[llvm-commits] [llvm] r173007 - /llvm/trunk/include/llvm/Object/ELF.h

[Kaylor, Andrew]

You probably already found this, but it looks like this code in RuntimeDyld.cpp is probably the cause:

        Check(i->getFileOffset(FileOffset));
        Check(i->getSection(si));
        if (si == obj->end_sections()) continue;
        Check(si->getContents(SectionData));
        Check(si->isText(IsCode));
        const uint8_t* SymPtr = (const uint8_t*)InputBuffer->getBufferStart() +
                                (uintptr_t)FileOffset;
        uintptr_t SectOffset = (uintptr_t)(SymPtr -
                                           (const uint8_t*)SectionData.begin());

This code is trying to calculate the offset into the section where the symbol belongs.  For ELF objects I think we could avoid this by using SymbolRef::getValue to grab the symbol's section offset directly, but I'm not sure how that would work for other object formats.

-Andy

-----Original Message-----
From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Michael Spencer
Sent: Sunday, January 20, 2013 11:58 PM
To: llvm-commits
Subject: Re: [llvm-commits] [llvm] r173007 - /llvm/trunk/include/llvm/Object/ELF.h

On Sun, Jan 20, 2013 at 10:46 PM, Michael J. Spencer <bigcheesegs at gmail.com> wrote:
> Author: mspencer
> Date: Mon Jan 21 00:46:11 2013
> New Revision: 173007
>
> URL: http://llvm.org/viewvc/llvm-project?rev=173007&view=rev
> Log:
> [Object] .bss sections have no content. PR15005.
>
> Modified:
>     llvm/trunk/include/llvm/Object/ELF.h
>
> Modified: llvm/trunk/include/llvm/Object/ELF.h
> URL: 
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Object/ELF
> .h?rev=173007&r1=173006&r2=173007&view=diff
> ======================================================================
> ========
> --- llvm/trunk/include/llvm/Object/ELF.h (original)
> +++ llvm/trunk/include/llvm/Object/ELF.h Mon Jan 21 00:46:11 2013
> @@ -1260,16 +1260,18 @@
>  error_code ELFObjectFile<ELFT>::getSectionContents(DataRefImpl Sec,
>                                                     StringRef &Result) const {
>    const Elf_Shdr *sec = reinterpret_cast<const Elf_Shdr *>(Sec.p);
> -  const char *start = (const char*)base() + sec->sh_offset;
> -  Result = StringRef(start, sec->sh_size);
> -  return object_error::success;
> +  return getSectionContents(sec, Result);
>  }
>
>  template<class ELFT>
>  error_code ELFObjectFile<ELFT>::getSectionContents(const Elf_Shdr *Sec,
>                                                     StringRef &Result) 
> const {
> -  const char *start = (const char*)base() + Sec->sh_offset;
> -  Result = StringRef(start, Sec->sh_size);
> +  if (Sec->sh_type == ELF::SHT_NOBITS)
> +    Result = StringRef();
> +  else {
> +    const char *start = (const char*)base() + Sec->sh_offset;
> +    Result = StringRef(start, Sec->sh_size);  }
>    return object_error::success;
>  }
>
>
>
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This broke some of the JIT tests. I'm working on figuring out why.

- Michael Spencer
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