Clone void* pointer to int

Question

I have this signature of a function:

void* cloneInt(const void* i);

This int represents a key for a hash function. I need to have this clone function as it is in my API for a generic implementation of a hash table (this function is a part of the int implementation, this function will be forwarded as a pointer to a function that my generic implementation will use). But I am having a problem understanding: how can you clone an int? I need to return a pointer that will point on the same value of int, but a different place in the memory. This got me very much confused.

Will this work? void* cloneInt(const void* i) { int myInt = (int*)malloc(sizeof(int)); myInt = *i; return &myInt; } — Eyzuky, Aug 24 '16 at 08:33
No it won't, you need to create `int* myInt`, and you need to assign it with `*myInt = *i`. — GSerg, Aug 24 '16 at 08:35
And when i want to free this int, should i free(myInt) or free(*myInt)? Should i free the pointer or the int itself? — Eyzuky, Aug 24 '16 at 08:35
I believe you should consult http://stackoverflow.com/q/562303/11683 before going any further @Eyzuky. — GSerg, Aug 24 '16 at 08:38
I all depends on how you designed the map. Who's responsible for allocating memory for the keys & objects stored, the map or the user? And When freeing it? — StoryTeller - Unslander Monica, Aug 24 '16 at 08:43
Why does a function called `cloneInt` accept/return a pointer to `void`? — Oliver Charlesworth, Aug 24 '16 at 08:43
@OliverCharlesworth OP said "_I need to have this clone function as it is in my API for a generic implementation of a hash table_" — Garf365, Aug 24 '16 at 09:13

score 5 · Accepted Answer · answered Aug 24 '16 at 08:38

This will work:

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

void* cloneInt(const void* i)
{
    int *myInt = malloc(sizeof(int));
    *myInt = *(int*)i;
    return myInt;
}

int main(int argc, char** argv)
{
    int i=10;
    int *j;
    j = cloneInt(&i);
    printf("j: %d i: %d\n", *j, i);
    free(j);
}

Clone void* pointer to int

1 Answers1