From -6506829599027772958 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,307cbe6f0ea2ccd3 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2003-06-11 12:12:49 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!kibo.news.demon.net!mutlu.news.demon.net!demon!mail2news.demon.co.uk!devnull From: andreytarasevich@hotmail.com (Andrey Tarasevich) Newsgroups: comp.std.c++ Subject: Re: Recommendation to the Standards Committee Date: Wed, 11 Jun 2003 19:12:48 +0000 (UTC) Organization: Posted via Supernews, http://www.supernews.com Lines: 52 Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <3EE62B88.6030208@hotmail.com> References: <_ULEa.10852$KF1.271850@amstwist00> <3EE50908.9060202@hotmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit X-Trace: mail2news.demon.co.uk 1055358768 28625 10.0.0.1 (11 Jun 2003 19:12:48 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Wed, 11 Jun 2003 19:12:48 +0000 (UTC) X-Received: from mulga.cs.mu.oz.au ([128.250.1.22]) by news.demon.co.uk with esmtp (Exim 4.12) id 19QB1b-0007RX-00 for mail2news@news.news.demon.net; Wed, 11 Jun 2003 19:12:47 +0000 X-Received: from localhost (localhost [[UNIX: localhost]]) by mulga.cs.mu.OZ.AU id FAA16248; Thu, 12 Jun 2003 05:12:44 +1000 (EST) X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Path: comp-std-cpp-robomod!not-for-mail X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Delivered-To: std-c++@ucar.edu X-Newsgroups: comp.std.c++ X-User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 X-Accept-Language: en-us, en X-Spam-Status: No, hits=-8.8 required=5.0 tests=FORGED_HOTMAIL_RCVD,NOSPAM_INC,QUOTED_EMAIL_TEXT, REFERENCES,SATISFACTION,SIGNATURE_SHORT_DENSE, SPAM_PHRASE_01_02,USER_AGENT,USER_AGENT_MOZILLA_UA, X_ACCEPT_LANG version=2.41 Xref: archiver1.google.com comp.std.c++:19688 Francis Glassborow wrote: > In article <3EE50908.9060202@hotmail.com>, Andrey Tarasevich > writes >>Yeah, but it looks like the main point of the method Brian is using is that >>the guarding '#ifndef'/'#endif' is placed _outside_ the header file. In this >>case the preprocessor doesn't even have to search for already included >>files, open them or try parsing them. The '#once' solution doesn't help in >>this case, since '#once' directive is supposed to be specified _inside_ >>header files. From this respect '#once' is not much different from the >>standard "internal '#ifndef'/'#define'/'#endif' approach". But it looks >>like Brian is not satisfied with the latter. Under this circumstances, I >>don't think he will be satisfied with any other "internal" solution. > > But I do not understand the problem. Only the designer of a header file > can know if it should or should not be multiply included into a TU. > > Being able to write: > > #once > > at the start of a header file would solve the problem because compilers > would then read the file the first time, mark it as read in its tables > and not try to read it again. Well, it all depends on the concrete specification of '#once'. BTW, if it will work is accordance with your suggestion, it won't matter whether it is specified at the start of a header file or in the middle of it. Note also that in order to support this specification '#once' directive should be always "visible" regardless of the surrounding '#ifdef'/'#endif' context, thus outlawing such techniques as the following #define SUPPRESS_ONCE ... #ifndef SUPPRESS_ONCE #once #endif // SUPPRESS_ONCE OK, as others already noted, it has been discussed to death here. I guess I should look through previous discussions first. -- Best regards, Andrey Tarasevich Brainbench C and C++ Programming MVP --- [ 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 ]