[LLVMdev] [PATCH] Seh exceptions on Win64

[Yaron Keren]

OK. The register name patch committed in r206565 and the SEH patch is on

  http://reviews.llvm.org/D3418




2014-04-17 22:40 GMT+03:00 Vadim Chugunov <vadimcn at gmail.com>:

> So I made a patch that fixes the "missing epilogue" problem by emitting a
> trap instruction for IR 'unreachable'.
> A secondary use for it would be for anyone wanting to make double-sure
> that 'noreturn' functions, indeed, do not return.
>
> Would LLVM devs entertain the idea of committing something like this?
>
>
> On Thu, Apr 17, 2014 at 10:10 AM, Kai Nacke <kai.nacke at redstar.de> wrote:
>
>> Hi,
>>
>>
>> On 15.04.2014 23:44, Vadim Chugunov wrote:
>>
>>> Hi,
>>> I am curious - how does clang deal with epilogue-less functions that
>>> result from _Raise_Exception being marked 'noreturn'?
>>> I've also been playing with Kai's patch, and discovered that this tends
>>> to greatly confuse Windows stack unwinder in cases when noreturn call is
>>> at the end of a function, so execution appears to flow directly into the
>>> prologue of the next function.
>>>
>>
>> Yes, that's true. The patch has a problem if the epilogue is dead code
>> and eliminated.
>>
>>  It looks like MSVC solves this problem by inserting 'int 3' after calls
>>> to noreturns.  This is actually the prime motivation for me wanting to
>>> emit code for 'unreachable'
>>> <http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-April/072145.html> ...
>>>
>>> Vadim
>>>
>>
>> Yaron also pointed out that
>>
>> int main() { throw 1; }
>>
>> generates two .seh_endprologue instructions. I still did not fix this bug.
>>
>> Regards,
>> Kai
>>
>>
>>
>>>
>>> On Tue, Apr 15, 2014 at 11:43 AM, Martell Malone
>>> <martellmalone at gmail.com <mailto:martellmalone at gmail.com>> wrote:
>>>
>>>     Hi,
>>>
>>>     I'd like to submit a patch to match the clang patch on the front end.
>>>     http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-
>>> Mon-20140414/103257.html
>>>
>>>     The front end doesn't need this patch to work but it's still
>>> important.
>>>     This is mostly based on work done by kai from redstar.de
>>>     <http://redstar.de>
>>>
>>>
>>>     Could I get some feedback on this?
>>>     I'm not sure if the emitting of the register names will effect msvc.
>>>
>>>     Many Thanks
>>>
>>>     Martell Malone
>>>
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>>> http://llvm.cs.uiuc.edu
>>>
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>>>
>>>
>>>
>>>
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>>
>
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