Q168385: BUG: The "this" Pointer Is Incorrect in Destructor of Base Class

Article: Q168385
Product(s): Microsoft C Compiler
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): kbtool kbCompiler kbVC500bug kbVC600bugkbbuglist
Last Modified: 13-FEB-2002

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
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SYMPTOMS
========

The "this" pointer is incorrectly set up in the destructor of a base class. This
problem occurs when the array delete is called and there is a class that
inherits from two base classes that have virtual functions and the second base
class has a virtual destructor.

RESOLUTION
==========

One workaround is to make the base classes virtual base classes. Another option
is to use something other than array new and array delete to allocate and
deallocate the memory. For example, declare the array statically.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

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

The following is example code:

     #include <iostream>
         using namespace std;
         class A {
         public:
            A(){}
            ~A(){}
            virtual void A1() {}
         };

         class B {
         public:
            B();
            virtual ~B();
            int marker;
         };

         B::B() {
            marker = 10;
            cout << "In constructor, this is " << this << endl;
         }

         B::~B() {
            cout << "In destructor, this is " << this << endl;
            if ( this->marker != 10)
               cout << "Data has been corrupted" << endl;
         }

         class C: public A, public B
         // class C: public A, virtual public B // Workaround
         {public:
            C(){}
            ~C(){}
         };

         int main() {
            C * pC;
            pC = new C[2];
            delete [] pC;
                 return 0 ;
         }

     /* Sample Program Output */ 
     In constructor, this is 00460DA8
     In constructor, this is 00460DB4
     In destructor, this is 00460DB0
     Data has been corrupted
     In destructor, this is 00460DA4
     Data has been corrupted

Additional query words:

======================================================================
Keywords          : kbtool kbCompiler kbVC500bug kbVC600bug kbbuglist
Technology        : kbVCsearch kbAudDeveloper kbVC500 kbVC600 kbVC32bitSearch kbVCNET kbVC500Search
Version           : :5.0,6.0
Issue type        : kbbug

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