[visionegg] Re: segmentation fault

Hi,

In Python, a seg fault is really bad -- it means something died at the C level, which exactly what Python is supposed to insulate you from. So, clearly there's something going on at a low level that's wrong. I'm not sure this is a Vision Egg specific problem, but here's what I'd do.

First, check the usual suspects:

You don't have any binary Python modules/packages compiled for the wrong version of Python do you? (You didn't copy site-packages/something from a different version of Python or otherwise hope to mix-and-match between precompiled binaries, did you?)

If you built some packages from source and then upgraded them, did you clear out the previously installed binaries?

Finally, if the above all checks out, I hunt down seg faults by bracketing the offending line with print statements and re-running the code iteratively to home in on the single Python line. This is necessary because the seg fault bypasses the normal Python exception handling machinery. (Although pygame apparently tries to catch even these problems, I don't understand the "pygame parachute" mechanism and therefore I'm still a bit suspicious.)

If you can identify the exact line in Grating.py where the segfault occurs, we have some hope. Line 307 of the most up-to-date Gratings.py is a call to PyOpenGL's glTexImage1D. So that may put the blame on PyOpenGL, but I can't understand why a call to glTexImage1D would do a free().

If you find the problem, please let us know.

Your check_config list looks good.

Cheers!
Andrew

richard srebro wrote:

Trying to run grating I get a segmentation fault.
Running on FC2

This is the traceback

Pygame Parachute Traceback:
Segmentation fault
[dick@fovea dick]$ python grating.py
2004-10-07 13:42:58,003 (4768) INFO: Script grating.py started Vision
Egg 1.0-cvs with process id 4768.
2004-10-07 13:43:18,933 (4768) INFO: Requesting window 640 x 700 24 bpp
(8 8 8 0 RGBA).
2004-10-07 13:43:19,028 (4768) INFO: OpenGL 1.2 Mesa 5.0.2, Mesa DRI
Intel(R) 845G 20021115 x86/MMX+/SSE2, 2d3D, Inc
2004-10-07 13:43:19,032 (4768) INFO: Video system reports 32 bpp (8 8 8
8 RGBA).
2004-10-07 13:43:19,036 (4768) WARNING: Could not sync buffer swapping
to vblank because you are running linux but not known/supported drivers
(only nVidia and recent Mesa DRI Radeon currently supported).
Pygame Parachute Traceback:
 File "/usr/lib/python2.3/site-packages/VisionEgg/Gratings.py", line
307, in __init__
free(): invalid pointer 0x9581468!
Segmentation fault


This is my config
[dick@fovea visionegg-1.0-cvs]$ python check-config.py
check-config.py for Vision Egg 1.0
[2003/09/22 05:37:03 CVS revision 1.20]
Beginning configuration check.
VisionEgg version 1.0-cvs

VisionEgg modules in /usr/lib/python2.3/site-packages/VisionEgg
VisionEgg system directory /usr/VisionEgg
VisionEgg user directory /home/dick/VisionEgg

Config file found at /usr/VisionEgg/VisionEgg.cfg

SYNCLYNC_PRESENT = 0
VISIONEGG_ALWAYS_START_LOGGING = 0
VISIONEGG_CONFIG_FILE = /usr/VisionEgg/VisionEgg.cfg
VISIONEGG_FRAMELESS_WINDOW = 0
VISIONEGG_FULLSCREEN = 0
VISIONEGG_GAMMA_FILE =
VISIONEGG_GAMMA_INVERT_BLUE = 2.1
VISIONEGG_GAMMA_INVERT_GREEN = 2.1
VISIONEGG_GAMMA_INVERT_RED = 2.1
VISIONEGG_GAMMA_SOURCE = none
VISIONEGG_GUI_INIT = 1
VISIONEGG_GUI_ON_ERROR = 1
VISIONEGG_HIDE_MOUSE = 0
VISIONEGG_LOG_FILE = VisionEgg.log
VISIONEGG_LOG_TO_STDERR = 1
VISIONEGG_MAXPRIORITY = 0
VISIONEGG_MONITOR_REFRESH_HZ = 200.0
VISIONEGG_PREFERRED_BPP = 24
VISIONEGG_REQUEST_ALPHA_BITS = 0
VISIONEGG_REQUEST_BLUE_BITS = 8
VISIONEGG_REQUEST_GREEN_BITS = 8
VISIONEGG_REQUEST_RED_BITS = 8
VISIONEGG_SCREEN_H = 480
VISIONEGG_SCREEN_W = 640
VISIONEGG_SYNC_SWAP = 1
VISIONEGG_SYSTEM_DIR = /usr/VisionEgg
VISIONEGG_TKINTER_OK = 1
VISIONEGG_USER_DIR = /home/dick/VisionEgg

Version checklist:

Python version 2.3.3 (OK)
extra Python info: (#1, May 7 2004, 10:31:40) [GCC 3.3.3 20040412 (Red
Hat Linux 3.3.3-7)]
Numeric version 23.1 (OK)
PyOpenGL (package "OpenGL") version 2.0.1.07 (OK)
pygame version 1.6 (OK)
Python Imaging Library (package "Image") version 1.1.4 (OK)

Optional module(s):

Pyro version 3.4 (OK)


Any help very much appreciated.

Thanks

Dick


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Andrew D. Straw Post-doctoral scholar
,-. Dickinson Lab
\_/ California Institute of Technology
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