How to debug crash in reference project?

I have a project in which I'm taking reference of another library. I have changed something in the classes of reference project. How do i find that crash is occurring because of the changes. Gdb shows nothing when application crashes开发者_如何学C.

The simpliest way i see is testing without the changes you made, and see if the app is still crashing... If you find out the modifications are not the source of crash, post some code, it will be better to solve your problem.