent to @samp{-Wformat +-Wformat-nonliteral -Wformat-security}. + +@item -Wimplicit-int +Warn when a declaration does not specify a type. + +@item -Wimplicit-function-declaration +@itemx -Werror-implicit-function-declaration +Give a warning (or error) whenever a function is used before being +declared. + +@item -Wimplicit +Same as @samp{-Wimplicit-int} and @samp{-Wimplicit-function-}@* +@samp{declaration}. + +@item -Wmain +Warn if the type of @samp{main} is suspicious. @samp{main} should be a +function with external linkage, returning int, taking either zero +arguments, two, or three arguments of appropriate types. + +@item -Wmissing-braces +Warn if an aggregate or union initializer is not fully bracketed. In +the following example, the initializer for @samp{a} is not fully +bracketed, but that for @samp{b} is fully bracketed. + +@smallexample +int a[2][2] = @{ 0, 1, 2, 3 @}; +int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @}; +@end smallexample + +@item -Wmultichar +Warn if a multicharacter constant (@samp{'FOOF'}) is used. Usually they +indicate a typo in the user's code, as they have implementation-defined +values, and should not be used in portable code. + +@item -Wparentheses +Warn if parentheses are omitted in certain contexts, such +as when there is an assignment in a context where a truth value +is expected, or when operators are nested whose precedence people +often get confused about. + +Also warn about constructions where there may be confusion to which +@code{if} statement an @code{else} branch belongs. Here is an example of +such a case: + +@smallexample +@{ + if (a) + if (b) + foo (); + else + bar (); +@} +@end smallexample + +In C, every @code{else} branch belongs to the innermost possible @code{if} +statement, which in this example is @code{if (b)}. This is often not +what the programmer expected, as illustrated in the above example by +indentation the programmer chose. When there is the potential for this +confusion, GNU C will issue a warning when this flag is specified. +To eliminate the warning, add explicit braces around the innermost +@code{if} statement so there is no way the @code{else} could belong to +the enclosing @code{if}. The resulting code would look like this: + +@smallexample +@{ + if (a) + @{ + if (b) + foo (); + else + bar (); + @} +@} +@end smallexample + +@item -Wsequence-point +Warn about code that may have undefined semantics because of violations +of sequence point rules in the C standard. + +The C standard defines the order in which expressions in a C program are +evaluated in terms of @dfn{sequence points}, which represent a partial +ordering between the execution of parts of the program: those executed +before the sequence point, and those executed after it. These occur +after the evaluation of a full expression (one which is not part of a +larger expression), after the evaluation of the first operand of a +@code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a +function is called (but after the evaluation of its arguments and the +expression denoting the called function), and in certain other places. +Other than as expressed by the sequence point rules, the order of +evaluation of subexpressions of an expression is not specified. All +these rules describe only a partial order rather than a total order, +since, for example, if two functions are called within one expression +with no sequence point between them, the order in which the functions +are called is not specified. However, the standards committee have +ruled that function calls do not overlap. + +It is not specified when between sequence points modifications to the +values of objects take effect. Programs whose behavior depends on this +have undefined behavior; the C standard specifies that ``Between the +previous and next sequence point an object shall have its stored value +modified at most once by the evaluation of an expression. Furthermore, +the prior value shall be read only to determine the value to be +stored.''. If a program breaks these rules, the results on any +particular implementation are entirely unpredictable. + +Examples of code with undefined behavior are @code{a = a++;}, @code{a[n] += b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not +diagnosed by this option, and it may give an occasional false positive +result, but in general it has been found fairly effective at detecting +this sort of problem in programs. + +The present implementation of this option only works for C programs. A +future implementation may also work for C++ programs. + +There is some controversy over the precise meaning of the sequence point +rules in subtle cases. Alternative formal definitions may be found in +Clive Feather's ``Annex S'' +@w{@uref{http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n925.htm}} and in +Michael Norrish's thesis +@w{@uref{http://www.cl.cam.ac.uk/users/mn200/PhD/thesis-report.ps.gz}}. +Other discussions are by Raymond Mak +@w{@uref{http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n926.htm}} and +D. Hugh Redelmeier +@w{@uref{http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n927.htm}}. + +@item -Wreturn-type +Warn whenever a function is defined with a return-type that defaults to +@code{int}. Also warn about any @code{return} statement with no +return-value in a function whose return-type is not @code{void}. + +For C++, a function without return type always produces a diagnostic +message, even when @samp{-Wno-return-type} is specified. The only +exceptions are @samp{main} and functions defined in system headers. + +@item -Wswitch +Warn whenever a @code{switch} statement has an index of enumeral type +and lacks a @code{case} for one or more of the named codes of that +enumeration. (The presence of a @code{default} label prevents this +warning.) @code{case} labels outside the enumeration range also +provoke warnings when this option is used. + +@item -Wtrigraphs +Warn if any trigraphs are encountered that might change the meaning of +the program (trigraphs within comments are not warned about). + +@item -Wunused-function +Warn whenever a static function is declared but not defined or a +non\-inline static function is unused. + +@item -Wunused-label +Warn whenever a label is declared but not used. + +To suppress this warning use the @samp{unused} attribute +(@pxref{Variable Attributes}). + +@item -Wunused-parameter +Warn whenever a function parameter is unused aside from its declaration. + +To suppress this warning use the @samp{unused} attribute +(@pxref{Variable Attributes}). + +@item -Wunused-variable +Warn whenever a local variable or non-constant static variable is unused +aside from its declaration + +To suppress this warning use the @samp{unused} attribute +(@pxref{Variable Attributes}). + +@item -Wunused-value +Warn whenever a statement computes a result that is explicitly not used. + +To suppress this warning cast the expression to @samp{void}. + +@item -Wunused +All all the above @samp{-Wunused} options combined. + +In order to get a warning about an unused function parameter, you must +either specify @samp{-W -Wunused} or separately specify +@samp{-Wunused-parameter}. + +@item -Wuninitialized +Warn if an automatic variable is used without first being initialized or +if a variable may be clobbered by a @code{setjmp} call. + +These warnings are possible only in optimizing compilation, +because they require data flow information that is computed only +when optimizing. If you don't specify @samp{-O}, you simply won't +get these warnings. + +These warnings occur only for variables that are candidates for +register allocation. Therefore, they do not occur for a variable that +is declared @code{volatile}, or whose address is taken, or whose size +is other than 1, 2, 4 or 8 bytes. Also, they do not occur for +structures, unions or arrays, even when they are in registers. + +Note that there may be no warning about a variable that is used only +to compute a value that itself is never used, because such +computations may be deleted by data flow analysis before the warnings +are printed. + +These warnings are made optional because GCC is not smart +enough to see all the reasons why the code might be correct +despite appearing to have an error. Here is one example of how +this can happen: + +@smallexample +@{ + int x; + switch (y) + @{ + case 1: x = 1; + break; + case 2: x = 4; + break; + case 3: x = 5; + @} + foo (x); +@} +@end smallexample + +@noindent +If the value of @code{y} is always 1, 2 or 3, then @code{x} is +always initialized, but GCC doesn't know this. Here is +another common case: + +@smallexample +@{ + int save_y; + if (change_y) save_y = y, y = new_y; + @dots{} + if (change_y) y = save_y; +@} +@end smallexample + +@noindent +This has no bug because @code{save_y} is used only if it is set. + +@cindex @code{longjmp} warnings +This option also warns when a non-volatile automatic variable might be +changed by a call to @code{longjmp}. These warnings as well are possible +only in optimizing compilation. + +The compiler sees only the calls to @code{setjmp}. It cannot know +where @code{longjmp} will be called; in fact, a signal handler could +call it at any point in the code. As a result, you may get a warning +even when there is in fact no problem because @code{longjmp} cannot +in fact be called at the place which would cause a problem. + +Some spurious warnings can be avoided if you declare all the functions +you use that never return as @code{noreturn}. @xref{Function +Attributes}. + +@item -Wreorder (C++ only) +@cindex reordering, warning +@cindex warning for reordering of member initializers +Warn when the order of member initializers given in the code does not +match the order in which they must be executed. For instance: + +@item -Wunknown-pragmas +@cindex warning for unknown pragmas +@cindex unknown pragmas, warning +@cindex pragmas, warning of unknown +Warn when a #pragma directive is encountered which is not understood by +GCC. If this command line option is used, warnings will even be issued +for unknown pragmas in system header files. This is not the case if +the warnings were only enabled by the @samp{-Wall} command line option. + +@item -Wall +All of the above @samp{-W} options combined. This enables all the +warnings about constructions that some users consider questionable, and +that are easy to avoid (or modify to prevent the warning), even in +conjunction with macros. + +@item -Wsystem-headers +@cindex warnings from system headers +@cindex system headers, warnings from +Print warning messages for constructs found in system header files. +Warnings from system headers are normally suppressed, on the assumption +that they usually do not indicate real problems and would only make the +compiler output harder to read. Using this command line option tells +GCC to emit warnings from system headers as if they occurred in user +code. However, note that using @samp{-Wall} in conjunction with this +option will @emph{not} warn about unknown pragmas in system +headers---for that, @samp{-Wunknown-pragmas} must also be used. +@end table + +The following @samp{-W@dots{}} options are not implied by @samp{-Wall}. +Some of them warn about constructions that users generally do not +consider questionable, but which occasionally you might wish to check +for; others warn about constructions that are necessary or hard to avoid +in some cases, and there is no simple way to modify the code to suppress +the warning. + +@table @gcctabopt +@item -W +Print extra warning messages for these events: + +@itemize @bullet +@item +A function can return either with or without a value. (Falling +off the end of the function body is considered returning without +a value.) For example, this function would evoke such a +warning: + +@smallexample +@group +foo (a) +@{ + if (a > 0) + return a; +@} +@end group +@end smallexample + +@item +An expression-statement or the left-hand side of a comma expression +contains no side effects. +To suppress the warning, cast the unused expression to void. +For example, an expression such as @samp{x[i,j]} will cause a warning, +but @samp{x[(void)i,j]} will not. + +@item +An unsigned value is compared against zero with @samp{<} or @samp{<=}. + +@item +A comparison like @samp{x<=y<=z} appears; this is equivalent to +@samp{(x<=y ? 1 : 0) <= z}, which is a different interpretation from +that of ordinary mathematical notation. + +@item +Storage-class specifiers like @code{static} are not the first things in +a declaration. According to the C Standard, this usage is obsolescent. + +@item +The return type of a function has a type qualifier such as @code{const}. +Such a type qualifier has no effect, since the value returned by a +function is not an lvalue. (But don't warn about the GNU extension of +@code{volatile void} return types. That extension will be warned about +if @samp{-pedantic} is specified.) + +@item +If @samp{-Wall} or @samp{-Wunused} is also specified, warn about unused +arguments. + +@item +A comparison between signed and unsigned values could produce an +incorrect result when the signed value is converted to unsigned. +(But don't warn if @samp{-Wno-sign-compare} is also specified.) + +@item +An aggregate has a partly bracketed initializer. +For example, the following code would evoke such a warning, +because braces are missing around the initializer for @code{x.h}: + +@smallexample +struct s @{ int f, g; @}; +struct t @{ struct s h; int i; @}; +struct t x = @{ 1, 2, 3 @}; +@end smallexample + +@item +An aggregate has an initializer which does not initialize all members. +For example, the following code would cause such a warning, because +@code{x.h} would be implicitly initialized to zero: + +@smallexample +struct s @{ int f, g, h; @}; +struct s x = @{ 3, 4 @}; +@end smallexample +@end itemize + +@item -Wfloat-equal +Warn if floating point values are used in equality comparisons. + +The idea behind this is that sometimes it is convenient (for the +programmer) to consider floating-point values as approximations to +infinitely precise real numbers. If you are doing this, then you need +to compute (by analysing the code, or in some other way) the maximum or +likely maximum error that the computation introduces, and allow for it +when performing comparisons (and when producing output, but that's a +different problem). In particular, instead of testing for equality, you +would check to see whether the two values have ranges that overlap; and +this is done with the relational operators, so equality comparisons are +probably mistaken. + +@item -Wtraditional (C only) +Warn about certain constructs that behave differently in traditional and +ISO C. Also warn about ISO C constructs that have no traditional C +equivalent, and/or problematic constructs which should be avoided. + +@itemize @bullet +@item +Macro parameters that appear within string literals in the macro body. +In traditional C macro replacement takes place within string literals, +but does not in ISO C. + +@item +In traditional C, some preprocessor directives did not exist. +Traditional preprocessors would only consider a line to be a directive +if the @samp{#} appeared in column 1 on the line. Therefore +@samp{-Wtraditional} warns about directives that traditional C +understands but would ignore because the @samp{#} does not appear as the +first character on the line. It also suggests you hide directives like +@samp{#pragma} not understood by traditional C by indenting them. Some +traditional implementations would not recognise @samp{#elif}, so it +suggests avoiding it altogether. + +@item +A function-like macro that appears without arguments. + +@item +The unary plus operator. + +@item +The `U' integer constant suffix, or the `F' or `L' floating point +constant suffixes. (Traditonal C does support the `L' suffix on integer +constants.) Note, these suffixes appear in macros defined in the system +headers of most modern systems, e.g. the _MIN/_MAX macros in limits.h. +Use of these macros in user code might normally lead to spurious +warnings, however gcc's integrated preprocessor has enough context to +avoid warning in these cases. + +@item +A function declared external in one block and then used after the end of +the block. + +@item +A @code{switch} statement has an operand of type @code{long}. + +@item +A non-@code{static} function declaration follows a @code{static} one. +This construct is not accepted by some traditional C compilers. + +@item +The ISO type of an integer constant has a different width or +signedness from its traditional type. This warning is only issued if +the base of the constant is ten. I.e. hexadecimal or octal values, which +typically represent bit patterns, are not warned about. + +@item +Usage of ISO string concatenation is detected. + +@item +Initialization of automatic aggregates. + +@item +Identifier conflicts with labels. Traditional C lacks a separate +namespace for labels. + +@item +Initialization of unions. If the initializer is zero, the warning is +omitted. This is done under the assumption that the zero initializer in +user code appears conditioned on e.g. @code{__STDC__} to avoid missing +initializer warnings and relies on default initialization to zero in the +traditional C case. + +@item +Conversions by prototypes between fixed/floating point values and vice +versa. The absence of these prototypes when compiling with traditional +C would cause serious problems. This is a subset of the possible +conversion warnings, for the full set use @samp{-Wconversion}. +@end itemize + +@item -Wundef +Warn if an undefined identifier is evaluated in an @samp{#if} directive. + +@item -Wshadow +Warn whenever a local variable shadows another local variable, parameter or +global variable or whenever a built-in function is shadowed. + +@item -Wlarger-than-@var{len} +Warn whenever an object of larger than @var{len} bytes is defined. + +@item -Wpointer-arith +Warn about anything that depends on the ``size of'' a function type or +of @code{void}. GNU C assigns these types a size of 1, for +convenience in calculations with @code{void *} pointers and pointers +to functions. + +@item -Wbad-function-cast (C only) +Warn whenever a function call is cast to a non-matching type. +For example, warn if @code{int malloc()} is cast to @code{anything *}. + +@item -Wcast-qual +Warn whenever a pointer is cast so as to remove a type qualifier from +the target type. For example, warn if a @code{const char *} is cast +to an ordinary @code{char *}. + +@item -Wcast-align +Warn whenever a pointer is cast such that the required alignment of the +target is increased. For example, warn if a @code{char *} is cast to +an @code{int *} on machines where integers can only be accessed at +two- or four-byte boundaries. + +@item -Wwrite-strings +Give string constants the type @code{const char[@var{length}]} so that +copying the address of one into a non-@code{const} @code{char *} +pointer will get a warning. These warnings will help you find at +compile time code that can try to write into a string constant, but +only if you have been very careful about using @code{const} in +declarations and prototypes. Otherwise, it will just be a nuisance; +this is why we did not make @samp{-Wall} request these warnings. + +@item -Wconversion +Warn if a prototype causes a type conversion that is different from what +would happen to the same argument in the absence of a prototype. This +includes conversions of fixed point to floating and vice versa, and +conversions changing the width or signedness of a fixed point argument +except when the same as the default promotion. + +Also, warn if a negative integer constant expression is implicitly +converted to an unsigned type. For example, warn about the assignment +@code{x = -1} if @code{x} is unsigned. But do not warn about explicit +casts like @code{(unsigned) -1}. + +@item -Wsign-compare +@cindex warning for comparison of signed and unsigned values +@cindex comparison of signed and unsigned values, warning +@cindex signed and unsigned values, comparison warning +Warn when a comparison between signed and unsigned values could produce +an incorrect result when the signed value is converted to unsigned. +This warning is also enabled by @samp{-W}; to get the other warnings +of @samp{-W} without this warning, use @samp{-W -Wno-sign-compare}. + +@item -Waggregate-return +Warn if any functions that return structures or unions are defined or +called. (In languages where you can return an array, this also elicits +a warning.) + +@item -Wstrict-prototypes (C only) +Warn if a function is declared or defined without specifying the +argument types. (An old-style function definition is permitted without +a warning if preceded by a declaration which specifies the argument +types.) + +@item -Wmissing-prototypes (C only) +Warn if a global function is defined without a previous prototype +declaration. This warning is issued even if the definition itself +provides a prototype. The aim is to detect global functions that fail +to be declared in header files. + +@item -Wmissing-declarations +Warn if a global function is defined without a previous declaration. +Do so even if the definition itself provides a prototype. +Use this option to detect global functions that are not declared in +header files. + +@item -Wmissing-noreturn +Warn about functions which might be candidates for attribute @code{noreturn}. +Note these are only possible candidates, not absolute ones. Care should +be taken to manually verify functions actually do not ever return before +adding the @code{noreturn} attribute, otherwise subtle code generation +bugs could be introduced. You will not get a warning for @code{main} in +hosted C environments. + +@item -Wmissing-format-attribute +If @samp{-Wformat} is enabled, also warn about functions which might be +candidates for @code{format} attributes. Note these are only possible +candidates, not absolute ones. GCC will guess that @code{format} +attributes might be appropriate for any function that calls a function +like @code{vprintf} or @code{vscanf}, but this might not always be the +case, and some functions for which @code{format} attributes are +appropriate may not be detected. This option has no effect unless +@samp{-Wformat} is enabled (possibly by @samp{-Wall}). + +@item -Wpacked +Warn if a structure is given the packed attribute, but the packed +attribute has no effect on the layout or size of the structure. +Such structures may be mis-aligned for little benefit. For +instance, in this code, the variable @code{f.x} in @code{struct bar} +will be misaligned even though @code{struct bar} does not itself +have the packed attribute: + +@smallexample +@group +struct foo @{ + int x; + char a, b, c, d; +@} __attribute__((packed)); +struct bar @{ + char z; + struct foo f; +@}; +@end group +@end smallexample + +@item -Wpadded +Warn if padding is included in a structure, either to align an element +of the structure or to align the whole structure. Sometimes when this +happens it is possible to rearrange the fields of the structure to +reduce the padding and so make the structure smaller. + +@item -Wredundant-decls +Warn if anything is declared more than once in the same scope, even in +cases where multiple declaration is valid and changes nothing. + +@item -Wnested-externs (C only) +Warn if an @code{extern} declaration is encountered within a function. + +@item -Wunreachable-code +Warn if the compiler detects that code will never be executed. + +This option is intended to warn when the compiler detects that at +least a whole line of source code will never be executed, because +some condition is never satisfied or because it is after a +procedure that never returns. + +It is possible for this option to produce a warning even though there +are circumstances under which part of the affected line can be executed, +so care should be taken when removing apparently-unreachable code. + +For instance, when a function is inlined, a warning may mean that the +line is unreachable in only one inlined copy of the function. + +This option is not made part of @samp{-Wall} because in a debugging +version of a program there is often substantial code which checks +correct functioning of the program and is, hopefully, unreachable +because the program does work. Another common use of unreachable +code is to provide behaviour which is selectable at compile-time. + +@item -Winline +Warn if a function can not be inlined and it was declared as inline. + +@item -Wlong-long +Warn if @samp{long long} type is used. This is default. To inhibit +the warning messages, use @samp{-Wno-long-long}. Flags +@samp{-Wlong-long} and @samp{-Wno-long-long} are taken into account +only when @samp{-pedantic} flag is used. + +@item -Wdisabled-optimization +Warn if a requested optimization pass is disabled. This warning does +not generally indicate that there is anything wrong with your code; it +merely indicates that GCC's optimizers were unable to handle the code +effectively. Often, the problem is that your code is too big or too +complex; GCC will refuse to optimize programs when the optimization +itself is likely to take inordinate amounts of time. + +@item -Werror +Make all warnings into errors. +@end table + +@node Debugging Options +@section Options for Debugging Your Program or GCC +@cindex options, debugging +@cindex debugging information options + +GCC has various special options that are used for debugging +either your program or GCC: + +@table @gcctabopt +@item -g +Produce debugging information in the operating system's native format +(stabs, COFF, XCOFF, or DWARF). GDB can work with this debugging +information. + +On most systems that use stabs format, @samp{-g} enables use of extra +debugging information that only GDB can use; this extra information +makes debugging work better in GDB but will probably make other debuggers +crash or +refuse to read the program. If you want to control for certain whether +to generate the extra information, use @samp{-gstabs+}, @samp{-gstabs}, +@samp{-gxcoff+}, @samp{-gxcoff}, @samp{-gdwarf-1+}, or @samp{-gdwarf-1} +(see below). + +Unlike most other C compilers, GCC allows you to use @samp{-g} with +@samp{-O}. The shortcuts taken by optimized code may occasionally +produce surprising results: some variables you declared may not exist +at all; flow of control may briefly move where you did not expect it; +some statements may not be executed because they compute constant +results or their values were already at hand; some statements may +execute in different places because they were moved out of loops. + +Nevertheless it proves possible to debug optimized output. This makes +it reasonable to use the optimizer for programs that might have bugs. + +The following options are useful when GCC is generated with the +capability for more than one debugging format. + +@item -ggdb +Produce debugging information for use by GDB. This means to use the +most expressive format available (DWARF 2, stabs, or the native format +if neither of those are supported), including GDB extensions if at all +possible. + +@item -gstabs +Produce debugging information in stabs format (if that is supported), +without GDB extensions. This is the format used by DBX on most BSD +systems. On MIPS, Alpha and System V Release 4 systems this option +produces stabs debugging output which is not understood by DBX or SDB. +On System V Release 4 systems this option requires the GNU assembler. + +@item -gstabs+ +Produce debugging information in stabs format (if that is supported), +using GNU extensions understood only by the GNU debugger (GDB). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program. + +@item -gcoff +Produce debugging information in COFF format (if that is supported). +This is the format used by SDB on most System V systems prior to +System V Release 4. + +@item -gxcoff +Produce debugging information in XCOFF format (if that is supported). +This is the format used by the DBX debugger on IBM RS/6000 systems. + +@item -gxcoff+ +Produce debugging information in XCOFF format (if that is supported), +using GNU extensions understood only by the GNU debugger (GDB). The +use of these extensions is likely to make other debuggers crash or +refuse to read the program, and may cause assemblers other than the GNU +assembler (GAS) to fail with an error. + +@item -gdwarf +Produce debugging information in DWARF version 1 format (if that is +supported). This is the format used by SDB on most System V Release 4 +systems. + +@item -gdwarf+ +Produce debugging information in DWARF version 1 format (if that is +supported), using GNU extensions understood only by the GNU debugger +(GDB). The use of these extensions is likely to make other debuggers +crash or refuse to read the program. + +@item -gdwarf-2 +Produce debugging information in DWARF version 2 format (if that is +supported). This is the format used by DBX on IRIX 6. + +@item -g@var{level} +@itemx -ggdb@var{level} +@itemx -gstabs@var{level} +@itemx -gcoff@var{level} +@itemx -gxcoff@var{level} +@itemx -gdwarf@var{level} +@itemx -gdwarf-2@var{level} +Request debugging information and also use @var{level} to specify how +much information. The default level is 2. + +Level 1 produces minimal information, enough for making backtraces in +parts of the program that you don't plan to debug. This includes +descriptions of functions and external variables, but no information +about local variables and no line numbers. + +Level 3 includes extra information, such as all the macro definitions +present in the program. Some debuggers support macro expansion when +you use @samp{-g3}. + +@cindex @code{prof} +@item -p +Generate extra code to write profile information suitable for the +analysis program @code{prof}. You must use this option when compiling +the source files you want data about, and you must also use it when +linking. + +@cindex @code{gprof} +@item -pg +Generate extra code to write profile information suitable for the +analysis program @code{gprof}. You must use this option when compiling +the source files you want data about, and you must also use it when +linking. + +@cindex @code{tcov} +@item -a +Generate extra code to write profile information for basic blocks, which will +record the number of times each basic block is executed, the basic block start +address, and the function name containing the basic block. If @samp{-g} is +used, the line number and filename of the start of the basic block will also be +recorded. If not overridden by the machine description, the default action is +to append to the text file @file{bb.out}. + +This data could be analyzed by a program like @code{tcov}. Note, +however, that the format of the data is not what @code{tcov} expects. +Eventually GNU @code{gprof} should be extended to process this data. + +@item -Q +Makes the compiler print out each function name as it is compiled, and +print some statistics about each pass when it finishes. + +@item -ftime-report +Makes the compiler print some statistics about the time consumed by each +pass when it finishes. + +@item -fmem-report +Makes the compiler print some statistics about permanent memory +allocation when it finishes. + +@item -ax +Generate extra code to profile basic blocks. Your executable will +produce output that is a superset of that produced when @samp{-a} is +used. Additional output is the source and target address of the basic +blocks where a jump takes place, the number of times a jump is executed, +and (optionally) the complete sequence of basic blocks being executed. +The output is appended to file @file{bb.out}. + +You can examine different profiling aspects without recompilation. Your +executable will read a list of function names from file @file{bb.in}. +Profiling starts when a function on the list is entered and stops when +that invocation is exited. To exclude a function from profiling, prefix +its name with `-'. If a function name is not unique, you can +disambiguate it by writing it in the form +@samp{/path/filename.d:functionname}. Your executable will write the +available paths and filenames in file @file{bb.out}. + +Several function names have a special meaning: +@table @code +@item __bb_jumps__ +Write source, target and frequency of jumps to file @file{bb.out}. +@item __bb_hidecall__ +Exclude function calls from frequency count. +@item __bb_showret__ +Include function returns in frequency count. +@item __bb_trace__ +Write the sequence of basic blocks executed to file @file{bbtrace.gz}. +The file will be compressed using the program @samp{gzip}, which must +exist in your @env{PATH}. On systems without the @samp{popen} +function, the file will be named @file{bbtrace} and will not be +compressed. @strong{Profiling for even a few seconds on these systems +will produce a very large file.} Note: @code{__bb_hidecall__} and +@code{__bb_showret__} will not affect the sequence written to +@file{bbtrace.gz}. +@end table + +Here's a short example using different profiling parameters +in file @file{bb.in}. Assume function @code{foo} consists of basic blocks +1 and 2 and is called twice from block 3 of function @code{main}. After +the calls, block 3 transfers control to block 4 of @code{main}. + +With @code{__bb_trace__} and @code{main} contained in file @file{bb.in}, +the following sequence of blocks is written to file @file{bbtrace.gz}: +0 3 1 2 1 2 4. The return from block 2 to block 3 is not shown, because +the return is to a point inside the block and not to the top. The +block address 0 always indicates, that control is transferred +to the trace from somewhere outside the observed functions. With +@samp{-foo} added to @file{bb.in}, the blocks of function +@code{foo} are removed from the trace, so only 0 3 4 remains. + +With @code{__bb_jumps__} and @code{main} contained in file @file{bb.in}, +jump frequencies will be written to file @file{bb.out}. The +frequencies are obtained by constructing a trace of blocks +and incrementing a counter for every neighbouring pair of blocks +in the trace. The trace 0 3 1 2 1 2 4 displays the following +frequencies: + +@example +Jump from block 0x0 to block 0x3 executed 1 time(s) +Jump from block 0x3 to block 0x1 executed 1 time(s) +Jump from block 0x1 to block 0x2 executed 2 time(s) +Jump from block 0x2 to block 0x1 executed 1 time(s) +Jump from block 0x2 to block 0x4 executed 1 time(s) +@end example + +With @code{__bb_hidecall__}, control transfer due to call instructions +is removed from the trace, that is the trace is cut into three parts: 0 +3 4, 0 1 2 and 0 1 2. With @code{__bb_showret__}, control transfer due +to return instructions is added to the trace. The trace becomes: 0 3 1 +2 3 1 2 3 4. Note, that this trace is not the same, as the sequence +written to @file{bbtrace.gz}. It is solely used for counting jump +frequencies. + +@item -fprofile-arcs +Instrument @dfn{arcs} during compilation. For each function of your +program, GCC creates a program flow graph, then finds a spanning tree +for the graph. Only arcs that are not on the spanning tree have to be +instrumented: the compiler adds code to count the number of times that these +arcs are executed. When an arc is the only exit or only entrance to a +block, the instrumentation code can be added to the block; otherwise, a +new basic block must be created to hold the instrumentation code. + +Since not every arc in the program must be instrumented, programs +compiled with this option run faster than programs compiled with +@samp{-a}, which adds instrumentation code to every basic block in the +program. The tradeoff: since @code{gcov} does not have +execution counts for all branches, it must start with the execution +counts for the instrumented branches, and then iterate over the program +flow graph until the entire graph has been solved. Hence, @code{gcov} +runs a little more slowly than a program which uses information from +@samp{-a}. + +@samp{-fprofile-arcs} also makes it possible to estimate branch +probabilities, and to calculate basic block execution counts. In +general, basic block execution counts do not give enough information to +estimate all branch probabilities. When the compiled program exits, it +saves the arc execution counts to a file called +@file{@var{sourcename}.da}. Use the compiler option +@samp{-fbranch-probabilities} (@pxref{Optimize Options,,Options that +Control Optimization}) when recompiling, to optimize using estimated +branch probabilities. + +@need 2000 +@item -ftest-coverage +Create data files for the @code{gcov} code-coverage utility +(@pxref{Gcov,, @code{gcov}: a GCC Test Coverage Program}). +The data file names begin with the name of your source file: + +@table @gcctabopt +@item @var{sourcename}.bb +A mapping from basic blocks to line numbers, which @code{gcov} uses to +associate basic block execution counts with line numbers. + +@item @var{sourcename}.bbg +A list of all arcs in the program flow graph. This allows @code{gcov} +to reconstruct the program flow graph, so that it can compute all basic +block and arc execution counts from the information in the +@code{@var{sourcename}.da} file (this last file is the output from +@samp{-fprofile-arcs}). +@end table + +@item -d@var{letters} +Says to make debugging dumps during compilation at times specified by +@var{letters}. This is used for debugging the compiler. The file names +for most of the dumps are made by appending a pass number and a word to +the source file name (e.g. @file{foo.c.00.rtl} or @file{foo.c.01.sibling}). +Here are the possible letters for use in @var{letters}, and their meanings: + +@table @samp +@item A +Annotate the assembler output with miscellaneous debugging information. +@item b +Dump after computing branch probabilities, to @file{@var{file}.11.bp}. +@item B +Dump after block reordering, to @file{@var{file}.26.bbro}. +@item c +Dump after instruction combination, to the file @file{@var{file}.14.combine}. +@item C +Dump after the first if conversion, to the file @file{@var{file}.15.ce}. +@item d +Dump after delayed branch scheduling, to @file{@var{file}.29.dbr}. +@item D +Dump all macro definitions, at the end of preprocessing, in addition to +normal output. +@item e +Dump after SSA optimizations, to @file{@var{file}.05.ssa} and +@file{@var{file}.06.ussa}. +@item E +Dump after the second if conversion, to @file{@var{file}.24.ce2}. +@item f +Dump after life analysis, to @file{@var{file}.13.life}. +@item F +Dump after purging @code{ADDRESSOF} codes, to @file{@var{file}.04.addressof}. +@item g +Dump after global register allocation, to @file{@var{file}.19.greg}. +@item o +Dump after post-reload CSE and other optimizations, to @file{@var{file}.20.postreload}. +@item G +Dump after GCSE, to @file{@var{file}.08.gcse}. +@item i +Dump after sibling call optimizations, to @file{@var{file}.01.sibling}. +@item j +Dump after the first jump optimization, to @file{@var{file}.02.jump}. +@item J +Dump after the last jump optimization, to @file{@var{file}.27.jump2}. +@item k +Dump after conversion from registers to stack, to @file{@var{file}.29.stack}. +@item l +Dump after local register allocation, to @file{@var{file}.18.lreg}. +@item L +Dump after loop optimization, to @file{@var{file}.09.loop}. +@item M +Dump after performing the machine dependent reorganisation pass, to +@file{@var{file}.28.mach}. +@item n +Dump after register renumbering, to @file{@var{file}.23.rnreg}. +@item N +Dump after the register move pass, to @file{@var{file}.16.regmove}. +@item r +Dump after RTL generation, to @file{@var{file}.00.rtl}. +@item R +Dump after the second instruction scheduling pass, to +@file{@var{file}.25.sched2}. +@item s +Dump after CSE (including the jump optimization that sometimes follows +CSE), to @file{@var{file}.03.cse}. +@item S +Dump after the first instruction scheduling pass, to +@file{@var{file}.17.sched}. +@item t +Dump after the second CSE pass (including the jump optimization that +sometimes follows CSE), to @file{@var{file}.10.cse2}. +@item w +Dump after the second flow pass, to @file{@var{file}.21.flow2}. +@item X +Dump after dead code elimination, to @file{@var{file}.06.dce}. +@item z +Dump after the peephole pass, to @file{@var{file}.22.peephole2}. +@item a +Produce all the dumps listed above. +@item m +Print statistics on memory usage, at the end of the run, to +standard error. +@item p +Annotate the assembler output with a comment indicating which +pattern and alternative was used. The length of each instruction is +also printed. +@item P +Dump the RTL in the assembler output as a comment before each instruction. +Also turns on @samp{-dp} annotation. +@item v +For each of the other indicated dump files (except for +@file{@var{file}.00.rtl}), dump a representation of the control flow graph +suitable for viewing with VCG to @file{@var{file}.@var{pass}.vcg}. +@item x +Just generate RTL for a function instead of compiling it. Usually used +with @samp{r}. +@item y +Dump debugging information during parsing, to standard error. +@end table + +@item -fdump-unnumbered +When doing debugging dumps (see -d option above), suppress instruction +numbers and line number note output. This makes it more feasible to +use diff on debugging dumps for compiler invocations with different +options, in particular with and without -g. + +@item -fdump-translation-unit=@var{file} (C and C++ only) +Dump a representation of the tree structure for the entire translation +unit to @var{file}. + +@item -fdump-class_layout=@var{file} (C++ only) +@item -fdump-class_layout (C++ only) +Dump a representation of each class's heirarchy to @var{file}, or +@code{stderr} if not specified. + +@item -fpretend-float +When running a cross-compiler, pretend that the target machine uses the +same floating point format as the host machine. This causes incorrect +output of the actual floating constants, but the actual instruction +sequence will probably be the same as GCC would make when running on +the target machine. + +@item -save-temps +Store the usual ``temporary'' intermediate files permanently; place them +in the current directory and name them based on the source file. Thus, +compiling @file{foo.c} with @samp{-c -save-temps} would produce files +@file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a +preprocessed @file{foo.i} output file even though the compiler now +normally uses an integrated preprocessor. + +@item -time +Report the CPU time taken by each subprocess in the compilation +sequence. For C source files, this is the compiler proper and assembler +(plus the linker if linking is done). The output looks like this: + +@smallexample +# cc1 0.12 0.01 +# as 0.00 0.01 +@end smallexample + +The first number on each line is the ``user time,'' that is time spent +executing the program itself. The second number is ``system time,'' +time spent executing operating system routines on behalf of the program. +Both numbers are in seconds. + +@item -print-file-name=@var{library} +Print the full absolute name of the library file @var{library} that +would be used when linking---and don't do anything else. With this +option, GCC does not compile or link anything; it just prints the +file name. + +@item -print-prog-name=@var{program} +Like @samp{-print-file-name}, but searches for a program such as @samp{cpp}. + +@item -print-libgcc-file-name +Same as @samp{-print-file-name=libgcc.a}. + +This is useful when you use @samp{-nostdlib} or @samp{-nodefaultlibs} +but you do want to link with @file{libgcc.a}. You can do + +@example +gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name` +@end example + +@item -print-search-dirs +Print the name of the configured installation directory and a list of +program and library directories gcc will search---and don't do anything else. + +This is useful when gcc prints the error message +@samp{installation problem, cannot exec cpp0: No such file or directory}. +To resolve this you either need to put @file{cpp0} and the other compiler +components where gcc expects to find them, or you can set the environment +variable @env{GCC_EXEC_PREFIX} to the directory where you installed them. +Don't forget the trailing '/'. +@xref{Environment Variables}. + +@item -dumpmachine +Print the compiler's target machine (for example, +@samp{i686-pc-linux-gnu})---and don't do anything else. + +@item -dumpversion +Print the compiler version (for example, @samp{3.0})---and don't do +anything else. + +@item -dumpspecs +Print the compiler's built-in specs---and don't do anything else. (This +is used when GCC itself is being built.) @xref{Spec Files}. +@end table + +@node Optimize Options +@section Options That Control Optimization +@cindex optimize options +@cindex options, optimization + +These options control various sorts of optimizations: + +@table @gcctabopt +@item -O +@itemx -O1 +Optimize. Optimizing compilation takes somewhat more time, and a lot +more memory for a large function. + +Without @samp{-O}, the compiler's goal is to reduce the cost of +compilation and to make debugging produce the expected results. +Statements are independent: if you stop the program with a breakpoint +between statements, you can then assign a new value to any variable or +change the program counter to any other statement in the function and +get exactly the results you would expect from the source code. + +Without @samp{-O}, the compiler only allocates variables declared +@code{register} in registers. The resulting compiled code is a little +worse than produced by PCC without @samp{-O}. + +With @samp{-O}, the compiler tries to reduce code size and execution +time. + +When you specify @samp{-O}, the compiler turns on @samp{-fthread-jumps} +and @samp{-fdefer-pop} on all machines. The compiler turns on +@samp{-fdelayed-branch} on machines that have delay slots, and +@samp{-fomit-frame-pointer} on machines that can support debugging even +without a frame pointer. On some machines the compiler also turns +on other flags.@refill + +@item -O2 +Optimize even more. GCC performs nearly all supported optimizations +that do not involve a space-speed tradeoff. The compiler does not +perform loop unrolling or function inlining when you specify @samp{-O2}. +As compared to @samp{-O}, this option increases both compilation time +and the performance of the generated code. + +@samp{-O2} turns on all optional optimizations except for loop unrolling, +function inlining, and register renaming. It also turns on the +@samp{-fforce-mem} option on all machines and frame pointer elimination +on machines where doing so does not interfere with debugging. + +@item -O3 +Optimize yet more. @samp{-O3} turns on all optimizations specified by +@samp{-O2} and also turns on the @samp{-finline-functions} and +@samp{-frename-registers} options. + +@item -O0 +Do not optimize. + +@item -Os +Optimize for size. @samp{-Os} enables all @samp{-O2} optimizations that +do not typically increase code size. It also performs further +optimizations designed to reduce code size. + +If you use multiple @samp{-O} options, with or without level numbers, +the last such option is the one that is effective. +@end table + +Options of the form @samp{-f@var{flag}} specify machine-independent +flags. Most flags have both positive and negative forms; the negative +form of @samp{-ffoo} would be @samp{-fno-foo}. In the table below, +only one of the forms is listed---the one which is not the default. +You can figure out the other form by either removing @samp{no-} or +adding it. + +@table @gcctabopt +@item -ffloat-store +Do not store floating point variables in registers, and inhibit other +options that might change whether a floating point value is taken from a +register or memory. + +@cindex floating point precision +This option prevents undesirable excess precision on machines such as +the 68000 where the floating registers (of the 68881) keep more +precision than a @code{double} is supposed to have. Similarly for the +x86 architecture. For most programs, the excess precision does only +good, but a few programs rely on the precise definition of IEEE floating +point. Use @samp{-ffloat-store} for such programs, after modifying +them to store all pertinent intermediate computations into variables. + +@item -fno-default-inline +Do not make member functions inline by default merely because they are +defined inside the class scope (C++ only). Otherwise, when you specify +@w{@samp{-O}}, member functions defined inside class scope are compiled +inline by default; i.e., you don't need to add @samp{inline} in front of +the member function name. + +@item -fno-defer-pop +Always pop the arguments to each function call as soon as that function +returns. For machines which must pop arguments after a function call, +the compiler normally lets arguments accumulate on the stack for several +function calls and pops them all at once. + +@item -fforce-mem +Force memory operands to be copied into registers before doing +arithmetic on them. This produces better code by making all memory +references potential common subexpressions. When they are not common +subexpressions, instruction combination should eliminate the separate +register-load. The @samp{-O2} option turns on this option. + +@item -fforce-addr +Force memory address constants to be copied into registers before +doing arithmetic on them. This may produce better code just as +@samp{-fforce-mem} may. + +@item -fomit-frame-pointer +Don't keep the frame pointer in a register for functions that +don't need one. This avoids the instructions to save, set up and +restore frame pointers; it also makes an extra register available +in many functions. @strong{It also makes debugging impossible on +some machines.} + +@ifset INTERNALS +On some machines, such as the Vax, this flag has no effect, because +the standard calling sequence automatically handles the frame pointer +and nothing is saved by pretending it doesn't exist. The +machine-description macro @code{FRAME_POINTER_REQUIRED} controls +whether a target machine supports this flag. @xref{Registers}.@refill +@end ifset +@ifclear INTERNALS +On some machines, such as the Vax, this flag has no effect, because +the standard calling sequence automatically handles the frame pointer +and nothing is saved by pretending it doesn't exist. The +machine-description macro @code{FRAME_POINTER_REQUIRED} controls +whether a target machine supports this flag. @xref{Registers,,Register +Usage, gcc.info, Using and Porting GCC}.@refill +@end ifclear + +@item -foptimize-sibling-calls +Optimize sibling and tail recursive calls. + +@item -ftrapv +This option generates traps for signed overflow on addition, subtraction, +multiplication operations. + +@item -fno-inline +Don't pay attention to the @code{inline} keyword. Normally this option +is used to keep the compiler from expanding any functions inline. +Note that if you are not optimizing, no functions can be expanded inline. + +@item -finline-functions +Integrate all simple functions into their callers. The compiler +heuristically decides which functions are simple enough to be worth +integrating in this way. + +If all calls to a given function are integrated, and the function is +declared @code{static}, then the function is normally not output as +assembler code in its own right. + +@item -finline-limit=@var{n} +By default, gcc limits the size of functions that can be inlined. This flag +allows the control of this limit for functions that are explicitly marked as +inline (ie marked with the inline keyword or defined within the class +definition in c++). @var{n} is the size of functions that can be inlined in +number of pseudo instructions (not counting parameter handling). The default +value of n is 10000. Increasing this value can result in more inlined code at +the cost of compilation time and memory consumption. Decreasing usually makes +the compilation faster and less code will be inlined (which presumably +means slower programs). This option is particularly useful for programs that +use inlining heavily such as those based on recursive templates with c++. + +@emph{Note:} pseudo instruction represents, in this particular context, an +abstract measurement of function's size. In no way, it represents a count +of assembly instructions and as such its exact meaning might change from one +release to an another. + +@item -fkeep-inline-functions +Even if all calls to a given function are integrated, and the function +is declared @code{static}, nevertheless output a separate run-time +callable version of the function. This switch does not affect +@code{extern inline} functions. + +@item -fkeep-static-consts +Emit variables declared @code{static const} when optimization isn't turned +on, even if the variables aren't referenced. + +GCC enables this option by default. If you want to force the compiler to +check if the variable was referenced, regardless of whether or not +optimization is turned on, use the @samp{-fno-keep-static-consts} option. + +@item -fno-function-cse +Do not put function addresses in registers; make each instruction that +calls a constant function contain the function's address explicitly. + +This option results in less efficient code, but some strange hacks +that alter the assembler output may be confused by the optimizations +performed when this option is not used. + +@item -ffast-math +Sets @samp{-fno-math-errno}, @samp{-funsafe-math-optimizations}, +and @samp{-fno-trapping-math}. + +This option causes the preprocessor macro __FAST_MATH__ to be defined. + +This option should never be turned on by any @samp{-O} option since +it can result in incorrect output for programs which depend on +an exact implementation of IEEE or ISO rules/specifications for +math functions. + +@item -fno-math-errno +Do not set ERRNO after calling math functions that are executed +with a single instruction, e.g., sqrt. A program that relies on +IEEE exceptions for math error handling may want to use this flag +for speed while maintaining IEEE arithmetic compatibility. + +This option should never be turned on by any @samp{-O} option since +it can result in incorrect output for programs which depend on +an exact implementation of IEEE or ISO rules/specifications for +math functions. + +The default is @samp{-fmath-errno}. The @samp{-ffast-math} option +sets @samp{-fno-math-errno}. + +@item -funsafe-math-optimizations +Allow optimizations for floating-point arithmetic that (a) assume +that arguments and results are valid and (b) may violate IEEE or +ANSI standards. + +This option should never be turned on by any @samp{-O} option since +it can result in incorrect output for programs which depend on +an exact implementation of IEEE or ISO rules/specifications for +math functions. + +The default is @samp{-fno-unsafe-math-optimizations}. The +@samp{-ffast-math} option sets @samp{-funsafe-math-optimizations}. + +@item -fno-trapping-math +Compile code assuming that floating-point operations cannot generate +user-visible traps. Setting this option may allow faster code +if one relies on ``non-stop'' IEEE arithmetic, for example. + +This option should never be turned on by any @samp{-O} option since +it can result in incorrect output for programs which depend on +an exact implementation of IEEE or ISO rules/specifications for +math functions. + +The default is @samp{-ftrapping-math}. The @samp{-ffast-math} +option sets @samp{-fno-trapping-math}. +@end table + +@c following causes underfulls.. they don't look great, but we deal. +@c --mew 26jan93 +The following options control specific optimizations. The @samp{-O2} +option turns on all of these optimizations except @samp{-funroll-loops} +and @samp{-funroll-all-loops}. On most machines, the @samp{-O} option +turns on the @samp{-fthread-jumps} and @samp{-fdelayed-branch} options, +but specific machines may handle it differently. + +You can use the following flags in the rare cases when ``fine-tuning'' +of optimizations to be performed is desired. + +@table @gcctabopt +@item -fstrength-reduce +Perform the optimizations of loop strength reduction and +elimination of iteration variables. + +@item -fthread-jumps +Perform optimizations where we check to see if a jump branches to a +location where another comparison subsumed by the first is found. If +so, the first branch is redirected to either the destination of the +second branch or a point immediately following it, depending on whether +the condition is known to be true or false. + +@item -fcse-follow-jumps +In common subexpression elimination, scan through jump instructions +when the target of the jump is not reached by any other path. For +example, when CSE encounters an @code{if} statement with an +@code{else} clause, CSE will follow the jump when the condition +tested is false. + +@item -fcse-skip-blocks +This is similar to @samp{-fcse-follow-jumps}, but causes CSE to +follow jumps which conditionally skip over blocks. When CSE +encounters a simple @code{if} statement with no else clause, +@samp{-fcse-skip-blocks} causes CSE to follow the jump around the +body of the @code{if}. + +@item -frerun-cse-after-loop +Re-run common subexpression elimination after loop optimizations has been +performed. + +@item -frerun-loop-opt +Run the loop optimizer twice. + +@item -fgcse +Perform a global common subexpression elimination pass. +This pass also performs global constant and copy propagation. + +@item -fgcse-lm +When -fgcse-lm is enabled, global common subexpression elimination will +attempt to move loads which are only killed by stores into themselves. This +allows a loop containing a load/store sequence to be changed to a load outside +the loop, and a copy/store within the loop. + +@item -fgcse-sm +When -fgcse-sm is enabled, A store motion pass is run after global common +subexpression elimination. This pass will attempt to move stores out of loops. +When used in conjunction with -fgcse-lm, loops containing a load/store sequence +can be changed to a load before the loop and a store after the loop. + +@item -fdelete-null-pointer-checks +Use global dataflow analysis to identify and eliminate useless null +pointer checks. Programs which rely on NULL pointer dereferences @emph{not} +halting the program may not work properly with this option. Use +-fno-delete-null-pointer-checks to disable this optimizing for programs +which depend on that behavior. + +@item -fexpensive-optimizations +Perform a number of minor optimizations that are relatively expensive. + +@item -foptimize-register-move +@itemx -fregmove +Attempt to reassign register numbers in move instructions and as +operands of other simple instructions in order to maximize the amount of +register tying. This is especially helpful on machines with two-operand +instructions. GCC enables this optimization by default with @samp{-O2} +or higher. + +Note @option{-fregmove} and @option{-foptimize-register-move} are the same +optimization. + +@item -fdelayed-branch +If supported for the target machine, attempt to reorder instructions +to exploit instruction slots available after delayed branch +instructions. + +@item -fschedule-insns +If supported for the target machine, attempt to reorder instructions to +eliminate execution stalls due to required data being unavailable. This +helps machines that have slow floating point or memory load instructions +by allowing other instructions to be issued until the result of the load +or floating point instruction is required. + +@item -fschedule-insns2 +Similar to @samp{-fschedule-insns}, but requests an additional pass of +instruction scheduling after register allocation has been done. This is +especially useful on machines with a relatively small number of +registers and where memory load instructions take more than one cycle. + +@item -ffunction-sections +@itemx -fdata-sections +Place each function or data item into its own section in the output +file if the target supports arbitrary sections. The name of the +function or the name of the data item determines the section's name +in the output file. + +Use these options on systems where the linker can perform optimizations +to improve locality of reference in the instruction space. HPPA +processors running HP-UX and Sparc processors running Solaris 2 have +linkers with such optimizations. Other systems using the ELF object format +as well as AIX may have these optimizations in the future. + +Only use these options when there are significant benefits from doing +so. When you specify these options, the assembler and linker will +create larger object and executable files and will also be slower. +You will not be able to use @code{gprof} on all systems if you +specify this option and you may have problems with debugging if +you specify both this option and @samp{-g}. + +@item -fcaller-saves +Enable values to be allocated in registers that will be clobbered by +function calls, by emitting extra instructions to save and restore the +registers around such calls. Such allocation is done only when it +seems to result in better code than would otherwise be produced. + +This option is always enabled by default on certain machines, usually +those which have no call-preserved registers to use instead. + +For all machines, optimization level 2 and higher enables this flag by +default. + +@item -funroll-loops +Perform the optimization of loop unrolling. This is only done for loops +whose number of iterations can be determined at compile time or run time. +@samp{-funroll-loops} implies both @samp{-fstrength-reduce} and +@samp{-frerun-cse-after-loop}. + +@item -funroll-all-loops +Perform the optimization of loop unrolling. This is done for all loops +and usually makes programs run more slowly. @samp{-funroll-all-loops} +implies @samp{-fstrength-reduce} as well as @samp{-frerun-cse-after-loop}. + +@item -fmove-all-movables +Forces all invariant computations in loops to be moved +outside the loop. + +@item -freduce-all-givs +Forces all general-induction variables in loops to be +strength-reduced. + +@emph{Note:} When compiling programs written in Fortran, +@samp{-fmove-all-movables} and @samp{-freduce-all-givs} are enabled +by default when you use the optimizer. + +These options may generate better or worse code; results are highly +dependent on the structure of loops within the source code. + +These two options are intended to be removed someday, once +they have helped determine the efficacy of various +approaches to improving loop optimizations. + +Please let us (@w{@email{gcc@@gcc.gnu.org}} and @w{@email{fortran@@gnu.org}}) +know how use of these options affects +the performance of your production code. +We're very interested in code that runs @emph{slower} +when these options are @emph{enabled}. + +@item -fno-peephole +Disable any machine-specific peephole optimizations. + +@item -fbranch-probabilities +After running a program compiled with @samp{-fprofile-arcs} +(@pxref{Debugging Options,, Options for Debugging Your Program or +@command{gcc}}), you can compile it a second time using +@samp{-fbranch-probabilities}, to improve optimizations based on +guessing the path a branch might take. + +@ifset INTERNALS +With @samp{-fbranch-probabilities}, GCC puts a @samp{REG_EXEC_COUNT} +note on the first instruction of each basic block, and a +@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}. +These can be used to improve optimization. Currently, they are only +used in one place: in @file{reorg.c}, instead of guessing which path a +branch is mostly to take, the @samp{REG_BR_PROB} values are used to +exactly determine which path is taken more often. +@end ifset + +@item -fno-guess-branch-probability +Sometimes gcc will opt to guess branch probabilities when none are +available from either profile directed feedback (@samp{-fprofile-arcs}) +or @samp{__builtin_expect}. In a hard real-time system, people don't +want different runs of the compiler to produce code that has different +behavior; minimizing non-determinism is of paramount import. This +switch allows users to reduce non-determinism, possibly at the expense +of inferior optimization. + +@item -fstrict-aliasing +Allows the compiler to assume the strictest aliasing rules applicable to +the language being compiled. For C (and C++), this activates +optimizations based on the type of expressions. In particular, an +object of one type is assumed never to reside at the same address as an +object of a different type, unless the types are almost the same. For +example, an @code{unsigned int} can alias an @code{int}, but not a +@code{void*} or a @code{double}. A character type may alias any other +type. + +Pay special attention to code like this: +@example +union a_union @{ + int i; + double d; +@}; + +int f() @{ + a_union t; + t.d = 3.0; + return t.i; +@} +@end example +The practice of reading from a different union member than the one most +recently written to (called ``type-punning'') is common. Even with +@samp{-fstrict-aliasing}, type-punning is allowed, provided the memory +is accessed through the union type. So, the code above will work as +expected. However, this code might not: +@example +int f() @{ + a_union t; + int* ip; + t.d = 3.0; + ip = &t.i; + return *ip; +@} +@end example + +@ifset INTERNALS +Every language that wishes to perform language-specific alias analysis +should define a function that computes, given an @code{tree} +node, an alias set for the node. Nodes in different alias sets are not +allowed to alias. For an example, see the C front-end function +@code{c_get_alias_set}. +@end ifset + +@item -falign-functions +@itemx -falign-functions=@var{n} +Align the start of functions to the next power-of-two greater than +@var{n}, skipping up to @var{n} bytes. For instance, +@samp{-falign-functions=32} aligns functions to the next 32-byte +boundary, but @samp{-falign-functions=24} would align to the next +32-byte boundary only if this can be done by skipping 23 bytes or less. + +@samp{-fno-align-functions} and @samp{-falign-functions=1} are +equivalent and mean that functions will not be aligned. + +Some assemblers only support this flag when @var{n} is a power of two; +in that case, it is rounded up. + +If @var{n} is not specified, use a machine-dependent default. + +@item -falign-labels +@itemx -falign-labels=@var{n} +Align all branch targets to a power-of-two boundary, skipping up to +@var{n} bytes like @samp{-falign-functions}. This option can easily +make code slower, because it must insert dummy operations for when the +branch target is reached in the usual flow of the code. + +If @samp{-falign-loops} or @samp{-falign-jumps} are applicable and +are greater than this value, then their values are used instead. + +If @var{n} is not specified, use a machine-dependent default which is +very likely to be @samp{1}, meaning no alignment. + +@item -falign-loops +@itemx -falign-loops=@var{n} +Align loops to a power-of-two boundary, skipping up to @var{n} bytes +like @samp{-falign-functions}. The hope is that the loop will be +executed many times, which will make up for any execution of the dummy +operations. + +If @var{n} is not specified, use a machine-dependent default. + +@item -falign-jumps +@itemx -falign-jumps=@var{n} +Align branch targets to a power-of-two boundary, for branch targets +where the targets can only be reached by jumping, skipping up to @var{n} +bytes like @samp{-falign-functions}. In this case, no dummy operations +need be executed. + +If @var{n} is not specified, use a machine-dependent default. + +@item -fssa +Perform optimizations in static single assignment form. Each function's +flow graph is translated into SSA form, optimizations are performed, and +the flow graph is translated back from SSA form. Users should not +specify this option, since it is not yet ready for production use. + +@item -fdce +Perform dead-code elimination in SSA form. Requires @samp{-fssa}. Like +@samp{-fssa}, this is an experimental feature. + +@item -fsingle-precision-constant +Treat floating point constant as single precision constant instead of +implicitly converting it to double precision constant. + +@item -frename-registers +Attempt to avoid false dependancies in scheduled code by making use +of registers left over after register allocation. This optimization +will most benefit processors with lots of registers. It can, however, +make debugging impossible, since variables will no longer stay in +a ``home register''. + +@item --param @var{name}=@var{value} +In some places, GCC uses various constants to control the amount of +optimization that is done. For example, GCC will not inline functions +that contain more that a certain number of instructions. You can +control some of these constants on the command-line using the +@samp{--param} option. + +In each case, the @var{value} is a integer. The allowable choices for +@var{name} are given in the following table: + +@table @gcctabopt +@item max-delay-slot-insn-search +The maximum number of instructions to consider when looking for an +instruction to fill a delay slot. If more than this arbitrary number of +instructions is searched, the time savings from filling the delay slot +will be minimal so stop searching. Increasing values mean more +aggressive optimization, making the compile time increase with probably +small improvement in executable run time. + +@item max-delay-slot-live-search +When trying to fill delay slots, the maximum number of instructions to +consider when searching for a block with valid live register +information. Increasing this arbitrarily chosen value means more +aggressive optimization, increasing the compile time. This parameter +should be removed when the delay slot code is rewritten to maintain the +control-flow graph. + +@item max-gcse-memory +The approximate maximum amount of memory that will be allocated in +order to perform the global common subexpression elimination +optimization. If more memory than specified is required, the +optimization will not be done. + +@item max-inline-insns +If an function contains more than this many instructions, it +will not be inlined. This option is precisely equivalent to +@samp{-finline-limit}. + +@end table +@end table + +@node Preprocessor Options +@section Options Controlling the Preprocessor +@cindex preprocessor options +@cindex options, preprocessor + +These options control the C preprocessor, which is run on each C source +file before actual compilation. + +If you use the @samp{-E} option, nothing is done except preprocessing. +Some of these options make sense only together with @samp{-E} because +they cause the preprocessor output to be unsuitable for actual +compilation. + +@table @gcctabopt +@item -include @var{file} +Process @var{file} as input before processing the regular input file. +In effect, the contents of @var{file} are compiled first. Any @samp{-D} +and @samp{-U} options on the command line are always processed before +@samp{-include @var{file}}, regardless of the order in which they are +written. All the @samp{-include} and @samp{-imacros} options are +processed in the order in which they are written. + +@item -imacros @var{file} +Process @var{file} as input, discarding the resulting output, before +processing the regular input file. Because the output generated from +@var{file} is discarded, the only effect of @samp{-imacros @var{file}} +is to make the macros defined in @var{file} available for use in the +main input. All the @samp{-include} and @samp{-imacros} options are +processed in the order in which they are written. + +@item -idirafter @var{dir} +@cindex second include path +Add the directory @var{dir} to the second include path. The directories +on the second include path are searched when a header file is not found +in any of the directories in the main include path (the one that +@samp{-I} adds to). + +@item -iprefix @var{prefix} +Specify @var{prefix} as the prefix for subsequent @samp{-iwithprefix} +options. + +@item -iwithprefix @var{dir} +Add a directory to the second include path. The directory's name is +made by concatenating @var{prefix} and @var{dir}, where @var{prefix} was +specified previously with @samp{-iprefix}. If you have not specified a +prefix yet, the directory containing the installed passes of the +compiler is used as the default. + +@item -iwithprefixbefore @var{dir} +Add a directory to the main include path. The directory's name is made +by concatenating @var{prefix} and @var{dir}, as in the case of +@samp{-iwithprefix}. + +@item -isystem @var{dir} +Add a directory to the beginning of the second include path, marking it +as a system directory, so that it gets the same special treatment as +is applied to the standard system directories. + +@item -nostdinc +Do not search the standard system directories for header files. Only +the directories you have specified with @samp{-I} options (and the +current directory, if appropriate) are searched. @xref{Directory +Options}, for information on @samp{-I}. + +By using both @samp{-nostdinc} and @samp{-I-}, you can limit the include-file +search path to only those directories you specify explicitly. + +@item -remap +@findex -remap +When searching for a header file in a directory, remap file names if a +file named @file{header.gcc} exists in that directory. This can be used +to work around limitations of file systems with file name restrictions. +The @file{header.gcc} file should contain a series of lines with two +tokens on each line: the first token is the name to map, and the second +token is the actual name to use. + +@item -undef +Do not predefine any nonstandard macros. (Including architecture flags). + +@item -E +Run only the C preprocessor. Preprocess all the C source files +specified and output the results to standard output or to the +specified output file. + +@item -C +Tell the preprocessor not to discard comments. Used with the +@samp{-E} option. + +@item -P +Tell the preprocessor not to generate @samp{#line} directives. +Used with the @samp{-E} option. + +@cindex make +@cindex dependencies, make +@item -M +@findex -M +Instead of outputting the result of preprocessing, output a rule +suitable for @code{make} describing the dependencies of the main source +file. The preprocessor outputs one @code{make} rule containing the +object file name for that source file, a colon, and the names of all the +included files. Unless overridden explicitly, the object file name +consists of the basename of the source file with any suffix replaced with +object file suffix. If there are many included files then the +rule is split into several lines using @samp{\}-newline. + +@samp{-M} implies @samp{-E}. + +@item -MM +@findex -MM +Like @samp{-M}, but mention only the files included with @samp{#include +"@var{file}"}. System header files included with @samp{#include +<@var{file}>} are omitted. + +@item -MD +@findex -MD +Like @samp{-M} but the dependency information is written to a file +rather than stdout. @code{gcc} will use the same file name and +directory as the object file, but with the suffix ".d" instead. + +This is in addition to compiling the main file as specified --- +@samp{-MD} does not inhibit ordinary compilation the way @samp{-M} does, +unless you also specify @samp{-MG}. + +With Mach, you can use the utility @code{md} to merge multiple +dependency files into a single dependency file suitable for using with +the @samp{make} command. + +@item -MMD +@findex -MMD +Like @samp{-MD} except mention only user header files, not system +-header files. + +@item -MF @var{file} +@findex -MF +When used with @samp{-M} or @samp{-MM}, specifies a file to write the +dependencies to. This allows the preprocessor to write the preprocessed +file to stdout normally. If no @samp{-MF} switch is given, CPP sends +the rules to stdout and suppresses normal preprocessed output. + +Another way to specify output of a @code{make} rule is by setting +the environment variable @env{DEPENDENCIES_OUTPUT} (@pxref{Environment +Variables}). + +@item -MG +@findex -MG +When used with @samp{-M} or @samp{-MM}, @samp{-MG} says to treat missing +header files as generated files and assume they live in the same +directory as the source file. It suppresses preprocessed output, as a +missing header file is ordinarily an error. + +This feature is used in automatic updating of makefiles. + +@item -MP +@findex -MP +This option instructs CPP to add a phony target for each dependency +other than the main file, causing each to depend on nothing. These +dummy rules work around errors @code{make} gives if you remove header +files without updating the @code{Makefile} to match. + +This is typical output:- + +@smallexample +/tmp/test.o: /tmp/test.c /tmp/test.h + +/tmp/test.h: +@end smallexample + +@item -MQ @var{target} +@item -MT @var{target} +@findex -MQ +@findex -MT +By default CPP uses the main file name, including any path, and appends +the object suffix, normally ``.o'', to it to obtain the name of the +target for dependency generation. With @samp{-MT} you can specify a +target yourself, overriding the default one. + +If you want multiple targets, you can specify them as a single argument +to @samp{-MT}, or use multiple @samp{-MT} options. + +The targets you specify are output in the order they appear on the +command line. @samp{-MQ} is identical to @samp{-MT}, except that the +target name is quoted for Make, but with @samp{-MT} it isn't. For +example, -MT '$(objpfx)foo.o' gives + +@smallexample +$(objpfx)foo.o: /tmp/foo.c +@end smallexample + +but -MQ '$(objpfx)foo.o' gives + +@smallexample +$$(objpfx)foo.o: /tmp/foo.c +@end smallexample + +The default target is automatically quoted, as if it were given with +@samp{-MQ}. + +@item -H +Print the name of each header file used, in addition to other normal +activities. + +@item -A@var{question}(@var{answer}) +Assert the answer @var{answer} for @var{question}, in case it is tested +with a preprocessing conditional such as @samp{#if +#@var{question}(@var{answer})}. @samp{-A-} disables the standard +assertions that normally describe the target machine. + +@item -D@var{macro} +Define macro @var{macro} with the string @samp{1} as its definition. + +@item -D@var{macro}=@var{defn} +Define macro @var{macro} as @var{defn}. All instances of @samp{-D} on +the command line are processed before any @samp{-U} options. + +Any @samp{-D} and @samp{-U} options on the command line are processed in +order, and always before @samp{-imacros @var{file}}, regardless of the +order in which they are written. + +@item -U@var{macro} +Undefine macro @var{macro}. @samp{-U} options are evaluated after all +@samp{-D} options, but before any @samp{-include} and @samp{-imacros} +options. + +Any @samp{-D} and @samp{-U} options on the command line are processed in +order, and always before @samp{-imacros @var{file}}, regardless of the +order in which they are written. + +@item -dM +Tell the preprocessor to output only a list of the macro definitions +that are in effect at the end of preprocessing. Used with the @samp{-E} +option. + +@item -dD +Tell the preprocessing to pass all macro definitions into the output, in +their proper sequence in the rest of the output. + +@item -dN +Like @samp{-dD} except that the macro arguments and contents are omitted. +Only @samp{#define @var{name}} is included in the output. + +@item -dI +@findex -dI +Output @samp{#include} directives in addition to the result of +preprocessing. + +@item -trigraphs +@findex -trigraphs +Process ISO standard trigraph sequences. These are three-character +sequences, all starting with @samp{??}, that are defined by ISO C to +stand for single characters. For example, @samp{??/} stands for +@samp{\}, so @samp{'??/n'} is a character constant for a newline. By +default, GCC ignores trigraphs, but in standard-conforming modes it +converts them. See the @samp{-std} and @samp{-ansi} options. + +The nine trigraph sequences are +@table @samp +@item ??( +-> @samp{[} + +@item ??) +-> @samp{]} + +@item ??< +-> @samp{@{} + +@item ??> +-> @samp{@}} + +@item ??= +-> @samp{#} + +@item ??/ +-> @samp{\} + +@item ??' +-> @samp{^} + +@item ??! +-> @samp{|} + +@item ??- +-> @samp{~} + +@end table + +Trigraph support is not popular, so many compilers do not implement it +properly. Portable code should not rely on trigraphs being either +converted or ignored. + +@item -Wp\,@var{option} +Pass @var{option} as an option to the preprocessor. If @var{option} +contains commas, it is split into multiple options at the commas. +@end table + +@node Assembler Options +@section Passing Options to the Assembler + +@c prevent bad page break with this line +You can pass options to the assembler. + +@table @gcctabopt +@item -Wa\,@var{option} +Pass @var{option} as an option to the assembler. If @var{option} +contains commas, it is split into multiple options at the commas. +@end table + +@node Link Options +@section Options for Linking +@cindex link options +@cindex options, linking + +These options come into play when the compiler links object files into +an executable output file. They are meaningless if the compiler is +not doing a link step. + +@table @gcctabopt +@cindex file names +@item @var{object-file-name} +A file name that does not end in a special recognized suffix is +considered to name an object file or library. (Object files are +distinguished from libraries by the linker according to the file +contents.) If linking is done, these object files are used as input +to the linker. + +@item -c +@itemx -S +@itemx -E +If any of these options is used, then the linker is not run, and +object file names should not be used as arguments. @xref{Overall +Options}. + +@cindex Libraries +@item -l@var{library} +@itemx -l @var{library} +Search the library named @var{library} when linking. (The second +alternative with the library as a separate argument is only for +POSIX compliance and is not recommended.) + +It makes a difference where in the command you write this option; the +linker searches and processes libraries and object files in the order they +are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z} +after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers +to functions in @samp{z}, those functions may not be loaded. + +The linker searches a standard list of directories for the library, +which is actually a file named @file{lib@var{library}.a}. The linker +then uses this file as if it had been specified precisely by name. + +The directories searched include several standard system directories +plus any that you specify with @samp{-L}. + +Normally the files found this way are library files---archive files +whose members are object files. The linker handles an archive file by +scanning through it for members which define symbols that have so far +been referenced but not defined. But if the file that is found is an +ordinary object file, it is linked in the usual fashion. The only +difference between using an @samp{-l} option and specifying a file name +is that @samp{-l} surrounds @var{library} with @samp{lib} and @samp{.a} +and searches several directories. + +@item -lobjc +You need this special case of the @samp{-l} option in order to +link an Objective C program. + +@item -nostartfiles +Do not use the standard system startup files when linking. +The standard system libraries are used normally, unless @option{-nostdlib} +or @option{-nodefaultlibs} is used. + +@item -nodefaultlibs +Do not use the standard system libraries when linking. +Only the libraries you specify will be passed to the linker. +The standard startup files are used normally, unless @option{-nostartfiles} +is used. The compiler may generate calls to memcmp, memset, and memcpy +for System V (and ISO C) environments or to bcopy and bzero for +BSD environments. These entries are usually resolved by entries in +libc. These entry points should be supplied through some other +mechanism when this option is specified. + +@item -nostdlib +Do not use the standard system startup files or libraries when linking. +No startup files and only the libraries you specify will be passed to +the linker. The compiler may generate calls to memcmp, memset, and memcpy +for System V (and ISO C) environments or to bcopy and bzero for +BSD environments. These entries are usually resolved by entries in +libc. These entry points should be supplied through some other +mechanism when this option is specified. + +@cindex @code{-lgcc}, use with @code{-nostdlib} +@cindex @code{-nostdlib} and unresolved references +@cindex unresolved references and @code{-nostdlib} +@cindex @code{-lgcc}, use with @code{-nodefaultlibs} +@cindex @code{-nodefaultlibs} and unresolved references +@cindex unresolved references and @code{-nodefaultlibs} +One of the standard libraries bypassed by @samp{-nostdlib} and +@samp{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines +that GCC uses to overcome shortcomings of particular machines, or special +needs for some languages. +@ifset INTERNALS +(@xref{Interface,,Interfacing to GCC Output}, for more discussion of +@file{libgcc.a}.) +@end ifset +@ifclear INTERNALS +(@xref{Interface,,Interfacing to GCC Output,gcc.info,Porting GCC}, +for more discussion of @file{libgcc.a}.) +@end ifclear +In most cases, you need @file{libgcc.a} even when you want to avoid +other standard libraries. In other words, when you specify @samp{-nostdlib} +or @samp{-nodefaultlibs} you should usually specify @samp{-lgcc} as well. +This ensures that you have no unresolved references to internal GCC +library subroutines. (For example, @samp{__main}, used to ensure C++ +constructors will be called; @pxref{Collect2,,@command{collect2}}.) + +@item -s +Remove all symbol table and relocation information from the executable. + +@item -static +On systems that support dynamic linking, this prevents linking with the shared +libraries. On other systems, this option has no effect. + +@item -shared +Produce a shared object which can then be linked with other objects to +form an executable. Not all systems support this option. For predictable +results, you must also specify the same set of options that were used to +generate code (@samp{-fpic}, @samp{-fPIC}, or model suboptions) +when you specify this option.@footnote{On some systems, @samp{gcc -shared} +needs to build supplementary stub code for constructors to work. On +multi-libbed systems, @samp{gcc -shared} must select the correct support +libraries to link against. Failing to supply the correct flags may lead +to subtle defects. Supplying them in cases where they are not necessary +is innocuous.} + +@item -shared-libgcc +@itemx -static-libgcc +On systems that provide @file{libgcc} as a shared library, these options +force the use of either the shared or static version respectively. +If no shared version of @file{libgcc} was built when the compiler was +configured, these options have no effect. + +There are several situations in which an application should use the +shared @file{libgcc} instead of the static version. The most common +of these is when the application wishes to throw and catch exceptions +across different shared libraries. In that case, each of the libraries +as well as the application itself should use the shared @file{libgcc}. + +Therefore, whenever you specify the @samp{-shared} option, the GCC +driver automatically adds @samp{-shared-libgcc}, unless you explicitly +specify @samp{-static-libgcc}. The G++ driver automatically adds +@samp{-shared-libgcc} when you build a main executable as well because +for C++ programs that is typically the right thing to do. +(Exception-handling will not work reliably otherwise.) + +However, when linking a main executable written in C, you must +explicitly say @samp{-shared-libgcc} if you want to use the shared +@file{libgcc}. + +@item -symbolic +Bind references to global symbols when building a shared object. Warn +about any unresolved references (unless overridden by the link editor +option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support +this option. + +@item -Xlinker @var{option} +Pass @var{option} as an option to the linker. You can use this to +supply system-specific linker options which GCC does not know how to +recognize. + +If you want to pass an option that takes an argument, you must use +@samp{-Xlinker} twice, once for the option and once for the argument. +For example, to pass @samp{-assert definitions}, you must write +@samp{-Xlinker -assert -Xlinker definitions}. It does not work to write +@samp{-Xlinker "-assert definitions"}, because this passes the entire +string as a single argument, which is not what the linker expects. + +@item -Wl\,@var{option} +Pass @var{option} as an option to the linker. If @var{option} contains +commas, it is split into multiple options at the commas. + +@item -u @var{symbol} +Pretend the symbol @var{symbol} is undefined, to force linking of +library modules to define it. You can use @samp{-u} multiple times with +different symbols to force loading of additional library modules. +@end table + +@node Directory Options +@section Options for Directory Search +@cindex directory options +@cindex options, directory search +@cindex search path + +These options specify directories to search for header files, for +libraries and for parts of the compiler: + +@table @gcctabopt +@item -I@var{dir} +Add the directory @var{dir} to the head of the list of directories to be +searched for header files. This can be used to override a system header +file, substituting your own version, since these directories are +searched before the system header file directories. However, you should +not use this option to add directories that contain vendor-supplied +system header files (use @samp{-isystem} for that). If you use more than +one @samp{-I} option, the directories are scanned in left-to-right +order; the standard system directories come after. + +@item -I- +Any directories you specify with @samp{-I} options before the @samp{-I-} +option are searched only for the case of @samp{#include "@var{file}"}; +they are not searched for @samp{#include <@var{file}>}. + +If additional directories are specified with @samp{-I} options after +the @samp{-I-}, these directories are searched for all @samp{#include} +directives. (Ordinarily @emph{all} @samp{-I} directories are used +this way.) + +In addition, the @samp{-I-} option inhibits the use of the current +directory (where the current input file came from) as the first search +directory for @samp{#include "@var{file}"}. There is no way to +override this effect of @samp{-I-}. With @samp{-I.} you can specify +searching the directory which was current when the compiler was +invoked. That is not exactly the same as what the preprocessor does +by default, but it is often satisfactory. + +@samp{-I-} does not inhibit the use of the standard system directories +for header files. Thus, @samp{-I-} and @samp{-nostdinc} are +independent. + +@item -L@var{dir} +Add directory @var{dir} to the list of directories to be searched +for @samp{-l}. + +@item -B@var{prefix} +This option specifies where to find the executables, libraries, +include files, and data files of the compiler itself. + +The compiler driver program runs one or more of the subprograms +@file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries +@var{prefix} as a prefix for each program it tries to run, both with and +without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}). + +For each subprogram to be run, the compiler driver first tries the +@samp{-B} prefix, if any. If that name is not found, or if @samp{-B} +was not specified, the driver tries two standard prefixes, which are +@file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc-lib/}. If neither of +those results in a file name that is found, the unmodified program +name is searched for using the directories specified in your +@env{PATH} environment variable. + +@samp{-B} prefixes that effectively specify directory names also apply +to libraries in the linker, because the compiler translates these +options into @samp{-L} options for the linker. They also apply to +includes files in the preprocessor, because the compiler translates these +options into @samp{-isystem} options for the preprocessor. In this case, +the compiler appends @samp{include} to the prefix. + +The run-time support file @file{libgcc.a} can also be searched for using +the @samp{-B} prefix, if needed. If it is not found there, the two +standard prefixes above are tried, and that is all. The file is left +out of the link if it is not found by those means. + +Another way to specify a prefix much like the @samp{-B} prefix is to use +the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment +Variables}. + +@item -specs=@var{file} +Process @var{file} after the compiler reads in the standard @file{specs} +file, in order to override the defaults that the @file{gcc} driver +program uses when determining what switches to pass to @file{cc1}, +@file{cc1plus}, @file{as}, @file{ld}, etc. More than one +@samp{-specs=}@var{file} can be specified on the command line, and they +are processed in order, from left to right. +@end table + +@c man end + +@node Spec Files +@section Specifying subprocesses and the switches to pass to them +@cindex Spec Files +@command{gcc} is a driver program. It performs its job by invoking a +sequence of other programs to do the work of compiling, assembling and +linking. GCC interprets its command-line parameters and uses these to +deduce which programs it should invoke, and which command-line options +it ought to place on their command lines. This behaviour is controlled +by @dfn{spec strings}. In most cases there is one spec string for each +program that GCC can invoke, but a few programs have multiple spec +strings to control their behaviour. The spec strings built into GCC can +be overridden by using the @samp{-specs=} command-line switch to specify +a spec file. + +@dfn{Spec files} are plaintext files that are used to construct spec +strings. They consist of a sequence of directives separated by blank +lines. The type of directive is determined by the first non-whitespace +character on the line and it can be one of the following: + +@table @code +@item %@var{command} +Issues a @var{command} to the spec file processor. The commands that can +appear here are: + +@table @code +@item %include <@var{file}> +@cindex %include +Search for @var{file} and insert its text at the current point in the +specs file. + +@item %include_noerr <@var{file}> +@cindex %include_noerr +Just like @samp{%include}, but do not generate an error message if the include +file cannot be found. + +@item %rename @var{old_name} @var{new_name} +@cindex %rename +Rename the spec string @var{old_name} to @var{new_name}. + +@end table + +@item *[@var{spec_name}]: +This tells the compiler to create, override or delete the named spec +string. All lines after this directive up to the next directive or +blank line are considered to be the text for the spec string. If this +results in an empty string then the spec will be deleted. (Or, if the +spec did not exist, then nothing will happened.) Otherwise, if the spec +does not currently exist a new spec will be created. If the spec does +exist then its contents will be overridden by the text of this +directive, unless the first character of that text is the @samp{+} +character, in which case the text will be appended to the spec. + +@item [@var{suffix}]: +Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive +and up to the next directive or blank line are considered to make up the +spec string for the indicated suffix. When the compiler encounters an +input file with the named suffix, it will processes the spec string in +order to work out how to compile that file. For example: + +@smallexample +.ZZ: +z-compile -input %i +@end smallexample + +This says that any input file whose name ends in @samp{.ZZ} should be +passed to the program @samp{z-compile}, which should be invoked with the +command-line switch @samp{-input} and with the result of performing the +@samp{%i} substitution. (See below.) + +As an alternative to providing a spec string, the text that follows a +suffix directive can be one of the following: + +@table @code +@item @@@var{language} +This says that the suffix is an alias for a known @var{language}. This is +similar to using the @option{-x} command-line switch to GCC to specify a +language explicitly. For example: + +@smallexample +.ZZ: +@@c++ +@end smallexample + +Says that .ZZ files are, in fact, C++ source files. + +@item #@var{name} +This causes an error messages saying: + +@smallexample +@var{name} compiler not installed on this system. +@end smallexample +@end table + +GCC already has an extensive list of suffixes built into it. +This directive will add an entry to the end of the list of suffixes, but +since the list is searched from the end backwards, it is effectively +possible to override earlier entries using this technique. + +@end table + +GCC has the following spec strings built into it. Spec files can +override these strings or create their own. Note that individual +targets can also add their own spec strings to this list. + +@smallexample +asm Options to pass to the assembler +asm_final Options to pass to the assembler post-processor +cpp Options to pass to the C preprocessor +cc1 Options to pass to the C compiler +cc1plus Options to pass to the C++ compiler +endfile Object files to include at the end of the link +link Options to pass to the linker +lib Libraries to include on the command line to the linker +libgcc Decides which GCC support library to pass to the linker +linker Sets the name of the linker +predefines Defines to be passed to the C preprocessor +signed_char Defines to pass to CPP to say whether @code{char} is signed + by default +startfile Object files to include at the start of the link +@end smallexample + +Here is a small example of a spec file: + +@smallexample +%rename lib old_lib + +*lib: +--start-group -lgcc -lc -leval1 --end-group %(old_lib) +@end smallexample + +This example renames the spec called @samp{lib} to @samp{old_lib} and +then overrides the previous definition of @samp{lib} with a new one. +The new definition adds in some extra command-line options before +including the text of the old definition. + +@dfn{Spec strings} are a list of command-line options to be passed to their +corresponding program. In addition, the spec strings can contain +@samp{%}-prefixed sequences to substitute variable text or to +conditionally insert text into the command line. Using these constructs +it is possible to generate quite complex command lines. + +Here is a table of all defined @samp{%}-sequences for spec +strings. Note that spaces are not generated automatically around the +results of expanding these sequences. Therefore you can concatenate them +together or combine them with constant text in a single argument. + +@table @code +@item %% +Substitute one @samp{%} into the program name or argument. + +@item %i +Substitute the name of the input file being processed. + +@item %b +Substitute the basename of the input file being processed. +This is the substring up to (and not including) the last period +and not including the directory. + +@item %B +This is the same as @samp{%b}, but include the file suffix (text after +the last period). + +@item %d +Marks the argument containing or following the @samp{%d} as a +temporary file name, so that that file will be deleted if GCC exits +successfully. Unlike @samp{%g}, this contributes no text to the +argument. + +@item %g@var{suffix} +Substitute a file name that has suffix @var{suffix} and is chosen +once per compilation, and mark the argument in the same way as +@samp{%d}. To reduce exposure to denial-of-service attacks, the file +name is now chosen in a way that is hard to predict even when previously +chosen file names are known. For example, @samp{%g.s ... %g.o ... %g.s} +might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches +the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is +treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g} +was simply substituted with a file name chosen once per compilation, +without regard to any appended suffix (which was therefore treated +just like ordinary text), making such attacks more likely to succeed. + +@item %u@var{suffix} +Like @samp{%g}, but generates a new temporary file name even if +@samp{%u@var{suffix}} was already seen. + +@item %U@var{suffix} +Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a +new one if there is no such last file name. In the absence of any +@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share +the same suffix @emph{space}, so @samp{%g.s ... %U.s ... %g.s ... %U.s} +would involve the generation of two distinct file names, one +for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was +simply substituted with a file name chosen for the previous @samp{%u}, +without regard to any appended suffix. + +@item %j@var{SUFFIX} +Substitutes the name of the HOST_BIT_BUCKET, if any, and if it is +writable, and if save-temps is off; otherwise, substitute the name +of a temporary file, just like @samp{%u}. This temporary file is not +meant for communication between processes, but rather as a junk +disposal mechanism. + +@item %.@var{SUFFIX} +Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args +when it is subsequently output with @samp{%*}. @var{SUFFIX} is +terminated by the next space or %. + +@item %w +Marks the argument containing or following the @samp{%w} as the +designated output file of this compilation. This puts the argument +into the sequence of arguments that @samp{%o} will substitute later. + +@item %o +Substitutes the names of all the output files, with spaces +automatically placed around them. You should write spaces +around the @samp{%o} as well or the results are undefined. +@samp{%o} is for use in the specs for running the linker. +Input files whose names have no recognized suffix are not compiled +at all, but they are included among the output files, so they will +be linked. + +@item %O +Substitutes the suffix for object files. Note that this is +handled specially when it immediately follows @samp{%g, %u, or %U}, +because of the need for those to form complete file names. The +handling is such that @samp{%O} is treated exactly as if it had already +been substituted, except that @samp{%g, %u, and %U} do not currently +support additional @var{suffix} characters following @samp{%O} as they would +following, for example, @samp{.o}. + +@item %p +Substitutes the standard macro predefinitions for the +current target machine. Use this when running @code{cpp}. + +@item %P +Like @samp{%p}, but puts @samp{__} before and after the name of each +predefined macro, except for macros that start with @samp{__} or with +@samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO +C. + +@item %I +Substitute a @samp{-iprefix} option made from GCC_EXEC_PREFIX. + +@item %s +Current argument is the name of a library or startup file of some sort. +Search for that file in a standard list of directories and substitute +the full name found. + +@item %e@var{str} +Print @var{str} as an error message. @var{str} is terminated by a newline. +Use this when inconsistent options are detected. + +@item %| +Output @samp{-} if the input for the current command is coming from a pipe. + +@item %(@var{name}) +Substitute the contents of spec string @var{name} at this point. + +@item %[@var{name}] +Like @samp{%(...)} but put @samp{__} around @samp{-D} arguments. + +@item %x@{@var{option}@} +Accumulate an option for @samp{%X}. + +@item %X +Output the accumulated linker options specified by @samp{-Wl} or a @samp{%x} +spec string. + +@item %Y +Output the accumulated assembler options specified by @samp{-Wa}. + +@item %Z +Output the accumulated preprocessor options specified by @samp{-Wp}. + +@item %v1 +Substitute the major version number of GCC. +(For version 2.9.5, this is 2.) + +@item %v2 +Substitute the minor version number of GCC. +(For version 2.9.5, this is 9.) + +@item %v3 +Substitute the patch level number of GCC. +(For version 2.9.5, this is 5.) + +@item %a +Process the @code{asm} spec. This is used to compute the +switches to be passed to the assembler. + +@item %A +Process the @code{asm_final} spec. This is a spec string for +passing switches to an assembler post-processor, if such a program is +needed. + +@item %l +Process the @code{link} spec. This is the spec for computing the +command line passed to the linker. Typically it will make use of the +@samp{%L %G %S %D and %E} sequences. + +@item %D +Dump out a @samp{-L} option for each directory that GCC believes might +contain startup files. If the target supports multilibs then the +current multilib directory will be prepended to each of these paths. + +@item %M +Output the multilib directory with directory seperators replaced with +"_". If multilib directories are not set, or the multilib directory is +"." then this option emits nothing. + +@item %L +Process the @code{lib} spec. This is a spec string for deciding which +libraries should be included on the command line to the linker. + +@item %G +Process the @code{libgcc} spec. This is a spec string for deciding +which GCC support library should be included on the command line to the linker. + +@item %S +Process the @code{startfile} spec. This is a spec for deciding which +object files should be the first ones passed to the linker. Typically +this might be a file named @file{crt0.o}. + +@item %E +Process the @code{endfile} spec. This is a spec string that specifies +the last object files that will be passed to the linker. + +@item %C +Process the @code{cpp} spec. This is used to construct the arguments +to be passed to the C preprocessor. + +@item %c +Process the @code{signed_char} spec. This is intended to be used +to tell cpp whether a char is signed. It typically has the definition: +@smallexample +%@{funsigned-char:-D__CHAR_UNSIGNED__@} +@end smallexample + +@item %1 +Process the @code{cc1} spec. This is used to construct the options to be +passed to the actual C compiler (@samp{cc1}). + +@item %2 +Process the @code{cc1plus} spec. This is used to construct the options to be +passed to the actual C++ compiler (@samp{cc1plus}). + +@item %* +Substitute the variable part of a matched option. See below. +Note that each comma in the substituted string is replaced by +a single space. + +@item %@{@code{S}@} +Substitutes the @code{-S} switch, if that switch was given to GCC. +If that switch was not specified, this substitutes nothing. Note that +the leading dash is omitted when specifying this option, and it is +automatically inserted if the substitution is performed. Thus the spec +string @samp{%@{foo@}} would match the command-line option @samp{-foo} +and would output the command line option @samp{-foo}. + +@item %W@{@code{S}@} +Like %@{@code{S}@} but mark last argument supplied within as a file to be +deleted on failure. + +@item %@{@code{S}*@} +Substitutes all the switches specified to GCC whose names start +with @code{-S}, but which also take an argument. This is used for +switches like @samp{-o, -D, -I}, etc. GCC considers @samp{-o foo} as being +one switch whose names starts with @samp{o}. %@{o*@} would substitute this +text, including the space. Thus two arguments would be generated. + +@item %@{^@code{S}*@} +Like %@{@code{S}*@}, but don't put a blank between a switch and its +argument. Thus %@{^o*@} would only generate one argument, not two. + +@item %@{@code{S}*&@code{T}*@} +Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options +(the order of @code{S} and @code{T} in the spec is not significant). +There can be any number of ampersand-separated variables; for each the +wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}. + +@item %@{<@code{S}@} +Remove all occurrences of @code{-S} from the command line. Note - this +command is position dependent. @samp{%} commands in the spec string +before this option will see @code{-S}, @samp{%} commands in the spec +string after this option will not. + +@item %@{@code{S}*:@code{X}@} +Substitutes @code{X} if one or more switches whose names start with +@code{-S} are specified to GCC. Note that the tail part of the +@code{-S} option (i.e. the part matched by the @samp{*}) will be substituted +for each occurrence of @samp{%*} within @code{X}. + +@item %@{@code{S}:@code{X}@} +Substitutes @code{X}, but only if the @samp{-S} switch was given to GCC. + +@item %@{!@code{S}:@code{X}@} +Substitutes @code{X}, but only if the @samp{-S} switch was @emph{not} given to GCC. + +@item %@{|@code{S}:@code{X}@} +Like %@{@code{S}:@code{X}@}, but if no @code{S} switch, substitute @samp{-}. + +@item %@{|!@code{S}:@code{X}@} +Like %@{!@code{S}:@code{X}@}, but if there is an @code{S} switch, substitute @samp{-}. + +@item %@{.@code{S}:@code{X}@} +Substitutes @code{X}, but only if processing a file with suffix @code{S}. + +@item %@{!.@code{S}:@code{X}@} +Substitutes @code{X}, but only if @emph{not} processing a file with suffix @code{S}. + +@item %@{@code{S}|@code{P}:@code{X}@} +Substitutes @code{X} if either @code{-S} or @code{-P} was given to GCC. This may be +combined with @samp{!} and @samp{.} sequences as well, although they +have a stronger binding than the @samp{|}. For example a spec string +like this: + +@smallexample +%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@} +@end smallexample + +will output the following command-line options from the following input +command-line options: + +@smallexample +fred.c -foo -baz +jim.d -bar -boggle +-d fred.c -foo -baz -boggle +-d jim.d -bar -baz -boggle +@end smallexample + +@end table + +The conditional text @code{X} in a %@{@code{S}:@code{X}@} or +%@{!@code{S}:@code{X}@} construct may contain other nested @samp{%} constructs +or spaces, or even newlines. They are processed as usual, as described +above. + +The @samp{-O, -f, -m, and -W} switches are handled specifically in these +constructs. If another value of @samp{-O} or the negated form of a @samp{-f, -m, or +-W} switch is found later in the command line, the earlier switch +value is ignored, except with @{@code{S}*@} where @code{S} is just one +letter, which passes all matching options. + +The character @samp{|} at the beginning of the predicate text is used to indicate +that a command should be piped to the following command, but only if @samp{-pipe} +is specified. + +It is built into GCC which switches take arguments and which do not. +(You might think it would be useful to generalize this to allow each +compiler's spec to say which switches take arguments. But this cannot +be done in a consistent fashion. GCC cannot even decide which input +files have been specified without knowing which switches take arguments, +and it must know which input files to compile in order to tell which +compilers to run). + +GCC also knows implicitly that arguments starting in @samp{-l} are to be +treated as compiler output files, and passed to the linker in their +proper position among the other output files. + +@c man begin OPTIONS + +@node Target Options +@section Specifying Target Machine and Compiler Version +@cindex target options +@cindex cross compiling +@cindex specifying machine version +@cindex specifying compiler version and target machine +@cindex compiler version, specifying +@cindex target machine, specifying + +By default, GCC compiles code for the same type of machine that you +are using. However, it can also be installed as a cross-compiler, to +compile for some other type of machine. In fact, several different +configurations of GCC, for different target machines, can be +installed side by side. Then you specify which one to use with the +@samp{-b} option. + +In addition, older and newer versions of GCC can be installed side +by side. One of them (probably the newest) will be the default, but +you may sometimes wish to use another. + +@table @gcctabopt +@item -b @var{machine} +The argument @var{machine} specifies the target machine for compilation. +This is useful when you have installed GCC as a cross-compiler. + +The value to use for @var{machine} is the same as was specified as the +machine type when configuring GCC as a cross-compiler. For +example, if a cross-compiler was configured with @samp{configure +i386v}, meaning to compile for an 80386 running System V, then you +would specify @samp{-b i386v} to run that cross compiler. + +When you do not specify @samp{-b}, it normally means to compile for +the same type of machine that you are using. + +@item -V @var{version} +The argument @var{version} specifies which version of GCC to run. +This is useful when multiple versions are installed. For example, +@var{version} might be @samp{2.0}, meaning to run GCC version 2.0. + +The default version, when you do not specify @samp{-V}, is the last +version of GCC that you installed. +@end table + +The @samp{-b} and @samp{-V} options actually work by controlling part of +the file name used for the executable files and libraries used for +compilation. A given version of GCC, for a given target machine, is +normally kept in the directory @file{/usr/local/lib/gcc-lib/@var{machine}/@var{version}}.@refill + +Thus, sites can customize the effect of @samp{-b} or @samp{-V} either by +changing the names of these directories or adding alternate names (or +symbolic links). If in directory @file{/usr/local/lib/gcc-lib/} the +file @file{80386} is a link to the file @file{i386v}, then @samp{-b +80386} becomes an alias for @samp{-b i386v}. + +In one respect, the @samp{-b} or @samp{-V} do not completely change +to a different compiler: the top-level driver program @command{gcc} +that you originally invoked continues to run and invoke the other +executables (preprocessor, compiler per se, assembler and linker) +that do the real work. However, since no real work is done in the +driver program, it usually does not matter that the driver program +in use is not the one for the specified target. It is common for the +interface to the other executables to change incompatibly between +compiler versions, so unless the version specified is very close to that +of the driver (for example, @samp{-V 3.0} with a driver program from GCC +version 3.0.1), use of @samp{-V} may not work; for example, using +@samp{-V 2.95.2} will not work with a driver program from GCC 3.0. + +The only way that the driver program depends on the target machine is +in the parsing and handling of special machine-specific options. +However, this is controlled by a file which is found, along with the +other executables, in the directory for the specified version and +target machine. As a result, a single installed driver program adapts +to any specified target machine, and sufficiently similar compiler +versions. + +The driver program executable does control one significant thing, +however: the default version and target machine. Therefore, you can +install different instances of the driver program, compiled for +different targets or versions, under different names. + +For example, if the driver for version 2.0 is installed as @command{ogcc} +and that for version 2.1 is installed as @command{gcc}, then the command +@command{gcc} will use version 2.1 by default, while @command{ogcc} will use +2.0 by default. However, you can choose either version with either +command with the @samp{-V} option. + +@node Submodel Options +@section Hardware Models and Configurations +@cindex submodel options +@cindex specifying hardware config +@cindex hardware models and configurations, specifying +@cindex machine dependent options + +Earlier we discussed the standard option @samp{-b} which chooses among +different installed compilers for completely different target +machines, such as Vax vs. 68000 vs. 80386. + +In addition, each of these target machine types can have its own +special options, starting with @samp{-m}, to choose among various +hardware models or configurations---for example, 68010 vs 68020, +floating coprocessor or none. A single installed version of the +compiler can compile for any model or configuration, according to the +options specified. + +Some configurations of the compiler also support additional special +options, usually for compatibility with other compilers on the same +platform. + +@ifset INTERNALS +These options are defined by the macro @code{TARGET_SWITCHES} in the +machine description. The default for the options is also defined by +that macro, which enables you to change the defaults. +@end ifset + +@menu +* M680x0 Options:: +* M68hc1x Options:: +* VAX Options:: +* SPARC Options:: +* Convex Options:: +* AMD29K Options:: +* ARM Options:: +* MN10200 Options:: +* MN10300 Options:: +* M32R/D Options:: +* M88K Options:: +* RS/6000 and PowerPC Options:: +* RT Options:: +* MIPS Options:: +* i386 Options:: +* HPPA Options:: +* Intel 960 Options:: +* DEC Alpha Options:: +* Clipper Options:: +* H8/300 Options:: +* SH Options:: +* System V Options:: +* TMS320C3x/C4x Options:: +* V850 Options:: +* ARC Options:: +* NS32K Options:: +* AVR Options:: +* MCore Options:: +* IA-64 Options:: +* D30V Options:: +@end menu + +@node M680x0 Options +@subsection M680x0 Options +@cindex M680x0 options + +These are the @samp{-m} options defined for the 68000 series. The default +values for these options depends on which style of 68000 was selected when +the compiler was configured; the defaults for the most common choices are +given below. + +@table @gcctabopt +@item -m68000 +@itemx -mc68000 +Generate output for a 68000. This is the default +when the compiler is configured for 68000-based systems. + +Use this option for microcontrollers with a 68000 or EC000 core, +including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. + +@item -m68020 +@itemx -mc68020 +Generate output for a 68020. This is the default +when the compiler is configured for 68020-based systems. + +@item -m68881 +Generate output containing 68881 instructions for floating point. +This is the default for most 68020 systems unless @samp{-nfp} was +specified when the compiler was configured. + +@item -m68030 +Generate output for a 68030. This is the default when the compiler is +configured for 68030-based systems. + +@item -m68040 +Generate output for a 68040. This is the default when the compiler is +configured for 68040-based systems. + +This option inhibits the use of 68881/68882 instructions that have to be +emulated by software on the 68040. Use this option if your 68040 does not +have code to emulate those instructions. + +@item -m68060 +Generate output for a 68060. This is the default when the compiler is +configured for 68060-based systems. + +This option inhibits the use of 68020 and 68881/68882 instructions that +have to be emulated by software on the 68060. Use this option if your 68060 +does not have code to emulate those instructions. + +@item -mcpu32 +Generate output for a CPU32. This is the default +when the compiler is configured for CPU32-based systems. + +Use this option for microcontrollers with a +CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, +68336, 68340, 68341, 68349 and 68360. + +@item -m5200 +Generate output for a 520X "coldfire" family cpu. This is the default +when the compiler is configured for 520X-based systems. + +Use this option for microcontroller with a 5200 core, including +the MCF5202, MCF5203, MCF5204 and MCF5202. + + +@item -m68020-40 +Generate output for a 68040, without using any of the new instructions. +This results in code which can run relatively efficiently on either a +68020/68881 or a 68030 or a 68040. The generated code does use the +68881 instructions that are emulated on the 68040. + +@item -m68020-60 +Generate output for a 68060, without using any of the new instructions. +This results in code which can run relatively efficiently on either a +68020/68881 or a 68030 or a 68040. The generated code does use the +68881 instructions that are emulated on the 68060. + +@item -mfpa +Generate output containing Sun FPA instructions for floating point. + +@item -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not available for all m68k +targets. Normally the facilities of the machine's usual C compiler are +used, but this can't be done directly in cross-compilation. You must +make your own arrangements to provide suitable library functions for +cross-compilation. The embedded targets @samp{m68k-*-aout} and +@samp{m68k-*-coff} do provide software floating point support. + +@item -mshort +Consider type @code{int} to be 16 bits wide, like @code{short int}. + +@item -mnobitfield +Do not use the bit-field instructions. The @samp{-m68000}, @samp{-mcpu32} +and @samp{-m5200} options imply @w{@samp{-mnobitfield}}. + +@item -mbitfield +Do use the bit-field instructions. The @samp{-m68020} option implies +@samp{-mbitfield}. This is the default if you use a configuration +designed for a 68020. + +@item -mrtd +Use a different function-calling convention, in which functions +that take a fixed number of arguments return with the @code{rtd} +instruction, which pops their arguments while returning. This +saves one instruction in the caller since there is no need to pop +the arguments there. + +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. + +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including @code{printf}); +otherwise incorrect code will be generated for calls to those +functions. + +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) + +The @code{rtd} instruction is supported by the 68010, 68020, 68030, +68040, 68060 and CPU32 processors, but not by the 68000 or 5200. + +@item -malign-int +@itemx -mno-align-int +Control whether GCC aligns @code{int}, @code{long}, @code{long long}, +@code{float}, @code{double}, and @code{long double} variables on a 32-bit +boundary (@samp{-malign-int}) or a 16-bit boundary (@samp{-mno-align-int}). +Aligning variables on 32-bit boundaries produces code that runs somewhat +faster on processors with 32-bit busses at the expense of more memory. + +@strong{Warning:} if you use the @samp{-malign-int} switch, GCC will +align structures containing the above types differently than +most published application binary interface specifications for the m68k. + +@item -mpcrel +Use the pc-relative addressing mode of the 68000 directly, instead of +using a global offset table. At present, this option implies -fpic, +allowing at most a 16-bit offset for pc-relative addressing. -fPIC is +not presently supported with -mpcrel, though this could be supported for +68020 and higher processors. + +@item -mno-strict-align +@itemx -mstrict-align +@kindex -mstrict-align +Do not (do) assume that unaligned memory references will be handled by +the system. + +@end table + +@node M68hc1x Options +@subsection M68hc1x Options +@cindex M68hc1x options + +These are the @samp{-m} options defined for the 68hc11 and 68hc12 +microcontrollers. The default values for these options depends on +which style of microcontroller was selected when the compiler was configured; +the defaults for the most common choices are given below. + +@table @gcctabopt +@item -m6811 +@itemx -m68hc11 +Generate output for a 68HC11. This is the default +when the compiler is configured for 68HC11-based systems. + +@item -m6812 +@itemx -m68hc12 +Generate output for a 68HC12. This is the default +when the compiler is configured for 68HC12-based systems. + +@item -mauto-incdec +Enable the use of 68HC12 pre and post auto-increment and auto-decrement +addressing modes. + +@item -mshort +Consider type @code{int} to be 16 bits wide, like @code{short int}. + +@item -msoft-reg-count=@var{count} +Specify the number of pseudo-soft registers which are used for the +code generation. The maximum number is 32. Using more pseudo-soft +register may or may not result in better code depending on the program. +The default is 4 for 68HC11 and 2 for 68HC12. + +@end table + +@node VAX Options +@subsection VAX Options +@cindex VAX options + +These @samp{-m} options are defined for the Vax: + +@table @gcctabopt +@item -munix +Do not output certain jump instructions (@code{aobleq} and so on) +that the Unix assembler for the Vax cannot handle across long +ranges. + +@item -mgnu +Do output those jump instructions, on the assumption that you +will assemble with the GNU assembler. + +@item -mg +Output code for g-format floating point numbers instead of d-format. +@end table + +@node SPARC Options +@subsection SPARC Options +@cindex SPARC options + +These @samp{-m} switches are supported on the SPARC: + +@table @gcctabopt +@item -mno-app-regs +@itemx -mapp-regs +Specify @samp{-mapp-regs} to generate output using the global registers +2 through 4, which the SPARC SVR4 ABI reserves for applications. This +is the default. + +To be fully SVR4 ABI compliant at the cost of some performance loss, +specify @samp{-mno-app-regs}. You should compile libraries and system +software with this option. + +@item -mfpu +@itemx -mhard-float +Generate output containing floating point instructions. This is the +default. + +@item -mno-fpu +@itemx -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not available for all SPARC +targets. Normally the facilities of the machine's usual C compiler are +used, but this cannot be done directly in cross-compilation. You must make +your own arrangements to provide suitable library functions for +cross-compilation. The embedded targets @samp{sparc-*-aout} and +@samp{sparclite-*-*} do provide software floating point support. + +@samp{-msoft-float} changes the calling convention in the output file; +therefore, it is only useful if you compile @emph{all} of a program with +this option. In particular, you need to compile @file{libgcc.a}, the +library that comes with GCC, with @samp{-msoft-float} in order for +this to work. + +@item -mhard-quad-float +Generate output containing quad-word (long double) floating point +instructions. + +@item -msoft-quad-float +Generate output containing library calls for quad-word (long double) +floating point instructions. The functions called are those specified +in the SPARC ABI. This is the default. + +As of this writing, there are no sparc implementations that have hardware +support for the quad-word floating point instructions. They all invoke +a trap handler for one of these instructions, and then the trap handler +emulates the effect of the instruction. Because of the trap handler overhead, +this is much slower than calling the ABI library routines. Thus the +@samp{-msoft-quad-float} option is the default. + +@item -mno-epilogue +@itemx -mepilogue +With @samp{-mepilogue} (the default), the compiler always emits code for +function exit at the end of each function. Any function exit in +the middle of the function (such as a return statement in C) will +generate a jump to the exit code at the end of the function. + +With @samp{-mno-epilogue}, the compiler tries to emit exit code inline +at every function exit. + +@item -mno-flat +@itemx -mflat +With @samp{-mflat}, the compiler does not generate save/restore instructions +and will use a "flat" or single register window calling convention. +This model uses %i7 as the frame pointer and is compatible with the normal +register window model. Code from either may be intermixed. +The local registers and the input registers (0-5) are still treated as +"call saved" registers and will be saved on the stack as necessary. + +With @samp{-mno-flat} (the default), the compiler emits save/restore +instructions (except for leaf functions) and is the normal mode of operation. + +@item -mno-unaligned-doubles +@itemx -munaligned-doubles +Assume that doubles have 8 byte alignment. This is the default. + +With @samp{-munaligned-doubles}, GCC assumes that doubles have 8 byte +alignment only if they are contained in another type, or if they have an +absolute address. Otherwise, it assumes they have 4 byte alignment. +Specifying this option avoids some rare compatibility problems with code +generated by other compilers. It is not the default because it results +in a performance loss, especially for floating point code. + +@item -mno-faster-structs +@itemx -mfaster-structs +With @samp{-mfaster-structs}, the compiler assumes that structures +should have 8 byte alignment. This enables the use of pairs of +@code{ldd} and @code{std} instructions for copies in structure +assignment, in place of twice as many @code{ld} and @code{st} pairs. +However, the use of this changed alignment directly violates the Sparc +ABI. Thus, it's intended only for use on targets where the developer +acknowledges that their resulting code will not be directly in line with +the rules of the ABI. + +@item -mv8 +@itemx -msparclite +These two options select variations on the SPARC architecture. + +By default (unless specifically configured for the Fujitsu SPARClite), +GCC generates code for the v7 variant of the SPARC architecture. + +@samp{-mv8} will give you SPARC v8 code. The only difference from v7 +code is that the compiler emits the integer multiply and integer +divide instructions which exist in SPARC v8 but not in SPARC v7. + +@samp{-msparclite} will give you SPARClite code. This adds the integer +multiply, integer divide step and scan (@code{ffs}) instructions which +exist in SPARClite but not in SPARC v7. + +These options are deprecated and will be deleted in a future GCC release. +They have been replaced with @samp{-mcpu=xxx}. + +@item -mcypress +@itemx -msupersparc +These two options select the processor for which the code is optimised. + +With @samp{-mcypress} (the default), the compiler optimizes code for the +Cypress CY7C602 chip, as used in the SparcStation/SparcServer 3xx series. +This is also appropriate for the older SparcStation 1, 2, IPX etc. + +With @samp{-msupersparc} the compiler optimizes code for the SuperSparc cpu, as +used in the SparcStation 10, 1000 and 2000 series. This flag also enables use +of the full SPARC v8 instruction set. + +These options are deprecated and will be deleted in a future GCC release. +They have been replaced with @samp{-mcpu=xxx}. + +@item -mcpu=@var{cpu_type} +Set the instruction set, register set, and instruction scheduling parameters +for machine type @var{cpu_type}. Supported values for @var{cpu_type} are +@samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite}, +@samp{hypersparc}, @samp{sparclite86x}, @samp{f930}, @samp{f934}, +@samp{sparclet}, @samp{tsc701}, @samp{v9}, and @samp{ultrasparc}. + +Default instruction scheduling parameters are used for values that select +an architecture and not an implementation. These are @samp{v7}, @samp{v8}, +@samp{sparclite}, @samp{sparclet}, @samp{v9}. + +Here is a list of each supported architecture and their supported +implementations. + +@smallexample + v7: cypress + v8: supersparc, hypersparc + sparclite: f930, f934, sparclite86x + sparclet: tsc701 + v9: ultrasparc +@end smallexample + +@item -mtune=@var{cpu_type} +Set the instruction scheduling parameters for machine type +@var{cpu_type}, but do not set the instruction set or register set that the +option @samp{-mcpu=}@var{cpu_type} would. + +The same values for @samp{-mcpu=}@var{cpu_type} are used for +@samp{-mtune=}@*@var{cpu_type}, though the only useful values are those that +select a particular cpu implementation: @samp{cypress}, @samp{supersparc}, +@samp{hypersparc}, @samp{f930}, @samp{f934}, @samp{sparclite86x}, +@samp{tsc701}, @samp{ultrasparc}. + +@end table + +These @samp{-m} switches are supported in addition to the above +on the SPARCLET processor. + +@table @gcctabopt +@item -mlittle-endian +Generate code for a processor running in little-endian mode. + +@item -mlive-g0 +Treat register @code{%g0} as a normal register. +GCC will continue to clobber it as necessary but will not assume +it always reads as 0. + +@item -mbroken-saverestore +Generate code that does not use non-trivial forms of the @code{save} and +@code{restore} instructions. Early versions of the SPARCLET processor do +not correctly handle @code{save} and @code{restore} instructions used with +arguments. They correctly handle them used without arguments. A @code{save} +instruction used without arguments increments the current window pointer +but does not allocate a new stack frame. It is assumed that the window +overflow trap handler will properly handle this case as will interrupt +handlers. +@end table + +These @samp{-m} switches are supported in addition to the above +on SPARC V9 processors in 64-bit environments. + +@table @gcctabopt +@item -mlittle-endian +Generate code for a processor running in little-endian mode. + +@item -m32 +@itemx -m64 +Generate code for a 32-bit or 64-bit environment. +The 32-bit environment sets int, long and pointer to 32 bits. +The 64-bit environment sets int to 32 bits and long and pointer +to 64 bits. + +@item -mcmodel=medlow +Generate code for the Medium/Low code model: the program must be linked +in the low 32 bits of the address space. Pointers are 64 bits. +Programs can be statically or dynamically linked. + +@item -mcmodel=medmid +Generate code for the Medium/Middle code model: the program must be linked +in the low 44 bits of the address space, the text segment must be less than +2G bytes, and data segment must be within 2G of the text segment. +Pointers are 64 bits. + +@item -mcmodel=medany +Generate code for the Medium/Anywhere code model: the program may be linked +anywhere in the address space, the text segment must be less than +2G bytes, and data segment must be within 2G of the text segment. +Pointers are 64 bits. + +@item -mcmodel=embmedany +Generate code for the Medium/Anywhere code model for embedded systems: +assume a 32-bit text and a 32-bit data segment, both starting anywhere +(determined at link time). Register %g4 points to the base of the +data segment. Pointers are still 64 bits. +Programs are statically linked, PIC is not supported. + +@item -mstack-bias +@itemx -mno-stack-bias +With @samp{-mstack-bias}, GCC assumes that the stack pointer, and +frame pointer if present, are offset by -2047 which must be added back +when making stack frame references. +Otherwise, assume no such offset is present. +@end table + +@node Convex Options +@subsection Convex Options +@cindex Convex options + +These @samp{-m} options are defined for Convex: + +@table @gcctabopt +@item -mc1 +Generate output for C1. The code will run on any Convex machine. +The preprocessor symbol @code{__convex__c1__} is defined. + +@item -mc2 +Generate output for C2. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C2. +The preprocessor symbol @code{__convex_c2__} is defined. + +@item -mc32 +Generate output for C32xx. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C32. +The preprocessor symbol @code{__convex_c32__} is defined. + +@item -mc34 +Generate output for C34xx. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C34. +The preprocessor symbol @code{__convex_c34__} is defined. + +@item -mc38 +Generate output for C38xx. Uses instructions not available on C1. +Scheduling and other optimizations are chosen for max performance on C38. +The preprocessor symbol @code{__convex_c38__} is defined. + +@item -margcount +Generate code which puts an argument count in the word preceding each +argument list. This is compatible with regular CC, and a few programs +may need the argument count word. GDB and other source-level debuggers +do not need it; this info is in the symbol table. + +@item -mnoargcount +Omit the argument count word. This is the default. + +@item -mvolatile-cache +Allow volatile references to be cached. This is the default. + +@item -mvolatile-nocache +Volatile references bypass the data cache, going all the way to memory. +This is only needed for multi-processor code that does not use standard +synchronization instructions. Making non-volatile references to volatile +locations will not necessarily work. + +@item -mlong32 +Type long is 32 bits, the same as type int. This is the default. + +@item -mlong64 +Type long is 64 bits, the same as type long long. This option is useless, +because no library support exists for it. +@end table + +@node AMD29K Options +@subsection AMD29K Options +@cindex AMD29K options + +These @samp{-m} options are defined for the AMD Am29000: + +@table @gcctabopt +@item -mdw +@kindex -mdw +@cindex DW bit (29k) +Generate code that assumes the @code{DW} bit is set, i.e., that byte and +halfword operations are directly supported by the hardware. This is the +default. + +@item -mndw +@kindex -mndw +Generate code that assumes the @code{DW} bit is not set. + +@item -mbw +@kindex -mbw +@cindex byte writes (29k) +Generate code that assumes the system supports byte and halfword write +operations. This is the default. + +@item -mnbw +@kindex -mnbw +Generate code that assumes the systems does not support byte and +halfword write operations. @samp{-mnbw} implies @samp{-mndw}. + +@item -msmall +@kindex -msmall +@cindex memory model (29k) +Use a small memory model that assumes that all function addresses are +either within a single 256 KB segment or at an absolute address of less +than 256k. This allows the @code{call} instruction to be used instead +of a @code{const}, @code{consth}, @code{calli} sequence. + +@item -mnormal +@kindex -mnormal +Use the normal memory model: Generate @code{call} instructions only when +calling functions in the same file and @code{calli} instructions +otherwise. This works if each file occupies less than 256 KB but allows +the entire executable to be larger than 256 KB. This is the default. + +@item -mlarge +Always use @code{calli} instructions. Specify this option if you expect +a single file to compile into more than 256 KB of code. + +@item -m29050 +@kindex -m29050 +@cindex processor selection (29k) +Generate code for the Am29050. + +@item -m29000 +@kindex -m29000 +Generate code for the Am29000. This is the default. + +@item -mkernel-registers +@kindex -mkernel-registers +@cindex kernel and user registers (29k) +Generate references to registers @code{gr64-gr95} instead of to +registers @code{gr96-gr127}. This option can be used when compiling +kernel code that wants a set of global registers disjoint from that used +by user-mode code. + +Note that when this option is used, register names in @samp{-f} flags +must use the normal, user-mode, names. + +@item -muser-registers +@kindex -muser-registers +Use the normal set of global registers, @code{gr96-gr127}. This is the +default. + +@item -mstack-check +@itemx -mno-stack-check +@kindex -mstack-check +@cindex stack checks (29k) +Insert (or do not insert) a call to @code{__msp_check} after each stack +adjustment. This is often used for kernel code. + +@item -mstorem-bug +@itemx -mno-storem-bug +@kindex -mstorem-bug +@cindex storem bug (29k) +@samp{-mstorem-bug} handles 29k processors which cannot handle the +separation of a mtsrim insn and a storem instruction (most 29000 chips +to date, but not the 29050). + +@item -mno-reuse-arg-regs +@itemx -mreuse-arg-regs +@kindex -mreuse-arg-regs +@samp{-mno-reuse-arg-regs} tells the compiler to only use incoming argument +registers for copying out arguments. This helps detect calling a function +with fewer arguments than it was declared with. + +@item -mno-impure-text +@itemx -mimpure-text +@kindex -mimpure-text +@samp{-mimpure-text}, used in addition to @samp{-shared}, tells the compiler to +not pass @samp{-assert pure-text} to the linker when linking a shared object. + +@item -msoft-float +@kindex -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not part of GCC. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. + +@item -mno-multm +@kindex -mno-multm +Do not generate multm or multmu instructions. This is useful for some embedded +systems which do not have trap handlers for these instructions. +@end table + +@node ARM Options +@subsection ARM Options +@cindex ARM options + +These @samp{-m} options are defined for Advanced RISC Machines (ARM) +architectures: + +@table @gcctabopt +@item -mapcs-frame +@kindex -mapcs-frame +Generate a stack frame that is compliant with the ARM Procedure Call +Standard for all functions, even if this is not strictly necessary for +correct execution of the code. Specifying @samp{-fomit-frame-pointer} +with this option will cause the stack frames not to be generated for +leaf functions. The default is @samp{-mno-apcs-frame}. + +@item -mapcs +@kindex -mapcs +This is a synonym for @samp{-mapcs-frame}. + +@item -mapcs-26 +@kindex -mapcs-26 +Generate code for a processor running with a 26-bit program counter, +and conforming to the function calling standards for the APCS 26-bit +option. This option replaces the @samp{-m2} and @samp{-m3} options +of previous releases of the compiler. + +@item -mapcs-32 +@kindex -mapcs-32 +Generate code for a processor running with a 32-bit program counter, +and conforming to the function calling standards for the APCS 32-bit +option. This option replaces the @samp{-m6} option of previous releases +of the compiler. + +@ignore +@c not currently implemented +@item -mapcs-stack-check +@kindex -mapcs-stack-check +@kindex -mno-apcs-stack-check +Generate code to check the amount of stack space available upon entry to +every function (that actually uses some stack space). If there is +insufficient space available then either the function +@samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be +called, depending upon the amount of stack space required. The run time +system is required to provide these functions. The default is +@samp{-mno-apcs-stack-check}, since this produces smaller code. + +@c not currently implemented +@item -mapcs-float +@kindex -mapcs-float +@kindex -mno-apcs-float +Pass floating point arguments using the float point registers. This is +one of the variants of the APCS. This option is recommended if the +target hardware has a floating point unit or if a lot of floating point +arithmetic is going to be performed by the code. The default is +@samp{-mno-apcs-float}, since integer only code is slightly increased in +size if @samp{-mapcs-float} is used. + +@c not currently implemented +@item -mapcs-reentrant +@kindex -mapcs-reentrant +@kindex -mno-apcs-reentrant +Generate reentrant, position independent code. The default is +@samp{-mno-apcs-reentrant}. +@end ignore + +@item -mthumb-interwork +@kindex -mthumb-interwork +@kindex -mno-thumb-interwork +Generate code which supports calling between the ARM and Thumb +instruction sets. Without this option the two instruction sets cannot +be reliably used inside one program. The default is +@samp{-mno-thumb-interwork}, since slightly larger code is generated +when @samp{-mthumb-interwork} is specified. + +@item -mno-sched-prolog +@kindex -mno-sched-prolog +@kindex -msched-prolog +Prevent the reordering of instructions in the function prolog, or the +merging of those instruction with the instructions in the function's +body. This means that all functions will start with a recognizable set +of instructions (or in fact one of a choice from a small set of +different function prologues), and this information can be used to +locate the start if functions inside an executable piece of code. The +default is @samp{-msched-prolog}. + +@item -mhard-float +Generate output containing floating point instructions. This is the +default. + +@item -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not available for all ARM +targets. Normally the facilities of the machine's usual C compiler are +used, but this cannot be done directly in cross-compilation. You must make +your own arrangements to provide suitable library functions for +cross-compilation. + +@samp{-msoft-float} changes the calling convention in the output file; +therefore, it is only useful if you compile @emph{all} of a program with +this option. In particular, you need to compile @file{libgcc.a}, the +library that comes with GCC, with @samp{-msoft-float} in order for +this to work. + +@item -mlittle-endian +Generate code for a processor running in little-endian mode. This is +the default for all standard configurations. + +@item -mbig-endian +Generate code for a processor running in big-endian mode; the default is +to compile code for a little-endian processor. + +@item -mwords-little-endian +This option only applies when generating code for big-endian processors. +Generate code for a little-endian word order but a big-endian byte +order. That is, a byte order of the form @samp{32107654}. Note: this +option should only be used if you require compatibility with code for +big-endian ARM processors generated by versions of the compiler prior to +2.8. + +@item -malignment-traps +@kindex -malignment-traps +Generate code that will not trap if the MMU has alignment traps enabled. +On ARM architectures prior to ARMv4, there were no instructions to +access half-word objects stored in memory. However, when reading from +memory a feature of the ARM architecture allows a word load to be used, +even if the address is unaligned, and the processor core will rotate the +data as it is being loaded. This option tells the compiler that such +misaligned accesses will cause a MMU trap and that it should instead +synthesise the access as a series of byte accesses. The compiler can +still use word accesses to load half-word data if it knows that the +address is aligned to a word boundary. + +This option is ignored when compiling for ARM architecture 4 or later, +since these processors have instructions to directly access half-word +objects in memory. + +@item -mno-alignment-traps +@kindex -mno-alignment-traps +Generate code that assumes that the MMU will not trap unaligned +accesses. This produces better code when the target instruction set +does not have half-word memory operations (i.e. implementations prior to +ARMv4). + +Note that you cannot use this option to access unaligned word objects, +since the processor will only fetch one 32-bit aligned object from +memory. + +The default setting for most targets is -mno-alignment-traps, since +this produces better code when there are no half-word memory +instructions available. + +@item -mshort-load-bytes +@itemx -mno-short-load-words +@kindex -mshort-load-bytes +@kindex -mno-short-load-words +These are deprecated aliases for @samp{-malignment-traps}. + +@item -mno-short-load-bytes +@itemx -mshort-load-words +@kindex -mno-short-load-bytes +@kindex -mshort-load-words +This are deprecated aliases for @samp{-mno-alignment-traps}. + +@item -mbsd +@kindex -mbsd +This option only applies to RISC iX. Emulate the native BSD-mode +compiler. This is the default if @samp{-ansi} is not specified. + +@item -mxopen +@kindex -mxopen +This option only applies to RISC iX. Emulate the native X/Open-mode +compiler. + +@item -mno-symrename +@kindex -mno-symrename +This option only applies to RISC iX. Do not run the assembler +post-processor, @samp{symrename}, after code has been assembled. +Normally it is necessary to modify some of the standard symbols in +preparation for linking with the RISC iX C library; this option +suppresses this pass. The post-processor is never run when the +compiler is built for cross-compilation. + +@item -mcpu= +@kindex -mcpu= +This specifies the name of the target ARM processor. GCC uses this name +to determine what kind of instructions it can emit when generating +assembly code. Permissible names are: arm2, arm250, arm3, arm6, arm60, +arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, +arm70, arm700, arm700i, arm710, arm710c, arm7100, arm7500, arm7500fe, +arm7tdmi, arm8, strongarm, strongarm110, strongarm1100, arm8, arm810, +arm9, arm9e, arm920, arm920t, arm940t, arm9tdmi, arm10tdmi, arm1020t, +xscale. + +@itemx -mtune= +@kindex -mtune= +This option is very similar to the @samp{-mcpu=} option, except that +instead of specifying the actual target processor type, and hence +restricting which instructions can be used, it specifies that GCC should +tune the performance of the code as if the target were of the type +specified in this option, but still choosing the instructions that it +will generate based on the cpu specified by a @samp{-mcpu=} option. +For some ARM implementations better performance can be obtained by using +this option. + +@item -march= +@kindex -march= +This specifies the name of the target ARM architecture. GCC uses this +name to determine what kind of instructions it can emit when generating +assembly code. This option can be used in conjunction with or instead +of the @samp{-mcpu=} option. Permissible names are: armv2, armv2a, +armv3, armv3m, armv4, armv4t, armv5, armv5t, armv5te. + +@item -mfpe= +@itemx -mfp= +@kindex -mfpe= +@kindex -mfp= +This specifies the version of the floating point emulation available on +the target. Permissible values are 2 and 3. @samp{-mfp=} is a synonym +for @samp{-mfpe=}, for compatibility with older versions of GCC. + +@item -mstructure-size-boundary= +@kindex -mstructure-size-boundary +The size of all structures and unions will be rounded up to a multiple +of the number of bits set by this option. Permissible values are 8 and +32. The default value varies for different toolchains. For the COFF +targeted toolchain the default value is 8. Specifying the larger number +can produce faster, more efficient code, but can also increase the size +of the program. The two values are potentially incompatible. Code +compiled with one value cannot necessarily expect to work with code or +libraries compiled with the other value, if they exchange information +using structures or unions. + +@item -mabort-on-noreturn +@kindex -mabort-on-noreturn +@kindex -mnoabort-on-noreturn +Generate a call to the function @code{abort} at the end of a +@code{noreturn} function. It will be executed if the function tries to +return. + +@item -mlong-calls +@itemx -mno-long-calls +Tells the compiler to perform function calls by first loading the +address of the function into a register and then performing a subroutine +call on this register. This switch is needed if the target function +will lie outside of the 64 megabyte addressing range of the offset based +version of subroutine call instruction. + +Even if this switch is enabled, not all function calls will be turned +into long calls. The heuristic is that static functions, functions +which have the @samp{short-call} attribute, functions that are inside +the scope of a @samp{#pragma no_long_calls} directive and functions whose +definitions have already been compiled within the current compilation +unit, will not be turned into long calls. The exception to this rule is +that weak function definitions, functions with the @samp{long-call} +attribute or the @samp{section} attribute, and functions that are within +the scope of a @samp{#pragma long_calls} directive, will always be +turned into long calls. + +This feature is not enabled by default. Specifying +@samp{-mno-long-calls} will restore the default behaviour, as will +placing the function calls within the scope of a @samp{#pragma +long_calls_off} directive. Note these switches have no effect on how +the compiler generates code to handle function calls via function +pointers. + +@item -mnop-fun-dllimport +@kindex -mnop-fun-dllimport +Disable support for the @emph{dllimport} attribute. + +@item -msingle-pic-base +@kindex -msingle-pic-base +Treat the register used for PIC addressing as read-only, rather than +loading it in the prologue for each function. The run-time system is +responsible for initialising this register with an appropriate value +before execution begins. + +@item -mpic-register= +@kindex -mpic-register= +Specify the register to be used for PIC addressing. The default is R10 +unless stack-checking is enabled, when R9 is used. + +@item -mpoke-function-name +@kindex -mpoke-function-name +Write the name of each function into the text section, directly +preceding the function prologue. The generated code is similar to this: + +@smallexample + t0 + .ascii "arm_poke_function_name", 0 + .align + t1 + .word 0xff000000 + (t1 - t0) + arm_poke_function_name + mov ip, sp + stmfd sp!, @{fp, ip, lr, pc@} + sub fp, ip, #4 +@end smallexample + +When performing a stack backtrace, code can inspect the value of +@code{pc} stored at @code{fp + 0}. If the trace function then looks at +location @code{pc - 12} and the top 8 bits are set, then we know that +there is a function name embedded immediately preceding this location +and has length @code{((pc[-3]) & 0xff000000)}. + +@item -mthumb +@kindex -mthumb +Generate code for the 16-bit Thumb instruction set. The default is to +use the 32-bit ARM instruction set. + +@item -mtpcs-frame +@kindex -mtpcs-frame +@kindex -mno-tpcs-frame +Generate a stack frame that is compliant with the Thumb Procedure Call +Standard for all non-leaf functions. (A leaf function is one that does +not call any other functions.) The default is @samp{-mno-tpcs-frame}. + +@item -mtpcs-leaf-frame +@kindex -mtpcs-leaf-frame +@kindex -mno-tpcs-leaf-frame +Generate a stack frame that is compliant with the Thumb Procedure Call +Standard for all leaf functions. (A leaf function is one that does +not call any other functions.) The default is @samp{-mno-apcs-leaf-frame}. + +@item -mcallee-super-interworking +@kindex -mcallee-super-interworking +Gives all externally visible functions in the file being compiled an ARM +instruction set header which switches to Thumb mode before executing the +rest of the function. This allows these functions to be called from +non-interworking code. + +@item -mcaller-super-interworking +@kindex -mcaller-super-interworking +Allows calls via function pointers (including virtual functions) to +execute correctly regardless of whether the target code has been +compiled for interworking or not. There is a small overhead in the cost +of executing a function pointer if this option is enabled. + +@end table + +@node MN10200 Options +@subsection MN10200 Options +@cindex MN10200 options +These @samp{-m} options are defined for Matsushita MN10200 architectures: +@table @gcctabopt + +@item -mrelax +Indicate to the linker that it should perform a relaxation optimization pass +to shorten branches, calls and absolute memory addresses. This option only +has an effect when used on the command line for the final link step. + +This option makes symbolic debugging impossible. +@end table + +@node MN10300 Options +@subsection MN10300 Options +@cindex MN10300 options +These @samp{-m} options are defined for Matsushita MN10300 architectures: + +@table @gcctabopt +@item -mmult-bug +Generate code to avoid bugs in the multiply instructions for the MN10300 +processors. This is the default. + +@item -mno-mult-bug +Do not generate code to avoid bugs in the multiply instructions for the +MN10300 processors. + +@item -mam33 +Generate code which uses features specific to the AM33 processor. + +@item -mno-am33 +Do not generate code which uses features specific to the AM33 processor. This +is the default. + +@item -mrelax +Indicate to the linker that it should perform a relaxation optimization pass +to shorten branches, calls and absolute memory addresses. This option only +has an effect when used on the command line for the final link step. + +This option makes symbolic debugging impossible. +@end table + + +@node M32R/D Options +@subsection M32R/D Options +@cindex M32R/D options + +These @samp{-m} options are defined for Mitsubishi M32R/D architectures: + +@table @gcctabopt +@item -mcode-model=small +Assume all objects live in the lower 16MB of memory (so that their addresses +can be loaded with the @code{ld24} instruction), and assume all subroutines +are reachable with the @code{bl} instruction. +This is the default. + +The addressability of a particular object can be set with the +@code{model} attribute. + +@item -mcode-model=medium +Assume objects may be anywhere in the 32-bit address space (the compiler +will generate @code{seth/add3} instructions to load their addresses), and +assume all subroutines are reachable with the @code{bl} instruction. + +@item -mcode-model=large +Assume objects may be anywhere in the 32-bit address space (the compiler +will generate @code{seth/add3} instructions to load their addresses), and +assume subroutines may not be reachable with the @code{bl} instruction +(the compiler will generate the much slower @code{seth/add3/jl} +instruction sequence). + +@item -msdata=none +Disable use of the small data area. Variables will be put into +one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the +@code{section} attribute has been specified). +This is the default. + +The small data area consists of sections @samp{.sdata} and @samp{.sbss}. +Objects may be explicitly put in the small data area with the +@code{section} attribute using one of these sections. + +@item -msdata=sdata +Put small global and static data in the small data area, but do not +generate special code to reference them. + +@item -msdata=use +Put small global and static data in the small data area, and generate +special instructions to reference them. + +@item -G @var{num} +@cindex smaller data references +Put global and static objects less than or equal to @var{num} bytes +into the small data or bss sections instead of the normal data or bss +sections. The default value of @var{num} is 8. +The @samp{-msdata} option must be set to one of @samp{sdata} or @samp{use} +for this option to have any effect. + +All modules should be compiled with the same @samp{-G @var{num}} value. +Compiling with different values of @var{num} may or may not work; if it +doesn't the linker will give an error message - incorrect code will not be +generated. + +@end table + +@node M88K Options +@subsection M88K Options +@cindex M88k options + +These @samp{-m} options are defined for Motorola 88k architectures: + +@table @gcctabopt +@item -m88000 +@kindex -m88000 +Generate code that works well on both the m88100 and the +m88110. + +@item -m88100 +@kindex -m88100 +Generate code that works best for the m88100, but that also +runs on the m88110. + +@item -m88110 +@kindex -m88110 +Generate code that works best for the m88110, and may not run +on the m88100. + +@item -mbig-pic +@kindex -mbig-pic +Obsolete option to be removed from the next revision. +Use @samp{-fPIC}. + +@item -midentify-revision +@kindex -midentify-revision +@kindex ident +@cindex identifying source, compiler (88k) +Include an @code{ident} directive in the assembler output recording the +source file name, compiler name and version, timestamp, and compilation +flags used. + +@item -mno-underscores +@kindex -mno-underscores +@cindex underscores, avoiding (88k) +In assembler output, emit symbol names without adding an underscore +character at the beginning of each name. The default is to use an +underscore as prefix on each name. + +@item -mocs-debug-info +@itemx -mno-ocs-debug-info +@kindex -mocs-debug-info +@kindex -mno-ocs-debug-info +@cindex OCS (88k) +@cindex debugging, 88k OCS +Include (or omit) additional debugging information (about registers used +in each stack frame) as specified in the 88open Object Compatibility +Standard, ``OCS''. This extra information allows debugging of code that +has had the frame pointer eliminated. The default for DG/UX, SVr4, and +Delta 88 SVr3.2 is to include this information; other 88k configurations +omit this information by default. + +@item -mocs-frame-position +@kindex -mocs-frame-position +@cindex register positions in frame (88k) +When emitting COFF debugging information for automatic variables and +parameters stored on the stack, use the offset from the canonical frame +address, which is the stack pointer (register 31) on entry to the +function. The DG/UX, SVr4, Delta88 SVr3.2, and BCS configurations use +@samp{-mocs-frame-position}; other 88k configurations have the default +@samp{-mno-ocs-frame-position}. + +@item -mno-ocs-frame-position +@kindex -mno-ocs-frame-position +@cindex register positions in frame (88k) +When emitting COFF debugging information for automatic variables and +parameters stored on the stack, use the offset from the frame pointer +register (register 30). When this option is in effect, the frame +pointer is not eliminated when debugging information is selected by the +-g switch. + +@item -moptimize-arg-area +@itemx -mno-optimize-arg-area +@kindex -moptimize-arg-area +@kindex -mno-optimize-arg-area +@cindex arguments in frame (88k) +Control how function arguments are stored in stack frames. +@samp{-moptimize-arg-area} saves space by optimizing them, but this +conflicts with the 88open specifications. The opposite alternative, +@samp{-mno-optimize-arg-area}, agrees with 88open standards. By default +GCC does not optimize the argument area. + +@item -mshort-data-@var{num} +@kindex -mshort-data-@var{num} +@cindex smaller data references (88k) +@cindex r0-relative references (88k) +Generate smaller data references by making them relative to @code{r0}, +which allows loading a value using a single instruction (rather than the +usual two). You control which data references are affected by +specifying @var{num} with this option. For example, if you specify +@samp{-mshort-data-512}, then the data references affected are those +involving displacements of less than 512 bytes. +@samp{-mshort-data-@var{num}} is not effective for @var{num} greater +than 64k. + +@item -mserialize-volatile +@kindex -mserialize-volatile +@itemx -mno-serialize-volatile +@kindex -mno-serialize-volatile +@cindex sequential consistency on 88k +Do, or don't, generate code to guarantee sequential consistency +of volatile memory references. By default, consistency is +guaranteed. + +The order of memory references made by the MC88110 processor does +not always match the order of the instructions requesting those +references. In particular, a load instruction may execute before +a preceding store instruction. Such reordering violates +sequential consistency of volatile memory references, when there +are multiple processors. When consistency must be guaranteed, +GNU C generates special instructions, as needed, to force +execution in the proper order. + +The MC88100 processor does not reorder memory references and so +always provides sequential consistency. However, by default, GNU +C generates the special instructions to guarantee consistency +even when you use @samp{-m88100}, so that the code may be run on an +MC88110 processor. If you intend to run your code only on the +MC88100 processor, you may use @samp{-mno-serialize-volatile}. + +The extra code generated to guarantee consistency may affect the +performance of your application. If you know that you can safely +forgo this guarantee, you may use @samp{-mno-serialize-volatile}. + +@item -msvr4 +@itemx -msvr3 +@kindex -msvr4 +@kindex -msvr3 +@cindex assembler syntax, 88k +@cindex SVr4 +Turn on (@samp{-msvr4}) or off (@samp{-msvr3}) compiler extensions +related to System V release 4 (SVr4). This controls the following: + +@enumerate +@item +Which variant of the assembler syntax to emit. +@item +@samp{-msvr4} makes the C preprocessor recognize @samp{#pragma weak} +that is used on System V release 4. +@item +@samp{-msvr4} makes GCC issue additional declaration directives used in +SVr4. +@end enumerate + +@samp{-msvr4} is the default for the m88k-motorola-sysv4 and +m88k-dg-dgux m88k configurations. @samp{-msvr3} is the default for all +other m88k configurations. + +@item -mversion-03.00 +@kindex -mversion-03.00 +This option is obsolete, and is ignored. +@c ??? which asm syntax better for GAS? option there too? + +@item -mno-check-zero-division +@itemx -mcheck-zero-division +@kindex -mno-check-zero-division +@kindex -mcheck-zero-division +@cindex zero division on 88k +Do, or don't, generate code to guarantee that integer division by +zero will be detected. By default, detection is guaranteed. + +Some models of the MC88100 processor fail to trap upon integer +division by zero under certain conditions. By default, when +compiling code that might be run on such a processor, GNU C +generates code that explicitly checks for zero-valued divisors +and traps with exception number 503 when one is detected. Use of +mno-check-zero-division suppresses such checking for code +generated to run on an MC88100 processor. + +GNU C assumes that the MC88110 processor correctly detects all +instances of integer division by zero. When @samp{-m88110} is +specified, both @samp{-mcheck-zero-division} and +@samp{-mno-check-zero-division} are ignored, and no explicit checks for +zero-valued divisors are generated. + +@item -muse-div-instruction +@kindex -muse-div-instruction +@cindex divide instruction, 88k +Use the div instruction for signed integer division on the +MC88100 processor. By default, the div instruction is not used. + +On the MC88100 processor the signed integer division instruction +div) traps to the operating system on a negative operand. The +operating system transparently completes the operation, but at a +large cost in execution time. By default, when compiling code +that might be run on an MC88100 processor, GNU C emulates signed +integer division using the unsigned integer division instruction +divu), thereby avoiding the large penalty of a trap to the +operating system. Such emulation has its own, smaller, execution +cost in both time and space. To the extent that your code's +important signed integer division operations are performed on two +nonnegative operands, it may be desirable to use the div +instruction directly. + +On the MC88110 processor the div instruction (also known as the +divs instruction) processes negative operands without trapping to +the operating system. When @samp{-m88110} is specified, +@samp{-muse-div-instruction} is ignored, and the div instruction is used +for signed integer division. + +Note that the result of dividing INT_MIN by -1 is undefined. In +particular, the behavior of such a division with and without +@samp{-muse-div-instruction} may differ. + +@item -mtrap-large-shift +@itemx -mhandle-large-shift +@kindex -mtrap-large-shift +@kindex -mhandle-large-shift +@cindex bit shift overflow (88k) +@cindex large bit shifts (88k) +Include code to detect bit-shifts of more than 31 bits; respectively, +trap such shifts or emit code to handle them properly. By default GCC +makes no special provision for large bit shifts. + +@item -mwarn-passed-structs +@kindex -mwarn-passed-structs +@cindex structure passing (88k) +Warn when a function passes a struct as an argument or result. +Structure-passing conventions have changed during the evolution of the C +language, and are often the source of portability problems. By default, +GCC issues no such warning. +@end table + +@node RS/6000 and PowerPC Options +@subsection IBM RS/6000 and PowerPC Options +@cindex RS/6000 and PowerPC Options +@cindex IBM RS/6000 and PowerPC Options + +These @samp{-m} options are defined for the IBM RS/6000 and PowerPC: +@table @gcctabopt +@item -mpower +@itemx -mno-power +@itemx -mpower2 +@itemx -mno-power2 +@itemx -mpowerpc +@itemx -mno-powerpc +@itemx -mpowerpc-gpopt +@itemx -mno-powerpc-gpopt +@itemx -mpowerpc-gfxopt +@itemx -mno-powerpc-gfxopt +@itemx -mpowerpc64 +@itemx -mno-powerpc64 +@kindex -mpower +@kindex -mpower2 +@kindex -mpowerpc +@kindex -mpowerpc-gpopt +@kindex -mpowerpc-gfxopt +@kindex -mpowerpc64 +GCC supports two related instruction set architectures for the +RS/6000 and PowerPC. The @dfn{POWER} instruction set are those +instructions supported by the @samp{rios} chip set used in the original +RS/6000 systems and the @dfn{PowerPC} instruction set is the +architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and +the IBM 4xx microprocessors. + +Neither architecture is a subset of the other. However there is a +large common subset of instructions supported by both. An MQ +register is included in processors supporting the POWER architecture. + +You use these options to specify which instructions are available on the +processor you are using. The default value of these options is +determined when configuring GCC. Specifying the +@samp{-mcpu=@var{cpu_type}} overrides the specification of these +options. We recommend you use the @samp{-mcpu=@var{cpu_type}} option +rather than the options listed above. + +The @samp{-mpower} option allows GCC to generate instructions that +are found only in the POWER architecture and to use the MQ register. +Specifying @samp{-mpower2} implies @samp{-power} and also allows GCC +to generate instructions that are present in the POWER2 architecture but +not the original POWER architecture. + +The @samp{-mpowerpc} option allows GCC to generate instructions that +are found only in the 32-bit subset of the PowerPC architecture. +Specifying @samp{-mpowerpc-gpopt} implies @samp{-mpowerpc} and also allows +GCC to use the optional PowerPC architecture instructions in the +General Purpose group, including floating-point square root. Specifying +@samp{-mpowerpc-gfxopt} implies @samp{-mpowerpc} and also allows GCC to +use the optional PowerPC architecture instructions in the Graphics +group, including floating-point select. + +The @samp{-mpowerpc64} option allows GCC to generate the additional +64-bit instructions that are found in the full PowerPC64 architecture +and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to +@samp{-mno-powerpc64}. + +If you specify both @samp{-mno-power} and @samp{-mno-powerpc}, GCC +will use only the instructions in the common subset of both +architectures plus some special AIX common-mode calls, and will not use +the MQ register. Specifying both @samp{-mpower} and @samp{-mpowerpc} +permits GCC to use any instruction from either architecture and to +allow use of the MQ register; specify this for the Motorola MPC601. + +@item -mnew-mnemonics +@itemx -mold-mnemonics +@kindex -mnew-mnemonics +@kindex -mold-mnemonics +Select which mnemonics to use in the generated assembler code. +@samp{-mnew-mnemonics} requests output that uses the assembler mnemonics +defined for the PowerPC architecture, while @samp{-mold-mnemonics} +requests the assembler mnemonics defined for the POWER architecture. +Instructions defined in only one architecture have only one mnemonic; +GCC uses that mnemonic irrespective of which of these options is +specified. + +GCC defaults to the mnemonics appropriate for the architecture in +use. Specifying @samp{-mcpu=@var{cpu_type}} sometimes overrides the +value of these option. Unless you are building a cross-compiler, you +should normally not specify either @samp{-mnew-mnemonics} or +@samp{-mold-mnemonics}, but should instead accept the default. + +@item -mcpu=@var{cpu_type} +@kindex -mcpu +Set architecture type, register usage, choice of mnemonics, and +instruction scheduling parameters for machine type @var{cpu_type}. +Supported values for @var{cpu_type} are @samp{rios}, @samp{rios1}, +@samp{rsc}, @samp{rios2}, @samp{rs64a}, @samp{601}, @samp{602}, +@samp{603}, @samp{603e}, @samp{604}, @samp{604e}, @samp{620}, +@samp{630}, @samp{740}, @samp{750}, @samp{power}, @samp{power2}, +@samp{powerpc}, @samp{403}, @samp{505}, @samp{801}, @samp{821}, +@samp{823}, and @samp{860} and @samp{common}. @samp{-mcpu=power}, +@samp{-mcpu=power2}, @samp{-mcpu=powerpc}, and @samp{-mcpu=powerpc64} +specify generic POWER, POWER2, pure 32-bit PowerPC (i.e., not MPC601), +and 64-bit PowerPC architecture machine types, with an appropriate, +generic processor model assumed for scheduling purposes.@refill + +Specifying any of the following options: +@samp{-mcpu=rios1}, @samp{-mcpu=rios2}, @samp{-mcpu=rsc}, +@samp{-mcpu=power}, or @samp{-mcpu=power2} +enables the @samp{-mpower} option and disables the @samp{-mpowerpc} option; +@samp{-mcpu=601} enables both the @samp{-mpower} and @samp{-mpowerpc} options. +All of @samp{-mcpu=rs64a}, @samp{-mcpu=602}, @samp{-mcpu=603}, +@samp{-mcpu=603e}, @samp{-mcpu=604}, @samp{-mcpu=620}, @samp{-mcpu=630}, +@samp{-mcpu=740}, and @samp{-mcpu=750} +enable the @samp{-mpowerpc} option and disable the @samp{-mpower} option. +Exactly similarly, all of @samp{-mcpu=403}, +@samp{-mcpu=505}, @samp{-mcpu=821}, @samp{-mcpu=860} and @samp{-mcpu=powerpc} +enable the @samp{-mpowerpc} option and disable the @samp{-mpower} option. +@samp{-mcpu=common} disables both the +@samp{-mpower} and @samp{-mpowerpc} options.@refill + +AIX versions 4 or greater selects @samp{-mcpu=common} by default, so +that code will operate on all members of the RS/6000 POWER and PowerPC +families. In that case, GCC will use only the instructions in the +common subset of both architectures plus some special AIX common-mode +calls, and will not use the MQ register. GCC assumes a generic +processor model for scheduling purposes. + +Specifying any of the options @samp{-mcpu=rios1}, @samp{-mcpu=rios2}, +@samp{-mcpu=rsc}, @samp{-mcpu=power}, or @samp{-mcpu=power2} also +disables the @samp{new-mnemonics} option. Specifying @samp{-mcpu=601}, +@samp{-mcpu=602}, @samp{-mcpu=603}, @samp{-mcpu=603e}, @samp{-mcpu=604}, +@samp{-mcpu=620}, @samp{-mcpu=630}, @samp{-mcpu=403}, @samp{-mcpu=505}, +@samp{-mcpu=821}, @samp{-mcpu=860} or @samp{-mcpu=powerpc} also enables +the @samp{new-mnemonics} option.@refill + +Specifying @samp{-mcpu=403}, @samp{-mcpu=821}, or @samp{-mcpu=860} also +enables the @samp{-msoft-float} option. + +@item -mtune=@var{cpu_type} +Set the instruction scheduling parameters for machine type +@var{cpu_type}, but do not set the architecture type, register usage, +choice of mnemonics like @samp{-mcpu=}@var{cpu_type} would. The same +values for @var{cpu_type} are used for @samp{-mtune=}@var{cpu_type} as +for @samp{-mcpu=}@var{cpu_type}. The @samp{-mtune=}@var{cpu_type} +option overrides the @samp{-mcpu=}@var{cpu_type} option in terms of +instruction scheduling parameters. + +@item -mfull-toc +@itemx -mno-fp-in-toc +@itemx -mno-sum-in-toc +@itemx -mminimal-toc +@kindex -mminimal-toc +Modify generation of the TOC (Table Of Contents), which is created for +every executable file. The @samp{-mfull-toc} option is selected by +default. In that case, GCC will allocate at least one TOC entry for +each unique non-automatic variable reference in your program. GCC +will also place floating-point constants in the TOC. However, only +16,384 entries are available in the TOC. + +If you receive a linker error message that saying you have overflowed +the available TOC space, you can reduce the amount of TOC space used +with the @samp{-mno-fp-in-toc} and @samp{-mno-sum-in-toc} options. +@samp{-mno-fp-in-toc} prevents GCC from putting floating-point +constants in the TOC and @samp{-mno-sum-in-toc} forces GCC to +generate code to calculate the sum of an address and a constant at +run-time instead of putting that sum into the TOC. You may specify one +or both of these options. Each causes GCC to produce very slightly +slower and larger code at the expense of conserving TOC space. + +If you still run out of space in the TOC even when you specify both of +these options, specify @samp{-mminimal-toc} instead. This option causes +GCC to make only one TOC entry for every file. When you specify this +option, GCC will produce code that is slower and larger but which +uses extremely little TOC space. You may wish to use this option +only on files that contain less frequently executed code. @refill + +@item -maix64 +@itemx -maix32 +@kindex -maix64 +@kindex -maix32 +Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit +@code{long} type, and the infrastructure needed to support them. +Specifying @samp{-maix64} implies @samp{-mpowerpc64} and +@samp{-mpowerpc}, while @samp{-maix32} disables the 64-bit ABI and +implies @samp{-mno-powerpc64}. GCC defaults to @samp{-maix32}. + +@item -mxl-call +@itemx -mno-xl-call +@kindex -mxl-call +On AIX, pass floating-point arguments to prototyped functions beyond the +register save area (RSA) on the stack in addition to argument FPRs. The +AIX calling convention was extended but not initially documented to +handle an obscure K&R C case of calling a function that takes the +address of its arguments with fewer arguments than declared. AIX XL +compilers access floating point arguments which do not fit in the +RSA from the stack when a subroutine is compiled without +optimization. Because always storing floating-point arguments on the +stack is inefficient and rarely needed, this option is not enabled by +default and only is necessary when calling subroutines compiled by AIX +XL compilers without optimization. + +@item -mthreads +@kindex -mthreads +Support @dfn{AIX Threads}. Link an application written to use +@dfn{pthreads} with special libraries and startup code to enable the +application to run. + +@item -mpe +@kindex -mpe +Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE). Link an +application written to use message passing with special startup code to +enable the application to run. The system must have PE installed in the +standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file +must be overridden with the @samp{-specs=} option to specify the +appropriate directory location. The Parallel Environment does not +support threads, so the @samp{-mpe} option and the @samp{-mthreads} +option are incompatible. + +@item -msoft-float +@itemx -mhard-float +@kindex -msoft-float +Generate code that does not use (uses) the floating-point register set. +Software floating point emulation is provided if you use the +@samp{-msoft-float} option, and pass the option to GCC when linking. + +@item -mmultiple +@itemx -mno-multiple +Generate code that uses (does not use) the load multiple word +instructions and the store multiple word instructions. These +instructions are generated by default on POWER systems, and not +generated on PowerPC systems. Do not use @samp{-mmultiple} on little +endian PowerPC systems, since those instructions do not work when the +processor is in little endian mode. The exceptions are PPC740 and +PPC750 which permit the instructions usage in little endian mode. + +@item -mstring +@itemx -mno-string +@kindex -mstring +Generate code that uses (does not use) the load string instructions +and the store string word instructions to save multiple registers and +do small block moves. These instructions are generated by default on +POWER systems, and not generated on PowerPC systems. Do not use +@samp{-mstring} on little endian PowerPC systems, since those +instructions do not work when the processor is in little endian mode. +The exceptions are PPC740 and PPC750 which permit the instructions +usage in little endian mode. + +@item -mupdate +@itemx -mno-update +@kindex -mupdate +Generate code that uses (does not use) the load or store instructions +that update the base register to the address of the calculated memory +location. These instructions are generated by default. If you use +@samp{-mno-update}, there is a small window between the time that the +stack pointer is updated and the address of the previous frame is +stored, which means code that walks the stack frame across interrupts or +signals may get corrupted data. + +@item -mfused-madd +@itemx -mno-fused-madd +@kindex -mfused-madd +Generate code that uses (does not use) the floating point multiply and +accumulate instructions. These instructions are generated by default if +hardware floating is used. + +@item -mno-bit-align +@itemx -mbit-align +@kindex -mbit-align +On System V.4 and embedded PowerPC systems do not (do) force structures +and unions that contain bit fields to be aligned to the base type of the +bit field. + +For example, by default a structure containing nothing but 8 +@code{unsigned} bitfields of length 1 would be aligned to a 4 byte +boundary and have a size of 4 bytes. By using @samp{-mno-bit-align}, +the structure would be aligned to a 1 byte boundary and be one byte in +size. + +@item -mno-strict-align +@itemx -mstrict-align +@kindex -mstrict-align +On System V.4 and embedded PowerPC systems do not (do) assume that +unaligned memory references will be handled by the system. + +@item -mrelocatable +@itemx -mno-relocatable +@kindex -mrelocatable +On embedded PowerPC systems generate code that allows (does not allow) +the program to be relocated to a different address at runtime. If you +use @samp{-mrelocatable} on any module, all objects linked together must +be compiled with @samp{-mrelocatable} or @samp{-mrelocatable-lib}. + +@item -mrelocatable-lib +@itemx -mno-relocatable-lib +On embedded PowerPC systems generate code that allows (does not allow) +the program to be relocated to a different address at runtime. Modules +compiled with @samp{-mrelocatable-lib} can be linked with either modules +compiled without @samp{-mrelocatable} and @samp{-mrelocatable-lib} or +with modules compiled with the @samp{-mrelocatable} options. + +@item -mno-toc +@itemx -mtoc +On System V.4 and embedded PowerPC systems do not (do) assume that +register 2 contains a pointer to a global area pointing to the addresses +used in the program. + +@item -mlittle +@itemx -mlittle-endian +On System V.4 and embedded PowerPC systems compile code for the +processor in little endian mode. The @samp{-mlittle-endian} option is +the same as @samp{-mlittle}. + +@item -mbig +@itemx -mbig-endian +On System V.4 and embedded PowerPC systems compile code for the +processor in big endian mode. The @samp{-mbig-endian} option is +the same as @samp{-mbig}. + +@item -mcall-sysv +On System V.4 and embedded PowerPC systems compile code using calling +conventions that adheres to the March 1995 draft of the System V +Application Binary Interface, PowerPC processor supplement. This is the +default unless you configured GCC using @samp{powerpc-*-eabiaix}. + +@item -mcall-sysv-eabi +Specify both @samp{-mcall-sysv} and @samp{-meabi} options. + +@item -mcall-sysv-noeabi +Specify both @samp{-mcall-sysv} and @samp{-mno-eabi} options. + +@item -mcall-aix +On System V.4 and embedded PowerPC systems compile code using calling +conventions that are similar to those used on AIX. This is the +default if you configured GCC using @samp{powerpc-*-eabiaix}. + +@item -mcall-solaris +On System V.4 and embedded PowerPC systems compile code for the Solaris +operating system. + +@item -mcall-linux +On System V.4 and embedded PowerPC systems compile code for the +Linux-based GNU system. + +@item -mprototype +@itemx -mno-prototype +On System V.4 and embedded PowerPC systems assume that all calls to +variable argument functions are properly prototyped. Otherwise, the +compiler must insert an instruction before every non prototyped call to +set or clear bit 6 of the condition code register (@var{CR}) to +indicate whether floating point values were passed in the floating point +registers in case the function takes a variable arguments. With +@samp{-mprototype}, only calls to prototyped variable argument functions +will set or clear the bit. + +@item -msim +On embedded PowerPC systems, assume that the startup module is called +@file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and +@file{libc.a}. This is the default for @samp{powerpc-*-eabisim}. +configurations. + +@item -mmvme +On embedded PowerPC systems, assume that the startup module is called +@file{crt0.o} and the standard C libraries are @file{libmvme.a} and +@file{libc.a}. + +@item -mads +On embedded PowerPC systems, assume that the startup module is called +@file{crt0.o} and the standard C libraries are @file{libads.a} and +@file{libc.a}. + +@item -myellowknife +On embedded PowerPC systems, assume that the startup module is called +@file{crt0.o} and the standard C libraries are @file{libyk.a} and +@file{libc.a}. + +@item -mvxworks +On System V.4 and embedded PowerPC systems, specify that you are +compiling for a VxWorks system. + +@item -memb +On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags +header to indicate that @samp{eabi} extended relocations are used. + +@item -meabi +@itemx -mno-eabi +On System V.4 and embedded PowerPC systems do (do not) adhere to the +Embedded Applications Binary Interface (eabi) which is a set of +modifications to the System V.4 specifications. Selecting @option{-meabi} +means that the stack is aligned to an 8 byte boundary, a function +@code{__eabi} is called to from @code{main} to set up the eabi +environment, and the @samp{-msdata} option can use both @code{r2} and +@code{r13} to point to two separate small data areas. Selecting +@option{-mno-eabi} means that the stack is aligned to a 16 byte boundary, +do not call an initialization function from @code{main}, and the +@samp{-msdata} option will only use @code{r13} to point to a single +small data area. The @samp{-meabi} option is on by default if you +configured GCC using one of the @samp{powerpc*-*-eabi*} options. + +@item -msdata=eabi +On System V.4 and embedded PowerPC systems, put small initialized +@code{const} global and static data in the @samp{.sdata2} section, which +is pointed to by register @code{r2}. Put small initialized +non-@code{const} global and static data in the @samp{.sdata} section, +which is pointed to by register @code{r13}. Put small uninitialized +global and static data in the @samp{.sbss} section, which is adjacent to +the @samp{.sdata} section. The @samp{-msdata=eabi} option is +incompatible with the @samp{-mrelocatable} option. The +@samp{-msdata=eabi} option also sets the @samp{-memb} option. + +@item -msdata=sysv +On System V.4 and embedded PowerPC systems, put small global and static +data in the @samp{.sdata} section, which is pointed to by register +@code{r13}. Put small uninitialized global and static data in the +@samp{.sbss} section, which is adjacent to the @samp{.sdata} section. +The @samp{-msdata=sysv} option is incompatible with the +@samp{-mrelocatable} option. + +@item -msdata=default +@itemx -msdata +On System V.4 and embedded PowerPC systems, if @samp{-meabi} is used, +compile code the same as @samp{-msdata=eabi}, otherwise compile code the +same as @samp{-msdata=sysv}. + +@item -msdata-data +On System V.4 and embedded PowerPC systems, put small global and static +data in the @samp{.sdata} section. Put small uninitialized global and +static data in the @samp{.sbss} section. Do not use register @code{r13} +to address small data however. This is the default behavior unless +other @samp{-msdata} options are used. + +@item -msdata=none +@itemx -mno-sdata +On embedded PowerPC systems, put all initialized global and static data +in the @samp{.data} section, and all uninitialized data in the +@samp{.bss} section. + +@item -G @var{num} +@cindex smaller data references (PowerPC) +@cindex .sdata/.sdata2 references (PowerPC) +On embedded PowerPC systems, put global and static items less than or +equal to @var{num} bytes into the small data or bss sections instead of +the normal data or bss section. By default, @var{num} is 8. The +@samp{-G @var{num}} switch is also passed to the linker. +All modules should be compiled with the same @samp{-G @var{num}} value. + +@item -mregnames +@itemx -mno-regnames +On System V.4 and embedded PowerPC systems do (do not) emit register +names in the assembly language output using symbolic forms. + +@end table + +@node RT Options +@subsection IBM RT Options +@cindex RT options +@cindex IBM RT options + +These @samp{-m} options are defined for the IBM RT PC: + +@table @gcctabopt +@item -min-line-mul +Use an in-line code sequence for integer multiplies. This is the +default. + +@item -mcall-lib-mul +Call @code{lmul$$} for integer multiples. + +@item -mfull-fp-blocks +Generate full-size floating point data blocks, including the minimum +amount of scratch space recommended by IBM. This is the default. + +@item -mminimum-fp-blocks +Do not include extra scratch space in floating point data blocks. This +results in smaller code, but slower execution, since scratch space must +be allocated dynamically. + +@cindex @file{varargs.h} and RT PC +@cindex @file{stdarg.h} and RT PC +@item -mfp-arg-in-fpregs +Use a calling sequence incompatible with the IBM calling convention in +which floating point arguments are passed in floating point registers. +Note that @code{varargs.h} and @code{stdargs.h} will not work with +floating point operands if this option is specified. + +@item -mfp-arg-in-gregs +Use the normal calling convention for floating point arguments. This is +the default. + +@item -mhc-struct-return +Return structures of more than one word in memory, rather than in a +register. This provides compatibility with the MetaWare HighC (hc) +compiler. Use the option @samp{-fpcc-struct-return} for compatibility +with the Portable C Compiler (pcc). + +@item -mnohc-struct-return +Return some structures of more than one word in registers, when +convenient. This is the default. For compatibility with the +IBM-supplied compilers, use the option @samp{-fpcc-struct-return} or the +option @samp{-mhc-struct-return}. +@end table + +@node MIPS Options +@subsection MIPS Options +@cindex MIPS options + +These @samp{-m} options are defined for the MIPS family of computers: + +@table @gcctabopt +@item -mcpu=@var{cpu type} +Assume the defaults for the machine type @var{cpu type} when scheduling +instructions. The choices for @var{cpu type} are @samp{r2000}, @samp{r3000}, +@samp{r3900}, @samp{r4000}, @samp{r4100}, @samp{r4300}, @samp{r4400}, +@samp{r4600}, @samp{r4650}, @samp{r5000}, @samp{r6000}, @samp{r8000}, +and @samp{orion}. Additionally, the @samp{r2000}, @samp{r3000}, +@samp{r4000}, @samp{r5000}, and @samp{r6000} can be abbreviated as +@samp{r2k} (or @samp{r2K}), @samp{r3k}, etc. While picking a specific +@var{cpu type} will schedule things appropriately for that particular +chip, the compiler will not generate any code that does not meet level 1 +of the MIPS ISA (instruction set architecture) without a @samp{-mipsX} +or @samp{-mabi} switch being used. + +@item -mips1 +Issue instructions from level 1 of the MIPS ISA. This is the default. +@samp{r3000} is the default @var{cpu type} at this ISA level. + +@item -mips2 +Issue instructions from level 2 of the MIPS ISA (branch likely, square +root instructions). @samp{r6000} is the default @var{cpu type} at this +ISA level. + +@item -mips3 +Issue instructions from level 3 of the MIPS ISA (64-bit instructions). +@samp{r4000} is the default @var{cpu type} at this ISA level. + +@item -mips4 +Issue instructions from level 4 of the MIPS ISA (conditional move, +prefetch, enhanced FPU instructions). @samp{r8000} is the default +@var{cpu type} at this ISA level. + +@item -mfp32 +Assume that 32 32-bit floating point registers are available. This is +the default. + +@item -mfp64 +Assume that 32 64-bit floating point registers are available. This is +the default when the @samp{-mips3} option is used. + +@item -mgp32 +Assume that 32 32-bit general purpose registers are available. This is +the default. + +@item -mgp64 +Assume that 32 64-bit general purpose registers are available. This is +the default when the @samp{-mips3} option is used. + +@item -mint64 +Force int and long types to be 64 bits wide. See @samp{-mlong32} for an +explanation of the default, and the width of pointers. + +@item -mlong64 +Force long types to be 64 bits wide. See @samp{-mlong32} for an +explanation of the default, and the width of pointers. + +@item -mlong32 +Force long, int, and pointer types to be 32 bits wide. + +If none of @samp{-mlong32}, @samp{-mlong64}, or @samp{-mint64} are set, +the size of ints, longs, and pointers depends on the ABI and ISA chosen. +For @samp{-mabi=32}, and @samp{-mabi=n32}, ints and longs are 32 bits +wide. For @samp{-mabi=64}, ints are 32 bits, and longs are 64 bits wide. +For @samp{-mabi=eabi} and either @samp{-mips1} or @samp{-mips2}, ints +and longs are 32 bits wide. For @samp{-mabi=eabi} and higher ISAs, ints +are 32 bits, and longs are 64 bits wide. The width of pointer types is +the smaller of the width of longs or the width of general purpose +registers (which in turn depends on the ISA). + +@item -mabi=32 +@itemx -mabi=o64 +@itemx -mabi=n32 +@itemx -mabi=64 +@itemx -mabi=eabi +Generate code for the indicated ABI. The default instruction level is +@samp{-mips1} for @samp{32}, @samp{-mips3} for @samp{n32}, and +@samp{-mips4} otherwise. Conversely, with @samp{-mips1} or +@samp{-mips2}, the default ABI is @samp{32}; otherwise, the default ABI +is @samp{64}. + +@item -mmips-as +Generate code for the MIPS assembler, and invoke @file{mips-tfile} to +add normal debug information. This is the default for all +platforms except for the OSF/1 reference platform, using the OSF/rose +object format. If the either of the @samp{-gstabs} or @samp{-gstabs+} +switches are used, the @file{mips-tfile} program will encapsulate the +stabs within MIPS ECOFF. + +@item -mgas +Generate code for the GNU assembler. This is the default on the OSF/1 +reference platform, using the OSF/rose object format. Also, this is +the default if the configure option @samp{--with-gnu-as} is used. + +@item -msplit-addresses +@itemx -mno-split-addresses +Generate code to load the high and low parts of address constants separately. +This allows @code{gcc} to optimize away redundant loads of the high order +bits of addresses. This optimization requires GNU as and GNU ld. +This optimization is enabled by default for some embedded targets where +GNU as and GNU ld are standard. + +@item -mrnames +@itemx -mno-rnames +The @samp{-mrnames} switch says to output code using the MIPS software +names for the registers, instead of the hardware names (ie, @var{a0} +instead of @var{$4}). The only known assembler that supports this option +is the Algorithmics assembler. + +@item -mgpopt +@itemx -mno-gpopt +The @samp{-mgpopt} switch says to write all of the data declarations +before the instructions in the text section, this allows the MIPS +assembler to generate one word memory references instead of using two +words for short global or static data items. This is on by default if +optimization is selected. + +@item -mstats +@itemx -mno-stats +For each non-inline function processed, the @samp{-mstats} switch +causes the compiler to emit one line to the standard error file to +print statistics about the program (number of registers saved, stack +size, etc.). + +@item -mmemcpy +@itemx -mno-memcpy +The @samp{-mmemcpy} switch makes all block moves call the appropriate +string function (@samp{memcpy} or @samp{bcopy}) instead of possibly +generating inline code. + +@item -mmips-tfile +@itemx -mno-mips-tfile +The @samp{-mno-mips-tfile} switch causes the compiler not +postprocess the object file with the @file{mips-tfile} program, +after the MIPS assembler has generated it to add debug support. If +@file{mips-tfile} is not run, then no local variables will be +available to the debugger. In addition, @file{stage2} and +@file{stage3} objects will have the temporary file names passed to the +assembler embedded in the object file, which means the objects will +not compare the same. The @samp{-mno-mips-tfile} switch should only +be used when there are bugs in the @file{mips-tfile} program that +prevents compilation. + +@item -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not part of GCC. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. + +@item -mhard-float +Generate output containing floating point instructions. This is the +default if you use the unmodified sources. + +@item -mabicalls +@itemx -mno-abicalls +Emit (or do not emit) the pseudo operations @samp{.abicalls}, +@samp{.cpload}, and @samp{.cprestore} that some System V.4 ports use for +position independent code. + +@item -mlong-calls +@itemx -mno-long-calls +Do all calls with the @samp{JALR} instruction, which requires +loading up a function's address into a register before the call. +You need to use this switch, if you call outside of the current +512 megabyte segment to functions that are not through pointers. + +@item -mhalf-pic +@itemx -mno-half-pic +Put pointers to extern references into the data section and load them +up, rather than put the references in the text section. + +@item -membedded-pic +@itemx -mno-embedded-pic +Generate PIC code suitable for some embedded systems. All calls are +made using PC relative address, and all data is addressed using the $gp +register. No more than 65536 bytes of global data may be used. This +requires GNU as and GNU ld which do most of the work. This currently +only works on targets which use ECOFF; it does not work with ELF. + +@item -membedded-data +@itemx -mno-embedded-data +Allocate variables to the read-only data section first if possible, then +next in the small data section if possible, otherwise in data. This gives +slightly slower code than the default, but reduces the amount of RAM required +when executing, and thus may be preferred for some embedded systems. + +@item -muninit-const-in-rodata +@itemx -mno-uninit-const-in-rodata +When used together with -membedded-data, it will always store uninitialized +const variables in the read-only data section. + +@item -msingle-float +@itemx -mdouble-float +The @samp{-msingle-float} switch tells gcc to assume that the floating +point coprocessor only supports single precision operations, as on the +@samp{r4650} chip. The @samp{-mdouble-float} switch permits gcc to use +double precision operations. This is the default. + +@item -mmad +@itemx -mno-mad +Permit use of the @samp{mad}, @samp{madu} and @samp{mul} instructions, +as on the @samp{r4650} chip. + +@item -m4650 +Turns on @samp{-msingle-float}, @samp{-mmad}, and, at least for now, +@samp{-mcpu=r4650}. + +@item -mips16 +@itemx -mno-mips16 +Enable 16-bit instructions. + +@item -mentry +Use the entry and exit pseudo ops. This option can only be used with +@samp{-mips16}. + +@item -EL +Compile code for the processor in little endian mode. +The requisite libraries are assumed to exist. + +@item -EB +Compile code for the processor in big endian mode. +The requisite libraries are assumed to exist. + +@item -G @var{num} +@cindex smaller data references (MIPS) +@cindex gp-relative references (MIPS) +Put global and static items less than or equal to @var{num} bytes into +the small data or bss sections instead of the normal data or bss +section. This allows the assembler to emit one word memory reference +instructions based on the global pointer (@var{gp} or @var{$28}), +instead of the normal two words used. By default, @var{num} is 8 when +the MIPS assembler is used, and 0 when the GNU assembler is used. The +@samp{-G @var{num}} switch is also passed to the assembler and linker. +All modules should be compiled with the same @samp{-G @var{num}} +value. + +@item -nocpp +Tell the MIPS assembler to not run its preprocessor over user +assembler files (with a @samp{.s} suffix) when assembling them. + +@item -mfix7000 +Pass an option to gas which will cause nops to be inserted if +the read of the destination register of an mfhi or mflo instruction +occurs in the following two instructions. + +@item -no-crt0 +Do not include the default crt0. +@end table + +@ifset INTERNALS +These options are defined by the macro +@code{TARGET_SWITCHES} in the machine description. The default for the +options is also defined by that macro, which enables you to change the +defaults. +@end ifset + +@node i386 Options +@subsection Intel 386 Options +@cindex i386 Options +@cindex Intel 386 Options + +These @samp{-m} options are defined for the i386 family of computers: + +@table @gcctabopt +@item -mcpu=@var{cpu type} +Assume the defaults for the machine type @var{cpu type} when scheduling +instructions. The choices for @var{cpu type} are @samp{i386}, +@samp{i486}, @samp{i586}, @samp{i686}, @samp{pentium}, +@samp{pentiumpro}, @samp{pentium4}, @samp{k6}, and @samp{athlon} + +While picking a specific @var{cpu type} will schedule things appropriately +for that particular chip, the compiler will not generate any code that +does not run on the i386 without the @samp{-march=@var{cpu type}} option +being used. @samp{i586} is equivalent to @samp{pentium} and @samp{i686} +is equivalent to @samp{pentiumpro}. @samp{k6} and @samp{athlon} are the +AMD chips as opposed to the Intel ones. + +@item -march=@var{cpu type} +Generate instructions for the machine type @var{cpu type}. The choices +for @var{cpu type} are the same as for @samp{-mcpu}. Moreover, +specifying @samp{-march=@var{cpu type}} implies @samp{-mcpu=@var{cpu type}}. + +@item -m386 +@itemx -m486 +@itemx -mpentium +@itemx -mpentiumpro +Synonyms for -mcpu=i386, -mcpu=i486, -mcpu=pentium, and -mcpu=pentiumpro +respectively. These synonyms are deprecated. + +@item -mintel-syntax +Emit assembly using Intel syntax opcodes instead of AT&T syntax. + +@item -mieee-fp +@itemx -mno-ieee-fp +Control whether or not the compiler uses IEEE floating point +comparisons. These handle correctly the case where the result of a +comparison is unordered. + +@item -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not part of GCC. +Normally the facilities of the machine's usual C compiler are used, but +this can't be done directly in cross-compilation. You must make your +own arrangements to provide suitable library functions for +cross-compilation. + +On machines where a function returns floating point results in the 80387 +register stack, some floating point opcodes may be emitted even if +@samp{-msoft-float} is used. + +@item -mno-fp-ret-in-387 +Do not use the FPU registers for return values of functions. + +The usual calling convention has functions return values of types +@code{float} and @code{double} in an FPU register, even if there +is no FPU. The idea is that the operating system should emulate +an FPU. + +The option @samp{-mno-fp-ret-in-387} causes such values to be returned +in ordinary CPU registers instead. + +@item -mno-fancy-math-387 +Some 387 emulators do not support the @code{sin}, @code{cos} and +@code{sqrt} instructions for the 387. Specify this option to avoid +generating those instructions. This option is the default on FreeBSD. +As of revision 2.6.1, these instructions are not generated unless you +also use the @samp{-funsafe-math-optimizations} switch. + +@item -malign-double +@itemx -mno-align-double +Control whether GCC aligns @code{double}, @code{long double}, and +@code{long long} variables on a two word boundary or a one word +boundary. Aligning @code{double} variables on a two word boundary will +produce code that runs somewhat faster on a @samp{Pentium} at the +expense of more memory. + +@item -m128bit-long-double +@itemx -m128bit-long-double +Control the size of @code{long double} type. i386 application binary interface +specify the size to be 12 bytes, while modern architectures (Pentium and newer) +preffer @code{long double} aligned to 8 or 16 byte boundary. This is +impossible to reach with 12 byte long doubles in the array accesses. + +@strong{Warning:} if you use the @samp{-m128bit-long-double} switch, the +structures and arrays containing @code{long double} will change their size as +well as function calling convention for function taking @code{long double} +will be modified. + +@item -m96bit-long-double +@itemx -m96bit-long-double +Set the size of @code{long double} to 96 bits as required by the i386 +application binary interface. This is the default. + +@item -msvr3-shlib +@itemx -mno-svr3-shlib +Control whether GCC places uninitialized locals into @code{bss} or +@code{data}. @samp{-msvr3-shlib} places these locals into @code{bss}. +These options are meaningful only on System V Release 3. + +@item -mno-wide-multiply +@itemx -mwide-multiply +Control whether GCC uses the @code{mul} and @code{imul} that produce +64-bit results in @code{eax:edx} from 32-bit operands to do @code{long +long} multiplies and 32-bit division by constants. + +@item -mrtd +Use a different function-calling convention, in which functions that +take a fixed number of arguments return with the @code{ret} @var{num} +instruction, which pops their arguments while returning. This saves one +instruction in the caller since there is no need to pop the arguments +there. + +You can specify that an individual function is called with this calling +sequence with the function attribute @samp{stdcall}. You can also +override the @samp{-mrtd} option by using the function attribute +@samp{cdecl}. @xref{Function Attributes}. + +@strong{Warning:} this calling convention is incompatible with the one +normally used on Unix, so you cannot use it if you need to call +libraries compiled with the Unix compiler. + +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including @code{printf}); +otherwise incorrect code will be generated for calls to those +functions. + +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) + +@item -mregparm=@var{num} +Control how many registers are used to pass integer arguments. By +default, no registers are used to pass arguments, and at most 3 +registers can be used. You can control this behavior for a specific +function by using the function attribute @samp{regparm}. +@xref{Function Attributes}. + +@strong{Warning:} if you use this switch, and +@var{num} is nonzero, then you must build all modules with the same +value, including any libraries. This includes the system libraries and +startup modules. + +@item -mpreferred-stack-boundary=@var{num} +Attempt to keep the stack boundary aligned to a 2 raised to @var{num} +byte boundary. If @samp{-mpreferred-stack-boundary} is not specified, +the default is 4 (16 bytes or 128 bits). + +The stack is required to be aligned on a 4 byte boundary. On Pentium +and PentiumPro, @code{double} and @code{long double} values should be +aligned to an 8 byte boundary (see @samp{-malign-double}) or suffer +significant run time performance penalties. On Pentium III, the +Streaming SIMD Extension (SSE) data type @code{__m128} suffers similar +penalties if it is not 16 byte aligned. + +To ensure proper alignment of this values on the stack, the stack boundary +must be as aligned as that required by any value stored on the stack. +Further, every function must be generated such that it keeps the stack +aligned. Thus calling a function compiled with a higher preferred +stack boundary from a function compiled with a lower preferred stack +boundary will most likely misalign the stack. It is recommended that +libraries that use callbacks always use the default setting. + +This extra alignment does consume extra stack space. Code that is sensitive +to stack space usage, such as embedded systems and operating system kernels, +may want to reduce the preferred alignment to +@samp{-mpreferred-stack-boundary=2}. + +@item -mpush-args +@kindex -mpush-args +Use PUSH operations to store outgoing parameters. This method is shorter +and usually equally fast as method using SUB/MOV operations and is enabled +by default. In some cases disabling it may improve performance because of +improved scheduling and reduced dependencies. + +@item -maccumulate-outgoing-args +@kindex -maccumulate-outgoing-args +If enabled, the maximum amount of space required for outgoing arguments will be +computed in the function prologue. This in faster on most modern CPUs +because of reduced dependencies, improved scheduling and reduced stack usage +when preferred stack boundary is not equal to 2. The drawback is a notable +increase in code size. This switch implies -mno-push-args. + +@item -mthreads +@kindex -mthreads +Support thread-safe exception handling on @samp{Mingw32}. Code that relies +on thread-safe exception handling must compile and link all code with the +@samp{-mthreads} option. When compiling, @samp{-mthreads} defines +@samp{-D_MT}; when linking, it links in a special thread helper library +@samp{-lmingwthrd} which cleans up per thread exception handling data. + +@item -mno-align-stringops +@kindex -mno-align-stringops +Do not align destination of inlined string operations. This switch reduces +code size and improves performance in case the destination is already aligned, +but gcc don't know about it. + +@item -minline-all-stringops +@kindex -minline-all-stringops +By default GCC inlines string operations only when destination is known to be +aligned at least to 4 byte boundary. This enables more inlining, increase code +size, but may improve performance of code that depends on fast memcpy, strlen +and memset for short lengths. + +@item -momit-leaf-frame-pointer +@kindex -momit-leaf-frame-pointer +Don't keep the frame pointer in a register for leaf functions. This +avoids the instructions to save, set up and restore frame pointers and +makes an extra register available in leaf functions. The option +@samp{-fomit-frame-pointer} removes the frame pointer for all functions +which might make debugging harder. +@end table + +@node HPPA Options +@subsection HPPA Options +@cindex HPPA Options + +These @samp{-m} options are defined for the HPPA family of computers: + +@table @gcctabopt +@item -march=@var{architecture type} +Generate code for the specified architecture. The choices for +@var{architecture type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA +1.1, and @samp{2.0} for PA 2.0 processors. Refer to +@file{/usr/lib/sched.models} on an HP-UX system to determine the proper +architecture option for your machine. Code compiled for lower numbered +architectures will run on higher numbered architectures, but not the +other way around. + +PA 2.0 support currently requires gas snapshot 19990413 or later. The +next release of binutils (current is 2.9.1) will probably contain PA 2.0 +support. + +@item -mpa-risc-1-0 +@itemx -mpa-risc-1-1 +@itemx -mpa-risc-2-0 +Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively. + +@item -mbig-switch +Generate code suitable for big switch tables. Use this option only if +the assembler/linker complain about out of range branches within a switch +table. + +@item -mjump-in-delay +Fill delay slots of function calls with unconditional jump instructions +by modifying the return pointer for the function call to be the target +of the conditional jump. + +@item -mdisable-fpregs +Prevent floating point registers from being used in any manner. This is +necessary for compiling kernels which perform lazy context switching of +floating point registers. If you use this option and attempt to perform +floating point operations, the compiler will abort. + +@item -mdisable-indexing +Prevent the compiler from using indexing address modes. This avoids some +rather obscure problems when compiling MIG generated code under MACH. + +@item -mno-space-regs +Generate code that assumes the target has no space registers. This allows +GCC to generate faster indirect calls and use unscaled index address modes. + +Such code is suitable for level 0 PA systems and kernels. + +@item -mfast-indirect-calls +Generate code that assumes calls never cross space boundaries. This +allows GCC to emit code which performs faster indirect calls. + +This option will not work in the presence of shared libraries or nested +functions. + +@item -mlong-load-store +Generate 3-instruction load and store sequences as sometimes required by +the HP-UX 10 linker. This is equivalent to the @samp{+k} option to +the HP compilers. + +@item -mportable-runtime +Use the portable calling conventions proposed by HP for ELF systems. + +@item -mgas +Enable the use of assembler directives only GAS understands. + +@item -mschedule=@var{cpu type} +Schedule code according to the constraints for the machine type +@var{cpu type}. The choices for @var{cpu type} are @samp{700} +@samp{7100}, @samp{7100LC}, @samp{7200}, and @samp{8000}. Refer to +@file{/usr/lib/sched.models} on an HP-UX system to determine the +proper scheduling option for your machine. + +@item -mlinker-opt +Enable the optimization pass in the HPUX linker. Note this makes symbolic +debugging impossible. It also triggers a bug in the HPUX 8 and HPUX 9 linkers +in which they give bogus error messages when linking some programs. + +@item -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries are not available for all HPPA +targets. Normally the facilities of the machine's usual C compiler are +used, but this cannot be done directly in cross-compilation. You must make +your own arrangements to provide suitable library functions for +cross-compilation. The embedded target @samp{hppa1.1-*-pro} +does provide software floating point support. + +@samp{-msoft-float} changes the calling convention in the output file; +therefore, it is only useful if you compile @emph{all} of a program with +this option. In particular, you need to compile @file{libgcc.a}, the +library that comes with GCC, with @samp{-msoft-float} in order for +this to work. +@end table + +@node Intel 960 Options +@subsection Intel 960 Options + +These @samp{-m} options are defined for the Intel 960 implementations: + +@table @gcctabopt +@item -m@var{cpu type} +Assume the defaults for the machine type @var{cpu type} for some of +the other options, including instruction scheduling, floating point +support, and addressing modes. The choices for @var{cpu type} are +@samp{ka}, @samp{kb}, @samp{mc}, @samp{ca}, @samp{cf}, +@samp{sa}, and @samp{sb}. +The default is +@samp{kb}. + +@item -mnumerics +@itemx -msoft-float +The @samp{-mnumerics} option indicates that the processor does support +floating-point instructions. The @samp{-msoft-float} option indicates +that floating-point support should not be assumed. + +@item -mleaf-procedures +@itemx -mno-leaf-procedures +Do (or do not) attempt to alter leaf procedures to be callable with the +@code{bal} instruction as well as @code{call}. This will result in more +efficient code for explicit calls when the @code{bal} instruction can be +substituted by the assembler or linker, but less efficient code in other +cases, such as calls via function pointers, or using a linker that doesn't +support this optimization. + +@item -mtail-call +@itemx -mno-tail-call +Do (or do not) make additional attempts (beyond those of the +machine-independent portions of the compiler) to optimize tail-recursive +calls into branches. You may not want to do this because the detection of +cases where this is not valid is not totally complete. The default is +@samp{-mno-tail-call}. + +@item -mcomplex-addr +@itemx -mno-complex-addr +Assume (or do not assume) that the use of a complex addressing mode is a +win on this implementation of the i960. Complex addressing modes may not +be worthwhile on the K-series, but they definitely are on the C-series. +The default is currently @samp{-mcomplex-addr} for all processors except +the CB and CC. + +@item -mcode-align +@itemx -mno-code-align +Align code to 8-byte boundaries for faster fetching (or don't bother). +Currently turned on by default for C-series implementations only. + +@ignore +@item -mclean-linkage +@itemx -mno-clean-linkage +These options are not fully implemented. +@end ignore + +@item -mic-compat +@itemx -mic2.0-compat +@itemx -mic3.0-compat +Enable compatibility with iC960 v2.0 or v3.0. + +@item -masm-compat +@itemx -mintel-asm +Enable compatibility with the iC960 assembler. + +@item -mstrict-align +@itemx -mno-strict-align +Do not permit (do permit) unaligned accesses. + +@item -mold-align +Enable structure-alignment compatibility with Intel's gcc release version +1.3 (based on gcc 1.37). This option implies @samp{-mstrict-align}. + +@item -mlong-double-64 +Implement type @samp{long double} as 64-bit floating point numbers. +Without the option @samp{long double} is implemented by 80-bit +floating point numbers. The only reason we have it because there is +no 128-bit @samp{long double} support in @samp{fp-bit.c} yet. So it +is only useful for people using soft-float targets. Otherwise, we +should recommend against use of it. + +@end table + +@node DEC Alpha Options +@subsection DEC Alpha Options + +These @samp{-m} options are defined for the DEC Alpha implementations: + +@table @gcctabopt +@item -mno-soft-float +@itemx -msoft-float +Use (do not use) the hardware floating-point instructions for +floating-point operations. When @option{-msoft-float} is specified, +functions in @file{libgcc.a} will be used to perform floating-point +operations. Unless they are replaced by routines that emulate the +floating-point operations, or compiled in such a way as to call such +emulations routines, these routines will issue floating-point +operations. If you are compiling for an Alpha without floating-point +operations, you must ensure that the library is built so as not to call +them. + +Note that Alpha implementations without floating-point operations are +required to have floating-point registers. + +@item -mfp-reg +@itemx -mno-fp-regs +Generate code that uses (does not use) the floating-point register set. +@option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point +register set is not used, floating point operands are passed in integer +registers as if they were integers and floating-point results are passed +in $0 instead of $f0. This is a non-standard calling sequence, so any +function with a floating-point argument or return value called by code +compiled with @option{-mno-fp-regs} must also be compiled with that +option. + +A typical use of this option is building a kernel that does not use, +and hence need not save and restore, any floating-point registers. + +@item -mieee +The Alpha architecture implements floating-point hardware optimized for +maximum performance. It is mostly compliant with the IEEE floating +point standard. However, for full compliance, software assistance is +required. This option generates code fully IEEE compliant code +@emph{except} that the @var{inexact flag} is not maintained (see below). +If this option is turned on, the CPP macro @code{_IEEE_FP} is defined +during compilation. The option is a shorthand for: @samp{-D_IEEE_FP +-mfp-trap-mode=su -mtrap-precision=i -mieee-conformant}. The resulting +code is less efficient but is able to correctly support denormalized +numbers and exceptional IEEE values such as not-a-number and plus/minus +infinity. Other Alpha compilers call this option +@option{-ieee_with_no_inexact}. + +@item -mieee-with-inexact +@c overfull hbox here --bob 22 jul96 +@c original text between ignore ... end ignore +@ignore +This is like @samp{-mieee} except the generated code also maintains the +IEEE @var{inexact flag}. Turning on this option causes the generated +code to implement fully-compliant IEEE math. The option is a shorthand +for @samp{-D_IEEE_FP -D_IEEE_FP_INEXACT} plus @samp{-mieee-conformant}, +@samp{-mfp-trap-mode=sui}, and @samp{-mtrap-precision=i}. On some Alpha +implementations the resulting code may execute significantly slower than +the code generated by default. Since there is very little code that +depends on the @var{inexact flag}, you should normally not specify this +option. Other Alpha compilers call this option +@samp{-ieee_with_inexact}. +@end ignore +@c changed paragraph +This is like @samp{-mieee} except the generated code also maintains the +IEEE @var{inexact flag}. Turning on this option causes the generated +code to implement fully-compliant IEEE math. The option is a shorthand +for @samp{-D_IEEE_FP -D_IEEE_FP_INEXACT} plus the three following: +@samp{-mieee-conformant}, +@samp{-mfp-trap-mode=sui}, +and @samp{-mtrap-precision=i}. +On some Alpha implementations the resulting code may execute +significantly slower than the code generated by default. Since there +is very little code that depends on the @var{inexact flag}, you should +normally not specify this option. Other Alpha compilers call this +option @samp{-ieee_with_inexact}. +@c end changes to prevent overfull hboxes + +@item -mfp-trap-mode=@var{trap mode} +This option controls what floating-point related traps are enabled. +Other Alpha compilers call this option @samp{-fptm }@var{trap mode}. +The trap mode can be set to one of four values: + +@table @samp +@item n +This is the default (normal) setting. The only traps that are enabled +are the ones that cannot be disabled in software (e.g., division by zero +trap). + +@item u +In addition to the traps enabled by @samp{n}, underflow traps are enabled +as well. + +@item su +Like @samp{su}, but the instructions are marked to be safe for software +completion (see Alpha architecture manual for details). + +@item sui +Like @samp{su}, but inexact traps are enabled as well. +@end table + +@item -mfp-rounding-mode=@var{rounding mode} +Selects the IEEE rounding mode. Other Alpha compilers call this option +@samp{-fprm }@var{rounding mode}. The @var{rounding mode} can be one +of: + +@table @samp +@item n +Normal IEEE rounding mode. Floating point numbers are rounded towards +the nearest machine number or towards the even machine number in case +of a tie. + +@item m +Round towards minus infinity. + +@item c +Chopped rounding mode. Floating point numbers are rounded towards zero. + +@item d +Dynamic rounding mode. A field in the floating point control register +(@var{fpcr}, see Alpha architecture reference manual) controls the +rounding mode in effect. The C library initializes this register for +rounding towards plus infinity. Thus, unless your program modifies the +@var{fpcr}, @samp{d} corresponds to round towards plus infinity. +@end table + +@item -mtrap-precision=@var{trap precision} +In the Alpha architecture, floating point traps are imprecise. This +means without software assistance it is impossible to recover from a +floating trap and program execution normally needs to be terminated. +GCC can generate code that can assist operating system trap handlers +in determining the exact location that caused a floating point trap. +Depending on the requirements of an application, different levels of +precisions can be selected: + +@table @samp +@item p +Program precision. This option is the default and means a trap handler +can only identify which program caused a floating point exception. + +@item f +Function precision. The trap handler can determine the function that +caused a floating point exception. + +@item i +Instruction precision. The trap handler can determine the exact +instruction that caused a floating point exception. +@end table + +Other Alpha compilers provide the equivalent options called +@samp{-scope_safe} and @samp{-resumption_safe}. + +@item -mieee-conformant +This option marks the generated code as IEEE conformant. You must not +use this option unless you also specify @samp{-mtrap-precision=i} and either +@samp{-mfp-trap-mode=su} or @samp{-mfp-trap-mode=sui}. Its only effect +is to emit the line @samp{.eflag 48} in the function prologue of the +generated assembly file. Under DEC Unix, this has the effect that +IEEE-conformant math library routines will be linked in. + +@item -mbuild-constants +Normally GCC examines a 32- or 64-bit integer constant to +see if it can construct it from smaller constants in two or three +instructions. If it cannot, it will output the constant as a literal and +generate code to load it from the data segment at runtime. + +Use this option to require GCC to construct @emph{all} integer constants +using code, even if it takes more instructions (the maximum is six). + +You would typically use this option to build a shared library dynamic +loader. Itself a shared library, it must relocate itself in memory +before it can find the variables and constants in its own data segment. + +@item -malpha-as +@itemx -mgas +Select whether to generate code to be assembled by the vendor-supplied +assembler (@samp{-malpha-as}) or by the GNU assembler @samp{-mgas}. + +@item -mbwx +@itemx -mno-bwx +@itemx -mcix +@itemx -mno-cix +@itemx -mmax +@itemx -mno-max +Indicate whether GCC should generate code to use the optional BWX, +CIX, and MAX instruction sets. The default is to use the instruction sets +supported by the CPU type specified via @samp{-mcpu=} option or that +of the CPU on which GCC was built if none was specified. + +@item -mcpu=@var{cpu_type} +Set the instruction set, register set, and instruction scheduling +parameters for machine type @var{cpu_type}. You can specify either the +@samp{EV} style name or the corresponding chip number. GCC +supports scheduling parameters for the EV4 and EV5 family of processors +and will choose the default values for the instruction set from +the processor you specify. If you do not specify a processor type, +GCC will default to the processor on which the compiler was built. + +Supported values for @var{cpu_type} are + +@table @samp +@item ev4 +@itemx 21064 +Schedules as an EV4 and has no instruction set extensions. + +@item ev5 +@itemx 21164 +Schedules as an EV5 and has no instruction set extensions. + +@item ev56 +@itemx 21164a +Schedules as an EV5 and supports the BWX extension. + +@item pca56 +@itemx 21164pc +@itemx 21164PC +Schedules as an EV5 and supports the BWX and MAX extensions. + +@item ev6 +@itemx 21264 +Schedules as an EV5 (until Digital releases the scheduling parameters +for the EV6) and supports the BWX, CIX, and MAX extensions. +@end table + +@item -mmemory-latency=@var{time} +Sets the latency the scheduler should assume for typical memory +references as seen by the application. This number is highly +dependent on the memory access patterns used by the application +and the size of the external cache on the machine. + +Valid options for @var{time} are + +@table @samp +@item @var{number} +A decimal number representing clock cycles. + +@item L1 +@itemx L2 +@itemx L3 +@itemx main +The compiler contains estimates of the number of clock cycles for +``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches +(also called Dcache, Scache, and Bcache), as well as to main memory. +Note that L3 is only valid for EV5. + +@end table +@end table + +@node Clipper Options +@subsection Clipper Options + +These @samp{-m} options are defined for the Clipper implementations: + +@table @gcctabopt +@item -mc300 +Produce code for a C300 Clipper processor. This is the default. + +@item -mc400 +Produce code for a C400 Clipper processor i.e. use floating point +registers f8..f15. +@end table + +@node H8/300 Options +@subsection H8/300 Options + +These @samp{-m} options are defined for the H8/300 implementations: + +@table @gcctabopt +@item -mrelax +Shorten some address references at link time, when possible; uses the +linker option @samp{-relax}. @xref{H8/300,, @code{ld} and the H8/300, +ld.info, Using ld}, for a fuller description. + +@item -mh +Generate code for the H8/300H. + +@item -ms +Generate code for the H8/S. + +@item -ms2600 +Generate code for the H8/S2600. This switch must be used with -ms. + +@item -mint32 +Make @code{int} data 32 bits by default. + +@item -malign-300 +On the H8/300H and H8/S, use the same alignment rules as for the H8/300. +The default for the H8/300H and H8/S is to align longs and floats on 4 +byte boundaries. +@samp{-malign-300} causes them to be aligned on 2 byte boundaries. +This option has no effect on the H8/300. +@end table + +@node SH Options +@subsection SH Options + +These @samp{-m} options are defined for the SH implementations: + +@table @gcctabopt +@item -m1 +Generate code for the SH1. + +@item -m2 +Generate code for the SH2. + +@item -m3 +Generate code for the SH3. + +@item -m3e +Generate code for the SH3e. + +@item -m4-nofpu +Generate code for the SH4 without a floating-point unit. + +@item -m4-single-only +Generate code for the SH4 with a floating-point unit that only +supports single-precision arithmentic. + +@item -m4-single +Generate code for the SH4 assuming the floating-point unit is in +single-precision mode by default. + +@item -m4 +Generate code for the SH4. + +@item -mb +Compile code for the processor in big endian mode. + +@item -ml +Compile code for the processor in little endian mode. + +@item -mdalign +Align doubles at 64-bit boundaries. Note that this changes the calling +conventions, and thus some functions from the standard C library will +not work unless you recompile it first with -mdalign. + +@item -mrelax +Shorten some address references at link time, when possible; uses the +linker option @samp{-relax}. + +@item -mbigtable +Use 32-bit offsets in @code{switch} tables. The default is to use +16-bit offsets. + +@item -mfmovd +Enable the use of the instruction @code{fmovd}. + +@item -mhitachi +Comply with the calling conventions defined by Hitachi. + +@item -mnomacsave +Mark the @code{MAC} register as call-clobbered, even if +@option{-mhitachi} is given. + +@item -misize +Dump instruction size and location in the assembly code. + +@item -mpadstruct +This option is deprecated. It pads structures to multiple of 4 bytes, +which is incompatible with the SH ABI. + +@item -mspace +Optimize for space instead of speed. Implied by @option{-Os}. + +@item -mprefergot +When generating position-independent code, emit function calls using +the Global Offset Table instead of the Procedure Linkage Table. + +@item -musermode +Generate a library function call to invalidate instruction cache +entries, after fixing up a trampoline. This library function call +doesn't assume it can write to the whole memory address space. This +is the default when the target is @code{sh-*-linux*}. +@end table + +@node System V Options +@subsection Options for System V + +These additional options are available on System V Release 4 for +compatibility with other compilers on those systems: + +@table @gcctabopt +@item -G +Create a shared object. +It is recommended that @samp{-symbolic} or @samp{-shared} be used instead. + +@item -Qy +Identify the versions of each tool used by the compiler, in a +@code{.ident} assembler directive in the output. + +@item -Qn +Refrain from adding @code{.ident} directives to the output file (this is +the default). + +@item -YP\,@var{dirs} +Search the directories @var{dirs}, and no others, for libraries +specified with @samp{-l}. + +@item -Ym\,@var{dir} +Look in the directory @var{dir} to find the M4 preprocessor. +The assembler uses this option. +@c This is supposed to go with a -Yd for predefined M4 macro files, but +@c the generic assembler that comes with Solaris takes just -Ym. +@end table + +@node TMS320C3x/C4x Options +@subsection TMS320C3x/C4x Options +@cindex TMS320C3x/C4x Options + +These @samp{-m} options are defined for TMS320C3x/C4x implementations: + +@table @gcctabopt + +@item -mcpu=@var{cpu_type} +Set the instruction set, register set, and instruction scheduling +parameters for machine type @var{cpu_type}. Supported values for +@var{cpu_type} are @samp{c30}, @samp{c31}, @samp{c32}, @samp{c40}, and +@samp{c44}. The default is @samp{c40} to generate code for the +TMS320C40. + +@item -mbig-memory +@item -mbig +@itemx -msmall-memory +@itemx -msmall +Generates code for the big or small memory model. The small memory +model assumed that all data fits into one 64K word page. At run-time +the data page (DP) register must be set to point to the 64K page +containing the .bss and .data program sections. The big memory model is +the default and requires reloading of the DP register for every direct +memory access. + +@item -mbk +@itemx -mno-bk +Allow (disallow) allocation of general integer operands into the block +count register BK. + +@item -mdb +@itemx -mno-db +Enable (disable) generation of code using decrement and branch, +DBcond(D), instructions. This is enabled by default for the C4x. To be +on the safe side, this is disabled for the C3x, since the maximum +iteration count on the C3x is 2^23 + 1 (but who iterates loops more than +2^23 times on the C3x?). Note that GCC will try to reverse a loop so +that it can utilise the decrement and branch instruction, but will give +up if there is more than one memory reference in the loop. Thus a loop +where the loop counter is decremented can generate slightly more +efficient code, in cases where the RPTB instruction cannot be utilised. + +@item -mdp-isr-reload +@itemx -mparanoid +Force the DP register to be saved on entry to an interrupt service +routine (ISR), reloaded to point to the data section, and restored on +exit from the ISR. This should not be required unless someone has +violated the small memory model by modifying the DP register, say within +an object library. + +@item -mmpyi +@itemx -mno-mpyi +For the C3x use the 24-bit MPYI instruction for integer multiplies +instead of a library call to guarantee 32-bit results. Note that if one +of the operands is a constant, then the multiplication will be performed +using shifts and adds. If the -mmpyi option is not specified for the C3x, +then squaring operations are performed inline instead of a library call. + +@item -mfast-fix +@itemx -mno-fast-fix +The C3x/C4x FIX instruction to convert a floating point value to an +integer value chooses the nearest integer less than or equal to the +floating point value rather than to the nearest integer. Thus if the +floating point number is negative, the result will be incorrectly +truncated an additional code is necessary to detect and correct this +case. This option can be used to disable generation of the additional +code required to correct the result. + +@item -mrptb +@itemx -mno-rptb +Enable (disable) generation of repeat block sequences using the RPTB +instruction for zero overhead looping. The RPTB construct is only used +for innermost loops that do not call functions or jump across the loop +boundaries. There is no advantage having nested RPTB loops due to the +overhead required to save and restore the RC, RS, and RE registers. +This is enabled by default with -O2. + +@item -mrpts=@var{count} +@itemx -mno-rpts +Enable (disable) the use of the single instruction repeat instruction +RPTS. If a repeat block contains a single instruction, and the loop +count can be guaranteed to be less than the value @var{count}, GCC will +emit a RPTS instruction instead of a RPTB. If no value is specified, +then a RPTS will be emitted even if the loop count cannot be determined +at compile time. Note that the repeated instruction following RPTS does +not have to be reloaded from memory each iteration, thus freeing up the +CPU buses for operands. However, since interrupts are blocked by this +instruction, it is disabled by default. + +@item -mloop-unsigned +@itemx -mno-loop-unsigned +The maximum iteration count when using RPTS and RPTB (and DB on the C40) +is 2^31 + 1 since these instructions test if the iteration count is +negative to terminate the loop. If the iteration count is unsigned +there is a possibility than the 2^31 + 1 maximum iteration count may be +exceeded. This switch allows an unsigned iteration count. + +@item -mti +Try to emit an assembler syntax that the TI assembler (asm30) is happy +with. This also enforces compatibility with the API employed by the TI +C3x C compiler. For example, long doubles are passed as structures +rather than in floating point registers. + +@item -mregparm +@itemx -mmemparm +Generate code that uses registers (stack) for passing arguments to functions. +By default, arguments are passed in registers where possible rather +than by pushing arguments on to the stack. + +@item -mparallel-insns +@itemx -mno-parallel-insns +Allow the generation of parallel instructions. This is enabled by +default with -O2. + +@item -mparallel-mpy +@itemx -mno-parallel-mpy +Allow the generation of MPY||ADD and MPY||SUB parallel instructions, +provided -mparallel-insns is also specified. These instructions have +tight register constraints which can pessimize the code generation +of large functions. + +@end table + +@node V850 Options +@subsection V850 Options +@cindex V850 Options + +These @samp{-m} options are defined for V850 implementations: + +@table @gcctabopt +@item -mlong-calls +@itemx -mno-long-calls +Treat all calls as being far away (near). If calls are assumed to be +far away, the compiler will always load the functions address up into a +register, and call indirect through the pointer. + +@item -mno-ep +@itemx -mep +Do not optimize (do optimize) basic blocks that use the same index +pointer 4 or more times to copy pointer into the @code{ep} register, and +use the shorter @code{sld} and @code{sst} instructions. The @samp{-mep} +option is on by default if you optimize. + +@item -mno-prolog-function +@itemx -mprolog-function +Do not use (do use) external functions to save and restore registers at +the prolog and epilog of a function. The external functions are slower, +but use less code space if more than one function saves the same number +of registers. The @samp{-mprolog-function} option is on by default if +you optimize. + +@item -mspace +Try to make the code as small as possible. At present, this just turns +on the @samp{-mep} and @samp{-mprolog-function} options. + +@item -mtda=@var{n} +Put static or global variables whose size is @var{n} bytes or less into +the tiny data area that register @code{ep} points to. The tiny data +area can hold up to 256 bytes in total (128 bytes for byte references). + +@item -msda=@var{n} +Put static or global variables whose size is @var{n} bytes or less into +the small data area that register @code{gp} points to. The small data +area can hold up to 64 kilobytes. + +@item -mzda=@var{n} +Put static or global variables whose size is @var{n} bytes or less into +the first 32 kilobytes of memory. + +@item -mv850 +Specify that the target processor is the V850. + +@item -mbig-switch +Generate code suitable for big switch tables. Use this option only if +the assembler/linker complain about out of range branches within a switch +table. +@end table + +@node ARC Options +@subsection ARC Options +@cindex ARC Options + +These options are defined for ARC implementations: + +@table @gcctabopt +@item -EL +Compile code for little endian mode. This is the default. + +@item -EB +Compile code for big endian mode. + +@item -mmangle-cpu +Prepend the name of the cpu to all public symbol names. +In multiple-processor systems, there are many ARC variants with different +instruction and register set characteristics. This flag prevents code +compiled for one cpu to be linked with code compiled for another. +No facility exists for handling variants that are "almost identical". +This is an all or nothing option. + +@item -mcpu=@var{cpu} +Compile code for ARC variant @var{cpu}. +Which variants are supported depend on the configuration. +All variants support @samp{-mcpu=base}, this is the default. + +@item -mtext=@var{text section} +@itemx -mdata=@var{data section} +@itemx -mrodata=@var{readonly data section} +Put functions, data, and readonly data in @var{text section}, +@var{data section}, and @var{readonly data section} respectively +by default. This can be overridden with the @code{section} attribute. +@xref{Variable Attributes}. + +@end table + +@node NS32K Options +@subsection NS32K Options +@cindex NS32K options + +These are the @samp{-m} options defined for the 32000 series. The default +values for these options depends on which style of 32000 was selected when +the compiler was configured; the defaults for the most common choices are +given below. + +@table @gcctabopt +@item -m32032 +@itemx -m32032 +Generate output for a 32032. This is the default +when the compiler is configured for 32032 and 32016 based systems. + +@item -m32332 +@itemx -m32332 +Generate output for a 32332. This is the default +when the compiler is configured for 32332-based systems. + +@item -m32532 +@itemx -m32532 +Generate output for a 32532. This is the default +when the compiler is configured for 32532-based systems. + +@item -m32081 +Generate output containing 32081 instructions for floating point. +This is the default for all systems. + +@item -m32381 +Generate output containing 32381 instructions for floating point. This +also implies @samp{-m32081}. The 32381 is only compatible with the 32332 +and 32532 cpus. This is the default for the pc532-netbsd configuration. + +@item -mmulti-add +Try and generate multiply-add floating point instructions @code{polyF} +and @code{dotF}. This option is only available if the @samp{-m32381} +option is in effect. Using these instructions requires changes to to +register allocation which generally has a negative impact on +performance. This option should only be enabled when compiling code +particularly likely to make heavy use of multiply-add instructions. + +@item -mnomulti-add +Do not try and generate multiply-add floating point instructions +@code{polyF} and @code{dotF}. This is the default on all platforms. + +@item -msoft-float +Generate output containing library calls for floating point. +@strong{Warning:} the requisite libraries may not be available. + +@item -mnobitfield +Do not use the bit-field instructions. On some machines it is faster to +use shifting and masking operations. This is the default for the pc532. + +@item -mbitfield +Do use the bit-field instructions. This is the default for all platforms +except the pc532. + +@item -mrtd +Use a different function-calling convention, in which functions +that take a fixed number of arguments return pop their +arguments on return with the @code{ret} instruction. + +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. + +Also, you must provide function prototypes for all functions that +take variable numbers of arguments (including @code{printf}); +otherwise incorrect code will be generated for calls to those +functions. + +In addition, seriously incorrect code will result if you call a +function with too many arguments. (Normally, extra arguments are +harmlessly ignored.) + +This option takes its name from the 680x0 @code{rtd} instruction. + + +@item -mregparam +Use a different function-calling convention where the first two arguments +are passed in registers. + +This calling convention is incompatible with the one normally +used on Unix, so you cannot use it if you need to call libraries +compiled with the Unix compiler. + +@item -mnoregparam +Do not pass any arguments in registers. This is the default for all +targets. + +@item -msb +It is OK to use the sb as an index register which is always loaded with +zero. This is the default for the pc532-netbsd target. + +@item -mnosb +The sb register is not available for use or has not been initialized to +zero by the run time system. This is the default for all targets except +the pc532-netbsd. It is also implied whenever @samp{-mhimem} or +@samp{-fpic} is set. + +@item -mhimem +Many ns32000 series addressing modes use displacements of up to 512MB. +If an address is above 512MB then displacements from zero can not be used. +This option causes code to be generated which can be loaded above 512MB. +This may be useful for operating systems or ROM code. + +@item -mnohimem +Assume code will be loaded in the first 512MB of virtual address space. +This is the default for all platforms. + + +@end table + +@node AVR Options +@subsection AVR Options +@cindex AVR Options + +These options are defined for AVR implementations: + +@table @gcctabopt +@item -mmcu=@var{mcu} +Specify ATMEL AVR instruction set or MCU type. + +Instruction set avr1 is for the minimal AVR core, not supported by the C +compiler, only for assembler programs (MCU types: at90s1200, attiny10, +attiny11, attiny12, attiny15, attiny28). + +Instruction set avr2 (default) is for the classic AVR core with up to +8K program memory space (MCU types: at90s2313, at90s2323, attiny22, +at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, +at90c8534, at90s8535). + +Instruction set avr3 is for the classic AVR core with up to 128K program +memory space (MCU types: atmega103, atmega603). + +Instruction set avr4 is for the enhanced AVR core with up to 8K program +memory space (MCU types: atmega83, atmega85). + +Instruction set avr5 is for the enhanced AVR core with up to 128K program +memory space (MCU types: atmega161, atmega163, atmega32, at94k). + +@item -msize +Output instruction sizes to the asm file. + +@item -minit-stack=@var{N} +Specify the initial stack address, which may be a symbol or numeric value, +__stack is the default. + +@item -mno-interrupts +Generated code is not compatible with hardware interrupts. +Code size will be smaller. + +@item -mcall-prologues +Functions prologues/epilogues expanded as call to appropriate +subroutines. Code size will be smaller. + +@item -mno-tablejump +Do not generate tablejump insns which sometimes increase code size. + +@item -mtiny-stack +Change only the low 8 bits of the stack pointer. +@end table + +@node MCore Options +@subsection MCore Options +@cindex MCore options + +These are the @samp{-m} options defined for the Motorola M*Core +processors. + +@table @gcctabopt + +@item -mhardlit +@itemx -mhardlit +@itemx -mno-hardlit +Inline constants into the code stream if it can be done in two +instructions or less. + +@item -mdiv +@itemx -mdiv +@itemx -mno-div +Use the divide instruction. (Enabled by default). + +@item -mrelax-immediate +@itemx -mrelax-immediate +@itemx -mno-relax-immediate +Allow arbitrary sized immediates in bit operations. + +@item -mwide-bitfields +@itemx -mwide-bitfields +@itemx -mno-wide-bitfields +Always treat bitfields as int-sized. + +@item -m4byte-functions +@itemx -m4byte-functions +@itemx -mno-4byte-functions +Force all functions to be aligned to a four byte boundary. + +@item -mcallgraph-data +@itemx -mcallgraph-data +@itemx -mno-callgraph-data +Emit callgraph information. + +@item -mslow-bytes +@itemx -mslow-bytes +@itemx -mno-slow-bytes +Prefer word access when reading byte quantities. + +@item -mlittle-endian +@itemx -mlittle-endian +@itemx -mbig-endian +Generate code for a little endian target. + +@item -m210 +@itemx -m210 +@itemx -m340 +Generate code for the 210 processor. +@end table + +@node IA-64 Options +@subsection IA-64 Options +@cindex IA-64 Options + +These are the @samp{-m} options defined for the Intel IA-64 architecture. + +@table @gcctabopt +@item -mbig-endian +Generate code for a big endian target. This is the default for HPUX. + +@item -mlittle-endian +Generate code for a little endian target. This is the default for AIX5 +and Linux. + +@item -mgnu-as +@itemx -mno-gnu-as +Generate (or don't) code for the GNU assembler. This is the default. +@c Also, this is the default if the configure option @samp{--with-gnu-as} +@c is used. + +@item -mgnu-ld +@itemx -mno-gnu-ld +Generate (or don't) code for the GNU linker. This is the default. +@c Also, this is the default if the configure option @samp{--with-gnu-ld} +@c is used. + +@item -mno-pic +Generate code that does not use a global pointer register. The result +is not position independent code, and violates the IA-64 ABI. + +@item -mvolatile-asm-stop +@itemx -mno-volatile-asm-stop +Generate (or don't) a stop bit immediately before and after volatile asm +statements. + +@item -mb-step +Generate code that works around Itanium B step errata. + +@item -mregister-names +@itemx -mno-register-names +Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for +the stacked registers. This may make assembler output more readable. + +@item -mno-sdata +@itemx -msdata +Disable (or enable) optimizations that use the small data section. This may +be useful for working around optimizer bugs. + +@item -mconstant-gp +Generate code that uses a single constant global pointer value. This is +useful when compiling kernel code. + +@item -mauto-pic +Generate code that is self-relocatable. This implies @samp{-mconstant-gp}. +This is useful when compiling firmware code. + +@item -minline-divide-min-latency +Generate code for inline divides using the minimum latency algorithm. + +@item -minline-divide-max-throughput +Generate code for inline divides using the maximum throughput algorithm. + +@item -mno-dwarf2-asm +@itemx -mdwarf2-asm +Don't (or do) generate assembler code for the DWARF2 line number debugging +info. This may be useful when not using the GNU assembler. + +@item -mfixed-range=@var{register range} +Generate code treating the given register range as fixed registers. +A fixed register is one that the register allocator can not use. This is +useful when compiling kernel code. A register range is specified as +two registers separated by a dash. Multiple register ranges can be +specified separated by a comma. +@end table + +@node D30V Options +@subsection D30V Options +@cindex D30V Options + +These @samp{-m} options are defined for D30V implementations: + +@table @gcctabopt +@item -mextmem +Link the @samp{.text}, @samp{.data}, @samp{.bss}, @samp{.strings}, +@samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections into external +memory, which starts at location @code{0x80000000}. + +@item -mextmemory +Same as the @samp{-mextmem} switch. + +@item -monchip +Link the @samp{.text} section into onchip text memory, which starts at +location @code{0x0}. Also link @samp{.data}, @samp{.bss}, +@samp{.strings}, @samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections +into onchip data memory, which starts at location @code{0x20000000}. + +@item -mno-asm-optimize +@itemx -masm-optimize +Disable (enable) passing @samp{-O} to the assembler when optimizing. +The assembler uses the @samp{-O} option to automatically parallelize +adjacent short instructions where possible. + +@item -mbranch-cost=@var{n} +Increase the internal costs of branches to @var{n}. Higher costs means +that the compiler will issue more instructions to avoid doing a branch. +The default is 2. + +@item -mcond-exec=@var{n} +Specify the maximum number of conditionally executed instructions that +replace a branch. The default is 4. +@end table + +@node Code Gen Options +@section Options for Code Generation Conventions +@cindex code generation conventions +@cindex options, code generation +@cindex run-time options + +These machine-independent options control the interface conventions +used in code generation. + +Most of them have both positive and negative forms; the negative form +of @samp{-ffoo} would be @samp{-fno-foo}. In the table below, only +one of the forms is listed---the one which is not the default. You +can figure out the other form by either removing @samp{no-} or adding +it. + +@table @gcctabopt +@item -fexceptions +Enable exception handling. Generates extra code needed to propagate +exceptions. For some targets, this implies GNU CC will generate frame +unwind information for all functions, which can produce significant data +size overhead, although it does not affect execution. If you do not +specify this option, GNU CC will enable it by default for languages like +C++ which normally require exception handling, and disable it for +languages like C that do not normally require it. However, you may need +to enable this option when compiling C code that needs to interoperate +properly with exception handlers written in C++. You may also wish to +disable this option if you are compiling older C++ programs that don't +use exception handling. + +@item -funwind-tables +Similar to @option{-fexceptions}, except that it will just generate any needed +static data, but will not affect the generated code in any other way. +You will normally not enable this option; instead, a language processor +that needs this handling would enable it on your behalf. + +@item -fpcc-struct-return +Return ``short'' @code{struct} and @code{union} values in memory like +longer ones, rather than in registers. This convention is less +efficient, but it has the advantage of allowing intercallability between +GCC-compiled files and files compiled with other compilers. + +The precise convention for returning structures in memory depends +on the target configuration macros. + +Short structures and unions are those whose size and alignment match +that of some integer type. + +@item -freg-struct-return +Use the convention that @code{struct} and @code{union} values are +returned in registers when possible. This is more efficient for small +structures than @samp{-fpcc-struct-return}. + +If you specify neither @samp{-fpcc-struct-return} nor its contrary +@samp{-freg-struct-return}, GCC defaults to whichever convention is +standard for the target. If there is no standard convention, GCC +defaults to @samp{-fpcc-struct-return}, except on targets where GCC +is the principal compiler. In those cases, we can choose the standard, +and we chose the more efficient register return alternative. + +@item -fshort-enums +Allocate to an @code{enum} type only as many bytes as it needs for the +declared range of possible values. Specifically, the @code{enum} type +will be equivalent to the smallest integer type which has enough room. + +@item -fshort-double +Use the same size for @code{double} as for @code{float}. + +@item -fshared-data +Requests that the data and non-@code{const} variables of this +compilation be shared data rather than private data. The distinction +makes sense only on certain operating systems, where shared data is +shared between processes running the same program, while private data +exists in one copy per process. + +@item -fno-common +In C, allocate even uninitialized global variables in the data section of the +object file, rather than generating them as common blocks. This has the +effect that if the same variable is declared (without @code{extern}) in +two different compilations, you will get an error when you link them. +The only reason this might be useful is if you wish to verify that the +program will work on other systems which always work this way. + +@item -fno-ident +Ignore the @samp{#ident} directive. + +@item -fno-gnu-linker +Do not output global initializations (such as C++ constructors and +destructors) in the form used by the GNU linker (on systems where the GNU +linker is the standard method of handling them). Use this option when +you want to use a non-GNU linker, which also requires using the +@command{collect2} program to make sure the system linker includes +constructors and destructors. (@command{collect2} is included in the GCC +distribution.) For systems which @emph{must} use @command{collect2}, the +compiler driver @command{gcc} is configured to do this automatically. + +@item -finhibit-size-directive +Don't output a @code{.size} assembler directive, or anything else that +would cause trouble if the function is split in the middle, and the +two halves are placed at locations far apart in memory. This option is +used when compiling @file{crtstuff.c}; you should not need to use it +for anything else. + +@item -fverbose-asm +Put extra commentary information in the generated assembly code to +make it more readable. This option is generally only of use to those +who actually need to read the generated assembly code (perhaps while +debugging the compiler itself). + +@samp{-fno-verbose-asm}, the default, causes the +extra information to be omitted and is useful when comparing two assembler +files. + +@item -fvolatile +Consider all memory references through pointers to be volatile. + +@item -fvolatile-global +Consider all memory references to extern and global data items to +be volatile. GCC does not consider static data items to be volatile +because of this switch. + +@item -fvolatile-static +Consider all memory references to static data to be volatile. + +@item -fpic +@cindex global offset table +@cindex PIC +Generate position-independent code (PIC) suitable for use in a shared +library, if supported for the target machine. Such code accesses all +constant addresses through a global offset table (GOT). The dynamic +loader resolves the GOT entries when the program starts (the dynamic +loader is not part of GCC; it is part of the operating system). If +the GOT size for the linked executable exceeds a machine-specific +maximum size, you get an error message from the linker indicating that +@samp{-fpic} does not work; in that case, recompile with @samp{-fPIC} +instead. (These maximums are 16k on the m88k, 8k on the Sparc, and 32k +on the m68k and RS/6000. The 386 has no such limit.) + +Position-independent code requires special support, and therefore works +only on certain machines. For the 386, GCC supports PIC for System V +but not for the Sun 386i. Code generated for the IBM RS/6000 is always +position-independent. + +@item -fPIC +If supported for the target machine, emit position-independent code, +suitable for dynamic linking and avoiding any limit on the size of the +global offset table. This option makes a difference on the m68k, m88k, +and the Sparc. + +Position-independent code requires special support, and therefore works +only on certain machines. + +@item -ffixed-@var{reg} +Treat the register named @var{reg} as a fixed register; generated code +should never refer to it (except perhaps as a stack pointer, frame +pointer or in some other fixed role). + +@var{reg} must be the name of a register. The register names accepted +are machine-specific and are defined in the @code{REGISTER_NAMES} +macro in the machine description macro file. + +This flag does not have a negative form, because it specifies a +three-way choice. + +@item -fcall-used-@var{reg} +Treat the register named @var{reg} as an allocable register that is +clobbered by function calls. It may be allocated for temporaries or +variables that do not live across a call. Functions compiled this way +will not save and restore the register @var{reg}. + +It is an error to used this flag with the frame pointer or stack pointer. +Use of this flag for other registers that have fixed pervasive roles in +the machine's execution model will produce disastrous results. + +This flag does not have a negative form, because it specifies a +three-way choice. + +@item -fcall-saved-@var{reg} +Treat the register named @var{reg} as an allocable register saved by +functions. It may be allocated even for temporaries or variables that +live across a call. Functions compiled this way will save and restore +the register @var{reg} if they use it. + +It is an error to used this flag with the frame pointer or stack pointer. +Use of this flag for other registers that have fixed pervasive roles in +the machine's execution model will produce disastrous results. + +A different sort of disaster will result from the use of this flag for +a register in which function values may be returned. + +This flag does not have a negative form, because it specifies a +three-way choice. + +@item -fpack-struct +Pack all structure members together without holes. Usually you would +not want to use this option, since it makes the code suboptimal, and +the offsets of structure members won't agree with system libraries. + +@item -fcheck-memory-usage +Generate extra code to check each memory access. GCC will generate +code that is suitable for a detector of bad memory accesses such as +@file{Checker}. + +Normally, you should compile all, or none, of your code with this option. + +If you do mix code compiled with and without this option, +you must ensure that all code that has side effects +and that is called by code compiled with this option +is, itself, compiled with this option. +If you do not, you might get erroneous messages from the detector. + +If you use functions from a library that have side-effects (such as +@code{read}), you might not be able to recompile the library and +specify this option. In that case, you can enable the +@samp{-fprefix-function-name} option, which requests GCC to encapsulate +your code and make other functions look as if they were compiled with +@samp{-fcheck-memory-usage}. This is done by calling ``stubs'', +which are provided by the detector. If you cannot find or build +stubs for every function you call, you might have to specify +@samp{-fcheck-memory-usage} without @samp{-fprefix-function-name}. + +If you specify this option, you can not use the @code{asm} or +@code{__asm__} keywords in functions with memory checking enabled. GNU +CC cannot understand what the @code{asm} statement may do, and therefore +cannot generate the appropriate code, so it will reject it. However, if +you specify the function attribute @code{no_check_memory_usage} +(@pxref{Function Attributes}), GNU CC will disable memory checking within a +function; you may use @code{asm} statements inside such functions. You +may have an inline expansion of a non-checked function within a checked +function; in that case GNU CC will not generate checks for the inlined +function's memory accesses. + +If you move your @code{asm} statements to non-checked inline functions +and they do access memory, you can add calls to the support code in your +inline function, to indicate any reads, writes, or copies being done. +These calls would be similar to those done in the stubs described above. + +@item -fprefix-function-name +Request GCC to add a prefix to the symbols generated for function names. +GCC adds a prefix to the names of functions defined as well as +functions called. Code compiled with this option and code compiled +without the option can't be linked together, unless stubs are used. + +If you compile the following code with @samp{-fprefix-function-name} +@example +extern void bar (int); +void +foo (int a) +@{ + return bar (a + 5); +@} +@end example + +@noindent +GCC will compile the code as if it was written: +@example +extern void prefix_bar (int); +void +prefix_foo (int a) +@{ + return prefix_bar (a + 5); +@} +@end example +This option is designed to be used with @samp{-fcheck-memory-usage}. + +@item -finstrument-functions +Generate instrumentation calls for entry and exit to functions. Just +after function entry and just before function exit, the following +profiling functions will be called with the address of the current +function and its call site. (On some platforms, +@code{__builtin_return_address} does not work beyond the current +function, so the call site information may not be available to the +profiling functions otherwise.) + +@example +void __cyg_profile_func_enter (void *this_fn, + void *call_site); +void __cyg_profile_func_exit (void *this_fn, + void *call_site); +@end example + +The first argument is the address of the start of the current function, +which may be looked up exactly in the symbol table. + +This instrumentation is also done for functions expanded inline in other +functions. The profiling calls will indicate where, conceptually, the +inline function is entered and exited. This means that addressable +versions of such functions must be available. If all your uses of a +function are expanded inline, this may mean an additional expansion of +code size. If you use @samp{extern inline} in your C code, an +addressable version of such functions must be provided. (This is +normally the case anyways, but if you get lucky and the optimizer always +expands the functions inline, you might have gotten away without +providing static copies.) + +A function may be given the attribute @code{no_instrument_function}, in +which case this instrumentation will not be done. This can be used, for +example, for the profiling functions listed above, high-priority +interrupt routines, and any functions from which the profiling functions +cannot safely be called (perhaps signal handlers, if the profiling +routines generate output or allocate memory). + +@item -fstack-check +Generate code to verify that you do not go beyond the boundary of the +stack. You should specify this flag if you are running in an +environment with multiple threads, but only rarely need to specify it in +a single-threaded environment since stack overflow is automatically +detected on nearly all systems if there is only one stack. + +Note that this switch does not actually cause checking to be done; the +operating system must do that. The switch causes generation of code +to ensure that the operating system sees the stack being extended. + +@item -fstack-limit-register=@var{reg} +@itemx -fstack-limit-symbol=@var{sym} +@itemx -fno-stack-limit +Generate code to ensure that the stack does not grow beyond a certain value, +either the value of a register or the address of a symbol. If the stack +would grow beyond the value, a signal is raised. For most targets, +the signal is raised before the stack overruns the boundary, so +it is possible to catch the signal without taking special precautions. + +For instance, if the stack starts at address @samp{0x80000000} and grows +downwards you can use the flags +@samp{-fstack-limit-symbol=__stack_limit} +@samp{-Wl,--defsym,__stack_limit=0x7ffe0000} which will enforce a stack +limit of 128K. + +@cindex aliasing of parameters +@cindex parameters, aliased +@item -fargument-alias +@itemx -fargument-noalias +@itemx -fargument-noalias-global +Specify the possible relationships among parameters and between +parameters and global data. + +@samp{-fargument-alias} specifies that arguments (parameters) may +alias each other and may alias global storage. +@samp{-fargument-noalias} specifies that arguments do not alias +each other, but may alias global storage. +@samp{-fargument-noalias-global} specifies that arguments do not +alias each other and do not alias global storage. + +Each language will automatically use whatever option is required by +the language standard. You should not need to use these options yourself. + +@item -fleading-underscore +This option and its counterpart, -fno-leading-underscore, forcibly +change the way C symbols are represented in the object file. One use +is to help link with legacy assembly code. + +Be warned that you should know what you are doing when invoking this +option, and that not all targets provide complete support for it. +@end table + +@c man end + +@node Environment Variables +@section Environment Variables Affecting GCC +@cindex environment variables + +@c man begin ENVIRONMENT + +This section describes several environment variables that affect how GCC +operates. Some of them work by specifying directories or prefixes to use +when searching for various kinds of files. Some are used to specify other +aspects of the compilation environment. + +@ifclear INTERNALS +Note that you can also specify places to search using options such as +@samp{-B}, @samp{-I} and @samp{-L} (@pxref{Directory Options}). These +take precedence over places specified using environment variables, which +in turn take precedence over those specified by the configuration of GCC. + +@end ifclear +@ifset INTERNALS +Note that you can also specify places to search using options such as +@samp{-B}, @samp{-I} and @samp{-L} (@pxref{Directory Options}). These +take precedence over places specified using environment variables, which +in turn take precedence over those specified by the configuration of GCC. +@xref{Driver}. +@end ifset + +@table @env +@item LANG +@itemx LC_CTYPE +@c @itemx LC_COLLATE +@itemx LC_MESSAGES +@c @itemx LC_MONETARY +@c @itemx LC_NUMERIC +@c @itemx LC_TIME +@itemx LC_ALL +@findex LANG +@findex LC_CTYPE +@c @findex LC_COLLATE +@findex LC_MESSAGES +@c @findex LC_MONETARY +@c @findex LC_NUMERIC +@c @findex LC_TIME +@findex LC_ALL +@cindex locale +These environment variables control the way that GCC uses +localization information that allow GCC to work with different +national conventions. GCC inspects the locale categories +@env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do +so. These locale categories can be set to any value supported by your +installation. A typical value is @samp{en_UK} for English in the United +Kingdom. + +The @env{LC_CTYPE} environment variable specifies character +classification. GCC uses it to determine the character boundaries in +a string; this is needed for some multibyte encodings that contain quote +and escape characters that would otherwise be interpreted as a string +end or escape. + +The @env{LC_MESSAGES} environment variable specifies the language to +use in diagnostic messages. + +If the @env{LC_ALL} environment variable is set, it overrides the value +of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE} +and @env{LC_MESSAGES} default to the value of the @env{LANG} +environment variable. If none of these variables are set, GCC +defaults to traditional C English behavior. + +@item TMPDIR +@findex TMPDIR +If @env{TMPDIR} is set, it specifies the directory to use for temporary +files. GCC uses temporary files to hold the output of one stage of +compilation which is to be used as input to the next stage: for example, +the output of the preprocessor, which is the input to the compiler +proper. + +@item GCC_EXEC_PREFIX +@findex GCC_EXEC_PREFIX +If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the +names of the subprograms executed by the compiler. No slash is added +when this prefix is combined with the name of a subprogram, but you can +specify a prefix that ends with a slash if you wish. + +If @env{GCC_EXEC_PREFIX} is not set, GNU CC will attempt to figure out +an appropriate prefix to use based on the pathname it was invoked with. + +If GCC cannot find the subprogram using the specified prefix, it +tries looking in the usual places for the subprogram. + +The default value of @env{GCC_EXEC_PREFIX} is +@file{@var{prefix}/lib/gcc-lib/} where @var{prefix} is the value +of @code{prefix} when you ran the @file{configure} script. + +Other prefixes specified with @samp{-B} take precedence over this prefix. + +This prefix is also used for finding files such as @file{crt0.o} that are +used for linking. + +In addition, the prefix is used in an unusual way in finding the +directories to search for header files. For each of the standard +directories whose name normally begins with @samp{/usr/local/lib/gcc-lib} +(more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries +replacing that beginning with the specified prefix to produce an +alternate directory name. Thus, with @samp{-Bfoo/}, GCC will search +@file{foo/bar} where it would normally search @file{/usr/local/lib/bar}. +These alternate directories are searched first; the standard directories +come next. + +@item COMPILER_PATH +@findex COMPILER_PATH +The value of @env{COMPILER_PATH} is a colon-separated list of +directories, much like @env{PATH}. GCC tries the directories thus +specified when searching for subprograms, if it can't find the +subprograms using @env{GCC_EXEC_PREFIX}. + +@item LIBRARY_PATH +@findex LIBRARY_PATH +The value of @env{LIBRARY_PATH} is a colon-separated list of +directories, much like @env{PATH}. When configured as a native compiler, +GCC tries the directories thus specified when searching for special +linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking +using GCC also uses these directories when searching for ordinary +libraries for the @samp{-l} option (but directories specified with +@samp{-L} come first). + +@item C_INCLUDE_PATH +@itemx CPLUS_INCLUDE_PATH +@itemx OBJC_INCLUDE_PATH +@findex C_INCLUDE_PATH +@findex CPLUS_INCLUDE_PATH +@findex OBJC_INCLUDE_PATH +@c @itemx OBJCPLUS_INCLUDE_PATH +These environment variables pertain to particular languages. Each +variable's value is a colon-separated list of directories, much like +@env{PATH}. When GCC searches for header files, it tries the +directories listed in the variable for the language you are using, after +the directories specified with @samp{-I} but before the standard header +file directories. + +@item DEPENDENCIES_OUTPUT +@findex DEPENDENCIES_OUTPUT +@cindex dependencies for make as output +If this variable is set, its value specifies how to output dependencies +for Make based on the header files processed by the compiler. This +output looks much like the output from the @samp{-M} option +(@pxref{Preprocessor Options}), but it goes to a separate file, and is +in addition to the usual results of compilation. + +The value of @env{DEPENDENCIES_OUTPUT} can be just a file name, in +which case the Make rules are written to that file, guessing the target +name from the source file name. Or the value can have the form +@samp{@var{file} @var{target}}, in which case the rules are written to +file @var{file} using @var{target} as the target name. + +@item LANG +@findex LANG +@cindex locale definition +This variable is used to pass locale information to the compiler. One way in +which this information is used is to determine the character set to be used +when character literals, string literals and comments are parsed in C and C++. +When the compiler is configured to allow multibyte characters, +the following values for @env{LANG} are recognized: + +@table @samp +@item C-JIS +Recognize JIS characters. +@item C-SJIS +Recognize SJIS characters. +@item C-EUCJP +Recognize EUCJP characters. +@end table + +If @env{LANG} is not defined, or if it has some other value, then the +compiler will use mblen and mbtowc as defined by the default locale to +recognize and translate multibyte characters. +@end table + +@c man end + +@node Running Protoize +@section Running Protoize + +The program @code{protoize} is an optional part of GNU C. You can use +it to add prototypes to a program, thus converting the program to ISO +C in one respect. The companion program @code{unprotoize} does the +reverse: it removes argument types from any prototypes that are found. + +When you run these programs, you must specify a set of source files as +command line arguments. The conversion programs start out by compiling +these files to see what functions they define. The information gathered +about a file @var{foo} is saved in a file named @file{@var{foo}.X}. + +After scanning comes actual conversion. The specified files are all +eligible to be converted; any files they include (whether sources or +just headers) are eligible as well. + +But not all the eligible files are converted. By default, +@code{protoize} and @code{unprotoize} convert only source and header +files in the current directory. You can specify additional directories +whose files should be converted with the @samp{-d @var{directory}} +option. You can also specify particular files to exclude with the +@samp{-x @var{file}} option. A file is converted if it is eligible, its +directory name matches one of the specified directory names, and its +name within the directory has not been excluded. + +Basic conversion with @code{protoize} consists of rewriting most +function definitions and function declarations to specify the types of +the arguments. The only ones not rewritten are those for varargs +functions. + +@code{protoize} optionally inserts prototype declarations at the +beginning of the source file, to make them available for any calls that +precede the function's definition. Or it can insert prototype +declarations with block scope in the blocks where undeclared functions +are called. + +Basic conversion with @code{unprotoize} consists of rewriting most +function declarations to remove any argument types, and rewriting +function definitions to the old-style pre-ISO form. + +Both conversion programs print a warning for any function declaration or +definition that they can't convert. You can suppress these warnings +with @samp{-q}. + +The output from @code{protoize} or @code{unprotoize} replaces the +original source file. The original file is renamed to a name ending +with @samp{.save} (for DOS, the saved filename ends in @samp{.sav} +without the original @samp{.c} suffix). If the @samp{.save} (@samp{.sav} +for DOS) file already exists, then the source file is simply discarded. + +@code{protoize} and @code{unprotoize} both depend on GCC itself to +scan the program and collect information about the functions it uses. +So neither of these programs will work until GCC is installed. + +Here is a table of the options you can use with @code{protoize} and +@code{unprotoize}. Each option works with both programs unless +otherwise stated. + +@table @code +@item -B @var{directory} +Look for the file @file{SYSCALLS.c.X} in @var{directory}, instead of the +usual directory (normally @file{/usr/local/lib}). This file contains +prototype information about standard system functions. This option +applies only to @code{protoize}. + +@item -c @var{compilation-options} +Use @var{compilation-options} as the options when running @code{gcc} to +produce the @samp{.X} files. The special option @samp{-aux-info} is +always passed in addition, to tell @code{gcc} to write a @samp{.X} file. + +Note that the compilation options must be given as a single argument to +@code{protoize} or @code{unprotoize}. If you want to specify several +@code{gcc} options, you must quote the entire set of compilation options +to make them a single word in the shell. + +There are certain @code{gcc} arguments that you cannot use, because they +would produce the wrong kind of output. These include @samp{-g}, +@samp{-O}, @samp{-c}, @samp{-S}, and @samp{-o} If you include these in +the @var{compilation-options}, they are ignored. + +@item -C +Rename files to end in @samp{.C} (@samp{.cc} for DOS-based file +systems) instead of @samp{.c}. This is convenient if you are converting +a C program to C++. This option applies only to @code{protoize}. + +@item -g +Add explicit global declarations. This means inserting explicit +declarations at the beginning of each source file for each function +that is called in the file and was not declared. These declarations +precede the first function definition that contains a call to an +undeclared function. This option applies only to @code{protoize}. + +@item -i @var{string} +Indent old-style parameter declarations with the string @var{string}. +This option applies only to @code{protoize}. + +@code{unprotoize} converts prototyped function definitions to old-style +function definitions, where the arguments are declared between the +argument list and the initial @samp{@{}. By default, @code{unprotoize} +uses five spaces as the indentation. If you want to indent with just +one space instead, use @samp{-i " "}. + +@item -k +Keep the @samp{.X} files. Normally, they are deleted after conversion +is finished. + +@item -l +Add explicit local declarations. @code{protoize} with @samp{-l} inserts +a prototype declaration for each function in each block which calls the +function without any declaration. This option applies only to +@code{protoize}. + +@item -n +Make no real changes. This mode just prints information about the conversions +that would have been done without @samp{-n}. + +@item -N +Make no @samp{.save} files. The original files are simply deleted. +Use this option with caution. + +@item -p @var{program} +Use the program @var{program} as the compiler. Normally, the name +@file{gcc} is used. + +@item -q +Work quietly. Most warnings are suppressed. + +@item -v +Print the version number, just like @samp{-v} for @code{gcc}. +@end table + +If you need special compiler options to compile one of your program's +source files, then you should generate that file's @samp{.X} file +specially, by running @code{gcc} on that source file with the +appropriate options and the option @samp{-aux-info}. Then run +@code{protoize} on the entire set of files. @code{protoize} will use +the existing @samp{.X} file because it is newer than the source file. +For example: + +@example +gcc -Dfoo=bar file1.c -aux-info +protoize *.c +@end example + +@noindent +You need to include the special files along with the rest in the +@code{protoize} command, even though their @samp{.X} files already +exist, because otherwise they won't get converted. + +@xref{Protoize Caveats}, for more information on how to use +@code{protoize} successfully. diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi new file mode 100644 index 00000000000..eec92cb5ebb --- /dev/null +++ b/gcc/doc/md.texi @@ -0,0 +1,5022 @@ +@c Copyright (C) 1988, 89, 92, 93, 94, 96, 1998, 2000, 2001 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@ifset INTERNALS +@node Machine Desc +@chapter Machine Descriptions +@cindex machine descriptions + +A machine description has two parts: a file of instruction patterns +(@file{.md} file) and a C header file of macro definitions. + +The @file{.md} file for a target machine contains a pattern for each +instruction that the target machine supports (or at least each instruction +that is worth telling the compiler about). It may also contain comments. +A semicolon causes the rest of the line to be a comment, unless the semicolon +is inside a quoted string. + +See the next chapter for information on the C header file. + +@menu +* Overview:: How the machine description is used. +* Patterns:: How to write instruction patterns. +* Example:: An explained example of a @code{define_insn} pattern. +* RTL Template:: The RTL template defines what insns match a pattern. +* Output Template:: The output template says how to make assembler code + from such an insn. +* Output Statement:: For more generality, write C code to output + the assembler code. +* Constraints:: When not all operands are general operands. +* Standard Names:: Names mark patterns to use for code generation. +* Pattern Ordering:: When the order of patterns makes a difference. +* Dependent Patterns:: Having one pattern may make you need another. +* Jump Patterns:: Special considerations for patterns for jump insns. +* Looping Patterns:: How to define patterns for special looping insns. +* Insn Canonicalizations::Canonicalization of Instructions +* Expander Definitions::Generating a sequence of several RTL insns + for a standard operation. +* Insn Splitting:: Splitting Instructions into Multiple Instructions. +* Peephole Definitions::Defining machine-specific peephole optimizations. +* Insn Attributes:: Specifying the value of attributes for generated insns. +* Conditional Execution::Generating @code{define_insn} patterns for + predication. +* Constant Definitions::Defining symbolic constants that can be used in the + md file. +@end menu + +@node Overview +@section Overview of How the Machine Description is Used + +There are three main conversions that happen in the compiler: + +@enumerate + +@item +The front end reads the source code and builds a parse tree. + +@item +The parse tree is used to generate an RTL insn list based on named +instruction patterns. + +@item +The insn list is matched against the RTL templates to produce assembler +code. + +@end enumerate + +For the generate pass, only the names of the insns matter, from either a +named @code{define_insn} or a @code{define_expand}. The compiler will +choose the pattern with the right name and apply the operands according +to the documentation later in this chapter, without regard for the RTL +template or operand constraints. Note that the names the compiler looks +for are hard-coded in the compiler - it will ignore unnamed patterns and +patterns with names it doesn't know about, but if you don't provide a +named pattern it needs, it will abort. + +If a @code{define_insn} is used, the template given is inserted into the +insn list. If a @code{define_expand} is used, one of three things +happens, based on the condition logic. The condition logic may manually +create new insns for the insn list, say via @code{emit_insn()}, and +invoke DONE. For certain named patterns, it may invoke FAIL to tell the +compiler to use an alternate way of performing that task. If it invokes +neither @code{DONE} nor @code{FAIL}, the template given in the pattern +is inserted, as if the @code{define_expand} were a @code{define_insn}. + +Once the insn list is generated, various optimization passes convert, +replace, and rearrange the insns in the insn list. This is where the +@code{define_split} and @code{define_peephole} patterns get used, for +example. + +Finally, the insn list's RTL is matched up with the RTL templates in the +@code{define_insn} patterns, and those patterns are used to emit the +final assembly code. For this purpose, each named @code{define_insn} +acts like it's unnamed, since the names are ignored. + +@node Patterns +@section Everything about Instruction Patterns +@cindex patterns +@cindex instruction patterns + +@findex define_insn +Each instruction pattern contains an incomplete RTL expression, with pieces +to be filled in later, operand constraints that restrict how the pieces can +be filled in, and an output pattern or C code to generate the assembler +output, all wrapped up in a @code{define_insn} expression. + +A @code{define_insn} is an RTL expression containing four or five operands: + +@enumerate +@item +An optional name. The presence of a name indicate that this instruction +pattern can perform a certain standard job for the RTL-generation +pass of the compiler. This pass knows certain names and will use +the instruction patterns with those names, if the names are defined +in the machine description. + +The absence of a name is indicated by writing an empty string +where the name should go. Nameless instruction patterns are never +used for generating RTL code, but they may permit several simpler insns +to be combined later on. + +Names that are not thus known and used in RTL-generation have no +effect; they are equivalent to no name at all. + +For the purpose of debugging the compiler, you may also specify a +name beginning with the @samp{*} character. Such a name is used only +for identifying the instruction in RTL dumps; it is entirely equivalent +to having a nameless pattern for all other purposes. + +@item +The @dfn{RTL template} (@pxref{RTL Template}) is a vector of incomplete +RTL expressions which show what the instruction should look like. It is +incomplete because it may contain @code{match_operand}, +@code{match_operator}, and @code{match_dup} expressions that stand for +operands of the instruction. + +If the vector has only one element, that element is the template for the +instruction pattern. If the vector has multiple elements, then the +instruction pattern is a @code{parallel} expression containing the +elements described. + +@item +@cindex pattern conditions +@cindex conditions, in patterns +A condition. This is a string which contains a C expression that is +the final test to decide whether an insn body matches this pattern. + +@cindex named patterns and conditions +For a named pattern, the condition (if present) may not depend on +the data in the insn being matched, but only the target-machine-type +flags. The compiler needs to test these conditions during +initialization in order to learn exactly which named instructions are +available in a particular run. + +@findex operands +For nameless patterns, the condition is applied only when matching an +individual insn, and only after the insn has matched the pattern's +recognition template. The insn's operands may be found in the vector +@code{operands}. + +@item +The @dfn{output template}: a string that says how to output matching +insns as assembler code. @samp{%} in this string specifies where +to substitute the value of an operand. @xref{Output Template}. + +When simple substitution isn't general enough, you can specify a piece +of C code to compute the output. @xref{Output Statement}. + +@item +Optionally, a vector containing the values of attributes for insns matching +this pattern. @xref{Insn Attributes}. +@end enumerate + +@node Example +@section Example of @code{define_insn} +@cindex @code{define_insn} example + +Here is an actual example of an instruction pattern, for the 68000/68020. + +@example +(define_insn "tstsi" + [(set (cc0) + (match_operand:SI 0 "general_operand" "rm"))] + "" + "* +@{ if (TARGET_68020 || ! ADDRESS_REG_P (operands[0])) + return \"tstl %0\"; + return \"cmpl #0,%0\"; @}") +@end example + +This is an instruction that sets the condition codes based on the value of +a general operand. It has no condition, so any insn whose RTL description +has the form shown may be handled according to this pattern. The name +@samp{tstsi} means ``test a @code{SImode} value'' and tells the RTL generation +pass that, when it is necessary to test such a value, an insn to do so +can be constructed using this pattern. + +The output control string is a piece of C code which chooses which +output template to return based on the kind of operand and the specific +type of CPU for which code is being generated. + +@samp{"rm"} is an operand constraint. Its meaning is explained below. + +@node RTL Template +@section RTL Template +@cindex RTL insn template +@cindex generating insns +@cindex insns, generating +@cindex recognizing insns +@cindex insns, recognizing + +The RTL template is used to define which insns match the particular pattern +and how to find their operands. For named patterns, the RTL template also +says how to construct an insn from specified operands. + +Construction involves substituting specified operands into a copy of the +template. Matching involves determining the values that serve as the +operands in the insn being matched. Both of these activities are +controlled by special expression types that direct matching and +substitution of the operands. + +@table @code +@findex match_operand +@item (match_operand:@var{m} @var{n} @var{predicate} @var{constraint}) +This expression is a placeholder for operand number @var{n} of +the insn. When constructing an insn, operand number @var{n} +will be substituted at this point. When matching an insn, whatever +appears at this position in the insn will be taken as operand +number @var{n}; but it must satisfy @var{predicate} or this instruction +pattern will not match at all. + +Operand numbers must be chosen consecutively counting from zero in +each instruction pattern. There may be only one @code{match_operand} +expression in the pattern for each operand number. Usually operands +are numbered in the order of appearance in @code{match_operand} +expressions. In the case of a @code{define_expand}, any operand numbers +used only in @code{match_dup} expressions have higher values than all +other operand numbers. + +@var{predicate} is a string that is the name of a C function that accepts two +arguments, an expression and a machine mode. During matching, the +function will be called with the putative operand as the expression and +@var{m} as the mode argument (if @var{m} is not specified, +@code{VOIDmode} will be used, which normally causes @var{predicate} to accept +any mode). If it returns zero, this instruction pattern fails to match. +@var{predicate} may be an empty string; then it means no test is to be done +on the operand, so anything which occurs in this position is valid. + +Most of the time, @var{predicate} will reject modes other than @var{m}---but +not always. For example, the predicate @code{address_operand} uses +@var{m} as the mode of memory ref that the address should be valid for. +Many predicates accept @code{const_int} nodes even though their mode is +@code{VOIDmode}. + +@var{constraint} controls reloading and the choice of the best register +class to use for a value, as explained later (@pxref{Constraints}). + +People are often unclear on the difference between the constraint and the +predicate. The predicate helps decide whether a given insn matches the +pattern. The constraint plays no role in this decision; instead, it +controls various decisions in the case of an insn which does match. + +@findex general_operand +On CISC machines, the most common @var{predicate} is +@code{"general_operand"}. This function checks that the putative +operand is either a constant, a register or a memory reference, and that +it is valid for mode @var{m}. + +@findex register_operand +For an operand that must be a register, @var{predicate} should be +@code{"register_operand"}. Using @code{"general_operand"} would be +valid, since the reload pass would copy any non-register operands +through registers, but this would make GNU CC do extra work, it would +prevent invariant operands (such as constant) from being removed from +loops, and it would prevent the register allocator from doing the best +possible job. On RISC machines, it is usually most efficient to allow +@var{predicate} to accept only objects that the constraints allow. + +@findex immediate_operand +For an operand that must be a constant, you must be sure to either use +@code{"immediate_operand"} for @var{predicate}, or make the instruction +pattern's extra condition require a constant, or both. You cannot +expect the constraints to do this work! If the constraints allow only +constants, but the predicate allows something else, the compiler will +crash when that case arises. + +@findex match_scratch +@item (match_scratch:@var{m} @var{n} @var{constraint}) +This expression is also a placeholder for operand number @var{n} +and indicates that operand must be a @code{scratch} or @code{reg} +expression. + +When matching patterns, this is equivalent to + +@smallexample +(match_operand:@var{m} @var{n} "scratch_operand" @var{pred}) +@end smallexample + +but, when generating RTL, it produces a (@code{scratch}:@var{m}) +expression. + +If the last few expressions in a @code{parallel} are @code{clobber} +expressions whose operands are either a hard register or +@code{match_scratch}, the combiner can add or delete them when +necessary. @xref{Side Effects}. + +@findex match_dup +@item (match_dup @var{n}) +This expression is also a placeholder for operand number @var{n}. +It is used when the operand needs to appear more than once in the +insn. + +In construction, @code{match_dup} acts just like @code{match_operand}: +the operand is substituted into the insn being constructed. But in +matching, @code{match_dup} behaves differently. It assumes that operand +number @var{n} has already been determined by a @code{match_operand} +appearing earlier in the recognition template, and it matches only an +identical-looking expression. + +Note that @code{match_dup} should not be used to tell the compiler that +a particular register is being used for two operands (example: +@code{add} that adds one register to another; the second register is +both an input operand and the output operand). Use a matching +constraint (@pxref{Simple Constraints}) for those. @code{match_dup} is for the cases where one +operand is used in two places in the template, such as an instruction +that computes both a quotient and a remainder, where the opcode takes +two input operands but the RTL template has to refer to each of those +twice; once for the quotient pattern and once for the remainder pattern. + +@findex match_operator +@item (match_operator:@var{m} @var{n} @var{predicate} [@var{operands}@dots{}]) +This pattern is a kind of placeholder for a variable RTL expression +code. + +When constructing an insn, it stands for an RTL expression whose +expression code is taken from that of operand @var{n}, and whose +operands are constructed from the patterns @var{operands}. + +When matching an expression, it matches an expression if the function +@var{predicate} returns nonzero on that expression @emph{and} the +patterns @var{operands} match the operands of the expression. + +Suppose that the function @code{commutative_operator} is defined as +follows, to match any expression whose operator is one of the +commutative arithmetic operators of RTL and whose mode is @var{mode}: + +@smallexample +int +commutative_operator (x, mode) + rtx x; + enum machine_mode mode; +@{ + enum rtx_code code = GET_CODE (x); + if (GET_MODE (x) != mode) + return 0; + return (GET_RTX_CLASS (code) == 'c' + || code == EQ || code == NE); +@} +@end smallexample + +Then the following pattern will match any RTL expression consisting +of a commutative operator applied to two general operands: + +@smallexample +(match_operator:SI 3 "commutative_operator" + [(match_operand:SI 1 "general_operand" "g") + (match_operand:SI 2 "general_operand" "g")]) +@end smallexample + +Here the vector @code{[@var{operands}@dots{}]} contains two patterns +because the expressions to be matched all contain two operands. + +When this pattern does match, the two operands of the commutative +operator are recorded as operands 1 and 2 of the insn. (This is done +by the two instances of @code{match_operand}.) Operand 3 of the insn +will be the entire commutative expression: use @code{GET_CODE +(operands[3])} to see which commutative operator was used. + +The machine mode @var{m} of @code{match_operator} works like that of +@code{match_operand}: it is passed as the second argument to the +predicate function, and that function is solely responsible for +deciding whether the expression to be matched ``has'' that mode. + +When constructing an insn, argument 3 of the gen-function will specify +the operation (i.e. the expression code) for the expression to be +made. It should be an RTL expression, whose expression code is copied +into a new expression whose operands are arguments 1 and 2 of the +gen-function. The subexpressions of argument 3 are not used; +only its expression code matters. + +When @code{match_operator} is used in a pattern for matching an insn, +it usually best if the operand number of the @code{match_operator} +is higher than that of the actual operands of the insn. This improves +register allocation because the register allocator often looks at +operands 1 and 2 of insns to see if it can do register tying. + +There is no way to specify constraints in @code{match_operator}. The +operand of the insn which corresponds to the @code{match_operator} +never has any constraints because it is never reloaded as a whole. +However, if parts of its @var{operands} are matched by +@code{match_operand} patterns, those parts may have constraints of +their own. + +@findex match_op_dup +@item (match_op_dup:@var{m} @var{n}[@var{operands}@dots{}]) +Like @code{match_dup}, except that it applies to operators instead of +operands. When constructing an insn, operand number @var{n} will be +substituted at this point. But in matching, @code{match_op_dup} behaves +differently. It assumes that operand number @var{n} has already been +determined by a @code{match_operator} appearing earlier in the +recognition template, and it matches only an identical-looking +expression. + +@findex match_parallel +@item (match_parallel @var{n} @var{predicate} [@var{subpat}@dots{}]) +This pattern is a placeholder for an insn that consists of a +@code{parallel} expression with a variable number of elements. This +expression should only appear at the top level of an insn pattern. + +When constructing an insn, operand number @var{n} will be substituted at +this point. When matching an insn, it matches if the body of the insn +is a @code{parallel} expression with at least as many elements as the +vector of @var{subpat} expressions in the @code{match_parallel}, if each +@var{subpat} matches the corresponding element of the @code{parallel}, +@emph{and} the function @var{predicate} returns nonzero on the +@code{parallel} that is the body of the insn. It is the responsibility +of the predicate to validate elements of the @code{parallel} beyond +those listed in the @code{match_parallel}.@refill + +A typical use of @code{match_parallel} is to match load and store +multiple expressions, which can contain a variable number of elements +in a @code{parallel}. For example, +@c the following is *still* going over. need to change the code. +@c also need to work on grouping of this example. --mew 1feb93 + +@smallexample +(define_insn "" + [(match_parallel 0 "load_multiple_operation" + [(set (match_operand:SI 1 "gpc_reg_operand" "=r") + (match_operand:SI 2 "memory_operand" "m")) + (use (reg:SI 179)) + (clobber (reg:SI 179))])] + "" + "loadm 0,0,%1,%2") +@end smallexample + +This example comes from @file{a29k.md}. The function +@code{load_multiple_operations} is defined in @file{a29k.c} and checks +that subsequent elements in the @code{parallel} are the same as the +@code{set} in the pattern, except that they are referencing subsequent +registers and memory locations. + +An insn that matches this pattern might look like: + +@smallexample +(parallel + [(set (reg:SI 20) (mem:SI (reg:SI 100))) + (use (reg:SI 179)) + (clobber (reg:SI 179)) + (set (reg:SI 21) + (mem:SI (plus:SI (reg:SI 100) + (const_int 4)))) + (set (reg:SI 22) + (mem:SI (plus:SI (reg:SI 100) + (const_int 8))))]) +@end smallexample + +@findex match_par_dup +@item (match_par_dup @var{n} [@var{subpat}@dots{}]) +Like @code{match_op_dup}, but for @code{match_parallel} instead of +@code{match_operator}. + +@findex match_insn +@item (match_insn @var{predicate}) +Match a complete insn. Unlike the other @code{match_*} recognizers, +@code{match_insn} does not take an operand number. + +The machine mode @var{m} of @code{match_insn} works like that of +@code{match_operand}: it is passed as the second argument to the +predicate function, and that function is solely responsible for +deciding whether the expression to be matched ``has'' that mode. + +@findex match_insn2 +@item (match_insn2 @var{n} @var{predicate}) +Match a complete insn. + +The machine mode @var{m} of @code{match_insn2} works like that of +@code{match_operand}: it is passed as the second argument to the +predicate function, and that function is solely responsible for +deciding whether the expression to be matched ``has'' that mode. + +@end table + +@node Output Template +@section Output Templates and Operand Substitution +@cindex output templates +@cindex operand substitution + +@cindex @samp{%} in template +@cindex percent sign +The @dfn{output template} is a string which specifies how to output the +assembler code for an instruction pattern. Most of the template is a +fixed string which is output literally. The character @samp{%} is used +to specify where to substitute an operand; it can also be used to +identify places where different variants of the assembler require +different syntax. + +In the simplest case, a @samp{%} followed by a digit @var{n} says to output +operand @var{n} at that point in the string. + +@samp{%} followed by a letter and a digit says to output an operand in an +alternate fashion. Four letters have standard, built-in meanings described +below. The machine description macro @code{PRINT_OPERAND} can define +additional letters with nonstandard meanings. + +@samp{%c@var{digit}} can be used to substitute an operand that is a +constant value without the syntax that normally indicates an immediate +operand. + +@samp{%n@var{digit}} is like @samp{%c@var{digit}} except that the value of +the constant is negated before printing. + +@samp{%a@var{digit}} can be used to substitute an operand as if it were a +memory reference, with the actual operand treated as the address. This may +be useful when outputting a ``load address'' instruction, because often the +assembler syntax for such an instruction requires you to write the operand +as if it were a memory reference. + +@samp{%l@var{digit}} is used to substitute a @code{label_ref} into a jump +instruction. + +@samp{%=} outputs a number which is unique to each instruction in the +entire compilation. This is useful for making local labels to be +referred to more than once in a single template that generates multiple +assembler instructions. + +@samp{%} followed by a punctuation character specifies a substitution that +does not use an operand. Only one case is standard: @samp{%%} outputs a +@samp{%} into the assembler code. Other nonstandard cases can be +defined in the @code{PRINT_OPERAND} macro. You must also define +which punctuation characters are valid with the +@code{PRINT_OPERAND_PUNCT_VALID_P} macro. + +@cindex \ +@cindex backslash +The template may generate multiple assembler instructions. Write the text +for the instructions, with @samp{\;} between them. + +@cindex matching operands +When the RTL contains two operands which are required by constraint to match +each other, the output template must refer only to the lower-numbered operand. +Matching operands are not always identical, and the rest of the compiler +arranges to put the proper RTL expression for printing into the lower-numbered +operand. + +One use of nonstandard letters or punctuation following @samp{%} is to +distinguish between different assembler languages for the same machine; for +example, Motorola syntax versus MIT syntax for the 68000. Motorola syntax +requires periods in most opcode names, while MIT syntax does not. For +example, the opcode @samp{movel} in MIT syntax is @samp{move.l} in Motorola +syntax. The same file of patterns is used for both kinds of output syntax, +but the character sequence @samp{%.} is used in each place where Motorola +syntax wants a period. The @code{PRINT_OPERAND} macro for Motorola syntax +defines the sequence to output a period; the macro for MIT syntax defines +it to do nothing. + +@cindex @code{#} in template +As a special case, a template consisting of the single character @code{#} +instructs the compiler to first split the insn, and then output the +resulting instructions separately. This helps eliminate redundancy in the +output templates. If you have a @code{define_insn} that needs to emit +multiple assembler instructions, and there is an matching @code{define_split} +already defined, then you can simply use @code{#} as the output template +instead of writing an output template that emits the multiple assembler +instructions. + +If the macro @code{ASSEMBLER_DIALECT} is defined, you can use construct +of the form @samp{@{option0|option1|option2@}} in the templates. These +describe multiple variants of assembler language syntax. +@xref{Instruction Output}. + +@node Output Statement +@section C Statements for Assembler Output +@cindex output statements +@cindex C statements for assembler output +@cindex generating assembler output + +Often a single fixed template string cannot produce correct and efficient +assembler code for all the cases that are recognized by a single +instruction pattern. For example, the opcodes may depend on the kinds of +operands; or some unfortunate combinations of operands may require extra +machine instructions. + +If the output control string starts with a @samp{@@}, then it is actually +a series of templates, each on a separate line. (Blank lines and +leading spaces and tabs are ignored.) The templates correspond to the +pattern's constraint alternatives (@pxref{Multi-Alternative}). For example, +if a target machine has a two-address add instruction @samp{addr} to add +into a register and another @samp{addm} to add a register to memory, you +might write this pattern: + +@smallexample +(define_insn "addsi3" + [(set (match_operand:SI 0 "general_operand" "=r,m") + (plus:SI (match_operand:SI 1 "general_operand" "0,0") + (match_operand:SI 2 "general_operand" "g,r")))] + "" + "@@ + addr %2,%0 + addm %2,%0") +@end smallexample + +@cindex @code{*} in template +@cindex asterisk in template +If the output control string starts with a @samp{*}, then it is not an +output template but rather a piece of C program that should compute a +template. It should execute a @code{return} statement to return the +template-string you want. Most such templates use C string literals, which +require doublequote characters to delimit them. To include these +doublequote characters in the string, prefix each one with @samp{\}. + +The operands may be found in the array @code{operands}, whose C data type +is @code{rtx []}. + +It is very common to select different ways of generating assembler code +based on whether an immediate operand is within a certain range. Be +careful when doing this, because the result of @code{INTVAL} is an +integer on the host machine. If the host machine has more bits in an +@code{int} than the target machine has in the mode in which the constant +will be used, then some of the bits you get from @code{INTVAL} will be +superfluous. For proper results, you must carefully disregard the +values of those bits. + +@findex output_asm_insn +It is possible to output an assembler instruction and then go on to output +or compute more of them, using the subroutine @code{output_asm_insn}. This +receives two arguments: a template-string and a vector of operands. The +vector may be @code{operands}, or it may be another array of @code{rtx} +that you declare locally and initialize yourself. + +@findex which_alternative +When an insn pattern has multiple alternatives in its constraints, often +the appearance of the assembler code is determined mostly by which alternative +was matched. When this is so, the C code can test the variable +@code{which_alternative}, which is the ordinal number of the alternative +that was actually satisfied (0 for the first, 1 for the second alternative, +etc.). + +For example, suppose there are two opcodes for storing zero, @samp{clrreg} +for registers and @samp{clrmem} for memory locations. Here is how +a pattern could use @code{which_alternative} to choose between them: + +@smallexample +(define_insn "" + [(set (match_operand:SI 0 "general_operand" "=r,m") + (const_int 0))] + "" + "* + return (which_alternative == 0 + ? \"clrreg %0\" : \"clrmem %0\"); + ") +@end smallexample + +The example above, where the assembler code to generate was +@emph{solely} determined by the alternative, could also have been specified +as follows, having the output control string start with a @samp{@@}: + +@smallexample +@group +(define_insn "" + [(set (match_operand:SI 0 "general_operand" "=r,m") + (const_int 0))] + "" + "@@ + clrreg %0 + clrmem %0") +@end group +@end smallexample +@end ifset + +@c Most of this node appears by itself (in a different place) even +@c when the INTERNALS flag is clear. Passages that require the full +@c manual's context are conditionalized to appear only in the full manual. +@ifset INTERNALS +@node Constraints +@section Operand Constraints +@cindex operand constraints +@cindex constraints + +Each @code{match_operand} in an instruction pattern can specify a +constraint for the type of operands allowed. +@end ifset +@ifclear INTERNALS +@node Constraints +@section Constraints for @code{asm} Operands +@cindex operand constraints, @code{asm} +@cindex constraints, @code{asm} +@cindex @code{asm} constraints + +Here are specific details on what constraint letters you can use with +@code{asm} operands. +@end ifclear +Constraints can say whether +an operand may be in a register, and which kinds of register; whether the +operand can be a memory reference, and which kinds of address; whether the +operand may be an immediate constant, and which possible values it may +have. Constraints can also require two operands to match. + +@ifset INTERNALS +@menu +* Simple Constraints:: Basic use of constraints. +* Multi-Alternative:: When an insn has two alternative constraint-patterns. +* Class Preferences:: Constraints guide which hard register to put things in. +* Modifiers:: More precise control over effects of constraints. +* Machine Constraints:: Existing constraints for some particular machines. +@end menu +@end ifset + +@ifclear INTERNALS +@menu +* Simple Constraints:: Basic use of constraints. +* Multi-Alternative:: When an insn has two alternative constraint-patterns. +* Modifiers:: More precise control over effects of constraints. +* Machine Constraints:: Special constraints for some particular machines. +@end menu +@end ifclear + +@node Simple Constraints +@subsection Simple Constraints +@cindex simple constraints + +The simplest kind of constraint is a string full of letters, each of +which describes one kind of operand that is permitted. Here are +the letters that are allowed: + +@table @asis +@item whitespace +Whitespace characters are ignored and can be inserted at any position +except the first. This enables each alternative for different operands to +be visually aligned in the machine description even if they have different +number of constraints and modifiers. + +@cindex @samp{m} in constraint +@cindex memory references in constraints +@item @samp{m} +A memory operand is allowed, with any kind of address that the machine +supports in general. + +@cindex offsettable address +@cindex @samp{o} in constraint +@item @samp{o} +A memory operand is allowed, but only if the address is +@dfn{offsettable}. This means that adding a small integer (actually, +the width in bytes of the operand, as determined by its machine mode) +may be added to the address and the result is also a valid memory +address. + +@cindex autoincrement/decrement addressing +For example, an address which is constant is offsettable; so is an +address that is the sum of a register and a constant (as long as a +slightly larger constant is also within the range of address-offsets +supported by the machine); but an autoincrement or autodecrement +address is not offsettable. More complicated indirect/indexed +addresses may or may not be offsettable depending on the other +addressing modes that the machine supports. + +Note that in an output operand which can be matched by another +operand, the constraint letter @samp{o} is valid only when accompanied +by both @samp{<} (if the target machine has predecrement addressing) +and @samp{>} (if the target machine has preincrement addressing). + +@cindex @samp{V} in constraint +@item @samp{V} +A memory operand that is not offsettable. In other words, anything that +would fit the @samp{m} constraint but not the @samp{o} constraint. + +@cindex @samp{<} in constraint +@item @samp{<} +A memory operand with autodecrement addressing (either predecrement or +postdecrement) is allowed. + +@cindex @samp{>} in constraint +@item @samp{>} +A memory operand with autoincrement addressing (either preincrement or +postincrement) is allowed. + +@cindex @samp{r} in constraint +@cindex registers in constraints +@item @samp{r} +A register operand is allowed provided that it is in a general +register. + +@cindex constants in constraints +@cindex @samp{i} in constraint +@item @samp{i} +An immediate integer operand (one with constant value) is allowed. +This includes symbolic constants whose values will be known only at +assembly time. + +@cindex @samp{n} in constraint +@item @samp{n} +An immediate integer operand with a known numeric value is allowed. +Many systems cannot support assembly-time constants for operands less +than a word wide. Constraints for these operands should use @samp{n} +rather than @samp{i}. + +@cindex @samp{I} in constraint +@item @samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P} +Other letters in the range @samp{I} through @samp{P} may be defined in +a machine-dependent fashion to permit immediate integer operands with +explicit integer values in specified ranges. For example, on the +68000, @samp{I} is defined to stand for the range of values 1 to 8. +This is the range permitted as a shift count in the shift +instructions. + +@cindex @samp{E} in constraint +@item @samp{E} +An immediate floating operand (expression code @code{const_double}) is +allowed, but only if the target floating point format is the same as +that of the host machine (on which the compiler is running). + +@cindex @samp{F} in constraint +@item @samp{F} +An immediate floating operand (expression code @code{const_double}) is +allowed. + +@cindex @samp{G} in constraint +@cindex @samp{H} in constraint +@item @samp{G}, @samp{H} +@samp{G} and @samp{H} may be defined in a machine-dependent fashion to +permit immediate floating operands in particular ranges of values. + +@cindex @samp{s} in constraint +@item @samp{s} +An immediate integer operand whose value is not an explicit integer is +allowed. + +This might appear strange; if an insn allows a constant operand with a +value not known at compile time, it certainly must allow any known +value. So why use @samp{s} instead of @samp{i}? Sometimes it allows +better code to be generated. + +For example, on the 68000 in a fullword instruction it is possible to +use an immediate operand; but if the immediate value is between -128 +and 127, better code results from loading the value into a register and +using the register. This is because the load into the register can be +done with a @samp{moveq} instruction. We arrange for this to happen +by defining the letter @samp{K} to mean ``any integer outside the +range -128 to 127'', and then specifying @samp{Ks} in the operand +constraints. + +@cindex @samp{g} in constraint +@item @samp{g} +Any register, memory or immediate integer operand is allowed, except for +registers that are not general registers. + +@cindex @samp{X} in constraint +@item @samp{X} +@ifset INTERNALS +Any operand whatsoever is allowed, even if it does not satisfy +@code{general_operand}. This is normally used in the constraint of +a @code{match_scratch} when certain alternatives will not actually +require a scratch register. +@end ifset +@ifclear INTERNALS +Any operand whatsoever is allowed. +@end ifclear + +@cindex @samp{0} in constraint +@cindex digits in constraint +@item @samp{0}, @samp{1}, @samp{2}, @dots{} @samp{9} +An operand that matches the specified operand number is allowed. If a +digit is used together with letters within the same alternative, the +digit should come last. + +@cindex matching constraint +@cindex constraint, matching +This is called a @dfn{matching constraint} and what it really means is +that the assembler has only a single operand that fills two roles +@ifset INTERNALS +considered separate in the RTL insn. For example, an add insn has two +input operands and one output operand in the RTL, but on most CISC +@end ifset +@ifclear INTERNALS +which @code{asm} distinguishes. For example, an add instruction uses +two input operands and an output operand, but on most CISC +@end ifclear +machines an add instruction really has only two operands, one of them an +input-output operand: + +@smallexample +addl #35,r12 +@end smallexample + +Matching constraints are used in these circumstances. +More precisely, the two operands that match must include one input-only +operand and one output-only operand. Moreover, the digit must be a +smaller number than the number of the operand that uses it in the +constraint. + +@ifset INTERNALS +For operands to match in a particular case usually means that they +are identical-looking RTL expressions. But in a few special cases +specific kinds of dissimilarity are allowed. For example, @code{*x} +as an input operand will match @code{*x++} as an output operand. +For proper results in such cases, the output template should always +use the output-operand's number when printing the operand. +@end ifset + +@cindex load address instruction +@cindex push address instruction +@cindex address constraints +@cindex @samp{p} in constraint +@item @samp{p} +An operand that is a valid memory address is allowed. This is +for ``load address'' and ``push address'' instructions. + +@findex address_operand +@samp{p} in the constraint must be accompanied by @code{address_operand} +as the predicate in the @code{match_operand}. This predicate interprets +the mode specified in the @code{match_operand} as the mode of the memory +reference for which the address would be valid. + +@cindex other register constraints +@cindex extensible constraints +@item @var{other letters} +Other letters can be defined in machine-dependent fashion to stand for +particular classes of registers or other arbitrary operand types. +@samp{d}, @samp{a} and @samp{f} are defined on the 68000/68020 to stand +for data, address and floating point registers. + +@ifset INTERNALS +The machine description macro @code{REG_CLASS_FROM_LETTER} has first +cut at the otherwise unused letters. If it evaluates to @code{NO_REGS}, +then @code{EXTRA_CONSTRAINT} is evaluated. + +A typical use for @code{EXTRA_CONSTRANT} would be to distinguish certain +types of memory references that affect other insn operands. +@end ifset +@end table + +@ifset INTERNALS +In order to have valid assembler code, each operand must satisfy +its constraint. But a failure to do so does not prevent the pattern +from applying to an insn. Instead, it directs the compiler to modify +the code so that the constraint will be satisfied. Usually this is +done by copying an operand into a register. + +Contrast, therefore, the two instruction patterns that follow: + +@smallexample +(define_insn "" + [(set (match_operand:SI 0 "general_operand" "=r") + (plus:SI (match_dup 0) + (match_operand:SI 1 "general_operand" "r")))] + "" + "@dots{}") +@end smallexample + +@noindent +which has two operands, one of which must appear in two places, and + +@smallexample +(define_insn "" + [(set (match_operand:SI 0 "general_operand" "=r") + (plus:SI (match_operand:SI 1 "general_operand" "0") + (match_operand:SI 2 "general_operand" "r")))] + "" + "@dots{}") +@end smallexample + +@noindent +which has three operands, two of which are required by a constraint to be +identical. If we are considering an insn of the form + +@smallexample +(insn @var{n} @var{prev} @var{next} + (set (reg:SI 3) + (plus:SI (reg:SI 6) (reg:SI 109))) + @dots{}) +@end smallexample + +@noindent +the first pattern would not apply at all, because this insn does not +contain two identical subexpressions in the right place. The pattern would +say, ``That does not look like an add instruction; try other patterns.'' +The second pattern would say, ``Yes, that's an add instruction, but there +is something wrong with it.'' It would direct the reload pass of the +compiler to generate additional insns to make the constraint true. The +results might look like this: + +@smallexample +(insn @var{n2} @var{prev} @var{n} + (set (reg:SI 3) (reg:SI 6)) + @dots{}) + +(insn @var{n} @var{n2} @var{next} + (set (reg:SI 3) + (plus:SI (reg:SI 3) (reg:SI 109))) + @dots{}) +@end smallexample + +It is up to you to make sure that each operand, in each pattern, has +constraints that can handle any RTL expression that could be present for +that operand. (When multiple alternatives are in use, each pattern must, +for each possible combination of operand expressions, have at least one +alternative which can handle that combination of operands.) The +constraints don't need to @emph{allow} any possible operand---when this is +the case, they do not constrain---but they must at least point the way to +reloading any possible operand so that it will fit. + +@itemize @bullet +@item +If the constraint accepts whatever operands the predicate permits, +there is no problem: reloading is never necessary for this operand. + +For example, an operand whose constraints permit everything except +registers is safe provided its predicate rejects registers. + +An operand whose predicate accepts only constant values is safe +provided its constraints include the letter @samp{i}. If any possible +constant value is accepted, then nothing less than @samp{i} will do; +if the predicate is more selective, then the constraints may also be +more selective. + +@item +Any operand expression can be reloaded by copying it into a register. +So if an operand's constraints allow some kind of register, it is +certain to be safe. It need not permit all classes of registers; the +compiler knows how to copy a register into another register of the +proper class in order to make an instruction valid. + +@cindex nonoffsettable memory reference +@cindex memory reference, nonoffsettable +@item +A nonoffsettable memory reference can be reloaded by copying the +address into a register. So if the constraint uses the letter +@samp{o}, all memory references are taken care of. + +@item +A constant operand can be reloaded by allocating space in memory to +hold it as preinitialized data. Then the memory reference can be used +in place of the constant. So if the constraint uses the letters +@samp{o} or @samp{m}, constant operands are not a problem. + +@item +If the constraint permits a constant and a pseudo register used in an insn +was not allocated to a hard register and is equivalent to a constant, +the register will be replaced with the constant. If the predicate does +not permit a constant and the insn is re-recognized for some reason, the +compiler will crash. Thus the predicate must always recognize any +objects allowed by the constraint. +@end itemize + +If the operand's predicate can recognize registers, but the constraint does +not permit them, it can make the compiler crash. When this operand happens +to be a register, the reload pass will be stymied, because it does not know +how to copy a register temporarily into memory. + +If the predicate accepts a unary operator, the constraint applies to the +operand. For example, the MIPS processor at ISA level 3 supports an +instruction which adds two registers in @code{SImode} to produce a +@code{DImode} result, but only if the registers are correctly sign +extended. This predicate for the input operands accepts a +@code{sign_extend} of an @code{SImode} register. Write the constraint +to indicate the type of register that is required for the operand of the +@code{sign_extend}. +@end ifset + +@node Multi-Alternative +@subsection Multiple Alternative Constraints +@cindex multiple alternative constraints + +Sometimes a single instruction has multiple alternative sets of possible +operands. For example, on the 68000, a logical-or instruction can combine +register or an immediate value into memory, or it can combine any kind of +operand into a register; but it cannot combine one memory location into +another. + +These constraints are represented as multiple alternatives. An alternative +can be described by a series of letters for each operand. The overall +constraint for an operand is made from the letters for this operand +from the first alternative, a comma, the letters for this operand from +the second alternative, a comma, and so on until the last alternative. +@ifset INTERNALS +Here is how it is done for fullword logical-or on the 68000: + +@smallexample +(define_insn "iorsi3" + [(set (match_operand:SI 0 "general_operand" "=m,d") + (ior:SI (match_operand:SI 1 "general_operand" "%0,0") + (match_operand:SI 2 "general_operand" "dKs,dmKs")))] + @dots{}) +@end smallexample + +The first alternative has @samp{m} (memory) for operand 0, @samp{0} for +operand 1 (meaning it must match operand 0), and @samp{dKs} for operand +2. The second alternative has @samp{d} (data register) for operand 0, +@samp{0} for operand 1, and @samp{dmKs} for operand 2. The @samp{=} and +@samp{%} in the constraints apply to all the alternatives; their +meaning is explained in the next section (@pxref{Class Preferences}). +@end ifset + +@c FIXME Is this ? and ! stuff of use in asm()? If not, hide unless INTERNAL +If all the operands fit any one alternative, the instruction is valid. +Otherwise, for each alternative, the compiler counts how many instructions +must be added to copy the operands so that that alternative applies. +The alternative requiring the least copying is chosen. If two alternatives +need the same amount of copying, the one that comes first is chosen. +These choices can be altered with the @samp{?} and @samp{!} characters: + +@table @code +@cindex @samp{?} in constraint +@cindex question mark +@item ? +Disparage slightly the alternative that the @samp{?} appears in, +as a choice when no alternative applies exactly. The compiler regards +this alternative as one unit more costly for each @samp{?} that appears +in it. + +@cindex @samp{!} in constraint +@cindex exclamation point +@item ! +Disparage severely the alternative that the @samp{!} appears in. +This alternative can still be used if it fits without reloading, +but if reloading is needed, some other alternative will be used. +@end table + +@ifset INTERNALS +When an insn pattern has multiple alternatives in its constraints, often +the appearance of the assembler code is determined mostly by which +alternative was matched. When this is so, the C code for writing the +assembler code can use the variable @code{which_alternative}, which is +the ordinal number of the alternative that was actually satisfied (0 for +the first, 1 for the second alternative, etc.). @xref{Output Statement}. +@end ifset + +@ifset INTERNALS +@node Class Preferences +@subsection Register Class Preferences +@cindex class preference constraints +@cindex register class preference constraints + +@cindex voting between constraint alternatives +The operand constraints have another function: they enable the compiler +to decide which kind of hardware register a pseudo register is best +allocated to. The compiler examines the constraints that apply to the +insns that use the pseudo register, looking for the machine-dependent +letters such as @samp{d} and @samp{a} that specify classes of registers. +The pseudo register is put in whichever class gets the most ``votes''. +The constraint letters @samp{g} and @samp{r} also vote: they vote in +favor of a general register. The machine description says which registers +are considered general. + +Of course, on some machines all registers are equivalent, and no register +classes are defined. Then none of this complexity is relevant. +@end ifset + +@node Modifiers +@subsection Constraint Modifier Characters +@cindex modifiers in constraints +@cindex constraint modifier characters + +@c prevent bad page break with this line +Here are constraint modifier characters. + +@table @samp +@cindex @samp{=} in constraint +@item = +Means that this operand is write-only for this instruction: the previous +value is discarded and replaced by output data. + +@cindex @samp{+} in constraint +@item + +Means that this operand is both read and written by the instruction. + +When the compiler fixes up the operands to satisfy the constraints, +it needs to know which operands are inputs to the instruction and +which are outputs from it. @samp{=} identifies an output; @samp{+} +identifies an operand that is both input and output; all other operands +are assumed to be input only. + +If you specify @samp{=} or @samp{+} in a constraint, you put it in the +first character of the constraint string. + +@cindex @samp{&} in constraint +@cindex earlyclobber operand +@item & +Means (in a particular alternative) that this operand is an +@dfn{earlyclobber} operand, which is modified before the instruction is +finished using the input operands. Therefore, this operand may not lie +in a register that is used as an input operand or as part of any memory +address. + +@samp{&} applies only to the alternative in which it is written. In +constraints with multiple alternatives, sometimes one alternative +requires @samp{&} while others do not. See, for example, the +@samp{movdf} insn of the 68000. + +An input operand can be tied to an earlyclobber operand if its only +use as an input occurs before the early result is written. Adding +alternatives of this form often allows GCC to produce better code +when only some of the inputs can be affected by the earlyclobber. +See, for example, the @samp{mulsi3} insn of the ARM. + +@samp{&} does not obviate the need to write @samp{=}. + +@cindex @samp{%} in constraint +@item % +Declares the instruction to be commutative for this operand and the +following operand. This means that the compiler may interchange the +two operands if that is the cheapest way to make all operands fit the +constraints. +@ifset INTERNALS +This is often used in patterns for addition instructions +that really have only two operands: the result must go in one of the +arguments. Here for example, is how the 68000 halfword-add +instruction is defined: + +@smallexample +(define_insn "addhi3" + [(set (match_operand:HI 0 "general_operand" "=m,r") + (plus:HI (match_operand:HI 1 "general_operand" "%0,0") + (match_operand:HI 2 "general_operand" "di,g")))] + @dots{}) +@end smallexample +@end ifset + +@cindex @samp{#} in constraint +@item # +Says that all following characters, up to the next comma, are to be +ignored as a constraint. They are significant only for choosing +register preferences. + +@ifset INTERNALS +@cindex @samp{*} in constraint +@item * +Says that the following character should be ignored when choosing +register preferences. @samp{*} has no effect on the meaning of the +constraint as a constraint, and no effect on reloading. + +Here is an example: the 68000 has an instruction to sign-extend a +halfword in a data register, and can also sign-extend a value by +copying it into an address register. While either kind of register is +acceptable, the constraints on an address-register destination are +less strict, so it is best if register allocation makes an address +register its goal. Therefore, @samp{*} is used so that the @samp{d} +constraint letter (for data register) is ignored when computing +register preferences. + +@smallexample +(define_insn "extendhisi2" + [(set (match_operand:SI 0 "general_operand" "=*d,a") + (sign_extend:SI + (match_operand:HI 1 "general_operand" "0,g")))] + @dots{}) +@end smallexample +@end ifset +@end table + +@node Machine Constraints +@subsection Constraints for Particular Machines +@cindex machine specific constraints +@cindex constraints, machine specific + +Whenever possible, you should use the general-purpose constraint letters +in @code{asm} arguments, since they will convey meaning more readily to +people reading your code. Failing that, use the constraint letters +that usually have very similar meanings across architectures. The most +commonly used constraints are @samp{m} and @samp{r} (for memory and +general-purpose registers respectively; @pxref{Simple Constraints}), and +@samp{I}, usually the letter indicating the most common +immediate-constant format. + +For each machine architecture, the @file{config/@var{machine}.h} file +defines additional constraints. These constraints are used by the +compiler itself for instruction generation, as well as for @code{asm} +statements; therefore, some of the constraints are not particularly +interesting for @code{asm}. The constraints are defined through these +macros: + +@table @code +@item REG_CLASS_FROM_LETTER +Register class constraints (usually lower case). + +@item CONST_OK_FOR_LETTER_P +Immediate constant constraints, for non-floating point constants of +word size or smaller precision (usually upper case). + +@item CONST_DOUBLE_OK_FOR_LETTER_P +Immediate constant constraints, for all floating point constants and for +constants of greater than word size precision (usually upper case). + +@item EXTRA_CONSTRAINT +Special cases of registers or memory. This macro is not required, and +is only defined for some machines. +@end table + +Inspecting these macro definitions in the compiler source for your +machine is the best way to be certain you have the right constraints. +However, here is a summary of the machine-dependent constraints +available on some particular machines. + +@table @emph +@item ARM family---@file{arm.h} +@table @code +@item f +Floating-point register + +@item F +One of the floating-point constants 0.0, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 +or 10.0 + +@item G +Floating-point constant that would satisfy the constraint @samp{F} if it +were negated + +@item I +Integer that is valid as an immediate operand in a data processing +instruction. That is, an integer in the range 0 to 255 rotated by a +multiple of 2 + +@item J +Integer in the range -4095 to 4095 + +@item K +Integer that satisfies constraint @samp{I} when inverted (ones complement) + +@item L +Integer that satisfies constraint @samp{I} when negated (twos complement) + +@item M +Integer in the range 0 to 32 + +@item Q +A memory reference where the exact address is in a single register +(`@samp{m}' is preferable for @code{asm} statements) + +@item R +An item in the constant pool + +@item S +A symbol in the text segment of the current file +@end table + +@item AMD 29000 family---@file{a29k.h} +@table @code +@item l +Local register 0 + +@item b +Byte Pointer (@samp{BP}) register + +@item q +@samp{Q} register + +@item h +Special purpose register + +@item A +First accumulator register + +@item a +Other accumulator register + +@item f +Floating point register + +@item I +Constant greater than 0, less than 0x100 + +@item J +Constant greater than 0, less than 0x10000 + +@item K +Constant whose high 24 bits are on (1) + +@item L +16-bit constant whose high 8 bits are on (1) + +@item M +32-bit constant whose high 16 bits are on (1) + +@item N +32-bit negative constant that fits in 8 bits + +@item O +The constant 0x80000000 or, on the 29050, any 32-bit constant +whose low 16 bits are 0. + +@item P +16-bit negative constant that fits in 8 bits + +@item G +@itemx H +A floating point constant (in @code{asm} statements, use the machine +independent @samp{E} or @samp{F} instead) +@end table + +@item AVR family---@file{avr.h} +@table @code +@item l +Registers from r0 to r15 + +@item a +Registers from r16 to r23 + +@item d +Registers from r16 to r31 + +@item w +Registers from r24 to r31. These registers can be used in @samp{adiw} command + +@item e +Pointer register (r26 - r31) + +@item b +Base pointer register (r28 - r31) + +@item q +Stack pointer register (SPH:SPL) + +@item t +Temporary register r0 + +@item x +Register pair X (r27:r26) + +@item y +Register pair Y (r29:r28) + +@item z +Register pair Z (r31:r30) + +@item I +Constant greater than -1, less than 64 + +@item J +Constant greater than -64, less than 1 + +@item K +Constant integer 2 + +@item L +Constant integer 0 + +@item M +Constant that fits in 8 bits + +@item N +Constant integer -1 + +@item O +Constant integer 8, 16, or 24 + +@item P +Constant integer 1 + +@item G +A floating point constant 0.0 +@end table + +@item IBM RS6000---@file{rs6000.h} +@table @code +@item b +Address base register + +@item f +Floating point register + +@item h +@samp{MQ}, @samp{CTR}, or @samp{LINK} register + +@item q +@samp{MQ} register + +@item c +@samp{CTR} register + +@item l +@samp{LINK} register + +@item x +@samp{CR} register (condition register) number 0 + +@item y +@samp{CR} register (condition register) + +@item z +@samp{FPMEM} stack memory for FPR-GPR transfers + +@item I +Signed 16-bit constant + +@item J +Unsigned 16-bit constant shifted left 16 bits (use @samp{L} instead for +@code{SImode} constants) + +@item K +Unsigned 16-bit constant + +@item L +Signed 16-bit constant shifted left 16 bits + +@item M +Constant larger than 31 + +@item N +Exact power of 2 + +@item O +Zero + +@item P +Constant whose negation is a signed 16-bit constant + +@item G +Floating point constant that can be loaded into a register with one +instruction per word + +@item Q +Memory operand that is an offset from a register (@samp{m} is preferable +for @code{asm} statements) + +@item R +AIX TOC entry + +@item S +Constant suitable as a 64-bit mask operand + +@item T +Constant suitable as a 32-bit mask operand + +@item U +System V Release 4 small data area reference +@end table + +@item Intel 386---@file{i386.h} +@table @code +@item q +@samp{a}, @code{b}, @code{c}, or @code{d} register for the i386. +For x86-64 it is equivalent to @samp{r} class. (for 8-bit instructions that +do not use upper halves) + +@item Q +@samp{a}, @code{b}, @code{c}, or @code{d} register. (for 8-bit instructions, +that do use upper halves) + +@item R +Legacy register --- equivalent to @code{r} class in i386 mode. +(for non-8-bit registers used together with 8-bit upper halves in a single +instruction) + +@item A +Specifies the @samp{a} or @samp{d} registers. This is primarily useful +for 64-bit integer values (when in 32-bit mode) intended to be returned +with the @samp{d} register holding the most significant bits and the +@samp{a} register holding the least significant bits. + +@item f +Floating point register + +@item t +First (top of stack) floating point register + +@item u +Second floating point register + +@item a +@samp{a} register + +@item b +@samp{b} register + +@item c +@samp{c} register + +@item d +@samp{d} register + +@item D +@samp{di} register + +@item S +@samp{si} register + +@item x +@samp{xmm} SSE register + +@item y +MMX register + +@item I +Constant in range 0 to 31 (for 32-bit shifts) + +@item J +Constant in range 0 to 63 (for 64-bit shifts) + +@item K +@samp{0xff} + +@item L +@samp{0xffff} + +@item M +0, 1, 2, or 3 (shifts for @code{lea} instruction) + +@item N +Constant in range 0 to 255 (for @code{out} instruction) + +@item Z +Constant in range 0 to 0xffffffff or symbolic reference known to fit specified range. +(for using immediates in zero extending 32-bit to 64-bit x86-64 instructions) + +@item e +Constant in range -2147483648 to 2147483647 or symbolic reference known to fit specified range. +(for using immediates in 64-bit x86-64 instructions) + +@item G +Standard 80387 floating point constant +@end table + +@item Intel 960---@file{i960.h} +@table @code +@item f +Floating point register (@code{fp0} to @code{fp3}) + +@item l +Local register (@code{r0} to @code{r15}) + +@item b +Global register (@code{g0} to @code{g15}) + +@item d +Any local or global register + +@item I +Integers from 0 to 31 + +@item J +0 + +@item K +Integers from -31 to 0 + +@item G +Floating point 0 + +@item H +Floating point 1 +@end table + +@item MIPS---@file{mips.h} +@table @code +@item d +General-purpose integer register + +@item f +Floating-point register (if available) + +@item h +@samp{Hi} register + +@item l +@samp{Lo} register + +@item x +@samp{Hi} or @samp{Lo} register + +@item y +General-purpose integer register + +@item z +Floating-point status register + +@item I +Signed 16-bit constant (for arithmetic instructions) + +@item J +Zero + +@item K +Zero-extended 16-bit constant (for logic instructions) + +@item L +Constant with low 16 bits zero (can be loaded with @code{lui}) + +@item M +32-bit constant which requires two instructions to load (a constant +which is not @samp{I}, @samp{K}, or @samp{L}) + +@item N +Negative 16-bit constant + +@item O +Exact power of two + +@item P +Positive 16-bit constant + +@item G +Floating point zero + +@item Q +Memory reference that can be loaded with more than one instruction +(@samp{m} is preferable for @code{asm} statements) + +@item R +Memory reference that can be loaded with one instruction +(@samp{m} is preferable for @code{asm} statements) + +@item S +Memory reference in external OSF/rose PIC format +(@samp{m} is preferable for @code{asm} statements) +@end table + +@item Motorola 680x0---@file{m68k.h} +@table @code +@item a +Address register + +@item d +Data register + +@item f +68881 floating-point register, if available + +@item x +Sun FPA (floating-point) register, if available + +@item y +First 16 Sun FPA registers, if available + +@item I +Integer in the range 1 to 8 + +@item J +16-bit signed number + +@item K +Signed number whose magnitude is greater than 0x80 + +@item L +Integer in the range -8 to -1 + +@item M +Signed number whose magnitude is greater than 0x100 + +@item G +Floating point constant that is not a 68881 constant + +@item H +Floating point constant that can be used by Sun FPA +@end table + +@item Motorola 68HC11 & 68HC12 families---@file{m68hc11.h} +@table @code +@item a +Register 'a' + +@item b +Register 'b' + +@item d +Register 'd' + +@item q +An 8-bit register + +@item t +Temporary soft register _.tmp + +@item u +A soft register _.d1 to _.d31 + +@item w +Stack pointer register + +@item x +Register 'x' + +@item y +Register 'y' + +@item z +Pseudo register 'z' (replaced by 'x' or 'y' at the end) + +@item A +An address register: x, y or z + +@item B +An address register: x or y + +@item D +Register pair (x:d) to form a 32-bit value + +@item L +Constants in the range -65536 to 65535 + +@item M +Constants whose 16-bit low part is zero + +@item N +Constant integer 1 or -1 + +@item O +Constant integer 16 + +@item P +Constants in the range -8 to 2 + +@end table + +@need 1000 +@item SPARC---@file{sparc.h} +@table @code +@item f +Floating-point register that can hold 32- or 64-bit values. + +@item e +Floating-point register that can hold 64- or 128-bit values. + +@item I +Signed 13-bit constant + +@item J +Zero + +@item K +32-bit constant with the low 12 bits clear (a constant that can be +loaded with the @code{sethi} instruction) + +@item G +Floating-point zero + +@item H +Signed 13-bit constant, sign-extended to 32 or 64 bits + +@item Q +Floating-point constant whose integral representation can +be moved into an integer register using a single sethi +instruction + +@item R +Floating-point constant whose integral representation can +be moved into an integer register using a single mov +instruction + +@item S +Floating-point constant whose integral representation can +be moved into an integer register using a high/lo_sum +instruction sequence + +@item T +Memory address aligned to an 8-byte boundary + +@item U +Even register + +@end table + +@item TMS320C3x/C4x---@file{c4x.h} +@table @code +@item a +Auxiliary (address) register (ar0-ar7) + +@item b +Stack pointer register (sp) + +@item c +Standard (32-bit) precision integer register + +@item f +Extended (40-bit) precision register (r0-r11) + +@item k +Block count register (bk) + +@item q +Extended (40-bit) precision low register (r0-r7) + +@item t +Extended (40-bit) precision register (r0-r1) + +@item u +Extended (40-bit) precision register (r2-r3) + +@item v +Repeat count register (rc) + +@item x +Index register (ir0-ir1) + +@item y +Status (condition code) register (st) + +@item z +Data page register (dp) + +@item G +Floating-point zero + +@item H +Immediate 16-bit floating-point constant + +@item I +Signed 16-bit constant + +@item J +Signed 8-bit constant + +@item K +Signed 5-bit constant + +@item L +Unsigned 16-bit constant + +@item M +Unsigned 8-bit constant + +@item N +Ones complement of unsigned 16-bit constant + +@item O +High 16-bit constant (32-bit constant with 16 LSBs zero) + +@item Q +Indirect memory reference with signed 8-bit or index register displacement + +@item R +Indirect memory reference with unsigned 5-bit displacement + +@item S +Indirect memory reference with 1 bit or index register displacement + +@item T +Direct memory reference + +@item U +Symbolic address + +@end table +@end table + +@ifset INTERNALS +@node Standard Names +@section Standard Pattern Names For Generation +@cindex standard pattern names +@cindex pattern names +@cindex names, pattern + +Here is a table of the instruction names that are meaningful in the RTL +generation pass of the compiler. Giving one of these names to an +instruction pattern tells the RTL generation pass that it can use the +pattern to accomplish a certain task. + +@table @asis +@cindex @code{mov@var{m}} instruction pattern +@item @samp{mov@var{m}} +Here @var{m} stands for a two-letter machine mode name, in lower case. +This instruction pattern moves data with that machine mode from operand +1 to operand 0. For example, @samp{movsi} moves full-word data. + +If operand 0 is a @code{subreg} with mode @var{m} of a register whose +own mode is wider than @var{m}, the effect of this instruction is +to store the specified value in the part of the register that corresponds +to mode @var{m}. The effect on the rest of the register is undefined. + +This class of patterns is special in several ways. First of all, each +of these names up to and including full word size @emph{must} be defined, +because there is no other way to copy a datum from one place to another. +If there are patterns accepting operands in larger modes, +@samp{mov@var{m}} must be defined for integer modes of those sizes. + +Second, these patterns are not used solely in the RTL generation pass. +Even the reload pass can generate move insns to copy values from stack +slots into temporary registers. When it does so, one of the operands is +a hard register and the other is an operand that can need to be reloaded +into a register. + +@findex force_reg +Therefore, when given such a pair of operands, the pattern must generate +RTL which needs no reloading and needs no temporary registers---no +registers other than the operands. For example, if you support the +pattern with a @code{define_expand}, then in such a case the +@code{define_expand} mustn't call @code{force_reg} or any other such +function which might generate new pseudo registers. + +This requirement exists even for subword modes on a RISC machine where +fetching those modes from memory normally requires several insns and +some temporary registers. + +@findex change_address +During reload a memory reference with an invalid address may be passed +as an operand. Such an address will be replaced with a valid address +later in the reload pass. In this case, nothing may be done with the +address except to use it as it stands. If it is copied, it will not be +replaced with a valid address. No attempt should be made to make such +an address into a valid address and no routine (such as +@code{change_address}) that will do so may be called. Note that +@code{general_operand} will fail when applied to such an address. + +@findex reload_in_progress +The global variable @code{reload_in_progress} (which must be explicitly +declared if required) can be used to determine whether such special +handling is required. + +The variety of operands that have reloads depends on the rest of the +machine description, but typically on a RISC machine these can only be +pseudo registers that did not get hard registers, while on other +machines explicit memory references will get optional reloads. + +If a scratch register is required to move an object to or from memory, +it can be allocated using @code{gen_reg_rtx} prior to life analysis. + +If there are cases needing +scratch registers after reload, you must define +@code{SECONDARY_INPUT_RELOAD_CLASS} and perhaps also +@code{SECONDARY_OUTPUT_RELOAD_CLASS} to detect them, and provide +patterns @samp{reload_in@var{m}} or @samp{reload_out@var{m}} to handle +them. @xref{Register Classes}. + +@findex no_new_pseudos +The global variable @code{no_new_pseudos} can be used to determine if it +is unsafe to create new pseudo registers. If this variable is nonzero, then +it is unsafe to call @code{gen_reg_rtx} to allocate a new pseudo. + +The constraints on a @samp{mov@var{m}} must permit moving any hard +register to any other hard register provided that +@code{HARD_REGNO_MODE_OK} permits mode @var{m} in both registers and +@code{REGISTER_MOVE_COST} applied to their classes returns a value of 2. + +It is obligatory to support floating point @samp{mov@var{m}} +instructions into and out of any registers that can hold fixed point +values, because unions and structures (which have modes @code{SImode} or +@code{DImode}) can be in those registers and they may have floating +point members. + +There may also be a need to support fixed point @samp{mov@var{m}} +instructions in and out of floating point registers. Unfortunately, I +have forgotten why this was so, and I don't know whether it is still +true. If @code{HARD_REGNO_MODE_OK} rejects fixed point values in +floating point registers, then the constraints of the fixed point +@samp{mov@var{m}} instructions must be designed to avoid ever trying to +reload into a floating point register. + +@cindex @code{reload_in} instruction pattern +@cindex @code{reload_out} instruction pattern +@item @samp{reload_in@var{m}} +@itemx @samp{reload_out@var{m}} +Like @samp{mov@var{m}}, but used when a scratch register is required to +move between operand 0 and operand 1. Operand 2 describes the scratch +register. See the discussion of the @code{SECONDARY_RELOAD_CLASS} +macro in @pxref{Register Classes}. + +@cindex @code{movstrict@var{m}} instruction pattern +@item @samp{movstrict@var{m}} +Like @samp{mov@var{m}} except that if operand 0 is a @code{subreg} +with mode @var{m} of a register whose natural mode is wider, +the @samp{movstrict@var{m}} instruction is guaranteed not to alter +any of the register except the part which belongs to mode @var{m}. + +@cindex @code{load_multiple} instruction pattern +@item @samp{load_multiple} +Load several consecutive memory locations into consecutive registers. +Operand 0 is the first of the consecutive registers, operand 1 +is the first memory location, and operand 2 is a constant: the +number of consecutive registers. + +Define this only if the target machine really has such an instruction; +do not define this if the most efficient way of loading consecutive +registers from memory is to do them one at a time. + +On some machines, there are restrictions as to which consecutive +registers can be stored into memory, such as particular starting or +ending register numbers or only a range of valid counts. For those +machines, use a @code{define_expand} (@pxref{Expander Definitions}) +and make the pattern fail if the restrictions are not met. + +Write the generated insn as a @code{parallel} with elements being a +@code{set} of one register from the appropriate memory location (you may +also need @code{use} or @code{clobber} elements). Use a +@code{match_parallel} (@pxref{RTL Template}) to recognize the insn. See +@file{a29k.md} and @file{rs6000.md} for examples of the use of this insn +pattern. + +@cindex @samp{store_multiple} instruction pattern +@item @samp{store_multiple} +Similar to @samp{load_multiple}, but store several consecutive registers +into consecutive memory locations. Operand 0 is the first of the +consecutive memory locations, operand 1 is the first register, and +operand 2 is a constant: the number of consecutive registers. + +@cindex @code{add@var{m}3} instruction pattern +@item @samp{add@var{m}3} +Add operand 2 and operand 1, storing the result in operand 0. All operands +must have mode @var{m}. This can be used even on two-address machines, by +means of constraints requiring operands 1 and 0 to be the same location. + +@cindex @code{sub@var{m}3} instruction pattern +@cindex @code{mul@var{m}3} instruction pattern +@cindex @code{div@var{m}3} instruction pattern +@cindex @code{udiv@var{m}3} instruction pattern +@cindex @code{mod@var{m}3} instruction pattern +@cindex @code{umod@var{m}3} instruction pattern +@cindex @code{smin@var{m}3} instruction pattern +@cindex @code{smax@var{m}3} instruction pattern +@cindex @code{umin@var{m}3} instruction pattern +@cindex @code{umax@var{m}3} instruction pattern +@cindex @code{and@var{m}3} instruction pattern +@cindex @code{ior@var{m}3} instruction pattern +@cindex @code{xor@var{m}3} instruction pattern +@item @samp{sub@var{m}3}, @samp{mul@var{m}3} +@itemx @samp{div@var{m}3}, @samp{udiv@var{m}3}, @samp{mod@var{m}3}, @samp{umod@var{m}3} +@itemx @samp{smin@var{m}3}, @samp{smax@var{m}3}, @samp{umin@var{m}3}, @samp{umax@var{m}3} +@itemx @samp{and@var{m}3}, @samp{ior@var{m}3}, @samp{xor@var{m}3} +Similar, for other arithmetic operations. +@cindex @code{min@var{m}3} instruction pattern +@cindex @code{max@var{m}3} instruction pattern +@itemx @samp{min@var{m}3}, @samp{max@var{m}3} +Floating point min and max operations. If both operands are zeros, +or if either operand is NaN, then it is unspecified which of the two +operands is returned as the result. + + +@cindex @code{mulhisi3} instruction pattern +@item @samp{mulhisi3} +Multiply operands 1 and 2, which have mode @code{HImode}, and store +a @code{SImode} product in operand 0. + +@cindex @code{mulqihi3} instruction pattern +@cindex @code{mulsidi3} instruction pattern +@item @samp{mulqihi3}, @samp{mulsidi3} +Similar widening-multiplication instructions of other widths. + +@cindex @code{umulqihi3} instruction pattern +@cindex @code{umulhisi3} instruction pattern +@cindex @code{umulsidi3} instruction pattern +@item @samp{umulqihi3}, @samp{umulhisi3}, @samp{umulsidi3} +Similar widening-multiplication instructions that do unsigned +multiplication. + +@cindex @code{smul@var{m}3_highpart} instruction pattern +@item @samp{smul@var{m}3_highpart} +Perform a signed multiplication of operands 1 and 2, which have mode +@var{m}, and store the most significant half of the product in operand 0. +The least significant half of the product is discarded. + +@cindex @code{umul@var{m}3_highpart} instruction pattern +@item @samp{umul@var{m}3_highpart} +Similar, but the multiplication is unsigned. + +@cindex @code{divmod@var{m}4} instruction pattern +@item @samp{divmod@var{m}4} +Signed division that produces both a quotient and a remainder. +Operand 1 is divided by operand 2 to produce a quotient stored +in operand 0 and a remainder stored in operand 3. + +For machines with an instruction that produces both a quotient and a +remainder, provide a pattern for @samp{divmod@var{m}4} but do not +provide patterns for @samp{div@var{m}3} and @samp{mod@var{m}3}. This +allows optimization in the relatively common case when both the quotient +and remainder are computed. + +If an instruction that just produces a quotient or just a remainder +exists and is more efficient than the instruction that produces both, +write the output routine of @samp{divmod@var{m}4} to call +@code{find_reg_note} and look for a @code{REG_UNUSED} note on the +quotient or remainder and generate the appropriate instruction. + +@cindex @code{udivmod@var{m}4} instruction pattern +@item @samp{udivmod@var{m}4} +Similar, but does unsigned division. + +@cindex @code{ashl@var{m}3} instruction pattern +@item @samp{ashl@var{m}3} +Arithmetic-shift operand 1 left by a number of bits specified by operand +2, and store the result in operand 0. Here @var{m} is the mode of +operand 0 and operand 1; operand 2's mode is specified by the +instruction pattern, and the compiler will convert the operand to that +mode before generating the instruction. + +@cindex @code{ashr@var{m}3} instruction pattern +@cindex @code{lshr@var{m}3} instruction pattern +@cindex @code{rotl@var{m}3} instruction pattern +@cindex @code{rotr@var{m}3} instruction pattern +@item @samp{ashr@var{m}3}, @samp{lshr@var{m}3}, @samp{rotl@var{m}3}, @samp{rotr@var{m}3} +Other shift and rotate instructions, analogous to the +@code{ashl@var{m}3} instructions. + +@cindex @code{neg@var{m}2} instruction pattern +@item @samp{neg@var{m}2} +Negate operand 1 and store the result in operand 0. + +@cindex @code{abs@var{m}2} instruction pattern +@item @samp{abs@var{m}2} +Store the absolute value of operand 1 into operand 0. + +@cindex @code{sqrt@var{m}2} instruction pattern +@item @samp{sqrt@var{m}2} +Store the square root of operand 1 into operand 0. + +The @code{sqrt} built-in function of C always uses the mode which +corresponds to the C data type @code{double}. + +@cindex @code{ffs@var{m}2} instruction pattern +@item @samp{ffs@var{m}2} +Store into operand 0 one plus the index of the least significant 1-bit +of operand 1. If operand 1 is zero, store zero. @var{m} is the mode +of operand 0; operand 1's mode is specified by the instruction +pattern, and the compiler will convert the operand to that mode before +generating the instruction. + +The @code{ffs} built-in function of C always uses the mode which +corresponds to the C data type @code{int}. + +@cindex @code{one_cmpl@var{m}2} instruction pattern +@item @samp{one_cmpl@var{m}2} +Store the bitwise-complement of operand 1 into operand 0. + +@cindex @code{cmp@var{m}} instruction pattern +@item @samp{cmp@var{m}} +Compare operand 0 and operand 1, and set the condition codes. +The RTL pattern should look like this: + +@smallexample +(set (cc0) (compare (match_operand:@var{m} 0 @dots{}) + (match_operand:@var{m} 1 @dots{}))) +@end smallexample + +@cindex @code{tst@var{m}} instruction pattern +@item @samp{tst@var{m}} +Compare operand 0 against zero, and set the condition codes. +The RTL pattern should look like this: + +@smallexample +(set (cc0) (match_operand:@var{m} 0 @dots{})) +@end smallexample + +@samp{tst@var{m}} patterns should not be defined for machines that do +not use @code{(cc0)}. Doing so would confuse the optimizer since it +would no longer be clear which @code{set} operations were comparisons. +The @samp{cmp@var{m}} patterns should be used instead. + +@cindex @code{movstr@var{m}} instruction pattern +@item @samp{movstr@var{m}} +Block move instruction. The addresses of the destination and source +strings are the first two operands, and both are in mode @code{Pmode}. + +The number of bytes to move is the third operand, in mode @var{m}. +Usually, you specify @code{word_mode} for @var{m}. However, if you can +generate better code knowing the range of valid lengths is smaller than +those representable in a full word, you should provide a pattern with a +mode corresponding to the range of values you can handle efficiently +(e.g., @code{QImode} for values in the range 0--127; note we avoid numbers +that appear negative) and also a pattern with @code{word_mode}. + +The fourth operand is the known shared alignment of the source and +destination, in the form of a @code{const_int} rtx. Thus, if the +compiler knows that both source and destination are word-aligned, +it may provide the value 4 for this operand. + +Descriptions of multiple @code{movstr@var{m}} patterns can only be +beneficial if the patterns for smaller modes have fewer restrictions +on their first, second and fourth operands. Note that the mode @var{m} +in @code{movstr@var{m}} does not impose any restriction on the mode of +individually moved data units in the block. + +These patterns need not give special consideration to the possibility +that the source and destination strings might overlap. + +@cindex @code{clrstr@var{m}} instruction pattern +@item @samp{clrstr@var{m}} +Block clear instruction. The addresses of the destination string is the +first operand, in mode @code{Pmode}. The number of bytes to clear is +the second operand, in mode @var{m}. See @samp{movstr@var{m}} for +a discussion of the choice of mode. + +The third operand is the known alignment of the destination, in the form +of a @code{const_int} rtx. Thus, if the compiler knows that the +destination is word-aligned, it may provide the value 4 for this +operand. + +The use for multiple @code{clrstr@var{m}} is as for @code{movstr@var{m}}. + +@cindex @code{cmpstr@var{m}} instruction pattern +@item @samp{cmpstr@var{m}} +Block compare instruction, with five operands. Operand 0 is the output; +it has mode @var{m}. The remaining four operands are like the operands +of @samp{movstr@var{m}}. The two memory blocks specified are compared +byte by byte in lexicographic order. The effect of the instruction is +to store a value in operand 0 whose sign indicates the result of the +comparison. + +@cindex @code{strlen@var{m}} instruction pattern +@item @samp{strlen@var{m}} +Compute the length of a string, with three operands. +Operand 0 is the result (of mode @var{m}), operand 1 is +a @code{mem} referring to the first character of the string, +operand 2 is the character to search for (normally zero), +and operand 3 is a constant describing the known alignment +of the beginning of the string. + +@cindex @code{float@var{mn}2} instruction pattern +@item @samp{float@var{m}@var{n}2} +Convert signed integer operand 1 (valid for fixed point mode @var{m}) to +floating point mode @var{n} and store in operand 0 (which has mode +@var{n}). + +@cindex @code{floatuns@var{mn}2} instruction pattern +@item @samp{floatuns@var{m}@var{n}2} +Convert unsigned integer operand 1 (valid for fixed point mode @var{m}) +to floating point mode @var{n} and store in operand 0 (which has mode +@var{n}). + +@cindex @code{fix@var{mn}2} instruction pattern +@item @samp{fix@var{m}@var{n}2} +Convert operand 1 (valid for floating point mode @var{m}) to fixed +point mode @var{n} as a signed number and store in operand 0 (which +has mode @var{n}). This instruction's result is defined only when +the value of operand 1 is an integer. + +@cindex @code{fixuns@var{mn}2} instruction pattern +@item @samp{fixuns@var{m}@var{n}2} +Convert operand 1 (valid for floating point mode @var{m}) to fixed +point mode @var{n} as an unsigned number and store in operand 0 (which +has mode @var{n}). This instruction's result is defined only when the +value of operand 1 is an integer. + +@cindex @code{ftrunc@var{m}2} instruction pattern +@item @samp{ftrunc@var{m}2} +Convert operand 1 (valid for floating point mode @var{m}) to an +integer value, still represented in floating point mode @var{m}, and +store it in operand 0 (valid for floating point mode @var{m}). + +@cindex @code{fix_trunc@var{mn}2} instruction pattern +@item @samp{fix_trunc@var{m}@var{n}2} +Like @samp{fix@var{m}@var{n}2} but works for any floating point value +of mode @var{m} by converting the value to an integer. + +@cindex @code{fixuns_trunc@var{mn}2} instruction pattern +@item @samp{fixuns_trunc@var{m}@var{n}2} +Like @samp{fixuns@var{m}@var{n}2} but works for any floating point +value of mode @var{m} by converting the value to an integer. + +@cindex @code{trunc@var{mn}2} instruction pattern +@item @samp{trunc@var{m}@var{n}2} +Truncate operand 1 (valid for mode @var{m}) to mode @var{n} and +store in operand 0 (which has mode @var{n}). Both modes must be fixed +point or both floating point. + +@cindex @code{extend@var{mn}2} instruction pattern +@item @samp{extend@var{m}@var{n}2} +Sign-extend operand 1 (valid for mode @var{m}) to mode @var{n} and +store in operand 0 (which has mode @var{n}). Both modes must be fixed +point or both floating point. + +@cindex @code{zero_extend@var{mn}2} instruction pattern +@item @samp{zero_extend@var{m}@var{n}2} +Zero-extend operand 1 (valid for mode @var{m}) to mode @var{n} and +store in operand 0 (which has mode @var{n}). Both modes must be fixed +point. + +@cindex @code{extv} instruction pattern +@item @samp{extv} +Extract a bit field from operand 1 (a register or memory operand), where +operand 2 specifies the width in bits and operand 3 the starting bit, +and store it in operand 0. Operand 0 must have mode @code{word_mode}. +Operand 1 may have mode @code{byte_mode} or @code{word_mode}; often +@code{word_mode} is allowed only for registers. Operands 2 and 3 must +be valid for @code{word_mode}. + +The RTL generation pass generates this instruction only with constants +for operands 2 and 3. + +The bit-field value is sign-extended to a full word integer +before it is stored in operand 0. + +@cindex @code{extzv} instruction pattern +@item @samp{extzv} +Like @samp{extv} except that the bit-field value is zero-extended. + +@cindex @code{insv} instruction pattern +@item @samp{insv} +Store operand 3 (which must be valid for @code{word_mode}) into a bit +field in operand 0, where operand 1 specifies the width in bits and +operand 2 the starting bit. Operand 0 may have mode @code{byte_mode} or +@code{word_mode}; often @code{word_mode} is allowed only for registers. +Operands 1 and 2 must be valid for @code{word_mode}. + +The RTL generation pass generates this instruction only with constants +for operands 1 and 2. + +@cindex @code{mov@var{mode}cc} instruction pattern +@item @samp{mov@var{mode}cc} +Conditionally move operand 2 or operand 3 into operand 0 according to the +comparison in operand 1. If the comparison is true, operand 2 is moved +into operand 0, otherwise operand 3 is moved. + +The mode of the operands being compared need not be the same as the operands +being moved. Some machines, sparc64 for example, have instructions that +conditionally move an integer value based on the floating point condition +codes and vice versa. + +If the machine does not have conditional move instructions, do not +define these patterns. + +@cindex @code{s@var{cond}} instruction pattern +@item @samp{s@var{cond}} +Store zero or nonzero in the operand according to the condition codes. +Value stored is nonzero iff the condition @var{cond} is true. +@var{cond} is the name of a comparison operation expression code, such +as @code{eq}, @code{lt} or @code{leu}. + +You specify the mode that the operand must have when you write the +@code{match_operand} expression. The compiler automatically sees +which mode you have used and supplies an operand of that mode. + +The value stored for a true condition must have 1 as its low bit, or +else must be negative. Otherwise the instruction is not suitable and +you should omit it from the machine description. You describe to the +compiler exactly which value is stored by defining the macro +@code{STORE_FLAG_VALUE} (@pxref{Misc}). If a description cannot be +found that can be used for all the @samp{s@var{cond}} patterns, you +should omit those operations from the machine description. + +These operations may fail, but should do so only in relatively +uncommon cases; if they would fail for common cases involving +integer comparisons, it is best to omit these patterns. + +If these operations are omitted, the compiler will usually generate code +that copies the constant one to the target and branches around an +assignment of zero to the target. If this code is more efficient than +the potential instructions used for the @samp{s@var{cond}} pattern +followed by those required to convert the result into a 1 or a zero in +@code{SImode}, you should omit the @samp{s@var{cond}} operations from +the machine description. + +@cindex @code{b@var{cond}} instruction pattern +@item @samp{b@var{cond}} +Conditional branch instruction. Operand 0 is a @code{label_ref} that +refers to the label to jump to. Jump if the condition codes meet +condition @var{cond}. + +Some machines do not follow the model assumed here where a comparison +instruction is followed by a conditional branch instruction. In that +case, the @samp{cmp@var{m}} (and @samp{tst@var{m}}) patterns should +simply store the operands away and generate all the required insns in a +@code{define_expand} (@pxref{Expander Definitions}) for the conditional +branch operations. All calls to expand @samp{b@var{cond}} patterns are +immediately preceded by calls to expand either a @samp{cmp@var{m}} +pattern or a @samp{tst@var{m}} pattern. + +Machines that use a pseudo register for the condition code value, or +where the mode used for the comparison depends on the condition being +tested, should also use the above mechanism. @xref{Jump Patterns}. + +The above discussion also applies to the @samp{mov@var{mode}cc} and +@samp{s@var{cond}} patterns. + +@cindex @code{jump} instruction pattern +@item @samp{jump} +A jump inside a function; an unconditional branch. Operand 0 is the +@code{label_ref} of the label to jump to. This pattern name is mandatory +on all machines. + +@cindex @code{call} instruction pattern +@item @samp{call} +Subroutine call instruction returning no value. Operand 0 is the +function to call; operand 1 is the number of bytes of arguments pushed +as a @code{const_int}; operand 2 is the number of registers used as +operands. + +On most machines, operand 2 is not actually stored into the RTL +pattern. It is supplied for the sake of some RISC machines which need +to put this information into the assembler code; they can put it in +the RTL instead of operand 1. + +Operand 0 should be a @code{mem} RTX whose address is the address of the +function. Note, however, that this address can be a @code{symbol_ref} +expression even if it would not be a legitimate memory address on the +target machine. If it is also not a valid argument for a call +instruction, the pattern for this operation should be a +@code{define_expand} (@pxref{Expander Definitions}) that places the +address into a register and uses that register in the call instruction. + +@cindex @code{call_value} instruction pattern +@item @samp{call_value} +Subroutine call instruction returning a value. Operand 0 is the hard +register in which the value is returned. There are three more +operands, the same as the three operands of the @samp{call} +instruction (but with numbers increased by one). + +Subroutines that return @code{BLKmode} objects use the @samp{call} +insn. + +@cindex @code{call_pop} instruction pattern +@cindex @code{call_value_pop} instruction pattern +@item @samp{call_pop}, @samp{call_value_pop} +Similar to @samp{call} and @samp{call_value}, except used if defined and +if @code{RETURN_POPS_ARGS} is non-zero. They should emit a @code{parallel} +that contains both the function call and a @code{set} to indicate the +adjustment made to the frame pointer. + +For machines where @code{RETURN_POPS_ARGS} can be non-zero, the use of these +patterns increases the number of functions for which the frame pointer +can be eliminated, if desired. + +@cindex @code{untyped_call} instruction pattern +@item @samp{untyped_call} +Subroutine call instruction returning a value of any type. Operand 0 is +the function to call; operand 1 is a memory location where the result of +calling the function is to be stored; operand 2 is a @code{parallel} +expression where each element is a @code{set} expression that indicates +the saving of a function return value into the result block. + +This instruction pattern should be defined to support +@code{__builtin_apply} on machines where special instructions are needed +to call a subroutine with arbitrary arguments or to save the value +returned. This instruction pattern is required on machines that have +multiple registers that can hold a return value (i.e. +@code{FUNCTION_VALUE_REGNO_P} is true for more than one register). + +@cindex @code{return} instruction pattern +@item @samp{return} +Subroutine return instruction. This instruction pattern name should be +defined only if a single instruction can do all the work of returning +from a function. + +Like the @samp{mov@var{m}} patterns, this pattern is also used after the +RTL generation phase. In this case it is to support machines where +multiple instructions are usually needed to return from a function, but +some class of functions only requires one instruction to implement a +return. Normally, the applicable functions are those which do not need +to save any registers or allocate stack space. + +@findex reload_completed +@findex leaf_function_p +For such machines, the condition specified in this pattern should only +be true when @code{reload_completed} is non-zero and the function's +epilogue would only be a single instruction. For machines with register +windows, the routine @code{leaf_function_p} may be used to determine if +a register window push is required. + +Machines that have conditional return instructions should define patterns +such as + +@smallexample +(define_insn "" + [(set (pc) + (if_then_else (match_operator + 0 "comparison_operator" + [(cc0) (const_int 0)]) + (return) + (pc)))] + "@var{condition}" + "@dots{}") +@end smallexample + +where @var{condition} would normally be the same condition specified on the +named @samp{return} pattern. + +@cindex @code{untyped_return} instruction pattern +@item @samp{untyped_return} +Untyped subroutine return instruction. This instruction pattern should +be defined to support @code{__builtin_return} on machines where special +instructions are needed to return a value of any type. + +Operand 0 is a memory location where the result of calling a function +with @code{__builtin_apply} is stored; operand 1 is a @code{parallel} +expression where each element is a @code{set} expression that indicates +the restoring of a function return value from the result block. + +@cindex @code{nop} instruction pattern +@item @samp{nop} +No-op instruction. This instruction pattern name should always be defined +to output a no-op in assembler code. @code{(const_int 0)} will do as an +RTL pattern. + +@cindex @code{indirect_jump} instruction pattern +@item @samp{indirect_jump} +An instruction to jump to an address which is operand zero. +This pattern name is mandatory on all machines. + +@cindex @code{casesi} instruction pattern +@item @samp{casesi} +Instruction to jump through a dispatch table, including bounds checking. +This instruction takes five operands: + +@enumerate +@item +The index to dispatch on, which has mode @code{SImode}. + +@item +The lower bound for indices in the table, an integer constant. + +@item +The total range of indices in the table---the largest index +minus the smallest one (both inclusive). + +@item +A label that precedes the table itself. + +@item +A label to jump to if the index has a value outside the bounds. +(If the machine-description macro @code{CASE_DROPS_THROUGH} is defined, +then an out-of-bounds index drops through to the code following +the jump table instead of jumping to this label. In that case, +this label is not actually used by the @samp{casesi} instruction, +but it is always provided as an operand.) +@end enumerate + +The table is a @code{addr_vec} or @code{addr_diff_vec} inside of a +@code{jump_insn}. The number of elements in the table is one plus the +difference between the upper bound and the lower bound. + +@cindex @code{tablejump} instruction pattern +@item @samp{tablejump} +Instruction to jump to a variable address. This is a low-level +capability which can be used to implement a dispatch table when there +is no @samp{casesi} pattern. + +This pattern requires two operands: the address or offset, and a label +which should immediately precede the jump table. If the macro +@code{CASE_VECTOR_PC_RELATIVE} evaluates to a nonzero value then the first +operand is an offset which counts from the address of the table; otherwise, +it is an absolute address to jump to. In either case, the first operand has +mode @code{Pmode}. + +The @samp{tablejump} insn is always the last insn before the jump +table it uses. Its assembler code normally has no need to use the +second operand, but you should incorporate it in the RTL pattern so +that the jump optimizer will not delete the table as unreachable code. + + +@cindex @code{decrement_and_branch_until_zero} instruction pattern +@item @samp{decrement_and_branch_until_zero} +Conditional branch instruction that decrements a register and +jumps if the register is non-zero. Operand 0 is the register to +decrement and test; operand 1 is the label to jump to if the +register is non-zero. @xref{Looping Patterns}. + +This optional instruction pattern is only used by the combiner, +typically for loops reversed by the loop optimizer when strength +reduction is enabled. + +@cindex @code{doloop_end} instruction pattern +@item @samp{doloop_end} +Conditional branch instruction that decrements a register and jumps if +the register is non-zero. This instruction takes five operands: Operand +0 is the register to decrement and test; operand 1 is the number of loop +iterations as a @code{const_int} or @code{const0_rtx} if this cannot be +determined until run-time; operand 2 is the actual or estimated maximum +number of iterations as a @code{const_int}; operand 3 is the number of +enclosed loops as a @code{const_int} (an innermost loop has a value of +1); operand 4 is the label to jump to if the register is non-zero. +@xref{Looping Patterns}. + +This optional instruction pattern should be defined for machines with +low-overhead looping instructions as the loop optimizer will try to +modify suitable loops to utilize it. If nested low-overhead looping is +not supported, use a @code{define_expand} (@pxref{Expander Definitions}) +and make the pattern fail if operand 3 is not @code{const1_rtx}. +Similarly, if the actual or estimated maximum number of iterations is +too large for this instruction, make it fail. + +@cindex @code{doloop_begin} instruction pattern +@item @samp{doloop_begin} +Companion instruction to @code{doloop_end} required for machines that +need to perform some initialisation, such as loading special registers +used by a low-overhead looping instruction. If initialisation insns do +not always need to be emitted, use a @code{define_expand} +(@pxref{Expander Definitions}) and make it fail. + + +@cindex @code{canonicalize_funcptr_for_compare} instruction pattern +@item @samp{canonicalize_funcptr_for_compare} +Canonicalize the function pointer in operand 1 and store the result +into operand 0. + +Operand 0 is always a @code{reg} and has mode @code{Pmode}; operand 1 +may be a @code{reg}, @code{mem}, @code{symbol_ref}, @code{const_int}, etc +and also has mode @code{Pmode}. + +Canonicalization of a function pointer usually involves computing +the address of the function which would be called if the function +pointer were used in an indirect call. + +Only define this pattern if function pointers on the target machine +can have different values but still call the same function when +used in an indirect call. + +@cindex @code{save_stack_block} instruction pattern +@cindex @code{save_stack_function} instruction pattern +@cindex @code{save_stack_nonlocal} instruction pattern +@cindex @code{restore_stack_block} instruction pattern +@cindex @code{restore_stack_function} instruction pattern +@cindex @code{restore_stack_nonlocal} instruction pattern +@item @samp{save_stack_block} +@itemx @samp{save_stack_function} +@itemx @samp{save_stack_nonlocal} +@itemx @samp{restore_stack_block} +@itemx @samp{restore_stack_function} +@itemx @samp{restore_stack_nonlocal} +Most machines save and restore the stack pointer by copying it to or +from an object of mode @code{Pmode}. Do not define these patterns on +such machines. + +Some machines require special handling for stack pointer saves and +restores. On those machines, define the patterns corresponding to the +non-standard cases by using a @code{define_expand} (@pxref{Expander +Definitions}) that produces the required insns. The three types of +saves and restores are: + +@enumerate +@item +@samp{save_stack_block} saves the stack pointer at the start of a block +that allocates a variable-sized object, and @samp{restore_stack_block} +restores the stack pointer when the block is exited. + +@item +@samp{save_stack_function} and @samp{restore_stack_function} do a +similar job for the outermost block of a function and are used when the +function allocates variable-sized objects or calls @code{alloca}. Only +the epilogue uses the restored stack pointer, allowing a simpler save or +restore sequence on some machines. + +@item +@samp{save_stack_nonlocal} is used in functions that contain labels +branched to by nested functions. It saves the stack pointer in such a +way that the inner function can use @samp{restore_stack_nonlocal} to +restore the stack pointer. The compiler generates code to restore the +frame and argument pointer registers, but some machines require saving +and restoring additional data such as register window information or +stack backchains. Place insns in these patterns to save and restore any +such required data. +@end enumerate + +When saving the stack pointer, operand 0 is the save area and operand 1 +is the stack pointer. The mode used to allocate the save area defaults +to @code{Pmode} but you can override that choice by defining the +@code{STACK_SAVEAREA_MODE} macro (@pxref{Storage Layout}). You must +specify an integral mode, or @code{VOIDmode} if no save area is needed +for a particular type of save (either because no save is needed or +because a machine-specific save area can be used). Operand 0 is the +stack pointer and operand 1 is the save area for restore operations. If +@samp{save_stack_block} is defined, operand 0 must not be +@code{VOIDmode} since these saves can be arbitrarily nested. + +A save area is a @code{mem} that is at a constant offset from +@code{virtual_stack_vars_rtx} when the stack pointer is saved for use by +nonlocal gotos and a @code{reg} in the other two cases. + +@cindex @code{allocate_stack} instruction pattern +@item @samp{allocate_stack} +Subtract (or add if @code{STACK_GROWS_DOWNWARD} is undefined) operand 1 from +the stack pointer to create space for dynamically allocated data. + +Store the resultant pointer to this space into operand 0. If you +are allocating space from the main stack, do this by emitting a +move insn to copy @code{virtual_stack_dynamic_rtx} to operand 0. +If you are allocating the space elsewhere, generate code to copy the +location of the space to operand 0. In the latter case, you must +ensure this space gets freed when the corresponding space on the main +stack is free. + +Do not define this pattern if all that must be done is the subtraction. +Some machines require other operations such as stack probes or +maintaining the back chain. Define this pattern to emit those +operations in addition to updating the stack pointer. + +@cindex @code{probe} instruction pattern +@item @samp{probe} +Some machines require instructions to be executed after space is +allocated from the stack, for example to generate a reference at +the bottom of the stack. + +If you need to emit instructions before the stack has been adjusted, +put them into the @samp{allocate_stack} pattern. Otherwise, define +this pattern to emit the required instructions. + +No operands are provided. + +@cindex @code{check_stack} instruction pattern +@item @samp{check_stack} +If stack checking cannot be done on your system by probing the stack with +a load or store instruction (@pxref{Stack Checking}), define this pattern +to perform the needed check and signaling an error if the stack +has overflowed. The single operand is the location in the stack furthest +from the current stack pointer that you need to validate. Normally, +on machines where this pattern is needed, you would obtain the stack +limit from a global or thread-specific variable or register. + +@cindex @code{nonlocal_goto} instruction pattern +@item @samp{nonlocal_goto} +Emit code to generate a non-local goto, e.g., a jump from one function +to a label in an outer function. This pattern has four arguments, +each representing a value to be used in the jump. The first +argument is to be loaded into the frame pointer, the second is +the address to branch to (code to dispatch to the actual label), +the third is the address of a location where the stack is saved, +and the last is the address of the label, to be placed in the +location for the incoming static chain. + +On most machines you need not define this pattern, since GNU CC will +already generate the correct code, which is to load the frame pointer +and static chain, restore the stack (using the +@samp{restore_stack_nonlocal} pattern, if defined), and jump indirectly +to the dispatcher. You need only define this pattern if this code will +not work on your machine. + +@cindex @code{nonlocal_goto_receiver} instruction pattern +@item @samp{nonlocal_goto_receiver} +This pattern, if defined, contains code needed at the target of a +nonlocal goto after the code already generated by GNU CC. You will not +normally need to define this pattern. A typical reason why you might +need this pattern is if some value, such as a pointer to a global table, +must be restored when the frame pointer is restored. Note that a nonlocal +goto only occurs within a unit-of-translation, so a global table pointer +that is shared by all functions of a given module need not be restored. +There are no arguments. + +@cindex @code{exception_receiver} instruction pattern +@item @samp{exception_receiver} +This pattern, if defined, contains code needed at the site of an +exception handler that isn't needed at the site of a nonlocal goto. You +will not normally need to define this pattern. A typical reason why you +might need this pattern is if some value, such as a pointer to a global +table, must be restored after control flow is branched to the handler of +an exception. There are no arguments. + +@cindex @code{builtin_setjmp_setup} instruction pattern +@item @samp{builtin_setjmp_setup} +This pattern, if defined, contains additional code needed to initialize +the @code{jmp_buf}. You will not normally need to define this pattern. +A typical reason why you might need this pattern is if some value, such +as a pointer to a global table, must be restored. Though it is +preferred that the pointer value be recalculated if possible (given the +address of a label for instance). The single argument is a pointer to +the @code{jmp_buf}. Note that the buffer is five words long and that +the first three are normally used by the generic mechanism. + +@cindex @code{builtin_setjmp_receiver} instruction pattern +@item @samp{builtin_setjmp_receiver} +This pattern, if defined, contains code needed at the site of an +builtin setjmp that isn't needed at the site of a nonlocal goto. You +will not normally need to define this pattern. A typical reason why you +might need this pattern is if some value, such as a pointer to a global +table, must be restored. It takes one argument, which is the label +to which builtin_longjmp transfered control; this pattern may be emitted +at a small offset from that label. + +@cindex @code{builtin_longjmp} instruction pattern +@item @samp{builtin_longjmp} +This pattern, if defined, performs the entire action of the longjmp. +You will not normally need to define this pattern unless you also define +@code{builtin_setjmp_setup}. The single argument is a pointer to the +@code{jmp_buf}. + +@cindex @code{eh_return} instruction pattern +@item @samp{eh_return} +This pattern, if defined, affects the way @code{__builtin_eh_return}, +and thence the call frame exception handling library routines, are +built. It is intended to handle non-trivial actions needed along +the abnormal return path. + +The pattern takes two arguments. The first is an offset to be applied +to the stack pointer. It will have been copied to some appropriate +location (typically @code{EH_RETURN_STACKADJ_RTX}) which will survive +until after reload to when the normal epilogue is generated. +The second argument is the address of the exception handler to which +the function should return. This will normally need to copied by the +pattern to some special register or memory location. + +This pattern only needs to be defined if call frame exception handling +is to be used, and simple moves to @code{EH_RETURN_STACKADJ_RTX} and +@code{EH_RETURN_HANDLER_RTX} are not sufficient. + +@cindex @code{prologue} instruction pattern +@item @samp{prologue} +This pattern, if defined, emits RTL for entry to a function. The function +entry is responsible for setting up the stack frame, initializing the frame +pointer register, saving callee saved registers, etc. + +Using a prologue pattern is generally preferred over defining +@code{FUNCTION_PROLOGUE} to emit assembly code for the prologue. + +The @code{prologue} pattern is particularly useful for targets which perform +instruction scheduling. + +@cindex @code{epilogue} instruction pattern +@item @samp{epilogue} +This pattern, if defined, emits RTL for exit from a function. The function +exit is responsible for deallocating the stack frame, restoring callee saved +registers and emitting the return instruction. + +Using an epilogue pattern is generally preferred over defining +@code{FUNCTION_EPILOGUE} to emit assembly code for the prologue. + +The @code{epilogue} pattern is particularly useful for targets which perform +instruction scheduling or which have delay slots for their return instruction. + +@cindex @code{sibcall_epilogue} instruction pattern +@item @samp{sibcall_epilogue} +This pattern, if defined, emits RTL for exit from a function without the final +branch back to the calling function. This pattern will be emitted before any +sibling call (aka tail call) sites. + +The @code{sibcall_epilogue} pattern must not clobber any arguments used for +parameter passing or any stack slots for arguments passed to the current +function. + +@cindex @code{trap} instruction pattern +@item @samp{trap} +This pattern, if defined, signals an error, typically by causing some +kind of signal to be raised. Among other places, it is used by the Java +frontend to signal `invalid array index' exceptions. + +@cindex @code{conditional_trap} instruction pattern +@item @samp{conditional_trap} +Conditional trap instruction. Operand 0 is a piece of RTL which +performs a comparison. Operand 1 is the trap code, an integer. + +A typical @code{conditional_trap} pattern looks like + +@smallexample +(define_insn "conditional_trap" + [(trap_if (match_operator 0 "trap_operator" + [(cc0) (const_int 0)]) + (match_operand 1 "const_int_operand" "i"))] + "" + "@dots{}") +@end smallexample + +@cindex @code{cycle_display} instruction pattern +@item @samp{cycle_display} + +This pattern, if present, will be emitted by the instruction scheduler at +the beginning of each new clock cycle. This can be used for annotating the +assembler output with cycle counts. Operand 0 is a @code{const_int} that +holds the clock cycle. + +@end table + +@node Pattern Ordering +@section When the Order of Patterns Matters +@cindex Pattern Ordering +@cindex Ordering of Patterns + +Sometimes an insn can match more than one instruction pattern. Then the +pattern that appears first in the machine description is the one used. +Therefore, more specific patterns (patterns that will match fewer things) +and faster instructions (those that will produce better code when they +do match) should usually go first in the description. + +In some cases the effect of ordering the patterns can be used to hide +a pattern when it is not valid. For example, the 68000 has an +instruction for converting a fullword to floating point and another +for converting a byte to floating point. An instruction converting +an integer to floating point could match either one. We put the +pattern to convert the fullword first to make sure that one will +be used rather than the other. (Otherwise a large integer might +be generated as a single-byte immediate quantity, which would not work.) +Instead of using this pattern ordering it would be possible to make the +pattern for convert-a-byte smart enough to deal properly with any +constant value. + +@node Dependent Patterns +@section Interdependence of Patterns +@cindex Dependent Patterns +@cindex Interdependence of Patterns + +Every machine description must have a named pattern for each of the +conditional branch names @samp{b@var{cond}}. The recognition template +must always have the form + +@example +(set (pc) + (if_then_else (@var{cond} (cc0) (const_int 0)) + (label_ref (match_operand 0 "" "")) + (pc))) +@end example + +@noindent +In addition, every machine description must have an anonymous pattern +for each of the possible reverse-conditional branches. Their templates +look like + +@example +(set (pc) + (if_then_else (@var{cond} (cc0) (const_int 0)) + (pc) + (label_ref (match_operand 0 "" "")))) +@end example + +@noindent +They are necessary because jump optimization can turn direct-conditional +branches into reverse-conditional branches. + +It is often convenient to use the @code{match_operator} construct to +reduce the number of patterns that must be specified for branches. For +example, + +@example +(define_insn "" + [(set (pc) + (if_then_else (match_operator 0 "comparison_operator" + [(cc0) (const_int 0)]) + (pc) + (label_ref (match_operand 1 "" ""))))] + "@var{condition}" + "@dots{}") +@end example + +In some cases machines support instructions identical except for the +machine mode of one or more operands. For example, there may be +``sign-extend halfword'' and ``sign-extend byte'' instructions whose +patterns are + +@example +(set (match_operand:SI 0 @dots{}) + (extend:SI (match_operand:HI 1 @dots{}))) + +(set (match_operand:SI 0 @dots{}) + (extend:SI (match_operand:QI 1 @dots{}))) +@end example + +@noindent +Constant integers do not specify a machine mode, so an instruction to +extend a constant value could match either pattern. The pattern it +actually will match is the one that appears first in the file. For correct +results, this must be the one for the widest possible mode (@code{HImode}, +here). If the pattern matches the @code{QImode} instruction, the results +will be incorrect if the constant value does not actually fit that mode. + +Such instructions to extend constants are rarely generated because they are +optimized away, but they do occasionally happen in nonoptimized +compilations. + +If a constraint in a pattern allows a constant, the reload pass may +replace a register with a constant permitted by the constraint in some +cases. Similarly for memory references. Because of this substitution, +you should not provide separate patterns for increment and decrement +instructions. Instead, they should be generated from the same pattern +that supports register-register add insns by examining the operands and +generating the appropriate machine instruction. + +@node Jump Patterns +@section Defining Jump Instruction Patterns +@cindex jump instruction patterns +@cindex defining jump instruction patterns + +For most machines, GNU CC assumes that the machine has a condition code. +A comparison insn sets the condition code, recording the results of both +signed and unsigned comparison of the given operands. A separate branch +insn tests the condition code and branches or not according its value. +The branch insns come in distinct signed and unsigned flavors. Many +common machines, such as the Vax, the 68000 and the 32000, work this +way. + +Some machines have distinct signed and unsigned compare instructions, and +only one set of conditional branch instructions. The easiest way to handle +these machines is to treat them just like the others until the final stage +where assembly code is written. At this time, when outputting code for the +compare instruction, peek ahead at the following branch using +@code{next_cc0_user (insn)}. (The variable @code{insn} refers to the insn +being output, in the output-writing code in an instruction pattern.) If +the RTL says that is an unsigned branch, output an unsigned compare; +otherwise output a signed compare. When the branch itself is output, you +can treat signed and unsigned branches identically. + +The reason you can do this is that GNU CC always generates a pair of +consecutive RTL insns, possibly separated by @code{note} insns, one to +set the condition code and one to test it, and keeps the pair inviolate +until the end. + +To go with this technique, you must define the machine-description macro +@code{NOTICE_UPDATE_CC} to do @code{CC_STATUS_INIT}; in other words, no +compare instruction is superfluous. + +Some machines have compare-and-branch instructions and no condition code. +A similar technique works for them. When it is time to ``output'' a +compare instruction, record its operands in two static variables. When +outputting the branch-on-condition-code instruction that follows, actually +output a compare-and-branch instruction that uses the remembered operands. + +It also works to define patterns for compare-and-branch instructions. +In optimizing compilation, the pair of compare and branch instructions +will be combined according to these patterns. But this does not happen +if optimization is not requested. So you must use one of the solutions +above in addition to any special patterns you define. + +In many RISC machines, most instructions do not affect the condition +code and there may not even be a separate condition code register. On +these machines, the restriction that the definition and use of the +condition code be adjacent insns is not necessary and can prevent +important optimizations. For example, on the IBM RS/6000, there is a +delay for taken branches unless the condition code register is set three +instructions earlier than the conditional branch. The instruction +scheduler cannot perform this optimization if it is not permitted to +separate the definition and use of the condition code register. + +On these machines, do not use @code{(cc0)}, but instead use a register +to represent the condition code. If there is a specific condition code +register in the machine, use a hard register. If the condition code or +comparison result can be placed in any general register, or if there are +multiple condition registers, use a pseudo register. + +@findex prev_cc0_setter +@findex next_cc0_user +On some machines, the type of branch instruction generated may depend on +the way the condition code was produced; for example, on the 68k and +Sparc, setting the condition code directly from an add or subtract +instruction does not clear the overflow bit the way that a test +instruction does, so a different branch instruction must be used for +some conditional branches. For machines that use @code{(cc0)}, the set +and use of the condition code must be adjacent (separated only by +@code{note} insns) allowing flags in @code{cc_status} to be used. +(@xref{Condition Code}.) Also, the comparison and branch insns can be +located from each other by using the functions @code{prev_cc0_setter} +and @code{next_cc0_user}. + +However, this is not true on machines that do not use @code{(cc0)}. On +those machines, no assumptions can be made about the adjacency of the +compare and branch insns and the above methods cannot be used. Instead, +we use the machine mode of the condition code register to record +different formats of the condition code register. + +Registers used to store the condition code value should have a mode that +is in class @code{MODE_CC}. Normally, it will be @code{CCmode}. If +additional modes are required (as for the add example mentioned above in +the Sparc), define the macro @code{EXTRA_CC_MODES} to list the +additional modes required (@pxref{Condition Code}). Also define +@code{SELECT_CC_MODE} to choose a mode given an operand of a compare. + +If it is known during RTL generation that a different mode will be +required (for example, if the machine has separate compare instructions +for signed and unsigned quantities, like most IBM processors), they can +be specified at that time. + +If the cases that require different modes would be made by instruction +combination, the macro @code{SELECT_CC_MODE} determines which machine +mode should be used for the comparison result. The patterns should be +written using that mode. To support the case of the add on the Sparc +discussed above, we have the pattern + +@smallexample +(define_insn "" + [(set (reg:CC_NOOV 0) + (compare:CC_NOOV + (plus:SI (match_operand:SI 0 "register_operand" "%r") + (match_operand:SI 1 "arith_operand" "rI")) + (const_int 0)))] + "" + "@dots{}") +@end smallexample + +The @code{SELECT_CC_MODE} macro on the Sparc returns @code{CC_NOOVmode} +for comparisons whose argument is a @code{plus}. + +@node Looping Patterns +@section Defining Looping Instruction Patterns +@cindex looping instruction patterns +@cindex defining looping instruction patterns + +Some machines have special jump instructions that can be utilised to +make loops more efficient. A common example is the 68000 @samp{dbra} +instruction which performs a decrement of a register and a branch if the +result was greater than zero. Other machines, in particular digital +signal processors (DSPs), have special block repeat instructions to +provide low-overhead loop support. For example, the TI TMS320C3x/C4x +DSPs have a block repeat instruction that loads special registers to +mark the top and end of a loop and to count the number of loop +iterations. This avoids the need for fetching and executing a +@samp{dbra}-like instruction and avoids pipeline stalls asociated with +the jump. + +GNU CC has three special named patterns to support low overhead looping, +@samp{decrement_and_branch_until_zero}, @samp{doloop_begin}, and +@samp{doloop_end}. The first pattern, +@samp{decrement_and_branch_until_zero}, is not emitted during RTL +generation but may be emitted during the instruction combination phase. +This requires the assistance of the loop optimizer, using information +collected during strength reduction, to reverse a loop to count down to +zero. Some targets also require the loop optimizer to add a +@code{REG_NONNEG} note to indicate that the iteration count is always +positive. This is needed if the target performs a signed loop +termination test. For example, the 68000 uses a pattern similar to the +following for its @code{dbra} instruction: + +@smallexample +@group +(define_insn "decrement_and_branch_until_zero" + [(set (pc) + (if_then_else + (ge (plus:SI (match_operand:SI 0 "general_operand" "+d*am") + (const_int -1)) + (const_int 0)) + (label_ref (match_operand 1 "" "")) + (pc))) + (set (match_dup 0) + (plus:SI (match_dup 0) + (const_int -1)))] + "find_reg_note (insn, REG_NONNEG, 0)" + "...") +@end group +@end smallexample + +Note that since the insn is both a jump insn and has an output, it must +deal with its own reloads, hence the `m' constraints. Also note that +since this insn is generated by the instruction combination phase +combining two sequential insns together into an implicit parallel insn, +the iteration counter needs to be biased by the same amount as the +decrement operation, in this case -1. Note that the following similar +pattern will not be matched by the combiner. + +@smallexample +@group +(define_insn "decrement_and_branch_until_zero" + [(set (pc) + (if_then_else + (ge (match_operand:SI 0 "general_operand" "+d*am") + (const_int 1)) + (label_ref (match_operand 1 "" "")) + (pc))) + (set (match_dup 0) + (plus:SI (match_dup 0) + (const_int -1)))] + "find_reg_note (insn, REG_NONNEG, 0)" + "...") +@end group +@end smallexample + +The other two special looping patterns, @samp{doloop_begin} and +@samp{doloop_end}, are emitted by the loop optimiser for certain +well-behaved loops with a finite number of loop iterations using +information collected during strength reduction. + +The @samp{doloop_end} pattern describes the actual looping instruction +(or the implicit looping operation) and the @samp{doloop_begin} pattern +is an optional companion pattern that can be used for initialisation +needed for some low-overhead looping instructions. + +Note that some machines require the actual looping instruction to be +emitted at the top of the loop (e.g., the TMS320C3x/C4x DSPs). Emitting +the true RTL for a looping instruction at the top of the loop can cause +problems with flow analysis. So instead, a dummy @code{doloop} insn is +emitted at the end of the loop. The machine dependent reorg pass checks +for the presence of this @code{doloop} insn and then searches back to +the top of the loop, where it inserts the true looping insn (provided +there are no instructions in the loop which would cause problems). Any +additional labels can be emitted at this point. In addition, if the +desired special iteration counter register was not allocated, this +machine dependent reorg pass could emit a traditional compare and jump +instruction pair. + +The essential difference between the +@samp{decrement_and_branch_until_zero} and the @samp{doloop_end} +patterns is that the loop optimizer allocates an additional pseudo +register for the latter as an iteration counter. This pseudo register +cannot be used within the loop (i.e., general induction variables cannot +be derived from it), however, in many cases the loop induction variable +may become redundant and removed by the flow pass. + + +@node Insn Canonicalizations +@section Canonicalization of Instructions +@cindex canonicalization of instructions +@cindex insn canonicalization + +There are often cases where multiple RTL expressions could represent an +operation performed by a single machine instruction. This situation is +most commonly encountered with logical, branch, and multiply-accumulate +instructions. In such cases, the compiler attempts to convert these +multiple RTL expressions into a single canonical form to reduce the +number of insn patterns required. + +In addition to algebraic simplifications, following canonicalizations +are performed: + +@itemize @bullet +@item +For commutative and comparison operators, a constant is always made the +second operand. If a machine only supports a constant as the second +operand, only patterns that match a constant in the second operand need +be supplied. + +@cindex @code{neg}, canonicalization of +@cindex @code{not}, canonicalization of +@cindex @code{mult}, canonicalization of +@cindex @code{plus}, canonicalization of +@cindex @code{minus}, canonicalization of +For these operators, if only one operand is a @code{neg}, @code{not}, +@code{mult}, @code{plus}, or @code{minus} expression, it will be the +first operand. + +@cindex @code{compare}, canonicalization of +@item +For the @code{compare} operator, a constant is always the second operand +on machines where @code{cc0} is used (@pxref{Jump Patterns}). On other +machines, there are rare cases where the compiler might want to construct +a @code{compare} with a constant as the first operand. However, these +cases are not common enough for it to be worthwhile to provide a pattern +matching a constant as the first operand unless the machine actually has +such an instruction. + +An operand of @code{neg}, @code{not}, @code{mult}, @code{plus}, or +@code{minus} is made the first operand under the same conditions as +above. + +@item +@code{(minus @var{x} (const_int @var{n}))} is converted to +@code{(plus @var{x} (const_int @var{-n}))}. + +@item +Within address computations (i.e., inside @code{mem}), a left shift is +converted into the appropriate multiplication by a power of two. + +@cindex @code{ior}, canonicalization of +@cindex @code{and}, canonicalization of +@cindex De Morgan's law +@item +De`Morgan's Law is used to move bitwise negation inside a bitwise +logical-and or logical-or operation. If this results in only one +operand being a @code{not} expression, it will be the first one. + +A machine that has an instruction that performs a bitwise logical-and of one +operand with the bitwise negation of the other should specify the pattern +for that instruction as + +@example +(define_insn "" + [(set (match_operand:@var{m} 0 @dots{}) + (and:@var{m} (not:@var{m} (match_operand:@var{m} 1 @dots{})) + (match_operand:@var{m} 2 @dots{})))] + "@dots{}" + "@dots{}") +@end example + +@noindent +Similarly, a pattern for a ``NAND'' instruction should be written + +@example +(define_insn "" + [(set (match_operand:@var{m} 0 @dots{}) + (ior:@var{m} (not:@var{m} (match_operand:@var{m} 1 @dots{})) + (not:@var{m} (match_operand:@var{m} 2 @dots{}))))] + "@dots{}" + "@dots{}") +@end example + +In both cases, it is not necessary to include patterns for the many +logically equivalent RTL expressions. + +@cindex @code{xor}, canonicalization of +@item +The only possible RTL expressions involving both bitwise exclusive-or +and bitwise negation are @code{(xor:@var{m} @var{x} @var{y})} +and @code{(not:@var{m} (xor:@var{m} @var{x} @var{y}))}.@refill + +@item +The sum of three items, one of which is a constant, will only appear in +the form + +@example +(plus:@var{m} (plus:@var{m} @var{x} @var{y}) @var{constant}) +@end example + +@item +On machines that do not use @code{cc0}, +@code{(compare @var{x} (const_int 0))} will be converted to +@var{x}.@refill + +@cindex @code{zero_extract}, canonicalization of +@cindex @code{sign_extract}, canonicalization of +@item +Equality comparisons of a group of bits (usually a single bit) with zero +will be written using @code{zero_extract} rather than the equivalent +@code{and} or @code{sign_extract} operations. + +@end itemize + +@node Expander Definitions +@section Defining RTL Sequences for Code Generation +@cindex expander definitions +@cindex code generation RTL sequences +@cindex defining RTL sequences for code generation + +On some target machines, some standard pattern names for RTL generation +cannot be handled with single insn, but a sequence of RTL insns can +represent them. For these target machines, you can write a +@code{define_expand} to specify how to generate the sequence of RTL. + +@findex define_expand +A @code{define_expand} is an RTL expression that looks almost like a +@code{define_insn}; but, unlike the latter, a @code{define_expand} is used +only for RTL generation and it can produce more than one RTL insn. + +A @code{define_expand} RTX has four operands: + +@itemize @bullet +@item +The name. Each @code{define_expand} must have a name, since the only +use for it is to refer to it by name. + +@item +The RTL template. This is a vector of RTL expressions representing +a sequence of separate instructions. Unlike @code{define_insn}, there +is no implicit surrounding @code{PARALLEL}. + +@item +The condition, a string containing a C expression. This expression is +used to express how the availability of this pattern depends on +subclasses of target machine, selected by command-line options when GNU +CC is run. This is just like the condition of a @code{define_insn} that +has a standard name. Therefore, the condition (if present) may not +depend on the data in the insn being matched, but only the +target-machine-type flags. The compiler needs to test these conditions +during initialization in order to learn exactly which named instructions +are available in a particular run. + +@item +The preparation statements, a string containing zero or more C +statements which are to be executed before RTL code is generated from +the RTL template. + +Usually these statements prepare temporary registers for use as +internal operands in the RTL template, but they can also generate RTL +insns directly by calling routines such as @code{emit_insn}, etc. +Any such insns precede the ones that come from the RTL template. +@end itemize + +Every RTL insn emitted by a @code{define_expand} must match some +@code{define_insn} in the machine description. Otherwise, the compiler +will crash when trying to generate code for the insn or trying to optimize +it. + +The RTL template, in addition to controlling generation of RTL insns, +also describes the operands that need to be specified when this pattern +is used. In particular, it gives a predicate for each operand. + +A true operand, which needs to be specified in order to generate RTL from +the pattern, should be described with a @code{match_operand} in its first +occurrence in the RTL template. This enters information on the operand's +predicate into the tables that record such things. GNU CC uses the +information to preload the operand into a register if that is required for +valid RTL code. If the operand is referred to more than once, subsequent +references should use @code{match_dup}. + +The RTL template may also refer to internal ``operands'' which are +temporary registers or labels used only within the sequence made by the +@code{define_expand}. Internal operands are substituted into the RTL +template with @code{match_dup}, never with @code{match_operand}. The +values of the internal operands are not passed in as arguments by the +compiler when it requests use of this pattern. Instead, they are computed +within the pattern, in the preparation statements. These statements +compute the values and store them into the appropriate elements of +@code{operands} so that @code{match_dup} can find them. + +There are two special macros defined for use in the preparation statements: +@code{DONE} and @code{FAIL}. Use them with a following semicolon, +as a statement. + +@table @code + +@findex DONE +@item DONE +Use the @code{DONE} macro to end RTL generation for the pattern. The +only RTL insns resulting from the pattern on this occasion will be +those already emitted by explicit calls to @code{emit_insn} within the +preparation statements; the RTL template will not be generated. + +@findex FAIL +@item FAIL +Make the pattern fail on this occasion. When a pattern fails, it means +that the pattern was not truly available. The calling routines in the +compiler will try other strategies for code generation using other patterns. + +Failure is currently supported only for binary (addition, multiplication, +shifting, etc.) and bitfield (@code{extv}, @code{extzv}, and @code{insv}) +operations. +@end table + +If the preparation falls through (invokes neither @code{DONE} nor +@code{FAIL}), then the @code{define_expand} acts like a +@code{define_insn} in that the RTL template is used to generate the +insn. + +The RTL template is not used for matching, only for generating the +initial insn list. If the preparation statement always invokes +@code{DONE} or @code{FAIL}, the RTL template may be reduced to a simple +list of operands, such as this example: + +@smallexample +@group +(define_expand "addsi3" + [(match_operand:SI 0 "register_operand" "") + (match_operand:SI 1 "register_operand" "") + (match_operand:SI 2 "register_operand" "")] +@end group +@group + "" + " +@{ + handle_add (operands[0], operands[1], operands[2]); + DONE; +@}") +@end group +@end smallexample + +Here is an example, the definition of left-shift for the SPUR chip: + +@smallexample +@group +(define_expand "ashlsi3" + [(set (match_operand:SI 0 "register_operand" "") + (ashift:SI +@end group +@group + (match_operand:SI 1 "register_operand" "") + (match_operand:SI 2 "nonmemory_operand" "")))] + "" + " +@end group +@end smallexample + +@smallexample +@group +@{ + if (GET_CODE (operands[2]) != CONST_INT + || (unsigned) INTVAL (operands[2]) > 3) + FAIL; +@}") +@end group +@end smallexample + +@noindent +This example uses @code{define_expand} so that it can generate an RTL insn +for shifting when the shift-count is in the supported range of 0 to 3 but +fail in other cases where machine insns aren't available. When it fails, +the compiler tries another strategy using different patterns (such as, a +library call). + +If the compiler were able to handle nontrivial condition-strings in +patterns with names, then it would be possible to use a +@code{define_insn} in that case. Here is another case (zero-extension +on the 68000) which makes more use of the power of @code{define_expand}: + +@smallexample +(define_expand "zero_extendhisi2" + [(set (match_operand:SI 0 "general_operand" "") + (const_int 0)) + (set (strict_low_part + (subreg:HI + (match_dup 0) + 0)) + (match_operand:HI 1 "general_operand" ""))] + "" + "operands[1] = make_safe_from (operands[1], operands[0]);") +@end smallexample + +@noindent +@findex make_safe_from +Here two RTL insns are generated, one to clear the entire output operand +and the other to copy the input operand into its low half. This sequence +is incorrect if the input operand refers to [the old value of] the output +operand, so the preparation statement makes sure this isn't so. The +function @code{make_safe_from} copies the @code{operands[1]} into a +temporary register if it refers to @code{operands[0]}. It does this +by emitting another RTL insn. + +Finally, a third example shows the use of an internal operand. +Zero-extension on the SPUR chip is done by @code{and}-ing the result +against a halfword mask. But this mask cannot be represented by a +@code{const_int} because the constant value is too large to be legitimate +on this machine. So it must be copied into a register with +@code{force_reg} and then the register used in the @code{and}. + +@smallexample +(define_expand "zero_extendhisi2" + [(set (match_operand:SI 0 "register_operand" "") + (and:SI (subreg:SI + (match_operand:HI 1 "register_operand" "") + 0) + (match_dup 2)))] + "" + "operands[2] + = force_reg (SImode, GEN_INT (65535)); ") +@end smallexample + +@strong{Note:} If the @code{define_expand} is used to serve a +standard binary or unary arithmetic operation or a bitfield operation, +then the last insn it generates must not be a @code{code_label}, +@code{barrier} or @code{note}. It must be an @code{insn}, +@code{jump_insn} or @code{call_insn}. If you don't need a real insn +at the end, emit an insn to copy the result of the operation into +itself. Such an insn will generate no code, but it can avoid problems +in the compiler.