[lld] r194349 - [ELF] Un-break undef-from-main-dso.test on MSVC 2012.

[Chandler Carruth]

This commit might help motivate the warnings we've discussed surrounding
MSVC record layout...


On Sat, Nov 9, 2013 at 11:48 PM, Rui Ueyama <ruiu at google.com> wrote:

> Author: ruiu
> Date: Sun Nov 10 01:48:33 2013
> New Revision: 194349
>
> URL: http://llvm.org/viewvc/llvm-project?rev=194349&view=rev
> Log:
> [ELF] Un-break undef-from-main-dso.test on MSVC 2012.
>
> The result of sizeof(SymbolTable<ELFT>::SymbolEntry) in DynamicSymbolTable
> <ELFT>::write() was different from the same expression in RelocationTable
> <ELFT>::write(), although the same template parameters were passed. They
> were
> 40 and 32, respectively. As a result, the same vector was treated as a
> vector of 40 byte values in some places and a vector of 32 values in other
> places. That caused an weird issue, resulting in collapse of the rela.dyn
> section.
>
> I suspect that this is a padding size calculation bug in MSVC 2012, but I
> may be wrong. Reordering the fields to eliminate padding seems to fix the
> issue.
>
> Modified:
>     lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h
>
> Modified: lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h?rev=194349&r1=194348&r2=194349&view=diff
>
> ==============================================================================
> --- lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h (original)
> +++ lld/trunk/lib/ReaderWriter/ELF/SectionChunks.h Sun Nov 10 01:48:33 2013
> @@ -614,12 +614,12 @@ class SymbolTable : public Section<ELFT>
>    struct SymbolEntry {
>      SymbolEntry(const Atom *a, const Elf_Sym &sym,
>                  const lld::AtomLayout *layout)
> -        : _atom(a), _symbol(sym), _atomLayout(layout) {}
> +        : _atom(a), _atomLayout(layout), _symbol(sym) {}
>      SymbolEntry() : _atom(nullptr) {}
>
>      const Atom *_atom;
> -    Elf_Sym _symbol;
>      const lld::AtomLayout *_atomLayout;
> +    Elf_Sym _symbol;
>    };
>
>  public:
>
>
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