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Q114013: BUG: General Protection Fault When Accessing an HFONT

Article: Q114013
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): kb16bitonly _IK kbSDKWin16
Last Modified: 27-JUN-1999

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

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Keywords          : kb16bitonly _IK kbSDKWin16 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbbug
Solution Type     : kbpending

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