220 31693 <633f2640-aef5-46a2-9ae2-6db626bc47fb@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Denis Kotov Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Simplify virtual inheritance rules Date: Sun, 19 Mar 2017 05:55:08 -0700 (PDT) Lines: 113 Approved: news@gmane.org Message-ID: <633f2640-aef5-46a2-9ae2-6db626bc47fb@isocpp.org> References: <6aa2e439-345e-4f04-8843-f38bb7b825b2@isocpp.org> <2340e1b0-09bd-4f5b-bf15-7605eaed858b@isocpp.org> <25e054ca-aac4-4bcc-805a-4e1357de4f37@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_782_2008942085.1489928108589" X-Trace: blaine.gmane.org 1489928112 14930 195.159.176.226 (19 Mar 2017 12:55:12 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 19 Mar 2017 12:55:12 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDY2PNGE6QOBBLP7XHDAKGQEICXFGJA@isocpp.org Sun Mar 19 13:55:07 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f70.google.com ([209.85.214.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cpaMS-00034C-Sl for gclcip-std-proposals@m.gmane.org; Sun, 19 Mar 2017 13:55:05 +0100 Original-Received: by mail-it0-f70.google.com with SMTP id g138sf92426030itb.4 for ; Sun, 19 Mar 2017 05:55:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=kz/aJzUqwsblR/Hv14IsmIRg2TCo/92zXhcbymvabZU=; b=yhVCQDuV4Qt1/kqdXiADy8NO9tE6J+4psKlkEGux4SSLyRC+6mg8a+rxZxXvyeq7IN xgxHSRvQU1E5RFdQacrGOZCvbKxvoQ+koKk97OIy5uVGkSBxUrCGR0Raahiw0kcoP/qc F5YNTTnTaQd7x14e9b+TBsQzNW6cZgFGCRdeNlPj+wx/bR7lbzbwg8WYMk3OYwgzrLt9 AYWcW/6jNYh4nC9conBUggXsNwXJpZvDbDfKZsEJ9rfhuEVna8zowzx170F1MrTOdY0l OqHXd5cyBky5aZRogEd8olXhB5aPzT8ape9hLHb6eYYGYVHirFLjiQoeTAN/KgY6InSU 46+g== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=kz/aJzUqwsblR/Hv14IsmIRg2TCo/92zXhcbymvabZU=; b=e2qcURfngRmlDPprYEmMVggfD8xR/1esCrGG8OzXzytk47fe0KFESALGU4JA2tUrUd n7bCFuBlyuBrJLnx+WLf45SnRg9tPN+pCpQt930wWCb4BR0JUScO/q2QUPTf91qA18rR WrDXjgMQqSgTqJBNgm4Z6MakdlBm30bWVlOFZUS+G3qrPZy4DJDc2qfxuCFrzAG0xgTJ h/pBNjyygXxcj7NgJGexnVHs56qpkVCQDFBP4vJOS5t3YZvMftQGd5RJV0kfp1w+qIg7 d4OEvvQtbI0bWVVfNiC/OF++e5KqWaYAYDyzi6W/u1gO9vjt0blsXIqjoTjSy+AkEvnW lRow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=kz/aJzUqwsblR/Hv14IsmIRg2TCo/92zXhcbymvabZU=; b=mT4Yk6T3tSOiNoNhbela1tycXZRwSnQu86zjJKWY1f0Dc4rG85FBRHp9rpilAishgF ChniWZmPPD6MLBdYASGzhDr9NzbC9jw6CkmYrPUpNWT2vzW0nd13m4qdto0Zc6D0w4hW ZibBvJWUOAtN2uGDV61BFE00WiHBYY04T1FXjmWY/qvtsYaw9js+FTf/pMR04n/ltK+0 xYEyEp7UGmw8Sx4K0/bTX3DDcCQpdp7tEsfZdO50F6lIFNVkbyF/xpHyPfzBAlbwRwYi uVDmhUII2P9Vxf13QqHa/AgfnufzkULd4Qbl4qiGlJ0a3Oizh+DzKRwC3hNXbHMIUOVV L1Hw== X-Gm-Message-State: AFeK/H2HL6W7gCwlRZTNjKGAWRrYkFr6G9BL/JFjGzuVwAEVO2jrKwSMyYNqR46BsSUIJg== X-Received: by 10.107.152.149 with SMTP id a143mr1755763ioe.30.1489928109895; Sun, 19 Mar 2017 05:55:09 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.56.232 with SMTP id k37ls11750569ote.15.gmail; Sun, 19 Mar 2017 05:55:09 -0700 (PDT) X-Received: by 10.157.82.47 with SMTP id e47mr2381112oth.18.1489928109075; Sun, 19 Mar 2017 05:55:09 -0700 (PDT) In-Reply-To: X-Original-Sender: redradist@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:31693 Archived-At: ------=_Part_782_2008942085.1489928108589 Content-Type: multipart/alternative; boundary="----=_Part_783_1796710921.1489928108590" ------=_Part_783_1796710921.1489928108590 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Ville Voutilainen, *That is the point:* We will anyway know that *VirtualBase *is performed,= =20 but by parent class where two *VirtualBase (VC class) *class inherites in= =20 class *C3*. Class *C5 *already knows that class *C3 *initialized *VirtualBase (VC=20 class)* *C5 *class should not know anything about *VirtualBase*, because *C3 *has= =20 already called constructor for *VirtualBase.* It is useless to call in *C5 = *constructor=20 for *VirtualBase* if *C5 *does not what to do with parent classes. =D0=B2=D0=BE=D1=81=D0=BA=D1=80=D0=B5=D1=81=D0=B5=D0=BD=D1=8C=D0=B5, 19 =D0= =BC=D0=B0=D1=80=D1=82=D0=B0 2017 =D0=B3., 14:28:17 UTC+2 =D0=BF=D0=BE=D0=BB= =D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1=8C Ville=20 Voutilainen =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB: > > On 19 March 2017 at 14:22, Denis Kotov >= =20 > wrote:=20 > > Thanks for comment T. C.,=20 > >=20 > > But I do not agree that it is not worth to do it.=20 > > Consider situation of very long chain of inheritance. Why in this chain= =20 > user=20 > > has to call every time constructor for VirtualBase ?=20 > > > The language statically guarantees that the initialization of the=20 > VirtualBase is performed. Your=20 > suggestion turns that static guarantee into undefined behavior.=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/633f2640-aef5-46a2-9ae2-6db626bc47fb%40isocpp.or= g. ------=_Part_783_1796710921.1489928108590 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
<= span class=3D"IVILX2C-D-a">Ville Voutilainen,