@refill + +@node Insn Splitting +@section Defining How to Split Instructions +@cindex insn splitting +@cindex instruction splitting +@cindex splitting instructions + +There are two cases where you should specify how to split a pattern into +multiple insns. On machines that have instructions requiring delay +slots (@pxref{Delay Slots}) or that have instructions whose output is +not available for multiple cycles (@pxref{Function Units}), the compiler +phases that optimize these cases need to be able to move insns into +one-instruction delay slots. However, some insns may generate more than one +machine instruction. These insns cannot be placed into a delay slot. + +Often you can rewrite the single insn as a list of individual insns, +each corresponding to one machine instruction. The disadvantage of +doing so is that it will cause the compilation to be slower and require +more space. If the resulting insns are too complex, it may also +suppress some optimizations. The compiler splits the insn if there is a +reason to believe that it might improve instruction or delay slot +scheduling. + +The insn combiner phase also splits putative insns. If three insns are +merged into one insn with a complex expression that cannot be matched by +some @code{define_insn} pattern, the combiner phase attempts to split +the complex pattern into two insns that are recognized. Usually it can +break the complex pattern into two patterns by splitting out some +subexpression. However, in some other cases, such as performing an +addition of a large constant in two insns on a RISC machine, the way to +split the addition into two insns is machine-dependent. + +@findex define_split +The @code{define_split} definition tells the compiler how to split a +complex insn into several simpler insns. It looks like this: + +@smallexample +(define_split + [@var{insn-pattern}] + "@var{condition}" + [@var{new-insn-pattern-1} + @var{new-insn-pattern-2} + @dots{}] + "@var{preparation statements}") +@end smallexample + +@var{insn-pattern} is a pattern that needs to be split and +@var{condition} is the final condition to be tested, as in a +@code{define_insn}. When an insn matching @var{insn-pattern} and +satisfying @var{condition} is found, it is replaced in the insn list +with the insns given by @var{new-insn-pattern-1}, +@var{new-insn-pattern-2}, etc. + +The @var{preparation statements} are similar to those statements that +are specified for @code{define_expand} (@pxref{Expander Definitions}) +and are executed before the new RTL is generated to prepare for the +generated code or emit some insns whose pattern is not fixed. Unlike +those in @code{define_expand}, however, these statements must not +generate any new pseudo-registers. Once reload has completed, they also +must not allocate any space in the stack frame. + +Patterns are matched against @var{insn-pattern} in two different +circumstances. If an insn needs to be split for delay slot scheduling +or insn scheduling, the insn is already known to be valid, which means +that it must have been matched by some @code{define_insn} and, if +@code{reload_completed} is non-zero, is known to satisfy the constraints +of that @code{define_insn}. In that case, the new insn patterns must +also be insns that are matched by some @code{define_insn} and, if +@code{reload_completed} is non-zero, must also satisfy the constraints +of those definitions. + +As an example of this usage of @code{define_split}, consider the following +example from @file{a29k.md}, which splits a @code{sign_extend} from +@code{HImode} to @code{SImode} into a pair of shift insns: + +@smallexample +(define_split + [(set (match_operand:SI 0 "gen_reg_operand" "") + (sign_extend:SI (match_operand:HI 1 "gen_reg_operand" "")))] + "" + [(set (match_dup 0) + (ashift:SI (match_dup 1) + (const_int 16))) + (set (match_dup 0) + (ashiftrt:SI (match_dup 0) + (const_int 16)))] + " +@{ operands[1] = gen_lowpart (SImode, operands[1]); @}") +@end smallexample + +When the combiner phase tries to split an insn pattern, it is always the +case that the pattern is @emph{not} matched by any @code{define_insn}. +The combiner pass first tries to split a single @code{set} expression +and then the same @code{set} expression inside a @code{parallel}, but +followed by a @code{clobber} of a pseudo-reg to use as a scratch +register. In these cases, the combiner expects exactly two new insn +patterns to be generated. It will verify that these patterns match some +@code{define_insn} definitions, so you need not do this test in the +@code{define_split} (of course, there is no point in writing a +@code{define_split} that will never produce insns that match). + +Here is an example of this use of @code{define_split}, taken from +@file{rs6000.md}: + +@smallexample +(define_split + [(set (match_operand:SI 0 "gen_reg_operand" "") + (plus:SI (match_operand:SI 1 "gen_reg_operand" "") + (match_operand:SI 2 "non_add_cint_operand" "")))] + "" + [(set (match_dup 0) (plus:SI (match_dup 1) (match_dup 3))) + (set (match_dup 0) (plus:SI (match_dup 0) (match_dup 4)))] +" +@{ + int low = INTVAL (operands[2]) & 0xffff; + int high = (unsigned) INTVAL (operands[2]) >> 16; + + if (low & 0x8000) + high++, low |= 0xffff0000; + + operands[3] = GEN_INT (high << 16); + operands[4] = GEN_INT (low); +@}") +@end smallexample + +Here the predicate @code{non_add_cint_operand} matches any +@code{const_int} that is @emph{not} a valid operand of a single add +insn. The add with the smaller displacement is written so that it +can be substituted into the address of a subsequent operation. + +An example that uses a scratch register, from the same file, generates +an equality comparison of a register and a large constant: + +@smallexample +(define_split + [(set (match_operand:CC 0 "cc_reg_operand" "") + (compare:CC (match_operand:SI 1 "gen_reg_operand" "") + (match_operand:SI 2 "non_short_cint_operand" ""))) + (clobber (match_operand:SI 3 "gen_reg_operand" ""))] + "find_single_use (operands[0], insn, 0) + && (GET_CODE (*find_single_use (operands[0], insn, 0)) == EQ + || GET_CODE (*find_single_use (operands[0], insn, 0)) == NE)" + [(set (match_dup 3) (xor:SI (match_dup 1) (match_dup 4))) + (set (match_dup 0) (compare:CC (match_dup 3) (match_dup 5)))] + " +@{ + /* Get the constant we are comparing against, C, and see what it + looks like sign-extended to 16 bits. Then see what constant + could be XOR'ed with C to get the sign-extended value. */ + + int c = INTVAL (operands[2]); + int sextc = (c << 16) >> 16; + int xorv = c ^ sextc; + + operands[4] = GEN_INT (xorv); + operands[5] = GEN_INT (sextc); +@}") +@end smallexample + +To avoid confusion, don't write a single @code{define_split} that +accepts some insns that match some @code{define_insn} as well as some +insns that don't. Instead, write two separate @code{define_split} +definitions, one for the insns that are valid and one for the insns that +are not valid. + +For the common case where the pattern of a define_split exactly matches the +pattern of a define_insn, use @code{define_insn_and_split}. It looks like +this: + +@smallexample +(define_insn_and_split + [@var{insn-pattern}] + "@var{condition}" + "@var{output-template}" + "@var{split-condition}" + [@var{new-insn-pattern-1} + @var{new-insn-pattern-2} + @dots{}] + "@var{preparation statements}" + [@var{insn-attributes}]) + +@end smallexample + +@var{insn-pattern}, @var{condition}, @var{output-template}, and +@var{insn-attributes} are used as in @code{define_insn}. The +@var{new-insn-pattern} vector and the @var{preparation-statements} are used as +in a @code{define_split}. The @var{split-condition} is also used as in +@code{define_split}, with the additional behavior that if the condition starts +with @samp{&&}, the condition used for the split will be the constructed as a +logical "and" of the split condition with the insn condition. For example, +from i386.md: + +@smallexample +(define_insn_and_split "zero_extendhisi2_and" + [(set (match_operand:SI 0 "register_operand" "=r") + (zero_extend:SI (match_operand:HI 1 "register_operand" "0"))) + (clobber (reg:CC 17))] + "TARGET_ZERO_EXTEND_WITH_AND && !optimize_size" + "#" + "&& reload_completed" + [(parallel [(set (match_dup 0) (and:SI (match_dup 0) (const_int 65535))) + (clobber (reg:CC 17))])] + "" + [(set_attr "type" "alu1")]) + +@end smallexample + +In this case, the actual split condition will be +"TARGET_ZERO_EXTEND_WITH_AND && !optimize_size && reload_completed." + +The @code{define_insn_and_split} construction provides exactly the same +functionality as two separate @code{define_insn} and @code{define_split} +patterns. It exists for compactness, and as a maintenance tool to prevent +having to ensure the two patterns' templates match. + +@node Peephole Definitions +@section Machine-Specific Peephole Optimizers +@cindex peephole optimizer definitions +@cindex defining peephole optimizers + +In addition to instruction patterns the @file{md} file may contain +definitions of machine-specific peephole optimizations. + +The combiner does not notice certain peephole optimizations when the data +flow in the program does not suggest that it should try them. For example, +sometimes two consecutive insns related in purpose can be combined even +though the second one does not appear to use a register computed in the +first one. A machine-specific peephole optimizer can detect such +opportunities. + +There are two forms of peephole definitions that may be used. The +original @code{define_peephole} is run at assembly output time to +match insns and substitute assembly text. Use of @code{define_peephole} +is deprecated. + +A newer @code{define_peephole2} matches insns and substitutes new +insns. The @code{peephole2} pass is run after register allocation +but before scheduling, which may result in much better code for +targets that do scheduling. + +@menu +* define_peephole:: RTL to Text Peephole Optimizers +* define_peephole2:: RTL to RTL Peephole Optimizers +@end menu + +@node define_peephole +@subsection RTL to Text Peephole Optimizers +@findex define_peephole + +@need 1000 +A definition looks like this: + +@smallexample +(define_peephole + [@var{insn-pattern-1} + @var{insn-pattern-2} + @dots{}] + "@var{condition}" + "@var{template}" + "@var{optional insn-attributes}") +@end smallexample + +@noindent +The last string operand may be omitted if you are not using any +machine-specific information in this machine description. If present, +it must obey the same rules as in a @code{define_insn}. + +In this skeleton, @var{insn-pattern-1} and so on are patterns to match +consecutive insns. The optimization applies to a sequence of insns when +@var{insn-pattern-1} matches the first one, @var{insn-pattern-2} matches +the next, and so on.@refill + +Each of the insns matched by a peephole must also match a +@code{define_insn}. Peepholes are checked only at the last stage just +before code generation, and only optionally. Therefore, any insn which +would match a peephole but no @code{define_insn} will cause a crash in code +generation in an unoptimized compilation, or at various optimization +stages. + +The operands of the insns are matched with @code{match_operands}, +@code{match_operator}, and @code{match_dup}, as usual. What is not +usual is that the operand numbers apply to all the insn patterns in the +definition. So, you can check for identical operands in two insns by +using @code{match_operand} in one insn and @code{match_dup} in the +other. + +The operand constraints used in @code{match_operand} patterns do not have +any direct effect on the applicability of the peephole, but they will +be validated afterward, so make sure your constraints are general enough +to apply whenever the peephole matches. If the peephole matches +but the constraints are not satisfied, the compiler will crash. + +It is safe to omit constraints in all the operands of the peephole; or +you can write constraints which serve as a double-check on the criteria +previously tested. + +Once a sequence of insns matches the patterns, the @var{condition} is +checked. This is a C expression which makes the final decision whether to +perform the optimization (we do so if the expression is nonzero). If +@var{condition} is omitted (in other words, the string is empty) then the +optimization is applied to every sequence of insns that matches the +patterns. + +The defined peephole optimizations are applied after register allocation +is complete. Therefore, the peephole definition can check which +operands have ended up in which kinds of registers, just by looking at +the operands. + +@findex prev_active_insn +The way to refer to the operands in @var{condition} is to write +@code{operands[@var{i}]} for operand number @var{i} (as matched by +@code{(match_operand @var{i} @dots{})}). Use the variable @code{insn} +to refer to the last of the insns being matched; use +@code{prev_active_insn} to find the preceding insns. + +@findex dead_or_set_p +When optimizing computations with intermediate results, you can use +@var{condition} to match only when the intermediate results are not used +elsewhere. Use the C expression @code{dead_or_set_p (@var{insn}, +@var{op})}, where @var{insn} is the insn in which you expect the value +to be used for the last time (from the value of @code{insn}, together +with use of @code{prev_nonnote_insn}), and @var{op} is the intermediate +value (from @code{operands[@var{i}]}).@refill + +Applying the optimization means replacing the sequence of insns with one +new insn. The @var{template} controls ultimate output of assembler code +for this combined insn. It works exactly like the template of a +@code{define_insn}. Operand numbers in this template are the same ones +used in matching the original sequence of insns. + +The result of a defined peephole optimizer does not need to match any of +the insn patterns in the machine description; it does not even have an +opportunity to match them. The peephole optimizer definition itself serves +as the insn pattern to control how the insn is output. + +Defined peephole optimizers are run as assembler code is being output, +so the insns they produce are never combined or rearranged in any way. + +Here is an example, taken from the 68000 machine description: + +@smallexample +(define_peephole + [(set (reg:SI 15) (plus:SI (reg:SI 15) (const_int 4))) + (set (match_operand:DF 0 "register_operand" "=f") + (match_operand:DF 1 "register_operand" "ad"))] + "FP_REG_P (operands[0]) && ! FP_REG_P (operands[1])" + "* +@{ + rtx xoperands[2]; + xoperands[1] = gen_rtx (REG, SImode, REGNO (operands[1]) + 1); +#ifdef MOTOROLA + output_asm_insn (\"move.l %1,(sp)\", xoperands); + output_asm_insn (\"move.l %1,-(sp)\", operands); + return \"fmove.d (sp)+,%0\"; +#else + output_asm_insn (\"movel %1,sp@@\", xoperands); + output_asm_insn (\"movel %1,sp@@-\", operands); + return \"fmoved sp@@+,%0\"; +#endif +@} +") +@end smallexample + +@need 1000 +The effect of this optimization is to change + +@smallexample +@group +jbsr _foobar +addql #4,sp +movel d1,sp@@- +movel d0,sp@@- +fmoved sp@@+,fp0 +@end group +@end smallexample + +@noindent +into + +@smallexample +@group +jbsr _foobar +movel d1,sp@@ +movel d0,sp@@- +fmoved sp@@+,fp0 +@end group +@end smallexample + +@ignore +@findex CC_REVERSED +If a peephole matches a sequence including one or more jump insns, you must +take account of the flags such as @code{CC_REVERSED} which specify that the +condition codes are represented in an unusual manner. The compiler +automatically alters any ordinary conditional jumps which occur in such +situations, but the compiler cannot alter jumps which have been replaced by +peephole optimizations. So it is up to you to alter the assembler code +that the peephole produces. Supply C code to write the assembler output, +and in this C code check the condition code status flags and change the +assembler code as appropriate. +@end ignore + +@var{insn-pattern-1} and so on look @emph{almost} like the second +operand of @code{define_insn}. There is one important difference: the +second operand of @code{define_insn} consists of one or more RTX's +enclosed in square brackets. Usually, there is only one: then the same +action can be written as an element of a @code{define_peephole}. But +when there are multiple actions in a @code{define_insn}, they are +implicitly enclosed in a @code{parallel}. Then you must explicitly +write the @code{parallel}, and the square brackets within it, in the +@code{define_peephole}. Thus, if an insn pattern looks like this, + +@smallexample +(define_insn "divmodsi4" + [(set (match_operand:SI 0 "general_operand" "=d") + (div:SI (match_operand:SI 1 "general_operand" "0") + (match_operand:SI 2 "general_operand" "dmsK"))) + (set (match_operand:SI 3 "general_operand" "=d") + (mod:SI (match_dup 1) (match_dup 2)))] + "TARGET_68020" + "divsl%.l %2,%3:%0") +@end smallexample + +@noindent +then the way to mention this insn in a peephole is as follows: + +@smallexample +(define_peephole + [@dots{} + (parallel + [(set (match_operand:SI 0 "general_operand" "=d") + (div:SI (match_operand:SI 1 "general_operand" "0") + (match_operand:SI 2 "general_operand" "dmsK"))) + (set (match_operand:SI 3 "general_operand" "=d") + (mod:SI (match_dup 1) (match_dup 2)))]) + @dots{}] + @dots{}) +@end smallexample + +@node define_peephole2 +@subsection RTL to RTL Peephole Optimizers +@findex define_peephole2 + +The @code{define_peephole2} definition tells the compiler how to +substitute one sequence of instructions for another sequence, +what additional scratch registers may be needed and what their +lifetimes must be. + +@smallexample +(define_peephole2 + [@var{insn-pattern-1} + @var{insn-pattern-2} + @dots{}] + "@var{condition}" + [@var{new-insn-pattern-1} + @var{new-insn-pattern-2} + @dots{}] + "@var{preparation statements}") +@end smallexample + +The definition is almost identical to @code{define_split} +(@pxref{Insn Splitting}) except that the pattern to match is not a +single instruction, but a sequence of instructions. + +It is possible to request additional scratch registers for use in the +output template. If appropriate registers are not free, the pattern +will simply not match. + +@findex match_scratch +@findex match_dup +Scratch registers are requested with a @code{match_scratch} pattern at +the top level of the input pattern. The allocated register (initially) will +be dead at the point requested within the original sequence. If the scratch +is used at more than a single point, a @code{match_dup} pattern at the +top level of the input pattern marks the last position in the input sequence +at which the register must be available. + +Here is an example from the IA-32 machine description: + +@smallexample +(define_peephole2 + [(match_scratch:SI 2 "r") + (parallel [(set (match_operand:SI 0 "register_operand" "") + (match_operator:SI 3 "arith_or_logical_operator" + [(match_dup 0) + (match_operand:SI 1 "memory_operand" "")])) + (clobber (reg:CC 17))])] + "! optimize_size && ! TARGET_READ_MODIFY" + [(set (match_dup 2) (match_dup 1)) + (parallel [(set (match_dup 0) + (match_op_dup 3 [(match_dup 0) (match_dup 2)])) + (clobber (reg:CC 17))])] + "") +@end smallexample + +@noindent +This pattern tries to split a load from its use in the hopes that we'll be +able to schedule around the memory load latency. It allocates a single +@code{SImode} register of class @code{GENERAL_REGS} (@code{"r"}) that needs +to be live only at the point just before the arithmetic. + +A real example requiring extended scratch lifetimes is harder to come by, +so here's a silly made-up example: + +@smallexample +(define_peephole2 + [(match_scratch:SI 4 "r") + (set (match_operand:SI 0 "" "") (match_operand:SI 1 "" "")) + (set (match_operand:SI 2 "" "") (match_dup 1)) + (match_dup 4) + (set (match_operand:SI 3 "" "") (match_dup 1))] + "@var{determine 1 does not overlap 0 and 2}" + [(set (match_dup 4) (match_dup 1)) + (set (match_dup 0) (match_dup 4)) + (set (match_dup 2) (match_dup 4))] + (set (match_dup 3) (match_dup 4))] + "") +@end smallexample + +@noindent +If we had not added the @code{(match_dup 4)} in the middle of the input +sequence, it might have been the case that the register we chose at the +beginning of the sequence is killed by the first or second @code{set}. + +@node Insn Attributes +@section Instruction Attributes +@cindex insn attributes +@cindex instruction attributes + +In addition to describing the instruction supported by the target machine, +the @file{md} file also defines a group of @dfn{attributes} and a set of +values for each. Every generated insn is assigned a value for each attribute. +One possible attribute would be the effect that the insn has on the machine's +condition code. This attribute can then be used by @code{NOTICE_UPDATE_CC} +to track the condition codes. + +@menu +* Defining Attributes:: Specifying attributes and their values. +* Expressions:: Valid expressions for attribute values. +* Tagging Insns:: Assigning attribute values to insns. +* Attr Example:: An example of assigning attributes. +* Insn Lengths:: Computing the length of insns. +* Constant Attributes:: Defining attributes that are constant. +* Delay Slots:: Defining delay slots required for a machine. +* Function Units:: Specifying information for insn scheduling. +@end menu + +@node Defining Attributes +@subsection Defining Attributes and their Values +@cindex defining attributes and their values +@cindex attributes, defining + +@findex define_attr +The @code{define_attr} expression is used to define each attribute required +by the target machine. It looks like: + +@smallexample +(define_attr @var{name} @var{list-of-values} @var{default}) +@end smallexample + +@var{name} is a string specifying the name of the attribute being defined. + +@var{list-of-values} is either a string that specifies a comma-separated +list of values that can be assigned to the attribute, or a null string to +indicate that the attribute takes numeric values. + +@var{default} is an attribute expression that gives the value of this +attribute for insns that match patterns whose definition does not include +an explicit value for this attribute. @xref{Attr Example}, for more +information on the handling of defaults. @xref{Constant Attributes}, +for information on attributes that do not depend on any particular insn. + +@findex insn-attr.h +For each defined attribute, a number of definitions are written to the +@file{insn-attr.h} file. For cases where an explicit set of values is +specified for an attribute, the following are defined: + +@itemize @bullet +@item +A @samp{#define} is written for the symbol @samp{HAVE_ATTR_@var{name}}. + +@item +An enumeral class is defined for @samp{attr_@var{name}} with +elements of the form @samp{@var{upper-name}_@var{upper-value}} where +the attribute name and value are first converted to upper case. + +@item +A function @samp{get_attr_@var{name}} is defined that is passed an insn and +returns the attribute value for that insn. +@end itemize + +For example, if the following is present in the @file{md} file: + +@smallexample +(define_attr "type" "branch,fp,load,store,arith" @dots{}) +@end smallexample + +@noindent +the following lines will be written to the file @file{insn-attr.h}. + +@smallexample +#define HAVE_ATTR_type +enum attr_type @{TYPE_BRANCH, TYPE_FP, TYPE_LOAD, + TYPE_STORE, TYPE_ARITH@}; +extern enum attr_type get_attr_type (); +@end smallexample + +If the attribute takes numeric values, no @code{enum} type will be +defined and the function to obtain the attribute's value will return +@code{int}. + +@node Expressions +@subsection Attribute Expressions +@cindex attribute expressions + +RTL expressions used to define attributes use the codes described above +plus a few specific to attribute definitions, to be discussed below. +Attribute value expressions must have one of the following forms: + +@table @code +@cindex @code{const_int} and attributes +@item (const_int @var{i}) +The integer @var{i} specifies the value of a numeric attribute. @var{i} +must be non-negative. + +The value of a numeric attribute can be specified either with a +@code{const_int}, or as an integer represented as a string in +@code{const_string}, @code{eq_attr} (see below), @code{attr}, +@code{symbol_ref}, simple arithmetic expressions, and @code{set_attr} +overrides on specific instructions (@pxref{Tagging Insns}). + +@cindex @code{const_string} and attributes +@item (const_string @var{value}) +The string @var{value} specifies a constant attribute value. +If @var{value} is specified as @samp{"*"}, it means that the default value of +the attribute is to be used for the insn containing this expression. +@samp{"*"} obviously cannot be used in the @var{default} expression +of a @code{define_attr}.@refill + +If the attribute whose value is being specified is numeric, @var{value} +must be a string containing a non-negative integer (normally +@code{const_int} would be used in this case). Otherwise, it must +contain one of the valid values for the attribute. + +@cindex @code{if_then_else} and attributes +@item (if_then_else @var{test} @var{true-value} @var{false-value}) +@var{test} specifies an attribute test, whose format is defined below. +The value of this expression is @var{true-value} if @var{test} is true, +otherwise it is @var{false-value}. + +@cindex @code{cond} and attributes +@item (cond [@var{test1} @var{value1} @dots{}] @var{default}) +The first operand of this expression is a vector containing an even +number of expressions and consisting of pairs of @var{test} and @var{value} +expressions. The value of the @code{cond} expression is that of the +@var{value} corresponding to the first true @var{test} expression. If +none of the @var{test} expressions are true, the value of the @code{cond} +expression is that of the @var{default} expression. +@end table + +@var{test} expressions can have one of the following forms: + +@table @code +@cindex @code{const_int} and attribute tests +@item (const_int @var{i}) +This test is true if @var{i} is non-zero and false otherwise. + +@cindex @code{not} and attributes +@cindex @code{ior} and attributes +@cindex @code{and} and attributes +@item (not @var{test}) +@itemx (ior @var{test1} @var{test2}) +@itemx (and @var{test1} @var{test2}) +These tests are true if the indicated logical function is true. + +@cindex @code{match_operand} and attributes +@item (match_operand:@var{m} @var{n} @var{pred} @var{constraints}) +This test is true if operand @var{n} of the insn whose attribute value +is being determined has mode @var{m} (this part of the test is ignored +if @var{m} is @code{VOIDmode}) and the function specified by the string +@var{pred} returns a non-zero value when passed operand @var{n} and mode +@var{m} (this part of the test is ignored if @var{pred} is the null +string). + +The @var{constraints} operand is ignored and should be the null string. + +@cindex @code{le} and attributes +@cindex @code{leu} and attributes +@cindex @code{lt} and attributes +@cindex @code{gt} and attributes +@cindex @code{gtu} and attributes +@cindex @code{ge} and attributes +@cindex @code{geu} and attributes +@cindex @code{ne} and attributes +@cindex @code{eq} and attributes +@cindex @code{plus} and attributes +@cindex @code{minus} and attributes +@cindex @code{mult} and attributes +@cindex @code{div} and attributes +@cindex @code{mod} and attributes +@cindex @code{abs} and attributes +@cindex @code{neg} and attributes +@cindex @code{ashift} and attributes +@cindex @code{lshiftrt} and attributes +@cindex @code{ashiftrt} and attributes +@item (le @var{arith1} @var{arith2}) +@itemx (leu @var{arith1} @var{arith2}) +@itemx (lt @var{arith1} @var{arith2}) +@itemx (ltu @var{arith1} @var{arith2}) +@itemx (gt @var{arith1} @var{arith2}) +@itemx (gtu @var{arith1} @var{arith2}) +@itemx (ge @var{arith1} @var{arith2}) +@itemx (geu @var{arith1} @var{arith2}) +@itemx (ne @var{arith1} @var{arith2}) +@itemx (eq @var{arith1} @var{arith2}) +These tests are true if the indicated comparison of the two arithmetic +expressions is true. Arithmetic expressions are formed with +@code{plus}, @code{minus}, @code{mult}, @code{div}, @code{mod}, +@code{abs}, @code{neg}, @code{and}, @code{ior}, @code{xor}, @code{not}, +@code{ashift}, @code{lshiftrt}, and @code{ashiftrt} expressions.@refill + +@findex get_attr +@code{const_int} and @code{symbol_ref} are always valid terms (@pxref{Insn +Lengths},for additional forms). @code{symbol_ref} is a string +denoting a C expression that yields an @code{int} when evaluated by the +@samp{get_attr_@dots{}} routine. It should normally be a global +variable.@refill + +@findex eq_attr +@item (eq_attr @var{name} @var{value}) +@var{name} is a string specifying the name of an attribute. + +@var{value} is a string that is either a valid value for attribute +@var{name}, a comma-separated list of values, or @samp{!} followed by a +value or list. If @var{value} does not begin with a @samp{!}, this +test is true if the value of the @var{name} attribute of the current +insn is in the list specified by @var{value}. If @var{value} begins +with a @samp{!}, this test is true if the attribute's value is +@emph{not} in the specified list. + +For example, + +@smallexample +(eq_attr "type" "load,store") +@end smallexample + +@noindent +is equivalent to + +@smallexample +(ior (eq_attr "type" "load") (eq_attr "type" "store")) +@end smallexample + +If @var{name} specifies an attribute of @samp{alternative}, it refers to the +value of the compiler variable @code{which_alternative} +(@pxref{Output Statement}) and the values must be small integers. For +example,@refill + +@smallexample +(eq_attr "alternative" "2,3") +@end smallexample + +@noindent +is equivalent to + +@smallexample +(ior (eq (symbol_ref "which_alternative") (const_int 2)) + (eq (symbol_ref "which_alternative") (const_int 3))) +@end smallexample + +Note that, for most attributes, an @code{eq_attr} test is simplified in cases +where the value of the attribute being tested is known for all insns matching +a particular pattern. This is by far the most common case.@refill + +@findex attr_flag +@item (attr_flag @var{name}) +The value of an @code{attr_flag} expression is true if the flag +specified by @var{name} is true for the @code{insn} currently being +scheduled. + +@var{name} is a string specifying one of a fixed set of flags to test. +Test the flags @code{forward} and @code{backward} to determine the +direction of a conditional branch. Test the flags @code{very_likely}, +@code{likely}, @code{very_unlikely}, and @code{unlikely} to determine +if a conditional branch is expected to be taken. + +If the @code{very_likely} flag is true, then the @code{likely} flag is also +true. Likewise for the @code{very_unlikely} and @code{unlikely} flags. + +This example describes a conditional branch delay slot which +can be nullified for forward branches that are taken (annul-true) or +for backward branches which are not taken (annul-false). + +@smallexample +(define_delay (eq_attr "type" "cbranch") + [(eq_attr "in_branch_delay" "true") + (and (eq_attr "in_branch_delay" "true") + (attr_flag "forward")) + (and (eq_attr "in_branch_delay" "true") + (attr_flag "backward"))]) +@end smallexample + +The @code{forward} and @code{backward} flags are false if the current +@code{insn} being scheduled is not a conditional branch. + +The @code{very_likely} and @code{likely} flags are true if the +@code{insn} being scheduled is not a conditional branch. +The @code{very_unlikely} and @code{unlikely} flags are false if the +@code{insn} being scheduled is not a conditional branch. + +@code{attr_flag} is only used during delay slot scheduling and has no +meaning to other passes of the compiler. + +@findex attr +@item (attr @var{name}) +The value of another attribute is returned. This is most useful +for numeric attributes, as @code{eq_attr} and @code{attr_flag} +produce more efficient code for non-numeric attributes. +@end table + +@node Tagging Insns +@subsection Assigning Attribute Values to Insns +@cindex tagging insns +@cindex assigning attribute values to insns + +The value assigned to an attribute of an insn is primarily determined by +which pattern is matched by that insn (or which @code{define_peephole} +generated it). Every @code{define_insn} and @code{define_peephole} can +have an optional last argument to specify the values of attributes for +matching insns. The value of any attribute not specified in a particular +insn is set to the default value for that attribute, as specified in its +@code{define_attr}. Extensive use of default values for attributes +permits the specification of the values for only one or two attributes +in the definition of most insn patterns, as seen in the example in the +next section.@refill + +The optional last argument of @code{define_insn} and +@code{define_peephole} is a vector of expressions, each of which defines +the value for a single attribute. The most general way of assigning an +attribute's value is to use a @code{set} expression whose first operand is an +@code{attr} expression giving the name of the attribute being set. The +second operand of the @code{set} is an attribute expression +(@pxref{Expressions}) giving the value of the attribute.@refill + +When the attribute value depends on the @samp{alternative} attribute +(i.e., which is the applicable alternative in the constraint of the +insn), the @code{set_attr_alternative} expression can be used. It +allows the specification of a vector of attribute expressions, one for +each alternative. + +@findex set_attr +When the generality of arbitrary attribute expressions is not required, +the simpler @code{set_attr} expression can be used, which allows +specifying a string giving either a single attribute value or a list +of attribute values, one for each alternative. + +The form of each of the above specifications is shown below. In each case, +@var{name} is a string specifying the attribute to be set. + +@table @code +@item (set_attr @var{name} @var{value-string}) +@var{value-string} is either a string giving the desired attribute value, +or a string containing a comma-separated list giving the values for +succeeding alternatives. The number of elements must match the number +of alternatives in the constraint of the insn pattern. + +Note that it may be useful to specify @samp{*} for some alternative, in +which case the attribute will assume its default value for insns matching +that alternative. + +@findex set_attr_alternative +@item (set_attr_alternative @var{name} [@var{value1} @var{value2} @dots{}]) +Depending on the alternative of the insn, the value will be one of the +specified values. This is a shorthand for using a @code{cond} with +tests on the @samp{alternative} attribute. + +@findex attr +@item (set (attr @var{name}) @var{value}) +The first operand of this @code{set} must be the special RTL expression +@code{attr}, whose sole operand is a string giving the name of the +attribute being set. @var{value} is the value of the attribute. +@end table + +The following shows three different ways of representing the same +attribute value specification: + +@smallexample +(set_attr "type" "load,store,arith") + +(set_attr_alternative "type" + [(const_string "load") (const_string "store") + (const_string "arith")]) + +(set (attr "type") + (cond [(eq_attr "alternative" "1") (const_string "load") + (eq_attr "alternative" "2") (const_string "store")] + (const_string "arith"))) +@end smallexample + +@need 1000 +@findex define_asm_attributes +The @code{define_asm_attributes} expression provides a mechanism to +specify the attributes assigned to insns produced from an @code{asm} +statement. It has the form: + +@smallexample +(define_asm_attributes [@var{attr-sets}]) +@end smallexample + +@noindent +where @var{attr-sets} is specified the same as for both the +@code{define_insn} and the @code{define_peephole} expressions. + +These values will typically be the ``worst case'' attribute values. For +example, they might indicate that the condition code will be clobbered. + +A specification for a @code{length} attribute is handled specially. The +way to compute the length of an @code{asm} insn is to multiply the +length specified in the expression @code{define_asm_attributes} by the +number of machine instructions specified in the @code{asm} statement, +determined by counting the number of semicolons and newlines in the +string. Therefore, the value of the @code{length} attribute specified +in a @code{define_asm_attributes} should be the maximum possible length +of a single machine instruction. + +@node Attr Example +@subsection Example of Attribute Specifications +@cindex attribute specifications example +@cindex attribute specifications + +The judicious use of defaulting is important in the efficient use of +insn attributes. Typically, insns are divided into @dfn{types} and an +attribute, customarily called @code{type}, is used to represent this +value. This attribute is normally used only to define the default value +for other attributes. An example will clarify this usage. + +Assume we have a RISC machine with a condition code and in which only +full-word operations are performed in registers. Let us assume that we +can divide all insns into loads, stores, (integer) arithmetic +operations, floating point operations, and branches. + +Here we will concern ourselves with determining the effect of an insn on +the condition code and will limit ourselves to the following possible +effects: The condition code can be set unpredictably (clobbered), not +be changed, be set to agree with the results of the operation, or only +changed if the item previously set into the condition code has been +modified. + +Here is part of a sample @file{md} file for such a machine: + +@smallexample +(define_attr "type" "load,store,arith,fp,branch" (const_string "arith")) + +(define_attr "cc" "clobber,unchanged,set,change0" + (cond [(eq_attr "type" "load") + (const_string "change0") + (eq_attr "type" "store,branch") + (const_string "unchanged") + (eq_attr "type" "arith") + (if_then_else (match_operand:SI 0 "" "") + (const_string "set") + (const_string "clobber"))] + (const_string "clobber"))) + +(define_insn "" + [(set (match_operand:SI 0 "general_operand" "=r,r,m") + (match_operand:SI 1 "general_operand" "r,m,r"))] + "" + "@@ + move %0,%1 + load %0,%1 + store %0,%1" + [(set_attr "type" "arith,load,store")]) +@end smallexample + +Note that we assume in the above example that arithmetic operations +performed on quantities smaller than a machine word clobber the condition +code since they will set the condition code to a value corresponding to the +full-word result. + +@node Insn Lengths +@subsection Computing the Length of an Insn +@cindex insn lengths, computing +@cindex computing the length of an insn + +For many machines, multiple types of branch instructions are provided, each +for different length branch displacements. In most cases, the assembler +will choose the correct instruction to use. However, when the assembler +cannot do so, GCC can when a special attribute, the @samp{length} +attribute, is defined. This attribute must be defined to have numeric +values by specifying a null string in its @code{define_attr}. + +In the case of the @samp{length} attribute, two additional forms of +arithmetic terms are allowed in test expressions: + +@table @code +@cindex @code{match_dup} and attributes +@item (match_dup @var{n}) +This refers to the address of operand @var{n} of the current insn, which +must be a @code{label_ref}. + +@cindex @code{pc} and attributes +@item (pc) +This refers to the address of the @emph{current} insn. It might have +been more consistent with other usage to make this the address of the +@emph{next} insn but this would be confusing because the length of the +current insn is to be computed. +@end table + +@cindex @code{addr_vec}, length of +@cindex @code{addr_diff_vec}, length of +For normal insns, the length will be determined by value of the +@samp{length} attribute. In the case of @code{addr_vec} and +@code{addr_diff_vec} insn patterns, the length is computed as +the number of vectors multiplied by the size of each vector. + +Lengths are measured in addressable storage units (bytes). + +The following macros can be used to refine the length computation: + +@table @code +@findex FIRST_INSN_ADDRESS +@item FIRST_INSN_ADDRESS +When the @code{length} insn attribute is used, this macro specifies the +value to be assigned to the address of the first insn in a function. If +not specified, 0 is used. + +@findex ADJUST_INSN_LENGTH +@item ADJUST_INSN_LENGTH (@var{insn}, @var{length}) +If defined, modifies the length assigned to instruction @var{insn} as a +function of the context in which it is used. @var{length} is an lvalue +that contains the initially computed length of the insn and should be +updated with the correct length of the insn. + +This macro will normally not be required. A case in which it is +required is the ROMP. On this machine, the size of an @code{addr_vec} +insn must be increased by two to compensate for the fact that alignment +may be required. +@end table + +@findex get_attr_length +The routine that returns @code{get_attr_length} (the value of the +@code{length} attribute) can be used by the output routine to +determine the form of the branch instruction to be written, as the +example below illustrates. + +As an example of the specification of variable-length branches, consider +the IBM 360. If we adopt the convention that a register will be set to +the starting address of a function, we can jump to labels within 4k of +the start using a four-byte instruction. Otherwise, we need a six-byte +sequence to load the address from memory and then branch to it. + +On such a machine, a pattern for a branch instruction might be specified +as follows: + +@smallexample +(define_insn "jump" + [(set (pc) + (label_ref (match_operand 0 "" "")))] + "" + "* +@{ + return (get_attr_length (insn) == 4 + ? \"b %l0\" : \"l r15,=a(%l0); br r15\"); +@}" + [(set (attr "length") (if_then_else (lt (match_dup 0) (const_int 4096)) + (const_int 4) + (const_int 6)))]) +@end smallexample + +@node Constant Attributes +@subsection Constant Attributes +@cindex constant attributes + +A special form of @code{define_attr}, where the expression for the +default value is a @code{const} expression, indicates an attribute that +is constant for a given run of the compiler. Constant attributes may be +used to specify which variety of processor is used. For example, + +@smallexample +(define_attr "cpu" "m88100,m88110,m88000" + (const + (cond [(symbol_ref "TARGET_88100") (const_string "m88100") + (symbol_ref "TARGET_88110") (const_string "m88110")] + (const_string "m88000")))) + +(define_attr "memory" "fast,slow" + (const + (if_then_else (symbol_ref "TARGET_FAST_MEM") + (const_string "fast") + (const_string "slow")))) +@end smallexample + +The routine generated for constant attributes has no parameters as it +does not depend on any particular insn. RTL expressions used to define +the value of a constant attribute may use the @code{symbol_ref} form, +but may not use either the @code{match_operand} form or @code{eq_attr} +forms involving insn attributes. + +@node Delay Slots +@subsection Delay Slot Scheduling +@cindex delay slots, defining + +The insn attribute mechanism can be used to specify the requirements for +delay slots, if any, on a target machine. An instruction is said to +require a @dfn{delay slot} if some instructions that are physically +after the instruction are executed as if they were located before it. +Classic examples are branch and call instructions, which often execute +the following instruction before the branch or call is performed. + +On some machines, conditional branch instructions can optionally +@dfn{annul} instructions in the delay slot. This means that the +instruction will not be executed for certain branch outcomes. Both +instructions that annul if the branch is true and instructions that +annul if the branch is false are supported. + +Delay slot scheduling differs from instruction scheduling in that +determining whether an instruction needs a delay slot is dependent only +on the type of instruction being generated, not on data flow between the +instructions. See the next section for a discussion of data-dependent +instruction scheduling. + +@findex define_delay +The requirement of an insn needing one or more delay slots is indicated +via the @code{define_delay} expression. It has the following form: + +@smallexample +(define_delay @var{test} + [@var{delay-1} @var{annul-true-1} @var{annul-false-1} + @var{delay-2} @var{annul-true-2} @var{annul-false-2} + @dots{}]) +@end smallexample + +@var{test} is an attribute test that indicates whether this +@code{define_delay} applies to a particular insn. If so, the number of +required delay slots is determined by the length of the vector specified +as the second argument. An insn placed in delay slot @var{n} must +satisfy attribute test @var{delay-n}. @var{annul-true-n} is an +attribute test that specifies which insns may be annulled if the branch +is true. Similarly, @var{annul-false-n} specifies which insns in the +delay slot may be annulled if the branch is false. If annulling is not +supported for that delay slot, @code{(nil)} should be coded.@refill + +For example, in the common case where branch and call insns require +a single delay slot, which may contain any insn other than a branch or +call, the following would be placed in the @file{md} file: + +@smallexample +(define_delay (eq_attr "type" "branch,call") + [(eq_attr "type" "!branch,call") (nil) (nil)]) +@end smallexample + +Multiple @code{define_delay} expressions may be specified. In this +case, each such expression specifies different delay slot requirements +and there must be no insn for which tests in two @code{define_delay} +expressions are both true. + +For example, if we have a machine that requires one delay slot for branches +but two for calls, no delay slot can contain a branch or call insn, +and any valid insn in the delay slot for the branch can be annulled if the +branch is true, we might represent this as follows: + +@smallexample +(define_delay (eq_attr "type" "branch") + [(eq_attr "type" "!branch,call") + (eq_attr "type" "!branch,call") + (nil)]) + +(define_delay (eq_attr "type" "call") + [(eq_attr "type" "!branch,call") (nil) (nil) + (eq_attr "type" "!branch,call") (nil) (nil)]) +@end smallexample +@c the above is *still* too long. --mew 4feb93 + +@node Function Units +@subsection Specifying Function Units +@cindex function units, for scheduling + +On most RISC machines, there are instructions whose results are not +available for a specific number of cycles. Common cases are instructions +that load data from memory. On many machines, a pipeline stall will result +if the data is referenced too soon after the load instruction. + +In addition, many newer microprocessors have multiple function units, usually +one for integer and one for floating point, and often will incur pipeline +stalls when a result that is needed is not yet ready. + +The descriptions in this section allow the specification of how much +time must elapse between the execution of an instruction and the time +when its result is used. It also allows specification of when the +execution of an instruction will delay execution of similar instructions +due to function unit conflicts. + +For the purposes of the specifications in this section, a machine is +divided into @dfn{function units}, each of which execute a specific +class of instructions in first-in-first-out order. Function units that +accept one instruction each cycle and allow a result to be used in the +succeeding instruction (usually via forwarding) need not be specified. +Classic RISC microprocessors will normally have a single function unit, +which we can call @samp{memory}. The newer ``superscalar'' processors +will often have function units for floating point operations, usually at +least a floating point adder and multiplier. + +@findex define_function_unit +Each usage of a function units by a class of insns is specified with a +@code{define_function_unit} expression, which looks like this: + +@smallexample +(define_function_unit @var{name} @var{multiplicity} @var{simultaneity} + @var{test} @var{ready-delay} @var{issue-delay} + [@var{conflict-list}]) +@end smallexample + +@var{name} is a string giving the name of the function unit. + +@var{multiplicity} is an integer specifying the number of identical +units in the processor. If more than one unit is specified, they will +be scheduled independently. Only truly independent units should be +counted; a pipelined unit should be specified as a single unit. (The +only common example of a machine that has multiple function units for a +single instruction class that are truly independent and not pipelined +are the two multiply and two increment units of the CDC 6600.) + +@var{simultaneity} specifies the maximum number of insns that can be +executing in each instance of the function unit simultaneously or zero +if the unit is pipelined and has no limit. + +All @code{define_function_unit} definitions referring to function unit +@var{name} must have the same name and values for @var{multiplicity} and +@var{simultaneity}. + +@var{test} is an attribute test that selects the insns we are describing +in this definition. Note that an insn may use more than one function +unit and a function unit may be specified in more than one +@code{define_function_unit}. + +@var{ready-delay} is an integer that specifies the number of cycles +after which the result of the instruction can be used without +introducing any stalls. + +@var{issue-delay} is an integer that specifies the number of cycles +after the instruction matching the @var{test} expression begins using +this unit until a subsequent instruction can begin. A cost of @var{N} +indicates an @var{N-1} cycle delay. A subsequent instruction may also +be delayed if an earlier instruction has a longer @var{ready-delay} +value. This blocking effect is computed using the @var{simultaneity}, +@var{ready-delay}, @var{issue-delay}, and @var{conflict-list} terms. +For a normal non-pipelined function unit, @var{simultaneity} is one, the +unit is taken to block for the @var{ready-delay} cycles of the executing +insn, and smaller values of @var{issue-delay} are ignored. + +@var{conflict-list} is an optional list giving detailed conflict costs +for this unit. If specified, it is a list of condition test expressions +to be applied to insns chosen to execute in @var{name} following the +particular insn matching @var{test} that is already executing in +@var{name}. For each insn in the list, @var{issue-delay} specifies the +conflict cost; for insns not in the list, the cost is zero. If not +specified, @var{conflict-list} defaults to all instructions that use the +function unit. + +Typical uses of this vector are where a floating point function unit can +pipeline either single- or double-precision operations, but not both, or +where a memory unit can pipeline loads, but not stores, etc. + +As an example, consider a classic RISC machine where the result of a +load instruction is not available for two cycles (a single ``delay'' +instruction is required) and where only one load instruction can be executed +simultaneously. This would be specified as: + +@smallexample +(define_function_unit "memory" 1 1 (eq_attr "type" "load") 2 0) +@end smallexample + +For the case of a floating point function unit that can pipeline either +single or double precision, but not both, the following could be specified: + +@smallexample +(define_function_unit + "fp" 1 0 (eq_attr "type" "sp_fp") 4 4 [(eq_attr "type" "dp_fp")]) +(define_function_unit + "fp" 1 0 (eq_attr "type" "dp_fp") 4 4 [(eq_attr "type" "sp_fp")]) +@end smallexample + +@strong{Note:} The scheduler attempts to avoid function unit conflicts +and uses all the specifications in the @code{define_function_unit} +expression. It has recently come to our attention that these +specifications may not allow modeling of some of the newer +``superscalar'' processors that have insns using multiple pipelined +units. These insns will cause a potential conflict for the second unit +used during their execution and there is no way of representing that +conflict. We welcome any examples of how function unit conflicts work +in such processors and suggestions for their representation. +@end ifset + +@node Conditional Execution +@section Conditional Execution +@cindex conditional execution +@cindex predication + +A number of architectures provide for some form of conditional +execution, or predication. The hallmark of this feature is the +ability to nullify most of the instructions in the instruction set. +When the instruction set is large and not entirely symmetric, it +can be quite tedious to describe these forms directly in the +@file{.md} file. An alternative is the @code{define_cond_exec} template. + +@findex define_cond_exec +@smallexample +(define_cond_exec + [@var{predicate-pattern}] + "@var{condition}" + "@var{output template}") +@end smallexample + +@var{predicate-pattern} is the condition that must be true for the +insn to be executed at runtime and should match a relational operator. +One can use @code{match_operator} to match several relational operators +at once. Any @code{match_operand} operands must have no more than one +alternative. + +@var{condition} is a C expression that must be true for the generated +pattern to match. + +@findex current_insn_predicate +@var{output template} is a string similar to the @code{define_insn} +output template (@pxref{Output Template}), except that the @samp{*} +and @samp{@@} special cases do not apply. This is only useful if the +assembly text for the predicate is a simple prefix to the main insn. +In order to handle the general case, there is a global variable +@code{current_insn_predicate} that will contain the entire predicate +if the current insn is predicated, and will otherwise be @code{NULL}. + +When @code{define_cond_exec} is used, an implicit reference to +the @code{predicable} instruction attribute is made. +@xref{Insn Attributes}. This attribute must be boolean (i.e. have +exactly two elements in its @var{list-of-values}). Further, it must +not be used with complex expressions. That is, the default and all +uses in the insns must be a simple constant, not dependent on the +alternative or anything else. + +For each @code{define_insn} for which the @code{predicable} +attribute is true, a new @code{define_insn} pattern will be +generated that matches a predicated version of the instruction. +For example, + +@smallexample +(define_insn "addsi" + [(set (match_operand:SI 0 "register_operand" "r") + (plus:SI (match_operand:SI 1 "register_operand" "r") + (match_operand:SI 2 "register_operand" "r")))] + "@var{test1}" + "add %2,%1,%0") + +(define_cond_exec + [(ne (match_operand:CC 0 "register_operand" "c") + (const_int 0))] + "@var{test2}" + "(%0)") +@end smallexample + +@noindent +generates a new pattern + +@smallexample +(define_insn "" + [(cond_exec + (ne (match_operand:CC 3 "register_operand" "c") (const_int 0)) + (set (match_operand:SI 0 "register_operand" "r") + (plus:SI (match_operand:SI 1 "register_operand" "r") + (match_operand:SI 2 "register_operand" "r"))))] + "(@var{test2}) && (@var{test1})" + "(%3) add %2,%1,%0") +@end smallexample + +@node Constant Definitions +@section Constant Definitions +@cindex constant definitions +@findex define_constants + +Using literal constants inside instruction patterns reduces legibility and +can be a maintenance problem. + +To overcome this problem, you may use the @code{define_constants} +expression. It contains a vector of name-value pairs. From that +point on, wherever any of the names appears in the MD file, it is as +if the corresponding value had been written instead. You may use +@code{define_constants} multiple times; each appearance adds more +constants to the table. It is an error to redefine a constant with +a different value. + +To come back to the a29k load multiple example, instead of + +@smallexample +(define_insn "" + [(match_parallel 0 "load_multiple_operation" + [(set (match_operand:SI 1 "gpc_reg_operand" "=r") + (match_operand:SI 2 "memory_operand" "m")) + (use (reg:SI 179)) + (clobber (reg:SI 179))])] + "" + "loadm 0,0,%1,%2") +@end smallexample + +You could write: + +@smallexample +(define_constants [ + (R_BP 177) + (R_FC 178) + (R_CR 179) + (R_Q 180) +]) + +(define_insn "" + [(match_parallel 0 "load_multiple_operation" + [(set (match_operand:SI 1 "gpc_reg_operand" "=r") + (match_operand:SI 2 "memory_operand" "m")) + (use (reg:SI R_CR)) + (clobber (reg:SI R_CR))])] + "" + "loadm 0,0,%1,%2") +@end smallexample + +The constants that are defined with a define_constant are also output +in the insn-codes.h header file as #defines. diff --git a/gcc/doc/objc.texi b/gcc/doc/objc.texi new file mode 100644 index 00000000000..b2e5c21bfeb --- /dev/null +++ b/gcc/doc/objc.texi @@ -0,0 +1,458 @@ +@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, +@c 1999, 2000, 2001 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@node Objective C +@comment node-name, next, previous, up + +@chapter GNU Objective-C runtime features + +This document is meant to describe some of the GNU Objective-C runtime +features. It is not intended to teach you Objective-C, there are several +resources on the Internet that present the language. Questions and +comments about this document to Ovidiu Predescu +@email{ovidiu@@cup.hp.com}. + +@menu +* Executing code before main:: +* Type encoding:: +* Garbage Collection:: +* Constant string objects:: +* compatibility_alias:: +@end menu + +@node Executing code before main, Type encoding, Objective C, Objective C +@section @code{+load}: Executing code before main + + +The GNU Objective-C runtime provides a way that allows you to execute +code before the execution of the program enters the @code{main} +function. The code is executed on a per-class and a per-category basis, +through a special class method @code{+load}. + +This facility is very useful if you want to initialize global variables +which can be accessed by the program directly, without sending a message +to the class first. The usual way to initialize global variables, in the +@code{+initialize} method, might not be useful because +@code{+initialize} is only called when the first message is sent to a +class object, which in some cases could be too late. + +Suppose for example you have a @code{FileStream} class that declares +@code{Stdin}, @code{Stdout} and @code{Stderr} as global variables, like +below: + +@example + +FileStream *Stdin = nil; +FileStream *Stdout = nil; +FileStream *Stderr = nil; + +@@implementation FileStream + ++ (void)initialize +@{ + Stdin = [[FileStream new] initWithFd:0]; + Stdout = [[FileStream new] initWithFd:1]; + Stderr = [[FileStream new] initWithFd:2]; +@} + +/* Other methods here */ +@@end + +@end example + +In this example, the initialization of @code{Stdin}, @code{Stdout} and +@code{Stderr} in @code{+initialize} occurs too late. The programmer can +send a message to one of these objects before the variables are actually +initialized, thus sending messages to the @code{nil} object. The +@code{+initialize} method which actually initializes the global +variables is not invoked until the first message is sent to the class +object. The solution would require these variables to be initialized +just before entering @code{main}. + +The correct solution of the above problem is to use the @code{+load} +method instead of @code{+initialize}: + +@example + +@@implementation FileStream + ++ (void)load +@{ + Stdin = [[FileStream new] initWithFd:0]; + Stdout = [[FileStream new] initWithFd:1]; + Stderr = [[FileStream new] initWithFd:2]; +@} + +/* Other methods here */ +@@end + +@end example + +The @code{+load} is a method that is not overridden by categories. If a +class and a category of it both implement @code{+load}, both methods are +invoked. This allows some additional initializations to be performed in +a category. + +This mechanism is not intended to be a replacement for @code{+initialize}. +You should be aware of its limitations when you decide to use it +instead of @code{+initialize}. + +@menu +* What you can and what you cannot do in +load:: +@end menu + + +@node What you can and what you cannot do in +load, , Executing code before main, Executing code before main +@subsection What you can and what you cannot do in @code{+load} + +The @code{+load} implementation in the GNU runtime guarantees you the following +things: + +@itemize @bullet + +@item +you can write whatever C code you like; + +@item +you can send messages to Objective-C constant strings (@@"this is a +constant string"); + +@item +you can allocate and send messages to objects whose class is implemented +in the same file; + +@item +the @code{+load} implementation of all super classes of a class are executed before the @code{+load} of that class is executed; + +@item +the @code{+load} implementation of a class is executed before the +@code{+load} implementation of any category. + +@end itemize + +In particular, the following things, even if they can work in a +particular case, are not guaranteed: + +@itemize @bullet + +@item +allocation of or sending messages to arbitrary objects; + +@item +allocation of or sending messages to objects whose classes have a +category implemented in the same file; + +@end itemize + +You should make no assumptions about receiving @code{+load} in sibling +classes when you write @code{+load} of a class. The order in which +sibling classes receive @code{+load} is not guaranteed. + +The order in which @code{+load} and @code{+initialize} are called could +be problematic if this matters. If you don't allocate objects inside +@code{+load}, it is guaranteed that @code{+load} is called before +@code{+initialize}. If you create an object inside @code{+load} the +@code{+initialize} method of object's class is invoked even if +@code{+load} was not invoked. Note if you explicitly call @code{+load} +on a class, @code{+initialize} will be called first. To avoid possible +problems try to implement only one of these methods. + +The @code{+load} method is also invoked when a bundle is dynamically +loaded into your running program. This happens automatically without any +intervening operation from you. When you write bundles and you need to +write @code{+load} you can safely create and send messages to objects whose +classes already exist in the running program. The same restrictions as +above apply to classes defined in bundle. + + + +@node Type encoding, Garbage Collection, Executing code before main, Objective C +@section Type encoding + +The Objective-C compiler generates type encodings for all the +types. These type encodings are used at runtime to find out information +about selectors and methods and about objects and classes. + +The types are encoded in the following way: + +@c @sp 1 + +@multitable @columnfractions .25 .75 +@item @code{char} +@tab @code{c} +@item @code{unsigned char} +@tab @code{C} +@item @code{short} +@tab @code{s} +@item @code{unsigned short} +@tab @code{S} +@item @code{int} +@tab @code{i} +@item @code{unsigned int} +@tab @code{I} +@item @code{long} +@tab @code{l} +@item @code{unsigned long} +@tab @code{L} +@item @code{long long} +@tab @code{q} +@item @code{unsigned long long} +@tab @code{Q} +@item @code{float} +@tab @code{f} +@item @code{double} +@tab @code{d} +@item @code{void} +@tab @code{v} +@item @code{id} +@tab @code{@@} +@item @code{Class} +@tab @code{#} +@item @code{SEL} +@tab @code{:} +@item @code{char*} +@tab @code{*} +@item unknown type +@tab @code{?} +@item bitfields +@tab @code{b} followed by the starting position of the bitfield, the type of the bitfield and the size of the bitfield (the bitfields encoding was changed from the NeXT's compiler encoding, see below) +@end multitable + +@c @sp 1 + +The encoding of bitfields has changed to allow bitfields to be properly +handled by the runtime functions that compute sizes and alignments of +types that contain bitfields. The previous encoding contained only the +size of the bitfield. Using only this information it is not possible to +reliably compute the size occupied by the bitfield. This is very +important in the presence of the Boehm's garbage collector because the +objects are allocated using the typed memory facility available in this +collector. The typed memory allocation requires information about where +the pointers are located inside the object. + +The position in the bitfield is the position, counting in bits, of the +bit closest to the beginning of the structure. + +The non-atomic types are encoded as follows: + +@c @sp 1 + +@multitable @columnfractions .2 .8 +@item pointers +@tab @code{'^'} followed by the pointed type. +@item arrays +@tab @code{'['} followed by the number of elements in the array followed by the type of the elements followed by @code{']'} +@item structures +@tab @code{'@{'} followed by the name of the structure (or '?' if the structure is unnamed), the '=' sign, the type of the members and by @code{'@}'} +@item unions +@tab @code{'('} followed by the name of the structure (or '?' if the union is unnamed), the '=' sign, the type of the members followed by @code{')'} +@end multitable + +Here are some types and their encodings, as they are generated by the +compiler on a i386 machine: + +@sp 1 + +@multitable @columnfractions .25 .75 +@item Objective-C type +@tab Compiler encoding +@item +@example +int a[10]; +@end example +@tab @code{[10i]} +@item +@example +struct @{ + int i; + float f[3]; + int a:3; + int b:2; + char c; +@} +@end example +@tab @code{@{?=i[3f]b128i3b131i2c@}} +@end multitable + +@sp 1 + +In addition to the types the compiler also encodes the type +specifiers. The table below describes the encoding of the current +Objective-C type specifiers: + +@sp 1 + +@multitable @columnfractions .25 .75 +@item Specifier +@tab Encoding +@item @code{const} +@tab @code{r} +@item @code{in} +@tab @code{n} +@item @code{inout} +@tab @code{N} +@item @code{out} +@tab @code{o} +@item @code{bycopy} +@tab @code{O} +@item @code{oneway} +@tab @code{V} +@end multitable + +@sp 1 + +The type specifiers are encoded just before the type. Unlike types +however, the type specifiers are only encoded when they appear in method +argument types. + + +@node Garbage Collection, Constant string objects, Type encoding, Objective C +@section Garbage Collection + +Support for a new memory management policy has been added by using a +powerful conservative garbage collector, known as the +Boehm-Demers-Weiser conservative garbage collector. It is available from +@w{@uref{http://www.hpl.hp.com/personal/Hans_Boehm/gc/}}. + +To enable the support for it you have to configure the compiler using an +additional argument, @w{@kbd{--enable-objc-gc}}. You need to have +garbage collector installed before building the compiler. This will +build an additional runtime library which has several enhancements to +support the garbage collector. The new library has a new name, +@kbd{libobjc_gc.a} to not conflict with the non-garbage-collected +library. + +When the garbage collector is used, the objects are allocated using the +so-called typed memory allocation mechanism available in the +Boehm-Demers-Weiser collector. This mode requires precise information on +where pointers are located inside objects. This information is computed +once per class, immediately after the class has been initialized. + +There is a new runtime function @code{class_ivar_set_gcinvisible()} +which can be used to declare a so-called @strong{weak pointer} +reference. Such a pointer is basically hidden for the garbage collector; +this can be useful in certain situations, especially when you want to +keep track of the allocated objects, yet allow them to be +collected. This kind of pointers can only be members of objects, you +cannot declare a global pointer as a weak reference. Every type which is +a pointer type can be declared a weak pointer, including @code{id}, +@code{Class} and @code{SEL}. + +Here is an example of how to use this feature. Suppose you want to +implement a class whose instances hold a weak pointer reference; the +following class does this: + +@example + +@@interface WeakPointer : Object +@{ + const void* weakPointer; +@} + +- initWithPointer:(const void*)p; +- (const void*)weakPointer; +@@end + + +@@implementation WeakPointer + ++ (void)initialize +@{ + class_ivar_set_gcinvisible (self, "weakPointer", YES); +@} + +- initWithPointer:(const void*)p +@{ + weakPointer = p; + return self; +@} + +- (const void*)weakPointer +@{ + return weakPointer; +@} + +@@end + +@end example + +Weak pointers are supported through a new type character specifier +represented by the @code{'!'} character. The +@code{class_ivar_set_gcinvisible()} function adds or removes this +specifier to the string type description of the instance variable named +as argument. + +@c ========================================================================= +@node Constant string objects +@section Constant string objects + +GNU Objective-C provides constant string objects that are generated +directly by the compiler. You declare a constant string object by +prefixing a C constant string with the character @code{@@}: + +@example + id myString = @@"this is a constant string object"; +@end example + +The constant string objects are usually instances of the +@code{NXConstantString} class which is provided by the GNU Objective-C +runtime. To get the definition of this class you must include the +@file{objc/NXConstStr.h} header file. + +User defined libraries may want to implement their own constant string +class. To be able to support them, the GNU Objective-C compiler provides +a new command line options @code{-fconstant-string-class=}. The provided class should adhere to a strict structure, the same +as @code{NXConstantString}'s structure: + +@example + +@@interface NXConstantString : Object +@{ + char *c_string; + unsigned int len; +@} +@@end + +@end example + +User class libraries may choose to inherit the customized constant +string class from a different class than @code{Object}. There is no +requirement in the methods the constant string class has to implement. + +When a file is compiled with the @code{-fconstant-string-class} option, +all the constant string objects will be instances of the class specified +as argument to this option. It is possible to have multiple compilation +units referring to different constant string classes, neither the +compiler nor the linker impose any restrictions in doing this. + +@c ========================================================================= +@node compatibility_alias +@section compatibility_alias + +This is a feature of the Objective-C compiler rather than of the +runtime, anyway since it is documented nowhere and its existence was +forgotten, we are documenting it here. + +The keyword @code{@@compatibility_alias} allows you to define a class name +as equivalent to another class name. For example: + +@example +@@compatibility_alias WOApplication GSWApplication; +@end example + +tells the compiler that each time it encounters @code{WOApplication} as +a class name, it should replace it with @code{GSWApplication} (that is, +@code{WOApplication} is just an alias for @code{GSWApplication}). + +There are some constraints on how this can be used - + +@itemize @bullet + +@item @code{WOApplication} (the alias) must not be an existing class; + +@item @code{GSWApplication} (the real class) must be an existing class. + +@end itemize diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi new file mode 100644 index 00000000000..2b393589d9d --- /dev/null +++ b/gcc/doc/rtl.texi @@ -0,0 +1,3191 @@ +@c Copyright (C) 1988, 1989, 1992, 1994, 1997, 1998, 1999, 2000, 2001 +@c Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@node RTL +@chapter RTL Representation +@cindex RTL representation +@cindex representation of RTL +@cindex Register Transfer Language (RTL) + +Most of the work of the compiler is done on an intermediate representation +called register transfer language. In this language, the instructions to be +output are described, pretty much one by one, in an algebraic form that +describes what the instruction does. + +RTL is inspired by Lisp lists. It has both an internal form, made up of +structures that point at other structures, and a textual form that is used +in the machine description and in printed debugging dumps. The textual +form uses nested parentheses to indicate the pointers in the internal form. + +@menu +* RTL Objects:: Expressions vs vectors vs strings vs integers. +* RTL Classes:: Categories of RTL expresion objects, and their structure. +* Accessors:: Macros to access expression operands or vector elts. +* Flags:: Other flags in an RTL expression. +* Machine Modes:: Describing the size and format of a datum. +* Constants:: Expressions with constant values. +* Regs and Memory:: Expressions representing register contents or memory. +* Arithmetic:: Expressions representing arithmetic on other expressions. +* Comparisons:: Expressions representing comparison of expressions. +* Bit Fields:: Expressions representing bitfields in memory or reg. +* Vector Operations:: Expressions involving vector datatypes. +* Conversions:: Extending, truncating, floating or fixing. +* RTL Declarations:: Declaring volatility, constancy, etc. +* Side Effects:: Expressions for storing in registers, etc. +* Incdec:: Embedded side-effects for autoincrement addressing. +* Assembler:: Representing @code{asm} with operands. +* Insns:: Expression types for entire insns. +* Calls:: RTL representation of function call insns. +* Sharing:: Some expressions are unique; others *must* be copied. +* Reading RTL:: Reading textual RTL from a file. +@end menu + +@node RTL Objects +@section RTL Object Types +@cindex RTL object types + +@cindex RTL integers +@cindex RTL strings +@cindex RTL vectors +@cindex RTL expression +@cindex RTX (See RTL) +RTL uses five kinds of objects: expressions, integers, wide integers, +strings and vectors. Expressions are the most important ones. An RTL +expression (``RTX'', for short) is a C structure, but it is usually +referred to with a pointer; a type that is given the typedef name +@code{rtx}. + +An integer is simply an @code{int}; their written form uses decimal digits. +A wide integer is an integral object whose type is @code{HOST_WIDE_INT} +(@pxref{Config}); their written form uses decimal digits. + +A string is a sequence of characters. In core it is represented as a +@code{char *} in usual C fashion, and it is written in C syntax as well. +However, strings in RTL may never be null. If you write an empty string in +a machine description, it is represented in core as a null pointer rather +than as a pointer to a null character. In certain contexts, these null +pointers instead of strings are valid. Within RTL code, strings are most +commonly found inside @code{symbol_ref} expressions, but they appear in +other contexts in the RTL expressions that make up machine descriptions. + +A vector contains an arbitrary number of pointers to expressions. The +number of elements in the vector is explicitly present in the vector. +The written form of a vector consists of square brackets +(@samp{[@dots{}]}) surrounding the elements, in sequence and with +whitespace separating them. Vectors of length zero are not created; +null pointers are used instead. + +@cindex expression codes +@cindex codes, RTL expression +@findex GET_CODE +@findex PUT_CODE +Expressions are classified by @dfn{expression codes} (also called RTX +codes). The expression code is a name defined in @file{rtl.def}, which is +also (in upper case) a C enumeration constant. The possible expression +codes and their meanings are machine-independent. The code of an RTX can +be extracted with the macro @code{GET_CODE (@var{x})} and altered with +@code{PUT_CODE (@var{x}, @var{newcode})}. + +The expression code determines how many operands the expression contains, +and what kinds of objects they are. In RTL, unlike Lisp, you cannot tell +by looking at an operand what kind of object it is. Instead, you must know +from its context---from the expression code of the containing expression. +For example, in an expression of code @code{subreg}, the first operand is +to be regarded as an expression and the second operand as an integer. In +an expression of code @code{plus}, there are two operands, both of which +are to be regarded as expressions. In a @code{symbol_ref} expression, +there is one operand, which is to be regarded as a string. + +Expressions are written as parentheses containing the name of the +expression type, its flags and machine mode if any, and then the operands +of the expression (separated by spaces). + +Expression code names in the @samp{md} file are written in lower case, +but when they appear in C code they are written in upper case. In this +manual, they are shown as follows: @code{const_int}. + +@cindex (nil) +@cindex nil +In a few contexts a null pointer is valid where an expression is normally +wanted. The written form of this is @code{(nil)}. + +@node RTL Classes +@section RTL Classes and Formats +@cindex RTL classes +@cindex classes of RTX codes +@cindex RTX codes, classes of +@findex GET_RTX_CLASS + +The various expression codes are divided into several @dfn{classes}, +which are represented by single characters. You can determine the class +of an RTX code with the macro @code{GET_RTX_CLASS (@var{code})}. +Currently, @file{rtx.def} defines these classes: + +@table @code +@item o +An RTX code that represents an actual object, such as a register +(@code{REG}) or a memory location (@code{MEM}, @code{SYMBOL_REF}). +Constants and basic transforms on objects (@code{ADDRESSOF}, +@code{HIGH}, @code{LO_SUM}) are also included. Note that @code{SUBREG} +and @code{STRICT_LOW_PART} are not in this class, but in class @code{x}. + +@item < +An RTX code for a comparison, such as @code{NE} or @code{LT}. + +@item 1 +An RTX code for a unary arithmetic operation, such as @code{NEG}, +@code{NOT}, or @code{ABS}. This category also includes value extension +(sign or zero) and conversions between integer and floating point. + +@item c +An RTX code for a commutative binary operation, such as @code{PLUS} or +@code{AND}. @code{NE} and @code{EQ} are comparisons, so they have class +@code{<}. + +@item 2 +An RTX code for a non-commutative binary operation, such as @code{MINUS}, +@code{DIV}, or @code{ASHIFTRT}. + +@item b +An RTX code for a bitfield operation. Currently only +@code{ZERO_EXTRACT} and @code{SIGN_EXTRACT}. These have three inputs +and are lvalues (so they can be used for insertion as well). @xref{Bit +Fields}. + +@item 3 +An RTX code for other three input operations. Currently only +@code{IF_THEN_ELSE}. + +@item i +An RTX code for an entire instruction: @code{INSN}, @code{JUMP_INSN}, and +@code{CALL_INSN}. @xref{Insns}. + +@item m +An RTX code for something that matches in insns, such as +@code{MATCH_DUP}. These only occur in machine descriptions. + +@item a +An RTX code for an auto-increment addressing mode, such as +@code{POST_INC}. + +@item x +All other RTX codes. This category includes the remaining codes used +only in machine descriptions (@code{DEFINE_*}, etc.). It also includes +all the codes describing side effects (@code{SET}, @code{USE}, +@code{CLOBBER}, etc.) and the non-insns that may appear on an insn +chain, such as @code{NOTE}, @code{BARRIER}, and @code{CODE_LABEL}. +@end table + +@cindex RTL format +For each expression type @file{rtl.def} specifies the number of +contained objects and their kinds, with four possibilities: @samp{e} for +expression (actually a pointer to an expression), @samp{i} for integer, +@samp{w} for wide integer, @samp{s} for string, and @samp{E} for vector +of expressions. The sequence of letters for an expression code is +called its @dfn{format}. For example, the format of @code{subreg} is +@samp{ei}.@refill + +@cindex RTL format characters +A few other format characters are used occasionally: + +@table @code +@item u +@samp{u} is equivalent to @samp{e} except that it is printed differently +in debugging dumps. It is used for pointers to insns. + +@item n +@samp{n} is equivalent to @samp{i} except that it is printed differently +in debugging dumps. It is used for the line number or code number of a +@code{note} insn. + +@item S +@samp{S} indicates a string which is optional. In the RTL objects in +core, @samp{S} is equivalent to @samp{s}, but when the object is read, +from an @samp{md} file, the string value of this operand may be omitted. +An omitted string is taken to be the null string. + +@item V +@samp{V} indicates a vector which is optional. In the RTL objects in +core, @samp{V} is equivalent to @samp{E}, but when the object is read +from an @samp{md} file, the vector value of this operand may be omitted. +An omitted vector is effectively the same as a vector of no elements. + +@item 0 +@samp{0} means a slot whose contents do not fit any normal category. +@samp{0} slots are not printed at all in dumps, and are often used in +special ways by small parts of the compiler. +@end table + +There are macros to get the number of operands and the format +of an expression code: + +@table @code +@findex GET_RTX_LENGTH +@item GET_RTX_LENGTH (@var{code}) +Number of operands of an RTX of code @var{code}. + +@findex GET_RTX_FORMAT +@item GET_RTX_FORMAT (@var{code}) +The format of an RTX of code @var{code}, as a C string. +@end table + +Some classes of RTX codes always have the same format. For example, it +is safe to assume that all comparison operations have format @code{ee}. + +@table @code +@item 1 +All codes of this class have format @code{e}. + +@item < +@itemx c +@itemx 2 +All codes of these classes have format @code{ee}. + +@item b +@itemx 3 +All codes of these classes have format @code{eee}. + +@item i +All codes of this class have formats that begin with @code{iuueiee}. +@xref{Insns}. Note that not all RTL objects linked onto an insn chain +are of class @code{i}. + +@item o +@itemx m +@itemx x +You can make no assumptions about the format of these codes. +@end table + +@node Accessors +@section Access to Operands +@cindex accessors +@cindex access to operands +@cindex operand access + +@findex XEXP +@findex XINT +@findex XWINT +@findex XSTR +Operands of expressions are accessed using the macros @code{XEXP}, +@code{XINT}, @code{XWINT} and @code{XSTR}. Each of these macros takes +two arguments: an expression-pointer (RTX) and an operand number +(counting from zero). Thus,@refill + +@example +XEXP (@var{x}, 2) +@end example + +@noindent +accesses operand 2 of expression @var{x}, as an expression. + +@example +XINT (@var{x}, 2) +@end example + +@noindent +accesses the same operand as an integer. @code{XSTR}, used in the same +fashion, would access it as a string. + +Any operand can be accessed as an integer, as an expression or as a string. +You must choose the correct method of access for the kind of value actually +stored in the operand. You would do this based on the expression code of +the containing expression. That is also how you would know how many +operands there are. + +For example, if @var{x} is a @code{subreg} expression, you know that it has +two operands which can be correctly accessed as @code{XEXP (@var{x}, 0)} +and @code{XINT (@var{x}, 1)}. If you did @code{XINT (@var{x}, 0)}, you +would get the address of the expression operand but cast as an integer; +that might occasionally be useful, but it would be cleaner to write +@code{(int) XEXP (@var{x}, 0)}. @code{XEXP (@var{x}, 1)} would also +compile without error, and would return the second, integer operand cast as +an expression pointer, which would probably result in a crash when +accessed. Nothing stops you from writing @code{XEXP (@var{x}, 28)} either, +but this will access memory past the end of the expression with +unpredictable results.@refill + +Access to operands which are vectors is more complicated. You can use the +macro @code{XVEC} to get the vector-pointer itself, or the macros +@code{XVECEXP} and @code{XVECLEN} to access the elements and length of a +vector. + +@table @code +@findex XVEC +@item XVEC (@var{exp}, @var{idx}) +Access the vector-pointer which is operand number @var{idx} in @var{exp}. + +@findex XVECLEN +@item XVECLEN (@var{exp}, @var{idx}) +Access the length (number of elements) in the vector which is +in operand number @var{idx} in @var{exp}. This value is an @code{int}. + +@findex XVECEXP +@item XVECEXP (@var{exp}, @var{idx}, @var{eltnum}) +Access element number @var{eltnum} in the vector which is +in operand number @var{idx} in @var{exp}. This value is an RTX. + +It is up to you to make sure that @var{eltnum} is not negative +and is less than @code{XVECLEN (@var{exp}, @var{idx})}. +@end table + +All the macros defined in this section expand into lvalues and therefore +can be used to assign the operands, lengths and vector elements as well as +to access them. + +@node Flags +@section Flags in an RTL Expression +@cindex flags in RTL expression + +RTL expressions contain several flags (one-bit bitfields) and other +values that are used in certain types of expression. Most often they +are accessed with the following macros: + +@table @code +@findex MEM_VOLATILE_P +@cindex @code{mem} and @samp{/v} +@cindex @code{volatil}, in @code{mem} +@cindex @samp{/v} in RTL dump +@item MEM_VOLATILE_P (@var{x}) +In @code{mem} expressions, nonzero for volatile memory references. +Stored in the @code{volatil} field and printed as @samp{/v}. + +@findex MEM_IN_STRUCT_P +@cindex @code{mem} and @samp{/s} +@cindex @code{in_struct}, in @code{mem} +@cindex @samp{/s} in RTL dump +@item MEM_IN_STRUCT_P (@var{x}) +In @code{mem} expressions, nonzero for reference to an entire structure, +union or array, or to a component of one. Zero for references to a +scalar variable or through a pointer to a scalar. Stored in the +@code{in_struct} field and printed as @samp{/s}. If both this flag and +MEM_SCALAR_P are clear, then we don't know whether this MEM is in a +structure or not. Both flags should never be simultaneously set. + +@findex MEM_SCALAR_P +@cindex @code{mem} and @samp{/f} +@cindex @code{frame_related}, in@code{mem} +@cindex @samp{/f} in RTL dump +@item MEM_SCALAR_P (@var{x}) +In @code{mem} expressions, nonzero for reference to a scalar known not +to be a member of a structure, union, or array. Zero for such +references and for indirections through pointers, even pointers pointing +to scalar types. If both this flag and MEM_STRUCT_P are clear, then we +don't know whether this MEM is in a structure or not. Both flags should +never be simultaneously set. + +@findex MEM_ALIAS_SET +@item MEM_ALIAS_SET (@var{x}) +In @code{mem} expressions, the alias set to which @var{x} belongs. If +zero, @var{x} is not in any alias set, and may alias anything. If +nonzero, @var{x} may only alias objects in the same alias set. This +value is set (in a language-specific manner) by the front-end. This +field is not a bit-field; it is in an integer, found as the second +argument to the @code{mem}. + +@findex REG_LOOP_TEST_P +@cindex @code{reg} and @samp{/s} +@cindex @code{in_struct}, in @code{reg} +@item REG_LOOP_TEST_P +In @code{reg} expressions, nonzero if this register's entire life is +contained in the exit test code for some loop. Stored in the +@code{in_struct} field and printed as @samp{/s}. + +@findex REG_USERVAR_P +@cindex @code{reg} and @samp{/v} +@cindex @code{volatil}, in @code{reg} +@item REG_USERVAR_P (@var{x}) +In a @code{reg}, nonzero if it corresponds to a variable present in +the user's source code. Zero for temporaries generated internally by +the compiler. Stored in the @code{volatil} field and printed as +@samp{/v}. + +@cindex @samp{/i} in RTL dump +@findex REG_FUNCTION_VALUE_P +@cindex @code{reg} and @samp{/i} +@cindex @code{integrated}, in @code{reg} +@item REG_FUNCTION_VALUE_P (@var{x}) +Nonzero in a @code{reg} if it is the place in which this function's +value is going to be returned. (This happens only in a hard +register.) Stored in the @code{integrated} field and printed as +@samp{/i}. + +The same hard register may be used also for collecting the values of +functions called by this one, but @code{REG_FUNCTION_VALUE_P} is zero +in this kind of use. + +@findex SUBREG_PROMOTED_VAR_P +@cindex @code{subreg} and @samp{/s} +@cindex @code{in_struct}, in @code{subreg} +@item SUBREG_PROMOTED_VAR_P +Nonzero in a @code{subreg} if it was made when accessing an object that +was promoted to a wider mode in accord with the @code{PROMOTED_MODE} machine +description macro (@pxref{Storage Layout}). In this case, the mode of +the @code{subreg} is the declared mode of the object and the mode of +@code{SUBREG_REG} is the mode of the register that holds the object. +Promoted variables are always either sign- or zero-extended to the wider +mode on every assignment. Stored in the @code{in_struct} field and +printed as @samp{/s}. + +@findex SUBREG_PROMOTED_UNSIGNED_P +@cindex @code{subreg} and @samp{/u} +@cindex @code{unchanging}, in @code{subreg} +@item SUBREG_PROMOTED_UNSIGNED_P +Nonzero in a @code{subreg} that has @code{SUBREG_PROMOTED_VAR_P} nonzero +if the object being referenced is kept zero-extended and zero if it +is kept sign-extended. Stored in the @code{unchanging} field and +printed as @samp{/u}. + +@findex RTX_UNCHANGING_P +@cindex @code{reg} and @samp{/u} +@cindex @code{mem} and @samp{/u} +@cindex @code{unchanging}, in @code{reg} and @code{mem} +@cindex @samp{/u} in RTL dump +@item RTX_UNCHANGING_P (@var{x}) +Nonzero in a @code{reg} or @code{mem} if the value is not changed. +(This flag is not set for memory references via pointers to constants. +Such pointers only guarantee that the object will not be changed +explicitly by the current function. The object might be changed by +other functions or by aliasing.) Stored in the +@code{unchanging} field and printed as @samp{/u}. + +@findex RTX_INTEGRATED_P +@cindex @code{integrated}, in @code{insn} +@item RTX_INTEGRATED_P (@var{insn}) +Nonzero in an insn if it resulted from an in-line function call. +Stored in the @code{integrated} field and printed as @samp{/i}. + +@findex RTX_FRAME_RELATED_P +@item RTX_FRAME_RELATED_P (@var{x}) +Nonzero in an insn or expression which is part of a function prologue +and sets the stack pointer, sets the frame pointer, or saves a register. +This flag should also be set on an instruction that sets up a temporary +register to use in place of the frame pointer. + +In particular, on RISC targets where there are limits on the sizes of +immediate constants, it is sometimes impossible to reach the register +save area directly from the stack pointer. In that case, a temporary +register is used that is near enough to the register save area, and the +Canonical Frame Address, i.e., DWARF2's logical frame pointer, register +must (temporarily) be changed to be this temporary register. So, the +instruction that sets this temporary register must be marked as +@code{RTX_FRAME_RELATED_P}. + +If the marked instruction is overly complex (defined in terms of what +@code{dwarf2out_frame_debug_expr} can handle), you will also have to +create a @code{REG_FRAME_RELATED_EXPR} note and attach it to the +instruction. This note should contain a simple expression of the +computation performed by this instruction, i.e., one that +@code{dwarf2out_frame_debug_expr} can handle. + +This flag is required for exception handling support on targets with RTL +prologues. + +@findex SYMBOL_REF_USED +@cindex @code{used}, in @code{symbol_ref} +@item SYMBOL_REF_USED (@var{x}) +In a @code{symbol_ref}, indicates that @var{x} has been used. This is +normally only used to ensure that @var{x} is only declared external +once. Stored in the @code{used} field. + +@findex SYMBOL_REF_FLAG +@cindex @code{symbol_ref} and @samp{/v} +@cindex @code{volatil}, in @code{symbol_ref} +@item SYMBOL_REF_FLAG (@var{x}) +In a @code{symbol_ref}, this is used as a flag for machine-specific purposes. +Stored in the @code{volatil} field and printed as @samp{/v}. + +@findex SYMBOL_REF_WEAK +@cindex @code{symbol_ref} and @samp{/i} +@cindex @code{integrated}, in @code{symbol_ref} +@item SYMBOL_REF_WEAK (@var{x}) +In a @code{symbol_ref}, indicates that @var{x} has been declared weak. +Stored in the @code{integrated} field and printed as @samp{/i}. + +@findex LABEL_OUTSIDE_LOOP_P +@cindex @code{label_ref} and @samp{/s} +@cindex @code{in_struct}, in @code{label_ref} +@item LABEL_OUTSIDE_LOOP_P +In @code{label_ref} expressions, nonzero if this is a reference to a +label that is outside the innermost loop containing the reference to the +label. Stored in the @code{in_struct} field and printed as @samp{/s}. + +@findex INSN_DELETED_P +@cindex @code{volatil}, in @code{insn} +@item INSN_DELETED_P (@var{insn}) +In an insn, nonzero if the insn has been deleted. Stored in the +@code{volatil} field and printed as @samp{/v}. + +@findex INSN_ANNULLED_BRANCH_P +@cindex @code{insn} and @samp{/u} +@cindex @code{unchanging}, in @code{insn} +@item INSN_ANNULLED_BRANCH_P (@var{insn}) +In an @code{insn} in the delay slot of a branch insn, indicates that an +annulling branch should be used. See the discussion under +@code{sequence} below. Stored in the @code{unchanging} field and printed +as @samp{/u}. + +@findex INSN_FROM_TARGET_P +@cindex @code{insn} and @samp{/s} +@cindex @code{in_struct}, in @code{insn} +@cindex @samp{/s} in RTL dump +@item INSN_FROM_TARGET_P (@var{insn}) +In an @code{insn} in a delay slot of a branch, indicates that the insn +is from the target of the branch. If the branch insn has +@code{INSN_ANNULLED_BRANCH_P} set, this insn will only be executed if +the branch is taken. For annulled branches with +@code{INSN_FROM_TARGET_P} clear, the insn will be executed only if the +branch is not taken. When @code{INSN_ANNULLED_BRANCH_P} is not set, +this insn will always be executed. Stored in the @code{in_struct} +field and printed as @samp{/s}. + +@findex CONSTANT_POOL_ADDRESS_P +@cindex @code{symbol_ref} and @samp{/u} +@cindex @code{unchanging}, in @code{symbol_ref} +@item CONSTANT_POOL_ADDRESS_P (@var{x}) +Nonzero in a @code{symbol_ref} if it refers to part of the current +function's ``constants pool''. These are addresses close to the +beginning of the function, and GNU CC assumes they can be addressed +directly (perhaps with the help of base registers). Stored in the +@code{unchanging} field and printed as @samp{/u}. + +@findex CONST_CALL_P +@cindex @code{call_insn} and @samp{/u} +@cindex @code{unchanging}, in @code{call_insn} +@item CONST_CALL_P (@var{x}) +In a @code{call_insn}, indicates that the insn represents a call to a const +function. Stored in the @code{unchanging} field and printed as @samp{/u}. + +@findex LABEL_PRESERVE_P +@cindex @code{code_label} and @samp{/i} +@cindex @code{in_struct}, in @code{code_label} +@item LABEL_PRESERVE_P (@var{x}) +In a @code{code_label}, indicates that the label can never be deleted. +Labels referenced by a non-local goto will have this bit set. Stored +in the @code{in_struct} field and printed as @samp{/s}. + +@findex SCHED_GROUP_P +@cindex @code{insn} and @samp{/i} +@cindex @code{in_struct}, in @code{insn} +@item SCHED_GROUP_P (@var{insn}) +During instruction scheduling, in an insn, indicates that the previous insn +must be scheduled together with this insn. This is used to ensure that +certain groups of instructions will not be split up by the instruction +scheduling pass, for example, @code{use} insns before a @code{call_insn} may +not be separated from the @code{call_insn}. Stored in the @code{in_struct} +field and printed as @samp{/s}. +@end table + +These are the fields which the above macros refer to: + +@table @code +@findex used +@item used +Normally, this flag is used only momentarily, at the end of RTL +generation for a function, to count the number of times an expression +appears in insns. Expressions that appear more than once are copied, +according to the rules for shared structure (@pxref{Sharing}). + +In a @code{symbol_ref}, it indicates that an external declaration for +the symbol has already been written. + +In a @code{reg}, it is used by the leaf register renumbering code to ensure +that each register is only renumbered once. + +@findex volatil +@item volatil +This flag is used in @code{mem}, @code{symbol_ref} and @code{reg} +expressions and in insns. In RTL dump files, it is printed as +@samp{/v}. + +@cindex volatile memory references +In a @code{mem} expression, it is 1 if the memory reference is volatile. +Volatile memory references may not be deleted, reordered or combined. + +In a @code{symbol_ref} expression, it is used for machine-specific +purposes. + +In a @code{reg} expression, it is 1 if the value is a user-level variable. +0 indicates an internal compiler temporary. + +In an insn, 1 means the insn has been deleted. + +@findex in_struct +@item in_struct +In @code{mem} expressions, it is 1 if the memory datum referred to is +all or part of a structure or array; 0 if it is (or might be) a scalar +variable. A reference through a C pointer has 0 because the pointer +might point to a scalar variable. This information allows the compiler +to determine something about possible cases of aliasing. + +In an insn in the delay slot of a branch, 1 means that this insn is from +the target of the branch. + +During instruction scheduling, in an insn, 1 means that this insn must be +scheduled as part of a group together with the previous insn. + +In @code{reg} expressions, it is 1 if the register has its entire life +contained within the test expression of some loop. + +In @code{subreg} expressions, 1 means that the @code{subreg} is accessing +an object that has had its mode promoted from a wider mode. + +In @code{label_ref} expressions, 1 means that the referenced label is +outside the innermost loop containing the insn in which the @code{label_ref} +was found. + +In @code{code_label} expressions, it is 1 if the label may never be deleted. +This is used for labels which are the target of non-local gotos. + +In an RTL dump, this flag is represented as @samp{/s}. + +@findex unchanging +@item unchanging +In @code{reg} and @code{mem} expressions, 1 means +that the value of the expression never changes. + +In @code{subreg} expressions, it is 1 if the @code{subreg} references an +unsigned object whose mode has been promoted to a wider mode. + +In an insn, 1 means that this is an annulling branch. + +In a @code{symbol_ref} expression, 1 means that this symbol addresses +something in the per-function constants pool. + +In a @code{call_insn}, 1 means that this instruction is a call to a +const function. + +In an RTL dump, this flag is represented as @samp{/u}. + +@findex integrated +@item integrated +In some kinds of expressions, including insns, this flag means the +rtl was produced by procedure integration. + +In a @code{reg} expression, this flag indicates the register +containing the value to be returned by the current function. On +machines that pass parameters in registers, the same register number +may be used for parameters as well, but this flag is not set on such +uses. +@end table + +@node Machine Modes +@section Machine Modes +@cindex machine modes + +@findex enum machine_mode +A machine mode describes a size of data object and the representation used +for it. In the C code, machine modes are represented by an enumeration +type, @code{enum machine_mode}, defined in @file{machmode.def}. Each RTL +expression has room for a machine mode and so do certain kinds of tree +expressions (declarations and types, to be precise). + +In debugging dumps and machine descriptions, the machine mode of an RTL +expression is written after the expression code with a colon to separate +them. The letters @samp{mode} which appear at the end of each machine mode +name are omitted. For example, @code{(reg:SI 38)} is a @code{reg} +expression with machine mode @code{SImode}. If the mode is +@code{VOIDmode}, it is not written at all. + +Here is a table of machine modes. The term ``byte'' below refers to an +object of @code{BITS_PER_UNIT} bits (@pxref{Storage Layout}). + +@table @code +@findex BImode +@item BImode +``Bit'' mode represents a single bit, for predicate registers. + +@findex QImode +@item QImode +``Quarter-Integer'' mode represents a single byte treated as an integer. + +@findex HImode +@item HImode +``Half-Integer'' mode represents a two-byte integer. + +@findex PSImode +@item PSImode +``Partial Single Integer'' mode represents an integer which occupies +four bytes but which doesn't really use all four. On some machines, +this is the right mode to use for pointers. + +@findex SImode +@item SImode +``Single Integer'' mode represents a four-byte integer. + +@findex PDImode +@item PDImode +``Partial Double Integer'' mode represents an integer which occupies +eight bytes but which doesn't really use all eight. On some machines, +this is the right mode to use for certain pointers. + +@findex DImode +@item DImode +``Double Integer'' mode represents an eight-byte integer. + +@findex TImode +@item TImode +``Tetra Integer'' (?) mode represents a sixteen-byte integer. + +@findex OImode +@item OImode +``Octa Integer'' (?) mode represents a thirty-two-byte integer. + +@findex SFmode +@item SFmode +``Single Floating'' mode represents a single-precision (four byte) floating +point number. + +@findex DFmode +@item DFmode +``Double Floating'' mode represents a double-precision (eight byte) floating +point number. + +@findex XFmode +@item XFmode +``Extended Floating'' mode represents a triple-precision (twelve byte) +floating point number. This mode is used for IEEE extended floating +point. On some systems not all bits within these bytes will actually +be used. + +@findex TFmode +@item TFmode +``Tetra Floating'' mode represents a quadruple-precision (sixteen byte) +floating point number. + +@findex CCmode +@item CCmode +``Condition Code'' mode represents the value of a condition code, which +is a machine-specific set of bits used to represent the result of a +comparison operation. Other machine-specific modes may also be used for +the condition code. These modes are not used on machines that use +@code{cc0} (see @pxref{Condition Code}). + +@findex BLKmode +@item BLKmode +``Block'' mode represents values that are aggregates to which none of +the other modes apply. In RTL, only memory references can have this mode, +and only if they appear in string-move or vector instructions. On machines +which have no such instructions, @code{BLKmode} will not appear in RTL. + +@findex VOIDmode +@item VOIDmode +Void mode means the absence of a mode or an unspecified mode. +For example, RTL expressions of code @code{const_int} have mode +@code{VOIDmode} because they can be taken to have whatever mode the context +requires. In debugging dumps of RTL, @code{VOIDmode} is expressed by +the absence of any mode. + +@findex SCmode +@findex DCmode +@findex XCmode +@findex TCmode +@item SCmode, DCmode, XCmode, TCmode +These modes stand for a complex number represented as a pair of floating +point values. The floating point values are in @code{SFmode}, +@code{DFmode}, @code{XFmode}, and @code{TFmode}, respectively. + +@findex CQImode +@findex CHImode +@findex CSImode +@findex CDImode +@findex CTImode +@findex COImode +@item CQImode, CHImode, CSImode, CDImode, CTImode, COImode +These modes stand for a complex number represented as a pair of integer +values. The integer values are in @code{QImode}, @code{HImode}, +@code{SImode}, @code{DImode}, @code{TImode}, and @code{OImode}, +respectively. +@end table + +The machine description defines @code{Pmode} as a C macro which expands +into the machine mode used for addresses. Normally this is the mode +whose size is @code{BITS_PER_WORD}, @code{SImode} on 32-bit machines. + +The only modes which a machine description @i{must} support are +@code{QImode}, and the modes corresponding to @code{BITS_PER_WORD}, +@code{FLOAT_TYPE_SIZE} and @code{DOUBLE_TYPE_SIZE}. +The compiler will attempt to use @code{DImode} for 8-byte structures and +unions, but this can be prevented by overriding the definition of +@code{MAX_FIXED_MODE_SIZE}. Alternatively, you can have the compiler +use @code{TImode} for 16-byte structures and unions. Likewise, you can +arrange for the C type @code{short int} to avoid using @code{HImode}. + +@cindex mode classes +Very few explicit references to machine modes remain in the compiler and +these few references will soon be removed. Instead, the machine modes +are divided into mode classes. These are represented by the enumeration +type @code{enum mode_class} defined in @file{machmode.h}. The possible +mode classes are: + +@table @code +@findex MODE_INT +@item MODE_INT +Integer modes. By default these are @code{QImode}, @code{HImode}, +@code{SImode}, @code{DImode}, and @code{TImode}. + +@findex MODE_PARTIAL_INT +@item MODE_PARTIAL_INT +The ``partial integer'' modes, @code{PSImode} and @code{PDImode}. + +@findex MODE_FLOAT +@item MODE_FLOAT +floating point modes. By default these are @code{SFmode}, @code{DFmode}, +@code{XFmode} and @code{TFmode}. + +@findex MODE_COMPLEX_INT +@item MODE_COMPLEX_INT +Complex integer modes. (These are not currently implemented). + +@findex MODE_COMPLEX_FLOAT +@item MODE_COMPLEX_FLOAT +Complex floating point modes. By default these are @code{SCmode}, +@code{DCmode}, @code{XCmode}, and @code{TCmode}. + +@findex MODE_FUNCTION +@item MODE_FUNCTION +Algol or Pascal function variables including a static chain. +(These are not currently implemented). + +@findex MODE_CC +@item MODE_CC +Modes representing condition code values. These are @code{CCmode} plus +any modes listed in the @code{EXTRA_CC_MODES} macro. @xref{Jump Patterns}, +also see @ref{Condition Code}. + +@findex MODE_RANDOM +@item MODE_RANDOM +This is a catchall mode class for modes which don't fit into the above +classes. Currently @code{VOIDmode} and @code{BLKmode} are in +@code{MODE_RANDOM}. +@end table + +Here are some C macros that relate to machine modes: + +@table @code +@findex GET_MODE +@item GET_MODE (@var{x}) +Returns the machine mode of the RTX @var{x}. + +@findex PUT_MODE +@item PUT_MODE (@var{x}, @var{newmode}) +Alters the machine mode of the RTX @var{x} to be @var{newmode}. + +@findex NUM_MACHINE_MODES +@item NUM_MACHINE_MODES +Stands for the number of machine modes available on the target +machine. This is one greater than the largest numeric value of any +machine mode. + +@findex GET_MODE_NAME +@item GET_MODE_NAME (@var{m}) +Returns the name of mode @var{m} as a string. + +@findex GET_MODE_CLASS +@item GET_MODE_CLASS (@var{m}) +Returns the mode class of mode @var{m}. + +@findex GET_MODE_WIDER_MODE +@item GET_MODE_WIDER_MODE (@var{m}) +Returns the next wider natural mode. For example, the expression +@code{GET_MODE_WIDER_MODE (QImode)} returns @code{HImode}. + +@findex GET_MODE_SIZE +@item GET_MODE_SIZE (@var{m}) +Returns the size in bytes of a datum of mode @var{m}. + +@findex GET_MODE_BITSIZE +@item GET_MODE_BITSIZE (@var{m}) +Returns the size in bits of a datum of mode @var{m}. + +@findex GET_MODE_MASK +@item GET_MODE_MASK (@var{m}) +Returns a bitmask containing 1 for all bits in a word that fit within +mode @var{m}. This macro can only be used for modes whose bitsize is +less than or equal to @code{HOST_BITS_PER_INT}. + +@findex GET_MODE_ALIGNMENT +@item GET_MODE_ALIGNMENT (@var{m}) +Return the required alignment, in bits, for an object of mode @var{m}. + +@findex GET_MODE_UNIT_SIZE +@item GET_MODE_UNIT_SIZE (@var{m}) +Returns the size in bytes of the subunits of a datum of mode @var{m}. +This is the same as @code{GET_MODE_SIZE} except in the case of complex +modes. For them, the unit size is the size of the real or imaginary +part. + +@findex GET_MODE_NUNITS +@item GET_MODE_NUNITS (@var{m}) +Returns the number of units contained in a mode, i.e., +@code{GET_MODE_SIZE} divided by @code{GET_MODE_UNIT_SIZE}. + +@findex GET_CLASS_NARROWEST_MODE +@item GET_CLASS_NARROWEST_MODE (@var{c}) +Returns the narrowest mode in mode class @var{c}. +@end table + +@findex byte_mode +@findex word_mode +The global variables @code{byte_mode} and @code{word_mode} contain modes +whose classes are @code{MODE_INT} and whose bitsizes are either +@code{BITS_PER_UNIT} or @code{BITS_PER_WORD}, respectively. On 32-bit +machines, these are @code{QImode} and @code{SImode}, respectively. + +@node Constants +@section Constant Expression Types +@cindex RTL constants +@cindex RTL constant expression types + +The simplest RTL expressions are those that represent constant values. + +@table @code +@findex const_int +@item (const_int @var{i}) +This type of expression represents the integer value @var{i}. @var{i} +is customarily accessed with the macro @code{INTVAL} as in +@code{INTVAL (@var{exp})}, which is equivalent to @code{XWINT (@var{exp}, 0)}. + +@findex const0_rtx +@findex const1_rtx +@findex const2_rtx +@findex constm1_rtx +There is only one expression object for the integer value zero; it is +the value of the variable @code{const0_rtx}. Likewise, the only +expression for integer value one is found in @code{const1_rtx}, the only +expression for integer value two is found in @code{const2_rtx}, and the +only expression for integer value negative one is found in +@code{constm1_rtx}. Any attempt to create an expression of code +@code{const_int} and value zero, one, two or negative one will return +@code{const0_rtx}, @code{const1_rtx}, @code{const2_rtx} or +@code{constm1_rtx} as appropriate.@refill + +@findex const_true_rtx +Similarly, there is only one object for the integer whose value is +@code{STORE_FLAG_VALUE}. It is found in @code{const_true_rtx}. If +@code{STORE_FLAG_VALUE} is one, @code{const_true_rtx} and +@code{const1_rtx} will point to the same object. If +@code{STORE_FLAG_VALUE} is -1, @code{const_true_rtx} and +@code{constm1_rtx} will point to the same object.@refill + +@findex const_double +@item (const_double:@var{m} @var{addr} @var{i0} @var{i1} @dots{}) +Represents either a floating-point constant of mode @var{m} or an +integer constant too large to fit into @code{HOST_BITS_PER_WIDE_INT} +bits but small enough to fit within twice that number of bits (GNU CC +does not provide a mechanism to represent even larger constants). In +the latter case, @var{m} will be @code{VOIDmode}. + +@findex CONST_DOUBLE_MEM +@findex CONST_DOUBLE_CHAIN +@var{addr} is used to contain the @code{mem} expression that corresponds +to the location in memory that at which the constant can be found. If +it has not been allocated a memory location, but is on the chain of all +@code{const_double} expressions in this compilation (maintained using an +undisplayed field), @var{addr} contains @code{const0_rtx}. If it is not +on the chain, @var{addr} contains @code{cc0_rtx}. @var{addr} is +customarily accessed with the macro @code{CONST_DOUBLE_MEM} and the +chain field via @code{CONST_DOUBLE_CHAIN}.@refill + +@findex CONST_DOUBLE_LOW +If @var{m} is @code{VOIDmode}, the bits of the value are stored in +@var{i0} and @var{i1}. @var{i0} is customarily accessed with the macro +@code{CONST_DOUBLE_LOW} and @var{i1} with @code{CONST_DOUBLE_HIGH}. + +If the constant is floating point (regardless of its precision), then +the number of integers used to store the value depends on the size of +@code{REAL_VALUE_TYPE} (@pxref{Cross-compilation}). The integers +represent a floating point number, but not precisely in the target +machine's or host machine's floating point format. To convert them to +the precise bit pattern used by the target machine, use the macro +@code{REAL_VALUE_TO_TARGET_DOUBLE} and friends (@pxref{Data Output}). + +@findex CONST0_RTX +@findex CONST1_RTX +@findex CONST2_RTX +The macro @code{CONST0_RTX (@var{mode})} refers to an expression with +value 0 in mode @var{mode}. If mode @var{mode} is of mode class +@code{MODE_INT}, it returns @code{const0_rtx}. Otherwise, it returns a +@code{CONST_DOUBLE} expression in mode @var{mode}. Similarly, the macro +@code{CONST1_RTX (@var{mode})} refers to an expression with value 1 in +mode @var{mode} and similarly for @code{CONST2_RTX}. + +@findex const_string +@item (const_string @var{str}) +Represents a constant string with value @var{str}. Currently this is +used only for insn attributes (@pxref{Insn Attributes}) since constant +strings in C are placed in memory. + +@findex symbol_ref +@item (symbol_ref:@var{mode} @var{symbol}) +Represents the value of an assembler label for data. @var{symbol} is +a string that describes the name of the assembler label. If it starts +with a @samp{*}, the label is the rest of @var{symbol} not including +the @samp{*}. Otherwise, the label is @var{symbol}, usually prefixed +with @samp{_}. + +The @code{symbol_ref} contains a mode, which is usually @code{Pmode}. +Usually that is the only mode for which a symbol is directly valid. + +@findex label_ref +@item (label_ref @var{label}) +Represents the value of an assembler label for code. It contains one +operand, an expression, which must be a @code{code_label} that appears +in the instruction sequence to identify the place where the label +should go. + +The reason for using a distinct expression type for code label +references is so that jump optimization can distinguish them. + +@item (const:@var{m} @var{exp}) +Represents a constant that is the result of an assembly-time +arithmetic computation. The operand, @var{exp}, is an expression that +contains only constants (@code{const_int}, @code{symbol_ref} and +@code{label_ref} expressions) combined with @code{plus} and +@code{minus}. However, not all combinations are valid, since the +assembler cannot do arbitrary arithmetic on relocatable symbols. + +@var{m} should be @code{Pmode}. + +@findex high +@item (high:@var{m} @var{exp}) +Represents the high-order bits of @var{exp}, usually a +@code{symbol_ref}. The number of bits is machine-dependent and is +normally the number of bits specified in an instruction that initializes +the high order bits of a register. It is used with @code{lo_sum} to +represent the typical two-instruction sequence used in RISC machines to +reference a global memory location. + +@var{m} should be @code{Pmode}. +@end table + +@node Regs and Memory +@section Registers and Memory +@cindex RTL register expressions +@cindex RTL memory expressions + +Here are the RTL expression types for describing access to machine +registers and to main memory. + +@table @code +@findex reg +@cindex hard registers +@cindex pseudo registers +@item (reg:@var{m} @var{n}) +For small values of the integer @var{n} (those that are less than +@code{FIRST_PSEUDO_REGISTER}), this stands for a reference to machine +register number @var{n}: a @dfn{hard register}. For larger values of +@var{n}, it stands for a temporary value or @dfn{pseudo register}. +The compiler's strategy is to generate code assuming an unlimited +number of such pseudo registers, and later convert them into hard +registers or into memory references. + +@var{m} is the machine mode of the reference. It is necessary because +machines can generally refer to each register in more than one mode. +For example, a register may contain a full word but there may be +instructions to refer to it as a half word or as a single byte, as +well as instructions to refer to it as a floating point number of +various precisions. + +Even for a register that the machine can access in only one mode, +the mode must always be specified. + +The symbol @code{FIRST_PSEUDO_REGISTER} is defined by the machine +description, since the number of hard registers on the machine is an +invariant characteristic of the machine. Note, however, that not +all of the machine registers must be general registers. All the +machine registers that can be used for storage of data are given +hard register numbers, even those that can be used only in certain +instructions or can hold only certain types of data. + +A hard register may be accessed in various modes throughout one +function, but each pseudo register is given a natural mode +and is accessed only in that mode. When it is necessary to describe +an access to a pseudo register using a nonnatural mode, a @code{subreg} +expression is used. + +A @code{reg} expression with a machine mode that specifies more than +one word of data may actually stand for several consecutive registers. +If in addition the register number specifies a hardware register, then +it actually represents several consecutive hardware registers starting +with the specified one. + +Each pseudo register number used in a function's RTL code is +represented by a unique @code{reg} expression. + +@findex FIRST_VIRTUAL_REGISTER +@findex LAST_VIRTUAL_REGISTER +Some pseudo register numbers, those within the range of +@code{FIRST_VIRTUAL_REGISTER} to @code{LAST_VIRTUAL_REGISTER} only +appear during the RTL generation phase and are eliminated before the +optimization phases. These represent locations in the stack frame that +cannot be determined until RTL generation for the function has been +completed. The following virtual register numbers are defined: + +@table @code +@findex VIRTUAL_INCOMING_ARGS_REGNUM +@item VIRTUAL_INCOMING_ARGS_REGNUM +This points to the first word of the incoming arguments passed on the +stack. Normally these arguments are placed there by the caller, but the +callee may have pushed some arguments that were previously passed in +registers. + +@cindex @code{FIRST_PARM_OFFSET} and virtual registers +@cindex @code{ARG_POINTER_REGNUM} and virtual registers +When RTL generation is complete, this virtual register is replaced +by the sum of the register given by @code{ARG_POINTER_REGNUM} and the +value of @code{FIRST_PARM_OFFSET}. + +@findex VIRTUAL_STACK_VARS_REGNUM +@cindex @code{FRAME_GROWS_DOWNWARD} and virtual registers +@item VIRTUAL_STACK_VARS_REGNUM +If @code{FRAME_GROWS_DOWNWARD} is defined, this points to immediately +above the first variable on the stack. Otherwise, it points to the +first variable on the stack. + +@cindex @code{STARTING_FRAME_OFFSET} and virtual registers +@cindex @code{FRAME_POINTER_REGNUM} and virtual registers +@code{VIRTUAL_STACK_VARS_REGNUM} is replaced with the sum of the +register given by @code{FRAME_POINTER_REGNUM} and the value +@code{STARTING_FRAME_OFFSET}. + +@findex VIRTUAL_STACK_DYNAMIC_REGNUM +@item VIRTUAL_STACK_DYNAMIC_REGNUM +This points to the location of dynamically allocated memory on the stack +immediately after the stack pointer has been adjusted by the amount of +memory desired. + +@cindex @code{STACK_DYNAMIC_OFFSET} and virtual registers +@cindex @code{STACK_POINTER_REGNUM} and virtual registers +This virtual register is replaced by the sum of the register given by +@code{STACK_POINTER_REGNUM} and the value @code{STACK_DYNAMIC_OFFSET}. + +@findex VIRTUAL_OUTGOING_ARGS_REGNUM +@item VIRTUAL_OUTGOING_ARGS_REGNUM +This points to the location in the stack at which outgoing arguments +should be written when the stack is pre-pushed (arguments pushed using +push insns should always use @code{STACK_POINTER_REGNUM}). + +@cindex @code{STACK_POINTER_OFFSET} and virtual registers +This virtual register is replaced by the sum of the register given by +@code{STACK_POINTER_REGNUM} and the value @code{STACK_POINTER_OFFSET}. +@end table + +@findex subreg +@item (subreg:@var{m} @var{reg} @var{bytenum}) +@code{subreg} expressions are used to refer to a register in a machine +mode other than its natural one, or to refer to one register of +a multi-part @code{reg} that actually refers to several registers. + +Each pseudo-register has a natural mode. If it is necessary to +operate on it in a different mode---for example, to perform a fullword +move instruction on a pseudo-register that contains a single +byte---the pseudo-register must be enclosed in a @code{subreg}. In +such a case, @var{bytenum} is zero. + +Usually @var{m} is at least as narrow as the mode of @var{reg}, in which +case it is restricting consideration to only the bits of @var{reg} that +are in @var{m}. + +Sometimes @var{m} is wider than the mode of @var{reg}. These +@code{subreg} expressions are often called @dfn{paradoxical}. They are +used in cases where we want to refer to an object in a wider mode but do +not care what value the additional bits have. The reload pass ensures +that paradoxical references are only made to hard registers. + +The other use of @code{subreg} is to extract the individual registers of +a multi-register value. Machine modes such as @code{DImode} and +@code{TImode} can indicate values longer than a word, values which +usually require two or more consecutive registers. To access one of the +registers, use a @code{subreg} with mode @code{SImode} and a +@var{bytenum} offset that says which register. + +Storing in a non-paradoxical @code{subreg} has undefined results for +bits belonging to the same word as the @code{subreg}. This laxity makes +it easier to generate efficient code for such instructions. To +represent an instruction that preserves all the bits outside of those in +the @code{subreg}, use @code{strict_low_part} around the @code{subreg}. + +@cindex @code{WORDS_BIG_ENDIAN}, effect on @code{subreg} +The compilation parameter @code{WORDS_BIG_ENDIAN}, if set to 1, says +that byte number zero is part of the most significant word; otherwise, +it is part of the least significant word. + +@cindex @code{BYTES_BIG_ENDIAN}, effect on @code{subreg} +The compilation parameter @code{BYTES_BIG_ENDIAN}, if set to 1, says +that byte number zero is the most significant byte within a word; +otherwise, it is the least significant byte within a word. + +@cindex @code{FLOAT_WORDS_BIG_ENDIAN}, (lack of) effect on @code{subreg} +On a few targets, @code{FLOAT_WORDS_BIG_ENDIAN} disagrees with +@code{WORDS_BIG_ENDIAN}. +However, most parts of the compiler treat floating point values as if +they had the same endianness as integer values. This works because +they handle them solely as a collection of integer values, with no +particular numerical value. Only real.c and the runtime libraries +care about @code{FLOAT_WORDS_BIG_ENDIAN}. + +@cindex combiner pass +@cindex reload pass +@cindex @code{subreg}, special reload handling +Between the combiner pass and the reload pass, it is possible to have a +paradoxical @code{subreg} which contains a @code{mem} instead of a +@code{reg} as its first operand. After the reload pass, it is also +possible to have a non-paradoxical @code{subreg} which contains a +@code{mem}; this usually occurs when the @code{mem} is a stack slot +which replaced a pseudo register. + +Note that it is not valid to access a @code{DFmode} value in @code{SFmode} +using a @code{subreg}. On some machines the most significant part of a +@code{DFmode} value does not have the same format as a single-precision +floating value. + +It is also not valid to access a single word of a multi-word value in a +hard register when less registers can hold the value than would be +expected from its size. For example, some 32-bit machines have +floating-point registers that can hold an entire @code{DFmode} value. +If register 10 were such a register @code{(subreg:SI (reg:DF 10) 1)} +would be invalid because there is no way to convert that reference to +a single machine register. The reload pass prevents @code{subreg} +expressions such as these from being formed. + +@findex SUBREG_REG +@findex SUBREG_BYTE +The first operand of a @code{subreg} expression is customarily accessed +with the @code{SUBREG_REG} macro and the second operand is customarily +accessed with the @code{SUBREG_BYTE} macro. + +@findex scratch +@cindex scratch operands +@item (scratch:@var{m}) +This represents a scratch register that will be required for the +execution of a single instruction and not used subsequently. It is +converted into a @code{reg} by either the local register allocator or +the reload pass. + +@code{scratch} is usually present inside a @code{clobber} operation +(@pxref{Side Effects}). + +@findex cc0 +@cindex condition code register +@item (cc0) +This refers to the machine's condition code register. It has no +operands and may not have a machine mode. There are two ways to use it: + +@itemize @bullet +@item +To stand for a complete set of condition code flags. This is best on +most machines, where each comparison sets the entire series of flags. + +With this technique, @code{(cc0)} may be validly used in only two +contexts: as the destination of an assignment (in test and compare +instructions) and in comparison operators comparing against zero +(@code{const_int} with value zero; that is to say, @code{const0_rtx}). + +@item +To stand for a single flag that is the result of a single condition. +This is useful on machines that have only a single flag bit, and in +which comparison instructions must specify the condition to test. + +With this technique, @code{(cc0)} may be validly used in only two +contexts: as the destination of an assignment (in test and compare +instructions) where the source is a comparison operator, and as the +first operand of @code{if_then_else} (in a conditional branch). +@end itemize + +@findex cc0_rtx +There is only one expression object of code @code{cc0}; it is the +value of the variable @code{cc0_rtx}. Any attempt to create an +expression of code @code{cc0} will return @code{cc0_rtx}. + +Instructions can set the condition code implicitly. On many machines, +nearly all instructions set the condition code based on the value that +they compute or store. It is not necessary to record these actions +explicitly in the RTL because the machine description includes a +prescription for recognizing the instructions that do so (by means of +the macro @code{NOTICE_UPDATE_CC}). @xref{Condition Code}. Only +instructions whose sole purpose is to set the condition code, and +instructions that use the condition code, need mention @code{(cc0)}. + +On some machines, the condition code register is given a register number +and a @code{reg} is used instead of @code{(cc0)}. This is usually the +preferable approach if only a small subset of instructions modify the +condition code. Other machines store condition codes in general +registers; in such cases a pseudo register should be used. + +Some machines, such as the Sparc and RS/6000, have two sets of +arithmetic instructions, one that sets and one that does not set the +condition code. This is best handled by normally generating the +instruction that does not set the condition code, and making a pattern +that both performs the arithmetic and sets the condition code register +(which would not be @code{(cc0)} in this case). For examples, search +for @samp{addcc} and @samp{andcc} in @file{sparc.md}. + +@findex pc +@item (pc) +@cindex program counter +This represents the machine's program counter. It has no operands and +may not have a machine mode. @code{(pc)} may be validly used only in +certain specific contexts in jump instructions. + +@findex pc_rtx +There is only one expression object of code @code{pc}; it is the value +of the variable @code{pc_rtx}. Any attempt to create an expression of +code @code{pc} will return @code{pc_rtx}. + +All instructions that do not jump alter the program counter implicitly +by incrementing it, but there is no need to mention this in the RTL. + +@findex mem +@item (mem:@var{m} @var{addr} @var{alias}) +This RTX represents a reference to main memory at an address +represented by the expression @var{addr}. @var{m} specifies how large +a unit of memory is accessed. @var{alias} specifies an alias set for the +reference. In general two items are in different alias sets if they cannot +reference the same memory address. + +@findex addressof +@item (addressof:@var{m} @var{reg}) +This RTX represents a request for the address of register @var{reg}. Its mode +is always @code{Pmode}. If there are any @code{addressof} +expressions left in the function after CSE, @var{reg} is forced into the +stack and the @code{addressof} expression is replaced with a @code{plus} +expression for the address of its stack slot. +@end table + +@node Arithmetic +@section RTL Expressions for Arithmetic +@cindex arithmetic, in RTL +@cindex math, in RTL +@cindex RTL expressions for arithmetic + +Unless otherwise specified, all the operands of arithmetic expressions +must be valid for mode @var{m}. An operand is valid for mode @var{m} +if it has mode @var{m}, or if it is a @code{const_int} or +@code{const_double} and @var{m} is a mode of class @code{MODE_INT}. + +For commutative binary operations, constants should be placed in the +second operand. + +@table @code +@findex plus +@cindex RTL addition +@cindex RTL sum +@item (plus:@var{m} @var{x} @var{y}) +Represents the sum of the values represented by @var{x} and @var{y} +carried out in machine mode @var{m}. + +@findex lo_sum +@item (lo_sum:@var{m} @var{x} @var{y}) +Like @code{plus}, except that it represents that sum of @var{x} and the +low-order bits of @var{y}. The number of low order bits is +machine-dependent but is normally the number of bits in a @code{Pmode} +item minus the number of bits set by the @code{high} code +(@pxref{Constants}). + +@var{m} should be @code{Pmode}. + +@findex minus +@cindex RTL subtraction +@cindex RTL difference +@item (minus:@var{m} @var{x} @var{y}) +Like @code{plus} but represents subtraction. + +@findex ss_plus +@cindex RTL addition with signed saturation +@item (ss_plus:@var{m} @var{x} @var{y}) + +Like @code{plus}, but using signed saturation in case of an overflow. + +@findex us_plus +@cindex RTL addition with unsigned saturation +@item (us_plus:@var{m} @var{x} @var{y}) + +Like @code{plus}, but using unsigned saturation in case of an overflow. + +@findex ss_minus +@cindex RTL addition with signed saturation +@item (ss_minus:@var{m} @var{x} @var{y}) + +Like @code{minus}, but using signed saturation in case of an overflow. + +@findex us_minus +@cindex RTL addition with unsigned saturation +@item (us_minus:@var{m} @var{x} @var{y}) + +Like @code{minus}, but using unsigned saturation in case of an overflow. + +@findex compare +@cindex RTL comparison +@item (compare:@var{m} @var{x} @var{y}) +Represents the result of subtracting @var{y} from @var{x} for purposes +of comparison. The result is computed without overflow, as if with +infinite precision. + +Of course, machines can't really subtract with infinite precision. +However, they can pretend to do so when only the sign of the result will +be used, which is the case when the result is stored in the condition +code. And that is the @emph{only} way this kind of expression may +validly be used: as a value to be stored in the condition codes, either +@code{(cc0)} or a register. @xref{Comparisons}. + +The mode @var{m} is not related to the modes of @var{x} and @var{y}, but +instead is the mode of the condition code value. If @code{(cc0)} is +used, it is @code{VOIDmode}. Otherwise it is some mode in class +@code{MODE_CC}, often @code{CCmode}. @xref{Condition Code}. If @var{m} +is @code{VOIDmode} or @code{CCmode}, the operation returns sufficient +information (in an unspecified format) so that any comparison operator +can be applied to the result of the @code{COMPARE} operation. For other +modes in class @code{MODE_CC}, the operation only returns a subset of +this information. + +Normally, @var{x} and @var{y} must have the same mode. Otherwise, +@code{compare} is valid only if the mode of @var{x} is in class +@code{MODE_INT} and @var{y} is a @code{const_int} or +@code{const_double} with mode @code{VOIDmode}. The mode of @var{x} +determines what mode the comparison is to be done in; thus it must not +be @code{VOIDmode}. + +If one of the operands is a constant, it should be placed in the +second operand and the comparison code adjusted as appropriate. + +A @code{compare} specifying two @code{VOIDmode} constants is not valid +since there is no way to know in what mode the comparison is to be +performed; the comparison must either be folded during the compilation +or the first operand must be loaded into a register while its mode is +still known. + +@findex neg +@item (neg:@var{m} @var{x}) +Represents the negation (subtraction from zero) of the value represented +by @var{x}, carried out in mode @var{m}. + +@findex mult +@cindex multiplication +@cindex product +@item (mult:@var{m} @var{x} @var{y}) +Represents the signed product of the values represented by @var{x} and +@var{y} carried out in machine mode @var{m}. + +Some machines support a multiplication that generates a product wider +than the operands. Write the pattern for this as + +@example +(mult:@var{m} (sign_extend:@var{m} @var{x}) (sign_extend:@var{m} @var{y})) +@end example + +where @var{m} is wider than the modes of @var{x} and @var{y}, which need +not be the same. + +Write patterns for unsigned widening multiplication similarly using +@code{zero_extend}. + +@findex div +@cindex division +@cindex signed division +@cindex quotient +@item (div:@var{m} @var{x} @var{y}) +Represents the quotient in signed division of @var{x} by @var{y}, +carried out in machine mode @var{m}. If @var{m} is a floating point +mode, it represents the exact quotient; otherwise, the integerized +quotient. + +Some machines have division instructions in which the operands and +quotient widths are not all the same; you should represent +such instructions using @code{truncate} and @code{sign_extend} as in, + +@example +(truncate:@var{m1} (div:@var{m2} @var{x} (sign_extend:@var{m2} @var{y}))) +@end example + +@findex udiv +@cindex unsigned division +@cindex division +@item (udiv:@var{m} @var{x} @var{y}) +Like @code{div} but represents unsigned division. + +@findex mod +@findex umod +@cindex remainder +@cindex division +@item (mod:@var{m} @var{x} @var{y}) +@itemx (umod:@var{m} @var{x} @var{y}) +Like @code{div} and @code{udiv} but represent the remainder instead of +the quotient. + +@findex smin +@findex smax +@cindex signed minimum +@cindex signed maximum +@item (smin:@var{m} @var{x} @var{y}) +@itemx (smax:@var{m} @var{x} @var{y}) +Represents the smaller (for @code{smin}) or larger (for @code{smax}) of +@var{x} and @var{y}, interpreted as signed integers in mode @var{m}. + +@findex umin +@findex umax +@cindex unsigned minimum and maximum +@item (umin:@var{m} @var{x} @var{y}) +@itemx (umax:@var{m} @var{x} @var{y}) +Like @code{smin} and @code{smax}, but the values are interpreted as unsigned +integers. + +@findex not +@cindex complement, bitwise +@cindex bitwise complement +@item (not:@var{m} @var{x}) +Represents the bitwise complement of the value represented by @var{x}, +carried out in mode @var{m}, which must be a fixed-point machine mode. + +@findex and +@cindex logical-and, bitwise +@cindex bitwise logical-and +@item (and:@var{m} @var{x} @var{y}) +Represents the bitwise logical-and of the values represented by +@var{x} and @var{y}, carried out in machine mode @var{m}, which must be +a fixed-point machine mode. + +@findex ior +@cindex inclusive-or, bitwise +@cindex bitwise inclusive-or +@item (ior:@var{m} @var{x} @var{y}) +Represents the bitwise inclusive-or of the values represented by @var{x} +and @var{y}, carried out in machine mode @var{m}, which must be a +fixed-point mode. + +@findex xor +@cindex exclusive-or, bitwise +@cindex bitwise exclusive-or +@item (xor:@var{m} @var{x} @var{y}) +Represents the bitwise exclusive-or of the values represented by @var{x} +and @var{y}, carried out in machine mode @var{m}, which must be a +fixed-point mode. + +@findex ashift +@cindex left shift +@cindex shift +@cindex arithmetic shift +@item (ashift:@var{m} @var{x} @var{c}) +Represents the result of arithmetically shifting @var{x} left by @var{c} +places. @var{x} have mode @var{m}, a fixed-point machine mode. @var{c} +be a fixed-point mode or be a constant with mode @code{VOIDmode}; which +mode is determined by the mode called for in the machine description +entry for the left-shift instruction. For example, on the Vax, the mode +of @var{c} is @code{QImode} regardless of @var{m}. + +@findex lshiftrt +@cindex right shift +@findex ashiftrt +@item (lshiftrt:@var{m} @var{x} @var{c}) +@itemx (ashiftrt:@var{m} @var{x} @var{c}) +Like @code{ashift} but for right shift. Unlike the case for left shift, +these two operations are distinct. + +@findex rotate +@cindex rotate +@cindex left rotate +@findex rotatert +@cindex right rotate +@item (rotate:@var{m} @var{x} @var{c}) +@itemx (rotatert:@var{m} @var{x} @var{c}) +Similar but represent left and right rotate. If @var{c} is a constant, +use @code{rotate}. + +@findex abs +@cindex absolute value +@item (abs:@var{m} @var{x}) +Represents the absolute value of @var{x}, computed in mode @var{m}. + +@findex sqrt +@cindex square root +@item (sqrt:@var{m} @var{x}) +Represents the square root of @var{x}, computed in mode @var{m}. +Most often @var{m} will be a floating point mode. + +@findex ffs +@item (ffs:@var{m} @var{x}) +Represents one plus the index of the least significant 1-bit in +@var{x}, represented as an integer of mode @var{m}. (The value is +zero if @var{x} is zero.) The mode of @var{x} need not be @var{m}; +depending on the target machine, various mode combinations may be +valid. +@end table + +@node Comparisons +@section Comparison Operations +@cindex RTL comparison operations + +Comparison operators test a relation on two operands and are considered +to represent a machine-dependent nonzero value described by, but not +necessarily equal to, @code{STORE_FLAG_VALUE} (@pxref{Misc}) +if the relation holds, or zero if it does not. The mode of the +comparison operation is independent of the mode of the data being +compared. If the comparison operation is being tested (e.g., the first +operand of an @code{if_then_else}), the mode must be @code{VOIDmode}. +If the comparison operation is producing data to be stored in some +variable, the mode must be in class @code{MODE_INT}. All comparison +operations producing data must use the same mode, which is +machine-specific. + +@cindex condition codes +There are two ways that comparison operations may be used. The +comparison operators may be used to compare the condition codes +@code{(cc0)} against zero, as in @code{(eq (cc0) (const_int 0))}. Such +a construct actually refers to the result of the preceding instruction +in which the condition codes were set. The instruction setting the +condition code must be adjacent to the instruction using the condition +code; only @code{note} insns may separate them. + +Alternatively, a comparison operation may directly compare two data +objects. The mode of the comparison is determined by the operands; they +must both be valid for a common machine mode. A comparison with both +operands constant would be invalid as the machine mode could not be +deduced from it, but such a comparison should never exist in RTL due to +constant folding. + +In the example above, if @code{(cc0)} were last set to +@code{(compare @var{x} @var{y})}, the comparison operation is +identical to @code{(eq @var{x} @var{y})}. Usually only one style +of comparisons is supported on a particular machine, but the combine +pass will try to merge the operations to produce the @code{eq} shown +in case it exists in the context of the particular insn involved. + +Inequality comparisons come in two flavors, signed and unsigned. Thus, +there are distinct expression codes @code{gt} and @code{gtu} for signed and +unsigned greater-than. These can produce different results for the same +pair of integer values: for example, 1 is signed greater-than -1 but not +unsigned greater-than, because -1 when regarded as unsigned is actually +@code{0xffffffff} which is greater than 1. + +The signed comparisons are also used for floating point values. Floating +point comparisons are distinguished by the machine modes of the operands. + +@table @code +@findex eq +@cindex equal +@item (eq:@var{m} @var{x} @var{y}) +@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y} +are equal, otherwise 0. + +@findex ne +@cindex not equal +@item (ne:@var{m} @var{x} @var{y}) +@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y} +are not equal, otherwise 0. + +@findex gt +@cindex greater than +@item (gt:@var{m} @var{x} @var{y}) +@code{STORE_FLAG_VALUE} if the @var{x} is greater than @var{y}. If they +are fixed-point, the comparison is done in a signed sense. + +@findex gtu +@cindex greater than +@cindex unsigned greater than +@item (gtu:@var{m} @var{x} @var{y}) +Like @code{gt} but does unsigned comparison, on fixed-point numbers only. + +@findex lt +@cindex less than +@findex ltu +@cindex unsigned less than +@item (lt:@var{m} @var{x} @var{y}) +@itemx (ltu:@var{m} @var{x} @var{y}) +Like @code{gt} and @code{gtu} but test for ``less than''. + +@findex ge +@cindex greater than +@findex geu +@cindex unsigned greater than +@item (ge:@var{m} @var{x} @var{y}) +@itemx (geu:@var{m} @var{x} @var{y}) +Like @code{gt} and @code{gtu} but test for ``greater than or equal''. + +@findex le +@cindex less than or equal +@findex leu +@cindex unsigned less than +@item (le:@var{m} @var{x} @var{y}) +@itemx (leu:@var{m} @var{x} @var{y}) +Like @code{gt} and @code{gtu} but test for ``less than or equal''. + +@findex if_then_else +@item (if_then_else @var{cond} @var{then} @var{else}) +This is not a comparison operation but is listed here because it is +always used in conjunction with a comparison operation. To be +precise, @var{cond} is a comparison expression. This expression +represents a choice, according to @var{cond}, between the value +represented by @var{then} and the one represented by @var{else}. + +On most machines, @code{if_then_else} expressions are valid only +to express conditional jumps. + +@findex cond +@item (cond [@var{test1} @var{value1} @var{test2} @var{value2} @dots{}] @var{default}) +Similar to @code{if_then_else}, but more general. Each of @var{test1}, +@var{test2}, @dots{} is performed in turn. The result of this expression is +the @var{value} corresponding to the first non-zero test, or @var{default} if +none of the tests are non-zero expressions. + +This is currently not valid for instruction patterns and is supported only +for insn attributes. @xref{Insn Attributes}. +@end table + +@node Bit Fields +@section Bit Fields +@cindex bit fields + +Special expression codes exist to represent bitfield instructions. +These types of expressions are lvalues in RTL; they may appear +on the left side of an assignment, indicating insertion of a value +into the specified bit field. + +@table @code +@findex sign_extract +@cindex @code{BITS_BIG_ENDIAN}, effect on @code{sign_extract} +@item (sign_extract:@var{m} @var{loc} @var{size} @var{pos}) +This represents a reference to a sign-extended bit field contained or +starting in @var{loc} (a memory or register reference). The bit field +is @var{size} bits wide and starts at bit @var{pos}. The compilation +option @code{BITS_BIG_ENDIAN} says which end of the memory unit +@var{pos} counts from. + +If @var{loc} is in memory, its mode must be a single-byte integer mode. +If @var{loc} is in a register, the mode to use is specified by the +operand of the @code{insv} or @code{extv} pattern +(@pxref{Standard Names}) and is usually a full-word integer mode, +which is the default if none is specified. + +The mode of @var{pos} is machine-specific and is also specified +in the @code{insv} or @code{extv} pattern. + +The mode @var{m} is the same as the mode that would be used for +@var{loc} if it were a register. + +@findex zero_extract +@item (zero_extract:@var{m} @var{loc} @var{size} @var{pos}) +Like @code{sign_extract} but refers to an unsigned or zero-extended +bit field. The same sequence of bits are extracted, but they +are filled to an entire word with zeros instead of by sign-extension. +@end table + +@node Vector Operations +@section Vector Operations +@cindex vector operations + +All normal rtl expressions can be used with vector modes; they are +interpreted as operating on each part of the vector independently. +Additionally, there are a few new expressions to describe specific vector +operations. + +@table @code +@findex vec_merge +@item (vec_merge:@var{m} @var{vec1} @var{vec2} @var{items}) +This describes a merge operation between two vectors. The result is a vector +of mode @var{m}; its elements are selected from either @var{vec1} or +@var{vec2}. Which elements are selected is described by @var{items}, which +is a bit mask represented by a @code{const_int}; a zero bit indicates the +corresponding element in the result vector is taken from @var{vec2} while +a set bit indicates it is taken from @var{vec1}. + +@findex vec_select +@item (vec_select:@var{m} @var{vec1} @var{selection}) +This describes an operation that selects parts of a vector. @var{vec1} is +the source vector, @var{selection} is a @code{parallel} that contains a +@code{const_int} for each of the subparts of the result vector, giving the +number of the source subpart that should be stored into it. + +@findex vec_concat +@item (vec_concat:@var{m} @var{vec1} @var{vec2}) +Describes a vector concat operation. The result is a concatenation of the +vectors @var{vec1} and @var{vec2}; its length is the sum of the lengths of +the two inputs. + +@findex vec_const +@item (vec_const:@var{m} @var{subparts}) +This describes a constant vector. @var{subparts} is a @code{parallel} that +contains a constant for each of the subparts of the vector. + +@findex vec_duplicate +@item (vec_duplicate:@var{m} @var{vec}) +This operation converts a small vector into a larger one by duplicating the +input values. The output vector mode must have the same submodes as the +input vector mode, and the number of output parts must be an integer multiple +of the number of input parts. + +@end table + +@node Conversions +@section Conversions +@cindex conversions +@cindex machine mode conversions + +All conversions between machine modes must be represented by +explicit conversion operations. For example, an expression +which is the sum of a byte and a full word cannot be written as +@code{(plus:SI (reg:QI 34) (reg:SI 80))} because the @code{plus} +operation requires two operands of the same machine mode. +Therefore, the byte-sized operand is enclosed in a conversion +operation, as in + +@example +(plus:SI (sign_extend:SI (reg:QI 34)) (reg:SI 80)) +@end example + +The conversion operation is not a mere placeholder, because there +may be more than one way of converting from a given starting mode +to the desired final mode. The conversion operation code says how +to do it. + +For all conversion operations, @var{x} must not be @code{VOIDmode} +because the mode in which to do the conversion would not be known. +The conversion must either be done at compile-time or @var{x} +must be placed into a register. + +@table @code +@findex sign_extend +@item (sign_extend:@var{m} @var{x}) +Represents the result of sign-extending the value @var{x} +to machine mode @var{m}. @var{m} must be a fixed-point mode +and @var{x} a fixed-point value of a mode narrower than @var{m}. + +@findex zero_extend +@item (zero_extend:@var{m} @var{x}) +Represents the result of zero-extending the value @var{x} +to machine mode @var{m}. @var{m} must be a fixed-point mode +and @var{x} a fixed-point value of a mode narrower than @var{m}. + +@findex float_extend +@item (float_extend:@var{m} @var{x}) +Represents the result of extending the value @var{x} +to machine mode @var{m}. @var{m} must be a floating point mode +and @var{x} a floating point value of a mode narrower than @var{m}. + +@findex truncate +@item (truncate:@var{m} @var{x}) +Represents the result of truncating the value @var{x} +to machine mode @var{m}. @var{m} must be a fixed-point mode +and @var{x} a fixed-point value of a mode wider than @var{m}. + +@findex ss_truncate +@item (ss_truncate:@var{m} @var{x}) +Represents the result of truncating the value @var{x} +to machine mode @var{m}, using signed saturation in the case of +overflow. Both @var{m} and the mode of @var{x} must be fixed-point +modes. + +@findex us_truncate +@item (us_truncate:@var{m} @var{x}) +Represents the result of truncating the value @var{x} +to machine mode @var{m}, using unsigned saturation in the case of +overflow. Both @var{m} and the mode of @var{x} must be fixed-point +modes. + +@findex float_truncate +@item (float_truncate:@var{m} @var{x}) +Represents the result of truncating the value @var{x} +to machine mode @var{m}. @var{m} must be a floating point mode +and @var{x} a floating point value of a mode wider than @var{m}. + +@findex float +@item (float:@var{m} @var{x}) +Represents the result of converting fixed point value @var{x}, +regarded as signed, to floating point mode @var{m}. + +@findex unsigned_float +@item (unsigned_float:@var{m} @var{x}) +Represents the result of converting fixed point value @var{x}, +regarded as unsigned, to floating point mode @var{m}. + +@findex fix +@item (fix:@var{m} @var{x}) +When @var{m} is a fixed point mode, represents the result of +converting floating point value @var{x} to mode @var{m}, regarded as +signed. How rounding is done is not specified, so this operation may +be used validly in compiling C code only for integer-valued operands. + +@findex unsigned_fix +@item (unsigned_fix:@var{m} @var{x}) +Represents the result of converting floating point value @var{x} to +fixed point mode @var{m}, regarded as unsigned. How rounding is done +is not specified. + +@findex fix +@item (fix:@var{m} @var{x}) +When @var{m} is a floating point mode, represents the result of +converting floating point value @var{x} (valid for mode @var{m}) to an +integer, still represented in floating point mode @var{m}, by rounding +towards zero. +@end table + +@node RTL Declarations +@section Declarations +@cindex RTL declarations +@cindex declarations, RTL + +Declaration expression codes do not represent arithmetic operations +but rather state assertions about their operands. + +@table @code +@findex strict_low_part +@cindex @code{subreg}, in @code{strict_low_part} +@item (strict_low_part (subreg:@var{m} (reg:@var{n} @var{r}) 0)) +This expression code is used in only one context: as the destination operand of a +@code{set} expression. In addition, the operand of this expression +must be a non-paradoxical @code{subreg} expression. + +The presence of @code{strict_low_part} says that the part of the +register which is meaningful in mode @var{n}, but is not part of +mode @var{m}, is not to be altered. Normally, an assignment to such +a subreg is allowed to have undefined effects on the rest of the +register when @var{m} is less than a word. +@end table + +@node Side Effects +@section Side Effect Expressions +@cindex RTL side effect expressions + +The expression codes described so far represent values, not actions. +But machine instructions never produce values; they are meaningful +only for their side effects on the state of the machine. Special +expression codes are used to represent side effects. + +The body of an instruction is always one of these side effect codes; +the codes described above, which represent values, appear only as +the operands of these. + +@table @code +@findex set +@item (set @var{lval} @var{x}) +Represents the action of storing the value of @var{x} into the place +represented by @var{lval}. @var{lval} must be an expression +representing a place that can be stored in: @code{reg} (or @code{subreg} +or @code{strict_low_part}), @code{mem}, @code{pc}, @code{parallel}, or +@code{cc0}.@refill + +If @var{lval} is a @code{reg}, @code{subreg} or @code{mem}, it has a +machine mode; then @var{x} must be valid for that mode.@refill + +If @var{lval} is a @code{reg} whose machine mode is less than the full +width of the register, then it means that the part of the register +specified by the machine mode is given the specified value and the +rest of the register receives an undefined value. Likewise, if +@var{lval} is a @code{subreg} whose machine mode is narrower than +the mode of the register, the rest of the register can be changed in +an undefined way. + +If @var{lval} is a @code{strict_low_part} of a @code{subreg}, then the +part of the register specified by the machine mode of the +@code{subreg} is given the value @var{x} and the rest of the register +is not changed.@refill + +If @var{lval} is @code{(cc0)}, it has no machine mode, and @var{x} may +be either a @code{compare} expression or a value that may have any mode. +The latter case represents a ``test'' instruction. The expression +@code{(set (cc0) (reg:@var{m} @var{n}))} is equivalent to +@code{(set (cc0) (compare (reg:@var{m} @var{n}) (const_int 0)))}. +Use the former expression to save space during the compilation. + +If @var{lval} is a @code{parallel}, it is used to represent the case of +a function returning a structure in multiple registers. Each element +of the @code{paralllel} is an @code{expr_list} whose first operand is a +@code{reg} and whose second operand is a @code{const_int} representing the +offset (in bytes) into the structure at which the data in that register +corresponds. The first element may be null to indicate that the structure +is also passed partly in memory. + +@cindex jump instructions and @code{set} +@cindex @code{if_then_else} usage +If @var{lval} is @code{(pc)}, we have a jump instruction, and the +possibilities for @var{x} are very limited. It may be a +@code{label_ref} expression (unconditional jump). It may be an +@code{if_then_else} (conditional jump), in which case either the +second or the third operand must be @code{(pc)} (for the case which +does not jump) and the other of the two must be a @code{label_ref} +(for the case which does jump). @var{x} may also be a @code{mem} or +@code{(plus:SI (pc) @var{y})}, where @var{y} may be a @code{reg} or a +@code{mem}; these unusual patterns are used to represent jumps through +branch tables.@refill + +If @var{lval} is neither @code{(cc0)} nor @code{(pc)}, the mode of +@var{lval} must not be @code{VOIDmode} and the mode of @var{x} must be +valid for the mode of @var{lval}. + +@findex SET_DEST +@findex SET_SRC +@var{lval} is customarily accessed with the @code{SET_DEST} macro and +@var{x} with the @code{SET_SRC} macro. + +@findex return +@item (return) +As the sole expression in a pattern, represents a return from the +current function, on machines where this can be done with one +instruction, such as Vaxes. On machines where a multi-instruction +``epilogue'' must be executed in order to return from the function, +returning is done by jumping to a label which precedes the epilogue, and +the @code{return} expression code is never used. + +Inside an @code{if_then_else} expression, represents the value to be +placed in @code{pc} to return to the caller. + +Note that an insn pattern of @code{(return)} is logically equivalent to +@code{(set (pc) (return))}, but the latter form is never used. + +@findex call +@item (call @var{function} @var{nargs}) +Represents a function call. @var{function} is a @code{mem} expression +whose address is the address of the function to be called. +@var{nargs} is an expression which can be used for two purposes: on +some machines it represents the number of bytes of stack argument; on +others, it represents the number of argument registers. + +Each machine has a standard machine mode which @var{function} must +have. The machine description defines macro @code{FUNCTION_MODE} to +expand into the requisite mode name. The purpose of this mode is to +specify what kind of addressing is allowed, on machines where the +allowed kinds of addressing depend on the machine mode being +addressed. + +@findex clobber +@item (clobber @var{x}) +Represents the storing or possible storing of an unpredictable, +undescribed value into @var{x}, which must be a @code{reg}, +@code{scratch}, @code{parallel} or @code{mem} expression. + +One place this is used is in string instructions that store standard +values into particular hard registers. It may not be worth the +trouble to describe the values that are stored, but it is essential to +inform the compiler that the registers will be altered, lest it +attempt to keep data in them across the string instruction. + +If @var{x} is @code{(mem:BLK (const_int 0))}, it means that all memory +locations must be presumed clobbered. If @var{x} is a @code{parallel}, +it has the same meaning as a @code{parallel} in a @code{set} expression. + +Note that the machine description classifies certain hard registers as +``call-clobbered''. All function call instructions are assumed by +default to clobber these registers, so there is no need to use +@code{clobber} expressions to indicate this fact. Also, each function +call is assumed to have the potential to alter any memory location, +unless the function is declared @code{const}. + +If the last group of expressions in a @code{parallel} are each a +@code{clobber} expression whose arguments are @code{reg} or +@code{match_scratch} (@pxref{RTL Template}) expressions, the combiner +phase can add the appropriate @code{clobber} expressions to an insn it +has constructed when doing so will cause a pattern to be matched. + +This feature can be used, for example, on a machine that whose multiply +and add instructions don't use an MQ register but which has an +add-accumulate instruction that does clobber the MQ register. Similarly, +a combined instruction might require a temporary register while the +constituent instructions might not. + +When a @code{clobber} expression for a register appears inside a +@code{parallel} with other side effects, the register allocator +guarantees that the register is unoccupied both before and after that +insn. However, the reload phase may allocate a register used for one of +the inputs unless the @samp{&} constraint is specified for the selected +alternative (@pxref{Modifiers}). You can clobber either a specific hard +register, a pseudo register, or a @code{scratch} expression; in the +latter two cases, GNU CC will allocate a hard register that is available +there for use as a temporary. + +For instructions that require a temporary register, you should use +@code{scratch} instead of a pseudo-register because this will allow the +combiner phase to add the @code{clobber} when required. You do this by +coding (@code{clobber} (@code{match_scratch} @dots{})). If you do +clobber a pseudo register, use one which appears nowhere else---generate +a new one each time. Otherwise, you may confuse CSE. + +There is one other known use for clobbering a pseudo register in a +@code{parallel}: when one of the input operands of the insn is also +clobbered by the insn. In this case, using the same pseudo register in +the clobber and elsewhere in the insn produces the expected results. + +@findex use +@item (use @var{x}) +Represents the use of the value of @var{x}. It indicates that the +value in @var{x} at this point in the program is needed, even though +it may not be apparent why this is so. Therefore, the compiler will +not attempt to delete previous instructions whose only effect is to +store a value in @var{x}. @var{x} must be a @code{reg} expression. + +In some situations, it may be tempting to add a @code{use} of a +register in a @code{parallel} to describe a situation where the value +of a special register will modify the behaviour of the instruction. +An hypothetical example might be a pattern for an addition that can +either wrap around or use saturating addition depending on the value +of a special control register: + +@example +(parallel [(set (reg:SI 2) (unspec:SI [(reg:SI 3) (reg:SI 4)] 0)) + (use (reg:SI 1))]) +@end example + +@noindent + +This will not work, several of the optimizers only look at expressions +locally; it is very likely that if you have multiple insns with +identical inputs to the @code{unspec}, they will be optimized away even +if register 1 changes in between. + +This means that @code{use} can @emph{only} be used to describe +that the register is live. You should think twice before adding +@code{use} statements, more often you will want to use @code{unspec} +instead. The @code{use} RTX is most commonly useful to describe that +a fixed register is implicitly used in an insn. It is also safe to use +in patterns where the compiler knows for other reasons that the result +of the whole pattern is variable, such as @samp{movstr@var{m}} or +@samp{call} patterns. + +During the reload phase, an insn that has a @code{use} as pattern +can carry a reg_equal note. These @code{use} insns will be deleted +before the reload phase exits. + +During the delayed branch scheduling phase, @var{x} may be an insn. +This indicates that @var{x} previously was located at this place in the +code and its data dependencies need to be taken into account. These +@code{use} insns will be deleted before the delayed branch scheduling +phase exits. + +@findex parallel +@item (parallel [@var{x0} @var{x1} @dots{}]) +Represents several side effects performed in parallel. The square +brackets stand for a vector; the operand of @code{parallel} is a +vector of expressions. @var{x0}, @var{x1} and so on are individual +side effect expressions---expressions of code @code{set}, @code{call}, +@code{return}, @code{clobber} or @code{use}.@refill + +``In parallel'' means that first all the values used in the individual +side-effects are computed, and second all the actual side-effects are +performed. For example, + +@example +(parallel [(set (reg:SI 1) (mem:SI (reg:SI 1))) + (set (mem:SI (reg:SI 1)) (reg:SI 1))]) +@end example + +@noindent +says unambiguously that the values of hard register 1 and the memory +location addressed by it are interchanged. In both places where +@code{(reg:SI 1)} appears as a memory address it refers to the value +in register 1 @emph{before} the execution of the insn. + +It follows that it is @emph{incorrect} to use @code{parallel} and +expect the result of one @code{set} to be available for the next one. +For example, people sometimes attempt to represent a jump-if-zero +instruction this way: + +@example +(parallel [(set (cc0) (reg:SI 34)) + (set (pc) (if_then_else + (eq (cc0) (const_int 0)) + (label_ref @dots{}) + (pc)))]) +@end example + +@noindent +But this is incorrect, because it says that the jump condition depends +on the condition code value @emph{before} this instruction, not on the +new value that is set by this instruction. + +@cindex peephole optimization, RTL representation +Peephole optimization, which takes place together with final assembly +code output, can produce insns whose patterns consist of a @code{parallel} +whose elements are the operands needed to output the resulting +assembler code---often @code{reg}, @code{mem} or constant expressions. +This would not be well-formed RTL at any other stage in compilation, +but it is ok then because no further optimization remains to be done. +However, the definition of the macro @code{NOTICE_UPDATE_CC}, if +any, must deal with such insns if you define any peephole optimizations. + +@findex sequence +@item (sequence [@var{insns} @dots{}]) +Represents a sequence of insns. Each of the @var{insns} that appears +in the vector is suitable for appearing in the chain of insns, so it +must be an @code{insn}, @code{jump_insn}, @code{call_insn}, +@code{code_label}, @code{barrier} or @code{note}. + +A @code{sequence} RTX is never placed in an actual insn during RTL +generation. It represents the sequence of insns that result from a +@code{define_expand} @emph{before} those insns are passed to +@code{emit_insn} to insert them in the chain of insns. When actually +inserted, the individual sub-insns are separated out and the +@code{sequence} is forgotten. + +After delay-slot scheduling is completed, an insn and all the insns that +reside in its delay slots are grouped together into a @code{sequence}. +The insn requiring the delay slot is the first insn in the vector; +subsequent insns are to be placed in the delay slot. + +@code{INSN_ANNULLED_BRANCH_P} is set on an insn in a delay slot to +indicate that a branch insn should be used that will conditionally annul +the effect of the insns in the delay slots. In such a case, +@code{INSN_FROM_TARGET_P} indicates that the insn is from the target of +the branch and should be executed only if the branch is taken; otherwise +the insn should be executed only if the branch is not taken. +@xref{Delay Slots}. +@end table + +These expression codes appear in place of a side effect, as the body of +an insn, though strictly speaking they do not always describe side +effects as such: + +@table @code +@findex asm_input +@item (asm_input @var{s}) +Represents literal assembler code as described by the string @var{s}. + +@findex unspec +@findex unspec_volatile +@item (unspec [@var{operands} @dots{}] @var{index}) +@itemx (unspec_volatile [@var{operands} @dots{}] @var{index}) +Represents a machine-specific operation on @var{operands}. @var{index} +selects between multiple machine-specific operations. +@code{unspec_volatile} is used for volatile operations and operations +that may trap; @code{unspec} is used for other operations. + +These codes may appear inside a @code{pattern} of an +insn, inside a @code{parallel}, or inside an expression. + +@findex addr_vec +@item (addr_vec:@var{m} [@var{lr0} @var{lr1} @dots{}]) +Represents a table of jump addresses. The vector elements @var{lr0}, +etc., are @code{label_ref} expressions. The mode @var{m} specifies +how much space is given to each address; normally @var{m} would be +@code{Pmode}. + +@findex addr_diff_vec +@item (addr_diff_vec:@var{m} @var{base} [@var{lr0} @var{lr1} @dots{}] @var{min} @var{max} @var{flags}) +Represents a table of jump addresses expressed as offsets from +@var{base}. The vector elements @var{lr0}, etc., are @code{label_ref} +expressions and so is @var{base}. The mode @var{m} specifies how much +space is given to each address-difference. @var{min} and @var{max} +are set up by branch shortening and hold a label with a minimum and a +maximum address, respectively. @var{flags} indicates the relative +position of @var{base}, @var{min} and @var{max} to the containing insn +and of @var{min} and @var{max} to @var{base}. See rtl.def for details.@refill +@end table + +@node Incdec +@section Embedded Side-Effects on Addresses +@cindex RTL preincrement +@cindex RTL postincrement +@cindex RTL predecrement +@cindex RTL postdecrement + +Six special side-effect expression codes appear as memory addresses. + +@table @code +@findex pre_dec +@item (pre_dec:@var{m} @var{x}) +Represents the side effect of decrementing @var{x} by a standard +amount and represents also the value that @var{x} has after being +decremented. @var{x} must be a @code{reg} or @code{mem}, but most +machines allow only a @code{reg}. @var{m} must be the machine mode +for pointers on the machine in use. The amount @var{x} is decremented +by is the length in bytes of the machine mode of the containing memory +reference of which this expression serves as the address. Here is an +example of its use:@refill + +@example +(mem:DF (pre_dec:SI (reg:SI 39))) +@end example + +@noindent +This says to decrement pseudo register 39 by the length of a @code{DFmode} +value and use the result to address a @code{DFmode} value. + +@findex pre_inc +@item (pre_inc:@var{m} @var{x}) +Similar, but specifies incrementing @var{x} instead of decrementing it. + +@findex post_dec +@item (post_dec:@var{m} @var{x}) +Represents the same side effect as @code{pre_dec} but a different +value. The value represented here is the value @var{x} has @i{before} +being decremented. + +@findex post_inc +@item (post_inc:@var{m} @var{x}) +Similar, but specifies incrementing @var{x} instead of decrementing it. + +@findex post_modify +@item (post_modify:@var{m} @var{x} @var{y}) + +Represents the side effect of setting @var{x} to @var{y} and +represents @var{x} before @var{x} is modified. @var{x} must be a +@code{reg} or @code{mem}, but most machines allow only a @code{reg}. +@var{m} must be the machine mode for pointers on the machine in use. +The amount @var{x} is decremented by is the length in bytes of the +machine mode of the containing memory reference of which this expression +serves as the address. Note that this is not currently implemented. + +The expression @var{y} must be one of three forms: +@table @code +@code{(plus:@var{m} @var{x} @var{z})}, +@code{(minus:@var{m} @var{x} @var{z})}, or +@code{(plus:@var{m} @var{x} @var{i})}, +@end table +where @var{z} is an index register and @var{i} is a constant. + +Here is an example of its use:@refill + +@example +(mem:SF (post_modify:SI (reg:SI 42) (plus (reg:SI 42) (reg:SI 48)))) +@end example + +This says to modify pseudo register 42 by adding the contents of pseudo +register 48 to it, after the use of what ever 42 points to. + +@findex post_modify +@item (pre_modify:@var{m} @var{x} @var{expr}) +Similar except side effects happen before the use. +@end table + +These embedded side effect expressions must be used with care. Instruction +patterns may not use them. Until the @samp{flow} pass of the compiler, +they may occur only to represent pushes onto the stack. The @samp{flow} +pass finds cases where registers are incremented or decremented in one +instruction and used as an address shortly before or after; these cases are +then transformed to use pre- or post-increment or -decrement. + +If a register used as the operand of these expressions is used in +another address in an insn, the original value of the register is used. +Uses of the register outside of an address are not permitted within the +same insn as a use in an embedded side effect expression because such +insns behave differently on different machines and hence must be treated +as ambiguous and disallowed. + +An instruction that can be represented with an embedded side effect +could also be represented using @code{parallel} containing an additional +@code{set} to describe how the address register is altered. This is not +done because machines that allow these operations at all typically +allow them wherever a memory address is called for. Describing them as +additional parallel stores would require doubling the number of entries +in the machine description. + +@node Assembler +@section Assembler Instructions as Expressions +@cindex assembler instructions in RTL + +@cindex @code{asm_operands}, usage +The RTX code @code{asm_operands} represents a value produced by a +user-specified assembler instruction. It is used to represent +an @code{asm} statement with arguments. An @code{asm} statement with +a single output operand, like this: + +@smallexample +asm ("foo %1,%2,%0" : "=a" (outputvar) : "g" (x + y), "di" (*z)); +@end smallexample + +@noindent +is represented using a single @code{asm_operands} RTX which represents +the value that is stored in @code{outputvar}: + +@smallexample +(set @var{rtx-for-outputvar} + (asm_operands "foo %1,%2,%0" "a" 0 + [@var{rtx-for-addition-result} @var{rtx-for-*z}] + [(asm_input:@var{m1} "g") + (asm_input:@var{m2} "di")])) +@end smallexample + +@noindent +Here the operands of the @code{asm_operands} RTX are the assembler +template string, the output-operand's constraint, the index-number of the +output operand among the output operands specified, a vector of input +operand RTX's, and a vector of input-operand modes and constraints. The +mode @var{m1} is the mode of the sum @code{x+y}; @var{m2} is that of +@code{*z}. + +When an @code{asm} statement has multiple output values, its insn has +several such @code{set} RTX's inside of a @code{parallel}. Each @code{set} +contains a @code{asm_operands}; all of these share the same assembler +template and vectors, but each contains the constraint for the respective +output operand. They are also distinguished by the output-operand index +number, which is 0, 1, @dots{} for successive output operands. + +@node Insns +@section Insns +@cindex insns + +The RTL representation of the code for a function is a doubly-linked +chain of objects called @dfn{insns}. Insns are expressions with +special codes that are used for no other purpose. Some insns are +actual instructions; others represent dispatch tables for @code{switch} +statements; others represent labels to jump to or various sorts of +declarative information. + +In addition to its own specific data, each insn must have a unique +id-number that distinguishes it from all other insns in the current +function (after delayed branch scheduling, copies of an insn with the +same id-number may be present in multiple places in a function, but +these copies will always be identical and will only appear inside a +@code{sequence}), and chain pointers to the preceding and following +insns. These three fields occupy the same position in every insn, +independent of the expression code of the insn. They could be accessed +with @code{XEXP} and @code{XINT}, but instead three special macros are +always used: + +@table @code +@findex INSN_UID +@item INSN_UID (@var{i}) +Accesses the unique id of insn @var{i}. + +@findex PREV_INSN +@item PREV_INSN (@var{i}) +Accesses the chain pointer to the insn preceding @var{i}. +If @var{i} is the first insn, this is a null pointer. + +@findex NEXT_INSN +@item NEXT_INSN (@var{i}) +Accesses the chain pointer to the insn following @var{i}. +If @var{i} is the last insn, this is a null pointer. +@end table + +@findex get_insns +@findex get_last_insn +The first insn in the chain is obtained by calling @code{get_insns}; the +last insn is the result of calling @code{get_last_insn}. Within the +chain delimited by these insns, the @code{NEXT_INSN} and +@code{PREV_INSN} pointers must always correspond: if @var{insn} is not +the first insn, + +@example +NEXT_INSN (PREV_INSN (@var{insn})) == @var{insn} +@end example + +@noindent +is always true and if @var{insn} is not the last insn, + +@example +PREV_INSN (NEXT_INSN (@var{insn})) == @var{insn} +@end example + +@noindent +is always true. + +After delay slot scheduling, some of the insns in the chain might be +@code{sequence} expressions, which contain a vector of insns. The value +of @code{NEXT_INSN} in all but the last of these insns is the next insn +in the vector; the value of @code{NEXT_INSN} of the last insn in the vector +is the same as the value of @code{NEXT_INSN} for the @code{sequence} in +which it is contained. Similar rules apply for @code{PREV_INSN}. + +This means that the above invariants are not necessarily true for insns +inside @code{sequence} expressions. Specifically, if @var{insn} is the +first insn in a @code{sequence}, @code{NEXT_INSN (PREV_INSN (@var{insn}))} +is the insn containing the @code{sequence} expression, as is the value +of @code{PREV_INSN (NEXT_INSN (@var{insn}))} is @var{insn} is the last +insn in the @code{sequence} expression. You can use these expressions +to find the containing @code{sequence} expression.@refill + +Every insn has one of the following six expression codes: + +@table @code +@findex insn +@item insn +The expression code @code{insn} is used for instructions that do not jump +and do not do function calls. @code{sequence} expressions are always +contained in insns with code @code{insn} even if one of those insns +should jump or do function calls. + +Insns with code @code{insn} have four additional fields beyond the three +mandatory ones listed above. These four are described in a table below. + +@findex jump_insn +@item jump_insn +The expression code @code{jump_insn} is used for instructions that may +jump (or, more generally, may contain @code{label_ref} expressions). If +there is an instruction to return from the current function, it is +recorded as a @code{jump_insn}. + +@findex JUMP_LABEL +@code{jump_insn} insns have the same extra fields as @code{insn} insns, +accessed in the same way and in addition contain a field +@code{JUMP_LABEL} which is defined once jump optimization has completed. + +For simple conditional and unconditional jumps, this field contains +the @code{code_label} to which this insn will (possibly conditionally) +branch. In a more complex jump, @code{JUMP_LABEL} records one of the +labels that the insn refers to; the only way to find the others is to +scan the entire body of the insn. In an @code{addr_vec}, +@code{JUMP_LABEL} is @code{NULL_RTX}. + +Return insns count as jumps, but since they do not refer to any +labels, their @code{JUMP_LABEL} is @code{NULL_RTX}. + +@findex call_insn +@item call_insn +The expression code @code{call_insn} is used for instructions that may do +function calls. It is important to distinguish these instructions because +they imply that certain registers and memory locations may be altered +unpredictably. + +@findex CALL_INSN_FUNCTION_USAGE +@code{call_insn} insns have the same extra fields as @code{insn} insns, +accessed in the same way and in addition contain a field +@code{CALL_INSN_FUNCTION_USAGE}, which contains a list (chain of +@code{expr_list} expressions) containing @code{use} and @code{clobber} +expressions that denote hard registers and @code{MEM}s used or +clobbered by the called function. + +A @code{MEM} generally points to a stack slots in which arguments passed +to the libcall by reference (@pxref{Register Arguments, +FUNCTION_ARG_PASS_BY_REFERENCE}) are stored. If the argument is +caller-copied (@pxref{Register Arguments, FUNCTION_ARG_CALLEE_COPIES}), +the stack slot will be mentioned in @code{CLOBBER} and @code{USE} +entries; if it's callee-copied, only a @code{USE} will appear, and the +@code{MEM} may point to addresses that are not stack slots. These +@code{MEM}s are used only in libcalls, because, unlike regular function +calls, @code{CONST_CALL}s (which libcalls generally are, @pxref{Flags, +CONST_CALL_P}) aren't assumed to read and write all memory, so flow +would consider the stores dead and remove them. Note that, since a +libcall must never return values in memory (@pxref{Aggregate Return, +RETURN_IN_MEMORY}), there will never be a @code{CLOBBER} for a memory +address holding a return value. + +@code{CLOBBER}ed registers in this list augment registers specified in +@code{CALL_USED_REGISTERS} (@pxref{Register Basics}). + +@findex code_label +@findex CODE_LABEL_NUMBER +@item code_label +A @code{code_label} insn represents a label that a jump insn can jump +to. It contains two special fields of data in addition to the three +standard ones. @code{CODE_LABEL_NUMBER} is used to hold the @dfn{label +number}, a number that identifies this label uniquely among all the +labels in the compilation (not just in the current function). +Ultimately, the label is represented in the assembler output as an +assembler label, usually of the form @samp{L@var{n}} where @var{n} is +the label number. + +When a @code{code_label} appears in an RTL expression, it normally +appears within a @code{label_ref} which represents the address of +the label, as a number. + +@findex LABEL_NUSES +The field @code{LABEL_NUSES} is only defined once the jump optimization +phase is completed and contains the number of times this label is +referenced in the current function. + +@findex LABEL_ALTERNATE_NAME +The field @code{LABEL_ALTERNATE_NAME} is used to associate a name with +a @code{code_label}. If this field is defined, the alternate name will +be emitted instead of an internally generated label name. + +@findex barrier +@item barrier +Barriers are placed in the instruction stream when control cannot flow +past them. They are placed after unconditional jump instructions to +indicate that the jumps are unconditional and after calls to +@code{volatile} functions, which do not return (e.g., @code{exit}). +They contain no information beyond the three standard fields. + +@findex note +@findex NOTE_LINE_NUMBER +@findex NOTE_SOURCE_FILE +@item note +@code{note} insns are used to represent additional debugging and +declarative information. They contain two nonstandard fields, an +integer which is accessed with the macro @code{NOTE_LINE_NUMBER} and a +string accessed with @code{NOTE_SOURCE_FILE}. + +If @code{NOTE_LINE_NUMBER} is positive, the note represents the +position of a source line and @code{NOTE_SOURCE_FILE} is the source file name +that the line came from. These notes control generation of line +number data in the assembler output. + +Otherwise, @code{NOTE_LINE_NUMBER} is not really a line number but a +code with one of the following values (and @code{NOTE_SOURCE_FILE} +must contain a null pointer): + +@table @code +@findex NOTE_INSN_DELETED +@item NOTE_INSN_DELETED +Such a note is completely ignorable. Some passes of the compiler +delete insns by altering them into notes of this kind. + +@findex NOTE_INSN_BLOCK_BEG +@findex NOTE_INSN_BLOCK_END +@item NOTE_INSN_BLOCK_BEG +@itemx NOTE_INSN_BLOCK_END +These types of notes indicate the position of the beginning and end +of a level of scoping of variable names. They control the output +of debugging information. + +@findex NOTE_INSN_EH_REGION_BEG +@findex NOTE_INSN_EH_REGION_END +@item NOTE_INSN_EH_REGION_BEG +@itemx NOTE_INSN_EH_REGION_END +These types of notes indicate the position of the beginning and end of a +level of scoping for exception handling. @code{NOTE_BLOCK_NUMBER} +identifies which @code{CODE_LABEL} is associated with the given region. + +@findex NOTE_INSN_LOOP_BEG +@findex NOTE_INSN_LOOP_END +@item NOTE_INSN_LOOP_BEG +@itemx NOTE_INSN_LOOP_END +These types of notes indicate the position of the beginning and end +of a @code{while} or @code{for} loop. They enable the loop optimizer +to find loops quickly. + +@findex NOTE_INSN_LOOP_CONT +@item NOTE_INSN_LOOP_CONT +Appears at the place in a loop that @code{continue} statements jump to. + +@findex NOTE_INSN_LOOP_VTOP +@item NOTE_INSN_LOOP_VTOP +This note indicates the place in a loop where the exit test begins for +those loops in which the exit test has been duplicated. This position +becomes another virtual start of the loop when considering loop +invariants. + +@findex NOTE_INSN_FUNCTION_END +@item NOTE_INSN_FUNCTION_END +Appears near the end of the function body, just before the label that +@code{return} statements jump to (on machine where a single instruction +does not suffice for returning). This note may be deleted by jump +optimization. + +@findex NOTE_INSN_SETJMP +@item NOTE_INSN_SETJMP +Appears following each call to @code{setjmp} or a related function. +@end table + +These codes are printed symbolically when they appear in debugging dumps. +@end table + +@cindex @code{TImode}, in @code{insn} +@cindex @code{HImode}, in @code{insn} +@cindex @code{QImode}, in @code{insn} +The machine mode of an insn is normally @code{VOIDmode}, but some +phases use the mode for various purposes. + +The common subexpression elimination pass sets the mode of an insn to +@code{QImode} when it is the first insn in a block that has already +been processed. + +The second Haifa scheduling pass, for targets that can multiple issue, +sets the mode of an insn to @code{TImode} when it is believed that the +instruction begins an issue group. That is, when the instruction +cannot issue simultaneously with the previous. This may be relied on +by later passes, in particular machine-dependant reorg. + +Here is a table of the extra fields of @code{insn}, @code{jump_insn} +and @code{call_insn} insns: + +@table @code +@findex PATTERN +@item PATTERN (@var{i}) +An expression for the side effect performed by this insn. This must be +one of the following codes: @code{set}, @code{call}, @code{use}, +@code{clobber}, @code{return}, @code{asm_input}, @code{asm_output}, +@code{addr_vec}, @code{addr_diff_vec}, @code{trap_if}, @code{unspec}, +@code{unspec_volatile}, @code{parallel}, or @code{sequence}. If it is a @code{parallel}, +each element of the @code{parallel} must be one these codes, except that +@code{parallel} expressions cannot be nested and @code{addr_vec} and +@code{addr_diff_vec} are not permitted inside a @code{parallel} expression. + +@findex INSN_CODE +@item INSN_CODE (@var{i}) +An integer that says which pattern in the machine description matches +this insn, or -1 if the matching has not yet been attempted. + +Such matching is never attempted and this field remains -1 on an insn +whose pattern consists of a single @code{use}, @code{clobber}, +@code{asm_input}, @code{addr_vec} or @code{addr_diff_vec} expression. + +@findex asm_noperands +Matching is also never attempted on insns that result from an @code{asm} +statement. These contain at least one @code{asm_operands} expression. +The function @code{asm_noperands} returns a non-negative value for +such insns. + +In the debugging output, this field is printed as a number followed by +a symbolic representation that locates the pattern in the @file{md} +file as some small positive or negative offset from a named pattern. + +@findex LOG_LINKS +@item LOG_LINKS (@var{i}) +A list (chain of @code{insn_list} expressions) giving information about +dependencies between instructions within a basic block. Neither a jump +nor a label may come between the related insns. + +@findex REG_NOTES +@item REG_NOTES (@var{i}) +A list (chain of @code{expr_list} and @code{insn_list} expressions) +giving miscellaneous information about the insn. It is often +information pertaining to the registers used in this insn. +@end table + +The @code{LOG_LINKS} field of an insn is a chain of @code{insn_list} +expressions. Each of these has two operands: the first is an insn, +and the second is another @code{insn_list} expression (the next one in +the chain). The last @code{insn_list} in the chain has a null pointer +as second operand. The significant thing about the chain is which +insns appear in it (as first operands of @code{insn_list} +expressions). Their order is not significant. + +This list is originally set up by the flow analysis pass; it is a null +pointer until then. Flow only adds links for those data dependencies +which can be used for instruction combination. For each insn, the flow +analysis pass adds a link to insns which store into registers values +that are used for the first time in this insn. The instruction +scheduling pass adds extra links so that every dependence will be +represented. Links represent data dependencies, antidependencies and +output dependencies; the machine mode of the link distinguishes these +three types: antidependencies have mode @code{REG_DEP_ANTI}, output +dependencies have mode @code{REG_DEP_OUTPUT}, and data dependencies have +mode @code{VOIDmode}. + +The @code{REG_NOTES} field of an insn is a chain similar to the +@code{LOG_LINKS} field but it includes @code{expr_list} expressions in +addition to @code{insn_list} expressions. There are several kinds of +register notes, which are distinguished by the machine mode, which in a +register note is really understood as being an @code{enum reg_note}. +The first operand @var{op} of the note is data whose meaning depends on +the kind of note. + +@findex REG_NOTE_KIND +@findex PUT_REG_NOTE_KIND +The macro @code{REG_NOTE_KIND (@var{x})} returns the kind of +register note. Its counterpart, the macro @code{PUT_REG_NOTE_KIND +(@var{x}, @var{newkind})} sets the register note type of @var{x} to be +@var{newkind}. + +Register notes are of three classes: They may say something about an +input to an insn, they may say something about an output of an insn, or +they may create a linkage between two insns. There are also a set +of values that are only used in @code{LOG_LINKS}. + +These register notes annotate inputs to an insn: + +@table @code +@findex REG_DEAD +@item REG_DEAD +The value in @var{op} dies in this insn; that is to say, altering the +value immediately after this insn would not affect the future behavior +of the program. + +This does not necessarily mean that the register @var{op} has no useful +value after this insn since it may also be an output of the insn. In +such a case, however, a @code{REG_DEAD} note would be redundant and is +usually not present until after the reload pass, but no code relies on +this fact. + +@findex REG_INC +@item REG_INC +The register @var{op} is incremented (or decremented; at this level +there is no distinction) by an embedded side effect inside this insn. +This means it appears in a @code{post_inc}, @code{pre_inc}, +@code{post_dec} or @code{pre_dec} expression. + +@findex REG_NONNEG +@item REG_NONNEG +The register @var{op} is known to have a nonnegative value when this +insn is reached. This is used so that decrement and branch until zero +instructions, such as the m68k dbra, can be matched. + +The @code{REG_NONNEG} note is added to insns only if the machine +description has a @samp{decrement_and_branch_until_zero} pattern. + +@findex REG_NO_CONFLICT +@item REG_NO_CONFLICT +This insn does not cause a conflict between @var{op} and the item +being set by this insn even though it might appear that it does. +In other words, if the destination register and @var{op} could +otherwise be assigned the same register, this insn does not +prevent that assignment. + +Insns with this note are usually part of a block that begins with a +@code{clobber} insn specifying a multi-word pseudo register (which will +be the output of the block), a group of insns that each set one word of +the value and have the @code{REG_NO_CONFLICT} note attached, and a final +insn that copies the output to itself with an attached @code{REG_EQUAL} +note giving the expression being computed. This block is encapsulated +with @code{REG_LIBCALL} and @code{REG_RETVAL} notes on the first and +last insns, respectively. + +@findex REG_LABEL +@item REG_LABEL +This insn uses @var{op}, a @code{code_label}, but is not a +@code{jump_insn}, or it is a @code{jump_insn} that required the label to +be held in a register. The presence of this note allows jump +optimization to be aware that @var{op} is, in fact, being used, and flow +optimization to build an accurate flow graph. +@end table + +The following notes describe attributes of outputs of an insn: + +@table @code +@findex REG_EQUIV +@findex REG_EQUAL +@item REG_EQUIV +@itemx REG_EQUAL +This note is only valid on an insn that sets only one register and +indicates that that register will be equal to @var{op} at run time; the +scope of this equivalence differs between the two types of notes. The +value which the insn explicitly copies into the register may look +different from @var{op}, but they will be equal at run time. If the +output of the single @code{set} is a @code{strict_low_part} expression, +the note refers to the register that is contained in @code{SUBREG_REG} +of the @code{subreg} expression. + +For @code{REG_EQUIV}, the register is equivalent to @var{op} throughout +the entire function, and could validly be replaced in all its +occurrences by @var{op}. (``Validly'' here refers to the data flow of +the program; simple replacement may make some insns invalid.) For +example, when a constant is loaded into a register that is never +assigned any other value, this kind of note is used. + +When a parameter is copied into a pseudo-register at entry to a function, +a note of this kind records that the register is equivalent to the stack +slot where the parameter was passed. Although in this case the register +may be set by other insns, it is still valid to replace the register +by the stack slot throughout the function. + +A @code{REG_EQUIV} note is also used on an instruction which copies a +register parameter into a pseudo-register at entry to a function, if +there is a stack slot where that parameter could be stored. Although +other insns may set the pseudo-register, it is valid for the compiler to +replace the pseudo-register by stack slot throughout the function, +provided the compiler ensures that the stack slot is properly +initialized by making the replacement in the initial copy instruction as +well. This is used on machines for which the calling convention +allocates stack space for register parameters. See +@code{REG_PARM_STACK_SPACE} in @ref{Stack Arguments}. + +In the case of @code{REG_EQUAL}, the register that is set by this insn +will be equal to @var{op} at run time at the end of this insn but not +necessarily elsewhere in the function. In this case, @var{op} +is typically an arithmetic expression. For example, when a sequence of +insns such as a library call is used to perform an arithmetic operation, +this kind of note is attached to the insn that produces or copies the +final value. + +These two notes are used in different ways by the compiler passes. +@code{REG_EQUAL} is used by passes prior to register allocation (such as +common subexpression elimination and loop optimization) to tell them how +to think of that value. @code{REG_EQUIV} notes are used by register +allocation to indicate that there is an available substitute expression +(either a constant or a @code{mem} expression for the location of a +parameter on the stack) that may be used in place of a register if +insufficient registers are available. + +Except for stack homes for parameters, which are indicated by a +@code{REG_EQUIV} note and are not useful to the early optimization +passes and pseudo registers that are equivalent to a memory location +throughout there entire life, which is not detected until later in +the compilation, all equivalences are initially indicated by an attached +@code{REG_EQUAL} note. In the early stages of register allocation, a +@code{REG_EQUAL} note is changed into a @code{REG_EQUIV} note if +@var{op} is a constant and the insn represents the only set of its +destination register. + +Thus, compiler passes prior to register allocation need only check for +@code{REG_EQUAL} notes and passes subsequent to register allocation +need only check for @code{REG_EQUIV} notes. + +@findex REG_UNUSED +@item REG_UNUSED +The register @var{op} being set by this insn will not be used in a +subsequent insn. This differs from a @code{REG_DEAD} note, which +indicates that the value in an input will not be used subsequently. +These two notes are independent; both may be present for the same +register. + +@findex REG_WAS_0 +@item REG_WAS_0 +The single output of this insn contained zero before this insn. +@var{op} is the insn that set it to zero. You can rely on this note if +it is present and @var{op} has not been deleted or turned into a @code{note}; +its absence implies nothing. +@end table + +These notes describe linkages between insns. They occur in pairs: one +insn has one of a pair of notes that points to a second insn, which has +the inverse note pointing back to the first insn. + +@table @code +@findex REG_RETVAL +@item REG_RETVAL +This insn copies the value of a multi-insn sequence (for example, a +library call), and @var{op} is the first insn of the sequence (for a +library call, the first insn that was generated to set up the arguments +for the library call). + +Loop optimization uses this note to treat such a sequence as a single +operation for code motion purposes and flow analysis uses this note to +delete such sequences whose results are dead. + +A @code{REG_EQUAL} note will also usually be attached to this insn to +provide the expression being computed by the sequence. + +These notes will be deleted after reload, since they are no longer +accurate or useful. + +@findex REG_LIBCALL +@item REG_LIBCALL +This is the inverse of @code{REG_RETVAL}: it is placed on the first +insn of a multi-insn sequence, and it points to the last one. + +These notes are deleted after reload, since they are no longer useful or +accurate. + +@findex REG_CC_SETTER +@findex REG_CC_USER +@item REG_CC_SETTER +@itemx REG_CC_USER +On machines that use @code{cc0}, the insns which set and use @code{cc0} +set and use @code{cc0} are adjacent. However, when branch delay slot +filling is done, this may no longer be true. In this case a +@code{REG_CC_USER} note will be placed on the insn setting @code{cc0} to +point to the insn using @code{cc0} and a @code{REG_CC_SETTER} note will +be placed on the insn using @code{cc0} to point to the insn setting +@code{cc0}.@refill +@end table + +These values are only used in the @code{LOG_LINKS} field, and indicate +the type of dependency that each link represents. Links which indicate +a data dependence (a read after write dependence) do not use any code, +they simply have mode @code{VOIDmode}, and are printed without any +descriptive text. + +@table @code +@findex REG_DEP_ANTI +@item REG_DEP_ANTI +This indicates an anti dependence (a write after read dependence). + +@findex REG_DEP_OUTPUT +@item REG_DEP_OUTPUT +This indicates an output dependence (a write after write dependence). +@end table + +These notes describe information gathered from gcov profile data. They +are stored in the @code{REG_NOTES} field of an insn as an +@code{expr_list}. + +@table @code +@findex REG_EXEC_COUNT +@item REG_EXEC_COUNT +This is used to indicate the number of times a basic block was executed +according to the profile data. The note is attached to the first insn in +the basic block. + +@findex REG_BR_PROB +@item REG_BR_PROB +This is used to specify the ratio of branches to non-branches of a +branch insn according to the profile data. The value is stored as a +value between 0 and REG_BR_PROB_BASE; larger values indicate a higher +probability that the branch will be taken. + +@findex REG_BR_PRED +@item REG_BR_PRED +These notes are found in JUMP insns after delayed branch scheduling +has taken place. They indicate both the direction and the likelihood +of the JUMP. The format is a bitmask of ATTR_FLAG_* values. + +@findex REG_FRAME_RELATED_EXPR +@item REG_FRAME_RELATED_EXPR +This is used on an RTX_FRAME_RELATED_P insn wherein the attached expression +is used in place of the actual insn pattern. This is done in cases where +the pattern is either complex or misleading. +@end table + +For convenience, the machine mode in an @code{insn_list} or +@code{expr_list} is printed using these symbolic codes in debugging dumps. + +@findex insn_list +@findex expr_list +The only difference between the expression codes @code{insn_list} and +@code{expr_list} is that the first operand of an @code{insn_list} is +assumed to be an insn and is printed in debugging dumps as the insn's +unique id; the first operand of an @code{expr_list} is printed in the +ordinary way as an expression. + +@node Calls +@section RTL Representation of Function-Call Insns +@cindex calling functions in RTL +@cindex RTL function-call insns +@cindex function-call insns + +Insns that call subroutines have the RTL expression code @code{call_insn}. +These insns must satisfy special rules, and their bodies must use a special +RTL expression code, @code{call}. + +@cindex @code{call} usage +A @code{call} expression has two operands, as follows: + +@example +(call (mem:@var{fm} @var{addr}) @var{nbytes}) +@end example + +@noindent +Here @var{nbytes} is an operand that represents the number of bytes of +argument data being passed to the subroutine, @var{fm} is a machine mode +(which must equal as the definition of the @code{FUNCTION_MODE} macro in +the machine description) and @var{addr} represents the address of the +subroutine. + +For a subroutine that returns no value, the @code{call} expression as +shown above is the entire body of the insn, except that the insn might +also contain @code{use} or @code{clobber} expressions. + +@cindex @code{BLKmode}, and function return values +For a subroutine that returns a value whose mode is not @code{BLKmode}, +the value is returned in a hard register. If this register's number is +@var{r}, then the body of the call insn looks like this: + +@example +(set (reg:@var{m} @var{r}) + (call (mem:@var{fm} @var{addr}) @var{nbytes})) +@end example + +@noindent +This RTL expression makes it clear (to the optimizer passes) that the +appropriate register receives a useful value in this insn. + +When a subroutine returns a @code{BLKmode} value, it is handled by +passing to the subroutine the address of a place to store the value. +So the call insn itself does not ``return'' any value, and it has the +same RTL form as a call that returns nothing. + +On some machines, the call instruction itself clobbers some register, +for example to contain the return address. @code{call_insn} insns +on these machines should have a body which is a @code{parallel} +that contains both the @code{call} expression and @code{clobber} +expressions that indicate which registers are destroyed. Similarly, +if the call instruction requires some register other than the stack +pointer that is not explicitly mentioned it its RTL, a @code{use} +subexpression should mention that register. + +Functions that are called are assumed to modify all registers listed in +the configuration macro @code{CALL_USED_REGISTERS} (@pxref{Register +Basics}) and, with the exception of @code{const} functions and library +calls, to modify all of memory. + +Insns containing just @code{use} expressions directly precede the +@code{call_insn} insn to indicate which registers contain inputs to the +function. Similarly, if registers other than those in +@code{CALL_USED_REGISTERS} are clobbered by the called function, insns +containing a single @code{clobber} follow immediately after the call to +indicate which registers. + +@node Sharing +@section Structure Sharing Assumptions +@cindex sharing of RTL components +@cindex RTL structure sharing assumptions + +The compiler assumes that certain kinds of RTL expressions are unique; +there do not exist two distinct objects representing the same value. +In other cases, it makes an opposite assumption: that no RTL expression +object of a certain kind appears in more than one place in the +containing structure. + +These assumptions refer to a single function; except for the RTL +objects that describe global variables and external functions, +and a few standard objects such as small integer constants, +no RTL objects are common to two functions. + +@itemize @bullet +@cindex @code{reg}, RTL sharing +@item +Each pseudo-register has only a single @code{reg} object to represent it, +and therefore only a single machine mode. + +@cindex symbolic label +@cindex @code{symbol_ref}, RTL sharing +@item +For any symbolic label, there is only one @code{symbol_ref} object +referring to it. + +@cindex @code{const_int}, RTL sharing +@item +All @code{const_int} expressions with equal values are shared. + +@cindex @code{pc}, RTL sharing +@item +There is only one @code{pc} expression. + +@cindex @code{cc0}, RTL sharing +@item +There is only one @code{cc0} expression. + +@cindex @code{const_double}, RTL sharing +@item +There is only one @code{const_double} expression with value 0 for +each floating point mode. Likewise for values 1 and 2. + +@cindex @code{label_ref}, RTL sharing +@cindex @code{scratch}, RTL sharing +@item +No @code{label_ref} or @code{scratch} appears in more than one place in +the RTL structure; in other words, it is safe to do a tree-walk of all +the insns in the function and assume that each time a @code{label_ref} +or @code{scratch} is seen it is distinct from all others that are seen. + +@cindex @code{mem}, RTL sharing +@item +Only one @code{mem} object is normally created for each static +variable or stack slot, so these objects are frequently shared in all +the places they appear. However, separate but equal objects for these +variables are occasionally made. + +@cindex @code{asm_operands}, RTL sharing +@item +When a single @code{asm} statement has multiple output operands, a +distinct @code{asm_operands} expression is made for each output operand. +However, these all share the vector which contains the sequence of input +operands. This sharing is used later on to test whether two +@code{asm_operands} expressions come from the same statement, so all +optimizations must carefully preserve the sharing if they copy the +vector at all. + +@item +No RTL object appears in more than one place in the RTL structure +except as described above. Many passes of the compiler rely on this +by assuming that they can modify RTL objects in place without unwanted +side-effects on other insns. + +@findex unshare_all_rtl +@item +During initial RTL generation, shared structure is freely introduced. +After all the RTL for a function has been generated, all shared +structure is copied by @code{unshare_all_rtl} in @file{emit-rtl.c}, +after which the above rules are guaranteed to be followed. + +@findex copy_rtx_if_shared +@item +During the combiner pass, shared structure within an insn can exist +temporarily. However, the shared structure is copied before the +combiner is finished with the insn. This is done by calling +@code{copy_rtx_if_shared}, which is a subroutine of +@code{unshare_all_rtl}. +@end itemize + +@node Reading RTL +@section Reading RTL + +To read an RTL object from a file, call @code{read_rtx}. It takes one +argument, a stdio stream, and returns a single RTL object. + +Reading RTL from a file is very slow. This is not currently a +problem since reading RTL occurs only as part of building the +compiler. + +People frequently have the idea of using RTL stored as text in a file as +an interface between a language front end and the bulk of GNU CC. This +idea is not feasible. + +GNU CC was designed to use RTL internally only. Correct RTL for a given +program is very dependent on the particular target machine. And the RTL +does not contain all the information about the program. + +The proper way to interface GNU CC to a new language front end is with +the ``tree'' data structure. There is no manual for this data +structure, but it is described in the files @file{tree.h} and +@file{tree.def}. diff --git a/gcc/doc/texinfo.tex b/gcc/doc/texinfo.tex new file mode 100644 index 00000000000..1889b4c6d1a --- /dev/null +++ b/gcc/doc/texinfo.tex @@ -0,0 +1,6200 @@ +% texinfo.tex -- TeX macros to handle Texinfo files. +% +% Load plain if necessary, i.e., if running under initex. +\expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi +% +\def\texinfoversion{2000-12-11.07} +% +% Copyright (C) 1985, 86, 88, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 2000 +% Free Software Foundation, Inc. +% +% This texinfo.tex file is free software; you can redistribute it and/or +% modify it under the terms of the GNU General Public License as +% published by the Free Software Foundation; either version 2, or (at +% your option) any later version. +% +% This texinfo.tex file is distributed in the hope that it will be +% useful, but WITHOUT ANY WARRANTY; without even the implied warranty +% of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +% General Public License for more details. +% +% You should have received a copy of the GNU General Public License +% along with this texinfo.tex file; see the file COPYING. If not, write +% to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, +% Boston, MA 02111-1307, USA. +% +% In other words, you are welcome to use, share and improve this program. +% You are forbidden to forbid anyone else to use, share and improve +% what you give them. Help stamp out software-hoarding! +% +% Please try the latest version of texinfo.tex before submitting bug +% reports; you can get the latest version from: +% ftp://ftp.gnu.org/gnu/texinfo.tex +% (and all GNU mirrors, see http://www.gnu.org/order/ftp.html) +% ftp://texinfo.org/tex/texinfo.tex +% ftp://us.ctan.org/macros/texinfo/texinfo.tex +% (and all CTAN mirrors, finger ctan@us.ctan.org for a list). +% /home/gd/gnu/doc/texinfo.tex on the GNU machines. +% The texinfo.tex in any given Texinfo distribution could well be out +% of date, so if that's what you're using, please check. +% Texinfo has a small home page at http://texinfo.org/. +% +% Send bug reports to bug-texinfo@gnu.org. Please include including a +% complete document in each bug report with which we can reproduce the +% problem. Patches are, of course, greatly appreciated. +% +% To process a Texinfo manual with TeX, it's most reliable to use the +% texi2dvi shell script that comes with the distribution. For a simple +% manual foo.texi, however, you can get away with this: +% tex foo.texi +% texindex foo.?? +% tex foo.texi +% tex foo.texi +% dvips foo.dvi -o # or whatever, to process the dvi file; this makes foo.ps. +% The extra runs of TeX get the cross-reference information correct. +% Sometimes one run after texindex suffices, and sometimes you need more +% than two; texi2dvi does it as many times as necessary. +% +% It is possible to adapt texinfo.tex for other languages. You can get +% the existing language-specific files from ftp://ftp.gnu.org/gnu/texinfo/. + +\message{Loading texinfo [version \texinfoversion]:} + +% If in a .fmt file, print the version number +% and turn on active characters that we couldn't do earlier because +% they might have appeared in the input file name. +\everyjob{\message{[Texinfo version \texinfoversion]}% + \catcode`+=\active \catcode`\_=\active} + +% Save some parts of plain tex whose names we will redefine. +\let\ptexb=\b +\let\ptexbullet=\bullet +\let\ptexc=\c +\let\ptexcomma=\, +\let\ptexdot=\. +\let\ptexdots=\dots +\let\ptexend=\end +\let\ptexequiv=\equiv +\let\ptexexclam=\! +\let\ptexi=\i +\let\ptexlbrace=\{ +\let\ptexrbrace=\} +\let\ptexstar=\* +\let\ptext=\t + +% We never want plain's outer \+ definition in Texinfo. +% For @tex, we can use \tabalign. +\let\+ = \relax + +\message{Basics,} +\chardef\other=12 + +% If this character appears in an error message or help string, it +% starts a new line in the output. +\newlinechar = `^^J + +% Set up fixed words for English if not already set. +\ifx\putwordAppendix\undefined \gdef\putwordAppendix{Appendix}\fi +\ifx\putwordChapter\undefined \gdef\putwordChapter{Chapter}\fi +\ifx\putwordfile\undefined \gdef\putwordfile{file}\fi +\ifx\putwordin\undefined \gdef\putwordin{in}\fi +\ifx\putwordIndexIsEmpty\undefined \gdef\putwordIndexIsEmpty{(Index is empty)}\fi +\ifx\putwordIndexNonexistent\undefined \gdef\putwordIndexNonexistent{(Index is nonexistent)}\fi +\ifx\putwordInfo\undefined \gdef\putwordInfo{Info}\fi +\ifx\putwordInstanceVariableof\undefined \gdef\putwordInstanceVariableof{Instance Variable of}\fi +\ifx\putwordMethodon\undefined \gdef\putwordMethodon{Method on}\fi +\ifx\putwordNoTitle\undefined \gdef\putwordNoTitle{No Title}\fi +\ifx\putwordof\undefined \gdef\putwordof{of}\fi +\ifx\putwordon\undefined \gdef\putwordon{on}\fi +\ifx\putwordpage\undefined \gdef\putwordpage{page}\fi +\ifx\putwordsection\undefined \gdef\putwordsection{section}\fi +\ifx\putwordSection\undefined \gdef\putwordSection{Section}\fi +\ifx\putwordsee\undefined \gdef\putwordsee{see}\fi +\ifx\putwordSee\undefined \gdef\putwordSee{See}\fi +\ifx\putwordShortTOC\undefined \gdef\putwordShortTOC{Short Contents}\fi +\ifx\putwordTOC\undefined \gdef\putwordTOC{Table of Contents}\fi +% +\ifx\putwordMJan\undefined \gdef\putwordMJan{January}\fi +\ifx\putwordMFeb\undefined \gdef\putwordMFeb{February}\fi +\ifx\putwordMMar\undefined \gdef\putwordMMar{March}\fi +\ifx\putwordMApr\undefined \gdef\putwordMApr{April}\fi +\ifx\putwordMMay\undefined \gdef\putwordMMay{May}\fi +\ifx\putwordMJun\undefined \gdef\putwordMJun{June}\fi +\ifx\putwordMJul\undefined \gdef\putwordMJul{July}\fi +\ifx\putwordMAug\undefined \gdef\putwordMAug{August}\fi +\ifx\putwordMSep\undefined \gdef\putwordMSep{September}\fi +\ifx\putwordMOct\undefined \gdef\putwordMOct{October}\fi +\ifx\putwordMNov\undefined \gdef\putwordMNov{November}\fi +\ifx\putwordMDec\undefined \gdef\putwordMDec{December}\fi +% +\ifx\putwordDefmac\undefined \gdef\putwordDefmac{Macro}\fi +\ifx\putwordDefspec\undefined \gdef\putwordDefspec{Special Form}\fi +\ifx\putwordDefvar\undefined \gdef\putwordDefvar{Variable}\fi +\ifx\putwordDefopt\undefined \gdef\putwordDefopt{User Option}\fi +\ifx\putwordDeftypevar\undefined\gdef\putwordDeftypevar{Variable}\fi +\ifx\putwordDeffunc\undefined \gdef\putwordDeffunc{Function}\fi +\ifx\putwordDeftypefun\undefined\gdef\putwordDeftypefun{Function}\fi + +% Ignore a token. +% +\def\gobble#1{} + +\hyphenation{ap-pen-dix} +\hyphenation{mini-buf-fer mini-buf-fers} +\hyphenation{eshell} +\hyphenation{white-space} + +% Margin to add to right of even pages, to left of odd pages. +\newdimen \bindingoffset +\newdimen \normaloffset +\newdimen\pagewidth \newdimen\pageheight + +% Sometimes it is convenient to have everything in the transcript file +% and nothing on the terminal. We don't just call \tracingall here, +% since that produces some useless output on the terminal. +% +\def\gloggingall{\begingroup \globaldefs = 1 \loggingall \endgroup}% +\ifx\eTeXversion\undefined +\def\loggingall{\tracingcommands2 \tracingstats2 + \tracingpages1 \tracingoutput1 \tracinglostchars1 + \tracingmacros2 \tracingparagraphs1 \tracingrestores1 + \showboxbreadth\maxdimen\showboxdepth\maxdimen +}% +\else +\def\loggingall{\tracingcommands3 \tracingstats2 + \tracingpages1 \tracingoutput1 \tracinglostchars1 + \tracingmacros2 \tracingparagraphs1 \tracingrestores1 + \tracingscantokens1 \tracingassigns1 \tracingifs1 + \tracinggroups1 \tracingnesting2 + \showboxbreadth\maxdimen\showboxdepth\maxdimen +}% +\fi + +% For @cropmarks command. +% Do @cropmarks to get crop marks. +% +\newif\ifcropmarks +\let\cropmarks = \cropmarkstrue +% +% Dimensions to add cropmarks at corners. +% Added by P. A. MacKay, 12 Nov. 1986 +% +\newdimen\outerhsize \newdimen\outervsize % set by the paper size routines +\newdimen\cornerlong \cornerlong=1pc +\newdimen\cornerthick \cornerthick=.3pt +\newdimen\topandbottommargin \topandbottommargin=.75in + +% Main output routine. +\chardef\PAGE = 255 +\output = {\onepageout{\pagecontents\PAGE}} + +\newbox\headlinebox +\newbox\footlinebox + +% \onepageout takes a vbox as an argument. Note that \pagecontents +% does insertions, but you have to call it yourself. +\def\onepageout#1{% + \ifcropmarks \hoffset=0pt \else \hoffset=\normaloffset \fi + % + \ifodd\pageno \advance\hoffset by \bindingoffset + \else \advance\hoffset by -\bindingoffset\fi + % + % Do this outside of the \shipout so @code etc. will be expanded in + % the headline as they should be, not taken literally (outputting ''code). + \setbox\headlinebox = \vbox{\let\hsize=\pagewidth \makeheadline}% + \setbox\footlinebox = \vbox{\let\hsize=\pagewidth \makefootline}% + % + {% + % Have to do this stuff outside the \shipout because we want it to + % take effect in \write's, yet the group defined by the \vbox ends + % before the \shipout runs. + % + \escapechar = `\\ % use backslash in output files. + \indexdummies % don't expand commands in the output. + \normalturnoffactive % \ in index entries must not stay \, e.g., if + % the page break happens to be in the middle of an example. + \shipout\vbox{% + % Do this early so pdf references go to the beginning of the page. + \ifpdfmakepagedest \pdfmkdest{\the\pageno} \fi + % + \ifcropmarks \vbox to \outervsize\bgroup + \hsize = \outerhsize + \vskip-\topandbottommargin + \vtop to0pt{% + \line{\ewtop\hfil\ewtop}% + \nointerlineskip + \line{% + \vbox{\moveleft\cornerthick\nstop}% + \hfill + \vbox{\moveright\cornerthick\nstop}% + }% + \vss}% + \vskip\topandbottommargin + \line\bgroup + \hfil % center the page within the outer (page) hsize. + \ifodd\pageno\hskip\bindingoffset\fi + \vbox\bgroup + \fi + % + \unvbox\headlinebox + \pagebody{#1}% + \ifdim\ht\footlinebox > 0pt + % Only leave this space if the footline is nonempty. + % (We lessened \vsize for it in \oddfootingxxx.) + % The \baselineskip=24pt in plain's \makefootline has no effect. + \vskip 2\baselineskip + \unvbox\footlinebox + \fi + % + \ifcropmarks + \egroup % end of \vbox\bgroup + \hfil\egroup % end of (centering) \line\bgroup + \vskip\topandbottommargin plus1fill minus1fill + \boxmaxdepth = \cornerthick + \vbox to0pt{\vss + \line{% + \vbox{\moveleft\cornerthick\nsbot}% + \hfill + \vbox{\moveright\cornerthick\nsbot}% + }% + \nointerlineskip + \line{\ewbot\hfil\ewbot}% + }% + \egroup % \vbox from first cropmarks clause + \fi + }% end of \shipout\vbox + }% end of group with \turnoffactive + \advancepageno + \ifnum\outputpenalty>-20000 \else\dosupereject\fi +} + +\newinsert\margin \dimen\margin=\maxdimen + +\def\pagebody#1{\vbox to\pageheight{\boxmaxdepth=\maxdepth #1}} +{\catcode`\@ =11 +\gdef\pagecontents#1{\ifvoid\topins\else\unvbox\topins\fi +% marginal hacks, juha@viisa.uucp (Juha Takala) +\ifvoid\margin\else % marginal info is present + \rlap{\kern\hsize\vbox to\z@{\kern1pt\box\margin \vss}}\fi +\dimen@=\dp#1 \unvbox#1 +\ifvoid\footins\else\vskip\skip\footins\footnoterule \unvbox\footins\fi +\ifr@ggedbottom \kern-\dimen@ \vfil \fi} +} + +% Here are the rules for the cropmarks. Note that they are +% offset so that the space between them is truly \outerhsize or \outervsize +% (P. A. MacKay, 12 November, 1986) +% +\def\ewtop{\vrule height\cornerthick depth0pt width\cornerlong} +\def\nstop{\vbox + {\hrule height\cornerthick depth\cornerlong width\cornerthick}} +\def\ewbot{\vrule height0pt depth\cornerthick width\cornerlong} +\def\nsbot{\vbox + {\hrule height\cornerlong depth\cornerthick width\cornerthick}} + +% Parse an argument, then pass it to #1. The argument is the rest of +% the input line (except we remove a trailing comment). #1 should be a +% macro which expects an ordinary undelimited TeX argument. +% +\def\parsearg#1{% + \let\next = #1% + \begingroup + \obeylines + \futurelet\temp\parseargx +} + +% If the next token is an obeyed space (from an @example environment or +% the like), remove it and recurse. Otherwise, we're done. +\def\parseargx{% + % \obeyedspace is defined far below, after the definition of \sepspaces. + \ifx\obeyedspace\temp + \expandafter\parseargdiscardspace + \else + \expandafter\parseargline + \fi +} + +% Remove a single space (as the delimiter token to the macro call). +{\obeyspaces % + \gdef\parseargdiscardspace {\futurelet\temp\parseargx}} + +{\obeylines % + \gdef\parseargline#1^^M{% + \endgroup % End of the group started in \parsearg. + % + % First remove any @c comment, then any @comment. + % Result of each macro is put in \toks0. + \argremovec #1\c\relax % + \expandafter\argremovecomment \the\toks0 \comment\relax % + % + % Call the caller's macro, saved as \next in \parsearg. + \expandafter\next\expandafter{\the\toks0}% + }% +} + +% Since all \c{,omment} does is throw away the argument, we can let TeX +% do that for us. The \relax here is matched by the \relax in the call +% in \parseargline; it could be more or less anything, its purpose is +% just to delimit the argument to the \c. +\def\argremovec#1\c#2\relax{\toks0 = {#1}} +\def\argremovecomment#1\comment#2\relax{\toks0 = {#1}} + +% \argremovec{,omment} might leave us with trailing spaces, though; e.g., +% @end itemize @c foo +% will have two active spaces as part of the argument with the +% `itemize'. Here we remove all active spaces from #1, and assign the +% result to \toks0. +% +% This loses if there are any *other* active characters besides spaces +% in the argument -- _ ^ +, for example -- since they get expanded. +% Fortunately, Texinfo does not define any such commands. (If it ever +% does, the catcode of the characters in questionwill have to be changed +% here.) But this means we cannot call \removeactivespaces as part of +% \argremovec{,omment}, since @c uses \parsearg, and thus the argument +% that \parsearg gets might well have any character at all in it. +% +\def\removeactivespaces#1{% + \begingroup + \ignoreactivespaces + \edef\temp{#1}% + \global\toks0 = \expandafter{\temp}% + \endgroup +} + +% Change the active space to expand to nothing. +% +\begingroup + \obeyspaces + \gdef\ignoreactivespaces{\obeyspaces\let =\empty} +\endgroup + + +\def\flushcr{\ifx\par\lisppar \def\next##1{}\else \let\next=\relax \fi \next} + +%% These are used to keep @begin/@end levels from running away +%% Call \inENV within environments (after a \begingroup) +\newif\ifENV \ENVfalse \def\inENV{\ifENV\relax\else\ENVtrue\fi} +\def\ENVcheck{% +\ifENV\errmessage{Still within an environment; press RETURN to continue} +\endgroup\fi} % This is not perfect, but it should reduce lossage + +% @begin foo is the same as @foo, for now. +\newhelp\EMsimple{Press RETURN to continue.} + +\outer\def\begin{\parsearg\beginxxx} + +\def\beginxxx #1{% +\expandafter\ifx\csname #1\endcsname\relax +{\errhelp=\EMsimple \errmessage{Undefined command @begin #1}}\else +\csname #1\endcsname\fi} + +% @end foo executes the definition of \Efoo. +% +\def\end{\parsearg\endxxx} +\def\endxxx #1{% + \removeactivespaces{#1}% + \edef\endthing{\the\toks0}% + % + \expandafter\ifx\csname E\endthing\endcsname\relax + \expandafter\ifx\csname \endthing\endcsname\relax + % There's no \foo, i.e., no ``environment'' foo. + \errhelp = \EMsimple + \errmessage{Undefined command `@end \endthing'}% + \else + \unmatchedenderror\endthing + \fi + \else + % Everything's ok; the right environment has been started. + \csname E\endthing\endcsname + \fi +} + +% There is an environment #1, but it hasn't been started. Give an error. +% +\def\unmatchedenderror#1{% + \errhelp = \EMsimple + \errmessage{This `@end #1' doesn't have a matching `@#1'}% +} + +% Define the control sequence \E#1 to give an unmatched @end error. +% +\def\defineunmatchedend#1{% + \expandafter\def\csname E#1\endcsname{\unmatchedenderror{#1}}% +} + + +% Single-spacing is done by various environments (specifically, in +% \nonfillstart and \quotations). +\newskip\singlespaceskip \singlespaceskip = 12.5pt +\def\singlespace{% + % Why was this kern here? It messes up equalizing space above and below + % environments. --karl, 6may93 + %{\advance \baselineskip by -\singlespaceskip + %\kern \baselineskip}% + \setleading \singlespaceskip +} + +%% Simple single-character @ commands + +% @@ prints an @ +% Kludge this until the fonts are right (grr). +\def\@{{\tt\char64}} + +% This is turned off because it was never documented +% and you can use @w{...} around a quote to suppress ligatures. +%% Define @` and @' to be the same as ` and ' +%% but suppressing ligatures. +%\def\`{{`}} +%\def\'{{'}} + +% Used to generate quoted braces. +\def\mylbrace {{\tt\char123}} +\def\myrbrace {{\tt\char125}} +\let\{=\mylbrace +\let\}=\myrbrace +\begingroup + % Definitions to produce actual \{ & \} command in an index. + \catcode`\{ = 12 \catcode`\} = 12 + \catcode`\[ = 1 \catcode`\] = 2 + \catcode`\@ = 0 \catcode`\\ = 12 + @gdef@lbracecmd[\{]% + @gdef@rbracecmd[\}]% +@endgroup + +% Accents: @, @dotaccent @ringaccent @ubaraccent @udotaccent +% Others are defined by plain TeX: @` @' @" @^ @~ @= @v @H. +\let\, = \c +\let\dotaccent = \. +\def\ringaccent#1{{\accent23 #1}} +\let\tieaccent = \t +\let\ubaraccent = \b +\let\udotaccent = \d + +% Other special characters: @questiondown @exclamdown +% Plain TeX defines: @AA @AE @O @OE @L (and lowercase versions) @ss. +\def\questiondown{?`} +\def\exclamdown{!`} + +% Dotless i and dotless j, used for accents. +\def\imacro{i} +\def\jmacro{j} +\def\dotless#1{% + \def\temp{#1}% + \ifx\temp\imacro \ptexi + \else\ifx\temp\jmacro \j + \else \errmessage{@dotless can be used only with i or j}% + \fi\fi +} + +% Be sure we're in horizontal mode when doing a tie, since we make space +% equivalent to this in @example-like environments. Otherwise, a space +% at the beginning of a line will start with \penalty -- and +% since \penalty is valid in vertical mode, we'd end up putting the +% penalty on the vertical list instead of in the new paragraph. +{\catcode`@ = 11 + % Avoid using \@M directly, because that causes trouble + % if the definition is written into an index file. + \global\let\tiepenalty = \@M + \gdef\tie{\leavevmode\penalty\tiepenalty\ } +} + +% @: forces normal size whitespace following. +\def\:{\spacefactor=1000 } + +% @* forces a line break. +\def\*{\hfil\break\hbox{}\ignorespaces} + +% @. is an end-of-sentence period. +\def\.{.\spacefactor=3000 } + +% @! is an end-of-sentence bang. +\def\!{!\spacefactor=3000 } + +% @? is an end-of-sentence query. +\def\?{?\spacefactor=3000 } + +% @w prevents a word break. Without the \leavevmode, @w at the +% beginning of a paragraph, when TeX is still in vertical mode, would +% produce a whole line of output instead of starting the paragraph. +\def\w#1{\leavevmode\hbox{#1}} + +% @group ... @end group forces ... to be all on one page, by enclosing +% it in a TeX vbox. We use \vtop instead of \vbox to construct the box +% to keep its height that of a normal line. According to the rules for +% \topskip (p.114 of the TeXbook), the glue inserted is +% max (\topskip - \ht (first item), 0). If that height is large, +% therefore, no glue is inserted, and the space between the headline and +% the text is small, which looks bad. +% +\def\group{\begingroup + \ifnum\catcode13=\active \else + \errhelp = \groupinvalidhelp + \errmessage{@group invalid in context where filling is enabled}% + \fi + % + % The \vtop we start below produces a box with normal height and large + % depth; thus, TeX puts \baselineskip glue before it, and (when the + % next line of text is done) \lineskip glue after it. (See p.82 of + % the TeXbook.) Thus, space below is not quite equal to space + % above. But it's pretty close. + \def\Egroup{% + \egroup % End the \vtop. + \endgroup % End the \group. + }% + % + \vtop\bgroup + % We have to put a strut on the last line in case the @group is in + % the midst of an example, rather than completely enclosing it. + % Otherwise, the interline space between the last line of the group + % and the first line afterwards is too small. But we can't put the + % strut in \Egroup, since there it would be on a line by itself. + % Hence this just inserts a strut at the beginning of each line. + \everypar = {\strut}% + % + % Since we have a strut on every line, we don't need any of TeX's + % normal interline spacing. + \offinterlineskip + % + % OK, but now we have to do something about blank + % lines in the input in @example-like environments, which normally + % just turn into \lisppar, which will insert no space now that we've + % turned off the interline space. Simplest is to make them be an + % empty paragraph. + \ifx\par\lisppar + \edef\par{\leavevmode \par}% + % + % Reset ^^M's definition to new definition of \par. + \obeylines + \fi + % + % Do @comment since we are called inside an environment such as + % @example, where each end-of-line in the input causes an + % end-of-line in the output. We don't want the end-of-line after + % the `@group' to put extra space in the output. Since @group + % should appear on a line by itself (according to the Texinfo + % manual), we don't worry about eating any user text. + \comment +} +% +% TeX puts in an \escapechar (i.e., `@') at the beginning of the help +% message, so this ends up printing `@group can only ...'. +% +\newhelp\groupinvalidhelp{% +group can only be used in environments such as @example,^^J% +where each line of input produces a line of output.} + +% @need space-in-mils +% forces a page break if there is not space-in-mils remaining. + +\newdimen\mil \mil=0.001in + +\def\need{\parsearg\needx} + +% Old definition--didn't work. +%\def\needx #1{\par % +%% This method tries to make TeX break the page naturally +%% if the depth of the box does not fit. +%{\baselineskip=0pt% +%\vtop to #1\mil{\vfil}\kern -#1\mil\nobreak +%\prevdepth=-1000pt +%}} + +\def\needx#1{% + % Ensure vertical mode, so we don't make a big box in the middle of a + % paragraph. + \par + % + % If the @need value is less than one line space, it's useless. + \dimen0 = #1\mil + \dimen2 = \ht\strutbox + \advance\dimen2 by \dp\strutbox + \ifdim\dimen0 > \dimen2 + % + % Do a \strut just to make the height of this box be normal, so the + % normal leading is inserted relative to the preceding line. + % And a page break here is fine. + \vtop to #1\mil{\strut\vfil}% + % + % TeX does not even consider page breaks if a penalty added to the + % main vertical list is 10000 or more. But in order to see if the + % empty box we just added fits on the page, we must make it consider + % page breaks. On the other hand, we don't want to actually break the + % page after the empty box. So we use a penalty of 9999. + % + % There is an extremely small chance that TeX will actually break the + % page at this \penalty, if there are no other feasible breakpoints in + % sight. (If the user is using lots of big @group commands, which + % almost-but-not-quite fill up a page, TeX will have a hard time doing + % good page breaking, for example.) However, I could not construct an + % example where a page broke at this \penalty; if it happens in a real + % document, then we can reconsider our strategy. + \penalty9999 + % + % Back up by the size of the box, whether we did a page break or not. + \kern -#1\mil + % + % Do not allow a page break right after this kern. + \nobreak + \fi +} + +% @br forces paragraph break + +\let\br = \par + +% @dots{} output an ellipsis using the current font. +% We do .5em per period so that it has the same spacing in a typewriter +% font as three actual period characters. +% +\def\dots{% + \leavevmode + \hbox to 1.5em{% + \hskip 0pt plus 0.25fil minus 0.25fil + .\hss.\hss.% + \hskip 0pt plus 0.5fil minus 0.5fil + }% +} + +% @enddots{} is an end-of-sentence ellipsis. +% +\def\enddots{% + \leavevmode + \hbox to 2em{% + \hskip 0pt plus 0.25fil minus 0.25fil + .\hss.\hss.\hss.% + \hskip 0pt plus 0.5fil minus 0.5fil + }% + \spacefactor=3000 +} + + +% @page forces the start of a new page +% +\def\page{\par\vfill\supereject} + +% @exdent text.... +% outputs text on separate line in roman font, starting at standard page margin + +% This records the amount of indent in the innermost environment. +% That's how much \exdent should take out. +\newskip\exdentamount + +% This defn is used inside fill environments such as @defun. +\def\exdent{\parsearg\exdentyyy} +\def\exdentyyy #1{{\hfil\break\hbox{\kern -\exdentamount{\rm#1}}\hfil\break}} + +% This defn is used inside nofill environments such as @example. +\def\nofillexdent{\parsearg\nofillexdentyyy} +\def\nofillexdentyyy #1{{\advance \leftskip by -\exdentamount +\leftline{\hskip\leftskip{\rm#1}}}} + +% @inmargin{WHICH}{TEXT} puts TEXT in the WHICH margin next to the current +% paragraph. For more general purposes, use the \margin insertion +% class. WHICH is `l' or `r'. +% +\newskip\inmarginspacing \inmarginspacing=1cm +\def\strutdepth{\dp\strutbox} +% +\def\doinmargin#1#2{\strut\vadjust{% + \nobreak + \kern-\strutdepth + \vtop to \strutdepth{% + \baselineskip=\strutdepth + \vss + % if you have multiple lines of stuff to put here, you'll need to + % make the vbox yourself of the appropriate size. + \ifx#1l% + \llap{\ignorespaces #2\hskip\inmarginspacing}% + \else + \rlap{\hskip\hsize \hskip\inmarginspacing \ignorespaces #2}% + \fi + \null + }% +}} +\def\inleftmargin{\doinmargin l} +\def\inrightmargin{\doinmargin r} +% +% @inmargin{TEXT [, RIGHT-TEXT]} +% (if RIGHT-TEXT is given, use TEXT for left page, RIGHT-TEXT for right; +% else use TEXT for both). +% +\def\inmargin#1{\parseinmargin #1,,\finish} +\def\parseinmargin#1,#2,#3\finish{% not perfect, but better than nothing. + \setbox0 = \hbox{\ignorespaces #2}% + \ifdim\wd0 > 0pt + \def\lefttext{#1}% have both texts + \def\righttext{#2}% + \else + \def\lefttext{#1}% have only one text + \def\righttext{#1}% + \fi + % + \ifodd\pageno + \def\temp{\inleftmargin\lefttext}% + \else + \def\temp{\inrightmargin\righttext}% + \fi + \temp +} + +% @include file insert text of that file as input. +% Allow normal characters that we make active in the argument (a file name). +\def\include{\begingroup + \catcode`\\=12 + \catcode`~=12 + \catcode`^=12 + \catcode`_=12 + \catcode`|=12 + \catcode`<=12 + \catcode`>=12 + \catcode`+=12 + \parsearg\includezzz} +% Restore active chars for included file. +\def\includezzz#1{\endgroup\begingroup + % Read the included file in a group so nested @include's work. + \def\thisfile{#1}% + \input\thisfile +\endgroup} + +\def\thisfile{} + +% @center line outputs that line, centered + +\def\center{\parsearg\centerzzz} +\def\centerzzz #1{{\advance\hsize by -\leftskip +\advance\hsize by -\rightskip +\centerline{#1}}} + +% @sp n outputs n lines of vertical space + +\def\sp{\parsearg\spxxx} +\def\spxxx #1{\vskip #1\baselineskip} + +% @comment ...line which is ignored... +% @c is the same as @comment +% @ignore ... @end ignore is another way to write a comment + +\def\comment{\begingroup \catcode`\^^M=\other% +\catcode`\@=\other \catcode`\{=\other \catcode`\}=\other% +\commentxxx} +{\catcode`\^^M=\other \gdef\commentxxx#1^^M{\endgroup}} + +\let\c=\comment + +% @paragraphindent NCHARS +% We'll use ems for NCHARS, close enough. +% We cannot implement @paragraphindent asis, though. +% +\def\asisword{asis} % no translation, these are keywords +\def\noneword{none} +% +\def\paragraphindent{\parsearg\doparagraphindent} +\def\doparagraphindent#1{% + \def\temp{#1}% + \ifx\temp\asisword + \else + \ifx\temp\noneword + \defaultparindent = 0pt + \else + \defaultparindent = #1em + \fi + \fi + \parindent = \defaultparindent +} + +% @exampleindent NCHARS +% We'll use ems for NCHARS like @paragraphindent. +% It seems @exampleindent asis isn't necessary, but +% I preserve it to make it similar to @paragraphindent. +\def\exampleindent{\parsearg\doexampleindent} +\def\doexampleindent#1{% + \def\temp{#1}% + \ifx\temp\asisword + \else + \ifx\temp\noneword + \lispnarrowing = 0pt + \else + \lispnarrowing = #1em + \fi + \fi +} + +% @asis just yields its argument. Used with @table, for example. +% +\def\asis#1{#1} + +% @math means output in math mode. +% We don't use $'s directly in the definition of \math because control +% sequences like \math are expanded when the toc file is written. Then, +% we read the toc file back, the $'s will be normal characters (as they +% should be, according to the definition of Texinfo). So we must use a +% control sequence to switch into and out of math mode. +% +% This isn't quite enough for @math to work properly in indices, but it +% seems unlikely it will ever be needed there. +% +\let\implicitmath = $ +\def\math#1{\implicitmath #1\implicitmath} + +% @bullet and @minus need the same treatment as @math, just above. +\def\bullet{\implicitmath\ptexbullet\implicitmath} +\def\minus{\implicitmath-\implicitmath} + +% @refill is a no-op. +\let\refill=\relax + +% If working on a large document in chapters, it is convenient to +% be able to disable indexing, cross-referencing, and contents, for test runs. +% This is done with @novalidate (before @setfilename). +% +\newif\iflinks \linkstrue % by default we want the aux files. +\let\novalidate = \linksfalse + +% @setfilename is done at the beginning of every texinfo file. +% So open here the files we need to have open while reading the input. +% This makes it possible to make a .fmt file for texinfo. +\def\setfilename{% + \iflinks + \readauxfile + \fi % \openindices needs to do some work in any case. + \openindices + \fixbackslash % Turn off hack to swallow `\input texinfo'. + \global\let\setfilename=\comment % Ignore extra @setfilename cmds. + % + % If texinfo.cnf is present on the system, read it. + % Useful for site-wide @afourpaper, etc. + % Just to be on the safe side, close the input stream before the \input. + \openin 1 texinfo.cnf + \ifeof1 \let\temp=\relax \else \def\temp{\input texinfo.cnf }\fi + \closein1 + \temp + % + \comment % Ignore the actual filename. +} + +% Called from \setfilename. +% +\def\openindices{% + \newindex{cp}% + \newcodeindex{fn}% + \newcodeindex{vr}% + \newcodeindex{tp}% + \newcodeindex{ky}% + \newcodeindex{pg}% +} + +% @bye. +\outer\def\bye{\pagealignmacro\tracingstats=1\ptexend} + + +\message{pdf,} +% adobe `portable' document format +\newcount\tempnum +\newcount\lnkcount +\newtoks\filename +\newcount\filenamelength +\newcount\pgn +\newtoks\toksA +\newtoks\toksB +\newtoks\toksC +\newtoks\toksD +\newbox\boxA +\newcount\countA +\newif\ifpdf +\newif\ifpdfmakepagedest + +\ifx\pdfoutput\undefined + \pdffalse + \let\pdfmkdest = \gobble + \let\pdfurl = \gobble + \let\endlink = \relax + \let\linkcolor = \relax + \let\pdfmakeoutlines = \relax +\else + \pdftrue + \pdfoutput = 1 + \input pdfcolor + \def\dopdfimage#1#2#3{% + \def\imagewidth{#2}% + \def\imageheight{#3}% + \ifnum\pdftexversion < 14 + \pdfimage + \else + \pdfximage + \fi + \ifx\empty\imagewidth\else width \imagewidth \fi + \ifx\empty\imageheight\else height \imageheight \fi + {#1.pdf}% + \ifnum\pdftexversion < 14 \else + \pdfrefximage \pdflastximage + \fi} + \def\pdfmkdest#1{\pdfdest name{#1@} xyz} + \def\pdfmkpgn#1{#1@} + \let\linkcolor = \Blue % was Cyan, but that seems light? + \def\endlink{\Black\pdfendlink} + % Adding outlines to PDF; macros for calculating structure of outlines + % come from Petr Olsak + \def\expnumber#1{\expandafter\ifx\csname#1\endcsname\relax 0% + \else \csname#1\endcsname \fi} + \def\advancenumber#1{\tempnum=\expnumber{#1}\relax + \advance\tempnum by1 + \expandafter\xdef\csname#1\endcsname{\the\tempnum}} + \def\pdfmakeoutlines{{% + \openin 1 \jobname.toc + \ifeof 1\else\bgroup + \closein 1 + \indexnofonts + \def\tt{} + \let\_ = \normalunderscore + % Thanh's hack / proper braces in bookmarks + \edef\mylbrace{\iftrue \string{\else}\fi}\let\{=\mylbrace + \edef\myrbrace{\iffalse{\else\string}\fi}\let\}=\myrbrace + % + \def\chapentry ##1##2##3{} + \def\unnumbchapentry ##1##2{} + \def\secentry ##1##2##3##4{\advancenumber{chap##2}} + \def\unnumbsecentry ##1##2{} + \def\subsecentry ##1##2##3##4##5{\advancenumber{sec##2.##3}} + \def\unnumbsubsecentry ##1##2{} + \def\subsubsecentry ##1##2##3##4##5##6{\advancenumber{subsec##2.##3.##4}} + \def\unnumbsubsubsecentry ##1##2{} + \input \jobname.toc + \def\chapentry ##1##2##3{% + \pdfoutline goto name{\pdfmkpgn{##3}}count-\expnumber{chap##2}{##1}} + \def\unnumbchapentry ##1##2{% + \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} + \def\secentry ##1##2##3##4{% + \pdfoutline goto name{\pdfmkpgn{##4}}count-\expnumber{sec##2.##3}{##1}} + \def\unnumbsecentry ##1##2{% + \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} + \def\subsecentry ##1##2##3##4##5{% + \pdfoutline goto name{\pdfmkpgn{##5}}count-\expnumber{subsec##2.##3.##4}{##1}} + \def\unnumbsubsecentry ##1##2{% + \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} + \def\subsubsecentry ##1##2##3##4##5##6{% + \pdfoutline goto name{\pdfmkpgn{##6}}{##1}} + \def\unnumbsubsubsecentry ##1##2{% + \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} + \input \jobname.toc + \egroup\fi + }} + \def\makelinks #1,{% + \def\params{#1}\def\E{END}% + \ifx\params\E + \let\nextmakelinks=\relax + \else + \let\nextmakelinks=\makelinks + \ifnum\lnkcount>0,\fi + \picknum{#1}% + \startlink attr{/Border [0 0 0]} + goto name{\pdfmkpgn{\the\pgn}}% + \linkcolor #1% + \advance\lnkcount by 1% + \endlink + \fi + \nextmakelinks + } + \def\picknum#1{\expandafter\pn#1} + \def\pn#1{% + \def\p{#1}% + \ifx\p\lbrace + \let\nextpn=\ppn + \else + \let\nextpn=\ppnn + \def\first{#1} + \fi + \nextpn + } + \def\ppn#1{\pgn=#1\gobble} + \def\ppnn{\pgn=\first} + \def\pdfmklnk#1{\lnkcount=0\makelinks #1,END,} + \def\addtokens#1#2{\edef\addtoks{\noexpand#1={\the#1#2}}\addtoks} + \def\skipspaces#1{\def\PP{#1}\def\D{|}% + \ifx\PP\D\let\nextsp\relax + \else\let\nextsp\skipspaces + \ifx\p\space\else\addtokens{\filename}{\PP}% + \advance\filenamelength by 1 + \fi + \fi + \nextsp} + \def\getfilename#1{\filenamelength=0\expandafter\skipspaces#1|\relax} + \ifnum\pdftexversion < 14 + \let \startlink \pdfannotlink + \else + \let \startlink \pdfstartlink + \fi + \def\pdfurl#1{% + \begingroup + \normalturnoffactive\def\@{@}% + \leavevmode\Red + \startlink attr{/Border [0 0 0]}% + user{/Subtype /Link /A << /S /URI /URI (#1) >>}% + % #1 + \endgroup} + \def\pdfgettoks#1.{\setbox\boxA=\hbox{\toksA={#1.}\toksB={}\maketoks}} + \def\addtokens#1#2{\edef\addtoks{\noexpand#1={\the#1#2}}\addtoks} + \def\adn#1{\addtokens{\toksC}{#1}\global\countA=1\let\next=\maketoks} + \def\poptoks#1#2|ENDTOKS|{\let\first=#1\toksD={#1}\toksA={#2}} + \def\maketoks{% + \expandafter\poptoks\the\toksA|ENDTOKS| + \ifx\first0\adn0 + \else\ifx\first1\adn1 \else\ifx\first2\adn2 \else\ifx\first3\adn3 + \else\ifx\first4\adn4 \else\ifx\first5\adn5 \else\ifx\first6\adn6 + \else\ifx\first7\adn7 \else\ifx\first8\adn8 \else\ifx\first9\adn9 + \else + \ifnum0=\countA\else\makelink\fi + \ifx\first.\let\next=\done\else + \let\next=\maketoks + \addtokens{\toksB}{\the\toksD} + \ifx\first,\addtokens{\toksB}{\space}\fi + \fi + \fi\fi\fi\fi\fi\fi\fi\fi\fi\fi + \next} + \def\makelink{\addtokens{\toksB}% + {\noexpand\pdflink{\the\toksC}}\toksC={}\global\countA=0} + \def\pdflink#1{% + \startlink attr{/Border [0 0 0]} goto name{\mkpgn{#1}} + \linkcolor #1\endlink} + \def\mkpgn#1{#1@} + \def\done{\edef\st{\global\noexpand\toksA={\the\toksB}}\st} +\fi % \ifx\pdfoutput + + +\message{fonts,} +% Font-change commands. + +% Texinfo sort of supports the sans serif font style, which plain TeX does not. +% So we set up a \sf analogous to plain's \rm, etc. +\newfam\sffam +\def\sf{\fam=\sffam \tensf} +\let\li = \sf % Sometimes we call it \li, not \sf. + +% We don't need math for this one. +\def\ttsl{\tenttsl} + +% Use Computer Modern fonts at \magstephalf (11pt). +\newcount\mainmagstep +\mainmagstep=\magstephalf + +% Set the font macro #1 to the font named #2, adding on the +% specified font prefix (normally `cm'). +% #3 is the font's design size, #4 is a scale factor +\def\setfont#1#2#3#4{\font#1=\fontprefix#2#3 scaled #4} + +% Use cm as the default font prefix. +% To specify the font prefix, you must define \fontprefix +% before you read in texinfo.tex. +\ifx\fontprefix\undefined +\def\fontprefix{cm} +\fi +% Support font families that don't use the same naming scheme as CM. +\def\rmshape{r} +\def\rmbshape{bx} %where the normal face is bold +\def\bfshape{b} +\def\bxshape{bx} +\def\ttshape{tt} +\def\ttbshape{tt} +\def\ttslshape{sltt} +\def\itshape{ti} +\def\itbshape{bxti} +\def\slshape{sl} +\def\slbshape{bxsl} +\def\sfshape{ss} +\def\sfbshape{ss} +\def\scshape{csc} +\def\scbshape{csc} + +\ifx\bigger\relax +\let\mainmagstep=\magstep1 +\setfont\textrm\rmshape{12}{1000} +\setfont\texttt\ttshape{12}{1000} +\else +\setfont\textrm\rmshape{10}{\mainmagstep} +\setfont\texttt\ttshape{10}{\mainmagstep} +\fi +% Instead of cmb10, you many want to use cmbx10. +% cmbx10 is a prettier font on its own, but cmb10 +% looks better when embedded in a line with cmr10. +\setfont\textbf\bfshape{10}{\mainmagstep} +\setfont\textit\itshape{10}{\mainmagstep} +\setfont\textsl\slshape{10}{\mainmagstep} +\setfont\textsf\sfshape{10}{\mainmagstep} +\setfont\textsc\scshape{10}{\mainmagstep} +\setfont\textttsl\ttslshape{10}{\mainmagstep} +\font\texti=cmmi10 scaled \mainmagstep +\font\textsy=cmsy10 scaled \mainmagstep + +% A few fonts for @defun, etc. +\setfont\defbf\bxshape{10}{\magstep1} %was 1314 +\setfont\deftt\ttshape{10}{\magstep1} +\def\df{\let\tentt=\deftt \let\tenbf = \defbf \bf} + +% Fonts for indices, footnotes, small examples (9pt). +\setfont\smallrm\rmshape{9}{1000} +\setfont\smalltt\ttshape{9}{1000} +\setfont\smallbf\bfshape{10}{900} +\setfont\smallit\itshape{9}{1000} +\setfont\smallsl\slshape{9}{1000} +\setfont\smallsf\sfshape{9}{1000} +\setfont\smallsc\scshape{10}{900} +\setfont\smallttsl\ttslshape{10}{900} +\font\smalli=cmmi9 +\font\smallsy=cmsy9 + +% Fonts for title page: +\setfont\titlerm\rmbshape{12}{\magstep3} +\setfont\titleit\itbshape{10}{\magstep4} +\setfont\titlesl\slbshape{10}{\magstep4} +\setfont\titlett\ttbshape{12}{\magstep3} +\setfont\titlettsl\ttslshape{10}{\magstep4} +\setfont\titlesf\sfbshape{17}{\magstep1} +\let\titlebf=\titlerm +\setfont\titlesc\scbshape{10}{\magstep4} +\font\titlei=cmmi12 scaled \magstep3 +\font\titlesy=cmsy10 scaled \magstep4 +\def\authorrm{\secrm} + +% Chapter (and unnumbered) fonts (17.28pt). +\setfont\chaprm\rmbshape{12}{\magstep2} +\setfont\chapit\itbshape{10}{\magstep3} +\setfont\chapsl\slbshape{10}{\magstep3} +\setfont\chaptt\ttbshape{12}{\magstep2} +\setfont\chapttsl\ttslshape{10}{\magstep3} +\setfont\chapsf\sfbshape{17}{1000} +\let\chapbf=\chaprm +\setfont\chapsc\scbshape{10}{\magstep3} +\font\chapi=cmmi12 scaled \magstep2 +\font\chapsy=cmsy10 scaled \magstep3 + +% Section fonts (14.4pt). +\setfont\secrm\rmbshape{12}{\magstep1} +\setfont\secit\itbshape{10}{\magstep2} +\setfont\secsl\slbshape{10}{\magstep2} +\setfont\sectt\ttbshape{12}{\magstep1} +\setfont\secttsl\ttslshape{10}{\magstep2} +\setfont\secsf\sfbshape{12}{\magstep1} +\let\secbf\secrm +\setfont\secsc\scbshape{10}{\magstep2} +\font\seci=cmmi12 scaled \magstep1 +\font\secsy=cmsy10 scaled \magstep2 + +% \setfont\ssecrm\bxshape{10}{\magstep1} % This size an font looked bad. +% \setfont\ssecit\itshape{10}{\magstep1} % The letters were too crowded. +% \setfont\ssecsl\slshape{10}{\magstep1} +% \setfont\ssectt\ttshape{10}{\magstep1} +% \setfont\ssecsf\sfshape{10}{\magstep1} + +%\setfont\ssecrm\bfshape{10}{1315} % Note the use of cmb rather than cmbx. +%\setfont\ssecit\itshape{10}{1315} % Also, the size is a little larger than +%\setfont\ssecsl\slshape{10}{1315} % being scaled magstep1. +%\setfont\ssectt\ttshape{10}{1315} +%\setfont\ssecsf\sfshape{10}{1315} + +%\let\ssecbf=\ssecrm + +% Subsection fonts (13.15pt). +\setfont\ssecrm\rmbshape{12}{\magstephalf} +\setfont\ssecit\itbshape{10}{1315} +\setfont\ssecsl\slbshape{10}{1315} +\setfont\ssectt\ttbshape{12}{\magstephalf} +\setfont\ssecttsl\ttslshape{10}{1315} +\setfont\ssecsf\sfbshape{12}{\magstephalf} +\let\ssecbf\ssecrm +\setfont\ssecsc\scbshape{10}{\magstep1} +\font\sseci=cmmi12 scaled \magstephalf +\font\ssecsy=cmsy10 scaled 1315 +% The smallcaps and symbol fonts should actually be scaled \magstep1.5, +% but that is not a standard magnification. + +% In order for the font changes to affect most math symbols and letters, +% we have to define the \textfont of the standard families. Since +% texinfo doesn't allow for producing subscripts and superscripts, we +% don't bother to reset \scriptfont and \scriptscriptfont (which would +% also require loading a lot more fonts). +% +\def\resetmathfonts{% + \textfont0 = \tenrm \textfont1 = \teni \textfont2 = \tensy + \textfont\itfam = \tenit \textfont\slfam = \tensl \textfont\bffam = \tenbf + \textfont\ttfam = \tentt \textfont\sffam = \tensf +} + + +% The font-changing commands redefine the meanings of \tenSTYLE, instead +% of just \STYLE. We do this so that font changes will continue to work +% in math mode, where it is the current \fam that is relevant in most +% cases, not the current font. Plain TeX does \def\bf{\fam=\bffam +% \tenbf}, for example. By redefining \tenbf, we obviate the need to +% redefine \bf itself. +\def\textfonts{% + \let\tenrm=\textrm \let\tenit=\textit \let\tensl=\textsl + \let\tenbf=\textbf \let\tentt=\texttt \let\smallcaps=\textsc + \let\tensf=\textsf \let\teni=\texti \let\tensy=\textsy \let\tenttsl=\textttsl + \resetmathfonts} +\def\titlefonts{% + \let\tenrm=\titlerm \let\tenit=\titleit \let\tensl=\titlesl + \let\tenbf=\titlebf \let\tentt=\titlett \let\smallcaps=\titlesc + \let\tensf=\titlesf \let\teni=\titlei \let\tensy=\titlesy + \let\tenttsl=\titlettsl + \resetmathfonts \setleading{25pt}} +\def\titlefont#1{{\titlefonts\rm #1}} +\def\chapfonts{% + \let\tenrm=\chaprm \let\tenit=\chapit \let\tensl=\chapsl + \let\tenbf=\chapbf \let\tentt=\chaptt \let\smallcaps=\chapsc + \let\tensf=\chapsf \let\teni=\chapi \let\tensy=\chapsy \let\tenttsl=\chapttsl + \resetmathfonts \setleading{19pt}} +\def\secfonts{% + \let\tenrm=\secrm \let\tenit=\secit \let\tensl=\secsl + \let\tenbf=\secbf \let\tentt=\sectt \let\smallcaps=\secsc + \let\tensf=\secsf \let\teni=\seci \let\tensy=\secsy \let\tenttsl=\secttsl + \resetmathfonts \setleading{16pt}} +\def\subsecfonts{% + \let\tenrm=\ssecrm \let\tenit=\ssecit \let\tensl=\ssecsl + \let\tenbf=\ssecbf \let\tentt=\ssectt \let\smallcaps=\ssecsc + \let\tensf=\ssecsf \let\teni=\sseci \let\tensy=\ssecsy \let\tenttsl=\ssecttsl + \resetmathfonts \setleading{15pt}} +\let\subsubsecfonts = \subsecfonts % Maybe make sssec fonts scaled magstephalf? +\def\smallfonts{% + \let\tenrm=\smallrm \let\tenit=\smallit \let\tensl=\smallsl + \let\tenbf=\smallbf \let\tentt=\smalltt \let\smallcaps=\smallsc + \let\tensf=\smallsf \let\teni=\smalli \let\tensy=\smallsy + \let\tenttsl=\smallttsl + \resetmathfonts \setleading{11pt}} + +% Set up the default fonts, so we can use them for creating boxes. +% +\textfonts + +% Define these so they can be easily changed for other fonts. +\def\angleleft{$\langle$} +\def\angleright{$\rangle$} + +% Count depth in font-changes, for error checks +\newcount\fontdepth \fontdepth=0 + +% Fonts for short table of contents. +\setfont\shortcontrm\rmshape{12}{1000} +\setfont\shortcontbf\bxshape{12}{1000} +\setfont\shortcontsl\slshape{12}{1000} + +%% Add scribe-like font environments, plus @l for inline lisp (usually sans +%% serif) and @ii for TeX italic + +% \smartitalic{ARG} outputs arg in italics, followed by an italic correction +% unless the following character is such as not to need one. +\def\smartitalicx{\ifx\next,\else\ifx\next-\else\ifx\next.\else\/\fi\fi\fi} +\def\smartslanted#1{{\sl #1}\futurelet\next\smartitalicx} +\def\smartitalic#1{{\it #1}\futurelet\next\smartitalicx} + +\let\i=\smartitalic +\let\var=\smartslanted +\let\dfn=\smartslanted +\let\emph=\smartitalic +\let\cite=\smartslanted + +\def\b#1{{\bf #1}} +\let\strong=\b + +% We can't just use \exhyphenpenalty, because that only has effect at +% the end of a paragraph. Restore normal hyphenation at the end of the +% group within which \nohyphenation is presumably called. +% +\def\nohyphenation{\hyphenchar\font = -1 \aftergroup\restorehyphenation} +\def\restorehyphenation{\hyphenchar\font = `- } + +\def\t#1{% + {\tt \rawbackslash \frenchspacing #1}% + \null +} +\let\ttfont=\t +\def\samp#1{`\tclose{#1}'\null} +\setfont\keyrm\rmshape{8}{1000} +\font\keysy=cmsy9 +\def\key#1{{\keyrm\textfont2=\keysy \leavevmode\hbox{% + \raise0.4pt\hbox{\angleleft}\kern-.08em\vtop{% + \vbox{\hrule\kern-0.4pt + \hbox{\raise0.4pt\hbox{\vphantom{\angleleft}}#1}}% + \kern-0.4pt\hrule}% + \kern-.06em\raise0.4pt\hbox{\angleright}}}} +% The old definition, with no lozenge: +%\def\key #1{{\ttsl \nohyphenation \uppercase{#1}}\null} +\def\ctrl #1{{\tt \rawbackslash \hat}#1} + +% @file, @option are the same as @samp. +\let\file=\samp +\let\option=\samp + +% @code is a modification of @t, +% which makes spaces the same size as normal in the surrounding text. +\def\tclose#1{% + {% + % Change normal interword space to be same as for the current font. + \spaceskip = \fontdimen2\font + % + % Switch to typewriter. + \tt + % + % But `\ ' produces the large typewriter interword space. + \def\ {{\spaceskip = 0pt{} }}% + % + % Turn off hyphenation. + \nohyphenation + % + \rawbackslash + \frenchspacing + #1% + }% + \null +} + +% We *must* turn on hyphenation at `-' and `_' in \code. +% Otherwise, it is too hard to avoid overfull hboxes +% in the Emacs manual, the Library manual, etc. + +% Unfortunately, TeX uses one parameter (\hyphenchar) to control +% both hyphenation at - and hyphenation within words. +% We must therefore turn them both off (\tclose does that) +% and arrange explicitly to hyphenate at a dash. +% -- rms. +{ + \catcode`\-=\active + \catcode`\_=\active + % + \global\def\code{\begingroup + \catcode`\-=\active \let-\codedash + \catcode`\_=\active \let_\codeunder + \codex + } + % + % If we end up with any active - characters when handling the index, + % just treat them as a normal -. + \global\def\indexbreaks{\catcode`\-=\active \let-\realdash} +} + +\def\realdash{-} +\def\codedash{-\discretionary{}{}{}} +\def\codeunder{\ifusingtt{\normalunderscore\discretionary{}{}{}}{\_}} +\def\codex #1{\tclose{#1}\endgroup} + +%\let\exp=\tclose %Was temporary + +% @kbd is like @code, except that if the argument is just one @key command, +% then @kbd has no effect. + +% @kbdinputstyle -- arg is `distinct' (@kbd uses slanted tty font always), +% `example' (@kbd uses ttsl only inside of @example and friends), +% or `code' (@kbd uses normal tty font always). +\def\kbdinputstyle{\parsearg\kbdinputstylexxx} +\def\kbdinputstylexxx#1{% + \def\arg{#1}% + \ifx\arg\worddistinct + \gdef\kbdexamplefont{\ttsl}\gdef\kbdfont{\ttsl}% + \else\ifx\arg\wordexample + \gdef\kbdexamplefont{\ttsl}\gdef\kbdfont{\tt}% + \else\ifx\arg\wordcode + \gdef\kbdexamplefont{\tt}\gdef\kbdfont{\tt}% + \fi\fi\fi +} +\def\worddistinct{distinct} +\def\wordexample{example} +\def\wordcode{code} + +% Default is kbdinputdistinct. (Too much of a hassle to call the macro, +% the catcodes are wrong for parsearg to work.) +\gdef\kbdexamplefont{\ttsl}\gdef\kbdfont{\ttsl} + +\def\xkey{\key} +\def\kbdfoo#1#2#3\par{\def\one{#1}\def\three{#3}\def\threex{??}% +\ifx\one\xkey\ifx\threex\three \key{#2}% +\else{\tclose{\kbdfont\look}}\fi +\else{\tclose{\kbdfont\look}}\fi} + +% For @url, @env, @command quotes seem unnecessary, so use \code. +\let\url=\code +\let\env=\code +\let\command=\code + +% @uref (abbreviation for `urlref') takes an optional (comma-separated) +% second argument specifying the text to display and an optional third +% arg as text to display instead of (rather than in addition to) the url +% itself. First (mandatory) arg is the url. Perhaps eventually put in +% a hypertex \special here. +% +\def\uref#1{\douref #1,,,\finish} +\def\douref#1,#2,#3,#4\finish{\begingroup + \unsepspaces + \pdfurl{#1}% + \setbox0 = \hbox{\ignorespaces #3}% + \ifdim\wd0 > 0pt + \unhbox0 % third arg given, show only that + \else + \setbox0 = \hbox{\ignorespaces #2}% + \ifdim\wd0 > 0pt + \ifpdf + \unhbox0 % PDF: 2nd arg given, show only it + \else + \unhbox0\ (\code{#1})% DVI: 2nd arg given, show both it and url + \fi + \else + \code{#1}% only url given, so show it + \fi + \fi + \endlink +\endgroup} + +% rms does not like angle brackets --karl, 17may97. +% So now @email is just like @uref, unless we are pdf. +% +%\def\email#1{\angleleft{\tt #1}\angleright} +\ifpdf + \def\email#1{\doemail#1,,\finish} + \def\doemail#1,#2,#3\finish{\begingroup + \unsepspaces + \pdfurl{mailto:#1}% + \setbox0 = \hbox{\ignorespaces #2}% + \ifdim\wd0>0pt\unhbox0\else\code{#1}\fi + \endlink + \endgroup} +\else + \let\email=\uref +\fi + +% Check if we are currently using a typewriter font. Since all the +% Computer Modern typewriter fonts have zero interword stretch (and +% shrink), and it is reasonable to expect all typewriter fonts to have +% this property, we can check that font parameter. +% +\def\ifmonospace{\ifdim\fontdimen3\font=0pt } + +% Typeset a dimension, e.g., `in' or `pt'. The only reason for the +% argument is to make the input look right: @dmn{pt} instead of @dmn{}pt. +% +\def\dmn#1{\thinspace #1} + +\def\kbd#1{\def\look{#1}\expandafter\kbdfoo\look??\par} + +% @l was never documented to mean ``switch to the Lisp font'', +% and it is not used as such in any manual I can find. We need it for +% Polish suppressed-l. --karl, 22sep96. +%\def\l#1{{\li #1}\null} + +% Explicit font changes: @r, @sc, undocumented @ii. +\def\r#1{{\rm #1}} % roman font +\def\sc#1{{\smallcaps#1}} % smallcaps font +\def\ii#1{{\it #1}} % italic font + +% @acronym downcases the argument and prints in smallcaps. +\def\acronym#1{{\smallcaps \lowercase{#1}}} + +% @pounds{} is a sterling sign. +\def\pounds{{\it\$}} + + +\message{page headings,} + +\newskip\titlepagetopglue \titlepagetopglue = 1.5in +\newskip\titlepagebottomglue \titlepagebottomglue = 2pc + +% First the title page. Must do @settitle before @titlepage. +\newif\ifseenauthor +\newif\iffinishedtitlepage + +% Do an implicit @contents or @shortcontents after @end titlepage if the +% user says @setcontentsaftertitlepage or @setshortcontentsaftertitlepage. +% +\newif\ifsetcontentsaftertitlepage + \let\setcontentsaftertitlepage = \setcontentsaftertitlepagetrue +\newif\ifsetshortcontentsaftertitlepage + \let\setshortcontentsaftertitlepage = \setshortcontentsaftertitlepagetrue + +\def\shorttitlepage{\parsearg\shorttitlepagezzz} +\def\shorttitlepagezzz #1{\begingroup\hbox{}\vskip 1.5in \chaprm \centerline{#1}% + \endgroup\page\hbox{}\page} + +\def\titlepage{\begingroup \parindent=0pt \textfonts + \let\subtitlerm=\tenrm + \def\subtitlefont{\subtitlerm \normalbaselineskip = 13pt \normalbaselines}% + % + \def\authorfont{\authorrm \normalbaselineskip = 16pt \normalbaselines}% + % + % Leave some space at the very top of the page. + \vglue\titlepagetopglue + % + % Now you can print the title using @title. + \def\title{\parsearg\titlezzz}% + \def\titlezzz##1{\leftline{\titlefonts\rm ##1} + % print a rule at the page bottom also. + \finishedtitlepagefalse + \vskip4pt \hrule height 4pt width \hsize \vskip4pt}% + % No rule at page bottom unless we print one at the top with @title. + \finishedtitlepagetrue + % + % Now you can put text using @subtitle. + \def\subtitle{\parsearg\subtitlezzz}% + \def\subtitlezzz##1{{\subtitlefont \rightline{##1}}}% + % + % @author should come last, but may come many times. + \def\author{\parsearg\authorzzz}% + \def\authorzzz##1{\ifseenauthor\else\vskip 0pt plus 1filll\seenauthortrue\fi + {\authorfont \leftline{##1}}}% + % + % Most title ``pages'' are actually two pages long, with space + % at the top of the second. We don't want the ragged left on the second. + \let\oldpage = \page + \def\page{% + \iffinishedtitlepage\else + \finishtitlepage + \fi + \oldpage + \let\page = \oldpage + \hbox{}}% +% \def\page{\oldpage \hbox{}} +} + +\def\Etitlepage{% + \iffinishedtitlepage\else + \finishtitlepage + \fi + % It is important to do the page break before ending the group, + % because the headline and footline are only empty inside the group. + % If we use the new definition of \page, we always get a blank page + % after the title page, which we certainly don't want. + \oldpage + \endgroup + % + % If they want short, they certainly want long too. + \ifsetshortcontentsaftertitlepage + \shortcontents + \contents + \global\let\shortcontents = \relax + \global\let\contents = \relax + \fi + % + \ifsetcontentsaftertitlepage + \contents + \global\let\contents = \relax + \global\let\shortcontents = \relax + \fi + % + \ifpdf \pdfmakepagedesttrue \fi + % + \HEADINGSon +} + +\def\finishtitlepage{% + \vskip4pt \hrule height 2pt width \hsize + \vskip\titlepagebottomglue + \finishedtitlepagetrue +} + +%%% Set up page headings and footings. + +\let\thispage=\folio + +\newtoks\evenheadline % headline on even pages +\newtoks\oddheadline % headline on odd pages +\newtoks\evenfootline % footline on even pages +\newtoks\oddfootline % footline on odd pages + +% Now make Tex use those variables +\headline={{\textfonts\rm \ifodd\pageno \the\oddheadline + \else \the\evenheadline \fi}} +\footline={{\textfonts\rm \ifodd\pageno \the\oddfootline + \else \the\evenfootline \fi}\HEADINGShook} +\let\HEADINGShook=\relax + +% Commands to set those variables. +% For example, this is what @headings on does +% @evenheading @thistitle|@thispage|@thischapter +% @oddheading @thischapter|@thispage|@thistitle +% @evenfooting @thisfile|| +% @oddfooting ||@thisfile + +\def\evenheading{\parsearg\evenheadingxxx} +\def\oddheading{\parsearg\oddheadingxxx} +\def\everyheading{\parsearg\everyheadingxxx} + +\def\evenfooting{\parsearg\evenfootingxxx} +\def\oddfooting{\parsearg\oddfootingxxx} +\def\everyfooting{\parsearg\everyfootingxxx} + +{\catcode`\@=0 % + +\gdef\evenheadingxxx #1{\evenheadingyyy #1@|@|@|@|\finish} +\gdef\evenheadingyyy #1@|#2@|#3@|#4\finish{% +\global\evenheadline={\rlap{\centerline{#2}}\line{#1\hfil#3}}} + +\gdef\oddheadingxxx #1{\oddheadingyyy #1@|@|@|@|\finish} +\gdef\oddheadingyyy #1@|#2@|#3@|#4\finish{% +\global\oddheadline={\rlap{\centerline{#2}}\line{#1\hfil#3}}} + +\gdef\everyheadingxxx#1{\oddheadingxxx{#1}\evenheadingxxx{#1}}% + +\gdef\evenfootingxxx #1{\evenfootingyyy #1@|@|@|@|\finish} +\gdef\evenfootingyyy #1@|#2@|#3@|#4\finish{% +\global\evenfootline={\rlap{\centerline{#2}}\line{#1\hfil#3}}} + +\gdef\oddfootingxxx #1{\oddfootingyyy #1@|@|@|@|\finish} +\gdef\oddfootingyyy #1@|#2@|#3@|#4\finish{% + \global\oddfootline = {\rlap{\centerline{#2}}\line{#1\hfil#3}}% + % + % Leave some space for the footline. Hopefully ok to assume + % @evenfooting will not be used by itself. + \global\advance\pageheight by -\baselineskip + \global\advance\vsize by -\baselineskip +} + +\gdef\everyfootingxxx#1{\oddfootingxxx{#1}\evenfootingxxx{#1}} +% +}% unbind the catcode of @. + +% @headings double turns headings on for double-sided printing. +% @headings single turns headings on for single-sided printing. +% @headings off turns them off. +% @headings on same as @headings double, retained for compatibility. +% @headings after turns on double-sided headings after this page. +% @headings doubleafter turns on double-sided headings after this page. +% @headings singleafter turns on single-sided headings after this page. +% By default, they are off at the start of a document, +% and turned `on' after @end titlepage. + +\def\headings #1 {\csname HEADINGS#1\endcsname} + +\def\HEADINGSoff{ +\global\evenheadline={\hfil} \global\evenfootline={\hfil} +\global\oddheadline={\hfil} \global\oddfootline={\hfil}} +\HEADINGSoff +% When we turn headings on, set the page number to 1. +% For double-sided printing, put current file name in lower left corner, +% chapter name on inside top of right hand pages, document +% title on inside top of left hand pages, and page numbers on outside top +% edge of all pages. +\def\HEADINGSdouble{ +\global\pageno=1 +\global\evenfootline={\hfil} +\global\oddfootline={\hfil} +\global\evenheadline={\line{\folio\hfil\thistitle}} +\global\oddheadline={\line{\thischapter\hfil\folio}} +\global\let\contentsalignmacro = \chapoddpage +} +\let\contentsalignmacro = \chappager + +% For single-sided printing, chapter title goes across top left of page, +% page number on top right. +\def\HEADINGSsingle{ +\global\pageno=1 +\global\evenfootline={\hfil} +\global\oddfootline={\hfil} +\global\evenheadline={\line{\thischapter\hfil\folio}} +\global\oddheadline={\line{\thischapter\hfil\folio}} +\global\let\contentsalignmacro = \chappager +} +\def\HEADINGSon{\HEADINGSdouble} + +\def\HEADINGSafter{\let\HEADINGShook=\HEADINGSdoublex} +\let\HEADINGSdoubleafter=\HEADINGSafter +\def\HEADINGSdoublex{% +\global\evenfootline={\hfil} +\global\oddfootline={\hfil} +\global\evenheadline={\line{\folio\hfil\thistitle}} +\global\oddheadline={\line{\thischapter\hfil\folio}} +\global\let\contentsalignmacro = \chapoddpage +} + +\def\HEADINGSsingleafter{\let\HEADINGShook=\HEADINGSsinglex} +\def\HEADINGSsinglex{% +\global\evenfootline={\hfil} +\global\oddfootline={\hfil} +\global\evenheadline={\line{\thischapter\hfil\folio}} +\global\oddheadline={\line{\thischapter\hfil\folio}} +\global\let\contentsalignmacro = \chappager +} + +% Subroutines used in generating headings +% This produces Day Month Year style of output. +% Only define if not already defined, in case a txi-??.tex file has set +% up a different format (e.g., txi-cs.tex does this). +\ifx\today\undefined +\def\today{% + \number\day\space + \ifcase\month + \or\putwordMJan\or\putwordMFeb\or\putwordMMar\or\putwordMApr + \or\putwordMMay\or\putwordMJun\or\putwordMJul\or\putwordMAug + \or\putwordMSep\or\putwordMOct\or\putwordMNov\or\putwordMDec + \fi + \space\number\year} +\fi + +% @settitle line... specifies the title of the document, for headings. +% It generates no output of its own. +\def\thistitle{\putwordNoTitle} +\def\settitle{\parsearg\settitlezzz} +\def\settitlezzz #1{\gdef\thistitle{#1}} + + +\message{tables,} +% Tables -- @table, @ftable, @vtable, @item(x), @kitem(x), @xitem(x). + +% default indentation of table text +\newdimen\tableindent \tableindent=.8in +% default indentation of @itemize and @enumerate text +\newdimen\itemindent \itemindent=.3in +% margin between end of table item and start of table text. +\newdimen\itemmargin \itemmargin=.1in + +% used internally for \itemindent minus \itemmargin +\newdimen\itemmax + +% Note @table, @vtable, and @vtable define @item, @itemx, etc., with +% these defs. +% They also define \itemindex +% to index the item name in whatever manner is desired (perhaps none). + +\newif\ifitemxneedsnegativevskip + +\def\itemxpar{\par\ifitemxneedsnegativevskip\nobreak\vskip-\parskip\nobreak\fi} + +\def\internalBitem{\smallbreak \parsearg\itemzzz} +\def\internalBitemx{\itemxpar \parsearg\itemzzz} + +\def\internalBxitem "#1"{\def\xitemsubtopix{#1} \smallbreak \parsearg\xitemzzz} +\def\internalBxitemx "#1"{\def\xitemsubtopix{#1} \itemxpar \parsearg\xitemzzz} + +\def\internalBkitem{\smallbreak \parsearg\kitemzzz} +\def\internalBkitemx{\itemxpar \parsearg\kitemzzz} + +\def\kitemzzz #1{\dosubind {kw}{\code{#1}}{for {\bf \lastfunction}}% + \itemzzz {#1}} + +\def\xitemzzz #1{\dosubind {kw}{\code{#1}}{for {\bf \xitemsubtopic}}% + \itemzzz {#1}} + +\def\itemzzz #1{\begingroup % + \advance\hsize by -\rightskip + \advance\hsize by -\tableindent + \setbox0=\hbox{\itemfont{#1}}% + \itemindex{#1}% + \nobreak % This prevents a break before @itemx. + % + % If the item text does not fit in the space we have, put it on a line + % by itself, and do not allow a page break either before or after that + % line. We do not start a paragraph here because then if the next + % command is, e.g., @kindex, the whatsit would get put into the + % horizontal list on a line by itself, resulting in extra blank space. + \ifdim \wd0>\itemmax + % + % Make this a paragraph so we get the \parskip glue and wrapping, + % but leave it ragged-right. + \begingroup + \advance\leftskip by-\tableindent + \advance\hsize by\tableindent + \advance\rightskip by0pt plus1fil + \leavevmode\unhbox0\par + \endgroup + % + % We're going to be starting a paragraph, but we don't want the + % \parskip glue -- logically it's part of the @item we just started. + \nobreak \vskip-\parskip + % + % Stop a page break at the \parskip glue coming up. Unfortunately + % we can't prevent a possible page break at the following + % \baselineskip glue. + \nobreak + \endgroup + \itemxneedsnegativevskipfalse + \else + % The item text fits into the space. Start a paragraph, so that the + % following text (if any) will end up on the same line. + \noindent + % Do this with kerns and \unhbox so that if there is a footnote in + % the item text, it can migrate to the main vertical list and + % eventually be printed. + \nobreak\kern-\tableindent + \dimen0 = \itemmax \advance\dimen0 by \itemmargin \advance\dimen0 by -\wd0 + \unhbox0 + \nobreak\kern\dimen0 + \endgroup + \itemxneedsnegativevskiptrue + \fi +} + +\def\item{\errmessage{@item while not in a table}} +\def\itemx{\errmessage{@itemx while not in a table}} +\def\kitem{\errmessage{@kitem while not in a table}} +\def\kitemx{\errmessage{@kitemx while not in a table}} +\def\xitem{\errmessage{@xitem while not in a table}} +\def\xitemx{\errmessage{@xitemx while not in a table}} + +% Contains a kludge to get @end[description] to work. +\def\description{\tablez{\dontindex}{1}{}{}{}{}} + +% @table, @ftable, @vtable. +\def\table{\begingroup\inENV\obeylines\obeyspaces\tablex} +{\obeylines\obeyspaces% +\gdef\tablex #1^^M{% +\tabley\dontindex#1 \endtabley}} + +\def\ftable{\begingroup\inENV\obeylines\obeyspaces\ftablex} +{\obeylines\obeyspaces% +\gdef\ftablex #1^^M{% +\tabley\fnitemindex#1 \endtabley +\def\Eftable{\endgraf\afterenvbreak\endgroup}% +\let\Etable=\relax}} + +\def\vtable{\begingroup\inENV\obeylines\obeyspaces\vtablex} +{\obeylines\obeyspaces% +\gdef\vtablex #1^^M{% +\tabley\vritemindex#1 \endtabley +\def\Evtable{\endgraf\afterenvbreak\endgroup}% +\let\Etable=\relax}} + +\def\dontindex #1{} +\def\fnitemindex #1{\doind {fn}{\code{#1}}}% +\def\vritemindex #1{\doind {vr}{\code{#1}}}% + +{\obeyspaces % +\gdef\tabley#1#2 #3 #4 #5 #6 #7\endtabley{\endgroup% +\tablez{#1}{#2}{#3}{#4}{#5}{#6}}} + +\def\tablez #1#2#3#4#5#6{% +\aboveenvbreak % +\begingroup % +\def\Edescription{\Etable}% Necessary kludge. +\let\itemindex=#1% +\ifnum 0#3>0 \advance \leftskip by #3\mil \fi % +\ifnum 0#4>0 \tableindent=#4\mil \fi % +\ifnum 0#5>0 \advance \rightskip by #5\mil \fi % +\def\itemfont{#2}% +\itemmax=\tableindent % +\advance \itemmax by -\itemmargin % +\advance \leftskip by \tableindent % +\exdentamount=\tableindent +\parindent = 0pt +\parskip = \smallskipamount +\ifdim \parskip=0pt \parskip=2pt \fi% +\def\Etable{\endgraf\afterenvbreak\endgroup}% +\let\item = \internalBitem % +\let\itemx = \internalBitemx % +\let\kitem = \internalBkitem % +\let\kitemx = \internalBkitemx % +\let\xitem = \internalBxitem % +\let\xitemx = \internalBxitemx % +} + +% This is the counter used by @enumerate, which is really @itemize + +\newcount \itemno + +\def\itemize{\parsearg\itemizezzz} + +\def\itemizezzz #1{% + \begingroup % ended by the @end itemize + \itemizey {#1}{\Eitemize} +} + +\def\itemizey #1#2{% +\aboveenvbreak % +\itemmax=\itemindent % +\advance \itemmax by -\itemmargin % +\advance \leftskip by \itemindent % +\exdentamount=\itemindent +\parindent = 0pt % +\parskip = \smallskipamount % +\ifdim \parskip=0pt \parskip=2pt \fi% +\def#2{\endgraf\afterenvbreak\endgroup}% +\def\itemcontents{#1}% +\let\item=\itemizeitem} + +% Set sfcode to normal for the chars that usually have another value. +% These are `.?!:;,' +\def\frenchspacing{\sfcode46=1000 \sfcode63=1000 \sfcode33=1000 + \sfcode58=1000 \sfcode59=1000 \sfcode44=1000 } + +% \splitoff TOKENS\endmark defines \first to be the first token in +% TOKENS, and \rest to be the remainder. +% +\def\splitoff#1#2\endmark{\def\first{#1}\def\rest{#2}}% + +% Allow an optional argument of an uppercase letter, lowercase letter, +% or number, to specify the first label in the enumerated list. No +% argument is the same as `1'. +% +\def\enumerate{\parsearg\enumeratezzz} +\def\enumeratezzz #1{\enumeratey #1 \endenumeratey} +\def\enumeratey #1 #2\endenumeratey{% + \begingroup % ended by the @end enumerate + % + % If we were given no argument, pretend we were given `1'. + \def\thearg{#1}% + \ifx\thearg\empty \def\thearg{1}\fi + % + % Detect if the argument is a single token. If so, it might be a + % letter. Otherwise, the only valid thing it can be is a number. + % (We will always have one token, because of the test we just made. + % This is a good thing, since \splitoff doesn't work given nothing at + % all -- the first parameter is undelimited.) + \expandafter\splitoff\thearg\endmark + \ifx\rest\empty + % Only one token in the argument. It could still be anything. + % A ``lowercase letter'' is one whose \lccode is nonzero. + % An ``uppercase letter'' is one whose \lccode is both nonzero, and + % not equal to itself. + % Otherwise, we assume it's a number. + % + % We need the \relax at the end of the \ifnum lines to stop TeX from + % continuing to look for a . + % + \ifnum\lccode\expandafter`\thearg=0\relax + \numericenumerate % a number (we hope) + \else + % It's a letter. + \ifnum\lccode\expandafter`\thearg=\expandafter`\thearg\relax + \lowercaseenumerate % lowercase letter + \else + \uppercaseenumerate % uppercase letter + \fi + \fi + \else + % Multiple tokens in the argument. We hope it's a number. + \numericenumerate + \fi +} + +% An @enumerate whose labels are integers. The starting integer is +% given in \thearg. +% +\def\numericenumerate{% + \itemno = \thearg + \startenumeration{\the\itemno}% +} + +% The starting (lowercase) letter is in \thearg. +\def\lowercaseenumerate{% + \itemno = \expandafter`\thearg + \startenumeration{% + % Be sure we're not beyond the end of the alphabet. + \ifnum\itemno=0 + \errmessage{No more lowercase letters in @enumerate; get a bigger + alphabet}% + \fi + \char\lccode\itemno + }% +} + +% The starting (uppercase) letter is in \thearg. +\def\uppercaseenumerate{% + \itemno = \expandafter`\thearg + \startenumeration{% + % Be sure we're not beyond the end of the alphabet. + \ifnum\itemno=0 + \errmessage{No more uppercase letters in @enumerate; get a bigger + alphabet} + \fi + \char\uccode\itemno + }% +} + +% Call itemizey, adding a period to the first argument and supplying the +% common last two arguments. Also subtract one from the initial value in +% \itemno, since @item increments \itemno. +% +\def\startenumeration#1{% + \advance\itemno by -1 + \itemizey{#1.}\Eenumerate\flushcr +} + +% @alphaenumerate and @capsenumerate are abbreviations for giving an arg +% to @enumerate. +% +\def\alphaenumerate{\enumerate{a}} +\def\capsenumerate{\enumerate{A}} +\def\Ealphaenumerate{\Eenumerate} +\def\Ecapsenumerate{\Eenumerate} + +% Definition of @item while inside @itemize. + +\def\itemizeitem{% +\advance\itemno by 1 +{\let\par=\endgraf \smallbreak}% +\ifhmode \errmessage{In hmode at itemizeitem}\fi +{\parskip=0in \hskip 0pt +\hbox to 0pt{\hss \itemcontents\hskip \itemmargin}% +\vadjust{\penalty 1200}}% +\flushcr} + +% @multitable macros +% Amy Hendrickson, 8/18/94, 3/6/96 +% +% @multitable ... @end multitable will make as many columns as desired. +% Contents of each column will wrap at width given in preamble. Width +% can be specified either with sample text given in a template line, +% or in percent of \hsize, the current width of text on page. + +% Table can continue over pages but will only break between lines. + +% To make preamble: +% +% Either define widths of columns in terms of percent of \hsize: +% @multitable @columnfractions .25 .3 .45 +% @item ... +% +% Numbers following @columnfractions are the percent of the total +% current hsize to be used for each column. You may use as many +% columns as desired. + + +% Or use a template: +% @multitable {Column 1 template} {Column 2 template} {Column 3 template} +% @item ... +% using the widest term desired in each column. +% +% For those who want to use more than one line's worth of words in +% the preamble, break the line within one argument and it +% will parse correctly, i.e., +% +% @multitable {Column 1 template} {Column 2 template} {Column 3 +% template} +% Not: +% @multitable {Column 1 template} {Column 2 template} +% {Column 3 template} + +% Each new table line starts with @item, each subsequent new column +% starts with @tab. Empty columns may be produced by supplying @tab's +% with nothing between them for as many times as empty columns are needed, +% ie, @tab@tab@tab will produce two empty columns. + +% @item, @tab, @multitable or @end multitable do not need to be on their +% own lines, but it will not hurt if they are. + +% Sample multitable: + +% @multitable {Column 1 template} {Column 2 template} {Column 3 template} +% @item first col stuff @tab second col stuff @tab third col +% @item +% first col stuff +% @tab +% second col stuff +% @tab +% third col +% @item first col stuff @tab second col stuff +% @tab Many paragraphs of text may be used in any column. +% +% They will wrap at the width determined by the template. +% @item@tab@tab This will be in third column. +% @end multitable + +% Default dimensions may be reset by user. +% @multitableparskip is vertical space between paragraphs in table. +% @multitableparindent is paragraph indent in table. +% @multitablecolmargin is horizontal space to be left between columns. +% @multitablelinespace is space to leave between table items, baseline +% to baseline. +% 0pt means it depends on current normal line spacing. +% +\newskip\multitableparskip +\newskip\multitableparindent +\newdimen\multitablecolspace +\newskip\multitablelinespace +\multitableparskip=0pt +\multitableparindent=6pt +\multitablecolspace=12pt +\multitablelinespace=0pt + +% Macros used to set up halign preamble: +% +\let\endsetuptable\relax +\def\xendsetuptable{\endsetuptable} +\let\columnfractions\relax +\def\xcolumnfractions{\columnfractions} +\newif\ifsetpercent + +% #1 is the part of the @columnfraction before the decimal point, which +% is presumably either 0 or the empty string (but we don't check, we +% just throw it away). #2 is the decimal part, which we use as the +% percent of \hsize for this column. +\def\pickupwholefraction#1.#2 {% + \global\advance\colcount by 1 + \expandafter\xdef\csname col\the\colcount\endcsname{.#2\hsize}% + \setuptable +} + +\newcount\colcount +\def\setuptable#1{% + \def\firstarg{#1}% + \ifx\firstarg\xendsetuptable + \let\go = \relax + \else + \ifx\firstarg\xcolumnfractions + \global\setpercenttrue + \else + \ifsetpercent + \let\go\pickupwholefraction + \else + \global\advance\colcount by 1 + \setbox0=\hbox{#1\unskip }% Add a normal word space as a separator; + % typically that is always in the input, anyway. + \expandafter\xdef\csname col\the\colcount\endcsname{\the\wd0}% + \fi + \fi + \ifx\go\pickupwholefraction + % Put the argument back for the \pickupwholefraction call, so + % we'll always have a period there to be parsed. + \def\go{\pickupwholefraction#1}% + \else + \let\go = \setuptable + \fi% + \fi + \go +} + +% This used to have \hskip1sp. But then the space in a template line is +% not enough. That is bad. So let's go back to just & until we +% encounter the problem it was intended to solve again. +% --karl, nathan@acm.org, 20apr99. +\def\tab{&} + +% @multitable ... @end multitable definitions: +% +\def\multitable{\parsearg\dotable} +\def\dotable#1{\bgroup + \vskip\parskip + \let\item\crcr + \tolerance=9500 + \hbadness=9500 + \setmultitablespacing + \parskip=\multitableparskip + \parindent=\multitableparindent + \overfullrule=0pt + \global\colcount=0 + \def\Emultitable{\global\setpercentfalse\cr\egroup\egroup}% + % + % To parse everything between @multitable and @item: + \setuptable#1 \endsetuptable + % + % \everycr will reset column counter, \colcount, at the end of + % each line. Every column entry will cause \colcount to advance by one. + % The table preamble + % looks at the current \colcount to find the correct column width. + \everycr{\noalign{% + % + % \filbreak%% keeps underfull box messages off when table breaks over pages. + % Maybe so, but it also creates really weird page breaks when the table + % breaks over pages. Wouldn't \vfil be better? Wait until the problem + % manifests itself, so it can be fixed for real --karl. + \global\colcount=0\relax}}% + % + % This preamble sets up a generic column definition, which will + % be used as many times as user calls for columns. + % \vtop will set a single line and will also let text wrap and + % continue for many paragraphs if desired. + \halign\bgroup&\global\advance\colcount by 1\relax + \multistrut\vtop{\hsize=\expandafter\csname col\the\colcount\endcsname + % + % In order to keep entries from bumping into each other + % we will add a \leftskip of \multitablecolspace to all columns after + % the first one. + % + % If a template has been used, we will add \multitablecolspace + % to the width of each template entry. + % + % If the user has set preamble in terms of percent of \hsize we will + % use that dimension as the width of the column, and the \leftskip + % will keep entries from bumping into each other. Table will start at + % left margin and final column will justify at right margin. + % + % Make sure we don't inherit \rightskip from the outer environment. + \rightskip=0pt + \ifnum\colcount=1 + % The first column will be indented with the surrounding text. + \advance\hsize by\leftskip + \else + \ifsetpercent \else + % If user has not set preamble in terms of percent of \hsize + % we will advance \hsize by \multitablecolspace. + \advance\hsize by \multitablecolspace + \fi + % In either case we will make \leftskip=\multitablecolspace: + \leftskip=\multitablecolspace + \fi + % Ignoring space at the beginning and end avoids an occasional spurious + % blank line, when TeX decides to break the line at the space before the + % box from the multistrut, so the strut ends up on a line by itself. + % For example: + % @multitable @columnfractions .11 .89 + % @item @code{#} + % @tab Legal holiday which is valid in major parts of the whole country. + % Is automatically provided with highlighting sequences respectively marking + % characters. + \noindent\ignorespaces##\unskip\multistrut}\cr +} + +\def\setmultitablespacing{% test to see if user has set \multitablelinespace. +% If so, do nothing. If not, give it an appropriate dimension based on +% current baselineskip. +\ifdim\multitablelinespace=0pt +\setbox0=\vbox{X}\global\multitablelinespace=\the\baselineskip +\global\advance\multitablelinespace by-\ht0 +%% strut to put in table in case some entry doesn't have descenders, +%% to keep lines equally spaced +\let\multistrut = \strut +\else +%% FIXME: what is \box0 supposed to be? +\gdef\multistrut{\vrule height\multitablelinespace depth\dp0 +width0pt\relax} \fi +%% Test to see if parskip is larger than space between lines of +%% table. If not, do nothing. +%% If so, set to same dimension as multitablelinespace. +\ifdim\multitableparskip>\multitablelinespace +\global\multitableparskip=\multitablelinespace +\global\advance\multitableparskip-7pt %% to keep parskip somewhat smaller + %% than skip between lines in the table. +\fi% +\ifdim\multitableparskip=0pt +\global\multitableparskip=\multitablelinespace +\global\advance\multitableparskip-7pt %% to keep parskip somewhat smaller + %% than skip between lines in the table. +\fi} + + +\message{conditionals,} +% Prevent errors for section commands. +% Used in @ignore and in failing conditionals. +\def\ignoresections{% + \let\chapter=\relax + \let\unnumbered=\relax + \let\top=\relax + \let\unnumberedsec=\relax + \let\unnumberedsection=\relax + \let\unnumberedsubsec=\relax + \let\unnumberedsubsection=\relax + \let\unnumberedsubsubsec=\relax + \let\unnumberedsubsubsection=\relax + \let\section=\relax + \let\subsec=\relax + \let\subsubsec=\relax + \let\subsection=\relax + \let\subsubsection=\relax + \let\appendix=\relax + \let\appendixsec=\relax + \let\appendixsection=\relax + \let\appendixsubsec=\relax + \let\appendixsubsection=\relax + \let\appendixsubsubsec=\relax + \let\appendixsubsubsection=\relax + \let\contents=\relax + \let\smallbook=\relax + \let\titlepage=\relax +} + +% Used in nested conditionals, where we have to parse the Texinfo source +% and so want to turn off most commands, in case they are used +% incorrectly. +% +\def\ignoremorecommands{% + \let\defcodeindex = \relax + \let\defcv = \relax + \let\deffn = \relax + \let\deffnx = \relax + \let\defindex = \relax + \let\defivar = \relax + \let\defmac = \relax + \let\defmethod = \relax + \let\defop = \relax + \let\defopt = \relax + \let\defspec = \relax + \let\deftp = \relax + \let\deftypefn = \relax + \let\deftypefun = \relax + \let\deftypeivar = \relax + \let\deftypeop = \relax + \let\deftypevar = \relax + \let\deftypevr = \relax + \let\defun = \relax + \let\defvar = \relax + \let\defvr = \relax + \let\ref = \relax + \let\xref = \relax + \let\printindex = \relax + \let\pxref = \relax + \let\settitle = \relax + \let\setchapternewpage = \relax + \let\setchapterstyle = \relax + \let\everyheading = \relax + \let\evenheading = \relax + \let\oddheading = \relax + \let\everyfooting = \relax + \let\evenfooting = \relax + \let\oddfooting = \relax + \let\headings = \relax + \let\include = \relax + \let\lowersections = \relax + \let\down = \relax + \let\raisesections = \relax + \let\up = \relax + \let\set = \relax + \let\clear = \relax + \let\item = \relax +} + +% Ignore @ignore ... @end ignore. +% +\def\ignore{\doignore{ignore}} + +% Ignore @ifinfo, @ifhtml, @ifnottex, @html, @menu, and @direntry text. +% +\def\ifinfo{\doignore{ifinfo}} +\def\ifhtml{\doignore{ifhtml}} +\def\ifnottex{\doignore{ifnottex}} +\def\html{\doignore{html}} +\def\menu{\doignore{menu}} +\def\direntry{\doignore{direntry}} + +% @dircategory CATEGORY -- specify a category of the dir file +% which this file should belong to. Ignore this in TeX. +\let\dircategory = \comment + +% Ignore text until a line `@end #1'. +% +\def\doignore#1{\begingroup + % Don't complain about control sequences we have declared \outer. + \ignoresections + % + % Define a command to swallow text until we reach `@end #1'. + % This @ is a catcode 12 token (that is the normal catcode of @ in + % this texinfo.tex file). We change the catcode of @ below to match. + \long\def\doignoretext##1@end #1{\enddoignore}% + % + % Make sure that spaces turn into tokens that match what \doignoretext wants. + \catcode32 = 10 + % + % Ignore braces, too, so mismatched braces don't cause trouble. + \catcode`\{ = 9 + \catcode`\} = 9 + % + % We must not have @c interpreted as a control sequence. + \catcode`\@ = 12 + % + % Make the letter c a comment character so that the rest of the line + % will be ignored. This way, the document can have (for example) + % @c @end ifinfo + % and the @end ifinfo will be properly ignored. + % (We've just changed @ to catcode 12.) + \catcode`\c = 14 + % + % And now expand that command. + \doignoretext +} + +% What we do to finish off ignored text. +% +\def\enddoignore{\endgroup\ignorespaces}% + +\newif\ifwarnedobs\warnedobsfalse +\def\obstexwarn{% + \ifwarnedobs\relax\else + % We need to warn folks that they may have trouble with TeX 3.0. + % This uses \immediate\write16 rather than \message to get newlines. + \immediate\write16{} + \immediate\write16{WARNING: for users of Unix TeX 3.0!} + \immediate\write16{This manual trips a bug in TeX version 3.0 (tex hangs).} + \immediate\write16{If you are running another version of TeX, relax.} + \immediate\write16{If you are running Unix TeX 3.0, kill this TeX process.} + \immediate\write16{ Then upgrade your TeX installation if you can.} + \immediate\write16{ (See ftp://ftp.gnu.org/pub/gnu/TeX.README.)} + \immediate\write16{If you are stuck with version 3.0, run the} + \immediate\write16{ script ``tex3patch'' from the Texinfo distribution} + \immediate\write16{ to use a workaround.} + \immediate\write16{} + \global\warnedobstrue + \fi +} + +% **In TeX 3.0, setting text in \nullfont hangs tex. For a +% workaround (which requires the file ``dummy.tfm'' to be installed), +% uncomment the following line: +%%%%%\font\nullfont=dummy\let\obstexwarn=\relax + +% Ignore text, except that we keep track of conditional commands for +% purposes of nesting, up to an `@end #1' command. +% +\def\nestedignore#1{% + \obstexwarn + % We must actually expand the ignored text to look for the @end + % command, so that nested ignore constructs work. Thus, we put the + % text into a \vbox and then do nothing with the result. To minimize + % the change of memory overflow, we follow the approach outlined on + % page 401 of the TeXbook: make the current font be a dummy font. + % + \setbox0 = \vbox\bgroup + % Don't complain about control sequences we have declared \outer. + \ignoresections + % + % Define `@end #1' to end the box, which will in turn undefine the + % @end command again. + \expandafter\def\csname E#1\endcsname{\egroup\ignorespaces}% + % + % We are going to be parsing Texinfo commands. Most cause no + % trouble when they are used incorrectly, but some commands do + % complicated argument parsing or otherwise get confused, so we + % undefine them. + % + % We can't do anything about stray @-signs, unfortunately; + % they'll produce `undefined control sequence' errors. + \ignoremorecommands + % + % Set the current font to be \nullfont, a TeX primitive, and define + % all the font commands to also use \nullfont. We don't use + % dummy.tfm, as suggested in the TeXbook, because not all sites + % might have that installed. Therefore, math mode will still + % produce output, but that should be an extremely small amount of + % stuff compared to the main input. + % + \nullfont + \let\tenrm=\nullfont \let\tenit=\nullfont \let\tensl=\nullfont + \let\tenbf=\nullfont \let\tentt=\nullfont \let\smallcaps=\nullfont + \let\tensf=\nullfont + % Similarly for index fonts (mostly for their use in smallexample). + \let\smallrm=\nullfont \let\smallit=\nullfont \let\smallsl=\nullfont + \let\smallbf=\nullfont \let\smalltt=\nullfont \let\smallsc=\nullfont + \let\smallsf=\nullfont + % + % Don't complain when characters are missing from the fonts. + \tracinglostchars = 0 + % + % Don't bother to do space factor calculations. + \frenchspacing + % + % Don't report underfull hboxes. + \hbadness = 10000 + % + % Do minimal line-breaking. + \pretolerance = 10000 + % + % Do not execute instructions in @tex + \def\tex{\doignore{tex}}% + % Do not execute macro definitions. + % `c' is a comment character, so the word `macro' will get cut off. + \def\macro{\doignore{ma}}% +} + +% @set VAR sets the variable VAR to an empty value. +% @set VAR REST-OF-LINE sets VAR to the value REST-OF-LINE. +% +% Since we want to separate VAR from REST-OF-LINE (which might be +% empty), we can't just use \parsearg; we have to insert a space of our +% own to delimit the rest of the line, and then take it out again if we +% didn't need it. Make sure the catcode of space is correct to avoid +% losing inside @example, for instance. +% +\def\set{\begingroup\catcode` =10 + \catcode`\-=12 \catcode`\_=12 % Allow - and _ in VAR. + \parsearg\setxxx} +\def\setxxx#1{\setyyy#1 \endsetyyy} +\def\setyyy#1 #2\endsetyyy{% + \def\temp{#2}% + \ifx\temp\empty \global\expandafter\let\csname SET#1\endcsname = \empty + \else \setzzz{#1}#2\endsetzzz % Remove the trailing space \setxxx inserted. + \fi + \endgroup +} +% Can't use \xdef to pre-expand #2 and save some time, since \temp or +% \next or other control sequences that we've defined might get us into +% an infinite loop. Consider `@set foo @cite{bar}'. +\def\setzzz#1#2 \endsetzzz{\expandafter\gdef\csname SET#1\endcsname{#2}} + +% @clear VAR clears (i.e., unsets) the variable VAR. +% +\def\clear{\parsearg\clearxxx} +\def\clearxxx#1{\global\expandafter\let\csname SET#1\endcsname=\relax} + +% @value{foo} gets the text saved in variable foo. +{ + \catcode`\_ = \active + % + % We might end up with active _ or - characters in the argument if + % we're called from @code, as @code{@value{foo-bar_}}. So \let any + % such active characters to their normal equivalents. + \gdef\value{\begingroup + \catcode`\-=12 \catcode`\_=12 + \indexbreaks \let_\normalunderscore + \valuexxx} +} +\def\valuexxx#1{\expandablevalue{#1}\endgroup} + +% We have this subroutine so that we can handle at least some @value's +% properly in indexes (we \let\value to this in \indexdummies). Ones +% whose names contain - or _ still won't work, but we can't do anything +% about that. The command has to be fully expandable, since the result +% winds up in the index file. This means that if the variable's value +% contains other Texinfo commands, it's almost certain it will fail +% (although perhaps we could fix that with sufficient work to do a +% one-level expansion on the result, instead of complete). +% +\def\expandablevalue#1{% + \expandafter\ifx\csname SET#1\endcsname\relax + {[No value for ``#1'']}% + \else + \csname SET#1\endcsname + \fi +} + +% @ifset VAR ... @end ifset reads the `...' iff VAR has been defined +% with @set. +% +\def\ifset{\parsearg\ifsetxxx} +\def\ifsetxxx #1{% + \expandafter\ifx\csname SET#1\endcsname\relax + \expandafter\ifsetfail + \else + \expandafter\ifsetsucceed + \fi +} +\def\ifsetsucceed{\conditionalsucceed{ifset}} +\def\ifsetfail{\nestedignore{ifset}} +\defineunmatchedend{ifset} + +% @ifclear VAR ... @end ifclear reads the `...' iff VAR has never been +% defined with @set, or has been undefined with @clear. +% +\def\ifclear{\parsearg\ifclearxxx} +\def\ifclearxxx #1{% + \expandafter\ifx\csname SET#1\endcsname\relax + \expandafter\ifclearsucceed + \else + \expandafter\ifclearfail + \fi +} +\def\ifclearsucceed{\conditionalsucceed{ifclear}} +\def\ifclearfail{\nestedignore{ifclear}} +\defineunmatchedend{ifclear} + +% @iftex, @ifnothtml, @ifnotinfo always succeed; we read the text +% following, through the first @end iftex (etc.). Make `@end iftex' +% (etc.) valid only after an @iftex. +% +\def\iftex{\conditionalsucceed{iftex}} +\def\ifnothtml{\conditionalsucceed{ifnothtml}} +\def\ifnotinfo{\conditionalsucceed{ifnotinfo}} +\defineunmatchedend{iftex} +\defineunmatchedend{ifnothtml} +\defineunmatchedend{ifnotinfo} + +% We can't just want to start a group at @iftex (for example) and end it +% at @end iftex, since then @set commands inside the conditional have no +% effect (they'd get reverted at the end of the group). So we must +% define \Eiftex to redefine itself to be its previous value. (We can't +% just define it to fail again with an ``unmatched end'' error, since +% the @ifset might be nested.) +% +\def\conditionalsucceed#1{% + \edef\temp{% + % Remember the current value of \E#1. + \let\nece{prevE#1} = \nece{E#1}% + % + % At the `@end #1', redefine \E#1 to be its previous value. + \def\nece{E#1}{\let\nece{E#1} = \nece{prevE#1}}% + }% + \temp +} + +% We need to expand lots of \csname's, but we don't want to expand the +% control sequences after we've constructed them. +% +\def\nece#1{\expandafter\noexpand\csname#1\endcsname} + +% @defininfoenclose. +\let\definfoenclose=\comment + + +\message{indexing,} +% Index generation facilities + +% Define \newwrite to be identical to plain tex's \newwrite +% except not \outer, so it can be used within \newindex. +{\catcode`\@=11 +\gdef\newwrite{\alloc@7\write\chardef\sixt@@n}} + +% \newindex {foo} defines an index named foo. +% It automatically defines \fooindex such that +% \fooindex ...rest of line... puts an entry in the index foo. +% It also defines \fooindfile to be the number of the output channel for +% the file that accumulates this index. The file's extension is foo. +% The name of an index should be no more than 2 characters long +% for the sake of vms. +% +\def\newindex#1{% + \iflinks + \expandafter\newwrite \csname#1indfile\endcsname + \openout \csname#1indfile\endcsname \jobname.#1 % Open the file + \fi + \expandafter\xdef\csname#1index\endcsname{% % Define @#1index + \noexpand\doindex{#1}} +} + +% @defindex foo == \newindex{foo} +% +\def\defindex{\parsearg\newindex} + +% Define @defcodeindex, like @defindex except put all entries in @code. +% +\def\defcodeindex{\parsearg\newcodeindex} +% +\def\newcodeindex#1{% + \iflinks + \expandafter\newwrite \csname#1indfile\endcsname + \openout \csname#1indfile\endcsname \jobname.#1 + \fi + \expandafter\xdef\csname#1index\endcsname{% + \noexpand\docodeindex{#1}}% +} + + +% @synindex foo bar makes index foo feed into index bar. +% Do this instead of @defindex foo if you don't want it as a separate index. +% +% @syncodeindex foo bar similar, but put all entries made for index foo +% inside @code. +% +\def\synindex#1 #2 {\dosynindex\doindex{#1}{#2}} +\def\syncodeindex#1 #2 {\dosynindex\docodeindex{#1}{#2}} + +% #1 is \doindex or \docodeindex, #2 the index getting redefined (foo), +% #3 the target index (bar). +\def\dosynindex#1#2#3{% + % Only do \closeout if we haven't already done it, else we'll end up + % closing the target index. + \expandafter \ifx\csname donesynindex#2\endcsname \undefined + % The \closeout helps reduce unnecessary open files; the limit on the + % Acorn RISC OS is a mere 16 files. + \expandafter\closeout\csname#2indfile\endcsname + \expandafter\let\csname\donesynindex#2\endcsname = 1 + \fi + % redefine \fooindfile: + \expandafter\let\expandafter\temp\expandafter=\csname#3indfile\endcsname + \expandafter\let\csname#2indfile\endcsname=\temp + % redefine \fooindex: + \expandafter\xdef\csname#2index\endcsname{\noexpand#1{#3}}% +} + +% Define \doindex, the driver for all \fooindex macros. +% Argument #1 is generated by the calling \fooindex macro, +% and it is "foo", the name of the index. + +% \doindex just uses \parsearg; it calls \doind for the actual work. +% This is because \doind is more useful to call from other macros. + +% There is also \dosubind {index}{topic}{subtopic} +% which makes an entry in a two-level index such as the operation index. + +\def\doindex#1{\edef\indexname{#1}\parsearg\singleindexer} +\def\singleindexer #1{\doind{\indexname}{#1}} + +% like the previous two, but they put @code around the argument. +\def\docodeindex#1{\edef\indexname{#1}\parsearg\singlecodeindexer} +\def\singlecodeindexer #1{\doind{\indexname}{\code{#1}}} + +\def\indexdummies{% +\def\ { }% +% Take care of the plain tex accent commands. +\def\"{\realbackslash "}% +\def\`{\realbackslash `}% +\def\'{\realbackslash '}% +\def\^{\realbackslash ^}% +\def\~{\realbackslash ~}% +\def\={\realbackslash =}% +\def\b{\realbackslash b}% +\def\c{\realbackslash c}% +\def\d{\realbackslash d}% +\def\u{\realbackslash u}% +\def\v{\realbackslash v}% +\def\H{\realbackslash H}% +% Take care of the plain tex special European modified letters. +\def\oe{\realbackslash oe}% +\def\ae{\realbackslash ae}% +\def\aa{\realbackslash aa}% +\def\OE{\realbackslash OE}% +\def\AE{\realbackslash AE}% +\def\AA{\realbackslash AA}% +\def\o{\realbackslash o}% +\def\O{\realbackslash O}% +\def\l{\realbackslash l}% +\def\L{\realbackslash L}% +\def\ss{\realbackslash ss}% +% Take care of texinfo commands likely to appear in an index entry. +% (Must be a way to avoid doing expansion at all, and thus not have to +% laboriously list every single command here.) +\def\@{@}% will be @@ when we switch to @ as escape char. +% Need these in case \tex is in effect and \{ is a \delimiter again. +% But can't use \lbracecmd and \rbracecmd because texindex assumes +% braces and backslashes are used only as delimiters. +\let\{ = \mylbrace +\let\} = \myrbrace +\def\_{{\realbackslash _}}% +\def\w{\realbackslash w }% +\def\bf{\realbackslash bf }% +%\def\rm{\realbackslash rm }% +\def\sl{\realbackslash sl }% +\def\sf{\realbackslash sf}% +\def\tt{\realbackslash tt}% +\def\gtr{\realbackslash gtr}% +\def\less{\realbackslash less}% +\def\hat{\realbackslash hat}% +\def\TeX{\realbackslash TeX}% +\def\dots{\realbackslash dots }% +\def\result{\realbackslash result}% +\def\equiv{\realbackslash equiv}% +\def\expansion{\realbackslash expansion}% +\def\print{\realbackslash print}% +\def\error{\realbackslash error}% +\def\point{\realbackslash point}% +\def\copyright{\realbackslash copyright}% +\def\tclose##1{\realbackslash tclose {##1}}% +\def\code##1{\realbackslash code {##1}}% +\def\uref##1{\realbackslash uref {##1}}% +\def\url##1{\realbackslash url {##1}}% +\def\env##1{\realbackslash env {##1}}% +\def\command##1{\realbackslash command {##1}}% +\def\option##1{\realbackslash option {##1}}% +\def\dotless##1{\realbackslash dotless {##1}}% +\def\samp##1{\realbackslash samp {##1}}% +\def\,##1{\realbackslash ,{##1}}% +\def\t##1{\realbackslash t {##1}}% +\def\r##1{\realbackslash r {##1}}% +\def\i##1{\realbackslash i {##1}}% +\def\b##1{\realbackslash b {##1}}% +\def\sc##1{\realbackslash sc {##1}}% +\def\cite##1{\realbackslash cite {##1}}% +\def\key##1{\realbackslash key {##1}}% +\def\file##1{\realbackslash file {##1}}% +\def\var##1{\realbackslash var {##1}}% +\def\kbd##1{\realbackslash kbd {##1}}% +\def\dfn##1{\realbackslash dfn {##1}}% +\def\emph##1{\realbackslash emph {##1}}% +\def\acronym##1{\realbackslash acronym {##1}}% +% +% Handle some cases of @value -- where the variable name does not +% contain - or _, and the value does not contain any +% (non-fully-expandable) commands. +\let\value = \expandablevalue +% +\unsepspaces +% Turn off macro expansion +\turnoffmacros +} + +% If an index command is used in an @example environment, any spaces +% therein should become regular spaces in the raw index file, not the +% expansion of \tie (\\leavevmode \penalty \@M \ ). +{\obeyspaces + \gdef\unsepspaces{\obeyspaces\let =\space}} + +% \indexnofonts no-ops all font-change commands. +% This is used when outputting the strings to sort the index by. +\def\indexdummyfont#1{#1} +\def\indexdummytex{TeX} +\def\indexdummydots{...} + +\def\indexnofonts{% +% Just ignore accents. +\let\,=\indexdummyfont +\let\"=\indexdummyfont +\let\`=\indexdummyfont +\let\'=\indexdummyfont +\let\^=\indexdummyfont +\let\~=\indexdummyfont +\let\==\indexdummyfont +\let\b=\indexdummyfont +\let\c=\indexdummyfont +\let\d=\indexdummyfont +\let\u=\indexdummyfont +\let\v=\indexdummyfont +\let\H=\indexdummyfont +\let\dotless=\indexdummyfont +% Take care of the plain tex special European modified letters. +\def\oe{oe}% +\def\ae{ae}% +\def\aa{aa}% +\def\OE{OE}% +\def\AE{AE}% +\def\AA{AA}% +\def\o{o}% +\def\O{O}% +\def\l{l}% +\def\L{L}% +\def\ss{ss}% +\let\w=\indexdummyfont +\let\t=\indexdummyfont +\let\r=\indexdummyfont +\let\i=\indexdummyfont +\let\b=\indexdummyfont +\let\emph=\indexdummyfont +\let\strong=\indexdummyfont +\let\cite=\indexdummyfont +\let\sc=\indexdummyfont +%Don't no-op \tt, since it isn't a user-level command +% and is used in the definitions of the active chars like <, >, |... +%\let\tt=\indexdummyfont +\let\tclose=\indexdummyfont +\let\code=\indexdummyfont +\let\url=\indexdummyfont +\let\uref=\indexdummyfont +\let\env=\indexdummyfont +\let\acronym=\indexdummyfont +\let\command=\indexdummyfont +\let\option=\indexdummyfont +\let\file=\indexdummyfont +\let\samp=\indexdummyfont +\let\kbd=\indexdummyfont +\let\key=\indexdummyfont +\let\var=\indexdummyfont +\let\TeX=\indexdummytex +\let\dots=\indexdummydots +\def\@{@}% +} + +% To define \realbackslash, we must make \ not be an escape. +% We must first make another character (@) an escape +% so we do not become unable to do a definition. + +{\catcode`\@=0 \catcode`\\=\other + @gdef@realbackslash{\}} + +\let\indexbackslash=0 %overridden during \printindex. +\let\SETmarginindex=\relax % put index entries in margin (undocumented)? + +% For \ifx comparisons. +\def\emptymacro{\empty} + +% Most index entries go through here, but \dosubind is the general case. +% +\def\doind#1#2{\dosubind{#1}{#2}\empty} + +% Workhorse for all \fooindexes. +% #1 is name of index, #2 is stuff to put there, #3 is subentry -- +% \empty if called from \doind, as we usually are. The main exception +% is with defuns, which call us directly. +% +\def\dosubind#1#2#3{% + % Put the index entry in the margin if desired. + \ifx\SETmarginindex\relax\else + \insert\margin{\hbox{\vrule height8pt depth3pt width0pt #2}}% + \fi + {% + \count255=\lastpenalty + {% + \indexdummies % Must do this here, since \bf, etc expand at this stage + \escapechar=`\\ + {% + \let\folio = 0% We will expand all macros now EXCEPT \folio. + \def\rawbackslashxx{\indexbackslash}% \indexbackslash isn't defined now + % so it will be output as is; and it will print as backslash. + % + \def\thirdarg{#3}% + % + % If third arg is present, precede it with space in sort key. + \ifx\thirdarg\emptymacro + \let\subentry = \empty + \else + \def\subentry{ #3}% + \fi + % + % First process the index entry with all font commands turned + % off to get the string to sort by. + {\indexnofonts \xdef\indexsorttmp{#2\subentry}}% + % + % Now the real index entry with the fonts. + \toks0 = {#2}% + % + % If third (subentry) arg is present, add it to the index + % string. And include a space. + \ifx\thirdarg\emptymacro \else + \toks0 = \expandafter{\the\toks0 \space #3}% + \fi + % + % Set up the complete index entry, with both the sort key + % and the original text, including any font commands. We write + % three arguments to \entry to the .?? file, texindex reduces to + % two when writing the .??s sorted result. + \edef\temp{% + \write\csname#1indfile\endcsname{% + \realbackslash entry{\indexsorttmp}{\folio}{\the\toks0}}% + }% + % + % If a skip is the last thing on the list now, preserve it + % by backing up by \lastskip, doing the \write, then inserting + % the skip again. Otherwise, the whatsit generated by the + % \write will make \lastskip zero. The result is that sequences + % like this: + % @end defun + % @tindex whatever + % @defun ... + % will have extra space inserted, because the \medbreak in the + % start of the @defun won't see the skip inserted by the @end of + % the previous defun. + % + % But don't do any of this if we're not in vertical mode. We + % don't want to do a \vskip and prematurely end a paragraph. + % + % Avoid page breaks due to these extra skips, too. + % + \iflinks + \ifvmode + \skip0 = \lastskip + \ifdim\lastskip = 0pt \else \nobreak\vskip-\lastskip \fi + \fi + % + \temp % do the write + % + % + \ifvmode \ifdim\skip0 = 0pt \else \nobreak\vskip\skip0 \fi \fi + \fi + }% + }% + \penalty\count255 + }% +} + +% The index entry written in the file actually looks like +% \entry {sortstring}{page}{topic} +% or +% \entry {sortstring}{page}{topic}{subtopic} +% The texindex program reads in these files and writes files +% containing these kinds of lines: +% \initial {c} +% before the first topic whose initial is c +% \entry {topic}{pagelist} +% for a topic that is used without subtopics +% \primary {topic} +% for the beginning of a topic that is used with subtopics +% \secondary {subtopic}{pagelist} +% for each subtopic. + +% Define the user-accessible indexing commands +% @findex, @vindex, @kindex, @cindex. + +\def\findex {\fnindex} +\def\kindex {\kyindex} +\def\cindex {\cpindex} +\def\vindex {\vrindex} +\def\tindex {\tpindex} +\def\pindex {\pgindex} + +\def\cindexsub {\begingroup\obeylines\cindexsub} +{\obeylines % +\gdef\cindexsub "#1" #2^^M{\endgroup % +\dosubind{cp}{#2}{#1}}} + +% Define the macros used in formatting output of the sorted index material. + +% @printindex causes a particular index (the ??s file) to get printed. +% It does not print any chapter heading (usually an @unnumbered). +% +\def\printindex{\parsearg\doprintindex} +\def\doprintindex#1{\begingroup + \dobreak \chapheadingskip{10000}% + % + \smallfonts \rm + \tolerance = 9500 + \indexbreaks + % + % See if the index file exists and is nonempty. + % Change catcode of @ here so that if the index file contains + % \initial {@} + % as its first line, TeX doesn't complain about mismatched braces + % (because it thinks @} is a control sequence). + \catcode`\@ = 11 + \openin 1 \jobname.#1s + \ifeof 1 + % \enddoublecolumns gets confused if there is no text in the index, + % and it loses the chapter title and the aux file entries for the + % index. The easiest way to prevent this problem is to make sure + % there is some text. + \putwordIndexNonexistent + \else + % + % If the index file exists but is empty, then \openin leaves \ifeof + % false. We have to make TeX try to read something from the file, so + % it can discover if there is anything in it. + \read 1 to \temp + \ifeof 1 + \putwordIndexIsEmpty + \else + % Index files are almost Texinfo source, but we use \ as the escape + % character. It would be better to use @, but that's too big a change + % to make right now. + \def\indexbackslash{\rawbackslashxx}% + \catcode`\\ = 0 + \escapechar = `\\ + \begindoublecolumns + \input \jobname.#1s + \enddoublecolumns + \fi + \fi + \closein 1 +\endgroup} + +% These macros are used by the sorted index file itself. +% Change them to control the appearance of the index. + +\def\initial#1{{% + % Some minor font changes for the special characters. + \let\tentt=\sectt \let\tt=\sectt \let\sf=\sectt + % + % Remove any glue we may have, we'll be inserting our own. + \removelastskip + % + % We like breaks before the index initials, so insert a bonus. + \penalty -300 + % + % Typeset the initial. Making this add up to a whole number of + % baselineskips increases the chance of the dots lining up from column + % to column. It still won't often be perfect, because of the stretch + % we need before each entry, but it's better. + % + % No shrink because it confuses \balancecolumns. + \vskip 1.67\baselineskip plus .5\baselineskip + \leftline{\secbf #1}% + \vskip .33\baselineskip plus .1\baselineskip + % + % Do our best not to break after the initial. + \nobreak +}} + +% This typesets a paragraph consisting of #1, dot leaders, and then #2 +% flush to the right margin. It is used for index and table of contents +% entries. The paragraph is indented by \leftskip. +% +\def\entry#1#2{\begingroup + % + % Start a new paragraph if necessary, so our assignments below can't + % affect previous text. + \par + % + % Do not fill out the last line with white space. + \parfillskip = 0in + % + % No extra space above this paragraph. + \parskip = 0in + % + % Do not prefer a separate line ending with a hyphen to fewer lines. + \finalhyphendemerits = 0 + % + % \hangindent is only relevant when the entry text and page number + % don't both fit on one line. In that case, bob suggests starting the + % dots pretty far over on the line. Unfortunately, a large + % indentation looks wrong when the entry text itself is broken across + % lines. So we use a small indentation and put up with long leaders. + % + % \hangafter is reset to 1 (which is the value we want) at the start + % of each paragraph, so we need not do anything with that. + \hangindent = 2em + % + % When the entry text needs to be broken, just fill out the first line + % with blank space. + \rightskip = 0pt plus1fil + % + % A bit of stretch before each entry for the benefit of balancing columns. + \vskip 0pt plus1pt + % + % Start a ``paragraph'' for the index entry so the line breaking + % parameters we've set above will have an effect. + \noindent + % + % Insert the text of the index entry. TeX will do line-breaking on it. + #1% + % The following is kludged to not output a line of dots in the index if + % there are no page numbers. The next person who breaks this will be + % cursed by a Unix daemon. + \def\tempa{{\rm }}% + \def\tempb{#2}% + \edef\tempc{\tempa}% + \edef\tempd{\tempb}% + \ifx\tempc\tempd\ \else% + % + % If we must, put the page number on a line of its own, and fill out + % this line with blank space. (The \hfil is overwhelmed with the + % fill leaders glue in \indexdotfill if the page number does fit.) + \hfil\penalty50 + \null\nobreak\indexdotfill % Have leaders before the page number. + % + % The `\ ' here is removed by the implicit \unskip that TeX does as + % part of (the primitive) \par. Without it, a spurious underfull + % \hbox ensues. + \ifpdf + \pdfgettoks#2.\ \the\toksA % The page number ends the paragraph. + \else + \ #2% The page number ends the paragraph. + \fi + \fi% + \par +\endgroup} + +% Like \dotfill except takes at least 1 em. +\def\indexdotfill{\cleaders + \hbox{$\mathsurround=0pt \mkern1.5mu ${\it .}$ \mkern1.5mu$}\hskip 1em plus 1fill} + +\def\primary #1{\line{#1\hfil}} + +\newskip\secondaryindent \secondaryindent=0.5cm + +\def\secondary #1#2{ +{\parfillskip=0in \parskip=0in +\hangindent =1in \hangafter=1 +\noindent\hskip\secondaryindent\hbox{#1}\indexdotfill #2\par +}} + +% Define two-column mode, which we use to typeset indexes. +% Adapted from the TeXbook, page 416, which is to say, +% the manmac.tex format used to print the TeXbook itself. +\catcode`\@=11 + +\newbox\partialpage +\newdimen\doublecolumnhsize + +\def\begindoublecolumns{\begingroup % ended by \enddoublecolumns + % Grab any single-column material above us. + \output = {% + % + % Here is a possibility not foreseen in manmac: if we accumulate a + % whole lot of material, we might end up calling this \output + % routine twice in a row (see the doublecol-lose test, which is + % essentially a couple of indexes with @setchapternewpage off). In + % that case we just ship out what is in \partialpage with the normal + % output routine. Generally, \partialpage will be empty when this + % runs and this will be a no-op. See the indexspread.tex test case. + \ifvoid\partialpage \else + \onepageout{\pagecontents\partialpage}% + \fi + % + \global\setbox\partialpage = \vbox{% + % Unvbox the main output page. + \unvbox\PAGE + \kern-\topskip \kern\baselineskip + }% + }% + \eject % run that output routine to set \partialpage + % + % Use the double-column output routine for subsequent pages. + \output = {\doublecolumnout}% + % + % Change the page size parameters. We could do this once outside this + % routine, in each of @smallbook, @afourpaper, and the default 8.5x11 + % format, but then we repeat the same computation. Repeating a couple + % of assignments once per index is clearly meaningless for the + % execution time, so we may as well do it in one place. + % + % First we halve the line length, less a little for the gutter between + % the columns. We compute the gutter based on the line length, so it + % changes automatically with the paper format. The magic constant + % below is chosen so that the gutter has the same value (well, +-<1pt) + % as it did when we hard-coded it. + % + % We put the result in a separate register, \doublecolumhsize, so we + % can restore it in \pagesofar, after \hsize itself has (potentially) + % been clobbered. + % + \doublecolumnhsize = \hsize + \advance\doublecolumnhsize by -.04154\hsize + \divide\doublecolumnhsize by 2 + \hsize = \doublecolumnhsize + % + % Double the \vsize as well. (We don't need a separate register here, + % since nobody clobbers \vsize.) + \vsize = 2\vsize +} + +% The double-column output routine for all double-column pages except +% the last. +% +\def\doublecolumnout{% + \splittopskip=\topskip \splitmaxdepth=\maxdepth + % Get the available space for the double columns -- the normal + % (undoubled) page height minus any material left over from the + % previous page. + \dimen@ = \vsize + \divide\dimen@ by 2 + \advance\dimen@ by -\ht\partialpage + % + % box0 will be the left-hand column, box2 the right. + \setbox0=\vsplit255 to\dimen@ \setbox2=\vsplit255 to\dimen@ + \onepageout\pagesofar + \unvbox255 + \penalty\outputpenalty +} +% +% Re-output the contents of the output page -- any previous material, +% followed by the two boxes we just split, in box0 and box2. +\def\pagesofar{% + \unvbox\partialpage + % + \hsize = \doublecolumnhsize + \wd0=\hsize \wd2=\hsize + \hbox to\pagewidth{\box0\hfil\box2}% +} +% +% All done with double columns. +\def\enddoublecolumns{% + \output = {% + % Split the last of the double-column material. Leave it on the + % current page, no automatic page break. + \balancecolumns + % + % If we end up splitting too much material for the current page, + % though, there will be another page break right after this \output + % invocation ends. Having called \balancecolumns once, we do not + % want to call it again. Therefore, reset \output to its normal + % definition right away. (We hope \balancecolumns will never be + % called on to balance too much material, but if it is, this makes + % the output somewhat more palatable.) + \global\output = {\onepageout{\pagecontents\PAGE}}% + }% + \eject + \endgroup % started in \begindoublecolumns + % + % \pagegoal was set to the doubled \vsize above, since we restarted + % the current page. We're now back to normal single-column + % typesetting, so reset \pagegoal to the normal \vsize (after the + % \endgroup where \vsize got restored). + \pagegoal = \vsize +} +% +% Called at the end of the double column material. +\def\balancecolumns{% + \setbox0 = \vbox{\unvbox255}% like \box255 but more efficient, see p.120. + \dimen@ = \ht0 + \advance\dimen@ by \topskip + \advance\dimen@ by-\baselineskip + \divide\dimen@ by 2 % target to split to + %debug\message{final 2-column material height=\the\ht0, target=\the\dimen@.}% + \splittopskip = \topskip + % Loop until we get a decent breakpoint. + {% + \vbadness = 10000 + \loop + \global\setbox3 = \copy0 + \global\setbox1 = \vsplit3 to \dimen@ + \ifdim\ht3>\dimen@ + \global\advance\dimen@ by 1pt + \repeat + }% + %debug\message{split to \the\dimen@, column heights: \the\ht1, \the\ht3.}% + \setbox0=\vbox to\dimen@{\unvbox1}% + \setbox2=\vbox to\dimen@{\unvbox3}% + % + \pagesofar +} +\catcode`\@ = \other + + +\message{sectioning,} +% Chapters, sections, etc. + +\newcount\chapno +\newcount\secno \secno=0 +\newcount\subsecno \subsecno=0 +\newcount\subsubsecno \subsubsecno=0 + +% This counter is funny since it counts through charcodes of letters A, B, ... +\newcount\appendixno \appendixno = `\@ +% \def\appendixletter{\char\the\appendixno} +% We do the following for the sake of pdftex, which needs the actual +% letter in the expansion, not just typeset. +\def\appendixletter{% + \ifnum\appendixno=`A A% + \else\ifnum\appendixno=`B B% + \else\ifnum\appendixno=`C C% + \else\ifnum\appendixno=`D D% + \else\ifnum\appendixno=`E E% + \else\ifnum\appendixno=`F F% + \else\ifnum\appendixno=`G G% + \else\ifnum\appendixno=`H H% + \else\ifnum\appendixno=`I I% + \else\ifnum\appendixno=`J J% + \else\ifnum\appendixno=`K K% + \else\ifnum\appendixno=`L L% + \else\ifnum\appendixno=`M M% + \else\ifnum\appendixno=`N N% + \else\ifnum\appendixno=`O O% + \else\ifnum\appendixno=`P P% + \else\ifnum\appendixno=`Q Q% + \else\ifnum\appendixno=`R R% + \else\ifnum\appendixno=`S S% + \else\ifnum\appendixno=`T T% + \else\ifnum\appendixno=`U U% + \else\ifnum\appendixno=`V V% + \else\ifnum\appendixno=`W W% + \else\ifnum\appendixno=`X X% + \else\ifnum\appendixno=`Y Y% + \else\ifnum\appendixno=`Z Z% + % The \the is necessary, despite appearances, because \appendixletter is + % expanded while writing the .toc file. \char\appendixno is not + % expandable, thus it is written literally, thus all appendixes come out + % with the same letter (or @) in the toc without it. + \else\char\the\appendixno + \fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi + \fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi} + +% Each @chapter defines this as the name of the chapter. +% page headings and footings can use it. @section does likewise. +\def\thischapter{} +\def\thissection{} + +\newcount\absseclevel % used to calculate proper heading level +\newcount\secbase\secbase=0 % @raise/lowersections modify this count + +% @raisesections: treat @section as chapter, @subsection as section, etc. +\def\raisesections{\global\advance\secbase by -1} +\let\up=\raisesections % original BFox name + +% @lowersections: treat @chapter as section, @section as subsection, etc. +\def\lowersections{\global\advance\secbase by 1} +\let\down=\lowersections % original BFox name + +% Choose a numbered-heading macro +% #1 is heading level if unmodified by @raisesections or @lowersections +% #2 is text for heading +\def\numhead#1#2{\absseclevel=\secbase\advance\absseclevel by #1 +\ifcase\absseclevel + \chapterzzz{#2} +\or + \seczzz{#2} +\or + \numberedsubseczzz{#2} +\or + \numberedsubsubseczzz{#2} +\else + \ifnum \absseclevel<0 + \chapterzzz{#2} + \else + \numberedsubsubseczzz{#2} + \fi +\fi +} + +% like \numhead, but chooses appendix heading levels +\def\apphead#1#2{\absseclevel=\secbase\advance\absseclevel by #1 +\ifcase\absseclevel + \appendixzzz{#2} +\or + \appendixsectionzzz{#2} +\or + \appendixsubseczzz{#2} +\or + \appendixsubsubseczzz{#2} +\else + \ifnum \absseclevel<0 + \appendixzzz{#2} + \else + \appendixsubsubseczzz{#2} + \fi +\fi +} + +% like \numhead, but chooses numberless heading levels +\def\unnmhead#1#2{\absseclevel=\secbase\advance\absseclevel by #1 +\ifcase\absseclevel + \unnumberedzzz{#2} +\or + \unnumberedseczzz{#2} +\or + \unnumberedsubseczzz{#2} +\or + \unnumberedsubsubseczzz{#2} +\else + \ifnum \absseclevel<0 + \unnumberedzzz{#2} + \else + \unnumberedsubsubseczzz{#2} + \fi +\fi +} + +% @chapter, @appendix, @unnumbered. +\def\thischaptername{No Chapter Title} +\outer\def\chapter{\parsearg\chapteryyy} +\def\chapteryyy #1{\numhead0{#1}} % normally numhead0 calls chapterzzz +\def\chapterzzz #1{% +\secno=0 \subsecno=0 \subsubsecno=0 +\global\advance \chapno by 1 \message{\putwordChapter\space \the\chapno}% +\chapmacro {#1}{\the\chapno}% +\gdef\thissection{#1}% +\gdef\thischaptername{#1}% +% We don't substitute the actual chapter name into \thischapter +% because we don't want its macros evaluated now. +\xdef\thischapter{\putwordChapter{} \the\chapno: \noexpand\thischaptername}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash chapentry{\the\toks0}% + {\the\chapno}}}% +\temp +\donoderef +\global\let\section = \numberedsec +\global\let\subsection = \numberedsubsec +\global\let\subsubsection = \numberedsubsubsec +} + +\outer\def\appendix{\parsearg\appendixyyy} +\def\appendixyyy #1{\apphead0{#1}} % normally apphead0 calls appendixzzz +\def\appendixzzz #1{% +\secno=0 \subsecno=0 \subsubsecno=0 +\global\advance \appendixno by 1 +\message{\putwordAppendix\space \appendixletter}% +\chapmacro {#1}{\putwordAppendix{} \appendixletter}% +\gdef\thissection{#1}% +\gdef\thischaptername{#1}% +\xdef\thischapter{\putwordAppendix{} \appendixletter: \noexpand\thischaptername}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash chapentry{\the\toks0}% + {\putwordAppendix{} \appendixletter}}}% +\temp +\appendixnoderef +\global\let\section = \appendixsec +\global\let\subsection = \appendixsubsec +\global\let\subsubsection = \appendixsubsubsec +} + +% @centerchap is like @unnumbered, but the heading is centered. +\outer\def\centerchap{\parsearg\centerchapyyy} +\def\centerchapyyy #1{{\let\unnumbchapmacro=\centerchapmacro \unnumberedyyy{#1}}} + +% @top is like @unnumbered. +\outer\def\top{\parsearg\unnumberedyyy} + +\outer\def\unnumbered{\parsearg\unnumberedyyy} +\def\unnumberedyyy #1{\unnmhead0{#1}} % normally unnmhead0 calls unnumberedzzz +\def\unnumberedzzz #1{% +\secno=0 \subsecno=0 \subsubsecno=0 +% +% This used to be simply \message{#1}, but TeX fully expands the +% argument to \message. Therefore, if #1 contained @-commands, TeX +% expanded them. For example, in `@unnumbered The @cite{Book}', TeX +% expanded @cite (which turns out to cause errors because \cite is meant +% to be executed, not expanded). +% +% Anyway, we don't want the fully-expanded definition of @cite to appear +% as a result of the \message, we just want `@cite' itself. We use +% \the to achieve this: TeX expands \the only once, +% simply yielding the contents of . (We also do this for +% the toc entries.) +\toks0 = {#1}\message{(\the\toks0)}% +% +\unnumbchapmacro {#1}% +\gdef\thischapter{#1}\gdef\thissection{#1}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash unnumbchapentry{\the\toks0}}}% +\temp +\unnumbnoderef +\global\let\section = \unnumberedsec +\global\let\subsection = \unnumberedsubsec +\global\let\subsubsection = \unnumberedsubsubsec +} + +% Sections. +\outer\def\numberedsec{\parsearg\secyyy} +\def\secyyy #1{\numhead1{#1}} % normally calls seczzz +\def\seczzz #1{% +\subsecno=0 \subsubsecno=0 \global\advance \secno by 1 % +\gdef\thissection{#1}\secheading {#1}{\the\chapno}{\the\secno}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash secentry{\the\toks0}% + {\the\chapno}{\the\secno}}}% +\temp +\donoderef +\nobreak +} + +\outer\def\appendixsection{\parsearg\appendixsecyyy} +\outer\def\appendixsec{\parsearg\appendixsecyyy} +\def\appendixsecyyy #1{\apphead1{#1}} % normally calls appendixsectionzzz +\def\appendixsectionzzz #1{% +\subsecno=0 \subsubsecno=0 \global\advance \secno by 1 % +\gdef\thissection{#1}\secheading {#1}{\appendixletter}{\the\secno}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash secentry{\the\toks0}% + {\appendixletter}{\the\secno}}}% +\temp +\appendixnoderef +\nobreak +} + +\outer\def\unnumberedsec{\parsearg\unnumberedsecyyy} +\def\unnumberedsecyyy #1{\unnmhead1{#1}} % normally calls unnumberedseczzz +\def\unnumberedseczzz #1{% +\plainsecheading {#1}\gdef\thissection{#1}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash unnumbsecentry{\the\toks0}}}% +\temp +\unnumbnoderef +\nobreak +} + +% Subsections. +\outer\def\numberedsubsec{\parsearg\numberedsubsecyyy} +\def\numberedsubsecyyy #1{\numhead2{#1}} % normally calls numberedsubseczzz +\def\numberedsubseczzz #1{% +\gdef\thissection{#1}\subsubsecno=0 \global\advance \subsecno by 1 % +\subsecheading {#1}{\the\chapno}{\the\secno}{\the\subsecno}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash subsecentry{\the\toks0}% + {\the\chapno}{\the\secno}{\the\subsecno}}}% +\temp +\donoderef +\nobreak +} + +\outer\def\appendixsubsec{\parsearg\appendixsubsecyyy} +\def\appendixsubsecyyy #1{\apphead2{#1}} % normally calls appendixsubseczzz +\def\appendixsubseczzz #1{% +\gdef\thissection{#1}\subsubsecno=0 \global\advance \subsecno by 1 % +\subsecheading {#1}{\appendixletter}{\the\secno}{\the\subsecno}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash subsecentry{\the\toks0}% + {\appendixletter}{\the\secno}{\the\subsecno}}}% +\temp +\appendixnoderef +\nobreak +} + +\outer\def\unnumberedsubsec{\parsearg\unnumberedsubsecyyy} +\def\unnumberedsubsecyyy #1{\unnmhead2{#1}} %normally calls unnumberedsubseczzz +\def\unnumberedsubseczzz #1{% +\plainsubsecheading {#1}\gdef\thissection{#1}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash unnumbsubsecentry% + {\the\toks0}}}% +\temp +\unnumbnoderef +\nobreak +} + +% Subsubsections. +\outer\def\numberedsubsubsec{\parsearg\numberedsubsubsecyyy} +\def\numberedsubsubsecyyy #1{\numhead3{#1}} % normally numberedsubsubseczzz +\def\numberedsubsubseczzz #1{% +\gdef\thissection{#1}\global\advance \subsubsecno by 1 % +\subsubsecheading {#1} + {\the\chapno}{\the\secno}{\the\subsecno}{\the\subsubsecno}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash subsubsecentry{\the\toks0}% + {\the\chapno}{\the\secno}{\the\subsecno}{\the\subsubsecno}}}% +\temp +\donoderef +\nobreak +} + +\outer\def\appendixsubsubsec{\parsearg\appendixsubsubsecyyy} +\def\appendixsubsubsecyyy #1{\apphead3{#1}} % normally appendixsubsubseczzz +\def\appendixsubsubseczzz #1{% +\gdef\thissection{#1}\global\advance \subsubsecno by 1 % +\subsubsecheading {#1} + {\appendixletter}{\the\secno}{\the\subsecno}{\the\subsubsecno}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash subsubsecentry{\the\toks0}% + {\appendixletter}{\the\secno}{\the\subsecno}{\the\subsubsecno}}}% +\temp +\appendixnoderef +\nobreak +} + +\outer\def\unnumberedsubsubsec{\parsearg\unnumberedsubsubsecyyy} +\def\unnumberedsubsubsecyyy #1{\unnmhead3{#1}} %normally unnumberedsubsubseczzz +\def\unnumberedsubsubseczzz #1{% +\plainsubsubsecheading {#1}\gdef\thissection{#1}% +\toks0 = {#1}% +\edef\temp{\noexpand\writetocentry{\realbackslash unnumbsubsubsecentry% + {\the\toks0}}}% +\temp +\unnumbnoderef +\nobreak +} + +% These are variants which are not "outer", so they can appear in @ifinfo. +% Actually, they should now be obsolete; ordinary section commands should work. +\def\infotop{\parsearg\unnumberedzzz} +\def\infounnumbered{\parsearg\unnumberedzzz} +\def\infounnumberedsec{\parsearg\unnumberedseczzz} +\def\infounnumberedsubsec{\parsearg\unnumberedsubseczzz} +\def\infounnumberedsubsubsec{\parsearg\unnumberedsubsubseczzz} + +\def\infoappendix{\parsearg\appendixzzz} +\def\infoappendixsec{\parsearg\appendixseczzz} +\def\infoappendixsubsec{\parsearg\appendixsubseczzz} +\def\infoappendixsubsubsec{\parsearg\appendixsubsubseczzz} + +\def\infochapter{\parsearg\chapterzzz} +\def\infosection{\parsearg\sectionzzz} +\def\infosubsection{\parsearg\subsectionzzz} +\def\infosubsubsection{\parsearg\subsubsectionzzz} + +% These macros control what the section commands do, according +% to what kind of chapter we are in (ordinary, appendix, or unnumbered). +% Define them by default for a numbered chapter. +\global\let\section = \numberedsec +\global\let\subsection = \numberedsubsec +\global\let\subsubsection = \numberedsubsubsec + +% Define @majorheading, @heading and @subheading + +% NOTE on use of \vbox for chapter headings, section headings, and such: +% 1) We use \vbox rather than the earlier \line to permit +% overlong headings to fold. +% 2) \hyphenpenalty is set to 10000 because hyphenation in a +% heading is obnoxious; this forbids it. +% 3) Likewise, headings look best if no \parindent is used, and +% if justification is not attempted. Hence \raggedright. + + +\def\majorheading{\parsearg\majorheadingzzz} +\def\majorheadingzzz #1{% +{\advance\chapheadingskip by 10pt \chapbreak }% +{\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 + \parindent=0pt\raggedright + \rm #1\hfill}}\bigskip \par\penalty 200} + +\def\chapheading{\parsearg\chapheadingzzz} +\def\chapheadingzzz #1{\chapbreak % +{\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 + \parindent=0pt\raggedright + \rm #1\hfill}}\bigskip \par\penalty 200} + +% @heading, @subheading, @subsubheading. +\def\heading{\parsearg\plainsecheading} +\def\subheading{\parsearg\plainsubsecheading} +\def\subsubheading{\parsearg\plainsubsubsecheading} + +% These macros generate a chapter, section, etc. heading only +% (including whitespace, linebreaking, etc. around it), +% given all the information in convenient, parsed form. + +%%% Args are the skip and penalty (usually negative) +\def\dobreak#1#2{\par\ifdim\lastskip<#1\removelastskip\penalty#2\vskip#1\fi} + +\def\setchapterstyle #1 {\csname CHAPF#1\endcsname} + +%%% Define plain chapter starts, and page on/off switching for it +% Parameter controlling skip before chapter headings (if needed) + +\newskip\chapheadingskip + +\def\chapbreak{\dobreak \chapheadingskip {-4000}} +\def\chappager{\par\vfill\supereject} +\def\chapoddpage{\chappager \ifodd\pageno \else \hbox to 0pt{} \chappager\fi} + +\def\setchapternewpage #1 {\csname CHAPPAG#1\endcsname} + +\def\CHAPPAGoff{% +\global\let\contentsalignmacro = \chappager +\global\let\pchapsepmacro=\chapbreak +\global\let\pagealignmacro=\chappager} + +\def\CHAPPAGon{% +\global\let\contentsalignmacro = \chappager +\global\let\pchapsepmacro=\chappager +\global\let\pagealignmacro=\chappager +\global\def\HEADINGSon{\HEADINGSsingle}} + +\def\CHAPPAGodd{ +\global\let\contentsalignmacro = \chapoddpage +\global\let\pchapsepmacro=\chapoddpage +\global\let\pagealignmacro=\chapoddpage +\global\def\HEADINGSon{\HEADINGSdouble}} + +\CHAPPAGon + +\def\CHAPFplain{ +\global\let\chapmacro=\chfplain +\global\let\unnumbchapmacro=\unnchfplain +\global\let\centerchapmacro=\centerchfplain} + +% Plain chapter opening. +% #1 is the text, #2 the chapter number or empty if unnumbered. +\def\chfplain#1#2{% + \pchapsepmacro + {% + \chapfonts \rm + \def\chapnum{#2}% + \setbox0 = \hbox{#2\ifx\chapnum\empty\else\enspace\fi}% + \vbox{\hyphenpenalty=10000 \tolerance=5000 \parindent=0pt \raggedright + \hangindent = \wd0 \centerparametersmaybe + \unhbox0 #1\par}% + }% + \nobreak\bigskip % no page break after a chapter title + \nobreak +} + +% Plain opening for unnumbered. +\def\unnchfplain#1{\chfplain{#1}{}} + +% @centerchap -- centered and unnumbered. +\let\centerparametersmaybe = \relax +\def\centerchfplain#1{{% + \def\centerparametersmaybe{% + \advance\rightskip by 3\rightskip + \leftskip = \rightskip + \parfillskip = 0pt + }% + \chfplain{#1}{}% +}} + +\CHAPFplain % The default + +\def\unnchfopen #1{% +\chapoddpage {\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 + \parindent=0pt\raggedright + \rm #1\hfill}}\bigskip \par\nobreak +} + +\def\chfopen #1#2{\chapoddpage {\chapfonts +\vbox to 3in{\vfil \hbox to\hsize{\hfil #2} \hbox to\hsize{\hfil #1} \vfil}}% +\par\penalty 5000 % +} + +\def\centerchfopen #1{% +\chapoddpage {\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 + \parindent=0pt + \hfill {\rm #1}\hfill}}\bigskip \par\nobreak +} + +\def\CHAPFopen{ +\global\let\chapmacro=\chfopen +\global\let\unnumbchapmacro=\unnchfopen +\global\let\centerchapmacro=\centerchfopen} + + +% Section titles. +\newskip\secheadingskip +\def\secheadingbreak{\dobreak \secheadingskip {-1000}} +\def\secheading#1#2#3{\sectionheading{sec}{#2.#3}{#1}} +\def\plainsecheading#1{\sectionheading{sec}{}{#1}} + +% Subsection titles. +\newskip \subsecheadingskip +\def\subsecheadingbreak{\dobreak \subsecheadingskip {-500}} +\def\subsecheading#1#2#3#4{\sectionheading{subsec}{#2.#3.#4}{#1}} +\def\plainsubsecheading#1{\sectionheading{subsec}{}{#1}} + +% Subsubsection titles. +\let\subsubsecheadingskip = \subsecheadingskip +\let\subsubsecheadingbreak = \subsecheadingbreak +\def\subsubsecheading#1#2#3#4#5{\sectionheading{subsubsec}{#2.#3.#4.#5}{#1}} +\def\plainsubsubsecheading#1{\sectionheading{subsubsec}{}{#1}} + + +% Print any size section title. +% +% #1 is the section type (sec/subsec/subsubsec), #2 is the section +% number (maybe empty), #3 the text. +\def\sectionheading#1#2#3{% + {% + \expandafter\advance\csname #1headingskip\endcsname by \parskip + \csname #1headingbreak\endcsname + }% + {% + % Switch to the right set of fonts. + \csname #1fonts\endcsname \rm + % + % Only insert the separating space if we have a section number. + \def\secnum{#2}% + \setbox0 = \hbox{#2\ifx\secnum\empty\else\enspace\fi}% + % + \vbox{\hyphenpenalty=10000 \tolerance=5000 \parindent=0pt \raggedright + \hangindent = \wd0 % zero if no section number + \unhbox0 #3}% + }% + \ifdim\parskip<10pt \nobreak\kern10pt\nobreak\kern-\parskip\fi \nobreak +} + + +\message{toc,} +% Table of contents. +\newwrite\tocfile + +% Write an entry to the toc file, opening it if necessary. +% Called from @chapter, etc. We supply {\folio} at the end of the +% argument, which will end up as the last argument to the \...entry macro. +% +% We open the .toc file here instead of at @setfilename or any other +% given time so that @contents can be put in the document anywhere. +% +\newif\iftocfileopened +\def\writetocentry#1{% + \iftocfileopened\else + \immediate\openout\tocfile = \jobname.toc + \global\tocfileopenedtrue + \fi + \iflinks \write\tocfile{#1{\folio}}\fi +} + +\newskip\contentsrightmargin \contentsrightmargin=1in +\newcount\savepageno +\newcount\lastnegativepageno \lastnegativepageno = -1 + +% Finish up the main text and prepare to read what we've written +% to \tocfile. +% +\def\startcontents#1{% + % If @setchapternewpage on, and @headings double, the contents should + % start on an odd page, unlike chapters. Thus, we maintain + % \contentsalignmacro in parallel with \pagealignmacro. + % From: Torbjorn Granlund + \contentsalignmacro + \immediate\closeout\tocfile + % + % Don't need to put `Contents' or `Short Contents' in the headline. + % It is abundantly clear what they are. + \unnumbchapmacro{#1}\def\thischapter{}% + \savepageno = \pageno + \begingroup % Set up to handle contents files properly. + \catcode`\\=0 \catcode`\{=1 \catcode`\}=2 \catcode`\@=11 + % We can't do this, because then an actual ^ in a section + % title fails, e.g., @chapter ^ -- exponentiation. --karl, 9jul97. + %\catcode`\^=7 % to see ^^e4 as \"a etc. juha@piuha.ydi.vtt.fi + \raggedbottom % Worry more about breakpoints than the bottom. + \advance\hsize by -\contentsrightmargin % Don't use the full line length. + % + % Roman numerals for page numbers. + \ifnum \pageno>0 \pageno = \lastnegativepageno \fi +} + + +% Normal (long) toc. +\def\contents{% + \startcontents{\putwordTOC}% + \openin 1 \jobname.toc + \ifeof 1 \else + \closein 1 + \input \jobname.toc + \fi + \vfill \eject + \contentsalignmacro % in case @setchapternewpage odd is in effect + \pdfmakeoutlines + \endgroup + \lastnegativepageno = \pageno + \pageno = \savepageno +} + +% And just the chapters. +\def\summarycontents{% + \startcontents{\putwordShortTOC}% + % + \let\chapentry = \shortchapentry + \let\unnumbchapentry = \shortunnumberedentry + % We want a true roman here for the page numbers. + \secfonts + \let\rm=\shortcontrm \let\bf=\shortcontbf \let\sl=\shortcontsl + \rm + \hyphenpenalty = 10000 + \advance\baselineskip by 1pt % Open it up a little. + \def\secentry ##1##2##3##4{} + \def\unnumbsecentry ##1##2{} + \def\subsecentry ##1##2##3##4##5{} + \def\unnumbsubsecentry ##1##2{} + \def\subsubsecentry ##1##2##3##4##5##6{} + \def\unnumbsubsubsecentry ##1##2{} + \openin 1 \jobname.toc + \ifeof 1 \else + \closein 1 + \input \jobname.toc + \fi + \vfill \eject + \contentsalignmacro % in case @setchapternewpage odd is in effect + \endgroup + \lastnegativepageno = \pageno + \pageno = \savepageno +} +\let\shortcontents = \summarycontents + +\ifpdf + \pdfcatalog{/PageMode /UseOutlines}% +\fi + +% These macros generate individual entries in the table of contents. +% The first argument is the chapter or section name. +% The last argument is the page number. +% The arguments in between are the chapter number, section number, ... + +% Chapter-level things, for both the long and short contents. +\def\chapentry#1#2#3{\dochapentry{#2\labelspace#1}{#3}} + +% See comments in \dochapentry re vbox and related settings +\def\shortchapentry#1#2#3{% + \tocentry{\shortchaplabel{#2}\labelspace #1}{\doshortpageno\bgroup#3\egroup}% +} + +% Typeset the label for a chapter or appendix for the short contents. +% The arg is, e.g. `Appendix A' for an appendix, or `3' for a chapter. +% We could simplify the code here by writing out an \appendixentry +% command in the toc file for appendices, instead of using \chapentry +% for both, but it doesn't seem worth it. +% +\newdimen\shortappendixwidth +% +\def\shortchaplabel#1{% + % Compute width of word "Appendix", may change with language. + \setbox0 = \hbox{\shortcontrm \putwordAppendix}% + \shortappendixwidth = \wd0 + % + % We typeset #1 in a box of constant width, regardless of the text of + % #1, so the chapter titles will come out aligned. + \setbox0 = \hbox{#1}% + \dimen0 = \ifdim\wd0 > \shortappendixwidth \shortappendixwidth \else 0pt \fi + % + % This space should be plenty, since a single number is .5em, and the + % widest letter (M) is 1em, at least in the Computer Modern fonts. + % (This space doesn't include the extra space that gets added after + % the label; that gets put in by \shortchapentry above.) + \advance\dimen0 by 1.1em + \hbox to \dimen0{#1\hfil}% +} + +\def\unnumbchapentry#1#2{\dochapentry{#1}{#2}} +\def\shortunnumberedentry#1#2{\tocentry{#1}{\doshortpageno\bgroup#2\egroup}} + +% Sections. +\def\secentry#1#2#3#4{\dosecentry{#2.#3\labelspace#1}{#4}} +\def\unnumbsecentry#1#2{\dosecentry{#1}{#2}} + +% Subsections. +\def\subsecentry#1#2#3#4#5{\dosubsecentry{#2.#3.#4\labelspace#1}{#5}} +\def\unnumbsubsecentry#1#2{\dosubsecentry{#1}{#2}} + +% And subsubsections. +\def\subsubsecentry#1#2#3#4#5#6{% + \dosubsubsecentry{#2.#3.#4.#5\labelspace#1}{#6}} +\def\unnumbsubsubsecentry#1#2{\dosubsubsecentry{#1}{#2}} + +% This parameter controls the indentation of the various levels. +\newdimen\tocindent \tocindent = 3pc + +% Now for the actual typesetting. In all these, #1 is the text and #2 is the +% page number. +% +% If the toc has to be broken over pages, we want it to be at chapters +% if at all possible; hence the \penalty. +\def\dochapentry#1#2{% + \penalty-300 \vskip1\baselineskip plus.33\baselineskip minus.25\baselineskip + \begingroup + \chapentryfonts + \tocentry{#1}{\dopageno\bgroup#2\egroup}% + \endgroup + \nobreak\vskip .25\baselineskip plus.1\baselineskip +} + +\def\dosecentry#1#2{\begingroup + \secentryfonts \leftskip=\tocindent + \tocentry{#1}{\dopageno\bgroup#2\egroup}% +\endgroup} + +\def\dosubsecentry#1#2{\begingroup + \subsecentryfonts \leftskip=2\tocindent + \tocentry{#1}{\dopageno\bgroup#2\egroup}% +\endgroup} + +\def\dosubsubsecentry#1#2{\begingroup + \subsubsecentryfonts \leftskip=3\tocindent + \tocentry{#1}{\dopageno\bgroup#2\egroup}% +\endgroup} + +% Final typesetting of a toc entry; we use the same \entry macro as for +% the index entries, but we want to suppress hyphenation here. (We +% can't do that in the \entry macro, since index entries might consist +% of hyphenated-identifiers-that-do-not-fit-on-a-line-and-nothing-else.) +\def\tocentry#1#2{\begingroup + \vskip 0pt plus1pt % allow a little stretch for the sake of nice page breaks + % Do not use \turnoffactive in these arguments. Since the toc is + % typeset in cmr, so characters such as _ would come out wrong; we + % have to do the usual translation tricks. + \entry{#1}{#2}% +\endgroup} + +% Space between chapter (or whatever) number and the title. +\def\labelspace{\hskip1em \relax} + +\def\dopageno#1{{\rm #1}} +\def\doshortpageno#1{{\rm #1}} + +\def\chapentryfonts{\secfonts \rm} +\def\secentryfonts{\textfonts} +\let\subsecentryfonts = \textfonts +\let\subsubsecentryfonts = \textfonts + + +\message{environments,} +% @foo ... @end foo. + +% Since these characters are used in examples, it should be an even number of +% \tt widths. Each \tt character is 1en, so two makes it 1em. +% Furthermore, these definitions must come after we define our fonts. +\newbox\dblarrowbox \newbox\longdblarrowbox +\newbox\pushcharbox \newbox\bullbox +\newbox\equivbox \newbox\errorbox + +%{\tentt +%\global\setbox\dblarrowbox = \hbox to 1em{\hfil$\Rightarrow$\hfil} +%\global\setbox\longdblarrowbox = \hbox to 1em{\hfil$\mapsto$\hfil} +%\global\setbox\pushcharbox = \hbox to 1em{\hfil$\dashv$\hfil} +%\global\setbox\equivbox = \hbox to 1em{\hfil$\ptexequiv$\hfil} +% Adapted from the manmac format (p.420 of TeXbook) +%\global\setbox\bullbox = \hbox to 1em{\kern.15em\vrule height .75ex width .85ex +% depth .1ex\hfil} +%} + +% @point{}, @result{}, @expansion{}, @print{}, @equiv{}. +\def\point{$\star$} +\def\result{\leavevmode\raise.15ex\hbox to 1em{\hfil$\Rightarrow$\hfil}} +\def\expansion{\leavevmode\raise.1ex\hbox to 1em{\hfil$\mapsto$\hfil}} +\def\print{\leavevmode\lower.1ex\hbox to 1em{\hfil$\dashv$\hfil}} +\def\equiv{\leavevmode\lower.1ex\hbox to 1em{\hfil$\ptexequiv$\hfil}} + +% Adapted from the TeXbook's \boxit. +{\tentt \global\dimen0 = 3em}% Width of the box. +\dimen2 = .55pt % Thickness of rules +% The text. (`r' is open on the right, `e' somewhat less so on the left.) +\setbox0 = \hbox{\kern-.75pt \tensf error\kern-1.5pt} + +\global\setbox\errorbox=\hbox to \dimen0{\hfil + \hsize = \dimen0 \advance\hsize by -5.8pt % Space to left+right. + \advance\hsize by -2\dimen2 % Rules. + \vbox{ + \hrule height\dimen2 + \hbox{\vrule width\dimen2 \kern3pt % Space to left of text. + \vtop{\kern2.4pt \box0 \kern2.4pt}% Space above/below. + \kern3pt\vrule width\dimen2}% Space to right. + \hrule height\dimen2} + \hfil} + +% The @error{} command. +\def\error{\leavevmode\lower.7ex\copy\errorbox} + +% @tex ... @end tex escapes into raw Tex temporarily. +% One exception: @ is still an escape character, so that @end tex works. +% But \@ or @@ will get a plain tex @ character. + +\def\tex{\begingroup + \catcode `\\=0 \catcode `\{=1 \catcode `\}=2 + \catcode `\$=3 \catcode `\&=4 \catcode `\#=6 + \catcode `\^=7 \catcode `\_=8 \catcode `\~=13 \let~=\tie + \catcode `\%=14 + \catcode 43=12 % plus + \catcode`\"=12 + \catcode`\==12 + \catcode`\|=12 + \catcode`\<=12 + \catcode`\>=12 + \escapechar=`\\ + % + \let\b=\ptexb + \let\bullet=\ptexbullet + \let\c=\ptexc + \let\,=\ptexcomma + \let\.=\ptexdot + \let\dots=\ptexdots + \let\equiv=\ptexequiv + \let\!=\ptexexclam + \let\i=\ptexi + \let\{=\ptexlbrace + \let\+=\tabalign + \let\}=\ptexrbrace + \let\*=\ptexstar + \let\t=\ptext + % + \def\endldots{\mathinner{\ldots\ldots\ldots\ldots}}% + \def\enddots{\relax\ifmmode\endldots\else$\mathsurround=0pt \endldots\,$\fi}% + \def\@{@}% +\let\Etex=\endgroup} + +% Define @lisp ... @endlisp. +% @lisp does a \begingroup so it can rebind things, +% including the definition of @endlisp (which normally is erroneous). + +% Amount to narrow the margins by for @lisp. +\newskip\lispnarrowing \lispnarrowing=0.4in + +% This is the definition that ^^M gets inside @lisp, @example, and other +% such environments. \null is better than a space, since it doesn't +% have any width. +\def\lisppar{\null\endgraf} + +% Make each space character in the input produce a normal interword +% space in the output. Don't allow a line break at this space, as this +% is used only in environments like @example, where each line of input +% should produce a line of output anyway. +% +{\obeyspaces % +\gdef\sepspaces{\obeyspaces\let =\tie}} + +% Define \obeyedspace to be our active space, whatever it is. This is +% for use in \parsearg. +{\sepspaces% +\global\let\obeyedspace= } + +% This space is always present above and below environments. +\newskip\envskipamount \envskipamount = 0pt + +% Make spacing and below environment symmetrical. We use \parskip here +% to help in doing that, since in @example-like environments \parskip +% is reset to zero; thus the \afterenvbreak inserts no space -- but the +% start of the next paragraph will insert \parskip +% +\def\aboveenvbreak{{\advance\envskipamount by \parskip +\endgraf \ifdim\lastskip<\envskipamount +\removelastskip \penalty-50 \vskip\envskipamount \fi}} + +\let\afterenvbreak = \aboveenvbreak + +% \nonarrowing is a flag. If "set", @lisp etc don't narrow margins. +\let\nonarrowing=\relax + +% @cartouche ... @end cartouche: draw rectangle w/rounded corners around +% environment contents. +\font\circle=lcircle10 +\newdimen\circthick +\newdimen\cartouter\newdimen\cartinner +\newskip\normbskip\newskip\normpskip\newskip\normlskip +\circthick=\fontdimen8\circle +% +\def\ctl{{\circle\char'013\hskip -6pt}}% 6pt from pl file: 1/2charwidth +\def\ctr{{\hskip 6pt\circle\char'010}} +\def\cbl{{\circle\char'012\hskip -6pt}} +\def\cbr{{\hskip 6pt\circle\char'011}} +\def\carttop{\hbox to \cartouter{\hskip\lskip + \ctl\leaders\hrule height\circthick\hfil\ctr + \hskip\rskip}} +\def\cartbot{\hbox to \cartouter{\hskip\lskip + \cbl\leaders\hrule height\circthick\hfil\cbr + \hskip\rskip}} +% +\newskip\lskip\newskip\rskip + +\long\def\cartouche{% +\begingroup + \lskip=\leftskip \rskip=\rightskip + \leftskip=0pt\rightskip=0pt %we want these *outside*. + \cartinner=\hsize \advance\cartinner by-\lskip + \advance\cartinner by-\rskip + \cartouter=\hsize + \advance\cartouter by 18.4pt % allow for 3pt kerns on either +% side, and for 6pt waste from +% each corner char, and rule thickness + \normbskip=\baselineskip \normpskip=\parskip \normlskip=\lineskip + % Flag to tell @lisp, etc., not to narrow margin. + \let\nonarrowing=\comment + \vbox\bgroup + \baselineskip=0pt\parskip=0pt\lineskip=0pt + \carttop + \hbox\bgroup + \hskip\lskip + \vrule\kern3pt + \vbox\bgroup + \hsize=\cartinner + \kern3pt + \begingroup + \baselineskip=\normbskip + \lineskip=\normlskip + \parskip=\normpskip + \vskip -\parskip +\def\Ecartouche{% + \endgroup + \kern3pt + \egroup + \kern3pt\vrule + \hskip\rskip + \egroup + \cartbot + \egroup +\endgroup +}} + + +% This macro is called at the beginning of all the @example variants, +% inside a group. +\def\nonfillstart{% + \aboveenvbreak + \inENV % This group ends at the end of the body + \hfuzz = 12pt % Don't be fussy + \sepspaces % Make spaces be word-separators rather than space tokens. + \singlespace + \let\par = \lisppar % don't ignore blank lines + \obeylines % each line of input is a line of output + \parskip = 0pt + \parindent = 0pt + \emergencystretch = 0pt % don't try to avoid overfull boxes + % @cartouche defines \nonarrowing to inhibit narrowing + % at next level down. + \ifx\nonarrowing\relax + \advance \leftskip by \lispnarrowing + \exdentamount=\lispnarrowing + \let\exdent=\nofillexdent + \let\nonarrowing=\relax + \fi +} + +% Define the \E... control sequence only if we are inside the particular +% environment, so the error checking in \end will work. +% +% To end an @example-like environment, we first end the paragraph (via +% \afterenvbreak's vertical glue), and then the group. That way we keep +% the zero \parskip that the environments set -- \parskip glue will be +% inserted at the beginning of the next paragraph in the document, after +% the environment. +% +\def\nonfillfinish{\afterenvbreak\endgroup} + +% @lisp: indented, narrowed, typewriter font. +\def\lisp{\begingroup + \nonfillstart + \let\Elisp = \nonfillfinish + \tt + \let\kbdfont = \kbdexamplefont % Allow @kbd to do something special. + \gobble % eat return +} + +% @example: Same as @lisp. +\def\example{\begingroup \def\Eexample{\nonfillfinish\endgroup}\lisp} + +% @small... is usually equivalent to the non-small (@smallbook +% redefines). We must call \example (or whatever) last in the +% definition, since it reads the return following the @example (or +% whatever) command. +% +% This actually allows (for example) @end display inside an +% @smalldisplay. Too bad, but makeinfo will catch the error anyway. +% +\def\smalldisplay{\begingroup\def\Esmalldisplay{\nonfillfinish\endgroup}\display} +\def\smallexample{\begingroup\def\Esmallexample{\nonfillfinish\endgroup}\lisp} +\def\smallformat{\begingroup\def\Esmallformat{\nonfillfinish\endgroup}\format} +\def\smalllisp{\begingroup\def\Esmalllisp{\nonfillfinish\endgroup}\lisp} + +% Real @smallexample and @smalllisp (when @smallbook): use smaller fonts. +% Originally contributed by Pavel@xerox. +\def\smalllispx{\begingroup + \def\Esmalllisp{\nonfillfinish\endgroup}% + \def\Esmallexample{\nonfillfinish\endgroup}% + \smallfonts + \lisp +} + +% @display: same as @lisp except keep current font. +% +\def\display{\begingroup + \nonfillstart + \let\Edisplay = \nonfillfinish + \gobble +} + +% @smalldisplay (when @smallbook): @display plus smaller fonts. +% +\def\smalldisplayx{\begingroup + \def\Esmalldisplay{\nonfillfinish\endgroup}% + \smallfonts \rm + \display +} + +% @format: same as @display except don't narrow margins. +% +\def\format{\begingroup + \let\nonarrowing = t + \nonfillstart + \let\Eformat = \nonfillfinish + \gobble +} + +% @smallformat (when @smallbook): @format plus smaller fonts. +% +\def\smallformatx{\begingroup + \def\Esmallformat{\nonfillfinish\endgroup}% + \smallfonts \rm + \format +} + +% @flushleft (same as @format). +% +\def\flushleft{\begingroup \def\Eflushleft{\nonfillfinish\endgroup}\format} + +% @flushright. +% +\def\flushright{\begingroup + \let\nonarrowing = t + \nonfillstart + \let\Eflushright = \nonfillfinish + \advance\leftskip by 0pt plus 1fill + \gobble +} + + +% @quotation does normal linebreaking (hence we can't use \nonfillstart) +% and narrows the margins. +% +\def\quotation{% + \begingroup\inENV %This group ends at the end of the @quotation body + {\parskip=0pt \aboveenvbreak}% because \aboveenvbreak inserts \parskip + \singlespace + \parindent=0pt + % We have retained a nonzero parskip for the environment, since we're + % doing normal filling. So to avoid extra space below the environment... + \def\Equotation{\parskip = 0pt \nonfillfinish}% + % + % @cartouche defines \nonarrowing to inhibit narrowing at next level down. + \ifx\nonarrowing\relax + \advance\leftskip by \lispnarrowing + \advance\rightskip by \lispnarrowing + \exdentamount = \lispnarrowing + \let\nonarrowing = \relax + \fi +} + + +% LaTeX-like @verbatim...@end verbatim and @verb{...} +% If we want to allow any as delimiter, +% we need the curly braces so that makeinfo sees the @verb command, eg: +% `@verbx...x' would look like the '@verbx' command. --janneke@gnu.org +% +% [Knuth]: Donald Ervin Knuth, 1996. The TeXbook. +% +% [Knuth] p. 344; only we need to do '@' too +\def\dospecials{% + \do\ \do\\\do\@\do\{\do\}\do\$\do\&% + \do\#\do\^\do\^^K\do\_\do\^^A\do\%\do\~} +% +% [Knuth] p. 380 +\def\uncatcodespecials{% + \def\do##1{\catcode`##1=12}\dospecials} +% +% [Knuth] pp. 380,381,391 +% Disable Spanish ligatures ?` and !` of \tt font +\begingroup + \catcode`\`=\active\gdef`{\relax\lq} +\endgroup +% +% Setup for the @verb command. +% +% Eight spaces for a tab +\begingroup + \catcode`\^^I=\active + \gdef\tabeightspaces{\catcode`\^^I=\active\def^^I{\ \ \ \ \ \ \ \ }} +\endgroup +% +\def\setupverb{% + \tt % easiest (and conventionally used) font for verbatim + \def\par{\leavevmode\endgraf}% + \catcode`\`=\active + \tabeightspaces + % Respect line breaks, + % print special symbols as themselves, and + % make each space count + % must do in this order: + \obeylines \uncatcodespecials \sepspaces +} + +% Setup for the @verbatim environment +% +% Real tab expansion +\newdimen\tabw \setbox0=\hbox{\tt\space} \tabw=8\wd0 % tab amount +% +\def\starttabbox{\setbox0=\hbox\bgroup} +\begingroup + \catcode`\^^I=\active + \gdef\tabexpand{% + \catcode`\^^I=\active + \def^^I{\leavevmode\egroup + \dimen0=\wd0 % the width so far, or since the previous tab + \divide\dimen0 by\tabw + \multiply\dimen0 by\tabw % compute previous multiple of \tabw + \advance\dimen0 by\tabw % advance to next multiple of \tabw + \wd0=\dimen0 \box0 \starttabbox + }% + } +\endgroup +\def\setupverbatim{% + % Easiest (and conventionally used) font for verbatim + \tt + \def\par{\leavevmode\egroup\box0\endgraf}% + \catcode`\`=\active + \tabexpand + % Respect line breaks, + % print special symbols as themselves, and + % make each space count + % must do in this order: + \obeylines \uncatcodespecials \sepspaces + \everypar{\starttabbox}% +} + +% Do the @verb magic: verbatim text is quoted by unique +% delimiter characters. Before first delimiter expect a +% right brace, after last delimiter expect closing brace: +% +% \def\doverb'{'#1'}'{#1} +% +% [Knuth] p. 382; only eat outer {} +\begingroup + \catcode`[=1\catcode`]=2\catcode`\{=12\catcode`\}=12 + \gdef\doverb{#1[\def\next##1#1}[##1\endgroup]\next] +\endgroup +% +\def\verb{\begingroup\setupverb\doverb} +% +% +% Do the @verbatim magic: define the macro \doverbatim so that +% the (first) argument ends when '@end verbatim' is reached, ie: +% +% \def\doverbatim#1@end verbatim{#1} +% +% For Texinfo it's a lot easier than for LaTeX, +% because texinfo's \verbatim doesn't stop at '\end{verbatim}': +% we need not redefine '\', '{' and '}' +% +% Inspired by LaTeX's verbatim command set [latex.ltx] +%% Include LaTeX hack for completeness -- never know +%% \begingroup +%% \catcode`|=0 \catcode`[=1 +%% \catcode`]=2\catcode`\{=12\catcode`\}=12\catcode`\ =\active +%% \catcode`\\=12|gdef|doverbatim#1@end verbatim[ +%% #1|endgroup|def|Everbatim[]|end[verbatim]] +%% |endgroup +\begingroup + \catcode`\ =\active + \gdef\doverbatim#1@end verbatim{#1\end{verbatim}} +\endgroup +% +\def\verbatim{% + \def\Everbatim{\nonfillfinish\endgroup}% + \begingroup + \nonfillstart + \advance\leftskip by -\defbodyindent + \begingroup\setupverbatim\doverbatim +} + +% @verbatiminclude FILE - insert text of file in verbatim environment. +% +% Allow normal characters that we make active in the argument (a file name). +\def\verbatiminclude{% + \begingroup + \catcode`\\=12 + \catcode`~=12 + \catcode`^=12 + \catcode`_=12 + \catcode`|=12 + \catcode`<=12 + \catcode`>=12 + \catcode`+=12 + \parsearg\doverbatiminclude +} +\def\setupverbatiminclude{% + \begingroup + \nonfillstart + \advance\leftskip by -\defbodyindent + \begingroup\setupverbatim +} +% +\def\doverbatiminclude#1{% + % Restore active chars for included file. + \endgroup + \begingroup + \def\thisfile{#1}% + \expandafter\expandafter\setupverbatiminclude\input\thisfile + \endgroup\nonfillfinish\endgroup +} + + +\message{defuns,} +% @defun etc. + +% Allow user to change definition object font (\df) internally +\def\setdeffont #1 {\csname DEF#1\endcsname} + +\newskip\defbodyindent \defbodyindent=.4in +\newskip\defargsindent \defargsindent=50pt +\newskip\deftypemargin \deftypemargin=12pt +\newskip\deflastargmargin \deflastargmargin=18pt + +\newcount\parencount +% define \functionparens, which makes ( and ) and & do special things. +% \functionparens affects the group it is contained in. +\def\activeparens{% +\catcode`\(=\active \catcode`\)=\active \catcode`\&=\active +\catcode`\[=\active \catcode`\]=\active} + +% Make control sequences which act like normal parenthesis chars. +\let\lparen = ( \let\rparen = ) + +{\activeparens % Now, smart parens don't turn on until &foo (see \amprm) + +% Be sure that we always have a definition for `(', etc. For example, +% if the fn name has parens in it, \boldbrax will not be in effect yet, +% so TeX would otherwise complain about undefined control sequence. +\global\let(=\lparen \global\let)=\rparen +\global\let[=\lbrack \global\let]=\rbrack + +\gdef\functionparens{\boldbrax\let&=\amprm\parencount=0 } +\gdef\boldbrax{\let(=\opnr\let)=\clnr\let[=\lbrb\let]=\rbrb} +% This is used to turn on special parens +% but make & act ordinary (given that it's active). +\gdef\boldbraxnoamp{\let(=\opnr\let)=\clnr\let[=\lbrb\let]=\rbrb\let&=\ampnr} + +% Definitions of (, ) and & used in args for functions. +% This is the definition of ( outside of all parentheses. +\gdef\oprm#1 {{\rm\char`\(}#1 \bf \let(=\opnested + \global\advance\parencount by 1 +} +% +% This is the definition of ( when already inside a level of parens. +\gdef\opnested{\char`\(\global\advance\parencount by 1 } +% +\gdef\clrm{% Print a paren in roman if it is taking us back to depth of 0. + % also in that case restore the outer-level definition of (. + \ifnum \parencount=1 {\rm \char `\)}\sl \let(=\oprm \else \char `\) \fi + \global\advance \parencount by -1 } +% If we encounter &foo, then turn on ()-hacking afterwards +\gdef\amprm#1 {{\rm\}\let(=\oprm \let)=\clrm\ } +% +\gdef\normalparens{\boldbrax\let&=\ampnr} +} % End of definition inside \activeparens +%% These parens (in \boldbrax) actually are a little bolder than the +%% contained text. This is especially needed for [ and ] +\def\opnr{{\sf\char`\(}\global\advance\parencount by 1 } +\def\clnr{{\sf\char`\)}\global\advance\parencount by -1 } +\let\ampnr = \& +\def\lbrb{{\bf\char`\[}} +\def\rbrb{{\bf\char`\]}} + +% Active &'s sneak into the index arguments, so make sure it's defined. +{ + \catcode`& = 13 + \global\let& = \ampnr +} + +% First, defname, which formats the header line itself. +% #1 should be the function name. +% #2 should be the type of definition, such as "Function". + +\def\defname #1#2{% +% Get the values of \leftskip and \rightskip as they were +% outside the @def... +\dimen2=\leftskip +\advance\dimen2 by -\defbodyindent +\noindent +\setbox0=\hbox{\hskip \deflastargmargin{\rm #2}\hskip \deftypemargin}% +\dimen0=\hsize \advance \dimen0 by -\wd0 % compute size for first line +\dimen1=\hsize \advance \dimen1 by -\defargsindent %size for continuations +\parshape 2 0in \dimen0 \defargsindent \dimen1 +% Now output arg 2 ("Function" or some such) +% ending at \deftypemargin from the right margin, +% but stuck inside a box of width 0 so it does not interfere with linebreaking +{% Adjust \hsize to exclude the ambient margins, +% so that \rightline will obey them. +\advance \hsize by -\dimen2 +\rlap{\rightline{{\rm #2}\hskip -1.25pc }}}% +% Make all lines underfull and no complaints: +\tolerance=10000 \hbadness=10000 +\advance\leftskip by -\defbodyindent +\exdentamount=\defbodyindent +{\df #1}\enskip % Generate function name +} + +% Actually process the body of a definition +% #1 should be the terminating control sequence, such as \Edefun. +% #2 should be the "another name" control sequence, such as \defunx. +% #3 should be the control sequence that actually processes the header, +% such as \defunheader. + +\def\defparsebody #1#2#3{\begingroup\inENV% Environment for definitionbody +\medbreak % +% Define the end token that this defining construct specifies +% so that it will exit this group. +\def#1{\endgraf\endgroup\medbreak}% +\def#2{\begingroup\obeylines\activeparens\spacesplit#3}% +\parindent=0in +\advance\leftskip by \defbodyindent +\exdentamount=\defbodyindent +\begingroup % +\catcode 61=\active % 61 is `=' +\obeylines\activeparens\spacesplit#3} + +% #1 is the \E... control sequence to end the definition (which we define). +% #2 is the \...x control sequence for consecutive fns (which we define). +% #3 is the control sequence to call to resume processing. +% #4, delimited by the space, is the class name. +% +\def\defmethparsebody#1#2#3#4 {\begingroup\inENV % +\medbreak % +% Define the end token that this defining construct specifies +% so that it will exit this group. +\def#1{\endgraf\endgroup\medbreak}% +\def#2##1 {\begingroup\obeylines\activeparens\spacesplit{#3{##1}}}% +\parindent=0in +\advance\leftskip by \defbodyindent +\exdentamount=\defbodyindent +\begingroup\obeylines\activeparens\spacesplit{#3{#4}}} + +% Used for @deftypemethod and @deftypeivar. +% #1 is the \E... control sequence to end the definition (which we define). +% #2 is the \...x control sequence for consecutive fns (which we define). +% #3 is the control sequence to call to resume processing. +% #4, delimited by a space, is the class name. +% #5 is the method's return type. +% +\def\deftypemethparsebody#1#2#3#4 #5 {\begingroup\inENV + \medbreak + \def#1{\endgraf\endgroup\medbreak}% + \def#2##1 ##2 {\begingroup\obeylines\activeparens\spacesplit{#3{##1}{##2}}}% + \parindent=0in + \advance\leftskip by \defbodyindent + \exdentamount=\defbodyindent + \begingroup\obeylines\activeparens\spacesplit{#3{#4}{#5}}} + +% Used for @deftypeop. The change from \deftypemethparsebody is an +% extra argument at the beginning which is the `category', instead of it +% being the hardwired string `Method' or `Instance Variable'. We have +% to account for this both in the \...x definition and in parsing the +% input at hand. Thus also need a control sequence (passed as #5) for +% the \E... definition to assign the category name to. +% +\def\deftypeopparsebody#1#2#3#4#5 #6 {\begingroup\inENV + \medbreak + \def#1{\endgraf\endgroup\medbreak}% + \def#2##1 ##2 ##3 {% + \def#4{##1}% + \begingroup\obeylines\activeparens\spacesplit{#3{##2}{##3}}}% + \parindent=0in + \advance\leftskip by \defbodyindent + \exdentamount=\defbodyindent + \begingroup\obeylines\activeparens\spacesplit{#3{#5}{#6}}} + +\def\defopparsebody #1#2#3#4#5 {\begingroup\inENV % +\medbreak % +% Define the end token that this defining construct specifies +% so that it will exit this group. +\def#1{\endgraf\endgroup\medbreak}% +\def#2##1 ##2 {\def#4{##1}% +\begingroup\obeylines\activeparens\spacesplit{#3{##2}}}% +\parindent=0in +\advance\leftskip by \defbodyindent +\exdentamount=\defbodyindent +\begingroup\obeylines\activeparens\spacesplit{#3{#5}}} + +% These parsing functions are similar to the preceding ones +% except that they do not make parens into active characters. +% These are used for "variables" since they have no arguments. + +\def\defvarparsebody #1#2#3{\begingroup\inENV% Environment for definitionbody +\medbreak % +% Define the end token that this defining construct specifies +% so that it will exit this group. +\def#1{\endgraf\endgroup\medbreak}% +\def#2{\begingroup\obeylines\spacesplit#3}% +\parindent=0in +\advance\leftskip by \defbodyindent +\exdentamount=\defbodyindent +\begingroup % +\catcode 61=\active % +\obeylines\spacesplit#3} + +% This is used for \def{tp,vr}parsebody. It could probably be used for +% some of the others, too, with some judicious conditionals. +% +\def\parsebodycommon#1#2#3{% + \begingroup\inENV % + \medbreak % + % Define the end token that this defining construct specifies + % so that it will exit this group. + \def#1{\endgraf\endgroup\medbreak}% + \def#2##1 {\begingroup\obeylines\spacesplit{#3{##1}}}% + \parindent=0in + \advance\leftskip by \defbodyindent + \exdentamount=\defbodyindent + \begingroup\obeylines +} + +\def\defvrparsebody#1#2#3#4 {% + \parsebodycommon{#1}{#2}{#3}% + \spacesplit{#3{#4}}% +} + +% This loses on `@deftp {Data Type} {struct termios}' -- it thinks the +% type is just `struct', because we lose the braces in `{struct +% termios}' when \spacesplit reads its undelimited argument. Sigh. +% \let\deftpparsebody=\defvrparsebody +% +% So, to get around this, we put \empty in with the type name. That +% way, TeX won't find exactly `{...}' as an undelimited argument, and +% won't strip off the braces. +% +\def\deftpparsebody #1#2#3#4 {% + \parsebodycommon{#1}{#2}{#3}% + \spacesplit{\parsetpheaderline{#3{#4}}}\empty +} + +% Fine, but then we have to eventually remove the \empty *and* the +% braces (if any). That's what this does. +% +\def\removeemptybraces\empty#1\relax{#1} + +% After \spacesplit has done its work, this is called -- #1 is the final +% thing to call, #2 the type name (which starts with \empty), and #3 +% (which might be empty) the arguments. +% +\def\parsetpheaderline#1#2#3{% + #1{\removeemptybraces#2\relax}{#3}% +}% + +\def\defopvarparsebody #1#2#3#4#5 {\begingroup\inENV % +\medbreak % +% Define the end token that this defining construct specifies +% so that it will exit this group. +\def#1{\endgraf\endgroup\medbreak}% +\def#2##1 ##2 {\def#4{##1}% +\begingroup\obeylines\spacesplit{#3{##2}}}% +\parindent=0in +\advance\leftskip by \defbodyindent +\exdentamount=\defbodyindent +\begingroup\obeylines\spacesplit{#3{#5}}} + +% Split up #2 at the first space token. +% call #1 with two arguments: +% the first is all of #2 before the space token, +% the second is all of #2 after that space token. +% If #2 contains no space token, all of it is passed as the first arg +% and the second is passed as empty. + +{\obeylines +\gdef\spacesplit#1#2^^M{\endgroup\spacesplitfoo{#1}#2 \relax\spacesplitfoo}% +\long\gdef\spacesplitfoo#1#2 #3#4\spacesplitfoo{% +\ifx\relax #3% +#1{#2}{}\else #1{#2}{#3#4}\fi}} + +% So much for the things common to all kinds of definitions. + +% Define @defun. + +% First, define the processing that is wanted for arguments of \defun +% Use this to expand the args and terminate the paragraph they make up + +\def\defunargs#1{\functionparens \sl +% Expand, preventing hyphenation at `-' chars. +% Note that groups don't affect changes in \hyphenchar. +% Set the font temporarily and use \font in case \setfont made \tensl a macro. +{\tensl\hyphenchar\font=0}% +#1% +{\tensl\hyphenchar\font=45}% +\ifnum\parencount=0 \else \errmessage{Unbalanced parentheses in @def}\fi% +\interlinepenalty=10000 +\advance\rightskip by 0pt plus 1fil +\endgraf\nobreak\vskip -\parskip\nobreak +} + +\def\deftypefunargs #1{% +% Expand, preventing hyphenation at `-' chars. +% Note that groups don't affect changes in \hyphenchar. +% Use \boldbraxnoamp, not \functionparens, so that & is not special. +\boldbraxnoamp +\tclose{#1}% avoid \code because of side effects on active chars +\interlinepenalty=10000 +\advance\rightskip by 0pt plus 1fil +\endgraf\nobreak\vskip -\parskip\nobreak +} + +% Do complete processing of one @defun or @defunx line already parsed. + +% @deffn Command forward-char nchars + +\def\deffn{\defmethparsebody\Edeffn\deffnx\deffnheader} + +\def\deffnheader #1#2#3{\doind {fn}{\code{#2}}% +\begingroup\defname {#2}{#1}\defunargs{#3}\endgroup % +\catcode 61=\other % Turn off change made in \defparsebody +} + +% @defun == @deffn Function + +\def\defun{\defparsebody\Edefun\defunx\defunheader} + +\def\defunheader #1#2{\doind {fn}{\code{#1}}% Make entry in function index +\begingroup\defname {#1}{\putwordDeffunc}% +\defunargs {#2}\endgroup % +\catcode 61=\other % Turn off change made in \defparsebody +} + +% @deftypefun int foobar (int @var{foo}, float @var{bar}) + +\def\deftypefun{\defparsebody\Edeftypefun\deftypefunx\deftypefunheader} + +% #1 is the data type. #2 is the name and args. +\def\deftypefunheader #1#2{\deftypefunheaderx{#1}#2 \relax} +% #1 is the data type, #2 the name, #3 the args. +\def\deftypefunheaderx #1#2 #3\relax{% +\doind {fn}{\code{#2}}% Make entry in function index +\begingroup\defname {\defheaderxcond#1\relax$$$#2}{\putwordDeftypefun}% +\deftypefunargs {#3}\endgroup % +\catcode 61=\other % Turn off change made in \defparsebody +} + +% @deftypefn {Library Function} int foobar (int @var{foo}, float @var{bar}) + +\def\deftypefn{\defmethparsebody\Edeftypefn\deftypefnx\deftypefnheader} + +% \defheaderxcond#1\relax$$$ +% puts #1 in @code, followed by a space, but does nothing if #1 is null. +\def\defheaderxcond#1#2$$${\ifx#1\relax\else\code{#1#2} \fi} + +% #1 is the classification. #2 is the data type. #3 is the name and args. +\def\deftypefnheader #1#2#3{\deftypefnheaderx{#1}{#2}#3 \relax} +% #1 is the classification, #2 the data type, #3 the name, #4 the args. +\def\deftypefnheaderx #1#2#3 #4\relax{% +\doind {fn}{\code{#3}}% Make entry in function index +\begingroup +\normalparens % notably, turn off `&' magic, which prevents +% at least some C++ text from working +\defname {\defheaderxcond#2\relax$$$#3}{#1}% +\deftypefunargs {#4}\endgroup % +\catcode 61=\other % Turn off change made in \defparsebody +} + +% @defmac == @deffn Macro + +\def\defmac{\defparsebody\Edefmac\defmacx\defmacheader} + +\def\defmacheader #1#2{\doind {fn}{\code{#1}}% Make entry in function index +\begingroup\defname {#1}{\putwordDefmac}% +\defunargs {#2}\endgroup % +\catcode 61=\other % Turn off change made in \defparsebody +} + +% @defspec == @deffn Special Form + +\def\defspec{\defparsebody\Edefspec\defspecx\defspecheader} + +\def\defspecheader #1#2{\doind {fn}{\code{#1}}% Make entry in function index +\begingroup\defname {#1}{\putwordDefspec}% +\defunargs {#2}\endgroup % +\catcode 61=\other % Turn off change made in \defparsebody +} + +% @defop CATEGORY CLASS OPERATION ARG... +% +\def\defop #1 {\def\defoptype{#1}% +\defopparsebody\Edefop\defopx\defopheader\defoptype} +% +\def\defopheader#1#2#3{% +\dosubind {fn}{\code{#2}}{\putwordon\ #1}% Make entry in function index +\begingroup\defname {#2}{\defoptype\ \putwordon\ #1}% +\defunargs {#3}\endgroup % +} + +% @deftypeop CATEGORY CLASS TYPE OPERATION ARG... +% +\def\deftypeop #1 {\def\deftypeopcategory{#1}% + \deftypeopparsebody\Edeftypeop\deftypeopx\deftypeopheader + \deftypeopcategory} +% +% #1 is the class name, #2 the data type, #3 the operation name, #4 the args. +\def\deftypeopheader#1#2#3#4{% + \dosubind{fn}{\code{#3}}{\putwordon\ \code{#1}}% entry in function index + \begingroup + \defname{\defheaderxcond#2\relax$$$#3} + {\deftypeopcategory\ \putwordon\ \code{#1}}% + \deftypefunargs{#4}% + \endgroup +} + +% @deftypemethod CLASS TYPE METHOD ARG... +% +\def\deftypemethod{% + \deftypemethparsebody\Edeftypemethod\deftypemethodx\deftypemethodheader} +% +% #1 is the class name, #2 the data type, #3 the method name, #4 the args. +\def\deftypemethodheader#1#2#3#4{% + \dosubind{fn}{\code{#3}}{\putwordon\ \code{#1}}% entry in function index + \begingroup + \defname{\defheaderxcond#2\relax$$$#3}{\putwordMethodon\ \code{#1}}% + \deftypefunargs{#4}% + \endgroup +} + +% @deftypeivar CLASS TYPE VARNAME +% +\def\deftypeivar{% + \deftypemethparsebody\Edeftypeivar\deftypeivarx\deftypeivarheader} +% +% #1 is the class name, #2 the data type, #3 the variable name. +\def\deftypeivarheader#1#2#3{% + \dosubind{vr}{\code{#3}}{\putwordof\ \code{#1}}% entry in variable index + \begingroup + \defname{\defheaderxcond#2\relax$$$#3} + {\putwordInstanceVariableof\ \code{#1}}% + \defvarargs{#3}% + \endgroup +} + +% @defmethod == @defop Method +% +\def\defmethod{\defmethparsebody\Edefmethod\defmethodx\defmethodheader} +% +% #1 is the class name, #2 the method name, #3 the args. +\def\defmethodheader#1#2#3{% + \dosubind{fn}{\code{#2}}{\putwordon\ \code{#1}}% entry in function index + \begingroup + \defname{#2}{\putwordMethodon\ \code{#1}}% + \defunargs{#3}% + \endgroup +} + +% @defcv {Class Option} foo-class foo-flag + +\def\defcv #1 {\def\defcvtype{#1}% +\defopvarparsebody\Edefcv\defcvx\defcvarheader\defcvtype} + +\def\defcvarheader #1#2#3{% +\dosubind {vr}{\code{#2}}{\putwordof\ #1}% Make entry in var index +\begingroup\defname {#2}{\defcvtype\ \putwordof\ #1}% +\defvarargs {#3}\endgroup % +} + +% @defivar CLASS VARNAME == @defcv {Instance Variable} CLASS VARNAME +% +\def\defivar{\defvrparsebody\Edefivar\defivarx\defivarheader} +% +\def\defivarheader#1#2#3{% + \dosubind {vr}{\code{#2}}{\putwordof\ #1}% entry in var index + \begingroup + \defname{#2}{\putwordInstanceVariableof\ #1}% + \defvarargs{#3}% + \endgroup +} + +% @defvar +% First, define the processing that is wanted for arguments of @defvar. +% This is actually simple: just print them in roman. +% This must expand the args and terminate the paragraph they make up +\def\defvarargs #1{\normalparens #1% +\interlinepenalty=10000 +\endgraf\nobreak\vskip -\parskip\nobreak} + +% @defvr Counter foo-count + +\def\defvr{\defvrparsebody\Edefvr\defvrx\defvrheader} + +\def\defvrheader #1#2#3{\doind {vr}{\code{#2}}% +\begingroup\defname {#2}{#1}\defvarargs{#3}\endgroup} + +% @defvar == @defvr Variable + +\def\defvar{\defvarparsebody\Edefvar\defvarx\defvarheader} + +\def\defvarheader #1#2{\doind {vr}{\code{#1}}% Make entry in var index +\begingroup\defname {#1}{\putwordDefvar}% +\defvarargs {#2}\endgroup % +} + +% @defopt == @defvr {User Option} + +\def\defopt{\defvarparsebody\Edefopt\defoptx\defoptheader} + +\def\defoptheader #1#2{\doind {vr}{\code{#1}}% Make entry in var index +\begingroup\defname {#1}{\putwordDefopt}% +\defvarargs {#2}\endgroup % +} + +% @deftypevar int foobar + +\def\deftypevar{\defvarparsebody\Edeftypevar\deftypevarx\deftypevarheader} + +% #1 is the data type. #2 is the name, perhaps followed by text that +% is actually part of the data type, which should not be put into the index. +\def\deftypevarheader #1#2{% +\dovarind#2 \relax% Make entry in variables index +\begingroup\defname {\defheaderxcond#1\relax$$$#2}{\putwordDeftypevar}% +\interlinepenalty=10000 +\endgraf\nobreak\vskip -\parskip\nobreak +\endgroup} +\def\dovarind#1 #2\relax{\doind{vr}{\code{#1}}} + +% @deftypevr {Global Flag} int enable + +\def\deftypevr{\defvrparsebody\Edeftypevr\deftypevrx\deftypevrheader} + +\def\deftypevrheader #1#2#3{\dovarind#3 \relax% +\begingroup\defname {\defheaderxcond#2\relax$$$#3}{#1} +\interlinepenalty=10000 +\endgraf\nobreak\vskip -\parskip\nobreak +\endgroup} + +% Now define @deftp +% Args are printed in bold, a slight difference from @defvar. + +\def\deftpargs #1{\bf \defvarargs{#1}} + +% @deftp Class window height width ... + +\def\deftp{\deftpparsebody\Edeftp\deftpx\deftpheader} + +\def\deftpheader #1#2#3{\doind {tp}{\code{#2}}% +\begingroup\defname {#2}{#1}\deftpargs{#3}\endgroup} + +% These definitions are used if you use @defunx (etc.) +% anywhere other than immediately after a @defun or @defunx. +% +\def\defcvx#1 {\errmessage{@defcvx in invalid context}} +\def\deffnx#1 {\errmessage{@deffnx in invalid context}} +\def\defivarx#1 {\errmessage{@defivarx in invalid context}} +\def\defmacx#1 {\errmessage{@defmacx in invalid context}} +\def\defmethodx#1 {\errmessage{@defmethodx in invalid context}} +\def\defoptx #1 {\errmessage{@defoptx in invalid context}} +\def\defopx#1 {\errmessage{@defopx in invalid context}} +\def\defspecx#1 {\errmessage{@defspecx in invalid context}} +\def\deftpx#1 {\errmessage{@deftpx in invalid context}} +\def\deftypefnx#1 {\errmessage{@deftypefnx in invalid context}} +\def\deftypefunx#1 {\errmessage{@deftypefunx in invalid context}} +\def\deftypeivarx#1 {\errmessage{@deftypeivarx in invalid context}} +\def\deftypemethodx#1 {\errmessage{@deftypemethodx in invalid context}} +\def\deftypeopx#1 {\errmessage{@deftypeopx in invalid context}} +\def\deftypevarx#1 {\errmessage{@deftypevarx in invalid context}} +\def\deftypevrx#1 {\errmessage{@deftypevrx in invalid context}} +\def\defunx#1 {\errmessage{@defunx in invalid context}} +\def\defvarx#1 {\errmessage{@defvarx in invalid context}} +\def\defvrx#1 {\errmessage{@defvrx in invalid context}} + + +\message{macros,} +% @macro. + +% To do this right we need a feature of e-TeX, \scantokens, +% which we arrange to emulate with a temporary file in ordinary TeX. +\ifx\eTeXversion\undefined + \newwrite\macscribble + \def\scanmacro#1{% + \begingroup \newlinechar`\^^M + % Undo catcode changes of \startcontents and \doprintindex + \catcode`\@=0 \catcode`\\=12 \escapechar=`\@ + % Append \endinput to make sure that TeX does not see the ending newline. + \toks0={#1\endinput}% + \immediate\openout\macscribble=\jobname.tmp + \immediate\write\macscribble{\the\toks0}% + \immediate\closeout\macscribble + \let\xeatspaces\eatspaces + \input \jobname.tmp + \endgroup +} +\else +\def\scanmacro#1{% +\begingroup \newlinechar`\^^M +% Undo catcode changes of \startcontents and \doprintindex +\catcode`\@=0 \catcode`\\=12 \escapechar=`\@ +\let\xeatspaces\eatspaces\scantokens{#1\endinput}\endgroup} +\fi + +\newcount\paramno % Count of parameters +\newtoks\macname % Macro name +\newif\ifrecursive % Is it recursive? +\def\macrolist{} % List of all defined macros in the form + % \do\macro1\do\macro2... + +% Utility routines. +% Thisdoes \let #1 = #2, except with \csnames. +\def\cslet#1#2{% +\expandafter\expandafter +\expandafter\let +\expandafter\expandafter +\csname#1\endcsname +\csname#2\endcsname} + +% Trim leading and trailing spaces off a string. +% Concepts from aro-bend problem 15 (see CTAN). +{\catcode`\@=11 +\gdef\eatspaces #1{\expandafter\trim@\expandafter{#1 }} +\gdef\trim@ #1{\trim@@ @#1 @ #1 @ @@} +\gdef\trim@@ #1@ #2@ #3@@{\trim@@@\empty #2 @} +\def\unbrace#1{#1} +\unbrace{\gdef\trim@@@ #1 } #2@{#1} +} + +% Trim a single trailing ^^M off a string. +{\catcode`\^^M=12\catcode`\Q=3% +\gdef\eatcr #1{\eatcra #1Q^^MQ}% +\gdef\eatcra#1^^MQ{\eatcrb#1Q}% +\gdef\eatcrb#1Q#2Q{#1}% +} + +% Macro bodies are absorbed as an argument in a context where +% all characters are catcode 10, 11 or 12, except \ which is active +% (as in normal texinfo). It is necessary to change the definition of \. + +% It's necessary to have hard CRs when the macro is executed. This is +% done by making ^^M (\endlinechar) catcode 12 when reading the macro +% body, and then making it the \newlinechar in \scanmacro. + +\def\macrobodyctxt{% + \catcode`\~=12 + \catcode`\^=12 + \catcode`\_=12 + \catcode`\|=12 + \catcode`\<=12 + \catcode`\>=12 + \catcode`\+=12 + \catcode`\{=12 + \catcode`\}=12 + \catcode`\@=12 + \catcode`\^^M=12 + \usembodybackslash} + +\def\macroargctxt{% + \catcode`\~=12 + \catcode`\^=12 + \catcode`\_=12 + \catcode`\|=12 + \catcode`\<=12 + \catcode`\>=12 + \catcode`\+=12 + \catcode`\@=12 + \catcode`\\=12} + +% \mbodybackslash is the definition of \ in @macro bodies. +% It maps \foo\ => \csname macarg.foo\endcsname => #N +% where N is the macro parameter number. +% We define \csname macarg.\endcsname to be \realbackslash, so +% \\ in macro replacement text gets you a backslash. + +{\catcode`@=0 @catcode`@\=@active + @gdef@usembodybackslash{@let\=@mbodybackslash} + @gdef@mbodybackslash#1\{@csname macarg.#1@endcsname} +} +\expandafter\def\csname macarg.\endcsname{\realbackslash} + +\def\macro{\recursivefalse\parsearg\macroxxx} +\def\rmacro{\recursivetrue\parsearg\macroxxx} + +\def\macroxxx#1{% + \getargs{#1}% now \macname is the macname and \argl the arglist + \ifx\argl\empty % no arguments + \paramno=0% + \else + \expandafter\parsemargdef \argl;% + \fi + \if1\csname ismacro.\the\macname\endcsname + \message{Warning: redefining \the\macname}% + \else + \expandafter\ifx\csname \the\macname\endcsname \relax + \else \errmessage{The name \the\macname\space is reserved}\fi + \global\cslet{macsave.\the\macname}{\the\macname}% + \global\expandafter\let\csname ismacro.\the\macname\endcsname=1% + % Add the macroname to \macrolist + \toks0 = \expandafter{\macrolist\do}% + \xdef\macrolist{\the\toks0 + \expandafter\noexpand\csname\the\macname\endcsname}% + \fi + \begingroup \macrobodyctxt + \ifrecursive \expandafter\parsermacbody + \else \expandafter\parsemacbody + \fi} + +\def\unmacro{\parsearg\unmacroxxx} +\def\unmacroxxx#1{% + \if1\csname ismacro.#1\endcsname + \global\cslet{#1}{macsave.#1}% + \global\expandafter\let \csname ismacro.#1\endcsname=0% + % Remove the macro name from \macrolist + \begingroup + \edef\tempa{\expandafter\noexpand\csname#1\endcsname}% + \def\do##1{% + \def\tempb{##1}% + \ifx\tempa\tempb + % remove this + \else + \toks0 = \expandafter{\newmacrolist\do}% + \edef\newmacrolist{\the\toks0\expandafter\noexpand\tempa}% + \fi}% + \def\newmacrolist{}% + % Execute macro list to define \newmacrolist + \macrolist + \global\let\macrolist\newmacrolist + \endgroup + \else + \errmessage{Macro #1 not defined}% + \fi +} + +% This makes use of the obscure feature that if the last token of a +% is #, then the preceding argument is delimited by +% an opening brace, and that opening brace is not consumed. +\def\getargs#1{\getargsxxx#1{}} +\def\getargsxxx#1#{\getmacname #1 \relax\getmacargs} +\def\getmacname #1 #2\relax{\macname={#1}} +\def\getmacargs#1{\def\argl{#1}} + +% Parse the optional {params} list. Set up \paramno and \paramlist +% so \defmacro knows what to do. Define \macarg.blah for each blah +% in the params list, to be ##N where N is the position in that list. +% That gets used by \mbodybackslash (above). + +% We need to get `macro parameter char #' into several definitions. +% The technique used is stolen from LaTeX: let \hash be something +% unexpandable, insert that wherever you need a #, and then redefine +% it to # just before using the token list produced. +% +% The same technique is used to protect \eatspaces till just before +% the macro is used. + +\def\parsemargdef#1;{\paramno=0\def\paramlist{}% + \let\hash\relax\let\xeatspaces\relax\parsemargdefxxx#1,;,} +\def\parsemargdefxxx#1,{% + \if#1;\let\next=\relax + \else \let\next=\parsemargdefxxx + \advance\paramno by 1% + \expandafter\edef\csname macarg.\eatspaces{#1}\endcsname + {\xeatspaces{\hash\the\paramno}}% + \edef\paramlist{\paramlist\hash\the\paramno,}% + \fi\next} + +% These two commands read recursive and nonrecursive macro bodies. +% (They're different since rec and nonrec macros end differently.) + +\long\def\parsemacbody#1@end macro% +{\xdef\temp{\eatcr{#1}}\endgroup\defmacro}% +\long\def\parsermacbody#1@end rmacro% +{\xdef\temp{\eatcr{#1}}\endgroup\defmacro}% + +% This defines the macro itself. There are six cases: recursive and +% nonrecursive macros of zero, one, and many arguments. +% Much magic with \expandafter here. +% \xdef is used so that macro definitions will survive the file +% they're defined in; @include reads the file inside a group. +\def\defmacro{% + \let\hash=##% convert placeholders to macro parameter chars + \ifrecursive + \ifcase\paramno + % 0 + \expandafter\xdef\csname\the\macname\endcsname{% + \noexpand\scanmacro{\temp}}% + \or % 1 + \expandafter\xdef\csname\the\macname\endcsname{% + \bgroup\noexpand\macroargctxt + \noexpand\braceorline + \expandafter\noexpand\csname\the\macname xxx\endcsname}% + \expandafter\xdef\csname\the\macname xxx\endcsname##1{% + \egroup\noexpand\scanmacro{\temp}}% + \else % many + \expandafter\xdef\csname\the\macname\endcsname{% + \bgroup\noexpand\macroargctxt + \noexpand\csname\the\macname xx\endcsname}% + \expandafter\xdef\csname\the\macname xx\endcsname##1{% + \expandafter\noexpand\csname\the\macname xxx\endcsname ##1,}% + \expandafter\expandafter + \expandafter\xdef + \expandafter\expandafter + \csname\the\macname xxx\endcsname + \paramlist{\egroup\noexpand\scanmacro{\temp}}% + \fi + \else + \ifcase\paramno + % 0 + \expandafter\xdef\csname\the\macname\endcsname{% + \noexpand\norecurse{\the\macname}% + \noexpand\scanmacro{\temp}\egroup}% + \or % 1 + \expandafter\xdef\csname\the\macname\endcsname{% + \bgroup\noexpand\macroargctxt + \noexpand\braceorline + \expandafter\noexpand\csname\the\macname xxx\endcsname}% + \expandafter\xdef\csname\the\macname xxx\endcsname##1{% + \egroup + \noexpand\norecurse{\the\macname}% + \noexpand\scanmacro{\temp}\egroup}% + \else % many + \expandafter\xdef\csname\the\macname\endcsname{% + \bgroup\noexpand\macroargctxt + \expandafter\noexpand\csname\the\macname xx\endcsname}% + \expandafter\xdef\csname\the\macname xx\endcsname##1{% + \expandafter\noexpand\csname\the\macname xxx\endcsname ##1,}% + \expandafter\expandafter + \expandafter\xdef + \expandafter\expandafter + \csname\the\macname xxx\endcsname + \paramlist{% + \egroup + \noexpand\norecurse{\the\macname}% + \noexpand\scanmacro{\temp}\egroup}% + \fi + \fi} + +\def\norecurse#1{\bgroup\cslet{#1}{macsave.#1}} + +% \braceorline decides whether the next nonwhitespace character is a +% {. If so it reads up to the closing }, if not, it reads the whole +% line. Whatever was read is then fed to the next control sequence +% as an argument (by \parsebrace or \parsearg) +\def\braceorline#1{\let\next=#1\futurelet\nchar\braceorlinexxx} +\def\braceorlinexxx{% + \ifx\nchar\bgroup\else + \expandafter\parsearg + \fi \next} + +% We mant to disable all macros during \shipout so that they are not +% expanded by \write. +\def\turnoffmacros{\begingroup \def\do##1{\let\noexpand##1=\relax}% + \edef\next{\macrolist}\expandafter\endgroup\next} + + +% @alias. +% We need some trickery to remove the optional spaces around the equal +% sign. Just make them active and then expand them all to nothing. +\def\alias{\begingroup\obeyspaces\parsearg\aliasxxx} +\def\aliasxxx #1{\aliasyyy#1\relax} +\def\aliasyyy #1=#2\relax{\ignoreactivespaces +\edef\next{\global\let\expandafter\noexpand\csname#1\endcsname=% + \expandafter\noexpand\csname#2\endcsname}% +\expandafter\endgroup\next} + + +\message{cross references,} +% @xref etc. + +\newwrite\auxfile + +\newif\ifhavexrefs % True if xref values are known. +\newif\ifwarnedxrefs % True if we warned once that they aren't known. + +% @inforef is relatively simple. +\def\inforef #1{\inforefzzz #1,,,,**} +\def\inforefzzz #1,#2,#3,#4**{\putwordSee{} \putwordInfo{} \putwordfile{} \file{\ignorespaces #3{}}, + node \samp{\ignorespaces#1{}}} + +% @node's job is to define \lastnode. +\def\node{\ENVcheck\parsearg\nodezzz} +\def\nodezzz#1{\nodexxx [#1,]} +\def\nodexxx[#1,#2]{\gdef\lastnode{#1}} +\let\nwnode=\node +\let\lastnode=\relax + +% The sectioning commands (@chapter, etc.) call these. +\def\donoderef{% + \ifx\lastnode\relax\else + \expandafter\expandafter\expandafter\setref{\lastnode}% + {Ysectionnumberandtype}% + \global\let\lastnode=\relax + \fi +} +\def\unnumbnoderef{% + \ifx\lastnode\relax\else + \expandafter\expandafter\expandafter\setref{\lastnode}{Ynothing}% + \global\let\lastnode=\relax + \fi +} +\def\appendixnoderef{% + \ifx\lastnode\relax\else + \expandafter\expandafter\expandafter\setref{\lastnode}% + {Yappendixletterandtype}% + \global\let\lastnode=\relax + \fi +} + + +% @anchor{NAME} -- define xref target at arbitrary point. +% +\newcount\savesfregister +\gdef\savesf{\relax \ifhmode \savesfregister=\spacefactor \fi} +\gdef\restoresf{\relax \ifhmode \spacefactor=\savesfregister \fi} +\gdef\anchor#1{\savesf \setref{#1}{Ynothing}\restoresf \ignorespaces} + +% \setref{NAME}{SNT} defines a cross-reference point NAME, namely +% NAME-title, NAME-pg, and NAME-SNT. Called from \foonoderef. We have +% to set \indexdummies so commands such as @code in a section title +% aren't expanded. It would be nicer not to expand the titles in the +% first place, but there's so many layers that that is hard to do. +% +\def\setref#1#2{{% + \indexdummies + \pdfmkdest{#1}% + \dosetq{#1-title}{Ytitle}% + \dosetq{#1-pg}{Ypagenumber}% + \dosetq{#1-snt}{#2}% +}} + +% @xref, @pxref, and @ref generate cross-references. For \xrefX, #1 is +% the node name, #2 the name of the Info cross-reference, #3 the printed +% node name, #4 the name of the Info file, #5 the name of the printed +% manual. All but the node name can be omitted. +% +\def\pxref#1{\putwordsee{} \xrefX[#1,,,,,,,]} +\def\xref#1{\putwordSee{} \xrefX[#1,,,,,,,]} +\def\ref#1{\xrefX[#1,,,,,,,]} +\def\xrefX[#1,#2,#3,#4,#5,#6]{\begingroup + \unsepspaces + \def\printedmanual{\ignorespaces #5}% + \def\printednodename{\ignorespaces #3}% + \setbox1=\hbox{\printedmanual}% + \setbox0=\hbox{\printednodename}% + \ifdim \wd0 = 0pt + % No printed node name was explicitly given. + \expandafter\ifx\csname SETxref-automatic-section-title\endcsname\relax + % Use the node name inside the square brackets. + \def\printednodename{\ignorespaces #1}% + \else + % Use the actual chapter/section title appear inside + % the square brackets. Use the real section title if we have it. + \ifdim \wd1 > 0pt + % It is in another manual, so we don't have it. + \def\printednodename{\ignorespaces #1}% + \else + \ifhavexrefs + % We know the real title if we have the xref values. + \def\printednodename{\refx{#1-title}{}}% + \else + % Otherwise just copy the Info node name. + \def\printednodename{\ignorespaces #1}% + \fi% + \fi + \fi + \fi + % + % If we use \unhbox0 and \unhbox1 to print the node names, TeX does not + % insert empty discretionaries after hyphens, which means that it will + % not find a line break at a hyphen in a node names. Since some manuals + % are best written with fairly long node names, containing hyphens, this + % is a loss. Therefore, we give the text of the node name again, so it + % is as if TeX is seeing it for the first time. + \ifpdf + \leavevmode + \getfilename{#4}% + \ifnum\filenamelength>0 + \startlink attr{/Border [0 0 0]}% + goto file{\the\filename.pdf} name{#1@}% + \else + \startlink attr{/Border [0 0 0]}% + goto name{#1@}% + \fi + \linkcolor + \fi + % + \ifdim \wd1 > 0pt + \putwordsection{} ``\printednodename'' \putwordin{} \cite{\printedmanual}% + \else + % _ (for example) has to be the character _ for the purposes of the + % control sequence corresponding to the node, but it has to expand + % into the usual \leavevmode...\vrule stuff for purposes of + % printing. So we \turnoffactive for the \refx-snt, back on for the + % printing, back off for the \refx-pg. + {\normalturnoffactive + % Only output a following space if the -snt ref is nonempty; for + % @unnumbered and @anchor, it won't be. + \setbox2 = \hbox{\ignorespaces \refx{#1-snt}{}}% + \ifdim \wd2 > 0pt \refx{#1-snt}\space\fi + }% + % [mynode], + [\printednodename],\space + % page 3 + \turnoffactive \putwordpage\tie\refx{#1-pg}{}% + \fi + \endlink +\endgroup} + +% \dosetq is the interface for calls from other macros + +% Use \normalturnoffactive so that punctuation chars such as underscore +% and backslash work in node names. (\turnoffactive doesn't do \.) +\def\dosetq#1#2{% + {\let\folio=0% + \normalturnoffactive + \edef\next{\write\auxfile{\internalsetq{#1}{#2}}}% + \iflinks + \next + \fi + }% +} + +% \internalsetq {foo}{page} expands into +% CHARACTERS 'xrdef {foo}{...expansion of \Ypage...} +% When the aux file is read, ' is the escape character + +\def\internalsetq #1#2{'xrdef {#1}{\csname #2\endcsname}} + +% Things to be expanded by \internalsetq + +\def\Ypagenumber{\folio} + +\def\Ytitle{\thissection} + +\def\Ynothing{} + +\def\Ysectionnumberandtype{% +\ifnum\secno=0 \putwordChapter\xreftie\the\chapno % +\else \ifnum \subsecno=0 \putwordSection\xreftie\the\chapno.\the\secno % +\else \ifnum \subsubsecno=0 % +\putwordSection\xreftie\the\chapno.\the\secno.\the\subsecno % +\else % +\putwordSection\xreftie\the\chapno.\the\secno.\the\subsecno.\the\subsubsecno % +\fi \fi \fi } + +\def\Yappendixletterandtype{% +\ifnum\secno=0 \putwordAppendix\xreftie'char\the\appendixno{}% +\else \ifnum \subsecno=0 \putwordSection\xreftie'char\the\appendixno.\the\secno % +\else \ifnum \subsubsecno=0 % +\putwordSection\xreftie'char\the\appendixno.\the\secno.\the\subsecno % +\else % +\putwordSection\xreftie'char\the\appendixno.\the\secno.\the\subsecno.\the\subsubsecno % +\fi \fi \fi } + +\gdef\xreftie{'tie} + +% Use TeX 3.0's \inputlineno to get the line number, for better error +% messages, but if we're using an old version of TeX, don't do anything. +% +\ifx\inputlineno\thisisundefined + \let\linenumber = \empty % Non-3.0. +\else + \def\linenumber{\the\inputlineno:\space} +\fi + +% Define \refx{NAME}{SUFFIX} to reference a cross-reference string named NAME. +% If its value is nonempty, SUFFIX is output afterward. + +\def\refx#1#2{% + \expandafter\ifx\csname X#1\endcsname\relax + % If not defined, say something at least. + \angleleft un\-de\-fined\angleright + \iflinks + \ifhavexrefs + \message{\linenumber Undefined cross reference `#1'.}% + \else + \ifwarnedxrefs\else + \global\warnedxrefstrue + \message{Cross reference values unknown; you must run TeX again.}% + \fi + \fi + \fi + \else + % It's defined, so just use it. + \csname X#1\endcsname + \fi + #2% Output the suffix in any case. +} + +% This is the macro invoked by entries in the aux file. +% +\def\xrdef#1{\begingroup + % Reenable \ as an escape while reading the second argument. + \catcode`\\ = 0 + \afterassignment\endgroup + \expandafter\gdef\csname X#1\endcsname +} + +% Read the last existing aux file, if any. No error if none exists. +\def\readauxfile{\begingroup + \catcode`\^^@=\other + \catcode`\^^A=\other + \catcode`\^^B=\other + \catcode`\^^C=\other + \catcode`\^^D=\other + \catcode`\^^E=\other + \catcode`\^^F=\other + \catcode`\^^G=\other + \catcode`\^^H=\other + \catcode`\^^K=\other + \catcode`\^^L=\other + \catcode`\^^N=\other + \catcode`\^^P=\other + \catcode`\^^Q=\other + \catcode`\^^R=\other + \catcode`\^^S=\other + \catcode`\^^T=\other + \catcode`\^^U=\other + \catcode`\^^V=\other + \catcode`\^^W=\other + \catcode`\^^X=\other + \catcode`\^^Z=\other + \catcode`\^^[=\other + \catcode`\^^\=\other + \catcode`\^^]=\other + \catcode`\^^^=\other + \catcode`\^^_=\other + \catcode`\@=\other + \catcode`\^=\other + % It was suggested to define this as 7, which would allow ^^e4 etc. + % in xref tags, i.e., node names. But since ^^e4 notation isn't + % supported in the main text, it doesn't seem desirable. Furthermore, + % that is not enough: for node names that actually contain a ^ + % character, we would end up writing a line like this: 'xrdef {'hat + % b-title}{'hat b} and \xrdef does a \csname...\endcsname on the first + % argument, and \hat is not an expandable control sequence. It could + % all be worked out, but why? Either we support ^^ or we don't. + % + % The other change necessary for this was to define \auxhat: + % \def\auxhat{\def^{'hat }}% extra space so ok if followed by letter + % and then to call \auxhat in \setq. + % + \catcode`\~=\other + \catcode`\[=\other + \catcode`\]=\other + \catcode`\"=\other + \catcode`\_=\other + \catcode`\|=\other + \catcode`\<=\other + \catcode`\>=\other + \catcode`\$=\other + \catcode`\#=\other + \catcode`\&=\other + \catcode`+=\other % avoid \+ for paranoia even though we've turned it off + % Make the characters 128-255 be printing characters + {% + \count 1=128 + \def\loop{% + \catcode\count 1=\other + \advance\count 1 by 1 + \ifnum \count 1<256 \loop \fi + }% + }% + % The aux file uses ' as the escape (for now). + % Turn off \ as an escape so we do not lose on + % entries which were dumped with control sequences in their names. + % For example, 'xrdef {$\leq $-fun}{page ...} made by @defun ^^ + % Reference to such entries still does not work the way one would wish, + % but at least they do not bomb out when the aux file is read in. + \catcode`\{=1 + \catcode`\}=2 + \catcode`\%=\other + \catcode`\'=0 + \catcode`\\=\other + % + \openin 1 \jobname.aux + \ifeof 1 \else + \closein 1 + \input \jobname.aux + \global\havexrefstrue + \global\warnedobstrue + \fi + % Open the new aux file. TeX will close it automatically at exit. + \openout\auxfile=\jobname.aux +\endgroup} + + +% Footnotes. + +\newcount \footnoteno + +% The trailing space in the following definition for supereject is +% vital for proper filling; pages come out unaligned when you do a +% pagealignmacro call if that space before the closing brace is +% removed. (Generally, numeric constants should always be followed by a +% space to prevent strange expansion errors.) +\def\supereject{\par\penalty -20000\footnoteno =0 } + +% @footnotestyle is meaningful for info output only. +\let\footnotestyle=\comment + +\let\ptexfootnote=\footnote + +{\catcode `\@=11 +% +% Auto-number footnotes. Otherwise like plain. +\gdef\footnote{% + \global\advance\footnoteno by \@ne + \edef\thisfootno{$^{\the\footnoteno}$}% + % + % In case the footnote comes at the end of a sentence, preserve the + % extra spacing after we do the footnote number. + \let\@sf\empty + \ifhmode\edef\@sf{\spacefactor\the\spacefactor}\/\fi + % + % Remove inadvertent blank space before typesetting the footnote number. + \unskip + \thisfootno\@sf + \footnotezzz +}% + +% Don't bother with the trickery in plain.tex to not require the +% footnote text as a parameter. Our footnotes don't need to be so general. +% +% Oh yes, they do; otherwise, @ifset and anything else that uses +% \parseargline fail inside footnotes because the tokens are fixed when +% the footnote is read. --karl, 16nov96. +% +\long\gdef\footnotezzz{\insert\footins\bgroup + % We want to typeset this text as a normal paragraph, even if the + % footnote reference occurs in (for example) a display environment. + % So reset some parameters. + \interlinepenalty\interfootnotelinepenalty + \splittopskip\ht\strutbox % top baseline for broken footnotes + \splitmaxdepth\dp\strutbox + \floatingpenalty\@MM + \leftskip\z@skip + \rightskip\z@skip + \spaceskip\z@skip + \xspaceskip\z@skip + \parindent\defaultparindent + % + \smallfonts \rm + % + % Hang the footnote text off the number. + \hang + \textindent{\thisfootno}% + % + % Don't crash into the line above the footnote text. Since this + % expands into a box, it must come within the paragraph, lest it + % provide a place where TeX can split the footnote. + \footstrut + \futurelet\next\fo@t +} +\def\fo@t{\ifcat\bgroup\noexpand\next \let\next\f@@t + \else\let\next\f@t\fi \next} +\def\f@@t{\bgroup\aftergroup\@foot\let\next} +\def\f@t#1{#1\@foot} +\def\@foot{\strut\par\egroup} + +}%end \catcode `\@=11 + +% Set the baselineskip to #1, and the lineskip and strut size +% correspondingly. There is no deep meaning behind these magic numbers +% used as factors; they just match (closely enough) what Knuth defined. +% +\def\lineskipfactor{.08333} +\def\strutheightpercent{.70833} +\def\strutdepthpercent {.29167} +% +\def\setleading#1{% + \normalbaselineskip = #1\relax + \normallineskip = \lineskipfactor\normalbaselineskip + \normalbaselines + \setbox\strutbox =\hbox{% + \vrule width0pt height\strutheightpercent\baselineskip + depth \strutdepthpercent \baselineskip + }% +} + +% @| inserts a changebar to the left of the current line. It should +% surround any changed text. This approach does *not* work if the +% change spans more than two lines of output. To handle that, we would +% have adopt a much more difficult approach (putting marks into the main +% vertical list for the beginning and end of each change). +% +\def\|{% + % \vadjust can only be used in horizontal mode. + \leavevmode + % + % Append this vertical mode material after the current line in the output. + \vadjust{% + % We want to insert a rule with the height and depth of the current + % leading; that is exactly what \strutbox is supposed to record. + \vskip-\baselineskip + % + % \vadjust-items are inserted at the left edge of the type. So + % the \llap here moves out into the left-hand margin. + \llap{% + % + % For a thicker or thinner bar, change the `1pt'. + \vrule height\baselineskip width1pt + % + % This is the space between the bar and the text. + \hskip 12pt + }% + }% +} + +% For a final copy, take out the rectangles +% that mark overfull boxes (in case you have decided +% that the text looks ok even though it passes the margin). +% +\def\finalout{\overfullrule=0pt} + +% @image. We use the macros from epsf.tex to support this. +% If epsf.tex is not installed and @image is used, we complain. +% +% Check for and read epsf.tex up front. If we read it only at @image +% time, we might be inside a group, and then its definitions would get +% undone and the next image would fail. +\openin 1 = epsf.tex +\ifeof 1 \else + \closein 1 + % Do not bother showing banner with post-v2.7 epsf.tex (available in + % doc/epsf.tex until it shows up on ctan). + \def\epsfannounce{\toks0 = }% + \input epsf.tex +\fi +% +% We will only complain once about lack of epsf.tex. +\newif\ifwarnednoepsf +\newhelp\noepsfhelp{epsf.tex must be installed for images to + work. It is also included in the Texinfo distribution, or you can get + it from ftp://tug.org/tex/epsf.tex.} +% +\def\image#1{% + \ifx\epsfbox\undefined + \ifwarnednoepsf \else + \errhelp = \noepsfhelp + \errmessage{epsf.tex not found, images will be ignored}% + \global\warnednoepsftrue + \fi + \else + \imagexxx #1,,,\finish + \fi +} +% +% Arguments to @image: +% #1 is (mandatory) image filename; we tack on .eps extension. +% #2 is (optional) width, #3 is (optional) height. +% #4 is just the usual extra ignored arg for parsing this stuff. +\def\imagexxx#1,#2,#3,#4\finish{% + \ifpdf + \centerline{\dopdfimage{#1}{#2}{#3}}% + \else + % \epsfbox itself resets \epsf?size at each figure. + \setbox0 = \hbox{\ignorespaces #2}\ifdim\wd0 > 0pt \epsfxsize=#2\relax \fi + \setbox0 = \hbox{\ignorespaces #3}\ifdim\wd0 > 0pt \epsfysize=#3\relax \fi + \begingroup + \catcode`\^^M = 5 % in case we're inside an example + % If the image is by itself, center it. + \ifvmode + \nobreak\bigskip + % Usually we'll have text after the image which will insert + % \parskip glue, so insert it here too to equalize the space + % above and below. + \nobreak\vskip\parskip + \nobreak + \centerline{\epsfbox{#1.eps}}% + \bigbreak + \else + % In the middle of a paragraph, no extra space. + \epsfbox{#1.eps}% + \fi + \endgroup + \fi +} + + +\message{localization,} +% and i18n. + +% @documentlanguage is usually given very early, just after +% @setfilename. If done too late, it may not override everything +% properly. Single argument is the language abbreviation. +% It would be nice if we could set up a hyphenation file here. +% +\def\documentlanguage{\parsearg\dodocumentlanguage} +\def\dodocumentlanguage#1{% + \tex % read txi-??.tex file in plain TeX. + % Read the file if it exists. + \openin 1 txi-#1.tex + \ifeof1 + \errhelp = \nolanghelp + \errmessage{Cannot read language file txi-#1.tex}% + \let\temp = \relax + \else + \def\temp{\input txi-#1.tex }% + \fi + \temp + \endgroup +} +\newhelp\nolanghelp{The given language definition file cannot be found or +is empty. Maybe you need to install it? In the current directory +should work if nowhere else does.} + + +% @documentencoding should change something in TeX eventually, most +% likely, but for now just recognize it. +\let\documentencoding = \comment + + +% Page size parameters. +% +\newdimen\defaultparindent \defaultparindent = 15pt + +\chapheadingskip = 15pt plus 4pt minus 2pt +\secheadingskip = 12pt plus 3pt minus 2pt +\subsecheadingskip = 9pt plus 2pt minus 2pt + +% Prevent underfull vbox error messages. +\vbadness = 10000 + +% Don't be so finicky about underfull hboxes, either. +\hbadness = 2000 + +% Following George Bush, just get rid of widows and orphans. +\widowpenalty=10000 +\clubpenalty=10000 + +% Use TeX 3.0's \emergencystretch to help line breaking, but if we're +% using an old version of TeX, don't do anything. We want the amount of +% stretch added to depend on the line length, hence the dependence on +% \hsize. We call this whenever the paper size is set. +% +\def\setemergencystretch{% + \ifx\emergencystretch\thisisundefined + % Allow us to assign to \emergencystretch anyway. + \def\emergencystretch{\dimen0}% + \else + \emergencystretch = .15\hsize + \fi +} + +% Parameters in order: 1) textheight; 2) textwidth; 3) voffset; +% 4) hoffset; 5) binding offset; 6) topskip. Then whoever calls us can +% set \parskip and call \setleading for \baselineskip. +% +\def\internalpagesizes#1#2#3#4#5#6{% + \voffset = #3\relax + \topskip = #6\relax + \splittopskip = \topskip + % + \vsize = #1\relax + \advance\vsize by \topskip + \outervsize = \vsize + \advance\outervsize by 2\topandbottommargin + \pageheight = \vsize + % + \hsize = #2\relax + \outerhsize = \hsize + \advance\outerhsize by 0.5in + \pagewidth = \hsize + % + \normaloffset = #4\relax + \bindingoffset = #5\relax + % + \parindent = \defaultparindent + \setemergencystretch +} + +% @letterpaper (the default). +\def\letterpaper{{\globaldefs = 1 + \parskip = 3pt plus 2pt minus 1pt + \setleading{13.2pt}% + % + % If page is nothing but text, make it come out even. + \internalpagesizes{46\baselineskip}{6in}{\voffset}{.25in}{\bindingoffset}{36pt}% +}} + +% Use @smallbook to reset parameters for 7x9.5 (or so) format. +\def\smallbook{{\globaldefs = 1 + \parskip = 2pt plus 1pt + \setleading{12pt}% + % + \internalpagesizes{7.5in}{5.in}{\voffset}{.25in}{\bindingoffset}{16pt}% + % + \lispnarrowing = 0.3in + \tolerance = 700 + \hfuzz = 1pt + \contentsrightmargin = 0pt + \deftypemargin = 0pt + \defbodyindent = .5cm + % + \let\smalldisplay = \smalldisplayx + \let\smallexample = \smalllispx + \let\smallformat = \smallformatx + \let\smalllisp = \smalllispx +}} + +% Use @afourpaper to print on European A4 paper. +\def\afourpaper{{\globaldefs = 1 + \setleading{12pt}% + \parskip = 3pt plus 2pt minus 1pt + % + \internalpagesizes{53\baselineskip}{160mm}{\voffset}{4mm}{\bindingoffset}{44pt}% + % + \tolerance = 700 + \hfuzz = 1pt +}} + +% A specific text layout, 24x15cm overall, intended for A4 paper. Top margin +% 29mm, hence bottom margin 28mm, nominal side margin 3cm. +\def\afourlatex{{\globaldefs = 1 + \setleading{13.6pt}% + % + \afourpaper + \internalpagesizes{237mm}{150mm}{3.6mm}{3.6mm}{3mm}{7mm}% + % + \globaldefs = 0 +}} + +% Use @afourwide to print on European A4 paper in wide format. +\def\afourwide{% + \afourpaper + \internalpagesizes{6.5in}{9.5in}{\hoffset}{\normaloffset}{\bindingoffset}{7mm}% + % + \globaldefs = 0 +} + +% @pagesizes TEXTHEIGHT[,TEXTWIDTH] +% Perhaps we should allow setting the margins, \topskip, \parskip, +% and/or leading, also. Or perhaps we should compute them somehow. +% +\def\pagesizes{\parsearg\pagesizesxxx} +\def\pagesizesxxx#1{\pagesizesyyy #1,,\finish} +\def\pagesizesyyy#1,#2,#3\finish{{% + \setbox0 = \hbox{\ignorespaces #2}\ifdim\wd0 > 0pt \hsize=#2\relax \fi + \globaldefs = 1 + % + \parskip = 3pt plus 2pt minus 1pt + \setleading{13.2pt}% + % + \internalpagesizes{#1}{\hsize}{\voffset}{\normaloffset}{\bindingoffset}{44pt}% +}} + +% Set default to letter. +% +\letterpaper + + +\message{and turning on texinfo input format.} + +% Define macros to output various characters with catcode for normal text. +\catcode`\"=\other +\catcode`\~=\other +\catcode`\^=\other +\catcode`\_=\other +\catcode`\|=\other +\catcode`\<=\other +\catcode`\>=\other +\catcode`\+=\other +\catcode`\$=\other +\def\normaldoublequote{"} +\def\normaltilde{~} +\def\normalcaret{^} +\def\normalunderscore{_} +\def\normalverticalbar{|} +\def\normalless{<} +\def\normalgreater{>} +\def\normalplus{+} +\def\normaldollar{$} + +% This macro is used to make a character print one way in ttfont +% where it can probably just be output, and another way in other fonts, +% where something hairier probably needs to be done. +% +% #1 is what to print if we are indeed using \tt; #2 is what to print +% otherwise. Since all the Computer Modern typewriter fonts have zero +% interword stretch (and shrink), and it is reasonable to expect all +% typewriter fonts to have this, we can check that font parameter. +% +\def\ifusingtt#1#2{\ifdim \fontdimen3\font=0pt #1\else #2\fi} + +% Same as above, but check for italic font. Actually this also catches +% non-italic slanted fonts since it is impossible to distinguish them from +% italic fonts. But since this is only used by $ and it uses \sl anyway +% this is not a problem. +\def\ifusingit#1#2{\ifdim \fontdimen1\font>0pt #1\else #2\fi} + +% Turn off all special characters except @ +% (and those which the user can use as if they were ordinary). +% Most of these we simply print from the \tt font, but for some, we can +% use math or other variants that look better in normal text. + +\catcode`\"=\active +\def\activedoublequote{{\tt\char34}} +\let"=\activedoublequote +\catcode`\~=\active +\def~{{\tt\char126}} +\chardef\hat=`\^ +\catcode`\^=\active +\def^{{\tt \hat}} + +\catcode`\_=\active +\def_{\ifusingtt\normalunderscore\_} +% Subroutine for the previous macro. +\def\_{\leavevmode \kern.06em \vbox{\hrule width.3em height.1ex}} + +\catcode`\|=\active +\def|{{\tt\char124}} +\chardef \less=`\< +\catcode`\<=\active +\def<{{\tt \less}} +\chardef \gtr=`\> +\catcode`\>=\active +\def>{{\tt \gtr}} +\catcode`\+=\active +\def+{{\tt \char 43}} +\catcode`\$=\active +\def${\ifusingit{{\sl\$}}\normaldollar} +%\catcode 27=\active +%\def^^[{$\diamondsuit$} + +% Set up an active definition for =, but don't enable it most of the time. +{\catcode`\==\active +\global\def={{\tt \char 61}}} + +\catcode`+=\active +\catcode`\_=\active + +% If a .fmt file is being used, characters that might appear in a file +% name cannot be active until we have parsed the command line. +% So turn them off again, and have \everyjob (or @setfilename) turn them on. +% \otherifyactive is called near the end of this file. +\def\otherifyactive{\catcode`+=\other \catcode`\_=\other} + +\catcode`\@=0 + +% \rawbackslashxx output one backslash character in current font +\global\chardef\rawbackslashxx=`\\ +%{\catcode`\\=\other +%@gdef@rawbackslashxx{\}} + +% \rawbackslash redefines \ as input to do \rawbackslashxx. +{\catcode`\\=\active +@gdef@rawbackslash{@let\=@rawbackslashxx }} + +% \normalbackslash outputs one backslash in fixed width font. +\def\normalbackslash{{\tt\rawbackslashxx}} + +% \catcode 17=0 % Define control-q +\catcode`\\=\active + +% Used sometimes to turn off (effectively) the active characters +% even after parsing them. +@def@turnoffactive{@let"=@normaldoublequote +@let\=@realbackslash +@let~=@normaltilde +@let^=@normalcaret +@let_=@normalunderscore +@let|=@normalverticalbar +@let<=@normalless +@let>=@normalgreater +@let+=@normalplus +@let$=@normaldollar} + +@def@normalturnoffactive{@let"=@normaldoublequote +@let\=@normalbackslash +@let~=@normaltilde +@let^=@normalcaret +@let_=@normalunderscore +@let|=@normalverticalbar +@let<=@normalless +@let>=@normalgreater +@let+=@normalplus +@let$=@normaldollar} + +% Make _ and + \other characters, temporarily. +% This is canceled by @fixbackslash. +@otherifyactive + +% If a .fmt file is being used, we don't want the `\input texinfo' to show up. +% That is what \eatinput is for; after that, the `\' should revert to printing +% a backslash. +% +@gdef@eatinput input texinfo{@fixbackslash} +@global@let\ = @eatinput + +% On the other hand, perhaps the file did not have a `\input texinfo'. Then +% the first `\{ in the file would cause an error. This macro tries to fix +% that, assuming it is called before the first `\' could plausibly occur. +% Also back turn on active characters that might appear in the input +% file name, in case not using a pre-dumped format. +% +@gdef@fixbackslash{% + @ifx\@eatinput @let\ = @normalbackslash @fi + @catcode`+=@active + @catcode`@_=@active +} + +% Say @foo, not \foo, in error messages. +@escapechar = `@@ + +% These look ok in all fonts, so just make them not special. +@catcode`@& = @other +@catcode`@# = @other +@catcode`@% = @other + +@c Set initial fonts. +@textfonts +@rm + + +@c Local variables: +@c eval: (add-hook 'write-file-hooks 'time-stamp) +@c page-delimiter: "^\\\\message" +@c time-stamp-start: "def\\\\texinfoversion{" +@c time-stamp-format: "%:y-%02m-%02d.