ANSI C: If a function pointer points to executable code does that mean less execution overhead than simply invoking the function? [duplicate]

Question

We know that using function pointers in C can be quite helpful when used in the proper scenarios (calling a function at runtime vs compile time, making the code more readable, etc.), but there isn't much literature around simple function invocation vs using a function pointer.

void foo(void) {
    printf("hello\n");
}

int testFcn(void) {

    // simple invokation
    foo();

    return 0;
}

// Or, declare function pointer and assign
void (*myFunc)(void) = foo;

int testFcn(myFunc) {

    // Function pointer invokation.
    myFunc();

    return 0;
}

Perhaps the only real way to tell is to analyze the .lst files and .map files?

Answer 1

In general case, when function pointer is stored in data segment's memory, invoking a function through such a pointer will involve more overhead, not less overhead.

The real-life performance might vary greatly, depending on whether the pointer is in the CPU cache, already loaded into CPU register, properly predicted by branch prediction mechanism and other factors.