intercept_malloc.c

static void *(*real_malloc)(unsigned long) = 0;                             // 1
int malloc_counter = 0;                                                     // 2

static void malloc_init(void) {                                             // 3
    real_malloc = (void *(*)(unsigned long))dlsym(RTLD_NEXT, "malloc");
    if (real_malloc == 0)
        fprintf(stderr, "Error in `dlsym`: %s\n", dlerror());
}

void *malloc(unsigned long size) {                                          // 4
    if (real_malloc == 0)
        malloc_init();                                                      // 5

    malloc_counter++;                                                       // 6

    return real_malloc(size);                                               // 7
}