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@section @code{typedef bfd}

A BFD has type @code{bfd}; objects of this type are the

cornerstone of any application using BFD. Using BFD

consists of making references though the BFD and to data in the BFD.

Here is the structure that defines the type @code{bfd}.  It

contains the major data about the file and pointers

to the rest of the data.

@example

struct _bfd

@{

  /* The filename the application opened the BFD with.  */

  const char *filename;

  /* A pointer to the target jump table.  */

  const struct bfd_target *xvec;

  /* To avoid dragging too many header files into every file that

     includes `@code{bfd.h}', IOSTREAM has been declared as a "char *",

     and MTIME as a "long".  Their correct types, to which they

     are cast when used, are "FILE *" and "time_t".    The iostream

     is the result of an fopen on the filename.  However, if the

     BFD_IN_MEMORY flag is set, then iostream is actually a pointer

     to a bfd_in_memory struct.  */

  PTR iostream;

  /* Is the file descriptor being cached?  That is, can it be closed as

     needed, and re-opened when accessed later?  */

  boolean cacheable;

  /* Marks whether there was a default target specified when the

     BFD was opened. This is used to select which matching algorithm

     to use to choose the back end.  */

  boolean target_defaulted;

  /* The caching routines use these to maintain a

     least-recently-used list of BFDs.  */

  struct _bfd *lru_prev, *lru_next;

  /* When a file is closed by the caching routines, BFD retains

     state information on the file here...  */

  ufile_ptr where;

  /* ... and here: (``once'' means at least once).  */

  boolean opened_once;

  /* Set if we have a locally maintained mtime value, rather than

     getting it from the file each time.  */

  boolean mtime_set;

  /* File modified time, if mtime_set is true.  */

  long mtime;

  /* Reserved for an unimplemented file locking extension.  */

  int ifd;

  /* The format which belongs to the BFD. (object, core, etc.)  */

  bfd_format format;

  /* The direction with which the BFD was opened.  */

  enum bfd_direction

    @{

      no_direction = 0,

      read_direction = 1,

      write_direction = 2,

      both_direction = 3

    @}

  direction;

  /* Format_specific flags.  */

  flagword flags;

  /* Currently my_archive is tested before adding origin to

     anything. I believe that this can become always an add of

     origin, with origin set to 0 for non archive files.  */

  ufile_ptr origin;

  /* Remember when output has begun, to stop strange things

     from happening.  */

  boolean output_has_begun;

  /* A hash table for section names.  */

  struct bfd_hash_table section_htab;

  /* Pointer to linked list of sections.  */

  struct sec *sections;

  /* The place where we add to the section list.  */

  struct sec **section_tail;

  /* The number of sections.  */

  unsigned int section_count;

  /* Stuff only useful for object files:

     The start address.  */

  bfd_vma start_address;

  /* Used for input and output.  */

  unsigned int symcount;

  /* Symbol table for output BFD (with symcount entries).  */

  struct symbol_cache_entry  **outsymbols;

  /* Pointer to structure which contains architecture information.  */

  const struct bfd_arch_info *arch_info;

  /* Stuff only useful for archives.  */

  PTR arelt_data;

  struct _bfd *my_archive;     /* The containing archive BFD.  */

  struct _bfd *next;           /* The next BFD in the archive.  */

  struct _bfd *archive_head;   /* The first BFD in the archive.  */

  boolean has_armap;

  /* A chain of BFD structures involved in a link.  */

  struct _bfd *link_next;

  /* A field used by _bfd_generic_link_add_archive_symbols.  This will

     be used only for archive elements.  */

  int archive_pass;

  /* Used by the back end to hold private data.  */

  union

    @{

      struct aout_data_struct *aout_data;

      struct artdata *aout_ar_data;

      struct _oasys_data *oasys_obj_data;

      struct _oasys_ar_data *oasys_ar_data;

      struct coff_tdata *coff_obj_data;

      struct pe_tdata *pe_obj_data;

      struct xcoff_tdata *xcoff_obj_data;

      struct ecoff_tdata *ecoff_obj_data;

      struct ieee_data_struct *ieee_data;

      struct ieee_ar_data_struct *ieee_ar_data;

      struct srec_data_struct *srec_data;

      struct ihex_data_struct *ihex_data;

      struct tekhex_data_struct *tekhex_data;

      struct elf_obj_tdata *elf_obj_data;

      struct nlm_obj_tdata *nlm_obj_data;

      struct bout_data_struct *bout_data;

      struct mmo_data_struct *mmo_data;

      struct sun_core_struct *sun_core_data;

      struct sco5_core_struct *sco5_core_data;

      struct trad_core_struct *trad_core_data;

      struct som_data_struct *som_data;

      struct hpux_core_struct *hpux_core_data;

      struct hppabsd_core_struct *hppabsd_core_data;

      struct sgi_core_struct *sgi_core_data;

      struct lynx_core_struct *lynx_core_data;

      struct osf_core_struct *osf_core_data;

      struct cisco_core_struct *cisco_core_data;

      struct versados_data_struct *versados_data;

      struct netbsd_core_struct *netbsd_core_data;

