KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Article: Q156067
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1,4.2
Operating System(s): 
Keyword(s): kbMFC kbToolTip KbUIDesign kbVC400bug kbVC410bug kbVC420bug kbVC500fix kbGrpDSMFCATL kb
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
-------------------------------------------------------------------------------

SYMPTOMS
========

Attempting to set the text for a tooltip in the OnToolHitTest function of a CWnd
by assigning a resource ID to the TOOLINFO struct's lpszText member causes the
following assertion to occur:

  

  Debug assertion failed
  File: dbgheap.c
  Line: 1011

For example, setting the TOOLINFO struct as follows:

     pTI->lpszText= MAKEINTRESOURCE(SomeId);
     pTI->hinst=AfxGetInstanceHandle();

where pTI is a pointer to the TOOLINFO struct, will cause the problem. Setting
the TOOLINFO struct members in this manner allows the programmer to specify a
resource that the tooltip uses to get the text for the tooltip.

CAUSE
=====

The CWnd::FilterToolTipMessage() function contains the following code:

     if (tiHit.lpszText != LPSTR_TEXTCALLBACK)
         free(tiHit.lpszText);

Because lpszText is not set to LPSTR_TEXTCALLBACK, the free function is called.
However, a resource ID, rather than a string, was specified in the
OnToolHitTest() function, and therefore the assertion occurs.

RESOLUTION
==========

Instead of specifying a resource ID to load, load the resource and assign the
text to the TOOLINFO struct's lpszText member as follows:

     pTI->lpszText = (char *)malloc(200, sizeof(char));
     if (::LoadString(AfxGetInstanceHandle(),pTI->uId, pTI->lpszText,200)==0)
     {
        ASSERT(FALSE);   //String resource doesn't exist
     }

MFC frees the allocated buffer after it has added the tool (that is, after it has
sent the TTM_ADDTOOL message).

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem has been fixed in Visual C++ version
5.0.

Additional query words: kbVC400bug tool tip

======================================================================
Keywords          : kbMFC kbToolTip KbUIDesign kbVC400bug kbVC410bug kbVC420bug kbVC500fix kbGrpDSMFCATL kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:4.0,4.1,4.2
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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.

Q156067: FIX: Setting Tooltip Text in OnToolHitTest Causes Assertion