Re: delete MyClass doing more than MyClass::operator delete()?

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Fri, 14 Jul 2006 08:44:17 -0400
Message-ID:
<e983j3$rvj$1@news.datemas.de>
tom wrote:

  I'm overriding my operator new and operator delete for two classes,
one inherited from the other, so I can use my own memory pool. A
simplified version of what I have is below:

class BaseClass {
  BaseClass();
  virtual ~BaseClass();
  virtual void baseFunction();
  static void operator delete(void* mem);
};

class InheritedClass : public BaseClass {
  IneritedClass();
  ~InheritedClass();
  void baseFunction();
  void nonBaseFunction();
  static void operator delete(void* mem);
};

I'm testing some things by making operator delete() do nothing, so the
memory shouldn't be deallocated. I've also made the ~BaseClass() and
~InheritedClass() functions do nothing. When I call delete on an
InheritedClass object, if I try to then call any inherited function on
that object (in this example, baseFunction()) I get a crash. If I
call a non-inherited function (nonBaseFunction() in this example)
then it goes along fine and nothing bad happens, as I would epect the
inherited function to have done (since, again, no memory should be
deallocated). In my actual code, I've tested to make sure that the
delete call is actually going through my InheritedClass's operator
delete function, and that it isn't doing anything in the base class's
operator delete function, though both have them defined to do
nothing. But it seems that delete is doing something more than what
I define in that function, and it's messing up things dealing with
inheritance. I'm using Visual Studio 2005. Any ideas would be
greatly appreciated.


Calling non-static member functions for an object after its lifetime
ended has *undefined behaviour* according to the language specification.
What else do you need to know about it?

If you'd like to learn what your code does under the covers, by all
means, explore the generated machine code and make your own conclusions
from that. However, it has no relevance here, in comp.lang.c++. Any
conclusion you make from looking at machine code is only relevant to
your particular platform (hardware and OS) and your particular compiler
implementation.

V
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