\input texinfo
+@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
+@c 2001, 2002, 2003
+@c Free Software Foundation, Inc.
@setfilename internals.info
@node Top
@top Assembler Internals
This chapter describes the internals of the assembler. It is incomplete, but
it may help a bit.
-This chapter was last modified on $Date$. It is not updated regularly, and it
-may be out of date.
+This chapter is not updated regularly, and it may be out of date.
@menu
* GAS versions:: GAS versions
@item sy_value
This is an @code{expressionS} that describes the value of the symbol. It might
refer to one or more other symbols; if so, its true value may not be known
-until @code{resolve_symbol_value} is called in @code{write_object_file}.
+until @code{resolve_symbol_value} is called with @var{finalize_syms} non-zero
+in @code{write_object_file}.
The expression is often simply a constant. Before @code{resolve_symbol_value}
-is called, the value is the offset from the frag (@pxref{Frags}). Afterward,
-the frag address has been added in.
+is called with @var{finalize_syms} set, the value is the offset from the frag
+(@pxref{Frags}). Afterward, the frag address has been added in.
@item sy_resolved
This field is non-zero if the symbol's value has been completely resolved. It
@item S_GET_VALUE
@cindex S_GET_VALUE
Get the symbol's value. This will cause @code{resolve_symbol_value} to be
-called if necessary, so @code{S_GET_VALUE} should only be called when it is
-safe to resolve symbols (i.e., after the entire input file has been read and
-all symbols have been defined).
+called if necessary.
@item S_SET_SEGMENT
@cindex S_SET_SEGMENT
An @code{operatorT} value of @code{O_big} indicates either a floating point
number, stored in the global variable @code{generic_floating_point_number}, or
-an integer to large to store in an @code{offsetT} type, stored in the global
+an integer too large to store in an @code{offsetT} type, stored in the global
array @code{generic_bignum}. This rather inflexible approach makes it
impossible to use floating point numbers or large expressions in complex
expressions.
@item fx_addnumber
Some CPU backends use this field to convey information between
-@code{md_apply_fix} and @code{tc_gen_reloc}. The machine independent code does
+@code{md_apply_fix3} and @code{tc_gen_reloc}. The machine independent code does
not use it.
@item fx_next
have this type.
@item rs_leb128
-This state is used to implement the DWARF ``little endian base 128''
+This state is used to implement the DWARF ``little endian base 128''
variable length number format. The @code{fr_symbol} is always an expression
symbol, as constant expressions are emitted directly. The @code{fr_offset}
field is used during relaxation to hold the previous size of the number so
configuration process will create a file named @file{targ-env.h} in the build
directory which includes @file{te-@var{em}.h}.
+There is a special case for COFF. For historical reason, the GNU COFF
+assembler doesn't follow the documented behavior on certain debug symbols for
+the compatibility with other COFF assemblers. A port can define
+@code{STRICTCOFF} in the configure script to make the GNU COFF assembler
+to follow the documented behavior.
+
Porting GAS to a new CPU requires writing the @file{tc-@var{CPU}} files.
Porting GAS to a new object file format requires writing the
@file{obj-@var{fmt}} files. There is sometimes some interaction between these
@itemx md_longopts_size
@itemx md_parse_option
@itemx md_show_usage
+@itemx md_after_parse_args
@cindex md_shortopts
@cindex md_longopts
@cindex md_longopts_size
@cindex md_parse_option
@cindex md_show_usage
+@cindex md_after_parse_args
GAS uses these variables and functions during option processing.
@code{md_shortopts} is a @code{const char *} which GAS adds to the machine
independent string passed to @code{getopt}. @code{md_longopts} is a
unrecognized code, presumably indicating a special code value which appears in
@code{md_longopts}. GAS will call @code{md_show_usage} when a usage message is
printed; it should print a description of the machine specific options.
+@code{md_after_pase_args}, if defined, is called after all options are
+processed, to let the backend override settings done by the generic option
+parsing.
@item md_begin
@cindex md_begin
If this macro is defined, GAS will call it with a @code{pseudo_typeS} argument.
It should return non-zero if the pseudo-op is a conditional which controls
whether code is assembled, such as @samp{.if}. GAS knows about the normal
-conditional pseudo-ops,and you should normally not have to define this macro.
