[lld] r278550 - [ELF] - Fix for: error "invalid section index: xxx" when linking FreeBSD kernel.

[Rafael Espíndola via llvm-commits]

On 12 August 2016 at 15:25, George Rimar via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: grimar
> Date: Fri Aug 12 14:25:54 2016
> New Revision: 278550
>
> URL: http://llvm.org/viewvc/llvm-project?rev=278550&view=rev
> Log:
> [ELF] - Fix for: error "invalid section index: xxx" when linking FreeBSD kernel.
>
> We found that GNU assembler 2.17.50 [FreeBSD] 2007-07-03
> could generate broken objects. STT_SECTION symbols can be
> associated with SHT_REL[A]/SHT_SYMTAB/SHT_STRTAB sections.
>
> This is PR28868, patch fixes handling of such files.
>
> Differential revision: https://reviews.llvm.org/D23201
>
> Added:
>     lld/trunk/test/ELF/section-symbols.test
> Modified:
>     lld/trunk/ELF/InputFiles.cpp
>
> Modified: lld/trunk/ELF/InputFiles.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=278550&r1=278549&r2=278550&view=diff
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.cpp (original)
> +++ lld/trunk/ELF/InputFiles.cpp Fri Aug 12 14:25:54 2016
> @@ -343,10 +343,15 @@ elf::ObjectFile<ELFT>::getSection(const
>    uint32_t Index = this->getSectionIndex(Sym);
>    if (Index == 0)
>      return nullptr;
> -  if (Index >= Sections.size() || !Sections[Index])
> +  if (Index >= Sections.size())
>      fatal(getFilename(this) + ": invalid section index: " + Twine(Index));
>    InputSectionBase<ELFT> *S = Sections[Index];
> -  if (S == &InputSectionBase<ELFT>::Discarded)
> +  // We found that GNU assembler 2.17.50 [FreeBSD] 2007-07-03
> +  // could generate broken objects. STT_SECTION symbols can be
> +  // associated with SHT_REL[A]/SHT_SYMTAB/SHT_STRTAB sections.
> +  // In this case it is fine for section to be null here as we
> +  // do not allocate sections of these types.

That gas bug can be avoided by using --strip-local-absolute, so it is
not clear that it is a good idea to hack around such a broken file in
lld.

Cheers,
Rafael