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

[Rui Ueyama]

What was proposed? Is that something that might have helped me find the
issue? It actually took a whole day to find it and workaround, so any help
would have been appreciated...


On Sat, Nov 9, 2013 at 11:56 PM, Chandler Carruth <chandlerc at google.com>wrote:

> 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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>>
>
>
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