From 8892520604976185995 X-Google-Thread: 7894ca11fe,661f9f6c1b45f277 X-Google-Attributes: gid7894ca11fe,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news1.google.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!news.giganews.com.POSTED!not-for-mail NNTP-Posting-Date: Fri, 30 Apr 2010 15:30:11 -0500 Return-Path: To: (Usenet) From: Olaf Krzikalla Newsgroups: comp.std.c++ Subject: Re: Two thoughts about attributes in the FCD Organization: albasani.net Sender: cppmods@cs.rpi.edu Approved: james.dennett@gmail.com Message-ID: References: <83rbioFejhU1@mid.individual.net> Content-Type: text/plain; charset=ISO-8859-15; format=flowed X-Original-Date: Fri, 30 Apr 2010 10:23:58 +0200 X-Submission-Address: std-c++@netlab.cs.rpi.edu Date: Fri, 30 Apr 2010 15:24:08 CST Lines: 47 X-Usenet-Provider: http://www.giganews.com X-Trace: sv3-w5hh0SqoErOevxaMZ+E6NnpDpWtnwTOPIzHg18UWBj9cGb28ujeVyL4ti0BBF6wjlImu0clxPhZnQ4o!B/memh12bUkzSPZyO/PN2sG9ZL0I9iCZkCc4Nkz6Kk0pI/3HPCKuU2lz X-Complaints-To: abuse@giganews.com X-DMCA-Notifications: http://www.giganews.com/info/dmca.html 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: 1.3.40 Xref: g2news2.google.com comp.std.c++:2488 Bo Persson schrieb: >> >> Olaf Krzikalla schrieb: >> >>> 2. =A77.6.1.5 states, that attibute tokens not being specified >>> behave implementation-defined. Shouldn't we restrict this in a >>> way, that attibutes unknown to an particular implementation shall >>> be ignored. Like: an implementation is not allowed to refuse >>> compilation only because a syntactically correct attribute-token >>> is unknown. Maybe someone can rephrase this to standard speak. >>> >> During a discussion about adding attributes to clang I noticed that >> section 7.6.1.5 as written IMHO opens a can of worms. If everybody >> is >> allowed to add arbitrary attributes then we can't extend the set of >> predefined attributes in the future without the danger of breaking >> standard-conform code. Thus I would propose that the use of >> attributes in the global and std attribute-namespace cause >> undefined behavior unless they are defined in the standard. This >> keeps the freedom to standardize more attributes in the future. For >> attributes in other namespaces the behavior is still implementation >> defined. But as I wrote in my previous post, we should add the >> sentence: >> "Any attribute (not in the global and std attribute-namespace) that >> is not recognized by the implementation is ignored." >> > > Including misspelled attributes? Could introduce interesting new bugs! For unknown attributes in the global and std namespace we can change from ub to ill-formed. Thus the issue exists (if at all) for implementation specific attributes only - as it does for pragmas. The attribute namespace makes things even better, since an implmentation can simply define, that any attribute in a particular namespace is recognized (and in case it is misspelled makes the program ill-formed). By all means I consider sec. 7.6.1.5 underspecified. Best regards Olaf Krzikalla -- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@netlab.cs.rpi.edu] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]