I have this function defined: struct heap_validation { size_t num_alloc; size_t num_alloc_sz; struct memory *mem; }; ... bool get_isallocated(struct metadata_record *); When I call the heap_validation function from hashtable_traverse and print the result, I've gotten the following values: 0,255 ,246 void hashtable_traverse(struct metadata_record *metarec, struct heap_validation *heap_val) { printf("get_isallocated(metarec): %d\n",get_isallocated(metarec)); bool retrieved = false; bool allocated = get_isallocated(metarec); if (allocated) { heap_val->num_alloc += 1; I also tried with %d and I get the same result.