RE: Bfd/binutils inconsistency re: *UND* and *ABS* and relocs against dummy (STT_NOTYPE) symbol entries in elf symbol tables!?

["Dave Korn" <dk at artimi dot com>]

> -----Original Message-----
> From: Ian Lance Taylor

> >  -  XXXX_relocate_section gets really confused by this whole 
> > situation, because it's generally written like this:
> > 
> > 	[...loop across all relocs....]
> >       r_symndx = ELF32_R_SYM (rel->r_info);
> >       if (r_symndx < symtab_hdr->sh_info)
> > 	{
> > 	  sym = local_syms + r_symndx;
> > 	  sec = local_sections[r_symndx];
> > 	  sym_name = bfd_elf_local_sym_name (input_bfd, sym);
> > 
> > 	  relocation = _bfd_elf_rela_local_sym (output_bfd, 
> sym, sec, rel);
> > 	}
> > 	[...else find out some other way...]
> > 
> > and if ELF32_R_SYM returns zero, sym ends up pointing to the dummy 
> > STT_NOTYPE entry and sec to the *UND* section.  That's not right.
> 
> I agree.  I believe sec should wind up being set to bfd_abs_sec_ptr.
> 
> Ian

  Mmm.  But what I'm now wondering is whether I should special case r_symndx
== 0 by replacing the assignment of sec (in XXX_relocate_section) like this:

> > 	  sec = r_symndx ? local_sections[r_symndx] : bfd_abs_sec_ptr;

or whether I should find the code that sets up the local_sections and
local_syms arrays, and make sure it sets entry zero to the ABS rather than
UND section.

  The second way of doing it seems more correct to me: since the dummy
symbol actually represents an absolute zero, the local_sections[0] entry
corresponding to the local_syms[0] entry for it should point to ABS, not
UND, because that's what section the symbol is actually in.  It's misleading
to claim the zero symbol is undefined: it isn't.

  However, it also seems to me that there might be other bits of code which
expect local_sections[0] to point to UND despite the zero symbol not
actually being undefined, and changing this might inadvertently break them.
So the safety-first approach leads me to consider just using the ternary
expression above.  

  Anyone else have an opinion on which approach is a better idea ?


    cheers, 
      DaveK
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