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From: cline@cheetah.ece.clarkson.edu (Marshall Cline)
Newsgroups: comp.lang.c++
Subject: ``delete[]p'' -- where is the actual size of *p stored?
Message-ID: <CLINE.90Aug21134409@cheetah.ece.clarkson.edu>
Date: 21 Aug 90 17:47:29 GMT
Sender: news@sun.soe.clarkson.edu
Reply-To: cline@sun.soe.clarkson.edu (Marshall Cline)
Distribution: comp
Organization: (I don't speak for the) ECE Dept, Clarkson Univ, Potsdam, NY
Lines: 39

`delete p' (where `p' is a pointer to a base class with a *virtual* dtor)
``does the right thing'' (calls the right dtor) based on the actual type of
the object pointed to by `p'.

But what if Derived is bigger than Base, and `p' points to a bunch of
Derived's (ie: p = new Derived[100]).  Will delete[] (or delete[100]) find
the actual size of the pointed-to objects from the vtable?  Or will it get
this size from something hidden near *p itself?  This information appears
to be necessary in order to avoid messing ones pants...

	class B {
	  //...
	public:
	  //...
	  virtual ~B();
	};

	class D : public B {
	  int D_is_bigger_than_B;
	public:
	  //...
	  ~D();
	};

	main()
	{
	  B* p = new D[100];
	  //...
	  delete [] p;
	}
--
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Marshall Cline / Asst.Prof / ECE Dept / Clarkson Univ / Potsdam, NY 13676
cline@sun.soe.clarkson.edu / Bitnet:BH0W@CLUTX / uunet!clutx.clarkson.edu!bh0w
Voice: 315-268-3868 / Secretary: 315-268-6511 / FAX: 315-268-7600
Career search in progress; ECE faculty; research oriented; will send vita.
PS: If your company is interested in on-site C++/OOD training, drop me a line!
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