From -7613410201650470047 X-Google-Thread: f78e5,8983dbb7c598f774,start X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news4.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!newsfeed.hanau.net!newsfeed.vmunix.org!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: rogero@howzatt.demon.co.uk ("Roger Orr") Newsgroups: comp.std.c++ Subject: Ambiguous conversion to base? Date: Sun, 30 Jul 2006 05:02:10 GMT Lines: 47 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: NNTP-Posting-Host: news.news.demon.net X-Trace: news.demon.co.uk 1154235735 18229 158.152.254.254 (30 Jul 2006 05:02:15 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Sun, 30 Jul 2006 05:02:15 +0000 (UTC) X-Original-To: std-c++@mailman.ucar.edu X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Priority: 3 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.504 X-Greylisting: NO DELAY (Relay+Sender autoqualified); processed by UCSD_GL-v2.1 on mailbox7.ucsd.edu; Sat, 29 July 2006 09:49:37 -0700 (PDT) X-Virus-Scanned: amavisd-new at csse.unimelb.edu.au X-MSMail-Priority: Normal X-Received: (from fjh@localhost) by mulga.csse.unimelb.edu.au (8.13.6+Sun/8.13.6/Submit) id k6U52Atd018730; Sun, 30 Jul 2006 15:02:10 +1000 (EST) X-Path: comp-std-cpp-robomod!not-for-mail X-NNTP-Posting-Date: Sat, 29 Jul 2006 16:49:34 +0000 (UTC) X-Delivered-To: std-c++@mailman.ucar.edu X-Spamscanner: mailbox7.ucsd.edu (v1.6 Jul 6 2006 16:38:12, -0.0/5.0 3.1.3) X-Authentication-Warning: mulga.csse.unimelb.edu.au: fjh set sender to devnull@stump.algebra.com using -f X-Newsreader: Microsoft Outlook Express 6.00.3790.504 X-Newsgroups: comp.std.c++ X-MailScanner: PASSED (v1.2.8 6713 k6TGnZLV014948 mailbox7.ucsd.edu) Xref: g2news2.google.com comp.std.c++:3125 Should this fragment compile? class Base { }; class Derived : public Base { public: Derived( Derived const & ); Derived( Base const ); // Note: no '&' }; class Final : public Derived { Final( Final const & f ) : Derived( f ) {} }; MSVC 2003 and Comeau say 'Yes' g++ 3.4.4 and 4.0.2 say 'No': copyctor.cpp: In copy constructor `Final::Final(const Final&)': copyctor.cpp:15: error: call of overloaded `Derived(const Final&)' is ambiguous copyctor.cpp:9: note: candidates are: Derived::Derived(Base) copyctor.cpp:8: note: Derived::Derived(const Derived&) As far as I understand it conversion from Final const & -> Derived const & should be a better conversion than any conversion to Base. Or have I missed something? [ Yes, I know the code fragment exbihits dubious programming practices but I want to know if it is legal :-) ] TIA, Roger Orr -- MVP in C++ at www.brainbench.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.comeaucomputing.com/csc/faq.html ]