Question

I’m writing an application in C for my university course. In a section of my application I increase an integer iteratively. Using a printf statement I can tell that int1 is increase to 20 as it should be but then the run fails. I would like to know why this is the case?

int main() {
    int i,int1=0, int2=0;
    for (i = 0; i<10; i++) {
        int1 = (int2 + 2);
        int2 = int1;
    }
}

The program has to by inline with ANSI C which I believe states that using:

int1 = (int2 + 2);

is undefined behaviour as the compiler cannot guarantee which of the ‘same’ variables is processed first. (Please do correct me if I am wrong however!) That is why I have taken the longer way around, but the application fails just the same using either way.

What is the reason this fails?

Answer 1

Your program doesn’t fail, you simply forgot to return 0; at the end of your program, to indicate that your program ran correctly.

As for the “undefined behavior”: No, that is perfectly valid C code.