c++ - access violation in WM_PAINT not caught

Question

To test this problem I have written a minimal windows application. If I force an access violation in the WM_PAINT handler this exception never gets to the debugger. If started without debugger the access violation also does not show up. Usually you should get the Windows Error Reporting dialog.

Digging a bit deeper it seems that something in user32.dll catches all incoming exceptions. Is this normal behavior? Can I control this somehow? Isn't catching all exceptions a security risk? At least it is annoying as hell.

This is with a 32- and 64-bit application on Vista 64. On XP the exception seems to be handled as expected. Other windows messages have the same problem. Maybe all of them?

The WM_PAINT handler:

case WM_PAINT:
    hdc = BeginPaint(hWnd, &ps);
    *(int*)0 = 0;
    EndPaint(hWnd, &ps);
    break;

Answer 1

As a workaround I remove all registered exception handlers in my window procedure. Quite ugly.

LRESULT CALLBACK window_proc( 
    HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
    // get thread information block
    NT_TIB* tib;
    __asm {
        mov EAX, FS:[18h]
        mov [tib], EAX
    }
    // old exception handler list
    _EXCEPTION_REGISTRATION_RECORD* old_exception_handler = tib->ExceptionList;
    // remove all exception handler with exception of the default handler
    while( tib->ExceptionList->Next != (_EXCEPTION_REGISTRATION_RECORD*)-1 ) {
        tib->ExceptionList = tib->ExceptionList->Next;
    }

    LRESULT result = DefWindowProc( hwnd, uMsg, wParam, lParam );

    // restore old exception handler
    tib->ExceptionList = old_exception_handler;

    return result;
}