Not given any more information, nobody will be able to tell you.
If your program runs fine otherwise, and this is the only thing you see (program does not execute) if you run it in the debugger, this can mean (among other things) that you either
- have an uninitialised variable or you do some nasty variable alias trickery, or have order of global variable initialisation issues
- do something that throws a signal early at startup (certain Windows API functions do that in normal operation)
It it happens when you run the program normally, then it just means that your program exits with code 3, which, knowing nothing about your program, means pretty much nothing or anything.
