Why does the compiler still warn me about unsafe strtok even after I define _CRT_SECURE_NO_WARNINGS?

Question

I am using Visual Studio Express 2012 for Windows Desktop.

I always get error

Error C4996: 'strtok': This function or variable may be unsafe.
  Consider using strtok_s instead.
  To disable deprecation, use _CRT_SECURE_NO_WARNINGS.
  See online help for details.

When I try to build the following:

#include "stdafx.h"
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstring>
using namespace std;
int main() {
    char the_string[81], *p;
    cout << "Input a string to parse: ";
    cin.getline(the_string, 81);
    p = strtok(the_string, ",");
    while (p != NULL) {
        cout << p << endl;
        p = strtok(NULL, ",");
    }
    system("PAUSE");
    return 0;
}

Why am I getting this error even though I define _CRT_SECURE_NO_WARNINGS, and how do I fix it?

Answer 1

Your #define doesn't work because of the content of your precompiled header file (stdafx.h). The boilerplate one looks like this:

#pragma once
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>

It is the last two #includes that cause the problem, those .h files themselves already #include string.h. Your #define is therefore too late.

Beyond defining the macro in the compiler settings instead, the simple workaround is to just move the #define into your stdafx.h file. Fix:

#pragma once
#define _CRT_SECURE_NO_WARNINGS
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>