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

MS-DOS | WINDOWS   | WINDOWS NT

The information in this article applies to:

• The Microsoft C/C++ Compiler (CL.EXE), included with:

      - Microsoft C/C++ for MS-DOS, version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
      - Microsoft Visual C++ 32-bit Edition, version 1.0
  

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 '

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;
   }