Function zmalloc_size

app/redis-6.2.6/src/zmalloc.c:273–277

 * information as the first bytes of every allocation. */
#ifndef HAVE_MALLOC_SIZE
size_t zmalloc_size(void *ptr) {
    void *realptr = (char*)ptr-PREFIX_SIZE;
    size_t size = *((size_t*)realptr);
    return size+PREFIX_SIZE;
}
size_t zmalloc_usable_size(void *ptr) {
    return zmalloc_size(ptr)-PREFIX_SIZE;
}