220 7744 <5347204.PXDO8jBI6L@tjmaciei-mobl2> article Path: news.gmane.org!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Proposal to add C99 designated initializers to C++ Date: Wed, 13 Nov 2013 14:53:11 -0800 Lines: 66 Approved: news@gmane.org Message-ID: <5347204.PXDO8jBI6L@tjmaciei-mobl2> References: <60181971.rjyeC72bSi@tjmaciei-mobl2> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1384383196 929 80.91.229.3 (13 Nov 2013 22:53:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 13 Nov 2013 22:53:16 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBXEFSCKAKGQESNBC7YQ@isocpp.org Wed Nov 13 23:53:21 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ea0-f199.google.com ([209.85.215.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VgjJG-0004GK-0E for gclcip-std-proposals@m.gmane.org; Wed, 13 Nov 2013 23:53:18 +0100 Original-Received: by mail-ea0-f199.google.com with SMTP id f15sf1312905eak.6 for ; Wed, 13 Nov 2013 14:53:17 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:subject:date:message-id:user-agent :in-reply-to:references:mime-version: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-transfer-encoding:content-type; bh=QvOPc1V6xbSU4GKlTtZzZK1nVSzVCYnwzTm8LqA4ZlY=; b=PvKYcNs29lINBBa7fkXcZfGLaQ9wnIzfzvZoTVg62sdajn4HclFFpX+oYEDV+D+PJG OnkvnjH8buKXFNoV/HCIuLG+WbF8fGlXCaAdFm+Nk57EYMHSA3Fg/amrNf1iensjlAjb jW95JNyj2ufB1FEOctGJFXoMnhCmZUT9wT30KD8AosOf2xLDeWLeZOrl35QWSiGJf+x6 cBCTqHZ6/UTtaeYCbRvUY0tLB8cPgtH10l8IPjTD1++W0RQUyIHXgtg1m+Ro5D39MNG+ abbHq+o3pHdpfNMtgxSCo1pDO7BYUCsDsCgC2+CqkHBeDPaoBuls37w5XhbHYVlrTY6M 8B0 X-Gm-Message-State: ALoCoQmC5u5Am6u7KKyOdpdfLpMzapg2W2xuqbm4L2Wploveucwkc2iXTeW+CFvPHO+YjoT3fLO3 X-Received: by 10.205.19.4 with SMTP id qi4mr37959bkb.1.1384383197444; Wed, 13 Nov 2013 14:53:17 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.211.49 with SMTP id mz17ls1120621wic.13.canary; Wed, 13 Nov 2013 14:53:16 -0800 (PST) X-Received: by 10.14.42.6 with SMTP id i6mr5043534eeb.65.1384383196260; Wed, 13 Nov 2013 14:53:16 -0800 (PST) Original-Received: from gondolin.macieira.info (gondolin.macieira.info. [2a01:4f8:d13:f81:21c:14ff:fe01:12a3]) by mx.google.com with ESMTP id j41si71288eeg.158.2013.11.13.14.53.16 for ; Wed, 13 Nov 2013 14:53:16 -0800 (PST) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 2a01:4f8:d13:f81:21c:14ff:fe01:12a3 as permitted sender) client-ip=2a01:4f8:d13:f81:21c:14ff:fe01:12a3; Original-Received: from tjmaciei-mobl2.localnet (unknown [IPv6:2a01:4f8:d13:f81:21c:14ff:fe01:12a3]) by gondolin.macieira.info (Postfix) with ESMTPSA id 97A9012C01B for ; Wed, 13 Nov 2013 14:53:15 -0800 (PST) User-Agent: KMail/4.12 pre (Linux/3.9.10-100+i915fix.fc17.x86_64; KDE/4.11.60; x86_64; git-8054221; 2013-08-01) In-Reply-To: X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 2a01:4f8:d13:f81:21c:14ff:fe01:12a3 as permitted sender) smtp.mail=thiago@macieira.org 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:7744 Archived-At: On ter=E7a-feira, 12 de novembro de 2013 17:36:03, Richard Smith wrote: > > Shouldn't compilers emit then a diagnostic if you fail to sequence them= in > > the > > right order? >=20 > Sure, they can, just as they do for constructor initializers. And, just a= s > with constructor initializers, we need to sequence the subobject > initialization in subobject order, in order to get destructors to run in > the right order. Good. >=20 > > struct S { > >=20 > > int a, b; > >=20 > > }; > >=20 > > int i; > > int f(int *i) { *i =3D 42; return 47; } > >=20 > > struct S g() > > { > >=20 > > struct S s =3D { .b =3D f(i), .a =3D i }; >=20 > I assume you meant f(&i) here? Yes. I had a reference first, then I changed to a pointer so I could compil= e in=20 C mode... > return s; >=20 > > } > >=20 > > When compiled as C99, the above returns { .a =3D 42, .b =3D 47 }. >=20 > Only by chance. C99 6.7.8/23 says: "The order in which any side effects > occur among the initialization list expressions is unspecified." Ah, ok. So my code actually has undefined behaviour. For C++, though, we do= =20 have an order and we also have to initialise sub-objects in the correct ord= er. --=20 Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center PGP/GPG: 0x6EF45358; fingerprint: E067 918B B660 DBD1 105C 966C 33F5 F005 6EF4 5358 --=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/. .