Dereferencing NULL pointer warning in C even it is assigned already

Question

I am trying to implement a unit cache structure and use calloc method(dynamic allocation) to give it memory space. I used the type-defined cache_unit as the type of the pointer to receive casted return type from calloc. Normally after calloc, all the bits in the allocated area should be 0. However my output is like random numbers instead of 0 and there're two warning messages.

Here's my code:

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

int main() {
    typedef struct {
        bool enabled;
        uint8_t block[10];
        int access_time;
    } cache_unit;
    

    cache_unit* cache = (cache_unit*) calloc(2, sizeof(cache_unit));
    printf("%x ", *cache);

    return 0;
}

Here are the warning messages on printf:

Answer 1

With printf("%x ", *cache);, "%x" expects a matching unsigned, not a cache_unit.

Try

printf("%d\n", cache->access_time);