Thread: warning: control reaches end of non-void function

I got this warning message
"warning: control reaches end of non-void function"

May I know exactly what does it mean?

Assumably, it means that you have to return a value using the return statement before the end of your function. This does not apply to void functions because a void function does not return a value.

And what is the difference between the compiling option -O2 and -O3?

GCC Help: Options That Control Optimization

Code:

int foo( void )
{
    int x = 10;

    /* note, we've now reached the end of the function,
        and we aren't returning anything like we should. */
}

Quzah.

> But does 03 should run faster, since it is suppose to optimize further?
Maybe.
There are way too many factors to take into account for each increment in optimisation level to always produce a gain. -O3 is better than -O2 on some programs (an average set IIRC), but not all programs.