FIX: CRuntimeClass Not Available for CInternetException

ID: Q181207

The information in this article applies to:

The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++, 32-bit Editions, 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
Version : WINDOWS:97,97sp3
Platform : WINDOWS
Issue type : kbbug