/*

Run at CSE like this

$ clang -Wno-everything invalid3.c -o invalid3
$ ./invalid3
I hate you.
$

*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

void f(void);

int main(void) {
    f();

    printf("I love you and will never say,\n");
    printf("I hate you.\n");

    return 0;
}

void f(void) {
    uint64_t a[1];

#ifdef __clang__
#if __clang_major__ >= 16
#error "Don't know the correct offset for this clang version"
#elif __clang_major__ >= 14
    a[2] += 14;
#elif __clang_major__ >= 4
    a[2] += 17;
#elif __clang_major__ == 3
#if __clang_minor__ >= 5
    a[2] += 17;
#elif __clang_minor__ >= 4
    a[2] += 15;
#else
// clang 3.0-3.3 are broken on godbolt.org
#error "Don't know the correct offset for this clang version"
#endif
#else
// clang <3.0 are not avalible on godbolt.org
#error "Don't know the correct offset for this clang version"
#endif
#else
#error "This program must be compiled with clang"
#endif

    // function f has it return address on the stack
    // the call of function f from main should return to
    // the next statement which is:  printf("I love you and will never say,\n");
    //
    // on CSE servers  (clang 11.0 x86_64/Linux)
    // f's return address is stored where a[2] would be
    //
    // so changing a[2] changes where the function returns
    //
    // adding 17 to a[12] happens to cause it to return 2 statements later
    // at:  printf("I hate you.\n");
}