%02H" +@c time-stamp-end: "}" +@c End: diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi new file mode 100644 index 00000000000..2e90a6f6095 --- /dev/null +++ b/gcc/doc/tm.texi @@ -0,0 +1,8494 @@ +@c Copyright (C) 1988,1989,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001 +@c Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@node Target Macros +@chapter Target Description Macros +@cindex machine description macros +@cindex target description macros +@cindex macros, target description +@cindex @file{tm.h} macros + +In addition to the file @file{@var{machine}.md}, a machine description +includes a C header file conventionally given the name +@file{@var{machine}.h}. This header file defines numerous macros +that convey the information about the target machine that does not fit +into the scheme of the @file{.md} file. The file @file{tm.h} should be +a link to @file{@var{machine}.h}. The header file @file{config.h} +includes @file{tm.h} and most compiler source files include +@file{config.h}. + +@menu +* Driver:: Controlling how the driver runs the compilation passes. +* Run-time Target:: Defining @samp{-m} options like @samp{-m68000} and @samp{-m68020}. +* Per-Function Data:: Defining data structures for per-function information. +* Storage Layout:: Defining sizes and alignments of data. +* Type Layout:: Defining sizes and properties of basic user data types. +* Registers:: Naming and describing the hardware registers. +* Register Classes:: Defining the classes of hardware registers. +* Stack and Calling:: Defining which way the stack grows and by how much. +* Varargs:: Defining the varargs macros. +* Trampolines:: Code set up at run time to enter a nested function. +* Library Calls:: Controlling how library routines are implicitly called. +* Addressing Modes:: Defining addressing modes valid for memory operands. +* Condition Code:: Defining how insns update the condition code. +* Costs:: Defining relative costs of different operations. +* Sections:: Dividing storage into text, data, and other sections. +* PIC:: Macros for position independent code. +* Assembler Format:: Defining how to write insns and pseudo-ops to output. +* Debugging Info:: Defining the format of debugging output. +* Cross-compilation:: Handling floating point for cross-compilers. +* Mode Switching:: Insertion of mode-switching instructions. +* Misc:: Everything else. +@end menu + +@node Driver +@section Controlling the Compilation Driver, @file{gcc} +@cindex driver +@cindex controlling the compilation driver + +@c prevent bad page break with this line +You can control the compilation driver. + +@table @code +@findex SWITCH_TAKES_ARG +@item SWITCH_TAKES_ARG (@var{char}) +A C expression which determines whether the option @samp{-@var{char}} +takes arguments. The value should be the number of arguments that +option takes--zero, for many options. + +By default, this macro is defined as +@code{DEFAULT_SWITCH_TAKES_ARG}, which handles the standard options +properly. You need not define @code{SWITCH_TAKES_ARG} unless you +wish to add additional options which take arguments. Any redefinition +should call @code{DEFAULT_SWITCH_TAKES_ARG} and then check for +additional options. + +@findex WORD_SWITCH_TAKES_ARG +@item WORD_SWITCH_TAKES_ARG (@var{name}) +A C expression which determines whether the option @samp{-@var{name}} +takes arguments. The value should be the number of arguments that +option takes--zero, for many options. This macro rather than +@code{SWITCH_TAKES_ARG} is used for multi-character option names. + +By default, this macro is defined as +@code{DEFAULT_WORD_SWITCH_TAKES_ARG}, which handles the standard options +properly. You need not define @code{WORD_SWITCH_TAKES_ARG} unless you +wish to add additional options which take arguments. Any redefinition +should call @code{DEFAULT_WORD_SWITCH_TAKES_ARG} and then check for +additional options. + +@findex SWITCH_CURTAILS_COMPILATION +@item SWITCH_CURTAILS_COMPILATION (@var{char}) +A C expression which determines whether the option @samp{-@var{char}} +stops compilation before the generation of an executable. The value is +boolean, non-zero if the option does stop an executable from being +generated, zero otherwise. + +By default, this macro is defined as +@code{DEFAULT_SWITCH_CURTAILS_COMPILATION}, which handles the standard +options properly. You need not define +@code{SWITCH_CURTAILS_COMPILATION} unless you wish to add additional +options which affect the generation of an executable. Any redefinition +should call @code{DEFAULT_SWITCH_CURTAILS_COMPILATION} and then check +for additional options. + +@findex SWITCHES_NEED_SPACES +@item SWITCHES_NEED_SPACES +A string-valued C expression which enumerates the options for which +the linker needs a space between the option and its argument. + +If this macro is not defined, the default value is @code{""}. + +@findex CPP_SPEC +@item CPP_SPEC +A C string constant that tells the GCC driver program options to +pass to CPP. It can also specify how to translate options you +give to GCC into options for GCC to pass to the CPP. + +Do not define this macro if it does not need to do anything. + +@findex CPLUSPLUS_CPP_SPEC +@item CPLUSPLUS_CPP_SPEC +This macro is just like @code{CPP_SPEC}, but is used for C++, rather +than C. If you do not define this macro, then the value of +@code{CPP_SPEC} (if any) will be used instead. + +@findex NO_BUILTIN_SIZE_TYPE +@item NO_BUILTIN_SIZE_TYPE +If this macro is defined, the preprocessor will not define the builtin macro +@code{__SIZE_TYPE__}. The macro @code{__SIZE_TYPE__} must then be defined +by @code{CPP_SPEC} instead. + +This should be defined if @code{SIZE_TYPE} depends on target dependent flags +which are not accessible to the preprocessor. Otherwise, it should not +be defined. + +@findex NO_BUILTIN_PTRDIFF_TYPE +@item NO_BUILTIN_PTRDIFF_TYPE +If this macro is defined, the preprocessor will not define the builtin macro +@code{__PTRDIFF_TYPE__}. The macro @code{__PTRDIFF_TYPE__} must then be +defined by @code{CPP_SPEC} instead. + +This should be defined if @code{PTRDIFF_TYPE} depends on target dependent flags +which are not accessible to the preprocessor. Otherwise, it should not +be defined. + +@findex NO_BUILTIN_WCHAR_TYPE +@item NO_BUILTIN_WCHAR_TYPE +If this macro is defined, the preprocessor will not define the builtin macro +@code{__WCHAR_TYPE__}. The macro @code{__WCHAR_TYPE__} must then be +defined by @code{CPP_SPEC} instead. + +This should be defined if @code{WCHAR_TYPE} depends on target dependent flags +which are not accessible to the preprocessor. Otherwise, it should not +be defined. + +@findex NO_BUILTIN_WINT_TYPE +@item NO_BUILTIN_WINT_TYPE +If this macro is defined, the preprocessor will not define the builtin macro +@code{__WINT_TYPE__}. The macro @code{__WINT_TYPE__} must then be +defined by @code{CPP_SPEC} instead. + +This should be defined if @code{WINT_TYPE} depends on target dependent flags +which are not accessible to the preprocessor. Otherwise, it should not +be defined. + +@findex SIGNED_CHAR_SPEC +@item SIGNED_CHAR_SPEC +A C string constant that tells the GCC driver program options to +pass to CPP. By default, this macro is defined to pass the option +@samp{-D__CHAR_UNSIGNED__} to CPP if @code{char} will be treated as +@code{unsigned char} by @code{cc1}. + +Do not define this macro unless you need to override the default +definition. + +@findex CC1_SPEC +@item CC1_SPEC +A C string constant that tells the GCC driver program options to +pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language +front ends. +It can also specify how to translate options you give to GCC into options +for GCC to pass to front ends.. + +Do not define this macro if it does not need to do anything. + +@findex CC1PLUS_SPEC +@item CC1PLUS_SPEC +A C string constant that tells the GCC driver program options to +pass to @code{cc1plus}. It can also specify how to translate options you +give to GCC into options for GCC to pass to the @code{cc1plus}. + +Do not define this macro if it does not need to do anything. +Note that everything defined in CC1_SPEC is already passed to +@code{cc1plus} so there is no need to duplicate the contents of +CC1_SPEC in CC1PLUS_SPEC. + +@findex ASM_SPEC +@item ASM_SPEC +A C string constant that tells the GCC driver program options to +pass to the assembler. It can also specify how to translate options +you give to GCC into options for GCC to pass to the assembler. +See the file @file{sun3.h} for an example of this. + +Do not define this macro if it does not need to do anything. + +@findex ASM_FINAL_SPEC +@item ASM_FINAL_SPEC +A C string constant that tells the GCC driver program how to +run any programs which cleanup after the normal assembler. +Normally, this is not needed. See the file @file{mips.h} for +an example of this. + +Do not define this macro if it does not need to do anything. + +@findex LINK_SPEC +@item LINK_SPEC +A C string constant that tells the GCC driver program options to +pass to the linker. It can also specify how to translate options you +give to GCC into options for GCC to pass to the linker. + +Do not define this macro if it does not need to do anything. + +@findex LIB_SPEC +@item LIB_SPEC +Another C string constant used much like @code{LINK_SPEC}. The difference +between the two is that @code{LIB_SPEC} is used at the end of the +command given to the linker. + +If this macro is not defined, a default is provided that +loads the standard C library from the usual place. See @file{gcc.c}. + +@findex LIBGCC_SPEC +@item LIBGCC_SPEC +Another C string constant that tells the GCC driver program +how and when to place a reference to @file{libgcc.a} into the +linker command line. This constant is placed both before and after +the value of @code{LIB_SPEC}. + +If this macro is not defined, the GCC driver provides a default that +passes the string @samp{-lgcc} to the linker. + +@findex STARTFILE_SPEC +@item STARTFILE_SPEC +Another C string constant used much like @code{LINK_SPEC}. The +difference between the two is that @code{STARTFILE_SPEC} is used at +the very beginning of the command given to the linker. + +If this macro is not defined, a default is provided that loads the +standard C startup file from the usual place. See @file{gcc.c}. + +@findex ENDFILE_SPEC +@item ENDFILE_SPEC +Another C string constant used much like @code{LINK_SPEC}. The +difference between the two is that @code{ENDFILE_SPEC} is used at +the very end of the command given to the linker. + +Do not define this macro if it does not need to do anything. + +@findex THREAD_MODEL_SPEC +@item THREAD_MODEL_SPEC +GCC @code{-v} will print the thread model GCC was configured to use. +However, this doesn't work on platforms that are multilibbed on thread +models, such as AIX 4.3. On such platforms, define +@code{THREAD_MODEL_SPEC} such that it evaluates to a string without +blanks that names one of the recognized thread models. @code{%*}, the +default value of this macro, will expand to the value of +@code{thread_file} set in @file{config.gcc}. + +@findex EXTRA_SPECS +@item EXTRA_SPECS +Define this macro to provide additional specifications to put in the +@file{specs} file that can be used in various specifications like +@code{CC1_SPEC}. + +The definition should be an initializer for an array of structures, +containing a string constant, that defines the specification name, and a +string constant that provides the specification. + +Do not define this macro if it does not need to do anything. + +@code{EXTRA_SPECS} is useful when an architecture contains several +related targets, which have various @code{..._SPECS} which are similar +to each other, and the maintainer would like one central place to keep +these definitions. + +For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to +define either @code{_CALL_SYSV} when the System V calling sequence is +used or @code{_CALL_AIX} when the older AIX-based calling sequence is +used. + +The @file{config/rs6000/rs6000.h} target file defines: + +@example +#define EXTRA_SPECS \ + @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @}, + +#define CPP_SYS_DEFAULT "" +@end example + +The @file{config/rs6000/sysv.h} target file defines: +@smallexample +#undef CPP_SPEC +#define CPP_SPEC \ +"%@{posix: -D_POSIX_SOURCE @} \ +%@{mcall-sysv: -D_CALL_SYSV @} %@{mcall-aix: -D_CALL_AIX @} \ +%@{!mcall-sysv: %@{!mcall-aix: %(cpp_sysv_default) @}@} \ +%@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}" + +#undef CPP_SYSV_DEFAULT +#define CPP_SYSV_DEFAULT "-D_CALL_SYSV" +@end smallexample + +while the @file{config/rs6000/eabiaix.h} target file defines +@code{CPP_SYSV_DEFAULT} as: + +@smallexample +#undef CPP_SYSV_DEFAULT +#define CPP_SYSV_DEFAULT "-D_CALL_AIX" +@end smallexample + +@findex LINK_LIBGCC_SPECIAL +@item LINK_LIBGCC_SPECIAL +Define this macro if the driver program should find the library +@file{libgcc.a} itself and should not pass @samp{-L} options to the +linker. If you do not define this macro, the driver program will pass +the argument @samp{-lgcc} to tell the linker to do the search and will +pass @samp{-L} options to it. + +@findex LINK_LIBGCC_SPECIAL_1 +@item LINK_LIBGCC_SPECIAL_1 +Define this macro if the driver program should find the library +@file{libgcc.a}. If you do not define this macro, the driver program will pass +the argument @samp{-lgcc} to tell the linker to do the search. +This macro is similar to @code{LINK_LIBGCC_SPECIAL}, except that it does +not affect @samp{-L} options. + +@findex LINK_COMMAND_SPEC +@item LINK_COMMAND_SPEC +A C string constant giving the complete command line need to execute the +linker. When you do this, you will need to update your port each time a +change is made to the link command line within @file{gcc.c}. Therefore, +define this macro only if you need to completely redefine the command +line for invoking the linker and there is no other way to accomplish +the effect you need. + +@findex LINK_ELIMINATE_DUPLICATE_LDIRECTORIES +@item LINK_ELIMINATE_DUPLICATE_LDIRECTORIES +A nonzero value causes collect2 to remove duplicate -L search +directories from linking commands. Do not give it a nonzero value if +removing duplicate search directories changes the linker's semantics. + +@findex MULTILIB_DEFAULTS +@item MULTILIB_DEFAULTS +Define this macro as a C expression for the initializer of an array of +string to tell the driver program which options are defaults for this +target and thus do not need to be handled specially when using +@code{MULTILIB_OPTIONS}. + +Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in +the target makefile fragment or if none of the options listed in +@code{MULTILIB_OPTIONS} are set by default. +@xref{Target Fragment}. + +@findex RELATIVE_PREFIX_NOT_LINKDIR +@item RELATIVE_PREFIX_NOT_LINKDIR +Define this macro to tell @code{gcc} that it should only translate +a @samp{-B} prefix into a @samp{-L} linker option if the prefix +indicates an absolute file name. + +@findex STANDARD_EXEC_PREFIX +@item STANDARD_EXEC_PREFIX +Define this macro as a C string constant if you wish to override the +standard choice of @file{/usr/local/lib/gcc-lib/} as the default prefix to +try when searching for the executable files of the compiler. + +@findex MD_EXEC_PREFIX +@item MD_EXEC_PREFIX +If defined, this macro is an additional prefix to try after +@code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched +when the @samp{-b} option is used, or the compiler is built as a cross +compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it +to the list of directories used to find the assembler in @file{configure.in}. + +@findex STANDARD_STARTFILE_PREFIX +@item STANDARD_STARTFILE_PREFIX +Define this macro as a C string constant if you wish to override the +standard choice of @file{/usr/local/lib/} as the default prefix to +try when searching for startup files such as @file{crt0.o}. + +@findex MD_STARTFILE_PREFIX +@item MD_STARTFILE_PREFIX +If defined, this macro supplies an additional prefix to try after the +standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the +@samp{-b} option is used, or when the compiler is built as a cross +compiler. + +@findex MD_STARTFILE_PREFIX_1 +@item MD_STARTFILE_PREFIX_1 +If defined, this macro supplies yet another prefix to try after the +standard prefixes. It is not searched when the @samp{-b} option is +used, or when the compiler is built as a cross compiler. + +@findex INIT_ENVIRONMENT +@item INIT_ENVIRONMENT +Define this macro as a C string constant if you wish to set environment +variables for programs called by the driver, such as the assembler and +loader. The driver passes the value of this macro to @code{putenv} to +initialize the necessary environment variables. + +@findex LOCAL_INCLUDE_DIR +@item LOCAL_INCLUDE_DIR +Define this macro as a C string constant if you wish to override the +standard choice of @file{/usr/local/include} as the default prefix to +try when searching for local header files. @code{LOCAL_INCLUDE_DIR} +comes before @code{SYSTEM_INCLUDE_DIR} in the search order. + +Cross compilers do not use this macro and do not search either +@file{/usr/local/include} or its replacement. + +@findex MODIFY_TARGET_NAME +@item MODIFY_TARGET_NAME +Define this macro if you with to define command-line switches that modify the +default target name + +For each switch, you can include a string to be appended to the first +part of the configuration name or a string to be deleted from the +configuration name, if present. The definition should be an initializer +for an array of structures. Each array element should have three +elements: the switch name (a string constant, including the initial +dash), one of the enumeration codes @code{ADD} or @code{DELETE} to +indicate whether the string should be inserted or deleted, and the string +to be inserted or deleted (a string constant). + +For example, on a machine where @samp{64} at the end of the +configuration name denotes a 64-bit target and you want the @samp{-32} +and @samp{-64} switches to select between 32- and 64-bit targets, you would +code + +@smallexample +#define MODIFY_TARGET_NAME \ + @{ @{ "-32", DELETE, "64"@}, \ + @{"-64", ADD, "64"@}@} +@end smallexample + + +@findex SYSTEM_INCLUDE_DIR +@item SYSTEM_INCLUDE_DIR +Define this macro as a C string constant if you wish to specify a +system-specific directory to search for header files before the standard +directory. @code{SYSTEM_INCLUDE_DIR} comes before +@code{STANDARD_INCLUDE_DIR} in the search order. + +Cross compilers do not use this macro and do not search the directory +specified. + +@findex STANDARD_INCLUDE_DIR +@item STANDARD_INCLUDE_DIR +Define this macro as a C string constant if you wish to override the +standard choice of @file{/usr/include} as the default prefix to +try when searching for header files. + +Cross compilers do not use this macro and do not search either +@file{/usr/include} or its replacement. + +@findex STANDARD_INCLUDE_COMPONENT +@item STANDARD_INCLUDE_COMPONENT +The ``component'' corresponding to @code{STANDARD_INCLUDE_DIR}. +See @code{INCLUDE_DEFAULTS}, below, for the description of components. +If you do not define this macro, no component is used. + +@findex INCLUDE_DEFAULTS +@item INCLUDE_DEFAULTS +Define this macro if you wish to override the entire default search path +for include files. For a native compiler, the default search path +usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR}, +@code{SYSTEM_INCLUDE_DIR}, @code{GPLUSPLUS_INCLUDE_DIR}, and +@code{STANDARD_INCLUDE_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR} +and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile}, +and specify private search areas for GCC. The directory +@code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs. + +The definition should be an initializer for an array of structures. +Each array element should have four elements: the directory name (a +string constant), the component name (also a string constant), a flag +for C++-only directories, +and a flag showing that the includes in the directory don't need to be +wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of +the array with a null element. + +The component name denotes what GNU package the include file is part of, +if any, in all upper-case letters. For example, it might be @samp{GCC} +or @samp{BINUTILS}. If the package is part of a vendor-supplied +operating system, code the component name as @samp{0}. + +For example, here is the definition used for VAX/VMS: + +@example +#define INCLUDE_DEFAULTS \ +@{ \ + @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \ + @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \ + @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \ + @{ ".", 0, 0, 0@}, \ + @{ 0, 0, 0, 0@} \ +@} +@end example +@end table + +Here is the order of prefixes tried for exec files: + +@enumerate +@item +Any prefixes specified by the user with @samp{-B}. + +@item +The environment variable @code{GCC_EXEC_PREFIX}, if any. + +@item +The directories specified by the environment variable @code{COMPILER_PATH}. + +@item +The macro @code{STANDARD_EXEC_PREFIX}. + +@item +@file{/usr/lib/gcc/}. + +@item +The macro @code{MD_EXEC_PREFIX}, if any. +@end enumerate + +Here is the order of prefixes tried for startfiles: + +@enumerate +@item +Any prefixes specified by the user with @samp{-B}. + +@item +The environment variable @code{GCC_EXEC_PREFIX}, if any. + +@item +The directories specified by the environment variable @code{LIBRARY_PATH} +(or port-specific name; native only, cross compilers do not use this). + +@item +The macro @code{STANDARD_EXEC_PREFIX}. + +@item +@file{/usr/lib/gcc/}. + +@item +The macro @code{MD_EXEC_PREFIX}, if any. + +@item +The macro @code{MD_STARTFILE_PREFIX}, if any. + +@item +The macro @code{STANDARD_STARTFILE_PREFIX}. + +@item +@file{/lib/}. + +@item +@file{/usr/lib/}. +@end enumerate + +@node Run-time Target +@section Run-time Target Specification +@cindex run-time target specification +@cindex predefined macros +@cindex target specifications + +@c prevent bad page break with this line +Here are run-time target specifications. + +@table @code +@findex CPP_PREDEFINES +@item CPP_PREDEFINES +Define this to be a string constant containing @samp{-D} options to +define the predefined macros that identify this machine and system. +These macros will be predefined unless the @option{-ansi} option (or a +@option{-std} option for strict ISO C conformance) is specified. + +In addition, a parallel set of macros are predefined, whose names are +made by appending @samp{__} at the beginning and at the end. These +@samp{__} macros are permitted by the ISO standard, so they are +predefined regardless of whether @option{-ansi} or a @option{-std} option +is specified. + +For example, on the Sun, one can use the following value: + +@smallexample +"-Dmc68000 -Dsun -Dunix" +@end smallexample + +The result is to define the macros @code{__mc68000__}, @code{__sun__} +and @code{__unix__} unconditionally, and the macros @code{mc68000}, +@code{sun} and @code{unix} provided @samp{-ansi} is not specified. + +@findex extern int target_flags +@item extern int target_flags; +This declaration should be present. + +@cindex optional hardware or system features +@cindex features, optional, in system conventions +@item TARGET_@dots{} +This series of macros is to allow compiler command arguments to +enable or disable the use of optional features of the target machine. +For example, one machine description serves both the 68000 and +the 68020; a command argument tells the compiler whether it should +use 68020-only instructions or not. This command argument works +by means of a macro @code{TARGET_68020} that tests a bit in +@code{target_flags}. + +Define a macro @code{TARGET_@var{featurename}} for each such option. +Its definition should test a bit in @code{target_flags}. It is +recommended that a helper macro @code{TARGET_MASK_@var{featurename}} +is defined for each bit-value to test, and used in +@code{TARGET_@var{featurename}} and @code{TARGET_SWITCHES}. For +example: + +@smallexample +#define TARGET_MASK_68020 1 +#define TARGET_68020 (target_flags & TARGET_MASK_68020) +@end smallexample + +One place where these macros are used is in the condition-expressions +of instruction patterns. Note how @code{TARGET_68020} appears +frequently in the 68000 machine description file, @file{m68k.md}. +Another place they are used is in the definitions of the other +macros in the @file{@var{machine}.h} file. + +@findex TARGET_SWITCHES +@item TARGET_SWITCHES +This macro defines names of command options to set and clear +bits in @code{target_flags}. Its definition is an initializer +with a subgrouping for each command option. + +Each subgrouping contains a string constant, that defines the option +name, a number, which contains the bits to set in +@code{target_flags}, and a second string which is the description +displayed by --help. If the number is negative then the bits specified +by the number are cleared instead of being set. If the description +string is present but empty, then no help information will be displayed +for that option, but it will not count as an undocumented option. The +actual option name is made by appending @samp{-m} to the specified name. + +One of the subgroupings should have a null string. The number in +this grouping is the default value for @code{target_flags}. Any +target options act starting with that value. + +Here is an example which defines @samp{-m68000} and @samp{-m68020} +with opposite meanings, and picks the latter as the default: + +@smallexample +#define TARGET_SWITCHES \ + @{ @{ "68020", TARGET_MASK_68020, "" @}, \ + @{ "68000", -TARGET_MASK_68020, "Compile for the 68000" @}, \ + @{ "", TARGET_MASK_68020, "" @}@} +@end smallexample + +@findex TARGET_OPTIONS +@item TARGET_OPTIONS +This macro is similar to @code{TARGET_SWITCHES} but defines names of command +options that have values. Its definition is an initializer with a +subgrouping for each command option. + +Each subgrouping contains a string constant, that defines the fixed part +of the option name, the address of a variable, and a description string. +The variable, type @code{char *}, is set to the variable part of the +given option if the fixed part matches. The actual option name is made +by appending @samp{-m} to the specified name. + +Here is an example which defines @samp{-mshort-data-@var{number}}. If the +given option is @samp{-mshort-data-512}, the variable @code{m88k_short_data} +will be set to the string @code{"512"}. + +@smallexample +extern char *m88k_short_data; +#define TARGET_OPTIONS \ + @{ @{ "short-data-", &m88k_short_data, "Specify the size of the short data section" @} @} +@end smallexample + +@findex TARGET_VERSION +@item TARGET_VERSION +This macro is a C statement to print on @code{stderr} a string +describing the particular machine description choice. Every machine +description should define @code{TARGET_VERSION}. For example: + +@smallexample +#ifdef MOTOROLA +#define TARGET_VERSION \ + fprintf (stderr, " (68k, Motorola syntax)"); +#else +#define TARGET_VERSION \ + fprintf (stderr, " (68k, MIT syntax)"); +#endif +@end smallexample + +@findex OVERRIDE_OPTIONS +@item OVERRIDE_OPTIONS +Sometimes certain combinations of command options do not make sense on +a particular target machine. You can define a macro +@code{OVERRIDE_OPTIONS} to take account of this. This macro, if +defined, is executed once just after all the command options have been +parsed. + +Don't use this macro to turn on various extra optimizations for +@samp{-O}. That is what @code{OPTIMIZATION_OPTIONS} is for. + +@findex OPTIMIZATION_OPTIONS +@item OPTIMIZATION_OPTIONS (@var{level}, @var{size}) +Some machines may desire to change what optimizations are performed for +various optimization levels. This macro, if defined, is executed once +just after the optimization level is determined and before the remainder +of the command options have been parsed. Values set in this macro are +used as the default values for the other command line options. + +@var{level} is the optimization level specified; 2 if @samp{-O2} is +specified, 1 if @samp{-O} is specified, and 0 if neither is specified. + +@var{size} is non-zero if @samp{-Os} is specified and zero otherwise. + +You should not use this macro to change options that are not +machine-specific. These should uniformly selected by the same +optimization level on all supported machines. Use this macro to enable +machine-specific optimizations. + +@strong{Do not examine @code{write_symbols} in +this macro!} The debugging options are not supposed to alter the +generated code. + +@findex CAN_DEBUG_WITHOUT_FP +@item CAN_DEBUG_WITHOUT_FP +Define this macro if debugging can be performed even without a frame +pointer. If this macro is defined, GCC will turn on the +@samp{-fomit-frame-pointer} option whenever @samp{-O} is specified. +@end table + +@node Per-Function Data +@section Defining data structures for per-function information. +@cindex per-function data +@cindex data structures + +If the target needs to store information on a per-function basis, GCC +provides a macro and a couple of variables to allow this. Note, just +using statics to store the information is a bad idea, since GCC supports +nested functions, so you can be halfway through encoding one function +when another one comes along. + +GCC defines a data structure called @code{struct function} which +contains all of the data specific to an individual function. This +structure contains a field called @code{machine} whose type is +@code{struct machine_function *}, which can be used by targets to point +to their own specific data. + +If a target needs per-function specific data it should define the type +@code{struct machine_function} and also the macro +@code{INIT_EXPANDERS}. This macro should be used to initialise some or +all of the function pointers @code{init_machine_status}, +@code{free_machine_status} and @code{mark_machine_status}. These +pointers are explained below. + +One typical use of per-function, target specific data is to create an +RTX to hold the register containing the function's return address. This +RTX can then be used to implement the @code{__builtin_return_address} +function, for level 0. + +Note - earlier implementations of GCC used a single data area to hold +all of the per-function information. Thus when processing of a nested +function began the old per-function data had to be pushed onto a +stack, and when the processing was finished, it had to be popped off the +stack. GCC used to provide function pointers called +@code{save_machine_status} and @code{restore_machine_status} to handle +the saving and restoring of the target specific information. Since the +single data area approach is no longer used, these pointers are no +longer supported. + +The macro and function pointers are described below. + +@table @code +@findex INIT_EXPANDERS +@item INIT_EXPANDERS +Macro called to initialise any target specific information. This macro +is called once per function, before generation of any RTL has begun. +The intention of this macro is to allow the initialisation of the +function pointers below. + +@findex init_machine_status +@item init_machine_status +This is a @code{void (*)(struct function *)} function pointer. If this +pointer is non-NULL it will be called once per function, before function +compilation starts, in order to allow the target to perform any target +specific initialisation of the @code{struct function} structure. It is +intended that this would be used to initialise the @code{machine} of +that struture. + +@findex free_machine_status +@item free_machine_status +This is a @code{void (*)(struct function *)} function pointer. If this +pointer is non-NULL it will be called once per function, after the +function has been compiled, in order to allow any memory allocated +during the @code{init_machine_status} function call to be freed. + +@findex mark_machine_status +@item mark_machine_status +This is a @code{void (*)(struct function *)} function pointer. If this +pointer is non-NULL it will be called once per function in order to mark +any data items in the @code{struct machine_function} structure which +need garbage collection. + +@end table + +@node Storage Layout +@section Storage Layout +@cindex storage layout + +Note that the definitions of the macros in this table which are sizes or +alignments measured in bits do not need to be constant. They can be C +expressions that refer to static variables, such as the @code{target_flags}. +@xref{Run-time Target}. + +@table @code +@findex BITS_BIG_ENDIAN +@item BITS_BIG_ENDIAN +Define this macro to have the value 1 if the most significant bit in a +byte has the lowest number; otherwise define it to have the value zero. +This means that bit-field instructions count from the most significant +bit. If the machine has no bit-field instructions, then this must still +be defined, but it doesn't matter which value it is defined to. This +macro need not be a constant. + +This macro does not affect the way structure fields are packed into +bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}. + +@findex BYTES_BIG_ENDIAN +@item BYTES_BIG_ENDIAN +Define this macro to have the value 1 if the most significant byte in a +word has the lowest number. This macro need not be a constant. + +@findex WORDS_BIG_ENDIAN +@item WORDS_BIG_ENDIAN +Define this macro to have the value 1 if, in a multiword object, the +most significant word has the lowest number. This applies to both +memory locations and registers; GCC fundamentally assumes that the +order of words in memory is the same as the order in registers. This +macro need not be a constant. + +@findex LIBGCC2_WORDS_BIG_ENDIAN +@item LIBGCC2_WORDS_BIG_ENDIAN +Define this macro if WORDS_BIG_ENDIAN is not constant. This must be a +constant value with the same meaning as WORDS_BIG_ENDIAN, which will be +used only when compiling libgcc2.c. Typically the value will be set +based on preprocessor defines. + +@findex FLOAT_WORDS_BIG_ENDIAN +@item FLOAT_WORDS_BIG_ENDIAN +Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or +@code{TFmode} floating point numbers are stored in memory with the word +containing the sign bit at the lowest address; otherwise define it to +have the value 0. This macro need not be a constant. + +You need not define this macro if the ordering is the same as for +multi-word integers. + +@findex BITS_PER_UNIT +@item BITS_PER_UNIT +Define this macro to be the number of bits in an addressable storage +unit (byte); normally 8. + +@findex BITS_PER_WORD +@item BITS_PER_WORD +Number of bits in a word; normally 32. + +@findex MAX_BITS_PER_WORD +@item MAX_BITS_PER_WORD +Maximum number of bits in a word. If this is undefined, the default is +@code{BITS_PER_WORD}. Otherwise, it is the constant value that is the +largest value that @code{BITS_PER_WORD} can have at run-time. + +@findex UNITS_PER_WORD +@item UNITS_PER_WORD +Number of storage units in a word; normally 4. + +@findex MIN_UNITS_PER_WORD +@item MIN_UNITS_PER_WORD +Minimum number of units in a word. If this is undefined, the default is +@code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the +smallest value that @code{UNITS_PER_WORD} can have at run-time. + +@findex POINTER_SIZE +@item POINTER_SIZE +Width of a pointer, in bits. You must specify a value no wider than the +width of @code{Pmode}. If it is not equal to the width of @code{Pmode}, +you must define @code{POINTERS_EXTEND_UNSIGNED}. + +@findex POINTERS_EXTEND_UNSIGNED +@item POINTERS_EXTEND_UNSIGNED +A C expression whose value is nonzero if pointers that need to be +extended from being @code{POINTER_SIZE} bits wide to @code{Pmode} are to +be zero-extended and zero if they are to be sign-extended. + +You need not define this macro if the @code{POINTER_SIZE} is equal +to the width of @code{Pmode}. + +@findex PROMOTE_MODE +@item PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type}) +A macro to update @var{m} and @var{unsignedp} when an object whose type +is @var{type} and which has the specified mode and signedness is to be +stored in a register. This macro is only called when @var{type} is a +scalar type. + +On most RISC machines, which only have operations that operate on a full +register, define this macro to set @var{m} to @code{word_mode} if +@var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most +cases, only integer modes should be widened because wider-precision +floating-point operations are usually more expensive than their narrower +counterparts. + +For most machines, the macro definition does not change @var{unsignedp}. +However, some machines, have instructions that preferentially handle +either signed or unsigned quantities of certain modes. For example, on +the DEC Alpha, 32-bit loads from memory and 32-bit add instructions +sign-extend the result to 64 bits. On such machines, set +@var{unsignedp} according to which kind of extension is more efficient. + +Do not define this macro if it would never modify @var{m}. + +@findex PROMOTE_FUNCTION_ARGS +@item PROMOTE_FUNCTION_ARGS +Define this macro if the promotion described by @code{PROMOTE_MODE} +should also be done for outgoing function arguments. + +@findex PROMOTE_FUNCTION_RETURN +@item PROMOTE_FUNCTION_RETURN +Define this macro if the promotion described by @code{PROMOTE_MODE} +should also be done for the return value of functions. + +If this macro is defined, @code{FUNCTION_VALUE} must perform the same +promotions done by @code{PROMOTE_MODE}. + +@findex PROMOTE_FOR_CALL_ONLY +@item PROMOTE_FOR_CALL_ONLY +Define this macro if the promotion described by @code{PROMOTE_MODE} +should @emph{only} be performed for outgoing function arguments or +function return values, as specified by @code{PROMOTE_FUNCTION_ARGS} +and @code{PROMOTE_FUNCTION_RETURN}, respectively. + +@findex PARM_BOUNDARY +@item PARM_BOUNDARY +Normal alignment required for function parameters on the stack, in +bits. All stack parameters receive at least this much alignment +regardless of data type. On most machines, this is the same as the +size of an integer. + +@findex STACK_BOUNDARY +@item STACK_BOUNDARY +Define this macro if there is a guaranteed alignment for the stack +pointer on this machine. The definition is a C expression +for the desired alignment (measured in bits). This value is used as a +default if PREFERRED_STACK_BOUNDARY is not defined. + +@findex PREFERRED_STACK_BOUNDARY +@item PREFERRED_STACK_BOUNDARY +Define this macro if you wish to preserve a certain alignment for +the stack pointer. The definition is a C expression +for the desired alignment (measured in bits). If STACK_BOUNDARY is +also defined, this macro must evaluate to a value equal to or larger +than STACK_BOUNDARY. + +@cindex @code{PUSH_ROUNDING}, interaction with @code{PREFERRED_STACK_BOUNDARY} +If @code{PUSH_ROUNDING} is not defined, the stack will always be aligned +to the specified boundary. If @code{PUSH_ROUNDING} is defined and specifies +a less strict alignment than @code{PREFERRED_STACK_BOUNDARY}, the stack may +be momentarily unaligned while pushing arguments. + +@findex FUNCTION_BOUNDARY +@item FUNCTION_BOUNDARY +Alignment required for a function entry point, in bits. + +@findex BIGGEST_ALIGNMENT +@item BIGGEST_ALIGNMENT +Biggest alignment that any data type can require on this machine, in bits. + +@findex MINIMUM_ATOMIC_ALIGNMENT +@item MINIMUM_ATOMIC_ALIGNMENT +If defined, the smallest alignment, in bits, that can be given to an +object that can be referenced in one operation, without disturbing any +nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger +on machines that don't have byte or half-word store operations. + +@findex BIGGEST_FIELD_ALIGNMENT +@item BIGGEST_FIELD_ALIGNMENT +Biggest alignment that any structure or union field can require on this +machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for +structure and union fields only, unless the field alignment has been set +by the @code{__attribute__ ((aligned (@var{n})))} construct. + +@findex ADJUST_FIELD_ALIGN +@item ADJUST_FIELD_ALIGN (@var{field}, @var{computed}) +An expression for the alignment of a structure field @var{field} if the +alignment computed in the usual way is @var{computed}. GCC uses +this value instead of the value in @code{BIGGEST_ALIGNMENT} or +@code{BIGGEST_FIELD_ALIGNMENT}, if defined, for structure fields only. + +@findex MAX_OFILE_ALIGNMENT +@item MAX_OFILE_ALIGNMENT +Biggest alignment supported by the object file format of this machine. +Use this macro to limit the alignment which can be specified using the +@code{__attribute__ ((aligned (@var{n})))} construct. If not defined, +the default value is @code{BIGGEST_ALIGNMENT}. + +@findex DATA_ALIGNMENT +@item DATA_ALIGNMENT (@var{type}, @var{basic-align}) +If defined, a C expression to compute the alignment for a variable in +the static store. @var{type} is the data type, and @var{basic-align} is +the alignment that the object would ordinarily have. The value of this +macro is used instead of that alignment to align the object. + +If this macro is not defined, then @var{basic-align} is used. + +@findex strcpy +One use of this macro is to increase alignment of medium-size data to +make it all fit in fewer cache lines. Another is to cause character +arrays to be word-aligned so that @code{strcpy} calls that copy +constants to character arrays can be done inline. + +@findex CONSTANT_ALIGNMENT +@item CONSTANT_ALIGNMENT (@var{constant}, @var{basic-align}) +If defined, a C expression to compute the alignment given to a constant +that is being placed in memory. @var{constant} is the constant and +@var{basic-align} is the alignment that the object would ordinarily +have. The value of this macro is used instead of that alignment to +align the object. + +If this macro is not defined, then @var{basic-align} is used. + +The typical use of this macro is to increase alignment for string +constants to be word aligned so that @code{strcpy} calls that copy +constants can be done inline. + +@findex LOCAL_ALIGNMENT +@item LOCAL_ALIGNMENT (@var{type}, @var{basic-align}) +If defined, a C expression to compute the alignment for a variable in +the local store. @var{type} is the data type, and @var{basic-align} is +the alignment that the object would ordinarily have. The value of this +macro is used instead of that alignment to align the object. + +If this macro is not defined, then @var{basic-align} is used. + +One use of this macro is to increase alignment of medium-size data to +make it all fit in fewer cache lines. + +@findex EMPTY_FIELD_BOUNDARY +@item EMPTY_FIELD_BOUNDARY +Alignment in bits to be given to a structure bit field that follows an +empty field such as @code{int : 0;}. + +Note that @code{PCC_BITFIELD_TYPE_MATTERS} also affects the alignment +that results from an empty field. + +@findex STRUCTURE_SIZE_BOUNDARY +@item STRUCTURE_SIZE_BOUNDARY +Number of bits which any structure or union's size must be a multiple of. +Each structure or union's size is rounded up to a multiple of this. + +If you do not define this macro, the default is the same as +@code{BITS_PER_UNIT}. + +@findex STRICT_ALIGNMENT +@item STRICT_ALIGNMENT +Define this macro to be the value 1 if instructions will fail to work +if given data not on the nominal alignment. If instructions will merely +go slower in that case, define this macro as 0. + +@findex PCC_BITFIELD_TYPE_MATTERS +@item PCC_BITFIELD_TYPE_MATTERS +Define this if you wish to imitate the way many other C compilers handle +alignment of bitfields and the structures that contain them. + +The behavior is that the type written for a bitfield (@code{int}, +@code{short}, or other integer type) imposes an alignment for the +entire structure, as if the structure really did contain an ordinary +field of that type. In addition, the bitfield is placed within the +structure so that it would fit within such a field, not crossing a +boundary for it. + +Thus, on most machines, a bitfield whose type is written as @code{int} +would not cross a four-byte boundary, and would force four-byte +alignment for the whole structure. (The alignment used may not be four +bytes; it is controlled by the other alignment parameters.) + +If the macro is defined, its definition should be a C expression; +a nonzero value for the expression enables this behavior. + +Note that if this macro is not defined, or its value is zero, some +bitfields may cross more than one alignment boundary. The compiler can +support such references if there are @samp{insv}, @samp{extv}, and +@samp{extzv} insns that can directly reference memory. + +The other known way of making bitfields work is to define +@code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}. +Then every structure can be accessed with fullwords. + +Unless the machine has bitfield instructions or you define +@code{STRUCTURE_SIZE_BOUNDARY} that way, you must define +@code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value. + +If your aim is to make GCC use the same conventions for laying out +bitfields as are used by another compiler, here is how to investigate +what the other compiler does. Compile and run this program: + +@example +struct foo1 +@{ + char x; + char :0; + char y; +@}; + +struct foo2 +@{ + char x; + int :0; + char y; +@}; + +main () +@{ + printf ("Size of foo1 is %d\n", + sizeof (struct foo1)); + printf ("Size of foo2 is %d\n", + sizeof (struct foo2)); + exit (0); +@} +@end example + +If this prints 2 and 5, then the compiler's behavior is what you would +get from @code{PCC_BITFIELD_TYPE_MATTERS}. + +@findex BITFIELD_NBYTES_LIMITED +@item BITFIELD_NBYTES_LIMITED +Like PCC_BITFIELD_TYPE_MATTERS except that its effect is limited to +aligning a bitfield within the structure. + +@findex MEMBER_TYPE_FORCES_BLK +@item MEMBER_TYPE_FORCES_BLK (@var{field}) +Return 1 if a structure or array containing @var{field} should be accessed using +@code{BLKMODE}. + +Normally, this is not needed. See the file @file{c4x.h} for an example +of how to use this macro to prevent a structure having a floating point +field from being accessed in an integer mode. + +@findex ROUND_TYPE_SIZE +@item ROUND_TYPE_SIZE (@var{type}, @var{computed}, @var{specified}) +Define this macro as an expression for the overall size of a type +(given by @var{type} as a tree node) when the size computed in the +usual way is @var{computed} and the alignment is @var{specified}. + +The default is to round @var{computed} up to a multiple of @var{specified}. + +@findex ROUND_TYPE_SIZE_UNIT +@item ROUND_TYPE_SIZE_UNIT (@var{type}, @var{computed}, @var{specified}) +Similar to @code{ROUND_TYPE_SIZE}, but sizes and alignments are +specified in units (bytes). If you define @code{ROUND_TYPE_SIZE}, +you must also define this macro and they must be defined consistently +with each other. + +@findex ROUND_TYPE_ALIGN +@item ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified}) +Define this macro as an expression for the alignment of a type (given +by @var{type} as a tree node) if the alignment computed in the usual +way is @var{computed} and the alignment explicitly specified was +@var{specified}. + +The default is to use @var{specified} if it is larger; otherwise, use +the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT} + +@findex MAX_FIXED_MODE_SIZE +@item MAX_FIXED_MODE_SIZE +An integer expression for the size in bits of the largest integer +machine mode that should actually be used. All integer machine modes of +this size or smaller can be used for structures and unions with the +appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE +(DImode)} is assumed. + +@findex VECTOR_MODE_SUPPORTED_P +@item VECTOR_MODE_SUPPORTED_P(@var{mode}) +Define this macro to be nonzero if the port is prepared to handle insns +involving vector mode @var{mode}. At the very least, it must have move +patterns for this mode. + +@findex STACK_SAVEAREA_MODE +@item STACK_SAVEAREA_MODE (@var{save_level}) +If defined, an expression of type @code{enum machine_mode} that +specifies the mode of the save area operand of a +@code{save_stack_@var{level}} named pattern (@pxref{Standard Names}). +@var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or +@code{SAVE_NONLOCAL} and selects which of the three named patterns is +having its mode specified. + +You need not define this macro if it always returns @code{Pmode}. You +would most commonly define this macro if the +@code{save_stack_@var{level}} patterns need to support both a 32- and a +64-bit mode. + +@findex STACK_SIZE_MODE +@item STACK_SIZE_MODE +If defined, an expression of type @code{enum machine_mode} that +specifies the mode of the size increment operand of an +@code{allocate_stack} named pattern (@pxref{Standard Names}). + +You need not define this macro if it always returns @code{word_mode}. +You would most commonly define this macro if the @code{allocate_stack} +pattern needs to support both a 32- and a 64-bit mode. + +@findex CHECK_FLOAT_VALUE +@item CHECK_FLOAT_VALUE (@var{mode}, @var{value}, @var{overflow}) +A C statement to validate the value @var{value} (of type +@code{double}) for mode @var{mode}. This means that you check whether +@var{value} fits within the possible range of values for mode +@var{mode} on this target machine. The mode @var{mode} is always +a mode of class @code{MODE_FLOAT}. @var{overflow} is nonzero if +the value is already known to be out of range. + +If @var{value} is not valid or if @var{overflow} is nonzero, you should +set @var{overflow} to 1 and then assign some valid value to @var{value}. +Allowing an invalid value to go through the compiler can produce +incorrect assembler code which may even cause Unix assemblers to crash. + +This macro need not be defined if there is no work for it to do. + +@findex TARGET_FLOAT_FORMAT +@item TARGET_FLOAT_FORMAT +A code distinguishing the floating point format of the target machine. +There are three defined values: + +@table @code +@findex IEEE_FLOAT_FORMAT +@item IEEE_FLOAT_FORMAT +This code indicates IEEE floating point. It is the default; there is no +need to define this macro when the format is IEEE. + +@findex VAX_FLOAT_FORMAT +@item VAX_FLOAT_FORMAT +This code indicates the peculiar format used on the Vax. + +@findex UNKNOWN_FLOAT_FORMAT +@item UNKNOWN_FLOAT_FORMAT +This code indicates any other format. +@end table + +The value of this macro is compared with @code{HOST_FLOAT_FORMAT} +(@pxref{Config}) to determine whether the target machine has the same +format as the host machine. If any other formats are actually in use on +supported machines, new codes should be defined for them. + +The ordering of the component words of floating point values stored in +memory is controlled by @code{FLOAT_WORDS_BIG_ENDIAN} for the target +machine and @code{HOST_FLOAT_WORDS_BIG_ENDIAN} for the host. + +@findex DEFAULT_VTABLE_THUNKS +@item DEFAULT_VTABLE_THUNKS +GCC supports two ways of implementing C++ vtables: traditional or with +so-called ``thunks''. The flag @samp{-fvtable-thunk} chooses between them. +Define this macro to be a C expression for the default value of that flag. +If @code{DEFAULT_VTABLE_THUNKS} is 0, GCC uses the traditional +implementation by default. The ``thunk'' implementation is more efficient +(especially if you have provided an implementation of +@code{ASM_OUTPUT_MI_THUNK}, see @ref{Function Entry}), but is not binary +compatible with code compiled using the traditional implementation. +If you are writing a new port, define @code{DEFAULT_VTABLE_THUNKS} to 1. + +If you do not define this macro, the default for @samp{-fvtable-thunk} is 0. +@end table + +@node Type Layout +@section Layout of Source Language Data Types + +These macros define the sizes and other characteristics of the standard +basic data types used in programs being compiled. Unlike the macros in +the previous section, these apply to specific features of C and related +languages, rather than to fundamental aspects of storage layout. + +@table @code +@findex INT_TYPE_SIZE +@item INT_TYPE_SIZE +A C expression for the size in bits of the type @code{int} on the +target machine. If you don't define this, the default is one word. + +@findex MAX_INT_TYPE_SIZE +@item MAX_INT_TYPE_SIZE +Maximum number for the size in bits of the type @code{int} on the target +machine. If this is undefined, the default is @code{INT_TYPE_SIZE}. +Otherwise, it is the constant value that is the largest value that +@code{INT_TYPE_SIZE} can have at run-time. This is used in @code{cpp}. + +@findex SHORT_TYPE_SIZE +@item SHORT_TYPE_SIZE +A C expression for the size in bits of the type @code{short} on the +target machine. If you don't define this, the default is half a word. +(If this would be less than one storage unit, it is rounded up to one +unit.) + +@findex LONG_TYPE_SIZE +@item LONG_TYPE_SIZE +A C expression for the size in bits of the type @code{long} on the +target machine. If you don't define this, the default is one word. + +@findex MAX_LONG_TYPE_SIZE +@item MAX_LONG_TYPE_SIZE +Maximum number for the size in bits of the type @code{long} on the +target machine. If this is undefined, the default is +@code{LONG_TYPE_SIZE}. Otherwise, it is the constant value that is the +largest value that @code{LONG_TYPE_SIZE} can have at run-time. This is +used in @code{cpp}. + +@findex LONG_LONG_TYPE_SIZE +@item LONG_LONG_TYPE_SIZE +A C expression for the size in bits of the type @code{long long} on the +target machine. If you don't define this, the default is two +words. If you want to support GNU Ada on your machine, the value of this +macro must be at least 64. + +@findex CHAR_TYPE_SIZE +@item CHAR_TYPE_SIZE +A C expression for the size in bits of the type @code{char} on the +target machine. If you don't define this, the default is +@code{BITS_PER_UNIT}. + +@findex MAX_CHAR_TYPE_SIZE +@item MAX_CHAR_TYPE_SIZE +Maximum number for the size in bits of the type @code{char} on the +target machine. If this is undefined, the default is +@code{CHAR_TYPE_SIZE}. Otherwise, it is the constant value that is the +largest value that @code{CHAR_TYPE_SIZE} can have at run-time. This is +used in @code{cpp}. + +@findex FLOAT_TYPE_SIZE +@item FLOAT_TYPE_SIZE +A C expression for the size in bits of the type @code{float} on the +target machine. If you don't define this, the default is one word. + +@findex DOUBLE_TYPE_SIZE +@item DOUBLE_TYPE_SIZE +A C expression for the size in bits of the type @code{double} on the +target machine. If you don't define this, the default is two +words. + +@findex LONG_DOUBLE_TYPE_SIZE +@item LONG_DOUBLE_TYPE_SIZE +A C expression for the size in bits of the type @code{long double} on +the target machine. If you don't define this, the default is two +words. + +@findex WIDEST_HARDWARE_FP_SIZE +@item WIDEST_HARDWARE_FP_SIZE +A C expression for the size in bits of the widest floating-point format +supported by the hardware. If you define this macro, you must specify a +value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}. +If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE} +is the default. + +@findex DEFAULT_SIGNED_CHAR +@item DEFAULT_SIGNED_CHAR +An expression whose value is 1 or 0, according to whether the type +@code{char} should be signed or unsigned by default. The user can +always override this default with the options @samp{-fsigned-char} +and @samp{-funsigned-char}. + +@findex DEFAULT_SHORT_ENUMS +@item DEFAULT_SHORT_ENUMS +A C expression to determine whether to give an @code{enum} type +only as many bytes as it takes to represent the range of possible values +of that type. A nonzero value means to do that; a zero value means all +@code{enum} types should be allocated like @code{int}. + +If you don't define the macro, the default is 0. + +@findex SIZE_TYPE +@item SIZE_TYPE +A C expression for a string describing the name of the data type to use +for size values. The typedef name @code{size_t} is defined using the +contents of the string. + +The string can contain more than one keyword. If so, separate them with +spaces, and write first any length keyword, then @code{unsigned} if +appropriate, and finally @code{int}. The string must exactly match one +of the data type names defined in the function +@code{init_decl_processing} in the file @file{c-decl.c}. You may not +omit @code{int} or change the order---that would cause the compiler to +crash on startup. + +If you don't define this macro, the default is @code{"long unsigned +int"}. + +@findex PTRDIFF_TYPE +@item PTRDIFF_TYPE +A C expression for a string describing the name of the data type to use +for the result of subtracting two pointers. The typedef name +@code{ptrdiff_t} is defined using the contents of the string. See +@code{SIZE_TYPE} above for more information. + +If you don't define this macro, the default is @code{"long int"}. + +@findex WCHAR_TYPE +@item WCHAR_TYPE +A C expression for a string describing the name of the data type to use +for wide characters. The typedef name @code{wchar_t} is defined using +the contents of the string. See @code{SIZE_TYPE} above for more +information. + +If you don't define this macro, the default is @code{"int"}. + +@findex WCHAR_TYPE_SIZE +@item WCHAR_TYPE_SIZE +A C expression for the size in bits of the data type for wide +characters. This is used in @code{cpp}, which cannot make use of +@code{WCHAR_TYPE}. + +@findex MAX_WCHAR_TYPE_SIZE +@item MAX_WCHAR_TYPE_SIZE +Maximum number for the size in bits of the data type for wide +characters. If this is undefined, the default is +@code{WCHAR_TYPE_SIZE}. Otherwise, it is the constant value that is the +largest value that @code{WCHAR_TYPE_SIZE} can have at run-time. This is +used in @code{cpp}. + +@findex WINT_TYPE +@item WINT_TYPE +A C expression for a string describing the name of the data type to +use for wide characters passed to @code{printf} and returned from +@code{getwc}. The typedef name @code{wint_t} is defined using the +contents of the string. See @code{SIZE_TYPE} above for more +information. + +If you don't define this macro, the default is @code{"unsigned int"}. + +@findex INTMAX_TYPE +@item INTMAX_TYPE +A C expression for a string describing the name of the data type that +can represent any value of any standard or extended signed integer type. +The typedef name @code{intmax_t} is defined using the contents of the +string. See @code{SIZE_TYPE} above for more information. + +If you don't define this macro, the default is the first of +@code{"int"}, @code{"long int"}, or @code{"long long int"} that has as +much precision as @code{long long int}. + +@findex UINTMAX_TYPE +@item UINTMAX_TYPE +A C expression for a string describing the name of the data type that +can represent any value of any standard or extended unsigned integer +type. The typedef name @code{uintmax_t} is defined using the contents +of the string. See @code{SIZE_TYPE} above for more information. + +If you don't define this macro, the default is the first of +@code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long +unsigned int"} that has as much precision as @code{long long unsigned +int}. + +@findex OBJC_SELECTORS_WITHOUT_LABELS +@item OBJC_SELECTORS_WITHOUT_LABELS +Define this macro if the compiler can group all the selectors together +into a vector and use just one label at the beginning of the vector. +Otherwise, the compiler must give each selector its own assembler +label. + +On certain machines, it is important to have a separate label for each +selector because this enables the linker to eliminate duplicate selectors. + +@findex TARGET_PTRMEMFUNC_VBIT_LOCATION +@item TARGET_PTRMEMFUNC_VBIT_LOCATION +The C++ compiler represents a pointer-to-member-function with a struct +that looks like: + +@example + struct @{ + union @{ + void (*fn)(); + ptrdiff_t vtable_index; + @}; + ptrdiff_t delta; + @}; +@end example + +@noindent +The C++ compiler must use one bit to indicate whether the function that +will be called through a pointer-to-member-function is virtual. +Normally, we assume that the low-order bit of a function pointer must +always be zero. Then, by ensuring that the vtable_index is odd, we can +distinguish which variant of the union is in use. But, on some +platforms function pointers can be odd, and so this doesn't work. In +that case, we use the low-order bit of the @code{delta} field, and shift +the remainder of the @code{delta} field to the left. + +GCC will automatically make the right selection about where to store +this bit using the @code{FUNCTION_BOUNDARY} setting for your platform. +However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY} +set such that functions always start at even addresses, but the lowest +bit of pointers to functions indicate whether the function at that +address is in ARM or Thumb mode. If this is the case of your +architecture, you should define this macro to +@code{ptrmemfunc_vbit_in_delta}. + +In general, you should not have to define this macro. On architectures +in which function addresses are always even, according to +@code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to +@code{ptrmemfunc_vbit_in_pfn}. + +@findex TARGET_BELL +@item TARGET_BELL +A C constant expression for the integer value for escape sequence +@samp{\a}. + +@findex TARGET_TAB +@findex TARGET_BS +@findex TARGET_NEWLINE +@item TARGET_BS +@itemx TARGET_TAB +@itemx TARGET_NEWLINE +C constant expressions for the integer values for escape sequences +@samp{\b}, @samp{\t} and @samp{\n}. + +@findex TARGET_VT +@findex TARGET_FF +@findex TARGET_CR +@item TARGET_VT +@itemx TARGET_FF +@itemx TARGET_CR +C constant expressions for the integer values for escape sequences +@samp{\v}, @samp{\f} and @samp{\r}. +@end table + +@node Registers +@section Register Usage +@cindex register usage + +This section explains how to describe what registers the target machine +has, and how (in general) they can be used. + +The description of which registers a specific instruction can use is +done with register classes; see @ref{Register Classes}. For information +on using registers to access a stack frame, see @ref{Frame Registers}. +For passing values in registers, see @ref{Register Arguments}. +For returning values in registers, see @ref{Scalar Return}. + +@menu +* Register Basics:: Number and kinds of registers. +* Allocation Order:: Order in which registers are allocated. +* Values in Registers:: What kinds of values each reg can hold. +* Leaf Functions:: Renumbering registers for leaf functions. +* Stack Registers:: Handling a register stack such as 80387. +@end menu + +@node Register Basics +@subsection Basic Characteristics of Registers + +@c prevent bad page break with this line +Registers have various characteristics. + +@table @code +@findex FIRST_PSEUDO_REGISTER +@item FIRST_PSEUDO_REGISTER +Number of hardware registers known to the compiler. They receive +numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first +pseudo register's number really is assigned the number +@code{FIRST_PSEUDO_REGISTER}. + +@item FIXED_REGISTERS +@findex FIXED_REGISTERS +@cindex fixed register +An initializer that says which registers are used for fixed purposes +all throughout the compiled code and are therefore not available for +general allocation. These would include the stack pointer, the frame +pointer (except on machines where that can be used as a general +register when no frame pointer is needed), the program counter on +machines where that is considered one of the addressable registers, +and any other numbered register with a standard use. + +This information is expressed as a sequence of numbers, separated by +commas and surrounded by braces. The @var{n}th number is 1 if +register @var{n} is fixed, 0 otherwise. + +The table initialized from this macro, and the table initialized by +the following one, may be overridden at run time either automatically, +by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by +the user with the command options @samp{-ffixed-@var{reg}}, +@samp{-fcall-used-@var{reg}} and @samp{-fcall-saved-@var{reg}}. + +@findex CALL_USED_REGISTERS +@item CALL_USED_REGISTERS +@cindex call-used register +@cindex call-clobbered register +@cindex call-saved register +Like @code{FIXED_REGISTERS} but has 1 for each register that is +clobbered (in general) by function calls as well as for fixed +registers. This macro therefore identifies the registers that are not +available for general allocation of values that must live across +function calls. + +If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler +automatically saves it on function entry and restores it on function +exit, if the register is used within the function. + +@findex HARD_REGNO_CALL_PART_CLOBBERED +@item HARD_REGNO_CALL_PART_CLOBBERED (@var{regno}, @var{mode}) +@cindex call-used register +@cindex call-clobbered register +@cindex call-saved register +A C expression that is non-zero if it is not permissible to store a +value of mode @var{mode} in hard register number @var{regno} across a +call without some part of it being clobbered. For most machines this +macro need not be defined. It is only required for machines that do not +preserve the entire contents of a register across a call. + +@findex CONDITIONAL_REGISTER_USAGE +@findex fixed_regs +@findex call_used_regs +@item CONDITIONAL_REGISTER_USAGE +Zero or more C statements that may conditionally modify five variables +@code{fixed_regs}, @code{call_used_regs}, @code{global_regs}, +(these three are of type @code{char []}), @code{reg_names} (of type +@code{const char * []}) and @code{reg_class_contents} (of type +@code{HARD_REG_SET}). +Before the macro is called @code{fixed_regs}, @code{call_used_regs} +@code{reg_class_contents} and @code{reg_names} have been initialized +from @code{FIXED_REGISTERS}, @code{CALL_USED_REGISTERS}, +@code{REG_CLASS_CONTENTS} and @code{REGISTER_NAMES}, respectively, +@code{global_regs} has been cleared, and any @samp{-ffixed-@var{reg}}, +@samp{-fcall-used-@var{reg}} and @samp{-fcall-saved-@var{reg}} command +options have been applied. + +This is necessary in case the fixed or call-clobbered registers depend +on target flags. + +You need not define this macro if it has no work to do. + +@cindex disabling certain registers +@cindex controlling register usage +If the usage of an entire class of registers depends on the target +flags, you may indicate this to GCC by using this macro to modify +@code{fixed_regs} and @code{call_used_regs} to 1 for each of the +registers in the classes which should not be used by GCC. Also define +the macro @code{REG_CLASS_FROM_LETTER} to return @code{NO_REGS} if it +is called with a letter for a class that shouldn't be used. + +(However, if this class is not included in @code{GENERAL_REGS} and all +of the insn patterns whose constraints permit this class are +controlled by target switches, then GCC will automatically avoid using +these registers when the target switches are opposed to them.) + +@findex NON_SAVING_SETJMP +@item NON_SAVING_SETJMP +If this macro is defined and has a nonzero value, it means that +@code{setjmp} and related functions fail to save the registers, or that +@code{longjmp} fails to restore them. To compensate, the compiler +avoids putting variables in registers in functions that use +@code{setjmp}. + +@findex INCOMING_REGNO +@item INCOMING_REGNO (@var{out}) +Define this macro if the target machine has register windows. This C +expression returns the register number as seen by the called function +corresponding to the register number @var{out} as seen by the calling +function. Return @var{out} if register number @var{out} is not an +outbound register. + +@findex OUTGOING_REGNO +@item OUTGOING_REGNO (@var{in}) +Define this macro if the target machine has register windows. This C +expression returns the register number as seen by the calling function +corresponding to the register number @var{in} as seen by the called +function. Return @var{in} if register number @var{in} is not an inbound +register. + +@findex LOCAL_REGNO +@item LOCAL_REGNO (@var{regno}) +Define this macro if the target machine has register windows. This C +expression returns true if the register is call-saved but is in the +register window. Unlike most call-saved registers, such registers +need not be explicitly restored on function exit or during non-local +gotos. + +@ignore +@findex PC_REGNUM +@item PC_REGNUM +If the program counter has a register number, define this as that +register number. Otherwise, do not define it. +@end ignore +@end table + +@node Allocation Order +@subsection Order of Allocation of Registers +@cindex order of register allocation +@cindex register allocation order + +@c prevent bad page break with this line +Registers are allocated in order. + +@table @code +@findex REG_ALLOC_ORDER +@item REG_ALLOC_ORDER +If defined, an initializer for a vector of integers, containing the +numbers of hard registers in the order in which GCC should prefer +to use them (from most preferred to least). + +If this macro is not defined, registers are used lowest numbered first +(all else being equal). + +One use of this macro is on machines where the highest numbered +registers must always be saved and the save-multiple-registers +instruction supports only sequences of consecutive registers. On such +machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists +the highest numbered allocable register first. + +@findex ORDER_REGS_FOR_LOCAL_ALLOC +@item ORDER_REGS_FOR_LOCAL_ALLOC +A C statement (sans semicolon) to choose the order in which to allocate +hard registers for pseudo-registers local to a basic block. + +Store the desired register order in the array @code{reg_alloc_order}. +Element 0 should be the register to allocate first; element 1, the next +register; and so on. + +The macro body should not assume anything about the contents of +@code{reg_alloc_order} before execution of the macro. + +On most machines, it is not necessary to define this macro. +@end table + +@node Values in Registers +@subsection How Values Fit in Registers + +This section discusses the macros that describe which kinds of values +(specifically, which machine modes) each register can hold, and how many +consecutive registers are needed for a given mode. + +@table @code +@findex HARD_REGNO_NREGS +@item HARD_REGNO_NREGS (@var{regno}, @var{mode}) +A C expression for the number of consecutive hard registers, starting +at register number @var{regno}, required to hold a value of mode +@var{mode}. + +On a machine where all registers are exactly one word, a suitable +definition of this macro is + +@smallexample +#define HARD_REGNO_NREGS(REGNO, MODE) \ + ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) \ + / UNITS_PER_WORD) +@end smallexample + +@findex HARD_REGNO_MODE_OK +@item HARD_REGNO_MODE_OK (@var{regno}, @var{mode}) +A C expression that is nonzero if it is permissible to store a value +of mode @var{mode} in hard register number @var{regno} (or in several +registers starting with that one). For a machine where all registers +are equivalent, a suitable definition is + +@smallexample +#define HARD_REGNO_MODE_OK(REGNO, MODE) 1 +@end smallexample + +You need not include code to check for the numbers of fixed registers, +because the allocation mechanism considers them to be always occupied. + +@cindex register pairs +On some machines, double-precision values must be kept in even/odd +register pairs. You can implement that by defining this macro to reject +odd register numbers for such modes. + +The minimum requirement for a mode to be OK in a register is that the +@samp{mov@var{mode}} instruction pattern support moves between the +register and other hard register in the same class and that moving a +value into the register and back out not alter it. + +Since the same instruction used to move @code{word_mode} will work for +all narrower integer modes, it is not necessary on any machine for +@code{HARD_REGNO_MODE_OK} to distinguish between these modes, provided +you define patterns @samp{movhi}, etc., to take advantage of this. This +is useful because of the interaction between @code{HARD_REGNO_MODE_OK} +and @code{MODES_TIEABLE_P}; it is very desirable for all integer modes +to be tieable. + +Many machines have special registers for floating point arithmetic. +Often people assume that floating point machine modes are allowed only +in floating point registers. This is not true. Any registers that +can hold integers can safely @emph{hold} a floating point machine +mode, whether or not floating arithmetic can be done on it in those +registers. Integer move instructions can be used to move the values. + +On some machines, though, the converse is true: fixed-point machine +modes may not go in floating registers. This is true if the floating +registers normalize any value stored in them, because storing a +non-floating value there would garble it. In this case, +@code{HARD_REGNO_MODE_OK} should reject fixed-point machine modes in +floating registers. But if the floating registers do not automatically +normalize, if you can store any bit pattern in one and retrieve it +unchanged without a trap, then any machine mode may go in a floating +register, so you can define this macro to say so. + +The primary significance of special floating registers is rather that +they are the registers acceptable in floating point arithmetic +instructions. However, this is of no concern to +@code{HARD_REGNO_MODE_OK}. You handle it by writing the proper +constraints for those instructions. + +On some machines, the floating registers are especially slow to access, +so that it is better to store a value in a stack frame than in such a +register if floating point arithmetic is not being done. As long as the +floating registers are not in class @code{GENERAL_REGS}, they will not +be used unless some pattern's constraint asks for one. + +@findex MODES_TIEABLE_P +@item MODES_TIEABLE_P (@var{mode1}, @var{mode2}) +A C expression that is nonzero if a value of mode +@var{mode1} is accessible in mode @var{mode2} without copying. + +If @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and +@code{HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always the same for +any @var{r}, then @code{MODES_TIEABLE_P (@var{mode1}, @var{mode2})} +should be nonzero. If they differ for any @var{r}, you should define +this macro to return zero unless some other mechanism ensures the +accessibility of the value in a narrower mode. + +You should define this macro to return nonzero in as many cases as +possible since doing so will allow GCC to perform better register +allocation. + +@findex AVOID_CCMODE_COPIES +@item AVOID_CCMODE_COPIES +Define this macro if the compiler should avoid copies to/from @code{CCmode} +registers. You should only define this macro if support for copying to/from +@code{CCmode} is incomplete. + +@findex SUBREG_REGNO_OFFSET +@item SUBREG_REGNO_OFFSET +Define this macro if the compiler needs to handle subregs in a non-standard +way. The macro returns the correct regno offset for mode @code{YMODE} given +a subreg of type @code{XMODE}. +This macro takes 4 parameters: +@code{XREGNO} - A regno of an inner hard subreg_reg (or what will become one). +@code{XMODE} - The mode of xregno. +@code{OFFSET} - The byte offset. +@code{YMODE} - The mode of a top level SUBREG (or what may become one). +The default function can be found in rtlanal.c, function +@code{subreg_regno_offset}. Normally this does not need to be defined. +@end table + +@node Leaf Functions +@subsection Handling Leaf Functions + +@cindex leaf functions +@cindex functions, leaf +On some machines, a leaf function (i.e., one which makes no calls) can run +more efficiently if it does not make its own register window. Often this +means it is required to receive its arguments in the registers where they +are passed by the caller, instead of the registers where they would +normally arrive. + +The special treatment for leaf functions generally applies only when +other conditions are met; for example, often they may use only those +registers for its own variables and temporaries. We use the term ``leaf +function'' to mean a function that is suitable for this special +handling, so that functions with no calls are not necessarily ``leaf +functions''. + +GCC assigns register numbers before it knows whether the function is +suitable for leaf function treatment. So it needs to renumber the +registers in order to output a leaf function. The following macros +accomplish this. + +@table @code +@findex LEAF_REGISTERS +@item LEAF_REGISTERS +Name of a char vector, indexed by hard register number, which +contains 1 for a register that is allowable in a candidate for leaf +function treatment. + +If leaf function treatment involves renumbering the registers, then the +registers marked here should be the ones before renumbering---those that +GCC would ordinarily allocate. The registers which will actually be +used in the assembler code, after renumbering, should not be marked with 1 +in this vector. + +Define this macro only if the target machine offers a way to optimize +the treatment of leaf functions. + +@findex LEAF_REG_REMAP +@item LEAF_REG_REMAP (@var{regno}) +A C expression whose value is the register number to which @var{regno} +should be renumbered, when a function is treated as a leaf function. + +If @var{regno} is a register number which should not appear in a leaf +function before renumbering, then the expression should yield -1, which +will cause the compiler to abort. + +Define this macro only if the target machine offers a way to optimize the +treatment of leaf functions, and registers need to be renumbered to do +this. +@end table + +@findex current_function_is_leaf +@findex current_function_uses_only_leaf_regs +Normally, @code{FUNCTION_PROLOGUE} and @code{FUNCTION_EPILOGUE} must +treat leaf functions specially. They can test the C variable +@code{current_function_is_leaf} which is nonzero for leaf functions. +@code{current_function_is_leaf} is set prior to local register allocation +and is valid for the remaining compiler passes. They can also test the C +variable @code{current_function_uses_only_leaf_regs} which is nonzero for +leaf functions which only use leaf registers. +@code{current_function_uses_only_leaf_regs} is valid after reload and is +only useful if @code{LEAF_REGISTERS} is defined. +@c changed this to fix overfull. ALSO: why the "it" at the beginning +@c of the next paragraph?! --mew 2feb93 + +@node Stack Registers +@subsection Registers That Form a Stack + +There are special features to handle computers where some of the +``registers'' form a stack, as in the 80387 coprocessor for the 80386. +Stack registers are normally written by pushing onto the stack, and are +numbered relative to the top of the stack. + +Currently, GCC can only handle one group of stack-like registers, and +they must be consecutively numbered. + +@table @code +@findex STACK_REGS +@item STACK_REGS +Define this if the machine has any stack-like registers. + +@findex FIRST_STACK_REG +@item FIRST_STACK_REG +The number of the first stack-like register. This one is the top +of the stack. + +@findex LAST_STACK_REG +@item LAST_STACK_REG +The number of the last stack-like register. This one is the bottom of +the stack. +@end table + +@node Register Classes +@section Register Classes +@cindex register class definitions +@cindex class definitions, register + +On many machines, the numbered registers are not all equivalent. +For example, certain registers may not be allowed for indexed addressing; +certain registers may not be allowed in some instructions. These machine +restrictions are described to the compiler using @dfn{register classes}. + +You define a number of register classes, giving each one a name and saying +which of the registers belong to it. Then you can specify register classes +that are allowed as operands to particular instruction patterns. + +@findex ALL_REGS +@findex NO_REGS +In general, each register will belong to several classes. In fact, one +class must be named @code{ALL_REGS} and contain all the registers. Another +class must be named @code{NO_REGS} and contain no registers. Often the +union of two classes will be another class; however, this is not required. + +@findex GENERAL_REGS +One of the classes must be named @code{GENERAL_REGS}. There is nothing +terribly special about the name, but the operand constraint letters +@samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is +the same as @code{ALL_REGS}, just define it as a macro which expands +to @code{ALL_REGS}. + +Order the classes so that if class @var{x} is contained in class @var{y} +then @var{x} has a lower class number than @var{y}. + +The way classes other than @code{GENERAL_REGS} are specified in operand +constraints is through machine-dependent operand constraint letters. +You can define such letters to correspond to various classes, then use +them in operand constraints. + +You should define a class for the union of two classes whenever some +instruction allows both classes. For example, if an instruction allows +either a floating point (coprocessor) register or a general register for a +certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS} +which includes both of them. Otherwise you will get suboptimal code. + +You must also specify certain redundant information about the register +classes: for each class, which classes contain it and which ones are +contained in it; for each pair of classes, the largest class contained +in their union. + +When a value occupying several consecutive registers is expected in a +certain class, all the registers used must belong to that class. +Therefore, register classes cannot be used to enforce a requirement for +a register pair to start with an even-numbered register. The way to +specify this requirement is with @code{HARD_REGNO_MODE_OK}. + +Register classes used for input-operands of bitwise-and or shift +instructions have a special requirement: each such class must have, for +each fixed-point machine mode, a subclass whose registers can transfer that +mode to or from memory. For example, on some machines, the operations for +single-byte values (@code{QImode}) are limited to certain registers. When +this is so, each register class that is used in a bitwise-and or shift +instruction must have a subclass consisting of registers from which +single-byte values can be loaded or stored. This is so that +@code{PREFERRED_RELOAD_CLASS} can always have a possible value to return. + +@table @code +@findex enum reg_class +@item enum reg_class +An enumeral type that must be defined with all the register class names +as enumeral values. @code{NO_REGS} must be first. @code{ALL_REGS} +must be the last register class, followed by one more enumeral value, +@code{LIM_REG_CLASSES}, which is not a register class but rather +tells how many classes there are. + +Each register class has a number, which is the value of casting +the class name to type @code{int}. The number serves as an index +in many of the tables described below. + +@findex N_REG_CLASSES +@item N_REG_CLASSES +The number of distinct register classes, defined as follows: + +@example +#define N_REG_CLASSES (int) LIM_REG_CLASSES +@end example + +@findex REG_CLASS_NAMES +@item REG_CLASS_NAMES +An initializer containing the names of the register classes as C string +constants. These names are used in writing some of the debugging dumps. + +@findex REG_CLASS_CONTENTS +@item REG_CLASS_CONTENTS +An initializer containing the contents of the register classes, as integers +which are bit masks. The @var{n}th integer specifies the contents of class +@var{n}. The way the integer @var{mask} is interpreted is that +register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1. + +When the machine has more than 32 registers, an integer does not suffice. +Then the integers are replaced by sub-initializers, braced groupings containing +several integers. Each sub-initializer must be suitable as an initializer +for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}. +In this situation, the first integer in each sub-initializer corresponds to +registers 0 through 31, the second integer to registers 32 through 63, and +so on. + +@findex REGNO_REG_CLASS +@item REGNO_REG_CLASS (@var{regno}) +A C expression whose value is a register class containing hard register +@var{regno}. In general there is more than one such class; choose a class +which is @dfn{minimal}, meaning that no smaller class also contains the +register. + +@findex BASE_REG_CLASS +@item BASE_REG_CLASS +A macro whose definition is the name of the class to which a valid +base register must belong. A base register is one used in an address +which is the register value plus a displacement. + +@findex INDEX_REG_CLASS +@item INDEX_REG_CLASS +A macro whose definition is the name of the class to which a valid +index register must belong. An index register is one used in an +address where its value is either multiplied by a scale factor or +added to another register (as well as added to a displacement). + +@findex REG_CLASS_FROM_LETTER +@item REG_CLASS_FROM_LETTER (@var{char}) +A C expression which defines the machine-dependent operand constraint +letters for register classes. If @var{char} is such a letter, the +value should be the register class corresponding to it. Otherwise, +the value should be @code{NO_REGS}. The register letter @samp{r}, +corresponding to class @code{GENERAL_REGS}, will not be passed +to this macro; you do not need to handle it. + +@findex REGNO_OK_FOR_BASE_P +@item REGNO_OK_FOR_BASE_P (@var{num}) +A C expression which is nonzero if register number @var{num} is +suitable for use as a base register in operand addresses. It may be +either a suitable hard register or a pseudo register that has been +allocated such a hard register. + +@findex REGNO_MODE_OK_FOR_BASE_P +@item REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode}) +A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that +that expression may examine the mode of the memory reference in +@var{mode}. You should define this macro if the mode of the memory +reference affects whether a register may be used as a base register. If +you define this macro, the compiler will use it instead of +@code{REGNO_OK_FOR_BASE_P}. + +@findex REGNO_OK_FOR_INDEX_P +@item REGNO_OK_FOR_INDEX_P (@var{num}) +A C expression which is nonzero if register number @var{num} is +suitable for use as an index register in operand addresses. It may be +either a suitable hard register or a pseudo register that has been +allocated such a hard register. + +The difference between an index register and a base register is that +the index register may be scaled. If an address involves the sum of +two registers, neither one of them scaled, then either one may be +labeled the ``base'' and the other the ``index''; but whichever +labeling is used must fit the machine's constraints of which registers +may serve in each capacity. The compiler will try both labelings, +looking for one that is valid, and will reload one or both registers +only if neither labeling works. + +@findex PREFERRED_RELOAD_CLASS +@item PREFERRED_RELOAD_CLASS (@var{x}, @var{class}) +A C expression that places additional restrictions on the register class +to use when it is necessary to copy value @var{x} into a register in class +@var{class}. The value is a register class; perhaps @var{class}, or perhaps +another, smaller class. On many machines, the following definition is +safe: + +@example +#define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS +@end example + +Sometimes returning a more restrictive class makes better code. For +example, on the 68000, when @var{x} is an integer constant that is in range +for a @samp{moveq} instruction, the value of this macro is always +@code{DATA_REGS} as long as @var{class} includes the data registers. +Requiring a data register guarantees that a @samp{moveq} will be used. + +If @var{x} is a @code{const_double}, by returning @code{NO_REGS} +you can force @var{x} into a memory constant. This is useful on +certain machines where immediate floating values cannot be loaded into +certain kinds of registers. + +@findex PREFERRED_OUTPUT_RELOAD_CLASS +@item PREFERRED_OUTPUT_RELOAD_CLASS (@var{x}, @var{class}) +Like @code{PREFERRED_RELOAD_CLASS}, but for output reloads instead of +input reloads. If you don't define this macro, the default is to use +@var{class}, unchanged. + +@findex LIMIT_RELOAD_CLASS +@item LIMIT_RELOAD_CLASS (@var{mode}, @var{class}) +A C expression that places additional restrictions on the register class +to use when it is necessary to be able to hold a value of mode +@var{mode} in a reload register for which class @var{class} would +ordinarily be used. + +Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when +there are certain modes that simply can't go in certain reload classes. + +The value is a register class; perhaps @var{class}, or perhaps another, +smaller class. + +Don't define this macro unless the target machine has limitations which +require the macro to do something nontrivial. + +@findex SECONDARY_RELOAD_CLASS +@findex SECONDARY_INPUT_RELOAD_CLASS +@findex SECONDARY_OUTPUT_RELOAD_CLASS +@item SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) +@itemx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) +@itemx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) +Many machines have some registers that cannot be copied directly to or +from memory or even from other types of registers. An example is the +@samp{MQ} register, which on most machines, can only be copied to or +from general registers, but not memory. Some machines allow copying all +registers to and from memory, but require a scratch register for stores +to some memory locations (e.g., those with symbolic address on the RT, +and those with certain symbolic address on the Sparc when compiling +PIC). In some cases, both an intermediate and a scratch register are +required. + +You should define these macros to indicate to the reload phase that it may +need to allocate at least one register for a reload in addition to the +register to contain the data. Specifically, if copying @var{x} to a +register @var{class} in @var{mode} requires an intermediate register, +you should define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the +largest register class all of whose registers can be used as +intermediate registers or scratch registers. + +If copying a register @var{class} in @var{mode} to @var{x} requires an +intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS} +should be defined to return the largest register class required. If the +requirements for input and output reloads are the same, the macro +@code{SECONDARY_RELOAD_CLASS} should be used instead of defining both +macros identically. + +The values returned by these macros are often @code{GENERAL_REGS}. +Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x} +can be directly copied to or from a register of @var{class} in +@var{mode} without requiring a scratch register. Do not define this +macro if it would always return @code{NO_REGS}. + +If a scratch register is required (either with or without an +intermediate register), you should define patterns for +@samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required +(@pxref{Standard Names}. These patterns, which will normally be +implemented with a @code{define_expand}, should be similar to the +@samp{mov@var{m}} patterns, except that operand 2 is the scratch +register. + +Define constraints for the reload register and scratch register that +contain a single register class. If the original reload register (whose +class is @var{class}) can meet the constraint given in the pattern, the +value returned by these macros is used for the class of the scratch +register. Otherwise, two additional reload registers are required. +Their classes are obtained from the constraints in the insn pattern. + +@var{x} might be a pseudo-register or a @code{subreg} of a +pseudo-register, which could either be in a hard register or in memory. +Use @code{true_regnum} to find out; it will return -1 if the pseudo is +in memory and the hard register number if it is in a register. + +These macros should not be used in the case where a particular class of +registers can only be copied to memory and not to another class of +registers. In that case, secondary reload registers are not needed and +would not be helpful. Instead, a stack location must be used to perform +the copy and the @code{mov@var{m}} pattern should use memory as a +intermediate storage. This case often occurs between floating-point and +general registers. + +@findex SECONDARY_MEMORY_NEEDED +@item SECONDARY_MEMORY_NEEDED (@var{class1}, @var{class2}, @var{m}) +Certain machines have the property that some registers cannot be copied +to some other registers without using memory. Define this macro on +those machines to be a C expression that is non-zero if objects of mode +@var{m} in registers of @var{class1} can only be copied to registers of +class @var{class2} by storing a register of @var{class1} into memory +and loading that memory location into a register of @var{class2}. + +Do not define this macro if its value would always be zero. + +@findex SECONDARY_MEMORY_NEEDED_RTX +@item SECONDARY_MEMORY_NEEDED_RTX (@var{mode}) +Normally when @code{SECONDARY_MEMORY_NEEDED} is defined, the compiler +allocates a stack slot for a memory location needed for register copies. +If this macro is defined, the compiler instead uses the memory location +defined by this macro. + +Do not define this macro if you do not define +@code{SECONDARY_MEMORY_NEEDED}. + +@findex SECONDARY_MEMORY_NEEDED_MODE +@item SECONDARY_MEMORY_NEEDED_MODE (@var{mode}) +When the compiler needs a secondary memory location to copy between two +registers of mode @var{mode}, it normally allocates sufficient memory to +hold a quantity of @code{BITS_PER_WORD} bits and performs the store and +load operations in a mode that many bits wide and whose class is the +same as that of @var{mode}. + +This is right thing to do on most machines because it ensures that all +bits of the register are copied and prevents accesses to the registers +in a narrower mode, which some machines prohibit for floating-point +registers. + +However, this default behavior is not correct on some machines, such as +the DEC Alpha, that store short integers in floating-point registers +differently than in integer registers. On those machines, the default +widening will not work correctly and you must define this macro to +suppress that widening in some cases. See the file @file{alpha.h} for +details. + +Do not define this macro if you do not define +@code{SECONDARY_MEMORY_NEEDED} or if widening @var{mode} to a mode that +is @code{BITS_PER_WORD} bits wide is correct for your machine. + +@findex SMALL_REGISTER_CLASSES +@item SMALL_REGISTER_CLASSES +On some machines, it is risky to let hard registers live across arbitrary +insns. Typically, these machines have instructions that require values +to be in specific registers (like an accumulator), and reload will fail +if the required hard register is used for another purpose across such an +insn. + +Define @code{SMALL_REGISTER_CLASSES} to be an expression with a non-zero +value on these machines. When this macro has a non-zero value, the +compiler will try to minimize the lifetime of hard registers. + +It is always safe to define this macro with a non-zero value, but if you +unnecessarily define it, you will reduce the amount of optimizations +that can be performed in some cases. If you do not define this macro +with a non-zero value when it is required, the compiler will run out of +spill registers and print a fatal error message. For most machines, you +should not define this macro at all. + +@findex CLASS_LIKELY_SPILLED_P +@item CLASS_LIKELY_SPILLED_P (@var{class}) +A C expression whose value is nonzero if pseudos that have been assigned +to registers of class @var{class} would likely be spilled because +registers of @var{class} are needed for spill registers. + +The default value of this macro returns 1 if @var{class} has exactly one +register and zero otherwise. On most machines, this default should be +used. Only define this macro to some other expression if pseudos +allocated by @file{local-alloc.c} end up in memory because their hard +registers were needed for spill registers. If this macro returns nonzero +for those classes, those pseudos will only be allocated by +@file{global.c}, which knows how to reallocate the pseudo to another +register. If there would not be another register available for +reallocation, you should not change the definition of this macro since +the only effect of such a definition would be to slow down register +allocation. + +@findex CLASS_MAX_NREGS +@item CLASS_MAX_NREGS (@var{class}, @var{mode}) +A C expression for the maximum number of consecutive registers +of class @var{class} needed to hold a value of mode @var{mode}. + +This is closely related to the macro @code{HARD_REGNO_NREGS}. In fact, +the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})} +should be the maximum value of @code{HARD_REGNO_NREGS (@var{regno}, +@var{mode})} for all @var{regno} values in the class @var{class}. + +This macro helps control the handling of multiple-word values +in the reload pass. + +@item CLASS_CANNOT_CHANGE_MODE +If defined, a C expression for a class that contains registers for +which the compiler may not change modes arbitrarily. + +@item CLASS_CANNOT_CHANGE_MODE_P(@var{from}, @var{to}) +A C expression that is true if, for a register in +@code{CLASS_CANNOT_CHANGE_MODE}, the requested mode punning is illegal. + +For the example, loading 32-bit integer or floating-point objects into +floating-point registers on the Alpha extends them to 64-bits. +Therefore loading a 64-bit object and then storing it as a 32-bit object +does not store the low-order 32-bits, as would be the case for a normal +register. Therefore, @file{alpha.h} defines @code{CLASS_CANNOT_CHANGE_MODE} +as @code{FLOAT_REGS} and @code{CLASS_CANNOT_CHANGE_MODE_P} restricts +mode changes to same-size modes. + +Compare this to IA-64, which extends floating-point values to 82-bits, +and stores 64-bit integers in a different format than 64-bit doubles. +Therefore @code{CLASS_CANNOT_CHANGE_MODE_P} is always true. +@end table + +Three other special macros describe which operands fit which constraint +letters. + +@table @code +@findex CONST_OK_FOR_LETTER_P +@item CONST_OK_FOR_LETTER_P (@var{value}, @var{c}) +A C expression that defines the machine-dependent operand constraint +letters (@samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P}) that specify +particular ranges of integer values. If @var{c} is one of those +letters, the expression should check that @var{value}, an integer, is in +the appropriate range and return 1 if so, 0 otherwise. If @var{c} is +not one of those letters, the value should be 0 regardless of +@var{value}. + +@findex CONST_DOUBLE_OK_FOR_LETTER_P +@item CONST_DOUBLE_OK_FOR_LETTER_P (@var{value}, @var{c}) +A C expression that defines the machine-dependent operand constraint +letters that specify particular ranges of @code{const_double} values +(@samp{G} or @samp{H}). + +If @var{c} is one of those letters, the expression should check that +@var{value}, an RTX of code @code{const_double}, is in the appropriate +range and return 1 if so, 0 otherwise. If @var{c} is not one of those +letters, the value should be 0 regardless of @var{value}. + +@code{const_double} is used for all floating-point constants and for +@code{DImode} fixed-point constants. A given letter can accept either +or both kinds of values. It can use @code{GET_MODE} to distinguish +between these kinds. + +@findex EXTRA_CONSTRAINT +@item EXTRA_CONSTRAINT (@var{value}, @var{c}) +A C expression that defines the optional machine-dependent constraint +letters that can be used to segregate specific types of operands, usually +memory references, for the target machine. Any letter that is not +elsewhere defined and not matched by @code{REG_CLASS_FROM_LETTER} +may be used. Normally this macro will not be defined. + +If it is required for a particular target machine, it should return 1 +if @var{value} corresponds to the operand type represented by the +constraint letter @var{c}. If @var{c} is not defined as an extra +constraint, the value returned should be 0 regardless of @var{value}. + +For example, on the ROMP, load instructions cannot have their output +in r0 if the memory reference contains a symbolic address. Constraint +letter @samp{Q} is defined as representing a memory address that does +@emph{not} contain a symbolic address. An alternative is specified with +a @samp{Q} constraint on the input and @samp{r} on the output. The next +alternative specifies @samp{m} on the input and a register class that +does not include r0 on the output. +@end table + +@node Stack and Calling +@section Stack Layout and Calling Conventions +@cindex calling conventions + +@c prevent bad page break with this line +This describes the stack layout and calling conventions. + +@menu +* Frame Layout:: +* Stack Checking:: +* Frame Registers:: +* Elimination:: +* Stack Arguments:: +* Register Arguments:: +* Scalar Return:: +* Aggregate Return:: +* Caller Saves:: +* Function Entry:: +* Profiling:: +* Inlining:: +* Tail Calling:: +@end menu + +@node Frame Layout +@subsection Basic Stack Layout +@cindex stack frame layout +@cindex frame layout + +@c prevent bad page break with this line +Here is the basic stack layout. + +@table @code +@findex STACK_GROWS_DOWNWARD +@item STACK_GROWS_DOWNWARD +Define this macro if pushing a word onto the stack moves the stack +pointer to a smaller address. + +When we say, ``define this macro if @dots{},'' it means that the +compiler checks this macro only with @code{#ifdef} so the precise +definition used does not matter. + +@findex FRAME_GROWS_DOWNWARD +@item FRAME_GROWS_DOWNWARD +Define this macro if the addresses of local variable slots are at negative +offsets from the frame pointer. + +@findex ARGS_GROW_DOWNWARD +@item ARGS_GROW_DOWNWARD +Define this macro if successive arguments to a function occupy decreasing +addresses on the stack. + +@findex STARTING_FRAME_OFFSET +@item STARTING_FRAME_OFFSET +Offset from the frame pointer to the first local variable slot to be allocated. + +If @code{FRAME_GROWS_DOWNWARD}, find the next slot's offset by +subtracting the first slot's length from @code{STARTING_FRAME_OFFSET}. +Otherwise, it is found by adding the length of the first slot to the +value @code{STARTING_FRAME_OFFSET}. +@c i'm not sure if the above is still correct.. had to change it to get +@c rid of an overfull. --mew 2feb93 + +@findex STACK_POINTER_OFFSET +@item STACK_POINTER_OFFSET +Offset from the stack pointer register to the first location at which +outgoing arguments are placed. If not specified, the default value of +zero is used. This is the proper value for most machines. + +If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above +the first location at which outgoing arguments are placed. + +@findex FIRST_PARM_OFFSET +@item FIRST_PARM_OFFSET (@var{fundecl}) +Offset from the argument pointer register to the first argument's +address. On some machines it may depend on the data type of the +function. + +If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above +the first argument's address. + +@findex STACK_DYNAMIC_OFFSET +@item STACK_DYNAMIC_OFFSET (@var{fundecl}) +Offset from the stack pointer register to an item dynamically allocated +on the stack, e.g., by @code{alloca}. + +The default value for this macro is @code{STACK_POINTER_OFFSET} plus the +length of the outgoing arguments. The default is correct for most +machines. See @file{function.c} for details. + +@findex DYNAMIC_CHAIN_ADDRESS +@item DYNAMIC_CHAIN_ADDRESS (@var{frameaddr}) +A C expression whose value is RTL representing the address in a stack +frame where the pointer to the caller's frame is stored. Assume that +@var{frameaddr} is an RTL expression for the address of the stack frame +itself. + +If you don't define this macro, the default is to return the value +of @var{frameaddr}---that is, the stack frame address is also the +address of the stack word that points to the previous frame. + +@findex SETUP_FRAME_ADDRESSES +@item SETUP_FRAME_ADDRESSES +If defined, a C expression that produces the machine-specific code to +setup the stack so that arbitrary frames can be accessed. For example, +on the Sparc, we must flush all of the register windows to the stack +before we can access arbitrary stack frames. You will seldom need to +define this macro. + +@findex BUILTIN_SETJMP_FRAME_VALUE +@item BUILTIN_SETJMP_FRAME_VALUE +If defined, a C expression that contains an rtx that is used to store +the address of the current frame into the built in @code{setjmp} buffer. +The default value, @code{virtual_stack_vars_rtx}, is correct for most +machines. One reason you may need to define this macro is if +@code{hard_frame_pointer_rtx} is the appropriate value on your machine. + +@findex RETURN_ADDR_RTX +@item RETURN_ADDR_RTX (@var{count}, @var{frameaddr}) +A C expression whose value is RTL representing the value of the return +address for the frame @var{count} steps up from the current frame, after +the prologue. @var{frameaddr} is the frame pointer of the @var{count} +frame, or the frame pointer of the @var{count} @minus{} 1 frame if +@code{RETURN_ADDR_IN_PREVIOUS_FRAME} is defined. + +The value of the expression must always be the correct address when +@var{count} is zero, but may be @code{NULL_RTX} if there is not way to +determine the return address of other frames. + +@findex RETURN_ADDR_IN_PREVIOUS_FRAME +@item RETURN_ADDR_IN_PREVIOUS_FRAME +Define this if the return address of a particular stack frame is accessed +from the frame pointer of the previous stack frame. + +@findex INCOMING_RETURN_ADDR_RTX +@item INCOMING_RETURN_ADDR_RTX +A C expression whose value is RTL representing the location of the +incoming return address at the beginning of any function, before the +prologue. This RTL is either a @code{REG}, indicating that the return +value is saved in @samp{REG}, or a @code{MEM} representing a location in +the stack. + +You only need to define this macro if you want to support call frame +debugging information like that provided by DWARF 2. + +If this RTL is a @code{REG}, you should also define +DWARF_FRAME_RETURN_COLUMN to @code{DWARF_FRAME_REGNUM (REGNO)}. + +@findex INCOMING_FRAME_SP_OFFSET +@item INCOMING_FRAME_SP_OFFSET +A C expression whose value is an integer giving the offset, in bytes, +from the value of the stack pointer register to the top of the stack +frame at the beginning of any function, before the prologue. The top of +the frame is defined to be the value of the stack pointer in the +previous frame, just before the call instruction. + +You only need to define this macro if you want to support call frame +debugging information like that provided by DWARF 2. + +@findex ARG_POINTER_CFA_OFFSET +@item ARG_POINTER_CFA_OFFSET (@var{fundecl}) +A C expression whose value is an integer giving the offset, in bytes, +from the argument pointer to the canonical frame address (cfa). The +final value should coincide with that calculated by +@code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable +during virtual register instantiation. + +The default value for this macro is @code{FIRST_PARM_OFFSET (fundecl)}, +which is correct for most machines; in general, the arguments are found +immediately before the stack frame. Note that this is not the case on +some targets that save registers into the caller's frame, such as SPARC +and rs6000, and so such targets need to define this macro. + +You only need to define this macro if the default is incorrect, and you +want to support call frame debugging information like that provided by +DWARF 2. + +@findex EH_RETURN_DATA_REGNO +@item EH_RETURN_DATA_REGNO (@var{N}) +A C expression whose value is the @var{N}th register number used for +data by exception handlers, or @code{INVALID_REGNUM} if fewer than +@var{N} registers are usable. + +The exception handling library routines communicate with the exception +handlers via a set of agreed upon registers. Ideally these registers +should be call-clobbered; it is possible to use call-saved registers, +but may negatively impact code size. The target must support at least +2 data registers, but should define 4 if there are enough free registers. + +You must define this macro if you want to support call frame exception +handling like that provided by DWARF 2. + +@findex EH_RETURN_STACKADJ_RTX +@item EH_RETURN_STACKADJ_RTX +A C expression whose value is RTL representing a location in which +to store a stack adjustment to be applied before function return. +This is used to unwind the stack to an exception handler's call frame. +It will be assigned zero on code paths that return normally. + +Typically this is a call-clobbered hard register that is otherwise +untouched by the epilogue, but could also be a stack slot. + +You must define this macro if you want to support call frame exception +handling like that provided by DWARF 2. + +@findex EH_RETURN_HANDLER_RTX +@item EH_RETURN_HANDLER_RTX +A C expression whose value is RTL representing a location in which +to store the address of an exception handler to which we should +return. It will not be assigned on code paths that return normally. + +Typically this is the location in the call frame at which the normal +return address is stored. For targets that return by popping an +address off the stack, this might be a memory address just below +the @emph{target} call frame rather than inside the current call +frame. @code{EH_RETURN_STACKADJ_RTX} will have already been assigned, +so it may be used to calculate the location of the target call frame. + +Some targets have more complex requirements than storing to an +address calculable during initial code generation. In that case +the @code{eh_return} instruction pattern should be used instead. + +If you want to support call frame exception handling, you must +define either this macro or the @code{eh_return} instruction pattern. + +@findex ASM_PREFERRED_EH_DATA_FORMAT +@item ASM_PREFERRED_EH_DATA_FORMAT(@var{CODE}, @var{GLOBAL}) +This macro chooses the encoding of pointers embedded in the exception +handling sections. If at all possible, this should be defined such +that the exception handling section will not require dynamic relocations, +and so may be read-only. + +@var{CODE} is 0 for data, 1 for code labels, 2 for function pointers. +@var{GLOBAL} is true if the symbol may be affected by dynamic relocations. +The macro should return a combination of the @code{DW_EH_PE_*} defines +as found in @file{dwarf2.h}. + +If this macro is not defined, pointers will not be encoded but +represented directly. + +@findex ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX +@item ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX(@var{FILE}, @var{ENCODING}, @var{SIZE}, @var{ADDR}, @var{DONE}) +This macro allows the target to emit whatever special magic is required +to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}. +Generic code takes care of pc-relative and indirect encodings; this must +be defined if the target uses text-relative or data-relative encodings. + +This is a C statement that branches to @var{DONE} if the format was +handled. @var{ENCODING} is the format chosen, @var{SIZE} is the number +of bytes that the format occupies, @var{ADDR} is the @code{SYMBOL_REF} +to be emitted. + +@findex SMALL_STACK +@item SMALL_STACK +Define this macro if the stack size for the target is very small. This +has the effect of disabling gcc's builtin @samp{alloca}, though +@samp{__builtin_alloca} is not affected. +@end table + +@node Stack Checking +@subsection Specifying How Stack Checking is Done + +GCC will check that stack references are within the boundaries of +the stack, if the @samp{-fstack-check} is specified, in one of three ways: + +@enumerate +@item +If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC +will assume that you have arranged for stack checking to be done at +appropriate places in the configuration files, e.g., in +@code{FUNCTION_PROLOGUE}. GCC will do not other special processing. + +@item +If @code{STACK_CHECK_BUILTIN} is zero and you defined a named pattern +called @code{check_stack} in your @file{md} file, GCC will call that +pattern with one argument which is the address to compare the stack +value against. You must arrange for this pattern to report an error if +the stack pointer is out of range. + +@item +If neither of the above are true, GCC will generate code to periodically +``probe'' the stack pointer using the values of the macros defined below. +@end enumerate + +Normally, you will use the default values of these macros, so GCC +will use the third approach. + +@table @code +@findex STACK_CHECK_BUILTIN +@item STACK_CHECK_BUILTIN +A nonzero value if stack checking is done by the configuration files in a +machine-dependent manner. You should define this macro if stack checking +is require by the ABI of your machine or if you would like to have to stack +checking in some more efficient way than GCC's portable approach. +The default value of this macro is zero. + +@findex STACK_CHECK_PROBE_INTERVAL +@item STACK_CHECK_PROBE_INTERVAL +An integer representing the interval at which GCC must generate stack +probe instructions. You will normally define this macro to be no larger +than the size of the ``guard pages'' at the end of a stack area. The +default value of 4096 is suitable for most systems. + +@findex STACK_CHECK_PROBE_LOAD +@item STACK_CHECK_PROBE_LOAD +A integer which is nonzero if GCC should perform the stack probe +as a load instruction and zero if GCC should use a store instruction. +The default is zero, which is the most efficient choice on most systems. + +@findex STACK_CHECK_PROTECT +@item STACK_CHECK_PROTECT +The number of bytes of stack needed to recover from a stack overflow, +for languages where such a recovery is supported. The default value of +75 words should be adequate for most machines. + +@findex STACK_CHECK_MAX_FRAME_SIZE +@item STACK_CHECK_MAX_FRAME_SIZE +The maximum size of a stack frame, in bytes. GCC will generate probe +instructions in non-leaf functions to ensure at least this many bytes of +stack are available. If a stack frame is larger than this size, stack +checking will not be reliable and GCC will issue a warning. The +default is chosen so that GCC only generates one instruction on most +systems. You should normally not change the default value of this macro. + +@findex STACK_CHECK_FIXED_FRAME_SIZE +@item STACK_CHECK_FIXED_FRAME_SIZE +GCC uses this value to generate the above warning message. It +represents the amount of fixed frame used by a function, not including +space for any callee-saved registers, temporaries and user variables. +You need only specify an upper bound for this amount and will normally +use the default of four words. + +@findex STACK_CHECK_MAX_VAR_SIZE +@item STACK_CHECK_MAX_VAR_SIZE +The maximum size, in bytes, of an object that GCC will place in the +fixed area of the stack frame when the user specifies +@samp{-fstack-check}. +GCC computed the default from the values of the above macros and you will +normally not need to override that default. +@end table + +@need 2000 +@node Frame Registers +@subsection Registers That Address the Stack Frame + +@c prevent bad page break with this line +This discusses registers that address the stack frame. + +@table @code +@findex STACK_POINTER_REGNUM +@item STACK_POINTER_REGNUM +The register number of the stack pointer register, which must also be a +fixed register according to @code{FIXED_REGISTERS}. On most machines, +the hardware determines which register this is. + +@findex FRAME_POINTER_REGNUM +@item FRAME_POINTER_REGNUM +The register number of the frame pointer register, which is used to +access automatic variables in the stack frame. On some machines, the +hardware determines which register this is. On other machines, you can +choose any register you wish for this purpose. + +@findex HARD_FRAME_POINTER_REGNUM +@item HARD_FRAME_POINTER_REGNUM +On some machines the offset between the frame pointer and starting +offset of the automatic variables is not known until after register +allocation has been done (for example, because the saved registers are +between these two locations). On those machines, define +@code{FRAME_POINTER_REGNUM} the number of a special, fixed register to +be used internally until the offset is known, and define +@code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number +used for the frame pointer. + +You should define this macro only in the very rare circumstances when it +is not possible to calculate the offset between the frame pointer and +the automatic variables until after register allocation has been +completed. When this macro is defined, you must also indicate in your +definition of @code{ELIMINABLE_REGS} how to eliminate +@code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM} +or @code{STACK_POINTER_REGNUM}. + +Do not define this macro if it would be the same as +@code{FRAME_POINTER_REGNUM}. + +@findex ARG_POINTER_REGNUM +@item ARG_POINTER_REGNUM +The register number of the arg pointer register, which is used to access +the function's argument list. On some machines, this is the same as the +frame pointer register. On some machines, the hardware determines which +register this is. On other machines, you can choose any register you +wish for this purpose. If this is not the same register as the frame +pointer register, then you must mark it as a fixed register according to +@code{FIXED_REGISTERS}, or arrange to be able to eliminate it +(@pxref{Elimination}). + +@findex RETURN_ADDRESS_POINTER_REGNUM +@item RETURN_ADDRESS_POINTER_REGNUM +The register number of the return address pointer register, which is used to +access the current function's return address from the stack. On some +machines, the return address is not at a fixed offset from the frame +pointer or stack pointer or argument pointer. This register can be defined +to point to the return address on the stack, and then be converted by +@code{ELIMINABLE_REGS} into either the frame pointer or stack pointer. + +Do not define this macro unless there is no other way to get the return +address from the stack. + +@findex STATIC_CHAIN_REGNUM +@findex STATIC_CHAIN_INCOMING_REGNUM +@item STATIC_CHAIN_REGNUM +@itemx STATIC_CHAIN_INCOMING_REGNUM +Register numbers used for passing a function's static chain pointer. If +register windows are used, the register number as seen by the called +function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register +number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If +these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need +not be defined.@refill + +The static chain register need not be a fixed register. + +If the static chain is passed in memory, these macros should not be +defined; instead, the next two macros should be defined. + +@findex STATIC_CHAIN +@findex STATIC_CHAIN_INCOMING +@item STATIC_CHAIN +@itemx STATIC_CHAIN_INCOMING +If the static chain is passed in memory, these macros provide rtx giving +@code{mem} expressions that denote where they are stored. +@code{STATIC_CHAIN} and @code{STATIC_CHAIN_INCOMING} give the locations +as seen by the calling and called functions, respectively. Often the former +will be at an offset from the stack pointer and the latter at an offset from +the frame pointer.@refill + +@findex stack_pointer_rtx +@findex frame_pointer_rtx +@findex arg_pointer_rtx +The variables @code{stack_pointer_rtx}, @code{frame_pointer_rtx}, and +@code{arg_pointer_rtx} will have been initialized prior to the use of these +macros and should be used to refer to those items. + +If the static chain is passed in a register, the two previous macros should +be defined instead. +@end table + +@node Elimination +@subsection Eliminating Frame Pointer and Arg Pointer + +@c prevent bad page break with this line +This is about eliminating the frame pointer and arg pointer. + +@table @code +@findex FRAME_POINTER_REQUIRED +@item FRAME_POINTER_REQUIRED +A C expression which is nonzero if a function must have and use a frame +pointer. This expression is evaluated in the reload pass. If its value is +nonzero the function will have a frame pointer. + +The expression can in principle examine the current function and decide +according to the facts, but on most machines the constant 0 or the +constant 1 suffices. Use 0 when the machine allows code to be generated +with no frame pointer, and doing so saves some time or space. Use 1 +when there is no possible advantage to avoiding a frame pointer. + +In certain cases, the compiler does not know how to produce valid code +without a frame pointer. The compiler recognizes those cases and +automatically gives the function a frame pointer regardless of what +@code{FRAME_POINTER_REQUIRED} says. You don't need to worry about +them.@refill + +In a function that does not require a frame pointer, the frame pointer +register can be allocated for ordinary usage, unless you mark it as a +fixed register. See @code{FIXED_REGISTERS} for more information. + +@findex INITIAL_FRAME_POINTER_OFFSET +@findex get_frame_size +@item INITIAL_FRAME_POINTER_OFFSET (@var{depth-var}) +A C statement to store in the variable @var{depth-var} the difference +between the frame pointer and the stack pointer values immediately after +the function prologue. The value would be computed from information +such as the result of @code{get_frame_size ()} and the tables of +registers @code{regs_ever_live} and @code{call_used_regs}. + +If @code{ELIMINABLE_REGS} is defined, this macro will be not be used and +need not be defined. Otherwise, it must be defined even if +@code{FRAME_POINTER_REQUIRED} is defined to always be true; in that +case, you may set @var{depth-var} to anything. + +@findex ELIMINABLE_REGS +@item ELIMINABLE_REGS +If defined, this macro specifies a table of register pairs used to +eliminate unneeded registers that point into the stack frame. If it is not +defined, the only elimination attempted by the compiler is to replace +references to the frame pointer with references to the stack pointer. + +The definition of this macro is a list of structure initializations, each +of which specifies an original and replacement register. + +On some machines, the position of the argument pointer is not known until +the compilation is completed. In such a case, a separate hard register +must be used for the argument pointer. This register can be eliminated by +replacing it with either the frame pointer or the argument pointer, +depending on whether or not the frame pointer has been eliminated. + +In this case, you might specify: +@example +#define ELIMINABLE_REGS \ +@{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \ + @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \ + @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@} +@end example + +Note that the elimination of the argument pointer with the stack pointer is +specified first since that is the preferred elimination. + +@findex CAN_ELIMINATE +@item CAN_ELIMINATE (@var{from-reg}, @var{to-reg}) +A C expression that returns non-zero if the compiler is allowed to try +to replace register number @var{from-reg} with register number +@var{to-reg}. This macro need only be defined if @code{ELIMINABLE_REGS} +is defined, and will usually be the constant 1, since most of the cases +preventing register elimination are things that the compiler already +knows about. + +@findex INITIAL_ELIMINATION_OFFSET +@item INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var}) +This macro is similar to @code{INITIAL_FRAME_POINTER_OFFSET}. It +specifies the initial difference between the specified pair of +registers. This macro must be defined if @code{ELIMINABLE_REGS} is +defined. + +@findex LONGJMP_RESTORE_FROM_STACK +@item LONGJMP_RESTORE_FROM_STACK +Define this macro if the @code{longjmp} function restores registers from +the stack frames, rather than from those saved specifically by +@code{setjmp}. Certain quantities must not be kept in registers across +a call to @code{setjmp} on such machines. +@end table + +@node Stack Arguments +@subsection Passing Function Arguments on the Stack +@cindex arguments on stack +@cindex stack arguments + +The macros in this section control how arguments are passed +on the stack. See the following section for other macros that +control passing certain arguments in registers. + +@table @code +@findex PROMOTE_PROTOTYPES +@item PROMOTE_PROTOTYPES +A C expression whose value is nonzero if an argument declared in +a prototype as an integral type smaller than @code{int} should +actually be passed as an @code{int}. In addition to avoiding +errors in certain cases of mismatch, it also makes for better +code on certain machines. If the macro is not defined in target +header files, it defaults to 0. + +@findex PUSH_ARGS +@item PUSH_ARGS +A C expression. If nonzero, push insns will be used to pass +outgoing arguments. +If the target machine does not have a push instruction, set it to zero. +That directs GCC to use an alternate strategy: to +allocate the entire argument block and then store the arguments into +it. When PUSH_ARGS is nonzero, PUSH_ROUNDING must be defined too. +On some machines, the definition + +@findex PUSH_ROUNDING +@item PUSH_ROUNDING (@var{npushed}) +A C expression that is the number of bytes actually pushed onto the +stack when an instruction attempts to push @var{npushed} bytes. + +On some machines, the definition + +@example +#define PUSH_ROUNDING(BYTES) (BYTES) +@end example + +@noindent +will suffice. But on other machines, instructions that appear +to push one byte actually push two bytes in an attempt to maintain +alignment. Then the definition should be + +@example +#define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1) +@end example + +@findex ACCUMULATE_OUTGOING_ARGS +@findex current_function_outgoing_args_size +@item ACCUMULATE_OUTGOING_ARGS +A C expression. If nonzero, the maximum amount of space required for outgoing arguments +will be computed and placed into the variable +@code{current_function_outgoing_args_size}. No space will be pushed +onto the stack for each call; instead, the function prologue should +increase the stack frame size by this amount. + +Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS} +is not proper. + +@findex REG_PARM_STACK_SPACE +@item REG_PARM_STACK_SPACE (@var{fndecl}) +Define this macro if functions should assume that stack space has been +allocated for arguments even when their values are passed in +registers. + +The value of this macro is the size, in bytes, of the area reserved for +arguments passed in registers for the function represented by @var{fndecl}, +which can be zero if GCC is calling a library function. + +This space can be allocated by the caller, or be a part of the +machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says +which. +@c above is overfull. not sure what to do. --mew 5feb93 did +@c something, not sure if it looks good. --mew 10feb93 + +@findex MAYBE_REG_PARM_STACK_SPACE +@findex FINAL_REG_PARM_STACK_SPACE +@item MAYBE_REG_PARM_STACK_SPACE +@itemx FINAL_REG_PARM_STACK_SPACE (@var{const_size}, @var{var_size}) +Define these macros in addition to the one above if functions might +allocate stack space for arguments even when their values are passed +in registers. These should be used when the stack space allocated +for arguments in registers is not a simple constant independent of the +function declaration. + +The value of the first macro is the size, in bytes, of the area that +we should initially assume would be reserved for arguments passed in registers. + +The value of the second macro is the actual size, in bytes, of the area +that will be reserved for arguments passed in registers. This takes two +arguments: an integer representing the number of bytes of fixed sized +arguments on the stack, and a tree representing the number of bytes of +variable sized arguments on the stack. + +When these macros are defined, @code{REG_PARM_STACK_SPACE} will only be +called for libcall functions, the current function, or for a function +being called when it is known that such stack space must be allocated. +In each case this value can be easily computed. + +When deciding whether a called function needs such stack space, and how +much space to reserve, GCC uses these two macros instead of +@code{REG_PARM_STACK_SPACE}. + +@findex OUTGOING_REG_PARM_STACK_SPACE +@item OUTGOING_REG_PARM_STACK_SPACE +Define this if it is the responsibility of the caller to allocate the area +reserved for arguments passed in registers. + +If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls +whether the space for these arguments counts in the value of +@code{current_function_outgoing_args_size}. + +@findex STACK_PARMS_IN_REG_PARM_AREA +@item STACK_PARMS_IN_REG_PARM_AREA +Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the +stack parameters don't skip the area specified by it. +@c i changed this, makes more sens and it should have taken care of the +@c overfull.. not as specific, tho. --mew 5feb93 + +Normally, when a parameter is not passed in registers, it is placed on the +stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro +suppresses this behavior and causes the parameter to be passed on the +stack in its natural location. + +@findex RETURN_POPS_ARGS +@item RETURN_POPS_ARGS (@var{fundecl}, @var{funtype}, @var{stack-size}) +A C expression that should indicate the number of bytes of its own +arguments that a function pops on returning, or 0 if the +function pops no arguments and the caller must therefore pop them all +after the function returns. + +@var{fundecl} is a C variable whose value is a tree node that describes +the function in question. Normally it is a node of type +@code{FUNCTION_DECL} that describes the declaration of the function. +From this you can obtain the DECL_MACHINE_ATTRIBUTES of the function. + +@var{funtype} is a C variable whose value is a tree node that +describes the function in question. Normally it is a node of type +@code{FUNCTION_TYPE} that describes the data type of the function. +From this it is possible to obtain the data types of the value and +arguments (if known). + +When a call to a library function is being considered, @var{fundecl} +will contain an identifier node for the library function. Thus, if +you need to distinguish among various library functions, you can do so +by their names. Note that ``library function'' in this context means +a function used to perform arithmetic, whose name is known specially +in the compiler and was not mentioned in the C code being compiled. + +@var{stack-size} is the number of bytes of arguments passed on the +stack. If a variable number of bytes is passed, it is zero, and +argument popping will always be the responsibility of the calling function. + +On the Vax, all functions always pop their arguments, so the definition +of this macro is @var{stack-size}. On the 68000, using the standard +calling convention, no functions pop their arguments, so the value of +the macro is always 0 in this case. But an alternative calling +convention is available in which functions that take a fixed number of +arguments pop them but other functions (such as @code{printf}) pop +nothing (the caller pops all). When this convention is in use, +@var{funtype} is examined to determine whether a function takes a fixed +number of arguments. +@end table + +@node Register Arguments +@subsection Passing Arguments in Registers +@cindex arguments in registers +@cindex registers arguments + +This section describes the macros which let you control how various +types of arguments are passed in registers or how they are arranged in +the stack. + +@table @code +@findex FUNCTION_ARG +@item FUNCTION_ARG (@var{cum}, @var{mode}, @var{type}, @var{named}) +A C expression that controls whether a function argument is passed +in a register, and which register. + +The arguments are @var{cum}, which summarizes all the previous +arguments; @var{mode}, the machine mode of the argument; @var{type}, +the data type of the argument as a tree node or 0 if that is not known +(which happens for C support library functions); and @var{named}, +which is 1 for an ordinary argument and 0 for nameless arguments that +correspond to @samp{@dots{}} in the called function's prototype. +@var{type} can be an incomplete type if a syntax error has previously +occurred. + +The value of the expression is usually either a @code{reg} RTX for the +hard register in which to pass the argument, or zero to pass the +argument on the stack. + +For machines like the Vax and 68000, where normally all arguments are +pushed, zero suffices as a definition. + +The value of the expression can also be a @code{parallel} RTX. This is +used when an argument is passed in multiple locations. The mode of the +of the @code{parallel} should be the mode of the entire argument. The +@code{parallel} holds any number of @code{expr_list} pairs; each one +describes where part of the argument is passed. In each +@code{expr_list} the first operand must be a @code{reg} RTX for the hard +register in which to pass this part of the argument, and the mode of the +register RTX indicates how large this part of the argument is. The +second operand of the @code{expr_list} is a @code{const_int} which gives +the offset in bytes into the entire argument of where this part starts. +As a special exception the first @code{expr_list} in the @code{parallel} +RTX may have a first operand of zero. This indicates that the entire +argument is also stored on the stack. + +@cindex @file{stdarg.h} and register arguments +The usual way to make the ISO library @file{stdarg.h} work on a machine +where some arguments are usually passed in registers, is to cause +nameless arguments to be passed on the stack instead. This is done +by making @code{FUNCTION_ARG} return 0 whenever @var{named} is 0. + +@cindex @code{MUST_PASS_IN_STACK}, and @code{FUNCTION_ARG} +@cindex @code{REG_PARM_STACK_SPACE}, and @code{FUNCTION_ARG} +You may use the macro @code{MUST_PASS_IN_STACK (@var{mode}, @var{type})} +in the definition of this macro to determine if this argument is of a +type that must be passed in the stack. If @code{REG_PARM_STACK_SPACE} +is not defined and @code{FUNCTION_ARG} returns non-zero for such an +argument, the compiler will abort. If @code{REG_PARM_STACK_SPACE} is +defined, the argument will be computed in the stack and then loaded into +a register. + +@findex MUST_PASS_IN_STACK +@item MUST_PASS_IN_STACK (@var{mode}, @var{type}) +Define as a C expression that evaluates to nonzero if we do not know how +to pass TYPE solely in registers. The file @file{expr.h} defines a +definition that is usually appropriate, refer to @file{expr.h} for additional +documentation. + +@findex FUNCTION_INCOMING_ARG +@item FUNCTION_INCOMING_ARG (@var{cum}, @var{mode}, @var{type}, @var{named}) +Define this macro if the target machine has ``register windows'', so +that the register in which a function sees an arguments is not +necessarily the same as the one in which the caller passed the +argument. + +For such machines, @code{FUNCTION_ARG} computes the register in which +the caller passes the value, and @code{FUNCTION_INCOMING_ARG} should +be defined in a similar fashion to tell the function being called +where the arguments will arrive. + +If @code{FUNCTION_INCOMING_ARG} is not defined, @code{FUNCTION_ARG} +serves both purposes.@refill + +@findex FUNCTION_ARG_PARTIAL_NREGS +@item FUNCTION_ARG_PARTIAL_NREGS (@var{cum}, @var{mode}, @var{type}, @var{named}) +A C expression for the number of words, at the beginning of an +argument, that must be put in registers. The value must be zero for +arguments that are passed entirely in registers or that are entirely +pushed on the stack. + +On some machines, certain arguments must be passed partially in +registers and partially in memory. On these machines, typically the +first @var{n} words of arguments are passed in registers, and the rest +on the stack. If a multi-word argument (a @code{double} or a +structure) crosses that boundary, its first few words must be passed +in registers and the rest must be pushed. This macro tells the +compiler when this occurs, and how many of the words should go in +registers. + +@code{FUNCTION_ARG} for these arguments should return the first +register to be used by the caller for this argument; likewise +@code{FUNCTION_INCOMING_ARG}, for the called function. + +@findex FUNCTION_ARG_PASS_BY_REFERENCE +@item FUNCTION_ARG_PASS_BY_REFERENCE (@var{cum}, @var{mode}, @var{type}, @var{named}) +A C expression that indicates when an argument must be passed by reference. +If nonzero for an argument, a copy of that argument is made in memory and a +pointer to the argument is passed instead of the argument itself. +The pointer is passed in whatever way is appropriate for passing a pointer +to that type. + +On machines where @code{REG_PARM_STACK_SPACE} is not defined, a suitable +definition of this macro might be +@smallexample +#define FUNCTION_ARG_PASS_BY_REFERENCE\ +(CUM, MODE, TYPE, NAMED) \ + MUST_PASS_IN_STACK (MODE, TYPE) +@end smallexample +@c this is *still* too long. --mew 5feb93 + +@findex FUNCTION_ARG_CALLEE_COPIES +@item FUNCTION_ARG_CALLEE_COPIES (@var{cum}, @var{mode}, @var{type}, @var{named}) +If defined, a C expression that indicates when it is the called function's +responsibility to make a copy of arguments passed by invisible reference. +Normally, the caller makes a copy and passes the address of the copy to the +routine being called. When FUNCTION_ARG_CALLEE_COPIES is defined and is +nonzero, the caller does not make a copy. Instead, it passes a pointer to the +``live'' value. The called function must not modify this value. If it can be +determined that the value won't be modified, it need not make a copy; +otherwise a copy must be made. + +@findex CUMULATIVE_ARGS +@item CUMULATIVE_ARGS +A C type for declaring a variable that is used as the first argument of +@code{FUNCTION_ARG} and other related values. For some target machines, +the type @code{int} suffices and can hold the number of bytes of +argument so far. + +There is no need to record in @code{CUMULATIVE_ARGS} anything about the +arguments that have been passed on the stack. The compiler has other +variables to keep track of that. For target machines on which all +arguments are passed on the stack, there is no need to store anything in +@code{CUMULATIVE_ARGS}; however, the data structure must exist and +should not be empty, so use @code{int}. + +@findex INIT_CUMULATIVE_ARGS +@item INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{indirect}) +A C statement (sans semicolon) for initializing the variable @var{cum} +for the state at the beginning of the argument list. The variable has +type @code{CUMULATIVE_ARGS}. The value of @var{fntype} is the tree node +for the data type of the function which will receive the args, or 0 +if the args are to a compiler support library function. The value of +@var{indirect} is nonzero when processing an indirect call, for example +a call through a function pointer. The value of @var{indirect} is zero +for a call to an explicitly named function, a library function call, or when +@code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function +being compiled. + +When processing a call to a compiler support library function, +@var{libname} identifies which one. It is a @code{symbol_ref} rtx which +contains the name of the function, as a string. @var{libname} is 0 when +an ordinary C function call is being processed. Thus, each time this +macro is called, either @var{libname} or @var{fntype} is nonzero, but +never both of them at once. + +@findex INIT_CUMULATIVE_LIBCALL_ARGS +@item INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname}) +Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls, +it gets a @code{MODE} argument instead of @var{fntype}, that would be +@code{NULL}. @var{indirect} would always be zero, too. If this macro +is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname, +0)} is used instead. + +@findex INIT_CUMULATIVE_INCOMING_ARGS +@item INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname}) +Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of +finding the arguments for the function being compiled. If this macro is +undefined, @code{INIT_CUMULATIVE_ARGS} is used instead. + +The value passed for @var{libname} is always 0, since library routines +with special calling conventions are never compiled with GCC. The +argument @var{libname} exists for symmetry with +@code{INIT_CUMULATIVE_ARGS}. +@c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe. +@c --mew 5feb93 i switched the order of the sentences. --mew 10feb93 + +@findex FUNCTION_ARG_ADVANCE +@item FUNCTION_ARG_ADVANCE (@var{cum}, @var{mode}, @var{type}, @var{named}) +A C statement (sans semicolon) to update the summarizer variable +@var{cum} to advance past an argument in the argument list. The +values @var{mode}, @var{type} and @var{named} describe that argument. +Once this is done, the variable @var{cum} is suitable for analyzing +the @emph{following} argument with @code{FUNCTION_ARG}, etc.@refill + +This macro need not do anything if the argument in question was passed +on the stack. The compiler knows how to track the amount of stack space +used for arguments without any special help. + +@findex FUNCTION_ARG_PADDING +@item FUNCTION_ARG_PADDING (@var{mode}, @var{type}) +If defined, a C expression which determines whether, and in which direction, +to pad out an argument with extra space. The value should be of type +@code{enum direction}: either @code{upward} to pad above the argument, +@code{downward} to pad below, or @code{none} to inhibit padding. + +The @emph{amount} of padding is always just enough to reach the next +multiple of @code{FUNCTION_ARG_BOUNDARY}; this macro does not control +it. + +This macro has a default definition which is right for most systems. +For little-endian machines, the default is to pad upward. For +big-endian machines, the default is to pad downward for an argument of +constant size shorter than an @code{int}, and upward otherwise. + +@findex PAD_VARARGS_DOWN +@item PAD_VARARGS_DOWN +If defined, a C expression which determines whether the default +implementation of va_arg will attempt to pad down before reading the +next argument, if that argument is smaller than its aligned space as +controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such +arguments are padded down if @code{BYTES_BIG_ENDIAN} is true. + +@findex FUNCTION_ARG_BOUNDARY +@item FUNCTION_ARG_BOUNDARY (@var{mode}, @var{type}) +If defined, a C expression that gives the alignment boundary, in bits, +of an argument with the specified mode and type. If it is not defined, +@code{PARM_BOUNDARY} is used for all arguments. + +@findex FUNCTION_ARG_REGNO_P +@item FUNCTION_ARG_REGNO_P (@var{regno}) +A C expression that is nonzero if @var{regno} is the number of a hard +register in which function arguments are sometimes passed. This does +@emph{not} include implicit arguments such as the static chain and +the structure-value address. On many machines, no registers can be +used for this purpose since all function arguments are pushed on the +stack. + +@findex LOAD_ARGS_REVERSED +@item LOAD_ARGS_REVERSED +If defined, the order in which arguments are loaded into their +respective argument registers is reversed so that the last +argument is loaded first. This macro only affects arguments +passed in registers. + +@end table + +@node Scalar Return +@subsection How Scalar Function Values Are Returned +@cindex return values in registers +@cindex values, returned by functions +@cindex scalars, returned as values + +This section discusses the macros that control returning scalars as +values---values that can fit in registers. + +@table @code +@findex TRADITIONAL_RETURN_FLOAT +@item TRADITIONAL_RETURN_FLOAT +Define this macro if @samp{-traditional} should not cause functions +declared to return @code{float} to convert the value to @code{double}. + +@findex FUNCTION_VALUE +@item FUNCTION_VALUE (@var{valtype}, @var{func}) +A C expression to create an RTX representing the place where a +function returns a value of data type @var{valtype}. @var{valtype} is +a tree node representing a data type. Write @code{TYPE_MODE +(@var{valtype})} to get the machine mode used to represent that type. +On many machines, only the mode is relevant. (Actually, on most +machines, scalar values are returned in the same place regardless of +mode).@refill + +The value of the expression is usually a @code{reg} RTX for the hard +register where the return value is stored. The value can also be a +@code{parallel} RTX, if the return value is in multiple places. See +@code{FUNCTION_ARG} for an explanation of the @code{parallel} form. + +If @code{PROMOTE_FUNCTION_RETURN} is defined, you must apply the same +promotion rules specified in @code{PROMOTE_MODE} if @var{valtype} is a +scalar type. + +If the precise function being called is known, @var{func} is a tree +node (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null +pointer. This makes it possible to use a different value-returning +convention for specific functions when all their calls are +known.@refill + +@code{FUNCTION_VALUE} is not used for return vales with aggregate data +types, because these are returned in another way. See +@code{STRUCT_VALUE_REGNUM} and related macros, below. + +@findex FUNCTION_OUTGOING_VALUE +@item FUNCTION_OUTGOING_VALUE (@var{valtype}, @var{func}) +Define this macro if the target machine has ``register windows'' +so that the register in which a function returns its value is not +the same as the one in which the caller sees the value. + +For such machines, @code{FUNCTION_VALUE} computes the register in which +the caller will see the value. @code{FUNCTION_OUTGOING_VALUE} should be +defined in a similar fashion to tell the function where to put the +value.@refill + +If @code{FUNCTION_OUTGOING_VALUE} is not defined, +@code{FUNCTION_VALUE} serves both purposes.@refill + +@code{FUNCTION_OUTGOING_VALUE} is not used for return vales with +aggregate data types, because these are returned in another way. See +@code{STRUCT_VALUE_REGNUM} and related macros, below. + +@findex LIBCALL_VALUE +@item LIBCALL_VALUE (@var{mode}) +A C expression to create an RTX representing the place where a library +function returns a value of mode @var{mode}. If the precise function +being called is known, @var{func} is a tree node +(@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null +pointer. This makes it possible to use a different value-returning +convention for specific functions when all their calls are +known.@refill + +Note that ``library function'' in this context means a compiler +support routine, used to perform arithmetic, whose name is known +specially by the compiler and was not mentioned in the C code being +compiled. + +The definition of @code{LIBRARY_VALUE} need not be concerned aggregate +data types, because none of the library functions returns such types. + +@findex FUNCTION_VALUE_REGNO_P +@item FUNCTION_VALUE_REGNO_P (@var{regno}) +A C expression that is nonzero if @var{regno} is the number of a hard +register in which the values of called function may come back. + +A register whose use for returning values is limited to serving as the +second of a pair (for a value of type @code{double}, say) need not be +recognized by this macro. So for most machines, this definition +suffices: + +@example +#define FUNCTION_VALUE_REGNO_P(N) ((N) == 0) +@end example + +If the machine has register windows, so that the caller and the called +function use different registers for the return value, this macro +should recognize only the caller's register numbers. + +@findex APPLY_RESULT_SIZE +@item APPLY_RESULT_SIZE +Define this macro if @samp{untyped_call} and @samp{untyped_return} +need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for +saving and restoring an arbitrary return value. +@end table + +@node Aggregate Return +@subsection How Large Values Are Returned +@cindex aggregates as return values +@cindex large return values +@cindex returning aggregate values +@cindex structure value address + +When a function value's mode is @code{BLKmode} (and in some other +cases), the value is not returned according to @code{FUNCTION_VALUE} +(@pxref{Scalar Return}). Instead, the caller passes the address of a +block of memory in which the value should be stored. This address +is called the @dfn{structure value address}. + +This section describes how to control returning structure values in +memory. + +@table @code +@findex RETURN_IN_MEMORY +@item RETURN_IN_MEMORY (@var{type}) +A C expression which can inhibit the returning of certain function +values in registers, based on the type of value. A nonzero value says +to return the function value in memory, just as large structures are +always returned. Here @var{type} will be a C expression of type +@code{tree}, representing the data type of the value. + +Note that values of mode @code{BLKmode} must be explicitly handled +by this macro. Also, the option @samp{-fpcc-struct-return} +takes effect regardless of this macro. On most systems, it is +possible to leave the macro undefined; this causes a default +definition to be used, whose value is the constant 1 for @code{BLKmode} +values, and 0 otherwise. + +Do not use this macro to indicate that structures and unions should always +be returned in memory. You should instead use @code{DEFAULT_PCC_STRUCT_RETURN} +to indicate this. + +@findex DEFAULT_PCC_STRUCT_RETURN +@item DEFAULT_PCC_STRUCT_RETURN +Define this macro to be 1 if all structure and union return values must be +in memory. Since this results in slower code, this should be defined +only if needed for compatibility with other compilers or with an ABI. +If you define this macro to be 0, then the conventions used for structure +and union return values are decided by the @code{RETURN_IN_MEMORY} macro. + +If not defined, this defaults to the value 1. + +@findex STRUCT_VALUE_REGNUM +@item STRUCT_VALUE_REGNUM +If the structure value address is passed in a register, then +@code{STRUCT_VALUE_REGNUM} should be the number of that register. + +@findex STRUCT_VALUE +@item STRUCT_VALUE +If the structure value address is not passed in a register, define +@code{STRUCT_VALUE} as an expression returning an RTX for the place +where the address is passed. If it returns 0, the address is passed as +an ``invisible'' first argument. + +@findex STRUCT_VALUE_INCOMING_REGNUM +@item STRUCT_VALUE_INCOMING_REGNUM +On some architectures the place where the structure value address +is found by the called function is not the same place that the +caller put it. This can be due to register windows, or it could +be because the function prologue moves it to a different place. + +If the incoming location of the structure value address is in a +register, define this macro as the register number. + +@findex STRUCT_VALUE_INCOMING +@item STRUCT_VALUE_INCOMING +If the incoming location is not a register, then you should define +@code{STRUCT_VALUE_INCOMING} as an expression for an RTX for where the +called function should find the value. If it should find the value on +the stack, define this to create a @code{mem} which refers to the frame +pointer. A definition of 0 means that the address is passed as an +``invisible'' first argument. + +@findex PCC_STATIC_STRUCT_RETURN +@item PCC_STATIC_STRUCT_RETURN +Define this macro if the usual system convention on the target machine +for returning structures and unions is for the called function to return +the address of a static variable containing the value. + +Do not define this if the usual system convention is for the caller to +pass an address to the subroutine. + +This macro has effect in @samp{-fpcc-struct-return} mode, but it does +nothing when you use @samp{-freg-struct-return} mode. +@end table + +@node Caller Saves +@subsection Caller-Saves Register Allocation + +If you enable it, GCC can save registers around function calls. This +makes it possible to use call-clobbered registers to hold variables that +must live across calls. + +@table @code +@findex DEFAULT_CALLER_SAVES +@item DEFAULT_CALLER_SAVES +Define this macro if function calls on the target machine do not preserve +any registers; in other words, if @code{CALL_USED_REGISTERS} has 1 +for all registers. When defined, this macro enables @samp{-fcaller-saves} +by default for all optimization levels. It has no effect for optimization +levels 2 and higher, where @samp{-fcaller-saves} is the default. + +@findex CALLER_SAVE_PROFITABLE +@item CALLER_SAVE_PROFITABLE (@var{refs}, @var{calls}) +A C expression to determine whether it is worthwhile to consider placing +a pseudo-register in a call-clobbered hard register and saving and +restoring it around each function call. The expression should be 1 when +this is worth doing, and 0 otherwise. + +If you don't define this macro, a default is used which is good on most +machines: @code{4 * @var{calls} < @var{refs}}. + +@findex HARD_REGNO_CALLER_SAVE_MODE +@item HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs}) +A C expression specifying which mode is required for saving @var{nregs} +of a pseudo-register in call-clobbered hard register @var{regno}. If +@var{regno} is unsuitable for caller save, @code{VOIDmode} should be +returned. For most machines this macro need not be defined since GCC +will select the smallest suitable mode. +@end table + +@node Function Entry +@subsection Function Entry and Exit +@cindex function entry and exit +@cindex prologue +@cindex epilogue + +This section describes the macros that output function entry +(@dfn{prologue}) and exit (@dfn{epilogue}) code. + +@table @code +@findex FUNCTION_PROLOGUE +@item FUNCTION_PROLOGUE (@var{file}, @var{size}) +A C compound statement that outputs the assembler code for entry to a +function. The prologue is responsible for setting up the stack frame, +initializing the frame pointer register, saving registers that must be +saved, and allocating @var{size} additional bytes of storage for the +local variables. @var{size} is an integer. @var{file} is a stdio +stream to which the assembler code should be output. + +The label for the beginning of the function need not be output by this +macro. That has already been done when the macro is run. + +@findex regs_ever_live +To determine which registers to save, the macro can refer to the array +@code{regs_ever_live}: element @var{r} is nonzero if hard register +@var{r} is used anywhere within the function. This implies the function +prologue should save register @var{r}, provided it is not one of the +call-used registers. (@code{FUNCTION_EPILOGUE} must likewise use +@code{regs_ever_live}.) + +On machines that have ``register windows'', the function entry code does +not save on the stack the registers that are in the windows, even if +they are supposed to be preserved by function calls; instead it takes +appropriate steps to ``push'' the register stack, if any non-call-used +registers are used in the function. + +@findex frame_pointer_needed +On machines where functions may or may not have frame-pointers, the +function entry code must vary accordingly; it must set up the frame +pointer if one is wanted, and not otherwise. To determine whether a +frame pointer is in wanted, the macro can refer to the variable +@code{frame_pointer_needed}. The variable's value will be 1 at run +time in a function that needs a frame pointer. @xref{Elimination}. + +The function entry code is responsible for allocating any stack space +required for the function. This stack space consists of the regions +listed below. In most cases, these regions are allocated in the +order listed, with the last listed region closest to the top of the +stack (the lowest address if @code{STACK_GROWS_DOWNWARD} is defined, and +the highest address if it is not defined). You can use a different order +for a machine if doing so is more convenient or required for +compatibility reasons. Except in cases where required by standard +or by a debugger, there is no reason why the stack layout used by GCC +need agree with that used by other compilers for a machine. + +@itemize @bullet +@item +@findex current_function_pretend_args_size +A region of @code{current_function_pretend_args_size} bytes of +uninitialized space just underneath the first argument arriving on the +stack. (This may not be at the very start of the allocated stack region +if the calling sequence has pushed anything else since pushing the stack +arguments. But usually, on such machines, nothing else has been pushed +yet, because the function prologue itself does all the pushing.) This +region is used on machines where an argument may be passed partly in +registers and partly in memory, and, in some cases to support the +features in @file{varargs.h} and @file{stdargs.h}. + +@item +An area of memory used to save certain registers used by the function. +The size of this area, which may also include space for such things as +the return address and pointers to previous stack frames, is +machine-specific and usually depends on which registers have been used +in the function. Machines with register windows often do not require +a save area. + +@item +A region of at least @var{size} bytes, possibly rounded up to an allocation +boundary, to contain the local variables of the function. On some machines, +this region and the save area may occur in the opposite order, with the +save area closer to the top of the stack. + +@item +@cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames +Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of +@code{current_function_outgoing_args_size} bytes to be used for outgoing +argument lists of the function. @xref{Stack Arguments}. +@end itemize + +Normally, it is necessary for the macros @code{FUNCTION_PROLOGUE} and +@code{FUNCTION_EPILOGUE} to treat leaf functions specially. The C +variable @code{current_function_is_leaf} is nonzero for such a function. + +@findex EXIT_IGNORE_STACK +@item EXIT_IGNORE_STACK +Define this macro as a C expression that is nonzero if the return +instruction or the function epilogue ignores the value of the stack +pointer; in other words, if it is safe to delete an instruction to +adjust the stack pointer before a return from the function. + +Note that this macro's value is relevant only for functions for which +frame pointers are maintained. It is never safe to delete a final +stack adjustment in a function that has no frame pointer, and the +compiler knows this regardless of @code{EXIT_IGNORE_STACK}. + +@findex EPILOGUE_USES +@item EPILOGUE_USES (@var{regno}) +Define this macro as a C expression that is nonzero for registers that are +used by the epilogue or the @samp{return} pattern. The stack and frame +pointer registers are already be assumed to be used as needed. + +@findex FUNCTION_EPILOGUE +@item FUNCTION_EPILOGUE (@var{file}, @var{size}) +A C compound statement that outputs the assembler code for exit from a +function. The epilogue is responsible for restoring the saved +registers and stack pointer to their values when the function was +called, and returning control to the caller. This macro takes the +same arguments as the macro @code{FUNCTION_PROLOGUE}, and the +registers to restore are determined from @code{regs_ever_live} and +@code{CALL_USED_REGISTERS} in the same way. + +On some machines, there is a single instruction that does all the work +of returning from the function. On these machines, give that +instruction the name @samp{return} and do not define the macro +@code{FUNCTION_EPILOGUE} at all. + +Do not define a pattern named @samp{return} if you want the +@code{FUNCTION_EPILOGUE} to be used. If you want the target switches +to control whether return instructions or epilogues are used, define a +@samp{return} pattern with a validity condition that tests the target +switches appropriately. If the @samp{return} pattern's validity +condition is false, epilogues will be used. + +On machines where functions may or may not have frame-pointers, the +function exit code must vary accordingly. Sometimes the code for these +two cases is completely different. To determine whether a frame pointer +is wanted, the macro can refer to the variable +@code{frame_pointer_needed}. The variable's value will be 1 when compiling +a function that needs a frame pointer. + +Normally, @code{FUNCTION_PROLOGUE} and @code{FUNCTION_EPILOGUE} must +treat leaf functions specially. The C variable @code{current_function_is_leaf} +is nonzero for such a function. @xref{Leaf Functions}. + +On some machines, some functions pop their arguments on exit while +others leave that for the caller to do. For example, the 68020 when +given @samp{-mrtd} pops arguments in functions that take a fixed +number of arguments. + +@findex current_function_pops_args +Your definition of the macro @code{RETURN_POPS_ARGS} decides which +functions pop their own arguments. @code{FUNCTION_EPILOGUE} needs to +know what was decided. The variable that is called +@code{current_function_pops_args} is the number of bytes of its +arguments that a function should pop. @xref{Scalar Return}. +@c what is the "its arguments" in the above sentence referring to, pray +@c tell? --mew 5feb93 + +@findex DELAY_SLOTS_FOR_EPILOGUE +@item DELAY_SLOTS_FOR_EPILOGUE +Define this macro if the function epilogue contains delay slots to which +instructions from the rest of the function can be ``moved''. The +definition should be a C expression whose value is an integer +representing the number of delay slots there. + +@findex ELIGIBLE_FOR_EPILOGUE_DELAY +@item ELIGIBLE_FOR_EPILOGUE_DELAY (@var{insn}, @var{n}) +A C expression that returns 1 if @var{insn} can be placed in delay +slot number @var{n} of the epilogue. + +The argument @var{n} is an integer which identifies the delay slot now +being considered (since different slots may have different rules of +eligibility). It is never negative and is always less than the number +of epilogue delay slots (what @code{DELAY_SLOTS_FOR_EPILOGUE} returns). +If you reject a particular insn for a given delay slot, in principle, it +may be reconsidered for a subsequent delay slot. Also, other insns may +(at least in principle) be considered for the so far unfilled delay +slot. + +@findex current_function_epilogue_delay_list +@findex final_scan_insn +The insns accepted to fill the epilogue delay slots are put in an RTL +list made with @code{insn_list} objects, stored in the variable +@code{current_function_epilogue_delay_list}. The insn for the first +delay slot comes first in the list. Your definition of the macro +@code{FUNCTION_EPILOGUE} should fill the delay slots by outputting the +insns in this list, usually by calling @code{final_scan_insn}. + +You need not define this macro if you did not define +@code{DELAY_SLOTS_FOR_EPILOGUE}. + +@findex ASM_OUTPUT_MI_THUNK +@item ASM_OUTPUT_MI_THUNK (@var{file}, @var{thunk_fndecl}, @var{delta}, @var{function}) +A C compound statement that outputs the assembler code for a thunk +function, used to implement C++ virtual function calls with multiple +inheritance. The thunk acts as a wrapper around a virtual function, +adjusting the implicit object parameter before handing control off to +the real function. + +First, emit code to add the integer @var{delta} to the location that +contains the incoming first argument. Assume that this argument +contains a pointer, and is the one used to pass the @code{this} pointer +in C++. This is the incoming argument @emph{before} the function prologue, +e.g. @samp{%o0} on a sparc. The addition must preserve the values of +all other incoming arguments. + +After the addition, emit code to jump to @var{function}, which is a +@code{FUNCTION_DECL}. This is a direct pure jump, not a call, and does +not touch the return address. Hence returning from @var{FUNCTION} will +return to whoever called the current @samp{thunk}. + +The effect must be as if @var{function} had been called directly with +the adjusted first argument. This macro is responsible for emitting all +of the code for a thunk function; @code{FUNCTION_PROLOGUE} and +@code{FUNCTION_EPILOGUE} are not invoked. + +The @var{thunk_fndecl} is redundant. (@var{delta} and @var{function} +have already been extracted from it.) It might possibly be useful on +some targets, but probably not. + +If you do not define this macro, the target-independent code in the C++ +frontend will generate a less efficient heavyweight thunk that calls +@var{function} instead of jumping to it. The generic approach does +not support varargs. +@end table + +@node Profiling +@subsection Generating Code for Profiling +@cindex profiling, code generation + +These macros will help you generate code for profiling. + +@table @code +@findex FUNCTION_PROFILER +@item FUNCTION_PROFILER (@var{file}, @var{labelno}) +A C statement or compound statement to output to @var{file} some +assembler code to call the profiling subroutine @code{mcount}. + +@findex mcount +The details of how @code{mcount} expects to be called are determined by +your operating system environment, not by GCC. To figure them out, +compile a small program for profiling using the system's installed C +compiler and look at the assembler code that results. + +Older implementations of @code{mcount} expect the address of a counter +variable to be loaded into some register. The name of this variable is +@samp{LP} followed by the number @var{labelno}, so you would generate +the name using @samp{LP%d} in a @code{fprintf}. + +@findex PROFILE_HOOK +@item PROFILE_HOOK +A C statement or compound statement to output to @var{file} some assembly +code to call the profiling subroutine @code{mcount} even the target does +not support profiling. + +@findex NO_PROFILE_COUNTERS +@item NO_PROFILE_COUNTERS +Define this macro if the @code{mcount} subroutine on your system does +not need a counter variable allocated for each function. This is true +for almost all modern implementations. If you define this macro, you +must not use the @var{labelno} argument to @code{FUNCTION_PROFILER}. + +@findex PROFILE_BEFORE_PROLOGUE +@item PROFILE_BEFORE_PROLOGUE +Define this macro if the code for function profiling should come before +the function prologue. Normally, the profiling code comes after. + +@findex FUNCTION_BLOCK_PROFILER +@vindex profile_block_flag +@item FUNCTION_BLOCK_PROFILER (@var{file}, @var{labelno}) +A C statement or compound statement to output to @var{file} some +assembler code to initialize basic-block profiling for the current +object module. The global compile flag @code{profile_block_flag} +distinguishes two profile modes. + +@table @code +@findex __bb_init_func +@item profile_block_flag != 2 +Output code to call the subroutine @code{__bb_init_func} once per +object module, passing it as its sole argument the address of a block +allocated in the object module. + +The name of the block is a local symbol made with this statement: + +@smallexample +ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 0); +@end smallexample + +Of course, since you are writing the definition of +@code{ASM_GENERATE_INTERNAL_LABEL} as well as that of this macro, you +can take a short cut in the definition of this macro and use the name +that you know will result. + +The first word of this block is a flag which will be nonzero if the +object module has already been initialized. So test this word first, +and do not call @code{__bb_init_func} if the flag is +nonzero. BLOCK_OR_LABEL contains a unique number which may be used to +generate a label as a branch destination when @code{__bb_init_func} +will not be called. + +Described in assembler language, the code to be output looks like: + +@example + cmp (LPBX0),0 + bne local_label + parameter1 <- LPBX0 + call __bb_init_func +local_label: +@end example + +@findex __bb_init_trace_func +@item profile_block_flag == 2 +Output code to call the subroutine @code{__bb_init_trace_func} +and pass two parameters to it. The first parameter is the same as +for @code{__bb_init_func}. The second parameter is the number of the +first basic block of the function as given by BLOCK_OR_LABEL. Note +that @code{__bb_init_trace_func} has to be called, even if the object +module has been initialized already. + +Described in assembler language, the code to be output looks like: +@example +parameter1 <- LPBX0 +parameter2 <- BLOCK_OR_LABEL +call __bb_init_trace_func +@end example +@end table + +@findex BLOCK_PROFILER +@vindex profile_block_flag +@item BLOCK_PROFILER (@var{file}, @var{blockno}) +A C statement or compound statement to output to @var{file} some +assembler code to increment the count associated with the basic +block number @var{blockno}. The global compile flag +@code{profile_block_flag} distinguishes two profile modes. + +@table @code +@item profile_block_flag != 2 +Output code to increment the counter directly. Basic blocks are +numbered separately from zero within each compilation. The count +associated with block number @var{blockno} is at index +@var{blockno} in a vector of words; the name of this array is a local +symbol made with this statement: + +@smallexample +ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 2); +@end smallexample + +@c This paragraph is the same as one a few paragraphs up. +@c That is not an error. +Of course, since you are writing the definition of +@code{ASM_GENERATE_INTERNAL_LABEL} as well as that of this macro, you +can take a short cut in the definition of this macro and use the name +that you know will result. + +Described in assembler language, the code to be output looks like: + +@smallexample +inc (LPBX2+4*BLOCKNO) +@end smallexample + +@vindex __bb +@findex __bb_trace_func +@item profile_block_flag == 2 +Output code to initialize the global structure @code{__bb} and +call the function @code{__bb_trace_func}, which will increment the +counter. + +@code{__bb} consists of two words. In the first word, the current +basic block number, as given by BLOCKNO, has to be stored. In +the second word, the address of a block allocated in the object +module has to be stored. The address is given by the label created +with this statement: + +@smallexample +ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 0); +@end smallexample + +Described in assembler language, the code to be output looks like: +@example +move BLOCKNO -> (__bb) +move LPBX0 -> (__bb+4) +call __bb_trace_func +@end example +@end table + +@findex FUNCTION_BLOCK_PROFILER_EXIT +@findex __bb_trace_ret +@vindex profile_block_flag +@item FUNCTION_BLOCK_PROFILER_EXIT (@var{file}) +A C statement or compound statement to output to @var{file} +assembler code to call function @code{__bb_trace_ret}. The +assembler code should only be output +if the global compile flag @code{profile_block_flag} == 2. This +macro has to be used at every place where code for returning from +a function is generated (e.g. @code{FUNCTION_EPILOGUE}). Although +you have to write the definition of @code{FUNCTION_EPILOGUE} +as well, you have to define this macro to tell the compiler, that +the proper call to @code{__bb_trace_ret} is produced. + +@findex MACHINE_STATE_SAVE +@findex __bb_init_trace_func +@findex __bb_trace_func +@findex __bb_trace_ret +@item MACHINE_STATE_SAVE (@var{id}) +A C statement or compound statement to save all registers, which may +be clobbered by a function call, including condition codes. The +@code{asm} statement will be mostly likely needed to handle this +task. Local labels in the assembler code can be concatenated with the +string @var{id}, to obtain a unique label name. + +Registers or condition codes clobbered by @code{FUNCTION_PROLOGUE} or +@code{FUNCTION_EPILOGUE} must be saved in the macros +@code{FUNCTION_BLOCK_PROFILER}, @code{FUNCTION_BLOCK_PROFILER_EXIT} and +@code{BLOCK_PROFILER} prior calling @code{__bb_init_trace_func}, +@code{__bb_trace_ret} and @code{__bb_trace_func} respectively. + +@findex MACHINE_STATE_RESTORE +@findex __bb_init_trace_func +@findex __bb_trace_func +@findex __bb_trace_ret +@item MACHINE_STATE_RESTORE (@var{id}) +A C statement or compound statement to restore all registers, including +condition codes, saved by @code{MACHINE_STATE_SAVE}. + +Registers or condition codes clobbered by @code{FUNCTION_PROLOGUE} or +@code{FUNCTION_EPILOGUE} must be restored in the macros +@code{FUNCTION_BLOCK_PROFILER}, @code{FUNCTION_BLOCK_PROFILER_EXIT} and +@code{BLOCK_PROFILER} after calling @code{__bb_init_trace_func}, +@code{__bb_trace_ret} and @code{__bb_trace_func} respectively. + +@findex BLOCK_PROFILER_CODE +@item BLOCK_PROFILER_CODE +A C function or functions which are needed in the library to +support block profiling. + +@findex TARGET_ALLOWS_PROFILING_WITHOUT_FRAME_POINTER +@item TARGET_ALLOWS_PROFILING_WITHOUT_FRAME_POINTER +On some targets, it is impossible to use profiling when the frame +pointer has been omitted. For example, on x86 GNU/Linux systems, +the @code{mcount} routine provided by the GNU C Library finds the +address of the routine that called the routine that called @code{mcount} +by looking in the immediate caller's stack frame. If the immediate +caller has no frame pointer, this lookup will fail. + +By default, GCC assumes that the target does allow profiling when the +frame pointer is omitted. This macro should be defined to a C +expression that evaluates to @code{false} if the target does not allow +profiling when the frame pointer is omitted. + +@end table + +@node Inlining +@subsection Permitting inlining of functions with attributes +@cindex inlining + +By default if a function has a target specific attribute attached to it, +it will not be inlined. This behaviour can be overridden if the target +defines the @samp{FUNCTION_ATTRIBUTE_INLINABLE_P} macro. This macro +takes one argument, a @samp{DECL} describing the function. It should +return non-zero if the function can be inlined, otherwise it should +return 0. + +@node Tail Calling +@subsection Permitting tail calls to functions +@cindex tail calls +@cindex sibling calls + +@table @code +@findex FUNCTION_OK_FOR_SIBCALL +@item FUNCTION_OK_FOR_SIBCALL (@var{decl}) +A C expression that evaluates to true if it is ok to perform a sibling +call to @var{decl}. + +It is not uncommon for limitations of calling conventions to prevent +tail calls to functions outside the current unit of translation, or +during PIC compilation. Use this macro to enforce these restrictions, +as the @code{sibcall} md pattern can not fail, or fall over to a +``normal'' call. +@end table + +@node Varargs +@section Implementing the Varargs Macros +@cindex varargs implementation + +GCC comes with an implementation of @file{varargs.h} and +@file{stdarg.h} that work without change on machines that pass arguments +on the stack. Other machines require their own implementations of +varargs, and the two machine independent header files must have +conditionals to include it. + +ISO @file{stdarg.h} differs from traditional @file{varargs.h} mainly in +the calling convention for @code{va_start}. The traditional +implementation takes just one argument, which is the variable in which +to store the argument pointer. The ISO implementation of +@code{va_start} takes an additional second argument. The user is +supposed to write the last named argument of the function here. + +However, @code{va_start} should not use this argument. The way to find +the end of the named arguments is with the built-in functions described +below. + +@table @code +@findex __builtin_saveregs +@item __builtin_saveregs () +Use this built-in function to save the argument registers in memory so +that the varargs mechanism can access them. Both ISO and traditional +versions of @code{va_start} must use @code{__builtin_saveregs}, unless +you use @code{SETUP_INCOMING_VARARGS} (see below) instead. + +On some machines, @code{__builtin_saveregs} is open-coded under the +control of the macro @code{EXPAND_BUILTIN_SAVEREGS}. On other machines, +it calls a routine written in assembler language, found in +@file{libgcc2.c}. + +Code generated for the call to @code{__builtin_saveregs} appears at the +beginning of the function, as opposed to where the call to +@code{__builtin_saveregs} is written, regardless of what the code is. +This is because the registers must be saved before the function starts +to use them for its own purposes. +@c i rewrote the first sentence above to fix an overfull hbox. --mew +@c 10feb93 + +@findex __builtin_args_info +@item __builtin_args_info (@var{category}) +Use this built-in function to find the first anonymous arguments in +registers. + +In general, a machine may have several categories of registers used for +arguments, each for a particular category of data types. (For example, +on some machines, floating-point registers are used for floating-point +arguments while other arguments are passed in the general registers.) +To make non-varargs functions use the proper calling convention, you +have defined the @code{CUMULATIVE_ARGS} data type to record how many +registers in each category have been used so far + +@code{__builtin_args_info} accesses the same data structure of type +@code{CUMULATIVE_ARGS} after the ordinary argument layout is finished +with it, with @var{category} specifying which word to access. Thus, the +value indicates the first unused register in a given category. + +Normally, you would use @code{__builtin_args_info} in the implementation +of @code{va_start}, accessing each category just once and storing the +value in the @code{va_list} object. This is because @code{va_list} will +have to update the values, and there is no way to alter the +values accessed by @code{__builtin_args_info}. + +@findex __builtin_next_arg +@item __builtin_next_arg (@var{lastarg}) +This is the equivalent of @code{__builtin_args_info}, for stack +arguments. It returns the address of the first anonymous stack +argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it +returns the address of the location above the first anonymous stack +argument. Use it in @code{va_start} to initialize the pointer for +fetching arguments from the stack. Also use it in @code{va_start} to +verify that the second parameter @var{lastarg} is the last named argument +of the current function. + +@findex __builtin_classify_type +@item __builtin_classify_type (@var{object}) +Since each machine has its own conventions for which data types are +passed in which kind of register, your implementation of @code{va_arg} +has to embody these conventions. The easiest way to categorize the +specified data type is to use @code{__builtin_classify_type} together +with @code{sizeof} and @code{__alignof__}. + +@code{__builtin_classify_type} ignores the value of @var{object}, +considering only its data type. It returns an integer describing what +kind of type that is---integer, floating, pointer, structure, and so on. + +The file @file{typeclass.h} defines an enumeration that you can use to +interpret the values of @code{__builtin_classify_type}. +@end table + +These machine description macros help implement varargs: + +@table @code +@findex EXPAND_BUILTIN_SAVEREGS +@item EXPAND_BUILTIN_SAVEREGS () +If defined, is a C expression that produces the machine-specific code +for a call to @code{__builtin_saveregs}. This code will be moved to the +very beginning of the function, before any parameter access are made. +The return value of this function should be an RTX that contains the +value to use as the return of @code{__builtin_saveregs}. + +@findex SETUP_INCOMING_VARARGS +@item SETUP_INCOMING_VARARGS (@var{args_so_far}, @var{mode}, @var{type}, @var{pretend_args_size}, @var{second_time}) +This macro offers an alternative to using @code{__builtin_saveregs} and +defining the macro @code{EXPAND_BUILTIN_SAVEREGS}. Use it to store the +anonymous register arguments into the stack so that all the arguments +appear to have been passed consecutively on the stack. Once this is +done, you can use the standard implementation of varargs that works for +machines that pass all their arguments on the stack. + +The argument @var{args_so_far} is the @code{CUMULATIVE_ARGS} data +structure, containing the values that are obtained after processing the +named arguments. The arguments @var{mode} and @var{type} describe the +last named argument---its machine mode and its data type as a tree node. + +The macro implementation should do two things: first, push onto the +stack all the argument registers @emph{not} used for the named +arguments, and second, store the size of the data thus pushed into the +@code{int}-valued variable whose name is supplied as the argument +@var{pretend_args_size}. The value that you store here will serve as +additional offset for setting up the stack frame. + +Because you must generate code to push the anonymous arguments at +compile time without knowing their data types, +@code{SETUP_INCOMING_VARARGS} is only useful on machines that have just +a single category of argument register and use it uniformly for all data +types. + +If the argument @var{second_time} is nonzero, it means that the +arguments of the function are being analyzed for the second time. This +happens for an inline function, which is not actually compiled until the +end of the source file. The macro @code{SETUP_INCOMING_VARARGS} should +not generate any instructions in this case. + +@findex STRICT_ARGUMENT_NAMING +@item STRICT_ARGUMENT_NAMING +Define this macro to be a nonzero value if the location where a function +argument is passed depends on whether or not it is a named argument. + +This macro controls how the @var{named} argument to @code{FUNCTION_ARG} +is set for varargs and stdarg functions. If this macro returns a +nonzero value, the @var{named} argument is always true for named +arguments, and false for unnamed arguments. If it returns a value of +zero, but @code{SETUP_INCOMING_VARARGS} is defined, then all arguments +are treated as named. Otherwise, all named arguments except the last +are treated as named. + +You need not define this macro if it always returns zero. + +@findex PRETEND_OUTGOING_VARARGS_NAMED +@item PRETEND_OUTGOING_VARARGS_NAMED +If you need to conditionally change ABIs so that one works with +@code{SETUP_INCOMING_VARARGS}, but the other works like neither +@code{SETUP_INCOMING_VARARGS} nor @code{STRICT_ARGUMENT_NAMING} was +defined, then define this macro to return nonzero if +@code{SETUP_INCOMING_VARARGS} is used, zero otherwise. +Otherwise, you should not define this macro. +@end table + +@node Trampolines +@section Trampolines for Nested Functions +@cindex trampolines for nested functions +@cindex nested functions, trampolines for + +A @dfn{trampoline} is a small piece of code that is created at run time +when the address of a nested function is taken. It normally resides on +the stack, in the stack frame of the containing function. These macros +tell GCC how to generate code to allocate and initialize a +trampoline. + +The instructions in the trampoline must do two things: load a constant +address into the static chain register, and jump to the real address of +the nested function. On CISC machines such as the m68k, this requires +two instructions, a move immediate and a jump. Then the two addresses +exist in the trampoline as word-long immediate operands. On RISC +machines, it is often necessary to load each address into a register in +two parts. Then pieces of each address form separate immediate +operands. + +The code generated to initialize the trampoline must store the variable +parts---the static chain value and the function address---into the +immediate operands of the instructions. On a CISC machine, this is +simply a matter of copying each address to a memory reference at the +proper offset from the start of the trampoline. On a RISC machine, it +may be necessary to take out pieces of the address and store them +separately. + +@table @code +@findex TRAMPOLINE_TEMPLATE +@item TRAMPOLINE_TEMPLATE (@var{file}) +A C statement to output, on the stream @var{file}, assembler code for a +block of data that contains the constant parts of a trampoline. This +code should not include a label---the label is taken care of +automatically. + +If you do not define this macro, it means no template is needed +for the target. Do not define this macro on systems where the block move +code to copy the trampoline into place would be larger than the code +to generate it on the spot. + +@findex TRAMPOLINE_SECTION +@item TRAMPOLINE_SECTION +The name of a subroutine to switch to the section in which the +trampoline template is to be placed (@pxref{Sections}). The default is +a value of @samp{readonly_data_section}, which places the trampoline in +the section containing read-only data. + +@findex TRAMPOLINE_SIZE +@item TRAMPOLINE_SIZE +A C expression for the size in bytes of the trampoline, as an integer. + +@findex TRAMPOLINE_ALIGNMENT +@item TRAMPOLINE_ALIGNMENT +Alignment required for trampolines, in bits. + +If you don't define this macro, the value of @code{BIGGEST_ALIGNMENT} +is used for aligning trampolines. + +@findex INITIALIZE_TRAMPOLINE +@item INITIALIZE_TRAMPOLINE (@var{addr}, @var{fnaddr}, @var{static_chain}) +A C statement to initialize the variable parts of a trampoline. +@var{addr} is an RTX for the address of the trampoline; @var{fnaddr} is +an RTX for the address of the nested function; @var{static_chain} is an +RTX for the static chain value that should be passed to the function +when it is called. + +@findex TRAMPOLINE_ADJUST_ADDRESS +@item TRAMPOLINE_ADJUST_ADDRESS (@var{addr}) +A C statement that should perform any machine-specific adjustment in +the address of the trampoline. Its argument contains the address that +was passed to @code{INITIALIZE_TRAMPOLINE}. In case the address to be +used for a function call should be different from the address in which +the template was stored, the different address should be assigned to +@var{addr}. If this macro is not defined, @var{addr} will be used for +function calls. + +@findex ALLOCATE_TRAMPOLINE +@item ALLOCATE_TRAMPOLINE (@var{fp}) +A C expression to allocate run-time space for a trampoline. The +expression value should be an RTX representing a memory reference to the +space for the trampoline. + +@cindex @code{FUNCTION_EPILOGUE} and trampolines +@cindex @code{FUNCTION_PROLOGUE} and trampolines +If this macro is not defined, by default the trampoline is allocated as +a stack slot. This default is right for most machines. The exceptions +are machines where it is impossible to execute instructions in the stack +area. On such machines, you may have to implement a separate stack, +using this macro in conjunction with @code{FUNCTION_PROLOGUE} and +@code{FUNCTION_EPILOGUE}. + +@var{fp} points to a data structure, a @code{struct function}, which +describes the compilation status of the immediate containing function of +the function which the trampoline is for. Normally (when +@code{ALLOCATE_TRAMPOLINE} is not defined), the stack slot for the +trampoline is in the stack frame of this containing function. Other +allocation strategies probably must do something analogous with this +information. +@end table + +Implementing trampolines is difficult on many machines because they have +separate instruction and data caches. Writing into a stack location +fails to clear the memory in the instruction cache, so when the program +jumps to that location, it executes the old contents. + +Here are two possible solutions. One is to clear the relevant parts of +the instruction cache whenever a trampoline is set up. The other is to +make all trampolines identical, by having them jump to a standard +subroutine. The former technique makes trampoline execution faster; the +latter makes initialization faster. + +To clear the instruction cache when a trampoline is initialized, define +the following macros which describe the shape of the cache. + +@table @code +@findex INSN_CACHE_SIZE +@item INSN_CACHE_SIZE +The total size in bytes of the cache. + +@findex INSN_CACHE_LINE_WIDTH +@item INSN_CACHE_LINE_WIDTH +The length in bytes of each cache line. The cache is divided into cache +lines which are disjoint slots, each holding a contiguous chunk of data +fetched from memory. Each time data is brought into the cache, an +entire line is read at once. The data loaded into a cache line is +always aligned on a boundary equal to the line size. + +@findex INSN_CACHE_DEPTH +@item INSN_CACHE_DEPTH +The number of alternative cache lines that can hold any particular memory +location. +@end table + +Alternatively, if the machine has system calls or instructions to clear +the instruction cache directly, you can define the following macro. + +@table @code +@findex CLEAR_INSN_CACHE +@item CLEAR_INSN_CACHE (@var{BEG}, @var{END}) +If defined, expands to a C expression clearing the @emph{instruction +cache} in the specified interval. If it is not defined, and the macro +INSN_CACHE_SIZE is defined, some generic code is generated to clear the +cache. The definition of this macro would typically be a series of +@code{asm} statements. Both @var{BEG} and @var{END} are both pointer +expressions. +@end table + +To use a standard subroutine, define the following macro. In addition, +you must make sure that the instructions in a trampoline fill an entire +cache line with identical instructions, or else ensure that the +beginning of the trampoline code is always aligned at the same point in +its cache line. Look in @file{m68k.h} as a guide. + +@table @code +@findex TRANSFER_FROM_TRAMPOLINE +@item TRANSFER_FROM_TRAMPOLINE +Define this macro if trampolines need a special subroutine to do their +work. The macro should expand to a series of @code{asm} statements +which will be compiled with GCC. They go in a library function named +@code{__transfer_from_trampoline}. + +If you need to avoid executing the ordinary prologue code of a compiled +C function when you jump to the subroutine, you can do so by placing a +special label of your own in the assembler code. Use one @code{asm} +statement to generate an assembler label, and another to make the label +global. Then trampolines can use that label to jump directly to your +special assembler code. +@end table + +@node Library Calls +@section Implicit Calls to Library Routines +@cindex library subroutine names +@cindex @file{libgcc.a} + +@c prevent bad page break with this line +Here is an explanation of implicit calls to library routines. + +@table @code +@findex MULSI3_LIBCALL +@item MULSI3_LIBCALL +A C string constant giving the name of the function to call for +multiplication of one signed full-word by another. If you do not +define this macro, the default name is used, which is @code{__mulsi3}, +a function defined in @file{libgcc.a}. + +@findex DIVSI3_LIBCALL +@item DIVSI3_LIBCALL +A C string constant giving the name of the function to call for +division of one signed full-word by another. If you do not define +this macro, the default name is used, which is @code{__divsi3}, a +function defined in @file{libgcc.a}. + +@findex UDIVSI3_LIBCALL +@item UDIVSI3_LIBCALL +A C string constant giving the name of the function to call for +division of one unsigned full-word by another. If you do not define +this macro, the default name is used, which is @code{__udivsi3}, a +function defined in @file{libgcc.a}. + +@findex MODSI3_LIBCALL +@item MODSI3_LIBCALL +A C string constant giving the name of the function to call for the +remainder in division of one signed full-word by another. If you do +not define this macro, the default name is used, which is +@code{__modsi3}, a function defined in @file{libgcc.a}. + +@findex UMODSI3_LIBCALL +@item UMODSI3_LIBCALL +A C string constant giving the name of the function to call for the +remainder in division of one unsigned full-word by another. If you do +not define this macro, the default name is used, which is +@code{__umodsi3}, a function defined in @file{libgcc.a}. + +@findex MULDI3_LIBCALL +@item MULDI3_LIBCALL +A C string constant giving the name of the function to call for +multiplication of one signed double-word by another. If you do not +define this macro, the default name is used, which is @code{__muldi3}, +a function defined in @file{libgcc.a}. + +@findex DIVDI3_LIBCALL +@item DIVDI3_LIBCALL +A C string constant giving the name of the function to call for +division of one signed double-word by another. If you do not define +this macro, the default name is used, which is @code{__divdi3}, a +function defined in @file{libgcc.a}. + +@findex UDIVDI3_LIBCALL +@item UDIVDI3_LIBCALL +A C string constant giving the name of the function to call for +division of one unsigned full-word by another. If you do not define +this macro, the default name is used, which is @code{__udivdi3}, a +function defined in @file{libgcc.a}. + +@findex MODDI3_LIBCALL +@item MODDI3_LIBCALL +A C string constant giving the name of the function to call for the +remainder in division of one signed double-word by another. If you do +not define this macro, the default name is used, which is +@code{__moddi3}, a function defined in @file{libgcc.a}. + +@findex UMODDI3_LIBCALL +@item UMODDI3_LIBCALL +A C string constant giving the name of the function to call for the +remainder in division of one unsigned full-word by another. If you do +not define this macro, the default name is used, which is +@code{__umoddi3}, a function defined in @file{libgcc.a}. + +@findex INIT_TARGET_OPTABS +@item INIT_TARGET_OPTABS +Define this macro as a C statement that declares additional library +routines renames existing ones. @code{init_optabs} calls this macro after +initializing all the normal library routines. + +@findex FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison}) +@item FLOAT_LIB_COMPARE_RETURNS_BOOL +Define this macro as a C statement that returns nonzero if a call to +the floating point comparison library function will return a boolean +value that indicates the result of the comparison. It should return +zero if one of gcc's own libgcc functions is called. + +Most ports don't need to define this macro. + +@findex TARGET_EDOM +@cindex @code{EDOM}, implicit usage +@item TARGET_EDOM +The value of @code{EDOM} on the target machine, as a C integer constant +expression. If you don't define this macro, GCC does not attempt to +deposit the value of @code{EDOM} into @code{errno} directly. Look in +@file{/usr/include/errno.h} to find the value of @code{EDOM} on your +system. + +If you do not define @code{TARGET_EDOM}, then compiled code reports +domain errors by calling the library function and letting it report the +error. If mathematical functions on your system use @code{matherr} when +there is an error, then you should leave @code{TARGET_EDOM} undefined so +that @code{matherr} is used normally. + +@findex GEN_ERRNO_RTX +@cindex @code{errno}, implicit usage +@item GEN_ERRNO_RTX +Define this macro as a C expression to create an rtl expression that +refers to the global ``variable'' @code{errno}. (On certain systems, +@code{errno} may not actually be a variable.) If you don't define this +macro, a reasonable default is used. + +@findex TARGET_MEM_FUNCTIONS +@cindex @code{bcopy}, implicit usage +@cindex @code{memcpy}, implicit usage +@cindex @code{memmove}, implicit usage +@cindex @code{bzero}, implicit usage +@cindex @code{memset}, implicit usage +@item TARGET_MEM_FUNCTIONS +Define this macro if GCC should generate calls to the ISO C +(and System V) library functions @code{memcpy}, @code{memmove} and +@code{memset} rather than the BSD functions @code{bcopy} and @code{bzero}. + +@findex LIBGCC_NEEDS_DOUBLE +@item LIBGCC_NEEDS_DOUBLE +Define this macro if @code{float} arguments cannot be passed to library +routines (so they must be converted to @code{double}). This macro +affects both how library calls are generated and how the library +routines in @file{libgcc.a} accept their arguments. It is useful on +machines where floating and fixed point arguments are passed +differently, such as the i860. + +@findex NEXT_OBJC_RUNTIME +@item NEXT_OBJC_RUNTIME +Define this macro to generate code for Objective C message sending using +the calling convention of the NeXT system. This calling convention +involves passing the object, the selector and the method arguments all +at once to the method-lookup library function. + +The default calling convention passes just the object and the selector +to the lookup function, which returns a pointer to the method. +@end table + +@node Addressing Modes +@section Addressing Modes +@cindex addressing modes + +@c prevent bad page break with this line +This is about addressing modes. + +@table @code +@findex HAVE_PRE_INCREMENT +@findex HAVE_PRE_DECREMENT +@findex HAVE_POST_INCREMENT +@findex HAVE_POST_DECREMENT +@item HAVE_PRE_INCREMENT +@itemx HAVE_PRE_DECREMENT +@itemx HAVE_POST_INCREMENT +@itemx HAVE_POST_DECREMENT +A C expression that is non-zero if the machine supports pre-increment, +pre-decrement, post-increment, or post-decrement addressing respectively. + +@findex HAVE_POST_MODIFY_DISP +@findex HAVE_PRE_MODIFY_DISP +@item HAVE_PRE_MODIFY_DISP +@itemx HAVE_POST_MODIFY_DISP +A C expression that is non-zero if the machine supports pre- or +post-address side-effect generation involving constants other than +the size of the memory operand. + +@findex HAVE_POST_MODIFY_REG +@findex HAVE_PRE_MODIFY_REG +@item HAVE_PRE_MODIFY_REG +@itemx HAVE_POST_MODIFY_REG +A C expression that is non-zero if the machine supports pre- or +post-address side-effect generation involving a register displacement. + +@findex CONSTANT_ADDRESS_P +@item CONSTANT_ADDRESS_P (@var{x}) +A C expression that is 1 if the RTX @var{x} is a constant which +is a valid address. On most machines, this can be defined as +@code{CONSTANT_P (@var{x})}, but a few machines are more restrictive +in which constant addresses are supported. + +@findex CONSTANT_P +@code{CONSTANT_P} accepts integer-values expressions whose values are +not explicitly known, such as @code{symbol_ref}, @code{label_ref}, and +@code{high} expressions and @code{const} arithmetic expressions, in +addition to @code{const_int} and @code{const_double} expressions. + +@findex MAX_REGS_PER_ADDRESS +@item MAX_REGS_PER_ADDRESS +A number, the maximum number of registers that can appear in a valid +memory address. Note that it is up to you to specify a value equal to +the maximum number that @code{GO_IF_LEGITIMATE_ADDRESS} would ever +accept. + +@findex GO_IF_LEGITIMATE_ADDRESS +@item GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{label}) +A C compound statement with a conditional @code{goto @var{label};} +executed if @var{x} (an RTX) is a legitimate memory address on the +target machine for a memory operand of mode @var{mode}. + +It usually pays to define several simpler macros to serve as +subroutines for this one. Otherwise it may be too complicated to +understand. + +This macro must exist in two variants: a strict variant and a +non-strict one. The strict variant is used in the reload pass. It +must be defined so that any pseudo-register that has not been +allocated a hard register is considered a memory reference. In +contexts where some kind of register is required, a pseudo-register +with no hard register must be rejected. + +The non-strict variant is used in other passes. It must be defined to +accept all pseudo-registers in every context where some kind of +register is required. + +@findex REG_OK_STRICT +Compiler source files that want to use the strict variant of this +macro define the macro @code{REG_OK_STRICT}. You should use an +@code{#ifdef REG_OK_STRICT} conditional to define the strict variant +in that case and the non-strict variant otherwise. + +Subroutines to check for acceptable registers for various purposes (one +for base registers, one for index registers, and so on) are typically +among the subroutines used to define @code{GO_IF_LEGITIMATE_ADDRESS}. +Then only these subroutine macros need have two variants; the higher +levels of macros may be the same whether strict or not.@refill + +Normally, constant addresses which are the sum of a @code{symbol_ref} +and an integer are stored inside a @code{const} RTX to mark them as +constant. Therefore, there is no need to recognize such sums +specifically as legitimate addresses. Normally you would simply +recognize any @code{const} as legitimate. + +Usually @code{PRINT_OPERAND_ADDRESS} is not prepared to handle constant +sums that are not marked with @code{const}. It assumes that a naked +@code{plus} indicates indexing. If so, then you @emph{must} reject such +naked constant sums as illegitimate addresses, so that none of them will +be given to @code{PRINT_OPERAND_ADDRESS}. + +@cindex @code{ENCODE_SECTION_INFO} and address validation +On some machines, whether a symbolic address is legitimate depends on +the section that the address refers to. On these machines, define the +macro @code{ENCODE_SECTION_INFO} to store the information into the +@code{symbol_ref}, and then check for it here. When you see a +@code{const}, you will have to look inside it to find the +@code{symbol_ref} in order to determine the section. @xref{Assembler +Format}. + +@findex saveable_obstack +The best way to modify the name string is by adding text to the +beginning, with suitable punctuation to prevent any ambiguity. Allocate +the new name in @code{saveable_obstack}. You will have to modify +@code{ASM_OUTPUT_LABELREF} to remove and decode the added text and +output the name accordingly, and define @code{STRIP_NAME_ENCODING} to +access the original name string. + +You can check the information stored here into the @code{symbol_ref} in +the definitions of the macros @code{GO_IF_LEGITIMATE_ADDRESS} and +@code{PRINT_OPERAND_ADDRESS}. + +@findex REG_OK_FOR_BASE_P +@item REG_OK_FOR_BASE_P (@var{x}) +A C expression that is nonzero if @var{x} (assumed to be a @code{reg} +RTX) is valid for use as a base register. For hard registers, it +should always accept those which the hardware permits and reject the +others. Whether the macro accepts or rejects pseudo registers must be +controlled by @code{REG_OK_STRICT} as described above. This usually +requires two variant definitions, of which @code{REG_OK_STRICT} +controls the one actually used. + +@findex REG_MODE_OK_FOR_BASE_P +@item REG_MODE_OK_FOR_BASE_P (@var{x}, @var{mode}) +A C expression that is just like @code{REG_OK_FOR_BASE_P}, except that +that expression may examine the mode of the memory reference in +@var{mode}. You should define this macro if the mode of the memory +reference affects whether a register may be used as a base register. If +you define this macro, the compiler will use it instead of +@code{REG_OK_FOR_BASE_P}. + +@findex REG_OK_FOR_INDEX_P +@item REG_OK_FOR_INDEX_P (@var{x}) +A C expression that is nonzero if @var{x} (assumed to be a @code{reg} +RTX) is valid for use as an index register. + +The difference between an index register and a base register is that +the index register may be scaled. If an address involves the sum of +two registers, neither one of them scaled, then either one may be +labeled the ``base'' and the other the ``index''; but whichever +labeling is used must fit the machine's constraints of which registers +may serve in each capacity. The compiler will try both labelings, +looking for one that is valid, and will reload one or both registers +only if neither labeling works. + +@findex FIND_BASE_TERM +@item FIND_BASE_TERM (@var{x}) +A C expression to determine the base term of address @var{x}. +This macro is used in only one place: `find_base_term' in alias.c. + +It is always safe for this macro to not be defined. It exists so +that alias analysis can understand machine-dependent addresses. + +The typical use of this macro is to handle addresses containing +a label_ref or symbol_ref within an UNSPEC. + +@findex LEGITIMIZE_ADDRESS +@item LEGITIMIZE_ADDRESS (@var{x}, @var{oldx}, @var{mode}, @var{win}) +A C compound statement that attempts to replace @var{x} with a valid +memory address for an operand of mode @var{mode}. @var{win} will be a +C statement label elsewhere in the code; the macro definition may use + +@example +GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{win}); +@end example + +@noindent +to avoid further processing if the address has become legitimate. + +@findex break_out_memory_refs +@var{x} will always be the result of a call to @code{break_out_memory_refs}, +and @var{oldx} will be the operand that was given to that function to produce +@var{x}. + +The code generated by this macro should not alter the substructure of +@var{x}. If it transforms @var{x} into a more legitimate form, it +should assign @var{x} (which will always be a C variable) a new value. + +It is not necessary for this macro to come up with a legitimate +address. The compiler has standard ways of doing so in all cases. In +fact, it is safe for this macro to do nothing. But often a +machine-dependent strategy can generate better code. + +@findex LEGITIMIZE_RELOAD_ADDRESS +@item LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win}) +A C compound statement that attempts to replace @var{x}, which is an address +that needs reloading, with a valid memory address for an operand of mode +@var{mode}. @var{win} will be a C statement label elsewhere in the code. +It is not necessary to define this macro, but it might be useful for +performance reasons. + +For example, on the i386, it is sometimes possible to use a single +reload register instead of two by reloading a sum of two pseudo +registers into a register. On the other hand, for number of RISC +processors offsets are limited so that often an intermediate address +needs to be generated in order to address a stack slot. By defining +LEGITIMIZE_RELOAD_ADDRESS appropriately, the intermediate addresses +generated for adjacent some stack slots can be made identical, and thus +be shared. + +@emph{Note}: This macro should be used with caution. It is necessary +to know something of how reload works in order to effectively use this, +and it is quite easy to produce macros that build in too much knowledge +of reload internals. + +@emph{Note}: This macro must be able to reload an address created by a +previous invocation of this macro. If it fails to handle such addresses +then the compiler may generate incorrect code or abort. + +@findex push_reload +The macro definition should use @code{push_reload} to indicate parts that +need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually +suitable to be passed unaltered to @code{push_reload}. + +The code generated by this macro must not alter the substructure of +@var{x}. If it transforms @var{x} into a more legitimate form, it +should assign @var{x} (which will always be a C variable) a new value. +This also applies to parts that you change indirectly by calling +@code{push_reload}. + +@findex strict_memory_address_p +The macro definition may use @code{strict_memory_address_p} to test if +the address has become legitimate. + +@findex copy_rtx +If you want to change only a part of @var{x}, one standard way of doing +this is to use @code{copy_rtx}. Note, however, that is unshares only a +single level of rtl. Thus, if the part to be changed is not at the +top level, you'll need to replace first the top leve +It is not necessary for this macro to come up with a legitimate +address; but often a machine-dependent strategy can generate better code. + +@findex GO_IF_MODE_DEPENDENT_ADDRESS +@item GO_IF_MODE_DEPENDENT_ADDRESS (@var{addr}, @var{label}) +A C statement or compound statement with a conditional @code{goto +@var{label};} executed if memory address @var{x} (an RTX) can have +different meanings depending on the machine mode of the memory +reference it is used for or if the address is valid for some modes +but not others. + +Autoincrement and autodecrement addresses typically have mode-dependent +effects because the amount of the increment or decrement is the size +of the operand being addressed. Some machines have other mode-dependent +addresses. Many RISC machines have no mode-dependent addresses. + +You may assume that @var{addr} is a valid address for the machine. + +@findex LEGITIMATE_CONSTANT_P +@item LEGITIMATE_CONSTANT_P (@var{x}) +A C expression that is nonzero if @var{x} is a legitimate constant for +an immediate operand on the target machine. You can assume that +@var{x} satisfies @code{CONSTANT_P}, so you need not check this. In fact, +@samp{1} is a suitable definition for this macro on machines where +anything @code{CONSTANT_P} is valid.@refill +@end table + +@node Condition Code +@section Condition Code Status +@cindex condition code status + +@c prevent bad page break with this line +This describes the condition code status. + +@findex cc_status +The file @file{conditions.h} defines a variable @code{cc_status} to +describe how the condition code was computed (in case the interpretation of +the condition code depends on the instruction that it was set by). This +variable contains the RTL expressions on which the condition code is +currently based, and several standard flags. + +Sometimes additional machine-specific flags must be defined in the machine +description header file. It can also add additional machine-specific +information by defining @code{CC_STATUS_MDEP}. + +@table @code +@findex CC_STATUS_MDEP +@item CC_STATUS_MDEP +C code for a data type which is used for declaring the @code{mdep} +component of @code{cc_status}. It defaults to @code{int}. + +This macro is not used on machines that do not use @code{cc0}. + +@findex CC_STATUS_MDEP_INIT +@item CC_STATUS_MDEP_INIT +A C expression to initialize the @code{mdep} field to ``empty''. +The default definition does nothing, since most machines don't use +the field anyway. If you want to use the field, you should probably +define this macro to initialize it. + +This macro is not used on machines that do not use @code{cc0}. + +@findex NOTICE_UPDATE_CC +@item NOTICE_UPDATE_CC (@var{exp}, @var{insn}) +A C compound statement to set the components of @code{cc_status} +appropriately for an insn @var{insn} whose body is @var{exp}. It is +this macro's responsibility to recognize insns that set the condition +code as a byproduct of other activity as well as those that explicitly +set @code{(cc0)}. + +This macro is not used on machines that do not use @code{cc0}. + +If there are insns that do not set the condition code but do alter +other machine registers, this macro must check to see whether they +invalidate the expressions that the condition code is recorded as +reflecting. For example, on the 68000, insns that store in address +registers do not set the condition code, which means that usually +@code{NOTICE_UPDATE_CC} can leave @code{cc_status} unaltered for such +insns. But suppose that the previous insn set the condition code +based on location @samp{a4@@(102)} and the current insn stores a new +value in @samp{a4}. Although the condition code is not changed by +this, it will no longer be true that it reflects the contents of +@samp{a4@@(102)}. Therefore, @code{NOTICE_UPDATE_CC} must alter +@code{cc_status} in this case to say that nothing is known about the +condition code value. + +The definition of @code{NOTICE_UPDATE_CC} must be prepared to deal +with the results of peephole optimization: insns whose patterns are +@code{parallel} RTXs containing various @code{reg}, @code{mem} or +constants which are just the operands. The RTL structure of these +insns is not sufficient to indicate what the insns actually do. What +@code{NOTICE_UPDATE_CC} should do when it sees one is just to run +@code{CC_STATUS_INIT}. + +A possible definition of @code{NOTICE_UPDATE_CC} is to call a function +that looks at an attribute (@pxref{Insn Attributes}) named, for example, +@samp{cc}. This avoids having detailed information about patterns in +two places, the @file{md} file and in @code{NOTICE_UPDATE_CC}. + +@findex EXTRA_CC_MODES +@item EXTRA_CC_MODES +A list of additional modes for condition code values in registers +(@pxref{Jump Patterns}). This macro should expand to a sequence of +calls of the macro @code{CC} separated by white space. @code{CC} takes +two arguments. The first is the enumeration name of the mode, which +should begin with @samp{CC} and end with @samp{mode}. The second is a C +string giving the printable name of the mode; it should be the same as +the first argument, but with the trailing @samp{mode} removed. + +You should only define this macro if additional modes are required. + +A sample definition of @code{EXTRA_CC_MODES} is: +@smallexample +#define EXTRA_CC_MODES \ + CC(CC_NOOVmode, "CC_NOOV") \ + CC(CCFPmode, "CCFP") \ + CC(CCFPEmode, "CCFPE") +@end smallexample + +@findex SELECT_CC_MODE +@item SELECT_CC_MODE (@var{op}, @var{x}, @var{y}) +Returns a mode from class @code{MODE_CC} to be used when comparison +operation code @var{op} is applied to rtx @var{x} and @var{y}. For +example, on the Sparc, @code{SELECT_CC_MODE} is defined as (see +@pxref{Jump Patterns} for a description of the reason for this +definition) + +@smallexample +#define SELECT_CC_MODE(OP,X,Y) \ + (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \ + ? ((OP == EQ || OP == NE) ? CCFPmode : CCFPEmode) \ + : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \ + || GET_CODE (X) == NEG) \ + ? CC_NOOVmode : CCmode)) +@end smallexample + +You need not define this macro if @code{EXTRA_CC_MODES} is not defined. + +@findex CANONICALIZE_COMPARISON +@item CANONICALIZE_COMPARISON (@var{code}, @var{op0}, @var{op1}) +On some machines not all possible comparisons are defined, but you can +convert an invalid comparison into a valid one. For example, the Alpha +does not have a @code{GT} comparison, but you can use an @code{LT} +comparison instead and swap the order of the operands. + +On such machines, define this macro to be a C statement to do any +required conversions. @var{code} is the initial comparison code +and @var{op0} and @var{op1} are the left and right operands of the +comparison, respectively. You should modify @var{code}, @var{op0}, and +@var{op1} as required. + +GCC will not assume that the comparison resulting from this macro is +valid but will see if the resulting insn matches a pattern in the +@file{md} file. + +You need not define this macro if it would never change the comparison +code or operands. + +@findex REVERSIBLE_CC_MODE +@item REVERSIBLE_CC_MODE (@var{mode}) +A C expression whose value is one if it is always safe to reverse a +comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE} +can ever return @var{mode} for a floating-point inequality comparison, +then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero. + +You need not define this macro if it would always returns zero or if the +floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}. +For example, here is the definition used on the Sparc, where floating-point +inequality comparisons are always given @code{CCFPEmode}: + +@smallexample +#define REVERSIBLE_CC_MODE(MODE) ((MODE) != CCFPEmode) +@end smallexample + +@findex REVERSE_CONDITION (@var{code}, @var{mode}) +A C expression whose value is reversed condition code of the @var{code} for +comparison done in CC_MODE @var{mode}. The macro is used only in case +@code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case +machine has some non-standard way how to reverse certain conditionals. For +instance in case all floating point conditions are non-trapping, compiler may +freely convert unordered compares to ordered one. Then definition may look +like: + +@smallexample +#define REVERSE_CONDITION(CODE, MODE) \ + ((MODE) != CCFPmode ? reverse_condtion (CODE) \ + : reverse_condition_maybe_unordered (CODE)) +@end smallexample + +@findex REVERSE_CONDEXEC_PREDICATES_P +@item REVERSE_CONDEXEC_PREDICATES_P (@var{code1}, @var{code2}) +A C expression that returns true if the conditional execution predicate +@var{code1} is the inverse of @var{code2} and vice versa. Define this to +return 0 if the target has conditional execution predicates that cannot be +reversed safely. If no expansion is specified, this macro is defined as +follows: + +@smallexample +#define REVERSE_CONDEXEC_PREDICATES_P (x, y) ((x) == reverse_condition (y)) +@end smallexample + +@end table + +@node Costs +@section Describing Relative Costs of Operations +@cindex costs of instructions +@cindex relative costs +@cindex speed of instructions + +These macros let you describe the relative speed of various operations +on the target machine. + +@table @code +@findex CONST_COSTS +@item CONST_COSTS (@var{x}, @var{code}, @var{outer_code}) +A part of a C @code{switch} statement that describes the relative costs +of constant RTL expressions. It must contain @code{case} labels for +expression codes @code{const_int}, @code{const}, @code{symbol_ref}, +@code{label_ref} and @code{const_double}. Each case must ultimately +reach a @code{return} statement to return the relative cost of the use +of that kind of constant value in an expression. The cost may depend on +the precise value of the constant, which is available for examination in +@var{x}, and the rtx code of the expression in which it is contained, +found in @var{outer_code}. + +@var{code} is the expression code---redundant, since it can be +obtained with @code{GET_CODE (@var{x})}. + +@findex RTX_COSTS +@findex COSTS_N_INSNS +@item RTX_COSTS (@var{x}, @var{code}, @var{outer_code}) +Like @code{CONST_COSTS} but applies to nonconstant RTL expressions. +This can be used, for example, to indicate how costly a multiply +instruction is. In writing this macro, you can use the construct +@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast +instructions. @var{outer_code} is the code of the expression in which +@var{x} is contained. + +This macro is optional; do not define it if the default cost assumptions +are adequate for the target machine. + +@findex DEFAULT_RTX_COSTS +@item DEFAULT_RTX_COSTS (@var{x}, @var{code}, @var{outer_code}) +This macro, if defined, is called for any case not handled by the +@code{RTX_COSTS} or @code{CONST_COSTS} macros. This eliminates the need +to put case labels into the macro, but the code, or any functions it +calls, must assume that the RTL in @var{x} could be of any type that has +not already been handled. The arguments are the same as for +@code{RTX_COSTS}, and the macro should execute a return statement giving +the cost of any RTL expressions that it can handle. The default cost +calculation is used for any RTL for which this macro does not return a +value. + +This macro is optional; do not define it if the default cost assumptions +are adequate for the target machine. + +@findex ADDRESS_COST +@item ADDRESS_COST (@var{address}) +An expression giving the cost of an addressing mode that contains +@var{address}. If not defined, the cost is computed from +the @var{address} expression and the @code{CONST_COSTS} values. + +For most CISC machines, the default cost is a good approximation of the +true cost of the addressing mode. However, on RISC machines, all +instructions normally have the same length and execution time. Hence +all addresses will have equal costs. + +In cases where more than one form of an address is known, the form with +the lowest cost will be used. If multiple forms have the same, lowest, +cost, the one that is the most complex will be used. + +For example, suppose an address that is equal to the sum of a register +and a constant is used twice in the same basic block. When this macro +is not defined, the address will be computed in a register and memory +references will be indirect through that register. On machines where +the cost of the addressing mode containing the sum is no higher than +that of a simple indirect reference, this will produce an additional +instruction and possibly require an additional register. Proper +specification of this macro eliminates this overhead for such machines. + +Similar use of this macro is made in strength reduction of loops. + +@var{address} need not be valid as an address. In such a case, the cost +is not relevant and can be any value; invalid addresses need not be +assigned a different cost. + +On machines where an address involving more than one register is as +cheap as an address computation involving only one register, defining +@code{ADDRESS_COST} to reflect this can cause two registers to be live +over a region of code where only one would have been if +@code{ADDRESS_COST} were not defined in that manner. This effect should +be considered in the definition of this macro. Equivalent costs should +probably only be given to addresses with different numbers of registers +on machines with lots of registers. + +This macro will normally either not be defined or be defined as a +constant. + +@findex REGISTER_MOVE_COST +@item REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to}) +A C expression for the cost of moving data of mode @var{mode} from a +register in class @var{from} to one in class @var{to}. The classes are +expressed using the enumeration values such as @code{GENERAL_REGS}. A +value of 2 is the default; other values are interpreted relative to +that. + +It is not required that the cost always equal 2 when @var{from} is the +same as @var{to}; on some machines it is expensive to move between +registers if they are not general registers. + +If reload sees an insn consisting of a single @code{set} between two +hard registers, and if @code{REGISTER_MOVE_COST} applied to their +classes returns a value of 2, reload does not check to ensure that the +constraints of the insn are met. Setting a cost of other than 2 will +allow reload to verify that the constraints are met. You should do this +if the @samp{mov@var{m}} pattern's constraints do not allow such copying. + +@findex MEMORY_MOVE_COST +@item MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in}) +A C expression for the cost of moving data of mode @var{mode} between a +register of class @var{class} and memory; @var{in} is zero if the value +is to be written to memory, non-zero if it is to be read in. This cost +is relative to those in @code{REGISTER_MOVE_COST}. If moving between +registers and memory is more expensive than between two registers, you +should define this macro to express the relative cost. + +If you do not define this macro, GCC uses a default cost of 4 plus +the cost of copying via a secondary reload register, if one is +needed. If your machine requires a secondary reload register to copy +between memory and a register of @var{class} but the reload mechanism is +more complex than copying via an intermediate, define this macro to +reflect the actual cost of the move. + +GCC defines the function @code{memory_move_secondary_cost} if +secondary reloads are needed. It computes the costs due to copying via +a secondary register. If your machine copies from memory using a +secondary register in the conventional way but the default base value of +4 is not correct for your machine, define this macro to add some other +value to the result of that function. The arguments to that function +are the same as to this macro. + +@findex BRANCH_COST +@item BRANCH_COST +A C expression for the cost of a branch instruction. A value of 1 is +the default; other values are interpreted relative to that. +@end table + +Here are additional macros which do not specify precise relative costs, +but only that certain actions are more expensive than GCC would +ordinarily expect. + +@table @code +@findex SLOW_BYTE_ACCESS +@item SLOW_BYTE_ACCESS +Define this macro as a C expression which is nonzero if accessing less +than a word of memory (i.e. a @code{char} or a @code{short}) is no +faster than accessing a word of memory, i.e., if such access +require more than one instruction or if there is no difference in cost +between byte and (aligned) word loads. + +When this macro is not defined, the compiler will access a field by +finding the smallest containing object; when it is defined, a fullword +load will be used if alignment permits. Unless bytes accesses are +faster than word accesses, using word accesses is preferable since it +may eliminate subsequent memory access if subsequent accesses occur to +other fields in the same word of the structure, but to different bytes. + +@findex SLOW_ZERO_EXTEND +@item SLOW_ZERO_EXTEND +Define this macro if zero-extension (of a @code{char} or @code{short} +to an @code{int}) can be done faster if the destination is a register +that is known to be zero. + +If you define this macro, you must have instruction patterns that +recognize RTL structures like this: + +@smallexample +(set (strict_low_part (subreg:QI (reg:SI @dots{}) 0)) @dots{}) +@end smallexample + +@noindent +and likewise for @code{HImode}. + +@findex SLOW_UNALIGNED_ACCESS +@item SLOW_UNALIGNED_ACCESS (@var{mode}, @var{alignment}) +Define this macro to be the value 1 if memory accesses described by the +@var{mode} and @var{alignment} parameters have a cost many times greater +than aligned accesses, for example if they are emulated in a trap +handler. + +When this macro is non-zero, the compiler will act as if +@code{STRICT_ALIGNMENT} were non-zero when generating code for block +moves. This can cause significantly more instructions to be produced. +Therefore, do not set this macro non-zero if unaligned accesses only add a +cycle or two to the time for a memory access. + +If the value of this macro is always zero, it need not be defined. If +this macro is defined, it should produce a non-zero value when +@code{STRICT_ALIGNMENT} is non-zero. + +@findex DONT_REDUCE_ADDR +@item DONT_REDUCE_ADDR +Define this macro to inhibit strength reduction of memory addresses. +(On some machines, such strength reduction seems to do harm rather +than good.) + +@findex MOVE_RATIO +@item MOVE_RATIO +The threshold of number of scalar memory-to-memory move insns, @emph{below} +which a sequence of insns should be generated instead of a +string move insn or a library call. Increasing the value will always +make code faster, but eventually incurs high cost in increased code size. + +Note that on machines where the corresponding move insn is a +@code{define_expand} that emits a sequence of insns, this macro counts +the number of such sequences. + +If you don't define this, a reasonable default is used. + +@findex MOVE_BY_PIECES_P +@item MOVE_BY_PIECES_P (@var{size}, @var{alignment}) +A C expression used to determine whether @code{move_by_pieces} will be used to +copy a chunk of memory, or whether some other block move mechanism +will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less +than @code{MOVE_RATIO}. + +@findex MOVE_MAX_PIECES +@item MOVE_MAX_PIECES +A C expression used by @code{move_by_pieces} to determine the largest unit +a load or store used to copy memory is. Defaults to @code{MOVE_MAX}. + +@findex USE_LOAD_POST_INCREMENT +@item USE_LOAD_POST_INCREMENT (@var{mode}) +A C expression used to determine whether a load postincrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_POST_INCREMENT}. + +@findex USE_LOAD_POST_DECREMENT +@item USE_LOAD_POST_DECREMENT (@var{mode}) +A C expression used to determine whether a load postdecrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_POST_DECREMENT}. + +@findex USE_LOAD_PRE_INCREMENT +@item USE_LOAD_PRE_INCREMENT (@var{mode}) +A C expression used to determine whether a load preincrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_PRE_INCREMENT}. + +@findex USE_LOAD_PRE_DECREMENT +@item USE_LOAD_PRE_DECREMENT (@var{mode}) +A C expression used to determine whether a load predecrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_PRE_DECREMENT}. + +@findex USE_STORE_POST_INCREMENT +@item USE_STORE_POST_INCREMENT (@var{mode}) +A C expression used to determine whether a store postincrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_POST_INCREMENT}. + +@findex USE_STORE_POST_DECREMENT +@item USE_STORE_POST_DECREMENT (@var{mode}) +A C expression used to determine whether a store postdeccrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_POST_DECREMENT}. + +@findex USE_STORE_PRE_INCREMENT +@item USE_STORE_PRE_INCREMENT (@var{mode}) +This macro is used to determine whether a store preincrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_PRE_INCREMENT}. + +@findex USE_STORE_PRE_DECREMENT +@item USE_STORE_PRE_DECREMENT (@var{mode}) +This macro is used to determine whether a store predecrement is a good +thing to use for a given mode. Defaults to the value of +@code{HAVE_PRE_DECREMENT}. + +@findex NO_FUNCTION_CSE +@item NO_FUNCTION_CSE +Define this macro if it is as good or better to call a constant +function address than to call an address kept in a register. + +@findex NO_RECURSIVE_FUNCTION_CSE +@item NO_RECURSIVE_FUNCTION_CSE +Define this macro if it is as good or better for a function to call +itself with an explicit address than to call an address kept in a +register. + +@findex ADJUST_COST +@item ADJUST_COST (@var{insn}, @var{link}, @var{dep_insn}, @var{cost}) +A C statement (sans semicolon) to update the integer variable @var{cost} +based on the relationship between @var{insn} that is dependent on +@var{dep_insn} through the dependence @var{link}. The default is to +make no adjustment to @var{cost}. This can be used for example to +specify to the scheduler that an output- or anti-dependence does not +incur the same cost as a data-dependence. + +@findex ADJUST_PRIORITY +@item ADJUST_PRIORITY (@var{insn}) +A C statement (sans semicolon) to update the integer scheduling +priority @code{INSN_PRIORITY(@var{insn})}. Reduce the priority +to execute the @var{insn} earlier, increase the priority to execute +@var{insn} later. Do not define this macro if you do not need to +adjust the scheduling priorities of insns. +@end table + +@node Sections +@section Dividing the Output into Sections (Texts, Data, @dots{}) +@c the above section title is WAY too long. maybe cut the part between +@c the (...)? --mew 10feb93 + +An object file is divided into sections containing different types of +data. In the most common case, there are three sections: the @dfn{text +section}, which holds instructions and read-only data; the @dfn{data +section}, which holds initialized writable data; and the @dfn{bss +section}, which holds uninitialized data. Some systems have other kinds +of sections. + +The compiler must tell the assembler when to switch sections. These +macros control what commands to output to tell the assembler this. You +can also define additional sections. + +@table @code +@findex TEXT_SECTION_ASM_OP +@item TEXT_SECTION_ASM_OP +A C expression whose value is a string, including spacing, containing the +assembler operation that should precede instructions and read-only data. +Normally @code{"\t.text"} is right. + +@findex DATA_SECTION_ASM_OP +@item DATA_SECTION_ASM_OP +A C expression whose value is a string, including spacing, containing the +assembler operation to identify the following data as writable initialized +data. Normally @code{"\t.data"} is right. + +@findex SHARED_SECTION_ASM_OP +@item SHARED_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +shared data. If not defined, @code{DATA_SECTION_ASM_OP} will be used. + +@findex BSS_SECTION_ASM_OP +@item BSS_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +uninitialized global data. If not defined, and neither +@code{ASM_OUTPUT_BSS} nor @code{ASM_OUTPUT_ALIGNED_BSS} are defined, +uninitialized global data will be output in the data section if +@samp{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be +used. + +@findex SHARED_BSS_SECTION_ASM_OP +@item SHARED_BSS_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +uninitialized global shared data. If not defined, and +@code{BSS_SECTION_ASM_OP} is, the latter will be used. + +@findex INIT_SECTION_ASM_OP +@item INIT_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +initialization code. If not defined, GCC will assume such a section does +not exist. + +@findex FINI_SECTION_ASM_OP +@item FINI_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +finalization code. If not defined, GCC will assume such a section does +not exist. + +@findex CRT_CALL_STATIC_FUNCTION +@item CRT_CALL_STATIC_FUNCTION +If defined, a C statement that calls the function named as the sole +argument of this macro. This is used in @file{crtstuff.c} if +@code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls to +initialization and finalization functions from the init and fini +sections. By default, this macro is a simple function call. Some +ports need hand-crafted assembly code to avoid dependencies on +registers initialized in the function prologue or to ensure that +constant pools don't end up too far way in the text section. + +@findex EXTRA_SECTIONS +@findex in_text +@findex in_data +@item EXTRA_SECTIONS +A list of names for sections other than the standard two, which are +@code{in_text} and @code{in_data}. You need not define this macro +on a system with no other sections (that GCC needs to use). + +@findex EXTRA_SECTION_FUNCTIONS +@findex text_section +@findex data_section +@item EXTRA_SECTION_FUNCTIONS +One or more functions to be defined in @file{varasm.c}. These +functions should do jobs analogous to those of @code{text_section} and +@code{data_section}, for your additional sections. Do not define this +macro if you do not define @code{EXTRA_SECTIONS}. + +@findex READONLY_DATA_SECTION +@item READONLY_DATA_SECTION +On most machines, read-only variables, constants, and jump tables are +placed in the text section. If this is not the case on your machine, +this macro should be defined to be the name of a function (either +@code{data_section} or a function defined in @code{EXTRA_SECTIONS}) that +switches to the section to be used for read-only items. + +If these items should be placed in the text section, this macro should +not be defined. + +@findex SELECT_SECTION +@item SELECT_SECTION (@var{exp}, @var{reloc}) +A C statement or statements to switch to the appropriate section for +output of @var{exp}. You can assume that @var{exp} is either a +@code{VAR_DECL} node or a constant of some sort. @var{reloc} +indicates whether the initial value of @var{exp} requires link-time +relocations. Select the section by calling @code{text_section} or one +of the alternatives for other sections. + +Do not define this macro if you put all read-only variables and +constants in the read-only data section (usually the text section). + +@findex SELECT_RTX_SECTION +@item SELECT_RTX_SECTION (@var{mode}, @var{rtx}) +A C statement or statements to switch to the appropriate section for +output of @var{rtx} in mode @var{mode}. You can assume that @var{rtx} +is some kind of constant in RTL. The argument @var{mode} is redundant +except in the case of a @code{const_int} rtx. Select the section by +calling @code{text_section} or one of the alternatives for other +sections. + +Do not define this macro if you put all constants in the read-only +data section. + +@findex JUMP_TABLES_IN_TEXT_SECTION +@item JUMP_TABLES_IN_TEXT_SECTION +Define this macro to be an expression with a non-zero value if jump +tables (for @code{tablejump} insns) should be output in the text +section, along with the assembler instructions. Otherwise, the +readonly data section is used. + +This macro is irrelevant if there is no separate readonly data section. + +@findex ENCODE_SECTION_INFO +@item ENCODE_SECTION_INFO (@var{decl}) +Define this macro if references to a symbol must be treated differently +depending on something about the variable or function named by the +symbol (such as what section it is in). + +The macro definition, if any, is executed immediately after the rtl for +@var{decl} has been created and stored in @code{DECL_RTL (@var{decl})}. +The value of the rtl will be a @code{mem} whose address is a +@code{symbol_ref}. + +@cindex @code{SYMBOL_REF_FLAG}, in @code{ENCODE_SECTION_INFO} +The usual thing for this macro to do is to record a flag in the +@code{symbol_ref} (such as @code{SYMBOL_REF_FLAG}) or to store a +modified name string in the @code{symbol_ref} (if one bit is not enough +information). + +@findex STRIP_NAME_ENCODING +@item STRIP_NAME_ENCODING (@var{var}, @var{sym_name}) +Decode @var{sym_name} and store the real name part in @var{var}, sans +the characters that encode section info. Define this macro if +@code{ENCODE_SECTION_INFO} alters the symbol's name string. + +@findex UNIQUE_SECTION_P +@item UNIQUE_SECTION_P (@var{decl}) +A C expression which evaluates to true if @var{decl} should be placed +into a unique section for some target-specific reason. If you do not +define this macro, the default is @samp{0}. Note that the flag +@samp{-ffunction-sections} will also cause functions to be placed into +unique sections. + +@findex UNIQUE_SECTION +@item UNIQUE_SECTION (@var{decl}, @var{reloc}) +A C statement to build up a unique section name, expressed as a +STRING_CST node, and assign it to @samp{DECL_SECTION_NAME (@var{decl})}. +@var{reloc} indicates whether the initial value of @var{exp} requires +link-time relocations. If you do not define this macro, GCC will use +the symbol name prefixed by @samp{.} as the section name. Note - this +macro can now be called for unitialised data items as well as +initialised data and functions. +@end table + +@node PIC +@section Position Independent Code +@cindex position independent code +@cindex PIC + +This section describes macros that help implement generation of position +independent code. Simply defining these macros is not enough to +generate valid PIC; you must also add support to the macros +@code{GO_IF_LEGITIMATE_ADDRESS} and @code{PRINT_OPERAND_ADDRESS}, as +well as @code{LEGITIMIZE_ADDRESS}. You must modify the definition of +@samp{movsi} to do something appropriate when the source operand +contains a symbolic address. You may also need to alter the handling of +switch statements so that they use relative addresses. +@c i rearranged the order of the macros above to try to force one of +@c them to the next line, to eliminate an overfull hbox. --mew 10feb93 + +@table @code +@findex PIC_OFFSET_TABLE_REGNUM +@item PIC_OFFSET_TABLE_REGNUM +The register number of the register used to address a table of static +data addresses in memory. In some cases this register is defined by a +processor's ``application binary interface'' (ABI). When this macro +is defined, RTL is generated for this register once, as with the stack +pointer and frame pointer registers. If this macro is not defined, it +is up to the machine-dependent files to allocate such a register (if +necessary). + +@findex PIC_OFFSET_TABLE_REG_CALL_CLOBBERED +@item PIC_OFFSET_TABLE_REG_CALL_CLOBBERED +Define this macro if the register defined by +@code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. Do not define +this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined. + +@findex FINALIZE_PIC +@item FINALIZE_PIC +By generating position-independent code, when two different programs (A +and B) share a common library (libC.a), the text of the library can be +shared whether or not the library is linked at the same address for both +programs. In some of these environments, position-independent code +requires not only the use of different addressing modes, but also +special code to enable the use of these addressing modes. + +The @code{FINALIZE_PIC} macro serves as a hook to emit these special +codes once the function is being compiled into assembly code, but not +before. (It is not done before, because in the case of compiling an +inline function, it would lead to multiple PIC prologues being +included in functions which used inline functions and were compiled to +assembly language.) + +@findex LEGITIMATE_PIC_OPERAND_P +@item LEGITIMATE_PIC_OPERAND_P (@var{x}) +A C expression that is nonzero if @var{x} is a legitimate immediate +operand on the target machine when generating position independent code. +You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not +check this. You can also assume @var{flag_pic} is true, so you need not +check it either. You need not define this macro if all constants +(including @code{SYMBOL_REF}) can be immediate operands when generating +position independent code. +@end table + +@node Assembler Format +@section Defining the Output Assembler Language + +This section describes macros whose principal purpose is to describe how +to write instructions in assembler language--rather than what the +instructions do. + +@menu +* File Framework:: Structural information for the assembler file. +* Data Output:: Output of constants (numbers, strings, addresses). +* Uninitialized Data:: Output of uninitialized variables. +* Label Output:: Output and generation of labels. +* Initialization:: General principles of initialization + and termination routines. +* Macros for Initialization:: + Specific macros that control the handling of + initialization and termination routines. +* Instruction Output:: Output of actual instructions. +* Dispatch Tables:: Output of jump tables. +* Exception Region Output:: Output of exception region code. +* Alignment Output:: Pseudo ops for alignment and skipping data. +@end menu + +@node File Framework +@subsection The Overall Framework of an Assembler File +@cindex assembler format +@cindex output of assembler code + +@c prevent bad page break with this line +This describes the overall framework of an assembler file. + +@table @code +@findex ASM_FILE_START +@item ASM_FILE_START (@var{stream}) +A C expression which outputs to the stdio stream @var{stream} +some appropriate text to go at the start of an assembler file. + +Normally this macro is defined to output a line containing +@samp{#NO_APP}, which is a comment that has no effect on most +assemblers but tells the GNU assembler that it can save time by not +checking for certain assembler constructs. + +On systems that use SDB, it is necessary to output certain commands; +see @file{attasm.h}. + +@findex ASM_FILE_END +@item ASM_FILE_END (@var{stream}) +A C expression which outputs to the stdio stream @var{stream} +some appropriate text to go at the end of an assembler file. + +If this macro is not defined, the default is to output nothing +special at the end of the file. Most systems don't require any +definition. + +On systems that use SDB, it is necessary to output certain commands; +see @file{attasm.h}. + +@findex ASM_COMMENT_START +@item ASM_COMMENT_START +A C string constant describing how to begin a comment in the target +assembler language. The compiler assumes that the comment will end at +the end of the line. + +@findex ASM_APP_ON +@item ASM_APP_ON +A C string constant for text to be output before each @code{asm} +statement or group of consecutive ones. Normally this is +@code{"#APP"}, which is a comment that has no effect on most +assemblers but tells the GNU assembler that it must check the lines +that follow for all valid assembler constructs. + +@findex ASM_APP_OFF +@item ASM_APP_OFF +A C string constant for text to be output after each @code{asm} +statement or group of consecutive ones. Normally this is +@code{"#NO_APP"}, which tells the GNU assembler to resume making the +time-saving assumptions that are valid for ordinary compiler output. + +@findex ASM_OUTPUT_SOURCE_FILENAME +@item ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) +A C statement to output COFF information or DWARF debugging information +which indicates that filename @var{name} is the current source file to +the stdio stream @var{stream}. + +This macro need not be defined if the standard form of output +for the file format in use is appropriate. + +@findex OUTPUT_QUOTED_STRING +@item OUTPUT_QUOTED_STRING (@var{stream}, @var{string}) +A C statement to output the string @var{string} to the stdio stream +@var{stream}. If you do not call the function @code{output_quoted_string} +in your config files, GCC will only call it to output filenames to +the assembler source. So you can use it to canonicalize the format +of the filename using this macro. + +@findex ASM_OUTPUT_SOURCE_LINE +@item ASM_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}) +A C statement to output DBX or SDB debugging information before code +for line number @var{line} of the current source file to the +stdio stream @var{stream}. + +This macro need not be defined if the standard form of debugging +information for the debugger in use is appropriate. + +@findex ASM_OUTPUT_IDENT +@item ASM_OUTPUT_IDENT (@var{stream}, @var{string}) +A C statement to output something to the assembler file to handle a +@samp{#ident} directive containing the text @var{string}. If this +macro is not defined, nothing is output for a @samp{#ident} directive. + +@findex ASM_OUTPUT_SECTION_NAME +@item ASM_OUTPUT_SECTION_NAME (@var{stream}, @var{decl}, @var{name}, @var{reloc}) +A C statement to output something to the assembler file to switch to section +@var{name} for object @var{decl} which is either a @code{FUNCTION_DECL}, a +@code{VAR_DECL} or @code{NULL_TREE}. @var{reloc} +indicates whether the initial value of @var{exp} requires link-time +relocations. The string given by @var{name} will always be the +canonical version stored in the global stringpool. + +Some target formats do not support arbitrary sections. Do not define +this macro in such cases. + +At present this macro is only used to support section attributes. +When this macro is undefined, section attributes are disabled. + +@findex OBJC_PROLOGUE +@item OBJC_PROLOGUE +A C statement to output any assembler statements which are required to +precede any Objective C object definitions or message sending. The +statement is executed only when compiling an Objective C program. +@end table + +@need 2000 +@node Data Output +@subsection Output of Data + +@c prevent bad page break with this line +This describes data output. + +@table @code +@findex ASM_OUTPUT_LONG_DOUBLE +@findex ASM_OUTPUT_DOUBLE +@findex ASM_OUTPUT_FLOAT +@item ASM_OUTPUT_LONG_DOUBLE (@var{stream}, @var{value}) +@itemx ASM_OUTPUT_DOUBLE (@var{stream}, @var{value}) +@itemx ASM_OUTPUT_FLOAT (@var{stream}, @var{value}) +@itemx ASM_OUTPUT_THREE_QUARTER_FLOAT (@var{stream}, @var{value}) +@itemx ASM_OUTPUT_SHORT_FLOAT (@var{stream}, @var{value}) +@itemx ASM_OUTPUT_BYTE_FLOAT (@var{stream}, @var{value}) +A C statement to output to the stdio stream @var{stream} an assembler +instruction to assemble a floating-point constant of @code{TFmode}, +@code{DFmode}, @code{SFmode}, @code{TQFmode}, @code{HFmode}, or +@code{QFmode}, respectively, whose value is @var{value}. @var{value} +will be a C expression of type @code{REAL_VALUE_TYPE}. Macros such as +@code{REAL_VALUE_TO_TARGET_DOUBLE} are useful for writing these +definitions. + +@findex ASM_OUTPUT_QUADRUPLE_INT +@findex ASM_OUTPUT_DOUBLE_INT +@findex ASM_OUTPUT_INT +@findex ASM_OUTPUT_SHORT +@findex ASM_OUTPUT_CHAR +@findex output_addr_const +@item ASM_OUTPUT_QUADRUPLE_INT (@var{stream}, @var{exp}) +@itemx ASM_OUTPUT_DOUBLE_INT (@var{stream}, @var{exp}) +@itemx ASM_OUTPUT_INT (@var{stream}, @var{exp}) +@itemx ASM_OUTPUT_SHORT (@var{stream}, @var{exp}) +@itemx ASM_OUTPUT_CHAR (@var{stream}, @var{exp}) +A C statement to output to the stdio stream @var{stream} an assembler +instruction to assemble an integer of 16, 8, 4, 2 or 1 bytes, +respectively, whose value is @var{value}. The argument @var{exp} will +be an RTL expression which represents a constant value. Use +@samp{output_addr_const (@var{stream}, @var{exp})} to output this value +as an assembler expression.@refill + +For sizes larger than @code{UNITS_PER_WORD}, if the action of a macro +would be identical to repeatedly calling the macro corresponding to +a size of @code{UNITS_PER_WORD}, once for each word, you need not define +the macro. + +@findex OUTPUT_ADDR_CONST_EXTRA +@item OUTPUT_ADDR_CONST_EXTRA (@var{stream}, @var{x}, @var{fail}) +A C statement to recognize @var{rtx} patterns that +@code{output_addr_const} can't deal with, and output assembly code to +@var{stream} corresponding to the pattern @var{x}. This may be used to +allow machine-dependent @code{UNSPEC}s to appear within constants. + +If @code{OUTPUT_ADDR_CONST_EXTRA} fails to recognize a pattern, it must +@code{goto fail}, so that a standard error message is printed. If it +prints an error message itself, by calling, for example, +@code{output_operand_lossage}, it may just complete normally. + +@findex ASM_OUTPUT_BYTE +@item ASM_OUTPUT_BYTE (@var{stream}, @var{value}) +A C statement to output to the stdio stream @var{stream} an assembler +instruction to assemble a single byte containing the number @var{value}. + +@findex ASM_BYTE_OP +@item ASM_BYTE_OP +A C string constant, including spacing, giving the pseudo-op to use for a +sequence of single-byte constants. If this macro is not defined, the +default is @code{"\t.byte\t"}. + +@findex UNALIGNED_SHORT_ASM_OP +@findex UNALIGNED_INT_ASM_OP +@findex UNALIGNED_DOUBLE_INT_ASM_OP +@item UNALIGNED_SHORT_ASM_OP +@itemx UNALIGNED_INT_ASM_OP +@itemx UNALIGNED_DOUBLE_INT_ASM_OP +A C string constant, including spacing, giving the pseudo-op to use +to assemble 16-, 32-, and 64-bit integers respectively @emph{without} +adding implicit padding or alignment. These macros are required if +DWARF 2 frame unwind is used. On ELF systems, these will default +to @code{.2byte}, @code{.4byte}, and @code{.8byte}.@refill + +@findex ASM_OUTPUT_ASCII +@item ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len}) +A C statement to output to the stdio stream @var{stream} an assembler +instruction to assemble a string constant containing the @var{len} +bytes at @var{ptr}. @var{ptr} will be a C expression of type +@code{char *} and @var{len} a C expression of type @code{int}. + +If the assembler has a @code{.ascii} pseudo-op as found in the +Berkeley Unix assembler, do not define the macro +@code{ASM_OUTPUT_ASCII}. + +@findex CONSTANT_POOL_BEFORE_FUNCTION +@item CONSTANT_POOL_BEFORE_FUNCTION +You may define this macro as a C expression. You should define the +expression to have a non-zero value if GCC should output the constant +pool for a function before the code for the function, or a zero value if +GCC should output the constant pool after the function. If you do +not define this macro, the usual case, GCC will output the constant +pool before the function. + +@findex ASM_OUTPUT_POOL_PROLOGUE +@item ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size}) +A C statement to output assembler commands to define the start of the +constant pool for a function. @var{funname} is a string giving +the name of the function. Should the return type of the function +be required, it can be obtained via @var{fundecl}. @var{size} +is the size, in bytes, of the constant pool that will be written +immediately after this call. + +If no constant-pool prefix is required, the usual case, this macro need +not be defined. + +@findex ASM_OUTPUT_SPECIAL_POOL_ENTRY +@item ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto}) +A C statement (with or without semicolon) to output a constant in the +constant pool, if it needs special treatment. (This macro need not do +anything for RTL expressions that can be output normally.) + +The argument @var{file} is the standard I/O stream to output the +assembler code on. @var{x} is the RTL expression for the constant to +output, and @var{mode} is the machine mode (in case @var{x} is a +@samp{const_int}). @var{align} is the required alignment for the value +@var{x}; you should output an assembler directive to force this much +alignment. + +The argument @var{labelno} is a number to use in an internal label for +the address of this pool entry. The definition of this macro is +responsible for outputting the label definition at the proper place. +Here is how to do this: + +@example +ASM_OUTPUT_INTERNAL_LABEL (@var{file}, "LC", @var{labelno}); +@end example + +When you output a pool entry specially, you should end with a +@code{goto} to the label @var{jumpto}. This will prevent the same pool +entry from being output a second time in the usual manner. + +You need not define this macro if it would do nothing. + +@findex CONSTANT_AFTER_FUNCTION_P +@item CONSTANT_AFTER_FUNCTION_P (@var{exp}) +Define this macro as a C expression which is nonzero if the constant +@var{exp}, of type @code{tree}, should be output after the code for a +function. The compiler will normally output all constants before the +function; you need not define this macro if this is OK. + +@findex ASM_OUTPUT_POOL_EPILOGUE +@item ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size}) +A C statement to output assembler commands to at the end of the constant +pool for a function. @var{funname} is a string giving the name of the +function. Should the return type of the function be required, you can +obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the +constant pool that GCC wrote immediately before this call. + +If no constant-pool epilogue is required, the usual case, you need not +define this macro. + +@findex IS_ASM_LOGICAL_LINE_SEPARATOR +@item IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}) +Define this macro as a C expression which is nonzero if @var{C} is +used as a logical line separator by the assembler. + +If you do not define this macro, the default is that only +the character @samp{;} is treated as a logical line separator. + + +@findex ASM_OPEN_PAREN +@findex ASM_CLOSE_PAREN +@item ASM_OPEN_PAREN +@itemx ASM_CLOSE_PAREN +These macros are defined as C string constants, describing the syntax +in the assembler for grouping arithmetic expressions. The following +definitions are correct for most assemblers: + +@example +#define ASM_OPEN_PAREN "(" +#define ASM_CLOSE_PAREN ")" +@end example +@end table + + These macros are provided by @file{real.h} for writing the definitions +of @code{ASM_OUTPUT_DOUBLE} and the like: + +@table @code +@item REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l}) +@itemx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l}) +@itemx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l}) +@findex REAL_VALUE_TO_TARGET_SINGLE +@findex REAL_VALUE_TO_TARGET_DOUBLE +@findex REAL_VALUE_TO_TARGET_LONG_DOUBLE +These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the target's +floating point representation, and store its bit pattern in the array of +@code{long int} whose address is @var{l}. The number of elements in the +output array is determined by the size of the desired target floating +point data type: 32 bits of it go in each @code{long int} array +element. Each array element holds 32 bits of the result, even if +@code{long int} is wider than 32 bits on the host machine. + +The array element values are designed so that you can print them out +using @code{fprintf} in the order they should appear in the target +machine's memory. + +@item REAL_VALUE_TO_DECIMAL (@var{x}, @var{format}, @var{string}) +@findex REAL_VALUE_TO_DECIMAL +This macro converts @var{x}, of type @code{REAL_VALUE_TYPE}, to a +decimal number and stores it as a string into @var{string}. +You must pass, as @var{string}, the address of a long enough block +of space to hold the result. + +The argument @var{format} is a @code{printf}-specification that serves +as a suggestion for how to format the output string. +@end table + +@node Uninitialized Data +@subsection Output of Uninitialized Variables + +Each of the macros in this section is used to do the whole job of +outputting a single uninitialized variable. + +@table @code +@findex ASM_OUTPUT_COMMON +@item ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} the assembler definition of a common-label named +@var{name} whose size is @var{size} bytes. The variable @var{rounded} +is the size rounded up to whatever alignment the caller wants. + +Use the expression @code{assemble_name (@var{stream}, @var{name})} to +output the name itself; before and after that, output the additional +assembler syntax for defining the name, and a newline. + +This macro controls how the assembler definitions of uninitialized +common global variables are output. + +@findex ASM_OUTPUT_ALIGNED_COMMON +@item ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment}) +Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a +separate, explicit argument. If you define this macro, it is used in +place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in +handling the required alignment of the variable. The alignment is specified +as the number of bits. + +@findex ASM_OUTPUT_ALIGNED_DECL_COMMON +@item ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) +Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the +variable to be output, if there is one, or @code{NULL_TREE} if there +is no corresponding variable. If you define this macro, GCC will use it +in place of both @code{ASM_OUTPUT_COMMON} and +@code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see +the variable's decl in order to chose what to output. + +@findex ASM_OUTPUT_SHARED_COMMON +@item ASM_OUTPUT_SHARED_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) +If defined, it is similar to @code{ASM_OUTPUT_COMMON}, except that it +is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_COMMON} +will be used. + +@findex ASM_OUTPUT_BSS +@item ASM_OUTPUT_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{rounded}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} the assembler definition of uninitialized global @var{decl} named +@var{name} whose size is @var{size} bytes. The variable @var{rounded} +is the size rounded up to whatever alignment the caller wants. + +Try to use function @code{asm_output_bss} defined in @file{varasm.c} when +defining this macro. If unable, use the expression +@code{assemble_name (@var{stream}, @var{name})} to output the name itself; +before and after that, output the additional assembler syntax for defining +the name, and a newline. + +This macro controls how the assembler definitions of uninitialized global +variables are output. This macro exists to properly support languages like +@code{c++} which do not have @code{common} data. However, this macro currently +is not defined for all targets. If this macro and +@code{ASM_OUTPUT_ALIGNED_BSS} are not defined then @code{ASM_OUTPUT_COMMON} +or @code{ASM_OUTPUT_ALIGNED_COMMON} or +@code{ASM_OUTPUT_ALIGNED_DECL_COMMON} is used. + +@findex ASM_OUTPUT_ALIGNED_BSS +@item ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) +Like @code{ASM_OUTPUT_BSS} except takes the required alignment as a +separate, explicit argument. If you define this macro, it is used in +place of @code{ASM_OUTPUT_BSS}, and gives you more flexibility in +handling the required alignment of the variable. The alignment is specified +as the number of bits. + +Try to use function @code{asm_output_aligned_bss} defined in file +@file{varasm.c} when defining this macro. + +@findex ASM_OUTPUT_SHARED_BSS +@item ASM_OUTPUT_SHARED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{rounded}) +If defined, it is similar to @code{ASM_OUTPUT_BSS}, except that it +is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_BSS} +will be used. + +@findex ASM_OUTPUT_LOCAL +@item ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} the assembler definition of a local-common-label named +@var{name} whose size is @var{size} bytes. The variable @var{rounded} +is the size rounded up to whatever alignment the caller wants. + +Use the expression @code{assemble_name (@var{stream}, @var{name})} to +output the name itself; before and after that, output the additional +assembler syntax for defining the name, and a newline. + +This macro controls how the assembler definitions of uninitialized +static variables are output. + +@findex ASM_OUTPUT_ALIGNED_LOCAL +@item ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment}) +Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a +separate, explicit argument. If you define this macro, it is used in +place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in +handling the required alignment of the variable. The alignment is specified +as the number of bits. + +@findex ASM_OUTPUT_ALIGNED_DECL_LOCAL +@item ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) +Like @code{ASM_OUTPUT_ALIGNED_DECL} except that @var{decl} of the +variable to be output, if there is one, or @code{NULL_TREE} if there +is no corresponding variable. If you define this macro, GCC will use it +in place of both @code{ASM_OUTPUT_DECL} and +@code{ASM_OUTPUT_ALIGNED_DECL}. Define this macro when you need to see +the variable's decl in order to chose what to output. + +@findex ASM_OUTPUT_SHARED_LOCAL +@item ASM_OUTPUT_SHARED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) +If defined, it is similar to @code{ASM_OUTPUT_LOCAL}, except that it +is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_LOCAL} +will be used. +@end table + +@node Label Output +@subsection Output and Generation of Labels + +@c prevent bad page break with this line +This is about outputting labels. + +@table @code +@findex ASM_OUTPUT_LABEL +@findex assemble_name +@item ASM_OUTPUT_LABEL (@var{stream}, @var{name}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} the assembler definition of a label named @var{name}. +Use the expression @code{assemble_name (@var{stream}, @var{name})} to +output the name itself; before and after that, output the additional +assembler syntax for defining the name, and a newline. + +@findex ASM_DECLARE_FUNCTION_NAME +@item ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} any text necessary for declaring the name @var{name} of a +function which is being defined. This macro is responsible for +outputting the label definition (perhaps using +@code{ASM_OUTPUT_LABEL}). The argument @var{decl} is the +@code{FUNCTION_DECL} tree node representing the function. + +If this macro is not defined, then the function name is defined in the +usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). + +@findex ASM_DECLARE_FUNCTION_SIZE +@item ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} any text necessary for declaring the size of a function +which is being defined. The argument @var{name} is the name of the +function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node +representing the function. + +If this macro is not defined, then the function size is not defined. + +@findex ASM_DECLARE_OBJECT_NAME +@item ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} any text necessary for declaring the name @var{name} of an +initialized variable which is being defined. This macro must output the +label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument +@var{decl} is the @code{VAR_DECL} tree node representing the variable. + +If this macro is not defined, then the variable name is defined in the +usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). + +@findex ASM_DECLARE_REGISTER_GLOBAL +@item ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} any text necessary for claiming a register @var{regno} +for a global variable @var{decl} with name @var{name}. + +If you don't define this macro, that is equivalent to defining it to do +nothing. + +@findex ASM_FINISH_DECLARE_OBJECT +@item ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend}) +A C statement (sans semicolon) to finish up declaring a variable name +once the compiler has processed its initializer fully and thus has had a +chance to determine the size of an array when controlled by an +initializer. This is used on systems where it's necessary to declare +something about the size of the object. + +If you don't define this macro, that is equivalent to defining it to do +nothing. + +@findex ASM_GLOBALIZE_LABEL +@item ASM_GLOBALIZE_LABEL (@var{stream}, @var{name}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} some commands that will make the label @var{name} global; +that is, available for reference from other files. Use the expression +@code{assemble_name (@var{stream}, @var{name})} to output the name +itself; before and after that, output the additional assembler syntax +for making that name global, and a newline. + +@findex ASM_WEAKEN_LABEL +@item ASM_WEAKEN_LABEL +A C statement (sans semicolon) to output to the stdio stream +@var{stream} some commands that will make the label @var{name} weak; +that is, available for reference from other files but only used if +no other definition is available. Use the expression +@code{assemble_name (@var{stream}, @var{name})} to output the name +itself; before and after that, output the additional assembler syntax +for making that name weak, and a newline. + +If you don't define this macro, GCC will not support weak +symbols and you should not define the @code{SUPPORTS_WEAK} macro. + +@findex SUPPORTS_WEAK +@item SUPPORTS_WEAK +A C expression which evaluates to true if the target supports weak symbols. + +If you don't define this macro, @file{defaults.h} provides a default +definition. If @code{ASM_WEAKEN_LABEL} is defined, the default +definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if +you want to control weak symbol support with a compiler flag such as +@samp{-melf}. + +@findex MAKE_DECL_ONE_ONLY (@var{decl}) +@item MAKE_DECL_ONE_ONLY +A C statement (sans semicolon) to mark @var{decl} to be emitted as a +public symbol such that extra copies in multiple translation units will +be discarded by the linker. Define this macro if your object file +format provides support for this concept, such as the @samp{COMDAT} +section flags in the Microsoft Windows PE/COFF format, and this support +requires changes to @var{decl}, such as putting it in a separate section. + +@findex SUPPORTS_ONE_ONLY +@item SUPPORTS_ONE_ONLY +A C expression which evaluates to true if the target supports one-only +semantics. + +If you don't define this macro, @file{varasm.c} provides a default +definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default +definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if +you want to control one-only symbol support with a compiler flag, or if +setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to +be emitted as one-only. + +@findex ASM_OUTPUT_EXTERNAL +@item ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} any text necessary for declaring the name of an external +symbol named @var{name} which is referenced in this compilation but +not defined. The value of @var{decl} is the tree node for the +declaration. + +This macro need not be defined if it does not need to output anything. +The GNU assembler and most Unix assemblers don't require anything. + +@findex ASM_OUTPUT_EXTERNAL_LIBCALL +@item ASM_OUTPUT_EXTERNAL_LIBCALL (@var{stream}, @var{symref}) +A C statement (sans semicolon) to output on @var{stream} an assembler +pseudo-op to declare a library function name external. The name of the +library function is given by @var{symref}, which has type @code{rtx} and +is a @code{symbol_ref}. + +This macro need not be defined if it does not need to output anything. +The GNU assembler and most Unix assemblers don't require anything. + +@findex ASM_OUTPUT_LABELREF +@item ASM_OUTPUT_LABELREF (@var{stream}, @var{name}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} a reference in assembler syntax to a label named +@var{name}. This should add @samp{_} to the front of the name, if that +is customary on your operating system, as it is in most Berkeley Unix +systems. This macro is used in @code{assemble_name}. + +@ignore @c Seems not to exist anymore. +@findex ASM_OUTPUT_LABELREF_AS_INT +@item ASM_OUTPUT_LABELREF_AS_INT (@var{file}, @var{label}) +Define this macro for systems that use the program @code{collect2}. +The definition should be a C statement to output a word containing +a reference to the label @var{label}. +@end ignore + +@findex ASM_OUTPUT_SYMBOL_REF +@item ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym}) +A C statement (sans semicolon) to output a reference to +@code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_output} +will be used to output the name of the symbol. This macro may be used +to modify the way a symbol is referenced depending on information +encoded by @code{ENCODE_SECTION_INFO}. + +@findex ASM_OUTPUT_INTERNAL_LABEL +@item ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{prefix}, @var{num}) +A C statement to output to the stdio stream @var{stream} a label whose +name is made from the string @var{prefix} and the number @var{num}. + +It is absolutely essential that these labels be distinct from the labels +used for user-level functions and variables. Otherwise, certain programs +will have name conflicts with internal labels. + +It is desirable to exclude internal labels from the symbol table of the +object file. Most assemblers have a naming convention for labels that +should be excluded; on many systems, the letter @samp{L} at the +beginning of a label has this effect. You should find out what +convention your system uses, and follow it. + +The usual definition of this macro is as follows: + +@example +fprintf (@var{stream}, "L%s%d:\n", @var{prefix}, @var{num}) +@end example + +@findex ASM_OUTPUT_DEBUG_LABEL +@item ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num}) +A C statement to output to the stdio stream @var{stream} a debug info +label whose name is made from the string @var{prefix} and the number +@var{num}. This is useful for VLIW targets, where debug info labels +may need to be treated differently than branch target labels. On some +systems, branch target labels must be at the beginning of instruction +bundles, but debug info labels can occur in the middle of instruction +bundles. + +If this macro is not defined, then @code{ASM_OUTPUT_INTERNAL_LABEL} will be +used. + +@findex ASM_OUTPUT_ALTERNATE_LABEL_NAME +@item ASM_OUTPUT_ALTERNATE_LABEL_NAME (@var{stream}, @var{string}) +A C statement to output to the stdio stream @var{stream} the string +@var{string}. + +The default definition of this macro is as follows: + +@example +fprintf (@var{stream}, "%s:\n", LABEL_ALTERNATE_NAME (INSN)) +@end example + +@findex ASM_GENERATE_INTERNAL_LABEL +@item ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num}) +A C statement to store into the string @var{string} a label whose name +is made from the string @var{prefix} and the number @var{num}. + +This string, when output subsequently by @code{assemble_name}, should +produce the output that @code{ASM_OUTPUT_INTERNAL_LABEL} would produce +with the same @var{prefix} and @var{num}. + +If the string begins with @samp{*}, then @code{assemble_name} will +output the rest of the string unchanged. It is often convenient for +@code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the +string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets +to output the string, and may change it. (Of course, +@code{ASM_OUTPUT_LABELREF} is also part of your machine description, so +you should know what it does on your machine.) + +@findex ASM_FORMAT_PRIVATE_NAME +@item ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number}) +A C expression to assign to @var{outvar} (which is a variable of type +@code{char *}) a newly allocated string made from the string +@var{name} and the number @var{number}, with some suitable punctuation +added. Use @code{alloca} to get space for the string. + +The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to +produce an assembler label for an internal static variable whose name is +@var{name}. Therefore, the string must be such as to result in valid +assembler code. The argument @var{number} is different each time this +macro is executed; it prevents conflicts between similarly-named +internal static variables in different scopes. + +Ideally this string should not be a valid C identifier, to prevent any +conflict with the user's own symbols. Most assemblers allow periods +or percent signs in assembler symbols; putting at least one of these +between the name and the number will suffice. + +@findex ASM_OUTPUT_DEF +@item ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value}) +A C statement to output to the stdio stream @var{stream} assembler code +which defines (equates) the symbol @var{name} to have the value @var{value}. + +@findex SET_ASM_OP +If SET_ASM_OP is defined, a default definition is provided which is +correct for most systems. + +@findex ASM_OUTPUT_DEF_FROM_DECLS +@item ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value}) +A C statement to output to the stdio stream @var{stream} assembler code +which defines (equates) the symbol whose tree node is @var{decl_of_name} +to have the value of the tree node @var{decl_of_value}. This macro will +be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if +the tree nodes are available. + +@findex ASM_OUTPUT_DEFINE_LABEL_DIFFERENCE_SYMBOL +@item ASM_OUTPUT_DEFINE_LABEL_DIFFERENCE_SYMBOL (@var{stream}, @var{symbol}, @var{high}, @var{low}) +A C statement to output to the stdio stream @var{stream} assembler code +which defines (equates) the symbol @var{symbol} to have a value equal to +the difference of the two symbols @var{high} and @var{low}, i.e. +@var{high} minus @var{low}. GCC guarantees that the symbols @var{high} +and @var{low} are already known by the assembler so that the difference +resolves into a constant. + +@findex SET_ASM_OP +If SET_ASM_OP is defined, a default definition is provided which is +correct for most systems. + +@findex ASM_OUTPUT_WEAK_ALIAS +@item ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value}) +A C statement to output to the stdio stream @var{stream} assembler code +which defines (equates) the weak symbol @var{name} to have the value +@var{value}. + +Define this macro if the target only supports weak aliases; define +ASM_OUTPUT_DEF instead if possible. + +@findex OBJC_GEN_METHOD_LABEL +@item OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name}) +Define this macro to override the default assembler names used for +Objective C methods. + +The default name is a unique method number followed by the name of the +class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of +the category is also included in the assembler name (e.g.@: +@samp{_1_Foo_Bar}). + +These names are safe on most systems, but make debugging difficult since +the method's selector is not present in the name. Therefore, particular +systems define other ways of computing names. + +@var{buf} is an expression of type @code{char *} which gives you a +buffer in which to store the name; its length is as long as +@var{class_name}, @var{cat_name} and @var{sel_name} put together, plus +50 characters extra. + +The argument @var{is_inst} specifies whether the method is an instance +method or a class method; @var{class_name} is the name of the class; +@var{cat_name} is the name of the category (or NULL if the method is not +in a category); and @var{sel_name} is the name of the selector. + +On systems where the assembler can handle quoted names, you can use this +macro to provide more human-readable names. + +@findex ASM_DECLARE_UNRESOLVED_REFERENCE +@item ASM_DECLARE_UNRESOLVED_REFERENCE (@var{stream}, @var{name}) +A C statement (sans semicolon) to output to the stdio stream +@var{stream} commands to declare that the label @var{name} is an +unresolved Objective-C class reference. This is only needed for targets +whose linkers have special support for NeXT-style runtimes. +@end table + +@node Initialization +@subsection How Initialization Functions Are Handled +@cindex initialization routines +@cindex termination routines +@cindex constructors, output of +@cindex destructors, output of + +The compiled code for certain languages includes @dfn{constructors} +(also called @dfn{initialization routines})---functions to initialize +data in the program when the program is started. These functions need +to be called before the program is ``started''---that is to say, before +@code{main} is called. + +Compiling some languages generates @dfn{destructors} (also called +@dfn{termination routines}) that should be called when the program +terminates. + +To make the initialization and termination functions work, the compiler +must output something in the assembler code to cause those functions to +be called at the appropriate time. When you port the compiler to a new +system, you need to specify how to do this. + +There are two major ways that GCC currently supports the execution of +initialization and termination functions. Each way has two variants. +Much of the structure is common to all four variations. + +@findex __CTOR_LIST__ +@findex __DTOR_LIST__ +The linker must build two lists of these functions---a list of +initialization functions, called @code{__CTOR_LIST__}, and a list of +termination functions, called @code{__DTOR_LIST__}. + +Each list always begins with an ignored function pointer (which may hold +0, @minus{}1, or a count of the function pointers after it, depending on +the environment). This is followed by a series of zero or more function +pointers to constructors (or destructors), followed by a function +pointer containing zero. + +Depending on the operating system and its executable file format, either +@file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup +time and exit time. Constructors are called in reverse order of the +list; destructors in forward order. + +The best way to handle static constructors works only for object file +formats which provide arbitrarily-named sections. A section is set +aside for a list of constructors, and another for a list of destructors. +Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each +object file that defines an initialization function also puts a word in +the constructor section to point to that function. The linker +accumulates all these words into one contiguous @samp{.ctors} section. +Termination functions are handled similarly. + +To use this method, you need appropriate definitions of the macros +@code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR}. Usually +you can get them by including @file{svr4.h}. + +When arbitrary sections are available, there are two variants, depending +upon how the code in @file{crtstuff.c} is called. On systems that +support an @dfn{init} section which is executed at program startup, +parts of @file{crtstuff.c} are compiled into that section. The +program is linked by the @code{gcc} driver like this: + +@example +ld -o @var{output_file} crtbegin.o @dots{} crtend.o -lgcc +@end example + +The head of a function (@code{__do_global_ctors}) appears in the init +section of @file{crtbegin.o}; the remainder of the function appears in +the init section of @file{crtend.o}. The linker will pull these two +parts of the section together, making a whole function. If any of the +user's object files linked into the middle of it contribute code, then that +code will be executed as part of the body of @code{__do_global_ctors}. + +To use this variant, you must define the @code{INIT_SECTION_ASM_OP} +macro properly. + +If no init section is available, do not define +@code{INIT_SECTION_ASM_OP}. Then @code{__do_global_ctors} is built into +the text section like all other functions, and resides in +@file{libgcc.a}. When GCC compiles any function called @code{main}, it +inserts a procedure call to @code{__main} as the first executable code +after the function prologue. The @code{__main} function, also defined +in @file{libgcc2.c}, simply calls @file{__do_global_ctors}. + +In file formats that don't support arbitrary sections, there are again +two variants. In the simplest variant, the GNU linker (GNU @code{ld}) +and an `a.out' format must be used. In this case, +@code{ASM_OUTPUT_CONSTRUCTOR} is defined to produce a @code{.stabs} +entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__}, +and with the address of the void function containing the initialization +code as its value. The GNU linker recognizes this as a request to add +the value to a ``set''; the values are accumulated, and are eventually +placed in the executable as a vector in the format described above, with +a leading (ignored) count and a trailing zero element. +@code{ASM_OUTPUT_DESTRUCTOR} is handled similarly. Since no init +section is available, the absence of @code{INIT_SECTION_ASM_OP} causes +the compilation of @code{main} to call @code{__main} as above, starting +the initialization process. + +The last variant uses neither arbitrary sections nor the GNU linker. +This is preferable when you want to do dynamic linking and when using +file formats which the GNU linker does not support, such as `ECOFF'. In +this case, @code{ASM_OUTPUT_CONSTRUCTOR} does not produce an +@code{N_SETT} symbol; initialization and termination functions are +recognized simply by their names. This requires an extra program in the +linkage step, called @code{collect2}. This program pretends to be the +linker, for use with GCC; it does its job by running the ordinary +linker, but also arranges to include the vectors of initialization and +termination functions. These functions are called via @code{__main} as +described above. + +Choosing among these configuration options has been simplified by a set +of operating-system-dependent files in the @file{config} subdirectory. +These files define all of the relevant parameters. Usually it is +sufficient to include one into your specific machine-dependent +configuration file. These files are: + +@table @file +@item aoutos.h +For operating systems using the `a.out' format. + +@item next.h +For operating systems using the `MachO' format. + +@item svr3.h +For System V Release 3 and similar systems using `COFF' format. + +@item svr4.h +For System V Release 4 and similar systems using `ELF' format. + +@item vms.h +For the VMS operating system. +@end table + +@ifinfo +The following section describes the specific macros that control and +customize the handling of initialization and termination functions. +@end ifinfo + +@node Macros for Initialization +@subsection Macros Controlling Initialization Routines + +Here are the macros that control how the compiler handles initialization +and termination functions: + +@table @code +@findex INIT_SECTION_ASM_OP +@item INIT_SECTION_ASM_OP +If defined, a C string constant, including spacing, for the assembler +operation to identify the following data as initialization code. If not +defined, GCC will assume such a section does not exist. When you are +using special sections for initialization and termination functions, this +macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to +run the initialization functions. + +@item HAS_INIT_SECTION +@findex HAS_INIT_SECTION +If defined, @code{main} will not call @code{__main} as described above. +This macro should be defined for systems that control the contents of the +init section on a symbol-by-symbol basis, such as OSF/1, and should not +be defined explicitly for systems that support +@code{INIT_SECTION_ASM_OP}. + +@item LD_INIT_SWITCH +@findex LD_INIT_SWITCH +If defined, a C string constant for a switch that tells the linker that +the following symbol is an initialization routine. + +@item LD_FINI_SWITCH +@findex LD_FINI_SWITCH +If defined, a C string constant for a switch that tells the linker that +the following symbol is a finalization routine. + +@item INVOKE__main +@findex INVOKE__main +If defined, @code{main} will call @code{__main} despite the presence of +@code{INIT_SECTION_ASM_OP}. This macro should be defined for systems +where the init section is not actually run automatically, but is still +useful for collecting the lists of constructors and destructors. + +@item SUPPORTS_INIT_PRIORITY +@findex SUPPORTS_INIT_PRIORITY +If nonzero, the C++ @code{init_priority} attribute is supported and the +compiler should emit instructions to control the order of initialization +of objects. If zero, the compiler will issue an error message upon +encountering an @code{init_priority} attribute. + +@item ASM_OUTPUT_CONSTRUCTOR (@var{stream}, @var{name}) +@findex ASM_OUTPUT_CONSTRUCTOR +Define this macro as a C statement to output on the stream @var{stream} +the assembler code to arrange to call the function named @var{name} at +initialization time. + +Assume that @var{name} is the name of a C function generated +automatically by the compiler. This function takes no arguments. Use +the function @code{assemble_name} to output the name @var{name}; this +performs any system-specific syntactic transformations such as adding an +underscore. + +If you don't define this macro, nothing special is output to arrange to +call the function. This is correct when the function will be called in +some other manner---for example, by means of the @code{collect2} program, +which looks through the symbol table to find these functions by their +names. + +@item ASM_OUTPUT_DESTRUCTOR (@var{stream}, @var{name}) +@findex ASM_OUTPUT_DESTRUCTOR +This is like @code{ASM_OUTPUT_CONSTRUCTOR} but used for termination +functions rather than initialization functions. + +When @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR} are +defined, the initialization routine generated for the generated object +file will have static linkage. +@end table + +If your system uses @code{collect2} as the means of processing +constructors, then that program normally uses @code{nm} to scan an +object file for constructor functions to be called. On such systems you +must not define @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR} +as the object file's initialization routine must have global scope. + +On certain kinds of systems, you can define these macros to make +@code{collect2} work faster (and, in some cases, make it work at all): + +@table @code +@findex OBJECT_FORMAT_COFF +@item OBJECT_FORMAT_COFF +Define this macro if the system uses COFF (Common Object File Format) +object files, so that @code{collect2} can assume this format and scan +object files directly for dynamic constructor/destructor functions. + +@findex OBJECT_FORMAT_ROSE +@item OBJECT_FORMAT_ROSE +Define this macro if the system uses ROSE format object files, so that +@code{collect2} can assume this format and scan object files directly +for dynamic constructor/destructor functions. + +These macros are effective only in a native compiler; @code{collect2} as +part of a cross compiler always uses @code{nm} for the target machine. + +@findex REAL_NM_FILE_NAME +@item REAL_NM_FILE_NAME +Define this macro as a C string constant containing the file name to use +to execute @code{nm}. The default is to search the path normally for +@code{nm}. + +If your system supports shared libraries and has a program to list the +dynamic dependencies of a given library or executable, you can define +these macros to enable support for running initialization and +termination functions in shared libraries: + +@findex LDD_SUFFIX +@item LDD_SUFFIX +Define this macro to a C string constant containing the name of the +program which lists dynamic dependencies, like @code{"ldd"} under SunOS 4. + +@findex PARSE_LDD_OUTPUT +@item PARSE_LDD_OUTPUT (@var{PTR}) +Define this macro to be C code that extracts filenames from the output +of the program denoted by @code{LDD_SUFFIX}. @var{PTR} is a variable +of type @code{char *} that points to the beginning of a line of output +from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the +code must advance @var{PTR} to the beginning of the filename on that +line. Otherwise, it must set @var{PTR} to @code{NULL}. + +@end table + +@node Instruction Output +@subsection Output of Assembler Instructions + +@c prevent bad page break with this line +This describes assembler instruction output. + +@table @code +@findex REGISTER_NAMES +@item REGISTER_NAMES +A C initializer containing the assembler's names for the machine +registers, each one as a C string constant. This is what translates +register numbers in the compiler into assembler language. + +@findex ADDITIONAL_REGISTER_NAMES +@item ADDITIONAL_REGISTER_NAMES +If defined, a C initializer for an array of structures containing a name +and a register number. This macro defines additional names for hard +registers, thus allowing the @code{asm} option in declarations to refer +to registers using alternate names. + +@findex ASM_OUTPUT_OPCODE +@item ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr}) +Define this macro if you are using an unusual assembler that +requires different names for the machine instructions. + +The definition is a C statement or statements which output an +assembler instruction opcode to the stdio stream @var{stream}. The +macro-operand @var{ptr} is a variable of type @code{char *} which +points to the opcode name in its ``internal'' form---the form that is +written in the machine description. The definition should output the +opcode name to @var{stream}, performing any translation you desire, and +increment the variable @var{ptr} to point at the end of the opcode +so that it will not be output twice. + +In fact, your macro definition may process less than the entire opcode +name, or more than the opcode name; but if you want to process text +that includes @samp{%}-sequences to substitute operands, you must take +care of the substitution yourself. Just be sure to increment +@var{ptr} over whatever text should not be output normally. + +@findex recog_operand +If you need to look at the operand values, they can be found as the +elements of @code{recog_operand}. + +If the macro definition does nothing, the instruction is output +in the usual way. + +@findex FINAL_PRESCAN_INSN +@item FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands}) +If defined, a C statement to be executed just prior to the output of +assembler code for @var{insn}, to modify the extracted operands so +they will be output differently. + +Here the argument @var{opvec} is the vector containing the operands +extracted from @var{insn}, and @var{noperands} is the number of +elements of the vector which contain meaningful data for this insn. +The contents of this vector are what will be used to convert the insn +template into assembler code, so you can change the assembler output +by changing the contents of the vector. + +This macro is useful when various assembler syntaxes share a single +file of instruction patterns; by defining this macro differently, you +can cause a large class of instructions to be output differently (such +as with rearranged operands). Naturally, variations in assembler +syntax affecting individual insn patterns ought to be handled by +writing conditional output routines in those patterns. + +If this macro is not defined, it is equivalent to a null statement. + +@findex FINAL_PRESCAN_LABEL +@item FINAL_PRESCAN_LABEL +If defined, @code{FINAL_PRESCAN_INSN} will be called on each +@code{CODE_LABEL}. In that case, @var{opvec} will be a null pointer and +@var{noperands} will be zero. + +@findex PRINT_OPERAND +@item PRINT_OPERAND (@var{stream}, @var{x}, @var{code}) +A C compound statement to output to stdio stream @var{stream} the +assembler syntax for an instruction operand @var{x}. @var{x} is an +RTL expression. + +@var{code} is a value that can be used to specify one of several ways +of printing the operand. It is used when identical operands must be +printed differently depending on the context. @var{code} comes from +the @samp{%} specification that was used to request printing of the +operand. If the specification was just @samp{%@var{digit}} then +@var{code} is 0; if the specification was @samp{%@var{ltr} +@var{digit}} then @var{code} is the ASCII code for @var{ltr}. + +@findex reg_names +If @var{x} is a register, this macro should print the register's name. +The names can be found in an array @code{reg_names} whose type is +@code{char *[]}. @code{reg_names} is initialized from +@code{REGISTER_NAMES}. + +When the machine description has a specification @samp{%@var{punct}} +(a @samp{%} followed by a punctuation character), this macro is called +with a null pointer for @var{x} and the punctuation character for +@var{code}. + +@findex PRINT_OPERAND_PUNCT_VALID_P +@item PRINT_OPERAND_PUNCT_VALID_P (@var{code}) +A C expression which evaluates to true if @var{code} is a valid +punctuation character for use in the @code{PRINT_OPERAND} macro. If +@code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no +punctuation characters (except for the standard one, @samp{%}) are used +in this way. + +@findex PRINT_OPERAND_ADDRESS +@item PRINT_OPERAND_ADDRESS (@var{stream}, @var{x}) +A C compound statement to output to stdio stream @var{stream} the +assembler syntax for an instruction operand that is a memory reference +whose address is @var{x}. @var{x} is an RTL expression. + +@cindex @code{ENCODE_SECTION_INFO} usage +On some machines, the syntax for a symbolic address depends on the +section that the address refers to. On these machines, define the macro +@code{ENCODE_SECTION_INFO} to store the information into the +@code{symbol_ref}, and then check for it here. @xref{Assembler Format}. + +@findex DBR_OUTPUT_SEQEND +@findex dbr_sequence_length +@item DBR_OUTPUT_SEQEND(@var{file}) +A C statement, to be executed after all slot-filler instructions have +been output. If necessary, call @code{dbr_sequence_length} to +determine the number of slots filled in a sequence (zero if not +currently outputting a sequence), to decide how many no-ops to output, +or whatever. + +Don't define this macro if it has nothing to do, but it is helpful in +reading assembly output if the extent of the delay sequence is made +explicit (e.g. with white space). + +@findex final_sequence +Note that output routines for instructions with delay slots must be +prepared to deal with not being output as part of a sequence (i.e. +when the scheduling pass is not run, or when no slot fillers could be +found.) The variable @code{final_sequence} is null when not +processing a sequence, otherwise it contains the @code{sequence} rtx +being output. + +@findex REGISTER_PREFIX +@findex LOCAL_LABEL_PREFIX +@findex USER_LABEL_PREFIX +@findex IMMEDIATE_PREFIX +@findex asm_fprintf +@item REGISTER_PREFIX +@itemx LOCAL_LABEL_PREFIX +@itemx USER_LABEL_PREFIX +@itemx IMMEDIATE_PREFIX +If defined, C string expressions to be used for the @samp{%R}, @samp{%L}, +@samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see +@file{final.c}). These are useful when a single @file{md} file must +support multiple assembler formats. In that case, the various @file{tm.h} +files can define these macros differently. + +@item ASM_FPRINTF_EXTENSIONS(@var{file}, @var{argptr}, @var{format}) +@findex ASM_FPRINTF_EXTENSIONS +If defined this macro should expand to a series of @code{case} +statements which will be parsed inside the @code{switch} statement of +the @code{asm_fprintf} function. This allows targets to define extra +printf formats which may useful when generating their assembler +statements. Note that upper case letters are reserved for future +generic extensions to asm_fprintf, and so are not available to target +specific code. The output file is given by the parameter @var{file}. +The varargs input pointer is @var{argptr} and the rest of the format +string, starting the character after the one that is being switched +upon, is pointed to by @var{format}. + +@findex ASSEMBLER_DIALECT +@item ASSEMBLER_DIALECT +If your target supports multiple dialects of assembler language (such as +different opcodes), define this macro as a C expression that gives the +numeric index of the assembler language dialect to use, with zero as the +first variant. + +If this macro is defined, you may use constructs of the form +@samp{@{option0|option1|option2@dots{}@}} in the output +templates of patterns (@pxref{Output Template}) or in the first argument +of @code{asm_fprintf}. This construct outputs @samp{option0}, +@samp{option1} or @samp{option2}, etc., if the value of +@code{ASSEMBLER_DIALECT} is zero, one or two, etc. Any special +characters within these strings retain their usual meaning. + +If you do not define this macro, the characters @samp{@{}, @samp{|} and +@samp{@}} do not have any special meaning when used in templates or +operands to @code{asm_fprintf}. + +Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX}, +@code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express +the variations in assembler language syntax with that mechanism. Define +@code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax +if the syntax variant are larger and involve such things as different +opcodes or operand order. + +@findex ASM_OUTPUT_REG_PUSH +@item ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno}) +A C expression to output to @var{stream} some assembler code +which will push hard register number @var{regno} onto the stack. +The code need not be optimal, since this macro is used only when +profiling. + +@findex ASM_OUTPUT_REG_POP +@item ASM_OUTPUT_REG_POP (@var{stream}, @var{regno}) +A C expression to output to @var{stream} some assembler code +which will pop hard register number @var{regno} off of the stack. +The code need not be optimal, since this macro is used only when +profiling. +@end table + +@node Dispatch Tables +@subsection Output of Dispatch Tables + +@c prevent bad page break with this line +This concerns dispatch tables. + +@table @code +@cindex dispatch table +@findex ASM_OUTPUT_ADDR_DIFF_ELT +@item ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel}) +A C statement to output to the stdio stream @var{stream} an assembler +pseudo-instruction to generate a difference between two labels. +@var{value} and @var{rel} are the numbers of two internal labels. The +definitions of these labels are output using +@code{ASM_OUTPUT_INTERNAL_LABEL}, and they must be printed in the same +way here. For example, + +@example +fprintf (@var{stream}, "\t.word L%d-L%d\n", + @var{value}, @var{rel}) +@end example + +You must provide this macro on machines where the addresses in a +dispatch table are relative to the table's own address. If defined, GNU +CC will also use this macro on all machines when producing PIC. +@var{body} is the body of the ADDR_DIFF_VEC; it is provided so that the +mode and flags can be read. + +@findex ASM_OUTPUT_ADDR_VEC_ELT +@item ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value}) +This macro should be provided on machines where the addresses +in a dispatch table are absolute. + +The definition should be a C statement to output to the stdio stream +@var{stream} an assembler pseudo-instruction to generate a reference to +a label. @var{value} is the number of an internal label whose +definition is output using @code{ASM_OUTPUT_INTERNAL_LABEL}. +For example, + +@example +fprintf (@var{stream}, "\t.word L%d\n", @var{value}) +@end example + +@findex ASM_OUTPUT_CASE_LABEL +@item ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table}) +Define this if the label before a jump-table needs to be output +specially. The first three arguments are the same as for +@code{ASM_OUTPUT_INTERNAL_LABEL}; the fourth argument is the +jump-table which follows (a @code{jump_insn} containing an +@code{addr_vec} or @code{addr_diff_vec}). + +This feature is used on system V to output a @code{swbeg} statement +for the table. + +If this macro is not defined, these labels are output with +@code{ASM_OUTPUT_INTERNAL_LABEL}. + +@findex ASM_OUTPUT_CASE_END +@item ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table}) +Define this if something special must be output at the end of a +jump-table. The definition should be a C statement to be executed +after the assembler code for the table is written. It should write +the appropriate code to stdio stream @var{stream}. The argument +@var{table} is the jump-table insn, and @var{num} is the label-number +of the preceding label. + +If this macro is not defined, nothing special is output at the end of +the jump-table. +@end table + +@node Exception Region Output +@subsection Assembler Commands for Exception Regions + +@c prevent bad page break with this line + +This describes commands marking the start and the end of an exception +region. + +@table @code +@findex ASM_OUTPUT_EH_REGION_BEG +@item ASM_OUTPUT_EH_REGION_BEG () +A C expression to output text to mark the start of an exception region. + +This macro need not be defined on most platforms. + +@findex ASM_OUTPUT_EH_REGION_END +@item ASM_OUTPUT_EH_REGION_END () +A C expression to output text to mark the end of an exception region. + +This macro need not be defined on most platforms. + +@findex EXCEPTION_SECTION +@item EXCEPTION_SECTION () +A C expression to switch to the section in which the main +exception table is to be placed (@pxref{Sections}). The default is a +section named @code{.gcc_except_table} on machines that support named +sections via @code{ASM_OUTPUT_SECTION_NAME}, otherwise if @samp{-fpic} +or @samp{-fPIC} is in effect, the @code{data_section}, otherwise the +@code{readonly_data_section}. + +@findex EH_FRAME_SECTION_ASM_OP +@item EH_FRAME_SECTION_ASM_OP +If defined, a C string constant, including spacing, for the assembler +operation to switch to the section for exception handling frame unwind +information. If not defined, GCC will provide a default definition if the +target supports named sections. @file{crtstuff.c} uses this macro to +switch to the appropriate section. + +You should define this symbol if your target supports DWARF 2 frame +unwind information and the default definition does not work. + +@findex OMIT_EH_TABLE +@item OMIT_EH_TABLE () +A C expression that is nonzero if the normal exception table output +should be omitted. + +This macro need not be defined on most platforms. + +@findex EH_TABLE_LOOKUP +@item EH_TABLE_LOOKUP () +Alternate runtime support for looking up an exception at runtime and +finding the associated handler, if the default method won't work. + +This macro need not be defined on most platforms. + +@findex DOESNT_NEED_UNWINDER +@item DOESNT_NEED_UNWINDER +A C expression that decides whether or not the current function needs to +have a function unwinder generated for it. See the file @code{except.c} +for details on when to define this, and how. + +@findex MASK_RETURN_ADDR +@item MASK_RETURN_ADDR +An rtx used to mask the return address found via RETURN_ADDR_RTX, so +that it does not contain any extraneous set bits in it. + +@findex DWARF2_UNWIND_INFO +@item DWARF2_UNWIND_INFO +Define this macro to 0 if your target supports DWARF 2 frame unwind +information, but it does not yet work with exception handling. +Otherwise, if your target supports this information (if it defines +@samp{INCOMING_RETURN_ADDR_RTX} and either @samp{UNALIGNED_INT_ASM_OP} +or @samp{OBJECT_FORMAT_ELF}), GCC will provide a default definition of +1. + +If this macro is defined to 1, the DWARF 2 unwinder will be the default +exception handling mechanism; otherwise, setjmp/longjmp will be used by +default. + +If this macro is defined to anything, the DWARF 2 unwinder will be used +instead of inline unwinders and __unwind_function in the non-setjmp case. + +@findex DWARF_CIE_DATA_ALIGNMENT +@item DWARF_CIE_DATA_ALIGNMENT +This macro need only be defined if the target might save registers in the +function prologue at an offset to the stack pointer that is not aligned to +@code{UNITS_PER_WORD}. The definition should be the negative minimum +alignment if @code{STACK_GROWS_DOWNWARD} is defined, and the positive +minimum alignment otherwise. @xref{SDB and DWARF}. Only applicable if +the target supports DWARF 2 frame unwind information. + +@end table + +@node Alignment Output +@subsection Assembler Commands for Alignment + +@c prevent bad page break with this line +This describes commands for alignment. + +@table @code +@findex LABEL_ALIGN_AFTER_BARRIER +@item LABEL_ALIGN_AFTER_BARRIER (@var{label}) +The alignment (log base 2) to put in front of @var{label}, which follows +a BARRIER. + +This macro need not be defined if you don't want any special alignment +to be done at such a time. Most machine descriptions do not currently +define the macro. + +Unless it's necessary to inspect the @var{label} parameter, it is better +to set the variable @var{align_jumps} in the target's +@code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's +selection in @var{align_jumps} in a @code{LABEL_ALIGN_AFTER_BARRIER} +implementation. + +@findex LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP +@item LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP +The maximum number of bytes to skip when applying +@code{LABEL_ALIGN_AFTER_BARRIER}. This works only if +@code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. + +@findex LOOP_ALIGN +@item LOOP_ALIGN (@var{label}) +The alignment (log base 2) to put in front of @var{label}, which follows +a NOTE_INSN_LOOP_BEG note. + +This macro need not be defined if you don't want any special alignment +to be done at such a time. Most machine descriptions do not currently +define the macro. + +Unless it's necessary to inspect the @var{label} parameter, it is better +to set the variable @var{align_loops} in the target's +@code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's +selection in @var{align_loops} in a @code{LOOP_ALIGN} implementation. + +@findex LOOP_ALIGN_MAX_SKIP +@item LOOP_ALIGN_MAX_SKIP +The maximum number of bytes to skip when applying @code{LOOP_ALIGN}. +This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. + +@findex LABEL_ALIGN +@item LABEL_ALIGN (@var{label}) +The alignment (log base 2) to put in front of @var{label}. +If LABEL_ALIGN_AFTER_BARRIER / LOOP_ALIGN specify a different alignment, +the maximum of the specified values is used. + +Unless it's necessary to inspect the @var{label} parameter, it is better +to set the variable @var{align_labels} in the target's +@code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's +selection in @var{align_labels} in a @code{LABEL_ALIGN} implementation. + +@findex LABEL_ALIGN_MAX_SKIP +@item LABEL_ALIGN_MAX_SKIP +The maximum number of bytes to skip when applying @code{LABEL_ALIGN}. +This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. + +@findex ASM_OUTPUT_SKIP +@item ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes}) +A C statement to output to the stdio stream @var{stream} an assembler +instruction to advance the location counter by @var{nbytes} bytes. +Those bytes should be zero when loaded. @var{nbytes} will be a C +expression of type @code{int}. + +@findex ASM_NO_SKIP_IN_TEXT +@item ASM_NO_SKIP_IN_TEXT +Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the +text section because it fails to put zeros in the bytes that are skipped. +This is true on many Unix systems, where the pseudo--op to skip bytes +produces no-op instructions rather than zeros when used in the text +section. + +@findex ASM_OUTPUT_ALIGN +@item ASM_OUTPUT_ALIGN (@var{stream}, @var{power}) +A C statement to output to the stdio stream @var{stream} an assembler +command to advance the location counter to a multiple of 2 to the +@var{power} bytes. @var{power} will be a C expression of type @code{int}. + +@findex ASM_OUTPUT_MAX_SKIP_ALIGN +@item ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip}) +A C statement to output to the stdio stream @var{stream} an assembler +command to advance the location counter to a multiple of 2 to the +@var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to +satisfy the alignment request. @var{power} and @var{max_skip} will be +a C expression of type @code{int}. +@end table + +@need 3000 +@node Debugging Info +@section Controlling Debugging Information Format + +@c prevent bad page break with this line +This describes how to specify debugging information. + +@menu +* All Debuggers:: Macros that affect all debugging formats uniformly. +* DBX Options:: Macros enabling specific options in DBX format. +* DBX Hooks:: Hook macros for varying DBX format. +* File Names and DBX:: Macros controlling output of file names in DBX format. +* SDB and DWARF:: Macros for SDB (COFF) and DWARF formats. +@end menu + +@node All Debuggers +@subsection Macros Affecting All Debugging Formats + +@c prevent bad page break with this line +These macros affect all debugging formats. + +@table @code +@findex DBX_REGISTER_NUMBER +@item DBX_REGISTER_NUMBER (@var{regno}) +A C expression that returns the DBX register number for the compiler +register number @var{regno}. In simple cases, the value of this +expression may be @var{regno} itself. But sometimes there are some +registers that the compiler knows about and DBX does not, or vice +versa. In such cases, some register may need to have one number in +the compiler and another for DBX. + +If two registers have consecutive numbers inside GCC, and they can be +used as a pair to hold a multiword value, then they @emph{must} have +consecutive numbers after renumbering with @code{DBX_REGISTER_NUMBER}. +Otherwise, debuggers will be unable to access such a pair, because they +expect register pairs to be consecutive in their own numbering scheme. + +If you find yourself defining @code{DBX_REGISTER_NUMBER} in way that +does not preserve register pairs, then what you must do instead is +redefine the actual register numbering scheme. + +@findex DEBUGGER_AUTO_OFFSET +@item DEBUGGER_AUTO_OFFSET (@var{x}) +A C expression that returns the integer offset value for an automatic +variable having address @var{x} (an RTL expression). The default +computation assumes that @var{x} is based on the frame-pointer and +gives the offset from the frame-pointer. This is required for targets +that produce debugging output for DBX or COFF-style debugging output +for SDB and allow the frame-pointer to be eliminated when the +@samp{-g} options is used. + +@findex DEBUGGER_ARG_OFFSET +@item DEBUGGER_ARG_OFFSET (@var{offset}, @var{x}) +A C expression that returns the integer offset value for an argument +having address @var{x} (an RTL expression). The nominal offset is +@var{offset}. + +@findex PREFERRED_DEBUGGING_TYPE +@item PREFERRED_DEBUGGING_TYPE +A C expression that returns the type of debugging output GCC should +produce when the user specifies just @samp{-g}. Define +this if you have arranged for GCC to support more than one format of +debugging output. Currently, the allowable values are @code{DBX_DEBUG}, +@code{SDB_DEBUG}, @code{DWARF_DEBUG}, @code{DWARF2_DEBUG}, and +@code{XCOFF_DEBUG}. + +When the user specifies @samp{-ggdb}, GCC normally also uses the +value of this macro to select the debugging output format, but with two +exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined and +@code{LINKER_DOES_NOT_WORK_WITH_DWARF2} is not defined, GCC uses the +value @code{DWARF2_DEBUG}. Otherwise, if @code{DBX_DEBUGGING_INFO} is +defined, GCC uses @code{DBX_DEBUG}. + +The value of this macro only affects the default debugging output; the +user can always get a specific type of output by using @samp{-gstabs}, +@samp{-gcoff}, @samp{-gdwarf-1}, @samp{-gdwarf-2}, or @samp{-gxcoff}. +@end table + +@node DBX Options +@subsection Specific Options for DBX Output + +@c prevent bad page break with this line +These are specific options for DBX output. + +@table @code +@findex DBX_DEBUGGING_INFO +@item DBX_DEBUGGING_INFO +Define this macro if GCC should produce debugging output for DBX +in response to the @samp{-g} option. + +@findex XCOFF_DEBUGGING_INFO +@item XCOFF_DEBUGGING_INFO +Define this macro if GCC should produce XCOFF format debugging output +in response to the @samp{-g} option. This is a variant of DBX format. + +@findex DEFAULT_GDB_EXTENSIONS +@item DEFAULT_GDB_EXTENSIONS +Define this macro to control whether GCC should by default generate +GDB's extended version of DBX debugging information (assuming DBX-format +debugging information is enabled at all). If you don't define the +macro, the default is 1: always generate the extended information +if there is any occasion to. + +@findex DEBUG_SYMS_TEXT +@item DEBUG_SYMS_TEXT +Define this macro if all @code{.stabs} commands should be output while +in the text section. + +@findex ASM_STABS_OP +@item ASM_STABS_OP +A C string constant, including spacing, naming the assembler pseudo op to +use instead of @code{"\t.stabs\t"} to define an ordinary debugging symbol. +If you don't define this macro, @code{"\t.stabs\t"} is used. This macro +applies only to DBX debugging information format. + +@findex ASM_STABD_OP +@item ASM_STABD_OP +A C string constant, including spacing, naming the assembler pseudo op to +use instead of @code{"\t.stabd\t"} to define a debugging symbol whose +value is the current location. If you don't define this macro, +@code{"\t.stabd\t"} is used. This macro applies only to DBX debugging +information format. + +@findex ASM_STABN_OP +@item ASM_STABN_OP +A C string constant, including spacing, naming the assembler pseudo op to +use instead of @code{"\t.stabn\t"} to define a debugging symbol with no +name. If you don't define this macro, @code{"\t.stabn\t"} is used. This +macro applies only to DBX debugging information format. + +@findex DBX_NO_XREFS +@item DBX_NO_XREFS +Define this macro if DBX on your system does not support the construct +@samp{xs@var{tagname}}. On some systems, this construct is used to +describe a forward reference to a structure named @var{tagname}. +On other systems, this construct is not supported at all. + +@findex DBX_CONTIN_LENGTH +@item DBX_CONTIN_LENGTH +A symbol name in DBX-format debugging information is normally +continued (split into two separate @code{.stabs} directives) when it +exceeds a certain length (by default, 80 characters). On some +operating systems, DBX requires this splitting; on others, splitting +must not be done. You can inhibit splitting by defining this macro +with the value zero. You can override the default splitting-length by +defining this macro as an expression for the length you desire. + +@findex DBX_CONTIN_CHAR +@item DBX_CONTIN_CHAR +Normally continuation is indicated by adding a @samp{\} character to +the end of a @code{.stabs} string when a continuation follows. To use +a different character instead, define this macro as a character +constant for the character you want to use. Do not define this macro +if backslash is correct for your system. + +@findex DBX_STATIC_STAB_DATA_SECTION +@item DBX_STATIC_STAB_DATA_SECTION +Define this macro if it is necessary to go to the data section before +outputting the @samp{.stabs} pseudo-op for a non-global static +variable. + +@findex DBX_TYPE_DECL_STABS_CODE +@item DBX_TYPE_DECL_STABS_CODE +The value to use in the ``code'' field of the @code{.stabs} directive +for a typedef. The default is @code{N_LSYM}. + +@findex DBX_STATIC_CONST_VAR_CODE +@item DBX_STATIC_CONST_VAR_CODE +The value to use in the ``code'' field of the @code{.stabs} directive +for a static variable located in the text section. DBX format does not +provide any ``right'' way to do this. The default is @code{N_FUN}. + +@findex DBX_REGPARM_STABS_CODE +@item DBX_REGPARM_STABS_CODE +The value to use in the ``code'' field of the @code{.stabs} directive +for a parameter passed in registers. DBX format does not provide any +``right'' way to do this. The default is @code{N_RSYM}. + +@findex DBX_REGPARM_STABS_LETTER +@item DBX_REGPARM_STABS_LETTER +The letter to use in DBX symbol data to identify a symbol as a parameter +passed in registers. DBX format does not customarily provide any way to +do this. The default is @code{'P'}. + +@findex DBX_MEMPARM_STABS_LETTER +@item DBX_MEMPARM_STABS_LETTER +The letter to use in DBX symbol data to identify a symbol as a stack +parameter. The default is @code{'p'}. + +@findex DBX_FUNCTION_FIRST +@item DBX_FUNCTION_FIRST +Define this macro if the DBX information for a function and its +arguments should precede the assembler code for the function. Normally, +in DBX format, the debugging information entirely follows the assembler +code. + +@findex DBX_LBRAC_FIRST +@item DBX_LBRAC_FIRST +Define this macro if the @code{N_LBRAC} symbol for a block should +precede the debugging information for variables and functions defined in +that block. Normally, in DBX format, the @code{N_LBRAC} symbol comes +first. + +@findex DBX_BLOCKS_FUNCTION_RELATIVE +@item DBX_BLOCKS_FUNCTION_RELATIVE +Define this macro if the value of a symbol describing the scope of a +block (@code{N_LBRAC} or @code{N_RBRAC}) should be relative to the start +of the enclosing function. Normally, GNU C uses an absolute address. + +@findex DBX_USE_BINCL +@item DBX_USE_BINCL +Define this macro if GNU C should generate @code{N_BINCL} and +@code{N_EINCL} stabs for included header files, as on Sun systems. This +macro also directs GNU C to output a type number as a pair of a file +number and a type number within the file. Normally, GNU C does not +generate @code{N_BINCL} or @code{N_EINCL} stabs, and it outputs a single +number for a type number. +@end table + +@node DBX Hooks +@subsection Open-Ended Hooks for DBX Format + +@c prevent bad page break with this line +These are hooks for DBX format. + +@table @code +@findex DBX_OUTPUT_LBRAC +@item DBX_OUTPUT_LBRAC (@var{stream}, @var{name}) +Define this macro to say how to output to @var{stream} the debugging +information for the start of a scope level for variable names. The +argument @var{name} is the name of an assembler symbol (for use with +@code{assemble_name}) whose value is the address where the scope begins. + +@findex DBX_OUTPUT_RBRAC +@item DBX_OUTPUT_RBRAC (@var{stream}, @var{name}) +Like @code{DBX_OUTPUT_LBRAC}, but for the end of a scope level. + +@findex DBX_OUTPUT_ENUM +@item DBX_OUTPUT_ENUM (@var{stream}, @var{type}) +Define this macro if the target machine requires special handling to +output an enumeration type. The definition should be a C statement +(sans semicolon) to output the appropriate information to @var{stream} +for the type @var{type}. + +@findex DBX_OUTPUT_FUNCTION_END +@item DBX_OUTPUT_FUNCTION_END (@var{stream}, @var{function}) +Define this macro if the target machine requires special output at the +end of the debugging information for a function. The definition should +be a C statement (sans semicolon) to output the appropriate information +to @var{stream}. @var{function} is the @code{FUNCTION_DECL} node for +the function. + +@findex DBX_OUTPUT_STANDARD_TYPES +@item DBX_OUTPUT_STANDARD_TYPES (@var{syms}) +Define this macro if you need to control the order of output of the +standard data types at the beginning of compilation. The argument +@var{syms} is a @code{tree} which is a chain of all the predefined +global symbols, including names of data types. + +Normally, DBX output starts with definitions of the types for integers +and characters, followed by all the other predefined types of the +particular language in no particular order. + +On some machines, it is necessary to output different particular types +first. To do this, define @code{DBX_OUTPUT_STANDARD_TYPES} to output +those symbols in the necessary order. Any predefined types that you +don't explicitly output will be output afterward in no particular order. + +Be careful not to define this macro so that it works only for C. There +are no global variables to access most of the built-in types, because +another language may have another set of types. The way to output a +particular type is to look through @var{syms} to see if you can find it. +Here is an example: + +@smallexample +@{ + tree decl; + for (decl = syms; decl; decl = TREE_CHAIN (decl)) + if (!strcmp (IDENTIFIER_POINTER (DECL_NAME (decl)), + "long int")) + dbxout_symbol (decl); + @dots{} +@} +@end smallexample + +@noindent +This does nothing if the expected type does not exist. + +See the function @code{init_decl_processing} in @file{c-decl.c} to find +the names to use for all the built-in C types. + +Here is another way of finding a particular type: + +@c this is still overfull. --mew 10feb93 +@smallexample +@{ + tree decl; + for (decl = syms; decl; decl = TREE_CHAIN (decl)) + if (TREE_CODE (decl) == TYPE_DECL + && (TREE_CODE (TREE_TYPE (decl)) + == INTEGER_CST) + && TYPE_PRECISION (TREE_TYPE (decl)) == 16 + && TYPE_UNSIGNED (TREE_TYPE (decl))) +@group + /* @r{This must be @code{unsigned short}.} */ + dbxout_symbol (decl); + @dots{} +@} +@end group +@end smallexample + +@findex NO_DBX_FUNCTION_END +@item NO_DBX_FUNCTION_END +Some stabs encapsulation formats (in particular ECOFF), cannot handle the +@code{.stabs "",N_FUN,,0,0,Lscope-function-1} gdb dbx extention construct. +On those machines, define this macro to turn this feature off without +disturbing the rest of the gdb extensions. + +@end table + +@node File Names and DBX +@subsection File Names in DBX Format + +@c prevent bad page break with this line +This describes file names in DBX format. + +@table @code +@findex DBX_WORKING_DIRECTORY +@item DBX_WORKING_DIRECTORY +Define this if DBX wants to have the current directory recorded in each +object file. + +Note that the working directory is always recorded if GDB extensions are +enabled. + +@findex DBX_OUTPUT_MAIN_SOURCE_FILENAME +@item DBX_OUTPUT_MAIN_SOURCE_FILENAME (@var{stream}, @var{name}) +A C statement to output DBX debugging information to the stdio stream +@var{stream} which indicates that file @var{name} is the main source +file---the file specified as the input file for compilation. +This macro is called only once, at the beginning of compilation. + +This macro need not be defined if the standard form of output +for DBX debugging information is appropriate. + +@findex DBX_OUTPUT_MAIN_SOURCE_DIRECTORY +@item DBX_OUTPUT_MAIN_SOURCE_DIRECTORY (@var{stream}, @var{name}) +A C statement to output DBX debugging information to the stdio stream +@var{stream} which indicates that the current directory during +compilation is named @var{name}. + +This macro need not be defined if the standard form of output +for DBX debugging information is appropriate. + +@findex DBX_OUTPUT_MAIN_SOURCE_FILE_END +@item DBX_OUTPUT_MAIN_SOURCE_FILE_END (@var{stream}, @var{name}) +A C statement to output DBX debugging information at the end of +compilation of the main source file @var{name}. + +If you don't define this macro, nothing special is output at the end +of compilation, which is correct for most machines. + +@findex DBX_OUTPUT_SOURCE_FILENAME +@item DBX_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) +A C statement to output DBX debugging information to the stdio stream +@var{stream} which indicates that file @var{name} is the current source +file. This output is generated each time input shifts to a different +source file as a result of @samp{#include}, the end of an included file, +or a @samp{#line} command. + +This macro need not be defined if the standard form of output +for DBX debugging information is appropriate. +@end table + +@need 2000 +@node SDB and DWARF +@subsection Macros for SDB and DWARF Output + +@c prevent bad page break with this line +Here are macros for SDB and DWARF output. + +@table @code +@findex SDB_DEBUGGING_INFO +@item SDB_DEBUGGING_INFO +Define this macro if GCC should produce COFF-style debugging output +for SDB in response to the @samp{-g} option. + +@findex DWARF_DEBUGGING_INFO +@item DWARF_DEBUGGING_INFO +Define this macro if GCC should produce dwarf format debugging output +in response to the @samp{-g} option. + +@findex DWARF2_DEBUGGING_INFO +@item DWARF2_DEBUGGING_INFO +Define this macro if GCC should produce dwarf version 2 format +debugging output in response to the @samp{-g} option. + +To support optional call frame debugging information, you must also +define @code{INCOMING_RETURN_ADDR_RTX} and either set +@code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the +prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save} +as appropriate from @code{FUNCTION_PROLOGUE} if you don't. + +@findex DWARF2_FRAME_INFO +@item DWARF2_FRAME_INFO +Define this macro to a nonzero value if GCC should always output +Dwarf 2 frame information. If @code{DWARF2_UNWIND_INFO} +(@pxref{Exception Region Output} is nonzero, GCC will output this +information not matter how you define @code{DWARF2_FRAME_INFO}. + +@findex LINKER_DOES_NOT_WORK_WITH_DWARF2 +@item LINKER_DOES_NOT_WORK_WITH_DWARF2 +Define this macro if the linker does not work with Dwarf version 2. +Normally, if the user specifies only @samp{-ggdb} GCC will use Dwarf +version 2 if available; this macro disables this. See the description +of the @code{PREFERRED_DEBUGGING_TYPE} macro for more details. + +@findex DWARF2_GENERATE_TEXT_SECTION_LABEL +@item DWARF2_GENERATE_TEXT_SECTION_LABEL +By default, the Dwarf 2 debugging information generator will generate a +label to mark the beginning of the text section. If it is better simply +to use the name of the text section itself, rather than an explicit label, +to indicate the beginning of the text section, define this macro to zero. + +@findex DWARF2_ASM_LINE_DEBUG_INFO +@item DWARF2_ASM_LINE_DEBUG_INFO +Define this macro to be a nonzero value if the assembler can generate Dwarf 2 +line debug info sections. This will result in much more compact line number +tables, and hence is desirable if it works. + +@findex PUT_SDB_@dots{} +@item PUT_SDB_@dots{} +Define these macros to override the assembler syntax for the special +SDB assembler directives. See @file{sdbout.c} for a list of these +macros and their arguments. If the standard syntax is used, you need +not define them yourself. + +@findex SDB_DELIM +@item SDB_DELIM +Some assemblers do not support a semicolon as a delimiter, even between +SDB assembler directives. In that case, define this macro to be the +delimiter to use (usually @samp{\n}). It is not necessary to define +a new set of @code{PUT_SDB_@var{op}} macros if this is the only change +required. + +@findex SDB_GENERATE_FAKE +@item SDB_GENERATE_FAKE +Define this macro to override the usual method of constructing a dummy +name for anonymous structure and union types. See @file{sdbout.c} for +more information. + +@findex SDB_ALLOW_UNKNOWN_REFERENCES +@item SDB_ALLOW_UNKNOWN_REFERENCES +Define this macro to allow references to unknown structure, +union, or enumeration tags to be emitted. Standard COFF does not +allow handling of unknown references, MIPS ECOFF has support for +it. + +@findex SDB_ALLOW_FORWARD_REFERENCES +@item SDB_ALLOW_FORWARD_REFERENCES +Define this macro to allow references to structure, union, or +enumeration tags that have not yet been seen to be handled. Some +assemblers choke if forward tags are used, while some require it. +@end table + +@node Cross-compilation +@section Cross Compilation and Floating Point +@cindex cross compilation and floating point +@cindex floating point and cross compilation + +While all modern machines use 2's complement representation for integers, +there are a variety of representations for floating point numbers. This +means that in a cross-compiler the representation of floating point numbers +in the compiled program may be different from that used in the machine +doing the compilation. + +@findex atof +Because different representation systems may offer different amounts of +range and precision, the cross compiler cannot safely use the host +machine's floating point arithmetic. Therefore, floating point constants +must be represented in the target machine's format. This means that the +cross compiler cannot use @code{atof} to parse a floating point constant; +it must have its own special routine to use instead. Also, constant +folding must emulate the target machine's arithmetic (or must not be done +at all). + +The macros in the following table should be defined only if you are cross +compiling between different floating point formats. + +Otherwise, don't define them. Then default definitions will be set up which +use @code{double} as the data type, @code{==} to test for equality, etc. + +You don't need to worry about how many times you use an operand of any +of these macros. The compiler never uses operands which have side effects. + +@table @code +@findex REAL_VALUE_TYPE +@item REAL_VALUE_TYPE +A macro for the C data type to be used to hold a floating point value +in the target machine's format. Typically this would be a +@code{struct} containing an array of @code{int}. + +@findex REAL_VALUES_EQUAL +@item REAL_VALUES_EQUAL (@var{x}, @var{y}) +A macro for a C expression which compares for equality the two values, +@var{x} and @var{y}, both of type @code{REAL_VALUE_TYPE}. + +@findex REAL_VALUES_LESS +@item REAL_VALUES_LESS (@var{x}, @var{y}) +A macro for a C expression which tests whether @var{x} is less than +@var{y}, both values being of type @code{REAL_VALUE_TYPE} and +interpreted as floating point numbers in the target machine's +representation. + +@findex REAL_VALUE_LDEXP +@findex ldexp +@item REAL_VALUE_LDEXP (@var{x}, @var{scale}) +A macro for a C expression which performs the standard library +function @code{ldexp}, but using the target machine's floating point +representation. Both @var{x} and the value of the expression have +type @code{REAL_VALUE_TYPE}. The second argument, @var{scale}, is an +integer. + +@findex REAL_VALUE_FIX +@item REAL_VALUE_FIX (@var{x}) +A macro whose definition is a C expression to convert the target-machine +floating point value @var{x} to a signed integer. @var{x} has type +@code{REAL_VALUE_TYPE}. + +@findex REAL_VALUE_UNSIGNED_FIX +@item REAL_VALUE_UNSIGNED_FIX (@var{x}) +A macro whose definition is a C expression to convert the target-machine +floating point value @var{x} to an unsigned integer. @var{x} has type +@code{REAL_VALUE_TYPE}. + +@findex REAL_VALUE_RNDZINT +@item REAL_VALUE_RNDZINT (@var{x}) +A macro whose definition is a C expression to round the target-machine +floating point value @var{x} towards zero to an integer value (but still +as a floating point number). @var{x} has type @code{REAL_VALUE_TYPE}, +and so does the value. + +@findex REAL_VALUE_UNSIGNED_RNDZINT +@item REAL_VALUE_UNSIGNED_RNDZINT (@var{x}) +A macro whose definition is a C expression to round the target-machine +floating point value @var{x} towards zero to an unsigned integer value +(but still represented as a floating point number). @var{x} has type +@code{REAL_VALUE_TYPE}, and so does the value. + +@findex REAL_VALUE_ATOF +@item REAL_VALUE_ATOF (@var{string}, @var{mode}) +A macro for a C expression which converts @var{string}, an expression of +type @code{char *}, into a floating point number in the target machine's +representation for mode @var{mode}. The value has type +@code{REAL_VALUE_TYPE}. + +@findex REAL_INFINITY +@item REAL_INFINITY +Define this macro if infinity is a possible floating point value, and +therefore division by 0 is legitimate. + +@findex REAL_VALUE_ISINF +@findex isinf +@item REAL_VALUE_ISINF (@var{x}) +A macro for a C expression which determines whether @var{x}, a floating +point value, is infinity. The value has type @code{int}. +By default, this is defined to call @code{isinf}. + +@findex REAL_VALUE_ISNAN +@findex isnan +@item REAL_VALUE_ISNAN (@var{x}) +A macro for a C expression which determines whether @var{x}, a floating +point value, is a ``nan'' (not-a-number). The value has type +@code{int}. By default, this is defined to call @code{isnan}. +@end table + +@cindex constant folding and floating point +Define the following additional macros if you want to make floating +point constant folding work while cross compiling. If you don't +define them, cross compilation is still possible, but constant folding +will not happen for floating point values. + +@table @code +@findex REAL_ARITHMETIC +@item REAL_ARITHMETIC (@var{output}, @var{code}, @var{x}, @var{y}) +A macro for a C statement which calculates an arithmetic operation of +the two floating point values @var{x} and @var{y}, both of type +@code{REAL_VALUE_TYPE} in the target machine's representation, to +produce a result of the same type and representation which is stored +in @var{output} (which will be a variable). + +The operation to be performed is specified by @var{code}, a tree code +which will always be one of the following: @code{PLUS_EXPR}, +@code{MINUS_EXPR}, @code{MULT_EXPR}, @code{RDIV_EXPR}, +@code{MAX_EXPR}, @code{MIN_EXPR}.@refill + +@cindex overflow while constant folding +The expansion of this macro is responsible for checking for overflow. +If overflow happens, the macro expansion should execute the statement +@code{return 0;}, which indicates the inability to perform the +arithmetic operation requested. + +@findex REAL_VALUE_NEGATE +@item REAL_VALUE_NEGATE (@var{x}) +A macro for a C expression which returns the negative of the floating +point value @var{x}. Both @var{x} and the value of the expression +have type @code{REAL_VALUE_TYPE} and are in the target machine's +floating point representation. + +There is no way for this macro to report overflow, since overflow +can't happen in the negation operation. + +@findex REAL_VALUE_TRUNCATE +@item REAL_VALUE_TRUNCATE (@var{mode}, @var{x}) +A macro for a C expression which converts the floating point value +@var{x} to mode @var{mode}. + +Both @var{x} and the value of the expression are in the target machine's +floating point representation and have type @code{REAL_VALUE_TYPE}. +However, the value should have an appropriate bit pattern to be output +properly as a floating constant whose precision accords with mode +@var{mode}. + +There is no way for this macro to report overflow. + +@findex REAL_VALUE_TO_INT +@item REAL_VALUE_TO_INT (@var{low}, @var{high}, @var{x}) +A macro for a C expression which converts a floating point value +@var{x} into a double-precision integer which is then stored into +@var{low} and @var{high}, two variables of type @var{int}. + +@item REAL_VALUE_FROM_INT (@var{x}, @var{low}, @var{high}, @var{mode}) +@findex REAL_VALUE_FROM_INT +A macro for a C expression which converts a double-precision integer +found in @var{low} and @var{high}, two variables of type @var{int}, +into a floating point value which is then stored into @var{x}. +The value is in the target machine's representation for mode @var{mode} +and has the type @code{REAL_VALUE_TYPE}. +@end table + +@node Mode Switching +@section Mode Switching Instructions +@cindex mode switching +The following macros control mode switching optimizations: + +@table @code +@findex OPTIMIZE_MODE_SWITCHING +@item OPTIMIZE_MODE_SWITCHING (@var{entity}) +Define this macro if the port needs extra instructions inserted for mode +switching in an optimizing compilation. + +For an example, the SH4 can perform both single and double precision +floating point operations, but to perform a single precision operation, +the FPSCR PR bit has to be cleared, while for a double precision +operation, this bit has to be set. Changing the PR bit requires a general +purpose register as a scratch register, hence these FPSCR sets have to +be inserted before reload, i.e. you can't put this into instruction emitting +or MACHINE_DEPENDENT_REORG. + +You can have multiple entities that are mode-switched, and select at run time +which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should +return non-zero for any @var{entity} that that needs mode-switching. +If you define this macro, you also have to define +@code{NUM_MODES_FOR_MODE_SWITCHING}, @code{MODE_NEEDED}, +@code{MODE_PRIORITY_TO_MODE} and @code{EMIT_MODE_SET}. +@code{NORMAL_MODE} is optional. + +@findex NUM_MODES_FOR_MODE_SWITCHING +@item NUM_MODES_FOR_MODE_SWITCHING +If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as +initializer for an array of integers. Each initializer element +N refers to an entity that needs mode switching, and specifies the number +of different modes that might need to be set for this entity. +The position of the initializer in the initializer - starting counting at +zero - determines the integer that is used to refer to the mode-switched +entity in question. +In macros that take mode arguments / yield a mode result, modes are +represented as numbers 0 .. N - 1. N is used to specify that no mode +switch is needed / supplied. + +@findex MODE_NEEDED +@item MODE_NEEDED (@var{entity}, @var{insn}) +@var{entity} is an integer specifying a mode-switched entity. If +@code{OPTIMIZE_MODE_SWITCHING} is defined, you must define this macro to +return an integer value not larger than the corresponding element in +NUM_MODES_FOR_MODE_SWITCHING, to denote the mode that @var{entity} must +be switched into prior to the execution of INSN. + +@findex NORMAL_MODE +@item NORMAL_MODE (@var{entity}) +If this macro is defined, it is evaluated for every @var{entity} that needs +mode switching. It should evaluate to an integer, which is a mode that +@var{entity} is assumed to be switched to at function entry and exit. + +@findex MODE_PRIORITY_TO_MODE +@item MODE_PRIORITY_TO_MODE (@var{entity}, @var{n}) +This macro specifies the order in which modes for ENTITY are processed. +0 is the highest priority, NUM_MODES_FOR_MODE_SWITCHING[ENTITY] - 1 the +lowest. The value of the macro should be an integer designating a mode +for ENTITY. For any fixed @var{entity}, @code{mode_priority_to_mode} +(@var{entity}, @var{n}) shall be a bijection in 0 .. +@code{num_modes_for_mode_switching}[@var{entity}] - 1 . + +@findex EMIT_MODE_SET +@item EMIT_MODE_SET (@var{entity}, @var{mode}, @var{hard_regs_live}) +Generate one or more insns to set @var{entity} to @var{mode}. +@var{hard_reg_live} is the set of hard registers live at the point where +the insn(s) are to be inserted. +@end table + +@node Misc +@section Miscellaneous Parameters +@cindex parameters, miscellaneous + +@c prevent bad page break with this line +Here are several miscellaneous parameters. + +@table @code +@item PREDICATE_CODES +@findex PREDICATE_CODES +Define this if you have defined special-purpose predicates in the file +@file{@var{machine}.c}. This macro is called within an initializer of an +array of structures. The first field in the structure is the name of a +predicate and the second field is an array of rtl codes. For each +predicate, list all rtl codes that can be in expressions matched by the +predicate. The list should have a trailing comma. Here is an example +of two entries in the list for a typical RISC machine: + +@smallexample +#define PREDICATE_CODES \ + @{"gen_reg_rtx_operand", @{SUBREG, REG@}@}, \ + @{"reg_or_short_cint_operand", @{SUBREG, REG, CONST_INT@}@}, +@end smallexample + +Defining this macro does not affect the generated code (however, +incorrect definitions that omit an rtl code that may be matched by the +predicate can cause the compiler to malfunction). Instead, it allows +the table built by @file{genrecog} to be more compact and efficient, +thus speeding up the compiler. The most important predicates to include +in the list specified by this macro are those used in the most insn +patterns. + +For each predicate function named in @var{PREDICATE_CODES}, a +declaration will be generated in @file{insn-codes.h}. + +@item SPECIAL_MODE_PREDICATES +@findex SPECIAL_MODE_PREDICATES +Define this if you have special predicates that know special things +about modes. Genrecog will warn about certain forms of +@code{match_operand} without a mode; if the operand predicate is +listed in @code{SPECIAL_MODE_PREDICATES}, the warning will be +suppressed. + +Here is an example from the IA-32 port (@code{ext_register_operand} +specially checks for @code{HImode} or @code{SImode} in preparation +for a byte extraction from @code{%ah} etc.). + +@smallexample +#define SPECIAL_MODE_PREDICATES \ + "ext_register_operand", +@end smallexample + +@findex CASE_VECTOR_MODE +@item CASE_VECTOR_MODE +An alias for a machine mode name. This is the machine mode that +elements of a jump-table should have. + +@findex CASE_VECTOR_SHORTEN_MODE +@item CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body}) +Optional: return the preferred mode for an @code{addr_diff_vec} +when the minimum and maximum offset are known. If you define this, +it enables extra code in branch shortening to deal with @code{addr_diff_vec}. +To make this work, you also have to define INSN_ALIGN and +make the alignment for @code{addr_diff_vec} explicit. +The @var{body} argument is provided so that the offset_unsigned and scale +flags can be updated. + +@findex CASE_VECTOR_PC_RELATIVE +@item CASE_VECTOR_PC_RELATIVE +Define this macro to be a C expression to indicate when jump-tables +should contain relative addresses. If jump-tables never contain +relative addresses, then you need not define this macro. + +@findex CASE_DROPS_THROUGH +@item CASE_DROPS_THROUGH +Define this if control falls through a @code{case} insn when the index +value is out of range. This means the specified default-label is +actually ignored by the @code{case} insn proper. + +@findex CASE_VALUES_THRESHOLD +@item CASE_VALUES_THRESHOLD +Define this to be the smallest number of different values for which it +is best to use a jump-table instead of a tree of conditional branches. +The default is four for machines with a @code{casesi} instruction and +five otherwise. This is best for most machines. + +@findex WORD_REGISTER_OPERATIONS +@item WORD_REGISTER_OPERATIONS +Define this macro if operations between registers with integral mode +smaller than a word are always performed on the entire register. +Most RISC machines have this property and most CISC machines do not. + +@findex LOAD_EXTEND_OP +@item LOAD_EXTEND_OP (@var{mode}) +Define this macro to be a C expression indicating when insns that read +memory in @var{mode}, an integral mode narrower than a word, set the +bits outside of @var{mode} to be either the sign-extension or the +zero-extension of the data read. Return @code{SIGN_EXTEND} for values +of @var{mode} for which the +insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and +@code{NIL} for other modes. + +This macro is not called with @var{mode} non-integral or with a width +greater than or equal to @code{BITS_PER_WORD}, so you may return any +value in this case. Do not define this macro if it would always return +@code{NIL}. On machines where this macro is defined, you will normally +define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}. + +@findex SHORT_IMMEDIATES_SIGN_EXTEND +@item SHORT_IMMEDIATES_SIGN_EXTEND +Define this macro if loading short immediate values into registers sign +extends. + +@findex IMPLICIT_FIX_EXPR +@item IMPLICIT_FIX_EXPR +An alias for a tree code that should be used by default for conversion +of floating point values to fixed point. Normally, +@code{FIX_ROUND_EXPR} is used.@refill + +@findex FIXUNS_TRUNC_LIKE_FIX_TRUNC +@item FIXUNS_TRUNC_LIKE_FIX_TRUNC +Define this macro if the same instructions that convert a floating +point number to a signed fixed point number also convert validly to an +unsigned one. + +@findex EASY_DIV_EXPR +@item EASY_DIV_EXPR +An alias for a tree code that is the easiest kind of division to +compile code for in the general case. It may be +@code{TRUNC_DIV_EXPR}, @code{FLOOR_DIV_EXPR}, @code{CEIL_DIV_EXPR} or +@code{ROUND_DIV_EXPR}. These four division operators differ in how +they round the result to an integer. @code{EASY_DIV_EXPR} is used +when it is permissible to use any of those kinds of division and the +choice should be made on the basis of efficiency.@refill + +@findex MOVE_MAX +@item MOVE_MAX +The maximum number of bytes that a single instruction can move quickly +between memory and registers or between two memory locations. + +@findex MAX_MOVE_MAX +@item MAX_MOVE_MAX +The maximum number of bytes that a single instruction can move quickly +between memory and registers or between two memory locations. If this +is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the +constant value that is the largest value that @code{MOVE_MAX} can have +at run-time. + +@findex SHIFT_COUNT_TRUNCATED +@item SHIFT_COUNT_TRUNCATED +A C expression that is nonzero if on this machine the number of bits +actually used for the count of a shift operation is equal to the number +of bits needed to represent the size of the object being shifted. When +this macro is non-zero, the compiler will assume that it is safe to omit +a sign-extend, zero-extend, and certain bitwise `and' instructions that +truncates the count of a shift operation. On machines that have +instructions that act on bitfields at variable positions, which may +include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED} +also enables deletion of truncations of the values that serve as +arguments to bitfield instructions. + +If both types of instructions truncate the count (for shifts) and +position (for bitfield operations), or if no variable-position bitfield +instructions exist, you should define this macro. + +However, on some machines, such as the 80386 and the 680x0, truncation +only applies to shift operations and not the (real or pretended) +bitfield operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on +such machines. Instead, add patterns to the @file{md} file that include +the implied truncation of the shift instructions. + +You need not define this macro if it would always have the value of zero. + +@findex TRULY_NOOP_TRUNCATION +@item TRULY_NOOP_TRUNCATION (@var{outprec}, @var{inprec}) +A C expression which is nonzero if on this machine it is safe to +``convert'' an integer of @var{inprec} bits to one of @var{outprec} +bits (where @var{outprec} is smaller than @var{inprec}) by merely +operating on it as if it had only @var{outprec} bits. + +On many machines, this expression can be 1. + +@c rearranged this, removed the phrase "it is reported that". this was +@c to fix an overfull hbox. --mew 10feb93 +When @code{TRULY_NOOP_TRUNCATION} returns 1 for a pair of sizes for +modes for which @code{MODES_TIEABLE_P} is 0, suboptimal code can result. +If this is the case, making @code{TRULY_NOOP_TRUNCATION} return 0 in +such cases may improve things. + +@findex STORE_FLAG_VALUE +@item STORE_FLAG_VALUE +A C expression describing the value returned by a comparison operator +with an integral mode and stored by a store-flag instruction +(@samp{s@var{cond}}) when the condition is true. This description must +apply to @emph{all} the @samp{s@var{cond}} patterns and all the +comparison operators whose results have a @code{MODE_INT} mode. + +A value of 1 or -1 means that the instruction implementing the +comparison operator returns exactly 1 or -1 when the comparison is true +and 0 when the comparison is false. Otherwise, the value indicates +which bits of the result are guaranteed to be 1 when the comparison is +true. This value is interpreted in the mode of the comparison +operation, which is given by the mode of the first operand in the +@samp{s@var{cond}} pattern. Either the low bit or the sign bit of +@code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by +the compiler. + +If @code{STORE_FLAG_VALUE} is neither 1 or -1, the compiler will +generate code that depends only on the specified bits. It can also +replace comparison operators with equivalent operations if they cause +the required bits to be set, even if the remaining bits are undefined. +For example, on a machine whose comparison operators return an +@code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as +@samp{0x80000000}, saying that just the sign bit is relevant, the +expression + +@smallexample +(ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0)) +@end smallexample + +@noindent +can be converted to + +@smallexample +(ashift:SI @var{x} (const_int @var{n})) +@end smallexample + +@noindent +where @var{n} is the appropriate shift count to move the bit being +tested into the sign bit. + +There is no way to describe a machine that always sets the low-order bit +for a true value, but does not guarantee the value of any other bits, +but we do not know of any machine that has such an instruction. If you +are trying to port GCC to such a machine, include an instruction to +perform a logical-and of the result with 1 in the pattern for the +comparison operators and let us know +@ifset USING +(@pxref{Bug Reporting,,How to Report Bugs}). +@end ifset +@ifclear USING +(@pxref{Bug Reporting,,How to Report Bugs,gcc.info,Using GCC}). +@end ifclear + +Often, a machine will have multiple instructions that obtain a value +from a comparison (or the condition codes). Here are rules to guide the +choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions +to be used: + +@itemize @bullet +@item +Use the shortest sequence that yields a valid definition for +@code{STORE_FLAG_VALUE}. It is more efficient for the compiler to +``normalize'' the value (convert it to, e.g., 1 or 0) than for the +comparison operators to do so because there may be opportunities to +combine the normalization with other operations. + +@item +For equal-length sequences, use a value of 1 or -1, with -1 being +slightly preferred on machines with expensive jumps and 1 preferred on +other machines. + +@item +As a second choice, choose a value of @samp{0x80000001} if instructions +exist that set both the sign and low-order bits but do not define the +others. + +@item +Otherwise, use a value of @samp{0x80000000}. +@end itemize + +Many machines can produce both the value chosen for +@code{STORE_FLAG_VALUE} and its negation in the same number of +instructions. On those machines, you should also define a pattern for +those cases, e.g., one matching + +@smallexample +(set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C}))) +@end smallexample + +Some machines can also perform @code{and} or @code{plus} operations on +condition code values with less instructions than the corresponding +@samp{s@var{cond}} insn followed by @code{and} or @code{plus}. On those +machines, define the appropriate patterns. Use the names @code{incscc} +and @code{decscc}, respectively, for the patterns which perform +@code{plus} or @code{minus} operations on condition code values. See +@file{rs6000.md} for some examples. The GNU Superoptizer can be used to +find such instruction sequences on other machines. + +You need not define @code{STORE_FLAG_VALUE} if the machine has no store-flag +instructions. + +@findex FLOAT_STORE_FLAG_VALUE +@item FLOAT_STORE_FLAG_VALUE (@var{mode}) +A C expression that gives a non-zero @code{REAL_VALUE_TYPE} value that is +returned when comparison operators with floating-point results are true. +Define this macro on machine that have comparison operations that return +floating-point values. If there are no such operations, do not define +this macro. + +@findex Pmode +@item Pmode +An alias for the machine mode for pointers. On most machines, define +this to be the integer mode corresponding to the width of a hardware +pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines. +On some machines you must define this to be one of the partial integer +modes, such as @code{PSImode}. + +The width of @code{Pmode} must be at least as large as the value of +@code{POINTER_SIZE}. If it is not equal, you must define the macro +@code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended +to @code{Pmode}. + +@findex FUNCTION_MODE +@item FUNCTION_MODE +An alias for the machine mode used for memory references to functions +being called, in @code{call} RTL expressions. On most machines this +should be @code{QImode}. + +@findex INTEGRATE_THRESHOLD +@item INTEGRATE_THRESHOLD (@var{decl}) +A C expression for the maximum number of instructions above which the +function @var{decl} should not be inlined. @var{decl} is a +@code{FUNCTION_DECL} node. + +The default definition of this macro is 64 plus 8 times the number of +arguments that the function accepts. Some people think a larger +threshold should be used on RISC machines. + +@findex SCCS_DIRECTIVE +@item SCCS_DIRECTIVE +Define this if the preprocessor should ignore @code{#sccs} directives +and print no error message. + +@findex NO_IMPLICIT_EXTERN_C +@item NO_IMPLICIT_EXTERN_C +Define this macro if the system header files support C++ as well as C. +This macro inhibits the usual method of using system header files in +C++, which is to pretend that the file's contents are enclosed in +@samp{extern "C" @{@dots{}@}}. + +@findex HANDLE_PRAGMA +@item HANDLE_PRAGMA (@var{getc}, @var{ungetc}, @var{name}) +This macro is no longer supported. You must use +@code{REGISTER_TARGET_PRAGMAS} instead. + +@findex REGISTER_TARGET_PRAGMAS +@findex #pragma +@findex pragma +@item REGISTER_TARGET_PRAGMAS (@var{pfile}) +Define this macro if you want to implement any target-specific pragmas. +If defined, it is a C expression which makes a series of calls to the +@code{cpp_register_pragma} and/or @code{cpp_register_pragma_space} +functions. The @var{pfile} argument is the first argument to supply to +these functions. The macro may also do setup required for the pragmas. + +The primary reason to define this macro is to provide compatibility with +other compilers for the same target. In general, we discourage +definition of target-specific pragmas for GCC. + +If the pragma can be implemented by attributes then the macro +@samp{INSERT_ATTRIBUTES} might be a useful one to define as well. + +Preprocessor macros that appear on pragma lines are not expanded. All +@samp{#pragma} directives that do not match any registered pragma are +silently ignored, unless the user specifies @samp{-Wunknown-pragmas}. + +@deftypefun void cpp_register_pragma (cpp_reader *@var{pfile}, const char *@var{space}, const char *@var{name}, void (*@var{callback}) (cpp_reader *)) + +Each call to @code{cpp_register_pragma} establishes one pragma. The +@var{callback} routine will be called when the preprocessor encounters a +pragma of the form + +@smallexample +#pragma [@var{space}] @var{name} @dots{} +@end smallexample + +@var{space} must have been the subject of a previous call to +@code{cpp_register_pragma_space}, or else be a null pointer. The +callback routine receives @var{pfile} as its first argument, but must +not use it for anything (this may change in the future). It may read +any text after the @var{name} by making calls to @code{c_lex}. Text +which is not read by the callback will be silently ignored. + +Note that both @var{space} and @var{name} are case sensitive. + +For an example use of this routine, see @file{c4x.h} and the callback +routines defined in @file{c4x.c}. + +Note that the use of @code{c_lex} is specific to the C and C++ +compilers. It will not work in the Java or Fortran compilers, or any +other language compilers for that matter. Thus if @code{c_lex} is going +to be called from target-specific code, it must only be done so when +building hte C and C++ compilers. This can be done by defining the +variables @code{c_target_objs} and @code{cxx_target_objs} in the +target entry in the @code{config.gcc} file. These variables should name +the target-specific, language-specific object file which contains the +code that uses @code{c_lex}. Note it will also be necessary to add a +rule to the makefile fragment pointed to by @code{tmake_file} that shows +how to build this object file. +@end deftypefun + +@deftypefun void cpp_register_pragma_space (cpp_reader *@var{pfile}, const char *@var{space}) +This routine establishes a namespace for pragmas, which will be +registered by subsequent calls to @code{cpp_register_pragma}. For +example, pragmas defined by the C standard are in the @samp{STDC} +namespace, and pragmas specific to GCC are in the @samp{GCC} namespace. + +For an example use of this routine in a target header, see @file{v850.h}. +@end deftypefun + +@findex HANDLE_SYSV_PRAGMA +@findex #pragma +@findex pragma +@item HANDLE_SYSV_PRAGMA +Define this macro (to a value of 1) if you want the System V style +pragmas @samp{#pragma pack()} and @samp{#pragma weak +[=]} to be supported by gcc. + +The pack pragma specifies the maximum alignment (in bytes) of fields +within a structure, in much the same way as the @samp{__aligned__} and +@samp{__packed__} @code{__attribute__}s do. A pack value of zero resets +the behaviour to the default. + +The weak pragma only works if @code{SUPPORTS_WEAK} and +@code{ASM_WEAKEN_LABEL} are defined. If enabled it allows the creation +of specifically named weak labels, optionally with a value. + +@findex HANDLE_PRAGMA_PACK_PUSH_POP +@findex #pragma +@findex pragma +@item HANDLE_PRAGMA_PACK_PUSH_POP +Define this macro (to a value of 1) if you want to support the Win32 +style pragmas @samp{#pragma pack(push,)} and @samp{#pragma +pack(pop)}. The pack(push,) pragma specifies the maximum alignment +(in bytes) of fields within a structure, in much the same way as the +@samp{__aligned__} and @samp{__packed__} @code{__attribute__}s do. A +pack value of zero resets the behaviour to the default. Successive +invocations of this pragma cause the previous values to be stacked, so +that invocations of @samp{#pragma pack(pop)} will return to the previous +value. + +@findex VALID_MACHINE_DECL_ATTRIBUTE +@item VALID_MACHINE_DECL_ATTRIBUTE (@var{decl}, @var{attributes}, @var{identifier}, @var{args}) +If defined, a C expression whose value is nonzero if @var{identifier} with +arguments @var{args} is a valid machine specific attribute for @var{decl}. +The attributes in @var{attributes} have previously been assigned to @var{decl}. + +@findex VALID_MACHINE_TYPE_ATTRIBUTE +@item VALID_MACHINE_TYPE_ATTRIBUTE (@var{type}, @var{attributes}, @var{identifier}, @var{args}) +If defined, a C expression whose value is nonzero if @var{identifier} with +arguments @var{args} is a valid machine specific attribute for @var{type}. +The attributes in @var{attributes} have previously been assigned to @var{type}. + +@findex COMP_TYPE_ATTRIBUTES +@item COMP_TYPE_ATTRIBUTES (@var{type1}, @var{type2}) +If defined, a C expression whose value is zero if the attributes on +@var{type1} and @var{type2} are incompatible, one if they are compatible, +and two if they are nearly compatible (which causes a warning to be +generated). + +@findex SET_DEFAULT_TYPE_ATTRIBUTES +@item SET_DEFAULT_TYPE_ATTRIBUTES (@var{type}) +If defined, a C statement that assigns default attributes to +newly defined @var{type}. + +@findex MERGE_MACHINE_TYPE_ATTRIBUTES +@item MERGE_MACHINE_TYPE_ATTRIBUTES (@var{type1}, @var{type2}) +Define this macro if the merging of type attributes needs special handling. +If defined, the result is a list of the combined TYPE_ATTRIBUTES of +@var{type1} and @var{type2}. It is assumed that comptypes has already been +called and returned 1. + +@findex MERGE_MACHINE_DECL_ATTRIBUTES +@item MERGE_MACHINE_DECL_ATTRIBUTES (@var{olddecl}, @var{newdecl}) +Define this macro if the merging of decl attributes needs special handling. +If defined, the result is a list of the combined DECL_MACHINE_ATTRIBUTES of +@var{olddecl} and @var{newdecl}. @var{newdecl} is a duplicate declaration +of @var{olddecl}. Examples of when this is needed are when one attribute +overrides another, or when an attribute is nullified by a subsequent +definition. + +@findex INSERT_ATTRIBUTES +@item INSERT_ATTRIBUTES (@var{node}, @var{attr_ptr}, @var{prefix_ptr}) +Define this macro if you want to be able to add attributes to a decl +when it is being created. This is normally useful for backends which +wish to implement a pragma by using the attributes which correspond to +the pragma's effect. The @var{node} argument is the decl which is being +created. The @var{attr_ptr} argument is a pointer to the attribute list +for this decl. The @var{prefix_ptr} is a pointer to the list of +attributes that have appeared after the specifiers and modifiers of the +declaration, but before the declaration proper. + +@findex SET_DEFAULT_DECL_ATTRIBUTES +@item SET_DEFAULT_DECL_ATTRIBUTES (@var{decl}, @var{attributes}) +If defined, a C statement that assigns default attributes to +newly defined @var{decl}. + +@findex DOLLARS_IN_IDENTIFIERS +@item DOLLARS_IN_IDENTIFIERS +Define this macro to control use of the character @samp{$} in identifier +names. 0 means @samp{$} is not allowed by default; 1 means it is allowed. +1 is the default; there is no need to define this macro in that case. +This macro controls the compiler proper; it does not affect the preprocessor. + +@findex NO_DOLLAR_IN_LABEL +@item NO_DOLLAR_IN_LABEL +Define this macro if the assembler does not accept the character +@samp{$} in label names. By default constructors and destructors in +G++ have @samp{$} in the identifiers. If this macro is defined, +@samp{.} is used instead. + +@findex NO_DOT_IN_LABEL +@item NO_DOT_IN_LABEL +Define this macro if the assembler does not accept the character +@samp{.} in label names. By default constructors and destructors in G++ +have names that use @samp{.}. If this macro is defined, these names +are rewritten to avoid @samp{.}. + +@findex DEFAULT_MAIN_RETURN +@item DEFAULT_MAIN_RETURN +Define this macro if the target system expects every program's @code{main} +function to return a standard ``success'' value by default (if no other +value is explicitly returned). + +The definition should be a C statement (sans semicolon) to generate the +appropriate rtl instructions. It is used only when compiling the end of +@code{main}. + +@item NEED_ATEXIT +@findex NEED_ATEXIT +Define this if the target system lacks the function @code{atexit} +from the ISO C standard. If this macro is defined, a default definition +will be provided to support C++. If @code{ON_EXIT} is not defined, +a default @code{exit} function will also be provided. + +@item ON_EXIT +@findex ON_EXIT +Define this macro if the target has another way to implement atexit +functionality without replacing @code{exit}. For instance, SunOS 4 has +a similar @code{on_exit} library function. + +The definition should be a functional macro which can be used just like +the @code{atexit} function. + +@item EXIT_BODY +@findex EXIT_BODY +Define this if your @code{exit} function needs to do something +besides calling an external function @code{_cleanup} before +terminating with @code{_exit}. The @code{EXIT_BODY} macro is +only needed if @code{NEED_ATEXIT} is defined and @code{ON_EXIT} is not +defined. + +@findex INSN_SETS_ARE_DELAYED +@item INSN_SETS_ARE_DELAYED (@var{insn}) +Define this macro as a C expression that is nonzero if it is safe for the +delay slot scheduler to place instructions in the delay slot of @var{insn}, +even if they appear to use a resource set or clobbered in @var{insn}. +@var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that +every @code{call_insn} has this behavior. On machines where some @code{insn} +or @code{jump_insn} is really a function call and hence has this behavior, +you should define this macro. + +You need not define this macro if it would always return zero. + +@findex INSN_REFERENCES_ARE_DELAYED +@item INSN_REFERENCES_ARE_DELAYED (@var{insn}) +Define this macro as a C expression that is nonzero if it is safe for the +delay slot scheduler to place instructions in the delay slot of @var{insn}, +even if they appear to set or clobber a resource referenced in @var{insn}. +@var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where +some @code{insn} or @code{jump_insn} is really a function call and its operands +are registers whose use is actually in the subroutine it calls, you should +define this macro. Doing so allows the delay slot scheduler to move +instructions which copy arguments into the argument registers into the delay +slot of @var{insn}. + +You need not define this macro if it would always return zero. + +@findex MACHINE_DEPENDENT_REORG +@item MACHINE_DEPENDENT_REORG (@var{insn}) +In rare cases, correct code generation requires extra machine +dependent processing between the second jump optimization pass and +delayed branch scheduling. On those machines, define this macro as a C +statement to act on the code starting at @var{insn}. + +@findex MULTIPLE_SYMBOL_SPACES +@item MULTIPLE_SYMBOL_SPACES +Define this macro if in some cases global symbols from one translation +unit may not be bound to undefined symbols in another translation unit +without user intervention. For instance, under Microsoft Windows +symbols must be explicitly imported from shared libraries (DLLs). + +@findex MD_ASM_CLOBBERS +@item MD_ASM_CLOBBERS +A C statement that adds to @var{CLOBBERS} @code{STRING_CST} trees for +any hard regs the port wishes to automatically clobber for all asms. + +@findex ISSUE_RATE +@item ISSUE_RATE +A C expression that returns how many instructions can be issued at the +same time if the machine is a superscalar machine. + +@findex MD_SCHED_INIT +@item MD_SCHED_INIT (@var{file}, @var{verbose}, @var{max_ready}) +A C statement which is executed by the scheduler at the +beginning of each block of instructions that are to be scheduled. +@var{file} is either a null pointer, or a stdio stream to write any +debug output to. @var{verbose} is the verbose level provided by +@samp{-fsched-verbose-}@var{n}. @var{max_ready} is the maximum number +of insns in the current scheduling region that can be live at the same +time. This can be used to allocate scratch space if it is needed. + +@findex MD_SCHED_FINISH +@item MD_SCHED_FINISH (@var{file}, @var{verbose}) +A C statement which is executed by the scheduler at the end of each block +of instructions that are to be scheduled. It can be used to perform +cleanup of any actions done by the other scheduling macros. +@var{file} is either a null pointer, or a stdio stream to write any +debug output to. @var{verbose} is the verbose level provided by +@samp{-fsched-verbose-}@var{n}. + +@findex MD_SCHED_REORDER +@item MD_SCHED_REORDER (@var{file}, @var{verbose}, @var{ready}, @var{n_ready}, @var{clock}, @var{can_issue_more}) +A C statement which is executed by the scheduler after it +has scheduled the ready list to allow the machine description to reorder +it (for example to combine two small instructions together on +@samp{VLIW} machines). @var{file} is either a null pointer, or a stdio +stream to write any debug output to. @var{verbose} is the verbose level +provided by @samp{-fsched-verbose-}@var{n}. @var{ready} is a pointer to +the ready list of instructions that are ready to be scheduled. +@var{n_ready} is the number of elements in the ready list. The +scheduler reads the ready list in reverse order, starting with +@var{ready}[@var{n_ready}-1] and going to @var{ready}[0]. @var{clock} +is the timer tick of the scheduler. @var{can_issue_more} is an output +parameter that is set to the number of insns that can issue this clock; +normally this is just @code{issue_rate}. See also @samp{MD_SCHED_REORDER2}. + +@findex MD_SCHED_REORDER2 +@item MD_SCHED_REORDER2 (@var{file}, @var{verbose}, @var{ready}, @var{n_ready}, @var{clock}, @var{can_issue_more}) +Like @samp{MD_SCHED_REORDER}, but called at a different time. While the +@samp{MD_SCHED_REORDER} macro is called whenever the scheduler starts a +new cycle, this macro is used immediately after @samp{MD_SCHED_VARIABLE_ISSUE} +is called; it can reorder the ready list and set @var{can_issue_more} to +determine whether there are more insns to be scheduled in the same cycle. +Defining this macro can be useful if there are frequent situations where +scheduling one insn causes other insns to become ready in the same cycle, +these other insns can then be taken into account properly. + +@findex MD_SCHED_VARIABLE_ISSUE +@item MD_SCHED_VARIABLE_ISSUE (@var{file}, @var{verbose}, @var{insn}, @var{more}) +A C statement which is executed by the scheduler after it +has scheduled an insn from the ready list. @var{file} is either a null +pointer, or a stdio stream to write any debug output to. @var{verbose} +is the verbose level provided by @samp{-fsched-verbose-}@var{n}. +@var{insn} is the instruction that was scheduled. @var{more} is the +number of instructions that can be issued in the current cycle. The +@samp{MD_SCHED_VARIABLE_ISSUE} macro is responsible for updating the +value of @var{more} (typically by @var{more}--). + +@findex MAX_INTEGER_COMPUTATION_MODE +@item MAX_INTEGER_COMPUTATION_MODE +Define this to the largest integer machine mode which can be used for +operations other than load, store and copy operations. + +You need only define this macro if the target holds values larger than +@code{word_mode} in general purpose registers. Most targets should not define +this macro. + +@findex MATH_LIBRARY +@item MATH_LIBRARY +Define this macro as a C string constant for the linker argument to link +in the system math library, or @samp{""} if the target does not have a +separate math library. + +You need only define this macro if the default of @samp{"-lm"} is wrong. + +@findex LIBRARY_PATH_ENV +@item LIBRARY_PATH_ENV +Define this macro as a C string constant for the environment variable that +specifies where the linker should look for libraries. + +You need only define this macro if the default of @samp{"LIBRARY_PATH"} +is wrong. + +@findex TARGET_HAS_F_SETLKW +@item TARGET_HAS_F_SETLKW +Define this macro if the target supports file locking with fcntl / F_SETLKW. +Note that this functionality is part of POSIX. +Defining @code{TARGET_HAS_F_SETLKW} will enable the test coverage code +to use file locking when exiting a program, which avoids race conditions +if the program has forked. + +@findex MAX_CONDITIONAL_EXECUTE +@item MAX_CONDITIONAL_EXECUTE + +A C expression for the maximum number of instructions to execute via +conditional execution instructions instead of a branch. A value of +@code{BRANCH_COST}+1 is the default if the machine does not use cc0, and +1 if it does use cc0. + +@findex IFCVT_MODIFY_TESTS +@item IFCVT_MODIFY_TESTS +A C expression to modify the tests in @code{TRUE_EXPR}, and +@code{FALSE_EXPPR} for use in converting insns in @code{TEST_BB}, +@code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB} basic blocks to +conditional execution. Set either @code{TRUE_EXPR} or @code{FALSE_EXPR} +to a null pointer if the tests cannot be converted. + +@findex IFCVT_MODIFY_INSN +@item IFCVT_MODIFY_INSN +A C expression to modify the @code{PATTERN} of an @code{INSN} that is to +be converted to conditional execution format. + +@findex IFCVT_MODIFY_FINAL +@item IFCVT_MODIFY_FINAL +A C expression to perform any final machine dependent modifications in +converting code to conditional execution in the basic blocks +@code{TEST_BB}, @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB}. + +@findex IFCVT_MODIFY_CANCEL +@item IFCVT_MODIFY_CANCEL +A C expression to cancel any machine dependent modifications in +converting code to conditional execution in the basic blocks +@code{TEST_BB}, @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB}. + +@findex MD_INIT_BUILTINS +@item MD_INIT_BUILTINS +Define this macro if you have any machine-specific builtin functions that +need to be defined. It should be a C expression that performs the +necessary setup. + +Machine specific builtins can be useful to expand special machine +instructions that would otherwise not normally be generated because +they have no equivalent in the source language (for example, SIMD vector +instructions or prefetch instructions). + +To create a builtin function, call the function @code{builtin_function} +which is defined by the language frontend. You can use any type nodes set +up by @code{build_common_tree_nodes} and @code{build_common_tree_nodes_2}; +only language frontends that use these two functions will use +@samp{MD_INIT_BUILTINS}. + +@findex MD_EXPAND_BUILTIN +@item MD_EXPAND_BUILTIN(@var{exp}, @var{target}, @var{subtarget}, @var{mode}, @var{ignore}) + +Expand a call to a machine specific builtin that was set up by +@samp{MD_INIT_BUILTINS}. @var{exp} is the expression for the function call; +the result should go to @var{target} if that is convenient, and have mode +@var{mode} if that is convenient. @var{subtarget} may be used as the target +for computing one of @var{exp}'s operands. @var{ignore} is nonzero if the value +is to be ignored. +This macro should return the result of the call to the builtin. + +@end table diff --git a/gcc/extend.texi b/gcc/extend.texi deleted file mode 100644 index 7e45b61e00a..00000000000 --- a/gcc/extend.texi +++ /dev/null @@ -1,4637 +0,0 @@ -@c Copyright (C) 1988,1989,1992,1993,1994,1996,1998,1999,2000,2001 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@node C Extensions -@chapter Extensions to the C Language Family -@cindex extensions, C language -@cindex C language extensions - -GNU C provides several language features not found in ISO standard C. -(The @samp{-pedantic} option directs GNU CC to print a warning message if -any of these features is used.) To test for the availability of these -features in conditional compilation, check for a predefined macro -@code{__GNUC__}, which is always defined under GNU CC. - -These extensions are available in C and Objective C. Most of them are -also available in C++. @xref{C++ Extensions,,Extensions to the -C++ Language}, for extensions that apply @emph{only} to C++. - -Some features that are in ISO C99 but not C89 or C++ are also, as -extensions, accepted by GCC in C89 mode and in C++. - -@c The only difference between the two versions of this menu is that the -@c version for clear INTERNALS has an extra node, "Constraints" (which -@c appears in a separate chapter in the other version of the manual). -@ifset INTERNALS -@menu -* Statement Exprs:: Putting statements and declarations inside expressions. -* Local Labels:: Labels local to a statement-expression. -* Labels as Values:: Getting pointers to labels, and computed gotos. -* Nested Functions:: As in Algol and Pascal, lexical scoping of functions. -* Constructing Calls:: Dispatching a call to another function. -* Naming Types:: Giving a name to the type of some expression. -* Typeof:: @code{typeof}: referring to the type of an expression. -* Lvalues:: Using @samp{?:}, @samp{,} and casts in lvalues. -* Conditionals:: Omitting the middle operand of a @samp{?:} expression. -* Long Long:: Double-word integers---@code{long long int}. -* Complex:: Data types for complex numbers. -* Hex Floats:: Hexadecimal floating-point constants. -* Zero Length:: Zero-length arrays. -* Variable Length:: Arrays whose length is computed at run time. -* Variadic Macros:: Macros with a variable number of arguments. -* Escaped Newlines:: Slightly looser rules for escaped newlines. -* Multi-line Strings:: String literals with embedded newlines. -* Subscripting:: Any array can be subscripted, even if not an lvalue. -* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers. -* Initializers:: Non-constant initializers. -* Compound Literals:: Compound literals give structures, unions - or arrays as values. -* Designated Inits:: Labeling elements of initializers. -* Cast to Union:: Casting to union type from any member of the union. -* Case Ranges:: `case 1 ... 9' and such. -* Mixed Declarations:: Mixing declarations and code. -* Function Attributes:: Declaring that functions have no side effects, - or that they can never return. -* Attribute Syntax:: Formal syntax for attributes. -* Function Prototypes:: Prototype declarations and old-style definitions. -* C++ Comments:: C++ comments are recognized. -* Dollar Signs:: Dollar sign is allowed in identifiers. -* Character Escapes:: @samp{\e} stands for the character @key{ESC}. -* Variable Attributes:: Specifying attributes of variables. -* Type Attributes:: Specifying attributes of types. -* Alignment:: Inquiring about the alignment of a type or variable. -* Inline:: Defining inline functions (as fast as macros). -* Extended Asm:: Assembler instructions with C expressions as operands. - (With them you can define ``built-in'' functions.) -* Asm Labels:: Specifying the assembler name to use for a C symbol. -* Explicit Reg Vars:: Defining variables residing in specified registers. -* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files. -* Incomplete Enums:: @code{enum foo;}, with details to follow. -* Function Names:: Printable strings which are the name of the current - function. -* Return Address:: Getting the return or frame address of a function. -* Other Builtins:: Other built-in functions. -@end menu -@end ifset -@ifclear INTERNALS -@menu -* Statement Exprs:: Putting statements and declarations inside expressions. -* Local Labels:: Labels local to a statement-expression. -* Labels as Values:: Getting pointers to labels, and computed gotos. -* Nested Functions:: As in Algol and Pascal, lexical scoping of functions. -* Constructing Calls:: Dispatching a call to another function. -* Naming Types:: Giving a name to the type of some expression. -* Typeof:: @code{typeof}: referring to the type of an expression. -* Lvalues:: Using @samp{?:}, @samp{,} and casts in lvalues. -* Conditionals:: Omitting the middle operand of a @samp{?:} expression. -* Long Long:: Double-word integers---@code{long long int}. -* Complex:: Data types for complex numbers. -* Hex Floats:: Hexadecimal floating-point constants. -* Zero Length:: Zero-length arrays. -* Variable Length:: Arrays whose length is computed at run time. -* Variadic Macros:: Macros with a variable number of arguments. -* Escaped Newlines:: Slightly looser rules for escaped newlines. -* Multi-line Strings:: String literals with embedded newlines. -* Subscripting:: Any array can be subscripted, even if not an lvalue. -* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers. -* Initializers:: Non-constant initializers. -* Compound Literals:: Compound literals give structures, unions - or arrays as values. -* Designated Inits:: Labeling elements of initializers. -* Cast to Union:: Casting to union type from any member of the union. -* Case Ranges:: `case 1 ... 9' and such. -* Mixed Declarations:: Mixing declarations and code. -* Function Attributes:: Declaring that functions have no side effects, - or that they can never return. -* Attribute Syntax:: Formal syntax for attributes. -* Function Prototypes:: Prototype declarations and old-style definitions. -* C++ Comments:: C++ comments are recognized. -* Dollar Signs:: Dollar sign is allowed in identifiers. -* Character Escapes:: @samp{\e} stands for the character @key{ESC}. -* Variable Attributes:: Specifying attributes of variables. -* Type Attributes:: Specifying attributes of types. -* Alignment:: Inquiring about the alignment of a type or variable. -* Inline:: Defining inline functions (as fast as macros). -* Extended Asm:: Assembler instructions with C expressions as operands. - (With them you can define ``built-in'' functions.) -* Constraints:: Constraints for asm operands -* Asm Labels:: Specifying the assembler name to use for a C symbol. -* Explicit Reg Vars:: Defining variables residing in specified registers. -* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files. -* Incomplete Enums:: @code{enum foo;}, with details to follow. -* Function Names:: Printable strings which are the name of the current - function. -* Return Address:: Getting the return or frame address of a function. -* Other Builtins:: Other built-in functions. -@end menu -@end ifclear - -@node Statement Exprs -@section Statements and Declarations in Expressions -@cindex statements inside expressions -@cindex declarations inside expressions -@cindex expressions containing statements -@cindex macros, statements in expressions - -@c the above section title wrapped and causes an underfull hbox.. i -@c changed it from "within" to "in". --mew 4feb93 - -A compound statement enclosed in parentheses may appear as an expression -in GNU C. This allows you to use loops, switches, and local variables -within an expression. - -Recall that a compound statement is a sequence of statements surrounded -by braces; in this construct, parentheses go around the braces. For -example: - -@example -(@{ int y = foo (); int z; - if (y > 0) z = y; - else z = - y; - z; @}) -@end example - -@noindent -is a valid (though slightly more complex than necessary) expression -for the absolute value of @code{foo ()}. - -The last thing in the compound statement should be an expression -followed by a semicolon; the value of this subexpression serves as the -value of the entire construct. (If you use some other kind of statement -last within the braces, the construct has type @code{void}, and thus -effectively no value.) - -This feature is especially useful in making macro definitions ``safe'' (so -that they evaluate each operand exactly once). For example, the -``maximum'' function is commonly defined as a macro in standard C as -follows: - -@example -#define max(a,b) ((a) > (b) ? (a) : (b)) -@end example - -@noindent -@cindex side effects, macro argument -But this definition computes either @var{a} or @var{b} twice, with bad -results if the operand has side effects. In GNU C, if you know the -type of the operands (here let's assume @code{int}), you can define -the macro safely as follows: - -@example -#define maxint(a,b) \ - (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @}) -@end example - -Embedded statements are not allowed in constant expressions, such as -the value of an enumeration constant, the width of a bit field, or -the initial value of a static variable. - -If you don't know the type of the operand, you can still do this, but you -must use @code{typeof} (@pxref{Typeof}) or type naming (@pxref{Naming -Types}). - -Statement expressions are not supported fully in G++, and their fate -there is unclear. (It is possible that they will become fully supported -at some point, or that they will be deprecated, or that the bugs that -are present will continue to exist indefinitely.) Presently, statement -expressions do not work well as default arguments. - -In addition, there are semantic issues with statement-expressions in -C++. If you try to use statement-expressions instead of inline -functions in C++, you may be surprised at the way object destruction is -handled. For example: - -@example -#define foo(a) (@{int b = (a); b + 3; @}) -@end example - -@noindent -does not work the same way as: - -@example -inline int foo(int a) @{ int b = a; return b + 3; @} -@end example - -@noindent -In particular, if the expression passed into @code{foo} involves the -creation of temporaries, the destructors for those temporaries will be -run earlier in the case of the macro than in the case of the function. - -These considerations mean that it is probably a bad idea to use -statement-expressions of this form in header files that are designed to -work with C++. (Note that some versions of the GNU C Library contained -header files using statement-expression that lead to precisely this -bug.) - -@node Local Labels -@section Locally Declared Labels -@cindex local labels -@cindex macros, local labels - -Each statement expression is a scope in which @dfn{local labels} can be -declared. A local label is simply an identifier; you can jump to it -with an ordinary @code{goto} statement, but only from within the -statement expression it belongs to. - -A local label declaration looks like this: - -@example -__label__ @var{label}; -@end example - -@noindent -or - -@example -__label__ @var{label1}, @var{label2}, @dots{}; -@end example - -Local label declarations must come at the beginning of the statement -expression, right after the @samp{(@{}, before any ordinary -declarations. - -The label declaration defines the label @emph{name}, but does not define -the label itself. You must do this in the usual way, with -@code{@var{label}:}, within the statements of the statement expression. - -The local label feature is useful because statement expressions are -often used in macros. If the macro contains nested loops, a @code{goto} -can be useful for breaking out of them. However, an ordinary label -whose scope is the whole function cannot be used: if the macro can be -expanded several times in one function, the label will be multiply -defined in that function. A local label avoids this problem. For -example: - -@example -#define SEARCH(array, target) \ -(@{ \ - __label__ found; \ - typeof (target) _SEARCH_target = (target); \ - typeof (*(array)) *_SEARCH_array = (array); \ - int i, j; \ - int value; \ - for (i = 0; i < max; i++) \ - for (j = 0; j < max; j++) \ - if (_SEARCH_array[i][j] == _SEARCH_target) \ - @{ value = i; goto found; @} \ - value = -1; \ - found: \ - value; \ -@}) -@end example - -@node Labels as Values -@section Labels as Values -@cindex labels as values -@cindex computed gotos -@cindex goto with computed label -@cindex address of a label - -You can get the address of a label defined in the current function -(or a containing function) with the unary operator @samp{&&}. The -value has type @code{void *}. This value is a constant and can be used -wherever a constant of that type is valid. For example: - -@example -void *ptr; -@dots{} -ptr = &&foo; -@end example - -To use these values, you need to be able to jump to one. This is done -with the computed goto statement@footnote{The analogous feature in -Fortran is called an assigned goto, but that name seems inappropriate in -C, where one can do more than simply store label addresses in label -variables.}, @code{goto *@var{exp};}. For example, - -@example -goto *ptr; -@end example - -@noindent -Any expression of type @code{void *} is allowed. - -One way of using these constants is in initializing a static array that -will serve as a jump table: - -@example -static void *array[] = @{ &&foo, &&bar, &&hack @}; -@end example - -Then you can select a label with indexing, like this: - -@example -goto *array[i]; -@end example - -@noindent -Note that this does not check whether the subscript is in bounds---array -indexing in C never does that. - -Such an array of label values serves a purpose much like that of the -@code{switch} statement. The @code{switch} statement is cleaner, so -use that rather than an array unless the problem does not fit a -@code{switch} statement very well. - -Another use of label values is in an interpreter for threaded code. -The labels within the interpreter function can be stored in the -threaded code for super-fast dispatching. - -You may not use this mechanism to jump to code in a different function. -If you do that, totally unpredictable things will happen. The best way to -avoid this is to store the label address only in automatic variables and -never pass it as an argument. - -An alternate way to write the above example is - -@example -static const int array[] = @{ &&foo - &&foo, &&bar - &&foo, - &&hack - &&foo @}; -goto *(&&foo + array[i]); -@end example - -@noindent -This is more friendly to code living in shared libraries, as it reduces -the number of dynamic relocations that are needed, and by consequence, -allows the data to be read-only. - -@node Nested Functions -@section Nested Functions -@cindex nested functions -@cindex downward funargs -@cindex thunks - -A @dfn{nested function} is a function defined inside another function. -(Nested functions are not supported for GNU C++.) The nested function's -name is local to the block where it is defined. For example, here we -define a nested function named @code{square}, and call it twice: - -@example -@group -foo (double a, double b) -@{ - double square (double z) @{ return z * z; @} - - return square (a) + square (b); -@} -@end group -@end example - -The nested function can access all the variables of the containing -function that are visible at the point of its definition. This is -called @dfn{lexical scoping}. For example, here we show a nested -function which uses an inherited variable named @code{offset}: - -@example -bar (int *array, int offset, int size) -@{ - int access (int *array, int index) - @{ return array[index + offset]; @} - int i; - @dots{} - for (i = 0; i < size; i++) - @dots{} access (array, i) @dots{} -@} -@end example - -Nested function definitions are permitted within functions in the places -where variable definitions are allowed; that is, in any block, before -the first statement in the block. - -It is possible to call the nested function from outside the scope of its -name by storing its address or passing the address to another function: - -@example -hack (int *array, int size) -@{ - void store (int index, int value) - @{ array[index] = value; @} - - intermediate (store, size); -@} -@end example - -Here, the function @code{intermediate} receives the address of -@code{store} as an argument. If @code{intermediate} calls @code{store}, -the arguments given to @code{store} are used to store into @code{array}. -But this technique works only so long as the containing function -(@code{hack}, in this example) does not exit. - -If you try to call the nested function through its address after the -containing function has exited, all hell will break loose. If you try -to call it after a containing scope level has exited, and if it refers -to some of the variables that are no longer in scope, you may be lucky, -but it's not wise to take the risk. If, however, the nested function -does not refer to anything that has gone out of scope, you should be -safe. - -GNU CC implements taking the address of a nested function using a -technique called @dfn{trampolines}. A paper describing them is -available as @uref{http://people.debian.org/~karlheg/Usenix88-lexic.pdf}. - -A nested function can jump to a label inherited from a containing -function, provided the label was explicitly declared in the containing -function (@pxref{Local Labels}). Such a jump returns instantly to the -containing function, exiting the nested function which did the -@code{goto} and any intermediate functions as well. Here is an example: - -@example -@group -bar (int *array, int offset, int size) -@{ - __label__ failure; - int access (int *array, int index) - @{ - if (index > size) - goto failure; - return array[index + offset]; - @} - int i; - @dots{} - for (i = 0; i < size; i++) - @dots{} access (array, i) @dots{} - @dots{} - return 0; - - /* @r{Control comes here from @code{access} - if it detects an error.} */ - failure: - return -1; -@} -@end group -@end example - -A nested function always has internal linkage. Declaring one with -@code{extern} is erroneous. If you need to declare the nested function -before its definition, use @code{auto} (which is otherwise meaningless -for function declarations). - -@example -bar (int *array, int offset, int size) -@{ - __label__ failure; - auto int access (int *, int); - @dots{} - int access (int *array, int index) - @{ - if (index > size) - goto failure; - return array[index + offset]; - @} - @dots{} -@} -@end example - -@node Constructing Calls -@section Constructing Function Calls -@cindex constructing calls -@cindex forwarding calls - -Using the built-in functions described below, you can record -the arguments a function received, and call another function -with the same arguments, without knowing the number or types -of the arguments. - -You can also record the return value of that function call, -and later return that value, without knowing what data type -the function tried to return (as long as your caller expects -that data type). - -@table @code -@findex __builtin_apply_args -@item __builtin_apply_args () -This built-in function returns a pointer of type @code{void *} to data -describing how to perform a call with the same arguments as were passed -to the current function. - -The function saves the arg pointer register, structure value address, -and all registers that might be used to pass arguments to a function -into a block of memory allocated on the stack. Then it returns the -address of that block. - -@findex __builtin_apply -@item __builtin_apply (@var{function}, @var{arguments}, @var{size}) -This built-in function invokes @var{function} (type @code{void (*)()}) -with a copy of the parameters described by @var{arguments} (type -@code{void *}) and @var{size} (type @code{int}). - -The value of @var{arguments} should be the value returned by -@code{__builtin_apply_args}. The argument @var{size} specifies the size -of the stack argument data, in bytes. - -This function returns a pointer of type @code{void *} to data describing -how to return whatever value was returned by @var{function}. The data -is saved in a block of memory allocated on the stack. - -It is not always simple to compute the proper value for @var{size}. The -value is used by @code{__builtin_apply} to compute the amount of data -that should be pushed on the stack and copied from the incoming argument -area. - -@findex __builtin_return -@item __builtin_return (@var{result}) -This built-in function returns the value described by @var{result} from -the containing function. You should specify, for @var{result}, a value -returned by @code{__builtin_apply}. -@end table - -@node Naming Types -@section Naming an Expression's Type -@cindex naming types - -You can give a name to the type of an expression using a @code{typedef} -declaration with an initializer. Here is how to define @var{name} as a -type name for the type of @var{exp}: - -@example -typedef @var{name} = @var{exp}; -@end example - -This is useful in conjunction with the statements-within-expressions -feature. Here is how the two together can be used to define a safe -``maximum'' macro that operates on any arithmetic type: - -@example -#define max(a,b) \ - (@{typedef _ta = (a), _tb = (b); \ - _ta _a = (a); _tb _b = (b); \ - _a > _b ? _a : _b; @}) -@end example - -@cindex underscores in variables in macros -@cindex @samp{_} in variables in macros -@cindex local variables in macros -@cindex variables, local, in macros -@cindex macros, local variables in - -The reason for using names that start with underscores for the local -variables is to avoid conflicts with variable names that occur within the -expressions that are substituted for @code{a} and @code{b}. Eventually we -hope to design a new form of declaration syntax that allows you to declare -variables whose scopes start only after their initializers; this will be a -more reliable way to prevent such conflicts. - -@node Typeof -@section Referring to a Type with @code{typeof} -@findex typeof -@findex sizeof -@cindex macros, types of arguments - -Another way to refer to the type of an expression is with @code{typeof}. -The syntax of using of this keyword looks like @code{sizeof}, but the -construct acts semantically like a type name defined with @code{typedef}. - -There are two ways of writing the argument to @code{typeof}: with an -expression or with a type. Here is an example with an expression: - -@example -typeof (x[0](1)) -@end example - -@noindent -This assumes that @code{x} is an array of pointers to functions; -the type described is that of the values of the functions. - -Here is an example with a typename as the argument: - -@example -typeof (int *) -@end example - -@noindent -Here the type described is that of pointers to @code{int}. - -If you are writing a header file that must work when included in ISO C -programs, write @code{__typeof__} instead of @code{typeof}. -@xref{Alternate Keywords}. - -A @code{typeof}-construct can be used anywhere a typedef name could be -used. For example, you can use it in a declaration, in a cast, or inside -of @code{sizeof} or @code{typeof}. - -@itemize @bullet -@item -This declares @code{y} with the type of what @code{x} points to. - -@example -typeof (*x) y; -@end example - -@item -This declares @code{y} as an array of such values. - -@example -typeof (*x) y[4]; -@end example - -@item -This declares @code{y} as an array of pointers to characters: - -@example -typeof (typeof (char *)[4]) y; -@end example - -@noindent -It is equivalent to the following traditional C declaration: - -@example -char *y[4]; -@end example - -To see the meaning of the declaration using @code{typeof}, and why it -might be a useful way to write, let's rewrite it with these macros: - -@example -#define pointer(T) typeof(T *) -#define array(T, N) typeof(T [N]) -@end example - -@noindent -Now the declaration can be rewritten this way: - -@example -array (pointer (char), 4) y; -@end example - -@noindent -Thus, @code{array (pointer (char), 4)} is the type of arrays of 4 -pointers to @code{char}. -@end itemize - -@node Lvalues -@section Generalized Lvalues -@cindex compound expressions as lvalues -@cindex expressions, compound, as lvalues -@cindex conditional expressions as lvalues -@cindex expressions, conditional, as lvalues -@cindex casts as lvalues -@cindex generalized lvalues -@cindex lvalues, generalized -@cindex extensions, @code{?:} -@cindex @code{?:} extensions -Compound expressions, conditional expressions and casts are allowed as -lvalues provided their operands are lvalues. This means that you can take -their addresses or store values into them. - -Standard C++ allows compound expressions and conditional expressions as -lvalues, and permits casts to reference type, so use of this extension -is deprecated for C++ code. - -For example, a compound expression can be assigned, provided the last -expression in the sequence is an lvalue. These two expressions are -equivalent: - -@example -(a, b) += 5 -a, (b += 5) -@end example - -Similarly, the address of the compound expression can be taken. These two -expressions are equivalent: - -@example -&(a, b) -a, &b -@end example - -A conditional expression is a valid lvalue if its type is not void and the -true and false branches are both valid lvalues. For example, these two -expressions are equivalent: - -@example -(a ? b : c) = 5 -(a ? b = 5 : (c = 5)) -@end example - -A cast is a valid lvalue if its operand is an lvalue. A simple -assignment whose left-hand side is a cast works by converting the -right-hand side first to the specified type, then to the type of the -inner left-hand side expression. After this is stored, the value is -converted back to the specified type to become the value of the -assignment. Thus, if @code{a} has type @code{char *}, the following two -expressions are equivalent: - -@example -(int)a = 5 -(int)(a = (char *)(int)5) -@end example - -An assignment-with-arithmetic operation such as @samp{+=} applied to a cast -performs the arithmetic using the type resulting from the cast, and then -continues as in the previous case. Therefore, these two expressions are -equivalent: - -@example -(int)a += 5 -(int)(a = (char *)(int) ((int)a + 5)) -@end example - -You cannot take the address of an lvalue cast, because the use of its -address would not work out coherently. Suppose that @code{&(int)f} were -permitted, where @code{f} has type @code{float}. Then the following -statement would try to store an integer bit-pattern where a floating -point number belongs: - -@example -*&(int)f = 1; -@end example - -This is quite different from what @code{(int)f = 1} would do---that -would convert 1 to floating point and store it. Rather than cause this -inconsistency, we think it is better to prohibit use of @samp{&} on a cast. - -If you really do want an @code{int *} pointer with the address of -@code{f}, you can simply write @code{(int *)&f}. - -@node Conditionals -@section Conditionals with Omitted Operands -@cindex conditional expressions, extensions -@cindex omitted middle-operands -@cindex middle-operands, omitted -@cindex extensions, @code{?:} -@cindex @code{?:} extensions - -The middle operand in a conditional expression may be omitted. Then -if the first operand is nonzero, its value is the value of the conditional -expression. - -Therefore, the expression - -@example -x ? : y -@end example - -@noindent -has the value of @code{x} if that is nonzero; otherwise, the value of -@code{y}. - -This example is perfectly equivalent to - -@example -x ? x : y -@end example - -@cindex side effect in ?: -@cindex ?: side effect -@noindent -In this simple case, the ability to omit the middle operand is not -especially useful. When it becomes useful is when the first operand does, -or may (if it is a macro argument), contain a side effect. Then repeating -the operand in the middle would perform the side effect twice. Omitting -the middle operand uses the value already computed without the undesirable -effects of recomputing it. - -@node Long Long -@section Double-Word Integers -@cindex @code{long long} data types -@cindex double-word arithmetic -@cindex multiprecision arithmetic -@cindex @code{LL} integer suffix -@cindex @code{ULL} integer suffix - -ISO C99 supports data types for integers that are at least 64 bits wide, -and as an extension GCC supports them in C89 mode and in C++. -Simply write @code{long long int} for a signed integer, or -@code{unsigned long long int} for an unsigned integer. To make an -integer constant of type @code{long long int}, add the suffix @code{LL} -to the integer. To make an integer constant of type @code{unsigned long -long int}, add the suffix @code{ULL} to the integer. - -You can use these types in arithmetic like any other integer types. -Addition, subtraction, and bitwise boolean operations on these types -are open-coded on all types of machines. Multiplication is open-coded -if the machine supports fullword-to-doubleword a widening multiply -instruction. Division and shifts are open-coded only on machines that -provide special support. The operations that are not open-coded use -special library routines that come with GNU CC. - -There may be pitfalls when you use @code{long long} types for function -arguments, unless you declare function prototypes. If a function -expects type @code{int} for its argument, and you pass a value of type -@code{long long int}, confusion will result because the caller and the -subroutine will disagree about the number of bytes for the argument. -Likewise, if the function expects @code{long long int} and you pass -@code{int}. The best way to avoid such problems is to use prototypes. - -@node Complex -@section Complex Numbers -@cindex complex numbers -@cindex @code{_Complex} keyword -@cindex @code{__complex__} keyword - -ISO C99 supports complex floating data types, and as an extension GCC -supports them in C89 mode and in C++, and supports complex integer data -types which are not part of ISO C99. You can declare complex types -using the keyword @code{_Complex}. As an extension, the older GNU -keyword @code{__complex__} is also supported. - -For example, @samp{_Complex double x;} declares @code{x} as a -variable whose real part and imaginary part are both of type -@code{double}. @samp{_Complex short int y;} declares @code{y} to -have real and imaginary parts of type @code{short int}; this is not -likely to be useful, but it shows that the set of complex types is -complete. - -To write a constant with a complex data type, use the suffix @samp{i} or -@samp{j} (either one; they are equivalent). For example, @code{2.5fi} -has type @code{_Complex float} and @code{3i} has type -@code{_Complex int}. Such a constant always has a pure imaginary -value, but you can form any complex value you like by adding one to a -real constant. This is a GNU extension; if you have an ISO C99 -conforming C library (such as GNU libc), and want to construct complex -constants of floating type, you should include @code{} and -use the macros @code{I} or @code{_Complex_I} instead. - -@cindex @code{__real__} keyword -@cindex @code{__imag__} keyword -To extract the real part of a complex-valued expression @var{exp}, write -@code{__real__ @var{exp}}. Likewise, use @code{__imag__} to -extract the imaginary part. This is a GNU extension; for values of -floating type, you should use the ISO C99 functions @code{crealf}, -@code{creal}, @code{creall}, @code{cimagf}, @code{cimag} and -@code{cimagl}, declared in @code{} and also provided as -builtin functions by GCC. - -@cindex complex conjugation -The operator @samp{~} performs complex conjugation when used on a value -with a complex type. This is a GNU extension; for values of -floating type, you should use the ISO C99 functions @code{conjf}, -@code{conj} and @code{conjl}, declared in @code{} and also -provided as builtin functions by GCC. - -GNU CC can allocate complex automatic variables in a noncontiguous -fashion; it's even possible for the real part to be in a register while -the imaginary part is on the stack (or vice-versa). None of the -supported debugging info formats has a way to represent noncontiguous -allocation like this, so GNU CC describes a noncontiguous complex -variable as if it were two separate variables of noncomplex type. -If the variable's actual name is @code{foo}, the two fictitious -variables are named @code{foo$real} and @code{foo$imag}. You can -examine and set these two fictitious variables with your debugger. - -A future version of GDB will know how to recognize such pairs and treat -them as a single variable with a complex type. - -@node Hex Floats -@section Hex Floats -@cindex hex floats - -ISO C99 supports floating-point numbers written not only in the usual -decimal notation, such as @code{1.55e1}, but also numbers such as -@code{0x1.fp3} written in hexadecimal format. As a GNU extension, GCC -supports this in C89 mode (except in some cases when strictly -conforming) and in C++. In that format the -@code{0x} hex introducer and the @code{p} or @code{P} exponent field are -mandatory. The exponent is a decimal number that indicates the power of -2 by which the significant part will be multiplied. Thus @code{0x1.f} is -1 15/16, @code{p3} multiplies it by 8, and the value of @code{0x1.fp3} -is the same as @code{1.55e1}. - -Unlike for floating-point numbers in the decimal notation the exponent -is always required in the hexadecimal notation. Otherwise the compiler -would not be able to resolve the ambiguity of, e.g., @code{0x1.f}. This -could mean @code{1.0f} or @code{1.9375} since @code{f} is also the -extension for floating-point constants of type @code{float}. - -@node Zero Length -@section Arrays of Length Zero -@cindex arrays of length zero -@cindex zero-length arrays -@cindex length-zero arrays -@cindex flexible array members - -Zero-length arrays are allowed in GNU C. They are very useful as the -last element of a structure which is really a header for a variable-length -object: - -@example -struct line @{ - int length; - char contents[0]; -@}; - -struct line *thisline = (struct line *) - malloc (sizeof (struct line) + this_length); -thisline->length = this_length; -@end example - -In ISO C89, you would have to give @code{contents} a length of 1, which -means either you waste space or complicate the argument to @code{malloc}. - -In ISO C99, you would use a @dfn{flexible array member}, which is -slightly different in syntax and semantics: - -@itemize @bullet -@item -Flexible array members are written as @code{contents[]} without -the @code{0}. - -@item -Flexible array members have incomplete type, and so the @code{sizeof} -operator may not be applied. As a quirk of the original implementation -of zero-length arrays, @code{sizeof} evaluates to zero. - -@item -Flexible array members may only appear as the last member of a -@code{struct} that is otherwise non-empty. GCC currently allows -zero-length arrays anywhere. You may encounter problems, however, -defining structures containing only a zero-length array. Such usage -is deprecated, and we recommend using zero-length arrays only in -places in which flexible array members would be allowed. -@end itemize - -GCC versions before 3.0 allowed zero-length arrays to be statically -initialized. In addition to those cases that were useful, it also -allowed initializations in situations that would corrupt later data. -Non-empty initialization of zero-length arrays is now deprecated. - -Instead GCC allows static initialization of flexible array members. -This is equivalent to defining a new structure containing the original -structure followed by an array of sufficient size to contain the data. -I.e. in the following, @code{f1} is constructed as if it were declared -like @code{f2}. - -@example -struct f1 @{ - int x; int y[]; -@} f1 = @{ 1, @{ 2, 3, 4 @} @}; - -struct f2 @{ - struct f1 f1; int data[3]; -@} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @}; -@end example - -@noindent -The convenience of this extension is that @code{f1} has the desired -type, eliminating the need to consistently refer to @code{f2.f1}. - -This has symmetry with normal static arrays, in that an array of -unknown size is also written with @code{[]}. - -Of course, this extension only makes sense if the extra data comes at -the end of a top-level object, as otherwise we would be overwriting -data at subsequent offsets. To avoid undue complication and confusion -with initialization of deeply nested arrays, we simply disallow any -non-empty initialization except when the structure is the top-level -object. For example: - -@example -struct foo @{ int x; int y[]; @}; -struct bar @{ struct foo z; @}; - -struct foo a = @{ 1, @{ 2, 3, 4 @} @}; // Legal. -struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // Illegal. -struct bar c = @{ @{ 1, @{ @} @} @}; // Legal. -struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @}; // Illegal. -@end example - -@node Variable Length -@section Arrays of Variable Length -@cindex variable-length arrays -@cindex arrays of variable length -@cindex VLAs - -Variable-length automatic arrays are allowed in ISO C99, and as an -extension GCC accepts them in C89 mode and in C++. (However, GCC's -implementation of variable-length arrays does not yet conform in detail -to the ISO C99 standard.) These arrays are -declared like any other automatic arrays, but with a length that is not -a constant expression. The storage is allocated at the point of -declaration and deallocated when the brace-level is exited. For -example: - -@example -FILE * -concat_fopen (char *s1, char *s2, char *mode) -@{ - char str[strlen (s1) + strlen (s2) + 1]; - strcpy (str, s1); - strcat (str, s2); - return fopen (str, mode); -@} -@end example - -@cindex scope of a variable length array -@cindex variable-length array scope -@cindex deallocating variable length arrays -Jumping or breaking out of the scope of the array name deallocates the -storage. Jumping into the scope is not allowed; you get an error -message for it. - -@cindex @code{alloca} vs variable-length arrays -You can use the function @code{alloca} to get an effect much like -variable-length arrays. The function @code{alloca} is available in -many other C implementations (but not in all). On the other hand, -variable-length arrays are more elegant. - -There are other differences between these two methods. Space allocated -with @code{alloca} exists until the containing @emph{function} returns. -The space for a variable-length array is deallocated as soon as the array -name's scope ends. (If you use both variable-length arrays and -@code{alloca} in the same function, deallocation of a variable-length array -will also deallocate anything more recently allocated with @code{alloca}.) - -You can also use variable-length arrays as arguments to functions: - -@example -struct entry -tester (int len, char data[len][len]) -@{ - @dots{} -@} -@end example - -The length of an array is computed once when the storage is allocated -and is remembered for the scope of the array in case you access it with -@code{sizeof}. - -If you want to pass the array first and the length afterward, you can -use a forward declaration in the parameter list---another GNU extension. - -@example -struct entry -tester (int len; char data[len][len], int len) -@{ - @dots{} -@} -@end example - -@cindex parameter forward declaration -The @samp{int len} before the semicolon is a @dfn{parameter forward -declaration}, and it serves the purpose of making the name @code{len} -known when the declaration of @code{data} is parsed. - -You can write any number of such parameter forward declarations in the -parameter list. They can be separated by commas or semicolons, but the -last one must end with a semicolon, which is followed by the ``real'' -parameter declarations. Each forward declaration must match a ``real'' -declaration in parameter name and data type. ISO C99 does not support -parameter forward declarations. - -@node Variadic Macros -@section Macros with a Variable Number of Arguments. -@cindex variable number of arguments -@cindex macro with variable arguments -@cindex rest argument (in macro) -@cindex variadic macros - -In the ISO C standard of 1999, a macro can be declared to accept a -variable number of arguments much as a function can. The syntax for -defining the macro is similar to that of a function. Here is an -example: - -@example -#define debug(format, ...) fprintf (stderr, format, __VA_ARGS__) -@end example - -Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of -such a macro, it represents the zero or more tokens until the closing -parenthesis that ends the invocation, including any commas. This set of -tokens replaces the identifier @code{__VA_ARGS__} in the macro body -wherever it appears. See the CPP manual for more information. - -GCC has long supported variadic macros, and used a different syntax that -allowed you to give a name to the variable arguments just like any other -argument. Here is an example: - -@example -#define debug(format, args...) fprintf (stderr, format, args) -@end example - -This is in all ways equivalent to the ISO C example above, but arguably -more readable and descriptive. - -GNU CPP has two further variadic macro extensions, and permits them to -be used with either of the above forms of macro definition. - -In standard C, you are not allowed to leave the variable argument out -entirely; but you are allowed to pass an empty argument. For example, -this invocation is invalid in ISO C, because there is no comma after -the string: - -@example -debug ("A message") -@end example - -GNU CPP permits you to completely omit the variable arguments in this -way. In the above examples, the compiler would complain, though since -the expansion of the macro still has the extra comma after the format -string. - -To help solve this problem, CPP behaves specially for variable arguments -used with the token paste operator, @samp{##}. If instead you write - -@example -#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__) -@end example - -and if the variable arguments are omitted or empty, the @samp{##} -operator causes the preprocessor to remove the comma before it. If you -do provide some variable arguments in your macro invocation, GNU CPP -does not complain about the paste operation and instead places the -variable arguments after the comma. Just like any other pasted macro -argument, these arguments are not macro expanded. - -@node Escaped Newlines -@section Slightly Looser Rules for Escaped Newlines -@cindex escaped newlines -@cindex newlines (escaped) - -Recently, the non-traditional preprocessor has relaxed its treatment of -escaped newlines. Previously, the newline had to immediately follow a -backslash. The current implementation allows whitespace in the form of -spaces, horizontal and vertical tabs, and form feeds between the -backslash and the subsequent newline. The preprocessor issues a -warning, but treats it as a valid escaped newline and combines the two -lines to form a single logical line. This works within comments and -tokens, including multi-line strings, as well as between tokens. -Comments are @emph{not} treated as whitespace for the purposes of this -relaxation, since they have not yet been replaced with spaces. - -@node Multi-line Strings -@section String Literals with Embedded Newlines -@cindex multi-line string literals - -As an extension, GNU CPP permits string literals to cross multiple lines -without escaping the embedded newlines. Each embedded newline is -replaced with a single @samp{\n} character in the resulting string -literal, regardless of what form the newline took originally. - -CPP currently allows such strings in directives as well (other than the -@samp{#include} family). This is deprecated and will eventually be -removed. - -@node Subscripting -@section Non-Lvalue Arrays May Have Subscripts -@cindex subscripting -@cindex arrays, non-lvalue - -@cindex subscripting and function values -Subscripting is allowed on arrays that are not lvalues, even though the -unary @samp{&} operator is not. (In ISO C99, both are allowed (though -the array may not be used after the next sequence point), but this ISO -C99 feature is not yet fully supported in GCC.) For example, -this is valid in GNU C though not valid in C89: - -@example -@group -struct foo @{int a[4];@}; - -struct foo f(); - -bar (int index) -@{ - return f().a[index]; -@} -@end group -@end example - -@node Pointer Arith -@section Arithmetic on @code{void}- and Function-Pointers -@cindex void pointers, arithmetic -@cindex void, size of pointer to -@cindex function pointers, arithmetic -@cindex function, size of pointer to - -In GNU C, addition and subtraction operations are supported on pointers to -@code{void} and on pointers to functions. This is done by treating the -size of a @code{void} or of a function as 1. - -A consequence of this is that @code{sizeof} is also allowed on @code{void} -and on function types, and returns 1. - -The option @samp{-Wpointer-arith} requests a warning if these extensions -are used. - -@node Initializers -@section Non-Constant Initializers -@cindex initializers, non-constant -@cindex non-constant initializers - -As in standard C++ and ISO C99, the elements of an aggregate initializer for an -automatic variable are not required to be constant expressions in GNU C. -Here is an example of an initializer with run-time varying elements: - -@example -foo (float f, float g) -@{ - float beat_freqs[2] = @{ f-g, f+g @}; - @dots{} -@} -@end example - -@node Compound Literals -@section Compound Literals -@cindex constructor expressions -@cindex initializations in expressions -@cindex structures, constructor expression -@cindex expressions, constructor -@cindex compound literals -@c The GNU C name for what C99 calls compound literals was "constructor expressions". - -ISO C99 supports compound literals. A compound literal looks like -a cast containing an initializer. Its value is an object of the -type specified in the cast, containing the elements specified in -the initializer. (GCC does not yet implement the full ISO C99 semantics -for compound literals.) As an extension, GCC supports compound literals -in C89 mode and in C++. - -Usually, the specified type is a structure. Assume that -@code{struct foo} and @code{structure} are declared as shown: - -@example -struct foo @{int a; char b[2];@} structure; -@end example - -@noindent -Here is an example of constructing a @code{struct foo} with a compound literal: - -@example -structure = ((struct foo) @{x + y, 'a', 0@}); -@end example - -@noindent -This is equivalent to writing the following: - -@example -@{ - struct foo temp = @{x + y, 'a', 0@}; - structure = temp; -@} -@end example - -You can also construct an array. If all the elements of the compound literal -are (made up of) simple constant expressions, suitable for use in -initializers, then the compound literal is an lvalue and can be coerced to a -pointer to its first element, as shown here: - -@example -char **foo = (char *[]) @{ "x", "y", "z" @}; -@end example - -Array compound literals whose elements are not simple constants are -not very useful, because the compound literal is not an lvalue; ISO C99 -specifies that it is, being a temporary object with automatic storage -duration associated with the enclosing block, but GCC does not yet -implement this. There are currently only two valid ways to use it with -GCC: to subscript it, or initialize -an array variable with it. The former is probably slower than a -@code{switch} statement, while the latter does the same thing an -ordinary C initializer would do. Here is an example of -subscripting an array compound literal: - -@example -output = ((int[]) @{ 2, x, 28 @}) [input]; -@end example - -Compound literals for scalar types and union types are is -also allowed, but then the compound literal is equivalent -to a cast. - -@node Designated Inits -@section Designated Initializers -@cindex initializers with labeled elements -@cindex labeled elements in initializers -@cindex case labels in initializers -@cindex designated initializers - -Standard C89 requires the elements of an initializer to appear in a fixed -order, the same as the order of the elements in the array or structure -being initialized. - -In ISO C99 you can give the elements in any order, specifying the array -indices or structure field names they apply to, and GNU C allows this as -an extension in C89 mode as well. This extension is not -implemented in GNU C++. - -To specify an array index, write -@samp{[@var{index}] =} before the element value. For example, - -@example -int a[6] = @{ [4] = 29, [2] = 15 @}; -@end example - -@noindent -is equivalent to - -@example -int a[6] = @{ 0, 0, 15, 0, 29, 0 @}; -@end example - -@noindent -The index values must be constant expressions, even if the array being -initialized is automatic. - -An alternative syntax for this which has been obsolete since GCC 2.5 but -GCC still accepts is to write @samp{[@var{index}]} before the element -value, with no @samp{=}. - -To initialize a range of elements to the same value, write -@samp{[@var{first} ... @var{last}] = @var{value}}. This is a GNU -extension. For example, - -@example -int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @}; -@end example - -@noindent -If the value in it has side-effects, the side-effects will happen only once, -not for each initialized field by the range initializer. - -@noindent -Note that the length of the array is the highest value specified -plus one. - -In a structure initializer, specify the name of a field to initialize -with @samp{.