.\" Automatically generated by Pod::Man version 1.16
-.\" Fri Jun 15 00:04:02 2001
+.\" Fri Jun 15 10:40:40 2001
.\"
.\" Standard preamble:
.\" ======================================================================
you are writing in. Modern versions of the \s-1GNU\s0 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 \f(CW@docref\fR{M4}.
+try a true general text processor, such as \s-1GNU\s0 M4.
.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
option and argument: \fB\-Ifoo\fR and \fB\-I foo\fR have the same
effect. Long options that take arguments require a space between option
and argument.
-.if n .Ip "\f(CW""\-D \f(CIname\f(CW""\fR" 4
-.el .Ip "\f(CW\-D \f(CIname\f(CW\fR" 4
+.Ip "\fB\-D\fR \fIname\fR" 4
.IX Item "-D name"
-Predefine \fIname\fR as a macro, with definition \fB1\fR.
-.if n .Ip "\f(CW""\-D \f(CIname\f(CW=\f(CIdefinition\f(CW""\fR" 4
-.el .Ip "\f(CW\-D \f(CIname\f(CW=\f(CIdefinition\f(CW\fR" 4
+Predefine \fIname\fR as a macro, with definition \f(CW\*(C`1\*(C'\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
(if any). Parentheses are meaningful to most shells, so you will need
to quote the option. With \fBsh\fR and \fBcsh\fR,
\&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
-.if n .Ip "\f(CW""\-U \f(CIname\f(CW""\fR" 4
-.el .Ip "\f(CW\-U \f(CIname\f(CW\fR" 4
+.Ip "\fB\-U\fR \fIname\fR" 4
.IX Item "-U name"
Cancel any previous definition of \fIname\fR, either built in or
provided with a \fB\-D\fR option.
.Sp
All \fB\-imacros\fR \fIfile\fR and \fB\-include\fR \fIfile\fR options
are processed after all \fB\-D\fR and \fB\-U\fR options.
-.if n .Ip "\f(CW""\-undef""\fR" 4
-.el .Ip "\f(CW\-undef\fR" 4
+.Ip "\fB\-undef\fR" 4
.IX Item "-undef"
Do not predefine any system-specific macros. The common predefined
macros remain defined.
-.if n .Ip "\f(CW""\-I \f(CIdir\f(CW""\fR" 4
-.el .Ip "\f(CW\-I \f(CIdir\f(CW\fR" 4
+.Ip "\fB\-I\fR \fIdir\fR" 4
.IX Item "-I dir"
Add the directory \fIdir\fR to the list of directories to be searched
for header files. Directories named by \fB\-I\fR
\&\fB\-I\fR option. This defeats the special treatment of system
headers. It can also defeat the repairs to
buggy system headers which \s-1GCC\s0 makes when it is installed.
-.if n .Ip "\f(CW""\-o \f(CIfile\f(CW""\fR" 4
-.el .Ip "\f(CW\-o \f(CIfile\f(CW\fR" 4
+.Ip "\fB\-o\fR \fIfile\fR" 4
.IX Item "-o file"
Write output to \fIfile\fR. This is the same as specifying \fIfile\fR
as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a
different interpretation of a second non-option argument, so you must
use \fB\-o\fR to specify the output file.
-.if n .Ip "\f(CW""\-Wall""\fR" 4
-.el .Ip "\f(CW\-Wall\fR" 4
+.Ip "\fB\-Wall\fR" 4
.IX Item "-Wall"
Turns on all optional warnings which are desirable for normal code. At
present this is \fB\-Wcomment\fR and \fB\-Wtrigraphs\fR. Note that
many of the preprocessor's warnings are on by default and have no
options to control them.
-.if n .Ip "\f(CW""\-Wcomment""\fR" 4
-.el .Ip "\f(CW\-Wcomment\fR" 4
+.Ip "\fB\-Wcomment\fR" 4
.IX Item "-Wcomment"
.PD 0
-.if n .Ip "\f(CW""\-Wcomments""\fR" 4
-.el .Ip "\f(CW\-Wcomments\fR" 4
+.Ip "\fB\-Wcomments\fR" 4
.IX Item "-Wcomments"
.PD
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.
(Both forms have the same effect.)
-.if n .Ip "\f(CW""\-Wtrigraphs""\fR" 4
-.el .Ip "\f(CW\-Wtrigraphs\fR" 4
+.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
they do not affect the meaning of the program.
-.if n .Ip "\f(CW""\-Wtraditional""\fR" 4
-.el .Ip "\f(CW\-Wtraditional\fR" 4
+.Ip "\fB\-Wtraditional\fR" 4
.IX Item "-Wtraditional"
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 problematic constructs which should be avoided.
-.if n .Ip "\f(CW""\-Wimport""\fR" 4
-.el .Ip "\f(CW\-Wimport\fR" 4
+.Ip "\fB\-Wimport\fR" 4
.IX Item "-Wimport"
Warn the first time \fB#import\fR is used.
-.if n .Ip "\f(CW""\-Wundef""\fR" 4
-.el .Ip "\f(CW\-Wundef\fR" 4
+.Ip "\fB\-Wundef\fR" 4
.IX Item "-Wundef"
Warn whenever an identifier which is not a macro is encountered in an
\&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
replaced with zero.
-.if n .Ip "\f(CW""\-Werror""\fR" 4
-.el .Ip "\f(CW\-Werror\fR" 4
+.Ip "\fB\-Werror\fR" 4
.IX Item "-Werror"
Make all warnings into hard errors. Source code which triggers warnings
will be rejected.
-.if n .Ip "\f(CW""\-Wsystem\-headers""\fR" 4
-.el .Ip "\f(CW\-Wsystem\-headers\fR" 4
+.Ip "\fB\-Wsystem-headers\fR" 4
.IX Item "-Wsystem-headers"
Issue warnings for code in system headers. These are normally unhelpful
in finding bugs in your own code, therefore suppressed. If you are
responsible for the system library, you may want to see them.
-.if n .Ip "\f(CW""\-w""\fR" 4
-.el .Ip "\f(CW\-w\fR" 4
+.Ip "\fB\-w\fR" 4
.IX Item "-w"
Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
-.if n .Ip "\f(CW""\-pedantic""\fR" 4
-.el .Ip "\f(CW\-pedantic\fR" 4
+.Ip "\fB\-pedantic\fR" 4
.IX Item "-pedantic"
Issue all the mandatory diagnostics listed in the C standard. Some of
them are left out by default, since they trigger frequently on harmless
code.
-.if n .Ip "\f(CW""\-pedantic\-errors""\fR" 4
-.el .Ip "\f(CW\-pedantic\-errors\fR" 4
+.Ip "\fB\-pedantic-errors\fR" 4
.IX Item "-pedantic-errors"
Issue all the mandatory diagnostics, and make all mandatory diagnostics
into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
without \fB\-pedantic\fR but treats as warnings.
-.if n .Ip "\f(CW""\-M""\fR" 4
-.el .Ip "\f(CW\-M\fR" 4
+.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
+suitable for \fBmake\fR describing the dependencies of the main
+source file. The preprocessor outputs one \fBmake\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.
.Sp
Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the
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.
The rule has no commands.
-.if n .Ip "\f(CW""\-MM""\fR" 4
-.el .Ip "\f(CW\-MM\fR" 4
+.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
+Like \fB\-M\fR, but mention only the files included with \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR or with \fB\-include\fR or \fB\-imacros\fR command line
+options. System header files included with \f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR
are omitted.
-.if n .Ip "\f(CW""\-MF \f(CIfile\f(CW""\fR" 4
-.el .Ip "\f(CW\-MF \f(CIfile\f(CW\fR" 4
+.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.
-.if n .Ip "\f(CW""\-MG""\fR" 4
-.el .Ip "\f(CW\-MG\fR" 4
+.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
missing header file is ordinarily an error.
.Sp
This feature is used in automatic updating of makefiles.
-.if n .Ip "\f(CW""\-MP""\fR" 4
-.el .Ip "\f(CW\-MP\fR" 4
+.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.
+dummy rules work around errors \fBmake\fR gives if you remove header
+files without updating the \fIMakefile\fR to match.
.Sp
This is typical output:
.Sp
.Vb 1
\& test.h:
.Ve
-.if n .Ip "\f(CW""\-MT \f(CItarget\f(CW""\fR" 4
-.el .Ip "\f(CW\-MT \f(CItarget\f(CW\fR" 4
+.Ip "\fB\-MT\fR \fItarget\fR" 4
.IX Item "-MT target"
Change the target of the rule emitted by dependency generation. By
default \s-1CPP\s0 takes the name of the main input file, including any path,
.Vb 1
\& $(objpfx)foo.o: foo.c
.Ve
-.if n .Ip "\f(CW""\-MQ \f(CItarget\f(CW""\fR" 4
-.el .Ip "\f(CW\-MQ \f(CItarget\f(CW\fR" 4
+.Ip "\fB\-MQ\fR \fItarget\fR" 4
.IX Item "-MQ target"
Same as \fB\-MT\fR, but it quotes any characters which are special to
Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
.Ve
The default target is automatically quoted, as if it were given with
\&\fB\-MQ\fR.
