PRB: Cannot Create More Child Windows and Other Problems When You Reach the Maximum Number of Allowable Child Windows in an MDI Application

This article was previously published under Q318677
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When a multiple-document interface (MDI) application runs and creates many child windows, the following problems may occur:
  • You cannot create any more child windows.
  • The Start button or menu items do not respond.
  • You cannot run other applications.
  • Other applications may be adversely affected.
This problem may occur even when there is adequate physical memory available in Microsoft Windows NT, Microsoft Windows 2000, or Microsoft Windows XP. This lack of physical memory occurs when the desktop heap in the WIN32 subsystem is depleted.
This behavior is by design.
You cannot determine the maximum number of child windows that can be created in an application because this depends on several factors:
  • How a program is implemented,
  • The environment of the program, such as:
    • Physical factors, such as implemented memory
    • Variable factors, such as the number of applications that are run concurrently.
NOTE: You cannot check the usage status of the desktop heap while an application is running.

You may also notice memory shortage problems when you run an MDI application that creates many document templates by using the same menu resource. MFC is not implemented with a function that deletes added document templates. For additional information about templates that share a menu resource, click the article number below to view the article in the Microsoft Knowledge Base:
118435 INFO: Sharing Menus Between MDI Child Windows
For additional information about the desktop heap, click the article numbers below to view the articles in the Microsoft Knowledge Base:
126962 Increasing the Desktop Application Heap
184802 PRB: User32.dll or Kernel32.dll Fails to Initialize

Article ID: 318677 - Last Review: 10/24/2013 10:07:23 - Revision: 2.1

Microsoft Foundation Class Library 4.2, Microsoft Visual C++ 4.0 Standard Edition, Microsoft Visual C++ 4.1 Subscription, Microsoft Visual C++ 4.2 Professional Edition, Microsoft Visual C++ 5.0 Standard Edition, Microsoft Visual C++ 6.0 Service Pack 5

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