fatal error C1189: #error : WINDOWS.H already included. MFC apps must not #include

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Hi,
In my project after including some header files,it is showing the below error.When I removed those statements it is showing a bulk error of '178' numbers.And I checked which are those including files.Can anyone help me how can I remove that error.

C#

#ifdef _WINDOWS_
#error WINDOWS.H already included.  MFC apps must not #include <windows.h>
#endif

Thanks,

Posted 14-Mar-13 18:36pm

danil33

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Matthew Faithfull 15-Mar-13 3:22am

Add one or more of these '178' errors to your post so we can see what we're really trying to solve.

Have you tried adding the #includes back in one at a time to see which one or more is causing the problem?

4 solutions

Solution 4

This may help someone. I got the same error from a UnitTest project.
I changed my stdafx.h to this:

XML

#include "targetver.h"

#include <afx.h>
#include <afxwin.h>         // MFC core and standard components

// Headers for CppUnitTest
#include "CppUnitTest.h"

// TODO: reference additional headers your program requires here

... and the error went.

Posted 26-Aug-15 4:02am

Member 7995632

Updated 26-Aug-15 4:03am

v2

Solution 2

Check probably `Windows.h` might be included in your `stdafx.h` file. If so, then comment `Windows.h` and then check, the error may go off. Because I had the same problem I resolve in same way.

Posted 29-Aug-13 1:07am

Rasmi Ranjan Nayak

Solution 3

thanks from all of you
your solutions were good and applicational.

i solved it through the following method:

just add below precompile definitions :

C++

#ifdef __windows__
#undef __windows__
#endif

and thanks again

Posted 14-Dec-14 1:21am

Mahdi Nejadsahebi

Comments

Jochen Arndt 9-Feb-15 8:16am

Don't do this!

While this avoids the error message it does not solve the problem and breaks the MFC header file inclusion checks.

The only solution:
Don't include windows.h when using MFC. It will be included by the MFC header files using special mechanisms.

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H.Brydon · Accepted Answer · 2013-03-15T04:17:00

Here are some of the rules I use for #include files which might be helpful to you:
- Use precompiled headers ("#include <stdafx.h>"). This must be the first include in your .cpp file. It should never be in a .h file. [I also routinely rename the file to something project specific (eg. util_stdafx.h) in a multi-project environment so that the wrong file is not included somewhere. You can choose whether or not to do this...]
- Immediately after the stdafx.h file include should be the #include corresponding to your .cpp file. This way, the .h file will #include anything it needs to work properly.
- After these 2 includes in your .cpp file, include anything else needed for the .cpp file to run correctly.
- Header files that come with the compiler are called "Stable headers". These should be the only ones that appear in stdafx.h, along with #defines used by these headers (eg. WIN32_LEAN_AND_MEAN, _WIN32_WINNT etc.). If you are on windows, then stdafx.h is the only place you should see "#include <windows.h>"
- The first non-blank non-comment lines in header files should be either "#pragma once" or guard block definition (or both).