2.17.3.3 Writing the symbol table

The _bfd_final_link function must gather all the symbols in the input files and write them out. It must also write out all the symbols in the global hash table. This must be controlled by the strip and discard fields of the bfd_link_info structure.

The local symbols of the input files will not have been entered into the linker hash table. The _bfd_final_link routine must consider each input file and include the symbols in the output file. It may be convenient to do this when looking through the link_order structures, or it may be done by stepping through the input_bfds list.

The _bfd_final_link routine must also traverse the global hash table to gather all the externally visible symbols. It is possible that most of the externally visible symbols may be written out when considering the symbols of each input file, but it is still necessary to traverse the hash table since the linker script may have defined some symbols that are not in any of the input files.

The strip field of the bfd_link_info structure controls which symbols are written out. The possible values are listed in bfdlink.h. If the value is strip_some, then the keep_hash field of the bfd_link_info structure is a hash table of symbols to keep; each symbol should be looked up in this hash table, and only symbols which are present should be included in the output file.

If the strip field of the bfd_link_info structure permits local symbols to be written out, the discard field is used to further controls which local symbols are included in the output file. If the value is discard_l, then all local symbols which begin with a certain prefix are discarded; this is controlled by the bfd_is_local_label_name entry point.

The a.out backend handles symbols by calling aout_link_write_symbols on each input BFD and then traversing the global hash table with the function aout_link_write_other_symbol. It builds a string table while writing out the symbols, which is written to the output file at the end of NAME(aout,final_link).

2.17.3.4 bfd_link_split_section

Synopsis

bfd_boolean bfd_link_split_section (bfd *abfd, asection *sec);

Description
Return nonzero if sec should be split during a reloceatable or final link.

#define bfd_link_split_section(abfd, sec) \
       BFD_SEND (abfd, _bfd_link_split_section, (abfd, sec))

2.17.3.5 bfd_section_already_linked

Synopsis

bfd_boolean bfd_section_already_linked (bfd *abfd,
    asection *sec,
    struct bfd_link_info *info);

Description
Check if data has been already linked during a reloceatable or final link. Return TRUE if it has.

#define bfd_section_already_linked(abfd, sec, info) \
       BFD_SEND (abfd, _section_already_linked, (abfd, sec, info))

2.17.3.6 bfd_generic_define_common_symbol

Synopsis

bfd_boolean bfd_generic_define_common_symbol
   (bfd *output_bfd, struct bfd_link_info *info,
    struct bfd_link_hash_entry *h);

Description
Convert common symbol h into a defined symbol. Return TRUE on success and FALSE on failure.

#define bfd_define_common_symbol(output_bfd, info, h) \
       BFD_SEND (output_bfd, _bfd_define_common_symbol, (output_bfd, info, h))

2.17.3.7 bfd_generic_define_start_stop

Synopsis

struct bfd_link_hash_entry *bfd_generic_define_start_stop
   (struct bfd_link_info *info,
    const char *symbol, asection *sec);

Description
Define a __start, __stop, .startof. or .sizeof. symbol. Return the symbol or NULL if no such undefined symbol exists.

#define bfd_define_start_stop(output_bfd, info, symbol, sec) \
       BFD_SEND (output_bfd, _bfd_define_start_stop, (info, symbol, sec))

2.17.3.8 bfd_find_version_for_sym

Synopsis

struct bfd_elf_version_tree * bfd_find_version_for_sym
   (struct bfd_elf_version_tree *verdefs,
    const char *sym_name, bfd_boolean *hide);

Description
Search an elf version script tree for symbol versioning info and export / don’t-export status for a given symbol. Return non-NULL on success and NULL on failure; also sets the output ‘hide’ boolean parameter.

2.17.3.9 bfd_hide_sym_by_version

Synopsis

bfd_boolean bfd_hide_sym_by_version
   (struct bfd_elf_version_tree *verdefs, const char *sym_name);

Description
Search an elf version script tree for symbol versioning info for a given symbol. Return TRUE if the symbol is hidden.

2.17.3.10 bfd_link_check_relocs

Synopsis

bfd_boolean bfd_link_check_relocs
   (bfd *abfd, struct bfd_link_info *info);

Description
Checks the relocs in ABFD for validity. Does not execute the relocs. Return TRUE if everything is OK, FALSE otherwise. This is the external entry point to this code.

2.17.3.11 _bfd_generic_link_check_relocs

Synopsis

bfd_boolean _bfd_generic_link_check_relocs
   (bfd *abfd, struct bfd_link_info *info);

Description
Stub function for targets that do not implement reloc checking. Return TRUE. This is an internal function. It should not be called from outside the BFD library.

2.17.3.12 bfd_merge_private_bfd_data

Synopsis

bfd_boolean bfd_merge_private_bfd_data
   (bfd *ibfd, struct bfd_link_info *info);

Description
Merge private BFD information from the BFD ibfd to the the output file BFD when linking. Return TRUE on success, FALSE on error. Possible error returns are:

• bfd_error_no_memory - Not enough memory exists to create private data for obfd.

#define bfd_merge_private_bfd_data(ibfd, info) \
       BFD_SEND ((info)->output_bfd, _bfd_merge_private_bfd_data, \
                 (ibfd, info))

2.17.3.13 _bfd_generic_verify_endian_match

Synopsis

bfd_boolean _bfd_generic_verify_endian_match
   (bfd *ibfd, struct bfd_link_info *info);

Description
Can be used from / for bfd_merge_private_bfd_data to check that endianness matches between input and output file. Returns TRUE for a match, otherwise returns FALSE and emits an error.