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types, @file{coff-i960.c} also includes some code to
types, @file{coff-i960.c} also includes some code to
manipulate the i960 relocs.  This code is not in
manipulate the i960 relocs.  This code is not in
@file{coffcode.h} because it would not be used by any other
@file{coffcode.h} because it would not be used by any other
target.
target.
 
 
 
@subsubsection Coff long section names
 
In the standard Coff object format, section names are limited to
 
the eight bytes available in the @code{s_name} field of the
 
@code{SCNHDR} section header structure.  The format requires the
 
field to be NUL-padded, but not necessarily NUL-terminated, so
 
the longest section names permitted are a full eight characters.
 
 
 
The Microsoft PE variants of the Coff object file format add
 
an extension to support the use of long section names.  This
 
extension is defined in section 4 of the Microsoft PE/COFF
 
specification (rev 8.1).  If a section name is too long to fit
 
into the section header's @code{s_name} field, it is instead
 
placed into the string table, and the @code{s_name} field is
 
filled with a slash ("/") followed by the ASCII decimal
 
representation of the offset of the full name relative to the
 
string table base.
 
 
 
Note that this implies that the extension can only be used in object
 
files, as executables do not contain a string table.  The standard
 
specifies that long section names from objects emitted into executable
 
images are to be truncated.
 
 
 
However, as a GNU extension, BFD can generate executable images
 
that contain a string table and long section names.  This
 
would appear to be technically valid, as the standard only says
 
that Coff debugging information is deprecated, not forbidden,
 
and in practice it works, although some tools that parse PE files
 
expecting the MS standard format may become confused; @file{PEview} is
 
one known example.
 
 
 
The functionality is supported in BFD by code implemented under
 
the control of the macro @code{COFF_LONG_SECTION_NAMES}.  If not
 
defined, the format does not support long section names in any way.
 
If defined, it is used to initialise a flag,
 
@code{_bfd_coff_long_section_names}, and a hook function pointer,
 
@code{_bfd_coff_set_long_section_names}, in the Coff backend data
 
structure.  The flag controls the generation of long section names
 
in output BFDs at runtime; if it is false, as it will be by default
 
when generating an executable image, long section names are truncated;
 
if true, the long section names extension is employed.  The hook
 
points to a function that allows the value of the flag to be altered
 
at runtime, on formats that support long section names at all; on
 
other formats it points to a stub that returns an error indication.
 
With input BFDs, the flag is set according to whether any long section
 
names are detected while reading the section headers.  For a completely
 
new BFD, the flag is set to the default for the target format.  This
 
information can be used by a client of the BFD library when deciding
 
what output format to generate, and means that a BFD that is opened
 
for read and subsequently converted to a writeable BFD and modified
 
in-place will retain whatever format it had on input.
 
 
 
If @code{COFF_LONG_SECTION_NAMES} is simply defined (blank), or is
 
defined to the value "1", then long section names are enabled by
 
default; if it is defined to the value zero, they are disabled by
 
default (but still accepted in input BFDs).  The header @file{coffcode.h}
 
defines a macro, @code{COFF_DEFAULT_LONG_SECTION_NAMES}, which is
 
used in the backends to initialise the backend data structure fields
 
appropriately; see the comments for further detail.
 
 
@subsubsection Bit twiddling
@subsubsection Bit twiddling
Each flavour of coff supported in BFD has its own header file
Each flavour of coff supported in BFD has its own header file
describing the external layout of the structures. There is also
describing the external layout of the structures. There is also
an internal description of the coff layout, in
an internal description of the coff layout, in
@file{coff/internal.h}. A major function of the
@file{coff/internal.h}. A major function of the
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  unsigned int _bfd_auxesz;
  unsigned int _bfd_auxesz;
  unsigned int _bfd_relsz;
  unsigned int _bfd_relsz;
  unsigned int _bfd_linesz;
  unsigned int _bfd_linesz;
  unsigned int _bfd_filnmlen;
  unsigned int _bfd_filnmlen;
  bfd_boolean _bfd_coff_long_filenames;
  bfd_boolean _bfd_coff_long_filenames;
 
 
  bfd_boolean _bfd_coff_long_section_names;
  bfd_boolean _bfd_coff_long_section_names;
 
  bfd_boolean (*_bfd_coff_set_long_section_names)
 
