do_no_evil.c

/*
Compile this with:

    $ clang -O3 do_no_evil.c && ./a.out

Reference http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html
*/

#include <stdio.h>
#include <stdlib.h>

static void (*WhatToDo)() = 0;

static void EvilThings() {
  printf("Do Evil\n");
}

void DoNotDoThis() {
  WhatToDo = EvilThings;
  printf("Do Not Do This!\n");
  // Fail Safe exit
  exit(1); // Don't do this ever
}

void DoSomething() {
  WhatToDo();
}


int main() {
  DoSomething();
}