That is the point: We will anyway know that Virt= ualBase is=C2=A0performed, but by parent class where two Virt= ualBase (VC class)=C2=A0class inherites in class C3.
C= lass C5 already knows that class C3 initialized VirtualBas= e (VC class)
C5 class should not know anything about=C2=A0= VirtualBase,=C2=A0because C3 has already called constructor for= =C2=A0VirtualBase. It is useless to call in=C2=A0C5=C2=A0cons= tructor for=C2=A0VirtualBase if C5 does not what to do with p= arent classes.

=D0=B2=D0=BE=D1=81=D0=BA=D1=80=D0=B5=D1=81=D0=B5=D0= =BD=D1=8C=D0=B5, 19 =D0=BC=D0=B0=D1=80=D1=82=D0=B0 2017 =D0=B3., 14:28:17 U= TC+2 =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=82=D0=B5=D0=BB=D1= =8C Ville Voutilainen =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:On 19 March 2017 at 14:22, Denis Kotov &= lt;re= dr...@gmail.com> wrote:
> Thanks for comment T. C.,
>
> But I do not agree that it is not worth to do it.
> Consider situation of very long chain of inheritance. Why in this = chain user
> has to call every time constructor for VirtualBase ?


The language statically guarantees that the initialization of the
VirtualBase is performed. Your
suggestion turns that static guarantee into undefined behavior.

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