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Date: Sun, 6 Apr 2025 14:58:05 -0600
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Subject: Re: Python 3.12 testing
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From: Brian Inglis via Cygwin <cygwin AT cygwin DOT com>
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On 2025-04-06 14:32, dwes1--- via Cygwin wrote:
> To the Python maintainer and anyone else testing Python 3.12:
> 
> A few weeks ago, the python developer requested help with evaluating the Python 
> 3.12 release.
> I downloaded the python312-test package, and worked out that
> python -m test.test_threading -v
> failed during the second test in the file, sometimes with an immediate segfault, 
> sometimes by hanging
> until I tried to attach gdb, which immediately reported an empty stack and a 
> null stack pointer.
> 
> Adding print calls to the test narrowed the point of failure to some time during 
> thread cleanup,
> so I ran the test under gdb, adding breakpoints to pthread_exit and 
> pthread::exit, which caught
> the test before the segfault, and displayed a stack working back to 
> pthread_wrapper, whose caller
> was set to null.  Stepping through the function eventually reached a call to 
> ExitThread, then the
> segfault with no reported stack.
> 
> My current guess is that ExitThread somehow returns, leading to control falling 
> off the end of
> pthread_wrapper and failing to return.  (This is rather more sensible than my 
> previous guess
> that Python had somehow managed to call the NULL pointer recursively, and not 
> noticed until
> gdb took a look at things)  I suppose I could try to compile Cygwin with an 
> error message after
> ExitThread to see if that prints, but I am otherwise out of ideas.
> 
> I first checked this around January on a Windows 10 machine from 2016, then on a 
> machine from
> within the last year that is says it is also Windows 10.
> 
> I hope this helps

Thanks for helping!

Have you tried running under strace and looking at the output from:

$ strace -o python-312-test-threading.strace python -m test.test_threading -v

or

$ strace -o python-312-test-threading-hung.strace -p PID

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher  but when there is no more to cut
                                 -- Antoine de Saint-Exupéry

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