Path: utzoo!utgpu!watserv1!watmath!att!dptg!ulysses!andante!alice!bs
From: bs@alice.UUCP (Bjarne Stroustrup)
Newsgroups: comp.std.c++
Subject: Re: Unnecessary copying of returned object
Summary: can be avoided
Message-ID: <11266@alice.UUCP>
Date: 1 Sep 90 13:09:19 GMT
References: <1990Aug31.234937.29938@athena.mit.edu> <1990Aug31.235606.166@athena.mit.edu>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 19



Antony Hodgson @ Massachusetts Institute of Technology writes

 > Consider the following:
 > 
 > 	Vector Vector::operator + ( Vector & A )
 > 		{
 > 			Vector temp;
 > 			// for all valid i, temp[i] = (*this)[i] + A[i]
 > 			return temp;  // copy of temp made here
 > 		} // temp deallocated here
 > 
 > Could an intelligent compiler bypass this copying without the help of
 > any new syntax? 

Yes it could. The technique is described in the annotated C++ reference
manual in section 12.1.1c. I believe the technique is used in the Zortech
compiler (existence proof).