@var{fieldname} =} before the element value. For example, -given the following structure, - -@example -struct point @{ int x, y; @}; -@end example - -@noindent -the following initialization - -@example -struct point p = @{ .y = yvalue, .x = xvalue @}; -@end example - -@noindent -is equivalent to - -@example -struct point p = @{ xvalue, yvalue @}; -@end example - -Another syntax which has the same meaning, obsolete since GCC 2.5, is -@samp{@var{fieldname}:}, as shown here: - -@example -struct point p = @{ y: yvalue, x: xvalue @}; -@end example - -@cindex designators -The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a -@dfn{designator}. You can also use a designator (or the obsolete colon -syntax) when initializing a union, to specify which element of the union -should be used. For example, - -@example -union foo @{ int i; double d; @}; - -union foo f = @{ .d = 4 @}; -@end example - -@noindent -will convert 4 to a @code{double} to store it in the union using -the second element. By contrast, casting 4 to type @code{union foo} -would store it into the union as the integer @code{i}, since it is -an integer. (@xref{Cast to Union}.) - -You can combine this technique of naming elements with ordinary C -initialization of successive elements. Each initializer element that -does not have a designator applies to the next consecutive element of the -array or structure. For example, - -@example -int a[6] = @{ [1] = v1, v2, [4] = v4 @}; -@end example - -@noindent -is equivalent to - -@example -int a[6] = @{ 0, v1, v2, 0, v4, 0 @}; -@end example - -Labeling the elements of an array initializer is especially useful -when the indices are characters or belong to an @code{enum} type. -For example: - -@example -int whitespace[256] - = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1, - ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @}; -@end example - -@cindex designator lists -You can also write a series of @samp{.@var{fieldname}} and -@samp{[@var{index}]} designators before an @samp{=} to specify a -nested subobject to initialize; the list is taken relative to the -subobject corresponding to the closest surrounding brace pair. For -example, with the @samp{struct point} declaration above: - -@example -struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @}; -@end example - -@noindent -If the same field is initialized multiple times, it will have value from -the last initialization. If any such overridden initialization has -side-effect, it is unspecified whether the side-effect happens or not. -Currently, gcc will discard them and issue a warning. - -@node Case Ranges -@section Case Ranges -@cindex case ranges -@cindex ranges in case statements - -You can specify a range of consecutive values in a single @code{case} label, -like this: - -@example -case @var{low} ... @var{high}: -@end example - -@noindent -This has the same effect as the proper number of individual @code{case} -labels, one for each integer value from @var{low} to @var{high}, inclusive. - -This feature is especially useful for ranges of ASCII character codes: - -@example -case 'A' ... 'Z': -@end example - -@strong{Be careful:} Write spaces around the @code{...}, for otherwise -it may be parsed wrong when you use it with integer values. For example, -write this: - -@example -case 1 ... 5: -@end example - -@noindent -rather than this: - -@example -case 1...5: -@end example - -@node Cast to Union -@section Cast to a Union Type -@cindex cast to a union -@cindex union, casting to a - -A cast to union type is similar to other casts, except that the type -specified is a union type. You can specify the type either with -@code{union @var{tag}} or with a typedef name. A cast to union is actually -a constructor though, not a cast, and hence does not yield an lvalue like -normal casts. (@xref{Compound Literals}.) - -The types that may be cast to the union type are those of the members -of the union. Thus, given the following union and variables: - -@example -union foo @{ int i; double d; @}; -int x; -double y; -@end example - -@noindent -both @code{x} and @code{y} can be cast to type @code{union} foo. - -Using the cast as the right-hand side of an assignment to a variable of -union type is equivalent to storing in a member of the union: - -@example -union foo u; -@dots{} -u = (union foo) x @equiv{} u.i = x -u = (union foo) y @equiv{} u.d = y -@end example - -You can also use the union cast as a function argument: - -@example -void hack (union foo); -@dots{} -hack ((union foo) x); -@end example - -@node Mixed Declarations -@section Mixed Declarations and Code -@cindex mixed declarations and code -@cindex declarations, mixed with code -@cindex code, mixed with declarations - -ISO C99 and ISO C++ allow declarations and code to be freely mixed -within compound statements. As an extension, GCC also allows this in -C89 mode. For example, you could do: - -@example -int i; -@dots{} -i++; -int j = i + 2; -@end example - -Each identifier is visible from where it is declared until the end of -the enclosing block. - -@node Function Attributes -@section Declaring Attributes of Functions -@cindex function attributes -@cindex declaring attributes of functions -@cindex functions that never return -@cindex functions that have no side effects -@cindex functions in arbitrary sections -@cindex functions that behave like malloc -@cindex @code{volatile} applied to function -@cindex @code{const} applied to function -@cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments -@cindex functions that are passed arguments in registers on the 386 -@cindex functions that pop the argument stack on the 386 -@cindex functions that do not pop the argument stack on the 386 - -In GNU C, you declare certain things about functions called in your program -which help the compiler optimize function calls and check your code more -carefully. - -The keyword @code{__attribute__} allows you to specify special -attributes when making a declaration. This keyword is followed by an -attribute specification inside double parentheses. Fourteen attributes, -@code{noreturn}, @code{pure}, @code{const}, @code{format}, -@code{format_arg}, @code{no_instrument_function}, @code{section}, -@code{constructor}, @code{destructor}, @code{unused}, @code{weak}, -@code{malloc}, @code{alias} and @code{no_check_memory_usage} are -currently defined for functions. Several other attributes are defined -for functions on particular target systems. Other attributes, including -@code{section} are supported for variables declarations (@pxref{Variable -Attributes}) and for types (@pxref{Type Attributes}). - -You may also specify attributes with @samp{__} preceding and following -each keyword. This allows you to use them in header files without -being concerned about a possible macro of the same name. For example, -you may use @code{__noreturn__} instead of @code{noreturn}. - -@xref{Attribute Syntax}, for details of the exact syntax for using -attributes. - -@table @code -@cindex @code{noreturn} function attribute -@item noreturn -A few standard library functions, such as @code{abort} and @code{exit}, -cannot return. GNU CC knows this automatically. Some programs define -their own functions that never return. You can declare them -@code{noreturn} to tell the compiler this fact. For example, - -@smallexample -void fatal () __attribute__ ((noreturn)); - -void -fatal (@dots{}) -@{ - @dots{} /* @r{Print error message.} */ @dots{} - exit (1); -@} -@end smallexample - -The @code{noreturn} keyword tells the compiler to assume that -@code{fatal} cannot return. It can then optimize without regard to what -would happen if @code{fatal} ever did return. This makes slightly -better code. More importantly, it helps avoid spurious warnings of -uninitialized variables. - -Do not assume that registers saved by the calling function are -restored before calling the @code{noreturn} function. - -It does not make sense for a @code{noreturn} function to have a return -type other than @code{void}. - -The attribute @code{noreturn} is not implemented in GNU C versions -earlier than 2.5. An alternative way to declare that a function does -not return, which works in the current version and in some older -versions, is as follows: - -@smallexample -typedef void voidfn (); - -volatile voidfn fatal; -@end smallexample - -@cindex @code{pure} function attribute -@item pure -Many functions have no effects except the return value and their -return value depends only on the parameters and/or global variables. -Such a function can be subject -to common subexpression elimination and loop optimization just as an -arithmetic operator would be. These functions should be declared -with the attribute @code{pure}. For example, - -@smallexample -int square (int) __attribute__ ((pure)); -@end smallexample - -@noindent -says that the hypothetical function @code{square} is safe to call -fewer times than the program says. - -Some of common examples of pure functions are @code{strlen} or @code{memcmp}. -Interesting non-pure functions are functions with infinite loops or those -depending on volatile memory or other system resource, that may change between -two consecutive calls (such as @code{feof} in a multithreading environment). - -The attribute @code{pure} is not implemented in GNU C versions earlier -than 2.96. -@cindex @code{const} function attribute -@item const -Many functions do not examine any values except their arguments, and -have no effects except the return value. Basically this is just slightly -more strict class than the "pure" attribute above, since function is not -allowed to read global memory. - -@cindex pointer arguments -Note that a function that has pointer arguments and examines the data -pointed to must @emph{not} be declared @code{const}. Likewise, a -function that calls a non-@code{const} function usually must not be -@code{const}. It does not make sense for a @code{const} function to -return @code{void}. - -The attribute @code{const} is not implemented in GNU C versions earlier -than 2.5. An alternative way to declare that a function has no side -effects, which works in the current version and in some older versions, -is as follows: - -@smallexample -typedef int intfn (); - -extern const intfn square; -@end smallexample - -This approach does not work in GNU C++ from 2.6.0 on, since the language -specifies that the @samp{const} must be attached to the return value. - - -@item format (@var{archetype}, @var{string-index}, @var{first-to-check}) -@cindex @code{format} function attribute -The @code{format} attribute specifies that a function takes @code{printf}, -@code{scanf}, @code{strftime} or @code{strfmon} style arguments which -should be type-checked against a format string. For example, the -declaration: - -@smallexample -extern int -my_printf (void *my_object, const char *my_format, ...) - __attribute__ ((format (printf, 2, 3))); -@end smallexample - -@noindent -causes the compiler to check the arguments in calls to @code{my_printf} -for consistency with the @code{printf} style format string argument -@code{my_format}. - -The parameter @var{archetype} determines how the format string is -interpreted, and should be @code{printf}, @code{scanf}, @code{strftime} -or @code{strfmon}. (You can also use @code{__printf__}, -@code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.) The -parameter @var{string-index} specifies which argument is the format -string argument (starting from 1), while @var{first-to-check} is the -number of the first argument to check against the format string. For -functions where the arguments are not available to be checked (such as -@code{vprintf}), specify the third parameter as zero. In this case the -compiler only checks the format string for consistency. For -@code{strftime} formats, the third parameter is required to be zero. - -In the example above, the format string (@code{my_format}) is the second -argument of the function @code{my_print}, and the arguments to check -start with the third argument, so the correct parameters for the format -attribute are 2 and 3. - -The @code{format} attribute allows you to identify your own functions -which take format strings as arguments, so that GNU CC can check the -calls to these functions for errors. The compiler always (unless -@samp{-ffreestanding} is used) checks formats -for the standard library functions @code{printf}, @code{fprintf}, -@code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime}, -@code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such -warnings are requested (using @samp{-Wformat}), so there is no need to -modify the header file @file{stdio.h}. In C99 mode, the functions -@code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and -@code{vsscanf} are also checked. Except in strictly conforming C -standard modes, the X/Open function @code{strfmon} is also checked. -@xref{C Dialect Options,,Options Controlling C Dialect}. - -@item format_arg (@var{string-index}) -@cindex @code{format_arg} function attribute -The @code{format_arg} attribute specifies that a function takes a format -string for a @code{printf}, @code{scanf}, @code{strftime} or -@code{strfmon} style function and modifies it (for example, to translate -it into another language), so the result can be passed to a -@code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style -function (with the remaining arguments to the format function the same -as they would have been for the unmodified string). For example, the -declaration: - -@smallexample -extern char * -my_dgettext (char *my_domain, const char *my_format) - __attribute__ ((format_arg (2))); -@end smallexample - -@noindent -causes the compiler to check the arguments in calls to a @code{printf}, -@code{scanf}, @code{strftime} or @code{strfmon} type function, whose -format string argument is a call to the @code{my_dgettext} function, for -consistency with the format string argument @code{my_format}. If the -@code{format_arg} attribute had not been specified, all the compiler -could tell in such calls to format functions would be that the format -string argument is not constant; this would generate a warning when -@code{-Wformat-nonliteral} is used, but the calls could not be checked -without the attribute. - -The parameter @var{string-index} specifies which argument is the format -string argument (starting from 1). - -The @code{format-arg} attribute allows you to identify your own -functions which modify format strings, so that GNU CC can check the -calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} -type function whose operands are a call to one of your own function. -The compiler always treats @code{gettext}, @code{dgettext}, and -@code{dcgettext} in this manner except when strict ISO C support is -requested by @samp{-ansi} or an appropriate @samp{-std} option, or -@samp{-ffreestanding} is used. @xref{C Dialect Options,,Options -Controlling C Dialect}. - -@item no_instrument_function -@cindex @code{no_instrument_function} function attribute -If @samp{-finstrument-functions} is given, profiling function calls will -be generated at entry and exit of most user-compiled functions. -Functions with this attribute will not be so instrumented. - -@item section ("section-name") -@cindex @code{section} function attribute -Normally, the compiler places the code it generates in the @code{text} section. -Sometimes, however, you need additional sections, or you need certain -particular functions to appear in special sections. The @code{section} -attribute specifies that a function lives in a particular section. -For example, the declaration: - -@smallexample -extern void foobar (void) __attribute__ ((section ("bar"))); -@end smallexample - -@noindent -puts the function @code{foobar} in the @code{bar} section. - -Some file formats do not support arbitrary sections so the @code{section} -attribute is not available on all platforms. -If you need to map the entire contents of a module to a particular -section, consider using the facilities of the linker instead. - -@item constructor -@itemx destructor -@cindex @code{constructor} function attribute -@cindex @code{destructor} function attribute -The @code{constructor} attribute causes the function to be called -automatically before execution enters @code{main ()}. Similarly, the -@code{destructor} attribute causes the function to be called -automatically after @code{main ()} has completed or @code{exit ()} has -been called. Functions with these attributes are useful for -initializing data that will be used implicitly during the execution of -the program. - -These attributes are not currently implemented for Objective C. - -@item unused -This attribute, attached to a function, means that the function is meant -to be possibly unused. GNU CC will not produce a warning for this -function. GNU C++ does not currently support this attribute as -definitions without parameters are valid in C++. - -@item weak -@cindex @code{weak} attribute -The @code{weak} attribute causes the declaration to be emitted as a weak -symbol rather than a global. This is primarily useful in defining -library functions which can be overridden in user code, though it can -also be used with non-function declarations. Weak symbols are supported -for ELF targets, and also for a.out targets when using the GNU assembler -and linker. - -@item malloc -@cindex @code{malloc} attribute -The @code{malloc} attribute is used to tell the compiler that a function -may be treated as if it were the malloc function. The compiler assumes -that calls to malloc result in a pointers that cannot alias anything. -This will often improve optimization. - -@item alias ("target") -@cindex @code{alias} attribute -The @code{alias} attribute causes the declaration to be emitted as an -alias for another symbol, which must be specified. For instance, - -@smallexample -void __f () @{ /* do something */; @} -void f () __attribute__ ((weak, alias ("__f"))); -@end smallexample - -declares @samp{f} to be a weak alias for @samp{__f}. In C++, the -mangled name for the target must be used. - -Not all target machines support this attribute. - -@item no_check_memory_usage -@cindex @code{no_check_memory_usage} function attribute -The @code{no_check_memory_usage} attribute causes GNU CC to omit checks -of memory references when it generates code for that function. Normally -if you specify @samp{-fcheck-memory-usage} (see @pxref{Code Gen -Options}), GNU CC generates calls to support routines before most memory -accesses to permit support code to record usage and detect uses of -uninitialized or unallocated storage. Since GNU CC cannot handle -@code{asm} statements properly they are not allowed in such functions. -If you declare a function with this attribute, GNU CC will not generate -memory checking code for that function, permitting the use of @code{asm} -statements without having to compile that function with different -options. This also allows you to write support routines of your own if -you wish, without getting infinite recursion if they get compiled with -@code{-fcheck-memory-usage}. - -@item regparm (@var{number}) -@cindex functions that are passed arguments in registers on the 386 -On the Intel 386, the @code{regparm} attribute causes the compiler to -pass up to @var{number} integer arguments in registers @var{EAX}, -@var{EDX}, and @var{ECX} instead of on the stack. Functions that take a -variable number of arguments will continue to be passed all of their -arguments on the stack. - -@item stdcall -@cindex functions that pop the argument stack on the 386 -On the Intel 386, the @code{stdcall} attribute causes the compiler to -assume that the called function will pop off the stack space used to -pass arguments, unless it takes a variable number of arguments. - -The PowerPC compiler for Windows NT currently ignores the @code{stdcall} -attribute. - -@item cdecl -@cindex functions that do pop the argument stack on the 386 -On the Intel 386, the @code{cdecl} attribute causes the compiler to -assume that the calling function will pop off the stack space used to -pass arguments. This is -useful to override the effects of the @samp{-mrtd} switch. - -The PowerPC compiler for Windows NT currently ignores the @code{cdecl} -attribute. - -@item longcall -@cindex functions called via pointer on the RS/6000 and PowerPC -On the RS/6000 and PowerPC, the @code{longcall} attribute causes the -compiler to always call the function via a pointer, so that functions -which reside further than 64 megabytes (67,108,864 bytes) from the -current location can be called. - -@item long_call/short_call -@cindex indirect calls on ARM -This attribute allows to specify how to call a particular function on -ARM. Both attributes override the @code{-mlong-calls} (@pxref{ARM Options}) -command line switch and @code{#pragma long_calls} settings. The -@code{long_call} attribute causes the compiler to always call the -function by first loading its address into a register and then using the -contents of that register. The @code{short_call} attribute always places -the offset to the function from the call site into the @samp{BL} -instruction directly. - -@item dllimport -@cindex functions which are imported from a dll on PowerPC Windows NT -On the PowerPC running Windows NT, the @code{dllimport} attribute causes -the compiler to call the function via a global pointer to the function -pointer that is set up by the Windows NT dll library. The pointer name -is formed by combining @code{__imp_} and the function name. - -@item dllexport -@cindex functions which are exported from a dll on PowerPC Windows NT -On the PowerPC running Windows NT, the @code{dllexport} attribute causes -the compiler to provide a global pointer to the function pointer, so -that it can be called with the @code{dllimport} attribute. The pointer -name is formed by combining @code{__imp_} and the function name. - -@item exception (@var{except-func} [, @var{except-arg}]) -@cindex functions which specify exception handling on PowerPC Windows NT -On the PowerPC running Windows NT, the @code{exception} attribute causes -the compiler to modify the structured exception table entry it emits for -the declared function. The string or identifier @var{except-func} is -placed in the third entry of the structured exception table. It -represents a function, which is called by the exception handling -mechanism if an exception occurs. If it was specified, the string or -identifier @var{except-arg} is placed in the fourth entry of the -structured exception table. - -@item function_vector -@cindex calling functions through the function vector on the H8/300 processors -Use this option on the H8/300 and H8/300H to indicate that the specified -function should be called through the function vector. Calling a -function through the function vector will reduce code size, however; -the function vector has a limited size (maximum 128 entries on the H8/300 -and 64 entries on the H8/300H) and shares space with the interrupt vector. - -You must use GAS and GLD from GNU binutils version 2.7 or later for -this option to work correctly. - -@item interrupt_handler -@cindex interrupt handler functions on the H8/300 processors -Use this option on the H8/300 and H8/300H to indicate that the specified -function is an interrupt handler. The compiler will generate function -entry and exit sequences suitable for use in an interrupt handler when this -attribute is present. - -@item interrupt -@cindex interrupt handler functions -Use this option on the ARM, AVR and M32R/D ports to indicate that the -specified function is an interrupt handler. The compiler will generate -function entry and exit sequences suitable for use in an interrupt -handler when this attribute is present. - -Note, interrupt handlers for the H8/300 and H8/300H processors can be -specified via the @code{interrupt_handler} attribute. - -Note, on the AVR interrupts will be enabled inside the function. - -Note, for the ARM you can specify the kind of interrupt to be handled by -adding an optional parameter to the interrupt attribute like this: - -@smallexample -void f () __attribute__ ((interrupt ("IRQ"))); -@end smallexample - -Permissible values for this parameter are: IRQ, FIQ, SWI, ABORT and UNDEF. - -@item eightbit_data -@cindex eight bit data on the H8/300 and H8/300H -Use this option on the H8/300 and H8/300H to indicate that the specified -variable should be placed into the eight bit data section. -The compiler will generate more efficient code for certain operations -on data in the eight bit data area. Note the eight bit data area is limited to -256 bytes of data. - -You must use GAS and GLD from GNU binutils version 2.7 or later for -this option to work correctly. - -@item tiny_data -@cindex tiny data section on the H8/300H -Use this option on the H8/300H to indicate that the specified -variable should be placed into the tiny data section. -The compiler will generate more efficient code for loads and stores -on data in the tiny data section. Note the tiny data area is limited to -slightly under 32kbytes of data. - -@item signal -@cindex signal handler functions on the AVR processors -Use this option on the AVR to indicate that the specified -function is an signal handler. The compiler will generate function -entry and exit sequences suitable for use in an signal handler when this -attribute is present. Interrupts will be disabled inside function. - -@item naked -@cindex function without a prologue/epilogue code -Use this option on the ARM or AVR ports to indicate that the specified -function do not need prologue/epilogue sequences generated by the -compiler. It is up to the programmer to provide these sequences. - -@item model (@var{model-name}) -@cindex function addressability on the M32R/D -Use this attribute on the M32R/D to set the addressability of an object, -and the code generated for a function. -The identifier @var{model-name} is one of @code{small}, @code{medium}, -or @code{large}, representing each of the code models. - -Small model objects live in the lower 16MB of memory (so that their -addresses can be loaded with the @code{ld24} instruction), and are -callable with the @code{bl} instruction. - -Medium model objects may live anywhere in the 32-bit address space (the -compiler will generate @code{seth/add3} instructions to load their addresses), -and are callable with the @code{bl} instruction. - -Large model objects may live anywhere in the 32-bit address space (the -compiler will generate @code{seth/add3} instructions to load their addresses), -and may not be reachable with the @code{bl} instruction (the compiler will -generate the much slower @code{seth/add3/jl} instruction sequence). - -@end table - -You can specify multiple attributes in a declaration by separating them -by commas within the double parentheses or by immediately following an -attribute declaration with another attribute declaration. - -@cindex @code{#pragma}, reason for not using -@cindex pragma, reason for not using -Some people object to the @code{__attribute__} feature, suggesting that -ISO C's @code{#pragma} should be used instead. At the time -@code{__attribute__} was designed, there were two reasons for not doing -this. - -@enumerate -@item -It is impossible to generate @code{#pragma} commands from a macro. - -@item -There is no telling what the same @code{#pragma} might mean in another -compiler. -@end enumerate - -These two reasons applied to almost any application that might have been -proposed for @code{#pragma}. It was basically a mistake to use -@code{#pragma} for @emph{anything}. - -The ISO C99 standard includes @code{_Pragma}, which now allows pragmas -to be generated from macros. In addition, a @code{#pragma GCC} -namespace is now in use for GCC-specific pragmas. However, it has been -found convenient to use @code{__attribute__} to achieve a natural -attachment of attributes to their corresponding declarations, whereas -@code{#pragma GCC} is of use for constructs that do not naturally form -part of the grammar. @xref{Other Directives,,Miscellaneous -Preprocessing Directives, cpp, The C Preprocessor}. - -@node Attribute Syntax -@section Attribute Syntax -@cindex attribute syntax - -This section describes the syntax with which @code{__attribute__} may be -used, and the constructs to which attribute specifiers bind, for the C -language. Some details may vary for C++ and Objective C. Because of -infelicities in the grammar for attributes, some forms described here -may not be successfully parsed in all cases. - -@xref{Function Attributes}, for details of the semantics of attributes -applying to functions. @xref{Variable Attributes}, for details of the -semantics of attributes applying to variables. @xref{Type Attributes}, -for details of the semantics of attributes applying to structure, union -and enumerated types. - -An @dfn{attribute specifier} is of the form -@code{__attribute__ ((@var{attribute-list}))}. An @dfn{attribute list} -is a possibly empty comma-separated sequence of @dfn{attributes}, where -each attribute is one of the following: - -@itemize @bullet -@item -Empty. Empty attributes are ignored. - -@item -A word (which may be an identifier such as @code{unused}, or a reserved -word such as @code{const}). - -@item -A word, followed by, in parentheses, parameters for the attribute. -These parameters take one of the following forms: - -@itemize @bullet -@item -An identifier. For example, @code{mode} attributes use this form. - -@item -An identifier followed by a comma and a non-empty comma-separated list -of expressions. For example, @code{format} attributes use this form. - -@item -A possibly empty comma-separated list of expressions. For example, -@code{format_arg} attributes use this form with the list being a single -integer constant expression, and @code{alias} attributes use this form -with the list being a single string constant. -@end itemize -@end itemize - -An @dfn{attribute specifier list} is a sequence of one or more attribute -specifiers, not separated by any other tokens. - -An attribute specifier list may appear after the colon following a -label, other than a @code{case} or @code{default} label. The only -attribute it makes sense to use after a label is @code{unused}. This -feature is intended for code generated by programs which contains labels -that may be unused but which is compiled with @option{-Wall}. It would -not normally be appropriate to use in it human-written code, though it -could be useful in cases where the code that jumps to the label is -contained within an @code{#ifdef} conditional. - -An attribute specifier list may appear as part of a @code{struct}, -@code{union} or @code{enum} specifier. It may go either immediately -after the @code{struct}, @code{union} or @code{enum} keyword, or after -the closing brace. It is ignored if the content of the structure, union -or enumerated type is not defined in the specifier in which the -attribute specifier list is used---that is, in usages such as -@code{struct __attribute__((foo)) bar} with no following opening brace. -Where attribute specifiers follow the closing brace, they are considered -to relate to the structure, union or enumerated type defined, not to any -enclosing declaration the type specifier appears in, and the type -defined is not complete until after the attribute specifiers. -@c Otherwise, there would be the following problems: a shift/reduce -@c conflict between attributes binding the the struct/union/enum and -@c binding to the list of specifiers/qualifiers; and "aligned" -@c attributes could use sizeof for the structure, but the size could be -@c changed later by "packed" attributes. - -Otherwise, an attribute specifier appears as part of a declaration, -counting declarations of unnamed parameters and type names, and relates -to that declaration (which may be nested in another declaration, for -example in the case of a parameter declaration). In future, attribute -specifiers in some places may however apply to a particular declarator -within a declaration instead; these cases are noted below. Where an -attribute specifier is applied to a parameter declared as a function or -an array, it should apply to the function or array rather than the -pointer to which the parameter is implicitly converted, but this is not -yet correctly implemented. - -Any list of specifiers and qualifiers at the start of a declaration may -contain attribute specifiers, whether or not such a list may in that -context contain storage class specifiers. (Some attributes, however, -are essentially in the nature of storage class specifiers, and only make -sense where storage class specifiers may be used; for example, -@code{section}.) There is one necessary limitation to this syntax: the -first old-style parameter declaration in a function definition cannot -begin with an attribute specifier, because such an attribute applies to -the function instead by syntax described below (which, however, is not -yet implemented in this case). In some other cases, attribute -specifiers are permitted by this grammar but not yet supported by the -compiler. All attribute specifiers in this place relate to the -declaration as a whole. In the obsolencent usage where a type of -@code{int} is implied by the absence of type specifiers, such a list of -specifiers and qualifiers may be an attribute specifier list with no -other specifiers or qualifiers. - -An attribute specifier list may appear immediately before a declarator -(other than the first) in a comma-separated list of declarators in a -declaration of more than one identifier using a single list of -specifiers and qualifiers. At present, such attribute specifiers apply -not only to the identifier before whose declarator they appear, but to -all subsequent identifiers declared in that declaration, but in future -they may apply only to that single identifier. For example, in -@code{__attribute__((noreturn)) void d0 (void), -__attribute__((format(printf, 1, 2))) d1 (const char *, ...), d2 -(void)}, the @code{noreturn} attribute applies to all the functions -declared; the @code{format} attribute should only apply to @code{d1}, -but at present applies to @code{d2} as well (and so causes an error). - -An attribute specifier list may appear immediately before the comma, -@code{=} or semicolon terminating the declaration of an identifier other -than a function definition. At present, such attribute specifiers apply -to the declared object or function, but in future they may attach to the -outermost adjacent declarator. In simple cases there is no difference, -but, for example, in @code{void (****f)(void) -__attribute__((noreturn));}, at present the @code{noreturn} attribute -applies to @code{f}, which causes a warning since @code{f} is not a -function, but in future it may apply to the function @code{****f}. The -precise semantics of what attributes in such cases will apply to are not -yet specified. Where an assembler name for an object or function is -specified (@pxref{Asm Labels}), at present the attribute must follow the -@code{asm} specification; in future, attributes before the @code{asm} -specification may apply to the adjacent declarator, and those after it -to the declared object or function. - -An attribute specifier list may, in future, be permitted to appear after -the declarator in a function definition (before any old-style parameter -declarations or the function body). - -Attribute specifiers may be mixed with type qualifiers appearing inside -the @code{[]} of a parameter array declarator, in the C99 construct by -which such qualifiers are applied to the pointer to which the array is -implicitly converted. Such attribute specifiers apply to the pointer, -not to the array, but at present this is not implemented and they are -ignored. - -An attribute specifier list may appear at the start of a nested -declarator. At present, there are some limitations in this usage: the -attributes apply to the identifer declared, and to all subsequent -identifiers declared in that declaration (if it includes a -comma-separated list of declarators), rather than to a specific -declarator. When attribute specifiers follow the @code{*} of a pointer -declarator, they must presently follow any type qualifiers present, and -cannot be mixed with them. The following describes intended future -semantics which make this syntax more useful only. It will make the -most sense if you are familiar with the formal specification of -declarators in the ISO C standard. - -Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T -D1}, where @code{T} contains declaration specifiers that specify a type -@var{Type} (such as @code{int}) and @code{D1} is a declarator that -contains an identifier @var{ident}. The type specified for @var{ident} -for derived declarators whose type does not include an attribute -specifier is as in the ISO C standard. - -If @code{D1} has the form @code{( @var{attribute-specifier-list} D )}, -and the declaration @code{T D} specifies the type -``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then -@code{T D1} specifies the type ``@var{derived-declarator-type-list} -@var{attribute-specifier-list} @var{Type}'' for @var{ident}. - -If @code{D1} has the form @code{* -@var{type-qualifier-and-attribute-specifier-list} D}, and the -declaration @code{T D} specifies the type -``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then -@code{T D1} specifies the type ``@var{derived-declarator-type-list} -@var{type-qualifier-and-attribute-specifier-list} @var{Type}'' for -@var{ident}. - -For example, @code{void (__attribute__((noreturn)) ****f)();} specifies -the type ``pointer to pointer to pointer to pointer to non-returning -function returning @code{void}''. As another example, @code{char -*__attribute__((aligned(8))) *f;} specifies the type ``pointer to -8-byte-aligned pointer to @code{char}''. Note again that this describes -intended future semantics, not current implementation. - -@node Function Prototypes -@section Prototypes and Old-Style Function Definitions -@cindex function prototype declarations -@cindex old-style function definitions -@cindex promotion of formal parameters - -GNU C extends ISO C to allow a function prototype to override a later -old-style non-prototype definition. Consider the following example: - -@example -/* @r{Use prototypes unless the compiler is old-fashioned.} */ -#ifdef __STDC__ -#define P(x) x -#else -#define P(x) () -#endif - -/* @r{Prototype function declaration.} */ -int isroot P((uid_t)); - -/* @r{Old-style function definition.} */ -int -isroot (x) /* ??? lossage here ??? */ - uid_t x; -@{ - return x == 0; -@} -@end example - -Suppose the type @code{uid_t} happens to be @code{short}. ISO C does -not allow this example, because subword arguments in old-style -non-prototype definitions are promoted. Therefore in this example the -function definition's argument is really an @code{int}, which does not -match the prototype argument type of @code{short}. - -This restriction of ISO C makes it hard to write code that is portable -to traditional C compilers, because the programmer does not know -whether the @code{uid_t} type is @code{short}, @code{int}, or -@code{long}. Therefore, in cases like these GNU C allows a prototype -to override a later old-style definition. More precisely, in GNU C, a -function prototype argument type overrides the argument type specified -by a later old-style definition if the former type is the same as the -latter type before promotion. Thus in GNU C the above example is -equivalent to the following: - -@example -int isroot (uid_t); - -int -isroot (uid_t x) -@{ - return x == 0; -@} -@end example - -GNU C++ does not support old-style function definitions, so this -extension is irrelevant. - -@node C++ Comments -@section C++ Style Comments -@cindex // -@cindex C++ comments -@cindex comments, C++ style - -In GNU C, you may use C++ style comments, which start with @samp{//} and -continue until the end of the line. Many other C implementations allow -such comments, and they are likely to be in a future C standard. -However, C++ style comments are not recognized if you specify -@w{@samp{-ansi}}, a @option{-std} option specifying a version of ISO C -before C99, or @w{@samp{-traditional}}, since they are incompatible -with traditional constructs like @code{dividend//*comment*/divisor}. - -@node Dollar Signs -@section Dollar Signs in Identifier Names -@cindex $ -@cindex dollar signs in identifier names -@cindex identifier names, dollar signs in - -In GNU C, you may normally use dollar signs in identifier names. -This is because many traditional C implementations allow such identifiers. -However, dollar signs in identifiers are not supported on a few target -machines, typically because the target assembler does not allow them. - -@node Character Escapes -@section The Character @key{ESC} in Constants - -You can use the sequence @samp{\e} in a string or character constant to -stand for the ASCII character @key{ESC}. - -@node Alignment -@section Inquiring on Alignment of Types or Variables -@cindex alignment -@cindex type alignment -@cindex variable alignment - -The keyword @code{__alignof__} allows you to inquire about how an object -is aligned, or the minimum alignment usually required by a type. Its -syntax is just like @code{sizeof}. - -For example, if the target machine requires a @code{double} value to be -aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8. -This is true on many RISC machines. On more traditional machine -designs, @code{__alignof__ (double)} is 4 or even 2. - -Some machines never actually require alignment; they allow reference to any -data type even at an odd addresses. For these machines, @code{__alignof__} -reports the @emph{recommended} alignment of a type. - -When the operand of @code{__alignof__} is an lvalue rather than a type, the -value is the largest alignment that the lvalue is known to have. It may -have this alignment as a result of its data type, or because it is part of -a structure and inherits alignment from that structure. For example, after -this declaration: - -@example -struct foo @{ int x; char y; @} foo1; -@end example - -@noindent -the value of @code{__alignof__ (foo1.y)} is probably 2 or 4, the same as -@code{__alignof__ (int)}, even though the data type of @code{foo1.y} -does not itself demand any alignment.@refill - -It is an error to ask for the alignment of an incomplete type. - -A related feature which lets you specify the alignment of an object is -@code{__attribute__ ((aligned (@var{alignment})))}; see the following -section. - -@node Variable Attributes -@section Specifying Attributes of Variables -@cindex attribute of variables -@cindex variable attributes - -The keyword @code{__attribute__} allows you to specify special -attributes of variables or structure fields. This keyword is followed -by an attribute specification inside double parentheses. Eight -attributes are currently defined for variables: @code{aligned}, -@code{mode}, @code{nocommon}, @code{packed}, @code{section}, -@code{transparent_union}, @code{unused}, and @code{weak}. Some other -attributes are defined for variables on particular target systems. Other -attributes are available for functions (@pxref{Function Attributes}) and -for types (@pxref{Type Attributes}). Other front-ends might define more -attributes (@pxref{C++ Extensions,,Extensions to the C++ Language}). - -You may also specify attributes with @samp{__} preceding and following -each keyword. This allows you to use them in header files without -being concerned about a possible macro of the same name. For example, -you may use @code{__aligned__} instead of @code{aligned}. - -@xref{Attribute Syntax}, for details of the exact syntax for using -attributes. - -@table @code -@cindex @code{aligned} attribute -@item aligned (@var{alignment}) -This attribute specifies a minimum alignment for the variable or -structure field, measured in bytes. For example, the declaration: - -@smallexample -int x __attribute__ ((aligned (16))) = 0; -@end smallexample - -@noindent -causes the compiler to allocate the global variable @code{x} on a -16-byte boundary. On a 68040, this could be used in conjunction with -an @code{asm} expression to access the @code{move16} instruction which -requires 16-byte aligned operands. - -You can also specify the alignment of structure fields. For example, to -create a double-word aligned @code{int} pair, you could write: - -@smallexample -struct foo @{ int x[2] __attribute__ ((aligned (8))); @}; -@end smallexample - -@noindent -This is an alternative to creating a union with a @code{double} member -that forces the union to be double-word aligned. - -It is not possible to specify the alignment of functions; the alignment -of functions is determined by the machine's requirements and cannot be -changed. You cannot specify alignment for a typedef name because such a -name is just an alias, not a distinct type. - -As in the preceding examples, you can explicitly specify the alignment -(in bytes) that you wish the compiler to use for a given variable or -structure field. Alternatively, you can leave out the alignment factor -and just ask the compiler to align a variable or field to the maximum -useful alignment for the target machine you are compiling for. For -example, you could write: - -@smallexample -short array[3] __attribute__ ((aligned)); -@end smallexample - -Whenever you leave out the alignment factor in an @code{aligned} attribute -specification, the compiler automatically sets the alignment for the declared -variable or field to the largest alignment which is ever used for any data -type on the target machine you are compiling for. Doing this can often make -copy operations more efficient, because the compiler can use whatever -instructions copy the biggest chunks of memory when performing copies to -or from the variables or fields that you have aligned this way. - -The @code{aligned} attribute can only increase the alignment; but you -can decrease it by specifying @code{packed} as well. See below. - -Note that the effectiveness of @code{aligned} attributes may be limited -by inherent limitations in your linker. On many systems, the linker is -only able to arrange for variables to be aligned up to a certain maximum -alignment. (For some linkers, the maximum supported alignment may -be very very small.) If your linker is only able to align variables -up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} -in an @code{__attribute__} will still only provide you with 8 byte -alignment. See your linker documentation for further information. - -@item mode (@var{mode}) -@cindex @code{mode} attribute -This attribute specifies the data type for the declaration---whichever -type corresponds to the mode @var{mode}. This in effect lets you -request an integer or floating point type according to its width. - -You may also specify a mode of @samp{byte} or @samp{__byte__} to -indicate the mode corresponding to a one-byte integer, @samp{word} or -@samp{__word__} for the mode of a one-word integer, and @samp{pointer} -or @samp{__pointer__} for the mode used to represent pointers. - -@item nocommon -@cindex @code{nocommon} attribute -This attribute specifies requests GNU CC not to place a variable -``common'' but instead to allocate space for it directly. If you -specify the @samp{-fno-common} flag, GNU CC will do this for all -variables. - -Specifying the @code{nocommon} attribute for a variable provides an -initialization of zeros. A variable may only be initialized in one -source file. - -@item packed -@cindex @code{packed} attribute -The @code{packed} attribute specifies that a variable or structure field -should have the smallest possible alignment---one byte for a variable, -and one bit for a field, unless you specify a larger value with the -@code{aligned} attribute. - -Here is a structure in which the field @code{x} is packed, so that it -immediately follows @code{a}: - -@example -struct foo -@{ - char a; - int x[2] __attribute__ ((packed)); -@}; -@end example - -@item section ("section-name") -@cindex @code{section} variable attribute -Normally, the compiler places the objects it generates in sections like -@code{data} and @code{bss}. Sometimes, however, you need additional sections, -or you need certain particular variables to appear in special sections, -for example to map to special hardware. The @code{section} -attribute specifies that a variable (or function) lives in a particular -section. For example, this small program uses several specific section names: - -@smallexample -struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @}; -struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @}; -char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @}; -int init_data __attribute__ ((section ("INITDATA"))) = 0; - -main() -@{ - /* Initialize stack pointer */ - init_sp (stack + sizeof (stack)); - - /* Initialize initialized data */ - memcpy (&init_data, &data, &edata - &data); - - /* Turn on the serial ports */ - init_duart (&a); - init_duart (&b); -@} -@end smallexample - -@noindent -Use the @code{section} attribute with an @emph{initialized} definition -of a @emph{global} variable, as shown in the example. GNU CC issues -a warning and otherwise ignores the @code{section} attribute in -uninitialized variable declarations. - -You may only use the @code{section} attribute with a fully initialized -global definition because of the way linkers work. The linker requires -each object be defined once, with the exception that uninitialized -variables tentatively go in the @code{common} (or @code{bss}) section -and can be multiply "defined". You can force a variable to be -initialized with the @samp{-fno-common} flag or the @code{nocommon} -attribute. - -Some file formats do not support arbitrary sections so the @code{section} -attribute is not available on all platforms. -If you need to map the entire contents of a module to a particular -section, consider using the facilities of the linker instead. - -@item shared -@cindex @code{shared} variable attribute -On Windows NT, in addition to putting variable definitions in a named -section, the section can also be shared among all running copies of an -executable or DLL. For example, this small program defines shared data -by putting it in a named section "shared" and marking the section -shareable: - -@smallexample -int foo __attribute__((section ("shared"), shared)) = 0; - -int -main() -@{ - /* Read and write foo. All running - copies see the same value. */ - return 0; -@} -@end smallexample - -@noindent -You may only use the @code{shared} attribute along with @code{section} -attribute with a fully initialized global definition because of the way -linkers work. See @code{section} attribute for more information. - -The @code{shared} attribute is only available on Windows NT. - -@item transparent_union -This attribute, attached to a function parameter which is a union, means -that the corresponding argument may have the type of any union member, -but the argument is passed as if its type were that of the first union -member. For more details see @xref{Type Attributes}. You can also use -this attribute on a @code{typedef} for a union data type; then it -applies to all function parameters with that type. - -@item unused -This attribute, attached to a variable, means that the variable is meant -to be possibly unused. GNU CC will not produce a warning for this -variable. - -@item weak -The @code{weak} attribute is described in @xref{Function Attributes}. - -@item model (@var{model-name}) -@cindex variable addressability on the M32R/D -Use this attribute on the M32R/D to set the addressability of an object. -The identifier @var{model-name} is one of @code{small}, @code{medium}, -or @code{large}, representing each of the code models. - -Small model objects live in the lower 16MB of memory (so that their -addresses can be loaded with the @code{ld24} instruction). - -Medium and large model objects may live anywhere in the 32-bit address space -(the compiler will generate @code{seth/add3} instructions to load their -addresses). - -@end table - -To specify multiple attributes, separate them by commas within the -double parentheses: for example, @samp{__attribute__ ((aligned (16), -packed))}. - -@node Type Attributes -@section Specifying Attributes of Types -@cindex attribute of types -@cindex type attributes - -The keyword @code{__attribute__} allows you to specify special -attributes of @code{struct} and @code{union} types when you define such -types. This keyword is followed by an attribute specification inside -double parentheses. Four attributes are currently defined for types: -@code{aligned}, @code{packed}, @code{transparent_union}, and @code{unused}. -Other attributes are defined for functions (@pxref{Function Attributes}) and -for variables (@pxref{Variable Attributes}). - -You may also specify any one of these attributes with @samp{__} -preceding and following its keyword. This allows you to use these -attributes in header files without being concerned about a possible -macro of the same name. For example, you may use @code{__aligned__} -instead of @code{aligned}. - -You may specify the @code{aligned} and @code{transparent_union} -attributes either in a @code{typedef} declaration or just past the -closing curly brace of a complete enum, struct or union type -@emph{definition} and the @code{packed} attribute only past the closing -brace of a definition. - -You may also specify attributes between the enum, struct or union -tag and the name of the type rather than after the closing brace. - -@xref{Attribute Syntax}, for details of the exact syntax for using -attributes. - -@table @code -@cindex @code{aligned} attribute -@item aligned (@var{alignment}) -This attribute specifies a minimum alignment (in bytes) for variables -of the specified type. For example, the declarations: - -@smallexample -struct S @{ short f[3]; @} __attribute__ ((aligned (8))); -typedef int more_aligned_int __attribute__ ((aligned (8))); -@end smallexample - -@noindent -force the compiler to insure (as far as it can) that each variable whose -type is @code{struct S} or @code{more_aligned_int} will be allocated and -aligned @emph{at least} on a 8-byte boundary. On a Sparc, having all -variables of type @code{struct S} aligned to 8-byte boundaries allows -the compiler to use the @code{ldd} and @code{std} (doubleword load and -store) instructions when copying one variable of type @code{struct S} to -another, thus improving run-time efficiency. - -Note that the alignment of any given @code{struct} or @code{union} type -is required by the ISO C standard to be at least a perfect multiple of -the lowest common multiple of the alignments of all of the members of -the @code{struct} or @code{union} in question. This means that you @emph{can} -effectively adjust the alignment of a @code{struct} or @code{union} -type by attaching an @code{aligned} attribute to any one of the members -of such a type, but the notation illustrated in the example above is a -more obvious, intuitive, and readable way to request the compiler to -adjust the alignment of an entire @code{struct} or @code{union} type. - -As in the preceding example, you can explicitly specify the alignment -(in bytes) that you wish the compiler to use for a given @code{struct} -or @code{union} type. Alternatively, you can leave out the alignment factor -and just ask the compiler to align a type to the maximum -useful alignment for the target machine you are compiling for. For -example, you could write: - -@smallexample -struct S @{ short f[3]; @} __attribute__ ((aligned)); -@end smallexample - -Whenever you leave out the alignment factor in an @code{aligned} -attribute specification, the compiler automatically sets the alignment -for the type to the largest alignment which is ever used for any data -type on the target machine you are compiling for. Doing this can often -make copy operations more efficient, because the compiler can use -whatever instructions copy the biggest chunks of memory when performing -copies to or from the variables which have types that you have aligned -this way. - -In the example above, if the size of each @code{short} is 2 bytes, then -the size of the entire @code{struct S} type is 6 bytes. The smallest -power of two which is greater than or equal to that is 8, so the -compiler sets the alignment for the entire @code{struct S} type to 8 -bytes. - -Note that although you can ask the compiler to select a time-efficient -alignment for a given type and then declare only individual stand-alone -objects of that type, the compiler's ability to select a time-efficient -alignment is primarily useful only when you plan to create arrays of -variables having the relevant (efficiently aligned) type. If you -declare or use arrays of variables of an efficiently-aligned type, then -it is likely that your program will also be doing pointer arithmetic (or -subscripting, which amounts to the same thing) on pointers to the -relevant type, and the code that the compiler generates for these -pointer arithmetic operations will often be more efficient for -efficiently-aligned types than for other types. - -The @code{aligned} attribute can only increase the alignment; but you -can decrease it by specifying @code{packed} as well. See below. - -Note that the effectiveness of @code{aligned} attributes may be limited -by inherent limitations in your linker. On many systems, the linker is -only able to arrange for variables to be aligned up to a certain maximum -alignment. (For some linkers, the maximum supported alignment may -be very very small.) If your linker is only able to align variables -up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} -in an @code{__attribute__} will still only provide you with 8 byte -alignment. See your linker documentation for further information. - -@item packed -This attribute, attached to an @code{enum}, @code{struct}, or -@code{union} type definition, specified that the minimum required memory -be used to represent the type. - -Specifying this attribute for @code{struct} and @code{union} types is -equivalent to specifying the @code{packed} attribute on each of the -structure or union members. Specifying the @samp{-fshort-enums} -flag on the line is equivalent to specifying the @code{packed} -attribute on all @code{enum} definitions. - -You may only specify this attribute after a closing curly brace on an -@code{enum} definition, not in a @code{typedef} declaration, unless that -declaration also contains the definition of the @code{enum}. - -@item transparent_union -This attribute, attached to a @code{union} type definition, indicates -that any function parameter having that union type causes calls to that -function to be treated in a special way. - -First, the argument corresponding to a transparent union type can be of -any type in the union; no cast is required. Also, if the union contains -a pointer type, the corresponding argument can be a null pointer -constant or a void pointer expression; and if the union contains a void -pointer type, the corresponding argument can be any pointer expression. -If the union member type is a pointer, qualifiers like @code{const} on -the referenced type must be respected, just as with normal pointer -conversions. - -Second, the argument is passed to the function using the calling -conventions of first member of the transparent union, not the calling -conventions of the union itself. All members of the union must have the -same machine representation; this is necessary for this argument passing -to work properly. - -Transparent unions are designed for library functions that have multiple -interfaces for compatibility reasons. For example, suppose the -@code{wait} function must accept either a value of type @code{int *} to -comply with Posix, or a value of type @code{union wait *} to comply with -the 4.1BSD interface. If @code{wait}'s parameter were @code{void *}, -@code{wait} would accept both kinds of arguments, but it would also -accept any other pointer type and this would make argument type checking -less useful. Instead, @code{} might define the interface -as follows: - -@smallexample -typedef union - @{ - int *__ip; - union wait *__up; - @} wait_status_ptr_t __attribute__ ((__transparent_union__)); - -pid_t wait (wait_status_ptr_t); -@end smallexample - -This interface allows either @code{int *} or @code{union wait *} -arguments to be passed, using the @code{int *} calling convention. -The program can call @code{wait} with arguments of either type: - -@example -int w1 () @{ int w; return wait (&w); @} -int w2 () @{ union wait w; return wait (&w); @} -@end example - -With this interface, @code{wait}'s implementation might look like this: - -@example -pid_t wait (wait_status_ptr_t p) -@{ - return waitpid (-1, p.__ip, 0); -@} -@end example - -@item unused -When attached to a type (including a @code{union} or a @code{struct}), -this attribute means that variables of that type are meant to appear -possibly unused. GNU CC will not produce a warning for any variables of -that type, even if the variable appears to do nothing. This is often -the case with lock or thread classes, which are usually defined and then -not referenced, but contain constructors and destructors that have -nontrivial bookkeeping functions. - -@end table - -To specify multiple attributes, separate them by commas within the -double parentheses: for example, @samp{__attribute__ ((aligned (16), -packed))}. - -@node Inline -@section An Inline Function is As Fast As a Macro -@cindex inline functions -@cindex integrating function code -@cindex open coding -@cindex macros, inline alternative - -By declaring a function @code{inline}, you can direct GNU CC to -integrate that function's code into the code for its callers. This -makes execution faster by eliminating the function-call overhead; in -addition, if any of the actual argument values are constant, their known -values may permit simplifications at compile time so that not all of the -inline function's code needs to be included. The effect on code size is -less predictable; object code may be larger or smaller with function -inlining, depending on the particular case. Inlining of functions is an -optimization and it really ``works'' only in optimizing compilation. If -you don't use @samp{-O}, no function is really inline. - -Inline functions are included in the ISO C99 standard, but there are -currently substantial differences between what GCC implements and what -the ISO C99 standard requires. - -To declare a function inline, use the @code{inline} keyword in its -declaration, like this: - -@example -inline int -inc (int *a) -@{ - (*a)++; -@} -@end example - -(If you are writing a header file to be included in ISO C programs, write -@code{__inline__} instead of @code{inline}. @xref{Alternate Keywords}.) -You can also make all ``simple enough'' functions inline with the option -@samp{-finline-functions}. - -Note that certain usages in a function definition can make it unsuitable -for inline substitution. Among these usages are: use of varargs, use of -alloca, use of variable sized data types (@pxref{Variable Length}), -use of computed goto (@pxref{Labels as Values}), use of nonlocal goto, -and nested functions (@pxref{Nested Functions}). Using @samp{-Winline} -will warn when a function marked @code{inline} could not be substituted, -and will give the reason for the failure. - -Note that in C and Objective C, unlike C++, the @code{inline} keyword -does not affect the linkage of the function. - -@cindex automatic @code{inline} for C++ member fns -@cindex @code{inline} automatic for C++ member fns -@cindex member fns, automatically @code{inline} -@cindex C++ member fns, automatically @code{inline} -GNU CC automatically inlines member functions defined within the class -body of C++ programs even if they are not explicitly declared -@code{inline}. (You can override this with @samp{-fno-default-inline}; -@pxref{C++ Dialect Options,,Options Controlling C++ Dialect}.) - -@cindex inline functions, omission of -When a function is both inline and @code{static}, if all calls to the -function are integrated into the caller, and the function's address is -never used, then the function's own assembler code is never referenced. -In this case, GNU CC does not actually output assembler code for the -function, unless you specify the option @samp{-fkeep-inline-functions}. -Some calls cannot be integrated for various reasons (in particular, -calls that precede the function's definition cannot be integrated, and -neither can recursive calls within the definition). If there is a -nonintegrated call, then the function is compiled to assembler code as -usual. The function must also be compiled as usual if the program -refers to its address, because that can't be inlined. - -@cindex non-static inline function -When an inline function is not @code{static}, then the compiler must assume -that there may be calls from other source files; since a global symbol can -be defined only once in any program, the function must not be defined in -the other source files, so the calls therein cannot be integrated. -Therefore, a non-@code{static} inline function is always compiled on its -own in the usual fashion. - -If you specify both @code{inline} and @code{extern} in the function -definition, then the definition is used only for inlining. In no case -is the function compiled on its own, not even if you refer to its -address explicitly. Such an address becomes an external reference, as -if you had only declared the function, and had not defined it. - -This combination of @code{inline} and @code{extern} has almost the -effect of a macro. The way to use it is to put a function definition in -a header file with these keywords, and put another copy of the -definition (lacking @code{inline} and @code{extern}) in a library file. -The definition in the header file will cause most calls to the function -to be inlined. If any uses of the function remain, they will refer to -the single copy in the library. - -For future compatibility with when GCC implements ISO C99 semantics for -inline functions, it is best to use @code{static inline} only. (The -existing semantics will remain available when @option{-std=gnu89} is -specified, but eventually the default will be @option{-std=gnu99} and -that will implement the C99 semantics, though it does not do so yet.) - -GNU C does not inline any functions when not optimizing. It is not -clear whether it is better to inline or not, in this case, but we found -that a correct implementation when not optimizing was difficult. So we -did the easy thing, and turned it off. - -@node Extended Asm -@section Assembler Instructions with C Expression Operands -@cindex extended @code{asm} -@cindex @code{asm} expressions -@cindex assembler instructions -@cindex registers - -In an assembler instruction using @code{asm}, you can specify the -operands of the instruction using C expressions. This means you need not -guess which registers or memory locations will contain the data you want -to use. - -You must specify an assembler instruction template much like what -appears in a machine description, plus an operand constraint string for -each operand. - -For example, here is how to use the 68881's @code{fsinx} instruction: - -@example -asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); -@end example - -@noindent -Here @code{angle} is the C expression for the input operand while -@code{result} is that of the output operand. Each has @samp{"f"} as its -operand constraint, saying that a floating point register is required. -The @samp{=} in @samp{=f} indicates that the operand is an output; all -output operands' constraints must use @samp{=}. The constraints use the -same language used in the machine description (@pxref{Constraints}). - -Each operand is described by an operand-constraint string followed by -the C expression in parentheses. A colon separates the assembler -template from the first output operand and another separates the last -output operand from the first input, if any. Commas separate the -operands within each group. The total number of operands is limited to -ten or to the maximum number of operands in any instruction pattern in -the machine description, whichever is greater. - -If there are no output operands but there are input operands, you must -place two consecutive colons surrounding the place where the output -operands would go. - -Output operand expressions must be lvalues; the compiler can check this. -The input operands need not be lvalues. The compiler cannot check -whether the operands have data types that are reasonable for the -instruction being executed. It does not parse the assembler instruction -template and does not know what it means or even whether it is valid -assembler input. The extended @code{asm} feature is most often used for -machine instructions the compiler itself does not know exist. If -the output expression cannot be directly addressed (for example, it is a -bit field), your constraint must allow a register. In that case, GNU CC -will use the register as the output of the @code{asm}, and then store -that register into the output. - -The ordinary output operands must be write-only; GNU CC will assume that -the values in these operands before the instruction are dead and need -not be generated. Extended asm supports input-output or read-write -operands. Use the constraint character @samp{+} to indicate such an -operand and list it with the output operands. - -When the constraints for the read-write operand (or the operand in which -only some of the bits are to be changed) allows a register, you may, as -an alternative, logically split its function into two separate operands, -one input operand and one write-only output operand. The connection -between them is expressed by constraints which say they need to be in -the same location when the instruction executes. You can use the same C -expression for both operands, or different expressions. For example, -here we write the (fictitious) @samp{combine} instruction with -@code{bar} as its read-only source operand and @code{foo} as its -read-write destination: - -@example -asm ("combine %2,%0" : "=r" (foo) : "0" (foo), "g" (bar)); -@end example - -@noindent -The constraint @samp{"0"} for operand 1 says that it must occupy the -same location as operand 0. A digit in constraint is allowed only in an -input operand and it must refer to an output operand. - -Only a digit in the constraint can guarantee that one operand will be in -the same place as another. The mere fact that @code{foo} is the value -of both operands is not enough to guarantee that they will be in the -same place in the generated assembler code. The following would not -work reliably: - -@example -asm ("combine %2,%0" : "=r" (foo) : "r" (foo), "g" (bar)); -@end example - -Various optimizations or reloading could cause operands 0 and 1 to be in -different registers; GNU CC knows no reason not to do so. For example, the -compiler might find a copy of the value of @code{foo} in one register and -use it for operand 1, but generate the output operand 0 in a different -register (copying it afterward to @code{foo}'s own address). Of course, -since the register for operand 1 is not even mentioned in the assembler -code, the result will not work, but GNU CC can't tell that. - -Some instructions clobber specific hard registers. To describe this, -write a third colon after the input operands, followed by the names of -the clobbered hard registers (given as strings). Here is a realistic -example for the VAX: - -@example -asm volatile ("movc3 %0,%1,%2" - : /* no outputs */ - : "g" (from), "g" (to), "g" (count) - : "r0", "r1", "r2", "r3", "r4", "r5"); -@end example - -You may not write a clobber description in a way that overlaps with an -input or output operand. For example, you may not have an operand -describing a register class with one member if you mention that register -in the clobber list. There is no way for you to specify that an input -operand is modified without also specifying it as an output -operand. Note that if all the output operands you specify are for this -purpose (and hence unused), you will then also need to specify -@code{volatile} for the @code{asm} construct, as described below, to -prevent GNU CC from deleting the @code{asm} statement as unused. - -If you refer to a particular hardware register from the assembler code, -you will probably have to list the register after the third colon to -tell the compiler the register's value is modified. In some assemblers, -the register names begin with @samp{%}; to produce one @samp{%} in the -assembler code, you must write @samp{%%} in the input. - -If your assembler instruction can alter the condition code register, add -@samp{cc} to the list of clobbered registers. GNU CC on some machines -represents the condition codes as a specific hardware register; -@samp{cc} serves to name this register. On other machines, the -condition code is handled differently, and specifying @samp{cc} has no -effect. But it is valid no matter what the machine. - -If your assembler instruction modifies memory in an unpredictable -fashion, add @samp{memory} to the list of clobbered registers. This -will cause GNU CC to not keep memory values cached in registers across -the assembler instruction. You will also want to add the -@code{volatile} keyword if the memory affected is not listed in the -inputs or outputs of the @code{asm}, as the @samp{memory} clobber does -not count as a side-effect of the @code{asm}. - -You can put multiple assembler instructions together in a single -@code{asm} template, separated by the characters normally used in assembly -code for the system. A combination that works in most places is a newline -to break the line, plus a tab character to move to the instruction field -(written as @samp{\n\t}). Sometimes semicolons can be used, if the -assembler allows semicolons as a line-breaking character. Note that some -assembler dialects use semicolons to start a comment. -The input operands are guaranteed not to use any of the clobbered -registers, and neither will the output operands' addresses, so you can -read and write the clobbered registers as many times as you like. Here -is an example of multiple instructions in a template; it assumes the -subroutine @code{_foo} accepts arguments in registers 9 and 10: - -@example -asm ("movl %0,r9\n\tmovl %1,r10\n\tcall _foo" - : /* no outputs */ - : "g" (from), "g" (to) - : "r9", "r10"); -@end example - -Unless an output operand has the @samp{&} constraint modifier, GNU CC -may allocate it in the same register as an unrelated input operand, on -the assumption the inputs are consumed before the outputs are produced. -This assumption may be false if the assembler code actually consists of -more than one instruction. In such a case, use @samp{&} for each output -operand that may not overlap an input. @xref{Modifiers}. - -If you want to test the condition code produced by an assembler -instruction, you must include a branch and a label in the @code{asm} -construct, as follows: - -@example -asm ("clr %0\n\tfrob %1\n\tbeq 0f\n\tmov #1,%0\n0:" - : "g" (result) - : "g" (input)); -@end example - -@noindent -This assumes your assembler supports local labels, as the GNU assembler -and most Unix assemblers do. - -Speaking of labels, jumps from one @code{asm} to another are not -supported. The compiler's optimizers do not know about these jumps, and -therefore they cannot take account of them when deciding how to -optimize. - -@cindex macros containing @code{asm} -Usually the most convenient way to use these @code{asm} instructions is to -encapsulate them in macros that look like functions. For example, - -@example -#define sin(x) \ -(@{ double __value, __arg = (x); \ - asm ("fsinx %1,%0": "=f" (__value): "f" (__arg)); \ - __value; @}) -@end example - -@noindent -Here the variable @code{__arg} is used to make sure that the instruction -operates on a proper @code{double} value, and to accept only those -arguments @code{x} which can convert automatically to a @code{double}. - -Another way to make sure the instruction operates on the correct data -type is to use a cast in the @code{asm}. This is different from using a -variable @code{__arg} in that it converts more different types. For -example, if the desired type were @code{int}, casting the argument to -@code{int} would accept a pointer with no complaint, while assigning the -argument to an @code{int} variable named @code{__arg} would warn about -using a pointer unless the caller explicitly casts it. - -If an @code{asm} has output operands, GNU CC assumes for optimization -purposes the instruction has no side effects except to change the output -operands. This does not mean instructions with a side effect cannot be -used, but you must be careful, because the compiler may eliminate them -if the output operands aren't used, or move them out of loops, or -replace two with one if they constitute a common subexpression. Also, -if your instruction does have a side effect on a variable that otherwise -appears not to change, the old value of the variable may be reused later -if it happens to be found in a register. - -You can prevent an @code{asm} instruction from being deleted, moved -significantly, or combined, by writing the keyword @code{volatile} after -the @code{asm}. For example: - -@example -#define get_and_set_priority(new) \ -(@{ int __old; \ - asm volatile ("get_and_set_priority %0, %1" \ - : "=g" (__old) : "g" (new)); \ - __old; @}) -@end example - -@noindent -If you write an @code{asm} instruction with no outputs, GNU CC will know -the instruction has side-effects and will not delete the instruction or -move it outside of loops. - -The @code{volatile} keyword indicates that the instruction has -important side-effects. GCC will not delete a volatile @code{asm} if -it is reachable. (The instruction can still be deleted if GCC can -prove that control-flow will never reach the location of the -instruction.) In addition, GCC will not reschedule instructions -across a volatile @code{asm} instruction. For example: - -@example -*(volatile int *)addr = foo; -asm volatile ("eieio" : : ); -@end example - -@noindent -Assume @code{addr} contains the address of a memory mapped device -register. The PowerPC @code{eieio} instruction (Enforce In-order -Execution of I/O) tells the cpu to make sure that the store to that -device register happens before it issues any other I/O. - -Note that even a volatile @code{asm} instruction can be moved in ways -that appear insignificant to the compiler, such as across jump -instructions. You can't expect a sequence of volatile @code{asm} -instructions to remain perfectly consecutive. If you want consecutive -output, use a single @code{asm}. Also, GCC will perform some -optimizations across a volatile @code{asm} instruction; GCC does not -``forget everything'' when it encounters a volatile @code{asm} -instruction the way some other compilers do. - -An @code{asm} instruction without any operands or clobbers (an ``old -style'' @code{asm}) will be treated identically to a volatile -@code{asm} instruction. - -It is a natural idea to look for a way to give access to the condition -code left by the assembler instruction. However, when we attempted to -implement this, we found no way to make it work reliably. The problem -is that output operands might need reloading, which would result in -additional following ``store'' instructions. On most machines, these -instructions would alter the condition code before there was time to -test it. This problem doesn't arise for ordinary ``test'' and -``compare'' instructions because they don't have any output operands. - -For reasons similar to those described above, it is not possible to give -an assembler instruction access to the condition code left by previous -instructions. - -If you are writing a header file that should be includable in ISO C -programs, write @code{__asm__} instead of @code{asm}. @xref{Alternate -Keywords}. - -@subsection i386 floating point asm operands - -There are several rules on the usage of stack-like regs in -asm_operands insns. These rules apply only to the operands that are -stack-like regs: - -@enumerate -@item -Given a set of input regs that die in an asm_operands, it is -necessary to know which are implicitly popped by the asm, and -which must be explicitly popped by gcc. - -An input reg that is implicitly popped by the asm must be -explicitly clobbered, unless it is constrained to match an -output operand. - -@item -For any input reg that is implicitly popped by an asm, it is -necessary to know how to adjust the stack to compensate for the pop. -If any non-popped input is closer to the top of the reg-stack than -the implicitly popped reg, it would not be possible to know what the -stack looked like --- it's not clear how the rest of the stack ``slides -up''. - -All implicitly popped input regs must be closer to the top of -the reg-stack than any input that is not implicitly popped. - -It is possible that if an input dies in an insn, reload might -use the input reg for an output reload. Consider this example: - -@example -asm ("foo" : "=t" (a) : "f" (b)); -@end example - -This asm says that input B is not popped by the asm, and that -the asm pushes a result onto the reg-stack, ie, the stack is one -deeper after the asm than it was before. But, it is possible that -reload will think that it can use the same reg for both the input and -the output, if input B dies in this insn. - -If any input operand uses the @code{f} constraint, all output reg -constraints must use the @code{&} earlyclobber. - -The asm above would be written as - -@example -asm ("foo" : "=&t" (a) : "f" (b)); -@end example - -@item -Some operands need to be in particular places on the stack. All -output operands fall in this category --- there is no other way to -know which regs the outputs appear in unless the user indicates -this in the constraints. - -Output operands must specifically indicate which reg an output -appears in after an asm. @code{=f} is not allowed: the operand -constraints must select a class with a single reg. - -@item -Output operands may not be ``inserted'' between existing stack regs. -Since no 387 opcode uses a read/write operand, all output operands -are dead before the asm_operands, and are pushed by the asm_operands. -It makes no sense to push anywhere but the top of the reg-stack. - -Output operands must start at the top of the reg-stack: output -operands may not ``skip'' a reg. - -@item -Some asm statements may need extra stack space for internal -calculations. This can be guaranteed by clobbering stack registers -unrelated to the inputs and outputs. - -@end enumerate - -Here are a couple of reasonable asms to want to write. This asm -takes one input, which is internally popped, and produces two outputs. - -@example -asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp)); -@end example - -This asm takes two inputs, which are popped by the @code{fyl2xp1} opcode, -and replaces them with one output. The user must code the @code{st(1)} -clobber for reg-stack.c to know that @code{fyl2xp1} pops both inputs. - -@example -asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)"); -@end example - -@ifclear INTERNALS -@c Show the details on constraints if they do not appear elsewhere in -@c the manual -@include md.texi -@end ifclear - -@node Asm Labels -@section Controlling Names Used in Assembler Code -@cindex assembler names for identifiers -@cindex names used in assembler code -@cindex identifiers, names in assembler code - -You can specify the name to be used in the assembler code for a C -function or variable by writing the @code{asm} (or @code{__asm__}) -keyword after the declarator as follows: - -@example -int foo asm ("myfoo") = 2; -@end example - -@noindent -This specifies that the name to be used for the variable @code{foo} in -the assembler code should be @samp{myfoo} rather than the usual -@samp{_foo}. - -On systems where an underscore is normally prepended to the name of a C -function or variable, this feature allows you to define names for the -linker that do not start with an underscore. - -It does not make sense to use this feature with a non-static local -variable since such variables do not have assembler names. If you are -trying to put the variable in a particular register, see @ref{Explicit -Reg Vars}. GCC presently accepts such code with a warning, but will -probably be changed to issue an error, rather than a warning, in the -future. - -You cannot use @code{asm} in this way in a function @emph{definition}; but -you can get the same effect by writing a declaration for the function -before its definition and putting @code{asm} there, like this: - -@example -extern func () asm ("FUNC"); - -func (x, y) - int x, y; -@dots{} -@end example - -It is up to you to make sure that the assembler names you choose do not -conflict with any other assembler symbols. Also, you must not use a -register name; that would produce completely invalid assembler code. GNU -CC does not as yet have the ability to store static variables in registers. -Perhaps that will be added. - -@node Explicit Reg Vars -@section Variables in Specified Registers -@cindex explicit register variables -@cindex variables in specified registers -@cindex specified registers -@cindex registers, global allocation - -GNU C allows you to put a few global variables into specified hardware -registers. You can also specify the register in which an ordinary -register variable should be allocated. - -@itemize @bullet -@item -Global register variables reserve registers throughout the program. -This may be useful in programs such as programming language -interpreters which have a couple of global variables that are accessed -very often. - -@item -Local register variables in specific registers do not reserve the -registers. The compiler's data flow analysis is capable of determining -where the specified registers contain live values, and where they are -available for other uses. Stores into local register variables may be deleted -when they appear to be dead according to dataflow analysis. References -to local register variables may be deleted or moved or simplified. - -These local variables are sometimes convenient for use with the extended -@code{asm} feature (@pxref{Extended Asm}), if you want to write one -output of the assembler instruction directly into a particular register. -(This will work provided the register you specify fits the constraints -specified for that operand in the @code{asm}.) -@end itemize - -@menu -* Global Reg Vars:: -* Local Reg Vars:: -@end menu - -@node Global Reg Vars -@subsection Defining Global Register Variables -@cindex global register variables -@cindex registers, global variables in - -You can define a global register variable in GNU C like this: - -@example -register int *foo asm ("a5"); -@end example - -@noindent -Here @code{a5} is the name of the register which should be used. Choose a -register which is normally saved and restored by function calls on your -machine, so that library routines will not clobber it. - -Naturally the register name is cpu-dependent, so you would need to -conditionalize your program according to cpu type. The register -@code{a5} would be a good choice on a 68000 for a variable of pointer -type. On machines with register windows, be sure to choose a ``global'' -register that is not affected magically by the function call mechanism. - -In addition, operating systems on one type of cpu may differ in how they -name the registers; then you would need additional conditionals. For -example, some 68000 operating systems call this register @code{%a5}. - -Eventually there may be a way of asking the compiler to choose a register -automatically, but first we need to figure out how it should choose and -how to enable you to guide the choice. No solution is evident. - -Defining a global register variable in a certain register reserves that -register entirely for this use, at least within the current compilation. -The register will not be allocated for any other purpose in the functions -in the current compilation. The register will not be saved and restored by -these functions. Stores into this register are never deleted even if they -would appear to be dead, but references may be deleted or moved or -simplified. - -It is not safe to access the global register variables from signal -handlers, or from more than one thread of control, because the system -library routines may temporarily use the register for other things (unless -you recompile them specially for the task at hand). - -@cindex @code{qsort}, and global register variables -It is not safe for one function that uses a global register variable to -call another such function @code{foo} by way of a third function -@code{lose} that was compiled without knowledge of this variable (i.e. in a -different source file in which the variable wasn't declared). This is -because @code{lose} might save the register and put some other value there. -For example, you can't expect a global register variable to be available in -the comparison-function that you pass to @code{qsort}, since @code{qsort} -might have put something else in that register. (If you are prepared to -recompile @code{qsort} with the same global register variable, you can -solve this problem.) - -If you want to recompile @code{qsort} or other source files which do not -actually use your global register variable, so that they will not use that -register for any other purpose, then it suffices to specify the compiler -option @samp{-ffixed-@var{reg}}. You need not actually add a global -register declaration to their source code. - -A function which can alter the value of a global register variable cannot -safely be called from a function compiled without this variable, because it -could clobber the value the caller expects to find there on return. -Therefore, the function which is the entry point into the part of the -program that uses the global register variable must explicitly save and -restore the value which belongs to its caller. - -@cindex register variable after @code{longjmp} -@cindex global register after @code{longjmp} -@cindex value after @code{longjmp} -@findex longjmp -@findex setjmp -On most machines, @code{longjmp} will restore to each global register -variable the value it had at the time of the @code{setjmp}. On some -machines, however, @code{longjmp} will not change the value of global -register variables. To be portable, the function that called @code{setjmp} -should make other arrangements to save the values of the global register -variables, and to restore them in a @code{longjmp}. This way, the same -thing will happen regardless of what @code{longjmp} does. - -All global register variable declarations must precede all function -definitions. If such a declaration could appear after function -definitions, the declaration would be too late to prevent the register from -being used for other purposes in the preceding functions. - -Global register variables may not have initial values, because an -executable file has no means to supply initial contents for a register. - -On the Sparc, there are reports that g3 @dots{} g7 are suitable -registers, but certain library functions, such as @code{getwd}, as well -as the subroutines for division and remainder, modify g3 and g4. g1 and -g2 are local temporaries. - -On the 68000, a2 @dots{} a5 should be suitable, as should d2 @dots{} d7. -Of course, it will not do to use more than a few of those. - -@node Local Reg Vars -@subsection Specifying Registers for Local Variables -@cindex local variables, specifying registers -@cindex specifying registers for local variables -@cindex registers for local variables - -You can define a local register variable with a specified register -like this: - -@example -register int *foo asm ("a5"); -@end example - -@noindent -Here @code{a5} is the name of the register which should be used. Note -that this is the same syntax used for defining global register -variables, but for a local variable it would appear within a function. - -Naturally the register name is cpu-dependent, but this is not a -problem, since specific registers are most often useful with explicit -assembler instructions (@pxref{Extended Asm}). Both of these things -generally require that you conditionalize your program according to -cpu type. - -In addition, operating systems on one type of cpu may differ in how they -name the registers; then you would need additional conditionals. For -example, some 68000 operating systems call this register @code{%a5}. - -Defining such a register variable does not reserve the register; it -remains available for other uses in places where flow control determines -the variable's value is not live. However, these registers are made -unavailable for use in the reload pass; excessive use of this feature -leaves the compiler too few available registers to compile certain -functions. - -This option does not guarantee that GNU CC will generate code that has -this variable in the register you specify at all times. You may not -code an explicit reference to this register in an @code{asm} statement -and assume it will always refer to this variable. - -Stores into local register variables may be deleted when they appear to be dead -according to dataflow analysis. References to local register variables may -be deleted or moved or simplified. - -@node Alternate Keywords -@section Alternate Keywords -@cindex alternate keywords -@cindex keywords, alternate - -The option @option{-traditional} disables certain keywords; -@option{-ansi} and the various @option{-std} options disable certain -others. This causes trouble when you want to use GNU C extensions, or -ISO C features, in a general-purpose header file that should be usable -by all programs, including ISO C programs and traditional ones. The -keywords @code{asm}, @code{typeof} and @code{inline} cannot be used -since they won't work in a program compiled with @option{-ansi} -(although @code{inline} can be used in a program compiled with -@option{-std=c99}), while the keywords @code{const}, @code{volatile}, -@code{signed}, @code{typeof} and @code{inline} won't work in a program -compiled with @option{-traditional}. The ISO C99 keyword -@code{restrict} is only available when @option{-std=gnu99} (which will -eventually be the default) or @option{-std=c99} (or the equivalent -@option{-std=iso9899:1999}) is used.@refill - -The way to solve these problems is to put @samp{__} at the beginning and -end of each problematical keyword. For example, use @code{__asm__} -instead of @code{asm}, @code{__const__} instead of @code{const}, and -@code{__inline__} instead of @code{inline}. - -Other C compilers won't accept these alternative keywords; if you want to -compile with another compiler, you can define the alternate keywords as -macros to replace them with the customary keywords. It looks like this: - -@example -#ifndef __GNUC__ -#define __asm__ asm -#endif -@end example - -@findex __extension__ -@samp{-pedantic} and other options cause warnings for many GNU C extensions. -You can -prevent such warnings within one expression by writing -@code{__extension__} before the expression. @code{__extension__} has no -effect aside from this. - -@node Incomplete Enums -@section Incomplete @code{enum} Types - -You can define an @code{enum} tag without specifying its possible values. -This results in an incomplete type, much like what you get if you write -@code{struct foo} without describing the elements. A later declaration -which does specify the possible values completes the type. - -You can't allocate variables or storage using the type while it is -incomplete. However, you can work with pointers to that type. - -This extension may not be very useful, but it makes the handling of -@code{enum} more consistent with the way @code{struct} and @code{union} -are handled. - -This extension is not supported by GNU C++. - -@node Function Names -@section Function Names as Strings -@cindex @code{__FUNCTION__} identifier -@cindex @code{__PRETTY_FUNCTION__} identifier -@cindex @code{__func__} identifier - -GNU CC predefines two magic identifiers to hold the name of the current -function. The identifier @code{__FUNCTION__} holds the name of the function -as it appears in the source. The identifier @code{__PRETTY_FUNCTION__} -holds the name of the function pretty printed in a language specific -fashion. - -These names are always the same in a C function, but in a C++ function -they may be different. For example, this program: - -@smallexample -extern "C" @{ -extern int printf (char *, ...); -@} - -class a @{ - public: - sub (int i) - @{ - printf ("__FUNCTION__ = %s\n", __FUNCTION__); - printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__); - @} -@}; - -int -main (void) -@{ - a ax; - ax.sub (0); - return 0; -@} -@end smallexample - -@noindent -gives this output: - -@smallexample -__FUNCTION__ = sub -__PRETTY_FUNCTION__ = int a::sub (int) -@end smallexample - -The compiler automagically replaces the identifiers with a string -literal containing the appropriate name. Thus, they are neither -preprocessor macros, like @code{__FILE__} and @code{__LINE__}, nor -variables. This means that they catenate with other string literals, and -that they can be used to initialize char arrays. For example - -@smallexample -char here[] = "Function " __FUNCTION__ " in " __FILE__; -@end smallexample - -On the other hand, @samp{#ifdef __FUNCTION__} does not have any special -meaning inside a function, since the preprocessor does not do anything -special with the identifier @code{__FUNCTION__}. - -GNU CC also supports the magic word @code{__func__}, defined by the -ISO standard C99: - -@display -The identifier @code{__func__} is implicitly declared by the translator -as if, immediately following the opening brace of each function -definition, the declaration - -@smallexample -static const char __func__[] = "function-name"; -@end smallexample - -appeared, where function-name is the name of the lexically-enclosing -function. This name is the unadorned name of the function. -@end display - -By this definition, @code{__func__} is a variable, not a string literal. -In particular, @code{__func__} does not catenate with other string -literals. - -In @code{C++}, @code{__FUNCTION__} and @code{__PRETTY_FUNCTION__} are -variables, declared in the same way as @code{__func__}. - -@node Return Address -@section Getting the Return or Frame Address of a Function - -These functions may be used to get information about the callers of a -function. - -@table @code -@findex __builtin_return_address -@item __builtin_return_address (@var{level}) -This function returns the return address of the current function, or of -one of its callers. The @var{level} argument is number of frames to -scan up the call stack. A value of @code{0} yields the return address -of the current function, a value of @code{1} yields the return address -of the caller of the current function, and so forth. - -The @var{level} argument must be a constant integer. - -On some machines it may be impossible to determine the return address of -any function other than the current one; in such cases, or when the top -of the stack has been reached, this function will return @code{0}. - -This function should only be used with a non-zero argument for debugging -purposes. - -@findex __builtin_frame_address -@item __builtin_frame_address (@var{level}) -This function is similar to @code{__builtin_return_address}, but it -returns the address of the function frame rather than the return address -of the function. Calling @code{__builtin_frame_address} with a value of -@code{0} yields the frame address of the current function, a value of -@code{1} yields the frame address of the caller of the current function, -and so forth. - -The frame is the area on the stack which holds local variables and saved -registers. The frame address is normally the address of the first word -pushed on to the stack by the function. However, the exact definition -depends upon the processor and the calling convention. If the processor -has a dedicated frame pointer register, and the function has a frame, -then @code{__builtin_frame_address} will return the value of the frame -pointer register. - -The caveats that apply to @code{__builtin_return_address} apply to this -function as well. -@end table - -@node Other Builtins -@section Other built-in functions provided by GNU CC -@cindex builtin functions -@findex __builtin_isgreater -@findex __builtin_isgreaterequal -@findex __builtin_isless -@findex __builtin_islessequal -@findex __builtin_islessgreater -@findex __builtin_isunordered -@findex abort -@findex abs -@findex alloca -@findex bcmp -@findex bzero -@findex cimag -@findex cimagf -@findex cimagl -@findex conj -@findex conjf -@findex conjl -@findex cos -@findex cosf -@findex cosl -@findex creal -@findex crealf -@findex creall -@findex exit -@findex _exit -@findex _Exit -@findex fabs -@findex fabsf -@findex fabsl -@findex ffs -@findex fprintf -@findex fputs -@findex imaxabs -@findex index -@findex labs -@findex llabs -@findex memcmp -@findex memcpy -@findex memset -@findex printf -@findex rindex -@findex sin -@findex sinf -@findex sinl -@findex sqrt -@findex sqrtf -@findex sqrtl -@findex strcat -@findex strchr -@findex strcmp -@findex strcpy -@findex strcspn -@findex strlen -@findex strncat -@findex strncmp -@findex strncpy -@findex strpbrk -@findex strrchr -@findex strspn -@findex strstr - -GNU CC provides a large number of built-in functions other than the ones -mentioned above. Some of these are for internal use in the processing -of exceptions or variable-length argument lists and will not be -documented here because they may change from time to time; we do not -recommend general use of these functions. - -The remaining functions are provided for optimization purposes. - -GNU CC includes builtin versions of many of the functions in the -standard C library. The versions prefixed with @code{__builtin_} will -always be treated as having the same meaning as the C library function -even if you specify the @samp{-fno-builtin} (@pxref{C Dialect Options}) -option. Many of these functions are only optimized in certain cases; if -not optimized in a particular case, a call to the library function will -be emitted. - -The functions @code{abort}, @code{exit}, @code{_Exit} and @code{_exit} -are recognized and presumed not to return, but otherwise are not built -in. @code{_exit} is not recognized in strict ISO C mode (@samp{-ansi}, -@samp{-std=c89} or @samp{-std=c99}). @code{_Exit} is not recognized in -strict C89 mode (@samp{-ansi} or @samp{-std=c89}). - -Outside strict ISO C mode, the functions @code{alloca}, @code{bcmp}, -@code{bzero}, @code{index}, @code{rindex} and @code{ffs} may be handled -as builtins. Corresponding versions @code{__builtin_alloca}, -@code{__builtin_bcmp}, @code{__builtin_bzero}, @code{__builtin_index}, -@code{__builtin_rindex} and @code{__builtin_ffs} are also recognized in -strict ISO C mode. - -The ISO C99 functions @code{conj}, @code{conjf}, @code{conjl}, -@code{creal}, @code{crealf}, @code{creall}, @code{cimag}, @code{cimagf}, -@code{cimagl}, @code{llabs} and @code{imaxabs} are handled as builtins -except in strict ISO C89 mode. There are also builtin versions of the ISO C99 -functions @code{cosf}, @code{cosl}, @code{fabsf}, @code{fabsl}, -@code{sinf}, @code{sinl}, @code{sqrtf}, and @code{sqrtl}, that are -recognized in any mode since ISO C89 reserves these names for the -purpose to which ISO C99 puts them. All these functions have -corresponding versions prefixed with @code{__builtin_}. - -The following ISO C89 functions are recognized as builtins unless -@samp{-fno-builtin} is specified: @code{abs}, @code{cos}, @code{fabs}, -@code{fprintf}, @code{fputs}, @code{labs}, @code{memcmp}, @code{memcpy}, -@code{memset}, @code{printf}, @code{sin}, @code{sqrt}, @code{strcat}, -@code{strchr}, @code{strcmp}, @code{strcpy}, @code{strcspn}, -@code{strlen}, @code{strncat}, @code{strncmp}, @code{strncpy}, -@code{strpbrk}, @code{strrchr}, @code{strspn}, and @code{strstr}. All -of these functions have corresponding versions prefixed with -@code{__builtin_}, except that the version for @code{sqrt} is called -@code{__builtin_fsqrt}. - -GNU CC provides builtin versions of the ISO C99 floating point -comparison macros (that avoid raising exceptions for unordered -operands): @code{__builtin_isgreater}, @code{__builtin_isgreaterequal}, -@code{__builtin_isless}, @code{__builtin_islessequal}, -@code{__builtin_islessgreater}, and @code{__builtin_isunordered}. - - -@table @code -@findex __builtin_constant_p -@item __builtin_constant_p (@var{exp}) -You can use the builtin function @code{__builtin_constant_p} to -determine if a value is known to be constant at compile-time and hence -that GNU CC can perform constant-folding on expressions involving that -value. The argument of the function is the value to test. The function -returns the integer 1 if the argument is known to be a compile-time -constant and 0 if it is not known to be a compile-time constant. A -return of 0 does not indicate that the value is @emph{not} a constant, -but merely that GNU CC cannot prove it is a constant with the specified -value of the @samp{-O} option. - -You would typically use this function in an embedded application where -memory was a critical resource. If you have some complex calculation, -you may want it to be folded if it involves constants, but need to call -a function if it does not. For example: - -@smallexample -#define Scale_Value(X) \ - (__builtin_constant_p (X) \ - ? ((X) * SCALE + OFFSET) : Scale (X)) -@end smallexample - -You may use this builtin function in either a macro or an inline -function. However, if you use it in an inlined function and pass an -argument of the function as the argument to the builtin, GNU CC will -never return 1 when you call the inline function with a string constant -or compound literal (@pxref{Compound Literals}) and will not return 1 -when you pass a constant numeric value to the inline function unless you -specify the @samp{-O} option. - -@findex __builtin_expect -@item __builtin_expect(@var{exp}, @var{c}) -You may use @code{__builtin_expect} to provide the compiler with -branch prediction information. In general, you should prefer to -use actual profile feedback for this (@samp{-fprofile-arcs}), as -programmers are notoriously bad at predicting how their programs -actually perform. However, there are applications in which this -data is hard to collect. - -The return value is the value of @var{exp}, which should be an -integral expression. The value of @var{c} must be a compile-time -constant. The semantics of the builtin are that it is expected -that @var{exp} == @var{c}. For example: - -@smallexample -if (__builtin_expect (x, 0)) - foo (); -@end smallexample - -@noindent -would indicate that we do not expect to call @code{foo}, since -we expect @code{x} to be zero. Since you are limited to integral -expressions for @var{exp}, you should use constructions such as - -@smallexample -if (__builtin_expect (ptr != NULL, 1)) - error (); -@end smallexample - -@noindent -when testing pointer or floating-point values. -@end table - -@node C++ Extensions -@chapter Extensions to the C++ Language -@cindex extensions, C++ language -@cindex C++ language extensions - -The GNU compiler provides these extensions to the C++ language (and you -can also use most of the C language extensions in your C++ programs). If you -want to write code that checks whether these features are available, you can -test for the GNU compiler the same way as for C programs: check for a -predefined macro @code{__GNUC__}. You can also use @code{__GNUG__} to -test specifically for GNU C++ (@pxref{Standard Predefined,,Standard -Predefined Macros,cpp.info,The C Preprocessor}). - -@menu -* Min and Max:: C++ Minimum and maximum operators. -* Volatiles:: What constitutes an access to a volatile object. -* Restricted Pointers:: C99 restricted pointers and references. -* Vague Linkage:: Where G++ puts inlines, vtables and such. -* C++ Interface:: You can use a single C++ header file for both - declarations and definitions. -* Template Instantiation:: Methods for ensuring that exactly one copy of - each needed template instantiation is emitted. -* Bound member functions:: You can extract a function pointer to the - method denoted by a @samp{->*} or @samp{.*} expression. -* C++ Attributes:: Variable, function, and type attributes for C++ only. -* Java Exceptions:: Tweaking exception handling to work with Java. -* Deprecated Features:: Things might disappear from g++. -* Backwards Compatibility:: Compatibilities with earlier definitions of C++. -@end menu - -@node Min and Max -@section Minimum and Maximum Operators in C++ - -It is very convenient to have operators which return the ``minimum'' or the -``maximum'' of two arguments. In GNU C++ (but not in GNU C), - -@table @code -@item @var{a} ? @var{b} -@findex >? -@cindex maximum operator -is the @dfn{maximum}, returning the larger of the numeric values @var{a} -and @var{b}. -@end table - -These operations are not primitive in ordinary C++, since you can -use a macro to return the minimum of two things in C++, as in the -following example. - -@example -#define MIN(X,Y) ((X) < (Y) ? : (X) : (Y)) -@end example - -@noindent -You might then use @w{@samp{int min = MIN (i, j);}} to set @var{min} to -the minimum value of variables @var{i} and @var{j}. - -However, side effects in @code{X} or @code{Y} may cause unintended -behavior. For example, @code{MIN (i++, j++)} will fail, incrementing -the smaller counter twice. A GNU C extension allows you to write safe -macros that avoid this kind of problem (@pxref{Naming Types,,Naming an -Expression's Type}). However, writing @code{MIN} and @code{MAX} as -macros also forces you to use function-call notation for a -fundamental arithmetic operation. Using GNU C++ extensions, you can -write @w{@samp{int min = i ?} are built into the compiler, they properly -handle expressions with side-effects; @w{@samp{int min = i++ ; -volatile int *src = ; -*dst = *src; -@end example - -@noindent -will cause a read of the volatile object pointed to by @var{src} and stores the -value into the volatile object pointed to by @var{dst}. There is no -guarantee that these reads and writes are atomic, especially for objects -larger than @code{int}. - -Less obvious expressions are where something which looks like an access -is used in a void context. An example would be, - -@example -volatile int *src = ; -*src; -@end example - -With C, such expressions are rvalues, and as rvalues cause a read of -the object, gcc interprets this as a read of the volatile being pointed -to. The C++ standard specifies that such expressions do not undergo -lvalue to rvalue conversion, and that the type of the dereferenced -object may be incomplete. The C++ standard does not specify explicitly -that it is this lvalue to rvalue conversion which is responsible for -causing an access. However, there is reason to believe that it is, -because otherwise certain simple expressions become undefined. However, -because it would surprise most programmers, g++ treats dereferencing a -pointer to volatile object of complete type in a void context as a read -of the object. When the object has incomplete type, g++ issues a -warning. - -@example -struct S; -struct T @{int m;@}; -volatile S *ptr1 = ; -volatile T *ptr2 = ; -*ptr1; -*ptr2; -@end example - -In this example, a warning is issued for @code{*ptr1}, and @code{*ptr2} -causes a read of the object pointed to. If you wish to force an error on -the first case, you must force a conversion to rvalue with, for instance -a static cast, @code{static_cast(*ptr1)}. - -When using a reference to volatile, g++ does not treat equivalent -expressions as accesses to volatiles, but instead issues a warning that -no volatile is accessed. The rationale for this is that otherwise it -becomes difficult to determine where volatile access occur, and not -possible to ignore the return value from functions returning volatile -references. Again, if you wish to force a read, cast the reference to -an rvalue. - -@node Restricted Pointers -@section Restricting Pointer Aliasing -@cindex restricted pointers -@cindex restricted references -@cindex restricted this pointer - -As with gcc, g++ understands the C99 feature of restricted pointers, -specified with the @code{__restrict__}, or @code{__restrict} type -qualifier. Because you cannot compile C++ by specifying the -std=c99 -language flag, @code{restrict} is not a keyword in C++. - -In addition to allowing restricted pointers, you can specify restricted -references, which indicate that the reference is not aliased in the local -context. - -@example -void fn (int *__restrict__ rptr, int &__restrict__ rref) -@{ - @dots{} -@} -@end example - -@noindent -In the body of @code{fn}, @var{rptr} points to an unaliased integer and -@var{rref} refers to a (different) unaliased integer. - -You may also specify whether a member function's @var{this} pointer is -unaliased by using @code{__restrict__} as a member function qualifier. - -@example -void T::fn () __restrict__ -@{ - @dots{} -@} -@end example - -@noindent -Within the body of @code{T::fn}, @var{this} will have the effective -definition @code{T *__restrict__ const this}. Notice that the -interpretation of a @code{__restrict__} member function qualifier is -different to that of @code{const} or @code{volatile} qualifier, in that it -is applied to the pointer rather than the object. This is consistent with -other compilers which implement restricted pointers. - -As with all outermost parameter qualifiers, @code{__restrict__} is -ignored in function definition matching. This means you only need to -specify @code{__restrict__} in a function definition, rather than -in a function prototype as well. - -@node Vague Linkage -@section Vague Linkage -@cindex vague linkage - -There are several constructs in C++ which require space in the object -file but are not clearly tied to a single translation unit. We say that -these constructs have ``vague linkage''. Typically such constructs are -emitted wherever they are needed, though sometimes we can be more -clever. - -@table @asis -@item Inline Functions -Inline functions are typically defined in a header file which can be -included in many different compilations. Hopefully they can usually be -inlined, but sometimes an out-of-line copy is necessary, if the address -of the function is taken or if inlining fails. In general, we emit an -out-of-line copy in all translation units where one is needed. As an -exception, we only emit inline virtual functions with the vtable, since -it will always require a copy. - -Local static variables and string constants used in an inline function -are also considered to have vague linkage, since they must be shared -between all inlined and out-of-line instances of the function. - -@item VTables -@cindex vtable -C++ virtual functions are implemented in most compilers using a lookup -table, known as a vtable. The vtable contains pointers to the virtual -functions provided by a class, and each object of the class contains a -pointer to its vtable (or vtables, in some multiple-inheritance -situations). If the class declares any non-inline, non-pure virtual -functions, the first one is chosen as the ``key method'' for the class, -and the vtable is only emitted in the translation unit where the key -method is defined. - -@emph{Note:} If the chosen key method is later defined as inline, the -vtable will still be emitted in every translation unit which defines it. -Make sure that any inline virtuals are declared inline in the class -body, even if they are not defined there. - -@item type_info objects -@cindex type_info -@cindex RTTI -C++ requires information about types to be written out in order to -implement @samp{dynamic_cast}, @samp{typeid} and exception handling. -For polymorphic classes (classes with virtual functions), the type_info -object is written out along with the vtable so that @samp{dynamic_cast} -can determine the dynamic type of a class object at runtime. For all -other types, we write out the type_info object when it is used: when -applying @samp{typeid} to an expression, throwing an object, or -referring to a type in a catch clause or exception specification. - -@item Template Instantiations -Most everything in this section also applies to template instantiations, -but there are other options as well. -@xref{Template Instantiation,,Where's the Template?}. - -@end table - -When used with GNU ld version 2.8 or later on an ELF system such as -Linux/GNU or Solaris 2, or on Microsoft Windows, duplicate copies of -these constructs will be discarded at link time. This is known as -COMDAT support. - -On targets that don't support COMDAT, but do support weak symbols, GCC -will use them. This way one copy will override all the others, but -the unused copies will still take up space in the executable. - -For targets which do not support either COMDAT or weak symbols, -most entities with vague linkage will be emitted as local symbols to -avoid duplicate definition errors from the linker. This will not happen -for local statics in inlines, however, as having multiple copies will -almost certainly break things. - -@xref{C++ Interface,,Declarations and Definitions in One Header}, for -another way to control placement of these constructs. - -@node C++ Interface -@section Declarations and Definitions in One Header - -@cindex interface and implementation headers, C++ -@cindex C++ interface and implementation headers -C++ object definitions can be quite complex. In principle, your source -code will need two kinds of things for each object that you use across -more than one source file. First, you need an @dfn{interface} -specification, describing its structure with type declarations and -function prototypes. Second, you need the @dfn{implementation} itself. -It can be tedious to maintain a separate interface description in a -header file, in parallel to the actual implementation. It is also -dangerous, since separate interface and implementation definitions may -not remain parallel. - -@cindex pragmas, interface and implementation -With GNU C++, you can use a single header file for both purposes. - -@quotation -@emph{Warning:} The mechanism to specify this is in transition. For the -nonce, you must use one of two @code{#pragma} commands; in a future -release of GNU C++, an alternative mechanism will make these -@code{#pragma} commands unnecessary. -@end quotation - -The header file contains the full definitions, but is marked with -@samp{#pragma interface} in the source code. This allows the compiler -to use the header file only as an interface specification when ordinary -source files incorporate it with @code{#include}. In the single source -file where the full implementation belongs, you can use either a naming -convention or @samp{#pragma implementation} to indicate this alternate -use of the header file. - -@table @code -@item #pragma interface -@itemx #pragma interface "@var{subdir}/@var{objects}.h" -@kindex #pragma interface -Use this directive in @emph{header files} that define object classes, to save -space in most of the object files that use those classes. Normally, -local copies of certain information (backup copies of inline member -functions, debugging information, and the internal tables that implement -virtual functions) must be kept in each object file that includes class -definitions. You can use this pragma to avoid such duplication. When a -header file containing @samp{#pragma interface} is included in a -compilation, this auxiliary information will not be generated (unless -the main input source file itself uses @samp{#pragma implementation}). -Instead, the object files will contain references to be resolved at link -time. - -The second form of this directive is useful for the case where you have -multiple headers with the same name in different directories. If you -use this form, you must specify the same string to @samp{#pragma -implementation}. - -@item #pragma implementation -@itemx #pragma implementation "@var{objects}.h" -@kindex #pragma implementation -Use this pragma in a @emph{main input file}, when you want full output from -included header files to be generated (and made globally visible). The -included header file, in turn, should use @samp{#pragma interface}. -Backup copies of inline member functions, debugging information, and the -internal tables used to implement virtual functions are all generated in -implementation files. - -@cindex implied @code{#pragma implementation} -@cindex @code{#pragma implementation}, implied -@cindex naming convention, implementation headers -If you use @samp{#pragma implementation} with no argument, it applies to -an include file with the same basename@footnote{A file's @dfn{basename} -was the name stripped of all leading path information and of trailing -suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source -file. For example, in @file{allclass.cc}, giving just -@samp{#pragma implementation} -by itself is equivalent to @samp{#pragma implementation "allclass.h"}. - -In versions of GNU C++ prior to 2.6.0 @file{allclass.h} was treated as -an implementation file whenever you would include it from -@file{allclass.cc} even if you never specified @samp{#pragma -implementation}. This was deemed to be more trouble than it was worth, -however, and disabled. - -If you use an explicit @samp{#pragma implementation}, it must appear in -your source file @emph{before} you include the affected header files. - -Use the string argument if you want a single implementation file to -include code from multiple header files. (You must also use -@samp{#include} to include the header file; @samp{#pragma -implementation} only specifies how to use the file---it doesn't actually -include it.) - -There is no way to split up the contents of a single header file into -multiple implementation files. -@end table - -@cindex inlining and C++ pragmas -@cindex C++ pragmas, effect on inlining -@cindex pragmas in C++, effect on inlining -@samp{#pragma implementation} and @samp{#pragma interface} also have an -effect on function inlining. - -If you define a class in a header file marked with @samp{#pragma -interface}, the effect on a function defined in that class is similar to -an explicit @code{extern} declaration---the compiler emits no code at -all to define an independent version of the function. Its definition -is used only for inlining with its callers. - -Conversely, when you include the same header file in a main source file -that declares it as @samp{#pragma implementation}, the compiler emits -code for the function itself; this defines a version of the function -that can be found via pointers (or by callers compiled without -inlining). If all calls to the function can be inlined, you can avoid -emitting the function by compiling with @samp{-fno-implement-inlines}. -If any calls were not inlined, you will get linker errors. - -@node Template Instantiation -@section Where's the Template? - -@cindex template instantiation - -C++ templates are the first language feature to require more -intelligence from the environment than one usually finds on a UNIX -system. Somehow the compiler and linker have to make sure that each -template instance occurs exactly once in the executable if it is needed, -and not at all otherwise. There are two basic approaches to this -problem, which I will refer to as the Borland model and the Cfront model. - -@table @asis -@item Borland model -Borland C++ solved the template instantiation problem by adding the code -equivalent of common blocks to their linker; the compiler emits template -instances in each translation unit that uses them, and the linker -collapses them together. The advantage of this model is that the linker -only has to consider the object files themselves; there is no external -complexity to worry about. This disadvantage is that compilation time -is increased because the template code is being compiled repeatedly. -Code written for this model tends to include definitions of all -templates in the header file, since they must be seen to be -instantiated. - -@item Cfront model -The AT&T C++ translator, Cfront, solved the template instantiation -problem by creating the notion of a template repository, an -automatically maintained place where template instances are stored. A -more modern version of the repository works as follows: As individual -object files are built, the compiler places any template definitions and -instantiations encountered in the repository. At link time, the link -wrapper adds in the objects in the repository and compiles any needed -instances that were not previously emitted. The advantages of this -model are more optimal compilation speed and the ability to use the -system linker; to implement the Borland model a compiler vendor also -needs to replace the linker. The disadvantages are vastly increased -complexity, and thus potential for error; for some code this can be -just as transparent, but in practice it can been very difficult to build -multiple programs in one directory and one program in multiple -directories. Code written for this model tends to separate definitions -of non-inline member templates into a separate file, which should be -compiled separately. -@end table - -When used with GNU ld version 2.8 or later on an ELF system such as -Linux/GNU or Solaris 2, or on Microsoft Windows, g++ supports the -Borland model. On other systems, g++ implements neither automatic -model. - -A future version of g++ will support a hybrid model whereby the compiler -will emit any instantiations for which the template definition is -included in the compile, and store template definitions and -instantiation context information into the object file for the rest. -The link wrapper will extract that information as necessary and invoke -the compiler to produce the remaining instantiations. The linker will -then combine duplicate instantiations. - -In the mean time, you have the following options for dealing with -template instantiations: - -@enumerate -@item -Compile your template-using code with @samp{-frepo}. The compiler will -generate files with the extension @samp{.rpo} listing all of the -template instantiations used in the corresponding object files which -could be instantiated there; the link wrapper, @samp{collect2}, will -then update the @samp{.rpo} files to tell the compiler where to place -those instantiations and rebuild any affected object files. The -link-time overhead is negligible after the first pass, as the compiler -will continue to place the instantiations in the same files. - -This is your best option for application code written for the Borland -model, as it will just work. Code written for the Cfront model will -need to be modified so that the template definitions are available at -one or more points of instantiation; usually this is as simple as adding -@code{#include } to the end of each template header. - -For library code, if you want the library to provide all of the template -instantiations it needs, just try to link all of its object files -together; the link will fail, but cause the instantiations to be -generated as a side effect. Be warned, however, that this may cause -conflicts if multiple libraries try to provide the same instantiations. -For greater control, use explicit instantiation as described in the next -option. - -@item -Compile your code with @samp{-fno-implicit-templates} to disable the -implicit generation of template instances, and explicitly instantiate -all the ones you use. This approach requires more knowledge of exactly -which instances you need than do the others, but it's less -mysterious and allows greater control. You can scatter the explicit -instantiations throughout your program, perhaps putting them in the -translation units where the instances are used or the translation units -that define the templates themselves; you can put all of the explicit -instantiations you need into one big file; or you can create small files -like - -@example -#include "Foo.h" -#include "Foo.cc" - -template class Foo; -template ostream& operator << - (ostream&, const Foo&); -@end example - -for each of the instances you need, and create a template instantiation -library from those. - -If you are using Cfront-model code, you can probably get away with not -using @samp{-fno-implicit-templates} when compiling files that don't -@samp{#include} the member template definitions. - -If you use one big file to do the instantiations, you may want to -compile it without @samp{-fno-implicit-templates} so you get all of the -instances required by your explicit instantiations (but not by any -other files) without having to specify them as well. - -g++ has extended the template instantiation syntax outlined in the -Working Paper to allow forward declaration of explicit instantiations -(with @code{extern}), instantiation of the compiler support data for a -template class (i.e. the vtable) without instantiating any of its -members (with @code{inline}), and instantiation of only the static data -members of a template class, without the support data or member -functions (with (@code{static}): - -@example -extern template int max (int, int); -inline template class Foo; -static template class Foo; -@end example - -@item -Do nothing. Pretend g++ does implement automatic instantiation -management. Code written for the Borland model will work fine, but -each translation unit will contain instances of each of the templates it -uses. In a large program, this can lead to an unacceptable amount of code -duplication. - -@item -Add @samp{#pragma interface} to all files containing template -definitions. For each of these files, add @samp{#pragma implementation -"@var{filename}"} to the top of some @samp{.C} file which -@samp{#include}s it. Then compile everything with -@samp{-fexternal-templates}. The templates will then only be expanded -in the translation unit which implements them (i.e. has a @samp{#pragma -implementation} line for the file where they live); all other files will -use external references. If you're lucky, everything should work -properly. If you get undefined symbol errors, you need to make sure -that each template instance which is used in the program is used in the -file which implements that template. If you don't have any use for a -particular instance in that file, you can just instantiate it -explicitly, using the syntax from the latest C++ working paper: - -@example -template class A; -template ostream& operator << (ostream&, const A&); -@end example - -This strategy will work with code written for either model. If you are -using code written for the Cfront model, the file containing a class -template and the file containing its member templates should be -implemented in the same translation unit. - -A slight variation on this approach is to instead use the flag -@samp{-falt-external-templates}; this flag causes template -instances to be emitted in the translation unit that implements the -header where they are first instantiated, rather than the one which -implements the file where the templates are defined. This header must -be the same in all translation units, or things are likely to break. - -@xref{C++ Interface,,Declarations and Definitions in One Header}, for -more discussion of these pragmas. -@end enumerate - -@node Bound member functions -@section Extracting the function pointer from a bound pointer to member function - -@cindex pmf -@cindex pointer to member function -@cindex bound pointer to member function - -In C++, pointer to member functions (PMFs) are implemented using a wide -pointer of sorts to handle all the possible call mechanisms; the PMF -needs to store information about how to adjust the @samp{this} pointer, -and if the function pointed to is virtual, where to find the vtable, and -where in the vtable to look for the member function. If you are using -PMFs in an inner loop, you should really reconsider that decision. If -that is not an option, you can extract the pointer to the function that -would be called for a given object/PMF pair and call it directly inside -the inner loop, to save a bit of time. - -Note that you will still be paying the penalty for the call through a -function pointer; on most modern architectures, such a call defeats the -branch prediction features of the CPU. This is also true of normal -virtual function calls. - -The syntax for this extension is - -@example -extern A a; -extern int (A::*fp)(); -typedef int (*fptr)(A *); - -fptr p = (fptr)(a.*fp); -@end example - -For PMF constants (i.e. expressions of the form @samp{&Klasse::Member}), -no object is needed to obtain the address of the function. They can be -converted to function pointers directly: - -@example -fptr p1 = (fptr)(&A::foo); -@end example - -You must specify @samp{-Wno-pmf-conversions} to use this extension. - -@node C++ Attributes -@section C++-Specific Variable, Function, and Type Attributes - -Some attributes only make sense for C++ programs. - -@table @code -@item init_priority (@var{priority}) -@cindex init_priority attribute - - -In Standard C++, objects defined at namespace scope are guaranteed to be -initialized in an order in strict accordance with that of their definitions -@emph{in a given translation unit}. No guarantee is made for initializations -across translation units. However, GNU C++ allows users to control the -order of initialization of objects defined at namespace scope with the -@code{init_priority} attribute by specifying a relative @var{priority}, -a constant integral expression currently bounded between 101 and 65535 -inclusive. Lower numbers indicate a higher priority. - -In the following example, @code{A} would normally be created before -@code{B}, but the @code{init_priority} attribute has reversed that order: - -@example -Some_Class A __attribute__ ((init_priority (2000))); -Some_Class B __attribute__ ((init_priority (543))); -@end example - -@noindent -Note that the particular values of @var{priority} do not matter; only their -relative ordering. - -@item java_interface -@cindex java_interface attribute - -This type attribute informs C++ that the class is a Java interface. It may -only be applied to classes declared within an @code{extern "Java"} block. -Calls to methods declared in this interface will be dispatched using GCJ's -interface table mechanism, instead of regular virtual table dispatch. - -@end table - -@node Java Exceptions -@section Java Exceptions - -The Java language uses a slightly different exception handling model -from C++. Normally, GNU C++ will automatically detect when you are -writing C++ code that uses Java exceptions, and handle them -appropriately. However, if C++ code only needs to execute destructors -when Java exceptions are thrown through it, GCC will guess incorrectly. -Sample problematic code: - -@example - struct S @{ ~S(); @}; - extern void bar(); // is implemented in Java and may throw exceptions - void foo() - @{ - S s; - bar(); - @} -@end example - -@noindent -The usual effect of an incorrect guess is a link failure, complaining of -a missing routine called @samp{__gxx_personality_v0}. - -You can inform the compiler that Java exceptions are to be used in a -translation unit, irrespective of what it might think, by writing -@samp{@w{#pragma GCC java_exceptions}} at the head of the file. This -@samp{#pragma} must appear before any functions that throw or catch -exceptions, or run destructors when exceptions are thrown through them. - -You cannot mix Java and C++ exceptions in the same translation unit. It -is believed to be safe to throw a C++ exception from one file through -another file compiled for the for the Java exception model, or vice -versa, but there may be bugs in this area. - -@node Deprecated Features -@section Deprecated Features - -In the past, the GNU C++ compiler was extended to experiment with new -features, at a time when the C++ language was still evolving. Now that -the C++ standard is complete, some of those features are superseded by -superior alternatives. Using the old features might cause a warning in -some cases that the feature will be dropped in the future. In other -cases, the feature might be gone already. - -While the list below is not exhaustive, it documents some of the options -that are now deprecated: - -@table @code -@item -fexternal-templates -@itemx -falt-external-templates -These are two of the many ways for g++ to implement template -instantiation. @xref{Template Instantiation}. The C++ standard clearly -defines how template definitions have to be organized across -implementation units. g++ has an implicit instantiation mechanism that -should work just fine for standard-conforming code. - -@item -fstrict-prototype -@itemx -fno-strict-prototype -Previously it was possible to use an empty prototype parameter list to -indicate an unspecified number of parameters (like C), rather than no -parameters, as C++ demands. This feature has been removed, except where -it is required for backwards compatibility @xref{Backwards Compatibility}. -@end table - -The named return value extension has been deprecated, and will be -removed from g++ at some point. - -The use of initializer lists with new expressions has been deprecated, -and will be removed from g++ at some point. - -@node Backwards Compatibility -@section Backwards Compatibility -@cindex Backwards Compatibility -@cindex ARM [Annotated C++ Reference Manual] - -Now that there is a definitive ISO standard C++, g++ has a specification -to adhere to. The C++ language evolved over time, and features that -used to be acceptable in previous drafts of the standard, such as the ARM -[Annotated C++ Reference Manual], are no longer accepted. In order to allow -compilation of C++ written to such drafts, g++ contains some backwards -compatibilities. @emph{All such backwards compatibility features are -liable to disappear in future versions of g++.} They should be considered -deprecated @xref{Deprecated Features}. - -@table @code -@item For scope -If a variable is declared at for scope, it used to remain in scope until -the end of the scope which contained the for statement (rather than just -within the for scope). g++ retains this, but issues a warning, if such a -variable is accessed outside the for scope. - -@item implicit C language -Old C system header files did not contain an @code{extern "C" @{...@}} -scope to set the language. On such systems, all header files are -implicitly scoped inside a C language scope. Also, an empty prototype -@code{()} will be treated as an unspecified number of arguments, rather -than no arguments, as C++ demands. -@end table diff --git a/gcc/f/Make-lang.in b/gcc/f/Make-lang.in index 6fadb436550..798bb267e93 100644 --- a/gcc/f/Make-lang.in +++ b/gcc/f/Make-lang.in @@ -172,27 +172,27 @@ f77.dvi: f/g77.dvi $(srcdir)/f/g77.info: $(srcdir)/f/g77.texi $(srcdir)/f/bugs.texi \ $(srcdir)/f/ffe.texi $(srcdir)/f/g77install.texi \ $(srcdir)/f/news.texi $(srcdir)/f/intdoc.texi \ - $(srcdir)/f/root.texi $(srcdir)/fdl.texi + $(srcdir)/f/root.texi $(srcdir)/doc/fdl.texi case "$(LANGUAGES)" in \ *[fF]77*) $(STAMP) lang-f77;; \ *) rm -f lang-f77;; \ esac if [ -f lang-f77 ] && [ x$(BUILD_INFO) = xinfo ]; then \ rm -f $(srcdir)/f/g77.info-*; \ - cd $(srcdir)/f && $(MAKEINFO) -I.. -o g77.info g77.texi; \ + cd $(srcdir)/f && $(MAKEINFO) -I../doc -o g77.info g77.texi; \ else true; fi f/g77.dvi: $(srcdir)/f/g77.texi $(srcdir)/f/bugs.texi \ $(srcdir)/f/ffe.texi $(srcdir)/f/g77install.texi \ $(srcdir)/f/news.texi $(srcdir)/f/intdoc.texi \ - $(srcdir)/f/root.texi $(srcdir)/fdl.texi + $(srcdir)/f/root.texi $(srcdir)/doc/fdl.texi case "$(LANGUAGES)" in \ *[fF]77*) $(STAMP) lang-f77;; \ *) rm -f lang-f77;; \ esac if [ -f lang-f77 ]; then \ s=`cd $(srcdir); pwd`; export s; \ - cd f && $(TEXI2DVI) -I $$s $$s/f/g77.texi; \ + cd f && $(TEXI2DVI) -I $$s/doc $$s/f/g77.texi; \ else true; fi # This dance is all about producing accurate documentation for g77's diff --git a/gcc/fdl.texi b/gcc/fdl.texi deleted file mode 100644 index db691df61ed..00000000000 --- a/gcc/fdl.texi +++ /dev/null @@ -1,403 +0,0 @@ - -@node GNU Free Documentation License -@unnumbered GNU Free Documentation License - -@cindex FDL, GNU Free Documentation License -@center Version 1.1, March 2000 - -@display -Copyright @copyright{} 2000 Free Software Foundation, Inc. -59 Temple Place, Suite 330, Boston, MA 02111-1307, USA - -Everyone is permitted to copy and distribute verbatim copies -of this license document, but changing it is not allowed. -@end display - -@enumerate 0 -@item -PREAMBLE - -The purpose of this License is to make a manual, textbook, or other -written document @dfn{free} in the sense of freedom: to assure everyone -the effective freedom to copy and redistribute it, with or without -modifying it, either commercially or noncommercially. Secondarily, -this License preserves for the author and publisher a way to get -credit for their work, while not being considered responsible for -modifications made by others. - -This License is a kind of ``copyleft'', which means that derivative -works of the document must themselves be free in the same sense. It -complements the GNU General Public License, which is a copyleft -license designed for free software. - -We have designed this License in order to use it for manuals for free -software, because free software needs free documentation: a free -program should come with manuals providing the same freedoms that the -software does. But this License is not limited to software manuals; -it can be used for any textual work, regardless of subject matter or -whether it is published as a printed book. We recommend this License -principally for works whose purpose is instruction or reference. - -@item -APPLICABILITY AND DEFINITIONS - -This License applies to any manual or other work that contains a -notice placed by the copyright holder saying it can be distributed -under the terms of this License. The ``Document'', below, refers to any -such manual or work. Any member of the public is a licensee, and is -addressed as ``you''. - -A ``Modified Version'' of the Document means any work containing the -Document or a portion of it, either copied verbatim, or with -modifications and/or translated into another language. - -A ``Secondary Section'' is a named appendix or a front-matter section of -the Document that deals exclusively with the relationship of the -publishers or authors of the Document to the Document's overall subject -(or to related matters) and contains nothing that could fall directly -within that overall subject. 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If the Document does not specify a version -number of this License, you may choose any version ever published (not -as a draft) by the Free Software Foundation. -@end enumerate - -@page -@unnumberedsec ADDENDUM: How to use this License for your documents - -To use this License in a document you have written, include a copy of -the License in the document and put the following copyright and -license notices just after the title page: - -@smallexample -@group - Copyright (C) @var{year} @var{your name}. - Permission is granted to copy, distribute and/or modify this document - under the terms of the GNU Free Documentation License, Version 1.1 - or any later version published by the Free Software Foundation; - with the Invariant Sections being @var{list their titles}, with the - Front-Cover Texts being @var{list}, and with the Back-Cover Texts being @var{list}. - A copy of the license is included in the section entitled ``GNU - Free Documentation License''. -@end group -@end smallexample - -If you have no Invariant Sections, write ``with no Invariant Sections'' -instead of saying which ones are invariant. If you have no -Front-Cover Texts, write ``no Front-Cover Texts'' instead of -``Front-Cover Texts being @var{list}''; likewise for Back-Cover Texts. - -If your document contains nontrivial examples of program code, we -recommend releasing these examples in parallel under your choice of -free software license, such as the GNU General Public License, -to permit their use in free software. - -@c Local Variables: -@c ispell-local-pdict: "ispell-dict" -@c End: - diff --git a/gcc/gcc.1 b/gcc/gcc.1 deleted file mode 100644 index 98fbab9b659..00000000000 --- a/gcc/gcc.1 +++ /dev/null @@ -1,8046 +0,0 @@ -.\" Automatically generated by Pod::Man version 1.15 -.\" Sun May 20 12:45:49 2001 -.\" -.\" Standard preamble: -.\" ====================================================================== -.de Sh \" Subsection heading -.br -.if t .Sp -.ne 5 -.PP -\fB\\$1\fR -.PP -.. -.de Sp \" Vertical space (when we can't use .PP) -.if t .sp .5v -.if n .sp -.. -.de Ip \" List item -.br -.ie \\n(.$>=3 .ne \\$3 -.el .ne 3 -.IP "\\$1" \\$2 -.. -.de Vb \" Begin verbatim text -.ft CW -.nf -.ne \\$1 -.. -.de Ve \" End verbatim text -.ft R - -.fi -.. -.\" Set up some character translations and predefined strings. \*(-- will -.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left -.\" double quote, and \*(R" will give a right double quote. | will give a -.\" real vertical bar. \*(C+ will give a nicer C++. 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The ``overall options'' allow you to stop this -process at an intermediate stage. For example, the \fB\-c\fR option -says not to run the linker. Then the output consists of object files -output by the assembler. -.PP -Other options are passed on to one stage of processing. Some options -control the preprocessor and others the compiler itself. Yet other -options control the assembler and linker; most of these are not -documented here, since you rarely need to use any of them. -.PP -Most of the command line options that you can use with \s-1GCC\s0 are useful -for C programs; when an option is only useful with another language -(usually \*(C+), the explanation says so explicitly. If the description -for a particular option does not mention a source language, you can use -that option with all supported languages. -.PP -The \fBgcc\fR program accepts options and file names as operands. Many -options have multi-letter names; therefore multiple single-letter options -may \fInot\fR be grouped: \fB\-dr\fR is very different from \fB\-d\ \-r\fR. -.PP -You can mix options and other arguments. For the most part, the order -you use doesn't matter. Order does matter when you use several options -of the same kind; for example, if you specify \fB\-L\fR more than once, -the directories are searched in the order specified. -.PP -Many options have long names starting with \fB\-f\fR or with -\&\fB\-W\fR\-\-\-for example, \fB\-fforce-mem\fR, -\&\fB\-fstrength-reduce\fR, \fB\-Wformat\fR and so on. Most of -these have both positive and negative forms; the negative form of -\&\fB\-ffoo\fR would be \fB\-fno-foo\fR. This manual documents -only one of these two forms, whichever one is not the default. -.SH "OPTIONS" -.IX Header "OPTIONS" -.Sh "Option Summary" -.IX Subsection "Option Summary" -Here is a summary of all the options, grouped by type. Explanations are -in the following sections. -.Ip "\fIOverall Options\fR" 4 -.IX Item "Overall Options" -\&\fB\-c \-S \-E \-o\fR \fIfile\fR \fB\-pipe \-pass-exit-codes \-x\fR \fIlanguage\fR -\&\fB\-v \-\-target-help \-\-help\fR -.Ip "\fIC Language Options\fR" 4 -.IX Item "C Language Options" -\&\fB\-ansi \-std=\fR\fIstandard\fR \fB\-fno-asm \-fno-builtin -\&\-fhosted \-ffreestanding -\&\-trigraphs \-traditional \-traditional-cpp -\&\-fallow-single-precision \-fcond-mismatch -\&\-fsigned-bitfields \-fsigned-char -\&\-funsigned-bitfields \-funsigned-char -\&\-fwritable-strings \-fshort-wchar\fR -.Ip "\fI\*(C+ Language Options\fR" 4 -.IX Item " Language Options" -\&\fB\-fno-access-control \-fcheck-new \-fconserve-space -\&\-fdollars-in-identifiers \-fno-elide-constructors -\&\-fno-enforce-eh-specs \-fexternal-templates -\&\-falt-external-templates -\&\-ffor-scope \-fno-for-scope \-fno-gnu-keywords \-fhonor-std -\&\-fhuge-objects \-fno-implicit-templates -\&\-fno-implicit-inline-templates -\&\-fno-implement-inlines \-fms-extensions -\&\-fno-operator-names -\&\-fno-optional-diags \-fpermissive -\&\-frepo \-fno-rtti \-ftemplate-depth-\fR\fIn\fR -\&\fB\-fuse-cxa-atexit \-fvtable-thunks \-nostdinc++ -\&\-fno-default-inline \-Wctor-dtor-privacy -\&\-Wnon-virtual-dtor \-Wreorder -\&\-Weffc++ \-Wno-deprecated -\&\-Wno-non-template-friend \-Wold-style-cast -\&\-Woverloaded-virtual \-Wno-pmf-conversions -\&\-Wsign-promo \-Wsynth\fR -.Ip "\fIObjective-C Language Options\fR" 4 -.IX Item "Objective-C Language Options" -\&\fB\-fconstant-string-class=\fR\fIclass name\fR -\&\fB\-fgnu-runtime \-fnext-runtime \-gen-decls -\&\-Wno-protocol \-Wselector\fR -.Ip "\fILanguage Independent Options\fR" 4 -.IX Item "Language Independent Options" -\&\fB\-fmessage-length=\fR\fIn\fR -\&\fB\-fdiagnostics-show-location=\fR[\fBonce\fR|\fBevery-line\fR] -.Ip "\fIWarning Options\fR" 4 -.IX Item "Warning Options" -\&\fB\-fsyntax-only \-pedantic \-pedantic-errors -\&\-w \-W \-Wall \-Waggregate-return -\&\-Wcast-align \-Wcast-qual \-Wchar-subscripts \-Wcomment -\&\-Wconversion \-Wdisabled-optimization \-Werror -\&\-Wfloat-equal \-Wformat \-Wformat=2 -\&\-Wformat-nonliteral \-Wformat-security -\&\-Wid-clash-\fR\fIlen\fR \fB\-Wimplicit \-Wimplicit-int -\&\-Wimplicit-function-declaration -\&\-Werror-implicit-function-declaration -\&\-Wimport \-Winline -\&\-Wlarger-than-\fR\fIlen\fR \fB\-Wlong-long -\&\-Wmain \-Wmissing-braces \-Wmissing-declarations -\&\-Wmissing-format-attribute \-Wmissing-noreturn -\&\-Wmultichar \-Wno-format-extra-args \-Wno-format-y2k -\&\-Wno-import \-Wpacked \-Wpadded -\&\-Wparentheses \-Wpointer-arith \-Wredundant-decls -\&\-Wreturn-type \-Wsequence-point \-Wshadow -\&\-Wsign-compare \-Wswitch \-Wsystem-headers -\&\-Wtrigraphs \-Wundef \-Wuninitialized -\&\-Wunknown-pragmas \-Wunreachable-code -\&\-Wunused \-Wunused-function \-Wunused-label \-Wunused-parameter -\&\-Wunused-value \-Wunused-variable \-Wwrite-strings\fR -.Ip "\fIC-only Warning Options\fR" 4 -.IX Item "C-only Warning Options" -\&\fB\-Wbad-function-cast \-Wmissing-prototypes \-Wnested-externs -\&\-Wstrict-prototypes \-Wtraditional\fR -.Ip "\fIDebugging Options\fR" 4 -.IX Item "Debugging Options" -\&\fB\-a \-ax \-d\fR\fIletters\fR \fB\-dumpspecs \-dumpmachine \-dumpversion -\&\-fdump-unnumbered \-fdump-translation-unit=\fR\fIfile\fR -\&\fB\-fdump-class-layout=\fR\fIfile\fR \fB\-fmem-report \-fpretend-float -\&\-fprofile-arcs \-ftest-coverage \-ftime-report -\&\-g \-g\fR\fIlevel\fR \fB\-gcoff \-gdwarf \-gdwarf-1 \-gdwarf-1+ \-gdwarf-2 -\&\-ggdb \-gstabs \-gstabs+ \-gxcoff \-gxcoff+ -\&\-p \-pg \-print-file-name=\fR\fIlibrary\fR \fB\-print-libgcc-file-name -\&\-print-prog-name=\fR\fIprogram\fR \fB\-print-search-dirs \-Q -\&\-save-temps \-time\fR -.Ip "\fIOptimization Options\fR" 4 -.IX Item "Optimization Options" -\&\fB\-falign-functions=\fR\fIn\fR \fB\-falign-jumps=\fR\fIn\fR -\&\fB\-falign-labels=\fR\fIn\fR \fB\-falign-loops=\fR\fIn\fR -\&\fB\-fbranch-probabilities \-fcaller-saves -\&\-fcse-follow-jumps \-fcse-skip-blocks \-fdata-sections \-fdce -\&\-fdelayed-branch \-fdelete-null-pointer-checks -\&\-fexpensive-optimizations \-ffast-math \-ffloat-store -\&\-fforce-addr \-fforce-mem \-ffunction-sections \-fgcse \-fgcse-lm \-fgcse-sm -\&\-finline-functions \-finline-limit=\fR\fIn\fR \fB\-fkeep-inline-functions -\&\-fkeep-static-consts \-fmove-all-movables -\&\-fno-default-inline \-fno-defer-pop -\&\-fno-function-cse \-fno-guess-branch-probability -\&\-fno-inline \-fno-math-errno \-fno-peephole -\&\-funsafe-math-optimizations \-fno-trapping-math -\&\-fomit-frame-pointer \-foptimize-register-move -\&\-foptimize-sibling-calls \-freduce-all-givs -\&\-fregmove \-frename-registers -\&\-frerun-cse-after-loop \-frerun-loop-opt -\&\-fschedule-insns \-fschedule-insns2 -\&\-fsingle-precision-constant \-fssa -\&\-fstrength-reduce \-fstrict-aliasing \-fthread-jumps \-ftrapv -\&\-funroll-all-loops \-funroll-loops -\&\-\-param\fR \fIname\fR\fB=\fR\fIvalue\fR -\&\fB\-O \-O0 \-O1 \-O2 \-O3 \-Os\fR -.Ip "\fIPreprocessor Options\fR" 4 -.IX Item "Preprocessor Options" -\&\fB\-$ \-A\fR\fIquestion\fR\fB=\fR\fIanswer\fR \fB\-A-\fR\fIquestion\fR[\fB=\fR\fIanswer\fR] -\&\fB\-C \-dD \-dI \-dM \-dN -\&\-D\fR\fImacro\fR[\fB=\fR\fIdefn\fR] \fB\-E \-H -\&\-idirafter\fR \fIdir\fR -\&\fB\-include\fR \fIfile\fR \fB\-imacros\fR \fIfile\fR -\&\fB\-iprefix\fR \fIfile\fR \fB\-iwithprefix\fR \fIdir\fR -\&\fB\-iwithprefixbefore\fR \fIdir\fR \fB\-isystem\fR \fIdir\fR \fB\-isystem-c++\fR \fIdir\fR -\&\fB\-M \-MM \-MF \-MG \-MP \-MQ \-MT \-nostdinc \-P \-remap -\&\-trigraphs \-undef \-U\fR\fImacro\fR \fB\-Wp,\fR\fIoption\fR -.Ip "\fIAssembler Option\fR" 4 -.IX Item "Assembler Option" -\&\fB\-Wa,\fR\fIoption\fR -.Ip "\fILinker Options\fR" 4 -.IX Item "Linker Options" -\&\fB -\&\fR\fIobject-file-name\fR \fB\-l\fR\fIlibrary\fR -\&\fB\-nostartfiles \-nodefaultlibs \-nostdlib -\&\-s \-static \-static-libgcc \-shared \-shared-libgcc \-symbolic -\&\-Wl,\fR\fIoption\fR \fB\-Xlinker\fR \fIoption\fR -\&\fB\-u\fR \fIsymbol\fR -.Ip "\fIDirectory Options\fR" 4 -.IX Item "Directory Options" -\&\fB\-B\fR\fIprefix\fR \fB\-I\fR\fIdir\fR \fB\-I- \-L\fR\fIdir\fR \fB\-specs=\fR\fIfile\fR -.Ip "\fITarget Options\fR" 4 -.IX Item "Target Options" -\&\fB\-b\fR \fImachine\fR \fB\-V\fR \fIversion\fR -.Ip "\fIMachine Dependent Options\fR" 4 -.IX Item "Machine Dependent Options" -\&\fIM680x0 Options\fR -.Sp -\&\fB\-m68000 \-m68020 \-m68020\-40 \-m68020\-60 \-m68030 \-m68040 -\&\-m68060 \-mcpu32 \-m5200 \-m68881 \-mbitfield \-mc68000 \-mc68020 -\&\-mfpa \-mnobitfield \-mrtd \-mshort \-msoft-float \-mpcrel -\&\-malign-int \-mstrict-align\fR -.Sp -\&\fIM68hc1x Options\fR -.Sp -\&\fB\-m6811 \-m6812 \-m68hc11 \-m68hc12 -\&\-mauto-incdec \-mshort \-msoft-reg-count=\fR\fIcount\fR -.Sp -\&\fI\s-1VAX\s0 Options\fR -.Sp -\&\fB\-mg \-mgnu \-munix\fR -.Sp -\&\fI\s-1SPARC\s0 Options\fR -.Sp -\&\fB\-mcpu=\fR\fIcpu type\fR -\&\fB\-mtune=\fR\fIcpu type\fR -\&\fB\-mcmodel=\fR\fIcode model\fR -\&\fB\-m32 \-m64 -\&\-mapp-regs \-mbroken-saverestore \-mcypress -\&\-mepilogue \-mfaster-structs \-mflat -\&\-mfpu \-mhard-float \-mhard-quad-float -\&\-mimpure-text \-mlive-g0 \-mno-app-regs -\&\-mno-epilogue \-mno-faster-structs \-mno-flat \-mno-fpu -\&\-mno-impure-text \-mno-stack-bias \-mno-unaligned-doubles -\&\-msoft-float \-msoft-quad-float \-msparclite \-mstack-bias -\&\-msupersparc \-munaligned-doubles \-mv8\fR -.Sp -\&\fIConvex Options\fR -.Sp -\&\fB\-mc1 \-mc2 \-mc32 \-mc34 \-mc38 -\&\-margcount \-mnoargcount -\&\-mlong32 \-mlong64 -\&\-mvolatile-cache \-mvolatile-nocache\fR -.Sp -\&\fI\s-1AMD29K\s0 Options\fR -.Sp -\&\fB\-m29000 \-m29050 \-mbw \-mnbw \-mdw \-mndw -\&\-mlarge \-mnormal \-msmall -\&\-mkernel-registers \-mno-reuse-arg-regs -\&\-mno-stack-check \-mno-storem-bug -\&\-mreuse-arg-regs \-msoft-float \-mstack-check -\&\-mstorem-bug \-muser-registers\fR -.Sp -\&\fI\s-1ARM\s0 Options\fR -.Sp -\&\fB\-mapcs-frame \-mno-apcs-frame -\&\-mapcs-26 \-mapcs-32 -\&\-mapcs-stack-check \-mno-apcs-stack-check -\&\-mapcs-float \-mno-apcs-float -\&\-mapcs-reentrant \-mno-apcs-reentrant -\&\-msched-prolog \-mno-sched-prolog -\&\-mlittle-endian \-mbig-endian \-mwords-little-endian -\&\-malignment-traps \-mno-alignment-traps -\&\-msoft-float \-mhard-float \-mfpe -\&\-mthumb-interwork \-mno-thumb-interwork -\&\-mcpu= \-march= \-mfpe= -\&\-mstructure-size-boundary= -\&\-mbsd \-mxopen \-mno-symrename -\&\-mabort-on-noreturn -\&\-mlong-calls \-mno-long-calls -\&\-mnop-fun-dllimport \-mno-nop-fun-dllimport -\&\-msingle-pic-base \-mno-single-pic-base -\&\-mpic-register=\fR -.Sp -\&\fIThumb Options\fR -.Sp -\&\fB\-mtpcs-frame \-mno-tpcs-frame -\&\-mtpcs-leaf-frame \-mno-tpcs-leaf-frame -\&\-mlittle-endian \-mbig-endian -\&\-mthumb-interwork \-mno-thumb-interwork -\&\-mstructure-size-boundary= -\&\-mnop-fun-dllimport \-mno-nop-fun-dllimport -\&\-mcallee-super-interworking \-mno-callee-super-interworking -\&\-mcaller-super-interworking \-mno-caller-super-interworking -\&\-msingle-pic-base \-mno-single-pic-base -\&\-mpic-register=\fR -.Sp -\&\fI\s-1MN10200\s0 Options\fR -.Sp -\&\fB\-mrelax\fR -.Sp -\&\fI\s-1MN10300\s0 Options\fR -.Sp -\&\fB\-mmult-bug -\&\-mno-mult-bug -\&\-mam33 -\&\-mno-am33 -\&\-mrelax\fR -.Sp -\&\fIM32R/D Options\fR -.Sp -\&\fB\-mcode-model=\fR\fImodel type\fR \fB\-msdata=\fR\fIsdata type\fR -\&\fB\-G\fR \fInum\fR -.Sp -\&\fIM88K Options\fR -.Sp -\&\fB\-m88000 \-m88100 \-m88110 \-mbig-pic -\&\-mcheck-zero-division \-mhandle-large-shift -\&\-midentify-revision \-mno-check-zero-division -\&\-mno-ocs-debug-info \-mno-ocs-frame-position -\&\-mno-optimize-arg-area \-mno-serialize-volatile -\&\-mno-underscores \-mocs-debug-info -\&\-mocs-frame-position \-moptimize-arg-area -\&\-mserialize-volatile \-mshort-data-\fR\fInum\fR \fB\-msvr3 -\&\-msvr4 \-mtrap-large-shift \-muse-div-instruction -\&\-mversion-03.00 \-mwarn-passed-structs\fR -.Sp -\&\fI\s-1RS/6000\s0 and PowerPC Options\fR -.Sp -\&\fB\-mcpu=\fR\fIcpu type\fR -\&\fB\-mtune=\fR\fIcpu type\fR -\&\fB\-mpower \-mno-power \-mpower2 \-mno-power2 -\&\-mpowerpc \-mpowerpc64 \-mno-powerpc -\&\-mpowerpc-gpopt \-mno-powerpc-gpopt -\&\-mpowerpc-gfxopt \-mno-powerpc-gfxopt -\&\-mnew-mnemonics \-mold-mnemonics -\&\-mfull-toc \-mminimal-toc \-mno-fop-in-toc \-mno-sum-in-toc -\&\-m64 \-m32 \-mxl-call \-mno-xl-call \-mthreads \-mpe -\&\-msoft-float \-mhard-float \-mmultiple \-mno-multiple -\&\-mstring \-mno-string \-mupdate \-mno-update -\&\-mfused-madd \-mno-fused-madd \-mbit-align \-mno-bit-align -\&\-mstrict-align \-mno-strict-align \-mrelocatable -\&\-mno-relocatable \-mrelocatable-lib \-mno-relocatable-lib -\&\-mtoc \-mno-toc \-mlittle \-mlittle-endian \-mbig \-mbig-endian -\&\-mcall-aix \-mcall-sysv \-mprototype \-mno-prototype -\&\-msim \-mmvme \-mads \-myellowknife \-memb \-msdata -\&\-msdata=\fR\fIopt\fR \fB\-mvxworks \-G\fR \fInum\fR -.Sp -\&\fI\s-1RT\s0 Options\fR -.Sp -\&\fB\-mcall-lib-mul \-mfp-arg-in-fpregs \-mfp-arg-in-gregs -\&\-mfull-fp-blocks \-mhc-struct-return \-min-line-mul -\&\-mminimum-fp-blocks \-mnohc-struct-return\fR -.Sp -\&\fI\s-1MIPS\s0 Options\fR -.Sp -\&\fB\-mabicalls \-mcpu=\fR\fIcpu type\fR -\&\fB\-membedded-data \-muninit-const-in-rodata -\&\-membedded-pic \-mfp32 \-mfp64 \-mgas \-mgp32 \-mgp64 -\&\-mgpopt \-mhalf-pic \-mhard-float \-mint64 \-mips1 -\&\-mips2 \-mips3 \-mips4 \-mlong64 \-mlong32 \-mlong-calls \-mmemcpy -\&\-mmips-as \-mmips-tfile \-mno-abicalls -\&\-mno-embedded-data \-mno-uninit-const-in-rodata \-mno-embedded-pic -\&\-mno-gpopt \-mno-long-calls -\&\-mno-memcpy \-mno-mips-tfile \-mno-rnames \-mno-stats -\&\-mrnames \-msoft-float -\&\-m4650 \-msingle-float \-mmad -\&\-mstats \-EL \-EB \-G\fR \fInum\fR \fB\-nocpp -\&\-mabi=32 \-mabi=n32 \-mabi=64 \-mabi=eabi -\&\-mfix7000 \-mno-crt0\fR -.Sp -\&\fIi386 Options\fR -.Sp -\&\fB\-mcpu=\fR\fIcpu type\fR \fB\-march=\fR\fIcpu type\fR -\&\fB\-mintel-syntax \-mieee-fp \-mno-fancy-math-387 -\&\-mno-fp-ret-in-387 \-msoft-float \-msvr3\-shlib -\&\-mno-wide-multiply \-mrtd \-malign-double -\&\-mpreferred-stack-boundary=\fR\fInum\fR -\&\fB\-mthreads \-mno-align-stringops \-minline-all-stringops -\&\-mpush-args \-maccumulate-outgoing-args \-m128bit-long-double -\&\-m96bit-long-double \-mregparm=\fR\fInum\fR \fB\-momit-leaf-frame-pointer\fR -.Sp -\&\fI\s-1HPPA\s0 Options\fR -.Sp -\&\fB\-march=\fR\fIarchitecture type\fR -\&\fB\-mbig-switch \-mdisable-fpregs \-mdisable-indexing -\&\-mfast-indirect-calls \-mgas \-mjump-in-delay -\&\-mlong-load-store \-mno-big-switch \-mno-disable-fpregs -\&\-mno-disable-indexing \-mno-fast-indirect-calls \-mno-gas -\&\-mno-jump-in-delay \-mno-long-load-store -\&\-mno-portable-runtime \-mno-soft-float -\&\-mno-space-regs \-msoft-float \-mpa-risc-1\-0 -\&\-mpa-risc-1\-1 \-mpa-risc-2\-0 \-mportable-runtime -\&\-mschedule=\fR\fIcpu type\fR \fB\-mspace-regs\fR -.Sp -\&\fIIntel 960 Options\fR -.Sp -\&\fB\-m\fR\fIcpu type\fR \fB\-masm-compat \-mclean-linkage -\&\-mcode-align \-mcomplex-addr \-mleaf-procedures -\&\-mic-compat \-mic2.0\-compat \-mic3.0\-compat -\&\-mintel-asm \-mno-clean-linkage \-mno-code-align -\&\-mno-complex-addr \-mno-leaf-procedures -\&\-mno-old-align \-mno-strict-align \-mno-tail-call -\&\-mnumerics \-mold-align \-msoft-float \-mstrict-align -\&\-mtail-call\fR -.Sp -\&\fI\s-1DEC\s0 Alpha Options\fR -.Sp -\&\fB\-mfp-regs \-mno-fp-regs \-mno-soft-float \-msoft-float -\&\-malpha-as \-mgas -\&\-mieee \-mieee-with-inexact \-mieee-conformant -\&\-mfp-trap-mode=\fR\fImode\fR \fB\-mfp-rounding-mode=\fR\fImode\fR -\&\fB\-mtrap-precision=\fR\fImode\fR \fB\-mbuild-constants -\&\-mcpu=\fR\fIcpu type\fR -\&\fB\-mbwx \-mno-bwx \-mcix \-mno-cix \-mmax \-mno-max -\&\-mmemory-latency=\fR\fItime\fR -.Sp -\&\fIClipper Options\fR -.Sp -\&\fB\-mc300 \-mc400\fR -.Sp -\&\fIH8/300 Options\fR -.Sp -\&\fB\-mrelax \-mh \-ms \-mint32 \-malign-300\fR -.Sp -\&\fI\s-1SH\s0 Options\fR -.Sp -\&\fB\-m1 \-m2 \-m3 \-m3e -\&\-m4\-nofpu \-m4\-single-only \-m4\-single \-m4 -\&\-mb \-ml \-mdalign \-mrelax -\&\-mbigtable \-mfmovd \-mhitachi \-mnomacsave -\&\-misize \-mpadstruct \-mspace -\&\-mprefergot -\&\-musermode\fR -.Sp -\&\fISystem V Options\fR -.Sp -\&\fB\-Qy \-Qn \-YP,\fR\fIpaths\fR \fB\-Ym,\fR\fIdir\fR -.Sp -\&\fI\s-1ARC\s0 Options\fR -.Sp -\&\fB\-EB \-EL -\&\-mmangle-cpu \-mcpu=\fR\fIcpu\fR \fB\-mtext=\fR\fItext section\fR -\&\fB\-mdata=\fR\fIdata section\fR \fB\-mrodata=\fR\fIreadonly data section\fR -.Sp -\&\fITMS320C3x/C4x Options\fR -.Sp -\&\fB\-mcpu=\fR\fIcpu\fR \fB\-mbig \-msmall \-mregparm \-mmemparm -\&\-mfast-fix \-mmpyi \-mbk \-mti \-mdp-isr-reload -\&\-mrpts=\fR\fIcount\fR \fB\-mrptb \-mdb \-mloop-unsigned -\&\-mparallel-insns \-mparallel-mpy \-mpreserve-float\fR -.Sp -\&\fIV850 Options\fR -.Sp -\&\fB\-mlong-calls \-mno-long-calls \-mep \-mno-ep -\&\-mprolog-function \-mno-prolog-function \-mspace -\&\-mtda=\fR\fIn\fR \fB\-msda=\fR\fIn\fR \fB\-mzda=\fR\fIn\fR -\&\fB\-mv850 \-mbig-switch\fR -.Sp -\&\fI\s-1NS32K\s0 Options\fR -.Sp -\&\fB\-m32032 \-m32332 \-m32532 \-m32081 \-m32381 \-mmult-add \-mnomult-add -\&\-msoft-float \-mrtd \-mnortd \-mregparam \-mnoregparam \-msb \-mnosb -\&\-mbitfield \-mnobitfield \-mhimem \-mnohimem\fR -.Sp -\&\fI\s-1AVR\s0 Options\fR -.Sp -\&\fB\-mmcu=\fR\fImcu\fR \fB\-msize \-minit-stack=\fR\fIn\fR \fB\-mno-interrupts -\&\-mcall-prologues \-mno-tablejump \-mtiny-stack\fR -.Sp -\&\fIMCore Options\fR -.Sp -\&\fB\-mhardlit \-mno-hardlit \-mdiv \-mno-div \-mrelax-immediates -\&\-mno-relax-immediates \-mwide-bitfields \-mno-wide-bitfields -\&\-m4byte-functions \-mno-4byte-functions \-mcallgraph-data -\&\-mno-callgraph-data \-mslow-bytes \-mno-slow-bytes \-mno-lsim -\&\-mlittle-endian \-mbig-endian \-m210 \-m340 \-mstack-increment\fR -.Sp -\&\fI\s-1IA-64\s0 Options\fR -.Sp -\&\fB\-mbig-endian \-mlittle-endian \-mgnu-as \-mgnu-ld \-mno-pic -\&\-mvolatile-asm-stop \-mb-step \-mregister-names \-mno-sdata -\&\-mconstant-gp \-mauto-pic \-minline-divide-min-latency -\&\-minline-divide-max-throughput \-mno-dwarf2\-asm -\&\-mfixed-range=\fR\fIregister range\fR -.Ip "\fICode Generation Options\fR" 4 -.IX Item "Code Generation Options" -\&\fB\-fcall-saved-\fR\fIreg\fR \fB\-fcall-used-\fR\fIreg\fR -\&\fB\-fexceptions \-funwind-tables \-ffixed-\fR\fIreg\fR -\&\fB\-finhibit-size-directive \-finstrument-functions -\&\-fcheck-memory-usage \-fprefix-function-name -\&\-fno-common \-fno-ident \-fno-gnu-linker -\&\-fpcc-struct-return \-fpic \-fPIC -\&\-freg-struct-return \-fshared-data \-fshort-enums -\&\-fshort-double \-fvolatile \-fvolatile-global \-fvolatile-static -\&\-fverbose-asm \-fpack-struct \-fstack-check -\&\-fstack-limit-register=\fR\fIreg\fR \fB\-fstack-limit-symbol=\fR\fIsym\fR -\&\fB\-fargument-alias \-fargument-noalias -\&\-fargument-noalias-global -\&\-fleading-underscore\fR -.Sh "Options Controlling the Kind of Output" -.IX Subsection "Options Controlling the Kind of Output" -Compilation can involve up to four stages: preprocessing, compilation -proper, assembly and linking, always in that order. The first three -stages apply to an individual source file, and end by producing an -object file; linking combines all the object files (those newly -compiled, and those specified as input) into an executable file. -.PP -For any given input file, the file name suffix determines what kind of -compilation is done: -.Ip "\fIfile\fR\fB.c\fR" 4 -.IX Item "file.c" -C source code which must be preprocessed. -.Ip "\fIfile\fR\fB.i\fR" 4 -.IX Item "file.i" -C source code which should not be preprocessed. -.Ip "\fIfile\fR\fB.ii\fR" 4 -.IX Item "file.ii" -\&\*(C+ source code which should not be preprocessed. -.Ip "\fIfile\fR\fB.m\fR" 4 -.IX Item "file.m" -Objective-C source code. Note that you must link with the library -\&\fIlibobjc.a\fR to make an Objective-C program work. -.Ip "\fIfile\fR\fB.mi\fR" 4 -.IX Item "file.mi" -Objective-C source code which should not be preprocessed. -.Ip "\fIfile\fR\fB.h\fR" 4 -.IX Item "file.h" -C header file (not to be compiled or linked). -.Ip "\fIfile\fR\fB.cc\fR" 4 -.IX Item "file.cc" -.PD 0 -.Ip "\fIfile\fR\fB.cp\fR" 4 -.IX Item "file.cp" -.Ip "\fIfile\fR\fB.cxx\fR" 4 -.IX Item "file.cxx" -.Ip "\fIfile\fR\fB.cpp\fR" 4 -.IX Item "file.cpp" -.Ip "\fIfile\fR\fB.c++\fR" 4 -.IX Item "file.c++" -.Ip "\fIfile\fR\fB.C\fR" 4 -.IX Item "file.C" -.PD -\&\*(C+ source code which must be preprocessed. Note that in \fB.cxx\fR, -the last two letters must both be literally \fBx\fR. Likewise, -\&\fB.C\fR refers to a literal capital C. -.Ip "\fIfile\fR\fB.f\fR" 4 -.IX Item "file.f" -.PD 0 -.Ip "\fIfile\fR\fB.for\fR" 4 -.IX Item "file.for" -.Ip "\fIfile\fR\fB.FOR\fR" 4 -.IX Item "file.FOR" -.PD -Fortran source code which should not be preprocessed. -.Ip "\fIfile\fR\fB.F\fR" 4 -.IX Item "file.F" -.PD 0 -.Ip "\fIfile\fR\fB.fpp\fR" 4 -.IX Item "file.fpp" -.Ip "\fIfile\fR\fB.FPP\fR" 4 -.IX Item "file.FPP" -.PD -Fortran source code which must be preprocessed (with the traditional -preprocessor). -.Ip "\fIfile\fR\fB.r\fR" 4 -.IX Item "file.r" -Fortran source code which must be preprocessed with a \s-1RATFOR\s0 -preprocessor (not included with \s-1GCC\s0). -.Ip "\fIfile\fR\fB.ch\fR" 4 -.IX Item "file.ch" -.PD 0 -.Ip "\fIfile\fR\fB.chi\fR" 4 -.IX Item "file.chi" -.PD -\&\s-1CHILL\s0 source code (preprocessed with the traditional preprocessor). -.Ip "\fIfile\fR\fB.s\fR" 4 -.IX Item "file.s" -Assembler code. -.Ip "\fIfile\fR\fB.S\fR" 4 -.IX Item "file.S" -Assembler code which must be preprocessed. -.Ip "\fIother\fR" 4 -.IX Item "other" -An object file to be fed straight into linking. -Any file name with no recognized suffix is treated this way. -.PP -You can specify the input language explicitly with the \fB\-x\fR option: -.Ip "\fB\-x\fR \fIlanguage\fR" 4 -.IX Item "-x language" -Specify explicitly the \fIlanguage\fR for the following input files -(rather than letting the compiler choose a default based on the file -name suffix). This option applies to all following input files until -the next \fB\-x\fR option. Possible values for \fIlanguage\fR are: -.Sp -.Vb 6 -\& c c-header cpp-output -\& c++ c++-cpp-output -\& objective-c objc-cpp-output -\& assembler assembler-with-cpp -\& f77 f77-cpp-input ratfor -\& java chill -.Ve -.Ip "\fB\-x none\fR" 4 -.IX Item "-x none" -Turn off any specification of a language, so that subsequent files are -handled according to their file name suffixes (as they are if \fB\-x\fR -has not been used at all). -.Ip "\fB\-pass-exit-codes\fR" 4 -.IX Item "-pass-exit-codes" -Normally the \fBgcc\fR program will exit with the code of 1 if any -phase of the compiler returns a non-success return code. If you specify -\&\fB\-pass-exit-codes\fR, the \fBgcc\fR program will instead return with -numerically highest error produced by any phase that returned an error -indication. -.PP -If you only want some of the stages of compilation, you can use -\&\fB\-x\fR (or filename suffixes) to tell \fBgcc\fR where to start, and -one of the options \fB\-c\fR, \fB\-S\fR, or \fB\-E\fR to say where -\&\fBgcc\fR is to stop. Note that some combinations (for example, -\&\fB\-x cpp-output \-E\fR) instruct \fBgcc\fR to do nothing at all. -.Ip "\fB\-c\fR" 4 -.IX Item "-c" -Compile or assemble the source files, but do not link. The linking -stage simply is not done. The ultimate output is in the form of an -object file for each source file. -.Sp -By default, the object file name for a source file is made by replacing -the suffix \fB.c\fR, \fB.i\fR, \fB.s\fR, etc., with \fB.o\fR. -.Sp -Unrecognized input files, not requiring compilation or assembly, are -ignored. -.Ip "\fB\-S\fR" 4 -.IX Item "-S" -Stop after the stage of compilation proper; do not assemble. The output -is in the form of an assembler code file for each non-assembler input -file specified. -.Sp -By default, the assembler file name for a source file is made by -replacing the suffix \fB.c\fR, \fB.i\fR, etc., with \fB.s\fR. -.Sp -Input files that don't require compilation are ignored. -.Ip "\fB\-E\fR" 4 -.IX Item "-E" -Stop after the preprocessing stage; do not run the compiler proper. The -output is in the form of preprocessed source code, which is sent to the -standard output. -.Sp -Input files which don't require preprocessing are ignored. -.Ip "\fB\-o\fR \fIfile\fR" 4 -.IX Item "-o file" -Place output in file \fIfile\fR. This applies regardless to whatever -sort of output is being produced, whether it be an executable file, -an object file, an assembler file or preprocessed C code. -.Sp -Since only one output file can be specified, it does not make sense to -use \fB\-o\fR when compiling more than one input file, unless you are -producing an executable file as output. -.Sp -If \fB\-o\fR is not specified, the default is to put an executable file -in \fIa.out\fR, the object file for \fI\fIsource\fI.\fIsuffix\fI\fR in -\&\fI\fIsource\fI.o\fR, its assembler file in \fI\fIsource\fI.s\fR, and -all preprocessed C source on standard output. -.Ip "\fB\-v\fR" 4 -.IX Item "-v" -Print (on standard error output) the commands executed to run the stages -of compilation. Also print the version number of the compiler driver -program and of the preprocessor and the compiler proper. -.Ip "\fB\-pipe\fR" 4 -.IX Item "-pipe" -Use pipes rather than temporary files for communication between the -various stages of compilation. This fails to work on some systems where -the assembler is unable to read from a pipe; but the \s-1GNU\s0 assembler has -no trouble. -.Ip "\fB\*(--help\fR" 4 -.IX Item "help" -Print (on the standard output) a description of the command line options -understood by \fBgcc\fR. If the \fB\-v\fR option is also specified -then \fB\*(--help\fR will also be passed on to the various processes -invoked by \fBgcc\fR, so that they can display the command line options -they accept. If the \fB\-W\fR option is also specified then command -line options which have no documentation associated with them will also -be displayed. -.Ip "\fB\*(--target-help\fR" 4 -.IX Item "target-help" -Print (on the standard output) a description of target specific command -line options for each tool. -.Sh "Compiling \*(C+ Programs" -.IX Subsection "Compiling Programs" -\&\*(C+ source files conventionally use one of the suffixes \fB.C\fR, -\&\fB.cc\fR, \fB.cpp\fR, \fB.c++\fR, \fB.cp\fR, or \fB.cxx\fR; -preprocessed \*(C+ files use the suffix \fB.ii\fR. \s-1GCC\s0 recognizes -files with these names and compiles them as \*(C+ programs even if you -call the compiler the same way as for compiling C programs (usually with -the name \fBgcc\fR). -.PP -However, \*(C+ programs often require class libraries as well as a -compiler that understands the \*(C+ language\-\-\-and under some -circumstances, you might want to compile programs from standard input, -or otherwise without a suffix that flags them as \*(C+ programs. -\&\fBg++\fR is a program that calls \s-1GCC\s0 with the default language -set to \*(C+, and automatically specifies linking against the \*(C+ -library. On many systems, \fBg++\fR is also -installed with the name \fBc++\fR. -.PP -When you compile \*(C+ programs, you may specify many of the same -command-line options that you use for compiling programs in any -language; or command-line options meaningful for C and related -languages; or options that are meaningful only for \*(C+ programs. -.Sh "Options Controlling C Dialect" -.IX Subsection "Options Controlling C Dialect" -The following options control the dialect of C (or languages derived -from C, such as \*(C+ and Objective C) that the compiler accepts: -.Ip "\fB\-ansi\fR" 4 -.IX Item "-ansi" -In C mode, support all \s-1ISO\s0 C89 programs. In \*(C+ mode, -remove \s-1GNU\s0 extensions that conflict with \s-1ISO\s0 \*(C+. -.Sp -This turns off certain features of \s-1GCC\s0 that are incompatible with \s-1ISO\s0 -C (when compiling C code), or of standard \*(C+ (when compiling \*(C+ code), -such as the \f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`typeof\*(C'\fR keywords, and -predefined macros such as \f(CW\*(C`unix\*(C'\fR and \f(CW\*(C`vax\*(C'\fR that identify the -type of system you are using. It also enables the undesirable and -rarely used \s-1ISO\s0 trigraph feature. For the C compiler, -it disables recognition of \*(C+ style \fB//\fR comments as well as -the \f(CW\*(C`inline\*(C'\fR keyword. -.Sp -The alternate keywords \f(CW\*(C`_\|_asm_\|_\*(C'\fR, \f(CW\*(C`_\|_extension_\|_\*(C'\fR, -\&\f(CW\*(C`_\|_inline_\|_\*(C'\fR and \f(CW\*(C`_\|_typeof_\|_\*(C'\fR continue to work despite -\&\fB\-ansi\fR. You would not want to use them in an \s-1ISO\s0 C program, of -course, but it is useful to put them in header files that might be included -in compilations done with \fB\-ansi\fR. Alternate predefined macros -such as \f(CW\*(C`_\|_unix_\|_\*(C'\fR and \f(CW\*(C`_\|_vax_\|_\*(C'\fR are also available, with or -without \fB\-ansi\fR. -.Sp -The \fB\-ansi\fR option does not cause non-ISO programs to be -rejected gratuitously. For that, \fB\-pedantic\fR is required in -addition to \fB\-ansi\fR. -.Sp -The macro \f(CW\*(C`_\|_STRICT_ANSI_\|_\*(C'\fR is predefined when the \fB\-ansi\fR -option is used. Some header files may notice this macro and refrain -from declaring certain functions or defining certain macros that the -\&\s-1ISO\s0 standard doesn't call for; this is to avoid interfering with any -programs that might use these names for other things. -.Sp -Functions which would normally be builtin but do not have semantics -defined by \s-1ISO\s0 C (such as \f(CW\*(C`alloca\*(C'\fR and \f(CW\*(C`ffs\*(C'\fR) are not builtin -functions with \fB\-ansi\fR is used. -.Ip "\fB\-std=\fR" 4 -.IX Item "-std=" -Determine the language standard. A value for this option must be provided; -possible values are -.RS 4 -.Ip "\fBiso9899:1990\fR" 4 -.IX Item "iso9899:1990" -Same as \fB\-ansi\fR -.Ip "\fBiso9899:199409\fR" 4 -.IX Item "iso9899:199409" -\&\s-1ISO\s0 C as modified in amend. 1 -.Ip "\fBiso9899:1999\fR" 4 -.IX Item "iso9899:1999" -\&\s-1ISO\s0 C99. Note that this standard is not yet fully supported; see -<\fBhttp://gcc.gnu.org/c99status.html\fR> for more information. -.Ip "\fBc89\fR" 4 -.IX Item "c89" -same as \fB\-std=iso9899:1990\fR -.Ip "\fBc99\fR" 4 -.IX Item "c99" -same as \fB\-std=iso9899:1999\fR -.Ip "\fBgnu89\fR" 4 -.IX Item "gnu89" -default, iso9899:1990 + gnu extensions -.Ip "\fBgnu99\fR" 4 -.IX Item "gnu99" -iso9899:1999 + gnu extensions -.Ip "\fBiso9899:199x\fR" 4 -.IX Item "iso9899:199x" -same as \fB\-std=iso9899:1999\fR, deprecated -.Ip "\fBc9x\fR" 4 -.IX Item "c9x" -same as \fB\-std=iso9899:1999\fR, deprecated -.Ip "\fBgnu9x\fR" 4 -.IX Item "gnu9x" -same as \fB\-std=gnu99\fR, deprecated -.RE -.RS 4 -.Sp -Even when this option is not specified, you can still use some of the -features of newer standards in so far as they do not conflict with -previous C standards. For example, you may use \f(CW\*(C`_\|_restrict_\|_\*(C'\fR even -when \fB\-std=c99\fR is not specified. -.Sp -The \fB\-std\fR options specifying some version of \s-1ISO\s0 C have the same -effects as \fB\-ansi\fR, except that features that were not in \s-1ISO\s0 C89 -but are in the specified version (for example, \fB//\fR comments and -the \f(CW\*(C`inline\*(C'\fR keyword in \s-1ISO\s0 C99) are not disabled. -.RE -.Ip "\fB\-fno-asm\fR" 4 -.IX Item "-fno-asm" -Do not recognize \f(CW\*(C`asm\*(C'\fR, \f(CW\*(C`inline\*(C'\fR or \f(CW\*(C`typeof\*(C'\fR as a -keyword, so that code can use these words as identifiers. You can use -the keywords \f(CW\*(C`_\|_asm_\|_\*(C'\fR, \f(CW\*(C`_\|_inline_\|_\*(C'\fR and \f(CW\*(C`_\|_typeof_\|_\*(C'\fR -instead. \fB\-ansi\fR implies \fB\-fno-asm\fR. -.Sp -In \*(C+, this switch only affects the \f(CW\*(C`typeof\*(C'\fR keyword, since -\&\f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`inline\*(C'\fR are standard keywords. You may want to -use the \fB\-fno-gnu-keywords\fR flag instead, which has the same -effect. In C99 mode (\fB\-std=c99\fR or \fB\-std=gnu99\fR), this -switch only affects the \f(CW\*(C`asm\*(C'\fR and \f(CW\*(C`typeof\*(C'\fR keywords, since -\&\f(CW\*(C`inline\*(C'\fR is a standard keyword in \s-1ISO\s0 C99. -.Ip "\fB\-fno-builtin\fR" 4 -.IX Item "-fno-builtin" -Don't recognize builtin functions that do not begin with -\&\fB_\|_builtin_\fR as prefix. -.Sp -\&\s-1GCC\s0 normally generates special code to handle certain builtin functions -more efficiently; for instance, calls to \f(CW\*(C`alloca\*(C'\fR may become single -instructions that adjust the stack directly, and calls to \f(CW\*(C`memcpy\*(C'\fR -may become inline copy loops. The resulting code is often both smaller -and faster, but since the function calls no longer appear as such, you -cannot set a breakpoint on those calls, nor can you change the behavior -of the functions by linking with a different library. -.Ip "\fB\-fhosted\fR" 4 -.IX Item "-fhosted" -Assert that compilation takes place in a hosted environment. This implies -\&\fB\-fbuiltin\fR. A hosted environment is one in which the -entire standard library is available, and in which \f(CW\*(C`main\*(C'\fR has a return -type of \f(CW\*(C`int\*(C'\fR. Examples are nearly everything except a kernel. -This is equivalent to \fB\-fno-freestanding\fR. -.Ip "\fB\-ffreestanding\fR" 4 -.IX Item "-ffreestanding" -Assert that compilation takes place in a freestanding environment. This -implies \fB\-fno-builtin\fR. A freestanding environment -is one in which the standard library may not exist, and program startup may -not necessarily be at \f(CW\*(C`main\*(C'\fR. The most obvious example is an \s-1OS\s0 kernel. -This is equivalent to \fB\-fno-hosted\fR. -.Ip "\fB\-trigraphs\fR" 4 -.IX Item "-trigraphs" -Support \s-1ISO\s0 C trigraphs. You don't want to know about this -brain-damage. The \fB\-ansi\fR option (and \fB\-std\fR options for -strict \s-1ISO\s0 C conformance) implies \fB\-trigraphs\fR. -.Ip "\fB\-traditional\fR" 4 -.IX Item "-traditional" -Attempt to support some aspects of traditional C compilers. -Specifically: -.RS 4 -.Ip "\(bu" 4 -All \f(CW\*(C`extern\*(C'\fR declarations take effect globally even if they -are written inside of a function definition. This includes implicit -declarations of functions. -.Ip "\(bu" 4 -The newer keywords \f(CW\*(C`typeof\*(C'\fR, \f(CW\*(C`inline\*(C'\fR, \f(CW\*(C`signed\*(C'\fR, \f(CW\*(C`const\*(C'\fR -and \f(CW\*(C`volatile\*(C'\fR are not recognized. (You can still use the -alternative keywords such as \f(CW\*(C`_\|_typeof_\|_\*(C'\fR, \f(CW\*(C`_\|_inline_\|_\*(C'\fR, and -so on.) -.Ip "\(bu" 4 -Comparisons between pointers and integers are always allowed. -.Ip "\(bu" 4 -Integer types \f(CW\*(C`unsigned short\*(C'\fR and \f(CW\*(C`unsigned char\*(C'\fR promote -to \f(CW\*(C`unsigned int\*(C'\fR. -.Ip "\(bu" 4 -Out-of-range floating point literals are not an error. -.Ip "\(bu" 4 -Certain constructs which \s-1ISO\s0 regards as a single invalid preprocessing -number, such as \fB0xe-0xd\fR, are treated as expressions instead. -.Ip "\(bu" 4 -String ``constants'' are not necessarily constant; they are stored in -writable space, and identical looking constants are allocated -separately. (This is the same as the effect of -\&\fB\-fwritable-strings\fR.) -.Ip "\(bu" 4 -All automatic variables not declared \f(CW\*(C`register\*(C'\fR are preserved by -\&\f(CW\*(C`longjmp\*(C'\fR. Ordinarily, \s-1GNU\s0 C follows \s-1ISO\s0 C: automatic variables -not declared \f(CW\*(C`volatile\*(C'\fR may be clobbered. -.Ip "\(bu" 4 -The character escape sequences \fB\ex\fR and \fB\ea\fR evaluate as the -literal characters \fBx\fR and \fBa\fR respectively. Without -\&\fB\-traditional\fR, \fB\ex\fR is a prefix for the hexadecimal -representation of a character, and \fB\ea\fR produces a bell. -.RE -.RS 4 -.Sp -You may wish to use \fB\-fno-builtin\fR as well as \fB\-traditional\fR -if your program uses names that are normally \s-1GNU\s0 C builtin functions for -other purposes of its own. -.Sp -You cannot use \fB\-traditional\fR if you include any header files that -rely on \s-1ISO\s0 C features. Some vendors are starting to ship systems with -\&\s-1ISO\s0 C header files and you cannot use \fB\-traditional\fR on such -systems to compile files that include any system headers. -.Sp -The \fB\-traditional\fR option also enables \fB\-traditional-cpp\fR, -which is described next. -.RE -.Ip "\fB\-traditional-cpp\fR" 4 -.IX Item "-traditional-cpp" -Attempt to support some aspects of traditional C preprocessors. -Specifically: -.RS 4 -.Ip "\(bu" 4 -Comments convert to nothing at all, rather than to a space. This allows -traditional token concatenation. -.Ip "\(bu" 4 -In a preprocessing directive, the \fB#\fR symbol must appear as the first -character of a line. -.Ip "\(bu" 4 -Macro arguments are recognized within string constants in a macro -definition (and their values are stringified, though without additional -quote marks, when they appear in such a context). The preprocessor -always considers a string constant to end at a newline. -.Ip "\(bu" 4 -The predefined macro \f(CW\*(C`_\|_STDC_\|_\*(C'\fR is not defined when you use -\&\fB\-traditional\fR, but \f(CW\*(C`_\|_GNUC_\|_\*(C'\fR is (since the \s-1GNU\s0 extensions -which \f(CW\*(C`_\|_GNUC_\|_\*(C'\fR indicates are not affected by -\&\fB\-traditional\fR). If you need to write header files that work -differently depending on whether \fB\-traditional\fR is in use, by -testing both of these predefined macros you can distinguish four -situations: \s-1GNU\s0 C, traditional \s-1GNU\s0 C, other \s-1ISO\s0 C compilers, and other -old C compilers. The predefined macro \f(CW\*(C`_\|_STDC_VERSION_\|_\*(C'\fR is also -not defined when you use \fB\-traditional\fR. -.Ip "\(bu" 4 -The preprocessor considers a string constant to end at a newline (unless -the newline is escaped with \fB\e\fR). (Without \fB\-traditional\fR, -string constants can contain the newline character as typed.) -.RE -.RS 4 -.RE -.Ip "\fB\-fcond-mismatch\fR" 4 -.IX Item "-fcond-mismatch" -Allow conditional expressions with mismatched types in the second and -third arguments. The value of such an expression is void. This option -is not supported for \*(C+. -.Ip "\fB\-funsigned-char\fR" 4 -.IX Item "-funsigned-char" -Let the type \f(CW\*(C`char\*(C'\fR be unsigned, like \f(CW\*(C`unsigned char\*(C'\fR. -.Sp -Each kind of machine has a default for what \f(CW\*(C`char\*(C'\fR should -be. It is either like \f(CW\*(C`unsigned char\*(C'\fR by default or like -\&\f(CW\*(C`signed char\*(C'\fR by default. -.Sp -Ideally, a portable program should always use \f(CW\*(C`signed char\*(C'\fR or -\&\f(CW\*(C`unsigned char\*(C'\fR when it depends on the signedness of an object. -But many programs have been written to use plain \f(CW\*(C`char\*(C'\fR and -expect it to be signed, or expect it to be unsigned, depending on the -machines they were written for. This option, and its inverse, let you -make such a program work with the opposite default. -.Sp -The type \f(CW\*(C`char\*(C'\fR is always a distinct type from each of -\&\f(CW\*(C`signed char\*(C'\fR or \f(CW\*(C`unsigned char\*(C'\fR, even though its behavior -is always just like one of those two. -.Ip "\fB\-fsigned-char\fR" 4 -.IX Item "-fsigned-char" -Let the type \f(CW\*(C`char\*(C'\fR be signed, like \f(CW\*(C`signed char\*(C'\fR. -.Sp -Note that this is equivalent to \fB\-fno-unsigned-char\fR, which is -the negative form of \fB\-funsigned-char\fR. Likewise, the option -\&\fB\-fno-signed-char\fR is equivalent to \fB\-funsigned-char\fR. -.Sp -You may wish to use \fB\-fno-builtin\fR as well as \fB\-traditional\fR -if your program uses names that are normally \s-1GNU\s0 C builtin functions for -other purposes of its own. -.Sp -You cannot use \fB\-traditional\fR if you include any header files that -rely on \s-1ISO\s0 C features. Some vendors are starting to ship systems with -\&\s-1ISO\s0 C header files and you cannot use \fB\-traditional\fR on such -systems to compile files that include any system headers. -.Ip "\fB\-fsigned-bitfields\fR" 4 -.IX Item "-fsigned-bitfields" -.PD 0 -.Ip "\fB\-funsigned-bitfields\fR" 4 -.IX Item "-funsigned-bitfields" -.Ip "\fB\-fno-signed-bitfields\fR" 4 -.IX Item "-fno-signed-bitfields" -.Ip "\fB\-fno-unsigned-bitfields\fR" 4 -.IX Item "-fno-unsigned-bitfields" -.PD -These options control whether a bitfield is signed or unsigned, when the -declaration does not use either \f(CW\*(C`signed\*(C'\fR or \f(CW\*(C`unsigned\*(C'\fR. By -default, such a bitfield is signed, because this is consistent: the -basic integer types such as \f(CW\*(C`int\*(C'\fR are signed types. -.Sp -However, when \fB\-traditional\fR is used, bitfields are all unsigned -no matter what. -.Ip "\fB\-fwritable-strings\fR" 4 -.IX Item "-fwritable-strings" -Store string constants in the writable data segment and don't uniquize -them. This is for compatibility with old programs which assume they can -write into string constants. The option \fB\-traditional\fR also has -this effect. -.Sp -Writing into string constants is a very bad idea; ``constants'' should -be constant. -.Ip "\fB\-fallow-single-precision\fR" 4 -.IX Item "-fallow-single-precision" -Do not promote single precision math operations to double precision, -even when compiling with \fB\-traditional\fR. -.Sp -Traditional K&R C promotes all floating point operations to double -precision, regardless of the sizes of the operands. On the -architecture for which you are compiling, single precision may be faster -than double precision. If you must use \fB\-traditional\fR, but want -to use single precision operations when the operands are single -precision, use this option. This option has no effect when compiling -with \s-1ISO\s0 or \s-1GNU\s0 C conventions (the default). -.Ip "\fB\-fshort-wchar\fR" 4 -.IX Item "-fshort-wchar" -Override the underlying type for \fBwchar_t\fR to be \fBshort -unsigned int\fR instead of the default for the target. This option is -useful for building programs to run under \s-1WINE\s0. -.Sh "Options Controlling \*(C+ Dialect" -.IX Subsection "Options Controlling Dialect" -This section describes the command-line options that are only meaningful -for \*(C+ programs; but you can also use most of the \s-1GNU\s0 compiler options -regardless of what language your program is in. For example, you -might compile a file \f(CW\*(C`firstClass.C\*(C'\fR like this: -.PP -.Vb 1 -\& g++ -g -frepo -O -c firstClass.C -.Ve -In this example, only \fB\-frepo\fR is an option meant -only for \*(C+ programs; you can use the other options with any -language supported by \s-1GCC\s0. -.PP -Here is a list of options that are \fIonly\fR for compiling \*(C+ programs: -.Ip "\fB\-fno-access-control\fR" 4 -.IX Item "-fno-access-control" -Turn off all access checking. This switch is mainly useful for working -around bugs in the access control code. -.Ip "\fB\-fcheck-new\fR" 4 -.IX Item "-fcheck-new" -Check that the pointer returned by \f(CW\*(C`operator new\*(C'\fR is non-null -before attempting to modify the storage allocated. The current Working -Paper requires that \f(CW\*(C`operator new\*(C'\fR never return a null pointer, so -this check is normally unnecessary. -.Sp -An alternative to using this option is to specify that your -\&\f(CW\*(C`operator new\*(C'\fR does not throw any exceptions; if you declare it -\&\fB\f(BIthrow()\fB\fR, g++ will check the return value. See also \fBnew -(nothrow)\fR. -.Ip "\fB\-fconserve-space\fR" 4 -.IX Item "-fconserve-space" -Put uninitialized or runtime-initialized global variables into the -common segment, as C does. This saves space in the executable at the -cost of not diagnosing duplicate definitions. If you compile with this -flag and your program mysteriously crashes after \f(CW\*(C`main()\*(C'\fR has -completed, you may have an object that is being destroyed twice because -two definitions were merged. -.Sp -This option is no longer useful on most targets, now that support has -been added for putting variables into \s-1BSS\s0 without making them common. -.Ip "\fB\-fno-const-strings\fR" 4 -.IX Item "-fno-const-strings" -Give string constants type \f(CW\*(C`char *\*(C'\fR instead of type \f(CW\*(C`const -char *\*(C'\fR. By default, G++ uses type \f(CW\*(C`const char *\*(C'\fR as required by -the standard. Even if you use \fB\-fno-const-strings\fR, you cannot -actually modify the value of a string constant, unless you also use -\&\fB\-fwritable-strings\fR. -.Sp -This option might be removed in a future release of G++. For maximum -portability, you should structure your code so that it works with -string constants that have type \f(CW\*(C`const char *\*(C'\fR. -.Ip "\fB\-fdollars-in-identifiers\fR" 4 -.IX Item "-fdollars-in-identifiers" -Accept \fB$\fR in identifiers. You can also explicitly prohibit use of -\&\fB$\fR with the option \fB\-fno-dollars-in-identifiers\fR. (\s-1GNU\s0 C allows -\&\fB$\fR by default on most target systems, but there are a few exceptions.) -Traditional C allowed the character \fB$\fR to form part of -identifiers. However, \s-1ISO\s0 C and \*(C+ forbid \fB$\fR in identifiers. -.Ip "\fB\-fno-elide-constructors\fR" 4 -.IX Item "-fno-elide-constructors" -The \*(C+ standard allows an implementation to omit creating a temporary -which is only used to initialize another object of the same type. -Specifying this option disables that optimization, and forces g++ to -call the copy constructor in all cases. -.Ip "\fB\-fno-enforce-eh-specs\fR" 4 -.IX Item "-fno-enforce-eh-specs" -Don't check for violation of exception specifications at runtime. This -option violates the \*(C+ standard, but may be useful for reducing code -size in production builds, much like defining \fB\s-1NDEBUG\s0\fR. The compiler -will still optimize based on the exception specifications. -.Ip "\fB\-fexternal-templates\fR" 4 -.IX Item "-fexternal-templates" -Cause template instantiations to obey \fB#pragma interface\fR and -\&\fBimplementation\fR; template instances are emitted or not according -to the location of the template definition. -.Sp -This option is deprecated. -.Ip "\fB\-falt-external-templates\fR" 4 -.IX Item "-falt-external-templates" -Similar to \-fexternal-templates, but template instances are emitted or -not according to the place where they are first instantiated. -.Sp -This option is deprecated. -.Ip "\fB\-ffor-scope\fR" 4 -.IX Item "-ffor-scope" -.PD 0 -.Ip "\fB\-fno-for-scope\fR" 4 -.IX Item "-fno-for-scope" -.PD -If \-ffor-scope is specified, the scope of variables declared in -a \fIfor-init-statement\fR is limited to the \fBfor\fR loop itself, -as specified by the \*(C+ standard. -If \-fno-for-scope is specified, the scope of variables declared in -a \fIfor-init-statement\fR extends to the end of the enclosing scope, -as was the case in old versions of gcc, and other (traditional) -implementations of \*(C+. -.Sp -The default if neither flag is given to follow the standard, -but to allow and give a warning for old-style code that would -otherwise be invalid, or have different behavior. -.Ip "\fB\-fno-gnu-keywords\fR" 4 -.IX Item "-fno-gnu-keywords" -Do not recognize \f(CW\*(C`typeof\*(C'\fR as a keyword, so that code can use this -word as an identifier. You can use the keyword \f(CW\*(C`_\|_typeof_\|_\*(C'\fR instead. -\&\fB\-ansi\fR implies \fB\-fno-gnu-keywords\fR. -.Ip "\fB\-fhonor-std\fR" 4 -.IX Item "-fhonor-std" -Treat the \f(CW\*(C`namespace std\*(C'\fR as a namespace, instead of ignoring -it. For compatibility with earlier versions of g++, the compiler will, -by default, ignore \f(CW\*(C`namespace\-declarations\*(C'\fR, -\&\f(CW\*(C`using\-declarations\*(C'\fR, \f(CW\*(C`using\-directives\*(C'\fR, and -\&\f(CW\*(C`namespace\-names\*(C'\fR, if they involve \f(CW\*(C`std\*(C'\fR. -.Ip "\fB\-fhuge-objects\fR" 4 -.IX Item "-fhuge-objects" -Support virtual function calls for objects that exceed the size -representable by a \fBshort int\fR. Users should not use this flag by -default; if you need to use it, the compiler will tell you so. -.Sp -This flag is not useful when compiling with \-fvtable-thunks. -.Sp -Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding -libgcc\fR must be built with the same setting of this option. -.Ip "\fB\-fno-implicit-templates\fR" 4 -.IX Item "-fno-implicit-templates" -Never emit code for non-inline templates which are instantiated -implicitly (i.e. by use); only emit code for explicit instantiations. -.Ip "\fB\-fno-implicit-inline-templates\fR" 4 -.IX Item "-fno-implicit-inline-templates" -Don't emit code for implicit instantiations of inline templates, either. -The default is to handle inlines differently so that compiles with and -without optimization will need the same set of explicit instantiations. -.Ip "\fB\-fno-implement-inlines\fR" 4 -.IX Item "-fno-implement-inlines" -To save space, do not emit out-of-line copies of inline functions -controlled by \fB#pragma implementation\fR. This will cause linker -errors if these functions are not inlined everywhere they are called. -.Ip "\fB\-fms-extensions\fR" 4 -.IX Item "-fms-extensions" -Disable pedantic warnings about constructs used in \s-1MFC\s0, such as implicit -int and getting a pointer to member function via non-standard syntax. -.Ip "\fB\-fno-nonansi-builtins\fR" 4 -.IX Item "-fno-nonansi-builtins" -Disable builtin declarations of functions that are not mandated by -\&\s-1ANSI/ISO\s0 C. These include \f(CW\*(C`ffs\*(C'\fR, \f(CW\*(C`alloca\*(C'\fR, \f(CW\*(C`_exit\*(C'\fR, -\&\f(CW\*(C`index\*(C'\fR, \f(CW\*(C`bzero\*(C'\fR, \f(CW\*(C`conjf\*(C'\fR, and other related functions. -.Ip "\fB\-fno-operator-names\fR" 4 -.IX Item "-fno-operator-names" -Do not treat the operator name keywords \f(CW\*(C`and\*(C'\fR, \f(CW\*(C`bitand\*(C'\fR, -\&\f(CW\*(C`bitor\*(C'\fR, \f(CW\*(C`compl\*(C'\fR, \f(CW\*(C`not\*(C'\fR, \f(CW\*(C`or\*(C'\fR and \f(CW\*(C`xor\*(C'\fR as -synonyms as keywords. -.Ip "\fB\-fno-optional-diags\fR" 4 -.IX Item "-fno-optional-diags" -Disable diagnostics that the standard says a compiler does not need to -issue. Currently, the only such diagnostic issued by g++ is the one for -a name having multiple meanings within a class. -.Ip "\fB\-fpermissive\fR" 4 -.IX Item "-fpermissive" -Downgrade messages about nonconformant code from errors to warnings. By -default, g++ effectively sets \fB\-pedantic-errors\fR without -\&\fB\-pedantic\fR; this option reverses that. This behavior and this -option are superseded by \fB\-pedantic\fR, which works as it does for \s-1GNU\s0 C. -.Ip "\fB\-frepo\fR" 4 -.IX Item "-frepo" -Enable automatic template instantiation. This option also implies -\&\fB\-fno-implicit-templates\fR. -.Ip "\fB\-fno-rtti\fR" 4 -.IX Item "-fno-rtti" -Disable generation of information about every class with virtual -functions for use by the \*(C+ runtime type identification features -(\fBdynamic_cast\fR and \fBtypeid\fR). If you don't use those parts -of the language, you can save some space by using this flag. Note that -exception handling uses the same information, but it will generate it as -needed. -.Ip "\fB\-fstats\fR" 4 -.IX Item "-fstats" -Emit statistics about front-end processing at the end of the compilation. -This information is generally only useful to the G++ development team. -.Ip "\fB\-ftemplate-depth-\fR\fIn\fR" 4 -.IX Item "-ftemplate-depth-n" -Set the maximum instantiation depth for template classes to \fIn\fR. -A limit on the template instantiation depth is needed to detect -endless recursions during template class instantiation. \s-1ANSI/ISO\s0 \*(C+ -conforming programs must not rely on a maximum depth greater than 17. -.Ip "\fB\-fuse-cxa-atexit\fR" 4 -.IX Item "-fuse-cxa-atexit" -Register destructors for objects with static storage duration with the -\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR function rather than the \f(CW\*(C`atexit\*(C'\fR function. -This option is required for fully standards-compliant handling of static -destructors, but will only work if your C library supports -\&\f(CW\*(C`_\|_cxa_atexit\*(C'\fR. -.Ip "\fB\-fvtable-thunks\fR" 4 -.IX Item "-fvtable-thunks" -Use \fBthunks\fR to implement the virtual function dispatch table -(\fBvtable\fR). The traditional (cfront-style) approach to -implementing vtables was to store a pointer to the function and two -offsets for adjusting the \fBthis\fR pointer at the call site. Newer -implementations store a single pointer to a \fBthunk\fR function which -does any necessary adjustment and then calls the target function. -.Sp -This option also enables a heuristic for controlling emission of -vtables; if a class has any non-inline virtual functions, the vtable -will be emitted in the translation unit containing the first one of -those. -.Sp -Like all options that change the \s-1ABI\s0, all \*(C+ code, \fIincluding -libgcc.a\fR must be built with the same setting of this option. -.Ip "\fB\-fno-weak\fR" 4 -.IX Item "-fno-weak" -Do not use weak symbol support, even if it is provied by the linker. -By default, G++ will use weak symbols if they are available. This -option exists only for testing, and should not be used by end-users; -it will result in inferior code and has no benefits. This option may -be removed in a future release of G++. -.Ip "\fB\-nostdinc++\fR" 4 -.IX Item "-nostdinc++" -Do not search for header files in the standard directories specific to -\&\*(C+, but do still search the other standard directories. (This option -is used when building the \*(C+ library.) -.PP -In addition, these optimization, warning, and code generation options -have meanings only for \*(C+ programs: -.Ip "\fB\-fno-default-inline\fR" 4 -.IX Item "-fno-default-inline" -Do not assume \fBinline\fR for functions defined inside a class scope. - Note that these -functions will have linkage like inline functions; they just won't be -inlined by default. -.Ip "\fB\-Wctor-dtor-privacy (\*(C+ only)\fR" 4 -.IX Item "-Wctor-dtor-privacy ( only)" -Warn when a class seems unusable, because all the constructors or -destructors in a class are private and the class has no friends or -public static member functions. -.Ip "\fB\-Wnon-virtual-dtor (\*(C+ only)\fR" 4 -.IX Item "-Wnon-virtual-dtor ( only)" -Warn when a class declares a non-virtual destructor that should probably -be virtual, because it looks like the class will be used polymorphically. -.Ip "\fB\-Wreorder (\*(C+ only)\fR" 4 -.IX Item "-Wreorder ( only)" -Warn when the order of member initializers given in the code does not -match the order in which they must be executed. For instance: -.Sp -.Vb 5 -\& struct A { -\& int i; -\& int j; -\& A(): j (0), i (1) { } -\& }; -.Ve -Here the compiler will warn that the member initializers for \fBi\fR -and \fBj\fR will be rearranged to match the declaration order of the -members. -.PP -The following \fB\-W...\fR options are not affected by \fB\-Wall\fR. -.Ip "\fB\-Weffc++ (\*(C+ only)\fR" 4 -.IX Item "-Weffc++ ( only)" -Warn about violations of various style guidelines from Scott Meyers' -\&\fIEffective \*(C+\fR books. If you use this option, you should be aware -that the standard library headers do not obey all of these guidelines; -you can use \fBgrep \-v\fR to filter out those warnings. -.Ip "\fB\-Wno-deprecated (\*(C+ only)\fR" 4 -.IX Item "-Wno-deprecated ( only)" -Do not warn about usage of deprecated features. -.Ip "\fB\-Wno-non-template-friend (\*(C+ only)\fR" 4 -.IX Item "-Wno-non-template-friend ( only)" -Disable warnings when non-templatized friend functions are declared -within a template. With the advent of explicit template specification -support in g++, if the name of the friend is an unqualified-id (ie, -\&\fBfriend foo(int)\fR), the \*(C+ language specification demands that the -friend declare or define an ordinary, nontemplate function. (Section -14.5.3). Before g++ implemented explicit specification, unqualified-ids -could be interpreted as a particular specialization of a templatized -function. Because this non-conforming behavior is no longer the default -behavior for g++, \fB\-Wnon-template-friend\fR allows the compiler to -check existing code for potential trouble spots, and is on by default. -This new compiler behavior can be turned off with -\&\fB\-Wno-non-template-friend\fR which keeps the conformant compiler code -but disables the helpful warning. -.Ip "\fB\-Wold-style-cast (\*(C+ only)\fR" 4 -.IX Item "-Wold-style-cast ( only)" -Warn if an old-style (C-style) cast is used within a \*(C+ program. The -new-style casts (\fBstatic_cast\fR, \fBreinterpret_cast\fR, and -\&\fBconst_cast\fR) are less vulnerable to unintended effects. -.Ip "\fB\-Woverloaded-virtual (\*(C+ only)\fR" 4 -.IX Item "-Woverloaded-virtual ( only)" -Warn when a function declaration hides virtual functions from a -base class. For example, in: -.Sp -.Vb 3 -\& struct A { -\& virtual void f(); -\& }; -.Ve -.Vb 3 -\& struct B: public A { -\& void f(int); -\& }; -.Ve -the \f(CW\*(C`A\*(C'\fR class version of \f(CW\*(C`f\*(C'\fR is hidden in \f(CW\*(C`B\*(C'\fR, and code -like this: -.Sp -.Vb 2 -\& B* b; -\& b->f(); -.Ve -will fail to compile. -.Ip "\fB\-Wno-pmf-conversions (\*(C+ only)\fR" 4 -.IX Item "-Wno-pmf-conversions ( only)" -Disable the diagnostic for converting a bound pointer to member function -to a plain pointer. -.Ip "\fB\-Wsign-promo (\*(C+ only)\fR" 4 -.IX Item "-Wsign-promo ( only)" -Warn when overload resolution chooses a promotion from unsigned or -enumeral type to a signed type over a conversion to an unsigned type of -the same size. Previous versions of g++ would try to preserve -unsignedness, but the standard mandates the current behavior. -.Ip "\fB\-Wsynth (\*(C+ only)\fR" 4 -.IX Item "-Wsynth ( only)" -Warn when g++'s synthesis behavior does not match that of cfront. For -instance: -.Sp -.Vb 4 -\& struct A { -\& operator int (); -\& A& operator = (int); -\& }; -.Ve -.Vb 5 -\& main () -\& { -\& A a,b; -\& a = b; -\& } -.Ve -In this example, g++ will synthesize a default \fBA& operator = -(const A&);\fR, while cfront will use the user-defined \fBoperator =\fR. -.Sh "Options Controlling Objective-C Dialect" -.IX Subsection "Options Controlling Objective-C Dialect" -This section describes the command-line options that are only meaningful -for Objective-C programs; but you can also use most of the \s-1GNU\s0 compiler -options regardless of what language your program is in. For example, -you might compile a file \f(CW\*(C`some_class.m\*(C'\fR like this: -.PP -.Vb 1 -\& gcc -g -fgnu-runtime -O -c some_class.m -.Ve -In this example, only \fB\-fgnu-runtime\fR is an option meant only for -Objective-C programs; you can use the other options with any language -supported by \s-1GCC\s0. -.PP -Here is a list of options that are \fIonly\fR for compiling Objective-C -programs: -.Ip "\fB\-fconstant-string-class=\fR\fIclass name\fR" 4 -.IX Item "-fconstant-string-class=class name" -Use \fIclass name\fR as the name of the class to instantiate for each -literal string specified with the syntax \f(CW\*(C`@"..."\*(C'\fR. The default -class name is \f(CW\*(C`NXConstantString\*(C'\fR. -.Ip "\fB\-fgnu-runtime\fR" 4 -.IX Item "-fgnu-runtime" -Generate object code compatible with the standard \s-1GNU\s0 Objective-C -runtime. This is the default for most types of systems. -.Ip "\fB\-fnext-runtime\fR" 4 -.IX Item "-fnext-runtime" -Generate output compatible with the NeXT runtime. This is the default -for NeXT-based systems, including Darwin and Mac \s-1OS\s0 X. -.Ip "\fB\-gen-decls\fR" 4 -.IX Item "-gen-decls" -Dump interface declarations for all classes seen in the source file to a -file named \fI\fIsourcename\fI.decl\fR. -.Ip "\fB\-Wno-protocol\fR" 4 -.IX Item "-Wno-protocol" -Do not warn if methods required by a protocol are not implemented -in the class adopting it. -.Ip "\fB\-Wselector\fR" 4 -.IX Item "-Wselector" -Warn if a selector has multiple methods of different types defined. -.Sh "Options to Control Diagnostic Messages Formatting" -.IX Subsection "Options to Control Diagnostic Messages Formatting" -Traditionally, diagnostic messages have been formatted irrespective of -the output device's aspect (e.g. its width, ...). The options described -below can be used to control the diagnostic messages formatting -algorithm, e.g. how many characters per line, how often source location -information should be reported. Right now, only the \*(C+ front-end can -honor these options. However it is expected, in the near future, that -the remaining front-ends would be able to digest them correctly. -.Ip "\fB\-fmessage-length=\fR\fIn\fR" 4 -.IX Item "-fmessage-length=n" -Try to format error messages so that they fit on lines of about \fIn\fR -characters. The default is 72 characters for g++ and 0 for the rest of -the front-ends supported by \s-1GCC\s0. If \fIn\fR is zero, then no -line-wrapping will be done; each error message will appear on a single -line. -.Ip "\fB\-fdiagnostics-show-location=once\fR" 4 -.IX Item "-fdiagnostics-show-location=once" -Only meaningful in line-wrapping mode. Instructs the diagnostic messages -reporter to emit \fIonce\fR source location information; that is, in -case the message is too long to fit on a single physical line and has to -be wrapped, the source location won't be emitted (as prefix) again, -over and over, in subsequent continuation lines. This is the default -behaviour. -.Ip "\fB\-fdiagnostics-show-location=every-line\fR" 4 -.IX Item "-fdiagnostics-show-location=every-line" -Only meaningful in line-wrapping mode. Instructs the diagnostic -messages reporter to emit the same source location information (as -prefix) for physical lines that result from the process of breaking a -a message which is too long to fit on a single line. -.Sh "Options to Request or Suppress Warnings" -.IX Subsection "Options to Request or Suppress Warnings" -Warnings are diagnostic messages that report constructions which -are not inherently erroneous but which are risky or suggest there -may have been an error. -.PP -You can request many specific warnings with options beginning \fB\-W\fR, -for example \fB\-Wimplicit\fR to request warnings on implicit -declarations. Each of these specific warning options also has a -negative form beginning \fB\-Wno-\fR to turn off warnings; -for example, \fB\-Wno-implicit\fR. This manual lists only one of the -two forms, whichever is not the default. -.PP -These options control the amount and kinds of warnings produced by \s-1GCC:\s0 -.Ip "\fB\-fsyntax-only\fR" 4 -.IX Item "-fsyntax-only" -Check the code for syntax errors, but don't do anything beyond that. -.Ip "\fB\-pedantic\fR" 4 -.IX Item "-pedantic" -Issue all the warnings demanded by strict \s-1ISO\s0 C and \s-1ISO\s0 \*(C+; -reject all programs that use forbidden extensions, and some other -programs that do not follow \s-1ISO\s0 C and \s-1ISO\s0 \*(C+. For \s-1ISO\s0 C, follows the -version of the \s-1ISO\s0 C standard specified by any \fB\-std\fR option used. -.Sp -Valid \s-1ISO\s0 C and \s-1ISO\s0 \*(C+ programs should compile properly with or without -this option (though a rare few will require \fB\-ansi\fR or a -\&\fB\-std\fR option specifying the required version of \s-1ISO\s0 C). However, -without this option, certain \s-1GNU\s0 extensions and traditional C and \*(C+ -features are supported as well. With this option, they are rejected. -.Sp -\&\fB\-pedantic\fR does not cause warning messages for use of the -alternate keywords whose names begin and end with \fB_\|_\fR. Pedantic -warnings are also disabled in the expression that follows -\&\f(CW\*(C`_\|_extension_\|_\*(C'\fR. However, only system header files should use -these escape routes; application programs should avoid them. -.Sp -Some users try to use \fB\-pedantic\fR to check programs for strict \s-1ISO\s0 -C conformance. They soon find that it does not do quite what they want: -it finds some non-ISO practices, but not all\-\-\-only those for which -\&\s-1ISO\s0 C \fIrequires\fR a diagnostic, and some others for which -diagnostics have been added. -.Sp -A feature to report any failure to conform to \s-1ISO\s0 C might be useful in -some instances, but would require considerable additional work and would -be quite different from \fB\-pedantic\fR. We don't have plans to -support such a feature in the near future. -.Sp -Where the standard specified with \fB\-std\fR represents a \s-1GNU\s0 -extended dialect of C, such as \fBgnu89\fR or \fBgnu99\fR, there is a -corresponding \fIbase standard\fR, the version of \s-1ISO\s0 C on which the \s-1GNU\s0 -extended dialect is based. Warnings from \fB\-pedantic\fR are given -where they are required by the base standard. (It would not make sense -for such warnings to be given only for features not in the specified \s-1GNU\s0 -C dialect, since by definition the \s-1GNU\s0 dialects of C include all -features the compiler supports with the given option, and there would be -nothing to warn about.) -.Ip "\fB\-pedantic-errors\fR" 4 -.IX Item "-pedantic-errors" -Like \fB\-pedantic\fR, except that errors are produced rather than -warnings. -.Ip "\fB\-w\fR" 4 -.IX Item "-w" -Inhibit all warning messages. -.Ip "\fB\-Wno-import\fR" 4 -.IX Item "-Wno-import" -Inhibit warning messages about the use of \fB#import\fR. -.Ip "\fB\-Wchar-subscripts\fR" 4 -.IX Item "-Wchar-subscripts" -Warn if an array subscript has type \f(CW\*(C`char\*(C'\fR. This is a common cause -of error, as programmers often forget that this type is signed on some -machines. -.Ip "\fB\-Wcomment\fR" 4 -.IX Item "-Wcomment" -Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR -comment, or whenever a Backslash-Newline appears in a \fB//\fR comment. -.Ip "\fB\-Wformat\fR" 4 -.IX Item "-Wformat" -Check calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR, etc., to make sure that -the arguments supplied have types appropriate to the format string -specified, and that the conversions specified in the format string make -sense. This includes standard functions, and others specified by format -attributes, in the \f(CW\*(C`printf\*(C'\fR, -\&\f(CW\*(C`scanf\*(C'\fR, \f(CW\*(C`strftime\*(C'\fR and \f(CW\*(C`strfmon\*(C'\fR (an X/Open extension, -not in the C standard) families. -.Sp -The formats are checked against the format features supported by \s-1GNU\s0 -libc version 2.2. These include all \s-1ISO\s0 C89 and C99 features, as well -as features from the Single Unix Specification and some \s-1BSD\s0 and \s-1GNU\s0 -extensions. Other library implementations may not support all these -features; \s-1GCC\s0 does not support warning about features that go beyond a -particular library's limitations. However, if \fB\-pedantic\fR is used -with \fB\-Wformat\fR, warnings will be given about format features not -in the selected standard version (but not for \f(CW\*(C`strfmon\*(C'\fR formats, -since those are not in any version of the C standard). -.Sp -\&\fB\-Wformat\fR is included in \fB\-Wall\fR. For more control over some -aspects of format checking, the options \fB\-Wno-format-y2k\fR, -\&\fB\-Wno-format-extra-args\fR, \fB\-Wformat-nonliteral\fR, -\&\fB\-Wformat-security\fR and \fB\-Wformat=2\fR are available, but are -not included in \fB\-Wall\fR. -.Ip "\fB\-Wno-format-y2k\fR" 4 -.IX Item "-Wno-format-y2k" -If \fB\-Wformat\fR is specified, do not warn about \f(CW\*(C`strftime\*(C'\fR -formats which may yield only a two-digit year. -.Ip "\fB\-Wno-format-extra-args\fR" 4 -.IX Item "-Wno-format-extra-args" -If \fB\-Wformat\fR is specified, do not warn about excess arguments to a -\&\f(CW\*(C`printf\*(C'\fR or \f(CW\*(C`scanf\*(C'\fR format function. The C standard specifies -that such arguments are ignored. -.Ip "\fB\-Wformat-nonliteral\fR" 4 -.IX Item "-Wformat-nonliteral" -If \fB\-Wformat\fR is specified, also warn if the format string is not a -string literal and so cannot be checked, unless the format function -takes its format arguments as a \f(CW\*(C`va_list\*(C'\fR. -.Ip "\fB\-Wformat-security\fR" 4 -.IX Item "-Wformat-security" -If \fB\-Wformat\fR is specified, also warn about uses of format -functions that represent possible security problems. At present, this -warns about calls to \f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`scanf\*(C'\fR functions where the -format string is not a string literal and there are no format arguments, -as in \f(CW\*(C`printf (foo);\*(C'\fR. This may be a security hole if the format -string came from untrusted input and contains \fB%n\fR. (This is -currently a subset of what \fB\-Wformat-nonliteral\fR warns about, but -in future warnings may be added to \fB\-Wformat-security\fR that are not -included in \fB\-Wformat-nonliteral\fR.) -.Ip "\fB\-Wformat=2\fR" 4 -.IX Item "-Wformat=2" -Enable \fB\-Wformat\fR plus format checks not included in -\&\fB\-Wformat\fR. Currently equivalent to \fB\-Wformat -\&\-Wformat-nonliteral \-Wformat-security\fR. -.Ip "\fB\-Wimplicit-int\fR" 4 -.IX Item "-Wimplicit-int" -Warn when a declaration does not specify a type. -.Ip "\fB\-Wimplicit-function-declaration\fR" 4 -.IX Item "-Wimplicit-function-declaration" -.PD 0 -.Ip "\fB\-Werror-implicit-function-declaration\fR" 4 -.IX Item "-Werror-implicit-function-declaration" -.PD -Give a warning (or error) whenever a function is used before being -declared. -.Ip "\fB\-Wimplicit\fR" 4 -.IX Item "-Wimplicit" -Same as \fB\-Wimplicit-int\fR and \fB\-Wimplicit-function-\fR\fBdeclaration\fR. -.Ip "\fB\-Wmain\fR" 4 -.IX Item "-Wmain" -Warn if the type of \fBmain\fR is suspicious. \fBmain\fR should be a -function with external linkage, returning int, taking either zero -arguments, two, or three arguments of appropriate types. -.Ip "\fB\-Wmissing-braces\fR" 4 -.IX Item "-Wmissing-braces" -Warn if an aggregate or union initializer is not fully bracketed. In -the following example, the initializer for \fBa\fR is not fully -bracketed, but that for \fBb\fR is fully bracketed. -.Sp -.Vb 2 -\& int a[2][2] = { 0, 1, 2, 3 }; -\& int b[2][2] = { { 0, 1 }, { 2, 3 } }; -.Ve -.Ip "\fB\-Wmultichar\fR" 4 -.IX Item "-Wmultichar" -Warn if a multicharacter constant (\fB'\s-1FOOF\s0'\fR) is used. Usually they -indicate a typo in the user's code, as they have implementation-defined -values, and should not be used in portable code. -.Ip "\fB\-Wparentheses\fR" 4 -.IX Item "-Wparentheses" -Warn if parentheses are omitted in certain contexts, such -as when there is an assignment in a context where a truth value -is expected, or when operators are nested whose precedence people -often get confused about. -.Sp -Also warn about constructions where there may be confusion to which -\&\f(CW\*(C`if\*(C'\fR statement an \f(CW\*(C`else\*(C'\fR branch belongs. Here is an example of -such a case: -.Sp -.Vb 7 -\& { -\& if (a) -\& if (b) -\& foo (); -\& else -\& bar (); -\& } -.Ve -In C, every \f(CW\*(C`else\*(C'\fR branch belongs to the innermost possible \f(CW\*(C`if\*(C'\fR -statement, which in this example is \f(CW\*(C`if (b)\*(C'\fR. This is often not -what the programmer expected, as illustrated in the above example by -indentation the programmer chose. When there is the potential for this -confusion, \s-1GNU\s0 C will issue a warning when this flag is specified. -To eliminate the warning, add explicit braces around the innermost -\&\f(CW\*(C`if\*(C'\fR statement so there is no way the \f(CW\*(C`else\*(C'\fR could belong to -the enclosing \f(CW\*(C`if\*(C'\fR. The resulting code would look like this: -.Sp -.Vb 9 -\& { -\& if (a) -\& { -\& if (b) -\& foo (); -\& else -\& bar (); -\& } -\& } -.Ve -.Ip "\fB\-Wsequence-point\fR" 4 -.IX Item "-Wsequence-point" -Warn about code that may have undefined semantics because of violations -of sequence point rules in the C standard. -.Sp -The C standard defines the order in which expressions in a C program are -evaluated in terms of \fIsequence points\fR, which represent a partial -ordering between the execution of parts of the program: those executed -before the sequence point, and those executed after it. These occur -after the evaluation of a full expression (one which is not part of a -larger expression), after the evaluation of the first operand of a -\&\f(CW\*(C`&&\*(C'\fR, \f(CW\*(C`||\*(C'\fR, \f(CW\*(C`? :\*(C'\fR or \f(CW\*(C`,\*(C'\fR (comma) operator, before a -function is called (but after the evaluation of its arguments and the -expression denoting the called function), and in certain other places. -Other than as expressed by the sequence point rules, the order of -evaluation of subexpressions of an expression is not specified. All -these rules describe only a partial order rather than a total order, -since, for example, if two functions are called within one expression -with no sequence point between them, the order in which the functions -are called is not specified. However, the standards committee have -ruled that function calls do not overlap. -.Sp -It is not specified when between sequence points modifications to the -values of objects take effect. Programs whose behavior depends on this -have undefined behavior; the C standard specifies that ``Between the -previous and next sequence point an object shall have its stored value -modified at most once by the evaluation of an expression. Furthermore, -the prior value shall be read only to determine the value to be -stored.''. If a program breaks these rules, the results on any -particular implementation are entirely unpredictable. -.Sp -Examples of code with undefined behavior are \f(CW\*(C`a = a++;\*(C'\fR, \f(CW\*(C`a[n] -= b[n++]\*(C'\fR and \f(CW\*(C`a[i++] = i;\*(C'\fR. Some more complicated cases are not -diagnosed by this option, and it may give an occasional false positive -result, but in general it has been found fairly effective at detecting -this sort of problem in programs. -.Sp -The present implementation of this option only works for C programs. A -future implementation may also work for \*(C+ programs. -.Sp -There is some controversy over the precise meaning of the sequence point -rules in subtle cases. Alternative formal definitions may be found in -Clive Feather's ``Annex S'' -<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n925.htm\fR> and in -Michael Norrish's thesis -<\fBhttp://www.cl.cam.ac.uk/users/mn200/PhD/thesis-report.ps.gz\fR>. -Other discussions are by Raymond Mak -<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n926.htm\fR> and -D. Hugh Redelmeier -<\fBhttp://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n927.htm\fR>. -.Ip "\fB\-Wreturn-type\fR" 4 -.IX Item "-Wreturn-type" -Warn whenever a function is defined with a return-type that defaults to -\&\f(CW\*(C`int\*(C'\fR. Also warn about any \f(CW\*(C`return\*(C'\fR statement with no -return-value in a function whose return-type is not \f(CW\*(C`void\*(C'\fR. -.Sp -For \*(C+, a function without return type always produces a diagnostic -message, even when \fB\-Wno-return-type\fR is specified. The only -exceptions are \fBmain\fR and functions defined in system headers. -.Ip "\fB\-Wswitch\fR" 4 -.IX Item "-Wswitch" -Warn whenever a \f(CW\*(C`switch\*(C'\fR statement has an index of enumeral type -and lacks a \f(CW\*(C`case\*(C'\fR for one or more of the named codes of that -enumeration. (The presence of a \f(CW\*(C`default\*(C'\fR label prevents this -warning.) \f(CW\*(C`case\*(C'\fR labels outside the enumeration range also -provoke warnings when this option is used. -.Ip "\fB\-Wtrigraphs\fR" 4 -.IX Item "-Wtrigraphs" -Warn if any trigraphs are encountered that might change the meaning of -the program (trigraphs within comments are not warned about). -.Ip "\fB\-Wunused-function\fR" 4 -.IX Item "-Wunused-function" -Warn whenever a static function is declared but not defined or a -non\e-inline static function is unused. -.Ip "\fB\-Wunused-label\fR" 4 -.IX Item "-Wunused-label" -Warn whenever a label is declared but not used. -.Sp -To suppress this warning use the \fBunused\fR attribute. -.Ip "\fB\-Wunused-parameter\fR" 4 -.IX Item "-Wunused-parameter" -Warn whenever a function parameter is unused aside from its declaration. -.Sp -To suppress this warning use the \fBunused\fR attribute. -.Ip "\fB\-Wunused-variable\fR" 4 -.IX Item "-Wunused-variable" -Warn whenever a local variable or non-constant static variable is unused -aside from its declaration -.Sp -To suppress this warning use the \fBunused\fR attribute. -.Ip "\fB\-Wunused-value\fR" 4 -.IX Item "-Wunused-value" -Warn whenever a statement computes a result that is explicitly not used. -.Sp -To suppress this warning cast the expression to \fBvoid\fR. -.Ip "\fB\-Wunused\fR" 4 -.IX Item "-Wunused" -All all the above \fB\-Wunused\fR options combined. -.Sp -In order to get a warning about an unused function parameter, you must -either specify \fB\-W \-Wunused\fR or separately specify -\&\fB\-Wunused-parameter\fR. -.Ip "\fB\-Wuninitialized\fR" 4 -.IX Item "-Wuninitialized" -Warn if an automatic variable is used without first being initialized or -if a variable may be clobbered by a \f(CW\*(C`setjmp\*(C'\fR call. -.Sp -These warnings are possible only in optimizing compilation, -because they require data flow information that is computed only -when optimizing. If you don't specify \fB\-O\fR, you simply won't -get these warnings. -.Sp -These warnings occur only for variables that are candidates for -register allocation. Therefore, they do not occur for a variable that -is declared \f(CW\*(C`volatile\*(C'\fR, or whose address is taken, or whose size -is other than 1, 2, 4 or 8 bytes. Also, they do not occur for -structures, unions or arrays, even when they are in registers. -.Sp -Note that there may be no warning about a variable that is used only -to compute a value that itself is never used, because such -computations may be deleted by data flow analysis before the warnings -are printed. -.Sp -These warnings are made optional because \s-1GCC\s0 is not smart -enough to see all the reasons why the code might be correct -despite appearing to have an error. Here is one example of how -this can happen: -.Sp -.Vb 12 -\& { -\& int x; -\& switch (y) -\& { -\& case 1: x = 1; -\& break; -\& case 2: x = 4; -\& break; -\& case 3: x = 5; -\& } -\& foo (x); -\& } -.Ve -If the value of \f(CW\*(C`y\*(C'\fR is always 1, 2 or 3, then \f(CW\*(C`x\*(C'\fR is -always initialized, but \s-1GCC\s0 doesn't know this. Here is -another common case: -.Sp -.Vb 6 -\& { -\& int save_y; -\& if (change_y) save_y = y, y = new_y; -\& ... -\& if (change_y) y = save_y; -\& } -.Ve -This has no bug because \f(CW\*(C`save_y\*(C'\fR is used only if it is set. -.Sp -This option also warns when a non-volatile automatic variable might be -changed by a call to \f(CW\*(C`longjmp\*(C'\fR. These warnings as well are possible -only in optimizing compilation. -.Sp -The compiler sees only the calls to \f(CW\*(C`setjmp\*(C'\fR. It cannot know -where \f(CW\*(C`longjmp\*(C'\fR will be called; in fact, a signal handler could -call it at any point in the code. As a result, you may get a warning -even when there is in fact no problem because \f(CW\*(C`longjmp\*(C'\fR cannot -in fact be called at the place which would cause a problem. -.Sp -Some spurious warnings can be avoided if you declare all the functions -you use that never return as \f(CW\*(C`noreturn\*(C'\fR. -.Ip "\fB\-Wreorder (\*(C+ only)\fR" 4 -.IX Item "-Wreorder ( only)" -Warn when the order of member initializers given in the code does not -match the order in which they must be executed. For instance: -.Ip "\fB\-Wunknown-pragmas\fR" 4 -.IX Item "-Wunknown-pragmas" -Warn when a #pragma directive is encountered which is not understood by -\&\s-1GCC\s0. If this command line option is used, warnings will even be issued -for unknown pragmas in system header files. This is not the case if -the warnings were only enabled by the \fB\-Wall\fR command line option. -.Ip "\fB\-Wall\fR" 4 -.IX Item "-Wall" -All of the above \fB\-W\fR options combined. This enables all the -warnings about constructions that some users consider questionable, and -that are easy to avoid (or modify to prevent the warning), even in -conjunction with macros. -.Ip "\fB\-Wsystem-headers\fR" 4 -.IX Item "-Wsystem-headers" -Print warning messages for constructs found in system header files. -Warnings from system headers are normally suppressed, on the assumption -that they usually do not indicate real problems and would only make the -compiler output harder to read. Using this command line option tells -\&\s-1GCC\s0 to emit warnings from system headers as if they occurred in user -code. However, note that using \fB\-Wall\fR in conjunction with this -option will \fInot\fR warn about unknown pragmas in system -headers\-\-\-for that, \fB\-Wunknown-pragmas\fR must also be used. -.PP -The following \fB\-W...\fR options are not implied by \fB\-Wall\fR. -Some of them warn about constructions that users generally do not -consider questionable, but which occasionally you might wish to check -for; others warn about constructions that are necessary or hard to avoid -in some cases, and there is no simple way to modify the code to suppress -the warning. -.Ip "\fB\-W\fR" 4 -.IX Item "-W" -Print extra warning messages for these events: -.RS 4 -.Ip "\(bu" 4 -A function can return either with or without a value. (Falling -off the end of the function body is considered returning without -a value.) For example, this function would evoke such a -warning: -.Sp -.Vb 5 -\& foo (a) -\& { -\& if (a > 0) -\& return a; -\& } -.Ve -.Ip "\(bu" 4 -An expression-statement or the left-hand side of a comma expression -contains no side effects. -To suppress the warning, cast the unused expression to void. -For example, an expression such as \fBx[i,j]\fR will cause a warning, -but \fBx[(void)i,j]\fR will not. -.Ip "\(bu" 4 -An unsigned value is compared against zero with \fB<\fR or \fB<=\fR. -.Ip "\(bu" 4 -A comparison like \fBx<=y<=z\fR appears; this is equivalent to -\&\fB(x<=y ? 1 : 0) <= z\fR, which is a different interpretation from -that of ordinary mathematical notation. -.Ip "\(bu" 4 -Storage-class specifiers like \f(CW\*(C`static\*(C'\fR are not the first things in -a declaration. According to the C Standard, this usage is obsolescent. -.Ip "\(bu" 4 -The return type of a function has a type qualifier such as \f(CW\*(C`const\*(C'\fR. -Such a type qualifier has no effect, since the value returned by a -function is not an lvalue. (But don't warn about the \s-1GNU\s0 extension of -\&\f(CW\*(C`volatile void\*(C'\fR return types. That extension will be warned about -if \fB\-pedantic\fR is specified.) -.Ip "\(bu" 4 -If \fB\-Wall\fR or \fB\-Wunused\fR is also specified, warn about unused -arguments. -.Ip "\(bu" 4 -A comparison between signed and unsigned values could produce an -incorrect result when the signed value is converted to unsigned. -(But don't warn if \fB\-Wno-sign-compare\fR is also specified.) -.Ip "\(bu" 4 -An aggregate has a partly bracketed initializer. -For example, the following code would evoke such a warning, -because braces are missing around the initializer for \f(CW\*(C`x.h\*(C'\fR: -.Sp -.Vb 3 -\& struct s { int f, g; }; -\& struct t { struct s h; int i; }; -\& struct t x = { 1, 2, 3 }; -.Ve -.Ip "\(bu" 4 -An aggregate has an initializer which does not initialize all members. -For example, the following code would cause such a warning, because -\&\f(CW\*(C`x.h\*(C'\fR would be implicitly initialized to zero: -.Sp -.Vb 2 -\& struct s { int f, g, h; }; -\& struct s x = { 3, 4 }; -.Ve -.RE -.RS 4 -.RE -.Ip "\fB\-Wfloat-equal\fR" 4 -.IX Item "-Wfloat-equal" -Warn if floating point values are used in equality comparisons. -.Sp -The idea behind this is that sometimes it is convenient (for the -programmer) to consider floating-point values as approximations to -infinitely precise real numbers. If you are doing this, then you need -to compute (by analysing the code, or in some other way) the maximum or -likely maximum error that the computation introduces, and allow for it -when performing comparisons (and when producing output, but that's a -different problem). In particular, instead of testing for equality, you -would check to see whether the two values have ranges that overlap; and -this is done with the relational operators, so equality comparisons are -probably mistaken. -.Ip "\fB\-Wtraditional (C only)\fR" 4 -.IX Item "-Wtraditional (C only)" -Warn about certain constructs that behave differently in traditional and -\&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C -equivalent, and/or problematic constructs which should be avoided. -.RS 4 -.Ip "\(bu" 4 -Macro parameters that appear within string literals in the macro body. -In traditional C macro replacement takes place within string literals, -but does not in \s-1ISO\s0 C. -.Ip "\(bu" 4 -In traditional C, some preprocessor directives did not exist. -Traditional preprocessors would only consider a line to be a directive -if the \fB#\fR appeared in column 1 on the line. Therefore -\&\fB\-Wtraditional\fR warns about directives that traditional C -understands but would ignore because the \fB#\fR does not appear as the -first character on the line. It also suggests you hide directives like -\&\fB#pragma\fR not understood by traditional C by indenting them. Some -traditional implementations would not recognise \fB#elif\fR, so it -suggests avoiding it altogether. -.Ip "\(bu" 4 -A function-like macro that appears without arguments. -.Ip "\(bu" 4 -The unary plus operator. -.Ip "\(bu" 4 -The `U' integer constant suffix, or the `F' or `L' floating point -constant suffixes. (Traditonal C does support the `L' suffix on integer -constants.) Note, these suffixes appear in macros defined in the system -headers of most modern systems, e.g. the _MIN/_MAX macros in limits.h. -Use of these macros in user code might normally lead to spurious -warnings, however gcc's integrated preprocessor has enough context to -avoid warning in these cases. -.Ip "\(bu" 4 -A function declared external in one block and then used after the end of -the block. -.Ip "\(bu" 4 -A \f(CW\*(C`switch\*(C'\fR statement has an operand of type \f(CW\*(C`long\*(C'\fR. -.Ip "\(bu" 4 -A non-\f(CW\*(C`static\*(C'\fR function declaration follows a \f(CW\*(C`static\*(C'\fR one. -This construct is not accepted by some traditional C compilers. -.Ip "\(bu" 4 -The \s-1ISO\s0 type of an integer constant has a different width or -signedness from its traditional type. This warning is only issued if -the base of the constant is ten. I.e. hexadecimal or octal values, which -typically represent bit patterns, are not warned about. -.Ip "\(bu" 4 -Usage of \s-1ISO\s0 string concatenation is detected. -.Ip "\(bu" 4 -Initialization of automatic aggregates. -.Ip "\(bu" 4 -Identifier conflicts with labels. Traditional C lacks a separate -namespace for labels. -.Ip "\(bu" 4 -Initialization of unions. If the initializer is zero, the warning is -omitted. This is done under the assumption that the zero initializer in -user code appears conditioned on e.g. \f(CW\*(C`_\|_STDC_\|_\*(C'\fR to avoid missing -initializer warnings and relies on default initialization to zero in the -traditional C case. -.Ip "\(bu" 4 -Conversions by prototypes between fixed/floating point values and vice -versa. The absence of these prototypes when compiling with traditional -C would cause serious problems. This is a subset of the possible -conversion warnings, for the full set use \fB\-Wconversion\fR. -.RE -.RS 4 -.RE -.Ip "\fB\-Wundef\fR" 4 -.IX Item "-Wundef" -Warn if an undefined identifier is evaluated in an \fB#if\fR directive. -.Ip "\fB\-Wshadow\fR" 4 -.IX Item "-Wshadow" -Warn whenever a local variable shadows another local variable, parameter or -global variable or whenever a built-in function is shadowed. -.Ip "\fB\-Wid-clash-\fR\fIlen\fR" 4 -.IX Item "-Wid-clash-len" -Warn whenever two distinct identifiers match in the first \fIlen\fR -characters. This may help you prepare a program that will compile -with certain obsolete, brain-damaged compilers. -.Ip "\fB\-Wlarger-than-\fR\fIlen\fR" 4 -.IX Item "-Wlarger-than-len" -Warn whenever an object of larger than \fIlen\fR bytes is defined. -.Ip "\fB\-Wpointer-arith\fR" 4 -.IX Item "-Wpointer-arith" -Warn about anything that depends on the ``size of'' a function type or -of \f(CW\*(C`void\*(C'\fR. \s-1GNU\s0 C assigns these types a size of 1, for -convenience in calculations with \f(CW\*(C`void *\*(C'\fR pointers and pointers -to functions. -.Ip "\fB\-Wbad-function-cast (C only)\fR" 4 -.IX Item "-Wbad-function-cast (C only)" -Warn whenever a function call is cast to a non-matching type. -For example, warn if \f(CW\*(C`int malloc()\*(C'\fR is cast to \f(CW\*(C`anything *\*(C'\fR. -.Ip "\fB\-Wcast-qual\fR" 4 -.IX Item "-Wcast-qual" -Warn whenever a pointer is cast so as to remove a type qualifier from -the target type. For example, warn if a \f(CW\*(C`const char *\*(C'\fR is cast -to an ordinary \f(CW\*(C`char *\*(C'\fR. -.Ip "\fB\-Wcast-align\fR" 4 -.IX Item "-Wcast-align" -Warn whenever a pointer is cast such that the required alignment of the -target is increased. For example, warn if a \f(CW\*(C`char *\*(C'\fR is cast to -an \f(CW\*(C`int *\*(C'\fR on machines where integers can only be accessed at -two- or four-byte boundaries. -.Ip "\fB\-Wwrite-strings\fR" 4 -.IX Item "-Wwrite-strings" -Give string constants the type \f(CW\*(C`const char[\f(CIlength\f(CW]\*(C'\fR so that -copying the address of one into a non-\f(CW\*(C`const\*(C'\fR \f(CW\*(C`char *\*(C'\fR -pointer will get a warning. These warnings will help you find at -compile time code that can try to write into a string constant, but -only if you have been very careful about using \f(CW\*(C`const\*(C'\fR in -declarations and prototypes. Otherwise, it will just be a nuisance; -this is why we did not make \fB\-Wall\fR request these warnings. -.Ip "\fB\-Wconversion\fR" 4 -.IX Item "-Wconversion" -Warn if a prototype causes a type conversion that is different from what -would happen to the same argument in the absence of a prototype. This -includes conversions of fixed point to floating and vice versa, and -conversions changing the width or signedness of a fixed point argument -except when the same as the default promotion. -.Sp -Also, warn if a negative integer constant expression is implicitly -converted to an unsigned type. For example, warn about the assignment -\&\f(CW\*(C`x = \-1\*(C'\fR if \f(CW\*(C`x\*(C'\fR is unsigned. But do not warn about explicit -casts like \f(CW\*(C`(unsigned) \-1\*(C'\fR. -.Ip "\fB\-Wsign-compare\fR" 4 -.IX Item "-Wsign-compare" -Warn when a comparison between signed and unsigned values could produce -an incorrect result when the signed value is converted to unsigned. -This warning is also enabled by \fB\-W\fR; to get the other warnings -of \fB\-W\fR without this warning, use \fB\-W \-Wno-sign-compare\fR. -.Ip "\fB\-Waggregate-return\fR" 4 -.IX Item "-Waggregate-return" -Warn if any functions that return structures or unions are defined or -called. (In languages where you can return an array, this also elicits -a warning.) -.Ip "\fB\-Wstrict-prototypes (C only)\fR" 4 -.IX Item "-Wstrict-prototypes (C only)" -Warn if a function is declared or defined without specifying the -argument types. (An old-style function definition is permitted without -a warning if preceded by a declaration which specifies the argument -types.) -.Ip "\fB\-Wmissing-prototypes (C only)\fR" 4 -.IX Item "-Wmissing-prototypes (C only)" -Warn if a global function is defined without a previous prototype -declaration. This warning is issued even if the definition itself -provides a prototype. The aim is to detect global functions that fail -to be declared in header files. -.Ip "\fB\-Wmissing-declarations\fR" 4 -.IX Item "-Wmissing-declarations" -Warn if a global function is defined without a previous declaration. -Do so even if the definition itself provides a prototype. -Use this option to detect global functions that are not declared in -header files. -.Ip "\fB\-Wmissing-noreturn\fR" 4 -.IX Item "-Wmissing-noreturn" -Warn about functions which might be candidates for attribute \f(CW\*(C`noreturn\*(C'\fR. -Note these are only possible candidates, not absolute ones. Care should -be taken to manually verify functions actually do not ever return before -adding the \f(CW\*(C`noreturn\*(C'\fR attribute, otherwise subtle code generation -bugs could be introduced. You will not get a warning for \f(CW\*(C`main\*(C'\fR in -hosted C environments. -.Ip "\fB\-Wmissing-format-attribute\fR" 4 -.IX Item "-Wmissing-format-attribute" -If \fB\-Wformat\fR is enabled, also warn about functions which might be -candidates for \f(CW\*(C`format\*(C'\fR attributes. Note these are only possible -candidates, not absolute ones. \s-1GCC\s0 will guess that \f(CW\*(C`format\*(C'\fR -attributes might be appropriate for any function that calls a function -like \f(CW\*(C`vprintf\*(C'\fR or \f(CW\*(C`vscanf\*(C'\fR, but this might not always be the -case, and some functions for which \f(CW\*(C`format\*(C'\fR attributes are -appropriate may not be detected. This option has no effect unless -\&\fB\-Wformat\fR is enabled (possibly by \fB\-Wall\fR). -.Ip "\fB\-Wpacked\fR" 4 -.IX Item "-Wpacked" -Warn if a structure is given the packed attribute, but the packed -attribute has no effect on the layout or size of the structure. -Such structures may be mis-aligned for little benefit. For -instance, in this code, the variable \f(CW\*(C`f.x\*(C'\fR in \f(CW\*(C`struct bar\*(C'\fR -will be misaligned even though \f(CW\*(C`struct bar\*(C'\fR does not itself -have the packed attribute: -.Sp -.Vb 8 -\& struct foo { -\& int x; -\& char a, b, c, d; -\& } __attribute__((packed)); -\& struct bar { -\& char z; -\& struct foo f; -\& }; -.Ve -.Ip "\fB\-Wpadded\fR" 4 -.IX Item "-Wpadded" -Warn if padding is included in a structure, either to align an element -of the structure or to align the whole structure. Sometimes when this -happens it is possible to rearrange the fields of the structure to -reduce the padding and so make the structure smaller. -.Ip "\fB\-Wredundant-decls\fR" 4 -.IX Item "-Wredundant-decls" -Warn if anything is declared more than once in the same scope, even in -cases where multiple declaration is valid and changes nothing. -.Ip "\fB\-Wnested-externs (C only)\fR" 4 -.IX Item "-Wnested-externs (C only)" -Warn if an \f(CW\*(C`extern\*(C'\fR declaration is encountered within a function. -.Ip "\fB\-Wunreachable-code\fR" 4 -.IX Item "-Wunreachable-code" -Warn if the compiler detects that code will never be executed. -.Sp -This option is intended to warn when the compiler detects that at -least a whole line of source code will never be executed, because -some condition is never satisfied or because it is after a -procedure that never returns. -.Sp -It is possible for this option to produce a warning even though there -are circumstances under which part of the affected line can be executed, -so care should be taken when removing apparently-unreachable code. -.Sp -For instance, when a function is inlined, a warning may mean that the -line is unreachable in only one inlined copy of the function. -.Sp -This option is not made part of \fB\-Wall\fR because in a debugging -version of a program there is often substantial code which checks -correct functioning of the program and is, hopefully, unreachable -because the program does work. Another common use of unreachable -code is to provide behaviour which is selectable at compile-time. -.Ip "\fB\-Winline\fR" 4 -.IX Item "-Winline" -Warn if a function can not be inlined and it was declared as inline. -.Ip "\fB\-Wlong-long\fR" 4 -.IX Item "-Wlong-long" -Warn if \fBlong long\fR type is used. This is default. To inhibit -the warning messages, use \fB\-Wno-long-long\fR. Flags -\&\fB\-Wlong-long\fR and \fB\-Wno-long-long\fR are taken into account -only when \fB\-pedantic\fR flag is used. -.Ip "\fB\-Wdisabled-optimization\fR" 4 -.IX Item "-Wdisabled-optimization" -Warn if a requested optimization pass is disabled. This warning does -not generally indicate that there is anything wrong with your code; it -merely indicates that \s-1GCC\s0's optimizers were unable to handle the code -effectively. Often, the problem is that your code is too big or too -complex; \s-1GCC\s0 will refuse to optimize programs when the optimization -itself is likely to take inordinate amounts of time. -.Ip "\fB\-Werror\fR" 4 -.IX Item "-Werror" -Make all warnings into errors. -.Sh "Options for Debugging Your Program or \s-1GCC\s0" -.IX Subsection "Options for Debugging Your Program or GCC" -\&\s-1GCC\s0 has various special options that are used for debugging -either your program or \s-1GCC:\s0 -.Ip "\fB\-g\fR" 4 -.IX Item "-g" -Produce debugging information in the operating system's native format -(stabs, \s-1COFF\s0, \s-1XCOFF\s0, or \s-1DWARF\s0). \s-1GDB\s0 can work with this debugging -information. -.Sp -On most systems that use stabs format, \fB\-g\fR enables use of extra -debugging information that only \s-1GDB\s0 can use; this extra information -makes debugging work better in \s-1GDB\s0 but will probably make other debuggers -crash or -refuse to read the program. If you want to control for certain whether -to generate the extra information, use \fB\-gstabs+\fR, \fB\-gstabs\fR, -\&\fB\-gxcoff+\fR, \fB\-gxcoff\fR, \fB\-gdwarf-1+\fR, or \fB\-gdwarf-1\fR -(see below). -.Sp -Unlike most other C compilers, \s-1GCC\s0 allows you to use \fB\-g\fR with -\&\fB\-O\fR. The shortcuts taken by optimized code may occasionally -produce surprising results: some variables you declared may not exist -at all; flow of control may briefly move where you did not expect it; -some statements may not be executed because they compute constant -results or their values were already at hand; some statements may -execute in different places because they were moved out of loops. -.Sp -Nevertheless it proves possible to debug optimized output. This makes -it reasonable to use the optimizer for programs that might have bugs. -.Sp -The following options are useful when \s-1GCC\s0 is generated with the -capability for more than one debugging format. -.Ip "\fB\-ggdb\fR" 4 -.IX Item "-ggdb" -Produce debugging information for use by \s-1GDB\s0. This means to use the -most expressive format available (\s-1DWARF\s0 2, stabs, or the native format -if neither of those are supported), including \s-1GDB\s0 extensions if at all -possible. -.Ip "\fB\-gstabs\fR" 4 -.IX Item "-gstabs" -Produce debugging information in stabs format (if that is supported), -without \s-1GDB\s0 extensions. This is the format used by \s-1DBX\s0 on most \s-1BSD\s0 -systems. On \s-1MIPS\s0, Alpha and System V Release 4 systems this option -produces stabs debugging output which is not understood by \s-1DBX\s0 or \s-1SDB\s0. -On System V Release 4 systems this option requires the \s-1GNU\s0 assembler. -.Ip "\fB\-gstabs+\fR" 4 -.IX Item "-gstabs+" -Produce debugging information in stabs format (if that is supported), -using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger (\s-1GDB\s0). The -use of these extensions is likely to make other debuggers crash or -refuse to read the program. -.Ip "\fB\-gcoff\fR" 4 -.IX Item "-gcoff" -Produce debugging information in \s-1COFF\s0 format (if that is supported). -This is the format used by \s-1SDB\s0 on most System V systems prior to -System V Release 4. -.Ip "\fB\-gxcoff\fR" 4 -.IX Item "-gxcoff" -Produce debugging information in \s-1XCOFF\s0 format (if that is supported). -This is the format used by the \s-1DBX\s0 debugger on \s-1IBM\s0 \s-1RS/6000\s0 systems. -.Ip "\fB\-gxcoff+\fR" 4 -.IX Item "-gxcoff+" -Produce debugging information in \s-1XCOFF\s0 format (if that is supported), -using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger (\s-1GDB\s0). The -use of these extensions is likely to make other debuggers crash or -refuse to read the program, and may cause assemblers other than the \s-1GNU\s0 -assembler (\s-1GAS\s0) to fail with an error. -.Ip "\fB\-gdwarf\fR" 4 -.IX Item "-gdwarf" -Produce debugging information in \s-1DWARF\s0 version 1 format (if that is -supported). This is the format used by \s-1SDB\s0 on most System V Release 4 -systems. -.Ip "\fB\-gdwarf+\fR" 4 -.IX Item "-gdwarf+" -Produce debugging information in \s-1DWARF\s0 version 1 format (if that is -supported), using \s-1GNU\s0 extensions understood only by the \s-1GNU\s0 debugger -(\s-1GDB\s0). The use of these extensions is likely to make other debuggers -crash or refuse to read the program. -.Ip "\fB\-gdwarf-2\fR" 4 -.IX Item "-gdwarf-2" -Produce debugging information in \s-1DWARF\s0 version 2 format (if that is -supported). This is the format used by \s-1DBX\s0 on \s-1IRIX\s0 6. -.Ip "\fB\-g\fR\fIlevel\fR" 4 -.IX Item "-glevel" -.PD 0 -.Ip "\fB\-ggdb\fR\fIlevel\fR" 4 -.IX Item "-ggdblevel" -.Ip "\fB\-gstabs\fR\fIlevel\fR" 4 -.IX Item "-gstabslevel" -.Ip "\fB\-gcoff\fR\fIlevel\fR" 4 -.IX Item "-gcofflevel" -.Ip "\fB\-gxcoff\fR\fIlevel\fR" 4 -.IX Item "-gxcofflevel" -.Ip "\fB\-gdwarf\fR\fIlevel\fR" 4 -.IX Item "-gdwarflevel" -.Ip "\fB\-gdwarf-2\fR\fIlevel\fR" 4 -.IX Item "-gdwarf-2level" -.PD -Request debugging information and also use \fIlevel\fR to specify how -much information. The default level is 2. -.Sp -Level 1 produces minimal information, enough for making backtraces in -parts of the program that you don't plan to debug. This includes -descriptions of functions and external variables, but no information -about local variables and no line numbers. -.Sp -Level 3 includes extra information, such as all the macro definitions -present in the program. Some debuggers support macro expansion when -you use \fB\-g3\fR. -.Ip "\fB\-p\fR" 4 -.IX Item "-p" -Generate extra code to write profile information suitable for the -analysis program \f(CW\*(C`prof\*(C'\fR. You must use this option when compiling -the source files you want data about, and you must also use it when -linking. -.Ip "\fB\-pg\fR" 4 -.IX Item "-pg" -Generate extra code to write profile information suitable for the -analysis program \f(CW\*(C`gprof\*(C'\fR. You must use this option when compiling -the source files you want data about, and you must also use it when -linking. -.Ip "\fB\-a\fR" 4 -.IX Item "-a" -Generate extra code to write profile information for basic blocks, which will -record the number of times each basic block is executed, the basic block start -address, and the function name containing the basic block. If \fB\-g\fR is -used, the line number and filename of the start of the basic block will also be -recorded. If not overridden by the machine description, the default action is -to append to the text file \fIbb.out\fR. -.Sp -This data could be analyzed by a program like \f(CW\*(C`tcov\*(C'\fR. Note, -however, that the format of the data is not what \f(CW\*(C`tcov\*(C'\fR expects. -Eventually \s-1GNU\s0 \f(CW\*(C`gprof\*(C'\fR should be extended to process this data. -.Ip "\fB\-Q\fR" 4 -.IX Item "-Q" -Makes the compiler print out each function name as it is compiled, and -print some statistics about each pass when it finishes. -.Ip "\fB\-ftime-report\fR" 4 -.IX Item "-ftime-report" -Makes the compiler print some statistics about the time consumed by each -pass when it finishes. -.Ip "\fB\-fmem-report\fR" 4 -.IX Item "-fmem-report" -Makes the compiler print some statistics about permanent memory -allocation when it finishes. -.Ip "\fB\-ax\fR" 4 -.IX Item "-ax" -Generate extra code to profile basic blocks. Your executable will -produce output that is a superset of that produced when \fB\-a\fR is -used. Additional output is the source and target address of the basic -blocks where a jump takes place, the number of times a jump is executed, -and (optionally) the complete sequence of basic blocks being executed. -The output is appended to file \fIbb.out\fR. -.Sp -You can examine different profiling aspects without recompilation. Your -executable will read a list of function names from file \fIbb.in\fR. -Profiling starts when a function on the list is entered and stops when -that invocation is exited. To exclude a function from profiling, prefix -its name with `\-'. If a function name is not unique, you can -disambiguate it by writing it in the form -\&\fB/path/filename.d:functionname\fR. Your executable will write the -available paths and filenames in file \fIbb.out\fR. -.Sp -Several function names have a special meaning: -.RS 4 -.if n .Ip "\f(CW""""_\|_bb_jumps_\|_""""\fR" 4 -.el .Ip "\f(CW_\|_bb_jumps_\|_\fR" 4 -.IX Item "__bb_jumps__" -Write source, target and frequency of jumps to file \fIbb.out\fR. -.if n .Ip "\f(CW""""_\|_bb_hidecall_\|_""""\fR" 4 -.el .Ip "\f(CW_\|_bb_hidecall_\|_\fR" 4 -.IX Item "__bb_hidecall__" -Exclude function calls from frequency count. -.if n .Ip "\f(CW""""_\|_bb_showret_\|_""""\fR" 4 -.el .Ip "\f(CW_\|_bb_showret_\|_\fR" 4 -.IX Item "__bb_showret__" -Include function returns in frequency count. -.if n .Ip "\f(CW""""_\|_bb_trace_\|_""""\fR" 4 -.el .Ip "\f(CW_\|_bb_trace_\|_\fR" 4 -.IX Item "__bb_trace__" -Write the sequence of basic blocks executed to file \fIbbtrace.gz\fR. -The file will be compressed using the program \fBgzip\fR, which must -exist in your \fB\s-1PATH\s0\fR. On systems without the \fBpopen\fR -function, the file will be named \fIbbtrace\fR and will not be -compressed. \fBProfiling for even a few seconds on these systems -will produce a very large file.\fR Note: \f(CW\*(C`_\|_bb_hidecall_\|_\*(C'\fR and -\&\f(CW\*(C`_\|_bb_showret_\|_\*(C'\fR will not affect the sequence written to -\&\fIbbtrace.gz\fR. -.RE -.RS 4 -.Sp -Here's a short example using different profiling parameters -in file \fIbb.in\fR. Assume function \f(CW\*(C`foo\*(C'\fR consists of basic blocks -1 and 2 and is called twice from block 3 of function \f(CW\*(C`main\*(C'\fR. After -the calls, block 3 transfers control to block 4 of \f(CW\*(C`main\*(C'\fR. -.Sp -With \f(CW\*(C`_\|_bb_trace_\|_\*(C'\fR and \f(CW\*(C`main\*(C'\fR contained in file \fIbb.in\fR, -the following sequence of blocks is written to file \fIbbtrace.gz\fR: -0 3 1 2 1 2 4. The return from block 2 to block 3 is not shown, because -the return is to a point inside the block and not to the top. The -block address 0 always indicates, that control is transferred -to the trace from somewhere outside the observed functions. With -\&\fB\-foo\fR added to \fIbb.in\fR, the blocks of function -\&\f(CW\*(C`foo\*(C'\fR are removed from the trace, so only 0 3 4 remains. -.Sp -With \f(CW\*(C`_\|_bb_jumps_\|_\*(C'\fR and \f(CW\*(C`main\*(C'\fR contained in file \fIbb.in\fR, -jump frequencies will be written to file \fIbb.out\fR. The -frequencies are obtained by constructing a trace of blocks -and incrementing a counter for every neighbouring pair of blocks -in the trace. The trace 0 3 1 2 1 2 4 displays the following -frequencies: -.Sp -.Vb 5 -\& Jump from block 0x0 to block 0x3 executed 1 time(s) -\& Jump from block 0x3 to block 0x1 executed 1 time(s) -\& Jump from block 0x1 to block 0x2 executed 2 time(s) -\& Jump from block 0x2 to block 0x1 executed 1 time(s) -\& Jump from block 0x2 to block 0x4 executed 1 time(s) -.Ve -With \f(CW\*(C`_\|_bb_hidecall_\|_\*(C'\fR, control transfer due to call instructions -is removed from the trace, that is the trace is cut into three parts: 0 -3 4, 0 1 2 and 0 1 2. With \f(CW\*(C`_\|_bb_showret_\|_\*(C'\fR, control transfer due -to return instructions is added to the trace. The trace becomes: 0 3 1 -2 3 1 2 3 4. Note, that this trace is not the same, as the sequence -written to \fIbbtrace.gz\fR. It is solely used for counting jump -frequencies. -.RE -.Ip "\fB\-fprofile-arcs\fR" 4 -.IX Item "-fprofile-arcs" -Instrument \fIarcs\fR during compilation. For each function of your -program, \s-1GCC\s0 creates a program flow graph, then finds a spanning tree -for the graph. Only arcs that are not on the spanning tree have to be -instrumented: the compiler adds code to count the number of times that these -arcs are executed. When an arc is the only exit or only entrance to a -block, the instrumentation code can be added to the block; otherwise, a -new basic block must be created to hold the instrumentation code. -.Sp -Since not every arc in the program must be instrumented, programs -compiled with this option run faster than programs compiled with -\&\fB\-a\fR, which adds instrumentation code to every basic block in the -program. The tradeoff: since \f(CW\*(C`gcov\*(C'\fR does not have -execution counts for all branches, it must start with the execution -counts for the instrumented branches, and then iterate over the program -flow graph until the entire graph has been solved. Hence, \f(CW\*(C`gcov\*(C'\fR -runs a little more slowly than a program which uses information from -\&\fB\-a\fR. -.Sp -\&\fB\-fprofile-arcs\fR also makes it possible to estimate branch -probabilities, and to calculate basic block execution counts. In -general, basic block execution counts do not give enough information to -estimate all branch probabilities. When the compiled program exits, it -saves the arc execution counts to a file called -\&\fI\fIsourcename\fI.da\fR. Use the compiler option -\&\fB\-fbranch-probabilities\fR when recompiling, to optimize using estimated -branch probabilities. -.Ip "\fB\-ftest-coverage\fR" 4 -.IX Item "-ftest-coverage" -Create data files for the \f(CW\*(C`gcov\*(C'\fR code-coverage utility. -The data file names begin with the name of your source file: -.RS 4 -.Ip "\fIsourcename\fR\fB.bb\fR" 4 -.IX Item "sourcename.bb" -A mapping from basic blocks to line numbers, which \f(CW\*(C`gcov\*(C'\fR uses to -associate basic block execution counts with line numbers. -.Ip "\fIsourcename\fR\fB.bbg\fR" 4 -.IX Item "sourcename.bbg" -A list of all arcs in the program flow graph. This allows \f(CW\*(C`gcov\*(C'\fR -to reconstruct the program flow graph, so that it can compute all basic -block and arc execution counts from the information in the -\&\f(CW\*(C`\f(CIsourcename\f(CW.da\*(C'\fR file (this last file is the output from -\&\fB\-fprofile-arcs\fR). -.RE -.RS 4 -.RE -.Ip "\fB\-d\fR\fIletters\fR" 4 -.IX Item "-dletters" -Says to make debugging dumps during compilation at times specified by -\&\fIletters\fR. This is used for debugging the compiler. The file names -for most of the dumps are made by appending a pass number and a word to -the source file name (e.g. \fIfoo.c.00.rtl\fR or \fIfoo.c.01.sibling\fR). -Here are the possible letters for use in \fIletters\fR, and their meanings: -.RS 4 -.Ip "\fBA\fR" 4 -.IX Item "A" -Annotate the assembler output with miscellaneous debugging information. -.Ip "\fBb\fR" 4 -.IX Item "b" -Dump after computing branch probabilities, to \fI\fIfile\fI.11.bp\fR. -.Ip "\fBB\fR" 4 -.IX Item "B" -Dump after block reordering, to \fI\fIfile\fI.26.bbro\fR. -.Ip "\fBc\fR" 4 -.IX Item "c" -Dump after instruction combination, to the file \fI\fIfile\fI.14.combine\fR. -.Ip "\fBC\fR" 4 -.IX Item "C" -Dump after the first if conversion, to the file \fI\fIfile\fI.15.ce\fR. -.Ip "\fBd\fR" 4 -.IX Item "d" -Dump after delayed branch scheduling, to \fI\fIfile\fI.29.dbr\fR. -.Ip "\fBD\fR" 4 -.IX Item "D" -Dump all macro definitions, at the end of preprocessing, in addition to -normal output. -.Ip "\fBe\fR" 4 -.IX Item "e" -Dump after \s-1SSA\s0 optimizations, to \fI\fIfile\fI.05.ssa\fR and -\&\fI\fIfile\fI.06.ussa\fR. -.Ip "\fBE\fR" 4 -.IX Item "E" -Dump after the second if conversion, to \fI\fIfile\fI.24.ce2\fR. -.Ip "\fBf\fR" 4 -.IX Item "f" -Dump after life analysis, to \fI\fIfile\fI.13.life\fR. -.Ip "\fBF\fR" 4 -.IX Item "F" -Dump after purging \f(CW\*(C`ADDRESSOF\*(C'\fR codes, to \fI\fIfile\fI.04.addressof\fR. -.Ip "\fBg\fR" 4 -.IX Item "g" -Dump after global register allocation, to \fI\fIfile\fI.19.greg\fR. -.Ip "\fBo\fR" 4 -.IX Item "o" -Dump after post-reload \s-1CSE\s0 and other optimizations, to \fI\fIfile\fI.20.postreload\fR. -.Ip "\fBG\fR" 4 -.IX Item "G" -Dump after \s-1GCSE\s0, to \fI\fIfile\fI.08.gcse\fR. -.Ip "\fBi\fR" 4 -.IX Item "i" -Dump after sibling call optimizations, to \fI\fIfile\fI.01.sibling\fR. -.Ip "\fBj\fR" 4 -.IX Item "j" -Dump after the first jump optimization, to \fI\fIfile\fI.02.jump\fR. -.Ip "\fBJ\fR" 4 -.IX Item "J" -Dump after the last jump optimization, to \fI\fIfile\fI.27.jump2\fR. -.Ip "\fBk\fR" 4 -.IX Item "k" -Dump after conversion from registers to stack, to \fI\fIfile\fI.29.stack\fR. -.Ip "\fBl\fR" 4 -.IX Item "l" -Dump after local register allocation, to \fI\fIfile\fI.18.lreg\fR. -.Ip "\fBL\fR" 4 -.IX Item "L" -Dump after loop optimization, to \fI\fIfile\fI.09.loop\fR. -.Ip "\fBM\fR" 4 -.IX Item "M" -Dump after performing the machine dependent reorganisation pass, to -\&\fI\fIfile\fI.28.mach\fR. -.Ip "\fBn\fR" 4 -.IX Item "n" -Dump after register renumbering, to \fI\fIfile\fI.23.rnreg\fR. -.Ip "\fBN\fR" 4 -.IX Item "N" -Dump after the register move pass, to \fI\fIfile\fI.16.regmove\fR. -.Ip "\fBr\fR" 4 -.IX Item "r" -Dump after \s-1RTL\s0 generation, to \fI\fIfile\fI.00.rtl\fR. -.Ip "\fBR\fR" 4 -.IX Item "R" -Dump after the second instruction scheduling pass, to -\&\fI\fIfile\fI.25.sched2\fR. -.Ip "\fBs\fR" 4 -.IX Item "s" -Dump after \s-1CSE\s0 (including the jump optimization that sometimes follows -\&\s-1CSE\s0), to \fI\fIfile\fI.03.cse\fR. -.Ip "\fBS\fR" 4 -.IX Item "S" -Dump after the first instruction scheduling pass, to -\&\fI\fIfile\fI.17.sched\fR. -.Ip "\fBt\fR" 4 -.IX Item "t" -Dump after the second \s-1CSE\s0 pass (including the jump optimization that -sometimes follows \s-1CSE\s0), to \fI\fIfile\fI.10.cse2\fR. -.Ip "\fBw\fR" 4 -.IX Item "w" -Dump after the second flow pass, to \fI\fIfile\fI.21.flow2\fR. -.Ip "\fBX\fR" 4 -.IX Item "X" -Dump after dead code elimination, to \fI\fIfile\fI.06.dce\fR. -.Ip "\fBz\fR" 4 -.IX Item "z" -Dump after the peephole pass, to \fI\fIfile\fI.22.peephole2\fR. -.Ip "\fBa\fR" 4 -.IX Item "a" -Produce all the dumps listed above. -.Ip "\fBm\fR" 4 -.IX Item "m" -Print statistics on memory usage, at the end of the run, to -standard error. -.Ip "\fBp\fR" 4 -.IX Item "p" -Annotate the assembler output with a comment indicating which -pattern and alternative was used. The length of each instruction is -also printed. -.Ip "\fBP\fR" 4 -.IX Item "P" -Dump the \s-1RTL\s0 in the assembler output as a comment before each instruction. -Also turns on \fB\-dp\fR annotation. -.Ip "\fBv\fR" 4 -.IX Item "v" -For each of the other indicated dump files (except for -\&\fI\fIfile\fI.00.rtl\fR), dump a representation of the control flow graph -suitable for viewing with \s-1VCG\s0 to \fI\fIfile\fI.\fIpass\fI.vcg\fR. -.Ip "\fBx\fR" 4 -.IX Item "x" -Just generate \s-1RTL\s0 for a function instead of compiling it. Usually used -with \fBr\fR. -.Ip "\fBy\fR" 4 -.IX Item "y" -Dump debugging information during parsing, to standard error. -.RE -.RS 4 -.RE -.Ip "\fB\-fdump-unnumbered\fR" 4 -.IX Item "-fdump-unnumbered" -When doing debugging dumps (see \-d option above), suppress instruction -numbers and line number note output. This makes it more feasible to -use diff on debugging dumps for compiler invocations with different -options, in particular with and without \-g. -.Ip "\fB\-fdump-translation-unit=\fR\fIfile\fR \fB(C and \*(C+ only)\fR" 4 -.IX Item "-fdump-translation-unit=file (C and only)" -Dump a representation of the tree structure for the entire translation -unit to \fIfile\fR. -.Ip "\fB\-fdump-class_layout=\fR\fIfile\fR \fB(\*(C+ only)\fR" 4 -.IX Item "-fdump-class_layout=file ( only)" -.PD 0 -.Ip "\fB\-fdump-class_layout (\*(C+ only)\fR" 4 -.IX Item "-fdump-class_layout ( only)" -.PD -Dump a representation of each class's heirarchy to \fIfile\fR, or -\&\f(CW\*(C`stderr\*(C'\fR if not specified. -.Ip "\fB\-fpretend-float\fR" 4 -.IX Item "-fpretend-float" -When running a cross-compiler, pretend that the target machine uses the -same floating point format as the host machine. This causes incorrect -output of the actual floating constants, but the actual instruction -sequence will probably be the same as \s-1GCC\s0 would make when running on -the target machine. -.Ip "\fB\-save-temps\fR" 4 -.IX Item "-save-temps" -Store the usual ``temporary'' intermediate files permanently; place them -in the current directory and name them based on the source file. Thus, -compiling \fIfoo.c\fR with \fB\-c \-save-temps\fR would produce files -\&\fIfoo.i\fR and \fIfoo.s\fR, as well as \fIfoo.o\fR. This creates a -preprocessed \fIfoo.i\fR output file even though the compiler now -normally uses an integrated preprocessor. -.Ip "\fB\-time\fR" 4 -.IX Item "-time" -Report the \s-1CPU\s0 time taken by each subprocess in the compilation -sequence. For C source files, this is the compiler proper and assembler -(plus the linker if linking is done). The output looks like this: -.Sp -.Vb 2 -\& # cc1 0.12 0.01 -\& # as 0.00 0.01 -.Ve -The first number on each line is the ``user time,'' that is time spent -executing the program itself. The second number is ``system time,'' -time spent executing operating system routines on behalf of the program. -Both numbers are in seconds. -.Ip "\fB\-print-file-name=\fR\fIlibrary\fR" 4 -.IX Item "-print-file-name=library" -Print the full absolute name of the library file \fIlibrary\fR that -would be used when linking\-\-\-and don't do anything else. With this -option, \s-1GCC\s0 does not compile or link anything; it just prints the -file name. -.Ip "\fB\-print-prog-name=\fR\fIprogram\fR" 4 -.IX Item "-print-prog-name=program" -Like \fB\-print-file-name\fR, but searches for a program such as \fBcpp\fR. -.Ip "\fB\-print-libgcc-file-name\fR" 4 -.IX Item "-print-libgcc-file-name" -Same as \fB\-print-file-name=libgcc.a\fR. -.Sp -This is useful when you use \fB\-nostdlib\fR or \fB\-nodefaultlibs\fR -but you do want to link with \fIlibgcc.a\fR. You can do -.Sp -.Vb 1 -\& gcc -nostdlib I... `gcc -print-libgcc-file-name` -.Ve -.Ip "\fB\-print-search-dirs\fR" 4 -.IX Item "-print-search-dirs" -Print the name of the configured installation directory and a list of -program and library directories gcc will search\-\-\-and don't do anything else. -.Sp -This is useful when gcc prints the error message -\&\fBinstallation problem, cannot exec cpp0: No such file or directory\fR. -To resolve this you either need to put \fIcpp0\fR and the other compiler -components where gcc expects to find them, or you can set the environment -variable \fB\s-1GCC_EXEC_PREFIX\s0\fR to the directory where you installed them. -Don't forget the trailing '/'. -.Ip "\fB\-dumpmachine\fR" 4 -.IX Item "-dumpmachine" -Print the compiler's target machine (for example, -\&\fBi686\-pc-linux-gnu\fR)\-\-\-and don't do anything else. -.Ip "\fB\-dumpversion\fR" 4 -.IX Item "-dumpversion" -Print the compiler version (for example, \fB3.0\fR)\-\-\-and don't do -anything else. -.Ip "\fB\-dumpspecs\fR" 4 -.IX Item "-dumpspecs" -Print the compiler's built-in specs\-\-\-and don't do anything else. (This -is used when \s-1GCC\s0 itself is being built.) -.Sh "Options That Control Optimization" -.IX Subsection "Options That Control Optimization" -These options control various sorts of optimizations: -.Ip "\fB\-O\fR" 4 -.IX Item "-O" -.PD 0 -.Ip "\fB\-O1\fR" 4 -.IX Item "-O1" -.PD -Optimize. Optimizing compilation takes somewhat more time, and a lot -more memory for a large function. -.Sp -Without \fB\-O\fR, the compiler's goal is to reduce the cost of -compilation and to make debugging produce the expected results. -Statements are independent: if you stop the program with a breakpoint -between statements, you can then assign a new value to any variable or -change the program counter to any other statement in the function and -get exactly the results you would expect from the source code. -.Sp -Without \fB\-O\fR, the compiler only allocates variables declared -\&\f(CW\*(C`register\*(C'\fR in registers. The resulting compiled code is a little -worse than produced by \s-1PCC\s0 without \fB\-O\fR. -.Sp -With \fB\-O\fR, the compiler tries to reduce code size and execution -time. -.Sp -When you specify \fB\-O\fR, the compiler turns on \fB\-fthread-jumps\fR -and \fB\-fdefer-pop\fR on all machines. The compiler turns on -\&\fB\-fdelayed-branch\fR on machines that have delay slots, and -\&\fB\-fomit-frame-pointer\fR on machines that can support debugging even -without a frame pointer. On some machines the compiler also turns -on other flags. -.Ip "\fB\-O2\fR" 4 -.IX Item "-O2" -Optimize even more. \s-1GCC\s0 performs nearly all supported optimizations -that do not involve a space-speed tradeoff. The compiler does not -perform loop unrolling or function inlining when you specify \fB\-O2\fR. -As compared to \fB\-O\fR, this option increases both compilation time -and the performance of the generated code. -.Sp -\&\fB\-O2\fR turns on all optional optimizations except for loop unrolling, -function inlining, and register renaming. It also turns on the -\&\fB\-fforce-mem\fR option on all machines and frame pointer elimination -on machines where doing so does not interfere with debugging. -.Ip "\fB\-O3\fR" 4 -.IX Item "-O3" -Optimize yet more. \fB\-O3\fR turns on all optimizations specified by -\&\fB\-O2\fR and also turns on the \fB\-finline-functions\fR and -\&\fB\-frename-registers\fR options. -.Ip "\fB\-O0\fR" 4 -.IX Item "-O0" -Do not optimize. -.Ip "\fB\-Os\fR" 4 -.IX Item "-Os" -Optimize for size. \fB\-Os\fR enables all \fB\-O2\fR optimizations that -do not typically increase code size. It also performs further -optimizations designed to reduce code size. -.Sp -If you use multiple \fB\-O\fR options, with or without level numbers, -the last such option is the one that is effective. -.PP -Options of the form \fB\-f\fR\fIflag\fR specify machine-independent -flags. Most flags have both positive and negative forms; the negative -form of \fB\-ffoo\fR would be \fB\-fno-foo\fR. In the table below, -only one of the forms is listed\-\-\-the one which is not the default. -You can figure out the other form by either removing \fBno-\fR or -adding it. -.Ip "\fB\-ffloat-store\fR" 4 -.IX Item "-ffloat-store" -Do not store floating point variables in registers, and inhibit other -options that might change whether a floating point value is taken from a -register or memory. -.Sp -This option prevents undesirable excess precision on machines such as -the 68000 where the floating registers (of the 68881) keep more -precision than a \f(CW\*(C`double\*(C'\fR is supposed to have. Similarly for the -x86 architecture. For most programs, the excess precision does only -good, but a few programs rely on the precise definition of \s-1IEEE\s0 floating -point. Use \fB\-ffloat-store\fR for such programs, after modifying -them to store all pertinent intermediate computations into variables. -.Ip "\fB\-fno-default-inline\fR" 4 -.IX Item "-fno-default-inline" -Do not make member functions inline by default merely because they are -defined inside the class scope (\*(C+ only). Otherwise, when you specify -\&\fB\-O\fR, member functions defined inside class scope are compiled -inline by default; i.e., you don't need to add \fBinline\fR in front of -the member function name. -.Ip "\fB\-fno-defer-pop\fR" 4 -.IX Item "-fno-defer-pop" -Always pop the arguments to each function call as soon as that function -returns. For machines which must pop arguments after a function call, -the compiler normally lets arguments accumulate on the stack for several -function calls and pops them all at once. -.Ip "\fB\-fforce-mem\fR" 4 -.IX Item "-fforce-mem" -Force memory operands to be copied into registers before doing -arithmetic on them. This produces better code by making all memory -references potential common subexpressions. When they are not common -subexpressions, instruction combination should eliminate the separate -register-load. The \fB\-O2\fR option turns on this option. -.Ip "\fB\-fforce-addr\fR" 4 -.IX Item "-fforce-addr" -Force memory address constants to be copied into registers before -doing arithmetic on them. This may produce better code just as -\&\fB\-fforce-mem\fR may. -.Ip "\fB\-fomit-frame-pointer\fR" 4 -.IX Item "-fomit-frame-pointer" -Don't keep the frame pointer in a register for functions that -don't need one. This avoids the instructions to save, set up and -restore frame pointers; it also makes an extra register available -in many functions. \fBIt also makes debugging impossible on -some machines.\fR -.Sp -On some machines, such as the Vax, this flag has no effect, because -the standard calling sequence automatically handles the frame pointer -and nothing is saved by pretending it doesn't exist. The -machine-description macro \f(CW\*(C`FRAME_POINTER_REQUIRED\*(C'\fR controls -whether a target machine supports this flag. -.Ip "\fB\-foptimize-sibling-calls\fR" 4 -.IX Item "-foptimize-sibling-calls" -Optimize sibling and tail recursive calls. -.Ip "\fB\-ftrapv\fR" 4 -.IX Item "-ftrapv" -This option generates traps for signed overflow on addition, subtraction, -multiplication operations. -.Ip "\fB\-fno-inline\fR" 4 -.IX Item "-fno-inline" -Don't pay attention to the \f(CW\*(C`inline\*(C'\fR keyword. Normally this option -is used to keep the compiler from expanding any functions inline. -Note that if you are not optimizing, no functions can be expanded inline. -.Ip "\fB\-finline-functions\fR" 4 -.IX Item "-finline-functions" -Integrate all simple functions into their callers. The compiler -heuristically decides which functions are simple enough to be worth -integrating in this way. -.Sp -If all calls to a given function are integrated, and the function is -declared \f(CW\*(C`static\*(C'\fR, then the function is normally not output as -assembler code in its own right. -.Ip "\fB\-finline-limit=\fR\fIn\fR" 4 -.IX Item "-finline-limit=n" -By default, gcc limits the size of functions that can be inlined. This flag -allows the control of this limit for functions that are explicitly marked as -inline (ie marked with the inline keyword or defined within the class -definition in c++). \fIn\fR is the size of functions that can be inlined in -number of pseudo instructions (not counting parameter handling). The default -value of n is 10000. Increasing this value can result in more inlined code at -the cost of compilation time and memory consumption. Decreasing usually makes -the compilation faster and less code will be inlined (which presumably -means slower programs). This option is particularly useful for programs that -use inlining heavily such as those based on recursive templates with c++. -.Sp -\&\fINote:\fR pseudo instruction represents, in this particular context, an -abstract measurement of function's size. In no way, it represents a count -of assembly instructions and as such its exact meaning might change from one -release to an another. -.Ip "\fB\-fkeep-inline-functions\fR" 4 -.IX Item "-fkeep-inline-functions" -Even if all calls to a given function are integrated, and the function -is declared \f(CW\*(C`static\*(C'\fR, nevertheless output a separate run-time -callable version of the function. This switch does not affect -\&\f(CW\*(C`extern inline\*(C'\fR functions. -.Ip "\fB\-fkeep-static-consts\fR" 4 -.IX Item "-fkeep-static-consts" -Emit variables declared \f(CW\*(C`static const\*(C'\fR when optimization isn't turned -on, even if the variables aren't referenced. -.Sp -\&\s-1GCC\s0 enables this option by default. If you want to force the compiler to -check if the variable was referenced, regardless of whether or not -optimization is turned on, use the \fB\-fno-keep-static-consts\fR option. -.Ip "\fB\-fno-function-cse\fR" 4 -.IX Item "-fno-function-cse" -Do not put function addresses in registers; make each instruction that -calls a constant function contain the function's address explicitly. -.Sp -This option results in less efficient code, but some strange hacks -that alter the assembler output may be confused by the optimizations -performed when this option is not used. -.Ip "\fB\-ffast-math\fR" 4 -.IX Item "-ffast-math" -Sets \fB\-fno-math-errno\fR, \fB\-funsafe-math-optimizations\fR, -and \fB\-fno-trapping-math\fR. -.Sp -This option causes the preprocessor macro _\|_FAST_MATH_\|_ to be defined. -.Sp -This option should never be turned on by any \fB\-O\fR option since -it can result in incorrect output for programs which depend on -an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for -math functions. -.Ip "\fB\-fno-math-errno\fR" 4 -.IX Item "-fno-math-errno" -Do not set \s-1ERRNO\s0 after calling math functions that are executed -with a single instruction, e.g., sqrt. A program that relies on -\&\s-1IEEE\s0 exceptions for math error handling may want to use this flag -for speed while maintaining \s-1IEEE\s0 arithmetic compatibility. -.Sp -This option should never be turned on by any \fB\-O\fR option since -it can result in incorrect output for programs which depend on -an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for -math functions. -.Sp -The default is \fB\-fmath-errno\fR. The \fB\-ffast-math\fR option -sets \fB\-fno-math-errno\fR. -.Ip "\fB\-funsafe-math-optimizations\fR" 4 -.IX Item "-funsafe-math-optimizations" -Allow optimizations for floating-point arithmetic that (a) assume -that arguments and results are valid and (b) may violate \s-1IEEE\s0 or -\&\s-1ANSI\s0 standards. -.Sp -This option should never be turned on by any \fB\-O\fR option since -it can result in incorrect output for programs which depend on -an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for -math functions. -.Sp -The default is \fB\-fno-unsafe-math-optimizations\fR. The -\&\fB\-ffast-math\fR option sets \fB\-funsafe-math-optimizations\fR. -.Ip "\fB\-fno-trapping-math\fR" 4 -.IX Item "-fno-trapping-math" -Compile code assuming that floating-point operations cannot generate -user-visible traps. Setting this option may allow faster code -if one relies on ``non-stop'' \s-1IEEE\s0 arithmetic, for example. -.Sp -This option should never be turned on by any \fB\-O\fR option since -it can result in incorrect output for programs which depend on -an exact implementation of \s-1IEEE\s0 or \s-1ISO\s0 rules/specifications for -math functions. -.Sp -The default is \fB\-ftrapping-math\fR. The \fB\-ffast-math\fR -option sets \fB\-fno-trapping-math\fR. -.PP -The following options control specific optimizations. The \fB\-O2\fR -option turns on all of these optimizations except \fB\-funroll-loops\fR -and \fB\-funroll-all-loops\fR. On most machines, the \fB\-O\fR option -turns on the \fB\-fthread-jumps\fR and \fB\-fdelayed-branch\fR options, -but specific machines may handle it differently. -.PP -You can use the following flags in the rare cases when ``fine-tuning'' -of optimizations to be performed is desired. -.Ip "\fB\-fstrength-reduce\fR" 4 -.IX Item "-fstrength-reduce" -Perform the optimizations of loop strength reduction and -elimination of iteration variables. -.Ip "\fB\-fthread-jumps\fR" 4 -.IX Item "-fthread-jumps" -Perform optimizations where we check to see if a jump branches to a -location where another comparison subsumed by the first is found. If -so, the first branch is redirected to either the destination of the -second branch or a point immediately following it, depending on whether -the condition is known to be true or false. -.Ip "\fB\-fcse-follow-jumps\fR" 4 -.IX Item "-fcse-follow-jumps" -In common subexpression elimination, scan through jump instructions -when the target of the jump is not reached by any other path. For -example, when \s-1CSE\s0 encounters an \f(CW\*(C`if\*(C'\fR statement with an -\&\f(CW\*(C`else\*(C'\fR clause, \s-1CSE\s0 will follow the jump when the condition -tested is false. -.Ip "\fB\-fcse-skip-blocks\fR" 4 -.IX Item "-fcse-skip-blocks" -This is similar to \fB\-fcse-follow-jumps\fR, but causes \s-1CSE\s0 to -follow jumps which conditionally skip over blocks. When \s-1CSE\s0 -encounters a simple \f(CW\*(C`if\*(C'\fR statement with no else clause, -\&\fB\-fcse-skip-blocks\fR causes \s-1CSE\s0 to follow the jump around the -body of the \f(CW\*(C`if\*(C'\fR. -.Ip "\fB\-frerun-cse-after-loop\fR" 4 -.IX Item "-frerun-cse-after-loop" -Re-run common subexpression elimination after loop optimizations has been -performed. -.Ip "\fB\-frerun-loop-opt\fR" 4 -.IX Item "-frerun-loop-opt" -Run the loop optimizer twice. -.Ip "\fB\-fgcse\fR" 4 -.IX Item "-fgcse" -Perform a global common subexpression elimination pass. -This pass also performs global constant and copy propagation. -.Ip "\fB\-fgcse-lm\fR" 4 -.IX Item "-fgcse-lm" -When \-fgcse-lm is enabled, global common subexpression elimination will -attempt to move loads which are only killed by stores into themselves. This -allows a loop containing a load/store sequence to be changed to a load outside -the loop, and a copy/store within the loop. -.Ip "\fB\-fgcse-sm\fR" 4 -.IX Item "-fgcse-sm" -When \-fgcse-sm is enabled, A store motion pass is run after global common -subexpression elimination. This pass will attempt to move stores out of loops. -When used in conjunction with \-fgcse-lm, loops containing a load/store sequence -can be changed to a load before the loop and a store after the loop. -.Ip "\fB\-fdelete-null-pointer-checks\fR" 4 -.IX Item "-fdelete-null-pointer-checks" -Use global dataflow analysis to identify and eliminate useless null -pointer checks. Programs which rely on \s-1NULL\s0 pointer dereferences \fInot\fR -halting the program may not work properly with this option. Use -\&\-fno-delete-null-pointer-checks to disable this optimizing for programs -which depend on that behavior. -.Ip "\fB\-fexpensive-optimizations\fR" 4 -.IX Item "-fexpensive-optimizations" -Perform a number of minor optimizations that are relatively expensive. -.Ip "\fB\-foptimize-register-move\fR" 4 -.IX Item "-foptimize-register-move" -.PD 0 -.Ip "\fB\-fregmove\fR" 4 -.IX Item "-fregmove" -.PD -Attempt to reassign register numbers in move instructions and as -operands of other simple instructions in order to maximize the amount of -register tying. This is especially helpful on machines with two-operand -instructions. \s-1GCC\s0 enables this optimization by default with \fB\-O2\fR -or higher. -.Sp -Note \fB\-fregmove\fR and \fB\-foptimize-register-move\fR are the same -optimization. -.Ip "\fB\-fdelayed-branch\fR" 4 -.IX Item "-fdelayed-branch" -If supported for the target machine, attempt to reorder instructions -to exploit instruction slots available after delayed branch -instructions. -.Ip "\fB\-fschedule-insns\fR" 4 -.IX Item "-fschedule-insns" -If supported for the target machine, attempt to reorder instructions to -eliminate execution stalls due to required data being unavailable. This -helps machines that have slow floating point or memory load instructions -by allowing other instructions to be issued until the result of the load -or floating point instruction is required. -.Ip "\fB\-fschedule-insns2\fR" 4 -.IX Item "-fschedule-insns2" -Similar to \fB\-fschedule-insns\fR, but requests an additional pass of -instruction scheduling after register allocation has been done. This is -especially useful on machines with a relatively small number of -registers and where memory load instructions take more than one cycle. -.Ip "\fB\-ffunction-sections\fR" 4 -.IX Item "-ffunction-sections" -.PD 0 -.Ip "\fB\-fdata-sections\fR" 4 -.IX Item "-fdata-sections" -.PD -Place each function or data item into its own section in the output -file if the target supports arbitrary sections. The name of the -function or the name of the data item determines the section's name -in the output file. -.Sp -Use these options on systems where the linker can perform optimizations -to improve locality of reference in the instruction space. \s-1HPPA\s0 -processors running \s-1HP-UX\s0 and Sparc processors running Solaris 2 have -linkers with such optimizations. Other systems using the \s-1ELF\s0 object format -as well as \s-1AIX\s0 may have these optimizations in the future. -.Sp -Only use these options when there are significant benefits from doing -so. When you specify these options, the assembler and linker will -create larger object and executable files and will also be slower. -You will not be able to use \f(CW\*(C`gprof\*(C'\fR on all systems if you -specify this option and you may have problems with debugging if -you specify both this option and \fB\-g\fR. -.Ip "\fB\-fcaller-saves\fR" 4 -.IX Item "-fcaller-saves" -Enable values to be allocated in registers that will be clobbered by -function calls, by emitting extra instructions to save and restore the -registers around such calls. Such allocation is done only when it -seems to result in better code than would otherwise be produced. -.Sp -This option is always enabled by default on certain machines, usually -those which have no call-preserved registers to use instead. -.Sp -For all machines, optimization level 2 and higher enables this flag by -default. -.Ip "\fB\-funroll-loops\fR" 4 -.IX Item "-funroll-loops" -Perform the optimization of loop unrolling. This is only done for loops -whose number of iterations can be determined at compile time or run time. -\&\fB\-funroll-loops\fR implies both \fB\-fstrength-reduce\fR and -\&\fB\-frerun-cse-after-loop\fR. -.Ip "\fB\-funroll-all-loops\fR" 4 -.IX Item "-funroll-all-loops" -Perform the optimization of loop unrolling. This is done for all loops -and usually makes programs run more slowly. \fB\-funroll-all-loops\fR -implies \fB\-fstrength-reduce\fR as well as \fB\-frerun-cse-after-loop\fR. -.Ip "\fB\-fmove-all-movables\fR" 4 -.IX Item "-fmove-all-movables" -Forces all invariant computations in loops to be moved -outside the loop. -.Ip "\fB\-freduce-all-givs\fR" 4 -.IX Item "-freduce-all-givs" -Forces all general-induction variables in loops to be -strength-reduced. -.Sp -\&\fINote:\fR When compiling programs written in Fortran, -\&\fB\-fmove-all-movables\fR and \fB\-freduce-all-givs\fR are enabled -by default when you use the optimizer. -.Sp -These options may generate better or worse code; results are highly -dependent on the structure of loops within the source code. -.Sp -These two options are intended to be removed someday, once -they have helped determine the efficacy of various -approaches to improving loop optimizations. -.Sp -Please let us (<\fBgcc@gcc.gnu.org\fR> and <\fBfortran@gnu.org\fR>) -know how use of these options affects -the performance of your production code. -We're very interested in code that runs \fIslower\fR -when these options are \fIenabled\fR. -.Ip "\fB\-fno-peephole\fR" 4 -.IX Item "-fno-peephole" -Disable any machine-specific peephole optimizations. -.Ip "\fB\-fbranch-probabilities\fR" 4 -.IX Item "-fbranch-probabilities" -After running a program compiled with \fB\-fprofile-arcs\fR, you can compile it a second time using -\&\fB\-fbranch-probabilities\fR, to improve optimizations based on -guessing the path a branch might take. -.Ip "\fB\-fno-guess-branch-probability\fR" 4 -.IX Item "-fno-guess-branch-probability" -Sometimes gcc will opt to guess branch probabilities when none are -available from either profile directed feedback (\fB\-fprofile-arcs\fR) -or \fB_\|_builtin_expect\fR. In a hard real-time system, people don't -want different runs of the compiler to produce code that has different -behavior; minimizing non-determinism is of paramount import. This -switch allows users to reduce non-determinism, possibly at the expense -of inferior optimization. -.Ip "\fB\-fstrict-aliasing\fR" 4 -.IX Item "-fstrict-aliasing" -Allows the compiler to assume the strictest aliasing rules applicable to -the language being compiled. For C (and \*(C+), this activates -optimizations based on the type of expressions. In particular, an -object of one type is assumed never to reside at the same address as an -object of a different type, unless the types are almost the same. For -example, an \f(CW\*(C`unsigned int\*(C'\fR can alias an \f(CW\*(C`int\*(C'\fR, but not a -\&\f(CW\*(C`void*\*(C'\fR or a \f(CW\*(C`double\*(C'\fR. A character type may alias any other -type. -.Sp -Pay special attention to code like this: -.Sp -.Vb 4 -\& union a_union { -\& int i; -\& double d; -\& }; -.Ve -.Vb 5 -\& int f() { -\& a_union t; -\& t.d = 3.0; -\& return t.i; -\& } -.Ve -The practice of reading from a different union member than the one most -recently written to (called ``type-punning'') is common. Even with -\&\fB\-fstrict-aliasing\fR, type-punning is allowed, provided the memory -is accessed through the union type. So, the code above will work as -expected. However, this code might not: -.Sp -.Vb 7 -\& int f() { -\& a_union t; -\& int* ip; -\& t.d = 3.0; -\& ip = &t.i; -\& return *ip; -\& } -.Ve -.Ip "\fB\-falign-functions\fR" 4 -.IX Item "-falign-functions" -.PD 0 -.Ip "\fB\-falign-functions=\fR\fIn\fR" 4 -.IX Item "-falign-functions=n" -.PD -Align the start of functions to the next power-of-two greater than -\&\fIn\fR, skipping up to \fIn\fR bytes. For instance, -\&\fB\-falign-functions=32\fR aligns functions to the next 32\-byte -boundary, but \fB\-falign-functions=24\fR would align to the next -32\-byte boundary only if this can be done by skipping 23 bytes or less. -.Sp -\&\fB\-fno-align-functions\fR and \fB\-falign-functions=1\fR are -equivalent and mean that functions will not be aligned. -.Sp -Some assemblers only support this flag when \fIn\fR is a power of two; -in that case, it is rounded up. -.Sp -If \fIn\fR is not specified, use a machine-dependent default. -.Ip "\fB\-falign-labels\fR" 4 -.IX Item "-falign-labels" -.PD 0 -.Ip "\fB\-falign-labels=\fR\fIn\fR" 4 -.IX Item "-falign-labels=n" -.PD -Align all branch targets to a power-of-two boundary, skipping up to -\&\fIn\fR bytes like \fB\-falign-functions\fR. This option can easily -make code slower, because it must insert dummy operations for when the -branch target is reached in the usual flow of the code. -.Sp -If \fB\-falign-loops\fR or \fB\-falign-jumps\fR are applicable and -are greater than this value, then their values are used instead. -.Sp -If \fIn\fR is not specified, use a machine-dependent default which is -very likely to be \fB1\fR, meaning no alignment. -.Ip "\fB\-falign-loops\fR" 4 -.IX Item "-falign-loops" -.PD 0 -.Ip "\fB\-falign-loops=\fR\fIn\fR" 4 -.IX Item "-falign-loops=n" -.PD -Align loops to a power-of-two boundary, skipping up to \fIn\fR bytes -like \fB\-falign-functions\fR. The hope is that the loop will be -executed many times, which will make up for any execution of the dummy -operations. -.Sp -If \fIn\fR is not specified, use a machine-dependent default. -.Ip "\fB\-falign-jumps\fR" 4 -.IX Item "-falign-jumps" -.PD 0 -.Ip "\fB\-falign-jumps=\fR\fIn\fR" 4 -.IX Item "-falign-jumps=n" -.PD -Align branch targets to a power-of-two boundary, for branch targets -where the targets can only be reached by jumping, skipping up to \fIn\fR -bytes like \fB\-falign-functions\fR. In this case, no dummy operations -need be executed. -.Sp -If \fIn\fR is not specified, use a machine-dependent default. -.Ip "\fB\-fssa\fR" 4 -.IX Item "-fssa" -Perform optimizations in static single assignment form. Each function's -flow graph is translated into \s-1SSA\s0 form, optimizations are performed, and -the flow graph is translated back from \s-1SSA\s0 form. User's should not -specify this option, since it is not yet ready for production use. -.Ip "\fB\-fdce\fR" 4 -.IX Item "-fdce" -Perform dead-code elimination in \s-1SSA\s0 form. Requires \fB\-fssa\fR. Like -\&\fB\-fssa\fR, this is an experimental feature. -.Ip "\fB\-fsingle-precision-constant\fR" 4 -.IX Item "-fsingle-precision-constant" -Treat floating point constant as single precision constant instead of -implicitly converting it to double precision constant. -.Ip "\fB\-frename-registers\fR" 4 -.IX Item "-frename-registers" -Attempt to avoid false dependancies in scheduled code by making use -of registers left over after register allocation. This optimization -will most benefit processors with lots of registers. It can, however, -make debugging impossible, since variables will no longer stay in -a ``home register''. -.Ip "\fB\*(--param\fR \fIname\fR\fB=\fR\fIvalue\fR" 4 -.IX Item "param name=value" -In some places, \s-1GCC\s0 uses various constants to control the amount of -optimization that is done. For example, \s-1GCC\s0 will not inline functions -that contain more that a certain number of instructions. You can -control some of these constants on the command-line using the -\&\fB\*(--param\fR option. -.Sp -In each case, the \fIvalue\fR is a integer. The allowable choices for -\&\fIname\fR are given in the following table: -.RS 4 -.Ip "\fBmax-delay-slot-insn-search\fR" 4 -.IX Item "max-delay-slot-insn-search" -The maximum number of instructions to consider when looking for an -instruction to fill a delay slot. If more than this arbitrary number of -instructions is searched, the time savings from filling the delay slot -will be minimal so stop searching. Increasing values mean more -aggressive optimization, making the compile time increase with probably -small improvement in executable run time. -.Ip "\fBmax-delay-slot-live-search\fR" 4 -.IX Item "max-delay-slot-live-search" -When trying to fill delay slots, the maximum number of instructions to -consider when searching for a block with valid live register -information. Increasing this arbitrarily chosen value means more -aggressive optimization, increasing the compile time. This parameter -should be removed when the delay slot code is rewritten to maintain the -control-flow graph. -.Ip "\fBmax-gcse-memory\fR" 4 -.IX Item "max-gcse-memory" -The approximate maximum amount of memory that will be allocated in -order to perform the global common subexpression elimination -optimization. If more memory than specified is required, the -optimization will not be done. -.Ip "\fBmax-inline-insns\fR" 4 -.IX Item "max-inline-insns" -If an function contains more than this many instructions, it -will not be inlined. This option is precisely equivalent to -\&\fB\-finline-limit\fR. -.RE -.RS 4 -.RE -.Sh "Options Controlling the Preprocessor" -.IX Subsection "Options Controlling the Preprocessor" -These options control the C preprocessor, which is run on each C source -file before actual compilation. -.PP -If you use the \fB\-E\fR option, nothing is done except preprocessing. -Some of these options make sense only together with \fB\-E\fR because -they cause the preprocessor output to be unsuitable for actual -compilation. -.Ip "\fB\-include\fR \fIfile\fR" 4 -.IX Item "-include file" -Process \fIfile\fR as input before processing the regular input file. -In effect, the contents of \fIfile\fR are compiled first. Any \fB\-D\fR -and \fB\-U\fR options on the command line are always processed before -\&\fB\-include\fR \fIfile\fR, regardless of the order in which they are -written. All the \fB\-include\fR and \fB\-imacros\fR options are -processed in the order in which they are written. -.Ip "\fB\-imacros\fR \fIfile\fR" 4 -.IX Item "-imacros file" -Process \fIfile\fR as input, discarding the resulting output, before -processing the regular input file. Because the output generated from -\&\fIfile\fR is discarded, the only effect of \fB\-imacros\fR \fIfile\fR -is to make the macros defined in \fIfile\fR available for use in the -main input. All the \fB\-include\fR and \fB\-imacros\fR options are -processed in the order in which they are written. -.Ip "\fB\-idirafter\fR \fIdir\fR" 4 -.IX Item "-idirafter dir" -Add the directory \fIdir\fR to the second include path. The directories -on the second include path are searched when a header file is not found -in any of the directories in the main include path (the one that -\&\fB\-I\fR adds to). -.Ip "\fB\-iprefix\fR \fIprefix\fR" 4 -.IX Item "-iprefix prefix" -Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR -options. -.Ip "\fB\-iwithprefix\fR \fIdir\fR" 4 -.IX Item "-iwithprefix dir" -Add a directory to the second include path. The directory's name is -made by concatenating \fIprefix\fR and \fIdir\fR, where \fIprefix\fR was -specified previously with \fB\-iprefix\fR. If you have not specified a -prefix yet, the directory containing the installed passes of the -compiler is used as the default. -.Ip "\fB\-iwithprefixbefore\fR \fIdir\fR" 4 -.IX Item "-iwithprefixbefore dir" -Add a directory to the main include path. The directory's name is made -by concatenating \fIprefix\fR and \fIdir\fR, as in the case of -\&\fB\-iwithprefix\fR. -.Ip "\fB\-isystem\fR \fIdir\fR" 4 -.IX Item "-isystem dir" -Add a directory to the beginning of the second include path, marking it -as a system directory, so that it gets the same special treatment as -is applied to the standard system directories. -.Ip "\fB\-nostdinc\fR" 4 -.IX Item "-nostdinc" -Do not search the standard system directories for header files. Only -the directories you have specified with \fB\-I\fR options (and the -current directory, if appropriate) are searched. -.Sp -By using both \fB\-nostdinc\fR and \fB\-I-\fR, you can limit the include-file -search path to only those directories you specify explicitly. -.Ip "\fB\-remap\fR" 4 -.IX Item "-remap" -When searching for a header file in a directory, remap file names if a -file named \fIheader.gcc\fR exists in that directory. This can be used -to work around limitations of file systems with file name restrictions. -The \fIheader.gcc\fR file should contain a series of lines with two -tokens on each line: the first token is the name to map, and the second -token is the actual name to use. -.Ip "\fB\-undef\fR" 4 -.IX Item "-undef" -Do not predefine any nonstandard macros. (Including architecture flags). -.Ip "\fB\-E\fR" 4 -.IX Item "-E" -Run only the C preprocessor. Preprocess all the C source files -specified and output the results to standard output or to the -specified output file. -.Ip "\fB\-C\fR" 4 -.IX Item "-C" -Tell the preprocessor not to discard comments. Used with the -\&\fB\-E\fR option. -.Ip "\fB\-P\fR" 4 -.IX Item "-P" -Tell the preprocessor not to generate \fB#line\fR directives. -Used with the \fB\-E\fR option. -.Ip "\fB\-M\fR" 4 -.IX Item "-M" -Instead of outputting the result of preprocessing, output a rule -suitable for \f(CW\*(C`make\*(C'\fR describing the dependencies of the main source -file. The preprocessor outputs one \f(CW\*(C`make\*(C'\fR rule containing the -object file name for that source file, a colon, and the names of all the -included files. Unless overridden explicitly, the object file name -consists of the basename of the source file with any suffix replaced with -object file suffix. If there are many included files then the -rule is split into several lines using \fB\e\fR\-newline. -.Sp -\&\fB\-M\fR implies \fB\-E\fR. -.Ip "\fB\-MM\fR" 4 -.IX Item "-MM" -Like \fB\-M\fR, but mention only the files included with \fB#include -"\fR\fIfile\fR\fB"\fR. System header files included with \fB#include -<\fR\fIfile\fR\fB>\fR are omitted. -.Ip "\fB\-MD\fR" 4 -.IX Item "-MD" -Like \fB\-M\fR but the dependency information is written to a file -rather than stdout. \f(CW\*(C`gcc\*(C'\fR will use the same file name and -directory as the object file, but with the suffix \*(L".d\*(R" instead. -.Sp -This is in addition to compiling the main file as specified \-\-\- -\&\fB\-MD\fR does not inhibit ordinary compilation the way \fB\-M\fR does, -unless you also specify \fB\-MG\fR. -.Sp -With Mach, you can use the utility \f(CW\*(C`md\*(C'\fR to merge multiple -dependency files into a single dependency file suitable for using with -the \fBmake\fR command. -.Ip "\fB\-MMD\fR" 4 -.IX Item "-MMD" -Like \fB\-MD\fR except mention only user header files, not system -\&\-header files. -.Ip "\fB\-MF\fR \fIfile\fR" 4 -.IX Item "-MF file" -When used with \fB\-M\fR or \fB\-MM\fR, specifies a file to write the -dependencies to. This allows the preprocessor to write the preprocessed -file to stdout normally. If no \fB\-MF\fR switch is given, \s-1CPP\s0 sends -the rules to stdout and suppresses normal preprocessed output. -.Sp -Another way to specify output of a \f(CW\*(C`make\*(C'\fR rule is by setting -the environment variable \fB\s-1DEPENDENCIES_OUTPUT\s0\fR. -.Ip "\fB\-MG\fR" 4 -.IX Item "-MG" -When used with \fB\-M\fR or \fB\-MM\fR, \fB\-MG\fR says to treat missing -header files as generated files and assume they live in the same -directory as the source file. It suppresses preprocessed output, as a -missing header file is ordinarily an error. -.Sp -This feature is used in automatic updating of makefiles. -.Ip "\fB\-MP\fR" 4 -.IX Item "-MP" -This option instructs \s-1CPP\s0 to add a phony target for each dependency -other than the main file, causing each to depend on nothing. These -dummy rules work around errors \f(CW\*(C`make\*(C'\fR gives if you remove header -files without updating the \f(CW\*(C`Makefile\*(C'\fR to match. -.Sp -This is typical output:\- -.Sp -.Vb 1 -\& /tmp/test.o: /tmp/test.c /tmp/test.h -.Ve -.Vb 1 -\& /tmp/test.h: -.Ve -.Ip "\fB\-MQ\fR \fItarget\fR" 4 -.IX Item "-MQ target" -.PD 0 -.Ip "\fB\-MT\fR \fItarget\fR" 4 -.IX Item "-MT target" -.PD -By default \s-1CPP\s0 uses the main file name, including any path, and appends -the object suffix, normally ``.o'', to it to obtain the name of the -target for dependency generation. With \fB\-MT\fR you can specify a -target yourself, overriding the default one. -.Sp -If you want multiple targets, you can specify them as a single argument -to \fB\-MT\fR, or use multiple \fB\-MT\fR options. -.Sp -The targets you specify are output in the order they appear on the -command line. \fB\-MQ\fR is identical to \fB\-MT\fR, except that the -target name is quoted for Make, but with \fB\-MT\fR it isn't. For -example, \-MT '$(objpfx)foo.o' gives -.Sp -.Vb 1 -\& $(objpfx)foo.o: /tmp/foo.c -.Ve -but \-MQ '$(objpfx)foo.o' gives -.Sp -.Vb 1 -\& $$(objpfx)foo.o: /tmp/foo.c -.Ve -The default target is automatically quoted, as if it were given with -\&\fB\-MQ\fR. -.Ip "\fB\-H\fR" 4 -.IX Item "-H" -Print the name of each header file used, in addition to other normal -activities. -.Ip "\fB\-A\fR\fIquestion\fR\fB(\fR\fIanswer\fR\fB)\fR" 4 -.IX Item "-Aquestion(answer)" -Assert the answer \fIanswer\fR for \fIquestion\fR, in case it is tested -with a preprocessing conditional such as \fB#if -#\fR\fIquestion\fR\fB(\fR\fIanswer\fR\fB)\fR. \fB\-A-\fR disables the standard -assertions that normally describe the target machine. -.Ip "\fB\-D\fR\fImacro\fR" 4 -.IX Item "-Dmacro" -Define macro \fImacro\fR with the string \fB1\fR as its definition. -.Ip "\fB\-D\fR\fImacro\fR\fB=\fR\fIdefn\fR" 4 -.IX Item "-Dmacro=defn" -Define macro \fImacro\fR as \fIdefn\fR. All instances of \fB\-D\fR on -the command line are processed before any \fB\-U\fR options. -.Sp -Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in -order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the -order in which they are written. -.Ip "\fB\-U\fR\fImacro\fR" 4 -.IX Item "-Umacro" -Undefine macro \fImacro\fR. \fB\-U\fR options are evaluated after all -\&\fB\-D\fR options, but before any \fB\-include\fR and \fB\-imacros\fR -options. -.Sp -Any \fB\-D\fR and \fB\-U\fR options on the command line are processed in -order, and always before \fB\-imacros\fR \fIfile\fR, regardless of the -order in which they are written. -.Ip "\fB\-dM\fR" 4 -.IX Item "-dM" -Tell the preprocessor to output only a list of the macro definitions -that are in effect at the end of preprocessing. Used with the \fB\-E\fR -option. -.Ip "\fB\-dD\fR" 4 -.IX Item "-dD" -Tell the preprocessing to pass all macro definitions into the output, in -their proper sequence in the rest of the output. -.Ip "\fB\-dN\fR" 4 -.IX Item "-dN" -Like \fB\-dD\fR except that the macro arguments and contents are omitted. -Only \fB#define\fR \fIname\fR is included in the output. -.Ip "\fB\-dI\fR" 4 -.IX Item "-dI" -Output \fB#include\fR directives in addition to the result of -preprocessing. -.Ip "\fB\-trigraphs\fR" 4 -.IX Item "-trigraphs" -Process \s-1ISO\s0 standard trigraph sequences. These are three-character -sequences, all starting with \fB??\fR, that are defined by \s-1ISO\s0 C to -stand for single characters. For example, \fB??/\fR stands for -\&\fB\e\fR, so \fB'??/n'\fR is a character constant for a newline. By -default, \s-1GCC\s0 ignores trigraphs, but in standard-conforming modes it -converts them. See the \fB\-std\fR and \fB\-ansi\fR options. -.Sp -The nine trigraph sequences are -.RS 4 -.Ip "\fB??(\fR" 4 -.IX Item "??(" --> \fB[\fR -.Ip "\fB??)\fR" 4 -.IX Item "??)" --> \fB]\fR -.Ip "\fB??<\fR" 4 -.IX Item "??<" --> \fB{\fR -.Ip "\fB??>\fR" 4 -.IX Item "??>" --> \fB}\fR -.Ip "\fB??=\fR" 4 -.IX Item "??=" --> \fB#\fR -.Ip "\fB??/\fR" 4 -.IX Item "??/" --> \fB\e\fR -.Ip "\fB??'\fR" 4 -.IX Item "??'" --> \fB^\fR -.Ip "\fB??!\fR" 4 -.IX Item "??!" --> \fB|\fR -.Ip "\fB??-\fR" 4 -.IX Item "??-" --> \fB~\fR -.RE -.RS 4 -.Sp -Trigraph support is not popular, so many compilers do not implement it -properly. Portable code should not rely on trigraphs being either -converted or ignored. -.RE -.Ip "\fB\-Wp,\fR\fIoption\fR" 4 -.IX Item "-Wp,option" -Pass \fIoption\fR as an option to the preprocessor. If \fIoption\fR -contains commas, it is split into multiple options at the commas. -.Sh "Passing Options to the Assembler" -.IX Subsection "Passing Options to the Assembler" -You can pass options to the assembler. -.Ip "\fB\-Wa,\fR\fIoption\fR" 4 -.IX Item "-Wa,option" -Pass \fIoption\fR as an option to the assembler. If \fIoption\fR -contains commas, it is split into multiple options at the commas. -.Sh "Options for Linking" -.IX Subsection "Options for Linking" -These options come into play when the compiler links object files into -an executable output file. They are meaningless if the compiler is -not doing a link step. -.Ip "\fIobject-file-name\fR" 4 -.IX Item "object-file-name" -A file name that does not end in a special recognized suffix is -considered to name an object file or library. (Object files are -distinguished from libraries by the linker according to the file -contents.) If linking is done, these object files are used as input -to the linker. -.Ip "\fB\-c\fR" 4 -.IX Item "-c" -.PD 0 -.Ip "\fB\-S\fR" 4 -.IX Item "-S" -.Ip "\fB\-E\fR" 4 -.IX Item "-E" -.PD -If any of these options is used, then the linker is not run, and -object file names should not be used as arguments. -.Ip "\fB\-l\fR\fIlibrary\fR" 4 -.IX Item "-llibrary" -.PD 0 -.Ip "\fB\-l\fR \fIlibrary\fR" 4 -.IX Item "-l library" -.PD -Search the library named \fIlibrary\fR when linking. (The second -alternative with the library as a separate argument is only for -\&\s-1POSIX\s0 compliance and is not recommended.) -.Sp -It makes a difference where in the command you write this option; the -linker searches and processes libraries and object files in the order they -are specified. Thus, \fBfoo.o \-lz bar.o\fR searches library \fBz\fR -after file \fIfoo.o\fR but before \fIbar.o\fR. If \fIbar.o\fR refers -to functions in \fBz\fR, those functions may not be loaded. -.Sp -The linker searches a standard list of directories for the library, -which is actually a file named \fIlib\fIlibrary\fI.a\fR. The linker -then uses this file as if it had been specified precisely by name. -.Sp -The directories searched include several standard system directories -plus any that you specify with \fB\-L\fR. -.Sp -Normally the files found this way are library files\-\-\-archive files -whose members are object files. The linker handles an archive file by -scanning through it for members which define symbols that have so far -been referenced but not defined. But if the file that is found is an -ordinary object file, it is linked in the usual fashion. The only -difference between using an \fB\-l\fR option and specifying a file name -is that \fB\-l\fR surrounds \fIlibrary\fR with \fBlib\fR and \fB.a\fR -and searches several directories. -.Ip "\fB\-lobjc\fR" 4 -.IX Item "-lobjc" -You need this special case of the \fB\-l\fR option in order to -link an Objective C program. -.Ip "\fB\-nostartfiles\fR" 4 -.IX Item "-nostartfiles" -Do not use the standard system startup files when linking. -The standard system libraries are used normally, unless \fB\-nostdlib\fR -or \fB\-nodefaultlibs\fR is used. -.Ip "\fB\-nodefaultlibs\fR" 4 -.IX Item "-nodefaultlibs" -Do not use the standard system libraries when linking. -Only the libraries you specify will be passed to the linker. -The standard startup files are used normally, unless \fB\-nostartfiles\fR -is used. The compiler may generate calls to memcmp, memset, and memcpy -for System V (and \s-1ISO\s0 C) environments or to bcopy and bzero for -\&\s-1BSD\s0 environments. These entries are usually resolved by entries in -libc. These entry points should be supplied through some other -mechanism when this option is specified. -.Ip "\fB\-nostdlib\fR" 4 -.IX Item "-nostdlib" -Do not use the standard system startup files or libraries when linking. -No startup files and only the libraries you specify will be passed to -the linker. The compiler may generate calls to memcmp, memset, and memcpy -for System V (and \s-1ISO\s0 C) environments or to bcopy and bzero for -\&\s-1BSD\s0 environments. These entries are usually resolved by entries in -libc. These entry points should be supplied through some other -mechanism when this option is specified. -.Sp -One of the standard libraries bypassed by \fB\-nostdlib\fR and -\&\fB\-nodefaultlibs\fR is \fIlibgcc.a\fR, a library of internal subroutines -that \s-1GCC\s0 uses to overcome shortcomings of particular machines, or special -needs for some languages. -.Sp -In most cases, you need \fIlibgcc.a\fR even when you want to avoid -other standard libraries. In other words, when you specify \fB\-nostdlib\fR -or \fB\-nodefaultlibs\fR you should usually specify \fB\-lgcc\fR as well. -This ensures that you have no unresolved references to internal \s-1GCC\s0 -library subroutines. (For example, \fB_\|_main\fR, used to ensure \*(C+ -constructors will be called.) -.Ip "\fB\-s\fR" 4 -.IX Item "-s" -Remove all symbol table and relocation information from the executable. -.Ip "\fB\-static\fR" 4 -.IX Item "-static" -On systems that support dynamic linking, this prevents linking with the shared -libraries. On other systems, this option has no effect. -.Ip "\fB\-shared\fR" 4 -.IX Item "-shared" -Produce a shared object which can then be linked with other objects to -form an executable. Not all systems support this option. For predictable -results, you must also specify the same set of options that were used to -generate code (\fB\-fpic\fR, \fB\-fPIC\fR, or model suboptions) -when you specify this option.[1] -.Ip "\fB\-shared-libgcc\fR" 4 -.IX Item "-shared-libgcc" -.PD 0 -.Ip "\fB\-static-libgcc\fR" 4 -.IX Item "-static-libgcc" -.PD -On systems that provide \fIlibgcc\fR as a shared library, these options -force the use of either the shared or static version respectively. -If no shared version of \fIlibgcc\fR was built when the compiler was -configured, these options have no effect. -.Sp -There are several situations in which an application should use the -shared \fIlibgcc\fR instead of the static version. The most common -of these is when the application wishes to throw and catch exceptions -across different shared libraries. In that case, each of the libraries -as well as the application itself should use the shared \fIlibgcc\fR. -.Sp -Therefore, whenever you specify the \fB\-shared\fR option, the \s-1GCC\s0 -driver automatically adds \fB\-shared-libgcc\fR, unless you explicitly -specify \fB\-static-libgcc\fR. The G++ driver automatically adds -\&\fB\-shared-libgcc\fR when you build a main executable as well because -for \*(C+ programs that is typically the right thing to do. -(Exception-handling will not work reliably otherwise.) -.Sp -However, when linking a main executable written in C, you must -explicitly say \fB\-shared-libgcc\fR if you want to use the shared -\&\fIlibgcc\fR. -.Ip "\fB\-symbolic\fR" 4 -.IX Item "-symbolic" -Bind references to global symbols when building a shared object. Warn -about any unresolved references (unless overridden by the link editor -option \fB\-Xlinker \-z \-Xlinker defs\fR). Only a few systems support -this option. -.Ip "\fB\-Xlinker\fR \fIoption\fR" 4 -.IX Item "-Xlinker option" -Pass \fIoption\fR as an option to the linker. You can use this to -supply system-specific linker options which \s-1GCC\s0 does not know how to -recognize. -.Sp -If you want to pass an option that takes an argument, you must use -\&\fB\-Xlinker\fR twice, once for the option and once for the argument. -For example, to pass \fB\-assert definitions\fR, you must write -\&\fB\-Xlinker \-assert \-Xlinker definitions\fR. It does not work to write -\&\fB\-Xlinker \*(L"\-assert definitions\*(R"\fR, because this passes the entire -string as a single argument, which is not what the linker expects. -.Ip "\fB\-Wl,\fR\fIoption\fR" 4 -.IX Item "-Wl,option" -Pass \fIoption\fR as an option to the linker. If \fIoption\fR contains -commas, it is split into multiple options at the commas. -.Ip "\fB\-u\fR \fIsymbol\fR" 4 -.IX Item "-u symbol" -Pretend the symbol \fIsymbol\fR is undefined, to force linking of -library modules to define it. You can use \fB\-u\fR multiple times with -different symbols to force loading of additional library modules. -.Sh "Options for Directory Search" -.IX Subsection "Options for Directory Search" -These options specify directories to search for header files, for -libraries and for parts of the compiler: -.Ip "\fB\-I\fR\fIdir\fR" 4 -.IX Item "-Idir" -Add the directory \fIdir\fR to the head of the list of directories to be -searched for header files. This can be used to override a system header -file, substituting your own version, since these directories are -searched before the system header file directories. However, you should -not use this option to add directories that contain vendor-supplied -system header files (use \fB\-isystem\fR for that). If you use more than -one \fB\-I\fR option, the directories are scanned in left-to-right -order; the standard system directories come after. -.Ip "\fB\-I-\fR" 4 -.IX Item "-I-" -Any directories you specify with \fB\-I\fR options before the \fB\-I-\fR -option are searched only for the case of \fB#include "\fR\fIfile\fR\fB"\fR; -they are not searched for \fB#include <\fR\fIfile\fR\fB>\fR. -.Sp -If additional directories are specified with \fB\-I\fR options after -the \fB\-I-\fR, these directories are searched for all \fB#include\fR -directives. (Ordinarily \fIall\fR \fB\-I\fR directories are used -this way.) -.Sp -In addition, the \fB\-I-\fR option inhibits the use of the current -directory (where the current input file came from) as the first search -directory for \fB#include "\fR\fIfile\fR\fB"\fR. There is no way to -override this effect of \fB\-I-\fR. With \fB\-I.\fR you can specify -searching the directory which was current when the compiler was -invoked. That is not exactly the same as what the preprocessor does -by default, but it is often satisfactory. -.Sp -\&\fB\-I-\fR does not inhibit the use of the standard system directories -for header files. Thus, \fB\-I-\fR and \fB\-nostdinc\fR are -independent. -.Ip "\fB\-L\fR\fIdir\fR" 4 -.IX Item "-Ldir" -Add directory \fIdir\fR to the list of directories to be searched -for \fB\-l\fR. -.Ip "\fB\-B\fR\fIprefix\fR" 4 -.IX Item "-Bprefix" -This option specifies where to find the executables, libraries, -include files, and data files of the compiler itself. -.Sp -The compiler driver program runs one or more of the subprograms -\&\fIcpp\fR, \fIcc1\fR, \fIas\fR and \fIld\fR. It tries -\&\fIprefix\fR as a prefix for each program it tries to run, both with and -without \fImachine\fR\fB/\fR\fIversion\fR\fB/\fR. -.Sp -For each subprogram to be run, the compiler driver first tries the -\&\fB\-B\fR prefix, if any. If that name is not found, or if \fB\-B\fR -was not specified, the driver tries two standard prefixes, which are -\&\fI/usr/lib/gcc/\fR and \fI/usr/local/lib/gcc-lib/\fR. If neither of -those results in a file name that is found, the unmodified program -name is searched for using the directories specified in your -\&\fB\s-1PATH\s0\fR environment variable. -.Sp -\&\fB\-B\fR prefixes that effectively specify directory names also apply -to libraries in the linker, because the compiler translates these -options into \fB\-L\fR options for the linker. They also apply to -includes files in the preprocessor, because the compiler translates these -options into \fB\-isystem\fR options for the preprocessor. In this case, -the compiler appends \fBinclude\fR to the prefix. -.Sp -The run-time support file \fIlibgcc.a\fR can also be searched for using -the \fB\-B\fR prefix, if needed. If it is not found there, the two -standard prefixes above are tried, and that is all. The file is left -out of the link if it is not found by those means. -.Sp -Another way to specify a prefix much like the \fB\-B\fR prefix is to use -the environment variable \fB\s-1GCC_EXEC_PREFIX\s0\fR. -.Ip "\fB\-specs=\fR\fIfile\fR" 4 -.IX Item "-specs=file" -Process \fIfile\fR after the compiler reads in the standard \fIspecs\fR -file, in order to override the defaults that the \fIgcc\fR driver -program uses when determining what switches to pass to \fIcc1\fR, -\&\fIcc1plus\fR, \fIas\fR, \fIld\fR, etc. More than one -\&\fB\-specs=\fR\fIfile\fR can be specified on the command line, and they -are processed in order, from left to right. -.Sh "Specifying Target Machine and Compiler Version" -.IX Subsection "Specifying Target Machine and Compiler Version" -By default, \s-1GCC\s0 compiles code for the same type of machine that you -are using. However, it can also be installed as a cross-compiler, to -compile for some other type of machine. In fact, several different -configurations of \s-1GCC\s0, for different target machines, can be -installed side by side. Then you specify which one to use with the -\&\fB\-b\fR option. -.PP -In addition, older and newer versions of \s-1GCC\s0 can be installed side -by side. One of them (probably the newest) will be the default, but -you may sometimes wish to use another. -.Ip "\fB\-b\fR \fImachine\fR" 4 -.IX Item "-b machine" -The argument \fImachine\fR specifies the target machine for compilation. -This is useful when you have installed \s-1GCC\s0 as a cross-compiler. -.Sp -The value to use for \fImachine\fR is the same as was specified as the -machine type when configuring \s-1GCC\s0 as a cross-compiler. For -example, if a cross-compiler was configured with \fBconfigure -i386v\fR, meaning to compile for an 80386 running System V, then you -would specify \fB\-b i386v\fR to run that cross compiler. -.Sp -When you do not specify \fB\-b\fR, it normally means to compile for -the same type of machine that you are using. -.Ip "\fB\-V\fR \fIversion\fR" 4 -.IX Item "-V version" -The argument \fIversion\fR specifies which version of \s-1GCC\s0 to run. -This is useful when multiple versions are installed. For example, -\&\fIversion\fR might be \fB2.0\fR, meaning to run \s-1GCC\s0 version 2.0. -.Sp -The default version, when you do not specify \fB\-V\fR, is the last -version of \s-1GCC\s0 that you installed. -.PP -The \fB\-b\fR and \fB\-V\fR options actually work by controlling part of -the file name used for the executable files and libraries used for -compilation. A given version of \s-1GCC\s0, for a given target machine, is -normally kept in the directory \fI/usr/local/lib/gcc-lib/\fImachine\fI/\fIversion\fI\fR. -.PP -Thus, sites can customize the effect of \fB\-b\fR or \fB\-V\fR either by -changing the names of these directories or adding alternate names (or -symbolic links). If in directory \fI/usr/local/lib/gcc-lib/\fR the -file \fI80386\fR is a link to the file \fIi386v\fR, then \fB\-b -80386\fR becomes an alias for \fB\-b i386v\fR. -.PP -In one respect, the \fB\-b\fR or \fB\-V\fR do not completely change -to a different compiler: the top-level driver program \fBgcc\fR -that you originally invoked continues to run and invoke the other -executables (preprocessor, compiler per se, assembler and linker) -that do the real work. However, since no real work is done in the -driver program, it usually does not matter that the driver program -in use is not the one for the specified target. It is common for the -interface to the other executables to change incompatibly between -compiler versions, so unless the version specified is very close to that -of the driver (for example, \fB\-V 3.0\fR with a driver program from \s-1GCC\s0 -version 3.0.1), use of \fB\-V\fR may not work; for example, using -\&\fB\-V 2.95.2\fR will not work with a driver program from \s-1GCC\s0 3.0. -.PP -The only way that the driver program depends on the target machine is -in the parsing and handling of special machine-specific options. -However, this is controlled by a file which is found, along with the -other executables, in the directory for the specified version and -target machine. As a result, a single installed driver program adapts -to any specified target machine, and sufficiently similar compiler -versions. -.PP -The driver program executable does control one significant thing, -however: the default version and target machine. Therefore, you can -install different instances of the driver program, compiled for -different targets or versions, under different names. -.PP -For example, if the driver for version 2.0 is installed as \fBogcc\fR -and that for version 2.1 is installed as \fBgcc\fR, then the command -\&\fBgcc\fR will use version 2.1 by default, while \fBogcc\fR will use -2.0 by default. However, you can choose either version with either -command with the \fB\-V\fR option. -.Sh "Hardware Models and Configurations" -.IX Subsection "Hardware Models and Configurations" -Earlier we discussed the standard option \fB\-b\fR which chooses among -different installed compilers for completely different target -machines, such as Vax vs. 68000 vs. 80386. -.PP -In addition, each of these target machine types can have its own -special options, starting with \fB\-m\fR, to choose among various -hardware models or configurations\-\-\-for example, 68010 vs 68020, -floating coprocessor or none. A single installed version of the -compiler can compile for any model or configuration, according to the -options specified. -.PP -Some configurations of the compiler also support additional special -options, usually for compatibility with other compilers on the same -platform. -.PP -.I "M680x0 Options" -.IX Subsection "M680x0 Options" -.PP -These are the \fB\-m\fR options defined for the 68000 series. The default -values for these options depends on which style of 68000 was selected when -the compiler was configured; the defaults for the most common choices are -given below. -.Ip "\fB\-m68000\fR" 4 -.IX Item "-m68000" -.PD 0 -.Ip "\fB\-mc68000\fR" 4 -.IX Item "-mc68000" -.PD -Generate output for a 68000. This is the default -when the compiler is configured for 68000\-based systems. -.Sp -Use this option for microcontrollers with a 68000 or \s-1EC000\s0 core, -including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. -.Ip "\fB\-m68020\fR" 4 -.IX Item "-m68020" -.PD 0 -.Ip "\fB\-mc68020\fR" 4 -.IX Item "-mc68020" -.PD -Generate output for a 68020. This is the default -when the compiler is configured for 68020\-based systems. -.Ip "\fB\-m68881\fR" 4 -.IX Item "-m68881" -Generate output containing 68881 instructions for floating point. -This is the default for most 68020 systems unless \fB\-nfp\fR was -specified when the compiler was configured. -.Ip "\fB\-m68030\fR" 4 -.IX Item "-m68030" -Generate output for a 68030. This is the default when the compiler is -configured for 68030\-based systems. -.Ip "\fB\-m68040\fR" 4 -.IX Item "-m68040" -Generate output for a 68040. This is the default when the compiler is -configured for 68040\-based systems. -.Sp -This option inhibits the use of 68881/68882 instructions that have to be -emulated by software on the 68040. Use this option if your 68040 does not -have code to emulate those instructions. -.Ip "\fB\-m68060\fR" 4 -.IX Item "-m68060" -Generate output for a 68060. This is the default when the compiler is -configured for 68060\-based systems. -.Sp -This option inhibits the use of 68020 and 68881/68882 instructions that -have to be emulated by software on the 68060. Use this option if your 68060 -does not have code to emulate those instructions. -.Ip "\fB\-mcpu32\fR" 4 -.IX Item "-mcpu32" -Generate output for a \s-1CPU32\s0. This is the default -when the compiler is configured for CPU32\-based systems. -.Sp -Use this option for microcontrollers with a -\&\s-1CPU32\s0 or \s-1CPU32+\s0 core, including the 68330, 68331, 68332, 68333, 68334, -68336, 68340, 68341, 68349 and 68360. -.Ip "\fB\-m5200\fR" 4 -.IX Item "-m5200" -Generate output for a 520X \*(L"coldfire\*(R" family cpu. This is the default -when the compiler is configured for 520X-based systems. -.Sp -Use this option for microcontroller with a 5200 core, including -the \s-1MCF5202\s0, \s-1MCF5203\s0, \s-1MCF5204\s0 and \s-1MCF5202\s0. -.Ip "\fB\-m68020\-40\fR" 4 -.IX Item "-m68020-40" -Generate output for a 68040, without using any of the new instructions. -This results in code which can run relatively efficiently on either a -68020/68881 or a 68030 or a 68040. The generated code does use the -68881 instructions that are emulated on the 68040. -.Ip "\fB\-m68020\-60\fR" 4 -.IX Item "-m68020-60" -Generate output for a 68060, without using any of the new instructions. -This results in code which can run relatively efficiently on either a -68020/68881 or a 68030 or a 68040. The generated code does use the -68881 instructions that are emulated on the 68060. -.Ip "\fB\-mfpa\fR" 4 -.IX Item "-mfpa" -Generate output containing Sun \s-1FPA\s0 instructions for floating point. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not available for all m68k -targets. Normally the facilities of the machine's usual C compiler are -used, but this can't be done directly in cross-compilation. You must -make your own arrangements to provide suitable library functions for -cross-compilation. The embedded targets \fBm68k-*\-aout\fR and -\&\fBm68k-*\-coff\fR do provide software floating point support. -.Ip "\fB\-mshort\fR" 4 -.IX Item "-mshort" -Consider type \f(CW\*(C`int\*(C'\fR to be 16 bits wide, like \f(CW\*(C`short int\*(C'\fR. -.Ip "\fB\-mnobitfield\fR" 4 -.IX Item "-mnobitfield" -Do not use the bit-field instructions. The \fB\-m68000\fR, \fB\-mcpu32\fR -and \fB\-m5200\fR options imply \fB\-mnobitfield\fR. -.Ip "\fB\-mbitfield\fR" 4 -.IX Item "-mbitfield" -Do use the bit-field instructions. The \fB\-m68020\fR option implies -\&\fB\-mbitfield\fR. This is the default if you use a configuration -designed for a 68020. -.Ip "\fB\-mrtd\fR" 4 -.IX Item "-mrtd" -Use a different function-calling convention, in which functions -that take a fixed number of arguments return with the \f(CW\*(C`rtd\*(C'\fR -instruction, which pops their arguments while returning. This -saves one instruction in the caller since there is no need to pop -the arguments there. -.Sp -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. -.Sp -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR); -otherwise incorrect code will be generated for calls to those -functions. -.Sp -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) -.Sp -The \f(CW\*(C`rtd\*(C'\fR instruction is supported by the 68010, 68020, 68030, -68040, 68060 and \s-1CPU32\s0 processors, but not by the 68000 or 5200. -.Ip "\fB\-malign-int\fR" 4 -.IX Item "-malign-int" -.PD 0 -.Ip "\fB\-mno-align-int\fR" 4 -.IX Item "-mno-align-int" -.PD -Control whether \s-1GCC\s0 aligns \f(CW\*(C`int\*(C'\fR, \f(CW\*(C`long\*(C'\fR, \f(CW\*(C`long long\*(C'\fR, -\&\f(CW\*(C`float\*(C'\fR, \f(CW\*(C`double\*(C'\fR, and \f(CW\*(C`long double\*(C'\fR variables on a 32\-bit -boundary (\fB\-malign-int\fR) or a 16\-bit boundary (\fB\-mno-align-int\fR). -Aligning variables on 32\-bit boundaries produces code that runs somewhat -faster on processors with 32\-bit busses at the expense of more memory. -.Sp -\&\fBWarning:\fR if you use the \fB\-malign-int\fR switch, \s-1GCC\s0 will -align structures containing the above types differently than -most published application binary interface specifications for the m68k. -.Ip "\fB\-mpcrel\fR" 4 -.IX Item "-mpcrel" -Use the pc-relative addressing mode of the 68000 directly, instead of -using a global offset table. At present, this option implies \-fpic, -allowing at most a 16\-bit offset for pc-relative addressing. \-fPIC is -not presently supported with \-mpcrel, though this could be supported for -68020 and higher processors. -.Ip "\fB\-mno-strict-align\fR" 4 -.IX Item "-mno-strict-align" -.PD 0 -.Ip "\fB\-mstrict-align\fR" 4 -.IX Item "-mstrict-align" -.PD -Do not (do) assume that unaligned memory references will be handled by -the system. -.PP -.I "M68hc1x Options" -.IX Subsection "M68hc1x Options" -.PP -These are the \fB\-m\fR options defined for the 68hc11 and 68hc12 -microcontrollers. The default values for these options depends on -which style of microcontroller was selected when the compiler was configured; -the defaults for the most common choices are given below. -.Ip "\fB\-m6811\fR" 4 -.IX Item "-m6811" -.PD 0 -.Ip "\fB\-m68hc11\fR" 4 -.IX Item "-m68hc11" -.PD -Generate output for a 68HC11. This is the default -when the compiler is configured for 68HC11\-based systems. -.Ip "\fB\-m6812\fR" 4 -.IX Item "-m6812" -.PD 0 -.Ip "\fB\-m68hc12\fR" 4 -.IX Item "-m68hc12" -.PD -Generate output for a 68HC12. This is the default -when the compiler is configured for 68HC12\-based systems. -.Ip "\fB\-mauto-incdec\fR" 4 -.IX Item "-mauto-incdec" -Enable the use of 68HC12 pre and post auto-increment and auto-decrement -addressing modes. -.Ip "\fB\-mshort\fR" 4 -.IX Item "-mshort" -Consider type \f(CW\*(C`int\*(C'\fR to be 16 bits wide, like \f(CW\*(C`short int\*(C'\fR. -.Ip "\fB\-msoft-reg-count=\fR\fIcount\fR" 4 -.IX Item "-msoft-reg-count=count" -Specify the number of pseudo-soft registers which are used for the -code generation. The maximum number is 32. Using more pseudo-soft -register may or may not result in better code depending on the program. -The default is 4 for 68HC11 and 2 for 68HC12. -.PP -.I "\s-1VAX\s0 Options" -.IX Subsection "VAX Options" -.PP -These \fB\-m\fR options are defined for the Vax: -.Ip "\fB\-munix\fR" 4 -.IX Item "-munix" -Do not output certain jump instructions (\f(CW\*(C`aobleq\*(C'\fR and so on) -that the Unix assembler for the Vax cannot handle across long -ranges. -.Ip "\fB\-mgnu\fR" 4 -.IX Item "-mgnu" -Do output those jump instructions, on the assumption that you -will assemble with the \s-1GNU\s0 assembler. -.Ip "\fB\-mg\fR" 4 -.IX Item "-mg" -Output code for g-format floating point numbers instead of d-format. -.PP -.I "\s-1SPARC\s0 Options" -.IX Subsection "SPARC Options" -.PP -These \fB\-m\fR switches are supported on the \s-1SPARC:\s0 -.Ip "\fB\-mno-app-regs\fR" 4 -.IX Item "-mno-app-regs" -.PD 0 -.Ip "\fB\-mapp-regs\fR" 4 -.IX Item "-mapp-regs" -.PD -Specify \fB\-mapp-regs\fR to generate output using the global registers -2 through 4, which the \s-1SPARC\s0 \s-1SVR4\s0 \s-1ABI\s0 reserves for applications. This -is the default. -.Sp -To be fully \s-1SVR4\s0 \s-1ABI\s0 compliant at the cost of some performance loss, -specify \fB\-mno-app-regs\fR. You should compile libraries and system -software with this option. -.Ip "\fB\-mfpu\fR" 4 -.IX Item "-mfpu" -.PD 0 -.Ip "\fB\-mhard-float\fR" 4 -.IX Item "-mhard-float" -.PD -Generate output containing floating point instructions. This is the -default. -.Ip "\fB\-mno-fpu\fR" 4 -.IX Item "-mno-fpu" -.PD 0 -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -.PD -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not available for all \s-1SPARC\s0 -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. The embedded targets \fBsparc-*\-aout\fR and -\&\fBsparclite-*\-*\fR do provide software floating point support. -.Sp -\&\fB\-msoft-float\fR changes the calling convention in the output file; -therefore, it is only useful if you compile \fIall\fR of a program with -this option. In particular, you need to compile \fIlibgcc.a\fR, the -library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for -this to work. -.Ip "\fB\-mhard-quad-float\fR" 4 -.IX Item "-mhard-quad-float" -Generate output containing quad-word (long double) floating point -instructions. -.Ip "\fB\-msoft-quad-float\fR" 4 -.IX Item "-msoft-quad-float" -Generate output containing library calls for quad-word (long double) -floating point instructions. The functions called are those specified -in the \s-1SPARC\s0 \s-1ABI\s0. This is the default. -.Sp -As of this writing, there are no sparc implementations that have hardware -support for the quad-word floating point instructions. They all invoke -a trap handler for one of these instructions, and then the trap handler -emulates the effect of the instruction. Because of the trap handler overhead, -this is much slower than calling the \s-1ABI\s0 library routines. Thus the -\&\fB\-msoft-quad-float\fR option is the default. -.Ip "\fB\-mno-epilogue\fR" 4 -.IX Item "-mno-epilogue" -.PD 0 -.Ip "\fB\-mepilogue\fR" 4 -.IX Item "-mepilogue" -.PD -With \fB\-mepilogue\fR (the default), the compiler always emits code for -function exit at the end of each function. Any function exit in -the middle of the function (such as a return statement in C) will -generate a jump to the exit code at the end of the function. -.Sp -With \fB\-mno-epilogue\fR, the compiler tries to emit exit code inline -at every function exit. -.Ip "\fB\-mno-flat\fR" 4 -.IX Item "-mno-flat" -.PD 0 -.Ip "\fB\-mflat\fR" 4 -.IX Item "-mflat" -.PD -With \fB\-mflat\fR, the compiler does not generate save/restore instructions -and will use a \*(L"flat\*(R" or single register window calling convention. -This model uses \f(CW%i7\fR as the frame pointer and is compatible with the normal -register window model. Code from either may be intermixed. -The local registers and the input registers (0\-5) are still treated as -\&\*(L"call saved\*(R" registers and will be saved on the stack as necessary. -.Sp -With \fB\-mno-flat\fR (the default), the compiler emits save/restore -instructions (except for leaf functions) and is the normal mode of operation. -.Ip "\fB\-mno-unaligned-doubles\fR" 4 -.IX Item "-mno-unaligned-doubles" -.PD 0 -.Ip "\fB\-munaligned-doubles\fR" 4 -.IX Item "-munaligned-doubles" -.PD -Assume that doubles have 8 byte alignment. This is the default. -.Sp -With \fB\-munaligned-doubles\fR, \s-1GCC\s0 assumes that doubles have 8 byte -alignment only if they are contained in another type, or if they have an -absolute address. Otherwise, it assumes they have 4 byte alignment. -Specifying this option avoids some rare compatibility problems with code -generated by other compilers. It is not the default because it results -in a performance loss, especially for floating point code. -.Ip "\fB\-mno-faster-structs\fR" 4 -.IX Item "-mno-faster-structs" -.PD 0 -.Ip "\fB\-mfaster-structs\fR" 4 -.IX Item "-mfaster-structs" -.PD -With \fB\-mfaster-structs\fR, the compiler assumes that structures -should have 8 byte alignment. This enables the use of pairs of -\&\f(CW\*(C`ldd\*(C'\fR and \f(CW\*(C`std\*(C'\fR instructions for copies in structure -assignment, in place of twice as many \f(CW\*(C`ld\*(C'\fR and \f(CW\*(C`st\*(C'\fR pairs. -However, the use of this changed alignment directly violates the Sparc -\&\s-1ABI\s0. Thus, it's intended only for use on targets where the developer -acknowledges that their resulting code will not be directly in line with -the rules of the \s-1ABI\s0. -.Ip "\fB\-mv8\fR" 4 -.IX Item "-mv8" -.PD 0 -.Ip "\fB\-msparclite\fR" 4 -.IX Item "-msparclite" -.PD -These two options select variations on the \s-1SPARC\s0 architecture. -.Sp -By default (unless specifically configured for the Fujitsu SPARClite), -\&\s-1GCC\s0 generates code for the v7 variant of the \s-1SPARC\s0 architecture. -.Sp -\&\fB\-mv8\fR will give you \s-1SPARC\s0 v8 code. The only difference from v7 -code is that the compiler emits the integer multiply and integer -divide instructions which exist in \s-1SPARC\s0 v8 but not in \s-1SPARC\s0 v7. -.Sp -\&\fB\-msparclite\fR will give you SPARClite code. This adds the integer -multiply, integer divide step and scan (\f(CW\*(C`ffs\*(C'\fR) instructions which -exist in SPARClite but not in \s-1SPARC\s0 v7. -.Sp -These options are deprecated and will be deleted in a future \s-1GCC\s0 release. -They have been replaced with \fB\-mcpu=xxx\fR. -.Ip "\fB\-mcypress\fR" 4 -.IX Item "-mcypress" -.PD 0 -.Ip "\fB\-msupersparc\fR" 4 -.IX Item "-msupersparc" -.PD -These two options select the processor for which the code is optimised. -.Sp -With \fB\-mcypress\fR (the default), the compiler optimizes code for the -Cypress \s-1CY7C602\s0 chip, as used in the SparcStation/SparcServer 3xx series. -This is also appropriate for the older SparcStation 1, 2, \s-1IPX\s0 etc. -.Sp -With \fB\-msupersparc\fR the compiler optimizes code for the SuperSparc cpu, as -used in the SparcStation 10, 1000 and 2000 series. This flag also enables use -of the full \s-1SPARC\s0 v8 instruction set. -.Sp -These options are deprecated and will be deleted in a future \s-1GCC\s0 release. -They have been replaced with \fB\-mcpu=xxx\fR. -.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 -.IX Item "-mcpu=cpu_type" -Set the instruction set, register set, and instruction scheduling parameters -for machine type \fIcpu_type\fR. Supported values for \fIcpu_type\fR are -\&\fBv7\fR, \fBcypress\fR, \fBv8\fR, \fBsupersparc\fR, \fBsparclite\fR, -\&\fBhypersparc\fR, \fBsparclite86x\fR, \fBf930\fR, \fBf934\fR, -\&\fBsparclet\fR, \fBtsc701\fR, \fBv9\fR, and \fBultrasparc\fR. -.Sp -Default instruction scheduling parameters are used for values that select -an architecture and not an implementation. These are \fBv7\fR, \fBv8\fR, -\&\fBsparclite\fR, \fBsparclet\fR, \fBv9\fR. -.Sp -Here is a list of each supported architecture and their supported -implementations. -.Sp -.Vb 5 -\& v7: cypress -\& v8: supersparc, hypersparc -\& sparclite: f930, f934, sparclite86x -\& sparclet: tsc701 -\& v9: ultrasparc -.Ve -.Ip "\fB\-mtune=\fR\fIcpu_type\fR" 4 -.IX Item "-mtune=cpu_type" -Set the instruction scheduling parameters for machine type -\&\fIcpu_type\fR, but do not set the instruction set or register set that the -option \fB\-mcpu=\fR\fIcpu_type\fR would. -.Sp -The same values for \fB\-mcpu=\fR\fIcpu_type\fR are used for -\&\fB\-mtune=\fR\fIcpu_type\fR, though the only useful values are those that -select a particular cpu implementation: \fBcypress\fR, \fBsupersparc\fR, -\&\fBhypersparc\fR, \fBf930\fR, \fBf934\fR, \fBsparclite86x\fR, -\&\fBtsc701\fR, \fBultrasparc\fR. -.PP -These \fB\-m\fR switches are supported in addition to the above -on the \s-1SPARCLET\s0 processor. -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -Generate code for a processor running in little-endian mode. -.Ip "\fB\-mlive-g0\fR" 4 -.IX Item "-mlive-g0" -Treat register \f(CW\*(C`%g0\*(C'\fR as a normal register. -\&\s-1GCC\s0 will continue to clobber it as necessary but will not assume -it always reads as 0. -.Ip "\fB\-mbroken-saverestore\fR" 4 -.IX Item "-mbroken-saverestore" -Generate code that does not use non-trivial forms of the \f(CW\*(C`save\*(C'\fR and -\&\f(CW\*(C`restore\*(C'\fR instructions. Early versions of the \s-1SPARCLET\s0 processor do -not correctly handle \f(CW\*(C`save\*(C'\fR and \f(CW\*(C`restore\*(C'\fR instructions used with -arguments. They correctly handle them used without arguments. A \f(CW\*(C`save\*(C'\fR -instruction used without arguments increments the current window pointer -but does not allocate a new stack frame. It is assumed that the window -overflow trap handler will properly handle this case as will interrupt -handlers. -.PP -These \fB\-m\fR switches are supported in addition to the above -on \s-1SPARC\s0 V9 processors in 64\-bit environments. -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -Generate code for a processor running in little-endian mode. -.Ip "\fB\-m32\fR" 4 -.IX Item "-m32" -.PD 0 -.Ip "\fB\-m64\fR" 4 -.IX Item "-m64" -.PD -Generate code for a 32\-bit or 64\-bit environment. -The 32\-bit environment sets int, long and pointer to 32 bits. -The 64\-bit environment sets int to 32 bits and long and pointer -to 64 bits. -.Ip "\fB\-mcmodel=medlow\fR" 4 -.IX Item "-mcmodel=medlow" -Generate code for the Medium/Low code model: the program must be linked -in the low 32 bits of the address space. Pointers are 64 bits. -Programs can be statically or dynamically linked. -.Ip "\fB\-mcmodel=medmid\fR" 4 -.IX Item "-mcmodel=medmid" -Generate code for the Medium/Middle code model: the program must be linked -in the low 44 bits of the address space, the text segment must be less than -2G bytes, and data segment must be within 2G of the text segment. -Pointers are 64 bits. -.Ip "\fB\-mcmodel=medany\fR" 4 -.IX Item "-mcmodel=medany" -Generate code for the Medium/Anywhere code model: the program may be linked -anywhere in the address space, the text segment must be less than -2G bytes, and data segment must be within 2G of the text segment. -Pointers are 64 bits. -.Ip "\fB\-mcmodel=embmedany\fR" 4 -.IX Item "-mcmodel=embmedany" -Generate code for the Medium/Anywhere code model for embedded systems: -assume a 32\-bit text and a 32\-bit data segment, both starting anywhere -(determined at link time). Register \f(CW%g4\fR points to the base of the -data segment. Pointers are still 64 bits. -Programs are statically linked, \s-1PIC\s0 is not supported. -.Ip "\fB\-mstack-bias\fR" 4 -.IX Item "-mstack-bias" -.PD 0 -.Ip "\fB\-mno-stack-bias\fR" 4 -.IX Item "-mno-stack-bias" -.PD -With \fB\-mstack-bias\fR, \s-1GCC\s0 assumes that the stack pointer, and -frame pointer if present, are offset by \-2047 which must be added back -when making stack frame references. -Otherwise, assume no such offset is present. -.PP -.I "Convex Options" -.IX Subsection "Convex Options" -.PP -These \fB\-m\fR options are defined for Convex: -.Ip "\fB\-mc1\fR" 4 -.IX Item "-mc1" -Generate output for C1. The code will run on any Convex machine. -The preprocessor symbol \f(CW\*(C`_\|_convex_\|_c1_\|_\*(C'\fR is defined. -.Ip "\fB\-mc2\fR" 4 -.IX Item "-mc2" -Generate output for C2. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C2. -The preprocessor symbol \f(CW\*(C`_\|_convex_c2_\|_\*(C'\fR is defined. -.Ip "\fB\-mc32\fR" 4 -.IX Item "-mc32" -Generate output for C32xx. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C32. -The preprocessor symbol \f(CW\*(C`_\|_convex_c32_\|_\*(C'\fR is defined. -.Ip "\fB\-mc34\fR" 4 -.IX Item "-mc34" -Generate output for C34xx. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C34. -The preprocessor symbol \f(CW\*(C`_\|_convex_c34_\|_\*(C'\fR is defined. -.Ip "\fB\-mc38\fR" 4 -.IX Item "-mc38" -Generate output for C38xx. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C38. -The preprocessor symbol \f(CW\*(C`_\|_convex_c38_\|_\*(C'\fR is defined. -.Ip "\fB\-margcount\fR" 4 -.IX Item "-margcount" -Generate code which puts an argument count in the word preceding each -argument list. This is compatible with regular \s-1CC\s0, and a few programs -may need the argument count word. \s-1GDB\s0 and other source-level debuggers -do not need it; this info is in the symbol table. -.Ip "\fB\-mnoargcount\fR" 4 -.IX Item "-mnoargcount" -Omit the argument count word. This is the default. -.Ip "\fB\-mvolatile-cache\fR" 4 -.IX Item "-mvolatile-cache" -Allow volatile references to be cached. This is the default. -.Ip "\fB\-mvolatile-nocache\fR" 4 -.IX Item "-mvolatile-nocache" -Volatile references bypass the data cache, going all the way to memory. -This is only needed for multi-processor code that does not use standard -synchronization instructions. Making non-volatile references to volatile -locations will not necessarily work. -.Ip "\fB\-mlong32\fR" 4 -.IX Item "-mlong32" -Type long is 32 bits, the same as type int. This is the default. -.Ip "\fB\-mlong64\fR" 4 -.IX Item "-mlong64" -Type long is 64 bits, the same as type long long. This option is useless, -because no library support exists for it. -.PP -.I "\s-1AMD29K\s0 Options" -.IX Subsection "AMD29K Options" -.PP -These \fB\-m\fR options are defined for the \s-1AMD\s0 Am29000: -.Ip "\fB\-mdw\fR" 4 -.IX Item "-mdw" -Generate code that assumes the \f(CW\*(C`DW\*(C'\fR bit is set, i.e., that byte and -halfword operations are directly supported by the hardware. This is the -default. -.Ip "\fB\-mndw\fR" 4 -.IX Item "-mndw" -Generate code that assumes the \f(CW\*(C`DW\*(C'\fR bit is not set. -.Ip "\fB\-mbw\fR" 4 -.IX Item "-mbw" -Generate code that assumes the system supports byte and halfword write -operations. This is the default. -.Ip "\fB\-mnbw\fR" 4 -.IX Item "-mnbw" -Generate code that assumes the systems does not support byte and -halfword write operations. \fB\-mnbw\fR implies \fB\-mndw\fR. -.Ip "\fB\-msmall\fR" 4 -.IX Item "-msmall" -Use a small memory model that assumes that all function addresses are -either within a single 256 \s-1KB\s0 segment or at an absolute address of less -than 256k. This allows the \f(CW\*(C`call\*(C'\fR instruction to be used instead -of a \f(CW\*(C`const\*(C'\fR, \f(CW\*(C`consth\*(C'\fR, \f(CW\*(C`calli\*(C'\fR sequence. -.Ip "\fB\-mnormal\fR" 4 -.IX Item "-mnormal" -Use the normal memory model: Generate \f(CW\*(C`call\*(C'\fR instructions only when -calling functions in the same file and \f(CW\*(C`calli\*(C'\fR instructions -otherwise. This works if each file occupies less than 256 \s-1KB\s0 but allows -the entire executable to be larger than 256 \s-1KB\s0. This is the default. -.Ip "\fB\-mlarge\fR" 4 -.IX Item "-mlarge" -Always use \f(CW\*(C`calli\*(C'\fR instructions. Specify this option if you expect -a single file to compile into more than 256 \s-1KB\s0 of code. -.Ip "\fB\-m29050\fR" 4 -.IX Item "-m29050" -Generate code for the Am29050. -.Ip "\fB\-m29000\fR" 4 -.IX Item "-m29000" -Generate code for the Am29000. This is the default. -.Ip "\fB\-mkernel-registers\fR" 4 -.IX Item "-mkernel-registers" -Generate references to registers \f(CW\*(C`gr64\-gr95\*(C'\fR instead of to -registers \f(CW\*(C`gr96\-gr127\*(C'\fR. This option can be used when compiling -kernel code that wants a set of global registers disjoint from that used -by user-mode code. -.Sp -Note that when this option is used, register names in \fB\-f\fR flags -must use the normal, user-mode, names. -.Ip "\fB\-muser-registers\fR" 4 -.IX Item "-muser-registers" -Use the normal set of global registers, \f(CW\*(C`gr96\-gr127\*(C'\fR. This is the -default. -.Ip "\fB\-mstack-check\fR" 4 -.IX Item "-mstack-check" -.PD 0 -.Ip "\fB\-mno-stack-check\fR" 4 -.IX Item "-mno-stack-check" -.PD -Insert (or do not insert) a call to \f(CW\*(C`_\|_msp_check\*(C'\fR after each stack -adjustment. This is often used for kernel code. -.Ip "\fB\-mstorem-bug\fR" 4 -.IX Item "-mstorem-bug" -.PD 0 -.Ip "\fB\-mno-storem-bug\fR" 4 -.IX Item "-mno-storem-bug" -.PD -\&\fB\-mstorem-bug\fR handles 29k processors which cannot handle the -separation of a mtsrim insn and a storem instruction (most 29000 chips -to date, but not the 29050). -.Ip "\fB\-mno-reuse-arg-regs\fR" 4 -.IX Item "-mno-reuse-arg-regs" -.PD 0 -.Ip "\fB\-mreuse-arg-regs\fR" 4 -.IX Item "-mreuse-arg-regs" -.PD -\&\fB\-mno-reuse-arg-regs\fR tells the compiler to only use incoming argument -registers for copying out arguments. This helps detect calling a function -with fewer arguments than it was declared with. -.Ip "\fB\-mno-impure-text\fR" 4 -.IX Item "-mno-impure-text" -.PD 0 -.Ip "\fB\-mimpure-text\fR" 4 -.IX Item "-mimpure-text" -.PD -\&\fB\-mimpure-text\fR, used in addition to \fB\-shared\fR, tells the compiler to -not pass \fB\-assert pure-text\fR to the linker when linking a shared object. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. -.Ip "\fB\-mno-multm\fR" 4 -.IX Item "-mno-multm" -Do not generate multm or multmu instructions. This is useful for some embedded -systems which do not have trap handlers for these instructions. -.PP -.I "\s-1ARM\s0 Options" -.IX Subsection "ARM Options" -.PP -These \fB\-m\fR options are defined for Advanced \s-1RISC\s0 Machines (\s-1ARM\s0) -architectures: -.Ip "\fB\-mapcs-frame\fR" 4 -.IX Item "-mapcs-frame" -Generate a stack frame that is compliant with the \s-1ARM\s0 Procedure Call -Standard for all functions, even if this is not strictly necessary for -correct execution of the code. Specifying \fB\-fomit-frame-pointer\fR -with this option will cause the stack frames not to be generated for -leaf functions. The default is \fB\-mno-apcs-frame\fR. -.Ip "\fB\-mapcs\fR" 4 -.IX Item "-mapcs" -This is a synonym for \fB\-mapcs-frame\fR. -.Ip "\fB\-mapcs-26\fR" 4 -.IX Item "-mapcs-26" -Generate code for a processor running with a 26\-bit program counter, -and conforming to the function calling standards for the \s-1APCS\s0 26\-bit -option. This option replaces the \fB\-m2\fR and \fB\-m3\fR options -of previous releases of the compiler. -.Ip "\fB\-mapcs-32\fR" 4 -.IX Item "-mapcs-32" -Generate code for a processor running with a 32\-bit program counter, -and conforming to the function calling standards for the \s-1APCS\s0 32\-bit -option. This option replaces the \fB\-m6\fR option of previous releases -of the compiler. -.Ip "\fB\-mapcs-stack-check\fR" 4 -.IX Item "-mapcs-stack-check" -Generate code to check the amount of stack space available upon entry to -every function (that actually uses some stack space). If there is -insufficient space available then either the function -\&\fB_\|_rt_stkovf_split_small\fR or \fB_\|_rt_stkovf_split_big\fR will be -called, depending upon the amount of stack space required. The run time -system is required to provide these functions. The default is -\&\fB\-mno-apcs-stack-check\fR, since this produces smaller code. -.Ip "\fB\-mapcs-float\fR" 4 -.IX Item "-mapcs-float" -Pass floating point arguments using the float point registers. This is -one of the variants of the \s-1APCS\s0. This option is recommended if the -target hardware has a floating point unit or if a lot of floating point -arithmetic is going to be performed by the code. The default is -\&\fB\-mno-apcs-float\fR, since integer only code is slightly increased in -size if \fB\-mapcs-float\fR is used. -.Ip "\fB\-mapcs-reentrant\fR" 4 -.IX Item "-mapcs-reentrant" -Generate reentrant, position independent code. This is the equivalent -to specifying the \fB\-fpic\fR option. The default is -\&\fB\-mno-apcs-reentrant\fR. -.Ip "\fB\-mthumb-interwork\fR" 4 -.IX Item "-mthumb-interwork" -Generate code which supports calling between the \s-1ARM\s0 and \s-1THUMB\s0 -instruction sets. Without this option the two instruction sets cannot -be reliably used inside one program. The default is -\&\fB\-mno-thumb-interwork\fR, since slightly larger code is generated -when \fB\-mthumb-interwork\fR is specified. -.Ip "\fB\-mno-sched-prolog\fR" 4 -.IX Item "-mno-sched-prolog" -Prevent the reordering of instructions in the function prolog, or the -merging of those instruction with the instructions in the function's -body. This means that all functions will start with a recognizable set -of instructions (or in fact one of a choice from a small set of -different function prologues), and this information can be used to -locate the start if functions inside an executable piece of code. The -default is \fB\-msched-prolog\fR. -.Ip "\fB\-mhard-float\fR" 4 -.IX Item "-mhard-float" -Generate output containing floating point instructions. This is the -default. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not available for all \s-1ARM\s0 -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. -.Sp -\&\fB\-msoft-float\fR changes the calling convention in the output file; -therefore, it is only useful if you compile \fIall\fR of a program with -this option. In particular, you need to compile \fIlibgcc.a\fR, the -library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for -this to work. -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -Generate code for a processor running in little-endian mode. This is -the default for all standard configurations. -.Ip "\fB\-mbig-endian\fR" 4 -.IX Item "-mbig-endian" -Generate code for a processor running in big-endian mode; the default is -to compile code for a little-endian processor. -.Ip "\fB\-mwords-little-endian\fR" 4 -.IX Item "-mwords-little-endian" -This option only applies when generating code for big-endian processors. -Generate code for a little-endian word order but a big-endian byte -order. That is, a byte order of the form \fB32107654\fR. Note: this -option should only be used if you require compatibility with code for -big-endian \s-1ARM\s0 processors generated by versions of the compiler prior to -2.8. -.Ip "\fB\-malignment-traps\fR" 4 -.IX Item "-malignment-traps" -Generate code that will not trap if the \s-1MMU\s0 has alignment traps enabled. -On \s-1ARM\s0 architectures prior to ARMv4, there were no instructions to -access half-word objects stored in memory. However, when reading from -memory a feature of the \s-1ARM\s0 architecture allows a word load to be used, -even if the address is unaligned, and the processor core will rotate the -data as it is being loaded. This option tells the compiler that such -misaligned accesses will cause a \s-1MMU\s0 trap and that it should instead -synthesise the access as a series of byte accesses. The compiler can -still use word accesses to load half-word data if it knows that the -address is aligned to a word boundary. -.Sp -This option is ignored when compiling for \s-1ARM\s0 architecture 4 or later, -since these processors have instructions to directly access half-word -objects in memory. -.Ip "\fB\-mno-alignment-traps\fR" 4 -.IX Item "-mno-alignment-traps" -Generate code that assumes that the \s-1MMU\s0 will not trap unaligned -accesses. This produces better code when the target instruction set -does not have half-word memory operations (implementations prior to -ARMv4). -.Sp -Note that you cannot use this option to access unaligned word objects, -since the processor will only fetch one 32\-bit aligned object from -memory. -.Sp -The default setting for most targets is \-mno-alignment-traps, since -this produces better code when there are no half-word memory -instructions available. -.Ip "\fB\-mshort-load-bytes\fR" 4 -.IX Item "-mshort-load-bytes" -This is a deprecated alias for \fB\-malignment-traps\fR. -.Ip "\fB\-mno-short-load-bytes\fR" 4 -.IX Item "-mno-short-load-bytes" -This is a deprecated alias for \fB\-mno-alignment-traps\fR. -.Ip "\fB\-mshort-load-words\fR" 4 -.IX Item "-mshort-load-words" -This is a deprecated alias for \fB\-mno-alignment-traps\fR. -.Ip "\fB\-mno-short-load-words\fR" 4 -.IX Item "-mno-short-load-words" -This is a deprecated alias for \fB\-malignment-traps\fR. -.Ip "\fB\-mbsd\fR" 4 -.IX Item "-mbsd" -This option only applies to \s-1RISC\s0 iX. Emulate the native BSD-mode -compiler. This is the default if \fB\-ansi\fR is not specified. -.Ip "\fB\-mxopen\fR" 4 -.IX Item "-mxopen" -This option only applies to \s-1RISC\s0 iX. Emulate the native X/Open-mode -compiler. -.Ip "\fB\-mno-symrename\fR" 4 -.IX Item "-mno-symrename" -This option only applies to \s-1RISC\s0 iX. Do not run the assembler -post-processor, \fBsymrename\fR, after code has been assembled. -Normally it is necessary to modify some of the standard symbols in -preparation for linking with the \s-1RISC\s0 iX C library; this option -suppresses this pass. The post-processor is never run when the -compiler is built for cross-compilation. -.Ip "\fB\-mcpu=\fR" 4 -.IX Item "-mcpu=" -This specifies the name of the target \s-1ARM\s0 processor. \s-1GCC\s0 uses this name -to determine what kind of instructions it can use when generating -assembly code. Permissible names are: arm2, arm250, arm3, arm6, arm60, -arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, -arm70, arm700, arm700i, arm710, arm710c, arm7100, arm7500, arm7500fe, -arm7tdmi, arm8, strongarm, strongarm110, strongarm1100, arm8, arm810, -arm9, arm920, arm920t, arm9tdmi. -.Ip "\fB\-mtune=\fR" 4 -.IX Item "-mtune=" -This option is very similar to the \fB\-mcpu=\fR option, except that -instead of specifying the actual target processor type, and hence -restricting which instructions can be used, it specifies that \s-1GCC\s0 should -tune the performance of the code as if the target were of the type -specified in this option, but still choosing the instructions that it -will generate based on the cpu specified by a \fB\-mcpu=\fR option. -For some arm implementations better performance can be obtained by using -this option. -.Ip "\fB\-march=\fR" 4 -.IX Item "-march=" -This specifies the name of the target \s-1ARM\s0 architecture. \s-1GCC\s0 uses this -name to determine what kind of instructions it can use when generating -assembly code. This option can be used in conjunction with or instead -of the \fB\-mcpu=\fR option. Permissible names are: armv2, armv2a, -armv3, armv3m, armv4, armv4t, armv5. -.Ip "\fB\-mfpe=\fR" 4 -.IX Item "-mfpe=" -.PD 0 -.Ip "\fB\-mfp=\fR" 4 -.IX Item "-mfp=" -.PD -This specifies the version of the floating point emulation available on -the target. Permissible values are 2 and 3. \fB\-mfp=\fR is a synonym -for \fB\-mfpe=\fR to support older versions of \s-1GCC\s0. -.Ip "\fB\-mstructure-size-boundary=\fR" 4 -.IX Item "-mstructure-size-boundary=" -The size of all structures and unions will be rounded up to a multiple -of the number of bits set by this option. Permissible values are 8 and -32. The default value varies for different toolchains. For the \s-1COFF\s0 -targeted toolchain the default value is 8. Specifying the larger number -can produce faster, more efficient code, but can also increase the size -of the program. The two values are potentially incompatible. Code -compiled with one value cannot necessarily expect to work with code or -libraries compiled with the other value, if they exchange information -using structures or unions. Programmers are encouraged to use the 32 -value as future versions of the toolchain may default to this value. -.Ip "\fB\-mabort-on-noreturn\fR" 4 -.IX Item "-mabort-on-noreturn" -Generate a call to the function abort at the end of a noreturn function. -It will be executed if the function tries to return. -.Ip "\fB\-mlong-calls\fR" 4 -.IX Item "-mlong-calls" -.PD 0 -.Ip "\fB\-mno-long-calls\fR" 4 -.IX Item "-mno-long-calls" -.PD -Tells the compiler to perform function calls by first loading the -address of the function into a register and then performing a subroutine -call on this register. This switch is needed if the target function -will lie outside of the 64 megabyte addressing range of the offset based -version of subroutine call instruction. -.Sp -Even if this switch is enabled, not all function calls will be turned -into long calls. The heuristic is that static functions, functions -which have the \fBshort-call\fR attribute, functions that are inside -the scope of a \fB#pragma no_long_calls\fR directive and functions whose -definitions have already been compiled within the current compilation -unit, will not be turned into long calls. The exception to this rule is -that weak function definitions, functions with the \fBlong-call\fR -attribute or the \fBsection\fR attribute, and functions that are within -the scope of a \fB#pragma long_calls\fR directive, will always be -turned into long calls. -.Sp -This feature is not enabled by default. Specifying -\&\fB\*(--no-long-calls\fR will restore the default behaviour, as will -placing the function calls within the scope of a \fB#pragma -long_calls_off\fR directive. Note these switches have no effect on how -the compiler generates code to handle function calls via function -pointers. -.Ip "\fB\-mnop-fun-dllimport\fR" 4 -.IX Item "-mnop-fun-dllimport" -Disable the support for the \fIdllimport\fR attribute. -.Ip "\fB\-msingle-pic-base\fR" 4 -.IX Item "-msingle-pic-base" -Treat the register used for \s-1PIC\s0 addressing as read-only, rather than -loading it in the prologue for each function. The run-time system is -responsible for initialising this register with an appropriate value -before execution begins. -.Ip "\fB\-mpic-register=\fR" 4 -.IX Item "-mpic-register=" -Specify the register to be used for \s-1PIC\s0 addressing. The default is R10 -unless stack-checking is enabled, when R9 is used. -.PP -.I "Thumb Options" -.IX Subsection "Thumb Options" -.Ip "\fB\-mthumb-interwork\fR" 4 -.IX Item "-mthumb-interwork" -Generate code which supports calling between the \s-1THUMB\s0 and \s-1ARM\s0 -instruction sets. Without this option the two instruction sets cannot -be reliably used inside one program. The default is -\&\fB\-mno-thumb-interwork\fR, since slightly smaller code is generated -with this option. -.Ip "\fB\-mtpcs-frame\fR" 4 -.IX Item "-mtpcs-frame" -Generate a stack frame that is compliant with the Thumb Procedure Call -Standard for all non-leaf functions. (A leaf function is one that does -not call any other functions). The default is \fB\-mno-apcs-frame\fR. -.Ip "\fB\-mtpcs-leaf-frame\fR" 4 -.IX Item "-mtpcs-leaf-frame" -Generate a stack frame that is compliant with the Thumb Procedure Call -Standard for all leaf functions. (A leaf function is one that does -not call any other functions). The default is \fB\-mno-apcs-leaf-frame\fR. -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -Generate code for a processor running in little-endian mode. This is -the default for all standard configurations. -.Ip "\fB\-mbig-endian\fR" 4 -.IX Item "-mbig-endian" -Generate code for a processor running in big-endian mode. -.Ip "\fB\-mstructure-size-boundary=\fR" 4 -.IX Item "-mstructure-size-boundary=" -The size of all structures and unions will be rounded up to a multiple -of the number of bits set by this option. Permissible values are 8 and -32. The default value varies for different toolchains. For the \s-1COFF\s0 -targeted toolchain the default value is 8. Specifying the larger number -can produced faster, more efficient code, but can also increase the size -of the program. The two values are potentially incompatible. Code -compiled with one value cannot necessarily expect to work with code or -libraries compiled with the other value, if they exchange information -using structures or unions. Programmers are encouraged to use the 32 -value as future versions of the toolchain may default to this value. -.Ip "\fB\-mnop-fun-dllimport\fR" 4 -.IX Item "-mnop-fun-dllimport" -Disable the support for the \fIdllimport\fR attribute. -.Ip "\fB\-mcallee-super-interworking\fR" 4 -.IX Item "-mcallee-super-interworking" -Gives all externally visible functions in the file being compiled an \s-1ARM\s0 -instruction set header which switches to Thumb mode before executing the -rest of the function. This allows these functions to be called from -non-interworking code. -.Ip "\fB\-mcaller-super-interworking\fR" 4 -.IX Item "-mcaller-super-interworking" -Allows calls via function pointers (including virtual functions) to -execute correctly regardless of whether the target code has been -compiled for interworking or not. There is a small overhead in the cost -of executing a function pointer if this option is enabled. -.Ip "\fB\-msingle-pic-base\fR" 4 -.IX Item "-msingle-pic-base" -Treat the register used for \s-1PIC\s0 addressing as read-only, rather than -loading it in the prologue for each function. The run-time system is -responsible for initialising this register with an appropriate value -before execution begins. -.Ip "\fB\-mpic-register=\fR" 4 -.IX Item "-mpic-register=" -Specify the register to be used for \s-1PIC\s0 addressing. The default is R10. -.PP -.I "\s-1MN10200\s0 Options" -.IX Subsection "MN10200 Options" -.PP -These \fB\-m\fR options are defined for Matsushita \s-1MN10200\s0 architectures: -.Ip "\fB\-mrelax\fR" 4 -.IX Item "-mrelax" -Indicate to the linker that it should perform a relaxation optimization pass -to shorten branches, calls and absolute memory addresses. This option only -has an effect when used on the command line for the final link step. -.Sp -This option makes symbolic debugging impossible. -.PP -.I "\s-1MN10300\s0 Options" -.IX Subsection "MN10300 Options" -.PP -These \fB\-m\fR options are defined for Matsushita \s-1MN10300\s0 architectures: -.Ip "\fB\-mmult-bug\fR" 4 -.IX Item "-mmult-bug" -Generate code to avoid bugs in the multiply instructions for the \s-1MN10300\s0 -processors. This is the default. -.Ip "\fB\-mno-mult-bug\fR" 4 -.IX Item "-mno-mult-bug" -Do not generate code to avoid bugs in the multiply instructions for the -\&\s-1MN10300\s0 processors. -.Ip "\fB\-mam33\fR" 4 -.IX Item "-mam33" -Generate code which uses features specific to the \s-1AM33\s0 processor. -.Ip "\fB\-mno-am33\fR" 4 -.IX Item "-mno-am33" -Do not generate code which uses features specific to the \s-1AM33\s0 processor. This -is the default. -.Ip "\fB\-mrelax\fR" 4 -.IX Item "-mrelax" -Indicate to the linker that it should perform a relaxation optimization pass -to shorten branches, calls and absolute memory addresses. This option only -has an effect when used on the command line for the final link step. -.Sp -This option makes symbolic debugging impossible. -.PP -.I "M32R/D Options" -.IX Subsection "M32R/D Options" -.PP -These \fB\-m\fR options are defined for Mitsubishi M32R/D architectures: -.Ip "\fB\-mcode-model=small\fR" 4 -.IX Item "-mcode-model=small" -Assume all objects live in the lower 16MB of memory (so that their addresses -can be loaded with the \f(CW\*(C`ld24\*(C'\fR instruction), and assume all subroutines -are reachable with the \f(CW\*(C`bl\*(C'\fR instruction. -This is the default. -.Sp -The addressability of a particular object can be set with the -\&\f(CW\*(C`model\*(C'\fR attribute. -.Ip "\fB\-mcode-model=medium\fR" 4 -.IX Item "-mcode-model=medium" -Assume objects may be anywhere in the 32\-bit address space (the compiler -will generate \f(CW\*(C`seth/add3\*(C'\fR instructions to load their addresses), and -assume all subroutines are reachable with the \f(CW\*(C`bl\*(C'\fR instruction. -.Ip "\fB\-mcode-model=large\fR" 4 -.IX Item "-mcode-model=large" -Assume objects may be anywhere in the 32\-bit address space (the compiler -will generate \f(CW\*(C`seth/add3\*(C'\fR instructions to load their addresses), and -assume subroutines may not be reachable with the \f(CW\*(C`bl\*(C'\fR instruction -(the compiler will generate the much slower \f(CW\*(C`seth/add3/jl\*(C'\fR -instruction sequence). -.Ip "\fB\-msdata=none\fR" 4 -.IX Item "-msdata=none" -Disable use of the small data area. Variables will be put into -one of \fB.data\fR, \fBbss\fR, or \fB.rodata\fR (unless the -\&\f(CW\*(C`section\*(C'\fR attribute has been specified). -This is the default. -.Sp -The small data area consists of sections \fB.sdata\fR and \fB.sbss\fR. -Objects may be explicitly put in the small data area with the -\&\f(CW\*(C`section\*(C'\fR attribute using one of these sections. -.Ip "\fB\-msdata=sdata\fR" 4 -.IX Item "-msdata=sdata" -Put small global and static data in the small data area, but do not -generate special code to reference them. -.Ip "\fB\-msdata=use\fR" 4 -.IX Item "-msdata=use" -Put small global and static data in the small data area, and generate -special instructions to reference them. -.Ip "\fB\-G\fR \fInum\fR" 4 -.IX Item "-G num" -Put global and static objects less than or equal to \fInum\fR bytes -into the small data or bss sections instead of the normal data or bss -sections. The default value of \fInum\fR is 8. -The \fB\-msdata\fR option must be set to one of \fBsdata\fR or \fBuse\fR -for this option to have any effect. -.Sp -All modules should be compiled with the same \fB\-G\fR \fInum\fR value. -Compiling with different values of \fInum\fR may or may not work; if it -doesn't the linker will give an error message \- incorrect code will not be -generated. -.PP -.I "M88K Options" -.IX Subsection "M88K Options" -.PP -These \fB\-m\fR options are defined for Motorola 88k architectures: -.Ip "\fB\-m88000\fR" 4 -.IX Item "-m88000" -Generate code that works well on both the m88100 and the -m88110. -.Ip "\fB\-m88100\fR" 4 -.IX Item "-m88100" -Generate code that works best for the m88100, but that also -runs on the m88110. -.Ip "\fB\-m88110\fR" 4 -.IX Item "-m88110" -Generate code that works best for the m88110, and may not run -on the m88100. -.Ip "\fB\-mbig-pic\fR" 4 -.IX Item "-mbig-pic" -Obsolete option to be removed from the next revision. -Use \fB\-fPIC\fR. -.Ip "\fB\-midentify-revision\fR" 4 -.IX Item "-midentify-revision" -Include an \f(CW\*(C`ident\*(C'\fR directive in the assembler output recording the -source file name, compiler name and version, timestamp, and compilation -flags used. -.Ip "\fB\-mno-underscores\fR" 4 -.IX Item "-mno-underscores" -In assembler output, emit symbol names without adding an underscore -character at the beginning of each name. The default is to use an -underscore as prefix on each name. -.Ip "\fB\-mocs-debug-info\fR" 4 -.IX Item "-mocs-debug-info" -.PD 0 -.Ip "\fB\-mno-ocs-debug-info\fR" 4 -.IX Item "-mno-ocs-debug-info" -.PD -Include (or omit) additional debugging information (about registers used -in each stack frame) as specified in the 88open Object Compatibility -Standard, ``\s-1OCS\s0''. This extra information allows debugging of code that -has had the frame pointer eliminated. The default for \s-1DG/UX\s0, SVr4, and -Delta 88 SVr3.2 is to include this information; other 88k configurations -omit this information by default. -.Ip "\fB\-mocs-frame-position\fR" 4 -.IX Item "-mocs-frame-position" -When emitting \s-1COFF\s0 debugging information for automatic variables and -parameters stored on the stack, use the offset from the canonical frame -address, which is the stack pointer (register 31) on entry to the -function. The \s-1DG/UX\s0, SVr4, Delta88 SVr3.2, and \s-1BCS\s0 configurations use -\&\fB\-mocs-frame-position\fR; other 88k configurations have the default -\&\fB\-mno-ocs-frame-position\fR. -.Ip "\fB\-mno-ocs-frame-position\fR" 4 -.IX Item "-mno-ocs-frame-position" -When emitting \s-1COFF\s0 debugging information for automatic variables and -parameters stored on the stack, use the offset from the frame pointer -register (register 30). When this option is in effect, the frame -pointer is not eliminated when debugging information is selected by the -\&\-g switch. -.Ip "\fB\-moptimize-arg-area\fR" 4 -.IX Item "-moptimize-arg-area" -.PD 0 -.Ip "\fB\-mno-optimize-arg-area\fR" 4 -.IX Item "-mno-optimize-arg-area" -.PD -Control how function arguments are stored in stack frames. -\&\fB\-moptimize-arg-area\fR saves space by optimizing them, but this -conflicts with the 88open specifications. The opposite alternative, -\&\fB\-mno-optimize-arg-area\fR, agrees with 88open standards. By default -\&\s-1GCC\s0 does not optimize the argument area. -.Ip "\fB\-mshort-data-\fR\fInum\fR" 4 -.IX Item "-mshort-data-num" -Generate smaller data references by making them relative to \f(CW\*(C`r0\*(C'\fR, -which allows loading a value using a single instruction (rather than the -usual two). You control which data references are affected by -specifying \fInum\fR with this option. For example, if you specify -\&\fB\-mshort-data-512\fR, then the data references affected are those -involving displacements of less than 512 bytes. -\&\fB\-mshort-data-\fR\fInum\fR is not effective for \fInum\fR greater -than 64k. -.Ip "\fB\-mserialize-volatile\fR" 4 -.IX Item "-mserialize-volatile" -.PD 0 -.Ip "\fB\-mno-serialize-volatile\fR" 4 -.IX Item "-mno-serialize-volatile" -.PD -Do, or don't, generate code to guarantee sequential consistency -of volatile memory references. By default, consistency is -guaranteed. -.Sp -The order of memory references made by the \s-1MC88110\s0 processor does -not always match the order of the instructions requesting those -references. In particular, a load instruction may execute before -a preceding store instruction. Such reordering violates -sequential consistency of volatile memory references, when there -are multiple processors. When consistency must be guaranteed, -\&\s-1GNU\s0 C generates special instructions, as needed, to force -execution in the proper order. -.Sp -The \s-1MC88100\s0 processor does not reorder memory references and so -always provides sequential consistency. However, by default, \s-1GNU\s0 -C generates the special instructions to guarantee consistency -even when you use \fB\-m88100\fR, so that the code may be run on an -\&\s-1MC88110\s0 processor. If you intend to run your code only on the -\&\s-1MC88100\s0 processor, you may use \fB\-mno-serialize-volatile\fR. -.Sp -The extra code generated to guarantee consistency may affect the -performance of your application. If you know that you can safely -forgo this guarantee, you may use \fB\-mno-serialize-volatile\fR. -.Ip "\fB\-msvr4\fR" 4 -.IX Item "-msvr4" -.PD 0 -.Ip "\fB\-msvr3\fR" 4 -.IX Item "-msvr3" -.PD -Turn on (\fB\-msvr4\fR) or off (\fB\-msvr3\fR) compiler extensions -related to System V release 4 (SVr4). This controls the following: -.RS 4 -.Ip "1." 4 -Which variant of the assembler syntax to emit. -.Ip "2." 4 -\&\fB\-msvr4\fR makes the C preprocessor recognize \fB#pragma weak\fR -that is used on System V release 4. -.Ip "3." 4 -\&\fB\-msvr4\fR makes \s-1GCC\s0 issue additional declaration directives used in -SVr4. -.RE -.RS 4 -.Sp -\&\fB\-msvr4\fR is the default for the m88k-motorola-sysv4 and -m88k-dg-dgux m88k configurations. \fB\-msvr3\fR is the default for all -other m88k configurations. -.RE -.Ip "\fB\-mversion-03.00\fR" 4 -.IX Item "-mversion-03.00" -This option is obsolete, and is ignored. -.Ip "\fB\-mno-check-zero-division\fR" 4 -.IX Item "-mno-check-zero-division" -.PD 0 -.Ip "\fB\-mcheck-zero-division\fR" 4 -.IX Item "-mcheck-zero-division" -.PD -Do, or don't, generate code to guarantee that integer division by -zero will be detected. By default, detection is guaranteed. -.Sp -Some models of the \s-1MC88100\s0 processor fail to trap upon integer -division by zero under certain conditions. By default, when -compiling code that might be run on such a processor, \s-1GNU\s0 C -generates code that explicitly checks for zero-valued divisors -and traps with exception number 503 when one is detected. Use of -mno-check-zero-division suppresses such checking for code -generated to run on an \s-1MC88100\s0 processor. -.Sp -\&\s-1GNU\s0 C assumes that the \s-1MC88110\s0 processor correctly detects all -instances of integer division by zero. When \fB\-m88110\fR is -specified, both \fB\-mcheck-zero-division\fR and -\&\fB\-mno-check-zero-division\fR are ignored, and no explicit checks for -zero-valued divisors are generated. -.Ip "\fB\-muse-div-instruction\fR" 4 -.IX Item "-muse-div-instruction" -Use the div instruction for signed integer division on the -\&\s-1MC88100\s0 processor. By default, the div instruction is not used. -.Sp -On the \s-1MC88100\s0 processor the signed integer division instruction -div) traps to the operating system on a negative operand. The -operating system transparently completes the operation, but at a -large cost in execution time. By default, when compiling code -that might be run on an \s-1MC88100\s0 processor, \s-1GNU\s0 C emulates signed -integer division using the unsigned integer division instruction -divu), thereby avoiding the large penalty of a trap to the -operating system. Such emulation has its own, smaller, execution -cost in both time and space. To the extent that your code's -important signed integer division operations are performed on two -nonnegative operands, it may be desirable to use the div -instruction directly. -.Sp -On the \s-1MC88110\s0 processor the div instruction (also known as the -divs instruction) processes negative operands without trapping to -the operating system. When \fB\-m88110\fR is specified, -\&\fB\-muse-div-instruction\fR is ignored, and the div instruction is used -for signed integer division. -.Sp -Note that the result of dividing \s-1INT_MIN\s0 by \-1 is undefined. In -particular, the behavior of such a division with and without -\&\fB\-muse-div-instruction\fR may differ. -.Ip "\fB\-mtrap-large-shift\fR" 4 -.IX Item "-mtrap-large-shift" -.PD 0 -.Ip "\fB\-mhandle-large-shift\fR" 4 -.IX Item "-mhandle-large-shift" -.PD -Include code to detect bit-shifts of more than 31 bits; respectively, -trap such shifts or emit code to handle them properly. By default \s-1GCC\s0 -makes no special provision for large bit shifts. -.Ip "\fB\-mwarn-passed-structs\fR" 4 -.IX Item "-mwarn-passed-structs" -Warn when a function passes a struct as an argument or result. -Structure-passing conventions have changed during the evolution of the C -language, and are often the source of portability problems. By default, -\&\s-1GCC\s0 issues no such warning. -.PP -.I "\s-1IBM\s0 \s-1RS/6000\s0 and PowerPC Options" -.IX Subsection "IBM RS/6000 and PowerPC Options" -.PP -These \fB\-m\fR options are defined for the \s-1IBM\s0 \s-1RS/6000\s0 and PowerPC: -.Ip "\fB\-mpower\fR" 4 -.IX Item "-mpower" -.PD 0 -.Ip "\fB\-mno-power\fR" 4 -.IX Item "-mno-power" -.Ip "\fB\-mpower2\fR" 4 -.IX Item "-mpower2" -.Ip "\fB\-mno-power2\fR" 4 -.IX Item "-mno-power2" -.Ip "\fB\-mpowerpc\fR" 4 -.IX Item "-mpowerpc" -.Ip "\fB\-mno-powerpc\fR" 4 -.IX Item "-mno-powerpc" -.Ip "\fB\-mpowerpc-gpopt\fR" 4 -.IX Item "-mpowerpc-gpopt" -.Ip "\fB\-mno-powerpc-gpopt\fR" 4 -.IX Item "-mno-powerpc-gpopt" -.Ip "\fB\-mpowerpc-gfxopt\fR" 4 -.IX Item "-mpowerpc-gfxopt" -.Ip "\fB\-mno-powerpc-gfxopt\fR" 4 -.IX Item "-mno-powerpc-gfxopt" -.Ip "\fB\-mpowerpc64\fR" 4 -.IX Item "-mpowerpc64" -.Ip "\fB\-mno-powerpc64\fR" 4 -.IX Item "-mno-powerpc64" -.PD -\&\s-1GCC\s0 supports two related instruction set architectures for the -\&\s-1RS/6000\s0 and PowerPC. The \fI\s-1POWER\s0\fR instruction set are those -instructions supported by the \fBrios\fR chip set used in the original -\&\s-1RS/6000\s0 systems and the \fIPowerPC\fR instruction set is the -architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and -the \s-1IBM\s0 4xx microprocessors. -.Sp -Neither architecture is a subset of the other. However there is a -large common subset of instructions supported by both. An \s-1MQ\s0 -register is included in processors supporting the \s-1POWER\s0 architecture. -.Sp -You use these options to specify which instructions are available on the -processor you are using. The default value of these options is -determined when configuring \s-1GCC\s0. Specifying the -\&\fB\-mcpu=\fR\fIcpu_type\fR overrides the specification of these -options. We recommend you use the \fB\-mcpu=\fR\fIcpu_type\fR option -rather than the options listed above. -.Sp -The \fB\-mpower\fR option allows \s-1GCC\s0 to generate instructions that -are found only in the \s-1POWER\s0 architecture and to use the \s-1MQ\s0 register. -Specifying \fB\-mpower2\fR implies \fB\-power\fR and also allows \s-1GCC\s0 -to generate instructions that are present in the \s-1POWER2\s0 architecture but -not the original \s-1POWER\s0 architecture. -.Sp -The \fB\-mpowerpc\fR option allows \s-1GCC\s0 to generate instructions that -are found only in the 32\-bit subset of the PowerPC architecture. -Specifying \fB\-mpowerpc-gpopt\fR implies \fB\-mpowerpc\fR and also allows -\&\s-1GCC\s0 to use the optional PowerPC architecture instructions in the -General Purpose group, including floating-point square root. Specifying -\&\fB\-mpowerpc-gfxopt\fR implies \fB\-mpowerpc\fR and also allows \s-1GCC\s0 to -use the optional PowerPC architecture instructions in the Graphics -group, including floating-point select. -.Sp -The \fB\-mpowerpc64\fR option allows \s-1GCC\s0 to generate the additional -64\-bit instructions that are found in the full PowerPC64 architecture -and to treat GPRs as 64\-bit, doubleword quantities. \s-1GCC\s0 defaults to -\&\fB\-mno-powerpc64\fR. -.Sp -If you specify both \fB\-mno-power\fR and \fB\-mno-powerpc\fR, \s-1GCC\s0 -will use only the instructions in the common subset of both -architectures plus some special \s-1AIX\s0 common-mode calls, and will not use -the \s-1MQ\s0 register. Specifying both \fB\-mpower\fR and \fB\-mpowerpc\fR -permits \s-1GCC\s0 to use any instruction from either architecture and to -allow use of the \s-1MQ\s0 register; specify this for the Motorola \s-1MPC601\s0. -.Ip "\fB\-mnew-mnemonics\fR" 4 -.IX Item "-mnew-mnemonics" -.PD 0 -.Ip "\fB\-mold-mnemonics\fR" 4 -.IX Item "-mold-mnemonics" -.PD -Select which mnemonics to use in the generated assembler code. -\&\fB\-mnew-mnemonics\fR requests output that uses the assembler mnemonics -defined for the PowerPC architecture, while \fB\-mold-mnemonics\fR -requests the assembler mnemonics defined for the \s-1POWER\s0 architecture. -Instructions defined in only one architecture have only one mnemonic; -\&\s-1GCC\s0 uses that mnemonic irrespective of which of these options is -specified. -.Sp -\&\s-1GCC\s0 defaults to the mnemonics appropriate for the architecture in -use. Specifying \fB\-mcpu=\fR\fIcpu_type\fR sometimes overrides the -value of these option. Unless you are building a cross-compiler, you -should normally not specify either \fB\-mnew-mnemonics\fR or -\&\fB\-mold-mnemonics\fR, but should instead accept the default. -.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 -.IX Item "-mcpu=cpu_type" -Set architecture type, register usage, choice of mnemonics, and -instruction scheduling parameters for machine type \fIcpu_type\fR. -Supported values for \fIcpu_type\fR are \fBrios\fR, \fBrios1\fR, -\&\fBrsc\fR, \fBrios2\fR, \fBrs64a\fR, \fB601\fR, \fB602\fR, -\&\fB603\fR, \fB603e\fR, \fB604\fR, \fB604e\fR, \fB620\fR, -\&\fB630\fR, \fB740\fR, \fB750\fR, \fBpower\fR, \fBpower2\fR, -\&\fBpowerpc\fR, \fB403\fR, \fB505\fR, \fB801\fR, \fB821\fR, -\&\fB823\fR, and \fB860\fR and \fBcommon\fR. \fB\-mcpu=power\fR, -\&\fB\-mcpu=power2\fR, \fB\-mcpu=powerpc\fR, and \fB\-mcpu=powerpc64\fR -specify generic \s-1POWER\s0, \s-1POWER2\s0, pure 32\-bit PowerPC (i.e., not \s-1MPC601\s0), -and 64\-bit PowerPC architecture machine types, with an appropriate, -generic processor model assumed for scheduling purposes. -.Sp -Specifying any of the following options: -\&\fB\-mcpu=rios1\fR, \fB\-mcpu=rios2\fR, \fB\-mcpu=rsc\fR, -\&\fB\-mcpu=power\fR, or \fB\-mcpu=power2\fR -enables the \fB\-mpower\fR option and disables the \fB\-mpowerpc\fR option; -\&\fB\-mcpu=601\fR enables both the \fB\-mpower\fR and \fB\-mpowerpc\fR options. -All of \fB\-mcpu=rs64a\fR, \fB\-mcpu=602\fR, \fB\-mcpu=603\fR, -\&\fB\-mcpu=603e\fR, \fB\-mcpu=604\fR, \fB\-mcpu=620\fR, \fB\-mcpu=630\fR, -\&\fB\-mcpu=740\fR, and \fB\-mcpu=750\fR -enable the \fB\-mpowerpc\fR option and disable the \fB\-mpower\fR option. -Exactly similarly, all of \fB\-mcpu=403\fR, -\&\fB\-mcpu=505\fR, \fB\-mcpu=821\fR, \fB\-mcpu=860\fR and \fB\-mcpu=powerpc\fR -enable the \fB\-mpowerpc\fR option and disable the \fB\-mpower\fR option. -\&\fB\-mcpu=common\fR disables both the -\&\fB\-mpower\fR and \fB\-mpowerpc\fR options. -.Sp -\&\s-1AIX\s0 versions 4 or greater selects \fB\-mcpu=common\fR by default, so -that code will operate on all members of the \s-1RS/6000\s0 \s-1POWER\s0 and PowerPC -families. In that case, \s-1GCC\s0 will use only the instructions in the -common subset of both architectures plus some special \s-1AIX\s0 common-mode -calls, and will not use the \s-1MQ\s0 register. \s-1GCC\s0 assumes a generic -processor model for scheduling purposes. -.Sp -Specifying any of the options \fB\-mcpu=rios1\fR, \fB\-mcpu=rios2\fR, -\&\fB\-mcpu=rsc\fR, \fB\-mcpu=power\fR, or \fB\-mcpu=power2\fR also -disables the \fBnew-mnemonics\fR option. Specifying \fB\-mcpu=601\fR, -\&\fB\-mcpu=602\fR, \fB\-mcpu=603\fR, \fB\-mcpu=603e\fR, \fB\-mcpu=604\fR, -\&\fB\-mcpu=620\fR, \fB\-mcpu=630\fR, \fB\-mcpu=403\fR, \fB\-mcpu=505\fR, -\&\fB\-mcpu=821\fR, \fB\-mcpu=860\fR or \fB\-mcpu=powerpc\fR also enables -the \fBnew-mnemonics\fR option. -.Sp -Specifying \fB\-mcpu=403\fR, \fB\-mcpu=821\fR, or \fB\-mcpu=860\fR also -enables the \fB\-msoft-float\fR option. -.Ip "\fB\-mtune=\fR\fIcpu_type\fR" 4 -.IX Item "-mtune=cpu_type" -Set the instruction scheduling parameters for machine type -\&\fIcpu_type\fR, but do not set the architecture type, register usage, -choice of mnemonics like \fB\-mcpu=\fR\fIcpu_type\fR would. The same -values for \fIcpu_type\fR are used for \fB\-mtune=\fR\fIcpu_type\fR as -for \fB\-mcpu=\fR\fIcpu_type\fR. The \fB\-mtune=\fR\fIcpu_type\fR -option overrides the \fB\-mcpu=\fR\fIcpu_type\fR option in terms of -instruction scheduling parameters. -.Ip "\fB\-mfull-toc\fR" 4 -.IX Item "-mfull-toc" -.PD 0 -.Ip "\fB\-mno-fp-in-toc\fR" 4 -.IX Item "-mno-fp-in-toc" -.Ip "\fB\-mno-sum-in-toc\fR" 4 -.IX Item "-mno-sum-in-toc" -.Ip "\fB\-mminimal-toc\fR" 4 -.IX Item "-mminimal-toc" -.PD -Modify generation of the \s-1TOC\s0 (Table Of Contents), which is created for -every executable file. The \fB\-mfull-toc\fR option is selected by -default. In that case, \s-1GCC\s0 will allocate at least one \s-1TOC\s0 entry for -each unique non-automatic variable reference in your program. \s-1GCC\s0 -will also place floating-point constants in the \s-1TOC\s0. However, only -16,384 entries are available in the \s-1TOC\s0. -.Sp -If you receive a linker error message that saying you have overflowed -the available \s-1TOC\s0 space, you can reduce the amount of \s-1TOC\s0 space used -with the \fB\-mno-fp-in-toc\fR and \fB\-mno-sum-in-toc\fR options. -\&\fB\-mno-fp-in-toc\fR prevents \s-1GCC\s0 from putting floating-point -constants in the \s-1TOC\s0 and \fB\-mno-sum-in-toc\fR forces \s-1GCC\s0 to -generate code to calculate the sum of an address and a constant at -run-time instead of putting that sum into the \s-1TOC\s0. You may specify one -or both of these options. Each causes \s-1GCC\s0 to produce very slightly -slower and larger code at the expense of conserving \s-1TOC\s0 space. -.Sp -If you still run out of space in the \s-1TOC\s0 even when you specify both of -these options, specify \fB\-mminimal-toc\fR instead. This option causes -\&\s-1GCC\s0 to make only one \s-1TOC\s0 entry for every file. When you specify this -option, \s-1GCC\s0 will produce code that is slower and larger but which -uses extremely little \s-1TOC\s0 space. You may wish to use this option -only on files that contain less frequently executed code. -.Ip "\fB\-maix64\fR" 4 -.IX Item "-maix64" -.PD 0 -.Ip "\fB\-maix32\fR" 4 -.IX Item "-maix32" -.PD -Enable 64\-bit \s-1AIX\s0 \s-1ABI\s0 and calling convention: 64\-bit pointers, 64\-bit -\&\f(CW\*(C`long\*(C'\fR type, and the infrastructure needed to support them. -Specifying \fB\-maix64\fR implies \fB\-mpowerpc64\fR and -\&\fB\-mpowerpc\fR, while \fB\-maix32\fR disables the 64\-bit \s-1ABI\s0 and -implies \fB\-mno-powerpc64\fR. \s-1GCC\s0 defaults to \fB\-maix32\fR. -.Ip "\fB\-mxl-call\fR" 4 -.IX Item "-mxl-call" -.PD 0 -.Ip "\fB\-mno-xl-call\fR" 4 -.IX Item "-mno-xl-call" -.PD -On \s-1AIX\s0, pass floating-point arguments to prototyped functions beyond the -register save area (\s-1RSA\s0) on the stack in addition to argument FPRs. The -\&\s-1AIX\s0 calling convention was extended but not initially documented to -handle an obscure K&R C case of calling a function that takes the -address of its arguments with fewer arguments than declared. \s-1AIX\s0 \s-1XL\s0 -compilers access floating point arguments which do not fit in the -\&\s-1RSA\s0 from the stack when a subroutine is compiled without -optimization. Because always storing floating-point arguments on the -stack is inefficient and rarely needed, this option is not enabled by -default and only is necessary when calling subroutines compiled by \s-1AIX\s0 -\&\s-1XL\s0 compilers without optimization. -.Ip "\fB\-mthreads\fR" 4 -.IX Item "-mthreads" -Support \fI\s-1AIX\s0 Threads\fR. Link an application written to use -\&\fIpthreads\fR with special libraries and startup code to enable the -application to run. -.Ip "\fB\-mpe\fR" 4 -.IX Item "-mpe" -Support \fI\s-1IBM\s0 \s-1RS/6000\s0 \s-1SP\s0\fR \fIParallel Environment\fR (\s-1PE\s0). Link an -application written to use message passing with special startup code to -enable the application to run. The system must have \s-1PE\s0 installed in the -standard location (\fI/usr/lpp/ppe.poe/\fR), or the \fIspecs\fR file -must be overridden with the \fB\-specs=\fR option to specify the -appropriate directory location. The Parallel Environment does not -support threads, so the \fB\-mpe\fR option and the \fB\-mthreads\fR -option are incompatible. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -.PD 0 -.Ip "\fB\-mhard-float\fR" 4 -.IX Item "-mhard-float" -.PD -Generate code that does not use (uses) the floating-point register set. -Software floating point emulation is provided if you use the -\&\fB\-msoft-float\fR option, and pass the option to \s-1GCC\s0 when linking. -.Ip "\fB\-mmultiple\fR" 4 -.IX Item "-mmultiple" -.PD 0 -.Ip "\fB\-mno-multiple\fR" 4 -.IX Item "-mno-multiple" -.PD -Generate code that uses (does not use) the load multiple word -instructions and the store multiple word instructions. These -instructions are generated by default on \s-1POWER\s0 systems, and not -generated on PowerPC systems. Do not use \fB\-mmultiple\fR on little -endian PowerPC systems, since those instructions do not work when the -processor is in little endian mode. The exceptions are \s-1PPC740\s0 and -\&\s-1PPC750\s0 which permit the instructions usage in little endian mode. -.Ip "\fB\-mstring\fR" 4 -.IX Item "-mstring" -.PD 0 -.Ip "\fB\-mno-string\fR" 4 -.IX Item "-mno-string" -.PD -Generate code that uses (does not use) the load string instructions -and the store string word instructions to save multiple registers and -do small block moves. These instructions are generated by default on -\&\s-1POWER\s0 systems, and not generated on PowerPC systems. Do not use -\&\fB\-mstring\fR on little endian PowerPC systems, since those -instructions do not work when the processor is in little endian mode. -The exceptions are \s-1PPC740\s0 and \s-1PPC750\s0 which permit the instructions -usage in little endian mode. -.Ip "\fB\-mupdate\fR" 4 -.IX Item "-mupdate" -.PD 0 -.Ip "\fB\-mno-update\fR" 4 -.IX Item "-mno-update" -.PD -Generate code that uses (does not use) the load or store instructions -that update the base register to the address of the calculated memory -location. These instructions are generated by default. If you use -\&\fB\-mno-update\fR, there is a small window between the time that the -stack pointer is updated and the address of the previous frame is -stored, which means code that walks the stack frame across interrupts or -signals may get corrupted data. -.Ip "\fB\-mfused-madd\fR" 4 -.IX Item "-mfused-madd" -.PD 0 -.Ip "\fB\-mno-fused-madd\fR" 4 -.IX Item "-mno-fused-madd" -.PD -Generate code that uses (does not use) the floating point multiply and -accumulate instructions. These instructions are generated by default if -hardware floating is used. -.Ip "\fB\-mno-bit-align\fR" 4 -.IX Item "-mno-bit-align" -.PD 0 -.Ip "\fB\-mbit-align\fR" 4 -.IX Item "-mbit-align" -.PD -On System V.4 and embedded PowerPC systems do not (do) force structures -and unions that contain bit fields to be aligned to the base type of the -bit field. -.Sp -For example, by default a structure containing nothing but 8 -\&\f(CW\*(C`unsigned\*(C'\fR bitfields of length 1 would be aligned to a 4 byte -boundary and have a size of 4 bytes. By using \fB\-mno-bit-align\fR, -the structure would be aligned to a 1 byte boundary and be one byte in -size. -.Ip "\fB\-mno-strict-align\fR" 4 -.IX Item "-mno-strict-align" -.PD 0 -.Ip "\fB\-mstrict-align\fR" 4 -.IX Item "-mstrict-align" -.PD -On System V.4 and embedded PowerPC systems do not (do) assume that -unaligned memory references will be handled by the system. -.Ip "\fB\-mrelocatable\fR" 4 -.IX Item "-mrelocatable" -.PD 0 -.Ip "\fB\-mno-relocatable\fR" 4 -.IX Item "-mno-relocatable" -.PD -On embedded PowerPC systems generate code that allows (does not allow) -the program to be relocated to a different address at runtime. If you -use \fB\-mrelocatable\fR on any module, all objects linked together must -be compiled with \fB\-mrelocatable\fR or \fB\-mrelocatable-lib\fR. -.Ip "\fB\-mrelocatable-lib\fR" 4 -.IX Item "-mrelocatable-lib" -.PD 0 -.Ip "\fB\-mno-relocatable-lib\fR" 4 -.IX Item "-mno-relocatable-lib" -.PD -On embedded PowerPC systems generate code that allows (does not allow) -the program to be relocated to a different address at runtime. Modules -compiled with \fB\-mrelocatable-lib\fR can be linked with either modules -compiled without \fB\-mrelocatable\fR and \fB\-mrelocatable-lib\fR or -with modules compiled with the \fB\-mrelocatable\fR options. -.Ip "\fB\-mno-toc\fR" 4 -.IX Item "-mno-toc" -.PD 0 -.Ip "\fB\-mtoc\fR" 4 -.IX Item "-mtoc" -.PD -On System V.4 and embedded PowerPC systems do not (do) assume that -register 2 contains a pointer to a global area pointing to the addresses -used in the program. -.Ip "\fB\-mlittle\fR" 4 -.IX Item "-mlittle" -.PD 0 -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -.PD -On System V.4 and embedded PowerPC systems compile code for the -processor in little endian mode. The \fB\-mlittle-endian\fR option is -the same as \fB\-mlittle\fR. -.Ip "\fB\-mbig\fR" 4 -.IX Item "-mbig" -.PD 0 -.Ip "\fB\-mbig-endian\fR" 4 -.IX Item "-mbig-endian" -.PD -On System V.4 and embedded PowerPC systems compile code for the -processor in big endian mode. The \fB\-mbig-endian\fR option is -the same as \fB\-mbig\fR. -.Ip "\fB\-mcall-sysv\fR" 4 -.IX Item "-mcall-sysv" -On System V.4 and embedded PowerPC systems compile code using calling -conventions that adheres to the March 1995 draft of the System V -Application Binary Interface, PowerPC processor supplement. This is the -default unless you configured \s-1GCC\s0 using \fBpowerpc-*\-eabiaix\fR. -.Ip "\fB\-mcall-sysv-eabi\fR" 4 -.IX Item "-mcall-sysv-eabi" -Specify both \fB\-mcall-sysv\fR and \fB\-meabi\fR options. -.Ip "\fB\-mcall-sysv-noeabi\fR" 4 -.IX Item "-mcall-sysv-noeabi" -Specify both \fB\-mcall-sysv\fR and \fB\-mno-eabi\fR options. -.Ip "\fB\-mcall-aix\fR" 4 -.IX Item "-mcall-aix" -On System V.4 and embedded PowerPC systems compile code using calling -conventions that are similar to those used on \s-1AIX\s0. This is the -default if you configured \s-1GCC\s0 using \fBpowerpc-*\-eabiaix\fR. -.Ip "\fB\-mcall-solaris\fR" 4 -.IX Item "-mcall-solaris" -On System V.4 and embedded PowerPC systems compile code for the Solaris -operating system. -.Ip "\fB\-mcall-linux\fR" 4 -.IX Item "-mcall-linux" -On System V.4 and embedded PowerPC systems compile code for the -Linux-based \s-1GNU\s0 system. -.Ip "\fB\-mprototype\fR" 4 -.IX Item "-mprototype" -.PD 0 -.Ip "\fB\-mno-prototype\fR" 4 -.IX Item "-mno-prototype" -.PD -On System V.4 and embedded PowerPC systems assume that all calls to -variable argument functions are properly prototyped. Otherwise, the -compiler must insert an instruction before every non prototyped call to -set or clear bit 6 of the condition code register (\fI\s-1CR\s0\fR) to -indicate whether floating point values were passed in the floating point -registers in case the function takes a variable arguments. With -\&\fB\-mprototype\fR, only calls to prototyped variable argument functions -will set or clear the bit. -.Ip "\fB\-msim\fR" 4 -.IX Item "-msim" -On embedded PowerPC systems, assume that the startup module is called -\&\fIsim-crt0.o\fR and that the standard C libraries are \fIlibsim.a\fR and -\&\fIlibc.a\fR. This is the default for \fBpowerpc-*\-eabisim\fR. -configurations. -.Ip "\fB\-mmvme\fR" 4 -.IX Item "-mmvme" -On embedded PowerPC systems, assume that the startup module is called -\&\fIcrt0.o\fR and the standard C libraries are \fIlibmvme.a\fR and -\&\fIlibc.a\fR. -.Ip "\fB\-mads\fR" 4 -.IX Item "-mads" -On embedded PowerPC systems, assume that the startup module is called -\&\fIcrt0.o\fR and the standard C libraries are \fIlibads.a\fR and -\&\fIlibc.a\fR. -.Ip "\fB\-myellowknife\fR" 4 -.IX Item "-myellowknife" -On embedded PowerPC systems, assume that the startup module is called -\&\fIcrt0.o\fR and the standard C libraries are \fIlibyk.a\fR and -\&\fIlibc.a\fR. -.Ip "\fB\-mvxworks\fR" 4 -.IX Item "-mvxworks" -On System V.4 and embedded PowerPC systems, specify that you are -compiling for a VxWorks system. -.Ip "\fB\-memb\fR" 4 -.IX Item "-memb" -On embedded PowerPC systems, set the \fI\s-1PPC_EMB\s0\fR bit in the \s-1ELF\s0 flags -header to indicate that \fBeabi\fR extended relocations are used. -.Ip "\fB\-meabi\fR" 4 -.IX Item "-meabi" -.PD 0 -.Ip "\fB\-mno-eabi\fR" 4 -.IX Item "-mno-eabi" -.PD -On System V.4 and embedded PowerPC systems do (do not) adhere to the -Embedded Applications Binary Interface (eabi) which is a set of -modifications to the System V.4 specifications. Selecting \fB\-meabi\fR -means that the stack is aligned to an 8 byte boundary, a function -\&\f(CW\*(C`_\|_eabi\*(C'\fR is called to from \f(CW\*(C`main\*(C'\fR to set up the eabi -environment, and the \fB\-msdata\fR option can use both \f(CW\*(C`r2\*(C'\fR and -\&\f(CW\*(C`r13\*(C'\fR to point to two separate small data areas. Selecting -\&\fB\-mno-eabi\fR means that the stack is aligned to a 16 byte boundary, -do not call an initialization function from \f(CW\*(C`main\*(C'\fR, and the -\&\fB\-msdata\fR option will only use \f(CW\*(C`r13\*(C'\fR to point to a single -small data area. The \fB\-meabi\fR option is on by default if you -configured \s-1GCC\s0 using one of the \fBpowerpc*\-*\-eabi*\fR options. -.Ip "\fB\-msdata=eabi\fR" 4 -.IX Item "-msdata=eabi" -On System V.4 and embedded PowerPC systems, put small initialized -\&\f(CW\*(C`const\*(C'\fR global and static data in the \fB.sdata2\fR section, which -is pointed to by register \f(CW\*(C`r2\*(C'\fR. Put small initialized -non-\f(CW\*(C`const\*(C'\fR global and static data in the \fB.sdata\fR section, -which is pointed to by register \f(CW\*(C`r13\*(C'\fR. Put small uninitialized -global and static data in the \fB.sbss\fR section, which is adjacent to -the \fB.sdata\fR section. The \fB\-msdata=eabi\fR option is -incompatible with the \fB\-mrelocatable\fR option. The -\&\fB\-msdata=eabi\fR option also sets the \fB\-memb\fR option. -.Ip "\fB\-msdata=sysv\fR" 4 -.IX Item "-msdata=sysv" -On System V.4 and embedded PowerPC systems, put small global and static -data in the \fB.sdata\fR section, which is pointed to by register -\&\f(CW\*(C`r13\*(C'\fR. Put small uninitialized global and static data in the -\&\fB.sbss\fR section, which is adjacent to the \fB.sdata\fR section. -The \fB\-msdata=sysv\fR option is incompatible with the -\&\fB\-mrelocatable\fR option. -.Ip "\fB\-msdata=default\fR" 4 -.IX Item "-msdata=default" -.PD 0 -.Ip "\fB\-msdata\fR" 4 -.IX Item "-msdata" -.PD -On System V.4 and embedded PowerPC systems, if \fB\-meabi\fR is used, -compile code the same as \fB\-msdata=eabi\fR, otherwise compile code the -same as \fB\-msdata=sysv\fR. -.Ip "\fB\-msdata-data\fR" 4 -.IX Item "-msdata-data" -On System V.4 and embedded PowerPC systems, put small global and static -data in the \fB.sdata\fR section. Put small uninitialized global and -static data in the \fB.sbss\fR section. Do not use register \f(CW\*(C`r13\*(C'\fR -to address small data however. This is the default behavior unless -other \fB\-msdata\fR options are used. -.Ip "\fB\-msdata=none\fR" 4 -.IX Item "-msdata=none" -.PD 0 -.Ip "\fB\-mno-sdata\fR" 4 -.IX Item "-mno-sdata" -.PD -On embedded PowerPC systems, put all initialized global and static data -in the \fB.data\fR section, and all uninitialized data in the -\&\fB.bss\fR section. -.Ip "\fB\-G\fR \fInum\fR" 4 -.IX Item "-G num" -On embedded PowerPC systems, put global and static items less than or -equal to \fInum\fR bytes into the small data or bss sections instead of -the normal data or bss section. By default, \fInum\fR is 8. The -\&\fB\-G\fR \fInum\fR switch is also passed to the linker. -All modules should be compiled with the same \fB\-G\fR \fInum\fR value. -.Ip "\fB\-mregnames\fR" 4 -.IX Item "-mregnames" -.PD 0 -.Ip "\fB\-mno-regnames\fR" 4 -.IX Item "-mno-regnames" -.PD -On System V.4 and embedded PowerPC systems do (do not) emit register -names in the assembly language output using symbolic forms. -.PP -.I "\s-1IBM\s0 \s-1RT\s0 Options" -.IX Subsection "IBM RT Options" -.PP -These \fB\-m\fR options are defined for the \s-1IBM\s0 \s-1RT\s0 \s-1PC:\s0 -.Ip "\fB\-min-line-mul\fR" 4 -.IX Item "-min-line-mul" -Use an in-line code sequence for integer multiplies. This is the -default. -.Ip "\fB\-mcall-lib-mul\fR" 4 -.IX Item "-mcall-lib-mul" -Call \f(CW\*(C`lmul$$\*(C'\fR for integer multiples. -.Ip "\fB\-mfull-fp-blocks\fR" 4 -.IX Item "-mfull-fp-blocks" -Generate full-size floating point data blocks, including the minimum -amount of scratch space recommended by \s-1IBM\s0. This is the default. -.Ip "\fB\-mminimum-fp-blocks\fR" 4 -.IX Item "-mminimum-fp-blocks" -Do not include extra scratch space in floating point data blocks. This -results in smaller code, but slower execution, since scratch space must -be allocated dynamically. -.Ip "\fB\-mfp-arg-in-fpregs\fR" 4 -.IX Item "-mfp-arg-in-fpregs" -Use a calling sequence incompatible with the \s-1IBM\s0 calling convention in -which floating point arguments are passed in floating point registers. -Note that \f(CW\*(C`varargs.h\*(C'\fR and \f(CW\*(C`stdargs.h\*(C'\fR will not work with -floating point operands if this option is specified. -.Ip "\fB\-mfp-arg-in-gregs\fR" 4 -.IX Item "-mfp-arg-in-gregs" -Use the normal calling convention for floating point arguments. This is -the default. -.Ip "\fB\-mhc-struct-return\fR" 4 -.IX Item "-mhc-struct-return" -Return structures of more than one word in memory, rather than in a -register. This provides compatibility with the MetaWare HighC (hc) -compiler. Use the option \fB\-fpcc-struct-return\fR for compatibility -with the Portable C Compiler (pcc). -.Ip "\fB\-mnohc-struct-return\fR" 4 -.IX Item "-mnohc-struct-return" -Return some structures of more than one word in registers, when -convenient. This is the default. For compatibility with the -IBM-supplied compilers, use the option \fB\-fpcc-struct-return\fR or the -option \fB\-mhc-struct-return\fR. -.PP -.I "\s-1MIPS\s0 Options" -.IX Subsection "MIPS Options" -.PP -These \fB\-m\fR options are defined for the \s-1MIPS\s0 family of computers: -.Ip "\fB\-mcpu=\fR\fIcpu type\fR" 4 -.IX Item "-mcpu=cpu type" -Assume the defaults for the machine type \fIcpu type\fR when scheduling -instructions. The choices for \fIcpu type\fR are \fBr2000\fR, \fBr3000\fR, -\&\fBr3900\fR, \fBr4000\fR, \fBr4100\fR, \fBr4300\fR, \fBr4400\fR, -\&\fBr4600\fR, \fBr4650\fR, \fBr5000\fR, \fBr6000\fR, \fBr8000\fR, -and \fBorion\fR. Additionally, the \fBr2000\fR, \fBr3000\fR, -\&\fBr4000\fR, \fBr5000\fR, and \fBr6000\fR can be abbreviated as -\&\fBr2k\fR (or \fBr2K\fR), \fBr3k\fR, etc. While picking a specific -\&\fIcpu type\fR will schedule things appropriately for that particular -chip, the compiler will not generate any code that does not meet level 1 -of the \s-1MIPS\s0 \s-1ISA\s0 (instruction set architecture) without a \fB\-mipsX\fR -or \fB\-mabi\fR switch being used. -.Ip "\fB\-mips1\fR" 4 -.IX Item "-mips1" -Issue instructions from level 1 of the \s-1MIPS\s0 \s-1ISA\s0. This is the default. -\&\fBr3000\fR is the default \fIcpu type\fR at this \s-1ISA\s0 level. -.Ip "\fB\-mips2\fR" 4 -.IX Item "-mips2" -Issue instructions from level 2 of the \s-1MIPS\s0 \s-1ISA\s0 (branch likely, square -root instructions). \fBr6000\fR is the default \fIcpu type\fR at this -\&\s-1ISA\s0 level. -.Ip "\fB\-mips3\fR" 4 -.IX Item "-mips3" -Issue instructions from level 3 of the \s-1MIPS\s0 \s-1ISA\s0 (64\-bit instructions). -\&\fBr4000\fR is the default \fIcpu type\fR at this \s-1ISA\s0 level. -.Ip "\fB\-mips4\fR" 4 -.IX Item "-mips4" -Issue instructions from level 4 of the \s-1MIPS\s0 \s-1ISA\s0 (conditional move, -prefetch, enhanced \s-1FPU\s0 instructions). \fBr8000\fR is the default -\&\fIcpu type\fR at this \s-1ISA\s0 level. -.Ip "\fB\-mfp32\fR" 4 -.IX Item "-mfp32" -Assume that 32 32\-bit floating point registers are available. This is -the default. -.Ip "\fB\-mfp64\fR" 4 -.IX Item "-mfp64" -Assume that 32 64\-bit floating point registers are available. This is -the default when the \fB\-mips3\fR option is used. -.Ip "\fB\-mgp32\fR" 4 -.IX Item "-mgp32" -Assume that 32 32\-bit general purpose registers are available. This is -the default. -.Ip "\fB\-mgp64\fR" 4 -.IX Item "-mgp64" -Assume that 32 64\-bit general purpose registers are available. This is -the default when the \fB\-mips3\fR option is used. -.Ip "\fB\-mint64\fR" 4 -.IX Item "-mint64" -Force int and long types to be 64 bits wide. See \fB\-mlong32\fR for an -explanation of the default, and the width of pointers. -.Ip "\fB\-mlong64\fR" 4 -.IX Item "-mlong64" -Force long types to be 64 bits wide. See \fB\-mlong32\fR for an -explanation of the default, and the width of pointers. -.Ip "\fB\-mlong32\fR" 4 -.IX Item "-mlong32" -Force long, int, and pointer types to be 32 bits wide. -.Sp -If none of \fB\-mlong32\fR, \fB\-mlong64\fR, or \fB\-mint64\fR are set, -the size of ints, longs, and pointers depends on the \s-1ABI\s0 and \s-1ISA\s0 chosen. -For \fB\-mabi=32\fR, and \fB\-mabi=n32\fR, ints and longs are 32 bits -wide. For \fB\-mabi=64\fR, ints are 32 bits, and longs are 64 bits wide. -For \fB\-mabi=eabi\fR and either \fB\-mips1\fR or \fB\-mips2\fR, ints -and longs are 32 bits wide. For \fB\-mabi=eabi\fR and higher ISAs, ints -are 32 bits, and longs are 64 bits wide. The width of pointer types is -the smaller of the width of longs or the width of general purpose -registers (which in turn depends on the \s-1ISA\s0). -.Ip "\fB\-mabi=32\fR" 4 -.IX Item "-mabi=32" -.PD 0 -.Ip "\fB\-mabi=o64\fR" 4 -.IX Item "-mabi=o64" -.Ip "\fB\-mabi=n32\fR" 4 -.IX Item "-mabi=n32" -.Ip "\fB\-mabi=64\fR" 4 -.IX Item "-mabi=64" -.Ip "\fB\-mabi=eabi\fR" 4 -.IX Item "-mabi=eabi" -.PD -Generate code for the indicated \s-1ABI\s0. The default instruction level is -\&\fB\-mips1\fR for \fB32\fR, \fB\-mips3\fR for \fBn32\fR, and -\&\fB\-mips4\fR otherwise. Conversely, with \fB\-mips1\fR or -\&\fB\-mips2\fR, the default \s-1ABI\s0 is \fB32\fR; otherwise, the default \s-1ABI\s0 -is \fB64\fR. -.Ip "\fB\-mmips-as\fR" 4 -.IX Item "-mmips-as" -Generate code for the \s-1MIPS\s0 assembler, and invoke \fImips-tfile\fR to -add normal debug information. This is the default for all -platforms except for the \s-1OSF/1\s0 reference platform, using the OSF/rose -object format. If the either of the \fB\-gstabs\fR or \fB\-gstabs+\fR -switches are used, the \fImips-tfile\fR program will encapsulate the -stabs within \s-1MIPS\s0 \s-1ECOFF\s0. -.Ip "\fB\-mgas\fR" 4 -.IX Item "-mgas" -Generate code for the \s-1GNU\s0 assembler. This is the default on the \s-1OSF/1\s0 -reference platform, using the OSF/rose object format. Also, this is -the default if the configure option \fB\*(--with-gnu-as\fR is used. -.Ip "\fB\-msplit-addresses\fR" 4 -.IX Item "-msplit-addresses" -.PD 0 -.Ip "\fB\-mno-split-addresses\fR" 4 -.IX Item "-mno-split-addresses" -.PD -Generate code to load the high and low parts of address constants separately. -This allows \f(CW\*(C`gcc\*(C'\fR to optimize away redundant loads of the high order -bits of addresses. This optimization requires \s-1GNU\s0 as and \s-1GNU\s0 ld. -This optimization is enabled by default for some embedded targets where -\&\s-1GNU\s0 as and \s-1GNU\s0 ld are standard. -.Ip "\fB\-mrnames\fR" 4 -.IX Item "-mrnames" -.PD 0 -.Ip "\fB\-mno-rnames\fR" 4 -.IX Item "-mno-rnames" -.PD -The \fB\-mrnames\fR switch says to output code using the \s-1MIPS\s0 software -names for the registers, instead of the hardware names (ie, \fIa0\fR -instead of \fI$4\fR). The only known assembler that supports this option -is the Algorithmics assembler. -.Ip "\fB\-mgpopt\fR" 4 -.IX Item "-mgpopt" -.PD 0 -.Ip "\fB\-mno-gpopt\fR" 4 -.IX Item "-mno-gpopt" -.PD -The \fB\-mgpopt\fR switch says to write all of the data declarations -before the instructions in the text section, this allows the \s-1MIPS\s0 -assembler to generate one word memory references instead of using two -words for short global or static data items. This is on by default if -optimization is selected. -.Ip "\fB\-mstats\fR" 4 -.IX Item "-mstats" -.PD 0 -.Ip "\fB\-mno-stats\fR" 4 -.IX Item "-mno-stats" -.PD -For each non-inline function processed, the \fB\-mstats\fR switch -causes the compiler to emit one line to the standard error file to -print statistics about the program (number of registers saved, stack -size, etc.). -.Ip "\fB\-mmemcpy\fR" 4 -.IX Item "-mmemcpy" -.PD 0 -.Ip "\fB\-mno-memcpy\fR" 4 -.IX Item "-mno-memcpy" -.PD -The \fB\-mmemcpy\fR switch makes all block moves call the appropriate -string function (\fBmemcpy\fR or \fBbcopy\fR) instead of possibly -generating inline code. -.Ip "\fB\-mmips-tfile\fR" 4 -.IX Item "-mmips-tfile" -.PD 0 -.Ip "\fB\-mno-mips-tfile\fR" 4 -.IX Item "-mno-mips-tfile" -.PD -The \fB\-mno-mips-tfile\fR switch causes the compiler not -postprocess the object file with the \fImips-tfile\fR program, -after the \s-1MIPS\s0 assembler has generated it to add debug support. If -\&\fImips-tfile\fR is not run, then no local variables will be -available to the debugger. In addition, \fIstage2\fR and -\&\fIstage3\fR objects will have the temporary file names passed to the -assembler embedded in the object file, which means the objects will -not compare the same. The \fB\-mno-mips-tfile\fR switch should only -be used when there are bugs in the \fImips-tfile\fR program that -prevents compilation. