220 31681 <2340e1b0-09bd-4f5b-bf15-7605eaed858b@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: Sat, 18 Mar 2017 14:18:26 -0700 (PDT) Lines: 166 Approved: news@gmane.org Message-ID: <2340e1b0-09bd-4f5b-bf15-7605eaed858b@isocpp.org> References: <6aa2e439-345e-4f04-8843-f38bb7b825b2@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_616_1307519651.1489871906742" X-Trace: blaine.gmane.org 1489871909 3316 195.159.176.226 (18 Mar 2017 21:18:29 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 18 Mar 2017 21:18:29 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDY2PNGE6QOBBI6IW3DAKGQETX5DGBY@isocpp.org Sat Mar 18 22:18:25 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f72.google.com ([74.125.83.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cpLjy-00005I-Gn for gclcip-std-proposals@m.gmane.org; Sat, 18 Mar 2017 22:18:22 +0100 Original-Received: by mail-pg0-f72.google.com with SMTP id 21sf40063441pgg.4 for ; Sat, 18 Mar 2017 14:18:28 -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=LBpqFT4sD6UHuiEkUtCGXwTNHvXLrUnbLsI0Vh+ifGc=; b=K4/LhmcpiIb4+tuqi4DyCYKJcfSgzvt2bl7OXNWSeM21+WMrD7Z5oSIlZhaBNa89lG EEAlBpA7UGFkd14ugLBpGgYSSEal+WxMbUUBmI4mLTXXHXdYLbarMicNADHved9VkEMQ aJSo2ZwgKtvQpbzT4hMAm0mQIdsVRBTt23lD31Pjbm6IrmpkcFcLY9GWyiUJju1dso/F eyJ1xwKDiodOMejj3Tvv7TGHYZtOmib3lh9BlafI82rXxmskJe8v0/bba2M632Vs24Zo Y7Jud5F1YOmMyF8vtSo0ooAwVNB/8itsfSnKlM5vewAdLGxBEjcNmfdkGxt8649qBagy lvjQ== 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=LBpqFT4sD6UHuiEkUtCGXwTNHvXLrUnbLsI0Vh+ifGc=; b=Y43Nicq0Va6xVhAePJQepNHBBMRDDasqS8cvr12/FMI16FYs91OcFT9u0qvGZvsoI0 kCFSWUEDQUbQbtnFF0SZ6ZHHHa/wSyXBNOnN1/Em+gA9BSVT9RzmBA5Gr+lgrHUhBfyB ofK/xioz71qLJEut8k5E7Mo2/wFUIz5/sNGSuKGDwflfqovPV57kMMAaSm8ONO3yvHC5 eZ76WBlU8CK3SrtnKYf8dg1zXr8ciITE1UX6oYOrEpw15Gh++pm9aP3c7ZeoxRriuf2o TluN70Jq4vlejP1CrhlYboheAfG7R+43z06hzWekpboIWAieydJNmn01srZ++g5ZZgdn +Zzw== 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=LBpqFT4sD6UHuiEkUtCGXwTNHvXLrUnbLsI0Vh+ifGc=; b=aOK9iy5ddlyhngu43e00KUe+Aml+SN+TBgLyU9hJKybgHfgtxUhC8m82+iduHXTAQK SZahW1KgTixR08cqpjDNCGVqb51slgLd0WoteKIKMK+Z2EbeRhCyDpbOf5OAzL1xF8wB QW3dg1hWXCMMDT9t9nK1Q4oAaQrGGXON253zPuIPkrE37R//fI5OKV3JaHE5RAjAdid+ AxtDsuASTYJI2sBNE6LvMqSPM9xv9r07iImnXP4mXqiVw66S8Vxi/7+FvxE5dAgsVxrx 68TUtpmqTaHqX5D1xNPUyaFPjVwalKyhEdr2/mTmrLM1su6PA1fT3VNKkTNjvU8nhaGk q2rQ== X-Gm-Message-State: AFeK/H2++NYZPlCEfPKR/ikURYfzUbLRy00uVOqjs3VIrkm+TImc40zUemlS0+oS1kBRmQ== X-Received: by 10.99.61.79 with SMTP id k76mr11077516pga.3.1489871908115; Sat, 18 Mar 2017 14:18:28 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.59.194 with SMTP id k60ls7854813otc.34.gmail; Sat, 18 Mar 2017 14:18:27 -0700 (PDT) X-Received: by 10.157.22.200 with SMTP id s8mr2317292ots.16.1489871907213; Sat, 18 Mar 2017 14:18:27 -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:31681 Archived-At: ------=_Part_616_1307519651.1489871906742 Content-Type: multipart/alternative; boundary="----=_Part_617_754500275.1489871906742" ------=_Part_617_754500275.1489871906742 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Yes your are right I have misspelled it. Should be something like this: class ComposedDerivedDerived : public ComposedDerived , public NewClass { public: ComposedDerivedDerived(std::string & str) // Here is no=20 VirtualBase(str) : ComposedDerived(str), , NewClass() { } }; But I do not see any problems with separate translation unit. We should not care about another separate unit, it is responsibility of=20 compiler that will support this rule to require an user calls a constructor= =20 for VirtualBase. We should not care because according to this rule we know that constructor= =20 had been called above. But if user want it can call it directly for backward compitability. VirtualBase constructor should be required to call only when class inherits= =20 from two or more classes those inhertits virtually from VirtualBase class. =D1=81=D1=83=D0=B1=D0=B1=D0=BE=D1=82=D0=B0, 18 =D0=BC=D0=B0=D1=80=D1=82=D0= =B0 2017 =D0=B3., 21:45:04 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 Voutilainen=20 =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB: > > > > On 18 March 2017 at 21:31, Denis Kotov >= =20 > wrote: > >> I want to simplify it like the following: >> >> class ComposedDerivedDerived >> : public ComposedDerived >> , public NewClass >> { >> public: >> ComposedDerivedDerived(std::string & str) // Here is no=20 >> VirtualBase(str) >> { >> >> } >> }; >> >> *Proposal is the following:* >> *Require to specify constructor for VirtualBase only if compiler find= =20 >> more the one path of virtual inheritance like for C3 (on diagram) or=20 >> ComposedDerived (in code) classes* >> > > > ComposedDerivedDerived didn't initialize ComposedDerived in your original= =20 > code or this modified code. Also, there's no reason that > a compiler could find an initialization for a virtual base, since that=20 > initialization may be in a separate translation unit that the compiler=20 > doesn't > see, so this idea doesn't work at all. > > --=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/2340e1b0-09bd-4f5b-bf15-7605eaed858b%40isocpp.or= g. ------=_Part_617_754500275.1489871906742 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Yes your are right I have misspelled it. Should be somethi= ng like this:

