[Python-Dev] Issue #8863 adds a new PYTHONNOFAULTHANDLER?environment variable

[Victor Stinner]

Le lundi 20 décembre 2010 15:55:57, Stefan Krah a écrit :
> > The backtrace is valid. Don't you think that this backtrace is more
> > useful than just "Segmentation fault"?
> 
> Perhaps I misunderstood, but I thought the purpose of the patch was to
> let developers act more quickly on bug reports. I wonder if this output
> really speeds up the process.

The fault handler helps developers because they don't have to have a Python 
compiled in debug mode and to run the application in a debugger (like gdb).

If the developer is unable to reproduce an error, because it's an Heisenbug, 
or because the developer doesn't have the same OS, libraries and/or 
applications, the fault handler helps the developer to isolate the problem.

Many bugs only occur once and you cannot report a bug report because you don't 
have any useful information.

But the fault handler doesn't help graphical applications not started from a 
terminal...

> Do you have an example bug where this patch helps in finding the precise
> location of a segfault?

Any bug report which only contain "Segmentation fault" information. But I 
cannot give you a revelant example because users are too shy to report an 
issue if they don't have more information than just "the program crashed". 
With a fault handler displaying the Python backtrace, I hope that more *users* 
will report bugs.

Example of an issue with only the "Segmentation fault" information:
http://bugs.python.org/issue6011#msg121551
I am unable to reproduce this crash, and I'm very frustrated because I want to 
fix it! :-)

Another example which might benefit from the fault handler:
http://bugs.python.org/issue7424
---
Compiling /usr/pkg/lib/python2.6/test/test_builtin.py ...
[1]   Segmentation fault (core dumped) PYTHONPATH=/usr/...
*** Error code 139
---

If the reporter already wrote a minimal script, it doesn't help. The fault 
handler helps to write the minimal script (to isolate the bug).

> I did use version 10. I've verified the same behavior with a fresh py3k
> checkout and this patch: (...)
> 
> My machine currently has a load average of 2. Perhaps you'll be able to
> reproduce it if you crank up the load average.

What is your OS (name, version)? I only tested crashers on Linux (Debian Sid).

Victor