-.if n .Ip "\f(CW""\-MD \f(CIfile\f(CW""\fR" 4
-.el .Ip "\f(CW\-MD \f(CIfile\f(CW\fR" 4
+.Ip "\fB\-MD\fR \fIfile\fR" 4
.IX Item "-MD file"
.PD 0
-.if n .Ip "\f(CW""\-MMD \f(CIfile\f(CW""\fR" 4
-.el .Ip "\f(CW\-MMD \f(CIfile\f(CW\fR" 4
+.Ip "\fB\-MMD\fR \fIfile\fR" 4
.IX Item "-MMD file"
.PD
\&\fB\-MD\fR \fIfile\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, and
Due to limitations in the compiler driver, you must use these switches
when you want to generate a dependency file as a side-effect of normal
compilation.
-.if n .Ip "\f(CW""\-x c""\fR" 4
-.el .Ip "\f(CW\-x c\fR" 4
+.Ip "\fB\-x c\fR" 4
.IX Item "-x c"
.PD 0
-.if n .Ip "\f(CW""\-x c++""\fR" 4
-.el .Ip "\f(CW\-x c++\fR" 4
+.Ip "\fB\-x c++\fR" 4
.IX Item "-x c++"
-.if n .Ip "\f(CW""\-x objective\-c""\fR" 4
-.el .Ip "\f(CW\-x objective\-c\fR" 4
+.Ip "\fB\-x objective-c\fR" 4
.IX Item "-x objective-c"
-.if n .Ip "\f(CW""\-x assembler\-with\-cpp""\fR" 4
-.el .Ip "\f(CW\-x assembler\-with\-cpp\fR" 4
+.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
which selected both the language and the standards conformance level.
This option has been removed, because it conflicts with the \fB\-l\fR
option.
-.if n .Ip "\f(CW""\-std=\f(CIstandard\f(CW""\fR" 4
-.el .Ip "\f(CW\-std=\f(CIstandard\f(CW\fR" 4
+.Ip "\fB\-std=\fR\fIstandard\fR" 4
.IX Item "-std=standard"
.PD 0
-.if n .Ip "\f(CW""\-ansi""\fR" 4
-.el .Ip "\f(CW\-ansi\fR" 4
+.Ip "\fB\-ansi\fR" 4
.IX Item "-ansi"
.PD
Specify the standard to which the code should conform. Currently cpp
\&\fIstandard\fR
may be one of:
.RS 4
-.if n .Ip "\f(CW""iso9899:1990""\fR" 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
+.if n .Ip "\f(CW""""c89""""\fR" 4
.el .Ip "\f(CWc89\fR" 4
.IX Item "c89"
.PD
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
+.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
+.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
+.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
+.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
+.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
+.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
+.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
+.if n .Ip "\f(CW""""gnu9x""""\fR" 4
.el .Ip "\f(CWgnu9x\fR" 4
.IX Item "gnu9x"
.PD
.RE
.RS 4
.RE
-.if n .Ip "\f(CW""\-I\-""\fR" 4
-.el .Ip "\f(CW\-I\-\fR" 4
+.Ip "\fB\-I-\fR" 4
.IX Item "-I-"
Split the include path. Any directories specified with \fB\-I\fR
options before \fB\-I-\fR are searched only for headers requested with
-\&\fB#include\ "\f(BIfile\fB"\fR; they are not searched for
-\&\fB#include\ <\f(BIfile\fB>\fR. If additional directories are
+\&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
+\&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
specified with \fB\-I\fR options after the \fB\-I-\fR, those
directories are searched for all \fB#include\fR directives.
.Sp
In addition, \fB\-I-\fR inhibits the use of the directory of the current
-file directory as the first search directory for \fB#include\ "\f(BIfile\fB"\fR.
-.if n .Ip "\f(CW""\-nostdinc""\fR" 4
-.el .Ip "\f(CW\-nostdinc\fR" 4
+file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
+.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 directory of the current file, if appropriate) are searched.
-.if n .Ip "\f(CW""\-nostdinc++""\fR" 4
-.el .Ip "\f(CW\-nostdinc++\fR" 4
+.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.)
-.if n .Ip "\f(CW""\-include \f(CIfile\f(CW""\fR" 4
-.el .Ip "\f(CW\-include \f(CIfile\f(CW\fR" 4
+.Ip "\fB\-include\fR \fIfile\fR" 4
.IX Item "-include file"
Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
line of the primary source file. However, the first directory searched
.Sp
If multiple \fB\-include\fR options are given, the files are included
in the order they appear on the command line.
-.if n .Ip "\f(CW""\-imacros \f(CIfile\f(CW""\fR" 4
-.el .Ip "\f(CW\-imacros \f(CIfile\f(CW\fR" 4
+.Ip "\fB\-imacros\fR \fIfile\fR" 4
.IX Item "-imacros file"
Exactly like \fB\-include\fR, except that any output produced by
scanning \fIfile\fR is thrown away. Macros it defines remain defined.
.Sp
All files specified by \fB\-imacros\fR are processed before all files
specified by \fB\-include\fR.
-.if n .Ip "\f(CW""\-idirafter \f(CIdir\f(CW""\fR" 4
-.el .Ip "\f(CW\-idirafter \f(CIdir\f(CW\fR" 4
+.Ip "\fB\-idirafter\fR \fIdir\fR" 4
.IX Item "-idirafter dir"
Search \fIdir\fR for header files, but do it \fIafter\fR all
directories specified with \fB\-I\fR and the standard system directories
have been exhausted. \fIdir\fR is treated as a system include directory.
-.if n .Ip "\f(CW""\-iprefix \f(CIprefix\f(CW""\fR" 4
-.el .Ip "\f(CW\-iprefix \f(CIprefix\f(CW\fR" 4
+.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.
-.if n .Ip "\f(CW""\-iwithprefix \f(CIdir\f(CW""\fR" 4
-.el .Ip "\f(CW\-iwithprefix \f(CIdir\f(CW\fR" 4
+.Ip "\fB\-iwithprefix\fR \fIdir\fR" 4
.IX Item "-iwithprefix dir"
.PD 0
-.if n .Ip "\f(CW""\-iwithprefixbefore \f(CIdir\f(CW""\fR" 4
-.el .Ip "\f(CW\-iwithprefixbefore \f(CIdir\f(CW\fR" 4
+.Ip "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
.IX Item "-iwithprefixbefore dir"
.PD
Append \fIdir\fR to the prefix specified previously with
would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
.Sp
Use of these options is discouraged.
-.if n .Ip "\f(CW""\-isystem \f(CIdir\f(CW""\fR" 4
-.el .Ip "\f(CW\-isystem \f(CIdir\f(CW\fR" 4
+.Ip "\fB\-isystem\fR \fIdir\fR" 4
.IX Item "-isystem dir"
Search \fIdir\fR for header files, after all directories specified by
\&\fB\-I\fR but before the standard system directories. Mark it
as a system directory, so that it gets the same special treatment as
is applied to the standard system directories.
-.if n .Ip "\f(CW""\-fpreprocessed""\fR" 4
-.el .Ip "\f(CW\-fpreprocessed\fR" 4
+.Ip "\fB\-fpreprocessed\fR" 4
.IX Item "-fpreprocessed"
Indicate to the preprocessor that the input file has already been
preprocessed. This suppresses things like macro expansion, trigraph
extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
extensions that \s-1GCC\s0 uses for preprocessed files created by
\&\fB\-save-temps\fR.
-.if n .Ip "\f(CW""\-ftabstop=\f(CIwidth\f(CW""\fR" 4
-.el .Ip "\f(CW\-ftabstop=\f(CIwidth\f(CW\fR" 4
+.Ip "\fB\-ftabstop=\fR\fIwidth\fR" 4
.IX Item "-ftabstop=width"
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. If the value is less than 1 or greater than 100, the option is
ignored. The default is 8.
-.if n .Ip "\f(CW""\-fno\-show\-column""\fR" 4
-.el .Ip "\f(CW\-fno\-show\-column\fR" 4
+.Ip "\fB\-fno-show-column\fR" 4
.IX Item "-fno-show-column"
Do not print column numbers in diagnostics. This may be necessary if
diagnostics are being scanned by a program that does not understand the
-column numbers, such as \f(CW\*(C`dejagnu\*(C'\fR.
-.if n .Ip "\f(CW""\-A \f(CIpredicate\f(CW=\f(CIanswer\f(CW""\fR" 4
-.el .Ip "\f(CW\-A \f(CIpredicate\f(CW=\f(CIanswer\f(CW\fR" 4
+column numbers, such as \fBdejagnu\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.
-.if n .Ip "\f(CW""\-A \-\f(CIpredicate\f(CW=\f(CIanswer\f(CW""\fR" 4
-.el .Ip "\f(CW\-A \-\f(CIpredicate\f(CW=\f(CIanswer\f(CW\fR" 4
+.Ip "\fB\-A -\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
.IX Item "-A -predicate=answer"
Cancel an assertion with the predicate \fIpredicate\fR and answer
\&\fIanswer\fR.
-.if n .Ip "\f(CW""\-A\-""\fR" 4
-.el .Ip "\f(CW\-A\-\fR" 4
+.Ip "\fB\-A-\fR" 4
.IX Item "-A-"
Cancel all predefined assertions and all assertions preceding it on
the command line. Also, undefine all predefined macros and all
macros preceding it on the command line. (This is a historical wart and
may change in the future.)
-.if n .Ip "\f(CW""\-dM""\fR" 4
-.el .Ip "\f(CW\-dM\fR" 4
+.Ip "\fB\-dM\fR" 4
.IX Item "-dM"
Instead of the normal output, generate 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
+Assuming you have no file \fIfoo.h\fR, the command
.Sp
.Vb 1
\& touch foo.h; cpp -dM foo.h
.Ve
will show all the predefined macros.