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. -.Ip "\fB\-mhard-float\fR" 4 -.IX Item "-mhard-float" -Generate output containing floating point instructions. This is the -default if you use the unmodified sources. -.Ip "\fB\-mabicalls\fR" 4 -.IX Item "-mabicalls" -.PD 0 -.Ip "\fB\-mno-abicalls\fR" 4 -.IX Item "-mno-abicalls" -.PD -Emit (or do not emit) the pseudo operations \fB.abicalls\fR, -\&\fB.cpload\fR, and \fB.cprestore\fR that some System V.4 ports use for -position independent code. -.Ip "\fB\-mlong-calls\fR" 4 -.IX Item "-mlong-calls" -.PD 0 -.Ip "\fB\-mno-long-calls\fR" 4 -.IX Item "-mno-long-calls" -.PD -Do all calls with the \fB\s-1JALR\s0\fR instruction, which requires -loading up a function's address into a register before the call. -You need to use this switch, if you call outside of the current -512 megabyte segment to functions that are not through pointers. -.Ip "\fB\-mhalf-pic\fR" 4 -.IX Item "-mhalf-pic" -.PD 0 -.Ip "\fB\-mno-half-pic\fR" 4 -.IX Item "-mno-half-pic" -.PD -Put pointers to extern references into the data section and load them -up, rather than put the references in the text section. -.Ip "\fB\-membedded-pic\fR" 4 -.IX Item "-membedded-pic" -.PD 0 -.Ip "\fB\-mno-embedded-pic\fR" 4 -.IX Item "-mno-embedded-pic" -.PD -Generate \s-1PIC\s0 code suitable for some embedded systems. All calls are -made using \s-1PC\s0 relative address, and all data is addressed using the \f(CW$gp\fR -register. No more than 65536 bytes of global data may be used. This -requires \s-1GNU\s0 as and \s-1GNU\s0 ld which do most of the work. This currently -only works on targets which use \s-1ECOFF\s0; it does not work with \s-1ELF\s0. -.Ip "\fB\-membedded-data\fR" 4 -.IX Item "-membedded-data" -.PD 0 -.Ip "\fB\-mno-embedded-data\fR" 4 -.IX Item "-mno-embedded-data" -.PD -Allocate variables to the read-only data section first if possible, then -next in the small data section if possible, otherwise in data. This gives -slightly slower code than the default, but reduces the amount of \s-1RAM\s0 required -when executing, and thus may be preferred for some embedded systems. -.Ip "\fB\-muninit-const-in-rodata\fR" 4 -.IX Item "-muninit-const-in-rodata" -.PD 0 -.Ip "\fB\-mno-uninit-const-in-rodata\fR" 4 -.IX Item "-mno-uninit-const-in-rodata" -.PD -When used together with \-membedded-data, it will always store uninitialized -const variables in the read-only data section. -.Ip "\fB\-msingle-float\fR" 4 -.IX Item "-msingle-float" -.PD 0 -.Ip "\fB\-mdouble-float\fR" 4 -.IX Item "-mdouble-float" -.PD -The \fB\-msingle-float\fR switch tells gcc to assume that the floating -point coprocessor only supports single precision operations, as on the -\&\fBr4650\fR chip. The \fB\-mdouble-float\fR switch permits gcc to use -double precision operations. This is the default. -.Ip "\fB\-mmad\fR" 4 -.IX Item "-mmad" -.PD 0 -.Ip "\fB\-mno-mad\fR" 4 -.IX Item "-mno-mad" -.PD -Permit use of the \fBmad\fR, \fBmadu\fR and \fBmul\fR instructions, -as on the \fBr4650\fR chip. -.Ip "\fB\-m4650\fR" 4 -.IX Item "-m4650" -Turns on \fB\-msingle-float\fR, \fB\-mmad\fR, and, at least for now, -\&\fB\-mcpu=r4650\fR. -.Ip "\fB\-mips16\fR" 4 -.IX Item "-mips16" -.PD 0 -.Ip "\fB\-mno-mips16\fR" 4 -.IX Item "-mno-mips16" -.PD -Enable 16\-bit instructions. -.Ip "\fB\-mentry\fR" 4 -.IX Item "-mentry" -Use the entry and exit pseudo ops. This option can only be used with -\&\fB\-mips16\fR. -.Ip "\fB\-EL\fR" 4 -.IX Item "-EL" -Compile code for the processor in little endian mode. -The requisite libraries are assumed to exist. -.Ip "\fB\-EB\fR" 4 -.IX Item "-EB" -Compile code for the processor in big endian mode. -The requisite libraries are assumed to exist. -.Ip "\fB\-G\fR \fInum\fR" 4 -.IX Item "-G num" -Put global and static items less than or equal to \fInum\fR bytes into -the small data or bss sections instead of the normal data or bss -section. This allows the assembler to emit one word memory reference -instructions based on the global pointer (\fIgp\fR or \fI$28\fR), -instead of the normal two words used. By default, \fInum\fR is 8 when -the \s-1MIPS\s0 assembler is used, and 0 when the \s-1GNU\s0 assembler is used. The -\&\fB\-G\fR \fInum\fR switch is also passed to the assembler and linker. -All modules should be compiled with the same \fB\-G\fR \fInum\fR -value. -.Ip "\fB\-nocpp\fR" 4 -.IX Item "-nocpp" -Tell the \s-1MIPS\s0 assembler to not run its preprocessor over user -assembler files (with a \fB.s\fR suffix) when assembling them. -.Ip "\fB\-mfix7000\fR" 4 -.IX Item "-mfix7000" -Pass an option to gas which will cause nops to be inserted if -the read of the destination register of an mfhi or mflo instruction -occurs in the following two instructions. -.Ip "\fB\-no-crt0\fR" 4 -.IX Item "-no-crt0" -Do not include the default crt0. -.PP -.I "Intel 386 Options" -.IX Subsection "Intel 386 Options" -.PP -These \fB\-m\fR options are defined for the i386 family of computers: -.Ip "\fB\-mcpu=\fR\fIcpu type\fR" 4 -.IX Item "-mcpu=cpu type" -Assume the defaults for the machine type \fIcpu type\fR when scheduling -instructions. The choices for \fIcpu type\fR are \fBi386\fR, -\&\fBi486\fR, \fBi586\fR, \fBi686\fR, \fBpentium\fR, -\&\fBpentiumpro\fR, \fBpentium4\fR, \fBk6\fR, and \fBathlon\fR -.Sp -While picking a specific \fIcpu type\fR will schedule things appropriately -for that particular chip, the compiler will not generate any code that -does not run on the i386 without the \fB\-march=\fR\fIcpu type\fR option -being used. \fBi586\fR is equivalent to \fBpentium\fR and \fBi686\fR -is equivalent to \fBpentiumpro\fR. \fBk6\fR and \fBathlon\fR are the -\&\s-1AMD\s0 chips as opposed to the Intel ones. -.Ip "\fB\-march=\fR\fIcpu type\fR" 4 -.IX Item "-march=cpu type" -Generate instructions for the machine type \fIcpu type\fR. The choices -for \fIcpu type\fR are the same as for \fB\-mcpu\fR. Moreover, -specifying \fB\-march=\fR\fIcpu type\fR implies \fB\-mcpu=\fR\fIcpu type\fR. -.Ip "\fB\-m386\fR" 4 -.IX Item "-m386" -.PD 0 -.Ip "\fB\-m486\fR" 4 -.IX Item "-m486" -.Ip "\fB\-mpentium\fR" 4 -.IX Item "-mpentium" -.Ip "\fB\-mpentiumpro\fR" 4 -.IX Item "-mpentiumpro" -.PD -Synonyms for \-mcpu=i386, \-mcpu=i486, \-mcpu=pentium, and \-mcpu=pentiumpro -respectively. These synonyms are deprecated. -.Ip "\fB\-mintel-syntax\fR" 4 -.IX Item "-mintel-syntax" -Emit assembly using Intel syntax opcodes instead of \s-1AT&T\s0 syntax. -.Ip "\fB\-mieee-fp\fR" 4 -.IX Item "-mieee-fp" -.PD 0 -.Ip "\fB\-mno-ieee-fp\fR" 4 -.IX Item "-mno-ieee-fp" -.PD -Control whether or not the compiler uses \s-1IEEE\s0 floating point -comparisons. These handle correctly the case where the result of a -comparison is unordered. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not part of \s-1GCC\s0. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. -.Sp -On machines where a function returns floating point results in the 80387 -register stack, some floating point opcodes may be emitted even if -\&\fB\-msoft-float\fR is used. -.Ip "\fB\-mno-fp-ret-in-387\fR" 4 -.IX Item "-mno-fp-ret-in-387" -Do not use the \s-1FPU\s0 registers for return values of functions. -.Sp -The usual calling convention has functions return values of types -\&\f(CW\*(C`float\*(C'\fR and \f(CW\*(C`double\*(C'\fR in an \s-1FPU\s0 register, even if there -is no \s-1FPU\s0. The idea is that the operating system should emulate -an \s-1FPU\s0. -.Sp -The option \fB\-mno-fp-ret-in-387\fR causes such values to be returned -in ordinary \s-1CPU\s0 registers instead. -.Ip "\fB\-mno-fancy-math-387\fR" 4 -.IX Item "-mno-fancy-math-387" -Some 387 emulators do not support the \f(CW\*(C`sin\*(C'\fR, \f(CW\*(C`cos\*(C'\fR and -\&\f(CW\*(C`sqrt\*(C'\fR instructions for the 387. Specify this option to avoid -generating those instructions. This option is the default on FreeBSD. -As of revision 2.6.1, these instructions are not generated unless you -also use the \fB\-funsafe-math-optimizations\fR switch. -.Ip "\fB\-malign-double\fR" 4 -.IX Item "-malign-double" -.PD 0 -.Ip "\fB\-mno-align-double\fR" 4 -.IX Item "-mno-align-double" -.PD -Control whether \s-1GCC\s0 aligns \f(CW\*(C`double\*(C'\fR, \f(CW\*(C`long double\*(C'\fR, and -\&\f(CW\*(C`long long\*(C'\fR variables on a two word boundary or a one word -boundary. Aligning \f(CW\*(C`double\*(C'\fR variables on a two word boundary will -produce code that runs somewhat faster on a \fBPentium\fR at the -expense of more memory. -.Ip "\fB\-m128bit-long-double\fR" 4 -.IX Item "-m128bit-long-double" -.PD 0 -.Ip "\fB\-m128bit-long-double\fR" 4 -.IX Item "-m128bit-long-double" -.PD -Control the size of \f(CW\*(C`long double\*(C'\fR type. i386 application binary interface -specify the size to be 12 bytes, while modern architectures (Pentium and newer) -preffer \f(CW\*(C`long double\*(C'\fR aligned to 8 or 16 byte boundary. This is -impossible to reach with 12 byte long doubles in the array accesses. -.Sp -\&\fBWarning:\fR if you use the \fB\-m128bit-long-double\fR switch, the -structures and arrays containing \f(CW\*(C`long double\*(C'\fR will change their size as -well as function calling convention for function taking \f(CW\*(C`long double\*(C'\fR -will be modified. -.Ip "\fB\-m96bit-long-double\fR" 4 -.IX Item "-m96bit-long-double" -.PD 0 -.Ip "\fB\-m96bit-long-double\fR" 4 -.IX Item "-m96bit-long-double" -.PD -Set the size of \f(CW\*(C`long double\*(C'\fR to 96 bits as required by the i386 -application binary interface. This is the default. -.Ip "\fB\-msvr3\-shlib\fR" 4 -.IX Item "-msvr3-shlib" -.PD 0 -.Ip "\fB\-mno-svr3\-shlib\fR" 4 -.IX Item "-mno-svr3-shlib" -.PD -Control whether \s-1GCC\s0 places uninitialized locals into \f(CW\*(C`bss\*(C'\fR or -\&\f(CW\*(C`data\*(C'\fR. \fB\-msvr3\-shlib\fR places these locals into \f(CW\*(C`bss\*(C'\fR. -These options are meaningful only on System V Release 3. -.Ip "\fB\-mno-wide-multiply\fR" 4 -.IX Item "-mno-wide-multiply" -.PD 0 -.Ip "\fB\-mwide-multiply\fR" 4 -.IX Item "-mwide-multiply" -.PD -Control whether \s-1GCC\s0 uses the \f(CW\*(C`mul\*(C'\fR and \f(CW\*(C`imul\*(C'\fR that produce -64\-bit results in \f(CW\*(C`eax:edx\*(C'\fR from 32\-bit operands to do \f(CW\*(C`long -long\*(C'\fR multiplies and 32\-bit division by constants. -.Ip "\fB\-mrtd\fR" 4 -.IX Item "-mrtd" -Use a different function-calling convention, in which functions that -take a fixed number of arguments return with the \f(CW\*(C`ret\*(C'\fR \fInum\fR -instruction, which pops their arguments while returning. This saves one -instruction in the caller since there is no need to pop the arguments -there. -.Sp -You can specify that an individual function is called with this calling -sequence with the function attribute \fBstdcall\fR. You can also -override the \fB\-mrtd\fR option by using the function attribute -\&\fBcdecl\fR. -.Sp -\&\fBWarning:\fR this calling convention is incompatible with the one -normally used on Unix, so you cannot use it if you need to call -libraries compiled with the Unix compiler. -.Sp -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR); -otherwise incorrect code will be generated for calls to those -functions. -.Sp -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) -.Ip "\fB\-mregparm=\fR\fInum\fR" 4 -.IX Item "-mregparm=num" -Control how many registers are used to pass integer arguments. By -default, no registers are used to pass arguments, and at most 3 -registers can be used. You can control this behavior for a specific -function by using the function attribute \fBregparm\fR. -.Sp -\&\fBWarning:\fR if you use this switch, and -\&\fInum\fR is nonzero, then you must build all modules with the same -value, including any libraries. This includes the system libraries and -startup modules. -.Ip "\fB\-mpreferred-stack-boundary=\fR\fInum\fR" 4 -.IX Item "-mpreferred-stack-boundary=num" -Attempt to keep the stack boundary aligned to a 2 raised to \fInum\fR -byte boundary. If \fB\-mpreferred-stack-boundary\fR is not specified, -the default is 4 (16 bytes or 128 bits). -.Sp -The stack is required to be aligned on a 4 byte boundary. On Pentium -and PentiumPro, \f(CW\*(C`double\*(C'\fR and \f(CW\*(C`long double\*(C'\fR values should be -aligned to an 8 byte boundary (see \fB\-malign-double\fR) or suffer -significant run time performance penalties. On Pentium \s-1III\s0, the -Streaming \s-1SIMD\s0 Extension (\s-1SSE\s0) data type \f(CW\*(C`_\|_m128\*(C'\fR suffers similar -penalties if it is not 16 byte aligned. -.Sp -To ensure proper alignment of this values on the stack, the stack boundary -must be as aligned as that required by any value stored on the stack. -Further, every function must be generated such that it keeps the stack -aligned. Thus calling a function compiled with a higher preferred -stack boundary from a function compiled with a lower preferred stack -boundary will most likely misalign the stack. It is recommended that -libraries that use callbacks always use the default setting. -.Sp -This extra alignment does consume extra stack space. Code that is sensitive -to stack space usage, such as embedded systems and operating system kernels, -may want to reduce the preferred alignment to -\&\fB\-mpreferred-stack-boundary=2\fR. -.Ip "\fB\-mpush-args\fR" 4 -.IX Item "-mpush-args" -Use \s-1PUSH\s0 operations to store outgoing parameters. This method is shorter -and usually equally fast as method using \s-1SUB/MOV\s0 operations and is enabled -by default. In some cases disabling it may improve performance because of -improved scheduling and reduced dependencies. -.Ip "\fB\-maccumulate-outgoing-args\fR" 4 -.IX Item "-maccumulate-outgoing-args" -If enabled, the maximum amount of space required for outgoing arguments will be -computed in the function prologue. This in faster on most modern CPUs -because of reduced dependencies, improved scheduling and reduced stack usage -when preferred stack boundary is not equal to 2. The drawback is a notable -increase in code size. This switch implies \-mno-push-args. -.Ip "\fB\-mthreads\fR" 4 -.IX Item "-mthreads" -Support thread-safe exception handling on \fBMingw32\fR. Code that relies -on thread-safe exception handling must compile and link all code with the -\&\fB\-mthreads\fR option. When compiling, \fB\-mthreads\fR defines -\&\fB\-D_MT\fR; when linking, it links in a special thread helper library -\&\fB\-lmingwthrd\fR which cleans up per thread exception handling data. -.Ip "\fB\-mno-align-stringops\fR" 4 -.IX Item "-mno-align-stringops" -Do not align destination of inlined string operations. This switch reduces -code size and improves performance in case the destination is already aligned, -but gcc don't know about it. -.Ip "\fB\-minline-all-stringops\fR" 4 -.IX Item "-minline-all-stringops" -By default \s-1GCC\s0 inlines string operations only when destination is known to be -aligned at least to 4 byte boundary. This enables more inlining, increase code -size, but may improve performance of code that depends on fast memcpy, strlen -and memset for short lengths. -.Ip "\fB\-momit-leaf-frame-pointer\fR" 4 -.IX Item "-momit-leaf-frame-pointer" -Don't keep the frame pointer in a register for leaf functions. This -avoids the instructions to save, set up and restore frame pointers and -makes an extra register available in leaf functions. The option -\&\fB\-fomit-frame-pointer\fR removes the frame pointer for all functions -which might make debugging harder. -.PP -.I "\s-1HPPA\s0 Options" -.IX Subsection "HPPA Options" -.PP -These \fB\-m\fR options are defined for the \s-1HPPA\s0 family of computers: -.Ip "\fB\-march=\fR\fIarchitecture type\fR" 4 -.IX Item "-march=architecture type" -Generate code for the specified architecture. The choices for -\&\fIarchitecture type\fR are \fB1.0\fR for \s-1PA\s0 1.0, \fB1.1\fR for \s-1PA\s0 -1.1, and \fB2.0\fR for \s-1PA\s0 2.0 processors. Refer to -\&\fI/usr/lib/sched.models\fR on an \s-1HP-UX\s0 system to determine the proper -architecture option for your machine. Code compiled for lower numbered -architectures will run on higher numbered architectures, but not the -other way around. -.Sp -\&\s-1PA\s0 2.0 support currently requires gas snapshot 19990413 or later. The -next release of binutils (current is 2.9.1) will probably contain \s-1PA\s0 2.0 -support. -.Ip "\fB\-mpa-risc-1\-0\fR" 4 -.IX Item "-mpa-risc-1-0" -.PD 0 -.Ip "\fB\-mpa-risc-1\-1\fR" 4 -.IX Item "-mpa-risc-1-1" -.Ip "\fB\-mpa-risc-2\-0\fR" 4 -.IX Item "-mpa-risc-2-0" -.PD -Synonyms for \-march=1.0, \-march=1.1, and \-march=2.0 respectively. -.Ip "\fB\-mbig-switch\fR" 4 -.IX Item "-mbig-switch" -Generate code suitable for big switch tables. Use this option only if -the assembler/linker complain about out of range branches within a switch -table. -.Ip "\fB\-mjump-in-delay\fR" 4 -.IX Item "-mjump-in-delay" -Fill delay slots of function calls with unconditional jump instructions -by modifying the return pointer for the function call to be the target -of the conditional jump. -.Ip "\fB\-mdisable-fpregs\fR" 4 -.IX Item "-mdisable-fpregs" -Prevent floating point registers from being used in any manner. This is -necessary for compiling kernels which perform lazy context switching of -floating point registers. If you use this option and attempt to perform -floating point operations, the compiler will abort. -.Ip "\fB\-mdisable-indexing\fR" 4 -.IX Item "-mdisable-indexing" -Prevent the compiler from using indexing address modes. This avoids some -rather obscure problems when compiling \s-1MIG\s0 generated code under \s-1MACH\s0. -.Ip "\fB\-mno-space-regs\fR" 4 -.IX Item "-mno-space-regs" -Generate code that assumes the target has no space registers. This allows -\&\s-1GCC\s0 to generate faster indirect calls and use unscaled index address modes. -.Sp -Such code is suitable for level 0 \s-1PA\s0 systems and kernels. -.Ip "\fB\-mfast-indirect-calls\fR" 4 -.IX Item "-mfast-indirect-calls" -Generate code that assumes calls never cross space boundaries. This -allows \s-1GCC\s0 to emit code which performs faster indirect calls. -.Sp -This option will not work in the presence of shared libraries or nested -functions. -.Ip "\fB\-mlong-load-store\fR" 4 -.IX Item "-mlong-load-store" -Generate 3\-instruction load and store sequences as sometimes required by -the \s-1HP-UX\s0 10 linker. This is equivalent to the \fB+k\fR option to -the \s-1HP\s0 compilers. -.Ip "\fB\-mportable-runtime\fR" 4 -.IX Item "-mportable-runtime" -Use the portable calling conventions proposed by \s-1HP\s0 for \s-1ELF\s0 systems. -.Ip "\fB\-mgas\fR" 4 -.IX Item "-mgas" -Enable the use of assembler directives only \s-1GAS\s0 understands. -.Ip "\fB\-mschedule=\fR\fIcpu type\fR" 4 -.IX Item "-mschedule=cpu type" -Schedule code according to the constraints for the machine type -\&\fIcpu type\fR. The choices for \fIcpu type\fR are \fB700\fR -\&\fB7100\fR, \fB7100LC\fR, \fB7200\fR, and \fB8000\fR. Refer to -\&\fI/usr/lib/sched.models\fR on an \s-1HP-UX\s0 system to determine the -proper scheduling option for your machine. -.Ip "\fB\-mlinker-opt\fR" 4 -.IX Item "-mlinker-opt" -Enable the optimization pass in the \s-1HPUX\s0 linker. Note this makes symbolic -debugging impossible. It also triggers a bug in the \s-1HPUX\s0 8 and \s-1HPUX\s0 9 linkers -in which they give bogus error messages when linking some programs. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries are not available for all \s-1HPPA\s0 -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. The embedded target \fBhppa1.1\-*\-pro\fR -does provide software floating point support. -.Sp -\&\fB\-msoft-float\fR changes the calling convention in the output file; -therefore, it is only useful if you compile \fIall\fR of a program with -this option. In particular, you need to compile \fIlibgcc.a\fR, the -library that comes with \s-1GCC\s0, with \fB\-msoft-float\fR in order for -this to work. -.PP -.I "Intel 960 Options" -.IX Subsection "Intel 960 Options" -.PP -These \fB\-m\fR options are defined for the Intel 960 implementations: -.Ip "\fB\-m\fR\fIcpu type\fR" 4 -.IX Item "-mcpu type" -Assume the defaults for the machine type \fIcpu type\fR for some of -the other options, including instruction scheduling, floating point -support, and addressing modes. The choices for \fIcpu type\fR are -\&\fBka\fR, \fBkb\fR, \fBmc\fR, \fBca\fR, \fBcf\fR, -\&\fBsa\fR, and \fBsb\fR. -The default is -\&\fBkb\fR. -.Ip "\fB\-mnumerics\fR" 4 -.IX Item "-mnumerics" -.PD 0 -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -.PD -The \fB\-mnumerics\fR option indicates that the processor does support -floating-point instructions. The \fB\-msoft-float\fR option indicates -that floating-point support should not be assumed. -.Ip "\fB\-mleaf-procedures\fR" 4 -.IX Item "-mleaf-procedures" -.PD 0 -.Ip "\fB\-mno-leaf-procedures\fR" 4 -.IX Item "-mno-leaf-procedures" -.PD -Do (or do not) attempt to alter leaf procedures to be callable with the -\&\f(CW\*(C`bal\*(C'\fR instruction as well as \f(CW\*(C`call\*(C'\fR. This will result in more -efficient code for explicit calls when the \f(CW\*(C`bal\*(C'\fR instruction can be -substituted by the assembler or linker, but less efficient code in other -cases, such as calls via function pointers, or using a linker that doesn't -support this optimization. -.Ip "\fB\-mtail-call\fR" 4 -.IX Item "-mtail-call" -.PD 0 -.Ip "\fB\-mno-tail-call\fR" 4 -.IX Item "-mno-tail-call" -.PD -Do (or do not) make additional attempts (beyond those of the -machine-independent portions of the compiler) to optimize tail-recursive -calls into branches. You may not want to do this because the detection of -cases where this is not valid is not totally complete. The default is -\&\fB\-mno-tail-call\fR. -.Ip "\fB\-mcomplex-addr\fR" 4 -.IX Item "-mcomplex-addr" -.PD 0 -.Ip "\fB\-mno-complex-addr\fR" 4 -.IX Item "-mno-complex-addr" -.PD -Assume (or do not assume) that the use of a complex addressing mode is a -win on this implementation of the i960. Complex addressing modes may not -be worthwhile on the K-series, but they definitely are on the C-series. -The default is currently \fB\-mcomplex-addr\fR for all processors except -the \s-1CB\s0 and \s-1CC\s0. -.Ip "\fB\-mcode-align\fR" 4 -.IX Item "-mcode-align" -.PD 0 -.Ip "\fB\-mno-code-align\fR" 4 -.IX Item "-mno-code-align" -.PD -Align code to 8\-byte boundaries for faster fetching (or don't bother). -Currently turned on by default for C-series implementations only. -.Ip "\fB\-mic-compat\fR" 4 -.IX Item "-mic-compat" -.PD 0 -.Ip "\fB\-mic2.0\-compat\fR" 4 -.IX Item "-mic2.0-compat" -.Ip "\fB\-mic3.0\-compat\fR" 4 -.IX Item "-mic3.0-compat" -.PD -Enable compatibility with iC960 v2.0 or v3.0. -.Ip "\fB\-masm-compat\fR" 4 -.IX Item "-masm-compat" -.PD 0 -.Ip "\fB\-mintel-asm\fR" 4 -.IX Item "-mintel-asm" -.PD -Enable compatibility with the iC960 assembler. -.Ip "\fB\-mstrict-align\fR" 4 -.IX Item "-mstrict-align" -.PD 0 -.Ip "\fB\-mno-strict-align\fR" 4 -.IX Item "-mno-strict-align" -.PD -Do not permit (do permit) unaligned accesses. -.Ip "\fB\-mold-align\fR" 4 -.IX Item "-mold-align" -Enable structure-alignment compatibility with Intel's gcc release version -1.3 (based on gcc 1.37). This option implies \fB\-mstrict-align\fR. -.Ip "\fB\-mlong-double-64\fR" 4 -.IX Item "-mlong-double-64" -Implement type \fBlong double\fR as 64\-bit floating point numbers. -Without the option \fBlong double\fR is implemented by 80\-bit -floating point numbers. The only reason we have it because there is -no 128\-bit \fBlong double\fR support in \fBfp-bit.c\fR yet. So it -is only useful for people using soft-float targets. Otherwise, we -should recommend against use of it. -.PP -.I "\s-1DEC\s0 Alpha Options" -.IX Subsection "DEC Alpha Options" -.PP -These \fB\-m\fR options are defined for the \s-1DEC\s0 Alpha implementations: -.Ip "\fB\-mno-soft-float\fR" 4 -.IX Item "-mno-soft-float" -.PD 0 -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -.PD -Use (do not use) the hardware floating-point instructions for -floating-point operations. When \fB\-msoft-float\fR is specified, -functions in \fIlibgcc.a\fR will be used to perform floating-point -operations. Unless they are replaced by routines that emulate the -floating-point operations, or compiled in such a way as to call such -emulations routines, these routines will issue floating-point -operations. If you are compiling for an Alpha without floating-point -operations, you must ensure that the library is built so as not to call -them. -.Sp -Note that Alpha implementations without floating-point operations are -required to have floating-point registers. -.Ip "\fB\-mfp-reg\fR" 4 -.IX Item "-mfp-reg" -.PD 0 -.Ip "\fB\-mno-fp-regs\fR" 4 -.IX Item "-mno-fp-regs" -.PD -Generate code that uses (does not use) the floating-point register set. -\&\fB\-mno-fp-regs\fR implies \fB\-msoft-float\fR. If the floating-point -register set is not used, floating point operands are passed in integer -registers as if they were integers and floating-point results are passed -in \f(CW$0\fR instead of \f(CW$f0\fR. This is a non-standard calling sequence, so any -function with a floating-point argument or return value called by code -compiled with \fB\-mno-fp-regs\fR must also be compiled with that -option. -.Sp -A typical use of this option is building a kernel that does not use, -and hence need not save and restore, any floating-point registers. -.Ip "\fB\-mieee\fR" 4 -.IX Item "-mieee" -The Alpha architecture implements floating-point hardware optimized for -maximum performance. It is mostly compliant with the \s-1IEEE\s0 floating -point standard. However, for full compliance, software assistance is -required. This option generates code fully \s-1IEEE\s0 compliant code -\&\fIexcept\fR that the \fIinexact flag\fR is not maintained (see below). -If this option is turned on, the \s-1CPP\s0 macro \f(CW\*(C`_IEEE_FP\*(C'\fR is defined -during compilation. The option is a shorthand for: \fB\-D_IEEE_FP -\&\-mfp-trap-mode=su \-mtrap-precision=i \-mieee-conformant\fR. The resulting -code is less efficient but is able to correctly support denormalized -numbers and exceptional \s-1IEEE\s0 values such as not-a-number and plus/minus -infinity. Other Alpha compilers call this option -\&\fB\-ieee_with_no_inexact\fR. -.Ip "\fB\-mieee-with-inexact\fR" 4 -.IX Item "-mieee-with-inexact" -This is like \fB\-mieee\fR except the generated code also maintains the -\&\s-1IEEE\s0 \fIinexact flag\fR. Turning on this option causes the generated -code to implement fully-compliant \s-1IEEE\s0 math. The option is a shorthand -for \fB\-D_IEEE_FP \-D_IEEE_FP_INEXACT\fR plus the three following: -\&\fB\-mieee-conformant\fR, -\&\fB\-mfp-trap-mode=sui\fR, -and \fB\-mtrap-precision=i\fR. -On some Alpha implementations the resulting code may execute -significantly slower than the code generated by default. Since there -is very little code that depends on the \fIinexact flag\fR, you should -normally not specify this option. Other Alpha compilers call this -option \fB\-ieee_with_inexact\fR. -.Ip "\fB\-mfp-trap-mode=\fR\fItrap mode\fR" 4 -.IX Item "-mfp-trap-mode=trap mode" -This option controls what floating-point related traps are enabled. -Other Alpha compilers call this option \fB\-fptm\fR \fItrap mode\fR. -The trap mode can be set to one of four values: -.RS 4 -.Ip "\fBn\fR" 4 -.IX Item "n" -This is the default (normal) setting. The only traps that are enabled -are the ones that cannot be disabled in software (e.g., division by zero -trap). -.Ip "\fBu\fR" 4 -.IX Item "u" -In addition to the traps enabled by \fBn\fR, underflow traps are enabled -as well. -.Ip "\fBsu\fR" 4 -.IX Item "su" -Like \fBsu\fR, but the instructions are marked to be safe for software -completion (see Alpha architecture manual for details). -.Ip "\fBsui\fR" 4 -.IX Item "sui" -Like \fBsu\fR, but inexact traps are enabled as well. -.RE -.RS 4 -.RE -.Ip "\fB\-mfp-rounding-mode=\fR\fIrounding mode\fR" 4 -.IX Item "-mfp-rounding-mode=rounding mode" -Selects the \s-1IEEE\s0 rounding mode. Other Alpha compilers call this option -\&\fB\-fprm\fR \fIrounding mode\fR. The \fIrounding mode\fR can be one -of: -.RS 4 -.Ip "\fBn\fR" 4 -.IX Item "n" -Normal \s-1IEEE\s0 rounding mode. Floating point numbers are rounded towards -the nearest machine number or towards the even machine number in case -of a tie. -.Ip "\fBm\fR" 4 -.IX Item "m" -Round towards minus infinity. -.Ip "\fBc\fR" 4 -.IX Item "c" -Chopped rounding mode. Floating point numbers are rounded towards zero. -.Ip "\fBd\fR" 4 -.IX Item "d" -Dynamic rounding mode. A field in the floating point control register -(\fIfpcr\fR, see Alpha architecture reference manual) controls the -rounding mode in effect. The C library initializes this register for -rounding towards plus infinity. Thus, unless your program modifies the -\&\fIfpcr\fR, \fBd\fR corresponds to round towards plus infinity. -.RE -.RS 4 -.RE -.Ip "\fB\-mtrap-precision=\fR\fItrap precision\fR" 4 -.IX Item "-mtrap-precision=trap precision" -In the Alpha architecture, floating point traps are imprecise. This -means without software assistance it is impossible to recover from a -floating trap and program execution normally needs to be terminated. -\&\s-1GCC\s0 can generate code that can assist operating system trap handlers -in determining the exact location that caused a floating point trap. -Depending on the requirements of an application, different levels of -precisions can be selected: -.RS 4 -.Ip "\fBp\fR" 4 -.IX Item "p" -Program precision. This option is the default and means a trap handler -can only identify which program caused a floating point exception. -.Ip "\fBf\fR" 4 -.IX Item "f" -Function precision. The trap handler can determine the function that -caused a floating point exception. -.Ip "\fBi\fR" 4 -.IX Item "i" -Instruction precision. The trap handler can determine the exact -instruction that caused a floating point exception. -.RE -.RS 4 -.Sp -Other Alpha compilers provide the equivalent options called -\&\fB\-scope_safe\fR and \fB\-resumption_safe\fR. -.RE -.Ip "\fB\-mieee-conformant\fR" 4 -.IX Item "-mieee-conformant" -This option marks the generated code as \s-1IEEE\s0 conformant. You must not -use this option unless you also specify \fB\-mtrap-precision=i\fR and either -\&\fB\-mfp-trap-mode=su\fR or \fB\-mfp-trap-mode=sui\fR. Its only effect -is to emit the line \fB.eflag 48\fR in the function prologue of the -generated assembly file. Under \s-1DEC\s0 Unix, this has the effect that -IEEE-conformant math library routines will be linked in. -.Ip "\fB\-mbuild-constants\fR" 4 -.IX Item "-mbuild-constants" -Normally \s-1GCC\s0 examines a 32\- or 64\-bit integer constant to -see if it can construct it from smaller constants in two or three -instructions. If it cannot, it will output the constant as a literal and -generate code to load it from the data segment at runtime. -.Sp -Use this option to require \s-1GCC\s0 to construct \fIall\fR integer constants -using code, even if it takes more instructions (the maximum is six). -.Sp -You would typically use this option to build a shared library dynamic -loader. Itself a shared library, it must relocate itself in memory -before it can find the variables and constants in its own data segment. -.Ip "\fB\-malpha-as\fR" 4 -.IX Item "-malpha-as" -.PD 0 -.Ip "\fB\-mgas\fR" 4 -.IX Item "-mgas" -.PD -Select whether to generate code to be assembled by the vendor-supplied -assembler (\fB\-malpha-as\fR) or by the \s-1GNU\s0 assembler \fB\-mgas\fR. -.Ip "\fB\-mbwx\fR" 4 -.IX Item "-mbwx" -.PD 0 -.Ip "\fB\-mno-bwx\fR" 4 -.IX Item "-mno-bwx" -.Ip "\fB\-mcix\fR" 4 -.IX Item "-mcix" -.Ip "\fB\-mno-cix\fR" 4 -.IX Item "-mno-cix" -.Ip "\fB\-mmax\fR" 4 -.IX Item "-mmax" -.Ip "\fB\-mno-max\fR" 4 -.IX Item "-mno-max" -.PD -Indicate whether \s-1GCC\s0 should generate code to use the optional \s-1BWX\s0, -\&\s-1CIX\s0, and \s-1MAX\s0 instruction sets. The default is to use the instruction sets -supported by the \s-1CPU\s0 type specified via \fB\-mcpu=\fR option or that -of the \s-1CPU\s0 on which \s-1GCC\s0 was built if none was specified. -.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 -.IX Item "-mcpu=cpu_type" -Set the instruction set, register set, and instruction scheduling -parameters for machine type \fIcpu_type\fR. You can specify either the -\&\fB\s-1EV\s0\fR style name or the corresponding chip number. \s-1GCC\s0 -supports scheduling parameters for the \s-1EV4\s0 and \s-1EV5\s0 family of processors -and will choose the default values for the instruction set from -the processor you specify. If you do not specify a processor type, -\&\s-1GCC\s0 will default to the processor on which the compiler was built. -.Sp -Supported values for \fIcpu_type\fR are -.RS 4 -.Ip "\fBev4\fR" 4 -.IX Item "ev4" -.PD 0 -.Ip "\fB21064\fR" 4 -.IX Item "21064" -.PD -Schedules as an \s-1EV4\s0 and has no instruction set extensions. -.Ip "\fBev5\fR" 4 -.IX Item "ev5" -.PD 0 -.Ip "\fB21164\fR" 4 -.IX Item "21164" -.PD -Schedules as an \s-1EV5\s0 and has no instruction set extensions. -.Ip "\fBev56\fR" 4 -.IX Item "ev56" -.PD 0 -.Ip "\fB21164a\fR" 4 -.IX Item "21164a" -.PD -Schedules as an \s-1EV5\s0 and supports the \s-1BWX\s0 extension. -.Ip "\fBpca56\fR" 4 -.IX Item "pca56" -.PD 0 -.Ip "\fB21164pc\fR" 4 -.IX Item "21164pc" -.Ip "\fB21164PC\fR" 4 -.IX Item "21164PC" -.PD -Schedules as an \s-1EV5\s0 and supports the \s-1BWX\s0 and \s-1MAX\s0 extensions. -.Ip "\fBev6\fR" 4 -.IX Item "ev6" -.PD 0 -.Ip "\fB21264\fR" 4 -.IX Item "21264" -.PD -Schedules as an \s-1EV5\s0 (until Digital releases the scheduling parameters -for the \s-1EV6\s0) and supports the \s-1BWX\s0, \s-1CIX\s0, and \s-1MAX\s0 extensions. -.RE -.RS 4 -.RE -.Ip "\fB\-mmemory-latency=\fR\fItime\fR" 4 -.IX Item "-mmemory-latency=time" -Sets the latency the scheduler should assume for typical memory -references as seen by the application. This number is highly -dependent on the memory access patterns used by the application -and the size of the external cache on the machine. -.Sp -Valid options for \fItime\fR are -.RS 4 -.Ip "\fInumber\fR" 4 -.IX Item "number" -A decimal number representing clock cycles. -.Ip "\fBL1\fR" 4 -.IX Item "L1" -.PD 0 -.Ip "\fBL2\fR" 4 -.IX Item "L2" -.Ip "\fBL3\fR" 4 -.IX Item "L3" -.Ip "\fBmain\fR" 4 -.IX Item "main" -.PD -The compiler contains estimates of the number of clock cycles for -``typical'' \s-1EV4\s0 & \s-1EV5\s0 hardware for the Level 1, 2 & 3 caches -(also called Dcache, Scache, and Bcache), as well as to main memory. -Note that L3 is only valid for \s-1EV5\s0. -.RE -.RS 4 -.RE -.PP -.I "Clipper Options" -.IX Subsection "Clipper Options" -.PP -These \fB\-m\fR options are defined for the Clipper implementations: -.Ip "\fB\-mc300\fR" 4 -.IX Item "-mc300" -Produce code for a C300 Clipper processor. This is the default. -.Ip "\fB\-mc400\fR" 4 -.IX Item "-mc400" -Produce code for a C400 Clipper processor i.e. use floating point -registers f8..f15. -.PP -.I "H8/300 Options" -.IX Subsection "H8/300 Options" -.PP -These \fB\-m\fR options are defined for the H8/300 implementations: -.Ip "\fB\-mrelax\fR" 4 -.IX Item "-mrelax" -Shorten some address references at link time, when possible; uses the -linker option \fB\-relax\fR. -.Ip "\fB\-mh\fR" 4 -.IX Item "-mh" -Generate code for the H8/300H. -.Ip "\fB\-ms\fR" 4 -.IX Item "-ms" -Generate code for the H8/S. -.Ip "\fB\-ms2600\fR" 4 -.IX Item "-ms2600" -Generate code for the H8/S2600. This switch must be used with \-ms. -.Ip "\fB\-mint32\fR" 4 -.IX Item "-mint32" -Make \f(CW\*(C`int\*(C'\fR data 32 bits by default. -.Ip "\fB\-malign-300\fR" 4 -.IX Item "-malign-300" -On the H8/300H and H8/S, use the same alignment rules as for the H8/300. -The default for the H8/300H and H8/S is to align longs and floats on 4 -byte boundaries. -\&\fB\-malign-300\fR causes them to be aligned on 2 byte boundaries. -This option has no effect on the H8/300. -.PP -.I "\s-1SH\s0 Options" -.IX Subsection "SH Options" -.PP -These \fB\-m\fR options are defined for the \s-1SH\s0 implementations: -.Ip "\fB\-m1\fR" 4 -.IX Item "-m1" -Generate code for the \s-1SH1\s0. -.Ip "\fB\-m2\fR" 4 -.IX Item "-m2" -Generate code for the \s-1SH2\s0. -.Ip "\fB\-m3\fR" 4 -.IX Item "-m3" -Generate code for the \s-1SH3\s0. -.Ip "\fB\-m3e\fR" 4 -.IX Item "-m3e" -Generate code for the SH3e. -.Ip "\fB\-m4\-nofpu\fR" 4 -.IX Item "-m4-nofpu" -Generate code for the \s-1SH4\s0 without a floating-point unit. -.Ip "\fB\-m4\-single-only\fR" 4 -.IX Item "-m4-single-only" -Generate code for the \s-1SH4\s0 with a floating-point unit that only -supports single-precision arithmentic. -.Ip "\fB\-m4\-single\fR" 4 -.IX Item "-m4-single" -Generate code for the \s-1SH4\s0 assuming the floating-point unit is in -single-precision mode by default. -.Ip "\fB\-m4\fR" 4 -.IX Item "-m4" -Generate code for the \s-1SH4\s0. -.Ip "\fB\-mb\fR" 4 -.IX Item "-mb" -Compile code for the processor in big endian mode. -.Ip "\fB\-ml\fR" 4 -.IX Item "-ml" -Compile code for the processor in little endian mode. -.Ip "\fB\-mdalign\fR" 4 -.IX Item "-mdalign" -Align doubles at 64\-bit boundaries. Note that this changes the calling -conventions, and thus some functions from the standard C library will -not work unless you recompile it first with \-mdalign. -.Ip "\fB\-mrelax\fR" 4 -.IX Item "-mrelax" -Shorten some address references at link time, when possible; uses the -linker option \fB\-relax\fR. -.Ip "\fB\-mbigtable\fR" 4 -.IX Item "-mbigtable" -Use 32\-bit offsets in \f(CW\*(C`switch\*(C'\fR tables. The default is to use -16\-bit offsets. -.Ip "\fB\-mfmovd\fR" 4 -.IX Item "-mfmovd" -Enable the use of the instruction \f(CW\*(C`fmovd\*(C'\fR. -.Ip "\fB\-mhitachi\fR" 4 -.IX Item "-mhitachi" -Comply with the calling conventions defined by Hitachi. -.Ip "\fB\-mnomacsave\fR" 4 -.IX Item "-mnomacsave" -Mark the \f(CW\*(C`MAC\*(C'\fR register as call-clobbered, even if -\&\fB\-mhitachi\fR is given. -.Ip "\fB\-misize\fR" 4 -.IX Item "-misize" -Dump instruction size and location in the assembly code. -.Ip "\fB\-mpadstruct\fR" 4 -.IX Item "-mpadstruct" -This option is deprecated. It pads structures to multiple of 4 bytes, -which is incompatible with the \s-1SH\s0 \s-1ABI\s0. -.Ip "\fB\-mspace\fR" 4 -.IX Item "-mspace" -Optimize for space instead of speed. Implied by \fB\-Os\fR. -.Ip "\fB\-mprefergot\fR" 4 -.IX Item "-mprefergot" -When generating position-independent code, emit function calls using -the Global Offset Table instead of the Procedure Linkage Table. -.Ip "\fB\-musermode\fR" 4 -.IX Item "-musermode" -Generate a library function call to invalidate instruction cache -entries, after fixing up a trampoline. This library function call -doesn't assume it can write to the whole memory address space. This -is the default when the target is \f(CW\*(C`sh\-*\-linux*\*(C'\fR. -.PP -.I "Options for System V" -.IX Subsection "Options for System V" -.PP -These additional options are available on System V Release 4 for -compatibility with other compilers on those systems: -.Ip "\fB\-G\fR" 4 -.IX Item "-G" -Create a shared object. -It is recommended that \fB\-symbolic\fR or \fB\-shared\fR be used instead. -.Ip "\fB\-Qy\fR" 4 -.IX Item "-Qy" -Identify the versions of each tool used by the compiler, in a -\&\f(CW\*(C`.ident\*(C'\fR assembler directive in the output. -.Ip "\fB\-Qn\fR" 4 -.IX Item "-Qn" -Refrain from adding \f(CW\*(C`.ident\*(C'\fR directives to the output file (this is -the default). -.Ip "\fB\-YP,\fR\fIdirs\fR" 4 -.IX Item "-YP,dirs" -Search the directories \fIdirs\fR, and no others, for libraries -specified with \fB\-l\fR. -.Ip "\fB\-Ym,\fR\fIdir\fR" 4 -.IX Item "-Ym,dir" -Look in the directory \fIdir\fR to find the M4 preprocessor. -The assembler uses this option. -.PP -.I "TMS320C3x/C4x Options" -.IX Subsection "TMS320C3x/C4x Options" -.PP -These \fB\-m\fR options are defined for TMS320C3x/C4x implementations: -.Ip "\fB\-mcpu=\fR\fIcpu_type\fR" 4 -.IX Item "-mcpu=cpu_type" -Set the instruction set, register set, and instruction scheduling -parameters for machine type \fIcpu_type\fR. Supported values for -\&\fIcpu_type\fR are \fBc30\fR, \fBc31\fR, \fBc32\fR, \fBc40\fR, and -\&\fBc44\fR. The default is \fBc40\fR to generate code for the -\&\s-1TMS320C40\s0. -.Ip "\fB\-mbig-memory\fR" 4 -.IX Item "-mbig-memory" -.PD 0 -.Ip "\fB\-mbig\fR" 4 -.IX Item "-mbig" -.Ip "\fB\-msmall-memory\fR" 4 -.IX Item "-msmall-memory" -.Ip "\fB\-msmall\fR" 4 -.IX Item "-msmall" -.PD -Generates code for the big or small memory model. The small memory -model assumed that all data fits into one 64K word page. At run-time -the data page (\s-1DP\s0) register must be set to point to the 64K page -containing the .bss and .data program sections. The big memory model is -the default and requires reloading of the \s-1DP\s0 register for every direct -memory access. -.Ip "\fB\-mbk\fR" 4 -.IX Item "-mbk" -.PD 0 -.Ip "\fB\-mno-bk\fR" 4 -.IX Item "-mno-bk" -.PD -Allow (disallow) allocation of general integer operands into the block -count register \s-1BK\s0. -.Ip "\fB\-mdb\fR" 4 -.IX Item "-mdb" -.PD 0 -.Ip "\fB\-mno-db\fR" 4 -.IX Item "-mno-db" -.PD -Enable (disable) generation of code using decrement and branch, -\&\fIDBcond\fR\|(D), instructions. This is enabled by default for the C4x. To be -on the safe side, this is disabled for the C3x, since the maximum -iteration count on the C3x is 2^23 + 1 (but who iterates loops more than -2^23 times on the C3x?). Note that \s-1GCC\s0 will try to reverse a loop so -that it can utilise the decrement and branch instruction, but will give -up if there is more than one memory reference in the loop. Thus a loop -where the loop counter is decremented can generate slightly more -efficient code, in cases where the \s-1RPTB\s0 instruction cannot be utilised. -.Ip "\fB\-mdp-isr-reload\fR" 4 -.IX Item "-mdp-isr-reload" -.PD 0 -.Ip "\fB\-mparanoid\fR" 4 -.IX Item "-mparanoid" -.PD -Force the \s-1DP\s0 register to be saved on entry to an interrupt service -routine (\s-1ISR\s0), reloaded to point to the data section, and restored on -exit from the \s-1ISR\s0. This should not be required unless someone has -violated the small memory model by modifying the \s-1DP\s0 register, say within -an object library. -.Ip "\fB\-mmpyi\fR" 4 -.IX Item "-mmpyi" -.PD 0 -.Ip "\fB\-mno-mpyi\fR" 4 -.IX Item "-mno-mpyi" -.PD -For the C3x use the 24\-bit \s-1MPYI\s0 instruction for integer multiplies -instead of a library call to guarantee 32\-bit results. Note that if one -of the operands is a constant, then the multiplication will be performed -using shifts and adds. If the \-mmpyi option is not specified for the C3x, -then squaring operations are performed inline instead of a library call. -.Ip "\fB\-mfast-fix\fR" 4 -.IX Item "-mfast-fix" -.PD 0 -.Ip "\fB\-mno-fast-fix\fR" 4 -.IX Item "-mno-fast-fix" -.PD -The C3x/C4x \s-1FIX\s0 instruction to convert a floating point value to an -integer value chooses the nearest integer less than or equal to the -floating point value rather than to the nearest integer. Thus if the -floating point number is negative, the result will be incorrectly -truncated an additional code is necessary to detect and correct this -case. This option can be used to disable generation of the additional -code required to correct the result. -.Ip "\fB\-mrptb\fR" 4 -.IX Item "-mrptb" -.PD 0 -.Ip "\fB\-mno-rptb\fR" 4 -.IX Item "-mno-rptb" -.PD -Enable (disable) generation of repeat block sequences using the \s-1RPTB\s0 -instruction for zero overhead looping. The \s-1RPTB\s0 construct is only used -for innermost loops that do not call functions or jump across the loop -boundaries. There is no advantage having nested \s-1RPTB\s0 loops due to the -overhead required to save and restore the \s-1RC\s0, \s-1RS\s0, and \s-1RE\s0 registers. -This is enabled by default with \-O2. -.Ip "\fB\-mrpts=\fR\fIcount\fR" 4 -.IX Item "-mrpts=count" -.PD 0 -.Ip "\fB\-mno-rpts\fR" 4 -.IX Item "-mno-rpts" -.PD -Enable (disable) the use of the single instruction repeat instruction -\&\s-1RPTS\s0. If a repeat block contains a single instruction, and the loop -count can be guaranteed to be less than the value \fIcount\fR, \s-1GCC\s0 will -emit a \s-1RPTS\s0 instruction instead of a \s-1RPTB\s0. If no value is specified, -then a \s-1RPTS\s0 will be emitted even if the loop count cannot be determined -at compile time. Note that the repeated instruction following \s-1RPTS\s0 does -not have to be reloaded from memory each iteration, thus freeing up the -\&\s-1CPU\s0 buses for operands. However, since interrupts are blocked by this -instruction, it is disabled by default. -.Ip "\fB\-mloop-unsigned\fR" 4 -.IX Item "-mloop-unsigned" -.PD 0 -.Ip "\fB\-mno-loop-unsigned\fR" 4 -.IX Item "-mno-loop-unsigned" -.PD -The maximum iteration count when using \s-1RPTS\s0 and \s-1RPTB\s0 (and \s-1DB\s0 on the C40) -is 2^31 + 1 since these instructions test if the iteration count is -negative to terminate the loop. If the iteration count is unsigned -there is a possibility than the 2^31 + 1 maximum iteration count may be -exceeded. This switch allows an unsigned iteration count. -.Ip "\fB\-mti\fR" 4 -.IX Item "-mti" -Try to emit an assembler syntax that the \s-1TI\s0 assembler (asm30) is happy -with. This also enforces compatibility with the \s-1API\s0 employed by the \s-1TI\s0 -C3x C compiler. For example, long doubles are passed as structures -rather than in floating point registers. -.Ip "\fB\-mregparm\fR" 4 -.IX Item "-mregparm" -.PD 0 -.Ip "\fB\-mmemparm\fR" 4 -.IX Item "-mmemparm" -.PD -Generate code that uses registers (stack) for passing arguments to functions. -By default, arguments are passed in registers where possible rather -than by pushing arguments on to the stack. -.Ip "\fB\-mparallel-insns\fR" 4 -.IX Item "-mparallel-insns" -.PD 0 -.Ip "\fB\-mno-parallel-insns\fR" 4 -.IX Item "-mno-parallel-insns" -.PD -Allow the generation of parallel instructions. This is enabled by -default with \-O2. -.Ip "\fB\-mparallel-mpy\fR" 4 -.IX Item "-mparallel-mpy" -.PD 0 -.Ip "\fB\-mno-parallel-mpy\fR" 4 -.IX Item "-mno-parallel-mpy" -.PD -Allow the generation of MPY||ADD and MPY||SUB parallel instructions, -provided \-mparallel-insns is also specified. These instructions have -tight register constraints which can pessimize the code generation -of large functions. -.PP -.I "V850 Options" -.IX Subsection "V850 Options" -.PP -These \fB\-m\fR options are defined for V850 implementations: -.Ip "\fB\-mlong-calls\fR" 4 -.IX Item "-mlong-calls" -.PD 0 -.Ip "\fB\-mno-long-calls\fR" 4 -.IX Item "-mno-long-calls" -.PD -Treat all calls as being far away (near). If calls are assumed to be -far away, the compiler will always load the functions address up into a -register, and call indirect through the pointer. -.Ip "\fB\-mno-ep\fR" 4 -.IX Item "-mno-ep" -.PD 0 -.Ip "\fB\-mep\fR" 4 -.IX Item "-mep" -.PD -Do not optimize (do optimize) basic blocks that use the same index -pointer 4 or more times to copy pointer into the \f(CW\*(C`ep\*(C'\fR register, and -use the shorter \f(CW\*(C`sld\*(C'\fR and \f(CW\*(C`sst\*(C'\fR instructions. The \fB\-mep\fR -option is on by default if you optimize. -.Ip "\fB\-mno-prolog-function\fR" 4 -.IX Item "-mno-prolog-function" -.PD 0 -.Ip "\fB\-mprolog-function\fR" 4 -.IX Item "-mprolog-function" -.PD -Do not use (do use) external functions to save and restore registers at -the prolog and epilog of a function. The external functions are slower, -but use less code space if more than one function saves the same number -of registers. The \fB\-mprolog-function\fR option is on by default if -you optimize. -.Ip "\fB\-mspace\fR" 4 -.IX Item "-mspace" -Try to make the code as small as possible. At present, this just turns -on the \fB\-mep\fR and \fB\-mprolog-function\fR options. -.Ip "\fB\-mtda=\fR\fIn\fR" 4 -.IX Item "-mtda=n" -Put static or global variables whose size is \fIn\fR bytes or less into -the tiny data area that register \f(CW\*(C`ep\*(C'\fR points to. The tiny data -area can hold up to 256 bytes in total (128 bytes for byte references). -.Ip "\fB\-msda=\fR\fIn\fR" 4 -.IX Item "-msda=n" -Put static or global variables whose size is \fIn\fR bytes or less into -the small data area that register \f(CW\*(C`gp\*(C'\fR points to. The small data -area can hold up to 64 kilobytes. -.Ip "\fB\-mzda=\fR\fIn\fR" 4 -.IX Item "-mzda=n" -Put static or global variables whose size is \fIn\fR bytes or less into -the first 32 kilobytes of memory. -.Ip "\fB\-mv850\fR" 4 -.IX Item "-mv850" -Specify that the target processor is the V850. -.Ip "\fB\-mbig-switch\fR" 4 -.IX Item "-mbig-switch" -Generate code suitable for big switch tables. Use this option only if -the assembler/linker complain about out of range branches within a switch -table. -.PP -.I "\s-1ARC\s0 Options" -.IX Subsection "ARC Options" -.PP -These options are defined for \s-1ARC\s0 implementations: -.Ip "\fB\-EL\fR" 4 -.IX Item "-EL" -Compile code for little endian mode. This is the default. -.Ip "\fB\-EB\fR" 4 -.IX Item "-EB" -Compile code for big endian mode. -.Ip "\fB\-mmangle-cpu\fR" 4 -.IX Item "-mmangle-cpu" -Prepend the name of the cpu to all public symbol names. -In multiple-processor systems, there are many \s-1ARC\s0 variants with different -instruction and register set characteristics. This flag prevents code -compiled for one cpu to be linked with code compiled for another. -No facility exists for handling variants that are \*(L"almost identical\*(R". -This is an all or nothing option. -.Ip "\fB\-mcpu=\fR\fIcpu\fR" 4 -.IX Item "-mcpu=cpu" -Compile code for \s-1ARC\s0 variant \fIcpu\fR. -Which variants are supported depend on the configuration. -All variants support \fB\-mcpu=base\fR, this is the default. -.Ip "\fB\-mtext=\fR\fItext section\fR" 4 -.IX Item "-mtext=text section" -.PD 0 -.Ip "\fB\-mdata=\fR\fIdata section\fR" 4 -.IX Item "-mdata=data section" -.Ip "\fB\-mrodata=\fR\fIreadonly data section\fR" 4 -.IX Item "-mrodata=readonly data section" -.PD -Put functions, data, and readonly data in \fItext section\fR, -\&\fIdata section\fR, and \fIreadonly data section\fR respectively -by default. This can be overridden with the \f(CW\*(C`section\*(C'\fR attribute. -.PP -.I "\s-1NS32K\s0 Options" -.IX Subsection "NS32K Options" -.PP -These are the \fB\-m\fR options defined for the 32000 series. The default -values for these options depends on which style of 32000 was selected when -the compiler was configured; the defaults for the most common choices are -given below. -.Ip "\fB\-m32032\fR" 4 -.IX Item "-m32032" -.PD 0 -.Ip "\fB\-m32032\fR" 4 -.IX Item "-m32032" -.PD -Generate output for a 32032. This is the default -when the compiler is configured for 32032 and 32016 based systems. -.Ip "\fB\-m32332\fR" 4 -.IX Item "-m32332" -.PD 0 -.Ip "\fB\-m32332\fR" 4 -.IX Item "-m32332" -.PD -Generate output for a 32332. This is the default -when the compiler is configured for 32332\-based systems. -.Ip "\fB\-m32532\fR" 4 -.IX Item "-m32532" -.PD 0 -.Ip "\fB\-m32532\fR" 4 -.IX Item "-m32532" -.PD -Generate output for a 32532. This is the default -when the compiler is configured for 32532\-based systems. -.Ip "\fB\-m32081\fR" 4 -.IX Item "-m32081" -Generate output containing 32081 instructions for floating point. -This is the default for all systems. -.Ip "\fB\-m32381\fR" 4 -.IX Item "-m32381" -Generate output containing 32381 instructions for floating point. This -also implies \fB\-m32081\fR. The 32381 is only compatible with the 32332 -and 32532 cpus. This is the default for the pc532\-netbsd configuration. -.Ip "\fB\-mmulti-add\fR" 4 -.IX Item "-mmulti-add" -Try and generate multiply-add floating point instructions \f(CW\*(C`polyF\*(C'\fR -and \f(CW\*(C`dotF\*(C'\fR. This option is only available if the \fB\-m32381\fR -option is in effect. Using these instructions requires changes to to -register allocation which generally has a negative impact on -performance. This option should only be enabled when compiling code -particularly likely to make heavy use of multiply-add instructions. -.Ip "\fB\-mnomulti-add\fR" 4 -.IX Item "-mnomulti-add" -Do not try and generate multiply-add floating point instructions -\&\f(CW\*(C`polyF\*(C'\fR and \f(CW\*(C`dotF\*(C'\fR. This is the default on all platforms. -.Ip "\fB\-msoft-float\fR" 4 -.IX Item "-msoft-float" -Generate output containing library calls for floating point. -\&\fBWarning:\fR the requisite libraries may not be available. -.Ip "\fB\-mnobitfield\fR" 4 -.IX Item "-mnobitfield" -Do not use the bit-field instructions. On some machines it is faster to -use shifting and masking operations. This is the default for the pc532. -.Ip "\fB\-mbitfield\fR" 4 -.IX Item "-mbitfield" -Do use the bit-field instructions. This is the default for all platforms -except the pc532. -.Ip "\fB\-mrtd\fR" 4 -.IX Item "-mrtd" -Use a different function-calling convention, in which functions -that take a fixed number of arguments return pop their -arguments on return with the \f(CW\*(C`ret\*(C'\fR instruction. -.Sp -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. -.Sp -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including \f(CW\*(C`printf\*(C'\fR); -otherwise incorrect code will be generated for calls to those -functions. -.Sp -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) -.Sp -This option takes its name from the 680x0 \f(CW\*(C`rtd\*(C'\fR instruction. -.Ip "\fB\-mregparam\fR" 4 -.IX Item "-mregparam" -Use a different function-calling convention where the first two arguments -are passed in registers. -.Sp -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. -.Ip "\fB\-mnoregparam\fR" 4 -.IX Item "-mnoregparam" -Do not pass any arguments in registers. This is the default for all -targets. -.Ip "\fB\-msb\fR" 4 -.IX Item "-msb" -It is \s-1OK\s0 to use the sb as an index register which is always loaded with -zero. This is the default for the pc532\-netbsd target. -.Ip "\fB\-mnosb\fR" 4 -.IX Item "-mnosb" -The sb register is not available for use or has not been initialized to -zero by the run time system. This is the default for all targets except -the pc532\-netbsd. It is also implied whenever \fB\-mhimem\fR or -\&\fB\-fpic\fR is set. -.Ip "\fB\-mhimem\fR" 4 -.IX Item "-mhimem" -Many ns32000 series addressing modes use displacements of up to 512MB. -If an address is above 512MB then displacements from zero can not be used. -This option causes code to be generated which can be loaded above 512MB. -This may be useful for operating systems or \s-1ROM\s0 code. -.Ip "\fB\-mnohimem\fR" 4 -.IX Item "-mnohimem" -Assume code will be loaded in the first 512MB of virtual address space. -This is the default for all platforms. -.PP -.I "\s-1AVR\s0 Options" -.IX Subsection "AVR Options" -.PP -These options are defined for \s-1AVR\s0 implementations: -.Ip "\fB\-mmcu=\fR\fImcu\fR" 4 -.IX Item "-mmcu=mcu" -Specify \s-1ATMEL\s0 \s-1AVR\s0 instruction set or \s-1MCU\s0 type. -.Sp -Instruction set avr1 is for the minimal \s-1AVR\s0 core, not supported by the C -compiler, only for assembler programs (\s-1MCU\s0 types: at90s1200, attiny10, -attiny11, attiny12, attiny15, attiny28). -.Sp -Instruction set avr2 (default) is for the classic \s-1AVR\s0 core with up to -8K program memory space (\s-1MCU\s0 types: at90s2313, at90s2323, attiny22, -at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, -at90c8534, at90s8535). -.Sp -Instruction set avr3 is for the classic \s-1AVR\s0 core with up to 128K program -memory space (\s-1MCU\s0 types: atmega103, atmega603). -.Sp -Instruction set avr4 is for the enhanced \s-1AVR\s0 core with up to 8K program -memory space (\s-1MCU\s0 types: atmega83, atmega85). -.Sp -Instruction set avr5 is for the enhanced \s-1AVR\s0 core with up to 128K program -memory space (\s-1MCU\s0 types: atmega161, atmega163, atmega32, at94k). -.Ip "\fB\-msize\fR" 4 -.IX Item "-msize" -Output instruction sizes to the asm file. -.Ip "\fB\-minit-stack=\fR\fIN\fR" 4 -.IX Item "-minit-stack=N" -Specify the initial stack address, which may be a symbol or numeric value, -_\|_stack is the default. -.Ip "\fB\-mno-interrupts\fR" 4 -.IX Item "-mno-interrupts" -Generated code is not compatible with hardware interrupts. -Code size will be smaller. -.Ip "\fB\-mcall-prologues\fR" 4 -.IX Item "-mcall-prologues" -Functions prologues/epilogues expanded as call to appropriate -subroutines. Code size will be smaller. -.Ip "\fB\-mno-tablejump\fR" 4 -.IX Item "-mno-tablejump" -Do not generate tablejump insns which sometimes increase code size. -.Ip "\fB\-mtiny-stack\fR" 4 -.IX Item "-mtiny-stack" -Change only the low 8 bits of the stack pointer. -.PP -.I "MCore Options" -.IX Subsection "MCore Options" -.PP -These are the \fB\-m\fR options defined for the Motorola M*Core -processors. -.Ip "\fB\-mhardlit\fR" 4 -.IX Item "-mhardlit" -.PD 0 -.Ip "\fB\-mhardlit\fR" 4 -.IX Item "-mhardlit" -.Ip "\fB\-mno-hardlit\fR" 4 -.IX Item "-mno-hardlit" -.PD -Inline constants into the code stream if it can be done in two -instructions or less. -.Ip "\fB\-mdiv\fR" 4 -.IX Item "-mdiv" -.PD 0 -.Ip "\fB\-mdiv\fR" 4 -.IX Item "-mdiv" -.Ip "\fB\-mno-div\fR" 4 -.IX Item "-mno-div" -.PD -Use the divide instruction. (Enabled by default). -.Ip "\fB\-mrelax-immediate\fR" 4 -.IX Item "-mrelax-immediate" -.PD 0 -.Ip "\fB\-mrelax-immediate\fR" 4 -.IX Item "-mrelax-immediate" -.Ip "\fB\-mno-relax-immediate\fR" 4 -.IX Item "-mno-relax-immediate" -.PD -Allow arbitrary sized immediates in bit operations. -.Ip "\fB\-mwide-bitfields\fR" 4 -.IX Item "-mwide-bitfields" -.PD 0 -.Ip "\fB\-mwide-bitfields\fR" 4 -.IX Item "-mwide-bitfields" -.Ip "\fB\-mno-wide-bitfields\fR" 4 -.IX Item "-mno-wide-bitfields" -.PD -Always treat bitfields as int-sized. -.Ip "\fB\-m4byte-functions\fR" 4 -.IX Item "-m4byte-functions" -.PD 0 -.Ip "\fB\-m4byte-functions\fR" 4 -.IX Item "-m4byte-functions" -.Ip "\fB\-mno-4byte-functions\fR" 4 -.IX Item "-mno-4byte-functions" -.PD -Force all functions to be aligned to a four byte boundary. -.Ip "\fB\-mcallgraph-data\fR" 4 -.IX Item "-mcallgraph-data" -.PD 0 -.Ip "\fB\-mcallgraph-data\fR" 4 -.IX Item "-mcallgraph-data" -.Ip "\fB\-mno-callgraph-data\fR" 4 -.IX Item "-mno-callgraph-data" -.PD -Emit callgraph information. -.Ip "\fB\-mslow-bytes\fR" 4 -.IX Item "-mslow-bytes" -.PD 0 -.Ip "\fB\-mslow-bytes\fR" 4 -.IX Item "-mslow-bytes" -.Ip "\fB\-mno-slow-bytes\fR" 4 -.IX Item "-mno-slow-bytes" -.PD -Prefer word access when reading byte quantities. -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -.PD 0 -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -.Ip "\fB\-mbig-endian\fR" 4 -.IX Item "-mbig-endian" -.PD -Generate code for a little endian target. -.Ip "\fB\-m210\fR" 4 -.IX Item "-m210" -.PD 0 -.Ip "\fB\-m210\fR" 4 -.IX Item "-m210" -.Ip "\fB\-m340\fR" 4 -.IX Item "-m340" -.PD -Generate code for the 210 processor. -.PP -.I "\s-1IA-64\s0 Options" -.IX Subsection "IA-64 Options" -.PP -These are the \fB\-m\fR options defined for the Intel \s-1IA-64\s0 architecture. -.Ip "\fB\-mbig-endian\fR" 4 -.IX Item "-mbig-endian" -Generate code for a big endian target. This is the default for \s-1HPUX\s0. -.Ip "\fB\-mlittle-endian\fR" 4 -.IX Item "-mlittle-endian" -Generate code for a little endian target. This is the default for \s-1AIX5\s0 -and Linux. -.Ip "\fB\-mgnu-as\fR" 4 -.IX Item "-mgnu-as" -.PD 0 -.Ip "\fB\-mno-gnu-as\fR" 4 -.IX Item "-mno-gnu-as" -.PD -Generate (or don't) code for the \s-1GNU\s0 assembler. This is the default. -.Ip "\fB\-mgnu-ld\fR" 4 -.IX Item "-mgnu-ld" -.PD 0 -.Ip "\fB\-mno-gnu-ld\fR" 4 -.IX Item "-mno-gnu-ld" -.PD -Generate (or don't) code for the \s-1GNU\s0 linker. This is the default. -.Ip "\fB\-mno-pic\fR" 4 -.IX Item "-mno-pic" -Generate code that does not use a global pointer register. The result -is not position independent code, and violates the \s-1IA-64\s0 \s-1ABI\s0. -.Ip "\fB\-mvolatile-asm-stop\fR" 4 -.IX Item "-mvolatile-asm-stop" -.PD 0 -.Ip "\fB\-mno-volatile-asm-stop\fR" 4 -.IX Item "-mno-volatile-asm-stop" -.PD -Generate (or don't) a stop bit immediately before and after volatile asm -statements. -.Ip "\fB\-mb-step\fR" 4 -.IX Item "-mb-step" -Generate code that works around Itanium B step errata. -.Ip "\fB\-mregister-names\fR" 4 -.IX Item "-mregister-names" -.PD 0 -.Ip "\fB\-mno-register-names\fR" 4 -.IX Item "-mno-register-names" -.PD -Generate (or don't) \fBin\fR, \fBloc\fR, and \fBout\fR register names for -the stacked registers. This may make assembler output more readable. -.Ip "\fB\-mno-sdata\fR" 4 -.IX Item "-mno-sdata" -.PD 0 -.Ip "\fB\-msdata\fR" 4 -.IX Item "-msdata" -.PD -Disable (or enable) optimizations that use the small data section. This may -be useful for working around optimizer bugs. -.Ip "\fB\-mconstant-gp\fR" 4 -.IX Item "-mconstant-gp" -Generate code that uses a single constant global pointer value. This is -useful when compiling kernel code. -.Ip "\fB\-mauto-pic\fR" 4 -.IX Item "-mauto-pic" -Generate code that is self-relocatable. This implies \fB\-mconstant-gp\fR. -This is useful when compiling firmware code. -.Ip "\fB\-minline-divide-min-latency\fR" 4 -.IX Item "-minline-divide-min-latency" -Generate code for inline divides using the minimum latency algorithm. -.Ip "\fB\-minline-divide-max-throughput\fR" 4 -.IX Item "-minline-divide-max-throughput" -Generate code for inline divides using the maximum throughput algorithm. -.Ip "\fB\-mno-dwarf2\-asm\fR" 4 -.IX Item "-mno-dwarf2-asm" -.PD 0 -.Ip "\fB\-mdwarf2\-asm\fR" 4 -.IX Item "-mdwarf2-asm" -.PD -Don't (or do) generate assembler code for the \s-1DWARF2\s0 line number debugging -info. This may be useful when not using the \s-1GNU\s0 assembler. -.Ip "\fB\-mfixed-range=\fR\fIregister range\fR" 4 -.IX Item "-mfixed-range=register range" -Generate code treating the given register range as fixed registers. -A fixed register is one that the register allocator can not use. This is -useful when compiling kernel code. A register range is specified as -two registers separated by a dash. Multiple register ranges can be -specified separated by a comma. -.PP -.I "D30V Options" -.IX Subsection "D30V Options" -.PP -These \fB\-m\fR options are defined for D30V implementations: -.Ip "\fB\-mextmem\fR" 4 -.IX Item "-mextmem" -Link the \fB.text\fR, \fB.data\fR, \fB.bss\fR, \fB.strings\fR, -\&\fB.rodata\fR, \fB.rodata1\fR, \fB.data1\fR sections into external -memory, which starts at location \f(CW\*(C`0x80000000\*(C'\fR. -.Ip "\fB\-mextmemory\fR" 4 -.IX Item "-mextmemory" -Same as the \fB\-mextmem\fR switch. -.Ip "\fB\-monchip\fR" 4 -.IX Item "-monchip" -Link the \fB.text\fR section into onchip text memory, which starts at -location \f(CW\*(C`0x0\*(C'\fR. Also link \fB.data\fR, \fB.bss\fR, -\&\fB.strings\fR, \fB.rodata\fR, \fB.rodata1\fR, \fB.data1\fR sections -into onchip data memory, which starts at location \f(CW\*(C`0x20000000\*(C'\fR. -.Ip "\fB\-mno-asm-optimize\fR" 4 -.IX Item "-mno-asm-optimize" -.PD 0 -.Ip "\fB\-masm-optimize\fR" 4 -.IX Item "-masm-optimize" -.PD -Disable (enable) passing \fB\-O\fR to the assembler when optimizing. -The assembler uses the \fB\-O\fR option to automatically parallelize -adjacent short instructions where possible. -.Ip "\fB\-mbranch-cost=\fR\fIn\fR" 4 -.IX Item "-mbranch-cost=n" -Increase the internal costs of branches to \fIn\fR. Higher costs means -that the compiler will issue more instructions to avoid doing a branch. -The default is 2. -.Ip "\fB\-mcond-exec=\fR\fIn\fR" 4 -.IX Item "-mcond-exec=n" -Specify the maximum number of conditionally executed instructions that -replace a branch. The default is 4. -.Sh "Options for Code Generation Conventions" -.IX Subsection "Options for Code Generation Conventions" -These machine-independent options control the interface conventions -used in code generation. -.PP -Most of them have both positive and negative forms; the negative form -of \fB\-ffoo\fR would be \fB\-fno-foo\fR. In the table below, only -one of the forms is listed\-\-\-the one which is not the default. You -can figure out the other form by either removing \fBno-\fR or adding -it. -.Ip "\fB\-fexceptions\fR" 4 -.IX Item "-fexceptions" -Enable exception handling. Generates extra code needed to propagate -exceptions. For some targets, this implies \s-1GNU\s0 \s-1CC\s0 will generate frame -unwind information for all functions, which can produce significant data -size overhead, although it does not affect execution. If you do not -specify this option, \s-1GNU\s0 \s-1CC\s0 will enable it by default for languages like -\&\*(C+ which normally require exception handling, and disable itfor -languages like C that do not normally require it. However, you may need -to enable this option when compiling C code that needs to interoperate -properly with exception handlers written in \*(C+. You may also wish to -disable this option if you are compiling older \*(C+ programs that don't -use exception handling. -.Ip "\fB\-funwind-tables\fR" 4 -.IX Item "-funwind-tables" -Similar to \fB\-fexceptions\fR, except that it will just generate any needed -static data, but will not affect the generated code in any other way. -You will normally not enable this option; instead, a language processor -that needs this handling would enable it on your behalf. -.Ip "\fB\-fpcc-struct-return\fR" 4 -.IX Item "-fpcc-struct-return" -Return ``short'' \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR values in memory like -longer ones, rather than in registers. This convention is less -efficient, but it has the advantage of allowing intercallability between -GCC-compiled files and files compiled with other compilers. -.Sp -The precise convention for returning structures in memory depends -on the target configuration macros. -.Sp -Short structures and unions are those whose size and alignment match -that of some integer type. -.Ip "\fB\-freg-struct-return\fR" 4 -.IX Item "-freg-struct-return" -Use the convention that \f(CW\*(C`struct\*(C'\fR and \f(CW\*(C`union\*(C'\fR values are -returned in registers when possible. This is more efficient for small -structures than \fB\-fpcc-struct-return\fR. -.Sp -If you specify neither \fB\-fpcc-struct-return\fR nor its contrary -\&\fB\-freg-struct-return\fR, \s-1GCC\s0 defaults to whichever convention is -standard for the target. If there is no standard convention, \s-1GCC\s0 -defaults to \fB\-fpcc-struct-return\fR, except on targets where \s-1GCC\s0 -is the principal compiler. In those cases, we can choose the standard, -and we chose the more efficient register return alternative. -.Ip "\fB\-fshort-enums\fR" 4 -.IX Item "-fshort-enums" -Allocate to an \f(CW\*(C`enum\*(C'\fR type only as many bytes as it needs for the -declared range of possible values. Specifically, the \f(CW\*(C`enum\*(C'\fR type -will be equivalent to the smallest integer type which has enough room. -.Ip "\fB\-fshort-double\fR" 4 -.IX Item "-fshort-double" -Use the same size for \f(CW\*(C`double\*(C'\fR as for \f(CW\*(C`float\*(C'\fR. -.Ip "\fB\-fshared-data\fR" 4 -.IX Item "-fshared-data" -Requests that the data and non-\f(CW\*(C`const\*(C'\fR variables of this -compilation be shared data rather than private data. The distinction -makes sense only on certain operating systems, where shared data is -shared between processes running the same program, while private data -exists in one copy per process. -.Ip "\fB\-fno-common\fR" 4 -.IX Item "-fno-common" -Allocate even uninitialized global variables in the data section of the -object file, rather than generating them as common blocks. This has the -effect that if the same variable is declared (without \f(CW\*(C`extern\*(C'\fR) in -two different compilations, you will get an error when you link them. -The only reason this might be useful is if you wish to verify that the -program will work on other systems which always work this way. -.Ip "\fB\-fno-ident\fR" 4 -.IX Item "-fno-ident" -Ignore the \fB#ident\fR directive. -.Ip "\fB\-fno-gnu-linker\fR" 4 -.IX Item "-fno-gnu-linker" -Do not output global initializations (such as \*(C+ constructors and -destructors) in the form used by the \s-1GNU\s0 linker (on systems where the \s-1GNU\s0 -linker is the standard method of handling them). Use this option when -you want to use a non-GNU linker, which also requires using the -\&\fBcollect2\fR program to make sure the system linker includes -constructors and destructors. (\fBcollect2\fR is included in the \s-1GCC\s0 -distribution.) For systems which \fImust\fR use \fBcollect2\fR, the -compiler driver \fBgcc\fR is configured to do this automatically. -.Ip "\fB\-finhibit-size-directive\fR" 4 -.IX Item "-finhibit-size-directive" -Don't output a \f(CW\*(C`.size\*(C'\fR assembler directive, or anything else that -would cause trouble if the function is split in the middle, and the -two halves are placed at locations far apart in memory. This option is -used when compiling \fIcrtstuff.c\fR; you should not need to use it -for anything else. -.Ip "\fB\-fverbose-asm\fR" 4 -.IX Item "-fverbose-asm" -Put extra commentary information in the generated assembly code to -make it more readable. This option is generally only of use to those -who actually need to read the generated assembly code (perhaps while -debugging the compiler itself). -.Sp -\&\fB\-fno-verbose-asm\fR, the default, causes the -extra information to be omitted and is useful when comparing two assembler -files. -.Ip "\fB\-fvolatile\fR" 4 -.IX Item "-fvolatile" -Consider all memory references through pointers to be volatile. -.Ip "\fB\-fvolatile-global\fR" 4 -.IX Item "-fvolatile-global" -Consider all memory references to extern and global data items to -be volatile. \s-1GCC\s0 does not consider static data items to be volatile -because of this switch. -.Ip "\fB\-fvolatile-static\fR" 4 -.IX Item "-fvolatile-static" -Consider all memory references to static data to be volatile. -.Ip "\fB\-fpic\fR" 4 -.IX Item "-fpic" -Generate position-independent code (\s-1PIC\s0) suitable for use in a shared -library, if supported for the target machine. Such code accesses all -constant addresses through a global offset table (\s-1GOT\s0). The dynamic -loader resolves the \s-1GOT\s0 entries when the program starts (the dynamic -loader is not part of \s-1GCC\s0; it is part of the operating system). If -the \s-1GOT\s0 size for the linked executable exceeds a machine-specific -maximum size, you get an error message from the linker indicating that -\&\fB\-fpic\fR does not work; in that case, recompile with \fB\-fPIC\fR -instead. (These maximums are 16k on the m88k, 8k on the Sparc, and 32k -on the m68k and \s-1RS/6000\s0. The 386 has no such limit.) -.Sp -Position-independent code requires special support, and therefore works -only on certain machines. For the 386, \s-1GCC\s0 supports \s-1PIC\s0 for System V -but not for the Sun 386i. Code generated for the \s-1IBM\s0 \s-1RS/6000\s0 is always -position-independent. -.Ip "\fB\-fPIC\fR" 4 -.IX Item "-fPIC" -If supported for the target machine, emit position-independent code, -suitable for dynamic linking and avoiding any limit on the size of the -global offset table. This option makes a difference on the m68k, m88k, -and the Sparc. -.Sp -Position-independent code requires special support, and therefore works -only on certain machines. -.Ip "\fB\-ffixed-\fR\fIreg\fR" 4 -.IX Item "-ffixed-reg" -Treat the register named \fIreg\fR as a fixed register; generated code -should never refer to it (except perhaps as a stack pointer, frame -pointer or in some other fixed role). -.Sp -\&\fIreg\fR must be the name of a register. The register names accepted -are machine-specific and are defined in the \f(CW\*(C`REGISTER_NAMES\*(C'\fR -macro in the machine description macro file. -.Sp -This flag does not have a negative form, because it specifies a -three-way choice. -.Ip "\fB\-fcall-used-\fR\fIreg\fR" 4 -.IX Item "-fcall-used-reg" -Treat the register named \fIreg\fR as an allocable register that is -clobbered by function calls. It may be allocated for temporaries or -variables that do not live across a call. Functions compiled this way -will not save and restore the register \fIreg\fR. -.Sp -It is an error to used this flag with the frame pointer or stack pointer. -Use of this flag for other registers that have fixed pervasive roles in -the machine's execution model will produce disastrous results. -.Sp -This flag does not have a negative form, because it specifies a -three-way choice. -.Ip "\fB\-fcall-saved-\fR\fIreg\fR" 4 -.IX Item "-fcall-saved-reg" -Treat the register named \fIreg\fR as an allocable register saved by -functions. It may be allocated even for temporaries or variables that -live across a call. Functions compiled this way will save and restore -the register \fIreg\fR if they use it. -.Sp -It is an error to used this flag with the frame pointer or stack pointer. -Use of this flag for other registers that have fixed pervasive roles in -the machine's execution model will produce disastrous results. -.Sp -A different sort of disaster will result from the use of this flag for -a register in which function values may be returned. -.Sp -This flag does not have a negative form, because it specifies a -three-way choice. -.Ip "\fB\-fpack-struct\fR" 4 -.IX Item "-fpack-struct" -Pack all structure members together without holes. Usually you would -not want to use this option, since it makes the code suboptimal, and -the offsets of structure members won't agree with system libraries. -.Ip "\fB\-fcheck-memory-usage\fR" 4 -.IX Item "-fcheck-memory-usage" -Generate extra code to check each memory access. \s-1GCC\s0 will generate -code that is suitable for a detector of bad memory accesses such as -\&\fIChecker\fR. -.Sp -Normally, you should compile all, or none, of your code with this option. -.Sp -If you do mix code compiled with and without this option, -you must ensure that all code that has side effects -and that is called by code compiled with this option -is, itself, compiled with this option. -If you do not, you might get erroneous messages from the detector. -.Sp -If you use functions from a library that have side-effects (such as -\&\f(CW\*(C`read\*(C'\fR), you might not be able to recompile the library and -specify this option. In that case, you can enable the -\&\fB\-fprefix-function-name\fR option, which requests \s-1GCC\s0 to encapsulate -your code and make other functions look as if they were compiled with -\&\fB\-fcheck-memory-usage\fR. This is done by calling ``stubs'', -which are provided by the detector. If you cannot find or build -stubs for every function you call, you might have to specify -\&\fB\-fcheck-memory-usage\fR without \fB\-fprefix-function-name\fR. -.Sp -If you specify this option, you can not use the \f(CW\*(C`asm\*(C'\fR or -\&\f(CW\*(C`_\|_asm_\|_\*(C'\fR keywords in functions with memory checking enabled. \s-1GNU\s0 -\&\s-1CC\s0 cannot understand what the \f(CW\*(C`asm\*(C'\fR statement may do, and therefore -cannot generate the appropriate code, so it will reject it. However, if -you specify the function attribute \f(CW\*(C`no_check_memory_usage\*(C'\fR, \s-1GNU\s0 \s-1CC\s0 will disable memory checking within a -function; you may use \f(CW\*(C`asm\*(C'\fR statements inside such functions. You -may have an inline expansion of a non-checked function within a checked -function; in that case \s-1GNU\s0 \s-1CC\s0 will not generate checks for the inlined -function's memory accesses. -.Sp -If you move your \f(CW\*(C`asm\*(C'\fR statements to non-checked inline functions -and they do access memory, you can add calls to the support code in your -inline function, to indicate any reads, writes, or copies being done. -These calls would be similar to those done in the stubs described above. -.Ip "\fB\-fprefix-function-name\fR" 4 -.IX Item "-fprefix-function-name" -Request \s-1GCC\s0 to add a prefix to the symbols generated for function names. -\&\s-1GCC\s0 adds a prefix to the names of functions defined as well as -functions called. Code compiled with this option and code compiled -without the option can't be linked together, unless stubs are used. -.Sp -If you compile the following code with \fB\-fprefix-function-name\fR -.Sp -.Vb 6 -\& extern void bar (int); -\& void -\& foo (int a) -\& { -\& return bar (a + 5); -\& } -.Ve -\&\s-1GCC\s0 will compile the code as if it was written: -.Sp -.Vb 6 -\& extern void prefix_bar (int); -\& void -\& prefix_foo (int a) -\& { -\& return prefix_bar (a + 5); -\& } -.Ve -This option is designed to be used with \fB\-fcheck-memory-usage\fR. -.Ip "\fB\-finstrument-functions\fR" 4 -.IX Item "-finstrument-functions" -Generate instrumentation calls for entry and exit to functions. Just -after function entry and just before function exit, the following -profiling functions will be called with the address of the current -function and its call site. (On some platforms, -\&\f(CW\*(C`_\|_builtin_return_address\*(C'\fR does not work beyond the current -function, so the call site information may not be available to the -profiling functions otherwise.) -.Sp -.Vb 2 -\& void __cyg_profile_func_enter (void *this_fn, void *call_site); -\& void __cyg_profile_func_exit (void *this_fn, void *call_site); -.Ve -The first argument is the address of the start of the current function, -which may be looked up exactly in the symbol table. -.Sp -This instrumentation is also done for functions expanded inline in other -functions. The profiling calls will indicate where, conceptually, the -inline function is entered and exited. This means that addressable -versions of such functions must be available. If all your uses of a -function are expanded inline, this may mean an additional expansion of -code size. If you use \fBextern inline\fR in your C code, an -addressable version of such functions must be provided. (This is -normally the case anyways, but if you get lucky and the optimizer always -expands the functions inline, you might have gotten away without -providing static copies.) -.Sp -A function may be given the attribute \f(CW\*(C`no_instrument_function\*(C'\fR, in -which case this instrumentation will not be done. This can be used, for -example, for the profiling functions listed above, high-priority -interrupt routines, and any functions from which the profiling functions -cannot safely be called (perhaps signal handlers, if the profiling -routines generate output or allocate memory). -.Ip "\fB\-fstack-check\fR" 4 -.IX Item "-fstack-check" -Generate code to verify that you do not go beyond the boundary of the -stack. You should specify this flag if you are running in an -environment with multiple threads, but only rarely need to specify it in -a single-threaded environment since stack overflow is automatically -detected on nearly all systems if there is only one stack. -.Sp -Note that this switch does not actually cause checking to be done; the -operating system must do that. The switch causes generation of code -to ensure that the operating system sees the stack being extended. -.Ip "\fB\-fstack-limit-register=\fR\fIreg\fR" 4 -.IX Item "-fstack-limit-register=reg" -.PD 0 -.Ip "\fB\-fstack-limit-symbol=\fR\fIsym\fR" 4 -.IX Item "-fstack-limit-symbol=sym" -.Ip "\fB\-fno-stack-limit\fR" 4 -.IX Item "-fno-stack-limit" -.PD -Generate code to ensure that the stack does not grow beyond a certain value, -either the value of a register or the address of a symbol. If the stack -would grow beyond the value, a signal is raised. For most targets, -the signal is raised before the stack overruns the boundary, so -it is possible to catch the signal without taking special precautions. -.Sp -For instance, if the stack starts at address \fB0x80000000\fR and grows -downwards you can use the flags -\&\fB\-fstack-limit-symbol=_\|_stack_limit\fR -\&\fB\-Wl,\-\-defsym,_\|_stack_limit=0x7ffe0000\fR which will enforce a stack -limit of 128K. -.Ip "\fB\-fargument-alias\fR" 4 -.IX Item "-fargument-alias" -.PD 0 -.Ip "\fB\-fargument-noalias\fR" 4 -.IX Item "-fargument-noalias" -.Ip "\fB\-fargument-noalias-global\fR" 4 -.IX Item "-fargument-noalias-global" -.PD -Specify the possible relationships among parameters and between -parameters and global data. -.Sp -\&\fB\-fargument-alias\fR specifies that arguments (parameters) may -alias each other and may alias global storage. -\&\fB\-fargument-noalias\fR specifies that arguments do not alias -each other, but may alias global storage. -\&\fB\-fargument-noalias-global\fR specifies that arguments do not -alias each other and do not alias global storage. -.Sp -Each language will automatically use whatever option is required by -the language standard. You should not need to use these options yourself. -.Ip "\fB\-fleading-underscore\fR" 4 -.IX Item "-fleading-underscore" -This option and its counterpart, \-fno-leading-underscore, forcibly -change the way C symbols are represented in the object file. One use -is to help link with legacy assembly code. -.Sp -Be warned that you should know what you are doing when invoking this -option, and that not all targets provide complete support for it. -.SH "ENVIRONMENT" -.IX Header "ENVIRONMENT" -This section describes several environment variables that affect how \s-1GCC\s0 -operates. Some of them work by specifying directories or prefixes to use -when searching for various kinds of files. Some are used to specify other -aspects of the compilation environment. -.PP -Note that you can also specify places to search using options such as -\&\fB\-B\fR, \fB\-I\fR and \fB\-L\fR. These -take precedence over places specified using environment variables, which -in turn take precedence over those specified by the configuration of \s-1GCC\s0. -.Ip "\fB\s-1LANG\s0\fR" 4 -.IX Item "LANG" -.PD 0 -.Ip "\fB\s-1LC_CTYPE\s0\fR" 4 -.IX Item "LC_CTYPE" -.Ip "\fB\s-1LC_MESSAGES\s0\fR" 4 -.IX Item "LC_MESSAGES" -.Ip "\fB\s-1LC_ALL\s0\fR" 4 -.IX Item "LC_ALL" -.PD -These environment variables control the way that \s-1GCC\s0 uses -localization information that allow \s-1GCC\s0 to work with different -national conventions. \s-1GCC\s0 inspects the locale categories -\&\fB\s-1LC_CTYPE\s0\fR and \fB\s-1LC_MESSAGES\s0\fR if it has been configured to do -so. These locale categories can be set to any value supported by your -installation. A typical value is \fBen_UK\fR for English in the United -Kingdom. -.Sp -The \fB\s-1LC_CTYPE\s0\fR environment variable specifies character -classification. \s-1GCC\s0 uses it to determine the character boundaries in -a string; this is needed for some multibyte encodings that contain quote -and escape characters that would otherwise be interpreted as a string -end or escape. -.Sp -The \fB\s-1LC_MESSAGES\s0\fR environment variable specifies the language to -use in diagnostic messages. -.Sp -If the \fB\s-1LC_ALL\s0\fR environment variable is set, it overrides the value -of \fB\s-1LC_CTYPE\s0\fR and \fB\s-1LC_MESSAGES\s0\fR; otherwise, \fB\s-1LC_CTYPE\s0\fR -and \fB\s-1LC_MESSAGES\s0\fR default to the value of the \fB\s-1LANG\s0\fR -environment variable. If none of these variables are set, \s-1GCC\s0 -defaults to traditional C English behavior. -.Ip "\fB\s-1TMPDIR\s0\fR" 4 -.IX Item "TMPDIR" -If \fB\s-1TMPDIR\s0\fR is set, it specifies the directory to use for temporary -files. \s-1GCC\s0 uses temporary files to hold the output of one stage of -compilation which is to be used as input to the next stage: for example, -the output of the preprocessor, which is the input to the compiler -proper. -.Ip "\fB\s-1GCC_EXEC_PREFIX\s0\fR" 4 -.IX Item "GCC_EXEC_PREFIX" -If \fB\s-1GCC_EXEC_PREFIX\s0\fR is set, it specifies a prefix to use in the -names of the subprograms executed by the compiler. No slash is added -when this prefix is combined with the name of a subprogram, but you can -specify a prefix that ends with a slash if you wish. -.Sp -If \fB\s-1GCC_EXEC_PREFIX\s0\fR is not set, \s-1GNU\s0 \s-1CC\s0 will attempt to figure out -an appropriate prefix to use based on the pathname it was invoked with. -.Sp -If \s-1GCC\s0 cannot find the subprogram using the specified prefix, it -tries looking in the usual places for the subprogram. -.Sp -The default value of \fB\s-1GCC_EXEC_PREFIX\s0\fR is -\&\fI\fIprefix\fI/lib/gcc-lib/\fR where \fIprefix\fR is the value -of \f(CW\*(C`prefix\*(C'\fR when you ran the \fIconfigure\fR script. -.Sp -Other prefixes specified with \fB\-B\fR take precedence over this prefix. -.Sp -This prefix is also used for finding files such as \fIcrt0.o\fR that are -used for linking. -.Sp -In addition, the prefix is used in an unusual way in finding the -directories to search for header files. For each of the standard -directories whose name normally begins with \fB/usr/local/lib/gcc-lib\fR -(more precisely, with the value of \fB\s-1GCC_INCLUDE_DIR\s0\fR), \s-1GCC\s0 tries -replacing that beginning with the specified prefix to produce an -alternate directory name. Thus, with \fB\-Bfoo/\fR, \s-1GCC\s0 will search -\&\fIfoo/bar\fR where it would normally search \fI/usr/local/lib/bar\fR. -These alternate directories are searched first; the standard directories -come next. -.Ip "\fB\s-1COMPILER_PATH\s0\fR" 4 -.IX Item "COMPILER_PATH" -The value of \fB\s-1COMPILER_PATH\s0\fR is a colon-separated list of -directories, much like \fB\s-1PATH\s0\fR. \s-1GCC\s0 tries the directories thus -specified when searching for subprograms, if it can't find the -subprograms using \fB\s-1GCC_EXEC_PREFIX\s0\fR. -.Ip "\fB\s-1LIBRARY_PATH\s0\fR" 4 -.IX Item "LIBRARY_PATH" -The value of \fB\s-1LIBRARY_PATH\s0\fR is a colon-separated list of -directories, much like \fB\s-1PATH\s0\fR. When configured as a native compiler, -\&\s-1GCC\s0 tries the directories thus specified when searching for special -linker files, if it can't find them using \fB\s-1GCC_EXEC_PREFIX\s0\fR. Linking -using \s-1GCC\s0 also uses these directories when searching for ordinary -libraries for the \fB\-l\fR option (but directories specified with -\&\fB\-L\fR come first). -.Ip "\fBC_INCLUDE_PATH\fR" 4 -.IX Item "C_INCLUDE_PATH" -.PD 0 -.Ip "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4 -.IX Item "CPLUS_INCLUDE_PATH" -.Ip "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4 -.IX Item "OBJC_INCLUDE_PATH" -.PD -These environment variables pertain to particular languages. Each -variable's value is a colon-separated list of directories, much like -\&\fB\s-1PATH\s0\fR. When \s-1GCC\s0 searches for header files, it tries the -directories listed in the variable for the language you are using, after -the directories specified with \fB\-I\fR but before the standard header -file directories. -.Ip "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4 -.IX Item "DEPENDENCIES_OUTPUT" -If this variable is set, its value specifies how to output dependencies -for Make based on the header files processed by the compiler. This -output looks much like the output from the \fB\-M\fR option, but it goes to a separate file, and is -in addition to the usual results of compilation. -.Sp -The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in -which case the Make rules are written to that file, guessing the target -name from the source file name. Or the value can have the form -\&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to -file \fIfile\fR using \fItarget\fR as the target name. -.Ip "\fB\s-1LANG\s0\fR" 4 -.IX Item "LANG" -This variable is used to pass locale information to the compiler. One way in -which this information is used is to determine the character set to be used -when character literals, string literals and comments are parsed in C and \*(C+. -When the compiler is configured to allow multibyte characters, -the following values for \fB\s-1LANG\s0\fR are recognized: -.RS 4 -.Ip "\fBC-JIS\fR" 4 -.IX Item "C-JIS" -Recognize \s-1JIS\s0 characters. -.Ip "\fBC-SJIS\fR" 4 -.IX Item "C-SJIS" -Recognize \s-1SJIS\s0 characters. -.Ip "\fBC-EUCJP\fR" 4 -.IX Item "C-EUCJP" -Recognize \s-1EUCJP\s0 characters. -.RE -.RS 4 -.Sp -If \fB\s-1LANG\s0\fR is not defined, or if it has some other value, then the -compiler will use mblen and mbtowc as defined by the default locale to -recognize and translate multibyte characters. -.RE -.SH "BUGS" -.IX Header "BUGS" -For instructions on reporting bugs, see -<\fBhttp://gcc.gnu.org/bugs.html\fR>. Use of the \fBgccbug\fR -script to report bugs is recommended. -.SH "FOOTNOTES" -.IX Header "FOOTNOTES" -.Ip "1." 4 -On some systems, \fBgcc \-shared\fR -needs to build supplementary stub code for constructors to work. On -multi-libbed systems, \fBgcc \-shared\fR must select the correct support -libraries to link against. Failing to supply the correct flags may lead -to subtle defects. Supplying them in cases where they are not necessary -is innocuous. -.SH "SEE ALSO" -.IX Header "SEE ALSO" -\&\fIcpp\fR\|(1), \fIgcov\fR\|(1), \fIg77\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), \fIgdb\fR\|(1), \fIadb\fR\|(1), \fIdbx\fR\|(1), \fIsdb\fR\|(1) -and the Info entries for \fIgcc\fR, \fIcpp\fR, \fIg77\fR, \fIas\fR, -\&\fIld\fR, \fIbinutils\fR and \fIgdb\fR. -.SH "AUTHOR" -.IX Header "AUTHOR" -See the Info entry for \fIgcc\fR, or -<\fBhttp://gcc.gnu.org/thanks.html\fR>, for contributors to \s-1GCC\s0. -.SH "COPYRIGHT" -.IX Header "COPYRIGHT" -Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, -1998, 1999, 2000, 2001 Free Software Foundation, Inc. -.PP -Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. -.PP -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -entire resulting derived work is distributed under the terms of a -permission notice identical to this one. -.PP -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that this permission notice may be included in translations -approved by the Free Software Foundation instead of in the original -English. diff --git a/gcc/gcc.texi b/gcc/gcc.texi deleted file mode 100644 index b618737c2cb..00000000000 --- a/gcc/gcc.texi +++ /dev/null @@ -1,4793 +0,0 @@ -\input texinfo @c -*-texinfo-*- -@c %**start of header -@setfilename gcc.info -@c @setfilename usegcc.info -@c @setfilename portgcc.info -@c To produce the full manual, use the "gcc.info" setfilename, and -@c make sure the following do NOT begin with '@c' (and the @clear lines DO) -@set INTERNALS -@set USING -@c To produce a user-only manual, use the "usegcc.info" setfilename, and -@c make sure the following does NOT begin with '@c': -@c @clear INTERNALS -@c To produce a porter-only manual, use the "portgcc.info" setfilename, -@c and make sure the following does NOT begin with '@c': -@c @clear USING - -@c (For FSF printing, turn on smallbook, comment out finalout below; -@c that is all that is needed.) - -@c 6/27/96 FSF DO wants smallbook fmt for 1st bound edition. -@c @smallbook - -@c i also commented out the finalout command, so if there *are* any -@c overfulls, you'll (hopefully) see the rectangle in the right hand -@c margin. -mew 15june93 -@c @finalout - -@c NOTE: checks/things to do: -@c -@c -have bob do a search in all seven files for "mew" (ideally --mew, -@c but i may have forgotten the occasional "--"..). -@c Just checked... all have `--'! Bob 22Jul96 -@c Use this to search: grep -n '\-\-mew' *.texi -@c -item/itemx, text after all (sub/sub)section titles, etc.. -@c -consider putting the lists of options on pp 17--> etc in columns or -@c some such. -@c -spellcheck -@c -continuity of phrasing; ie, bit-field vs bitfield in rtl.texi -@c -overfulls. do a search for "mew" in the files, and you will see -@c overfulls that i noted but could not deal with. -@c -have to add text: beginning of chapter 8 - -@c -@c anything else? --mew 10feb93 - -@macro gcctabopt{body} -@code{\body\} -@end macro -@macro gccoptlist{body} -@smallexample -\body\ -@end smallexample -@end macro -@c Makeinfo handles the above macro OK, TeX needs manual line breaks; -@c they get lost at some point in handling the macro. But if @macro is -@c used here rather than @alias, it produces double line breaks. -@iftex -@alias gol = * -@end iftex -@ifnottex -@macro gol -@end macro -@end ifnottex - -@ifset INTERNALS -@ifset USING -@settitle Using and Porting the GNU Compiler Collection (GCC) -@end ifset -@end ifset -@c seems reasonable to assume at least one of INTERNALS or USING is set... -@ifclear INTERNALS -@settitle Using the GNU Compiler Collection -@end ifclear -@ifclear USING -@settitle Porting the GNU Compiler Collection -@end ifclear - -@syncodeindex fn cp -@syncodeindex vr cp -@syncodeindex ky cp -@syncodeindex pg cp -@syncodeindex tp cp - -@c %**end of header - -@c Use with @@smallbook. - -@c Cause even numbered pages to be printed on the left hand side of -@c the page and odd numbered pages to be printed on the right hand -@c side of the page. Using this, you can print on both sides of a -@c sheet of paper and have the text on the same part of the sheet. - -@c The text on right hand pages is pushed towards the right hand -@c margin and the text on left hand pages is pushed toward the left -@c hand margin. -@c (To provide the reverse effect, set bindingoffset to -0.75in.) - -@c @tex -@c \global\bindingoffset=0.75in -@c \global\normaloffset =0.75in -@c @end tex - -@ifnottex -@dircategory Programming -@direntry -* gcc: (gcc). The GNU Compiler Collection. -@end direntry -@ifset INTERNALS -@ifset USING -This file documents the use and the internals of the GNU compiler. -@end ifset -@end ifset -@ifclear USING -This file documents the internals of the GNU compiler. -@end ifclear -@ifclear INTERNALS -This file documents the use of the GNU compiler. -@end ifclear -@sp 1 -Published by the Free Software Foundation@* -59 Temple Place - Suite 330@* -Boston, MA 02111-1307 USA -@sp 1 -@c When you update the list of years below, search for copyright{} and -@c update the other copy too. -Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, -1999, 2000, 2001 Free Software Foundation, Inc. -@sp 1 -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.1 or -any later version published by the Free Software Foundation; with the -Invariant Sections being ``GNU General Public License'' and ``Funding -Free Software'', the Front-Cover texts being (a) (see below), and with -the Back-Cover Texts being (b) (see below). A copy of the license is -included in the section entitled ``GNU Free Documentation License''. - -(a) The FSF's Front-Cover Text is: - - A GNU Manual - -(b) The FSF's Back-Cover Text is: - - You have freedom to copy and modify this GNU Manual, like GNU - software. Copies published by the Free Software Foundation raise - funds for GNU development. -@end ifnottex - -@setchapternewpage odd -@c @finalout -@titlepage -@ifset INTERNALS -@ifset USING -@center @titlefont{Using and Porting the GNU Compiler Collection} - -@end ifset -@end ifset -@ifclear INTERNALS -@title Using the GNU Compiler Collection -@end ifclear -@ifclear USING -@title Porting the GNU Compiler Collection -@end ifclear -@sp 2 -@center Richard M. Stallman -@sp 3 -@center Last updated 9 May 2001 -@sp 1 -@c The version number appears five times more in this file. - -@center for gcc-3.1 -@page -@vskip 0pt plus 1filll -Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1998, -1999, 2000, 2001 Free Software Foundation, Inc. -@sp 2 -For GCC Version 3.1@* -@sp 1 -Published by the Free Software Foundation @* -59 Temple Place - Suite 330@* -Boston, MA 02111-1307, USA@* -Last printed April, 1998.@* -Printed copies are available for $50 each.@* -ISBN 1-882114-37-X -@sp 1 -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.1 or -any later version published by the Free Software Foundation; with the -Invariant Sections being ``GNU General Public License'', the Front-Cover -texts being (a) (see below), and with the Back-Cover Texts being (b) -(see below). A copy of the license is included in the section entitled -``GNU Free Documentation License''. - -(a) The FSF's Front-Cover Text is: - - A GNU Manual - -(b) The FSF's Back-Cover Text is: - - You have freedom to copy and modify this GNU Manual, like GNU - software. Copies published by the Free Software Foundation raise - funds for GNU development. -@end titlepage -@page - -@node Top, G++ and GCC,, (DIR) -@top Introduction -@cindex introduction - -@ifset INTERNALS -@ifset USING -This manual documents how to run, install and port the GNU -compiler, as well as its new features and incompatibilities, and how to -report bugs. It corresponds to GCC version 3.1. -@end ifset -@end ifset - -@ifclear INTERNALS -This manual documents how to run and install the GNU compiler, -as well as its new features and incompatibilities, and how to report -bugs. It corresponds to GCC version 3.1. -@end ifclear -@ifclear USING -This manual documents how to port the GNU compiler, -as well as its new features and incompatibilities, and how to report -bugs. It corresponds to GCC version 3.1. -@end ifclear - -@menu -@ifset USING -* G++ and GCC:: You can compile C or C++ programs. -* Standards:: Language standards supported by GCC. -* Invoking GCC:: Command options supported by @samp{gcc}. -* Installation:: How to configure, compile and install GCC. -* C Extensions:: GNU extensions to the C language family. -* C++ Extensions:: GNU extensions to the C++ language. -* Objective C:: GNU Objective-C runtime features. -* Gcov:: gcov: a GCC test coverage program. -* Trouble:: If you have trouble installing GCC. -* Bugs:: How, why and where to report bugs. -* Service:: How to find suppliers of support for GCC. -* Contributing:: How to contribute to testing and developing GCC. -* VMS:: Using GCC on VMS. -* Makefile:: List of Makefile targets. -@end ifset -@ifset INTERNALS -* Portability:: Goals of GCC's portability features. -* Interface:: Function-call interface of GCC output. -* Passes:: Order of passes, what they do, and what each file is for. -* Trees:: The source representation used by the C and C++ front-ends. -* RTL:: The intermediate representation that most passes work on. -* Machine Desc:: How to write machine description instruction patterns. -* Target Macros:: How to write the machine description C macros. -* Config:: Writing the @file{xm-@var{machine}.h} file. -* Fragments:: Writing the @file{t-@var{target}} and @file{x-@var{host}} files. -@end ifset - -* Funding:: How to help assure funding for free software. -* GNU/Linux:: Linux and the GNU Project - -* Copying:: GNU General Public License says - how you can copy and share GCC. -* GNU Free Documentation License:: How you can copy and share this manual. -* Contributors:: People who have contributed to GCC. - -* Index:: Index of concepts and symbol names. -@end menu - -@ifset USING -@node G++ and GCC -@chapter Compile C, C++, Objective C, Fortran, Java or CHILL - -@cindex Objective C -Several versions of the compiler (C, C++, Objective C, Fortran, Java -and CHILL) are integrated; this is why we use the name -``GNU Compiler Collection''. GCC can compile programs written in any of these -languages. The Fortran, CHILL, and Java compilers are described in -separate manuals. - -@cindex GCC -``GCC'' is a common shorthand term for the GNU Compiler Collection. This is both -the most general name for the compiler, and the name used when the -emphasis is on compiling C programs (as the abbreviation formerly -stood for ``GNU C Compiler''). - -@cindex C++ -@cindex G++ -When referring to C++ compilation, it is usual to call the compiler -``G++''. Since there is only one compiler, it is also accurate to call -it ``GCC'' no matter what the language context; however, the term -``G++'' is more useful when the emphasis is on compiling C++ programs. - -We use the name ``GCC'' to refer to the compilation system as a -whole, and more specifically to the language-independent part of the -compiler. For example, we refer to the optimization options as -affecting the behavior of ``GCC'' or sometimes just ``the compiler''. - -Front ends for other languages, such as Ada 95 and Pascal exist but -have not yet been integrated into GCC. These front-ends, like that for C++, -are built in subdirectories of GCC and link to it. The result is an -integrated compiler that can compile programs written in C, C++, -Objective C, or any of the languages for which you have installed front -ends. - -In this manual, we only discuss the options for the C, Objective-C, and -C++ compilers and those of the GCC core. Consult the documentation -of the other front ends for the options to use when compiling programs -written in other languages. - -@cindex compiler compared to C++ preprocessor -@cindex intermediate C version, nonexistent -@cindex C intermediate output, nonexistent -G++ is a @emph{compiler}, not merely a preprocessor. G++ builds object -code directly from your C++ program source. There is no intermediate C -version of the program. (By contrast, for example, some other -implementations use a program that generates a C program from your C++ -source.) Avoiding an intermediate C representation of the program means -that you get better object code, and better debugging information. The -GNU debugger, GDB, works with this information in the object code to -give you comprehensive C++ source-level editing capabilities -(@pxref{C,,C and C++,gdb.info, Debugging with GDB}). - -@c FIXME! Someone who knows something about Objective C ought to put in -@c a paragraph or two about it here, and move the index entry down when -@c there is more to point to than the general mention in the 1st par. - -@node Standards -@chapter Language Standards Supported by GCC -@cindex C standard -@cindex C standards -@cindex ANSI C standard -@cindex ANSI C -@cindex ANSI C89 -@cindex C89 -@cindex ANSI X3.159-1989 -@cindex X3.159-1989 -@cindex ISO C standard -@cindex ISO C -@cindex ISO C89 -@cindex ISO C90 -@cindex ISO/IEC 9899 -@cindex ISO 9899 -@cindex C90 -@cindex ISO C94 -@cindex C94 -@cindex ISO C95 -@cindex C95 -@cindex ISO C99 -@cindex C99 -@cindex ISO C9X -@cindex C9X -@cindex Technical Corrigenda -@cindex TC1 -@cindex Technical Corrigendum 1 -@cindex TC2 -@cindex Technical Corrigendum 2 -@cindex AMD1 -@cindex freestanding implementation -@cindex freestanding environment -@cindex hosted implementation -@cindex hosted environment -@findex __STDC_HOSTED__ - -For each language compiled by GCC for which there is a standard, GCC -attempts to follow one or more versions of that standard, possibly -with some exceptions, and possibly with some extensions. - -GCC supports three versions of the C standard, although support for -the most recent version is not yet complete. - -The original ANSI C standard (X3.159-1989) was ratified in 1989 and -published in 1990. This standard was ratified as an ISO standard -(ISO/IEC 9899:1990) later in 1990. There were no technical -differences between these publications, although the sections of the -ANSI standard were renumbered and became clauses in the ISO standard. -This standard, in both its forms, is commonly known as @dfn{C89}, or -occasionally as @dfn{C90}, from the dates of ratification. The ANSI -standard, but not the ISO standard, also came with a Rationale -document. To select this standard in GCC, use one of the options -@samp{-ansi}, @samp{-std=c89} or @samp{-std=iso9899:1990}; to obtain -all the diagnostics required by the standard, you should also specify -@samp{-pedantic} (or @samp{-pedantic-errors} if you want them to be -errors rather than warnings). @xref{C Dialect Options,,Options -Controlling C Dialect}. - -Errors in the 1990 ISO C standard were corrected in two Technical -Corrigenda published in 1994 and 1996. GCC does not support the -uncorrected version. - -An amendment to the 1990 standard was published in 1995. This -amendment added digraphs and @code{__STDC_VERSION__} to the language, -but otherwise concerned the library. This amendment is commonly known -as @dfn{AMD1}; the amended standard is sometimes known as @dfn{C94} or -@dfn{C95}. To select this standard in GCC, use the option -@samp{-std=iso9899:199409} (with, as for other standard versions, -@samp{-pedantic} to receive all required diagnostics). - -A new edition of the ISO C standard was published in 1999 as ISO/IEC -9899:1999, and is commonly known as @dfn{C99}. GCC has incomplete -support for this standard version; see -@uref{http://gcc.gnu.org/c99status.html} for details. To select this -standard, use @samp{-std=c99} or @samp{-std=iso9899:1999}. (While in -development, drafts of this standard version were referred to as -@dfn{C9X}.) - -GCC also has some limited support for traditional (pre-ISO) C with the -@samp{-traditional} option. This support may be of use for compiling -some very old programs that have not been updated to ISO C, but should -not be used for new programs. It will not work with some modern C -libraries such as the GNU C library. - -By default, GCC provides some extensions to the C language that on -rare occasions conflict with the C standard. @xref{C -Extensions,,Extensions to the C Language Family}. Use of the -@samp{-std} options listed above will disable these extensions where -they conflict with the C standard version selected. You may also -select an extended version of the C language explicitly with -@samp{-std=gnu89} (for C89 with GNU extensions) or @samp{-std=gnu99} -(for C99 with GNU extensions). The default, if no C language dialect -options are given, is @samp{-std=gnu89}; this will change to -@samp{-std=gnu99} in some future release when the C99 support is -complete. Some features that are part of the C99 standard are -accepted as extensions in C89 mode. - -The ISO C standard defines (in clause 4) two classes of conforming -implementation. A @dfn{conforming hosted implementation} supports the -whole standard including all the library facilities; a @dfn{conforming -freestanding implementation} is only required to provide certain -library facilities: those in @code{}, @code{}, -@code{}, and @code{}; since AMD1, also those in -@code{}; and in C99, also those in @code{} and -@code{}. In addition, complex types, added in C99, are not -required for freestanding implementations. The standard also defines -two environments for programs, a @dfn{freestanding environment}, -required of all implementations and which may not have library -facilities beyond those required of freestanding implementations, -where the handling of program startup and termination are -implementation-defined, and a @dfn{hosted environment}, which is not -required, in which all the library facilities are provided and startup -is through a function @code{int main (void)} or @code{int main (int, -char *[])}. An OS kernel would be a freestanding environment; a -program using the facilities of an operating system would normally be -in a hosted implementation. - -GNU CC aims towards being usable as a conforming freestanding -implementation, or as the compiler for a conforming hosted -implementation. By default, it will act as the compiler for a hosted -implementation, defining @code{__STDC_HOSTED__} as @code{1} and -presuming that when the names of ISO C functions are used, they have -the semantics defined in the standard. To make it act as a conforming -freestanding implementation for a freestanding environment, use the -option @samp{-ffreestanding}; it will then define -@code{__STDC_HOSTED__} to @code{0} and not make assumptions about the -meanings of function names from the standard library. To build an OS -kernel, you may well still need to make your own arrangements for -linking and startup. @xref{C Dialect Options,,Options Controlling C -Dialect}. - -GNU CC does not provide the library facilities required only of hosted -implementations, nor yet all the facilities required by C99 of -freestanding implementations; to use the facilities of a hosted -environment, you will need to find them elsewhere (for example, in the -GNU C library). @xref{Standard Libraries,,Standard Libraries}. - -For references to Technical Corrigenda, Rationale documents and -information concerning the history of C that is available online, see -@uref{http://gcc.gnu.org/readings.html} - -@c FIXME: details of C++ standard. - -There is no formal written standard for Objective-C. The most -authoritative manual is ``Object-Oriented Programming and the -Objective-C Language'', available at a number of web sites; -@uref{http://developer.apple.com/techpubs/macosx/Cocoa/ObjectiveC} has a -recent version, while @uref{http://www.toodarkpark.org/computers/objc/} -is an older example. @uref{http://www.gnustep.org} includes useful -information as well. - -@xref{Language,,The GNU Fortran Language, g77, Using and Porting GNU -Fortran}, for details of the Fortran language supported by GCC. - -@xref{Compatibility,,Compatibility with the Java Platform, gcj, GNU gcj}, -for details of compatibility between @code{gcj} and the Java Platform. - -@xref{References,,Language Definition References, chill, GNU Chill}, -for details of the CHILL standard. - -@include invoke.texi - -@include install.texi - -@include extend.texi - -@include objc.texi - -@include gcov.texi - -@node Trouble -@chapter Known Causes of Trouble with GCC -@cindex bugs, known -@cindex installation trouble -@cindex known causes of trouble - -This section describes known problems that affect users of GCC. Most -of these are not GCC bugs per se---if they were, we would fix them. -But the result for a user may be like the result of a bug. - -Some of these problems are due to bugs in other software, some are -missing features that are too much work to add, and some are places -where people's opinions differ as to what is best. - -@menu -* Actual Bugs:: Bugs we will fix later. -* Installation Problems:: Problems that manifest when you install GCC. -* Cross-Compiler Problems:: Common problems of cross compiling with GCC. -* Interoperation:: Problems using GCC with other compilers, - and with certain linkers, assemblers and debuggers. -* External Bugs:: Problems compiling certain programs. -* Incompatibilities:: GCC is incompatible with traditional C. -* Fixed Headers:: GNU C uses corrected versions of system header files. - This is necessary, but doesn't always work smoothly. -* Standard Libraries:: GNU C uses the system C library, which might not be - compliant with the ISO C standard. -* Disappointments:: Regrettable things we can't change, but not quite bugs. -* C++ Misunderstandings:: Common misunderstandings with GNU C++. -* Protoize Caveats:: Things to watch out for when using @code{protoize}. -* Non-bugs:: Things we think are right, but some others disagree. -* Warnings and Errors:: Which problems in your code get warnings, - and which get errors. -@end menu - -@node Actual Bugs -@section Actual Bugs We Haven't Fixed Yet - -@itemize @bullet -@item -The @code{fixincludes} script interacts badly with automounters; if the -directory of system header files is automounted, it tends to be -unmounted while @code{fixincludes} is running. This would seem to be a -bug in the automounter. We don't know any good way to work around it. - -@item -The @code{fixproto} script will sometimes add prototypes for the -@code{sigsetjmp} and @code{siglongjmp} functions that reference the -@code{jmp_buf} type before that type is defined. To work around this, -edit the offending file and place the typedef in front of the -prototypes. - -@item -When @samp{-pedantic-errors} is specified, GCC will incorrectly give -an error message when a function name is specified in an expression -involving the comma operator. -@end itemize - -@node Installation Problems -@section Installation Problems - -This is a list of problems (and some apparent problems which don't -really mean anything is wrong) that show up during installation of GNU -CC. - -@itemize @bullet -@item -On certain systems, defining certain environment variables such as -@code{CC} can interfere with the functioning of @code{make}. - -@item -If you encounter seemingly strange errors when trying to build the -compiler in a directory other than the source directory, it could be -because you have previously configured the compiler in the source -directory. Make sure you have done all the necessary preparations. -@xref{Other Dir}. - -@item -If you build GCC on a BSD system using a directory stored in a System -V file system, problems may occur in running @code{fixincludes} if the -System V file system doesn't support symbolic links. These problems -result in a failure to fix the declaration of @code{size_t} in -@file{sys/types.h}. If you find that @code{size_t} is a signed type and -that type mismatches occur, this could be the cause. - -The solution is not to use such a directory for building GCC. - -@item -Some commands executed when making the compiler may fail (return a -non-zero status) and be ignored by @code{make}. These failures, which -are often due to files that were not found, are expected, and can safely -be ignored. - -@item -It is normal to have warnings in compiling certain files about -unreachable code and about enumeration type clashes. These files' names -begin with @samp{insn-}. Also, @file{real.c} may get some warnings that -you can ignore. - -@item -Sometimes @code{make} recompiles parts of the compiler when installing -the compiler. In one case, this was traced down to a bug in -@code{make}. Either ignore the problem or switch to GNU Make. - -@item -On GNU/Linux SLS 1.01, there is a problem with @file{libc.a}: it does not -contain the obstack functions. However, GCC assumes that the obstack -functions are in @file{libc.a} when it is the GNU C library. To work -around this problem, change the @code{__GNU_LIBRARY__} conditional -around line 31 to @samp{#if 1}. - -@item -On SCO systems, when compiling GCC with the system's compiler, -do not use @samp{-O}. Some versions of the system's compiler miscompile -GCC with @samp{-O}. - -@cindex @code{genflags}, crash on Sun 4 -@item -Sometimes on a Sun 4 you may observe a crash in the program -@code{genflags} or @code{genoutput} while building GCC. This is said to -be due to a bug in @code{sh}. You can probably get around it by running -@code{genflags} or @code{genoutput} manually and then retrying the -@code{make}. - -@item -On Solaris 2, executables of GCC version 2.0.2 are commonly -available, but they have a bug that shows up when compiling current -versions of GCC: undefined symbol errors occur during assembly if you -use @samp{-g}. - -The solution is to compile the current version of GCC without -@samp{-g}. That makes a working compiler which you can use to recompile -with @samp{-g}. - -@item -Solaris 2 comes with a number of optional OS packages. Some of these -packages are needed to use GCC fully. If you did not install all -optional packages when installing Solaris, you will need to verify that -the packages that GCC needs are installed. - -To check whether an optional package is installed, use -the @code{pkginfo} command. To add an optional package, use the -@code{pkgadd} command. For further details, see the Solaris -documentation. - -For Solaris 2.0 and 2.1, GCC needs six packages: @samp{SUNWarc}, -@samp{SUNWbtool}, @samp{SUNWesu}, @samp{SUNWhea}, @samp{SUNWlibm}, and -@samp{SUNWtoo}. - -For Solaris 2.2, GCC needs an additional seventh package: @samp{SUNWsprot}. - -@item -On Solaris 2, trying to use the linker and other tools in -@file{/usr/ucb} to install GCC has been observed to cause trouble. -For example, the linker may hang indefinitely. The fix is to remove -@file{/usr/ucb} from your @code{PATH}. - -@item -If you use the 1.31 version of the MIPS assembler (such as was shipped -with Ultrix 3.1), you will need to use the -fno-delayed-branch switch -when optimizing floating point code. Otherwise, the assembler will -complain when the GCC compiler fills a branch delay slot with a -floating point instruction, such as @code{add.d}. - -@item -If on a MIPS system you get an error message saying ``does not have gp -sections for all it's [sic] sectons [sic]'', don't worry about it. This -happens whenever you use GAS with the MIPS linker, but there is not -really anything wrong, and it is okay to use the output file. You can -stop such warnings by installing the GNU linker. - -It would be nice to extend GAS to produce the gp tables, but they are -optional, and there should not be a warning about their absence. - -@item -Users have reported some problems with version 2.0 of the MIPS -compiler tools that were shipped with Ultrix 4.1. Version 2.10 -which came with Ultrix 4.2 seems to work fine. - -Users have also reported some problems with version 2.20 of the -MIPS compiler tools that were shipped with RISC/os 4.x. The earlier -version 2.11 seems to work fine. - -@item -Some versions of the MIPS linker will issue an assertion failure -when linking code that uses @code{alloca} against shared -libraries on RISC-OS 5.0, and DEC's OSF/1 systems. This is a bug -in the linker, that is supposed to be fixed in future revisions. -To protect against this, GCC passes @samp{-non_shared} to the -linker unless you pass an explicit @samp{-shared} or -@samp{-call_shared} switch. - -@item -On System V release 3, you may get this error message -while linking: - -@smallexample -ld fatal: failed to write symbol name @var{something} - in strings table for file @var{whatever} -@end smallexample - -This probably indicates that the disk is full or your ULIMIT won't allow -the file to be as large as it needs to be. - -This problem can also result because the kernel parameter @code{MAXUMEM} -is too small. If so, you must regenerate the kernel and make the value -much larger. The default value is reported to be 1024; a value of 32768 -is said to work. Smaller values may also work. - -@item -On System V, if you get an error like this, - -@example -/usr/local/lib/bison.simple: In function `yyparse': -/usr/local/lib/bison.simple:625: virtual memory exhausted -@end example - -@noindent -that too indicates a problem with disk space, ULIMIT, or @code{MAXUMEM}. - -@item -Current GCC versions probably do not work on version 2 of the NeXT -operating system. - -@item -On NeXTStep 3.0, the Objective C compiler does not work, due, -apparently, to a kernel bug that it happens to trigger. This problem -does not happen on 3.1. - -@item -On the Tower models 4@var{n}0 and 6@var{n}0, by default a process is not -allowed to have more than one megabyte of memory. GCC cannot compile -itself (or many other programs) with @samp{-O} in that much memory. - -To solve this problem, reconfigure the kernel adding the following line -to the configuration file: - -@smallexample -MAXUMEM = 4096 -@end smallexample - -@item -On HP 9000 series 300 or 400 running HP-UX release 8.0, there is a bug -in the assembler that must be fixed before GCC can be built. This -bug manifests itself during the first stage of compilation, while -building @file{libgcc2.a}: - -@smallexample -_floatdisf -cc1: warning: `-g' option not supported on this version of GCC -cc1: warning: `-g1' option not supported on this version of GCC -./xgcc: Internal compiler error: program as got fatal signal 11 -@end smallexample - -A patched version of the assembler is available as the file -@uref{ftp://altdorf.ai.mit.edu/archive/cph/hpux-8.0-assembler}. If you -have HP software support, the patch can also be obtained directly from -HP, as described in the following note: - -@quotation -This is the patched assembler, to patch SR#1653-010439, where the -assembler aborts on floating point constants. - -The bug is not really in the assembler, but in the shared library -version of the function ``cvtnum(3c)''. The bug on ``cvtnum(3c)'' is -SR#4701-078451. Anyway, the attached assembler uses the archive -library version of ``cvtnum(3c)'' and thus does not exhibit the bug. -@end quotation - -This patch is also known as PHCO_4484. - -@item -On HP-UX version 8.05, but not on 8.07 or more recent versions, -the @code{fixproto} shell script triggers a bug in the system shell. -If you encounter this problem, upgrade your operating system or -use BASH (the GNU shell) to run @code{fixproto}. - -@item -There may be similar problems on System V Release 3.1 on 386 systems. - -@item -On the Intel Paragon (an i860 machine), if you are using operating -system version 1.0, you will get warnings or errors about redefinition -of @code{va_arg} when you build GCC. - -If this happens, then you need to link most programs with the library -@file{iclib.a}. You must also modify @file{stdio.h} as follows: before -the lines - -@example -#if defined(__i860__) && !defined(_VA_LIST) -#include -@end example - -@noindent -insert the line - -@example -#if __PGC__ -@end example - -@noindent -and after the lines - -@example -extern int vprintf(const char *, va_list ); -extern int vsprintf(char *, const char *, va_list ); -#endif -@end example - -@noindent -insert the line - -@example -#endif /* __PGC__ */ -@end example - -These problems don't exist in operating system version 1.1. - -@item -On the Altos 3068, programs compiled with GCC won't work unless you -fix a kernel bug. This happens using system versions V.2.2 1.0gT1 and -V.2.2 1.0e and perhaps later versions as well. See the file -@file{README.ALTOS}. - -@item -You will get several sorts of compilation and linking errors on the -we32k if you don't follow the special instructions. @xref{Configurations}. - -@item -A bug in the HP-UX 8.05 (and earlier) shell will cause the fixproto -program to report an error of the form: - -@example -./fixproto: sh internal 1K buffer overflow -@end example - -To fix this, change the first line of the fixproto script to look like: - -@example -#!/bin/ksh -@end example -@end itemize - -@node Cross-Compiler Problems -@section Cross-Compiler Problems - -You may run into problems with cross compilation on certain machines, -for several reasons. - -@itemize @bullet -@item -Cross compilation can run into trouble for certain machines because -some target machines' assemblers require floating point numbers to be -written as @emph{integer} constants in certain contexts. - -The compiler writes these integer constants by examining the floating -point value as an integer and printing that integer, because this is -simple to write and independent of the details of the floating point -representation. But this does not work if the compiler is running on -a different machine with an incompatible floating point format, or -even a different byte-ordering. - -In addition, correct constant folding of floating point values -requires representing them in the target machine's format. -(The C standard does not quite require this, but in practice -it is the only way to win.) - -It is now possible to overcome these problems by defining macros such -as @code{REAL_VALUE_TYPE}. But doing so is a substantial amount of -work for each target machine. -@ifset INTERNALS -@xref{Cross-compilation}. -@end ifset -@ifclear INTERNALS -@xref{Cross-compilation,,Cross Compilation and Floating Point Format, -gcc.info, Using and Porting GCC}. -@end ifclear - -@item -At present, the program @file{mips-tfile} which adds debug -support to object files on MIPS systems does not work in a cross -compile environment. -@end itemize - -@node Interoperation -@section Interoperation - -This section lists various difficulties encountered in using GNU C or -GNU C++ together with other compilers or with the assemblers, linkers, -libraries and debuggers on certain systems. - -@itemize @bullet -@item -Objective C does not work on the RS/6000. - -@item -GNU C++ does not do name mangling in the same way as other C++ -compilers. This means that object files compiled with one compiler -cannot be used with another. - -This effect is intentional, to protect you from more subtle problems. -Compilers differ as to many internal details of C++ implementation, -including: how class instances are laid out, how multiple inheritance is -implemented, and how virtual function calls are handled. If the name -encoding were made the same, your programs would link against libraries -provided from other compilers---but the programs would then crash when -run. Incompatible libraries are then detected at link time, rather than -at run time. - -@item -Older GDB versions sometimes fail to read the output of GCC version -2. If you have trouble, get GDB version 4.4 or later. - -@item -@cindex DBX -DBX rejects some files produced by GCC, though it accepts similar -constructs in output from PCC. Until someone can supply a coherent -description of what is valid DBX input and what is not, there is -nothing I can do about these problems. You are on your own. - -@item -The GNU assembler (GAS) does not support PIC. To generate PIC code, you -must use some other assembler, such as @file{/bin/as}. - -@item -On some BSD systems, including some versions of Ultrix, use of profiling -causes static variable destructors (currently used only in C++) not to -be run. - -@item -Use of @samp{-I/usr/include} may cause trouble. - -Many systems come with header files that won't work with GCC unless -corrected by @code{fixincludes}. The corrected header files go in a new -directory; GCC searches this directory before @file{/usr/include}. -If you use @samp{-I/usr/include}, this tells GCC to search -@file{/usr/include} earlier on, before the corrected headers. The -result is that you get the uncorrected header files. - -Instead, you should use these options (when compiling C programs): - -@smallexample --I/usr/local/lib/gcc-lib/@var{target}/@var{version}/include -I/usr/include -@end smallexample - -For C++ programs, GCC also uses a special directory that defines C++ -interfaces to standard C subroutines. This directory is meant to be -searched @emph{before} other standard include directories, so that it -takes precedence. If you are compiling C++ programs and specifying -include directories explicitly, use this option first, then the two -options above: - -@example --I/usr/local/lib/g++-include -@end example - -@ignore -@cindex @code{vfork}, for the Sun-4 -@item -There is a bug in @code{vfork} on the Sun-4 which causes the registers -of the child process to clobber those of the parent. Because of this, -programs that call @code{vfork} are likely to lose when compiled -optimized with GCC when the child code alters registers which contain -C variables in the parent. This affects variables which are live in the -parent across the call to @code{vfork}. - -If you encounter this, you can work around the problem by declaring -variables @code{volatile} in the function that calls @code{vfork}, until -the problem goes away, or by not declaring them @code{register} and not -using @samp{-O} for those source files. -@end ignore - -@item -On some SGI systems, when you use @samp{-lgl_s} as an option, -it gets translated magically to @samp{-lgl_s -lX11_s -lc_s}. -Naturally, this does not happen when you use GCC. -You must specify all three options explicitly. - -@item -On a Sparc, GCC aligns all values of type @code{double} on an 8-byte -boundary, and it expects every @code{double} to be so aligned. The Sun -compiler usually gives @code{double} values 8-byte alignment, with one -exception: function arguments of type @code{double} may not be aligned. - -As a result, if a function compiled with Sun CC takes the address of an -argument of type @code{double} and passes this pointer of type -@code{double *} to a function compiled with GCC, dereferencing the -pointer may cause a fatal signal. - -One way to solve this problem is to compile your entire program with GNU -CC. Another solution is to modify the function that is compiled with -Sun CC to copy the argument into a local variable; local variables -are always properly aligned. A third solution is to modify the function -that uses the pointer to dereference it via the following function -@code{access_double} instead of directly with @samp{*}: - -@smallexample -inline double -access_double (double *unaligned_ptr) -@{ - union d2i @{ double d; int i[2]; @}; - - union d2i *p = (union d2i *) unaligned_ptr; - union d2i u; - - u.i[0] = p->i[0]; - u.i[1] = p->i[1]; - - return u.d; -@} -@end smallexample - -@noindent -Storing into the pointer can be done likewise with the same union. - -@item -On Solaris, the @code{malloc} function in the @file{libmalloc.a} library -may allocate memory that is only 4 byte aligned. Since GCC on the -Sparc assumes that doubles are 8 byte aligned, this may result in a -fatal signal if doubles are stored in memory allocated by the -@file{libmalloc.a} library. - -The solution is to not use the @file{libmalloc.a} library. Use instead -@code{malloc} and related functions from @file{libc.a}; they do not have -this problem. - -@item -Sun forgot to include a static version of @file{libdl.a} with some -versions of SunOS (mainly 4.1). This results in undefined symbols when -linking static binaries (that is, if you use @samp{-static}). If you -see undefined symbols @code{_dlclose}, @code{_dlsym} or @code{_dlopen} -when linking, compile and link against the file -@file{mit/util/misc/dlsym.c} from the MIT version of X windows. - -@item -The 128-bit long double format that the Sparc port supports currently -works by using the architecturally defined quad-word floating point -instructions. Since there is no hardware that supports these -instructions they must be emulated by the operating system. Long -doubles do not work in Sun OS versions 4.0.3 and earlier, because the -kernel emulator uses an obsolete and incompatible format. Long doubles -do not work in Sun OS version 4.1.1 due to a problem in a Sun library. -Long doubles do work on Sun OS versions 4.1.2 and higher, but GCC -does not enable them by default. Long doubles appear to work in Sun OS -5.x (Solaris 2.x). - -@item -On HP-UX version 9.01 on the HP PA, the HP compiler @code{cc} does not -compile GCC correctly. We do not yet know why. However, GCC -compiled on earlier HP-UX versions works properly on HP-UX 9.01 and can -compile itself properly on 9.01. - -@item -On the HP PA machine, ADB sometimes fails to work on functions compiled -with GCC. Specifically, it fails to work on functions that use -@code{alloca} or variable-size arrays. This is because GCC doesn't -generate HP-UX unwind descriptors for such functions. It may even be -impossible to generate them. - -@item -Debugging (@samp{-g}) is not supported on the HP PA machine, unless you use -the preliminary GNU tools (@pxref{Installation}). - -@item -Taking the address of a label may generate errors from the HP-UX -PA assembler. GAS for the PA does not have this problem. - -@item -Using floating point parameters for indirect calls to static functions -will not work when using the HP assembler. There simply is no way for GCC -to specify what registers hold arguments for static functions when using -the HP assembler. GAS for the PA does not have this problem. - -@item -In extremely rare cases involving some very large functions you may -receive errors from the HP linker complaining about an out of bounds -unconditional branch offset. This used to occur more often in previous -versions of GCC, but is now exceptionally rare. If you should run -into it, you can work around by making your function smaller. - -@item -GCC compiled code sometimes emits warnings from the HP-UX assembler of -the form: - -@smallexample -(warning) Use of GR3 when - frame >= 8192 may cause conflict. -@end smallexample - -These warnings are harmless and can be safely ignored. - -@item -The current version of the assembler (@file{/bin/as}) for the RS/6000 -has certain problems that prevent the @samp{-g} option in GCC from -working. Note that @file{Makefile.in} uses @samp{-g} by default when -compiling @file{libgcc2.c}. - -IBM has produced a fixed version of the assembler. The upgraded -assembler unfortunately was not included in any of the AIX 3.2 update -PTF releases (3.2.2, 3.2.3, or 3.2.3e). Users of AIX 3.1 should request -PTF U403044 from IBM and users of AIX 3.2 should request PTF U416277. -See the file @file{README.RS6000} for more details on these updates. - -You can test for the presence of a fixed assembler by using the -command - -@smallexample -as -u < /dev/null -@end smallexample - -@noindent -If the command exits normally, the assembler fix already is installed. -If the assembler complains that "-u" is an unknown flag, you need to -order the fix. - -@item -On the IBM RS/6000, compiling code of the form - -@smallexample -extern int foo; - -@dots{} foo @dots{} - -static int foo; -@end smallexample - -@noindent -will cause the linker to report an undefined symbol @code{foo}. -Although this behavior differs from most other systems, it is not a -bug because redefining an @code{extern} variable as @code{static} -is undefined in ISO C. - -@item -AIX on the RS/6000 provides support (NLS) for environments outside of -the United States. Compilers and assemblers use NLS to support -locale-specific representations of various objects including -floating-point numbers ("." vs "," for separating decimal fractions). -There have been problems reported where the library linked with GCC does -not produce the same floating-point formats that the assembler accepts. -If you have this problem, set the LANG environment variable to "C" or -"En_US". - -@item -Even if you specify @samp{-fdollars-in-identifiers}, -you cannot successfully use @samp{$} in identifiers on the RS/6000 due -to a restriction in the IBM assembler. GAS supports these -identifiers. - -@item -On the RS/6000, XLC version 1.3.0.0 will miscompile @file{jump.c}. XLC -version 1.3.0.1 or later fixes this problem. You can obtain XLC-1.3.0.2 -by requesting PTF 421749 from IBM. - -@item -There is an assembler bug in versions of DG/UX prior to 5.4.2.01 that -occurs when the @samp{fldcr} instruction is used. GCC uses -@samp{fldcr} on the 88100 to serialize volatile memory references. Use -the option @samp{-mno-serialize-volatile} if your version of the -assembler has this bug. - -@item -On VMS, GAS versions 1.38.1 and earlier may cause spurious warning -messages from the linker. These warning messages complain of mismatched -psect attributes. You can ignore them. @xref{VMS Install}. - -@item -On NewsOS version 3, if you include both of the files @file{stddef.h} -and @file{sys/types.h}, you get an error because there are two typedefs -of @code{size_t}. You should change @file{sys/types.h} by adding these -lines around the definition of @code{size_t}: - -@smallexample -#ifndef _SIZE_T -#define _SIZE_T -@var{actual typedef here} -#endif -@end smallexample - -@cindex Alliant -@item -On the Alliant, the system's own convention for returning structures -and unions is unusual, and is not compatible with GCC no matter -what options are used. - -@cindex RT PC -@cindex IBM RT PC -@item -On the IBM RT PC, the MetaWare HighC compiler (hc) uses a different -convention for structure and union returning. Use the option -@samp{-mhc-struct-return} to tell GCC to use a convention compatible -with it. - -@cindex Vax calling convention -@cindex Ultrix calling convention -@item -On Ultrix, the Fortran compiler expects registers 2 through 5 to be saved -by function calls. However, the C compiler uses conventions compatible -with BSD Unix: registers 2 through 5 may be clobbered by function calls. - -GCC uses the same convention as the Ultrix C compiler. You can use -these options to produce code compatible with the Fortran compiler: - -@smallexample --fcall-saved-r2 -fcall-saved-r3 -fcall-saved-r4 -fcall-saved-r5 -@end smallexample - -@item -On the WE32k, you may find that programs compiled with GCC do not -work with the standard shared C library. You may need to link with -the ordinary C compiler. If you do so, you must specify the following -options: - -@smallexample --L/usr/local/lib/gcc-lib/we32k-att-sysv/2.8.1 -lgcc -lc_s -@end smallexample - -The first specifies where to find the library @file{libgcc.a} -specified with the @samp{-lgcc} option. - -GCC does linking by invoking @code{ld}, just as @code{cc} does, and -there is no reason why it @emph{should} matter which compilation program -you use to invoke @code{ld}. If someone tracks this problem down, -it can probably be fixed easily. - -@item -On the Alpha, you may get assembler errors about invalid syntax as a -result of floating point constants. This is due to a bug in the C -library functions @code{ecvt}, @code{fcvt} and @code{gcvt}. Given valid -floating point numbers, they sometimes print @samp{NaN}. - -@item -On Irix 4.0.5F (and perhaps in some other versions), an assembler bug -sometimes reorders instructions incorrectly when optimization is turned -on. If you think this may be happening to you, try using the GNU -assembler; GAS version 2.1 supports ECOFF on Irix. - -Or use the @samp{-noasmopt} option when you compile GCC with itself, -and then again when you compile your program. (This is a temporary -kludge to turn off assembler optimization on Irix.) If this proves to -be what you need, edit the assembler spec in the file @file{specs} so -that it unconditionally passes @samp{-O0} to the assembler, and never -passes @samp{-O2} or @samp{-O3}. -@end itemize - -@node External Bugs -@section Problems Compiling Certain Programs - -@c prevent bad page break with this line -Certain programs have problems compiling. - -@itemize @bullet -@item -Parse errors may occur compiling X11 on a Decstation running Ultrix 4.2 -because of problems in DEC's versions of the X11 header files -@file{X11/Xlib.h} and @file{X11/Xutil.h}. People recommend adding -@samp{-I/usr/include/mit} to use the MIT versions of the header files, -using the @samp{-traditional} switch to turn off ISO C, or fixing the -header files by adding this: - -@example -#ifdef __STDC__ -#define NeedFunctionPrototypes 0 -#endif -@end example - -@item -On various 386 Unix systems derived from System V, including SCO, ISC, -and ESIX, you may get error messages about running out of virtual memory -while compiling certain programs. - -You can prevent this problem by linking GCC with the GNU malloc -(which thus replaces the malloc that comes with the system). GNU malloc -is available as a separate package, and also in the file -@file{src/gmalloc.c} in the GNU Emacs 19 distribution. - -If you have installed GNU malloc as a separate library package, use this -option when you relink GCC: - -@example -MALLOC=/usr/local/lib/libgmalloc.a -@end example - -Alternatively, if you have compiled @file{gmalloc.c} from Emacs 19, copy -the object file to @file{gmalloc.o} and use this option when you relink -GCC: - -@example -MALLOC=gmalloc.o -@end example -@end itemize - -@node Incompatibilities -@section Incompatibilities of GCC -@cindex incompatibilities of GCC - -There are several noteworthy incompatibilities between GNU C and K&R -(non-ISO) versions of C. The @samp{-traditional} option -eliminates many of these incompatibilities, @emph{but not all}, by -telling GNU C to behave like a K&R C compiler. - -@itemize @bullet -@cindex string constants -@cindex read-only strings -@cindex shared strings -@item -GCC normally makes string constants read-only. If several -identical-looking string constants are used, GCC stores only one -copy of the string. - -@cindex @code{mktemp}, and constant strings -One consequence is that you cannot call @code{mktemp} with a string -constant argument. The function @code{mktemp} always alters the -string its argument points to. - -@cindex @code{sscanf}, and constant strings -@cindex @code{fscanf}, and constant strings -@cindex @code{scanf}, and constant strings -Another consequence is that @code{sscanf} does not work on some systems -when passed a string constant as its format control string or input. -This is because @code{sscanf} incorrectly tries to write into the string -constant. Likewise @code{fscanf} and @code{scanf}. - -The best solution to these problems is to change the program to use -@code{char}-array variables with initialization strings for these -purposes instead of string constants. But if this is not possible, -you can use the @samp{-fwritable-strings} flag, which directs GCC -to handle string constants the same way most C compilers do. -@samp{-traditional} also has this effect, among others. - -@item -@code{-2147483648} is positive. - -This is because 2147483648 cannot fit in the type @code{int}, so -(following the ISO C rules) its data type is @code{unsigned long int}. -Negating this value yields 2147483648 again. - -@item -GCC does not substitute macro arguments when they appear inside of -string constants. For example, the following macro in GCC - -@example -#define foo(a) "a" -@end example - -@noindent -will produce output @code{"a"} regardless of what the argument @var{a} is. - -The @samp{-traditional} option directs GCC to handle such cases -(among others) in the old-fashioned (non-ISO) fashion. - -@cindex @code{setjmp} incompatibilities -@cindex @code{longjmp} incompatibilities -@item -When you use @code{setjmp} and @code{longjmp}, the only automatic -variables guaranteed to remain valid are those declared -@code{volatile}. This is a consequence of automatic register -allocation. Consider this function: - -@example -jmp_buf j; - -foo () -@{ - int a, b; - - a = fun1 (); - if (setjmp (j)) - return a; - - a = fun2 (); - /* @r{@code{longjmp (j)} may occur in @code{fun3}.} */ - return a + fun3 (); -@} -@end example - -Here @code{a} may or may not be restored to its first value when the -@code{longjmp} occurs. If @code{a} is allocated in a register, then -its first value is restored; otherwise, it keeps the last value stored -in it. - -If you use the @samp{-W} option with the @samp{-O} option, you will -get a warning when GCC thinks such a problem might be possible. - -The @samp{-traditional} option directs GNU C to put variables in -the stack by default, rather than in registers, in functions that -call @code{setjmp}. This results in the behavior found in -traditional C compilers. - -@item -Programs that use preprocessing directives in the middle of macro -arguments do not work with GCC. For example, a program like this -will not work: - -@example -foobar ( -#define luser - hack) -@end example - -ISO C does not permit such a construct. It would make sense to support -it when @samp{-traditional} is used, but it is too much work to -implement. - -@item -K&R compilers allow comments to cross over an inclusion boundary (i.e. -started in an include file and ended in the including file). I think -this would be quite ugly and can't imagine it could be needed. - -@cindex external declaration scope -@cindex scope of external declarations -@cindex declaration scope -@item -Declarations of external variables and functions within a block apply -only to the block containing the declaration. In other words, they -have the same scope as any other declaration in the same place. - -In some other C compilers, a @code{extern} declaration affects all the -rest of the file even if it happens within a block. - -The @samp{-traditional} option directs GNU C to treat all @code{extern} -declarations as global, like traditional compilers. - -@item -In traditional C, you can combine @code{long}, etc., with a typedef name, -as shown here: - -@example -typedef int foo; -typedef long foo bar; -@end example - -In ISO C, this is not allowed: @code{long} and other type modifiers -require an explicit @code{int}. Because this criterion is expressed -by Bison grammar rules rather than C code, the @samp{-traditional} -flag cannot alter it. - -@cindex typedef names as function parameters -@item -PCC allows typedef names to be used as function parameters. The -difficulty described immediately above applies here too. - -@item -When in @samp{-traditional} mode, GCC allows the following erroneous -pair of declarations to appear together in a given scope: - -@example -typedef int foo; -typedef foo foo; -@end example - -@item -GCC treats all characters of identifiers as significant, even when in -@samp{-traditional} mode. According to K&R-1 (2.2), ``No more than the -first eight characters are significant, although more may be used.''. -Also according to K&R-1 (2.2), ``An identifier is a sequence of letters -and digits; the first character must be a letter. The underscore _ -counts as a letter.'', but GCC also allows dollar signs in identifiers. - -@cindex whitespace -@item -PCC allows whitespace in the middle of compound assignment operators -such as @samp{+=}. GCC, following the ISO standard, does not -allow this. The difficulty described immediately above applies here -too. - -@cindex apostrophes -@cindex ' -@item -GCC complains about unterminated character constants inside of -preprocessing conditionals that fail. Some programs have English -comments enclosed in conditionals that are guaranteed to fail; if these -comments contain apostrophes, GCC will probably report an error. For -example, this code would produce an error: - -@example -#if 0 -You can't expect this to work. -#endif -@end example - -The best solution to such a problem is to put the text into an actual -C comment delimited by @samp{/*@dots{}*/}. However, -@samp{-traditional} suppresses these error messages. - -@item -Many user programs contain the declaration @samp{long time ();}. In the -past, the system header files on many systems did not actually declare -@code{time}, so it did not matter what type your program declared it to -return. But in systems with ISO C headers, @code{time} is declared to -return @code{time_t}, and if that is not the same as @code{long}, then -@samp{long time ();} is erroneous. - -The solution is to change your program to use appropriate system headers -(@code{} on systems with ISO C headers) and not to declare -@code{time} if the system header files declare it, or failing that to -use @code{time_t} as the return type of @code{time}. - -@cindex @code{float} as function value type -@item -When compiling functions that return @code{float}, PCC converts it to -a double. GCC actually returns a @code{float}. If you are concerned -with PCC compatibility, you should declare your functions to return -@code{double}; you might as well say what you mean. - -@cindex structures -@cindex unions -@item -When compiling functions that return structures or unions, GCC -output code normally uses a method different from that used on most -versions of Unix. As a result, code compiled with GCC cannot call -a structure-returning function compiled with PCC, and vice versa. - -The method used by GCC is as follows: a structure or union which is -1, 2, 4 or 8 bytes long is returned like a scalar. A structure or union -with any other size is stored into an address supplied by the caller -(usually in a special, fixed register, but on some machines it is passed -on the stack). The machine-description macros @code{STRUCT_VALUE} and -@code{STRUCT_INCOMING_VALUE} tell GCC where to pass this address. - -By contrast, PCC on most target machines returns structures and unions -of any size by copying the data into an area of static storage, and then -returning the address of that storage as if it were a pointer value. -The caller must copy the data from that memory area to the place where -the value is wanted. GCC does not use this method because it is -slower and nonreentrant. - -On some newer machines, PCC uses a reentrant convention for all -structure and union returning. GCC on most of these machines uses a -compatible convention when returning structures and unions in memory, -but still returns small structures and unions in registers. - -You can tell GCC to use a compatible convention for all structure and -union returning with the option @samp{-fpcc-struct-return}. - -@cindex preprocessing tokens -@cindex preprocessing numbers -@item -GNU C complains about program fragments such as @samp{0x74ae-0x4000} -which appear to be two hexadecimal constants separated by the minus -operator. Actually, this string is a single @dfn{preprocessing token}. -Each such token must correspond to one token in C. Since this does not, -GNU C prints an error message. Although it may appear obvious that what -is meant is an operator and two values, the ISO C standard specifically -requires that this be treated as erroneous. - -A @dfn{preprocessing token} is a @dfn{preprocessing number} if it -begins with a digit and is followed by letters, underscores, digits, -periods and @samp{e+}, @samp{e-}, @samp{E+}, @samp{E-}, @samp{p+}, -@samp{p-}, @samp{P+}, or @samp{P-} character sequences. (In strict C89 -mode, the sequences @samp{p+}, @samp{p-}, @samp{P+} and @samp{P-} cannot -appear in preprocessing numbers.) - -To make the above program fragment valid, place whitespace in front of -the minus sign. This whitespace will end the preprocessing number. -@end itemize - -@node Fixed Headers -@section Fixed Header Files - -GCC needs to install corrected versions of some system header files. -This is because most target systems have some header files that won't -work with GCC unless they are changed. Some have bugs, some are -incompatible with ISO C, and some depend on special features of other -compilers. - -Installing GCC automatically creates and installs the fixed header -files, by running a program called @code{fixincludes} (or for certain -targets an alternative such as @code{fixinc.svr4}). Normally, you -don't need to pay attention to this. But there are cases where it -doesn't do the right thing automatically. - -@itemize @bullet -@item -If you update the system's header files, such as by installing a new -system version, the fixed header files of GCC are not automatically -updated. The easiest way to update them is to reinstall GCC. (If -you want to be clever, look in the makefile and you can find a -shortcut.) - -@item -On some systems, in particular SunOS 4, header file directories contain -machine-specific symbolic links in certain places. This makes it -possible to share most of the header files among hosts running the -same version of SunOS 4 on different machine models. - -The programs that fix the header files do not understand this special -way of using symbolic links; therefore, the directory of fixed header -files is good only for the machine model used to build it. - -In SunOS 4, only programs that look inside the kernel will notice the -difference between machine models. Therefore, for most purposes, you -need not be concerned about this. - -It is possible to make separate sets of fixed header files for the -different machine models, and arrange a structure of symbolic links so -as to use the proper set, but you'll have to do this by hand. - -@item -On Lynxos, GCC by default does not fix the header files. This is -because bugs in the shell cause the @code{fixincludes} script to fail. - -This means you will encounter problems due to bugs in the system header -files. It may be no comfort that they aren't GCC's fault, but it -does mean that there's nothing for us to do about them. -@end itemize - -@node Standard Libraries -@section Standard Libraries - -GCC by itself attempts to be a conforming freestanding implementation. -@xref{Standards,,Language Standards Supported by GCC}, for details of -what this means. Beyond the library facilities required of such an -implementation, the rest of the C library is supplied by the vendor of -the operating system. If that C library doesn't conform to the C -standards, then your programs might get warnings (especially when using -@samp{-Wall}) that you don't expect. - -For example, the @code{sprintf} function on SunOS 4.1.3 returns -@code{char *} while the C standard says that @code{sprintf} returns an -@code{int}. The @code{fixincludes} program could make the prototype for -this function match the Standard, but that would be wrong, since the -function will still return @code{char *}. - -If you need a Standard compliant library, then you need to find one, as -GCC does not provide one. The GNU C library (called @code{glibc}) -provides ISO C, POSIX, BSD, SystemV and X/Open compatibility for -GNU/Linux and HURD-based GNU systems; no recent version of it supports -other systems, though some very old versions did. Version 2.2 of the -GNU C library includes nearly complete C99 support. You could also ask -your operating system vendor if newer libraries are available. - -@node Disappointments -@section Disappointments and Misunderstandings - -These problems are perhaps regrettable, but we don't know any practical -way around them. - -@itemize @bullet -@item -Certain local variables aren't recognized by debuggers when you compile -with optimization. - -This occurs because sometimes GCC optimizes the variable out of -existence. There is no way to tell the debugger how to compute the -value such a variable ``would have had'', and it is not clear that would -be desirable anyway. So GCC simply does not mention the eliminated -variable when it writes debugging information. - -You have to expect a certain amount of disagreement between the -executable and your source code, when you use optimization. - -@cindex conflicting types -@cindex scope of declaration -@item -Users often think it is a bug when GCC reports an error for code -like this: - -@example -int foo (struct mumble *); - -struct mumble @{ @dots{} @}; - -int foo (struct mumble *x) -@{ @dots{} @} -@end example - -This code really is erroneous, because the scope of @code{struct -mumble} in the prototype is limited to the argument list containing it. -It does not refer to the @code{struct mumble} defined with file scope -immediately below---they are two unrelated types with similar names in -different scopes. - -But in the definition of @code{foo}, the file-scope type is used -because that is available to be inherited. Thus, the definition and -the prototype do not match, and you get an error. - -This behavior may seem silly, but it's what the ISO standard specifies. -It is easy enough for you to make your code work by moving the -definition of @code{struct mumble} above the prototype. It's not worth -being incompatible with ISO C just to avoid an error for the example -shown above. - -@item -Accesses to bitfields even in volatile objects works by accessing larger -objects, such as a byte or a word. You cannot rely on what size of -object is accessed in order to read or write the bitfield; it may even -vary for a given bitfield according to the precise usage. - -If you care about controlling the amount of memory that is accessed, use -volatile but do not use bitfields. - -@item -GCC comes with shell scripts to fix certain known problems in system -header files. They install corrected copies of various header files in -a special directory where only GCC will normally look for them. The -scripts adapt to various systems by searching all the system header -files for the problem cases that we know about. - -If new system header files are installed, nothing automatically arranges -to update the corrected header files. You will have to reinstall GCC -to fix the new header files. More specifically, go to the build -directory and delete the files @file{stmp-fixinc} and -@file{stmp-headers}, and the subdirectory @code{include}; then do -@samp{make install} again. - -@item -@cindex floating point precision -On 68000 and x86 systems, for instance, you can get paradoxical results -if you test the precise values of floating point numbers. For example, -you can find that a floating point value which is not a NaN is not equal -to itself. This results from the fact that the floating point registers -hold a few more bits of precision than fit in a @code{double} in memory. -Compiled code moves values between memory and floating point registers -at its convenience, and moving them into memory truncates them. - -You can partially avoid this problem by using the @samp{-ffloat-store} -option (@pxref{Optimize Options}). - -@item -On the MIPS, variable argument functions using @file{varargs.h} -cannot have a floating point value for the first argument. The -reason for this is that in the absence of a prototype in scope, -if the first argument is a floating point, it is passed in a -floating point register, rather than an integer register. - -If the code is rewritten to use the ISO standard @file{stdarg.h} -method of variable arguments, and the prototype is in scope at -the time of the call, everything will work fine. - -@item -On the H8/300 and H8/300H, variable argument functions must be -implemented using the ISO standard @file{stdarg.h} method of -variable arguments. Furthermore, calls to functions using @file{stdarg.h} -variable arguments must have a prototype for the called function -in scope at the time of the call. -@end itemize - -@node C++ Misunderstandings -@section Common Misunderstandings with GNU C++ - -@cindex misunderstandings in C++ -@cindex surprises in C++ -@cindex C++ misunderstandings -C++ is a complex language and an evolving one, and its standard -definition (the ISO C++ standard) was only recently completed. As a -result, your C++ compiler may occasionally surprise you, even when its -behavior is correct. This section discusses some areas that frequently -give rise to questions of this sort. - -@menu -* Static Definitions:: Static member declarations are not definitions -* Temporaries:: Temporaries may vanish before you expect -* Copy Assignment:: Copy Assignment operators copy virtual bases twice -@end menu - -@node Static Definitions -@subsection Declare @emph{and} Define Static Members - -@cindex C++ static data, declaring and defining -@cindex static data in C++, declaring and defining -@cindex declaring static data in C++ -@cindex defining static data in C++ -When a class has static data members, it is not enough to @emph{declare} -the static member; you must also @emph{define} it. For example: - -@example -class Foo -@{ - @dots{} - void method(); - static int bar; -@}; -@end example - -This declaration only establishes that the class @code{Foo} has an -@code{int} named @code{Foo::bar}, and a member function named -@code{Foo::method}. But you still need to define @emph{both} -@code{method} and @code{bar} elsewhere. According to the ISO -standard, you must supply an initializer in one (and only one) source -file, such as: - -@example -int Foo::bar = 0; -@end example - -Other C++ compilers may not correctly implement the standard behavior. -As a result, when you switch to @code{g++} from one of these compilers, -you may discover that a program that appeared to work correctly in fact -does not conform to the standard: @code{g++} reports as undefined -symbols any static data members that lack definitions. - -@node Temporaries -@subsection Temporaries May Vanish Before You Expect - -@cindex temporaries, lifetime of -@cindex portions of temporary objects, pointers to -It is dangerous to use pointers or references to @emph{portions} of a -temporary object. The compiler may very well delete the object before -you expect it to, leaving a pointer to garbage. The most common place -where this problem crops up is in classes like string classes, -especially ones that define a conversion function to type @code{char *} -or @code{const char *} -- which is one reason why the standard -@code{string} class requires you to call the @code{c_str} member -function. However, any class that returns a pointer to some internal -structure is potentially subject to this problem. - -For example, a program may use a function @code{strfunc} that returns -@code{string} objects, and another function @code{charfunc} that -operates on pointers to @code{char}: - -@example -string strfunc (); -void charfunc (const char *); - -void -f () -@{ - const char *p = strfunc().c_str(); - ... - charfunc (p); - ... - charfunc (p); -@} -@end example - -@noindent -In this situation, it may seem reasonable to save a pointer to the C -string returned by the @code{c_str} member function and use that rather -than call @code{c_str} repeatedly. However, the temporary string -created by the call to @code{strfunc} is destroyed after @code{p} is -initialized, at which point @code{p} is left pointing to freed memory. - -Code like this may run successfully under some other compilers, -particularly obsolete cfront-based compilers that delete temporaries -along with normal local variables. However, the GNU C++ behavior is -standard-conforming, so if your program depends on late destruction of -temporaries it is not portable. - -The safe way to write such code is to give the temporary a name, which -forces it to remain until the end of the scope of the name. For -example: - -@example -string& tmp = strfunc (); -charfunc (tmp.c_str ()); -@end example - -@node Copy Assignment -@subsection Implicit Copy-Assignment for Virtual Bases - -When a base class is virtual, only one subobject of the base class -belongs to each full object. Also, the constructors and destructors are -invoked only once, and called from the most-derived class. However, such -objects behave unspecified when being assigned. For example: - -@example -struct Base@{ - char *name; - Base(char *n) : name(strdup(n))@{@} - Base& operator= (const Base& other)@{ - free (name); - name = strdup (other.name); - @} -@}; - -struct A:virtual Base@{ - int val; - A():Base("A")@{@} -@}; - -struct B:virtual Base@{ - int bval; - B():Base("B")@{@} -@}; - -struct Derived:public A, public B@{ - Derived():Base("Derived")@{@} -@}; - -void func(Derived &d1, Derived &d2) -@{ - d1 = d2; -@} -@end example - -The C++ standard specifies that @samp{Base::Base} is only called once -when constructing or copy-constructing a Derived object. It is -unspecified whether @samp{Base::operator=} is called more than once when -the implicit copy-assignment for Derived objects is invoked (as it is -inside @samp{func} in the example). - -g++ implements the "intuitive" algorithm for copy-assignment: assign all -direct bases, then assign all members. In that algorithm, the virtual -base subobject can be encountered many times. In the example, copying -proceeds in the following order: @samp{val}, @samp{name} (via -@code{strdup}), @samp{bval}, and @samp{name} again. - -If application code relies on copy-assignment, a user-defined -copy-assignment operator removes any uncertainties. With such an -operator, the application can define whether and how the virtual base -subobject is assigned. - -@node Protoize Caveats -@section Caveats of using @code{protoize} - -The conversion programs @code{protoize} and @code{unprotoize} can -sometimes change a source file in a way that won't work unless you -rearrange it. - -@itemize @bullet -@item -@code{protoize} can insert references to a type name or type tag before -the definition, or in a file where they are not defined. - -If this happens, compiler error messages should show you where the new -references are, so fixing the file by hand is straightforward. - -@item -There are some C constructs which @code{protoize} cannot figure out. -For example, it can't determine argument types for declaring a -pointer-to-function variable; this you must do by hand. @code{protoize} -inserts a comment containing @samp{???} each time it finds such a -variable; so you can find all such variables by searching for this -string. ISO C does not require declaring the argument types of -pointer-to-function types. - -@item -Using @code{unprotoize} can easily introduce bugs. If the program -relied on prototypes to bring about conversion of arguments, these -conversions will not take place in the program without prototypes. -One case in which you can be sure @code{unprotoize} is safe is when -you are removing prototypes that were made with @code{protoize}; if -the program worked before without any prototypes, it will work again -without them. - -You can find all the places where this problem might occur by compiling -the program with the @samp{-Wconversion} option. It prints a warning -whenever an argument is converted. - -@item -Both conversion programs can be confused if there are macro calls in and -around the text to be converted. In other words, the standard syntax -for a declaration or definition must not result from expanding a macro. -This problem is inherent in the design of C and cannot be fixed. If -only a few functions have confusing macro calls, you can easily convert -them manually. - -@item -@code{protoize} cannot get the argument types for a function whose -definition was not actually compiled due to preprocessing conditionals. -When this happens, @code{protoize} changes nothing in regard to such -a function. @code{protoize} tries to detect such instances and warn -about them. - -You can generally work around this problem by using @code{protoize} step -by step, each time specifying a different set of @samp{-D} options for -compilation, until all of the functions have been converted. There is -no automatic way to verify that you have got them all, however. - -@item -Confusion may result if there is an occasion to convert a function -declaration or definition in a region of source code where there is more -than one formal parameter list present. Thus, attempts to convert code -containing multiple (conditionally compiled) versions of a single -function header (in the same vicinity) may not produce the desired (or -expected) results. - -If you plan on converting source files which contain such code, it is -recommended that you first make sure that each conditionally compiled -region of source code which contains an alternative function header also -contains at least one additional follower token (past the final right -parenthesis of the function header). This should circumvent the -problem. - -@item -@code{unprotoize} can become confused when trying to convert a function -definition or declaration which contains a declaration for a -pointer-to-function formal argument which has the same name as the -function being defined or declared. We recommend you avoid such choices -of formal parameter names. - -@item -You might also want to correct some of the indentation by hand and break -long lines. (The conversion programs don't write lines longer than -eighty characters in any case.) -@end itemize - -@node Non-bugs -@section Certain Changes We Don't Want to Make - -This section lists changes that people frequently request, but which -we do not make because we think GCC is better without them. - -@itemize @bullet -@item -Checking the number and type of arguments to a function which has an -old-fashioned definition and no prototype. - -Such a feature would work only occasionally---only for calls that appear -in the same file as the called function, following the definition. The -only way to check all calls reliably is to add a prototype for the -function. But adding a prototype eliminates the motivation for this -feature. So the feature is not worthwhile. - -@item -Warning about using an expression whose type is signed as a shift count. - -Shift count operands are probably signed more often than unsigned. -Warning about this would cause far more annoyance than good. - -@item -Warning about assigning a signed value to an unsigned variable. - -Such assignments must be very common; warning about them would cause -more annoyance than good. - -@item -Warning when a non-void function value is ignored. - -Coming as I do from a Lisp background, I balk at the idea that there is -something dangerous about discarding a value. There are functions that -return values which some callers may find useful; it makes no sense to -clutter the program with a cast to @code{void} whenever the value isn't -useful. - -@item -Making @samp{-fshort-enums} the default. - -This would cause storage layout to be incompatible with most other C -compilers. And it doesn't seem very important, given that you can get -the same result in other ways. The case where it matters most is when -the enumeration-valued object is inside a structure, and in that case -you can specify a field width explicitly. - -@item -Making bitfields unsigned by default on particular machines where ``the -ABI standard'' says to do so. - -The ISO C standard leaves it up to the implementation whether a bitfield -declared plain @code{int} is signed or not. This in effect creates two -alternative dialects of C. - -The GNU C compiler supports both dialects; you can specify the signed -dialect with @samp{-fsigned-bitfields} and the unsigned dialect with -@samp{-funsigned-bitfields}. However, this leaves open the question of -which dialect to use by default. - -Currently, the preferred dialect makes plain bitfields signed, because -this is simplest. Since @code{int} is the same as @code{signed int} in -every other context, it is cleanest for them to be the same in bitfields -as well. - -Some computer manufacturers have published Application Binary Interface -standards which specify that plain bitfields should be unsigned. It is -a mistake, however, to say anything about this issue in an ABI. This is -because the handling of plain bitfields distinguishes two dialects of C. -Both dialects are meaningful on every type of machine. Whether a -particular object file was compiled using signed bitfields or unsigned -is of no concern to other object files, even if they access the same -bitfields in the same data structures. - -A given program is written in one or the other of these two dialects. -The program stands a chance to work on most any machine if it is -compiled with the proper dialect. It is unlikely to work at all if -compiled with the wrong dialect. - -Many users appreciate the GNU C compiler because it provides an -environment that is uniform across machines. These users would be -inconvenienced if the compiler treated plain bitfields differently on -certain machines. - -Occasionally users write programs intended only for a particular machine -type. On these occasions, the users would benefit if the GNU C compiler -were to support by default the same dialect as the other compilers on -that machine. But such applications are rare. And users writing a -program to run on more than one type of machine cannot possibly benefit -from this kind of compatibility. - -This is why GCC does and will treat plain bitfields in the same -fashion on all types of machines (by default). - -There are some arguments for making bitfields unsigned by default on all -machines. If, for example, this becomes a universal de facto standard, -it would make sense for GCC to go along with it. This is something -to be considered in the future. - -(Of course, users strongly concerned about portability should indicate -explicitly in each bitfield whether it is signed or not. In this way, -they write programs which have the same meaning in both C dialects.) - -@item -Undefining @code{__STDC__} when @samp{-ansi} is not used. - -Currently, GCC defines @code{__STDC__} as long as you don't use -@samp{-traditional}. This provides good results in practice. - -Programmers normally use conditionals on @code{__STDC__} to ask whether -it is safe to use certain features of ISO C, such as function -prototypes or ISO token concatenation. Since plain @samp{gcc} supports -all the features of ISO C, the correct answer to these questions is -``yes''. - -Some users try to use @code{__STDC__} to check for the availability of -certain library facilities. This is actually incorrect usage in an ISO -C program, because the ISO C standard says that a conforming -freestanding implementation should define @code{__STDC__} even though it -does not have the library facilities. @samp{gcc -ansi -pedantic} is a -conforming freestanding implementation, and it is therefore required to -define @code{__STDC__}, even though it does not come with an ISO C -library. - -Sometimes people say that defining @code{__STDC__} in a compiler that -does not completely conform to the ISO C standard somehow violates the -standard. This is illogical. The standard is a standard for compilers -that claim to support ISO C, such as @samp{gcc -ansi}---not for other -compilers such as plain @samp{gcc}. Whatever the ISO C standard says -is relevant to the design of plain @samp{gcc} without @samp{-ansi} only -for pragmatic reasons, not as a requirement. - -GCC normally defines @code{__STDC__} to be 1, and in addition -defines @code{__STRICT_ANSI__} if you specify the @option{-ansi} option, -or a @option{-std} option for strict conformance to some version of ISO C. -On some hosts, system include files use a different convention, where -@code{__STDC__} is normally 0, but is 1 if the user specifies strict -conformance to the C Standard. GCC follows the host convention when -processing system include files, but when processing user files it follows -the usual GNU C convention. - -@item -Undefining @code{__STDC__} in C++. - -Programs written to compile with C++-to-C translators get the -value of @code{__STDC__} that goes with the C compiler that is -subsequently used. These programs must test @code{__STDC__} -to determine what kind of C preprocessor that compiler uses: -whether they should concatenate tokens in the ISO C fashion -or in the traditional fashion. - -These programs work properly with GNU C++ if @code{__STDC__} is defined. -They would not work otherwise. - -In addition, many header files are written to provide prototypes in ISO -C but not in traditional C. Many of these header files can work without -change in C++ provided @code{__STDC__} is defined. If @code{__STDC__} -is not defined, they will all fail, and will all need to be changed to -test explicitly for C++ as well. - -@item -Deleting ``empty'' loops. - -Historically, GCC has not deleted ``empty'' loops under the -assumption that the most likely reason you would put one in a program is -to have a delay, so deleting them will not make real programs run any -faster. - -However, the rationale here is that optimization of a nonempty loop -cannot produce an empty one, which holds for C but is not always the -case for C++. - -Moreover, with @samp{-funroll-loops} small ``empty'' loops are already -removed, so the current behavior is both sub-optimal and inconsistent -and will change in the future. - -@item -Making side effects happen in the same order as in some other compiler. - -@cindex side effects, order of evaluation -@cindex order of evaluation, side effects -It is never safe to depend on the order of evaluation of side effects. -For example, a function call like this may very well behave differently -from one compiler to another: - -@example -void func (int, int); - -int i = 2; -func (i++, i++); -@end example - -There is no guarantee (in either the C or the C++ standard language -definitions) that the increments will be evaluated in any particular -order. Either increment might happen first. @code{func} might get the -arguments @samp{2, 3}, or it might get @samp{3, 2}, or even @samp{2, 2}. - -@item -Not allowing structures with volatile fields in registers. - -Strictly speaking, there is no prohibition in the ISO C standard -against allowing structures with volatile fields in registers, but -it does not seem to make any sense and is probably not what you wanted -to do. So the compiler will give an error message in this case. - -@item -Making certain warnings into errors by default. - -Some ISO C testsuites report failure when the compiler does not produce -an error message for a certain program. - -ISO C requires a ``diagnostic'' message for certain kinds of invalid -programs, but a warning is defined by GCC to count as a diagnostic. If -GCC produces a warning but not an error, that is correct ISO C support. -If test suites call this ``failure'', they should be run with the GCC -option @samp{-pedantic-errors}, which will turn these warnings into -errors. - -@end itemize - -@node Warnings and Errors -@section Warning Messages and Error Messages - -@cindex error messages -@cindex warnings vs errors -@cindex messages, warning and error -The GNU compiler can produce two kinds of diagnostics: errors and -warnings. Each kind has a different purpose: - -@itemize @w{} -@item -@emph{Errors} report problems that make it impossible to compile your -program. GCC reports errors with the source file name and line -number where the problem is apparent. - -@item -@emph{Warnings} report other unusual conditions in your code that -@emph{may} indicate a problem, although compilation can (and does) -proceed. Warning messages also report the source file name and line -number, but include the text @samp{warning:} to distinguish them -from error messages. -@end itemize - -Warnings may indicate danger points where you should check to make sure -that your program really does what you intend; or the use of obsolete -features; or the use of nonstandard features of GNU C or C++. Many -warnings are issued only if you ask for them, with one of the @samp{-W} -options (for instance, @samp{-Wall} requests a variety of useful -warnings). - -GCC always tries to compile your program if possible; it never -gratuitously rejects a program whose meaning is clear merely because -(for instance) it fails to conform to a standard. In some cases, -however, the C and C++ standards specify that certain extensions are -forbidden, and a diagnostic @emph{must} be issued by a conforming -compiler. The @samp{-pedantic} option tells GCC to issue warnings in -such cases; @samp{-pedantic-errors} says to make them errors instead. -This does not mean that @emph{all} non-ISO constructs get warnings -or errors. - -@xref{Warning Options,,Options to Request or Suppress Warnings}, for -more detail on these and related command-line options. - -@node Bugs -@chapter Reporting Bugs -@cindex bugs -@cindex reporting bugs - -Your bug reports play an essential role in making GCC reliable. - -When you encounter a problem, the first thing to do is to see if it is -already known. @xref{Trouble}. If it isn't known, then you should -report the problem. - -Reporting a bug may help you by bringing a solution to your problem, or -it may not. (If it does not, look in the service directory; see -@ref{Service}.) In any case, the principal function of a bug report is -to help the entire community by making the next version of GCC work -better. Bug reports are your contribution to the maintenance of GCC. - -Since the maintainers are very overloaded, we cannot respond to every -bug report. However, if the bug has not been fixed, we are likely to -send you a patch and ask you to tell us whether it works. - -In order for a bug report to serve its purpose, you must include the -information that makes for fixing the bug. - -@menu -* Criteria: Bug Criteria. Have you really found a bug? -* Where: Bug Lists. Where to send your bug report. -* Reporting: Bug Reporting. How to report a bug effectively. -* GNATS: gccbug. You can use a bug reporting tool. -* Patches: Sending Patches. How to send a patch for GCC. -* Known: Trouble. Known problems. -* Help: Service. Where to ask for help. -@end menu - -@node Bug Criteria,Bug Lists,,Bugs -@section Have You Found a Bug? -@cindex bug criteria - -If you are not sure whether you have found a bug, here are some guidelines: - -@itemize @bullet -@cindex fatal signal -@cindex core dump -@item -If the compiler gets a fatal signal, for any input whatever, that is a -compiler bug. Reliable compilers never crash. - -@cindex invalid assembly code -@cindex assembly code, invalid -@item -If the compiler produces invalid assembly code, for any input whatever -(except an @code{asm} statement), that is a compiler bug, unless the -compiler reports errors (not just warnings) which would ordinarily -prevent the assembler from being run. - -@cindex undefined behavior -@cindex undefined function value -@cindex increment operators -@item -If the compiler produces valid assembly code that does not correctly -execute the input source code, that is a compiler bug. - -However, you must double-check to make sure, because you may have run -into an incompatibility between GNU C and traditional C -(@pxref{Incompatibilities}). These incompatibilities might be considered -bugs, but they are inescapable consequences of valuable features. - -Or you may have a program whose behavior is undefined, which happened -by chance to give the desired results with another C or C++ compiler. - -For example, in many nonoptimizing compilers, you can write @samp{x;} -at the end of a function instead of @samp{return x;}, with the same -results. But the value of the function is undefined if @code{return} -is omitted; it is not a bug when GCC produces different results. - -Problems often result from expressions with two increment operators, -as in @code{f (*p++, *p++)}. Your previous compiler might have -interpreted that expression the way you intended; GCC might -interpret it another way. Neither compiler is wrong. The bug is -in your code. - -After you have localized the error to a single source line, it should -be easy to check for these things. If your program is correct and -well defined, you have found a compiler bug. - -@item -If the compiler produces an error message for valid input, that is a -compiler bug. - -@cindex invalid input -@item -If the compiler does not produce an error message for invalid input, -that is a compiler bug. However, you should note that your idea of -``invalid input'' might be my idea of ``an extension'' or ``support -for traditional practice''. - -@item -If you are an experienced user of one of the languages GCC supports, your -suggestions for improvement of GCC are welcome in any case. -@end itemize - -@node Bug Lists,Bug Reporting,Bug Criteria,Bugs -@section Where to Report Bugs -@cindex bug report mailing lists -@kindex gcc-bugs@@gcc.gnu.org or bug-gcc@@gnu.org -Send bug reports for the GNU Compiler Collection to -@email{gcc-bugs@@gcc.gnu.org}. In accordance with the GNU-wide -convention, in which bug reports for tool ``foo'' are sent -to @samp{bug-foo@@gnu.org}, the address @email{bug-gcc@@gnu.org} -may also be used; it will forward to the address given above. - -Please read @uref{http://gcc.gnu.org/bugs.html} for additional and/or -more up-to-date bug reporting instructions before you post a bug report. - -@node Bug Reporting,gccbug,Bug Lists,Bugs -@section How to Report Bugs -@cindex compiler bugs, reporting - -The fundamental principle of reporting bugs usefully is this: -@strong{report all the facts}. If you are not sure whether to state a -fact or leave it out, state it! - -Often people omit facts because they think they know what causes the -problem and they conclude that some details don't matter. Thus, you might -assume that the name of the variable you use in an example does not matter. -Well, probably it doesn't, but one cannot be sure. Perhaps the bug is a -stray memory reference which happens to fetch from the location where that -name is stored in memory; perhaps, if the name were different, the contents -of that location would fool the compiler into doing the right thing despite -the bug. Play it safe and give a specific, complete example. That is the -easiest thing for you to do, and the most helpful. - -Keep in mind that the purpose of a bug report is to enable someone to -fix the bug if it is not known. It isn't very important what happens if -the bug is already known. Therefore, always write your bug reports on -the assumption that the bug is not known. - -Sometimes people give a few sketchy facts and ask, ``Does this ring a -bell?'' This cannot help us fix a bug, so it is basically useless. We -respond by asking for enough details to enable us to investigate. -You might as well expedite matters by sending them to begin with. - -Try to make your bug report self-contained. If we have to ask you for -more information, it is best if you include all the previous information -in your response, as well as the information that was missing. - -Please report each bug in a separate message. This makes it easier for -us to track which bugs have been fixed and to forward your bugs reports -to the appropriate maintainer. - -To enable someone to investigate the bug, you should include all these -things: - -@itemize @bullet -@item -The version of GCC. You can get this by running it with the -@samp{-v} option. - -Without this, we won't know whether there is any point in looking for -the bug in the current version of GCC. - -@item -A complete input file that will reproduce the bug. If the bug is in the -C preprocessor, send a source file and any header files that it -requires. If the bug is in the compiler proper (@file{cc1}), send the -preprocessor output generated by adding @samp{-save-temps} to the -compilation command (@pxref{Debugging Options}). When you do this, use -the same @samp{-I}, @samp{-D} or @samp{-U} options that you used in -actual compilation. Then send the @var{input}.i or @var{input}.ii files -generated. - -A single statement is not enough of an example. In order to compile it, -it must be embedded in a complete file of compiler input; and the bug -might depend on the details of how this is done. - -Without a real example one can compile, all anyone can do about your bug -report is wish you luck. It would be futile to try to guess how to -provoke the bug. For example, bugs in register allocation and reloading -frequently depend on every little detail of the function they happen in. - -Even if the input file that fails comes from a GNU program, you should -still send the complete test case. Don't ask the GCC maintainers to -do the extra work of obtaining the program in question---they are all -overworked as it is. Also, the problem may depend on what is in the -header files on your system; it is unreliable for the GCC maintainers -to try the problem with the header files available to them. By sending -CPP output, you can eliminate this source of uncertainty and save us -a certain percentage of wild goose chases. - -@item -The command arguments you gave GCC to compile that example -and observe the bug. For example, did you use @samp{-O}? To guarantee -you won't omit something important, list all the options. - -If we were to try to guess the arguments, we would probably guess wrong -and then we would not encounter the bug. - -@item -The type of machine you are using, and the operating system name and -version number. - -@item -The operands you gave to the @code{configure} command when you installed -the compiler. - -@item -A complete list of any modifications you have made to the compiler -source. (We don't promise to investigate the bug unless it happens in -an unmodified compiler. But if you've made modifications and don't tell -us, then you are sending us on a wild goose chase.) - -Be precise about these changes. A description in English is not -enough---send a context diff for them. - -Adding files of your own (such as a machine description for a machine we -don't support) is a modification of the compiler source. - -@item -Details of any other deviations from the standard procedure for installing -GCC. - -@item -A description of what behavior you observe that you believe is -incorrect. For example, ``The compiler gets a fatal signal,'' or, -``The assembler instruction at line 208 in the output is incorrect.'' - -Of course, if the bug is that the compiler gets a fatal signal, then one -can't miss it. But if the bug is incorrect output, the maintainer might -not notice unless it is glaringly wrong. None of us has time to study -all the assembler code from a 50-line C program just on the chance that -one instruction might be wrong. We need @emph{you} to do this part! - -Even if the problem you experience is a fatal signal, you should still -say so explicitly. Suppose something strange is going on, such as, your -copy of the compiler is out of synch, or you have encountered a bug in -the C library on your system. (This has happened!) Your copy might -crash and the copy here would not. If you @i{said} to expect a crash, -then when the compiler here fails to crash, we would know that the bug -was not happening. If you don't say to expect a crash, then we would -not know whether the bug was happening. We would not be able to draw -any conclusion from our observations. - -If the problem is a diagnostic when compiling GCC with some other -compiler, say whether it is a warning or an error. - -Often the observed symptom is incorrect output when your program is run. -Sad to say, this is not enough information unless the program is short -and simple. None of us has time to study a large program to figure out -how it would work if compiled correctly, much less which line of it was -compiled wrong. So you will have to do that. Tell us which source line -it is, and what incorrect result happens when that line is executed. A -person who understands the program can find this as easily as finding a -bug in the program itself. - -@item -If you send examples of assembler code output from GCC, -please use @samp{-g} when you make them. The debugging information -includes source line numbers which are essential for correlating the -output with the input. - -@item -If you wish to mention something in the GCC source, refer to it by -context, not by line number. - -The line numbers in the development sources don't match those in your -sources. Your line numbers would convey no useful information to the -maintainers. - -@item -Additional information from a debugger might enable someone to find a -problem on a machine which he does not have available. However, you -need to think when you collect this information if you want it to have -any chance of being useful. - -@cindex backtrace for bug reports -For example, many people send just a backtrace, but that is never -useful by itself. A simple backtrace with arguments conveys little -about GCC because the compiler is largely data-driven; the same -functions are called over and over for different RTL insns, doing -different things depending on the details of the insn. - -Most of the arguments listed in the backtrace are useless because they -are pointers to RTL list structure. The numeric values of the -pointers, which the debugger prints in the backtrace, have no -significance whatever; all that matters is the contents of the objects -they point to (and most of the contents are other such pointers). - -In addition, most compiler passes consist of one or more loops that -scan the RTL insn sequence. The most vital piece of information about -such a loop---which insn it has reached---is usually in a local variable, -not in an argument. - -@findex debug_rtx -What you need to provide in addition to a backtrace are the values of -the local variables for several stack frames up. When a local -variable or an argument is an RTX, first print its value and then use -the GDB command @code{pr} to print the RTL expression that it points -to. (If GDB doesn't run on your machine, use your debugger to call -the function @code{debug_rtx} with the RTX as an argument.) In -general, whenever a variable is a pointer, its value is no use -without the data it points to. -@end itemize - -Here are some things that are not necessary: - -@itemize @bullet -@item -A description of the envelope of the bug. - -Often people who encounter a bug spend a lot of time investigating -which changes to the input file will make the bug go away and which -changes will not affect it. - -This is often time consuming and not very useful, because the way we -will find the bug is by running a single example under the debugger with -breakpoints, not by pure deduction from a series of examples. You might -as well save your time for something else. - -Of course, if you can find a simpler example to report @emph{instead} of -the original one, that is a convenience. Errors in the output will be -easier to spot, running under the debugger will take less time, etc. -Most GCC bugs involve just one function, so the most straightforward -way to simplify an example is to delete all the function definitions -except the one where the bug occurs. Those earlier in the file may be -replaced by external declarations if the crucial function depends on -them. (Exception: inline functions may affect compilation of functions -defined later in the file.) - -However, simplification is not vital; if you don't want to do this, -report the bug anyway and send the entire test case you used. - -@item -In particular, some people insert conditionals @samp{#ifdef BUG} around -a statement which, if removed, makes the bug not happen. These are just -clutter; we won't pay any attention to them anyway. Besides, you should -send us cpp output, and that can't have conditionals. - -@item -A patch for the bug. - -A patch for the bug is useful if it is a good one. But don't omit the -necessary information, such as the test case, on the assumption that a -patch is all we need. We might see problems with your patch and decide -to fix the problem another way, or we might not understand it at all. - -Sometimes with a program as complicated as GCC it is very hard to -construct an example that will make the program follow a certain path -through the code. If you don't send the example, we won't be able to -construct one, so we won't be able to verify that the bug is fixed. - -And if we can't understand what bug you are trying to fix, or why your -patch should be an improvement, we won't install it. A test case will -help us to understand. - -@xref{Sending Patches}, for guidelines on how to make it easy for us to -understand and install your patches. - -@item -A guess about what the bug is or what it depends on. - -Such guesses are usually wrong. Even I can't guess right about such -things without first using the debugger to find the facts. - -@item -A core dump file. - -We have no way of examining a core dump for your type of machine -unless we have an identical system---and if we do have one, -we should be able to reproduce the crash ourselves. -@end itemize - -@node gccbug,Sending Patches, Bug Reporting, Bugs -@section The gccbug script -@cindex gccbug script - -To simplify creation of bug reports, and to allow better tracking of -reports, we use the GNATS bug tracking system. Part of that system is -the @code{gccbug} script. This is a Unix shell script, so you need a -shell to run it. It is normally installed in the same directory where -@code{gcc} is installed. - -The gccbug script is derived from send-pr, @pxref{using -send-pr,,Creating new Problem Reports,send-pr,Reporting Problems}. When -invoked, it starts a text editor so you can fill out the various fields -of the report. When the you quit the editor, the report is automatically -send to the bug reporting address. - -A number of fields in this bug report form are specific to GCC, and are -explained at @uref{http://gcc.gnu.org/gnats.html}. - -@node Sending Patches,, gccbug, Bugs -@section Sending Patches for GCC - -If you would like to write bug fixes or improvements for the GNU C -compiler, that is very helpful. Send suggested fixes to the patches -mailing list, @email{gcc-patches@@gcc.gnu.org}. - -Please follow these guidelines so we can study your patches efficiently. -If you don't follow these guidelines, your information might still be -useful, but using it will take extra work. Maintaining GNU C is a lot -of work in the best of circumstances, and we can't keep up unless you do -your best to help. - -@itemize @bullet -@item -Send an explanation with your changes of what problem they fix or what -improvement they bring about. For a bug fix, just include a copy of the -bug report, and explain why the change fixes the bug. - -(Referring to a bug report is not as good as including it, because then -we will have to look it up, and we have probably already deleted it if -we've already fixed the bug.) - -@item -Always include a proper bug report for the problem you think you have -fixed. We need to convince ourselves that the change is right before -installing it. Even if it is right, we might have trouble judging it if -we don't have a way to reproduce the problem. - -@item -Include all the comments that are appropriate to help people reading the -source in the future understand why this change was needed. - -@item -Don't mix together changes made for different reasons. -Send them @emph{individually}. - -If you make two changes for separate reasons, then we might not want to -install them both. We might want to install just one. If you send them -all jumbled together in a single set of diffs, we have to do extra work -to disentangle them---to figure out which parts of the change serve -which purpose. If we don't have time for this, we might have to ignore -your changes entirely. - -If you send each change as soon as you have written it, with its own -explanation, then the two changes never get tangled up, and we can -consider each one properly without any extra work to disentangle them. - -Ideally, each change you send should be impossible to subdivide into -parts that we might want to consider separately, because each of its -parts gets its motivation from the other parts. - -@item -Send each change as soon as that change is finished. Sometimes people -think they are helping us by accumulating many changes to send them all -together. As explained above, this is absolutely the worst thing you -could do. - -Since you should send each change separately, you might as well send it -right away. That gives us the option of installing it immediately if it -is important. - -@item -Use @samp{diff -c} to make your diffs. Diffs without context are hard -for us to install reliably. More than that, they make it hard for us to -study the diffs to decide whether we want to install them. Unidiff -format is better than contextless diffs, but not as easy to read as -@samp{-c} format. - -If you have GNU diff, use @samp{diff -cp}, which shows the name of the -function that each change occurs in. - -@item -Write the change log entries for your changes. We get lots of changes, -and we don't have time to do all the change log writing ourselves. - -Read the @file{ChangeLog} file to see what sorts of information to put -in, and to learn the style that we use. The purpose of the change log -is to show people where to find what was changed. So you need to be -specific about what functions you changed; in large functions, it's -often helpful to indicate where within the function the change was. - -On the other hand, once you have shown people where to find the change, -you need not explain its purpose. Thus, if you add a new function, all -you need to say about it is that it is new. If you feel that the -purpose needs explaining, it probably does---but the explanation will be -much more useful if you put it in comments in the code. - -If you would like your name to appear in the header line for who made -the change, send us the header line. - -@item -When you write the fix, keep in mind that we can't install a change that -would break other systems. - -People often suggest fixing a problem by changing machine-independent -files such as @file{toplev.c} to do something special that a particular -system needs. Sometimes it is totally obvious that such changes would -break GCC for almost all users. We can't possibly make a change like -that. At best it might tell us how to write another patch that would -solve the problem acceptably. - -Sometimes people send fixes that @emph{might} be an improvement in -general---but it is hard to be sure of this. It's hard to install -such changes because we have to study them very carefully. Of course, -a good explanation of the reasoning by which you concluded the change -was correct can help convince us. - -The safest changes are changes to the configuration files for a -particular machine. These are safe because they can't create new bugs -on other machines. - -Please help us keep up with the workload by designing the patch in a -form that is good to install. -@end itemize - -@node Service -@chapter How To Get Help with GCC - -If you need help installing, using or changing GCC, there are two -ways to find it: - -@itemize @bullet -@item -Send a message to a suitable network mailing list. First try -@email{gcc-help@@gcc.gnu.org} (for help installing or using GCC), and if -that brings no response, try @email{gcc@@gcc.gnu.org}. For help -changing GCC, ask @email{gcc@@gcc.gnu.org}. If you think you have found -a bug in GCC, please report it following the instructions at -@pxref{Bug Reporting}. - -@item -Look in the service directory for someone who might help you for a fee. -The service directory is found at -@uref{http://www.gnu.org/prep/service.html}. -@end itemize - -@c For further information, see -@c @uref{http://gcc.gnu.org/cgi-bin/fom.cgi?file=12}. -@c FIXME: this URL may be too volatile, this FAQ entry needs to move to -@c the regular web pages before we can uncomment the reference. - -@node Contributing -@chapter Contributing to GCC Development - -If you would like to help pretest GCC releases to assure they work well, -our current development sources are available by CVS (see -@uref{http://gcc.gnu.org/cvs.html}). Source and binary snapshots are -also available for FTP; see @uref{http://gcc.gnu.org/snapshots.html}. - -If you would like to work on improvements to GCC, please read -@uref{http://gcc.gnu.org/contribute.html} and -@uref{http://gcc.gnu.org/contributewhy.html} for information on how to -make useful contributions and avoid duplication of effort. Suggested -projects are listed at @uref{http://gcc.gnu.org/projects/}. - -@node VMS -@chapter Using GCC on VMS - -@c prevent bad page break with this line -Here is how to use GCC on VMS. - -@menu -* Include Files and VMS:: Where the preprocessor looks for the include files. -* Global Declarations:: How to do globaldef, globalref and globalvalue with - GCC. -* VMS Misc:: Misc information. -@end menu - -@node Include Files and VMS -@section Include Files and VMS - -@cindex include files and VMS -@cindex VMS and include files -@cindex header files and VMS -Due to the differences between the filesystems of Unix and VMS, GCC -attempts to translate file names in @samp{#include} into names that VMS -will understand. The basic strategy is to prepend a prefix to the -specification of the include file, convert the whole filename to a VMS -filename, and then try to open the file. GCC tries various prefixes -one by one until one of them succeeds: - -@enumerate -@item -The first prefix is the @samp{GNU_CC_INCLUDE:} logical name: this is -where GNU C header files are traditionally stored. If you wish to store -header files in non-standard locations, then you can assign the logical -@samp{GNU_CC_INCLUDE} to be a search list, where each element of the -list is suitable for use with a rooted logical. - -@item -The next prefix tried is @samp{SYS$SYSROOT:[SYSLIB.]}. This is where -VAX-C header files are traditionally stored. - -@item -If the include file specification by itself is a valid VMS filename, the -preprocessor then uses this name with no prefix in an attempt to open -the include file. - -@item -If the file specification is not a valid VMS filename (i.e. does not -contain a device or a directory specifier, and contains a @samp{/} -character), the preprocessor tries to convert it from Unix syntax to -VMS syntax. - -Conversion works like this: the first directory name becomes a device, -and the rest of the directories are converted into VMS-format directory -names. For example, the name @file{X11/foobar.h} is -translated to @file{X11:[000000]foobar.h} or @file{X11:foobar.h}, -whichever one can be opened. This strategy allows you to assign a -logical name to point to the actual location of the header files. - -@item -If none of these strategies succeeds, the @samp{#include} fails. -@end enumerate - -Include directives of the form: - -@example -#include foobar -@end example - -@noindent -are a common source of incompatibility between VAX-C and GCC. VAX-C -treats this much like a standard @code{#include } directive. -That is incompatible with the ISO C behavior implemented by GCC: to -expand the name @code{foobar} as a macro. Macro expansion should -eventually yield one of the two standard formats for @code{#include}: - -@example -#include "@var{file}" -#include <@var{file}> -@end example - -If you have this problem, the best solution is to modify the source to -convert the @code{#include} directives to one of the two standard forms. -That will work with either compiler. If you want a quick and dirty fix, -define the file names as macros with the proper expansion, like this: - -@example -#define stdio -@end example - -@noindent -This will work, as long as the name doesn't conflict with anything else -in the program. - -Another source of incompatibility is that VAX-C assumes that: - -@example -#include "foobar" -@end example - -@noindent -is actually asking for the file @file{foobar.h}. GCC does not -make this assumption, and instead takes what you ask for literally; -it tries to read the file @file{foobar}. The best way to avoid this -problem is to always specify the desired file extension in your include -directives. - -GCC for VMS is distributed with a set of include files that is -sufficient to compile most general purpose programs. Even though the -GCC distribution does not contain header files to define constants -and structures for some VMS system-specific functions, there is no -reason why you cannot use GCC with any of these functions. You first -may have to generate or create header files, either by using the public -domain utility @code{UNSDL} (which can be found on a DECUS tape), or by -extracting the relevant modules from one of the system macro libraries, -and using an editor to construct a C header file. - -A @code{#include} file name cannot contain a DECNET node name. The -preprocessor reports an I/O error if you attempt to use a node name, -whether explicitly, or implicitly via a logical name. - -@node Global Declarations -@section Global Declarations and VMS - -@findex GLOBALREF -@findex GLOBALDEF -@findex GLOBALVALUEDEF -@findex GLOBALVALUEREF -GCC does not provide the @code{globalref}, @code{globaldef} and -@code{globalvalue} keywords of VAX-C. You can get the same effect with -an obscure feature of GAS, the GNU assembler. (This requires GAS -version 1.39 or later.) The following macros allow you to use this -feature in a fairly natural way: - -@smallexample -#ifdef __GNUC__ -#define GLOBALREF(TYPE,NAME) \ - TYPE NAME \ - asm ("_$$PsectAttributes_GLOBALSYMBOL$$" #NAME) -#define GLOBALDEF(TYPE,NAME,VALUE) \ - TYPE NAME \ - asm ("_$$PsectAttributes_GLOBALSYMBOL$$" #NAME) \ - = VALUE -#define GLOBALVALUEREF(TYPE,NAME) \ - const TYPE NAME[1] \ - asm ("_$$PsectAttributes_GLOBALVALUE$$" #NAME) -#define GLOBALVALUEDEF(TYPE,NAME,VALUE) \ - const TYPE NAME[1] \ - asm ("_$$PsectAttributes_GLOBALVALUE$$" #NAME) \ - = @{VALUE@} -#else -#define GLOBALREF(TYPE,NAME) \ - globalref TYPE NAME -#define GLOBALDEF(TYPE,NAME,VALUE) \ - globaldef TYPE NAME = VALUE -#define GLOBALVALUEDEF(TYPE,NAME,VALUE) \ - globalvalue TYPE NAME = VALUE -#define GLOBALVALUEREF(TYPE,NAME) \ - globalvalue TYPE NAME -#endif -@end smallexample - -@noindent -(The @code{_$$PsectAttributes_GLOBALSYMBOL} prefix at the start of the -name is removed by the assembler, after it has modified the attributes -of the symbol). These macros are provided in the VMS binaries -distribution in a header file @file{GNU_HACKS.H}. An example of the -usage is: - -@example -GLOBALREF (int, ijk); -GLOBALDEF (int, jkl, 0); -@end example - -The macros @code{GLOBALREF} and @code{GLOBALDEF} cannot be used -straightforwardly for arrays, since there is no way to insert the array -dimension into the declaration at the right place. However, you can -declare an array with these macros if you first define a typedef for the -array type, like this: - -@example -typedef int intvector[10]; -GLOBALREF (intvector, foo); -@end example - -Array and structure initializers will also break the macros; you can -define the initializer to be a macro of its own, or you can expand the -@code{GLOBALDEF} macro by hand. You may find a case where you wish to -use the @code{GLOBALDEF} macro with a large array, but you are not -interested in explicitly initializing each element of the array. In -such cases you can use an initializer like: @code{@{0,@}}, which will -initialize the entire array to @code{0}. - -A shortcoming of this implementation is that a variable declared with -@code{GLOBALVALUEREF} or @code{GLOBALVALUEDEF} is always an array. For -example, the declaration: - -@example -GLOBALVALUEREF(int, ijk); -@end example - -@noindent -declares the variable @code{ijk} as an array of type @code{int [1]}. -This is done because a globalvalue is actually a constant; its ``value'' -is what the linker would normally consider an address. That is not how -an integer value works in C, but it is how an array works. So treating -the symbol as an array name gives consistent results---with the -exception that the value seems to have the wrong type. @strong{Don't -try to access an element of the array.} It doesn't have any elements. -The array ``address'' may not be the address of actual storage. - -The fact that the symbol is an array may lead to warnings where the -variable is used. Insert type casts to avoid the warnings. Here is an -example; it takes advantage of the ISO C feature allowing macros that -expand to use the same name as the macro itself. - -@example -GLOBALVALUEREF (int, ss$_normal); -GLOBALVALUEDEF (int, xyzzy,123); -#ifdef __GNUC__ -#define ss$_normal ((int) ss$_normal) -#define xyzzy ((int) xyzzy) -#endif -@end example - -Don't use @code{globaldef} or @code{globalref} with a variable whose -type is an enumeration type; this is not implemented. Instead, make the -variable an integer, and use a @code{globalvaluedef} for each of the -enumeration values. An example of this would be: - -@example -#ifdef __GNUC__ -GLOBALDEF (int, color, 0); -GLOBALVALUEDEF (int, RED, 0); -GLOBALVALUEDEF (int, BLUE, 1); -GLOBALVALUEDEF (int, GREEN, 3); -#else -enum globaldef color @{RED, BLUE, GREEN = 3@}; -#endif -@end example - -@node VMS Misc -@section Other VMS Issues - -@cindex exit status and VMS -@cindex return value of @code{main} -@cindex @code{main} and the exit status -GCC automatically arranges for @code{main} to return 1 by default if -you fail to specify an explicit return value. This will be interpreted -by VMS as a status code indicating a normal successful completion. -Version 1 of GCC did not provide this default. - -GCC on VMS works only with the GNU assembler, GAS. You need version -1.37 or later of GAS in order to produce value debugging information for -the VMS debugger. Use the ordinary VMS linker with the object files -produced by GAS. - -@cindex shared VMS run time system -@cindex @file{VAXCRTL} -Under previous versions of GCC, the generated code would occasionally -give strange results when linked to the sharable @file{VAXCRTL} library. -Now this should work. - -A caveat for use of @code{const} global variables: the @code{const} -modifier must be specified in every external declaration of the variable -in all of the source files that use that variable. Otherwise the linker -will issue warnings about conflicting attributes for the variable. Your -program will still work despite the warnings, but the variable will be -placed in writable storage. - -@cindex name augmentation -@cindex case sensitivity and VMS -@cindex VMS and case sensitivity -Although the VMS linker does distinguish between upper and lower case -letters in global symbols, most VMS compilers convert all such symbols -into upper case and most run-time library routines also have upper case -names. To be able to reliably call such routines, GCC (by means of -the assembler GAS) converts global symbols into upper case like other -VMS compilers. However, since the usual practice in C is to distinguish -case, GCC (via GAS) tries to preserve usual C behavior by augmenting -each name that is not all lower case. This means truncating the name -to at most 23 characters and then adding more characters at the end -which encode the case pattern of those 23. Names which contain at -least one dollar sign are an exception; they are converted directly into -upper case without augmentation. - -Name augmentation yields bad results for programs that use precompiled -libraries (such as Xlib) which were generated by another compiler. You -can use the compiler option @samp{/NOCASE_HACK} to inhibit augmentation; -it makes external C functions and variables case-independent as is usual -on VMS. Alternatively, you could write all references to the functions -and variables in such libraries using lower case; this will work on VMS, -but is not portable to other systems. The compiler option @samp{/NAMES} -also provides control over global name handling. - -Function and variable names are handled somewhat differently with GNU -C++. The GNU C++ compiler performs @dfn{name mangling} on function -names, which means that it adds information to the function name to -describe the data types of the arguments that the function takes. One -result of this is that the name of a function can become very long. -Since the VMS linker only recognizes the first 31 characters in a name, -special action is taken to ensure that each function and variable has a -unique name that can be represented in 31 characters. - -If the name (plus a name augmentation, if required) is less than 32 -characters in length, then no special action is performed. If the name -is longer than 31 characters, the assembler (GAS) will generate a -hash string based upon the function name, truncate the function name to -23 characters, and append the hash string to the truncated name. If the -@samp{/VERBOSE} compiler option is used, the assembler will print both -the full and truncated names of each symbol that is truncated. - -The @samp{/NOCASE_HACK} compiler option should not be used when you are -compiling programs that use libg++. libg++ has several instances of -objects (i.e. @code{Filebuf} and @code{filebuf}) which become -indistinguishable in a case-insensitive environment. This leads to -cases where you need to inhibit augmentation selectively (if you were -using libg++ and Xlib in the same program, for example). There is no -special feature for doing this, but you can get the result by defining a -macro for each mixed case symbol for which you wish to inhibit -augmentation. The macro should expand into the lower case equivalent of -itself. For example: - -@example -#define StuDlyCapS studlycaps -@end example - -These macro definitions can be placed in a header file to minimize the -number of changes to your source code. - -@node Makefile -@chapter Makefile Targets -@cindex makefile targets -@cindex targets, makefile - -@table @code -@item all -This is the default target. Depending on what your build/host/target -configuration is, it coordinates all the things that need to be built. - -@item doc -Produce info-formatted documentation. Also, @code{make dvi} is -available for DVI-formatted documentation, and @code{make -generated-manpages} to generate man pages. - -@item mostlyclean -Delete the files made while building the compiler. - -@item clean -That, and all the other files built by @code{make all}. - -@item distclean -That, and all the files created by @code{configure}. - -@item extraclean -That, and any temporary or intermediate files, like emacs backup files. - -@item maintainer-clean -Distclean plus any file that can be generated from other files. Note -that additional tools may be required beyond what is normally needed to -build gcc. - -@item install -Installs gcc. - -@item uninstall -Deletes installed files. - -@item check -Run the testsuite. This creates a @file{testsuite} subdirectory that -has various @file{.sum} and @file{.log} files containing the results of -the testing. You can run subsets with, for example, @code{make check-gcc}. -You can specify specific tests by setting RUNTESTFLAGS to be the name -of the @file{.exp} file, optionally followed by (for some tests) an equals -and a file wildcard, like: - -@example -make check-gcc RUNTESTFLAGS="execute.exp=19980413-*" -@end example - -Note that running the testsuite may require additional tools be -installed, such as TCL or dejagnu. - -@item bootstrap -Builds gcc three times - once with the native compiler, once with the -native-built compiler it just built, and once with the compiler it built -the second time. In theory, the last two should produce the same -results, which @code{make compare} can check. Each step of this process -is called a "stage", and the results of each stage N (N=1..3) are copied -to a subdirectory @file{stageN/}. - -@item bootstrap-lean -Like @code{bootstrap}, except that the various stages are removed once -they're no longer needed. This saves disk space. - -@item bubblestrap -Once bootstrapped, this incrementally rebuilds each of the three stages, -one at a time. It does this by "bubbling" the stages up from their -stubdirectories, rebuilding them, and copying them back to their -subdirectories. This will allow you to, for example, quickly rebuild a -bootstrapped compiler after changing the sources, without having to do a -full bootstrap. - -@item quickstrap -Rebuilds the most recently built stage. Since each stage requires -special invocation, using this target means you don't have to keep track -of which stage you're on or what invocation that stage needs. - -@item cleanstrap -Removed everything (@code{make clean}) and rebuilds (@code{make bootstrap}). - -@item stageN (N=1..4) -For each stage, moves the appropriate files to the stageN subdirectory. - -@item unstageN (N=1..4) -Undoes the corresponding @code{stageN}. - -@item restageN (N=1..4) -Undoes the corresponding @code{stageN} and rebuilds it with the -appropriate flags. - -@item compare -Compares the results of stages 2 and 3. This ensures that the compiler -is running properly, since it should produce the same object files -regardless of how it itself was compiled. - -@end table - -@end ifset - -@ifset INTERNALS -@node Portability -@chapter GCC and Portability -@cindex portability -@cindex GCC and portability - -The main goal of GCC was to make a good, fast compiler for machines in -the class that the GNU system aims to run on: 32-bit machines that address -8-bit bytes and have several general registers. Elegance, theoretical -power and simplicity are only secondary. - -GCC gets most of the information about the target machine from a machine -description which gives an algebraic formula for each of the machine's -instructions. This is a very clean way to describe the target. But when -the compiler needs information that is difficult to express in this -fashion, I have not hesitated to define an ad-hoc parameter to the machine -description. The purpose of portability is to reduce the total work needed -on the compiler; it was not of interest for its own sake. - -@cindex endianness -@cindex autoincrement addressing, availability -@findex abort -GCC does not contain machine dependent code, but it does contain code -that depends on machine parameters such as endianness (whether the most -significant byte has the highest or lowest address of the bytes in a word) -and the availability of autoincrement addressing. In the RTL-generation -pass, it is often necessary to have multiple strategies for generating code -for a particular kind of syntax tree, strategies that are usable for different -combinations of parameters. Often I have not tried to address all possible -cases, but only the common ones or only the ones that I have encountered. -As a result, a new target may require additional strategies. You will know -if this happens because the compiler will call @code{abort}. Fortunately, -the new strategies can be added in a machine-independent fashion, and will -affect only the target machines that need them. -@end ifset - -@ifset INTERNALS -@node Interface -@chapter Interfacing to GCC Output -@cindex interfacing to GCC output -@cindex run-time conventions -@cindex function call conventions -@cindex conventions, run-time - -GCC is normally configured to use the same function calling convention -normally in use on the target system. This is done with the -machine-description macros described (@pxref{Target Macros}). - -@cindex unions, returning -@cindex structures, returning -@cindex returning structures and unions -However, returning of structure and union values is done differently on -some target machines. As a result, functions compiled with PCC -returning such types cannot be called from code compiled with GCC, -and vice versa. This does not cause trouble often because few Unix -library routines return structures or unions. - -GCC code returns structures and unions that are 1, 2, 4 or 8 bytes -long in the same registers used for @code{int} or @code{double} return -values. (GCC typically allocates variables of such types in -registers also.) Structures and unions of other sizes are returned by -storing them into an address passed by the caller (usually in a -register). The machine-description macros @code{STRUCT_VALUE} and -@code{STRUCT_INCOMING_VALUE} tell GCC where to pass this address. - -By contrast, PCC on most target machines returns structures and unions -of any size by copying the data into an area of static storage, and then -returning the address of that storage as if it were a pointer value. -The caller must copy the data from that memory area to the place where -the value is wanted. This is slower than the method used by GCC, and -fails to be reentrant. - -On some target machines, such as RISC machines and the 80386, the -standard system convention is to pass to the subroutine the address of -where to return the value. On these machines, GCC has been -configured to be compatible with the standard compiler, when this method -is used. It may not be compatible for structures of 1, 2, 4 or 8 bytes. - -@cindex argument passing -@cindex passing arguments -GCC uses the system's standard convention for passing arguments. On -some machines, the first few arguments are passed in registers; in -others, all are passed on the stack. It would be possible to use -registers for argument passing on any machine, and this would probably -result in a significant speedup. But the result would be complete -incompatibility with code that follows the standard convention. So this -change is practical only if you are switching to GCC as the sole C -compiler for the system. We may implement register argument passing on -certain machines once we have a complete GNU system so that we can -compile the libraries with GCC. - -On some machines (particularly the Sparc), certain types of arguments -are passed ``by invisible reference''. This means that the value is -stored in memory, and the address of the memory location is passed to -the subroutine. - -@cindex @code{longjmp} and automatic variables -If you use @code{longjmp}, beware of automatic variables. ISO C says that -automatic variables that are not declared @code{volatile} have undefined -values after a @code{longjmp}. And this is all GCC promises to do, -because it is very difficult to restore register variables correctly, and -one of GCC's features is that it can put variables in registers without -your asking it to. - -If you want a variable to be unaltered by @code{longjmp}, and you don't -want to write @code{volatile} because old C compilers don't accept it, -just take the address of the variable. If a variable's address is ever -taken, even if just to compute it and ignore it, then the variable cannot -go in a register: - -@example -@{ - int careful; - &careful; - @dots{} -@} -@end example - -@cindex arithmetic libraries -@cindex math libraries -Code compiled with GCC may call certain library routines. Most of -them handle arithmetic for which there are no instructions. This -includes multiply and divide on some machines, and floating point -operations on any machine for which floating point support is disabled -with @samp{-msoft-float}. Some standard parts of the C library, such as -@code{bcopy} or @code{memcpy}, are also called automatically. The usual -function call interface is used for calling the library routines. - -Some of these routines can be defined in mostly machine-independent C; -they appear in @file{libgcc2.c}. Others must be hand-written in -assembly language for each processor. Wherever they are defined, they -are compiled into the support library, @file{libgcc.a}, which is -automatically searched when you link programs with GCC. -@end ifset - -@ifset INTERNALS -@node Passes -@chapter Passes and Files of the Compiler -@cindex passes and files of the compiler -@cindex files and passes of the compiler -@cindex compiler passes and files - -@cindex top level of compiler -The overall control structure of the compiler is in @file{toplev.c}. This -file is responsible for initialization, decoding arguments, opening and -closing files, and sequencing the passes. - -@cindex parsing pass -The parsing pass is invoked only once, to parse the entire input. The RTL -intermediate code for a function is generated as the function is parsed, a -statement at a time. Each statement is read in as a syntax tree and then -converted to RTL; then the storage for the tree for the statement is -reclaimed. Storage for types (and the expressions for their sizes), -declarations, and a representation of the binding contours and how they nest, -remain until the function is finished being compiled; these are all needed -to output the debugging information. - -@findex rest_of_compilation -@findex rest_of_decl_compilation -Each time the parsing pass reads a complete function definition or -top-level declaration, it calls either the function -@code{rest_of_compilation}, or the function -@code{rest_of_decl_compilation} in @file{toplev.c}, which are -responsible for all further processing necessary, ending with output of -the assembler language. All other compiler passes run, in sequence, -within @code{rest_of_compilation}. When that function returns from -compiling a function definition, the storage used for that function -definition's compilation is entirely freed, unless it is an inline -function -@ifset USING -(@pxref{Inline,,An Inline Function is As Fast As a Macro}). -@end ifset -@ifclear USING -(@pxref{Inline,,An Inline Function is As Fast As a Macro,gcc.texi,Using GCC}). -@end ifclear - -Here is a list of all the passes of the compiler and their source files. -Also included is a description of where debugging dumps can be requested -with @samp{-d} options. - -@itemize @bullet -@item -Parsing. This pass reads the entire text of a function definition, -constructing partial syntax trees. This and RTL generation are no longer -truly separate passes (formerly they were), but it is easier to think -of them as separate. - -The tree representation does not entirely follow C syntax, because it is -intended to support other languages as well. - -Language-specific data type analysis is also done in this pass, and every -tree node that represents an expression has a data type attached. -Variables are represented as declaration nodes. - -@cindex constant folding -@cindex arithmetic simplifications -@cindex simplifications, arithmetic -Constant folding and some arithmetic simplifications are also done -during this pass. - -The language-independent source files for parsing are -@file{stor-layout.c}, @file{fold-const.c}, and @file{tree.c}. -There are also header files @file{tree.h} and @file{tree.def} -which define the format of the tree representation.@refill - -@c Avoiding overfull is tricky here. -The source files to parse C are -@file{c-parse.in}, -@file{c-decl.c}, -@file{c-typeck.c}, -@file{c-aux-info.c}, -@file{c-convert.c}, -and @file{c-lang.c} -along with header files -@file{c-lex.h}, and -@file{c-tree.h}. - -The source files for parsing C++ are in @file{cp/}. -They are @file{parse.y}, -@file{class.c},@* -@file{cvt.c}, @file{decl.c}, @file{decl2.c}, -@file{except.c},@* -@file{expr.c}, @file{init.c}, @file{lex.c}, -@file{method.c}, @file{ptree.c},@* -@file{search.c}, @file{tree.c}, -@file{typeck2.c}, and -@file{typeck.c}, along with header files @file{cp-tree.def}, -@file{cp-tree.h}, and @file{decl.h}. - -The special source files for parsing Objective C are in @file{objc/}. -They are @file{objc-parse.y}, @file{objc-act.c}, @file{objc-tree.def}, and -@file{objc-act.h}. Certain C-specific files are used for this as -well. - -The file @file{c-common.c} is also used for all of the above languages. - -@cindex RTL generation -@item -RTL generation. This is the conversion of syntax tree into RTL code. -It is actually done statement-by-statement during parsing, but for -most purposes it can be thought of as a separate pass. - -@cindex target-parameter-dependent code -This is where the bulk of target-parameter-dependent code is found, -since often it is necessary for strategies to apply only when certain -standard kinds of instructions are available. The purpose of named -instruction patterns is to provide this information to the RTL -generation pass. - -@cindex tail recursion optimization -Optimization is done in this pass for @code{if}-conditions that are -comparisons, boolean operations or conditional expressions. Tail -recursion is detected at this time also. Decisions are made about how -best to arrange loops and how to output @code{switch} statements. - -@c Avoiding overfull is tricky here. -The source files for RTL generation include -@file{stmt.c}, -@file{calls.c}, -@file{expr.c}, -@file{explow.c}, -@file{expmed.c}, -@file{function.c}, -@file{optabs.c} -and @file{emit-rtl.c}. -Also, the file -@file{insn-emit.c}, generated from the machine description by the -program @code{genemit}, is used in this pass. The header file -@file{expr.h} is used for communication within this pass.@refill - -@findex genflags -@findex gencodes -The header files @file{insn-flags.h} and @file{insn-codes.h}, -generated from the machine description by the programs @code{genflags} -and @code{gencodes}, tell this pass which standard names are available -for use and which patterns correspond to them.@refill - -Aside from debugging information output, none of the following passes -refers to the tree structure representation of the function (only -part of which is saved). - -@cindex inline, automatic -The decision of whether the function can and should be expanded inline -in its subsequent callers is made at the end of rtl generation. The -function must meet certain criteria, currently related to the size of -the function and the types and number of parameters it has. Note that -this function may contain loops, recursive calls to itself -(tail-recursive functions can be inlined!), gotos, in short, all -constructs supported by GCC. The file @file{integrate.c} contains -the code to save a function's rtl for later inlining and to inline that -rtl when the function is called. The header file @file{integrate.h} -is also used for this purpose. - -The option @samp{-dr} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.rtl} to -the input file name. - -@cindex jump optimization -@cindex unreachable code -@cindex dead code -@item -Jump optimization. This pass simplifies jumps to the following -instruction, jumps across jumps, and jumps to jumps. It deletes -unreferenced labels and unreachable code, except that unreachable code -that contains a loop is not recognized as unreachable in this pass. -(Such loops are deleted later in the basic block analysis.) It also -converts some code originally written with jumps into sequences of -instructions that directly set values from the results of comparisons, -if the machine has such instructions. - -Jump optimization is performed two or three times. The first time is -immediately following RTL generation. The second time is after CSE, -but only if CSE says repeated jump optimization is needed. The -last time is right before the final pass. That time, cross-jumping -and deletion of no-op move instructions are done together with the -optimizations described above. - -The source file of this pass is @file{jump.c}. - -The option @samp{-dj} causes a debugging dump of the RTL code after -this pass is run for the first time. This dump file's name is made by -appending @samp{.jump} to the input file name. - -@cindex register use analysis -@item -Register scan. This pass finds the first and last use of each -register, as a guide for common subexpression elimination. Its source -is in @file{regclass.c}. - -@cindex jump threading -@item -Jump threading. This pass detects a condition jump that branches to an -identical or inverse test. Such jumps can be @samp{threaded} through -the second conditional test. The source code for this pass is in -@file{jump.c}. This optimization is only performed if -@samp{-fthread-jumps} is enabled. - -@cindex common subexpression elimination -@cindex constant propagation -@item -Common subexpression elimination. This pass also does constant -propagation. Its source file is @file{cse.c}. If constant -propagation causes conditional jumps to become unconditional or to -become no-ops, jump optimization is run again when CSE is finished. - -The option @samp{-ds} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.cse} to -the input file name. - -@cindex global common subexpression elimination -@cindex constant propagation -@cindex copy propagation -@item -Global common subexpression elimination. This pass performs GCSE -using Morel-Renvoise Partial Redundancy Elimination, with the exception -that it does not try to move invariants out of loops - that is left to -the loop optimization pass. This pass also performs global constant -and copy propagation. - -The source file for this pass is gcse.c. - -The option @samp{-dG} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.gcse} to -the input file name. - -@cindex loop optimization -@cindex code motion -@cindex strength-reduction -@item -Loop optimization. This pass moves constant expressions out of loops, -and optionally does strength-reduction and loop unrolling as well. -Its source files are @file{loop.c} and @file{unroll.c}, plus the header -@file{loop.h} used for communication between them. Loop unrolling uses -some functions in @file{integrate.c} and the header @file{integrate.h}. - -The option @samp{-dL} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.loop} to -the input file name. - -@item -If @samp{-frerun-cse-after-loop} was enabled, a second common -subexpression elimination pass is performed after the loop optimization -pass. Jump threading is also done again at this time if it was specified. - -The option @samp{-dt} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.cse2} to -the input file name. - -@cindex data flow analysis -@cindex analysis, data flow -@cindex basic blocks -@item -Data flow analysis (@file{flow.c}). This pass divides the program -into basic blocks (and in the process deletes unreachable loops); then -it computes which pseudo-registers are live at each point in the -program, and makes the first instruction that uses a value point at -the instruction that computed the value. - -@cindex autoincrement/decrement analysis -This pass also deletes computations whose results are never used, and -combines memory references with add or subtract instructions to make -autoincrement or autodecrement addressing. - -The option @samp{-df} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.flow} to -the input file name. If stupid register allocation is in use, this -dump file reflects the full results of such allocation. - -@cindex instruction combination -@item -Instruction combination (@file{combine.c}). This pass attempts to -combine groups of two or three instructions that are related by data -flow into single instructions. It combines the RTL expressions for -the instructions by substitution, simplifies the result using algebra, -and then attempts to match the result against the machine description. - -The option @samp{-dc} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.combine} -to the input file name. - -@cindex register movement -@item -Register movement (@file{regmove.c}). This pass looks for cases where -matching constraints would force an instruction to need a reload, and -this reload would be a register to register move. It then attempts -to change the registers used by the instruction to avoid the move -instruction. - -The option @samp{-dN} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.regmove} -to the input file name. - -@cindex instruction scheduling -@cindex scheduling, instruction -@item -Instruction scheduling (@file{sched.c}). This pass looks for -instructions whose output will not be available by the time that it is -used in subsequent instructions. (Memory loads and floating point -instructions often have this behavior on RISC machines). It re-orders -instructions within a basic block to try to separate the definition and -use of items that otherwise would cause pipeline stalls. - -Instruction scheduling is performed twice. The first time is immediately -after instruction combination and the second is immediately after reload. - -The option @samp{-dS} causes a debugging dump of the RTL code after this -pass is run for the first time. The dump file's name is made by -appending @samp{.sched} to the input file name. - -@cindex register class preference pass -@item -Register class preferencing. The RTL code is scanned to find out -which register class is best for each pseudo register. The source -file is @file{regclass.c}. - -@cindex register allocation -@cindex local register allocation -@item -Local register allocation (@file{local-alloc.c}). This pass allocates -hard registers to pseudo registers that are used only within one basic -block. Because the basic block is linear, it can use fast and -powerful techniques to do a very good job. - -The option @samp{-dl} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.lreg} to -the input file name. - -@cindex global register allocation -@item -Global register allocation (@file{global.c}). This pass -allocates hard registers for the remaining pseudo registers (those -whose life spans are not contained in one basic block). - -@cindex reloading -@item -Reloading. This pass renumbers pseudo registers with the hardware -registers numbers they were allocated. Pseudo registers that did not -get hard registers are replaced with stack slots. Then it finds -instructions that are invalid because a value has failed to end up in -a register, or has ended up in a register of the wrong kind. It fixes -up these instructions by reloading the problematical values -temporarily into registers. Additional instructions are generated to -do the copying. - -The reload pass also optionally eliminates the frame pointer and inserts -instructions to save and restore call-clobbered registers around calls. - -Source files are @file{reload.c} and @file{reload1.c}, plus the header -@file{reload.h} used for communication between them. - -The option @samp{-dg} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.greg} to -the input file name. - -@cindex instruction scheduling -@cindex scheduling, instruction -@item -Instruction scheduling is repeated here to try to avoid pipeline stalls -due to memory loads generated for spilled pseudo registers. - -The option @samp{-dR} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.sched2} -to the input file name. - -@cindex cross-jumping -@cindex no-op move instructions -@item -Jump optimization is repeated, this time including cross-jumping -and deletion of no-op move instructions. - -The option @samp{-dJ} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.jump2} -to the input file name. - -@cindex delayed branch scheduling -@cindex scheduling, delayed branch -@item -Delayed branch scheduling. This optional pass attempts to find -instructions that can go into the delay slots of other instructions, -usually jumps and calls. The source file name is @file{reorg.c}. - -The option @samp{-dd} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.dbr} -to the input file name. - -@cindex branch shortening -@item -Branch shortening. On many RISC machines, branch instructions have a -limited range. Thus, longer sequences of instructions must be used for -long branches. In this pass, the compiler figures out what how far each -instruction will be from each other instruction, and therefore whether -the usual instructions, or the longer sequences, must be used for each -branch. - -@cindex register-to-stack conversion -@item -Conversion from usage of some hard registers to usage of a register -stack may be done at this point. Currently, this is supported only -for the floating-point registers of the Intel 80387 coprocessor. The -source file name is @file{reg-stack.c}. - -The options @samp{-dk} causes a debugging dump of the RTL code after -this pass. This dump file's name is made by appending @samp{.stack} -to the input file name. - -@cindex final pass -@cindex peephole optimization -@item -Final. This pass outputs the assembler code for the function. It is -also responsible for identifying spurious test and compare -instructions. Machine-specific peephole optimizations are performed -at the same time. The function entry and exit sequences are generated -directly as assembler code in this pass; they never exist as RTL. - -The source files are @file{final.c} plus @file{insn-output.c}; the -latter is generated automatically from the machine description by the -tool @file{genoutput}. The header file @file{conditions.h} is used -for communication between these files. - -@cindex debugging information generation -@item -Debugging information output. This is run after final because it must -output the stack slot offsets for pseudo registers that did not get -hard registers. Source files are @file{dbxout.c} for DBX symbol table -format, @file{sdbout.c} for SDB symbol table format, and -@file{dwarfout.c} for DWARF symbol table format. -@end itemize - -Some additional files are used by all or many passes: - -@itemize @bullet -@item -Every pass uses @file{machmode.def} and @file{machmode.h} which define -the machine modes. - -@item -Several passes use @file{real.h}, which defines the default -representation of floating point constants and how to operate on them. - -@item -All the passes that work with RTL use the header files @file{rtl.h} -and @file{rtl.def}, and subroutines in file @file{rtl.c}. The tools -@code{gen*} also use these files to read and work with the machine -description RTL. - -@findex genconfig -@item -Several passes refer to the header file @file{insn-config.h} which -contains a few parameters (C macro definitions) generated -automatically from the machine description RTL by the tool -@code{genconfig}. - -@cindex instruction recognizer -@item -Several passes use the instruction recognizer, which consists of -@file{recog.c} and @file{recog.h}, plus the files @file{insn-recog.c} -and @file{insn-extract.c} that are generated automatically from the -machine description by the tools @file{genrecog} and -@file{genextract}.@refill - -@item -Several passes use the header files @file{regs.h} which defines the -information recorded about pseudo register usage, and @file{basic-block.h} -which defines the information recorded about basic blocks. - -@item -@file{hard-reg-set.h} defines the type @code{HARD_REG_SET}, a bit-vector -with a bit for each hard register, and some macros to manipulate it. -This type is just @code{int} if the machine has few enough hard registers; -otherwise it is an array of @code{int} and some of the macros expand -into loops. - -@item -Several passes use instruction attributes. A definition of the -attributes defined for a particular machine is in file -@file{insn-attr.h}, which is generated from the machine description by -the program @file{genattr}. The file @file{insn-attrtab.c} contains -subroutines to obtain the attribute values for insns. It is generated -from the machine description by the program @file{genattrtab}.@refill -@end itemize -@end ifset - -@ifset INTERNALS -@include c-tree.texi -@include rtl.texi -@include md.texi -@include tm.texi -@end ifset - -@ifset INTERNALS -@node Config -@chapter The Configuration File -@cindex configuration file -@cindex @file{xm-@var{machine}.h} - -The configuration file @file{xm-@var{machine}.h} contains macro -definitions that describe the machine and system on which the compiler -is running, unlike the definitions in @file{@var{machine}.h}, which -describe the machine for which the compiler is producing output. Most -of the values in @file{xm-@var{machine}.h} are actually the same on all -machines that GCC runs on, so large parts of all configuration files -are identical. But there are some macros that vary: - -@table @code -@findex USG -@item USG -Define this macro if the host system is System V. - -@findex VMS -@item VMS -Define this macro if the host system is VMS. - -@findex FATAL_EXIT_CODE -@item FATAL_EXIT_CODE -A C expression for the status code to be returned when the compiler -exits after serious errors. The default is the system-provided macro -@samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that -macro. Define this macro only if these defaults are incorrect. - -@findex SUCCESS_EXIT_CODE -@item SUCCESS_EXIT_CODE -A C expression for the status code to be returned when the compiler -exits without serious errors. (Warnings are not serious errors.) The -default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if -the system doesn't define that macro. Define this macro only if these -defaults are incorrect. - -@findex HOST_WORDS_BIG_ENDIAN -@item HOST_WORDS_BIG_ENDIAN -Defined if the host machine stores words of multi-word values in -big-endian order. (GCC does not depend on the host byte ordering -within a word.) - -@findex HOST_FLOAT_WORDS_BIG_ENDIAN -@item HOST_FLOAT_WORDS_BIG_ENDIAN -Define this macro to be 1 if the host machine stores @code{DFmode}, -@code{XFmode} or @code{TFmode} floating point numbers in memory with the -word containing the sign bit at the lowest address; otherwise, define it -to be zero. - -This macro need not be defined if the ordering is the same as for -multi-word integers. - -@findex HOST_FLOAT_FORMAT -@item HOST_FLOAT_FORMAT -A numeric code distinguishing the floating point format for the host -machine. See @code{TARGET_FLOAT_FORMAT} in @ref{Storage Layout} for the -alternatives and default. - -@findex HOST_BITS_PER_CHAR -@item HOST_BITS_PER_CHAR -A C expression for the number of bits in @code{char} on the host -machine. - -@findex HOST_BITS_PER_SHORT -@item HOST_BITS_PER_SHORT -A C expression for the number of bits in @code{short} on the host -machine. - -@findex HOST_BITS_PER_INT -@item HOST_BITS_PER_INT -A C expression for the number of bits in @code{int} on the host -machine. - -@findex HOST_BITS_PER_LONG -@item HOST_BITS_PER_LONG -A C expression for the number of bits in @code{long} on the host -machine. - -@findex ONLY_INT_FIELDS -@item ONLY_INT_FIELDS -Define this macro to indicate that the host compiler only supports -@code{int} bit fields, rather than other integral types, including -@code{enum}, as do most C compilers. - -@findex OBSTACK_CHUNK_SIZE -@item OBSTACK_CHUNK_SIZE -A C expression for the size of ordinary obstack chunks. -If you don't define this, a usually-reasonable default is used. - -@findex OBSTACK_CHUNK_ALLOC -@item OBSTACK_CHUNK_ALLOC -The function used to allocate obstack chunks. -If you don't define this, @code{xmalloc} is used. - -@findex OBSTACK_CHUNK_FREE -@item OBSTACK_CHUNK_FREE -The function used to free obstack chunks. -If you don't define this, @code{free} is used. - -@findex USE_C_ALLOCA -@item USE_C_ALLOCA -Define this macro to indicate that the compiler is running with the -@code{alloca} implemented in C. This version of @code{alloca} can be -found in the file @file{alloca.c}; to use it, you must also alter the -@file{Makefile} variable @code{ALLOCA}. (This is done automatically -for the systems on which we know it is needed.) - -If you do define this macro, you should probably do it as follows: - -@example -#ifndef __GNUC__ -#define USE_C_ALLOCA -#else -#define alloca __builtin_alloca -#endif -@end example - -@noindent -so that when the compiler is compiled with GCC it uses the more -efficient built-in @code{alloca} function. - -@item FUNCTION_CONVERSION_BUG -@findex FUNCTION_CONVERSION_BUG -Define this macro to indicate that the host compiler does not properly -handle converting a function value to a pointer-to-function when it is -used in an expression. - -@findex MULTIBYTE_CHARS -@item MULTIBYTE_CHARS -Define this macro to enable support for multibyte characters in the -input to GCC. This requires that the host system support the ISO C -library functions for converting multibyte characters to wide -characters. - -@findex POSIX -@item POSIX -Define this if your system is POSIX.1 compliant. - -@findex PATH_SEPARATOR -@item PATH_SEPARATOR -Define this macro to be a C character constant representing the -character used to separate components in paths. The default value is -the colon character - -@findex DIR_SEPARATOR -@item DIR_SEPARATOR -If your system uses some character other than slash to separate -directory names within a file specification, define this macro to be a C -character constant specifying that character. When GCC displays file -names, the character you specify will be used. GCC will test for -both slash and the character you specify when parsing filenames. - -@findex TARGET_OBJECT_SUFFIX -@item TARGET_OBJECT_SUFFIX -Define this macro to be a C string representing the suffix for object -files on your target machine. If you do not define this macro, GCC will -use @samp{.o} as the suffix for object files. - -@findex TARGET_EXECUTABLE_SUFFIX -@item TARGET_EXECUTABLE_SUFFIX -Define this macro to be a C string representing the suffix to be -automatically added to executable files on your target machine. If you -do not define this macro, GCC will use the null string as the suffix for -executable files. - -@findex HOST_OBJECT_SUFFIX -@item HOST_OBJECT_SUFFIX -Define this macro to be a C string representing the suffix for object -files on your host machine (@samp{xm-*.h}). If you do not define this -macro, GCC will use @samp{.o} as the suffix for object files. - -@findex HOST_EXECUTABLE_SUFFIX -@item HOST_EXECUTABLE_SUFFIX -Define this macro to be a C string representing the suffix for -executable files on your host machine (@samp{xm-*.h}). If you do not -define this macro, GCC will use the null string as the suffix for -executable files. - -@findex HOST_BIT_BUCKET -@item HOST_BIT_BUCKET -The name of a file or file-like object on the host system which acts as -a ``bit bucket''. If you do not define this macro, GCC will use -@samp{/dev/null} as the bit bucket. If the target does not support a -bit bucket, this should be defined to the null string, or some other -illegal filename. If the bit bucket is not writable, GCC will use a -temporary file instead. - -@findex COLLECT_EXPORT_LIST -@item COLLECT_EXPORT_LIST -If defined, @code{collect2} will scan the individual object files -specified on its command line and create an export list for the linker. -Define this macro for systems like AIX, where the linker discards -object files that are not referenced from @code{main} and uses export -lists. - -@findex COLLECT2_HOST_INITIALIZATION -@item COLLECT2_HOST_INITIALIZATION -If defined, a C statement (sans semicolon) that performs host-dependent -initialization when @code{collect2} is being initialized. - -@findex GCC_DRIVER_HOST_INITIALIZATION -@item GCC_DRIVER_HOST_INITIALIZATION -If defined, a C statement (sans semicolon) that performs host-dependent -initialization when a compilation driver is being initialized. - -@findex UPDATE_PATH_HOST_CANONICALIZE -@item UPDATE_PATH_HOST_CANONICALIZE (@var{path}, @var{key}) -If defined, a C statement (sans semicolon) that performs host-dependent -canonicalization when a path used in a compilation driver or preprocessor is -canonicalized. @var{path} is the path to be canonicalized, and @var{key} is -a translation prefix when its value isn't @code{NULL}. If the C statement -does canonicalize @var{path}, the new path should be returned. -@end table - -@findex bzero -@findex bcmp -In addition, configuration files for system V define @code{bcopy}, -@code{bzero} and @code{bcmp} as aliases. Some files define @code{alloca} -as a macro when compiled with GCC, in order to take advantage of the -benefit of GCC's built-in @code{alloca}. - -@node Fragments -@chapter Makefile Fragments -@cindex makefile fragment - -When you configure GCC using the @file{configure} script -(@pxref{Installation}), it will construct the file @file{Makefile} from -the template file @file{Makefile.in}. When it does this, it will -incorporate makefile fragment files from the @file{config} directory, -named @file{t-@var{target}} and @file{x-@var{host}}. If these files do -not exist, it means nothing needs to be added for a given target or -host. - -@menu -* Target Fragment:: Writing the @file{t-@var{target}} file. -* Host Fragment:: Writing the @file{x-@var{host}} file. -@end menu - -@node Target Fragment -@section The Target Makefile Fragment -@cindex target makefile fragment -@cindex @file{t-@var{target}} - -The target makefile fragment, @file{t-@var{target}}, defines special -target dependent variables and targets used in the @file{Makefile}: - -@table @code -@findex LIBGCC2_CFLAGS -@item LIBGCC2_CFLAGS -Compiler flags to use when compiling @file{libgcc2.c}. - -@findex LIB2FUNCS_EXTRA -@item LIB2FUNCS_EXTRA -A list of source file names to be compiled or assembled and inserted -into @file{libgcc.a}. - -@findex Floating Point Emulation -@item Floating Point Emulation -To have GCC include software floating point libraries in @file{libgcc.a} -define @code{FPBIT} and @code{DPBIT} along with a few rules as follows: -@smallexample -# We want fine grained libraries, so use the new code -# to build the floating point emulation libraries. -FPBIT = fp-bit.c -DPBIT = dp-bit.c - - -fp-bit.c: $(srcdir)/config/fp-bit.c - echo '#define FLOAT' > fp-bit.c - cat $(srcdir)/config/fp-bit.c >> fp-bit.c - -dp-bit.c: $(srcdir)/config/fp-bit.c - cat $(srcdir)/config/fp-bit.c > dp-bit.c -@end smallexample - -You may need to provide additional #defines at the beginning of @file{fp-bit.c} -and @file{dp-bit.c} to control target endianness and other options. - - -@findex CRTSTUFF_T_CFLAGS -@item CRTSTUFF_T_CFLAGS -Special flags used when compiling @file{crtstuff.c}. -@xref{Initialization}. - -@findex CRTSTUFF_T_CFLAGS_S -@item CRTSTUFF_T_CFLAGS_S -Special flags used when compiling @file{crtstuff.c} for shared -linking. Used if you use @file{crtbeginS.o} and @file{crtendS.o} -in @code{EXTRA-PARTS}. -@xref{Initialization}. - -@findex MULTILIB_OPTIONS -@item MULTILIB_OPTIONS -For some targets, invoking GCC in different ways produces objects -that can not be linked together. For example, for some targets GCC -produces both big and little endian code. For these targets, you must -arrange for multiple versions of @file{libgcc.a} to be compiled, one for -each set of incompatible options. When GCC invokes the linker, it -arranges to link in the right version of @file{libgcc.a}, based on -the command line options used. - -The @code{MULTILIB_OPTIONS} macro lists the set of options for which -special versions of @file{libgcc.a} must be built. Write options that -are mutually incompatible side by side, separated by a slash. Write -options that may be used together separated by a space. The build -procedure will build all combinations of compatible options. - -For example, if you set @code{MULTILIB_OPTIONS} to @samp{m68000/m68020 -msoft-float}, @file{Makefile} will build special versions of -@file{libgcc.a} using the following sets of options: @samp{-m68000}, -@samp{-m68020}, @samp{-msoft-float}, @samp{-m68000 -msoft-float}, and -@samp{-m68020 -msoft-float}. - -@findex MULTILIB_DIRNAMES -@item MULTILIB_DIRNAMES -If @code{MULTILIB_OPTIONS} is used, this variable specifies the -directory names that should be used to hold the various libraries. -Write one element in @code{MULTILIB_DIRNAMES} for each element in -@code{MULTILIB_OPTIONS}. If @code{MULTILIB_DIRNAMES} is not used, the -default value will be @code{MULTILIB_OPTIONS}, with all slashes treated -as spaces. - -For example, if @code{MULTILIB_OPTIONS} is set to @samp{m68000/m68020 -msoft-float}, then the default value of @code{MULTILIB_DIRNAMES} is -@samp{m68000 m68020 msoft-float}. You may specify a different value if -you desire a different set of directory names. - -@findex MULTILIB_MATCHES -@item MULTILIB_MATCHES -Sometimes the same option may be written in two different ways. If an -option is listed in @code{MULTILIB_OPTIONS}, GCC needs to know about -any synonyms. In that case, set @code{MULTILIB_MATCHES} to a list of -items of the form @samp{option=option} to describe all relevant -synonyms. For example, @samp{m68000=mc68000 m68020=mc68020}. - -@findex MULTILIB_EXCEPTIONS -@item MULTILIB_EXCEPTIONS -Sometimes when there are multiple sets of @code{MULTILIB_OPTIONS} being -specified, there are combinations that should not be built. In that -case, set @code{MULTILIB_EXCEPTIONS} to be all of the switch exceptions -in shell case syntax that should not be built. - -For example, in the PowerPC embedded ABI support, it is not desirable -to build libraries compiled with the @samp{-mcall-aix} option -and either of the @samp{-fleading-underscore} or @samp{-mlittle} options -at the same time. Therefore @code{MULTILIB_EXCEPTIONS} is set to -@code{*mcall-aix/*fleading-underscore* *mlittle/*mcall-aix*}. - -@findex MULTILIB_EXTRA_OPTS -@item MULTILIB_EXTRA_OPTS -Sometimes it is desirable that when building multiple versions of -@file{libgcc.a} certain options should always be passed on to the -compiler. In that case, set @code{MULTILIB_EXTRA_OPTS} to be the list -of options to be used for all builds. -@end table - -@node Host Fragment -@section The Host Makefile Fragment -@cindex host makefile fragment -@cindex @file{x-@var{host}} - -The host makefile fragment, @file{x-@var{host}}, defines special host -dependent variables and targets used in the @file{Makefile}: - -@table @code -@findex CC -@item CC -The compiler to use when building the first stage. - -@findex INSTALL -@item INSTALL -The install program to use. -@end table -@end ifset - -@node Funding -@unnumbered Funding Free Software - -If you want to have more free software a few years from now, it makes -sense for you to help encourage people to contribute funds for its -development. The most effective approach known is to encourage -commercial redistributors to donate. - -Users of free software systems can boost the pace of development by -encouraging for-a-fee distributors to donate part of their selling price -to free software developers---the Free Software Foundation, and others. - -The way to convince distributors to do this is to demand it and expect -it from them. So when you compare distributors, judge them partly by -how much they give to free software development. Show distributors -they must compete to be the one who gives the most. - -To make this approach work, you must insist on numbers that you can -compare, such as, ``We will donate ten dollars to the Frobnitz project -for each disk sold.'' Don't be satisfied with a vague promise, such as -``A portion of the profits are donated,'' since it doesn't give a basis -for comparison. - -Even a precise fraction ``of the profits from this disk'' is not very -meaningful, since creative accounting and unrelated business decisions -can greatly alter what fraction of the sales price counts as profit. -If the price you pay is $50, ten percent of the profit is probably -less than a dollar; it might be a few cents, or nothing at all. - -Some redistributors do development work themselves. This is useful too; -but to keep everyone honest, you need to inquire how much they do, and -what kind. Some kinds of development make much more long-term -difference than others. For example, maintaining a separate version of -a program contributes very little; maintaining the standard version of a -program for the whole community contributes much. Easy new ports -contribute little, since someone else would surely do them; difficult -ports such as adding a new CPU to the GNU Compiler Collection contribute more; -major new features or packages contribute the most. - -By establishing the idea that supporting further development is ``the -proper thing to do'' when distributing free software for a fee, we can -assure a steady flow of resources into making more free software. - -@display -Copyright (C) 1994 Free Software Foundation, Inc. -Verbatim copying and redistribution of this section is permitted -without royalty; alteration is not permitted. -@end display - -@node GNU/Linux -@unnumbered Linux and the GNU Project - -Many computer users run a modified version of the GNU system every -day, without realizing it. Through a peculiar turn of events, the -version of GNU which is widely used today is more often known as -``Linux'', and many users are not aware of the extent of its -connection with the GNU Project. - -There really is a Linux; it is a kernel, and these people are using -it. But you can't use a kernel by itself; a kernel is useful only as -part of a whole system. The system in which Linux is typically used -is a modified variant of the GNU system---in other words, a Linux-based -GNU system. - -Many users are not fully aware of the distinction between the kernel, -which is Linux, and the whole system, which they also call ``Linux''. -The ambiguous use of the name doesn't promote understanding. - -Programmers generally know that Linux is a kernel. But since they -have generally heard the whole system called ``Linux'' as well, they -often envisage a history which fits that name. For example, many -believe that once Linus Torvalds finished writing the kernel, his -friends looked around for other free software, and for no particular -reason most everything necessary to make a Unix-like system was -already available. - -What they found was no accident---it was the GNU system. The available -free software added up to a complete system because the GNU Project -had been working since 1984 to make one. The GNU Manifesto -had set forth the goal of developing a free Unix-like system, called -GNU. By the time Linux was written, the system was almost finished. - -Most free software projects have the goal of developing a particular -program for a particular job. For example, Linus Torvalds set out to -write a Unix-like kernel (Linux); Donald Knuth set out to write a text -formatter (TeX); Bob Scheifler set out to develop a window system (X -Windows). It's natural to measure the contribution of this kind of -project by specific programs that came from the project. - -If we tried to measure the GNU Project's contribution in this way, -what would we conclude? One CD-ROM vendor found that in their ``Linux -distribution'', GNU software was the largest single contingent, around -28% of the total source code, and this included some of the essential -major components without which there could be no system. Linux itself -was about 3%. So if you were going to pick a name for the system -based on who wrote the programs in the system, the most appropriate -single choice would be ``GNU''. - -But we don't think that is the right way to consider the question. -The GNU Project was not, is not, a project to develop specific -software packages. It was not a project to develop a C compiler, -although we did. It was not a project to develop a text editor, -although we developed one. The GNU Project's aim was to develop -@emph{a complete free Unix-like system}. - -Many people have made major contributions to the free software in the -system, and they all deserve credit. But the reason it is @emph{a -system}---and not just a collection of useful programs---is because the -GNU Project set out to make it one. We wrote the programs that were -needed to make a @emph{complete} free system. We wrote essential but -unexciting major components, such as the assembler and linker, because -you can't have a system without them. A complete system needs more -than just programming tools, so we wrote other components as well, -such as the Bourne Again SHell, the PostScript interpreter -Ghostscript, and the GNU C library. - -By the early 90s we had put together the whole system aside from the -kernel (and we were also working on a kernel, the GNU Hurd, which runs -on top of Mach). Developing this kernel has been a lot harder than we -expected, and we are still working on finishing it. - -Fortunately, you don't have to wait for it, because Linux is working -now. When Linus Torvalds wrote Linux, he filled the last major gap. -People could then put Linux together with the GNU system to make a -complete free system: a Linux-based GNU system (or GNU/Linux system, -for short). - -Putting them together sounds simple, but it was not a trivial job. -The GNU C library (called glibc for short) needed substantial changes. -Integrating a complete system as a distribution that would work ``out -of the box'' was a big job, too. It required addressing the issue of -how to install and boot the system---a problem we had not tackled, -because we hadn't yet reached that point. The people who developed -the various system distributions made a substantial contribution. - -The GNU Project supports GNU/Linux systems as well as @emph{the} -GNU system---even with funds. We funded the rewriting of the -Linux-related extensions to the GNU C library, so that now they are -well integrated, and the newest GNU/Linux systems use the current -library release with no changes. We also funded an early stage of the -development of Debian GNU/Linux. - -We use Linux-based GNU systems today for most of our work, and we hope -you use them too. But please don't confuse the public by using the -name ``Linux'' ambiguously. Linux is the kernel, one of the essential -major components of the system. The system as a whole is more or less -the GNU system. - -@node Copying -@unnumbered GNU GENERAL PUBLIC LICENSE -@center Version 2, June 1991 - -@display -Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. -59 Temple Place - Suite 330, Boston, MA 02111-1307, USA - -Everyone is permitted to copy and distribute verbatim copies -of this license document, but changing it is not allowed. -@end display - -@unnumberedsec Preamble - - The licenses for most software are designed to take away your -freedom to share and change it. By contrast, the GNU General Public -License is intended to guarantee your freedom to share and change free -software---to make sure the software is free for all its users. This -General Public License applies to most of the Free Software -Foundation's software and to any other program whose authors commit to -using it. (Some other Free Software Foundation software is covered by -the GNU Library General Public License instead.) You can apply it to -your programs, too. - - When we speak of free software, we are referring to freedom, not -price. Our General Public Licenses are designed to make sure that you -have the freedom to distribute copies of free software (and charge for -this service if you wish), that you receive source code or can get it -if you want it, that you can change the software or use pieces of it -in new free programs; and that you know you can do these things. - - To protect your rights, we need to make restrictions that forbid -anyone to deny you these rights or to ask you to surrender the rights. -These restrictions translate to certain responsibilities for you if you -distribute copies of the software, or if you modify it. - - For example, if you distribute copies of such a program, whether -gratis or for a fee, you must give the recipients all the rights that -you have. You must make sure that they, too, receive or can get the -source code. And you must show them these terms so they know their -rights. - - We protect your rights with two steps: (1) copyright the software, and -(2) offer you this license which gives you legal permission to copy, -distribute and/or modify the software. - - Also, for each author's protection and ours, we want to make certain -that everyone understands that there is no warranty for this free -software. If the software is modified by someone else and passed on, we -want its recipients to know that what they have is not the original, so -that any problems introduced by others will not reflect on the original -authors' reputations. - - Finally, any free program is threatened constantly by software -patents. We wish to avoid the danger that redistributors of a free -program will individually obtain patent licenses, in effect making the -program proprietary. To prevent this, we have made it clear that any -patent must be licensed for everyone's free use or not licensed at all. - - The precise terms and conditions for copying, distribution and -modification follow. - -@iftex -@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION -@end iftex -@ifnottex -@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION -@end ifnottex - -@enumerate 0 -@item -This License applies to any program or other work which contains -a notice placed by the copyright holder saying it may be distributed -under the terms of this General Public License. The ``Program'', below, -refers to any such program or work, and a ``work based on the Program'' -means either the Program or any derivative work under copyright law: -that is to say, a work containing the Program or a portion of it, -either verbatim or with modifications and/or translated into another -language. (Hereinafter, translation is included without limitation in -the term ``modification''.) Each licensee is addressed as ``you''. - -Activities other than copying, distribution and modification are not -covered by this License; they are outside its scope. The act of -running the Program is not restricted, and the output from the Program -is covered only if its contents constitute a work based on the -Program (independent of having been made by running the Program). -Whether that is true depends on what the Program does. - -@item -You may copy and distribute verbatim copies of the Program's -source code as you receive it, in any medium, provided that you -conspicuously and appropriately publish on each copy an appropriate -copyright notice and disclaimer of warranty; keep intact all the -notices that refer to this License and to the absence of any warranty; -and give any other recipients of the Program a copy of this License -along with the Program. - -You may charge a fee for the physical act of transferring a copy, and -you may at your option offer warranty protection in exchange for a fee. - -@item -You may modify your copy or copies of the Program or any portion -of it, thus forming a work based on the Program, and copy and -distribute such modifications or work under the terms of Section 1 -above, provided that you also meet all of these conditions: - -@enumerate a -@item -You must cause the modified files to carry prominent notices -stating that you changed the files and the date of any change. - -@item -You must cause any work that you distribute or publish, that in -whole or in part contains or is derived from the Program or any -part thereof, to be licensed as a whole at no charge to all third -parties under the terms of this License. - -@item -If the modified program normally reads commands interactively -when run, you must cause it, when started running for such -interactive use in the most ordinary way, to print or display an -announcement including an appropriate copyright notice and a -notice that there is no warranty (or else, saying that you provide -a warranty) and that users may redistribute the program under -these conditions, and telling the user how to view a copy of this -License. (Exception: if the Program itself is interactive but -does not normally print such an announcement, your work based on -the Program is not required to print an announcement.) -@end enumerate - -These requirements apply to the modified work as a whole. If -identifiable sections of that work are not derived from the Program, -and can be reasonably considered independent and separate works in -themselves, then this License, and its terms, do not apply to those -sections when you distribute them as separate works. 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It is safest -to attach them to the start of each source file to most effectively -convey the exclusion of warranty; and each file should have at least -the ``copyright'' line and a pointer to where the full notice is found. - -@smallexample -@var{one line to give the program's name and a brief idea of what it does.} -Copyright (C) @var{yyyy} @var{name of author} - -This program is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 2 of the License, or -(at your option) any later version. - -This program is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with this program; if not, write to the Free Software -Foundation, Inc., 59 Temple Place - Suite 330, -Boston, MA 02111-1307, USA. -@end smallexample - -Also add information on how to contact you by electronic and paper mail. - -If the program is interactive, make it output a short notice like this -when it starts in an interactive mode: - -@smallexample -Gnomovision version 69, Copyright (C) @var{yyyy} @var{name of author} -Gnomovision comes with ABSOLUTELY NO WARRANTY; for details -type `show w'. -This is free software, and you are welcome to redistribute it -under certain conditions; type `show c' for details. -@end smallexample - -The hypothetical commands @samp{show w} and @samp{show c} should show -the appropriate parts of the General Public License. Of course, the -commands you use may be called something other than @samp{show w} and -@samp{show c}; they could even be mouse-clicks or menu items---whatever -suits your program. - -You should also get your employer (if you work as a programmer) or your -school, if any, to sign a ``copyright disclaimer'' for the program, if -necessary. Here is a sample; alter the names: - -@smallexample -Yoyodyne, Inc., hereby disclaims all copyright interest in the program -`Gnomovision' (which makes passes at compilers) written by James Hacker. - -@var{signature of Ty Coon}, 1 April 1989 -Ty Coon, President of Vice -@end smallexample - -This General Public License does not permit incorporating your program into -proprietary programs. If your program is a subroutine library, you may -consider it more useful to permit linking proprietary applications with the -library. If this is what you want to do, use the GNU Library General -Public License instead of this License. - -@c --------------------------------------------------------------------- -@c GFDL -@c --------------------------------------------------------------------- - -@include fdl.texi - -@node Contributors -@unnumbered Contributors to GCC -@cindex contributors -@include contrib.texi - -@c --------------------------------------------------------------------- -@c Node Index -@c --------------------------------------------------------------------- - -@node Index -@unnumbered Index - -@printindex cp - -@c --------------------------------------------------------------------- -@c Epilogue -@c --------------------------------------------------------------------- - -@summarycontents -@contents -@bye diff --git a/gcc/gcov.1 b/gcc/gcov.1 deleted file mode 100644 index 633d7546384..00000000000 --- a/gcc/gcov.1 +++ /dev/null @@ -1,414 +0,0 @@ -.\" Automatically generated by Pod::Man version 1.1 -.\" Mon Feb 19 19:31:56 2001 -.\" -.\" Standard preamble: -.\" ====================================================================== -.de Sh \" Subsection heading -.br -.if t .Sp -.ne 5 -.PP -\fB\\$1\fR -.PP -.. -.de Sp \" Vertical space (when we can't use .PP) -.if t .sp .5v -.if n .sp -.. -.de Ip \" List item -.br -.ie \\n(.$>=3 .ne \\$3 -.el .ne 3 -.IP "\\$1" \\$2 -.. -.de Vb \" Begin verbatim text -.ft CW -.nf -.ne \\$1 -.. -.de Ve \" End verbatim text -.ft R - -.fi -.. -.\" Set up some character translations and predefined strings. \*(-- will -.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left -.\" double quote, and \*(R" will give a right double quote. | will give a -.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used -.\" to do unbreakable dashes and therefore won't be available. \*(C` and -.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<> -.tr \(*W-|\(bv\*(Tr -.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' -.ie n \{\ -. ds -- \(*W- -. ds PI pi -. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch -. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch -. ds L" "" -. ds R" "" -. ds C` "" -. ds C' "" -'br\} -.el\{\ -. ds -- \|\(em\| -. ds PI \(*p -. ds L" `` -. ds R" '' -'br\} -.\" -.\" If the F register is turned on, we'll generate index entries on stderr -.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and -.\" index entries marked with X<> in POD. Of course, you'll have to process -.\" the output yourself in some meaningful fashion. -.if \nF \{\ -. de IX -. tm Index:\\$1\t\\n%\t"\\$2" -.. -. nr % 0 -. rr F -.\} -.\" -.\" For nroff, turn off justification. Always turn off hyphenation; it -.\" makes way too many mistakes in technical documents. -.hy 0 -.if n .na -.\" -.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). -.\" Fear. Run. Save yourself. No user-serviceable parts. -.bd B 3 -. \" fudge factors for nroff and troff -.if n \{\ -. ds #H 0 -. ds #V .8m -. ds #F .3m -. ds #[ \f1 -. ds #] \fP -.\} -.if t \{\ -. ds #H ((1u-(\\\\n(.fu%2u))*.13m) -. ds #V .6m -. ds #F 0 -. ds #[ \& -. ds #] \& -.\} -. \" simple accents for nroff and troff -.if n \{\ -. ds ' \& -. ds ` \& -. ds ^ \& -. ds , \& -. ds ~ ~ -. ds / -.\} -.if t \{\ -. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" -. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' -. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' -. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' -. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' -. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' -.\} -. \" troff and (daisy-wheel) nroff accents -.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' -.ds 8 \h'\*(#H'\(*b\h'-\*(#H' -.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] -.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' -.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' -.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] -.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] -.ds ae a\h'-(\w'a'u*4/10)'e -.ds Ae A\h'-(\w'A'u*4/10)'E -. \" corrections for vroff -.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' -.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' -. \" for low resolution devices (crt and lpr) -.if \n(.H>23 .if \n(.V>19 \ -\{\ -. ds : e -. ds 8 ss -. ds o a -. ds d- d\h'-1'\(ga -. ds D- D\h'-1'\(hy -. ds th \o'bp' -. ds Th \o'LP' -. ds ae ae -. ds Ae AE -.\} -.rm #[ #] #H #V #F C -.\" ====================================================================== -.\" -.IX Title "GCOV 1" -.TH GCOV 1 "gcc-3.1" "2001-02-19" "GNU" -.UC -.SH "NAME" -gcov \- coverage testing tool -.SH "SYNOPSIS" -.IX Header "SYNOPSIS" -gcov [\fB\-b\fR] [\fB\-c\fR] [\fB\-v\fR] [\fB\-n\fR] [\fB\-l\fR] [\fB\-f\fR] [\fB\-o\fR \fIdirectory\fR] \fIsourcefile\fR -.SH "DESCRIPTION" -.IX Header "DESCRIPTION" -\&\f(CW\*(C`gcov\*(C'\fR is a test coverage program. Use it in concert with \s-1GNU\s0 -\&\s-1CC\s0 to analyze your programs to help create more efficient, faster -running code. You can use \f(CW\*(C`gcov\*(C'\fR as a profiling tool to help -discover where your optimization efforts will best affect your code. You -can also use \f(CW\*(C`gcov\*(C'\fR along with the other profiling tool, -\&\f(CW\*(C`gprof\*(C'\fR, to assess which parts of your code use the greatest amount -of computing time. -.PP -Profiling tools help you analyze your code's performance. Using a -profiler such as \f(CW\*(C`gcov\*(C'\fR or \f(CW\*(C`gprof\*(C'\fR, you can find out some -basic performance statistics, such as: -.Ip "\(bu" 4 -how often each line of code executes -.Ip "\(bu" 4 -what lines of code are actually executed -.Ip "\(bu" 4 -how much computing time each section of code uses -.PP -Once you know these things about how your code works when compiled, you -can look at each module to see which modules should be optimized. -\&\f(CW\*(C`gcov\*(C'\fR helps you determine where to work on optimization. -.PP -Software developers also use coverage testing in concert with -testsuites, to make sure software is actually good enough for a release. -Testsuites can verify that a program works as expected; a coverage -program tests to see how much of the program is exercised by the -testsuite. Developers can then determine what kinds of test cases need -to be added to the testsuites to create both better testing and a better -final product. -.PP -You should compile your code without optimization if you plan to use -\&\f(CW\*(C`gcov\*(C'\fR because the optimization, by combining some lines of code -into one function, may not give you as much information as you need to -look for `hot spots' where the code is using a great deal of computer -time. Likewise, because \f(CW\*(C`gcov\*(C'\fR accumulates statistics by line (at -the lowest resolution), it works best with a programming style that -places only one statement on each line. If you use complicated macros -that expand to loops or to other control structures, the statistics are -less helpful\-\-\-they only report on the line where the macro call -appears. If your complex macros behave like functions, you can replace -them with inline functions to solve this problem. -.PP -\&\f(CW\*(C`gcov\*(C'\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which -indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR -has executed. You can use these logfiles along with \f(CW\*(C`gprof\*(C'\fR to aid -in fine-tuning the performance of your programs. \f(CW\*(C`gprof\*(C'\fR gives -timing information you can use along with the information you get from -\&\f(CW\*(C`gcov\*(C'\fR. -.PP -\&\f(CW\*(C`gcov\*(C'\fR works only on code compiled with \s-1GNU\s0 \s-1CC\s0. It is not -compatible with any other profiling or test coverage mechanism. -.SH "OPTIONS" -.IX Header "OPTIONS" -.if n .Ip "\f(CW""\-b""\fR" 4 -.el .Ip "\f(CW\-b\fR" 4 -.IX Item "-b" -Write branch frequencies to the output file, and write branch summary -info to the standard output. This option allows you to see how often -each branch in your program was taken. -.if n .Ip "\f(CW""\-c""\fR" 4 -.el .Ip "\f(CW\-c\fR" 4 -.IX Item "-c" -Write branch frequencies as the number of branches taken, rather than -the percentage of branches taken. -.if n .Ip "\f(CW""\-v""\fR" 4 -.el .Ip "\f(CW\-v\fR" 4 -.IX Item "-v" -Display the \f(CW\*(C`gcov\*(C'\fR version number (on the standard error stream). -.if n .Ip "\f(CW""\-n""\fR" 4 -.el .Ip "\f(CW\-n\fR" 4 -.IX Item "-n" -Do not create the \f(CW\*(C`gcov\*(C'\fR output file. -.if n .Ip "\f(CW""\-l""\fR" 4 -.el .Ip "\f(CW\-l\fR" 4 -.IX Item "-l" -Create long file names for included source files. For example, if the -header file \fBx.h\fR contains code, and was included in the file -\&\fBa.c\fR, then running \f(CW\*(C`gcov\*(C'\fR on the file \fBa.c\fR will produce -an output file called \fBa.c.x.h.gcov\fR instead of \fBx.h.gcov\fR. -This can be useful if \fBx.h\fR is included in multiple source files. -.if n .Ip "\f(CW""\-f""\fR" 4 -.el .Ip "\f(CW\-f\fR" 4 -.IX Item "-f" -Output summaries for each function in addition to the file level summary. -.if n .Ip "\f(CW""\-o""\fR" 4 -.el .Ip "\f(CW\-o\fR" 4 -.IX Item "-o" -The directory where the object files live. Gcov will search for \f(CW\*(C`.bb\*(C'\fR, -\&\f(CW\*(C`.bbg\*(C'\fR, and \f(CW\*(C`.da\*(C'\fR files in this directory. -.PP -When using \f(CW\*(C`gcov\*(C'\fR, you must first compile your program with two -special \s-1GNU\s0 \s-1CC\s0 options: \fB\-fprofile-arcs \-ftest-coverage\fR. -This tells the compiler to generate additional information needed by -gcov (basically a flow graph of the program) and also includes -additional code in the object files for generating the extra profiling -information needed by gcov. These additional files are placed in the -directory where the source code is located. -.PP -Running the program will cause profile output to be generated. For each -source file compiled with \-fprofile-arcs, an accompanying \f(CW\*(C`.da\*(C'\fR -file will be placed in the source directory. -.PP -Running \f(CW\*(C`gcov\*(C'\fR with your program's source file names as arguments -will now produce a listing of the code along with frequency of execution -for each line. For example, if your program is called \fBtmp.c\fR, this -is what you see when you use the basic \f(CW\*(C`gcov\*(C'\fR facility: -.PP -.Vb 5 -\& $ gcc -fprofile-arcs -ftest-coverage tmp.c -\& $ a.out -\& $ gcov tmp.c -\& 87.50% of 8 source lines executed in file tmp.c -\& Creating tmp.c.gcov. -.Ve -The file \fItmp.c.gcov\fR contains output from \f(CW\*(C`gcov\*(C'\fR. -Here is a sample: -.PP -.Vb 3 -\& main() -\& { -\& 1 int i, total; -.Ve -.Vb 1 -\& 1 total = 0; -.Ve -.Vb 2 -\& 11 for (i = 0; i < 10; i++) -\& 10 total += i; -.Ve -.Vb 5 -\& 1 if (total != 45) -\& ###### printf ("Failure\en"); -\& else -\& 1 printf ("Success\en"); -\& 1 } -.Ve -When you use the \fB\-b\fR option, your output looks like this: -.PP -.Vb 6 -\& $ gcov -b tmp.c -\& 87.50% of 8 source lines executed in file tmp.c -\& 80.00% of 5 branches executed in file tmp.c -\& 80.00% of 5 branches taken at least once in file tmp.c -\& 50.00% of 2 calls executed in file tmp.c -\& Creating tmp.c.gcov. -.Ve -Here is a sample of a resulting \fItmp.c.gcov\fR file: -.PP -.Vb 3 -\& main() -\& { -\& 1 int i, total; -.Ve -.Vb 1 -\& 1 total = 0; -.Ve -.Vb 5 -\& 11 for (i = 0; i < 10; i++) -\& branch 0 taken = 91% -\& branch 1 taken = 100% -\& branch 2 taken = 100% -\& 10 total += i; -.Ve -.Vb 9 -\& 1 if (total != 45) -\& branch 0 taken = 100% -\& ###### printf ("Failure\en"); -\& call 0 never executed -\& branch 1 never executed -\& else -\& 1 printf ("Success\en"); -\& call 0 returns = 100% -\& 1 } -.Ve -For each basic block, a line is printed after the last line of the basic -block describing the branch or call that ends the basic block. There can -be multiple branches and calls listed for a single source line if there -are multiple basic blocks that end on that line. In this case, the -branches and calls are each given a number. There is no simple way to map -these branches and calls back to source constructs. In general, though, -the lowest numbered branch or call will correspond to the leftmost construct -on the source line. -.PP -For a branch, if it was executed at least once, then a percentage -indicating the number of times the branch was taken divided by the -number of times the branch was executed will be printed. Otherwise, the -message ``never executed'' is printed. -.PP -For a call, if it was executed at least once, then a percentage -indicating the number of times the call returned divided by the number -of times the call was executed will be printed. This will usually be -100%, but may be less for functions call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR, -and thus may not return every time they are called. -.PP -The execution counts are cumulative. If the example program were -executed again without removing the \f(CW\*(C`.da\*(C'\fR file, the count for the -number of times each line in the source was executed would be added to -the results of the previous \fIrun\fR\|(s). This is potentially useful in -several ways. For example, it could be used to accumulate data over a -number of program runs as part of a test verification suite, or to -provide more accurate long-term information over a large number of -program runs. -.PP -The data in the \f(CW\*(C`.da\*(C'\fR files is saved immediately before the program -exits. For each source file compiled with \-fprofile-arcs, the profiling -code first attempts to read in an existing \f(CW\*(C`.da\*(C'\fR file; if the file -doesn't match the executable (differing number of basic block counts) it -will ignore the contents of the file. It then adds in the new execution -counts and finally writes the data to the file. -.if n .Sh "Using \f(CW""gcov""\fP with \s-1GCC\s0 Optimization" -.el .Sh "Using \f(CWgcov\fP with \s-1GCC\s0 Optimization" -.IX Subsection "Using gcov with GCC Optimization" -If you plan to use \f(CW\*(C`gcov\*(C'\fR to help optimize your code, you must -first compile your program with two special \s-1GNU\s0 \s-1CC\s0 options: -\&\fB\-fprofile-arcs \-ftest-coverage\fR. Aside from that, you can use any -other \s-1GNU\s0 \s-1CC\s0 options; but if you want to prove that every single line -in your program was executed, you should not compile with optimization -at the same time. On some machines the optimizer can eliminate some -simple code lines by combining them with other lines. For example, code -like this: -.PP -.Vb 4 -\& if (a != b) -\& c = 1; -\& else -\& c = 0; -.Ve -can be compiled into one instruction on some machines. In this case, -there is no way for \f(CW\*(C`gcov\*(C'\fR to calculate separate execution counts -for each line because there isn't separate code for each line. Hence -the \f(CW\*(C`gcov\*(C'\fR output looks like this if you compiled the program with -optimization: -.PP -.Vb 4 -\& 100 if (a != b) -\& 100 c = 1; -\& 100 else -\& 100 c = 0; -.Ve -The output shows that this block of code, combined by optimization, -executed 100 times. In one sense this result is correct, because there -was only one instruction representing all four of these lines. However, -the output does not indicate how many times the result was 0 and how -many times the result was 1. -.SH "SEE ALSO" -.IX Header "SEE ALSO" -\&\fIgcc\fR\|(1) and the Info entry for \fIgcc\fR. -.SH "COPYRIGHT" -.IX Header "COPYRIGHT" -Copyright (c) 1996, 1997, 1999, 2000 Free Software Foundation, Inc. -.PP -Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. -.PP -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -entire resulting derived work is distributed under the terms of a -permission notice identical to this one. -.PP -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that this permission notice may be included in translations -approved by the Free Software Foundation instead of in the original -English. diff --git a/gcc/gcov.texi b/gcc/gcov.texi deleted file mode 100644 index 5fc46d297a5..00000000000 --- a/gcc/gcov.texi +++ /dev/null @@ -1,386 +0,0 @@ -@c Copyright (C) 1996, 1997, 1999, 2000 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@ignore -@c man begin COPYRIGHT -Copyright @copyright{} 1996, 1997, 1999, 2000 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that this permission notice may be included in translations -approved by the Free Software Foundation instead of in the original -English. -@c man end -@c Set file name and title for the man page. -@setfilename gcov -@settitle coverage testing tool -@end ignore - -@node Gcov -@chapter @code{gcov}: a Test Coverage Program - -@code{gcov} is a tool you can use in conjunction with @sc{gnu} CC to -test code coverage in your programs. - -This chapter describes version 1.5 of @code{gcov}. - -@menu -* Gcov Intro:: Introduction to gcov. -* Invoking Gcov:: How to use gcov. -* Gcov and Optimization:: Using gcov with GCC optimization. -* Gcov Data Files:: The files used by gcov. -@end menu - -@node Gcov Intro -@section Introduction to @code{gcov} -@c man begin DESCRIPTION - -@code{gcov} is a test coverage program. Use it in concert with @sc{gnu} -CC to analyze your programs to help create more efficient, faster -running code. You can use @code{gcov} as a profiling tool to help -discover where your optimization efforts will best affect your code. You -can also use @code{gcov} along with the other profiling tool, -@code{gprof}, to assess which parts of your code use the greatest amount -of computing time. - -Profiling tools help you analyze your code's performance. Using a -profiler such as @code{gcov} or @code{gprof}, you can find out some -basic performance statistics, such as: - -@itemize @bullet -@item -how often each line of code executes - -@item -what lines of code are actually executed - -@item -how much computing time each section of code uses -@end itemize - -Once you know these things about how your code works when compiled, you -can look at each module to see which modules should be optimized. -@code{gcov} helps you determine where to work on optimization. - -Software developers also use coverage testing in concert with -testsuites, to make sure software is actually good enough for a release. -Testsuites can verify that a program works as expected; a coverage -program tests to see how much of the program is exercised by the -testsuite. Developers can then determine what kinds of test cases need -to be added to the testsuites to create both better testing and a better -final product. - -You should compile your code without optimization if you plan to use -@code{gcov} because the optimization, by combining some lines of code -into one function, may not give you as much information as you need to -look for `hot spots' where the code is using a great deal of computer -time. Likewise, because @code{gcov} accumulates statistics by line (at -the lowest resolution), it works best with a programming style that -places only one statement on each line. If you use complicated macros -that expand to loops or to other control structures, the statistics are -less helpful---they only report on the line where the macro call -appears. If your complex macros behave like functions, you can replace -them with inline functions to solve this problem. - -@code{gcov} creates a logfile called @file{@var{sourcefile}.gcov} which -indicates how many times each line of a source file @file{@var{sourcefile}.c} -has executed. You can use these logfiles along with @code{gprof} to aid -in fine-tuning the performance of your programs. @code{gprof} gives -timing information you can use along with the information you get from -@code{gcov}. - -@code{gcov} works only on code compiled with @sc{gnu} CC. It is not -compatible with any other profiling or test coverage mechanism. - -@c man end - -@node Invoking Gcov -@section Invoking gcov - -@smallexample -gcov [-b] [-c] [-v] [-n] [-l] [-f] [-o directory] @var{sourcefile} -@end smallexample - -@ignore -@c man begin SYNOPSIS -gcov [@samp{-b}] [@samp{-c}] [@samp{-v}] [@samp{-n}] [@samp{-l}] [@samp{-f}] [@samp{-o} @var{directory}] @var{sourcefile} -@c man end -@c man begin SEEALSO -gcc(1) and the Info entry for @file{gcc}. -@c man end -@end ignore - -@c man begin OPTIONS -@table @code -@item -b -Write branch frequencies to the output file, and write branch summary -info to the standard output. This option allows you to see how often -each branch in your program was taken. - -@item -c -Write branch frequencies as the number of branches taken, rather than -the percentage of branches taken. - -@item -v -Display the @code{gcov} version number (on the standard error stream). - -@item -n -Do not create the @code{gcov} output file. - -@item -l -Create long file names for included source files. For example, if the -header file @samp{x.h} contains code, and was included in the file -@samp{a.c}, then running @code{gcov} on the file @samp{a.c} will produce -an output file called @samp{a.c.x.h.gcov} instead of @samp{x.h.gcov}. -This can be useful if @samp{x.h} is included in multiple source files. - -@item -f -Output summaries for each function in addition to the file level summary. - -@item -o -The directory where the object files live. Gcov will search for @code{.bb}, -@code{.bbg}, and @code{.da} files in this directory. -@end table - -@need 3000 -When using @code{gcov}, you must first compile your program with two -special @sc{gnu} CC options: @samp{-fprofile-arcs -ftest-coverage}. -This tells the compiler to generate additional information needed by -gcov (basically a flow graph of the program) and also includes -additional code in the object files for generating the extra profiling -information needed by gcov. These additional files are placed in the -directory where the source code is located. - -Running the program will cause profile output to be generated. For each -source file compiled with -fprofile-arcs, an accompanying @code{.da} -file will be placed in the source directory. - -Running @code{gcov} with your program's source file names as arguments -will now produce a listing of the code along with frequency of execution -for each line. For example, if your program is called @samp{tmp.c}, this -is what you see when you use the basic @code{gcov} facility: - -@smallexample -$ gcc -fprofile-arcs -ftest-coverage tmp.c -$ a.out -$ gcov tmp.c - 87.50% of 8 source lines executed in file tmp.c -Creating tmp.c.gcov. -@end smallexample - -The file @file{tmp.c.gcov} contains output from @code{gcov}. -Here is a sample: - -@smallexample - main() - @{ - 1 int i, total; - - 1 total = 0; - - 11 for (i = 0; i < 10; i++) - 10 total += i; - - 1 if (total != 45) - ###### printf ("Failure\n"); - else - 1 printf ("Success\n"); - 1 @} -@end smallexample - -@need 450 -When you use the @samp{-b} option, your output looks like this: - -@smallexample -$ gcov -b tmp.c - 87.50% of 8 source lines executed in file tmp.c - 80.00% of 5 branches executed in file tmp.c - 80.00% of 5 branches taken at least once in file tmp.c - 50.00% of 2 calls executed in file tmp.c -Creating tmp.c.gcov. -@end smallexample - -Here is a sample of a resulting @file{tmp.c.gcov} file: - -@smallexample - main() - @{ - 1 int i, total; - - 1 total = 0; - - 11 for (i = 0; i < 10; i++) -branch 0 taken = 91% -branch 1 taken = 100% -branch 2 taken = 100% - 10 total += i; - - 1 if (total != 45) -branch 0 taken = 100% - ###### printf ("Failure\n"); -call 0 never executed -branch 1 never executed - else - 1 printf ("Success\n"); -call 0 returns = 100% - 1 @} -@end smallexample - -For each basic block, a line is printed after the last line of the basic -block describing the branch or call that ends the basic block. There can -be multiple branches and calls listed for a single source line if there -are multiple basic blocks that end on that line. In this case, the -branches and calls are each given a number. There is no simple way to map -these branches and calls back to source constructs. In general, though, -the lowest numbered branch or call will correspond to the leftmost construct -on the source line. - -For a branch, if it was executed at least once, then a percentage -indicating the number of times the branch was taken divided by the -number of times the branch was executed will be printed. Otherwise, the -message ``never executed'' is printed. - -For a call, if it was executed at least once, then a percentage -indicating the number of times the call returned divided by the number -of times the call was executed will be printed. This will usually be -100%, but may be less for functions call @code{exit} or @code{longjmp}, -and thus may not return every time they are called. - -The execution counts are cumulative. If the example program were -executed again without removing the @code{.da} file, the count for the -number of times each line in the source was executed would be added to -the results of the previous run(s). This is potentially useful in -several ways. For example, it could be used to accumulate data over a -number of program runs as part of a test verification suite, or to -provide more accurate long-term information over a large number of -program runs. - -The data in the @code{.da} files is saved immediately before the program -exits. For each source file compiled with -fprofile-arcs, the profiling -code first attempts to read in an existing @code{.da} file; if the file -doesn't match the executable (differing number of basic block counts) it -will ignore the contents of the file. It then adds in the new execution -counts and finally writes the data to the file. - -@node Gcov and Optimization -@section Using @code{gcov} with GCC Optimization - -If you plan to use @code{gcov} to help optimize your code, you must -first compile your program with two special @sc{gnu} CC options: -@samp{-fprofile-arcs -ftest-coverage}. Aside from that, you can use any -other @sc{gnu} CC options; but if you want to prove that every single line -in your program was executed, you should not compile with optimization -at the same time. On some machines the optimizer can eliminate some -simple code lines by combining them with other lines. For example, code -like this: - -@smallexample -if (a != b) - c = 1; -else - c = 0; -@end smallexample - -@noindent -can be compiled into one instruction on some machines. In this case, -there is no way for @code{gcov} to calculate separate execution counts -for each line because there isn't separate code for each line. Hence -the @code{gcov} output looks like this if you compiled the program with -optimization: - -@smallexample - 100 if (a != b) - 100 c = 1; - 100 else - 100 c = 0; -@end smallexample - -The output shows that this block of code, combined by optimization, -executed 100 times. In one sense this result is correct, because there -was only one instruction representing all four of these lines. However, -the output does not indicate how many times the result was 0 and how -many times the result was 1. -@c man end - -@node Gcov Data Files -@section Brief description of @code{gcov} data files - -@code{gcov} uses three files for doing profiling. The names of these -files are derived from the original @emph{source} file by substituting -the file suffix with either @code{.bb}, @code{.bbg}, or @code{.da}. All -of these files are placed in the same directory as the source file, and -contain data stored in a platform-independent method. - -The @code{.bb} and @code{.bbg} files are generated when the source file -is compiled with the @sc{gnu} CC @samp{-ftest-coverage} option. The -@code{.bb} file contains a list of source files (including headers), -functions within those files, and line numbers corresponding to each -basic block in the source file. - -The @code{.bb} file format consists of several lists of 4-byte integers -which correspond to the line numbers of each basic block in the -file. Each list is terminated by a line number of 0. A line number of -1 -is used to designate that the source file name (padded to a 4-byte -boundary and followed by another -1) follows. In addition, a line number -of -2 is used to designate that the name of a function (also padded to a -4-byte boundary and followed by a -2) follows. - -The @code{.bbg} file is used to reconstruct the program flow graph for -the source file. It contains a list of the program flow arcs (possible -branches taken from one basic block to another) for each function which, -in combination with the @code{.bb} file, enables gcov to reconstruct the -program flow. - -In the @code{.bbg} file, the format is: -@smallexample - number of basic blocks for function #0 (4-byte number) - total number of arcs for function #0 (4-byte number) - count of arcs in basic block #0 (4-byte number) - destination basic block of arc #0 (4-byte number) - flag bits (4-byte number) - destination basic block of arc #1 (4-byte number) - flag bits (4-byte number) - ... - destination basic block of arc #N (4-byte number) - flag bits (4-byte number) - count of arcs in basic block #1 (4-byte number) - destination basic block of arc #0 (4-byte number) - flag bits (4-byte number) - ... -@end smallexample - -A -1 (stored as a 4-byte number) is used to separate each function's -list of basic blocks, and to verify that the file has been read -correctly. - -The @code{.da} file is generated when a program containing object files -built with the @sc{gnu} CC @samp{-fprofile-arcs} option is executed. A -separate @code{.da} file is created for each source file compiled with -this option, and the name of the @code{.da} file is stored as an -absolute pathname in the resulting object file. This path name is -derived from the source file name by substituting a @code{.da} suffix. - -The format of the @code{.da} file is fairly simple. The first 8-byte -number is the number of counts in the file, followed by the counts -(stored as 8-byte numbers). Each count corresponds to the number of -times each arc in the program is executed. The counts are cumulative; -each time the program is executed, it attempts to combine the existing -@code{.da} files with the new counts for this invocation of the -program. It ignores the contents of any @code{.da} files whose number of -arcs doesn't correspond to the current program, and merely overwrites -them instead. - -All three of these files use the functions in @code{gcov-io.h} to store -integers; the functions in this header provide a machine-independent -mechanism for storing and retrieving data from a stream. - diff --git a/gcc/install.texi b/gcc/install.texi deleted file mode 100644 index be00cd49cc7..00000000000 --- a/gcc/install.texi +++ /dev/null @@ -1,2102 +0,0 @@ -@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@c The text of this file appears in the file INSTALL -@c in the GCC distribution, as well as in the GCC manual. - -Note most of this information is out of date and superseded by the -online GCC install procedures @uref{http://gcc.gnu.org/install/}. It is -provided for historical reference only. - -@ifclear INSTALLONLY -@node Installation -@chapter Installing GNU CC -@end ifclear -@cindex installing GNU CC - -@menu -* Configuration Files:: Files created by running @code{configure}. -* Configurations:: Configurations Supported by GNU CC. -* Other Dir:: Compiling in a separate directory (not where the source is). -* Cross-Compiler:: Building and installing a cross-compiler. -* VMS Install:: See below for installation on VMS. -* Collect2:: How @code{collect2} works; how it finds @code{ld}. -* Header Dirs:: Understanding the standard header file directories. -@end menu - -Here is the procedure for installing GNU CC on a GNU or Unix system. -See @ref{VMS Install}, for VMS systems. In this section we assume you -compile in the same directory that contains the source files; see -@ref{Other Dir}, to find out how to compile in a separate directory on -Unix systems. - -You cannot install GNU C by itself on MSDOS; it will not compile under -any MSDOS compiler except itself. You need to get the complete -compilation package DJGPP, which includes binaries as well as sources, -and includes all the necessary compilation tools and libraries. - -@enumerate -@item -If you have built GNU CC previously in the same directory for a -different target machine, do @samp{make distclean} to delete all files -that might be invalid. One of the files this deletes is -@file{Makefile}; if @samp{make distclean} complains that @file{Makefile} -does not exist, it probably means that the directory is already suitably -clean. - -@item -On a System V release 4 system, make sure @file{/usr/bin} precedes -@file{/usr/ucb} in @code{PATH}. The @code{cc} command in -@file{/usr/ucb} uses libraries which have bugs. - -@cindex Bison parser generator -@cindex parser generator, Bison -@item -Make sure the Bison parser generator is installed. (This is unnecessary -if the Bison output file @file{c-parse.c} is more recent than -@file{c-parse.y},and you do not plan to change the @samp{.y} file.) - -Bison versions older than Sept 8, 1988 will produce incorrect output -for @file{c-parse.c}. - -@item -If you have chosen a configuration for GNU CC which requires other GNU -tools (such as GAS or the GNU linker) instead of the standard system -tools, install the required tools in the build directory under the names -@file{as}, @file{ld} or whatever is appropriate. This will enable the -compiler to find the proper tools for compilation of the program -@file{enquire}. - -Alternatively, you can do subsequent compilation using a value of the -@code{PATH} environment variable such that the necessary GNU tools come -before the standard system tools. - -@item -Specify the host, build and target machine configurations. You do this -when you run the @file{configure} script. - -The @dfn{build} machine is the system which you are using, the -@dfn{host} machine is the system where you want to run the resulting -compiler (normally the build machine), and the @dfn{target} machine is -the system for which you want the compiler to generate code. - -If you are building a compiler to produce code for the machine it runs -on (a native compiler), you normally do not need to specify any operands -to @file{configure}; it will try to guess the type of machine you are on -and use that as the build, host and target machines. So you don't need -to specify a configuration when building a native compiler unless -@file{configure} cannot figure out what your configuration is or guesses -wrong. - -In those cases, specify the build machine's @dfn{configuration name} -with the @samp{--host} option; the host and target will default to be -the same as the host machine. (If you are building a cross-compiler, -see @ref{Cross-Compiler}.) - -Here is an example: - -@smallexample -./configure --host=sparc-sun-sunos4.1 -@end smallexample - -A configuration name may be canonical or it may be more or less -abbreviated. - -A canonical configuration name has three parts, separated by dashes. -It looks like this: @samp{@var{cpu}-@var{company}-@var{system}}. -(The three parts may themselves contain dashes; @file{configure} -can figure out which dashes serve which purpose.) For example, -@samp{m68k-sun-sunos4.1} specifies a Sun 3. - -You can also replace parts of the configuration by nicknames or aliases. -For example, @samp{sun3} stands for @samp{m68k-sun}, so -@samp{sun3-sunos4.1} is another way to specify a Sun 3. - -You can specify a version number after any of the system types, and some -of the CPU types. In most cases, the version is irrelevant, and will be -ignored. So you might as well specify the version if you know it. - -See @ref{Configurations}, for a list of supported configuration names and -notes on many of the configurations. You should check the notes in that -section before proceeding any further with the installation of GNU CC. - -@item -When running @code{configure}, you may also need to specify certain -additional options that describe variant hardware and software -configurations. These are @samp{--with-gnu-as}, @samp{--with-gnu-ld}, -@samp{--with-stabs} and @samp{--nfp}. - -@table @samp -@item --with-gnu-as -If you will use GNU CC with the GNU assembler (GAS), you should declare -this by using the @samp{--with-gnu-as} option when you run -@file{configure}. - -Using this option does not install GAS. It only modifies the output of -GNU CC to work with GAS. Building and installing GAS is up to you. - -Conversely, if you @emph{do not} wish to use GAS and do not specify -@samp{--with-gnu-as} when building GNU CC, it is up to you to make sure -that GAS is not installed. GNU CC searches for a program named -@code{as} in various directories; if the program it finds is GAS, then -it runs GAS. If you are not sure where GNU CC finds the assembler it is -using, try specifying @samp{-v} when you run it. - -The systems where it makes a difference whether you use GAS are@* -@samp{hppa1.0-@var{any}-@var{any}}, @samp{hppa1.1-@var{any}-@var{any}}, -@samp{i386-@var{any}-sysv}, @samp{i386-@var{any}-isc},@* -@samp{i860-@var{any}-bsd}, @samp{m68k-bull-sysv},@* -@samp{m68k-hp-hpux}, @samp{m68k-sony-bsd},@* -@samp{m68k-altos-sysv}, @samp{m68000-hp-hpux},@* -@samp{m68000-att-sysv}, @samp{@var{any}-lynx-lynxos}, -and @samp{mips-@var{any}}). -On any other system, @samp{--with-gnu-as} has no effect. - -On the systems listed above (except for the HP-PA, for ISC on the -386, and for @samp{mips-sgi-irix5.*}), if you use GAS, you should also -use the GNU linker (and specify @samp{--with-gnu-ld}). - -@item --with-gnu-ld -Specify the option @samp{--with-gnu-ld} if you plan to use the GNU -linker with GNU CC. - -This option does not cause the GNU linker to be installed; it just -modifies the behavior of GNU CC to work with the GNU linker. -@c Specifically, it inhibits the installation of @code{collect2}, a program -@c which otherwise serves as a front-end for the system's linker on most -@c configurations. - -@item --with-stabs -On MIPS based systems and on Alphas, you must specify whether you want -GNU CC to create the normal ECOFF debugging format, or to use BSD-style -stabs passed through the ECOFF symbol table. The normal ECOFF debug -format cannot fully handle languages other than C. BSD stabs format can -handle other languages, but it only works with the GNU debugger GDB. - -Normally, GNU CC uses the ECOFF debugging format by default; if you -prefer BSD stabs, specify @samp{--with-stabs} when you configure GNU -CC. - -No matter which default you choose when you configure GNU CC, the user -can use the @samp{-gcoff} and @samp{-gstabs+} options to specify explicitly -the debug format for a particular compilation. - -@samp{--with-stabs} is meaningful on the ISC system on the 386, also, if -@samp{--with-gas} is used. It selects use of stabs debugging -information embedded in COFF output. This kind of debugging information -supports C++ well; ordinary COFF debugging information does not. - -@samp{--with-stabs} is also meaningful on 386 systems running SVR4. It -selects use of stabs debugging information embedded in ELF output. The -C++ compiler currently (2.6.0) does not support the DWARF debugging -information normally used on 386 SVR4 platforms; stabs provide a -workable alternative. This requires gas and gdb, as the normal SVR4 -tools can not generate or interpret stabs. - -@item --nfp -On certain systems, you must specify whether the machine has a floating -point unit. These systems include @samp{m68k-sun-sunos@var{n}} and -@samp{m68k-isi-bsd}. On any other system, @samp{--nfp} currently has no -effect, though perhaps there are other systems where it could usefully -make a difference. - -@cindex Haifa scheduler -@cindex scheduler, experimental -@item --enable-haifa -@itemx --disable-haifa -Use @samp{--enable-haifa} to enable use of an experimental instruction -scheduler (from IBM Haifa). This may or may not produce better code. -Some targets on which it is known to be a win enable it by default; use -@samp{--disable-haifa} to disable it in these cases. @code{configure} -will print out whether the Haifa scheduler is enabled when it is run. - -@cindex Objective C threads -@cindex threads, Objective C -@item --enable-threads=@var{type} -Certain systems, notably Linux-based GNU systems, can't be relied on to -supply a threads facility for the Objective C runtime and so will -default to single-threaded runtime. They may, however, have a library -threads implementation available, in which case threads can be enabled -with this option by supplying a suitable @var{type}, probably -@samp{posix}. The possibilities for @var{type} are @samp{single}, -@samp{posix}, @samp{win32}, @samp{solaris}, @samp{irix} and @samp{mach}. - -@cindex Internal Compiler Checking -@item --enable-checking -When you specify this option, the compiler is built to perform checking -of tree node types when referencing fields of that node. This does not -change the generated code, but adds error checking within the compiler. -This will slow down the compiler and may only work properly if you -are building the compiler with GNU C. - -@cindex Native Language Support -@cindex NLS -@item --enable-nls -@itemx --disable-nls -The @samp{--enable-nls} option enables Native Language Support (NLS), -which lets GCC output diagnostics in languages other than American -English. Native Language Support is enabled by default if not doing a -canadian cross build. The @samp{--disable-nls} option disables NLS. - -@cindex @code{gettext} -@item --with-included-gettext -If NLS is enbled, the @samp{--with-included-gettext} option causes the build -procedure to prefer its copy of GNU @code{gettext}. This is the default. If -you want the GCC build procedure to prefer the host's @code{gettext} -libraries, use @samp{--without-included-gettext}. - -@cindex @code{catgets} -@item --with-catgets -If NLS is enabled, and if the host lacks @code{gettext} but has the -inferior @code{catgets} interface, the GCC build procedure normally -ignores @code{catgets} and instead uses GCC's copy of the GNU -@code{gettext} library. The @samp{--with-catgets} option causes the -build procedure to use the host's @code{catgets} in this situation. - -@cindex @code{maintainer-mode} -@item --enable-maintainer-mode -The build rules that regenerate the GCC master message catalog -@code{gcc.pot} are normally disabled. This is because it can only be rebuilt -if the complete source tree is present. If you have changed the sources and -want to rebuild the catalog, configuring with -@samp{--enable-maintainer-mode} will enable this. Note that you need a -special version of the @code{gettext} tools to do so. - -@cindex Windows32 Registry support -@item --enable-win32-registry -@itemx --enable-win32-registry=@var{KEY} -@itemx --disable-win32-registry -The @samp{--enable-win32-registry} option enables Windows-hosted GCC -to look up installations paths in the registry using the following key: - -@smallexample -@code{HKEY_LOCAL_MACHINE\SOFTWARE\Free Software Foundation\} -@end smallexample - - defaults to GCC version number, and can be overridden by the -@code{--enable-win32-registry=KEY} option. Vendors and distributors -who use custom installers are encouraged to provide a different key, -perhaps one comprised of vendor name and GCC version number, to -avoid conflict with existing installations. This feature is enabled -by default, and can be disabled by @code{--disable-win32-registry} -option. This option has no effect on the other hosts. -@end table - -@item -In certain cases, you should specify certain other options when you run -@code{configure}. - -@itemize @bullet -@item -The standard directory for installing GNU CC is @file{/usr/local/lib}. -If you want to install its files somewhere else, specify -@samp{--prefix=@var{dir}} when you run @file{configure}. Here @var{dir} -is a directory name to use instead of @file{/usr/local} for all purposes -with one exception: the directory @file{/usr/local/include} is searched -for header files no matter where you install the compiler. To override -this name, use the @code{--with-local-prefix} option below. The directory -you specify need not exist, but its parent directory must exist. - -@item -Specify @samp{--with-local-prefix=@var{dir}} if you want the compiler to -search directory @file{@var{dir}/include} for locally installed header -files @emph{instead} of @file{/usr/local/include}. - -You should specify @samp{--with-local-prefix} @strong{only} if your site has -a different convention (not @file{/usr/local}) for where to put -site-specific files. - -The default value for @samp{--with-local-prefix} is @file{/usr/local} -regardless of the value of @samp{--prefix}. Specifying @samp{--prefix} -has no effect on which directory GNU CC searches for local header files. -This may seem counterintuitive, but actually it is logical. - -The purpose of @samp{--prefix} is to specify where to @emph{install GNU -CC}. The local header files in @file{/usr/local/include}---if you put -any in that directory---are not part of GNU CC. They are part of other -programs---perhaps many others. (GNU CC installs its own header files -in another directory which is based on the @samp{--prefix} value.) - -@strong{Do not} specify @file{/usr} as the @samp{--with-local-prefix}! The -directory you use for @samp{--with-local-prefix} @strong{must not} contain -any of the system's standard header files. If it did contain them, -certain programs would be miscompiled (including GNU Emacs, on certain -targets), because this would override and nullify the header file -corrections made by the @code{fixincludes} script. - -Indications are that people who use this option use it based on -mistaken ideas of what it is for. People use it as if it specified -where to install part of GNU CC. Perhaps they make this assumption -because installing GNU CC creates the directory. -@end itemize - -@item -Build the compiler. Just type @samp{make LANGUAGES=c} in the compiler -directory. - -@samp{LANGUAGES=c} specifies that only the C compiler should be -compiled. The makefile normally builds compilers for all the supported -languages; currently, C, C++, Objective C, Java, FORTRAN, and CHILL. -However, C is the only language that is sure to work when you build with -other non-GNU C compilers. In addition, building anything but C at this -stage is a waste of time. - -In general, you can specify the languages to build by typing the -argument @samp{LANGUAGES="@var{list}"}, where @var{list} is one or more -words from the list @samp{c}, @samp{c++}, @samp{objective-c}, -@samp{java}, @samp{f77}, and @samp{CHILL}. If you have any additional -GNU compilers as subdirectories of the GNU CC source directory, you may -also specify their names in this list. - -Ignore any warnings you may see about ``statement not reached'' in -@file{insn-emit.c}; they are normal. Also, warnings about ``unknown -escape sequence'' are normal in @file{genopinit.c} and perhaps some -other files. Likewise, you should ignore warnings about ``constant is -so large that it is unsigned'' in @file{insn-emit.c} and -@file{insn-recog.c}, and a warning about a comparison always being zero -in @file{enquire.o}. Any other compilation errors may represent bugs in -the port to your machine or operating system, and -@ifclear INSTALLONLY -should be investigated and reported (@pxref{Bugs}). -@end ifclear -@ifset INSTALLONLY -should be investigated and reported. -@end ifset - -Some compilers fail to compile GNU CC because they have bugs or -limitations. For example, the Microsoft compiler is said to run out of -macro space. Some Ultrix compilers run out of expression space; then -you need to break up the statement where the problem happens. - -@item -If you are building a cross-compiler, stop here. @xref{Cross-Compiler}. - -@cindex stage1 -@item -Move the first-stage object files and executables into a subdirectory -with this command: - -@smallexample -make stage1 -@end smallexample - -The files are moved into a subdirectory named @file{stage1}. -Once installation is complete, you may wish to delete these files -with @code{rm -r stage1}. - -@item -If you have chosen a configuration for GNU CC which requires other GNU -tools (such as GAS or the GNU linker) instead of the standard system -tools, install the required tools in the @file{stage1} subdirectory -under the names @file{as}, @file{ld} or whatever is appropriate. This -will enable the stage 1 compiler to find the proper tools in the -following stage. - -Alternatively, you can do subsequent compilation using a value of the -@code{PATH} environment variable such that the necessary GNU tools come -before the standard system tools. - -@item -Recompile the compiler with itself, with this command: - -@smallexample -make CC="stage1/xgcc -Bstage1/" CFLAGS="-g -O2" -@end smallexample - -This is called making the stage 2 compiler. - -The command shown above builds compilers for all the supported -languages. If you don't want them all, you can specify the languages to -build by typing the argument @samp{LANGUAGES="@var{list}"}. @var{list} -should contain one or more words from the list @samp{c}, @samp{c++}, -@samp{objective-c}, and @samp{proto}. Separate the words with spaces. -@samp{proto} stands for the programs @code{protoize} and -@code{unprotoize}; they are not a separate language, but you use -@code{LANGUAGES} to enable or disable their installation. - -If you are going to build the stage 3 compiler, then you might want to -build only the C language in stage 2. - -Once you have built the stage 2 compiler, if you are short of disk -space, you can delete the subdirectory @file{stage1}. - -On a 68000 or 68020 system lacking floating point hardware, -unless you have selected a @file{tm.h} file that expects by default -that there is no such hardware, do this instead: - -@smallexample -make CC="stage1/xgcc -Bstage1/" CFLAGS="-g -O2 -msoft-float" -@end smallexample - -@item -If you wish to test the compiler by compiling it with itself one more -time, install any other necessary GNU tools (such as GAS or the GNU -linker) in the @file{stage2} subdirectory as you did in the -@file{stage1} subdirectory, then do this: - -@smallexample -make stage2 -make CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O2" -@end smallexample - -@noindent -This is called making the stage 3 compiler. Aside from the @samp{-B} -option, the compiler options should be the same as when you made the -stage 2 compiler. But the @code{LANGUAGES} option need not be the -same. The command shown above builds compilers for all the supported -languages; if you don't want them all, you can specify the languages to -build by typing the argument @samp{LANGUAGES="@var{list}"}, as described -above. - -If you do not have to install any additional GNU tools, you may use the -command - -@smallexample -make bootstrap LANGUAGES=@var{language-list} BOOT_CFLAGS=@var{option-list} -@end smallexample - -@noindent -instead of making @file{stage1}, @file{stage2}, and performing -the two compiler builds. - -@item -Compare the latest object files with the stage 2 object files---they -ought to be identical, aside from time stamps (if any). - -On some systems, meaningful comparison of object files is impossible; -they always appear ``different.'' This is currently true on Solaris and -some systems that use ELF object file format. On some versions of Irix -on SGI machines and DEC Unix (OSF/1) on Alpha systems, you will not be -able to compare the files without specifying @file{-save-temps}; see the -description of individual systems above to see if you get comparison -failures. You may have similar problems on other systems. - -Use this command to compare the files: - -@smallexample -make compare -@end smallexample - -This will mention any object files that differ between stage 2 and stage -3. Any difference, no matter how innocuous, indicates that the stage 2 -compiler has compiled GNU CC incorrectly, and is therefore a potentially -@ifclear INSTALLONLY -serious bug which you should investigate and report (@pxref{Bugs}). -@end ifclear -@ifset INSTALLONLY -serious bug which you should investigate and report. -@end ifset - -If your system does not put time stamps in the object files, then this -is a faster way to compare them (using the Bourne shell): - -@smallexample -for file in *.o; do -cmp $file stage2/$file -done -@end smallexample - -If you have built the compiler with the @samp{-mno-mips-tfile} option on -MIPS machines, you will not be able to compare the files. - -@item -Install the compiler driver, the compiler's passes and run-time support -with @samp{make install}. Use the same value for @code{CC}, -@code{CFLAGS} and @code{LANGUAGES} that you used when compiling the -files that are being installed. One reason this is necessary is that -some versions of Make have bugs and recompile files gratuitously when -you do this step. If you use the same variable values, those files will -be recompiled properly. - -For example, if you have built the stage 2 compiler, you can use the -following command: - -@smallexample -make install CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O" LANGUAGES="@var{list}" -@end smallexample - -@noindent -This copies the files @file{cc1}, @file{cpp} and @file{libgcc.a} to -files @file{cc1}, @file{cpp} and @file{libgcc.a} in the directory -@file{/usr/local/lib/gcc-lib/@var{target}/@var{version}}, which is where -the compiler driver program looks for them. Here @var{target} is the -canonicalized form of target machine type specified when you ran -@file{configure}, and @var{version} is the version number of GNU CC. -This naming scheme permits various versions and/or cross-compilers to -coexist. It also copies the executables for compilers for other -languages (e.g., @file{cc1plus} for C++) to the same directory. - -This also copies the driver program @file{xgcc} into -@file{/usr/local/bin/gcc}, so that it appears in typical execution -search paths. It also copies @file{gcc.1} into -@file{/usr/local/man/man1} and info pages into @file{/usr/local/info}. - -On some systems, this command causes recompilation of some files. This -is usually due to bugs in @code{make}. You should either ignore this -problem, or use GNU Make. - -(It is usually better to install GNU CC executables from stage 2 or 3, -since they usually run faster than the ones compiled with some other -compiler.) - -@item -GNU CC includes a runtime library for Objective-C because it is an -integral part of the language. You can find the files associated with -the library in the subdirectory @file{objc}. The GNU Objective-C -Runtime Library requires header files for the target's C library in -order to be compiled,and also requires the header files for the target's -thread library if you want thread support. @xref{Cross Headers, -Cross-Compilers and Header Files, Cross-Compilers and Header Files}, for -discussion about header files issues for cross-compilation. - -When you run @file{configure}, it picks the appropriate Objective-C -thread implementation file for the target platform. In some situations, -you may wish to choose a different back-end as some platforms support -multiple thread implementations or you may wish to disable thread -support completely. You do this by specifying a value for the -@var{OBJC_THREAD_FILE} makefile variable on the command line when you -run make, for example: - -@smallexample -make CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O2" OBJC_THREAD_FILE=thr-single -@end smallexample - -@noindent -Below is a list of the currently available back-ends. - -@itemize @bullet -@item thr-single -Disable thread support, should work for all platforms. -@item thr-decosf1 -DEC OSF/1 thread support. -@item thr-irix -SGI IRIX thread support. -@item thr-mach -Generic MACH thread support, known to work on NEXTSTEP. -@item thr-os2 -IBM OS/2 thread support. -@item thr-posix -Generix POSIX thread support. -@item thr-pthreads -PCThreads on Linux-based GNU systems. -@item thr-solaris -SUN Solaris thread support. -@item thr-win32 -Microsoft Win32 API thread support. -@end itemize -@end enumerate - -@node Configuration Files -@section Files Created by @code{configure} - -Here we spell out what files will be set up by @code{configure}. Normally -you need not be concerned with these files. - -@itemize @bullet -@item -@ifset INTERNALS -A file named @file{config.h} is created that contains a @samp{#include} -of the top-level config file for the machine you will run the compiler -on (@pxref{Config}). This file is responsible for defining information -about the host machine. It includes @file{tm.h}. -@end ifset -@ifclear INTERNALS -A file named @file{config.h} is created that contains a @samp{#include} -of the top-level config file for the machine you will run the compiler -on (@pxref{Config,,The Configuration File, gcc.info, Using and Porting -GCC}). This file is responsible for defining information about the host -machine. It includes @file{tm.h}. -@end ifclear - -The top-level config file is located in the subdirectory @file{config}. -Its name is always @file{xm-@var{something}.h}; usually -@file{xm-@var{machine}.h}, but there are some exceptions. - -If your system does not support symbolic links, you might want to -set up @file{config.h} to contain a @samp{#include} command which -refers to the appropriate file. - -@item -A file named @file{tconfig.h} is created which includes the top-level config -file for your target machine. This is used for compiling certain -programs to run on that machine. - -@item -A file named @file{tm.h} is created which includes the -machine-description macro file for your target machine. It should be in -the subdirectory @file{config} and its name is often -@file{@var{machine}.h}. - -@item -The command file @file{configure} also constructs the file -@file{Makefile} by adding some text to the template file -@file{Makefile.in}. The additional text comes from files in the -@file{config} directory, named @file{t-@var{target}} and -@file{x-@var{host}}. If these files do not exist, it means nothing -needs to be added for a given target or host. -@end itemize - -@node Configurations -@section Configurations Supported by GNU CC -@cindex configurations supported by GNU CC - -Here are the possible CPU types: - -@quotation -@c gmicro, fx80, spur and tahoe omitted since they don't work. -1750a, a29k, alpha, arm, avr, c@var{n}, clipper, dsp16xx, elxsi, fr30, h8300, -hppa1.0, hppa1.1, i370, i386, i486, i586, i686, i786, i860, i960, m32r, -m68000, m68k, m6811, m6812, m88k, mcore, mips, mipsel, mips64, mips64el, -mn10200, mn10300, ns32k, pdp11, powerpc, powerpcle, romp, rs6000, sh, sparc, -sparclite, sparc64, v850, vax, we32k. -@end quotation - -Here are the recognized company names. As you can see, customary -abbreviations are used rather than the longer official names. - -@c What should be done about merlin, tek*, dolphin? -@quotation -acorn, alliant, altos, apollo, apple, att, bull, -cbm, convergent, convex, crds, dec, dg, dolphin, -elxsi, encore, harris, hitachi, hp, ibm, intergraph, isi, -mips, motorola, ncr, next, ns, omron, plexus, -sequent, sgi, sony, sun, tti, unicom, wrs. -@end quotation - -The company name is meaningful only to disambiguate when the rest of -the information supplied is insufficient. You can omit it, writing -just @samp{@var{cpu}-@var{system}}, if it is not needed. For example, -@samp{vax-ultrix4.2} is equivalent to @samp{vax-dec-ultrix4.2}. - -Here is a list of system types: - -@quotation -386bsd, aix, acis, amigaos, aos, aout, aux, bosx, bsd, clix, coff, ctix, cxux, -dgux, dynix, ebmon, ecoff, elf, esix, freebsd, hms, genix, gnu, linux, -linux-gnu, hiux, hpux, iris, irix, isc, luna, lynxos, mach, minix, msdos, mvs, -netbsd, newsos, nindy, ns, osf, osfrose, ptx, riscix, riscos, rtu, sco, sim, -solaris, sunos, sym, sysv, udi, ultrix, unicos, uniplus, unos, vms, vsta, -vxworks, winnt, xenix. -@end quotation - -@noindent -You can omit the system type; then @file{configure} guesses the -operating system from the CPU and company. - -You can add a version number to the system type; this may or may not -make a difference. For example, you can write @samp{bsd4.3} or -@samp{bsd4.4} to distinguish versions of BSD. In practice, the version -number is most needed for @samp{sysv3} and @samp{sysv4}, which are often -treated differently. - -@samp{linux-gnu} is the canonical name for the GNU/Linux target; however -GNU CC will also accept @samp{linux}. The version of the kernel in use is -not relevant on these systems. A suffix such as @samp{libc1} or @samp{aout} -distinguishes major versions of the C library; all of the suffixed versions -are obsolete. - -If you specify an impossible combination such as @samp{i860-dg-vms}, -then you may get an error message from @file{configure}, or it may -ignore part of the information and do the best it can with the rest. -@file{configure} always prints the canonical name for the alternative -that it used. GNU CC does not support all possible alternatives. - -Often a particular model of machine has a name. Many machine names are -recognized as aliases for CPU/company combinations. Thus, the machine -name @samp{sun3}, mentioned above, is an alias for @samp{m68k-sun}. -Sometimes we accept a company name as a machine name, when the name is -popularly used for a particular machine. Here is a table of the known -machine names: - -@quotation -3300, 3b1, 3b@var{n}, 7300, altos3068, altos, -apollo68, att-7300, balance, -convex-c@var{n}, crds, decstation-3100, -decstation, delta, encore, -fx2800, gmicro, hp7@var{nn}, hp8@var{nn}, -hp9k2@var{nn}, hp9k3@var{nn}, hp9k7@var{nn}, -hp9k8@var{nn}, iris4d, iris, isi68, -m3230, magnum, merlin, miniframe, -mmax, news-3600, news800, news, next, -pbd, pc532, pmax, powerpc, powerpcle, ps2, risc-news, -rtpc, sun2, sun386i, sun386, sun3, -sun4, symmetry, tower-32, tower. -@end quotation - -@noindent -Remember that a machine name specifies both the cpu type and the company -name. -If you want to install your own homemade configuration files, you can -use @samp{local} as the company name to access them. If you use -configuration @samp{@var{cpu}-local}, the configuration name -without the cpu prefix -is used to form the configuration file names. - -Thus, if you specify @samp{m68k-local}, configuration uses -files @file{m68k.md}, @file{local.h}, @file{m68k.c}, -@file{xm-local.h}, @file{t-local}, and @file{x-local}, all in the -directory @file{config/m68k}. - -Here is a list of configurations that have special treatment or special -things you must know: - -@table @samp -@item 1750a-*-* -MIL-STD-1750A processors. - -The MIL-STD-1750A cross configuration produces output for -@code{as1750}, an assembler/linker available under the GNU Public -License for the 1750A. @code{as1750} can be obtained at -@uref{ftp://ftp.fta-berlin.de/pub/crossgcc/1750gals/}. -A similarly licensed simulator for -the 1750A is available from same address. - -You should ignore a fatal error during the building of libgcc (libgcc is -not yet implemented for the 1750A.) - -The @code{as1750} assembler requires the file @file{ms1750.inc}, which is -found in the directory @file{config/1750a}. - -GNU CC produced the same sections as the Fairchild F9450 C Compiler, -namely: - -@table @code -@item Normal -The program code section. - -@item Static -The read/write (RAM) data section. - -@item Konst -The read-only (ROM) constants section. - -@item Init -Initialization section (code to copy KREL to SREL). -@end table - -The smallest addressable unit is 16 bits (BITS_PER_UNIT is 16). This -means that type `char' is represented with a 16-bit word per character. -The 1750A's "Load/Store Upper/Lower Byte" instructions are not used by -GNU CC. - -@item alpha-*-osf1 -Systems using processors that implement the DEC Alpha architecture and -are running the DEC Unix (OSF/1) operating system, for example the DEC -Alpha AXP systems.CC.) - -GNU CC writes a @samp{.verstamp} directive to the assembler output file -unless it is built as a cross-compiler. It gets the version to use from -the system header file @file{/usr/include/stamp.h}. If you install a -new version of DEC Unix, you should rebuild GCC to pick up the new version -stamp. - -Note that since the Alpha is a 64-bit architecture, cross-compilers from -32-bit machines will not generate code as efficient as that generated -when the compiler is running on a 64-bit machine because many -optimizations that depend on being able to represent a word on the -target in an integral value on the host cannot be performed. Building -cross-compilers on the Alpha for 32-bit machines has only been tested in -a few cases and may not work properly. - -@code{make compare} may fail on old versions of DEC Unix unless you add -@samp{-save-temps} to @code{CFLAGS}. On these systems, the name of the -assembler input file is stored in the object file, and that makes -comparison fail if it differs between the @code{stage1} and -@code{stage2} compilations. The option @samp{-save-temps} forces a -fixed name to be used for the assembler input file, instead of a -randomly chosen name in @file{/tmp}. Do not add @samp{-save-temps} -unless the comparisons fail without that option. If you add -@samp{-save-temps}, you will have to manually delete the @samp{.i} and -@samp{.s} files after each series of compilations. - -GNU CC now supports both the native (ECOFF) debugging format used by DBX -and GDB and an encapsulated STABS format for use only with GDB. See the -discussion of the @samp{--with-stabs} option of @file{configure} above -for more information on these formats and how to select them. - -There is a bug in DEC's assembler that produces incorrect line numbers -for ECOFF format when the @samp{.align} directive is used. To work -around this problem, GNU CC will not emit such alignment directives -while writing ECOFF format debugging information even if optimization is -being performed. Unfortunately, this has the very undesirable -side-effect that code addresses when @samp{-O} is specified are -different depending on whether or not @samp{-g} is also specified. - -To avoid this behavior, specify @samp{-gstabs+} and use GDB instead of -DBX. DEC is now aware of this problem with the assembler and hopes to -provide a fix shortly. - -@item arc-*-elf -Argonaut ARC processor. -This configuration is intended for embedded systems. - -@item arm-*-aout -Advanced RISC Machines ARM-family processors. These are often used in -embedded applications. There are no standard Unix configurations. -This configuration corresponds to the basic instruction sequences and will -produce @file{a.out} format object modules. - -You may need to make a variant of the file @file{arm.h} for your particular -configuration. - -@item arm-*-elf -This configuration is intended for embedded systems. - -@item arm-*-linux*aout -Any of the ARM-family processors running the Linux-based GNU system with -the @file{a.out} binary format. This is an obsolete configuration. - -@item arm-*-linux -@itemx arm-*-linux-gnu -@itemx arm-*-linux*oldld -Any of the ARM-family processors running the Linux-based GNU system with -the @file{ELF} binary format. You must use version 2.9.1.0.22 or later -of the GNU/Linux binutils, which you can download from -@uref{ftp://ftp.varesearch.com/pub/support/hjl/binutils/}. - -These two configurations differ only in the required version of GNU -binutils. For binutils 2.9.1.0.x, use @samp{arm-*-linux-gnuoldld}. For -newer versions of binutils, use @samp{arm-*-linux-gnu}. - -@item arm-*-riscix -The ARM2 or ARM3 processor running RISC iX, Acorn's port of BSD Unix. -If you are running a version of RISC iX prior to 1.2 then you must -specify the version number during configuration. Note that the -assembler shipped with RISC iX does not support stabs debugging -information; a new version of the assembler, with stabs support -included, is now available from Acorn and via ftp -@uref{ftp://ftp.acorn.com/pub/riscix/as+xterm.tar.Z}. To enable stabs -debugging, pass @samp{--with-gnu-as} to configure. - -You will need to install GNU @file{sed} before you can run configure. - -@item a29k -AMD Am29k-family processors. These are normally used in embedded -applications. There are no standard Unix configurations. -This configuration -corresponds to AMD's standard calling sequence and binary interface -and is compatible with other 29k tools. - -You may need to make a variant of the file @file{a29k.h} for your -particular configuration. - -@item a29k-*-bsd -AMD Am29050 used in a system running a variant of BSD Unix. - -@item avr -ATMEL AVR-family micro controllers. These are used in embedded -applications. There are no standard Unix configurations. -@xref{AVR Options}, for the list of supported MCU types. - -@item decstation-* -MIPS-based DECstations can support three different personalities: -Ultrix, DEC OSF/1, and OSF/rose. (Alpha-based DECstation products have -a configuration name beginning with @samp{alpha-dec}.) To configure GCC -for these platforms use the following configurations: - -@table @samp -@item decstation-ultrix -Ultrix configuration. - -@item decstation-osf1 -Dec's version of OSF/1. - -@item decstation-osfrose -Open Software Foundation reference port of OSF/1 which uses the -OSF/rose object file format instead of ECOFF. Normally, you -would not select this configuration. -@end table - -The MIPS C compiler needs to be told to increase its table size -for switch statements with the @samp{-Wf,-XNg1500} option in -order to compile @file{cp/parse.c}. If you use the @samp{-O2} -optimization option, you also need to use @samp{-Olimit 3000}. -Both of these options are automatically generated in the -@file{Makefile} that the shell script @file{configure} builds. -If you override the @code{CC} make variable and use the MIPS -compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. - -@item elxsi-elxsi-bsd -The Elxsi's C compiler has known limitations that prevent it from -compiling GNU C. Please contact @email{mrs@@cygnus.com} for more details. - -@item dsp16xx -A port to the AT&T DSP1610 family of processors. - -@ignore -@item fx80 -Alliant FX/8 computer. Note that the standard installed C compiler in -Concentrix 5.0 has a bug which prevent it from compiling GNU CC -correctly. You can patch the compiler bug as follows: - -@smallexample -cp /bin/pcc ./pcc -adb -w ./pcc - << EOF -15f6?w 6610 -EOF -@end smallexample - -Then you must use the @samp{-ip12} option when compiling GNU CC -with the patched compiler, as shown here: - -@smallexample -make CC="./pcc -ip12" CFLAGS=-w -@end smallexample - -Note also that Alliant's version of DBX does not manage to work with the -output from GNU CC. -@end ignore - -@item h8300-*-* -Hitachi H8/300 series of processors. - -The calling convention and structure layout has changed in release 2.6. -All code must be recompiled. The calling convention now passes the -first three arguments in function calls in registers. Structures are no -longer a multiple of 2 bytes. - -@item i370-*-* -This port is very preliminary and has many known bugs. We hope to -have a higher-quality port for this machine soon. - -@item i386-*-linux*oldld -Use this configuration to generate @file{a.out} binaries on Linux-based -GNU systems if you do not have gas/binutils version 2.5.2 or later -installed. This is an obsolete configuration. - -@item i386-*-linux*aout -Use this configuration to generate @file{a.out} binaries on Linux-based -GNU systems. This configuration is being superseded. You must use -gas/binutils version 2.5.2 or later. - -@item i386-*-linux -@itemx i386-*-linux-gnu -Use this configuration to generate ELF binaries on Linux-based GNU -systems. You must use gas/binutils version 2.5.2 or later. - -@item i386-*-sco -Compilation with RCC is recommended. Also, it may be a good idea to -link with GNU malloc instead of the malloc that comes with the system. - -@item i386-*-sco3.2v4 -Use this configuration for SCO release 3.2 version 4. - -@item i386-*-sco3.2v5* -Use this for the SCO OpenServer Release 5 family of operating systems. - -@item i386-*-isc -It may be a good idea to link with GNU malloc instead of the malloc that -comes with the system. - -In ISC version 4.1, @file{sed} core dumps when building -@file{deduced.h}. Use the version of @file{sed} from version 4.0. - -@item i386-*-esix -It may be good idea to link with GNU malloc instead of the malloc that -comes with the system. - -@item i386-ibm-aix -You need to use GAS version 2.1 or later, and LD from -GNU binutils version 2.2 or later. - -@item i386-sequent-bsd -Go to the Berkeley universe before compiling. - -@item i386-sequent-ptx1* -@itemx i386-sequent-ptx2* -You must install GNU @file{sed} before running @file{configure}. - -@item *-lynx-lynxos -LynxOS 2.2 and earlier comes with GNU CC 1.x already installed as -@file{/bin/gcc}. You should compile with this instead of @file{/bin/cc}. -You can tell GNU CC to use the GNU assembler and linker, by specifying -@samp{--with-gnu-as --with-gnu-ld} when configuring. These will produce -COFF format object files and executables; otherwise GNU CC will use the -installed tools, which produce @file{a.out} format executables. - -@item m32r-*-elf -Mitsubishi M32R processor. -This configuration is intended for embedded systems. - -@item m68000-hp-bsd -HP 9000 series 200 running BSD. Note that the C compiler that comes -with this system cannot compile GNU CC; contact @email{law@@cygnus.com} -to get binaries of GNU CC for bootstrapping. - -@item m68k-altos -Altos 3068. You must use the GNU assembler, linker and debugger. -Also, you must fix a kernel bug. Details in the file @file{README.ALTOS}. - -@item m68k-apple-aux -Apple Macintosh running A/UX. -You may configure GCC to use either the system assembler and -linker or the GNU assembler and linker. You should use the GNU configuration -if you can, especially if you also want to use GNU C++. You enabled -that configuration with + the @samp{--with-gnu-as} and @samp{--with-gnu-ld} -options to @code{configure}. - -Note the C compiler that comes -with this system cannot compile GNU CC. You can find binaries of GNU CC -for bootstrapping on @code{jagubox.gsfc.nasa.gov}. -You will also a patched version of @file{/bin/ld} there that -raises some of the arbitrary limits found in the original. - -@item m68k-att-sysv -AT&T 3b1, a.k.a. 7300 PC. This version of GNU CC cannot -be compiled with the system C compiler, which is too buggy. -You will need to get a previous version of GCC and use it to -bootstrap. Binaries are available from the OSU-CIS archive, at -@uref{ftp://archive.cis.ohio-state.edu/pub/att7300/}. - -@item m68k-bull-sysv -Bull DPX/2 series 200 and 300 with BOS-2.00.45 up to BOS-2.01. GNU CC works -either with native assembler or GNU assembler. You can use -GNU assembler with native coff generation by providing @samp{--with-gnu-as} to -the configure script or use GNU assembler with dbx-in-coff encapsulation -by providing @samp{--with-gnu-as --stabs}. For any problem with native -assembler or for availability of the DPX/2 port of GAS, contact -@email{F.Pierresteguy@@frcl.bull.fr}. - -@item m68k-crds-unox -Use @samp{configure unos} for building on Unos. - -The Unos assembler is named @code{casm} instead of @code{as}. For some -strange reason linking @file{/bin/as} to @file{/bin/casm} changes the -behavior, and does not work. So, when installing GNU CC, you should -install the following script as @file{as} in the subdirectory where -the passes of GCC are installed: - -@example -#!/bin/sh -casm $* -@end example - -The default Unos library is named @file{libunos.a} instead of -@file{libc.a}. To allow GNU CC to function, either change all -references to @samp{-lc} in @file{gcc.c} to @samp{-lunos} or link -@file{/lib/libc.a} to @file{/lib/libunos.a}. - -@cindex @code{alloca}, for Unos -When compiling GNU CC with the standard compiler, to overcome bugs in -the support of @code{alloca}, do not use @samp{-O} when making stage 2. -Then use the stage 2 compiler with @samp{-O} to make the stage 3 -compiler. This compiler will have the same characteristics as the usual -stage 2 compiler on other systems. Use it to make a stage 4 compiler -and compare that with stage 3 to verify proper compilation. - -(Perhaps simply defining @code{ALLOCA} in @file{x-crds} as described in -the comments there will make the above paragraph superfluous. Please -inform us of whether this works.) - -Unos uses memory segmentation instead of demand paging, so you will need -a lot of memory. 5 Mb is barely enough if no other tasks are running. -If linking @file{cc1} fails, try putting the object files into a library -and linking from that library. - -@item m68k-hp-hpux -HP 9000 series 300 or 400 running HP-UX. HP-UX version 8.0 has a bug in -the assembler that prevents compilation of GNU CC. To fix it, get patch -PHCO_4484 from HP. - -In addition, if you wish to use gas @samp{--with-gnu-as} you must use -gas version 2.1 or later, and you must use the GNU linker version 2.1 or -later. Earlier versions of gas relied upon a program which converted the -gas output into the native HP-UX format, but that program has not been -kept up to date. gdb does not understand that native HP-UX format, so -you must use gas if you wish to use gdb. - -@item m68k-sun -Sun 3. We do not provide a configuration file to use the Sun FPA by -default, because programs that establish signal handlers for floating -point traps inherently cannot work with the FPA. - -@item m6811-elf -Motorola 68HC11 family micro controllers. These are used in embedded -applications. There are no standard Unix configurations. - -@item m6812-elf -Motorola 68HC12 family micro controllers. These are used in embedded -applications. There are no standard Unix configurations. - -@item m88k-*-svr3 -Motorola m88k running the AT&T/Unisoft/Motorola V.3 reference port. -These systems tend to use the Green Hills C, revision 1.8.5, as the -standard C compiler. There are apparently bugs in this compiler that -result in object files differences between stage 2 and stage 3. If this -happens, make the stage 4 compiler and compare it to the stage 3 -compiler. If the stage 3 and stage 4 object files are identical, this -suggests you encountered a problem with the standard C compiler; the -stage 3 and 4 compilers may be usable. - -It is best, however, to use an older version of GNU CC for bootstrapping -if you have one. - -@item m88k-*-dgux -Motorola m88k running DG/UX. To build 88open BCS native or cross -compilers on DG/UX, specify the configuration name as -@samp{m88k-*-dguxbcs} and build in the 88open BCS software development -environment. To build ELF native or cross compilers on DG/UX, specify -@samp{m88k-*-dgux} and build in the DG/UX ELF development environment. -You set the software development environment by issuing -@samp{sde-target} command and specifying either @samp{m88kbcs} or -@samp{m88kdguxelf} as the operand. - -If you do not specify a configuration name, @file{configure} guesses the -configuration based on the current software development environment. - -@item m88k-tektronix-sysv3 -Tektronix XD88 running UTekV 3.2e. Do not turn on -optimization while building stage1 if you bootstrap with -the buggy Green Hills compiler. Also, The bundled LAI -System V NFS is buggy so if you build in an NFS mounted -directory, start from a fresh reboot, or avoid NFS all together. -Otherwise you may have trouble getting clean comparisons -between stages. - -@item mips-mips-bsd -MIPS machines running the MIPS operating system in BSD mode. It's -possible that some old versions of the system lack the functions -@code{memcpy}, @code{memmove}, @code{memcmp}, and @code{memset}. If your -system lacks these, you must remove or undo the definition of -@code{TARGET_MEM_FUNCTIONS} in @file{mips-bsd.h}. - -The MIPS C compiler needs to be told to increase its table size -for switch statements with the @samp{-Wf,-XNg1500} option in -order to compile @file{cp/parse.c}. If you use the @samp{-O2} -optimization option, you also need to use @samp{-Olimit 3000}. -Both of these options are automatically generated in the -@file{Makefile} that the shell script @file{configure} builds. -If you override the @code{CC} make variable and use the MIPS -compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. - -@item mips-mips-riscos* -The MIPS C compiler needs to be told to increase its table size -for switch statements with the @samp{-Wf,-XNg1500} option in -order to compile @file{cp/parse.c}. If you use the @samp{-O2} -optimization option, you also need to use @samp{-Olimit 3000}. -Both of these options are automatically generated in the -@file{Makefile} that the shell script @file{configure} builds. -If you override the @code{CC} make variable and use the MIPS -compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. - -MIPS computers running RISC-OS can support four different -personalities: default, BSD 4.3, System V.3, and System V.4 -(older versions of RISC-OS don't support V.4). To configure GCC -for these platforms use the following configurations: - -@table @samp -@item mips-mips-riscos@code{rev} -Default configuration for RISC-OS, revision @code{rev}. - -@item mips-mips-riscos@code{rev}bsd -BSD 4.3 configuration for RISC-OS, revision @code{rev}. - -@item mips-mips-riscos@code{rev}sysv4 -System V.4 configuration for RISC-OS, revision @code{rev}. - -@item mips-mips-riscos@code{rev}sysv -System V.3 configuration for RISC-OS, revision @code{rev}. -@end table - -The revision @code{rev} mentioned above is the revision of -RISC-OS to use. You must reconfigure GCC when going from a -RISC-OS revision 4 to RISC-OS revision 5. This has the effect of -avoiding a linker -@ifclear INSTALLONLY -bug (see @ref{Installation Problems}, for more details). -@end ifclear -@ifset INSTALLONLY -bug. -@end ifset - -@item mips-sgi-* -In order to compile GCC on an SGI running IRIX 4, the "c.hdr.lib" -option must be installed from the CD-ROM supplied from Silicon Graphics. -This is found on the 2nd CD in release 4.0.1. - -In order to compile GCC on an SGI running IRIX 5, the "compiler_dev.hdr" -subsystem must be installed from the IDO CD-ROM supplied by Silicon -Graphics. - -@code{make compare} may fail on version 5 of IRIX unless you add -@samp{-save-temps} to @code{CFLAGS}. On these systems, the name of the -assembler input file is stored in the object file, and that makes -comparison fail if it differs between the @code{stage1} and -@code{stage2} compilations. The option @samp{-save-temps} forces a -fixed name to be used for the assembler input file, instead of a -randomly chosen name in @file{/tmp}. Do not add @samp{-save-temps} -unless the comparisons fail without that option. If you do you -@samp{-save-temps}, you will have to manually delete the @samp{.i} and -@samp{.s} files after each series of compilations. - -The MIPS C compiler needs to be told to increase its table size -for switch statements with the @samp{-Wf,-XNg1500} option in -order to compile @file{cp/parse.c}. If you use the @samp{-O2} -optimization option, you also need to use @samp{-Olimit 3000}. -Both of these options are automatically generated in the -@file{Makefile} that the shell script @file{configure} builds. -If you override the @code{CC} make variable and use the MIPS -compilers, you may need to add @samp{-Wf,-XNg1500 -Olimit 3000}. - -On Irix version 4.0.5F, and perhaps on some other versions as well, -there is an assembler bug that reorders instructions incorrectly. To -work around it, specify the target configuration -@samp{mips-sgi-irix4loser}. This configuration inhibits assembler -optimization. - -In a compiler configured with target @samp{mips-sgi-irix4}, you can turn -off assembler optimization by using the @samp{-noasmopt} option. This -compiler option passes the option @samp{-O0} to the assembler, to -inhibit reordering. - -The @samp{-noasmopt} option can be useful for testing whether a problem -is due to erroneous assembler reordering. Even if a problem does not go -away with @samp{-noasmopt}, it may still be due to assembler -reordering---perhaps GNU CC itself was miscompiled as a result. - -To enable debugging under Irix 5, you must use GNU as 2.5 or later, -and use the @samp{--with-gnu-as} configure option when configuring gcc. -GNU as is distributed as part of the binutils package. - -@item mips-sony-sysv -Sony MIPS NEWS. This works in NEWSOS 5.0.1, but not in 5.0.2 (which -uses ELF instead of COFF). Support for 5.0.2 will probably be provided -soon by volunteers. In particular, the linker does not like the -code generated by GCC when shared libraries are linked in. - -@item ns32k-encore -Encore ns32000 system. Encore systems are supported only under BSD. - -@item ns32k-*-genix -National Semiconductor ns32000 system. Genix has bugs in @code{alloca} -and @code{malloc}; you must get the compiled versions of these from GNU -Emacs. - -@item ns32k-sequent -Go to the Berkeley universe before compiling. - -@item ns32k-utek -UTEK ns32000 system (``merlin''). The C compiler that comes with this -system cannot compile GNU CC; contact @samp{tektronix!reed!mason} to get -binaries of GNU CC for bootstrapping. - -@item romp-*-aos -@itemx romp-*-mach -The only operating systems supported for the IBM RT PC are AOS and -MACH. GNU CC does not support AIX running on the RT. We recommend you -compile GNU CC with an earlier version of itself; if you compile GNU CC -with @code{hc}, the Metaware compiler, it will work, but you will get -mismatches between the stage 2 and stage 3 compilers in various files. -These errors are minor differences in some floating-point constants and -can be safely ignored; the stage 3 compiler is correct. - -@item rs6000-*-aix -@itemx powerpc-*-aix -Various early versions of each release of the IBM XLC compiler will not -bootstrap GNU CC. Symptoms include differences between the stage2 and -stage3 object files, and errors when compiling @file{libgcc.a} or -@file{enquire}. Known problematic releases include: xlc-1.2.1.8, -xlc-1.3.0.0 (distributed with AIX 3.2.5), and xlc-1.3.0.19. Both -xlc-1.2.1.28 and xlc-1.3.0.24 (PTF 432238) are known to produce working -versions of GNU CC, but most other recent releases correctly bootstrap -GNU CC. - -Release 4.3.0 of AIX and ones prior to AIX 3.2.4 include a version of -the IBM assembler which does not accept debugging directives: assembler -updates are available as PTFs. Also, if you are using AIX 3.2.5 or -greater and the GNU assembler, you must have a version modified after -October 16th, 1995 in order for the GNU C compiler to build. See the -file @file{README.RS6000} for more details on any of these problems. - -GNU CC does not yet support the 64-bit PowerPC instructions. - -Objective C does not work on this architecture because it makes assumptions -that are incompatible with the calling conventions. - -AIX on the RS/6000 provides support (NLS) for environments outside of -the United States. Compilers and assemblers use NLS to support -locale-specific representations of various objects including -floating-point numbers ("." vs "," for separating decimal fractions). -There have been problems reported where the library linked with GNU CC -does not produce the same floating-point formats that the assembler -accepts. If you have this problem, set the LANG environment variable to -"C" or "En_US". - -Due to changes in the way that GNU CC invokes the binder (linker) for AIX -4.1, you may now receive warnings of duplicate symbols from the link step -that were not reported before. The assembly files generated by GNU CC for -AIX have always included multiple symbol definitions for certain global -variable and function declarations in the original program. The warnings -should not prevent the linker from producing a correct library or runnable -executable. - -By default, AIX 4.1 produces code that can be used on either Power or -PowerPC processors. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpc-*-elf -@itemx powerpc-*-sysv4 -PowerPC system in big endian mode, running System V.4. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpc-*-linux -@itemx powerpc-*-linux-gnu -PowerPC system in big endian mode, running the Linux-based GNU system. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpc-*-eabiaix -Embedded PowerPC system in big endian mode with -mcall-aix selected as -the default. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpc-*-eabisim -Embedded PowerPC system in big endian mode for use in running under the -PSIM simulator. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpc-*-eabi -Embedded PowerPC system in big endian mode. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpcle-*-elf -@itemx powerpcle-*-sysv4 -PowerPC system in little endian mode, running System V.4. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpcle-*-eabisim -Embedded PowerPC system in little endian mode for use in running under -the PSIM simulator. - -@itemx powerpcle-*-eabi -Embedded PowerPC system in little endian mode. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item powerpcle-*-winnt -@itemx powerpcle-*-pe -PowerPC system in little endian mode running Windows NT. - -You can specify a default version for the @samp{-mcpu=}@var{cpu_type} -switch by using the configure option @samp{--with-cpu-}@var{cpu_type}. - -@item vax-dec-ultrix -Don't try compiling with Vax C (@code{vcc}). It produces incorrect code -in some cases (for example, when @code{alloca} is used). - -Meanwhile, compiling @file{cp/parse.c} with pcc does not work because of -an internal table size limitation in that compiler. To avoid this -problem, compile just the GNU C compiler first, and use it to recompile -building all the languages that you want to run. - -@item vax-dec-vms -See @ref{VMS Install}, for details on how to install GNU CC on VMS. - -@item we32k-*-* -These computers are also known as the 3b2, 3b5, 3b20 and other similar -names. (However, the 3b1 is actually a 68000; see -@ref{Configurations}.) - -Don't use @samp{-g} when compiling with the system's compiler. The -system's linker seems to be unable to handle such a large program with -debugging information. - -The system's compiler runs out of capacity when compiling @file{stmt.c} -in GNU CC. You can work around this by building @file{cpp} in GNU CC -first, then use that instead of the system's preprocessor with the -system's C compiler to compile @file{stmt.c}. Here is how: - -@smallexample -mv /lib/cpp /lib/cpp.att -cp cpp /lib/cpp.gnu -echo '/lib/cpp.gnu -traditional $@{1+"$@@"@}' > /lib/cpp -chmod +x /lib/cpp -@end smallexample - -The system's compiler produces bad code for some of the GNU CC -optimization files. So you must build the stage 2 compiler without -optimization. Then build a stage 3 compiler with optimization. -That executable should work. Here are the necessary commands: - -@smallexample -make LANGUAGES=c CC=stage1/xgcc CFLAGS="-Bstage1/ -g" -make stage2 -make CC=stage2/xgcc CFLAGS="-Bstage2/ -g -O" -@end smallexample - -You may need to raise the ULIMIT setting to build a C++ compiler, -as the file @file{cc1plus} is larger than one megabyte. -@end table - -@node Other Dir -@section Compilation in a Separate Directory -@cindex other directory, compilation in -@cindex compilation in a separate directory -@cindex separate directory, compilation in - -If you wish to build the object files and executables in a directory -other than the one containing the source files, here is what you must -do differently: - -@enumerate -@item -Make sure you have a version of Make that supports the @code{VPATH} -feature. (GNU Make supports it, as do Make versions on most BSD -systems.) - -@item -If you have ever run @file{configure} in the source directory, you must undo -the configuration. Do this by running: - -@example -make distclean -@end example - -@item -Go to the directory in which you want to build the compiler before -running @file{configure}: - -@example -mkdir gcc-sun3 -cd gcc-sun3 -@end example - -On systems that do not support symbolic links, this directory must be -on the same file system as the source code directory. - -@item -Specify where to find @file{configure} when you run it: - -@example -../gcc/configure @dots{} -@end example - -This also tells @code{configure} where to find the compiler sources; -@code{configure} takes the directory from the file name that was used to -invoke it. But if you want to be sure, you can specify the source -directory with the @samp{--srcdir} option, like this: - -@example -../gcc/configure --srcdir=../gcc @var{other options} -@end example - -The directory you specify with @samp{--srcdir} need not be the same -as the one that @code{configure} is found in. -@end enumerate - -Now, you can run @code{make} in that directory. You need not repeat the -configuration steps shown above, when ordinary source files change. You -must, however, run @code{configure} again when the configuration files -change, if your system does not support symbolic links. - -@node Cross-Compiler -@section Building and Installing a Cross-Compiler -@cindex cross-compiler, installation - -GNU CC can function as a cross-compiler for many machines, but not all. - -@itemize @bullet -@item -Cross-compilers for the Mips as target using the Mips assembler -currently do not work, because the auxiliary programs -@file{mips-tdump.c} and @file{mips-tfile.c} can't be compiled on -anything but a Mips. It does work to cross compile for a Mips -if you use the GNU assembler and linker. - -@item -Cross-compilers between machines with different floating point formats -have not all been made to work. GNU CC now has a floating point -emulator with which these can work, but each target machine description -needs to be updated to take advantage of it. - -@item -Cross-compilation between machines of different word sizes is -somewhat problematic and sometimes does not work. -@end itemize - -Since GNU CC generates assembler code, you probably need a -cross-assembler that GNU CC can run, in order to produce object files. -If you want to link on other than the target machine, you need a -cross-linker as well. You also need header files and libraries suitable -for the target machine that you can install on the host machine. - -@menu -* Steps of Cross:: Using a cross-compiler involves several steps - that may be carried out on different machines. -* Configure Cross:: Configuring a cross-compiler. -* Tools and Libraries:: Where to put the linker and assembler, and the C library. -* Cross Headers:: Finding and installing header files - for a cross-compiler. -* Build Cross:: Actually compiling the cross-compiler. -@end menu - -@node Steps of Cross -@subsection Steps of Cross-Compilation - -To compile and run a program using a cross-compiler involves several -steps: - -@itemize @bullet -@item -Run the cross-compiler on the host machine to produce assembler files -for the target machine. This requires header files for the target -machine. - -@item -Assemble the files produced by the cross-compiler. You can do this -either with an assembler on the target machine, or with a -cross-assembler on the host machine. - -@item -Link those files to make an executable. You can do this either with a -linker on the target machine, or with a cross-linker on the host -machine. Whichever machine you use, you need libraries and certain -startup files (typically @file{crt@dots{}.o}) for the target machine. -@end itemize - -It is most convenient to do all of these steps on the same host machine, -since then you can do it all with a single invocation of GNU CC. This -requires a suitable cross-assembler and cross-linker. For some targets, -the GNU assembler and linker are available. - -@node Configure Cross -@subsection Configuring a Cross-Compiler - -To build GNU CC as a cross-compiler, you start out by running -@file{configure}. Use the @samp{--target=@var{target}} to specify the -target type. If @file{configure} was unable to correctly identify the -system you are running on, also specify the @samp{--build=@var{build}} -option. For example, here is how to configure for a cross-compiler that -produces code for an HP 68030 system running BSD on a system that -@file{configure} can correctly identify: - -@smallexample -./configure --target=m68k-hp-bsd4.3 -@end smallexample - -@node Tools and Libraries -@subsection Tools and Libraries for a Cross-Compiler - -If you have a cross-assembler and cross-linker available, you should -install them now. Put them in the directory -@file{/usr/local/@var{target}/bin}. Here is a table of the tools -you should put in this directory: - -@table @file -@item as -This should be the cross-assembler. - -@item ld -This should be the cross-linker. - -@item ar -This should be the cross-archiver: a program which can manipulate -archive files (linker libraries) in the target machine's format. - -@item ranlib -This should be a program to construct a symbol table in an archive file. -@end table - -The installation of GNU CC will find these programs in that directory, -and copy or link them to the proper place to for the cross-compiler to -find them when run later. - -The easiest way to provide these files is to build the Binutils package -and GAS. Configure them with the same @samp{--host} and @samp{--target} -options that you use for configuring GNU CC, then build and install -them. They install their executables automatically into the proper -directory. Alas, they do not support all the targets that GNU CC -supports. - -If you want to install libraries to use with the cross-compiler, such as -a standard C library, put them in the directory -@file{/usr/local/@var{target}/lib}; installation of GNU CC copies -all the files in that subdirectory into the proper place for GNU CC to -find them and link with them. Here's an example of copying some -libraries from a target machine: - -@example -ftp @var{target-machine} -lcd /usr/local/@var{target}/lib -cd /lib -get libc.a -cd /usr/lib -get libg.a -get libm.a -quit -@end example - -@noindent -The precise set of libraries you'll need, and their locations on -the target machine, vary depending on its operating system. - -@cindex start files -Many targets require ``start files'' such as @file{crt0.o} and -@file{crtn.o} which are linked into each executable; these too should be -placed in @file{/usr/local/@var{target}/lib}. There may be several -alternatives for @file{crt0.o}, for use with profiling or other -compilation options. Check your target's definition of -@code{STARTFILE_SPEC} to find out what start files it uses. -Here's an example of copying these files from a target machine: - -@example -ftp @var{target-machine} -lcd /usr/local/@var{target}/lib -prompt -cd /lib -mget *crt*.o -cd /usr/lib -mget *crt*.o -quit -@end example - -@node Cross Headers -@subsection Cross-Compilers and Header Files - -If you are cross-compiling a standalone program or a program for an -embedded system, then you may not need any header files except the few -that are part of GNU CC (and those of your program). However, if you -intend to link your program with a standard C library such as -@file{libc.a}, then you probably need to compile with the header files -that go with the library you use. - -The GNU C compiler does not come with these files, because (1) they are -system-specific, and (2) they belong in a C library, not in a compiler. - -If the GNU C library supports your target machine, then you can get the -header files from there (assuming you actually use the GNU library when -you link your program). - -If your target machine comes with a C compiler, it probably comes with -suitable header files also. If you make these files accessible from the host -machine, the cross-compiler can use them also. - -Otherwise, you're on your own in finding header files to use when -cross-compiling. - -When you have found suitable header files, put them in the directory -@file{/usr/local/@var{target}/include}, before building the cross -compiler. Then installation will run fixincludes properly and install -the corrected versions of the header files where the compiler will use -them. - -Provide the header files before you build the cross-compiler, because -the build stage actually runs the cross-compiler to produce parts of -@file{libgcc.a}. (These are the parts that @emph{can} be compiled with -GNU CC.) Some of them need suitable header files. - -Here's an example showing how to copy the header files from a target -machine. On the target machine, do this: - -@example -(cd /usr/include; tar cf - .) > tarfile -@end example - -Then, on the host machine, do this: - -@example -ftp @var{target-machine} -lcd /usr/local/@var{target}/include -get tarfile -quit -tar xf tarfile -@end example - -@node Build Cross -@subsection Actually Building the Cross-Compiler - -Now you can proceed just as for compiling a single-machine compiler -through the step of building stage 1. - -If your target is exotic, you may need to provide the header file -@file{float.h}.One way to do this is to compile @file{enquire} and run -it on your target machine. The job of @file{enquire} is to run on the -target machine and figure out by experiment the nature of its floating -point representation. @file{enquire} records its findings in the header -file @file{float.h}. If you can't produce this file by running -@file{enquire} on the target machine, then you will need to come up with -a suitable @file{float.h} in some other way (or else, avoid using it in -your programs). - -Do not try to build stage 2 for a cross-compiler. It doesn't work to -rebuild GNU CC as a cross-compiler using the cross-compiler, because -that would produce a program that runs on the target machine, not on the -host. For example, if you compile a 386-to-68030 cross-compiler with -itself, the result will not be right either for the 386 (because it was -compiled into 68030 code) or for the 68030 (because it was configured -for a 386 as the host). If you want to compile GNU CC into 68030 code, -whether you compile it on a 68030 or with a cross-compiler on a 386, you -must specify a 68030 as the host when you configure it. - -To install the cross-compiler, use @samp{make install}, as usual. - -@node VMS Install -@section Installing GNU CC on VMS -@cindex VMS installation -@cindex installing GNU CC on VMS - -The VMS version of GNU CC is distributed in a backup saveset containing -both source code and precompiled binaries. - -To install the @file{gcc} command so you can use the compiler easily, in -the same manner as you use the VMS C compiler, you must install the VMS CLD -file for GNU CC as follows: - -@enumerate -@item -Define the VMS logical names @samp{GNU_CC} and @samp{GNU_CC_INCLUDE} -to point to the directories where the GNU CC executables -(@file{gcc-cpp.exe}, @file{gcc-cc1.exe}, etc.) and the C include files are -kept respectively. This should be done with the commands:@refill - -@smallexample -$ assign /system /translation=concealed - - disk:[gcc.] gnu_cc -$ assign /system /translation=concealed - - disk:[gcc.include.] gnu_cc_include -@end smallexample - -@noindent -with the appropriate disk and directory names. These commands can be -placed in your system startup file so they will be executed whenever -the machine is rebooted. You may, if you choose, do this via the -@file{GCC_INSTALL.COM} script in the @file{[GCC]} directory. - -@item -Install the @file{GCC} command with the command line: - -@smallexample -$ set command /table=sys$common:[syslib]dcltables - - /output=sys$common:[syslib]dcltables gnu_cc:[000000]gcc -$ install replace sys$common:[syslib]dcltables -@end smallexample - -@item -To install the help file, do the following: - -@smallexample -$ library/help sys$library:helplib.hlb gcc.hlp -@end smallexample - -@noindent -Now you can invoke the compiler with a command like @samp{gcc /verbose -file.c}, which is equivalent to the command @samp{gcc -v -c file.c} in -Unix. -@end enumerate - -If you wish to use GNU C++ you must first install GNU CC, and then -perform the following steps: - -@enumerate -@item -Define the VMS logical name @samp{GNU_GXX_INCLUDE} to point to the -directory where the preprocessor will search for the C++ header files. -This can be done with the command:@refill - -@smallexample -$ assign /system /translation=concealed - - disk:[gcc.gxx_include.] gnu_gxx_include -@end smallexample - -@noindent -with the appropriate disk and directory name. If you are going to be -using a C++ runtime library, this is where its install procedure will install -its header files. - -@item -Obtain the file @file{gcc-cc1plus.exe}, and place this in the same -directory that @file{gcc-cc1.exe} is kept. - -The GNU C++ compiler can be invoked with a command like @samp{gcc /plus -/verbose file.cc}, which is equivalent to the command @samp{g++ -v -c -file.cc} in Unix. -@end enumerate - -We try to put corresponding binaries and sources on the VMS distribution -tape. But sometimes the binaries will be from an older version than the -sources, because we don't always have time to update them. (Use the -@samp{/version} option to determine the version number of the binaries and -compare it with the source file @file{version.c} to tell whether this is -so.) In this case, you should use the binaries you get to recompile the -sources. If you must recompile, here is how: - -@enumerate -@item -Execute the command procedure @file{vmsconfig.com} to set up the files -@file{tm.h}, @file{config.h}, @file{aux-output.c}, and @file{md.}, and -to create files @file{tconfig.h} and @file{hconfig.h}. This procedure -also creates several linker option files used by @file{make-cc1.com} and -a data file used by @file{make-l2.com}.@refill - -@smallexample -$ @@vmsconfig.com -@end smallexample - -@item -Setup the logical names and command tables as defined above. In -addition, define the VMS logical name @samp{GNU_BISON} to point at the -to the directories where the Bison executable is kept. This should be -done with the command:@refill - -@smallexample -$ assign /system /translation=concealed - - disk:[bison.] gnu_bison -@end smallexample - -You may, if you choose, use the @file{INSTALL_BISON.COM} script in the -@file{[BISON]} directory. - -@item -Install the @samp{BISON} command with the command line:@refill - -@smallexample -$ set command /table=sys$common:[syslib]dcltables - - /output=sys$common:[syslib]dcltables - - gnu_bison:[000000]bison -$ install replace sys$common:[syslib]dcltables -@end smallexample - -@item -Type @samp{@@make-gcc} to recompile everything (alternatively, submit -the file @file{make-gcc.com} to a batch queue). If you wish to build -the GNU C++ compiler as well as the GNU CC compiler, you must first edit -@file{make-gcc.com} and follow the instructions that appear in the -comments.@refill - -@item -In order to use GCC, you need a library of functions which GCC compiled code -will call to perform certain tasks, and these functions are defined in the -file @file{libgcc2.c}. To compile this you should use the command procedure -@file{make-l2.com}, which will generate the library @file{libgcc2.olb}. -@file{libgcc2.olb} should be built using the compiler built from -the same distribution that @file{libgcc2.c} came from, and -@file{make-gcc.com} will automatically do all of this for you. - -To install the library, use the following commands:@refill - -@smallexample -$ library gnu_cc:[000000]gcclib/delete=(new,eprintf) -$ library gnu_cc:[000000]gcclib/delete=L_* -$ library libgcc2/extract=*/output=libgcc2.obj -$ library gnu_cc:[000000]gcclib libgcc2.obj -@end smallexample - -The first command simply removes old modules that will be replaced with -modules from @file{libgcc2} under different module names. The modules -@code{new} and @code{eprintf} may not actually be present in your -@file{gcclib.olb}---if the VMS librarian complains about those modules -not being present, simply ignore the message and continue on with the -next command. The second command removes the modules that came from the -previous version of the library @file{libgcc2.c}. - -Whenever you update the compiler on your system, you should also update the -library with the above procedure. - -@item -You may wish to build GCC in such a way that no files are written to the -directory where the source files reside. An example would be the when -the source files are on a read-only disk. In these cases, execute the -following DCL commands (substituting your actual path names): - -@smallexample -$ assign dua0:[gcc.build_dir.]/translation=concealed, - - dua1:[gcc.source_dir.]/translation=concealed gcc_build -$ set default gcc_build:[000000] -@end smallexample - -@noindent -where the directory @file{dua1:[gcc.source_dir]} contains the source -code, and the directory @file{dua0:[gcc.build_dir]} is meant to contain -all of the generated object files and executables. Once you have done -this, you can proceed building GCC as described above. (Keep in mind -that @file{gcc_build} is a rooted logical name, and thus the device -names in each element of the search list must be an actual physical -device name rather than another rooted logical name). - -@item -@strong{If you are building GNU CC with a previous version of GNU CC, -you also should check to see that you have the newest version of the -assembler}. In particular, GNU CC version 2 treats global constant -variables slightly differently from GNU CC version 1, and GAS version -1.38.1 does not have the patches required to work with GCC version 2. -If you use GAS 1.38.1, then @code{extern const} variables will not have -the read-only bit set, and the linker will generate warning messages -about mismatched psect attributes for these variables. These warning -messages are merely a nuisance, and can safely be ignored. - -If you are compiling with a version of GNU CC older than 1.33, specify -@samp{/DEFINE=("inline=")} as an option in all the compilations. This -requires editing all the @code{gcc} commands in @file{make-cc1.com}. -(The older versions had problems supporting @code{inline}.) Once you -have a working 1.33 or newer GNU CC, you can change this file back. - -@item -If you want to build GNU CC with the VAX C compiler, you will need to -make minor changes in @file{make-cccp.com} and @file{make-cc1.com} -to choose alternate definitions of @code{CC}, @code{CFLAGS}, and -@code{LIBS}. See comments in those files. However, you must -also have a working version of the GNU assembler (GNU as, aka GAS) as -it is used as the back-end for GNU CC to produce binary object modules -and is not included in the GNU CC sources. GAS is also needed to -compile @file{libgcc2} in order to build @file{gcclib} (see above); -@file{make-l2.com} expects to be able to find it operational in -@file{gnu_cc:[000000]gnu-as.exe}. - -To use GNU CC on VMS, you need the VMS driver programs -@file{gcc.exe}, @file{gcc.com}, and @file{gcc.cld}. They are -distributed with the VMS binaries (@file{gcc-vms}) rather than the -GNU CC sources. GAS is also included in @file{gcc-vms}, as is Bison. - -Once you have successfully built GNU CC with VAX C, you should use the -resulting compiler to rebuild itself. Before doing this, be sure to -restore the @code{CC}, @code{CFLAGS}, and @code{LIBS} definitions in -@file{make-cccp.com} and @file{make-cc1.com}. The second generation -compiler will be able to take advantage of many optimizations that must -be suppressed when building with other compilers. -@end enumerate - -Under previous versions of GNU CC, the generated code would occasionally -give strange results when linked with the sharable @file{VAXCRTL} library. -Now this should work. - -Even with this version, however, GNU CC itself should not be linked with -the sharable @file{VAXCRTL}. The version of @code{qsort} in -@file{VAXCRTL} has a bug (known to be present in VMS versions V4.6 -through V5.5) which causes the compiler to fail. - -The executables are generated by @file{make-cc1.com} and -@file{make-cccp.com} use the object library version of @file{VAXCRTL} in -order to make use of the @code{qsort} routine in @file{gcclib.olb}. If -you wish to link the compiler executables with the shareable image -version of @file{VAXCRTL}, you should edit the file @file{tm.h} (created -by @file{vmsconfig.com}) to define the macro @code{QSORT_WORKAROUND}. - -@code{QSORT_WORKAROUND} is always defined when GNU CC is compiled with -VAX C, to avoid a problem in case @file{gcclib.olb} is not yet -available. - -@node Collect2 -@section @code{collect2} - -GNU CC uses a utility called @code{collect2} on nearly all systems to arrange -to call various initialization functions at start time. - -The program @code{collect2} works by linking the program once and -looking through the linker output file for symbols with particular names -indicating they are constructor functions. If it finds any, it -creates a new temporary @samp{.c} file containing a table of them, -compiles it, and links the program a second time including that file. - -@findex __main -@cindex constructors, automatic calls -The actual calls to the constructors are carried out by a subroutine -called @code{__main}, which is called (automatically) at the beginning -of the body of @code{main} (provided @code{main} was compiled with GNU -CC). Calling @code{__main} is necessary, even when compiling C code, to -allow linking C and C++ object code together. (If you use -@samp{-nostdlib}, you get an unresolved reference to @code{__main}, -since it's defined in the standard GCC library. Include @samp{-lgcc} at -the end of your compiler command line to resolve this reference.) - -The program @code{collect2} is installed as @code{ld} in the directory -where the passes of the compiler are installed. When @code{collect2} -needs to find the @emph{real} @code{ld}, it tries the following file -names: - -@itemize @bullet -@item -@file{real-ld} in the directories listed in the compiler's search -directories. - -@item -@file{real-ld} in the directories listed in the environment variable -@code{PATH}. - -@item -The file specified in the @code{REAL_LD_FILE_NAME} configuration macro, -if specified. - -@item -@file{ld} in the compiler's search directories, except that -@code{collect2} will not execute itself recursively. - -@item -@file{ld} in @code{PATH}. -@end itemize - -``The compiler's search directories'' means all the directories where -@code{gcc} searches for passes of the compiler. This includes -directories that you specify with @samp{-B}. - -Cross-compilers search a little differently: - -@itemize @bullet -@item -@file{real-ld} in the compiler's search directories. - -@item -@file{@var{target}-real-ld} in @code{PATH}. - -@item -The file specified in the @code{REAL_LD_FILE_NAME} configuration macro, -if specified. - -@item -@file{ld} in the compiler's search directories. - -@item -@file{@var{target}-ld} in @code{PATH}. -@end itemize - -@code{collect2} explicitly avoids running @code{ld} using the file name -under which @code{collect2} itself was invoked. In fact, it remembers -up a list of such names---in case one copy of @code{collect2} finds -another copy (or version) of @code{collect2} installed as @code{ld} in a -second place in the search path. - -@code{collect2} searches for the utilities @code{nm} and @code{strip} -using the same algorithm as above for @code{ld}. - -@node Header Dirs -@section Standard Header File Directories - -@code{GCC_INCLUDE_DIR} means the same thing for native and cross. It is -where GNU CC stores its private include files, and also where GNU CC -stores the fixed include files. A cross compiled GNU CC runs -@code{fixincludes} on the header files in @file{$(tooldir)/include}. -(If the cross compilation header files need to be fixed, they must be -installed before GNU CC is built. If the cross compilation header files -are already suitable for ISO C and GNU CC, nothing special need be -done). - -@code{GPLUSPLUS_INCLUDE_DIR} means the same thing for native and cross. It -is where @code{g++} looks first for header files. The C++ library -installs only target independent header files in that directory. - -@code{LOCAL_INCLUDE_DIR} is used only for a native compiler. It is -normally @file{/usr/local/include}. GNU CC searches this directory so -that users can install header files in @file{/usr/local/include}. - -@code{CROSS_INCLUDE_DIR} is used only for a cross compiler. GNU CC -doesn't install anything there. - -@code{TOOL_INCLUDE_DIR} is used for both native and cross compilers. It -is the place for other packages to install header files that GNU CC will -use. For a cross-compiler, this is the equivalent of -@file{/usr/include}. When you build a cross-compiler, -@code{fixincludes} processes any header files in this directory. diff --git a/gcc/invoke.texi b/gcc/invoke.texi deleted file mode 100644 index 2fab624fa94..00000000000 --- a/gcc/invoke.texi +++ /dev/null @@ -1,8722 +0,0 @@ -@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, -@c 2000, 2001 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@ignore -@c man begin COPYRIGHT -Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, -1998, 1999, 2000, 2001 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of this -manual provided the copyright notice and this permission notice are -preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -entire resulting derived work is distributed under the terms of a -permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that this permission notice may be included in translations -approved by the Free Software Foundation instead of in the original -English. -@c man end -@c Set file name and title for the man page. -@setfilename gcc -@settitle GNU project C and C++ compiler -@c man begin SYNOPSIS -gcc [@samp{-c}|@samp{-S}|@samp{-E}] [@samp{-std=}@var{standard}] - [@samp{-g}] [@samp{-pg}] [@samp{-O}@var{level}] - [@samp{-W}@var{warn}...] [@samp{-pedantic}] - [@samp{-I}@var{dir}...] [@samp{-L}@var{dir}...] - [@samp{-D}@var{macro}[=@var{defn}]...] [@samp{-U}@var{macro}] - [@samp{-f}@var{option}...] [@samp{-m}@var{machine-option}...] - [@samp{-o} @var{outfile}] @var{infile}... - -Only the most useful options are listed here; see below for the -remainder. @samp{g++} accepts mostly the same options as @samp{gcc}. -@c man end -@c man begin SEEALSO -cpp(1), gcov(1), g77(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1) -and the Info entries for @file{gcc}, @file{cpp}, @file{g77}, @file{as}, -@file{ld}, @file{binutils} and @file{gdb}. -@c man end -@c man begin BUGS -For instructions on reporting bugs, see -@w{@uref{http://gcc.gnu.org/bugs.html}}. Use of the @command{gccbug} -script to report bugs is recommended. -@c man end -@c man begin AUTHOR -See the Info entry for @file{gcc}, or -@w{@uref{http://gcc.gnu.org/thanks.html}}, for contributors to GCC. -@c man end -@end ignore - -@node Invoking GCC -@chapter GCC Command Options -@cindex GCC command options -@cindex command options -@cindex options, GCC command - -@c man begin DESCRIPTION - -When you invoke GCC, it normally does preprocessing, compilation, -assembly and linking. The ``overall options'' allow you to stop this -process at an intermediate stage. For example, the @samp{-c} option -says not to run the linker. Then the output consists of object files -output by the assembler. - -Other options are passed on to one stage of processing. Some options -control the preprocessor and others the compiler itself. Yet other -options control the assembler and linker; most of these are not -documented here, since you rarely need to use any of them. - -@cindex C compilation options -Most of the command line options that you can use with GCC are useful -for C programs; when an option is only useful with another language -(usually C++), the explanation says so explicitly. If the description -for a particular option does not mention a source language, you can use -that option with all supported languages. - -@cindex C++ compilation options -@xref{Invoking G++,,Compiling C++ Programs}, for a summary of special -options for compiling C++ programs. - -@cindex grouping options -@cindex options, grouping -The @command{gcc} program accepts options and file names as operands. Many -options have multi-letter names; therefore multiple single-letter options -may @emph{not} be grouped: @samp{-dr} is very different from @w{@samp{-d --r}}. - -@cindex order of options -@cindex options, order -You can mix options and other arguments. For the most part, the order -you use doesn't matter. Order does matter when you use several options -of the same kind; for example, if you specify @samp{-L} more than once, -the directories are searched in the order specified. - -Many options have long names starting with @samp{-f} or with -@samp{-W}---for example, @samp{-fforce-mem}, -@samp{-fstrength-reduce}, @samp{-Wformat} and so on. Most of -these have both positive and negative forms; the negative form of -@samp{-ffoo} would be @samp{-fno-foo}. This manual documents -only one of these two forms, whichever one is not the default. - -@c man end - -@menu -* Option Summary:: Brief list of all options, without explanations. -* Overall Options:: Controlling the kind of output: - an executable, object files, assembler files, - or preprocessed source. -* Invoking G++:: Compiling C++ programs. -* C Dialect Options:: Controlling the variant of C language compiled. -* C++ Dialect Options:: Variations on C++. -* Objective-C Dialect Options:: Variations on Objective-C. -* Language Independent Options:: Controlling how diagnostics should be - formatted. -* Warning Options:: How picky should the compiler be? -* Debugging Options:: Symbol tables, measurements, and debugging dumps. -* Optimize Options:: How much optimization? -* Preprocessor Options:: Controlling header files and macro definitions. - Also, getting dependency information for Make. -* Assembler Options:: Passing options to the assembler. -* Link Options:: Specifying libraries and so on. -* Directory Options:: Where to find header files and libraries. - Where to find the compiler executable files. -* Spec Files:: How to pass switches to sub-processes. -* Target Options:: Running a cross-compiler, or an old version of GCC. -* Submodel Options:: Specifying minor hardware or convention variations, - such as 68010 vs 68020. -* Code Gen Options:: Specifying conventions for function calls, data layout - and register usage. -* Environment Variables:: Env vars that affect GCC. -* Running Protoize:: Automatically adding or removing function prototypes. -@end menu - -@c man begin OPTIONS - -@node Option Summary -@section Option Summary - -Here is a summary of all the options, grouped by type. Explanations are -in the following sections. - -@table @emph -@item Overall Options -@xref{Overall Options,,Options Controlling the Kind of Output}. -@gccoptlist{ --c -S -E -o @var{file} -pipe -pass-exit-codes -x @var{language} @gol --v --target-help --help} - -@item C Language Options -@xref{C Dialect Options,,Options Controlling C Dialect}. -@gccoptlist{ --ansi -std=@var{standard} -fno-asm -fno-builtin @gol --fhosted -ffreestanding @gol --trigraphs -traditional -traditional-cpp @gol --fallow-single-precision -fcond-mismatch @gol --fsigned-bitfields -fsigned-char @gol --funsigned-bitfields -funsigned-char @gol --fwritable-strings -fshort-wchar} - -@item C++ Language Options -@xref{C++ Dialect Options,,Options Controlling C++ Dialect}. -@gccoptlist{ --fno-access-control -fcheck-new -fconserve-space @gol --fno-const-strings -fdollars-in-identifiers @gol --fno-elide-constructors @gol --fno-enforce-eh-specs -fexternal-templates @gol --falt-external-templates @gol --ffor-scope -fno-for-scope -fno-gnu-keywords -fhonor-std @gol --fno-implicit-templates @gol --fno-implicit-inline-templates @gol --fno-implement-inlines -fms-extensions @gol --fno-nonansi-builtins -fno-operator-names @gol --fno-optional-diags -fpermissive @gol --frepo -fno-rtti -fstats -ftemplate-depth-@var{n} @gol --fuse-cxa-atexit -fvtable-gc -fno-weak -nostdinc++ @gol --fno-default-inline -Wctor-dtor-privacy @gol --Wnon-virtual-dtor -Wreorder @gol --Weffc++ -Wno-deprecated @gol --Wno-non-template-friend -Wold-style-cast @gol --Woverloaded-virtual -Wno-pmf-conversions @gol --Wsign-promo -Wsynth} - -@item Objective-C Language Options -@xref{Objective-C Dialect Options,,Options Controlling Objective-C Dialect}. -@gccoptlist{ --fconstant-string-class=@var{class name} @gol --fgnu-runtime -fnext-runtime -gen-decls @gol --Wno-protocol -Wselector} - -@item Language Independent Options -@xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}. -@gccoptlist{ --fmessage-length=@var{n} @gol --fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}} - -@item Warning Options -@xref{Warning Options,,Options to Request or Suppress Warnings}. -@gccoptlist{ --fsyntax-only -pedantic -pedantic-errors @gol --w -W -Wall -Waggregate-return @gol --Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol --Wconversion -Wdisabled-optimization -Werror @gol --Wfloat-equal -Wformat -Wformat=2 @gol --Wformat-nonliteral -Wformat-security @gol --Wimplicit -Wimplicit-int @gol --Wimplicit-function-declaration @gol --Werror-implicit-function-declaration @gol --Wimport -Winline @gol --Wlarger-than-@var{len} -Wlong-long @gol --Wmain -Wmissing-braces -Wmissing-declarations @gol --Wmissing-format-attribute -Wmissing-noreturn @gol --Wmultichar -Wno-format-extra-args -Wno-format-y2k @gol --Wno-import -Wpacked -Wpadded @gol --Wparentheses -Wpointer-arith -Wredundant-decls @gol --Wreturn-type -Wsequence-point -Wshadow @gol --Wsign-compare -Wswitch -Wsystem-headers @gol --Wtrigraphs -Wundef -Wuninitialized @gol --Wunknown-pragmas -Wunreachable-code @gol --Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol --Wunused-value -Wunused-variable -Wwrite-strings} - -@item C-only Warning Options -@gccoptlist{ --Wbad-function-cast -Wmissing-prototypes -Wnested-externs @gol --Wstrict-prototypes -Wtraditional} - -@item Debugging Options -@xref{Debugging Options,,Options for Debugging Your Program or GCC}. -@gccoptlist{ --a -ax -d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol --fdump-unnumbered -fdump-translation-unit=@var{file} @gol --fdump-class-layout=@var{file} -fmem-report -fpretend-float @gol --fprofile-arcs -ftest-coverage -ftime-report @gol --g -g@var{level} -gcoff -gdwarf -gdwarf-1 -gdwarf-1+ -gdwarf-2 @gol --ggdb -gstabs -gstabs+ -gxcoff -gxcoff+ @gol --p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol --print-prog-name=@var{program} -print-search-dirs -Q @gol --save-temps -time} - -@item Optimization Options -@xref{Optimize Options,,Options that Control Optimization}. -@gccoptlist{ --falign-functions=@var{n} -falign-jumps=@var{n} @gol --falign-labels=@var{n} -falign-loops=@var{n} @gol --fbranch-probabilities -fcaller-saves @gol --fcse-follow-jumps -fcse-skip-blocks -fdata-sections -fdce @gol --fdelayed-branch -fdelete-null-pointer-checks @gol --fexpensive-optimizations -ffast-math -ffloat-store @gol --fforce-addr -fforce-mem -ffunction-sections @gol --fgcse -fgcse-lm -fgcse-sm @gol --finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol --fkeep-static-consts -fmove-all-movables @gol --fno-default-inline -fno-defer-pop @gol --fno-function-cse -fno-guess-branch-probability @gol --fno-inline -fno-math-errno -fno-peephole @gol --funsafe-math-optimizations -fno-trapping-math @gol --fomit-frame-pointer -foptimize-register-move @gol --foptimize-sibling-calls -freduce-all-givs @gol --fregmove -frename-registers @gol --frerun-cse-after-loop -frerun-loop-opt @gol --fschedule-insns -fschedule-insns2 @gol --fsingle-precision-constant -fssa @gol --fstrength-reduce -fstrict-aliasing -fthread-jumps -ftrapv @gol --funroll-all-loops -funroll-loops @gol ---param @var{name}=@var{value} --O -O0 -O1 -O2 -O3 -Os} - -@item Preprocessor Options -@xref{Preprocessor Options,,Options Controlling the Preprocessor}. -@gccoptlist{ --$ -A@var{question}=@var{answer} -A-@var{question}@r{[}=@var{answer}@r{]} @gol --C -dD -dI -dM -dN @gol --D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol --idirafter @var{dir} @gol --include @var{file} -imacros @var{file} @gol --iprefix @var{file} -iwithprefix @var{dir} @gol --iwithprefixbefore @var{dir} -isystem @var{dir} @gol --M -MM -MF -MG -MP -MQ -MT -nostdinc -P -remap @gol --trigraphs -undef -U@var{macro} -Wp\,@var{option}} - -@item Assembler Option -@xref{Assembler Options,,Passing Options to the Assembler}. -@gccoptlist{ --Wa\,@var{option}} - -@item Linker Options -@xref{Link Options,,Options for Linking}. -@gccoptlist{ -@var{object-file-name} -l@var{library} @gol --nostartfiles -nodefaultlibs -nostdlib @gol --s -static -static-libgcc -shared -shared-libgcc -symbolic @gol --Wl\,@var{option} -Xlinker @var{option} @gol --u @var{symbol}} - -@item Directory Options -@xref{Directory Options,,Options for Directory Search}. -@gccoptlist{ --B@var{prefix} -I@var{dir} -I- -L@var{dir} -specs=@var{file}} - -@item Target Options -@c I wrote this xref this way to avoid overfull hbox. -- rms -@xref{Target Options}. -@gccoptlist{ --b @var{machine} -V @var{version}} - -@item Machine Dependent Options -@xref{Submodel Options,,Hardware Models and Configurations}. -@emph{M680x0 Options} -@gccoptlist{ --m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol --m68060 -mcpu32 -m5200 -m68881 -mbitfield -mc68000 -mc68020 @gol --mfpa -mnobitfield -mrtd -mshort -msoft-float -mpcrel @gol --malign-int -mstrict-align} - -@emph{M68hc1x Options} -@gccoptlist{ --m6811 -m6812 -m68hc11 -m68hc12 @gol --mauto-incdec -mshort -msoft-reg-count=@var{count}} - -@emph{VAX Options} -@gccoptlist{ --mg -mgnu -munix} - -@emph{SPARC Options} -@gccoptlist{ --mcpu=@var{cpu type} @gol --mtune=@var{cpu type} @gol --mcmodel=@var{code model} @gol --m32 -m64 @gol --mapp-regs -mbroken-saverestore -mcypress @gol --mepilogue -mfaster-structs -mflat @gol --mfpu -mhard-float -mhard-quad-float @gol --mimpure-text -mlive-g0 -mno-app-regs @gol --mno-epilogue -mno-faster-structs -mno-flat -mno-fpu @gol --mno-impure-text -mno-stack-bias -mno-unaligned-doubles @gol --msoft-float -msoft-quad-float -msparclite -mstack-bias @gol --msupersparc -munaligned-doubles -mv8} - -@emph{Convex Options} -@gccoptlist{ --mc1 -mc2 -mc32 -mc34 -mc38 @gol --margcount -mnoargcount @gol --mlong32 -mlong64 @gol --mvolatile-cache -mvolatile-nocache} - -@emph{AMD29K Options} -@gccoptlist{ --m29000 -m29050 -mbw -mnbw -mdw -mndw @gol --mlarge -mnormal -msmall @gol --mkernel-registers -mno-reuse-arg-regs @gol --mno-stack-check -mno-storem-bug @gol --mreuse-arg-regs -msoft-float -mstack-check @gol --mstorem-bug -muser-registers} - -@emph{ARM Options} -@gccoptlist{ --mapcs-frame -mno-apcs-frame @gol --mapcs-26 -mapcs-32 @gol --mapcs-stack-check -mno-apcs-stack-check @gol --mapcs-float -mno-apcs-float @gol --mapcs-reentrant -mno-apcs-reentrant @gol --msched-prolog -mno-sched-prolog @gol --mlittle-endian -mbig-endian -mwords-little-endian @gol --malignment-traps -mno-alignment-traps @gol --msoft-float -mhard-float -mfpe @gol --mthumb-interwork -mno-thumb-interwork @gol --mcpu=@var{name} -march=@var{name} -mfpe=@var{name} @gol --mstructure-size-boundary=@var{n} @gol --mbsd -mxopen -mno-symrename @gol --mabort-on-noreturn @gol --mlong-calls -mno-long-calls @gol --msingle-pic-base -mno-single-pic-base @gol --mpic-register=@var{reg} @gol --mnop-fun-dllimport @gol --mpoke-function-name @gol --mthumb -marm @gol --mtpcs-frame -mtpcs-leaf-frame @gol --mcaller-super-interworking -mcallee-super-interworking } - -@emph{MN10200 Options} -@gccoptlist{ --mrelax} - -@emph{MN10300 Options} -@gccoptlist{ --mmult-bug @gol --mno-mult-bug @gol --mam33 @gol --mno-am33 @gol --mrelax} - -@emph{M32R/D Options} -@gccoptlist{ --mcode-model=@var{model type} -msdata=@var{sdata type} @gol --G @var{num}} - -@emph{M88K Options} -@gccoptlist{ --m88000 -m88100 -m88110 -mbig-pic @gol --mcheck-zero-division -mhandle-large-shift @gol --midentify-revision -mno-check-zero-division @gol --mno-ocs-debug-info -mno-ocs-frame-position @gol --mno-optimize-arg-area -mno-serialize-volatile @gol --mno-underscores -mocs-debug-info @gol --mocs-frame-position -moptimize-arg-area @gol --mserialize-volatile -mshort-data-@var{num} -msvr3 @gol --msvr4 -mtrap-large-shift -muse-div-instruction @gol --mversion-03.00 -mwarn-passed-structs} - -@emph{RS/6000 and PowerPC Options} -@gccoptlist{ --mcpu=@var{cpu type} @gol --mtune=@var{cpu type} @gol --mpower -mno-power -mpower2 -mno-power2 @gol --mpowerpc -mpowerpc64 -mno-powerpc @gol --mpowerpc-gpopt -mno-powerpc-gpopt @gol --mpowerpc-gfxopt -mno-powerpc-gfxopt @gol --mnew-mnemonics -mold-mnemonics @gol --mfull-toc -mminimal-toc -mno-fop-in-toc -mno-sum-in-toc @gol --m64 -m32 -mxl-call -mno-xl-call -mthreads -mpe @gol --msoft-float -mhard-float -mmultiple -mno-multiple @gol --mstring -mno-string -mupdate -mno-update @gol --mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol --mstrict-align -mno-strict-align -mrelocatable @gol --mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol --mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol --mcall-aix -mcall-sysv -mprototype -mno-prototype @gol --msim -mmvme -mads -myellowknife -memb -msdata @gol --msdata=@var{opt} -mvxworks -G @var{num}} - -@emph{RT Options} -@gccoptlist{ --mcall-lib-mul -mfp-arg-in-fpregs -mfp-arg-in-gregs @gol --mfull-fp-blocks -mhc-struct-return -min-line-mul @gol --mminimum-fp-blocks -mnohc-struct-return} - -@emph{MIPS Options} -@gccoptlist{ --mabicalls -mcpu=@var{cpu type} @gol --membedded-data -muninit-const-in-rodata @gol --membedded-pic -mfp32 -mfp64 -mgas -mgp32 -mgp64 @gol --mgpopt -mhalf-pic -mhard-float -mint64 -mips1 @gol --mips2 -mips3 -mips4 -mlong64 -mlong32 -mlong-calls -mmemcpy @gol --mmips-as -mmips-tfile -mno-abicalls @gol --mno-embedded-data -mno-uninit-const-in-rodata @gol --mno-embedded-pic -mno-gpopt -mno-long-calls @gol --mno-memcpy -mno-mips-tfile -mno-rnames -mno-stats @gol --mrnames -msoft-float @gol --m4650 -msingle-float -mmad @gol --mstats -EL -EB -G @var{num} -nocpp @gol --mabi=32 -mabi=n32 -mabi=64 -mabi=eabi @gol --mfix7000 -mno-crt0} - -@emph{i386 Options} -@gccoptlist{ --mcpu=@var{cpu type} -march=@var{cpu type} @gol --mintel-syntax -mieee-fp -mno-fancy-math-387 @gol --mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol --mno-wide-multiply -mrtd -malign-double @gol --mpreferred-stack-boundary=@var{num} @gol --mthreads -mno-align-stringops -minline-all-stringops @gol --mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol --m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer} - -@emph{HPPA Options} -@gccoptlist{ --march=@var{architecture type} @gol --mbig-switch -mdisable-fpregs -mdisable-indexing @gol --mfast-indirect-calls -mgas -mjump-in-delay @gol --mlong-load-store -mno-big-switch -mno-disable-fpregs @gol --mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol --mno-jump-in-delay -mno-long-load-store @gol --mno-portable-runtime -mno-soft-float @gol --mno-space-regs -msoft-float -mpa-risc-1-0 @gol --mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol --mschedule=@var{cpu type} -mspace-regs} - -@emph{Intel 960 Options} -@gccoptlist{ --m@var{cpu type} -masm-compat -mclean-linkage @gol --mcode-align -mcomplex-addr -mleaf-procedures @gol --mic-compat -mic2.0-compat -mic3.0-compat @gol --mintel-asm -mno-clean-linkage -mno-code-align @gol --mno-complex-addr -mno-leaf-procedures @gol --mno-old-align -mno-strict-align -mno-tail-call @gol --mnumerics -mold-align -msoft-float -mstrict-align @gol --mtail-call} - -@emph{DEC Alpha Options} -@gccoptlist{ --mfp-regs -mno-fp-regs -mno-soft-float -msoft-float @gol --malpha-as -mgas @gol --mieee -mieee-with-inexact -mieee-conformant @gol --mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol --mtrap-precision=@var{mode} -mbuild-constants @gol --mcpu=@var{cpu type} @gol --mbwx -mno-bwx -mcix -mno-cix -mmax -mno-max @gol --mmemory-latency=@var{time}} - -@emph{Clipper Options} -@gccoptlist{ --mc300 -mc400} - -@emph{H8/300 Options} -@gccoptlist{ --mrelax -mh -ms -mint32 -malign-300} - -@emph{SH Options} -@gccoptlist{ --m1 -m2 -m3 -m3e @gol --m4-nofpu -m4-single-only -m4-single -m4 @gol --mb -ml -mdalign -mrelax @gol --mbigtable -mfmovd -mhitachi -mnomacsave @gol --misize -mpadstruct -mspace @gol --mprefergot --musermode} - -@emph{System V Options} -@gccoptlist{ --Qy -Qn -YP\,@var{paths} -Ym\,@var{dir}} - -@emph{ARC Options} -@gccoptlist{ --EB -EL @gol --mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text section} @gol --mdata=@var{data section} -mrodata=@var{readonly data section}} - -@emph{TMS320C3x/C4x Options} -@gccoptlist{ --mcpu=@var{cpu} -mbig -msmall -mregparm -mmemparm @gol --mfast-fix -mmpyi -mbk -mti -mdp-isr-reload @gol --mrpts=@var{count} -mrptb -mdb -mloop-unsigned @gol --mparallel-insns -mparallel-mpy -mpreserve-float} - -@emph{V850 Options} -@gccoptlist{ --mlong-calls -mno-long-calls -mep -mno-ep @gol --mprolog-function -mno-prolog-function -mspace @gol --mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol --mv850 -mbig-switch} - -@emph{NS32K Options} -@gccoptlist{ --m32032 -m32332 -m32532 -m32081 -m32381 @gol --mmult-add -mnomult-add -msoft-float -mrtd -mnortd @gol --mregparam -mnoregparam -msb -mnosb @gol --mbitfield -mnobitfield -mhimem -mnohimem} - -@emph{AVR Options} -@gccoptlist{ --mmcu=@var{mcu} -msize -minit-stack=@var{n} -mno-interrupts @gol --mcall-prologues -mno-tablejump -mtiny-stack} - -@emph{MCore Options} -@gccoptlist{ --mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol --mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol --m4byte-functions -mno-4byte-functions -mcallgraph-data @gol --mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol --mlittle-endian -mbig-endian -m210 -m340 -mstack-increment} - -@emph{IA-64 Options} -@gccoptlist{ --mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol --mvolatile-asm-stop -mb-step -mregister-names -mno-sdata @gol --mconstant-gp -mauto-pic -minline-divide-min-latency @gol --minline-divide-max-throughput -mno-dwarf2-asm @gol --mfixed-range=@var{register range}} - -@item Code Generation Options -@xref{Code Gen Options,,Options for Code Generation Conventions}. -@gccoptlist{ --fcall-saved-@var{reg} -fcall-used-@var{reg} @gol --fexceptions -funwind-tables -ffixed-@var{reg} @gol --finhibit-size-directive -finstrument-functions @gol --fcheck-memory-usage -fprefix-function-name @gol --fno-common -fno-ident -fno-gnu-linker @gol --fpcc-struct-return -fpic -fPIC @gol --freg-struct-return -fshared-data -fshort-enums @gol --fshort-double -fvolatile @gol --fvolatile-global -fvolatile-static @gol --fverbose-asm -fpack-struct -fstack-check @gol --fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol --fargument-alias -fargument-noalias @gol --fargument-noalias-global -fleading-underscore} -@end table - -@menu -* Overall Options:: Controlling the kind of output: - an executable, object files, assembler files, - or preprocessed source. -* C Dialect Options:: Controlling the variant of C language compiled. -* C++ Dialect Options:: Variations on C++. -* Objective-C Dialect Options:: Variations on Objective-C. -* Language Independent Options:: Controlling how diagnostics should be - formatted. -* Warning Options:: How picky should the compiler be? -* Debugging Options:: Symbol tables, measurements, and debugging dumps. -* Optimize Options:: How much optimization? -* Preprocessor Options:: Controlling header files and macro definitions. - Also, getting dependency information for Make. -* Assembler Options:: Passing options to the assembler. -* Link Options:: Specifying libraries and so on. -* Directory Options:: Where to find header files and libraries. - Where to find the compiler executable files. -* Spec Files:: How to pass switches to sub-processes. -* Target Options:: Running a cross-compiler, or an old version of GCC. -@end menu - -@node Overall Options -@section Options Controlling the Kind of Output - -Compilation can involve up to four stages: preprocessing, compilation -proper, assembly and linking, always in that order. The first three -stages apply to an individual source file, and end by producing an -object file; linking combines all the object files (those newly -compiled, and those specified as input) into an executable file. - -@cindex file name suffix -For any given input file, the file name suffix determines what kind of -compilation is done: - -@table @gcctabopt -@item @var{file}.c -C source code which must be preprocessed. - -@item @var{file}.i -C source code which should not be preprocessed. - -@item @var{file}.ii -C++ source code which should not be preprocessed. - -@item @var{file}.m -Objective-C source code. Note that you must link with the library -@file{libobjc.a} to make an Objective-C program work. - -@item @var{file}.mi -Objective-C source code which should not be preprocessed. - -@item @var{file}.h -C header file (not to be compiled or linked). - -@item @var{file}.cc -@itemx @var{file}.cp -@itemx @var{file}.cxx -@itemx @var{file}.cpp -@itemx @var{file}.c++ -@itemx @var{file}.C -C++ source code which must be preprocessed. Note that in @samp{.cxx}, -the last two letters must both be literally @samp{x}. Likewise, -@samp{.C} refers to a literal capital C. - -@item @var{file}.f -@itemx @var{file}.for -@itemx @var{file}.FOR -Fortran source code which should not be preprocessed. - -@item @var{file}.F -@itemx @var{file}.fpp -@itemx @var{file}.FPP -Fortran source code which must be preprocessed (with the traditional -preprocessor). - -@item @var{file}.r -Fortran source code which must be preprocessed with a RATFOR -preprocessor (not included with GCC). - -@xref{Overall Options,,Options Controlling the Kind of Output, g77, -Using and Porting GNU Fortran}, for more details of the handling of -Fortran input files. - -@c FIXME: Descriptions of Java file types. -@c @var{file}.java -@c @var{file}.class -@c @var{file}.zip -@c @var{file}.jar - -@c GCC also knows about some suffixes for languages not yet included: -@c Ada: -@c @var{file}.ads -@c @var{file}.adb -@c @var{file}.ada -@c Pascal: -@c @var{file}.p -@c @var{file}.pas - -@item @var{file}.ch -@itemx @var{file}.chi -CHILL source code (preprocessed with the traditional preprocessor). - -@item @var{file}.s -Assembler code. - -@item @var{file}.S -Assembler code which must be preprocessed. - -@item @var{other} -An object file to be fed straight into linking. -Any file name with no recognized suffix is treated this way. -@end table - -You can specify the input language explicitly with the @samp{-x} option: - -@table @gcctabopt -@item -x @var{language} -Specify explicitly the @var{language} for the following input files -(rather than letting the compiler choose a default based on the file -name suffix). This option applies to all following input files until -the next @samp{-x} option. Possible values for @var{language} are: -@example -c c-header cpp-output -c++ c++-cpp-output -objective-c objc-cpp-output -assembler assembler-with-cpp -f77 f77-cpp-input ratfor -java chill -@end example -@c Also f77-version, for internal use only. - -@item -x none -Turn off any specification of a language, so that subsequent files are -handled according to their file name suffixes (as they are if @samp{-x} -has not been used at all). - -@item -pass-exit-codes -Normally the @command{gcc} program will exit with the code of 1 if any -phase of the compiler returns a non-success return code. If you specify -@samp{-pass-exit-codes}, the @command{gcc} program will instead return with -numerically highest error produced by any phase that returned an error -indication. -@end table - -If you only want some of the stages of compilation, you can use -@samp{-x} (or filename suffixes) to tell @command{gcc} where to start, and -one of the options @samp{-c}, @samp{-S}, or @samp{-E} to say where -@command{gcc} is to stop. Note that some combinations (for example, -@samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all. - -@table @gcctabopt -@item -c -Compile or assemble the source files, but do not link. The linking -stage simply is not done. The ultimate output is in the form of an -object file for each source file. - -By default, the object file name for a source file is made by replacing -the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}. - -Unrecognized input files, not requiring compilation or assembly, are -ignored. - -@item -S -Stop after the stage of compilation proper; do not assemble. The output -is in the form of an assembler code file for each non-assembler input -file specified. - -By default, the assembler file name for a source file is made by -replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}. - -Input files that don't require compilation are ignored. - -@item -E -Stop after the preprocessing stage; do not run the compiler proper. The -output is in the form of preprocessed source code, which is sent to the -standard output. - -Input files which don't require preprocessing are ignored. - -@cindex output file option -@item -o @var{file} -Place output in file @var{file}. This applies regardless to whatever -sort of output is being produced, whether it be an executable file, -an object file, an assembler file or preprocessed C code. - -Since only one output file can be specified, it does not make sense to -use @samp{-o} when compiling more than one input file, unless you are -producing an executable file as output. - -If @samp{-o} is not specified, the default is to put an executable file -in @file{a.out}, the object file for @file{@var{source}.