From -7037353452890877972 X-Google-Thread: f78e5,e2cfdf64f67c7793 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news1.google.com!news.glorb.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local1.nntp.dca.giganews.com!nntp.speakeasy.net!news.speakeasy.net.POSTED!not-for-mail NNTP-Posting-Date: Tue, 28 Sep 2004 14:00:05 -0500 Return-Path: X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) Date: Tue, 28 Sep 2004 18:56:07 GMT Delivered-To: std-c++@ucar.edu From: brangdon@cix.co.uk (Dave Harris) Newsgroups: comp.std.c++ Subject: Re: Eliminating uninitialised variables Message-ID: References: <41573b0a$0$29917$cc9e4d1f@news.dial.pipex.com> Reply-To: brangdon@cix.co.uk X-Orig-X-Trace: news.uni-berlin.de eGNygg8Ork+nDbFF3UjzBQk2g/5B3Sj6tjwXczSeorBLNLu/0= Approved: Fergus Henderson , moderator of comp.std.c++ X-Spam-Checker-Version: SpamAssassin 2.64 (2004-01-11) on manifold.algebra.com X-Spam-Status: No, hits=0.0 required=3.0 tests=none autolearn=no version=2.64 Lines: 40 NNTP-Posting-Host: 64.81.147.48 X-Trace: sv3-FAvUDjlHhz+xRfiSr8y6xy/NcCO+1j6cGyl0R5ApEAuDdysBfwwOyvXjAE0BS2QRsBJ/oquFozBGjA2!gsIU5iVYr0DGcOQdh+Pc0MvMKPHGu5Nk9k9tRaTFEigQkIQItQHJ+cOGh0vhhcBQnH6WlJ8Z49Ed!UuAEmPOwz9BJpUAJaQ== X-Complaints-To: abuse@speakeasy.net X-DMCA-Complaints-To: abuse@speakeasy.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.16 Xref: g2news1.google.com comp.std.c++:2901 sjhoweATdialDOTpipexDOTcom@eu.uu.net (Stephen Howe) wrote (abridged): > And does zero-initialising mean that the program is correct or will > behave more correctly? In many cases, yes. It at least makes the behaviour consistent, so that the problem is easier to track down. > I have to say in the past 5 years, I have not been bitten once by > "uninitialised variables". > It is not a signicant problem to me. Data point noted. I'm guessing you're a relatively experienced programmer? I've been bitten by it, mainly in code written by other people. In particular with IEEE doubles, which sometimes became signalling NaNs in release mode. As I recall, the code which read them was a copy-constructor. It didn't matter what their value was so long as they could be read without the access throwing an exception, so in this case zero-initialisation would have been fine. Whether they threw depended on the history of the heap, so it was quite hard to debug. I was using a compiler which initialises heap to a known state in debug releases, which masked the problem further. > I don't see that this gains anything. I hope I have now convinced you otherwise. In my view, eliminating potential undefined behaviour always has some benefit; the question is whether the benefit is worth the cost. And in this case I think the cost can be made small. -- Dave Harris, Nottingham, UK --- [ 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 ]