Hello every body

My processor is PPC440EP which has QNX 6.5 as Operating system on it.
An application is run which I has developed by myself and after a while (about 10 hours), the OS is getting restarted.
In my code in some places I called "shutdown" system call for a certain purpose and before I call that system call, I 
put down "printf" and "fflush (stdout);" in the code. I suppose that after the OS is getting restarted, I see the logs 
from "printf", but I do not.
Is it possible that the OS is getting restarted from somewhere else?(such as socket programming section or corruption on
 network's driver or something like that? )
Is it possible the restarting situation is because of the SIGSEGV or SEGFAULT or any other signals like them?

King regards.