From 4707967613245903800 X-Google-Thread: f78e5,473009b7dc4fc05d X-Google-NewGroupId: yes X-Google-Attributes: gid7894ca11fe,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII Received: by 10.68.6.70 with SMTP id y6mr1409pby.6.1319561969082; Tue, 25 Oct 2011 09:59:29 -0700 (PDT) MIME-Version: 1.0 Path: p6ni351pbn.0!nntp.google.com!news2.google.com!news4.google.com!feeder.news-service.com!news.albasani.net!.POSTED!not-for-mail From: =?ISO-8859-1?Q?Daniel_Kr=FCgler?= Newsgroups: comp.std.c++ Subject: Re: Defect report: integral-to-boolean conversion in converted constant expressions Date: Tue, 25 Oct 2011 09:59:26 -0700 (PDT) Organization: A noiseless patient Spider Lines: 36 Sender: std-cpp-request@vandevoorde.com Approved: stephen.clamage@oracle.com Message-ID: References: <37779.10.0.7.178.1319061824.squirrel@webmail.secure.aluminati.net> X-Trace: news.albasani.net 2vugsaOtdkBmcEoTnDGJTdCx+Cj//0cpuFVgnMxQR/2vnhgdml+7t6A3p069jNTKezreX0VSclNIX4kIQ1/b4g== NNTP-Posting-Date: Tue, 25 Oct 2011 16:59:28 +0000 (UTC) Injection-Info: news.albasani.net; logging-data="KO2ZitrKKwycH6MLGzZSnKerIYIXoTeq/95CoWQIrH1uH3YV++F6QWsXMnH836H1b12HTCftvbWAp5nPLy183scKazB1XGu9vczSfMtIdEDeP85iceJi0FkFOmSKZP3z"; mail-complaints-to="abuse@albasani.net" X-Mailer: Perl5 Mail::Internet v2.05 X-Submission-Address: std-cpp-submit@vandevoorde.com Cancel-Lock: sha1:FbJuuDxSeVYRoUr/PqISvVrGwOY= X-Original-Date: Mon, 24 Oct 2011 20:38:57 +0200 Xref: news2.google.com comp.std.c++:2093 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Am 20.10.2011 00:24, schrieb Richard Smith: > Hi, > > In both C++98 and C++11, the following code appears to be ill-formed: > > template struct S {}; > S<0> s; > > However, EDG, g++ and clang all accept it. The reason this is ill-formed is > that the non-type template argument is a converted constant expression of type > 'bool' (see [temp.arg.nontype]p5), and the second conversion in the implicit > conversion sequence is a boolean conversion, which is not allowed in the > conversion for a converted constant expression (see [expr.const]p3). > Conversions in the other direction (from 'bool' to integer types) are > permitted here, since they're integral promotions. > > Suggested resolution: In [expr.const]p3, add "boolean conversions from > integral or unscoped enumeration type other than narrowing conversions" to the > list of conversions allowed in a converted constant expression. Forwarded to CWG. It seems to me that the actual issue is, whether it is clear or not that [conv.integral] p4 already implies what you are suggesting here. Greetings from Bremen, Daniel Kr�gler -- [ comp.std.c++ is moderated. To submit articles, try posting with your ] [ newsreader. If that fails, use mailto:std-cpp-submit@vandevoorde.com ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]