Hi All,
I am getting a segmentation fault in gift-extract-features using the
latest version from CVS. It is occurring in code of which I wrote the
first version years ago, but that code has been modified a *lot* since I
last looked at it.
The error is occurring in function gabor_filter in file gabor.c, at
lines 112-113. Specifically it is target_image[k] on line 113 that is
causing the seg. fault. This is occuring with k = 1, but even "print
*target_image" in gdb is causing a problem, so it would see that the
original calculation of the pointer target_image is the problem. This
occurs earlier in the function, with the line:
target_image=&image[(width*height-1)-(y*width+x+kernel_size[filter_scale]/2)];
It appears that a lot of this sort of pointer arithmetic has been
introduced in order to try to avoid redundant calculations inside loops
- which is fine so long as the calculations are correct. In many cases I
suspect that the optimizer would have picked such things up anyway, and
with less risk.
I've added some code to print the values of the pointers, and I observe
that immediately prior to the crash:
image = 0x35525010
target_image = 0x35525008
So, we see that it has tried to read from before the start of image[].
The seg. fault is thus not surprising.
That "-1" in the calculation above is ringing alarm bells for me. Why is
it there?
Anyway, I would be very glad if the person who made these changes is
still reading these lists, and could re-check the calculations that they
made. That would probably be a lot more efficient than me trying to
decipher it all.
Any other thoughts also very welcome.
Regards,
David
--
Dr David McG. Squire, Senior Lecturer
Clayton School of Information Technology, Monash University, Australia
CRICOS Provider No. 00008C http://www.csse.monash.edu.au/~davids/
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