\input texinfo
-@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-@c 2001, 2002, 2003, 2004, 2005, 2006
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1991-2022 Free Software Foundation, Inc.
@setfilename internals.info
@node Top
@top Assembler Internals
@cindex symbolS structure
The definition for the symbol structure, @code{symbolS}, is located in
-@file{struc-symbol.h}.
+@file{symbols.c}.
-In general, the fields of this structure may not be referred to directly.
+The fields of this structure may not be referred to directly.
Instead, you must use one of the accessor functions defined in @file{symbol.h}.
-These accessor functions should work for any GAS version.
Symbol structures contain the following fields:
@cindex S_IS_EXTERNAL
Return non-zero if the symbol is externally visible.
-@item S_IS_EXTERN
-@cindex S_IS_EXTERN
-A synonym for @code{S_IS_EXTERNAL}. Don't use it.
-
@item S_IS_WEAK
@cindex S_IS_WEAK
Return non-zero if the symbol is weak, or if it is a @code{weakref} alias or
be determined upon use.
@item S_GET_TYPE
-@item S_GET_DESC
-@item S_GET_OTHER
+@itemx S_GET_DESC
+@itemx S_GET_OTHER
@cindex S_GET_TYPE
@cindex S_GET_DESC
@cindex S_GET_OTHER
a.out).
@item S_SET_TYPE
-@item S_SET_DESC
-@item S_SET_OTHER
+@itemx S_SET_DESC
+@itemx S_SET_OTHER
@cindex S_SET_TYPE
@cindex S_SET_DESC
@cindex S_SET_OTHER
@code{symbolS} (which also automatically creates a bfd @code{asymbol}
structure), so this saves space when assembling large files.
-The first field of @code{symbolS} is @code{bsym}, the pointer to the BFD
-symbol. The first field of @code{struct local_symbol} is a pointer which is
-always set to NULL. This is how the symbol accessor functions can distinguish
-local symbols from ordinary symbols. The symbol accessor functions
-automatically convert a local symbol into an ordinary symbol when necessary.
-
@node Expressions
@subsection Expressions
@cindex internals, expressions
@cindex porting
Each GAS target specifies two main things: the CPU file and the object format
-file. Two main switches in the @file{configure.in} file handle this. The
+file. Two main switches in the @file{configure.ac} file handle this. The
first switches on CPU type to set the shell variable @code{cpu_type}. The
second switches on the entire target to set the shell variable @code{fmt}.
@item tc_comment_chars
@cindex tc_comment_chars
If this macro is defined, GAS will use it instead of @code{comment_chars}.
+This has the advantage that this macro does not have to refer to a constant
+array.
@item tc_symbol_chars
@cindex tc_symbol_chars
if found in a comment, such as after a character in line_comment_chars or
comment_chars.
+@item tc_line_separator_chars
+@cindex tc_line_separator_chars
+If this macro is defined, GAS will use it instead of
+@code{line_separator_chars}. This has the advantage that this macro does not
+have to refer to a constant array.
+
+
@item EXP_CHARS
@cindex EXP_CHARS
This is a null terminated @code{const char} array of characters which may be
codes, are typically entered directly into the symbol table when @code{md_begin}
is called. One argument is passed, a @code{char *} for the symbol.
+@item md_resolve_symbol
+@cindex md_resolve_symbol
+If this macro is defined, GAS will call it upon resolving machine-dependent
+symbols (that is, for any symbol with operation O_md1..O_md32 inclusively).
+If this functions returns zero, then the symbol could not be resolved.
+
@item md_operand
@cindex md_operand
GAS will call this function with one argument, an @code{expressionS}
is called, @code{input_line_pointer} will point to the start of the
expression.
+@item md_register_arithmetic
+@cindex md_register_arithmetic
+If this macro is defined and evaluates to zero then GAS will not fold
+expressions that add or subtract a constant to/from a register to give
+another register. For example GAS's default behaviour is to fold the
+expression "r8 + 1" into "r9", which is probably not the result
+intended by the programmer. The default is to allow such folding,
+since this maintains backwards compatibility with earlier releases of
+GAS.
+
@item tc_unrecognized_line
@cindex tc_unrecognized_line
If you define this macro, GAS will call it when it finds a line that it can not
pseudo-op such as @code{.word}. You can use this to recognize relocation
directives that may appear in such directives.
