Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!bellcore!faline!thumper!ulysses!andante!alice!bs
From: bs@alice.UUCP (Bjarne Stroustrup)
Newsgroups: comp.lang.c++
Subject: Re: overloading new operator in C++
Message-ID: <8283@alice.UUCP>
Date: 10 Oct 88 01:24:00 GMT
References: <774@paris.ics.uci.edu>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 50



Doug Schmidt of University of California, Irvine - Dept of ICS writes:

 > Hi,
 > 
 >    Would someone please inform me whether the following code is legal
 > in C++?  If it is, then is the result defined?  G++ 1.27 performs 20
 > NOPS for the main for loop.  My basic question is:
 > 
 > ``Is is possible to hide the new operator in the same fashion as hiding
 >   the assignment operator `=' , i.e., making it a compile-time error
 >   to use new?''

	operator new() obeys the usual hiding rules so using new to create an
	individual object of class X is an error when X::operator new() is
	private. Using a 2.0beta cfront I get

"", line 20: error:  main() cannot access Tree_Node::operator new(): private  member

	Using new to create a vector of X objects is OK, though,
	since X::operator new() is used only for individual objects.

	Had Tree_Node::operator  new() been public Tree_Node::Base would have
	been incremented 20 times.

 > ----------------------------------------
 > #include <stream.h>
 > 
 > class Tree_Node {
 > public:
 >    static Tree_Node *Base;
 > 
 > private:
 > 
 >    void * operator new ( long ) {
 >       return ( Base++ );
 >    } 
 > 
 > };
 > 
 > main() {
 >    Tree_Node::Base = new Tree_Node [ 20 ];
 > 
 >    for ( int i = 0; i < 20; i++ ) {
 >       cout << int ( new Tree_Node ) << "\n";
 >    }
 > }