OK, you might get a different backtrace now using a build without -fomit-frame-pointer. If so please post it back to the list - this could be why there were ?? entries.
Unfortunately the backtrace is identical.
For debug, the flag is -g, but the Geany build system normally enables this already. Also for debugging it's best not to optimize higher than -O2.
Im using -O2
Regards Sascha Heid