-.if n .Ip "\f(CW""\-dD""\fR" 4
-.el .Ip "\f(CW\-dD\fR" 4
+.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.
-.if n .Ip "\f(CW""\-dN""\fR" 4
-.el .Ip "\f(CW\-dN\fR" 4
+.Ip "\fB\-dN\fR" 4
.IX Item "-dN"
Like \fB\-dD\fR, but emit only the macro names, not their expansions.
-.if n .Ip "\f(CW""\-dI""\fR" 4
-.el .Ip "\f(CW\-dI\fR" 4
+.Ip "\fB\-dI\fR" 4
.IX Item "-dI"
Output \fB#include\fR directives in addition to the result of
preprocessing.
-.if n .Ip "\f(CW""\-P""\fR" 4
-.el .Ip "\f(CW\-P\fR" 4
+.Ip "\fB\-P\fR" 4
.IX Item "-P"
Inhibit generation of linemarkers 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
linemarkers.
-.if n .Ip "\f(CW""\-C""\fR" 4
-.el .Ip "\f(CW\-C\fR" 4
+.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
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.
-.if n .Ip "\f(CW""\-gcc""\fR" 4
-.el .Ip "\f(CW\-gcc\fR" 4
+.Ip "\fB\-gcc\fR" 4
.IX Item "-gcc"
Define the macros _\|_GNUC_\|_, _\|_GNUC_MINOR_\|_ and
_\|_GNUC_PATCHLEVEL_\|_. These are defined automatically when you use
-\&\fBgcc \-E\fR; you can turn them off in that case with \fB\-no-gcc\fR.
-.if n .Ip "\f(CW""\-traditional""\fR" 4
-.el .Ip "\f(CW\-traditional\fR" 4
+\&\fBgcc \-E\fR; you can turn them off in that case with
+\&\fB\-no-gcc\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.
-.if n .Ip "\f(CW""\-trigraphs""\fR" 4
-.el .Ip "\f(CW\-trigraphs\fR" 4
+.Ip "\fB\-trigraphs\fR" 4
.IX Item "-trigraphs"
Process trigraph sequences.
-.if n .Ip "\f(CW""\-remap""\fR" 4
-.el .Ip "\f(CW\-remap\fR" 4
+.Ip "\fB\-remap\fR" 4
.IX Item "-remap"
Enable special code to work around file systems which only permit very
short file names, such as \s-1MS-DOS\s0.
-.if n .Ip "\f(CW""\-$""\fR" 4
-.el .Ip "\f(CW\-$\fR" 4
+.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.
-.if n .Ip "\f(CW""\-h""\fR" 4
-.el .Ip "\f(CW\-h\fR" 4
+identifiers. By default \s-1GNU\s0 \s-1CPP\s0 permits \fB$\fR, a common extension.
+.Ip "\fB\-h\fR" 4
.IX Item "-h"
.PD 0
-.if n .Ip "\f(CW""\-\-help""\fR" 4
-.el .Ip "\f(CW\-\-help\fR" 4
-.IX Item "--help"
-.if n .Ip "\f(CW""\-\-target\-help""\fR" 4
-.el .Ip "\f(CW\-\-target\-help\fR" 4
-.IX Item "--target-help"
+.Ip "\fB\*(--help\fR" 4
+.IX Item "help"
+.Ip "\fB\*(--target-help\fR" 4
+.IX Item "target-help"
.PD
Print text describing all the command line options instead of
preprocessing anything.
-.if n .Ip "\f(CW""\-v""\fR" 4
-.el .Ip "\f(CW\-v\fR" 4
+.Ip "\fB\-v\fR" 4
.IX Item "-v"
Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
execution, and report the final form of the include path.
-.if n .Ip "\f(CW""\-H""\fR" 4
-.el .Ip "\f(CW\-H\fR" 4
+.Ip "\fB\-H\fR" 4
.IX Item "-H"
Print the name of each header file used, in addition to other normal
activities. Each name is indented to show how deep in the
\&\fB#include\fR stack it is.
-.if n .Ip "\f(CW""\-version""\fR" 4
-.el .Ip "\f(CW\-version\fR" 4
+.Ip "\fB\-version\fR" 4
.IX Item "-version"
.PD 0
-.if n .Ip "\f(CW""\-\-version""\fR" 4
-.el .Ip "\f(CW\-\-version\fR" 4
-.IX Item "--version"
+.Ip "\fB\*(--version\fR" 4
+.IX Item "version"
.PD
Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
preprocess as normal. With two dashes, exit immediately.
Permission is granted to copy, distribute and/or modify this document
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation. A copy of
-the license is included in the accompanying manual for \s-1GNU\s0 \s-1CC\s0, in the
+the license is included in the accompanying manual for \s-1GCC\s0, in the
section ``\s-1GNU\s0 Free Documentation License''.
This manual contains no Invariant Sections, and has no Front-Cover Texts
or Back-Cover Texts.
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. A copy of
-the license is included in the accompanying manual for GNU CC, in the
+the license is included in the accompanying manual for GCC, in the
section ``GNU Free Documentation License''.
@c man end
@end macro
funds for GNU development.
@end macro
-@c Better form for references to other manuals.
-@ifinfo
-@macro docref{docname}
-GNU \docname\. @ref{Top, \docname\, , \docname\}@c
-@end macro
-@end ifinfo
-@ifnotinfo
-@macro docref{docname}
-GNU \docname\@c
+@macro gcctabopt{body}
+@code{\body\}
@end macro
-@end ifnotinfo
@ifinfo
@dircategory Programming
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 @docref{M4}.
+try a true general text processor, such as GNU M4.
C preprocessors vary in some details. This manual discusses the GNU C
preprocessor, which provides a small superset of the features of ISO
// @r{this is} // @r{one comment}
@r{text outside comment}
@end example
+@end enumerate
It is safe to put line comments inside block comments, or vice versa.
Line comments are not in the 1989 edition of the C standard, but they
are recognized by GCC as an extension. In C++ and in the 1999 edition
of the C standard, they are an official part of the language.
-@end enumerate
Since these transformations happen before all other processing, you can
split a line mechanically with backslash-newline anywhere. You can
@end example
@noindent
-is equivalent to @samp{@w{#define FOO 1020}}. All these tricks are
+is equivalent to @code{@w{#define FOO 1020}}. All these tricks are
extremely confusing and should not be used in code intended to be
readable.
When faced with a sequence of characters that has more than one possible
tokenization, the preprocessor is greedy. It always makes each token,
starting from the left, as big as possible before moving on to the next
-token. For instance, @samp{a+++++b} is interpreted as
-@samp{@w{a ++ ++ + b}}, not as @samp{@w{a ++ + ++ b}}, even though the
+token. For instance, @code{a+++++b} is interpreted as
+@code{@w{a ++ ++ + b}}, not as @code{@w{a ++ + ++ b}}, even though the
latter tokenization could be part of a valid C program and the former
could not.
Once the input file is broken into tokens, the token boundaries never
-change, except when the @samp{##} preprocessing operator is used to glue
+change, except when the @samp{##} preprocessing operator is used to paste
tokens together. @xref{Concatenation}. For example,
@example
underscore. Keywords of C have no significance to the preprocessor;
they are ordinary identifiers. You can define a macro whose name is a
keyword, for instance. The only identifier which can be considered a
-preprocessing keyword is @samp{defined}. @xref{Defined}.
+preprocessing keyword is @code{defined}. @xref{Defined}.
This is mostly true of other languages which use the C preprocessor.
However, a few of the keywords of C++ are significant even in the
part of the ``basic source character set,'' at the implementation's
discretion (such as accented Latin letters, Greek letters, or Chinese
ideograms). This may be done with an extended character set, or the
-@samp{\u} and @samp{\U} escape sequences. GNU C does not presently
+@samp{\u} and @samp{\U} escape sequences. GCC does not presently
implement either feature in the preprocessor or the compiler.
+As an extension, GCC treats @samp{$} as a letter. This is for
+compatibility with some systems, such as VMS, where @samp{$} is commonly
+used in system-defined function and object names. @samp{$} is not a
+letter in strictly conforming mode, or if you specify the @option{-$}
+option. @xref{Invocation}.
+
@cindex numbers
@cindex preprocessing numbers
A @dfn{preprocessing number} has a rather bizarre definition. The
distinguish between lexically valid and invalid floating-point numbers,
which is complicated. The definition also permits you to split an
identifier at any position and get exactly two tokens, which can then be
-glued back together with the @samp{##} operator.
+pasted back together with the @samp{##} operator.
It's possible for preprocessing numbers to cause programs to be
-misinterpreted. For example, @samp{0xE+12} is a preprocessing number
+misinterpreted. For example, @code{0xE+12} is a preprocessing number
which does not translate to any valid numeric constant, therefore a
-syntax error. It does not mean @samp{@w{0xE + 12}}, which is what you
+syntax error. It does not mean @code{@w{0xE + 12}}, which is what you
might have intended.
@cindex string literals
header file names (the argument of @samp{#include}).@footnote{The C
standard uses the term @dfn{string literal} to refer only to what we are
calling @dfn{string constants}.} String constants and character
-constants are straightforward: @t{"..."} or @t{'...'}. In either case
-the closing quote may be escaped with a backslash: @t{'\'@:'} is the
-character constant for @samp{'}. There is no limit on the length of a
-character constant, but the value of a character constant that contains
-more than one character is implementation-defined. @xref{Implementation
-Details}.
