[GOLD][PATCH PROPOSAL] prevent discarding of needed local symbols for the relocatable objects

[Viktor Kutuzov]

Ian,
please find attached updated patch, which fix the local symbol
discarding behavior for the relocatable output objects (when used the -r
and -X/-x linker options together). I've updated this patch and the unit
tests accordingly. 

2010-02-24  Viktor Kutuzov (vkutuzov@accesssoftek.com)
    * target-reloc.h (scan_relocatable_relocs): Marking needed local
symbols for the relocatable objects.
    * object.h (Symbol_value<int>::set_output_symtab_index): Updated
assert to support a special index value (-2) for the needed local
symbols.
    (Symbol_value<size>::set_no_output_symtab_entry): Likewise.
    (Symbol_value<size>::set_needs_in_output_symtab): New method.
    (Symbol_value<size>::needs_in_output_symtab): New method.
    (Sized_relobj<size, big_endianl>::set_needs_in_output_symtab): New
method.
    * object.cc (Sized_relobj<size,
big_endian>::do_count_local_symbols): prevent discarding needed local
symbols for the relocatable output objects.
    (Sized_relobj<size, big_endian>::write_local_symbols): Likewise.
    * testsuite/discard_locals_relocatable_test.c: New file.
    * testsuite/discard_locals_test.sh: Updated with new test cases.
    * testsuite/Makefile.am: Likewise.
    * testsuite/Makefile.in: Likewise.

-Viktor.

On Wed, 2010-02-10 at 18:14 -0800, Ian Lance Taylor wrote:
> Viktor Kutuzov <vkutuzov@accesssoftek.com> writes:
> 
> > I'm trying to cross build llvm and llvm-gcc on Linux for ARM by using
> > GOLD as the linker. This has exposed some problems we have in GOLD. 
> >
> > One of them related to the assert in the relocate_for_relocatable()
> > method (target-reloc.h, line 557):
> >
> >   new_symndx = object->symtab_index(r_sym);
> >   gold_assert(new_symndx != -1U);
> >
> > This assert gets triggered when the build links glibc with the -r -X
> > flags (remove local symbols).
> >
> > This happens because with the given -X option GOLD removes all local
> > symbols, including those which still needed to resolve static relocs
> > later.
> >
> > LD keeps that kind of local symbols in the symbol table even if -X
> > requested. I guess GOLD should do the same.
> >
> > Please find attached the patch that fixes this issue.
> 
> Thanks, but this patch doesn't work.  It fails the testsuite.  The
> problem is that at the time your patch checks
> needs_output_symtab_entry, it will always return true.
> needs_output_symtab_entry will only return false if
> set_no_output_symtab_entry has been called, and that only happens at
> the end of the loop you patched.
> 
> I think what we need to do here is mark the local symbol as
> appropriate in scan_relocatable_relocs.  The use of the
> output_symtab_index_ field right now is a bit complicated.  It is
> initialized to 0.  In Sized_relobj::do_count_local_symbols we set the
> field to -1 if the symbol is not needed.  In
> Sized_relobj::do_finalize_local_symbols, if the field is still 0, we
> set it to the index in the output file.  Perhaps we should change that
> 0 == uninitialized, -1 == no index, -2 == needs index.  Then
> do_finalize_local_symbols should never see 0.
> 
> Ian


-- 
-Viktor
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