Microsoft KB Archive/114013

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BUG: General Protection Fault When Accessing an HFONT

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Q114013

3.10 WINDOWS kbprg kbbuglist

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The information in this article applies to:


 * Microsoft Windows Software Development Kit (SDK) 3.1

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SYMPTOMS
On rare occasions, in low memory situations or after calling the function GlobalCompact(-1), a general protection fault (GP) Fault may occur when calling SelectObject to select a handle to a logical font (HFONT) into a device context. This happens when the application caches the handle to the logical font.

CAUSE
Part of the internal data structure for the font resides in global memory that is allocated as GMEM_DISCARDABLE. In tight memory situations, this global memory may be discarded and GDI does not detect this situation before attempting to access the memory.

STATUS
Microsoft has confirmed this to be a bug in Windows version 3.1.

This problem does not occur in Windows 95.

MORE INFORMATION
To avoid this bug, applications should not cache font handles but instead hold onto the LOGFONT structure that contains the information for recreating the font. By holding onto the LOGFONT and calling the function CreateFontIndirect each time a font is needed, applications should be able to safely avoid this bug.

NOTE: The call to CreateFontIndirect is not an expensive call in terms of performance. The actual mapping of logical font to physical font happens when you call SelectObject. When you cache HFONTs, you still have to call SelectObject each time before calling any of the Windows text APIs so this approach only requires one additional function call.

Additional query words: buglist3.10 3.10 font fault error

Keywords : kb16bitonly _IK kbSDKWin16

Issue type : kbbug

Technology : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310