+conditional pseudo-ops, and you should normally not have to define this macro.
@item comment_chars
@cindex comment_chars
@item line_separator_chars
@cindex line_separator_chars
This is a null terminated @code{const char} array of characters which separate
-lines (semicolon and newline are such characters by default, and need not be
-listed in this array).
+lines (null and newline are such characters by default, and need not be
+listed in this array). Note that line_separator_chars do not separate lines
+if found in a comment, such as after a character in line_comment_chars or
+comment_chars.
@item EXP_CHARS
@cindex EXP_CHARS
@item LEX_AT
@cindex LEX_AT
-You may define this macro to the lexical type of the @kbd{@}} character. The
+You may define this macro to the lexical type of the @kbd{@@} character. The
default is zero.
Lexical types are a combination of @code{LEX_NAME} and @code{LEX_BEGIN_NAME},
both defined in @file{read.h}. @code{LEX_NAME} indicates that the character
may appear in a name. @code{LEX_BEGIN_NAME} indicates that the character may
-appear at the beginning of a nem.
+appear at the beginning of a name.
@item LEX_BR
@cindex LEX_BR
You may define this macro to the lexical type of the @kbd{$} character. The
default value is @code{LEX_NAME | LEX_BEGIN_NAME}.
+@item NUMBERS_WITH_SUFFIX
+@cindex NUMBERS_WITH_SUFFIX
+When this macro is defined to be non-zero, the parser allows the radix of a
+constant to be indicated with a suffix. Valid suffixes are binary (B),
+octal (Q), and hexadecimal (H). Case is not significant.
+
@item SINGLE_QUOTE_STRINGS
@cindex SINGLE_QUOTE_STRINGS
If you define this macro, GAS will treat single quotes as string delimiters.
is a label, even if it does not have a colon.
@item TC_START_LABEL
+@itemx TC_START_LABEL_WITHOUT_COLON
@cindex TC_START_LABEL
You may define this macro to control what GAS considers to be a label. The
default definition is to accept any name followed by a colon character.
+@item TC_START_LABEL_WITHOUT_COLON
+@cindex TC_START_LABEL_WITHOUT_COLON
+Same as TC_START_LABEL, but should be used instead of TC_START_LABEL when
+LABELS_WITHOUT_COLONS is defined.
+
@item NO_PSEUDO_DOT
@cindex NO_PSEUDO_DOT
If you define this macro, GAS will not require pseudo-ops to start with a
@item TC_EQUAL_IN_INSN
@cindex TC_EQUAL_IN_INSN
If you define this macro, it should return nonzero if the instruction is
-permitted to contain an @kbd{=} character. GAS will use this to decide if a
+permitted to contain an @kbd{=} character. GAS will call it with two
+arguments, the character before the @kbd{=} character, and the value of
+@code{input_line_pointer} at that point. GAS uses this macro to decide if a
@kbd{=} is an assignment or an instruction.
@item TC_EOL_IN_INSN
name or value changes dynamically, possibly in a context sensitive way.
Predefined symbols with fixed values, such as register names or condition
codes, are typically entered directly into the symbol table when @code{md_begin}
-is called.
+is called. One argument is passed, a @code{char *} for the symbol.
@item md_operand
@cindex md_operand
-GAS will call this function for any expression that can not be recognized.
-When the function is called, @code{input_line_pointer} will point to the start
-of the expression.
+GAS will call this function with one argument, an @code{expressionS}
+pointer, for any expression that can not be recognized. When the function
+is called, @code{input_line_pointer} will point to the start of the
+expression.
@item tc_unrecognized_line
@cindex tc_unrecognized_line
You may define this macro to do special handling for an alignment directive.
GAS will call it at the end of the assembly.
+@item TC_IMPLICIT_LCOMM_ALIGNMENT (@var{size}, @var{p2var})
+@cindex TC_IMPLICIT_LCOMM_ALIGNMENT
+An @code{.lcomm} directive with no explicit alignment parameter will use this
+macro to set @var{p2var} to the alignment that a request for @var{size} bytes
+will have. The alignment is expressed as a power of two. If no alignment
+should take place, the macro definition should do nothing. Some targets define
+a @code{.bss} directive that is also affected by this macro. The default
+definition will set @var{p2var} to the truncated power of two of sizes up to
+eight bytes.
