Knowledge Base

FIX: C2662: "'__vbaseDtor' cannot convert 'this' pointer"

Article ID: 117833

Article Last Modified on 7/5/2005

Microsoft C/C++ Professional Development System 7.0
Microsoft Visual C++ 1.0 Professional Edition
Microsoft Visual C++ 1.5 Professional Edition

This article was previously published under Q117833

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: kbbug kbfix kbcpponly kbcompiler KB117833