DOCUMENT:Q181207  17-JUL-2001  [visualc]
TITLE   :FIX: CRuntimeClass Not Available for CInternetException
PRODUCT :Microsoft C Compiler
PROD/VER:WINDOWS:97,97sp3
OPER/SYS:
KEYWORDS:kbcode kbVC500bug kbVC600fix

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

 - The Microsoft Foundation Classes (MFC), included with:
    - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
    - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

Attempting to obtain run-time class information for CInternetException by using
the RUNTIME_CLASS macro fails. The CRuntimeClass structure returned for
CInternetException is empty.

RESOLUTION
==========

C++ exception handling can determine the type of exception thrown. A typical
handler has a format similar to the following:

      try
      {
         // Execute some code that might throw an exception.
      }
      catch( CInternetException* e )
      {
         // Handle the Internet exception here.
      }
      catch( CException* e )
      {
         // Handle all other types of exceptions here.
      }

If for some reason it is still necessary to obtain the run-time class information
for a class that may be CinternetException, it is possible to use the Run-Time
Type Information (RTTI) provided by Visual C++. To use RTTI, the Run-Time Type
Information must be enabled in the C++ Language settings for the project. Then,
the dynamic_cast operator can be used to attempt a conversion of the exception
to CInternetException. If the cast fails, the exception is of another type. It
is also possible to obtain the Run-Time Type Information directly as follows:

      const type_info& info = typeid(*e);

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem was corrected in Visual C++ version 6.0.

MORE INFORMATION
================

The following code demonstrates the problem:

      CRuntimeClass* prt;
      prt = RUNTIME_CLASS( CInternetException );

Looking at prt in the debugger shows that the CRuntimeClass structure is empty.
This behavior is not observed in projects that are statically linked to MFC.

Additional query words: RTTI

======================================================================
Keywords          : kbcode kbVC500bug kbVC600fix 
Technology        : kbAudDeveloper kbMFC
Version           : WINDOWS:97,97sp3
Issue type        : kbbug
Solution Type     : kbfix

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

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