220 9482 article Path: news.gmane.org!not-for-mail From: Andrew Tomazos Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: #requre "header.h" Date: Sat, 1 Mar 2014 17:03:52 +0100 Lines: 164 Approved: news@gmane.org Message-ID: References: <5311f640.426b440a.3b13.ffff8533@mx.google.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=f46d041703f36432e904f38db3ed X-Trace: ger.gmane.org 1393689825 22462 80.91.229.3 (1 Mar 2014 16:03:45 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 1 Mar 2014 16:03:45 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD5KHQXXWYPRB2MJZCMAKGQE4O5MVJA@isocpp.org Sat Mar 01 17:03:54 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-la0-f72.google.com ([209.85.215.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WJmOI-0005Do-9z for gclcip-std-proposals@m.gmane.org; Sat, 01 Mar 2014 17:03:54 +0100 Original-Received: by mail-la0-f72.google.com with SMTP id gl10sf8548984lab.11 for ; Sat, 01 Mar 2014 08:03:54 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=p63/85GjUitTTGLFY8bD8uOl8Sk6cQWGCGqvcJXc7sY=; b=MlC8oSz5u8Z53RHnbA+QVuqp64J5RI4UXPpRKzrR0mabmW0ygayS+9KwebjUsNIQp1 qdvrEL7rGf88YMo/HLVueNWmAK/YkEAm0mwRh4XI1zhove25vDKRXaGQVBdLzE3qJwaI pVcpzTX0m+SKkixY7im/nGYcwrdbGtUxrtvXVH2LfyfjwY8PhmgQpd6dSjj4D4L9aDwq Cw3gABwSPPqtDPkwG0N/hmfIR04Hs3SZvFoKkAjUlfa1lbBXYb4PN10GEnfkLm2FzoOv 5vVZP92QEDnOzJWx/gyPliWjKNuvJkpu5CN6Uak+h+tlDarNIMzcwE52QCh/QiVJ1NJG IR1Q== X-Gm-Message-State: ALoCoQmaR/Zzkja9+X7lIgx5TiyJREGoi91D7tHXeypC6fsl/SSif+MM5dB5N+rxD0elZTFuASUr X-Received: by 10.152.45.105 with SMTP id l9mr10199724lam.5.1393689833829; Sat, 01 Mar 2014 08:03:53 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.96.193 with SMTP id du1ls246261wib.28.gmail; Sat, 01 Mar 2014 08:03:52 -0800 (PST) X-Received: by 10.14.175.129 with SMTP id z1mr364186eel.97.1393689832757; Sat, 01 Mar 2014 08:03:52 -0800 (PST) Original-Received: from mail-ee0-x22f.google.com (mail-ee0-x22f.google.com [2a00:1450:4013:c00::22f]) by mx.google.com with ESMTPS id t3si6326473eeg.64.2014.03.01.08.03.52 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 01 Mar 2014 08:03:52 -0800 (PST) Received-SPF: pass (google.com: domain of andrewtomazos@gmail.com designates 2a00:1450:4013:c00::22f as permitted sender) client-ip=2a00:1450:4013:c00::22f; Original-Received: by mail-ee0-f47.google.com with SMTP id b15so205650eek.34 for ; Sat, 01 Mar 2014 08:03:52 -0800 (PST) X-Received: by 10.205.99.1 with SMTP id cq1mr5191099bkc.5.1393689832456; Sat, 01 Mar 2014 08:03:52 -0800 (PST) Original-Received: by 10.205.9.197 with HTTP; Sat, 1 Mar 2014 08:03:52 -0800 (PST) In-Reply-To: X-Original-Sender: andrewtomazos@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of andrewtomazos@gmail.com designates 2a00:1450:4013:c00::22f as permitted sender) smtp.mail=andrewtomazos@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; 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:9482 Archived-At: --f46d041703f36432e904f38db3ed Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Yes, NDEBUG is kind of disappointing: Standard headers may be included in any order; each may be included more than once in a given scope, with no effect different from being included only once, except that the effect of including depends on the de=EF=AC=81nition of NDEBUG (= see 7.2) The header de=EF=AC=81nes the assert macro and refers to another= macro, NDEBUG which is not de=EF=AC=81ned by . If NDEBUG is de=EF=AC=81ned as a= macro name at the point in the source =EF=AC=81le where is included, the assert ma= cro is de=EF=AC=81ned simply as #define assert(ignore) ((void)0) The assert macro is rede=EF=AC=81ned according to the current state of NDEB= UG each time that is included. So assert.h is implemented like: // no header guard #ifdef NDEBUG #undef assert #define assert(ignore) ((void)0) #else #undef assert #define assert(x) (__real_assert_def(x)) #endif I'm sure the people working in modules enjoy talking about these 7 lines of code. :) On Sat, Mar 1, 2014 at 4:34 PM, Daniel Kr=C3=BCgler wrote: > 2014-03-01 16:33 GMT+01:00 Andrew Tomazos : > > What are some examples of header files that are designed for multiple > > inclusion? > > and come to my mind. > > - Daniel > > -- > > --- > 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 > email to std-proposals+unsubscribe@isocpp.org. > To post to this group, send email to std-proposals@isocpp.org. > Visit this group at > http://groups.google.com/a/isocpp.org/group/std-proposals/. > --=20 ---=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --f46d041703f36432e904f38db3ed Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Yes, NDEBUG is kind of disappointing:

<= /div>
Standard headers may be included in any order; each may be includ= ed more than once in
a given scope, with no effect different from= being included only once, except that the
effect of including <assert.h> depends on the de=EF=AC=81nition = of NDEBUG (see 7.2)

The header <assert.h&g= t; de=EF=AC=81nes the assert macro and refers to another macro,
<= br>
=C2=A0 =C2=A0NDEBUG

which is not de=EF=AC=81ned by= <assert.h>. If NDEBUG is de=EF=AC=81ned as a macro name at the
=
point in the source =EF=AC=81le where <assert.h> is included, th= e assert macro is de=EF=AC=81ned
simply as

=C2=A0 =C2=A0#define assert(ignore)= ((void)0)

The assert macro is rede=EF=AC=81ned ac= cording to the current state of NDEBUG each time that
<assert.= h> is included.

So assert.h is implemented like:

// no header guard
#ifdef NDEBUG

=C2=A0 =C2=A0 #undef assert
=C2=A0 =C2=A0 #define assert(i= gnore) ((void)0)

#else

=C2=A0 =C2=A0= #undef assert
=C2=A0 =C2=A0 #define assert(x) (__real_assert_def= (x))

#endif

I'm= sure the people working in modules enjoy talking about these 7 lines of co= de. :)



On Sat, Mar 1, 2014 at 4:34 PM, Daniel Kr=C3=BCgler <danie= l.kruegler@gmail.com> wrote:
2014-03-01 16:33 GMT+01:00 Andrew Tomazos &l= t;andrewtomazos@gmail.com>= ;:
> What are some examples of header files that are design= ed for multiple
> inclusion?

<assert.h> and <cassert> come to my mind.

- Daniel

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