Q168936: FIX: Virtual Base Class Destructor Called More than Once

Article: Q168936
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1,4.2,5.0
Operating System(s): 
Keyword(s): kbtool kbCompiler kbCPPonly kbVC kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600fix
Last Modified: 04-MAY-2001

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
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SYMPTOMS
========

If an exception is thrown from the constructor of a class that is derived from a
virtual base class, the destructor for the virtual base class is called more
than once. This doesn't happen if the exception is thrown from any other member
function.

RESOLUTION
==========

There is no workaround. Avoid throwing exceptions from the constructor.

For additional information about the two-phased construction, please see the
following article in the Microsoft Knowledge Base:

  Q132893 PRB: Exceptions Thrown During Construction Can Orphan Memory

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
for Windows.

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

Steps to Reproduce Behavior
---------------------------

     //compiler options needed  /GX

      #include <iostream.h>
      class A
      {
        public:
              A() { cout << "In A-ctor" << endl;}
              ~A(){ cout << "In A-dtor" << endl;}
      };

      class B1 : public  virtual   A
      {
        public:
                B1() { cout << "In B1-ctor" << endl;}
              ~B1(){ cout << "In B1-dtor" << endl;}
      };

      class B2 : public  virtual  A
      {
        public:
                B2() { cout << "In B2-ctor" << endl;}
              ~B2(){ cout << "In B2-dtor" << endl;}
      };

      class C : public B1 ,public B2
      {
        public:
            C(){
           cout << "In C-ctor...throw Exception" << endl;
           throw int(1); //incorrect destructor calls...
               }

            ~C(){ cout << "In C-dtor" << endl;}
      };

      void main()
      {
        try
         {
           C c;

         }
        catch (int ex)
         {
           cout << "Caught Exception #" << ex << endl;
           }
      }

The program output is:

  In A-ctor
  In B1-ctor
  In B2-ctor
  In C-ctor...throw Exception
  In B2-dtor
  In A-dtor
  In B1-dtor
  In A-dtor
  In A-dtor
  Caught Exception #1

The expected output is:

  In A-ctor
  In B1-ctor
  In B2-ctor
  In C-ctor...throw Exception
  In B2-dtor
  In B1-dtor
  In A-dtor
  Caught Exception #1

Additional query words:

======================================================================
Keywords          : kbtool kbCompiler kbCPPonly kbVC kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600fix 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:4.0,4.1,4.2,5.0
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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