DOCUMENT:Q199540 06-FEB-2000 [visualc] TITLE :BUG: Memory Leaks When Using Bitmaps in VC++ Mac 4.0b 68K Apps PRODUCT :Microsoft C Compiler PROD/VER:MACINTOSH:4.0b OPER/SYS: KEYWORDS:kbgraphic kbHWMAC kbVC kbVC400bug kbDSupportkbbuglist ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual C++, Macintosh Cross-Development Addon, version 4.0b ------------------------------------------------------------------------------- SYMPTOMS ======== When selecting a bitmap into a device context, SelectObject may return NULL. CAUSE ===== When a bitmap is deleted, the memory allocated for it is not released from the application heap space. This problem occurs only for bitmaps that are not read-only (see SetBitmapReadOnly) and only with 68K applications developed using Visual C++ for Macintosh 4.0b. RESOLUTION ========== Following are five different resolutions: - Set the bitmaps as read-only using SetBitmapReadOnly(hBitmap, BRO_READONLY) before selecting them into the DC. - Reuse the same bitmap object. - Develop using Visual C++ for Macintosh 4.0. - Call the undocumented internal function _FreeGWorldCache(). - Increase memory requirements. STATUS ====== Microsoft has confirmed this to be a problem in the Microsoft products that are listed at the beginning of this article. MORE INFORMATION ================ When a bitmap is created and selected into a device context on the Macintosh using the Windows Portability Library (WPL), a new GWorld object is created (if needed) and stored in a cache of four GWorlds. This cache is also used when deleting bitmap objects. Unfortunately the cache is filled but never automatically cleared. Additionally QuickDraw allocates memory for each GWorld, which is also not released. One workaround involves clearing the cache (which also clears the QuickDraw overhead information) using _FreeGWorldCache(). When using this function manually, enter the function prototype: void _FreeGWorldCache(void); Sometimes the problem can be reduced by using CreateBitmapIndirect() instead of CreateBitmap() when creating the bitmap. As a debugging aid, the Macintosh application's heap space can be viewed using ZoneRanger, which can be obtained from Metrowerk's web site: http://www.metrowerks.com REFERENCES ========== (c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Adam Kim, Microsoft Corporation. Additional query words: DeleteObject Bitmap SelectObject leak CreateBitmap CreateBitmapIndirect ====================================================================== Keywords : kbgraphic kbHWMAC kbVC kbVC400bug kbDSupport kbbuglist Technology : kbVCsearch kbHWMAC kbOSMAC kbAudDeveloper kbVCXDev400bMac Version : MACINTOSH:4.0b Issue type : kbbug ============================================================================= 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 2000.