=C2=A0 =C2=A0 class ComposedDerivedDe= rived
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0: public ComposedD= erived
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0, public NewClass=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 {
=C2=A0 =C2=A0 =C2=A0 =C2= =A0 public:
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0ComposedDeri= vedDerived(std::string & str) // Here is no VirtualBase(str)
=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0: ComposedDeriv= ed(str),
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0,= NewClass()
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0{
=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0}
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 };

But I do not see any = problems with separate translation unit.
We should not care about= another separate unit, it is responsibility of compiler that will support = this rule to require an user calls a constructor for VirtualBase.
We should not care because according to this rule we know that constructor= had been called above.
But if user want it can call it directly = for backward compitability.

VirtualBase constructo= r should be required to call only when class inherits from two or more clas= ses those inhertits virtually from VirtualBase class.

=D1=81= =D1=83=D0=B1=D0=B1=D0=BE=D1=82=D0=B0, 18 =D0=BC=D0=B0=D1=80=D1=82=D0=B0 201= 7 =D0=B3., 21:45:04 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 Voutilainen =D0=BD=D0=B0=D0=BF=D0=B8=D1=81= =D0=B0=D0=BB:
=

On 18 March 2017 at 21:31, Denis Ko= tov <redr...@gmail.com> wrote:
I want to simplify it like the follo= wing:

=C2=A0 =C2=A0 class ComposedDerivedDeriv= ed
=C2=A0 =C2=A0 =C2=A0 =C2=A0: public ComposedDerived
= =C2=A0 =C2=A0 =C2=A0 =C2=A0, public NewClass
=C2=A0 =C2=A0 {
=C2=A0 =C2=A0 public:
=C2=A0 =C2=A0 =C2=A0 =C2=A0ComposedDe= rivedDerived(std::string & str) // Here is no VirtualBase(str)
=C2=A0 =C2=A0 =C2=A0 =C2=A0{

=C2=A0 =C2=A0 = =C2=A0 =C2=A0}
=C2=A0 =C2=A0 };

<= div>Proposal is the foll= owing:
=C2=A0 =C2=A0Require to specify constructor = for VirtualBase only if compiler find more the one path of virtual inherita= nce like for C3 (on diagram) or ComposedDerived (in code) classes
=


ComposedDerivedDerived didn'= t initialize ComposedDerived in your original code or this modified code. A= lso, there's no reason that
a compiler could find an init= ialization for a virtual base, since that initialization may be in a separa= te translation unit that the compiler doesn't
see, so thi= s idea doesn't work at all.

--
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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/2340e1b0-09bd-4f5b-bf15-7605eaed858b= %40isocpp.org.
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