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Date: Thu, 23 Oct 2014 21:07:04 -0400
From: Ken Brown <kbrown AT cornell DOT edu>
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On 10/23/2014 4:32 PM, Ken Brown wrote:
> On 10/23/2014 11:37 AM, Corinna Vinschen wrote:
>> On Oct 23 08:04, Ken Brown wrote:
>>> On 10/23/2014 7:31 AM, Jon TURNEY wrote:
>>>> On 20/10/2014 14:03, Ken Brown wrote:
>>>>> Or is there some other plausible explanation for "impossible" crashes?
>>>>> This can't just be a result of a gdb bug, because in at least one case
>>>>> the assertion can be shown to be valid by using printf instead of gdb.
>>>>>
>>>>> [*] By "impossible" I mean that examination of the relevant
>>>>> variables in
>>>>> gdb shows that the assertions are in fact true.  Two ongoing
>>>>> examples are
>>>>>
>>>>>     http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18438
>>>>>     http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18769
>>>>
>>>> As a suggestion, you might want to also take a careful look at how
>>>> signal
>>>> delivery is implemented in cygwin on x86_64
>>>>
>>>> I had a vague idea that there was, at some time in the past, a fix
>>>> made for
>>>> register corruption on x86_64 after a signal was handled, but I
>>>> can't find it
>>>> now, so maybe I imagined it.
>>>
>>> Is this what you're thinking of?
>>>
>>>    https://cygwin.com/ml/cygwin-cvs/2014-q1/msg00020.html
>>>
>>>> But if for e.g. the flags register was getting
>>>> corrupted when a signal interrupts the main thread, that could
>>>> perhaps also
>>>> explain what is being seen.
>>>
>>> Yes, flags register corruption is exactly what Eli suggested in the
>>> other
>>> bug report I cited.
>>
>> The aforementioned patch was supposed to fix this problem and it is
>> definitely in the current 1.7.32 release...
>
> The ChangeLog entry just mentions the FPU control word and the XMM
> registers, but not the ordinary FLAGS register (or rather EFLAGS for x86
> and RFLAGS for x86_64, if I'm understanding correctly what I find in
> Wikipedia).  Did the patch also take care of that?

Never mind, it looks like that was already OK before the patch.  I see 
that there are pushf and popf instructions in gendef.

Ken


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