220 35066 <1638034.bOiPUqA2XK@tjmaciei-mobl1> article Path: news.gmane.org!.POSTED!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: std::vector, std::string attach/detach external buffer Date: Fri, 20 Oct 2017 14:44:31 -0700 Lines: 39 Approved: news@gmane.org Message-ID: <1638034.bOiPUqA2XK@tjmaciei-mobl1> References: <2688395.4cN1N1XxoH@tjmaciei-mobl1> <98f471c3-2a05-4dfa-8a48-b0ed8fb0212a@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Trace: blaine.gmane.org 1508535891 2067 195.159.176.226 (20 Oct 2017 21:44:51 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 20 Oct 2017 21:44:51 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBRO4VHHQKGQE2SQY43I@isocpp.org Fri Oct 20 23:44:44 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wr0-f199.google.com ([209.85.128.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e5f5j-0006WF-E3 for gclcip-std-proposals@m.gmane.org; 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[78.47.120.188]) by mx.google.com with ESMTP id p77si1527956wma.88.2017.10.20.14.44.36 for ; Fri, 20 Oct 2017 14:44:36 -0700 (PDT) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) client-ip=78.47.120.188; Original-Received: from tjmaciei-mobl1.localnet (jfdmzpr04-ext.jf.intel.com [134.134.139.73]) by gondolin.macieira.info (Postfix) with ESMTPSA id D7D5211B50A for ; Fri, 20 Oct 2017 14:44:33 -0700 (PDT) In-Reply-To: <98f471c3-2a05-4dfa-8a48-b0ed8fb0212a@isocpp.org> X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) smtp.mailfrom=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:35066 Archived-At: On Friday, 20 October 2017 14:11:49 PDT Nicol Bolas wrote: > > Note, however, the consequence: > > char *ptr = cstring.detach_buffer(); > > > > may fail. > > ... I disagree; this *must* succeed. But it doesn't have to *empty* the > buffer, just like moving from a `basic_string` can still do a copy if the > string is in the SSO buffer. This should be able to allocate memory, and > therefore represents a potentially throwing operation. Read: it may fail :-) > This is another reason why I feel that the "detach_buffer" mechanism needs > to be wrapped in a type. So instead of getting a `char*`, you get: > > buffer buf = cstring.detach_buffer(); > > `buf` now owns that memory, with full RAII semantics. You can call > `buf.data()` to get a pointer to the array, but it doesn't have any of the > container machinery like `begin/end/operator[]/insert/remove/etc`. It's > just a buffer with a size, capacity, and allocator. I don't see how this helps with this particular problem. If the string was SSO, then detach_buffer() may still throw, because it can't point to the cstring object's area. It may be a good idea as a general principle, though. -- Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center -- 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/1638034.bOiPUqA2XK%40tjmaciei-mobl1. .