      PTR any;

    @}

  tdata;

  /* Used by the application to hold private data.  */

  PTR usrdata;

  /* Where all the allocated stuff under this BFD goes.  This is a

     struct objalloc *, but we use PTR to avoid requiring the inclusion of

     objalloc.h.  */

  PTR memory;

@};

@end example

@section Error reporting

Most BFD functions return nonzero on success (check their

individual documentation for precise semantics).  On an error,

they call @code{bfd_set_error} to set an error condition that callers

can check by calling @code{bfd_get_error}.

If that returns @code{bfd_error_system_call}, then check

@code{errno}.

The easiest way to report a BFD error to the user is to

use @code{bfd_perror}.

@subsection Type @code{bfd_error_type}

The values returned by @code{bfd_get_error} are defined by the

enumerated type @code{bfd_error_type}.

@example

typedef enum bfd_error

@{

  bfd_error_no_error = 0,

  bfd_error_system_call,

  bfd_error_invalid_target,

  bfd_error_wrong_format,

  bfd_error_wrong_object_format,

  bfd_error_invalid_operation,

  bfd_error_no_memory,

  bfd_error_no_symbols,

  bfd_error_no_armap,

  bfd_error_no_more_archived_files,

  bfd_error_malformed_archive,

  bfd_error_file_not_recognized,

  bfd_error_file_ambiguously_recognized,

  bfd_error_no_contents,

  bfd_error_nonrepresentable_section,

  bfd_error_no_debug_section,

  bfd_error_bad_value,

  bfd_error_file_truncated,

  bfd_error_file_too_big,

  bfd_error_invalid_error_code

@}

bfd_error_type;

@end example

@findex bfd_get_error

@subsubsection @code{bfd_get_error}

@strong{Synopsis}

@example

bfd_error_type bfd_get_error (void);

@end example

@strong{Description}@*

Return the current BFD error condition.

@findex bfd_set_error

@subsubsection @code{bfd_set_error}

@strong{Synopsis}

@example

void bfd_set_error (bfd_error_type error_tag);

@end example

@strong{Description}@*

Set the BFD error condition to be @var{error_tag}.

@findex bfd_errmsg

@subsubsection @code{bfd_errmsg}

@strong{Synopsis}

@example

const char *bfd_errmsg (bfd_error_type error_tag);

@end example

@strong{Description}@*

Return a string describing the error @var{error_tag}, or

the system error if @var{error_tag} is @code{bfd_error_system_call}.

@findex bfd_perror

@subsubsection @code{bfd_perror}

@strong{Synopsis}

@example

void bfd_perror (const char *message);

@end example

@strong{Description}@*

Print to the standard error stream a string describing the

last BFD error that occurred, or the last system error if

the last BFD error was a system call failure.  If @var{message}

is non-NULL and non-empty, the error string printed is preceded

by @var{message}, a colon, and a space.  It is followed by a newline.

@subsection BFD error handler

Some BFD functions want to print messages describing the

problem.  They call a BFD error handler function.  This

function may be overriden by the program.

The BFD error handler acts like printf.

@example

typedef void (*bfd_error_handler_type) PARAMS ((const char *, ...));

@end example

@findex bfd_set_error_handler

@subsubsection @code{bfd_set_error_handler}

@strong{Synopsis}

@example

bfd_error_handler_type bfd_set_error_handler (bfd_error_handler_type);

@end example

@strong{Description}@*

Set the BFD error handler function.  Returns the previous

function.

@findex bfd_set_error_program_name

@subsubsection @code{bfd_set_error_program_name}

@strong{Synopsis}

@example

void bfd_set_error_program_name (const char *);

@end example

@strong{Description}@*

Set the program name to use when printing a BFD error.  This

is printed before the error message followed by a colon and

space.  The string must not be changed after it is passed to

this function.

@findex bfd_get_error_handler

@subsubsection @code{bfd_get_error_handler}

@strong{Synopsis}

@example

bfd_error_handler_type bfd_get_error_handler (void);

@end example

@strong{Description}@*

Return the BFD error handler function.