+
@item md_flush_pending_output
@cindex md_flush_pending_output
If you define this macro, GAS will call it each time it skips any space because of a
is a runtime decision. On other targets, @code{md_number_to_chars} can be a
simple macro.
+@item md_atof (@var{type},@var{litP},@var{sizeP})
+@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.
+
+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.
+
+@item TC_LARGEST_EXPONENT_IS_NORMAL
+@cindex TC_LARGEST_EXPONENT_IS_NORMAL (@var{precision})
+This macro is used only by @file{atof-ieee.c}. It should evaluate to true
+if floats of the given precision use the largest exponent for normal numbers
+instead of NaNs and infinities. @var{precision} is @samp{F_PRECISION} for
+single precision, @samp{D_PRECISION} for double precision, or
+@samp{X_PRECISION} for extended double precision.
+
+The macro has a default definition which returns 0 for all cases.
+
@item md_reloc_size
@cindex md_reloc_size
This variable is only used in the original version of gas (not
@itemx md_long_jump_size
@itemx md_create_short_jump
@itemx md_create_long_jump
+@itemx TC_CHECK_ADJUSTED_BROKEN_DOT_WORD
@cindex WORKING_DOT_WORD
@cindex md_short_jump_size
@cindex md_long_jump_size
@cindex md_create_short_jump
@cindex md_create_long_jump
+@cindex TC_CHECK_ADJUSTED_BROKEN_DOT_WORD
If @code{WORKING_DOT_WORD} is defined, GAS will not do broken word processing
(@pxref{Broken words}). Otherwise, you should set @code{md_short_jump_size} to
-the size of a short jump (a jump that is just long enough to jump around a long
-jmp) and @code{md_long_jump_size} to the size of a long jump (a jump that can
-go anywhere in the function), You should define @code{md_create_short_jump} to
-create a short jump around a long jump, and define @code{md_create_long_jump}
-to create a long jump.
+the size of a short jump (a jump that is just long enough to jump around a
+number of long jumps) and @code{md_long_jump_size} to the size of a long jump
+(a jump that can go anywhere in the function). You should define
+@code{md_create_short_jump} to create a short jump around a number of long
+jumps, and define @code{md_create_long_jump} to create a long jump.
+If defined, the macro TC_CHECK_ADJUSTED_BROKEN_DOT_WORD will be called for each
+adjusted word just before the word is output. The macro takes two arguments,
+an @code{addressT} with the adjusted word and a pointer to the current
+@code{struct broken_word}.
@item md_estimate_size_before_relax
@cindex md_estimate_size_before_relax
@item md_relax_frag
@cindex md_relax_frag
-This macro may be defined to relax a frag. GAS will call this with the frag
-and the change in size of all previous frags; @code{md_relax_frag} should
-return the change in size of the frag. @xref{Relaxation}.
+This macro may be defined to relax a frag. GAS will call this with the
+segment, the frag, and the change in size of all previous frags;
+@code{md_relax_frag} should return the change in size of the frag.
+@xref{Relaxation}.
@item TC_GENERIC_RELAX_TABLE
@cindex TC_GENERIC_RELAX_TABLE
@samp{.align} directive will cause extra space to be allocated. The linker can
then discard this space when relaxing the section.
+@item TC_LINKRELAX_FIXUP (@var{segT})
+@cindex TC_LINKRELAX_FIXUP
+If defined, this macro allows control over whether fixups for a
+given section will be processed when the @var{linkrelax} variable is
+set. The macro is given the N_TYPE bits for the section in its
+@var{segT} argument. If the macro evaluates to a non-zero value
+then the fixups will be converted into relocs, otherwise they will
+be passed to @var{md_apply_fix3} as normal.
+
@item md_convert_frag
@cindex md_convert_frag
GAS will call this for each rs_machine_dependent fragment.
It may also create any necessary relocations.
@xref{Relaxation}.
-@item md_apply_fix
-@cindex md_apply_fix
-GAS will call this for each fixup. It should store the correct value in the
-object file. @code{fixup_segment} performs a generic overflow check on the
-@code{valueT *val} argument after @code{md_apply_fix} returns. If the overflow
-check is relevant for the target machine, then @code{md_apply_fix} should
-modify @code{valueT *val}, typically to the value stored in the object file.
