[PATCH] D44622: [ELF] - Fix for "LLD crashes with --emit-relocs when trying to proccess .eh_frame"

[Domagoj Stolfa via Phabricator via llvm-commits]

dstolfa added a comment.

In https://reviews.llvm.org/D44622#1042505, @rafael wrote:

> Domagoj Stolfa via Phabricator via llvm-commits
>  <llvm-commits at lists.llvm.org> writes:
>
> > dstolfa added a comment.
> > 
> > In https://reviews.llvm.org/D44622#1042429, @espindola wrote:
> > 
> >> The crash is from
> >> 
> >>   // This is for --emit-relocs. If .text.foo is emitted as .text.bar, we want
> >>   // to emit .rela.text.foo as .rela.text.bar for consistency (this is not
> >>   // technically required, but not doing it is odd). This code guarantees that.
> >>   if ((S->Type == SHT_REL || S->Type == SHT_RELA) &&
> >>       !isa<SyntheticSection>(S)) {
> >>     OutputSection *Out =
> >>         cast<InputSection>(S)->getRelocatedSection()->getOutputSection();
> >> 
> >> 
> >> Where Out is null because we call this for the relocation section before .eh_frame. The caller is
> >> 
> >>   std::vector<OutputSection *> V;
> >>   for (InputSectionBase *S : InputSections) {
> >>     if (!S->Live || S->Parent)
> >>       continue;
> >>   
> >>     StringRef Name = getOutputSectionName(S);
> >> 
> >> 
> >> So this suggests two options that might be simpler.
> >> 
> >> - Just handle Out being null. We are just trying to get a better looking output section name. It is not critical.
> >> - Do two passes over the input section in LinkerScript::addOrphanSections.
> > 
> > This is the approach I've taken in https://reviews.llvm.org/D44601 (though it was still a workaround at that point). @arichardson pointed out that we should probably have an output similar to ld.bfd and gold, so I suppose the fix should be guided by that as well as where it would be best to handle this case?
>
> Instead of returning "" it could return S->Name and that would handle
>  all real world cases I think.
>
> I think doing two passes in LinkerScript::addOrphanSections might be the
>  best solution as it is simple and handles even synthetic tests like using
>  a linker script to assign .eh_frame to an output section with a
>  different name.
>
> Cheers,
> Rafael


I believe the change I've just added in the review fixes the issue in the most minimal way possible.


https://reviews.llvm.org/D44622