-
-Header file names either look like string constants, @t{"..."}, or are
-written with angle brackets instead, @t{<...>}. In either case,
+constants are straightforward: @t{"@dots{}"} or @t{'@dots{}'}. In
+either case the closing quote may be escaped with a backslash:
+@t{'\'@:'} is the character constant for @samp{'}. There is no limit on
+the length of a character constant, but the value of a character
+constant that contains more than one character is
+implementation-defined. @xref{Implementation Details}.
+
+Header file names either look like string constants, @t{"@dots{}"}, or are
+written with angle brackets instead, @t{<@dots{}>}. In either case,
backslash is an ordinary character. There is no way to escape the
closing quote or angle bracket. The preprocessor looks for the header
file in different places depending on which form you use. @xref{Include
the preprocessor's output unmolested. The C compiler will almost
certainly reject source code containing ``other'' tokens. In ASCII, the
only other characters are @samp{@@}, @samp{$}, @samp{`}, and control
-characters other than NUL (all bits zero). All characters with the high
-bit set (numeric range 0x7F--0xFF) are also ``other'' in the present
+characters other than NUL (all bits zero). (Note that @samp{$} is
+normally considered a letter.) All characters with the high bit set
+(numeric range 0x7F--0xFF) are also ``other'' in the present
implementation. This will change when proper support for international
character sets is added to GCC.
The @samp{#} which begins a directive cannot come from a macro
expansion. Also, the directive name is not macro expanded. Thus, if
-@samp{foo} is defined as a macro expanding to @samp{define}, that does
+@code{foo} is defined as a macro expanding to @code{define}, that does
not make @samp{#foo} a valid preprocessing directive.
The set of valid directive names is fixed. Programs cannot define new
The argument of @samp{#include}, whether delimited with quote marks or
angle brackets, behaves like a string constant in that comments are not
-recognized, and macro names are not expanded. Thus, @samp{@w{#include
+recognized, and macro names are not expanded. Thus, @code{@w{#include
<x/*y>}} specifies inclusion of a system header file named @file{x/*y}.
However, 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{@w{#include "x\n\\y"}} specifies a filename containing three
+Thus, @code{@w{#include "x\n\\y"}} specifies a filename containing three
backslashes. (Some systems interpret @samp{\} as a pathname separator.
All of these also interpret @samp{/} the same way. It is most portable
to use only @samp{/}.)
considered to end (with an error message) at the end of the file.
To avoid confusion, it is best if header files contain only complete
-syntactic units --- function declarations or definitions, type
+syntactic units---function declarations or definitions, type
declarations, etc.
The line following the @samp{#include} directive is always treated as a
GCC looks in several different places for headers. On a normal Unix
system, if you do not instruct it otherwise, it will look for headers
-requested with @samp{@w{#include <@var{file}>}} in:
+requested with @code{@w{#include <@var{file}>}} in:
@example
/usr/local/include
/usr/include
@end example
-For C++ programs, it will also look in @samp{/usr/include/g++-v3},
+For C++ programs, it will also look in @file{/usr/include/g++-v3},
first. In the above, @var{target} is the canonical name of the system
GCC was configured to compile code for; often but not always the same as
the canonical name of the system it runs on. @var{version} is the
operating system kernel or some other program that does not use the
standard C library facilities, or the standard C library itself.
-GCC looks for headers requested with @samp{@w{#include "@var{file}"}}
+GCC looks for headers requested with @code{@w{#include "@var{file}"}}
first in the directory containing the current file, then in the same
places it would have looked for a header requested with angle brackets.
For example, if @file{/usr/include/sys/stat.h} contains
-@samp{@w{#include "types.h"}}, GCC looks for @file{types.h} first in
+@code{@w{#include "types.h"}}, GCC looks for @file{types.h} first in
@file{/usr/include/sys}, then in its usual search path.
@samp{#line} (@pxref{Line Control}) does not change GCC's idea of the
#include SYSTEM_H
@end example
-@samp{SYSTEM_H} will be expanded, and the preprocessor will look for
+@noindent
+@code{SYSTEM_H} will be expanded, and the preprocessor will look for
@file{system_1.h} as if the @samp{#include} had been written that way
-originally. @samp{SYSTEM_H} could be defined by your Makefile with a
+originally. @code{SYSTEM_H} could be defined by your Makefile with a
@option{-D} option.
You must be careful when you define the macro. @samp{#define} saves
#include HEADER
@end example
+@noindent
looks for a file named @file{a\"b}. CPP searches for the file according
to the rules for double-quoted includes.
@findex #include_next
Sometimes it is necessary to adjust the contents of a system-provided
-header file without editing it directly. GCC's @samp{fixincludes}
+header file without editing it directly. GCC's @command{fixincludes}
operation does this, for example. One way to do that would be to create
a new header file with the same name and insert it in the search path
before the original header. That works fine as long as you're willing
Suppose you specify @option{-I /usr/local/include}, and the list of
directories to search also includes @file{/usr/include}; and suppose
-both directories contain @file{signal.h}. Ordinary @samp{#include
-<signal.h>} finds the file under @file{/usr/local/include}. If that
-file contains @samp{#include_next <signal.h>}, it starts searching
+both directories contain @file{signal.h}. Ordinary @code{@w{#include
+<signal.h>}} finds the file under @file{/usr/local/include}. If that
+file contains @code{@w{#include_next <signal.h>}}, it starts searching
after that directory, and finds the file in @file{/usr/include}.
-@samp{#include_next} does not distinguish between @samp{<@var{file}>}
-and @samp{"@var{file}"} inclusion, nor does it check that the file you
+@samp{#include_next} does not distinguish between @code{<@var{file}>}
+and @code{"@var{file}"} inclusion, nor does it check that the file you
specify has the same name as the current file. It simply looks for the
file named, starting with the directory in the search path after the one
where the current file was found.
recommend it be used only when there is no other alternative. In
particular, it should not be used in the headers belonging to a
specific program, only to make global corrections along the lines
-of @samp{fixincludes}.
+of @command{fixincludes}.
@node System Headers
@section System Headers
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
+Therefore, GCC gives code found in @dfn{system headers} special
treatment. All warnings, other than those generated by @samp{#warning}
(@pxref{Diagnostics}), are suppressed while GCC is processing a system
header. Macros defined in a system header are immune to a few warnings
had never been specified at all.
@findex #pragma GCC system_header
-There is also a directive, @samp{@w{#pragma GCC system_header}}, which
+There is also a directive, @code{@w{#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{@w{#pragma GCC
+@samp{#pragma} in the file will not be affected. @code{@w{#pragma GCC
system_header}} has no effect in the primary source file.
On very old systems, some of the pre-defined system header directories
You may define any valid identifier as a macro, even if it is a C
keyword. The preprocessor does not know anything about keywords. This
-can be useful if you wish to hide a keyword such as @samp{const} from an
+can be useful if you wish to hide a keyword such as @code{const} from an
older compiler that does not understand it. However, the preprocessor
-operator @samp{defined} (@pxref{Defined}) can never be defined as a
+operator @code{defined} (@pxref{Defined}) can never be defined as a
macro, and C++'s named operators (@pxref{C++ Named Operators}) cannot be
macros when you are compiling C++.
@end example
@noindent
-defines a macro named @samp{BUFFER_SIZE} as an abbreviation for the
-token @samp{1024}. If somewhere after this @samp{#define} directive
+defines a macro named @code{BUFFER_SIZE} as an abbreviation for the
+token @code{1024}. If somewhere after this @samp{#define} directive
there comes a C statement of the form
@example
@noindent
then the C preprocessor will recognize and @dfn{expand} the macro
-@samp{BUFFER_SIZE}. The C compiler will see the same tokens as it would
+@code{BUFFER_SIZE}. The C compiler will see the same tokens as it would
if you had written
@example
@end example
@noindent
-@samp{TABLESIZE} is expanded first to produce @samp{BUFSIZE}, then that
-macro is expanded to produce the final result, @samp{1024}.
+@code{TABLESIZE} is expanded first to produce @code{BUFSIZE}, then that
+macro is expanded to produce the final result, @code{1024}.
-Notice that @samp{BUFSIZE} was not defined when @samp{TABLESIZE} was
-defined. The @samp{#define} for @samp{TABLESIZE} uses exactly the
-expansion you specify --- in this case, @samp{BUFSIZE} --- and does not
+Notice that @code{BUFSIZE} was not defined when @code{TABLESIZE} was
+defined. The @samp{#define} for @code{TABLESIZE} uses exactly the
+expansion you specify---in this case, @code{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
+@emph{use} @code{TABLESIZE} is the result of its expansion scanned 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
+This makes a difference if you change the definition of @code{BUFSIZE}
+at some point in the source file. @code{TABLESIZE}, defined as shown,
+will always expand using the definition of @code{BUFSIZE} that is
currently in effect:
@example
@end example
@noindent
-Now @samp{TABLESIZE} expands (in two stages) to @samp{37}.
+Now @code{TABLESIZE} expands (in two stages) to @code{37}.
If the expansion of a macro contains its own name, either directly or
via intermediate macros, it is not expanded again when the expansion is
funcptr = foo;
@end example
-Here the call to @samp{foo()} will use the macro, but the function
+Here the call to @code{foo()} will use the macro, but the function
pointer will get the address of the real function. If the macro were to
be expanded, it would cause a syntax error.
