From 459603140497179769 X-Google-Thread: f78e5,174aa7b34b06a51 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!newscon06.news.prodigy.com!prodigy.net!newsfeed.cw.net!cw.net!news-FFM2.ecrc.de!newsfeed.vmunix.org!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: dave@boost-consulting.com (David Abrahams) Newsgroups: comp.std.c++ Subject: Re: Is this really unspecified behavior? Date: Thu, 15 Dec 2005 00:42:32 GMT Lines: 48 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: References: <1132759176.368850.264850@g43g2000cwa.googlegroups.com> <1132933832.802917.153350@g14g2000cwa.googlegroups.com> <1133551647.532929.325730@z14g2000cwz.googlegroups.com> <1133583412.951239.208510@g49g2000cwa.googlegroups.com> <1133910546.716987.80030@g14g2000cwa.googlegroups.com> <0l5ep1ppfhdj5p1pcu7e4na4ub0vjajlq3@4ax.com> <200512131507.jBDF72uC006630@horus.isnic.is> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: news.demon.co.uk 1134607359 18809 158.152.254.254 (15 Dec 2005 00:42:39 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Thu, 15 Dec 2005 00:42:39 +0000 (UTC) X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/22.0.50 (windows-nt) X-DMCA-Complaints-To: abuse@rcn.net X-Greylisting: NO DELAY (Relay+Sender autoqualified); processed by UCSD_GL-v2.1 on mailbox8.ucsd.edu; Wed, 14 December 2005 15:19:04 -0800 (PST) X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Cancel-Lock: sha1:lHtBM1yOp/DOn6tK+hNbfioDaJc= X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id jBF0gWw5025531; Thu, 15 Dec 2005 11:42:32 +1100 (EST) X-Path: comp-std-cpp-robomod!not-for-mail X-NNTP-Posting-Date: Wed, 14 Dec 2005 17:19:02 -0600 X-Delivered-To: std-c++@ucar.edu X-Spamscanner: mailbox8.ucsd.edu (v1.6 Aug 4 2005 15:27:38, 0.0/5.0 3.0.4) X-Postfilter: 1.3.32 X-Authentication-Warning: serv3.gc.dca.giganews.com: news set sender to poster@giganews.com using -f X-Newsgroups: comp.std.c++ X-MailScanner: PASSED (v1.2.8 52874 jBENJ3CW072611 mailbox8.ucsd.edu) Xref: g2news1.google.com comp.std.c++:2771 hyrosen@mail.com (Hyman Rosen) writes: > David Abrahams wrote: >> Let me just point out that the general form >> of that problem is insoluble: >> // safe under left-to-right ordering? >> f(g(), new T); >> As a matter of fact it isn't safe, if f has default arguments. >> Leaving that aside, will users be reticent to make this transformation >> f(new T, g()) >> Does one of those look safer to you? > > I'm sorry, but I don't understand what you mean. > > Under my proposed new regime, function parameters > will be constructed from arguments in the call in > strict left-to-right order, and the arguments will > be evaluated in strict left-to-right order. If > constructing a parameter throws an exception, > previously constructed parameters are destructed > in reverse order. So in the examples, if the new T > argument is for an auto_ptr parameter, then both > versions are equally safe. In the first case, if > g() throws then new T will never be called, and in > the second case if g() throws then the auto_ptr > parameter of f will be destructed and thus the > new T pointer will be freed. f doesn't have an auto_ptr parameter. It takes two pointers. > So please explain why you think that the general > case is unsafe, or why people will have to change > parameter order. It's not about "having to" change. It's about whether you'll notice that the change affects safety. -- Dave Abrahams Boost Consulting www.boost-consulting.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ]