I am currently trying to write a python extension and am using gdb to find and fix problems in c. However recently i have found when building with -g. The extension crashes with malloc() memory corruption. When i try and create a python list with PyList_New. This does not happen when i remove -g. So im guessing -g has altered the way memory gets allocated in order to capture the info for debugging which is also breaking the extension. How do i fix this?

Possibly try using -ggdb or maybe even -gstabs+, -feliminate-unused-debug-symbols or a combination to give the desired debug information without causing the crashes.
The Python C API documentation mentions in it's memory management section that you should not use the C library memory management functions (like malloc) on python objects but I assume you are not doing this?

If you have not looked at this reference it may be useful anyway.I would be interested in the results if you manage to track this down.

Edit : Just thought I'd add this.. I've recently been looking at the cython method of writing C extensions for python - you may find it useful. You can find it here if you are interested.