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Mysterious quitting problem...

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I just made a basic window shell application for about the tenth time (as practice). It doesn''t do anything right now except handle messages, but I''m having trouble quitting! Every time I quit the application (using the X close button), I get an error! I debugged and I got this unusual message: First-chance exception in bitmaps.exe: 0xC0000005: Access Violation. The program ''C:\WINDOWS\Start Menu\Geoff''s Stuff\C++\DirectDraw\bitmaps\Debug\bitmaps.exe'' has exited with code 0 (0x0). My WM_DESTROY code is simply PostQuitMessage(0); I have no idea what''s wrong; everything seems perfect!

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Guest Anonymous Poster
Just a guess, but maybe you should try PostQuitMessage(1);

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Well, maybe... but what''s the differences b-tween PostQuitMessage(0) and PostQuitMesage(1), what is it stands?

The road may be long, wind may be rough. But with a will at heart, all shall begone. ~savage chant

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Well, that parameter is the exit code, a value that can be queried by other applications when the application in question terminates. The value you pass will be assigned to the wParam member of the MSG structure used in your app''s message pump which you''re then supposed to use as the final return value in WinMain. Although I haven''t seen any definitive word on this, Microsoft''s sample code always uses 0 as the parameter to PostQuitMessage, so I''d say that it''s probably the right value to use.

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Guest Anonymous Poster
quote:
Original post by Fundy Glostna
I just made a basic window shell application for about the tenth time (as practice). It doesn''t do anything right now except handle messages, but I''m having trouble quitting! Every time I quit the application (using the X close button), I get an error!

I debugged and I got this unusual message:

First-chance exception in bitmaps.exe: 0xC0000005: Access Violation.
The program ''C:\WINDOWS\Start Menu\Geoff''s Stuff\C++\DirectDraw\bitmaps\Debug\bitmaps.exe'' has exited with code 0 (0x0).

My WM_DESTROY code is simply
PostQuitMessage(0);

I have no idea what''s wrong; everything seems perfect!


Hi,

Try sticking the call to PostQuitMessage() in an WM_CLOSE message handler. I had a problem similar to yours the other day where my app wouldn''t terminate properly when I clicked the close button (the app window would disappear but the app would still be listed as an active proces when you clicked Ctrl + Alt + Del). I don''t know why but using a WM_CLOSE handler instead of a WM_DESTROY handler fixed the problem.

case (WM_CLOSE):
{
PostQuitMessage(0);
return 0;
} break;




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I disagree. This is how it should be done:
    
...
case WM_CLOSE:
DestroyWindow(hwnd);
return 0;

case WM_DESTROY:
PostQuitMessage(0);
return 0;


I'll bet that your problem has nothing to do with your app's message pump but, rather, something that happens when it terminates. For instance, that you might be using some resource that had just been deallocated or some such thing. Sadly, the debugger won't help you much with this sort of error. My suggestion is to start commenting out portions of your code no having to do with the message pump. Eventually, you'll hit the problem.

Edited by - merlin9x9 on January 28, 2002 1:42:58 AM

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Well, I re-wrote the code in a fresh workspace and project, and it worked perfectly. The problem might have been external, but I may never know!

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Aha! I figured it out after all! I had created a direct draw interface and a primary surface with a backbuffer in that application. After the main loop breaked, I released the main direct draw interface pointer FIRST, before releasing the surfaces, and that''s what caused the error.

BEFORE (BAD):
  
if(lpdd) lpdd->Release();
if(lpddsPrimary) lpddsPrimary->Release();
if(lpddsBack) lpddsBack->Release();


AFTER (GOOD):
  
if(lpddsPrimary) lpddsPrimary->Release();
if(lpddsBack) lpddsBack->Release();
if(lpdd) lpdd->Release();

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