Print the requested, usable, and real sizes of a heap chunk

print_heap_sizes.c

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

int main() {
    printf("size of size_t: %zu\n", sizeof(size_t));
    int i;
    for (i = 0; i < 10; i++) {
        size_t size = i * 8;
        void *m = malloc(size);
        printf("requested chunk of size %zu\n", size);
        printf("malloc_usable_size: %zu\n", malloc_usable_size(m));
        printf("real_size: %zu\n", *((size_t*) (m - sizeof(size_t))) - 1);
    }
}