INFO: SetMessageQueue Used in MFC WinMain (118611)


The information in this article applies to:

  • The Microsoft Foundation Classes (MFC), when used with:
    • Microsoft Visual C++ for Windows, 16-bit edition 1.5
    • Microsoft Visual C++ for Windows, 16-bit edition 1.51
    • Microsoft Visual C++ for Windows, 16-bit edition 1.52
    • Microsoft Visual C++, 32-bit Editions 2.0
    • Microsoft Visual C++, 32-bit Editions 2.1
This article was previously published under Q118611

SUMMARY

Functions that use the applications message queue do not work correctly if they are called in the constructor of a global or static object. SetMessageQueue is called in the initialization code at the beginning of the MFC WinMain() function. SetMessageQueue replaces the current message queue with a new message queue. The constructors of global or static C++ objects are called before WinMain(). If these constructors call functions that rely on the message queue, the objects do not work properly.

MORE INFORMATION

MFC for Windows, version 2.5, calls SetMessageQueue in the AfxWinInit() function, which is called by the MFC WinMain() function. The constructors for global and static objects are called before WinMain(). These constructors should not call functions that use the applications message queue or rely on the message queue remaining the same after the constructor is executed. These functions include:

  • Creating a window
  • Setting a timer (using SetTimer)
  • Setting a hook (using SetWindowsHook)
  • Posting a message
If any one of these things is done in the constructor and is not processed or removed from the application's message queue before the constructor exits, it will not work later in the application. To work around this, initialize each of these objects in the CWinApp::InitInstance() function: Define an initialization member function for the object and call it in the CWinApp::InitInstance() function.
Modification Type:MajorLast Reviewed:12/2/2003
Keywords:kbArchitecture kbinfo KB118611
©2003 Microsoft Corporation. All rights reserved.