mac os x dyld plug

// libinterposers.c

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

typedef struct interpose_s {
    void *new_func;
    void *orig_func;
} interpose_t;

int my_open(const char *, int, mode_t);
int my_close(int);

static const interpose_t interposers[] \
    __attribute__ ((section("__DATA, __interpose"))) = {
        { (void *)my_open,  (void *)open  },
        { (void *)my_close, (void *)close },
    };

int
my_open(const char *path, int flags, mode_t mode)
{
    int ret = open(path, flags, mode);
    printf("--> %d = open(%s, %x, %x)\n", ret, path, flags, mode);
    return ret;
}

int
my_close(int d)
{
    int ret = close(d);
    printf("--> %d = close(%d)\n", ret, d);
    return ret;
}

But did not enter into effect here first

haidragondeMacBook-Air:2-11 haidragon$ gcc -Wall -dynamiclib -o /tmp/libinterposers.dylib ./libinterposers.c 
./libinterposers.c:15:26: warning: unused variable 'interposers' [-Wunused-const-variable]
static const interpose_t interposers[] \
                         ^
1 warning generated.
haidragondeMacBook-Air:2-11 haidragon$ DYLD_INSERT_LIBRARIES=/tmp/libinterposers.dylib cat /dev/null
haidragondeMacBook-Air:2-11 haidragon$