@findex bfd_archive_filename

@subsubsection @code{bfd_archive_filename}

@strong{Synopsis}

@example

const char *bfd_archive_filename (bfd *);

@end example

@strong{Description}@*

For a BFD that is a component of an archive, returns a string

with both the archive name and file name.  For other BFDs, just

returns the file name.

@section Symbols

@findex bfd_get_reloc_upper_bound

@subsubsection @code{bfd_get_reloc_upper_bound}

@strong{Synopsis}

@example

long bfd_get_reloc_upper_bound(bfd *abfd, asection *sect);

@end example

@strong{Description}@*

Return the number of bytes required to store the

relocation information associated with section @var{sect}

attached to bfd @var{abfd}.  If an error occurs, return -1.

@findex bfd_canonicalize_reloc

@subsubsection @code{bfd_canonicalize_reloc}

@strong{Synopsis}

@example

long bfd_canonicalize_reloc

   (bfd *abfd,

    asection *sec,

    arelent **loc,

    asymbol **syms);

@end example

@strong{Description}@*

Call the back end associated with the open BFD

@var{abfd} and translate the external form of the relocation

information attached to @var{sec} into the internal canonical

form.  Place the table into memory at @var{loc}, which has

been preallocated, usually by a call to

@code{bfd_get_reloc_upper_bound}.  Returns the number of relocs, or

-1 on error.

The @var{syms} table is also needed for horrible internal magic

reasons.

@findex bfd_set_reloc

@subsubsection @code{bfd_set_reloc}

@strong{Synopsis}

@example

void bfd_set_reloc

   (bfd *abfd, asection *sec, arelent **rel, unsigned int count);

@end example

@strong{Description}@*

Set the relocation pointer and count within

section @var{sec} to the values @var{rel} and @var{count}.

The argument @var{abfd} is ignored.

@findex bfd_set_file_flags

@subsubsection @code{bfd_set_file_flags}

@strong{Synopsis}

@example

boolean bfd_set_file_flags(bfd *abfd, flagword flags);

@end example

@strong{Description}@*

Set the flag word in the BFD @var{abfd} to the value @var{flags}.

Possible errors are:

@itemize @bullet

@item

@code{bfd_error_wrong_format} - The target bfd was not of object format.

@item

@code{bfd_error_invalid_operation} - The target bfd was open for reading.

@item

@code{bfd_error_invalid_operation} -

The flag word contained a bit which was not applicable to the

type of file.  E.g., an attempt was made to set the @code{D_PAGED} bit

on a BFD format which does not support demand paging.

@end itemize

@findex bfd_get_arch_size

@subsubsection @code{bfd_get_arch_size}

@strong{Synopsis}

@example

int bfd_get_arch_size (bfd *abfd);

@end example

@strong{Description}@*

Returns the architecture address size, in bits, as determined

by the object file's format.  For ELF, this information is

included in the header.

@strong{Returns}@*

Returns the arch size in bits if known, @code{-1} otherwise.

@findex bfd_get_sign_extend_vma

@subsubsection @code{bfd_get_sign_extend_vma}

@strong{Synopsis}

@example

int bfd_get_sign_extend_vma (bfd *abfd);

@end example

@strong{Description}@*

Indicates if the target architecture "naturally" sign extends

an address.  Some architectures implicitly sign extend address

values when they are converted to types larger than the size

of an address.  For instance, bfd_get_start_address() will

return an address sign extended to fill a bfd_vma when this is

the case.

@strong{Returns}@*

Returns @code{1} if the target architecture is known to sign

extend addresses, @code{0} if the target architecture is known to

not sign extend addresses, and @code{-1} otherwise.

@findex bfd_set_start_address

@subsubsection @code{bfd_set_start_address}

@strong{Synopsis}

@example

boolean bfd_set_start_address(bfd *abfd, bfd_vma vma);

@end example

@strong{Description}@*

Make @var{vma} the entry point of output BFD @var{abfd}.

@strong{Returns}@*

Returns @code{true} on success, @code{false} otherwise.

@findex bfd_get_mtime

@subsubsection @code{bfd_get_mtime}

@strong{Synopsis}

@example

long bfd_get_mtime(bfd *abfd);

@end example

@strong{Description}@*

Return the file modification time (as read from the file system, or

from the archive header for archive members).

@findex bfd_get_size

@subsubsection @code{bfd_get_size}

@strong{Synopsis}

@example

long bfd_get_size(bfd *abfd);

@end example

@strong{Description}@*

Return the file size (as read from file system) for the file

associated with BFD @var{abfd}.

