Q125049: BUG: ExtractIcon Not Freeing Up Memory

Article: Q125049
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): 
Last Modified: 06-NOV-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

Calling ExtractIcon() with a -1 as the iIcon parameter to obtain the total
number of icons in a file results in a loss of system resources. Each time an
application calls ExtractIcon() in this manner, the system loses some resources.
However, when the application that called ExtractIcon() terminates, the
resources are freed. This situation can cause low memory conditions when an
application that is running calls ExtractIcon() many times to find the number of
icons in a number of different files.

CAUSE
=====

The problem occurs when you call ExtractIcon() with the iIcon parameter set to
-1 in order to count the number of icons. ExtractIcon() erroneously omits a
GlobalFree call that is supposed to free some intermediate global memory used to
count the number of icons in the specified file. As a result, each call made to
ExtractIcon() in this manner results in a loss of memory and an occupied
selector until the application terminates.

RESOLUTION
==========

To work around the problem, you can extract consecutive icons in a file until
ExtractIcon() fails. This will give you the total number of icons in the file
without memory loss.

STATUS
======

Microsoft has confirmed this to be a bug in the products listed at the beginning
of this article. We are researching this bug and will post new information here
in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

Below is a function that you could call to retrieve the number of icons in a
file:

  int NumIcons(HINSTANCE hinst, LPCSTR lpszExeName)
     {
     int i = 0;
     HICON hIcon;

     while (hIcon = ExtractIcon(hinst,lpszExeName,i))
       {
       i++;
       DestroyIcon(hIcon);
       }
     return (i);
     }

Additional query words: 3.1

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.