From -7999505289279631575 X-Google-Thread: f78e5,508c8df5e45a47fc,start X-Google-NewGroupId: yes X-Google-Attributes: gid7894ca11fe,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news2.google.com!news.glorb.com!news2.arglkargh.de!news.albasani.net!.POSTED!not-for-mail From: Edward Diener Newsgroups: comp.std.c++ Subject: Evaluation of #elif statement Date: Thu, 1 Sep 2011 11:05:03 -0700 (PDT) Organization: A noiseless patient Spider Lines: 20 Sender: std-cpp-request@vandevoorde.com Approved: austern@google.com Message-ID: Reply-To: eldiener@tropicsoft.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed X-Trace: news.albasani.net SPK2Ng6AjUQ1edk9QKMMxEC4SEAYtzWnwb6pX9TSiMiBA8PUSrnf1y42Djha77VB86p0JSKk82wW2w0FXZ7WMw== NNTP-Posting-Date: Thu, 1 Sep 2011 18:05:07 +0000 (UTC) Injection-Info: news.albasani.net; logging-data="bJNhZIvcl4qPIaWxxieZaPrH+G3WjYyvc4YSoQ/DXnQTLQtkDmDyQS+AmxzkuEesLsEtFhrU3pviW9cX1LgqluFCOLjxKJkJx9oIOCFSOgkyY2a5wg2LMcFVRZ2hnog1"; mail-complaints-to="abuse@albasani.net" X-Mailer: Perl5 Mail::Internet v2.05 X-Submission-Address: std-cpp-submit@vandevoorde.com Cancel-Lock: sha1:6QdgBnLc/Hy5YBbEkJ4sk96oVXs= X-Original-Date: Wed, 31 Aug 2011 16:49:55 -0400 Xref: g2news2.google.com comp.std.c++:3412 In code such as: #if SOME_MACRO(x) #elif ANOTHER_MACRO(y) #endif is ANOTHER_MACRO expanded and evaluated for C++ correctness even when the result of SOME_MACRO's expansion is 1. I had always thought that ANOTHER_MACRO(y) could be anything, even incorrect C++, as long as SOME_MACRO(x) is 1. But gcc always evaluates ANOTHER_MACRO(y) and, if it is invalid C++, gives a compiler error, even when SOME_MACRO(x) expands to 1. -- [ 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 ]