-@item BITFIELD_CONS_EXPRESSION
-@cindex BITFIELD_CONS_EXPRESSION
-If you define this macro, GAS will recognize bitfield instructions in data
-allocation pseudo-ops, as used on the i960.
-
@item REPEAT_CONS_EXPRESSION
@cindex REPEAT_CONS_EXPRESSION
If you define this macro, GAS will recognize repeat counts in data allocation
@item TC_ADDRESS_BYTES
@cindex TC_ADDRESS_BYTES
Define this macro to specify the number of bytes used to store an address.
-Used to implement @code{dc.a}. The target must have a reloc for this size.
+Used to implement @code{dc.a}. If not defined by the target, a default will
+be supplied. Targets are assumed to have a reloc for this size.
@item TC_INIT_FIX_DATA (@var{fixp})
@cindex TC_INIT_FIX_DATA
A C statement to output target specific debugging information for
fixup @var{fixp} to @var{stream}. This macro is called by @code{print_fixup}.
-@item TC_FRAG_INIT (@var{fragp})
+@item TC_FRAG_INIT (@var{fragp}, @var{max_bytes})
@cindex TC_FRAG_INIT
-A C statement to initialize the target specific fields of frag @var{fragp}.
-These fields are defined with the @code{TC_FRAG_TYPE} macro.
+A C statement to initialize the target specific fields of frag @var{fragp}
+with maximum number of bytes @var{max_bytes}. These fields are defined
+with the @code{TC_FRAG_TYPE} macro.
@item md_number_to_chars
@cindex md_number_to_chars
@cindex md_atof
This function is called to convert an ASCII string into a floating point value
in format used by the CPU. It takes three arguments. The first is @var{type}
-which is a byte describing the type of floating point number to be created.
-Possible values are @var{'f'} or @var{'s'} for single precision, @var{'d'} or
-@var{'r'} for double precision and @var{'x'} or @var{'p'} for extended
-precision. Either lower or upper case versions of these letters can be used.
+which is a byte describing the type of floating point number to be created. It
+is one of the characters defined in the @code{FLT_CHARS} macro. Possible
+values are @var{'f'} or @var{'s'} for single precision, @var{'d'} or @var{'r'}
+for double precision and @var{'x'} or @var{'p'} for extended precision. Either
+lower or upper case versions of these letters can be used. Note: some targets
+do not support all of these types, and some targets may also support other
+types not mentioned here.
The second parameter is @var{litP} which is a pointer to a byte array where the
-converted value should be stored. The third argument is @var{sizeP}, which is
-a pointer to a integer that should be filled in with the number of
-@var{LITTLENUM}s emitted into the byte array. (@var{LITTLENUM} is defined in
-gas/bignum.h). The function should return NULL upon success or an error string
-upon failure.
+converted value should be stored. The value is converted into LITTLENUMs and
+is stored in the target's endian-ness order. (@var{LITTLENUM} is defined in
+gas/bignum.h). Single precision values occupy 2 littlenums. Double precision
+values occupy 4 littlenums and extended precision values occupy either 5 or 6
+littlenums, depending upon the target.
+
+The third argument is @var{sizeP}, which is a pointer to a integer that should
+be filled in with the number of chars emitted into the byte array.
+
+The function should return NULL upon success or an error string upon failure.
@item TC_LARGEST_EXPONENT_IS_NORMAL
@cindex TC_LARGEST_EXPONENT_IS_NORMAL (@var{precision})
machine independent code knows how to use such a table to relax PC relative
references. See @file{tc-m68k.c} for an example. @xref{Relaxation}.
+@item md_generic_table_relax_frag
+@cindex md_generic_table_relax_frag
+If defined, it is a C statement that is invoked, instead of
+the default implementation, to scan @code{TC_GENERIC_RELAX_TABLE}.
+
@item md_prepare_relax_scan
@cindex md_prepare_relax_scan
If defined, it is a C statement that is invoked prior to scanning
@item LINKER_RELAXING_SHRINKS_ONLY
@cindex LINKER_RELAXING_SHRINKS_ONLY
If you define this macro, and the global variable @samp{linkrelax} is set
-(because of a command line option, or unconditionally in @code{md_begin}), a
+(because of a command-line option, or unconditionally in @code{md_begin}), a
@samp{.align} directive will cause extra space to be allocated. The linker can
then discard this space when relaxing the section.