The first two pairs of parentheses in this expansion come from the
macro. The third is the pair that was originally after the macro
-invocation. Since @samp{lang_init} is an object-like macro, it does not
+invocation. Since @code{lang_init} is an object-like macro, it does not
consume those parentheses.
@node Macro Arguments
To invoke a macro that takes arguments, you write the name of the macro
followed by a list of @dfn{actual 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
+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. When the macro is expanded, each
use of a parameter in its body is replaced by the tokens of the
@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 can write it as @samp{array[(x = y, x + 1)]}, which is equivalent C
+passes two arguments to @code{macro}: @code{array[x = y} and @code{x +
+1]}. If you want to supply @code{array[x = y, x + 1]} as an argument,
+you can write it as @code{array[(x = y, x + 1)]}, which is equivalent C
code.
All arguments to a macro are completely macro-expanded before they are
run into trouble if you try to be too clever, though. @xref{Argument
Prescan}, for detailed discussion.
-For example, @samp{min (min (a, b), c)} is first expanded to
+For example, @code{min (min (a, b), c)} is first expanded to
@example
min (((a) < (b) ? (a) : (b)), (c))
preprocessor (but many macros will then expand to invalid code).
You cannot leave out arguments entirely; if a macro takes two arguments,
there must be exactly one comma at the top level of its argument list.
-Here are some silly examples using @samp{min}:
+Here are some silly examples using @code{min}:
@example
min(, b) @expansion{} (( ) < (b) ? ( ) : (b))
@end example
Whitespace is not a preprocessing token, so if a macro @code{foo} takes
-one argument, @samp{@w{foo ()}} and @samp{@w{foo ( )}} both supply it an
+one argument, @code{@w{foo ()}} and @code{@w{foo ( )}} both supply it an
empty argument. 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
@end example
@noindent
-The argument for @samp{EXP} is substituted once, as-is, into the
-@samp{if} statement, and once, stringified, into the argument to
-@samp{fprintf}. If @samp{x} were a macro, it would be expanded in the
-@samp{if} statement, but not in the string.
-
-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
+The argument for @code{EXP} is substituted once, as-is, into the
+@code{if} statement, and once, stringified, into the argument to
+@code{fprintf}. If @code{x} were a macro, it would be expanded in the
+@code{if} statement, but not in the string.
+
+The @code{do} and @code{while (0)} are a kludge to make it possible to
+write @code{WARN_IF (@var{arg});}, which the resemblance of
+@code{WARN_IF} to a function would make C programmers want to do; see
@ref{Swallowing the Semicolon}.
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{@w{p = "foo\n";}} results in
+proper contents. Thus, stringifying @code{@w{p = "foo\n";}} results in
@t{@w{"p = \"foo\\n\";"}}. However, backslashes that are not inside string
or character constants are not duplicated: @samp{\n} by itself
stringifies to @t{"\n"}.
identifiers, or one will be an identifier and the other a preprocessing
number. When pasted, they make a longer identifier. 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
+number and a name, such as @code{1.5} and @code{e3}) into a number.
+Also, multi-character operators such as @code{+=} can be formed by
token pasting.
However, two tokens that don't together form a valid token cannot be
-pasted together. For example, you cannot concatenate @samp{x} with
-@samp{+} in either order. If you try, the preprocessor issues a warning
+pasted together. For example, you cannot concatenate @code{x} with
+@code{+} in either order. If you try, the preprocessor issues a warning
and emits the two tokens as if they had been written next to each other.
It is common to find unnecessary uses of @samp{##} in complex macros.
If you get this warning, it is likely that you can simply remove the
a function. Here is an example:
@example
-#define eprintf(...) fprintf (stderr, __VA_ARGS__)
+#define eprintf(@dots{}) fprintf (stderr, __VA_ARGS__)
@end example
This kind of macro is called @dfn{variadic}. When the macro is invoked,
The @code{eprintf} macro above could be written
@example
-#define eprintf(args...) fprintf (stderr, args)
+#define eprintf(args@dots{}) fprintf (stderr, args)
@end example
@noindent
macro. We could define @code{eprintf} like this, instead:
@example
-#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__)
+#define eprintf(format, @dots{}) fprintf (stderr, format, __VA_ARGS__)
@end example
+@noindent
This formulation looks more descriptive, but unfortunately it is less
flexible: you must now supply at least one argument after the format
string. In standard C, you cannot omit the comma separating the named
@expansion{} fprintf(stderr, "success!\n", );
@end example
+@noindent
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__)
+#define eprintf(format, @dots{}) fprintf (stderr, format, ##__VA_ARGS__)
@end example
-and the variable argument is left out when the @samp{eprintf} macro is
+@noindent
+and the variable argument is left out when the @code{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.
Variadic macros are a new feature in C99. GNU CPP has supported them
for a long time, but only with a named variable argument
-(@samp{args...}, not @samp{...} and @code{@w{__VA_ARGS__}}). If you are
+(@samp{args@dots{}}, not @samp{@dots{}} and @code{@w{__VA_ARGS__}}). If you are
concerned with portability to previous versions of GCC, you should use
only named variable arguments. On the other hand, if you are concerned
with portability to other conforming implementations of C99, you should
whatever comes immediately before it:
@example
-#define eprintf(format, args...) fprintf (stderr, format , ##args)
+#define eprintf(format, args@dots{}) fprintf (stderr, format , ##args)
@end example
@noindent
a C string constant. This is the path by which the preprocessor opened
the file, not the short name 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
+@code{"/usr/local/include/myheader.h"} is a possible expansion of this
macro.
@item __LINE__
new line of source code.
@end table
-@samp{__FILE__} and @samp{__LINE__} are useful in generating an error
+@code{__FILE__} and @code{__LINE__} 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,
length, __FILE__, __LINE__);
@end example
-An @samp{#include} directive changes the expansions of @samp{__FILE__}
-and @samp{__LINE__} to correspond to the included file. At the end of
+An @samp{#include} directive changes the expansions of @code{__FILE__}
+and @code{__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
+the @samp{#include} directive, the expansions of @code{__FILE__} and
+@code{__LINE__} revert to the values they had before the
+@samp{#include} (but @code{__LINE__} is then incremented by one as
processing moves to the line after the @samp{#include}).
-A @samp{#line} directive changes @samp{__LINE__}, and may change
-@samp{__FILE__} as well. @xref{Line Control}.
+A @samp{#line} directive changes @code{__LINE__}, and may change
+@code{__FILE__} as well. @xref{Line Control}.
-C99 introduces @samp{__func__}, and GCC has provided @samp{__FUNCTION__}
+C99 introduces @code{__func__}, and GCC has provided @code{__FUNCTION__}
for a long time. Both of these are strings containing the name of the
current function (there are slight semantic differences; see the GCC
manual). Neither of them is a macro; the preprocessor does not know the
name of the current function. They tend to be useful in conjunction
-with @samp{__FILE__} and @samp{__LINE__}, though.
+with @code{__FILE__} and @code{__LINE__}, though.
@table @code
@item __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 12 1996"}}. If the day of the
+characters and looks like @code{@w{"Feb 12 1996"}}. If the day of the
month is less than 10, it is padded with a space on the left.
@item __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"}.
+eight characters and looks like @code{"23:59:01"}.
@item __STDC__
In normal operation, this macro expands to the constant 1, to signify
that this compiler conforms to ISO Standard C@. If GNU CPP is used with
-a compiler other than GNU CC, this is not necessarily true; however, the
+a compiler other than GCC, this is not necessarily true; however, the
preprocessor always conforms to the standard, unless the
@option{-traditional} option is used.
@item __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
+constant of the form @code{@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 compiler conforms to. Like
-@samp{__STDC__}, this is not necessarily accurate for the entire
-implementation, unless GNU CPP is being used with GNU CC.
+@code{__STDC__}, this is not necessarily accurate for the entire
+implementation, unless GNU CPP is being used with GCC.
-The value @samp{199409L} signifies the 1989 C standard as amended in
-1994, which is the current default; the value @samp{199901L} signifies
+The value @code{199409L} signifies the 1989 C standard as amended in
+1994, which is the current default; the value @code{199901L} signifies
the 1999 revision of the C standard. Support for the 1999 revision is
not yet complete.
@item __cplusplus
This macro is defined when the C++ compiler is in use. You can use
-@samp{__cplusplus} to test whether a header is compiled by a C compiler
-or a C++ compiler. This macro is similar to @samp{__STDC_VERSION__}, in
+@code{__cplusplus} to test whether a header is compiled by a C compiler
+or a C++ compiler. This macro is similar to @code{__STDC_VERSION__}, in
that it expands to a version number. A fully conforming implementation
-of the 1998 C++ standard will define this macro to @samp{199711L}. The
-GNU C++ compiler is not yet fully conforming, so it uses @samp{1}
+of the 1998 C++ standard will define this macro to @code{199711L}. The
+GNU C++ compiler is not yet fully conforming, so it uses @code{1}
instead. We hope to complete our implementation in the near future.
@end table
are defined only when the entire compiler is in use; if you invoke the
preprocessor directly, they are not defined.