-
-@item TC_HANDLES_FX_DONE
-@cindex TC_HANDLES_FX_DONE
-If this macro is defined, it means that @code{md_apply_fix} correctly sets the
-@code{fx_done} field in the fixup.
+@item TC_FINALIZE_SYMS_BEFORE_SIZE_SEG
+@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
+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
+@code{md_convert_frag} the frag information may or may not be necessary, as may
+the resolved values of the symbols. The default value is 1.
+
+@item TC_VALIDATE_FIX (@var{fixP}, @var{seg}, @var{skip})
+@cindex TC_VALIDATE_FIX
+This macro is evaluated for each fixup (when @var{linkrelax} is not set).
+It may be used to change the fixup in @code{struct fix *@var{fixP}} before
+the generic code sees it, or to fully process the fixup. In the latter case,
+a @code{goto @var{skip}} will bypass the generic code.
+
+@item md_apply_fix3 (@var{fixP}, @var{valP}, @var{seg})
+@cindex md_apply_fix3
+GAS will call this for each fixup that passes the @code{TC_VALIDATE_FIX} test
+when @var{linkrelax} is not set. It should store the correct value in the
+object file. @code{struct fix *@var{fixP}} is the fixup @code{md_apply_fix3}
+is operating on. @code{valueT *@var{valP}} is the value to store into the
+object files, or at least is the generic code's best guess. Specifically,
+*@var{valP} is the value of the fixup symbol, perhaps modified by
+@code{MD_APPLY_SYM_VALUE}, plus @code{@var{fixP}->fx_offset} (symbol addend),
+less @code{MD_PCREL_FROM_SECTION} for pc-relative fixups.
+@code{segT @var{seg}} is the section the fix is in.
+@code{fixup_segment} performs a generic overflow check on *@var{valP} after
+@code{md_apply_fix3} returns. If the overflow check is relevant for the target
+machine, then @code{md_apply_fix3} should modify *@var{valP}, typically to the
+value stored in the object file.
+
+@item TC_FORCE_RELOCATION (@var{fix})
+@cindex TC_FORCE_RELOCATION
+If this macro returns non-zero, it guarantees that a relocation will be emitted
+even when the value can be resolved locally, as @code{fixup_segment} tries to
+reduce the number of relocations emitted. For example, a fixup expression
+against an absolute symbol will normally not require a reloc. If undefined,
+a default of @w{@code{(S_FORCE_RELOC ((@var{fix})->fx_addsy))}} is used.
+
+@item TC_FORCE_RELOCATION_ABS (@var{fix})
+@cindex TC_FORCE_RELOCATION_ABS
+Like @code{TC_FORCE_RELOCATION}, but used only for fixup expressions against an
+absolute symbol. If undefined, @code{TC_FORCE_RELOCATION} will be used.
+
+@item TC_FORCE_RELOCATION_LOCAL (@var{fix})
+@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}
+returns non-zero, will emit relocs.
+
+@item TC_FORCE_RELOCATION_SUB_SAME (@var{fix}, @var{seg})
+@cindex TC_FORCE_RELOCATION_SUB_SAME
+This macro controls resolution of fixup expressions involving the
+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_fix3}. If undefined, the default of
+@w{@code{! SEG_NORMAL (@var{seg}) || TC_FORCE_RELOCATION (@var{fix})}} will
+be used.
+
+@item TC_FORCE_RELOCATION_SUB_ABS (@var{fix})
+@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})
+@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})
+@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 MD_APPLY_SYM_VALUE (@var{fix})
+@cindex MD_APPLY_SYM_VALUE
+This macro controls whether the symbol value becomes part of the value passed
+to @code{md_apply_fix3}. If the macro is undefined, or returns non-zero, the
+symbol value will be included. For ELF, a suitable definition might simply be
+@code{0}, because ELF relocations don't include the symbol value in the addend.
+
+@item S_FORCE_RELOC (@var{sym}, @var{strict})
+@cindex S_FORCE_RELOC
+This macro (or function, for @code{BFD_ASSEMBLER} gas) returns true for symbols
+that should not be reduced to section symbols or eliminated from expressions,
+because they may be overridden by the linker. ie. for symbols that are
+undefined or common, and when @var{strict} is set, weak, or global (for ELF
+assemblers that support ELF shared library linking semantics).
