'_WIN32_WINNT' / 'WINVER' : macro redefinition

Question

I have a VS2015 C++ project. app has to run on both Windows 7 and XP. So, I want to set _WIN32_WINNT & WINVER to _WIN32_WINNT_WINXP .

This is how stdafx.h of my project looks like:

stdafx.h

#pragma once

#include "targetver.h"

#define _WIN32_WINNT        _WIN32_WINNT_WINXP         
#define WINVER              _WIN32_WINNT_WINXP   

#include <WinSDKVer.h>

// Windows Header Files:
#include <windows.h>

When compiled, I see the following warning/error:

stdafx.h(12): error C2220: warning treated as error - no 'object' file generated
1>stdafx.h(12): warning C4005: '_WIN32_WINNT': macro redefinition
1>  C:\Program Files (x86)\Microsoft SDKs\Windows\v7.1A\include\SDKDDKVer.h(197): note: see previous definition of '_WIN32_WINNT'
1>stdafx.h(13): warning C4005: 'WINVER': macro redefinition
1>  C:\Program Files (x86)\Microsoft SDKs\Windows\v7.1A\include\SDKDDKVer.h(212): note: see previous definition of 'WINVER'

Answer 1

Because the #include "targetver.h" is including <sdkddkver.h> which already defines the constants _WIN32_WINNT and WINVER when they aren't already defined by the build environment.

As a matter of fact, the auto-generated targetver.h tells you exactly how to fix this:

#pragma once

// Including SDKDDKVer.h defines the highest available Windows platform.

// If you wish to build your application for a previous Windows platform, include WinSDKVer.h and
// set the _WIN32_WINNT macro to the platform you wish to support before including SDKDDKVer.h.

#include <SDKDDKVer.h>

Simple solution. Just define those constants before the inclusion of targetver.h . You might have to use the actual literal value for XP since you haven't include the header file that defines

Like this:

// x501 is XP
#define _WIN32_WINNT        0x0501         
#define WINVER              0x0501  

#include "targetver.h"
#include <windows.h>

Answer 2

Try

#include <winsdkver.h>
#undef _WIN32_WINNT
#define _WIN32_WINNT _WIN32_WINNT_WINXP
#include <SDKDDKVer.h>

You #include <winsdkver.h> so you can use _WIN32_WIN_WINXP. However, then you need to #undef _WIN32_WINNT because it is defined in <winsdkver.h>. That way when you use #define _WIN32_WINNT _WIN32_WINNT_WINXP you don't get the redefinition of _WIN32_WINNT warning.