how to use gdb to debug something in asterisk (I used this to help the chan_sccp_b developers to find a bug in the module unloading/loading process

gdb asterisk
then type
set args -cf
(enter)
run
(enter)

Then cause the crash

you should just copy and paste the backtrace once asterisk crashes
type:
bt full
(enter)

That's the information a developer would need to know to find the bug in the module.