Debugging segmentation faults

[John Nagle]

    You're using Python on a web server to do something
complicated.  You must suffer.

    Are you trying to fork off a subprocess in a multithreaded
program?  That's unlikely to work.  The sematics differ
from OS to OS (Solaris forks all the threads, most other
operating systems don't; most UNIX-based OSs copy all the
open file descriptors, but some give you control of which
open files are passed), and Python may not be thread-safe
in that area.

				John Nagle

SPE - Stani's Python Editor wrote:
> If the error is reproducable and you can run wxPython, you could use
> the excellent WinPdb debugger, which ships with SPE (python editor):
> http://www.digitalpeers.com/pythondebugger/
> 
> ... but if you can only run your script on a remote server this won't
> help you.
> 
> Stani
> 
> --
> SPE - http://pythonide.stani.be
> 
> On 7 Mrz., 20:15, "George Sakkis" <george.sak... at gmail.com> wrote:
> 
>>I have a pure python program (no C extensions) that occasionally core
>>dumps in a non-reproducible way. The program is started by a (non-
>>python) cgi script when a form is submitted. It involves running a
>>bunch of other programs through subprocess in multiple threads and
>>writing its output in several files. So the only suspicious parts I
>>can think of is subprocess and/or multithreading. For the
>>multithreading part I'm using a modified version of threadpool.py
>>(http://www.chrisarndt.de/en/software/python/threadpool/), which is
>>built on top of the threading and Queue stdlib modules. Whatever bugs
>>may linger there, I'd hope that they would show up as normal Python
>>exceptions instead of segfaults.
>>
>>All I have now is a few not particularly insightful core files (actual
>>path names and args changed for privacy):
>>
>>/home/gsakkis/foo>gdb --core core.20140
>>GNU gdb Red Hat Linux (5.2-2)
>>Copyright 2002 Free Software Foundation, Inc.
>>GDB is free software, covered by the GNU General Public License, and
>>you are
>>welcome to change it and/or distribute copies of it under certain
>>conditions.
>>Type "show copying" to see the conditions.
>>There is absolutely no warranty for GDB.  Type "show warranty" for
>>details.
>>This GDB was configured as "i386-redhat-linux".
>>Core was generated by `python2.5 /home/gsakkis/foo/foo.py --XXX --
>>max=30 --bar=/tmp/83840`
>>Program terminated with signal 11, Segmentation fault.
>>#0  0x080b222d in ?? ()
>>(gdb) backtrace
>>#0  0x080b222d in ?? ()
>>#1  0x080b28d1 in ?? ()
>>#2  0x080fa8ab in ?? ()
>>#3  0x0805c918 in ?? ()
>>(...)
>>#28 0x080b310f in ?? ()
>>#29 0x080dbfdd in ?? ()
>>#30 0x40021fef in ?? ()
>>
>>Any hints ?
> 
> 
>