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Why can't I include windows.h in afx(MFC) projects?
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h is a Windows-specific header file for the C and C++ programming languages which contains declarations for all of the functions in the Windows API, all the common macros used by Windows programmers, and all the data types used by the various functions and subsystems.
h" or "cannot open include file 'winres. h'". That problem happens because the file, which is needed to compile programs that make calls to the Windows operating system, is not installed. To fix this, download and install the Microsoft Windows SDK for your system (it is free).
Search for and locate the windows. h header file in the C:\Program Files\Microsoft SDKs directory. Open the file C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin\vcvars32.
Typically, MFC application code includes afx.h or afxwin.h (the latter includes former). First two lines of windows.h are
#ifndef _WINDOWS_
#define _WINDOWS_
which means that _WINDOWS_ becomes defined if this header is included.
Afx.h includes afxver_.h and this header includes afxv_w32.h which contains following code:
#ifdef _WINDOWS_
#error WINDOWS.H already included. MFC apps must not #include <windows.h>
#endif
...
#include <windows.h>
So, if you include windows.h before MFC headers, you'll get this error generated in compile time and, as you can see, if you include afxwin.h you don't need to include windows.h yourself - it will already be included by afxv_w32.h.
68
Because in MFC you are not supposed to use it directly. AFAIR you should include afx.h instead, which in turn indirectly includes windows.h the proper way.
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