+
+@item EXTERN_FORCE_RELOC
+@cindex EXTERN_FORCE_RELOC
+This macro controls whether @code{S_FORCE_RELOC} returns true for global
+symbols. If undefined, the default is @code{true} for ELF assemblers, and
+@code{false} for non-ELF.
@item tc_gen_reloc
@cindex tc_gen_reloc
symbol should be adjusted to be against the section symbol. It should return a
non-zero value if the adjustment is acceptable.
-@item MD_PCREL_FROM_SECTION
+@item MD_PCREL_FROM_SECTION (@var{fixp}, @var{section})
@cindex MD_PCREL_FROM_SECTION
-If you define this macro, it should return the offset between the address of a
-PC relative fixup and the position from which the PC relative adjustment should
-be made. On many processors, the base of a PC relative instruction is the next
-instruction, so this macro would return the length of an instruction.
+If you define this macro, it should return the position from which the PC
+relative adjustment for a PC relative fixup should be made. On many
+processors, the base of a PC relative instruction is the next instruction,
+so this macro would return the length of an instruction, plus the address of
+the PC relative fixup. The latter can be calculated as
+@var{fixp}->fx_where + @var{fixp}->fx_frag->fr_address .
@item md_pcrel_from
@cindex md_pcrel_from
@item md_section_align
@cindex md_section_align
GAS will call this function for each section at the end of the assembly, to
-permit the CPU backend to adjust the alignment of a section.
+permit the CPU backend to adjust the alignment of a section. The function
+must take two arguments, a @code{segT} for the section and a @code{valueT}
+for the size of the section, and return a @code{valueT} for the rounded
+size.
+
+@item md_macro_start
+@cindex md_macro_start
+If defined, GAS will call this macro when it starts to include a macro
+expansion. @code{macro_nest} indicates the current macro nesting level, which
+includes the one being expanded.
+
+@item md_macro_info
+@cindex md_macro_info
+If defined, GAS will call this macro after the macro expansion has been
+included in the input and after parsing the macro arguments. The single
+argument is a pointer to the macro processing's internal representation of the
+macro (macro_entry *), which includes expansion of the formal arguments.
+
+@item md_macro_end
+@cindex md_macro_end
+Complement to md_macro_start. If defined, it is called when finished
+processing an inserted macro expansion, just before decrementing macro_nest.
+
+@item DOUBLEBAR_PARALLEL
+@cindex DOUBLEBAR_PARALLEL
+Affects the preprocessor so that lines containing '||' don't have their
+whitespace stripped following the double bar. This is useful for targets that
+implement parallel instructions.
+
+@item KEEP_WHITE_AROUND_COLON
+@cindex KEEP_WHITE_AROUND_COLON
+Normally, whitespace is compressed and removed when, in the presence of the
+colon, the adjoining tokens can be distinguished. This option affects the
+preprocessor so that whitespace around colons is preserved. This is useful
+when colons might be removed from the input after preprocessing but before
+assembling, so that adjoining tokens can still be distinguished if there is
+whitespace, or concatenated if there is not.
@item tc_frob_section
@cindex tc_frob_section
@item tc_frob_symbol
@cindex tc_frob_symbol
If you define this macro, GAS will call it for each symbol. You can indicate
-that the symbol should not be included in the object file by definining this
+that the symbol should not be included in the object file by defining this
macro to set its second argument to a non-zero value.
@item tc_frob_file
If you define this macro, GAS will call it after the relocs have been
generated.
+@item md_post_relax_hook
+If you define this macro, GAS will call it after relaxing and sizing the
+segments.
+
@item LISTING_HEADER
A string to use on the header line of a listing. The default value is simply
@code{"GAS LISTING"}.
@item LISTING_RHS_WIDTH
The maximum number of characters to print from one line of the input file. The
default value is 100.
+
+@item TC_COFF_SECTION_DEFAULT_ATTRIBUTES
+@cindex TC_COFF_SECTION_DEFAULT_ATTRIBUTES
+The COFF @code{.section} directive will use the value of this macro to set
+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 ()
+@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
+the size of internal DWARF section offsets and the format of the DWARF initial
+length fields. When @code{dwarf2_format_32bit} is returned, the initial
+length field will be 4 bytes long and section offsets are 32 bits in size.