The initial motivation for, and use of, this routine is not

so we can get the exact size of the object the BFD applies to, since

that might not be generally possible (archive members for example).

It would be ideal if someone could eventually modify

it so that such results were guaranteed.

Instead, we want to ask questions like "is this NNN byte sized

object I'm about to try read from file offset YYY reasonable?"

As as example of where we might do this, some object formats

use string tables for which the first @code{sizeof (long)} bytes of the

table contain the size of the table itself, including the size bytes.

If an application tries to read what it thinks is one of these

string tables, without some way to validate the size, and for

some reason the size is wrong (byte swapping error, wrong location

for the string table, etc.), the only clue is likely to be a read

error when it tries to read the table, or a "virtual memory

exhausted" error when it tries to allocate 15 bazillon bytes

of space for the 15 bazillon byte table it is about to read.

This function at least allows us to answer the quesion, "is the

size reasonable?".

@findex bfd_get_gp_size

@subsubsection @code{bfd_get_gp_size}

@strong{Synopsis}

@example

unsigned int bfd_get_gp_size(bfd *abfd);

@end example

@strong{Description}@*

Return the maximum size of objects to be optimized using the GP

register under MIPS ECOFF.  This is typically set by the @code{-G}

argument to the compiler, assembler or linker.

@findex bfd_set_gp_size

@subsubsection @code{bfd_set_gp_size}

@strong{Synopsis}

@example

void bfd_set_gp_size(bfd *abfd, unsigned int i);

@end example

@strong{Description}@*

Set the maximum size of objects to be optimized using the GP

register under ECOFF or MIPS ELF.  This is typically set by

the @code{-G} argument to the compiler, assembler or linker.

@findex bfd_scan_vma

@subsubsection @code{bfd_scan_vma}

@strong{Synopsis}

@example

bfd_vma bfd_scan_vma(const char *string, const char **end, int base);

@end example

@strong{Description}@*

Convert, like @code{strtoul}, a numerical expression

@var{string} into a @code{bfd_vma} integer, and return that integer.

(Though without as many bells and whistles as @code{strtoul}.)

The expression is assumed to be unsigned (i.e., positive).

If given a @var{base}, it is used as the base for conversion.

A base of 0 causes the function to interpret the string

in hex if a leading "0x" or "0X" is found, otherwise

in octal if a leading zero is found, otherwise in decimal.

If the value would overflow, the maximum @code{bfd_vma} value is

returned.

@findex bfd_copy_private_bfd_data

@subsubsection @code{bfd_copy_private_bfd_data}

@strong{Synopsis}

@example

boolean bfd_copy_private_bfd_data(bfd *ibfd, bfd *obfd);

@end example

@strong{Description}@*

Copy private BFD information from the BFD @var{ibfd} to the

the BFD @var{obfd}.  Return @code{true} on success, @code{false} on error.

Possible error returns are:

@itemize @bullet

@item

@code{bfd_error_no_memory} -

Not enough memory exists to create private data for @var{obfd}.

@end itemize

@example

#define bfd_copy_private_bfd_data(ibfd, obfd) \

     BFD_SEND (obfd, _bfd_copy_private_bfd_data, \

               (ibfd, obfd))

@end example

@findex bfd_merge_private_bfd_data

@subsubsection @code{bfd_merge_private_bfd_data}

@strong{Synopsis}

@example

boolean bfd_merge_private_bfd_data(bfd *ibfd, bfd *obfd);

@end example

@strong{Description}@*

Merge private BFD information from the BFD @var{ibfd} to the

the output file BFD @var{obfd} when linking.  Return @code{true}

on success, @code{false} on error.  Possible error returns are:

@itemize @bullet

@item

@code{bfd_error_no_memory} -

Not enough memory exists to create private data for @var{obfd}.

@end itemize

@example

#define bfd_merge_private_bfd_data(ibfd, obfd) \

     BFD_SEND (obfd, _bfd_merge_private_bfd_data, \

               (ibfd, obfd))

@end example

@findex bfd_set_private_flags

@subsubsection @code{bfd_set_private_flags}

@strong{Synopsis}

@example

boolean bfd_set_private_flags(bfd *abfd, flagword flags);

@end example

@strong{Description}@*

Set private BFD flag information in the BFD @var{abfd}.

Return @code{true} on success, @code{false} on error.  Possible error

returns are:

@itemize @bullet

@item

@code{bfd_error_no_memory} -

Not enough memory exists to create private data for @var{obfd}.