-
-
@code{__GNUC_PATCHLEVEL__} is new to GCC 3.0; it is also present in the
widely-used development snapshots leading up to 3.0 (which identify
themselves as GCC 2.96 or 2.97, depending on which snapshot you have).
which depends on a specific version, you must be more careful. Each
time the minor version is increased, the patch level is reset to zero;
each time the major version is increased (which happens rarely), the
-minor version and patch level are reset. The simplest way to write the
-conditional is like this:
+minor version and patch level are reset. If you wish to use the
+predefined macros directly in the conditional, you will need to write it
+like this:
@example
/* @r{Test for GCC > 3.2.0} */
-#if __GNUC__ > 3 || __GNUC_MINOR__ > 2 \
- || __GNUC_PATCHLEVEL__ > 0
+#if __GNUC__ > 3 || \
+ (__GNUC__ == 3 && (__GNUC_MINOR__ > 2 || \
+ (__GNUC_MINOR__ == 2 && \
+ __GNUC_PATCHLEVEL__ > 0))
@end example
@noindent
-This takes advantage of the rule that an undefined macro evaluates to
-zero in an @samp{#if}. The conditional will be false if
-@code{__GNUC__} is not defined (that is, if you are not using @w{GNU CC}).
+Another approach is to use the predefined macros to
+calculate a single number, then compare that against a threshold:
+
+@example
+#define GCC_VERSION (__GNUC__ * 10000 \
+ + __GNUC_MINOR__ * 100 \
+ + __GNUC_PATCHLEVEL__)
+@dots{}
+/* @r{Test for GCC > 3.2.0} */
+#if GCC_VERSION > 30200
+@end example
+
+@noindent
+Many people find this form easier to understand.
@item __GNUG__
The GNU C++ compiler defines this. Testing it is equivalent to
-testing @samp{(__GNUC__ && __cplusplus)}.
+testing @code{@w{(__GNUC__ && __cplusplus)}}.
@item __STRICT_ANSI__
-GNU C defines this macro if and only if the @option{-ansi} switch, or a
+GCC 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.
+was specified when GCC was invoked. Its definition is the null string.
This macro exists primarily to direct GNU libc's header files to
restrict their definitions to the minimal set found in the 1989 C
standard.
are defined. If they are defined, their value is 1.
@item __CHAR_UNSIGNED__
-GNU C defines this macro if and only if the data type @code{char} is
+GCC 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 use this macro
yourself; instead, refer to the standard macros defined in @file{limits.h}.
This macro expands to a single token (not a string constant) which is
the prefix applied to CPU register names in assembly language for this
target. You can use it to write assembly that is usable in multiple
-environments. For example, in the @samp{m68k-aout} environment it
-expands to nothing, but in the @samp{m68k-coff} environment it expands
+environments. For example, in the @code{m68k-aout} environment it
+expands to nothing, but in the @code{m68k-coff} environment it expands
to a single @samp{%}.
@item __USER_LABEL_PREFIX__
This macro expands to a single token which is the the prefix applied to
user labels (symbols visible to C code) in assembly. For example, in
-the @samp{m68k-aout} environment it expands to an @samp{_}, but in the
-@samp{m68k-coff} environment it expands to nothing.
+the @code{m68k-aout} environment it expands to an @samp{_}, but in the
+@code{m68k-coff} environment it expands to nothing.
This macro will have the correct definition even if
@option{-f(no-)underscores} is in use, but it will not be correct if
The C preprocessor normally predefines several macros that indicate what
type of system and machine is in use. They are obviously different on
-each target supported by GNU C@. This manual, being for all systems and
+each target supported by GCC@. This manual, being for all systems and
machines, cannot tell you what their names are, but you can use
-@samp{cpp -dM} to see them all. @xref{Invocation}. All system-specific
+@command{cpp -dM} to see them all. @xref{Invocation}. All system-specific
predefined macros expand to the constant 1, so you can test them with
either @samp{#ifdef} or @samp{#if}.
or an underscore and a capital letter, are reserved for the compiler and
library to use as they wish. However, historically system-specific
macros have had names with no special prefix; for instance, it is common
-to find @samp{unix} defined on Unix systems. For all such macros, GCC
+to find @code{unix} defined on Unix systems. For all such macros, GCC
provides a parallel macro with two underscores added at the beginning
-and the end. If @samp{unix} is defined, @samp{__unix__} will be defined
+and the end. If @code{unix} is defined, @code{__unix__} will be defined
too. There will never be more than two underscores; the parallel of
-@samp{_mips} is @samp{__mips__}.
+@code{_mips} is @code{__mips__}.
When the @option{-ansi} option, or any @option{-std} option that
requests strict conformance, is given to the compiler, all the
you find it. We don't recommend you use the system-specific macros that
are in the reserved namespace, either. It is better in the long run to
check specifically for features you need, using a tool such as
-@docref{autoconf}.
+@command{autoconf}.
@node C++ Named Operators
@subsection C++ Named Operators
@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:
+to compute how many @code{int} objects are needed to hold a certain
+number of @code{char} objects.) Then suppose it is used as follows:
@example
a = ceil_div (b & c, sizeof (int));
@noindent
provides the desired result.
-Unintended grouping can result in another way. Consider @samp{sizeof
+Unintended grouping can result in another way. Consider @code{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
+compute the size of the type of @code{ceil_div (1, 2)}, but in fact it
means something very different. Here is what it expands to:
@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
+precedence rules have put the division outside the @code{sizeof} when it
was intended to be inside.
Parentheses around the entire macro definition prevent such problems.
-Here, then, is the recommended way to define @samp{ceil_div}:
+Here, then, is the recommended way to define @code{ceil_div}:
@example
#define ceil_div(x, y) (((x) + (y) - 1) / (y))
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
+pointer (the argument @code{p} says where to find it) across whitespace
characters:
@example
be a single logical line, so that it resembles the way such 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
+A call to this macro might be @code{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);}
+@code{SKIP_SPACES (p, lim);}
-This can cause trouble before @samp{else} statements, because the
+This can cause trouble before @code{else} statements, because the
semicolon is actually a null statement. Suppose you write
@example
@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}
+The presence of two statements---the compound statement and a null
+statement---in between the @code{if} condition and the @code{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:
+The definition of the macro @code{SKIP_SPACES} can be altered to solve
+this problem, using a @code{do @dots{} while} statement. Here is how:
@example
#define SKIP_SPACES(p, limit) \
while (0)
@end example
-Now @samp{SKIP_SPACES (p, lim);} expands into
+Now @code{SKIP_SPACES (p, lim);} expands into
@example
do @{@dots{}@} while (0);
@cindex side effects (in macro arguments)
@cindex unsafe macros
-Many C programs define a macro @samp{min}, for ``minimum'', like this:
+Many C programs define a macro @code{min}, for ``minimum'', like this:
@example
#define min(X, Y) ((X) < (Y) ? (X) : (Y))
@end example
@noindent
-where @samp{x + y} has been substituted for @samp{X} and @samp{foo (z)}
-for @samp{Y}.
+where @code{x + y} has been substituted for @code{X} and @code{foo (z)}
+for @code{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
+The function @code{foo} is used only once in the statement as it appears
+in the program, but the expression @code{foo (z)} has been substituted
+twice into the macro expansion. As a result, @code{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.
+intended. We say that @code{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
+The best solution to this problem is to define @code{min} in a way that
+computes the value of @code{foo (z)} only once. The C language offers
no standard way to do this, but it can be done with GNU extensions as
follows:
to avoid this entirely). Now each argument is evaluated exactly once.
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}:
+careful when @emph{using} the macro @code{min}. For example, you can
+calculate the value of @code{foo (z)}, save it in a variable, and use
+that variable in @code{min}:
@example
+@group
#define min(X, Y) ((X) < (Y) ? (X) : (Y))
@dots{}
@{
int tem = foo (z);
next = min (x + y, tem);
@}
+@end group
@end example
@noindent
-(where we assume that @samp{foo} returns type @samp{int}).
+(where we assume that @code{foo} returns type @code{int}).
@node Self-Referential Macros
@subsection Self-Referential Macros
@end example
@noindent
-where @samp{foo} is also a variable in your program.
+where @code{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 the computer runs out of memory.
+Following the ordinary rules, each reference to @code{foo} will expand
+into @code{(4 + foo)}; then this will be rescanned and will expand into
+@code{(4 + (4 + foo))}; and so on until the computer runs out of memory.
The self-reference rule 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.
+@code{(4 + foo)}. Therefore, this macro definition has the possibly
+useful effect of causing the program to add 4 to the value of @code{foo}
+wherever @code{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
+person reading the program who sees that @code{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.
+identifier @code{foo} in the program and think its value should be that
+of the variable @code{foo}, whereas in fact the value is four greater.
One common, useful use of self-reference is to create a macro which
expands to itself. If you write
@end example
@noindent
-then the macro @code{EPERM} expands to @samp{EPERM}. Effectively, it is
+then the macro @code{EPERM} expands to @code{EPERM}. Effectively, it is
left alone by the preprocessor whenever it's used in running text. You
can tell that it's a macro with @samp{#ifdef}. You might do this if you
-want to define numeric constants with an @samp{enum}, but have
+want to define numeric constants with an @code{enum}, but have
@samp{#ifdef} be true for each constant.
If a macro @code{x} expands to use a macro @code{y}, and the expansion of
@end example
@noindent
-then @samp{x} and @samp{y} expand as follows:
+then @code{x} and @code{y} expand as follows:
@example
@group
Nested calls to a macro.
