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From: stuart@NECAM.tdd.sj.nec.com (Stuart Palmer)
Newsgroups: comp.lang.c++
Subject: Calling virtuals from destructors
Message-ID: <424@nec-gw.nec.com>
Date: 8 Jan 91 06:03:21 GMT
Sender: news@nec-gw.nec.com
Distribution: na
Organization: NEC-AM TDD, San Jose, California
Lines: 67


If you call a virtual member function from a destructor, what is
the behavior?  We ran some tests and found differences between
Glockenspiel 1.2 and Sun 2.0 compilers.

In Sun 2.0, if you call a virtual member function from
a destructor, the "actual" virtual function that is compiled into
the class vtbl will not get called.  Rather, the virtual function
at the class level where the call was made gets called.  If this is
confusing, see the code sample below.

This is different than Glockenspiel 1.2.  1.2 calls the virtual
function from the vtbl (as might be expected?).

Is this a bug in one of the compilers?  I looked throught the Turbo
C++ bug list and found a similar bug concerning virtual functions
called from member functions.  I would appreciate someone 
describing the Correct (tm) behavior to me.

Thanks!


**********************************Code example********************************

class Base {
  public:
   Base();
   virtual ~Base();
   virtual void some_func();
}
Base::Base(){}
Base::~Base(){ some_func(); }
void Base::some_func(){ printf ("Base called.\n"); }

class Derived : public Base {
  public:
   Derived();
   ~Derived();
   void some_func();
}
Derived::Derived(){}
Derived::~Derived(){ }
void Derived::some_func(){ printf ("Derived called.\n"); }

main() { 
   Derived d;
}


**********************************Output**************************************

1.2 output:
Derived called.

2.0 output:
Base called.

******************************************************************************




--
Stuart Palmer                    stuart@tdd.sj.nec.com
NEC America, Inc.
110 Rio Robles
San Jose, CA 95134