weak_alias.c

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

void* backed_malloc(size_t size) __attribute__ ((weak, alias ("malloc")));

void* hook_malloc(size_t size) {
  printf("%ld\n", size);
  return backed_malloc(size + 1);
}

void* malloc(size_t size) __attribute__ ((weak, alias ("hook_malloc")));

int main() {
  char *buf = malloc(12);
  return 0;
}