LIBCACHE.H

#pragma once

#ifdef __cplusplus
extern "C" {
#endif

typedef struct Cache Cache;

int CreateCache(Cache *cache);
int DestroyCache(Cache *cache);

#ifdef __cplusplus
}
#endif


CACHE.CPP

#include "libcache.h"

#ifdef __cplusplus
extern "C" {
#endif
    int CreateCache(Cache *cache)
    {
        std::cout << "AAA: " << cache << std::endl;
        cache = new Cache();
        std::cout << "BBB: " << cache << std::endl;
        return 0;
    }

    int DestroyCache(Cache *cache)
    {
        delete cache;
        cache = NULL;
        return 0;
    }
#ifdef __cplusplus
}
#endif

MAIN.C

int main(int argc, char *argv[])
{
    Cache *cache = NULL;
    CreateCache(cache);
    printf("%s - %p\n", "Cache created", cache);
    //DestroyCache(cache);
    printf("%s - %p\n", "Cache destroyed", cache);
    return 0;
}