@cindex TC_FINALIZE_SYMS_BEFORE_SIZE_SEG
Specifies the value to be assigned to @code{finalize_syms} before the function
@code{size_segs} is called. Since @code{size_segs} calls @code{cvt_frag_to_fill}
-which can call @code{md_convert_frag}, this constant governs whether the symbols
+which can call @code{md_convert_frag}, this constant governs whether the symbols
accessed in @code{md_convert_frag} will be fully resolved. In particular it
governs whether local symbols will have been resolved, and had their frag
information removed. Depending upon the processing performed by
@cindex TC_FORCE_RELOCATION_LOCAL
Like @code{TC_FORCE_RELOCATION}, but used only for fixup expressions against a
symbol in the current section. If undefined, fixups that are not
-@code{fx_pcrel} or @code{fx_plt} or for which @code{TC_FORCE_RELOCATION}
+@code{fx_pcrel} or for which @code{TC_FORCE_RELOCATION}
returns non-zero, will emit relocs.
@item TC_FORCE_RELOCATION_SUB_SAME (@var{fix}, @var{seg})
difference of two symbols in the same section. If this macro returns zero,
the subtrahend will be resolved and @code{fx_subsy} set to @code{NULL} for
@code{md_apply_fix}. If undefined, the default of
-@w{@code{! SEG_NORMAL (@var{seg}) || TC_FORCE_RELOCATION (@var{fix})}} will
-be used.
+@w{@code{! SEG_NORMAL (@var{seg})}} will be used.
-@item TC_FORCE_RELOCATION_SUB_ABS (@var{fix})
+@item TC_FORCE_RELOCATION_SUB_ABS (@var{fix}, @var{seg})
@cindex TC_FORCE_RELOCATION_SUB_ABS
Like @code{TC_FORCE_RELOCATION_SUB_SAME}, but used when the subtrahend is an
absolute symbol. If the macro is undefined a default of @code{0} is used.
-@item TC_FORCE_RELOCATION_SUB_LOCAL (@var{fix})
+@item TC_FORCE_RELOCATION_SUB_LOCAL (@var{fix}, @var{seg})
@cindex TC_FORCE_RELOCATION_SUB_LOCAL
Like @code{TC_FORCE_RELOCATION_SUB_ABS}, but the subtrahend is a symbol in the
same section as the fixup.
-@item TC_VALIDATE_FIX_SUB (@var{fix})
+@item TC_VALIDATE_FIX_SUB (@var{fix}, @var{seg})
@cindex TC_VALIDATE_FIX_SUB
This macro is evaluated for any fixup with a @code{fx_subsy} that
@code{fixup_segment} cannot reduce to a number. If the macro returns
@code{false} an error will be reported.
+@item TC_GLOBAL_REGISTER_SYMBOL_OK
+@cindex TC_GLOBAL_REGISTER_SYMBOL_OK
+Define this macro if global register symbols are supported. The default
+is to disallow global register symbols.
+
@item MD_APPLY_SYM_VALUE (@var{fix})
@cindex MD_APPLY_SYM_VALUE
This macro controls whether the symbol value becomes part of the value passed
@cindex tc_frob_label
If you define this macro, GAS will call it each time a label is defined.
+@item tc_new_dot_label
+@cindex tc_new_dot_label
+If you define this macro, GAS will call it each time a fake label is created
+off the special dot symbol.
+
@item md_section_align
@cindex md_section_align
GAS will call this function for each section at the end of the assembly, to
If you define this macro, GAS will call it after the relocs have been
generated.
+@item tc_cfi_reloc_for_encoding
+@cindex tc_cfi_reloc_for_encoding
+This macro is used to indicate whether a cfi encoding requires a relocation.
+It should return the required relocation type. Defining this macro implies
+that Compact EH is supported.
+
@item md_post_relax_hook
If you define this macro, GAS will call it after relaxing and sizing the
segments.
a new section's attributes when a directive has no valid flags or when the
flag is @code{w}. The default value of the macro is @code{SEC_LOAD | SEC_DATA}.
