From -2483526026875354041 X-Google-Thread: f78e5,f1baa317914feeaf X-Google-Attributes: gidf78e5,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news2.google.com!news.glorb.com!news.alt.net!frodo.cs.rpi.edu!not-for-mail From: Pavel Minaev Newsgroups: comp.std.c++ Subject: Re: typeof keyword Date: Tue, 31 Mar 2009 13:08:31 CST Organization: http://groups.google.com Lines: 34 Sender: cppmods@cs.rpi.edu Approved: stephen.clamage@sun.com Message-ID: <7252ad7a-a2e2-49a3-a758-cc7015e564bb@x1g2000prh.googlegroups.com> References: <488de3d4-77ac-4c01-8130-d196dec70bc8@v15g2000yqn.googlegroups.com> <4c6295e4-2e8d-44e3-85cd-7e9eb9e72ce0@p11g2000yqe.googlegroups.com> <04297129-6b1b-479e-ab60-44eb7d288725@v38g2000yqb.googlegroups.com> NNTP-Posting-Host: netlab.cs.rpi.edu Content-Type: text/plain; charset=ISO-8859-1 To: (Usenet) Return-Path: X-Original-Date: Mon, 30 Mar 2009 10:54:47 -0700 (PDT) X-Submission-Address: std-c++@netlab.cs.rpi.edu Xref: g2news2.google.com comp.std.c++:377 On Mar 29, 2:51 pm, goo...@dalvander.com wrote: > Let's say I have a class which is heavy to copy assign and copy > construct: HeavyObject. And a function which returns a HeavyObject by > const-reference: > const HeavyObject& getHeavy(int howHeavy); > > And then do the following: > auto heavy = getHeavy(42); > > The copy constructor will be called? Yes. > Do I need to use the following to prevent the copy constructor to be > called? > const auto& heavy = getHeavy(42); Yes. The very simple rule of thumb is that "auto" works the same way as template argument deduction works (in fact, the draft standard says as much about auto: "Once the type of a declarator-id has been determined according to 8.3, the type of the declared variable using the declarator-id is determined from the type of its initializer using the rules for template argument deduction."). -- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@netlab.cs.rpi.edu] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]