Article ID: 148455
Article Last Modified on 6/1/2005
APPLIES TO
- Microsoft Foundation Class Library 4.2, when used with:
- Microsoft Visual C++ 2.0 Professional Edition
- Microsoft Visual C++ 4.0 Standard Edition
- Microsoft Visual C++ 4.1 Subscription
- Microsoft Visual C++ 4.2 Enterprise Edition
- Microsoft Visual C++ 5.0 Enterprise Edition
- Microsoft Visual C++ 6.0 Enterprise Edition
- Microsoft Visual C++ 4.2 Professional Edition
- Microsoft Visual C++ 5.0 Professional Edition
- Microsoft Visual C++ 6.0 Professional Edition
- Microsoft Visual C++ 6.0 Standard Edition
This article was previously published under Q148455
SYMPTOMS
Under the Checked build of Windows NT or a diagnostic
utility you receive an error similar to this one:
BASE:
GlobalFree called with a locked object.
The Checked build of Windows
NT causes a Hard-Coded breakpoint to occur, which generates a message similar
to this one:
User Breakpoint called from code at:
0x77f2706f
CAUSE
The CSharedFile class maintains a global memory block. As
soon as an HGLOBAL is allocated by a CSharedFile object (or specified in a call
to SetHandle), it calls GlobalLock to lock this memory block.
If the
CSharedFile object is destroyed, then a call to GlobalUnlock() and GlobalFree()
will correctly unlock and free the global memory block. However, if a call to
Detach() is made to retrieve the HGLOBAL, then the handle returned is still
locked. There is no call to GlobalUnlock() made to match the call to
GlobalLock().
The memory block referenced by the HGLOBAL cannot be
moved because it has a positive reference count. Also, if an attempt is made to
free the HGLOBAL by way of a call to GlobalFree(), the symptoms given in this
article will occur.
RESOLUTION
After calling CSharedFile::Detach(), you can unlock the
global memory block by making a call yourself to GlobalUnlock(). Because this
workaround is dependent on the implementation of CSharedFile(), you should be
sure to use conditional compilation for this block of code as demonstrated
here:
CSharedFile file;
// Do stuff to fill in the CSharedFile
HGLOBAL hGlob = file.Detach();
#if _MFC_VER <= 0x0600
::GlobalUnlock(hGlob);
#endif
STATUS
Microsoft has confirmed this to be a bug in the Microsoft
products listed at the beginning of this article. We are researching this
problem and will post new information here in the Microsoft Knowledge Base as
it becomes available.
Keywords: kbbug KB148455