From 786125308745239641 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,d53338cd62537f87 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2002-04-17 17:16:01 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!kibo.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: "Giovanni Bajo" Newsgroups: comp.std.c++ Subject: Re: What does the standard say about Loki's ConversionHelper Date: Thu, 18 Apr 2002 00:15:14 GMT Organization: [Infostrada] Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: References: <3cbdd850.75707781@news.mar.lmco.com> X-Trace: mail2news.demon.co.uk 1019088919 mail2news:14740 mail2news mail2news.demon.co.uk X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au 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) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4807.1700 X-MIMEOLE: Produced By Microsoft MimeOLE V5.50.4910.0300 NNTP-Posting-Date: Thu, 18 Apr 2002 00:32:55 MET DST Lines: 50 Xref: archiver1.google.com comp.std.c++:10679 "Mark Heaps" ha scritto nel messaggio news:3cbdd850.75707781@news.mar.lmco.com... > My compiler rejects the following snippet from the Loki library: > [...] > enum { exists = sizeof(H::Test(H::MakeT())) == sizeof(H::Small) }; > [...] > The last of several exchanges with the compiler vendor, resulted in > this analysis: > - in the example given, the class 'Conversion' is referring to the > class 'Private::ConversionHelper' which hasn't been instantiated. When > a member of the latter class is looked up, none of its internal > information is known, so the expressions in the sizeof operator are > viewed as not having complete types. >[...] > So my questions are: > What paragraphs of the standard support (or refute) that analysis? > Is the code legal or illegal? The code is legal. 14.7.1/1 [temp.inst]: "Unless a class template specialization has been explicitly instanciated or explicitly specialized, the class template specialization is implicitly instanciated when the specialization is referenced in a context that requires a completely-defined object type or when the completeness of the class type affects the semantics of the problem". The context above clearly requires a "completly-defined object type", so the argument of the vendor, specifically "the expressions [...] are viewed as not having complete types" does not apply: they do not have complete type because the template has not been instanciated, but 14.7.1 mandates an implicitly instanciation whenever a complete type is needed. Giovanni Bajo --- [ 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 ]