    (bfd *, int);
 
 
  unsigned int _bfd_coff_default_section_alignment_power;
  unsigned int _bfd_coff_default_section_alignment_power;
  bfd_boolean _bfd_coff_force_symnames_in_strings;
  bfd_boolean _bfd_coff_force_symnames_in_strings;
  unsigned int _bfd_coff_debug_string_prefix_length;
  unsigned int _bfd_coff_debug_string_prefix_length;
 
 
  void (*_bfd_coff_swap_filehdr_in)
  void (*_bfd_coff_swap_filehdr_in)
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    (bfd *, struct coff_final_link_info *);
    (bfd *, struct coff_final_link_info *);
 
 
  bfd_boolean (*_bfd_coff_final_link_postscript)
  bfd_boolean (*_bfd_coff_final_link_postscript)
    (bfd *, struct coff_final_link_info *);
    (bfd *, struct coff_final_link_info *);
 
 
 
  bfd_boolean (*_bfd_coff_print_pdata)
 
    (bfd *, void *);
 
 
@} bfd_coff_backend_data;
@} bfd_coff_backend_data;
 
 
#define coff_backend_info(abfd) \
#define coff_backend_info(abfd) \
  ((bfd_coff_backend_data *) (abfd)->xvec->backend_data)
  ((bfd_coff_backend_data *) (abfd)->xvec->backend_data)
 
 
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#define bfd_coff_filnmlen(abfd) (coff_backend_info (abfd)->_bfd_filnmlen)
#define bfd_coff_filnmlen(abfd) (coff_backend_info (abfd)->_bfd_filnmlen)
#define bfd_coff_long_filenames(abfd) \
#define bfd_coff_long_filenames(abfd) \
  (coff_backend_info (abfd)->_bfd_coff_long_filenames)
  (coff_backend_info (abfd)->_bfd_coff_long_filenames)
#define bfd_coff_long_section_names(abfd) \
#define bfd_coff_long_section_names(abfd) \
  (coff_backend_info (abfd)->_bfd_coff_long_section_names)
  (coff_backend_info (abfd)->_bfd_coff_long_section_names)
 
#define bfd_coff_set_long_section_names(abfd, enable) \
 
  ((coff_backend_info (abfd)->_bfd_coff_set_long_section_names) (abfd, enable))
#define bfd_coff_default_section_alignment_power(abfd) \
#define bfd_coff_default_section_alignment_power(abfd) \
  (coff_backend_info (abfd)->_bfd_coff_default_section_alignment_power)
  (coff_backend_info (abfd)->_bfd_coff_default_section_alignment_power)
#define bfd_coff_swap_filehdr_in(abfd, i,o) \
#define bfd_coff_swap_filehdr_in(abfd, i,o) \
  ((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_in) (abfd, i, o))
  ((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_in) (abfd, i, o))
 
 
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#define bfd_coff_link_output_has_begun(a,p) \
#define bfd_coff_link_output_has_begun(a,p) \
  ((coff_backend_info (a)->_bfd_coff_link_output_has_begun) (a, p))
  ((coff_backend_info (a)->_bfd_coff_link_output_has_begun) (a, p))
#define bfd_coff_final_link_postscript(a,p) \
#define bfd_coff_final_link_postscript(a,p) \
  ((coff_backend_info (a)->_bfd_coff_final_link_postscript) (a, p))
  ((coff_backend_info (a)->_bfd_coff_final_link_postscript) (a, p))
 
 
 
#define bfd_coff_have_print_pdata(a) \
 
  (coff_backend_info (a)->_bfd_coff_print_pdata)
 
#define bfd_coff_print_pdata(a,p) \
 
  ((coff_backend_info (a)->_bfd_coff_print_pdata) (a, p))
 
 
 
/* Macro: Returns true if the bfd is a PE executable as opposed to a
 
   PE object file.  */
 
#define bfd_pei_p(abfd) \
 
  (CONST_STRNEQ ((abfd)->xvec->name, "pei-"))
@end example
@end example
@subsubsection Writing relocations
@subsubsection Writing relocations
To write relocations, the back end steps though the
To write relocations, the back end steps though the
canonical relocation table and create an
canonical relocation table and create an
@code{internal_reloc}. The symbol index to use is removed from
@code{internal_reloc}. The symbol index to use is removed from

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