@var{suffix}} in -@file{@var{source}.o}, its assembler file in @file{@var{source}.s}, and -all preprocessed C source on standard output.@refill - -@item -v -Print (on standard error output) the commands executed to run the stages -of compilation. Also print the version number of the compiler driver -program and of the preprocessor and the compiler proper. - -@item -pipe -Use pipes rather than temporary files for communication between the -various stages of compilation. This fails to work on some systems where -the assembler is unable to read from a pipe; but the GNU assembler has -no trouble. - -@item --help -Print (on the standard output) a description of the command line options -understood by @command{gcc}. If the @option{-v} option is also specified -then @option{--help} will also be passed on to the various processes -invoked by @command{gcc}, so that they can display the command line options -they accept. If the @option{-W} option is also specified then command -line options which have no documentation associated with them will also -be displayed. - -@item --target-help -Print (on the standard output) a description of target specific command -line options for each tool. -@end table - -@node Invoking G++ -@section Compiling C++ Programs - -@cindex suffixes for C++ source -@cindex C++ source file suffixes -C++ source files conventionally use one of the suffixes @samp{.C}, -@samp{.cc}, @samp{.cpp}, @samp{.c++}, @samp{.cp}, or @samp{.cxx}; -preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes -files with these names and compiles them as C++ programs even if you -call the compiler the same way as for compiling C programs (usually with -the name @command{gcc}). - -@findex g++ -@findex c++ -However, C++ programs often require class libraries as well as a -compiler that understands the C++ language---and under some -circumstances, you might want to compile programs from standard input, -or otherwise without a suffix that flags them as C++ programs. -@command{g++} is a program that calls GCC with the default language -set to C++, and automatically specifies linking against the C++ -library. On many systems, @command{g++} is also -installed with the name @command{c++}. - -@cindex invoking @command{g++} -When you compile C++ programs, you may specify many of the same -command-line options that you use for compiling programs in any -language; or command-line options meaningful for C and related -languages; or options that are meaningful only for C++ programs. -@xref{C Dialect Options,,Options Controlling C Dialect}, for -explanations of options for languages related to C. -@xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for -explanations of options that are meaningful only for C++ programs. - -@node C Dialect Options -@section Options Controlling C Dialect -@cindex dialect options -@cindex language dialect options -@cindex options, dialect - -The following options control the dialect of C (or languages derived -from C, such as C++ and Objective C) that the compiler accepts: - -@table @gcctabopt -@cindex ANSI support -@cindex ISO support -@item -ansi -In C mode, support all ISO C89 programs. In C++ mode, -remove GNU extensions that conflict with ISO C++. - -This turns off certain features of GCC that are incompatible with ISO -C (when compiling C code), or of standard C++ (when compiling C++ code), -such as the @code{asm} and @code{typeof} keywords, and -predefined macros such as @code{unix} and @code{vax} that identify the -type of system you are using. It also enables the undesirable and -rarely used ISO trigraph feature. For the C compiler, -it disables recognition of C++ style @samp{//} comments as well as -the @code{inline} keyword. - -The alternate keywords @code{__asm__}, @code{__extension__}, -@code{__inline__} and @code{__typeof__} continue to work despite -@samp{-ansi}. You would not want to use them in an ISO C program, of -course, but it is useful to put them in header files that might be included -in compilations done with @samp{-ansi}. Alternate predefined macros -such as @code{__unix__} and @code{__vax__} are also available, with or -without @samp{-ansi}. - -The @samp{-ansi} option does not cause non-ISO programs to be -rejected gratuitously. For that, @samp{-pedantic} is required in -addition to @samp{-ansi}. @xref{Warning Options}. - -The macro @code{__STRICT_ANSI__} is predefined when the @samp{-ansi} -option is used. Some header files may notice this macro and refrain -from declaring certain functions or defining certain macros that the -ISO standard doesn't call for; this is to avoid interfering with any -programs that might use these names for other things. - -Functions which would normally be builtin but do not have semantics -defined by ISO C (such as @code{alloca} and @code{ffs}) are not builtin -functions with @samp{-ansi} is used. @xref{Other Builtins,,Other -built-in functions provided by GNU CC}, for details of the functions -affected. - -@item -std= -Determine the language standard. A value for this option must be provided; -possible values are - -@table @samp -@item iso9899:1990 -Same as @option{-ansi} - -@item iso9899:199409 -ISO C as modified in amend. 1 - -@item iso9899:1999 -ISO C99. Note that this standard is not yet fully supported; see -@w{@uref{http://gcc.gnu.org/c99status.html}} for more information. - -@item c89 -same as @option{-std=iso9899:1990} - -@item c99 -same as @option{-std=iso9899:1999} - -@item gnu89 -default, iso9899:1990 + gnu extensions - -@item gnu99 -iso9899:1999 + gnu extensions - -@item iso9899:199x -same as @option{-std=iso9899:1999}, deprecated - -@item c9x -same as @option{-std=iso9899:1999}, deprecated - -@item gnu9x -same as @option{-std=gnu99}, deprecated - -@end table - -Even when this option is not specified, you can still use some of the -features of newer standards in so far as they do not conflict with -previous C standards. For example, you may use @code{__restrict__} even -when @option{-std=c99} is not specified. - -The @option{-std} options specifying some version of ISO C have the same -effects as @option{-ansi}, except that features that were not in ISO C89 -but are in the specified version (for example, @samp{//} comments and -the @code{inline} keyword in ISO C99) are not disabled. - -@xref{Standards,,Language Standards Supported by GCC}, for details of -these standard versions. - -@item -fno-asm -Do not recognize @code{asm}, @code{inline} or @code{typeof} as a -keyword, so that code can use these words as identifiers. You can use -the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__} -instead. @samp{-ansi} implies @samp{-fno-asm}. - -In C++, this switch only affects the @code{typeof} keyword, since -@code{asm} and @code{inline} are standard keywords. You may want to -use the @samp{-fno-gnu-keywords} flag instead, which has the same -effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this -switch only affects the @code{asm} and @code{typeof} keywords, since -@code{inline} is a standard keyword in ISO C99. - -@item -fno-builtin -@cindex builtin functions -Don't recognize builtin functions that do not begin with -@samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in -functions provided by GNU CC}, for details of the functions affected, -including those which are not builtin functions when @option{-ansi} or -@option{-std} options for strict ISO C conformance are used because they -do not have an ISO standard meaning. - -GCC normally generates special code to handle certain builtin functions -more efficiently; for instance, calls to @code{alloca} may become single -instructions that adjust the stack directly, and calls to @code{memcpy} -may become inline copy loops. The resulting code is often both smaller -and faster, but since the function calls no longer appear as such, you -cannot set a breakpoint on those calls, nor can you change the behavior -of the functions by linking with a different library. - -In C++, @samp{-fno-builtin} is always in effect. The @samp{-fbuiltin} -option has no effect. Therefore, in C++, the only way to get the -optimization benefits of builtin functions is to call the function -using the @samp{__builtin_} prefix. The GNU C++ Standard Library uses -builtin functions to implement many functions (like -@code{std::strchr}), so that you automatically get efficient code. - -@item -fhosted -@cindex hosted environment - -Assert that compilation takes place in a hosted environment. This implies -@samp{-fbuiltin}. A hosted environment is one in which the -entire standard library is available, and in which @code{main} has a return -type of @code{int}. Examples are nearly everything except a kernel. -This is equivalent to @samp{-fno-freestanding}. - -@item -ffreestanding -@cindex hosted environment - -Assert that compilation takes place in a freestanding environment. This -implies @samp{-fno-builtin}. A freestanding environment -is one in which the standard library may not exist, and program startup may -not necessarily be at @code{main}. The most obvious example is an OS kernel. -This is equivalent to @samp{-fno-hosted}. - -@xref{Standards,,Language Standards Supported by GCC}, for details of -freestanding and hosted environments. - -@item -trigraphs -Support ISO C trigraphs. You don't want to know about this -brain-damage. The @option{-ansi} option (and @option{-std} options for -strict ISO C conformance) implies @option{-trigraphs}. - -@cindex traditional C language -@cindex C language, traditional -@item -traditional -Attempt to support some aspects of traditional C compilers. -Specifically: - -@itemize @bullet -@item -All @code{extern} declarations take effect globally even if they -are written inside of a function definition. This includes implicit -declarations of functions. - -@item -The newer keywords @code{typeof}, @code{inline}, @code{signed}, @code{const} -and @code{volatile} are not recognized. (You can still use the -alternative keywords such as @code{__typeof__}, @code{__inline__}, and -so on.) - -@item -Comparisons between pointers and integers are always allowed. - -@item -Integer types @code{unsigned short} and @code{unsigned char} promote -to @code{unsigned int}. - -@item -Out-of-range floating point literals are not an error. - -@item -Certain constructs which ISO regards as a single invalid preprocessing -number, such as @samp{0xe-0xd}, are treated as expressions instead. - -@item -String ``constants'' are not necessarily constant; they are stored in -writable space, and identical looking constants are allocated -separately. (This is the same as the effect of -@samp{-fwritable-strings}.) - -@cindex @code{longjmp} and automatic variables -@item -All automatic variables not declared @code{register} are preserved by -@code{longjmp}. Ordinarily, GNU C follows ISO C: automatic variables -not declared @code{volatile} may be clobbered. - -@item -@kindex \x -@kindex \a -@cindex escape sequences, traditional -The character escape sequences @samp{\x} and @samp{\a} evaluate as the -literal characters @samp{x} and @samp{a} respectively. Without -@w{@samp{-traditional}}, @samp{\x} is a prefix for the hexadecimal -representation of a character, and @samp{\a} produces a bell. -@end itemize - -You may wish to use @samp{-fno-builtin} as well as @samp{-traditional} -if your program uses names that are normally GNU C builtin functions for -other purposes of its own. - -You cannot use @samp{-traditional} if you include any header files that -rely on ISO C features. Some vendors are starting to ship systems with -ISO C header files and you cannot use @samp{-traditional} on such -systems to compile files that include any system headers. - -The @samp{-traditional} option also enables @samp{-traditional-cpp}, -which is described next. - -@item -traditional-cpp -Attempt to support some aspects of traditional C preprocessors. -Specifically: - -@itemize @bullet -@item -Comments convert to nothing at all, rather than to a space. This allows -traditional token concatenation. - -@item -In a preprocessing directive, the @samp{#} symbol must appear as the first -character of a line. - -@item -Macro arguments are recognized within string constants in a macro -definition (and their values are stringified, though without additional -quote marks, when they appear in such a context). The preprocessor -always considers a string constant to end at a newline. - -@item -@cindex detecting @w{@samp{-traditional}} -The predefined macro @code{__STDC__} is not defined when you use -@samp{-traditional}, but @code{__GNUC__} is (since the GNU extensions -which @code{__GNUC__} indicates are not affected by -@samp{-traditional}). If you need to write header files that work -differently depending on whether @samp{-traditional} is in use, by -testing both of these predefined macros you can distinguish four -situations: GNU C, traditional GNU C, other ISO C compilers, and other -old C compilers. The predefined macro @code{__STDC_VERSION__} is also -not defined when you use @samp{-traditional}. @xref{Standard -Predefined,,Standard Predefined Macros,cpp.info,The C Preprocessor}, -for more discussion of these and other predefined macros. - -@item -@cindex string constants vs newline -@cindex newline vs string constants -The preprocessor considers a string constant to end at a newline (unless -the newline is escaped with @samp{\}). (Without @w{@samp{-traditional}}, -string constants can contain the newline character as typed.) -@end itemize - -@item -fcond-mismatch -Allow conditional expressions with mismatched types in the second and -third arguments. The value of such an expression is void. This option -is not supported for C++. - -@item -funsigned-char -Let the type @code{char} be unsigned, like @code{unsigned char}. - -Each kind of machine has a default for what @code{char} should -be. It is either like @code{unsigned char} by default or like -@code{signed char} by default. - -Ideally, a portable program should always use @code{signed char} or -@code{unsigned char} when it depends on the signedness of an object. -But many programs have been written to use plain @code{char} and -expect it to be signed, or expect it to be unsigned, depending on the -machines they were written for. This option, and its inverse, let you -make such a program work with the opposite default. - -The type @code{char} is always a distinct type from each of -@code{signed char} or @code{unsigned char}, even though its behavior -is always just like one of those two. - -@item -fsigned-char -Let the type @code{char} be signed, like @code{signed char}. - -Note that this is equivalent to @samp{-fno-unsigned-char}, which is -the negative form of @samp{-funsigned-char}. Likewise, the option -@samp{-fno-signed-char} is equivalent to @samp{-funsigned-char}. - -You may wish to use @samp{-fno-builtin} as well as @samp{-traditional} -if your program uses names that are normally GNU C builtin functions for -other purposes of its own. - -You cannot use @samp{-traditional} if you include any header files that -rely on ISO C features. Some vendors are starting to ship systems with -ISO C header files and you cannot use @samp{-traditional} on such -systems to compile files that include any system headers. - -@item -fsigned-bitfields -@itemx -funsigned-bitfields -@itemx -fno-signed-bitfields -@itemx -fno-unsigned-bitfields -These options control whether a bitfield is signed or unsigned, when the -declaration does not use either @code{signed} or @code{unsigned}. By -default, such a bitfield is signed, because this is consistent: the -basic integer types such as @code{int} are signed types. - -However, when @samp{-traditional} is used, bitfields are all unsigned -no matter what. - -@item -fwritable-strings -Store string constants in the writable data segment and don't uniquize -them. This is for compatibility with old programs which assume they can -write into string constants. The option @samp{-traditional} also has -this effect. - -Writing into string constants is a very bad idea; ``constants'' should -be constant. - -@item -fallow-single-precision -Do not promote single precision math operations to double precision, -even when compiling with @samp{-traditional}. - -Traditional K&R C promotes all floating point operations to double -precision, regardless of the sizes of the operands. On the -architecture for which you are compiling, single precision may be faster -than double precision. If you must use @samp{-traditional}, but want -to use single precision operations when the operands are single -precision, use this option. This option has no effect when compiling -with ISO or GNU C conventions (the default). - -@item -fshort-wchar -Override the underlying type for @samp{wchar_t} to be @samp{short -unsigned int} instead of the default for the target. This option is -useful for building programs to run under WINE. -@end table - -@node C++ Dialect Options -@section Options Controlling C++ Dialect - -@cindex compiler options, C++ -@cindex C++ options, command line -@cindex options, C++ -This section describes the command-line options that are only meaningful -for C++ programs; but you can also use most of the GNU compiler options -regardless of what language your program is in. For example, you -might compile a file @code{firstClass.C} like this: - -@example -g++ -g -frepo -O -c firstClass.C -@end example - -@noindent -In this example, only @samp{-frepo} is an option meant -only for C++ programs; you can use the other options with any -language supported by GCC. - -Here is a list of options that are @emph{only} for compiling C++ programs: - -@table @gcctabopt -@item -fno-access-control -Turn off all access checking. This switch is mainly useful for working -around bugs in the access control code. - -@item -fcheck-new -Check that the pointer returned by @code{operator new} is non-null -before attempting to modify the storage allocated. The current Working -Paper requires that @code{operator new} never return a null pointer, so -this check is normally unnecessary. - -An alternative to using this option is to specify that your -@code{operator new} does not throw any exceptions; if you declare it -@samp{throw()}, g++ will check the return value. See also @samp{new -(nothrow)}. - -@item -fconserve-space -Put uninitialized or runtime-initialized global variables into the -common segment, as C does. This saves space in the executable at the -cost of not diagnosing duplicate definitions. If you compile with this -flag and your program mysteriously crashes after @code{main()} has -completed, you may have an object that is being destroyed twice because -two definitions were merged. - -This option is no longer useful on most targets, now that support has -been added for putting variables into BSS without making them common. - -@item -fno-const-strings -Give string constants type @code{char *} instead of type @code{const -char *}. By default, G++ uses type @code{const char *} as required by -the standard. Even if you use @samp{-fno-const-strings}, you cannot -actually modify the value of a string constant, unless you also use -@samp{-fwritable-strings}. - -This option might be removed in a future release of G++. For maximum -portability, you should structure your code so that it works with -string constants that have type @code{const char *}. - -@item -fdollars-in-identifiers -Accept @samp{$} in identifiers. You can also explicitly prohibit use of -@samp{$} with the option @samp{-fno-dollars-in-identifiers}. (GNU C allows -@samp{$} by default on most target systems, but there are a few exceptions.) -Traditional C allowed the character @samp{$} to form part of -identifiers. However, ISO C and C++ forbid @samp{$} in identifiers. - -@item -fno-elide-constructors -The C++ standard allows an implementation to omit creating a temporary -which is only used to initialize another object of the same type. -Specifying this option disables that optimization, and forces g++ to -call the copy constructor in all cases. - -@item -fno-enforce-eh-specs -Don't check for violation of exception specifications at runtime. This -option violates the C++ standard, but may be useful for reducing code -size in production builds, much like defining @samp{NDEBUG}. The compiler -will still optimize based on the exception specifications. - -@item -fexternal-templates -Cause template instantiations to obey @samp{#pragma interface} and -@samp{implementation}; template instances are emitted or not according -to the location of the template definition. @xref{Template -Instantiation}, for more information. - -This option is deprecated. - -@item -falt-external-templates -Similar to -fexternal-templates, but template instances are emitted or -not according to the place where they are first instantiated. -@xref{Template Instantiation}, for more information. - -This option is deprecated. - -@item -ffor-scope -@itemx -fno-for-scope -If -ffor-scope is specified, the scope of variables declared in -a @i{for-init-statement} is limited to the @samp{for} loop itself, -as specified by the C++ standard. -If -fno-for-scope is specified, the scope of variables declared in -a @i{for-init-statement} extends to the end of the enclosing scope, -as was the case in old versions of gcc, and other (traditional) -implementations of C++. - -The default if neither flag is given to follow the standard, -but to allow and give a warning for old-style code that would -otherwise be invalid, or have different behavior. - -@item -fno-gnu-keywords -Do not recognize @code{typeof} as a keyword, so that code can use this -word as an identifier. You can use the keyword @code{__typeof__} instead. -@samp{-ansi} implies @samp{-fno-gnu-keywords}. - -@item -fhonor-std -Treat the @code{namespace std} as a namespace, instead of ignoring -it. For compatibility with earlier versions of g++, the compiler will, -by default, ignore @code{namespace-declarations}, -@code{using-declarations}, @code{using-directives}, and -@code{namespace-names}, if they involve @code{std}. - -@item -fno-implicit-templates -Never emit code for non-inline templates which are instantiated -implicitly (i.e. by use); only emit code for explicit instantiations. -@xref{Template Instantiation}, for more information. - -@item -fno-implicit-inline-templates -Don't emit code for implicit instantiations of inline templates, either. -The default is to handle inlines differently so that compiles with and -without optimization will need the same set of explicit instantiations. - -@item -fno-implement-inlines -To save space, do not emit out-of-line copies of inline functions -controlled by @samp{#pragma implementation}. This will cause linker -errors if these functions are not inlined everywhere they are called. - -@item -fms-extensions -Disable pedantic warnings about constructs used in MFC, such as implicit -int and getting a pointer to member function via non-standard syntax. - -@item -fno-nonansi-builtins -Disable builtin declarations of functions that are not mandated by -ANSI/ISO C. These include @code{ffs}, @code{alloca}, @code{_exit}, -@code{index}, @code{bzero}, @code{conjf}, and other related functions. - -@item -fno-operator-names -Do not treat the operator name keywords @code{and}, @code{bitand}, -@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as -synonyms as keywords. - -@item -fno-optional-diags -Disable diagnostics that the standard says a compiler does not need to -issue. Currently, the only such diagnostic issued by g++ is the one for -a name having multiple meanings within a class. - -@item -fpermissive -Downgrade messages about nonconformant code from errors to warnings. By -default, g++ effectively sets @samp{-pedantic-errors} without -@samp{-pedantic}; this option reverses that. This behavior and this -option are superseded by @samp{-pedantic}, which works as it does for GNU C. - -@item -frepo -Enable automatic template instantiation. This option also implies -@samp{-fno-implicit-templates}. @xref{Template Instantiation}, for more -information. - -@item -fno-rtti -Disable generation of information about every class with virtual -functions for use by the C++ runtime type identification features -(@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts -of the language, you can save some space by using this flag. Note that -exception handling uses the same information, but it will generate it as -needed. - -@item -fstats -Emit statistics about front-end processing at the end of the compilation. -This information is generally only useful to the G++ development team. - -@item -ftemplate-depth-@var{n} -Set the maximum instantiation depth for template classes to @var{n}. -A limit on the template instantiation depth is needed to detect -endless recursions during template class instantiation. ANSI/ISO C++ -conforming programs must not rely on a maximum depth greater than 17. - -@item -fuse-cxa-atexit -Register destructors for objects with static storage duration with the -@code{__cxa_atexit} function rather than the @code{atexit} function. -This option is required for fully standards-compliant handling of static -destructors, but will only work if your C library supports -@code{__cxa_atexit}. - -@item -fvtable-gc -Emit special relocations for vtables and virtual function references -so that the linker can identify unused virtual functions and zero out -vtable slots that refer to them. This is most useful with -@samp{-ffunction-sections} and @samp{-Wl,--gc-sections}, in order to -also discard the functions themselves. - -This optimization requires GNU as and GNU ld. Not all systems support -this option. @samp{-Wl,--gc-sections} is ignored without @samp{-static}. - -@item -fno-weak -Do not use weak symbol support, even if it is provided by the linker. -By default, G++ will use weak symbols if they are available. This -option exists only for testing, and should not be used by end-users; -it will result in inferior code and has no benefits. This option may -be removed in a future release of G++. - -@item -nostdinc++ -Do not search for header files in the standard directories specific to -C++, but do still search the other standard directories. (This option -is used when building the C++ library.) -@end table - -In addition, these optimization, warning, and code generation options -have meanings only for C++ programs: - -@table @gcctabopt -@item -fno-default-inline -Do not assume @samp{inline} for functions defined inside a class scope. -@xref{Optimize Options,,Options That Control Optimization}. Note that these -functions will have linkage like inline functions; they just won't be -inlined by default. - -@item -Wctor-dtor-privacy (C++ only) -Warn when a class seems unusable, because all the constructors or -destructors in a class are private and the class has no friends or -public static member functions. - -@item -Wnon-virtual-dtor (C++ only) -Warn when a class declares a non-virtual destructor that should probably -be virtual, because it looks like the class will be used polymorphically. - -@item -Wreorder (C++ only) -@cindex reordering, warning -@cindex warning for reordering of member initializers -Warn when the order of member initializers given in the code does not -match the order in which they must be executed. For instance: - -@smallexample -struct A @{ - int i; - int j; - A(): j (0), i (1) @{ @} -@}; -@end smallexample - -Here the compiler will warn that the member initializers for @samp{i} -and @samp{j} will be rearranged to match the declaration order of the -members. -@end table - -The following @samp{-W@dots{}} options are not affected by @samp{-Wall}. - -@table @gcctabopt -@item -Weffc++ (C++ only) -Warn about violations of various style guidelines from Scott Meyers' -@cite{Effective C++} books. If you use this option, you should be aware -that the standard library headers do not obey all of these guidelines; -you can use @samp{grep -v} to filter out those warnings. - -@item -Wno-deprecated (C++ only) -Do not warn about usage of deprecated features. @xref{Deprecated Features}. - -@item -Wno-non-template-friend (C++ only) -Disable warnings when non-templatized friend functions are declared -within a template. With the advent of explicit template specification -support in g++, if the name of the friend is an unqualified-id (ie, -@samp{friend foo(int)}), the C++ language specification demands that the -friend declare or define an ordinary, nontemplate function. (Section -14.5.3). Before g++ implemented explicit specification, unqualified-ids -could be interpreted as a particular specialization of a templatized -function. Because this non-conforming behavior is no longer the default -behavior for g++, @samp{-Wnon-template-friend} allows the compiler to -check existing code for potential trouble spots, and is on by default. -This new compiler behavior can be turned off with -@samp{-Wno-non-template-friend} which keeps the conformant compiler code -but disables the helpful warning. - -@item -Wold-style-cast (C++ only) -Warn if an old-style (C-style) cast is used within a C++ program. The -new-style casts (@samp{static_cast}, @samp{reinterpret_cast}, and -@samp{const_cast}) are less vulnerable to unintended effects, and much -easier to grep for. - -@item -Woverloaded-virtual (C++ only) -@cindex overloaded virtual fn, warning -@cindex warning for overloaded virtual fn -Warn when a function declaration hides virtual functions from a -base class. For example, in: - -@smallexample -struct A @{ - virtual void f(); -@}; - -struct B: public A @{ - void f(int); -@}; -@end smallexample - -the @code{A} class version of @code{f} is hidden in @code{B}, and code -like this: - -@smallexample -B* b; -b->f(); -@end smallexample - -will fail to compile. - -@item -Wno-pmf-conversions (C++ only) -Disable the diagnostic for converting a bound pointer to member function -to a plain pointer. - -@item -Wsign-promo (C++ only) -Warn when overload resolution chooses a promotion from unsigned or -enumeral type to a signed type over a conversion to an unsigned type of -the same size. Previous versions of g++ would try to preserve -unsignedness, but the standard mandates the current behavior. - -@item -Wsynth (C++ only) -@cindex warning for synthesized methods -@cindex synthesized methods, warning -Warn when g++'s synthesis behavior does not match that of cfront. For -instance: - -@smallexample -struct A @{ - operator int (); - A& operator = (int); -@}; - -main () -@{ - A a,b; - a = b; -@} -@end smallexample - -In this example, g++ will synthesize a default @samp{A& operator = -(const A&);}, while cfront will use the user-defined @samp{operator =}. -@end table - -@node Objective-C Dialect Options -@section Options Controlling Objective-C Dialect - -@cindex compiler options, Objective-C -@cindex Objective-C options, command line -@cindex options, Objective-C -This section describes the command-line options that are only meaningful -for Objective-C programs; but you can also use most of the GNU compiler -options regardless of what language your program is in. For example, -you might compile a file @code{some_class.m} like this: - -@example -gcc -g -fgnu-runtime -O -c some_class.m -@end example - -@noindent -In this example, only @samp{-fgnu-runtime} is an option meant only for -Objective-C programs; you can use the other options with any language -supported by GCC. - -Here is a list of options that are @emph{only} for compiling Objective-C -programs: - -@table @gcctabopt -@item -fconstant-string-class=@var{class name} -Use @var{class name} as the name of the class to instantiate for each -literal string specified with the syntax @code{@@"..."}. The default -class name is @code{NXConstantString}. - -@item -fgnu-runtime -Generate object code compatible with the standard GNU Objective-C -runtime. This is the default for most types of systems. - -@item -fnext-runtime -Generate output compatible with the NeXT runtime. This is the default -for NeXT-based systems, including Darwin and Mac OS X. - -@item -gen-decls -Dump interface declarations for all classes seen in the source file to a -file named @file{@var{sourcename}.decl}. - -@item -Wno-protocol -Do not warn if methods required by a protocol are not implemented -in the class adopting it. - -@item -Wselector -Warn if a selector has multiple methods of different types defined. - -@c not documented because only avail via -Wp -@c @item -print-objc-runtime-info - -@end table - -@node Language Independent Options -@section Options to Control Diagnostic Messages Formatting -@cindex options to control diagnostics formatting -@cindex diagnostic messages -@cindex message formatting - -Traditionally, diagnostic messages have been formatted irrespective of -the output device's aspect (e.g. its width, ...). The options described -below can be used to control the diagnostic messages formatting -algorithm, e.g. how many characters per line, how often source location -information should be reported. Right now, only the C++ front-end can -honor these options. However it is expected, in the near future, that -the remaining front-ends would be able to digest them correctly. - -@table @gcctabopt -@item -fmessage-length=@var{n} -Try to format error messages so that they fit on lines of about @var{n} -characters. The default is 72 characters for g++ and 0 for the rest of -the front-ends supported by GCC. If @var{n} is zero, then no -line-wrapping will be done; each error message will appear on a single -line. - -@item -fdiagnostics-show-location=once -Only meaningful in line-wrapping mode. Instructs the diagnostic messages -reporter to emit @emph{once} source location information; that is, in -case the message is too long to fit on a single physical line and has to -be wrapped, the source location won't be emitted (as prefix) again, -over and over, in subsequent continuation lines. This is the default -behaviour. - -@item -fdiagnostics-show-location=every-line -Only meaningful in line-wrapping mode. Instructs the diagnostic -messages reporter to emit the same source location information (as -prefix) for physical lines that result from the process of breaking a -a message which is too long to fit on a single line. - -@end table - -@node Warning Options -@section Options to Request or Suppress Warnings -@cindex options to control warnings -@cindex warning messages -@cindex messages, warning -@cindex suppressing warnings - -Warnings are diagnostic messages that report constructions which -are not inherently erroneous but which are risky or suggest there -may have been an error. - -You can request many specific warnings with options beginning @samp{-W}, -for example @samp{-Wimplicit} to request warnings on implicit -declarations. Each of these specific warning options also has a -negative form beginning @samp{-Wno-} to turn off warnings; -for example, @samp{-Wno-implicit}. This manual lists only one of the -two forms, whichever is not the default. - -These options control the amount and kinds of warnings produced by GCC: - -@table @gcctabopt -@cindex syntax checking -@item -fsyntax-only -Check the code for syntax errors, but don't do anything beyond that. - -@item -pedantic -Issue all the warnings demanded by strict ISO C and ISO C++; -reject all programs that use forbidden extensions, and some other -programs that do not follow ISO C and ISO C++. For ISO C, follows the -version of the ISO C standard specified by any @samp{-std} option used. - -Valid ISO C and ISO C++ programs should compile properly with or without -this option (though a rare few will require @option{-ansi} or a -@option{-std} option specifying the required version of ISO C). However, -without this option, certain GNU extensions and traditional C and C++ -features are supported as well. With this option, they are rejected. - -@samp{-pedantic} does not cause warning messages for use of the -alternate keywords whose names begin and end with @samp{__}. Pedantic -warnings are also disabled in the expression that follows -@code{__extension__}. However, only system header files should use -these escape routes; application programs should avoid them. -@xref{Alternate Keywords}. - -Some users try to use @samp{-pedantic} to check programs for strict ISO -C conformance. They soon find that it does not do quite what they want: -it finds some non-ISO practices, but not all---only those for which -ISO C @emph{requires} a diagnostic, and some others for which -diagnostics have been added. - -A feature to report any failure to conform to ISO C might be useful in -some instances, but would require considerable additional work and would -be quite different from @samp{-pedantic}. We don't have plans to -support such a feature in the near future. - -Where the standard specified with @option{-std} represents a GNU -extended dialect of C, such as @samp{gnu89} or @samp{gnu99}, there is a -corresponding @dfn{base standard}, the version of ISO C on which the GNU -extended dialect is based. Warnings from @option{-pedantic} are given -where they are required by the base standard. (It would not make sense -for such warnings to be given only for features not in the specified GNU -C dialect, since by definition the GNU dialects of C include all -features the compiler supports with the given option, and there would be -nothing to warn about.) - -@item -pedantic-errors -Like @samp{-pedantic}, except that errors are produced rather than -warnings. - -@item -w -Inhibit all warning messages. - -@item -Wno-import -Inhibit warning messages about the use of @samp{#import}. - -@item -Wchar-subscripts -Warn if an array subscript has type @code{char}. This is a common cause -of error, as programmers often forget that this type is signed on some -machines. - -@item -Wcomment -Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*} -comment, or whenever a Backslash-Newline appears in a @samp{//} comment. - -@item -Wformat -Check calls to @code{printf} and @code{scanf}, etc., to make sure that -the arguments supplied have types appropriate to the format string -specified, and that the conversions specified in the format string make -sense. This includes standard functions, and others specified by format -attributes (@pxref{Function Attributes}), in the @code{printf}, -@code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension, -not in the C standard) families. - -The formats are checked against the format features supported by GNU -libc version 2.2. These include all ISO C89 and C99 features, as well -as features from the Single Unix Specification and some BSD and GNU -extensions. Other library implementations may not support all these -features; GCC does not support warning about features that go beyond a -particular library's limitations. However, if @samp{-pedantic} is used -with @samp{-Wformat}, warnings will be given about format features not -in the selected standard version (but not for @code{strfmon} formats, -since those are not in any version of the C standard). @xref{C Dialect -Options,,Options Controlling C Dialect}. - -@samp{-Wformat} is included in @samp{-Wall}. For more control over some -aspects of format checking, the options @samp{-Wno-format-y2k}, -@samp{-Wno-format-extra-args}, @samp{-Wformat-nonliteral}, -@samp{-Wformat-security} and @samp{-Wformat=2} are available, but are -not included in @samp{-Wall}. - -@item -Wno-format-y2k -If @samp{-Wformat} is specified, do not warn about @code{strftime} -formats which may yield only a two-digit year. - -@item -Wno-format-extra-args -If @samp{-Wformat} is specified, do not warn about excess arguments to a -@code{printf} or @code{scanf} format function. The C standard specifies -that such arguments are ignored. - -@item -Wformat-nonliteral -If @samp{-Wformat} is specified, also warn if the format string is not a -string literal and so cannot be checked, unless the format function -takes its format arguments as a @code{va_list}. - -@item -Wformat-security -If @samp{-Wformat} is specified, also warn about uses of format -functions that represent possible security problems. At present, this -warns about calls to @code{printf} and @code{scanf} functions where the -format string is not a string literal and there are no format arguments, -as in @code{printf (foo);}. This may be a security hole if the format -string came from untrusted input and contains @samp{%n}. (This is -currently a subset of what @samp{-Wformat-nonliteral} warns about, but -in future warnings may be added to @samp{-Wformat-security} that are not -included in @samp{-Wformat-nonliteral}.) - -@item -Wformat=2 -Enable @samp{-Wformat} plus format checks not included in -@samp{-Wformat}. Currently equivalent to @samp{-Wformat --Wformat-nonliteral -Wformat-security}. - -@item -Wimplicit-int -Warn when a declaration does not specify a type. - -@item -Wimplicit-function-declaration -@itemx -Werror-implicit-function-declaration -Give a warning (or error) whenever a function is used before being -declared. - -@item -Wimplicit -Same as @samp{-Wimplicit-int} and @samp{-Wimplicit-function-}@* -@samp{declaration}. - -@item -Wmain -Warn if the type of @samp{main} is suspicious. @samp{main} should be a -function with external linkage, returning int, taking either zero -arguments, two, or three arguments of appropriate types. - -@item -Wmissing-braces -Warn if an aggregate or union initializer is not fully bracketed. In -the following example, the initializer for @samp{a} is not fully -bracketed, but that for @samp{b} is fully bracketed. - -@smallexample -int a[2][2] = @{ 0, 1, 2, 3 @}; -int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @}; -@end smallexample - -@item -Wmultichar -Warn if a multicharacter constant (@samp{'FOOF'}) is used. Usually they -indicate a typo in the user's code, as they have implementation-defined -values, and should not be used in portable code. - -@item -Wparentheses -Warn if parentheses are omitted in certain contexts, such -as when there is an assignment in a context where a truth value -is expected, or when operators are nested whose precedence people -often get confused about. - -Also warn about constructions where there may be confusion to which -@code{if} statement an @code{else} branch belongs. Here is an example of -such a case: - -@smallexample -@{ - if (a) - if (b) - foo (); - else - bar (); -@} -@end smallexample - -In C, every @code{else} branch belongs to the innermost possible @code{if} -statement, which in this example is @code{if (b)}. This is often not -what the programmer expected, as illustrated in the above example by -indentation the programmer chose. When there is the potential for this -confusion, GNU C will issue a warning when this flag is specified. -To eliminate the warning, add explicit braces around the innermost -@code{if} statement so there is no way the @code{else} could belong to -the enclosing @code{if}. The resulting code would look like this: - -@smallexample -@{ - if (a) - @{ - if (b) - foo (); - else - bar (); - @} -@} -@end smallexample - -@item -Wsequence-point -Warn about code that may have undefined semantics because of violations -of sequence point rules in the C standard. - -The C standard defines the order in which expressions in a C program are -evaluated in terms of @dfn{sequence points}, which represent a partial -ordering between the execution of parts of the program: those executed -before the sequence point, and those executed after it. These occur -after the evaluation of a full expression (one which is not part of a -larger expression), after the evaluation of the first operand of a -@code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a -function is called (but after the evaluation of its arguments and the -expression denoting the called function), and in certain other places. -Other than as expressed by the sequence point rules, the order of -evaluation of subexpressions of an expression is not specified. All -these rules describe only a partial order rather than a total order, -since, for example, if two functions are called within one expression -with no sequence point between them, the order in which the functions -are called is not specified. However, the standards committee have -ruled that function calls do not overlap. - -It is not specified when between sequence points modifications to the -values of objects take effect. Programs whose behavior depends on this -have undefined behavior; the C standard specifies that ``Between the -previous and next sequence point an object shall have its stored value -modified at most once by the evaluation of an expression. Furthermore, -the prior value shall be read only to determine the value to be -stored.''. If a program breaks these rules, the results on any -particular implementation are entirely unpredictable. - -Examples of code with undefined behavior are @code{a = a++;}, @code{a[n] -= b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not -diagnosed by this option, and it may give an occasional false positive -result, but in general it has been found fairly effective at detecting -this sort of problem in programs. - -The present implementation of this option only works for C programs. A -future implementation may also work for C++ programs. - -There is some controversy over the precise meaning of the sequence point -rules in subtle cases. Alternative formal definitions may be found in -Clive Feather's ``Annex S'' -@w{@uref{http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n925.htm}} and in -Michael Norrish's thesis -@w{@uref{http://www.cl.cam.ac.uk/users/mn200/PhD/thesis-report.ps.gz}}. -Other discussions are by Raymond Mak -@w{@uref{http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n926.htm}} and -D. Hugh Redelmeier -@w{@uref{http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/n927.htm}}. - -@item -Wreturn-type -Warn whenever a function is defined with a return-type that defaults to -@code{int}. Also warn about any @code{return} statement with no -return-value in a function whose return-type is not @code{void}. - -For C++, a function without return type always produces a diagnostic -message, even when @samp{-Wno-return-type} is specified. The only -exceptions are @samp{main} and functions defined in system headers. - -@item -Wswitch -Warn whenever a @code{switch} statement has an index of enumeral type -and lacks a @code{case} for one or more of the named codes of that -enumeration. (The presence of a @code{default} label prevents this -warning.) @code{case} labels outside the enumeration range also -provoke warnings when this option is used. - -@item -Wtrigraphs -Warn if any trigraphs are encountered that might change the meaning of -the program (trigraphs within comments are not warned about). - -@item -Wunused-function -Warn whenever a static function is declared but not defined or a -non\-inline static function is unused. - -@item -Wunused-label -Warn whenever a label is declared but not used. - -To suppress this warning use the @samp{unused} attribute -(@pxref{Variable Attributes}). - -@item -Wunused-parameter -Warn whenever a function parameter is unused aside from its declaration. - -To suppress this warning use the @samp{unused} attribute -(@pxref{Variable Attributes}). - -@item -Wunused-variable -Warn whenever a local variable or non-constant static variable is unused -aside from its declaration - -To suppress this warning use the @samp{unused} attribute -(@pxref{Variable Attributes}). - -@item -Wunused-value -Warn whenever a statement computes a result that is explicitly not used. - -To suppress this warning cast the expression to @samp{void}. - -@item -Wunused -All all the above @samp{-Wunused} options combined. - -In order to get a warning about an unused function parameter, you must -either specify @samp{-W -Wunused} or separately specify -@samp{-Wunused-parameter}. - -@item -Wuninitialized -Warn if an automatic variable is used without first being initialized or -if a variable may be clobbered by a @code{setjmp} call. - -These warnings are possible only in optimizing compilation, -because they require data flow information that is computed only -when optimizing. If you don't specify @samp{-O}, you simply won't -get these warnings. - -These warnings occur only for variables that are candidates for -register allocation. Therefore, they do not occur for a variable that -is declared @code{volatile}, or whose address is taken, or whose size -is other than 1, 2, 4 or 8 bytes. Also, they do not occur for -structures, unions or arrays, even when they are in registers. - -Note that there may be no warning about a variable that is used only -to compute a value that itself is never used, because such -computations may be deleted by data flow analysis before the warnings -are printed. - -These warnings are made optional because GCC is not smart -enough to see all the reasons why the code might be correct -despite appearing to have an error. Here is one example of how -this can happen: - -@smallexample -@{ - int x; - switch (y) - @{ - case 1: x = 1; - break; - case 2: x = 4; - break; - case 3: x = 5; - @} - foo (x); -@} -@end smallexample - -@noindent -If the value of @code{y} is always 1, 2 or 3, then @code{x} is -always initialized, but GCC doesn't know this. Here is -another common case: - -@smallexample -@{ - int save_y; - if (change_y) save_y = y, y = new_y; - @dots{} - if (change_y) y = save_y; -@} -@end smallexample - -@noindent -This has no bug because @code{save_y} is used only if it is set. - -@cindex @code{longjmp} warnings -This option also warns when a non-volatile automatic variable might be -changed by a call to @code{longjmp}. These warnings as well are possible -only in optimizing compilation. - -The compiler sees only the calls to @code{setjmp}. It cannot know -where @code{longjmp} will be called; in fact, a signal handler could -call it at any point in the code. As a result, you may get a warning -even when there is in fact no problem because @code{longjmp} cannot -in fact be called at the place which would cause a problem. - -Some spurious warnings can be avoided if you declare all the functions -you use that never return as @code{noreturn}. @xref{Function -Attributes}. - -@item -Wreorder (C++ only) -@cindex reordering, warning -@cindex warning for reordering of member initializers -Warn when the order of member initializers given in the code does not -match the order in which they must be executed. For instance: - -@item -Wunknown-pragmas -@cindex warning for unknown pragmas -@cindex unknown pragmas, warning -@cindex pragmas, warning of unknown -Warn when a #pragma directive is encountered which is not understood by -GCC. If this command line option is used, warnings will even be issued -for unknown pragmas in system header files. This is not the case if -the warnings were only enabled by the @samp{-Wall} command line option. - -@item -Wall -All of the above @samp{-W} options combined. This enables all the -warnings about constructions that some users consider questionable, and -that are easy to avoid (or modify to prevent the warning), even in -conjunction with macros. - -@item -Wsystem-headers -@cindex warnings from system headers -@cindex system headers, warnings from -Print warning messages for constructs found in system header files. -Warnings from system headers are normally suppressed, on the assumption -that they usually do not indicate real problems and would only make the -compiler output harder to read. Using this command line option tells -GCC to emit warnings from system headers as if they occurred in user -code. However, note that using @samp{-Wall} in conjunction with this -option will @emph{not} warn about unknown pragmas in system -headers---for that, @samp{-Wunknown-pragmas} must also be used. -@end table - -The following @samp{-W@dots{}} options are not implied by @samp{-Wall}. -Some of them warn about constructions that users generally do not -consider questionable, but which occasionally you might wish to check -for; others warn about constructions that are necessary or hard to avoid -in some cases, and there is no simple way to modify the code to suppress -the warning. - -@table @gcctabopt -@item -W -Print extra warning messages for these events: - -@itemize @bullet -@item -A function can return either with or without a value. (Falling -off the end of the function body is considered returning without -a value.) For example, this function would evoke such a -warning: - -@smallexample -@group -foo (a) -@{ - if (a > 0) - return a; -@} -@end group -@end smallexample - -@item -An expression-statement or the left-hand side of a comma expression -contains no side effects. -To suppress the warning, cast the unused expression to void. -For example, an expression such as @samp{x[i,j]} will cause a warning, -but @samp{x[(void)i,j]} will not. - -@item -An unsigned value is compared against zero with @samp{<} or @samp{<=}. - -@item -A comparison like @samp{x<=y<=z} appears; this is equivalent to -@samp{(x<=y ? 1 : 0) <= z}, which is a different interpretation from -that of ordinary mathematical notation. - -@item -Storage-class specifiers like @code{static} are not the first things in -a declaration. According to the C Standard, this usage is obsolescent. - -@item -The return type of a function has a type qualifier such as @code{const}. -Such a type qualifier has no effect, since the value returned by a -function is not an lvalue. (But don't warn about the GNU extension of -@code{volatile void} return types. That extension will be warned about -if @samp{-pedantic} is specified.) - -@item -If @samp{-Wall} or @samp{-Wunused} is also specified, warn about unused -arguments. - -@item -A comparison between signed and unsigned values could produce an -incorrect result when the signed value is converted to unsigned. -(But don't warn if @samp{-Wno-sign-compare} is also specified.) - -@item -An aggregate has a partly bracketed initializer. -For example, the following code would evoke such a warning, -because braces are missing around the initializer for @code{x.h}: - -@smallexample -struct s @{ int f, g; @}; -struct t @{ struct s h; int i; @}; -struct t x = @{ 1, 2, 3 @}; -@end smallexample - -@item -An aggregate has an initializer which does not initialize all members. -For example, the following code would cause such a warning, because -@code{x.h} would be implicitly initialized to zero: - -@smallexample -struct s @{ int f, g, h; @}; -struct s x = @{ 3, 4 @}; -@end smallexample -@end itemize - -@item -Wfloat-equal -Warn if floating point values are used in equality comparisons. - -The idea behind this is that sometimes it is convenient (for the -programmer) to consider floating-point values as approximations to -infinitely precise real numbers. If you are doing this, then you need -to compute (by analysing the code, or in some other way) the maximum or -likely maximum error that the computation introduces, and allow for it -when performing comparisons (and when producing output, but that's a -different problem). In particular, instead of testing for equality, you -would check to see whether the two values have ranges that overlap; and -this is done with the relational operators, so equality comparisons are -probably mistaken. - -@item -Wtraditional (C only) -Warn about certain constructs that behave differently in traditional and -ISO C. Also warn about ISO C constructs that have no traditional C -equivalent, and/or problematic constructs which should be avoided. - -@itemize @bullet -@item -Macro parameters that appear within string literals in the macro body. -In traditional C macro replacement takes place within string literals, -but does not in ISO C. - -@item -In traditional C, some preprocessor directives did not exist. -Traditional preprocessors would only consider a line to be a directive -if the @samp{#} appeared in column 1 on the line. Therefore -@samp{-Wtraditional} warns about directives that traditional C -understands but would ignore because the @samp{#} does not appear as the -first character on the line. It also suggests you hide directives like -@samp{#pragma} not understood by traditional C by indenting them. Some -traditional implementations would not recognise @samp{#elif}, so it -suggests avoiding it altogether. - -@item -A function-like macro that appears without arguments. - -@item -The unary plus operator. - -@item -The `U' integer constant suffix, or the `F' or `L' floating point -constant suffixes. (Traditonal C does support the `L' suffix on integer -constants.) Note, these suffixes appear in macros defined in the system -headers of most modern systems, e.g. the _MIN/_MAX macros in limits.h. -Use of these macros in user code might normally lead to spurious -warnings, however gcc's integrated preprocessor has enough context to -avoid warning in these cases. - -@item -A function declared external in one block and then used after the end of -the block. - -@item -A @code{switch} statement has an operand of type @code{long}. - -@item -A non-@code{static} function declaration follows a @code{static} one. -This construct is not accepted by some traditional C compilers. - -@item -The ISO type of an integer constant has a different width or -signedness from its traditional type. This warning is only issued if -the base of the constant is ten. I.e. hexadecimal or octal values, which -typically represent bit patterns, are not warned about. - -@item -Usage of ISO string concatenation is detected. - -@item -Initialization of automatic aggregates. - -@item -Identifier conflicts with labels. Traditional C lacks a separate -namespace for labels. - -@item -Initialization of unions. If the initializer is zero, the warning is -omitted. This is done under the assumption that the zero initializer in -user code appears conditioned on e.g. @code{__STDC__} to avoid missing -initializer warnings and relies on default initialization to zero in the -traditional C case. - -@item -Conversions by prototypes between fixed/floating point values and vice -versa. The absence of these prototypes when compiling with traditional -C would cause serious problems. This is a subset of the possible -conversion warnings, for the full set use @samp{-Wconversion}. -@end itemize - -@item -Wundef -Warn if an undefined identifier is evaluated in an @samp{#if} directive. - -@item -Wshadow -Warn whenever a local variable shadows another local variable, parameter or -global variable or whenever a built-in function is shadowed. - -@item -Wlarger-than-@var{len} -Warn whenever an object of larger than @var{len} bytes is defined. - -@item -Wpointer-arith -Warn about anything that depends on the ``size of'' a function type or -of @code{void}. GNU C assigns these types a size of 1, for -convenience in calculations with @code{void *} pointers and pointers -to functions. - -@item -Wbad-function-cast (C only) -Warn whenever a function call is cast to a non-matching type. -For example, warn if @code{int malloc()} is cast to @code{anything *}. - -@item -Wcast-qual -Warn whenever a pointer is cast so as to remove a type qualifier from -the target type. For example, warn if a @code{const char *} is cast -to an ordinary @code{char *}. - -@item -Wcast-align -Warn whenever a pointer is cast such that the required alignment of the -target is increased. For example, warn if a @code{char *} is cast to -an @code{int *} on machines where integers can only be accessed at -two- or four-byte boundaries. - -@item -Wwrite-strings -Give string constants the type @code{const char[@var{length}]} so that -copying the address of one into a non-@code{const} @code{char *} -pointer will get a warning. These warnings will help you find at -compile time code that can try to write into a string constant, but -only if you have been very careful about using @code{const} in -declarations and prototypes. Otherwise, it will just be a nuisance; -this is why we did not make @samp{-Wall} request these warnings. - -@item -Wconversion -Warn if a prototype causes a type conversion that is different from what -would happen to the same argument in the absence of a prototype. This -includes conversions of fixed point to floating and vice versa, and -conversions changing the width or signedness of a fixed point argument -except when the same as the default promotion. - -Also, warn if a negative integer constant expression is implicitly -converted to an unsigned type. For example, warn about the assignment -@code{x = -1} if @code{x} is unsigned. But do not warn about explicit -casts like @code{(unsigned) -1}. - -@item -Wsign-compare -@cindex warning for comparison of signed and unsigned values -@cindex comparison of signed and unsigned values, warning -@cindex signed and unsigned values, comparison warning -Warn when a comparison between signed and unsigned values could produce -an incorrect result when the signed value is converted to unsigned. -This warning is also enabled by @samp{-W}; to get the other warnings -of @samp{-W} without this warning, use @samp{-W -Wno-sign-compare}. - -@item -Waggregate-return -Warn if any functions that return structures or unions are defined or -called. (In languages where you can return an array, this also elicits -a warning.) - -@item -Wstrict-prototypes (C only) -Warn if a function is declared or defined without specifying the -argument types. (An old-style function definition is permitted without -a warning if preceded by a declaration which specifies the argument -types.) - -@item -Wmissing-prototypes (C only) -Warn if a global function is defined without a previous prototype -declaration. This warning is issued even if the definition itself -provides a prototype. The aim is to detect global functions that fail -to be declared in header files. - -@item -Wmissing-declarations -Warn if a global function is defined without a previous declaration. -Do so even if the definition itself provides a prototype. -Use this option to detect global functions that are not declared in -header files. - -@item -Wmissing-noreturn -Warn about functions which might be candidates for attribute @code{noreturn}. -Note these are only possible candidates, not absolute ones. Care should -be taken to manually verify functions actually do not ever return before -adding the @code{noreturn} attribute, otherwise subtle code generation -bugs could be introduced. You will not get a warning for @code{main} in -hosted C environments. - -@item -Wmissing-format-attribute -If @samp{-Wformat} is enabled, also warn about functions which might be -candidates for @code{format} attributes. Note these are only possible -candidates, not absolute ones. GCC will guess that @code{format} -attributes might be appropriate for any function that calls a function -like @code{vprintf} or @code{vscanf}, but this might not always be the -case, and some functions for which @code{format} attributes are -appropriate may not be detected. This option has no effect unless -@samp{-Wformat} is enabled (possibly by @samp{-Wall}). - -@item -Wpacked -Warn if a structure is given the packed attribute, but the packed -attribute has no effect on the layout or size of the structure. -Such structures may be mis-aligned for little benefit. For -instance, in this code, the variable @code{f.x} in @code{struct bar} -will be misaligned even though @code{struct bar} does not itself -have the packed attribute: - -@smallexample -@group -struct foo @{ - int x; - char a, b, c, d; -@} __attribute__((packed)); -struct bar @{ - char z; - struct foo f; -@}; -@end group -@end smallexample - -@item -Wpadded -Warn if padding is included in a structure, either to align an element -of the structure or to align the whole structure. Sometimes when this -happens it is possible to rearrange the fields of the structure to -reduce the padding and so make the structure smaller. - -@item -Wredundant-decls -Warn if anything is declared more than once in the same scope, even in -cases where multiple declaration is valid and changes nothing. - -@item -Wnested-externs (C only) -Warn if an @code{extern} declaration is encountered within a function. - -@item -Wunreachable-code -Warn if the compiler detects that code will never be executed. - -This option is intended to warn when the compiler detects that at -least a whole line of source code will never be executed, because -some condition is never satisfied or because it is after a -procedure that never returns. - -It is possible for this option to produce a warning even though there -are circumstances under which part of the affected line can be executed, -so care should be taken when removing apparently-unreachable code. - -For instance, when a function is inlined, a warning may mean that the -line is unreachable in only one inlined copy of the function. - -This option is not made part of @samp{-Wall} because in a debugging -version of a program there is often substantial code which checks -correct functioning of the program and is, hopefully, unreachable -because the program does work. Another common use of unreachable -code is to provide behaviour which is selectable at compile-time. - -@item -Winline -Warn if a function can not be inlined and it was declared as inline. - -@item -Wlong-long -Warn if @samp{long long} type is used. This is default. To inhibit -the warning messages, use @samp{-Wno-long-long}. Flags -@samp{-Wlong-long} and @samp{-Wno-long-long} are taken into account -only when @samp{-pedantic} flag is used. - -@item -Wdisabled-optimization -Warn if a requested optimization pass is disabled. This warning does -not generally indicate that there is anything wrong with your code; it -merely indicates that GCC's optimizers were unable to handle the code -effectively. Often, the problem is that your code is too big or too -complex; GCC will refuse to optimize programs when the optimization -itself is likely to take inordinate amounts of time. - -@item -Werror -Make all warnings into errors. -@end table - -@node Debugging Options -@section Options for Debugging Your Program or GCC -@cindex options, debugging -@cindex debugging information options - -GCC has various special options that are used for debugging -either your program or GCC: - -@table @gcctabopt -@item -g -Produce debugging information in the operating system's native format -(stabs, COFF, XCOFF, or DWARF). GDB can work with this debugging -information. - -On most systems that use stabs format, @samp{-g} enables use of extra -debugging information that only GDB can use; this extra information -makes debugging work better in GDB but will probably make other debuggers -crash or -refuse to read the program. If you want to control for certain whether -to generate the extra information, use @samp{-gstabs+}, @samp{-gstabs}, -@samp{-gxcoff+}, @samp{-gxcoff}, @samp{-gdwarf-1+}, or @samp{-gdwarf-1} -(see below). - -Unlike most other C compilers, GCC allows you to use @samp{-g} with -@samp{-O}. The shortcuts taken by optimized code may occasionally -produce surprising results: some variables you declared may not exist -at all; flow of control may briefly move where you did not expect it; -some statements may not be executed because they compute constant -results or their values were already at hand; some statements may -execute in different places because they were moved out of loops. - -Nevertheless it proves possible to debug optimized output. This makes -it reasonable to use the optimizer for programs that might have bugs. - -The following options are useful when GCC is generated with the -capability for more than one debugging format. - -@item -ggdb -Produce debugging information for use by GDB. This means to use the -most expressive format available (DWARF 2, stabs, or the native format -if neither of those are supported), including GDB extensions if at all -possible. - -@item -gstabs -Produce debugging information in stabs format (if that is supported), -without GDB extensions. This is the format used by DBX on most BSD -systems. On MIPS, Alpha and System V Release 4 systems this option -produces stabs debugging output which is not understood by DBX or SDB. -On System V Release 4 systems this option requires the GNU assembler. - -@item -gstabs+ -Produce debugging information in stabs format (if that is supported), -using GNU extensions understood only by the GNU debugger (GDB). The -use of these extensions is likely to make other debuggers crash or -refuse to read the program. - -@item -gcoff -Produce debugging information in COFF format (if that is supported). -This is the format used by SDB on most System V systems prior to -System V Release 4. - -@item -gxcoff -Produce debugging information in XCOFF format (if that is supported). -This is the format used by the DBX debugger on IBM RS/6000 systems. - -@item -gxcoff+ -Produce debugging information in XCOFF format (if that is supported), -using GNU extensions understood only by the GNU debugger (GDB). The -use of these extensions is likely to make other debuggers crash or -refuse to read the program, and may cause assemblers other than the GNU -assembler (GAS) to fail with an error. - -@item -gdwarf -Produce debugging information in DWARF version 1 format (if that is -supported). This is the format used by SDB on most System V Release 4 -systems. - -@item -gdwarf+ -Produce debugging information in DWARF version 1 format (if that is -supported), using GNU extensions understood only by the GNU debugger -(GDB). The use of these extensions is likely to make other debuggers -crash or refuse to read the program. - -@item -gdwarf-2 -Produce debugging information in DWARF version 2 format (if that is -supported). This is the format used by DBX on IRIX 6. - -@item -g@var{level} -@itemx -ggdb@var{level} -@itemx -gstabs@var{level} -@itemx -gcoff@var{level} -@itemx -gxcoff@var{level} -@itemx -gdwarf@var{level} -@itemx -gdwarf-2@var{level} -Request debugging information and also use @var{level} to specify how -much information. The default level is 2. - -Level 1 produces minimal information, enough for making backtraces in -parts of the program that you don't plan to debug. This includes -descriptions of functions and external variables, but no information -about local variables and no line numbers. - -Level 3 includes extra information, such as all the macro definitions -present in the program. Some debuggers support macro expansion when -you use @samp{-g3}. - -@cindex @code{prof} -@item -p -Generate extra code to write profile information suitable for the -analysis program @code{prof}. You must use this option when compiling -the source files you want data about, and you must also use it when -linking. - -@cindex @code{gprof} -@item -pg -Generate extra code to write profile information suitable for the -analysis program @code{gprof}. You must use this option when compiling -the source files you want data about, and you must also use it when -linking. - -@cindex @code{tcov} -@item -a -Generate extra code to write profile information for basic blocks, which will -record the number of times each basic block is executed, the basic block start -address, and the function name containing the basic block. If @samp{-g} is -used, the line number and filename of the start of the basic block will also be -recorded. If not overridden by the machine description, the default action is -to append to the text file @file{bb.out}. - -This data could be analyzed by a program like @code{tcov}. Note, -however, that the format of the data is not what @code{tcov} expects. -Eventually GNU @code{gprof} should be extended to process this data. - -@item -Q -Makes the compiler print out each function name as it is compiled, and -print some statistics about each pass when it finishes. - -@item -ftime-report -Makes the compiler print some statistics about the time consumed by each -pass when it finishes. - -@item -fmem-report -Makes the compiler print some statistics about permanent memory -allocation when it finishes. - -@item -ax -Generate extra code to profile basic blocks. Your executable will -produce output that is a superset of that produced when @samp{-a} is -used. Additional output is the source and target address of the basic -blocks where a jump takes place, the number of times a jump is executed, -and (optionally) the complete sequence of basic blocks being executed. -The output is appended to file @file{bb.out}. - -You can examine different profiling aspects without recompilation. Your -executable will read a list of function names from file @file{bb.in}. -Profiling starts when a function on the list is entered and stops when -that invocation is exited. To exclude a function from profiling, prefix -its name with `-'. If a function name is not unique, you can -disambiguate it by writing it in the form -@samp{/path/filename.d:functionname}. Your executable will write the -available paths and filenames in file @file{bb.out}. - -Several function names have a special meaning: -@table @code -@item __bb_jumps__ -Write source, target and frequency of jumps to file @file{bb.out}. -@item __bb_hidecall__ -Exclude function calls from frequency count. -@item __bb_showret__ -Include function returns in frequency count. -@item __bb_trace__ -Write the sequence of basic blocks executed to file @file{bbtrace.gz}. -The file will be compressed using the program @samp{gzip}, which must -exist in your @env{PATH}. On systems without the @samp{popen} -function, the file will be named @file{bbtrace} and will not be -compressed. @strong{Profiling for even a few seconds on these systems -will produce a very large file.} Note: @code{__bb_hidecall__} and -@code{__bb_showret__} will not affect the sequence written to -@file{bbtrace.gz}. -@end table - -Here's a short example using different profiling parameters -in file @file{bb.in}. Assume function @code{foo} consists of basic blocks -1 and 2 and is called twice from block 3 of function @code{main}. After -the calls, block 3 transfers control to block 4 of @code{main}. - -With @code{__bb_trace__} and @code{main} contained in file @file{bb.in}, -the following sequence of blocks is written to file @file{bbtrace.gz}: -0 3 1 2 1 2 4. The return from block 2 to block 3 is not shown, because -the return is to a point inside the block and not to the top. The -block address 0 always indicates, that control is transferred -to the trace from somewhere outside the observed functions. With -@samp{-foo} added to @file{bb.in}, the blocks of function -@code{foo} are removed from the trace, so only 0 3 4 remains. - -With @code{__bb_jumps__} and @code{main} contained in file @file{bb.in}, -jump frequencies will be written to file @file{bb.out}. The -frequencies are obtained by constructing a trace of blocks -and incrementing a counter for every neighbouring pair of blocks -in the trace. The trace 0 3 1 2 1 2 4 displays the following -frequencies: - -@example -Jump from block 0x0 to block 0x3 executed 1 time(s) -Jump from block 0x3 to block 0x1 executed 1 time(s) -Jump from block 0x1 to block 0x2 executed 2 time(s) -Jump from block 0x2 to block 0x1 executed 1 time(s) -Jump from block 0x2 to block 0x4 executed 1 time(s) -@end example - -With @code{__bb_hidecall__}, control transfer due to call instructions -is removed from the trace, that is the trace is cut into three parts: 0 -3 4, 0 1 2 and 0 1 2. With @code{__bb_showret__}, control transfer due -to return instructions is added to the trace. The trace becomes: 0 3 1 -2 3 1 2 3 4. Note, that this trace is not the same, as the sequence -written to @file{bbtrace.gz}. It is solely used for counting jump -frequencies. - -@item -fprofile-arcs -Instrument @dfn{arcs} during compilation. For each function of your -program, GCC creates a program flow graph, then finds a spanning tree -for the graph. Only arcs that are not on the spanning tree have to be -instrumented: the compiler adds code to count the number of times that these -arcs are executed. When an arc is the only exit or only entrance to a -block, the instrumentation code can be added to the block; otherwise, a -new basic block must be created to hold the instrumentation code. - -Since not every arc in the program must be instrumented, programs -compiled with this option run faster than programs compiled with -@samp{-a}, which adds instrumentation code to every basic block in the -program. The tradeoff: since @code{gcov} does not have -execution counts for all branches, it must start with the execution -counts for the instrumented branches, and then iterate over the program -flow graph until the entire graph has been solved. Hence, @code{gcov} -runs a little more slowly than a program which uses information from -@samp{-a}. - -@samp{-fprofile-arcs} also makes it possible to estimate branch -probabilities, and to calculate basic block execution counts. In -general, basic block execution counts do not give enough information to -estimate all branch probabilities. When the compiled program exits, it -saves the arc execution counts to a file called -@file{@var{sourcename}.da}. Use the compiler option -@samp{-fbranch-probabilities} (@pxref{Optimize Options,,Options that -Control Optimization}) when recompiling, to optimize using estimated -branch probabilities. - -@need 2000 -@item -ftest-coverage -Create data files for the @code{gcov} code-coverage utility -(@pxref{Gcov,, @code{gcov}: a GCC Test Coverage Program}). -The data file names begin with the name of your source file: - -@table @gcctabopt -@item @var{sourcename}.bb -A mapping from basic blocks to line numbers, which @code{gcov} uses to -associate basic block execution counts with line numbers. - -@item @var{sourcename}.bbg -A list of all arcs in the program flow graph. This allows @code{gcov} -to reconstruct the program flow graph, so that it can compute all basic -block and arc execution counts from the information in the -@code{@var{sourcename}.da} file (this last file is the output from -@samp{-fprofile-arcs}). -@end table - -@item -d@var{letters} -Says to make debugging dumps during compilation at times specified by -@var{letters}. This is used for debugging the compiler. The file names -for most of the dumps are made by appending a pass number and a word to -the source file name (e.g. @file{foo.c.00.rtl} or @file{foo.c.01.sibling}). -Here are the possible letters for use in @var{letters}, and their meanings: - -@table @samp -@item A -Annotate the assembler output with miscellaneous debugging information. -@item b -Dump after computing branch probabilities, to @file{@var{file}.11.bp}. -@item B -Dump after block reordering, to @file{@var{file}.26.bbro}. -@item c -Dump after instruction combination, to the file @file{@var{file}.14.combine}. -@item C -Dump after the first if conversion, to the file @file{@var{file}.15.ce}. -@item d -Dump after delayed branch scheduling, to @file{@var{file}.29.dbr}. -@item D -Dump all macro definitions, at the end of preprocessing, in addition to -normal output. -@item e -Dump after SSA optimizations, to @file{@var{file}.05.ssa} and -@file{@var{file}.06.ussa}. -@item E -Dump after the second if conversion, to @file{@var{file}.24.ce2}. -@item f -Dump after life analysis, to @file{@var{file}.13.life}. -@item F -Dump after purging @code{ADDRESSOF} codes, to @file{@var{file}.04.addressof}. -@item g -Dump after global register allocation, to @file{@var{file}.19.greg}. -@item o -Dump after post-reload CSE and other optimizations, to @file{@var{file}.20.postreload}. -@item G -Dump after GCSE, to @file{@var{file}.08.gcse}. -@item i -Dump after sibling call optimizations, to @file{@var{file}.01.sibling}. -@item j -Dump after the first jump optimization, to @file{@var{file}.02.jump}. -@item J -Dump after the last jump optimization, to @file{@var{file}.27.jump2}. -@item k -Dump after conversion from registers to stack, to @file{@var{file}.29.stack}. -@item l -Dump after local register allocation, to @file{@var{file}.18.lreg}. -@item L -Dump after loop optimization, to @file{@var{file}.09.loop}. -@item M -Dump after performing the machine dependent reorganisation pass, to -@file{@var{file}.28.mach}. -@item n -Dump after register renumbering, to @file{@var{file}.23.rnreg}. -@item N -Dump after the register move pass, to @file{@var{file}.16.regmove}. -@item r -Dump after RTL generation, to @file{@var{file}.00.rtl}. -@item R -Dump after the second instruction scheduling pass, to -@file{@var{file}.25.sched2}. -@item s -Dump after CSE (including the jump optimization that sometimes follows -CSE), to @file{@var{file}.03.cse}. -@item S -Dump after the first instruction scheduling pass, to -@file{@var{file}.17.sched}. -@item t -Dump after the second CSE pass (including the jump optimization that -sometimes follows CSE), to @file{@var{file}.10.cse2}. -@item w -Dump after the second flow pass, to @file{@var{file}.21.flow2}. -@item X -Dump after dead code elimination, to @file{@var{file}.06.dce}. -@item z -Dump after the peephole pass, to @file{@var{file}.22.peephole2}. -@item a -Produce all the dumps listed above. -@item m -Print statistics on memory usage, at the end of the run, to -standard error. -@item p -Annotate the assembler output with a comment indicating which -pattern and alternative was used. The length of each instruction is -also printed. -@item P -Dump the RTL in the assembler output as a comment before each instruction. -Also turns on @samp{-dp} annotation. -@item v -For each of the other indicated dump files (except for -@file{@var{file}.00.rtl}), dump a representation of the control flow graph -suitable for viewing with VCG to @file{@var{file}.@var{pass}.vcg}. -@item x -Just generate RTL for a function instead of compiling it. Usually used -with @samp{r}. -@item y -Dump debugging information during parsing, to standard error. -@end table - -@item -fdump-unnumbered -When doing debugging dumps (see -d option above), suppress instruction -numbers and line number note output. This makes it more feasible to -use diff on debugging dumps for compiler invocations with different -options, in particular with and without -g. - -@item -fdump-translation-unit=@var{file} (C and C++ only) -Dump a representation of the tree structure for the entire translation -unit to @var{file}. - -@item -fdump-class_layout=@var{file} (C++ only) -@item -fdump-class_layout (C++ only) -Dump a representation of each class's heirarchy to @var{file}, or -@code{stderr} if not specified. - -@item -fpretend-float -When running a cross-compiler, pretend that the target machine uses the -same floating point format as the host machine. This causes incorrect -output of the actual floating constants, but the actual instruction -sequence will probably be the same as GCC would make when running on -the target machine. - -@item -save-temps -Store the usual ``temporary'' intermediate files permanently; place them -in the current directory and name them based on the source file. Thus, -compiling @file{foo.c} with @samp{-c -save-temps} would produce files -@file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a -preprocessed @file{foo.i} output file even though the compiler now -normally uses an integrated preprocessor. - -@item -time -Report the CPU time taken by each subprocess in the compilation -sequence. For C source files, this is the compiler proper and assembler -(plus the linker if linking is done). The output looks like this: - -@smallexample -# cc1 0.12 0.01 -# as 0.00 0.01 -@end smallexample - -The first number on each line is the ``user time,'' that is time spent -executing the program itself. The second number is ``system time,'' -time spent executing operating system routines on behalf of the program. -Both numbers are in seconds. - -@item -print-file-name=@var{library} -Print the full absolute name of the library file @var{library} that -would be used when linking---and don't do anything else. With this -option, GCC does not compile or link anything; it just prints the -file name. - -@item -print-prog-name=@var{program} -Like @samp{-print-file-name}, but searches for a program such as @samp{cpp}. - -@item -print-libgcc-file-name -Same as @samp{-print-file-name=libgcc.a}. - -This is useful when you use @samp{-nostdlib} or @samp{-nodefaultlibs} -but you do want to link with @file{libgcc.a}. You can do - -@example -gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name` -@end example - -@item -print-search-dirs -Print the name of the configured installation directory and a list of -program and library directories gcc will search---and don't do anything else. - -This is useful when gcc prints the error message -@samp{installation problem, cannot exec cpp0: No such file or directory}. -To resolve this you either need to put @file{cpp0} and the other compiler -components where gcc expects to find them, or you can set the environment -variable @env{GCC_EXEC_PREFIX} to the directory where you installed them. -Don't forget the trailing '/'. -@xref{Environment Variables}. - -@item -dumpmachine -Print the compiler's target machine (for example, -@samp{i686-pc-linux-gnu})---and don't do anything else. - -@item -dumpversion -Print the compiler version (for example, @samp{3.0})---and don't do -anything else. - -@item -dumpspecs -Print the compiler's built-in specs---and don't do anything else. (This -is used when GCC itself is being built.) @xref{Spec Files}. -@end table - -@node Optimize Options -@section Options That Control Optimization -@cindex optimize options -@cindex options, optimization - -These options control various sorts of optimizations: - -@table @gcctabopt -@item -O -@itemx -O1 -Optimize. Optimizing compilation takes somewhat more time, and a lot -more memory for a large function. - -Without @samp{-O}, the compiler's goal is to reduce the cost of -compilation and to make debugging produce the expected results. -Statements are independent: if you stop the program with a breakpoint -between statements, you can then assign a new value to any variable or -change the program counter to any other statement in the function and -get exactly the results you would expect from the source code. - -Without @samp{-O}, the compiler only allocates variables declared -@code{register} in registers. The resulting compiled code is a little -worse than produced by PCC without @samp{-O}. - -With @samp{-O}, the compiler tries to reduce code size and execution -time. - -When you specify @samp{-O}, the compiler turns on @samp{-fthread-jumps} -and @samp{-fdefer-pop} on all machines. The compiler turns on -@samp{-fdelayed-branch} on machines that have delay slots, and -@samp{-fomit-frame-pointer} on machines that can support debugging even -without a frame pointer. On some machines the compiler also turns -on other flags.@refill - -@item -O2 -Optimize even more. GCC performs nearly all supported optimizations -that do not involve a space-speed tradeoff. The compiler does not -perform loop unrolling or function inlining when you specify @samp{-O2}. -As compared to @samp{-O}, this option increases both compilation time -and the performance of the generated code. - -@samp{-O2} turns on all optional optimizations except for loop unrolling, -function inlining, and register renaming. It also turns on the -@samp{-fforce-mem} option on all machines and frame pointer elimination -on machines where doing so does not interfere with debugging. - -@item -O3 -Optimize yet more. @samp{-O3} turns on all optimizations specified by -@samp{-O2} and also turns on the @samp{-finline-functions} and -@samp{-frename-registers} options. - -@item -O0 -Do not optimize. - -@item -Os -Optimize for size. @samp{-Os} enables all @samp{-O2} optimizations that -do not typically increase code size. It also performs further -optimizations designed to reduce code size. - -If you use multiple @samp{-O} options, with or without level numbers, -the last such option is the one that is effective. -@end table - -Options of the form @samp{-f@var{flag}} specify machine-independent -flags. Most flags have both positive and negative forms; the negative -form of @samp{-ffoo} would be @samp{-fno-foo}. In the table below, -only one of the forms is listed---the one which is not the default. -You can figure out the other form by either removing @samp{no-} or -adding it. - -@table @gcctabopt -@item -ffloat-store -Do not store floating point variables in registers, and inhibit other -options that might change whether a floating point value is taken from a -register or memory. - -@cindex floating point precision -This option prevents undesirable excess precision on machines such as -the 68000 where the floating registers (of the 68881) keep more -precision than a @code{double} is supposed to have. Similarly for the -x86 architecture. For most programs, the excess precision does only -good, but a few programs rely on the precise definition of IEEE floating -point. Use @samp{-ffloat-store} for such programs, after modifying -them to store all pertinent intermediate computations into variables. - -@item -fno-default-inline -Do not make member functions inline by default merely because they are -defined inside the class scope (C++ only). Otherwise, when you specify -@w{@samp{-O}}, member functions defined inside class scope are compiled -inline by default; i.e., you don't need to add @samp{inline} in front of -the member function name. - -@item -fno-defer-pop -Always pop the arguments to each function call as soon as that function -returns. For machines which must pop arguments after a function call, -the compiler normally lets arguments accumulate on the stack for several -function calls and pops them all at once. - -@item -fforce-mem -Force memory operands to be copied into registers before doing -arithmetic on them. This produces better code by making all memory -references potential common subexpressions. When they are not common -subexpressions, instruction combination should eliminate the separate -register-load. The @samp{-O2} option turns on this option. - -@item -fforce-addr -Force memory address constants to be copied into registers before -doing arithmetic on them. This may produce better code just as -@samp{-fforce-mem} may. - -@item -fomit-frame-pointer -Don't keep the frame pointer in a register for functions that -don't need one. This avoids the instructions to save, set up and -restore frame pointers; it also makes an extra register available -in many functions. @strong{It also makes debugging impossible on -some machines.} - -@ifset INTERNALS -On some machines, such as the Vax, this flag has no effect, because -the standard calling sequence automatically handles the frame pointer -and nothing is saved by pretending it doesn't exist. The -machine-description macro @code{FRAME_POINTER_REQUIRED} controls -whether a target machine supports this flag. @xref{Registers}.@refill -@end ifset -@ifclear INTERNALS -On some machines, such as the Vax, this flag has no effect, because -the standard calling sequence automatically handles the frame pointer -and nothing is saved by pretending it doesn't exist. The -machine-description macro @code{FRAME_POINTER_REQUIRED} controls -whether a target machine supports this flag. @xref{Registers,,Register -Usage, gcc.info, Using and Porting GCC}.@refill -@end ifclear - -@item -foptimize-sibling-calls -Optimize sibling and tail recursive calls. - -@item -ftrapv -This option generates traps for signed overflow on addition, subtraction, -multiplication operations. - -@item -fno-inline -Don't pay attention to the @code{inline} keyword. Normally this option -is used to keep the compiler from expanding any functions inline. -Note that if you are not optimizing, no functions can be expanded inline. - -@item -finline-functions -Integrate all simple functions into their callers. The compiler -heuristically decides which functions are simple enough to be worth -integrating in this way. - -If all calls to a given function are integrated, and the function is -declared @code{static}, then the function is normally not output as -assembler code in its own right. - -@item -finline-limit=@var{n} -By default, gcc limits the size of functions that can be inlined. This flag -allows the control of this limit for functions that are explicitly marked as -inline (ie marked with the inline keyword or defined within the class -definition in c++). @var{n} is the size of functions that can be inlined in -number of pseudo instructions (not counting parameter handling). The default -value of n is 10000. Increasing this value can result in more inlined code at -the cost of compilation time and memory consumption. Decreasing usually makes -the compilation faster and less code will be inlined (which presumably -means slower programs). This option is particularly useful for programs that -use inlining heavily such as those based on recursive templates with c++. - -@emph{Note:} pseudo instruction represents, in this particular context, an -abstract measurement of function's size. In no way, it represents a count -of assembly instructions and as such its exact meaning might change from one -release to an another. - -@item -fkeep-inline-functions -Even if all calls to a given function are integrated, and the function -is declared @code{static}, nevertheless output a separate run-time -callable version of the function. This switch does not affect -@code{extern inline} functions. - -@item -fkeep-static-consts -Emit variables declared @code{static const} when optimization isn't turned -on, even if the variables aren't referenced. - -GCC enables this option by default. If you want to force the compiler to -check if the variable was referenced, regardless of whether or not -optimization is turned on, use the @samp{-fno-keep-static-consts} option. - -@item -fno-function-cse -Do not put function addresses in registers; make each instruction that -calls a constant function contain the function's address explicitly. - -This option results in less efficient code, but some strange hacks -that alter the assembler output may be confused by the optimizations -performed when this option is not used. - -@item -ffast-math -Sets @samp{-fno-math-errno}, @samp{-funsafe-math-optimizations}, -and @samp{-fno-trapping-math}. - -This option causes the preprocessor macro __FAST_MATH__ to be defined. - -This option should never be turned on by any @samp{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -@item -fno-math-errno -Do not set ERRNO after calling math functions that are executed -with a single instruction, e.g., sqrt. A program that relies on -IEEE exceptions for math error handling may want to use this flag -for speed while maintaining IEEE arithmetic compatibility. - -This option should never be turned on by any @samp{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -The default is @samp{-fmath-errno}. The @samp{-ffast-math} option -sets @samp{-fno-math-errno}. - -@item -funsafe-math-optimizations -Allow optimizations for floating-point arithmetic that (a) assume -that arguments and results are valid and (b) may violate IEEE or -ANSI standards. - -This option should never be turned on by any @samp{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -The default is @samp{-fno-unsafe-math-optimizations}. The -@samp{-ffast-math} option sets @samp{-funsafe-math-optimizations}. - -@item -fno-trapping-math -Compile code assuming that floating-point operations cannot generate -user-visible traps. Setting this option may allow faster code -if one relies on ``non-stop'' IEEE arithmetic, for example. - -This option should never be turned on by any @samp{-O} option since -it can result in incorrect output for programs which depend on -an exact implementation of IEEE or ISO rules/specifications for -math functions. - -The default is @samp{-ftrapping-math}. The @samp{-ffast-math} -option sets @samp{-fno-trapping-math}. -@end table - -@c following causes underfulls.. they don't look great, but we deal. -@c --mew 26jan93 -The following options control specific optimizations. The @samp{-O2} -option turns on all of these optimizations except @samp{-funroll-loops} -and @samp{-funroll-all-loops}. On most machines, the @samp{-O} option -turns on the @samp{-fthread-jumps} and @samp{-fdelayed-branch} options, -but specific machines may handle it differently. - -You can use the following flags in the rare cases when ``fine-tuning'' -of optimizations to be performed is desired. - -@table @gcctabopt -@item -fstrength-reduce -Perform the optimizations of loop strength reduction and -elimination of iteration variables. - -@item -fthread-jumps -Perform optimizations where we check to see if a jump branches to a -location where another comparison subsumed by the first is found. If -so, the first branch is redirected to either the destination of the -second branch or a point immediately following it, depending on whether -the condition is known to be true or false. - -@item -fcse-follow-jumps -In common subexpression elimination, scan through jump instructions -when the target of the jump is not reached by any other path. For -example, when CSE encounters an @code{if} statement with an -@code{else} clause, CSE will follow the jump when the condition -tested is false. - -@item -fcse-skip-blocks -This is similar to @samp{-fcse-follow-jumps}, but causes CSE to -follow jumps which conditionally skip over blocks. When CSE -encounters a simple @code{if} statement with no else clause, -@samp{-fcse-skip-blocks} causes CSE to follow the jump around the -body of the @code{if}. - -@item -frerun-cse-after-loop -Re-run common subexpression elimination after loop optimizations has been -performed. - -@item -frerun-loop-opt -Run the loop optimizer twice. - -@item -fgcse -Perform a global common subexpression elimination pass. -This pass also performs global constant and copy propagation. - -@item -fgcse-lm -When -fgcse-lm is enabled, global common subexpression elimination will -attempt to move loads which are only killed by stores into themselves. This -allows a loop containing a load/store sequence to be changed to a load outside -the loop, and a copy/store within the loop. - -@item -fgcse-sm -When -fgcse-sm is enabled, A store motion pass is run after global common -subexpression elimination. This pass will attempt to move stores out of loops. -When used in conjunction with -fgcse-lm, loops containing a load/store sequence -can be changed to a load before the loop and a store after the loop. - -@item -fdelete-null-pointer-checks -Use global dataflow analysis to identify and eliminate useless null -pointer checks. Programs which rely on NULL pointer dereferences @emph{not} -halting the program may not work properly with this option. Use --fno-delete-null-pointer-checks to disable this optimizing for programs -which depend on that behavior. - -@item -fexpensive-optimizations -Perform a number of minor optimizations that are relatively expensive. - -@item -foptimize-register-move -@itemx -fregmove -Attempt to reassign register numbers in move instructions and as -operands of other simple instructions in order to maximize the amount of -register tying. This is especially helpful on machines with two-operand -instructions. GCC enables this optimization by default with @samp{-O2} -or higher. - -Note @option{-fregmove} and @option{-foptimize-register-move} are the same -optimization. - -@item -fdelayed-branch -If supported for the target machine, attempt to reorder instructions -to exploit instruction slots available after delayed branch -instructions. - -@item -fschedule-insns -If supported for the target machine, attempt to reorder instructions to -eliminate execution stalls due to required data being unavailable. This -helps machines that have slow floating point or memory load instructions -by allowing other instructions to be issued until the result of the load -or floating point instruction is required. - -@item -fschedule-insns2 -Similar to @samp{-fschedule-insns}, but requests an additional pass of -instruction scheduling after register allocation has been done. This is -especially useful on machines with a relatively small number of -registers and where memory load instructions take more than one cycle. - -@item -ffunction-sections -@itemx -fdata-sections -Place each function or data item into its own section in the output -file if the target supports arbitrary sections. The name of the -function or the name of the data item determines the section's name -in the output file. - -Use these options on systems where the linker can perform optimizations -to improve locality of reference in the instruction space. HPPA -processors running HP-UX and Sparc processors running Solaris 2 have -linkers with such optimizations. Other systems using the ELF object format -as well as AIX may have these optimizations in the future. - -Only use these options when there are significant benefits from doing -so. When you specify these options, the assembler and linker will -create larger object and executable files and will also be slower. -You will not be able to use @code{gprof} on all systems if you -specify this option and you may have problems with debugging if -you specify both this option and @samp{-g}. - -@item -fcaller-saves -Enable values to be allocated in registers that will be clobbered by -function calls, by emitting extra instructions to save and restore the -registers around such calls. Such allocation is done only when it -seems to result in better code than would otherwise be produced. - -This option is always enabled by default on certain machines, usually -those which have no call-preserved registers to use instead. - -For all machines, optimization level 2 and higher enables this flag by -default. - -@item -funroll-loops -Perform the optimization of loop unrolling. This is only done for loops -whose number of iterations can be determined at compile time or run time. -@samp{-funroll-loops} implies both @samp{-fstrength-reduce} and -@samp{-frerun-cse-after-loop}. - -@item -funroll-all-loops -Perform the optimization of loop unrolling. This is done for all loops -and usually makes programs run more slowly. @samp{-funroll-all-loops} -implies @samp{-fstrength-reduce} as well as @samp{-frerun-cse-after-loop}. - -@item -fmove-all-movables -Forces all invariant computations in loops to be moved -outside the loop. - -@item -freduce-all-givs -Forces all general-induction variables in loops to be -strength-reduced. - -@emph{Note:} When compiling programs written in Fortran, -@samp{-fmove-all-movables} and @samp{-freduce-all-givs} are enabled -by default when you use the optimizer. - -These options may generate better or worse code; results are highly -dependent on the structure of loops within the source code. - -These two options are intended to be removed someday, once -they have helped determine the efficacy of various -approaches to improving loop optimizations. - -Please let us (@w{@email{gcc@@gcc.gnu.org}} and @w{@email{fortran@@gnu.org}}) -know how use of these options affects -the performance of your production code. -We're very interested in code that runs @emph{slower} -when these options are @emph{enabled}. - -@item -fno-peephole -Disable any machine-specific peephole optimizations. - -@item -fbranch-probabilities -After running a program compiled with @samp{-fprofile-arcs} -(@pxref{Debugging Options,, Options for Debugging Your Program or -@command{gcc}}), you can compile it a second time using -@samp{-fbranch-probabilities}, to improve optimizations based on -guessing the path a branch might take. - -@ifset INTERNALS -With @samp{-fbranch-probabilities}, GCC puts a @samp{REG_EXEC_COUNT} -note on the first instruction of each basic block, and a -@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}. -These can be used to improve optimization. Currently, they are only -used in one place: in @file{reorg.c}, instead of guessing which path a -branch is mostly to take, the @samp{REG_BR_PROB} values are used to -exactly determine which path is taken more often. -@end ifset - -@item -fno-guess-branch-probability -Sometimes gcc will opt to guess branch probabilities when none are -available from either profile directed feedback (@samp{-fprofile-arcs}) -or @samp{__builtin_expect}. In a hard real-time system, people don't -want different runs of the compiler to produce code that has different -behavior; minimizing non-determinism is of paramount import. This -switch allows users to reduce non-determinism, possibly at the expense -of inferior optimization. - -@item -fstrict-aliasing -Allows the compiler to assume the strictest aliasing rules applicable to -the language being compiled. For C (and C++), this activates -optimizations based on the type of expressions. In particular, an -object of one type is assumed never to reside at the same address as an -object of a different type, unless the types are almost the same. For -example, an @code{unsigned int} can alias an @code{int}, but not a -@code{void*} or a @code{double}. A character type may alias any other -type. - -Pay special attention to code like this: -@example -union a_union @{ - int i; - double d; -@}; - -int f() @{ - a_union t; - t.d = 3.0; - return t.i; -@} -@end example -The practice of reading from a different union member than the one most -recently written to (called ``type-punning'') is common. Even with -@samp{-fstrict-aliasing}, type-punning is allowed, provided the memory -is accessed through the union type. So, the code above will work as -expected. However, this code might not: -@example -int f() @{ - a_union t; - int* ip; - t.d = 3.0; - ip = &t.i; - return *ip; -@} -@end example - -@ifset INTERNALS -Every language that wishes to perform language-specific alias analysis -should define a function that computes, given an @code{tree} -node, an alias set for the node. Nodes in different alias sets are not -allowed to alias. For an example, see the C front-end function -@code{c_get_alias_set}. -@end ifset - -@item -falign-functions -@itemx -falign-functions=@var{n} -Align the start of functions to the next power-of-two greater than -@var{n}, skipping up to @var{n} bytes. For instance, -@samp{-falign-functions=32} aligns functions to the next 32-byte -boundary, but @samp{-falign-functions=24} would align to the next -32-byte boundary only if this can be done by skipping 23 bytes or less. - -@samp{-fno-align-functions} and @samp{-falign-functions=1} are -equivalent and mean that functions will not be aligned. - -Some assemblers only support this flag when @var{n} is a power of two; -in that case, it is rounded up. - -If @var{n} is not specified, use a machine-dependent default. - -@item -falign-labels -@itemx -falign-labels=@var{n} -Align all branch targets to a power-of-two boundary, skipping up to -@var{n} bytes like @samp{-falign-functions}. This option can easily -make code slower, because it must insert dummy operations for when the -branch target is reached in the usual flow of the code. - -If @samp{-falign-loops} or @samp{-falign-jumps} are applicable and -are greater than this value, then their values are used instead. - -If @var{n} is not specified, use a machine-dependent default which is -very likely to be @samp{1}, meaning no alignment. - -@item -falign-loops -@itemx -falign-loops=@var{n} -Align loops to a power-of-two boundary, skipping up to @var{n} bytes -like @samp{-falign-functions}. The hope is that the loop will be -executed many times, which will make up for any execution of the dummy -operations. - -If @var{n} is not specified, use a machine-dependent default. - -@item -falign-jumps -@itemx -falign-jumps=@var{n} -Align branch targets to a power-of-two boundary, for branch targets -where the targets can only be reached by jumping, skipping up to @var{n} -bytes like @samp{-falign-functions}. In this case, no dummy operations -need be executed. - -If @var{n} is not specified, use a machine-dependent default. - -@item -fssa -Perform optimizations in static single assignment form. Each function's -flow graph is translated into SSA form, optimizations are performed, and -the flow graph is translated back from SSA form. Users should not -specify this option, since it is not yet ready for production use. - -@item -fdce -Perform dead-code elimination in SSA form. Requires @samp{-fssa}. Like -@samp{-fssa}, this is an experimental feature. - -@item -fsingle-precision-constant -Treat floating point constant as single precision constant instead of -implicitly converting it to double precision constant. - -@item -frename-registers -Attempt to avoid false dependancies in scheduled code by making use -of registers left over after register allocation. This optimization -will most benefit processors with lots of registers. It can, however, -make debugging impossible, since variables will no longer stay in -a ``home register''. - -@item --param @var{name}=@var{value} -In some places, GCC uses various constants to control the amount of -optimization that is done. For example, GCC will not inline functions -that contain more that a certain number of instructions. You can -control some of these constants on the command-line using the -@samp{--param} option. - -In each case, the @var{value} is a integer. The allowable choices for -@var{name} are given in the following table: - -@table @gcctabopt -@item max-delay-slot-insn-search -The maximum number of instructions to consider when looking for an -instruction to fill a delay slot. If more than this arbitrary number of -instructions is searched, the time savings from filling the delay slot -will be minimal so stop searching. Increasing values mean more -aggressive optimization, making the compile time increase with probably -small improvement in executable run time. - -@item max-delay-slot-live-search -When trying to fill delay slots, the maximum number of instructions to -consider when searching for a block with valid live register -information. Increasing this arbitrarily chosen value means more -aggressive optimization, increasing the compile time. This parameter -should be removed when the delay slot code is rewritten to maintain the -control-flow graph. - -@item max-gcse-memory -The approximate maximum amount of memory that will be allocated in -order to perform the global common subexpression elimination -optimization. If more memory than specified is required, the -optimization will not be done. - -@item max-inline-insns -If an function contains more than this many instructions, it -will not be inlined. This option is precisely equivalent to -@samp{-finline-limit}. - -@end table -@end table - -@node Preprocessor Options -@section Options Controlling the Preprocessor -@cindex preprocessor options -@cindex options, preprocessor - -These options control the C preprocessor, which is run on each C source -file before actual compilation. - -If you use the @samp{-E} option, nothing is done except preprocessing. -Some of these options make sense only together with @samp{-E} because -they cause the preprocessor output to be unsuitable for actual -compilation. - -@table @gcctabopt -@item -include @var{file} -Process @var{file} as input before processing the regular input file. -In effect, the contents of @var{file} are compiled first. Any @samp{-D} -and @samp{-U} options on the command line are always processed before -@samp{-include @var{file}}, regardless of the order in which they are -written. All the @samp{-include} and @samp{-imacros} options are -processed in the order in which they are written. - -@item -imacros @var{file} -Process @var{file} as input, discarding the resulting output, before -processing the regular input file. Because the output generated from -@var{file} is discarded, the only effect of @samp{-imacros @var{file}} -is to make the macros defined in @var{file} available for use in the -main input. All the @samp{-include} and @samp{-imacros} options are -processed in the order in which they are written. - -@item -idirafter @var{dir} -@cindex second include path -Add the directory @var{dir} to the second include path. The directories -on the second include path are searched when a header file is not found -in any of the directories in the main include path (the one that -@samp{-I} adds to). - -@item -iprefix @var{prefix} -Specify @var{prefix} as the prefix for subsequent @samp{-iwithprefix} -options. - -@item -iwithprefix @var{dir} -Add a directory to the second include path. The directory's name is -made by concatenating @var{prefix} and @var{dir}, where @var{prefix} was -specified previously with @samp{-iprefix}. If you have not specified a -prefix yet, the directory containing the installed passes of the -compiler is used as the default. - -@item -iwithprefixbefore @var{dir} -Add a directory to the main include path. The directory's name is made -by concatenating @var{prefix} and @var{dir}, as in the case of -@samp{-iwithprefix}. - -@item -isystem @var{dir} -Add a directory to the beginning of the second include path, marking it -as a system directory, so that it gets the same special treatment as -is applied to the standard system directories. - -@item -nostdinc -Do not search the standard system directories for header files. Only -the directories you have specified with @samp{-I} options (and the -current directory, if appropriate) are searched. @xref{Directory -Options}, for information on @samp{-I}. - -By using both @samp{-nostdinc} and @samp{-I-}, you can limit the include-file -search path to only those directories you specify explicitly. - -@item -remap -@findex -remap -When searching for a header file in a directory, remap file names if a -file named @file{header.gcc} exists in that directory. This can be used -to work around limitations of file systems with file name restrictions. -The @file{header.gcc} file should contain a series of lines with two -tokens on each line: the first token is the name to map, and the second -token is the actual name to use. - -@item -undef -Do not predefine any nonstandard macros. (Including architecture flags). - -@item -E -Run only the C preprocessor. Preprocess all the C source files -specified and output the results to standard output or to the -specified output file. - -@item -C -Tell the preprocessor not to discard comments. Used with the -@samp{-E} option. - -@item -P -Tell the preprocessor not to generate @samp{#line} directives. -Used with the @samp{-E} option. - -@cindex make -@cindex dependencies, make -@item -M -@findex -M -Instead of outputting the result of preprocessing, output a rule -suitable for @code{make} describing the dependencies of the main source -file. The preprocessor outputs one @code{make} rule containing the -object file name for that source file, a colon, and the names of all the -included files. Unless overridden explicitly, the object file name -consists of the basename of the source file with any suffix replaced with -object file suffix. If there are many included files then the -rule is split into several lines using @samp{\}-newline. - -@samp{-M} implies @samp{-E}. - -@item -MM -@findex -MM -Like @samp{-M}, but mention only the files included with @samp{#include -"@var{file}"}. System header files included with @samp{#include -<@var{file}>} are omitted. - -@item -MD -@findex -MD -Like @samp{-M} but the dependency information is written to a file -rather than stdout. @code{gcc} will use the same file name and -directory as the object file, but with the suffix ".d" instead. - -This is in addition to compiling the main file as specified --- -@samp{-MD} does not inhibit ordinary compilation the way @samp{-M} does, -unless you also specify @samp{-MG}. - -With Mach, you can use the utility @code{md} to merge multiple -dependency files into a single dependency file suitable for using with -the @samp{make} command. - -@item -MMD -@findex -MMD -Like @samp{-MD} except mention only user header files, not system --header files. - -@item -MF @var{file} -@findex -MF -When used with @samp{-M} or @samp{-MM}, specifies a file to write the -dependencies to. This allows the preprocessor to write the preprocessed -file to stdout normally. If no @samp{-MF} switch is given, CPP sends -the rules to stdout and suppresses normal preprocessed output. - -Another way to specify output of a @code{make} rule is by setting -the environment variable @env{DEPENDENCIES_OUTPUT} (@pxref{Environment -Variables}). - -@item -MG -@findex -MG -When used with @samp{-M} or @samp{-MM}, @samp{-MG} says to treat missing -header files as generated files and assume they live in the same -directory as the source file. It suppresses preprocessed output, as a -missing header file is ordinarily an error. - -This feature is used in automatic updating of makefiles. - -@item -MP -@findex -MP -This option instructs CPP to add a phony target for each dependency -other than the main file, causing each to depend on nothing. These -dummy rules work around errors @code{make} gives if you remove header -files without updating the @code{Makefile} to match. - -This is typical output:- - -@smallexample -/tmp/test.o: /tmp/test.c /tmp/test.h - -/tmp/test.h: -@end smallexample - -@item -MQ @var{target} -@item -MT @var{target} -@findex -MQ -@findex -MT -By default CPP uses the main file name, including any path, and appends -the object suffix, normally ``.o'', to it to obtain the name of the -target for dependency generation. With @samp{-MT} you can specify a -target yourself, overriding the default one. - -If you want multiple targets, you can specify them as a single argument -to @samp{-MT}, or use multiple @samp{-MT} options. - -The targets you specify are output in the order they appear on the -command line. @samp{-MQ} is identical to @samp{-MT}, except that the -target name is quoted for Make, but with @samp{-MT} it isn't. For -example, -MT '$(objpfx)foo.o' gives - -@smallexample -$(objpfx)foo.o: /tmp/foo.c -@end smallexample - -but -MQ '$(objpfx)foo.o' gives - -@smallexample -$$(objpfx)foo.o: /tmp/foo.c -@end smallexample - -The default target is automatically quoted, as if it were given with -@samp{-MQ}. - -@item -H -Print the name of each header file used, in addition to other normal -activities. - -@item -A@var{question}(@var{answer}) -Assert the answer @var{answer} for @var{question}, in case it is tested -with a preprocessing conditional such as @samp{#if -#@var{question}(@var{answer})}. @samp{-A-} disables the standard -assertions that normally describe the target machine. - -@item -D@var{macro} -Define macro @var{macro} with the string @samp{1} as its definition. - -@item -D@var{macro}=@var{defn} -Define macro @var{macro} as @var{defn}. All instances of @samp{-D} on -the command line are processed before any @samp{-U} options. - -Any @samp{-D} and @samp{-U} options on the command line are processed in -order, and always before @samp{-imacros @var{file}}, regardless of the -order in which they are written. - -@item -U@var{macro} -Undefine macro @var{macro}. @samp{-U} options are evaluated after all -@samp{-D} options, but before any @samp{-include} and @samp{-imacros} -options. - -Any @samp{-D} and @samp{-U} options on the command line are processed in -order, and always before @samp{-imacros @var{file}}, regardless of the -order in which they are written. - -@item -dM -Tell the preprocessor to output only a list of the macro definitions -that are in effect at the end of preprocessing. Used with the @samp{-E} -option. - -@item -dD -Tell the preprocessing to pass all macro definitions into the output, in -their proper sequence in the rest of the output. - -@item -dN -Like @samp{-dD} except that the macro arguments and contents are omitted. -Only @samp{#define @var{name}} is included in the output. - -@item -dI -@findex -dI -Output @samp{#include} directives in addition to the result of -preprocessing. - -@item -trigraphs -@findex -trigraphs -Process ISO standard trigraph sequences. These are three-character -sequences, all starting with @samp{??}, that are defined by ISO C to -stand for single characters. For example, @samp{??/} stands for -@samp{\}, so @samp{'??/n'} is a character constant for a newline. By -default, GCC ignores trigraphs, but in standard-conforming modes it -converts them. See the @samp{-std} and @samp{-ansi} options. - -The nine trigraph sequences are -@table @samp -@item ??( --> @samp{[} - -@item ??) --> @samp{]} - -@item ??< --> @samp{@{} - -@item ??> --> @samp{@}} - -@item ??= --> @samp{#} - -@item ??/ --> @samp{\} - -@item ??' --> @samp{^} - -@item ??! --> @samp{|} - -@item ??- --> @samp{~} - -@end table - -Trigraph support is not popular, so many compilers do not implement it -properly. Portable code should not rely on trigraphs being either -converted or ignored. - -@item -Wp\,@var{option} -Pass @var{option} as an option to the preprocessor. If @var{option} -contains commas, it is split into multiple options at the commas. -@end table - -@node Assembler Options -@section Passing Options to the Assembler - -@c prevent bad page break with this line -You can pass options to the assembler. - -@table @gcctabopt -@item -Wa\,@var{option} -Pass @var{option} as an option to the assembler. If @var{option} -contains commas, it is split into multiple options at the commas. -@end table - -@node Link Options -@section Options for Linking -@cindex link options -@cindex options, linking - -These options come into play when the compiler links object files into -an executable output file. They are meaningless if the compiler is -not doing a link step. - -@table @gcctabopt -@cindex file names -@item @var{object-file-name} -A file name that does not end in a special recognized suffix is -considered to name an object file or library. (Object files are -distinguished from libraries by the linker according to the file -contents.) If linking is done, these object files are used as input -to the linker. - -@item -c -@itemx -S -@itemx -E -If any of these options is used, then the linker is not run, and -object file names should not be used as arguments. @xref{Overall -Options}. - -@cindex Libraries -@item -l@var{library} -@itemx -l @var{library} -Search the library named @var{library} when linking. (The second -alternative with the library as a separate argument is only for -POSIX compliance and is not recommended.) - -It makes a difference where in the command you write this option; the -linker searches and processes libraries and object files in the order they -are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z} -after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers -to functions in @samp{z}, those functions may not be loaded. - -The linker searches a standard list of directories for the library, -which is actually a file named @file{lib@var{library}.a}. The linker -then uses this file as if it had been specified precisely by name. - -The directories searched include several standard system directories -plus any that you specify with @samp{-L}. - -Normally the files found this way are library files---archive files -whose members are object files. The linker handles an archive file by -scanning through it for members which define symbols that have so far -been referenced but not defined. But if the file that is found is an -ordinary object file, it is linked in the usual fashion. The only -difference between using an @samp{-l} option and specifying a file name -is that @samp{-l} surrounds @var{library} with @samp{lib} and @samp{.a} -and searches several directories. - -@item -lobjc -You need this special case of the @samp{-l} option in order to -link an Objective C program. - -@item -nostartfiles -Do not use the standard system startup files when linking. -The standard system libraries are used normally, unless @option{-nostdlib} -or @option{-nodefaultlibs} is used. - -@item -nodefaultlibs -Do not use the standard system libraries when linking. -Only the libraries you specify will be passed to the linker. -The standard startup files are used normally, unless @option{-nostartfiles} -is used. The compiler may generate calls to memcmp, memset, and memcpy -for System V (and ISO C) environments or to bcopy and bzero for -BSD environments. These entries are usually resolved by entries in -libc. These entry points should be supplied through some other -mechanism when this option is specified. - -@item -nostdlib -Do not use the standard system startup files or libraries when linking. -No startup files and only the libraries you specify will be passed to -the linker. The compiler may generate calls to memcmp, memset, and memcpy -for System V (and ISO C) environments or to bcopy and bzero for -BSD environments. These entries are usually resolved by entries in -libc. These entry points should be supplied through some other -mechanism when this option is specified. - -@cindex @code{-lgcc}, use with @code{-nostdlib} -@cindex @code{-nostdlib} and unresolved references -@cindex unresolved references and @code{-nostdlib} -@cindex @code{-lgcc}, use with @code{-nodefaultlibs} -@cindex @code{-nodefaultlibs} and unresolved references -@cindex unresolved references and @code{-nodefaultlibs} -One of the standard libraries bypassed by @samp{-nostdlib} and -@samp{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines -that GCC uses to overcome shortcomings of particular machines, or special -needs for some languages. -@ifset INTERNALS -(@xref{Interface,,Interfacing to GCC Output}, for more discussion of -@file{libgcc.a}.) -@end ifset -@ifclear INTERNALS -(@xref{Interface,,Interfacing to GCC Output,gcc.info,Porting GCC}, -for more discussion of @file{libgcc.a}.) -@end ifclear -In most cases, you need @file{libgcc.a} even when you want to avoid -other standard libraries. In other words, when you specify @samp{-nostdlib} -or @samp{-nodefaultlibs} you should usually specify @samp{-lgcc} as well. -This ensures that you have no unresolved references to internal GCC -library subroutines. (For example, @samp{__main}, used to ensure C++ -constructors will be called; @pxref{Collect2,,@command{collect2}}.) - -@item -s -Remove all symbol table and relocation information from the executable. - -@item -static -On systems that support dynamic linking, this prevents linking with the shared -libraries. On other systems, this option has no effect. - -@item -shared -Produce a shared object which can then be linked with other objects to -form an executable. Not all systems support this option. For predictable -results, you must also specify the same set of options that were used to -generate code (@samp{-fpic}, @samp{-fPIC}, or model suboptions) -when you specify this option.@footnote{On some systems, @samp{gcc -shared} -needs to build supplementary stub code for constructors to work. On -multi-libbed systems, @samp{gcc -shared} must select the correct support -libraries to link against. Failing to supply the correct flags may lead -to subtle defects. Supplying them in cases where they are not necessary -is innocuous.} - -@item -shared-libgcc -@itemx -static-libgcc -On systems that provide @file{libgcc} as a shared library, these options -force the use of either the shared or static version respectively. -If no shared version of @file{libgcc} was built when the compiler was -configured, these options have no effect. - -There are several situations in which an application should use the -shared @file{libgcc} instead of the static version. The most common -of these is when the application wishes to throw and catch exceptions -across different shared libraries. In that case, each of the libraries -as well as the application itself should use the shared @file{libgcc}. - -Therefore, whenever you specify the @samp{-shared} option, the GCC -driver automatically adds @samp{-shared-libgcc}, unless you explicitly -specify @samp{-static-libgcc}. The G++ driver automatically adds -@samp{-shared-libgcc} when you build a main executable as well because -for C++ programs that is typically the right thing to do. -(Exception-handling will not work reliably otherwise.) - -However, when linking a main executable written in C, you must -explicitly say @samp{-shared-libgcc} if you want to use the shared -@file{libgcc}. - -@item -symbolic -Bind references to global symbols when building a shared object. Warn -about any unresolved references (unless overridden by the link editor -option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support -this option. - -@item -Xlinker @var{option} -Pass @var{option} as an option to the linker. You can use this to -supply system-specific linker options which GCC does not know how to -recognize. - -If you want to pass an option that takes an argument, you must use -@samp{-Xlinker} twice, once for the option and once for the argument. -For example, to pass @samp{-assert definitions}, you must write -@samp{-Xlinker -assert -Xlinker definitions}. It does not work to write -@samp{-Xlinker "-assert definitions"}, because this passes the entire -string as a single argument, which is not what the linker expects. - -@item -Wl\,@var{option} -Pass @var{option} as an option to the linker. If @var{option} contains -commas, it is split into multiple options at the commas. - -@item -u @var{symbol} -Pretend the symbol @var{symbol} is undefined, to force linking of -library modules to define it. You can use @samp{-u} multiple times with -different symbols to force loading of additional library modules. -@end table - -@node Directory Options -@section Options for Directory Search -@cindex directory options -@cindex options, directory search -@cindex search path - -These options specify directories to search for header files, for -libraries and for parts of the compiler: - -@table @gcctabopt -@item -I@var{dir} -Add the directory @var{dir} to the head of the list of directories to be -searched for header files. This can be used to override a system header -file, substituting your own version, since these directories are -searched before the system header file directories. However, you should -not use this option to add directories that contain vendor-supplied -system header files (use @samp{-isystem} for that). If you use more than -one @samp{-I} option, the directories are scanned in left-to-right -order; the standard system directories come after. - -@item -I- -Any directories you specify with @samp{-I} options before the @samp{-I-} -option are searched only for the case of @samp{#include "@var{file}"}; -they are not searched for @samp{#include <@var{file}>}. - -If additional directories are specified with @samp{-I} options after -the @samp{-I-}, these directories are searched for all @samp{#include} -directives. (Ordinarily @emph{all} @samp{-I} directories are used -this way.) - -In addition, the @samp{-I-} option inhibits the use of the current -directory (where the current input file came from) as the first search -directory for @samp{#include "@var{file}"}. There is no way to -override this effect of @samp{-I-}. With @samp{-I.} you can specify -searching the directory which was current when the compiler was -invoked. That is not exactly the same as what the preprocessor does -by default, but it is often satisfactory. - -@samp{-I-} does not inhibit the use of the standard system directories -for header files. Thus, @samp{-I-} and @samp{-nostdinc} are -independent. - -@item -L@var{dir} -Add directory @var{dir} to the list of directories to be searched -for @samp{-l}. - -@item -B@var{prefix} -This option specifies where to find the executables, libraries, -include files, and data files of the compiler itself. - -The compiler driver program runs one or more of the subprograms -@file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries -@var{prefix} as a prefix for each program it tries to run, both with and -without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}). - -For each subprogram to be run, the compiler driver first tries the -@samp{-B} prefix, if any. If that name is not found, or if @samp{-B} -was not specified, the driver tries two standard prefixes, which are -@file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc-lib/}. If neither of -those results in a file name that is found, the unmodified program -name is searched for using the directories specified in your -@env{PATH} environment variable. - -@samp{-B} prefixes that effectively specify directory names also apply -to libraries in the linker, because the compiler translates these -options into @samp{-L} options for the linker. They also apply to -includes files in the preprocessor, because the compiler translates these -options into @samp{-isystem} options for the preprocessor. In this case, -the compiler appends @samp{include} to the prefix. - -The run-time support file @file{libgcc.a} can also be searched for using -the @samp{-B} prefix, if needed. If it is not found there, the two -standard prefixes above are tried, and that is all. The file is left -out of the link if it is not found by those means. - -Another way to specify a prefix much like the @samp{-B} prefix is to use -the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment -Variables}. - -@item -specs=@var{file} -Process @var{file} after the compiler reads in the standard @file{specs} -file, in order to override the defaults that the @file{gcc} driver -program uses when determining what switches to pass to @file{cc1}, -@file{cc1plus}, @file{as}, @file{ld}, etc. More than one -@samp{-specs=}@var{file} can be specified on the command line, and they -are processed in order, from left to right. -@end table - -@c man end - -@node Spec Files -@section Specifying subprocesses and the switches to pass to them -@cindex Spec Files -@command{gcc} is a driver program. It performs its job by invoking a -sequence of other programs to do the work of compiling, assembling and -linking. GCC interprets its command-line parameters and uses these to -deduce which programs it should invoke, and which command-line options -it ought to place on their command lines. This behaviour is controlled -by @dfn{spec strings}. In most cases there is one spec string for each -program that GCC can invoke, but a few programs have multiple spec -strings to control their behaviour. The spec strings built into GCC can -be overridden by using the @samp{-specs=} command-line switch to specify -a spec file. - -@dfn{Spec files} are plaintext files that are used to construct spec -strings. They consist of a sequence of directives separated by blank -lines. The type of directive is determined by the first non-whitespace -character on the line and it can be one of the following: - -@table @code -@item %@var{command} -Issues a @var{command} to the spec file processor. The commands that can -appear here are: - -@table @code -@item %include <@var{file}> -@cindex %include -Search for @var{file} and insert its text at the current point in the -specs file. - -@item %include_noerr <@var{file}> -@cindex %include_noerr -Just like @samp{%include}, but do not generate an error message if the include -file cannot be found. - -@item %rename @var{old_name} @var{new_name} -@cindex %rename -Rename the spec string @var{old_name} to @var{new_name}. - -@end table - -@item *[@var{spec_name}]: -This tells the compiler to create, override or delete the named spec -string. All lines after this directive up to the next directive or -blank line are considered to be the text for the spec string. If this -results in an empty string then the spec will be deleted. (Or, if the -spec did not exist, then nothing will happened.) Otherwise, if the spec -does not currently exist a new spec will be created. If the spec does -exist then its contents will be overridden by the text of this -directive, unless the first character of that text is the @samp{+} -character, in which case the text will be appended to the spec. - -@item [@var{suffix}]: -Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive -and up to the next directive or blank line are considered to make up the -spec string for the indicated suffix. When the compiler encounters an -input file with the named suffix, it will processes the spec string in -order to work out how to compile that file. For example: - -@smallexample -.ZZ: -z-compile -input %i -@end smallexample - -This says that any input file whose name ends in @samp{.ZZ} should be -passed to the program @samp{z-compile}, which should be invoked with the -command-line switch @samp{-input} and with the result of performing the -@samp{%i} substitution. (See below.) - -As an alternative to providing a spec string, the text that follows a -suffix directive can be one of the following: - -@table @code -@item @@@var{language} -This says that the suffix is an alias for a known @var{language}. This is -similar to using the @option{-x} command-line switch to GCC to specify a -language explicitly. For example: - -@smallexample -.ZZ: -@@c++ -@end smallexample - -Says that .ZZ files are, in fact, C++ source files. - -@item #@var{name} -This causes an error messages saying: - -@smallexample -@var{name} compiler not installed on this system. -@end smallexample -@end table - -GCC already has an extensive list of suffixes built into it. -This directive will add an entry to the end of the list of suffixes, but -since the list is searched from the end backwards, it is effectively -possible to override earlier entries using this technique. - -@end table - -GCC has the following spec strings built into it. Spec files can -override these strings or create their own. Note that individual -targets can also add their own spec strings to this list. - -@smallexample -asm Options to pass to the assembler -asm_final Options to pass to the assembler post-processor -cpp Options to pass to the C preprocessor -cc1 Options to pass to the C compiler -cc1plus Options to pass to the C++ compiler -endfile Object files to include at the end of the link -link Options to pass to the linker -lib Libraries to include on the command line to the linker -libgcc Decides which GCC support library to pass to the linker -linker Sets the name of the linker -predefines Defines to be passed to the C preprocessor -signed_char Defines to pass to CPP to say whether @code{char} is signed - by default -startfile Object files to include at the start of the link -@end smallexample - -Here is a small example of a spec file: - -@smallexample -%rename lib old_lib - -*lib: ---start-group -lgcc -lc -leval1 --end-group %(old_lib) -@end smallexample - -This example renames the spec called @samp{lib} to @samp{old_lib} and -then overrides the previous definition of @samp{lib} with a new one. -The new definition adds in some extra command-line options before -including the text of the old definition. - -@dfn{Spec strings} are a list of command-line options to be passed to their -corresponding program. In addition, the spec strings can contain -@samp{%}-prefixed sequences to substitute variable text or to -conditionally insert text into the command line. Using these constructs -it is possible to generate quite complex command lines. - -Here is a table of all defined @samp{%}-sequences for spec -strings. Note that spaces are not generated automatically around the -results of expanding these sequences. Therefore you can concatenate them -together or combine them with constant text in a single argument. - -@table @code -@item %% -Substitute one @samp{%} into the program name or argument. - -@item %i -Substitute the name of the input file being processed. - -@item %b -Substitute the basename of the input file being processed. -This is the substring up to (and not including) the last period -and not including the directory. - -@item %B -This is the same as @samp{%b}, but include the file suffix (text after -the last period). - -@item %d -Marks the argument containing or following the @samp{%d} as a -temporary file name, so that that file will be deleted if GCC exits -successfully. Unlike @samp{%g}, this contributes no text to the -argument. - -@item %g@var{suffix} -Substitute a file name that has suffix @var{suffix} and is chosen -once per compilation, and mark the argument in the same way as -@samp{%d}. To reduce exposure to denial-of-service attacks, the file -name is now chosen in a way that is hard to predict even when previously -chosen file names are known. For example, @samp{%g.s ... %g.o ... %g.s} -might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches -the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is -treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g} -was simply substituted with a file name chosen once per compilation, -without regard to any appended suffix (which was therefore treated -just like ordinary text), making such attacks more likely to succeed. - -@item %u@var{suffix} -Like @samp{%g}, but generates a new temporary file name even if -@samp{%u@var{suffix}} was already seen. - -@item %U@var{suffix} -Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a -new one if there is no such last file name. In the absence of any -@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share -the same suffix @emph{space}, so @samp{%g.s ... %U.s ... %g.s ... %U.s} -would involve the generation of two distinct file names, one -for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was -simply substituted with a file name chosen for the previous @samp{%u}, -without regard to any appended suffix. - -@item %j@var{SUFFIX} -Substitutes the name of the HOST_BIT_BUCKET, if any, and if it is -writable, and if save-temps is off; otherwise, substitute the name -of a temporary file, just like @samp{%u}. This temporary file is not -meant for communication between processes, but rather as a junk -disposal mechanism. - -@item %.@var{SUFFIX} -Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args -when it is subsequently output with @samp{%*}. @var{SUFFIX} is -terminated by the next space or %. - -@item %w -Marks the argument containing or following the @samp{%w} as the -designated output file of this compilation. This puts the argument -into the sequence of arguments that @samp{%o} will substitute later. - -@item %o -Substitutes the names of all the output files, with spaces -automatically placed around them. You should write spaces -around the @samp{%o} as well or the results are undefined. -@samp{%o} is for use in the specs for running the linker. -Input files whose names have no recognized suffix are not compiled -at all, but they are included among the output files, so they will -be linked. - -@item %O -Substitutes the suffix for object files. Note that this is -handled specially when it immediately follows @samp{%g, %u, or %U}, -because of the need for those to form complete file names. The -handling is such that @samp{%O} is treated exactly as if it had already -been substituted, except that @samp{%g, %u, and %U} do not currently -support additional @var{suffix} characters following @samp{%O} as they would -following, for example, @samp{.o}. - -@item %p -Substitutes the standard macro predefinitions for the -current target machine. Use this when running @code{cpp}. - -@item %P -Like @samp{%p}, but puts @samp{__} before and after the name of each -predefined macro, except for macros that start with @samp{__} or with -@samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO -C. - -@item %I -Substitute a @samp{-iprefix} option made from GCC_EXEC_PREFIX. - -@item %s -Current argument is the name of a library or startup file of some sort. -Search for that file in a standard list of directories and substitute -the full name found. - -@item %e@var{str} -Print @var{str} as an error message. @var{str} is terminated by a newline. -Use this when inconsistent options are detected. - -@item %| -Output @samp{-} if the input for the current command is coming from a pipe. - -@item %(@var{name}) -Substitute the contents of spec string @var{name} at this point. - -@item %[@var{name}] -Like @samp{%(...)} but put @samp{__} around @samp{-D} arguments. - -@item %x@{@var{option}@} -Accumulate an option for @samp{%X}. - -@item %X -Output the accumulated linker options specified by @samp{-Wl} or a @samp{%x} -spec string. - -@item %Y -Output the accumulated assembler options specified by @samp{-Wa}. - -@item %Z -Output the accumulated preprocessor options specified by @samp{-Wp}. - -@item %v1 -Substitute the major version number of GCC. -(For version 2.9.5, this is 2.) - -@item %v2 -Substitute the minor version number of GCC. -(For version 2.9.5, this is 9.) - -@item %v3 -Substitute the patch level number of GCC. -(For version 2.9.5, this is 5.) - -@item %a -Process the @code{asm} spec. This is used to compute the -switches to be passed to the assembler. - -@item %A -Process the @code{asm_final} spec. This is a spec string for -passing switches to an assembler post-processor, if such a program is -needed. - -@item %l -Process the @code{link} spec. This is the spec for computing the -command line passed to the linker. Typically it will make use of the -@samp{%L %G %S %D and %E} sequences. - -@item %D -Dump out a @samp{-L} option for each directory that GCC believes might -contain startup files. If the target supports multilibs then the -current multilib directory will be prepended to each of these paths. - -@item %M -Output the multilib directory with directory seperators replaced with -"_". If multilib directories are not set, or the multilib directory is -"." then this option emits nothing. - -@item %L -Process the @code{lib} spec. This is a spec string for deciding which -libraries should be included on the command line to the linker. - -@item %G -Process the @code{libgcc} spec. This is a spec string for deciding -which GCC support library should be included on the command line to the linker. - -@item %S -Process the @code{startfile} spec. This is a spec for deciding which -object files should be the first ones passed to the linker. Typically -this might be a file named @file{crt0.o}. - -@item %E -Process the @code{endfile} spec. This is a spec string that specifies -the last object files that will be passed to the linker. - -@item %C -Process the @code{cpp} spec. This is used to construct the arguments -to be passed to the C preprocessor. - -@item %c -Process the @code{signed_char} spec. This is intended to be used -to tell cpp whether a char is signed. It typically has the definition: -@smallexample -%@{funsigned-char:-D__CHAR_UNSIGNED__@} -@end smallexample - -@item %1 -Process the @code{cc1} spec. This is used to construct the options to be -passed to the actual C compiler (@samp{cc1}). - -@item %2 -Process the @code{cc1plus} spec. This is used to construct the options to be -passed to the actual C++ compiler (@samp{cc1plus}). - -@item %* -Substitute the variable part of a matched option. See below. -Note that each comma in the substituted string is replaced by -a single space. - -@item %@{@code{S}@} -Substitutes the @code{-S} switch, if that switch was given to GCC. -If that switch was not specified, this substitutes nothing. Note that -the leading dash is omitted when specifying this option, and it is -automatically inserted if the substitution is performed. Thus the spec -string @samp{%@{foo@}} would match the command-line option @samp{-foo} -and would output the command line option @samp{-foo}. - -@item %W@{@code{S}@} -Like %@{@code{S}@} but mark last argument supplied within as a file to be -deleted on failure. - -@item %@{@code{S}*@} -Substitutes all the switches specified to GCC whose names start -with @code{-S}, but which also take an argument. This is used for -switches like @samp{-o, -D, -I}, etc. GCC considers @samp{-o foo} as being -one switch whose names starts with @samp{o}. %@{o*@} would substitute this -text, including the space. Thus two arguments would be generated. - -@item %@{^@code{S}*@} -Like %@{@code{S}*@}, but don't put a blank between a switch and its -argument. Thus %@{^o*@} would only generate one argument, not two. - -@item %@{@code{S}*&@code{T}*@} -Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options -(the order of @code{S} and @code{T} in the spec is not significant). -There can be any number of ampersand-separated variables; for each the -wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}. - -@item %@{<@code{S}@} -Remove all occurrences of @code{-S} from the command line. Note - this -command is position dependent. @samp{%} commands in the spec string -before this option will see @code{-S}, @samp{%} commands in the spec -string after this option will not. - -@item %@{@code{S}*:@code{X}@} -Substitutes @code{X} if one or more switches whose names start with -@code{-S} are specified to GCC. Note that the tail part of the -@code{-S} option (i.e. the part matched by the @samp{*}) will be substituted -for each occurrence of @samp{%*} within @code{X}. - -@item %@{@code{S}:@code{X}@} -Substitutes @code{X}, but only if the @samp{-S} switch was given to GCC. - -@item %@{!@code{S}:@code{X}@} -Substitutes @code{X}, but only if the @samp{-S} switch was @emph{not} given to GCC. - -@item %@{|@code{S}:@code{X}@} -Like %@{@code{S}:@code{X}@}, but if no @code{S} switch, substitute @samp{-}. - -@item %@{|!@code{S}:@code{X}@} -Like %@{!@code{S}:@code{X}@}, but if there is an @code{S} switch, substitute @samp{-}. - -@item %@{.@code{S}:@code{X}@} -Substitutes @code{X}, but only if processing a file with suffix @code{S}. - -@item %@{!.@code{S}:@code{X}@} -Substitutes @code{X}, but only if @emph{not} processing a file with suffix @code{S}. - -@item %@{@code{S}|@code{P}:@code{X}@} -Substitutes @code{X} if either @code{-S} or @code{-P} was given to GCC. This may be -combined with @samp{!} and @samp{.} sequences as well, although they -have a stronger binding than the @samp{|}. For example a spec string -like this: - -@smallexample -%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@} -@end smallexample - -will output the following command-line options from the following input -command-line options: - -@smallexample -fred.c -foo -baz -jim.d -bar -boggle --d fred.c -foo -baz -boggle --d jim.d -bar -baz -boggle -@end smallexample - -@end table - -The conditional text @code{X} in a %@{@code{S}:@code{X}@} or -%@{!@code{S}:@code{X}@} construct may contain other nested @samp{%} constructs -or spaces, or even newlines. They are processed as usual, as described -above. - -The @samp{-O, -f, -m, and -W} switches are handled specifically in these -constructs. If another value of @samp{-O} or the negated form of a @samp{-f, -m, or --W} switch is found later in the command line, the earlier switch -value is ignored, except with @{@code{S}*@} where @code{S} is just one -letter, which passes all matching options. - -The character @samp{|} at the beginning of the predicate text is used to indicate -that a command should be piped to the following command, but only if @samp{-pipe} -is specified. - -It is built into GCC which switches take arguments and which do not. -(You might think it would be useful to generalize this to allow each -compiler's spec to say which switches take arguments. But this cannot -be done in a consistent fashion. GCC cannot even decide which input -files have been specified without knowing which switches take arguments, -and it must know which input files to compile in order to tell which -compilers to run). - -GCC also knows implicitly that arguments starting in @samp{-l} are to be -treated as compiler output files, and passed to the linker in their -proper position among the other output files. - -@c man begin OPTIONS - -@node Target Options -@section Specifying Target Machine and Compiler Version -@cindex target options -@cindex cross compiling -@cindex specifying machine version -@cindex specifying compiler version and target machine -@cindex compiler version, specifying -@cindex target machine, specifying - -By default, GCC compiles code for the same type of machine that you -are using. However, it can also be installed as a cross-compiler, to -compile for some other type of machine. In fact, several different -configurations of GCC, for different target machines, can be -installed side by side. Then you specify which one to use with the -@samp{-b} option. - -In addition, older and newer versions of GCC can be installed side -by side. One of them (probably the newest) will be the default, but -you may sometimes wish to use another. - -@table @gcctabopt -@item -b @var{machine} -The argument @var{machine} specifies the target machine for compilation. -This is useful when you have installed GCC as a cross-compiler. - -The value to use for @var{machine} is the same as was specified as the -machine type when configuring GCC as a cross-compiler. For -example, if a cross-compiler was configured with @samp{configure -i386v}, meaning to compile for an 80386 running System V, then you -would specify @samp{-b i386v} to run that cross compiler. - -When you do not specify @samp{-b}, it normally means to compile for -the same type of machine that you are using. - -@item -V @var{version} -The argument @var{version} specifies which version of GCC to run. -This is useful when multiple versions are installed. For example, -@var{version} might be @samp{2.0}, meaning to run GCC version 2.0. - -The default version, when you do not specify @samp{-V}, is the last -version of GCC that you installed. -@end table - -The @samp{-b} and @samp{-V} options actually work by controlling part of -the file name used for the executable files and libraries used for -compilation. A given version of GCC, for a given target machine, is -normally kept in the directory @file{/usr/local/lib/gcc-lib/@var{machine}/@var{version}}.@refill - -Thus, sites can customize the effect of @samp{-b} or @samp{-V} either by -changing the names of these directories or adding alternate names (or -symbolic links). If in directory @file{/usr/local/lib/gcc-lib/} the -file @file{80386} is a link to the file @file{i386v}, then @samp{-b -80386} becomes an alias for @samp{-b i386v}. - -In one respect, the @samp{-b} or @samp{-V} do not completely change -to a different compiler: the top-level driver program @command{gcc} -that you originally invoked continues to run and invoke the other -executables (preprocessor, compiler per se, assembler and linker) -that do the real work. However, since no real work is done in the -driver program, it usually does not matter that the driver program -in use is not the one for the specified target. It is common for the -interface to the other executables to change incompatibly between -compiler versions, so unless the version specified is very close to that -of the driver (for example, @samp{-V 3.0} with a driver program from GCC -version 3.0.1), use of @samp{-V} may not work; for example, using -@samp{-V 2.95.2} will not work with a driver program from GCC 3.0. - -The only way that the driver program depends on the target machine is -in the parsing and handling of special machine-specific options. -However, this is controlled by a file which is found, along with the -other executables, in the directory for the specified version and -target machine. As a result, a single installed driver program adapts -to any specified target machine, and sufficiently similar compiler -versions. - -The driver program executable does control one significant thing, -however: the default version and target machine. Therefore, you can -install different instances of the driver program, compiled for -different targets or versions, under different names. - -For example, if the driver for version 2.0 is installed as @command{ogcc} -and that for version 2.1 is installed as @command{gcc}, then the command -@command{gcc} will use version 2.1 by default, while @command{ogcc} will use -2.0 by default. However, you can choose either version with either -command with the @samp{-V} option. - -@node Submodel Options -@section Hardware Models and Configurations -@cindex submodel options -@cindex specifying hardware config -@cindex hardware models and configurations, specifying -@cindex machine dependent options - -Earlier we discussed the standard option @samp{-b} which chooses among -different installed compilers for completely different target -machines, such as Vax vs. 68000 vs. 80386. - -In addition, each of these target machine types can have its own -special options, starting with @samp{-m}, to choose among various -hardware models or configurations---for example, 68010 vs 68020, -floating coprocessor or none. A single installed version of the -compiler can compile for any model or configuration, according to the -options specified. - -Some configurations of the compiler also support additional special -options, usually for compatibility with other compilers on the same -platform. - -@ifset INTERNALS -These options are defined by the macro @code{TARGET_SWITCHES} in the -machine description. The default for the options is also defined by -that macro, which enables you to change the defaults. -@end ifset - -@menu -* M680x0 Options:: -* M68hc1x Options:: -* VAX Options:: -* SPARC Options:: -* Convex Options:: -* AMD29K Options:: -* ARM Options:: -* MN10200 Options:: -* MN10300 Options:: -* M32R/D Options:: -* M88K Options:: -* RS/6000 and PowerPC Options:: -* RT Options:: -* MIPS Options:: -* i386 Options:: -* HPPA Options:: -* Intel 960 Options:: -* DEC Alpha Options:: -* Clipper Options:: -* H8/300 Options:: -* SH Options:: -* System V Options:: -* TMS320C3x/C4x Options:: -* V850 Options:: -* ARC Options:: -* NS32K Options:: -* AVR Options:: -* MCore Options:: -* IA-64 Options:: -* D30V Options:: -@end menu - -@node M680x0 Options -@subsection M680x0 Options -@cindex M680x0 options - -These are the @samp{-m} options defined for the 68000 series. The default -values for these options depends on which style of 68000 was selected when -the compiler was configured; the defaults for the most common choices are -given below. - -@table @gcctabopt -@item -m68000 -@itemx -mc68000 -Generate output for a 68000. This is the default -when the compiler is configured for 68000-based systems. - -Use this option for microcontrollers with a 68000 or EC000 core, -including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. - -@item -m68020 -@itemx -mc68020 -Generate output for a 68020. This is the default -when the compiler is configured for 68020-based systems. - -@item -m68881 -Generate output containing 68881 instructions for floating point. -This is the default for most 68020 systems unless @samp{-nfp} was -specified when the compiler was configured. - -@item -m68030 -Generate output for a 68030. This is the default when the compiler is -configured for 68030-based systems. - -@item -m68040 -Generate output for a 68040. This is the default when the compiler is -configured for 68040-based systems. - -This option inhibits the use of 68881/68882 instructions that have to be -emulated by software on the 68040. Use this option if your 68040 does not -have code to emulate those instructions. - -@item -m68060 -Generate output for a 68060. This is the default when the compiler is -configured for 68060-based systems. - -This option inhibits the use of 68020 and 68881/68882 instructions that -have to be emulated by software on the 68060. Use this option if your 68060 -does not have code to emulate those instructions. - -@item -mcpu32 -Generate output for a CPU32. This is the default -when the compiler is configured for CPU32-based systems. - -Use this option for microcontrollers with a -CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, -68336, 68340, 68341, 68349 and 68360. - -@item -m5200 -Generate output for a 520X "coldfire" family cpu. This is the default -when the compiler is configured for 520X-based systems. - -Use this option for microcontroller with a 5200 core, including -the MCF5202, MCF5203, MCF5204 and MCF5202. - - -@item -m68020-40 -Generate output for a 68040, without using any of the new instructions. -This results in code which can run relatively efficiently on either a -68020/68881 or a 68030 or a 68040. The generated code does use the -68881 instructions that are emulated on the 68040. - -@item -m68020-60 -Generate output for a 68060, without using any of the new instructions. -This results in code which can run relatively efficiently on either a -68020/68881 or a 68030 or a 68040. The generated code does use the -68881 instructions that are emulated on the 68060. - -@item -mfpa -Generate output containing Sun FPA instructions for floating point. - -@item -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all m68k -targets. Normally the facilities of the machine's usual C compiler are -used, but this can't be done directly in cross-compilation. You must -make your own arrangements to provide suitable library functions for -cross-compilation. The embedded targets @samp{m68k-*-aout} and -@samp{m68k-*-coff} do provide software floating point support. - -@item -mshort -Consider type @code{int} to be 16 bits wide, like @code{short int}. - -@item -mnobitfield -Do not use the bit-field instructions. The @samp{-m68000}, @samp{-mcpu32} -and @samp{-m5200} options imply @w{@samp{-mnobitfield}}. - -@item -mbitfield -Do use the bit-field instructions. The @samp{-m68020} option implies -@samp{-mbitfield}. This is the default if you use a configuration -designed for a 68020. - -@item -mrtd -Use a different function-calling convention, in which functions -that take a fixed number of arguments return with the @code{rtd} -instruction, which pops their arguments while returning. This -saves one instruction in the caller since there is no need to pop -the arguments there. - -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. - -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including @code{printf}); -otherwise incorrect code will be generated for calls to those -functions. - -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) - -The @code{rtd} instruction is supported by the 68010, 68020, 68030, -68040, 68060 and CPU32 processors, but not by the 68000 or 5200. - -@item -malign-int -@itemx -mno-align-int -Control whether GCC aligns @code{int}, @code{long}, @code{long long}, -@code{float}, @code{double}, and @code{long double} variables on a 32-bit -boundary (@samp{-malign-int}) or a 16-bit boundary (@samp{-mno-align-int}). -Aligning variables on 32-bit boundaries produces code that runs somewhat -faster on processors with 32-bit busses at the expense of more memory. - -@strong{Warning:} if you use the @samp{-malign-int} switch, GCC will -align structures containing the above types differently than -most published application binary interface specifications for the m68k. - -@item -mpcrel -Use the pc-relative addressing mode of the 68000 directly, instead of -using a global offset table. At present, this option implies -fpic, -allowing at most a 16-bit offset for pc-relative addressing. -fPIC is -not presently supported with -mpcrel, though this could be supported for -68020 and higher processors. - -@item -mno-strict-align -@itemx -mstrict-align -@kindex -mstrict-align -Do not (do) assume that unaligned memory references will be handled by -the system. - -@end table - -@node M68hc1x Options -@subsection M68hc1x Options -@cindex M68hc1x options - -These are the @samp{-m} options defined for the 68hc11 and 68hc12 -microcontrollers. The default values for these options depends on -which style of microcontroller was selected when the compiler was configured; -the defaults for the most common choices are given below. - -@table @gcctabopt -@item -m6811 -@itemx -m68hc11 -Generate output for a 68HC11. This is the default -when the compiler is configured for 68HC11-based systems. - -@item -m6812 -@itemx -m68hc12 -Generate output for a 68HC12. This is the default -when the compiler is configured for 68HC12-based systems. - -@item -mauto-incdec -Enable the use of 68HC12 pre and post auto-increment and auto-decrement -addressing modes. - -@item -mshort -Consider type @code{int} to be 16 bits wide, like @code{short int}. - -@item -msoft-reg-count=@var{count} -Specify the number of pseudo-soft registers which are used for the -code generation. The maximum number is 32. Using more pseudo-soft -register may or may not result in better code depending on the program. -The default is 4 for 68HC11 and 2 for 68HC12. - -@end table - -@node VAX Options -@subsection VAX Options -@cindex VAX options - -These @samp{-m} options are defined for the Vax: - -@table @gcctabopt -@item -munix -Do not output certain jump instructions (@code{aobleq} and so on) -that the Unix assembler for the Vax cannot handle across long -ranges. - -@item -mgnu -Do output those jump instructions, on the assumption that you -will assemble with the GNU assembler. - -@item -mg -Output code for g-format floating point numbers instead of d-format. -@end table - -@node SPARC Options -@subsection SPARC Options -@cindex SPARC options - -These @samp{-m} switches are supported on the SPARC: - -@table @gcctabopt -@item -mno-app-regs -@itemx -mapp-regs -Specify @samp{-mapp-regs} to generate output using the global registers -2 through 4, which the SPARC SVR4 ABI reserves for applications. This -is the default. - -To be fully SVR4 ABI compliant at the cost of some performance loss, -specify @samp{-mno-app-regs}. You should compile libraries and system -software with this option. - -@item -mfpu -@itemx -mhard-float -Generate output containing floating point instructions. This is the -default. - -@item -mno-fpu -@itemx -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all SPARC -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. The embedded targets @samp{sparc-*-aout} and -@samp{sparclite-*-*} do provide software floating point support. - -@samp{-msoft-float} changes the calling convention in the output file; -therefore, it is only useful if you compile @emph{all} of a program with -this option. In particular, you need to compile @file{libgcc.a}, the -library that comes with GCC, with @samp{-msoft-float} in order for -this to work. - -@item -mhard-quad-float -Generate output containing quad-word (long double) floating point -instructions. - -@item -msoft-quad-float -Generate output containing library calls for quad-word (long double) -floating point instructions. The functions called are those specified -in the SPARC ABI. This is the default. - -As of this writing, there are no sparc implementations that have hardware -support for the quad-word floating point instructions. They all invoke -a trap handler for one of these instructions, and then the trap handler -emulates the effect of the instruction. Because of the trap handler overhead, -this is much slower than calling the ABI library routines. Thus the -@samp{-msoft-quad-float} option is the default. - -@item -mno-epilogue -@itemx -mepilogue -With @samp{-mepilogue} (the default), the compiler always emits code for -function exit at the end of each function. Any function exit in -the middle of the function (such as a return statement in C) will -generate a jump to the exit code at the end of the function. - -With @samp{-mno-epilogue}, the compiler tries to emit exit code inline -at every function exit. - -@item -mno-flat -@itemx -mflat -With @samp{-mflat}, the compiler does not generate save/restore instructions -and will use a "flat" or single register window calling convention. -This model uses %i7 as the frame pointer and is compatible with the normal -register window model. Code from either may be intermixed. -The local registers and the input registers (0-5) are still treated as -"call saved" registers and will be saved on the stack as necessary. - -With @samp{-mno-flat} (the default), the compiler emits save/restore -instructions (except for leaf functions) and is the normal mode of operation. - -@item -mno-unaligned-doubles -@itemx -munaligned-doubles -Assume that doubles have 8 byte alignment. This is the default. - -With @samp{-munaligned-doubles}, GCC assumes that doubles have 8 byte -alignment only if they are contained in another type, or if they have an -absolute address. Otherwise, it assumes they have 4 byte alignment. -Specifying this option avoids some rare compatibility problems with code -generated by other compilers. It is not the default because it results -in a performance loss, especially for floating point code. - -@item -mno-faster-structs -@itemx -mfaster-structs -With @samp{-mfaster-structs}, the compiler assumes that structures -should have 8 byte alignment. This enables the use of pairs of -@code{ldd} and @code{std} instructions for copies in structure -assignment, in place of twice as many @code{ld} and @code{st} pairs. -However, the use of this changed alignment directly violates the Sparc -ABI. Thus, it's intended only for use on targets where the developer -acknowledges that their resulting code will not be directly in line with -the rules of the ABI. - -@item -mv8 -@itemx -msparclite -These two options select variations on the SPARC architecture. - -By default (unless specifically configured for the Fujitsu SPARClite), -GCC generates code for the v7 variant of the SPARC architecture. - -@samp{-mv8} will give you SPARC v8 code. The only difference from v7 -code is that the compiler emits the integer multiply and integer -divide instructions which exist in SPARC v8 but not in SPARC v7. - -@samp{-msparclite} will give you SPARClite code. This adds the integer -multiply, integer divide step and scan (@code{ffs}) instructions which -exist in SPARClite but not in SPARC v7. - -These options are deprecated and will be deleted in a future GCC release. -They have been replaced with @samp{-mcpu=xxx}. - -@item -mcypress -@itemx -msupersparc -These two options select the processor for which the code is optimised. - -With @samp{-mcypress} (the default), the compiler optimizes code for the -Cypress CY7C602 chip, as used in the SparcStation/SparcServer 3xx series. -This is also appropriate for the older SparcStation 1, 2, IPX etc. - -With @samp{-msupersparc} the compiler optimizes code for the SuperSparc cpu, as -used in the SparcStation 10, 1000 and 2000 series. This flag also enables use -of the full SPARC v8 instruction set. - -These options are deprecated and will be deleted in a future GCC release. -They have been replaced with @samp{-mcpu=xxx}. - -@item -mcpu=@var{cpu_type} -Set the instruction set, register set, and instruction scheduling parameters -for machine type @var{cpu_type}. Supported values for @var{cpu_type} are -@samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite}, -@samp{hypersparc}, @samp{sparclite86x}, @samp{f930}, @samp{f934}, -@samp{sparclet}, @samp{tsc701}, @samp{v9}, and @samp{ultrasparc}. - -Default instruction scheduling parameters are used for values that select -an architecture and not an implementation. These are @samp{v7}, @samp{v8}, -@samp{sparclite}, @samp{sparclet}, @samp{v9}. - -Here is a list of each supported architecture and their supported -implementations. - -@smallexample - v7: cypress - v8: supersparc, hypersparc - sparclite: f930, f934, sparclite86x - sparclet: tsc701 - v9: ultrasparc -@end smallexample - -@item -mtune=@var{cpu_type} -Set the instruction scheduling parameters for machine type -@var{cpu_type}, but do not set the instruction set or register set that the -option @samp{-mcpu=}@var{cpu_type} would. - -The same values for @samp{-mcpu=}@var{cpu_type} are used for -@samp{-mtune=}@*@var{cpu_type}, though the only useful values are those that -select a particular cpu implementation: @samp{cypress}, @samp{supersparc}, -@samp{hypersparc}, @samp{f930}, @samp{f934}, @samp{sparclite86x}, -@samp{tsc701}, @samp{ultrasparc}. - -@end table - -These @samp{-m} switches are supported in addition to the above -on the SPARCLET processor. - -@table @gcctabopt -@item -mlittle-endian -Generate code for a processor running in little-endian mode. - -@item -mlive-g0 -Treat register @code{%g0} as a normal register. -GCC will continue to clobber it as necessary but will not assume -it always reads as 0. - -@item -mbroken-saverestore -Generate code that does not use non-trivial forms of the @code{save} and -@code{restore} instructions. Early versions of the SPARCLET processor do -not correctly handle @code{save} and @code{restore} instructions used with -arguments. They correctly handle them used without arguments. A @code{save} -instruction used without arguments increments the current window pointer -but does not allocate a new stack frame. It is assumed that the window -overflow trap handler will properly handle this case as will interrupt -handlers. -@end table - -These @samp{-m} switches are supported in addition to the above -on SPARC V9 processors in 64-bit environments. - -@table @gcctabopt -@item -mlittle-endian -Generate code for a processor running in little-endian mode. - -@item -m32 -@itemx -m64 -Generate code for a 32-bit or 64-bit environment. -The 32-bit environment sets int, long and pointer to 32 bits. -The 64-bit environment sets int to 32 bits and long and pointer -to 64 bits. - -@item -mcmodel=medlow -Generate code for the Medium/Low code model: the program must be linked -in the low 32 bits of the address space. Pointers are 64 bits. -Programs can be statically or dynamically linked. - -@item -mcmodel=medmid -Generate code for the Medium/Middle code model: the program must be linked -in the low 44 bits of the address space, the text segment must be less than -2G bytes, and data segment must be within 2G of the text segment. -Pointers are 64 bits. - -@item -mcmodel=medany -Generate code for the Medium/Anywhere code model: the program may be linked -anywhere in the address space, the text segment must be less than -2G bytes, and data segment must be within 2G of the text segment. -Pointers are 64 bits. - -@item -mcmodel=embmedany -Generate code for the Medium/Anywhere code model for embedded systems: -assume a 32-bit text and a 32-bit data segment, both starting anywhere -(determined at link time). Register %g4 points to the base of the -data segment. Pointers are still 64 bits. -Programs are statically linked, PIC is not supported. - -@item -mstack-bias -@itemx -mno-stack-bias -With @samp{-mstack-bias}, GCC assumes that the stack pointer, and -frame pointer if present, are offset by -2047 which must be added back -when making stack frame references. -Otherwise, assume no such offset is present. -@end table - -@node Convex Options -@subsection Convex Options -@cindex Convex options - -These @samp{-m} options are defined for Convex: - -@table @gcctabopt -@item -mc1 -Generate output for C1. The code will run on any Convex machine. -The preprocessor symbol @code{__convex__c1__} is defined. - -@item -mc2 -Generate output for C2. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C2. -The preprocessor symbol @code{__convex_c2__} is defined. - -@item -mc32 -Generate output for C32xx. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C32. -The preprocessor symbol @code{__convex_c32__} is defined. - -@item -mc34 -Generate output for C34xx. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C34. -The preprocessor symbol @code{__convex_c34__} is defined. - -@item -mc38 -Generate output for C38xx. Uses instructions not available on C1. -Scheduling and other optimizations are chosen for max performance on C38. -The preprocessor symbol @code{__convex_c38__} is defined. - -@item -margcount -Generate code which puts an argument count in the word preceding each -argument list. This is compatible with regular CC, and a few programs -may need the argument count word. GDB and other source-level debuggers -do not need it; this info is in the symbol table. - -@item -mnoargcount -Omit the argument count word. This is the default. - -@item -mvolatile-cache -Allow volatile references to be cached. This is the default. - -@item -mvolatile-nocache -Volatile references bypass the data cache, going all the way to memory. -This is only needed for multi-processor code that does not use standard -synchronization instructions. Making non-volatile references to volatile -locations will not necessarily work. - -@item -mlong32 -Type long is 32 bits, the same as type int. This is the default. - -@item -mlong64 -Type long is 64 bits, the same as type long long. This option is useless, -because no library support exists for it. -@end table - -@node AMD29K Options -@subsection AMD29K Options -@cindex AMD29K options - -These @samp{-m} options are defined for the AMD Am29000: - -@table @gcctabopt -@item -mdw -@kindex -mdw -@cindex DW bit (29k) -Generate code that assumes the @code{DW} bit is set, i.e., that byte and -halfword operations are directly supported by the hardware. This is the -default. - -@item -mndw -@kindex -mndw -Generate code that assumes the @code{DW} bit is not set. - -@item -mbw -@kindex -mbw -@cindex byte writes (29k) -Generate code that assumes the system supports byte and halfword write -operations. This is the default. - -@item -mnbw -@kindex -mnbw -Generate code that assumes the systems does not support byte and -halfword write operations. @samp{-mnbw} implies @samp{-mndw}. - -@item -msmall -@kindex -msmall -@cindex memory model (29k) -Use a small memory model that assumes that all function addresses are -either within a single 256 KB segment or at an absolute address of less -than 256k. This allows the @code{call} instruction to be used instead -of a @code{const}, @code{consth}, @code{calli} sequence. - -@item -mnormal -@kindex -mnormal -Use the normal memory model: Generate @code{call} instructions only when -calling functions in the same file and @code{calli} instructions -otherwise. This works if each file occupies less than 256 KB but allows -the entire executable to be larger than 256 KB. This is the default. - -@item -mlarge -Always use @code{calli} instructions. Specify this option if you expect -a single file to compile into more than 256 KB of code. - -@item -m29050 -@kindex -m29050 -@cindex processor selection (29k) -Generate code for the Am29050. - -@item -m29000 -@kindex -m29000 -Generate code for the Am29000. This is the default. - -@item -mkernel-registers -@kindex -mkernel-registers -@cindex kernel and user registers (29k) -Generate references to registers @code{gr64-gr95} instead of to -registers @code{gr96-gr127}. This option can be used when compiling -kernel code that wants a set of global registers disjoint from that used -by user-mode code. - -Note that when this option is used, register names in @samp{-f} flags -must use the normal, user-mode, names. - -@item -muser-registers -@kindex -muser-registers -Use the normal set of global registers, @code{gr96-gr127}. This is the -default. - -@item -mstack-check -@itemx -mno-stack-check -@kindex -mstack-check -@cindex stack checks (29k) -Insert (or do not insert) a call to @code{__msp_check} after each stack -adjustment. This is often used for kernel code. - -@item -mstorem-bug -@itemx -mno-storem-bug -@kindex -mstorem-bug -@cindex storem bug (29k) -@samp{-mstorem-bug} handles 29k processors which cannot handle the -separation of a mtsrim insn and a storem instruction (most 29000 chips -to date, but not the 29050). - -@item -mno-reuse-arg-regs -@itemx -mreuse-arg-regs -@kindex -mreuse-arg-regs -@samp{-mno-reuse-arg-regs} tells the compiler to only use incoming argument -registers for copying out arguments. This helps detect calling a function -with fewer arguments than it was declared with. - -@item -mno-impure-text -@itemx -mimpure-text -@kindex -mimpure-text -@samp{-mimpure-text}, used in addition to @samp{-shared}, tells the compiler to -not pass @samp{-assert pure-text} to the linker when linking a shared object. - -@item -msoft-float -@kindex -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not part of GCC. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. - -@item -mno-multm -@kindex -mno-multm -Do not generate multm or multmu instructions. This is useful for some embedded -systems which do not have trap handlers for these instructions. -@end table - -@node ARM Options -@subsection ARM Options -@cindex ARM options - -These @samp{-m} options are defined for Advanced RISC Machines (ARM) -architectures: - -@table @gcctabopt -@item -mapcs-frame -@kindex -mapcs-frame -Generate a stack frame that is compliant with the ARM Procedure Call -Standard for all functions, even if this is not strictly necessary for -correct execution of the code. Specifying @samp{-fomit-frame-pointer} -with this option will cause the stack frames not to be generated for -leaf functions. The default is @samp{-mno-apcs-frame}. - -@item -mapcs -@kindex -mapcs -This is a synonym for @samp{-mapcs-frame}. - -@item -mapcs-26 -@kindex -mapcs-26 -Generate code for a processor running with a 26-bit program counter, -and conforming to the function calling standards for the APCS 26-bit -option. This option replaces the @samp{-m2} and @samp{-m3} options -of previous releases of the compiler. - -@item -mapcs-32 -@kindex -mapcs-32 -Generate code for a processor running with a 32-bit program counter, -and conforming to the function calling standards for the APCS 32-bit -option. This option replaces the @samp{-m6} option of previous releases -of the compiler. - -@ignore -@c not currently implemented -@item -mapcs-stack-check -@kindex -mapcs-stack-check -@kindex -mno-apcs-stack-check -Generate code to check the amount of stack space available upon entry to -every function (that actually uses some stack space). If there is -insufficient space available then either the function -@samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be -called, depending upon the amount of stack space required. The run time -system is required to provide these functions. The default is -@samp{-mno-apcs-stack-check}, since this produces smaller code. - -@c not currently implemented -@item -mapcs-float -@kindex -mapcs-float -@kindex -mno-apcs-float -Pass floating point arguments using the float point registers. This is -one of the variants of the APCS. This option is recommended if the -target hardware has a floating point unit or if a lot of floating point -arithmetic is going to be performed by the code. The default is -@samp{-mno-apcs-float}, since integer only code is slightly increased in -size if @samp{-mapcs-float} is used. - -@c not currently implemented -@item -mapcs-reentrant -@kindex -mapcs-reentrant -@kindex -mno-apcs-reentrant -Generate reentrant, position independent code. The default is -@samp{-mno-apcs-reentrant}. -@end ignore - -@item -mthumb-interwork -@kindex -mthumb-interwork -@kindex -mno-thumb-interwork -Generate code which supports calling between the ARM and Thumb -instruction sets. Without this option the two instruction sets cannot -be reliably used inside one program. The default is -@samp{-mno-thumb-interwork}, since slightly larger code is generated -when @samp{-mthumb-interwork} is specified. - -@item -mno-sched-prolog -@kindex -mno-sched-prolog -@kindex -msched-prolog -Prevent the reordering of instructions in the function prolog, or the -merging of those instruction with the instructions in the function's -body. This means that all functions will start with a recognizable set -of instructions (or in fact one of a choice from a small set of -different function prologues), and this information can be used to -locate the start if functions inside an executable piece of code. The -default is @samp{-msched-prolog}. - -@item -mhard-float -Generate output containing floating point instructions. This is the -default. - -@item -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all ARM -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. - -@samp{-msoft-float} changes the calling convention in the output file; -therefore, it is only useful if you compile @emph{all} of a program with -this option. In particular, you need to compile @file{libgcc.a}, the -library that comes with GCC, with @samp{-msoft-float} in order for -this to work. - -@item -mlittle-endian -Generate code for a processor running in little-endian mode. This is -the default for all standard configurations. - -@item -mbig-endian -Generate code for a processor running in big-endian mode; the default is -to compile code for a little-endian processor. - -@item -mwords-little-endian -This option only applies when generating code for big-endian processors. -Generate code for a little-endian word order but a big-endian byte -order. That is, a byte order of the form @samp{32107654}. Note: this -option should only be used if you require compatibility with code for -big-endian ARM processors generated by versions of the compiler prior to -2.8. - -@item -malignment-traps -@kindex -malignment-traps -Generate code that will not trap if the MMU has alignment traps enabled. -On ARM architectures prior to ARMv4, there were no instructions to -access half-word objects stored in memory. However, when reading from -memory a feature of the ARM architecture allows a word load to be used, -even if the address is unaligned, and the processor core will rotate the -data as it is being loaded. This option tells the compiler that such -misaligned accesses will cause a MMU trap and that it should instead -synthesise the access as a series of byte accesses. The compiler can -still use word accesses to load half-word data if it knows that the -address is aligned to a word boundary. - -This option is ignored when compiling for ARM architecture 4 or later, -since these processors have instructions to directly access half-word -objects in memory. - -@item -mno-alignment-traps -@kindex -mno-alignment-traps -Generate code that assumes that the MMU will not trap unaligned -accesses. This produces better code when the target instruction set -does not have half-word memory operations (i.e. implementations prior to -ARMv4). - -Note that you cannot use this option to access unaligned word objects, -since the processor will only fetch one 32-bit aligned object from -memory. - -The default setting for most targets is -mno-alignment-traps, since -this produces better code when there are no half-word memory -instructions available. - -@item -mshort-load-bytes -@itemx -mno-short-load-words -@kindex -mshort-load-bytes -@kindex -mno-short-load-words -These are deprecated aliases for @samp{-malignment-traps}. - -@item -mno-short-load-bytes -@itemx -mshort-load-words -@kindex -mno-short-load-bytes -@kindex -mshort-load-words -This are deprecated aliases for @samp{-mno-alignment-traps}. - -@item -mbsd -@kindex -mbsd -This option only applies to RISC iX. Emulate the native BSD-mode -compiler. This is the default if @samp{-ansi} is not specified. - -@item -mxopen -@kindex -mxopen -This option only applies to RISC iX. Emulate the native X/Open-mode -compiler. - -@item -mno-symrename -@kindex -mno-symrename -This option only applies to RISC iX. Do not run the assembler -post-processor, @samp{symrename}, after code has been assembled. -Normally it is necessary to modify some of the standard symbols in -preparation for linking with the RISC iX C library; this option -suppresses this pass. The post-processor is never run when the -compiler is built for cross-compilation. - -@item -mcpu= -@kindex -mcpu= -This specifies the name of the target ARM processor. GCC uses this name -to determine what kind of instructions it can emit when generating -assembly code. Permissible names are: arm2, arm250, arm3, arm6, arm60, -arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, -arm70, arm700, arm700i, arm710, arm710c, arm7100, arm7500, arm7500fe, -arm7tdmi, arm8, strongarm, strongarm110, strongarm1100, arm8, arm810, -arm9, arm9e, arm920, arm920t, arm940t, arm9tdmi, arm10tdmi, arm1020t, -xscale. - -@itemx -mtune= -@kindex -mtune= -This option is very similar to the @samp{-mcpu=} option, except that -instead of specifying the actual target processor type, and hence -restricting which instructions can be used, it specifies that GCC should -tune the performance of the code as if the target were of the type -specified in this option, but still choosing the instructions that it -will generate based on the cpu specified by a @samp{-mcpu=} option. -For some ARM implementations better performance can be obtained by using -this option. - -@item -march= -@kindex -march= -This specifies the name of the target ARM architecture. GCC uses this -name to determine what kind of instructions it can emit when generating -assembly code. This option can be used in conjunction with or instead -of the @samp{-mcpu=} option. Permissible names are: armv2, armv2a, -armv3, armv3m, armv4, armv4t, armv5, armv5t, armv5te. - -@item -mfpe= -@itemx -mfp= -@kindex -mfpe= -@kindex -mfp= -This specifies the version of the floating point emulation available on -the target. Permissible values are 2 and 3. @samp{-mfp=} is a synonym -for @samp{-mfpe=}, for compatibility with older versions of GCC. - -@item -mstructure-size-boundary= -@kindex -mstructure-size-boundary -The size of all structures and unions will be rounded up to a multiple -of the number of bits set by this option. Permissible values are 8 and -32. The default value varies for different toolchains. For the COFF -targeted toolchain the default value is 8. Specifying the larger number -can produce faster, more efficient code, but can also increase the size -of the program. The two values are potentially incompatible. Code -compiled with one value cannot necessarily expect to work with code or -libraries compiled with the other value, if they exchange information -using structures or unions. - -@item -mabort-on-noreturn -@kindex -mabort-on-noreturn -@kindex -mnoabort-on-noreturn -Generate a call to the function @code{abort} at the end of a -@code{noreturn} function. It will be executed if the function tries to -return. - -@item -mlong-calls -@itemx -mno-long-calls -Tells the compiler to perform function calls by first loading the -address of the function into a register and then performing a subroutine -call on this register. This switch is needed if the target function -will lie outside of the 64 megabyte addressing range of the offset based -version of subroutine call instruction. - -Even if this switch is enabled, not all function calls will be turned -into long calls. The heuristic is that static functions, functions -which have the @samp{short-call} attribute, functions that are inside -the scope of a @samp{#pragma no_long_calls} directive and functions whose -definitions have already been compiled within the current compilation -unit, will not be turned into long calls. The exception to this rule is -that weak function definitions, functions with the @samp{long-call} -attribute or the @samp{section} attribute, and functions that are within -the scope of a @samp{#pragma long_calls} directive, will always be -turned into long calls. - -This feature is not enabled by default. Specifying -@samp{-mno-long-calls} will restore the default behaviour, as will -placing the function calls within the scope of a @samp{#pragma -long_calls_off} directive. Note these switches have no effect on how -the compiler generates code to handle function calls via function -pointers. - -@item -mnop-fun-dllimport -@kindex -mnop-fun-dllimport -Disable support for the @emph{dllimport} attribute. - -@item -msingle-pic-base -@kindex -msingle-pic-base -Treat the register used for PIC addressing as read-only, rather than -loading it in the prologue for each function. The run-time system is -responsible for initialising this register with an appropriate value -before execution begins. - -@item -mpic-register= -@kindex -mpic-register= -Specify the register to be used for PIC addressing. The default is R10 -unless stack-checking is enabled, when R9 is used. - -@item -mpoke-function-name -@kindex -mpoke-function-name -Write the name of each function into the text section, directly -preceding the function prologue. The generated code is similar to this: - -@smallexample - t0 - .ascii "arm_poke_function_name", 0 - .align - t1 - .word 0xff000000 + (t1 - t0) - arm_poke_function_name - mov ip, sp - stmfd sp!, @{fp, ip, lr, pc@} - sub fp, ip, #4 -@end smallexample - -When performing a stack backtrace, code can inspect the value of -@code{pc} stored at @code{fp + 0}. If the trace function then looks at -location @code{pc - 12} and the top 8 bits are set, then we know that -there is a function name embedded immediately preceding this location -and has length @code{((pc[-3]) & 0xff000000)}. - -@item -mthumb -@kindex -mthumb -Generate code for the 16-bit Thumb instruction set. The default is to -use the 32-bit ARM instruction set. - -@item -mtpcs-frame -@kindex -mtpcs-frame -@kindex -mno-tpcs-frame -Generate a stack frame that is compliant with the Thumb Procedure Call -Standard for all non-leaf functions. (A leaf function is one that does -not call any other functions.) The default is @samp{-mno-tpcs-frame}. - -@item -mtpcs-leaf-frame -@kindex -mtpcs-leaf-frame -@kindex -mno-tpcs-leaf-frame -Generate a stack frame that is compliant with the Thumb Procedure Call -Standard for all leaf functions. (A leaf function is one that does -not call any other functions.) The default is @samp{-mno-apcs-leaf-frame}. - -@item -mcallee-super-interworking -@kindex -mcallee-super-interworking -Gives all externally visible functions in the file being compiled an ARM -instruction set header which switches to Thumb mode before executing the -rest of the function. This allows these functions to be called from -non-interworking code. - -@item -mcaller-super-interworking -@kindex -mcaller-super-interworking -Allows calls via function pointers (including virtual functions) to -execute correctly regardless of whether the target code has been -compiled for interworking or not. There is a small overhead in the cost -of executing a function pointer if this option is enabled. - -@end table - -@node MN10200 Options -@subsection MN10200 Options -@cindex MN10200 options -These @samp{-m} options are defined for Matsushita MN10200 architectures: -@table @gcctabopt - -@item -mrelax -Indicate to the linker that it should perform a relaxation optimization pass -to shorten branches, calls and absolute memory addresses. This option only -has an effect when used on the command line for the final link step. - -This option makes symbolic debugging impossible. -@end table - -@node MN10300 Options -@subsection MN10300 Options -@cindex MN10300 options -These @samp{-m} options are defined for Matsushita MN10300 architectures: - -@table @gcctabopt -@item -mmult-bug -Generate code to avoid bugs in the multiply instructions for the MN10300 -processors. This is the default. - -@item -mno-mult-bug -Do not generate code to avoid bugs in the multiply instructions for the -MN10300 processors. - -@item -mam33 -Generate code which uses features specific to the AM33 processor. - -@item -mno-am33 -Do not generate code which uses features specific to the AM33 processor. This -is the default. - -@item -mrelax -Indicate to the linker that it should perform a relaxation optimization pass -to shorten branches, calls and absolute memory addresses. This option only -has an effect when used on the command line for the final link step. - -This option makes symbolic debugging impossible. -@end table - - -@node M32R/D Options -@subsection M32R/D Options -@cindex M32R/D options - -These @samp{-m} options are defined for Mitsubishi M32R/D architectures: - -@table @gcctabopt -@item -mcode-model=small -Assume all objects live in the lower 16MB of memory (so that their addresses -can be loaded with the @code{ld24} instruction), and assume all subroutines -are reachable with the @code{bl} instruction. -This is the default. - -The addressability of a particular object can be set with the -@code{model} attribute. - -@item -mcode-model=medium -Assume objects may be anywhere in the 32-bit address space (the compiler -will generate @code{seth/add3} instructions to load their addresses), and -assume all subroutines are reachable with the @code{bl} instruction. - -@item -mcode-model=large -Assume objects may be anywhere in the 32-bit address space (the compiler -will generate @code{seth/add3} instructions to load their addresses), and -assume subroutines may not be reachable with the @code{bl} instruction -(the compiler will generate the much slower @code{seth/add3/jl} -instruction sequence). - -@item -msdata=none -Disable use of the small data area. Variables will be put into -one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the -@code{section} attribute has been specified). -This is the default. - -The small data area consists of sections @samp{.sdata} and @samp{.sbss}. -Objects may be explicitly put in the small data area with the -@code{section} attribute using one of these sections. - -@item -msdata=sdata -Put small global and static data in the small data area, but do not -generate special code to reference them. - -@item -msdata=use -Put small global and static data in the small data area, and generate -special instructions to reference them. - -@item -G @var{num} -@cindex smaller data references -Put global and static objects less than or equal to @var{num} bytes -into the small data or bss sections instead of the normal data or bss -sections. The default value of @var{num} is 8. -The @samp{-msdata} option must be set to one of @samp{sdata} or @samp{use} -for this option to have any effect. - -All modules should be compiled with the same @samp{-G @var{num}} value. -Compiling with different values of @var{num} may or may not work; if it -doesn't the linker will give an error message - incorrect code will not be -generated. - -@end table - -@node M88K Options -@subsection M88K Options -@cindex M88k options - -These @samp{-m} options are defined for Motorola 88k architectures: - -@table @gcctabopt -@item -m88000 -@kindex -m88000 -Generate code that works well on both the m88100 and the -m88110. - -@item -m88100 -@kindex -m88100 -Generate code that works best for the m88100, but that also -runs on the m88110. - -@item -m88110 -@kindex -m88110 -Generate code that works best for the m88110, and may not run -on the m88100. - -@item -mbig-pic -@kindex -mbig-pic -Obsolete option to be removed from the next revision. -Use @samp{-fPIC}. - -@item -midentify-revision -@kindex -midentify-revision -@kindex ident -@cindex identifying source, compiler (88k) -Include an @code{ident} directive in the assembler output recording the -source file name, compiler name and version, timestamp, and compilation -flags used. - -@item -mno-underscores -@kindex -mno-underscores -@cindex underscores, avoiding (88k) -In assembler output, emit symbol names without adding an underscore -character at the beginning of each name. The default is to use an -underscore as prefix on each name. - -@item -mocs-debug-info -@itemx -mno-ocs-debug-info -@kindex -mocs-debug-info -@kindex -mno-ocs-debug-info -@cindex OCS (88k) -@cindex debugging, 88k OCS -Include (or omit) additional debugging information (about registers used -in each stack frame) as specified in the 88open Object Compatibility -Standard, ``OCS''. This extra information allows debugging of code that -has had the frame pointer eliminated. The default for DG/UX, SVr4, and -Delta 88 SVr3.2 is to include this information; other 88k configurations -omit this information by default. - -@item -mocs-frame-position -@kindex -mocs-frame-position -@cindex register positions in frame (88k) -When emitting COFF debugging information for automatic variables and -parameters stored on the stack, use the offset from the canonical frame -address, which is the stack pointer (register 31) on entry to the -function. The DG/UX, SVr4, Delta88 SVr3.2, and BCS configurations use -@samp{-mocs-frame-position}; other 88k configurations have the default -@samp{-mno-ocs-frame-position}. - -@item -mno-ocs-frame-position -@kindex -mno-ocs-frame-position -@cindex register positions in frame (88k) -When emitting COFF debugging information for automatic variables and -parameters stored on the stack, use the offset from the frame pointer -register (register 30). When this option is in effect, the frame -pointer is not eliminated when debugging information is selected by the --g switch. - -@item -moptimize-arg-area -@itemx -mno-optimize-arg-area -@kindex -moptimize-arg-area -@kindex -mno-optimize-arg-area -@cindex arguments in frame (88k) -Control how function arguments are stored in stack frames. -@samp{-moptimize-arg-area} saves space by optimizing them, but this -conflicts with the 88open specifications. The opposite alternative, -@samp{-mno-optimize-arg-area}, agrees with 88open standards. By default -GCC does not optimize the argument area. - -@item -mshort-data-@var{num} -@kindex -mshort-data-@var{num} -@cindex smaller data references (88k) -@cindex r0-relative references (88k) -Generate smaller data references by making them relative to @code{r0}, -which allows loading a value using a single instruction (rather than the -usual two). You control which data references are affected by -specifying @var{num} with this option. For example, if you specify -@samp{-mshort-data-512}, then the data references affected are those -involving displacements of less than 512 bytes. -@samp{-mshort-data-@var{num}} is not effective for @var{num} greater -than 64k. - -@item -mserialize-volatile -@kindex -mserialize-volatile -@itemx -mno-serialize-volatile -@kindex -mno-serialize-volatile -@cindex sequential consistency on 88k -Do, or don't, generate code to guarantee sequential consistency -of volatile memory references. By default, consistency is -guaranteed. - -The order of memory references made by the MC88110 processor does -not always match the order of the instructions requesting those -references. In particular, a load instruction may execute before -a preceding store instruction. Such reordering violates -sequential consistency of volatile memory references, when there -are multiple processors. When consistency must be guaranteed, -GNU C generates special instructions, as needed, to force -execution in the proper order. - -The MC88100 processor does not reorder memory references and so -always provides sequential consistency. However, by default, GNU -C generates the special instructions to guarantee consistency -even when you use @samp{-m88100}, so that the code may be run on an -MC88110 processor. If you intend to run your code only on the -MC88100 processor, you may use @samp{-mno-serialize-volatile}. - -The extra code generated to guarantee consistency may affect the -performance of your application. If you know that you can safely -forgo this guarantee, you may use @samp{-mno-serialize-volatile}. - -@item -msvr4 -@itemx -msvr3 -@kindex -msvr4 -@kindex -msvr3 -@cindex assembler syntax, 88k -@cindex SVr4 -Turn on (@samp{-msvr4}) or off (@samp{-msvr3}) compiler extensions -related to System V release 4 (SVr4). This controls the following: - -@enumerate -@item -Which variant of the assembler syntax to emit. -@item -@samp{-msvr4} makes the C preprocessor recognize @samp{#pragma weak} -that is used on System V release 4. -@item -@samp{-msvr4} makes GCC issue additional declaration directives used in -SVr4. -@end enumerate - -@samp{-msvr4} is the default for the m88k-motorola-sysv4 and -m88k-dg-dgux m88k configurations. @samp{-msvr3} is the default for all -other m88k configurations. - -@item -mversion-03.00 -@kindex -mversion-03.00 -This option is obsolete, and is ignored. -@c ??? which asm syntax better for GAS? option there too? - -@item -mno-check-zero-division -@itemx -mcheck-zero-division -@kindex -mno-check-zero-division -@kindex -mcheck-zero-division -@cindex zero division on 88k -Do, or don't, generate code to guarantee that integer division by -zero will be detected. By default, detection is guaranteed. - -Some models of the MC88100 processor fail to trap upon integer -division by zero under certain conditions. By default, when -compiling code that might be run on such a processor, GNU C -generates code that explicitly checks for zero-valued divisors -and traps with exception number 503 when one is detected. Use of -mno-check-zero-division suppresses such checking for code -generated to run on an MC88100 processor. - -GNU C assumes that the MC88110 processor correctly detects all -instances of integer division by zero. When @samp{-m88110} is -specified, both @samp{-mcheck-zero-division} and -@samp{-mno-check-zero-division} are ignored, and no explicit checks for -zero-valued divisors are generated. - -@item -muse-div-instruction -@kindex -muse-div-instruction -@cindex divide instruction, 88k -Use the div instruction for signed integer division on the -MC88100 processor. By default, the div instruction is not used. - -On the MC88100 processor the signed integer division instruction -div) traps to the operating system on a negative operand. The -operating system transparently completes the operation, but at a -large cost in execution time. By default, when compiling code -that might be run on an MC88100 processor, GNU C emulates signed -integer division using the unsigned integer division instruction -divu), thereby avoiding the large penalty of a trap to the -operating system. Such emulation has its own, smaller, execution -cost in both time and space. To the extent that your code's -important signed integer division operations are performed on two -nonnegative operands, it may be desirable to use the div -instruction directly. - -On the MC88110 processor the div instruction (also known as the -divs instruction) processes negative operands without trapping to -the operating system. When @samp{-m88110} is specified, -@samp{-muse-div-instruction} is ignored, and the div instruction is used -for signed integer division. - -Note that the result of dividing INT_MIN by -1 is undefined. In -particular, the behavior of such a division with and without -@samp{-muse-div-instruction} may differ. - -@item -mtrap-large-shift -@itemx -mhandle-large-shift -@kindex -mtrap-large-shift -@kindex -mhandle-large-shift -@cindex bit shift overflow (88k) -@cindex large bit shifts (88k) -Include code to detect bit-shifts of more than 31 bits; respectively, -trap such shifts or emit code to handle them properly. By default GCC -makes no special provision for large bit shifts. - -@item -mwarn-passed-structs -@kindex -mwarn-passed-structs -@cindex structure passing (88k) -Warn when a function passes a struct as an argument or result. -Structure-passing conventions have changed during the evolution of the C -language, and are often the source of portability problems. By default, -GCC issues no such warning. -@end table - -@node RS/6000 and PowerPC Options -@subsection IBM RS/6000 and PowerPC Options -@cindex RS/6000 and PowerPC Options -@cindex IBM RS/6000 and PowerPC Options - -These @samp{-m} options are defined for the IBM RS/6000 and PowerPC: -@table @gcctabopt -@item -mpower -@itemx -mno-power -@itemx -mpower2 -@itemx -mno-power2 -@itemx -mpowerpc -@itemx -mno-powerpc -@itemx -mpowerpc-gpopt -@itemx -mno-powerpc-gpopt -@itemx -mpowerpc-gfxopt -@itemx -mno-powerpc-gfxopt -@itemx -mpowerpc64 -@itemx -mno-powerpc64 -@kindex -mpower -@kindex -mpower2 -@kindex -mpowerpc -@kindex -mpowerpc-gpopt -@kindex -mpowerpc-gfxopt -@kindex -mpowerpc64 -GCC supports two related instruction set architectures for the -RS/6000 and PowerPC. The @dfn{POWER} instruction set are those -instructions supported by the @samp{rios} chip set used in the original -RS/6000 systems and the @dfn{PowerPC} instruction set is the -architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and -the IBM 4xx microprocessors. - -Neither architecture is a subset of the other. However there is a -large common subset of instructions supported by both. An MQ -register is included in processors supporting the POWER architecture. - -You use these options to specify which instructions are available on the -processor you are using. The default value of these options is -determined when configuring GCC. Specifying the -@samp{-mcpu=@var{cpu_type}} overrides the specification of these -options. We recommend you use the @samp{-mcpu=@var{cpu_type}} option -rather than the options listed above. - -The @samp{-mpower} option allows GCC to generate instructions that -are found only in the POWER architecture and to use the MQ register. -Specifying @samp{-mpower2} implies @samp{-power} and also allows GCC -to generate instructions that are present in the POWER2 architecture but -not the original POWER architecture. - -The @samp{-mpowerpc} option allows GCC to generate instructions that -are found only in the 32-bit subset of the PowerPC architecture. -Specifying @samp{-mpowerpc-gpopt} implies @samp{-mpowerpc} and also allows -GCC to use the optional PowerPC architecture instructions in the -General Purpose group, including floating-point square root. Specifying -@samp{-mpowerpc-gfxopt} implies @samp{-mpowerpc} and also allows GCC to -use the optional PowerPC architecture instructions in the Graphics -group, including floating-point select. - -The @samp{-mpowerpc64} option allows GCC to generate the additional -64-bit instructions that are found in the full PowerPC64 architecture -and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to -@samp{-mno-powerpc64}. - -If you specify both @samp{-mno-power} and @samp{-mno-powerpc}, GCC -will use only the instructions in the common subset of both -architectures plus some special AIX common-mode calls, and will not use -the MQ register. Specifying both @samp{-mpower} and @samp{-mpowerpc} -permits GCC to use any instruction from either architecture and to -allow use of the MQ register; specify this for the Motorola MPC601. - -@item -mnew-mnemonics -@itemx -mold-mnemonics -@kindex -mnew-mnemonics -@kindex -mold-mnemonics -Select which mnemonics to use in the generated assembler code. -@samp{-mnew-mnemonics} requests output that uses the assembler mnemonics -defined for the PowerPC architecture, while @samp{-mold-mnemonics} -requests the assembler mnemonics defined for the POWER architecture. -Instructions defined in only one architecture have only one mnemonic; -GCC uses that mnemonic irrespective of which of these options is -specified. - -GCC defaults to the mnemonics appropriate for the architecture in -use. Specifying @samp{-mcpu=@var{cpu_type}} sometimes overrides the -value of these option. Unless you are building a cross-compiler, you -should normally not specify either @samp{-mnew-mnemonics} or -@samp{-mold-mnemonics}, but should instead accept the default. - -@item -mcpu=@var{cpu_type} -@kindex -mcpu -Set architecture type, register usage, choice of mnemonics, and -instruction scheduling parameters for machine type @var{cpu_type}. -Supported values for @var{cpu_type} are @samp{rios}, @samp{rios1}, -@samp{rsc}, @samp{rios2}, @samp{rs64a}, @samp{601}, @samp{602}, -@samp{603}, @samp{603e}, @samp{604}, @samp{604e}, @samp{620}, -@samp{630}, @samp{740}, @samp{750}, @samp{power}, @samp{power2}, -@samp{powerpc}, @samp{403}, @samp{505}, @samp{801}, @samp{821}, -@samp{823}, and @samp{860} and @samp{common}. @samp{-mcpu=power}, -@samp{-mcpu=power2}, @samp{-mcpu=powerpc}, and @samp{-mcpu=powerpc64} -specify generic POWER, POWER2, pure 32-bit PowerPC (i.e., not MPC601), -and 64-bit PowerPC architecture machine types, with an appropriate, -generic processor model assumed for scheduling purposes.@refill - -Specifying any of the following options: -@samp{-mcpu=rios1}, @samp{-mcpu=rios2}, @samp{-mcpu=rsc}, -@samp{-mcpu=power}, or @samp{-mcpu=power2} -enables the @samp{-mpower} option and disables the @samp{-mpowerpc} option; -@samp{-mcpu=601} enables both the @samp{-mpower} and @samp{-mpowerpc} options. -All of @samp{-mcpu=rs64a}, @samp{-mcpu=602}, @samp{-mcpu=603}, -@samp{-mcpu=603e}, @samp{-mcpu=604}, @samp{-mcpu=620}, @samp{-mcpu=630}, -@samp{-mcpu=740}, and @samp{-mcpu=750} -enable the @samp{-mpowerpc} option and disable the @samp{-mpower} option. -Exactly similarly, all of @samp{-mcpu=403}, -@samp{-mcpu=505}, @samp{-mcpu=821}, @samp{-mcpu=860} and @samp{-mcpu=powerpc} -enable the @samp{-mpowerpc} option and disable the @samp{-mpower} option. -@samp{-mcpu=common} disables both the -@samp{-mpower} and @samp{-mpowerpc} options.@refill - -AIX versions 4 or greater selects @samp{-mcpu=common} by default, so -that code will operate on all members of the RS/6000 POWER and PowerPC -families. In that case, GCC will use only the instructions in the -common subset of both architectures plus some special AIX common-mode -calls, and will not use the MQ register. GCC assumes a generic -processor model for scheduling purposes. - -Specifying any of the options @samp{-mcpu=rios1}, @samp{-mcpu=rios2}, -@samp{-mcpu=rsc}, @samp{-mcpu=power}, or @samp{-mcpu=power2} also -disables the @samp{new-mnemonics} option. Specifying @samp{-mcpu=601}, -@samp{-mcpu=602}, @samp{-mcpu=603}, @samp{-mcpu=603e}, @samp{-mcpu=604}, -@samp{-mcpu=620}, @samp{-mcpu=630}, @samp{-mcpu=403}, @samp{-mcpu=505}, -@samp{-mcpu=821}, @samp{-mcpu=860} or @samp{-mcpu=powerpc} also enables -the @samp{new-mnemonics} option.@refill - -Specifying @samp{-mcpu=403}, @samp{-mcpu=821}, or @samp{-mcpu=860} also -enables the @samp{-msoft-float} option. - -@item -mtune=@var{cpu_type} -Set the instruction scheduling parameters for machine type -@var{cpu_type}, but do not set the architecture type, register usage, -choice of mnemonics like @samp{-mcpu=}@var{cpu_type} would. The same -values for @var{cpu_type} are used for @samp{-mtune=}@var{cpu_type} as -for @samp{-mcpu=}@var{cpu_type}. The @samp{-mtune=}@var{cpu_type} -option overrides the @samp{-mcpu=}@var{cpu_type} option in terms of -instruction scheduling parameters. - -@item -mfull-toc -@itemx -mno-fp-in-toc -@itemx -mno-sum-in-toc -@itemx -mminimal-toc -@kindex -mminimal-toc -Modify generation of the TOC (Table Of Contents), which is created for -every executable file. The @samp{-mfull-toc} option is selected by -default. In that case, GCC will allocate at least one TOC entry for -each unique non-automatic variable reference in your program. GCC -will also place floating-point constants in the TOC. However, only -16,384 entries are available in the TOC. - -If you receive a linker error message that saying you have overflowed -the available TOC space, you can reduce the amount of TOC space used -with the @samp{-mno-fp-in-toc} and @samp{-mno-sum-in-toc} options. -@samp{-mno-fp-in-toc} prevents GCC from putting floating-point -constants in the TOC and @samp{-mno-sum-in-toc} forces GCC to -generate code to calculate the sum of an address and a constant at -run-time instead of putting that sum into the TOC. You may specify one -or both of these options. Each causes GCC to produce very slightly -slower and larger code at the expense of conserving TOC space. - -If you still run out of space in the TOC even when you specify both of -these options, specify @samp{-mminimal-toc} instead. This option causes -GCC to make only one TOC entry for every file. When you specify this -option, GCC will produce code that is slower and larger but which -uses extremely little TOC space. You may wish to use this option -only on files that contain less frequently executed code. @refill - -@item -maix64 -@itemx -maix32 -@kindex -maix64 -@kindex -maix32 -Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit -@code{long} type, and the infrastructure needed to support them. -Specifying @samp{-maix64} implies @samp{-mpowerpc64} and -@samp{-mpowerpc}, while @samp{-maix32} disables the 64-bit ABI and -implies @samp{-mno-powerpc64}. GCC defaults to @samp{-maix32}. - -@item -mxl-call -@itemx -mno-xl-call -@kindex -mxl-call -On AIX, pass floating-point arguments to prototyped functions beyond the -register save area (RSA) on the stack in addition to argument FPRs. The -AIX calling convention was extended but not initially documented to -handle an obscure K&R C case of calling a function that takes the -address of its arguments with fewer arguments than declared. AIX XL -compilers access floating point arguments which do not fit in the -RSA from the stack when a subroutine is compiled without -optimization. Because always storing floating-point arguments on the -stack is inefficient and rarely needed, this option is not enabled by -default and only is necessary when calling subroutines compiled by AIX -XL compilers without optimization. - -@item -mthreads -@kindex -mthreads -Support @dfn{AIX Threads}. Link an application written to use -@dfn{pthreads} with special libraries and startup code to enable the -application to run. - -@item -mpe -@kindex -mpe -Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE). Link an -application written to use message passing with special startup code to -enable the application to run. The system must have PE installed in the -standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file -must be overridden with the @samp{-specs=} option to specify the -appropriate directory location. The Parallel Environment does not -support threads, so the @samp{-mpe} option and the @samp{-mthreads} -option are incompatible. - -@item -msoft-float -@itemx -mhard-float -@kindex -msoft-float -Generate code that does not use (uses) the floating-point register set. -Software floating point emulation is provided if you use the -@samp{-msoft-float} option, and pass the option to GCC when linking. - -@item -mmultiple -@itemx -mno-multiple -Generate code that uses (does not use) the load multiple word -instructions and the store multiple word instructions. These -instructions are generated by default on POWER systems, and not -generated on PowerPC systems. Do not use @samp{-mmultiple} on little -endian PowerPC systems, since those instructions do not work when the -processor is in little endian mode. The exceptions are PPC740 and -PPC750 which permit the instructions usage in little endian mode. - -@item -mstring -@itemx -mno-string -@kindex -mstring -Generate code that uses (does not use) the load string instructions -and the store string word instructions to save multiple registers and -do small block moves. These instructions are generated by default on -POWER systems, and not generated on PowerPC systems. Do not use -@samp{-mstring} on little endian PowerPC systems, since those -instructions do not work when the processor is in little endian mode. -The exceptions are PPC740 and PPC750 which permit the instructions -usage in little endian mode. - -@item -mupdate -@itemx -mno-update -@kindex -mupdate -Generate code that uses (does not use) the load or store instructions -that update the base register to the address of the calculated memory -location. These instructions are generated by default. If you use -@samp{-mno-update}, there is a small window between the time that the -stack pointer is updated and the address of the previous frame is -stored, which means code that walks the stack frame across interrupts or -signals may get corrupted data. - -@item -mfused-madd -@itemx -mno-fused-madd -@kindex -mfused-madd -Generate code that uses (does not use) the floating point multiply and -accumulate instructions. These instructions are generated by default if -hardware floating is used. - -@item -mno-bit-align -@itemx -mbit-align -@kindex -mbit-align -On System V.4 and embedded PowerPC systems do not (do) force structures -and unions that contain bit fields to be aligned to the base type of the -bit field. - -For example, by default a structure containing nothing but 8 -@code{unsigned} bitfields of length 1 would be aligned to a 4 byte -boundary and have a size of 4 bytes. By using @samp{-mno-bit-align}, -the structure would be aligned to a 1 byte boundary and be one byte in -size. - -@item -mno-strict-align -@itemx -mstrict-align -@kindex -mstrict-align -On System V.4 and embedded PowerPC systems do not (do) assume that -unaligned memory references will be handled by the system. - -@item -mrelocatable -@itemx -mno-relocatable -@kindex -mrelocatable -On embedded PowerPC systems generate code that allows (does not allow) -the program to be relocated to a different address at runtime. If you -use @samp{-mrelocatable} on any module, all objects linked together must -be compiled with @samp{-mrelocatable} or @samp{-mrelocatable-lib}. - -@item -mrelocatable-lib -@itemx -mno-relocatable-lib -On embedded PowerPC systems generate code that allows (does not allow) -the program to be relocated to a different address at runtime. Modules -compiled with @samp{-mrelocatable-lib} can be linked with either modules -compiled without @samp{-mrelocatable} and @samp{-mrelocatable-lib} or -with modules compiled with the @samp{-mrelocatable} options. - -@item -mno-toc -@itemx -mtoc -On System V.4 and embedded PowerPC systems do not (do) assume that -register 2 contains a pointer to a global area pointing to the addresses -used in the program. - -@item -mlittle -@itemx -mlittle-endian -On System V.4 and embedded PowerPC systems compile code for the -processor in little endian mode. The @samp{-mlittle-endian} option is -the same as @samp{-mlittle}. - -@item -mbig -@itemx -mbig-endian -On System V.4 and embedded PowerPC systems compile code for the -processor in big endian mode. The @samp{-mbig-endian} option is -the same as @samp{-mbig}. - -@item -mcall-sysv -On System V.4 and embedded PowerPC systems compile code using calling -conventions that adheres to the March 1995 draft of the System V -Application Binary Interface, PowerPC processor supplement. This is the -default unless you configured GCC using @samp{powerpc-*-eabiaix}. - -@item -mcall-sysv-eabi -Specify both @samp{-mcall-sysv} and @samp{-meabi} options. - -@item -mcall-sysv-noeabi -Specify both @samp{-mcall-sysv} and @samp{-mno-eabi} options. - -@item -mcall-aix -On System V.4 and embedded PowerPC systems compile code using calling -conventions that are similar to those used on AIX. This is the -default if you configured GCC using @samp{powerpc-*-eabiaix}. - -@item -mcall-solaris -On System V.4 and embedded PowerPC systems compile code for the Solaris -operating system. - -@item -mcall-linux -On System V.4 and embedded PowerPC systems compile code for the -Linux-based GNU system. - -@item -mprototype -@itemx -mno-prototype -On System V.4 and embedded PowerPC systems assume that all calls to -variable argument functions are properly prototyped. Otherwise, the -compiler must insert an instruction before every non prototyped call to -set or clear bit 6 of the condition code register (@var{CR}) to -indicate whether floating point values were passed in the floating point -registers in case the function takes a variable arguments. With -@samp{-mprototype}, only calls to prototyped variable argument functions -will set or clear the bit. - -@item -msim -On embedded PowerPC systems, assume that the startup module is called -@file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and -@file{libc.a}. This is the default for @samp{powerpc-*-eabisim}. -configurations. - -@item -mmvme -On embedded PowerPC systems, assume that the startup module is called -@file{crt0.o} and the standard C libraries are @file{libmvme.a} and -@file{libc.a}. - -@item -mads -On embedded PowerPC systems, assume that the startup module is called -@file{crt0.o} and the standard C libraries are @file{libads.a} and -@file{libc.a}. - -@item -myellowknife -On embedded PowerPC systems, assume that the startup module is called -@file{crt0.o} and the standard C libraries are @file{libyk.a} and -@file{libc.a}. - -@item -mvxworks -On System V.4 and embedded PowerPC systems, specify that you are -compiling for a VxWorks system. - -@item -memb -On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags -header to indicate that @samp{eabi} extended relocations are used. - -@item -meabi -@itemx -mno-eabi -On System V.4 and embedded PowerPC systems do (do not) adhere to the -Embedded Applications Binary Interface (eabi) which is a set of -modifications to the System V.4 specifications. Selecting @option{-meabi} -means that the stack is aligned to an 8 byte boundary, a function -@code{__eabi} is called to from @code{main} to set up the eabi -environment, and the @samp{-msdata} option can use both @code{r2} and -@code{r13} to point to two separate small data areas. Selecting -@option{-mno-eabi} means that the stack is aligned to a 16 byte boundary, -do not call an initialization function from @code{main}, and the -@samp{-msdata} option will only use @code{r13} to point to a single -small data area. The @samp{-meabi} option is on by default if you -configured GCC using one of the @samp{powerpc*-*-eabi*} options. - -@item -msdata=eabi -On System V.4 and embedded PowerPC systems, put small initialized -@code{const} global and static data in the @samp{.sdata2} section, which -is pointed to by register @code{r2}. Put small initialized -non-@code{const} global and static data in the @samp{.sdata} section, -which is pointed to by register @code{r13}. Put small uninitialized -global and static data in the @samp{.sbss} section, which is adjacent to -the @samp{.sdata} section. The @samp{-msdata=eabi} option is -incompatible with the @samp{-mrelocatable} option. The -@samp{-msdata=eabi} option also sets the @samp{-memb} option. - -@item -msdata=sysv -On System V.4 and embedded PowerPC systems, put small global and static -data in the @samp{.sdata} section, which is pointed to by register -@code{r13}. Put small uninitialized global and static data in the -@samp{.sbss} section, which is adjacent to the @samp{.sdata} section. -The @samp{-msdata=sysv} option is incompatible with the -@samp{-mrelocatable} option. - -@item -msdata=default -@itemx -msdata -On System V.4 and embedded PowerPC systems, if @samp{-meabi} is used, -compile code the same as @samp{-msdata=eabi}, otherwise compile code the -same as @samp{-msdata=sysv}. - -@item -msdata-data -On System V.4 and embedded PowerPC systems, put small global and static -data in the @samp{.sdata} section. Put small uninitialized global and -static data in the @samp{.sbss} section. Do not use register @code{r13} -to address small data however. This is the default behavior unless -other @samp{-msdata} options are used. - -@item -msdata=none -@itemx -mno-sdata -On embedded PowerPC systems, put all initialized global and static data -in the @samp{.data} section, and all uninitialized data in the -@samp{.bss} section. - -@item -G @var{num} -@cindex smaller data references (PowerPC) -@cindex .sdata/.sdata2 references (PowerPC) -On embedded PowerPC systems, put global and static items less than or -equal to @var{num} bytes into the small data or bss sections instead of -the normal data or bss section. By default, @var{num} is 8. The -@samp{-G @var{num}} switch is also passed to the linker. -All modules should be compiled with the same @samp{-G @var{num}} value. - -@item -mregnames -@itemx -mno-regnames -On System V.4 and embedded PowerPC systems do (do not) emit register -names in the assembly language output using symbolic forms. - -@end table - -@node RT Options -@subsection IBM RT Options -@cindex RT options -@cindex IBM RT options - -These @samp{-m} options are defined for the IBM RT PC: - -@table @gcctabopt -@item -min-line-mul -Use an in-line code sequence for integer multiplies. This is the -default. - -@item -mcall-lib-mul -Call @code{lmul$$} for integer multiples. - -@item -mfull-fp-blocks -Generate full-size floating point data blocks, including the minimum -amount of scratch space recommended by IBM. This is the default. - -@item -mminimum-fp-blocks -Do not include extra scratch space in floating point data blocks. This -results in smaller code, but slower execution, since scratch space must -be allocated dynamically. - -@cindex @file{varargs.h} and RT PC -@cindex @file{stdarg.h} and RT PC -@item -mfp-arg-in-fpregs -Use a calling sequence incompatible with the IBM calling convention in -which floating point arguments are passed in floating point registers. -Note that @code{varargs.h} and @code{stdargs.h} will not work with -floating point operands if this option is specified. - -@item -mfp-arg-in-gregs -Use the normal calling convention for floating point arguments. This is -the default. - -@item -mhc-struct-return -Return structures of more than one word in memory, rather than in a -register. This provides compatibility with the MetaWare HighC (hc) -compiler. Use the option @samp{-fpcc-struct-return} for compatibility -with the Portable C Compiler (pcc). - -@item -mnohc-struct-return -Return some structures of more than one word in registers, when -convenient. This is the default. For compatibility with the -IBM-supplied compilers, use the option @samp{-fpcc-struct-return} or the -option @samp{-mhc-struct-return}. -@end table - -@node MIPS Options -@subsection MIPS Options -@cindex MIPS options - -These @samp{-m} options are defined for the MIPS family of computers: - -@table @gcctabopt -@item -mcpu=@var{cpu type} -Assume the defaults for the machine type @var{cpu type} when scheduling -instructions. The choices for @var{cpu type} are @samp{r2000}, @samp{r3000}, -@samp{r3900}, @samp{r4000}, @samp{r4100}, @samp{r4300}, @samp{r4400}, -@samp{r4600}, @samp{r4650}, @samp{r5000}, @samp{r6000}, @samp{r8000}, -and @samp{orion}. Additionally, the @samp{r2000}, @samp{r3000}, -@samp{r4000}, @samp{r5000}, and @samp{r6000} can be abbreviated as -@samp{r2k} (or @samp{r2K}), @samp{r3k}, etc. While picking a specific -@var{cpu type} will schedule things appropriately for that particular -chip, the compiler will not generate any code that does not meet level 1 -of the MIPS ISA (instruction set architecture) without a @samp{-mipsX} -or @samp{-mabi} switch being used. - -@item -mips1 -Issue instructions from level 1 of the MIPS ISA. This is the default. -@samp{r3000} is the default @var{cpu type} at this ISA level. - -@item -mips2 -Issue instructions from level 2 of the MIPS ISA (branch likely, square -root instructions). @samp{r6000} is the default @var{cpu type} at this -ISA level. - -@item -mips3 -Issue instructions from level 3 of the MIPS ISA (64-bit instructions). -@samp{r4000} is the default @var{cpu type} at this ISA level. - -@item -mips4 -Issue instructions from level 4 of the MIPS ISA (conditional move, -prefetch, enhanced FPU instructions). @samp{r8000} is the default -@var{cpu type} at this ISA level. - -@item -mfp32 -Assume that 32 32-bit floating point registers are available. This is -the default. - -@item -mfp64 -Assume that 32 64-bit floating point registers are available. This is -the default when the @samp{-mips3} option is used. - -@item -mgp32 -Assume that 32 32-bit general purpose registers are available. This is -the default. - -@item -mgp64 -Assume that 32 64-bit general purpose registers are available. This is -the default when the @samp{-mips3} option is used. - -@item -mint64 -Force int and long types to be 64 bits wide. See @samp{-mlong32} for an -explanation of the default, and the width of pointers. - -@item -mlong64 -Force long types to be 64 bits wide. See @samp{-mlong32} for an -explanation of the default, and the width of pointers. - -@item -mlong32 -Force long, int, and pointer types to be 32 bits wide. - -If none of @samp{-mlong32}, @samp{-mlong64}, or @samp{-mint64} are set, -the size of ints, longs, and pointers depends on the ABI and ISA chosen. -For @samp{-mabi=32}, and @samp{-mabi=n32}, ints and longs are 32 bits -wide. For @samp{-mabi=64}, ints are 32 bits, and longs are 64 bits wide. -For @samp{-mabi=eabi} and either @samp{-mips1} or @samp{-mips2}, ints -and longs are 32 bits wide. For @samp{-mabi=eabi} and higher ISAs, ints -are 32 bits, and longs are 64 bits wide. The width of pointer types is -the smaller of the width of longs or the width of general purpose -registers (which in turn depends on the ISA). - -@item -mabi=32 -@itemx -mabi=o64 -@itemx -mabi=n32 -@itemx -mabi=64 -@itemx -mabi=eabi -Generate code for the indicated ABI. The default instruction level is -@samp{-mips1} for @samp{32}, @samp{-mips3} for @samp{n32}, and -@samp{-mips4} otherwise. Conversely, with @samp{-mips1} or -@samp{-mips2}, the default ABI is @samp{32}; otherwise, the default ABI -is @samp{64}. - -@item -mmips-as -Generate code for the MIPS assembler, and invoke @file{mips-tfile} to -add normal debug information. This is the default for all -platforms except for the OSF/1 reference platform, using the OSF/rose -object format. If the either of the @samp{-gstabs} or @samp{-gstabs+} -switches are used, the @file{mips-tfile} program will encapsulate the -stabs within MIPS ECOFF. - -@item -mgas -Generate code for the GNU assembler. This is the default on the OSF/1 -reference platform, using the OSF/rose object format. Also, this is -the default if the configure option @samp{--with-gnu-as} is used. - -@item -msplit-addresses -@itemx -mno-split-addresses -Generate code to load the high and low parts of address constants separately. -This allows @code{gcc} to optimize away redundant loads of the high order -bits of addresses. This optimization requires GNU as and GNU ld. -This optimization is enabled by default for some embedded targets where -GNU as and GNU ld are standard. - -@item -mrnames -@itemx -mno-rnames -The @samp{-mrnames} switch says to output code using the MIPS software -names for the registers, instead of the hardware names (ie, @var{a0} -instead of @var{$4}). The only known assembler that supports this option -is the Algorithmics assembler. - -@item -mgpopt -@itemx -mno-gpopt -The @samp{-mgpopt} switch says to write all of the data declarations -before the instructions in the text section, this allows the MIPS -assembler to generate one word memory references instead of using two -words for short global or static data items. This is on by default if -optimization is selected. - -@item -mstats -@itemx -mno-stats -For each non-inline function processed, the @samp{-mstats} switch -causes the compiler to emit one line to the standard error file to -print statistics about the program (number of registers saved, stack -size, etc.). - -@item -mmemcpy -@itemx -mno-memcpy -The @samp{-mmemcpy} switch makes all block moves call the appropriate -string function (@samp{memcpy} or @samp{bcopy}) instead of possibly -generating inline code. - -@item -mmips-tfile -@itemx -mno-mips-tfile -The @samp{-mno-mips-tfile} switch causes the compiler not -postprocess the object file with the @file{mips-tfile} program, -after the MIPS assembler has generated it to add debug support. If -@file{mips-tfile} is not run, then no local variables will be -available to the debugger. In addition, @file{stage2} and -@file{stage3} objects will have the temporary file names passed to the -assembler embedded in the object file, which means the objects will -not compare the same. The @samp{-mno-mips-tfile} switch should only -be used when there are bugs in the @file{mips-tfile} program that -prevents compilation. - -@item -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not part of GCC. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. - -@item -mhard-float -Generate output containing floating point instructions. This is the -default if you use the unmodified sources. - -@item -mabicalls -@itemx -mno-abicalls -Emit (or do not emit) the pseudo operations @samp{.abicalls}, -@samp{.cpload}, and @samp{.cprestore} that some System V.4 ports use for -position independent code. - -@item -mlong-calls -@itemx -mno-long-calls -Do all calls with the @samp{JALR} instruction, which requires -loading up a function's address into a register before the call. -You need to use this switch, if you call outside of the current -512 megabyte segment to functions that are not through pointers. - -@item -mhalf-pic -@itemx -mno-half-pic -Put pointers to extern references into the data section and load them -up, rather than put the references in the text section. - -@item -membedded-pic -@itemx -mno-embedded-pic -Generate PIC code suitable for some embedded systems. All calls are -made using PC relative address, and all data is addressed using the $gp -register. No more than 65536 bytes of global data may be used. This -requires GNU as and GNU ld which do most of the work. This currently -only works on targets which use ECOFF; it does not work with ELF. - -@item -membedded-data -@itemx -mno-embedded-data -Allocate variables to the read-only data section first if possible, then -next in the small data section if possible, otherwise in data. This gives -slightly slower code than the default, but reduces the amount of RAM required -when executing, and thus may be preferred for some embedded systems. - -@item -muninit-const-in-rodata -@itemx -mno-uninit-const-in-rodata -When used together with -membedded-data, it will always store uninitialized -const variables in the read-only data section. - -@item -msingle-float -@itemx -mdouble-float -The @samp{-msingle-float} switch tells gcc to assume that the floating -point coprocessor only supports single precision operations, as on the -@samp{r4650} chip. The @samp{-mdouble-float} switch permits gcc to use -double precision operations. This is the default. - -@item -mmad -@itemx -mno-mad -Permit use of the @samp{mad}, @samp{madu} and @samp{mul} instructions, -as on the @samp{r4650} chip. - -@item -m4650 -Turns on @samp{-msingle-float}, @samp{-mmad}, and, at least for now, -@samp{-mcpu=r4650}. - -@item -mips16 -@itemx -mno-mips16 -Enable 16-bit instructions. - -@item -mentry -Use the entry and exit pseudo ops. This option can only be used with -@samp{-mips16}. - -@item -EL -Compile code for the processor in little endian mode. -The requisite libraries are assumed to exist. - -@item -EB -Compile code for the processor in big endian mode. -The requisite libraries are assumed to exist. - -@item -G @var{num} -@cindex smaller data references (MIPS) -@cindex gp-relative references (MIPS) -Put global and static items less than or equal to @var{num} bytes into -the small data or bss sections instead of the normal data or bss -section. This allows the assembler to emit one word memory reference -instructions based on the global pointer (@var{gp} or @var{$28}), -instead of the normal two words used. By default, @var{num} is 8 when -the MIPS assembler is used, and 0 when the GNU assembler is used. The -@samp{-G @var{num}} switch is also passed to the assembler and linker. -All modules should be compiled with the same @samp{-G @var{num}} -value. - -@item -nocpp -Tell the MIPS assembler to not run its preprocessor over user -assembler files (with a @samp{.s} suffix) when assembling them. - -@item -mfix7000 -Pass an option to gas which will cause nops to be inserted if -the read of the destination register of an mfhi or mflo instruction -occurs in the following two instructions. - -@item -no-crt0 -Do not include the default crt0. -@end table - -@ifset INTERNALS -These options are defined by the macro -@code{TARGET_SWITCHES} in the machine description. The default for the -options is also defined by that macro, which enables you to change the -defaults. -@end ifset - -@node i386 Options -@subsection Intel 386 Options -@cindex i386 Options -@cindex Intel 386 Options - -These @samp{-m} options are defined for the i386 family of computers: - -@table @gcctabopt -@item -mcpu=@var{cpu type} -Assume the defaults for the machine type @var{cpu type} when scheduling -instructions. The choices for @var{cpu type} are @samp{i386}, -@samp{i486}, @samp{i586}, @samp{i686}, @samp{pentium}, -@samp{pentiumpro}, @samp{pentium4}, @samp{k6}, and @samp{athlon} - -While picking a specific @var{cpu type} will schedule things appropriately -for that particular chip, the compiler will not generate any code that -does not run on the i386 without the @samp{-march=@var{cpu type}} option -being used. @samp{i586} is equivalent to @samp{pentium} and @samp{i686} -is equivalent to @samp{pentiumpro}. @samp{k6} and @samp{athlon} are the -AMD chips as opposed to the Intel ones. - -@item -march=@var{cpu type} -Generate instructions for the machine type @var{cpu type}. The choices -for @var{cpu type} are the same as for @samp{-mcpu}. Moreover, -specifying @samp{-march=@var{cpu type}} implies @samp{-mcpu=@var{cpu type}}. - -@item -m386 -@itemx -m486 -@itemx -mpentium -@itemx -mpentiumpro -Synonyms for -mcpu=i386, -mcpu=i486, -mcpu=pentium, and -mcpu=pentiumpro -respectively. These synonyms are deprecated. - -@item -mintel-syntax -Emit assembly using Intel syntax opcodes instead of AT&T syntax. - -@item -mieee-fp -@itemx -mno-ieee-fp -Control whether or not the compiler uses IEEE floating point -comparisons. These handle correctly the case where the result of a -comparison is unordered. - -@item -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not part of GCC. -Normally the facilities of the machine's usual C compiler are used, but -this can't be done directly in cross-compilation. You must make your -own arrangements to provide suitable library functions for -cross-compilation. - -On machines where a function returns floating point results in the 80387 -register stack, some floating point opcodes may be emitted even if -@samp{-msoft-float} is used. - -@item -mno-fp-ret-in-387 -Do not use the FPU registers for return values of functions. - -The usual calling convention has functions return values of types -@code{float} and @code{double} in an FPU register, even if there -is no FPU. The idea is that the operating system should emulate -an FPU. - -The option @samp{-mno-fp-ret-in-387} causes such values to be returned -in ordinary CPU registers instead. - -@item -mno-fancy-math-387 -Some 387 emulators do not support the @code{sin}, @code{cos} and -@code{sqrt} instructions for the 387. Specify this option to avoid -generating those instructions. This option is the default on FreeBSD. -As of revision 2.6.1, these instructions are not generated unless you -also use the @samp{-funsafe-math-optimizations} switch. - -@item -malign-double -@itemx -mno-align-double -Control whether GCC aligns @code{double}, @code{long double}, and -@code{long long} variables on a two word boundary or a one word -boundary. Aligning @code{double} variables on a two word boundary will -produce code that runs somewhat faster on a @samp{Pentium} at the -expense of more memory. - -@item -m128bit-long-double -@itemx -m128bit-long-double -Control the size of @code{long double} type. i386 application binary interface -specify the size to be 12 bytes, while modern architectures (Pentium and newer) -preffer @code{long double} aligned to 8 or 16 byte boundary. This is -impossible to reach with 12 byte long doubles in the array accesses. - -@strong{Warning:} if you use the @samp{-m128bit-long-double} switch, the -structures and arrays containing @code{long double} will change their size as -well as function calling convention for function taking @code{long double} -will be modified. - -@item -m96bit-long-double -@itemx -m96bit-long-double -Set the size of @code{long double} to 96 bits as required by the i386 -application binary interface. This is the default. - -@item -msvr3-shlib -@itemx -mno-svr3-shlib -Control whether GCC places uninitialized locals into @code{bss} or -@code{data}. @samp{-msvr3-shlib} places these locals into @code{bss}. -These options are meaningful only on System V Release 3. - -@item -mno-wide-multiply -@itemx -mwide-multiply -Control whether GCC uses the @code{mul} and @code{imul} that produce -64-bit results in @code{eax:edx} from 32-bit operands to do @code{long -long} multiplies and 32-bit division by constants. - -@item -mrtd -Use a different function-calling convention, in which functions that -take a fixed number of arguments return with the @code{ret} @var{num} -instruction, which pops their arguments while returning. This saves one -instruction in the caller since there is no need to pop the arguments -there. - -You can specify that an individual function is called with this calling -sequence with the function attribute @samp{stdcall}. You can also -override the @samp{-mrtd} option by using the function attribute -@samp{cdecl}. @xref{Function Attributes}. - -@strong{Warning:} this calling convention is incompatible with the one -normally used on Unix, so you cannot use it if you need to call -libraries compiled with the Unix compiler. - -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including @code{printf}); -otherwise incorrect code will be generated for calls to those -functions. - -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) - -@item -mregparm=@var{num} -Control how many registers are used to pass integer arguments. By -default, no registers are used to pass arguments, and at most 3 -registers can be used. You can control this behavior for a specific -function by using the function attribute @samp{regparm}. -@xref{Function Attributes}. - -@strong{Warning:} if you use this switch, and -@var{num} is nonzero, then you must build all modules with the same -value, including any libraries. This includes the system libraries and -startup modules. - -@item -mpreferred-stack-boundary=@var{num} -Attempt to keep the stack boundary aligned to a 2 raised to @var{num} -byte boundary. If @samp{-mpreferred-stack-boundary} is not specified, -the default is 4 (16 bytes or 128 bits). - -The stack is required to be aligned on a 4 byte boundary. On Pentium -and PentiumPro, @code{double} and @code{long double} values should be -aligned to an 8 byte boundary (see @samp{-malign-double}) or suffer -significant run time performance penalties. On Pentium III, the -Streaming SIMD Extension (SSE) data type @code{__m128} suffers similar -penalties if it is not 16 byte aligned. - -To ensure proper alignment of this values on the stack, the stack boundary -must be as aligned as that required by any value stored on the stack. -Further, every function must be generated such that it keeps the stack -aligned. Thus calling a function compiled with a higher preferred -stack boundary from a function compiled with a lower preferred stack -boundary will most likely misalign the stack. It is recommended that -libraries that use callbacks always use the default setting. - -This extra alignment does consume extra stack space. Code that is sensitive -to stack space usage, such as embedded systems and operating system kernels, -may want to reduce the preferred alignment to -@samp{-mpreferred-stack-boundary=2}. - -@item -mpush-args -@kindex -mpush-args -Use PUSH operations to store outgoing parameters. This method is shorter -and usually equally fast as method using SUB/MOV operations and is enabled -by default. In some cases disabling it may improve performance because of -improved scheduling and reduced dependencies. - -@item -maccumulate-outgoing-args -@kindex -maccumulate-outgoing-args -If enabled, the maximum amount of space required for outgoing arguments will be -computed in the function prologue. This in faster on most modern CPUs -because of reduced dependencies, improved scheduling and reduced stack usage -when preferred stack boundary is not equal to 2. The drawback is a notable -increase in code size. This switch implies -mno-push-args. - -@item -mthreads -@kindex -mthreads -Support thread-safe exception handling on @samp{Mingw32}. Code that relies -on thread-safe exception handling must compile and link all code with the -@samp{-mthreads} option. When compiling, @samp{-mthreads} defines -@samp{-D_MT}; when linking, it links in a special thread helper library -@samp{-lmingwthrd} which cleans up per thread exception handling data. - -@item -mno-align-stringops -@kindex -mno-align-stringops -Do not align destination of inlined string operations. This switch reduces -code size and improves performance in case the destination is already aligned, -but gcc don't know about it. - -@item -minline-all-stringops -@kindex -minline-all-stringops -By default GCC inlines string operations only when destination is known to be -aligned at least to 4 byte boundary. This enables more inlining, increase code -size, but may improve performance of code that depends on fast memcpy, strlen -and memset for short lengths. - -@item -momit-leaf-frame-pointer -@kindex -momit-leaf-frame-pointer -Don't keep the frame pointer in a register for leaf functions. This -avoids the instructions to save, set up and restore frame pointers and -makes an extra register available in leaf functions. The option -@samp{-fomit-frame-pointer} removes the frame pointer for all functions -which might make debugging harder. -@end table - -@node HPPA Options -@subsection HPPA Options -@cindex HPPA Options - -These @samp{-m} options are defined for the HPPA family of computers: - -@table @gcctabopt -@item -march=@var{architecture type} -Generate code for the specified architecture. The choices for -@var{architecture type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA -1.1, and @samp{2.0} for PA 2.0 processors. Refer to -@file{/usr/lib/sched.models} on an HP-UX system to determine the proper -architecture option for your machine. Code compiled for lower numbered -architectures will run on higher numbered architectures, but not the -other way around. - -PA 2.0 support currently requires gas snapshot 19990413 or later. The -next release of binutils (current is 2.9.1) will probably contain PA 2.0 -support. - -@item -mpa-risc-1-0 -@itemx -mpa-risc-1-1 -@itemx -mpa-risc-2-0 -Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively. - -@item -mbig-switch -Generate code suitable for big switch tables. Use this option only if -the assembler/linker complain about out of range branches within a switch -table. - -@item -mjump-in-delay -Fill delay slots of function calls with unconditional jump instructions -by modifying the return pointer for the function call to be the target -of the conditional jump. - -@item -mdisable-fpregs -Prevent floating point registers from being used in any manner. This is -necessary for compiling kernels which perform lazy context switching of -floating point registers. If you use this option and attempt to perform -floating point operations, the compiler will abort. - -@item -mdisable-indexing -Prevent the compiler from using indexing address modes. This avoids some -rather obscure problems when compiling MIG generated code under MACH. - -@item -mno-space-regs -Generate code that assumes the target has no space registers. This allows -GCC to generate faster indirect calls and use unscaled index address modes. - -Such code is suitable for level 0 PA systems and kernels. - -@item -mfast-indirect-calls -Generate code that assumes calls never cross space boundaries. This -allows GCC to emit code which performs faster indirect calls. - -This option will not work in the presence of shared libraries or nested -functions. - -@item -mlong-load-store -Generate 3-instruction load and store sequences as sometimes required by -the HP-UX 10 linker. This is equivalent to the @samp{+k} option to -the HP compilers. - -@item -mportable-runtime -Use the portable calling conventions proposed by HP for ELF systems. - -@item -mgas -Enable the use of assembler directives only GAS understands. - -@item -mschedule=@var{cpu type} -Schedule code according to the constraints for the machine type -@var{cpu type}. The choices for @var{cpu type} are @samp{700} -@samp{7100}, @samp{7100LC}, @samp{7200}, and @samp{8000}. Refer to -@file{/usr/lib/sched.models} on an HP-UX system to determine the -proper scheduling option for your machine. - -@item -mlinker-opt -Enable the optimization pass in the HPUX linker. Note this makes symbolic -debugging impossible. It also triggers a bug in the HPUX 8 and HPUX 9 linkers -in which they give bogus error messages when linking some programs. - -@item -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries are not available for all HPPA -targets. Normally the facilities of the machine's usual C compiler are -used, but this cannot be done directly in cross-compilation. You must make -your own arrangements to provide suitable library functions for -cross-compilation. The embedded target @samp{hppa1.1-*-pro} -does provide software floating point support. - -@samp{-msoft-float} changes the calling convention in the output file; -therefore, it is only useful if you compile @emph{all} of a program with -this option. In particular, you need to compile @file{libgcc.a}, the -library that comes with GCC, with @samp{-msoft-float} in order for -this to work. -@end table - -@node Intel 960 Options -@subsection Intel 960 Options - -These @samp{-m} options are defined for the Intel 960 implementations: - -@table @gcctabopt -@item -m@var{cpu type} -Assume the defaults for the machine type @var{cpu type} for some of -the other options, including instruction scheduling, floating point -support, and addressing modes. The choices for @var{cpu type} are -@samp{ka}, @samp{kb}, @samp{mc}, @samp{ca}, @samp{cf}, -@samp{sa}, and @samp{sb}. -The default is -@samp{kb}. - -@item -mnumerics -@itemx -msoft-float -The @samp{-mnumerics} option indicates that the processor does support -floating-point instructions. The @samp{-msoft-float} option indicates -that floating-point support should not be assumed. - -@item -mleaf-procedures -@itemx -mno-leaf-procedures -Do (or do not) attempt to alter leaf procedures to be callable with the -@code{bal} instruction as well as @code{call}. This will result in more -efficient code for explicit calls when the @code{bal} instruction can be -substituted by the assembler or linker, but less efficient code in other -cases, such as calls via function pointers, or using a linker that doesn't -support this optimization. - -@item -mtail-call -@itemx -mno-tail-call -Do (or do not) make additional attempts (beyond those of the -machine-independent portions of the compiler) to optimize tail-recursive -calls into branches. You may not want to do this because the detection of -cases where this is not valid is not totally complete. The default is -@samp{-mno-tail-call}. - -@item -mcomplex-addr -@itemx -mno-complex-addr -Assume (or do not assume) that the use of a complex addressing mode is a -win on this implementation of the i960. Complex addressing modes may not -be worthwhile on the K-series, but they definitely are on the C-series. -The default is currently @samp{-mcomplex-addr} for all processors except -the CB and CC. - -@item -mcode-align -@itemx -mno-code-align -Align code to 8-byte boundaries for faster fetching (or don't bother). -Currently turned on by default for C-series implementations only. - -@ignore -@item -mclean-linkage -@itemx -mno-clean-linkage -These options are not fully implemented. -@end ignore - -@item -mic-compat -@itemx -mic2.0-compat -@itemx -mic3.0-compat -Enable compatibility with iC960 v2.0 or v3.0. - -@item -masm-compat -@itemx -mintel-asm -Enable compatibility with the iC960 assembler. - -@item -mstrict-align -@itemx -mno-strict-align -Do not permit (do permit) unaligned accesses. - -@item -mold-align -Enable structure-alignment compatibility with Intel's gcc release version -1.3 (based on gcc 1.37). This option implies @samp{-mstrict-align}. - -@item -mlong-double-64 -Implement type @samp{long double} as 64-bit floating point numbers. -Without the option @samp{long double} is implemented by 80-bit -floating point numbers. The only reason we have it because there is -no 128-bit @samp{long double} support in @samp{fp-bit.c} yet. So it -is only useful for people using soft-float targets. Otherwise, we -should recommend against use of it. - -@end table - -@node DEC Alpha Options -@subsection DEC Alpha Options - -These @samp{-m} options are defined for the DEC Alpha implementations: - -@table @gcctabopt -@item -mno-soft-float -@itemx -msoft-float -Use (do not use) the hardware floating-point instructions for -floating-point operations. When @option{-msoft-float} is specified, -functions in @file{libgcc.a} will be used to perform floating-point -operations. Unless they are replaced by routines that emulate the -floating-point operations, or compiled in such a way as to call such -emulations routines, these routines will issue floating-point -operations. If you are compiling for an Alpha without floating-point -operations, you must ensure that the library is built so as not to call -them. - -Note that Alpha implementations without floating-point operations are -required to have floating-point registers. - -@item -mfp-reg -@itemx -mno-fp-regs -Generate code that uses (does not use) the floating-point register set. -@option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point -register set is not used, floating point operands are passed in integer -registers as if they were integers and floating-point results are passed -in $0 instead of $f0. This is a non-standard calling sequence, so any -function with a floating-point argument or return value called by code -compiled with @option{-mno-fp-regs} must also be compiled with that -option. - -A typical use of this option is building a kernel that does not use, -and hence need not save and restore, any floating-point registers. - -@item -mieee -The Alpha architecture implements floating-point hardware optimized for -maximum performance. It is mostly compliant with the IEEE floating -point standard. However, for full compliance, software assistance is -required. This option generates code fully IEEE compliant code -@emph{except} that the @var{inexact flag} is not maintained (see below). -If this option is turned on, the CPP macro @code{_IEEE_FP} is defined -during compilation. The option is a shorthand for: @samp{-D_IEEE_FP --mfp-trap-mode=su -mtrap-precision=i -mieee-conformant}. The resulting -code is less efficient but is able to correctly support denormalized -numbers and exceptional IEEE values such as not-a-number and plus/minus -infinity. Other Alpha compilers call this option -@option{-ieee_with_no_inexact}. - -@item -mieee-with-inexact -@c overfull hbox here --bob 22 jul96 -@c original text between ignore ... end ignore -@ignore -This is like @samp{-mieee} except the generated code also maintains the -IEEE @var{inexact flag}. Turning on this option causes the generated -code to implement fully-compliant IEEE math. The option is a shorthand -for @samp{-D_IEEE_FP -D_IEEE_FP_INEXACT} plus @samp{-mieee-conformant}, -@samp{-mfp-trap-mode=sui}, and @samp{-mtrap-precision=i}. On some Alpha -implementations the resulting code may execute significantly slower than -the code generated by default. Since there is very little code that -depends on the @var{inexact flag}, you should normally not specify this -option. Other Alpha compilers call this option -@samp{-ieee_with_inexact}. -@end ignore -@c changed paragraph -This is like @samp{-mieee} except the generated code also maintains the -IEEE @var{inexact flag}. Turning on this option causes the generated -code to implement fully-compliant IEEE math. The option is a shorthand -for @samp{-D_IEEE_FP -D_IEEE_FP_INEXACT} plus the three following: -@samp{-mieee-conformant}, -@samp{-mfp-trap-mode=sui}, -and @samp{-mtrap-precision=i}. -On some Alpha implementations the resulting code may execute -significantly slower than the code generated by default. Since there -is very little code that depends on the @var{inexact flag}, you should -normally not specify this option. Other Alpha compilers call this -option @samp{-ieee_with_inexact}. -@c end changes to prevent overfull hboxes - -@item -mfp-trap-mode=@var{trap mode} -This option controls what floating-point related traps are enabled. -Other Alpha compilers call this option @samp{-fptm }@var{trap mode}. -The trap mode can be set to one of four values: - -@table @samp -@item n -This is the default (normal) setting. The only traps that are enabled -are the ones that cannot be disabled in software (e.g., division by zero -trap). - -@item u -In addition to the traps enabled by @samp{n}, underflow traps are enabled -as well. - -@item su -Like @samp{su}, but the instructions are marked to be safe for software -completion (see Alpha architecture manual for details). - -@item sui -Like @samp{su}, but inexact traps are enabled as well. -@end table - -@item -mfp-rounding-mode=@var{rounding mode} -Selects the IEEE rounding mode. Other Alpha compilers call this option -@samp{-fprm }@var{rounding mode}. The @var{rounding mode} can be one -of: - -@table @samp -@item n -Normal IEEE rounding mode. Floating point numbers are rounded towards -the nearest machine number or towards the even machine number in case -of a tie. - -@item m -Round towards minus infinity. - -@item c -Chopped rounding mode. Floating point numbers are rounded towards zero. - -@item d -Dynamic rounding mode. A field in the floating point control register -(@var{fpcr}, see Alpha architecture reference manual) controls the -rounding mode in effect. The C library initializes this register for -rounding towards plus infinity. Thus, unless your program modifies the -@var{fpcr}, @samp{d} corresponds to round towards plus infinity. -@end table - -@item -mtrap-precision=@var{trap precision} -In the Alpha architecture, floating point traps are imprecise. This -means without software assistance it is impossible to recover from a -floating trap and program execution normally needs to be terminated. -GCC can generate code that can assist operating system trap handlers -in determining the exact location that caused a floating point trap. -Depending on the requirements of an application, different levels of -precisions can be selected: - -@table @samp -@item p -Program precision. This option is the default and means a trap handler -can only identify which program caused a floating point exception. - -@item f -Function precision. The trap handler can determine the function that -caused a floating point exception. - -@item i -Instruction precision. The trap handler can determine the exact -instruction that caused a floating point exception. -@end table - -Other Alpha compilers provide the equivalent options called -@samp{-scope_safe} and @samp{-resumption_safe}. - -@item -mieee-conformant -This option marks the generated code as IEEE conformant. You must not -use this option unless you also specify @samp{-mtrap-precision=i} and either -@samp{-mfp-trap-mode=su} or @samp{-mfp-trap-mode=sui}. Its only effect -is to emit the line @samp{.eflag 48} in the function prologue of the -generated assembly file. Under DEC Unix, this has the effect that -IEEE-conformant math library routines will be linked in. - -@item -mbuild-constants -Normally GCC examines a 32- or 64-bit integer constant to -see if it can construct it from smaller constants in two or three -instructions. If it cannot, it will output the constant as a literal and -generate code to load it from the data segment at runtime. - -Use this option to require GCC to construct @emph{all} integer constants -using code, even if it takes more instructions (the maximum is six). - -You would typically use this option to build a shared library dynamic -loader. Itself a shared library, it must relocate itself in memory -before it can find the variables and constants in its own data segment. - -@item -malpha-as -@itemx -mgas -Select whether to generate code to be assembled by the vendor-supplied -assembler (@samp{-malpha-as}) or by the GNU assembler @samp{-mgas}. - -@item -mbwx -@itemx -mno-bwx -@itemx -mcix -@itemx -mno-cix -@itemx -mmax -@itemx -mno-max -Indicate whether GCC should generate code to use the optional BWX, -CIX, and MAX instruction sets. The default is to use the instruction sets -supported by the CPU type specified via @samp{-mcpu=} option or that -of the CPU on which GCC was built if none was specified. - -@item -mcpu=@var{cpu_type} -Set the instruction set, register set, and instruction scheduling -parameters for machine type @var{cpu_type}. You can specify either the -@samp{EV} style name or the corresponding chip number. GCC -supports scheduling parameters for the EV4 and EV5 family of processors -and will choose the default values for the instruction set from -the processor you specify. If you do not specify a processor type, -GCC will default to the processor on which the compiler was built. - -Supported values for @var{cpu_type} are - -@table @samp -@item ev4 -@itemx 21064 -Schedules as an EV4 and has no instruction set extensions. - -@item ev5 -@itemx 21164 -Schedules as an EV5 and has no instruction set extensions. - -@item ev56 -@itemx 21164a -Schedules as an EV5 and supports the BWX extension. - -@item pca56 -@itemx 21164pc -@itemx 21164PC -Schedules as an EV5 and supports the BWX and MAX extensions. - -@item ev6 -@itemx 21264 -Schedules as an EV5 (until Digital releases the scheduling parameters -for the EV6) and supports the BWX, CIX, and MAX extensions. -@end table - -@item -mmemory-latency=@var{time} -Sets the latency the scheduler should assume for typical memory -references as seen by the application. This number is highly -dependent on the memory access patterns used by the application -and the size of the external cache on the machine. - -Valid options for @var{time} are - -@table @samp -@item @var{number} -A decimal number representing clock cycles. - -@item L1 -@itemx L2 -@itemx L3 -@itemx main -The compiler contains estimates of the number of clock cycles for -``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches -(also called Dcache, Scache, and Bcache), as well as to main memory. -Note that L3 is only valid for EV5. - -@end table -@end table - -@node Clipper Options -@subsection Clipper Options - -These @samp{-m} options are defined for the Clipper implementations: - -@table @gcctabopt -@item -mc300 -Produce code for a C300 Clipper processor. This is the default. - -@item -mc400 -Produce code for a C400 Clipper processor i.e. use floating point -registers f8..f15. -@end table - -@node H8/300 Options -@subsection H8/300 Options - -These @samp{-m} options are defined for the H8/300 implementations: - -@table @gcctabopt -@item -mrelax -Shorten some address references at link time, when possible; uses the -linker option @samp{-relax}. @xref{H8/300,, @code{ld} and the H8/300, -ld.info, Using ld}, for a fuller description. - -@item -mh -Generate code for the H8/300H. - -@item -ms -Generate code for the H8/S. - -@item -ms2600 -Generate code for the H8/S2600. This switch must be used with -ms. - -@item -mint32 -Make @code{int} data 32 bits by default. - -@item -malign-300 -On the H8/300H and H8/S, use the same alignment rules as for the H8/300. -The default for the H8/300H and H8/S is to align longs and floats on 4 -byte boundaries. -@samp{-malign-300} causes them to be aligned on 2 byte boundaries. -This option has no effect on the H8/300. -@end table - -@node SH Options -@subsection SH Options - -These @samp{-m} options are defined for the SH implementations: - -@table @gcctabopt -@item -m1 -Generate code for the SH1. - -@item -m2 -Generate code for the SH2. - -@item -m3 -Generate code for the SH3. - -@item -m3e -Generate code for the SH3e. - -@item -m4-nofpu -Generate code for the SH4 without a floating-point unit. - -@item -m4-single-only -Generate code for the SH4 with a floating-point unit that only -supports single-precision arithmentic. - -@item -m4-single -Generate code for the SH4 assuming the floating-point unit is in -single-precision mode by default. - -@item -m4 -Generate code for the SH4. - -@item -mb -Compile code for the processor in big endian mode. - -@item -ml -Compile code for the processor in little endian mode. - -@item -mdalign -Align doubles at 64-bit boundaries. Note that this changes the calling -conventions, and thus some functions from the standard C library will -not work unless you recompile it first with -mdalign. - -@item -mrelax -Shorten some address references at link time, when possible; uses the -linker option @samp{-relax}. - -@item -mbigtable -Use 32-bit offsets in @code{switch} tables. The default is to use -16-bit offsets. - -@item -mfmovd -Enable the use of the instruction @code{fmovd}. - -@item -mhitachi -Comply with the calling conventions defined by Hitachi. - -@item -mnomacsave -Mark the @code{MAC} register as call-clobbered, even if -@option{-mhitachi} is given. - -@item -misize -Dump instruction size and location in the assembly code. - -@item -mpadstruct -This option is deprecated. It pads structures to multiple of 4 bytes, -which is incompatible with the SH ABI. - -@item -mspace -Optimize for space instead of speed. Implied by @option{-Os}. - -@item -mprefergot -When generating position-independent code, emit function calls using -the Global Offset Table instead of the Procedure Linkage Table. - -@item -musermode -Generate a library function call to invalidate instruction cache -entries, after fixing up a trampoline. This library function call -doesn't assume it can write to the whole memory address space. This -is the default when the target is @code{sh-*-linux*}. -@end table - -@node System V Options -@subsection Options for System V - -These additional options are available on System V Release 4 for -compatibility with other compilers on those systems: - -@table @gcctabopt -@item -G -Create a shared object. -It is recommended that @samp{-symbolic} or @samp{-shared} be used instead. - -@item -Qy -Identify the versions of each tool used by the compiler, in a -@code{.ident} assembler directive in the output. - -@item -Qn -Refrain from adding @code{.ident} directives to the output file (this is -the default). - -@item -YP\,@var{dirs} -Search the directories @var{dirs}, and no others, for libraries -specified with @samp{-l}. - -@item -Ym\,@var{dir} -Look in the directory @var{dir} to find the M4 preprocessor. -The assembler uses this option. -@c This is supposed to go with a -Yd for predefined M4 macro files, but -@c the generic assembler that comes with Solaris takes just -Ym. -@end table - -@node TMS320C3x/C4x Options -@subsection TMS320C3x/C4x Options -@cindex TMS320C3x/C4x Options - -These @samp{-m} options are defined for TMS320C3x/C4x implementations: - -@table @gcctabopt - -@item -mcpu=@var{cpu_type} -Set the instruction set, register set, and instruction scheduling -parameters for machine type @var{cpu_type}. Supported values for -@var{cpu_type} are @samp{c30}, @samp{c31}, @samp{c32}, @samp{c40}, and -@samp{c44}. The default is @samp{c40} to generate code for the -TMS320C40. - -@item -mbig-memory -@item -mbig -@itemx -msmall-memory -@itemx -msmall -Generates code for the big or small memory model. The small memory -model assumed that all data fits into one 64K word page. At run-time -the data page (DP) register must be set to point to the 64K page -containing the .bss and .data program sections. The big memory model is -the default and requires reloading of the DP register for every direct -memory access. - -@item -mbk -@itemx -mno-bk -Allow (disallow) allocation of general integer operands into the block -count register BK. - -@item -mdb -@itemx -mno-db -Enable (disable) generation of code using decrement and branch, -DBcond(D), instructions. This is enabled by default for the C4x. To be -on the safe side, this is disabled for the C3x, since the maximum -iteration count on the C3x is 2^23 + 1 (but who iterates loops more than -2^23 times on the C3x?). Note that GCC will try to reverse a loop so -that it can utilise the decrement and branch instruction, but will give -up if there is more than one memory reference in the loop. Thus a loop -where the loop counter is decremented can generate slightly more -efficient code, in cases where the RPTB instruction cannot be utilised. - -@item -mdp-isr-reload -@itemx -mparanoid -Force the DP register to be saved on entry to an interrupt service -routine (ISR), reloaded to point to the data section, and restored on -exit from the ISR. This should not be required unless someone has -violated the small memory model by modifying the DP register, say within -an object library. - -@item -mmpyi -@itemx -mno-mpyi -For the C3x use the 24-bit MPYI instruction for integer multiplies -instead of a library call to guarantee 32-bit results. Note that if one -of the operands is a constant, then the multiplication will be performed -using shifts and adds. If the -mmpyi option is not specified for the C3x, -then squaring operations are performed inline instead of a library call. - -@item -mfast-fix -@itemx -mno-fast-fix -The C3x/C4x FIX instruction to convert a floating point value to an -integer value chooses the nearest integer less than or equal to the -floating point value rather than to the nearest integer. Thus if the -floating point number is negative, the result will be incorrectly -truncated an additional code is necessary to detect and correct this -case. This option can be used to disable generation of the additional -code required to correct the result. - -@item -mrptb -@itemx -mno-rptb -Enable (disable) generation of repeat block sequences using the RPTB -instruction for zero overhead looping. The RPTB construct is only used -for innermost loops that do not call functions or jump across the loop -boundaries. There is no advantage having nested RPTB loops due to the -overhead required to save and restore the RC, RS, and RE registers. -This is enabled by default with -O2. - -@item -mrpts=@var{count} -@itemx -mno-rpts -Enable (disable) the use of the single instruction repeat instruction -RPTS. If a repeat block contains a single instruction, and the loop -count can be guaranteed to be less than the value @var{count}, GCC will -emit a RPTS instruction instead of a RPTB. If no value is specified, -then a RPTS will be emitted even if the loop count cannot be determined -at compile time. Note that the repeated instruction following RPTS does -not have to be reloaded from memory each iteration, thus freeing up the -CPU buses for operands. However, since interrupts are blocked by this -instruction, it is disabled by default. - -@item -mloop-unsigned -@itemx -mno-loop-unsigned -The maximum iteration count when using RPTS and RPTB (and DB on the C40) -is 2^31 + 1 since these instructions test if the iteration count is -negative to terminate the loop. If the iteration count is unsigned -there is a possibility than the 2^31 + 1 maximum iteration count may be -exceeded. This switch allows an unsigned iteration count. - -@item -mti -Try to emit an assembler syntax that the TI assembler (asm30) is happy -with. This also enforces compatibility with the API employed by the TI -C3x C compiler. For example, long doubles are passed as structures -rather than in floating point registers. - -@item -mregparm -@itemx -mmemparm -Generate code that uses registers (stack) for passing arguments to functions. -By default, arguments are passed in registers where possible rather -than by pushing arguments on to the stack. - -@item -mparallel-insns -@itemx -mno-parallel-insns -Allow the generation of parallel instructions. This is enabled by -default with -O2. - -@item -mparallel-mpy -@itemx -mno-parallel-mpy -Allow the generation of MPY||ADD and MPY||SUB parallel instructions, -provided -mparallel-insns is also specified. These instructions have -tight register constraints which can pessimize the code generation -of large functions. - -@end table - -@node V850 Options -@subsection V850 Options -@cindex V850 Options - -These @samp{-m} options are defined for V850 implementations: - -@table @gcctabopt -@item -mlong-calls -@itemx -mno-long-calls -Treat all calls as being far away (near). If calls are assumed to be -far away, the compiler will always load the functions address up into a -register, and call indirect through the pointer. - -@item -mno-ep -@itemx -mep -Do not optimize (do optimize) basic blocks that use the same index -pointer 4 or more times to copy pointer into the @code{ep} register, and -use the shorter @code{sld} and @code{sst} instructions. The @samp{-mep} -option is on by default if you optimize. - -@item -mno-prolog-function -@itemx -mprolog-function -Do not use (do use) external functions to save and restore registers at -the prolog and epilog of a function. The external functions are slower, -but use less code space if more than one function saves the same number -of registers. The @samp{-mprolog-function} option is on by default if -you optimize. - -@item -mspace -Try to make the code as small as possible. At present, this just turns -on the @samp{-mep} and @samp{-mprolog-function} options. - -@item -mtda=@var{n} -Put static or global variables whose size is @var{n} bytes or less into -the tiny data area that register @code{ep} points to. The tiny data -area can hold up to 256 bytes in total (128 bytes for byte references). - -@item -msda=@var{n} -Put static or global variables whose size is @var{n} bytes or less into -the small data area that register @code{gp} points to. The small data -area can hold up to 64 kilobytes. - -@item -mzda=@var{n} -Put static or global variables whose size is @var{n} bytes or less into -the first 32 kilobytes of memory. - -@item -mv850 -Specify that the target processor is the V850. - -@item -mbig-switch -Generate code suitable for big switch tables. Use this option only if -the assembler/linker complain about out of range branches within a switch -table. -@end table - -@node ARC Options -@subsection ARC Options -@cindex ARC Options - -These options are defined for ARC implementations: - -@table @gcctabopt -@item -EL -Compile code for little endian mode. This is the default. - -@item -EB -Compile code for big endian mode. - -@item -mmangle-cpu -Prepend the name of the cpu to all public symbol names. -In multiple-processor systems, there are many ARC variants with different -instruction and register set characteristics. This flag prevents code -compiled for one cpu to be linked with code compiled for another. -No facility exists for handling variants that are "almost identical". -This is an all or nothing option. - -@item -mcpu=@var{cpu} -Compile code for ARC variant @var{cpu}. -Which variants are supported depend on the configuration. -All variants support @samp{-mcpu=base}, this is the default. - -@item -mtext=@var{text section} -@itemx -mdata=@var{data section} -@itemx -mrodata=@var{readonly data section} -Put functions, data, and readonly data in @var{text section}, -@var{data section}, and @var{readonly data section} respectively -by default. This can be overridden with the @code{section} attribute. -@xref{Variable Attributes}. - -@end table - -@node NS32K Options -@subsection NS32K Options -@cindex NS32K options - -These are the @samp{-m} options defined for the 32000 series. The default -values for these options depends on which style of 32000 was selected when -the compiler was configured; the defaults for the most common choices are -given below. - -@table @gcctabopt -@item -m32032 -@itemx -m32032 -Generate output for a 32032. This is the default -when the compiler is configured for 32032 and 32016 based systems. - -@item -m32332 -@itemx -m32332 -Generate output for a 32332. This is the default -when the compiler is configured for 32332-based systems. - -@item -m32532 -@itemx -m32532 -Generate output for a 32532. This is the default -when the compiler is configured for 32532-based systems. - -@item -m32081 -Generate output containing 32081 instructions for floating point. -This is the default for all systems. - -@item -m32381 -Generate output containing 32381 instructions for floating point. This -also implies @samp{-m32081}. The 32381 is only compatible with the 32332 -and 32532 cpus. This is the default for the pc532-netbsd configuration. - -@item -mmulti-add -Try and generate multiply-add floating point instructions @code{polyF} -and @code{dotF}. This option is only available if the @samp{-m32381} -option is in effect. Using these instructions requires changes to to -register allocation which generally has a negative impact on -performance. This option should only be enabled when compiling code -particularly likely to make heavy use of multiply-add instructions. - -@item -mnomulti-add -Do not try and generate multiply-add floating point instructions -@code{polyF} and @code{dotF}. This is the default on all platforms. - -@item -msoft-float -Generate output containing library calls for floating point. -@strong{Warning:} the requisite libraries may not be available. - -@item -mnobitfield -Do not use the bit-field instructions. On some machines it is faster to -use shifting and masking operations. This is the default for the pc532. - -@item -mbitfield -Do use the bit-field instructions. This is the default for all platforms -except the pc532. - -@item -mrtd -Use a different function-calling convention, in which functions -that take a fixed number of arguments return pop their -arguments on return with the @code{ret} instruction. - -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. - -Also, you must provide function prototypes for all functions that -take variable numbers of arguments (including @code{printf}); -otherwise incorrect code will be generated for calls to those -functions. - -In addition, seriously incorrect code will result if you call a -function with too many arguments. (Normally, extra arguments are -harmlessly ignored.) - -This option takes its name from the 680x0 @code{rtd} instruction. - - -@item -mregparam -Use a different function-calling convention where the first two arguments -are passed in registers. - -This calling convention is incompatible with the one normally -used on Unix, so you cannot use it if you need to call libraries -compiled with the Unix compiler. - -@item -mnoregparam -Do not pass any arguments in registers. This is the default for all -targets. - -@item -msb -It is OK to use the sb as an index register which is always loaded with -zero. This is the default for the pc532-netbsd target. - -@item -mnosb -The sb register is not available for use or has not been initialized to -zero by the run time system. This is the default for all targets except -the pc532-netbsd. It is also implied whenever @samp{-mhimem} or -@samp{-fpic} is set. - -@item -mhimem -Many ns32000 series addressing modes use displacements of up to 512MB. -If an address is above 512MB then displacements from zero can not be used. -This option causes code to be generated which can be loaded above 512MB. -This may be useful for operating systems or ROM code. - -@item -mnohimem -Assume code will be loaded in the first 512MB of virtual address space. -This is the default for all platforms. - - -@end table - -@node AVR Options -@subsection AVR Options -@cindex AVR Options - -These options are defined for AVR implementations: - -@table @gcctabopt -@item -mmcu=@var{mcu} -Specify ATMEL AVR instruction set or MCU type. - -Instruction set avr1 is for the minimal AVR core, not supported by the C -compiler, only for assembler programs (MCU types: at90s1200, attiny10, -attiny11, attiny12, attiny15, attiny28). - -Instruction set avr2 (default) is for the classic AVR core with up to -8K program memory space (MCU types: at90s2313, at90s2323, attiny22, -at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, -at90c8534, at90s8535). - -Instruction set avr3 is for the classic AVR core with up to 128K program -memory space (MCU types: atmega103, atmega603). - -Instruction set avr4 is for the enhanced AVR core with up to 8K program -memory space (MCU types: atmega83, atmega85). - -Instruction set avr5 is for the enhanced AVR core with up to 128K program -memory space (MCU types: atmega161, atmega163, atmega32, at94k). - -@item -msize -Output instruction sizes to the asm file. - -@item -minit-stack=@var{N} -Specify the initial stack address, which may be a symbol or numeric value, -__stack is the default. - -@item -mno-interrupts -Generated code is not compatible with hardware interrupts. -Code size will be smaller. - -@item -mcall-prologues -Functions prologues/epilogues expanded as call to appropriate -subroutines. Code size will be smaller. - -@item -mno-tablejump -Do not generate tablejump insns which sometimes increase code size. - -@item -mtiny-stack -Change only the low 8 bits of the stack pointer. -@end table - -@node MCore Options -@subsection MCore Options -@cindex MCore options - -These are the @samp{-m} options defined for the Motorola M*Core -processors. - -@table @gcctabopt - -@item -mhardlit -@itemx -mhardlit -@itemx -mno-hardlit -Inline constants into the code stream if it can be done in two -instructions or less. - -@item -mdiv -@itemx -mdiv -@itemx -mno-div -Use the divide instruction. (Enabled by default). - -@item -mrelax-immediate -@itemx -mrelax-immediate -@itemx -mno-relax-immediate -Allow arbitrary sized immediates in bit operations. - -@item -mwide-bitfields -@itemx -mwide-bitfields -@itemx -mno-wide-bitfields -Always treat bitfields as int-sized. - -@item -m4byte-functions -@itemx -m4byte-functions -@itemx -mno-4byte-functions -Force all functions to be aligned to a four byte boundary. - -@item -mcallgraph-data -@itemx -mcallgraph-data -@itemx -mno-callgraph-data -Emit callgraph information. - -@item -mslow-bytes -@itemx -mslow-bytes -@itemx -mno-slow-bytes -Prefer word access when reading byte quantities. - -@item -mlittle-endian -@itemx -mlittle-endian -@itemx -mbig-endian -Generate code for a little endian target. - -@item -m210 -@itemx -m210 -@itemx -m340 -Generate code for the 210 processor. -@end table - -@node IA-64 Options -@subsection IA-64 Options -@cindex IA-64 Options - -These are the @samp{-m} options defined for the Intel IA-64 architecture. - -@table @gcctabopt -@item -mbig-endian -Generate code for a big endian target. This is the default for HPUX. - -@item -mlittle-endian -Generate code for a little endian target. This is the default for AIX5 -and Linux. - -@item -mgnu-as -@itemx -mno-gnu-as -Generate (or don't) code for the GNU assembler. This is the default. -@c Also, this is the default if the configure option @samp{--with-gnu-as} -@c is used. - -@item -mgnu-ld -@itemx -mno-gnu-ld -Generate (or don't) code for the GNU linker. This is the default. -@c Also, this is the default if the configure option @samp{--with-gnu-ld} -@c is used. - -@item -mno-pic -Generate code that does not use a global pointer register. The result -is not position independent code, and violates the IA-64 ABI. - -@item -mvolatile-asm-stop -@itemx -mno-volatile-asm-stop -Generate (or don't) a stop bit immediately before and after volatile asm -statements. - -@item -mb-step -Generate code that works around Itanium B step errata. - -@item -mregister-names -@itemx -mno-register-names -Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for -the stacked registers. This may make assembler output more readable. - -@item -mno-sdata -@itemx -msdata -Disable (or enable) optimizations that use the small data section. This may -be useful for working around optimizer bugs. - -@item -mconstant-gp -Generate code that uses a single constant global pointer value. This is -useful when compiling kernel code. - -@item -mauto-pic -Generate code that is self-relocatable. This implies @samp{-mconstant-gp}. -This is useful when compiling firmware code. - -@item -minline-divide-min-latency -Generate code for inline divides using the minimum latency algorithm. - -@item -minline-divide-max-throughput -Generate code for inline divides using the maximum throughput algorithm. - -@item -mno-dwarf2-asm -@itemx -mdwarf2-asm -Don't (or do) generate assembler code for the DWARF2 line number debugging -info. This may be useful when not using the GNU assembler. - -@item -mfixed-range=@var{register range} -Generate code treating the given register range as fixed registers. -A fixed register is one that the register allocator can not use. This is -useful when compiling kernel code. A register range is specified as -two registers separated by a dash. Multiple register ranges can be -specified separated by a comma. -@end table - -@node D30V Options -@subsection D30V Options -@cindex D30V Options - -These @samp{-m} options are defined for D30V implementations: - -@table @gcctabopt -@item -mextmem -Link the @samp{.text}, @samp{.data}, @samp{.bss}, @samp{.strings}, -@samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections into external -memory, which starts at location @code{0x80000000}. - -@item -mextmemory -Same as the @samp{-mextmem} switch. - -@item -monchip -Link the @samp{.text} section into onchip text memory, which starts at -location @code{0x0}. Also link @samp{.data}, @samp{.bss}, -@samp{.strings}, @samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections -into onchip data memory, which starts at location @code{0x20000000}. - -@item -mno-asm-optimize -@itemx -masm-optimize -Disable (enable) passing @samp{-O} to the assembler when optimizing. -The assembler uses the @samp{-O} option to automatically parallelize -adjacent short instructions where possible. - -@item -mbranch-cost=@var{n} -Increase the internal costs of branches to @var{n}. Higher costs means -that the compiler will issue more instructions to avoid doing a branch. -The default is 2. - -@item -mcond-exec=@var{n} -Specify the maximum number of conditionally executed instructions that -replace a branch. The default is 4. -@end table - -@node Code Gen Options -@section Options for Code Generation Conventions -@cindex code generation conventions -@cindex options, code generation -@cindex run-time options - -These machine-independent options control the interface conventions -used in code generation. - -Most of them have both positive and negative forms; the negative form -of @samp{-ffoo} would be @samp{-fno-foo}. In the table below, only -one of the forms is listed---the one which is not the default. You -can figure out the other form by either removing @samp{no-} or adding -it. - -@table @gcctabopt -@item -fexceptions -Enable exception handling. Generates extra code needed to propagate -exceptions. For some targets, this implies GNU CC will generate frame -unwind information for all functions, which can produce significant data -size overhead, although it does not affect execution. If you do not -specify this option, GNU CC will enable it by default for languages like -C++ which normally require exception handling, and disable it for -languages like C that do not normally require it. However, you may need -to enable this option when compiling C code that needs to interoperate -properly with exception handlers written in C++. You may also wish to -disable this option if you are compiling older C++ programs that don't -use exception handling. - -@item -funwind-tables -Similar to @option{-fexceptions}, except that it will just generate any needed -static data, but will not affect the generated code in any other way. -You will normally not enable this option; instead, a language processor -that needs this handling would enable it on your behalf. - -@item -fpcc-struct-return -Return ``short'' @code{struct} and @code{union} values in memory like -longer ones, rather than in registers. This convention is less -efficient, but it has the advantage of allowing intercallability between -GCC-compiled files and files compiled with other compilers. - -The precise convention for returning structures in memory depends -on the target configuration macros. - -Short structures and unions are those whose size and alignment match -that of some integer type. - -@item -freg-struct-return -Use the convention that @code{struct} and @code{union} values are -returned in registers when possible. This is more efficient for small -structures than @samp{-fpcc-struct-return}. - -If you specify neither @samp{-fpcc-struct-return} nor its contrary -@samp{-freg-struct-return}, GCC defaults to whichever convention is -standard for the target. If there is no standard convention, GCC -defaults to @samp{-fpcc-struct-return}, except on targets where GCC -is the principal compiler. In those cases, we can choose the standard, -and we chose the more efficient register return alternative. - -@item -fshort-enums -Allocate to an @code{enum} type only as many bytes as it needs for the -declared range of possible values. Specifically, the @code{enum} type -will be equivalent to the smallest integer type which has enough room. - -@item -fshort-double -Use the same size for @code{double} as for @code{float}. - -@item -fshared-data -Requests that the data and non-@code{const} variables of this -compilation be shared data rather than private data. The distinction -makes sense only on certain operating systems, where shared data is -shared between processes running the same program, while private data -exists in one copy per process. - -@item -fno-common -In C, allocate even uninitialized global variables in the data section of the -object file, rather than generating them as common blocks. This has the -effect that if the same variable is declared (without @code{extern}) in -two different compilations, you will get an error when you link them. -The only reason this might be useful is if you wish to verify that the -program will work on other systems which always work this way. - -@item -fno-ident -Ignore the @samp{#ident} directive. - -@item -fno-gnu-linker -Do not output global initializations (such as C++ constructors and -destructors) in the form used by the GNU linker (on systems where the GNU -linker is the standard method of handling them). Use this option when -you want to use a non-GNU linker, which also requires using the -@command{collect2} program to make sure the system linker includes -constructors and destructors. (@command{collect2} is included in the GCC -distribution.) For systems which @emph{must} use @command{collect2}, the -compiler driver @command{gcc} is configured to do this automatically. - -@item -finhibit-size-directive -Don't output a @code{.size} assembler directive, or anything else that -would cause trouble if the function is split in the middle, and the -two halves are placed at locations far apart in memory. This option is -used when compiling @file{crtstuff.c}; you should not need to use it -for anything else. - -@item -fverbose-asm -Put extra commentary information in the generated assembly code to -make it more readable. This option is generally only of use to those -who actually need to read the generated assembly code (perhaps while -debugging the compiler itself). - -@samp{-fno-verbose-asm}, the default, causes the -extra information to be omitted and is useful when comparing two assembler -files. - -@item -fvolatile -Consider all memory references through pointers to be volatile. - -@item -fvolatile-global -Consider all memory references to extern and global data items to -be volatile. GCC does not consider static data items to be volatile -because of this switch. - -@item -fvolatile-static -Consider all memory references to static data to be volatile. - -@item -fpic -@cindex global offset table -@cindex PIC -Generate position-independent code (PIC) suitable for use in a shared -library, if supported for the target machine. Such code accesses all -constant addresses through a global offset table (GOT). The dynamic -loader resolves the GOT entries when the program starts (the dynamic -loader is not part of GCC; it is part of the operating system). If -the GOT size for the linked executable exceeds a machine-specific -maximum size, you get an error message from the linker indicating that -@samp{-fpic} does not work; in that case, recompile with @samp{-fPIC} -instead. (These maximums are 16k on the m88k, 8k on the Sparc, and 32k -on the m68k and RS/6000. The 386 has no such limit.) - -Position-independent code requires special support, and therefore works -only on certain machines. For the 386, GCC supports PIC for System V -but not for the Sun 386i. Code generated for the IBM RS/6000 is always -position-independent. - -@item -fPIC -If supported for the target machine, emit position-independent code, -suitable for dynamic linking and avoiding any limit on the size of the -global offset table. This option makes a difference on the m68k, m88k, -and the Sparc. - -Position-independent code requires special support, and therefore works -only on certain machines. - -@item -ffixed-@var{reg} -Treat the register named @var{reg} as a fixed register; generated code -should never refer to it (except perhaps as a stack pointer, frame -pointer or in some other fixed role). - -@var{reg} must be the name of a register. The register names accepted -are machine-specific and are defined in the @code{REGISTER_NAMES} -macro in the machine description macro file. - -This flag does not have a negative form, because it specifies a -three-way choice. - -@item -fcall-used-@var{reg} -Treat the register named @var{reg} as an allocable register that is -clobbered by function calls. It may be allocated for temporaries or -variables that do not live across a call. Functions compiled this way -will not save and restore the register @var{reg}. - -It is an error to used this flag with the frame pointer or stack pointer. -Use of this flag for other registers that have fixed pervasive roles in -the machine's execution model will produce disastrous results. - -This flag does not have a negative form, because it specifies a -three-way choice. - -@item -fcall-saved-@var{reg} -Treat the register named @var{reg} as an allocable register saved by -functions. It may be allocated even for temporaries or variables that -live across a call. Functions compiled this way will save and restore -the register @var{reg} if they use it. - -It is an error to used this flag with the frame pointer or stack pointer. -Use of this flag for other registers that have fixed pervasive roles in -the machine's execution model will produce disastrous results. - -A different sort of disaster will result from the use of this flag for -a register in which function values may be returned. - -This flag does not have a negative form, because it specifies a -three-way choice. - -@item -fpack-struct -Pack all structure members together without holes. Usually you would -not want to use this option, since it makes the code suboptimal, and -the offsets of structure members won't agree with system libraries. - -@item -fcheck-memory-usage -Generate extra code to check each memory access. GCC will generate -code that is suitable for a detector of bad memory accesses such as -@file{Checker}. - -Normally, you should compile all, or none, of your code with this option. - -If you do mix code compiled with and without this option, -you must ensure that all code that has side effects -and that is called by code compiled with this option -is, itself, compiled with this option. -If you do not, you might get erroneous messages from the detector. - -If you use functions from a library that have side-effects (such as -@code{read}), you might not be able to recompile the library and -specify this option. In that case, you can enable the -@samp{-fprefix-function-name} option, which requests GCC to encapsulate -your code and make other functions look as if they were compiled with -@samp{-fcheck-memory-usage}. This is done by calling ``stubs'', -which are provided by the detector. If you cannot find or build -stubs for every function you call, you might have to specify -@samp{-fcheck-memory-usage} without @samp{-fprefix-function-name}. - -If you specify this option, you can not use the @code{asm} or -@code{__asm__} keywords in functions with memory checking enabled. GNU -CC cannot understand what the @code{asm} statement may do, and therefore -cannot generate the appropriate code, so it will reject it. However, if -you specify the function attribute @code{no_check_memory_usage} -(@pxref{Function Attributes}), GNU CC will disable memory checking within a -function; you may use @code{asm} statements inside such functions. You -may have an inline expansion of a non-checked function within a checked -function; in that case GNU CC will not generate checks for the inlined -function's memory accesses. - -If you move your @code{asm} statements to non-checked inline functions -and they do access memory, you can add calls to the support code in your -inline function, to indicate any reads, writes, or copies being done. -These calls would be similar to those done in the stubs described above. - -@item -fprefix-function-name -Request GCC to add a prefix to the symbols generated for function names. -GCC adds a prefix to the names of functions defined as well as -functions called. Code compiled with this option and code compiled -without the option can't be linked together, unless stubs are used. - -If you compile the following code with @samp{-fprefix-function-name} -@example -extern void bar (int); -void -foo (int a) -@{ - return bar (a + 5); -@} -@end example - -@noindent -GCC will compile the code as if it was written: -@example -extern void prefix_bar (int); -void -prefix_foo (int a) -@{ - return prefix_bar (a + 5); -@} -@end example -This option is designed to be used with @samp{-fcheck-memory-usage}. - -@item -finstrument-functions -Generate instrumentation calls for entry and exit to functions. Just -after function entry and just before function exit, the following -profiling functions will be called with the address of the current -function and its call site. (On some platforms, -@code{__builtin_return_address} does not work beyond the current -function, so the call site information may not be available to the -profiling functions otherwise.) - -@example -void __cyg_profile_func_enter (void *this_fn, - void *call_site); -void __cyg_profile_func_exit (void *this_fn, - void *call_site); -@end example - -The first argument is the address of the start of the current function, -which may be looked up exactly in the symbol table. - -This instrumentation is also done for functions expanded inline in other -functions. The profiling calls will indicate where, conceptually, the -inline function is entered and exited. This means that addressable -versions of such functions must be available. If all your uses of a -function are expanded inline, this may mean an additional expansion of -code size. If you use @samp{extern inline} in your C code, an -addressable version of such functions must be provided. (This is -normally the case anyways, but if you get lucky and the optimizer always -expands the functions inline, you might have gotten away without -providing static copies.) - -A function may be given the attribute @code{no_instrument_function}, in -which case this instrumentation will not be done. This can be used, for -example, for the profiling functions listed above, high-priority -interrupt routines, and any functions from which the profiling functions -cannot safely be called (perhaps signal handlers, if the profiling -routines generate output or allocate memory). - -@item -fstack-check -Generate code to verify that you do not go beyond the boundary of the -stack. You should specify this flag if you are running in an -environment with multiple threads, but only rarely need to specify it in -a single-threaded environment since stack overflow is automatically -detected on nearly all systems if there is only one stack. - -Note that this switch does not actually cause checking to be done; the -operating system must do that. The switch causes generation of code -to ensure that the operating system sees the stack being extended. - -@item -fstack-limit-register=@var{reg} -@itemx -fstack-limit-symbol=@var{sym} -@itemx -fno-stack-limit -Generate code to ensure that the stack does not grow beyond a certain value, -either the value of a register or the address of a symbol. If the stack -would grow beyond the value, a signal is raised. For most targets, -the signal is raised before the stack overruns the boundary, so -it is possible to catch the signal without taking special precautions. - -For instance, if the stack starts at address @samp{0x80000000} and grows -downwards you can use the flags -@samp{-fstack-limit-symbol=__stack_limit} -@samp{-Wl,--defsym,__stack_limit=0x7ffe0000} which will enforce a stack -limit of 128K. - -@cindex aliasing of parameters -@cindex parameters, aliased -@item -fargument-alias -@itemx -fargument-noalias -@itemx -fargument-noalias-global -Specify the possible relationships among parameters and between -parameters and global data. - -@samp{-fargument-alias} specifies that arguments (parameters) may -alias each other and may alias global storage. -@samp{-fargument-noalias} specifies that arguments do not alias -each other, but may alias global storage. -@samp{-fargument-noalias-global} specifies that arguments do not -alias each other and do not alias global storage. - -Each language will automatically use whatever option is required by -the language standard. You should not need to use these options yourself. - -@item -fleading-underscore -This option and its counterpart, -fno-leading-underscore, forcibly -change the way C symbols are represented in the object file. One use -is to help link with legacy assembly code. - -Be warned that you should know what you are doing when invoking this -option, and that not all targets provide complete support for it. -@end table - -@c man end - -@node Environment Variables -@section Environment Variables Affecting GCC -@cindex environment variables - -@c man begin ENVIRONMENT - -This section describes several environment variables that affect how GCC -operates. Some of them work by specifying directories or prefixes to use -when searching for various kinds of files. Some are used to specify other -aspects of the compilation environment. - -@ifclear INTERNALS -Note that you can also specify places to search using options such as -@samp{-B}, @samp{-I} and @samp{-L} (@pxref{Directory Options}). These -take precedence over places specified using environment variables, which -in turn take precedence over those specified by the configuration of GCC. - -@end ifclear -@ifset INTERNALS -Note that you can also specify places to search using options such as -@samp{-B}, @samp{-I} and @samp{-L} (@pxref{Directory Options}). These -take precedence over places specified using environment variables, which -in turn take precedence over those specified by the configuration of GCC. -@xref{Driver}. -@end ifset - -@table @env -@item LANG -@itemx LC_CTYPE -@c @itemx LC_COLLATE -@itemx LC_MESSAGES -@c @itemx LC_MONETARY -@c @itemx LC_NUMERIC -@c @itemx LC_TIME -@itemx LC_ALL -@findex LANG -@findex LC_CTYPE -@c @findex LC_COLLATE -@findex LC_MESSAGES -@c @findex LC_MONETARY -@c @findex LC_NUMERIC -@c @findex LC_TIME -@findex LC_ALL -@cindex locale -These environment variables control the way that GCC uses -localization information that allow GCC to work with different -national conventions. GCC inspects the locale categories -@env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do -so. These locale categories can be set to any value supported by your -installation. A typical value is @samp{en_UK} for English in the United -Kingdom. - -The @env{LC_CTYPE} environment variable specifies character -classification. GCC uses it to determine the character boundaries in -a string; this is needed for some multibyte encodings that contain quote -and escape characters that would otherwise be interpreted as a string -end or escape. - -The @env{LC_MESSAGES} environment variable specifies the language to -use in diagnostic messages. - -If the @env{LC_ALL} environment variable is set, it overrides the value -of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE} -and @env{LC_MESSAGES} default to the value of the @env{LANG} -environment variable. If none of these variables are set, GCC -defaults to traditional C English behavior. - -@item TMPDIR -@findex TMPDIR -If @env{TMPDIR} is set, it specifies the directory to use for temporary -files. GCC uses temporary files to hold the output of one stage of -compilation which is to be used as input to the next stage: for example, -the output of the preprocessor, which is the input to the compiler -proper. - -@item GCC_EXEC_PREFIX -@findex GCC_EXEC_PREFIX -If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the -names of the subprograms executed by the compiler. No slash is added -when this prefix is combined with the name of a subprogram, but you can -specify a prefix that ends with a slash if you wish. - -If @env{GCC_EXEC_PREFIX} is not set, GNU CC will attempt to figure out -an appropriate prefix to use based on the pathname it was invoked with. - -If GCC cannot find the subprogram using the specified prefix, it -tries looking in the usual places for the subprogram. - -The default value of @env{GCC_EXEC_PREFIX} is -@file{@var{prefix}/lib/gcc-lib/} where @var{prefix} is the value -of @code{prefix} when you ran the @file{configure} script. - -Other prefixes specified with @samp{-B} take precedence over this prefix. - -This prefix is also used for finding files such as @file{crt0.o} that are -used for linking. - -In addition, the prefix is used in an unusual way in finding the -directories to search for header files. For each of the standard -directories whose name normally begins with @samp{/usr/local/lib/gcc-lib} -(more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries -replacing that beginning with the specified prefix to produce an -alternate directory name. Thus, with @samp{-Bfoo/}, GCC will search -@file{foo/bar} where it would normally search @file{/usr/local/lib/bar}. -These alternate directories are searched first; the standard directories -come next. - -@item COMPILER_PATH -@findex COMPILER_PATH -The value of @env{COMPILER_PATH} is a colon-separated list of -directories, much like @env{PATH}. GCC tries the directories thus -specified when searching for subprograms, if it can't find the -subprograms using @env{GCC_EXEC_PREFIX}. - -@item LIBRARY_PATH -@findex LIBRARY_PATH -The value of @env{LIBRARY_PATH} is a colon-separated list of -directories, much like @env{PATH}. When configured as a native compiler, -GCC tries the directories thus specified when searching for special -linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking -using GCC also uses these directories when searching for ordinary -libraries for the @samp{-l} option (but directories specified with -@samp{-L} come first). - -@item C_INCLUDE_PATH -@itemx CPLUS_INCLUDE_PATH -@itemx OBJC_INCLUDE_PATH -@findex C_INCLUDE_PATH -@findex CPLUS_INCLUDE_PATH -@findex OBJC_INCLUDE_PATH -@c @itemx OBJCPLUS_INCLUDE_PATH -These environment variables pertain to particular languages. Each -variable's value is a colon-separated list of directories, much like -@env{PATH}. When GCC searches for header files, it tries the -directories listed in the variable for the language you are using, after -the directories specified with @samp{-I} but before the standard header -file directories. - -@item DEPENDENCIES_OUTPUT -@findex DEPENDENCIES_OUTPUT -@cindex dependencies for make as output -If this variable is set, its value specifies how to output dependencies -for Make based on the header files processed by the compiler. This -output looks much like the output from the @samp{-M} option -(@pxref{Preprocessor Options}), but it goes to a separate file, and is -in addition to the usual results of compilation. - -The value of @env{DEPENDENCIES_OUTPUT} can be just a file name, in -which case the Make rules are written to that file, guessing the target -name from the source file name. Or the value can have the form -@samp{@var{file} @var{target}}, in which case the rules are written to -file @var{file} using @var{target} as the target name. - -@item LANG -@findex LANG -@cindex locale definition -This variable is used to pass locale information to the compiler. One way in -which this information is used is to determine the character set to be used -when character literals, string literals and comments are parsed in C and C++. -When the compiler is configured to allow multibyte characters, -the following values for @env{LANG} are recognized: - -@table @samp -@item C-JIS -Recognize JIS characters. -@item C-SJIS -Recognize SJIS characters. -@item C-EUCJP -Recognize EUCJP characters. -@end table - -If @env{LANG} is not defined, or if it has some other value, then the -compiler will use mblen and mbtowc as defined by the default locale to -recognize and translate multibyte characters. -@end table - -@c man end - -@node Running Protoize -@section Running Protoize - -The program @code{protoize} is an optional part of GNU C. You can use -it to add prototypes to a program, thus converting the program to ISO -C in one respect. The companion program @code{unprotoize} does the -reverse: it removes argument types from any prototypes that are found. - -When you run these programs, you must specify a set of source files as -command line arguments. The conversion programs start out by compiling -these files to see what functions they define. The information gathered -about a file @var{foo} is saved in a file named @file{@var{foo}.X}. - -After scanning comes actual conversion. The specified files are all -eligible to be converted; any files they include (whether sources or -just headers) are eligible as well. - -But not all the eligible files are converted. By default, -@code{protoize} and @code{unprotoize} convert only source and header -files in the current directory. You can specify additional directories -whose files should be converted with the @samp{-d @var{directory}} -option. You can also specify particular files to exclude with the -@samp{-x @var{file}} option. A file is converted if it is eligible, its -directory name matches one of the specified directory names, and its -name within the directory has not been excluded. - -Basic conversion with @code{protoize} consists of rewriting most -function definitions and function declarations to specify the types of -the arguments. The only ones not rewritten are those for varargs -functions. - -@code{protoize} optionally inserts prototype declarations at the -beginning of the source file, to make them available for any calls that -precede the function's definition. Or it can insert prototype -declarations with block scope in the blocks where undeclared functions -are called. - -Basic conversion with @code{unprotoize} consists of rewriting most -function declarations to remove any argument types, and rewriting -function definitions to the old-style pre-ISO form. - -Both conversion programs print a warning for any function declaration or -definition that they can't convert. You can suppress these warnings -with @samp{-q}. - -The output from @code{protoize} or @code{unprotoize} replaces the -original source file. The original file is renamed to a name ending -with @samp{.save} (for DOS, the saved filename ends in @samp{.sav} -without the original @samp{.c} suffix). If the @samp{.save} (@samp{.sav} -for DOS) file already exists, then the source file is simply discarded. - -@code{protoize} and @code{unprotoize} both depend on GCC itself to -scan the program and collect information about the functions it uses. -So neither of these programs will work until GCC is installed. - -Here is a table of the options you can use with @code{protoize} and -@code{unprotoize}. Each option works with both programs unless -otherwise stated. - -@table @code -@item -B @var{directory} -Look for the file @file{SYSCALLS.c.X} in @var{directory}, instead of the -usual directory (normally @file{/usr/local/lib}). This file contains -prototype information about standard system functions. This option -applies only to @code{protoize}. - -@item -c @var{compilation-options} -Use @var{compilation-options} as the options when running @code{gcc} to -produce the @samp{.X} files. The special option @samp{-aux-info} is -always passed in addition, to tell @code{gcc} to write a @samp{.X} file. - -Note that the compilation options must be given as a single argument to -@code{protoize} or @code{unprotoize}. If you want to specify several -@code{gcc} options, you must quote the entire set of compilation options -to make them a single word in the shell. - -There are certain @code{gcc} arguments that you cannot use, because they -would produce the wrong kind of output. These include @samp{-g}, -@samp{-O}, @samp{-c}, @samp{-S}, and @samp{-o} If you include these in -the @var{compilation-options}, they are ignored. - -@item -C -Rename files to end in @samp{.C} (@samp{.cc} for DOS-based file -systems) instead of @samp{.c}. This is convenient if you are converting -a C program to C++. This option applies only to @code{protoize}. - -@item -g -Add explicit global declarations. This means inserting explicit -declarations at the beginning of each source file for each function -that is called in the file and was not declared. These declarations -precede the first function definition that contains a call to an -undeclared function. This option applies only to @code{protoize}. - -@item -i @var{string} -Indent old-style parameter declarations with the string @var{string}. -This option applies only to @code{protoize}. - -@code{unprotoize} converts prototyped function definitions to old-style -function definitions, where the arguments are declared between the -argument list and the initial @samp{@{}. By default, @code{unprotoize} -uses five spaces as the indentation. If you want to indent with just -one space instead, use @samp{-i " "}. - -@item -k -Keep the @samp{.X} files. Normally, they are deleted after conversion -is finished. - -@item -l -Add explicit local declarations. @code{protoize} with @samp{-l} inserts -a prototype declaration for each function in each block which calls the -function without any declaration. This option applies only to -@code{protoize}. - -@item -n -Make no real changes. This mode just prints information about the conversions -that would have been done without @samp{-n}. - -@item -N -Make no @samp{.save} files. The original files are simply deleted. -Use this option with caution. - -@item -p @var{program} -Use the program @var{program} as the compiler. Normally, the name -@file{gcc} is used. - -@item -q -Work quietly. Most warnings are suppressed. - -@item -v -Print the version number, just like @samp{-v} for @code{gcc}. -@end table - -If you need special compiler options to compile one of your program's -source files, then you should generate that file's @samp{.X} file -specially, by running @code{gcc} on that source file with the -appropriate options and the option @samp{-aux-info}. Then run -@code{protoize} on the entire set of files. @code{protoize} will use -the existing @samp{.X} file because it is newer than the source file. -For example: - -@example -gcc -Dfoo=bar file1.c -aux-info -protoize *.c -@end example - -@noindent -You need to include the special files along with the rest in the -@code{protoize} command, even though their @samp{.X} files already -exist, because otherwise they won't get converted. - -@xref{Protoize Caveats}, for more information on how to use -@code{protoize} successfully. diff --git a/gcc/java/Make-lang.in b/gcc/java/Make-lang.in index 2737f93292f..0cae9b2312b 100644 --- a/gcc/java/Make-lang.in +++ b/gcc/java/Make-lang.in @@ -293,12 +293,12 @@ java/jcf-path.o: java/jcf-path.c $(CONFIG_H) $(SYSTEM_H) java/jcf.h $(srcdir)/java/jcf-path.c $(OUTPUT_OPTION) # Documentation -$(srcdir)/java/gcj.info: $(srcdir)/java/gcj.texi $(srcdir)/fdl.texi +$(srcdir)/java/gcj.info: $(srcdir)/java/gcj.texi $(srcdir)/doc/fdl.texi if test "x$(BUILD_INFO)" = xinfo; then \ rm -f $(srcdir)/java/gcc.info*; \ - cd $(srcdir)/java && $(MAKEINFO) -I.. -o gcj.info gcj.texi; \ + cd $(srcdir)/java && $(MAKEINFO) -I../doc -o gcj.info gcj.texi; \ else true; fi -java/gcj.dvi: $(srcdir)/java/gcj.texi $(srcdir)/fdl.texi +java/gcj.dvi: $(srcdir)/java/gcj.texi $(srcdir)/doc/fdl.texi s=`cd $(srcdir); pwd`; export s; \ - cd java && $(TEXI2DVI) -I $$s $$s/java/gcj.texi + cd java && $(TEXI2DVI) -I $$s/doc $$s/java/gcj.texi diff --git a/gcc/md.texi b/gcc/md.texi deleted file mode 100644 index eec92cb5ebb..00000000000 --- a/gcc/md.texi +++ /dev/null @@ -1,5022 +0,0 @@ -@c Copyright (C) 1988, 89, 92, 93, 94, 96, 1998, 2000, 2001 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@ifset INTERNALS -@node Machine Desc -@chapter Machine Descriptions -@cindex machine descriptions - -A machine description has two parts: a file of instruction patterns -(@file{.md} file) and a C header file of macro definitions. - -The @file{.md} file for a target machine contains a pattern for each -instruction that the target machine supports (or at least each instruction -that is worth telling the compiler about). It may also contain comments. -A semicolon causes the rest of the line to be a comment, unless the semicolon -is inside a quoted string. - -See the next chapter for information on the C header file. - -@menu -* Overview:: How the machine description is used. -* Patterns:: How to write instruction patterns. -* Example:: An explained example of a @code{define_insn} pattern. -* RTL Template:: The RTL template defines what insns match a pattern. -* Output Template:: The output template says how to make assembler code - from such an insn. -* Output Statement:: For more generality, write C code to output - the assembler code. -* Constraints:: When not all operands are general operands. -* Standard Names:: Names mark patterns to use for code generation. -* Pattern Ordering:: When the order of patterns makes a difference. -* Dependent Patterns:: Having one pattern may make you need another. -* Jump Patterns:: Special considerations for patterns for jump insns. -* Looping Patterns:: How to define patterns for special looping insns. -* Insn Canonicalizations::Canonicalization of Instructions -* Expander Definitions::Generating a sequence of several RTL insns - for a standard operation. -* Insn Splitting:: Splitting Instructions into Multiple Instructions. -* Peephole Definitions::Defining machine-specific peephole optimizations. -* Insn Attributes:: Specifying the value of attributes for generated insns. -* Conditional Execution::Generating @code{define_insn} patterns for - predication. -* Constant Definitions::Defining symbolic constants that can be used in the - md file. -@end menu - -@node Overview -@section Overview of How the Machine Description is Used - -There are three main conversions that happen in the compiler: - -@enumerate - -@item -The front end reads the source code and builds a parse tree. - -@item -The parse tree is used to generate an RTL insn list based on named -instruction patterns. - -@item -The insn list is matched against the RTL templates to produce assembler -code. - -@end enumerate - -For the generate pass, only the names of the insns matter, from either a -named @code{define_insn} or a @code{define_expand}. The compiler will -choose the pattern with the right name and apply the operands according -to the documentation later in this chapter, without regard for the RTL -template or operand constraints. Note that the names the compiler looks -for are hard-coded in the compiler - it will ignore unnamed patterns and -patterns with names it doesn't know about, but if you don't provide a -named pattern it needs, it will abort. - -If a @code{define_insn} is used, the template given is inserted into the -insn list. If a @code{define_expand} is used, one of three things -happens, based on the condition logic. The condition logic may manually -create new insns for the insn list, say via @code{emit_insn()}, and -invoke DONE. For certain named patterns, it may invoke FAIL to tell the -compiler to use an alternate way of performing that task. If it invokes -neither @code{DONE} nor @code{FAIL}, the template given in the pattern -is inserted, as if the @code{define_expand} were a @code{define_insn}. - -Once the insn list is generated, various optimization passes convert, -replace, and rearrange the insns in the insn list. This is where the -@code{define_split} and @code{define_peephole} patterns get used, for -example. - -Finally, the insn list's RTL is matched up with the RTL templates in the -@code{define_insn} patterns, and those patterns are used to emit the -final assembly code. For this purpose, each named @code{define_insn} -acts like it's unnamed, since the names are ignored. - -@node Patterns -@section Everything about Instruction Patterns -@cindex patterns -@cindex instruction patterns - -@findex define_insn -Each instruction pattern contains an incomplete RTL expression, with pieces -to be filled in later, operand constraints that restrict how the pieces can -be filled in, and an output pattern or C code to generate the assembler -output, all wrapped up in a @code{define_insn} expression. - -A @code{define_insn} is an RTL expression containing four or five operands: - -@enumerate -@item -An optional name. The presence of a name indicate that this instruction -pattern can perform a certain standard job for the RTL-generation -pass of the compiler. This pass knows certain names and will use -the instruction patterns with those names, if the names are defined -in the machine description. - -The absence of a name is indicated by writing an empty string -where the name should go. Nameless instruction patterns are never -used for generating RTL code, but they may permit several simpler insns -to be combined later on. - -Names that are not thus known and used in RTL-generation have no -effect; they are equivalent to no name at all. - -For the purpose of debugging the compiler, you may also specify a -name beginning with the @samp{*} character. Such a name is used only -for identifying the instruction in RTL dumps; it is entirely equivalent -to having a nameless pattern for all other purposes. - -@item -The @dfn{RTL template} (@pxref{RTL Template}) is a vector of incomplete -RTL expressions which show what the instruction should look like. It is -incomplete because it may contain @code{match_operand}, -@code{match_operator}, and @code{match_dup} expressions that stand for -operands of the instruction. - -If the vector has only one element, that element is the template for the -instruction pattern. If the vector has multiple elements, then the -instruction pattern is a @code{parallel} expression containing the -elements described. - -@item -@cindex pattern conditions -@cindex conditions, in patterns -A condition. This is a string which contains a C expression that is -the final test to decide whether an insn body matches this pattern. - -@cindex named patterns and conditions -For a named pattern, the condition (if present) may not depend on -the data in the insn being matched, but only the target-machine-type -flags. The compiler needs to test these conditions during -initialization in order to learn exactly which named instructions are -available in a particular run. - -@findex operands -For nameless patterns, the condition is applied only when matching an -individual insn, and only after the insn has matched the pattern's -recognition template. The insn's operands may be found in the vector -@code{operands}. - -@item -The @dfn{output template}: a string that says how to output matching -insns as assembler code. @samp{%} in this string specifies where -to substitute the value of an operand. @xref{Output Template}. - -When simple substitution isn't general enough, you can specify a piece -of C code to compute the output. @xref{Output Statement}. - -@item -Optionally, a vector containing the values of attributes for insns matching -this pattern. @xref{Insn Attributes}. -@end enumerate - -@node Example -@section Example of @code{define_insn} -@cindex @code{define_insn} example - -Here is an actual example of an instruction pattern, for the 68000/68020. - -@example -(define_insn "tstsi" - [(set (cc0) - (match_operand:SI 0 "general_operand" "rm"))] - "" - "* -@{ if (TARGET_68020 || ! ADDRESS_REG_P (operands[0])) - return \"tstl %0\"; - return \"cmpl #0,%0\"; @}") -@end example - -This is an instruction that sets the condition codes based on the value of -a general operand. It has no condition, so any insn whose RTL description -has the form shown may be handled according to this pattern. The name -@samp{tstsi} means ``test a @code{SImode} value'' and tells the RTL generation -pass that, when it is necessary to test such a value, an insn to do so -can be constructed using this pattern. - -The output control string is a piece of C code which chooses which -output template to return based on the kind of operand and the specific -type of CPU for which code is being generated. - -@samp{"rm"} is an operand constraint. Its meaning is explained below. - -@node RTL Template -@section RTL Template -@cindex RTL insn template -@cindex generating insns -@cindex insns, generating -@cindex recognizing insns -@cindex insns, recognizing - -The RTL template is used to define which insns match the particular pattern -and how to find their operands. For named patterns, the RTL template also -says how to construct an insn from specified operands. - -Construction involves substituting specified operands into a copy of the -template. Matching involves determining the values that serve as the -operands in the insn being matched. Both of these activities are -controlled by special expression types that direct matching and -substitution of the operands. - -@table @code -@findex match_operand -@item (match_operand:@var{m} @var{n} @var{predicate} @var{constraint}) -This expression is a placeholder for operand number @var{n} of -the insn. When constructing an insn, operand number @var{n} -will be substituted at this point. When matching an insn, whatever -appears at this position in the insn will be taken as operand -number @var{n}; but it must satisfy @var{predicate} or this instruction -pattern will not match at all. - -Operand numbers must be chosen consecutively counting from zero in -each instruction pattern. There may be only one @code{match_operand} -expression in the pattern for each operand number. Usually operands -are numbered in the order of appearance in @code{match_operand} -expressions. In the case of a @code{define_expand}, any operand numbers -used only in @code{match_dup} expressions have higher values than all -other operand numbers. - -@var{predicate} is a string that is the name of a C function that accepts two -arguments, an expression and a machine mode. During matching, the -function will be called with the putative operand as the expression and -@var{m} as the mode argument (if @var{m} is not specified, -@code{VOIDmode} will be used, which normally causes @var{predicate} to accept -any mode). If it returns zero, this instruction pattern fails to match. -@var{predicate} may be an empty string; then it means no test is to be done -on the operand, so anything which occurs in this position is valid. - -Most of the time, @var{predicate} will reject modes other than @var{m}---but -not always. For example, the predicate @code{address_operand} uses -@var{m} as the mode of memory ref that the address should be valid for. -Many predicates accept @code{const_int} nodes even though their mode is -@code{VOIDmode}. - -@var{constraint} controls reloading and the choice of the best register -class to use for a value, as explained later (@pxref{Constraints}). - -People are often unclear on the difference between the constraint and the -predicate. The predicate helps decide whether a given insn matches the -pattern. The constraint plays no role in this decision; instead, it -controls various decisions in the case of an insn which does match. - -@findex general_operand -On CISC machines, the most common @var{predicate} is -@code{"general_operand"}. This function checks that the putative -operand is either a constant, a register or a memory reference, and that -it is valid for mode @var{m}. - -@findex register_operand -For an operand that must be a register, @var{predicate} should be -@code{"register_operand"}. Using @code{"general_operand"} would be -valid, since the reload pass would copy any non-register operands -through registers, but this would make GNU CC do extra work, it would -prevent invariant operands (such as constant) from being removed from -loops, and it would prevent the register allocator from doing the best -possible job. On RISC machines, it is usually most efficient to allow -@var{predicate} to accept only objects that the constraints allow. - -@findex immediate_operand -For an operand that must be a constant, you must be sure to either use -@code{"immediate_operand"} for @var{predicate}, or make the instruction -pattern's extra condition require a constant, or both. You cannot -expect the constraints to do this work! If the constraints allow only -constants, but the predicate allows something else, the compiler will -crash when that case arises. - -@findex match_scratch -@item (match_scratch:@var{m} @var{n} @var{constraint}) -This expression is also a placeholder for operand number @var{n} -and indicates that operand must be a @code{scratch} or @code{reg} -expression. - -When matching patterns, this is equivalent to - -@smallexample -(match_operand:@var{m} @var{n} "scratch_operand" @var{pred}) -@end smallexample - -but, when generating RTL, it produces a (@code{scratch}:@var{m}) -expression. - -If the last few expressions in a @code{parallel} are @code{clobber} -expressions whose operands are either a hard register or -@code{match_scratch}, the combiner can add or delete them when -necessary. @xref{Side Effects}. - -@findex match_dup -@item (match_dup @var{n}) -This expression is also a placeholder for operand number @var{n}. -It is used when the operand needs to appear more than once in the -insn. - -In construction, @code{match_dup} acts just like @code{match_operand}: -the operand is substituted into the insn being constructed. But in -matching, @code{match_dup} behaves differently. It assumes that operand -number @var{n} has already been determined by a @code{match_operand} -appearing earlier in the recognition template, and it matches only an -identical-looking expression. - -Note that @code{match_dup} should not be used to tell the compiler that -a particular register is being used for two operands (example: -@code{add} that adds one register to another; the second register is -both an input operand and the output operand). Use a matching -constraint (@pxref{Simple Constraints}) for those. @code{match_dup} is for the cases where one -operand is used in two places in the template, such as an instruction -that computes both a quotient and a remainder, where the opcode takes -two input operands but the RTL template has to refer to each of those -twice; once for the quotient pattern and once for the remainder pattern. - -@findex match_operator -@item (match_operator:@var{m} @var{n} @var{predicate} [@var{operands}@dots{}]) -This pattern is a kind of placeholder for a variable RTL expression -code. - -When constructing an insn, it stands for an RTL expression whose -expression code is taken from that of operand @var{n}, and whose -operands are constructed from the patterns @var{operands}. - -When matching an expression, it matches an expression if the function -@var{predicate} returns nonzero on that expression @emph{and} the -patterns @var{operands} match the operands of the expression. - -Suppose that the function @code{commutative_operator} is defined as -follows, to match any expression whose operator is one of the -commutative arithmetic operators of RTL and whose mode is @var{mode}: - -@smallexample -int -commutative_operator (x, mode) - rtx x; - enum machine_mode mode; -@{ - enum rtx_code code = GET_CODE (x); - if (GET_MODE (x) != mode) - return 0; - return (GET_RTX_CLASS (code) == 'c' - || code == EQ || code == NE); -@} -@end smallexample - -Then the following pattern will match any RTL expression consisting -of a commutative operator applied to two general operands: - -@smallexample -(match_operator:SI 3 "commutative_operator" - [(match_operand:SI 1 "general_operand" "g") - (match_operand:SI 2 "general_operand" "g")]) -@end smallexample - -Here the vector @code{[@var{operands}@dots{}]} contains two patterns -because the expressions to be matched all contain two operands. - -When this pattern does match, the two operands of the commutative -operator are recorded as operands 1 and 2 of the insn. (This is done -by the two instances of @code{match_operand}.) Operand 3 of the insn -will be the entire commutative expression: use @code{GET_CODE -(operands[3])} to see which commutative operator was used. - -The machine mode @var{m} of @code{match_operator} works like that of -@code{match_operand}: it is passed as the second argument to the -predicate function, and that function is solely responsible for -deciding whether the expression to be matched ``has'' that mode. - -When constructing an insn, argument 3 of the gen-function will specify -the operation (i.e. the expression code) for the expression to be -made. It should be an RTL expression, whose expression code is copied -into a new expression whose operands are arguments 1 and 2 of the -gen-function. The subexpressions of argument 3 are not used; -only its expression code matters. - -When @code{match_operator} is used in a pattern for matching an insn, -it usually best if the operand number of the @code{match_operator} -is higher than that of the actual operands of the insn. This improves -register allocation because the register allocator often looks at -operands 1 and 2 of insns to see if it can do register tying. - -There is no way to specify constraints in @code{match_operator}. The -operand of the insn which corresponds to the @code{match_operator} -never has any constraints because it is never reloaded as a whole. -However, if parts of its @var{operands} are matched by -@code{match_operand} patterns, those parts may have constraints of -their own. - -@findex match_op_dup -@item (match_op_dup:@var{m} @var{n}[@var{operands}@dots{}]) -Like @code{match_dup}, except that it applies to operators instead of -operands. When constructing an insn, operand number @var{n} will be -substituted at this point. But in matching, @code{match_op_dup} behaves -differently. It assumes that operand number @var{n} has already been -determined by a @code{match_operator} appearing earlier in the -recognition template, and it matches only an identical-looking -expression. - -@findex match_parallel -@item (match_parallel @var{n} @var{predicate} [@var{subpat}@dots{}]) -This pattern is a placeholder for an insn that consists of a -@code{parallel} expression with a variable number of elements. This -expression should only appear at the top level of an insn pattern. - -When constructing an insn, operand number @var{n} will be substituted at -this point. When matching an insn, it matches if the body of the insn -is a @code{parallel} expression with at least as many elements as the -vector of @var{subpat} expressions in the @code{match_parallel}, if each -@var{subpat} matches the corresponding element of the @code{parallel}, -@emph{and} the function @var{predicate} returns nonzero on the -@code{parallel} that is the body of the insn. It is the responsibility -of the predicate to validate elements of the @code{parallel} beyond -those listed in the @code{match_parallel}.@refill - -A typical use of @code{match_parallel} is to match load and store -multiple expressions, which can contain a variable number of elements -in a @code{parallel}. For example, -@c the following is *still* going over. need to change the code. -@c also need to work on grouping of this example. --mew 1feb93 - -@smallexample -(define_insn "" - [(match_parallel 0 "load_multiple_operation" - [(set (match_operand:SI 1 "gpc_reg_operand" "=r") - (match_operand:SI 2 "memory_operand" "m")) - (use (reg:SI 179)) - (clobber (reg:SI 179))])] - "" - "loadm 0,0,%1,%2") -@end smallexample - -This example comes from @file{a29k.md}. The function -@code{load_multiple_operations} is defined in @file{a29k.c} and checks -that subsequent elements in the @code{parallel} are the same as the -@code{set} in the pattern, except that they are referencing subsequent -registers and memory locations. - -An insn that matches this pattern might look like: - -@smallexample -(parallel - [(set (reg:SI 20) (mem:SI (reg:SI 100))) - (use (reg:SI 179)) - (clobber (reg:SI 179)) - (set (reg:SI 21) - (mem:SI (plus:SI (reg:SI 100) - (const_int 4)))) - (set (reg:SI 22) - (mem:SI (plus:SI (reg:SI 100) - (const_int 8))))]) -@end smallexample - -@findex match_par_dup -@item (match_par_dup @var{n} [@var{subpat}@dots{}]) -Like @code{match_op_dup}, but for @code{match_parallel} instead of -@code{match_operator}. - -@findex match_insn -@item (match_insn @var{predicate}) -Match a complete insn. Unlike the other @code{match_*} recognizers, -@code{match_insn} does not take an operand number. - -The machine mode @var{m} of @code{match_insn} works like that of -@code{match_operand}: it is passed as the second argument to the -predicate function, and that function is solely responsible for -deciding whether the expression to be matched ``has'' that mode. - -@findex match_insn2 -@item (match_insn2 @var{n} @var{predicate}) -Match a complete insn. - -The machine mode @var{m} of @code{match_insn2} works like that of -@code{match_operand}: it is passed as the second argument to the -predicate function, and that function is solely responsible for -deciding whether the expression to be matched ``has'' that mode. - -@end table - -@node Output Template -@section Output Templates and Operand Substitution -@cindex output templates -@cindex operand substitution - -@cindex @samp{%} in template -@cindex percent sign -The @dfn{output template} is a string which specifies how to output the -assembler code for an instruction pattern. Most of the template is a -fixed string which is output literally. The character @samp{%} is used -to specify where to substitute an operand; it can also be used to -identify places where different variants of the assembler require -different syntax. - -In the simplest case, a @samp{%} followed by a digit @var{n} says to output -operand @var{n} at that point in the string. - -@samp{%} followed by a letter and a digit says to output an operand in an -alternate fashion. Four letters have standard, built-in meanings described -below. The machine description macro @code{PRINT_OPERAND} can define -additional letters with nonstandard meanings. - -@samp{%c@var{digit}} can be used to substitute an operand that is a -constant value without the syntax that normally indicates an immediate -operand. - -@samp{%n@var{digit}} is like @samp{%c@var{digit}} except that the value of -the constant is negated before printing. - -@samp{%a@var{digit}} can be used to substitute an operand as if it were a -memory reference, with the actual operand treated as the address. This may -be useful when outputting a ``load address'' instruction, because often the -assembler syntax for such an instruction requires you to write the operand -as if it were a memory reference. - -@samp{%l@var{digit}} is used to substitute a @code{label_ref} into a jump -instruction. - -@samp{%=} outputs a number which is unique to each instruction in the -entire compilation. This is useful for making local labels to be -referred to more than once in a single template that generates multiple -assembler instructions. - -@samp{%} followed by a punctuation character specifies a substitution that -does not use an operand. Only one case is standard: @samp{%%} outputs a -@samp{%} into the assembler code. Other nonstandard cases can be -defined in the @code{PRINT_OPERAND} macro. You must also define -which punctuation characters are valid with the -@code{PRINT_OPERAND_PUNCT_VALID_P} macro. - -@cindex \ -@cindex backslash -The template may generate multiple assembler instructions. Write the text -for the instructions, with @samp{\;} between them. - -@cindex matching operands -When the RTL contains two operands which are required by constraint to match -each other, the output template must refer only to the lower-numbered operand. -Matching operands are not always identical, and the rest of the compiler -arranges to put the proper RTL expression for printing into the lower-numbered -operand. - -One use of nonstandard letters or punctuation following @samp{%} is to -distinguish between different assembler languages for the same machine; for -example, Motorola syntax versus MIT syntax for the 68000. Motorola syntax -requires periods in most opcode names, while MIT syntax does not. For -example, the opcode @samp{movel} in MIT syntax is @samp{move.l} in Motorola -syntax. The same file of patterns is used for both kinds of output syntax, -but the character sequence @samp{%.} is used in each place where Motorola -syntax wants a period. The @code{PRINT_OPERAND} macro for Motorola syntax -defines the sequence to output a period; the macro for MIT syntax defines -it to do nothing. - -@cindex @code{#} in template -As a special case, a template consisting of the single character @code{#} -instructs the compiler to first split the insn, and then output the -resulting instructions separately. This helps eliminate redundancy in the -output templates. If you have a @code{define_insn} that needs to emit -multiple assembler instructions, and there is an matching @code{define_split} -already defined, then you can simply use @code{#} as the output template -instead of writing an output template that emits the multiple assembler -instructions. - -If the macro @code{ASSEMBLER_DIALECT} is defined, you can use construct -of the form @samp{@{option0|option1|option2@}} in the templates. These -describe multiple variants of assembler language syntax. -@xref{Instruction Output}. - -@node Output Statement -@section C Statements for Assembler Output -@cindex output statements -@cindex C statements for assembler output -@cindex generating assembler output - -Often a single fixed template string cannot produce correct and efficient -assembler code for all the cases that are recognized by a single -instruction pattern. For example, the opcodes may depend on the kinds of -operands; or some unfortunate combinations of operands may require extra -machine instructions. - -If the output control string starts with a @samp{@@}, then it is actually -a series of templates, each on a separate line. (Blank lines and -leading spaces and tabs are ignored.) The templates correspond to the -pattern's constraint alternatives (@pxref{Multi-Alternative}). For example, -if a target machine has a two-address add instruction @samp{addr} to add -into a register and another @samp{addm} to add a register to memory, you -might write this pattern: - -@smallexample -(define_insn "addsi3" - [(set (match_operand:SI 0 "general_operand" "=r,m") - (plus:SI (match_operand:SI 1 "general_operand" "0,0") - (match_operand:SI 2 "general_operand" "g,r")))] - "" - "@@ - addr %2,%0 - addm %2,%0") -@end smallexample - -@cindex @code{*} in template -@cindex asterisk in template -If the output control string starts with a @samp{*}, then it is not an -output template but rather a piece of C program that should compute a -template. It should execute a @code{return} statement to return the -template-string you want. Most such templates use C string literals, which -require doublequote characters to delimit them. To include these -doublequote characters in the string, prefix each one with @samp{\}. - -The operands may be found in the array @code{operands}, whose C data type -is @code{rtx []}. - -It is very common to select different ways of generating assembler code -based on whether an immediate operand is within a certain range. Be -careful when doing this, because the result of @code{INTVAL} is an -integer on the host machine. If the host machine has more bits in an -@code{int} than the target machine has in the mode in which the constant -will be used, then some of the bits you get from @code{INTVAL} will be -superfluous. For proper results, you must carefully disregard the -values of those bits. - -@findex output_asm_insn -It is possible to output an assembler instruction and then go on to output -or compute more of them, using the subroutine @code{output_asm_insn}. This -receives two arguments: a template-string and a vector of operands. The -vector may be @code{operands}, or it may be another array of @code{rtx} -that you declare locally and initialize yourself. - -@findex which_alternative -When an insn pattern has multiple alternatives in its constraints, often -the appearance of the assembler code is determined mostly by which alternative -was matched. When this is so, the C code can test the variable -@code{which_alternative}, which is the ordinal number of the alternative -that was actually satisfied (0 for the first, 1 for the second alternative, -etc.). - -For example, suppose there are two opcodes for storing zero, @samp{clrreg} -for registers and @samp{clrmem} for memory locations. Here is how -a pattern could use @code{which_alternative} to choose between them: - -@smallexample -(define_insn "" - [(set (match_operand:SI 0 "general_operand" "=r,m") - (const_int 0))] - "" - "* - return (which_alternative == 0 - ? \"clrreg %0\" : \"clrmem %0\"); - ") -@end smallexample - -The example above, where the assembler code to generate was -@emph{solely} determined by the alternative, could also have been specified -as follows, having the output control string start with a @samp{@@}: - -@smallexample -@group -(define_insn "" - [(set (match_operand:SI 0 "general_operand" "=r,m") - (const_int 0))] - "" - "@@ - clrreg %0 - clrmem %0") -@end group -@end smallexample -@end ifset - -@c Most of this node appears by itself (in a different place) even -@c when the INTERNALS flag is clear. Passages that require the full -@c manual's context are conditionalized to appear only in the full manual. -@ifset INTERNALS -@node Constraints -@section Operand Constraints -@cindex operand constraints -@cindex constraints - -Each @code{match_operand} in an instruction pattern can specify a -constraint for the type of operands allowed. -@end ifset -@ifclear INTERNALS -@node Constraints -@section Constraints for @code{asm} Operands -@cindex operand constraints, @code{asm} -@cindex constraints, @code{asm} -@cindex @code{asm} constraints - -Here are specific details on what constraint letters you can use with -@code{asm} operands. -@end ifclear -Constraints can say whether -an operand may be in a register, and which kinds of register; whether the -operand can be a memory reference, and which kinds of address; whether the -operand may be an immediate constant, and which possible values it may -have. Constraints can also require two operands to match. - -@ifset INTERNALS -@menu -* Simple Constraints:: Basic use of constraints. -* Multi-Alternative:: When an insn has two alternative constraint-patterns. -* Class Preferences:: Constraints guide which hard register to put things in. -* Modifiers:: More precise control over effects of constraints. -* Machine Constraints:: Existing constraints for some particular machines. -@end menu -@end ifset - -@ifclear INTERNALS -@menu -* Simple Constraints:: Basic use of constraints. -* Multi-Alternative:: When an insn has two alternative constraint-patterns. -* Modifiers:: More precise control over effects of constraints. -* Machine Constraints:: Special constraints for some particular machines. -@end menu -@end ifclear - -@node Simple Constraints -@subsection Simple Constraints -@cindex simple constraints - -The simplest kind of constraint is a string full of letters, each of -which describes one kind of operand that is permitted. Here are -the letters that are allowed: - -@table @asis -@item whitespace -Whitespace characters are ignored and can be inserted at any position -except the first. This enables each alternative for different operands to -be visually aligned in the machine description even if they have different -number of constraints and modifiers. - -@cindex @samp{m} in constraint -@cindex memory references in constraints -@item @samp{m} -A memory operand is allowed, with any kind of address that the machine -supports in general. - -@cindex offsettable address -@cindex @samp{o} in constraint -@item @samp{o} -A memory operand is allowed, but only if the address is -@dfn{offsettable}. This means that adding a small integer (actually, -the width in bytes of the operand, as determined by its machine mode) -may be added to the address and the result is also a valid memory -address. - -@cindex autoincrement/decrement addressing -For example, an address which is constant is offsettable; so is an -address that is the sum of a register and a constant (as long as a -slightly larger constant is also within the range of address-offsets -supported by the machine); but an autoincrement or autodecrement -address is not offsettable. More complicated indirect/indexed -addresses may or may not be offsettable depending on the other -addressing modes that the machine supports. - -Note that in an output operand which can be matched by another -operand, the constraint letter @samp{o} is valid only when accompanied -by both @samp{<} (if the target machine has predecrement addressing) -and @samp{>} (if the target machine has preincrement addressing). - -@cindex @samp{V} in constraint -@item @samp{V} -A memory operand that is not offsettable. In other words, anything that -would fit the @samp{m} constraint but not the @samp{o} constraint. - -@cindex @samp{<} in constraint -@item @samp{<} -A memory operand with autodecrement addressing (either predecrement or -postdecrement) is allowed. - -@cindex @samp{>} in constraint -@item @samp{>} -A memory operand with autoincrement addressing (either preincrement or -postincrement) is allowed. - -@cindex @samp{r} in constraint -@cindex registers in constraints -@item @samp{r} -A register operand is allowed provided that it is in a general -register. - -@cindex constants in constraints -@cindex @samp{i} in constraint -@item @samp{i} -An immediate integer operand (one with constant value) is allowed. -This includes symbolic constants whose values will be known only at -assembly time. - -@cindex @samp{n} in constraint -@item @samp{n} -An immediate integer operand with a known numeric value is allowed. -Many systems cannot support assembly-time constants for operands less -than a word wide. Constraints for these operands should use @samp{n} -rather than @samp{i}. - -@cindex @samp{I} in constraint -@item @samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P} -Other letters in the range @samp{I} through @samp{P} may be defined in -a machine-dependent fashion to permit immediate integer operands with -explicit integer values in specified ranges. For example, on the -68000, @samp{I} is defined to stand for the range of values 1 to 8. -This is the range permitted as a shift count in the shift -instructions. - -@cindex @samp{E} in constraint -@item @samp{E} -An immediate floating operand (expression code @code{const_double}) is -allowed, but only if the target floating point format is the same as -that of the host machine (on which the compiler is running). - -@cindex @samp{F} in constraint -@item @samp{F} -An immediate floating operand (expression code @code{const_double}) is -allowed. - -@cindex @samp{G} in constraint -@cindex @samp{H} in constraint -@item @samp{G}, @samp{H} -@samp{G} and @samp{H} may be defined in a machine-dependent fashion to -permit immediate floating operands in particular ranges of values. - -@cindex @samp{s} in constraint -@item @samp{s} -An immediate integer operand whose value is not an explicit integer is -allowed. - -This might appear strange; if an insn allows a constant operand with a -value not known at compile time, it certainly must allow any known -value. So why use @samp{s} instead of @samp{i}? Sometimes it allows -better code to be generated. - -For example, on the 68000 in a fullword instruction it is possible to -use an immediate operand; but if the immediate value is between -128 -and 127, better code results from loading the value into a register and -using the register. This is because the load into the register can be -done with a @samp{moveq} instruction. We arrange for this to happen -by defining the letter @samp{K} to mean ``any integer outside the -range -128 to 127'', and then specifying @samp{Ks} in the operand -constraints. - -@cindex @samp{g} in constraint -@item @samp{g} -Any register, memory or immediate integer operand is allowed, except for -registers that are not general registers. - -@cindex @samp{X} in constraint -@item @samp{X} -@ifset INTERNALS -Any operand whatsoever is allowed, even if it does not satisfy -@code{general_operand}. This is normally used in the constraint of -a @code{match_scratch} when certain alternatives will not actually -require a scratch register. -@end ifset -@ifclear INTERNALS -Any operand whatsoever is allowed. -@end ifclear - -@cindex @samp{0} in constraint -@cindex digits in constraint -@item @samp{0}, @samp{1}, @samp{2}, @dots{} @samp{9} -An operand that matches the specified operand number is allowed. If a -digit is used together with letters within the same alternative, the -digit should come last. - -@cindex matching constraint -@cindex constraint, matching -This is called a @dfn{matching constraint} and what it really means is -that the assembler has only a single operand that fills two roles -@ifset INTERNALS -considered separate in the RTL insn. For example, an add insn has two -input operands and one output operand in the RTL, but on most CISC -@end ifset -@ifclear INTERNALS -which @code{asm} distinguishes. For example, an add instruction uses -two input operands and an output operand, but on most CISC -@end ifclear -machines an add instruction really has only two operands, one of them an -input-output operand: - -@smallexample -addl #35,r12 -@end smallexample - -Matching constraints are used in these circumstances. -More precisely, the two operands that match must include one input-only -operand and one output-only operand. Moreover, the digit must be a -smaller number than the number of the operand that uses it in the -constraint. - -@ifset INTERNALS -For operands to match in a particular case usually means that they -are identical-looking RTL expressions. But in a few special cases -specific kinds of dissimilarity are allowed. For example, @code{*x} -as an input operand will match @code{*x++} as an output operand. -For proper results in such cases, the output template should always -use the output-operand's number when printing the operand. -@end ifset - -@cindex load address instruction -@cindex push address instruction -@cindex address constraints -@cindex @samp{p} in constraint -@item @samp{p} -An operand that is a valid memory address is allowed. This is -for ``load address'' and ``push address'' instructions. - -@findex address_operand -@samp{p} in the constraint must be accompanied by @code{address_operand} -as the predicate in the @code{match_operand}. This predicate interprets -the mode specified in the @code{match_operand} as the mode of the memory -reference for which the address would be valid. - -@cindex other register constraints -@cindex extensible constraints -@item @var{other letters} -Other letters can be defined in machine-dependent fashion to stand for -particular classes of registers or other arbitrary operand types. -@samp{d}, @samp{a} and @samp{f} are defined on the 68000/68020 to stand -for data, address and floating point registers. - -@ifset INTERNALS -The machine description macro @code{REG_CLASS_FROM_LETTER} has first -cut at the otherwise unused letters. If it evaluates to @code{NO_REGS}, -then @code{EXTRA_CONSTRAINT} is evaluated. - -A typical use for @code{EXTRA_CONSTRANT} would be to distinguish certain -types of memory references that affect other insn operands. -@end ifset -@end table - -@ifset INTERNALS -In order to have valid assembler code, each operand must satisfy -its constraint. But a failure to do so does not prevent the pattern -from applying to an insn. Instead, it directs the compiler to modify -the code so that the constraint will be satisfied. Usually this is -done by copying an operand into a register. - -Contrast, therefore, the two instruction patterns that follow: - -@smallexample -(define_insn "" - [(set (match_operand:SI 0 "general_operand" "=r") - (plus:SI (match_dup 0) - (match_operand:SI 1 "general_operand" "r")))] - "" - "@dots{}") -@end smallexample - -@noindent -which has two operands, one of which must appear in two places, and - -@smallexample -(define_insn "" - [(set (match_operand:SI 0 "general_operand" "=r") - (plus:SI (match_operand:SI 1 "general_operand" "0") - (match_operand:SI 2 "general_operand" "r")))] - "" - "@dots{}") -@end smallexample - -@noindent -which has three operands, two of which are required by a constraint to be -identical. If we are considering an insn of the form - -@smallexample -(insn @var{n} @var{prev} @var{next} - (set (reg:SI 3) - (plus:SI (reg:SI 6) (reg:SI 109))) - @dots{}) -@end smallexample - -@noindent -the first pattern would not apply at all, because this insn does not -contain two identical subexpressions in the right place. The pattern would -say, ``That does not look like an add instruction; try other patterns.'' -The second pattern would say, ``Yes, that's an add instruction, but there -is something wrong with it.'' It would direct the reload pass of the -compiler to generate additional insns to make the constraint true. The -results might look like this: - -@smallexample -(insn @var{n2} @var{prev} @var{n} - (set (reg:SI 3) (reg:SI 6)) - @dots{}) - -(insn @var{n} @var{n2} @var{next} - (set (reg:SI 3) - (plus:SI (reg:SI 3) (reg:SI 109))) - @dots{}) -@end smallexample - -It is up to you to make sure that each operand, in each pattern, has -constraints that can handle any RTL expression that could be present for -that operand. (When multiple alternatives are in use, each pattern must, -for each possible combination of operand expressions, have at least one -alternative which can handle that combination of operands.) The -constraints don't need to @emph{allow} any possible operand---when this is -the case, they do not constrain---but they must at least point the way to -reloading any possible operand so that it will fit. - -@itemize @bullet -@item -If the constraint accepts whatever operands the predicate permits, -there is no problem: reloading is never necessary for this operand. - -For example, an operand whose constraints permit everything except -registers is safe provided its predicate rejects registers. - -An operand whose predicate accepts only constant values is safe -provided its constraints include the letter @samp{i}. If any possible -constant value is accepted, then nothing less than @samp{i} will do; -if the predicate is more selective, then the constraints may also be -more selective. - -@item -Any operand expression can be reloaded by copying it into a register. -So if an operand's constraints allow some kind of register, it is -certain to be safe. It need not permit all classes of registers; the -compiler knows how to copy a register into another register of the -proper class in order to make an instruction valid. - -@cindex nonoffsettable memory reference -@cindex memory reference, nonoffsettable -@item -A nonoffsettable memory reference can be reloaded by copying the -address into a register. So if the constraint uses the letter -@samp{o}, all memory references are taken care of. - -@item -A constant operand can be reloaded by allocating space in memory to -hold it as preinitialized data. Then the memory reference can be used -in place of the constant. So if the constraint uses the letters -@samp{o} or @samp{m}, constant operands are not a problem. - -@item -If the constraint permits a constant and a pseudo register used in an insn -was not allocated to a hard register and is equivalent to a constant, -the register will be replaced with the constant. If the predicate does -not permit a constant and the insn is re-recognized for some reason, the -compiler will crash. Thus the predicate must always recognize any -objects allowed by the constraint. -@end itemize - -If the operand's predicate can recognize registers, but the constraint does -not permit them, it can make the compiler crash. When this operand happens -to be a register, the reload pass will be stymied, because it does not know -how to copy a register temporarily into memory. - -If the predicate accepts a unary operator, the constraint applies to the -operand. For example, the MIPS processor at ISA level 3 supports an -instruction which adds two registers in @code{SImode} to produce a -@code{DImode} result, but only if the registers are correctly sign -extended. This predicate for the input operands accepts a -@code{sign_extend} of an @code{SImode} register. Write the constraint -to indicate the type of register that is required for the operand of the -@code{sign_extend}. -@end ifset - -@node Multi-Alternative -@subsection Multiple Alternative Constraints -@cindex multiple alternative constraints - -Sometimes a single instruction has multiple alternative sets of possible -operands. For example, on the 68000, a logical-or instruction can combine -register or an immediate value into memory, or it can combine any kind of -operand into a register; but it cannot combine one memory location into -another. - -These constraints are represented as multiple alternatives. An alternative -can be described by a series of letters for each operand. The overall -constraint for an operand is made from the letters for this operand -from the first alternative, a comma, the letters for this operand from -the second alternative, a comma, and so on until the last alternative. -@ifset INTERNALS -Here is how it is done for fullword logical-or on the 68000: - -@smallexample -(define_insn "iorsi3" - [(set (match_operand:SI 0 "general_operand" "=m,d") - (ior:SI (match_operand:SI 1 "general_operand" "%0,0") - (match_operand:SI 2 "general_operand" "dKs,dmKs")))] - @dots{}) -@end smallexample - -The first alternative has @samp{m} (memory) for operand 0, @samp{0} for -operand 1 (meaning it must match operand 0), and @samp{dKs} for operand -2. The second alternative has @samp{d} (data register) for operand 0, -@samp{0} for operand 1, and @samp{dmKs} for operand 2. The @samp{=} and -@samp{%} in the constraints apply to all the alternatives; their -meaning is explained in the next section (@pxref{Class Preferences}). -@end ifset - -@c FIXME Is this ? and ! stuff of use in asm()? If not, hide unless INTERNAL -If all the operands fit any one alternative, the instruction is valid. -Otherwise, for each alternative, the compiler counts how many instructions -must be added to copy the operands so that that alternative applies. -The alternative requiring the least copying is chosen. If two alternatives -need the same amount of copying, the one that comes first is chosen. -These choices can be altered with the @samp{?} and @samp{!} characters: - -@table @code -@cindex @samp{?} in constraint -@cindex question mark -@item ? -Disparage slightly the alternative that the @samp{?} appears in, -as a choice when no alternative applies exactly. The compiler regards -this alternative as one unit more costly for each @samp{?} that appears -in it. - -@cindex @samp{!} in constraint -@cindex exclamation point -@item ! -Disparage severely the alternative that the @samp{!} appears in. -This alternative can still be used if it fits without reloading, -but if reloading is needed, some other alternative will be used. -@end table - -@ifset INTERNALS -When an insn pattern has multiple alternatives in its constraints, often -the appearance of the assembler code is determined mostly by which -alternative was matched. When this is so, the C code for writing the -assembler code can use the variable @code{which_alternative}, which is -the ordinal number of the alternative that was actually satisfied (0 for -the first, 1 for the second alternative, etc.). @xref{Output Statement}. -@end ifset - -@ifset INTERNALS -@node Class Preferences -@subsection Register Class Preferences -@cindex class preference constraints -@cindex register class preference constraints - -@cindex voting between constraint alternatives -The operand constraints have another function: they enable the compiler -to decide which kind of hardware register a pseudo register is best -allocated to. The compiler examines the constraints that apply to the -insns that use the pseudo register, looking for the machine-dependent -letters such as @samp{d} and @samp{a} that specify classes of registers. -The pseudo register is put in whichever class gets the most ``votes''. -The constraint letters @samp{g} and @samp{r} also vote: they vote in -favor of a general register. The machine description says which registers -are considered general. - -Of course, on some machines all registers are equivalent, and no register -classes are defined. Then none of this complexity is relevant. -@end ifset - -@node Modifiers -@subsection Constraint Modifier Characters -@cindex modifiers in constraints -@cindex constraint modifier characters - -@c prevent bad page break with this line -Here are constraint modifier characters. - -@table @samp -@cindex @samp{=} in constraint -@item = -Means that this operand is write-only for this instruction: the previous -value is discarded and replaced by output data. - -@cindex @samp{+} in constraint -@item + -Means that this operand is both read and written by the instruction. - -When the compiler fixes up the operands to satisfy the constraints, -it needs to know which operands are inputs to the instruction and -which are outputs from it. @samp{=} identifies an output; @samp{+} -identifies an operand that is both input and output; all other operands -are assumed to be input only. - -If you specify @samp{=} or @samp{+} in a constraint, you put it in the -first character of the constraint string. - -@cindex @samp{&} in constraint -@cindex earlyclobber operand -@item & -Means (in a particular alternative) that this operand is an -@dfn{earlyclobber} operand, which is modified before the instruction is -finished using the input operands. Therefore, this operand may not lie -in a register that is used as an input operand or as part of any memory -address. - -@samp{&} applies only to the alternative in which it is written. In -constraints with multiple alternatives, sometimes one alternative -requires @samp{&} while others do not. See, for example, the -@samp{movdf} insn of the 68000. - -An input operand can be tied to an earlyclobber operand if its only -use as an input occurs before the early result is written. Adding -alternatives of this form often allows GCC to produce better code -when only some of the inputs can be affected by the earlyclobber. -See, for example, the @samp{mulsi3} insn of the ARM. - -@samp{&} does not obviate the need to write @samp{=}. - -@cindex @samp{%} in constraint -@item % -Declares the instruction to be commutative for this operand and the -following operand. This means that the compiler may interchange the -two operands if that is the cheapest way to make all operands fit the -constraints. -@ifset INTERNALS -This is often used in patterns for addition instructions -that really have only two operands: the result must go in one of the -arguments. Here for example, is how the 68000 halfword-add -instruction is defined: - -@smallexample -(define_insn "addhi3" - [(set (match_operand:HI 0 "general_operand" "=m,r") - (plus:HI (match_operand:HI 1 "general_operand" "%0,0") - (match_operand:HI 2 "general_operand" "di,g")))] - @dots{}) -@end smallexample -@end ifset - -@cindex @samp{#} in constraint -@item # -Says that all following characters, up to the next comma, are to be -ignored as a constraint. They are significant only for choosing -register preferences. - -@ifset INTERNALS -@cindex @samp{*} in constraint -@item * -Says that the following character should be ignored when choosing -register preferences. @samp{*} has no effect on the meaning of the -constraint as a constraint, and no effect on reloading. - -Here is an example: the 68000 has an instruction to sign-extend a -halfword in a data register, and can also sign-extend a value by -copying it into an address register. While either kind of register is -acceptable, the constraints on an address-register destination are -less strict, so it is best if register allocation makes an address -register its goal. Therefore, @samp{*} is used so that the @samp{d} -constraint letter (for data register) is ignored when computing -register preferences. - -@smallexample -(define_insn "extendhisi2" - [(set (match_operand:SI 0 "general_operand" "=*d,a") - (sign_extend:SI - (match_operand:HI 1 "general_operand" "0,g")))] - @dots{}) -@end smallexample -@end ifset -@end table - -@node Machine Constraints -@subsection Constraints for Particular Machines -@cindex machine specific constraints -@cindex constraints, machine specific - -Whenever possible, you should use the general-purpose constraint letters -in @code{asm} arguments, since they will convey meaning more readily to -people reading your code. Failing that, use the constraint letters -that usually have very similar meanings across architectures. The most -commonly used constraints are @samp{m} and @samp{r} (for memory and -general-purpose registers respectively; @pxref{Simple Constraints}), and -@samp{I}, usually the letter indicating the most common -immediate-constant format. - -For each machine architecture, the @file{config/@var{machine}.h} file -defines additional constraints. These constraints are used by the -compiler itself for instruction generation, as well as for @code{asm} -statements; therefore, some of the constraints are not particularly -interesting for @code{asm}. The constraints are defined through these -macros: - -@table @code -@item REG_CLASS_FROM_LETTER -Register class constraints (usually lower case). - -@item CONST_OK_FOR_LETTER_P -Immediate constant constraints, for non-floating point constants of -word size or smaller precision (usually upper case). - -@item CONST_DOUBLE_OK_FOR_LETTER_P -Immediate constant constraints, for all floating point constants and for -constants of greater than word size precision (usually upper case). - -@item EXTRA_CONSTRAINT -Special cases of registers or memory. This macro is not required, and -is only defined for some machines. -@end table - -Inspecting these macro definitions in the compiler source for your -machine is the best way to be certain you have the right constraints. -However, here is a summary of the machine-dependent constraints -available on some particular machines. - -@table @emph -@item ARM family---@file{arm.h} -@table @code -@item f -Floating-point register - -@item F -One of the floating-point constants 0.0, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 -or 10.0 - -@item G -Floating-point constant that would satisfy the constraint @samp{F} if it -were negated - -@item I -Integer that is valid as an immediate operand in a data processing -instruction. That is, an integer in the range 0 to 255 rotated by a -multiple of 2 - -@item J -Integer in the range -4095 to 4095 - -@item K -Integer that satisfies constraint @samp{I} when inverted (ones complement) - -@item L -Integer that satisfies constraint @samp{I} when negated (twos complement) - -@item M -Integer in the range 0 to 32 - -@item Q -A memory reference where the exact address is in a single register -(`@samp{m}' is preferable for @code{asm} statements) - -@item R -An item in the constant pool - -@item S -A symbol in the text segment of the current file -@end table - -@item AMD 29000 family---@file{a29k.h} -@table @code -@item l -Local register 0 - -@item b -Byte Pointer (@samp{BP}) register - -@item q -@samp{Q} register - -@item h -Special purpose register - -@item A -First accumulator register - -@item a -Other accumulator register - -@item f -Floating point register - -@item I -Constant greater than 0, less than 0x100 - -@item J -Constant greater than 0, less than 0x10000 - -@item K -Constant whose high 24 bits are on (1) - -@item L -16-bit constant whose high 8 bits are on (1) - -@item M -32-bit constant whose high 16 bits are on (1) - -@item N -32-bit negative constant that fits in 8 bits - -@item O -The constant 0x80000000 or, on the 29050, any 32-bit constant -whose low 16 bits are 0. - -@item P -16-bit negative constant that fits in 8 bits - -@item G -@itemx H -A floating point constant (in @code{asm} statements, use the machine -independent @samp{E} or @samp{F} instead) -@end table - -@item AVR family---@file{avr.h} -@table @code -@item l -Registers from r0 to r15 - -@item a -Registers from r16 to r23 - -@item d -Registers from r16 to r31 - -@item w -Registers from r24 to r31. These registers can be used in @samp{adiw} command - -@item e -Pointer register (r26 - r31) - -@item b -Base pointer register (r28 - r31) - -@item q -Stack pointer register (SPH:SPL) - -@item t -Temporary register r0 - -@item x -Register pair X (r27:r26) - -@item y -Register pair Y (r29:r28) - -@item z -Register pair Z (r31:r30) - -@item I -Constant greater than -1, less than 64 - -@item J -Constant greater than -64, less than 1 - -@item K -Constant integer 2 - -@item L -Constant integer 0 - -@item M -Constant that fits in 8 bits - -@item N -Constant integer -1 - -@item O -Constant integer 8, 16, or 24 - -@item P -Constant integer 1 - -@item G -A floating point constant 0.0 -@end table - -@item IBM RS6000---@file{rs6000.h} -@table @code -@item b -Address base register - -@item f -Floating point register - -@item h -@samp{MQ}, @samp{CTR}, or @samp{LINK} register - -@item q -@samp{MQ} register - -@item c -@samp{CTR} register - -@item l -@samp{LINK} register - -@item x -@samp{CR} register (condition register) number 0 - -@item y -@samp{CR} register (condition register) - -@item z -@samp{FPMEM} stack memory for FPR-GPR transfers - -@item I -Signed 16-bit constant - -@item J -Unsigned 16-bit constant shifted left 16 bits (use @samp{L} instead for -@code{SImode} constants) - -@item K -Unsigned 16-bit constant - -@item L -Signed 16-bit constant shifted left 16 bits - -@item M -Constant larger than 31 - -@item N -Exact power of 2 - -@item O -Zero - -@item P -Constant whose negation is a signed 16-bit constant - -@item G -Floating point constant that can be loaded into a register with one -instruction per word - -@item Q -Memory operand that is an offset from a register (@samp{m} is preferable -for @code{asm} statements) - -@item R -AIX TOC entry - -@item S -Constant suitable as a 64-bit mask operand - -@item T -Constant suitable as a 32-bit mask operand - -@item U -System V Release 4 small data area reference -@end table - -@item Intel 386---@file{i386.h} -@table @code -@item q -@samp{a}, @code{b}, @code{c}, or @code{d} register for the i386. -For x86-64 it is equivalent to @samp{r} class. (for 8-bit instructions that -do not use upper halves) - -@item Q -@samp{a}, @code{b}, @code{c}, or @code{d} register. (for 8-bit instructions, -that do use upper halves) - -@item R -Legacy register --- equivalent to @code{r} class in i386 mode. -(for non-8-bit registers used together with 8-bit upper halves in a single -instruction) - -@item A -Specifies the @samp{a} or @samp{d} registers. This is primarily useful -for 64-bit integer values (when in 32-bit mode) intended to be returned -with the @samp{d} register holding the most significant bits and the -@samp{a} register holding the least significant bits. - -@item f -Floating point register - -@item t -First (top of stack) floating point register - -@item u -Second floating point register - -@item a -@samp{a} register - -@item b -@samp{b} register - -@item c -@samp{c} register - -@item d -@samp{d} register - -@item D -@samp{di} register - -@item S -@samp{si} register - -@item x -@samp{xmm} SSE register - -@item y -MMX register - -@item I -Constant in range 0 to 31 (for 32-bit shifts) - -@item J -Constant in range 0 to 63 (for 64-bit shifts) - -@item K -@samp{0xff} - -@item L -@samp{0xffff} - -@item M -0, 1, 2, or 3 (shifts for @code{lea} instruction) - -@item N -Constant in range 0 to 255 (for @code{out} instruction) - -@item Z -Constant in range 0 to 0xffffffff or symbolic reference known to fit specified range. -(for using immediates in zero extending 32-bit to 64-bit x86-64 instructions) - -@item e -Constant in range -2147483648 to 2147483647 or symbolic reference known to fit specified range. -(for using immediates in 64-bit x86-64 instructions) - -@item G -Standard 80387 floating point constant -@end table - -@item Intel 960---@file{i960.h} -@table @code -@item f -Floating point register (@code{fp0} to @code{fp3}) - -@item l -Local register (@code{r0} to @code{r15}) - -@item b -Global register (@code{g0} to @code{g15}) - -@item d -Any local or global register - -@item I -Integers from 0 to 31 - -@item J -0 - -@item K -Integers from -31 to 0 - -@item G -Floating point 0 - -@item H -Floating point 1 -@end table - -@item MIPS---@file{mips.h} -@table @code -@item d -General-purpose integer register - -@item f -Floating-point register (if available) - -@item h -@samp{Hi} register - -@item l -@samp{Lo} register - -@item x -@samp{Hi} or @samp{Lo} register - -@item y -General-purpose integer register - -@item z -Floating-point status register - -@item I -Signed 16-bit constant (for arithmetic instructions) - -@item J -Zero - -@item K -Zero-extended 16-bit constant (for logic instructions) - -@item L -Constant with low 16 bits zero (can be loaded with @code{lui}) - -@item M -32-bit constant which requires two instructions to load (a constant -which is not @samp{I}, @samp{K}, or @samp{L}) - -@item N -Negative 16-bit constant - -@item O -Exact power of two - -@item P -Positive 16-bit constant - -@item G -Floating point zero - -@item Q -Memory reference that can be loaded with more than one instruction -(@samp{m} is preferable for @code{asm} statements) - -@item R -Memory reference that can be loaded with one instruction -(@samp{m} is preferable for @code{asm} statements) - -@item S -Memory reference in external OSF/rose PIC format -(@samp{m} is preferable for @code{asm} statements) -@end table - -@item Motorola 680x0---@file{m68k.h} -@table @code -@item a -Address register - -@item d -Data register - -@item f -68881 floating-point register, if available - -@item x -Sun FPA (floating-point) register, if available - -@item y -First 16 Sun FPA registers, if available - -@item I -Integer in the range 1 to 8 - -@item J -16-bit signed number - -@item K -Signed number whose magnitude is greater than 0x80 - -@item L -Integer in the range -8 to -1 - -@item M -Signed number whose magnitude is greater than 0x100 - -@item G -Floating point constant that is not a 68881 constant - -@item H -Floating point constant that can be used by Sun FPA -@end table - -@item Motorola 68HC11 & 68HC12 families---@file{m68hc11.h} -@table @code -@item a -Register 'a' - -@item b -Register 'b' - -@item d -Register 'd' - -@item q -An 8-bit register - -@item t -Temporary soft register _.tmp - -@item u -A soft register _.d1 to _.d31 - -@item w -Stack pointer register - -@item x -Register 'x' - -@item y -Register 'y' - -@item z -Pseudo register 'z' (replaced by 'x' or 'y' at the end) - -@item A -An address register: x, y or z - -@item B -An address register: x or y - -@item D -Register pair (x:d) to form a 32-bit value - -@item L -Constants in the range -65536 to 65535 - -@item M -Constants whose 16-bit low part is zero - -@item N -Constant integer 1 or -1 - -@item O -Constant integer 16 - -@item P -Constants in the range -8 to 2 - -@end table - -@need 1000 -@item SPARC---@file{sparc.h} -@table @code -@item f -Floating-point register that can hold 32- or 64-bit values. - -@item e -Floating-point register that can hold 64- or 128-bit values. - -@item I -Signed 13-bit constant - -@item J -Zero - -@item K -32-bit constant with the low 12 bits clear (a constant that can be -loaded with the @code{sethi} instruction) - -@item G -Floating-point zero - -@item H -Signed 13-bit constant, sign-extended to 32 or 64 bits - -@item Q -Floating-point constant whose integral representation can -be moved into an integer register using a single sethi -instruction - -@item R -Floating-point constant whose integral representation can -be moved into an integer register using a single mov -instruction - -@item S -Floating-point constant whose integral representation can -be moved into an integer register using a high/lo_sum -instruction sequence - -@item T -Memory address aligned to an 8-byte boundary - -@item U -Even register - -@end table - -@item TMS320C3x/C4x---@file{c4x.h} -@table @code -@item a -Auxiliary (address) register (ar0-ar7) - -@item b -Stack pointer register (sp) - -@item c -Standard (32-bit) precision integer register - -@item f -Extended (40-bit) precision register (r0-r11) - -@item k -Block count register (bk) - -@item q -Extended (40-bit) precision low register (r0-r7) - -@item t -Extended (40-bit) precision register (r0-r1) - -@item u -Extended (40-bit) precision register (r2-r3) - -@item v -Repeat count register (rc) - -@item x -Index register (ir0-ir1) - -@item y -Status (condition code) register (st) - -@item z -Data page register (dp) - -@item G -Floating-point zero - -@item H -Immediate 16-bit floating-point constant - -@item I -Signed 16-bit constant - -@item J -Signed 8-bit constant - -@item K -Signed 5-bit constant - -@item L -Unsigned 16-bit constant - -@item M -Unsigned 8-bit constant - -@item N -Ones complement of unsigned 16-bit constant - -@item O -High 16-bit constant (32-bit constant with 16 LSBs zero) - -@item Q -Indirect memory reference with signed 8-bit or index register displacement - -@item R -Indirect memory reference with unsigned 5-bit displacement - -@item S -Indirect memory reference with 1 bit or index register displacement - -@item T -Direct memory reference - -@item U -Symbolic address - -@end table -@end table - -@ifset INTERNALS -@node Standard Names -@section Standard Pattern Names For Generation -@cindex standard pattern names -@cindex pattern names -@cindex names, pattern - -Here is a table of the instruction names that are meaningful in the RTL -generation pass of the compiler. Giving one of these names to an -instruction pattern tells the RTL generation pass that it can use the -pattern to accomplish a certain task. - -@table @asis -@cindex @code{mov@var{m}} instruction pattern -@item @samp{mov@var{m}} -Here @var{m} stands for a two-letter machine mode name, in lower case. -This instruction pattern moves data with that machine mode from operand -1 to operand 0. For example, @samp{movsi} moves full-word data. - -If operand 0 is a @code{subreg} with mode @var{m} of a register whose -own mode is wider than @var{m}, the effect of this instruction is -to store the specified value in the part of the register that corresponds -to mode @var{m}. The effect on the rest of the register is undefined. - -This class of patterns is special in several ways. First of all, each -of these names up to and including full word size @emph{must} be defined, -because there is no other way to copy a datum from one place to another. -If there are patterns accepting operands in larger modes, -@samp{mov@var{m}} must be defined for integer modes of those sizes. - -Second, these patterns are not used solely in the RTL generation pass. -Even the reload pass can generate move insns to copy values from stack -slots into temporary registers. When it does so, one of the operands is -a hard register and the other is an operand that can need to be reloaded -into a register. - -@findex force_reg -Therefore, when given such a pair of operands, the pattern must generate -RTL which needs no reloading and needs no temporary registers---no -registers other than the operands. For example, if you support the -pattern with a @code{define_expand}, then in such a case the -@code{define_expand} mustn't call @code{force_reg} or any other such -function which might generate new pseudo registers. - -This requirement exists even for subword modes on a RISC machine where -fetching those modes from memory normally requires several insns and -some temporary registers. - -@findex change_address -During reload a memory reference with an invalid address may be passed -as an operand. Such an address will be replaced with a valid address -later in the reload pass. In this case, nothing may be done with the -address except to use it as it stands. If it is copied, it will not be -replaced with a valid address. No attempt should be made to make such -an address into a valid address and no routine (such as -@code{change_address}) that will do so may be called. Note that -@code{general_operand} will fail when applied to such an address. - -@findex reload_in_progress -The global variable @code{reload_in_progress} (which must be explicitly -declared if required) can be used to determine whether such special -handling is required. - -The variety of operands that have reloads depends on the rest of the -machine description, but typically on a RISC machine these can only be -pseudo registers that did not get hard registers, while on other -machines explicit memory references will get optional reloads. - -If a scratch register is required to move an object to or from memory, -it can be allocated using @code{gen_reg_rtx} prior to life analysis. - -If there are cases needing -scratch registers after reload, you must define -@code{SECONDARY_INPUT_RELOAD_CLASS} and perhaps also -@code{SECONDARY_OUTPUT_RELOAD_CLASS} to detect them, and provide -patterns @samp{reload_in@var{m}} or @samp{reload_out@var{m}} to handle -them. @xref{Register Classes}. - -@findex no_new_pseudos -The global variable @code{no_new_pseudos} can be used to determine if it -is unsafe to create new pseudo registers. If this variable is nonzero, then -it is unsafe to call @code{gen_reg_rtx} to allocate a new pseudo. - -The constraints on a @samp{mov@var{m}} must permit moving any hard -register to any other hard register provided that -@code{HARD_REGNO_MODE_OK} permits mode @var{m} in both registers and -@code{REGISTER_MOVE_COST} applied to their classes returns a value of 2. - -It is obligatory to support floating point @samp{mov@var{m}} -instructions into and out of any registers that can hold fixed point -values, because unions and structures (which have modes @code{SImode} or -@code{DImode}) can be in those registers and they may have floating -point members. - -There may also be a need to support fixed point @samp{mov@var{m}} -instructions in and out of floating point registers. Unfortunately, I -have forgotten why this was so, and I don't know whether it is still -true. If @code{HARD_REGNO_MODE_OK} rejects fixed point values in -floating point registers, then the constraints of the fixed point -@samp{mov@var{m}} instructions must be designed to avoid ever trying to -reload into a floating point register. - -@cindex @code{reload_in} instruction pattern -@cindex @code{reload_out} instruction pattern -@item @samp{reload_in@var{m}} -@itemx @samp{reload_out@var{m}} -Like @samp{mov@var{m}}, but used when a scratch register is required to -move between operand 0 and operand 1. Operand 2 describes the scratch -register. See the discussion of the @code{SECONDARY_RELOAD_CLASS} -macro in @pxref{Register Classes}. - -@cindex @code{movstrict@var{m}} instruction pattern -@item @samp{movstrict@var{m}} -Like @samp{mov@var{m}} except that if operand 0 is a @code{subreg} -with mode @var{m} of a register whose natural mode is wider, -the @samp{movstrict@var{m}} instruction is guaranteed not to alter -any of the register except the part which belongs to mode @var{m}. - -@cindex @code{load_multiple} instruction pattern -@item @samp{load_multiple} -Load several consecutive memory locations into consecutive registers. -Operand 0 is the first of the consecutive registers, operand 1 -is the first memory location, and operand 2 is a constant: the -number of consecutive registers. - -Define this only if the target machine really has such an instruction; -do not define this if the most efficient way of loading consecutive -registers from memory is to do them one at a time. - -On some machines, there are restrictions as to which consecutive -registers can be stored into memory, such as particular starting or -ending register numbers or only a range of valid counts. For those -machines, use a @code{define_expand} (@pxref{Expander Definitions}) -and make the pattern fail if the restrictions are not met. - -Write the generated insn as a @code{parallel} with elements being a -@code{set} of one register from the appropriate memory location (you may -also need @code{use} or @code{clobber} elements). Use a -@code{match_parallel} (@pxref{RTL Template}) to recognize the insn. See -@file{a29k.md} and @file{rs6000.md} for examples of the use of this insn -pattern. - -@cindex @samp{store_multiple} instruction pattern -@item @samp{store_multiple} -Similar to @samp{load_multiple}, but store several consecutive registers -into consecutive memory locations. Operand 0 is the first of the -consecutive memory locations, operand 1 is the first register, and -operand 2 is a constant: the number of consecutive registers. - -@cindex @code{add@var{m}3} instruction pattern -@item @samp{add@var{m}3} -Add operand 2 and operand 1, storing the result in operand 0. All operands -must have mode @var{m}. This can be used even on two-address machines, by -means of constraints requiring operands 1 and 0 to be the same location. - -@cindex @code{sub@var{m}3} instruction pattern -@cindex @code{mul@var{m}3} instruction pattern -@cindex @code{div@var{m}3} instruction pattern -@cindex @code{udiv@var{m}3} instruction pattern -@cindex @code{mod@var{m}3} instruction pattern -@cindex @code{umod@var{m}3} instruction pattern -@cindex @code{smin@var{m}3} instruction pattern -@cindex @code{smax@var{m}3} instruction pattern -@cindex @code{umin@var{m}3} instruction pattern -@cindex @code{umax@var{m}3} instruction pattern -@cindex @code{and@var{m}3} instruction pattern -@cindex @code{ior@var{m}3} instruction pattern -@cindex @code{xor@var{m}3} instruction pattern -@item @samp{sub@var{m}3}, @samp{mul@var{m}3} -@itemx @samp{div@var{m}3}, @samp{udiv@var{m}3}, @samp{mod@var{m}3}, @samp{umod@var{m}3} -@itemx @samp{smin@var{m}3}, @samp{smax@var{m}3}, @samp{umin@var{m}3}, @samp{umax@var{m}3} -@itemx @samp{and@var{m}3}, @samp{ior@var{m}3}, @samp{xor@var{m}3} -Similar, for other arithmetic operations. -@cindex @code{min@var{m}3} instruction pattern -@cindex @code{max@var{m}3} instruction pattern -@itemx @samp{min@var{m}3}, @samp{max@var{m}3} -Floating point min and max operations. If both operands are zeros, -or if either operand is NaN, then it is unspecified which of the two -operands is returned as the result. - - -@cindex @code{mulhisi3} instruction pattern -@item @samp{mulhisi3} -Multiply operands 1 and 2, which have mode @code{HImode}, and store -a @code{SImode} product in operand 0. - -@cindex @code{mulqihi3} instruction pattern -@cindex @code{mulsidi3} instruction pattern -@item @samp{mulqihi3}, @samp{mulsidi3} -Similar widening-multiplication instructions of other widths. - -@cindex @code{umulqihi3} instruction pattern -@cindex @code{umulhisi3} instruction pattern -@cindex @code{umulsidi3} instruction pattern -@item @samp{umulqihi3}, @samp{umulhisi3}, @samp{umulsidi3} -Similar widening-multiplication instructions that do unsigned -multiplication. - -@cindex @code{smul@var{m}3_highpart} instruction pattern -@item @samp{smul@var{m}3_highpart} -Perform a signed multiplication of operands 1 and 2, which have mode -@var{m}, and store the most significant half of the product in operand 0. -The least significant half of the product is discarded. - -@cindex @code{umul@var{m}3_highpart} instruction pattern -@item @samp{umul@var{m}3_highpart} -Similar, but the multiplication is unsigned. - -@cindex @code{divmod@var{m}4} instruction pattern -@item @samp{divmod@var{m}4} -Signed division that produces both a quotient and a remainder. -Operand 1 is divided by operand 2 to produce a quotient stored -in operand 0 and a remainder stored in operand 3. - -For machines with an instruction that produces both a quotient and a -remainder, provide a pattern for @samp{divmod@var{m}4} but do not -provide patterns for @samp{div@var{m}3} and @samp{mod@var{m}3}. This -allows optimization in the relatively common case when both the quotient -and remainder are computed. - -If an instruction that just produces a quotient or just a remainder -exists and is more efficient than the instruction that produces both, -write the output routine of @samp{divmod@var{m}4} to call -@code{find_reg_note} and look for a @code{REG_UNUSED} note on the -quotient or remainder and generate the appropriate instruction. - -@cindex @code{udivmod@var{m}4} instruction pattern -@item @samp{udivmod@var{m}4} -Similar, but does unsigned division. - -@cindex @code{ashl@var{m}3} instruction pattern -@item @samp{ashl@var{m}3} -Arithmetic-shift operand 1 left by a number of bits specified by operand -2, and store the result in operand 0. Here @var{m} is the mode of -operand 0 and operand 1; operand 2's mode is specified by the -instruction pattern, and the compiler will convert the operand to that -mode before generating the instruction. - -@cindex @code{ashr@var{m}3} instruction pattern -@cindex @code{lshr@var{m}3} instruction pattern -@cindex @code{rotl@var{m}3} instruction pattern -@cindex @code{rotr@var{m}3} instruction pattern -@item @samp{ashr@var{m}3}, @samp{lshr@var{m}3}, @samp{rotl@var{m}3}, @samp{rotr@var{m}3} -Other shift and rotate instructions, analogous to the -@code{ashl@var{m}3} instructions. - -@cindex @code{neg@var{m}2} instruction pattern -@item @samp{neg@var{m}2} -Negate operand 1 and store the result in operand 0. - -@cindex @code{abs@var{m}2} instruction pattern -@item @samp{abs@var{m}2} -Store the absolute value of operand 1 into operand 0. - -@cindex @code{sqrt@var{m}2} instruction pattern -@item @samp{sqrt@var{m}2} -Store the square root of operand 1 into operand 0. - -The @code{sqrt} built-in function of C always uses the mode which -corresponds to the C data type @code{double}. - -@cindex @code{ffs@var{m}2} instruction pattern -@item @samp{ffs@var{m}2} -Store into operand 0 one plus the index of the least significant 1-bit -of operand 1. If operand 1 is zero, store zero. @var{m} is the mode -of operand 0; operand 1's mode is specified by the instruction -pattern, and the compiler will convert the operand to that mode before -generating the instruction. - -The @code{ffs} built-in function of C always uses the mode which -corresponds to the C data type @code{int}. - -@cindex @code{one_cmpl@var{m}2} instruction pattern -@item @samp{one_cmpl@var{m}2} -Store the bitwise-complement of operand 1 into operand 0. - -@cindex @code{cmp@var{m}} instruction pattern -@item @samp{cmp@var{m}} -Compare operand 0 and operand 1, and set the condition codes. -The RTL pattern should look like this: - -@smallexample -(set (cc0) (compare (match_operand:@var{m} 0 @dots{}) - (match_operand:@var{m} 1 @dots{}))) -@end smallexample - -@cindex @code{tst@var{m}} instruction pattern -@item @samp{tst@var{m}} -Compare operand 0 against zero, and set the condition codes. -The RTL pattern should look like this: - -@smallexample -(set (cc0) (match_operand:@var{m} 0 @dots{})) -@end smallexample - -@samp{tst@var{m}} patterns should not be defined for machines that do -not use @code{(cc0)}. Doing so would confuse the optimizer since it -would no longer be clear which @code{set} operations were comparisons. -The @samp{cmp@var{m}} patterns should be used instead. - -@cindex @code{movstr@var{m}} instruction pattern -@item @samp{movstr@var{m}} -Block move instruction. The addresses of the destination and source -strings are the first two operands, and both are in mode @code{Pmode}. - -The number of bytes to move is the third operand, in mode @var{m}. -Usually, you specify @code{word_mode} for @var{m}. However, if you can -generate better code knowing the range of valid lengths is smaller than -those representable in a full word, you should provide a pattern with a -mode corresponding to the range of values you can handle efficiently -(e.g., @code{QImode} for values in the range 0--127; note we avoid numbers -that appear negative) and also a pattern with @code{word_mode}. - -The fourth operand is the known shared alignment of the source and -destination, in the form of a @code{const_int} rtx. Thus, if the -compiler knows that both source and destination are word-aligned, -it may provide the value 4 for this operand. - -Descriptions of multiple @code{movstr@var{m}} patterns can only be -beneficial if the patterns for smaller modes have fewer restrictions -on their first, second and fourth operands. Note that the mode @var{m} -in @code{movstr@var{m}} does not impose any restriction on the mode of -individually moved data units in the block. - -These patterns need not give special consideration to the possibility -that the source and destination strings might overlap. - -@cindex @code{clrstr@var{m}} instruction pattern -@item @samp{clrstr@var{m}} -Block clear instruction. The addresses of the destination string is the -first operand, in mode @code{Pmode}. The number of bytes to clear is -the second operand, in mode @var{m}. See @samp{movstr@var{m}} for -a discussion of the choice of mode. - -The third operand is the known alignment of the destination, in the form -of a @code{const_int} rtx. Thus, if the compiler knows that the -destination is word-aligned, it may provide the value 4 for this -operand. - -The use for multiple @code{clrstr@var{m}} is as for @code{movstr@var{m}}. - -@cindex @code{cmpstr@var{m}} instruction pattern -@item @samp{cmpstr@var{m}} -Block compare instruction, with five operands. Operand 0 is the output; -it has mode @var{m}. The remaining four operands are like the operands -of @samp{movstr@var{m}}. The two memory blocks specified are compared -byte by byte in lexicographic order. The effect of the instruction is -to store a value in operand 0 whose sign indicates the result of the -comparison. - -@cindex @code{strlen@var{m}} instruction pattern -@item @samp{strlen@var{m}} -Compute the length of a string, with three operands. -Operand 0 is the result (of mode @var{m}), operand 1 is -a @code{mem} referring to the first character of the string, -operand 2 is the character to search for (normally zero), -and operand 3 is a constant describing the known alignment -of the beginning of the string. - -@cindex @code{float@var{mn}2} instruction pattern -@item @samp{float@var{m}@var{n}2} -Convert signed integer operand 1 (valid for fixed point mode @var{m}) to -floating point mode @var{n} and store in operand 0 (which has mode -@var{n}). - -@cindex @code{floatuns@var{mn}2} instruction pattern -@item @samp{floatuns@var{m}@var{n}2} -Convert unsigned integer operand 1 (valid for fixed point mode @var{m}) -to floating point mode @var{n} and store in operand 0 (which has mode -@var{n}). - -@cindex @code{fix@var{mn}2} instruction pattern -@item @samp{fix@var{m}@var{n}2} -Convert operand 1 (valid for floating point mode @var{m}) to fixed -point mode @var{n} as a signed number and store in operand 0 (which -has mode @var{n}). This instruction's result is defined only when -the value of operand 1 is an integer. - -@cindex @code{fixuns@var{mn}2} instruction pattern -@item @samp{fixuns@var{m}@var{n}2} -Convert operand 1 (valid for floating point mode @var{m}) to fixed -point mode @var{n} as an unsigned number and store in operand 0 (which -has mode @var{n}). This instruction's result is defined only when the -value of operand 1 is an integer. - -@cindex @code{ftrunc@var{m}2} instruction pattern -@item @samp{ftrunc@var{m}2} -Convert operand 1 (valid for floating point mode @var{m}) to an -integer value, still represented in floating point mode @var{m}, and -store it in operand 0 (valid for floating point mode @var{m}). - -@cindex @code{fix_trunc@var{mn}2} instruction pattern -@item @samp{fix_trunc@var{m}@var{n}2} -Like @samp{fix@var{m}@var{n}2} but works for any floating point value -of mode @var{m} by converting the value to an integer. - -@cindex @code{fixuns_trunc@var{mn}2} instruction pattern -@item @samp{fixuns_trunc@var{m}@var{n}2} -Like @samp{fixuns@var{m}@var{n}2} but works for any floating point -value of mode @var{m} by converting the value to an integer. - -@cindex @code{trunc@var{mn}2} instruction pattern -@item @samp{trunc@var{m}@var{n}2} -Truncate operand 1 (valid for mode @var{m}) to mode @var{n} and -store in operand 0 (which has mode @var{n}). Both modes must be fixed -point or both floating point. - -@cindex @code{extend@var{mn}2} instruction pattern -@item @samp{extend@var{m}@var{n}2} -Sign-extend operand 1 (valid for mode @var{m}) to mode @var{n} and -store in operand 0 (which has mode @var{n}). Both modes must be fixed -point or both floating point. - -@cindex @code{zero_extend@var{mn}2} instruction pattern -@item @samp{zero_extend@var{m}@var{n}2} -Zero-extend operand 1 (valid for mode @var{m}) to mode @var{n} and -store in operand 0 (which has mode @var{n}). Both modes must be fixed -point. - -@cindex @code{extv} instruction pattern -@item @samp{extv} -Extract a bit field from operand 1 (a register or memory operand), where -operand 2 specifies the width in bits and operand 3 the starting bit, -and store it in operand 0. Operand 0 must have mode @code{word_mode}. -Operand 1 may have mode @code{byte_mode} or @code{word_mode}; often -@code{word_mode} is allowed only for registers. Operands 2 and 3 must -be valid for @code{word_mode}. - -The RTL generation pass generates this instruction only with constants -for operands 2 and 3. - -The bit-field value is sign-extended to a full word integer -before it is stored in operand 0. - -@cindex @code{extzv} instruction pattern -@item @samp{extzv} -Like @samp{extv} except that the bit-field value is zero-extended. - -@cindex @code{insv} instruction pattern -@item @samp{insv} -Store operand 3 (which must be valid for @code{word_mode}) into a bit -field in operand 0, where operand 1 specifies the width in bits and -operand 2 the starting bit. Operand 0 may have mode @code{byte_mode} or -@code{word_mode}; often @code{word_mode} is allowed only for registers. -Operands 1 and 2 must be valid for @code{word_mode}. - -The RTL generation pass generates this instruction only with constants -for operands 1 and 2. - -@cindex @code{mov@var{mode}cc} instruction pattern -@item @samp{mov@var{mode}cc} -Conditionally move operand 2 or operand 3 into operand 0 according to the -comparison in operand 1. If the comparison is true, operand 2 is moved -into operand 0, otherwise operand 3 is moved. - -The mode of the operands being compared need not be the same as the operands -being moved. Some machines, sparc64 for example, have instructions that -conditionally move an integer value based on the floating point condition -codes and vice versa. - -If the machine does not have conditional move instructions, do not -define these patterns. - -@cindex @code{s@var{cond}} instruction pattern -@item @samp{s@var{cond}} -Store zero or nonzero in the operand according to the condition codes. -Value stored is nonzero iff the condition @var{cond} is true. -@var{cond} is the name of a comparison operation expression code, such -as @code{eq}, @code{lt} or @code{leu}. - -You specify the mode that the operand must have when you write the -@code{match_operand} expression. The compiler automatically sees -which mode you have used and supplies an operand of that mode. - -The value stored for a true condition must have 1 as its low bit, or -else must be negative. Otherwise the instruction is not suitable and -you should omit it from the machine description. You describe to the -compiler exactly which value is stored by defining the macro -@code{STORE_FLAG_VALUE} (@pxref{Misc}). If a description cannot be -found that can be used for all the @samp{s@var{cond}} patterns, you -should omit those operations from the machine description. - -These operations may fail, but should do so only in relatively -uncommon cases; if they would fail for common cases involving -integer comparisons, it is best to omit these patterns. - -If these operations are omitted, the compiler will usually generate code -that copies the constant one to the target and branches around an -assignment of zero to the target. If this code is more efficient than -the potential instructions used for the @samp{s@var{cond}} pattern -followed by those required to convert the result into a 1 or a zero in -@code{SImode}, you should omit the @samp{s@var{cond}} operations from -the machine description. - -@cindex @code{b@var{cond}} instruction pattern -@item @samp{b@var{cond}} -Conditional branch instruction. Operand 0 is a @code{label_ref} that -refers to the label to jump to. Jump if the condition codes meet -condition @var{cond}. - -Some machines do not follow the model assumed here where a comparison -instruction is followed by a conditional branch instruction. In that -case, the @samp{cmp@var{m}} (and @samp{tst@var{m}}) patterns should -simply store the operands away and generate all the required insns in a -@code{define_expand} (@pxref{Expander Definitions}) for the conditional -branch operations. All calls to expand @samp{b@var{cond}} patterns are -immediately preceded by calls to expand either a @samp{cmp@var{m}} -pattern or a @samp{tst@var{m}} pattern. - -Machines that use a pseudo register for the condition code value, or -where the mode used for the comparison depends on the condition being -tested, should also use the above mechanism. @xref{Jump Patterns}. - -The above discussion also applies to the @samp{mov@var{mode}cc} and -@samp{s@var{cond}} patterns. - -@cindex @code{jump} instruction pattern -@item @samp{jump} -A jump inside a function; an unconditional branch. Operand 0 is the -@code{label_ref} of the label to jump to. This pattern name is mandatory -on all machines. - -@cindex @code{call} instruction pattern -@item @samp{call} -Subroutine call instruction returning no value. Operand 0 is the -function to call; operand 1 is the number of bytes of arguments pushed -as a @code{const_int}; operand 2 is the number of registers used as -operands. - -On most machines, operand 2 is not actually stored into the RTL -pattern. It is supplied for the sake of some RISC machines which need -to put this information into the assembler code; they can put it in -the RTL instead of operand 1. - -Operand 0 should be a @code{mem} RTX whose address is the address of the -function. Note, however, that this address can be a @code{symbol_ref} -expression even if it would not be a legitimate memory address on the -target machine. If it is also not a valid argument for a call -instruction, the pattern for this operation should be a -@code{define_expand} (@pxref{Expander Definitions}) that places the -address into a register and uses that register in the call instruction. - -@cindex @code{call_value} instruction pattern -@item @samp{call_value} -Subroutine call instruction returning a value. Operand 0 is the hard -register in which the value is returned. There are three more -operands, the same as the three operands of the @samp{call} -instruction (but with numbers increased by one). - -Subroutines that return @code{BLKmode} objects use the @samp{call} -insn. - -@cindex @code{call_pop} instruction pattern -@cindex @code{call_value_pop} instruction pattern -@item @samp{call_pop}, @samp{call_value_pop} -Similar to @samp{call} and @samp{call_value}, except used if defined and -if @code{RETURN_POPS_ARGS} is non-zero. They should emit a @code{parallel} -that contains both the function call and a @code{set} to indicate the -adjustment made to the frame pointer. - -For machines where @code{RETURN_POPS_ARGS} can be non-zero, the use of these -patterns increases the number of functions for which the frame pointer -can be eliminated, if desired. - -@cindex @code{untyped_call} instruction pattern -@item @samp{untyped_call} -Subroutine call instruction returning a value of any type. Operand 0 is -the function to call; operand 1 is a memory location where the result of -calling the function is to be stored; operand 2 is a @code{parallel} -expression where each element is a @code{set} expression that indicates -the saving of a function return value into the result block. - -This instruction pattern should be defined to support -@code{__builtin_apply} on machines where special instructions are needed -to call a subroutine with arbitrary arguments or to save the value -returned. This instruction pattern is required on machines that have -multiple registers that can hold a return value (i.e. -@code{FUNCTION_VALUE_REGNO_P} is true for more than one register). - -@cindex @code{return} instruction pattern -@item @samp{return} -Subroutine return instruction. This instruction pattern name should be -defined only if a single instruction can do all the work of returning -from a function. - -Like the @samp{mov@var{m}} patterns, this pattern is also used after the -RTL generation phase. In this case it is to support machines where -multiple instructions are usually needed to return from a function, but -some class of functions only requires one instruction to implement a -return. Normally, the applicable functions are those which do not need -to save any registers or allocate stack space. - -@findex reload_completed -@findex leaf_function_p -For such machines, the condition specified in this pattern should only -be true when @code{reload_completed} is non-zero and the function's -epilogue would only be a single instruction. For machines with register -windows, the routine @code{leaf_function_p} may be used to determine if -a register window push is required. - -Machines that have conditional return instructions should define patterns -such as - -@smallexample -(define_insn "" - [(set (pc) - (if_then_else (match_operator - 0 "comparison_operator" - [(cc0) (const_int 0)]) - (return) - (pc)))] - "@var{condition}" - "@dots{}") -@end smallexample - -where @var{condition} would normally be the same condition specified on the -named @samp{return} pattern. - -@cindex @code{untyped_return} instruction pattern -@item @samp{untyped_return} -Untyped subroutine return instruction. This instruction pattern should -be defined to support @code{__builtin_return} on machines where special -instructions are needed to return a value of any type. - -Operand 0 is a memory location where the result of calling a function -with @code{__builtin_apply} is stored; operand 1 is a @code{parallel} -expression where each element is a @code{set} expression that indicates -the restoring of a function return value from the result block. - -@cindex @code{nop} instruction pattern -@item @samp{nop} -No-op instruction. This instruction pattern name should always be defined -to output a no-op in assembler code. @code{(const_int 0)} will do as an -RTL pattern. - -@cindex @code{indirect_jump} instruction pattern -@item @samp{indirect_jump} -An instruction to jump to an address which is operand zero. -This pattern name is mandatory on all machines. - -@cindex @code{casesi} instruction pattern -@item @samp{casesi} -Instruction to jump through a dispatch table, including bounds checking. -This instruction takes five operands: - -@enumerate -@item -The index to dispatch on, which has mode @code{SImode}. - -@item -The lower bound for indices in the table, an integer constant. - -@item -The total range of indices in the table---the largest index -minus the smallest one (both inclusive). - -@item -A label that precedes the table itself. - -@item -A label to jump to if the index has a value outside the bounds. -(If the machine-description macro @code{CASE_DROPS_THROUGH} is defined, -then an out-of-bounds index drops through to the code following -the jump table instead of jumping to this label. In that case, -this label is not actually used by the @samp{casesi} instruction, -but it is always provided as an operand.) -@end enumerate - -The table is a @code{addr_vec} or @code{addr_diff_vec} inside of a -@code{jump_insn}. The number of elements in the table is one plus the -difference between the upper bound and the lower bound. - -@cindex @code{tablejump} instruction pattern -@item @samp{tablejump} -Instruction to jump to a variable address. This is a low-level -capability which can be used to implement a dispatch table when there -is no @samp{casesi} pattern. - -This pattern requires two operands: the address or offset, and a label -which should immediately precede the jump table. If the macro -@code{CASE_VECTOR_PC_RELATIVE} evaluates to a nonzero value then the first -operand is an offset which counts from the address of the table; otherwise, -it is an absolute address to jump to. In either case, the first operand has -mode @code{Pmode}. - -The @samp{tablejump} insn is always the last insn before the jump -table it uses. Its assembler code normally has no need to use the -second operand, but you should incorporate it in the RTL pattern so -that the jump optimizer will not delete the table as unreachable code. - - -@cindex @code{decrement_and_branch_until_zero} instruction pattern -@item @samp{decrement_and_branch_until_zero} -Conditional branch instruction that decrements a register and -jumps if the register is non-zero. Operand 0 is the register to -decrement and test; operand 1 is the label to jump to if the -register is non-zero. @xref{Looping Patterns}. - -This optional instruction pattern is only used by the combiner, -typically for loops reversed by the loop optimizer when strength -reduction is enabled. - -@cindex @code{doloop_end} instruction pattern -@item @samp{doloop_end} -Conditional branch instruction that decrements a register and jumps if -the register is non-zero. This instruction takes five operands: Operand -0 is the register to decrement and test; operand 1 is the number of loop -iterations as a @code{const_int} or @code{const0_rtx} if this cannot be -determined until run-time; operand 2 is the actual or estimated maximum -number of iterations as a @code{const_int}; operand 3 is the number of -enclosed loops as a @code{const_int} (an innermost loop has a value of -1); operand 4 is the label to jump to if the register is non-zero. -@xref{Looping Patterns}. - -This optional instruction pattern should be defined for machines with -low-overhead looping instructions as the loop optimizer will try to -modify suitable loops to utilize it. If nested low-overhead looping is -not supported, use a @code{define_expand} (@pxref{Expander Definitions}) -and make the pattern fail if operand 3 is not @code{const1_rtx}. -Similarly, if the actual or estimated maximum number of iterations is -too large for this instruction, make it fail. - -@cindex @code{doloop_begin} instruction pattern -@item @samp{doloop_begin} -Companion instruction to @code{doloop_end} required for machines that -need to perform some initialisation, such as loading special registers -used by a low-overhead looping instruction. If initialisation insns do -not always need to be emitted, use a @code{define_expand} -(@pxref{Expander Definitions}) and make it fail. - - -@cindex @code{canonicalize_funcptr_for_compare} instruction pattern -@item @samp{canonicalize_funcptr_for_compare} -Canonicalize the function pointer in operand 1 and store the result -into operand 0. - -Operand 0 is always a @code{reg} and has mode @code{Pmode}; operand 1 -may be a @code{reg}, @code{mem}, @code{symbol_ref}, @code{const_int}, etc -and also has mode @code{Pmode}. - -Canonicalization of a function pointer usually involves computing -the address of the function which would be called if the function -pointer were used in an indirect call. - -Only define this pattern if function pointers on the target machine -can have different values but still call the same function when -used in an indirect call. - -@cindex @code{save_stack_block} instruction pattern -@cindex @code{save_stack_function} instruction pattern -@cindex @code{save_stack_nonlocal} instruction pattern -@cindex @code{restore_stack_block} instruction pattern -@cindex @code{restore_stack_function} instruction pattern -@cindex @code{restore_stack_nonlocal} instruction pattern -@item @samp{save_stack_block} -@itemx @samp{save_stack_function} -@itemx @samp{save_stack_nonlocal} -@itemx @samp{restore_stack_block} -@itemx @samp{restore_stack_function} -@itemx @samp{restore_stack_nonlocal} -Most machines save and restore the stack pointer by copying it to or -from an object of mode @code{Pmode}. Do not define these patterns on -such machines. - -Some machines require special handling for stack pointer saves and -restores. On those machines, define the patterns corresponding to the -non-standard cases by using a @code{define_expand} (@pxref{Expander -Definitions}) that produces the required insns. The three types of -saves and restores are: - -@enumerate -@item -@samp{save_stack_block} saves the stack pointer at the start of a block -that allocates a variable-sized object, and @samp{restore_stack_block} -restores the stack pointer when the block is exited. - -@item -@samp{save_stack_function} and @samp{restore_stack_function} do a -similar job for the outermost block of a function and are used when the -function allocates variable-sized objects or calls @code{alloca}. Only -the epilogue uses the restored stack pointer, allowing a simpler save or -restore sequence on some machines. - -@item -@samp{save_stack_nonlocal} is used in functions that contain labels -branched to by nested functions. It saves the stack pointer in such a -way that the inner function can use @samp{restore_stack_nonlocal} to -restore the stack pointer. The compiler generates code to restore the -frame and argument pointer registers, but some machines require saving -and restoring additional data such as register window information or -stack backchains. Place insns in these patterns to save and restore any -such required data. -@end enumerate - -When saving the stack pointer, operand 0 is the save area and operand 1 -is the stack pointer. The mode used to allocate the save area defaults -to @code{Pmode} but you can override that choice by defining the -@code{STACK_SAVEAREA_MODE} macro (@pxref{Storage Layout}). You must -specify an integral mode, or @code{VOIDmode} if no save area is needed -for a particular type of save (either because no save is needed or -because a machine-specific save area can be used). Operand 0 is the -stack pointer and operand 1 is the save area for restore operations. If -@samp{save_stack_block} is defined, operand 0 must not be -@code{VOIDmode} since these saves can be arbitrarily nested. - -A save area is a @code{mem} that is at a constant offset from -@code{virtual_stack_vars_rtx} when the stack pointer is saved for use by -nonlocal gotos and a @code{reg} in the other two cases. - -@cindex @code{allocate_stack} instruction pattern -@item @samp{allocate_stack} -Subtract (or add if @code{STACK_GROWS_DOWNWARD} is undefined) operand 1 from -the stack pointer to create space for dynamically allocated data. - -Store the resultant pointer to this space into operand 0. If you -are allocating space from the main stack, do this by emitting a -move insn to copy @code{virtual_stack_dynamic_rtx} to operand 0. -If you are allocating the space elsewhere, generate code to copy the -location of the space to operand 0. In the latter case, you must -ensure this space gets freed when the corresponding space on the main -stack is free. - -Do not define this pattern if all that must be done is the subtraction. -Some machines require other operations such as stack probes or -maintaining the back chain. Define this pattern to emit those -operations in addition to updating the stack pointer. - -@cindex @code{probe} instruction pattern -@item @samp{probe} -Some machines require instructions to be executed after space is -allocated from the stack, for example to generate a reference at -the bottom of the stack. - -If you need to emit instructions before the stack has been adjusted, -put them into the @samp{allocate_stack} pattern. Otherwise, define -this pattern to emit the required instructions. - -No operands are provided. - -@cindex @code{check_stack} instruction pattern -@item @samp{check_stack} -If stack checking cannot be done on your system by probing the stack with -a load or store instruction (@pxref{Stack Checking}), define this pattern -to perform the needed check and signaling an error if the stack -has overflowed. The single operand is the location in the stack furthest -from the current stack pointer that you need to validate. Normally, -on machines where this pattern is needed, you would obtain the stack -limit from a global or thread-specific variable or register. - -@cindex @code{nonlocal_goto} instruction pattern -@item @samp{nonlocal_goto} -Emit code to generate a non-local goto, e.g., a jump from one function -to a label in an outer function. This pattern has four arguments, -each representing a value to be used in the jump. The first -argument is to be loaded into the frame pointer, the second is -the address to branch to (code to dispatch to the actual label), -the third is the address of a location where the stack is saved, -and the last is the address of the label, to be placed in the -location for the incoming static chain. - -On most machines you need not define this pattern, since GNU CC will -already generate the correct code, which is to load the frame pointer -and static chain, restore the stack (using the -@samp{restore_stack_nonlocal} pattern, if defined), and jump indirectly -to the dispatcher. You need only define this pattern if this code will -not work on your machine. - -@cindex @code{nonlocal_goto_receiver} instruction pattern -@item @samp{nonlocal_goto_receiver} -This pattern, if defined, contains code needed at the target of a -nonlocal goto after the code already generated by GNU CC. You will not -normally need to define this pattern. A typical reason why you might -need this pattern is if some value, such as a pointer to a global table, -must be restored when the frame pointer is restored. Note that a nonlocal -goto only occurs within a unit-of-translation, so a global table pointer -that is shared by all functions of a given module need not be restored. -There are no arguments. - -@cindex @code{exception_receiver} instruction pattern -@item @samp{exception_receiver} -This pattern, if defined, contains code needed at the site of an -exception handler that isn't needed at the site of a nonlocal goto. You -will not normally need to define this pattern. A typical reason why you -might need this pattern is if some value, such as a pointer to a global -table, must be restored after control flow is branched to the handler of -an exception. There are no arguments. - -@cindex @code{builtin_setjmp_setup} instruction pattern -@item @samp{builtin_setjmp_setup} -This pattern, if defined, contains additional code needed to initialize -the @code{jmp_buf}. You will not normally need to define this pattern. -A typical reason why you might need this pattern is if some value, such -as a pointer to a global table, must be restored. Though it is -preferred that the pointer value be recalculated if possible (given the -address of a label for instance). The single argument is a pointer to -the @code{jmp_buf}. Note that the buffer is five words long and that -the first three are normally used by the generic mechanism. - -@cindex @code{builtin_setjmp_receiver} instruction pattern -@item @samp{builtin_setjmp_receiver} -This pattern, if defined, contains code needed at the site of an -builtin setjmp that isn't needed at the site of a nonlocal goto. You -will not normally need to define this pattern. A typical reason why you -might need this pattern is if some value, such as a pointer to a global -table, must be restored. It takes one argument, which is the label -to which builtin_longjmp transfered control; this pattern may be emitted -at a small offset from that label. - -@cindex @code{builtin_longjmp} instruction pattern -@item @samp{builtin_longjmp} -This pattern, if defined, performs the entire action of the longjmp. -You will not normally need to define this pattern unless you also define -@code{builtin_setjmp_setup}. The single argument is a pointer to the -@code{jmp_buf}. - -@cindex @code{eh_return} instruction pattern -@item @samp{eh_return} -This pattern, if defined, affects the way @code{__builtin_eh_return}, -and thence the call frame exception handling library routines, are -built. It is intended to handle non-trivial actions needed along -the abnormal return path. - -The pattern takes two arguments. The first is an offset to be applied -to the stack pointer. It will have been copied to some appropriate -location (typically @code{EH_RETURN_STACKADJ_RTX}) which will survive -until after reload to when the normal epilogue is generated. -The second argument is the address of the exception handler to which -the function should return. This will normally need to copied by the -pattern to some special register or memory location. - -This pattern only needs to be defined if call frame exception handling -is to be used, and simple moves to @code{EH_RETURN_STACKADJ_RTX} and -@code{EH_RETURN_HANDLER_RTX} are not sufficient. - -@cindex @code{prologue} instruction pattern -@item @samp{prologue} -This pattern, if defined, emits RTL for entry to a function. The function -entry is responsible for setting up the stack frame, initializing the frame -pointer register, saving callee saved registers, etc. - -Using a prologue pattern is generally preferred over defining -@code{FUNCTION_PROLOGUE} to emit assembly code for the prologue. - -The @code{prologue} pattern is particularly useful for targets which perform -instruction scheduling. - -@cindex @code{epilogue} instruction pattern -@item @samp{epilogue} -This pattern, if defined, emits RTL for exit from a function. The function -exit is responsible for deallocating the stack frame, restoring callee saved -registers and emitting the return instruction. - -Using an epilogue pattern is generally preferred over defining -@code{FUNCTION_EPILOGUE} to emit assembly code for the prologue. - -The @code{epilogue} pattern is particularly useful for targets which perform -instruction scheduling or which have delay slots for their return instruction. - -@cindex @code{sibcall_epilogue} instruction pattern -@item @samp{sibcall_epilogue} -This pattern, if defined, emits RTL for exit from a function without the final -branch back to the calling function. This pattern will be emitted before any -sibling call (aka tail call) sites. - -The @code{sibcall_epilogue} pattern must not clobber any arguments used for -parameter passing or any stack slots for arguments passed to the current -function. - -@cindex @code{trap} instruction pattern -@item @samp{trap} -This pattern, if defined, signals an error, typically by causing some -kind of signal to be raised. Among other places, it is used by the Java -frontend to signal `invalid array index' exceptions. - -@cindex @code{conditional_trap} instruction pattern -@item @samp{conditional_trap} -Conditional trap instruction. Operand 0 is a piece of RTL which -performs a comparison. Operand 1 is the trap code, an integer. - -A typical @code{conditional_trap} pattern looks like - -@smallexample -(define_insn "conditional_trap" - [(trap_if (match_operator 0 "trap_operator" - [(cc0) (const_int 0)]) - (match_operand 1 "const_int_operand" "i"))] - "" - "@dots{}") -@end smallexample - -@cindex @code{cycle_display} instruction pattern -@item @samp{cycle_display} - -This pattern, if present, will be emitted by the instruction scheduler at -the beginning of each new clock cycle. This can be used for annotating the -assembler output with cycle counts. Operand 0 is a @code{const_int} that -holds the clock cycle. - -@end table - -@node Pattern Ordering -@section When the Order of Patterns Matters -@cindex Pattern Ordering -@cindex Ordering of Patterns - -Sometimes an insn can match more than one instruction pattern. Then the -pattern that appears first in the machine description is the one used. -Therefore, more specific patterns (patterns that will match fewer things) -and faster instructions (those that will produce better code when they -do match) should usually go first in the description. - -In some cases the effect of ordering the patterns can be used to hide -a pattern when it is not valid. For example, the 68000 has an -instruction for converting a fullword to floating point and another -for converting a byte to floating point. An instruction converting -an integer to floating point could match either one. We put the -pattern to convert the fullword first to make sure that one will -be used rather than the other. (Otherwise a large integer might -be generated as a single-byte immediate quantity, which would not work.) -Instead of using this pattern ordering it would be possible to make the -pattern for convert-a-byte smart enough to deal properly with any -constant value. - -@node Dependent Patterns -@section Interdependence of Patterns -@cindex Dependent Patterns -@cindex Interdependence of Patterns - -Every machine description must have a named pattern for each of the -conditional branch names @samp{b@var{cond}}. The recognition template -must always have the form - -@example -(set (pc) - (if_then_else (@var{cond} (cc0) (const_int 0)) - (label_ref (match_operand 0 "" "")) - (pc))) -@end example - -@noindent -In addition, every machine description must have an anonymous pattern -for each of the possible reverse-conditional branches. Their templates -look like - -@example -(set (pc) - (if_then_else (@var{cond} (cc0) (const_int 0)) - (pc) - (label_ref (match_operand 0 "" "")))) -@end example - -@noindent -They are necessary because jump optimization can turn direct-conditional -branches into reverse-conditional branches. - -It is often convenient to use the @code{match_operator} construct to -reduce the number of patterns that must be specified for branches. For -example, - -@example -(define_insn "" - [(set (pc) - (if_then_else (match_operator 0 "comparison_operator" - [(cc0) (const_int 0)]) - (pc) - (label_ref (match_operand 1 "" ""))))] - "@var{condition}" - "@dots{}") -@end example - -In some cases machines support instructions identical except for the -machine mode of one or more operands. For example, there may be -``sign-extend halfword'' and ``sign-extend byte'' instructions whose -patterns are - -@example -(set (match_operand:SI 0 @dots{}) - (extend:SI (match_operand:HI 1 @dots{}))) - -(set (match_operand:SI 0 @dots{}) - (extend:SI (match_operand:QI 1 @dots{}))) -@end example - -@noindent -Constant integers do not specify a machine mode, so an instruction to -extend a constant value could match either pattern. The pattern it -actually will match is the one that appears first in the file. For correct -results, this must be the one for the widest possible mode (@code{HImode}, -here). If the pattern matches the @code{QImode} instruction, the results -will be incorrect if the constant value does not actually fit that mode. - -Such instructions to extend constants are rarely generated because they are -optimized away, but they do occasionally happen in nonoptimized -compilations. - -If a constraint in a pattern allows a constant, the reload pass may -replace a register with a constant permitted by the constraint in some -cases. Similarly for memory references. Because of this substitution, -you should not provide separate patterns for increment and decrement -instructions. Instead, they should be generated from the same pattern -that supports register-register add insns by examining the operands and -generating the appropriate machine instruction. - -@node Jump Patterns -@section Defining Jump Instruction Patterns -@cindex jump instruction patterns -@cindex defining jump instruction patterns - -For most machines, GNU CC assumes that the machine has a condition code. -A comparison insn sets the condition code, recording the results of both -signed and unsigned comparison of the given operands. A separate branch -insn tests the condition code and branches or not according its value. -The branch insns come in distinct signed and unsigned flavors. Many -common machines, such as the Vax, the 68000 and the 32000, work this -way. - -Some machines have distinct signed and unsigned compare instructions, and -only one set of conditional branch instructions. The easiest way to handle -these machines is to treat them just like the others until the final stage -where assembly code is written. At this time, when outputting code for the -compare instruction, peek ahead at the following branch using -@code{next_cc0_user (insn)}. (The variable @code{insn} refers to the insn -being output, in the output-writing code in an instruction pattern.) If -the RTL says that is an unsigned branch, output an unsigned compare; -otherwise output a signed compare. When the branch itself is output, you -can treat signed and unsigned branches identically. - -The reason you can do this is that GNU CC always generates a pair of -consecutive RTL insns, possibly separated by @code{note} insns, one to -set the condition code and one to test it, and keeps the pair inviolate -until the end. - -To go with this technique, you must define the machine-description macro -@code{NOTICE_UPDATE_CC} to do @code{CC_STATUS_INIT}; in other words, no -compare instruction is superfluous. - -Some machines have compare-and-branch instructions and no condition code. -A similar technique works for them. When it is time to ``output'' a -compare instruction, record its operands in two static variables. When -outputting the branch-on-condition-code instruction that follows, actually -output a compare-and-branch instruction that uses the remembered operands. - -It also works to define patterns for compare-and-branch instructions. -In optimizing compilation, the pair of compare and branch instructions -will be combined according to these patterns. But this does not happen -if optimization is not requested. So you must use one of the solutions -above in addition to any special patterns you define. - -In many RISC machines, most instructions do not affect the condition -code and there may not even be a separate condition code register. On -these machines, the restriction that the definition and use of the -condition code be adjacent insns is not necessary and can prevent -important optimizations. For example, on the IBM RS/6000, there is a -delay for taken branches unless the condition code register is set three -instructions earlier than the conditional branch. The instruction -scheduler cannot perform this optimization if it is not permitted to -separate the definition and use of the condition code register. - -On these machines, do not use @code{(cc0)}, but instead use a register -to represent the condition code. If there is a specific condition code -register in the machine, use a hard register. If the condition code or -comparison result can be placed in any general register, or if there are -multiple condition registers, use a pseudo register. - -@findex prev_cc0_setter -@findex next_cc0_user -On some machines, the type of branch instruction generated may depend on -the way the condition code was produced; for example, on the 68k and -Sparc, setting the condition code directly from an add or subtract -instruction does not clear the overflow bit the way that a test -instruction does, so a different branch instruction must be used for -some conditional branches. For machines that use @code{(cc0)}, the set -and use of the condition code must be adjacent (separated only by -@code{note} insns) allowing flags in @code{cc_status} to be used. -(@xref{Condition Code}.) Also, the comparison and branch insns can be -located from each other by using the functions @code{prev_cc0_setter} -and @code{next_cc0_user}. - -However, this is not true on machines that do not use @code{(cc0)}. On -those machines, no assumptions can be made about the adjacency of the -compare and branch insns and the above methods cannot be used. Instead, -we use the machine mode of the condition code register to record -different formats of the condition code register. - -Registers used to store the condition code value should have a mode that -is in class @code{MODE_CC}. Normally, it will be @code{CCmode}. If -additional modes are required (as for the add example mentioned above in -the Sparc), define the macro @code{EXTRA_CC_MODES} to list the -additional modes required (@pxref{Condition Code}). Also define -@code{SELECT_CC_MODE} to choose a mode given an operand of a compare. - -If it is known during RTL generation that a different mode will be -required (for example, if the machine has separate compare instructions -for signed and unsigned quantities, like most IBM processors), they can -be specified at that time. - -If the cases that require different modes would be made by instruction -combination, the macro @code{SELECT_CC_MODE} determines which machine -mode should be used for the comparison result. The patterns should be -written using that mode. To support the case of the add on the Sparc -discussed above, we have the pattern - -@smallexample -(define_insn "" - [(set (reg:CC_NOOV 0) - (compare:CC_NOOV - (plus:SI (match_operand:SI 0 "register_operand" "%r") - (match_operand:SI 1 "arith_operand" "rI")) - (const_int 0)))] - "" - "@dots{}") -@end smallexample - -The @code{SELECT_CC_MODE} macro on the Sparc returns @code{CC_NOOVmode} -for comparisons whose argument is a @code{plus}. - -@node Looping Patterns -@section Defining Looping Instruction Patterns -@cindex looping instruction patterns -@cindex defining looping instruction patterns - -Some machines have special jump instructions that can be utilised to -make loops more efficient. A common example is the 68000 @samp{dbra} -instruction which performs a decrement of a register and a branch if the -result was greater than zero. Other machines, in particular digital -signal processors (DSPs), have special block repeat instructions to -provide low-overhead loop support. For example, the TI TMS320C3x/C4x -DSPs have a block repeat instruction that loads special registers to -mark the top and end of a loop and to count the number of loop -iterations. This avoids the need for fetching and executing a -@samp{dbra}-like instruction and avoids pipeline stalls asociated with -the jump. - -GNU CC has three special named patterns to support low overhead looping, -@samp{decrement_and_branch_until_zero}, @samp{doloop_begin}, and -@samp{doloop_end}. The first pattern, -@samp{decrement_and_branch_until_zero}, is not emitted during RTL -generation but may be emitted during the instruction combination phase. -This requires the assistance of the loop optimizer, using information -collected during strength reduction, to reverse a loop to count down to -zero. Some targets also require the loop optimizer to add a -@code{REG_NONNEG} note to indicate that the iteration count is always -positive. This is needed if the target performs a signed loop -termination test. For example, the 68000 uses a pattern similar to the -following for its @code{dbra} instruction: - -@smallexample -@group -(define_insn "decrement_and_branch_until_zero" - [(set (pc) - (if_then_else - (ge (plus:SI (match_operand:SI 0 "general_operand" "+d*am") - (const_int -1)) - (const_int 0)) - (label_ref (match_operand 1 "" "")) - (pc))) - (set (match_dup 0) - (plus:SI (match_dup 0) - (const_int -1)))] - "find_reg_note (insn, REG_NONNEG, 0)" - "...") -@end group -@end smallexample - -Note that since the insn is both a jump insn and has an output, it must -deal with its own reloads, hence the `m' constraints. Also note that -since this insn is generated by the instruction combination phase -combining two sequential insns together into an implicit parallel insn, -the iteration counter needs to be biased by the same amount as the -decrement operation, in this case -1. Note that the following similar -pattern will not be matched by the combiner. - -@smallexample -@group -(define_insn "decrement_and_branch_until_zero" - [(set (pc) - (if_then_else - (ge (match_operand:SI 0 "general_operand" "+d*am") - (const_int 1)) - (label_ref (match_operand 1 "" "")) - (pc))) - (set (match_dup 0) - (plus:SI (match_dup 0) - (const_int -1)))] - "find_reg_note (insn, REG_NONNEG, 0)" - "...") -@end group -@end smallexample - -The other two special looping patterns, @samp{doloop_begin} and -@samp{doloop_end}, are emitted by the loop optimiser for certain -well-behaved loops with a finite number of loop iterations using -information collected during strength reduction. - -The @samp{doloop_end} pattern describes the actual looping instruction -(or the implicit looping operation) and the @samp{doloop_begin} pattern -is an optional companion pattern that can be used for initialisation -needed for some low-overhead looping instructions. - -Note that some machines require the actual looping instruction to be -emitted at the top of the loop (e.g., the TMS320C3x/C4x DSPs). Emitting -the true RTL for a looping instruction at the top of the loop can cause -problems with flow analysis. So instead, a dummy @code{doloop} insn is -emitted at the end of the loop. The machine dependent reorg pass checks -for the presence of this @code{doloop} insn and then searches back to -the top of the loop, where it inserts the true looping insn (provided -there are no instructions in the loop which would cause problems). Any -additional labels can be emitted at this point. In addition, if the -desired special iteration counter register was not allocated, this -machine dependent reorg pass could emit a traditional compare and jump -instruction pair. - -The essential difference between the -@samp{decrement_and_branch_until_zero} and the @samp{doloop_end} -patterns is that the loop optimizer allocates an additional pseudo -register for the latter as an iteration counter. This pseudo register -cannot be used within the loop (i.e., general induction variables cannot -be derived from it), however, in many cases the loop induction variable -may become redundant and removed by the flow pass. - - -@node Insn Canonicalizations -@section Canonicalization of Instructions -@cindex canonicalization of instructions -@cindex insn canonicalization - -There are often cases where multiple RTL expressions could represent an -operation performed by a single machine instruction. This situation is -most commonly encountered with logical, branch, and multiply-accumulate -instructions. In such cases, the compiler attempts to convert these -multiple RTL expressions into a single canonical form to reduce the -number of insn patterns required. - -In addition to algebraic simplifications, following canonicalizations -are performed: - -@itemize @bullet -@item -For commutative and comparison operators, a constant is always made the -second operand. If a machine only supports a constant as the second -operand, only patterns that match a constant in the second operand need -be supplied. - -@cindex @code{neg}, canonicalization of -@cindex @code{not}, canonicalization of -@cindex @code{mult}, canonicalization of -@cindex @code{plus}, canonicalization of -@cindex @code{minus}, canonicalization of -For these operators, if only one operand is a @code{neg}, @code{not}, -@code{mult}, @code{plus}, or @code{minus} expression, it will be the -first operand. - -@cindex @code{compare}, canonicalization of -@item -For the @code{compare} operator, a constant is always the second operand -on machines where @code{cc0} is used (@pxref{Jump Patterns}). On other -machines, there are rare cases where the compiler might want to construct -a @code{compare} with a constant as the first operand. However, these -cases are not common enough for it to be worthwhile to provide a pattern -matching a constant as the first operand unless the machine actually has -such an instruction. - -An operand of @code{neg}, @code{not}, @code{mult}, @code{plus}, or -@code{minus} is made the first operand under the same conditions as -above. - -@item -@code{(minus @var{x} (const_int @var{n}))} is converted to -@code{(plus @var{x} (const_int @var{-n}))}. - -@item -Within address computations (i.e., inside @code{mem}), a left shift is -converted into the appropriate multiplication by a power of two. - -@cindex @code{ior}, canonicalization of -@cindex @code{and}, canonicalization of -@cindex De Morgan's law -@item -De`Morgan's Law is used to move bitwise negation inside a bitwise -logical-and or logical-or operation. If this results in only one -operand being a @code{not} expression, it will be the first one. - -A machine that has an instruction that performs a bitwise logical-and of one -operand with the bitwise negation of the other should specify the pattern -for that instruction as - -@example -(define_insn "" - [(set (match_operand:@var{m} 0 @dots{}) - (and:@var{m} (not:@var{m} (match_operand:@var{m} 1 @dots{})) - (match_operand:@var{m} 2 @dots{})))] - "@dots{}" - "@dots{}") -@end example - -@noindent -Similarly, a pattern for a ``NAND'' instruction should be written - -@example -(define_insn "" - [(set (match_operand:@var{m} 0 @dots{}) - (ior:@var{m} (not:@var{m} (match_operand:@var{m} 1 @dots{})) - (not:@var{m} (match_operand:@var{m} 2 @dots{}))))] - "@dots{}" - "@dots{}") -@end example - -In both cases, it is not necessary to include patterns for the many -logically equivalent RTL expressions. - -@cindex @code{xor}, canonicalization of -@item -The only possible RTL expressions involving both bitwise exclusive-or -and bitwise negation are @code{(xor:@var{m} @var{x} @var{y})} -and @code{(not:@var{m} (xor:@var{m} @var{x} @var{y}))}.