From 6752331581827886679 X-Google-Thread: f78e5,6f5c74c3d7959916 X-Google-NewGroupId: yes X-Google-Attributes: gid7894ca11fe,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Received: by 10.68.232.42 with SMTP id tl10mr12779998pbc.7.1335657636676; Sat, 28 Apr 2012 17:00:36 -0700 (PDT) MIME-Version: 1.0 Path: r9ni109992pbh.0!nntp.google.com!news1.google.com!goblin3!goblin1!goblin.stu.neva.ru!news.albasani.net!.POSTED!not-for-mail From: "Alf P. Steinbach" Newsgroups: comp.std.c++ Subject: Re: make_shared and friends. Date: Sat, 28 Apr 2012 17:00:32 -0700 (PDT) Organization: A noiseless patient Spider Lines: 37 Sender: std-cpp-request@vandevoorde.com Approved: james.dennett@gmail.com Message-ID: References: <5583145.28.1335476739188.JavaMail.geo-discussion-forums@ynnn35> NNTP-Posting-Host: tmKkPRGO2cMrLNG5jY21G++OJ1otg1MODH9D4r9WD3g= X-Trace: news.albasani.net c/A3W3wZmIfGEv6xDaBr0k/BZxt3/GjZI3e27wAbCwNYWsHLPjgpw66HjxXGPm+BT46tpj0/XfCnRQWX5ZjfBw== X-Complaints-To: abuse@albasani.net NNTP-Posting-Date: Sun, 29 Apr 2012 00:00:34 +0000 (UTC) X-Mailer: Perl5 Mail::Internet v2.05 X-Submission-Address: std-cpp-submit@vandevoorde.com Cancel-Lock: sha1:aNfn3wnhQKBttSy1aBgV/zvRr4E= X-Original-Date: Fri, 27 Apr 2012 20:52:37 +0200 Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 27.04.2012 20:12, Jason McKesson wrote: > > Does the C++11 specification allow you to say that the `make_shared` > template is a friend, and thus guarantee that it can access the > appropriate private constructors of a class? Yes, there is syntax that > would make `make_shared` a friend. But does the spec *require* that > the constructors are called directly from `make_shared` itself, since > it cannot transfer friendship to any subsidiary object types? I don't think so. But as a practical matter make your destructor protected (or private), instead of the constructors. If the private constructors imply factory functions, then by switching to making the destructor non-public for the general case you reduce the number of construction/destruction support functions from M class specific factory functions, where M is the average number of constructors, to 1 common destroy function, which you can make a friend. And if you have make_shared as a single common factory function (note that this can be a bit unsafe since it or its wrapper will then have access to /all/ the constructors), then by doing the switch you introduce just 1 more function. No matter the number of such classes you create. Cheers & hth., - Alf -- [ comp.std.c++ is moderated. To submit articles, try posting with your ] [ newsreader. If that fails, use mailto:std-cpp-submit@vandevoorde.com ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]