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Q181207: FIX: CRuntimeClass Not Available for CInternetException

Article: Q181207
Product(s): Microsoft C Compiler
Version(s): WINDOWS:97,97sp3
Operating System(s): 
Keyword(s): kbcode kbVC500bug kbVC600fix
Last Modified: 17-JUL-2001

-------------------------------------------------------------------------------
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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