Steps to do when you think you found a bug:
Tracing crash bugs
Configure your ZNC version with --enable-debug.
./configure --enable-debug --enable-other-things-you-may-want make make install
Then you can run ZNC under gdb:
gdb ./znc handle SIGPIPE nostop run -D
If znc is already running, you can attach gdb to the already-running instance (where pid is znc's process id):
gdb ./znc attach pid handle SIGPIPE nostop cont
Now you use ZNC as you would always do and try to make it crash. Once it crashed, gdb will show you something like this:
Program received signal SIGSEGV, Segmentation fault.
Now we can get the useful info. This info, together with an explanation how the bug happened are then very useful to the developers.
Why use --enable-debug?
With this flag
bt full shows much more info, which is needed to understand why the crash had happened.
If you're interested in details, search the Web for "debug symbols" or just try with and without.