1#include <stdio.h>  // fprintf(), NULL
2#include <stdlib.h> // exit(), EXIT_SUCCESS
3#include <string.h>
4#include <dlfcn.h>
5#include <crt_externs.h>
6#include <mach-o/dyld_priv.h>
7
8
9int foo() { return 0; }
10
11int alt_foo() { return 10; }
12
13
14
15
16static const struct dyld_interpose_tuple sTable[] = { {&alt_foo, &foo} };
17
18
19__attribute__((constructor))
20void init()
21{
22  // switch main executable to use alt_foo() when it calls foo()
23  dyld_dynamic_interpose((const struct mach_header*)_NSGetMachExecuteHeader(), sTable, 1);
24
25}
26
27