Question

I have the following code in one cpp file which is part of a project in visual c++ 2010 I’m not understanding why the call to free fails.

#include <time.h>

#include "stdafx.h"
#include <wchar.h>
#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>

wchar_t * getRandomShortToken(){

    int       i;
    wchar_t * token = 0;

    srand((unsigned int)time(NULL));

    token = (wchar_t*)malloc(sizeof(wchar_t) * 6);
    memset(token, 0, sizeof(wchar_t*) *6);

    for(i = 0; i < 5; i++){

        token[i] = ( rand() % 20 ) + 64;

    }

    return token;

}

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

    wchar_t * token = 0;

    system("pause");

    token = getRandomShortToken();
    printf("My Token is '%ls'\n', token);
    system("pause");
    free(token);

    system("pause");

    return 0;
}

Note that the token is properly populated in the printf!

Answer 1

Your code corrupts memory in this statement:

memset(token, 0, sizeof(wchar_t*) *6); 

You probably meant:

memset(token, 0, sizeof(wchar_t) * 6);

There’s a syntax error in:

printf("My Token is '%ls'\n', token);

Should be:

printf("My Token is '%ls'\n", token);