Is this a bfd bug? (binutils version 2.13)

[Bharathi Seshadri <bseshadr at cisco dot com>]

Hello,

I came across a linker crash in binutils version 2.13. (gcc version used is 
2.95.3).
(I tried with binutils-2.13.90.0.20 too and I observed the crash).

This is the backtrace.

#0 mips_elf_output_extsym (h=0x15c9a0, data=0xeffff698) at 
../../src/bfd/elfxx-mips.c:1319
#1 0x41814 in bfd_hash_traverse (table=0x1462c0, func=0x4d668 
<mips_elf_output_extsym>, info=0xeffff698) at ../../src/bfd/hash.c:493
#2 0x41db4 in bfd_link_hash_traverse (table=0x1462c0, func=0x4d668 
<mips_elf_output_extsym>, info=0xeffff698) at ../../src/bfd/linker.c:615 #3 
0x57ca0 in _bfd_mips_elf_final_link (abfd=0x1402d8, info=0x138180) at 
../../src/bfd/elfxx-mips.c:7324
#4 0x2c67c in ldwrite () at ../../src/ld/ldwrite.c:540
#5 0x2a624 in main (argc=10, argv=0xdf400) at ../../src/ld/ldmain.c:415

The line of crash is
sec = hd->root.root.u.def.section; (in function 'mips_elf_output_extsym' in 
bfd/elfxx-mips.c)

I think it is accessing the wrong member of the union here.

On debugging, I find that the type of hd->root.root.type is 
bfd_link_hash_undefined
and it is trying to access the union member def, which is some invalid 
address here.
The other types are already checked for before and so the type of symbol at 
this place
is likely to be bfd_link_hash_undefweak or bfd_link_hash_undefined.

If the value of hd->root.root.type is either bfd_link_hash_undefined or 
bfd_link_hash_undefweak,
the right union member to be accessed is hd->root.root.u.undef (inferred 
from definition of
struct bfd_link_hash_entry in bfdlink.h).

I see that this causes the dump and replacing the line at this place (sec = 
hd->root.root.u.def.section;) to

if ((hd->root.root.type == bfd_link_hash_undefined) 
||   (hd->root.root.type == bfd_link_hash_undefweak))
     if (hd->root.root.u.undef.abfd != NULL)
         sec = hd->root.root.u.undef.abfd->sections

seems to solve the problem.

Please correct my understanding. I'm not sure, if its likely to impact 
anything else.

Thanks,
Bharathi