CreateWindow() class function conflicts with CreateWindowA()?

[Josh]

#pragma once

#include "../../../le3.h"
#include <windows.h>

namespace le3
{

class WindowsWindow;

class WindowsWindowDriver : public WindowDriver
{
	LRESULT CALLBACK WndProc( HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam );
	int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR szCmdLine, int iCmdShow );
	public:
	virtual WindowsWindow* CreateWindow(const int& width,const int& height);
};

}

 

The compiler is complaining:

C:\Engine\engine\Drivers\Graphics\../../Drivers/Window/Windows/WindowsWindowDriver.h:16:73: error: macro "CreateWindowA" requires 11 arguments, but only 2 given

c:\program files (x86)\codeblocks\mingw\bin\../lib/gcc/mingw32/4.4.1/../../../../include/winuser.h:4328: error: 'CreateWindowA' declared as a 'virtual' field

[Rick]

In C, CreateWindow is a macro that calls CreateWindowA (or CreateWindowW). CreateWindowA is a macro that calls the CreateWindowExA WinAPI function.

[Josh]

Right, but does that mean you can never have a class function called CreateWindow???

[Azazel226]

Right, but does that mean you can never have a class function called CreateWindow???

 

 

Greetings,

 

This appears to be a common issue. Here's a quote from http://www.winvistatips.com/opos-so-linedisplay-createwindow-problem-t194728.html

 

The reason is a "misunderstanding" between the Class Wizard and the MSVC system headers. In the system headers the name CreateWindow and DestroyWindow are used as macro definitions and they are mapped to DestroyWindowA and CreateWindowA in the ANSI version. Microsoft uses this macro-replacing -mechanism to allow ANSI and UNICODE compiling. However, if you have C++ classes with a method using a "reserved" word the compiler will generate errors. In general: you should not use method names which are already used in the Window API. This is not a restriction of the language C++ but of the MSVC compiler.

 

Later on in the thread the author got around this problem by doing a #undef on the CreateWindow macro.

 

Problem solved!

 

In translation unit that #includes compiler generated header which

has

CreateWindow hassle (#included windows.h):

-#include windows.h

-#undef CreateWindow

-#include compiler generated header

 

 

 

Oh yeah, first post, and hello

[Rick]

Right, but does that mean you can never have a class function called CreateWindow???

 

Unless you undefine the macro, like posted above. Since macros can be used anywhere, it's seeing that as a Macro. It doesn't know if you mean to use the macro or not. Given how macros work, how could it?

 

This is just 1 of the reasons macros are evil. It sucks that Win 32 API is loaded with them. It servers as a good warning to all library creators though.

[Josh]

Here's what I did:

#pragma once

#include "../../../le3.h"
#include <windows.h>

#undef CreateWindow

namespace le3
{

class WindowsWindow;

class WindowsWindowDriver : public WindowDriver
{
	LRESULT CALLBACK WndProc( HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam );
	public:
	virtual WindowsWindow* CreateWindow(const int& width,const int& height);
};

}