@end itemize

@example

#define bfd_set_private_flags(abfd, flags) \

     BFD_SEND (abfd, _bfd_set_private_flags, \

               (abfd, flags))

@end example

@findex stuff

@subsubsection @code{stuff}

@strong{Description}@*

Stuff which should be documented:

@example

#define bfd_sizeof_headers(abfd, reloc) \

     BFD_SEND (abfd, _bfd_sizeof_headers, (abfd, reloc))

#define bfd_find_nearest_line(abfd, sec, syms, off, file, func, line) \

     BFD_SEND (abfd, _bfd_find_nearest_line,  (abfd, sec, syms, off, file, func, line))

       /* Do these three do anything useful at all, for any back end?  */

#define bfd_debug_info_start(abfd) \

        BFD_SEND (abfd, _bfd_debug_info_start, (abfd))

#define bfd_debug_info_end(abfd) \

        BFD_SEND (abfd, _bfd_debug_info_end, (abfd))

#define bfd_debug_info_accumulate(abfd, section) \

        BFD_SEND (abfd, _bfd_debug_info_accumulate, (abfd, section))

#define bfd_stat_arch_elt(abfd, stat) \

        BFD_SEND (abfd, _bfd_stat_arch_elt,(abfd, stat))

#define bfd_update_armap_timestamp(abfd) \

        BFD_SEND (abfd, _bfd_update_armap_timestamp, (abfd))

#define bfd_set_arch_mach(abfd, arch, mach)\

        BFD_SEND ( abfd, _bfd_set_arch_mach, (abfd, arch, mach))

#define bfd_relax_section(abfd, section, link_info, again) \

       BFD_SEND (abfd, _bfd_relax_section, (abfd, section, link_info, again))

#define bfd_gc_sections(abfd, link_info) \

       BFD_SEND (abfd, _bfd_gc_sections, (abfd, link_info))

#define bfd_merge_sections(abfd, link_info) \

       BFD_SEND (abfd, _bfd_merge_sections, (abfd, link_info))

#define bfd_discard_group(abfd, sec) \

       BFD_SEND (abfd, _bfd_discard_group, (abfd, sec))

#define bfd_link_hash_table_create(abfd) \

       BFD_SEND (abfd, _bfd_link_hash_table_create, (abfd))

#define bfd_link_hash_table_free(abfd, hash) \

       BFD_SEND (abfd, _bfd_link_hash_table_free, (hash))

#define bfd_link_add_symbols(abfd, info) \

       BFD_SEND (abfd, _bfd_link_add_symbols, (abfd, info))

#define bfd_link_just_syms(sec, info) \

       BFD_SEND (abfd, _bfd_link_just_syms, (sec, info))

#define bfd_final_link(abfd, info) \

       BFD_SEND (abfd, _bfd_final_link, (abfd, info))

#define bfd_free_cached_info(abfd) \

       BFD_SEND (abfd, _bfd_free_cached_info, (abfd))

#define bfd_get_dynamic_symtab_upper_bound(abfd) \

       BFD_SEND (abfd, _bfd_get_dynamic_symtab_upper_bound, (abfd))

#define bfd_print_private_bfd_data(abfd, file)\

       BFD_SEND (abfd, _bfd_print_private_bfd_data, (abfd, file))

#define bfd_canonicalize_dynamic_symtab(abfd, asymbols) \

       BFD_SEND (abfd, _bfd_canonicalize_dynamic_symtab, (abfd, asymbols))

#define bfd_get_dynamic_reloc_upper_bound(abfd) \

       BFD_SEND (abfd, _bfd_get_dynamic_reloc_upper_bound, (abfd))

#define bfd_canonicalize_dynamic_reloc(abfd, arels, asyms) \

       BFD_SEND (abfd, _bfd_canonicalize_dynamic_reloc, (abfd, arels, asyms))

extern bfd_byte *bfd_get_relocated_section_contents

       PARAMS ((bfd *, struct bfd_link_info *,

                 struct bfd_link_order *, bfd_byte *,

                 boolean, asymbol **));

@end example

@findex bfd_alt_mach_code

@subsubsection @code{bfd_alt_mach_code}

@strong{Synopsis}

@example

boolean bfd_alt_mach_code(bfd *abfd, int alternative);

@end example

@strong{Description}@*

When more than one machine code number is available for the

same machine type, this function can be used to switch between

the preferred one (alternative == 0) and any others.  Currently,

only ELF supports this feature, with up to two alternate

machine codes.