FIX: CControlBar Crashes When TOOLTIPTEXT.lpszText Is the ID for a String Resource

• The Microsoft Foundation Classes (MFC), used with:
  • Microsoft Visual C++, 32-bit Editions, version 6.0

SYMPTOMS

An access violation occurs with the CControlBar::WindowProc() file when executing the statement:

if ((pNMHDR->code == TTN_NEEDTEXTA && (!pTTTA->lpszText || !*pTTTA->lpszText)) ||
(pNMHDR->code == TTN_NEEDTEXTW && (!pTTTW->lpszText || !*pTTTW->lpszText))) 

CAUSE

The assertion occurs in the preceding code if the lpszText member of the TOOLTIP structure is an identifier of a string resource. In this case, the code is trying to dereference a pointer; however, *pTTTA->lpszText is "pointing" to a value instead of a valid memory location.

RESOLUTION

Copy the address of the buffer that contains the text to the lpszText TOOLTIP member. If the text to appear as tool tip text is stored as a string resource, use the LoadString function to load the string from the string table into a buffer and assign that buffer to the lpszText TOOLTIP member.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

MORE INFORMATION

This bug was introduced in Visual C++ version 6.0 with the reimplementation of the CControlBar::WindowProc() function.

REFERENCES

See the document titled "The TOOLTIPTEXT Structure" in the online documentation included with Visual C++ 6.0 for more information about how to initialize the members of the TOOLTIPTEXT structure.

Additional query words: TTN_NEEDTEXTA TTN_NEEDTEXTW tooltip control

Keywords          : kbservicepack kbMFC kbToolbar kbToolTip kbVC600bug kbVS600sp2 kbVS600SP1 kbVS600sp3fix 
Version           : winnt:6.0
Platform          : winnt 
Issue type        : kbbug 

Last Reviewed: May 19, 1999