How can I free uint32_t pointer?

Question

I'm newbie with pointer in c. I'm just testing code like this

void test(uint32_t *data)
{
    unsigned char raw_data[] = "this is a test data";
    unsigned char *raw = (unsigned char*)malloc(strlen((char*)raw_data));
    memcpy(raw, raw_data, strlen((char*)raw_data)+1);
    *data = (uint32_t)raw;
}

int _tmain(int argc, _TCHAR* argv[])
{
    uint32_t data;

    test(&data);
    printf("%s\n", data);
    if (data != NULL)
    {
        free(data);
    }
    return 0;
}

I use a uint32_t to store a unsigned char* , when I try to free data , I meet a error error C2664: “void free(void *)”: uint32_t can not convert to “void *" .

How can I free data ?

First, thanks to Phạm Anh Tuấn, Gerhardh, KBlr and son on. You are very kind.

Solution:

void test(uintptr_t *data)
{
    unsigned char raw_data[] = "this is a test data";
    unsigned char *raw = (unsigned char*)malloc(strlen((char*)raw_data) + 1);
    memcpy(raw, raw_data, strlen((char*)raw_data));
    raw[strlen((char *)raw_data)] = '\0';
    *data = (uintptr_t)raw;
}

int _tmain(int argc, _TCHAR* argv[])
{
    uintptr_t data;

    test(&data);
    printf("%s\n", data);
    if (data != NULL)
    {
        free((void *)data);
    }
    getchar();
    return 0;
}

Must add a '\\0' to raw as terminating string, then free works. And for working on 64bit , change uint32_t to intptr_t .

Answer 1

Your program will not work on 64bit machine since size of pointer on 64bit machine is 8bytes .

You can use uintptr_t instead uint32_t to hold the address. While freeing cast the uintptr_t to void* as below sample code shows.

#include<stdint.h>
#include<stdlib.h>
#include<stdio.h>
void test(uintptr_t *data)
{
    unsigned char raw_data[] = "this is a test data";
    unsigned char *raw = (unsigned char*)malloc(strlen((char*)raw_data));
    memcpy(raw, raw_data, strlen((char*)raw_data)+1);
    *data = (uintptr_t)raw;
}

int main(int argc, char* argv[])
{
    uintptr_t data;

    test(&data);
    printf("%s\n", (char *)data);
    if ((void *)data != NULL)
    {
        free((void *)data);
    }
    return 0;
}