Getting more advanced, you can generally do this anywhere GDB will accept a value. Which means you can do things like:

> break my_file.c:123 if my_function() == 0x5

i.e. please stop at `my_file.c` line 123 but when `my_function()` is returning the value 0x5. GDB will handle calling the function and checking its value every time you get there.