Thread: Help needed.

Hi All,
I am very new to VC++ programming. I tried to create a window. That's all. I wrote a program and it runs but doesn't shows the window. When I tried to Build it again it needs the exe file to overwrite it. But since the window is invisible and it has not ended, VC++ compiler says that
fatal error LNK1168: cannot open Debug/test.exe for writing.
I will paste code here

Code:

#include<windows.h>
long _stdcall WndProc(HWND,UINT,UINT,long);
WNDCLASS wndclass;
int _stdcall WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,char *CmdLine,int nCmdShow)
{
	HWND hwnd;
	MSG msg;
	wndclass.hInstance=hInstance;
	wndclass.lpfnWndProc=WndProc;
	wndclass.lpszClassName="My Class";
	wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
	RegisterClass(&wndclass);
	hwnd=CreateWindow("My Class","First Window",WS_OVERLAPPEDWINDOW,20,20,100,100,0,0,hInstance,0);
	ShowWindow(hwnd,nCmdShow);
	while(GetMessage(&msg,0,0,0))
	{
		DispatchMessage(&msg);
	}
	return 0;
}
long _stdcall WndProc(HWND hwnd,UINT x ,UINT y,long z)
{
	switch(x)
	{
	case WM_DESTROY:
		PostQuitMessage(0);
		break;
	default:
		DefWindowProc(hwnd,x,y,z);
	}
	return 0L;
}

I ran the program Again. Now it gives strange error message
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/test.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.
Whatz happening.
Can any one rescue me.

>>> fatal error LNK1168: cannot open Debug/test.exe for writing.

A common cause of that error is still having the program open somewhere. Make sure you close the last version of the program before trying to compile it again. (Code does not cause this problem).

>>> error LNK2001: unresolved external symbol _main

That is typical when you have mixed up a windows app and a console app. Windows apps use WinMain, console apps main(). When you start your project make sure you start it with the correct application type.

By the way...

>>> should be a TranslateMessage in that message loop too

... he's right.

Originally posted by _Elixia_
I'm pretty sure there's should be a TranslateMessage in that message loop too.

It is just for translating virtual key messages into character messages, so the program will still work, just certain key combinations will not work, if you wish to process the character messages.

You should also have an UpdateWindow() call after ShowWindow() to force the window to be shown.

>>> It is just for translating virtual key messages into character messages,

True, let me re-phrase, for the vast majority of Windows app, there should be a call to TranslateMessage() in the dispatch loop.

Putting it in doesn't really do any harm, and it'll fix an otherwise confusing problem should you actually need it.

Yes, of course. I should have pointed out that I only stated that it was not needed in his program so that the original poster would understand that it was not the cause of his problems. A proper windows program should call it, just in case you require it in a future update.

I should also point out that not calling UpdateWindow() is also not the cause of his problems.