Q117833: FIX: C2662: "‘__vbaseDtor’ cannot convert ‘this’ pointer"

Article: Q117833
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbVCkbbuglist kbfixlist
Last Modified: 22-JUL-2001

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The information in this article applies to:

- Microsoft C/C++ Compiler (CL.EXE), included with:
   - Microsoft C/C++ for MS-DOS, version 7.0 
   - Microsoft Visual C++, versions 1.0, 1.5 
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 1.0 
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SYMPTOMS
========

Compiling the sample code shown below using the C/C++ compilers for MS-DOS
versions 7.0, 8.0, and 8.0c, or the C/C++ 32-bit compiler for Windows NT,
version 8.0, causes the compiler to generate one of the following error
messages:

  error C2662: '__vbaseDtor': cannot convert 'this' pointer from 'const
  class::DerivedClass __near *' to 'class::DerivedClass __near *const'

  -or-

  error C2662: '__vbaseDtor' : cannot convert 'this' pointer from 'const class
  ::DerivedClass *' to 'class ::DerivedClass *const '

The error message usually is generated when the program tries to instantiate a
local constant object of a class that is virtually derived from a base class in
which a user-defined destructor is defined.

RESOLUTION
==========

To alleviate the C2662 error, use one of the following workarounds:

- Instantiate the constant object in file scope. For example, declare it as a
  global object.

-or-

- Delare the constant object static. For example:

        static const DerivedClass myobject;

-or-

- Use the compiler supplied default destructor for the base class by removing
  the user-defined destructor in the base class.

-or-

- Do not declare the object constant by removing keyword const.

-or-

- If possible, do not derive the class virtually.

STATUS
======

Microsoft has confirmed this to be a problem in the products and versions listed
above. This problem was corrected in C/C++ compiler version 9.0, included with
Visual C++ 32-bit Edition, version 2.0.

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

The following sample code can be used to demonstrate the problem:

Sample Code
-----------

  /* Compile options needed: None
  */ 

     class BaseClass
     {
        public:
          ~BaseClass(){}
     };

     class DerivedClass: virtual public BaseClass
     {
       public:
         DerivedClass(){}
         ~DerivedClass(){}
     };

     void main()
     {
       const DerivedClass _myClass;
     }

Additional query words: 1.00 1.50 7.00 8.00 8.00c

======================================================================
Keywords          : kbCompiler kbCPPonly kbVC kbbuglist kbfixlist
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :1.0,1.5
Issue type        : kbbug
Solution Type     : kbfix

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