From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca (simark.ca [158.69.221.121]) by sourceware.org (Postfix) with ESMTPS id 24BFD388F052 for ; Thu, 21 May 2020 17:11:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 24BFD388F052 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=simark.ca Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=simark@simark.ca Received: from [172.16.0.95] (192-222-181-218.qc.cable.ebox.net [192.222.181.218]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id 6E9C11E072; Thu, 21 May 2020 13:11:47 -0400 (EDT) Subject: Re: [PATCH] gdb: remove unnecessary NULL checks before xfree To: Pedro Alves , Simon Marchi , gdb-patches@sourceware.org References: <20200521151032.3116197-1-simon.marchi@efficios.com> <9267cb3e-36ae-5d05-d636-37ef2d177190@redhat.com> From: Simon Marchi Message-ID: Date: Thu, 21 May 2020 13:11:46 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <9267cb3e-36ae-5d05-d636-37ef2d177190@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: tl Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-9.3 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, SPF_HELO_PASS, 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: Thu, 21 May 2020 17:11:49 -0000 On 2020-05-21 12:59 p.m., Pedro Alves via Gdb-patches wrote: > On 5/21/20 4:10 PM, Simon Marchi via Gdb-patches wrote: >> I was inspired by a series of patches merged by Alan Modra in the other >> projects, so I did the same in GDB with a bit of Coccinelle and grep. >> >> This patch removes the unnecessary NULL checks before calls to xfree. >> They are unnecessary because xfree already does a NULL check. Since >> free is supposed to handle NULL values correctly, the NULL check in >> xfree itself is also questionable, but I've left it there for now. > > xfree was invented exactly because some ancient hosts did not handle > free(NULL) gracefully: > > https://sourceware.org/legacy-ml/gdb/2000-11/msg00276.html > > I'd like to believe that such hosts are long gone. > > (It's a reasonable micro-optimization to check for NULL > before calling free, to avoid the function call overhead, > but I don't think this is the motivation for any of the > cases here. Since xfree is inline, I guess we're applying > that micro-optimization everywhere, by chance.) I'm fine leaving it in xfree for that reason, it doesn't really hurt. Simon