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Date:	Thu, 23 Oct 2014 08:04:15 -0400
From:	Ken Brown <kbrown AT cornell DOT edu>
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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.

> (More generally, it doesn't have to be another thread which is causing these
> problems, it could be some form of interrupt)
>

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