@refill - -@item -The sum of three items, one of which is a constant, will only appear in -the form - -@example -(plus:@var{m} (plus:@var{m} @var{x} @var{y}) @var{constant}) -@end example - -@item -On machines that do not use @code{cc0}, -@code{(compare @var{x} (const_int 0))} will be converted to -@var{x}.@refill - -@cindex @code{zero_extract}, canonicalization of -@cindex @code{sign_extract}, canonicalization of -@item -Equality comparisons of a group of bits (usually a single bit) with zero -will be written using @code{zero_extract} rather than the equivalent -@code{and} or @code{sign_extract} operations. - -@end itemize - -@node Expander Definitions -@section Defining RTL Sequences for Code Generation -@cindex expander definitions -@cindex code generation RTL sequences -@cindex defining RTL sequences for code generation - -On some target machines, some standard pattern names for RTL generation -cannot be handled with single insn, but a sequence of RTL insns can -represent them. For these target machines, you can write a -@code{define_expand} to specify how to generate the sequence of RTL. - -@findex define_expand -A @code{define_expand} is an RTL expression that looks almost like a -@code{define_insn}; but, unlike the latter, a @code{define_expand} is used -only for RTL generation and it can produce more than one RTL insn. - -A @code{define_expand} RTX has four operands: - -@itemize @bullet -@item -The name. Each @code{define_expand} must have a name, since the only -use for it is to refer to it by name. - -@item -The RTL template. This is a vector of RTL expressions representing -a sequence of separate instructions. Unlike @code{define_insn}, there -is no implicit surrounding @code{PARALLEL}. - -@item -The condition, a string containing a C expression. This expression is -used to express how the availability of this pattern depends on -subclasses of target machine, selected by command-line options when GNU -CC is run. This is just like the condition of a @code{define_insn} that -has a standard name. Therefore, the condition (if present) may not -depend on the data in the insn being matched, but only the -target-machine-type flags. The compiler needs to test these conditions -during initialization in order to learn exactly which named instructions -are available in a particular run. - -@item -The preparation statements, a string containing zero or more C -statements which are to be executed before RTL code is generated from -the RTL template. - -Usually these statements prepare temporary registers for use as -internal operands in the RTL template, but they can also generate RTL -insns directly by calling routines such as @code{emit_insn}, etc. -Any such insns precede the ones that come from the RTL template. -@end itemize - -Every RTL insn emitted by a @code{define_expand} must match some -@code{define_insn} in the machine description. Otherwise, the compiler -will crash when trying to generate code for the insn or trying to optimize -it. - -The RTL template, in addition to controlling generation of RTL insns, -also describes the operands that need to be specified when this pattern -is used. In particular, it gives a predicate for each operand. - -A true operand, which needs to be specified in order to generate RTL from -the pattern, should be described with a @code{match_operand} in its first -occurrence in the RTL template. This enters information on the operand's -predicate into the tables that record such things. GNU CC uses the -information to preload the operand into a register if that is required for -valid RTL code. If the operand is referred to more than once, subsequent -references should use @code{match_dup}. - -The RTL template may also refer to internal ``operands'' which are -temporary registers or labels used only within the sequence made by the -@code{define_expand}. Internal operands are substituted into the RTL -template with @code{match_dup}, never with @code{match_operand}. The -values of the internal operands are not passed in as arguments by the -compiler when it requests use of this pattern. Instead, they are computed -within the pattern, in the preparation statements. These statements -compute the values and store them into the appropriate elements of -@code{operands} so that @code{match_dup} can find them. - -There are two special macros defined for use in the preparation statements: -@code{DONE} and @code{FAIL}. Use them with a following semicolon, -as a statement. - -@table @code - -@findex DONE -@item DONE -Use the @code{DONE} macro to end RTL generation for the pattern. The -only RTL insns resulting from the pattern on this occasion will be -those already emitted by explicit calls to @code{emit_insn} within the -preparation statements; the RTL template will not be generated. - -@findex FAIL -@item FAIL -Make the pattern fail on this occasion. When a pattern fails, it means -that the pattern was not truly available. The calling routines in the -compiler will try other strategies for code generation using other patterns. - -Failure is currently supported only for binary (addition, multiplication, -shifting, etc.) and bitfield (@code{extv}, @code{extzv}, and @code{insv}) -operations. -@end table - -If the preparation falls through (invokes neither @code{DONE} nor -@code{FAIL}), then the @code{define_expand} acts like a -@code{define_insn} in that the RTL template is used to generate the -insn. - -The RTL template is not used for matching, only for generating the -initial insn list. If the preparation statement always invokes -@code{DONE} or @code{FAIL}, the RTL template may be reduced to a simple -list of operands, such as this example: - -@smallexample -@group -(define_expand "addsi3" - [(match_operand:SI 0 "register_operand" "") - (match_operand:SI 1 "register_operand" "") - (match_operand:SI 2 "register_operand" "")] -@end group -@group - "" - " -@{ - handle_add (operands[0], operands[1], operands[2]); - DONE; -@}") -@end group -@end smallexample - -Here is an example, the definition of left-shift for the SPUR chip: - -@smallexample -@group -(define_expand "ashlsi3" - [(set (match_operand:SI 0 "register_operand" "") - (ashift:SI -@end group -@group - (match_operand:SI 1 "register_operand" "") - (match_operand:SI 2 "nonmemory_operand" "")))] - "" - " -@end group -@end smallexample - -@smallexample -@group -@{ - if (GET_CODE (operands[2]) != CONST_INT - || (unsigned) INTVAL (operands[2]) > 3) - FAIL; -@}") -@end group -@end smallexample - -@noindent -This example uses @code{define_expand} so that it can generate an RTL insn -for shifting when the shift-count is in the supported range of 0 to 3 but -fail in other cases where machine insns aren't available. When it fails, -the compiler tries another strategy using different patterns (such as, a -library call). - -If the compiler were able to handle nontrivial condition-strings in -patterns with names, then it would be possible to use a -@code{define_insn} in that case. Here is another case (zero-extension -on the 68000) which makes more use of the power of @code{define_expand}: - -@smallexample -(define_expand "zero_extendhisi2" - [(set (match_operand:SI 0 "general_operand" "") - (const_int 0)) - (set (strict_low_part - (subreg:HI - (match_dup 0) - 0)) - (match_operand:HI 1 "general_operand" ""))] - "" - "operands[1] = make_safe_from (operands[1], operands[0]);") -@end smallexample - -@noindent -@findex make_safe_from -Here two RTL insns are generated, one to clear the entire output operand -and the other to copy the input operand into its low half. This sequence -is incorrect if the input operand refers to [the old value of] the output -operand, so the preparation statement makes sure this isn't so. The -function @code{make_safe_from} copies the @code{operands[1]} into a -temporary register if it refers to @code{operands[0]}. It does this -by emitting another RTL insn. - -Finally, a third example shows the use of an internal operand. -Zero-extension on the SPUR chip is done by @code{and}-ing the result -against a halfword mask. But this mask cannot be represented by a -@code{const_int} because the constant value is too large to be legitimate -on this machine. So it must be copied into a register with -@code{force_reg} and then the register used in the @code{and}. - -@smallexample -(define_expand "zero_extendhisi2" - [(set (match_operand:SI 0 "register_operand" "") - (and:SI (subreg:SI - (match_operand:HI 1 "register_operand" "") - 0) - (match_dup 2)))] - "" - "operands[2] - = force_reg (SImode, GEN_INT (65535)); ") -@end smallexample - -@strong{Note:} If the @code{define_expand} is used to serve a -standard binary or unary arithmetic operation or a bitfield operation, -then the last insn it generates must not be a @code{code_label}, -@code{barrier} or @code{note}. It must be an @code{insn}, -@code{jump_insn} or @code{call_insn}. If you don't need a real insn -at the end, emit an insn to copy the result of the operation into -itself. Such an insn will generate no code, but it can avoid problems -in the compiler.@refill - -@node Insn Splitting -@section Defining How to Split Instructions -@cindex insn splitting -@cindex instruction splitting -@cindex splitting instructions - -There are two cases where you should specify how to split a pattern into -multiple insns. On machines that have instructions requiring delay -slots (@pxref{Delay Slots}) or that have instructions whose output is -not available for multiple cycles (@pxref{Function Units}), the compiler -phases that optimize these cases need to be able to move insns into -one-instruction delay slots. However, some insns may generate more than one -machine instruction. These insns cannot be placed into a delay slot. - -Often you can rewrite the single insn as a list of individual insns, -each corresponding to one machine instruction. The disadvantage of -doing so is that it will cause the compilation to be slower and require -more space. If the resulting insns are too complex, it may also -suppress some optimizations. The compiler splits the insn if there is a -reason to believe that it might improve instruction or delay slot -scheduling. - -The insn combiner phase also splits putative insns. If three insns are -merged into one insn with a complex expression that cannot be matched by -some @code{define_insn} pattern, the combiner phase attempts to split -the complex pattern into two insns that are recognized. Usually it can -break the complex pattern into two patterns by splitting out some -subexpression. However, in some other cases, such as performing an -addition of a large constant in two insns on a RISC machine, the way to -split the addition into two insns is machine-dependent. - -@findex define_split -The @code{define_split} definition tells the compiler how to split a -complex insn into several simpler insns. It looks like this: - -@smallexample -(define_split - [@var{insn-pattern}] - "@var{condition}" - [@var{new-insn-pattern-1} - @var{new-insn-pattern-2} - @dots{}] - "@var{preparation statements}") -@end smallexample - -@var{insn-pattern} is a pattern that needs to be split and -@var{condition} is the final condition to be tested, as in a -@code{define_insn}. When an insn matching @var{insn-pattern} and -satisfying @var{condition} is found, it is replaced in the insn list -with the insns given by @var{new-insn-pattern-1}, -@var{new-insn-pattern-2}, etc. - -The @var{preparation statements} are similar to those statements that -are specified for @code{define_expand} (@pxref{Expander Definitions}) -and are executed before the new RTL is generated to prepare for the -generated code or emit some insns whose pattern is not fixed. Unlike -those in @code{define_expand}, however, these statements must not -generate any new pseudo-registers. Once reload has completed, they also -must not allocate any space in the stack frame. - -Patterns are matched against @var{insn-pattern} in two different -circumstances. If an insn needs to be split for delay slot scheduling -or insn scheduling, the insn is already known to be valid, which means -that it must have been matched by some @code{define_insn} and, if -@code{reload_completed} is non-zero, is known to satisfy the constraints -of that @code{define_insn}. In that case, the new insn patterns must -also be insns that are matched by some @code{define_insn} and, if -@code{reload_completed} is non-zero, must also satisfy the constraints -of those definitions. - -As an example of this usage of @code{define_split}, consider the following -example from @file{a29k.md}, which splits a @code{sign_extend} from -@code{HImode} to @code{SImode} into a pair of shift insns: - -@smallexample -(define_split - [(set (match_operand:SI 0 "gen_reg_operand" "") - (sign_extend:SI (match_operand:HI 1 "gen_reg_operand" "")))] - "" - [(set (match_dup 0) - (ashift:SI (match_dup 1) - (const_int 16))) - (set (match_dup 0) - (ashiftrt:SI (match_dup 0) - (const_int 16)))] - " -@{ operands[1] = gen_lowpart (SImode, operands[1]); @}") -@end smallexample - -When the combiner phase tries to split an insn pattern, it is always the -case that the pattern is @emph{not} matched by any @code{define_insn}. -The combiner pass first tries to split a single @code{set} expression -and then the same @code{set} expression inside a @code{parallel}, but -followed by a @code{clobber} of a pseudo-reg to use as a scratch -register. In these cases, the combiner expects exactly two new insn -patterns to be generated. It will verify that these patterns match some -@code{define_insn} definitions, so you need not do this test in the -@code{define_split} (of course, there is no point in writing a -@code{define_split} that will never produce insns that match). - -Here is an example of this use of @code{define_split}, taken from -@file{rs6000.md}: - -@smallexample -(define_split - [(set (match_operand:SI 0 "gen_reg_operand" "") - (plus:SI (match_operand:SI 1 "gen_reg_operand" "") - (match_operand:SI 2 "non_add_cint_operand" "")))] - "" - [(set (match_dup 0) (plus:SI (match_dup 1) (match_dup 3))) - (set (match_dup 0) (plus:SI (match_dup 0) (match_dup 4)))] -" -@{ - int low = INTVAL (operands[2]) & 0xffff; - int high = (unsigned) INTVAL (operands[2]) >> 16; - - if (low & 0x8000) - high++, low |= 0xffff0000; - - operands[3] = GEN_INT (high << 16); - operands[4] = GEN_INT (low); -@}") -@end smallexample - -Here the predicate @code{non_add_cint_operand} matches any -@code{const_int} that is @emph{not} a valid operand of a single add -insn. The add with the smaller displacement is written so that it -can be substituted into the address of a subsequent operation. - -An example that uses a scratch register, from the same file, generates -an equality comparison of a register and a large constant: - -@smallexample -(define_split - [(set (match_operand:CC 0 "cc_reg_operand" "") - (compare:CC (match_operand:SI 1 "gen_reg_operand" "") - (match_operand:SI 2 "non_short_cint_operand" ""))) - (clobber (match_operand:SI 3 "gen_reg_operand" ""))] - "find_single_use (operands[0], insn, 0) - && (GET_CODE (*find_single_use (operands[0], insn, 0)) == EQ - || GET_CODE (*find_single_use (operands[0], insn, 0)) == NE)" - [(set (match_dup 3) (xor:SI (match_dup 1) (match_dup 4))) - (set (match_dup 0) (compare:CC (match_dup 3) (match_dup 5)))] - " -@{ - /* Get the constant we are comparing against, C, and see what it - looks like sign-extended to 16 bits. Then see what constant - could be XOR'ed with C to get the sign-extended value. */ - - int c = INTVAL (operands[2]); - int sextc = (c << 16) >> 16; - int xorv = c ^ sextc; - - operands[4] = GEN_INT (xorv); - operands[5] = GEN_INT (sextc); -@}") -@end smallexample - -To avoid confusion, don't write a single @code{define_split} that -accepts some insns that match some @code{define_insn} as well as some -insns that don't. Instead, write two separate @code{define_split} -definitions, one for the insns that are valid and one for the insns that -are not valid. - -For the common case where the pattern of a define_split exactly matches the -pattern of a define_insn, use @code{define_insn_and_split}. It looks like -this: - -@smallexample -(define_insn_and_split - [@var{insn-pattern}] - "@var{condition}" - "@var{output-template}" - "@var{split-condition}" - [@var{new-insn-pattern-1} - @var{new-insn-pattern-2} - @dots{}] - "@var{preparation statements}" - [@var{insn-attributes}]) - -@end smallexample - -@var{insn-pattern}, @var{condition}, @var{output-template}, and -@var{insn-attributes} are used as in @code{define_insn}. The -@var{new-insn-pattern} vector and the @var{preparation-statements} are used as -in a @code{define_split}. The @var{split-condition} is also used as in -@code{define_split}, with the additional behavior that if the condition starts -with @samp{&&}, the condition used for the split will be the constructed as a -logical "and" of the split condition with the insn condition. For example, -from i386.md: - -@smallexample -(define_insn_and_split "zero_extendhisi2_and" - [(set (match_operand:SI 0 "register_operand" "=r") - (zero_extend:SI (match_operand:HI 1 "register_operand" "0"))) - (clobber (reg:CC 17))] - "TARGET_ZERO_EXTEND_WITH_AND && !optimize_size" - "#" - "&& reload_completed" - [(parallel [(set (match_dup 0) (and:SI (match_dup 0) (const_int 65535))) - (clobber (reg:CC 17))])] - "" - [(set_attr "type" "alu1")]) - -@end smallexample - -In this case, the actual split condition will be -"TARGET_ZERO_EXTEND_WITH_AND && !optimize_size && reload_completed." - -The @code{define_insn_and_split} construction provides exactly the same -functionality as two separate @code{define_insn} and @code{define_split} -patterns. It exists for compactness, and as a maintenance tool to prevent -having to ensure the two patterns' templates match. - -@node Peephole Definitions -@section Machine-Specific Peephole Optimizers -@cindex peephole optimizer definitions -@cindex defining peephole optimizers - -In addition to instruction patterns the @file{md} file may contain -definitions of machine-specific peephole optimizations. - -The combiner does not notice certain peephole optimizations when the data -flow in the program does not suggest that it should try them. For example, -sometimes two consecutive insns related in purpose can be combined even -though the second one does not appear to use a register computed in the -first one. A machine-specific peephole optimizer can detect such -opportunities. - -There are two forms of peephole definitions that may be used. The -original @code{define_peephole} is run at assembly output time to -match insns and substitute assembly text. Use of @code{define_peephole} -is deprecated. - -A newer @code{define_peephole2} matches insns and substitutes new -insns. The @code{peephole2} pass is run after register allocation -but before scheduling, which may result in much better code for -targets that do scheduling. - -@menu -* define_peephole:: RTL to Text Peephole Optimizers -* define_peephole2:: RTL to RTL Peephole Optimizers -@end menu - -@node define_peephole -@subsection RTL to Text Peephole Optimizers -@findex define_peephole - -@need 1000 -A definition looks like this: - -@smallexample -(define_peephole - [@var{insn-pattern-1} - @var{insn-pattern-2} - @dots{}] - "@var{condition}" - "@var{template}" - "@var{optional insn-attributes}") -@end smallexample - -@noindent -The last string operand may be omitted if you are not using any -machine-specific information in this machine description. If present, -it must obey the same rules as in a @code{define_insn}. - -In this skeleton, @var{insn-pattern-1} and so on are patterns to match -consecutive insns. The optimization applies to a sequence of insns when -@var{insn-pattern-1} matches the first one, @var{insn-pattern-2} matches -the next, and so on.@refill - -Each of the insns matched by a peephole must also match a -@code{define_insn}. Peepholes are checked only at the last stage just -before code generation, and only optionally. Therefore, any insn which -would match a peephole but no @code{define_insn} will cause a crash in code -generation in an unoptimized compilation, or at various optimization -stages. - -The operands of the insns are matched with @code{match_operands}, -@code{match_operator}, and @code{match_dup}, as usual. What is not -usual is that the operand numbers apply to all the insn patterns in the -definition. So, you can check for identical operands in two insns by -using @code{match_operand} in one insn and @code{match_dup} in the -other. - -The operand constraints used in @code{match_operand} patterns do not have -any direct effect on the applicability of the peephole, but they will -be validated afterward, so make sure your constraints are general enough -to apply whenever the peephole matches. If the peephole matches -but the constraints are not satisfied, the compiler will crash. - -It is safe to omit constraints in all the operands of the peephole; or -you can write constraints which serve as a double-check on the criteria -previously tested. - -Once a sequence of insns matches the patterns, the @var{condition} is -checked. This is a C expression which makes the final decision whether to -perform the optimization (we do so if the expression is nonzero). If -@var{condition} is omitted (in other words, the string is empty) then the -optimization is applied to every sequence of insns that matches the -patterns. - -The defined peephole optimizations are applied after register allocation -is complete. Therefore, the peephole definition can check which -operands have ended up in which kinds of registers, just by looking at -the operands. - -@findex prev_active_insn -The way to refer to the operands in @var{condition} is to write -@code{operands[@var{i}]} for operand number @var{i} (as matched by -@code{(match_operand @var{i} @dots{})}). Use the variable @code{insn} -to refer to the last of the insns being matched; use -@code{prev_active_insn} to find the preceding insns. - -@findex dead_or_set_p -When optimizing computations with intermediate results, you can use -@var{condition} to match only when the intermediate results are not used -elsewhere. Use the C expression @code{dead_or_set_p (@var{insn}, -@var{op})}, where @var{insn} is the insn in which you expect the value -to be used for the last time (from the value of @code{insn}, together -with use of @code{prev_nonnote_insn}), and @var{op} is the intermediate -value (from @code{operands[@var{i}]}).@refill - -Applying the optimization means replacing the sequence of insns with one -new insn. The @var{template} controls ultimate output of assembler code -for this combined insn. It works exactly like the template of a -@code{define_insn}. Operand numbers in this template are the same ones -used in matching the original sequence of insns. - -The result of a defined peephole optimizer does not need to match any of -the insn patterns in the machine description; it does not even have an -opportunity to match them. The peephole optimizer definition itself serves -as the insn pattern to control how the insn is output. - -Defined peephole optimizers are run as assembler code is being output, -so the insns they produce are never combined or rearranged in any way. - -Here is an example, taken from the 68000 machine description: - -@smallexample -(define_peephole - [(set (reg:SI 15) (plus:SI (reg:SI 15) (const_int 4))) - (set (match_operand:DF 0 "register_operand" "=f") - (match_operand:DF 1 "register_operand" "ad"))] - "FP_REG_P (operands[0]) && ! FP_REG_P (operands[1])" - "* -@{ - rtx xoperands[2]; - xoperands[1] = gen_rtx (REG, SImode, REGNO (operands[1]) + 1); -#ifdef MOTOROLA - output_asm_insn (\"move.l %1,(sp)\", xoperands); - output_asm_insn (\"move.l %1,-(sp)\", operands); - return \"fmove.d (sp)+,%0\"; -#else - output_asm_insn (\"movel %1,sp@@\", xoperands); - output_asm_insn (\"movel %1,sp@@-\", operands); - return \"fmoved sp@@+,%0\"; -#endif -@} -") -@end smallexample - -@need 1000 -The effect of this optimization is to change - -@smallexample -@group -jbsr _foobar -addql #4,sp -movel d1,sp@@- -movel d0,sp@@- -fmoved sp@@+,fp0 -@end group -@end smallexample - -@noindent -into - -@smallexample -@group -jbsr _foobar -movel d1,sp@@ -movel d0,sp@@- -fmoved sp@@+,fp0 -@end group -@end smallexample - -@ignore -@findex CC_REVERSED -If a peephole matches a sequence including one or more jump insns, you must -take account of the flags such as @code{CC_REVERSED} which specify that the -condition codes are represented in an unusual manner. The compiler -automatically alters any ordinary conditional jumps which occur in such -situations, but the compiler cannot alter jumps which have been replaced by -peephole optimizations. So it is up to you to alter the assembler code -that the peephole produces. Supply C code to write the assembler output, -and in this C code check the condition code status flags and change the -assembler code as appropriate. -@end ignore - -@var{insn-pattern-1} and so on look @emph{almost} like the second -operand of @code{define_insn}. There is one important difference: the -second operand of @code{define_insn} consists of one or more RTX's -enclosed in square brackets. Usually, there is only one: then the same -action can be written as an element of a @code{define_peephole}. But -when there are multiple actions in a @code{define_insn}, they are -implicitly enclosed in a @code{parallel}. Then you must explicitly -write the @code{parallel}, and the square brackets within it, in the -@code{define_peephole}. Thus, if an insn pattern looks like this, - -@smallexample -(define_insn "divmodsi4" - [(set (match_operand:SI 0 "general_operand" "=d") - (div:SI (match_operand:SI 1 "general_operand" "0") - (match_operand:SI 2 "general_operand" "dmsK"))) - (set (match_operand:SI 3 "general_operand" "=d") - (mod:SI (match_dup 1) (match_dup 2)))] - "TARGET_68020" - "divsl%.l %2,%3:%0") -@end smallexample - -@noindent -then the way to mention this insn in a peephole is as follows: - -@smallexample -(define_peephole - [@dots{} - (parallel - [(set (match_operand:SI 0 "general_operand" "=d") - (div:SI (match_operand:SI 1 "general_operand" "0") - (match_operand:SI 2 "general_operand" "dmsK"))) - (set (match_operand:SI 3 "general_operand" "=d") - (mod:SI (match_dup 1) (match_dup 2)))]) - @dots{}] - @dots{}) -@end smallexample - -@node define_peephole2 -@subsection RTL to RTL Peephole Optimizers -@findex define_peephole2 - -The @code{define_peephole2} definition tells the compiler how to -substitute one sequence of instructions for another sequence, -what additional scratch registers may be needed and what their -lifetimes must be. - -@smallexample -(define_peephole2 - [@var{insn-pattern-1} - @var{insn-pattern-2} - @dots{}] - "@var{condition}" - [@var{new-insn-pattern-1} - @var{new-insn-pattern-2} - @dots{}] - "@var{preparation statements}") -@end smallexample - -The definition is almost identical to @code{define_split} -(@pxref{Insn Splitting}) except that the pattern to match is not a -single instruction, but a sequence of instructions. - -It is possible to request additional scratch registers for use in the -output template. If appropriate registers are not free, the pattern -will simply not match. - -@findex match_scratch -@findex match_dup -Scratch registers are requested with a @code{match_scratch} pattern at -the top level of the input pattern. The allocated register (initially) will -be dead at the point requested within the original sequence. If the scratch -is used at more than a single point, a @code{match_dup} pattern at the -top level of the input pattern marks the last position in the input sequence -at which the register must be available. - -Here is an example from the IA-32 machine description: - -@smallexample -(define_peephole2 - [(match_scratch:SI 2 "r") - (parallel [(set (match_operand:SI 0 "register_operand" "") - (match_operator:SI 3 "arith_or_logical_operator" - [(match_dup 0) - (match_operand:SI 1 "memory_operand" "")])) - (clobber (reg:CC 17))])] - "! optimize_size && ! TARGET_READ_MODIFY" - [(set (match_dup 2) (match_dup 1)) - (parallel [(set (match_dup 0) - (match_op_dup 3 [(match_dup 0) (match_dup 2)])) - (clobber (reg:CC 17))])] - "") -@end smallexample - -@noindent -This pattern tries to split a load from its use in the hopes that we'll be -able to schedule around the memory load latency. It allocates a single -@code{SImode} register of class @code{GENERAL_REGS} (@code{"r"}) that needs -to be live only at the point just before the arithmetic. - -A real example requiring extended scratch lifetimes is harder to come by, -so here's a silly made-up example: - -@smallexample -(define_peephole2 - [(match_scratch:SI 4 "r") - (set (match_operand:SI 0 "" "") (match_operand:SI 1 "" "")) - (set (match_operand:SI 2 "" "") (match_dup 1)) - (match_dup 4) - (set (match_operand:SI 3 "" "") (match_dup 1))] - "@var{determine 1 does not overlap 0 and 2}" - [(set (match_dup 4) (match_dup 1)) - (set (match_dup 0) (match_dup 4)) - (set (match_dup 2) (match_dup 4))] - (set (match_dup 3) (match_dup 4))] - "") -@end smallexample - -@noindent -If we had not added the @code{(match_dup 4)} in the middle of the input -sequence, it might have been the case that the register we chose at the -beginning of the sequence is killed by the first or second @code{set}. - -@node Insn Attributes -@section Instruction Attributes -@cindex insn attributes -@cindex instruction attributes - -In addition to describing the instruction supported by the target machine, -the @file{md} file also defines a group of @dfn{attributes} and a set of -values for each. Every generated insn is assigned a value for each attribute. -One possible attribute would be the effect that the insn has on the machine's -condition code. This attribute can then be used by @code{NOTICE_UPDATE_CC} -to track the condition codes. - -@menu -* Defining Attributes:: Specifying attributes and their values. -* Expressions:: Valid expressions for attribute values. -* Tagging Insns:: Assigning attribute values to insns. -* Attr Example:: An example of assigning attributes. -* Insn Lengths:: Computing the length of insns. -* Constant Attributes:: Defining attributes that are constant. -* Delay Slots:: Defining delay slots required for a machine. -* Function Units:: Specifying information for insn scheduling. -@end menu - -@node Defining Attributes -@subsection Defining Attributes and their Values -@cindex defining attributes and their values -@cindex attributes, defining - -@findex define_attr -The @code{define_attr} expression is used to define each attribute required -by the target machine. It looks like: - -@smallexample -(define_attr @var{name} @var{list-of-values} @var{default}) -@end smallexample - -@var{name} is a string specifying the name of the attribute being defined. - -@var{list-of-values} is either a string that specifies a comma-separated -list of values that can be assigned to the attribute, or a null string to -indicate that the attribute takes numeric values. - -@var{default} is an attribute expression that gives the value of this -attribute for insns that match patterns whose definition does not include -an explicit value for this attribute. @xref{Attr Example}, for more -information on the handling of defaults. @xref{Constant Attributes}, -for information on attributes that do not depend on any particular insn. - -@findex insn-attr.h -For each defined attribute, a number of definitions are written to the -@file{insn-attr.h} file. For cases where an explicit set of values is -specified for an attribute, the following are defined: - -@itemize @bullet -@item -A @samp{#define} is written for the symbol @samp{HAVE_ATTR_@var{name}}. - -@item -An enumeral class is defined for @samp{attr_@var{name}} with -elements of the form @samp{@var{upper-name}_@var{upper-value}} where -the attribute name and value are first converted to upper case. - -@item -A function @samp{get_attr_@var{name}} is defined that is passed an insn and -returns the attribute value for that insn. -@end itemize - -For example, if the following is present in the @file{md} file: - -@smallexample -(define_attr "type" "branch,fp,load,store,arith" @dots{}) -@end smallexample - -@noindent -the following lines will be written to the file @file{insn-attr.h}. - -@smallexample -#define HAVE_ATTR_type -enum attr_type @{TYPE_BRANCH, TYPE_FP, TYPE_LOAD, - TYPE_STORE, TYPE_ARITH@}; -extern enum attr_type get_attr_type (); -@end smallexample - -If the attribute takes numeric values, no @code{enum} type will be -defined and the function to obtain the attribute's value will return -@code{int}. - -@node Expressions -@subsection Attribute Expressions -@cindex attribute expressions - -RTL expressions used to define attributes use the codes described above -plus a few specific to attribute definitions, to be discussed below. -Attribute value expressions must have one of the following forms: - -@table @code -@cindex @code{const_int} and attributes -@item (const_int @var{i}) -The integer @var{i} specifies the value of a numeric attribute. @var{i} -must be non-negative. - -The value of a numeric attribute can be specified either with a -@code{const_int}, or as an integer represented as a string in -@code{const_string}, @code{eq_attr} (see below), @code{attr}, -@code{symbol_ref}, simple arithmetic expressions, and @code{set_attr} -overrides on specific instructions (@pxref{Tagging Insns}). - -@cindex @code{const_string} and attributes -@item (const_string @var{value}) -The string @var{value} specifies a constant attribute value. -If @var{value} is specified as @samp{"*"}, it means that the default value of -the attribute is to be used for the insn containing this expression. -@samp{"*"} obviously cannot be used in the @var{default} expression -of a @code{define_attr}.@refill - -If the attribute whose value is being specified is numeric, @var{value} -must be a string containing a non-negative integer (normally -@code{const_int} would be used in this case). Otherwise, it must -contain one of the valid values for the attribute. - -@cindex @code{if_then_else} and attributes -@item (if_then_else @var{test} @var{true-value} @var{false-value}) -@var{test} specifies an attribute test, whose format is defined below. -The value of this expression is @var{true-value} if @var{test} is true, -otherwise it is @var{false-value}. - -@cindex @code{cond} and attributes -@item (cond [@var{test1} @var{value1} @dots{}] @var{default}) -The first operand of this expression is a vector containing an even -number of expressions and consisting of pairs of @var{test} and @var{value} -expressions. The value of the @code{cond} expression is that of the -@var{value} corresponding to the first true @var{test} expression. If -none of the @var{test} expressions are true, the value of the @code{cond} -expression is that of the @var{default} expression. -@end table - -@var{test} expressions can have one of the following forms: - -@table @code -@cindex @code{const_int} and attribute tests -@item (const_int @var{i}) -This test is true if @var{i} is non-zero and false otherwise. - -@cindex @code{not} and attributes -@cindex @code{ior} and attributes -@cindex @code{and} and attributes -@item (not @var{test}) -@itemx (ior @var{test1} @var{test2}) -@itemx (and @var{test1} @var{test2}) -These tests are true if the indicated logical function is true. - -@cindex @code{match_operand} and attributes -@item (match_operand:@var{m} @var{n} @var{pred} @var{constraints}) -This test is true if operand @var{n} of the insn whose attribute value -is being determined has mode @var{m} (this part of the test is ignored -if @var{m} is @code{VOIDmode}) and the function specified by the string -@var{pred} returns a non-zero value when passed operand @var{n} and mode -@var{m} (this part of the test is ignored if @var{pred} is the null -string). - -The @var{constraints} operand is ignored and should be the null string. - -@cindex @code{le} and attributes -@cindex @code{leu} and attributes -@cindex @code{lt} and attributes -@cindex @code{gt} and attributes -@cindex @code{gtu} and attributes -@cindex @code{ge} and attributes -@cindex @code{geu} and attributes -@cindex @code{ne} and attributes -@cindex @code{eq} and attributes -@cindex @code{plus} and attributes -@cindex @code{minus} and attributes -@cindex @code{mult} and attributes -@cindex @code{div} and attributes -@cindex @code{mod} and attributes -@cindex @code{abs} and attributes -@cindex @code{neg} and attributes -@cindex @code{ashift} and attributes -@cindex @code{lshiftrt} and attributes -@cindex @code{ashiftrt} and attributes -@item (le @var{arith1} @var{arith2}) -@itemx (leu @var{arith1} @var{arith2}) -@itemx (lt @var{arith1} @var{arith2}) -@itemx (ltu @var{arith1} @var{arith2}) -@itemx (gt @var{arith1} @var{arith2}) -@itemx (gtu @var{arith1} @var{arith2}) -@itemx (ge @var{arith1} @var{arith2}) -@itemx (geu @var{arith1} @var{arith2}) -@itemx (ne @var{arith1} @var{arith2}) -@itemx (eq @var{arith1} @var{arith2}) -These tests are true if the indicated comparison of the two arithmetic -expressions is true. Arithmetic expressions are formed with -@code{plus}, @code{minus}, @code{mult}, @code{div}, @code{mod}, -@code{abs}, @code{neg}, @code{and}, @code{ior}, @code{xor}, @code{not}, -@code{ashift}, @code{lshiftrt}, and @code{ashiftrt} expressions.@refill - -@findex get_attr -@code{const_int} and @code{symbol_ref} are always valid terms (@pxref{Insn -Lengths},for additional forms). @code{symbol_ref} is a string -denoting a C expression that yields an @code{int} when evaluated by the -@samp{get_attr_@dots{}} routine. It should normally be a global -variable.@refill - -@findex eq_attr -@item (eq_attr @var{name} @var{value}) -@var{name} is a string specifying the name of an attribute. - -@var{value} is a string that is either a valid value for attribute -@var{name}, a comma-separated list of values, or @samp{!} followed by a -value or list. If @var{value} does not begin with a @samp{!}, this -test is true if the value of the @var{name} attribute of the current -insn is in the list specified by @var{value}. If @var{value} begins -with a @samp{!}, this test is true if the attribute's value is -@emph{not} in the specified list. - -For example, - -@smallexample -(eq_attr "type" "load,store") -@end smallexample - -@noindent -is equivalent to - -@smallexample -(ior (eq_attr "type" "load") (eq_attr "type" "store")) -@end smallexample - -If @var{name} specifies an attribute of @samp{alternative}, it refers to the -value of the compiler variable @code{which_alternative} -(@pxref{Output Statement}) and the values must be small integers. For -example,@refill - -@smallexample -(eq_attr "alternative" "2,3") -@end smallexample - -@noindent -is equivalent to - -@smallexample -(ior (eq (symbol_ref "which_alternative") (const_int 2)) - (eq (symbol_ref "which_alternative") (const_int 3))) -@end smallexample - -Note that, for most attributes, an @code{eq_attr} test is simplified in cases -where the value of the attribute being tested is known for all insns matching -a particular pattern. This is by far the most common case.@refill - -@findex attr_flag -@item (attr_flag @var{name}) -The value of an @code{attr_flag} expression is true if the flag -specified by @var{name} is true for the @code{insn} currently being -scheduled. - -@var{name} is a string specifying one of a fixed set of flags to test. -Test the flags @code{forward} and @code{backward} to determine the -direction of a conditional branch. Test the flags @code{very_likely}, -@code{likely}, @code{very_unlikely}, and @code{unlikely} to determine -if a conditional branch is expected to be taken. - -If the @code{very_likely} flag is true, then the @code{likely} flag is also -true. Likewise for the @code{very_unlikely} and @code{unlikely} flags. - -This example describes a conditional branch delay slot which -can be nullified for forward branches that are taken (annul-true) or -for backward branches which are not taken (annul-false). - -@smallexample -(define_delay (eq_attr "type" "cbranch") - [(eq_attr "in_branch_delay" "true") - (and (eq_attr "in_branch_delay" "true") - (attr_flag "forward")) - (and (eq_attr "in_branch_delay" "true") - (attr_flag "backward"))]) -@end smallexample - -The @code{forward} and @code{backward} flags are false if the current -@code{insn} being scheduled is not a conditional branch. - -The @code{very_likely} and @code{likely} flags are true if the -@code{insn} being scheduled is not a conditional branch. -The @code{very_unlikely} and @code{unlikely} flags are false if the -@code{insn} being scheduled is not a conditional branch. - -@code{attr_flag} is only used during delay slot scheduling and has no -meaning to other passes of the compiler. - -@findex attr -@item (attr @var{name}) -The value of another attribute is returned. This is most useful -for numeric attributes, as @code{eq_attr} and @code{attr_flag} -produce more efficient code for non-numeric attributes. -@end table - -@node Tagging Insns -@subsection Assigning Attribute Values to Insns -@cindex tagging insns -@cindex assigning attribute values to insns - -The value assigned to an attribute of an insn is primarily determined by -which pattern is matched by that insn (or which @code{define_peephole} -generated it). Every @code{define_insn} and @code{define_peephole} can -have an optional last argument to specify the values of attributes for -matching insns. The value of any attribute not specified in a particular -insn is set to the default value for that attribute, as specified in its -@code{define_attr}. Extensive use of default values for attributes -permits the specification of the values for only one or two attributes -in the definition of most insn patterns, as seen in the example in the -next section.@refill - -The optional last argument of @code{define_insn} and -@code{define_peephole} is a vector of expressions, each of which defines -the value for a single attribute. The most general way of assigning an -attribute's value is to use a @code{set} expression whose first operand is an -@code{attr} expression giving the name of the attribute being set. The -second operand of the @code{set} is an attribute expression -(@pxref{Expressions}) giving the value of the attribute.@refill - -When the attribute value depends on the @samp{alternative} attribute -(i.e., which is the applicable alternative in the constraint of the -insn), the @code{set_attr_alternative} expression can be used. It -allows the specification of a vector of attribute expressions, one for -each alternative. - -@findex set_attr -When the generality of arbitrary attribute expressions is not required, -the simpler @code{set_attr} expression can be used, which allows -specifying a string giving either a single attribute value or a list -of attribute values, one for each alternative. - -The form of each of the above specifications is shown below. In each case, -@var{name} is a string specifying the attribute to be set. - -@table @code -@item (set_attr @var{name} @var{value-string}) -@var{value-string} is either a string giving the desired attribute value, -or a string containing a comma-separated list giving the values for -succeeding alternatives. The number of elements must match the number -of alternatives in the constraint of the insn pattern. - -Note that it may be useful to specify @samp{*} for some alternative, in -which case the attribute will assume its default value for insns matching -that alternative. - -@findex set_attr_alternative -@item (set_attr_alternative @var{name} [@var{value1} @var{value2} @dots{}]) -Depending on the alternative of the insn, the value will be one of the -specified values. This is a shorthand for using a @code{cond} with -tests on the @samp{alternative} attribute. - -@findex attr -@item (set (attr @var{name}) @var{value}) -The first operand of this @code{set} must be the special RTL expression -@code{attr}, whose sole operand is a string giving the name of the -attribute being set. @var{value} is the value of the attribute. -@end table - -The following shows three different ways of representing the same -attribute value specification: - -@smallexample -(set_attr "type" "load,store,arith") - -(set_attr_alternative "type" - [(const_string "load") (const_string "store") - (const_string "arith")]) - -(set (attr "type") - (cond [(eq_attr "alternative" "1") (const_string "load") - (eq_attr "alternative" "2") (const_string "store")] - (const_string "arith"))) -@end smallexample - -@need 1000 -@findex define_asm_attributes -The @code{define_asm_attributes} expression provides a mechanism to -specify the attributes assigned to insns produced from an @code{asm} -statement. It has the form: - -@smallexample -(define_asm_attributes [@var{attr-sets}]) -@end smallexample - -@noindent -where @var{attr-sets} is specified the same as for both the -@code{define_insn} and the @code{define_peephole} expressions. - -These values will typically be the ``worst case'' attribute values. For -example, they might indicate that the condition code will be clobbered. - -A specification for a @code{length} attribute is handled specially. The -way to compute the length of an @code{asm} insn is to multiply the -length specified in the expression @code{define_asm_attributes} by the -number of machine instructions specified in the @code{asm} statement, -determined by counting the number of semicolons and newlines in the -string. Therefore, the value of the @code{length} attribute specified -in a @code{define_asm_attributes} should be the maximum possible length -of a single machine instruction. - -@node Attr Example -@subsection Example of Attribute Specifications -@cindex attribute specifications example -@cindex attribute specifications - -The judicious use of defaulting is important in the efficient use of -insn attributes. Typically, insns are divided into @dfn{types} and an -attribute, customarily called @code{type}, is used to represent this -value. This attribute is normally used only to define the default value -for other attributes. An example will clarify this usage. - -Assume we have a RISC machine with a condition code and in which only -full-word operations are performed in registers. Let us assume that we -can divide all insns into loads, stores, (integer) arithmetic -operations, floating point operations, and branches. - -Here we will concern ourselves with determining the effect of an insn on -the condition code and will limit ourselves to the following possible -effects: The condition code can be set unpredictably (clobbered), not -be changed, be set to agree with the results of the operation, or only -changed if the item previously set into the condition code has been -modified. - -Here is part of a sample @file{md} file for such a machine: - -@smallexample -(define_attr "type" "load,store,arith,fp,branch" (const_string "arith")) - -(define_attr "cc" "clobber,unchanged,set,change0" - (cond [(eq_attr "type" "load") - (const_string "change0") - (eq_attr "type" "store,branch") - (const_string "unchanged") - (eq_attr "type" "arith") - (if_then_else (match_operand:SI 0 "" "") - (const_string "set") - (const_string "clobber"))] - (const_string "clobber"))) - -(define_insn "" - [(set (match_operand:SI 0 "general_operand" "=r,r,m") - (match_operand:SI 1 "general_operand" "r,m,r"))] - "" - "@@ - move %0,%1 - load %0,%1 - store %0,%1" - [(set_attr "type" "arith,load,store")]) -@end smallexample - -Note that we assume in the above example that arithmetic operations -performed on quantities smaller than a machine word clobber the condition -code since they will set the condition code to a value corresponding to the -full-word result. - -@node Insn Lengths -@subsection Computing the Length of an Insn -@cindex insn lengths, computing -@cindex computing the length of an insn - -For many machines, multiple types of branch instructions are provided, each -for different length branch displacements. In most cases, the assembler -will choose the correct instruction to use. However, when the assembler -cannot do so, GCC can when a special attribute, the @samp{length} -attribute, is defined. This attribute must be defined to have numeric -values by specifying a null string in its @code{define_attr}. - -In the case of the @samp{length} attribute, two additional forms of -arithmetic terms are allowed in test expressions: - -@table @code -@cindex @code{match_dup} and attributes -@item (match_dup @var{n}) -This refers to the address of operand @var{n} of the current insn, which -must be a @code{label_ref}. - -@cindex @code{pc} and attributes -@item (pc) -This refers to the address of the @emph{current} insn. It might have -been more consistent with other usage to make this the address of the -@emph{next} insn but this would be confusing because the length of the -current insn is to be computed. -@end table - -@cindex @code{addr_vec}, length of -@cindex @code{addr_diff_vec}, length of -For normal insns, the length will be determined by value of the -@samp{length} attribute. In the case of @code{addr_vec} and -@code{addr_diff_vec} insn patterns, the length is computed as -the number of vectors multiplied by the size of each vector. - -Lengths are measured in addressable storage units (bytes). - -The following macros can be used to refine the length computation: - -@table @code -@findex FIRST_INSN_ADDRESS -@item FIRST_INSN_ADDRESS -When the @code{length} insn attribute is used, this macro specifies the -value to be assigned to the address of the first insn in a function. If -not specified, 0 is used. - -@findex ADJUST_INSN_LENGTH -@item ADJUST_INSN_LENGTH (@var{insn}, @var{length}) -If defined, modifies the length assigned to instruction @var{insn} as a -function of the context in which it is used. @var{length} is an lvalue -that contains the initially computed length of the insn and should be -updated with the correct length of the insn. - -This macro will normally not be required. A case in which it is -required is the ROMP. On this machine, the size of an @code{addr_vec} -insn must be increased by two to compensate for the fact that alignment -may be required. -@end table - -@findex get_attr_length -The routine that returns @code{get_attr_length} (the value of the -@code{length} attribute) can be used by the output routine to -determine the form of the branch instruction to be written, as the -example below illustrates. - -As an example of the specification of variable-length branches, consider -the IBM 360. If we adopt the convention that a register will be set to -the starting address of a function, we can jump to labels within 4k of -the start using a four-byte instruction. Otherwise, we need a six-byte -sequence to load the address from memory and then branch to it. - -On such a machine, a pattern for a branch instruction might be specified -as follows: - -@smallexample -(define_insn "jump" - [(set (pc) - (label_ref (match_operand 0 "" "")))] - "" - "* -@{ - return (get_attr_length (insn) == 4 - ? \"b %l0\" : \"l r15,=a(%l0); br r15\"); -@}" - [(set (attr "length") (if_then_else (lt (match_dup 0) (const_int 4096)) - (const_int 4) - (const_int 6)))]) -@end smallexample - -@node Constant Attributes -@subsection Constant Attributes -@cindex constant attributes - -A special form of @code{define_attr}, where the expression for the -default value is a @code{const} expression, indicates an attribute that -is constant for a given run of the compiler. Constant attributes may be -used to specify which variety of processor is used. For example, - -@smallexample -(define_attr "cpu" "m88100,m88110,m88000" - (const - (cond [(symbol_ref "TARGET_88100") (const_string "m88100") - (symbol_ref "TARGET_88110") (const_string "m88110")] - (const_string "m88000")))) - -(define_attr "memory" "fast,slow" - (const - (if_then_else (symbol_ref "TARGET_FAST_MEM") - (const_string "fast") - (const_string "slow")))) -@end smallexample - -The routine generated for constant attributes has no parameters as it -does not depend on any particular insn. RTL expressions used to define -the value of a constant attribute may use the @code{symbol_ref} form, -but may not use either the @code{match_operand} form or @code{eq_attr} -forms involving insn attributes. - -@node Delay Slots -@subsection Delay Slot Scheduling -@cindex delay slots, defining - -The insn attribute mechanism can be used to specify the requirements for -delay slots, if any, on a target machine. An instruction is said to -require a @dfn{delay slot} if some instructions that are physically -after the instruction are executed as if they were located before it. -Classic examples are branch and call instructions, which often execute -the following instruction before the branch or call is performed. - -On some machines, conditional branch instructions can optionally -@dfn{annul} instructions in the delay slot. This means that the -instruction will not be executed for certain branch outcomes. Both -instructions that annul if the branch is true and instructions that -annul if the branch is false are supported. - -Delay slot scheduling differs from instruction scheduling in that -determining whether an instruction needs a delay slot is dependent only -on the type of instruction being generated, not on data flow between the -instructions. See the next section for a discussion of data-dependent -instruction scheduling. - -@findex define_delay -The requirement of an insn needing one or more delay slots is indicated -via the @code{define_delay} expression. It has the following form: - -@smallexample -(define_delay @var{test} - [@var{delay-1} @var{annul-true-1} @var{annul-false-1} - @var{delay-2} @var{annul-true-2} @var{annul-false-2} - @dots{}]) -@end smallexample - -@var{test} is an attribute test that indicates whether this -@code{define_delay} applies to a particular insn. If so, the number of -required delay slots is determined by the length of the vector specified -as the second argument. An insn placed in delay slot @var{n} must -satisfy attribute test @var{delay-n}. @var{annul-true-n} is an -attribute test that specifies which insns may be annulled if the branch -is true. Similarly, @var{annul-false-n} specifies which insns in the -delay slot may be annulled if the branch is false. If annulling is not -supported for that delay slot, @code{(nil)} should be coded.@refill - -For example, in the common case where branch and call insns require -a single delay slot, which may contain any insn other than a branch or -call, the following would be placed in the @file{md} file: - -@smallexample -(define_delay (eq_attr "type" "branch,call") - [(eq_attr "type" "!branch,call") (nil) (nil)]) -@end smallexample - -Multiple @code{define_delay} expressions may be specified. In this -case, each such expression specifies different delay slot requirements -and there must be no insn for which tests in two @code{define_delay} -expressions are both true. - -For example, if we have a machine that requires one delay slot for branches -but two for calls, no delay slot can contain a branch or call insn, -and any valid insn in the delay slot for the branch can be annulled if the -branch is true, we might represent this as follows: - -@smallexample -(define_delay (eq_attr "type" "branch") - [(eq_attr "type" "!branch,call") - (eq_attr "type" "!branch,call") - (nil)]) - -(define_delay (eq_attr "type" "call") - [(eq_attr "type" "!branch,call") (nil) (nil) - (eq_attr "type" "!branch,call") (nil) (nil)]) -@end smallexample -@c the above is *still* too long. --mew 4feb93 - -@node Function Units -@subsection Specifying Function Units -@cindex function units, for scheduling - -On most RISC machines, there are instructions whose results are not -available for a specific number of cycles. Common cases are instructions -that load data from memory. On many machines, a pipeline stall will result -if the data is referenced too soon after the load instruction. - -In addition, many newer microprocessors have multiple function units, usually -one for integer and one for floating point, and often will incur pipeline -stalls when a result that is needed is not yet ready. - -The descriptions in this section allow the specification of how much -time must elapse between the execution of an instruction and the time -when its result is used. It also allows specification of when the -execution of an instruction will delay execution of similar instructions -due to function unit conflicts. - -For the purposes of the specifications in this section, a machine is -divided into @dfn{function units}, each of which execute a specific -class of instructions in first-in-first-out order. Function units that -accept one instruction each cycle and allow a result to be used in the -succeeding instruction (usually via forwarding) need not be specified. -Classic RISC microprocessors will normally have a single function unit, -which we can call @samp{memory}. The newer ``superscalar'' processors -will often have function units for floating point operations, usually at -least a floating point adder and multiplier. - -@findex define_function_unit -Each usage of a function units by a class of insns is specified with a -@code{define_function_unit} expression, which looks like this: - -@smallexample -(define_function_unit @var{name} @var{multiplicity} @var{simultaneity} - @var{test} @var{ready-delay} @var{issue-delay} - [@var{conflict-list}]) -@end smallexample - -@var{name} is a string giving the name of the function unit. - -@var{multiplicity} is an integer specifying the number of identical -units in the processor. If more than one unit is specified, they will -be scheduled independently. Only truly independent units should be -counted; a pipelined unit should be specified as a single unit. (The -only common example of a machine that has multiple function units for a -single instruction class that are truly independent and not pipelined -are the two multiply and two increment units of the CDC 6600.) - -@var{simultaneity} specifies the maximum number of insns that can be -executing in each instance of the function unit simultaneously or zero -if the unit is pipelined and has no limit. - -All @code{define_function_unit} definitions referring to function unit -@var{name} must have the same name and values for @var{multiplicity} and -@var{simultaneity}. - -@var{test} is an attribute test that selects the insns we are describing -in this definition. Note that an insn may use more than one function -unit and a function unit may be specified in more than one -@code{define_function_unit}. - -@var{ready-delay} is an integer that specifies the number of cycles -after which the result of the instruction can be used without -introducing any stalls. - -@var{issue-delay} is an integer that specifies the number of cycles -after the instruction matching the @var{test} expression begins using -this unit until a subsequent instruction can begin. A cost of @var{N} -indicates an @var{N-1} cycle delay. A subsequent instruction may also -be delayed if an earlier instruction has a longer @var{ready-delay} -value. This blocking effect is computed using the @var{simultaneity}, -@var{ready-delay}, @var{issue-delay}, and @var{conflict-list} terms. -For a normal non-pipelined function unit, @var{simultaneity} is one, the -unit is taken to block for the @var{ready-delay} cycles of the executing -insn, and smaller values of @var{issue-delay} are ignored. - -@var{conflict-list} is an optional list giving detailed conflict costs -for this unit. If specified, it is a list of condition test expressions -to be applied to insns chosen to execute in @var{name} following the -particular insn matching @var{test} that is already executing in -@var{name}. For each insn in the list, @var{issue-delay} specifies the -conflict cost; for insns not in the list, the cost is zero. If not -specified, @var{conflict-list} defaults to all instructions that use the -function unit. - -Typical uses of this vector are where a floating point function unit can -pipeline either single- or double-precision operations, but not both, or -where a memory unit can pipeline loads, but not stores, etc. - -As an example, consider a classic RISC machine where the result of a -load instruction is not available for two cycles (a single ``delay'' -instruction is required) and where only one load instruction can be executed -simultaneously. This would be specified as: - -@smallexample -(define_function_unit "memory" 1 1 (eq_attr "type" "load") 2 0) -@end smallexample - -For the case of a floating point function unit that can pipeline either -single or double precision, but not both, the following could be specified: - -@smallexample -(define_function_unit - "fp" 1 0 (eq_attr "type" "sp_fp") 4 4 [(eq_attr "type" "dp_fp")]) -(define_function_unit - "fp" 1 0 (eq_attr "type" "dp_fp") 4 4 [(eq_attr "type" "sp_fp")]) -@end smallexample - -@strong{Note:} The scheduler attempts to avoid function unit conflicts -and uses all the specifications in the @code{define_function_unit} -expression. It has recently come to our attention that these -specifications may not allow modeling of some of the newer -``superscalar'' processors that have insns using multiple pipelined -units. These insns will cause a potential conflict for the second unit -used during their execution and there is no way of representing that -conflict. We welcome any examples of how function unit conflicts work -in such processors and suggestions for their representation. -@end ifset - -@node Conditional Execution -@section Conditional Execution -@cindex conditional execution -@cindex predication - -A number of architectures provide for some form of conditional -execution, or predication. The hallmark of this feature is the -ability to nullify most of the instructions in the instruction set. -When the instruction set is large and not entirely symmetric, it -can be quite tedious to describe these forms directly in the -@file{.md} file. An alternative is the @code{define_cond_exec} template. - -@findex define_cond_exec -@smallexample -(define_cond_exec - [@var{predicate-pattern}] - "@var{condition}" - "@var{output template}") -@end smallexample - -@var{predicate-pattern} is the condition that must be true for the -insn to be executed at runtime and should match a relational operator. -One can use @code{match_operator} to match several relational operators -at once. Any @code{match_operand} operands must have no more than one -alternative. - -@var{condition} is a C expression that must be true for the generated -pattern to match. - -@findex current_insn_predicate -@var{output template} is a string similar to the @code{define_insn} -output template (@pxref{Output Template}), except that the @samp{*} -and @samp{@@} special cases do not apply. This is only useful if the -assembly text for the predicate is a simple prefix to the main insn. -In order to handle the general case, there is a global variable -@code{current_insn_predicate} that will contain the entire predicate -if the current insn is predicated, and will otherwise be @code{NULL}. - -When @code{define_cond_exec} is used, an implicit reference to -the @code{predicable} instruction attribute is made. -@xref{Insn Attributes}. This attribute must be boolean (i.e. have -exactly two elements in its @var{list-of-values}). Further, it must -not be used with complex expressions. That is, the default and all -uses in the insns must be a simple constant, not dependent on the -alternative or anything else. - -For each @code{define_insn} for which the @code{predicable} -attribute is true, a new @code{define_insn} pattern will be -generated that matches a predicated version of the instruction. -For example, - -@smallexample -(define_insn "addsi" - [(set (match_operand:SI 0 "register_operand" "r") - (plus:SI (match_operand:SI 1 "register_operand" "r") - (match_operand:SI 2 "register_operand" "r")))] - "@var{test1}" - "add %2,%1,%0") - -(define_cond_exec - [(ne (match_operand:CC 0 "register_operand" "c") - (const_int 0))] - "@var{test2}" - "(%0)") -@end smallexample - -@noindent -generates a new pattern - -@smallexample -(define_insn "" - [(cond_exec - (ne (match_operand:CC 3 "register_operand" "c") (const_int 0)) - (set (match_operand:SI 0 "register_operand" "r") - (plus:SI (match_operand:SI 1 "register_operand" "r") - (match_operand:SI 2 "register_operand" "r"))))] - "(@var{test2}) && (@var{test1})" - "(%3) add %2,%1,%0") -@end smallexample - -@node Constant Definitions -@section Constant Definitions -@cindex constant definitions -@findex define_constants - -Using literal constants inside instruction patterns reduces legibility and -can be a maintenance problem. - -To overcome this problem, you may use the @code{define_constants} -expression. It contains a vector of name-value pairs. From that -point on, wherever any of the names appears in the MD file, it is as -if the corresponding value had been written instead. You may use -@code{define_constants} multiple times; each appearance adds more -constants to the table. It is an error to redefine a constant with -a different value. - -To come back to the a29k load multiple example, instead of - -@smallexample -(define_insn "" - [(match_parallel 0 "load_multiple_operation" - [(set (match_operand:SI 1 "gpc_reg_operand" "=r") - (match_operand:SI 2 "memory_operand" "m")) - (use (reg:SI 179)) - (clobber (reg:SI 179))])] - "" - "loadm 0,0,%1,%2") -@end smallexample - -You could write: - -@smallexample -(define_constants [ - (R_BP 177) - (R_FC 178) - (R_CR 179) - (R_Q 180) -]) - -(define_insn "" - [(match_parallel 0 "load_multiple_operation" - [(set (match_operand:SI 1 "gpc_reg_operand" "=r") - (match_operand:SI 2 "memory_operand" "m")) - (use (reg:SI R_CR)) - (clobber (reg:SI R_CR))])] - "" - "loadm 0,0,%1,%2") -@end smallexample - -The constants that are defined with a define_constant are also output -in the insn-codes.h header file as #defines. diff --git a/gcc/objc.texi b/gcc/objc.texi deleted file mode 100644 index b2e5c21bfeb..00000000000 --- a/gcc/objc.texi +++ /dev/null @@ -1,458 +0,0 @@ -@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, -@c 1999, 2000, 2001 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@node Objective C -@comment node-name, next, previous, up - -@chapter GNU Objective-C runtime features - -This document is meant to describe some of the GNU Objective-C runtime -features. It is not intended to teach you Objective-C, there are several -resources on the Internet that present the language. Questions and -comments about this document to Ovidiu Predescu -@email{ovidiu@@cup.hp.com}. - -@menu -* Executing code before main:: -* Type encoding:: -* Garbage Collection:: -* Constant string objects:: -* compatibility_alias:: -@end menu - -@node Executing code before main, Type encoding, Objective C, Objective C -@section @code{+load}: Executing code before main - - -The GNU Objective-C runtime provides a way that allows you to execute -code before the execution of the program enters the @code{main} -function. The code is executed on a per-class and a per-category basis, -through a special class method @code{+load}. - -This facility is very useful if you want to initialize global variables -which can be accessed by the program directly, without sending a message -to the class first. The usual way to initialize global variables, in the -@code{+initialize} method, might not be useful because -@code{+initialize} is only called when the first message is sent to a -class object, which in some cases could be too late. - -Suppose for example you have a @code{FileStream} class that declares -@code{Stdin}, @code{Stdout} and @code{Stderr} as global variables, like -below: - -@example - -FileStream *Stdin = nil; -FileStream *Stdout = nil; -FileStream *Stderr = nil; - -@@implementation FileStream - -+ (void)initialize -@{ - Stdin = [[FileStream new] initWithFd:0]; - Stdout = [[FileStream new] initWithFd:1]; - Stderr = [[FileStream new] initWithFd:2]; -@} - -/* Other methods here */ -@@end - -@end example - -In this example, the initialization of @code{Stdin}, @code{Stdout} and -@code{Stderr} in @code{+initialize} occurs too late. The programmer can -send a message to one of these objects before the variables are actually -initialized, thus sending messages to the @code{nil} object. The -@code{+initialize} method which actually initializes the global -variables is not invoked until the first message is sent to the class -object. The solution would require these variables to be initialized -just before entering @code{main}. - -The correct solution of the above problem is to use the @code{+load} -method instead of @code{+initialize}: - -@example - -@@implementation FileStream - -+ (void)load -@{ - Stdin = [[FileStream new] initWithFd:0]; - Stdout = [[FileStream new] initWithFd:1]; - Stderr = [[FileStream new] initWithFd:2]; -@} - -/* Other methods here */ -@@end - -@end example - -The @code{+load} is a method that is not overridden by categories. If a -class and a category of it both implement @code{+load}, both methods are -invoked. This allows some additional initializations to be performed in -a category. - -This mechanism is not intended to be a replacement for @code{+initialize}. -You should be aware of its limitations when you decide to use it -instead of @code{+initialize}. - -@menu -* What you can and what you cannot do in +load:: -@end menu - - -@node What you can and what you cannot do in +load, , Executing code before main, Executing code before main -@subsection What you can and what you cannot do in @code{+load} - -The @code{+load} implementation in the GNU runtime guarantees you the following -things: - -@itemize @bullet - -@item -you can write whatever C code you like; - -@item -you can send messages to Objective-C constant strings (@@"this is a -constant string"); - -@item -you can allocate and send messages to objects whose class is implemented -in the same file; - -@item -the @code{+load} implementation of all super classes of a class are executed before the @code{+load} of that class is executed; - -@item -the @code{+load} implementation of a class is executed before the -@code{+load} implementation of any category. - -@end itemize - -In particular, the following things, even if they can work in a -particular case, are not guaranteed: - -@itemize @bullet - -@item -allocation of or sending messages to arbitrary objects; - -@item -allocation of or sending messages to objects whose classes have a -category implemented in the same file; - -@end itemize - -You should make no assumptions about receiving @code{+load} in sibling -classes when you write @code{+load} of a class. The order in which -sibling classes receive @code{+load} is not guaranteed. - -The order in which @code{+load} and @code{+initialize} are called could -be problematic if this matters. If you don't allocate objects inside -@code{+load}, it is guaranteed that @code{+load} is called before -@code{+initialize}. If you create an object inside @code{+load} the -@code{+initialize} method of object's class is invoked even if -@code{+load} was not invoked. Note if you explicitly call @code{+load} -on a class, @code{+initialize} will be called first. To avoid possible -problems try to implement only one of these methods. - -The @code{+load} method is also invoked when a bundle is dynamically -loaded into your running program. This happens automatically without any -intervening operation from you. When you write bundles and you need to -write @code{+load} you can safely create and send messages to objects whose -classes already exist in the running program. The same restrictions as -above apply to classes defined in bundle. - - - -@node Type encoding, Garbage Collection, Executing code before main, Objective C -@section Type encoding - -The Objective-C compiler generates type encodings for all the -types. These type encodings are used at runtime to find out information -about selectors and methods and about objects and classes. - -The types are encoded in the following way: - -@c @sp 1 - -@multitable @columnfractions .25 .75 -@item @code{char} -@tab @code{c} -@item @code{unsigned char} -@tab @code{C} -@item @code{short} -@tab @code{s} -@item @code{unsigned short} -@tab @code{S} -@item @code{int} -@tab @code{i} -@item @code{unsigned int} -@tab @code{I} -@item @code{long} -@tab @code{l} -@item @code{unsigned long} -@tab @code{L} -@item @code{long long} -@tab @code{q} -@item @code{unsigned long long} -@tab @code{Q} -@item @code{float} -@tab @code{f} -@item @code{double} -@tab @code{d} -@item @code{void} -@tab @code{v} -@item @code{id} -@tab @code{@@} -@item @code{Class} -@tab @code{#} -@item @code{SEL} -@tab @code{:} -@item @code{char*} -@tab @code{*} -@item unknown type -@tab @code{?} -@item bitfields -@tab @code{b} followed by the starting position of the bitfield, the type of the bitfield and the size of the bitfield (the bitfields encoding was changed from the NeXT's compiler encoding, see below) -@end multitable - -@c @sp 1 - -The encoding of bitfields has changed to allow bitfields to be properly -handled by the runtime functions that compute sizes and alignments of -types that contain bitfields. The previous encoding contained only the -size of the bitfield. Using only this information it is not possible to -reliably compute the size occupied by the bitfield. This is very -important in the presence of the Boehm's garbage collector because the -objects are allocated using the typed memory facility available in this -collector. The typed memory allocation requires information about where -the pointers are located inside the object. - -The position in the bitfield is the position, counting in bits, of the -bit closest to the beginning of the structure. - -The non-atomic types are encoded as follows: - -@c @sp 1 - -@multitable @columnfractions .2 .8 -@item pointers -@tab @code{'^'} followed by the pointed type. -@item arrays -@tab @code{'['} followed by the number of elements in the array followed by the type of the elements followed by @code{']'} -@item structures -@tab @code{'@{'} followed by the name of the structure (or '?' if the structure is unnamed), the '=' sign, the type of the members and by @code{'@}'} -@item unions -@tab @code{'('} followed by the name of the structure (or '?' if the union is unnamed), the '=' sign, the type of the members followed by @code{')'} -@end multitable - -Here are some types and their encodings, as they are generated by the -compiler on a i386 machine: - -@sp 1 - -@multitable @columnfractions .25 .75 -@item Objective-C type -@tab Compiler encoding -@item -@example -int a[10]; -@end example -@tab @code{[10i]} -@item -@example -struct @{ - int i; - float f[3]; - int a:3; - int b:2; - char c; -@} -@end example -@tab @code{@{?=i[3f]b128i3b131i2c@}} -@end multitable - -@sp 1 - -In addition to the types the compiler also encodes the type -specifiers. The table below describes the encoding of the current -Objective-C type specifiers: - -@sp 1 - -@multitable @columnfractions .25 .75 -@item Specifier -@tab Encoding -@item @code{const} -@tab @code{r} -@item @code{in} -@tab @code{n} -@item @code{inout} -@tab @code{N} -@item @code{out} -@tab @code{o} -@item @code{bycopy} -@tab @code{O} -@item @code{oneway} -@tab @code{V} -@end multitable - -@sp 1 - -The type specifiers are encoded just before the type. Unlike types -however, the type specifiers are only encoded when they appear in method -argument types. - - -@node Garbage Collection, Constant string objects, Type encoding, Objective C -@section Garbage Collection - -Support for a new memory management policy has been added by using a -powerful conservative garbage collector, known as the -Boehm-Demers-Weiser conservative garbage collector. It is available from -@w{@uref{http://www.hpl.hp.com/personal/Hans_Boehm/gc/}}. - -To enable the support for it you have to configure the compiler using an -additional argument, @w{@kbd{--enable-objc-gc}}. You need to have -garbage collector installed before building the compiler. This will -build an additional runtime library which has several enhancements to -support the garbage collector. The new library has a new name, -@kbd{libobjc_gc.a} to not conflict with the non-garbage-collected -library. - -When the garbage collector is used, the objects are allocated using the -so-called typed memory allocation mechanism available in the -Boehm-Demers-Weiser collector. This mode requires precise information on -where pointers are located inside objects. This information is computed -once per class, immediately after the class has been initialized. - -There is a new runtime function @code{class_ivar_set_gcinvisible()} -which can be used to declare a so-called @strong{weak pointer} -reference. Such a pointer is basically hidden for the garbage collector; -this can be useful in certain situations, especially when you want to -keep track of the allocated objects, yet allow them to be -collected. This kind of pointers can only be members of objects, you -cannot declare a global pointer as a weak reference. Every type which is -a pointer type can be declared a weak pointer, including @code{id}, -@code{Class} and @code{SEL}. - -Here is an example of how to use this feature. Suppose you want to -implement a class whose instances hold a weak pointer reference; the -following class does this: - -@example - -@@interface WeakPointer : Object -@{ - const void* weakPointer; -@} - -- initWithPointer:(const void*)p; -- (const void*)weakPointer; -@@end - - -@@implementation WeakPointer - -+ (void)initialize -@{ - class_ivar_set_gcinvisible (self, "weakPointer", YES); -@} - -- initWithPointer:(const void*)p -@{ - weakPointer = p; - return self; -@} - -- (const void*)weakPointer -@{ - return weakPointer; -@} - -@@end - -@end example - -Weak pointers are supported through a new type character specifier -represented by the @code{'!'} character. The -@code{class_ivar_set_gcinvisible()} function adds or removes this -specifier to the string type description of the instance variable named -as argument. - -@c ========================================================================= -@node Constant string objects -@section Constant string objects - -GNU Objective-C provides constant string objects that are generated -directly by the compiler. You declare a constant string object by -prefixing a C constant string with the character @code{@@}: - -@example - id myString = @@"this is a constant string object"; -@end example - -The constant string objects are usually instances of the -@code{NXConstantString} class which is provided by the GNU Objective-C -runtime. To get the definition of this class you must include the -@file{objc/NXConstStr.h} header file. - -User defined libraries may want to implement their own constant string -class. To be able to support them, the GNU Objective-C compiler provides -a new command line options @code{-fconstant-string-class=}. The provided class should adhere to a strict structure, the same -as @code{NXConstantString}'s structure: - -@example - -@@interface NXConstantString : Object -@{ - char *c_string; - unsigned int len; -@} -@@end - -@end example - -User class libraries may choose to inherit the customized constant -string class from a different class than @code{Object}. There is no -requirement in the methods the constant string class has to implement. - -When a file is compiled with the @code{-fconstant-string-class} option, -all the constant string objects will be instances of the class specified -as argument to this option. It is possible to have multiple compilation -units referring to different constant string classes, neither the -compiler nor the linker impose any restrictions in doing this. - -@c ========================================================================= -@node compatibility_alias -@section compatibility_alias - -This is a feature of the Objective-C compiler rather than of the -runtime, anyway since it is documented nowhere and its existence was -forgotten, we are documenting it here. - -The keyword @code{@@compatibility_alias} allows you to define a class name -as equivalent to another class name. For example: - -@example -@@compatibility_alias WOApplication GSWApplication; -@end example - -tells the compiler that each time it encounters @code{WOApplication} as -a class name, it should replace it with @code{GSWApplication} (that is, -@code{WOApplication} is just an alias for @code{GSWApplication}). - -There are some constraints on how this can be used - - -@itemize @bullet - -@item @code{WOApplication} (the alias) must not be an existing class; - -@item @code{GSWApplication} (the real class) must be an existing class. - -@end itemize diff --git a/gcc/rtl.texi b/gcc/rtl.texi deleted file mode 100644 index 2b393589d9d..00000000000 --- a/gcc/rtl.texi +++ /dev/null @@ -1,3191 +0,0 @@ -@c Copyright (C) 1988, 1989, 1992, 1994, 1997, 1998, 1999, 2000, 2001 -@c Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@node RTL -@chapter RTL Representation -@cindex RTL representation -@cindex representation of RTL -@cindex Register Transfer Language (RTL) - -Most of the work of the compiler is done on an intermediate representation -called register transfer language. In this language, the instructions to be -output are described, pretty much one by one, in an algebraic form that -describes what the instruction does. - -RTL is inspired by Lisp lists. It has both an internal form, made up of -structures that point at other structures, and a textual form that is used -in the machine description and in printed debugging dumps. The textual -form uses nested parentheses to indicate the pointers in the internal form. - -@menu -* RTL Objects:: Expressions vs vectors vs strings vs integers. -* RTL Classes:: Categories of RTL expresion objects, and their structure. -* Accessors:: Macros to access expression operands or vector elts. -* Flags:: Other flags in an RTL expression. -* Machine Modes:: Describing the size and format of a datum. -* Constants:: Expressions with constant values. -* Regs and Memory:: Expressions representing register contents or memory. -* Arithmetic:: Expressions representing arithmetic on other expressions. -* Comparisons:: Expressions representing comparison of expressions. -* Bit Fields:: Expressions representing bitfields in memory or reg. -* Vector Operations:: Expressions involving vector datatypes. -* Conversions:: Extending, truncating, floating or fixing. -* RTL Declarations:: Declaring volatility, constancy, etc. -* Side Effects:: Expressions for storing in registers, etc. -* Incdec:: Embedded side-effects for autoincrement addressing. -* Assembler:: Representing @code{asm} with operands. -* Insns:: Expression types for entire insns. -* Calls:: RTL representation of function call insns. -* Sharing:: Some expressions are unique; others *must* be copied. -* Reading RTL:: Reading textual RTL from a file. -@end menu - -@node RTL Objects -@section RTL Object Types -@cindex RTL object types - -@cindex RTL integers -@cindex RTL strings -@cindex RTL vectors -@cindex RTL expression -@cindex RTX (See RTL) -RTL uses five kinds of objects: expressions, integers, wide integers, -strings and vectors. Expressions are the most important ones. An RTL -expression (``RTX'', for short) is a C structure, but it is usually -referred to with a pointer; a type that is given the typedef name -@code{rtx}. - -An integer is simply an @code{int}; their written form uses decimal digits. -A wide integer is an integral object whose type is @code{HOST_WIDE_INT} -(@pxref{Config}); their written form uses decimal digits. - -A string is a sequence of characters. In core it is represented as a -@code{char *} in usual C fashion, and it is written in C syntax as well. -However, strings in RTL may never be null. If you write an empty string in -a machine description, it is represented in core as a null pointer rather -than as a pointer to a null character. In certain contexts, these null -pointers instead of strings are valid. Within RTL code, strings are most -commonly found inside @code{symbol_ref} expressions, but they appear in -other contexts in the RTL expressions that make up machine descriptions. - -A vector contains an arbitrary number of pointers to expressions. The -number of elements in the vector is explicitly present in the vector. -The written form of a vector consists of square brackets -(@samp{[@dots{}]}) surrounding the elements, in sequence and with -whitespace separating them. Vectors of length zero are not created; -null pointers are used instead. - -@cindex expression codes -@cindex codes, RTL expression -@findex GET_CODE -@findex PUT_CODE -Expressions are classified by @dfn{expression codes} (also called RTX -codes). The expression code is a name defined in @file{rtl.def}, which is -also (in upper case) a C enumeration constant. The possible expression -codes and their meanings are machine-independent. The code of an RTX can -be extracted with the macro @code{GET_CODE (@var{x})} and altered with -@code{PUT_CODE (@var{x}, @var{newcode})}. - -The expression code determines how many operands the expression contains, -and what kinds of objects they are. In RTL, unlike Lisp, you cannot tell -by looking at an operand what kind of object it is. Instead, you must know -from its context---from the expression code of the containing expression. -For example, in an expression of code @code{subreg}, the first operand is -to be regarded as an expression and the second operand as an integer. In -an expression of code @code{plus}, there are two operands, both of which -are to be regarded as expressions. In a @code{symbol_ref} expression, -there is one operand, which is to be regarded as a string. - -Expressions are written as parentheses containing the name of the -expression type, its flags and machine mode if any, and then the operands -of the expression (separated by spaces). - -Expression code names in the @samp{md} file are written in lower case, -but when they appear in C code they are written in upper case. In this -manual, they are shown as follows: @code{const_int}. - -@cindex (nil) -@cindex nil -In a few contexts a null pointer is valid where an expression is normally -wanted. The written form of this is @code{(nil)}. - -@node RTL Classes -@section RTL Classes and Formats -@cindex RTL classes -@cindex classes of RTX codes -@cindex RTX codes, classes of -@findex GET_RTX_CLASS - -The various expression codes are divided into several @dfn{classes}, -which are represented by single characters. You can determine the class -of an RTX code with the macro @code{GET_RTX_CLASS (@var{code})}. -Currently, @file{rtx.def} defines these classes: - -@table @code -@item o -An RTX code that represents an actual object, such as a register -(@code{REG}) or a memory location (@code{MEM}, @code{SYMBOL_REF}). -Constants and basic transforms on objects (@code{ADDRESSOF}, -@code{HIGH}, @code{LO_SUM}) are also included. Note that @code{SUBREG} -and @code{STRICT_LOW_PART} are not in this class, but in class @code{x}. - -@item < -An RTX code for a comparison, such as @code{NE} or @code{LT}. - -@item 1 -An RTX code for a unary arithmetic operation, such as @code{NEG}, -@code{NOT}, or @code{ABS}. This category also includes value extension -(sign or zero) and conversions between integer and floating point. - -@item c -An RTX code for a commutative binary operation, such as @code{PLUS} or -@code{AND}. @code{NE} and @code{EQ} are comparisons, so they have class -@code{<}. - -@item 2 -An RTX code for a non-commutative binary operation, such as @code{MINUS}, -@code{DIV}, or @code{ASHIFTRT}. - -@item b -An RTX code for a bitfield operation. Currently only -@code{ZERO_EXTRACT} and @code{SIGN_EXTRACT}. These have three inputs -and are lvalues (so they can be used for insertion as well). @xref{Bit -Fields}. - -@item 3 -An RTX code for other three input operations. Currently only -@code{IF_THEN_ELSE}. - -@item i -An RTX code for an entire instruction: @code{INSN}, @code{JUMP_INSN}, and -@code{CALL_INSN}. @xref{Insns}. - -@item m -An RTX code for something that matches in insns, such as -@code{MATCH_DUP}. These only occur in machine descriptions. - -@item a -An RTX code for an auto-increment addressing mode, such as -@code{POST_INC}. - -@item x -All other RTX codes. This category includes the remaining codes used -only in machine descriptions (@code{DEFINE_*}, etc.). It also includes -all the codes describing side effects (@code{SET}, @code{USE}, -@code{CLOBBER}, etc.) and the non-insns that may appear on an insn -chain, such as @code{NOTE}, @code{BARRIER}, and @code{CODE_LABEL}. -@end table - -@cindex RTL format -For each expression type @file{rtl.def} specifies the number of -contained objects and their kinds, with four possibilities: @samp{e} for -expression (actually a pointer to an expression), @samp{i} for integer, -@samp{w} for wide integer, @samp{s} for string, and @samp{E} for vector -of expressions. The sequence of letters for an expression code is -called its @dfn{format}. For example, the format of @code{subreg} is -@samp{ei}.@refill - -@cindex RTL format characters -A few other format characters are used occasionally: - -@table @code -@item u -@samp{u} is equivalent to @samp{e} except that it is printed differently -in debugging dumps. It is used for pointers to insns. - -@item n -@samp{n} is equivalent to @samp{i} except that it is printed differently -in debugging dumps. It is used for the line number or code number of a -@code{note} insn. - -@item S -@samp{S} indicates a string which is optional. In the RTL objects in -core, @samp{S} is equivalent to @samp{s}, but when the object is read, -from an @samp{md} file, the string value of this operand may be omitted. -An omitted string is taken to be the null string. - -@item V -@samp{V} indicates a vector which is optional. In the RTL objects in -core, @samp{V} is equivalent to @samp{E}, but when the object is read -from an @samp{md} file, the vector value of this operand may be omitted. -An omitted vector is effectively the same as a vector of no elements. - -@item 0 -@samp{0} means a slot whose contents do not fit any normal category. -@samp{0} slots are not printed at all in dumps, and are often used in -special ways by small parts of the compiler. -@end table - -There are macros to get the number of operands and the format -of an expression code: - -@table @code -@findex GET_RTX_LENGTH -@item GET_RTX_LENGTH (@var{code}) -Number of operands of an RTX of code @var{code}. - -@findex GET_RTX_FORMAT -@item GET_RTX_FORMAT (@var{code}) -The format of an RTX of code @var{code}, as a C string. -@end table - -Some classes of RTX codes always have the same format. For example, it -is safe to assume that all comparison operations have format @code{ee}. - -@table @code -@item 1 -All codes of this class have format @code{e}. - -@item < -@itemx c -@itemx 2 -All codes of these classes have format @code{ee}. - -@item b -@itemx 3 -All codes of these classes have format @code{eee}. - -@item i -All codes of this class have formats that begin with @code{iuueiee}. -@xref{Insns}. Note that not all RTL objects linked onto an insn chain -are of class @code{i}. - -@item o -@itemx m -@itemx x -You can make no assumptions about the format of these codes. -@end table - -@node Accessors -@section Access to Operands -@cindex accessors -@cindex access to operands -@cindex operand access - -@findex XEXP -@findex XINT -@findex XWINT -@findex XSTR -Operands of expressions are accessed using the macros @code{XEXP}, -@code{XINT}, @code{XWINT} and @code{XSTR}. Each of these macros takes -two arguments: an expression-pointer (RTX) and an operand number -(counting from zero). Thus,@refill - -@example -XEXP (@var{x}, 2) -@end example - -@noindent -accesses operand 2 of expression @var{x}, as an expression. - -@example -XINT (@var{x}, 2) -@end example - -@noindent -accesses the same operand as an integer. @code{XSTR}, used in the same -fashion, would access it as a string. - -Any operand can be accessed as an integer, as an expression or as a string. -You must choose the correct method of access for the kind of value actually -stored in the operand. You would do this based on the expression code of -the containing expression. That is also how you would know how many -operands there are. - -For example, if @var{x} is a @code{subreg} expression, you know that it has -two operands which can be correctly accessed as @code{XEXP (@var{x}, 0)} -and @code{XINT (@var{x}, 1)}. If you did @code{XINT (@var{x}, 0)}, you -would get the address of the expression operand but cast as an integer; -that might occasionally be useful, but it would be cleaner to write -@code{(int) XEXP (@var{x}, 0)}. @code{XEXP (@var{x}, 1)} would also -compile without error, and would return the second, integer operand cast as -an expression pointer, which would probably result in a crash when -accessed. Nothing stops you from writing @code{XEXP (@var{x}, 28)} either, -but this will access memory past the end of the expression with -unpredictable results.@refill - -Access to operands which are vectors is more complicated. You can use the -macro @code{XVEC} to get the vector-pointer itself, or the macros -@code{XVECEXP} and @code{XVECLEN} to access the elements and length of a -vector. - -@table @code -@findex XVEC -@item XVEC (@var{exp}, @var{idx}) -Access the vector-pointer which is operand number @var{idx} in @var{exp}. - -@findex XVECLEN -@item XVECLEN (@var{exp}, @var{idx}) -Access the length (number of elements) in the vector which is -in operand number @var{idx} in @var{exp}. This value is an @code{int}. - -@findex XVECEXP -@item XVECEXP (@var{exp}, @var{idx}, @var{eltnum}) -Access element number @var{eltnum} in the vector which is -in operand number @var{idx} in @var{exp}. This value is an RTX. - -It is up to you to make sure that @var{eltnum} is not negative -and is less than @code{XVECLEN (@var{exp}, @var{idx})}. -@end table - -All the macros defined in this section expand into lvalues and therefore -can be used to assign the operands, lengths and vector elements as well as -to access them. - -@node Flags -@section Flags in an RTL Expression -@cindex flags in RTL expression - -RTL expressions contain several flags (one-bit bitfields) and other -values that are used in certain types of expression. Most often they -are accessed with the following macros: - -@table @code -@findex MEM_VOLATILE_P -@cindex @code{mem} and @samp{/v} -@cindex @code{volatil}, in @code{mem} -@cindex @samp{/v} in RTL dump -@item MEM_VOLATILE_P (@var{x}) -In @code{mem} expressions, nonzero for volatile memory references. -Stored in the @code{volatil} field and printed as @samp{/v}. - -@findex MEM_IN_STRUCT_P -@cindex @code{mem} and @samp{/s} -@cindex @code{in_struct}, in @code{mem} -@cindex @samp{/s} in RTL dump -@item MEM_IN_STRUCT_P (@var{x}) -In @code{mem} expressions, nonzero for reference to an entire structure, -union or array, or to a component of one. Zero for references to a -scalar variable or through a pointer to a scalar. Stored in the -@code{in_struct} field and printed as @samp{/s}. If both this flag and -MEM_SCALAR_P are clear, then we don't know whether this MEM is in a -structure or not. Both flags should never be simultaneously set. - -@findex MEM_SCALAR_P -@cindex @code{mem} and @samp{/f} -@cindex @code{frame_related}, in@code{mem} -@cindex @samp{/f} in RTL dump -@item MEM_SCALAR_P (@var{x}) -In @code{mem} expressions, nonzero for reference to a scalar known not -to be a member of a structure, union, or array. Zero for such -references and for indirections through pointers, even pointers pointing -to scalar types. If both this flag and MEM_STRUCT_P are clear, then we -don't know whether this MEM is in a structure or not. Both flags should -never be simultaneously set. - -@findex MEM_ALIAS_SET -@item MEM_ALIAS_SET (@var{x}) -In @code{mem} expressions, the alias set to which @var{x} belongs. If -zero, @var{x} is not in any alias set, and may alias anything. If -nonzero, @var{x} may only alias objects in the same alias set. This -value is set (in a language-specific manner) by the front-end. This -field is not a bit-field; it is in an integer, found as the second -argument to the @code{mem}. - -@findex REG_LOOP_TEST_P -@cindex @code{reg} and @samp{/s} -@cindex @code{in_struct}, in @code{reg} -@item REG_LOOP_TEST_P -In @code{reg} expressions, nonzero if this register's entire life is -contained in the exit test code for some loop. Stored in the -@code{in_struct} field and printed as @samp{/s}. - -@findex REG_USERVAR_P -@cindex @code{reg} and @samp{/v} -@cindex @code{volatil}, in @code{reg} -@item REG_USERVAR_P (@var{x}) -In a @code{reg}, nonzero if it corresponds to a variable present in -the user's source code. Zero for temporaries generated internally by -the compiler. Stored in the @code{volatil} field and printed as -@samp{/v}. - -@cindex @samp{/i} in RTL dump -@findex REG_FUNCTION_VALUE_P -@cindex @code{reg} and @samp{/i} -@cindex @code{integrated}, in @code{reg} -@item REG_FUNCTION_VALUE_P (@var{x}) -Nonzero in a @code{reg} if it is the place in which this function's -value is going to be returned. (This happens only in a hard -register.) Stored in the @code{integrated} field and printed as -@samp{/i}. - -The same hard register may be used also for collecting the values of -functions called by this one, but @code{REG_FUNCTION_VALUE_P} is zero -in this kind of use. - -@findex SUBREG_PROMOTED_VAR_P -@cindex @code{subreg} and @samp{/s} -@cindex @code{in_struct}, in @code{subreg} -@item SUBREG_PROMOTED_VAR_P -Nonzero in a @code{subreg} if it was made when accessing an object that -was promoted to a wider mode in accord with the @code{PROMOTED_MODE} machine -description macro (@pxref{Storage Layout}). In this case, the mode of -the @code{subreg} is the declared mode of the object and the mode of -@code{SUBREG_REG} is the mode of the register that holds the object. -Promoted variables are always either sign- or zero-extended to the wider -mode on every assignment. Stored in the @code{in_struct} field and -printed as @samp{/s}. - -@findex SUBREG_PROMOTED_UNSIGNED_P -@cindex @code{subreg} and @samp{/u} -@cindex @code{unchanging}, in @code{subreg} -@item SUBREG_PROMOTED_UNSIGNED_P -Nonzero in a @code{subreg} that has @code{SUBREG_PROMOTED_VAR_P} nonzero -if the object being referenced is kept zero-extended and zero if it -is kept sign-extended. Stored in the @code{unchanging} field and -printed as @samp{/u}. - -@findex RTX_UNCHANGING_P -@cindex @code{reg} and @samp{/u} -@cindex @code{mem} and @samp{/u} -@cindex @code{unchanging}, in @code{reg} and @code{mem} -@cindex @samp{/u} in RTL dump -@item RTX_UNCHANGING_P (@var{x}) -Nonzero in a @code{reg} or @code{mem} if the value is not changed. -(This flag is not set for memory references via pointers to constants. -Such pointers only guarantee that the object will not be changed -explicitly by the current function. The object might be changed by -other functions or by aliasing.) Stored in the -@code{unchanging} field and printed as @samp{/u}. - -@findex RTX_INTEGRATED_P -@cindex @code{integrated}, in @code{insn} -@item RTX_INTEGRATED_P (@var{insn}) -Nonzero in an insn if it resulted from an in-line function call. -Stored in the @code{integrated} field and printed as @samp{/i}. - -@findex RTX_FRAME_RELATED_P -@item RTX_FRAME_RELATED_P (@var{x}) -Nonzero in an insn or expression which is part of a function prologue -and sets the stack pointer, sets the frame pointer, or saves a register. -This flag should also be set on an instruction that sets up a temporary -register to use in place of the frame pointer. - -In particular, on RISC targets where there are limits on the sizes of -immediate constants, it is sometimes impossible to reach the register -save area directly from the stack pointer. In that case, a temporary -register is used that is near enough to the register save area, and the -Canonical Frame Address, i.e., DWARF2's logical frame pointer, register -must (temporarily) be changed to be this temporary register. So, the -instruction that sets this temporary register must be marked as -@code{RTX_FRAME_RELATED_P}. - -If the marked instruction is overly complex (defined in terms of what -@code{dwarf2out_frame_debug_expr} can handle), you will also have to -create a @code{REG_FRAME_RELATED_EXPR} note and attach it to the -instruction. This note should contain a simple expression of the -computation performed by this instruction, i.e., one that -@code{dwarf2out_frame_debug_expr} can handle. - -This flag is required for exception handling support on targets with RTL -prologues. - -@findex SYMBOL_REF_USED -@cindex @code{used}, in @code{symbol_ref} -@item SYMBOL_REF_USED (@var{x}) -In a @code{symbol_ref}, indicates that @var{x} has been used. This is -normally only used to ensure that @var{x} is only declared external -once. Stored in the @code{used} field. - -@findex SYMBOL_REF_FLAG -@cindex @code{symbol_ref} and @samp{/v} -@cindex @code{volatil}, in @code{symbol_ref} -@item SYMBOL_REF_FLAG (@var{x}) -In a @code{symbol_ref}, this is used as a flag for machine-specific purposes. -Stored in the @code{volatil} field and printed as @samp{/v}. - -@findex SYMBOL_REF_WEAK -@cindex @code{symbol_ref} and @samp{/i} -@cindex @code{integrated}, in @code{symbol_ref} -@item SYMBOL_REF_WEAK (@var{x}) -In a @code{symbol_ref}, indicates that @var{x} has been declared weak. -Stored in the @code{integrated} field and printed as @samp{/i}. - -@findex LABEL_OUTSIDE_LOOP_P -@cindex @code{label_ref} and @samp{/s} -@cindex @code{in_struct}, in @code{label_ref} -@item LABEL_OUTSIDE_LOOP_P -In @code{label_ref} expressions, nonzero if this is a reference to a -label that is outside the innermost loop containing the reference to the -label. Stored in the @code{in_struct} field and printed as @samp{/s}. - -@findex INSN_DELETED_P -@cindex @code{volatil}, in @code{insn} -@item INSN_DELETED_P (@var{insn}) -In an insn, nonzero if the insn has been deleted. Stored in the -@code{volatil} field and printed as @samp{/v}. - -@findex INSN_ANNULLED_BRANCH_P -@cindex @code{insn} and @samp{/u} -@cindex @code{unchanging}, in @code{insn} -@item INSN_ANNULLED_BRANCH_P (@var{insn}) -In an @code{insn} in the delay slot of a branch insn, indicates that an -annulling branch should be used. See the discussion under -@code{sequence} below. Stored in the @code{unchanging} field and printed -as @samp{/u}. - -@findex INSN_FROM_TARGET_P -@cindex @code{insn} and @samp{/s} -@cindex @code{in_struct}, in @code{insn} -@cindex @samp{/s} in RTL dump -@item INSN_FROM_TARGET_P (@var{insn}) -In an @code{insn} in a delay slot of a branch, indicates that the insn -is from the target of the branch. If the branch insn has -@code{INSN_ANNULLED_BRANCH_P} set, this insn will only be executed if -the branch is taken. For annulled branches with -@code{INSN_FROM_TARGET_P} clear, the insn will be executed only if the -branch is not taken. When @code{INSN_ANNULLED_BRANCH_P} is not set, -this insn will always be executed. Stored in the @code{in_struct} -field and printed as @samp{/s}. - -@findex CONSTANT_POOL_ADDRESS_P -@cindex @code{symbol_ref} and @samp{/u} -@cindex @code{unchanging}, in @code{symbol_ref} -@item CONSTANT_POOL_ADDRESS_P (@var{x}) -Nonzero in a @code{symbol_ref} if it refers to part of the current -function's ``constants pool''. These are addresses close to the -beginning of the function, and GNU CC assumes they can be addressed -directly (perhaps with the help of base registers). Stored in the -@code{unchanging} field and printed as @samp{/u}. - -@findex CONST_CALL_P -@cindex @code{call_insn} and @samp{/u} -@cindex @code{unchanging}, in @code{call_insn} -@item CONST_CALL_P (@var{x}) -In a @code{call_insn}, indicates that the insn represents a call to a const -function. Stored in the @code{unchanging} field and printed as @samp{/u}. - -@findex LABEL_PRESERVE_P -@cindex @code{code_label} and @samp{/i} -@cindex @code{in_struct}, in @code{code_label} -@item LABEL_PRESERVE_P (@var{x}) -In a @code{code_label}, indicates that the label can never be deleted. -Labels referenced by a non-local goto will have this bit set. Stored -in the @code{in_struct} field and printed as @samp{/s}. - -@findex SCHED_GROUP_P -@cindex @code{insn} and @samp{/i} -@cindex @code{in_struct}, in @code{insn} -@item SCHED_GROUP_P (@var{insn}) -During instruction scheduling, in an insn, indicates that the previous insn -must be scheduled together with this insn. This is used to ensure that -certain groups of instructions will not be split up by the instruction -scheduling pass, for example, @code{use} insns before a @code{call_insn} may -not be separated from the @code{call_insn}. Stored in the @code{in_struct} -field and printed as @samp{/s}. -@end table - -These are the fields which the above macros refer to: - -@table @code -@findex used -@item used -Normally, this flag is used only momentarily, at the end of RTL -generation for a function, to count the number of times an expression -appears in insns. Expressions that appear more than once are copied, -according to the rules for shared structure (@pxref{Sharing}). - -In a @code{symbol_ref}, it indicates that an external declaration for -the symbol has already been written. - -In a @code{reg}, it is used by the leaf register renumbering code to ensure -that each register is only renumbered once. - -@findex volatil -@item volatil -This flag is used in @code{mem}, @code{symbol_ref} and @code{reg} -expressions and in insns. In RTL dump files, it is printed as -@samp{/v}. - -@cindex volatile memory references -In a @code{mem} expression, it is 1 if the memory reference is volatile. -Volatile memory references may not be deleted, reordered or combined. - -In a @code{symbol_ref} expression, it is used for machine-specific -purposes. - -In a @code{reg} expression, it is 1 if the value is a user-level variable. -0 indicates an internal compiler temporary. - -In an insn, 1 means the insn has been deleted. - -@findex in_struct -@item in_struct -In @code{mem} expressions, it is 1 if the memory datum referred to is -all or part of a structure or array; 0 if it is (or might be) a scalar -variable. A reference through a C pointer has 0 because the pointer -might point to a scalar variable. This information allows the compiler -to determine something about possible cases of aliasing. - -In an insn in the delay slot of a branch, 1 means that this insn is from -the target of the branch. - -During instruction scheduling, in an insn, 1 means that this insn must be -scheduled as part of a group together with the previous insn. - -In @code{reg} expressions, it is 1 if the register has its entire life -contained within the test expression of some loop. - -In @code{subreg} expressions, 1 means that the @code{subreg} is accessing -an object that has had its mode promoted from a wider mode. - -In @code{label_ref} expressions, 1 means that the referenced label is -outside the innermost loop containing the insn in which the @code{label_ref} -was found. - -In @code{code_label} expressions, it is 1 if the label may never be deleted. -This is used for labels which are the target of non-local gotos. - -In an RTL dump, this flag is represented as @samp{/s}. - -@findex unchanging -@item unchanging -In @code{reg} and @code{mem} expressions, 1 means -that the value of the expression never changes. - -In @code{subreg} expressions, it is 1 if the @code{subreg} references an -unsigned object whose mode has been promoted to a wider mode. - -In an insn, 1 means that this is an annulling branch. - -In a @code{symbol_ref} expression, 1 means that this symbol addresses -something in the per-function constants pool. - -In a @code{call_insn}, 1 means that this instruction is a call to a -const function. - -In an RTL dump, this flag is represented as @samp{/u}. - -@findex integrated -@item integrated -In some kinds of expressions, including insns, this flag means the -rtl was produced by procedure integration. - -In a @code{reg} expression, this flag indicates the register -containing the value to be returned by the current function. On -machines that pass parameters in registers, the same register number -may be used for parameters as well, but this flag is not set on such -uses. -@end table - -@node Machine Modes -@section Machine Modes -@cindex machine modes - -@findex enum machine_mode -A machine mode describes a size of data object and the representation used -for it. In the C code, machine modes are represented by an enumeration -type, @code{enum machine_mode}, defined in @file{machmode.def}. Each RTL -expression has room for a machine mode and so do certain kinds of tree -expressions (declarations and types, to be precise). - -In debugging dumps and machine descriptions, the machine mode of an RTL -expression is written after the expression code with a colon to separate -them. The letters @samp{mode} which appear at the end of each machine mode -name are omitted. For example, @code{(reg:SI 38)} is a @code{reg} -expression with machine mode @code{SImode}. If the mode is -@code{VOIDmode}, it is not written at all. - -Here is a table of machine modes. The term ``byte'' below refers to an -object of @code{BITS_PER_UNIT} bits (@pxref{Storage Layout}). - -@table @code -@findex BImode -@item BImode -``Bit'' mode represents a single bit, for predicate registers. - -@findex QImode -@item QImode -``Quarter-Integer'' mode represents a single byte treated as an integer. - -@findex HImode -@item HImode -``Half-Integer'' mode represents a two-byte integer. - -@findex PSImode -@item PSImode -``Partial Single Integer'' mode represents an integer which occupies -four bytes but which doesn't really use all four. On some machines, -this is the right mode to use for pointers. - -@findex SImode -@item SImode -``Single Integer'' mode represents a four-byte integer. - -@findex PDImode -@item PDImode -``Partial Double Integer'' mode represents an integer which occupies -eight bytes but which doesn't really use all eight. On some machines, -this is the right mode to use for certain pointers. - -@findex DImode -@item DImode -``Double Integer'' mode represents an eight-byte integer. - -@findex TImode -@item TImode -``Tetra Integer'' (?) mode represents a sixteen-byte integer. - -@findex OImode -@item OImode -``Octa Integer'' (?) mode represents a thirty-two-byte integer. - -@findex SFmode -@item SFmode -``Single Floating'' mode represents a single-precision (four byte) floating -point number. - -@findex DFmode -@item DFmode -``Double Floating'' mode represents a double-precision (eight byte) floating -point number. - -@findex XFmode -@item XFmode -``Extended Floating'' mode represents a triple-precision (twelve byte) -floating point number. This mode is used for IEEE extended floating -point. On some systems not all bits within these bytes will actually -be used. - -@findex TFmode -@item TFmode -``Tetra Floating'' mode represents a quadruple-precision (sixteen byte) -floating point number. - -@findex CCmode -@item CCmode -``Condition Code'' mode represents the value of a condition code, which -is a machine-specific set of bits used to represent the result of a -comparison operation. Other machine-specific modes may also be used for -the condition code. These modes are not used on machines that use -@code{cc0} (see @pxref{Condition Code}). - -@findex BLKmode -@item BLKmode -``Block'' mode represents values that are aggregates to which none of -the other modes apply. In RTL, only memory references can have this mode, -and only if they appear in string-move or vector instructions. On machines -which have no such instructions, @code{BLKmode} will not appear in RTL. - -@findex VOIDmode -@item VOIDmode -Void mode means the absence of a mode or an unspecified mode. -For example, RTL expressions of code @code{const_int} have mode -@code{VOIDmode} because they can be taken to have whatever mode the context -requires. In debugging dumps of RTL, @code{VOIDmode} is expressed by -the absence of any mode. - -@findex SCmode -@findex DCmode -@findex XCmode -@findex TCmode -@item SCmode, DCmode, XCmode, TCmode -These modes stand for a complex number represented as a pair of floating -point values. The floating point values are in @code{SFmode}, -@code{DFmode}, @code{XFmode}, and @code{TFmode}, respectively. - -@findex CQImode -@findex CHImode -@findex CSImode -@findex CDImode -@findex CTImode -@findex COImode -@item CQImode, CHImode, CSImode, CDImode, CTImode, COImode -These modes stand for a complex number represented as a pair of integer -values. The integer values are in @code{QImode}, @code{HImode}, -@code{SImode}, @code{DImode}, @code{TImode}, and @code{OImode}, -respectively. -@end table - -The machine description defines @code{Pmode} as a C macro which expands -into the machine mode used for addresses. Normally this is the mode -whose size is @code{BITS_PER_WORD}, @code{SImode} on 32-bit machines. - -The only modes which a machine description @i{must} support are -@code{QImode}, and the modes corresponding to @code{BITS_PER_WORD}, -@code{FLOAT_TYPE_SIZE} and @code{DOUBLE_TYPE_SIZE}. -The compiler will attempt to use @code{DImode} for 8-byte structures and -unions, but this can be prevented by overriding the definition of -@code{MAX_FIXED_MODE_SIZE}. Alternatively, you can have the compiler -use @code{TImode} for 16-byte structures and unions. Likewise, you can -arrange for the C type @code{short int} to avoid using @code{HImode}. - -@cindex mode classes -Very few explicit references to machine modes remain in the compiler and -these few references will soon be removed. Instead, the machine modes -are divided into mode classes. These are represented by the enumeration -type @code{enum mode_class} defined in @file{machmode.h}. The possible -mode classes are: - -@table @code -@findex MODE_INT -@item MODE_INT -Integer modes. By default these are @code{QImode}, @code{HImode}, -@code{SImode}, @code{DImode}, and @code{TImode}. - -@findex MODE_PARTIAL_INT -@item MODE_PARTIAL_INT -The ``partial integer'' modes, @code{PSImode} and @code{PDImode}. - -@findex MODE_FLOAT -@item MODE_FLOAT -floating point modes. By default these are @code{SFmode}, @code{DFmode}, -@code{XFmode} and @code{TFmode}. - -@findex MODE_COMPLEX_INT -@item MODE_COMPLEX_INT -Complex integer modes. (These are not currently implemented). - -@findex MODE_COMPLEX_FLOAT -@item MODE_COMPLEX_FLOAT -Complex floating point modes. By default these are @code{SCmode}, -@code{DCmode}, @code{XCmode}, and @code{TCmode}. - -@findex MODE_FUNCTION -@item MODE_FUNCTION -Algol or Pascal function variables including a static chain. -(These are not currently implemented). - -@findex MODE_CC -@item MODE_CC -Modes representing condition code values. These are @code{CCmode} plus -any modes listed in the @code{EXTRA_CC_MODES} macro. @xref{Jump Patterns}, -also see @ref{Condition Code}. - -@findex MODE_RANDOM -@item MODE_RANDOM -This is a catchall mode class for modes which don't fit into the above -classes. Currently @code{VOIDmode} and @code{BLKmode} are in -@code{MODE_RANDOM}. -@end table - -Here are some C macros that relate to machine modes: - -@table @code -@findex GET_MODE -@item GET_MODE (@var{x}) -Returns the machine mode of the RTX @var{x}. - -@findex PUT_MODE -@item PUT_MODE (@var{x}, @var{newmode}) -Alters the machine mode of the RTX @var{x} to be @var{newmode}. - -@findex NUM_MACHINE_MODES -@item NUM_MACHINE_MODES -Stands for the number of machine modes available on the target -machine. This is one greater than the largest numeric value of any -machine mode. - -@findex GET_MODE_NAME -@item GET_MODE_NAME (@var{m}) -Returns the name of mode @var{m} as a string. - -@findex GET_MODE_CLASS -@item GET_MODE_CLASS (@var{m}) -Returns the mode class of mode @var{m}. - -@findex GET_MODE_WIDER_MODE -@item GET_MODE_WIDER_MODE (@var{m}) -Returns the next wider natural mode. For example, the expression -@code{GET_MODE_WIDER_MODE (QImode)} returns @code{HImode}. - -@findex GET_MODE_SIZE -@item GET_MODE_SIZE (@var{m}) -Returns the size in bytes of a datum of mode @var{m}. - -@findex GET_MODE_BITSIZE -@item GET_MODE_BITSIZE (@var{m}) -Returns the size in bits of a datum of mode @var{m}. - -@findex GET_MODE_MASK -@item GET_MODE_MASK (@var{m}) -Returns a bitmask containing 1 for all bits in a word that fit within -mode @var{m}. This macro can only be used for modes whose bitsize is -less than or equal to @code{HOST_BITS_PER_INT}. - -@findex GET_MODE_ALIGNMENT -@item GET_MODE_ALIGNMENT (@var{m}) -Return the required alignment, in bits, for an object of mode @var{m}. - -@findex GET_MODE_UNIT_SIZE -@item GET_MODE_UNIT_SIZE (@var{m}) -Returns the size in bytes of the subunits of a datum of mode @var{m}. -This is the same as @code{GET_MODE_SIZE} except in the case of complex -modes. For them, the unit size is the size of the real or imaginary -part. - -@findex GET_MODE_NUNITS -@item GET_MODE_NUNITS (@var{m}) -Returns the number of units contained in a mode, i.e., -@code{GET_MODE_SIZE} divided by @code{GET_MODE_UNIT_SIZE}. - -@findex GET_CLASS_NARROWEST_MODE -@item GET_CLASS_NARROWEST_MODE (@var{c}) -Returns the narrowest mode in mode class @var{c}. -@end table - -@findex byte_mode -@findex word_mode -The global variables @code{byte_mode} and @code{word_mode} contain modes -whose classes are @code{MODE_INT} and whose bitsizes are either -@code{BITS_PER_UNIT} or @code{BITS_PER_WORD}, respectively. On 32-bit -machines, these are @code{QImode} and @code{SImode}, respectively. - -@node Constants -@section Constant Expression Types -@cindex RTL constants -@cindex RTL constant expression types - -The simplest RTL expressions are those that represent constant values. - -@table @code -@findex const_int -@item (const_int @var{i}) -This type of expression represents the integer value @var{i}. @var{i} -is customarily accessed with the macro @code{INTVAL} as in -@code{INTVAL (@var{exp})}, which is equivalent to @code{XWINT (@var{exp}, 0)}. - -@findex const0_rtx -@findex const1_rtx -@findex const2_rtx -@findex constm1_rtx -There is only one expression object for the integer value zero; it is -the value of the variable @code{const0_rtx}. Likewise, the only -expression for integer value one is found in @code{const1_rtx}, the only -expression for integer value two is found in @code{const2_rtx}, and the -only expression for integer value negative one is found in -@code{constm1_rtx}. Any attempt to create an expression of code -@code{const_int} and value zero, one, two or negative one will return -@code{const0_rtx}, @code{const1_rtx}, @code{const2_rtx} or -@code{constm1_rtx} as appropriate.@refill - -@findex const_true_rtx -Similarly, there is only one object for the integer whose value is -@code{STORE_FLAG_VALUE}. It is found in @code{const_true_rtx}. If -@code{STORE_FLAG_VALUE} is one, @code{const_true_rtx} and -@code{const1_rtx} will point to the same object. If -@code{STORE_FLAG_VALUE} is -1, @code{const_true_rtx} and -@code{constm1_rtx} will point to the same object.@refill - -@findex const_double -@item (const_double:@var{m} @var{addr} @var{i0} @var{i1} @dots{}) -Represents either a floating-point constant of mode @var{m} or an -integer constant too large to fit into @code{HOST_BITS_PER_WIDE_INT} -bits but small enough to fit within twice that number of bits (GNU CC -does not provide a mechanism to represent even larger constants). In -the latter case, @var{m} will be @code{VOIDmode}. - -@findex CONST_DOUBLE_MEM -@findex CONST_DOUBLE_CHAIN -@var{addr} is used to contain the @code{mem} expression that corresponds -to the location in memory that at which the constant can be found. If -it has not been allocated a memory location, but is on the chain of all -@code{const_double} expressions in this compilation (maintained using an -undisplayed field), @var{addr} contains @code{const0_rtx}. If it is not -on the chain, @var{addr} contains @code{cc0_rtx}. @var{addr} is -customarily accessed with the macro @code{CONST_DOUBLE_MEM} and the -chain field via @code{CONST_DOUBLE_CHAIN}.@refill - -@findex CONST_DOUBLE_LOW -If @var{m} is @code{VOIDmode}, the bits of the value are stored in -@var{i0} and @var{i1}. @var{i0} is customarily accessed with the macro -@code{CONST_DOUBLE_LOW} and @var{i1} with @code{CONST_DOUBLE_HIGH}. - -If the constant is floating point (regardless of its precision), then -the number of integers used to store the value depends on the size of -@code{REAL_VALUE_TYPE} (@pxref{Cross-compilation}). The integers -represent a floating point number, but not precisely in the target -machine's or host machine's floating point format. To convert them to -the precise bit pattern used by the target machine, use the macro -@code{REAL_VALUE_TO_TARGET_DOUBLE} and friends (@pxref{Data Output}). - -@findex CONST0_RTX -@findex CONST1_RTX -@findex CONST2_RTX -The macro @code{CONST0_RTX (@var{mode})} refers to an expression with -value 0 in mode @var{mode}. If mode @var{mode} is of mode class -@code{MODE_INT}, it returns @code{const0_rtx}. Otherwise, it returns a -@code{CONST_DOUBLE} expression in mode @var{mode}. Similarly, the macro -@code{CONST1_RTX (@var{mode})} refers to an expression with value 1 in -mode @var{mode} and similarly for @code{CONST2_RTX}. - -@findex const_string -@item (const_string @var{str}) -Represents a constant string with value @var{str}. Currently this is -used only for insn attributes (@pxref{Insn Attributes}) since constant -strings in C are placed in memory. - -@findex symbol_ref -@item (symbol_ref:@var{mode} @var{symbol}) -Represents the value of an assembler label for data. @var{symbol} is -a string that describes the name of the assembler label. If it starts -with a @samp{*}, the label is the rest of @var{symbol} not including -the @samp{*}. Otherwise, the label is @var{symbol}, usually prefixed -with @samp{_}. - -The @code{symbol_ref} contains a mode, which is usually @code{Pmode}. -Usually that is the only mode for which a symbol is directly valid. - -@findex label_ref -@item (label_ref @var{label}) -Represents the value of an assembler label for code. It contains one -operand, an expression, which must be a @code{code_label} that appears -in the instruction sequence to identify the place where the label -should go. - -The reason for using a distinct expression type for code label -references is so that jump optimization can distinguish them. - -@item (const:@var{m} @var{exp}) -Represents a constant that is the result of an assembly-time -arithmetic computation. The operand, @var{exp}, is an expression that -contains only constants (@code{const_int}, @code{symbol_ref} and -@code{label_ref} expressions) combined with @code{plus} and -@code{minus}. However, not all combinations are valid, since the -assembler cannot do arbitrary arithmetic on relocatable symbols. - -@var{m} should be @code{Pmode}. - -@findex high -@item (high:@var{m} @var{exp}) -Represents the high-order bits of @var{exp}, usually a -@code{symbol_ref}. The number of bits is machine-dependent and is -normally the number of bits specified in an instruction that initializes -the high order bits of a register. It is used with @code{lo_sum} to -represent the typical two-instruction sequence used in RISC machines to -reference a global memory location. - -@var{m} should be @code{Pmode}. -@end table - -@node Regs and Memory -@section Registers and Memory -@cindex RTL register expressions -@cindex RTL memory expressions - -Here are the RTL expression types for describing access to machine -registers and to main memory. - -@table @code -@findex reg -@cindex hard registers -@cindex pseudo registers -@item (reg:@var{m} @var{n}) -For small values of the integer @var{n} (those that are less than -@code{FIRST_PSEUDO_REGISTER}), this stands for a reference to machine -register number @var{n}: a @dfn{hard register}. For larger values of -@var{n}, it stands for a temporary value or @dfn{pseudo register}. -The compiler's strategy is to generate code assuming an unlimited -number of such pseudo registers, and later convert them into hard -registers or into memory references. - -@var{m} is the machine mode of the reference. It is necessary because -machines can generally refer to each register in more than one mode. -For example, a register may contain a full word but there may be -instructions to refer to it as a half word or as a single byte, as -well as instructions to refer to it as a floating point number of -various precisions. - -Even for a register that the machine can access in only one mode, -the mode must always be specified. - -The symbol @code{FIRST_PSEUDO_REGISTER} is defined by the machine -description, since the number of hard registers on the machine is an -invariant characteristic of the machine. Note, however, that not -all of the machine registers must be general registers. All the -machine registers that can be used for storage of data are given -hard register numbers, even those that can be used only in certain -instructions or can hold only certain types of data. - -A hard register may be accessed in various modes throughout one -function, but each pseudo register is given a natural mode -and is accessed only in that mode. When it is necessary to describe -an access to a pseudo register using a nonnatural mode, a @code{subreg} -expression is used. - -A @code{reg} expression with a machine mode that specifies more than -one word of data may actually stand for several consecutive registers. -If in addition the register number specifies a hardware register, then -it actually represents several consecutive hardware registers starting -with the specified one. - -Each pseudo register number used in a function's RTL code is -represented by a unique @code{reg} expression. - -@findex FIRST_VIRTUAL_REGISTER -@findex LAST_VIRTUAL_REGISTER -Some pseudo register numbers, those within the range of -@code{FIRST_VIRTUAL_REGISTER} to @code{LAST_VIRTUAL_REGISTER} only -appear during the RTL generation phase and are eliminated before the -optimization phases. These represent locations in the stack frame that -cannot be determined until RTL generation for the function has been -completed. The following virtual register numbers are defined: - -@table @code -@findex VIRTUAL_INCOMING_ARGS_REGNUM -@item VIRTUAL_INCOMING_ARGS_REGNUM -This points to the first word of the incoming arguments passed on the -stack. Normally these arguments are placed there by the caller, but the -callee may have pushed some arguments that were previously passed in -registers. - -@cindex @code{FIRST_PARM_OFFSET} and virtual registers -@cindex @code{ARG_POINTER_REGNUM} and virtual registers -When RTL generation is complete, this virtual register is replaced -by the sum of the register given by @code{ARG_POINTER_REGNUM} and the -value of @code{FIRST_PARM_OFFSET}. - -@findex VIRTUAL_STACK_VARS_REGNUM -@cindex @code{FRAME_GROWS_DOWNWARD} and virtual registers -@item VIRTUAL_STACK_VARS_REGNUM -If @code{FRAME_GROWS_DOWNWARD} is defined, this points to immediately -above the first variable on the stack. Otherwise, it points to the -first variable on the stack. - -@cindex @code{STARTING_FRAME_OFFSET} and virtual registers -@cindex @code{FRAME_POINTER_REGNUM} and virtual registers -@code{VIRTUAL_STACK_VARS_REGNUM} is replaced with the sum of the -register given by @code{FRAME_POINTER_REGNUM} and the value -@code{STARTING_FRAME_OFFSET}. - -@findex VIRTUAL_STACK_DYNAMIC_REGNUM -@item VIRTUAL_STACK_DYNAMIC_REGNUM -This points to the location of dynamically allocated memory on the stack -immediately after the stack pointer has been adjusted by the amount of -memory desired. - -@cindex @code{STACK_DYNAMIC_OFFSET} and virtual registers -@cindex @code{STACK_POINTER_REGNUM} and virtual registers -This virtual register is replaced by the sum of the register given by -@code{STACK_POINTER_REGNUM} and the value @code{STACK_DYNAMIC_OFFSET}. - -@findex VIRTUAL_OUTGOING_ARGS_REGNUM -@item VIRTUAL_OUTGOING_ARGS_REGNUM -This points to the location in the stack at which outgoing arguments -should be written when the stack is pre-pushed (arguments pushed using -push insns should always use @code{STACK_POINTER_REGNUM}). - -@cindex @code{STACK_POINTER_OFFSET} and virtual registers -This virtual register is replaced by the sum of the register given by -@code{STACK_POINTER_REGNUM} and the value @code{STACK_POINTER_OFFSET}. -@end table - -@findex subreg -@item (subreg:@var{m} @var{reg} @var{bytenum}) -@code{subreg} expressions are used to refer to a register in a machine -mode other than its natural one, or to refer to one register of -a multi-part @code{reg} that actually refers to several registers. - -Each pseudo-register has a natural mode. If it is necessary to -operate on it in a different mode---for example, to perform a fullword -move instruction on a pseudo-register that contains a single -byte---the pseudo-register must be enclosed in a @code{subreg}. In -such a case, @var{bytenum} is zero. - -Usually @var{m} is at least as narrow as the mode of @var{reg}, in which -case it is restricting consideration to only the bits of @var{reg} that -are in @var{m}. - -Sometimes @var{m} is wider than the mode of @var{reg}. These -@code{subreg} expressions are often called @dfn{paradoxical}. They are -used in cases where we want to refer to an object in a wider mode but do -not care what value the additional bits have. The reload pass ensures -that paradoxical references are only made to hard registers. - -The other use of @code{subreg} is to extract the individual registers of -a multi-register value. Machine modes such as @code{DImode} and -@code{TImode} can indicate values longer than a word, values which -usually require two or more consecutive registers. To access one of the -registers, use a @code{subreg} with mode @code{SImode} and a -@var{bytenum} offset that says which register. - -Storing in a non-paradoxical @code{subreg} has undefined results for -bits belonging to the same word as the @code{subreg}. This laxity makes -it easier to generate efficient code for such instructions. To -represent an instruction that preserves all the bits outside of those in -the @code{subreg}, use @code{strict_low_part} around the @code{subreg}. - -@cindex @code{WORDS_BIG_ENDIAN}, effect on @code{subreg} -The compilation parameter @code{WORDS_BIG_ENDIAN}, if set to 1, says -that byte number zero is part of the most significant word; otherwise, -it is part of the least significant word. - -@cindex @code{BYTES_BIG_ENDIAN}, effect on @code{subreg} -The compilation parameter @code{BYTES_BIG_ENDIAN}, if set to 1, says -that byte number zero is the most significant byte within a word; -otherwise, it is the least significant byte within a word. - -@cindex @code{FLOAT_WORDS_BIG_ENDIAN}, (lack of) effect on @code{subreg} -On a few targets, @code{FLOAT_WORDS_BIG_ENDIAN} disagrees with -@code{WORDS_BIG_ENDIAN}. -However, most parts of the compiler treat floating point values as if -they had the same endianness as integer values. This works because -they handle them solely as a collection of integer values, with no -particular numerical value. Only real.c and the runtime libraries -care about @code{FLOAT_WORDS_BIG_ENDIAN}. - -@cindex combiner pass -@cindex reload pass -@cindex @code{subreg}, special reload handling -Between the combiner pass and the reload pass, it is possible to have a -paradoxical @code{subreg} which contains a @code{mem} instead of a -@code{reg} as its first operand. After the reload pass, it is also -possible to have a non-paradoxical @code{subreg} which contains a -@code{mem}; this usually occurs when the @code{mem} is a stack slot -which replaced a pseudo register. - -Note that it is not valid to access a @code{DFmode} value in @code{SFmode} -using a @code{subreg}. On some machines the most significant part of a -@code{DFmode} value does not have the same format as a single-precision -floating value. - -It is also not valid to access a single word of a multi-word value in a -hard register when less registers can hold the value than would be -expected from its size. For example, some 32-bit machines have -floating-point registers that can hold an entire @code{DFmode} value. -If register 10 were such a register @code{(subreg:SI (reg:DF 10) 1)} -would be invalid because there is no way to convert that reference to -a single machine register. The reload pass prevents @code{subreg} -expressions such as these from being formed. - -@findex SUBREG_REG -@findex SUBREG_BYTE -The first operand of a @code{subreg} expression is customarily accessed -with the @code{SUBREG_REG} macro and the second operand is customarily -accessed with the @code{SUBREG_BYTE} macro. - -@findex scratch -@cindex scratch operands -@item (scratch:@var{m}) -This represents a scratch register that will be required for the -execution of a single instruction and not used subsequently. It is -converted into a @code{reg} by either the local register allocator or -the reload pass. - -@code{scratch} is usually present inside a @code{clobber} operation -(@pxref{Side Effects}). - -@findex cc0 -@cindex condition code register -@item (cc0) -This refers to the machine's condition code register. It has no -operands and may not have a machine mode. There are two ways to use it: - -@itemize @bullet -@item -To stand for a complete set of condition code flags. This is best on -most machines, where each comparison sets the entire series of flags. - -With this technique, @code{(cc0)} may be validly used in only two -contexts: as the destination of an assignment (in test and compare -instructions) and in comparison operators comparing against zero -(@code{const_int} with value zero; that is to say, @code{const0_rtx}). - -@item -To stand for a single flag that is the result of a single condition. -This is useful on machines that have only a single flag bit, and in -which comparison instructions must specify the condition to test. - -With this technique, @code{(cc0)} may be validly used in only two -contexts: as the destination of an assignment (in test and compare -instructions) where the source is a comparison operator, and as the -first operand of @code{if_then_else} (in a conditional branch). -@end itemize - -@findex cc0_rtx -There is only one expression object of code @code{cc0}; it is the -value of the variable @code{cc0_rtx}. Any attempt to create an -expression of code @code{cc0} will return @code{cc0_rtx}. - -Instructions can set the condition code implicitly. On many machines, -nearly all instructions set the condition code based on the value that -they compute or store. It is not necessary to record these actions -explicitly in the RTL because the machine description includes a -prescription for recognizing the instructions that do so (by means of -the macro @code{NOTICE_UPDATE_CC}). @xref{Condition Code}. Only -instructions whose sole purpose is to set the condition code, and -instructions that use the condition code, need mention @code{(cc0)}. - -On some machines, the condition code register is given a register number -and a @code{reg} is used instead of @code{(cc0)}. This is usually the -preferable approach if only a small subset of instructions modify the -condition code. Other machines store condition codes in general -registers; in such cases a pseudo register should be used. - -Some machines, such as the Sparc and RS/6000, have two sets of -arithmetic instructions, one that sets and one that does not set the -condition code. This is best handled by normally generating the -instruction that does not set the condition code, and making a pattern -that both performs the arithmetic and sets the condition code register -(which would not be @code{(cc0)} in this case). For examples, search -for @samp{addcc} and @samp{andcc} in @file{sparc.md}. - -@findex pc -@item (pc) -@cindex program counter -This represents the machine's program counter. It has no operands and -may not have a machine mode. @code{(pc)} may be validly used only in -certain specific contexts in jump instructions. - -@findex pc_rtx -There is only one expression object of code @code{pc}; it is the value -of the variable @code{pc_rtx}. Any attempt to create an expression of -code @code{pc} will return @code{pc_rtx}. - -All instructions that do not jump alter the program counter implicitly -by incrementing it, but there is no need to mention this in the RTL. - -@findex mem -@item (mem:@var{m} @var{addr} @var{alias}) -This RTX represents a reference to main memory at an address -represented by the expression @var{addr}. @var{m} specifies how large -a unit of memory is accessed. @var{alias} specifies an alias set for the -reference. In general two items are in different alias sets if they cannot -reference the same memory address. - -@findex addressof -@item (addressof:@var{m} @var{reg}) -This RTX represents a request for the address of register @var{reg}. Its mode -is always @code{Pmode}. If there are any @code{addressof} -expressions left in the function after CSE, @var{reg} is forced into the -stack and the @code{addressof} expression is replaced with a @code{plus} -expression for the address of its stack slot. -@end table - -@node Arithmetic -@section RTL Expressions for Arithmetic -@cindex arithmetic, in RTL -@cindex math, in RTL -@cindex RTL expressions for arithmetic - -Unless otherwise specified, all the operands of arithmetic expressions -must be valid for mode @var{m}. An operand is valid for mode @var{m} -if it has mode @var{m}, or if it is a @code{const_int} or -@code{const_double} and @var{m} is a mode of class @code{MODE_INT}. - -For commutative binary operations, constants should be placed in the -second operand. - -@table @code -@findex plus -@cindex RTL addition -@cindex RTL sum -@item (plus:@var{m} @var{x} @var{y}) -Represents the sum of the values represented by @var{x} and @var{y} -carried out in machine mode @var{m}. - -@findex lo_sum -@item (lo_sum:@var{m} @var{x} @var{y}) -Like @code{plus}, except that it represents that sum of @var{x} and the -low-order bits of @var{y}. The number of low order bits is -machine-dependent but is normally the number of bits in a @code{Pmode} -item minus the number of bits set by the @code{high} code -(@pxref{Constants}). - -@var{m} should be @code{Pmode}. - -@findex minus -@cindex RTL subtraction -@cindex RTL difference -@item (minus:@var{m} @var{x} @var{y}) -Like @code{plus} but represents subtraction. - -@findex ss_plus -@cindex RTL addition with signed saturation -@item (ss_plus:@var{m} @var{x} @var{y}) - -Like @code{plus}, but using signed saturation in case of an overflow. - -@findex us_plus -@cindex RTL addition with unsigned saturation -@item (us_plus:@var{m} @var{x} @var{y}) - -Like @code{plus}, but using unsigned saturation in case of an overflow. - -@findex ss_minus -@cindex RTL addition with signed saturation -@item (ss_minus:@var{m} @var{x} @var{y}) - -Like @code{minus}, but using signed saturation in case of an overflow. - -@findex us_minus -@cindex RTL addition with unsigned saturation -@item (us_minus:@var{m} @var{x} @var{y}) - -Like @code{minus}, but using unsigned saturation in case of an overflow. - -@findex compare -@cindex RTL comparison -@item (compare:@var{m} @var{x} @var{y}) -Represents the result of subtracting @var{y} from @var{x} for purposes -of comparison. The result is computed without overflow, as if with -infinite precision. - -Of course, machines can't really subtract with infinite precision. -However, they can pretend to do so when only the sign of the result will -be used, which is the case when the result is stored in the condition -code. And that is the @emph{only} way this kind of expression may -validly be used: as a value to be stored in the condition codes, either -@code{(cc0)} or a register. @xref{Comparisons}. - -The mode @var{m} is not related to the modes of @var{x} and @var{y}, but -instead is the mode of the condition code value. If @code{(cc0)} is -used, it is @code{VOIDmode}. Otherwise it is some mode in class -@code{MODE_CC}, often @code{CCmode}. @xref{Condition Code}. If @var{m} -is @code{VOIDmode} or @code{CCmode}, the operation returns sufficient -information (in an unspecified format) so that any comparison operator -can be applied to the result of the @code{COMPARE} operation. For other -modes in class @code{MODE_CC}, the operation only returns a subset of -this information. - -Normally, @var{x} and @var{y} must have the same mode. Otherwise, -@code{compare} is valid only if the mode of @var{x} is in class -@code{MODE_INT} and @var{y} is a @code{const_int} or -@code{const_double} with mode @code{VOIDmode}. The mode of @var{x} -determines what mode the comparison is to be done in; thus it must not -be @code{VOIDmode}. - -If one of the operands is a constant, it should be placed in the -second operand and the comparison code adjusted as appropriate. - -A @code{compare} specifying two @code{VOIDmode} constants is not valid -since there is no way to know in what mode the comparison is to be -performed; the comparison must either be folded during the compilation -or the first operand must be loaded into a register while its mode is -still known. - -@findex neg -@item (neg:@var{m} @var{x}) -Represents the negation (subtraction from zero) of the value represented -by @var{x}, carried out in mode @var{m}. - -@findex mult -@cindex multiplication -@cindex product -@item (mult:@var{m} @var{x} @var{y}) -Represents the signed product of the values represented by @var{x} and -@var{y} carried out in machine mode @var{m}. - -Some machines support a multiplication that generates a product wider -than the operands. Write the pattern for this as - -@example -(mult:@var{m} (sign_extend:@var{m} @var{x}) (sign_extend:@var{m} @var{y})) -@end example - -where @var{m} is wider than the modes of @var{x} and @var{y}, which need -not be the same. - -Write patterns for unsigned widening multiplication similarly using -@code{zero_extend}. - -@findex div -@cindex division -@cindex signed division -@cindex quotient -@item (div:@var{m} @var{x} @var{y}) -Represents the quotient in signed division of @var{x} by @var{y}, -carried out in machine mode @var{m}. If @var{m} is a floating point -mode, it represents the exact quotient; otherwise, the integerized -quotient. - -Some machines have division instructions in which the operands and -quotient widths are not all the same; you should represent -such instructions using @code{truncate} and @code{sign_extend} as in, - -@example -(truncate:@var{m1} (div:@var{m2} @var{x} (sign_extend:@var{m2} @var{y}))) -@end example - -@findex udiv -@cindex unsigned division -@cindex division -@item (udiv:@var{m} @var{x} @var{y}) -Like @code{div} but represents unsigned division. - -@findex mod -@findex umod -@cindex remainder -@cindex division -@item (mod:@var{m} @var{x} @var{y}) -@itemx (umod:@var{m} @var{x} @var{y}) -Like @code{div} and @code{udiv} but represent the remainder instead of -the quotient. - -@findex smin -@findex smax -@cindex signed minimum -@cindex signed maximum -@item (smin:@var{m} @var{x} @var{y}) -@itemx (smax:@var{m} @var{x} @var{y}) -Represents the smaller (for @code{smin}) or larger (for @code{smax}) of -@var{x} and @var{y}, interpreted as signed integers in mode @var{m}. - -@findex umin -@findex umax -@cindex unsigned minimum and maximum -@item (umin:@var{m} @var{x} @var{y}) -@itemx (umax:@var{m} @var{x} @var{y}) -Like @code{smin} and @code{smax}, but the values are interpreted as unsigned -integers. - -@findex not -@cindex complement, bitwise -@cindex bitwise complement -@item (not:@var{m} @var{x}) -Represents the bitwise complement of the value represented by @var{x}, -carried out in mode @var{m}, which must be a fixed-point machine mode. - -@findex and -@cindex logical-and, bitwise -@cindex bitwise logical-and -@item (and:@var{m} @var{x} @var{y}) -Represents the bitwise logical-and of the values represented by -@var{x} and @var{y}, carried out in machine mode @var{m}, which must be -a fixed-point machine mode. - -@findex ior -@cindex inclusive-or, bitwise -@cindex bitwise inclusive-or -@item (ior:@var{m} @var{x} @var{y}) -Represents the bitwise inclusive-or of the values represented by @var{x} -and @var{y}, carried out in machine mode @var{m}, which must be a -fixed-point mode. - -@findex xor -@cindex exclusive-or, bitwise -@cindex bitwise exclusive-or -@item (xor:@var{m} @var{x} @var{y}) -Represents the bitwise exclusive-or of the values represented by @var{x} -and @var{y}, carried out in machine mode @var{m}, which must be a -fixed-point mode. - -@findex ashift -@cindex left shift -@cindex shift -@cindex arithmetic shift -@item (ashift:@var{m} @var{x} @var{c}) -Represents the result of arithmetically shifting @var{x} left by @var{c} -places. @var{x} have mode @var{m}, a fixed-point machine mode. @var{c} -be a fixed-point mode or be a constant with mode @code{VOIDmode}; which -mode is determined by the mode called for in the machine description -entry for the left-shift instruction. For example, on the Vax, the mode -of @var{c} is @code{QImode} regardless of @var{m}. - -@findex lshiftrt -@cindex right shift -@findex ashiftrt -@item (lshiftrt:@var{m} @var{x} @var{c}) -@itemx (ashiftrt:@var{m} @var{x} @var{c}) -Like @code{ashift} but for right shift. Unlike the case for left shift, -these two operations are distinct. - -@findex rotate -@cindex rotate -@cindex left rotate -@findex rotatert -@cindex right rotate -@item (rotate:@var{m} @var{x} @var{c}) -@itemx (rotatert:@var{m} @var{x} @var{c}) -Similar but represent left and right rotate. If @var{c} is a constant, -use @code{rotate}. - -@findex abs -@cindex absolute value -@item (abs:@var{m} @var{x}) -Represents the absolute value of @var{x}, computed in mode @var{m}. - -@findex sqrt -@cindex square root -@item (sqrt:@var{m} @var{x}) -Represents the square root of @var{x}, computed in mode @var{m}. -Most often @var{m} will be a floating point mode. - -@findex ffs -@item (ffs:@var{m} @var{x}) -Represents one plus the index of the least significant 1-bit in -@var{x}, represented as an integer of mode @var{m}. (The value is -zero if @var{x} is zero.) The mode of @var{x} need not be @var{m}; -depending on the target machine, various mode combinations may be -valid. -@end table - -@node Comparisons -@section Comparison Operations -@cindex RTL comparison operations - -Comparison operators test a relation on two operands and are considered -to represent a machine-dependent nonzero value described by, but not -necessarily equal to, @code{STORE_FLAG_VALUE} (@pxref{Misc}) -if the relation holds, or zero if it does not. The mode of the -comparison operation is independent of the mode of the data being -compared. If the comparison operation is being tested (e.g., the first -operand of an @code{if_then_else}), the mode must be @code{VOIDmode}. -If the comparison operation is producing data to be stored in some -variable, the mode must be in class @code{MODE_INT}. All comparison -operations producing data must use the same mode, which is -machine-specific. - -@cindex condition codes -There are two ways that comparison operations may be used. The -comparison operators may be used to compare the condition codes -@code{(cc0)} against zero, as in @code{(eq (cc0) (const_int 0))}. Such -a construct actually refers to the result of the preceding instruction -in which the condition codes were set. The instruction setting the -condition code must be adjacent to the instruction using the condition -code; only @code{note} insns may separate them. - -Alternatively, a comparison operation may directly compare two data -objects. The mode of the comparison is determined by the operands; they -must both be valid for a common machine mode. A comparison with both -operands constant would be invalid as the machine mode could not be -deduced from it, but such a comparison should never exist in RTL due to -constant folding. - -In the example above, if @code{(cc0)} were last set to -@code{(compare @var{x} @var{y})}, the comparison operation is -identical to @code{(eq @var{x} @var{y})}. Usually only one style -of comparisons is supported on a particular machine, but the combine -pass will try to merge the operations to produce the @code{eq} shown -in case it exists in the context of the particular insn involved. - -Inequality comparisons come in two flavors, signed and unsigned. Thus, -there are distinct expression codes @code{gt} and @code{gtu} for signed and -unsigned greater-than. These can produce different results for the same -pair of integer values: for example, 1 is signed greater-than -1 but not -unsigned greater-than, because -1 when regarded as unsigned is actually -@code{0xffffffff} which is greater than 1. - -The signed comparisons are also used for floating point values. Floating -point comparisons are distinguished by the machine modes of the operands. - -@table @code -@findex eq -@cindex equal -@item (eq:@var{m} @var{x} @var{y}) -@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y} -are equal, otherwise 0. - -@findex ne -@cindex not equal -@item (ne:@var{m} @var{x} @var{y}) -@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y} -are not equal, otherwise 0. - -@findex gt -@cindex greater than -@item (gt:@var{m} @var{x} @var{y}) -@code{STORE_FLAG_VALUE} if the @var{x} is greater than @var{y}. If they -are fixed-point, the comparison is done in a signed sense. - -@findex gtu -@cindex greater than -@cindex unsigned greater than -@item (gtu:@var{m} @var{x} @var{y}) -Like @code{gt} but does unsigned comparison, on fixed-point numbers only. - -@findex lt -@cindex less than -@findex ltu -@cindex unsigned less than -@item (lt:@var{m} @var{x} @var{y}) -@itemx (ltu:@var{m} @var{x} @var{y}) -Like @code{gt} and @code{gtu} but test for ``less than''. - -@findex ge -@cindex greater than -@findex geu -@cindex unsigned greater than -@item (ge:@var{m} @var{x} @var{y}) -@itemx (geu:@var{m} @var{x} @var{y}) -Like @code{gt} and @code{gtu} but test for ``greater than or equal''. - -@findex le -@cindex less than or equal -@findex leu -@cindex unsigned less than -@item (le:@var{m} @var{x} @var{y}) -@itemx (leu:@var{m} @var{x} @var{y}) -Like @code{gt} and @code{gtu} but test for ``less than or equal''. - -@findex if_then_else -@item (if_then_else @var{cond} @var{then} @var{else}) -This is not a comparison operation but is listed here because it is -always used in conjunction with a comparison operation. To be -precise, @var{cond} is a comparison expression. This expression -represents a choice, according to @var{cond}, between the value -represented by @var{then} and the one represented by @var{else}. - -On most machines, @code{if_then_else} expressions are valid only -to express conditional jumps. - -@findex cond -@item (cond [@var{test1} @var{value1} @var{test2} @var{value2} @dots{}] @var{default}) -Similar to @code{if_then_else}, but more general. Each of @var{test1}, -@var{test2}, @dots{} is performed in turn. The result of this expression is -the @var{value} corresponding to the first non-zero test, or @var{default} if -none of the tests are non-zero expressions. - -This is currently not valid for instruction patterns and is supported only -for insn attributes. @xref{Insn Attributes}. -@end table - -@node Bit Fields -@section Bit Fields -@cindex bit fields - -Special expression codes exist to represent bitfield instructions. -These types of expressions are lvalues in RTL; they may appear -on the left side of an assignment, indicating insertion of a value -into the specified bit field. - -@table @code -@findex sign_extract -@cindex @code{BITS_BIG_ENDIAN}, effect on @code{sign_extract} -@item (sign_extract:@var{m} @var{loc} @var{size} @var{pos}) -This represents a reference to a sign-extended bit field contained or -starting in @var{loc} (a memory or register reference). The bit field -is @var{size} bits wide and starts at bit @var{pos}. The compilation -option @code{BITS_BIG_ENDIAN} says which end of the memory unit -@var{pos} counts from. - -If @var{loc} is in memory, its mode must be a single-byte integer mode. -If @var{loc} is in a register, the mode to use is specified by the -operand of the @code{insv} or @code{extv} pattern -(@pxref{Standard Names}) and is usually a full-word integer mode, -which is the default if none is specified. - -The mode of @var{pos} is machine-specific and is also specified -in the @code{insv} or @code{extv} pattern. - -The mode @var{m} is the same as the mode that would be used for -@var{loc} if it were a register. - -@findex zero_extract -@item (zero_extract:@var{m} @var{loc} @var{size} @var{pos}) -Like @code{sign_extract} but refers to an unsigned or zero-extended -bit field. The same sequence of bits are extracted, but they -are filled to an entire word with zeros instead of by sign-extension. -@end table - -@node Vector Operations -@section Vector Operations -@cindex vector operations - -All normal rtl expressions can be used with vector modes; they are -interpreted as operating on each part of the vector independently. -Additionally, there are a few new expressions to describe specific vector -operations. - -@table @code -@findex vec_merge -@item (vec_merge:@var{m} @var{vec1} @var{vec2} @var{items}) -This describes a merge operation between two vectors. The result is a vector -of mode @var{m}; its elements are selected from either @var{vec1} or -@var{vec2}. Which elements are selected is described by @var{items}, which -is a bit mask represented by a @code{const_int}; a zero bit indicates the -corresponding element in the result vector is taken from @var{vec2} while -a set bit indicates it is taken from @var{vec1}. - -@findex vec_select -@item (vec_select:@var{m} @var{vec1} @var{selection}) -This describes an operation that selects parts of a vector. @var{vec1} is -the source vector, @var{selection} is a @code{parallel} that contains a -@code{const_int} for each of the subparts of the result vector, giving the -number of the source subpart that should be stored into it. - -@findex vec_concat -@item (vec_concat:@var{m} @var{vec1} @var{vec2}) -Describes a vector concat operation. The result is a concatenation of the -vectors @var{vec1} and @var{vec2}; its length is the sum of the lengths of -the two inputs. - -@findex vec_const -@item (vec_const:@var{m} @var{subparts}) -This describes a constant vector. @var{subparts} is a @code{parallel} that -contains a constant for each of the subparts of the vector. - -@findex vec_duplicate -@item (vec_duplicate:@var{m} @var{vec}) -This operation converts a small vector into a larger one by duplicating the -input values. The output vector mode must have the same submodes as the -input vector mode, and the number of output parts must be an integer multiple -of the number of input parts. - -@end table - -@node Conversions -@section Conversions -@cindex conversions -@cindex machine mode conversions - -All conversions between machine modes must be represented by -explicit conversion operations. For example, an expression -which is the sum of a byte and a full word cannot be written as -@code{(plus:SI (reg:QI 34) (reg:SI 80))} because the @code{plus} -operation requires two operands of the same machine mode. -Therefore, the byte-sized operand is enclosed in a conversion -operation, as in - -@example -(plus:SI (sign_extend:SI (reg:QI 34)) (reg:SI 80)) -@end example - -The conversion operation is not a mere placeholder, because there -may be more than one way of converting from a given starting mode -to the desired final mode. The conversion operation code says how -to do it. - -For all conversion operations, @var{x} must not be @code{VOIDmode} -because the mode in which to do the conversion would not be known. -The conversion must either be done at compile-time or @var{x} -must be placed into a register. - -@table @code -@findex sign_extend -@item (sign_extend:@var{m} @var{x}) -Represents the result of sign-extending the value @var{x} -to machine mode @var{m}. @var{m} must be a fixed-point mode -and @var{x} a fixed-point value of a mode narrower than @var{m}. - -@findex zero_extend -@item (zero_extend:@var{m} @var{x}) -Represents the result of zero-extending the value @var{x} -to machine mode @var{m}. @var{m} must be a fixed-point mode -and @var{x} a fixed-point value of a mode narrower than @var{m}. - -@findex float_extend -@item (float_extend:@var{m} @var{x}) -Represents the result of extending the value @var{x} -to machine mode @var{m}. @var{m} must be a floating point mode -and @var{x} a floating point value of a mode narrower than @var{m}. - -@findex truncate -@item (truncate:@var{m} @var{x}) -Represents the result of truncating the value @var{x} -to machine mode @var{m}. @var{m} must be a fixed-point mode -and @var{x} a fixed-point value of a mode wider than @var{m}. - -@findex ss_truncate -@item (ss_truncate:@var{m} @var{x}) -Represents the result of truncating the value @var{x} -to machine mode @var{m}, using signed saturation in the case of -overflow. Both @var{m} and the mode of @var{x} must be fixed-point -modes. - -@findex us_truncate -@item (us_truncate:@var{m} @var{x}) -Represents the result of truncating the value @var{x} -to machine mode @var{m}, using unsigned saturation in the case of -overflow. Both @var{m} and the mode of @var{x} must be fixed-point -modes. - -@findex float_truncate -@item (float_truncate:@var{m} @var{x}) -Represents the result of truncating the value @var{x} -to machine mode @var{m}. @var{m} must be a floating point mode -and @var{x} a floating point value of a mode wider than @var{m}. - -@findex float -@item (float:@var{m} @var{x}) -Represents the result of converting fixed point value @var{x}, -regarded as signed, to floating point mode @var{m}. - -@findex unsigned_float -@item (unsigned_float:@var{m} @var{x}) -Represents the result of converting fixed point value @var{x}, -regarded as unsigned, to floating point mode @var{m}. - -@findex fix -@item (fix:@var{m} @var{x}) -When @var{m} is a fixed point mode, represents the result of -converting floating point value @var{x} to mode @var{m}, regarded as -signed. How rounding is done is not specified, so this operation may -be used validly in compiling C code only for integer-valued operands. - -@findex unsigned_fix -@item (unsigned_fix:@var{m} @var{x}) -Represents the result of converting floating point value @var{x} to -fixed point mode @var{m}, regarded as unsigned. How rounding is done -is not specified. - -@findex fix -@item (fix:@var{m} @var{x}) -When @var{m} is a floating point mode, represents the result of -converting floating point value @var{x} (valid for mode @var{m}) to an -integer, still represented in floating point mode @var{m}, by rounding -towards zero. -@end table - -@node RTL Declarations -@section Declarations -@cindex RTL declarations -@cindex declarations, RTL - -Declaration expression codes do not represent arithmetic operations -but rather state assertions about their operands. - -@table @code -@findex strict_low_part -@cindex @code{subreg}, in @code{strict_low_part} -@item (strict_low_part (subreg:@var{m} (reg:@var{n} @var{r}) 0)) -This expression code is used in only one context: as the destination operand of a -@code{set} expression. In addition, the operand of this expression -must be a non-paradoxical @code{subreg} expression. - -The presence of @code{strict_low_part} says that the part of the -register which is meaningful in mode @var{n}, but is not part of -mode @var{m}, is not to be altered. Normally, an assignment to such -a subreg is allowed to have undefined effects on the rest of the -register when @var{m} is less than a word. -@end table - -@node Side Effects -@section Side Effect Expressions -@cindex RTL side effect expressions - -The expression codes described so far represent values, not actions. -But machine instructions never produce values; they are meaningful -only for their side effects on the state of the machine. Special -expression codes are used to represent side effects. - -The body of an instruction is always one of these side effect codes; -the codes described above, which represent values, appear only as -the operands of these. - -@table @code -@findex set -@item (set @var{lval} @var{x}) -Represents the action of storing the value of @var{x} into the place -represented by @var{lval}. @var{lval} must be an expression -representing a place that can be stored in: @code{reg} (or @code{subreg} -or @code{strict_low_part}), @code{mem}, @code{pc}, @code{parallel}, or -@code{cc0}.@refill - -If @var{lval} is a @code{reg}, @code{subreg} or @code{mem}, it has a -machine mode; then @var{x} must be valid for that mode.@refill - -If @var{lval} is a @code{reg} whose machine mode is less than the full -width of the register, then it means that the part of the register -specified by the machine mode is given the specified value and the -rest of the register receives an undefined value. Likewise, if -@var{lval} is a @code{subreg} whose machine mode is narrower than -the mode of the register, the rest of the register can be changed in -an undefined way. - -If @var{lval} is a @code{strict_low_part} of a @code{subreg}, then the -part of the register specified by the machine mode of the -@code{subreg} is given the value @var{x} and the rest of the register -is not changed.@refill - -If @var{lval} is @code{(cc0)}, it has no machine mode, and @var{x} may -be either a @code{compare} expression or a value that may have any mode. -The latter case represents a ``test'' instruction. The expression -@code{(set (cc0) (reg:@var{m} @var{n}))} is equivalent to -@code{(set (cc0) (compare (reg:@var{m} @var{n}) (const_int 0)))}. -Use the former expression to save space during the compilation. - -If @var{lval} is a @code{parallel}, it is used to represent the case of -a function returning a structure in multiple registers. Each element -of the @code{paralllel} is an @code{expr_list} whose first operand is a -@code{reg} and whose second operand is a @code{const_int} representing the -offset (in bytes) into the structure at which the data in that register -corresponds. The first element may be null to indicate that the structure -is also passed partly in memory. - -@cindex jump instructions and @code{set} -@cindex @code{if_then_else} usage -If @var{lval} is @code{(pc)}, we have a jump instruction, and the -possibilities for @var{x} are very limited. It may be a -@code{label_ref} expression (unconditional jump). It may be an -@code{if_then_else} (conditional jump), in which case either the -second or the third operand must be @code{(pc)} (for the case which -does not jump) and the other of the two must be a @code{label_ref} -(for the case which does jump). @var{x} may also be a @code{mem} or -@code{(plus:SI (pc) @var{y})}, where @var{y} may be a @code{reg} or a -@code{mem}; these unusual patterns are used to represent jumps through -branch tables.@refill - -If @var{lval} is neither @code{(cc0)} nor @code{(pc)}, the mode of -@var{lval} must not be @code{VOIDmode} and the mode of @var{x} must be -valid for the mode of @var{lval}. - -@findex SET_DEST -@findex SET_SRC -@var{lval} is customarily accessed with the @code{SET_DEST} macro and -@var{x} with the @code{SET_SRC} macro. - -@findex return -@item (return) -As the sole expression in a pattern, represents a return from the -current function, on machines where this can be done with one -instruction, such as Vaxes. On machines where a multi-instruction -``epilogue'' must be executed in order to return from the function, -returning is done by jumping to a label which precedes the epilogue, and -the @code{return} expression code is never used. - -Inside an @code{if_then_else} expression, represents the value to be -placed in @code{pc} to return to the caller. - -Note that an insn pattern of @code{(return)} is logically equivalent to -@code{(set (pc) (return))}, but the latter form is never used. - -@findex call -@item (call @var{function} @var{nargs}) -Represents a function call. @var{function} is a @code{mem} expression -whose address is the address of the function to be called. -@var{nargs} is an expression which can be used for two purposes: on -some machines it represents the number of bytes of stack argument; on -others, it represents the number of argument registers. - -Each machine has a standard machine mode which @var{function} must -have. The machine description defines macro @code{FUNCTION_MODE} to -expand into the requisite mode name. The purpose of this mode is to -specify what kind of addressing is allowed, on machines where the -allowed kinds of addressing depend on the machine mode being -addressed. - -@findex clobber -@item (clobber @var{x}) -Represents the storing or possible storing of an unpredictable, -undescribed value into @var{x}, which must be a @code{reg}, -@code{scratch}, @code{parallel} or @code{mem} expression. - -One place this is used is in string instructions that store standard -values into particular hard registers. It may not be worth the -trouble to describe the values that are stored, but it is essential to -inform the compiler that the registers will be altered, lest it -attempt to keep data in them across the string instruction. - -If @var{x} is @code{(mem:BLK (const_int 0))}, it means that all memory -locations must be presumed clobbered. If @var{x} is a @code{parallel}, -it has the same meaning as a @code{parallel} in a @code{set} expression. - -Note that the machine description classifies certain hard registers as -``call-clobbered''. All function call instructions are assumed by -default to clobber these registers, so there is no need to use -@code{clobber} expressions to indicate this fact. Also, each function -call is assumed to have the potential to alter any memory location, -unless the function is declared @code{const}. - -If the last group of expressions in a @code{parallel} are each a -@code{clobber} expression whose arguments are @code{reg} or -@code{match_scratch} (@pxref{RTL Template}) expressions, the combiner -phase can add the appropriate @code{clobber} expressions to an insn it -has constructed when doing so will cause a pattern to be matched. - -This feature can be used, for example, on a machine that whose multiply -and add instructions don't use an MQ register but which has an -add-accumulate instruction that does clobber the MQ register. Similarly, -a combined instruction might require a temporary register while the -constituent instructions might not. - -When a @code{clobber} expression for a register appears inside a -@code{parallel} with other side effects, the register allocator -guarantees that the register is unoccupied both before and after that -insn. However, the reload phase may allocate a register used for one of -the inputs unless the @samp{&} constraint is specified for the selected -alternative (@pxref{Modifiers}). You can clobber either a specific hard -register, a pseudo register, or a @code{scratch} expression; in the -latter two cases, GNU CC will allocate a hard register that is available -there for use as a temporary. - -For instructions that require a temporary register, you should use -@code{scratch} instead of a pseudo-register because this will allow the -combiner phase to add the @code{clobber} when required. You do this by -coding (@code{clobber} (@code{match_scratch} @dots{})). If you do -clobber a pseudo register, use one which appears nowhere else---generate -a new one each time. Otherwise, you may confuse CSE. - -There is one other known use for clobbering a pseudo register in a -@code{parallel}: when one of the input operands of the insn is also -clobbered by the insn. In this case, using the same pseudo register in -the clobber and elsewhere in the insn produces the expected results. - -@findex use -@item (use @var{x}) -Represents the use of the value of @var{x}. It indicates that the -value in @var{x} at this point in the program is needed, even though -it may not be apparent why this is so. Therefore, the compiler will -not attempt to delete previous instructions whose only effect is to -store a value in @var{x}. @var{x} must be a @code{reg} expression. - -In some situations, it may be tempting to add a @code{use} of a -register in a @code{parallel} to describe a situation where the value -of a special register will modify the behaviour of the instruction. -An hypothetical example might be a pattern for an addition that can -either wrap around or use saturating addition depending on the value -of a special control register: - -@example -(parallel [(set (reg:SI 2) (unspec:SI [(reg:SI 3) (reg:SI 4)] 0)) - (use (reg:SI 1))]) -@end example - -@noindent - -This will not work, several of the optimizers only look at expressions -locally; it is very likely that if you have multiple insns with -identical inputs to the @code{unspec}, they will be optimized away even -if register 1 changes in between. - -This means that @code{use} can @emph{only} be used to describe -that the register is live. You should think twice before adding -@code{use} statements, more often you will want to use @code{unspec} -instead. The @code{use} RTX is most commonly useful to describe that -a fixed register is implicitly used in an insn. It is also safe to use -in patterns where the compiler knows for other reasons that the result -of the whole pattern is variable, such as @samp{movstr@var{m}} or -@samp{call} patterns. - -During the reload phase, an insn that has a @code{use} as pattern -can carry a reg_equal note. These @code{use} insns will be deleted -before the reload phase exits. - -During the delayed branch scheduling phase, @var{x} may be an insn. -This indicates that @var{x} previously was located at this place in the -code and its data dependencies need to be taken into account. These -@code{use} insns will be deleted before the delayed branch scheduling -phase exits. - -@findex parallel -@item (parallel [@var{x0} @var{x1} @dots{}]) -Represents several side effects performed in parallel. The square -brackets stand for a vector; the operand of @code{parallel} is a -vector of expressions. @var{x0}, @var{x1} and so on are individual -side effect expressions---expressions of code @code{set}, @code{call}, -@code{return}, @code{clobber} or @code{use}.@refill - -``In parallel'' means that first all the values used in the individual -side-effects are computed, and second all the actual side-effects are -performed. For example, - -@example -(parallel [(set (reg:SI 1) (mem:SI (reg:SI 1))) - (set (mem:SI (reg:SI 1)) (reg:SI 1))]) -@end example - -@noindent -says unambiguously that the values of hard register 1 and the memory -location addressed by it are interchanged. In both places where -@code{(reg:SI 1)} appears as a memory address it refers to the value -in register 1 @emph{before} the execution of the insn. - -It follows that it is @emph{incorrect} to use @code{parallel} and -expect the result of one @code{set} to be available for the next one. -For example, people sometimes attempt to represent a jump-if-zero -instruction this way: - -@example -(parallel [(set (cc0) (reg:SI 34)) - (set (pc) (if_then_else - (eq (cc0) (const_int 0)) - (label_ref @dots{}) - (pc)))]) -@end example - -@noindent -But this is incorrect, because it says that the jump condition depends -on the condition code value @emph{before} this instruction, not on the -new value that is set by this instruction. - -@cindex peephole optimization, RTL representation -Peephole optimization, which takes place together with final assembly -code output, can produce insns whose patterns consist of a @code{parallel} -whose elements are the operands needed to output the resulting -assembler code---often @code{reg}, @code{mem} or constant expressions. -This would not be well-formed RTL at any other stage in compilation, -but it is ok then because no further optimization remains to be done. -However, the definition of the macro @code{NOTICE_UPDATE_CC}, if -any, must deal with such insns if you define any peephole optimizations. - -@findex sequence -@item (sequence [@var{insns} @dots{}]) -Represents a sequence of insns. Each of the @var{insns} that appears -in the vector is suitable for appearing in the chain of insns, so it -must be an @code{insn}, @code{jump_insn}, @code{call_insn}, -@code{code_label}, @code{barrier} or @code{note}. - -A @code{sequence} RTX is never placed in an actual insn during RTL -generation. It represents the sequence of insns that result from a -@code{define_expand} @emph{before} those insns are passed to -@code{emit_insn} to insert them in the chain of insns. When actually -inserted, the individual sub-insns are separated out and the -@code{sequence} is forgotten. - -After delay-slot scheduling is completed, an insn and all the insns that -reside in its delay slots are grouped together into a @code{sequence}. -The insn requiring the delay slot is the first insn in the vector; -subsequent insns are to be placed in the delay slot. - -@code{INSN_ANNULLED_BRANCH_P} is set on an insn in a delay slot to -indicate that a branch insn should be used that will conditionally annul -the effect of the insns in the delay slots. In such a case, -@code{INSN_FROM_TARGET_P} indicates that the insn is from the target of -the branch and should be executed only if the branch is taken; otherwise -the insn should be executed only if the branch is not taken. -@xref{Delay Slots}. -@end table - -These expression codes appear in place of a side effect, as the body of -an insn, though strictly speaking they do not always describe side -effects as such: - -@table @code -@findex asm_input -@item (asm_input @var{s}) -Represents literal assembler code as described by the string @var{s}. - -@findex unspec -@findex unspec_volatile -@item (unspec [@var{operands} @dots{}] @var{index}) -@itemx (unspec_volatile [@var{operands} @dots{}] @var{index}) -Represents a machine-specific operation on @var{operands}. @var{index} -selects between multiple machine-specific operations. -@code{unspec_volatile} is used for volatile operations and operations -that may trap; @code{unspec} is used for other operations. - -These codes may appear inside a @code{pattern} of an -insn, inside a @code{parallel}, or inside an expression. - -@findex addr_vec -@item (addr_vec:@var{m} [@var{lr0} @var{lr1} @dots{}]) -Represents a table of jump addresses. The vector elements @var{lr0}, -etc., are @code{label_ref} expressions. The mode @var{m} specifies -how much space is given to each address; normally @var{m} would be -@code{Pmode}. - -@findex addr_diff_vec -@item (addr_diff_vec:@var{m} @var{base} [@var{lr0} @var{lr1} @dots{}] @var{min} @var{max} @var{flags}) -Represents a table of jump addresses expressed as offsets from -@var{base}. The vector elements @var{lr0}, etc., are @code{label_ref} -expressions and so is @var{base}. The mode @var{m} specifies how much -space is given to each address-difference. @var{min} and @var{max} -are set up by branch shortening and hold a label with a minimum and a -maximum address, respectively. @var{flags} indicates the relative -position of @var{base}, @var{min} and @var{max} to the containing insn -and of @var{min} and @var{max} to @var{base}. See rtl.def for details.@refill -@end table - -@node Incdec -@section Embedded Side-Effects on Addresses -@cindex RTL preincrement -@cindex RTL postincrement -@cindex RTL predecrement -@cindex RTL postdecrement - -Six special side-effect expression codes appear as memory addresses. - -@table @code -@findex pre_dec -@item (pre_dec:@var{m} @var{x}) -Represents the side effect of decrementing @var{x} by a standard -amount and represents also the value that @var{x} has after being -decremented. @var{x} must be a @code{reg} or @code{mem}, but most -machines allow only a @code{reg}. @var{m} must be the machine mode -for pointers on the machine in use. The amount @var{x} is decremented -by is the length in bytes of the machine mode of the containing memory -reference of which this expression serves as the address. Here is an -example of its use:@refill - -@example -(mem:DF (pre_dec:SI (reg:SI 39))) -@end example - -@noindent -This says to decrement pseudo register 39 by the length of a @code{DFmode} -value and use the result to address a @code{DFmode} value. - -@findex pre_inc -@item (pre_inc:@var{m} @var{x}) -Similar, but specifies incrementing @var{x} instead of decrementing it. - -@findex post_dec -@item (post_dec:@var{m} @var{x}) -Represents the same side effect as @code{pre_dec} but a different -value. The value represented here is the value @var{x} has @i{before} -being decremented. - -@findex post_inc -@item (post_inc:@var{m} @var{x}) -Similar, but specifies incrementing @var{x} instead of decrementing it. - -@findex post_modify -@item (post_modify:@var{m} @var{x} @var{y}) - -Represents the side effect of setting @var{x} to @var{y} and -represents @var{x} before @var{x} is modified. @var{x} must be a -@code{reg} or @code{mem}, but most machines allow only a @code{reg}. -@var{m} must be the machine mode for pointers on the machine in use. -The amount @var{x} is decremented by is the length in bytes of the -machine mode of the containing memory reference of which this expression -serves as the address. Note that this is not currently implemented. - -The expression @var{y} must be one of three forms: -@table @code -@code{(plus:@var{m} @var{x} @var{z})}, -@code{(minus:@var{m} @var{x} @var{z})}, or -@code{(plus:@var{m} @var{x} @var{i})}, -@end table -where @var{z} is an index register and @var{i} is a constant. - -Here is an example of its use:@refill - -@example -(mem:SF (post_modify:SI (reg:SI 42) (plus (reg:SI 42) (reg:SI 48)))) -@end example - -This says to modify pseudo register 42 by adding the contents of pseudo -register 48 to it, after the use of what ever 42 points to. - -@findex post_modify -@item (pre_modify:@var{m} @var{x} @var{expr}) -Similar except side effects happen before the use. -@end table - -These embedded side effect expressions must be used with care. Instruction -patterns may not use them. Until the @samp{flow} pass of the compiler, -they may occur only to represent pushes onto the stack. The @samp{flow} -pass finds cases where registers are incremented or decremented in one -instruction and used as an address shortly before or after; these cases are -then transformed to use pre- or post-increment or -decrement. - -If a register used as the operand of these expressions is used in -another address in an insn, the original value of the register is used. -Uses of the register outside of an address are not permitted within the -same insn as a use in an embedded side effect expression because such -insns behave differently on different machines and hence must be treated -as ambiguous and disallowed. - -An instruction that can be represented with an embedded side effect -could also be represented using @code{parallel} containing an additional -@code{set} to describe how the address register is altered. This is not -done because machines that allow these operations at all typically -allow them wherever a memory address is called for. Describing them as -additional parallel stores would require doubling the number of entries -in the machine description. - -@node Assembler -@section Assembler Instructions as Expressions -@cindex assembler instructions in RTL - -@cindex @code{asm_operands}, usage -The RTX code @code{asm_operands} represents a value produced by a -user-specified assembler instruction. It is used to represent -an @code{asm} statement with arguments. An @code{asm} statement with -a single output operand, like this: - -@smallexample -asm ("foo %1,%2,%0" : "=a" (outputvar) : "g" (x + y), "di" (*z)); -@end smallexample - -@noindent -is represented using a single @code{asm_operands} RTX which represents -the value that is stored in @code{outputvar}: - -@smallexample -(set @var{rtx-for-outputvar} - (asm_operands "foo %1,%2,%0" "a" 0 - [@var{rtx-for-addition-result} @var{rtx-for-*z}] - [(asm_input:@var{m1} "g") - (asm_input:@var{m2} "di")])) -@end smallexample - -@noindent -Here the operands of the @code{asm_operands} RTX are the assembler -template string, the output-operand's constraint, the index-number of the -output operand among the output operands specified, a vector of input -operand RTX's, and a vector of input-operand modes and constraints. The -mode @var{m1} is the mode of the sum @code{x+y}; @var{m2} is that of -@code{*z}. - -When an @code{asm} statement has multiple output values, its insn has -several such @code{set} RTX's inside of a @code{parallel}. Each @code{set} -contains a @code{asm_operands}; all of these share the same assembler -template and vectors, but each contains the constraint for the respective -output operand. They are also distinguished by the output-operand index -number, which is 0, 1, @dots{} for successive output operands. - -@node Insns -@section Insns -@cindex insns - -The RTL representation of the code for a function is a doubly-linked -chain of objects called @dfn{insns}. Insns are expressions with -special codes that are used for no other purpose. Some insns are -actual instructions; others represent dispatch tables for @code{switch} -statements; others represent labels to jump to or various sorts of -declarative information. - -In addition to its own specific data, each insn must have a unique -id-number that distinguishes it from all other insns in the current -function (after delayed branch scheduling, copies of an insn with the -same id-number may be present in multiple places in a function, but -these copies will always be identical and will only appear inside a -@code{sequence}), and chain pointers to the preceding and following -insns. These three fields occupy the same position in every insn, -independent of the expression code of the insn. They could be accessed -with @code{XEXP} and @code{XINT}, but instead three special macros are -always used: - -@table @code -@findex INSN_UID -@item INSN_UID (@var{i}) -Accesses the unique id of insn @var{i}. - -@findex PREV_INSN -@item PREV_INSN (@var{i}) -Accesses the chain pointer to the insn preceding @var{i}. -If @var{i} is the first insn, this is a null pointer. - -@findex NEXT_INSN -@item NEXT_INSN (@var{i}) -Accesses the chain pointer to the insn following @var{i}. -If @var{i} is the last insn, this is a null pointer. -@end table - -@findex get_insns -@findex get_last_insn -The first insn in the chain is obtained by calling @code{get_insns}; the -last insn is the result of calling @code{get_last_insn}. Within the -chain delimited by these insns, the @code{NEXT_INSN} and -@code{PREV_INSN} pointers must always correspond: if @var{insn} is not -the first insn, - -@example -NEXT_INSN (PREV_INSN (@var{insn})) == @var{insn} -@end example - -@noindent -is always true and if @var{insn} is not the last insn, - -@example -PREV_INSN (NEXT_INSN (@var{insn})) == @var{insn} -@end example - -@noindent -is always true. - -After delay slot scheduling, some of the insns in the chain might be -@code{sequence} expressions, which contain a vector of insns. The value -of @code{NEXT_INSN} in all but the last of these insns is the next insn -in the vector; the value of @code{NEXT_INSN} of the last insn in the vector -is the same as the value of @code{NEXT_INSN} for the @code{sequence} in -which it is contained. Similar rules apply for @code{PREV_INSN}. - -This means that the above invariants are not necessarily true for insns -inside @code{sequence} expressions. Specifically, if @var{insn} is the -first insn in a @code{sequence}, @code{NEXT_INSN (PREV_INSN (@var{insn}))} -is the insn containing the @code{sequence} expression, as is the value -of @code{PREV_INSN (NEXT_INSN (@var{insn}))} is @var{insn} is the last -insn in the @code{sequence} expression. You can use these expressions -to find the containing @code{sequence} expression.@refill - -Every insn has one of the following six expression codes: - -@table @code -@findex insn -@item insn -The expression code @code{insn} is used for instructions that do not jump -and do not do function calls. @code{sequence} expressions are always -contained in insns with code @code{insn} even if one of those insns -should jump or do function calls. - -Insns with code @code{insn} have four additional fields beyond the three -mandatory ones listed above. These four are described in a table below. - -@findex jump_insn -@item jump_insn -The expression code @code{jump_insn} is used for instructions that may -jump (or, more generally, may contain @code{label_ref} expressions). If -there is an instruction to return from the current function, it is -recorded as a @code{jump_insn}. - -@findex JUMP_LABEL -@code{jump_insn} insns have the same extra fields as @code{insn} insns, -accessed in the same way and in addition contain a field -@code{JUMP_LABEL} which is defined once jump optimization has completed. - -For simple conditional and unconditional jumps, this field contains -the @code{code_label} to which this insn will (possibly conditionally) -branch. In a more complex jump, @code{JUMP_LABEL} records one of the -labels that the insn refers to; the only way to find the others is to -scan the entire body of the insn. In an @code{addr_vec}, -@code{JUMP_LABEL} is @code{NULL_RTX}. - -Return insns count as jumps, but since they do not refer to any -labels, their @code{JUMP_LABEL} is @code{NULL_RTX}. - -@findex call_insn -@item call_insn -The expression code @code{call_insn} is used for instructions that may do -function calls. It is important to distinguish these instructions because -they imply that certain registers and memory locations may be altered -unpredictably. - -@findex CALL_INSN_FUNCTION_USAGE -@code{call_insn} insns have the same extra fields as @code{insn} insns, -accessed in the same way and in addition contain a field -@code{CALL_INSN_FUNCTION_USAGE}, which contains a list (chain of -@code{expr_list} expressions) containing @code{use} and @code{clobber} -expressions that denote hard registers and @code{MEM}s used or -clobbered by the called function. - -A @code{MEM} generally points to a stack slots in which arguments passed -to the libcall by reference (@pxref{Register Arguments, -FUNCTION_ARG_PASS_BY_REFERENCE}) are stored. If the argument is -caller-copied (@pxref{Register Arguments, FUNCTION_ARG_CALLEE_COPIES}), -the stack slot will be mentioned in @code{CLOBBER} and @code{USE} -entries; if it's callee-copied, only a @code{USE} will appear, and the -@code{MEM} may point to addresses that are not stack slots. These -@code{MEM}s are used only in libcalls, because, unlike regular function -calls, @code{CONST_CALL}s (which libcalls generally are, @pxref{Flags, -CONST_CALL_P}) aren't assumed to read and write all memory, so flow -would consider the stores dead and remove them. Note that, since a -libcall must never return values in memory (@pxref{Aggregate Return, -RETURN_IN_MEMORY}), there will never be a @code{CLOBBER} for a memory -address holding a return value. - -@code{CLOBBER}ed registers in this list augment registers specified in -@code{CALL_USED_REGISTERS} (@pxref{Register Basics}). - -@findex code_label -@findex CODE_LABEL_NUMBER -@item code_label -A @code{code_label} insn represents a label that a jump insn can jump -to. It contains two special fields of data in addition to the three -standard ones. @code{CODE_LABEL_NUMBER} is used to hold the @dfn{label -number}, a number that identifies this label uniquely among all the -labels in the compilation (not just in the current function). -Ultimately, the label is represented in the assembler output as an -assembler label, usually of the form @samp{L@var{n}} where @var{n} is -the label number. - -When a @code{code_label} appears in an RTL expression, it normally -appears within a @code{label_ref} which represents the address of -the label, as a number. - -@findex LABEL_NUSES -The field @code{LABEL_NUSES} is only defined once the jump optimization -phase is completed and contains the number of times this label is -referenced in the current function. - -@findex LABEL_ALTERNATE_NAME -The field @code{LABEL_ALTERNATE_NAME} is used to associate a name with -a @code{code_label}. If this field is defined, the alternate name will -be emitted instead of an internally generated label name. - -@findex barrier -@item barrier -Barriers are placed in the instruction stream when control cannot flow -past them. They are placed after unconditional jump instructions to -indicate that the jumps are unconditional and after calls to -@code{volatile} functions, which do not return (e.g., @code{exit}). -They contain no information beyond the three standard fields. - -@findex note -@findex NOTE_LINE_NUMBER -@findex NOTE_SOURCE_FILE -@item note -@code{note} insns are used to represent additional debugging and -declarative information. They contain two nonstandard fields, an -integer which is accessed with the macro @code{NOTE_LINE_NUMBER} and a -string accessed with @code{NOTE_SOURCE_FILE}. - -If @code{NOTE_LINE_NUMBER} is positive, the note represents the -position of a source line and @code{NOTE_SOURCE_FILE} is the source file name -that the line came from. These notes control generation of line -number data in the assembler output. - -Otherwise, @code{NOTE_LINE_NUMBER} is not really a line number but a -code with one of the following values (and @code{NOTE_SOURCE_FILE} -must contain a null pointer): - -@table @code -@findex NOTE_INSN_DELETED -@item NOTE_INSN_DELETED -Such a note is completely ignorable. Some passes of the compiler -delete insns by altering them into notes of this kind. - -@findex NOTE_INSN_BLOCK_BEG -@findex NOTE_INSN_BLOCK_END -@item NOTE_INSN_BLOCK_BEG -@itemx NOTE_INSN_BLOCK_END -These types of notes indicate the position of the beginning and end -of a level of scoping of variable names. They control the output -of debugging information. - -@findex NOTE_INSN_EH_REGION_BEG -@findex NOTE_INSN_EH_REGION_END -@item NOTE_INSN_EH_REGION_BEG -@itemx NOTE_INSN_EH_REGION_END -These types of notes indicate the position of the beginning and end of a -level of scoping for exception handling. @code{NOTE_BLOCK_NUMBER} -identifies which @code{CODE_LABEL} is associated with the given region. - -@findex NOTE_INSN_LOOP_BEG -@findex NOTE_INSN_LOOP_END -@item NOTE_INSN_LOOP_BEG -@itemx NOTE_INSN_LOOP_END -These types of notes indicate the position of the beginning and end -of a @code{while} or @code{for} loop. They enable the loop optimizer -to find loops quickly. - -@findex NOTE_INSN_LOOP_CONT -@item NOTE_INSN_LOOP_CONT -Appears at the place in a loop that @code{continue} statements jump to. - -@findex NOTE_INSN_LOOP_VTOP -@item NOTE_INSN_LOOP_VTOP -This note indicates the place in a loop where the exit test begins for -those loops in which the exit test has been duplicated. This position -becomes another virtual start of the loop when considering loop -invariants. - -@findex NOTE_INSN_FUNCTION_END -@item NOTE_INSN_FUNCTION_END -Appears near the end of the function body, just before the label that -@code{return} statements jump to (on machine where a single instruction -does not suffice for returning). This note may be deleted by jump -optimization. - -@findex NOTE_INSN_SETJMP -@item NOTE_INSN_SETJMP -Appears following each call to @code{setjmp} or a related function. -@end table - -These codes are printed symbolically when they appear in debugging dumps. -@end table - -@cindex @code{TImode}, in @code{insn} -@cindex @code{HImode}, in @code{insn} -@cindex @code{QImode}, in @code{insn} -The machine mode of an insn is normally @code{VOIDmode}, but some -phases use the mode for various purposes. - -The common subexpression elimination pass sets the mode of an insn to -@code{QImode} when it is the first insn in a block that has already -been processed. - -The second Haifa scheduling pass, for targets that can multiple issue, -sets the mode of an insn to @code{TImode} when it is believed that the -instruction begins an issue group. That is, when the instruction -cannot issue simultaneously with the previous. This may be relied on -by later passes, in particular machine-dependant reorg. - -Here is a table of the extra fields of @code{insn}, @code{jump_insn} -and @code{call_insn} insns: - -@table @code -@findex PATTERN -@item PATTERN (@var{i}) -An expression for the side effect performed by this insn. This must be -one of the following codes: @code{set}, @code{call}, @code{use}, -@code{clobber}, @code{return}, @code{asm_input}, @code{asm_output}, -@code{addr_vec}, @code{addr_diff_vec}, @code{trap_if}, @code{unspec}, -@code{unspec_volatile}, @code{parallel}, or @code{sequence}. If it is a @code{parallel}, -each element of the @code{parallel} must be one these codes, except that -@code{parallel} expressions cannot be nested and @code{addr_vec} and -@code{addr_diff_vec} are not permitted inside a @code{parallel} expression. - -@findex INSN_CODE -@item INSN_CODE (@var{i}) -An integer that says which pattern in the machine description matches -this insn, or -1 if the matching has not yet been attempted. - -Such matching is never attempted and this field remains -1 on an insn -whose pattern consists of a single @code{use}, @code{clobber}, -@code{asm_input}, @code{addr_vec} or @code{addr_diff_vec} expression. - -@findex asm_noperands -Matching is also never attempted on insns that result from an @code{asm} -statement. These contain at least one @code{asm_operands} expression. -The function @code{asm_noperands} returns a non-negative value for -such insns. - -In the debugging output, this field is printed as a number followed by -a symbolic representation that locates the pattern in the @file{md} -file as some small positive or negative offset from a named pattern. - -@findex LOG_LINKS -@item LOG_LINKS (@var{i}) -A list (chain of @code{insn_list} expressions) giving information about -dependencies between instructions within a basic block. Neither a jump -nor a label may come between the related insns. - -@findex REG_NOTES -@item REG_NOTES (@var{i}) -A list (chain of @code{expr_list} and @code{insn_list} expressions) -giving miscellaneous information about the insn. It is often -information pertaining to the registers used in this insn. -@end table - -The @code{LOG_LINKS} field of an insn is a chain of @code{insn_list} -expressions. Each of these has two operands: the first is an insn, -and the second is another @code{insn_list} expression (the next one in -the chain). The last @code{insn_list} in the chain has a null pointer -as second operand. The significant thing about the chain is which -insns appear in it (as first operands of @code{insn_list} -expressions). Their order is not significant. - -This list is originally set up by the flow analysis pass; it is a null -pointer until then. Flow only adds links for those data dependencies -which can be used for instruction combination. For each insn, the flow -analysis pass adds a link to insns which store into registers values -that are used for the first time in this insn. The instruction -scheduling pass adds extra links so that every dependence will be -represented. Links represent data dependencies, antidependencies and -output dependencies; the machine mode of the link distinguishes these -three types: antidependencies have mode @code{REG_DEP_ANTI}, output -dependencies have mode @code{REG_DEP_OUTPUT}, and data dependencies have -mode @code{VOIDmode}. - -The @code{REG_NOTES} field of an insn is a chain similar to the -@code{LOG_LINKS} field but it includes @code{expr_list} expressions in -addition to @code{insn_list} expressions. There are several kinds of -register notes, which are distinguished by the machine mode, which in a -register note is really understood as being an @code{enum reg_note}. -The first operand @var{op} of the note is data whose meaning depends on -the kind of note. - -@findex REG_NOTE_KIND -@findex PUT_REG_NOTE_KIND -The macro @code{REG_NOTE_KIND (@var{x})} returns the kind of -register note. Its counterpart, the macro @code{PUT_REG_NOTE_KIND -(@var{x}, @var{newkind})} sets the register note type of @var{x} to be -@var{newkind}. - -Register notes are of three classes: They may say something about an -input to an insn, they may say something about an output of an insn, or -they may create a linkage between two insns. There are also a set -of values that are only used in @code{LOG_LINKS}. - -These register notes annotate inputs to an insn: - -@table @code -@findex REG_DEAD -@item REG_DEAD -The value in @var{op} dies in this insn; that is to say, altering the -value immediately after this insn would not affect the future behavior -of the program. - -This does not necessarily mean that the register @var{op} has no useful -value after this insn since it may also be an output of the insn. In -such a case, however, a @code{REG_DEAD} note would be redundant and is -usually not present until after the reload pass, but no code relies on -this fact. - -@findex REG_INC -@item REG_INC -The register @var{op} is incremented (or decremented; at this level -there is no distinction) by an embedded side effect inside this insn. -This means it appears in a @code{post_inc}, @code{pre_inc}, -@code{post_dec} or @code{pre_dec} expression. - -@findex REG_NONNEG -@item REG_NONNEG -The register @var{op} is known to have a nonnegative value when this -insn is reached. This is used so that decrement and branch until zero -instructions, such as the m68k dbra, can be matched. - -The @code{REG_NONNEG} note is added to insns only if the machine -description has a @samp{decrement_and_branch_until_zero} pattern. - -@findex REG_NO_CONFLICT -@item REG_NO_CONFLICT -This insn does not cause a conflict between @var{op} and the item -being set by this insn even though it might appear that it does. -In other words, if the destination register and @var{op} could -otherwise be assigned the same register, this insn does not -prevent that assignment. - -Insns with this note are usually part of a block that begins with a -@code{clobber} insn specifying a multi-word pseudo register (which will -be the output of the block), a group of insns that each set one word of -the value and have the @code{REG_NO_CONFLICT} note attached, and a final -insn that copies the output to itself with an attached @code{REG_EQUAL} -note giving the expression being computed. This block is encapsulated -with @code{REG_LIBCALL} and @code{REG_RETVAL} notes on the first and -last insns, respectively. - -@findex REG_LABEL -@item REG_LABEL -This insn uses @var{op}, a @code{code_label}, but is not a -@code{jump_insn}, or it is a @code{jump_insn} that required the label to -be held in a register. The presence of this note allows jump -optimization to be aware that @var{op} is, in fact, being used, and flow -optimization to build an accurate flow graph. -@end table - -The following notes describe attributes of outputs of an insn: - -@table @code -@findex REG_EQUIV -@findex REG_EQUAL -@item REG_EQUIV -@itemx REG_EQUAL -This note is only valid on an insn that sets only one register and -indicates that that register will be equal to @var{op} at run time; the -scope of this equivalence differs between the two types of notes. The -value which the insn explicitly copies into the register may look -different from @var{op}, but they will be equal at run time. If the -output of the single @code{set} is a @code{strict_low_part} expression, -the note refers to the register that is contained in @code{SUBREG_REG} -of the @code{subreg} expression. - -For @code{REG_EQUIV}, the register is equivalent to @var{op} throughout -the entire function, and could validly be replaced in all its -occurrences by @var{op}. (``Validly'' here refers to the data flow of -the program; simple replacement may make some insns invalid.) For -example, when a constant is loaded into a register that is never -assigned any other value, this kind of note is used. - -When a parameter is copied into a pseudo-register at entry to a function, -a note of this kind records that the register is equivalent to the stack -slot where the parameter was passed. Although in this case the register -may be set by other insns, it is still valid to replace the register -by the stack slot throughout the function. - -A @code{REG_EQUIV} note is also used on an instruction which copies a -register parameter into a pseudo-register at entry to a function, if -there is a stack slot where that parameter could be stored. Although -other insns may set the pseudo-register, it is valid for the compiler to -replace the pseudo-register by stack slot throughout the function, -provided the compiler ensures that the stack slot is properly -initialized by making the replacement in the initial copy instruction as -well. This is used on machines for which the calling convention -allocates stack space for register parameters. See -@code{REG_PARM_STACK_SPACE} in @ref{Stack Arguments}. - -In the case of @code{REG_EQUAL}, the register that is set by this insn -will be equal to @var{op} at run time at the end of this insn but not -necessarily elsewhere in the function. In this case, @var{op} -is typically an arithmetic expression. For example, when a sequence of -insns such as a library call is used to perform an arithmetic operation, -this kind of note is attached to the insn that produces or copies the -final value. - -These two notes are used in different ways by the compiler passes. -@code{REG_EQUAL} is used by passes prior to register allocation (such as -common subexpression elimination and loop optimization) to tell them how -to think of that value. @code{REG_EQUIV} notes are used by register -allocation to indicate that there is an available substitute expression -(either a constant or a @code{mem} expression for the location of a -parameter on the stack) that may be used in place of a register if -insufficient registers are available. - -Except for stack homes for parameters, which are indicated by a -@code{REG_EQUIV} note and are not useful to the early optimization -passes and pseudo registers that are equivalent to a memory location -throughout there entire life, which is not detected until later in -the compilation, all equivalences are initially indicated by an attached -@code{REG_EQUAL} note. In the early stages of register allocation, a -@code{REG_EQUAL} note is changed into a @code{REG_EQUIV} note if -@var{op} is a constant and the insn represents the only set of its -destination register. - -Thus, compiler passes prior to register allocation need only check for -@code{REG_EQUAL} notes and passes subsequent to register allocation -need only check for @code{REG_EQUIV} notes. - -@findex REG_UNUSED -@item REG_UNUSED -The register @var{op} being set by this insn will not be used in a -subsequent insn. This differs from a @code{REG_DEAD} note, which -indicates that the value in an input will not be used subsequently. -These two notes are independent; both may be present for the same -register. - -@findex REG_WAS_0 -@item REG_WAS_0 -The single output of this insn contained zero before this insn. -@var{op} is the insn that set it to zero. You can rely on this note if -it is present and @var{op} has not been deleted or turned into a @code{note}; -its absence implies nothing. -@end table - -These notes describe linkages between insns. They occur in pairs: one -insn has one of a pair of notes that points to a second insn, which has -the inverse note pointing back to the first insn. - -@table @code -@findex REG_RETVAL -@item REG_RETVAL -This insn copies the value of a multi-insn sequence (for example, a -library call), and @var{op} is the first insn of the sequence (for a -library call, the first insn that was generated to set up the arguments -for the library call). - -Loop optimization uses this note to treat such a sequence as a single -operation for code motion purposes and flow analysis uses this note to -delete such sequences whose results are dead. - -A @code{REG_EQUAL} note will also usually be attached to this insn to -provide the expression being computed by the sequence. - -These notes will be deleted after reload, since they are no longer -accurate or useful. - -@findex REG_LIBCALL -@item REG_LIBCALL -This is the inverse of @code{REG_RETVAL}: it is placed on the first -insn of a multi-insn sequence, and it points to the last one. - -These notes are deleted after reload, since they are no longer useful or -accurate. - -@findex REG_CC_SETTER -@findex REG_CC_USER -@item REG_CC_SETTER -@itemx REG_CC_USER -On machines that use @code{cc0}, the insns which set and use @code{cc0} -set and use @code{cc0} are adjacent. However, when branch delay slot -filling is done, this may no longer be true. In this case a -@code{REG_CC_USER} note will be placed on the insn setting @code{cc0} to -point to the insn using @code{cc0} and a @code{REG_CC_SETTER} note will -be placed on the insn using @code{cc0} to point to the insn setting -@code{cc0}.@refill -@end table - -These values are only used in the @code{LOG_LINKS} field, and indicate -the type of dependency that each link represents. Links which indicate -a data dependence (a read after write dependence) do not use any code, -they simply have mode @code{VOIDmode}, and are printed without any -descriptive text. - -@table @code -@findex REG_DEP_ANTI -@item REG_DEP_ANTI -This indicates an anti dependence (a write after read dependence). - -@findex REG_DEP_OUTPUT -@item REG_DEP_OUTPUT -This indicates an output dependence (a write after write dependence). -@end table - -These notes describe information gathered from gcov profile data. They -are stored in the @code{REG_NOTES} field of an insn as an -@code{expr_list}. - -@table @code -@findex REG_EXEC_COUNT -@item REG_EXEC_COUNT -This is used to indicate the number of times a basic block was executed -according to the profile data. The note is attached to the first insn in -the basic block. - -@findex REG_BR_PROB -@item REG_BR_PROB -This is used to specify the ratio of branches to non-branches of a -branch insn according to the profile data. The value is stored as a -value between 0 and REG_BR_PROB_BASE; larger values indicate a higher -probability that the branch will be taken. - -@findex REG_BR_PRED -@item REG_BR_PRED -These notes are found in JUMP insns after delayed branch scheduling -has taken place. They indicate both the direction and the likelihood -of the JUMP. The format is a bitmask of ATTR_FLAG_* values. - -@findex REG_FRAME_RELATED_EXPR -@item REG_FRAME_RELATED_EXPR -This is used on an RTX_FRAME_RELATED_P insn wherein the attached expression -is used in place of the actual insn pattern. This is done in cases where -the pattern is either complex or misleading. -@end table - -For convenience, the machine mode in an @code{insn_list} or -@code{expr_list} is printed using these symbolic codes in debugging dumps. - -@findex insn_list -@findex expr_list -The only difference between the expression codes @code{insn_list} and -@code{expr_list} is that the first operand of an @code{insn_list} is -assumed to be an insn and is printed in debugging dumps as the insn's -unique id; the first operand of an @code{expr_list} is printed in the -ordinary way as an expression. - -@node Calls -@section RTL Representation of Function-Call Insns -@cindex calling functions in RTL -@cindex RTL function-call insns -@cindex function-call insns - -Insns that call subroutines have the RTL expression code @code{call_insn}. -These insns must satisfy special rules, and their bodies must use a special -RTL expression code, @code{call}. - -@cindex @code{call} usage -A @code{call} expression has two operands, as follows: - -@example -(call (mem:@var{fm} @var{addr}) @var{nbytes}) -@end example - -@noindent -Here @var{nbytes} is an operand that represents the number of bytes of -argument data being passed to the subroutine, @var{fm} is a machine mode -(which must equal as the definition of the @code{FUNCTION_MODE} macro in -the machine description) and @var{addr} represents the address of the -subroutine. - -For a subroutine that returns no value, the @code{call} expression as -shown above is the entire body of the insn, except that the insn might -also contain @code{use} or @code{clobber} expressions. - -@cindex @code{BLKmode}, and function return values -For a subroutine that returns a value whose mode is not @code{BLKmode}, -the value is returned in a hard register. If this register's number is -@var{r}, then the body of the call insn looks like this: - -@example -(set (reg:@var{m} @var{r}) - (call (mem:@var{fm} @var{addr}) @var{nbytes})) -@end example - -@noindent -This RTL expression makes it clear (to the optimizer passes) that the -appropriate register receives a useful value in this insn. - -When a subroutine returns a @code{BLKmode} value, it is handled by -passing to the subroutine the address of a place to store the value. -So the call insn itself does not ``return'' any value, and it has the -same RTL form as a call that returns nothing. - -On some machines, the call instruction itself clobbers some register, -for example to contain the return address. @code{call_insn} insns -on these machines should have a body which is a @code{parallel} -that contains both the @code{call} expression and @code{clobber} -expressions that indicate which registers are destroyed. Similarly, -if the call instruction requires some register other than the stack -pointer that is not explicitly mentioned it its RTL, a @code{use} -subexpression should mention that register. - -Functions that are called are assumed to modify all registers listed in -the configuration macro @code{CALL_USED_REGISTERS} (@pxref{Register -Basics}) and, with the exception of @code{const} functions and library -calls, to modify all of memory. - -Insns containing just @code{use} expressions directly precede the -@code{call_insn} insn to indicate which registers contain inputs to the -function. Similarly, if registers other than those in -@code{CALL_USED_REGISTERS} are clobbered by the called function, insns -containing a single @code{clobber} follow immediately after the call to -indicate which registers. - -@node Sharing -@section Structure Sharing Assumptions -@cindex sharing of RTL components -@cindex RTL structure sharing assumptions - -The compiler assumes that certain kinds of RTL expressions are unique; -there do not exist two distinct objects representing the same value. -In other cases, it makes an opposite assumption: that no RTL expression -object of a certain kind appears in more than one place in the -containing structure. - -These assumptions refer to a single function; except for the RTL -objects that describe global variables and external functions, -and a few standard objects such as small integer constants, -no RTL objects are common to two functions. - -@itemize @bullet -@cindex @code{reg}, RTL sharing -@item -Each pseudo-register has only a single @code{reg} object to represent it, -and therefore only a single machine mode. - -@cindex symbolic label -@cindex @code{symbol_ref}, RTL sharing -@item -For any symbolic label, there is only one @code{symbol_ref} object -referring to it. - -@cindex @code{const_int}, RTL sharing -@item -All @code{const_int} expressions with equal values are shared. - -@cindex @code{pc}, RTL sharing -@item -There is only one @code{pc} expression. - -@cindex @code{cc0}, RTL sharing -@item -There is only one @code{cc0} expression. - -@cindex @code{const_double}, RTL sharing -@item -There is only one @code{const_double} expression with value 0 for -each floating point mode. Likewise for values 1 and 2. - -@cindex @code{label_ref}, RTL sharing -@cindex @code{scratch}, RTL sharing -@item -No @code{label_ref} or @code{scratch} appears in more than one place in -the RTL structure; in other words, it is safe to do a tree-walk of all -the insns in the function and assume that each time a @code{label_ref} -or @code{scratch} is seen it is distinct from all others that are seen. - -@cindex @code{mem}, RTL sharing -@item -Only one @code{mem} object is normally created for each static -variable or stack slot, so these objects are frequently shared in all -the places they appear. However, separate but equal objects for these -variables are occasionally made. - -@cindex @code{asm_operands}, RTL sharing -@item -When a single @code{asm} statement has multiple output operands, a -distinct @code{asm_operands} expression is made for each output operand. -However, these all share the vector which contains the sequence of input -operands. This sharing is used later on to test whether two -@code{asm_operands} expressions come from the same statement, so all -optimizations must carefully preserve the sharing if they copy the -vector at all. - -@item -No RTL object appears in more than one place in the RTL structure -except as described above. Many passes of the compiler rely on this -by assuming that they can modify RTL objects in place without unwanted -side-effects on other insns. - -@findex unshare_all_rtl -@item -During initial RTL generation, shared structure is freely introduced. -After all the RTL for a function has been generated, all shared -structure is copied by @code{unshare_all_rtl} in @file{emit-rtl.c}, -after which the above rules are guaranteed to be followed. - -@findex copy_rtx_if_shared -@item -During the combiner pass, shared structure within an insn can exist -temporarily. However, the shared structure is copied before the -combiner is finished with the insn. This is done by calling -@code{copy_rtx_if_shared}, which is a subroutine of -@code{unshare_all_rtl}. -@end itemize - -@node Reading RTL -@section Reading RTL - -To read an RTL object from a file, call @code{read_rtx}. It takes one -argument, a stdio stream, and returns a single RTL object. - -Reading RTL from a file is very slow. This is not currently a -problem since reading RTL occurs only as part of building the -compiler. - -People frequently have the idea of using RTL stored as text in a file as -an interface between a language front end and the bulk of GNU CC. This -idea is not feasible. - -GNU CC was designed to use RTL internally only. Correct RTL for a given -program is very dependent on the particular target machine. And the RTL -does not contain all the information about the program. - -The proper way to interface GNU CC to a new language front end is with -the ``tree'' data structure. There is no manual for this data -structure, but it is described in the files @file{tree.h} and -@file{tree.def}. diff --git a/gcc/texinfo.tex b/gcc/texinfo.tex deleted file mode 100644 index 1889b4c6d1a..00000000000 --- a/gcc/texinfo.tex +++ /dev/null @@ -1,6200 +0,0 @@ -% texinfo.tex -- TeX macros to handle Texinfo files. -% -% Load plain if necessary, i.e., if running under initex. -\expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi -% -\def\texinfoversion{2000-12-11.07} -% -% Copyright (C) 1985, 86, 88, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 2000 -% Free Software Foundation, Inc. -% -% This texinfo.tex file is free software; you can redistribute it and/or -% modify it under the terms of the GNU General Public License as -% published by the Free Software Foundation; either version 2, or (at -% your option) any later version. -% -% This texinfo.tex file is distributed in the hope that it will be -% useful, but WITHOUT ANY WARRANTY; without even the implied warranty -% of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -% General Public License for more details. -% -% You should have received a copy of the GNU General Public License -% along with this texinfo.tex file; see the file COPYING. If not, write -% to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, -% Boston, MA 02111-1307, USA. -% -% In other words, you are welcome to use, share and improve this program. -% You are forbidden to forbid anyone else to use, share and improve -% what you give them. Help stamp out software-hoarding! -% -% Please try the latest version of texinfo.tex before submitting bug -% reports; you can get the latest version from: -% ftp://ftp.gnu.org/gnu/texinfo.tex -% (and all GNU mirrors, see http://www.gnu.org/order/ftp.html) -% ftp://texinfo.org/tex/texinfo.tex -% ftp://us.ctan.org/macros/texinfo/texinfo.tex -% (and all CTAN mirrors, finger ctan@us.ctan.org for a list). -% /home/gd/gnu/doc/texinfo.tex on the GNU machines. -% The texinfo.tex in any given Texinfo distribution could well be out -% of date, so if that's what you're using, please check. -% Texinfo has a small home page at http://texinfo.org/. -% -% Send bug reports to bug-texinfo@gnu.org. Please include including a -% complete document in each bug report with which we can reproduce the -% problem. Patches are, of course, greatly appreciated. -% -% To process a Texinfo manual with TeX, it's most reliable to use the -% texi2dvi shell script that comes with the distribution. For a simple -% manual foo.texi, however, you can get away with this: -% tex foo.texi -% texindex foo.?? -% tex foo.texi -% tex foo.texi -% dvips foo.dvi -o # or whatever, to process the dvi file; this makes foo.ps. -% The extra runs of TeX get the cross-reference information correct. -% Sometimes one run after texindex suffices, and sometimes you need more -% than two; texi2dvi does it as many times as necessary. -% -% It is possible to adapt texinfo.tex for other languages. You can get -% the existing language-specific files from ftp://ftp.gnu.org/gnu/texinfo/. - -\message{Loading texinfo [version \texinfoversion]:} - -% If in a .fmt file, print the version number -% and turn on active characters that we couldn't do earlier because -% they might have appeared in the input file name. -\everyjob{\message{[Texinfo version \texinfoversion]}% - \catcode`+=\active \catcode`\_=\active} - -% Save some parts of plain tex whose names we will redefine. -\let\ptexb=\b -\let\ptexbullet=\bullet -\let\ptexc=\c -\let\ptexcomma=\, -\let\ptexdot=\. -\let\ptexdots=\dots -\let\ptexend=\end -\let\ptexequiv=\equiv -\let\ptexexclam=\! -\let\ptexi=\i -\let\ptexlbrace=\{ -\let\ptexrbrace=\} -\let\ptexstar=\* -\let\ptext=\t - -% We never want plain's outer \+ definition in Texinfo. -% For @tex, we can use \tabalign. -\let\+ = \relax - -\message{Basics,} -\chardef\other=12 - -% If this character appears in an error message or help string, it -% starts a new line in the output. -\newlinechar = `^^J - -% Set up fixed words for English if not already set. -\ifx\putwordAppendix\undefined \gdef\putwordAppendix{Appendix}\fi -\ifx\putwordChapter\undefined \gdef\putwordChapter{Chapter}\fi -\ifx\putwordfile\undefined \gdef\putwordfile{file}\fi -\ifx\putwordin\undefined \gdef\putwordin{in}\fi -\ifx\putwordIndexIsEmpty\undefined \gdef\putwordIndexIsEmpty{(Index is empty)}\fi -\ifx\putwordIndexNonexistent\undefined \gdef\putwordIndexNonexistent{(Index is nonexistent)}\fi -\ifx\putwordInfo\undefined \gdef\putwordInfo{Info}\fi -\ifx\putwordInstanceVariableof\undefined \gdef\putwordInstanceVariableof{Instance Variable of}\fi -\ifx\putwordMethodon\undefined \gdef\putwordMethodon{Method on}\fi -\ifx\putwordNoTitle\undefined \gdef\putwordNoTitle{No Title}\fi -\ifx\putwordof\undefined \gdef\putwordof{of}\fi -\ifx\putwordon\undefined \gdef\putwordon{on}\fi -\ifx\putwordpage\undefined \gdef\putwordpage{page}\fi -\ifx\putwordsection\undefined \gdef\putwordsection{section}\fi -\ifx\putwordSection\undefined \gdef\putwordSection{Section}\fi -\ifx\putwordsee\undefined \gdef\putwordsee{see}\fi -\ifx\putwordSee\undefined \gdef\putwordSee{See}\fi -\ifx\putwordShortTOC\undefined \gdef\putwordShortTOC{Short Contents}\fi -\ifx\putwordTOC\undefined \gdef\putwordTOC{Table of Contents}\fi -% -\ifx\putwordMJan\undefined \gdef\putwordMJan{January}\fi -\ifx\putwordMFeb\undefined \gdef\putwordMFeb{February}\fi -\ifx\putwordMMar\undefined \gdef\putwordMMar{March}\fi -\ifx\putwordMApr\undefined \gdef\putwordMApr{April}\fi -\ifx\putwordMMay\undefined \gdef\putwordMMay{May}\fi -\ifx\putwordMJun\undefined \gdef\putwordMJun{June}\fi -\ifx\putwordMJul\undefined \gdef\putwordMJul{July}\fi -\ifx\putwordMAug\undefined \gdef\putwordMAug{August}\fi -\ifx\putwordMSep\undefined \gdef\putwordMSep{September}\fi -\ifx\putwordMOct\undefined \gdef\putwordMOct{October}\fi -\ifx\putwordMNov\undefined \gdef\putwordMNov{November}\fi -\ifx\putwordMDec\undefined \gdef\putwordMDec{December}\fi -% -\ifx\putwordDefmac\undefined \gdef\putwordDefmac{Macro}\fi -\ifx\putwordDefspec\undefined \gdef\putwordDefspec{Special Form}\fi -\ifx\putwordDefvar\undefined \gdef\putwordDefvar{Variable}\fi -\ifx\putwordDefopt\undefined \gdef\putwordDefopt{User Option}\fi -\ifx\putwordDeftypevar\undefined\gdef\putwordDeftypevar{Variable}\fi -\ifx\putwordDeffunc\undefined \gdef\putwordDeffunc{Function}\fi -\ifx\putwordDeftypefun\undefined\gdef\putwordDeftypefun{Function}\fi - -% Ignore a token. -% -\def\gobble#1{} - -\hyphenation{ap-pen-dix} -\hyphenation{mini-buf-fer mini-buf-fers} -\hyphenation{eshell} -\hyphenation{white-space} - -% Margin to add to right of even pages, to left of odd pages. -\newdimen \bindingoffset -\newdimen \normaloffset -\newdimen\pagewidth \newdimen\pageheight - -% Sometimes it is convenient to have everything in the transcript file -% and nothing on the terminal. We don't just call \tracingall here, -% since that produces some useless output on the terminal. -% -\def\gloggingall{\begingroup \globaldefs = 1 \loggingall \endgroup}% -\ifx\eTeXversion\undefined -\def\loggingall{\tracingcommands2 \tracingstats2 - \tracingpages1 \tracingoutput1 \tracinglostchars1 - \tracingmacros2 \tracingparagraphs1 \tracingrestores1 - \showboxbreadth\maxdimen\showboxdepth\maxdimen -}% -\else -\def\loggingall{\tracingcommands3 \tracingstats2 - \tracingpages1 \tracingoutput1 \tracinglostchars1 - \tracingmacros2 \tracingparagraphs1 \tracingrestores1 - \tracingscantokens1 \tracingassigns1 \tracingifs1 - \tracinggroups1 \tracingnesting2 - \showboxbreadth\maxdimen\showboxdepth\maxdimen -}% -\fi - -% For @cropmarks command. -% Do @cropmarks to get crop marks. -% -\newif\ifcropmarks -\let\cropmarks = \cropmarkstrue -% -% Dimensions to add cropmarks at corners. -% Added by P. A. MacKay, 12 Nov. 1986 -% -\newdimen\outerhsize \newdimen\outervsize % set by the paper size routines -\newdimen\cornerlong \cornerlong=1pc -\newdimen\cornerthick \cornerthick=.3pt -\newdimen\topandbottommargin \topandbottommargin=.75in - -% Main output routine. -\chardef\PAGE = 255 -\output = {\onepageout{\pagecontents\PAGE}} - -\newbox\headlinebox -\newbox\footlinebox - -% \onepageout takes a vbox as an argument. Note that \pagecontents -% does insertions, but you have to call it yourself. -\def\onepageout#1{% - \ifcropmarks \hoffset=0pt \else \hoffset=\normaloffset \fi - % - \ifodd\pageno \advance\hoffset by \bindingoffset - \else \advance\hoffset by -\bindingoffset\fi - % - % Do this outside of the \shipout so @code etc. will be expanded in - % the headline as they should be, not taken literally (outputting ''code). - \setbox\headlinebox = \vbox{\let\hsize=\pagewidth \makeheadline}% - \setbox\footlinebox = \vbox{\let\hsize=\pagewidth \makefootline}% - % - {% - % Have to do this stuff outside the \shipout because we want it to - % take effect in \write's, yet the group defined by the \vbox ends - % before the \shipout runs. - % - \escapechar = `\\ % use backslash in output files. - \indexdummies % don't expand commands in the output. - \normalturnoffactive % \ in index entries must not stay \, e.g., if - % the page break happens to be in the middle of an example. - \shipout\vbox{% - % Do this early so pdf references go to the beginning of the page. - \ifpdfmakepagedest \pdfmkdest{\the\pageno} \fi - % - \ifcropmarks \vbox to \outervsize\bgroup - \hsize = \outerhsize - \vskip-\topandbottommargin - \vtop to0pt{% - \line{\ewtop\hfil\ewtop}% - \nointerlineskip - \line{% - \vbox{\moveleft\cornerthick\nstop}% - \hfill - \vbox{\moveright\cornerthick\nstop}% - }% - \vss}% - \vskip\topandbottommargin - \line\bgroup - \hfil % center the page within the outer (page) hsize. - \ifodd\pageno\hskip\bindingoffset\fi - \vbox\bgroup - \fi - % - \unvbox\headlinebox - \pagebody{#1}% - \ifdim\ht\footlinebox > 0pt - % Only leave this space if the footline is nonempty. - % (We lessened \vsize for it in \oddfootingxxx.) - % The \baselineskip=24pt in plain's \makefootline has no effect. - \vskip 2\baselineskip - \unvbox\footlinebox - \fi - % - \ifcropmarks - \egroup % end of \vbox\bgroup - \hfil\egroup % end of (centering) \line\bgroup - \vskip\topandbottommargin plus1fill minus1fill - \boxmaxdepth = \cornerthick - \vbox to0pt{\vss - \line{% - \vbox{\moveleft\cornerthick\nsbot}% - \hfill - \vbox{\moveright\cornerthick\nsbot}% - }% - \nointerlineskip - \line{\ewbot\hfil\ewbot}% - }% - \egroup % \vbox from first cropmarks clause - \fi - }% end of \shipout\vbox - }% end of group with \turnoffactive - \advancepageno - \ifnum\outputpenalty>-20000 \else\dosupereject\fi -} - -\newinsert\margin \dimen\margin=\maxdimen - -\def\pagebody#1{\vbox to\pageheight{\boxmaxdepth=\maxdepth #1}} -{\catcode`\@ =11 -\gdef\pagecontents#1{\ifvoid\topins\else\unvbox\topins\fi -% marginal hacks, juha@viisa.uucp (Juha Takala) -\ifvoid\margin\else % marginal info is present - \rlap{\kern\hsize\vbox to\z@{\kern1pt\box\margin \vss}}\fi -\dimen@=\dp#1 \unvbox#1 -\ifvoid\footins\else\vskip\skip\footins\footnoterule \unvbox\footins\fi -\ifr@ggedbottom \kern-\dimen@ \vfil \fi} -} - -% Here are the rules for the cropmarks. Note that they are -% offset so that the space between them is truly \outerhsize or \outervsize -% (P. A. MacKay, 12 November, 1986) -% -\def\ewtop{\vrule height\cornerthick depth0pt width\cornerlong} -\def\nstop{\vbox - {\hrule height\cornerthick depth\cornerlong width\cornerthick}} -\def\ewbot{\vrule height0pt depth\cornerthick width\cornerlong} -\def\nsbot{\vbox - {\hrule height\cornerlong depth\cornerthick width\cornerthick}} - -% Parse an argument, then pass it to #1. The argument is the rest of -% the input line (except we remove a trailing comment). #1 should be a -% macro which expects an ordinary undelimited TeX argument. -% -\def\parsearg#1{% - \let\next = #1% - \begingroup - \obeylines - \futurelet\temp\parseargx -} - -% If the next token is an obeyed space (from an @example environment or -% the like), remove it and recurse. Otherwise, we're done. -\def\parseargx{% - % \obeyedspace is defined far below, after the definition of \sepspaces. - \ifx\obeyedspace\temp - \expandafter\parseargdiscardspace - \else - \expandafter\parseargline - \fi -} - -% Remove a single space (as the delimiter token to the macro call). -{\obeyspaces % - \gdef\parseargdiscardspace {\futurelet\temp\parseargx}} - -{\obeylines % - \gdef\parseargline#1^^M{% - \endgroup % End of the group started in \parsearg. - % - % First remove any @c comment, then any @comment. - % Result of each macro is put in \toks0. - \argremovec #1\c\relax % - \expandafter\argremovecomment \the\toks0 \comment\relax % - % - % Call the caller's macro, saved as \next in \parsearg. - \expandafter\next\expandafter{\the\toks0}% - }% -} - -% Since all \c{,omment} does is throw away the argument, we can let TeX -% do that for us. The \relax here is matched by the \relax in the call -% in \parseargline; it could be more or less anything, its purpose is -% just to delimit the argument to the \c. -\def\argremovec#1\c#2\relax{\toks0 = {#1}} -\def\argremovecomment#1\comment#2\relax{\toks0 = {#1}} - -% \argremovec{,omment} might leave us with trailing spaces, though; e.g., -% @end itemize @c foo -% will have two active spaces as part of the argument with the -% `itemize'. Here we remove all active spaces from #1, and assign the -% result to \toks0. -% -% This loses if there are any *other* active characters besides spaces -% in the argument -- _ ^ +, for example -- since they get expanded. -% Fortunately, Texinfo does not define any such commands. (If it ever -% does, the catcode of the characters in questionwill have to be changed -% here.) But this means we cannot call \removeactivespaces as part of -% \argremovec{,omment}, since @c uses \parsearg, and thus the argument -% that \parsearg gets might well have any character at all in it. -% -\def\removeactivespaces#1{% - \begingroup - \ignoreactivespaces - \edef\temp{#1}% - \global\toks0 = \expandafter{\temp}% - \endgroup -} - -% Change the active space to expand to nothing. -% -\begingroup - \obeyspaces - \gdef\ignoreactivespaces{\obeyspaces\let =\empty} -\endgroup - - -\def\flushcr{\ifx\par\lisppar \def\next##1{}\else \let\next=\relax \fi \next} - -%% These are used to keep @begin/@end levels from running away -%% Call \inENV within environments (after a \begingroup) -\newif\ifENV \ENVfalse \def\inENV{\ifENV\relax\else\ENVtrue\fi} -\def\ENVcheck{% -\ifENV\errmessage{Still within an environment; press RETURN to continue} -\endgroup\fi} % This is not perfect, but it should reduce lossage - -% @begin foo is the same as @foo, for now. -\newhelp\EMsimple{Press RETURN to continue.} - -\outer\def\begin{\parsearg\beginxxx} - -\def\beginxxx #1{% -\expandafter\ifx\csname #1\endcsname\relax -{\errhelp=\EMsimple \errmessage{Undefined command @begin #1}}\else -\csname #1\endcsname\fi} - -% @end foo executes the definition of \Efoo. -% -\def\end{\parsearg\endxxx} -\def\endxxx #1{% - \removeactivespaces{#1}% - \edef\endthing{\the\toks0}% - % - \expandafter\ifx\csname E\endthing\endcsname\relax - \expandafter\ifx\csname \endthing\endcsname\relax - % There's no \foo, i.e., no ``environment'' foo. - \errhelp = \EMsimple - \errmessage{Undefined command `@end \endthing'}% - \else - \unmatchedenderror\endthing - \fi - \else - % Everything's ok; the right environment has been started. - \csname E\endthing\endcsname - \fi -} - -% There is an environment #1, but it hasn't been started. Give an error. -% -\def\unmatchedenderror#1{% - \errhelp = \EMsimple - \errmessage{This `@end #1' doesn't have a matching `@#1'}% -} - -% Define the control sequence \E#1 to give an unmatched @end error. -% -\def\defineunmatchedend#1{% - \expandafter\def\csname E#1\endcsname{\unmatchedenderror{#1}}% -} - - -% Single-spacing is done by various environments (specifically, in -% \nonfillstart and \quotations). -\newskip\singlespaceskip \singlespaceskip = 12.5pt -\def\singlespace{% - % Why was this kern here? It messes up equalizing space above and below - % environments. --karl, 6may93 - %{\advance \baselineskip by -\singlespaceskip - %\kern \baselineskip}% - \setleading \singlespaceskip -} - -%% Simple single-character @ commands - -% @@ prints an @ -% Kludge this until the fonts are right (grr). -\def\@{{\tt\char64}} - -% This is turned off because it was never documented -% and you can use @w{...} around a quote to suppress ligatures. -%% Define @` and @' to be the same as ` and ' -%% but suppressing ligatures. -%\def\`{{`}} -%\def\'{{'}} - -% Used to generate quoted braces. -\def\mylbrace {{\tt\char123}} -\def\myrbrace {{\tt\char125}} -\let\{=\mylbrace -\let\}=\myrbrace -\begingroup - % Definitions to produce actual \{ & \} command in an index. - \catcode`\{ = 12 \catcode`\} = 12 - \catcode`\[ = 1 \catcode`\] = 2 - \catcode`\@ = 0 \catcode`\\ = 12 - @gdef@lbracecmd[\{]% - @gdef@rbracecmd[\}]% -@endgroup - -% Accents: @, @dotaccent @ringaccent @ubaraccent @udotaccent -% Others are defined by plain TeX: @` @' @" @^ @~ @= @v @H. -\let\, = \c -\let\dotaccent = \. -\def\ringaccent#1{{\accent23 #1}} -\let\tieaccent = \t -\let\ubaraccent = \b -\let\udotaccent = \d - -% Other special characters: @questiondown @exclamdown -% Plain TeX defines: @AA @AE @O @OE @L (and lowercase versions) @ss. -\def\questiondown{?`} -\def\exclamdown{!`} - -% Dotless i and dotless j, used for accents. -\def\imacro{i} -\def\jmacro{j} -\def\dotless#1{% - \def\temp{#1}% - \ifx\temp\imacro \ptexi - \else\ifx\temp\jmacro \j - \else \errmessage{@dotless can be used only with i or j}% - \fi\fi -} - -% Be sure we're in horizontal mode when doing a tie, since we make space -% equivalent to this in @example-like environments. Otherwise, a space -% at the beginning of a line will start with \penalty -- and -% since \penalty is valid in vertical mode, we'd end up putting the -% penalty on the vertical list instead of in the new paragraph. -{\catcode`@ = 11 - % Avoid using \@M directly, because that causes trouble - % if the definition is written into an index file. - \global\let\tiepenalty = \@M - \gdef\tie{\leavevmode\penalty\tiepenalty\ } -} - -% @: forces normal size whitespace following. -\def\:{\spacefactor=1000 } - -% @* forces a line break. -\def\*{\hfil\break\hbox{}\ignorespaces} - -% @. is an end-of-sentence period. -\def\.{.\spacefactor=3000 } - -% @! is an end-of-sentence bang. -\def\!{!\spacefactor=3000 } - -% @? is an end-of-sentence query. -\def\?{?\spacefactor=3000 } - -% @w prevents a word break. Without the \leavevmode, @w at the -% beginning of a paragraph, when TeX is still in vertical mode, would -% produce a whole line of output instead of starting the paragraph. -\def\w#1{\leavevmode\hbox{#1}} - -% @group ... @end group forces ... to be all on one page, by enclosing -% it in a TeX vbox. We use \vtop instead of \vbox to construct the box -% to keep its height that of a normal line. According to the rules for -% \topskip (p.114 of the TeXbook), the glue inserted is -% max (\topskip - \ht (first item), 0). If that height is large, -% therefore, no glue is inserted, and the space between the headline and -% the text is small, which looks bad. -% -\def\group{\begingroup - \ifnum\catcode13=\active \else - \errhelp = \groupinvalidhelp - \errmessage{@group invalid in context where filling is enabled}% - \fi - % - % The \vtop we start below produces a box with normal height and large - % depth; thus, TeX puts \baselineskip glue before it, and (when the - % next line of text is done) \lineskip glue after it. (See p.82 of - % the TeXbook.) Thus, space below is not quite equal to space - % above. But it's pretty close. - \def\Egroup{% - \egroup % End the \vtop. - \endgroup % End the \group. - }% - % - \vtop\bgroup - % We have to put a strut on the last line in case the @group is in - % the midst of an example, rather than completely enclosing it. - % Otherwise, the interline space between the last line of the group - % and the first line afterwards is too small. But we can't put the - % strut in \Egroup, since there it would be on a line by itself. - % Hence this just inserts a strut at the beginning of each line. - \everypar = {\strut}% - % - % Since we have a strut on every line, we don't need any of TeX's - % normal interline spacing. - \offinterlineskip - % - % OK, but now we have to do something about blank - % lines in the input in @example-like environments, which normally - % just turn into \lisppar, which will insert no space now that we've - % turned off the interline space. Simplest is to make them be an - % empty paragraph. - \ifx\par\lisppar - \edef\par{\leavevmode \par}% - % - % Reset ^^M's definition to new definition of \par. - \obeylines - \fi - % - % Do @comment since we are called inside an environment such as - % @example, where each end-of-line in the input causes an - % end-of-line in the output. We don't want the end-of-line after - % the `@group' to put extra space in the output. Since @group - % should appear on a line by itself (according to the Texinfo - % manual), we don't worry about eating any user text. - \comment -} -% -% TeX puts in an \escapechar (i.e., `@') at the beginning of the help -% message, so this ends up printing `@group can only ...'. -% -\newhelp\groupinvalidhelp{% -group can only be used in environments such as @example,^^J% -where each line of input produces a line of output.} - -% @need space-in-mils -% forces a page break if there is not space-in-mils remaining. - -\newdimen\mil \mil=0.001in - -\def\need{\parsearg\needx} - -% Old definition--didn't work. -%\def\needx #1{\par % -%% This method tries to make TeX break the page naturally -%% if the depth of the box does not fit. -%{\baselineskip=0pt% -%\vtop to #1\mil{\vfil}\kern -#1\mil\nobreak -%\prevdepth=-1000pt -%}} - -\def\needx#1{% - % Ensure vertical mode, so we don't make a big box in the middle of a - % paragraph. - \par - % - % If the @need value is less than one line space, it's useless. - \dimen0 = #1\mil - \dimen2 = \ht\strutbox - \advance\dimen2 by \dp\strutbox - \ifdim\dimen0 > \dimen2 - % - % Do a \strut just to make the height of this box be normal, so the - % normal leading is inserted relative to the preceding line. - % And a page break here is fine. - \vtop to #1\mil{\strut\vfil}% - % - % TeX does not even consider page breaks if a penalty added to the - % main vertical list is 10000 or more. But in order to see if the - % empty box we just added fits on the page, we must make it consider - % page breaks. On the other hand, we don't want to actually break the - % page after the empty box. So we use a penalty of 9999. - % - % There is an extremely small chance that TeX will actually break the - % page at this \penalty, if there are no other feasible breakpoints in - % sight. (If the user is using lots of big @group commands, which - % almost-but-not-quite fill up a page, TeX will have a hard time doing - % good page breaking, for example.) However, I could not construct an - % example where a page broke at this \penalty; if it happens in a real - % document, then we can reconsider our strategy. - \penalty9999 - % - % Back up by the size of the box, whether we did a page break or not. - \kern -#1\mil - % - % Do not allow a page break right after this kern. - \nobreak - \fi -} - -% @br forces paragraph break - -\let\br = \par - -% @dots{} output an ellipsis using the current font. -% We do .5em per period so that it has the same spacing in a typewriter -% font as three actual period characters. -% -\def\dots{% - \leavevmode - \hbox to 1.5em{% - \hskip 0pt plus 0.25fil minus 0.25fil - .\hss.\hss.% - \hskip 0pt plus 0.5fil minus 0.5fil - }% -} - -% @enddots{} is an end-of-sentence ellipsis. -% -\def\enddots{% - \leavevmode - \hbox to 2em{% - \hskip 0pt plus 0.25fil minus 0.25fil - .\hss.\hss.\hss.% - \hskip 0pt plus 0.5fil minus 0.5fil - }% - \spacefactor=3000 -} - - -% @page forces the start of a new page -% -\def\page{\par\vfill\supereject} - -% @exdent text.... -% outputs text on separate line in roman font, starting at standard page margin - -% This records the amount of indent in the innermost environment. -% That's how much \exdent should take out. -\newskip\exdentamount - -% This defn is used inside fill environments such as @defun. -\def\exdent{\parsearg\exdentyyy} -\def\exdentyyy #1{{\hfil\break\hbox{\kern -\exdentamount{\rm#1}}\hfil\break}} - -% This defn is used inside nofill environments such as @example. -\def\nofillexdent{\parsearg\nofillexdentyyy} -\def\nofillexdentyyy #1{{\advance \leftskip by -\exdentamount -\leftline{\hskip\leftskip{\rm#1}}}} - -% @inmargin{WHICH}{TEXT} puts TEXT in the WHICH margin next to the current -% paragraph. For more general purposes, use the \margin insertion -% class. WHICH is `l' or `r'. -% -\newskip\inmarginspacing \inmarginspacing=1cm -\def\strutdepth{\dp\strutbox} -% -\def\doinmargin#1#2{\strut\vadjust{% - \nobreak - \kern-\strutdepth - \vtop to \strutdepth{% - \baselineskip=\strutdepth - \vss - % if you have multiple lines of stuff to put here, you'll need to - % make the vbox yourself of the appropriate size. - \ifx#1l% - \llap{\ignorespaces #2\hskip\inmarginspacing}% - \else - \rlap{\hskip\hsize \hskip\inmarginspacing \ignorespaces #2}% - \fi - \null - }% -}} -\def\inleftmargin{\doinmargin l} -\def\inrightmargin{\doinmargin r} -% -% @inmargin{TEXT [, RIGHT-TEXT]} -% (if RIGHT-TEXT is given, use TEXT for left page, RIGHT-TEXT for right; -% else use TEXT for both). -% -\def\inmargin#1{\parseinmargin #1,,\finish} -\def\parseinmargin#1,#2,#3\finish{% not perfect, but better than nothing. - \setbox0 = \hbox{\ignorespaces #2}% - \ifdim\wd0 > 0pt - \def\lefttext{#1}% have both texts - \def\righttext{#2}% - \else - \def\lefttext{#1}% have only one text - \def\righttext{#1}% - \fi - % - \ifodd\pageno - \def\temp{\inleftmargin\lefttext}% - \else - \def\temp{\inrightmargin\righttext}% - \fi - \temp -} - -% @include file insert text of that file as input. -% Allow normal characters that we make active in the argument (a file name). -\def\include{\begingroup - \catcode`\\=12 - \catcode`~=12 - \catcode`^=12 - \catcode`_=12 - \catcode`|=12 - \catcode`<=12 - \catcode`>=12 - \catcode`+=12 - \parsearg\includezzz} -% Restore active chars for included file. -\def\includezzz#1{\endgroup\begingroup - % Read the included file in a group so nested @include's work. - \def\thisfile{#1}% - \input\thisfile -\endgroup} - -\def\thisfile{} - -% @center line outputs that line, centered - -\def\center{\parsearg\centerzzz} -\def\centerzzz #1{{\advance\hsize by -\leftskip -\advance\hsize by -\rightskip -\centerline{#1}}} - -% @sp n outputs n lines of vertical space - -\def\sp{\parsearg\spxxx} -\def\spxxx #1{\vskip #1\baselineskip} - -% @comment ...line which is ignored... -% @c is the same as @comment -% @ignore ... @end ignore is another way to write a comment - -\def\comment{\begingroup \catcode`\^^M=\other% -\catcode`\@=\other \catcode`\{=\other \catcode`\}=\other% -\commentxxx} -{\catcode`\^^M=\other \gdef\commentxxx#1^^M{\endgroup}} - -\let\c=\comment - -% @paragraphindent NCHARS -% We'll use ems for NCHARS, close enough. -% We cannot implement @paragraphindent asis, though. -% -\def\asisword{asis} % no translation, these are keywords -\def\noneword{none} -% -\def\paragraphindent{\parsearg\doparagraphindent} -\def\doparagraphindent#1{% - \def\temp{#1}% - \ifx\temp\asisword - \else - \ifx\temp\noneword - \defaultparindent = 0pt - \else - \defaultparindent = #1em - \fi - \fi - \parindent = \defaultparindent -} - -% @exampleindent NCHARS -% We'll use ems for NCHARS like @paragraphindent. -% It seems @exampleindent asis isn't necessary, but -% I preserve it to make it similar to @paragraphindent. -\def\exampleindent{\parsearg\doexampleindent} -\def\doexampleindent#1{% - \def\temp{#1}% - \ifx\temp\asisword - \else - \ifx\temp\noneword - \lispnarrowing = 0pt - \else - \lispnarrowing = #1em - \fi - \fi -} - -% @asis just yields its argument. Used with @table, for example. -% -\def\asis#1{#1} - -% @math means output in math mode. -% We don't use $'s directly in the definition of \math because control -% sequences like \math are expanded when the toc file is written. Then, -% we read the toc file back, the $'s will be normal characters (as they -% should be, according to the definition of Texinfo). So we must use a -% control sequence to switch into and out of math mode. -% -% This isn't quite enough for @math to work properly in indices, but it -% seems unlikely it will ever be needed there. -% -\let\implicitmath = $ -\def\math#1{\implicitmath #1\implicitmath} - -% @bullet and @minus need the same treatment as @math, just above. -\def\bullet{\implicitmath\ptexbullet\implicitmath} -\def\minus{\implicitmath-\implicitmath} - -% @refill is a no-op. -\let\refill=\relax - -% If working on a large document in chapters, it is convenient to -% be able to disable indexing, cross-referencing, and contents, for test runs. -% This is done with @novalidate (before @setfilename). -% -\newif\iflinks \linkstrue % by default we want the aux files. -\let\novalidate = \linksfalse - -% @setfilename is done at the beginning of every texinfo file. -% So open here the files we need to have open while reading the input. -% This makes it possible to make a .fmt file for texinfo. -\def\setfilename{% - \iflinks - \readauxfile - \fi % \openindices needs to do some work in any case. - \openindices - \fixbackslash % Turn off hack to swallow `\input texinfo'. - \global\let\setfilename=\comment % Ignore extra @setfilename cmds. - % - % If texinfo.cnf is present on the system, read it. - % Useful for site-wide @afourpaper, etc. - % Just to be on the safe side, close the input stream before the \input. - \openin 1 texinfo.cnf - \ifeof1 \let\temp=\relax \else \def\temp{\input texinfo.cnf }\fi - \closein1 - \temp - % - \comment % Ignore the actual filename. -} - -% Called from \setfilename. -% -\def\openindices{% - \newindex{cp}% - \newcodeindex{fn}% - \newcodeindex{vr}% - \newcodeindex{tp}% - \newcodeindex{ky}% - \newcodeindex{pg}% -} - -% @bye. -\outer\def\bye{\pagealignmacro\tracingstats=1\ptexend} - - -\message{pdf,} -% adobe `portable' document format -\newcount\tempnum -\newcount\lnkcount -\newtoks\filename -\newcount\filenamelength -\newcount\pgn -\newtoks\toksA -\newtoks\toksB -\newtoks\toksC -\newtoks\toksD -\newbox\boxA -\newcount\countA -\newif\ifpdf -\newif\ifpdfmakepagedest - -\ifx\pdfoutput\undefined - \pdffalse - \let\pdfmkdest = \gobble - \let\pdfurl = \gobble - \let\endlink = \relax - \let\linkcolor = \relax - \let\pdfmakeoutlines = \relax -\else - \pdftrue - \pdfoutput = 1 - \input pdfcolor - \def\dopdfimage#1#2#3{% - \def\imagewidth{#2}% - \def\imageheight{#3}% - \ifnum\pdftexversion < 14 - \pdfimage - \else - \pdfximage - \fi - \ifx\empty\imagewidth\else width \imagewidth \fi - \ifx\empty\imageheight\else height \imageheight \fi - {#1.pdf}% - \ifnum\pdftexversion < 14 \else - \pdfrefximage \pdflastximage - \fi} - \def\pdfmkdest#1{\pdfdest name{#1@} xyz} - \def\pdfmkpgn#1{#1@} - \let\linkcolor = \Blue % was Cyan, but that seems light? - \def\endlink{\Black\pdfendlink} - % Adding outlines to PDF; macros for calculating structure of outlines - % come from Petr Olsak - \def\expnumber#1{\expandafter\ifx\csname#1\endcsname\relax 0% - \else \csname#1\endcsname \fi} - \def\advancenumber#1{\tempnum=\expnumber{#1}\relax - \advance\tempnum by1 - \expandafter\xdef\csname#1\endcsname{\the\tempnum}} - \def\pdfmakeoutlines{{% - \openin 1 \jobname.toc - \ifeof 1\else\bgroup - \closein 1 - \indexnofonts - \def\tt{} - \let\_ = \normalunderscore - % Thanh's hack / proper braces in bookmarks - \edef\mylbrace{\iftrue \string{\else}\fi}\let\{=\mylbrace - \edef\myrbrace{\iffalse{\else\string}\fi}\let\}=\myrbrace - % - \def\chapentry ##1##2##3{} - \def\unnumbchapentry ##1##2{} - \def\secentry ##1##2##3##4{\advancenumber{chap##2}} - \def\unnumbsecentry ##1##2{} - \def\subsecentry ##1##2##3##4##5{\advancenumber{sec##2.##3}} - \def\unnumbsubsecentry ##1##2{} - \def\subsubsecentry ##1##2##3##4##5##6{\advancenumber{subsec##2.##3.##4}} - \def\unnumbsubsubsecentry ##1##2{} - \input \jobname.toc - \def\chapentry ##1##2##3{% - \pdfoutline goto name{\pdfmkpgn{##3}}count-\expnumber{chap##2}{##1}} - \def\unnumbchapentry ##1##2{% - \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} - \def\secentry ##1##2##3##4{% - \pdfoutline goto name{\pdfmkpgn{##4}}count-\expnumber{sec##2.##3}{##1}} - \def\unnumbsecentry ##1##2{% - \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} - \def\subsecentry ##1##2##3##4##5{% - \pdfoutline goto name{\pdfmkpgn{##5}}count-\expnumber{subsec##2.##3.##4}{##1}} - \def\unnumbsubsecentry ##1##2{% - \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} - \def\subsubsecentry ##1##2##3##4##5##6{% - \pdfoutline goto name{\pdfmkpgn{##6}}{##1}} - \def\unnumbsubsubsecentry ##1##2{% - \pdfoutline goto name{\pdfmkpgn{##2}}{##1}} - \input \jobname.toc - \egroup\fi - }} - \def\makelinks #1,{% - \def\params{#1}\def\E{END}% - \ifx\params\E - \let\nextmakelinks=\relax - \else - \let\nextmakelinks=\makelinks - \ifnum\lnkcount>0,\fi - \picknum{#1}% - \startlink attr{/Border [0 0 0]} - goto name{\pdfmkpgn{\the\pgn}}% - \linkcolor #1% - \advance\lnkcount by 1% - \endlink - \fi - \nextmakelinks - } - \def\picknum#1{\expandafter\pn#1} - \def\pn#1{% - \def\p{#1}% - \ifx\p\lbrace - \let\nextpn=\ppn - \else - \let\nextpn=\ppnn - \def\first{#1} - \fi - \nextpn - } - \def\ppn#1{\pgn=#1\gobble} - \def\ppnn{\pgn=\first} - \def\pdfmklnk#1{\lnkcount=0\makelinks #1,END,} - \def\addtokens#1#2{\edef\addtoks{\noexpand#1={\the#1#2}}\addtoks} - \def\skipspaces#1{\def\PP{#1}\def\D{|}% - \ifx\PP\D\let\nextsp\relax - \else\let\nextsp\skipspaces - \ifx\p\space\else\addtokens{\filename}{\PP}% - \advance\filenamelength by 1 - \fi - \fi - \nextsp} - \def\getfilename#1{\filenamelength=0\expandafter\skipspaces#1|\relax} - \ifnum\pdftexversion < 14 - \let \startlink \pdfannotlink - \else - \let \startlink \pdfstartlink - \fi - \def\pdfurl#1{% - \begingroup - \normalturnoffactive\def\@{@}% - \leavevmode\Red - \startlink attr{/Border [0 0 0]}% - user{/Subtype /Link /A << /S /URI /URI (#1) >>}% - % #1 - \endgroup} - \def\pdfgettoks#1.{\setbox\boxA=\hbox{\toksA={#1.}\toksB={}\maketoks}} - \def\addtokens#1#2{\edef\addtoks{\noexpand#1={\the#1#2}}\addtoks} - \def\adn#1{\addtokens{\toksC}{#1}\global\countA=1\let\next=\maketoks} - \def\poptoks#1#2|ENDTOKS|{\let\first=#1\toksD={#1}\toksA={#2}} - \def\maketoks{% - \expandafter\poptoks\the\toksA|ENDTOKS| - \ifx\first0\adn0 - \else\ifx\first1\adn1 \else\ifx\first2\adn2 \else\ifx\first3\adn3 - \else\ifx\first4\adn4 \else\ifx\first5\adn5 \else\ifx\first6\adn6 - \else\ifx\first7\adn7 \else\ifx\first8\adn8 \else\ifx\first9\adn9 - \else - \ifnum0=\countA\else\makelink\fi - \ifx\first.\let\next=\done\else - \let\next=\maketoks - \addtokens{\toksB}{\the\toksD} - \ifx\first,\addtokens{\toksB}{\space}\fi - \fi - \fi\fi\fi\fi\fi\fi\fi\fi\fi\fi - \next} - \def\makelink{\addtokens{\toksB}% - {\noexpand\pdflink{\the\toksC}}\toksC={}\global\countA=0} - \def\pdflink#1{% - \startlink attr{/Border [0 0 0]} goto name{\mkpgn{#1}} - \linkcolor #1\endlink} - \def\mkpgn#1{#1@} - \def\done{\edef\st{\global\noexpand\toksA={\the\toksB}}\st} -\fi % \ifx\pdfoutput - - -\message{fonts,} -% Font-change commands. - -% Texinfo sort of supports the sans serif font style, which plain TeX does not. -% So we set up a \sf analogous to plain's \rm, etc. -\newfam\sffam -\def\sf{\fam=\sffam \tensf} -\let\li = \sf % Sometimes we call it \li, not \sf. - -% We don't need math for this one. -\def\ttsl{\tenttsl} - -% Use Computer Modern fonts at \magstephalf (11pt). -\newcount\mainmagstep -\mainmagstep=\magstephalf - -% Set the font macro #1 to the font named #2, adding on the -% specified font prefix (normally `cm'). -% #3 is the font's design size, #4 is a scale factor -\def\setfont#1#2#3#4{\font#1=\fontprefix#2#3 scaled #4} - -% Use cm as the default font prefix. -% To specify the font prefix, you must define \fontprefix -% before you read in texinfo.tex. -\ifx\fontprefix\undefined -\def\fontprefix{cm} -\fi -% Support font families that don't use the same naming scheme as CM. -\def\rmshape{r} -\def\rmbshape{bx} %where the normal face is bold -\def\bfshape{b} -\def\bxshape{bx} -\def\ttshape{tt} -\def\ttbshape{tt} -\def\ttslshape{sltt} -\def\itshape{ti} -\def\itbshape{bxti} -\def\slshape{sl} -\def\slbshape{bxsl} -\def\sfshape{ss} -\def\sfbshape{ss} -\def\scshape{csc} -\def\scbshape{csc} - -\ifx\bigger\relax -\let\mainmagstep=\magstep1 -\setfont\textrm\rmshape{12}{1000} -\setfont\texttt\ttshape{12}{1000} -\else -\setfont\textrm\rmshape{10}{\mainmagstep} -\setfont\texttt\ttshape{10}{\mainmagstep} -\fi -% Instead of cmb10, you many want to use cmbx10. -% cmbx10 is a prettier font on its own, but cmb10 -% looks better when embedded in a line with cmr10. -\setfont\textbf\bfshape{10}{\mainmagstep} -\setfont\textit\itshape{10}{\mainmagstep} -\setfont\textsl\slshape{10}{\mainmagstep} -\setfont\textsf\sfshape{10}{\mainmagstep} -\setfont\textsc\scshape{10}{\mainmagstep} -\setfont\textttsl\ttslshape{10}{\mainmagstep} -\font\texti=cmmi10 scaled \mainmagstep -\font\textsy=cmsy10 scaled \mainmagstep - -% A few fonts for @defun, etc. -\setfont\defbf\bxshape{10}{\magstep1} %was 1314 -\setfont\deftt\ttshape{10}{\magstep1} -\def\df{\let\tentt=\deftt \let\tenbf = \defbf \bf} - -% Fonts for indices, footnotes, small examples (9pt). -\setfont\smallrm\rmshape{9}{1000} -\setfont\smalltt\ttshape{9}{1000} -\setfont\smallbf\bfshape{10}{900} -\setfont\smallit\itshape{9}{1000} -\setfont\smallsl\slshape{9}{1000} -\setfont\smallsf\sfshape{9}{1000} -\setfont\smallsc\scshape{10}{900} -\setfont\smallttsl\ttslshape{10}{900} -\font\smalli=cmmi9 -\font\smallsy=cmsy9 - -% Fonts for title page: -\setfont\titlerm\rmbshape{12}{\magstep3} -\setfont\titleit\itbshape{10}{\magstep4} -\setfont\titlesl\slbshape{10}{\magstep4} -\setfont\titlett\ttbshape{12}{\magstep3} -\setfont\titlettsl\ttslshape{10}{\magstep4} -\setfont\titlesf\sfbshape{17}{\magstep1} -\let\titlebf=\titlerm -\setfont\titlesc\scbshape{10}{\magstep4} -\font\titlei=cmmi12 scaled \magstep3 -\font\titlesy=cmsy10 scaled \magstep4 -\def\authorrm{\secrm} - -% Chapter (and unnumbered) fonts (17.28pt). -\setfont\chaprm\rmbshape{12}{\magstep2} -\setfont\chapit\itbshape{10}{\magstep3} -\setfont\chapsl\slbshape{10}{\magstep3} -\setfont\chaptt\ttbshape{12}{\magstep2} -\setfont\chapttsl\ttslshape{10}{\magstep3} -\setfont\chapsf\sfbshape{17}{1000} -\let\chapbf=\chaprm -\setfont\chapsc\scbshape{10}{\magstep3} -\font\chapi=cmmi12 scaled \magstep2 -\font\chapsy=cmsy10 scaled \magstep3 - -% Section fonts (14.4pt). -\setfont\secrm\rmbshape{12}{\magstep1} -\setfont\secit\itbshape{10}{\magstep2} -\setfont\secsl\slbshape{10}{\magstep2} -\setfont\sectt\ttbshape{12}{\magstep1} -\setfont\secttsl\ttslshape{10}{\magstep2} -\setfont\secsf\sfbshape{12}{\magstep1} -\let\secbf\secrm -\setfont\secsc\scbshape{10}{\magstep2} -\font\seci=cmmi12 scaled \magstep1 -\font\secsy=cmsy10 scaled \magstep2 - -% \setfont\ssecrm\bxshape{10}{\magstep1} % This size an font looked bad. -% \setfont\ssecit\itshape{10}{\magstep1} % The letters were too crowded. -% \setfont\ssecsl\slshape{10}{\magstep1} -% \setfont\ssectt\ttshape{10}{\magstep1} -% \setfont\ssecsf\sfshape{10}{\magstep1} - -%\setfont\ssecrm\bfshape{10}{1315} % Note the use of cmb rather than cmbx. -%\setfont\ssecit\itshape{10}{1315} % Also, the size is a little larger than -%\setfont\ssecsl\slshape{10}{1315} % being scaled magstep1. -%\setfont\ssectt\ttshape{10}{1315} -%\setfont\ssecsf\sfshape{10}{1315} - -%\let\ssecbf=\ssecrm - -% Subsection fonts (13.15pt). -\setfont\ssecrm\rmbshape{12}{\magstephalf} -\setfont\ssecit\itbshape{10}{1315} -\setfont\ssecsl\slbshape{10}{1315} -\setfont\ssectt\ttbshape{12}{\magstephalf} -\setfont\ssecttsl\ttslshape{10}{1315} -\setfont\ssecsf\sfbshape{12}{\magstephalf} -\let\ssecbf\ssecrm -\setfont\ssecsc\scbshape{10}{\magstep1} -\font\sseci=cmmi12 scaled \magstephalf -\font\ssecsy=cmsy10 scaled 1315 -% The smallcaps and symbol fonts should actually be scaled \magstep1.5, -% but that is not a standard magnification. - -% In order for the font changes to affect most math symbols and letters, -% we have to define the \textfont of the standard families. Since -% texinfo doesn't allow for producing subscripts and superscripts, we -% don't bother to reset \scriptfont and \scriptscriptfont (which would -% also require loading a lot more fonts). -% -\def\resetmathfonts{% - \textfont0 = \tenrm \textfont1 = \teni \textfont2 = \tensy - \textfont\itfam = \tenit \textfont\slfam = \tensl \textfont\bffam = \tenbf - \textfont\ttfam = \tentt \textfont\sffam = \tensf -} - - -% The font-changing commands redefine the meanings of \tenSTYLE, instead -% of just \STYLE. We do this so that font changes will continue to work -% in math mode, where it is the current \fam that is relevant in most -% cases, not the current font. Plain TeX does \def\bf{\fam=\bffam -% \tenbf}, for example. By redefining \tenbf, we obviate the need to -% redefine \bf itself. -\def\textfonts{% - \let\tenrm=\textrm \let\tenit=\textit \let\tensl=\textsl - \let\tenbf=\textbf \let\tentt=\texttt \let\smallcaps=\textsc - \let\tensf=\textsf \let\teni=\texti \let\tensy=\textsy \let\tenttsl=\textttsl - \resetmathfonts} -\def\titlefonts{% - \let\tenrm=\titlerm \let\tenit=\titleit \let\tensl=\titlesl - \let\tenbf=\titlebf \let\tentt=\titlett \let\smallcaps=\titlesc - \let\tensf=\titlesf \let\teni=\titlei \let\tensy=\titlesy - \let\tenttsl=\titlettsl - \resetmathfonts \setleading{25pt}} -\def\titlefont#1{{\titlefonts\rm #1}} -\def\chapfonts{% - \let\tenrm=\chaprm \let\tenit=\chapit \let\tensl=\chapsl - \let\tenbf=\chapbf \let\tentt=\chaptt \let\smallcaps=\chapsc - \let\tensf=\chapsf \let\teni=\chapi \let\tensy=\chapsy \let\tenttsl=\chapttsl - \resetmathfonts \setleading{19pt}} -\def\secfonts{% - \let\tenrm=\secrm \let\tenit=\secit \let\tensl=\secsl - \let\tenbf=\secbf \let\tentt=\sectt \let\smallcaps=\secsc - \let\tensf=\secsf \let\teni=\seci \let\tensy=\secsy \let\tenttsl=\secttsl - \resetmathfonts \setleading{16pt}} -\def\subsecfonts{% - \let\tenrm=\ssecrm \let\tenit=\ssecit \let\tensl=\ssecsl - \let\tenbf=\ssecbf \let\tentt=\ssectt \let\smallcaps=\ssecsc - \let\tensf=\ssecsf \let\teni=\sseci \let\tensy=\ssecsy \let\tenttsl=\ssecttsl - \resetmathfonts \setleading{15pt}} -\let\subsubsecfonts = \subsecfonts % Maybe make sssec fonts scaled magstephalf? -\def\smallfonts{% - \let\tenrm=\smallrm \let\tenit=\smallit \let\tensl=\smallsl - \let\tenbf=\smallbf \let\tentt=\smalltt \let\smallcaps=\smallsc - \let\tensf=\smallsf \let\teni=\smalli \let\tensy=\smallsy - \let\tenttsl=\smallttsl - \resetmathfonts \setleading{11pt}} - -% Set up the default fonts, so we can use them for creating boxes. -% -\textfonts - -% Define these so they can be easily changed for other fonts. -\def\angleleft{$\langle$} -\def\angleright{$\rangle$} - -% Count depth in font-changes, for error checks -\newcount\fontdepth \fontdepth=0 - -% Fonts for short table of contents. -\setfont\shortcontrm\rmshape{12}{1000} -\setfont\shortcontbf\bxshape{12}{1000} -\setfont\shortcontsl\slshape{12}{1000} - -%% Add scribe-like font environments, plus @l for inline lisp (usually sans -%% serif) and @ii for TeX italic - -% \smartitalic{ARG} outputs arg in italics, followed by an italic correction -% unless the following character is such as not to need one. -\def\smartitalicx{\ifx\next,\else\ifx\next-\else\ifx\next.\else\/\fi\fi\fi} -\def\smartslanted#1{{\sl #1}\futurelet\next\smartitalicx} -\def\smartitalic#1{{\it #1}\futurelet\next\smartitalicx} - -\let\i=\smartitalic -\let\var=\smartslanted -\let\dfn=\smartslanted -\let\emph=\smartitalic -\let\cite=\smartslanted - -\def\b#1{{\bf #1}} -\let\strong=\b - -% We can't just use \exhyphenpenalty, because that only has effect at -% the end of a paragraph. Restore normal hyphenation at the end of the -% group within which \nohyphenation is presumably called. -% -\def\nohyphenation{\hyphenchar\font = -1 \aftergroup\restorehyphenation} -\def\restorehyphenation{\hyphenchar\font = `- } - -\def\t#1{% - {\tt \rawbackslash \frenchspacing #1}% - \null -} -\let\ttfont=\t -\def\samp#1{`\tclose{#1}'\null} -\setfont\keyrm\rmshape{8}{1000} -\font\keysy=cmsy9 -\def\key#1{{\keyrm\textfont2=\keysy \leavevmode\hbox{% - \raise0.4pt\hbox{\angleleft}\kern-.08em\vtop{% - \vbox{\hrule\kern-0.4pt - \hbox{\raise0.4pt\hbox{\vphantom{\angleleft}}#1}}% - \kern-0.4pt\hrule}% - \kern-.06em\raise0.4pt\hbox{\angleright}}}} -% The old definition, with no lozenge: -%\def\key #1{{\ttsl \nohyphenation \uppercase{#1}}\null} -\def\ctrl #1{{\tt \rawbackslash \hat}#1} - -% @file, @option are the same as @samp. -\let\file=\samp -\let\option=\samp - -% @code is a modification of @t, -% which makes spaces the same size as normal in the surrounding text. -\def\tclose#1{% - {% - % Change normal interword space to be same as for the current font. - \spaceskip = \fontdimen2\font - % - % Switch to typewriter. - \tt - % - % But `\ ' produces the large typewriter interword space. - \def\ {{\spaceskip = 0pt{} }}% - % - % Turn off hyphenation. - \nohyphenation - % - \rawbackslash - \frenchspacing - #1% - }% - \null -} - -% We *must* turn on hyphenation at `-' and `_' in \code. -% Otherwise, it is too hard to avoid overfull hboxes -% in the Emacs manual, the Library manual, etc. - -% Unfortunately, TeX uses one parameter (\hyphenchar) to control -% both hyphenation at - and hyphenation within words. -% We must therefore turn them both off (\tclose does that) -% and arrange explicitly to hyphenate at a dash. -% -- rms. -{ - \catcode`\-=\active - \catcode`\_=\active - % - \global\def\code{\begingroup - \catcode`\-=\active \let-\codedash - \catcode`\_=\active \let_\codeunder - \codex - } - % - % If we end up with any active - characters when handling the index, - % just treat them as a normal -. - \global\def\indexbreaks{\catcode`\-=\active \let-\realdash} -} - -\def\realdash{-} -\def\codedash{-\discretionary{}{}{}} -\def\codeunder{\ifusingtt{\normalunderscore\discretionary{}{}{}}{\_}} -\def\codex #1{\tclose{#1}\endgroup} - -%\let\exp=\tclose %Was temporary - -% @kbd is like @code, except that if the argument is just one @key command, -% then @kbd has no effect. - -% @kbdinputstyle -- arg is `distinct' (@kbd uses slanted tty font always), -% `example' (@kbd uses ttsl only inside of @example and friends), -% or `code' (@kbd uses normal tty font always). -\def\kbdinputstyle{\parsearg\kbdinputstylexxx} -\def\kbdinputstylexxx#1{% - \def\arg{#1}% - \ifx\arg\worddistinct - \gdef\kbdexamplefont{\ttsl}\gdef\kbdfont{\ttsl}% - \else\ifx\arg\wordexample - \gdef\kbdexamplefont{\ttsl}\gdef\kbdfont{\tt}% - \else\ifx\arg\wordcode - \gdef\kbdexamplefont{\tt}\gdef\kbdfont{\tt}% - \fi\fi\fi -} -\def\worddistinct{distinct} -\def\wordexample{example} -\def\wordcode{code} - -% Default is kbdinputdistinct. (Too much of a hassle to call the macro, -% the catcodes are wrong for parsearg to work.) -\gdef\kbdexamplefont{\ttsl}\gdef\kbdfont{\ttsl} - -\def\xkey{\key} -\def\kbdfoo#1#2#3\par{\def\one{#1}\def\three{#3}\def\threex{??}% -\ifx\one\xkey\ifx\threex\three \key{#2}% -\else{\tclose{\kbdfont\look}}\fi -\else{\tclose{\kbdfont\look}}\fi} - -% For @url, @env, @command quotes seem unnecessary, so use \code. -\let\url=\code -\let\env=\code -\let\command=\code - -% @uref (abbreviation for `urlref') takes an optional (comma-separated) -% second argument specifying the text to display and an optional third -% arg as text to display instead of (rather than in addition to) the url -% itself. First (mandatory) arg is the url. Perhaps eventually put in -% a hypertex \special here. -% -\def\uref#1{\douref #1,,,\finish} -\def\douref#1,#2,#3,#4\finish{\begingroup - \unsepspaces - \pdfurl{#1}% - \setbox0 = \hbox{\ignorespaces #3}% - \ifdim\wd0 > 0pt - \unhbox0 % third arg given, show only that - \else - \setbox0 = \hbox{\ignorespaces #2}% - \ifdim\wd0 > 0pt - \ifpdf - \unhbox0 % PDF: 2nd arg given, show only it - \else - \unhbox0\ (\code{#1})% DVI: 2nd arg given, show both it and url - \fi - \else - \code{#1}% only url given, so show it - \fi - \fi - \endlink -\endgroup} - -% rms does not like angle brackets --karl, 17may97. -% So now @email is just like @uref, unless we are pdf. -% -%\def\email#1{\angleleft{\tt #1}\angleright} -\ifpdf - \def\email#1{\doemail#1,,\finish} - \def\doemail#1,#2,#3\finish{\begingroup - \unsepspaces - \pdfurl{mailto:#1}% - \setbox0 = \hbox{\ignorespaces #2}% - \ifdim\wd0>0pt\unhbox0\else\code{#1}\fi - \endlink - \endgroup} -\else - \let\email=\uref -\fi - -% Check if we are currently using a typewriter font. Since all the -% Computer Modern typewriter fonts have zero interword stretch (and -% shrink), and it is reasonable to expect all typewriter fonts to have -% this property, we can check that font parameter. -% -\def\ifmonospace{\ifdim\fontdimen3\font=0pt } - -% Typeset a dimension, e.g., `in' or `pt'. The only reason for the -% argument is to make the input look right: @dmn{pt} instead of @dmn{}pt. -% -\def\dmn#1{\thinspace #1} - -\def\kbd#1{\def\look{#1}\expandafter\kbdfoo\look??\par} - -% @l was never documented to mean ``switch to the Lisp font'', -% and it is not used as such in any manual I can find. We need it for -% Polish suppressed-l. --karl, 22sep96. -%\def\l#1{{\li #1}\null} - -% Explicit font changes: @r, @sc, undocumented @ii. -\def\r#1{{\rm #1}} % roman font -\def\sc#1{{\smallcaps#1}} % smallcaps font -\def\ii#1{{\it #1}} % italic font - -% @acronym downcases the argument and prints in smallcaps. -\def\acronym#1{{\smallcaps \lowercase{#1}}} - -% @pounds{} is a sterling sign. -\def\pounds{{\it\$}} - - -\message{page headings,} - -\newskip\titlepagetopglue \titlepagetopglue = 1.5in -\newskip\titlepagebottomglue \titlepagebottomglue = 2pc - -% First the title page. Must do @settitle before @titlepage. -\newif\ifseenauthor -\newif\iffinishedtitlepage - -% Do an implicit @contents or @shortcontents after @end titlepage if the -% user says @setcontentsaftertitlepage or @setshortcontentsaftertitlepage. -% -\newif\ifsetcontentsaftertitlepage - \let\setcontentsaftertitlepage = \setcontentsaftertitlepagetrue -\newif\ifsetshortcontentsaftertitlepage - \let\setshortcontentsaftertitlepage = \setshortcontentsaftertitlepagetrue - -\def\shorttitlepage{\parsearg\shorttitlepagezzz} -\def\shorttitlepagezzz #1{\begingroup\hbox{}\vskip 1.5in \chaprm \centerline{#1}% - \endgroup\page\hbox{}\page} - -\def\titlepage{\begingroup \parindent=0pt \textfonts - \let\subtitlerm=\tenrm - \def\subtitlefont{\subtitlerm \normalbaselineskip = 13pt \normalbaselines}% - % - \def\authorfont{\authorrm \normalbaselineskip = 16pt \normalbaselines}% - % - % Leave some space at the very top of the page. - \vglue\titlepagetopglue - % - % Now you can print the title using @title. - \def\title{\parsearg\titlezzz}% - \def\titlezzz##1{\leftline{\titlefonts\rm ##1} - % print a rule at the page bottom also. - \finishedtitlepagefalse - \vskip4pt \hrule height 4pt width \hsize \vskip4pt}% - % No rule at page bottom unless we print one at the top with @title. - \finishedtitlepagetrue - % - % Now you can put text using @subtitle. - \def\subtitle{\parsearg\subtitlezzz}% - \def\subtitlezzz##1{{\subtitlefont \rightline{##1}}}% - % - % @author should come last, but may come many times. - \def\author{\parsearg\authorzzz}% - \def\authorzzz##1{\ifseenauthor\else\vskip 0pt plus 1filll\seenauthortrue\fi - {\authorfont \leftline{##1}}}% - % - % Most title ``pages'' are actually two pages long, with space - % at the top of the second. We don't want the ragged left on the second. - \let\oldpage = \page - \def\page{% - \iffinishedtitlepage\else - \finishtitlepage - \fi - \oldpage - \let\page = \oldpage - \hbox{}}% -% \def\page{\oldpage \hbox{}} -} - -\def\Etitlepage{% - \iffinishedtitlepage\else - \finishtitlepage - \fi - % It is important to do the page break before ending the group, - % because the headline and footline are only empty inside the group. - % If we use the new definition of \page, we always get a blank page - % after the title page, which we certainly don't want. - \oldpage - \endgroup - % - % If they want short, they certainly want long too. - \ifsetshortcontentsaftertitlepage - \shortcontents - \contents - \global\let\shortcontents = \relax - \global\let\contents = \relax - \fi - % - \ifsetcontentsaftertitlepage - \contents - \global\let\contents = \relax - \global\let\shortcontents = \relax - \fi - % - \ifpdf \pdfmakepagedesttrue \fi - % - \HEADINGSon -} - -\def\finishtitlepage{% - \vskip4pt \hrule height 2pt width \hsize - \vskip\titlepagebottomglue - \finishedtitlepagetrue -} - -%%% Set up page headings and footings. - -\let\thispage=\folio - -\newtoks\evenheadline % headline on even pages -\newtoks\oddheadline % headline on odd pages -\newtoks\evenfootline % footline on even pages -\newtoks\oddfootline % footline on odd pages - -% Now make Tex use those variables -\headline={{\textfonts\rm \ifodd\pageno \the\oddheadline - \else \the\evenheadline \fi}} -\footline={{\textfonts\rm \ifodd\pageno \the\oddfootline - \else \the\evenfootline \fi}\HEADINGShook} -\let\HEADINGShook=\relax - -% Commands to set those variables. -% For example, this is what @headings on does -% @evenheading @thistitle|@thispage|@thischapter -% @oddheading @thischapter|@thispage|@thistitle -% @evenfooting @thisfile|| -% @oddfooting ||@thisfile - -\def\evenheading{\parsearg\evenheadingxxx} -\def\oddheading{\parsearg\oddheadingxxx} -\def\everyheading{\parsearg\everyheadingxxx} - -\def\evenfooting{\parsearg\evenfootingxxx} -\def\oddfooting{\parsearg\oddfootingxxx} -\def\everyfooting{\parsearg\everyfootingxxx} - -{\catcode`\@=0 % - -\gdef\evenheadingxxx #1{\evenheadingyyy #1@|@|@|@|\finish} -\gdef\evenheadingyyy #1@|#2@|#3@|#4\finish{% -\global\evenheadline={\rlap{\centerline{#2}}\line{#1\hfil#3}}} - -\gdef\oddheadingxxx #1{\oddheadingyyy #1@|@|@|@|\finish} -\gdef\oddheadingyyy #1@|#2@|#3@|#4\finish{% -\global\oddheadline={\rlap{\centerline{#2}}\line{#1\hfil#3}}} - -\gdef\everyheadingxxx#1{\oddheadingxxx{#1}\evenheadingxxx{#1}}% - -\gdef\evenfootingxxx #1{\evenfootingyyy #1@|@|@|@|\finish} -\gdef\evenfootingyyy #1@|#2@|#3@|#4\finish{% -\global\evenfootline={\rlap{\centerline{#2}}\line{#1\hfil#3}}} - -\gdef\oddfootingxxx #1{\oddfootingyyy #1@|@|@|@|\finish} -\gdef\oddfootingyyy #1@|#2@|#3@|#4\finish{% - \global\oddfootline = {\rlap{\centerline{#2}}\line{#1\hfil#3}}% - % - % Leave some space for the footline. Hopefully ok to assume - % @evenfooting will not be used by itself. - \global\advance\pageheight by -\baselineskip - \global\advance\vsize by -\baselineskip -} - -\gdef\everyfootingxxx#1{\oddfootingxxx{#1}\evenfootingxxx{#1}} -% -}% unbind the catcode of @. - -% @headings double turns headings on for double-sided printing. -% @headings single turns headings on for single-sided printing. -% @headings off turns them off. -% @headings on same as @headings double, retained for compatibility. -% @headings after turns on double-sided headings after this page. -% @headings doubleafter turns on double-sided headings after this page. -% @headings singleafter turns on single-sided headings after this page. -% By default, they are off at the start of a document, -% and turned `on' after @end titlepage. - -\def\headings #1 {\csname HEADINGS#1\endcsname} - -\def\HEADINGSoff{ -\global\evenheadline={\hfil} \global\evenfootline={\hfil} -\global\oddheadline={\hfil} \global\oddfootline={\hfil}} -\HEADINGSoff -% When we turn headings on, set the page number to 1. -% For double-sided printing, put current file name in lower left corner, -% chapter name on inside top of right hand pages, document -% title on inside top of left hand pages, and page numbers on outside top -% edge of all pages. -\def\HEADINGSdouble{ -\global\pageno=1 -\global\evenfootline={\hfil} -\global\oddfootline={\hfil} -\global\evenheadline={\line{\folio\hfil\thistitle}} -\global\oddheadline={\line{\thischapter\hfil\folio}} -\global\let\contentsalignmacro = \chapoddpage -} -\let\contentsalignmacro = \chappager - -% For single-sided printing, chapter title goes across top left of page, -% page number on top right. -\def\HEADINGSsingle{ -\global\pageno=1 -\global\evenfootline={\hfil} -\global\oddfootline={\hfil} -\global\evenheadline={\line{\thischapter\hfil\folio}} -\global\oddheadline={\line{\thischapter\hfil\folio}} -\global\let\contentsalignmacro = \chappager -} -\def\HEADINGSon{\HEADINGSdouble} - -\def\HEADINGSafter{\let\HEADINGShook=\HEADINGSdoublex} -\let\HEADINGSdoubleafter=\HEADINGSafter -\def\HEADINGSdoublex{% -\global\evenfootline={\hfil} -\global\oddfootline={\hfil} -\global\evenheadline={\line{\folio\hfil\thistitle}} -\global\oddheadline={\line{\thischapter\hfil\folio}} -\global\let\contentsalignmacro = \chapoddpage -} - -\def\HEADINGSsingleafter{\let\HEADINGShook=\HEADINGSsinglex} -\def\HEADINGSsinglex{% -\global\evenfootline={\hfil} -\global\oddfootline={\hfil} -\global\evenheadline={\line{\thischapter\hfil\folio}} -\global\oddheadline={\line{\thischapter\hfil\folio}} -\global\let\contentsalignmacro = \chappager -} - -% Subroutines used in generating headings -% This produces Day Month Year style of output. -% Only define if not already defined, in case a txi-??.tex file has set -% up a different format (e.g., txi-cs.tex does this). -\ifx\today\undefined -\def\today{% - \number\day\space - \ifcase\month - \or\putwordMJan\or\putwordMFeb\or\putwordMMar\or\putwordMApr - \or\putwordMMay\or\putwordMJun\or\putwordMJul\or\putwordMAug - \or\putwordMSep\or\putwordMOct\or\putwordMNov\or\putwordMDec - \fi - \space\number\year} -\fi - -% @settitle line... specifies the title of the document, for headings. -% It generates no output of its own. -\def\thistitle{\putwordNoTitle} -\def\settitle{\parsearg\settitlezzz} -\def\settitlezzz #1{\gdef\thistitle{#1}} - - -\message{tables,} -% Tables -- @table, @ftable, @vtable, @item(x), @kitem(x), @xitem(x). - -% default indentation of table text -\newdimen\tableindent \tableindent=.8in -% default indentation of @itemize and @enumerate text -\newdimen\itemindent \itemindent=.3in -% margin between end of table item and start of table text. -\newdimen\itemmargin \itemmargin=.1in - -% used internally for \itemindent minus \itemmargin -\newdimen\itemmax - -% Note @table, @vtable, and @vtable define @item, @itemx, etc., with -% these defs. -% They also define \itemindex -% to index the item name in whatever manner is desired (perhaps none). - -\newif\ifitemxneedsnegativevskip - -\def\itemxpar{\par\ifitemxneedsnegativevskip\nobreak\vskip-\parskip\nobreak\fi} - -\def\internalBitem{\smallbreak \parsearg\itemzzz} -\def\internalBitemx{\itemxpar \parsearg\itemzzz} - -\def\internalBxitem "#1"{\def\xitemsubtopix{#1} \smallbreak \parsearg\xitemzzz} -\def\internalBxitemx "#1"{\def\xitemsubtopix{#1} \itemxpar \parsearg\xitemzzz} - -\def\internalBkitem{\smallbreak \parsearg\kitemzzz} -\def\internalBkitemx{\itemxpar \parsearg\kitemzzz} - -\def\kitemzzz #1{\dosubind {kw}{\code{#1}}{for {\bf \lastfunction}}% - \itemzzz {#1}} - -\def\xitemzzz #1{\dosubind {kw}{\code{#1}}{for {\bf \xitemsubtopic}}% - \itemzzz {#1}} - -\def\itemzzz #1{\begingroup % - \advance\hsize by -\rightskip - \advance\hsize by -\tableindent - \setbox0=\hbox{\itemfont{#1}}% - \itemindex{#1}% - \nobreak % This prevents a break before @itemx. - % - % If the item text does not fit in the space we have, put it on a line - % by itself, and do not allow a page break either before or after that - % line. We do not start a paragraph here because then if the next - % command is, e.g., @kindex, the whatsit would get put into the - % horizontal list on a line by itself, resulting in extra blank space. - \ifdim \wd0>\itemmax - % - % Make this a paragraph so we get the \parskip glue and wrapping, - % but leave it ragged-right. - \begingroup - \advance\leftskip by-\tableindent - \advance\hsize by\tableindent - \advance\rightskip by0pt plus1fil - \leavevmode\unhbox0\par - \endgroup - % - % We're going to be starting a paragraph, but we don't want the - % \parskip glue -- logically it's part of the @item we just started. - \nobreak \vskip-\parskip - % - % Stop a page break at the \parskip glue coming up. Unfortunately - % we can't prevent a possible page break at the following - % \baselineskip glue. - \nobreak - \endgroup - \itemxneedsnegativevskipfalse - \else - % The item text fits into the space. Start a paragraph, so that the - % following text (if any) will end up on the same line. - \noindent - % Do this with kerns and \unhbox so that if there is a footnote in - % the item text, it can migrate to the main vertical list and - % eventually be printed. - \nobreak\kern-\tableindent - \dimen0 = \itemmax \advance\dimen0 by \itemmargin \advance\dimen0 by -\wd0 - \unhbox0 - \nobreak\kern\dimen0 - \endgroup - \itemxneedsnegativevskiptrue - \fi -} - -\def\item{\errmessage{@item while not in a table}} -\def\itemx{\errmessage{@itemx while not in a table}} -\def\kitem{\errmessage{@kitem while not in a table}} -\def\kitemx{\errmessage{@kitemx while not in a table}} -\def\xitem{\errmessage{@xitem while not in a table}} -\def\xitemx{\errmessage{@xitemx while not in a table}} - -% Contains a kludge to get @end[description] to work. -\def\description{\tablez{\dontindex}{1}{}{}{}{}} - -% @table, @ftable, @vtable. -\def\table{\begingroup\inENV\obeylines\obeyspaces\tablex} -{\obeylines\obeyspaces% -\gdef\tablex #1^^M{% -\tabley\dontindex#1 \endtabley}} - -\def\ftable{\begingroup\inENV\obeylines\obeyspaces\ftablex} -{\obeylines\obeyspaces% -\gdef\ftablex #1^^M{% -\tabley\fnitemindex#1 \endtabley -\def\Eftable{\endgraf\afterenvbreak\endgroup}% -\let\Etable=\relax}} - -\def\vtable{\begingroup\inENV\obeylines\obeyspaces\vtablex} -{\obeylines\obeyspaces% -\gdef\vtablex #1^^M{% -\tabley\vritemindex#1 \endtabley -\def\Evtable{\endgraf\afterenvbreak\endgroup}% -\let\Etable=\relax}} - -\def\dontindex #1{} -\def\fnitemindex #1{\doind {fn}{\code{#1}}}% -\def\vritemindex #1{\doind {vr}{\code{#1}}}% - -{\obeyspaces % -\gdef\tabley#1#2 #3 #4 #5 #6 #7\endtabley{\endgroup% -\tablez{#1}{#2}{#3}{#4}{#5}{#6}}} - -\def\tablez #1#2#3#4#5#6{% -\aboveenvbreak % -\begingroup % -\def\Edescription{\Etable}% Necessary kludge. -\let\itemindex=#1% -\ifnum 0#3>0 \advance \leftskip by #3\mil \fi % -\ifnum 0#4>0 \tableindent=#4\mil \fi % -\ifnum 0#5>0 \advance \rightskip by #5\mil \fi % -\def\itemfont{#2}% -\itemmax=\tableindent % -\advance \itemmax by -\itemmargin % -\advance \leftskip by \tableindent % -\exdentamount=\tableindent -\parindent = 0pt -\parskip = \smallskipamount -\ifdim \parskip=0pt \parskip=2pt \fi% -\def\Etable{\endgraf\afterenvbreak\endgroup}% -\let\item = \internalBitem % -\let\itemx = \internalBitemx % -\let\kitem = \internalBkitem % -\let\kitemx = \internalBkitemx % -\let\xitem = \internalBxitem % -\let\xitemx = \internalBxitemx % -} - -% This is the counter used by @enumerate, which is really @itemize - -\newcount \itemno - -\def\itemize{\parsearg\itemizezzz} - -\def\itemizezzz #1{% - \begingroup % ended by the @end itemize - \itemizey {#1}{\Eitemize} -} - -\def\itemizey #1#2{% -\aboveenvbreak % -\itemmax=\itemindent % -\advance \itemmax by -\itemmargin % -\advance \leftskip by \itemindent % -\exdentamount=\itemindent -\parindent = 0pt % -\parskip = \smallskipamount % -\ifdim \parskip=0pt \parskip=2pt \fi% -\def#2{\endgraf\afterenvbreak\endgroup}% -\def\itemcontents{#1}% -\let\item=\itemizeitem} - -% Set sfcode to normal for the chars that usually have another value. -% These are `.?!:;,' -\def\frenchspacing{\sfcode46=1000 \sfcode63=1000 \sfcode33=1000 - \sfcode58=1000 \sfcode59=1000 \sfcode44=1000 } - -% \splitoff TOKENS\endmark defines \first to be the first token in -% TOKENS, and \rest to be the remainder. -% -\def\splitoff#1#2\endmark{\def\first{#1}\def\rest{#2}}% - -% Allow an optional argument of an uppercase letter, lowercase letter, -% or number, to specify the first label in the enumerated list. No -% argument is the same as `1'. -% -\def\enumerate{\parsearg\enumeratezzz} -\def\enumeratezzz #1{\enumeratey #1 \endenumeratey} -\def\enumeratey #1 #2\endenumeratey{% - \begingroup % ended by the @end enumerate - % - % If we were given no argument, pretend we were given `1'. - \def\thearg{#1}% - \ifx\thearg\empty \def\thearg{1}\fi - % - % Detect if the argument is a single token. If so, it might be a - % letter. Otherwise, the only valid thing it can be is a number. - % (We will always have one token, because of the test we just made. - % This is a good thing, since \splitoff doesn't work given nothing at - % all -- the first parameter is undelimited.) - \expandafter\splitoff\thearg\endmark - \ifx\rest\empty - % Only one token in the argument. It could still be anything. - % A ``lowercase letter'' is one whose \lccode is nonzero. - % An ``uppercase letter'' is one whose \lccode is both nonzero, and - % not equal to itself. - % Otherwise, we assume it's a number. - % - % We need the \relax at the end of the \ifnum lines to stop TeX from - % continuing to look for a . - % - \ifnum\lccode\expandafter`\thearg=0\relax - \numericenumerate % a number (we hope) - \else - % It's a letter. - \ifnum\lccode\expandafter`\thearg=\expandafter`\thearg\relax - \lowercaseenumerate % lowercase letter - \else - \uppercaseenumerate % uppercase letter - \fi - \fi - \else - % Multiple tokens in the argument. We hope it's a number. - \numericenumerate - \fi -} - -% An @enumerate whose labels are integers. The starting integer is -% given in \thearg. -% -\def\numericenumerate{% - \itemno = \thearg - \startenumeration{\the\itemno}% -} - -% The starting (lowercase) letter is in \thearg. -\def\lowercaseenumerate{% - \itemno = \expandafter`\thearg - \startenumeration{% - % Be sure we're not beyond the end of the alphabet. - \ifnum\itemno=0 - \errmessage{No more lowercase letters in @enumerate; get a bigger - alphabet}% - \fi - \char\lccode\itemno - }% -} - -% The starting (uppercase) letter is in \thearg. -\def\uppercaseenumerate{% - \itemno = \expandafter`\thearg - \startenumeration{% - % Be sure we're not beyond the end of the alphabet. - \ifnum\itemno=0 - \errmessage{No more uppercase letters in @enumerate; get a bigger - alphabet} - \fi - \char\uccode\itemno - }% -} - -% Call itemizey, adding a period to the first argument and supplying the -% common last two arguments. Also subtract one from the initial value in -% \itemno, since @item increments \itemno. -% -\def\startenumeration#1{% - \advance\itemno by -1 - \itemizey{#1.}\Eenumerate\flushcr -} - -% @alphaenumerate and @capsenumerate are abbreviations for giving an arg -% to @enumerate. -% -\def\alphaenumerate{\enumerate{a}} -\def\capsenumerate{\enumerate{A}} -\def\Ealphaenumerate{\Eenumerate} -\def\Ecapsenumerate{\Eenumerate} - -% Definition of @item while inside @itemize. - -\def\itemizeitem{% -\advance\itemno by 1 -{\let\par=\endgraf \smallbreak}% -\ifhmode \errmessage{In hmode at itemizeitem}\fi -{\parskip=0in \hskip 0pt -\hbox to 0pt{\hss \itemcontents\hskip \itemmargin}% -\vadjust{\penalty 1200}}% -\flushcr} - -% @multitable macros -% Amy Hendrickson, 8/18/94, 3/6/96 -% -% @multitable ... @end multitable will make as many columns as desired. -% Contents of each column will wrap at width given in preamble. Width -% can be specified either with sample text given in a template line, -% or in percent of \hsize, the current width of text on page. - -% Table can continue over pages but will only break between lines. - -% To make preamble: -% -% Either define widths of columns in terms of percent of \hsize: -% @multitable @columnfractions .25 .3 .45 -% @item ... -% -% Numbers following @columnfractions are the percent of the total -% current hsize to be used for each column. You may use as many -% columns as desired. - - -% Or use a template: -% @multitable {Column 1 template} {Column 2 template} {Column 3 template} -% @item ... -% using the widest term desired in each column. -% -% For those who want to use more than one line's worth of words in -% the preamble, break the line within one argument and it -% will parse correctly, i.e., -% -% @multitable {Column 1 template} {Column 2 template} {Column 3 -% template} -% Not: -% @multitable {Column 1 template} {Column 2 template} -% {Column 3 template} - -% Each new table line starts with @item, each subsequent new column -% starts with @tab. Empty columns may be produced by supplying @tab's -% with nothing between them for as many times as empty columns are needed, -% ie, @tab@tab@tab will produce two empty columns. - -% @item, @tab, @multitable or @end multitable do not need to be on their -% own lines, but it will not hurt if they are. - -% Sample multitable: - -% @multitable {Column 1 template} {Column 2 template} {Column 3 template} -% @item first col stuff @tab second col stuff @tab third col -% @item -% first col stuff -% @tab -% second col stuff -% @tab -% third col -% @item first col stuff @tab second col stuff -% @tab Many paragraphs of text may be used in any column. -% -% They will wrap at the width determined by the template. -% @item@tab@tab This will be in third column. -% @end multitable - -% Default dimensions may be reset by user. -% @multitableparskip is vertical space between paragraphs in table. -% @multitableparindent is paragraph indent in table. -% @multitablecolmargin is horizontal space to be left between columns. -% @multitablelinespace is space to leave between table items, baseline -% to baseline. -% 0pt means it depends on current normal line spacing. -% -\newskip\multitableparskip -\newskip\multitableparindent -\newdimen\multitablecolspace -\newskip\multitablelinespace -\multitableparskip=0pt -\multitableparindent=6pt -\multitablecolspace=12pt -\multitablelinespace=0pt - -% Macros used to set up halign preamble: -% -\let\endsetuptable\relax -\def\xendsetuptable{\endsetuptable} -\let\columnfractions\relax -\def\xcolumnfractions{\columnfractions} -\newif\ifsetpercent - -% #1 is the part of the @columnfraction before the decimal point, which -% is presumably either 0 or the empty string (but we don't check, we -% just throw it away). #2 is the decimal part, which we use as the -% percent of \hsize for this column. -\def\pickupwholefraction#1.#2 {% - \global\advance\colcount by 1 - \expandafter\xdef\csname col\the\colcount\endcsname{.#2\hsize}% - \setuptable -} - -\newcount\colcount -\def\setuptable#1{% - \def\firstarg{#1}% - \ifx\firstarg\xendsetuptable - \let\go = \relax - \else - \ifx\firstarg\xcolumnfractions - \global\setpercenttrue - \else - \ifsetpercent - \let\go\pickupwholefraction - \else - \global\advance\colcount by 1 - \setbox0=\hbox{#1\unskip }% Add a normal word space as a separator; - % typically that is always in the input, anyway. - \expandafter\xdef\csname col\the\colcount\endcsname{\the\wd0}% - \fi - \fi - \ifx\go\pickupwholefraction - % Put the argument back for the \pickupwholefraction call, so - % we'll always have a period there to be parsed. - \def\go{\pickupwholefraction#1}% - \else - \let\go = \setuptable - \fi% - \fi - \go -} - -% This used to have \hskip1sp. But then the space in a template line is -% not enough. That is bad. So let's go back to just & until we -% encounter the problem it was intended to solve again. -% --karl, nathan@acm.org, 20apr99. -\def\tab{&} - -% @multitable ... @end multitable definitions: -% -\def\multitable{\parsearg\dotable} -\def\dotable#1{\bgroup - \vskip\parskip - \let\item\crcr - \tolerance=9500 - \hbadness=9500 - \setmultitablespacing - \parskip=\multitableparskip - \parindent=\multitableparindent - \overfullrule=0pt - \global\colcount=0 - \def\Emultitable{\global\setpercentfalse\cr\egroup\egroup}% - % - % To parse everything between @multitable and @item: - \setuptable#1 \endsetuptable - % - % \everycr will reset column counter, \colcount, at the end of - % each line. Every column entry will cause \colcount to advance by one. - % The table preamble - % looks at the current \colcount to find the correct column width. - \everycr{\noalign{% - % - % \filbreak%% keeps underfull box messages off when table breaks over pages. - % Maybe so, but it also creates really weird page breaks when the table - % breaks over pages. Wouldn't \vfil be better? Wait until the problem - % manifests itself, so it can be fixed for real --karl. - \global\colcount=0\relax}}% - % - % This preamble sets up a generic column definition, which will - % be used as many times as user calls for columns. - % \vtop will set a single line and will also let text wrap and - % continue for many paragraphs if desired. - \halign\bgroup&\global\advance\colcount by 1\relax - \multistrut\vtop{\hsize=\expandafter\csname col\the\colcount\endcsname - % - % In order to keep entries from bumping into each other - % we will add a \leftskip of \multitablecolspace to all columns after - % the first one. - % - % If a template has been used, we will add \multitablecolspace - % to the width of each template entry. - % - % If the user has set preamble in terms of percent of \hsize we will - % use that dimension as the width of the column, and the \leftskip - % will keep entries from bumping into each other. Table will start at - % left margin and final column will justify at right margin. - % - % Make sure we don't inherit \rightskip from the outer environment. - \rightskip=0pt - \ifnum\colcount=1 - % The first column will be indented with the surrounding text. - \advance\hsize by\leftskip - \else - \ifsetpercent \else - % If user has not set preamble in terms of percent of \hsize - % we will advance \hsize by \multitablecolspace. - \advance\hsize by \multitablecolspace - \fi - % In either case we will make \leftskip=\multitablecolspace: - \leftskip=\multitablecolspace - \fi - % Ignoring space at the beginning and end avoids an occasional spurious - % blank line, when TeX decides to break the line at the space before the - % box from the multistrut, so the strut ends up on a line by itself. - % For example: - % @multitable @columnfractions .11 .89 - % @item @code{#} - % @tab Legal holiday which is valid in major parts of the whole country. - % Is automatically provided with highlighting sequences respectively marking - % characters. - \noindent\ignorespaces##\unskip\multistrut}\cr -} - -\def\setmultitablespacing{% test to see if user has set \multitablelinespace. -% If so, do nothing. If not, give it an appropriate dimension based on -% current baselineskip. -\ifdim\multitablelinespace=0pt -\setbox0=\vbox{X}\global\multitablelinespace=\the\baselineskip -\global\advance\multitablelinespace by-\ht0 -%% strut to put in table in case some entry doesn't have descenders, -%% to keep lines equally spaced -\let\multistrut = \strut -\else -%% FIXME: what is \box0 supposed to be? -\gdef\multistrut{\vrule height\multitablelinespace depth\dp0 -width0pt\relax} \fi -%% Test to see if parskip is larger than space between lines of -%% table. If not, do nothing. -%% If so, set to same dimension as multitablelinespace. -\ifdim\multitableparskip>\multitablelinespace -\global\multitableparskip=\multitablelinespace -\global\advance\multitableparskip-7pt %% to keep parskip somewhat smaller - %% than skip between lines in the table. -\fi% -\ifdim\multitableparskip=0pt -\global\multitableparskip=\multitablelinespace -\global\advance\multitableparskip-7pt %% to keep parskip somewhat smaller - %% than skip between lines in the table. -\fi} - - -\message{conditionals,} -% Prevent errors for section commands. -% Used in @ignore and in failing conditionals. -\def\ignoresections{% - \let\chapter=\relax - \let\unnumbered=\relax - \let\top=\relax - \let\unnumberedsec=\relax - \let\unnumberedsection=\relax - \let\unnumberedsubsec=\relax - \let\unnumberedsubsection=\relax - \let\unnumberedsubsubsec=\relax - \let\unnumberedsubsubsection=\relax - \let\section=\relax - \let\subsec=\relax - \let\subsubsec=\relax - \let\subsection=\relax - \let\subsubsection=\relax - \let\appendix=\relax - \let\appendixsec=\relax - \let\appendixsection=\relax - \let\appendixsubsec=\relax - \let\appendixsubsection=\relax - \let\appendixsubsubsec=\relax - \let\appendixsubsubsection=\relax - \let\contents=\relax - \let\smallbook=\relax - \let\titlepage=\relax -} - -% Used in nested conditionals, where we have to parse the Texinfo source -% and so want to turn off most commands, in case they are used -% incorrectly. -% -\def\ignoremorecommands{% - \let\defcodeindex = \relax - \let\defcv = \relax - \let\deffn = \relax - \let\deffnx = \relax - \let\defindex = \relax - \let\defivar = \relax - \let\defmac = \relax - \let\defmethod = \relax - \let\defop = \relax - \let\defopt = \relax - \let\defspec = \relax - \let\deftp = \relax - \let\deftypefn = \relax - \let\deftypefun = \relax - \let\deftypeivar = \relax - \let\deftypeop = \relax - \let\deftypevar = \relax - \let\deftypevr = \relax - \let\defun = \relax - \let\defvar = \relax - \let\defvr = \relax - \let\ref = \relax - \let\xref = \relax - \let\printindex = \relax - \let\pxref = \relax - \let\settitle = \relax - \let\setchapternewpage = \relax - \let\setchapterstyle = \relax - \let\everyheading = \relax - \let\evenheading = \relax - \let\oddheading = \relax - \let\everyfooting = \relax - \let\evenfooting = \relax - \let\oddfooting = \relax - \let\headings = \relax - \let\include = \relax - \let\lowersections = \relax - \let\down = \relax - \let\raisesections = \relax - \let\up = \relax - \let\set = \relax - \let\clear = \relax - \let\item = \relax -} - -% Ignore @ignore ... @end ignore. -% -\def\ignore{\doignore{ignore}} - -% Ignore @ifinfo, @ifhtml, @ifnottex, @html, @menu, and @direntry text. -% -\def\ifinfo{\doignore{ifinfo}} -\def\ifhtml{\doignore{ifhtml}} -\def\ifnottex{\doignore{ifnottex}} -\def\html{\doignore{html}} -\def\menu{\doignore{menu}} -\def\direntry{\doignore{direntry}} - -% @dircategory CATEGORY -- specify a category of the dir file -% which this file should belong to. Ignore this in TeX. -\let\dircategory = \comment - -% Ignore text until a line `@end #1'. -% -\def\doignore#1{\begingroup - % Don't complain about control sequences we have declared \outer. - \ignoresections - % - % Define a command to swallow text until we reach `@end #1'. - % This @ is a catcode 12 token (that is the normal catcode of @ in - % this texinfo.tex file). We change the catcode of @ below to match. - \long\def\doignoretext##1@end #1{\enddoignore}% - % - % Make sure that spaces turn into tokens that match what \doignoretext wants. - \catcode32 = 10 - % - % Ignore braces, too, so mismatched braces don't cause trouble. - \catcode`\{ = 9 - \catcode`\} = 9 - % - % We must not have @c interpreted as a control sequence. - \catcode`\@ = 12 - % - % Make the letter c a comment character so that the rest of the line - % will be ignored. This way, the document can have (for example) - % @c @end ifinfo - % and the @end ifinfo will be properly ignored. - % (We've just changed @ to catcode 12.) - \catcode`\c = 14 - % - % And now expand that command. - \doignoretext -} - -% What we do to finish off ignored text. -% -\def\enddoignore{\endgroup\ignorespaces}% - -\newif\ifwarnedobs\warnedobsfalse -\def\obstexwarn{% - \ifwarnedobs\relax\else - % We need to warn folks that they may have trouble with TeX 3.0. - % This uses \immediate\write16 rather than \message to get newlines. - \immediate\write16{} - \immediate\write16{WARNING: for users of Unix TeX 3.0!} - \immediate\write16{This manual trips a bug in TeX version 3.0 (tex hangs).} - \immediate\write16{If you are running another version of TeX, relax.} - \immediate\write16{If you are running Unix TeX 3.0, kill this TeX process.} - \immediate\write16{ Then upgrade your TeX installation if you can.} - \immediate\write16{ (See ftp://ftp.gnu.org/pub/gnu/TeX.README.)} - \immediate\write16{If you are stuck with version 3.0, run the} - \immediate\write16{ script ``tex3patch'' from the Texinfo distribution} - \immediate\write16{ to use a workaround.} - \immediate\write16{} - \global\warnedobstrue - \fi -} - -% **In TeX 3.0, setting text in \nullfont hangs tex. For a -% workaround (which requires the file ``dummy.tfm'' to be installed), -% uncomment the following line: -%%%%%\font\nullfont=dummy\let\obstexwarn=\relax - -% Ignore text, except that we keep track of conditional commands for -% purposes of nesting, up to an `@end #1' command. -% -\def\nestedignore#1{% - \obstexwarn - % We must actually expand the ignored text to look for the @end - % command, so that nested ignore constructs work. Thus, we put the - % text into a \vbox and then do nothing with the result. To minimize - % the change of memory overflow, we follow the approach outlined on - % page 401 of the TeXbook: make the current font be a dummy font. - % - \setbox0 = \vbox\bgroup - % Don't complain about control sequences we have declared \outer. - \ignoresections - % - % Define `@end #1' to end the box, which will in turn undefine the - % @end command again. - \expandafter\def\csname E#1\endcsname{\egroup\ignorespaces}% - % - % We are going to be parsing Texinfo commands. Most cause no - % trouble when they are used incorrectly, but some commands do - % complicated argument parsing or otherwise get confused, so we - % undefine them. - % - % We can't do anything about stray @-signs, unfortunately; - % they'll produce `undefined control sequence' errors. - \ignoremorecommands - % - % Set the current font to be \nullfont, a TeX primitive, and define - % all the font commands to also use \nullfont. We don't use - % dummy.tfm, as suggested in the TeXbook, because not all sites - % might have that installed. Therefore, math mode will still - % produce output, but that should be an extremely small amount of - % stuff compared to the main input. - % - \nullfont - \let\tenrm=\nullfont \let\tenit=\nullfont \let\tensl=\nullfont - \let\tenbf=\nullfont \let\tentt=\nullfont \let\smallcaps=\nullfont - \let\tensf=\nullfont - % Similarly for index fonts (mostly for their use in smallexample). - \let\smallrm=\nullfont \let\smallit=\nullfont \let\smallsl=\nullfont - \let\smallbf=\nullfont \let\smalltt=\nullfont \let\smallsc=\nullfont - \let\smallsf=\nullfont - % - % Don't complain when characters are missing from the fonts. - \tracinglostchars = 0 - % - % Don't bother to do space factor calculations. - \frenchspacing - % - % Don't report underfull hboxes. - \hbadness = 10000 - % - % Do minimal line-breaking. - \pretolerance = 10000 - % - % Do not execute instructions in @tex - \def\tex{\doignore{tex}}% - % Do not execute macro definitions. - % `c' is a comment character, so the word `macro' will get cut off. - \def\macro{\doignore{ma}}% -} - -% @set VAR sets the variable VAR to an empty value. -% @set VAR REST-OF-LINE sets VAR to the value REST-OF-LINE. -% -% Since we want to separate VAR from REST-OF-LINE (which might be -% empty), we can't just use \parsearg; we have to insert a space of our -% own to delimit the rest of the line, and then take it out again if we -% didn't need it. Make sure the catcode of space is correct to avoid -% losing inside @example, for instance. -% -\def\set{\begingroup\catcode` =10 - \catcode`\-=12 \catcode`\_=12 % Allow - and _ in VAR. - \parsearg\setxxx} -\def\setxxx#1{\setyyy#1 \endsetyyy} -\def\setyyy#1 #2\endsetyyy{% - \def\temp{#2}% - \ifx\temp\empty \global\expandafter\let\csname SET#1\endcsname = \empty - \else \setzzz{#1}#2\endsetzzz % Remove the trailing space \setxxx inserted. - \fi - \endgroup -} -% Can't use \xdef to pre-expand #2 and save some time, since \temp or -% \next or other control sequences that we've defined might get us into -% an infinite loop. Consider `@set foo @cite{bar}'. -\def\setzzz#1#2 \endsetzzz{\expandafter\gdef\csname SET#1\endcsname{#2}} - -% @clear VAR clears (i.e., unsets) the variable VAR. -% -\def\clear{\parsearg\clearxxx} -\def\clearxxx#1{\global\expandafter\let\csname SET#1\endcsname=\relax} - -% @value{foo} gets the text saved in variable foo. -{ - \catcode`\_ = \active - % - % We might end up with active _ or - characters in the argument if - % we're called from @code, as @code{@value{foo-bar_}}. So \let any - % such active characters to their normal equivalents. - \gdef\value{\begingroup - \catcode`\-=12 \catcode`\_=12 - \indexbreaks \let_\normalunderscore - \valuexxx} -} -\def\valuexxx#1{\expandablevalue{#1}\endgroup} - -% We have this subroutine so that we can handle at least some @value's -% properly in indexes (we \let\value to this in \indexdummies). Ones -% whose names contain - or _ still won't work, but we can't do anything -% about that. The command has to be fully expandable, since the result -% winds up in the index file. This means that if the variable's value -% contains other Texinfo commands, it's almost certain it will fail -% (although perhaps we could fix that with sufficient work to do a -% one-level expansion on the result, instead of complete). -% -\def\expandablevalue#1{% - \expandafter\ifx\csname SET#1\endcsname\relax - {[No value for ``#1'']}% - \else - \csname SET#1\endcsname - \fi -} - -% @ifset VAR ... @end ifset reads the `...' iff VAR has been defined -% with @set. -% -\def\ifset{\parsearg\ifsetxxx} -\def\ifsetxxx #1{% - \expandafter\ifx\csname SET#1\endcsname\relax - \expandafter\ifsetfail - \else - \expandafter\ifsetsucceed - \fi -} -\def\ifsetsucceed{\conditionalsucceed{ifset}} -\def\ifsetfail{\nestedignore{ifset}} -\defineunmatchedend{ifset} - -% @ifclear VAR ... @end ifclear reads the `...' iff VAR has never been -% defined with @set, or has been undefined with @clear. -% -\def\ifclear{\parsearg\ifclearxxx} -\def\ifclearxxx #1{% - \expandafter\ifx\csname SET#1\endcsname\relax - \expandafter\ifclearsucceed - \else - \expandafter\ifclearfail - \fi -} -\def\ifclearsucceed{\conditionalsucceed{ifclear}} -\def\ifclearfail{\nestedignore{ifclear}} -\defineunmatchedend{ifclear} - -% @iftex, @ifnothtml, @ifnotinfo always succeed; we read the text -% following, through the first @end iftex (etc.). Make `@end iftex' -% (etc.) valid only after an @iftex. -% -\def\iftex{\conditionalsucceed{iftex}} -\def\ifnothtml{\conditionalsucceed{ifnothtml}} -\def\ifnotinfo{\conditionalsucceed{ifnotinfo}} -\defineunmatchedend{iftex} -\defineunmatchedend{ifnothtml} -\defineunmatchedend{ifnotinfo} - -% We can't just want to start a group at @iftex (for example) and end it -% at @end iftex, since then @set commands inside the conditional have no -% effect (they'd get reverted at the end of the group). So we must -% define \Eiftex to redefine itself to be its previous value. (We can't -% just define it to fail again with an ``unmatched end'' error, since -% the @ifset might be nested.) -% -\def\conditionalsucceed#1{% - \edef\temp{% - % Remember the current value of \E#1. - \let\nece{prevE#1} = \nece{E#1}% - % - % At the `@end #1', redefine \E#1 to be its previous value. - \def\nece{E#1}{\let\nece{E#1} = \nece{prevE#1}}% - }% - \temp -} - -% We need to expand lots of \csname's, but we don't want to expand the -% control sequences after we've constructed them. -% -\def\nece#1{\expandafter\noexpand\csname#1\endcsname} - -% @defininfoenclose. -\let\definfoenclose=\comment - - -\message{indexing,} -% Index generation facilities - -% Define \newwrite to be identical to plain tex's \newwrite -% except not \outer, so it can be used within \newindex. -{\catcode`\@=11 -\gdef\newwrite{\alloc@7\write\chardef\sixt@@n}} - -% \newindex {foo} defines an index named foo. -% It automatically defines \fooindex such that -% \fooindex ...rest of line... puts an entry in the index foo. -% It also defines \fooindfile to be the number of the output channel for -% the file that accumulates this index. The file's extension is foo. -% The name of an index should be no more than 2 characters long -% for the sake of vms. -% -\def\newindex#1{% - \iflinks - \expandafter\newwrite \csname#1indfile\endcsname - \openout \csname#1indfile\endcsname \jobname.#1 % Open the file - \fi - \expandafter\xdef\csname#1index\endcsname{% % Define @#1index - \noexpand\doindex{#1}} -} - -% @defindex foo == \newindex{foo} -% -\def\defindex{\parsearg\newindex} - -% Define @defcodeindex, like @defindex except put all entries in @code. -% -\def\defcodeindex{\parsearg\newcodeindex} -% -\def\newcodeindex#1{% - \iflinks - \expandafter\newwrite \csname#1indfile\endcsname - \openout \csname#1indfile\endcsname \jobname.#1 - \fi - \expandafter\xdef\csname#1index\endcsname{% - \noexpand\docodeindex{#1}}% -} - - -% @synindex foo bar makes index foo feed into index bar. -% Do this instead of @defindex foo if you don't want it as a separate index. -% -% @syncodeindex foo bar similar, but put all entries made for index foo -% inside @code. -% -\def\synindex#1 #2 {\dosynindex\doindex{#1}{#2}} -\def\syncodeindex#1 #2 {\dosynindex\docodeindex{#1}{#2}} - -% #1 is \doindex or \docodeindex, #2 the index getting redefined (foo), -% #3 the target index (bar). -\def\dosynindex#1#2#3{% - % Only do \closeout if we haven't already done it, else we'll end up - % closing the target index. - \expandafter \ifx\csname donesynindex#2\endcsname \undefined - % The \closeout helps reduce unnecessary open files; the limit on the - % Acorn RISC OS is a mere 16 files. - \expandafter\closeout\csname#2indfile\endcsname - \expandafter\let\csname\donesynindex#2\endcsname = 1 - \fi - % redefine \fooindfile: - \expandafter\let\expandafter\temp\expandafter=\csname#3indfile\endcsname - \expandafter\let\csname#2indfile\endcsname=\temp - % redefine \fooindex: - \expandafter\xdef\csname#2index\endcsname{\noexpand#1{#3}}% -} - -% Define \doindex, the driver for all \fooindex macros. -% Argument #1 is generated by the calling \fooindex macro, -% and it is "foo", the name of the index. - -% \doindex just uses \parsearg; it calls \doind for the actual work. -% This is because \doind is more useful to call from other macros. - -% There is also \dosubind {index}{topic}{subtopic} -% which makes an entry in a two-level index such as the operation index. - -\def\doindex#1{\edef\indexname{#1}\parsearg\singleindexer} -\def\singleindexer #1{\doind{\indexname}{#1}} - -% like the previous two, but they put @code around the argument. -\def\docodeindex#1{\edef\indexname{#1}\parsearg\singlecodeindexer} -\def\singlecodeindexer #1{\doind{\indexname}{\code{#1}}} - -\def\indexdummies{% -\def\ { }% -% Take care of the plain tex accent commands. -\def\"{\realbackslash "}% -\def\`{\realbackslash `}% -\def\'{\realbackslash '}% -\def\^{\realbackslash ^}% -\def\~{\realbackslash ~}% -\def\={\realbackslash =}% -\def\b{\realbackslash b}% -\def\c{\realbackslash c}% -\def\d{\realbackslash d}% -\def\u{\realbackslash u}% -\def\v{\realbackslash v}% -\def\H{\realbackslash H}% -% Take care of the plain tex special European modified letters. -\def\oe{\realbackslash oe}% -\def\ae{\realbackslash ae}% -\def\aa{\realbackslash aa}% -\def\OE{\realbackslash OE}% -\def\AE{\realbackslash AE}% -\def\AA{\realbackslash AA}% -\def\o{\realbackslash o}% -\def\O{\realbackslash O}% -\def\l{\realbackslash l}% -\def\L{\realbackslash L}% -\def\ss{\realbackslash ss}% -% Take care of texinfo commands likely to appear in an index entry. -% (Must be a way to avoid doing expansion at all, and thus not have to -% laboriously list every single command here.) -\def\@{@}% will be @@ when we switch to @ as escape char. -% Need these in case \tex is in effect and \{ is a \delimiter again. -% But can't use \lbracecmd and \rbracecmd because texindex assumes -% braces and backslashes are used only as delimiters. -\let\{ = \mylbrace -\let\} = \myrbrace -\def\_{{\realbackslash _}}% -\def\w{\realbackslash w }% -\def\bf{\realbackslash bf }% -%\def\rm{\realbackslash rm }% -\def\sl{\realbackslash sl }% -\def\sf{\realbackslash sf}% -\def\tt{\realbackslash tt}% -\def\gtr{\realbackslash gtr}% -\def\less{\realbackslash less}% -\def\hat{\realbackslash hat}% -\def\TeX{\realbackslash TeX}% -\def\dots{\realbackslash dots }% -\def\result{\realbackslash result}% -\def\equiv{\realbackslash equiv}% -\def\expansion{\realbackslash expansion}% -\def\print{\realbackslash print}% -\def\error{\realbackslash error}% -\def\point{\realbackslash point}% -\def\copyright{\realbackslash copyright}% -\def\tclose##1{\realbackslash tclose {##1}}% -\def\code##1{\realbackslash code {##1}}% -\def\uref##1{\realbackslash uref {##1}}% -\def\url##1{\realbackslash url {##1}}% -\def\env##1{\realbackslash env {##1}}% -\def\command##1{\realbackslash command {##1}}% -\def\option##1{\realbackslash option {##1}}% -\def\dotless##1{\realbackslash dotless {##1}}% -\def\samp##1{\realbackslash samp {##1}}% -\def\,##1{\realbackslash ,{##1}}% -\def\t##1{\realbackslash t {##1}}% -\def\r##1{\realbackslash r {##1}}% -\def\i##1{\realbackslash i {##1}}% -\def\b##1{\realbackslash b {##1}}% -\def\sc##1{\realbackslash sc {##1}}% -\def\cite##1{\realbackslash cite {##1}}% -\def\key##1{\realbackslash key {##1}}% -\def\file##1{\realbackslash file {##1}}% -\def\var##1{\realbackslash var {##1}}% -\def\kbd##1{\realbackslash kbd {##1}}% -\def\dfn##1{\realbackslash dfn {##1}}% -\def\emph##1{\realbackslash emph {##1}}% -\def\acronym##1{\realbackslash acronym {##1}}% -% -% Handle some cases of @value -- where the variable name does not -% contain - or _, and the value does not contain any -% (non-fully-expandable) commands. -\let\value = \expandablevalue -% -\unsepspaces -% Turn off macro expansion -\turnoffmacros -} - -% If an index command is used in an @example environment, any spaces -% therein should become regular spaces in the raw index file, not the -% expansion of \tie (\\leavevmode \penalty \@M \ ). -{\obeyspaces - \gdef\unsepspaces{\obeyspaces\let =\space}} - -% \indexnofonts no-ops all font-change commands. -% This is used when outputting the strings to sort the index by. -\def\indexdummyfont#1{#1} -\def\indexdummytex{TeX} -\def\indexdummydots{...} - -\def\indexnofonts{% -% Just ignore accents. -\let\,=\indexdummyfont -\let\"=\indexdummyfont -\let\`=\indexdummyfont -\let\'=\indexdummyfont -\let\^=\indexdummyfont -\let\~=\indexdummyfont -\let\==\indexdummyfont -\let\b=\indexdummyfont -\let\c=\indexdummyfont -\let\d=\indexdummyfont -\let\u=\indexdummyfont -\let\v=\indexdummyfont -\let\H=\indexdummyfont -\let\dotless=\indexdummyfont -% Take care of the plain tex special European modified letters. -\def\oe{oe}% -\def\ae{ae}% -\def\aa{aa}% -\def\OE{OE}% -\def\AE{AE}% -\def\AA{AA}% -\def\o{o}% -\def\O{O}% -\def\l{l}% -\def\L{L}% -\def\ss{ss}% -\let\w=\indexdummyfont -\let\t=\indexdummyfont -\let\r=\indexdummyfont -\let\i=\indexdummyfont -\let\b=\indexdummyfont -\let\emph=\indexdummyfont -\let\strong=\indexdummyfont -\let\cite=\indexdummyfont -\let\sc=\indexdummyfont -%Don't no-op \tt, since it isn't a user-level command -% and is used in the definitions of the active chars like <, >, |... -%\let\tt=\indexdummyfont -\let\tclose=\indexdummyfont -\let\code=\indexdummyfont -\let\url=\indexdummyfont -\let\uref=\indexdummyfont -\let\env=\indexdummyfont -\let\acronym=\indexdummyfont -\let\command=\indexdummyfont -\let\option=\indexdummyfont -\let\file=\indexdummyfont -\let\samp=\indexdummyfont -\let\kbd=\indexdummyfont -\let\key=\indexdummyfont -\let\var=\indexdummyfont -\let\TeX=\indexdummytex -\let\dots=\indexdummydots -\def\@{@}% -} - -% To define \realbackslash, we must make \ not be an escape. -% We must first make another character (@) an escape -% so we do not become unable to do a definition. - -{\catcode`\@=0 \catcode`\\=\other - @gdef@realbackslash{\}} - -\let\indexbackslash=0 %overridden during \printindex. -\let\SETmarginindex=\relax % put index entries in margin (undocumented)? - -% For \ifx comparisons. -\def\emptymacro{\empty} - -% Most index entries go through here, but \dosubind is the general case. -% -\def\doind#1#2{\dosubind{#1}{#2}\empty} - -% Workhorse for all \fooindexes. -% #1 is name of index, #2 is stuff to put there, #3 is subentry -- -% \empty if called from \doind, as we usually are. The main exception -% is with defuns, which call us directly. -% -\def\dosubind#1#2#3{% - % Put the index entry in the margin if desired. - \ifx\SETmarginindex\relax\else - \insert\margin{\hbox{\vrule height8pt depth3pt width0pt #2}}% - \fi - {% - \count255=\lastpenalty - {% - \indexdummies % Must do this here, since \bf, etc expand at this stage - \escapechar=`\\ - {% - \let\folio = 0% We will expand all macros now EXCEPT \folio. - \def\rawbackslashxx{\indexbackslash}% \indexbackslash isn't defined now - % so it will be output as is; and it will print as backslash. - % - \def\thirdarg{#3}% - % - % If third arg is present, precede it with space in sort key. - \ifx\thirdarg\emptymacro - \let\subentry = \empty - \else - \def\subentry{ #3}% - \fi - % - % First process the index entry with all font commands turned - % off to get the string to sort by. - {\indexnofonts \xdef\indexsorttmp{#2\subentry}}% - % - % Now the real index entry with the fonts. - \toks0 = {#2}% - % - % If third (subentry) arg is present, add it to the index - % string. And include a space. - \ifx\thirdarg\emptymacro \else - \toks0 = \expandafter{\the\toks0 \space #3}% - \fi - % - % Set up the complete index entry, with both the sort key - % and the original text, including any font commands. We write - % three arguments to \entry to the .?? file, texindex reduces to - % two when writing the .??s sorted result. - \edef\temp{% - \write\csname#1indfile\endcsname{% - \realbackslash entry{\indexsorttmp}{\folio}{\the\toks0}}% - }% - % - % If a skip is the last thing on the list now, preserve it - % by backing up by \lastskip, doing the \write, then inserting - % the skip again. Otherwise, the whatsit generated by the - % \write will make \lastskip zero. The result is that sequences - % like this: - % @end defun - % @tindex whatever - % @defun ... - % will have extra space inserted, because the \medbreak in the - % start of the @defun won't see the skip inserted by the @end of - % the previous defun. - % - % But don't do any of this if we're not in vertical mode. We - % don't want to do a \vskip and prematurely end a paragraph. - % - % Avoid page breaks due to these extra skips, too. - % - \iflinks - \ifvmode - \skip0 = \lastskip - \ifdim\lastskip = 0pt \else \nobreak\vskip-\lastskip \fi - \fi - % - \temp % do the write - % - % - \ifvmode \ifdim\skip0 = 0pt \else \nobreak\vskip\skip0 \fi \fi - \fi - }% - }% - \penalty\count255 - }% -} - -% The index entry written in the file actually looks like -% \entry {sortstring}{page}{topic} -% or -% \entry {sortstring}{page}{topic}{subtopic} -% The texindex program reads in these files and writes files -% containing these kinds of lines: -% \initial {c} -% before the first topic whose initial is c -% \entry {topic}{pagelist} -% for a topic that is used without subtopics -% \primary {topic} -% for the beginning of a topic that is used with subtopics -% \secondary {subtopic}{pagelist} -% for each subtopic. - -% Define the user-accessible indexing commands -% @findex, @vindex, @kindex, @cindex. - -\def\findex {\fnindex} -\def\kindex {\kyindex} -\def\cindex {\cpindex} -\def\vindex {\vrindex} -\def\tindex {\tpindex} -\def\pindex {\pgindex} - -\def\cindexsub {\begingroup\obeylines\cindexsub} -{\obeylines % -\gdef\cindexsub "#1" #2^^M{\endgroup % -\dosubind{cp}{#2}{#1}}} - -% Define the macros used in formatting output of the sorted index material. - -% @printindex causes a particular index (the ??s file) to get printed. -% It does not print any chapter heading (usually an @unnumbered). -% -\def\printindex{\parsearg\doprintindex} -\def\doprintindex#1{\begingroup - \dobreak \chapheadingskip{10000}% - % - \smallfonts \rm - \tolerance = 9500 - \indexbreaks - % - % See if the index file exists and is nonempty. - % Change catcode of @ here so that if the index file contains - % \initial {@} - % as its first line, TeX doesn't complain about mismatched braces - % (because it thinks @} is a control sequence). - \catcode`\@ = 11 - \openin 1 \jobname.#1s - \ifeof 1 - % \enddoublecolumns gets confused if there is no text in the index, - % and it loses the chapter title and the aux file entries for the - % index. The easiest way to prevent this problem is to make sure - % there is some text. - \putwordIndexNonexistent - \else - % - % If the index file exists but is empty, then \openin leaves \ifeof - % false. We have to make TeX try to read something from the file, so - % it can discover if there is anything in it. - \read 1 to \temp - \ifeof 1 - \putwordIndexIsEmpty - \else - % Index files are almost Texinfo source, but we use \ as the escape - % character. It would be better to use @, but that's too big a change - % to make right now. - \def\indexbackslash{\rawbackslashxx}% - \catcode`\\ = 0 - \escapechar = `\\ - \begindoublecolumns - \input \jobname.#1s - \enddoublecolumns - \fi - \fi - \closein 1 -\endgroup} - -% These macros are used by the sorted index file itself. -% Change them to control the appearance of the index. - -\def\initial#1{{% - % Some minor font changes for the special characters. - \let\tentt=\sectt \let\tt=\sectt \let\sf=\sectt - % - % Remove any glue we may have, we'll be inserting our own. - \removelastskip - % - % We like breaks before the index initials, so insert a bonus. - \penalty -300 - % - % Typeset the initial. Making this add up to a whole number of - % baselineskips increases the chance of the dots lining up from column - % to column. It still won't often be perfect, because of the stretch - % we need before each entry, but it's better. - % - % No shrink because it confuses \balancecolumns. - \vskip 1.67\baselineskip plus .5\baselineskip - \leftline{\secbf #1}% - \vskip .33\baselineskip plus .1\baselineskip - % - % Do our best not to break after the initial. - \nobreak -}} - -% This typesets a paragraph consisting of #1, dot leaders, and then #2 -% flush to the right margin. It is used for index and table of contents -% entries. The paragraph is indented by \leftskip. -% -\def\entry#1#2{\begingroup - % - % Start a new paragraph if necessary, so our assignments below can't - % affect previous text. - \par - % - % Do not fill out the last line with white space. - \parfillskip = 0in - % - % No extra space above this paragraph. - \parskip = 0in - % - % Do not prefer a separate line ending with a hyphen to fewer lines. - \finalhyphendemerits = 0 - % - % \hangindent is only relevant when the entry text and page number - % don't both fit on one line. In that case, bob suggests starting the - % dots pretty far over on the line. Unfortunately, a large - % indentation looks wrong when the entry text itself is broken across - % lines. So we use a small indentation and put up with long leaders. - % - % \hangafter is reset to 1 (which is the value we want) at the start - % of each paragraph, so we need not do anything with that. - \hangindent = 2em - % - % When the entry text needs to be broken, just fill out the first line - % with blank space. - \rightskip = 0pt plus1fil - % - % A bit of stretch before each entry for the benefit of balancing columns. - \vskip 0pt plus1pt - % - % Start a ``paragraph'' for the index entry so the line breaking - % parameters we've set above will have an effect. - \noindent - % - % Insert the text of the index entry. TeX will do line-breaking on it. - #1% - % The following is kludged to not output a line of dots in the index if - % there are no page numbers. The next person who breaks this will be - % cursed by a Unix daemon. - \def\tempa{{\rm }}% - \def\tempb{#2}% - \edef\tempc{\tempa}% - \edef\tempd{\tempb}% - \ifx\tempc\tempd\ \else% - % - % If we must, put the page number on a line of its own, and fill out - % this line with blank space. (The \hfil is overwhelmed with the - % fill leaders glue in \indexdotfill if the page number does fit.) - \hfil\penalty50 - \null\nobreak\indexdotfill % Have leaders before the page number. - % - % The `\ ' here is removed by the implicit \unskip that TeX does as - % part of (the primitive) \par. Without it, a spurious underfull - % \hbox ensues. - \ifpdf - \pdfgettoks#2.\ \the\toksA % The page number ends the paragraph. - \else - \ #2% The page number ends the paragraph. - \fi - \fi% - \par -\endgroup} - -% Like \dotfill except takes at least 1 em. -\def\indexdotfill{\cleaders - \hbox{$\mathsurround=0pt \mkern1.5mu ${\it .}$ \mkern1.5mu$}\hskip 1em plus 1fill} - -\def\primary #1{\line{#1\hfil}} - -\newskip\secondaryindent \secondaryindent=0.5cm - -\def\secondary #1#2{ -{\parfillskip=0in \parskip=0in -\hangindent =1in \hangafter=1 -\noindent\hskip\secondaryindent\hbox{#1}\indexdotfill #2\par -}} - -% Define two-column mode, which we use to typeset indexes. -% Adapted from the TeXbook, page 416, which is to say, -% the manmac.tex format used to print the TeXbook itself. -\catcode`\@=11 - -\newbox\partialpage -\newdimen\doublecolumnhsize - -\def\begindoublecolumns{\begingroup % ended by \enddoublecolumns - % Grab any single-column material above us. - \output = {% - % - % Here is a possibility not foreseen in manmac: if we accumulate a - % whole lot of material, we might end up calling this \output - % routine twice in a row (see the doublecol-lose test, which is - % essentially a couple of indexes with @setchapternewpage off). In - % that case we just ship out what is in \partialpage with the normal - % output routine. Generally, \partialpage will be empty when this - % runs and this will be a no-op. See the indexspread.tex test case. - \ifvoid\partialpage \else - \onepageout{\pagecontents\partialpage}% - \fi - % - \global\setbox\partialpage = \vbox{% - % Unvbox the main output page. - \unvbox\PAGE - \kern-\topskip \kern\baselineskip - }% - }% - \eject % run that output routine to set \partialpage - % - % Use the double-column output routine for subsequent pages. - \output = {\doublecolumnout}% - % - % Change the page size parameters. We could do this once outside this - % routine, in each of @smallbook, @afourpaper, and the default 8.5x11 - % format, but then we repeat the same computation. Repeating a couple - % of assignments once per index is clearly meaningless for the - % execution time, so we may as well do it in one place. - % - % First we halve the line length, less a little for the gutter between - % the columns. We compute the gutter based on the line length, so it - % changes automatically with the paper format. The magic constant - % below is chosen so that the gutter has the same value (well, +-<1pt) - % as it did when we hard-coded it. - % - % We put the result in a separate register, \doublecolumhsize, so we - % can restore it in \pagesofar, after \hsize itself has (potentially) - % been clobbered. - % - \doublecolumnhsize = \hsize - \advance\doublecolumnhsize by -.04154\hsize - \divide\doublecolumnhsize by 2 - \hsize = \doublecolumnhsize - % - % Double the \vsize as well. (We don't need a separate register here, - % since nobody clobbers \vsize.) - \vsize = 2\vsize -} - -% The double-column output routine for all double-column pages except -% the last. -% -\def\doublecolumnout{% - \splittopskip=\topskip \splitmaxdepth=\maxdepth - % Get the available space for the double columns -- the normal - % (undoubled) page height minus any material left over from the - % previous page. - \dimen@ = \vsize - \divide\dimen@ by 2 - \advance\dimen@ by -\ht\partialpage - % - % box0 will be the left-hand column, box2 the right. - \setbox0=\vsplit255 to\dimen@ \setbox2=\vsplit255 to\dimen@ - \onepageout\pagesofar - \unvbox255 - \penalty\outputpenalty -} -% -% Re-output the contents of the output page -- any previous material, -% followed by the two boxes we just split, in box0 and box2. -\def\pagesofar{% - \unvbox\partialpage - % - \hsize = \doublecolumnhsize - \wd0=\hsize \wd2=\hsize - \hbox to\pagewidth{\box0\hfil\box2}% -} -% -% All done with double columns. -\def\enddoublecolumns{% - \output = {% - % Split the last of the double-column material. Leave it on the - % current page, no automatic page break. - \balancecolumns - % - % If we end up splitting too much material for the current page, - % though, there will be another page break right after this \output - % invocation ends. Having called \balancecolumns once, we do not - % want to call it again. Therefore, reset \output to its normal - % definition right away. (We hope \balancecolumns will never be - % called on to balance too much material, but if it is, this makes - % the output somewhat more palatable.) - \global\output = {\onepageout{\pagecontents\PAGE}}% - }% - \eject - \endgroup % started in \begindoublecolumns - % - % \pagegoal was set to the doubled \vsize above, since we restarted - % the current page. We're now back to normal single-column - % typesetting, so reset \pagegoal to the normal \vsize (after the - % \endgroup where \vsize got restored). - \pagegoal = \vsize -} -% -% Called at the end of the double column material. -\def\balancecolumns{% - \setbox0 = \vbox{\unvbox255}% like \box255 but more efficient, see p.120. - \dimen@ = \ht0 - \advance\dimen@ by \topskip - \advance\dimen@ by-\baselineskip - \divide\dimen@ by 2 % target to split to - %debug\message{final 2-column material height=\the\ht0, target=\the\dimen@.}% - \splittopskip = \topskip - % Loop until we get a decent breakpoint. - {% - \vbadness = 10000 - \loop - \global\setbox3 = \copy0 - \global\setbox1 = \vsplit3 to \dimen@ - \ifdim\ht3>\dimen@ - \global\advance\dimen@ by 1pt - \repeat - }% - %debug\message{split to \the\dimen@, column heights: \the\ht1, \the\ht3.}% - \setbox0=\vbox to\dimen@{\unvbox1}% - \setbox2=\vbox to\dimen@{\unvbox3}% - % - \pagesofar -} -\catcode`\@ = \other - - -\message{sectioning,} -% Chapters, sections, etc. - -\newcount\chapno -\newcount\secno \secno=0 -\newcount\subsecno \subsecno=0 -\newcount\subsubsecno \subsubsecno=0 - -% This counter is funny since it counts through charcodes of letters A, B, ... -\newcount\appendixno \appendixno = `\@ -% \def\appendixletter{\char\the\appendixno} -% We do the following for the sake of pdftex, which needs the actual -% letter in the expansion, not just typeset. -\def\appendixletter{% - \ifnum\appendixno=`A A% - \else\ifnum\appendixno=`B B% - \else\ifnum\appendixno=`C C% - \else\ifnum\appendixno=`D D% - \else\ifnum\appendixno=`E E% - \else\ifnum\appendixno=`F F% - \else\ifnum\appendixno=`G G% - \else\ifnum\appendixno=`H H% - \else\ifnum\appendixno=`I I% - \else\ifnum\appendixno=`J J% - \else\ifnum\appendixno=`K K% - \else\ifnum\appendixno=`L L% - \else\ifnum\appendixno=`M M% - \else\ifnum\appendixno=`N N% - \else\ifnum\appendixno=`O O% - \else\ifnum\appendixno=`P P% - \else\ifnum\appendixno=`Q Q% - \else\ifnum\appendixno=`R R% - \else\ifnum\appendixno=`S S% - \else\ifnum\appendixno=`T T% - \else\ifnum\appendixno=`U U% - \else\ifnum\appendixno=`V V% - \else\ifnum\appendixno=`W W% - \else\ifnum\appendixno=`X X% - \else\ifnum\appendixno=`Y Y% - \else\ifnum\appendixno=`Z Z% - % The \the is necessary, despite appearances, because \appendixletter is - % expanded while writing the .toc file. \char\appendixno is not - % expandable, thus it is written literally, thus all appendixes come out - % with the same letter (or @) in the toc without it. - \else\char\the\appendixno - \fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi - \fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi} - -% Each @chapter defines this as the name of the chapter. -% page headings and footings can use it. @section does likewise. -\def\thischapter{} -\def\thissection{} - -\newcount\absseclevel % used to calculate proper heading level -\newcount\secbase\secbase=0 % @raise/lowersections modify this count - -% @raisesections: treat @section as chapter, @subsection as section, etc. -\def\raisesections{\global\advance\secbase by -1} -\let\up=\raisesections % original BFox name - -% @lowersections: treat @chapter as section, @section as subsection, etc. -\def\lowersections{\global\advance\secbase by 1} -\let\down=\lowersections % original BFox name - -% Choose a numbered-heading macro -% #1 is heading level if unmodified by @raisesections or @lowersections -% #2 is text for heading -\def\numhead#1#2{\absseclevel=\secbase\advance\absseclevel by #1 -\ifcase\absseclevel - \chapterzzz{#2} -\or - \seczzz{#2} -\or - \numberedsubseczzz{#2} -\or - \numberedsubsubseczzz{#2} -\else - \ifnum \absseclevel<0 - \chapterzzz{#2} - \else - \numberedsubsubseczzz{#2} - \fi -\fi -} - -% like \numhead, but chooses appendix heading levels -\def\apphead#1#2{\absseclevel=\secbase\advance\absseclevel by #1 -\ifcase\absseclevel - \appendixzzz{#2} -\or - \appendixsectionzzz{#2} -\or - \appendixsubseczzz{#2} -\or - \appendixsubsubseczzz{#2} -\else - \ifnum \absseclevel<0 - \appendixzzz{#2} - \else - \appendixsubsubseczzz{#2} - \fi -\fi -} - -% like \numhead, but chooses numberless heading levels -\def\unnmhead#1#2{\absseclevel=\secbase\advance\absseclevel by #1 -\ifcase\absseclevel - \unnumberedzzz{#2} -\or - \unnumberedseczzz{#2} -\or - \unnumberedsubseczzz{#2} -\or - \unnumberedsubsubseczzz{#2} -\else - \ifnum \absseclevel<0 - \unnumberedzzz{#2} - \else - \unnumberedsubsubseczzz{#2} - \fi -\fi -} - -% @chapter, @appendix, @unnumbered. -\def\thischaptername{No Chapter Title} -\outer\def\chapter{\parsearg\chapteryyy} -\def\chapteryyy #1{\numhead0{#1}} % normally numhead0 calls chapterzzz -\def\chapterzzz #1{% -\secno=0 \subsecno=0 \subsubsecno=0 -\global\advance \chapno by 1 \message{\putwordChapter\space \the\chapno}% -\chapmacro {#1}{\the\chapno}% -\gdef\thissection{#1}% -\gdef\thischaptername{#1}% -% We don't substitute the actual chapter name into \thischapter -% because we don't want its macros evaluated now. -\xdef\thischapter{\putwordChapter{} \the\chapno: \noexpand\thischaptername}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash chapentry{\the\toks0}% - {\the\chapno}}}% -\temp -\donoderef -\global\let\section = \numberedsec -\global\let\subsection = \numberedsubsec -\global\let\subsubsection = \numberedsubsubsec -} - -\outer\def\appendix{\parsearg\appendixyyy} -\def\appendixyyy #1{\apphead0{#1}} % normally apphead0 calls appendixzzz -\def\appendixzzz #1{% -\secno=0 \subsecno=0 \subsubsecno=0 -\global\advance \appendixno by 1 -\message{\putwordAppendix\space \appendixletter}% -\chapmacro {#1}{\putwordAppendix{} \appendixletter}% -\gdef\thissection{#1}% -\gdef\thischaptername{#1}% -\xdef\thischapter{\putwordAppendix{} \appendixletter: \noexpand\thischaptername}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash chapentry{\the\toks0}% - {\putwordAppendix{} \appendixletter}}}% -\temp -\appendixnoderef -\global\let\section = \appendixsec -\global\let\subsection = \appendixsubsec -\global\let\subsubsection = \appendixsubsubsec -} - -% @centerchap is like @unnumbered, but the heading is centered. -\outer\def\centerchap{\parsearg\centerchapyyy} -\def\centerchapyyy #1{{\let\unnumbchapmacro=\centerchapmacro \unnumberedyyy{#1}}} - -% @top is like @unnumbered. -\outer\def\top{\parsearg\unnumberedyyy} - -\outer\def\unnumbered{\parsearg\unnumberedyyy} -\def\unnumberedyyy #1{\unnmhead0{#1}} % normally unnmhead0 calls unnumberedzzz -\def\unnumberedzzz #1{% -\secno=0 \subsecno=0 \subsubsecno=0 -% -% This used to be simply \message{#1}, but TeX fully expands the -% argument to \message. Therefore, if #1 contained @-commands, TeX -% expanded them. For example, in `@unnumbered The @cite{Book}', TeX -% expanded @cite (which turns out to cause errors because \cite is meant -% to be executed, not expanded). -% -% Anyway, we don't want the fully-expanded definition of @cite to appear -% as a result of the \message, we just want `@cite' itself. We use -% \the to achieve this: TeX expands \the only once, -% simply yielding the contents of . (We also do this for -% the toc entries.) -\toks0 = {#1}\message{(\the\toks0)}% -% -\unnumbchapmacro {#1}% -\gdef\thischapter{#1}\gdef\thissection{#1}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash unnumbchapentry{\the\toks0}}}% -\temp -\unnumbnoderef -\global\let\section = \unnumberedsec -\global\let\subsection = \unnumberedsubsec -\global\let\subsubsection = \unnumberedsubsubsec -} - -% Sections. -\outer\def\numberedsec{\parsearg\secyyy} -\def\secyyy #1{\numhead1{#1}} % normally calls seczzz -\def\seczzz #1{% -\subsecno=0 \subsubsecno=0 \global\advance \secno by 1 % -\gdef\thissection{#1}\secheading {#1}{\the\chapno}{\the\secno}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash secentry{\the\toks0}% - {\the\chapno}{\the\secno}}}% -\temp -\donoderef -\nobreak -} - -\outer\def\appendixsection{\parsearg\appendixsecyyy} -\outer\def\appendixsec{\parsearg\appendixsecyyy} -\def\appendixsecyyy #1{\apphead1{#1}} % normally calls appendixsectionzzz -\def\appendixsectionzzz #1{% -\subsecno=0 \subsubsecno=0 \global\advance \secno by 1 % -\gdef\thissection{#1}\secheading {#1}{\appendixletter}{\the\secno}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash secentry{\the\toks0}% - {\appendixletter}{\the\secno}}}% -\temp -\appendixnoderef -\nobreak -} - -\outer\def\unnumberedsec{\parsearg\unnumberedsecyyy} -\def\unnumberedsecyyy #1{\unnmhead1{#1}} % normally calls unnumberedseczzz -\def\unnumberedseczzz #1{% -\plainsecheading {#1}\gdef\thissection{#1}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash unnumbsecentry{\the\toks0}}}% -\temp -\unnumbnoderef -\nobreak -} - -% Subsections. -\outer\def\numberedsubsec{\parsearg\numberedsubsecyyy} -\def\numberedsubsecyyy #1{\numhead2{#1}} % normally calls numberedsubseczzz -\def\numberedsubseczzz #1{% -\gdef\thissection{#1}\subsubsecno=0 \global\advance \subsecno by 1 % -\subsecheading {#1}{\the\chapno}{\the\secno}{\the\subsecno}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash subsecentry{\the\toks0}% - {\the\chapno}{\the\secno}{\the\subsecno}}}% -\temp -\donoderef -\nobreak -} - -\outer\def\appendixsubsec{\parsearg\appendixsubsecyyy} -\def\appendixsubsecyyy #1{\apphead2{#1}} % normally calls appendixsubseczzz -\def\appendixsubseczzz #1{% -\gdef\thissection{#1}\subsubsecno=0 \global\advance \subsecno by 1 % -\subsecheading {#1}{\appendixletter}{\the\secno}{\the\subsecno}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash subsecentry{\the\toks0}% - {\appendixletter}{\the\secno}{\the\subsecno}}}% -\temp -\appendixnoderef -\nobreak -} - -\outer\def\unnumberedsubsec{\parsearg\unnumberedsubsecyyy} -\def\unnumberedsubsecyyy #1{\unnmhead2{#1}} %normally calls unnumberedsubseczzz -\def\unnumberedsubseczzz #1{% -\plainsubsecheading {#1}\gdef\thissection{#1}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash unnumbsubsecentry% - {\the\toks0}}}% -\temp -\unnumbnoderef -\nobreak -} - -% Subsubsections. -\outer\def\numberedsubsubsec{\parsearg\numberedsubsubsecyyy} -\def\numberedsubsubsecyyy #1{\numhead3{#1}} % normally numberedsubsubseczzz -\def\numberedsubsubseczzz #1{% -\gdef\thissection{#1}\global\advance \subsubsecno by 1 % -\subsubsecheading {#1} - {\the\chapno}{\the\secno}{\the\subsecno}{\the\subsubsecno}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash subsubsecentry{\the\toks0}% - {\the\chapno}{\the\secno}{\the\subsecno}{\the\subsubsecno}}}% -\temp -\donoderef -\nobreak -} - -\outer\def\appendixsubsubsec{\parsearg\appendixsubsubsecyyy} -\def\appendixsubsubsecyyy #1{\apphead3{#1}} % normally appendixsubsubseczzz -\def\appendixsubsubseczzz #1{% -\gdef\thissection{#1}\global\advance \subsubsecno by 1 % -\subsubsecheading {#1} - {\appendixletter}{\the\secno}{\the\subsecno}{\the\subsubsecno}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash subsubsecentry{\the\toks0}% - {\appendixletter}{\the\secno}{\the\subsecno}{\the\subsubsecno}}}% -\temp -\appendixnoderef -\nobreak -} - -\outer\def\unnumberedsubsubsec{\parsearg\unnumberedsubsubsecyyy} -\def\unnumberedsubsubsecyyy #1{\unnmhead3{#1}} %normally unnumberedsubsubseczzz -\def\unnumberedsubsubseczzz #1{% -\plainsubsubsecheading {#1}\gdef\thissection{#1}% -\toks0 = {#1}% -\edef\temp{\noexpand\writetocentry{\realbackslash unnumbsubsubsecentry% - {\the\toks0}}}% -\temp -\unnumbnoderef -\nobreak -} - -% These are variants which are not "outer", so they can appear in @ifinfo. -% Actually, they should now be obsolete; ordinary section commands should work. -\def\infotop{\parsearg\unnumberedzzz} -\def\infounnumbered{\parsearg\unnumberedzzz} -\def\infounnumberedsec{\parsearg\unnumberedseczzz} -\def\infounnumberedsubsec{\parsearg\unnumberedsubseczzz} -\def\infounnumberedsubsubsec{\parsearg\unnumberedsubsubseczzz} - -\def\infoappendix{\parsearg\appendixzzz} -\def\infoappendixsec{\parsearg\appendixseczzz} -\def\infoappendixsubsec{\parsearg\appendixsubseczzz} -\def\infoappendixsubsubsec{\parsearg\appendixsubsubseczzz} - -\def\infochapter{\parsearg\chapterzzz} -\def\infosection{\parsearg\sectionzzz} -\def\infosubsection{\parsearg\subsectionzzz} -\def\infosubsubsection{\parsearg\subsubsectionzzz} - -% These macros control what the section commands do, according -% to what kind of chapter we are in (ordinary, appendix, or unnumbered). -% Define them by default for a numbered chapter. -\global\let\section = \numberedsec -\global\let\subsection = \numberedsubsec -\global\let\subsubsection = \numberedsubsubsec - -% Define @majorheading, @heading and @subheading - -% NOTE on use of \vbox for chapter headings, section headings, and such: -% 1) We use \vbox rather than the earlier \line to permit -% overlong headings to fold. -% 2) \hyphenpenalty is set to 10000 because hyphenation in a -% heading is obnoxious; this forbids it. -% 3) Likewise, headings look best if no \parindent is used, and -% if justification is not attempted. Hence \raggedright. - - -\def\majorheading{\parsearg\majorheadingzzz} -\def\majorheadingzzz #1{% -{\advance\chapheadingskip by 10pt \chapbreak }% -{\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 - \parindent=0pt\raggedright - \rm #1\hfill}}\bigskip \par\penalty 200} - -\def\chapheading{\parsearg\chapheadingzzz} -\def\chapheadingzzz #1{\chapbreak % -{\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 - \parindent=0pt\raggedright - \rm #1\hfill}}\bigskip \par\penalty 200} - -% @heading, @subheading, @subsubheading. -\def\heading{\parsearg\plainsecheading} -\def\subheading{\parsearg\plainsubsecheading} -\def\subsubheading{\parsearg\plainsubsubsecheading} - -% These macros generate a chapter, section, etc. heading only -% (including whitespace, linebreaking, etc. around it), -% given all the information in convenient, parsed form. - -%%% Args are the skip and penalty (usually negative) -\def\dobreak#1#2{\par\ifdim\lastskip<#1\removelastskip\penalty#2\vskip#1\fi} - -\def\setchapterstyle #1 {\csname CHAPF#1\endcsname} - -%%% Define plain chapter starts, and page on/off switching for it -% Parameter controlling skip before chapter headings (if needed) - -\newskip\chapheadingskip - -\def\chapbreak{\dobreak \chapheadingskip {-4000}} -\def\chappager{\par\vfill\supereject} -\def\chapoddpage{\chappager \ifodd\pageno \else \hbox to 0pt{} \chappager\fi} - -\def\setchapternewpage #1 {\csname CHAPPAG#1\endcsname} - -\def\CHAPPAGoff{% -\global\let\contentsalignmacro = \chappager -\global\let\pchapsepmacro=\chapbreak -\global\let\pagealignmacro=\chappager} - -\def\CHAPPAGon{% -\global\let\contentsalignmacro = \chappager -\global\let\pchapsepmacro=\chappager -\global\let\pagealignmacro=\chappager -\global\def\HEADINGSon{\HEADINGSsingle}} - -\def\CHAPPAGodd{ -\global\let\contentsalignmacro = \chapoddpage -\global\let\pchapsepmacro=\chapoddpage -\global\let\pagealignmacro=\chapoddpage -\global\def\HEADINGSon{\HEADINGSdouble}} - -\CHAPPAGon - -\def\CHAPFplain{ -\global\let\chapmacro=\chfplain -\global\let\unnumbchapmacro=\unnchfplain -\global\let\centerchapmacro=\centerchfplain} - -% Plain chapter opening. -% #1 is the text, #2 the chapter number or empty if unnumbered. -\def\chfplain#1#2{% - \pchapsepmacro - {% - \chapfonts \rm - \def\chapnum{#2}% - \setbox0 = \hbox{#2\ifx\chapnum\empty\else\enspace\fi}% - \vbox{\hyphenpenalty=10000 \tolerance=5000 \parindent=0pt \raggedright - \hangindent = \wd0 \centerparametersmaybe - \unhbox0 #1\par}% - }% - \nobreak\bigskip % no page break after a chapter title - \nobreak -} - -% Plain opening for unnumbered. -\def\unnchfplain#1{\chfplain{#1}{}} - -% @centerchap -- centered and unnumbered. -\let\centerparametersmaybe = \relax -\def\centerchfplain#1{{% - \def\centerparametersmaybe{% - \advance\rightskip by 3\rightskip - \leftskip = \rightskip - \parfillskip = 0pt - }% - \chfplain{#1}{}% -}} - -\CHAPFplain % The default - -\def\unnchfopen #1{% -\chapoddpage {\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 - \parindent=0pt\raggedright - \rm #1\hfill}}\bigskip \par\nobreak -} - -\def\chfopen #1#2{\chapoddpage {\chapfonts -\vbox to 3in{\vfil \hbox to\hsize{\hfil #2} \hbox to\hsize{\hfil #1} \vfil}}% -\par\penalty 5000 % -} - -\def\centerchfopen #1{% -\chapoddpage {\chapfonts \vbox{\hyphenpenalty=10000\tolerance=5000 - \parindent=0pt - \hfill {\rm #1}\hfill}}\bigskip \par\nobreak -} - -\def\CHAPFopen{ -\global\let\chapmacro=\chfopen -\global\let\unnumbchapmacro=\unnchfopen -\global\let\centerchapmacro=\centerchfopen} - - -% Section titles. -\newskip\secheadingskip -\def\secheadingbreak{\dobreak \secheadingskip {-1000}} -\def\secheading#1#2#3{\sectionheading{sec}{#2.#3}{#1}} -\def\plainsecheading#1{\sectionheading{sec}{}{#1}} - -% Subsection titles. -\newskip \subsecheadingskip -\def\subsecheadingbreak{\dobreak \subsecheadingskip {-500}} -\def\subsecheading#1#2#3#4{\sectionheading{subsec}{#2.#3.#4}{#1}} -\def\plainsubsecheading#1{\sectionheading{subsec}{}{#1}} - -% Subsubsection titles. -\let\subsubsecheadingskip = \subsecheadingskip -\let\subsubsecheadingbreak = \subsecheadingbreak -\def\subsubsecheading#1#2#3#4#5{\sectionheading{subsubsec}{#2.#3.#4.#5}{#1}} -\def\plainsubsubsecheading#1{\sectionheading{subsubsec}{}{#1}} - - -% Print any size section title. -% -% #1 is the section type (sec/subsec/subsubsec), #2 is the section -% number (maybe empty), #3 the text. -\def\sectionheading#1#2#3{% - {% - \expandafter\advance\csname #1headingskip\endcsname by \parskip - \csname #1headingbreak\endcsname - }% - {% - % Switch to the right set of fonts. - \csname #1fonts\endcsname \rm - % - % Only insert the separating space if we have a section number. - \def\secnum{#2}% - \setbox0 = \hbox{#2\ifx\secnum\empty\else\enspace\fi}% - % - \vbox{\hyphenpenalty=10000 \tolerance=5000 \parindent=0pt \raggedright - \hangindent = \wd0 % zero if no section number - \unhbox0 #3}% - }% - \ifdim\parskip<10pt \nobreak\kern10pt\nobreak\kern-\parskip\fi \nobreak -} - - -\message{toc,} -% Table of contents. -\newwrite\tocfile - -% Write an entry to the toc file, opening it if necessary. -% Called from @chapter, etc. We supply {\folio} at the end of the -% argument, which will end up as the last argument to the \...entry macro. -% -% We open the .toc file here instead of at @setfilename or any other -% given time so that @contents can be put in the document anywhere. -% -\newif\iftocfileopened -\def\writetocentry#1{% - \iftocfileopened\else - \immediate\openout\tocfile = \jobname.toc - \global\tocfileopenedtrue - \fi - \iflinks \write\tocfile{#1{\folio}}\fi -} - -\newskip\contentsrightmargin \contentsrightmargin=1in -\newcount\savepageno -\newcount\lastnegativepageno \lastnegativepageno = -1 - -% Finish up the main text and prepare to read what we've written -% to \tocfile. -% -\def\startcontents#1{% - % If @setchapternewpage on, and @headings double, the contents should - % start on an odd page, unlike chapters. Thus, we maintain - % \contentsalignmacro in parallel with \pagealignmacro. - % From: Torbjorn Granlund - \contentsalignmacro - \immediate\closeout\tocfile - % - % Don't need to put `Contents' or `Short Contents' in the headline. - % It is abundantly clear what they are. - \unnumbchapmacro{#1}\def\thischapter{}% - \savepageno = \pageno - \begingroup % Set up to handle contents files properly. - \catcode`\\=0 \catcode`\{=1 \catcode`\}=2 \catcode`\@=11 - % We can't do this, because then an actual ^ in a section - % title fails, e.g., @chapter ^ -- exponentiation. --karl, 9jul97. - %\catcode`\^=7 % to see ^^e4 as \"a etc. juha@piuha.ydi.vtt.fi - \raggedbottom % Worry more about breakpoints than the bottom. - \advance\hsize by -\contentsrightmargin % Don't use the full line length. - % - % Roman numerals for page numbers. - \ifnum \pageno>0 \pageno = \lastnegativepageno \fi -} - - -% Normal (long) toc. -\def\contents{% - \startcontents{\putwordTOC}% - \openin 1 \jobname.toc - \ifeof 1 \else - \closein 1 - \input \jobname.toc - \fi - \vfill \eject - \contentsalignmacro % in case @setchapternewpage odd is in effect - \pdfmakeoutlines - \endgroup - \lastnegativepageno = \pageno - \pageno = \savepageno -} - -% And just the chapters. -\def\summarycontents{% - \startcontents{\putwordShortTOC}% - % - \let\chapentry = \shortchapentry - \let\unnumbchapentry = \shortunnumberedentry - % We want a true roman here for the page numbers. - \secfonts - \let\rm=\shortcontrm \let\bf=\shortcontbf \let\sl=\shortcontsl - \rm - \hyphenpenalty = 10000 - \advance\baselineskip by 1pt % Open it up a little. - \def\secentry ##1##2##3##4{} - \def\unnumbsecentry ##1##2{} - \def\subsecentry ##1##2##3##4##5{} - \def\unnumbsubsecentry ##1##2{} - \def\subsubsecentry ##1##2##3##4##5##6{} - \def\unnumbsubsubsecentry ##1##2{} - \openin 1 \jobname.toc - \ifeof 1 \else - \closein 1 - \input \jobname.toc - \fi - \vfill \eject - \contentsalignmacro % in case @setchapternewpage odd is in effect - \endgroup - \lastnegativepageno = \pageno - \pageno = \savepageno -} -\let\shortcontents = \summarycontents - -\ifpdf - \pdfcatalog{/PageMode /UseOutlines}% -\fi - -% These macros generate individual entries in the table of contents. -% The first argument is the chapter or section name. -% The last argument is the page number. -% The arguments in between are the chapter number, section number, ... - -% Chapter-level things, for both the long and short contents. -\def\chapentry#1#2#3{\dochapentry{#2\labelspace#1}{#3}} - -% See comments in \dochapentry re vbox and related settings -\def\shortchapentry#1#2#3{% - \tocentry{\shortchaplabel{#2}\labelspace #1}{\doshortpageno\bgroup#3\egroup}% -} - -% Typeset the label for a chapter or appendix for the short contents. -% The arg is, e.g. `Appendix A' for an appendix, or `3' for a chapter. -% We could simplify the code here by writing out an \appendixentry -% command in the toc file for appendices, instead of using \chapentry -% for both, but it doesn't seem worth it. -% -\newdimen\shortappendixwidth -% -\def\shortchaplabel#1{% - % Compute width of word "Appendix", may change with language. - \setbox0 = \hbox{\shortcontrm \putwordAppendix}% - \shortappendixwidth = \wd0 - % - % We typeset #1 in a box of constant width, regardless of the text of - % #1, so the chapter titles will come out aligned. - \setbox0 = \hbox{#1}% - \dimen0 = \ifdim\wd0 > \shortappendixwidth \shortappendixwidth \else 0pt \fi - % - % This space should be plenty, since a single number is .5em, and the - % widest letter (M) is 1em, at least in the Computer Modern fonts. - % (This space doesn't include the extra space that gets added after - % the label; that gets put in by \shortchapentry above.) - \advance\dimen0 by 1.1em - \hbox to \dimen0{#1\hfil}% -} - -\def\unnumbchapentry#1#2{\dochapentry{#1}{#2}} -\def\shortunnumberedentry#1#2{\tocentry{#1}{\doshortpageno\bgroup#2\egroup}} - -% Sections. -\def\secentry#1#2#3#4{\dosecentry{#2.#3\labelspace#1}{#4}} -\def\unnumbsecentry#1#2{\dosecentry{#1}{#2}} - -% Subsections. -\def\subsecentry#1#2#3#4#5{\dosubsecentry{#2.#3.#4\labelspace#1}{#5}} -\def\unnumbsubsecentry#1#2{\dosubsecentry{#1}{#2}} - -% And subsubsections. -\def\subsubsecentry#1#2#3#4#5#6{% - \dosubsubsecentry{#2.#3.#4.#5\labelspace#1}{#6}} -\def\unnumbsubsubsecentry#1#2{\dosubsubsecentry{#1}{#2}} - -% This parameter controls the indentation of the various levels. -\newdimen\tocindent \tocindent = 3pc - -% Now for the actual typesetting. In all these, #1 is the text and #2 is the -% page number. -% -% If the toc has to be broken over pages, we want it to be at chapters -% if at all possible; hence the \penalty. -\def\dochapentry#1#2{% - \penalty-300 \vskip1\baselineskip plus.33\baselineskip minus.25\baselineskip - \begingroup - \chapentryfonts - \tocentry{#1}{\dopageno\bgroup#2\egroup}% - \endgroup - \nobreak\vskip .25\baselineskip plus.1\baselineskip -} - -\def\dosecentry#1#2{\begingroup - \secentryfonts \leftskip=\tocindent - \tocentry{#1}{\dopageno\bgroup#2\egroup}% -\endgroup} - -\def\dosubsecentry#1#2{\begingroup - \subsecentryfonts \leftskip=2\tocindent - \tocentry{#1}{\dopageno\bgroup#2\egroup}% -\endgroup} - -\def\dosubsubsecentry#1#2{\begingroup - \subsubsecentryfonts \leftskip=3\tocindent - \tocentry{#1}{\dopageno\bgroup#2\egroup}% -\endgroup} - -% Final typesetting of a toc entry; we use the same \entry macro as for -% the index entries, but we want to suppress hyphenation here. (We -% can't do that in the \entry macro, since index entries might consist -% of hyphenated-identifiers-that-do-not-fit-on-a-line-and-nothing-else.) -\def\tocentry#1#2{\begingroup - \vskip 0pt plus1pt % allow a little stretch for the sake of nice page breaks - % Do not use \turnoffactive in these arguments. Since the toc is - % typeset in cmr, so characters such as _ would come out wrong; we - % have to do the usual translation tricks. - \entry{#1}{#2}% -\endgroup} - -% Space between chapter (or whatever) number and the title. -\def\labelspace{\hskip1em \relax} - -\def\dopageno#1{{\rm #1}} -\def\doshortpageno#1{{\rm #1}} - -\def\chapentryfonts{\secfonts \rm} -\def\secentryfonts{\textfonts} -\let\subsecentryfonts = \textfonts -\let\subsubsecentryfonts = \textfonts - - -\message{environments,} -% @foo ... @end foo. - -% Since these characters are used in examples, it should be an even number of -% \tt widths. Each \tt character is 1en, so two makes it 1em. -% Furthermore, these definitions must come after we define our fonts. -\newbox\dblarrowbox \newbox\longdblarrowbox -\newbox\pushcharbox \newbox\bullbox -\newbox\equivbox \newbox\errorbox - -%{\tentt -%\global\setbox\dblarrowbox = \hbox to 1em{\hfil$\Rightarrow$\hfil} -%\global\setbox\longdblarrowbox = \hbox to 1em{\hfil$\mapsto$\hfil} -%\global\setbox\pushcharbox = \hbox to 1em{\hfil$\dashv$\hfil} -%\global\setbox\equivbox = \hbox to 1em{\hfil$\ptexequiv$\hfil} -% Adapted from the manmac format (p.420 of TeXbook) -%\global\setbox\bullbox = \hbox to 1em{\kern.15em\vrule height .75ex width .85ex -% depth .1ex\hfil} -%} - -% @point{}, @result{}, @expansion{}, @print{}, @equiv{}. -\def\point{$\star$} -\def\result{\leavevmode\raise.15ex\hbox to 1em{\hfil$\Rightarrow$\hfil}} -\def\expansion{\leavevmode\raise.1ex\hbox to 1em{\hfil$\mapsto$\hfil}} -\def\print{\leavevmode\lower.1ex\hbox to 1em{\hfil$\dashv$\hfil}} -\def\equiv{\leavevmode\lower.1ex\hbox to 1em{\hfil$\ptexequiv$\hfil}} - -% Adapted from the TeXbook's \boxit. -{\tentt \global\dimen0 = 3em}% Width of the box. -\dimen2 = .55pt % Thickness of rules -% The text. (`r' is open on the right, `e' somewhat less so on the left.) -\setbox0 = \hbox{\kern-.75pt \tensf error\kern-1.5pt} - -\global\setbox\errorbox=\hbox to \dimen0{\hfil - \hsize = \dimen0 \advance\hsize by -5.8pt % Space to left+right. - \advance\hsize by -2\dimen2 % Rules. - \vbox{ - \hrule height\dimen2 - \hbox{\vrule width\dimen2 \kern3pt % Space to left of text. - \vtop{\kern2.4pt \box0 \kern2.4pt}% Space above/below. - \kern3pt\vrule width\dimen2}% Space to right. - \hrule height\dimen2} - \hfil} - -% The @error{} command. -\def\error{\leavevmode\lower.7ex\copy\errorbox} - -% @tex ... @end tex escapes into raw Tex temporarily. -% One exception: @ is still an escape character, so that @end tex works. -% But \@ or @@ will get a plain tex @ character. - -\def\tex{\begingroup - \catcode `\\=0 \catcode `\{=1 \catcode `\}=2 - \catcode `\$=3 \catcode `\&=4 \catcode `\#=6 - \catcode `\^=7 \catcode `\_=8 \catcode `\~=13 \let~=\tie - \catcode `\%=14 - \catcode 43=12 % plus - \catcode`\"=12 - \catcode`\==12 - \catcode`\|=12 - \catcode`\<=12 - \catcode`\>=12 - \escapechar=`\\ - % - \let\b=\ptexb - \let\bullet=\ptexbullet - \let\c=\ptexc - \let\,=\ptexcomma - \let\.=\ptexdot - \let\dots=\ptexdots - \let\equiv=\ptexequiv - \let\!=\ptexexclam - \let\i=\ptexi - \let\{=\ptexlbrace - \let\+=\tabalign - \let\}=\ptexrbrace - \let\*=\ptexstar - \let\t=\ptext - % - \def\endldots{\mathinner{\ldots\ldots\ldots\ldots}}% - \def\enddots{\relax\ifmmode\endldots\else$\mathsurround=0pt \endldots\,$\fi}% - \def\@{@}% -\let\Etex=\endgroup} - -% Define @lisp ... @endlisp. -% @lisp does a \begingroup so it can rebind things, -% including the definition of @endlisp (which normally is erroneous). - -% Amount to narrow the margins by for @lisp. -\newskip\lispnarrowing \lispnarrowing=0.4in - -% This is the definition that ^^M gets inside @lisp, @example, and other -% such environments. \null is better than a space, since it doesn't -% have any width. -\def\lisppar{\null\endgraf} - -% Make each space character in the input produce a normal interword -% space in the output. Don't allow a line break at this space, as this -% is used only in environments like @example, where each line of input -% should produce a line of output anyway. -% -{\obeyspaces % -\gdef\sepspaces{\obeyspaces\let =\tie}} - -% Define \obeyedspace to be our active space, whatever it is. This is -% for use in \parsearg. -{\sepspaces% -\global\let\obeyedspace= } - -% This space is always present above and below environments. -\newskip\envskipamount \envskipamount = 0pt - -% Make spacing and below environment symmetrical. We use \parskip here -% to help in doing that, since in @example-like environments \parskip -% is reset to zero; thus the \afterenvbreak inserts no space -- but the -% start of the next paragraph will insert \parskip -% -\def\aboveenvbreak{{\advance\envskipamount by \parskip -\endgraf \ifdim\lastskip<\envskipamount -\removelastskip \penalty-50 \vskip\envskipamount \fi}} - -\let\afterenvbreak = \aboveenvbreak - -% \nonarrowing is a flag. If "set", @lisp etc don't narrow margins. -\let\nonarrowing=\relax - -% @cartouche ... @end cartouche: draw rectangle w/rounded corners around -% environment contents. -\font\circle=lcircle10 -\newdimen\circthick -\newdimen\cartouter\newdimen\cartinner -\newskip\normbskip\newskip\normpskip\newskip\normlskip -\circthick=\fontdimen8\circle -% -\def\ctl{{\circle\char'013\hskip -6pt}}% 6pt from pl file: 1/2charwidth -\def\ctr{{\hskip 6pt\circle\char'010}} -\def\cbl{{\circle\char'012\hskip -6pt}} -\def\cbr{{\hskip 6pt\circle\char'011}} -\def\carttop{\hbox to \cartouter{\hskip\lskip - \ctl\leaders\hrule height\circthick\hfil\ctr - \hskip\rskip}} -\def\cartbot{\hbox to \cartouter{\hskip\lskip - \cbl\leaders\hrule height\circthick\hfil\cbr - \hskip\rskip}} -% -\newskip\lskip\newskip\rskip - -\long\def\cartouche{% -\begingroup - \lskip=\leftskip \rskip=\rightskip - \leftskip=0pt\rightskip=0pt %we want these *outside*. - \cartinner=\hsize \advance\cartinner by-\lskip - \advance\cartinner by-\rskip - \cartouter=\hsize - \advance\cartouter by 18.4pt % allow for 3pt kerns on either -% side, and for 6pt waste from -% each corner char, and rule thickness - \normbskip=\baselineskip \normpskip=\parskip \normlskip=\lineskip - % Flag to tell @lisp, etc., not to narrow margin. - \let\nonarrowing=\comment - \vbox\bgroup - \baselineskip=0pt\parskip=0pt\lineskip=0pt - \carttop - \hbox\bgroup - \hskip\lskip - \vrule\kern3pt - \vbox\bgroup - \hsize=\cartinner - \kern3pt - \begingroup - \baselineskip=\normbskip - \lineskip=\normlskip - \parskip=\normpskip - \vskip -\parskip -\def\Ecartouche{% - \endgroup - \kern3pt - \egroup - \kern3pt\vrule - \hskip\rskip - \egroup - \cartbot - \egroup -\endgroup -}} - - -% This macro is called at the beginning of all the @example variants, -% inside a group. -\def\nonfillstart{% - \aboveenvbreak - \inENV % This group ends at the end of the body - \hfuzz = 12pt % Don't be fussy - \sepspaces % Make spaces be word-separators rather than space tokens. - \singlespace - \let\par = \lisppar % don't ignore blank lines - \obeylines % each line of input is a line of output - \parskip = 0pt - \parindent = 0pt - \emergencystretch = 0pt % don't try to avoid overfull boxes - % @cartouche defines \nonarrowing to inhibit narrowing - % at next level down. - \ifx\nonarrowing\relax - \advance \leftskip by \lispnarrowing - \exdentamount=\lispnarrowing - \let\exdent=\nofillexdent - \let\nonarrowing=\relax - \fi -} - -% Define the \E... control sequence only if we are inside the particular -% environment, so the error checking in \end will work. -% -% To end an @example-like environment, we first end the paragraph (via -% \afterenvbreak's vertical glue), and then the group. That way we keep -% the zero \parskip that the environments set -- \parskip glue will be -% inserted at the beginning of the next paragraph in the document, after -% the environment. -% -\def\nonfillfinish{\afterenvbreak\endgroup} - -% @lisp: indented, narrowed, typewriter font. -\def\lisp{\begingroup - \nonfillstart - \let\Elisp = \nonfillfinish - \tt - \let\kbdfont = \kbdexamplefont % Allow @kbd to do something special. - \gobble % eat return -} - -% @example: Same as @lisp. -\def\example{\begingroup \def\Eexample{\nonfillfinish\endgroup}\lisp} - -% @small... is usually equivalent to the non-small (@smallbook -% redefines). We must call \example (or whatever) last in the -% definition, since it reads the return following the @example (or -% whatever) command. -% -% This actually allows (for example) @end display inside an -% @smalldisplay. Too bad, but makeinfo will catch the error anyway. -% -\def\smalldisplay{\begingroup\def\Esmalldisplay{\nonfillfinish\endgroup}\display} -\def\smallexample{\begingroup\def\Esmallexample{\nonfillfinish\endgroup}\lisp} -\def\smallformat{\begingroup\def\Esmallformat{\nonfillfinish\endgroup}\format} -\def\smalllisp{\begingroup\def\Esmalllisp{\nonfillfinish\endgroup}\lisp} - -% Real @smallexample and @smalllisp (when @smallbook): use smaller fonts. -% Originally contributed by Pavel@xerox. -\def\smalllispx{\begingroup - \def\Esmalllisp{\nonfillfinish\endgroup}% - \def\Esmallexample{\nonfillfinish\endgroup}% - \smallfonts - \lisp -} - -% @display: same as @lisp except keep current font. -% -\def\display{\begingroup - \nonfillstart - \let\Edisplay = \nonfillfinish - \gobble -} - -% @smalldisplay (when @smallbook): @display plus smaller fonts. -% -\def\smalldisplayx{\begingroup - \def\Esmalldisplay{\nonfillfinish\endgroup}% - \smallfonts \rm - \display -} - -% @format: same as @display except don't narrow margins. -% -\def\format{\begingroup - \let\nonarrowing = t - \nonfillstart - \let\Eformat = \nonfillfinish - \gobble -} - -% @smallformat (when @smallbook): @format plus smaller fonts. -% -\def\smallformatx{\begingroup - \def\Esmallformat{\nonfillfinish\endgroup}% - \smallfonts \rm - \format -} - -% @flushleft (same as @format). -% -\def\flushleft{\begingroup \def\Eflushleft{\nonfillfinish\endgroup}\format} - -% @flushright. -% -\def\flushright{\begingroup - \let\nonarrowing = t - \nonfillstart - \let\Eflushright = \nonfillfinish - \advance\leftskip by 0pt plus 1fill - \gobble -} - - -% @quotation does normal linebreaking (hence we can't use \nonfillstart) -% and narrows the margins. -% -\def\quotation{% - \begingroup\inENV %This group ends at the end of the @quotation body - {\parskip=0pt \aboveenvbreak}% because \aboveenvbreak inserts \parskip - \singlespace - \parindent=0pt - % We have retained a nonzero parskip for the environment, since we're - % doing normal filling. So to avoid extra space below the environment... - \def\Equotation{\parskip = 0pt \nonfillfinish}% - % - % @cartouche defines \nonarrowing to inhibit narrowing at next level down. - \ifx\nonarrowing\relax - \advance\leftskip by \lispnarrowing - \advance\rightskip by \lispnarrowing - \exdentamount = \lispnarrowing - \let\nonarrowing = \relax - \fi -} - - -% LaTeX-like @verbatim...@end verbatim and @verb{...} -% If we want to allow any as delimiter, -% we need the curly braces so that makeinfo sees the @verb command, eg: -% `@verbx...x' would look like the '@verbx' command. --janneke@gnu.org -% -% [Knuth]: Donald Ervin Knuth, 1996. The TeXbook. -% -% [Knuth] p. 344; only we need to do '@' too -\def\dospecials{% - \do\ \do\\\do\@\do\{\do\}\do\$\do\&% - \do\#\do\^\do\^^K\do\_\do\^^A\do\%\do\~} -% -% [Knuth] p. 380 -\def\uncatcodespecials{% - \def\do##1{\catcode`##1=12}\dospecials} -% -% [Knuth] pp. 380,381,391 -% Disable Spanish ligatures ?` and !` of \tt font -\begingroup - \catcode`\`=\active\gdef`{\relax\lq} -\endgroup -% -% Setup for the @verb command. -% -% Eight spaces for a tab -\begingroup - \catcode`\^^I=\active - \gdef\tabeightspaces{\catcode`\^^I=\active\def^^I{\ \ \ \ \ \ \ \ }} -\endgroup -% -\def\setupverb{% - \tt % easiest (and conventionally used) font for verbatim - \def\par{\leavevmode\endgraf}% - \catcode`\`=\active - \tabeightspaces - % Respect line breaks, - % print special symbols as themselves, and - % make each space count - % must do in this order: - \obeylines \uncatcodespecials \sepspaces -} - -% Setup for the @verbatim environment -% -% Real tab expansion -\newdimen\tabw \setbox0=\hbox{\tt\space} \tabw=8\wd0 % tab amount -% -\def\starttabbox{\setbox0=\hbox\bgroup} -\begingroup - \catcode`\^^I=\active - \gdef\tabexpand{% - \catcode`\^^I=\active - \def^^I{\leavevmode\egroup - \dimen0=\wd0 % the width so far, or since the previous tab - \divide\dimen0 by\tabw - \multiply\dimen0 by\tabw % compute previous multiple of \tabw - \advance\dimen0 by\tabw % advance to next multiple of \tabw - \wd0=\dimen0 \box0 \starttabbox - }% - } -\endgroup -\def\setupverbatim{% - % Easiest (and conventionally used) font for verbatim - \tt - \def\par{\leavevmode\egroup\box0\endgraf}% - \catcode`\`=\active - \tabexpand - % Respect line breaks, - % print special symbols as themselves, and - % make each space count - % must do in this order: - \obeylines \uncatcodespecials \sepspaces - \everypar{\starttabbox}% -} - -% Do the @verb magic: verbatim text is quoted by unique -% delimiter characters. Before first delimiter expect a -% right brace, after last delimiter expect closing brace: -% -% \def\doverb'{'#1'}'{#1} -% -% [Knuth] p. 382; only eat outer {} -\begingroup - \catcode`[=1\catcode`]=2\catcode`\{=12\catcode`\}=12 - \gdef\doverb{#1[\def\next##1#1}[##1\endgroup]\next] -\endgroup -% -\def\verb{\begingroup\setupverb\doverb} -% -% -% Do the @verbatim magic: define the macro \doverbatim so that -% the (first) argument ends when '@end verbatim' is reached, ie: -% -% \def\doverbatim#1@end verbatim{#1} -% -% For Texinfo it's a lot easier than for LaTeX, -% because texinfo's \verbatim doesn't stop at '\end{verbatim}': -% we need not redefine '\', '{' and '}' -% -% Inspired by LaTeX's verbatim command set [latex.ltx] -%% Include LaTeX hack for completeness -- never know -%% \begingroup -%% \catcode`|=0 \catcode`[=1 -%% \catcode`]=2\catcode`\{=12\catcode`\}=12\catcode`\ =\active -%% \catcode`\\=12|gdef|doverbatim#1@end verbatim[ -%% #1|endgroup|def|Everbatim[]|end[verbatim]] -%% |endgroup -\begingroup - \catcode`\ =\active - \gdef\doverbatim#1@end verbatim{#1\end{verbatim}} -\endgroup -% -\def\verbatim{% - \def\Everbatim{\nonfillfinish\endgroup}% - \begingroup - \nonfillstart - \advance\leftskip by -\defbodyindent - \begingroup\setupverbatim\doverbatim -} - -% @verbatiminclude FILE - insert text of file in verbatim environment. -% -% Allow normal characters that we make active in the argument (a file name). -\def\verbatiminclude{% - \begingroup - \catcode`\\=12 - \catcode`~=12 - \catcode`^=12 - \catcode`_=12 - \catcode`|=12 - \catcode`<=12 - \catcode`>=12 - \catcode`+=12 - \parsearg\doverbatiminclude -} -\def\setupverbatiminclude{% - \begingroup - \nonfillstart - \advance\leftskip by -\defbodyindent - \begingroup\setupverbatim -} -% -\def\doverbatiminclude#1{% - % Restore active chars for included file. - \endgroup - \begingroup - \def\thisfile{#1}% - \expandafter\expandafter\setupverbatiminclude\input\thisfile - \endgroup\nonfillfinish\endgroup -} - - -\message{defuns,} -% @defun etc. - -% Allow user to change definition object font (\df) internally -\def\setdeffont #1 {\csname DEF#1\endcsname} - -\newskip\defbodyindent \defbodyindent=.4in -\newskip\defargsindent \defargsindent=50pt -\newskip\deftypemargin \deftypemargin=12pt -\newskip\deflastargmargin \deflastargmargin=18pt - -\newcount\parencount -% define \functionparens, which makes ( and ) and & do special things. -% \functionparens affects the group it is contained in. -\def\activeparens{% -\catcode`\(=\active \catcode`\)=\active \catcode`\&=\active -\catcode`\[=\active \catcode`\]=\active} - -% Make control sequences which act like normal parenthesis chars. -\let\lparen = ( \let\rparen = ) - -{\activeparens % Now, smart parens don't turn on until &foo (see \amprm) - -% Be sure that we always have a definition for `(', etc. For example, -% if the fn name has parens in it, \boldbrax will not be in effect yet, -% so TeX would otherwise complain about undefined control sequence. -\global\let(=\lparen \global\let)=\rparen -\global\let[=\lbrack \global\let]=\rbrack - -\gdef\functionparens{\boldbrax\let&=\amprm\parencount=0 } -\gdef\boldbrax{\let(=\opnr\let)=\clnr\let[=\lbrb\let]=\rbrb} -% This is used to turn on special parens -% but make & act ordinary (given that it's active). -\gdef\boldbraxnoamp{\let(=\opnr\let)=\clnr\let[=\lbrb\let]=\rbrb\let&=\ampnr} - -% Definitions of (, ) and & used in args for functions. -% This is the definition of ( outside of all parentheses. -\gdef\oprm#1 {{\rm\char`\(}#1 \bf \let(=\opnested - \global\advance\parencount by 1 -} -% -% This is the definition of ( when already inside a level of parens. -\gdef\opnested{\char`\(\global\advance\parencount by 1 } -% -\gdef\clrm{% Print a paren in roman if it is taking us back to depth of 0. - % also in that case restore the outer-level definition of (. - \ifnum \parencount=1 {\rm \char `\)}\sl \let(=\oprm \else \char `\) \fi - \global\advance \parencount by -1 } -% If we encounter &foo, then turn on ()-hacking afterwards -\gdef\amprm#1 {{\rm\}\let(=\oprm \let)=\clrm\ } -% -\gdef\normalparens{\boldbrax\let&=\ampnr} -} % End of definition inside \activeparens -%% These parens (in \boldbrax) actually are a little bolder than the -%% contained text. This is especially needed for [ and ] -\def\opnr{{\sf\char`\(}\global\advance\parencount by 1 } -\def\clnr{{\sf\char`\)}\global\advance\parencount by -1 } -\let\ampnr = \& -\def\lbrb{{\bf\char`\[}} -\def\rbrb{{\bf\char`\]}} - -% Active &'s sneak into the index arguments, so make sure it's defined. -{ - \catcode`& = 13 - \global\let& = \ampnr -} - -% First, defname, which formats the header line itself. -% #1 should be the function name. -% #2 should be the type of definition, such as "Function". - -\def\defname #1#2{% -% Get the values of \leftskip and \rightskip as they were -% outside the @def... -\dimen2=\leftskip -\advance\dimen2 by -\defbodyindent -\noindent -\setbox0=\hbox{\hskip \deflastargmargin{\rm #2}\hskip \deftypemargin}% -\dimen0=\hsize \advance \dimen0 by -\wd0 % compute size for first line -\dimen1=\hsize \advance \dimen1 by -\defargsindent %size for continuations -\parshape 2 0in \dimen0 \defargsindent \dimen1 -% Now output arg 2 ("Function" or some such) -% ending at \deftypemargin from the right margin, -% but stuck inside a box of width 0 so it does not interfere with linebreaking -{% Adjust \hsize to exclude the ambient margins, -% so that \rightline will obey them. -\advance \hsize by -\dimen2 -\rlap{\rightline{{\rm #2}\hskip -1.25pc }}}% -% Make all lines underfull and no complaints: -\tolerance=10000 \hbadness=10000 -\advance\leftskip by -\defbodyindent -\exdentamount=\defbodyindent -{\df #1}\enskip % Generate function name -} - -% Actually process the body of a definition -% #1 should be the terminating control sequence, such as \Edefun. -% #2 should be the "another name" control sequence, such as \defunx. -% #3 should be the control sequence that actually processes the header, -% such as \defunheader. - -\def\defparsebody #1#2#3{\begingroup\inENV% Environment for definitionbody -\medbreak % -% Define the end token that this defining construct specifies -% so that it will exit this group. -\def#1{\endgraf\endgroup\medbreak}% -\def#2{\begingroup\obeylines\activeparens\spacesplit#3}% -\parindent=0in -\advance\leftskip by \defbodyindent -\exdentamount=\defbodyindent -\begingroup % -\catcode 61=\active % 61 is `=' -\obeylines\activeparens\spacesplit#3} - -% #1 is the \E... control sequence to end the definition (which we define). -% #2 is the \...x control sequence for consecutive fns (which we define). -% #3 is the control sequence to call to resume processing. -% #4, delimited by the space, is the class name. -% -\def\defmethparsebody#1#2#3#4 {\begingroup\inENV % -\medbreak % -% Define the end token that this defining construct specifies -% so that it will exit this group. -\def#1{\endgraf\endgroup\medbreak}% -\def#2##1 {\begingroup\obeylines\activeparens\spacesplit{#3{##1}}}% -\parindent=0in -\advance\leftskip by \defbodyindent -\exdentamount=\defbodyindent -\begingroup\obeylines\activeparens\spacesplit{#3{#4}}} - -% Used for @deftypemethod and @deftypeivar. -% #1 is the \E... control sequence to end the definition (which we define). -% #2 is the \...x control sequence for consecutive fns (which we define). -% #3 is the control sequence to call to resume processing. -% #4, delimited by a space, is the class name. -% #5 is the method's return type. -% -\def\deftypemethparsebody#1#2#3#4 #5 {\begingroup\inENV - \medbreak - \def#1{\endgraf\endgroup\medbreak}% - \def#2##1 ##2 {\begingroup\obeylines\activeparens\spacesplit{#3{##1}{##2}}}% - \parindent=0in - \advance\leftskip by \defbodyindent - \exdentamount=\defbodyindent - \begingroup\obeylines\activeparens\spacesplit{#3{#4}{#5}}} - -% Used for @deftypeop. The change from \deftypemethparsebody is an -% extra argument at the beginning which is the `category', instead of it -% being the hardwired string `Method' or `Instance Variable'. We have -% to account for this both in the \...x definition and in parsing the -% input at hand. Thus also need a control sequence (passed as #5) for -% the \E... definition to assign the category name to. -% -\def\deftypeopparsebody#1#2#3#4#5 #6 {\begingroup\inENV - \medbreak - \def#1{\endgraf\endgroup\medbreak}% - \def#2##1 ##2 ##3 {% - \def#4{##1}% - \begingroup\obeylines\activeparens\spacesplit{#3{##2}{##3}}}% - \parindent=0in - \advance\leftskip by \defbodyindent - \exdentamount=\defbodyindent - \begingroup\obeylines\activeparens\spacesplit{#3{#5}{#6}}} - -\def\defopparsebody #1#2#3#4#5 {\begingroup\inENV % -\medbreak % -% Define the end token that this defining construct specifies -% so that it will exit this group. -\def#1{\endgraf\endgroup\medbreak}% -\def#2##1 ##2 {\def#4{##1}% -\begingroup\obeylines\activeparens\spacesplit{#3{##2}}}% -\parindent=0in -\advance\leftskip by \defbodyindent -\exdentamount=\defbodyindent -\begingroup\obeylines\activeparens\spacesplit{#3{#5}}} - -% These parsing functions are similar to the preceding ones -% except that they do not make parens into active characters. -% These are used for "variables" since they have no arguments. - -\def\defvarparsebody #1#2#3{\begingroup\inENV% Environment for definitionbody -\medbreak % -% Define the end token that this defining construct specifies -% so that it will exit this group. -\def#1{\endgraf\endgroup\medbreak}% -\def#2{\begingroup\obeylines\spacesplit#3}% -\parindent=0in -\advance\leftskip by \defbodyindent -\exdentamount=\defbodyindent -\begingroup % -\catcode 61=\active % -\obeylines\spacesplit#3} - -% This is used for \def{tp,vr}parsebody. It could probably be used for -% some of the others, too, with some judicious conditionals. -% -\def\parsebodycommon#1#2#3{% - \begingroup\inENV % - \medbreak % - % Define the end token that this defining construct specifies - % so that it will exit this group. - \def#1{\endgraf\endgroup\medbreak}% - \def#2##1 {\begingroup\obeylines\spacesplit{#3{##1}}}% - \parindent=0in - \advance\leftskip by \defbodyindent - \exdentamount=\defbodyindent - \begingroup\obeylines -} - -\def\defvrparsebody#1#2#3#4 {% - \parsebodycommon{#1}{#2}{#3}% - \spacesplit{#3{#4}}% -} - -% This loses on `@deftp {Data Type} {struct termios}' -- it thinks the -% type is just `struct', because we lose the braces in `{struct -% termios}' when \spacesplit reads its undelimited argument. Sigh. -% \let\deftpparsebody=\defvrparsebody -% -% So, to get around this, we put \empty in with the type name. That -% way, TeX won't find exactly `{...