FIX: Virtual Base Class Destructor Called More than Once (168936)


The information in this article applies to:

  • Microsoft Visual C++, 32-bit Professional Edition 5.0
  • Microsoft Visual C++, 32-bit Enterprise Edition 5.0
  • Microsoft Visual C++, 32-bit Professional Edition 4.2
  • Microsoft Visual C++, 32-bit Enterprise Edition 4.2
  • Microsoft Visual C++, 32-bit Editions 4.1
  • Microsoft Visual C++, 32-bit Editions 4.0
This article was previously published under Q168936

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:

132893 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
Modification Type:MinorLast Reviewed:7/5/2005
Keywords:kbBug kbCompiler kbCPPonly kbfix kbVC600fix KB168936
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