#include <dlfcn.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#ifdef __APPLE__
#define LIBC "libc.dylib"
#else
#define LIBC "libc.so"
#endif

const char *libc_err = "Could not load " LIBC "\n";
static void*(*malloc_orig)(size_t);

bool perturb = false;
uint8_t perturb_byte = 0;
void init() {
    static void *handle = 0;
    if (!handle)
        handle = dlopen(LIBC, RTLD_LOCAL);
    if (!handle) {
        write(STDERR_FILENO, libc_err, strlen(libc_err));
        abort();
    }
    *(void**)&malloc_orig = dlsym(handle, "malloc");
    const char *s = getenv("MALLOC_PERTURB_");
    if (s) {
        perturb = true;
        perturb_byte = atoi(s) % 256;
    }
}

#ifdef __cplusplus
extern "C"
#endif
void *malloc(size_t size) {
    if (!malloc_orig)
        init();
    void *ptr = malloc_orig(size);
    if (perturb)
        memset(ptr, perturb_byte, size);
    return ptr;
}