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
+contains a call to that very macro. For example, if @code{f} is a macro
+that expects one argument, @code{f (f (1))} is a nested pair of calls to
+@code{f}. The desired expansion is made by expanding @code{f (1)} and
+substituting that into the definition of @code{f}. The prescan causes
+the expected result to happen. Without the prescan, @code{f (1)} itself
+would be substituted as an argument, and the inner use of @code{f} would
appear during the main scan as an indirect self-reference and would not
be expanded.
#define BUFSIZE TABLESIZE
@end example
-then @samp{AFTERX(BUFSIZE)} expands to @samp{X_BUFSIZE}, and
-@samp{XAFTERX(BUFSIZE)} expands to @samp{X_1024}. (Not to
-@samp{X_TABLESIZE}. Prescan always does a complete expansion.)
+then @code{AFTERX(BUFSIZE)} expands to @code{X_BUFSIZE}, and
+@code{XAFTERX(BUFSIZE)} expands to @code{X_1024}. (Not to
+@code{X_TABLESIZE}. Prescan always does a complete expansion.)
@item
Macros used in arguments, whose expansions contain unshielded commas.
#define lose(x) (1 + (x))
@end example
-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}
+We would like @code{bar(foo)} to turn into @code{(1 + (foo))}, which
+would then turn into @code{(1 + (a,b))}. Instead, @code{bar(foo)}
+expands into @code{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:
@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 ---
+The syntax error triggered by the tokens @code{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.
We consider this a bug, and intend to fix it in the near future.
select whether or not to include a chunk of code in the final token
stream passed to the compiler. Preprocessor conditionals can test
arithmetic expressions, or whether a name is defined as a macro, or both
-simultaneously using the special @samp{defined} operator.
+simultaneously using the special @code{defined} operator.
-A conditional in the C preprocessor resembles in some ways an @samp{if}
+A conditional in the C preprocessor resembles in some ways an @code{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
+them. The condition in an @code{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
time of compilation.
However, the distinction is becoming less clear. Modern compilers often
-do test @samp{if} statements when a program is compiled, if their
+do test @code{if} statements when a program is compiled, if their
conditions are known not to vary at run time, and eliminate code which
can never be executed. If you can count on your compiler to do this,
-you may find that your program is more readable if you use @samp{if}
+you may find that your program is more readable if you use @code{if}
statements with constant conditions (perhaps determined by macros). Of
course, you can only use this to exclude code, not type definitions or
other preprocessing directives, and you can only do it if the code
remains syntactically valid when it is not to be used.
-GNU C version 3 eliminates this kind of never-executed code even when
+GCC version 3 eliminates this kind of never-executed code even when
not optimizing. Older versions did it only when optimizing.
@menu
@file{config.h}) that is adjusted when the program is compiled. It can
define or not define macros depending on the features of the system and
the desired capabilities of the program. The adjustment can be
-automated by a tool such as @docref{autoconf}, or done by hand.
+automated by a tool such as @command{autoconf}, or done by hand.
@end itemize
@node If
@item
Arithmetic operators for addition, subtraction, multiplication,
division, bitwise operations, shifts, comparisons, and logical
-operations (@samp{&&} and @samp{||}). The latter two obey the usual
+operations (@code{&&} and @code{||}). The latter two obey the usual
short-circuiting rules of standard C.
@item
computation of the expression's value begins.
@item
-Uses of the @samp{defined} operator, which lets you check whether macros
+Uses of the @code{defined} operator, which lets you check whether macros
are defined in the middle of an @samp{#if}.
@item
Identifiers that are not macros, which are all considered to be the
-number zero. This allows you to write @samp{@w{#if MACRO}} instead of
-@samp{@w{#ifdef MACRO}}, if you know that MACRO, when defined, will
+number zero. This allows you to write @code{@w{#if MACRO}} instead of
+@code{@w{#ifdef MACRO}}, if you know that MACRO, when defined, will
always have a nonzero value. Function-like macros used without their
function call parentheses are also treated as zero.
@subsection Defined
@cindex @code{defined}
-The special operator @samp{defined} is used in @samp{#if} and
+The special operator @code{defined} is used in @samp{#if} and
@samp{#elif} expressions to test whether a certain name is defined as a
-macro. @samp{defined @var{name}} and @samp{defined (@var{name})} are
+macro. @code{defined @var{name}} and @code{defined (@var{name})} are
both expressions whose value is 1 if @var{name} is defined as a macro at
-the current point in the program, and 0 otherwise. Thus, @samp{@w{#if
-defined MACRO}} is precisely equivalent to @samp{@w{#ifdef MACRO}}.
+the current point in the program, and 0 otherwise. Thus, @code{@w{#if
+defined MACRO}} is precisely equivalent to @code{@w{#ifdef MACRO}}.
-@samp{defined} is useful when you wish to test more than one macro for
+@code{defined} is useful when you wish to test more than one macro for
existence at once. For example,
@example
@end example
@noindent
-would succeed if either of the names @samp{__vax__} or
-@samp{__ns16000__} is defined as a macro.
+would succeed if either of the names @code{__vax__} or
+@code{__ns16000__} is defined as a macro.
Conditionals written like this:
@end example
@noindent
-can generally be simplified to just @samp{@w{#if BUFSIZE >= 1024}},
-since if @samp{BUFSIZE} is not defined, it will be interpreted as having
+can generally be simplified to just @code{@w{#if BUFSIZE >= 1024}},
+since if @code{BUFSIZE} is not defined, it will be interpreted as having
the value zero.
-If the @samp{defined} operator appears as a result of a macro expansion,
+If the @code{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
+genuine @code{defined} operator and evaluates it normally. It will warn
wherever your code uses this feature if you use the command-line option
@option{-pedantic}, since other compilers may handle it differently.
looks like:
@example
+@group
#if @var{expression}
@var{text-if-true}
#else /* Not @var{expression} */
@var{text-if-false}
#endif /* Not @var{expression} */
+@end group
@end example
+@noindent
If @var{expression} is nonzero, the @var{text-if-true} is included and
the @var{text-if-false} is skipped. If @var{expression} is zero, the
opposite happens.
syntax errors.
One way to avoid this problem is to use an always-false conditional
-instead. For instance, put @samp{#if 0} before the deleted code and
-@samp{#endif} after it. This This works even if the code being turned
+instead. For instance, put @code{#if 0} before the deleted code and
+@code{#endif} after it. This This works even if the code being turned
off contains conditionals, but they must be entire conditionals
(balanced @samp{#if} and @samp{#endif}).
-Some people use @samp{#ifdef notdef} instead. This is risky, because
-@samp{notdef} might be accidentally defined as a macro, and then the
-conditional would succeed. @samp{#if 0} can be counted on to fail.
+Some people use @code{#ifdef notdef} instead. This is risky, because
+@code{notdef} might be accidentally defined as a macro, and then the
+conditional would succeed. @code{#if 0} can be counted on to fail.
-Do not use @samp{#if 0} for comments which are not C code. Use a real
-comment, instead. The interior of @samp{#if 0} must consist of complete
+Do not use @code{#if 0} for comments which are not C code. Use a real
+comment, instead. The interior of @code{#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 don't confuse
+apostrophes). These confuse @code{#if 0}. They don't confuse
@samp{/*}.
@node Diagnostics
outermost macro was used. We intend to be more accurate in the future.
If you write a program which generates source code, such as the
-@code{bison} parser generator, you may want to adjust the preprocessor's
+@command{bison} parser generator, you may want to adjust the preprocessor's
notion of the current file name and line number by hand. Parts of the
-output from @code{bison} are generated from scratch, other parts come
+output from @command{bison} are generated from scratch, other parts come
from a standard parser file. The rest are copied verbatim from
-@code{bison}'s input. You would like compiler error messages and
+@command{bison}'s input. You would like compiler error messages and
symbolic debuggers to be able to refer to @code{bison}'s input file.
@findex #line
-@code{bison} or any such program can arrange this by writing
+@command{bison} or any such program can arrange 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.
A C compiler is free to attach any meaning it likes to other pragmas.
GCC has historically preferred to use extensions to the syntax of the
-language, such as @samp{__attribute__}, for this purpose. However, GCC
+language, such as @code{__attribute__}, for this purpose. However, GCC
does define a few pragmas of its own. These mostly have effects on the
entire translation unit or source file.
In GCC version 3, all GNU-defined, supported pragmas have been given a
-@samp{GCC} prefix. This is in line with the @samp{STDC} prefix on all
+@code{GCC} prefix. This is in line with the @code{STDC} prefix on all
pragmas defined by C99. For backward compatibility, pragmas which were
recognized by previous versions are still recognized without the
-@samp{GCC} prefix, but that usage is deprecated. Some older pragmas are
+@code{GCC} prefix, but that usage is deprecated. Some older pragmas are
deprecated in their entirety. They are not recognized with the
-@samp{GCC} prefix. @xref{Obsolete Features}.
+@code{GCC} prefix. @xref{Obsolete Features}.
@cindex @code{_Pragma}
-C99 introduces the @samp{_Pragma} operator. This feature addresses a
+C99 introduces the @code{@w{_Pragma}} operator. This feature addresses a
major problem with @samp{#pragma}: being a directive, it cannot be
-produced as the result of macro expansion. @samp{_Pragma} is an
-operator, much like @samp{sizeof} or @samp{defined}, and can be embedded
+produced as the result of macro expansion. @code{@w{_Pragma}} is an
+operator, much like @code{sizeof} or @code{defined}, and can be embedded
in a macro.
