Path: utzoo!attcan!uunet!samsung!emory!att!dptg!ulysses!andante!alice!ark
From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: comp.lang.c++
Subject: Re: ``delete[]p'' -- where is the actual size of *p stored?
Message-ID: <11255@alice.UUCP>
Date: 30 Aug 90 16:51:13 GMT
References: <CLINE.90Aug21134409@cheetah.ece.clarkson.edu> <56956@microsoft.UUCP> <1180@fornax.UUCP>
Distribution: comp
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 29

In article <1180@fornax.UUCP>, miron@fornax.UUCP (Miron Cuperman) writes:
> jimad@microsoft.UUCP (Jim ADCOCK) writes:

> >In article <CLINE.90Aug21134409@cheetah.ece.clarkson.edu> cline@sun.soe.clarkson.edu (Marshall Cline) writes:
> >>	  B* p = new D[100];
> >>	  delete [] p;

> >C++ will already "do the wrong thing" with any attempts to address the d's
> >referred to by p, thus rendering any problems with delete [] p moot.

> This is not correct.  A pointer to an object may be cast to a pointer
> to a base class of that object.  Therefore the above syntax is correct.

Indeed.  However, p is being used here as a pointer to the initial
element of an array, and that makes all the difference.

If you allocate an array of objects, you must free it through a
pointer to the same type.  Therefore this is illegal:

	B* p = new D[100];
	delete [] p;

For that matter, this won't work either:

	for (int i = 0; i < 100; i++)
		p[i] = /* something */ ;
-- 
				--Andrew Koenig
				  ark@europa.att.com