CODEWITHSUNDEEP
c++winapi
user1476981
user1476981

Reputation: 11

Windows API Crash when window displayed

I have created a Windows application. It should be noted that this issue only occurs on certain computers (it runs fine on mine). I create the window as follows:

RECT wr = {0, 0, rOp->resX, rOp->resY};
AdjustWindowRect(&wr, WS_OVERLAPPEDWINDOW, FALSE);
WNDCLASS wc;
wc.style         = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc   = WndProc;
wc.cbClsExtra    = 0;
wc.cbWndExtra    = 0;
wc.hInstance     = hAppInst;
wc.hIcon         = NULL;
wc.hCursor       = LoadCursor(0, IDC_ARROW);
wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wc.lpszMenuName  = NULL;
wc.lpszClassName = L"App";
if (!RegisterClass(&wc))
{
    return false;
}
hAppWnd = CreateWindow( L"App", lpWindowName, WS_VISIBLE | WS_OVERLAPPED, 0, 0, wr.right - wr.left, wr.bottom - wr.top, NULL, NULL, hAppInst, NULL );

On the PCs of two of my friends, this crashes when the window is displayed. If I remove WS_VISIBLE, the application continues to run fine until ShowWindow is called, upon which time it crashes. My friends report seeing a white window immediately before it crashes, so the window appears to be being displayed.

Does anyone have any theories as to why this might be happening?

EDIT: WndProc is as follows:

LRESULT CALLBACK WndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
    switch (Msg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    case WM_PAINT:
        reng->draw();
        return 0;
    case WM_ERASEBKGND:
        return 1;
    default:
        return reng->DefProc(hWnd, Msg, wParam, lParam);
    }
}

DefProc is a function pointer to this:

LRESULT CALLBACK DefProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
    switch (Msg)
    {
    case GM_NEWGAME:
        newGame();
        return 0;
    default:
        return DefWindowProc(hWnd, Msg, wParam, lParam);
    }
}

(GM_NEWGAME is a user-defined message)

The DefProc function pointer is always set before the window is created.

Upvotes: 1

Views: 826

Answers (2)

Ivan Shcherbakov
Ivan Shcherbakov

Reputation: 2113

As the code you have posted here has nothing that can explicitly cause a crash, and as it only happens when the window is actually shown, it looks like the bug is inside the draw() method.

The best solution would be to build a debug version of your application and ask your friend to create a dump file with task manager when it crashes. They you can open it in Visual Studio and see the exact line in your code that caused the crash.

Upvotes: 1

jgou
jgou

Reputation: 93

The must be in your wndproc. Maybe there is a synchronization problem between an object creation and its use in there.

Upvotes: 1

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