(bfd.info)BFD front end


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BFD front end
*************

`typedef bfd'
=============

   A BFD has type `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 `bfd'.  It contains the major data about the file and
pointers to the rest of the data.
.
     struct _bfd
     {
         	/* The filename the application opened the BFD with.  */
         CONST char *filename;
     
         	/* A pointer to the target jump table.             */
         struct bfd_target *xvec;
     
         	/* To avoid dragging too many header files into every file that
            includes ``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. */
         char *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: */
     
         file_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 the BFD was opened with*/
     
         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.   */
     
         file_ptr origin;
     
         	/* Remember when output has begun, to stop strange things
            from happening. */
         boolean output_has_begun;
     
         	/* Pointer to linked list of sections*/
         struct sec  *sections;
     
         	/* 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*/
         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 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 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 sun_core_struct *sun_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;
           PTR any;
           } tdata;
     
         	/* Used by the application to hold private data*/
         PTR usrdata;
     
         	/* Where all the allocated stuff under this BFD goes */
         struct obstack memory;
     };

`bfd_get_reloc_upper_bound'
...........................

   *Synopsis*
     unsigned int bfd_get_reloc_upper_bound(bfd *abfd, asection *sect);
   *Description*
Return the number of bytes required to store the relocation information
associated with section SECT attached to bfd ABFD.
`bfd_canonicalize_reloc'
........................

*Synopsis*
     unsigned int bfd_canonicalize_reloc
        (bfd *abfd,
         asection *sec,
         arelent **loc,
         asymbol	**syms);
   *Description*
Call the back end associated with the open BFD ABFD and translate the
external form of the relocation information attached to SEC into the
internal canonical form.  Place the table into memory at LOC, which has
been preallocated, usually by a call to `bfd_get_reloc_upper_bound'.
The SYMS table is also needed for horrible internal magic reasons.
`bfd_set_reloc'
...............

*Synopsis*
     void bfd_set_reloc
        (bfd *abfd, asection *sec, arelent **rel, unsigned int count)
   *Description*
Set the relocation pointer and count within section SEC to the values
REL and COUNT.  The argument ABFD is ignored.
`bfd_set_file_flags'
....................

*Synopsis*
     boolean bfd_set_file_flags(bfd *abfd, flagword flags);
   *Description*
Set the flag word in the BFD ABFD to the value FLAGS.  Possible errors
are:
   * `wrong_format' - The target bfd was not of object format.

   * `invalid_operation' - The target bfd was open for reading.

   * `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 `D_PAGED' bit on a BFD format which does not support demand
     paging.
`bfd_set_start_address'
.......................

*Synopsis*
     boolean bfd_set_start_address(bfd *abfd, bfd_vma vma);
   *Description*
Make VMA the entry point of output BFD ABFD.
*Returns*
Returns `true' on success, `false' otherwise.
`bfd_get_mtime'
...............

*Synopsis*
     long bfd_get_mtime(bfd *abfd);
   *Description*
Return the file modification time (as read from the file system, or
from the archive header for archive members).
`bfd_get_size'
..............

*Synopsis*
     long bfd_get_size(bfd *abfd);
   *Description*
Return the file size (as read from file system) for the file associated
with BFD 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 `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?".
`bfd_get_gp_size'
.................

*Synopsis*
     int bfd_get_gp_size(bfd *abfd);
   *Description*
Return the maximum size of objects to be optimized using the GP
register under MIPS ECOFF.  This is typically set by the `-G' argument
to the compiler, assembler or linker.
`bfd_set_gp_size'
.................

*Synopsis*
     void bfd_set_gp_size(bfd *abfd, int i);
   *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 `-G' argument to
the compiler, assembler or linker.
`bfd_scan_vma'
..............

*Synopsis*
     bfd_vma bfd_scan_vma(CONST char *string, CONST char **end, int base);
   *Description*
Convert, like `strtoul', a numerical expression STRING into a `bfd_vma'
integer, and return that integer.  (Though without as many bells and
whistles as `strtoul'.) The expression is assumed to be unsigned (i.e.,
positive).  If given a 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.  Overflow is not detected.
`stuff'
.......

*Description*
Stuff which should be documented:
     #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_set_arch_mach(abfd, arch, mach)\
             BFD_SEND ( abfd, _bfd_set_arch_mach, (abfd, arch, mach))
     
     #define bfd_get_relocated_section_contents(abfd, link_info, link_order, data, relocateable, symbols) \
     	BFD_SEND (abfd, _bfd_get_relocated_section_contents, \
                      (abfd, link_info, link_order, data, relocateable, symbols))
     
     #define bfd_relax_section(abfd, section, link_info, symbols) \
            BFD_SEND (abfd, _bfd_relax_section, \
                      (abfd, section, link_info, symbols))
     
     #define bfd_link_hash_table_create(abfd) \
     	BFD_SEND (abfd, _bfd_link_hash_table_create, (abfd))
     
     #define bfd_link_add_symbols(abfd, info) \
     	BFD_SEND (abfd, _bfd_link_add_symbols, (abfd, info))
     
     #define bfd_final_link(abfd, info) \
     	BFD_SEND (abfd, _bfd_final_link, (abfd, info))

* Memory Usage
* Initialization
* Sections
* Symbols
* Archives
* Formats
* Relocations
* Core Files
* Targets
* Architectures
* Opening and Closing
* Constructors
* Internal
* File Caching
* Linker Functions
* Hash Tables

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