-@item DWARF2_FORMAT ()
+@item DWARF2_FORMAT (@var{sec})
@cindex DWARF2_FORMAT
If you define this, it should return one of @code{dwarf2_format_32bit},
@code{dwarf2_format_64bit}, or @code{dwarf2_format_64bit_irix} to indicate
If you don't define this, @code{dwarf2_format_32bit} will be used as
the default.
-This define only affects @code{.debug_info} and @code{.debug_line}
+This define only affects debug
sections generated by the assembler. DWARF 2 sections generated by
other tools will be unaffected by this setting.
backend. This format will be used when generating assembler specific debug
information.
+@item md_emit_single_noop_insn
+@itemx md_single_noop_insn
+These macro facilitate the @var{.nop} directive. If defined the
+@var{md_emit_single_noop_insn) macro provides code to insert a single no-op
+instruction into the output stream. If this involves calling @var{md_assemble}
+with a fixed string then the alternative macro @var{md_single_noop_insn} can be
+defined, specifying the string to pass. If neither of these macros are defined
+then the @var{.nop} directive will call @var{md_assemble} with the string
+@option{nop}.
+
+@item md_allow_local_subtract (@var{left}, @var{right}, @var{section})
+If defined, GAS will call this macro when evaluating an expression which is the
+difference of two symbols defined in the same section. It takes three
+arguments: @code{expressioS * @var{left}} which is the symbolic expression on
+the left hand side of the subtraction operation, @code{expressionS *
+@var{right}} which is the symbolic expression on the right hand side of the
+subtraction, and @code{segT @var{section}} which is the section containing the two
+symbols. The macro should return a non-zero value if the expression should be
+evaluated. Targets which implement link time relaxation which may change the
+position of the two symbols relative to each other should ensure that this
+macro returns zero in situations where this can occur.
+
+@item md_allow_eh_opt
+If defined, GAS will check this macro before performing any optimizations on
+the DWARF call frame debug information that is emitted. Targets which
+implement link time relaxation may need to define this macro and set it to zero
+if it is possible to change the size of a function's prologue.
@end table
@node Object format backend
@item obj_begin
If you define this macro, GAS will call it at the start of the assembly, after
-the command line arguments have been parsed and all the machine independent
+the command-line arguments have been parsed and all the machine independent
initializations have been completed.
@item obj_app_file
while still preserving intra-section references and meeting alignment
requirements.
-For the i960 using b.out format, no expansion is done; instead, each
-@samp{.align} directive causes extra space to be allocated, enough that when
-the linker is relaxing a section and removing unneeded space, it can discard
-some or all of this extra padding and cause the following data to be correctly
-aligned.
-
For the H8/300, I think the linker expands calls that can't reach, and doesn't
worry about alignment issues; the cpu probably never needs any significant
alignment beyond the instruction size.
original filename and line number that they are applicable to.
@end deftypefun
-@deftypefun @{@} void sprint_value (char *@var{buf}, valueT @var{val})
-This function is helpful for converting a @code{valueT} value into printable
-format, in case it's wider than modes that @code{*printf} can handle. If the
-type is narrow enough, a decimal number will be produced; otherwise, it will be
-in hexadecimal. The value itself is not examined to make this determination.
-@end deftypefun
-
-@node Hash tables
-@subsection Hash tables
-@cindex hash tables
-
-@deftypefun @{@} @{struct hash_control *@} hash_new (void)
-Creates the hash table control structure.
-@end deftypefun
-
-@deftypefun @{@} void hash_die (struct hash_control *)
-Destroy a hash table.
-@end deftypefun
-
-@deftypefun @{@} PTR hash_delete (struct hash_control *, const char *)
-Deletes entry from the hash table, returns the value it had.
-@end deftypefun
-
-@deftypefun @{@} PTR hash_replace (struct hash_control *, const char *, PTR)
-Updates the value for an entry already in the table, returning the old value.
-If no entry was found, just returns NULL.
-@end deftypefun
-
-@deftypefun @{@} @{const char *@} hash_insert (struct hash_control *, const char *, PTR)
-Inserting a value already in the table is an error.
-Returns an error message or NULL.
-@end deftypefun
-
-@deftypefun @{@} @{const char *@} hash_jam (struct hash_control *, const char *, PTR)
-Inserts if the value isn't already present, updates it if it is.
-@end deftypefun
-
@node Test suite
@section Test suite
@cindex test suite
projects / binutils-gdb.git / blobdiff