Question

Title pretty much sums this up. How come it’s possible that i can assign a locally created Point a (in the function ReadPoint()) into a variable that’s in a different scope. Doesn’t the locally created Point a gets ‘popped’ away along with stack of function readPoint() ? What exactly is going on ?

struct Point readPoint(void)
        {
            struct Point a;

                printf("x = ");
                scanf("%lf",&b.x);

                printf("y = ");
                scanf("%lf",&b.y);

            return a;
        }

        int main(int argc, char **argv) {
            Point test = readPoint();
            printPoint(test);
            return 0
        }

Answer 1

structs are no different to primitive types in this regard. It’s exactly the same principle as:

int foo(void)
{
    int x = 5;
    return x;
}

int main(void)
{
    int y = foo();
    printf("%d\n", y);
}

The details of how this is achieved are implementation-dependent. But usually, the return value (whether it’s an int or a struct) is placed onto the stack by the called function, and then the caller then can then access that stack location.