220 29557 article Path: news.gmane.org!.POSTED!not-for-mail From: Domen Vrankar Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Instantiation of default destructor Date: Mon, 28 Nov 2016 13:14:13 +0100 Lines: 105 Approved: news@gmane.org Message-ID: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=94eb2c06105c5269c405425b6b3d X-Trace: blaine.gmane.org 1480335301 476 195.159.176.226 (28 Nov 2016 12:15:01 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 28 Nov 2016 12:15:01 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCHJ3Z4NUUFBBPV76DAQKGQE4V6HERY@isocpp.org Mon Nov 28 13:14:53 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f71.google.com ([74.125.83.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cBKpf-0007EQ-Rc for gclcip-std-proposals@m.gmane.org; Mon, 28 Nov 2016 13:14:52 +0100 Original-Received: by mail-pg0-f71.google.com with SMTP id q10sf354713082pgq.7 for ; Mon, 28 Nov 2016 04:14:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:from:date:message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=DYbJa6GQ57/WHSMFXlIOvCw106FyUaVOyponq4fzRy8=; b=y/K+4X3IzT5bZ57n+G1hS08/5W4KHH0db4Y6P/upHr0BPf8fLnIv1fP95f2NjuCEUp iLVKsnLEdCgq7lp5wGX+w8amG/QlniJBn6XZjXxKeJoRhsRxOPNczGzS07u74Y4zpEpc qMQ0pWdCsDEUSzXBb/xkWnCfZ1A5r7f5vwfO/I5BzhPMOxwjKC83/KcnVkiFTYsmynDa Zvu+XhJIEWSFSO6wzuJ4ogZCgbRy5h3O9dXH9sDi9QiYAXDTlRKvE6zWmKn958KuEVdJ +0ZHgYDSWywf2YOcNGRRLP48Yh+Eux8Uhl81c0c9A/A961oIdyn5XNnQLHBCGv4BqxbH +o/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:from:date:message-id:subject:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=DYbJa6GQ57/WHSMFXlIOvCw106FyUaVOyponq4fzRy8=; b=JYtA49GCNUDmJayWRBb08Waexx7XOgY0OH6gCDgPWoabJnCK0eGP7e++XNtMr06F/9 tWmDVXnur5R87Uh8W75tGZKviKxZ0U4iJtvvKIUXmkGHFUnvq3s1a/pqbnbh4vFiY6II NDrY+YrPxB3zmKGrwPPZInWv5EROyv69Nx2JeylfqwVbddHqQ0QkxHoGawbHkd7Gr7UU ch1LDoislzbhFCMvIJsM7k4eMPQhnnR9rGcMAEbTyhY6FsJxUIWbGwPlKkUM8wmnXXaa vcu1FlFNGtIzScW2/5bSRF2moyPHRzQhV5mybZSIilnIxyZBi9FVQ+ZiEvKycwXsJjfl Y+Cw== X-Gm-Message-State: AKaTC01segIIZxj2YRwAO09vlPr8MxuZ8FIPppdxH7OrD48KvykJL+xauneHuBojAUHH9A== X-Received: by 10.99.67.194 with SMTP id q185mr10353643pga.31.1480335295356; Mon, 28 Nov 2016 04:14:55 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.136.90 with SMTP id k87ls2968453iod.19.gmail; Mon, 28 Nov 2016 04:14:54 -0800 (PST) X-Received: by 10.107.189.196 with SMTP id n187mr18266668iof.88.1480335294147; Mon, 28 Nov 2016 04:14:54 -0800 (PST) Original-Received: from mail-io0-x233.google.com (mail-io0-x233.google.com. [2607:f8b0:4001:c06::233]) by mx.google.com with ESMTPS id 66si18569692itx.49.2016.11.28.04.14.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Nov 2016 04:14:54 -0800 (PST) Received-SPF: pass (google.com: domain of domen.vrankar@gmail.com designates 2607:f8b0:4001:c06::233 as permitted sender) client-ip=2607:f8b0:4001:c06::233; Original-Received: by mail-io0-x233.google.com with SMTP id c21so220766322ioj.1 for ; Mon, 28 Nov 2016 04:14:54 -0800 (PST) X-Received: by 10.107.62.195 with SMTP id l186mr5228221ioa.1.1480335293571; Mon, 28 Nov 2016 04:14:53 -0800 (PST) Original-Received: by 10.50.235.15 with HTTP; Mon, 28 Nov 2016 04:14:13 -0800 (PST) X-Original-Sender: Domen.Vrankar@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of domen.vrankar@gmail.com designates 2607:f8b0:4001:c06::233 as permitted sender) smtp.mailfrom=domen.vrankar@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:29557 Archived-At: --94eb2c06105c5269c405425b6b3d Content-Type: text/plain; charset=UTF-8 Hi, In this video [1] (time 57:40) Jason Jurecka was talking about the need to write empty/defaulted destructor in cpp file if you want to declare a class in header file, use it in std::unique_ptr and include its declaration only in cpp file: //a.h .... class T; struct A { A(T* ptr_); // intentionally before A() constructor - see the question below A(); std::unique_ptr ptr; }; .... //a.cpp #include "a.h" #include "t.h" // declaration of T class .... A::A() {} A::A(T* ptr_) : ptr{ptr_} {} .... This won't work since default destructor is (if I understood the reason why Tomasz Wota's example in the comment worked: [2] ) implemented at the end of the compilation unit. For me it's not a big deal to write A::~A() = default; in cpp file but still since we've had that debate I was wondering if it would be feasible to change the wording (don't know how much the standard would have to be changed for that) so that implicit default destructor would be added to the code at the point of first constructor implementation (in the above example at the point of A::A(T* ptr_); implementation in .cpp file) and not at the end of the file where the class was declared? Thanks, Domen [1] https://www.youtube.com/watch?v=8AjRD6mU96s [2] http://melpon.org/wandbox/permlink/k8UpfCT8DlYv1hv3 -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAKgx6B%2B8zzZ131-UZobmUvCgB4YeQ1%2BwTZadcuT6ieDCofDndg%40mail.gmail.com. --94eb2c06105c5269c405425b6b3d Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Hi,

In this video [1] (time 57:40) Jason Jurecka= was talking about the need to write empty/defaulted destructor in cpp file= if you want to declare a class in header file, use it in std::unique_ptr a= nd include its declaration only in cpp file:

//a.h
...=
class T;

struct A
{
A(T* = ptr_); // intentionally before A() constructor - see the question below
=
A();
std::unique_ptr<T> ptr;
};
...

//a.cpp
#include "a.h&= quot;
#include "t.h" // declaration of T class
<= /div>
...
A::A() {}
A::A(T* ptr_) : ptr{ptr= _} {}
...

This won't work since default= destructor is (if I understood the reason why Tomasz Wota's example in= the comment worked: [2]) implemented at the end of the compilation unit.

<= /div>
For me it's not a big deal to write A::~A() =3D default; in c= pp file but still since we've had that debate I was wondering if it wou= ld be feasible to change the wording (don't know how much the standard = would have to be changed for that) so that implicit default destructor woul= d be added to the code at the point of first constructor implementation (in= the above example at the point of A::A(T* ptr_); implementation in .cpp fi= le) and not at the end of the file where the class was declared?

Thanks,
Domen

--
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