+For @code{dwarf2_format_64bit} and @code{dwarf2_format_64bit_irix}, section
+offsets are 64 bits in size, but the initial length field differs. An 8 byte
+initial length is indicated by @code{dwarf2_format_64bit_irix} and
+@code{dwarf2_format_64bit} indicates a 12 byte initial length field in
+which the first four bytes are 0xffffffff and the next 8 bytes are
+the section's length.
+
+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}
+sections generated by the assembler. DWARF 2 sections generated by
+other tools will be unaffected by this setting.
+
+@item DWARF2_ADDR_SIZE (@var{bfd})
+@cindex DWARF2_ADDR_SIZE
+It should return the size of an address, as it should be represented in
+debugging info. If you don't define this macro, the default definition uses
+the number of bits per address, as defined in @var{bfd}, divided by 8.
+
@end table
@node Object format backend
one symbol to another. GAS will call it when one symbol is equated to
another.
-@item obj_fix_adjustable
-@cindex obj_fix_adjustable
-You may define this macro to indicate whether a fixup against a locally defined
-symbol should be adjusted to be against the section symbol. It should return a
-non-zero value if the adjustment is acceptable.
-
@item obj_sec_sym_ok_for_reloc
@cindex obj_sec_sym_ok_for_reloc
You may define this macro to indicate that it is OK to use a section symbol in
-a relocateion entry. If it is not, GAS will define a new symbol at the start
+a relocation entry. If it is not, GAS will define a new symbol at the start
of a section.
@item EMIT_SECTION_SYMBOLS
@item SEPARATE_STAB_SECTIONS
@cindex SEPARATE_STAB_SECTIONS
-You may define this macro to indicate that stabs should be placed in separate
-sections, as in ELF.
+You may define this macro to a nonzero value to indicate that stabs should be
+placed in separate sections, as in ELF.
@item INIT_STAB_SECTION
@cindex INIT_STAB_SECTION
@item obj_frob_symbol
@cindex obj_frob_symbol
If you define this macro, GAS will call it for each symbol. You can indicate
-that the symbol should not be included in the object file by definining this
+that the symbol should not be included in the object file by defining this
macro to set its second argument to a non-zero value.
@item obj_frob_file
@item obj_frob_file_after_relocs
If you define this macro, GAS will call it after the relocs have been
generated.
+
+@item SET_SECTION_RELOCS (@var{sec}, @var{relocs}, @var{n})
+@cindex SET_SECTION_RELOCS
+If you define this, it will be called after the relocations have been set for
+the section @var{sec}. The list of relocations is in @var{relocs}, and the
+number of relocations is in @var{n}. This is only used with
+@code{BFD_ASSEMBLER}.
@end table
@node Emulations
The @code{fr_subtype} field of a frag is an index into a CPU-specific
relaxation table. That table entry indicates the range of values that can be
stored, the number of bytes that will have to be added to the frag to
-accomodate the addressing mode, and the index of the next entry to examine if
+accommodate the addressing mode, and the index of the next entry to examine if
the value to be stored is outside the range accessible by the current
addressing mode. The @code{fr_symbol} field of the frag indicates what symbol
is to be accessed; the @code{fr_offset} field is added in.
Sometimes changing addressing modes may also require rewriting the instruction.
It can be accessed via @code{fr_opcode} or @code{fr_fix}.
+If you generate frags separately for the basic insn opcode and any relaxable
+operands, do not call @code{fix_new} thinking you can emit fixups for the
+opcode field from the relaxable frag. It is not guaranteed to be the same frag.
+If you need to emit fixups for the opcode field from inspection of the
+relaxable frag, then you need to generate a common frag for both the basic
+opcode and relaxable fields, or you need to provide the frag for the opcode to
+pass to @code{fix_new}. The latter can be done for example by defining
+@code{TC_FRAG_TYPE} to include a pointer to it and defining @code{TC_FRAG_INIT}
+to set the pointer.
+
Sometimes @code{fr_var} is increased instead, and @code{frag_wane} is not
called. I'm not sure, but I think this is to keep @code{fr_fix} referring to
an earlier byte, and @code{fr_subtype} set to @code{rs_machine_dependent} so
projects / deliverable / binutils-gdb.git / blobdiff