Writing Symbols - Untitled















Next: Mini Symbols,
Previous: Reading Symbols,
Up: Symbols



2.7.2 Writing symbols

Writing of a symbol table is automatic when a BFD open for
writing is closed. The application attaches a vector of
pointers to pointers to symbols to the BFD being written, and
fills in the symbol count. The close and cleanup code reads
through the table provided and performs all the necessary
operations. The BFD output code must always be provided with an
“owned” symbol: one which has come from another BFD, or one
which has been created using bfd_make_empty_symbol. Here is an
example showing the creation of a symbol table with only one element:

#include "bfd.h"
int main (void)
{
bfd *abfd;
asymbol *ptrs[2];
asymbol *new;

abfd = bfd_openw ("foo","a.out-sunos-big");
bfd_set_format (abfd, bfd_object);
new = bfd_make_empty_symbol (abfd);
new->name = "dummy_symbol";
new->section = bfd_make_section_old_way (abfd, ".text");
new->flags = BSF_GLOBAL;
new->value = 0x12345;

ptrs[0] = new;
ptrs[1] = 0;

bfd_set_symtab (abfd, ptrs, 1);
bfd_close (abfd);
return 0;
}

./makesym
nm foo
00012345 A dummy_symbol

Many formats cannot represent arbitrary symbol information; for
instance, the a.out object format does not allow an
arbitrary number of sections. A symbol pointing to a section
which is not one of .text, .data or .bss cannot
be described.