[PATCH] D30080: MC/COFF: Do not emit forward associative section referenceds.

[David Majnemer via llvm-commits]

No, COMDATs cannot be associated in that way. They should always form a DAG.

On Thu, Feb 16, 2017 at 9:47 PM, Rui Ueyama <ruiu at google.com> wrote:

> That is probably not hard indeed, but you can create cycles if you use
> LLVM IR, can't you?
>
> On Thu, Feb 16, 2017 at 9:33 PM, David Majnemer <david.majnemer at gmail.com>
> wrote:
>
>> I believe its possible via LLVM IR, I don't think it'd be too hard to
>> make it work.
>>
>>
>> On Thu, Feb 16, 2017 at 6:53 PM, Rui Ueyama <ruiu at google.com> wrote:
>>
>>> On Thu, Feb 16, 2017 at 6:49 PM, David Majnemer <
>>> david.majnemer at gmail.com> wrote:
>>>
>>>> Does MSCOFF permit chains of associated sections? I can't remember if
>>>> they do.
>>>>
>>>
>>> IIRC that is not explicitly banned by the spec, but no one produces
>>> chained associated sections, and I can't imagine a valid of use it.
>>>
>>>
>>>> On Thu, Feb 16, 2017 at 6:35 PM Rui Ueyama via Phabricator via
>>>> llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>>>
>>>>> ruiu created this revision.
>>>>>
>>>>> MSVC link.exe cannot handle associative sections that refer later
>>>>> sections in the section header. Technically, such COFF object doesn't
>>>>> violate the Microsoft COFF spec, as the spec doesn't say anything
>>>>> about that, but still we should avoid doing that to make it compatible
>>>>> with MS tools.
>>>>>
>>>>> This patch assigns smaller section numbers to non-associative sections
>>>>> and larger numbers to associative sections. This should resolve the
>>>>> compatibility issue.
>>>>>
>>>>>
>>>>> https://reviews.llvm.org/D30080
>>>>>
>>>>> Files:
>>>>>   llvm/lib/MC/WinCOFFObjectWriter.cpp
>>>>>   llvm/test/DebugInfo/COFF/globals.ll
>>>>>   llvm/test/DebugInfo/COFF/types-data-members.ll
>>>>>   llvm/test/MC/COFF/section-comdat.s
>>>>>
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>>>
>>>>
>>>
>>
>
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