From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rock.gnat.com (rock.gnat.com [205.232.38.15]) by sourceware.org (Postfix) with ESMTP id 6B869385BF83 for ; Tue, 31 Mar 2020 19:11:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 6B869385BF83 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=adacore.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tromey@adacore.com Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id 40B481168D6; Tue, 31 Mar 2020 15:11:22 -0400 (EDT) X-Virus-Scanned: Debian amavisd-new at gnat.com Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id Xn067g77sDgi; Tue, 31 Mar 2020 15:11:22 -0400 (EDT) Received: from murgatroyd (97-118-117-21.hlrn.qwest.net [97.118.117.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by rock.gnat.com (Postfix) with ESMTPSA id D5D39116883; Tue, 31 Mar 2020 15:11:21 -0400 (EDT) From: Tom Tromey To: Pedro Alves Cc: Tom Tromey , gdb-patches@sourceware.org Subject: Re: [PATCH 2/2] Avoid copying in lookup_name_info References: <20200320204935.19509-1-tromey@adacore.com> <20200320204935.19509-3-tromey@adacore.com> X-Attribution: Tom Date: Tue, 31 Mar 2020 13:11:21 -0600 In-Reply-To: (Pedro Alves's message of "Tue, 31 Mar 2020 19:18:08 +0100") Message-ID: <87wo70baqu.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 31 Mar 2020 19:11:23 -0000 >>>>> "Pedro" == Pedro Alves writes: Pedro> I think it would be better for this overload to take a Pedro> gdb::string_view instead of a const std::string& . That Pedro> way, it still works if you only have a string_view handy. Pedro> As is, there's no way to created a lookup_name_info starting Pedro> with a string_view without copying. WDYT? The issue is that there's a trick in the implementation: /* Like the "name" method but guarantees that the returned string is \0-terminated. */ const char *c_str () const { /* Actually this is always guaranteed due to how the class is constructed. */ return m_name.data (); } This is needed in some spots. However, if we take a string_view at construction, then we'd be violating the string_view contract, or we'd need to make a copy -- but the former is bad, and the latter is the goal the patch. Pedro> And if we do that, do we have any case where we really need the Pedro> "std::string &&" overload? Indeed we don't seem to need this. Tom