220 29232 article Path: news.gmane.org!.POSTED!not-for-mail From: Bo Persson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: pragma once Date: Sat, 29 Oct 2016 13:08:23 +0200 Lines: 52 Approved: news@gmane.org Message-ID: References: <2c278558-0dbc-4568-9b6b-7f159c94707e@isocpp.org> <4610802.tOzma7na2T@tjmaciei-mobl1> <58136277.409@gmail.com> <58137760.6070202@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1477739351 20246 195.159.176.226 (29 Oct 2016 11:09:11 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 29 Oct 2016 11:09:11 +0000 (UTC) User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCZ6RLW3UIKBBQMG2LAAKGQENDZIB4I@isocpp.org Sat Oct 29 13:09:06 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f71.google.com ([209.85.215.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c0RVH-0002Kf-75 for gclcip-std-proposals@m.gmane.org; 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contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:29232 Archived-At: On 2016-10-28 18:05, Matthew Woehlke wrote: > On 2016-10-28 11:02, Miro Knejp wrote: >> On 28 Oct 2016, at 16:36 , Matthew Woehlke wrote: >>> On 2016-10-27 19:48, Miro Knejp wrote: >>>> It unfortunately doesn't solve the problem of having to come up wth a >>>> guard that is unique within the multiverse. For example boost_date_tim= e >>>> has an include guard called ISO_FORMAT_HPP___. That's not exactly the >>>> most unique guard in the world. The less this relies on human >>>> (non-)creativity or discipline the better. >>> >>> Um... >>> >>> #once boost::date_time::iso_format >>> >>> QED. >>> >>> I also suggested that compilers *might* be able to go as far as warning >>> if the namespace of the guard "looks suspicious". It *will* squawk at >>> you if you get the `iso_format` part wrong. >> >> If you can specify a behavior that is consistent and won=E2=80=99t annoy >> anyone, sure. > > The unqualified name shall match the basename of the included file. > (There are some corner cases, but since this is a non-mandated > diagnostic, we can figure them out as they come. If the include is via a > pipe or something strange, this check would likely be skipped, which is > somewhat unfortunate, but no worse than the current situation.) > Some of the corner cases are that the mapping from the physical source=20 file to the source character set, as well as the mapping from=20 #include-names to file names, are both implementation-defined. One or=20 more of those could be EBCDIC, for example. Also, the base name "iso_format" might no be allowed as a file name=20 because of OS restrictions (length and/or allowed characters). Bo Persson --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/nv1vv4%24s3h%241%40blaine.gmane.org. .