}' as an undelimited argument, and -% won't strip off the braces. -% -\def\deftpparsebody #1#2#3#4 {% - \parsebodycommon{#1}{#2}{#3}% - \spacesplit{\parsetpheaderline{#3{#4}}}\empty -} - -% Fine, but then we have to eventually remove the \empty *and* the -% braces (if any). That's what this does. -% -\def\removeemptybraces\empty#1\relax{#1} - -% After \spacesplit has done its work, this is called -- #1 is the final -% thing to call, #2 the type name (which starts with \empty), and #3 -% (which might be empty) the arguments. -% -\def\parsetpheaderline#1#2#3{% - #1{\removeemptybraces#2\relax}{#3}% -}% - -\def\defopvarparsebody #1#2#3#4#5 {\begingroup\inENV % -\medbreak % -% Define the end token that this defining construct specifies -% so that it will exit this group. -\def#1{\endgraf\endgroup\medbreak}% -\def#2##1 ##2 {\def#4{##1}% -\begingroup\obeylines\spacesplit{#3{##2}}}% -\parindent=0in -\advance\leftskip by \defbodyindent -\exdentamount=\defbodyindent -\begingroup\obeylines\spacesplit{#3{#5}}} - -% Split up #2 at the first space token. -% call #1 with two arguments: -% the first is all of #2 before the space token, -% the second is all of #2 after that space token. -% If #2 contains no space token, all of it is passed as the first arg -% and the second is passed as empty. - -{\obeylines -\gdef\spacesplit#1#2^^M{\endgroup\spacesplitfoo{#1}#2 \relax\spacesplitfoo}% -\long\gdef\spacesplitfoo#1#2 #3#4\spacesplitfoo{% -\ifx\relax #3% -#1{#2}{}\else #1{#2}{#3#4}\fi}} - -% So much for the things common to all kinds of definitions. - -% Define @defun. - -% First, define the processing that is wanted for arguments of \defun -% Use this to expand the args and terminate the paragraph they make up - -\def\defunargs#1{\functionparens \sl -% Expand, preventing hyphenation at `-' chars. -% Note that groups don't affect changes in \hyphenchar. -% Set the font temporarily and use \font in case \setfont made \tensl a macro. -{\tensl\hyphenchar\font=0}% -#1% -{\tensl\hyphenchar\font=45}% -\ifnum\parencount=0 \else \errmessage{Unbalanced parentheses in @def}\fi% -\interlinepenalty=10000 -\advance\rightskip by 0pt plus 1fil -\endgraf\nobreak\vskip -\parskip\nobreak -} - -\def\deftypefunargs #1{% -% Expand, preventing hyphenation at `-' chars. -% Note that groups don't affect changes in \hyphenchar. -% Use \boldbraxnoamp, not \functionparens, so that & is not special. -\boldbraxnoamp -\tclose{#1}% avoid \code because of side effects on active chars -\interlinepenalty=10000 -\advance\rightskip by 0pt plus 1fil -\endgraf\nobreak\vskip -\parskip\nobreak -} - -% Do complete processing of one @defun or @defunx line already parsed. - -% @deffn Command forward-char nchars - -\def\deffn{\defmethparsebody\Edeffn\deffnx\deffnheader} - -\def\deffnheader #1#2#3{\doind {fn}{\code{#2}}% -\begingroup\defname {#2}{#1}\defunargs{#3}\endgroup % -\catcode 61=\other % Turn off change made in \defparsebody -} - -% @defun == @deffn Function - -\def\defun{\defparsebody\Edefun\defunx\defunheader} - -\def\defunheader #1#2{\doind {fn}{\code{#1}}% Make entry in function index -\begingroup\defname {#1}{\putwordDeffunc}% -\defunargs {#2}\endgroup % -\catcode 61=\other % Turn off change made in \defparsebody -} - -% @deftypefun int foobar (int @var{foo}, float @var{bar}) - -\def\deftypefun{\defparsebody\Edeftypefun\deftypefunx\deftypefunheader} - -% #1 is the data type. #2 is the name and args. -\def\deftypefunheader #1#2{\deftypefunheaderx{#1}#2 \relax} -% #1 is the data type, #2 the name, #3 the args. -\def\deftypefunheaderx #1#2 #3\relax{% -\doind {fn}{\code{#2}}% Make entry in function index -\begingroup\defname {\defheaderxcond#1\relax$$$#2}{\putwordDeftypefun}% -\deftypefunargs {#3}\endgroup % -\catcode 61=\other % Turn off change made in \defparsebody -} - -% @deftypefn {Library Function} int foobar (int @var{foo}, float @var{bar}) - -\def\deftypefn{\defmethparsebody\Edeftypefn\deftypefnx\deftypefnheader} - -% \defheaderxcond#1\relax$$$ -% puts #1 in @code, followed by a space, but does nothing if #1 is null. -\def\defheaderxcond#1#2$$${\ifx#1\relax\else\code{#1#2} \fi} - -% #1 is the classification. #2 is the data type. #3 is the name and args. -\def\deftypefnheader #1#2#3{\deftypefnheaderx{#1}{#2}#3 \relax} -% #1 is the classification, #2 the data type, #3 the name, #4 the args. -\def\deftypefnheaderx #1#2#3 #4\relax{% -\doind {fn}{\code{#3}}% Make entry in function index -\begingroup -\normalparens % notably, turn off `&' magic, which prevents -% at least some C++ text from working -\defname {\defheaderxcond#2\relax$$$#3}{#1}% -\deftypefunargs {#4}\endgroup % -\catcode 61=\other % Turn off change made in \defparsebody -} - -% @defmac == @deffn Macro - -\def\defmac{\defparsebody\Edefmac\defmacx\defmacheader} - -\def\defmacheader #1#2{\doind {fn}{\code{#1}}% Make entry in function index -\begingroup\defname {#1}{\putwordDefmac}% -\defunargs {#2}\endgroup % -\catcode 61=\other % Turn off change made in \defparsebody -} - -% @defspec == @deffn Special Form - -\def\defspec{\defparsebody\Edefspec\defspecx\defspecheader} - -\def\defspecheader #1#2{\doind {fn}{\code{#1}}% Make entry in function index -\begingroup\defname {#1}{\putwordDefspec}% -\defunargs {#2}\endgroup % -\catcode 61=\other % Turn off change made in \defparsebody -} - -% @defop CATEGORY CLASS OPERATION ARG... -% -\def\defop #1 {\def\defoptype{#1}% -\defopparsebody\Edefop\defopx\defopheader\defoptype} -% -\def\defopheader#1#2#3{% -\dosubind {fn}{\code{#2}}{\putwordon\ #1}% Make entry in function index -\begingroup\defname {#2}{\defoptype\ \putwordon\ #1}% -\defunargs {#3}\endgroup % -} - -% @deftypeop CATEGORY CLASS TYPE OPERATION ARG... -% -\def\deftypeop #1 {\def\deftypeopcategory{#1}% - \deftypeopparsebody\Edeftypeop\deftypeopx\deftypeopheader - \deftypeopcategory} -% -% #1 is the class name, #2 the data type, #3 the operation name, #4 the args. -\def\deftypeopheader#1#2#3#4{% - \dosubind{fn}{\code{#3}}{\putwordon\ \code{#1}}% entry in function index - \begingroup - \defname{\defheaderxcond#2\relax$$$#3} - {\deftypeopcategory\ \putwordon\ \code{#1}}% - \deftypefunargs{#4}% - \endgroup -} - -% @deftypemethod CLASS TYPE METHOD ARG... -% -\def\deftypemethod{% - \deftypemethparsebody\Edeftypemethod\deftypemethodx\deftypemethodheader} -% -% #1 is the class name, #2 the data type, #3 the method name, #4 the args. -\def\deftypemethodheader#1#2#3#4{% - \dosubind{fn}{\code{#3}}{\putwordon\ \code{#1}}% entry in function index - \begingroup - \defname{\defheaderxcond#2\relax$$$#3}{\putwordMethodon\ \code{#1}}% - \deftypefunargs{#4}% - \endgroup -} - -% @deftypeivar CLASS TYPE VARNAME -% -\def\deftypeivar{% - \deftypemethparsebody\Edeftypeivar\deftypeivarx\deftypeivarheader} -% -% #1 is the class name, #2 the data type, #3 the variable name. -\def\deftypeivarheader#1#2#3{% - \dosubind{vr}{\code{#3}}{\putwordof\ \code{#1}}% entry in variable index - \begingroup - \defname{\defheaderxcond#2\relax$$$#3} - {\putwordInstanceVariableof\ \code{#1}}% - \defvarargs{#3}% - \endgroup -} - -% @defmethod == @defop Method -% -\def\defmethod{\defmethparsebody\Edefmethod\defmethodx\defmethodheader} -% -% #1 is the class name, #2 the method name, #3 the args. -\def\defmethodheader#1#2#3{% - \dosubind{fn}{\code{#2}}{\putwordon\ \code{#1}}% entry in function index - \begingroup - \defname{#2}{\putwordMethodon\ \code{#1}}% - \defunargs{#3}% - \endgroup -} - -% @defcv {Class Option} foo-class foo-flag - -\def\defcv #1 {\def\defcvtype{#1}% -\defopvarparsebody\Edefcv\defcvx\defcvarheader\defcvtype} - -\def\defcvarheader #1#2#3{% -\dosubind {vr}{\code{#2}}{\putwordof\ #1}% Make entry in var index -\begingroup\defname {#2}{\defcvtype\ \putwordof\ #1}% -\defvarargs {#3}\endgroup % -} - -% @defivar CLASS VARNAME == @defcv {Instance Variable} CLASS VARNAME -% -\def\defivar{\defvrparsebody\Edefivar\defivarx\defivarheader} -% -\def\defivarheader#1#2#3{% - \dosubind {vr}{\code{#2}}{\putwordof\ #1}% entry in var index - \begingroup - \defname{#2}{\putwordInstanceVariableof\ #1}% - \defvarargs{#3}% - \endgroup -} - -% @defvar -% First, define the processing that is wanted for arguments of @defvar. -% This is actually simple: just print them in roman. -% This must expand the args and terminate the paragraph they make up -\def\defvarargs #1{\normalparens #1% -\interlinepenalty=10000 -\endgraf\nobreak\vskip -\parskip\nobreak} - -% @defvr Counter foo-count - -\def\defvr{\defvrparsebody\Edefvr\defvrx\defvrheader} - -\def\defvrheader #1#2#3{\doind {vr}{\code{#2}}% -\begingroup\defname {#2}{#1}\defvarargs{#3}\endgroup} - -% @defvar == @defvr Variable - -\def\defvar{\defvarparsebody\Edefvar\defvarx\defvarheader} - -\def\defvarheader #1#2{\doind {vr}{\code{#1}}% Make entry in var index -\begingroup\defname {#1}{\putwordDefvar}% -\defvarargs {#2}\endgroup % -} - -% @defopt == @defvr {User Option} - -\def\defopt{\defvarparsebody\Edefopt\defoptx\defoptheader} - -\def\defoptheader #1#2{\doind {vr}{\code{#1}}% Make entry in var index -\begingroup\defname {#1}{\putwordDefopt}% -\defvarargs {#2}\endgroup % -} - -% @deftypevar int foobar - -\def\deftypevar{\defvarparsebody\Edeftypevar\deftypevarx\deftypevarheader} - -% #1 is the data type. #2 is the name, perhaps followed by text that -% is actually part of the data type, which should not be put into the index. -\def\deftypevarheader #1#2{% -\dovarind#2 \relax% Make entry in variables index -\begingroup\defname {\defheaderxcond#1\relax$$$#2}{\putwordDeftypevar}% -\interlinepenalty=10000 -\endgraf\nobreak\vskip -\parskip\nobreak -\endgroup} -\def\dovarind#1 #2\relax{\doind{vr}{\code{#1}}} - -% @deftypevr {Global Flag} int enable - -\def\deftypevr{\defvrparsebody\Edeftypevr\deftypevrx\deftypevrheader} - -\def\deftypevrheader #1#2#3{\dovarind#3 \relax% -\begingroup\defname {\defheaderxcond#2\relax$$$#3}{#1} -\interlinepenalty=10000 -\endgraf\nobreak\vskip -\parskip\nobreak -\endgroup} - -% Now define @deftp -% Args are printed in bold, a slight difference from @defvar. - -\def\deftpargs #1{\bf \defvarargs{#1}} - -% @deftp Class window height width ... - -\def\deftp{\deftpparsebody\Edeftp\deftpx\deftpheader} - -\def\deftpheader #1#2#3{\doind {tp}{\code{#2}}% -\begingroup\defname {#2}{#1}\deftpargs{#3}\endgroup} - -% These definitions are used if you use @defunx (etc.) -% anywhere other than immediately after a @defun or @defunx. -% -\def\defcvx#1 {\errmessage{@defcvx in invalid context}} -\def\deffnx#1 {\errmessage{@deffnx in invalid context}} -\def\defivarx#1 {\errmessage{@defivarx in invalid context}} -\def\defmacx#1 {\errmessage{@defmacx in invalid context}} -\def\defmethodx#1 {\errmessage{@defmethodx in invalid context}} -\def\defoptx #1 {\errmessage{@defoptx in invalid context}} -\def\defopx#1 {\errmessage{@defopx in invalid context}} -\def\defspecx#1 {\errmessage{@defspecx in invalid context}} -\def\deftpx#1 {\errmessage{@deftpx in invalid context}} -\def\deftypefnx#1 {\errmessage{@deftypefnx in invalid context}} -\def\deftypefunx#1 {\errmessage{@deftypefunx in invalid context}} -\def\deftypeivarx#1 {\errmessage{@deftypeivarx in invalid context}} -\def\deftypemethodx#1 {\errmessage{@deftypemethodx in invalid context}} -\def\deftypeopx#1 {\errmessage{@deftypeopx in invalid context}} -\def\deftypevarx#1 {\errmessage{@deftypevarx in invalid context}} -\def\deftypevrx#1 {\errmessage{@deftypevrx in invalid context}} -\def\defunx#1 {\errmessage{@defunx in invalid context}} -\def\defvarx#1 {\errmessage{@defvarx in invalid context}} -\def\defvrx#1 {\errmessage{@defvrx in invalid context}} - - -\message{macros,} -% @macro. - -% To do this right we need a feature of e-TeX, \scantokens, -% which we arrange to emulate with a temporary file in ordinary TeX. -\ifx\eTeXversion\undefined - \newwrite\macscribble - \def\scanmacro#1{% - \begingroup \newlinechar`\^^M - % Undo catcode changes of \startcontents and \doprintindex - \catcode`\@=0 \catcode`\\=12 \escapechar=`\@ - % Append \endinput to make sure that TeX does not see the ending newline. - \toks0={#1\endinput}% - \immediate\openout\macscribble=\jobname.tmp - \immediate\write\macscribble{\the\toks0}% - \immediate\closeout\macscribble - \let\xeatspaces\eatspaces - \input \jobname.tmp - \endgroup -} -\else -\def\scanmacro#1{% -\begingroup \newlinechar`\^^M -% Undo catcode changes of \startcontents and \doprintindex -\catcode`\@=0 \catcode`\\=12 \escapechar=`\@ -\let\xeatspaces\eatspaces\scantokens{#1\endinput}\endgroup} -\fi - -\newcount\paramno % Count of parameters -\newtoks\macname % Macro name -\newif\ifrecursive % Is it recursive? -\def\macrolist{} % List of all defined macros in the form - % \do\macro1\do\macro2... - -% Utility routines. -% Thisdoes \let #1 = #2, except with \csnames. -\def\cslet#1#2{% -\expandafter\expandafter -\expandafter\let -\expandafter\expandafter -\csname#1\endcsname -\csname#2\endcsname} - -% Trim leading and trailing spaces off a string. -% Concepts from aro-bend problem 15 (see CTAN). -{\catcode`\@=11 -\gdef\eatspaces #1{\expandafter\trim@\expandafter{#1 }} -\gdef\trim@ #1{\trim@@ @#1 @ #1 @ @@} -\gdef\trim@@ #1@ #2@ #3@@{\trim@@@\empty #2 @} -\def\unbrace#1{#1} -\unbrace{\gdef\trim@@@ #1 } #2@{#1} -} - -% Trim a single trailing ^^M off a string. -{\catcode`\^^M=12\catcode`\Q=3% -\gdef\eatcr #1{\eatcra #1Q^^MQ}% -\gdef\eatcra#1^^MQ{\eatcrb#1Q}% -\gdef\eatcrb#1Q#2Q{#1}% -} - -% Macro bodies are absorbed as an argument in a context where -% all characters are catcode 10, 11 or 12, except \ which is active -% (as in normal texinfo). It is necessary to change the definition of \. - -% It's necessary to have hard CRs when the macro is executed. This is -% done by making ^^M (\endlinechar) catcode 12 when reading the macro -% body, and then making it the \newlinechar in \scanmacro. - -\def\macrobodyctxt{% - \catcode`\~=12 - \catcode`\^=12 - \catcode`\_=12 - \catcode`\|=12 - \catcode`\<=12 - \catcode`\>=12 - \catcode`\+=12 - \catcode`\{=12 - \catcode`\}=12 - \catcode`\@=12 - \catcode`\^^M=12 - \usembodybackslash} - -\def\macroargctxt{% - \catcode`\~=12 - \catcode`\^=12 - \catcode`\_=12 - \catcode`\|=12 - \catcode`\<=12 - \catcode`\>=12 - \catcode`\+=12 - \catcode`\@=12 - \catcode`\\=12} - -% \mbodybackslash is the definition of \ in @macro bodies. -% It maps \foo\ => \csname macarg.foo\endcsname => #N -% where N is the macro parameter number. -% We define \csname macarg.\endcsname to be \realbackslash, so -% \\ in macro replacement text gets you a backslash. - -{\catcode`@=0 @catcode`@\=@active - @gdef@usembodybackslash{@let\=@mbodybackslash} - @gdef@mbodybackslash#1\{@csname macarg.#1@endcsname} -} -\expandafter\def\csname macarg.\endcsname{\realbackslash} - -\def\macro{\recursivefalse\parsearg\macroxxx} -\def\rmacro{\recursivetrue\parsearg\macroxxx} - -\def\macroxxx#1{% - \getargs{#1}% now \macname is the macname and \argl the arglist - \ifx\argl\empty % no arguments - \paramno=0% - \else - \expandafter\parsemargdef \argl;% - \fi - \if1\csname ismacro.\the\macname\endcsname - \message{Warning: redefining \the\macname}% - \else - \expandafter\ifx\csname \the\macname\endcsname \relax - \else \errmessage{The name \the\macname\space is reserved}\fi - \global\cslet{macsave.\the\macname}{\the\macname}% - \global\expandafter\let\csname ismacro.\the\macname\endcsname=1% - % Add the macroname to \macrolist - \toks0 = \expandafter{\macrolist\do}% - \xdef\macrolist{\the\toks0 - \expandafter\noexpand\csname\the\macname\endcsname}% - \fi - \begingroup \macrobodyctxt - \ifrecursive \expandafter\parsermacbody - \else \expandafter\parsemacbody - \fi} - -\def\unmacro{\parsearg\unmacroxxx} -\def\unmacroxxx#1{% - \if1\csname ismacro.#1\endcsname - \global\cslet{#1}{macsave.#1}% - \global\expandafter\let \csname ismacro.#1\endcsname=0% - % Remove the macro name from \macrolist - \begingroup - \edef\tempa{\expandafter\noexpand\csname#1\endcsname}% - \def\do##1{% - \def\tempb{##1}% - \ifx\tempa\tempb - % remove this - \else - \toks0 = \expandafter{\newmacrolist\do}% - \edef\newmacrolist{\the\toks0\expandafter\noexpand\tempa}% - \fi}% - \def\newmacrolist{}% - % Execute macro list to define \newmacrolist - \macrolist - \global\let\macrolist\newmacrolist - \endgroup - \else - \errmessage{Macro #1 not defined}% - \fi -} - -% This makes use of the obscure feature that if the last token of a -% is #, then the preceding argument is delimited by -% an opening brace, and that opening brace is not consumed. -\def\getargs#1{\getargsxxx#1{}} -\def\getargsxxx#1#{\getmacname #1 \relax\getmacargs} -\def\getmacname #1 #2\relax{\macname={#1}} -\def\getmacargs#1{\def\argl{#1}} - -% Parse the optional {params} list. Set up \paramno and \paramlist -% so \defmacro knows what to do. Define \macarg.blah for each blah -% in the params list, to be ##N where N is the position in that list. -% That gets used by \mbodybackslash (above). - -% We need to get `macro parameter char #' into several definitions. -% The technique used is stolen from LaTeX: let \hash be something -% unexpandable, insert that wherever you need a #, and then redefine -% it to # just before using the token list produced. -% -% The same technique is used to protect \eatspaces till just before -% the macro is used. - -\def\parsemargdef#1;{\paramno=0\def\paramlist{}% - \let\hash\relax\let\xeatspaces\relax\parsemargdefxxx#1,;,} -\def\parsemargdefxxx#1,{% - \if#1;\let\next=\relax - \else \let\next=\parsemargdefxxx - \advance\paramno by 1% - \expandafter\edef\csname macarg.\eatspaces{#1}\endcsname - {\xeatspaces{\hash\the\paramno}}% - \edef\paramlist{\paramlist\hash\the\paramno,}% - \fi\next} - -% These two commands read recursive and nonrecursive macro bodies. -% (They're different since rec and nonrec macros end differently.) - -\long\def\parsemacbody#1@end macro% -{\xdef\temp{\eatcr{#1}}\endgroup\defmacro}% -\long\def\parsermacbody#1@end rmacro% -{\xdef\temp{\eatcr{#1}}\endgroup\defmacro}% - -% This defines the macro itself. There are six cases: recursive and -% nonrecursive macros of zero, one, and many arguments. -% Much magic with \expandafter here. -% \xdef is used so that macro definitions will survive the file -% they're defined in; @include reads the file inside a group. -\def\defmacro{% - \let\hash=##% convert placeholders to macro parameter chars - \ifrecursive - \ifcase\paramno - % 0 - \expandafter\xdef\csname\the\macname\endcsname{% - \noexpand\scanmacro{\temp}}% - \or % 1 - \expandafter\xdef\csname\the\macname\endcsname{% - \bgroup\noexpand\macroargctxt - \noexpand\braceorline - \expandafter\noexpand\csname\the\macname xxx\endcsname}% - \expandafter\xdef\csname\the\macname xxx\endcsname##1{% - \egroup\noexpand\scanmacro{\temp}}% - \else % many - \expandafter\xdef\csname\the\macname\endcsname{% - \bgroup\noexpand\macroargctxt - \noexpand\csname\the\macname xx\endcsname}% - \expandafter\xdef\csname\the\macname xx\endcsname##1{% - \expandafter\noexpand\csname\the\macname xxx\endcsname ##1,}% - \expandafter\expandafter - \expandafter\xdef - \expandafter\expandafter - \csname\the\macname xxx\endcsname - \paramlist{\egroup\noexpand\scanmacro{\temp}}% - \fi - \else - \ifcase\paramno - % 0 - \expandafter\xdef\csname\the\macname\endcsname{% - \noexpand\norecurse{\the\macname}% - \noexpand\scanmacro{\temp}\egroup}% - \or % 1 - \expandafter\xdef\csname\the\macname\endcsname{% - \bgroup\noexpand\macroargctxt - \noexpand\braceorline - \expandafter\noexpand\csname\the\macname xxx\endcsname}% - \expandafter\xdef\csname\the\macname xxx\endcsname##1{% - \egroup - \noexpand\norecurse{\the\macname}% - \noexpand\scanmacro{\temp}\egroup}% - \else % many - \expandafter\xdef\csname\the\macname\endcsname{% - \bgroup\noexpand\macroargctxt - \expandafter\noexpand\csname\the\macname xx\endcsname}% - \expandafter\xdef\csname\the\macname xx\endcsname##1{% - \expandafter\noexpand\csname\the\macname xxx\endcsname ##1,}% - \expandafter\expandafter - \expandafter\xdef - \expandafter\expandafter - \csname\the\macname xxx\endcsname - \paramlist{% - \egroup - \noexpand\norecurse{\the\macname}% - \noexpand\scanmacro{\temp}\egroup}% - \fi - \fi} - -\def\norecurse#1{\bgroup\cslet{#1}{macsave.#1}} - -% \braceorline decides whether the next nonwhitespace character is a -% {. If so it reads up to the closing }, if not, it reads the whole -% line. Whatever was read is then fed to the next control sequence -% as an argument (by \parsebrace or \parsearg) -\def\braceorline#1{\let\next=#1\futurelet\nchar\braceorlinexxx} -\def\braceorlinexxx{% - \ifx\nchar\bgroup\else - \expandafter\parsearg - \fi \next} - -% We mant to disable all macros during \shipout so that they are not -% expanded by \write. -\def\turnoffmacros{\begingroup \def\do##1{\let\noexpand##1=\relax}% - \edef\next{\macrolist}\expandafter\endgroup\next} - - -% @alias. -% We need some trickery to remove the optional spaces around the equal -% sign. Just make them active and then expand them all to nothing. -\def\alias{\begingroup\obeyspaces\parsearg\aliasxxx} -\def\aliasxxx #1{\aliasyyy#1\relax} -\def\aliasyyy #1=#2\relax{\ignoreactivespaces -\edef\next{\global\let\expandafter\noexpand\csname#1\endcsname=% - \expandafter\noexpand\csname#2\endcsname}% -\expandafter\endgroup\next} - - -\message{cross references,} -% @xref etc. - -\newwrite\auxfile - -\newif\ifhavexrefs % True if xref values are known. -\newif\ifwarnedxrefs % True if we warned once that they aren't known. - -% @inforef is relatively simple. -\def\inforef #1{\inforefzzz #1,,,,**} -\def\inforefzzz #1,#2,#3,#4**{\putwordSee{} \putwordInfo{} \putwordfile{} \file{\ignorespaces #3{}}, - node \samp{\ignorespaces#1{}}} - -% @node's job is to define \lastnode. -\def\node{\ENVcheck\parsearg\nodezzz} -\def\nodezzz#1{\nodexxx [#1,]} -\def\nodexxx[#1,#2]{\gdef\lastnode{#1}} -\let\nwnode=\node -\let\lastnode=\relax - -% The sectioning commands (@chapter, etc.) call these. -\def\donoderef{% - \ifx\lastnode\relax\else - \expandafter\expandafter\expandafter\setref{\lastnode}% - {Ysectionnumberandtype}% - \global\let\lastnode=\relax - \fi -} -\def\unnumbnoderef{% - \ifx\lastnode\relax\else - \expandafter\expandafter\expandafter\setref{\lastnode}{Ynothing}% - \global\let\lastnode=\relax - \fi -} -\def\appendixnoderef{% - \ifx\lastnode\relax\else - \expandafter\expandafter\expandafter\setref{\lastnode}% - {Yappendixletterandtype}% - \global\let\lastnode=\relax - \fi -} - - -% @anchor{NAME} -- define xref target at arbitrary point. -% -\newcount\savesfregister -\gdef\savesf{\relax \ifhmode \savesfregister=\spacefactor \fi} -\gdef\restoresf{\relax \ifhmode \spacefactor=\savesfregister \fi} -\gdef\anchor#1{\savesf \setref{#1}{Ynothing}\restoresf \ignorespaces} - -% \setref{NAME}{SNT} defines a cross-reference point NAME, namely -% NAME-title, NAME-pg, and NAME-SNT. Called from \foonoderef. We have -% to set \indexdummies so commands such as @code in a section title -% aren't expanded. It would be nicer not to expand the titles in the -% first place, but there's so many layers that that is hard to do. -% -\def\setref#1#2{{% - \indexdummies - \pdfmkdest{#1}% - \dosetq{#1-title}{Ytitle}% - \dosetq{#1-pg}{Ypagenumber}% - \dosetq{#1-snt}{#2}% -}} - -% @xref, @pxref, and @ref generate cross-references. For \xrefX, #1 is -% the node name, #2 the name of the Info cross-reference, #3 the printed -% node name, #4 the name of the Info file, #5 the name of the printed -% manual. All but the node name can be omitted. -% -\def\pxref#1{\putwordsee{} \xrefX[#1,,,,,,,]} -\def\xref#1{\putwordSee{} \xrefX[#1,,,,,,,]} -\def\ref#1{\xrefX[#1,,,,,,,]} -\def\xrefX[#1,#2,#3,#4,#5,#6]{\begingroup - \unsepspaces - \def\printedmanual{\ignorespaces #5}% - \def\printednodename{\ignorespaces #3}% - \setbox1=\hbox{\printedmanual}% - \setbox0=\hbox{\printednodename}% - \ifdim \wd0 = 0pt - % No printed node name was explicitly given. - \expandafter\ifx\csname SETxref-automatic-section-title\endcsname\relax - % Use the node name inside the square brackets. - \def\printednodename{\ignorespaces #1}% - \else - % Use the actual chapter/section title appear inside - % the square brackets. Use the real section title if we have it. - \ifdim \wd1 > 0pt - % It is in another manual, so we don't have it. - \def\printednodename{\ignorespaces #1}% - \else - \ifhavexrefs - % We know the real title if we have the xref values. - \def\printednodename{\refx{#1-title}{}}% - \else - % Otherwise just copy the Info node name. - \def\printednodename{\ignorespaces #1}% - \fi% - \fi - \fi - \fi - % - % If we use \unhbox0 and \unhbox1 to print the node names, TeX does not - % insert empty discretionaries after hyphens, which means that it will - % not find a line break at a hyphen in a node names. Since some manuals - % are best written with fairly long node names, containing hyphens, this - % is a loss. Therefore, we give the text of the node name again, so it - % is as if TeX is seeing it for the first time. - \ifpdf - \leavevmode - \getfilename{#4}% - \ifnum\filenamelength>0 - \startlink attr{/Border [0 0 0]}% - goto file{\the\filename.pdf} name{#1@}% - \else - \startlink attr{/Border [0 0 0]}% - goto name{#1@}% - \fi - \linkcolor - \fi - % - \ifdim \wd1 > 0pt - \putwordsection{} ``\printednodename'' \putwordin{} \cite{\printedmanual}% - \else - % _ (for example) has to be the character _ for the purposes of the - % control sequence corresponding to the node, but it has to expand - % into the usual \leavevmode...\vrule stuff for purposes of - % printing. So we \turnoffactive for the \refx-snt, back on for the - % printing, back off for the \refx-pg. - {\normalturnoffactive - % Only output a following space if the -snt ref is nonempty; for - % @unnumbered and @anchor, it won't be. - \setbox2 = \hbox{\ignorespaces \refx{#1-snt}{}}% - \ifdim \wd2 > 0pt \refx{#1-snt}\space\fi - }% - % [mynode], - [\printednodename],\space - % page 3 - \turnoffactive \putwordpage\tie\refx{#1-pg}{}% - \fi - \endlink -\endgroup} - -% \dosetq is the interface for calls from other macros - -% Use \normalturnoffactive so that punctuation chars such as underscore -% and backslash work in node names. (\turnoffactive doesn't do \.) -\def\dosetq#1#2{% - {\let\folio=0% - \normalturnoffactive - \edef\next{\write\auxfile{\internalsetq{#1}{#2}}}% - \iflinks - \next - \fi - }% -} - -% \internalsetq {foo}{page} expands into -% CHARACTERS 'xrdef {foo}{...expansion of \Ypage...} -% When the aux file is read, ' is the escape character - -\def\internalsetq #1#2{'xrdef {#1}{\csname #2\endcsname}} - -% Things to be expanded by \internalsetq - -\def\Ypagenumber{\folio} - -\def\Ytitle{\thissection} - -\def\Ynothing{} - -\def\Ysectionnumberandtype{% -\ifnum\secno=0 \putwordChapter\xreftie\the\chapno % -\else \ifnum \subsecno=0 \putwordSection\xreftie\the\chapno.\the\secno % -\else \ifnum \subsubsecno=0 % -\putwordSection\xreftie\the\chapno.\the\secno.\the\subsecno % -\else % -\putwordSection\xreftie\the\chapno.\the\secno.\the\subsecno.\the\subsubsecno % -\fi \fi \fi } - -\def\Yappendixletterandtype{% -\ifnum\secno=0 \putwordAppendix\xreftie'char\the\appendixno{}% -\else \ifnum \subsecno=0 \putwordSection\xreftie'char\the\appendixno.\the\secno % -\else \ifnum \subsubsecno=0 % -\putwordSection\xreftie'char\the\appendixno.\the\secno.\the\subsecno % -\else % -\putwordSection\xreftie'char\the\appendixno.\the\secno.\the\subsecno.\the\subsubsecno % -\fi \fi \fi } - -\gdef\xreftie{'tie} - -% Use TeX 3.0's \inputlineno to get the line number, for better error -% messages, but if we're using an old version of TeX, don't do anything. -% -\ifx\inputlineno\thisisundefined - \let\linenumber = \empty % Non-3.0. -\else - \def\linenumber{\the\inputlineno:\space} -\fi - -% Define \refx{NAME}{SUFFIX} to reference a cross-reference string named NAME. -% If its value is nonempty, SUFFIX is output afterward. - -\def\refx#1#2{% - \expandafter\ifx\csname X#1\endcsname\relax - % If not defined, say something at least. - \angleleft un\-de\-fined\angleright - \iflinks - \ifhavexrefs - \message{\linenumber Undefined cross reference `#1'.}% - \else - \ifwarnedxrefs\else - \global\warnedxrefstrue - \message{Cross reference values unknown; you must run TeX again.}% - \fi - \fi - \fi - \else - % It's defined, so just use it. - \csname X#1\endcsname - \fi - #2% Output the suffix in any case. -} - -% This is the macro invoked by entries in the aux file. -% -\def\xrdef#1{\begingroup - % Reenable \ as an escape while reading the second argument. - \catcode`\\ = 0 - \afterassignment\endgroup - \expandafter\gdef\csname X#1\endcsname -} - -% Read the last existing aux file, if any. No error if none exists. -\def\readauxfile{\begingroup - \catcode`\^^@=\other - \catcode`\^^A=\other - \catcode`\^^B=\other - \catcode`\^^C=\other - \catcode`\^^D=\other - \catcode`\^^E=\other - \catcode`\^^F=\other - \catcode`\^^G=\other - \catcode`\^^H=\other - \catcode`\^^K=\other - \catcode`\^^L=\other - \catcode`\^^N=\other - \catcode`\^^P=\other - \catcode`\^^Q=\other - \catcode`\^^R=\other - \catcode`\^^S=\other - \catcode`\^^T=\other - \catcode`\^^U=\other - \catcode`\^^V=\other - \catcode`\^^W=\other - \catcode`\^^X=\other - \catcode`\^^Z=\other - \catcode`\^^[=\other - \catcode`\^^\=\other - \catcode`\^^]=\other - \catcode`\^^^=\other - \catcode`\^^_=\other - \catcode`\@=\other - \catcode`\^=\other - % It was suggested to define this as 7, which would allow ^^e4 etc. - % in xref tags, i.e., node names. But since ^^e4 notation isn't - % supported in the main text, it doesn't seem desirable. Furthermore, - % that is not enough: for node names that actually contain a ^ - % character, we would end up writing a line like this: 'xrdef {'hat - % b-title}{'hat b} and \xrdef does a \csname...\endcsname on the first - % argument, and \hat is not an expandable control sequence. It could - % all be worked out, but why? Either we support ^^ or we don't. - % - % The other change necessary for this was to define \auxhat: - % \def\auxhat{\def^{'hat }}% extra space so ok if followed by letter - % and then to call \auxhat in \setq. - % - \catcode`\~=\other - \catcode`\[=\other - \catcode`\]=\other - \catcode`\"=\other - \catcode`\_=\other - \catcode`\|=\other - \catcode`\<=\other - \catcode`\>=\other - \catcode`\$=\other - \catcode`\#=\other - \catcode`\&=\other - \catcode`+=\other % avoid \+ for paranoia even though we've turned it off - % Make the characters 128-255 be printing characters - {% - \count 1=128 - \def\loop{% - \catcode\count 1=\other - \advance\count 1 by 1 - \ifnum \count 1<256 \loop \fi - }% - }% - % The aux file uses ' as the escape (for now). - % Turn off \ as an escape so we do not lose on - % entries which were dumped with control sequences in their names. - % For example, 'xrdef {$\leq $-fun}{page ...} made by @defun ^^ - % Reference to such entries still does not work the way one would wish, - % but at least they do not bomb out when the aux file is read in. - \catcode`\{=1 - \catcode`\}=2 - \catcode`\%=\other - \catcode`\'=0 - \catcode`\\=\other - % - \openin 1 \jobname.aux - \ifeof 1 \else - \closein 1 - \input \jobname.aux - \global\havexrefstrue - \global\warnedobstrue - \fi - % Open the new aux file. TeX will close it automatically at exit. - \openout\auxfile=\jobname.aux -\endgroup} - - -% Footnotes. - -\newcount \footnoteno - -% The trailing space in the following definition for supereject is -% vital for proper filling; pages come out unaligned when you do a -% pagealignmacro call if that space before the closing brace is -% removed. (Generally, numeric constants should always be followed by a -% space to prevent strange expansion errors.) -\def\supereject{\par\penalty -20000\footnoteno =0 } - -% @footnotestyle is meaningful for info output only. -\let\footnotestyle=\comment - -\let\ptexfootnote=\footnote - -{\catcode `\@=11 -% -% Auto-number footnotes. Otherwise like plain. -\gdef\footnote{% - \global\advance\footnoteno by \@ne - \edef\thisfootno{$^{\the\footnoteno}$}% - % - % In case the footnote comes at the end of a sentence, preserve the - % extra spacing after we do the footnote number. - \let\@sf\empty - \ifhmode\edef\@sf{\spacefactor\the\spacefactor}\/\fi - % - % Remove inadvertent blank space before typesetting the footnote number. - \unskip - \thisfootno\@sf - \footnotezzz -}% - -% Don't bother with the trickery in plain.tex to not require the -% footnote text as a parameter. Our footnotes don't need to be so general. -% -% Oh yes, they do; otherwise, @ifset and anything else that uses -% \parseargline fail inside footnotes because the tokens are fixed when -% the footnote is read. --karl, 16nov96. -% -\long\gdef\footnotezzz{\insert\footins\bgroup - % We want to typeset this text as a normal paragraph, even if the - % footnote reference occurs in (for example) a display environment. - % So reset some parameters. - \interlinepenalty\interfootnotelinepenalty - \splittopskip\ht\strutbox % top baseline for broken footnotes - \splitmaxdepth\dp\strutbox - \floatingpenalty\@MM - \leftskip\z@skip - \rightskip\z@skip - \spaceskip\z@skip - \xspaceskip\z@skip - \parindent\defaultparindent - % - \smallfonts \rm - % - % Hang the footnote text off the number. - \hang - \textindent{\thisfootno}% - % - % Don't crash into the line above the footnote text. Since this - % expands into a box, it must come within the paragraph, lest it - % provide a place where TeX can split the footnote. - \footstrut - \futurelet\next\fo@t -} -\def\fo@t{\ifcat\bgroup\noexpand\next \let\next\f@@t - \else\let\next\f@t\fi \next} -\def\f@@t{\bgroup\aftergroup\@foot\let\next} -\def\f@t#1{#1\@foot} -\def\@foot{\strut\par\egroup} - -}%end \catcode `\@=11 - -% Set the baselineskip to #1, and the lineskip and strut size -% correspondingly. There is no deep meaning behind these magic numbers -% used as factors; they just match (closely enough) what Knuth defined. -% -\def\lineskipfactor{.08333} -\def\strutheightpercent{.70833} -\def\strutdepthpercent {.29167} -% -\def\setleading#1{% - \normalbaselineskip = #1\relax - \normallineskip = \lineskipfactor\normalbaselineskip - \normalbaselines - \setbox\strutbox =\hbox{% - \vrule width0pt height\strutheightpercent\baselineskip - depth \strutdepthpercent \baselineskip - }% -} - -% @| inserts a changebar to the left of the current line. It should -% surround any changed text. This approach does *not* work if the -% change spans more than two lines of output. To handle that, we would -% have adopt a much more difficult approach (putting marks into the main -% vertical list for the beginning and end of each change). -% -\def\|{% - % \vadjust can only be used in horizontal mode. - \leavevmode - % - % Append this vertical mode material after the current line in the output. - \vadjust{% - % We want to insert a rule with the height and depth of the current - % leading; that is exactly what \strutbox is supposed to record. - \vskip-\baselineskip - % - % \vadjust-items are inserted at the left edge of the type. So - % the \llap here moves out into the left-hand margin. - \llap{% - % - % For a thicker or thinner bar, change the `1pt'. - \vrule height\baselineskip width1pt - % - % This is the space between the bar and the text. - \hskip 12pt - }% - }% -} - -% For a final copy, take out the rectangles -% that mark overfull boxes (in case you have decided -% that the text looks ok even though it passes the margin). -% -\def\finalout{\overfullrule=0pt} - -% @image. We use the macros from epsf.tex to support this. -% If epsf.tex is not installed and @image is used, we complain. -% -% Check for and read epsf.tex up front. If we read it only at @image -% time, we might be inside a group, and then its definitions would get -% undone and the next image would fail. -\openin 1 = epsf.tex -\ifeof 1 \else - \closein 1 - % Do not bother showing banner with post-v2.7 epsf.tex (available in - % doc/epsf.tex until it shows up on ctan). - \def\epsfannounce{\toks0 = }% - \input epsf.tex -\fi -% -% We will only complain once about lack of epsf.tex. -\newif\ifwarnednoepsf -\newhelp\noepsfhelp{epsf.tex must be installed for images to - work. It is also included in the Texinfo distribution, or you can get - it from ftp://tug.org/tex/epsf.tex.} -% -\def\image#1{% - \ifx\epsfbox\undefined - \ifwarnednoepsf \else - \errhelp = \noepsfhelp - \errmessage{epsf.tex not found, images will be ignored}% - \global\warnednoepsftrue - \fi - \else - \imagexxx #1,,,\finish - \fi -} -% -% Arguments to @image: -% #1 is (mandatory) image filename; we tack on .eps extension. -% #2 is (optional) width, #3 is (optional) height. -% #4 is just the usual extra ignored arg for parsing this stuff. -\def\imagexxx#1,#2,#3,#4\finish{% - \ifpdf - \centerline{\dopdfimage{#1}{#2}{#3}}% - \else - % \epsfbox itself resets \epsf?size at each figure. - \setbox0 = \hbox{\ignorespaces #2}\ifdim\wd0 > 0pt \epsfxsize=#2\relax \fi - \setbox0 = \hbox{\ignorespaces #3}\ifdim\wd0 > 0pt \epsfysize=#3\relax \fi - \begingroup - \catcode`\^^M = 5 % in case we're inside an example - % If the image is by itself, center it. - \ifvmode - \nobreak\bigskip - % Usually we'll have text after the image which will insert - % \parskip glue, so insert it here too to equalize the space - % above and below. - \nobreak\vskip\parskip - \nobreak - \centerline{\epsfbox{#1.eps}}% - \bigbreak - \else - % In the middle of a paragraph, no extra space. - \epsfbox{#1.eps}% - \fi - \endgroup - \fi -} - - -\message{localization,} -% and i18n. - -% @documentlanguage is usually given very early, just after -% @setfilename. If done too late, it may not override everything -% properly. Single argument is the language abbreviation. -% It would be nice if we could set up a hyphenation file here. -% -\def\documentlanguage{\parsearg\dodocumentlanguage} -\def\dodocumentlanguage#1{% - \tex % read txi-??.tex file in plain TeX. - % Read the file if it exists. - \openin 1 txi-#1.tex - \ifeof1 - \errhelp = \nolanghelp - \errmessage{Cannot read language file txi-#1.tex}% - \let\temp = \relax - \else - \def\temp{\input txi-#1.tex }% - \fi - \temp - \endgroup -} -\newhelp\nolanghelp{The given language definition file cannot be found or -is empty. Maybe you need to install it? In the current directory -should work if nowhere else does.} - - -% @documentencoding should change something in TeX eventually, most -% likely, but for now just recognize it. -\let\documentencoding = \comment - - -% Page size parameters. -% -\newdimen\defaultparindent \defaultparindent = 15pt - -\chapheadingskip = 15pt plus 4pt minus 2pt -\secheadingskip = 12pt plus 3pt minus 2pt -\subsecheadingskip = 9pt plus 2pt minus 2pt - -% Prevent underfull vbox error messages. -\vbadness = 10000 - -% Don't be so finicky about underfull hboxes, either. -\hbadness = 2000 - -% Following George Bush, just get rid of widows and orphans. -\widowpenalty=10000 -\clubpenalty=10000 - -% Use TeX 3.0's \emergencystretch to help line breaking, but if we're -% using an old version of TeX, don't do anything. We want the amount of -% stretch added to depend on the line length, hence the dependence on -% \hsize. We call this whenever the paper size is set. -% -\def\setemergencystretch{% - \ifx\emergencystretch\thisisundefined - % Allow us to assign to \emergencystretch anyway. - \def\emergencystretch{\dimen0}% - \else - \emergencystretch = .15\hsize - \fi -} - -% Parameters in order: 1) textheight; 2) textwidth; 3) voffset; -% 4) hoffset; 5) binding offset; 6) topskip. Then whoever calls us can -% set \parskip and call \setleading for \baselineskip. -% -\def\internalpagesizes#1#2#3#4#5#6{% - \voffset = #3\relax - \topskip = #6\relax - \splittopskip = \topskip - % - \vsize = #1\relax - \advance\vsize by \topskip - \outervsize = \vsize - \advance\outervsize by 2\topandbottommargin - \pageheight = \vsize - % - \hsize = #2\relax - \outerhsize = \hsize - \advance\outerhsize by 0.5in - \pagewidth = \hsize - % - \normaloffset = #4\relax - \bindingoffset = #5\relax - % - \parindent = \defaultparindent - \setemergencystretch -} - -% @letterpaper (the default). -\def\letterpaper{{\globaldefs = 1 - \parskip = 3pt plus 2pt minus 1pt - \setleading{13.2pt}% - % - % If page is nothing but text, make it come out even. - \internalpagesizes{46\baselineskip}{6in}{\voffset}{.25in}{\bindingoffset}{36pt}% -}} - -% Use @smallbook to reset parameters for 7x9.5 (or so) format. -\def\smallbook{{\globaldefs = 1 - \parskip = 2pt plus 1pt - \setleading{12pt}% - % - \internalpagesizes{7.5in}{5.in}{\voffset}{.25in}{\bindingoffset}{16pt}% - % - \lispnarrowing = 0.3in - \tolerance = 700 - \hfuzz = 1pt - \contentsrightmargin = 0pt - \deftypemargin = 0pt - \defbodyindent = .5cm - % - \let\smalldisplay = \smalldisplayx - \let\smallexample = \smalllispx - \let\smallformat = \smallformatx - \let\smalllisp = \smalllispx -}} - -% Use @afourpaper to print on European A4 paper. -\def\afourpaper{{\globaldefs = 1 - \setleading{12pt}% - \parskip = 3pt plus 2pt minus 1pt - % - \internalpagesizes{53\baselineskip}{160mm}{\voffset}{4mm}{\bindingoffset}{44pt}% - % - \tolerance = 700 - \hfuzz = 1pt -}} - -% A specific text layout, 24x15cm overall, intended for A4 paper. Top margin -% 29mm, hence bottom margin 28mm, nominal side margin 3cm. -\def\afourlatex{{\globaldefs = 1 - \setleading{13.6pt}% - % - \afourpaper - \internalpagesizes{237mm}{150mm}{3.6mm}{3.6mm}{3mm}{7mm}% - % - \globaldefs = 0 -}} - -% Use @afourwide to print on European A4 paper in wide format. -\def\afourwide{% - \afourpaper - \internalpagesizes{6.5in}{9.5in}{\hoffset}{\normaloffset}{\bindingoffset}{7mm}% - % - \globaldefs = 0 -} - -% @pagesizes TEXTHEIGHT[,TEXTWIDTH] -% Perhaps we should allow setting the margins, \topskip, \parskip, -% and/or leading, also. Or perhaps we should compute them somehow. -% -\def\pagesizes{\parsearg\pagesizesxxx} -\def\pagesizesxxx#1{\pagesizesyyy #1,,\finish} -\def\pagesizesyyy#1,#2,#3\finish{{% - \setbox0 = \hbox{\ignorespaces #2}\ifdim\wd0 > 0pt \hsize=#2\relax \fi - \globaldefs = 1 - % - \parskip = 3pt plus 2pt minus 1pt - \setleading{13.2pt}% - % - \internalpagesizes{#1}{\hsize}{\voffset}{\normaloffset}{\bindingoffset}{44pt}% -}} - -% Set default to letter. -% -\letterpaper - - -\message{and turning on texinfo input format.} - -% Define macros to output various characters with catcode for normal text. -\catcode`\"=\other -\catcode`\~=\other -\catcode`\^=\other -\catcode`\_=\other -\catcode`\|=\other -\catcode`\<=\other -\catcode`\>=\other -\catcode`\+=\other -\catcode`\$=\other -\def\normaldoublequote{"} -\def\normaltilde{~} -\def\normalcaret{^} -\def\normalunderscore{_} -\def\normalverticalbar{|} -\def\normalless{<} -\def\normalgreater{>} -\def\normalplus{+} -\def\normaldollar{$} - -% This macro is used to make a character print one way in ttfont -% where it can probably just be output, and another way in other fonts, -% where something hairier probably needs to be done. -% -% #1 is what to print if we are indeed using \tt; #2 is what to print -% otherwise. Since all the Computer Modern typewriter fonts have zero -% interword stretch (and shrink), and it is reasonable to expect all -% typewriter fonts to have this, we can check that font parameter. -% -\def\ifusingtt#1#2{\ifdim \fontdimen3\font=0pt #1\else #2\fi} - -% Same as above, but check for italic font. Actually this also catches -% non-italic slanted fonts since it is impossible to distinguish them from -% italic fonts. But since this is only used by $ and it uses \sl anyway -% this is not a problem. -\def\ifusingit#1#2{\ifdim \fontdimen1\font>0pt #1\else #2\fi} - -% Turn off all special characters except @ -% (and those which the user can use as if they were ordinary). -% Most of these we simply print from the \tt font, but for some, we can -% use math or other variants that look better in normal text. - -\catcode`\"=\active -\def\activedoublequote{{\tt\char34}} -\let"=\activedoublequote -\catcode`\~=\active -\def~{{\tt\char126}} -\chardef\hat=`\^ -\catcode`\^=\active -\def^{{\tt \hat}} - -\catcode`\_=\active -\def_{\ifusingtt\normalunderscore\_} -% Subroutine for the previous macro. -\def\_{\leavevmode \kern.06em \vbox{\hrule width.3em height.1ex}} - -\catcode`\|=\active -\def|{{\tt\char124}} -\chardef \less=`\< -\catcode`\<=\active -\def<{{\tt \less}} -\chardef \gtr=`\> -\catcode`\>=\active -\def>{{\tt \gtr}} -\catcode`\+=\active -\def+{{\tt \char 43}} -\catcode`\$=\active -\def${\ifusingit{{\sl\$}}\normaldollar} -%\catcode 27=\active -%\def^^[{$\diamondsuit$} - -% Set up an active definition for =, but don't enable it most of the time. -{\catcode`\==\active -\global\def={{\tt \char 61}}} - -\catcode`+=\active -\catcode`\_=\active - -% If a .fmt file is being used, characters that might appear in a file -% name cannot be active until we have parsed the command line. -% So turn them off again, and have \everyjob (or @setfilename) turn them on. -% \otherifyactive is called near the end of this file. -\def\otherifyactive{\catcode`+=\other \catcode`\_=\other} - -\catcode`\@=0 - -% \rawbackslashxx output one backslash character in current font -\global\chardef\rawbackslashxx=`\\ -%{\catcode`\\=\other -%@gdef@rawbackslashxx{\}} - -% \rawbackslash redefines \ as input to do \rawbackslashxx. -{\catcode`\\=\active -@gdef@rawbackslash{@let\=@rawbackslashxx }} - -% \normalbackslash outputs one backslash in fixed width font. -\def\normalbackslash{{\tt\rawbackslashxx}} - -% \catcode 17=0 % Define control-q -\catcode`\\=\active - -% Used sometimes to turn off (effectively) the active characters -% even after parsing them. -@def@turnoffactive{@let"=@normaldoublequote -@let\=@realbackslash -@let~=@normaltilde -@let^=@normalcaret -@let_=@normalunderscore -@let|=@normalverticalbar -@let<=@normalless -@let>=@normalgreater -@let+=@normalplus -@let$=@normaldollar} - -@def@normalturnoffactive{@let"=@normaldoublequote -@let\=@normalbackslash -@let~=@normaltilde -@let^=@normalcaret -@let_=@normalunderscore -@let|=@normalverticalbar -@let<=@normalless -@let>=@normalgreater -@let+=@normalplus -@let$=@normaldollar} - -% Make _ and + \other characters, temporarily. -% This is canceled by @fixbackslash. -@otherifyactive - -% If a .fmt file is being used, we don't want the `\input texinfo' to show up. -% That is what \eatinput is for; after that, the `\' should revert to printing -% a backslash. -% -@gdef@eatinput input texinfo{@fixbackslash} -@global@let\ = @eatinput - -% On the other hand, perhaps the file did not have a `\input texinfo'. Then -% the first `\{ in the file would cause an error. This macro tries to fix -% that, assuming it is called before the first `\' could plausibly occur. -% Also back turn on active characters that might appear in the input -% file name, in case not using a pre-dumped format. -% -@gdef@fixbackslash{% - @ifx\@eatinput @let\ = @normalbackslash @fi - @catcode`+=@active - @catcode`@_=@active -} - -% Say @foo, not \foo, in error messages. -@escapechar = `@@ - -% These look ok in all fonts, so just make them not special. -@catcode`@& = @other -@catcode`@# = @other -@catcode`@% = @other - -@c Set initial fonts. -@textfonts -@rm - - -@c Local variables: -@c eval: (add-hook 'write-file-hooks 'time-stamp) -@c page-delimiter: "^\\\\message" -@c time-stamp-start: "def\\\\texinfoversion{" -@c time-stamp-format: "%:y-%02m-%02d.%02H" -@c time-stamp-end: "}" -@c End: diff --git a/gcc/tm.texi b/gcc/tm.texi deleted file mode 100644 index 2e90a6f6095..00000000000 --- a/gcc/tm.texi +++ /dev/null @@ -1,8494 +0,0 @@ -@c Copyright (C) 1988,1989,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001 -@c Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@node Target Macros -@chapter Target Description Macros -@cindex machine description macros -@cindex target description macros -@cindex macros, target description -@cindex @file{tm.h} macros - -In addition to the file @file{@var{machine}.md}, a machine description -includes a C header file conventionally given the name -@file{@var{machine}.h}. This header file defines numerous macros -that convey the information about the target machine that does not fit -into the scheme of the @file{.md} file. The file @file{tm.h} should be -a link to @file{@var{machine}.h}. The header file @file{config.h} -includes @file{tm.h} and most compiler source files include -@file{config.h}. - -@menu -* Driver:: Controlling how the driver runs the compilation passes. -* Run-time Target:: Defining @samp{-m} options like @samp{-m68000} and @samp{-m68020}. -* Per-Function Data:: Defining data structures for per-function information. -* Storage Layout:: Defining sizes and alignments of data. -* Type Layout:: Defining sizes and properties of basic user data types. -* Registers:: Naming and describing the hardware registers. -* Register Classes:: Defining the classes of hardware registers. -* Stack and Calling:: Defining which way the stack grows and by how much. -* Varargs:: Defining the varargs macros. -* Trampolines:: Code set up at run time to enter a nested function. -* Library Calls:: Controlling how library routines are implicitly called. -* Addressing Modes:: Defining addressing modes valid for memory operands. -* Condition Code:: Defining how insns update the condition code. -* Costs:: Defining relative costs of different operations. -* Sections:: Dividing storage into text, data, and other sections. -* PIC:: Macros for position independent code. -* Assembler Format:: Defining how to write insns and pseudo-ops to output. -* Debugging Info:: Defining the format of debugging output. -* Cross-compilation:: Handling floating point for cross-compilers. -* Mode Switching:: Insertion of mode-switching instructions. -* Misc:: Everything else. -@end menu - -@node Driver -@section Controlling the Compilation Driver, @file{gcc} -@cindex driver -@cindex controlling the compilation driver - -@c prevent bad page break with this line -You can control the compilation driver. - -@table @code -@findex SWITCH_TAKES_ARG -@item SWITCH_TAKES_ARG (@var{char}) -A C expression which determines whether the option @samp{-@var{char}} -takes arguments. The value should be the number of arguments that -option takes--zero, for many options. - -By default, this macro is defined as -@code{DEFAULT_SWITCH_TAKES_ARG}, which handles the standard options -properly. You need not define @code{SWITCH_TAKES_ARG} unless you -wish to add additional options which take arguments. Any redefinition -should call @code{DEFAULT_SWITCH_TAKES_ARG} and then check for -additional options. - -@findex WORD_SWITCH_TAKES_ARG -@item WORD_SWITCH_TAKES_ARG (@var{name}) -A C expression which determines whether the option @samp{-@var{name}} -takes arguments. The value should be the number of arguments that -option takes--zero, for many options. This macro rather than -@code{SWITCH_TAKES_ARG} is used for multi-character option names. - -By default, this macro is defined as -@code{DEFAULT_WORD_SWITCH_TAKES_ARG}, which handles the standard options -properly. You need not define @code{WORD_SWITCH_TAKES_ARG} unless you -wish to add additional options which take arguments. Any redefinition -should call @code{DEFAULT_WORD_SWITCH_TAKES_ARG} and then check for -additional options. - -@findex SWITCH_CURTAILS_COMPILATION -@item SWITCH_CURTAILS_COMPILATION (@var{char}) -A C expression which determines whether the option @samp{-@var{char}} -stops compilation before the generation of an executable. The value is -boolean, non-zero if the option does stop an executable from being -generated, zero otherwise. - -By default, this macro is defined as -@code{DEFAULT_SWITCH_CURTAILS_COMPILATION}, which handles the standard -options properly. You need not define -@code{SWITCH_CURTAILS_COMPILATION} unless you wish to add additional -options which affect the generation of an executable. Any redefinition -should call @code{DEFAULT_SWITCH_CURTAILS_COMPILATION} and then check -for additional options. - -@findex SWITCHES_NEED_SPACES -@item SWITCHES_NEED_SPACES -A string-valued C expression which enumerates the options for which -the linker needs a space between the option and its argument. - -If this macro is not defined, the default value is @code{""}. - -@findex CPP_SPEC -@item CPP_SPEC -A C string constant that tells the GCC driver program options to -pass to CPP. It can also specify how to translate options you -give to GCC into options for GCC to pass to the CPP. - -Do not define this macro if it does not need to do anything. - -@findex CPLUSPLUS_CPP_SPEC -@item CPLUSPLUS_CPP_SPEC -This macro is just like @code{CPP_SPEC}, but is used for C++, rather -than C. If you do not define this macro, then the value of -@code{CPP_SPEC} (if any) will be used instead. - -@findex NO_BUILTIN_SIZE_TYPE -@item NO_BUILTIN_SIZE_TYPE -If this macro is defined, the preprocessor will not define the builtin macro -@code{__SIZE_TYPE__}. The macro @code{__SIZE_TYPE__} must then be defined -by @code{CPP_SPEC} instead. - -This should be defined if @code{SIZE_TYPE} depends on target dependent flags -which are not accessible to the preprocessor. Otherwise, it should not -be defined. - -@findex NO_BUILTIN_PTRDIFF_TYPE -@item NO_BUILTIN_PTRDIFF_TYPE -If this macro is defined, the preprocessor will not define the builtin macro -@code{__PTRDIFF_TYPE__}. The macro @code{__PTRDIFF_TYPE__} must then be -defined by @code{CPP_SPEC} instead. - -This should be defined if @code{PTRDIFF_TYPE} depends on target dependent flags -which are not accessible to the preprocessor. Otherwise, it should not -be defined. - -@findex NO_BUILTIN_WCHAR_TYPE -@item NO_BUILTIN_WCHAR_TYPE -If this macro is defined, the preprocessor will not define the builtin macro -@code{__WCHAR_TYPE__}. The macro @code{__WCHAR_TYPE__} must then be -defined by @code{CPP_SPEC} instead. - -This should be defined if @code{WCHAR_TYPE} depends on target dependent flags -which are not accessible to the preprocessor. Otherwise, it should not -be defined. - -@findex NO_BUILTIN_WINT_TYPE -@item NO_BUILTIN_WINT_TYPE -If this macro is defined, the preprocessor will not define the builtin macro -@code{__WINT_TYPE__}. The macro @code{__WINT_TYPE__} must then be -defined by @code{CPP_SPEC} instead. - -This should be defined if @code{WINT_TYPE} depends on target dependent flags -which are not accessible to the preprocessor. Otherwise, it should not -be defined. - -@findex SIGNED_CHAR_SPEC -@item SIGNED_CHAR_SPEC -A C string constant that tells the GCC driver program options to -pass to CPP. By default, this macro is defined to pass the option -@samp{-D__CHAR_UNSIGNED__} to CPP if @code{char} will be treated as -@code{unsigned char} by @code{cc1}. - -Do not define this macro unless you need to override the default -definition. - -@findex CC1_SPEC -@item CC1_SPEC -A C string constant that tells the GCC driver program options to -pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language -front ends. -It can also specify how to translate options you give to GCC into options -for GCC to pass to front ends.. - -Do not define this macro if it does not need to do anything. - -@findex CC1PLUS_SPEC -@item CC1PLUS_SPEC -A C string constant that tells the GCC driver program options to -pass to @code{cc1plus}. It can also specify how to translate options you -give to GCC into options for GCC to pass to the @code{cc1plus}. - -Do not define this macro if it does not need to do anything. -Note that everything defined in CC1_SPEC is already passed to -@code{cc1plus} so there is no need to duplicate the contents of -CC1_SPEC in CC1PLUS_SPEC. - -@findex ASM_SPEC -@item ASM_SPEC -A C string constant that tells the GCC driver program options to -pass to the assembler. It can also specify how to translate options -you give to GCC into options for GCC to pass to the assembler. -See the file @file{sun3.h} for an example of this. - -Do not define this macro if it does not need to do anything. - -@findex ASM_FINAL_SPEC -@item ASM_FINAL_SPEC -A C string constant that tells the GCC driver program how to -run any programs which cleanup after the normal assembler. -Normally, this is not needed. See the file @file{mips.h} for -an example of this. - -Do not define this macro if it does not need to do anything. - -@findex LINK_SPEC -@item LINK_SPEC -A C string constant that tells the GCC driver program options to -pass to the linker. It can also specify how to translate options you -give to GCC into options for GCC to pass to the linker. - -Do not define this macro if it does not need to do anything. - -@findex LIB_SPEC -@item LIB_SPEC -Another C string constant used much like @code{LINK_SPEC}. The difference -between the two is that @code{LIB_SPEC} is used at the end of the -command given to the linker. - -If this macro is not defined, a default is provided that -loads the standard C library from the usual place. See @file{gcc.c}. - -@findex LIBGCC_SPEC -@item LIBGCC_SPEC -Another C string constant that tells the GCC driver program -how and when to place a reference to @file{libgcc.a} into the -linker command line. This constant is placed both before and after -the value of @code{LIB_SPEC}. - -If this macro is not defined, the GCC driver provides a default that -passes the string @samp{-lgcc} to the linker. - -@findex STARTFILE_SPEC -@item STARTFILE_SPEC -Another C string constant used much like @code{LINK_SPEC}. The -difference between the two is that @code{STARTFILE_SPEC} is used at -the very beginning of the command given to the linker. - -If this macro is not defined, a default is provided that loads the -standard C startup file from the usual place. See @file{gcc.c}. - -@findex ENDFILE_SPEC -@item ENDFILE_SPEC -Another C string constant used much like @code{LINK_SPEC}. The -difference between the two is that @code{ENDFILE_SPEC} is used at -the very end of the command given to the linker. - -Do not define this macro if it does not need to do anything. - -@findex THREAD_MODEL_SPEC -@item THREAD_MODEL_SPEC -GCC @code{-v} will print the thread model GCC was configured to use. -However, this doesn't work on platforms that are multilibbed on thread -models, such as AIX 4.3. On such platforms, define -@code{THREAD_MODEL_SPEC} such that it evaluates to a string without -blanks that names one of the recognized thread models. @code{%*}, the -default value of this macro, will expand to the value of -@code{thread_file} set in @file{config.gcc}. - -@findex EXTRA_SPECS -@item EXTRA_SPECS -Define this macro to provide additional specifications to put in the -@file{specs} file that can be used in various specifications like -@code{CC1_SPEC}. - -The definition should be an initializer for an array of structures, -containing a string constant, that defines the specification name, and a -string constant that provides the specification. - -Do not define this macro if it does not need to do anything. - -@code{EXTRA_SPECS} is useful when an architecture contains several -related targets, which have various @code{..._SPECS} which are similar -to each other, and the maintainer would like one central place to keep -these definitions. - -For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to -define either @code{_CALL_SYSV} when the System V calling sequence is -used or @code{_CALL_AIX} when the older AIX-based calling sequence is -used. - -The @file{config/rs6000/rs6000.h} target file defines: - -@example -#define EXTRA_SPECS \ - @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @}, - -#define CPP_SYS_DEFAULT "" -@end example - -The @file{config/rs6000/sysv.h} target file defines: -@smallexample -#undef CPP_SPEC -#define CPP_SPEC \ -"%@{posix: -D_POSIX_SOURCE @} \ -%@{mcall-sysv: -D_CALL_SYSV @} %@{mcall-aix: -D_CALL_AIX @} \ -%@{!mcall-sysv: %@{!mcall-aix: %(cpp_sysv_default) @}@} \ -%@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}" - -#undef CPP_SYSV_DEFAULT -#define CPP_SYSV_DEFAULT "-D_CALL_SYSV" -@end smallexample - -while the @file{config/rs6000/eabiaix.h} target file defines -@code{CPP_SYSV_DEFAULT} as: - -@smallexample -#undef CPP_SYSV_DEFAULT -#define CPP_SYSV_DEFAULT "-D_CALL_AIX" -@end smallexample - -@findex LINK_LIBGCC_SPECIAL -@item LINK_LIBGCC_SPECIAL -Define this macro if the driver program should find the library -@file{libgcc.a} itself and should not pass @samp{-L} options to the -linker. If you do not define this macro, the driver program will pass -the argument @samp{-lgcc} to tell the linker to do the search and will -pass @samp{-L} options to it. - -@findex LINK_LIBGCC_SPECIAL_1 -@item LINK_LIBGCC_SPECIAL_1 -Define this macro if the driver program should find the library -@file{libgcc.a}. If you do not define this macro, the driver program will pass -the argument @samp{-lgcc} to tell the linker to do the search. -This macro is similar to @code{LINK_LIBGCC_SPECIAL}, except that it does -not affect @samp{-L} options. - -@findex LINK_COMMAND_SPEC -@item LINK_COMMAND_SPEC -A C string constant giving the complete command line need to execute the -linker. When you do this, you will need to update your port each time a -change is made to the link command line within @file{gcc.c}. Therefore, -define this macro only if you need to completely redefine the command -line for invoking the linker and there is no other way to accomplish -the effect you need. - -@findex LINK_ELIMINATE_DUPLICATE_LDIRECTORIES -@item LINK_ELIMINATE_DUPLICATE_LDIRECTORIES -A nonzero value causes collect2 to remove duplicate -L search -directories from linking commands. Do not give it a nonzero value if -removing duplicate search directories changes the linker's semantics. - -@findex MULTILIB_DEFAULTS -@item MULTILIB_DEFAULTS -Define this macro as a C expression for the initializer of an array of -string to tell the driver program which options are defaults for this -target and thus do not need to be handled specially when using -@code{MULTILIB_OPTIONS}. - -Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in -the target makefile fragment or if none of the options listed in -@code{MULTILIB_OPTIONS} are set by default. -@xref{Target Fragment}. - -@findex RELATIVE_PREFIX_NOT_LINKDIR -@item RELATIVE_PREFIX_NOT_LINKDIR -Define this macro to tell @code{gcc} that it should only translate -a @samp{-B} prefix into a @samp{-L} linker option if the prefix -indicates an absolute file name. - -@findex STANDARD_EXEC_PREFIX -@item STANDARD_EXEC_PREFIX -Define this macro as a C string constant if you wish to override the -standard choice of @file{/usr/local/lib/gcc-lib/} as the default prefix to -try when searching for the executable files of the compiler. - -@findex MD_EXEC_PREFIX -@item MD_EXEC_PREFIX -If defined, this macro is an additional prefix to try after -@code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched -when the @samp{-b} option is used, or the compiler is built as a cross -compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it -to the list of directories used to find the assembler in @file{configure.in}. - -@findex STANDARD_STARTFILE_PREFIX -@item STANDARD_STARTFILE_PREFIX -Define this macro as a C string constant if you wish to override the -standard choice of @file{/usr/local/lib/} as the default prefix to -try when searching for startup files such as @file{crt0.o}. - -@findex MD_STARTFILE_PREFIX -@item MD_STARTFILE_PREFIX -If defined, this macro supplies an additional prefix to try after the -standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the -@samp{-b} option is used, or when the compiler is built as a cross -compiler. - -@findex MD_STARTFILE_PREFIX_1 -@item MD_STARTFILE_PREFIX_1 -If defined, this macro supplies yet another prefix to try after the -standard prefixes. It is not searched when the @samp{-b} option is -used, or when the compiler is built as a cross compiler. - -@findex INIT_ENVIRONMENT -@item INIT_ENVIRONMENT -Define this macro as a C string constant if you wish to set environment -variables for programs called by the driver, such as the assembler and -loader. The driver passes the value of this macro to @code{putenv} to -initialize the necessary environment variables. - -@findex LOCAL_INCLUDE_DIR -@item LOCAL_INCLUDE_DIR -Define this macro as a C string constant if you wish to override the -standard choice of @file{/usr/local/include} as the default prefix to -try when searching for local header files. @code{LOCAL_INCLUDE_DIR} -comes before @code{SYSTEM_INCLUDE_DIR} in the search order. - -Cross compilers do not use this macro and do not search either -@file{/usr/local/include} or its replacement. - -@findex MODIFY_TARGET_NAME -@item MODIFY_TARGET_NAME -Define this macro if you with to define command-line switches that modify the -default target name - -For each switch, you can include a string to be appended to the first -part of the configuration name or a string to be deleted from the -configuration name, if present. The definition should be an initializer -for an array of structures. Each array element should have three -elements: the switch name (a string constant, including the initial -dash), one of the enumeration codes @code{ADD} or @code{DELETE} to -indicate whether the string should be inserted or deleted, and the string -to be inserted or deleted (a string constant). - -For example, on a machine where @samp{64} at the end of the -configuration name denotes a 64-bit target and you want the @samp{-32} -and @samp{-64} switches to select between 32- and 64-bit targets, you would -code - -@smallexample -#define MODIFY_TARGET_NAME \ - @{ @{ "-32", DELETE, "64"@}, \ - @{"-64", ADD, "64"@}@} -@end smallexample - - -@findex SYSTEM_INCLUDE_DIR -@item SYSTEM_INCLUDE_DIR -Define this macro as a C string constant if you wish to specify a -system-specific directory to search for header files before the standard -directory. @code{SYSTEM_INCLUDE_DIR} comes before -@code{STANDARD_INCLUDE_DIR} in the search order. - -Cross compilers do not use this macro and do not search the directory -specified. - -@findex STANDARD_INCLUDE_DIR -@item STANDARD_INCLUDE_DIR -Define this macro as a C string constant if you wish to override the -standard choice of @file{/usr/include} as the default prefix to -try when searching for header files. - -Cross compilers do not use this macro and do not search either -@file{/usr/include} or its replacement. - -@findex STANDARD_INCLUDE_COMPONENT -@item STANDARD_INCLUDE_COMPONENT -The ``component'' corresponding to @code{STANDARD_INCLUDE_DIR}. -See @code{INCLUDE_DEFAULTS}, below, for the description of components. -If you do not define this macro, no component is used. - -@findex INCLUDE_DEFAULTS -@item INCLUDE_DEFAULTS -Define this macro if you wish to override the entire default search path -for include files. For a native compiler, the default search path -usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR}, -@code{SYSTEM_INCLUDE_DIR}, @code{GPLUSPLUS_INCLUDE_DIR}, and -@code{STANDARD_INCLUDE_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR} -and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile}, -and specify private search areas for GCC. The directory -@code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs. - -The definition should be an initializer for an array of structures. -Each array element should have four elements: the directory name (a -string constant), the component name (also a string constant), a flag -for C++-only directories, -and a flag showing that the includes in the directory don't need to be -wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of -the array with a null element. - -The component name denotes what GNU package the include file is part of, -if any, in all upper-case letters. For example, it might be @samp{GCC} -or @samp{BINUTILS}. If the package is part of a vendor-supplied -operating system, code the component name as @samp{0}. - -For example, here is the definition used for VAX/VMS: - -@example -#define INCLUDE_DEFAULTS \ -@{ \ - @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \ - @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \ - @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \ - @{ ".", 0, 0, 0@}, \ - @{ 0, 0, 0, 0@} \ -@} -@end example -@end table - -Here is the order of prefixes tried for exec files: - -@enumerate -@item -Any prefixes specified by the user with @samp{-B}. - -@item -The environment variable @code{GCC_EXEC_PREFIX}, if any. - -@item -The directories specified by the environment variable @code{COMPILER_PATH}. - -@item -The macro @code{STANDARD_EXEC_PREFIX}. - -@item -@file{/usr/lib/gcc/}. - -@item -The macro @code{MD_EXEC_PREFIX}, if any. -@end enumerate - -Here is the order of prefixes tried for startfiles: - -@enumerate -@item -Any prefixes specified by the user with @samp{-B}. - -@item -The environment variable @code{GCC_EXEC_PREFIX}, if any. - -@item -The directories specified by the environment variable @code{LIBRARY_PATH} -(or port-specific name; native only, cross compilers do not use this). - -@item -The macro @code{STANDARD_EXEC_PREFIX}. - -@item -@file{/usr/lib/gcc/}. - -@item -The macro @code{MD_EXEC_PREFIX}, if any. - -@item -The macro @code{MD_STARTFILE_PREFIX}, if any. - -@item -The macro @code{STANDARD_STARTFILE_PREFIX}. - -@item -@file{/lib/}. - -@item -@file{/usr/lib/}. -@end enumerate - -@node Run-time Target -@section Run-time Target Specification -@cindex run-time target specification -@cindex predefined macros -@cindex target specifications - -@c prevent bad page break with this line -Here are run-time target specifications. - -@table @code -@findex CPP_PREDEFINES -@item CPP_PREDEFINES -Define this to be a string constant containing @samp{-D} options to -define the predefined macros that identify this machine and system. -These macros will be predefined unless the @option{-ansi} option (or a -@option{-std} option for strict ISO C conformance) is specified. - -In addition, a parallel set of macros are predefined, whose names are -made by appending @samp{__} at the beginning and at the end. These -@samp{__} macros are permitted by the ISO standard, so they are -predefined regardless of whether @option{-ansi} or a @option{-std} option -is specified. - -For example, on the Sun, one can use the following value: - -@smallexample -"-Dmc68000 -Dsun -Dunix" -@end smallexample - -The result is to define the macros @code{__mc68000__}, @code{__sun__} -and @code{__unix__} unconditionally, and the macros @code{mc68000}, -@code{sun} and @code{unix} provided @samp{-ansi} is not specified. - -@findex extern int target_flags -@item extern int target_flags; -This declaration should be present. - -@cindex optional hardware or system features -@cindex features, optional, in system conventions -@item TARGET_@dots{} -This series of macros is to allow compiler command arguments to -enable or disable the use of optional features of the target machine. -For example, one machine description serves both the 68000 and -the 68020; a command argument tells the compiler whether it should -use 68020-only instructions or not. This command argument works -by means of a macro @code{TARGET_68020} that tests a bit in -@code{target_flags}. - -Define a macro @code{TARGET_@var{featurename}} for each such option. -Its definition should test a bit in @code{target_flags}. It is -recommended that a helper macro @code{TARGET_MASK_@var{featurename}} -is defined for each bit-value to test, and used in -@code{TARGET_@var{featurename}} and @code{TARGET_SWITCHES}. For -example: - -@smallexample -#define TARGET_MASK_68020 1 -#define TARGET_68020 (target_flags & TARGET_MASK_68020) -@end smallexample - -One place where these macros are used is in the condition-expressions -of instruction patterns. Note how @code{TARGET_68020} appears -frequently in the 68000 machine description file, @file{m68k.md}. -Another place they are used is in the definitions of the other -macros in the @file{@var{machine}.h} file. - -@findex TARGET_SWITCHES -@item TARGET_SWITCHES -This macro defines names of command options to set and clear -bits in @code{target_flags}. Its definition is an initializer -with a subgrouping for each command option. - -Each subgrouping contains a string constant, that defines the option -name, a number, which contains the bits to set in -@code{target_flags}, and a second string which is the description -displayed by --help. If the number is negative then the bits specified -by the number are cleared instead of being set. If the description -string is present but empty, then no help information will be displayed -for that option, but it will not count as an undocumented option. The -actual option name is made by appending @samp{-m} to the specified name. - -One of the subgroupings should have a null string. The number in -this grouping is the default value for @code{target_flags}. Any -target options act starting with that value. - -Here is an example which defines @samp{-m68000} and @samp{-m68020} -with opposite meanings, and picks the latter as the default: - -@smallexample -#define TARGET_SWITCHES \ - @{ @{ "68020", TARGET_MASK_68020, "" @}, \ - @{ "68000", -TARGET_MASK_68020, "Compile for the 68000" @}, \ - @{ "", TARGET_MASK_68020, "" @}@} -@end smallexample - -@findex TARGET_OPTIONS -@item TARGET_OPTIONS -This macro is similar to @code{TARGET_SWITCHES} but defines names of command -options that have values. Its definition is an initializer with a -subgrouping for each command option. - -Each subgrouping contains a string constant, that defines the fixed part -of the option name, the address of a variable, and a description string. -The variable, type @code{char *}, is set to the variable part of the -given option if the fixed part matches. The actual option name is made -by appending @samp{-m} to the specified name. - -Here is an example which defines @samp{-mshort-data-@var{number}}. If the -given option is @samp{-mshort-data-512}, the variable @code{m88k_short_data} -will be set to the string @code{"512"}. - -@smallexample -extern char *m88k_short_data; -#define TARGET_OPTIONS \ - @{ @{ "short-data-", &m88k_short_data, "Specify the size of the short data section" @} @} -@end smallexample - -@findex TARGET_VERSION -@item TARGET_VERSION -This macro is a C statement to print on @code{stderr} a string -describing the particular machine description choice. Every machine -description should define @code{TARGET_VERSION}. For example: - -@smallexample -#ifdef MOTOROLA -#define TARGET_VERSION \ - fprintf (stderr, " (68k, Motorola syntax)"); -#else -#define TARGET_VERSION \ - fprintf (stderr, " (68k, MIT syntax)"); -#endif -@end smallexample - -@findex OVERRIDE_OPTIONS -@item OVERRIDE_OPTIONS -Sometimes certain combinations of command options do not make sense on -a particular target machine. You can define a macro -@code{OVERRIDE_OPTIONS} to take account of this. This macro, if -defined, is executed once just after all the command options have been -parsed. - -Don't use this macro to turn on various extra optimizations for -@samp{-O}. That is what @code{OPTIMIZATION_OPTIONS} is for. - -@findex OPTIMIZATION_OPTIONS -@item OPTIMIZATION_OPTIONS (@var{level}, @var{size}) -Some machines may desire to change what optimizations are performed for -various optimization levels. This macro, if defined, is executed once -just after the optimization level is determined and before the remainder -of the command options have been parsed. Values set in this macro are -used as the default values for the other command line options. - -@var{level} is the optimization level specified; 2 if @samp{-O2} is -specified, 1 if @samp{-O} is specified, and 0 if neither is specified. - -@var{size} is non-zero if @samp{-Os} is specified and zero otherwise. - -You should not use this macro to change options that are not -machine-specific. These should uniformly selected by the same -optimization level on all supported machines. Use this macro to enable -machine-specific optimizations. - -@strong{Do not examine @code{write_symbols} in -this macro!} The debugging options are not supposed to alter the -generated code. - -@findex CAN_DEBUG_WITHOUT_FP -@item CAN_DEBUG_WITHOUT_FP -Define this macro if debugging can be performed even without a frame -pointer. If this macro is defined, GCC will turn on the -@samp{-fomit-frame-pointer} option whenever @samp{-O} is specified. -@end table - -@node Per-Function Data -@section Defining data structures for per-function information. -@cindex per-function data -@cindex data structures - -If the target needs to store information on a per-function basis, GCC -provides a macro and a couple of variables to allow this. Note, just -using statics to store the information is a bad idea, since GCC supports -nested functions, so you can be halfway through encoding one function -when another one comes along. - -GCC defines a data structure called @code{struct function} which -contains all of the data specific to an individual function. This -structure contains a field called @code{machine} whose type is -@code{struct machine_function *}, which can be used by targets to point -to their own specific data. - -If a target needs per-function specific data it should define the type -@code{struct machine_function} and also the macro -@code{INIT_EXPANDERS}. This macro should be used to initialise some or -all of the function pointers @code{init_machine_status}, -@code{free_machine_status} and @code{mark_machine_status}. These -pointers are explained below. - -One typical use of per-function, target specific data is to create an -RTX to hold the register containing the function's return address. This -RTX can then be used to implement the @code{__builtin_return_address} -function, for level 0. - -Note - earlier implementations of GCC used a single data area to hold -all of the per-function information. Thus when processing of a nested -function began the old per-function data had to be pushed onto a -stack, and when the processing was finished, it had to be popped off the -stack. GCC used to provide function pointers called -@code{save_machine_status} and @code{restore_machine_status} to handle -the saving and restoring of the target specific information. Since the -single data area approach is no longer used, these pointers are no -longer supported. - -The macro and function pointers are described below. - -@table @code -@findex INIT_EXPANDERS -@item INIT_EXPANDERS -Macro called to initialise any target specific information. This macro -is called once per function, before generation of any RTL has begun. -The intention of this macro is to allow the initialisation of the -function pointers below. - -@findex init_machine_status -@item init_machine_status -This is a @code{void (*)(struct function *)} function pointer. If this -pointer is non-NULL it will be called once per function, before function -compilation starts, in order to allow the target to perform any target -specific initialisation of the @code{struct function} structure. It is -intended that this would be used to initialise the @code{machine} of -that struture. - -@findex free_machine_status -@item free_machine_status -This is a @code{void (*)(struct function *)} function pointer. If this -pointer is non-NULL it will be called once per function, after the -function has been compiled, in order to allow any memory allocated -during the @code{init_machine_status} function call to be freed. - -@findex mark_machine_status -@item mark_machine_status -This is a @code{void (*)(struct function *)} function pointer. If this -pointer is non-NULL it will be called once per function in order to mark -any data items in the @code{struct machine_function} structure which -need garbage collection. - -@end table - -@node Storage Layout -@section Storage Layout -@cindex storage layout - -Note that the definitions of the macros in this table which are sizes or -alignments measured in bits do not need to be constant. They can be C -expressions that refer to static variables, such as the @code{target_flags}. -@xref{Run-time Target}. - -@table @code -@findex BITS_BIG_ENDIAN -@item BITS_BIG_ENDIAN -Define this macro to have the value 1 if the most significant bit in a -byte has the lowest number; otherwise define it to have the value zero. -This means that bit-field instructions count from the most significant -bit. If the machine has no bit-field instructions, then this must still -be defined, but it doesn't matter which value it is defined to. This -macro need not be a constant. - -This macro does not affect the way structure fields are packed into -bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}. - -@findex BYTES_BIG_ENDIAN -@item BYTES_BIG_ENDIAN -Define this macro to have the value 1 if the most significant byte in a -word has the lowest number. This macro need not be a constant. - -@findex WORDS_BIG_ENDIAN -@item WORDS_BIG_ENDIAN -Define this macro to have the value 1 if, in a multiword object, the -most significant word has the lowest number. This applies to both -memory locations and registers; GCC fundamentally assumes that the -order of words in memory is the same as the order in registers. This -macro need not be a constant. - -@findex LIBGCC2_WORDS_BIG_ENDIAN -@item LIBGCC2_WORDS_BIG_ENDIAN -Define this macro if WORDS_BIG_ENDIAN is not constant. This must be a -constant value with the same meaning as WORDS_BIG_ENDIAN, which will be -used only when compiling libgcc2.c. Typically the value will be set -based on preprocessor defines. - -@findex FLOAT_WORDS_BIG_ENDIAN -@item FLOAT_WORDS_BIG_ENDIAN -Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or -@code{TFmode} floating point numbers are stored in memory with the word -containing the sign bit at the lowest address; otherwise define it to -have the value 0. This macro need not be a constant. - -You need not define this macro if the ordering is the same as for -multi-word integers. - -@findex BITS_PER_UNIT -@item BITS_PER_UNIT -Define this macro to be the number of bits in an addressable storage -unit (byte); normally 8. - -@findex BITS_PER_WORD -@item BITS_PER_WORD -Number of bits in a word; normally 32. - -@findex MAX_BITS_PER_WORD -@item MAX_BITS_PER_WORD -Maximum number of bits in a word. If this is undefined, the default is -@code{BITS_PER_WORD}. Otherwise, it is the constant value that is the -largest value that @code{BITS_PER_WORD} can have at run-time. - -@findex UNITS_PER_WORD -@item UNITS_PER_WORD -Number of storage units in a word; normally 4. - -@findex MIN_UNITS_PER_WORD -@item MIN_UNITS_PER_WORD -Minimum number of units in a word. If this is undefined, the default is -@code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the -smallest value that @code{UNITS_PER_WORD} can have at run-time. - -@findex POINTER_SIZE -@item POINTER_SIZE -Width of a pointer, in bits. You must specify a value no wider than the -width of @code{Pmode}. If it is not equal to the width of @code{Pmode}, -you must define @code{POINTERS_EXTEND_UNSIGNED}. - -@findex POINTERS_EXTEND_UNSIGNED -@item POINTERS_EXTEND_UNSIGNED -A C expression whose value is nonzero if pointers that need to be -extended from being @code{POINTER_SIZE} bits wide to @code{Pmode} are to -be zero-extended and zero if they are to be sign-extended. - -You need not define this macro if the @code{POINTER_SIZE} is equal -to the width of @code{Pmode}. - -@findex PROMOTE_MODE -@item PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type}) -A macro to update @var{m} and @var{unsignedp} when an object whose type -is @var{type} and which has the specified mode and signedness is to be -stored in a register. This macro is only called when @var{type} is a -scalar type. - -On most RISC machines, which only have operations that operate on a full -register, define this macro to set @var{m} to @code{word_mode} if -@var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most -cases, only integer modes should be widened because wider-precision -floating-point operations are usually more expensive than their narrower -counterparts. - -For most machines, the macro definition does not change @var{unsignedp}. -However, some machines, have instructions that preferentially handle -either signed or unsigned quantities of certain modes. For example, on -the DEC Alpha, 32-bit loads from memory and 32-bit add instructions -sign-extend the result to 64 bits. On such machines, set -@var{unsignedp} according to which kind of extension is more efficient. - -Do not define this macro if it would never modify @var{m}. - -@findex PROMOTE_FUNCTION_ARGS -@item PROMOTE_FUNCTION_ARGS -Define this macro if the promotion described by @code{PROMOTE_MODE} -should also be done for outgoing function arguments. - -@findex PROMOTE_FUNCTION_RETURN -@item PROMOTE_FUNCTION_RETURN -Define this macro if the promotion described by @code{PROMOTE_MODE} -should also be done for the return value of functions. - -If this macro is defined, @code{FUNCTION_VALUE} must perform the same -promotions done by @code{PROMOTE_MODE}. - -@findex PROMOTE_FOR_CALL_ONLY -@item PROMOTE_FOR_CALL_ONLY -Define this macro if the promotion described by @code{PROMOTE_MODE} -should @emph{only} be performed for outgoing function arguments or -function return values, as specified by @code{PROMOTE_FUNCTION_ARGS} -and @code{PROMOTE_FUNCTION_RETURN}, respectively. - -@findex PARM_BOUNDARY -@item PARM_BOUNDARY -Normal alignment required for function parameters on the stack, in -bits. All stack parameters receive at least this much alignment -regardless of data type. On most machines, this is the same as the -size of an integer. - -@findex STACK_BOUNDARY -@item STACK_BOUNDARY -Define this macro if there is a guaranteed alignment for the stack -pointer on this machine. The definition is a C expression -for the desired alignment (measured in bits). This value is used as a -default if PREFERRED_STACK_BOUNDARY is not defined. - -@findex PREFERRED_STACK_BOUNDARY -@item PREFERRED_STACK_BOUNDARY -Define this macro if you wish to preserve a certain alignment for -the stack pointer. The definition is a C expression -for the desired alignment (measured in bits). If STACK_BOUNDARY is -also defined, this macro must evaluate to a value equal to or larger -than STACK_BOUNDARY. - -@cindex @code{PUSH_ROUNDING}, interaction with @code{PREFERRED_STACK_BOUNDARY} -If @code{PUSH_ROUNDING} is not defined, the stack will always be aligned -to the specified boundary. If @code{PUSH_ROUNDING} is defined and specifies -a less strict alignment than @code{PREFERRED_STACK_BOUNDARY}, the stack may -be momentarily unaligned while pushing arguments. - -@findex FUNCTION_BOUNDARY -@item FUNCTION_BOUNDARY -Alignment required for a function entry point, in bits. - -@findex BIGGEST_ALIGNMENT -@item BIGGEST_ALIGNMENT -Biggest alignment that any data type can require on this machine, in bits. - -@findex MINIMUM_ATOMIC_ALIGNMENT -@item MINIMUM_ATOMIC_ALIGNMENT -If defined, the smallest alignment, in bits, that can be given to an -object that can be referenced in one operation, without disturbing any -nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger -on machines that don't have byte or half-word store operations. - -@findex BIGGEST_FIELD_ALIGNMENT -@item BIGGEST_FIELD_ALIGNMENT -Biggest alignment that any structure or union field can require on this -machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for -structure and union fields only, unless the field alignment has been set -by the @code{__attribute__ ((aligned (@var{n})))} construct. - -@findex ADJUST_FIELD_ALIGN -@item ADJUST_FIELD_ALIGN (@var{field}, @var{computed}) -An expression for the alignment of a structure field @var{field} if the -alignment computed in the usual way is @var{computed}. GCC uses -this value instead of the value in @code{BIGGEST_ALIGNMENT} or -@code{BIGGEST_FIELD_ALIGNMENT}, if defined, for structure fields only. - -@findex MAX_OFILE_ALIGNMENT -@item MAX_OFILE_ALIGNMENT -Biggest alignment supported by the object file format of this machine. -Use this macro to limit the alignment which can be specified using the -@code{__attribute__ ((aligned (@var{n})))} construct. If not defined, -the default value is @code{BIGGEST_ALIGNMENT}. - -@findex DATA_ALIGNMENT -@item DATA_ALIGNMENT (@var{type}, @var{basic-align}) -If defined, a C expression to compute the alignment for a variable in -the static store. @var{type} is the data type, and @var{basic-align} is -the alignment that the object would ordinarily have. The value of this -macro is used instead of that alignment to align the object. - -If this macro is not defined, then @var{basic-align} is used. - -@findex strcpy -One use of this macro is to increase alignment of medium-size data to -make it all fit in fewer cache lines. Another is to cause character -arrays to be word-aligned so that @code{strcpy} calls that copy -constants to character arrays can be done inline. - -@findex CONSTANT_ALIGNMENT -@item CONSTANT_ALIGNMENT (@var{constant}, @var{basic-align}) -If defined, a C expression to compute the alignment given to a constant -that is being placed in memory. @var{constant} is the constant and -@var{basic-align} is the alignment that the object would ordinarily -have. The value of this macro is used instead of that alignment to -align the object. - -If this macro is not defined, then @var{basic-align} is used. - -The typical use of this macro is to increase alignment for string -constants to be word aligned so that @code{strcpy} calls that copy -constants can be done inline. - -@findex LOCAL_ALIGNMENT -@item LOCAL_ALIGNMENT (@var{type}, @var{basic-align}) -If defined, a C expression to compute the alignment for a variable in -the local store. @var{type} is the data type, and @var{basic-align} is -the alignment that the object would ordinarily have. The value of this -macro is used instead of that alignment to align the object. - -If this macro is not defined, then @var{basic-align} is used. - -One use of this macro is to increase alignment of medium-size data to -make it all fit in fewer cache lines. - -@findex EMPTY_FIELD_BOUNDARY -@item EMPTY_FIELD_BOUNDARY -Alignment in bits to be given to a structure bit field that follows an -empty field such as @code{int : 0;}. - -Note that @code{PCC_BITFIELD_TYPE_MATTERS} also affects the alignment -that results from an empty field. - -@findex STRUCTURE_SIZE_BOUNDARY -@item STRUCTURE_SIZE_BOUNDARY -Number of bits which any structure or union's size must be a multiple of. -Each structure or union's size is rounded up to a multiple of this. - -If you do not define this macro, the default is the same as -@code{BITS_PER_UNIT}. - -@findex STRICT_ALIGNMENT -@item STRICT_ALIGNMENT -Define this macro to be the value 1 if instructions will fail to work -if given data not on the nominal alignment. If instructions will merely -go slower in that case, define this macro as 0. - -@findex PCC_BITFIELD_TYPE_MATTERS -@item PCC_BITFIELD_TYPE_MATTERS -Define this if you wish to imitate the way many other C compilers handle -alignment of bitfields and the structures that contain them. - -The behavior is that the type written for a bitfield (@code{int}, -@code{short}, or other integer type) imposes an alignment for the -entire structure, as if the structure really did contain an ordinary -field of that type. In addition, the bitfield is placed within the -structure so that it would fit within such a field, not crossing a -boundary for it. - -Thus, on most machines, a bitfield whose type is written as @code{int} -would not cross a four-byte boundary, and would force four-byte -alignment for the whole structure. (The alignment used may not be four -bytes; it is controlled by the other alignment parameters.) - -If the macro is defined, its definition should be a C expression; -a nonzero value for the expression enables this behavior. - -Note that if this macro is not defined, or its value is zero, some -bitfields may cross more than one alignment boundary. The compiler can -support such references if there are @samp{insv}, @samp{extv}, and -@samp{extzv} insns that can directly reference memory. - -The other known way of making bitfields work is to define -@code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}. -Then every structure can be accessed with fullwords. - -Unless the machine has bitfield instructions or you define -@code{STRUCTURE_SIZE_BOUNDARY} that way, you must define -@code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value. - -If your aim is to make GCC use the same conventions for laying out -bitfields as are used by another compiler, here is how to investigate -what the other compiler does. Compile and run this program: - -@example -struct foo1 -@{ - char x; - char :0; - char y; -@}; - -struct foo2 -@{ - char x; - int :0; - char y; -@}; - -main () -@{ - printf ("Size of foo1 is %d\n", - sizeof (struct foo1)); - printf ("Size of foo2 is %d\n", - sizeof (struct foo2)); - exit (0); -@} -@end example - -If this prints 2 and 5, then the compiler's behavior is what you would -get from @code{PCC_BITFIELD_TYPE_MATTERS}. - -@findex BITFIELD_NBYTES_LIMITED -@item BITFIELD_NBYTES_LIMITED -Like PCC_BITFIELD_TYPE_MATTERS except that its effect is limited to -aligning a bitfield within the structure. - -@findex MEMBER_TYPE_FORCES_BLK -@item MEMBER_TYPE_FORCES_BLK (@var{field}) -Return 1 if a structure or array containing @var{field} should be accessed using -@code{BLKMODE}. - -Normally, this is not needed. See the file @file{c4x.h} for an example -of how to use this macro to prevent a structure having a floating point -field from being accessed in an integer mode. - -@findex ROUND_TYPE_SIZE -@item ROUND_TYPE_SIZE (@var{type}, @var{computed}, @var{specified}) -Define this macro as an expression for the overall size of a type -(given by @var{type} as a tree node) when the size computed in the -usual way is @var{computed} and the alignment is @var{specified}. - -The default is to round @var{computed} up to a multiple of @var{specified}. - -@findex ROUND_TYPE_SIZE_UNIT -@item ROUND_TYPE_SIZE_UNIT (@var{type}, @var{computed}, @var{specified}) -Similar to @code{ROUND_TYPE_SIZE}, but sizes and alignments are -specified in units (bytes). If you define @code{ROUND_TYPE_SIZE}, -you must also define this macro and they must be defined consistently -with each other. - -@findex ROUND_TYPE_ALIGN -@item ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified}) -Define this macro as an expression for the alignment of a type (given -by @var{type} as a tree node) if the alignment computed in the usual -way is @var{computed} and the alignment explicitly specified was -@var{specified}. - -The default is to use @var{specified} if it is larger; otherwise, use -the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT} - -@findex MAX_FIXED_MODE_SIZE -@item MAX_FIXED_MODE_SIZE -An integer expression for the size in bits of the largest integer -machine mode that should actually be used. All integer machine modes of -this size or smaller can be used for structures and unions with the -appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE -(DImode)} is assumed. - -@findex VECTOR_MODE_SUPPORTED_P -@item VECTOR_MODE_SUPPORTED_P(@var{mode}) -Define this macro to be nonzero if the port is prepared to handle insns -involving vector mode @var{mode}. At the very least, it must have move -patterns for this mode. - -@findex STACK_SAVEAREA_MODE -@item STACK_SAVEAREA_MODE (@var{save_level}) -If defined, an expression of type @code{enum machine_mode} that -specifies the mode of the save area operand of a -@code{save_stack_@var{level}} named pattern (@pxref{Standard Names}). -@var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or -@code{SAVE_NONLOCAL} and selects which of the three named patterns is -having its mode specified. - -You need not define this macro if it always returns @code{Pmode}. You -would most commonly define this macro if the -@code{save_stack_@var{level}} patterns need to support both a 32- and a -64-bit mode. - -@findex STACK_SIZE_MODE -@item STACK_SIZE_MODE -If defined, an expression of type @code{enum machine_mode} that -specifies the mode of the size increment operand of an -@code{allocate_stack} named pattern (@pxref{Standard Names}). - -You need not define this macro if it always returns @code{word_mode}. -You would most commonly define this macro if the @code{allocate_stack} -pattern needs to support both a 32- and a 64-bit mode. - -@findex CHECK_FLOAT_VALUE -@item CHECK_FLOAT_VALUE (@var{mode}, @var{value}, @var{overflow}) -A C statement to validate the value @var{value} (of type -@code{double}) for mode @var{mode}. This means that you check whether -@var{value} fits within the possible range of values for mode -@var{mode} on this target machine. The mode @var{mode} is always -a mode of class @code{MODE_FLOAT}. @var{overflow} is nonzero if -the value is already known to be out of range. - -If @var{value} is not valid or if @var{overflow} is nonzero, you should -set @var{overflow} to 1 and then assign some valid value to @var{value}. -Allowing an invalid value to go through the compiler can produce -incorrect assembler code which may even cause Unix assemblers to crash. - -This macro need not be defined if there is no work for it to do. - -@findex TARGET_FLOAT_FORMAT -@item TARGET_FLOAT_FORMAT -A code distinguishing the floating point format of the target machine. -There are three defined values: - -@table @code -@findex IEEE_FLOAT_FORMAT -@item IEEE_FLOAT_FORMAT -This code indicates IEEE floating point. It is the default; there is no -need to define this macro when the format is IEEE. - -@findex VAX_FLOAT_FORMAT -@item VAX_FLOAT_FORMAT -This code indicates the peculiar format used on the Vax. - -@findex UNKNOWN_FLOAT_FORMAT -@item UNKNOWN_FLOAT_FORMAT -This code indicates any other format. -@end table - -The value of this macro is compared with @code{HOST_FLOAT_FORMAT} -(@pxref{Config}) to determine whether the target machine has the same -format as the host machine. If any other formats are actually in use on -supported machines, new codes should be defined for them. - -The ordering of the component words of floating point values stored in -memory is controlled by @code{FLOAT_WORDS_BIG_ENDIAN} for the target -machine and @code{HOST_FLOAT_WORDS_BIG_ENDIAN} for the host. - -@findex DEFAULT_VTABLE_THUNKS -@item DEFAULT_VTABLE_THUNKS -GCC supports two ways of implementing C++ vtables: traditional or with -so-called ``thunks''. The flag @samp{-fvtable-thunk} chooses between them. -Define this macro to be a C expression for the default value of that flag. -If @code{DEFAULT_VTABLE_THUNKS} is 0, GCC uses the traditional -implementation by default. The ``thunk'' implementation is more efficient -(especially if you have provided an implementation of -@code{ASM_OUTPUT_MI_THUNK}, see @ref{Function Entry}), but is not binary -compatible with code compiled using the traditional implementation. -If you are writing a new port, define @code{DEFAULT_VTABLE_THUNKS} to 1. - -If you do not define this macro, the default for @samp{-fvtable-thunk} is 0. -@end table - -@node Type Layout -@section Layout of Source Language Data Types - -These macros define the sizes and other characteristics of the standard -basic data types used in programs being compiled. Unlike the macros in -the previous section, these apply to specific features of C and related -languages, rather than to fundamental aspects of storage layout. - -@table @code -@findex INT_TYPE_SIZE -@item INT_TYPE_SIZE -A C expression for the size in bits of the type @code{int} on the -target machine. If you don't define this, the default is one word. - -@findex MAX_INT_TYPE_SIZE -@item MAX_INT_TYPE_SIZE -Maximum number for the size in bits of the type @code{int} on the target -machine. If this is undefined, the default is @code{INT_TYPE_SIZE}. -Otherwise, it is the constant value that is the largest value that -@code{INT_TYPE_SIZE} can have at run-time. This is used in @code{cpp}. - -@findex SHORT_TYPE_SIZE -@item SHORT_TYPE_SIZE -A C expression for the size in bits of the type @code{short} on the -target machine. If you don't define this, the default is half a word. -(If this would be less than one storage unit, it is rounded up to one -unit.) - -@findex LONG_TYPE_SIZE -@item LONG_TYPE_SIZE -A C expression for the size in bits of the type @code{long} on the -target machine. If you don't define this, the default is one word. - -@findex MAX_LONG_TYPE_SIZE -@item MAX_LONG_TYPE_SIZE -Maximum number for the size in bits of the type @code{long} on the -target machine. If this is undefined, the default is -@code{LONG_TYPE_SIZE}. Otherwise, it is the constant value that is the -largest value that @code{LONG_TYPE_SIZE} can have at run-time. This is -used in @code{cpp}. - -@findex LONG_LONG_TYPE_SIZE -@item LONG_LONG_TYPE_SIZE -A C expression for the size in bits of the type @code{long long} on the -target machine. If you don't define this, the default is two -words. If you want to support GNU Ada on your machine, the value of this -macro must be at least 64. - -@findex CHAR_TYPE_SIZE -@item CHAR_TYPE_SIZE -A C expression for the size in bits of the type @code{char} on the -target machine. If you don't define this, the default is -@code{BITS_PER_UNIT}. - -@findex MAX_CHAR_TYPE_SIZE -@item MAX_CHAR_TYPE_SIZE -Maximum number for the size in bits of the type @code{char} on the -target machine. If this is undefined, the default is -@code{CHAR_TYPE_SIZE}. Otherwise, it is the constant value that is the -largest value that @code{CHAR_TYPE_SIZE} can have at run-time. This is -used in @code{cpp}. - -@findex FLOAT_TYPE_SIZE -@item FLOAT_TYPE_SIZE -A C expression for the size in bits of the type @code{float} on the -target machine. If you don't define this, the default is one word. - -@findex DOUBLE_TYPE_SIZE -@item DOUBLE_TYPE_SIZE -A C expression for the size in bits of the type @code{double} on the -target machine. If you don't define this, the default is two -words. - -@findex LONG_DOUBLE_TYPE_SIZE -@item LONG_DOUBLE_TYPE_SIZE -A C expression for the size in bits of the type @code{long double} on -the target machine. If you don't define this, the default is two -words. - -@findex WIDEST_HARDWARE_FP_SIZE -@item WIDEST_HARDWARE_FP_SIZE -A C expression for the size in bits of the widest floating-point format -supported by the hardware. If you define this macro, you must specify a -value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}. -If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE} -is the default. - -@findex DEFAULT_SIGNED_CHAR -@item DEFAULT_SIGNED_CHAR -An expression whose value is 1 or 0, according to whether the type -@code{char} should be signed or unsigned by default. The user can -always override this default with the options @samp{-fsigned-char} -and @samp{-funsigned-char}. - -@findex DEFAULT_SHORT_ENUMS -@item DEFAULT_SHORT_ENUMS -A C expression to determine whether to give an @code{enum} type -only as many bytes as it takes to represent the range of possible values -of that type. A nonzero value means to do that; a zero value means all -@code{enum} types should be allocated like @code{int}. - -If you don't define the macro, the default is 0. - -@findex SIZE_TYPE -@item SIZE_TYPE -A C expression for a string describing the name of the data type to use -for size values. The typedef name @code{size_t} is defined using the -contents of the string. - -The string can contain more than one keyword. If so, separate them with -spaces, and write first any length keyword, then @code{unsigned} if -appropriate, and finally @code{int}. The string must exactly match one -of the data type names defined in the function -@code{init_decl_processing} in the file @file{c-decl.c}. You may not -omit @code{int} or change the order---that would cause the compiler to -crash on startup. - -If you don't define this macro, the default is @code{"long unsigned -int"}. - -@findex PTRDIFF_TYPE -@item PTRDIFF_TYPE -A C expression for a string describing the name of the data type to use -for the result of subtracting two pointers. The typedef name -@code{ptrdiff_t} is defined using the contents of the string. See -@code{SIZE_TYPE} above for more information. - -If you don't define this macro, the default is @code{"long int"}. - -@findex WCHAR_TYPE -@item WCHAR_TYPE -A C expression for a string describing the name of the data type to use -for wide characters. The typedef name @code{wchar_t} is defined using -the contents of the string. See @code{SIZE_TYPE} above for more -information. - -If you don't define this macro, the default is @code{"int"}. - -@findex WCHAR_TYPE_SIZE -@item WCHAR_TYPE_SIZE -A C expression for the size in bits of the data type for wide -characters. This is used in @code{cpp}, which cannot make use of -@code{WCHAR_TYPE}. - -@findex MAX_WCHAR_TYPE_SIZE -@item MAX_WCHAR_TYPE_SIZE -Maximum number for the size in bits of the data type for wide -characters. If this is undefined, the default is -@code{WCHAR_TYPE_SIZE}. Otherwise, it is the constant value that is the -largest value that @code{WCHAR_TYPE_SIZE} can have at run-time. This is -used in @code{cpp}. - -@findex WINT_TYPE -@item WINT_TYPE -A C expression for a string describing the name of the data type to -use for wide characters passed to @code{printf} and returned from -@code{getwc}. The typedef name @code{wint_t} is defined using the -contents of the string. See @code{SIZE_TYPE} above for more -information. - -If you don't define this macro, the default is @code{"unsigned int"}. - -@findex INTMAX_TYPE -@item INTMAX_TYPE -A C expression for a string describing the name of the data type that -can represent any value of any standard or extended signed integer type. -The typedef name @code{intmax_t} is defined using the contents of the -string. See @code{SIZE_TYPE} above for more information. - -If you don't define this macro, the default is the first of -@code{"int"}, @code{"long int"}, or @code{"long long int"} that has as -much precision as @code{long long int}. - -@findex UINTMAX_TYPE -@item UINTMAX_TYPE -A C expression for a string describing the name of the data type that -can represent any value of any standard or extended unsigned integer -type. The typedef name @code{uintmax_t} is defined using the contents -of the string. See @code{SIZE_TYPE} above for more information. - -If you don't define this macro, the default is the first of -@code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long -unsigned int"} that has as much precision as @code{long long unsigned -int}. - -@findex OBJC_SELECTORS_WITHOUT_LABELS -@item OBJC_SELECTORS_WITHOUT_LABELS -Define this macro if the compiler can group all the selectors together -into a vector and use just one label at the beginning of the vector. -Otherwise, the compiler must give each selector its own assembler -label. - -On certain machines, it is important to have a separate label for each -selector because this enables the linker to eliminate duplicate selectors. - -@findex TARGET_PTRMEMFUNC_VBIT_LOCATION -@item TARGET_PTRMEMFUNC_VBIT_LOCATION -The C++ compiler represents a pointer-to-member-function with a struct -that looks like: - -@example - struct @{ - union @{ - void (*fn)(); - ptrdiff_t vtable_index; - @}; - ptrdiff_t delta; - @}; -@end example - -@noindent -The C++ compiler must use one bit to indicate whether the function that -will be called through a pointer-to-member-function is virtual. -Normally, we assume that the low-order bit of a function pointer must -always be zero. Then, by ensuring that the vtable_index is odd, we can -distinguish which variant of the union is in use. But, on some -platforms function pointers can be odd, and so this doesn't work. In -that case, we use the low-order bit of the @code{delta} field, and shift -the remainder of the @code{delta} field to the left. - -GCC will automatically make the right selection about where to store -this bit using the @code{FUNCTION_BOUNDARY} setting for your platform. -However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY} -set such that functions always start at even addresses, but the lowest -bit of pointers to functions indicate whether the function at that -address is in ARM or Thumb mode. If this is the case of your -architecture, you should define this macro to -@code{ptrmemfunc_vbit_in_delta}. - -In general, you should not have to define this macro. On architectures -in which function addresses are always even, according to -@code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to -@code{ptrmemfunc_vbit_in_pfn}. - -@findex TARGET_BELL -@item TARGET_BELL -A C constant expression for the integer value for escape sequence -@samp{\a}. - -@findex TARGET_TAB -@findex TARGET_BS -@findex TARGET_NEWLINE -@item TARGET_BS -@itemx TARGET_TAB -@itemx TARGET_NEWLINE -C constant expressions for the integer values for escape sequences -@samp{\b}, @samp{\t} and @samp{\n}. - -@findex TARGET_VT -@findex TARGET_FF -@findex TARGET_CR -@item TARGET_VT -@itemx TARGET_FF -@itemx TARGET_CR -C constant expressions for the integer values for escape sequences -@samp{\v}, @samp{\f} and @samp{\r}. -@end table - -@node Registers -@section Register Usage -@cindex register usage - -This section explains how to describe what registers the target machine -has, and how (in general) they can be used. - -The description of which registers a specific instruction can use is -done with register classes; see @ref{Register Classes}. For information -on using registers to access a stack frame, see @ref{Frame Registers}. -For passing values in registers, see @ref{Register Arguments}. -For returning values in registers, see @ref{Scalar Return}. - -@menu -* Register Basics:: Number and kinds of registers. -* Allocation Order:: Order in which registers are allocated. -* Values in Registers:: What kinds of values each reg can hold. -* Leaf Functions:: Renumbering registers for leaf functions. -* Stack Registers:: Handling a register stack such as 80387. -@end menu - -@node Register Basics -@subsection Basic Characteristics of Registers - -@c prevent bad page break with this line -Registers have various characteristics. - -@table @code -@findex FIRST_PSEUDO_REGISTER -@item FIRST_PSEUDO_REGISTER -Number of hardware registers known to the compiler. They receive -numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first -pseudo register's number really is assigned the number -@code{FIRST_PSEUDO_REGISTER}. - -@item FIXED_REGISTERS -@findex FIXED_REGISTERS -@cindex fixed register -An initializer that says which registers are used for fixed purposes -all throughout the compiled code and are therefore not available for -general allocation. These would include the stack pointer, the frame -pointer (except on machines where that can be used as a general -register when no frame pointer is needed), the program counter on -machines where that is considered one of the addressable registers, -and any other numbered register with a standard use. - -This information is expressed as a sequence of numbers, separated by -commas and surrounded by braces. The @var{n}th number is 1 if -register @var{n} is fixed, 0 otherwise. - -The table initialized from this macro, and the table initialized by -the following one, may be overridden at run time either automatically, -by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by -the user with the command options @samp{-ffixed-@var{reg}}, -@samp{-fcall-used-@var{reg}} and @samp{-fcall-saved-@var{reg}}. - -@findex CALL_USED_REGISTERS -@item CALL_USED_REGISTERS -@cindex call-used register -@cindex call-clobbered register -@cindex call-saved register -Like @code{FIXED_REGISTERS} but has 1 for each register that is -clobbered (in general) by function calls as well as for fixed -registers. This macro therefore identifies the registers that are not -available for general allocation of values that must live across -function calls. - -If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler -automatically saves it on function entry and restores it on function -exit, if the register is used within the function. - -@findex HARD_REGNO_CALL_PART_CLOBBERED -@item HARD_REGNO_CALL_PART_CLOBBERED (@var{regno}, @var{mode}) -@cindex call-used register -@cindex call-clobbered register -@cindex call-saved register -A C expression that is non-zero if it is not permissible to store a -value of mode @var{mode} in hard register number @var{regno} across a -call without some part of it being clobbered. For most machines this -macro need not be defined. It is only required for machines that do not -preserve the entire contents of a register across a call. - -@findex CONDITIONAL_REGISTER_USAGE -@findex fixed_regs -@findex call_used_regs -@item CONDITIONAL_REGISTER_USAGE -Zero or more C statements that may conditionally modify five variables -@code{fixed_regs}, @code{call_used_regs}, @code{global_regs}, -(these three are of type @code{char []}), @code{reg_names} (of type -@code{const char * []}) and @code{reg_class_contents} (of type -@code{HARD_REG_SET}). -Before the macro is called @code{fixed_regs}, @code{call_used_regs} -@code{reg_class_contents} and @code{reg_names} have been initialized -from @code{FIXED_REGISTERS}, @code{CALL_USED_REGISTERS}, -@code{REG_CLASS_CONTENTS} and @code{REGISTER_NAMES}, respectively, -@code{global_regs} has been cleared, and any @samp{-ffixed-@var{reg}}, -@samp{-fcall-used-@var{reg}} and @samp{-fcall-saved-@var{reg}} command -options have been applied. - -This is necessary in case the fixed or call-clobbered registers depend -on target flags. - -You need not define this macro if it has no work to do. - -@cindex disabling certain registers -@cindex controlling register usage -If the usage of an entire class of registers depends on the target -flags, you may indicate this to GCC by using this macro to modify -@code{fixed_regs} and @code{call_used_regs} to 1 for each of the -registers in the classes which should not be used by GCC. Also define -the macro @code{REG_CLASS_FROM_LETTER} to return @code{NO_REGS} if it -is called with a letter for a class that shouldn't be used. - -(However, if this class is not included in @code{GENERAL_REGS} and all -of the insn patterns whose constraints permit this class are -controlled by target switches, then GCC will automatically avoid using -these registers when the target switches are opposed to them.) - -@findex NON_SAVING_SETJMP -@item NON_SAVING_SETJMP -If this macro is defined and has a nonzero value, it means that -@code{setjmp} and related functions fail to save the registers, or that -@code{longjmp} fails to restore them. To compensate, the compiler -avoids putting variables in registers in functions that use -@code{setjmp}. - -@findex INCOMING_REGNO -@item INCOMING_REGNO (@var{out}) -Define this macro if the target machine has register windows. This C -expression returns the register number as seen by the called function -corresponding to the register number @var{out} as seen by the calling -function. Return @var{out} if register number @var{out} is not an -outbound register. - -@findex OUTGOING_REGNO -@item OUTGOING_REGNO (@var{in}) -Define this macro if the target machine has register windows. This C -expression returns the register number as seen by the calling function -corresponding to the register number @var{in} as seen by the called -function. Return @var{in} if register number @var{in} is not an inbound -register. - -@findex LOCAL_REGNO -@item LOCAL_REGNO (@var{regno}) -Define this macro if the target machine has register windows. This C -expression returns true if the register is call-saved but is in the -register window. Unlike most call-saved registers, such registers -need not be explicitly restored on function exit or during non-local -gotos. - -@ignore -@findex PC_REGNUM -@item PC_REGNUM -If the program counter has a register number, define this as that -register number. Otherwise, do not define it. -@end ignore -@end table - -@node Allocation Order -@subsection Order of Allocation of Registers -@cindex order of register allocation -@cindex register allocation order - -@c prevent bad page break with this line -Registers are allocated in order. - -@table @code -@findex REG_ALLOC_ORDER -@item REG_ALLOC_ORDER -If defined, an initializer for a vector of integers, containing the -numbers of hard registers in the order in which GCC should prefer -to use them (from most preferred to least). - -If this macro is not defined, registers are used lowest numbered first -(all else being equal). - -One use of this macro is on machines where the highest numbered -registers must always be saved and the save-multiple-registers -instruction supports only sequences of consecutive registers. On such -machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists -the highest numbered allocable register first. - -@findex ORDER_REGS_FOR_LOCAL_ALLOC -@item ORDER_REGS_FOR_LOCAL_ALLOC -A C statement (sans semicolon) to choose the order in which to allocate -hard registers for pseudo-registers local to a basic block. - -Store the desired register order in the array @code{reg_alloc_order}. -Element 0 should be the register to allocate first; element 1, the next -register; and so on. - -The macro body should not assume anything about the contents of -@code{reg_alloc_order} before execution of the macro. - -On most machines, it is not necessary to define this macro. -@end table - -@node Values in Registers -@subsection How Values Fit in Registers - -This section discusses the macros that describe which kinds of values -(specifically, which machine modes) each register can hold, and how many -consecutive registers are needed for a given mode. - -@table @code -@findex HARD_REGNO_NREGS -@item HARD_REGNO_NREGS (@var{regno}, @var{mode}) -A C expression for the number of consecutive hard registers, starting -at register number @var{regno}, required to hold a value of mode -@var{mode}. - -On a machine where all registers are exactly one word, a suitable -definition of this macro is - -@smallexample -#define HARD_REGNO_NREGS(REGNO, MODE) \ - ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) \ - / UNITS_PER_WORD) -@end smallexample - -@findex HARD_REGNO_MODE_OK -@item HARD_REGNO_MODE_OK (@var{regno}, @var{mode}) -A C expression that is nonzero if it is permissible to store a value -of mode @var{mode} in hard register number @var{regno} (or in several -registers starting with that one). For a machine where all registers -are equivalent, a suitable definition is - -@smallexample -#define HARD_REGNO_MODE_OK(REGNO, MODE) 1 -@end smallexample - -You need not include code to check for the numbers of fixed registers, -because the allocation mechanism considers them to be always occupied. - -@cindex register pairs -On some machines, double-precision values must be kept in even/odd -register pairs. You can implement that by defining this macro to reject -odd register numbers for such modes. - -The minimum requirement for a mode to be OK in a register is that the -@samp{mov@var{mode}} instruction pattern support moves between the -register and other hard register in the same class and that moving a -value into the register and back out not alter it. - -Since the same instruction used to move @code{word_mode} will work for -all narrower integer modes, it is not necessary on any machine for -@code{HARD_REGNO_MODE_OK} to distinguish between these modes, provided -you define patterns @samp{movhi}, etc., to take advantage of this. This -is useful because of the interaction between @code{HARD_REGNO_MODE_OK} -and @code{MODES_TIEABLE_P}; it is very desirable for all integer modes -to be tieable. - -Many machines have special registers for floating point arithmetic. -Often people assume that floating point machine modes are allowed only -in floating point registers. This is not true. Any registers that -can hold integers can safely @emph{hold} a floating point machine -mode, whether or not floating arithmetic can be done on it in those -registers. Integer move instructions can be used to move the values. - -On some machines, though, the converse is true: fixed-point machine -modes may not go in floating registers. This is true if the floating -registers normalize any value stored in them, because storing a -non-floating value there would garble it. In this case, -@code{HARD_REGNO_MODE_OK} should reject fixed-point machine modes in -floating registers. But if the floating registers do not automatically -normalize, if you can store any bit pattern in one and retrieve it -unchanged without a trap, then any machine mode may go in a floating -register, so you can define this macro to say so. - -The primary significance of special floating registers is rather that -they are the registers acceptable in floating point arithmetic -instructions. However, this is of no concern to -@code{HARD_REGNO_MODE_OK}. You handle it by writing the proper -constraints for those instructions. - -On some machines, the floating registers are especially slow to access, -so that it is better to store a value in a stack frame than in such a -register if floating point arithmetic is not being done. As long as the -floating registers are not in class @code{GENERAL_REGS}, they will not -be used unless some pattern's constraint asks for one. - -@findex MODES_TIEABLE_P -@item MODES_TIEABLE_P (@var{mode1}, @var{mode2}) -A C expression that is nonzero if a value of mode -@var{mode1} is accessible in mode @var{mode2} without copying. - -If @code{HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and -@code{HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always the same for -any @var{r}, then @code{MODES_TIEABLE_P (@var{mode1}, @var{mode2})} -should be nonzero. If they differ for any @var{r}, you should define -this macro to return zero unless some other mechanism ensures the -accessibility of the value in a narrower mode. - -You should define this macro to return nonzero in as many cases as -possible since doing so will allow GCC to perform better register -allocation. - -@findex AVOID_CCMODE_COPIES -@item AVOID_CCMODE_COPIES -Define this macro if the compiler should avoid copies to/from @code{CCmode} -registers. You should only define this macro if support for copying to/from -@code{CCmode} is incomplete. - -@findex SUBREG_REGNO_OFFSET -@item SUBREG_REGNO_OFFSET -Define this macro if the compiler needs to handle subregs in a non-standard -way. The macro returns the correct regno offset for mode @code{YMODE} given -a subreg of type @code{XMODE}. -This macro takes 4 parameters: -@code{XREGNO} - A regno of an inner hard subreg_reg (or what will become one). -@code{XMODE} - The mode of xregno. -@code{OFFSET} - The byte offset. -@code{YMODE} - The mode of a top level SUBREG (or what may become one). -The default function can be found in rtlanal.c, function -@code{subreg_regno_offset}. Normally this does not need to be defined. -@end table - -@node Leaf Functions -@subsection Handling Leaf Functions - -@cindex leaf functions -@cindex functions, leaf -On some machines, a leaf function (i.e., one which makes no calls) can run -more efficiently if it does not make its own register window. Often this -means it is required to receive its arguments in the registers where they -are passed by the caller, instead of the registers where they would -normally arrive. - -The special treatment for leaf functions generally applies only when -other conditions are met; for example, often they may use only those -registers for its own variables and temporaries. We use the term ``leaf -function'' to mean a function that is suitable for this special -handling, so that functions with no calls are not necessarily ``leaf -functions''. - -GCC assigns register numbers before it knows whether the function is -suitable for leaf function treatment. So it needs to renumber the -registers in order to output a leaf function. The following macros -accomplish this. - -@table @code -@findex LEAF_REGISTERS -@item LEAF_REGISTERS -Name of a char vector, indexed by hard register number, which -contains 1 for a register that is allowable in a candidate for leaf -function treatment. - -If leaf function treatment involves renumbering the registers, then the -registers marked here should be the ones before renumbering---those that -GCC would ordinarily allocate. The registers which will actually be -used in the assembler code, after renumbering, should not be marked with 1 -in this vector. - -Define this macro only if the target machine offers a way to optimize -the treatment of leaf functions. - -@findex LEAF_REG_REMAP -@item LEAF_REG_REMAP (@var{regno}) -A C expression whose value is the register number to which @var{regno} -should be renumbered, when a function is treated as a leaf function. - -If @var{regno} is a register number which should not appear in a leaf -function before renumbering, then the expression should yield -1, which -will cause the compiler to abort. - -Define this macro only if the target machine offers a way to optimize the -treatment of leaf functions, and registers need to be renumbered to do -this. -@end table - -@findex current_function_is_leaf -@findex current_function_uses_only_leaf_regs -Normally, @code{FUNCTION_PROLOGUE} and @code{FUNCTION_EPILOGUE} must -treat leaf functions specially. They can test the C variable -@code{current_function_is_leaf} which is nonzero for leaf functions. -@code{current_function_is_leaf} is set prior to local register allocation -and is valid for the remaining compiler passes. They can also test the C -variable @code{current_function_uses_only_leaf_regs} which is nonzero for -leaf functions which only use leaf registers. -@code{current_function_uses_only_leaf_regs} is valid after reload and is -only useful if @code{LEAF_REGISTERS} is defined. -@c changed this to fix overfull. ALSO: why the "it" at the beginning -@c of the next paragraph?! --mew 2feb93 - -@node Stack Registers -@subsection Registers That Form a Stack - -There are special features to handle computers where some of the -``registers'' form a stack, as in the 80387 coprocessor for the 80386. -Stack registers are normally written by pushing onto the stack, and are -numbered relative to the top of the stack. - -Currently, GCC can only handle one group of stack-like registers, and -they must be consecutively numbered. - -@table @code -@findex STACK_REGS -@item STACK_REGS -Define this if the machine has any stack-like registers. - -@findex FIRST_STACK_REG -@item FIRST_STACK_REG -The number of the first stack-like register. This one is the top -of the stack. - -@findex LAST_STACK_REG -@item LAST_STACK_REG -The number of the last stack-like register. This one is the bottom of -the stack. -@end table - -@node Register Classes -@section Register Classes -@cindex register class definitions -@cindex class definitions, register - -On many machines, the numbered registers are not all equivalent. -For example, certain registers may not be allowed for indexed addressing; -certain registers may not be allowed in some instructions. These machine -restrictions are described to the compiler using @dfn{register classes}. - -You define a number of register classes, giving each one a name and saying -which of the registers belong to it. Then you can specify register classes -that are allowed as operands to particular instruction patterns. - -@findex ALL_REGS -@findex NO_REGS -In general, each register will belong to several classes. In fact, one -class must be named @code{ALL_REGS} and contain all the registers. Another -class must be named @code{NO_REGS} and contain no registers. Often the -union of two classes will be another class; however, this is not required. - -@findex GENERAL_REGS -One of the classes must be named @code{GENERAL_REGS}. There is nothing -terribly special about the name, but the operand constraint letters -@samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is -the same as @code{ALL_REGS}, just define it as a macro which expands -to @code{ALL_REGS}. - -Order the classes so that if class @var{x} is contained in class @var{y} -then @var{x} has a lower class number than @var{y}. - -The way classes other than @code{GENERAL_REGS} are specified in operand -constraints is through machine-dependent operand constraint letters. -You can define such letters to correspond to various classes, then use -them in operand constraints. - -You should define a class for the union of two classes whenever some -instruction allows both classes. For example, if an instruction allows -either a floating point (coprocessor) register or a general register for a -certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS} -which includes both of them. Otherwise you will get suboptimal code. - -You must also specify certain redundant information about the register -classes: for each class, which classes contain it and which ones are -contained in it; for each pair of classes, the largest class contained -in their union. - -When a value occupying several consecutive registers is expected in a -certain class, all the registers used must belong to that class. -Therefore, register classes cannot be used to enforce a requirement for -a register pair to start with an even-numbered register. The way to -specify this requirement is with @code{HARD_REGNO_MODE_OK}. - -Register classes used for input-operands of bitwise-and or shift -instructions have a special requirement: each such class must have, for -each fixed-point machine mode, a subclass whose registers can transfer that -mode to or from memory. For example, on some machines, the operations for -single-byte values (@code{QImode}) are limited to certain registers. When -this is so, each register class that is used in a bitwise-and or shift -instruction must have a subclass consisting of registers from which -single-byte values can be loaded or stored. This is so that -@code{PREFERRED_RELOAD_CLASS} can always have a possible value to return. - -@table @code -@findex enum reg_class -@item enum reg_class -An enumeral type that must be defined with all the register class names -as enumeral values. @code{NO_REGS} must be first. @code{ALL_REGS} -must be the last register class, followed by one more enumeral value, -@code{LIM_REG_CLASSES}, which is not a register class but rather -tells how many classes there are. - -Each register class has a number, which is the value of casting -the class name to type @code{int}. The number serves as an index -in many of the tables described below. - -@findex N_REG_CLASSES -@item N_REG_CLASSES -The number of distinct register classes, defined as follows: - -@example -#define N_REG_CLASSES (int) LIM_REG_CLASSES -@end example - -@findex REG_CLASS_NAMES -@item REG_CLASS_NAMES -An initializer containing the names of the register classes as C string -constants. These names are used in writing some of the debugging dumps. - -@findex REG_CLASS_CONTENTS -@item REG_CLASS_CONTENTS -An initializer containing the contents of the register classes, as integers -which are bit masks. The @var{n}th integer specifies the contents of class -@var{n}. The way the integer @var{mask} is interpreted is that -register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1. - -When the machine has more than 32 registers, an integer does not suffice. -Then the integers are replaced by sub-initializers, braced groupings containing -several integers. Each sub-initializer must be suitable as an initializer -for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}. -In this situation, the first integer in each sub-initializer corresponds to -registers 0 through 31, the second integer to registers 32 through 63, and -so on. - -@findex REGNO_REG_CLASS -@item REGNO_REG_CLASS (@var{regno}) -A C expression whose value is a register class containing hard register -@var{regno}. In general there is more than one such class; choose a class -which is @dfn{minimal}, meaning that no smaller class also contains the -register. - -@findex BASE_REG_CLASS -@item BASE_REG_CLASS -A macro whose definition is the name of the class to which a valid -base register must belong. A base register is one used in an address -which is the register value plus a displacement. - -@findex INDEX_REG_CLASS -@item INDEX_REG_CLASS -A macro whose definition is the name of the class to which a valid -index register must belong. An index register is one used in an -address where its value is either multiplied by a scale factor or -added to another register (as well as added to a displacement). - -@findex REG_CLASS_FROM_LETTER -@item REG_CLASS_FROM_LETTER (@var{char}) -A C expression which defines the machine-dependent operand constraint -letters for register classes. If @var{char} is such a letter, the -value should be the register class corresponding to it. Otherwise, -the value should be @code{NO_REGS}. The register letter @samp{r}, -corresponding to class @code{GENERAL_REGS}, will not be passed -to this macro; you do not need to handle it. - -@findex REGNO_OK_FOR_BASE_P -@item REGNO_OK_FOR_BASE_P (@var{num}) -A C expression which is nonzero if register number @var{num} is -suitable for use as a base register in operand addresses. It may be -either a suitable hard register or a pseudo register that has been -allocated such a hard register. - -@findex REGNO_MODE_OK_FOR_BASE_P -@item REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode}) -A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that -that expression may examine the mode of the memory reference in -@var{mode}. You should define this macro if the mode of the memory -reference affects whether a register may be used as a base register. If -you define this macro, the compiler will use it instead of -@code{REGNO_OK_FOR_BASE_P}. - -@findex REGNO_OK_FOR_INDEX_P -@item REGNO_OK_FOR_INDEX_P (@var{num}) -A C expression which is nonzero if register number @var{num} is -suitable for use as an index register in operand addresses. It may be -either a suitable hard register or a pseudo register that has been -allocated such a hard register. - -The difference between an index register and a base register is that -the index register may be scaled. If an address involves the sum of -two registers, neither one of them scaled, then either one may be -labeled the ``base'' and the other the ``index''; but whichever -labeling is used must fit the machine's constraints of which registers -may serve in each capacity. The compiler will try both labelings, -looking for one that is valid, and will reload one or both registers -only if neither labeling works. - -@findex PREFERRED_RELOAD_CLASS -@item PREFERRED_RELOAD_CLASS (@var{x}, @var{class}) -A C expression that places additional restrictions on the register class -to use when it is necessary to copy value @var{x} into a register in class -@var{class}. The value is a register class; perhaps @var{class}, or perhaps -another, smaller class. On many machines, the following definition is -safe: - -@example -#define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS -@end example - -Sometimes returning a more restrictive class makes better code. For -example, on the 68000, when @var{x} is an integer constant that is in range -for a @samp{moveq} instruction, the value of this macro is always -@code{DATA_REGS} as long as @var{class} includes the data registers. -Requiring a data register guarantees that a @samp{moveq} will be used. - -If @var{x} is a @code{const_double}, by returning @code{NO_REGS} -you can force @var{x} into a memory constant. This is useful on -certain machines where immediate floating values cannot be loaded into -certain kinds of registers. - -@findex PREFERRED_OUTPUT_RELOAD_CLASS -@item PREFERRED_OUTPUT_RELOAD_CLASS (@var{x}, @var{class}) -Like @code{PREFERRED_RELOAD_CLASS}, but for output reloads instead of -input reloads. If you don't define this macro, the default is to use -@var{class}, unchanged. - -@findex LIMIT_RELOAD_CLASS -@item LIMIT_RELOAD_CLASS (@var{mode}, @var{class}) -A C expression that places additional restrictions on the register class -to use when it is necessary to be able to hold a value of mode -@var{mode} in a reload register for which class @var{class} would -ordinarily be used. - -Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when -there are certain modes that simply can't go in certain reload classes. - -The value is a register class; perhaps @var{class}, or perhaps another, -smaller class. - -Don't define this macro unless the target machine has limitations which -require the macro to do something nontrivial. - -@findex SECONDARY_RELOAD_CLASS -@findex SECONDARY_INPUT_RELOAD_CLASS -@findex SECONDARY_OUTPUT_RELOAD_CLASS -@item SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) -@itemx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) -@itemx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) -Many machines have some registers that cannot be copied directly to or -from memory or even from other types of registers. An example is the -@samp{MQ} register, which on most machines, can only be copied to or -from general registers, but not memory. Some machines allow copying all -registers to and from memory, but require a scratch register for stores -to some memory locations (e.g., those with symbolic address on the RT, -and those with certain symbolic address on the Sparc when compiling -PIC). In some cases, both an intermediate and a scratch register are -required. - -You should define these macros to indicate to the reload phase that it may -need to allocate at least one register for a reload in addition to the -register to contain the data. Specifically, if copying @var{x} to a -register @var{class} in @var{mode} requires an intermediate register, -you should define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the -largest register class all of whose registers can be used as -intermediate registers or scratch registers. - -If copying a register @var{class} in @var{mode} to @var{x} requires an -intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS} -should be defined to return the largest register class required. If the -requirements for input and output reloads are the same, the macro -@code{SECONDARY_RELOAD_CLASS} should be used instead of defining both -macros identically. - -The values returned by these macros are often @code{GENERAL_REGS}. -Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x} -can be directly copied to or from a register of @var{class} in -@var{mode} without requiring a scratch register. Do not define this -macro if it would always return @code{NO_REGS}. - -If a scratch register is required (either with or without an -intermediate register), you should define patterns for -@samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required -(@pxref{Standard Names}. These patterns, which will normally be -implemented with a @code{define_expand}, should be similar to the -@samp{mov@var{m}} patterns, except that operand 2 is the scratch -register. - -Define constraints for the reload register and scratch register that -contain a single register class. If the original reload register (whose -class is @var{class}) can meet the constraint given in the pattern, the -value returned by these macros is used for the class of the scratch -register. Otherwise, two additional reload registers are required. -Their classes are obtained from the constraints in the insn pattern. - -@var{x} might be a pseudo-register or a @code{subreg} of a -pseudo-register, which could either be in a hard register or in memory. -Use @code{true_regnum} to find out; it will return -1 if the pseudo is -in memory and the hard register number if it is in a register. - -These macros should not be used in the case where a particular class of -registers can only be copied to memory and not to another class of -registers. In that case, secondary reload registers are not needed and -would not be helpful. Instead, a stack location must be used to perform -the copy and the @code{mov@var{m}} pattern should use memory as a -intermediate storage. This case often occurs between floating-point and -general registers. - -@findex SECONDARY_MEMORY_NEEDED -@item SECONDARY_MEMORY_NEEDED (@var{class1}, @var{class2}, @var{m}) -Certain machines have the property that some registers cannot be copied -to some other registers without using memory. Define this macro on -those machines to be a C expression that is non-zero if objects of mode -@var{m} in registers of @var{class1} can only be copied to registers of -class @var{class2} by storing a register of @var{class1} into memory -and loading that memory location into a register of @var{class2}. - -Do not define this macro if its value would always be zero. - -@findex SECONDARY_MEMORY_NEEDED_RTX -@item SECONDARY_MEMORY_NEEDED_RTX (@var{mode}) -Normally when @code{SECONDARY_MEMORY_NEEDED} is defined, the compiler -allocates a stack slot for a memory location needed for register copies. -If this macro is defined, the compiler instead uses the memory location -defined by this macro. - -Do not define this macro if you do not define -@code{SECONDARY_MEMORY_NEEDED}. - -@findex SECONDARY_MEMORY_NEEDED_MODE -@item SECONDARY_MEMORY_NEEDED_MODE (@var{mode}) -When the compiler needs a secondary memory location to copy between two -registers of mode @var{mode}, it normally allocates sufficient memory to -hold a quantity of @code{BITS_PER_WORD} bits and performs the store and -load operations in a mode that many bits wide and whose class is the -same as that of @var{mode}. - -This is right thing to do on most machines because it ensures that all -bits of the register are copied and prevents accesses to the registers -in a narrower mode, which some machines prohibit for floating-point -registers. - -However, this default behavior is not correct on some machines, such as -the DEC Alpha, that store short integers in floating-point registers -differently than in integer registers. On those machines, the default -widening will not work correctly and you must define this macro to -suppress that widening in some cases. See the file @file{alpha.h} for -details. - -Do not define this macro if you do not define -@code{SECONDARY_MEMORY_NEEDED} or if widening @var{mode} to a mode that -is @code{BITS_PER_WORD} bits wide is correct for your machine. - -@findex SMALL_REGISTER_CLASSES -@item SMALL_REGISTER_CLASSES -On some machines, it is risky to let hard registers live across arbitrary -insns. Typically, these machines have instructions that require values -to be in specific registers (like an accumulator), and reload will fail -if the required hard register is used for another purpose across such an -insn. - -Define @code{SMALL_REGISTER_CLASSES} to be an expression with a non-zero -value on these machines. When this macro has a non-zero value, the -compiler will try to minimize the lifetime of hard registers. - -It is always safe to define this macro with a non-zero value, but if you -unnecessarily define it, you will reduce the amount of optimizations -that can be performed in some cases. If you do not define this macro -with a non-zero value when it is required, the compiler will run out of -spill registers and print a fatal error message. For most machines, you -should not define this macro at all. - -@findex CLASS_LIKELY_SPILLED_P -@item CLASS_LIKELY_SPILLED_P (@var{class}) -A C expression whose value is nonzero if pseudos that have been assigned -to registers of class @var{class} would likely be spilled because -registers of @var{class} are needed for spill registers. - -The default value of this macro returns 1 if @var{class} has exactly one -register and zero otherwise. On most machines, this default should be -used. Only define this macro to some other expression if pseudos -allocated by @file{local-alloc.c} end up in memory because their hard -registers were needed for spill registers. If this macro returns nonzero -for those classes, those pseudos will only be allocated by -@file{global.c}, which knows how to reallocate the pseudo to another -register. If there would not be another register available for -reallocation, you should not change the definition of this macro since -the only effect of such a definition would be to slow down register -allocation. - -@findex CLASS_MAX_NREGS -@item CLASS_MAX_NREGS (@var{class}, @var{mode}) -A C expression for the maximum number of consecutive registers -of class @var{class} needed to hold a value of mode @var{mode}. - -This is closely related to the macro @code{HARD_REGNO_NREGS}. In fact, -the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})} -should be the maximum value of @code{HARD_REGNO_NREGS (@var{regno}, -@var{mode})} for all @var{regno} values in the class @var{class}. - -This macro helps control the handling of multiple-word values -in the reload pass. - -@item CLASS_CANNOT_CHANGE_MODE -If defined, a C expression for a class that contains registers for -which the compiler may not change modes arbitrarily. - -@item CLASS_CANNOT_CHANGE_MODE_P(@var{from}, @var{to}) -A C expression that is true if, for a register in -@code{CLASS_CANNOT_CHANGE_MODE}, the requested mode punning is illegal. - -For the example, loading 32-bit integer or floating-point objects into -floating-point registers on the Alpha extends them to 64-bits. -Therefore loading a 64-bit object and then storing it as a 32-bit object -does not store the low-order 32-bits, as would be the case for a normal -register. Therefore, @file{alpha.h} defines @code{CLASS_CANNOT_CHANGE_MODE} -as @code{FLOAT_REGS} and @code{CLASS_CANNOT_CHANGE_MODE_P} restricts -mode changes to same-size modes. - -Compare this to IA-64, which extends floating-point values to 82-bits, -and stores 64-bit integers in a different format than 64-bit doubles. -Therefore @code{CLASS_CANNOT_CHANGE_MODE_P} is always true. -@end table - -Three other special macros describe which operands fit which constraint -letters. - -@table @code -@findex CONST_OK_FOR_LETTER_P -@item CONST_OK_FOR_LETTER_P (@var{value}, @var{c}) -A C expression that defines the machine-dependent operand constraint -letters (@samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P}) that specify -particular ranges of integer values. If @var{c} is one of those -letters, the expression should check that @var{value}, an integer, is in -the appropriate range and return 1 if so, 0 otherwise. If @var{c} is -not one of those letters, the value should be 0 regardless of -@var{value}. - -@findex CONST_DOUBLE_OK_FOR_LETTER_P -@item CONST_DOUBLE_OK_FOR_LETTER_P (@var{value}, @var{c}) -A C expression that defines the machine-dependent operand constraint -letters that specify particular ranges of @code{const_double} values -(@samp{G} or @samp{H}). - -If @var{c} is one of those letters, the expression should check that -@var{value}, an RTX of code @code{const_double}, is in the appropriate -range and return 1 if so, 0 otherwise. If @var{c} is not one of those -letters, the value should be 0 regardless of @var{value}. - -@code{const_double} is used for all floating-point constants and for -@code{DImode} fixed-point constants. A given letter can accept either -or both kinds of values. It can use @code{GET_MODE} to distinguish -between these kinds. - -@findex EXTRA_CONSTRAINT -@item EXTRA_CONSTRAINT (@var{value}, @var{c}) -A C expression that defines the optional machine-dependent constraint -letters that can be used to segregate specific types of operands, usually -memory references, for the target machine. Any letter that is not -elsewhere defined and not matched by @code{REG_CLASS_FROM_LETTER} -may be used. Normally this macro will not be defined. - -If it is required for a particular target machine, it should return 1 -if @var{value} corresponds to the operand type represented by the -constraint letter @var{c}. If @var{c} is not defined as an extra -constraint, the value returned should be 0 regardless of @var{value}. - -For example, on the ROMP, load instructions cannot have their output -in r0 if the memory reference contains a symbolic address. Constraint -letter @samp{Q} is defined as representing a memory address that does -@emph{not} contain a symbolic address. An alternative is specified with -a @samp{Q} constraint on the input and @samp{r} on the output. The next -alternative specifies @samp{m} on the input and a register class that -does not include r0 on the output. -@end table - -@node Stack and Calling -@section Stack Layout and Calling Conventions -@cindex calling conventions - -@c prevent bad page break with this line -This describes the stack layout and calling conventions. - -@menu -* Frame Layout:: -* Stack Checking:: -* Frame Registers:: -* Elimination:: -* Stack Arguments:: -* Register Arguments:: -* Scalar Return:: -* Aggregate Return:: -* Caller Saves:: -* Function Entry:: -* Profiling:: -* Inlining:: -* Tail Calling:: -@end menu - -@node Frame Layout -@subsection Basic Stack Layout -@cindex stack frame layout -@cindex frame layout - -@c prevent bad page break with this line -Here is the basic stack layout. - -@table @code -@findex STACK_GROWS_DOWNWARD -@item STACK_GROWS_DOWNWARD -Define this macro if pushing a word onto the stack moves the stack -pointer to a smaller address. - -When we say, ``define this macro if @dots{},'' it means that the -compiler checks this macro only with @code{#ifdef} so the precise -definition used does not matter. - -@findex FRAME_GROWS_DOWNWARD -@item FRAME_GROWS_DOWNWARD -Define this macro if the addresses of local variable slots are at negative -offsets from the frame pointer. - -@findex ARGS_GROW_DOWNWARD -@item ARGS_GROW_DOWNWARD -Define this macro if successive arguments to a function occupy decreasing -addresses on the stack. - -@findex STARTING_FRAME_OFFSET -@item STARTING_FRAME_OFFSET -Offset from the frame pointer to the first local variable slot to be allocated. - -If @code{FRAME_GROWS_DOWNWARD}, find the next slot's offset by -subtracting the first slot's length from @code{STARTING_FRAME_OFFSET}. -Otherwise, it is found by adding the length of the first slot to the -value @code{STARTING_FRAME_OFFSET}. -@c i'm not sure if the above is still correct.. had to change it to get -@c rid of an overfull. --mew 2feb93 - -@findex STACK_POINTER_OFFSET -@item STACK_POINTER_OFFSET -Offset from the stack pointer register to the first location at which -outgoing arguments are placed. If not specified, the default value of -zero is used. This is the proper value for most machines. - -If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above -the first location at which outgoing arguments are placed. - -@findex FIRST_PARM_OFFSET -@item FIRST_PARM_OFFSET (@var{fundecl}) -Offset from the argument pointer register to the first argument's -address. On some machines it may depend on the data type of the -function. - -If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above -the first argument's address. - -@findex STACK_DYNAMIC_OFFSET -@item STACK_DYNAMIC_OFFSET (@var{fundecl}) -Offset from the stack pointer register to an item dynamically allocated -on the stack, e.g., by @code{alloca}. - -The default value for this macro is @code{STACK_POINTER_OFFSET} plus the -length of the outgoing arguments. The default is correct for most -machines. See @file{function.c} for details. - -@findex DYNAMIC_CHAIN_ADDRESS -@item DYNAMIC_CHAIN_ADDRESS (@var{frameaddr}) -A C expression whose value is RTL representing the address in a stack -frame where the pointer to the caller's frame is stored. Assume that -@var{frameaddr} is an RTL expression for the address of the stack frame -itself. - -If you don't define this macro, the default is to return the value -of @var{frameaddr}---that is, the stack frame address is also the -address of the stack word that points to the previous frame. - -@findex SETUP_FRAME_ADDRESSES -@item SETUP_FRAME_ADDRESSES -If defined, a C expression that produces the machine-specific code to -setup the stack so that arbitrary frames can be accessed. For example, -on the Sparc, we must flush all of the register windows to the stack -before we can access arbitrary stack frames. You will seldom need to -define this macro. - -@findex BUILTIN_SETJMP_FRAME_VALUE -@item BUILTIN_SETJMP_FRAME_VALUE -If defined, a C expression that contains an rtx that is used to store -the address of the current frame into the built in @code{setjmp} buffer. -The default value, @code{virtual_stack_vars_rtx}, is correct for most -machines. One reason you may need to define this macro is if -@code{hard_frame_pointer_rtx} is the appropriate value on your machine. - -@findex RETURN_ADDR_RTX -@item RETURN_ADDR_RTX (@var{count}, @var{frameaddr}) -A C expression whose value is RTL representing the value of the return -address for the frame @var{count} steps up from the current frame, after -the prologue. @var{frameaddr} is the frame pointer of the @var{count} -frame, or the frame pointer of the @var{count} @minus{} 1 frame if -@code{RETURN_ADDR_IN_PREVIOUS_FRAME} is defined. - -The value of the expression must always be the correct address when -@var{count} is zero, but may be @code{NULL_RTX} if there is not way to -determine the return address of other frames. - -@findex RETURN_ADDR_IN_PREVIOUS_FRAME -@item RETURN_ADDR_IN_PREVIOUS_FRAME -Define this if the return address of a particular stack frame is accessed -from the frame pointer of the previous stack frame. - -@findex INCOMING_RETURN_ADDR_RTX -@item INCOMING_RETURN_ADDR_RTX -A C expression whose value is RTL representing the location of the -incoming return address at the beginning of any function, before the -prologue. This RTL is either a @code{REG}, indicating that the return -value is saved in @samp{REG}, or a @code{MEM} representing a location in -the stack. - -You only need to define this macro if you want to support call frame -debugging information like that provided by DWARF 2. - -If this RTL is a @code{REG}, you should also define -DWARF_FRAME_RETURN_COLUMN to @code{DWARF_FRAME_REGNUM (REGNO)}. - -@findex INCOMING_FRAME_SP_OFFSET -@item INCOMING_FRAME_SP_OFFSET -A C expression whose value is an integer giving the offset, in bytes, -from the value of the stack pointer register to the top of the stack -frame at the beginning of any function, before the prologue. The top of -the frame is defined to be the value of the stack pointer in the -previous frame, just before the call instruction. - -You only need to define this macro if you want to support call frame -debugging information like that provided by DWARF 2. - -@findex ARG_POINTER_CFA_OFFSET -@item ARG_POINTER_CFA_OFFSET (@var{fundecl}) -A C expression whose value is an integer giving the offset, in bytes, -from the argument pointer to the canonical frame address (cfa). The -final value should coincide with that calculated by -@code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable -during virtual register instantiation. - -The default value for this macro is @code{FIRST_PARM_OFFSET (fundecl)}, -which is correct for most machines; in general, the arguments are found -immediately before the stack frame. Note that this is not the case on -some targets that save registers into the caller's frame, such as SPARC -and rs6000, and so such targets need to define this macro. - -You only need to define this macro if the default is incorrect, and you -want to support call frame debugging information like that provided by -DWARF 2. - -@findex EH_RETURN_DATA_REGNO -@item EH_RETURN_DATA_REGNO (@var{N}) -A C expression whose value is the @var{N}th register number used for -data by exception handlers, or @code{INVALID_REGNUM} if fewer than -@var{N} registers are usable. - -The exception handling library routines communicate with the exception -handlers via a set of agreed upon registers. Ideally these registers -should be call-clobbered; it is possible to use call-saved registers, -but may negatively impact code size. The target must support at least -2 data registers, but should define 4 if there are enough free registers. - -You must define this macro if you want to support call frame exception -handling like that provided by DWARF 2. - -@findex EH_RETURN_STACKADJ_RTX -@item EH_RETURN_STACKADJ_RTX -A C expression whose value is RTL representing a location in which -to store a stack adjustment to be applied before function return. -This is used to unwind the stack to an exception handler's call frame. -It will be assigned zero on code paths that return normally. - -Typically this is a call-clobbered hard register that is otherwise -untouched by the epilogue, but could also be a stack slot. - -You must define this macro if you want to support call frame exception -handling like that provided by DWARF 2. - -@findex EH_RETURN_HANDLER_RTX -@item EH_RETURN_HANDLER_RTX -A C expression whose value is RTL representing a location in which -to store the address of an exception handler to which we should -return. It will not be assigned on code paths that return normally. - -Typically this is the location in the call frame at which the normal -return address is stored. For targets that return by popping an -address off the stack, this might be a memory address just below -the @emph{target} call frame rather than inside the current call -frame. @code{EH_RETURN_STACKADJ_RTX} will have already been assigned, -so it may be used to calculate the location of the target call frame. - -Some targets have more complex requirements than storing to an -address calculable during initial code generation. In that case -the @code{eh_return} instruction pattern should be used instead. - -If you want to support call frame exception handling, you must -define either this macro or the @code{eh_return} instruction pattern. - -@findex ASM_PREFERRED_EH_DATA_FORMAT -@item ASM_PREFERRED_EH_DATA_FORMAT(@var{CODE}, @var{GLOBAL}) -This macro chooses the encoding of pointers embedded in the exception -handling sections. If at all possible, this should be defined such -that the exception handling section will not require dynamic relocations, -and so may be read-only. - -@var{CODE} is 0 for data, 1 for code labels, 2 for function pointers. -@var{GLOBAL} is true if the symbol may be affected by dynamic relocations. -The macro should return a combination of the @code{DW_EH_PE_*} defines -as found in @file{dwarf2.h}. - -If this macro is not defined, pointers will not be encoded but -represented directly. - -@findex ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX -@item ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX(@var{FILE}, @var{ENCODING}, @var{SIZE}, @var{ADDR}, @var{DONE}) -This macro allows the target to emit whatever special magic is required -to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}. -Generic code takes care of pc-relative and indirect encodings; this must -be defined if the target uses text-relative or data-relative encodings. - -This is a C statement that branches to @var{DONE} if the format was -handled. @var{ENCODING} is the format chosen, @var{SIZE} is the number -of bytes that the format occupies, @var{ADDR} is the @code{SYMBOL_REF} -to be emitted. - -@findex SMALL_STACK -@item SMALL_STACK -Define this macro if the stack size for the target is very small. This -has the effect of disabling gcc's builtin @samp{alloca}, though -@samp{__builtin_alloca} is not affected. -@end table - -@node Stack Checking -@subsection Specifying How Stack Checking is Done - -GCC will check that stack references are within the boundaries of -the stack, if the @samp{-fstack-check} is specified, in one of three ways: - -@enumerate -@item -If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC -will assume that you have arranged for stack checking to be done at -appropriate places in the configuration files, e.g., in -@code{FUNCTION_PROLOGUE}. GCC will do not other special processing. - -@item -If @code{STACK_CHECK_BUILTIN} is zero and you defined a named pattern -called @code{check_stack} in your @file{md} file, GCC will call that -pattern with one argument which is the address to compare the stack -value against. You must arrange for this pattern to report an error if -the stack pointer is out of range. - -@item -If neither of the above are true, GCC will generate code to periodically -``probe'' the stack pointer using the values of the macros defined below. -@end enumerate - -Normally, you will use the default values of these macros, so GCC -will use the third approach. - -@table @code -@findex STACK_CHECK_BUILTIN -@item STACK_CHECK_BUILTIN -A nonzero value if stack checking is done by the configuration files in a -machine-dependent manner. You should define this macro if stack checking -is require by the ABI of your machine or if you would like to have to stack -checking in some more efficient way than GCC's portable approach. -The default value of this macro is zero. - -@findex STACK_CHECK_PROBE_INTERVAL -@item STACK_CHECK_PROBE_INTERVAL -An integer representing the interval at which GCC must generate stack -probe instructions. You will normally define this macro to be no larger -than the size of the ``guard pages'' at the end of a stack area. The -default value of 4096 is suitable for most systems. - -@findex STACK_CHECK_PROBE_LOAD -@item STACK_CHECK_PROBE_LOAD -A integer which is nonzero if GCC should perform the stack probe -as a load instruction and zero if GCC should use a store instruction. -The default is zero, which is the most efficient choice on most systems. - -@findex STACK_CHECK_PROTECT -@item STACK_CHECK_PROTECT -The number of bytes of stack needed to recover from a stack overflow, -for languages where such a recovery is supported. The default value of -75 words should be adequate for most machines. - -@findex STACK_CHECK_MAX_FRAME_SIZE -@item STACK_CHECK_MAX_FRAME_SIZE -The maximum size of a stack frame, in bytes. GCC will generate probe -instructions in non-leaf functions to ensure at least this many bytes of -stack are available. If a stack frame is larger than this size, stack -checking will not be reliable and GCC will issue a warning. The -default is chosen so that GCC only generates one instruction on most -systems. You should normally not change the default value of this macro. - -@findex STACK_CHECK_FIXED_FRAME_SIZE -@item STACK_CHECK_FIXED_FRAME_SIZE -GCC uses this value to generate the above warning message. It -represents the amount of fixed frame used by a function, not including -space for any callee-saved registers, temporaries and user variables. -You need only specify an upper bound for this amount and will normally -use the default of four words. - -@findex STACK_CHECK_MAX_VAR_SIZE -@item STACK_CHECK_MAX_VAR_SIZE -The maximum size, in bytes, of an object that GCC will place in the -fixed area of the stack frame when the user specifies -@samp{-fstack-check}. -GCC computed the default from the values of the above macros and you will -normally not need to override that default. -@end table - -@need 2000 -@node Frame Registers -@subsection Registers That Address the Stack Frame - -@c prevent bad page break with this line -This discusses registers that address the stack frame. - -@table @code -@findex STACK_POINTER_REGNUM -@item STACK_POINTER_REGNUM -The register number of the stack pointer register, which must also be a -fixed register according to @code{FIXED_REGISTERS}. On most machines, -the hardware determines which register this is. - -@findex FRAME_POINTER_REGNUM -@item FRAME_POINTER_REGNUM -The register number of the frame pointer register, which is used to -access automatic variables in the stack frame. On some machines, the -hardware determines which register this is. On other machines, you can -choose any register you wish for this purpose. - -@findex HARD_FRAME_POINTER_REGNUM -@item HARD_FRAME_POINTER_REGNUM -On some machines the offset between the frame pointer and starting -offset of the automatic variables is not known until after register -allocation has been done (for example, because the saved registers are -between these two locations). On those machines, define -@code{FRAME_POINTER_REGNUM} the number of a special, fixed register to -be used internally until the offset is known, and define -@code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number -used for the frame pointer. - -You should define this macro only in the very rare circumstances when it -is not possible to calculate the offset between the frame pointer and -the automatic variables until after register allocation has been -completed. When this macro is defined, you must also indicate in your -definition of @code{ELIMINABLE_REGS} how to eliminate -@code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM} -or @code{STACK_POINTER_REGNUM}. - -Do not define this macro if it would be the same as -@code{FRAME_POINTER_REGNUM}. - -@findex ARG_POINTER_REGNUM -@item ARG_POINTER_REGNUM -The register number of the arg pointer register, which is used to access -the function's argument list. On some machines, this is the same as the -frame pointer register. On some machines, the hardware determines which -register this is. On other machines, you can choose any register you -wish for this purpose. If this is not the same register as the frame -pointer register, then you must mark it as a fixed register according to -@code{FIXED_REGISTERS}, or arrange to be able to eliminate it -(@pxref{Elimination}). - -@findex RETURN_ADDRESS_POINTER_REGNUM -@item RETURN_ADDRESS_POINTER_REGNUM -The register number of the return address pointer register, which is used to -access the current function's return address from the stack. On some -machines, the return address is not at a fixed offset from the frame -pointer or stack pointer or argument pointer. This register can be defined -to point to the return address on the stack, and then be converted by -@code{ELIMINABLE_REGS} into either the frame pointer or stack pointer. - -Do not define this macro unless there is no other way to get the return -address from the stack. - -@findex STATIC_CHAIN_REGNUM -@findex STATIC_CHAIN_INCOMING_REGNUM -@item STATIC_CHAIN_REGNUM -@itemx STATIC_CHAIN_INCOMING_REGNUM -Register numbers used for passing a function's static chain pointer. If -register windows are used, the register number as seen by the called -function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register -number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If -these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need -not be defined.@refill - -The static chain register need not be a fixed register. - -If the static chain is passed in memory, these macros should not be -defined; instead, the next two macros should be defined. - -@findex STATIC_CHAIN -@findex STATIC_CHAIN_INCOMING -@item STATIC_CHAIN -@itemx STATIC_CHAIN_INCOMING -If the static chain is passed in memory, these macros provide rtx giving -@code{mem} expressions that denote where they are stored. -@code{STATIC_CHAIN} and @code{STATIC_CHAIN_INCOMING} give the locations -as seen by the calling and called functions, respectively. Often the former -will be at an offset from the stack pointer and the latter at an offset from -the frame pointer.@refill - -@findex stack_pointer_rtx -@findex frame_pointer_rtx -@findex arg_pointer_rtx -The variables @code{stack_pointer_rtx}, @code{frame_pointer_rtx}, and -@code{arg_pointer_rtx} will have been initialized prior to the use of these -macros and should be used to refer to those items. - -If the static chain is passed in a register, the two previous macros should -be defined instead. -@end table - -@node Elimination -@subsection Eliminating Frame Pointer and Arg Pointer - -@c prevent bad page break with this line -This is about eliminating the frame pointer and arg pointer. - -@table @code -@findex FRAME_POINTER_REQUIRED -@item FRAME_POINTER_REQUIRED -A C expression which is nonzero if a function must have and use a frame -pointer. This expression is evaluated in the reload pass. If its value is -nonzero the function will have a frame pointer. - -The expression can in principle examine the current function and decide -according to the facts, but on most machines the constant 0 or the -constant 1 suffices. Use 0 when the machine allows code to be generated -with no frame pointer, and doing so saves some time or space. Use 1 -when there is no possible advantage to avoiding a frame pointer. - -In certain cases, the compiler does not know how to produce valid code -without a frame pointer. The compiler recognizes those cases and -automatically gives the function a frame pointer regardless of what -@code{FRAME_POINTER_REQUIRED} says. You don't need to worry about -them.@refill - -In a function that does not require a frame pointer, the frame pointer -register can be allocated for ordinary usage, unless you mark it as a -fixed register. See @code{FIXED_REGISTERS} for more information. - -@findex INITIAL_FRAME_POINTER_OFFSET -@findex get_frame_size -@item INITIAL_FRAME_POINTER_OFFSET (@var{depth-var}) -A C statement to store in the variable @var{depth-var} the difference -between the frame pointer and the stack pointer values immediately after -the function prologue. The value would be computed from information -such as the result of @code{get_frame_size ()} and the tables of -registers @code{regs_ever_live} and @code{call_used_regs}. - -If @code{ELIMINABLE_REGS} is defined, this macro will be not be used and -need not be defined. Otherwise, it must be defined even if -@code{FRAME_POINTER_REQUIRED} is defined to always be true; in that -case, you may set @var{depth-var} to anything. - -@findex ELIMINABLE_REGS -@item ELIMINABLE_REGS -If defined, this macro specifies a table of register pairs used to -eliminate unneeded registers that point into the stack frame. If it is not -defined, the only elimination attempted by the compiler is to replace -references to the frame pointer with references to the stack pointer. - -The definition of this macro is a list of structure initializations, each -of which specifies an original and replacement register. - -On some machines, the position of the argument pointer is not known until -the compilation is completed. In such a case, a separate hard register -must be used for the argument pointer. This register can be eliminated by -replacing it with either the frame pointer or the argument pointer, -depending on whether or not the frame pointer has been eliminated. - -In this case, you might specify: -@example -#define ELIMINABLE_REGS \ -@{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \ - @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \ - @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@} -@end example - -Note that the elimination of the argument pointer with the stack pointer is -specified first since that is the preferred elimination. - -@findex CAN_ELIMINATE -@item CAN_ELIMINATE (@var{from-reg}, @var{to-reg}) -A C expression that returns non-zero if the compiler is allowed to try -to replace register number @var{from-reg} with register number -@var{to-reg}. This macro need only be defined if @code{ELIMINABLE_REGS} -is defined, and will usually be the constant 1, since most of the cases -preventing register elimination are things that the compiler already -knows about. - -@findex INITIAL_ELIMINATION_OFFSET -@item INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var}) -This macro is similar to @code{INITIAL_FRAME_POINTER_OFFSET}. It -specifies the initial difference between the specified pair of -registers. This macro must be defined if @code{ELIMINABLE_REGS} is -defined. - -@findex LONGJMP_RESTORE_FROM_STACK -@item LONGJMP_RESTORE_FROM_STACK -Define this macro if the @code{longjmp} function restores registers from -the stack frames, rather than from those saved specifically by -@code{setjmp}. Certain quantities must not be kept in registers across -a call to @code{setjmp} on such machines. -@end table - -@node Stack Arguments -@subsection Passing Function Arguments on the Stack -@cindex arguments on stack -@cindex stack arguments - -The macros in this section control how arguments are passed -on the stack. See the following section for other macros that -control passing certain arguments in registers. - -@table @code -@findex PROMOTE_PROTOTYPES -@item PROMOTE_PROTOTYPES -A C expression whose value is nonzero if an argument declared in -a prototype as an integral type smaller than @code{int} should -actually be passed as an @code{int}. In addition to avoiding -errors in certain cases of mismatch, it also makes for better -code on certain machines. If the macro is not defined in target -header files, it defaults to 0. - -@findex PUSH_ARGS -@item PUSH_ARGS -A C expression. If nonzero, push insns will be used to pass -outgoing arguments. -If the target machine does not have a push instruction, set it to zero. -That directs GCC to use an alternate strategy: to -allocate the entire argument block and then store the arguments into -it. When PUSH_ARGS is nonzero, PUSH_ROUNDING must be defined too. -On some machines, the definition - -@findex PUSH_ROUNDING -@item PUSH_ROUNDING (@var{npushed}) -A C expression that is the number of bytes actually pushed onto the -stack when an instruction attempts to push @var{npushed} bytes. - -On some machines, the definition - -@example -#define PUSH_ROUNDING(BYTES) (BYTES) -@end example - -@noindent -will suffice. But on other machines, instructions that appear -to push one byte actually push two bytes in an attempt to maintain -alignment. Then the definition should be - -@example -#define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1) -@end example - -@findex ACCUMULATE_OUTGOING_ARGS -@findex current_function_outgoing_args_size -@item ACCUMULATE_OUTGOING_ARGS -A C expression. If nonzero, the maximum amount of space required for outgoing arguments -will be computed and placed into the variable -@code{current_function_outgoing_args_size}. No space will be pushed -onto the stack for each call; instead, the function prologue should -increase the stack frame size by this amount. - -Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS} -is not proper. - -@findex REG_PARM_STACK_SPACE -@item REG_PARM_STACK_SPACE (@var{fndecl}) -Define this macro if functions should assume that stack space has been -allocated for arguments even when their values are passed in -registers. - -The value of this macro is the size, in bytes, of the area reserved for -arguments passed in registers for the function represented by @var{fndecl}, -which can be zero if GCC is calling a library function. - -This space can be allocated by the caller, or be a part of the -machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says -which. -@c above is overfull. not sure what to do. --mew 5feb93 did -@c something, not sure if it looks good. --mew 10feb93 - -@findex MAYBE_REG_PARM_STACK_SPACE -@findex FINAL_REG_PARM_STACK_SPACE -@item MAYBE_REG_PARM_STACK_SPACE -@itemx FINAL_REG_PARM_STACK_SPACE (@var{const_size}, @var{var_size}) -Define these macros in addition to the one above if functions might -allocate stack space for arguments even when their values are passed -in registers. These should be used when the stack space allocated -for arguments in registers is not a simple constant independent of the -function declaration. - -The value of the first macro is the size, in bytes, of the area that -we should initially assume would be reserved for arguments passed in registers. - -The value of the second macro is the actual size, in bytes, of the area -that will be reserved for arguments passed in registers. This takes two -arguments: an integer representing the number of bytes of fixed sized -arguments on the stack, and a tree representing the number of bytes of -variable sized arguments on the stack. - -When these macros are defined, @code{REG_PARM_STACK_SPACE} will only be -called for libcall functions, the current function, or for a function -being called when it is known that such stack space must be allocated. -In each case this value can be easily computed. - -When deciding whether a called function needs such stack space, and how -much space to reserve, GCC uses these two macros instead of -@code{REG_PARM_STACK_SPACE}. - -@findex OUTGOING_REG_PARM_STACK_SPACE -@item OUTGOING_REG_PARM_STACK_SPACE -Define this if it is the responsibility of the caller to allocate the area -reserved for arguments passed in registers. - -If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls -whether the space for these arguments counts in the value of -@code{current_function_outgoing_args_size}. - -@findex STACK_PARMS_IN_REG_PARM_AREA -@item STACK_PARMS_IN_REG_PARM_AREA -Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the -stack parameters don't skip the area specified by it. -@c i changed this, makes more sens and it should have taken care of the -@c overfull.. not as specific, tho. --mew 5feb93 - -Normally, when a parameter is not passed in registers, it is placed on the -stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro -suppresses this behavior and causes the parameter to be passed on the -stack in its natural location. - -@findex RETURN_POPS_ARGS -@item RETURN_POPS_ARGS (@var{fundecl}, @var{funtype}, @var{stack-size}) -A C expression that should indicate the number of bytes of its own -arguments that a function pops on returning, or 0 if the -function pops no arguments and the caller must therefore pop them all -after the function returns. - -@var{fundecl} is a C variable whose value is a tree node that describes -the function in question. Normally it is a node of type -@code{FUNCTION_DECL} that describes the declaration of the function. -From this you can obtain the DECL_MACHINE_ATTRIBUTES of the function. - -@var{funtype} is a C variable whose value is a tree node that -describes the function in question. Normally it is a node of type -@code{FUNCTION_TYPE} that describes the data type of the function. -From this it is possible to obtain the data types of the value and -arguments (if known). - -When a call to a library function is being considered, @var{fundecl} -will contain an identifier node for the library function. Thus, if -you need to distinguish among various library functions, you can do so -by their names. Note that ``library function'' in this context means -a function used to perform arithmetic, whose name is known specially -in the compiler and was not mentioned in the C code being compiled. - -@var{stack-size} is the number of bytes of arguments passed on the -stack. If a variable number of bytes is passed, it is zero, and -argument popping will always be the responsibility of the calling function. - -On the Vax, all functions always pop their arguments, so the definition -of this macro is @var{stack-size}. On the 68000, using the standard -calling convention, no functions pop their arguments, so the value of -the macro is always 0 in this case. But an alternative calling -convention is available in which functions that take a fixed number of -arguments pop them but other functions (such as @code{printf}) pop -nothing (the caller pops all). When this convention is in use, -@var{funtype} is examined to determine whether a function takes a fixed -number of arguments. -@end table - -@node Register Arguments -@subsection Passing Arguments in Registers -@cindex arguments in registers -@cindex registers arguments - -This section describes the macros which let you control how various -types of arguments are passed in registers or how they are arranged in -the stack. - -@table @code -@findex FUNCTION_ARG -@item FUNCTION_ARG (@var{cum}, @var{mode}, @var{type}, @var{named}) -A C expression that controls whether a function argument is passed -in a register, and which register. - -The arguments are @var{cum}, which summarizes all the previous -arguments; @var{mode}, the machine mode of the argument; @var{type}, -the data type of the argument as a tree node or 0 if that is not known -(which happens for C support library functions); and @var{named}, -which is 1 for an ordinary argument and 0 for nameless arguments that -correspond to @samp{@dots{}} in the called function's prototype. -@var{type} can be an incomplete type if a syntax error has previously -occurred. - -The value of the expression is usually either a @code{reg} RTX for the -hard register in which to pass the argument, or zero to pass the -argument on the stack. - -For machines like the Vax and 68000, where normally all arguments are -pushed, zero suffices as a definition. - -The value of the expression can also be a @code{parallel} RTX. This is -used when an argument is passed in multiple locations. The mode of the -of the @code{parallel} should be the mode of the entire argument. The -@code{parallel} holds any number of @code{expr_list} pairs; each one -describes where part of the argument is passed. In each -@code{expr_list} the first operand must be a @code{reg} RTX for the hard -register in which to pass this part of the argument, and the mode of the -register RTX indicates how large this part of the argument is. The -second operand of the @code{expr_list} is a @code{const_int} which gives -the offset in bytes into the entire argument of where this part starts. -As a special exception the first @code{expr_list} in the @code{parallel} -RTX may have a first operand of zero. This indicates that the entire -argument is also stored on the stack. - -@cindex @file{stdarg.h} and register arguments -The usual way to make the ISO library @file{stdarg.h} work on a machine -where some arguments are usually passed in registers, is to cause -nameless arguments to be passed on the stack instead. This is done -by making @code{FUNCTION_ARG} return 0 whenever @var{named} is 0. - -@cindex @code{MUST_PASS_IN_STACK}, and @code{FUNCTION_ARG} -@cindex @code{REG_PARM_STACK_SPACE}, and @code{FUNCTION_ARG} -You may use the macro @code{MUST_PASS_IN_STACK (@var{mode}, @var{type})} -in the definition of this macro to determine if this argument is of a -type that must be passed in the stack. If @code{REG_PARM_STACK_SPACE} -is not defined and @code{FUNCTION_ARG} returns non-zero for such an -argument, the compiler will abort. If @code{REG_PARM_STACK_SPACE} is -defined, the argument will be computed in the stack and then loaded into -a register. - -@findex MUST_PASS_IN_STACK -@item MUST_PASS_IN_STACK (@var{mode}, @var{type}) -Define as a C expression that evaluates to nonzero if we do not know how -to pass TYPE solely in registers. The file @file{expr.h} defines a -definition that is usually appropriate, refer to @file{expr.h} for additional -documentation. - -@findex FUNCTION_INCOMING_ARG -@item FUNCTION_INCOMING_ARG (@var{cum}, @var{mode}, @var{type}, @var{named}) -Define this macro if the target machine has ``register windows'', so -that the register in which a function sees an arguments is not -necessarily the same as the one in which the caller passed the -argument. - -For such machines, @code{FUNCTION_ARG} computes the register in which -the caller passes the value, and @code{FUNCTION_INCOMING_ARG} should -be defined in a similar fashion to tell the function being called -where the arguments will arrive. - -If @code{FUNCTION_INCOMING_ARG} is not defined, @code{FUNCTION_ARG} -serves both purposes.@refill - -@findex FUNCTION_ARG_PARTIAL_NREGS -@item FUNCTION_ARG_PARTIAL_NREGS (@var{cum}, @var{mode}, @var{type}, @var{named}) -A C expression for the number of words, at the beginning of an -argument, that must be put in registers. The value must be zero for -arguments that are passed entirely in registers or that are entirely -pushed on the stack. - -On some machines, certain arguments must be passed partially in -registers and partially in memory. On these machines, typically the -first @var{n} words of arguments are passed in registers, and the rest -on the stack. If a multi-word argument (a @code{double} or a -structure) crosses that boundary, its first few words must be passed -in registers and the rest must be pushed. This macro tells the -compiler when this occurs, and how many of the words should go in -registers. - -@code{FUNCTION_ARG} for these arguments should return the first -register to be used by the caller for this argument; likewise -@code{FUNCTION_INCOMING_ARG}, for the called function. - -@findex FUNCTION_ARG_PASS_BY_REFERENCE -@item FUNCTION_ARG_PASS_BY_REFERENCE (@var{cum}, @var{mode}, @var{type}, @var{named}) -A C expression that indicates when an argument must be passed by reference. -If nonzero for an argument, a copy of that argument is made in memory and a -pointer to the argument is passed instead of the argument itself. -The pointer is passed in whatever way is appropriate for passing a pointer -to that type. - -On machines where @code{REG_PARM_STACK_SPACE} is not defined, a suitable -definition of this macro might be -@smallexample -#define FUNCTION_ARG_PASS_BY_REFERENCE\ -(CUM, MODE, TYPE, NAMED) \ - MUST_PASS_IN_STACK (MODE, TYPE) -@end smallexample -@c this is *still* too long. --mew 5feb93 - -@findex FUNCTION_ARG_CALLEE_COPIES -@item FUNCTION_ARG_CALLEE_COPIES (@var{cum}, @var{mode}, @var{type}, @var{named}) -If defined, a C expression that indicates when it is the called function's -responsibility to make a copy of arguments passed by invisible reference. -Normally, the caller makes a copy and passes the address of the copy to the -routine being called. When FUNCTION_ARG_CALLEE_COPIES is defined and is -nonzero, the caller does not make a copy. Instead, it passes a pointer to the -``live'' value. The called function must not modify this value. If it can be -determined that the value won't be modified, it need not make a copy; -otherwise a copy must be made. - -@findex CUMULATIVE_ARGS -@item CUMULATIVE_ARGS -A C type for declaring a variable that is used as the first argument of -@code{FUNCTION_ARG} and other related values. For some target machines, -the type @code{int} suffices and can hold the number of bytes of -argument so far. - -There is no need to record in @code{CUMULATIVE_ARGS} anything about the -arguments that have been passed on the stack. The compiler has other -variables to keep track of that. For target machines on which all -arguments are passed on the stack, there is no need to store anything in -@code{CUMULATIVE_ARGS}; however, the data structure must exist and -should not be empty, so use @code{int}. - -@findex INIT_CUMULATIVE_ARGS -@item INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{indirect}) -A C statement (sans semicolon) for initializing the variable @var{cum} -for the state at the beginning of the argument list. The variable has -type @code{CUMULATIVE_ARGS}. The value of @var{fntype} is the tree node -for the data type of the function which will receive the args, or 0 -if the args are to a compiler support library function. The value of -@var{indirect} is nonzero when processing an indirect call, for example -a call through a function pointer. The value of @var{indirect} is zero -for a call to an explicitly named function, a library function call, or when -@code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function -being compiled. - -When processing a call to a compiler support library function, -@var{libname} identifies which one. It is a @code{symbol_ref} rtx which -contains the name of the function, as a string. @var{libname} is 0 when -an ordinary C function call is being processed. Thus, each time this -macro is called, either @var{libname} or @var{fntype} is nonzero, but -never both of them at once. - -@findex INIT_CUMULATIVE_LIBCALL_ARGS -@item INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname}) -Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls, -it gets a @code{MODE} argument instead of @var{fntype}, that would be -@code{NULL}. @var{indirect} would always be zero, too. If this macro -is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname, -0)} is used instead. - -@findex INIT_CUMULATIVE_INCOMING_ARGS -@item INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname}) -Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of -finding the arguments for the function being compiled. If this macro is -undefined, @code{INIT_CUMULATIVE_ARGS} is used instead. - -The value passed for @var{libname} is always 0, since library routines -with special calling conventions are never compiled with GCC. The -argument @var{libname} exists for symmetry with -@code{INIT_CUMULATIVE_ARGS}. -@c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe. -@c --mew 5feb93 i switched the order of the sentences. --mew 10feb93 - -@findex FUNCTION_ARG_ADVANCE -@item FUNCTION_ARG_ADVANCE (@var{cum}, @var{mode}, @var{type}, @var{named}) -A C statement (sans semicolon) to update the summarizer variable -@var{cum} to advance past an argument in the argument list. The -values @var{mode}, @var{type} and @var{named} describe that argument. -Once this is done, the variable @var{cum} is suitable for analyzing -the @emph{following} argument with @code{FUNCTION_ARG}, etc.@refill - -This macro need not do anything if the argument in question was passed -on the stack. The compiler knows how to track the amount of stack space -used for arguments without any special help. - -@findex FUNCTION_ARG_PADDING -@item FUNCTION_ARG_PADDING (@var{mode}, @var{type}) -If defined, a C expression which determines whether, and in which direction, -to pad out an argument with extra space. The value should be of type -@code{enum direction}: either @code{upward} to pad above the argument, -@code{downward} to pad below, or @code{none} to inhibit padding. - -The @emph{amount} of padding is always just enough to reach the next -multiple of @code{FUNCTION_ARG_BOUNDARY}; this macro does not control -it. - -This macro has a default definition which is right for most systems. -For little-endian machines, the default is to pad upward. For -big-endian machines, the default is to pad downward for an argument of -constant size shorter than an @code{int}, and upward otherwise. - -@findex PAD_VARARGS_DOWN -@item PAD_VARARGS_DOWN -If defined, a C expression which determines whether the default -implementation of va_arg will attempt to pad down before reading the -next argument, if that argument is smaller than its aligned space as -controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such -arguments are padded down if @code{BYTES_BIG_ENDIAN} is true. - -@findex FUNCTION_ARG_BOUNDARY -@item FUNCTION_ARG_BOUNDARY (@var{mode}, @var{type}) -If defined, a C expression that gives the alignment boundary, in bits, -of an argument with the specified mode and type. If it is not defined, -@code{PARM_BOUNDARY} is used for all arguments. - -@findex FUNCTION_ARG_REGNO_P -@item FUNCTION_ARG_REGNO_P (@var{regno}) -A C expression that is nonzero if @var{regno} is the number of a hard -register in which function arguments are sometimes passed. This does -@emph{not} include implicit arguments such as the static chain and -the structure-value address. On many machines, no registers can be -used for this purpose since all function arguments are pushed on the -stack. - -@findex LOAD_ARGS_REVERSED -@item LOAD_ARGS_REVERSED -If defined, the order in which arguments are loaded into their -respective argument registers is reversed so that the last -argument is loaded first. This macro only affects arguments -passed in registers. - -@end table - -@node Scalar Return -@subsection How Scalar Function Values Are Returned -@cindex return values in registers -@cindex values, returned by functions -@cindex scalars, returned as values - -This section discusses the macros that control returning scalars as -values---values that can fit in registers. - -@table @code -@findex TRADITIONAL_RETURN_FLOAT -@item TRADITIONAL_RETURN_FLOAT -Define this macro if @samp{-traditional} should not cause functions -declared to return @code{float} to convert the value to @code{double}. - -@findex FUNCTION_VALUE -@item FUNCTION_VALUE (@var{valtype}, @var{func}) -A C expression to create an RTX representing the place where a -function returns a value of data type @var{valtype}. @var{valtype} is -a tree node representing a data type. Write @code{TYPE_MODE -(@var{valtype})} to get the machine mode used to represent that type. -On many machines, only the mode is relevant. (Actually, on most -machines, scalar values are returned in the same place regardless of -mode).@refill - -The value of the expression is usually a @code{reg} RTX for the hard -register where the return value is stored. The value can also be a -@code{parallel} RTX, if the return value is in multiple places. See -@code{FUNCTION_ARG} for an explanation of the @code{parallel} form. - -If @code{PROMOTE_FUNCTION_RETURN} is defined, you must apply the same -promotion rules specified in @code{PROMOTE_MODE} if @var{valtype} is a -scalar type. - -If the precise function being called is known, @var{func} is a tree -node (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null -pointer. This makes it possible to use a different value-returning -convention for specific functions when all their calls are -known.@refill - -@code{FUNCTION_VALUE} is not used for return vales with aggregate data -types, because these are returned in another way. See -@code{STRUCT_VALUE_REGNUM} and related macros, below. - -@findex FUNCTION_OUTGOING_VALUE -@item FUNCTION_OUTGOING_VALUE (@var{valtype}, @var{func}) -Define this macro if the target machine has ``register windows'' -so that the register in which a function returns its value is not -the same as the one in which the caller sees the value. - -For such machines, @code{FUNCTION_VALUE} computes the register in which -the caller will see the value. @code{FUNCTION_OUTGOING_VALUE} should be -defined in a similar fashion to tell the function where to put the -value.@refill - -If @code{FUNCTION_OUTGOING_VALUE} is not defined, -@code{FUNCTION_VALUE} serves both purposes.@refill - -@code{FUNCTION_OUTGOING_VALUE} is not used for return vales with -aggregate data types, because these are returned in another way. See -@code{STRUCT_VALUE_REGNUM} and related macros, below. - -@findex LIBCALL_VALUE -@item LIBCALL_VALUE (@var{mode}) -A C expression to create an RTX representing the place where a library -function returns a value of mode @var{mode}. If the precise function -being called is known, @var{func} is a tree node -(@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null -pointer. This makes it possible to use a different value-returning -convention for specific functions when all their calls are -known.@refill - -Note that ``library function'' in this context means a compiler -support routine, used to perform arithmetic, whose name is known -specially by the compiler and was not mentioned in the C code being -compiled. - -The definition of @code{LIBRARY_VALUE} need not be concerned aggregate -data types, because none of the library functions returns such types. - -@findex FUNCTION_VALUE_REGNO_P -@item FUNCTION_VALUE_REGNO_P (@var{regno}) -A C expression that is nonzero if @var{regno} is the number of a hard -register in which the values of called function may come back. - -A register whose use for returning values is limited to serving as the -second of a pair (for a value of type @code{double}, say) need not be -recognized by this macro. So for most machines, this definition -suffices: - -@example -#define FUNCTION_VALUE_REGNO_P(N) ((N) == 0) -@end example - -If the machine has register windows, so that the caller and the called -function use different registers for the return value, this macro -should recognize only the caller's register numbers. - -@findex APPLY_RESULT_SIZE -@item APPLY_RESULT_SIZE -Define this macro if @samp{untyped_call} and @samp{untyped_return} -need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for -saving and restoring an arbitrary return value. -@end table - -@node Aggregate Return -@subsection How Large Values Are Returned -@cindex aggregates as return values -@cindex large return values -@cindex returning aggregate values -@cindex structure value address - -When a function value's mode is @code{BLKmode} (and in some other -cases), the value is not returned according to @code{FUNCTION_VALUE} -(@pxref{Scalar Return}). Instead, the caller passes the address of a -block of memory in which the value should be stored. This address -is called the @dfn{structure value address}. - -This section describes how to control returning structure values in -memory. - -@table @code -@findex RETURN_IN_MEMORY -@item RETURN_IN_MEMORY (@var{type}) -A C expression which can inhibit the returning of certain function -values in registers, based on the type of value. A nonzero value says -to return the function value in memory, just as large structures are -always returned. Here @var{type} will be a C expression of type -@code{tree}, representing the data type of the value. - -Note that values of mode @code{BLKmode} must be explicitly handled -by this macro. Also, the option @samp{-fpcc-struct-return} -takes effect regardless of this macro. On most systems, it is -possible to leave the macro undefined; this causes a default -definition to be used, whose value is the constant 1 for @code{BLKmode} -values, and 0 otherwise. - -Do not use this macro to indicate that structures and unions should always -be returned in memory. You should instead use @code{DEFAULT_PCC_STRUCT_RETURN} -to indicate this. - -@findex DEFAULT_PCC_STRUCT_RETURN -@item DEFAULT_PCC_STRUCT_RETURN -Define this macro to be 1 if all structure and union return values must be -in memory. Since this results in slower code, this should be defined -only if needed for compatibility with other compilers or with an ABI. -If you define this macro to be 0, then the conventions used for structure -and union return values are decided by the @code{RETURN_IN_MEMORY} macro. - -If not defined, this defaults to the value 1. - -@findex STRUCT_VALUE_REGNUM -@item STRUCT_VALUE_REGNUM -If the structure value address is passed in a register, then -@code{STRUCT_VALUE_REGNUM} should be the number of that register. - -@findex STRUCT_VALUE -@item STRUCT_VALUE -If the structure value address is not passed in a register, define -@code{STRUCT_VALUE} as an expression returning an RTX for the place -where the address is passed. If it returns 0, the address is passed as -an ``invisible'' first argument. - -@findex STRUCT_VALUE_INCOMING_REGNUM -@item STRUCT_VALUE_INCOMING_REGNUM -On some architectures the place where the structure value address -is found by the called function is not the same place that the -caller put it. This can be due to register windows, or it could -be because the function prologue moves it to a different place. - -If the incoming location of the structure value address is in a -register, define this macro as the register number. - -@findex STRUCT_VALUE_INCOMING -@item STRUCT_VALUE_INCOMING -If the incoming location is not a register, then you should define -@code{STRUCT_VALUE_INCOMING} as an expression for an RTX for where the -called function should find the value. If it should find the value on -the stack, define this to create a @code{mem} which refers to the frame -pointer. A definition of 0 means that the address is passed as an -``invisible'' first argument. - -@findex PCC_STATIC_STRUCT_RETURN -@item PCC_STATIC_STRUCT_RETURN -Define this macro if the usual system convention on the target machine -for returning structures and unions is for the called function to return -the address of a static variable containing the value. - -Do not define this if the usual system convention is for the caller to -pass an address to the subroutine. - -This macro has effect in @samp{-fpcc-struct-return} mode, but it does -nothing when you use @samp{-freg-struct-return} mode. -@end table - -@node Caller Saves -@subsection Caller-Saves Register Allocation - -If you enable it, GCC can save registers around function calls. This -makes it possible to use call-clobbered registers to hold variables that -must live across calls. - -@table @code -@findex DEFAULT_CALLER_SAVES -@item DEFAULT_CALLER_SAVES -Define this macro if function calls on the target machine do not preserve -any registers; in other words, if @code{CALL_USED_REGISTERS} has 1 -for all registers. When defined, this macro enables @samp{-fcaller-saves} -by default for all optimization levels. It has no effect for optimization -levels 2 and higher, where @samp{-fcaller-saves} is the default. - -@findex CALLER_SAVE_PROFITABLE -@item CALLER_SAVE_PROFITABLE (@var{refs}, @var{calls}) -A C expression to determine whether it is worthwhile to consider placing -a pseudo-register in a call-clobbered hard register and saving and -restoring it around each function call. The expression should be 1 when -this is worth doing, and 0 otherwise. - -If you don't define this macro, a default is used which is good on most -machines: @code{4 * @var{calls} < @var{refs}}. - -@findex HARD_REGNO_CALLER_SAVE_MODE -@item HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs}) -A C expression specifying which mode is required for saving @var{nregs} -of a pseudo-register in call-clobbered hard register @var{regno}. If -@var{regno} is unsuitable for caller save, @code{VOIDmode} should be -returned. For most machines this macro need not be defined since GCC -will select the smallest suitable mode. -@end table - -@node Function Entry -@subsection Function Entry and Exit -@cindex function entry and exit -@cindex prologue -@cindex epilogue - -This section describes the macros that output function entry -(@dfn{prologue}) and exit (@dfn{epilogue}) code. - -@table @code -@findex FUNCTION_PROLOGUE -@item FUNCTION_PROLOGUE (@var{file}, @var{size}) -A C compound statement that outputs the assembler code for entry to a -function. The prologue is responsible for setting up the stack frame, -initializing the frame pointer register, saving registers that must be -saved, and allocating @var{size} additional bytes of storage for the -local variables. @var{size} is an integer. @var{file} is a stdio -stream to which the assembler code should be output. - -The label for the beginning of the function need not be output by this -macro. That has already been done when the macro is run. - -@findex regs_ever_live -To determine which registers to save, the macro can refer to the array -@code{regs_ever_live}: element @var{r} is nonzero if hard register -@var{r} is used anywhere within the function. This implies the function -prologue should save register @var{r}, provided it is not one of the -call-used registers. (@code{FUNCTION_EPILOGUE} must likewise use -@code{regs_ever_live}.) - -On machines that have ``register windows'', the function entry code does -not save on the stack the registers that are in the windows, even if -they are supposed to be preserved by function calls; instead it takes -appropriate steps to ``push'' the register stack, if any non-call-used -registers are used in the function. - -@findex frame_pointer_needed -On machines where functions may or may not have frame-pointers, the -function entry code must vary accordingly; it must set up the frame -pointer if one is wanted, and not otherwise. To determine whether a -frame pointer is in wanted, the macro can refer to the variable -@code{frame_pointer_needed}. The variable's value will be 1 at run -time in a function that needs a frame pointer. @xref{Elimination}. - -The function entry code is responsible for allocating any stack space -required for the function. This stack space consists of the regions -listed below. In most cases, these regions are allocated in the -order listed, with the last listed region closest to the top of the -stack (the lowest address if @code{STACK_GROWS_DOWNWARD} is defined, and -the highest address if it is not defined). You can use a different order -for a machine if doing so is more convenient or required for -compatibility reasons. Except in cases where required by standard -or by a debugger, there is no reason why the stack layout used by GCC -need agree with that used by other compilers for a machine. - -@itemize @bullet -@item -@findex current_function_pretend_args_size -A region of @code{current_function_pretend_args_size} bytes of -uninitialized space just underneath the first argument arriving on the -stack. (This may not be at the very start of the allocated stack region -if the calling sequence has pushed anything else since pushing the stack -arguments. But usually, on such machines, nothing else has been pushed -yet, because the function prologue itself does all the pushing.) This -region is used on machines where an argument may be passed partly in -registers and partly in memory, and, in some cases to support the -features in @file{varargs.h} and @file{stdargs.h}. - -@item -An area of memory used to save certain registers used by the function. -The size of this area, which may also include space for such things as -the return address and pointers to previous stack frames, is -machine-specific and usually depends on which registers have been used -in the function. Machines with register windows often do not require -a save area. - -@item -A region of at least @var{size} bytes, possibly rounded up to an allocation -boundary, to contain the local variables of the function. On some machines, -this region and the save area may occur in the opposite order, with the -save area closer to the top of the stack. - -@item -@cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames -Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of -@code{current_function_outgoing_args_size} bytes to be used for outgoing -argument lists of the function. @xref{Stack Arguments}. -@end itemize - -Normally, it is necessary for the macros @code{FUNCTION_PROLOGUE} and -@code{FUNCTION_EPILOGUE} to treat leaf functions specially. The C -variable @code{current_function_is_leaf} is nonzero for such a function. - -@findex EXIT_IGNORE_STACK -@item EXIT_IGNORE_STACK -Define this macro as a C expression that is nonzero if the return -instruction or the function epilogue ignores the value of the stack -pointer; in other words, if it is safe to delete an instruction to -adjust the stack pointer before a return from the function. - -Note that this macro's value is relevant only for functions for which -frame pointers are maintained. It is never safe to delete a final -stack adjustment in a function that has no frame pointer, and the -compiler knows this regardless of @code{EXIT_IGNORE_STACK}. - -@findex EPILOGUE_USES -@item EPILOGUE_USES (@var{regno}) -Define this macro as a C expression that is nonzero for registers that are -used by the epilogue or the @samp{return} pattern. The stack and frame -pointer registers are already be assumed to be used as needed. - -@findex FUNCTION_EPILOGUE -@item FUNCTION_EPILOGUE (@var{file}, @var{size}) -A C compound statement that outputs the assembler code for exit from a -function. The epilogue is responsible for restoring the saved -registers and stack pointer to their values when the function was -called, and returning control to the caller. This macro takes the -same arguments as the macro @code{FUNCTION_PROLOGUE}, and the -registers to restore are determined from @code{regs_ever_live} and -@code{CALL_USED_REGISTERS} in the same way. - -On some machines, there is a single instruction that does all the work -of returning from the function. On these machines, give that -instruction the name @samp{return} and do not define the macro -@code{FUNCTION_EPILOGUE} at all. - -Do not define a pattern named @samp{return} if you want the -@code{FUNCTION_EPILOGUE} to be used. If you want the target switches -to control whether return instructions or epilogues are used, define a -@samp{return} pattern with a validity condition that tests the target -switches appropriately. If the @samp{return} pattern's validity -condition is false, epilogues will be used. - -On machines where functions may or may not have frame-pointers, the -function exit code must vary accordingly. Sometimes the code for these -two cases is completely different. To determine whether a frame pointer -is wanted, the macro can refer to the variable -@code{frame_pointer_needed}. The variable's value will be 1 when compiling -a function that needs a frame pointer. - -Normally, @code{FUNCTION_PROLOGUE} and @code{FUNCTION_EPILOGUE} must -treat leaf functions specially. The C variable @code{current_function_is_leaf} -is nonzero for such a function. @xref{Leaf Functions}. - -On some machines, some functions pop their arguments on exit while -others leave that for the caller to do. For example, the 68020 when -given @samp{-mrtd} pops arguments in functions that take a fixed -number of arguments. - -@findex current_function_pops_args -Your definition of the macro @code{RETURN_POPS_ARGS} decides which -functions pop their own arguments. @code{FUNCTION_EPILOGUE} needs to -know what was decided. The variable that is called -@code{current_function_pops_args} is the number of bytes of its -arguments that a function should pop. @xref{Scalar Return}. -@c what is the "its arguments" in the above sentence referring to, pray -@c tell? --mew 5feb93 - -@findex DELAY_SLOTS_FOR_EPILOGUE -@item DELAY_SLOTS_FOR_EPILOGUE -Define this macro if the function epilogue contains delay slots to which -instructions from the rest of the function can be ``moved''. The -definition should be a C expression whose value is an integer -representing the number of delay slots there. - -@findex ELIGIBLE_FOR_EPILOGUE_DELAY -@item ELIGIBLE_FOR_EPILOGUE_DELAY (@var{insn}, @var{n}) -A C expression that returns 1 if @var{insn} can be placed in delay -slot number @var{n} of the epilogue. - -The argument @var{n} is an integer which identifies the delay slot now -being considered (since different slots may have different rules of -eligibility). It is never negative and is always less than the number -of epilogue delay slots (what @code{DELAY_SLOTS_FOR_EPILOGUE} returns). -If you reject a particular insn for a given delay slot, in principle, it -may be reconsidered for a subsequent delay slot. Also, other insns may -(at least in principle) be considered for the so far unfilled delay -slot. - -@findex current_function_epilogue_delay_list -@findex final_scan_insn -The insns accepted to fill the epilogue delay slots are put in an RTL -list made with @code{insn_list} objects, stored in the variable -@code{current_function_epilogue_delay_list}. The insn for the first -delay slot comes first in the list. Your definition of the macro -@code{FUNCTION_EPILOGUE} should fill the delay slots by outputting the -insns in this list, usually by calling @code{final_scan_insn}. - -You need not define this macro if you did not define -@code{DELAY_SLOTS_FOR_EPILOGUE}. - -@findex ASM_OUTPUT_MI_THUNK -@item ASM_OUTPUT_MI_THUNK (@var{file}, @var{thunk_fndecl}, @var{delta}, @var{function}) -A C compound statement that outputs the assembler code for a thunk -function, used to implement C++ virtual function calls with multiple -inheritance. The thunk acts as a wrapper around a virtual function, -adjusting the implicit object parameter before handing control off to -the real function. - -First, emit code to add the integer @var{delta} to the location that -contains the incoming first argument. Assume that this argument -contains a pointer, and is the one used to pass the @code{this} pointer -in C++. This is the incoming argument @emph{before} the function prologue, -e.g. @samp{%o0} on a sparc. The addition must preserve the values of -all other incoming arguments. - -After the addition, emit code to jump to @var{function}, which is a -@code{FUNCTION_DECL}. This is a direct pure jump, not a call, and does -not touch the return address. Hence returning from @var{FUNCTION} will -return to whoever called the current @samp{thunk}. - -The effect must be as if @var{function} had been called directly with -the adjusted first argument. This macro is responsible for emitting all -of the code for a thunk function; @code{FUNCTION_PROLOGUE} and -@code{FUNCTION_EPILOGUE} are not invoked. - -The @var{thunk_fndecl} is redundant. (@var{delta} and @var{function} -have already been extracted from it.) It might possibly be useful on -some targets, but probably not. - -If you do not define this macro, the target-independent code in the C++ -frontend will generate a less efficient heavyweight thunk that calls -@var{function} instead of jumping to it. The generic approach does -not support varargs. -@end table - -@node Profiling -@subsection Generating Code for Profiling -@cindex profiling, code generation - -These macros will help you generate code for profiling. - -@table @code -@findex FUNCTION_PROFILER -@item FUNCTION_PROFILER (@var{file}, @var{labelno}) -A C statement or compound statement to output to @var{file} some -assembler code to call the profiling subroutine @code{mcount}. - -@findex mcount -The details of how @code{mcount} expects to be called are determined by -your operating system environment, not by GCC. To figure them out, -compile a small program for profiling using the system's installed C -compiler and look at the assembler code that results. - -Older implementations of @code{mcount} expect the address of a counter -variable to be loaded into some register. The name of this variable is -@samp{LP} followed by the number @var{labelno}, so you would generate -the name using @samp{LP%d} in a @code{fprintf}. - -@findex PROFILE_HOOK -@item PROFILE_HOOK -A C statement or compound statement to output to @var{file} some assembly -code to call the profiling subroutine @code{mcount} even the target does -not support profiling. - -@findex NO_PROFILE_COUNTERS -@item NO_PROFILE_COUNTERS -Define this macro if the @code{mcount} subroutine on your system does -not need a counter variable allocated for each function. This is true -for almost all modern implementations. If you define this macro, you -must not use the @var{labelno} argument to @code{FUNCTION_PROFILER}. - -@findex PROFILE_BEFORE_PROLOGUE -@item PROFILE_BEFORE_PROLOGUE -Define this macro if the code for function profiling should come before -the function prologue. Normally, the profiling code comes after. - -@findex FUNCTION_BLOCK_PROFILER -@vindex profile_block_flag -@item FUNCTION_BLOCK_PROFILER (@var{file}, @var{labelno}) -A C statement or compound statement to output to @var{file} some -assembler code to initialize basic-block profiling for the current -object module. The global compile flag @code{profile_block_flag} -distinguishes two profile modes. - -@table @code -@findex __bb_init_func -@item profile_block_flag != 2 -Output code to call the subroutine @code{__bb_init_func} once per -object module, passing it as its sole argument the address of a block -allocated in the object module. - -The name of the block is a local symbol made with this statement: - -@smallexample -ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 0); -@end smallexample - -Of course, since you are writing the definition of -@code{ASM_GENERATE_INTERNAL_LABEL} as well as that of this macro, you -can take a short cut in the definition of this macro and use the name -that you know will result. - -The first word of this block is a flag which will be nonzero if the -object module has already been initialized. So test this word first, -and do not call @code{__bb_init_func} if the flag is -nonzero. BLOCK_OR_LABEL contains a unique number which may be used to -generate a label as a branch destination when @code{__bb_init_func} -will not be called. - -Described in assembler language, the code to be output looks like: - -@example - cmp (LPBX0),0 - bne local_label - parameter1 <- LPBX0 - call __bb_init_func -local_label: -@end example - -@findex __bb_init_trace_func -@item profile_block_flag == 2 -Output code to call the subroutine @code{__bb_init_trace_func} -and pass two parameters to it. The first parameter is the same as -for @code{__bb_init_func}. The second parameter is the number of the -first basic block of the function as given by BLOCK_OR_LABEL. Note -that @code{__bb_init_trace_func} has to be called, even if the object -module has been initialized already. - -Described in assembler language, the code to be output looks like: -@example -parameter1 <- LPBX0 -parameter2 <- BLOCK_OR_LABEL -call __bb_init_trace_func -@end example -@end table - -@findex BLOCK_PROFILER -@vindex profile_block_flag -@item BLOCK_PROFILER (@var{file}, @var{blockno}) -A C statement or compound statement to output to @var{file} some -assembler code to increment the count associated with the basic -block number @var{blockno}. The global compile flag -@code{profile_block_flag} distinguishes two profile modes. - -@table @code -@item profile_block_flag != 2 -Output code to increment the counter directly. Basic blocks are -numbered separately from zero within each compilation. The count -associated with block number @var{blockno} is at index -@var{blockno} in a vector of words; the name of this array is a local -symbol made with this statement: - -@smallexample -ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 2); -@end smallexample - -@c This paragraph is the same as one a few paragraphs up. -@c That is not an error. -Of course, since you are writing the definition of -@code{ASM_GENERATE_INTERNAL_LABEL} as well as that of this macro, you -can take a short cut in the definition of this macro and use the name -that you know will result. - -Described in assembler language, the code to be output looks like: - -@smallexample -inc (LPBX2+4*BLOCKNO) -@end smallexample - -@vindex __bb -@findex __bb_trace_func -@item profile_block_flag == 2 -Output code to initialize the global structure @code{__bb} and -call the function @code{__bb_trace_func}, which will increment the -counter. - -@code{__bb} consists of two words. In the first word, the current -basic block number, as given by BLOCKNO, has to be stored. In -the second word, the address of a block allocated in the object -module has to be stored. The address is given by the label created -with this statement: - -@smallexample -ASM_GENERATE_INTERNAL_LABEL (@var{buffer}, "LPBX", 0); -@end smallexample - -Described in assembler language, the code to be output looks like: -@example -move BLOCKNO -> (__bb) -move LPBX0 -> (__bb+4) -call __bb_trace_func -@end example -@end table - -@findex FUNCTION_BLOCK_PROFILER_EXIT -@findex __bb_trace_ret -@vindex profile_block_flag -@item FUNCTION_BLOCK_PROFILER_EXIT (@var{file}) -A C statement or compound statement to output to @var{file} -assembler code to call function @code{__bb_trace_ret}. The -assembler code should only be output -if the global compile flag @code{profile_block_flag} == 2. This -macro has to be used at every place where code for returning from -a function is generated (e.g. @code{FUNCTION_EPILOGUE}). Although -you have to write the definition of @code{FUNCTION_EPILOGUE} -as well, you have to define this macro to tell the compiler, that -the proper call to @code{__bb_trace_ret} is produced. - -@findex MACHINE_STATE_SAVE -@findex __bb_init_trace_func -@findex __bb_trace_func -@findex __bb_trace_ret -@item MACHINE_STATE_SAVE (@var{id}) -A C statement or compound statement to save all registers, which may -be clobbered by a function call, including condition codes. The -@code{asm} statement will be mostly likely needed to handle this -task. Local labels in the assembler code can be concatenated with the -string @var{id}, to obtain a unique label name. - -Registers or condition codes clobbered by @code{FUNCTION_PROLOGUE} or -@code{FUNCTION_EPILOGUE} must be saved in the macros -@code{FUNCTION_BLOCK_PROFILER}, @code{FUNCTION_BLOCK_PROFILER_EXIT} and -@code{BLOCK_PROFILER} prior calling @code{__bb_init_trace_func}, -@code{__bb_trace_ret} and @code{__bb_trace_func} respectively. - -@findex MACHINE_STATE_RESTORE -@findex __bb_init_trace_func -@findex __bb_trace_func -@findex __bb_trace_ret -@item MACHINE_STATE_RESTORE (@var{id}) -A C statement or compound statement to restore all registers, including -condition codes, saved by @code{MACHINE_STATE_SAVE}. - -Registers or condition codes clobbered by @code{FUNCTION_PROLOGUE} or -@code{FUNCTION_EPILOGUE} must be restored in the macros -@code{FUNCTION_BLOCK_PROFILER}, @code{FUNCTION_BLOCK_PROFILER_EXIT} and -@code{BLOCK_PROFILER} after calling @code{__bb_init_trace_func}, -@code{__bb_trace_ret} and @code{__bb_trace_func} respectively. - -@findex BLOCK_PROFILER_CODE -@item BLOCK_PROFILER_CODE -A C function or functions which are needed in the library to -support block profiling. - -@findex TARGET_ALLOWS_PROFILING_WITHOUT_FRAME_POINTER -@item TARGET_ALLOWS_PROFILING_WITHOUT_FRAME_POINTER -On some targets, it is impossible to use profiling when the frame -pointer has been omitted. For example, on x86 GNU/Linux systems, -the @code{mcount} routine provided by the GNU C Library finds the -address of the routine that called the routine that called @code{mcount} -by looking in the immediate caller's stack frame. If the immediate -caller has no frame pointer, this lookup will fail. - -By default, GCC assumes that the target does allow profiling when the -frame pointer is omitted. This macro should be defined to a C -expression that evaluates to @code{false} if the target does not allow -profiling when the frame pointer is omitted. - -@end table - -@node Inlining -@subsection Permitting inlining of functions with attributes -@cindex inlining - -By default if a function has a target specific attribute attached to it, -it will not be inlined. This behaviour can be overridden if the target -defines the @samp{FUNCTION_ATTRIBUTE_INLINABLE_P} macro. This macro -takes one argument, a @samp{DECL} describing the function. It should -return non-zero if the function can be inlined, otherwise it should -return 0. - -@node Tail Calling -@subsection Permitting tail calls to functions -@cindex tail calls -@cindex sibling calls - -@table @code -@findex FUNCTION_OK_FOR_SIBCALL -@item FUNCTION_OK_FOR_SIBCALL (@var{decl}) -A C expression that evaluates to true if it is ok to perform a sibling -call to @var{decl}. - -It is not uncommon for limitations of calling conventions to prevent -tail calls to functions outside the current unit of translation, or -during PIC compilation. Use this macro to enforce these restrictions, -as the @code{sibcall} md pattern can not fail, or fall over to a -``normal'' call. -@end table - -@node Varargs -@section Implementing the Varargs Macros -@cindex varargs implementation - -GCC comes with an implementation of @file{varargs.h} and -@file{stdarg.h} that work without change on machines that pass arguments -on the stack. Other machines require their own implementations of -varargs, and the two machine independent header files must have -conditionals to include it. - -ISO @file{stdarg.h} differs from traditional @file{varargs.h} mainly in -the calling convention for @code{va_start}. The traditional -implementation takes just one argument, which is the variable in which -to store the argument pointer. The ISO implementation of -@code{va_start} takes an additional second argument. The user is -supposed to write the last named argument of the function here. - -However, @code{va_start} should not use this argument. The way to find -the end of the named arguments is with the built-in functions described -below. - -@table @code -@findex __builtin_saveregs -@item __builtin_saveregs () -Use this built-in function to save the argument registers in memory so -that the varargs mechanism can access them. Both ISO and traditional -versions of @code{va_start} must use @code{__builtin_saveregs}, unless -you use @code{SETUP_INCOMING_VARARGS} (see below) instead. - -On some machines, @code{__builtin_saveregs} is open-coded under the -control of the macro @code{EXPAND_BUILTIN_SAVEREGS}. On other machines, -it calls a routine written in assembler language, found in -@file{libgcc2.c}. - -Code generated for the call to @code{__builtin_saveregs} appears at the -beginning of the function, as opposed to where the call to -@code{__builtin_saveregs} is written, regardless of what the code is. -This is because the registers must be saved before the function starts -to use them for its own purposes. -@c i rewrote the first sentence above to fix an overfull hbox. --mew -@c 10feb93 - -@findex __builtin_args_info -@item __builtin_args_info (@var{category}) -Use this built-in function to find the first anonymous arguments in -registers. - -In general, a machine may have several categories of registers used for -arguments, each for a particular category of data types. (For example, -on some machines, floating-point registers are used for floating-point -arguments while other arguments are passed in the general registers.) -To make non-varargs functions use the proper calling convention, you -have defined the @code{CUMULATIVE_ARGS} data type to record how many -registers in each category have been used so far - -@code{__builtin_args_info} accesses the same data structure of type -@code{CUMULATIVE_ARGS} after the ordinary argument layout is finished -with it, with @var{category} specifying which word to access. Thus, the -value indicates the first unused register in a given category. - -Normally, you would use @code{__builtin_args_info} in the implementation -of @code{va_start}, accessing each category just once and storing the -value in the @code{va_list} object. This is because @code{va_list} will -have to update the values, and there is no way to alter the -values accessed by @code{__builtin_args_info}. - -@findex __builtin_next_arg -@item __builtin_next_arg (@var{lastarg}) -This is the equivalent of @code{__builtin_args_info}, for stack -arguments. It returns the address of the first anonymous stack -argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it -returns the address of the location above the first anonymous stack -argument. Use it in @code{va_start} to initialize the pointer for -fetching arguments from the stack. Also use it in @code{va_start} to -verify that the second parameter @var{lastarg} is the last named argument -of the current function. - -@findex __builtin_classify_type -@item __builtin_classify_type (@var{object}) -Since each machine has its own conventions for which data types are -passed in which kind of register, your implementation of @code{va_arg} -has to embody these conventions. The easiest way to categorize the -specified data type is to use @code{__builtin_classify_type} together -with @code{sizeof} and @code{__alignof__}. - -@code{__builtin_classify_type} ignores the value of @var{object}, -considering only its data type. It returns an integer describing what -kind of type that is---integer, floating, pointer, structure, and so on. - -The file @file{typeclass.h} defines an enumeration that you can use to -interpret the values of @code{__builtin_classify_type}. -@end table - -These machine description macros help implement varargs: - -@table @code -@findex EXPAND_BUILTIN_SAVEREGS -@item EXPAND_BUILTIN_SAVEREGS () -If defined, is a C expression that produces the machine-specific code -for a call to @code{__builtin_saveregs}. This code will be moved to the -very beginning of the function, before any parameter access are made. -The return value of this function should be an RTX that contains the -value to use as the return of @code{__builtin_saveregs}. - -@findex SETUP_INCOMING_VARARGS -@item SETUP_INCOMING_VARARGS (@var{args_so_far}, @var{mode}, @var{type}, @var{pretend_args_size}, @var{second_time}) -This macro offers an alternative to using @code{__builtin_saveregs} and -defining the macro @code{EXPAND_BUILTIN_SAVEREGS}. Use it to store the -anonymous register arguments into the stack so that all the arguments -appear to have been passed consecutively on the stack. Once this is -done, you can use the standard implementation of varargs that works for -machines that pass all their arguments on the stack. - -The argument @var{args_so_far} is the @code{CUMULATIVE_ARGS} data -structure, containing the values that are obtained after processing the -named arguments. The arguments @var{mode} and @var{type} describe the -last named argument---its machine mode and its data type as a tree node. - -The macro implementation should do two things: first, push onto the -stack all the argument registers @emph{not} used for the named -arguments, and second, store the size of the data thus pushed into the -@code{int}-valued variable whose name is supplied as the argument -@var{pretend_args_size}. The value that you store here will serve as -additional offset for setting up the stack frame. - -Because you must generate code to push the anonymous arguments at -compile time without knowing their data types, -@code{SETUP_INCOMING_VARARGS} is only useful on machines that have just -a single category of argument register and use it uniformly for all data -types. - -If the argument @var{second_time} is nonzero, it means that the -arguments of the function are being analyzed for the second time. This -happens for an inline function, which is not actually compiled until the -end of the source file. The macro @code{SETUP_INCOMING_VARARGS} should -not generate any instructions in this case. - -@findex STRICT_ARGUMENT_NAMING -@item STRICT_ARGUMENT_NAMING -Define this macro to be a nonzero value if the location where a function -argument is passed depends on whether or not it is a named argument. - -This macro controls how the @var{named} argument to @code{FUNCTION_ARG} -is set for varargs and stdarg functions. If this macro returns a -nonzero value, the @var{named} argument is always true for named -arguments, and false for unnamed arguments. If it returns a value of -zero, but @code{SETUP_INCOMING_VARARGS} is defined, then all arguments -are treated as named. Otherwise, all named arguments except the last -are treated as named. - -You need not define this macro if it always returns zero. - -@findex PRETEND_OUTGOING_VARARGS_NAMED -@item PRETEND_OUTGOING_VARARGS_NAMED -If you need to conditionally change ABIs so that one works with -@code{SETUP_INCOMING_VARARGS}, but the other works like neither -@code{SETUP_INCOMING_VARARGS} nor @code{STRICT_ARGUMENT_NAMING} was -defined, then define this macro to return nonzero if -@code{SETUP_INCOMING_VARARGS} is used, zero otherwise. -Otherwise, you should not define this macro. -@end table - -@node Trampolines -@section Trampolines for Nested Functions -@cindex trampolines for nested functions -@cindex nested functions, trampolines for - -A @dfn{trampoline} is a small piece of code that is created at run time -when the address of a nested function is taken. It normally resides on -the stack, in the stack frame of the containing function. These macros -tell GCC how to generate code to allocate and initialize a -trampoline. - -The instructions in the trampoline must do two things: load a constant -address into the static chain register, and jump to the real address of -the nested function. On CISC machines such as the m68k, this requires -two instructions, a move immediate and a jump. Then the two addresses -exist in the trampoline as word-long immediate operands. On RISC -machines, it is often necessary to load each address into a register in -two parts. Then pieces of each address form separate immediate -operands. - -The code generated to initialize the trampoline must store the variable -parts---the static chain value and the function address---into the -immediate operands of the instructions. On a CISC machine, this is -simply a matter of copying each address to a memory reference at the -proper offset from the start of the trampoline. On a RISC machine, it -may be necessary to take out pieces of the address and store them -separately. - -@table @code -@findex TRAMPOLINE_TEMPLATE -@item TRAMPOLINE_TEMPLATE (@var{file}) -A C statement to output, on the stream @var{file}, assembler code for a -block of data that contains the constant parts of a trampoline. This -code should not include a label---the label is taken care of -automatically. - -If you do not define this macro, it means no template is needed -for the target. Do not define this macro on systems where the block move -code to copy the trampoline into place would be larger than the code -to generate it on the spot. - -@findex TRAMPOLINE_SECTION -@item TRAMPOLINE_SECTION -The name of a subroutine to switch to the section in which the -trampoline template is to be placed (@pxref{Sections}). The default is -a value of @samp{readonly_data_section}, which places the trampoline in -the section containing read-only data. - -@findex TRAMPOLINE_SIZE -@item TRAMPOLINE_SIZE -A C expression for the size in bytes of the trampoline, as an integer. - -@findex TRAMPOLINE_ALIGNMENT -@item TRAMPOLINE_ALIGNMENT -Alignment required for trampolines, in bits. - -If you don't define this macro, the value of @code{BIGGEST_ALIGNMENT} -is used for aligning trampolines. - -@findex INITIALIZE_TRAMPOLINE -@item INITIALIZE_TRAMPOLINE (@var{addr}, @var{fnaddr}, @var{static_chain}) -A C statement to initialize the variable parts of a trampoline. -@var{addr} is an RTX for the address of the trampoline; @var{fnaddr} is -an RTX for the address of the nested function; @var{static_chain} is an -RTX for the static chain value that should be passed to the function -when it is called. - -@findex TRAMPOLINE_ADJUST_ADDRESS -@item TRAMPOLINE_ADJUST_ADDRESS (@var{addr}) -A C statement that should perform any machine-specific adjustment in -the address of the trampoline. Its argument contains the address that -was passed to @code{INITIALIZE_TRAMPOLINE}. In case the address to be -used for a function call should be different from the address in which -the template was stored, the different address should be assigned to -@var{addr}. If this macro is not defined, @var{addr} will be used for -function calls. - -@findex ALLOCATE_TRAMPOLINE -@item ALLOCATE_TRAMPOLINE (@var{fp}) -A C expression to allocate run-time space for a trampoline. The -expression value should be an RTX representing a memory reference to the -space for the trampoline. - -@cindex @code{FUNCTION_EPILOGUE} and trampolines -@cindex @code{FUNCTION_PROLOGUE} and trampolines -If this macro is not defined, by default the trampoline is allocated as -a stack slot. This default is right for most machines. The exceptions -are machines where it is impossible to execute instructions in the stack -area. On such machines, you may have to implement a separate stack, -using this macro in conjunction with @code{FUNCTION_PROLOGUE} and -@code{FUNCTION_EPILOGUE}. - -@var{fp} points to a data structure, a @code{struct function}, which -describes the compilation status of the immediate containing function of -the function which the trampoline is for. Normally (when -@code{ALLOCATE_TRAMPOLINE} is not defined), the stack slot for the -trampoline is in the stack frame of this containing function. Other -allocation strategies probably must do something analogous with this -information. -@end table - -Implementing trampolines is difficult on many machines because they have -separate instruction and data caches. Writing into a stack location -fails to clear the memory in the instruction cache, so when the program -jumps to that location, it executes the old contents. - -Here are two possible solutions. One is to clear the relevant parts of -the instruction cache whenever a trampoline is set up. The other is to -make all trampolines identical, by having them jump to a standard -subroutine. The former technique makes trampoline execution faster; the -latter makes initialization faster. - -To clear the instruction cache when a trampoline is initialized, define -the following macros which describe the shape of the cache. - -@table @code -@findex INSN_CACHE_SIZE -@item INSN_CACHE_SIZE -The total size in bytes of the cache. - -@findex INSN_CACHE_LINE_WIDTH -@item INSN_CACHE_LINE_WIDTH -The length in bytes of each cache line. The cache is divided into cache -lines which are disjoint slots, each holding a contiguous chunk of data -fetched from memory. Each time data is brought into the cache, an -entire line is read at once. The data loaded into a cache line is -always aligned on a boundary equal to the line size. - -@findex INSN_CACHE_DEPTH -@item INSN_CACHE_DEPTH -The number of alternative cache lines that can hold any particular memory -location. -@end table - -Alternatively, if the machine has system calls or instructions to clear -the instruction cache directly, you can define the following macro. - -@table @code -@findex CLEAR_INSN_CACHE -@item CLEAR_INSN_CACHE (@var{BEG}, @var{END}) -If defined, expands to a C expression clearing the @emph{instruction -cache} in the specified interval. If it is not defined, and the macro -INSN_CACHE_SIZE is defined, some generic code is generated to clear the -cache. The definition of this macro would typically be a series of -@code{asm} statements. Both @var{BEG} and @var{END} are both pointer -expressions. -@end table - -To use a standard subroutine, define the following macro. In addition, -you must make sure that the instructions in a trampoline fill an entire -cache line with identical instructions, or else ensure that the -beginning of the trampoline code is always aligned at the same point in -its cache line. Look in @file{m68k.h} as a guide. - -@table @code -@findex TRANSFER_FROM_TRAMPOLINE -@item TRANSFER_FROM_TRAMPOLINE -Define this macro if trampolines need a special subroutine to do their -work. The macro should expand to a series of @code{asm} statements -which will be compiled with GCC. They go in a library function named -@code{__transfer_from_trampoline}. - -If you need to avoid executing the ordinary prologue code of a compiled -C function when you jump to the subroutine, you can do so by placing a -special label of your own in the assembler code. Use one @code{asm} -statement to generate an assembler label, and another to make the label -global. Then trampolines can use that label to jump directly to your -special assembler code. -@end table - -@node Library Calls -@section Implicit Calls to Library Routines -@cindex library subroutine names -@cindex @file{libgcc.a} - -@c prevent bad page break with this line -Here is an explanation of implicit calls to library routines. - -@table @code -@findex MULSI3_LIBCALL -@item MULSI3_LIBCALL -A C string constant giving the name of the function to call for -multiplication of one signed full-word by another. If you do not -define this macro, the default name is used, which is @code{__mulsi3}, -a function defined in @file{libgcc.a}. - -@findex DIVSI3_LIBCALL -@item DIVSI3_LIBCALL -A C string constant giving the name of the function to call for -division of one signed full-word by another. If you do not define -this macro, the default name is used, which is @code{__divsi3}, a -function defined in @file{libgcc.a}. - -@findex UDIVSI3_LIBCALL -@item UDIVSI3_LIBCALL -A C string constant giving the name of the function to call for -division of one unsigned full-word by another. If you do not define -this macro, the default name is used, which is @code{__udivsi3}, a -function defined in @file{libgcc.a}. - -@findex MODSI3_LIBCALL -@item MODSI3_LIBCALL -A C string constant giving the name of the function to call for the -remainder in division of one signed full-word by another. If you do -not define this macro, the default name is used, which is -@code{__modsi3}, a function defined in @file{libgcc.a}. - -@findex UMODSI3_LIBCALL -@item UMODSI3_LIBCALL -A C string constant giving the name of the function to call for the -remainder in division of one unsigned full-word by another. If you do -not define this macro, the default name is used, which is -@code{__umodsi3}, a function defined in @file{libgcc.a}. - -@findex MULDI3_LIBCALL -@item MULDI3_LIBCALL -A C string constant giving the name of the function to call for -multiplication of one signed double-word by another. If you do not -define this macro, the default name is used, which is @code{__muldi3}, -a function defined in @file{libgcc.a}. - -@findex DIVDI3_LIBCALL -@item DIVDI3_LIBCALL -A C string constant giving the name of the function to call for -division of one signed double-word by another. If you do not define -this macro, the default name is used, which is @code{__divdi3}, a -function defined in @file{libgcc.a}. - -@findex UDIVDI3_LIBCALL -@item UDIVDI3_LIBCALL -A C string constant giving the name of the function to call for -division of one unsigned full-word by another. If you do not define -this macro, the default name is used, which is @code{__udivdi3}, a -function defined in @file{libgcc.a}. - -@findex MODDI3_LIBCALL -@item MODDI3_LIBCALL -A C string constant giving the name of the function to call for the -remainder in division of one signed double-word by another. If you do -not define this macro, the default name is used, which is -@code{__moddi3}, a function defined in @file{libgcc.a}. - -@findex UMODDI3_LIBCALL -@item UMODDI3_LIBCALL -A C string constant giving the name of the function to call for the -remainder in division of one unsigned full-word by another. If you do -not define this macro, the default name is used, which is -@code{__umoddi3}, a function defined in @file{libgcc.a}. - -@findex INIT_TARGET_OPTABS -@item INIT_TARGET_OPTABS -Define this macro as a C statement that declares additional library -routines renames existing ones. @code{init_optabs} calls this macro after -initializing all the normal library routines. - -@findex FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison}) -@item FLOAT_LIB_COMPARE_RETURNS_BOOL -Define this macro as a C statement that returns nonzero if a call to -the floating point comparison library function will return a boolean -value that indicates the result of the comparison. It should return -zero if one of gcc's own libgcc functions is called. - -Most ports don't need to define this macro. - -@findex TARGET_EDOM -@cindex @code{EDOM}, implicit usage -@item TARGET_EDOM -The value of @code{EDOM} on the target machine, as a C integer constant -expression. If you don't define this macro, GCC does not attempt to -deposit the value of @code{EDOM} into @code{errno} directly. Look in -@file{/usr/include/errno.h} to find the value of @code{EDOM} on your -system. - -If you do not define @code{TARGET_EDOM}, then compiled code reports -domain errors by calling the library function and letting it report the -error. If mathematical functions on your system use @code{matherr} when -there is an error, then you should leave @code{TARGET_EDOM} undefined so -that @code{matherr} is used normally. - -@findex GEN_ERRNO_RTX -@cindex @code{errno}, implicit usage -@item GEN_ERRNO_RTX -Define this macro as a C expression to create an rtl expression that -refers to the global ``variable'' @code{errno}. (On certain systems, -@code{errno} may not actually be a variable.) If you don't define this -macro, a reasonable default is used. - -@findex TARGET_MEM_FUNCTIONS -@cindex @code{bcopy}, implicit usage -@cindex @code{memcpy}, implicit usage -@cindex @code{memmove}, implicit usage -@cindex @code{bzero}, implicit usage -@cindex @code{memset}, implicit usage -@item TARGET_MEM_FUNCTIONS -Define this macro if GCC should generate calls to the ISO C -(and System V) library functions @code{memcpy}, @code{memmove} and -@code{memset} rather than the BSD functions @code{bcopy} and @code{bzero}. - -@findex LIBGCC_NEEDS_DOUBLE -@item LIBGCC_NEEDS_DOUBLE -Define this macro if @code{float} arguments cannot be passed to library -routines (so they must be converted to @code{double}). This macro -affects both how library calls are generated and how the library -routines in @file{libgcc.a} accept their arguments. It is useful on -machines where floating and fixed point arguments are passed -differently, such as the i860. - -@findex NEXT_OBJC_RUNTIME -@item NEXT_OBJC_RUNTIME -Define this macro to generate code for Objective C message sending using -the calling convention of the NeXT system. This calling convention -involves passing the object, the selector and the method arguments all -at once to the method-lookup library function. - -The default calling convention passes just the object and the selector -to the lookup function, which returns a pointer to the method. -@end table - -@node Addressing Modes -@section Addressing Modes -@cindex addressing modes - -@c prevent bad page break with this line -This is about addressing modes. - -@table @code -@findex HAVE_PRE_INCREMENT -@findex HAVE_PRE_DECREMENT -@findex HAVE_POST_INCREMENT -@findex HAVE_POST_DECREMENT -@item HAVE_PRE_INCREMENT -@itemx HAVE_PRE_DECREMENT -@itemx HAVE_POST_INCREMENT -@itemx HAVE_POST_DECREMENT -A C expression that is non-zero if the machine supports pre-increment, -pre-decrement, post-increment, or post-decrement addressing respectively. - -@findex HAVE_POST_MODIFY_DISP -@findex HAVE_PRE_MODIFY_DISP -@item HAVE_PRE_MODIFY_DISP -@itemx HAVE_POST_MODIFY_DISP -A C expression that is non-zero if the machine supports pre- or -post-address side-effect generation involving constants other than -the size of the memory operand. - -@findex HAVE_POST_MODIFY_REG -@findex HAVE_PRE_MODIFY_REG -@item HAVE_PRE_MODIFY_REG -@itemx HAVE_POST_MODIFY_REG -A C expression that is non-zero if the machine supports pre- or -post-address side-effect generation involving a register displacement. - -@findex CONSTANT_ADDRESS_P -@item CONSTANT_ADDRESS_P (@var{x}) -A C expression that is 1 if the RTX @var{x} is a constant which -is a valid address. On most machines, this can be defined as -@code{CONSTANT_P (@var{x})}, but a few machines are more restrictive -in which constant addresses are supported. - -@findex CONSTANT_P -@code{CONSTANT_P} accepts integer-values expressions whose values are -not explicitly known, such as @code{symbol_ref}, @code{label_ref}, and -@code{high} expressions and @code{const} arithmetic expressions, in -addition to @code{const_int} and @code{const_double} expressions. - -@findex MAX_REGS_PER_ADDRESS -@item MAX_REGS_PER_ADDRESS -A number, the maximum number of registers that can appear in a valid -memory address. Note that it is up to you to specify a value equal to -the maximum number that @code{GO_IF_LEGITIMATE_ADDRESS} would ever -accept. - -@findex GO_IF_LEGITIMATE_ADDRESS -@item GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{label}) -A C compound statement with a conditional @code{goto @var{label};} -executed if @var{x} (an RTX) is a legitimate memory address on the -target machine for a memory operand of mode @var{mode}. - -It usually pays to define several simpler macros to serve as -subroutines for this one. Otherwise it may be too complicated to -understand. - -This macro must exist in two variants: a strict variant and a -non-strict one. The strict variant is used in the reload pass. It -must be defined so that any pseudo-register that has not been -allocated a hard register is considered a memory reference. In -contexts where some kind of register is required, a pseudo-register -with no hard register must be rejected. - -The non-strict variant is used in other passes. It must be defined to -accept all pseudo-registers in every context where some kind of -register is required. - -@findex REG_OK_STRICT -Compiler source files that want to use the strict variant of this -macro define the macro @code{REG_OK_STRICT}. You should use an -@code{#ifdef REG_OK_STRICT} conditional to define the strict variant -in that case and the non-strict variant otherwise. - -Subroutines to check for acceptable registers for various purposes (one -for base registers, one for index registers, and so on) are typically -among the subroutines used to define @code{GO_IF_LEGITIMATE_ADDRESS}. -Then only these subroutine macros need have two variants; the higher -levels of macros may be the same whether strict or not.@refill - -Normally, constant addresses which are the sum of a @code{symbol_ref} -and an integer are stored inside a @code{const} RTX to mark them as -constant. Therefore, there is no need to recognize such sums -specifically as legitimate addresses. Normally you would simply -recognize any @code{const} as legitimate. - -Usually @code{PRINT_OPERAND_ADDRESS} is not prepared to handle constant -sums that are not marked with @code{const}. It assumes that a naked -@code{plus} indicates indexing. If so, then you @emph{must} reject such -naked constant sums as illegitimate addresses, so that none of them will -be given to @code{PRINT_OPERAND_ADDRESS}. - -@cindex @code{ENCODE_SECTION_INFO} and address validation -On some machines, whether a symbolic address is legitimate depends on -the section that the address refers to. On these machines, define the -macro @code{ENCODE_SECTION_INFO} to store the information into the -@code{symbol_ref}, and then check for it here. When you see a -@code{const}, you will have to look inside it to find the -@code{symbol_ref} in order to determine the section. @xref{Assembler -Format}. - -@findex saveable_obstack -The best way to modify the name string is by adding text to the -beginning, with suitable punctuation to prevent any ambiguity. Allocate -the new name in @code{saveable_obstack}. You will have to modify -@code{ASM_OUTPUT_LABELREF} to remove and decode the added text and -output the name accordingly, and define @code{STRIP_NAME_ENCODING} to -access the original name string. - -You can check the information stored here into the @code{symbol_ref} in -the definitions of the macros @code{GO_IF_LEGITIMATE_ADDRESS} and -@code{PRINT_OPERAND_ADDRESS}. - -@findex REG_OK_FOR_BASE_P -@item REG_OK_FOR_BASE_P (@var{x}) -A C expression that is nonzero if @var{x} (assumed to be a @code{reg} -RTX) is valid for use as a base register. For hard registers, it -should always accept those which the hardware permits and reject the -others. Whether the macro accepts or rejects pseudo registers must be -controlled by @code{REG_OK_STRICT} as described above. This usually -requires two variant definitions, of which @code{REG_OK_STRICT} -controls the one actually used. - -@findex REG_MODE_OK_FOR_BASE_P -@item REG_MODE_OK_FOR_BASE_P (@var{x}, @var{mode}) -A C expression that is just like @code{REG_OK_FOR_BASE_P}, except that -that expression may examine the mode of the memory reference in -@var{mode}. You should define this macro if the mode of the memory -reference affects whether a register may be used as a base register. If -you define this macro, the compiler will use it instead of -@code{REG_OK_FOR_BASE_P}. - -@findex REG_OK_FOR_INDEX_P -@item REG_OK_FOR_INDEX_P (@var{x}) -A C expression that is nonzero if @var{x} (assumed to be a @code{reg} -RTX) is valid for use as an index register. - -The difference between an index register and a base register is that -the index register may be scaled. If an address involves the sum of -two registers, neither one of them scaled, then either one may be -labeled the ``base'' and the other the ``index''; but whichever -labeling is used must fit the machine's constraints of which registers -may serve in each capacity. The compiler will try both labelings, -looking for one that is valid, and will reload one or both registers -only if neither labeling works. - -@findex FIND_BASE_TERM -@item FIND_BASE_TERM (@var{x}) -A C expression to determine the base term of address @var{x}. -This macro is used in only one place: `find_base_term' in alias.c. - -It is always safe for this macro to not be defined. It exists so -that alias analysis can understand machine-dependent addresses. - -The typical use of this macro is to handle addresses containing -a label_ref or symbol_ref within an UNSPEC. - -@findex LEGITIMIZE_ADDRESS -@item LEGITIMIZE_ADDRESS (@var{x}, @var{oldx}, @var{mode}, @var{win}) -A C compound statement that attempts to replace @var{x} with a valid -memory address for an operand of mode @var{mode}. @var{win} will be a -C statement label elsewhere in the code; the macro definition may use - -@example -GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{win}); -@end example - -@noindent -to avoid further processing if the address has become legitimate. - -@findex break_out_memory_refs -@var{x} will always be the result of a call to @code{break_out_memory_refs}, -and @var{oldx} will be the operand that was given to that function to produce -@var{x}. - -The code generated by this macro should not alter the substructure of -@var{x}. If it transforms @var{x} into a more legitimate form, it -should assign @var{x} (which will always be a C variable) a new value. - -It is not necessary for this macro to come up with a legitimate -address. The compiler has standard ways of doing so in all cases. In -fact, it is safe for this macro to do nothing. But often a -machine-dependent strategy can generate better code. - -@findex LEGITIMIZE_RELOAD_ADDRESS -@item LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win}) -A C compound statement that attempts to replace @var{x}, which is an address -that needs reloading, with a valid memory address for an operand of mode -@var{mode}. @var{win} will be a C statement label elsewhere in the code. -It is not necessary to define this macro, but it might be useful for -performance reasons. - -For example, on the i386, it is sometimes possible to use a single -reload register instead of two by reloading a sum of two pseudo -registers into a register. On the other hand, for number of RISC -processors offsets are limited so that often an intermediate address -needs to be generated in order to address a stack slot. By defining -LEGITIMIZE_RELOAD_ADDRESS appropriately, the intermediate addresses -generated for adjacent some stack slots can be made identical, and thus -be shared. - -@emph{Note}: This macro should be used with caution. It is necessary -to know something of how reload works in order to effectively use this, -and it is quite easy to produce macros that build in too much knowledge -of reload internals. - -@emph{Note}: This macro must be able to reload an address created by a -previous invocation of this macro. If it fails to handle such addresses -then the compiler may generate incorrect code or abort. - -@findex push_reload -The macro definition should use @code{push_reload} to indicate parts that -need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually -suitable to be passed unaltered to @code{push_reload}. - -The code generated by this macro must not alter the substructure of -@var{x}. If it transforms @var{x} into a more legitimate form, it -should assign @var{x} (which will always be a C variable) a new value. -This also applies to parts that you change indirectly by calling -@code{push_reload}. - -@findex strict_memory_address_p -The macro definition may use @code{strict_memory_address_p} to test if -the address has become legitimate. - -@findex copy_rtx -If you want to change only a part of @var{x}, one standard way of doing -this is to use @code{copy_rtx}. Note, however, that is unshares only a -single level of rtl. Thus, if the part to be changed is not at the -top level, you'll need to replace first the top leve -It is not necessary for this macro to come up with a legitimate -address; but often a machine-dependent strategy can generate better code. - -@findex GO_IF_MODE_DEPENDENT_ADDRESS -@item GO_IF_MODE_DEPENDENT_ADDRESS (@var{addr}, @var{label}) -A C statement or compound statement with a conditional @code{goto -@var{label};} executed if memory address @var{x} (an RTX) can have -different meanings depending on the machine mode of the memory -reference it is used for or if the address is valid for some modes -but not others. - -Autoincrement and autodecrement addresses typically have mode-dependent -effects because the amount of the increment or decrement is the size -of the operand being addressed. Some machines have other mode-dependent -addresses. Many RISC machines have no mode-dependent addresses. - -You may assume that @var{addr} is a valid address for the machine. - -@findex LEGITIMATE_CONSTANT_P -@item LEGITIMATE_CONSTANT_P (@var{x}) -A C expression that is nonzero if @var{x} is a legitimate constant for -an immediate operand on the target machine. You can assume that -@var{x} satisfies @code{CONSTANT_P}, so you need not check this. In fact, -@samp{1} is a suitable definition for this macro on machines where -anything @code{CONSTANT_P} is valid.@refill -@end table - -@node Condition Code -@section Condition Code Status -@cindex condition code status - -@c prevent bad page break with this line -This describes the condition code status. - -@findex cc_status -The file @file{conditions.h} defines a variable @code{cc_status} to -describe how the condition code was computed (in case the interpretation of -the condition code depends on the instruction that it was set by). This -variable contains the RTL expressions on which the condition code is -currently based, and several standard flags. - -Sometimes additional machine-specific flags must be defined in the machine -description header file. It can also add additional machine-specific -information by defining @code{CC_STATUS_MDEP}. - -@table @code -@findex CC_STATUS_MDEP -@item CC_STATUS_MDEP -C code for a data type which is used for declaring the @code{mdep} -component of @code{cc_status}. It defaults to @code{int}. - -This macro is not used on machines that do not use @code{cc0}. - -@findex CC_STATUS_MDEP_INIT -@item CC_STATUS_MDEP_INIT -A C expression to initialize the @code{mdep} field to ``empty''. -The default definition does nothing, since most machines don't use -the field anyway. If you want to use the field, you should probably -define this macro to initialize it. - -This macro is not used on machines that do not use @code{cc0}. - -@findex NOTICE_UPDATE_CC -@item NOTICE_UPDATE_CC (@var{exp}, @var{insn}) -A C compound statement to set the components of @code{cc_status} -appropriately for an insn @var{insn} whose body is @var{exp}. It is -this macro's responsibility to recognize insns that set the condition -code as a byproduct of other activity as well as those that explicitly -set @code{(cc0)}. - -This macro is not used on machines that do not use @code{cc0}. - -If there are insns that do not set the condition code but do alter -other machine registers, this macro must check to see whether they -invalidate the expressions that the condition code is recorded as -reflecting. For example, on the 68000, insns that store in address -registers do not set the condition code, which means that usually -@code{NOTICE_UPDATE_CC} can leave @code{cc_status} unaltered for such -insns. But suppose that the previous insn set the condition code -based on location @samp{a4@@(102)} and the current insn stores a new -value in @samp{a4}. Although the condition code is not changed by -this, it will no longer be true that it reflects the contents of -@samp{a4@@(102)}. Therefore, @code{NOTICE_UPDATE_CC} must alter -@code{cc_status} in this case to say that nothing is known about the -condition code value. - -The definition of @code{NOTICE_UPDATE_CC} must be prepared to deal -with the results of peephole optimization: insns whose patterns are -@code{parallel} RTXs containing various @code{reg}, @code{mem} or -constants which are just the operands. The RTL structure of these -insns is not sufficient to indicate what the insns actually do. What -@code{NOTICE_UPDATE_CC} should do when it sees one is just to run -@code{CC_STATUS_INIT}. - -A possible definition of @code{NOTICE_UPDATE_CC} is to call a function -that looks at an attribute (@pxref{Insn Attributes}) named, for example, -@samp{cc}. This avoids having detailed information about patterns in -two places, the @file{md} file and in @code{NOTICE_UPDATE_CC}. - -@findex EXTRA_CC_MODES -@item EXTRA_CC_MODES -A list of additional modes for condition code values in registers -(@pxref{Jump Patterns}). This macro should expand to a sequence of -calls of the macro @code{CC} separated by white space. @code{CC} takes -two arguments. The first is the enumeration name of the mode, which -should begin with @samp{CC} and end with @samp{mode}. The second is a C -string giving the printable name of the mode; it should be the same as -the first argument, but with the trailing @samp{mode} removed. - -You should only define this macro if additional modes are required. - -A sample definition of @code{EXTRA_CC_MODES} is: -@smallexample -#define EXTRA_CC_MODES \ - CC(CC_NOOVmode, "CC_NOOV") \ - CC(CCFPmode, "CCFP") \ - CC(CCFPEmode, "CCFPE") -@end smallexample - -@findex SELECT_CC_MODE -@item SELECT_CC_MODE (@var{op}, @var{x}, @var{y}) -Returns a mode from class @code{MODE_CC} to be used when comparison -operation code @var{op} is applied to rtx @var{x} and @var{y}. For -example, on the Sparc, @code{SELECT_CC_MODE} is defined as (see -@pxref{Jump Patterns} for a description of the reason for this -definition) - -@smallexample -#define SELECT_CC_MODE(OP,X,Y) \ - (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \ - ? ((OP == EQ || OP == NE) ? CCFPmode : CCFPEmode) \ - : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \ - || GET_CODE (X) == NEG) \ - ? CC_NOOVmode : CCmode)) -@end smallexample - -You need not define this macro if @code{EXTRA_CC_MODES} is not defined. - -@findex CANONICALIZE_COMPARISON -@item CANONICALIZE_COMPARISON (@var{code}, @var{op0}, @var{op1}) -On some machines not all possible comparisons are defined, but you can -convert an invalid comparison into a valid one. For example, the Alpha -does not have a @code{GT} comparison, but you can use an @code{LT} -comparison instead and swap the order of the operands. - -On such machines, define this macro to be a C statement to do any -required conversions. @var{code} is the initial comparison code -and @var{op0} and @var{op1} are the left and right operands of the -comparison, respectively. You should modify @var{code}, @var{op0}, and -@var{op1} as required. - -GCC will not assume that the comparison resulting from this macro is -valid but will see if the resulting insn matches a pattern in the -@file{md} file. - -You need not define this macro if it would never change the comparison -code or operands. - -@findex REVERSIBLE_CC_MODE -@item REVERSIBLE_CC_MODE (@var{mode}) -A C expression whose value is one if it is always safe to reverse a -comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE} -can ever return @var{mode} for a floating-point inequality comparison, -then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero. - -You need not define this macro if it would always returns zero or if the -floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}. -For example, here is the definition used on the Sparc, where floating-point -inequality comparisons are always given @code{CCFPEmode}: - -@smallexample -#define REVERSIBLE_CC_MODE(MODE) ((MODE) != CCFPEmode) -@end smallexample - -@findex REVERSE_CONDITION (@var{code}, @var{mode}) -A C expression whose value is reversed condition code of the @var{code} for -comparison done in CC_MODE @var{mode}. The macro is used only in case -@code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case -machine has some non-standard way how to reverse certain conditionals. For -instance in case all floating point conditions are non-trapping, compiler may -freely convert unordered compares to ordered one. Then definition may look -like: - -@smallexample -#define REVERSE_CONDITION(CODE, MODE) \ - ((MODE) != CCFPmode ? reverse_condtion (CODE) \ - : reverse_condition_maybe_unordered (CODE)) -@end smallexample - -@findex REVERSE_CONDEXEC_PREDICATES_P -@item REVERSE_CONDEXEC_PREDICATES_P (@var{code1}, @var{code2}) -A C expression that returns true if the conditional execution predicate -@var{code1} is the inverse of @var{code2} and vice versa. Define this to -return 0 if the target has conditional execution predicates that cannot be -reversed safely. If no expansion is specified, this macro is defined as -follows: - -@smallexample -#define REVERSE_CONDEXEC_PREDICATES_P (x, y) ((x) == reverse_condition (y)) -@end smallexample - -@end table - -@node Costs -@section Describing Relative Costs of Operations -@cindex costs of instructions -@cindex relative costs -@cindex speed of instructions - -These macros let you describe the relative speed of various operations -on the target machine. - -@table @code -@findex CONST_COSTS -@item CONST_COSTS (@var{x}, @var{code}, @var{outer_code}) -A part of a C @code{switch} statement that describes the relative costs -of constant RTL expressions. It must contain @code{case} labels for -expression codes @code{const_int}, @code{const}, @code{symbol_ref}, -@code{label_ref} and @code{const_double}. Each case must ultimately -reach a @code{return} statement to return the relative cost of the use -of that kind of constant value in an expression. The cost may depend on -the precise value of the constant, which is available for examination in -@var{x}, and the rtx code of the expression in which it is contained, -found in @var{outer_code}. - -@var{code} is the expression code---redundant, since it can be -obtained with @code{GET_CODE (@var{x})}. - -@findex RTX_COSTS -@findex COSTS_N_INSNS -@item RTX_COSTS (@var{x}, @var{code}, @var{outer_code}) -Like @code{CONST_COSTS} but applies to nonconstant RTL expressions. -This can be used, for example, to indicate how costly a multiply -instruction is. In writing this macro, you can use the construct -@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast -instructions. @var{outer_code} is the code of the expression in which -@var{x} is contained. - -This macro is optional; do not define it if the default cost assumptions -are adequate for the target machine. - -@findex DEFAULT_RTX_COSTS -@item DEFAULT_RTX_COSTS (@var{x}, @var{code}, @var{outer_code}) -This macro, if defined, is called for any case not handled by the -@code{RTX_COSTS} or @code{CONST_COSTS} macros. This eliminates the need -to put case labels into the macro, but the code, or any functions it -calls, must assume that the RTL in @var{x} could be of any type that has -not already been handled. The arguments are the same as for -@code{RTX_COSTS}, and the macro should execute a return statement giving -the cost of any RTL expressions that it can handle. The default cost -calculation is used for any RTL for which this macro does not return a -value. - -This macro is optional; do not define it if the default cost assumptions -are adequate for the target machine. - -@findex ADDRESS_COST -@item ADDRESS_COST (@var{address}) -An expression giving the cost of an addressing mode that contains -@var{address}. If not defined, the cost is computed from -the @var{address} expression and the @code{CONST_COSTS} values. - -For most CISC machines, the default cost is a good approximation of the -true cost of the addressing mode. However, on RISC machines, all -instructions normally have the same length and execution time. Hence -all addresses will have equal costs. - -In cases where more than one form of an address is known, the form with -the lowest cost will be used. If multiple forms have the same, lowest, -cost, the one that is the most complex will be used. - -For example, suppose an address that is equal to the sum of a register -and a constant is used twice in the same basic block. When this macro -is not defined, the address will be computed in a register and memory -references will be indirect through that register. On machines where -the cost of the addressing mode containing the sum is no higher than -that of a simple indirect reference, this will produce an additional -instruction and possibly require an additional register. Proper -specification of this macro eliminates this overhead for such machines. - -Similar use of this macro is made in strength reduction of loops. - -@var{address} need not be valid as an address. In such a case, the cost -is not relevant and can be any value; invalid addresses need not be -assigned a different cost. - -On machines where an address involving more than one register is as -cheap as an address computation involving only one register, defining -@code{ADDRESS_COST} to reflect this can cause two registers to be live -over a region of code where only one would have been if -@code{ADDRESS_COST} were not defined in that manner. This effect should -be considered in the definition of this macro. Equivalent costs should -probably only be given to addresses with different numbers of registers -on machines with lots of registers. - -This macro will normally either not be defined or be defined as a -constant. - -@findex REGISTER_MOVE_COST -@item REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to}) -A C expression for the cost of moving data of mode @var{mode} from a -register in class @var{from} to one in class @var{to}. The classes are -expressed using the enumeration values such as @code{GENERAL_REGS}. A -value of 2 is the default; other values are interpreted relative to -that. - -It is not required that the cost always equal 2 when @var{from} is the -same as @var{to}; on some machines it is expensive to move between -registers if they are not general registers. - -If reload sees an insn consisting of a single @code{set} between two -hard registers, and if @code{REGISTER_MOVE_COST} applied to their -classes returns a value of 2, reload does not check to ensure that the -constraints of the insn are met. Setting a cost of other than 2 will -allow reload to verify that the constraints are met. You should do this -if the @samp{mov@var{m}} pattern's constraints do not allow such copying. - -@findex MEMORY_MOVE_COST -@item MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in}) -A C expression for the cost of moving data of mode @var{mode} between a -register of class @var{class} and memory; @var{in} is zero if the value -is to be written to memory, non-zero if it is to be read in. This cost -is relative to those in @code{REGISTER_MOVE_COST}. If moving between -registers and memory is more expensive than between two registers, you -should define this macro to express the relative cost. - -If you do not define this macro, GCC uses a default cost of 4 plus -the cost of copying via a secondary reload register, if one is -needed. If your machine requires a secondary reload register to copy -between memory and a register of @var{class} but the reload mechanism is -more complex than copying via an intermediate, define this macro to -reflect the actual cost of the move. - -GCC defines the function @code{memory_move_secondary_cost} if -secondary reloads are needed. It computes the costs due to copying via -a secondary register. If your machine copies from memory using a -secondary register in the conventional way but the default base value of -4 is not correct for your machine, define this macro to add some other -value to the result of that function. The arguments to that function -are the same as to this macro. - -@findex BRANCH_COST -@item BRANCH_COST -A C expression for the cost of a branch instruction. A value of 1 is -the default; other values are interpreted relative to that. -@end table - -Here are additional macros which do not specify precise relative costs, -but only that certain actions are more expensive than GCC would -ordinarily expect. - -@table @code -@findex SLOW_BYTE_ACCESS -@item SLOW_BYTE_ACCESS -Define this macro as a C expression which is nonzero if accessing less -than a word of memory (i.e. a @code{char} or a @code{short}) is no -faster than accessing a word of memory, i.e., if such access -require more than one instruction or if there is no difference in cost -between byte and (aligned) word loads. - -When this macro is not defined, the compiler will access a field by -finding the smallest containing object; when it is defined, a fullword -load will be used if alignment permits. Unless bytes accesses are -faster than word accesses, using word accesses is preferable since it -may eliminate subsequent memory access if subsequent accesses occur to -other fields in the same word of the structure, but to different bytes. - -@findex SLOW_ZERO_EXTEND -@item SLOW_ZERO_EXTEND -Define this macro if zero-extension (of a @code{char} or @code{short} -to an @code{int}) can be done faster if the destination is a register -that is known to be zero. - -If you define this macro, you must have instruction patterns that -recognize RTL structures like this: - -@smallexample -(set (strict_low_part (subreg:QI (reg:SI @dots{}) 0)) @dots{}) -@end smallexample - -@noindent -and likewise for @code{HImode}. - -@findex SLOW_UNALIGNED_ACCESS -@item SLOW_UNALIGNED_ACCESS (@var{mode}, @var{alignment}) -Define this macro to be the value 1 if memory accesses described by the -@var{mode} and @var{alignment} parameters have a cost many times greater -than aligned accesses, for example if they are emulated in a trap -handler. - -When this macro is non-zero, the compiler will act as if -@code{STRICT_ALIGNMENT} were non-zero when generating code for block -moves. This can cause significantly more instructions to be produced. -Therefore, do not set this macro non-zero if unaligned accesses only add a -cycle or two to the time for a memory access. - -If the value of this macro is always zero, it need not be defined. If -this macro is defined, it should produce a non-zero value when -@code{STRICT_ALIGNMENT} is non-zero. - -@findex DONT_REDUCE_ADDR -@item DONT_REDUCE_ADDR -Define this macro to inhibit strength reduction of memory addresses. -(On some machines, such strength reduction seems to do harm rather -than good.) - -@findex MOVE_RATIO -@item MOVE_RATIO -The threshold of number of scalar memory-to-memory move insns, @emph{below} -which a sequence of insns should be generated instead of a -string move insn or a library call. Increasing the value will always -make code faster, but eventually incurs high cost in increased code size. - -Note that on machines where the corresponding move insn is a -@code{define_expand} that emits a sequence of insns, this macro counts -the number of such sequences. - -If you don't define this, a reasonable default is used. - -@findex MOVE_BY_PIECES_P -@item MOVE_BY_PIECES_P (@var{size}, @var{alignment}) -A C expression used to determine whether @code{move_by_pieces} will be used to -copy a chunk of memory, or whether some other block move mechanism -will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less -than @code{MOVE_RATIO}. - -@findex MOVE_MAX_PIECES -@item MOVE_MAX_PIECES -A C expression used by @code{move_by_pieces} to determine the largest unit -a load or store used to copy memory is. Defaults to @code{MOVE_MAX}. - -@findex USE_LOAD_POST_INCREMENT -@item USE_LOAD_POST_INCREMENT (@var{mode}) -A C expression used to determine whether a load postincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_INCREMENT}. - -@findex USE_LOAD_POST_DECREMENT -@item USE_LOAD_POST_DECREMENT (@var{mode}) -A C expression used to determine whether a load postdecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_DECREMENT}. - -@findex USE_LOAD_PRE_INCREMENT -@item USE_LOAD_PRE_INCREMENT (@var{mode}) -A C expression used to determine whether a load preincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_INCREMENT}. - -@findex USE_LOAD_PRE_DECREMENT -@item USE_LOAD_PRE_DECREMENT (@var{mode}) -A C expression used to determine whether a load predecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_DECREMENT}. - -@findex USE_STORE_POST_INCREMENT -@item USE_STORE_POST_INCREMENT (@var{mode}) -A C expression used to determine whether a store postincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_INCREMENT}. - -@findex USE_STORE_POST_DECREMENT -@item USE_STORE_POST_DECREMENT (@var{mode}) -A C expression used to determine whether a store postdeccrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_DECREMENT}. - -@findex USE_STORE_PRE_INCREMENT -@item USE_STORE_PRE_INCREMENT (@var{mode}) -This macro is used to determine whether a store preincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_INCREMENT}. - -@findex USE_STORE_PRE_DECREMENT -@item USE_STORE_PRE_DECREMENT (@var{mode}) -This macro is used to determine whether a store predecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_DECREMENT}. - -@findex NO_FUNCTION_CSE -@item NO_FUNCTION_CSE -Define this macro if it is as good or better to call a constant -function address than to call an address kept in a register. - -@findex NO_RECURSIVE_FUNCTION_CSE -@item NO_RECURSIVE_FUNCTION_CSE -Define this macro if it is as good or better for a function to call -itself with an explicit address than to call an address kept in a -register. - -@findex ADJUST_COST -@item ADJUST_COST (@var{insn}, @var{link}, @var{dep_insn}, @var{cost}) -A C statement (sans semicolon) to update the integer variable @var{cost} -based on the relationship between @var{insn} that is dependent on -@var{dep_insn} through the dependence @var{link}. The default is to -make no adjustment to @var{cost}. This can be used for example to -specify to the scheduler that an output- or anti-dependence does not -incur the same cost as a data-dependence. - -@findex ADJUST_PRIORITY -@item ADJUST_PRIORITY (@var{insn}) -A C statement (sans semicolon) to update the integer scheduling -priority @code{INSN_PRIORITY(@var{insn})}. Reduce the priority -to execute the @var{insn} earlier, increase the priority to execute -@var{insn} later. Do not define this macro if you do not need to -adjust the scheduling priorities of insns. -@end table - -@node Sections -@section Dividing the Output into Sections (Texts, Data, @dots{}) -@c the above section title is WAY too long. maybe cut the part between -@c the (...)? --mew 10feb93 - -An object file is divided into sections containing different types of -data. In the most common case, there are three sections: the @dfn{text -section}, which holds instructions and read-only data; the @dfn{data -section}, which holds initialized writable data; and the @dfn{bss -section}, which holds uninitialized data. Some systems have other kinds -of sections. - -The compiler must tell the assembler when to switch sections. These -macros control what commands to output to tell the assembler this. You -can also define additional sections. - -@table @code -@findex TEXT_SECTION_ASM_OP -@item TEXT_SECTION_ASM_OP -A C expression whose value is a string, including spacing, containing the -assembler operation that should precede instructions and read-only data. -Normally @code{"\t.text"} is right. - -@findex DATA_SECTION_ASM_OP -@item DATA_SECTION_ASM_OP -A C expression whose value is a string, including spacing, containing the -assembler operation to identify the following data as writable initialized -data. Normally @code{"\t.data"} is right. - -@findex SHARED_SECTION_ASM_OP -@item SHARED_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -shared data. If not defined, @code{DATA_SECTION_ASM_OP} will be used. - -@findex BSS_SECTION_ASM_OP -@item BSS_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -uninitialized global data. If not defined, and neither -@code{ASM_OUTPUT_BSS} nor @code{ASM_OUTPUT_ALIGNED_BSS} are defined, -uninitialized global data will be output in the data section if -@samp{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be -used. - -@findex SHARED_BSS_SECTION_ASM_OP -@item SHARED_BSS_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -uninitialized global shared data. If not defined, and -@code{BSS_SECTION_ASM_OP} is, the latter will be used. - -@findex INIT_SECTION_ASM_OP -@item INIT_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -initialization code. If not defined, GCC will assume such a section does -not exist. - -@findex FINI_SECTION_ASM_OP -@item FINI_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -finalization code. If not defined, GCC will assume such a section does -not exist. - -@findex CRT_CALL_STATIC_FUNCTION -@item CRT_CALL_STATIC_FUNCTION -If defined, a C statement that calls the function named as the sole -argument of this macro. This is used in @file{crtstuff.c} if -@code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls to -initialization and finalization functions from the init and fini -sections. By default, this macro is a simple function call. Some -ports need hand-crafted assembly code to avoid dependencies on -registers initialized in the function prologue or to ensure that -constant pools don't end up too far way in the text section. - -@findex EXTRA_SECTIONS -@findex in_text -@findex in_data -@item EXTRA_SECTIONS -A list of names for sections other than the standard two, which are -@code{in_text} and @code{in_data}. You need not define this macro -on a system with no other sections (that GCC needs to use). - -@findex EXTRA_SECTION_FUNCTIONS -@findex text_section -@findex data_section -@item EXTRA_SECTION_FUNCTIONS -One or more functions to be defined in @file{varasm.c}. These -functions should do jobs analogous to those of @code{text_section} and -@code{data_section}, for your additional sections. Do not define this -macro if you do not define @code{EXTRA_SECTIONS}. - -@findex READONLY_DATA_SECTION -@item READONLY_DATA_SECTION -On most machines, read-only variables, constants, and jump tables are -placed in the text section. If this is not the case on your machine, -this macro should be defined to be the name of a function (either -@code{data_section} or a function defined in @code{EXTRA_SECTIONS}) that -switches to the section to be used for read-only items. - -If these items should be placed in the text section, this macro should -not be defined. - -@findex SELECT_SECTION -@item SELECT_SECTION (@var{exp}, @var{reloc}) -A C statement or statements to switch to the appropriate section for -output of @var{exp}. You can assume that @var{exp} is either a -@code{VAR_DECL} node or a constant of some sort. @var{reloc} -indicates whether the initial value of @var{exp} requires link-time -relocations. Select the section by calling @code{text_section} or one -of the alternatives for other sections. - -Do not define this macro if you put all read-only variables and -constants in the read-only data section (usually the text section). - -@findex SELECT_RTX_SECTION -@item SELECT_RTX_SECTION (@var{mode}, @var{rtx}) -A C statement or statements to switch to the appropriate section for -output of @var{rtx} in mode @var{mode}. You can assume that @var{rtx} -is some kind of constant in RTL. The argument @var{mode} is redundant -except in the case of a @code{const_int} rtx. Select the section by -calling @code{text_section} or one of the alternatives for other -sections. - -Do not define this macro if you put all constants in the read-only -data section. - -@findex JUMP_TABLES_IN_TEXT_SECTION -@item JUMP_TABLES_IN_TEXT_SECTION -Define this macro to be an expression with a non-zero value if jump -tables (for @code{tablejump} insns) should be output in the text -section, along with the assembler instructions. Otherwise, the -readonly data section is used. - -This macro is irrelevant if there is no separate readonly data section. - -@findex ENCODE_SECTION_INFO -@item ENCODE_SECTION_INFO (@var{decl}) -Define this macro if references to a symbol must be treated differently -depending on something about the variable or function named by the -symbol (such as what section it is in). - -The macro definition, if any, is executed immediately after the rtl for -@var{decl} has been created and stored in @code{DECL_RTL (@var{decl})}. -The value of the rtl will be a @code{mem} whose address is a -@code{symbol_ref}. - -@cindex @code{SYMBOL_REF_FLAG}, in @code{ENCODE_SECTION_INFO} -The usual thing for this macro to do is to record a flag in the -@code{symbol_ref} (such as @code{SYMBOL_REF_FLAG}) or to store a -modified name string in the @code{symbol_ref} (if one bit is not enough -information). - -@findex STRIP_NAME_ENCODING -@item STRIP_NAME_ENCODING (@var{var}, @var{sym_name}) -Decode @var{sym_name} and store the real name part in @var{var}, sans -the characters that encode section info. Define this macro if -@code{ENCODE_SECTION_INFO} alters the symbol's name string. - -@findex UNIQUE_SECTION_P -@item UNIQUE_SECTION_P (@var{decl}) -A C expression which evaluates to true if @var{decl} should be placed -into a unique section for some target-specific reason. If you do not -define this macro, the default is @samp{0}. Note that the flag -@samp{-ffunction-sections} will also cause functions to be placed into -unique sections. - -@findex UNIQUE_SECTION -@item UNIQUE_SECTION (@var{decl}, @var{reloc}) -A C statement to build up a unique section name, expressed as a -STRING_CST node, and assign it to @samp{DECL_SECTION_NAME (@var{decl})}. -@var{reloc} indicates whether the initial value of @var{exp} requires -link-time relocations. If you do not define this macro, GCC will use -the symbol name prefixed by @samp{.} as the section name. Note - this -macro can now be called for unitialised data items as well as -initialised data and functions. -@end table - -@node PIC -@section Position Independent Code -@cindex position independent code -@cindex PIC - -This section describes macros that help implement generation of position -independent code. Simply defining these macros is not enough to -generate valid PIC; you must also add support to the macros -@code{GO_IF_LEGITIMATE_ADDRESS} and @code{PRINT_OPERAND_ADDRESS}, as -well as @code{LEGITIMIZE_ADDRESS}. You must modify the definition of -@samp{movsi} to do something appropriate when the source operand -contains a symbolic address. You may also need to alter the handling of -switch statements so that they use relative addresses. -@c i rearranged the order of the macros above to try to force one of -@c them to the next line, to eliminate an overfull hbox. --mew 10feb93 - -@table @code -@findex PIC_OFFSET_TABLE_REGNUM -@item PIC_OFFSET_TABLE_REGNUM -The register number of the register used to address a table of static -data addresses in memory. In some cases this register is defined by a -processor's ``application binary interface'' (ABI). When this macro -is defined, RTL is generated for this register once, as with the stack -pointer and frame pointer registers. If this macro is not defined, it -is up to the machine-dependent files to allocate such a register (if -necessary). - -@findex PIC_OFFSET_TABLE_REG_CALL_CLOBBERED -@item PIC_OFFSET_TABLE_REG_CALL_CLOBBERED -Define this macro if the register defined by -@code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. Do not define -this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined. - -@findex FINALIZE_PIC -@item FINALIZE_PIC -By generating position-independent code, when two different programs (A -and B) share a common library (libC.a), the text of the library can be -shared whether or not the library is linked at the same address for both -programs. In some of these environments, position-independent code -requires not only the use of different addressing modes, but also -special code to enable the use of these addressing modes. - -The @code{FINALIZE_PIC} macro serves as a hook to emit these special -codes once the function is being compiled into assembly code, but not -before. (It is not done before, because in the case of compiling an -inline function, it would lead to multiple PIC prologues being -included in functions which used inline functions and were compiled to -assembly language.) - -@findex LEGITIMATE_PIC_OPERAND_P -@item LEGITIMATE_PIC_OPERAND_P (@var{x}) -A C expression that is nonzero if @var{x} is a legitimate immediate -operand on the target machine when generating position independent code. -You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not -check this. You can also assume @var{flag_pic} is true, so you need not -check it either. You need not define this macro if all constants -(including @code{SYMBOL_REF}) can be immediate operands when generating -position independent code. -@end table - -@node Assembler Format -@section Defining the Output Assembler Language - -This section describes macros whose principal purpose is to describe how -to write instructions in assembler language--rather than what the -instructions do. - -@menu -* File Framework:: Structural information for the assembler file. -* Data Output:: Output of constants (numbers, strings, addresses). -* Uninitialized Data:: Output of uninitialized variables. -* Label Output:: Output and generation of labels. -* Initialization:: General principles of initialization - and termination routines. -* Macros for Initialization:: - Specific macros that control the handling of - initialization and termination routines. -* Instruction Output:: Output of actual instructions. -* Dispatch Tables:: Output of jump tables. -* Exception Region Output:: Output of exception region code. -* Alignment Output:: Pseudo ops for alignment and skipping data. -@end menu - -@node File Framework -@subsection The Overall Framework of an Assembler File -@cindex assembler format -@cindex output of assembler code - -@c prevent bad page break with this line -This describes the overall framework of an assembler file. - -@table @code -@findex ASM_FILE_START -@item ASM_FILE_START (@var{stream}) -A C expression which outputs to the stdio stream @var{stream} -some appropriate text to go at the start of an assembler file. - -Normally this macro is defined to output a line containing -@samp{#NO_APP}, which is a comment that has no effect on most -assemblers but tells the GNU assembler that it can save time by not -checking for certain assembler constructs. - -On systems that use SDB, it is necessary to output certain commands; -see @file{attasm.h}. - -@findex ASM_FILE_END -@item ASM_FILE_END (@var{stream}) -A C expression which outputs to the stdio stream @var{stream} -some appropriate text to go at the end of an assembler file. - -If this macro is not defined, the default is to output nothing -special at the end of the file. Most systems don't require any -definition. - -On systems that use SDB, it is necessary to output certain commands; -see @file{attasm.h}. - -@findex ASM_COMMENT_START -@item ASM_COMMENT_START -A C string constant describing how to begin a comment in the target -assembler language. The compiler assumes that the comment will end at -the end of the line. - -@findex ASM_APP_ON -@item ASM_APP_ON -A C string constant for text to be output before each @code{asm} -statement or group of consecutive ones. Normally this is -@code{"#APP"}, which is a comment that has no effect on most -assemblers but tells the GNU assembler that it must check the lines -that follow for all valid assembler constructs. - -@findex ASM_APP_OFF -@item ASM_APP_OFF -A C string constant for text to be output after each @code{asm} -statement or group of consecutive ones. Normally this is -@code{"#NO_APP"}, which tells the GNU assembler to resume making the -time-saving assumptions that are valid for ordinary compiler output. - -@findex ASM_OUTPUT_SOURCE_FILENAME -@item ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) -A C statement to output COFF information or DWARF debugging information -which indicates that filename @var{name} is the current source file to -the stdio stream @var{stream}. - -This macro need not be defined if the standard form of output -for the file format in use is appropriate. - -@findex OUTPUT_QUOTED_STRING -@item OUTPUT_QUOTED_STRING (@var{stream}, @var{string}) -A C statement to output the string @var{string} to the stdio stream -@var{stream}. If you do not call the function @code{output_quoted_string} -in your config files, GCC will only call it to output filenames to -the assembler source. So you can use it to canonicalize the format -of the filename using this macro. - -@findex ASM_OUTPUT_SOURCE_LINE -@item ASM_OUTPUT_SOURCE_LINE (@var{stream}, @var{line}) -A C statement to output DBX or SDB debugging information before code -for line number @var{line} of the current source file to the -stdio stream @var{stream}. - -This macro need not be defined if the standard form of debugging -information for the debugger in use is appropriate. - -@findex ASM_OUTPUT_IDENT -@item ASM_OUTPUT_IDENT (@var{stream}, @var{string}) -A C statement to output something to the assembler file to handle a -@samp{#ident} directive containing the text @var{string}. If this -macro is not defined, nothing is output for a @samp{#ident} directive. - -@findex ASM_OUTPUT_SECTION_NAME -@item ASM_OUTPUT_SECTION_NAME (@var{stream}, @var{decl}, @var{name}, @var{reloc}) -A C statement to output something to the assembler file to switch to section -@var{name} for object @var{decl} which is either a @code{FUNCTION_DECL}, a -@code{VAR_DECL} or @code{NULL_TREE}. @var{reloc} -indicates whether the initial value of @var{exp} requires link-time -relocations. The string given by @var{name} will always be the -canonical version stored in the global stringpool. - -Some target formats do not support arbitrary sections. Do not define -this macro in such cases. - -At present this macro is only used to support section attributes. -When this macro is undefined, section attributes are disabled. - -@findex OBJC_PROLOGUE -@item OBJC_PROLOGUE -A C statement to output any assembler statements which are required to -precede any Objective C object definitions or message sending. The -statement is executed only when compiling an Objective C program. -@end table - -@need 2000 -@node Data Output -@subsection Output of Data - -@c prevent bad page break with this line -This describes data output. - -@table @code -@findex ASM_OUTPUT_LONG_DOUBLE -@findex ASM_OUTPUT_DOUBLE -@findex ASM_OUTPUT_FLOAT -@item ASM_OUTPUT_LONG_DOUBLE (@var{stream}, @var{value}) -@itemx ASM_OUTPUT_DOUBLE (@var{stream}, @var{value}) -@itemx ASM_OUTPUT_FLOAT (@var{stream}, @var{value}) -@itemx ASM_OUTPUT_THREE_QUARTER_FLOAT (@var{stream}, @var{value}) -@itemx ASM_OUTPUT_SHORT_FLOAT (@var{stream}, @var{value}) -@itemx ASM_OUTPUT_BYTE_FLOAT (@var{stream}, @var{value}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to assemble a floating-point constant of @code{TFmode}, -@code{DFmode}, @code{SFmode}, @code{TQFmode}, @code{HFmode}, or -@code{QFmode}, respectively, whose value is @var{value}. @var{value} -will be a C expression of type @code{REAL_VALUE_TYPE}. Macros such as -@code{REAL_VALUE_TO_TARGET_DOUBLE} are useful for writing these -definitions. - -@findex ASM_OUTPUT_QUADRUPLE_INT -@findex ASM_OUTPUT_DOUBLE_INT -@findex ASM_OUTPUT_INT -@findex ASM_OUTPUT_SHORT -@findex ASM_OUTPUT_CHAR -@findex output_addr_const -@item ASM_OUTPUT_QUADRUPLE_INT (@var{stream}, @var{exp}) -@itemx ASM_OUTPUT_DOUBLE_INT (@var{stream}, @var{exp}) -@itemx ASM_OUTPUT_INT (@var{stream}, @var{exp}) -@itemx ASM_OUTPUT_SHORT (@var{stream}, @var{exp}) -@itemx ASM_OUTPUT_CHAR (@var{stream}, @var{exp}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to assemble an integer of 16, 8, 4, 2 or 1 bytes, -respectively, whose value is @var{value}. The argument @var{exp} will -be an RTL expression which represents a constant value. Use -@samp{output_addr_const (@var{stream}, @var{exp})} to output this value -as an assembler expression.@refill - -For sizes larger than @code{UNITS_PER_WORD}, if the action of a macro -would be identical to repeatedly calling the macro corresponding to -a size of @code{UNITS_PER_WORD}, once for each word, you need not define -the macro. - -@findex OUTPUT_ADDR_CONST_EXTRA -@item OUTPUT_ADDR_CONST_EXTRA (@var{stream}, @var{x}, @var{fail}) -A C statement to recognize @var{rtx} patterns that -@code{output_addr_const} can't deal with, and output assembly code to -@var{stream} corresponding to the pattern @var{x}. This may be used to -allow machine-dependent @code{UNSPEC}s to appear within constants. - -If @code{OUTPUT_ADDR_CONST_EXTRA} fails to recognize a pattern, it must -@code{goto fail}, so that a standard error message is printed. If it -prints an error message itself, by calling, for example, -@code{output_operand_lossage}, it may just complete normally. - -@findex ASM_OUTPUT_BYTE -@item ASM_OUTPUT_BYTE (@var{stream}, @var{value}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to assemble a single byte containing the number @var{value}. - -@findex ASM_BYTE_OP -@item ASM_BYTE_OP -A C string constant, including spacing, giving the pseudo-op to use for a -sequence of single-byte constants. If this macro is not defined, the -default is @code{"\t.byte\t"}. - -@findex UNALIGNED_SHORT_ASM_OP -@findex UNALIGNED_INT_ASM_OP -@findex UNALIGNED_DOUBLE_INT_ASM_OP -@item UNALIGNED_SHORT_ASM_OP -@itemx UNALIGNED_INT_ASM_OP -@itemx UNALIGNED_DOUBLE_INT_ASM_OP -A C string constant, including spacing, giving the pseudo-op to use -to assemble 16-, 32-, and 64-bit integers respectively @emph{without} -adding implicit padding or alignment. These macros are required if -DWARF 2 frame unwind is used. On ELF systems, these will default -to @code{.2byte}, @code{.4byte}, and @code{.8byte}.@refill - -@findex ASM_OUTPUT_ASCII -@item ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to assemble a string constant containing the @var{len} -bytes at @var{ptr}. @var{ptr} will be a C expression of type -@code{char *} and @var{len} a C expression of type @code{int}. - -If the assembler has a @code{.ascii} pseudo-op as found in the -Berkeley Unix assembler, do not define the macro -@code{ASM_OUTPUT_ASCII}. - -@findex CONSTANT_POOL_BEFORE_FUNCTION -@item CONSTANT_POOL_BEFORE_FUNCTION -You may define this macro as a C expression. You should define the -expression to have a non-zero value if GCC should output the constant -pool for a function before the code for the function, or a zero value if -GCC should output the constant pool after the function. If you do -not define this macro, the usual case, GCC will output the constant -pool before the function. - -@findex ASM_OUTPUT_POOL_PROLOGUE -@item ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size}) -A C statement to output assembler commands to define the start of the -constant pool for a function. @var{funname} is a string giving -the name of the function. Should the return type of the function -be required, it can be obtained via @var{fundecl}. @var{size} -is the size, in bytes, of the constant pool that will be written -immediately after this call. - -If no constant-pool prefix is required, the usual case, this macro need -not be defined. - -@findex ASM_OUTPUT_SPECIAL_POOL_ENTRY -@item ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto}) -A C statement (with or without semicolon) to output a constant in the -constant pool, if it needs special treatment. (This macro need not do -anything for RTL expressions that can be output normally.) - -The argument @var{file} is the standard I/O stream to output the -assembler code on. @var{x} is the RTL expression for the constant to -output, and @var{mode} is the machine mode (in case @var{x} is a -@samp{const_int}). @var{align} is the required alignment for the value -@var{x}; you should output an assembler directive to force this much -alignment. - -The argument @var{labelno} is a number to use in an internal label for -the address of this pool entry. The definition of this macro is -responsible for outputting the label definition at the proper place. -Here is how to do this: - -@example -ASM_OUTPUT_INTERNAL_LABEL (@var{file}, "LC", @var{labelno}); -@end example - -When you output a pool entry specially, you should end with a -@code{goto} to the label @var{jumpto}. This will prevent the same pool -entry from being output a second time in the usual manner. - -You need not define this macro if it would do nothing. - -@findex CONSTANT_AFTER_FUNCTION_P -@item CONSTANT_AFTER_FUNCTION_P (@var{exp}) -Define this macro as a C expression which is nonzero if the constant -@var{exp}, of type @code{tree}, should be output after the code for a -function. The compiler will normally output all constants before the -function; you need not define this macro if this is OK. - -@findex ASM_OUTPUT_POOL_EPILOGUE -@item ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size}) -A C statement to output assembler commands to at the end of the constant -pool for a function. @var{funname} is a string giving the name of the -function. Should the return type of the function be required, you can -obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the -constant pool that GCC wrote immediately before this call. - -If no constant-pool epilogue is required, the usual case, you need not -define this macro. - -@findex IS_ASM_LOGICAL_LINE_SEPARATOR -@item IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}) -Define this macro as a C expression which is nonzero if @var{C} is -used as a logical line separator by the assembler. - -If you do not define this macro, the default is that only -the character @samp{;} is treated as a logical line separator. - - -@findex ASM_OPEN_PAREN -@findex ASM_CLOSE_PAREN -@item ASM_OPEN_PAREN -@itemx ASM_CLOSE_PAREN -These macros are defined as C string constants, describing the syntax -in the assembler for grouping arithmetic expressions. The following -definitions are correct for most assemblers: - -@example -#define ASM_OPEN_PAREN "(" -#define ASM_CLOSE_PAREN ")" -@end example -@end table - - These macros are provided by @file{real.h} for writing the definitions -of @code{ASM_OUTPUT_DOUBLE} and the like: - -@table @code -@item REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l}) -@itemx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l}) -@itemx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l}) -@findex REAL_VALUE_TO_TARGET_SINGLE -@findex REAL_VALUE_TO_TARGET_DOUBLE -@findex REAL_VALUE_TO_TARGET_LONG_DOUBLE -These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the target's -floating point representation, and store its bit pattern in the array of -@code{long int} whose address is @var{l}. The number of elements in the -output array is determined by the size of the desired target floating -point data type: 32 bits of it go in each @code{long int} array -element. Each array element holds 32 bits of the result, even if -@code{long int} is wider than 32 bits on the host machine. - -The array element values are designed so that you can print them out -using @code{fprintf} in the order they should appear in the target -machine's memory. - -@item REAL_VALUE_TO_DECIMAL (@var{x}, @var{format}, @var{string}) -@findex REAL_VALUE_TO_DECIMAL -This macro converts @var{x}, of type @code{REAL_VALUE_TYPE}, to a -decimal number and stores it as a string into @var{string}. -You must pass, as @var{string}, the address of a long enough block -of space to hold the result. - -The argument @var{format} is a @code{printf}-specification that serves -as a suggestion for how to format the output string. -@end table - -@node Uninitialized Data -@subsection Output of Uninitialized Variables - -Each of the macros in this section is used to do the whole job of -outputting a single uninitialized variable. - -@table @code -@findex ASM_OUTPUT_COMMON -@item ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a common-label named -@var{name} whose size is @var{size} bytes. The variable @var{rounded} -is the size rounded up to whatever alignment the caller wants. - -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. - -This macro controls how the assembler definitions of uninitialized -common global variables are output. - -@findex ASM_OUTPUT_ALIGNED_COMMON -@item ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a -separate, explicit argument. If you define this macro, it is used in -place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in -handling the required alignment of the variable. The alignment is specified -as the number of bits. - -@findex ASM_OUTPUT_ALIGNED_DECL_COMMON -@item ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the -variable to be output, if there is one, or @code{NULL_TREE} if there -is no corresponding variable. If you define this macro, GCC will use it -in place of both @code{ASM_OUTPUT_COMMON} and -@code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see -the variable's decl in order to chose what to output. - -@findex ASM_OUTPUT_SHARED_COMMON -@item ASM_OUTPUT_SHARED_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) -If defined, it is similar to @code{ASM_OUTPUT_COMMON}, except that it -is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_COMMON} -will be used. - -@findex ASM_OUTPUT_BSS -@item ASM_OUTPUT_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{rounded}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of uninitialized global @var{decl} named -@var{name} whose size is @var{size} bytes. The variable @var{rounded} -is the size rounded up to whatever alignment the caller wants. - -Try to use function @code{asm_output_bss} defined in @file{varasm.c} when -defining this macro. If unable, use the expression -@code{assemble_name (@var{stream}, @var{name})} to output the name itself; -before and after that, output the additional assembler syntax for defining -the name, and a newline. - -This macro controls how the assembler definitions of uninitialized global -variables are output. This macro exists to properly support languages like -@code{c++} which do not have @code{common} data. However, this macro currently -is not defined for all targets. If this macro and -@code{ASM_OUTPUT_ALIGNED_BSS} are not defined then @code{ASM_OUTPUT_COMMON} -or @code{ASM_OUTPUT_ALIGNED_COMMON} or -@code{ASM_OUTPUT_ALIGNED_DECL_COMMON} is used. - -@findex ASM_OUTPUT_ALIGNED_BSS -@item ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_BSS} except takes the required alignment as a -separate, explicit argument. If you define this macro, it is used in -place of @code{ASM_OUTPUT_BSS}, and gives you more flexibility in -handling the required alignment of the variable. The alignment is specified -as the number of bits. - -Try to use function @code{asm_output_aligned_bss} defined in file -@file{varasm.c} when defining this macro. - -@findex ASM_OUTPUT_SHARED_BSS -@item ASM_OUTPUT_SHARED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{rounded}) -If defined, it is similar to @code{ASM_OUTPUT_BSS}, except that it -is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_BSS} -will be used. - -@findex ASM_OUTPUT_LOCAL -@item ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a local-common-label named -@var{name} whose size is @var{size} bytes. The variable @var{rounded} -is the size rounded up to whatever alignment the caller wants. - -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. - -This macro controls how the assembler definitions of uninitialized -static variables are output. - -@findex ASM_OUTPUT_ALIGNED_LOCAL -@item ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a -separate, explicit argument. If you define this macro, it is used in -place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in -handling the required alignment of the variable. The alignment is specified -as the number of bits. - -@findex ASM_OUTPUT_ALIGNED_DECL_LOCAL -@item ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_ALIGNED_DECL} except that @var{decl} of the -variable to be output, if there is one, or @code{NULL_TREE} if there -is no corresponding variable. If you define this macro, GCC will use it -in place of both @code{ASM_OUTPUT_DECL} and -@code{ASM_OUTPUT_ALIGNED_DECL}. Define this macro when you need to see -the variable's decl in order to chose what to output. - -@findex ASM_OUTPUT_SHARED_LOCAL -@item ASM_OUTPUT_SHARED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) -If defined, it is similar to @code{ASM_OUTPUT_LOCAL}, except that it -is used when @var{name} is shared. If not defined, @code{ASM_OUTPUT_LOCAL} -will be used. -@end table - -@node Label Output -@subsection Output and Generation of Labels - -@c prevent bad page break with this line -This is about outputting labels. - -@table @code -@findex ASM_OUTPUT_LABEL -@findex assemble_name -@item ASM_OUTPUT_LABEL (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a label named @var{name}. -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. - -@findex ASM_DECLARE_FUNCTION_NAME -@item ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name @var{name} of a -function which is being defined. This macro is responsible for -outputting the label definition (perhaps using -@code{ASM_OUTPUT_LABEL}). The argument @var{decl} is the -@code{FUNCTION_DECL} tree node representing the function. - -If this macro is not defined, then the function name is defined in the -usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). - -@findex ASM_DECLARE_FUNCTION_SIZE -@item ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the size of a function -which is being defined. The argument @var{name} is the name of the -function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node -representing the function. - -If this macro is not defined, then the function size is not defined. - -@findex ASM_DECLARE_OBJECT_NAME -@item ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name @var{name} of an -initialized variable which is being defined. This macro must output the -label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument -@var{decl} is the @code{VAR_DECL} tree node representing the variable. - -If this macro is not defined, then the variable name is defined in the -usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). - -@findex ASM_DECLARE_REGISTER_GLOBAL -@item ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for claiming a register @var{regno} -for a global variable @var{decl} with name @var{name}. - -If you don't define this macro, that is equivalent to defining it to do -nothing. - -@findex ASM_FINISH_DECLARE_OBJECT -@item ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend}) -A C statement (sans semicolon) to finish up declaring a variable name -once the compiler has processed its initializer fully and thus has had a -chance to determine the size of an array when controlled by an -initializer. This is used on systems where it's necessary to declare -something about the size of the object. - -If you don't define this macro, that is equivalent to defining it to do -nothing. - -@findex ASM_GLOBALIZE_LABEL -@item ASM_GLOBALIZE_LABEL (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} some commands that will make the label @var{name} global; -that is, available for reference from other files. Use the expression -@code{assemble_name (@var{stream}, @var{name})} to output the name -itself; before and after that, output the additional assembler syntax -for making that name global, and a newline. - -@findex ASM_WEAKEN_LABEL -@item ASM_WEAKEN_LABEL -A C statement (sans semicolon) to output to the stdio stream -@var{stream} some commands that will make the label @var{name} weak; -that is, available for reference from other files but only used if -no other definition is available. Use the expression -@code{assemble_name (@var{stream}, @var{name})} to output the name -itself; before and after that, output the additional assembler syntax -for making that name weak, and a newline. - -If you don't define this macro, GCC will not support weak -symbols and you should not define the @code{SUPPORTS_WEAK} macro. - -@findex SUPPORTS_WEAK -@item SUPPORTS_WEAK -A C expression which evaluates to true if the target supports weak symbols. - -If you don't define this macro, @file{defaults.h} provides a default -definition. If @code{ASM_WEAKEN_LABEL} is defined, the default -definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if -you want to control weak symbol support with a compiler flag such as -@samp{-melf}. - -@findex MAKE_DECL_ONE_ONLY (@var{decl}) -@item MAKE_DECL_ONE_ONLY -A C statement (sans semicolon) to mark @var{decl} to be emitted as a -public symbol such that extra copies in multiple translation units will -be discarded by the linker. Define this macro if your object file -format provides support for this concept, such as the @samp{COMDAT} -section flags in the Microsoft Windows PE/COFF format, and this support -requires changes to @var{decl}, such as putting it in a separate section. - -@findex SUPPORTS_ONE_ONLY -@item SUPPORTS_ONE_ONLY -A C expression which evaluates to true if the target supports one-only -semantics. - -If you don't define this macro, @file{varasm.c} provides a default -definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default -definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if -you want to control one-only symbol support with a compiler flag, or if -setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to -be emitted as one-only. - -@findex ASM_OUTPUT_EXTERNAL -@item ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name of an external -symbol named @var{name} which is referenced in this compilation but -not defined. The value of @var{decl} is the tree node for the -declaration. - -This macro need not be defined if it does not need to output anything. -The GNU assembler and most Unix assemblers don't require anything. - -@findex ASM_OUTPUT_EXTERNAL_LIBCALL -@item ASM_OUTPUT_EXTERNAL_LIBCALL (@var{stream}, @var{symref}) -A C statement (sans semicolon) to output on @var{stream} an assembler -pseudo-op to declare a library function name external. The name of the -library function is given by @var{symref}, which has type @code{rtx} and -is a @code{symbol_ref}. - -This macro need not be defined if it does not need to output anything. -The GNU assembler and most Unix assemblers don't require anything. - -@findex ASM_OUTPUT_LABELREF -@item ASM_OUTPUT_LABELREF (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} a reference in assembler syntax to a label named -@var{name}. This should add @samp{_} to the front of the name, if that -is customary on your operating system, as it is in most Berkeley Unix -systems. This macro is used in @code{assemble_name}. - -@ignore @c Seems not to exist anymore. -@findex ASM_OUTPUT_LABELREF_AS_INT -@item ASM_OUTPUT_LABELREF_AS_INT (@var{file}, @var{label}) -Define this macro for systems that use the program @code{collect2}. -The definition should be a C statement to output a word containing -a reference to the label @var{label}. -@end ignore - -@findex ASM_OUTPUT_SYMBOL_REF -@item ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym}) -A C statement (sans semicolon) to output a reference to -@code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_output} -will be used to output the name of the symbol. This macro may be used -to modify the way a symbol is referenced depending on information -encoded by @code{ENCODE_SECTION_INFO}. - -@findex ASM_OUTPUT_INTERNAL_LABEL -@item ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{prefix}, @var{num}) -A C statement to output to the stdio stream @var{stream} a label whose -name is made from the string @var{prefix} and the number @var{num}. - -It is absolutely essential that these labels be distinct from the labels -used for user-level functions and variables. Otherwise, certain programs -will have name conflicts with internal labels. - -It is desirable to exclude internal labels from the symbol table of the -object file. Most assemblers have a naming convention for labels that -should be excluded; on many systems, the letter @samp{L} at the -beginning of a label has this effect. You should find out what -convention your system uses, and follow it. - -The usual definition of this macro is as follows: - -@example -fprintf (@var{stream}, "L%s%d:\n", @var{prefix}, @var{num}) -@end example - -@findex ASM_OUTPUT_DEBUG_LABEL -@item ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num}) -A C statement to output to the stdio stream @var{stream} a debug info -label whose name is made from the string @var{prefix} and the number -@var{num}. This is useful for VLIW targets, where debug info labels -may need to be treated differently than branch target labels. On some -systems, branch target labels must be at the beginning of instruction -bundles, but debug info labels can occur in the middle of instruction -bundles. - -If this macro is not defined, then @code{ASM_OUTPUT_INTERNAL_LABEL} will be -used. - -@findex ASM_OUTPUT_ALTERNATE_LABEL_NAME -@item ASM_OUTPUT_ALTERNATE_LABEL_NAME (@var{stream}, @var{string}) -A C statement to output to the stdio stream @var{stream} the string -@var{string}. - -The default definition of this macro is as follows: - -@example -fprintf (@var{stream}, "%s:\n", LABEL_ALTERNATE_NAME (INSN)) -@end example - -@findex ASM_GENERATE_INTERNAL_LABEL -@item ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num}) -A C statement to store into the string @var{string} a label whose name -is made from the string @var{prefix} and the number @var{num}. - -This string, when output subsequently by @code{assemble_name}, should -produce the output that @code{ASM_OUTPUT_INTERNAL_LABEL} would produce -with the same @var{prefix} and @var{num}. - -If the string begins with @samp{*}, then @code{assemble_name} will -output the rest of the string unchanged. It is often convenient for -@code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the -string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets -to output the string, and may change it. (Of course, -@code{ASM_OUTPUT_LABELREF} is also part of your machine description, so -you should know what it does on your machine.) - -@findex ASM_FORMAT_PRIVATE_NAME -@item ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number}) -A C expression to assign to @var{outvar} (which is a variable of type -@code{char *}) a newly allocated string made from the string -@var{name} and the number @var{number}, with some suitable punctuation -added. Use @code{alloca} to get space for the string. - -The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to -produce an assembler label for an internal static variable whose name is -@var{name}. Therefore, the string must be such as to result in valid -assembler code. The argument @var{number} is different each time this -macro is executed; it prevents conflicts between similarly-named -internal static variables in different scopes. - -Ideally this string should not be a valid C identifier, to prevent any -conflict with the user's own symbols. Most assemblers allow periods -or percent signs in assembler symbols; putting at least one of these -between the name and the number will suffice. - -@findex ASM_OUTPUT_DEF -@item ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the symbol @var{name} to have the value @var{value}. - -@findex SET_ASM_OP -If SET_ASM_OP is defined, a default definition is provided which is -correct for most systems. - -@findex ASM_OUTPUT_DEF_FROM_DECLS -@item ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the symbol whose tree node is @var{decl_of_name} -to have the value of the tree node @var{decl_of_value}. This macro will -be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if -the tree nodes are available. - -@findex ASM_OUTPUT_DEFINE_LABEL_DIFFERENCE_SYMBOL -@item ASM_OUTPUT_DEFINE_LABEL_DIFFERENCE_SYMBOL (@var{stream}, @var{symbol}, @var{high}, @var{low}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the symbol @var{symbol} to have a value equal to -the difference of the two symbols @var{high} and @var{low}, i.e. -@var{high} minus @var{low}. GCC guarantees that the symbols @var{high} -and @var{low} are already known by the assembler so that the difference -resolves into a constant. - -@findex SET_ASM_OP -If SET_ASM_OP is defined, a default definition is provided which is -correct for most systems. - -@findex ASM_OUTPUT_WEAK_ALIAS -@item ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the weak symbol @var{name} to have the value -@var{value}. - -Define this macro if the target only supports weak aliases; define -ASM_OUTPUT_DEF instead if possible. - -@findex OBJC_GEN_METHOD_LABEL -@item OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name}) -Define this macro to override the default assembler names used for -Objective C methods. - -The default name is a unique method number followed by the name of the -class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of -the category is also included in the assembler name (e.g.@: -@samp{_1_Foo_Bar}). - -These names are safe on most systems, but make debugging difficult since -the method's selector is not present in the name. Therefore, particular -systems define other ways of computing names. - -@var{buf} is an expression of type @code{char *} which gives you a -buffer in which to store the name; its length is as long as -@var{class_name}, @var{cat_name} and @var{sel_name} put together, plus -50 characters extra. - -The argument @var{is_inst} specifies whether the method is an instance -method or a class method; @var{class_name} is the name of the class; -@var{cat_name} is the name of the category (or NULL if the method is not -in a category); and @var{sel_name} is the name of the selector. - -On systems where the assembler can handle quoted names, you can use this -macro to provide more human-readable names. - -@findex ASM_DECLARE_UNRESOLVED_REFERENCE -@item ASM_DECLARE_UNRESOLVED_REFERENCE (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} commands to declare that the label @var{name} is an -unresolved Objective-C class reference. This is only needed for targets -whose linkers have special support for NeXT-style runtimes. -@end table - -@node Initialization -@subsection How Initialization Functions Are Handled -@cindex initialization routines -@cindex termination routines -@cindex constructors, output of -@cindex destructors, output of - -The compiled code for certain languages includes @dfn{constructors} -(also called @dfn{initialization routines})---functions to initialize -data in the program when the program is started. These functions need -to be called before the program is ``started''---that is to say, before -@code{main} is called. - -Compiling some languages generates @dfn{destructors} (also called -@dfn{termination routines}) that should be called when the program -terminates. - -To make the initialization and termination functions work, the compiler -must output something in the assembler code to cause those functions to -be called at the appropriate time. When you port the compiler to a new -system, you need to specify how to do this. - -There are two major ways that GCC currently supports the execution of -initialization and termination functions. Each way has two variants. -Much of the structure is common to all four variations. - -@findex __CTOR_LIST__ -@findex __DTOR_LIST__ -The linker must build two lists of these functions---a list of -initialization functions, called @code{__CTOR_LIST__}, and a list of -termination functions, called @code{__DTOR_LIST__}. - -Each list always begins with an ignored function pointer (which may hold -0, @minus{}1, or a count of the function pointers after it, depending on -the environment). This is followed by a series of zero or more function -pointers to constructors (or destructors), followed by a function -pointer containing zero. - -Depending on the operating system and its executable file format, either -@file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup -time and exit time. Constructors are called in reverse order of the -list; destructors in forward order. - -The best way to handle static constructors works only for object file -formats which provide arbitrarily-named sections. A section is set -aside for a list of constructors, and another for a list of destructors. -Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each -object file that defines an initialization function also puts a word in -the constructor section to point to that function. The linker -accumulates all these words into one contiguous @samp{.ctors} section. -Termination functions are handled similarly. - -To use this method, you need appropriate definitions of the macros -@code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR}. Usually -you can get them by including @file{svr4.h}. - -When arbitrary sections are available, there are two variants, depending -upon how the code in @file{crtstuff.c} is called. On systems that -support an @dfn{init} section which is executed at program startup, -parts of @file{crtstuff.c} are compiled into that section. The -program is linked by the @code{gcc} driver like this: - -@example -ld -o @var{output_file} crtbegin.o @dots{} crtend.o -lgcc -@end example - -The head of a function (@code{__do_global_ctors}) appears in the init -section of @file{crtbegin.o}; the remainder of the function appears in -the init section of @file{crtend.o}. The linker will pull these two -parts of the section together, making a whole function. If any of the -user's object files linked into the middle of it contribute code, then that -code will be executed as part of the body of @code{__do_global_ctors}. - -To use this variant, you must define the @code{INIT_SECTION_ASM_OP} -macro properly. - -If no init section is available, do not define -@code{INIT_SECTION_ASM_OP}. Then @code{__do_global_ctors} is built into -the text section like all other functions, and resides in -@file{libgcc.a}. When GCC compiles any function called @code{main}, it -inserts a procedure call to @code{__main} as the first executable code -after the function prologue. The @code{__main} function, also defined -in @file{libgcc2.c}, simply calls @file{__do_global_ctors}. - -In file formats that don't support arbitrary sections, there are again -two variants. In the simplest variant, the GNU linker (GNU @code{ld}) -and an `a.out' format must be used. In this case, -@code{ASM_OUTPUT_CONSTRUCTOR} is defined to produce a @code{.stabs} -entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__}, -and with the address of the void function containing the initialization -code as its value. The GNU linker recognizes this as a request to add -the value to a ``set''; the values are accumulated, and are eventually -placed in the executable as a vector in the format described above, with -a leading (ignored) count and a trailing zero element. -@code{ASM_OUTPUT_DESTRUCTOR} is handled similarly. Since no init -section is available, the absence of @code{INIT_SECTION_ASM_OP} causes -the compilation of @code{main} to call @code{__main} as above, starting -the initialization process. - -The last variant uses neither arbitrary sections nor the GNU linker. -This is preferable when you want to do dynamic linking and when using -file formats which the GNU linker does not support, such as `ECOFF'. In -this case, @code{ASM_OUTPUT_CONSTRUCTOR} does not produce an -@code{N_SETT} symbol; initialization and termination functions are -recognized simply by their names. This requires an extra program in the -linkage step, called @code{collect2}. This program pretends to be the -linker, for use with GCC; it does its job by running the ordinary -linker, but also arranges to include the vectors of initialization and -termination functions. These functions are called via @code{__main} as -described above. - -Choosing among these configuration options has been simplified by a set -of operating-system-dependent files in the @file{config} subdirectory. -These files define all of the relevant parameters. Usually it is -sufficient to include one into your specific machine-dependent -configuration file. These files are: - -@table @file -@item aoutos.h -For operating systems using the `a.out' format. - -@item next.h -For operating systems using the `MachO' format. - -@item svr3.h -For System V Release 3 and similar systems using `COFF' format. - -@item svr4.h -For System V Release 4 and similar systems using `ELF' format. - -@item vms.h -For the VMS operating system. -@end table - -@ifinfo -The following section describes the specific macros that control and -customize the handling of initialization and termination functions. -@end ifinfo - -@node Macros for Initialization -@subsection Macros Controlling Initialization Routines - -Here are the macros that control how the compiler handles initialization -and termination functions: - -@table @code -@findex INIT_SECTION_ASM_OP -@item INIT_SECTION_ASM_OP -If defined, a C string constant, including spacing, for the assembler -operation to identify the following data as initialization code. If not -defined, GCC will assume such a section does not exist. When you are -using special sections for initialization and termination functions, this -macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to -run the initialization functions. - -@item HAS_INIT_SECTION -@findex HAS_INIT_SECTION -If defined, @code{main} will not call @code{__main} as described above. -This macro should be defined for systems that control the contents of the -init section on a symbol-by-symbol basis, such as OSF/1, and should not -be defined explicitly for systems that support -@code{INIT_SECTION_ASM_OP}. - -@item LD_INIT_SWITCH -@findex LD_INIT_SWITCH -If defined, a C string constant for a switch that tells the linker that -the following symbol is an initialization routine. - -@item LD_FINI_SWITCH -@findex LD_FINI_SWITCH -If defined, a C string constant for a switch that tells the linker that -the following symbol is a finalization routine. - -@item INVOKE__main -@findex INVOKE__main -If defined, @code{main} will call @code{__main} despite the presence of -@code{INIT_SECTION_ASM_OP}. This macro should be defined for systems -where the init section is not actually run automatically, but is still -useful for collecting the lists of constructors and destructors. - -@item SUPPORTS_INIT_PRIORITY -@findex SUPPORTS_INIT_PRIORITY -If nonzero, the C++ @code{init_priority} attribute is supported and the -compiler should emit instructions to control the order of initialization -of objects. If zero, the compiler will issue an error message upon -encountering an @code{init_priority} attribute. - -@item ASM_OUTPUT_CONSTRUCTOR (@var{stream}, @var{name}) -@findex ASM_OUTPUT_CONSTRUCTOR -Define this macro as a C statement to output on the stream @var{stream} -the assembler code to arrange to call the function named @var{name} at -initialization time. - -Assume that @var{name} is the name of a C function generated -automatically by the compiler. This function takes no arguments. Use -the function @code{assemble_name} to output the name @var{name}; this -performs any system-specific syntactic transformations such as adding an -underscore. - -If you don't define this macro, nothing special is output to arrange to -call the function. This is correct when the function will be called in -some other manner---for example, by means of the @code{collect2} program, -which looks through the symbol table to find these functions by their -names. - -@item ASM_OUTPUT_DESTRUCTOR (@var{stream}, @var{name}) -@findex ASM_OUTPUT_DESTRUCTOR -This is like @code{ASM_OUTPUT_CONSTRUCTOR} but used for termination -functions rather than initialization functions. - -When @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR} are -defined, the initialization routine generated for the generated object -file will have static linkage. -@end table - -If your system uses @code{collect2} as the means of processing -constructors, then that program normally uses @code{nm} to scan an -object file for constructor functions to be called. On such systems you -must not define @code{ASM_OUTPUT_CONSTRUCTOR} and @code{ASM_OUTPUT_DESTRUCTOR} -as the object file's initialization routine must have global scope. - -On certain kinds of systems, you can define these macros to make -@code{collect2} work faster (and, in some cases, make it work at all): - -@table @code -@findex OBJECT_FORMAT_COFF -@item OBJECT_FORMAT_COFF -Define this macro if the system uses COFF (Common Object File Format) -object files, so that @code{collect2} can assume this format and scan -object files directly for dynamic constructor/destructor functions. - -@findex OBJECT_FORMAT_ROSE -@item OBJECT_FORMAT_ROSE -Define this macro if the system uses ROSE format object files, so that -@code{collect2} can assume this format and scan object files directly -for dynamic constructor/destructor functions. - -These macros are effective only in a native compiler; @code{collect2} as -part of a cross compiler always uses @code{nm} for the target machine. - -@findex REAL_NM_FILE_NAME -@item REAL_NM_FILE_NAME -Define this macro as a C string constant containing the file name to use -to execute @code{nm}. The default is to search the path normally for -@code{nm}. - -If your system supports shared libraries and has a program to list the -dynamic dependencies of a given library or executable, you can define -these macros to enable support for running initialization and -termination functions in shared libraries: - -@findex LDD_SUFFIX -@item LDD_SUFFIX -Define this macro to a C string constant containing the name of the -program which lists dynamic dependencies, like @code{"ldd"} under SunOS 4. - -@findex PARSE_LDD_OUTPUT -@item PARSE_LDD_OUTPUT (@var{PTR}) -Define this macro to be C code that extracts filenames from the output -of the program denoted by @code{LDD_SUFFIX}. @var{PTR} is a variable -of type @code{char *} that points to the beginning of a line of output -from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the -code must advance @var{PTR} to the beginning of the filename on that -line. Otherwise, it must set @var{PTR} to @code{NULL}. - -@end table - -@node Instruction Output -@subsection Output of Assembler Instructions - -@c prevent bad page break with this line -This describes assembler instruction output. - -@table @code -@findex REGISTER_NAMES -@item REGISTER_NAMES -A C initializer containing the assembler's names for the machine -registers, each one as a C string constant. This is what translates -register numbers in the compiler into assembler language. - -@findex ADDITIONAL_REGISTER_NAMES -@item ADDITIONAL_REGISTER_NAMES -If defined, a C initializer for an array of structures containing a name -and a register number. This macro defines additional names for hard -registers, thus allowing the @code{asm} option in declarations to refer -to registers using alternate names. - -@findex ASM_OUTPUT_OPCODE -@item ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr}) -Define this macro if you are using an unusual assembler that -requires different names for the machine instructions. - -The definition is a C statement or statements which output an -assembler instruction opcode to the stdio stream @var{stream}. The -macro-operand @var{ptr} is a variable of type @code{char *} which -points to the opcode name in its ``internal'' form---the form that is -written in the machine description. The definition should output the -opcode name to @var{stream}, performing any translation you desire, and -increment the variable @var{ptr} to point at the end of the opcode -so that it will not be output twice. - -In fact, your macro definition may process less than the entire opcode -name, or more than the opcode name; but if you want to process text -that includes @samp{%}-sequences to substitute operands, you must take -care of the substitution yourself. Just be sure to increment -@var{ptr} over whatever text should not be output normally. - -@findex recog_operand -If you need to look at the operand values, they can be found as the -elements of @code{recog_operand}. - -If the macro definition does nothing, the instruction is output -in the usual way. - -@findex FINAL_PRESCAN_INSN -@item FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands}) -If defined, a C statement to be executed just prior to the output of -assembler code for @var{insn}, to modify the extracted operands so -they will be output differently. - -Here the argument @var{opvec} is the vector containing the operands -extracted from @var{insn}, and @var{noperands} is the number of -elements of the vector which contain meaningful data for this insn. -The contents of this vector are what will be used to convert the insn -template into assembler code, so you can change the assembler output -by changing the contents of the vector. - -This macro is useful when various assembler syntaxes share a single -file of instruction patterns; by defining this macro differently, you -can cause a large class of instructions to be output differently (such -as with rearranged operands). Naturally, variations in assembler -syntax affecting individual insn patterns ought to be handled by -writing conditional output routines in those patterns. - -If this macro is not defined, it is equivalent to a null statement. - -@findex FINAL_PRESCAN_LABEL -@item FINAL_PRESCAN_LABEL -If defined, @code{FINAL_PRESCAN_INSN} will be called on each -@code{CODE_LABEL}. In that case, @var{opvec} will be a null pointer and -@var{noperands} will be zero. - -@findex PRINT_OPERAND -@item PRINT_OPERAND (@var{stream}, @var{x}, @var{code}) -A C compound statement to output to stdio stream @var{stream} the -assembler syntax for an instruction operand @var{x}. @var{x} is an -RTL expression. - -@var{code} is a value that can be used to specify one of several ways -of printing the operand. It is used when identical operands must be -printed differently depending on the context. @var{code} comes from -the @samp{%} specification that was used to request printing of the -operand. If the specification was just @samp{%@var{digit}} then -@var{code} is 0; if the specification was @samp{%@var{ltr} -@var{digit}} then @var{code} is the ASCII code for @var{ltr}. - -@findex reg_names -If @var{x} is a register, this macro should print the register's name. -The names can be found in an array @code{reg_names} whose type is -@code{char *[]}. @code{reg_names} is initialized from -@code{REGISTER_NAMES}. - -When the machine description has a specification @samp{%@var{punct}} -(a @samp{%} followed by a punctuation character), this macro is called -with a null pointer for @var{x} and the punctuation character for -@var{code}. - -@findex PRINT_OPERAND_PUNCT_VALID_P -@item PRINT_OPERAND_PUNCT_VALID_P (@var{code}) -A C expression which evaluates to true if @var{code} is a valid -punctuation character for use in the @code{PRINT_OPERAND} macro. If -@code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no -punctuation characters (except for the standard one, @samp{%}) are used -in this way. - -@findex PRINT_OPERAND_ADDRESS -@item PRINT_OPERAND_ADDRESS (@var{stream}, @var{x}) -A C compound statement to output to stdio stream @var{stream} the -assembler syntax for an instruction operand that is a memory reference -whose address is @var{x}. @var{x} is an RTL expression. - -@cindex @code{ENCODE_SECTION_INFO} usage -On some machines, the syntax for a symbolic address depends on the -section that the address refers to. On these machines, define the macro -@code{ENCODE_SECTION_INFO} to store the information into the -@code{symbol_ref}, and then check for it here. @xref{Assembler Format}. - -@findex DBR_OUTPUT_SEQEND -@findex dbr_sequence_length -@item DBR_OUTPUT_SEQEND(@var{file}) -A C statement, to be executed after all slot-filler instructions have -been output. If necessary, call @code{dbr_sequence_length} to -determine the number of slots filled in a sequence (zero if not -currently outputting a sequence), to decide how many no-ops to output, -or whatever. - -Don't define this macro if it has nothing to do, but it is helpful in -reading assembly output if the extent of the delay sequence is made -explicit (e.g. with white space). - -@findex final_sequence -Note that output routines for instructions with delay slots must be -prepared to deal with not being output as part of a sequence (i.e. -when the scheduling pass is not run, or when no slot fillers could be -found.) The variable @code{final_sequence} is null when not -processing a sequence, otherwise it contains the @code{sequence} rtx -being output. - -@findex REGISTER_PREFIX -@findex LOCAL_LABEL_PREFIX -@findex USER_LABEL_PREFIX -@findex IMMEDIATE_PREFIX -@findex asm_fprintf -@item REGISTER_PREFIX -@itemx LOCAL_LABEL_PREFIX -@itemx USER_LABEL_PREFIX -@itemx IMMEDIATE_PREFIX -If defined, C string expressions to be used for the @samp{%R}, @samp{%L}, -@samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see -@file{final.c}). These are useful when a single @file{md} file must -support multiple assembler formats. In that case, the various @file{tm.h} -files can define these macros differently. - -@item ASM_FPRINTF_EXTENSIONS(@var{file}, @var{argptr}, @var{format}) -@findex ASM_FPRINTF_EXTENSIONS -If defined this macro should expand to a series of @code{case} -statements which will be parsed inside the @code{switch} statement of -the @code{asm_fprintf} function. This allows targets to define extra -printf formats which may useful when generating their assembler -statements. Note that upper case letters are reserved for future -generic extensions to asm_fprintf, and so are not available to target -specific code. The output file is given by the parameter @var{file}. -The varargs input pointer is @var{argptr} and the rest of the format -string, starting the character after the one that is being switched -upon, is pointed to by @var{format}. - -@findex ASSEMBLER_DIALECT -@item ASSEMBLER_DIALECT -If your target supports multiple dialects of assembler language (such as -different opcodes), define this macro as a C expression that gives the -numeric index of the assembler language dialect to use, with zero as the -first variant. - -If this macro is defined, you may use constructs of the form -@samp{@{option0|option1|option2@dots{}@}} in the output -templates of patterns (@pxref{Output Template}) or in the first argument -of @code{asm_fprintf}. This construct outputs @samp{option0}, -@samp{option1} or @samp{option2}, etc., if the value of -@code{ASSEMBLER_DIALECT} is zero, one or two, etc. Any special -characters within these strings retain their usual meaning. - -If you do not define this macro, the characters @samp{@{}, @samp{|} and -@samp{@}} do not have any special meaning when used in templates or -operands to @code{asm_fprintf}. - -Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX}, -@code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express -the variations in assembler language syntax with that mechanism. Define -@code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax -if the syntax variant are larger and involve such things as different -opcodes or operand order. - -@findex ASM_OUTPUT_REG_PUSH -@item ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno}) -A C expression to output to @var{stream} some assembler code -which will push hard register number @var{regno} onto the stack. -The code need not be optimal, since this macro is used only when -profiling. - -@findex ASM_OUTPUT_REG_POP -@item ASM_OUTPUT_REG_POP (@var{stream}, @var{regno}) -A C expression to output to @var{stream} some assembler code -which will pop hard register number @var{regno} off of the stack. -The code need not be optimal, since this macro is used only when -profiling. -@end table - -@node Dispatch Tables -@subsection Output of Dispatch Tables - -@c prevent bad page break with this line -This concerns dispatch tables. - -@table @code -@cindex dispatch table -@findex ASM_OUTPUT_ADDR_DIFF_ELT -@item ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel}) -A C statement to output to the stdio stream @var{stream} an assembler -pseudo-instruction to generate a difference between two labels. -@var{value} and @var{rel} are the numbers of two internal labels. The -definitions of these labels are output using -@code{ASM_OUTPUT_INTERNAL_LABEL}, and they must be printed in the same -way here. For example, - -@example -fprintf (@var{stream}, "\t.word L%d-L%d\n", - @var{value}, @var{rel}) -@end example - -You must provide this macro on machines where the addresses in a -dispatch table are relative to the table's own address. If defined, GNU -CC will also use this macro on all machines when producing PIC. -@var{body} is the body of the ADDR_DIFF_VEC; it is provided so that the -mode and flags can be read. - -@findex ASM_OUTPUT_ADDR_VEC_ELT -@item ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value}) -This macro should be provided on machines where the addresses -in a dispatch table are absolute. - -The definition should be a C statement to output to the stdio stream -@var{stream} an assembler pseudo-instruction to generate a reference to -a label. @var{value} is the number of an internal label whose -definition is output using @code{ASM_OUTPUT_INTERNAL_LABEL}. -For example, - -@example -fprintf (@var{stream}, "\t.word L%d\n", @var{value}) -@end example - -@findex ASM_OUTPUT_CASE_LABEL -@item ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table}) -Define this if the label before a jump-table needs to be output -specially. The first three arguments are the same as for -@code{ASM_OUTPUT_INTERNAL_LABEL}; the fourth argument is the -jump-table which follows (a @code{jump_insn} containing an -@code{addr_vec} or @code{addr_diff_vec}). - -This feature is used on system V to output a @code{swbeg} statement -for the table. - -If this macro is not defined, these labels are output with -@code{ASM_OUTPUT_INTERNAL_LABEL}. - -@findex ASM_OUTPUT_CASE_END -@item ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table}) -Define this if something special must be output at the end of a -jump-table. The definition should be a C statement to be executed -after the assembler code for the table is written. It should write -the appropriate code to stdio stream @var{stream}. The argument -@var{table} is the jump-table insn, and @var{num} is the label-number -of the preceding label. - -If this macro is not defined, nothing special is output at the end of -the jump-table. -@end table - -@node Exception Region Output -@subsection Assembler Commands for Exception Regions - -@c prevent bad page break with this line - -This describes commands marking the start and the end of an exception -region. - -@table @code -@findex ASM_OUTPUT_EH_REGION_BEG -@item ASM_OUTPUT_EH_REGION_BEG () -A C expression to output text to mark the start of an exception region. - -This macro need not be defined on most platforms. - -@findex ASM_OUTPUT_EH_REGION_END -@item ASM_OUTPUT_EH_REGION_END () -A C expression to output text to mark the end of an exception region. - -This macro need not be defined on most platforms. - -@findex EXCEPTION_SECTION -@item EXCEPTION_SECTION () -A C expression to switch to the section in which the main -exception table is to be placed (@pxref{Sections}). The default is a -section named @code{.gcc_except_table} on machines that support named -sections via @code{ASM_OUTPUT_SECTION_NAME}, otherwise if @samp{-fpic} -or @samp{-fPIC} is in effect, the @code{data_section}, otherwise the -@code{readonly_data_section}. - -@findex EH_FRAME_SECTION_ASM_OP -@item EH_FRAME_SECTION_ASM_OP -If defined, a C string constant, including spacing, for the assembler -operation to switch to the section for exception handling frame unwind -information. If not defined, GCC will provide a default definition if the -target supports named sections. @file{crtstuff.c} uses this macro to -switch to the appropriate section. - -You should define this symbol if your target supports DWARF 2 frame -unwind information and the default definition does not work. - -@findex OMIT_EH_TABLE -@item OMIT_EH_TABLE () -A C expression that is nonzero if the normal exception table output -should be omitted. - -This macro need not be defined on most platforms. - -@findex EH_TABLE_LOOKUP -@item EH_TABLE_LOOKUP () -Alternate runtime support for looking up an exception at runtime and -finding the associated handler, if the default method won't work. - -This macro need not be defined on most platforms. - -@findex DOESNT_NEED_UNWINDER -@item DOESNT_NEED_UNWINDER -A C expression that decides whether or not the current function needs to -have a function unwinder generated for it. See the file @code{except.c} -for details on when to define this, and how. - -@findex MASK_RETURN_ADDR -@item MASK_RETURN_ADDR -An rtx used to mask the return address found via RETURN_ADDR_RTX, so -that it does not contain any extraneous set bits in it. - -@findex DWARF2_UNWIND_INFO -@item DWARF2_UNWIND_INFO -Define this macro to 0 if your target supports DWARF 2 frame unwind -information, but it does not yet work with exception handling. -Otherwise, if your target supports this information (if it defines -@samp{INCOMING_RETURN_ADDR_RTX} and either @samp{UNALIGNED_INT_ASM_OP} -or @samp{OBJECT_FORMAT_ELF}), GCC will provide a default definition of -1. - -If this macro is defined to 1, the DWARF 2 unwinder will be the default -exception handling mechanism; otherwise, setjmp/longjmp will be used by -default. - -If this macro is defined to anything, the DWARF 2 unwinder will be used -instead of inline unwinders and __unwind_function in the non-setjmp case. - -@findex DWARF_CIE_DATA_ALIGNMENT -@item DWARF_CIE_DATA_ALIGNMENT -This macro need only be defined if the target might save registers in the -function prologue at an offset to the stack pointer that is not aligned to -@code{UNITS_PER_WORD}. The definition should be the negative minimum -alignment if @code{STACK_GROWS_DOWNWARD} is defined, and the positive -minimum alignment otherwise. @xref{SDB and DWARF}. Only applicable if -the target supports DWARF 2 frame unwind information. - -@end table - -@node Alignment Output -@subsection Assembler Commands for Alignment - -@c prevent bad page break with this line -This describes commands for alignment. - -@table @code -@findex LABEL_ALIGN_AFTER_BARRIER -@item LABEL_ALIGN_AFTER_BARRIER (@var{label}) -The alignment (log base 2) to put in front of @var{label}, which follows -a BARRIER. - -This macro need not be defined if you don't want any special alignment -to be done at such a time. Most machine descriptions do not currently -define the macro. - -Unless it's necessary to inspect the @var{label} parameter, it is better -to set the variable @var{align_jumps} in the target's -@code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's -selection in @var{align_jumps} in a @code{LABEL_ALIGN_AFTER_BARRIER} -implementation. - -@findex LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP -@item LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP -The maximum number of bytes to skip when applying -@code{LABEL_ALIGN_AFTER_BARRIER}. This works only if -@code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. - -@findex LOOP_ALIGN -@item LOOP_ALIGN (@var{label}) -The alignment (log base 2) to put in front of @var{label}, which follows -a NOTE_INSN_LOOP_BEG note. - -This macro need not be defined if you don't want any special alignment -to be done at such a time. Most machine descriptions do not currently -define the macro. - -Unless it's necessary to inspect the @var{label} parameter, it is better -to set the variable @var{align_loops} in the target's -@code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's -selection in @var{align_loops} in a @code{LOOP_ALIGN} implementation. - -@findex LOOP_ALIGN_MAX_SKIP -@item LOOP_ALIGN_MAX_SKIP -The maximum number of bytes to skip when applying @code{LOOP_ALIGN}. -This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. - -@findex LABEL_ALIGN -@item LABEL_ALIGN (@var{label}) -The alignment (log base 2) to put in front of @var{label}. -If LABEL_ALIGN_AFTER_BARRIER / LOOP_ALIGN specify a different alignment, -the maximum of the specified values is used. - -Unless it's necessary to inspect the @var{label} parameter, it is better -to set the variable @var{align_labels} in the target's -@code{OVERRIDE_OPTIONS}. Otherwise, you should try to honour the user's -selection in @var{align_labels} in a @code{LABEL_ALIGN} implementation. - -@findex LABEL_ALIGN_MAX_SKIP -@item LABEL_ALIGN_MAX_SKIP -The maximum number of bytes to skip when applying @code{LABEL_ALIGN}. -This works only if @code{ASM_OUTPUT_MAX_SKIP_ALIGN} is defined. - -@findex ASM_OUTPUT_SKIP -@item ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to advance the location counter by @var{nbytes} bytes. -Those bytes should be zero when loaded. @var{nbytes} will be a C -expression of type @code{int}. - -@findex ASM_NO_SKIP_IN_TEXT -@item ASM_NO_SKIP_IN_TEXT -Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the -text section because it fails to put zeros in the bytes that are skipped. -This is true on many Unix systems, where the pseudo--op to skip bytes -produces no-op instructions rather than zeros when used in the text -section. - -@findex ASM_OUTPUT_ALIGN -@item ASM_OUTPUT_ALIGN (@var{stream}, @var{power}) -A C statement to output to the stdio stream @var{stream} an assembler -command to advance the location counter to a multiple of 2 to the -@var{power} bytes. @var{power} will be a C expression of type @code{int}. - -@findex ASM_OUTPUT_MAX_SKIP_ALIGN -@item ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip}) -A C statement to output to the stdio stream @var{stream} an assembler -command to advance the location counter to a multiple of 2 to the -@var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to -satisfy the alignment request. @var{power} and @var{max_skip} will be -a C expression of type @code{int}. -@end table - -@need 3000 -@node Debugging Info -@section Controlling Debugging Information Format - -@c prevent bad page break with this line -This describes how to specify debugging information. - -@menu -* All Debuggers:: Macros that affect all debugging formats uniformly. -* DBX Options:: Macros enabling specific options in DBX format. -* DBX Hooks:: Hook macros for varying DBX format. -* File Names and DBX:: Macros controlling output of file names in DBX format. -* SDB and DWARF:: Macros for SDB (COFF) and DWARF formats. -@end menu - -@node All Debuggers -@subsection Macros Affecting All Debugging Formats - -@c prevent bad page break with this line -These macros affect all debugging formats. - -@table @code -@findex DBX_REGISTER_NUMBER -@item DBX_REGISTER_NUMBER (@var{regno}) -A C expression that returns the DBX register number for the compiler -register number @var{regno}. In simple cases, the value of this -expression may be @var{regno} itself. But sometimes there are some -registers that the compiler knows about and DBX does not, or vice -versa. In such cases, some register may need to have one number in -the compiler and another for DBX. - -If two registers have consecutive numbers inside GCC, and they can be -used as a pair to hold a multiword value, then they @emph{must} have -consecutive numbers after renumbering with @code{DBX_REGISTER_NUMBER}. -Otherwise, debuggers will be unable to access such a pair, because they -expect register pairs to be consecutive in their own numbering scheme. - -If you find yourself defining @code{DBX_REGISTER_NUMBER} in way that -does not preserve register pairs, then what you must do instead is -redefine the actual register numbering scheme. - -@findex DEBUGGER_AUTO_OFFSET -@item DEBUGGER_AUTO_OFFSET (@var{x}) -A C expression that returns the integer offset value for an automatic -variable having address @var{x} (an RTL expression). The default -computation assumes that @var{x} is based on the frame-pointer and -gives the offset from the frame-pointer. This is required for targets -that produce debugging output for DBX or COFF-style debugging output -for SDB and allow the frame-pointer to be eliminated when the -@samp{-g} options is used. - -@findex DEBUGGER_ARG_OFFSET -@item DEBUGGER_ARG_OFFSET (@var{offset}, @var{x}) -A C expression that returns the integer offset value for an argument -having address @var{x} (an RTL expression). The nominal offset is -@var{offset}. - -@findex PREFERRED_DEBUGGING_TYPE -@item PREFERRED_DEBUGGING_TYPE -A C expression that returns the type of debugging output GCC should -produce when the user specifies just @samp{-g}. Define -this if you have arranged for GCC to support more than one format of -debugging output. Currently, the allowable values are @code{DBX_DEBUG}, -@code{SDB_DEBUG}, @code{DWARF_DEBUG}, @code{DWARF2_DEBUG}, and -@code{XCOFF_DEBUG}. - -When the user specifies @samp{-ggdb}, GCC normally also uses the -value of this macro to select the debugging output format, but with two -exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined and -@code{LINKER_DOES_NOT_WORK_WITH_DWARF2} is not defined, GCC uses the -value @code{DWARF2_DEBUG}. Otherwise, if @code{DBX_DEBUGGING_INFO} is -defined, GCC uses @code{DBX_DEBUG}. - -The value of this macro only affects the default debugging output; the -user can always get a specific type of output by using @samp{-gstabs}, -@samp{-gcoff}, @samp{-gdwarf-1}, @samp{-gdwarf-2}, or @samp{-gxcoff}. -@end table - -@node DBX Options -@subsection Specific Options for DBX Output - -@c prevent bad page break with this line -These are specific options for DBX output. - -@table @code -@findex DBX_DEBUGGING_INFO -@item DBX_DEBUGGING_INFO -Define this macro if GCC should produce debugging output for DBX -in response to the @samp{-g} option. - -@findex XCOFF_DEBUGGING_INFO -@item XCOFF_DEBUGGING_INFO -Define this macro if GCC should produce XCOFF format debugging output -in response to the @samp{-g} option. This is a variant of DBX format. - -@findex DEFAULT_GDB_EXTENSIONS -@item DEFAULT_GDB_EXTENSIONS -Define this macro to control whether GCC should by default generate -GDB's extended version of DBX debugging information (assuming DBX-format -debugging information is enabled at all). If you don't define the -macro, the default is 1: always generate the extended information -if there is any occasion to. - -@findex DEBUG_SYMS_TEXT -@item DEBUG_SYMS_TEXT -Define this macro if all @code{.stabs} commands should be output while -in the text section. - -@findex ASM_STABS_OP -@item ASM_STABS_OP -A C string constant, including spacing, naming the assembler pseudo op to -use instead of @code{"\t.stabs\t"} to define an ordinary debugging symbol. -If you don't define this macro, @code{"\t.stabs\t"} is used. This macro -applies only to DBX debugging information format. - -@findex ASM_STABD_OP -@item ASM_STABD_OP -A C string constant, including spacing, naming the assembler pseudo op to -use instead of @code{"\t.stabd\t"} to define a debugging symbol whose -value is the current location. If you don't define this macro, -@code{"\t.stabd\t"} is used. This macro applies only to DBX debugging -information format. - -@findex ASM_STABN_OP -@item ASM_STABN_OP -A C string constant, including spacing, naming the assembler pseudo op to -use instead of @code{"\t.stabn\t"} to define a debugging symbol with no -name. If you don't define this macro, @code{"\t.stabn\t"} is used. This -macro applies only to DBX debugging information format. - -@findex DBX_NO_XREFS -@item DBX_NO_XREFS -Define this macro if DBX on your system does not support the construct -@samp{xs@var{tagname}}. On some systems, this construct is used to -describe a forward reference to a structure named @var{tagname}. -On other systems, this construct is not supported at all. - -@findex DBX_CONTIN_LENGTH -@item DBX_CONTIN_LENGTH -A symbol name in DBX-format debugging information is normally -continued (split into two separate @code{.stabs} directives) when it -exceeds a certain length (by default, 80 characters). On some -operating systems, DBX requires this splitting; on others, splitting -must not be done. You can inhibit splitting by defining this macro -with the value zero. You can override the default splitting-length by -defining this macro as an expression for the length you desire. - -@findex DBX_CONTIN_CHAR -@item DBX_CONTIN_CHAR -Normally continuation is indicated by adding a @samp{\} character to -the end of a @code{.stabs} string when a continuation follows. To use -a different character instead, define this macro as a character -constant for the character you want to use. Do not define this macro -if backslash is correct for your system. - -@findex DBX_STATIC_STAB_DATA_SECTION -@item DBX_STATIC_STAB_DATA_SECTION -Define this macro if it is necessary to go to the data section before -outputting the @samp{.stabs} pseudo-op for a non-global static -variable. - -@findex DBX_TYPE_DECL_STABS_CODE -@item DBX_TYPE_DECL_STABS_CODE -The value to use in the ``code'' field of the @code{.stabs} directive -for a typedef. The default is @code{N_LSYM}. - -@findex DBX_STATIC_CONST_VAR_CODE -@item DBX_STATIC_CONST_VAR_CODE -The value to use in the ``code'' field of the @code{.stabs} directive -for a static variable located in the text section. DBX format does not -provide any ``right'' way to do this. The default is @code{N_FUN}. - -@findex DBX_REGPARM_STABS_CODE -@item DBX_REGPARM_STABS_CODE -The value to use in the ``code'' field of the @code{.stabs} directive -for a parameter passed in registers. DBX format does not provide any -``right'' way to do this. The default is @code{N_RSYM}. - -@findex DBX_REGPARM_STABS_LETTER -@item DBX_REGPARM_STABS_LETTER -The letter to use in DBX symbol data to identify a symbol as a parameter -passed in registers. DBX format does not customarily provide any way to -do this. The default is @code{'P'}. - -@findex DBX_MEMPARM_STABS_LETTER -@item DBX_MEMPARM_STABS_LETTER -The letter to use in DBX symbol data to identify a symbol as a stack -parameter. The default is @code{'p'}. - -@findex DBX_FUNCTION_FIRST -@item DBX_FUNCTION_FIRST -Define this macro if the DBX information for a function and its -arguments should precede the assembler code for the function. Normally, -in DBX format, the debugging information entirely follows the assembler -code. - -@findex DBX_LBRAC_FIRST -@item DBX_LBRAC_FIRST -Define this macro if the @code{N_LBRAC} symbol for a block should -precede the debugging information for variables and functions defined in -that block. Normally, in DBX format, the @code{N_LBRAC} symbol comes -first. - -@findex DBX_BLOCKS_FUNCTION_RELATIVE -@item DBX_BLOCKS_FUNCTION_RELATIVE -Define this macro if the value of a symbol describing the scope of a -block (@code{N_LBRAC} or @code{N_RBRAC}) should be relative to the start -of the enclosing function. Normally, GNU C uses an absolute address. - -@findex DBX_USE_BINCL -@item DBX_USE_BINCL -Define this macro if GNU C should generate @code{N_BINCL} and -@code{N_EINCL} stabs for included header files, as on Sun systems. This -macro also directs GNU C to output a type number as a pair of a file -number and a type number within the file. Normally, GNU C does not -generate @code{N_BINCL} or @code{N_EINCL} stabs, and it outputs a single -number for a type number. -@end table - -@node DBX Hooks -@subsection Open-Ended Hooks for DBX Format - -@c prevent bad page break with this line -These are hooks for DBX format. - -@table @code -@findex DBX_OUTPUT_LBRAC -@item DBX_OUTPUT_LBRAC (@var{stream}, @var{name}) -Define this macro to say how to output to @var{stream} the debugging -information for the start of a scope level for variable names. The -argument @var{name} is the name of an assembler symbol (for use with -@code{assemble_name}) whose value is the address where the scope begins. - -@findex DBX_OUTPUT_RBRAC -@item DBX_OUTPUT_RBRAC (@var{stream}, @var{name}) -Like @code{DBX_OUTPUT_LBRAC}, but for the end of a scope level. - -@findex DBX_OUTPUT_ENUM -@item DBX_OUTPUT_ENUM (@var{stream}, @var{type}) -Define this macro if the target machine requires special handling to -output an enumeration type. The definition should be a C statement -(sans semicolon) to output the appropriate information to @var{stream} -for the type @var{type}. - -@findex DBX_OUTPUT_FUNCTION_END -@item DBX_OUTPUT_FUNCTION_END (@var{stream}, @var{function}) -Define this macro if the target machine requires special output at the -end of the debugging information for a function. The definition should -be a C statement (sans semicolon) to output the appropriate information -to @var{stream}. @var{function} is the @code{FUNCTION_DECL} node for -the function. - -@findex DBX_OUTPUT_STANDARD_TYPES -@item DBX_OUTPUT_STANDARD_TYPES (@var{syms}) -Define this macro if you need to control the order of output of the -standard data types at the beginning of compilation. The argument -@var{syms} is a @code{tree} which is a chain of all the predefined -global symbols, including names of data types. - -Normally, DBX output starts with definitions of the types for integers -and characters, followed by all the other predefined types of the -particular language in no particular order. - -On some machines, it is necessary to output different particular types -first. To do this, define @code{DBX_OUTPUT_STANDARD_TYPES} to output -those symbols in the necessary order. Any predefined types that you -don't explicitly output will be output afterward in no particular order. - -Be careful not to define this macro so that it works only for C. There -are no global variables to access most of the built-in types, because -another language may have another set of types. The way to output a -particular type is to look through @var{syms} to see if you can find it. -Here is an example: - -@smallexample -@{ - tree decl; - for (decl = syms; decl; decl = TREE_CHAIN (decl)) - if (!strcmp (IDENTIFIER_POINTER (DECL_NAME (decl)), - "long int")) - dbxout_symbol (decl); - @dots{} -@} -@end smallexample - -@noindent -This does nothing if the expected type does not exist. - -See the function @code{init_decl_processing} in @file{c-decl.c} to find -the names to use for all the built-in C types. - -Here is another way of finding a particular type: - -@c this is still overfull. --mew 10feb93 -@smallexample -@{ - tree decl; - for (decl = syms; decl; decl = TREE_CHAIN (decl)) - if (TREE_CODE (decl) == TYPE_DECL - && (TREE_CODE (TREE_TYPE (decl)) - == INTEGER_CST) - && TYPE_PRECISION (TREE_TYPE (decl)) == 16 - && TYPE_UNSIGNED (TREE_TYPE (decl))) -@group - /* @r{This must be @code{unsigned short}.} */ - dbxout_symbol (decl); - @dots{} -@} -@end group -@end smallexample - -@findex NO_DBX_FUNCTION_END -@item NO_DBX_FUNCTION_END -Some stabs encapsulation formats (in particular ECOFF), cannot handle the -@code{.stabs "",N_FUN,,0,0,Lscope-function-1} gdb dbx extention construct. -On those machines, define this macro to turn this feature off without -disturbing the rest of the gdb extensions. - -@end table - -@node File Names and DBX -@subsection File Names in DBX Format - -@c prevent bad page break with this line -This describes file names in DBX format. - -@table @code -@findex DBX_WORKING_DIRECTORY -@item DBX_WORKING_DIRECTORY -Define this if DBX wants to have the current directory recorded in each -object file. - -Note that the working directory is always recorded if GDB extensions are -enabled. - -@findex DBX_OUTPUT_MAIN_SOURCE_FILENAME -@item DBX_OUTPUT_MAIN_SOURCE_FILENAME (@var{stream}, @var{name}) -A C statement to output DBX debugging information to the stdio stream -@var{stream} which indicates that file @var{name} is the main source -file---the file specified as the input file for compilation. -This macro is called only once, at the beginning of compilation. - -This macro need not be defined if the standard form of output -for DBX debugging information is appropriate. - -@findex DBX_OUTPUT_MAIN_SOURCE_DIRECTORY -@item DBX_OUTPUT_MAIN_SOURCE_DIRECTORY (@var{stream}, @var{name}) -A C statement to output DBX debugging information to the stdio stream -@var{stream} which indicates that the current directory during -compilation is named @var{name}. - -This macro need not be defined if the standard form of output -for DBX debugging information is appropriate. - -@findex DBX_OUTPUT_MAIN_SOURCE_FILE_END -@item DBX_OUTPUT_MAIN_SOURCE_FILE_END (@var{stream}, @var{name}) -A C statement to output DBX debugging information at the end of -compilation of the main source file @var{name}. - -If you don't define this macro, nothing special is output at the end -of compilation, which is correct for most machines. - -@findex DBX_OUTPUT_SOURCE_FILENAME -@item DBX_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) -A C statement to output DBX debugging information to the stdio stream -@var{stream} which indicates that file @var{name} is the current source -file. This output is generated each time input shifts to a different -source file as a result of @samp{#include}, the end of an included file, -or a @samp{#line} command. - -This macro need not be defined if the standard form of output -for DBX debugging information is appropriate. -@end table - -@need 2000 -@node SDB and DWARF -@subsection Macros for SDB and DWARF Output - -@c prevent bad page break with this line -Here are macros for SDB and DWARF output. - -@table @code -@findex SDB_DEBUGGING_INFO -@item SDB_DEBUGGING_INFO -Define this macro if GCC should produce COFF-style debugging output -for SDB in response to the @samp{-g} option. - -@findex DWARF_DEBUGGING_INFO -@item DWARF_DEBUGGING_INFO -Define this macro if GCC should produce dwarf format debugging output -in response to the @samp{-g} option. - -@findex DWARF2_DEBUGGING_INFO -@item DWARF2_DEBUGGING_INFO -Define this macro if GCC should produce dwarf version 2 format -debugging output in response to the @samp{-g} option. - -To support optional call frame debugging information, you must also -define @code{INCOMING_RETURN_ADDR_RTX} and either set -@code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the -prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save} -as appropriate from @code{FUNCTION_PROLOGUE} if you don't. - -@findex DWARF2_FRAME_INFO -@item DWARF2_FRAME_INFO -Define this macro to a nonzero value if GCC should always output -Dwarf 2 frame information. If @code{DWARF2_UNWIND_INFO} -(@pxref{Exception Region Output} is nonzero, GCC will output this -information not matter how you define @code{DWARF2_FRAME_INFO}. - -@findex LINKER_DOES_NOT_WORK_WITH_DWARF2 -@item LINKER_DOES_NOT_WORK_WITH_DWARF2 -Define this macro if the linker does not work with Dwarf version 2. -Normally, if the user specifies only @samp{-ggdb} GCC will use Dwarf -version 2 if available; this macro disables this. See the description -of the @code{PREFERRED_DEBUGGING_TYPE} macro for more details. - -@findex DWARF2_GENERATE_TEXT_SECTION_LABEL -@item DWARF2_GENERATE_TEXT_SECTION_LABEL -By default, the Dwarf 2 debugging information generator will generate a -label to mark the beginning of the text section. If it is better simply -to use the name of the text section itself, rather than an explicit label, -to indicate the beginning of the text section, define this macro to zero. - -@findex DWARF2_ASM_LINE_DEBUG_INFO -@item DWARF2_ASM_LINE_DEBUG_INFO -Define this macro to be a nonzero value if the assembler can generate Dwarf 2 -line debug info sections. This will result in much more compact line number -tables, and hence is desirable if it works. - -@findex PUT_SDB_@dots{} -@item PUT_SDB_@dots{} -Define these macros to override the assembler syntax for the special -SDB assembler directives. See @file{sdbout.c} for a list of these -macros and their arguments. If the standard syntax is used, you need -not define them yourself. - -@findex SDB_DELIM -@item SDB_DELIM -Some assemblers do not support a semicolon as a delimiter, even between -SDB assembler directives. In that case, define this macro to be the -delimiter to use (usually @samp{\n}). It is not necessary to define -a new set of @code{PUT_SDB_@var{op}} macros if this is the only change -required. - -@findex SDB_GENERATE_FAKE -@item SDB_GENERATE_FAKE -Define this macro to override the usual method of constructing a dummy -name for anonymous structure and union types. See @file{sdbout.c} for -more information. - -@findex SDB_ALLOW_UNKNOWN_REFERENCES -@item SDB_ALLOW_UNKNOWN_REFERENCES -Define this macro to allow references to unknown structure, -union, or enumeration tags to be emitted. Standard COFF does not -allow handling of unknown references, MIPS ECOFF has support for -it. - -@findex SDB_ALLOW_FORWARD_REFERENCES -@item SDB_ALLOW_FORWARD_REFERENCES -Define this macro to allow references to structure, union, or -enumeration tags that have not yet been seen to be handled. Some -assemblers choke if forward tags are used, while some require it. -@end table - -@node Cross-compilation -@section Cross Compilation and Floating Point -@cindex cross compilation and floating point -@cindex floating point and cross compilation - -While all modern machines use 2's complement representation for integers, -there are a variety of representations for floating point numbers. This -means that in a cross-compiler the representation of floating point numbers -in the compiled program may be different from that used in the machine -doing the compilation. - -@findex atof -Because different representation systems may offer different amounts of -range and precision, the cross compiler cannot safely use the host -machine's floating point arithmetic. Therefore, floating point constants -must be represented in the target machine's format. This means that the -cross compiler cannot use @code{atof} to parse a floating point constant; -it must have its own special routine to use instead. Also, constant -folding must emulate the target machine's arithmetic (or must not be done -at all). - -The macros in the following table should be defined only if you are cross -compiling between different floating point formats. - -Otherwise, don't define them. Then default definitions will be set up which -use @code{double} as the data type, @code{==} to test for equality, etc. - -You don't need to worry about how many times you use an operand of any -of these macros. The compiler never uses operands which have side effects. - -@table @code -@findex REAL_VALUE_TYPE -@item REAL_VALUE_TYPE -A macro for the C data type to be used to hold a floating point value -in the target machine's format. Typically this would be a -@code{struct} containing an array of @code{int}. - -@findex REAL_VALUES_EQUAL -@item REAL_VALUES_EQUAL (@var{x}, @var{y}) -A macro for a C expression which compares for equality the two values, -@var{x} and @var{y}, both of type @code{REAL_VALUE_TYPE}. - -@findex REAL_VALUES_LESS -@item REAL_VALUES_LESS (@var{x}, @var{y}) -A macro for a C expression which tests whether @var{x} is less than -@var{y}, both values being of type @code{REAL_VALUE_TYPE} and -interpreted as floating point numbers in the target machine's -representation. - -@findex REAL_VALUE_LDEXP -@findex ldexp -@item REAL_VALUE_LDEXP (@var{x}, @var{scale}) -A macro for a C expression which performs the standard library -function @code{ldexp}, but using the target machine's floating point -representation. Both @var{x} and the value of the expression have -type @code{REAL_VALUE_TYPE}. The second argument, @var{scale}, is an -integer. - -@findex REAL_VALUE_FIX -@item REAL_VALUE_FIX (@var{x}) -A macro whose definition is a C expression to convert the target-machine -floating point value @var{x} to a signed integer. @var{x} has type -@code{REAL_VALUE_TYPE}. - -@findex REAL_VALUE_UNSIGNED_FIX -@item REAL_VALUE_UNSIGNED_FIX (@var{x}) -A macro whose definition is a C expression to convert the target-machine -floating point value @var{x} to an unsigned integer. @var{x} has type -@code{REAL_VALUE_TYPE}. - -@findex REAL_VALUE_RNDZINT -@item REAL_VALUE_RNDZINT (@var{x}) -A macro whose definition is a C expression to round the target-machine -floating point value @var{x} towards zero to an integer value (but still -as a floating point number). @var{x} has type @code{REAL_VALUE_TYPE}, -and so does the value. - -@findex REAL_VALUE_UNSIGNED_RNDZINT -@item REAL_VALUE_UNSIGNED_RNDZINT (@var{x}) -A macro whose definition is a C expression to round the target-machine -floating point value @var{x} towards zero to an unsigned integer value -(but still represented as a floating point number). @var{x} has type -@code{REAL_VALUE_TYPE}, and so does the value. - -@findex REAL_VALUE_ATOF -@item REAL_VALUE_ATOF (@var{string}, @var{mode}) -A macro for a C expression which converts @var{string}, an expression of -type @code{char *}, into a floating point number in the target machine's -representation for mode @var{mode}. The value has type -@code{REAL_VALUE_TYPE}. - -@findex REAL_INFINITY -@item REAL_INFINITY -Define this macro if infinity is a possible floating point value, and -therefore division by 0 is legitimate. - -@findex REAL_VALUE_ISINF -@findex isinf -@item REAL_VALUE_ISINF (@var{x}) -A macro for a C expression which determines whether @var{x}, a floating -point value, is infinity. The value has type @code{int}. -By default, this is defined to call @code{isinf}. - -@findex REAL_VALUE_ISNAN -@findex isnan -@item REAL_VALUE_ISNAN (@var{x}) -A macro for a C expression which determines whether @var{x}, a floating -point value, is a ``nan'' (not-a-number). The value has type -@code{int}. By default, this is defined to call @code{isnan}. -@end table - -@cindex constant folding and floating point -Define the following additional macros if you want to make floating -point constant folding work while cross compiling. If you don't -define them, cross compilation is still possible, but constant folding -will not happen for floating point values. - -@table @code -@findex REAL_ARITHMETIC -@item REAL_ARITHMETIC (@var{output}, @var{code}, @var{x}, @var{y}) -A macro for a C statement which calculates an arithmetic operation of -the two floating point values @var{x} and @var{y}, both of type -@code{REAL_VALUE_TYPE} in the target machine's representation, to -produce a result of the same type and representation which is stored -in @var{output} (which will be a variable). - -The operation to be performed is specified by @var{code}, a tree code -which will always be one of the following: @code{PLUS_EXPR}, -@code{MINUS_EXPR}, @code{MULT_EXPR}, @code{RDIV_EXPR}, -@code{MAX_EXPR}, @code{MIN_EXPR}.@refill - -@cindex overflow while constant folding -The expansion of this macro is responsible for checking for overflow. -If overflow happens, the macro expansion should execute the statement -@code{return 0;}, which indicates the inability to perform the -arithmetic operation requested. - -@findex REAL_VALUE_NEGATE -@item REAL_VALUE_NEGATE (@var{x}) -A macro for a C expression which returns the negative of the floating -point value @var{x}. Both @var{x} and the value of the expression -have type @code{REAL_VALUE_TYPE} and are in the target machine's -floating point representation. - -There is no way for this macro to report overflow, since overflow -can't happen in the negation operation. - -@findex REAL_VALUE_TRUNCATE -@item REAL_VALUE_TRUNCATE (@var{mode}, @var{x}) -A macro for a C expression which converts the floating point value -@var{x} to mode @var{mode}. - -Both @var{x} and the value of the expression are in the target machine's -floating point representation and have type @code{REAL_VALUE_TYPE}. -However, the value should have an appropriate bit pattern to be output -properly as a floating constant whose precision accords with mode -@var{mode}. - -There is no way for this macro to report overflow. - -@findex REAL_VALUE_TO_INT -@item REAL_VALUE_TO_INT (@var{low}, @var{high}, @var{x}) -A macro for a C expression which converts a floating point value -@var{x} into a double-precision integer which is then stored into -@var{low} and @var{high}, two variables of type @var{int}. - -@item REAL_VALUE_FROM_INT (@var{x}, @var{low}, @var{high}, @var{mode}) -@findex REAL_VALUE_FROM_INT -A macro for a C expression which converts a double-precision integer -found in @var{low} and @var{high}, two variables of type @var{int}, -into a floating point value which is then stored into @var{x}. -The value is in the target machine's representation for mode @var{mode} -and has the type @code{REAL_VALUE_TYPE}. -@end table - -@node Mode Switching -@section Mode Switching Instructions -@cindex mode switching -The following macros control mode switching optimizations: - -@table @code -@findex OPTIMIZE_MODE_SWITCHING -@item OPTIMIZE_MODE_SWITCHING (@var{entity}) -Define this macro if the port needs extra instructions inserted for mode -switching in an optimizing compilation. - -For an example, the SH4 can perform both single and double precision -floating point operations, but to perform a single precision operation, -the FPSCR PR bit has to be cleared, while for a double precision -operation, this bit has to be set. Changing the PR bit requires a general -purpose register as a scratch register, hence these FPSCR sets have to -be inserted before reload, i.e. you can't put this into instruction emitting -or MACHINE_DEPENDENT_REORG. - -You can have multiple entities that are mode-switched, and select at run time -which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should -return non-zero for any @var{entity} that that needs mode-switching. -If you define this macro, you also have to define -@code{NUM_MODES_FOR_MODE_SWITCHING}, @code{MODE_NEEDED}, -@code{MODE_PRIORITY_TO_MODE} and @code{EMIT_MODE_SET}. -@code{NORMAL_MODE} is optional. - -@findex NUM_MODES_FOR_MODE_SWITCHING -@item NUM_MODES_FOR_MODE_SWITCHING -If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as -initializer for an array of integers. Each initializer element -N refers to an entity that needs mode switching, and specifies the number -of different modes that might need to be set for this entity. -The position of the initializer in the initializer - starting counting at -zero - determines the integer that is used to refer to the mode-switched -entity in question. -In macros that take mode arguments / yield a mode result, modes are -represented as numbers 0 .. N - 1. N is used to specify that no mode -switch is needed / supplied. - -@findex MODE_NEEDED -@item MODE_NEEDED (@var{entity}, @var{insn}) -@var{entity} is an integer specifying a mode-switched entity. If -@code{OPTIMIZE_MODE_SWITCHING} is defined, you must define this macro to -return an integer value not larger than the corresponding element in -NUM_MODES_FOR_MODE_SWITCHING, to denote the mode that @var{entity} must -be switched into prior to the execution of INSN. - -@findex NORMAL_MODE -@item NORMAL_MODE (@var{entity}) -If this macro is defined, it is evaluated for every @var{entity} that needs -mode switching. It should evaluate to an integer, which is a mode that -@var{entity} is assumed to be switched to at function entry and exit. - -@findex MODE_PRIORITY_TO_MODE -@item MODE_PRIORITY_TO_MODE (@var{entity}, @var{n}) -This macro specifies the order in which modes for ENTITY are processed. -0 is the highest priority, NUM_MODES_FOR_MODE_SWITCHING[ENTITY] - 1 the -lowest. The value of the macro should be an integer designating a mode -for ENTITY. For any fixed @var{entity}, @code{mode_priority_to_mode} -(@var{entity}, @var{n}) shall be a bijection in 0 .. -@code{num_modes_for_mode_switching}[@var{entity}] - 1 . - -@findex EMIT_MODE_SET -@item EMIT_MODE_SET (@var{entity}, @var{mode}, @var{hard_regs_live}) -Generate one or more insns to set @var{entity} to @var{mode}. -@var{hard_reg_live} is the set of hard registers live at the point where -the insn(s) are to be inserted. -@end table - -@node Misc -@section Miscellaneous Parameters -@cindex parameters, miscellaneous - -@c prevent bad page break with this line -Here are several miscellaneous parameters. - -@table @code -@item PREDICATE_CODES -@findex PREDICATE_CODES -Define this if you have defined special-purpose predicates in the file -@file{@var{machine}.c}. This macro is called within an initializer of an -array of structures. The first field in the structure is the name of a -predicate and the second field is an array of rtl codes. For each -predicate, list all rtl codes that can be in expressions matched by the -predicate. The list should have a trailing comma. Here is an example -of two entries in the list for a typical RISC machine: - -@smallexample -#define PREDICATE_CODES \ - @{"gen_reg_rtx_operand", @{SUBREG, REG@}@}, \ - @{"reg_or_short_cint_operand", @{SUBREG, REG, CONST_INT@}@}, -@end smallexample - -Defining this macro does not affect the generated code (however, -incorrect definitions that omit an rtl code that may be matched by the -predicate can cause the compiler to malfunction). Instead, it allows -the table built by @file{genrecog} to be more compact and efficient, -thus speeding up the compiler. The most important predicates to include -in the list specified by this macro are those used in the most insn -patterns. - -For each predicate function named in @var{PREDICATE_CODES}, a -declaration will be generated in @file{insn-codes.h}. - -@item SPECIAL_MODE_PREDICATES -@findex SPECIAL_MODE_PREDICATES -Define this if you have special predicates that know special things -about modes. Genrecog will warn about certain forms of -@code{match_operand} without a mode; if the operand predicate is -listed in @code{SPECIAL_MODE_PREDICATES}, the warning will be -suppressed. - -Here is an example from the IA-32 port (@code{ext_register_operand} -specially checks for @code{HImode} or @code{SImode} in preparation -for a byte extraction from @code{%ah} etc.). - -@smallexample -#define SPECIAL_MODE_PREDICATES \ - "ext_register_operand", -@end smallexample - -@findex CASE_VECTOR_MODE -@item CASE_VECTOR_MODE -An alias for a machine mode name. This is the machine mode that -elements of a jump-table should have. - -@findex CASE_VECTOR_SHORTEN_MODE -@item CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body}) -Optional: return the preferred mode for an @code{addr_diff_vec} -when the minimum and maximum offset are known. If you define this, -it enables extra code in branch shortening to deal with @code{addr_diff_vec}. -To make this work, you also have to define INSN_ALIGN and -make the alignment for @code{addr_diff_vec} explicit. -The @var{body} argument is provided so that the offset_unsigned and scale -flags can be updated. - -@findex CASE_VECTOR_PC_RELATIVE -@item CASE_VECTOR_PC_RELATIVE -Define this macro to be a C expression to indicate when jump-tables -should contain relative addresses. If jump-tables never contain -relative addresses, then you need not define this macro. - -@findex CASE_DROPS_THROUGH -@item CASE_DROPS_THROUGH -Define this if control falls through a @code{case} insn when the index -value is out of range. This means the specified default-label is -actually ignored by the @code{case} insn proper. - -@findex CASE_VALUES_THRESHOLD -@item CASE_VALUES_THRESHOLD -Define this to be the smallest number of different values for which it -is best to use a jump-table instead of a tree of conditional branches. -The default is four for machines with a @code{casesi} instruction and -five otherwise. This is best for most machines. - -@findex WORD_REGISTER_OPERATIONS -@item WORD_REGISTER_OPERATIONS -Define this macro if operations between registers with integral mode -smaller than a word are always performed on the entire register. -Most RISC machines have this property and most CISC machines do not. - -@findex LOAD_EXTEND_OP -@item LOAD_EXTEND_OP (@var{mode}) -Define this macro to be a C expression indicating when insns that read -memory in @var{mode}, an integral mode narrower than a word, set the -bits outside of @var{mode} to be either the sign-extension or the -zero-extension of the data read. Return @code{SIGN_EXTEND} for values -of @var{mode} for which the -insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and -@code{NIL} for other modes. - -This macro is not called with @var{mode} non-integral or with a width -greater than or equal to @code{BITS_PER_WORD}, so you may return any -value in this case. Do not define this macro if it would always return -@code{NIL}. On machines where this macro is defined, you will normally -define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}. - -@findex SHORT_IMMEDIATES_SIGN_EXTEND -@item SHORT_IMMEDIATES_SIGN_EXTEND -Define this macro if loading short immediate values into registers sign -extends. - -@findex IMPLICIT_FIX_EXPR -@item IMPLICIT_FIX_EXPR -An alias for a tree code that should be used by default for conversion -of floating point values to fixed point. Normally, -@code{FIX_ROUND_EXPR} is used.@refill - -@findex FIXUNS_TRUNC_LIKE_FIX_TRUNC -@item FIXUNS_TRUNC_LIKE_FIX_TRUNC -Define this macro if the same instructions that convert a floating -point number to a signed fixed point number also convert validly to an -unsigned one. - -@findex EASY_DIV_EXPR -@item EASY_DIV_EXPR -An alias for a tree code that is the easiest kind of division to -compile code for in the general case. It may be -@code{TRUNC_DIV_EXPR}, @code{FLOOR_DIV_EXPR}, @code{CEIL_DIV_EXPR} or -@code{ROUND_DIV_EXPR}. These four division operators differ in how -they round the result to an integer. @code{EASY_DIV_EXPR} is used -when it is permissible to use any of those kinds of division and the -choice should be made on the basis of efficiency.@refill - -@findex MOVE_MAX -@item MOVE_MAX -The maximum number of bytes that a single instruction can move quickly -between memory and registers or between two memory locations. - -@findex MAX_MOVE_MAX -@item MAX_MOVE_MAX -The maximum number of bytes that a single instruction can move quickly -between memory and registers or between two memory locations. If this -is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the -constant value that is the largest value that @code{MOVE_MAX} can have -at run-time. - -@findex SHIFT_COUNT_TRUNCATED -@item SHIFT_COUNT_TRUNCATED -A C expression that is nonzero if on this machine the number of bits -actually used for the count of a shift operation is equal to the number -of bits needed to represent the size of the object being shifted. When -this macro is non-zero, the compiler will assume that it is safe to omit -a sign-extend, zero-extend, and certain bitwise `and' instructions that -truncates the count of a shift operation. On machines that have -instructions that act on bitfields at variable positions, which may -include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED} -also enables deletion of truncations of the values that serve as -arguments to bitfield instructions. - -If both types of instructions truncate the count (for shifts) and -position (for bitfield operations), or if no variable-position bitfield -instructions exist, you should define this macro. - -However, on some machines, such as the 80386 and the 680x0, truncation -only applies to shift operations and not the (real or pretended) -bitfield operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on -such machines. Instead, add patterns to the @file{md} file that include -the implied truncation of the shift instructions. - -You need not define this macro if it would always have the value of zero. - -@findex TRULY_NOOP_TRUNCATION -@item TRULY_NOOP_TRUNCATION (@var{outprec}, @var{inprec}) -A C expression which is nonzero if on this machine it is safe to -``convert'' an integer of @var{inprec} bits to one of @var{outprec} -bits (where @var{outprec} is smaller than @var{inprec}) by merely -operating on it as if it had only @var{outprec} bits. - -On many machines, this expression can be 1. - -@c rearranged this, removed the phrase "it is reported that". this was -@c to fix an overfull hbox. --mew 10feb93 -When @code{TRULY_NOOP_TRUNCATION} returns 1 for a pair of sizes for -modes for which @code{MODES_TIEABLE_P} is 0, suboptimal code can result. -If this is the case, making @code{TRULY_NOOP_TRUNCATION} return 0 in -such cases may improve things. - -@findex STORE_FLAG_VALUE -@item STORE_FLAG_VALUE -A C expression describing the value returned by a comparison operator -with an integral mode and stored by a store-flag instruction -(@samp{s@var{cond}}) when the condition is true. This description must -apply to @emph{all} the @samp{s@var{cond}} patterns and all the -comparison operators whose results have a @code{MODE_INT} mode. - -A value of 1 or -1 means that the instruction implementing the -comparison operator returns exactly 1 or -1 when the comparison is true -and 0 when the comparison is false. Otherwise, the value indicates -which bits of the result are guaranteed to be 1 when the comparison is -true. This value is interpreted in the mode of the comparison -operation, which is given by the mode of the first operand in the -@samp{s@var{cond}} pattern. Either the low bit or the sign bit of -@code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by -the compiler. - -If @code{STORE_FLAG_VALUE} is neither 1 or -1, the compiler will -generate code that depends only on the specified bits. It can also -replace comparison operators with equivalent operations if they cause -the required bits to be set, even if the remaining bits are undefined. -For example, on a machine whose comparison operators return an -@code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as -@samp{0x80000000}, saying that just the sign bit is relevant, the -expression - -@smallexample -(ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0)) -@end smallexample - -@noindent -can be converted to - -@smallexample -(ashift:SI @var{x} (const_int @var{n})) -@end smallexample - -@noindent -where @var{n} is the appropriate shift count to move the bit being -tested into the sign bit. - -There is no way to describe a machine that always sets the low-order bit -for a true value, but does not guarantee the value of any other bits, -but we do not know of any machine that has such an instruction. If you -are trying to port GCC to such a machine, include an instruction to -perform a logical-and of the result with 1 in the pattern for the -comparison operators and let us know -@ifset USING -(@pxref{Bug Reporting,,How to Report Bugs}). -@end ifset -@ifclear USING -(@pxref{Bug Reporting,,How to Report Bugs,gcc.info,Using GCC}). -@end ifclear - -Often, a machine will have multiple instructions that obtain a value -from a comparison (or the condition codes). Here are rules to guide the -choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions -to be used: - -@itemize @bullet -@item -Use the shortest sequence that yields a valid definition for -@code{STORE_FLAG_VALUE}. It is more efficient for the compiler to -``normalize'' the value (convert it to, e.g., 1 or 0) than for the -comparison operators to do so because there may be opportunities to -combine the normalization with other operations. - -@item -For equal-length sequences, use a value of 1 or -1, with -1 being -slightly preferred on machines with expensive jumps and 1 preferred on -other machines. - -@item -As a second choice, choose a value of @samp{0x80000001} if instructions -exist that set both the sign and low-order bits but do not define the -others. - -@item -Otherwise, use a value of @samp{0x80000000}. -@end itemize - -Many machines can produce both the value chosen for -@code{STORE_FLAG_VALUE} and its negation in the same number of -instructions. On those machines, you should also define a pattern for -those cases, e.g., one matching - -@smallexample -(set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C}))) -@end smallexample - -Some machines can also perform @code{and} or @code{plus} operations on -condition code values with less instructions than the corresponding -@samp{s@var{cond}} insn followed by @code{and} or @code{plus}. On those -machines, define the appropriate patterns. Use the names @code{incscc} -and @code{decscc}, respectively, for the patterns which perform -@code{plus} or @code{minus} operations on condition code values. See -@file{rs6000.md} for some examples. The GNU Superoptizer can be used to -find such instruction sequences on other machines. - -You need not define @code{STORE_FLAG_VALUE} if the machine has no store-flag -instructions. - -@findex FLOAT_STORE_FLAG_VALUE -@item FLOAT_STORE_FLAG_VALUE (@var{mode}) -A C expression that gives a non-zero @code{REAL_VALUE_TYPE} value that is -returned when comparison operators with floating-point results are true. -Define this macro on machine that have comparison operations that return -floating-point values. If there are no such operations, do not define -this macro. - -@findex Pmode -@item Pmode -An alias for the machine mode for pointers. On most machines, define -this to be the integer mode corresponding to the width of a hardware -pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines. -On some machines you must define this to be one of the partial integer -modes, such as @code{PSImode}. - -The width of @code{Pmode} must be at least as large as the value of -@code{POINTER_SIZE}. If it is not equal, you must define the macro -@code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended -to @code{Pmode}. - -@findex FUNCTION_MODE -@item FUNCTION_MODE -An alias for the machine mode used for memory references to functions -being called, in @code{call} RTL expressions. On most machines this -should be @code{QImode}. - -@findex INTEGRATE_THRESHOLD -@item INTEGRATE_THRESHOLD (@var{decl}) -A C expression for the maximum number of instructions above which the -function @var{decl} should not be inlined. @var{decl} is a -@code{FUNCTION_DECL} node. - -The default definition of this macro is 64 plus 8 times the number of -arguments that the function accepts. Some people think a larger -threshold should be used on RISC machines. - -@findex SCCS_DIRECTIVE -@item SCCS_DIRECTIVE -Define this if the preprocessor should ignore @code{#sccs} directives -and print no error message. - -@findex NO_IMPLICIT_EXTERN_C -@item NO_IMPLICIT_EXTERN_C -Define this macro if the system header files support C++ as well as C. -This macro inhibits the usual method of using system header files in -C++, which is to pretend that the file's contents are enclosed in -@samp{extern "C" @{@dots{}@}}. - -@findex HANDLE_PRAGMA -@item HANDLE_PRAGMA (@var{getc}, @var{ungetc}, @var{name}) -This macro is no longer supported. You must use -@code{REGISTER_TARGET_PRAGMAS} instead. - -@findex REGISTER_TARGET_PRAGMAS -@findex #pragma -@findex pragma -@item REGISTER_TARGET_PRAGMAS (@var{pfile}) -Define this macro if you want to implement any target-specific pragmas. -If defined, it is a C expression which makes a series of calls to the -@code{cpp_register_pragma} and/or @code{cpp_register_pragma_space} -functions. The @var{pfile} argument is the first argument to supply to -these functions. The macro may also do setup required for the pragmas. - -The primary reason to define this macro is to provide compatibility with -other compilers for the same target. In general, we discourage -definition of target-specific pragmas for GCC. - -If the pragma can be implemented by attributes then the macro -@samp{INSERT_ATTRIBUTES} might be a useful one to define as well. - -Preprocessor macros that appear on pragma lines are not expanded. All -@samp{#pragma} directives that do not match any registered pragma are -silently ignored, unless the user specifies @samp{-Wunknown-pragmas}. - -@deftypefun void cpp_register_pragma (cpp_reader *@var{pfile}, const char *@var{space}, const char *@var{name}, void (*@var{callback}) (cpp_reader *)) - -Each call to @code{cpp_register_pragma} establishes one pragma. The -@var{callback} routine will be called when the preprocessor encounters a -pragma of the form - -@smallexample -#pragma [@var{space}] @var{name} @dots{} -@end smallexample - -@var{space} must have been the subject of a previous call to -@code{cpp_register_pragma_space}, or else be a null pointer. The -callback routine receives @var{pfile} as its first argument, but must -not use it for anything (this may change in the future). It may read -any text after the @var{name} by making calls to @code{c_lex}. Text -which is not read by the callback will be silently ignored. - -Note that both @var{space} and @var{name} are case sensitive. - -For an example use of this routine, see @file{c4x.h} and the callback -routines defined in @file{c4x.c}. - -Note that the use of @code{c_lex} is specific to the C and C++ -compilers. It will not work in the Java or Fortran compilers, or any -other language compilers for that matter. Thus if @code{c_lex} is going -to be called from target-specific code, it must only be done so when -building hte C and C++ compilers. This can be done by defining the -variables @code{c_target_objs} and @code{cxx_target_objs} in the -target entry in the @code{config.gcc} file. These variables should name -the target-specific, language-specific object file which contains the -code that uses @code{c_lex}. Note it will also be necessary to add a -rule to the makefile fragment pointed to by @code{tmake_file} that shows -how to build this object file. -@end deftypefun - -@deftypefun void cpp_register_pragma_space (cpp_reader *@var{pfile}, const char *@var{space}) -This routine establishes a namespace for pragmas, which will be -registered by subsequent calls to @code{cpp_register_pragma}. For -example, pragmas defined by the C standard are in the @samp{STDC} -namespace, and pragmas specific to GCC are in the @samp{GCC} namespace. - -For an example use of this routine in a target header, see @file{v850.h}. -@end deftypefun - -@findex HANDLE_SYSV_PRAGMA -@findex #pragma -@findex pragma -@item HANDLE_SYSV_PRAGMA -Define this macro (to a value of 1) if you want the System V style -pragmas @samp{#pragma pack()} and @samp{#pragma weak -[=]} to be supported by gcc. - -The pack pragma specifies the maximum alignment (in bytes) of fields -within a structure, in much the same way as the @samp{__aligned__} and -@samp{__packed__} @code{__attribute__}s do. A pack value of zero resets -the behaviour to the default. - -The weak pragma only works if @code{SUPPORTS_WEAK} and -@code{ASM_WEAKEN_LABEL} are defined. If enabled it allows the creation -of specifically named weak labels, optionally with a value. - -@findex HANDLE_PRAGMA_PACK_PUSH_POP -@findex #pragma -@findex pragma -@item HANDLE_PRAGMA_PACK_PUSH_POP -Define this macro (to a value of 1) if you want to support the Win32 -style pragmas @samp{#pragma pack(push,)} and @samp{#pragma -pack(pop)}. The pack(push,) pragma specifies the maximum alignment -(in bytes) of fields within a structure, in much the same way as the -@samp{__aligned__} and @samp{__packed__} @code{__attribute__}s do. A -pack value of zero resets the behaviour to the default. Successive -invocations of this pragma cause the previous values to be stacked, so -that invocations of @samp{#pragma pack(pop)} will return to the previous -value. - -@findex VALID_MACHINE_DECL_ATTRIBUTE -@item VALID_MACHINE_DECL_ATTRIBUTE (@var{decl}, @var{attributes}, @var{identifier}, @var{args}) -If defined, a C expression whose value is nonzero if @var{identifier} with -arguments @var{args} is a valid machine specific attribute for @var{decl}. -The attributes in @var{attributes} have previously been assigned to @var{decl}. - -@findex VALID_MACHINE_TYPE_ATTRIBUTE -@item VALID_MACHINE_TYPE_ATTRIBUTE (@var{type}, @var{attributes}, @var{identifier}, @var{args}) -If defined, a C expression whose value is nonzero if @var{identifier} with -arguments @var{args} is a valid machine specific attribute for @var{type}. -The attributes in @var{attributes} have previously been assigned to @var{type}. - -@findex COMP_TYPE_ATTRIBUTES -@item COMP_TYPE_ATTRIBUTES (@var{type1}, @var{type2}) -If defined, a C expression whose value is zero if the attributes on -@var{type1} and @var{type2} are incompatible, one if they are compatible, -and two if they are nearly compatible (which causes a warning to be -generated). - -@findex SET_DEFAULT_TYPE_ATTRIBUTES -@item SET_DEFAULT_TYPE_ATTRIBUTES (@var{type}) -If defined, a C statement that assigns default attributes to -newly defined @var{type}. - -@findex MERGE_MACHINE_TYPE_ATTRIBUTES -@item MERGE_MACHINE_TYPE_ATTRIBUTES (@var{type1}, @var{type2}) -Define this macro if the merging of type attributes needs special handling. -If defined, the result is a list of the combined TYPE_ATTRIBUTES of -@var{type1} and @var{type2}. It is assumed that comptypes has already been -called and returned 1. - -@findex MERGE_MACHINE_DECL_ATTRIBUTES -@item MERGE_MACHINE_DECL_ATTRIBUTES (@var{olddecl}, @var{newdecl}) -Define this macro if the merging of decl attributes needs special handling. -If defined, the result is a list of the combined DECL_MACHINE_ATTRIBUTES of -@var{olddecl} and @var{newdecl}. @var{newdecl} is a duplicate declaration -of @var{olddecl}. Examples of when this is needed are when one attribute -overrides another, or when an attribute is nullified by a subsequent -definition. - -@findex INSERT_ATTRIBUTES -@item INSERT_ATTRIBUTES (@var{node}, @var{attr_ptr}, @var{prefix_ptr}) -Define this macro if you want to be able to add attributes to a decl -when it is being created. This is normally useful for backends which -wish to implement a pragma by using the attributes which correspond to -the pragma's effect. The @var{node} argument is the decl which is being -created. The @var{attr_ptr} argument is a pointer to the attribute list -for this decl. The @var{prefix_ptr} is a pointer to the list of -attributes that have appeared after the specifiers and modifiers of the -declaration, but before the declaration proper. - -@findex SET_DEFAULT_DECL_ATTRIBUTES -@item SET_DEFAULT_DECL_ATTRIBUTES (@var{decl}, @var{attributes}) -If defined, a C statement that assigns default attributes to -newly defined @var{decl}. - -@findex DOLLARS_IN_IDENTIFIERS -@item DOLLARS_IN_IDENTIFIERS -Define this macro to control use of the character @samp{$} in identifier -names. 0 means @samp{$} is not allowed by default; 1 means it is allowed. -1 is the default; there is no need to define this macro in that case. -This macro controls the compiler proper; it does not affect the preprocessor. - -@findex NO_DOLLAR_IN_LABEL -@item NO_DOLLAR_IN_LABEL -Define this macro if the assembler does not accept the character -@samp{$} in label names. By default constructors and destructors in -G++ have @samp{$} in the identifiers. If this macro is defined, -@samp{.} is used instead. - -@findex NO_DOT_IN_LABEL -@item NO_DOT_IN_LABEL -Define this macro if the assembler does not accept the character -@samp{.} in label names. By default constructors and destructors in G++ -have names that use @samp{.}. If this macro is defined, these names -are rewritten to avoid @samp{.}. - -@findex DEFAULT_MAIN_RETURN -@item DEFAULT_MAIN_RETURN -Define this macro if the target system expects every program's @code{main} -function to return a standard ``success'' value by default (if no other -value is explicitly returned). - -The definition should be a C statement (sans semicolon) to generate the -appropriate rtl instructions. It is used only when compiling the end of -@code{main}. - -@item NEED_ATEXIT -@findex NEED_ATEXIT -Define this if the target system lacks the function @code{atexit} -from the ISO C standard. If this macro is defined, a default definition -will be provided to support C++. If @code{ON_EXIT} is not defined, -a default @code{exit} function will also be provided. - -@item ON_EXIT -@findex ON_EXIT -Define this macro if the target has another way to implement atexit -functionality without replacing @code{exit}. For instance, SunOS 4 has -a similar @code{on_exit} library function. - -The definition should be a functional macro which can be used just like -the @code{atexit} function. - -@item EXIT_BODY -@findex EXIT_BODY -Define this if your @code{exit} function needs to do something -besides calling an external function @code{_cleanup} before -terminating with @code{_exit}. The @code{EXIT_BODY} macro is -only needed if @code{NEED_ATEXIT} is defined and @code{ON_EXIT} is not -defined. - -@findex INSN_SETS_ARE_DELAYED -@item INSN_SETS_ARE_DELAYED (@var{insn}) -Define this macro as a C expression that is nonzero if it is safe for the -delay slot scheduler to place instructions in the delay slot of @var{insn}, -even if they appear to use a resource set or clobbered in @var{insn}. -@var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that -every @code{call_insn} has this behavior. On machines where some @code{insn} -or @code{jump_insn} is really a function call and hence has this behavior, -you should define this macro. - -You need not define this macro if it would always return zero. - -@findex INSN_REFERENCES_ARE_DELAYED -@item INSN_REFERENCES_ARE_DELAYED (@var{insn}) -Define this macro as a C expression that is nonzero if it is safe for the -delay slot scheduler to place instructions in the delay slot of @var{insn}, -even if they appear to set or clobber a resource referenced in @var{insn}. -@var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where -some @code{insn} or @code{jump_insn} is really a function call and its operands -are registers whose use is actually in the subroutine it calls, you should -define this macro. Doing so allows the delay slot scheduler to move -instructions which copy arguments into the argument registers into the delay -slot of @var{insn}. - -You need not define this macro if it would always return zero. - -@findex MACHINE_DEPENDENT_REORG -@item MACHINE_DEPENDENT_REORG (@var{insn}) -In rare cases, correct code generation requires extra machine -dependent processing between the second jump optimization pass and -delayed branch scheduling. On those machines, define this macro as a C -statement to act on the code starting at @var{insn}. - -@findex MULTIPLE_SYMBOL_SPACES -@item MULTIPLE_SYMBOL_SPACES -Define this macro if in some cases global symbols from one translation -unit may not be bound to undefined symbols in another translation unit -without user intervention. For instance, under Microsoft Windows -symbols must be explicitly imported from shared libraries (DLLs). - -@findex MD_ASM_CLOBBERS -@item MD_ASM_CLOBBERS -A C statement that adds to @var{CLOBBERS} @code{STRING_CST} trees for -any hard regs the port wishes to automatically clobber for all asms. - -@findex ISSUE_RATE -@item ISSUE_RATE -A C expression that returns how many instructions can be issued at the -same time if the machine is a superscalar machine. - -@findex MD_SCHED_INIT -@item MD_SCHED_INIT (@var{file}, @var{verbose}, @var{max_ready}) -A C statement which is executed by the scheduler at the -beginning of each block of instructions that are to be scheduled. -@var{file} is either a null pointer, or a stdio stream to write any -debug output to. @var{verbose} is the verbose level provided by -@samp{-fsched-verbose-}@var{n}. @var{max_ready} is the maximum number -of insns in the current scheduling region that can be live at the same -time. This can be used to allocate scratch space if it is needed. - -@findex MD_SCHED_FINISH -@item MD_SCHED_FINISH (@var{file}, @var{verbose}) -A C statement which is executed by the scheduler at the end of each block -of instructions that are to be scheduled. It can be used to perform -cleanup of any actions done by the other scheduling macros. -@var{file} is either a null pointer, or a stdio stream to write any -debug output to. @var{verbose} is the verbose level provided by -@samp{-fsched-verbose-}@var{n}. - -@findex MD_SCHED_REORDER -@item MD_SCHED_REORDER (@var{file}, @var{verbose}, @var{ready}, @var{n_ready}, @var{clock}, @var{can_issue_more}) -A C statement which is executed by the scheduler after it -has scheduled the ready list to allow the machine description to reorder -it (for example to combine two small instructions together on -@samp{VLIW} machines). @var{file} is either a null pointer, or a stdio -stream to write any debug output to. @var{verbose} is the verbose level -provided by @samp{-fsched-verbose-}@var{n}. @var{ready} is a pointer to -the ready list of instructions that are ready to be scheduled. -@var{n_ready} is the number of elements in the ready list. The -scheduler reads the ready list in reverse order, starting with -@var{ready}[@var{n_ready}-1] and going to @var{ready}[0]. @var{clock} -is the timer tick of the scheduler. @var{can_issue_more} is an output -parameter that is set to the number of insns that can issue this clock; -normally this is just @code{issue_rate}. See also @samp{MD_SCHED_REORDER2}. - -@findex MD_SCHED_REORDER2 -@item MD_SCHED_REORDER2 (@var{file}, @var{verbose}, @var{ready}, @var{n_ready}, @var{clock}, @var{can_issue_more}) -Like @samp{MD_SCHED_REORDER}, but called at a different time. While the -@samp{MD_SCHED_REORDER} macro is called whenever the scheduler starts a -new cycle, this macro is used immediately after @samp{MD_SCHED_VARIABLE_ISSUE} -is called; it can reorder the ready list and set @var{can_issue_more} to -determine whether there are more insns to be scheduled in the same cycle. -Defining this macro can be useful if there are frequent situations where -scheduling one insn causes other insns to become ready in the same cycle, -these other insns can then be taken into account properly. - -@findex MD_SCHED_VARIABLE_ISSUE -@item MD_SCHED_VARIABLE_ISSUE (@var{file}, @var{verbose}, @var{insn}, @var{more}) -A C statement which is executed by the scheduler after it -has scheduled an insn from the ready list. @var{file} is either a null -pointer, or a stdio stream to write any debug output to. @var{verbose} -is the verbose level provided by @samp{-fsched-verbose-}@var{n}. -@var{insn} is the instruction that was scheduled. @var{more} is the -number of instructions that can be issued in the current cycle. The -@samp{MD_SCHED_VARIABLE_ISSUE} macro is responsible for updating the -value of @var{more} (typically by @var{more}--). - -@findex MAX_INTEGER_COMPUTATION_MODE -@item MAX_INTEGER_COMPUTATION_MODE -Define this to the largest integer machine mode which can be used for -operations other than load, store and copy operations. - -You need only define this macro if the target holds values larger than -@code{word_mode} in general purpose registers. Most targets should not define -this macro. - -@findex MATH_LIBRARY -@item MATH_LIBRARY -Define this macro as a C string constant for the linker argument to link -in the system math library, or @samp{""} if the target does not have a -separate math library. - -You need only define this macro if the default of @samp{"-lm"} is wrong. - -@findex LIBRARY_PATH_ENV -@item LIBRARY_PATH_ENV -Define this macro as a C string constant for the environment variable that -specifies where the linker should look for libraries. - -You need only define this macro if the default of @samp{"LIBRARY_PATH"} -is wrong. - -@findex TARGET_HAS_F_SETLKW -@item TARGET_HAS_F_SETLKW -Define this macro if the target supports file locking with fcntl / F_SETLKW. -Note that this functionality is part of POSIX. -Defining @code{TARGET_HAS_F_SETLKW} will enable the test coverage code -to use file locking when exiting a program, which avoids race conditions -if the program has forked. - -@findex MAX_CONDITIONAL_EXECUTE -@item MAX_CONDITIONAL_EXECUTE - -A C expression for the maximum number of instructions to execute via -conditional execution instructions instead of a branch. A value of -@code{BRANCH_COST}+1 is the default if the machine does not use cc0, and -1 if it does use cc0. - -@findex IFCVT_MODIFY_TESTS -@item IFCVT_MODIFY_TESTS -A C expression to modify the tests in @code{TRUE_EXPR}, and -@code{FALSE_EXPPR} for use in converting insns in @code{TEST_BB}, -@code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB} basic blocks to -conditional execution. Set either @code{TRUE_EXPR} or @code{FALSE_EXPR} -to a null pointer if the tests cannot be converted. - -@findex IFCVT_MODIFY_INSN -@item IFCVT_MODIFY_INSN -A C expression to modify the @code{PATTERN} of an @code{INSN} that is to -be converted to conditional execution format. - -@findex IFCVT_MODIFY_FINAL -@item IFCVT_MODIFY_FINAL -A C expression to perform any final machine dependent modifications in -converting code to conditional execution in the basic blocks -@code{TEST_BB}, @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB}. - -@findex IFCVT_MODIFY_CANCEL -@item IFCVT_MODIFY_CANCEL -A C expression to cancel any machine dependent modifications in -converting code to conditional execution in the basic blocks -@code{TEST_BB}, @code{THEN_BB}, @code{ELSE_BB}, and @code{JOIN_BB}. - -@findex MD_INIT_BUILTINS -@item MD_INIT_BUILTINS -Define this macro if you have any machine-specific builtin functions that -need to be defined. It should be a C expression that performs the -necessary setup. - -Machine specific builtins can be useful to expand special machine -instructions that would otherwise not normally be generated because -they have no equivalent in the source language (for example, SIMD vector -instructions or prefetch instructions). - -To create a builtin function, call the function @code{builtin_function} -which is defined by the language frontend. You can use any type nodes set -up by @code{build_common_tree_nodes} and @code{build_common_tree_nodes_2}; -only language frontends that use these two functions will use -@samp{MD_INIT_BUILTINS}. - -@findex MD_EXPAND_BUILTIN -@item MD_EXPAND_BUILTIN(@var{exp}, @var{target}, @var{subtarget}, @var{mode}, @var{ignore}) - -Expand a call to a machine specific builtin that was set up by -@samp{MD_INIT_BUILTINS}. @var{exp} is the expression for the function call; -the result should go to @var{target} if that is convenient, and have mode -@var{mode} if that is convenient. @var{subtarget} may be used as the target -for computing one of @var{exp}'s operands. @var{ignore} is nonzero if the value -is to be ignored. -This macro should return the result of the call to the builtin. - -@end table