Free function not working

Question

I have the following C code.

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

int main()
{
    while (1) {
        int *test = malloc(sizeof(*test));
        test = 500;
        free(test);
    }
    return 0;
}

The free function does not seem to work as the allocated memory grows to 2GB within a few seconds. What is the problem?

Answer 1

You can only free a pointer that is a return of malloc.

In writing test = 500, you've changed the memory location pointed to by test. Trying to free that is undefined behaviour.

To assign a value to your allocated integer, derefence it: *test = 500;

Answer 2

test = 500;

This changed the memory address. Therefor the original memory you allocated was never freed.

Maybe you meant to write:

*test = 500;