From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 84119 invoked by alias); 16 Nov 2017 09:39:11 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 84102 invoked by uid 89); 16 Nov 2017 09:39:10 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.7 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,KAM_SHORT,KB_WAM_FROM_NAME_SINGLEWORD,RP_MATCHES_RCVD autolearn=no version=3.3.2 spammy=place, Prohibited, Hx-languages-length:813, letter X-Spam-User: qpsmtpd, 2 recipients X-HELO: userp1040.oracle.com Received: from userp1040.oracle.com (HELO userp1040.oracle.com) (156.151.31.81) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 16 Nov 2017 09:39:09 +0000 Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by userp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id vAG9d6Lq007413 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Nov 2017 09:39:07 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id vAG9d6oE030065 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Nov 2017 09:39:06 GMT Received: from abhmp0019.oracle.com (abhmp0019.oracle.com [141.146.116.25]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id vAG9d5Me027509; Thu, 16 Nov 2017 09:39:05 GMT Received: from [192.168.1.4] (/95.247.133.51) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 16 Nov 2017 01:39:05 -0800 Subject: Re: [PATCH 3/4] libstdc++: avoid character accumulation in istreambuf_iterator To: Petr Ovtchenkov Cc: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org References: <04e468027f8bad7858583db836073af1d7c524f1.1510778853.git.ptr@void-ptr.info> <069c0a67-6f8c-67a0-c0bd-a404264d8dc1@oracle.com> <20171116083122.54714b4a@void-ptr.info> From: Paolo Carlini Message-ID: <33717f79-e6f2-c7a6-6cfb-bf01efebb7a3@oracle.com> Date: Thu, 16 Nov 2017 09:51:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171116083122.54714b4a@void-ptr.info> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2017-11/txt/msg01283.txt.bz2 Hi, On 16/11/2017 06:31, Petr Ovtchenkov wrote: > Is we really worry about frozen sizeof of instantiated template? Yes we do. See https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html under "Prohibited Changes", point 8. Of course removing the buffering has performance implications too - that's why it's there in the first place! - which I remember we investigated a bit again in the past when somebody reported that a few implementations had it other did not. But I can't say to have followed all the (recently uncovered) conformance implications, it could well be that we cannot be 100% conforming to the letter of the current standard while taking advantage of a buffering mechanism. Jonathan will provide feedback. Paolo.