-The syntax is @code{_Pragma (string-literal)}, where
-@samp{string-literal} can be either a normal or wide-character string
+Its syntax is @code{@w{_Pragma (@var{string-literal})}}, where
+@var{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
@end example
@noindent
-has the same effect as @samp{#pragma GCC dependency "parse.y"}. The
+has the same effect as @code{#pragma GCC dependency "parse.y"}. The
same effect could be achieved using macros, for example
@example
DO_PRAGMA (GCC dependency "parse.y")
@end example
-The standard is unclear on where a @samp{_Pragma} operator can appear.
+The standard is unclear on where a @code{_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
preprocessor itself. Other pragmas are meaningful to the C or C++
compilers. They are documented in the GCC manual.
-@ftable @samp
+@ftable @code
@item #pragma GCC dependency
-@samp{#pragma GCC dependency} allows you to check the relative dates of
+@code{#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 current
file is derived from the other file, and should be regenerated. The
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, you can @dfn{poison} the identifier with this pragma.
-@samp{#pragma GCC poison} is followed by a list of identifiers to
+@code{#pragma GCC poison} is followed by a list of identifiers to
poison. If any of those identifiers appears anywhere in the source
after the directive, it is a hard error. For example,
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{Differences from previous versions}. CPP does
-not insert any whitespace where there was none in the original source,
-except where necessary to prevent an accidental token paste.
+e.g. a single space. In GNU CPP, 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{Differences from previous versions}. CPP does not insert any
+whitespace where there was none in the original source, except where
+necessary to prevent an accidental token paste.
@cindex linemarkers
Source file name and line number information is conveyed by lines
so certain warnings should be suppressed.
@item 4
This indicates that the following text should be treated as being
-wrapped in an implicit @samp{extern "C"} block.
+wrapped in an implicit @code{extern "C"} block.
@c maybe cross reference NO_IMPLICIT_EXTERN_C
@end table
available in traditional C@. (Traditional C does support the @samp{L}
suffix for simple long integer constants.) You are not warned about
uses of these suffixes in macros defined in system headers. For
-instance, @samp{UINT_MAX} may well be defined as @samp{4294967295U}, but
-you will not be warned if you use @samp{UINT_MAX}.
+instance, @code{UINT_MAX} may well be defined as @code{4294967295U}, but
+you will not be warned if you use @code{UINT_MAX}.
You can usually avoid the warning, and the related warning about
constants which are so large that they are unsigned, by writing the
@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
+way; escape sequences such as @samp{\a} are given the values they would
have on the target machine.
Multi-character character constants are interpreted a character at a
character on the host, and adding the new character. For example, 'ab'
on an 8-bit host would be interpreted as @w{'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
+integer type on the host, usually a @code{long}, the excess characters
are ignored and a diagnostic is given.
@item Source file inclusion.
@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.
+The C standard mandates this be at least 63. GNU CPP is limited only by
+available memory.
@item Levels of parenthesised expressions within a full expression.
@item Number of macros simultaneously defined in a single translation unit.
-The standard requires at least 4095 be possible; GNU cpp is limited only
+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.
sequence of tokens; 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{@w{( x + y )}}. Parentheses do not nest inside an
+redefinition.) Thus, @code{(x + y)} is different from @code{(x+y)} but
+equivalent to @code{@w{( x + y )}}. Parentheses do not nest inside an
answer.
@cindex testing predicates
@node Obsolete once-only headers
@subsection Obsolete once-only headers
-GNU C supports two more ways of indicating that a header file should be
+GNU CPP supports two more ways of indicating that a header file should be
read only once. Neither one is as portable as a wrapper @samp{#ifndef},
and we recommend you do not use them in new programs.
@cindex pragma poison
@item @code{#pragma poison}
-This is the same as @samp{#pragma GCC poison}. The version without the
+This is the same as @code{#pragma GCC poison}. The version without the
@code{GCC} prefix is deprecated. @xref{Pragmas}.
@cindex multi-line string constants
@item @samp{##} 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.
+arguments parameter, and the set of tokens specified for that argument
+in the macro invocation was empty, previous versions of GNU CPP 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
@ignore
@c man begin SYNOPSIS
-cpp [@option{-D}@var{macro}[=@var{defn}]...] [@option{-U}@var{macro}]
- [@option{-I}@var{dir}...] [@option{-W}@var{warn}...]
+cpp [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
+ [@option{-I}@var{dir}@dots{}] [@option{-W}@var{warn}@dots{}]
[@option{-M}|@option{-MM}] [@option{-MG}] [@option{-MF} @var{filename}]
- [@option{-MP}] [@option{-MQ} @var{target}...] [@option{-MT} @var{target}...]
+ [@option{-MP}] [@option{-MQ} @var{target}@dots{}] [@option{-MT} @var{target}@dots{}]
[@option{-x} @var{language}] [@option{-std=}@var{standard}]
@var{infile} @var{outfile}
and argument.
@cindex options
-@table @code
+@table @gcctabopt
@item -D @var{name}
-Predefine @var{name} as a macro, with definition @samp{1}.
+Predefine @var{name} as a macro, with definition @code{1}.
@item -D @var{name}=@var{definition}
Predefine @var{name} as a macro, with definition @var{definition}.
its argument list with surrounding parentheses before the equals sign
(if any). Parentheses are meaningful to most shells, so you will need
to quote the option. With @command{sh} and @command{csh},
-@option{-D'@var{name}(@var{args...})=@var{definition}'} works.
+@option{-D'@var{name}(@var{args@dots{}})=@var{definition}'} works.
@item -U @var{name}
Cancel any previous definition of @var{name}, either built in or
@item -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 @option{-include} or
+suitable for @command{make} describing the dependencies of the main
+source file. The preprocessor outputs one @command{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 @option{-include} or
@option{-imacros} command line options.
Unless specified explicitly (with @option{-MT} or @option{-MQ}), the
The rule has no commands.
@item -MM
-Like @option{-M}, but mention only the files included with @samp{#include
-"@var{file}"} or with @option{-include} or @option{-imacros} command line
-options. System header files included with @samp{#include <@var{file}>}
+Like @option{-M}, but mention only the files included with @code{@w{#include
+"@var{file}"}} or with @option{-include} or @option{-imacros} command line
+options. System header files included with @code{@w{#include <@var{file}>}}
are omitted.
@item -MF @var{file}
@item -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.
+dummy rules work around errors @command{make} gives if you remove header
+files without updating the @file{Makefile} to match.
This is typical output:
specify. If you want multiple targets, you can specify them as a single
argument to @option{-MT}, or use multiple @option{-MT} options.
-For example, @samp{@w{-MT '$(objpfx)foo.o'}} might give
+For example, @option{@w{-MT '$(objpfx)foo.o'}} might give
@example
$(objpfx)foo.o: foo.c
@item -MQ @var{target}
Same as @option{-MT}, but it quotes any characters which are special to
-Make. @samp{@w{-MQ '$(objpfx)foo.o'}} gives
+Make. @option{@w{-MQ '$(objpfx)foo.o'}} gives
@example
$$(objpfx)foo.o: foo.c
@item -I-
Split the include path. Any directories specified with @option{-I}
options before @option{-I-} are searched only for headers requested with
-@samp{@w{#include "@var{file}"}}; they are not searched for
-@samp{@w{#include <@var{file}>}}. If additional directories are
+@code{@w{#include "@var{file}"}}; they are not searched for
+@code{@w{#include <@var{file}>}}. If additional directories are
specified with @option{-I} options after the @option{-I-}, those
directories are searched for all @samp{#include} directives.
In addition, @option{-I-} inhibits the use of the directory of the current
-file directory as the first search directory for @samp{@w{#include
+file directory as the first search directory for @code{@w{#include
"@var{file}"}}. @xref{Search Path}.
@item -nostdinc
line of the primary source file. However, 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
+is searched for in the remainder of the @code{#include "@dots{}"} search
chain as normal.
If multiple @option{-include} options are given, the files are included
In this mode the integrated preprocessor is little more than a tokenizer
for the front ends.
-@samp{-fpreprocessed} is implicit if the input file has one of the
+@option{-fpreprocessed} is implicit if the input file has one of the
extensions @samp{.i}, @samp{.ii} or @samp{.mi}. These are the
extensions that GCC uses for preprocessed files created by
@option{-save-temps}.
@item -fno-show-column
Do not print column numbers in diagnostics. This may be necessary if
diagnostics are being scanned by a program that does not understand the
-column numbers, such as @code{dejagnu}.
+column numbers, such as @command{dejagnu}.
@item -A @var{predicate}=@var{answer}
Make an assertion with the predicate @var{predicate} and answer
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
+Assuming you have no file @file{foo.h}, the command
@example
touch foo.h; cpp -dM foo.h
@item -gcc
Define the macros @sc{__gnuc__}, @sc{__gnuc_minor__} and
@sc{__gnuc_patchlevel__}. These are defined automatically when you use
-@samp{gcc -E}; you can turn them off in that case with @option{-no-gcc}.
+@command{gcc -E}; you can turn them off in that case with
+@option{-no-gcc}.
@item -traditional
Try to imitate the behavior of old-fashioned C, as opposed to ISO
@item -$
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.
+identifiers. By default GNU CPP permits @samp{$}, a common extension.
@item -h
@itemx --help
projects / gcc.git / commitdiff