No there is a bug in free_size.c (at least).
You didn't solve the conflict in addH.
What conflict ? i think addH is ok.
Why not rewrite free_size.c with GLib's GHashTable?
I didn't know it exists :P but now that i've wrtten my own hash, I'll leave it.
I found the problem: it was in my_malloc_hook.c, when i printed a NULL pointer, it would print "(nil)" in the file and then free_size reads "(nil)" with %p and it's not NULL. I fixed it, however I encounter another error:
I run the hooks with
LD_PREOAD=/path/to/my_malloc_hook.so pidgin and sometimes I get Segmentation Fault after about 10 seconds of execution. So there is still something wrong with my_malloc_hook.c
Do you know what it could be ?