From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 7D4681F803 for ; Wed, 9 Jan 2019 23:11:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726513AbfAIXLK (ORCPT ); Wed, 9 Jan 2019 18:11:10 -0500 Received: from mail-qk1-f196.google.com ([209.85.222.196]:33935 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726492AbfAIXLK (ORCPT ); Wed, 9 Jan 2019 18:11:10 -0500 Received: by mail-qk1-f196.google.com with SMTP id q8so5495117qke.1 for ; Wed, 09 Jan 2019 15:11:09 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=xrztkiiu4vSp3xeS0Nh3QmkdPI+ZsPnsNb1MXsRDwLU=; b=A6BSF6GhpioOCXebbGKG8UA9IFytjRpptPmLsJT/fp3UfiboA55pYTyOChINmIUKVG TBzO3+fAamoRk/dnAiWuyvdywf/0TztLsTAO2zPL+Bxq9c4pKPqc70kiGM73Fj+FvP81 b/mJ8pJWByKawvEVsgxrW/BN/AuxOZhinJT4X3F/OnXlwTscHyNTay83/Hg3ULM8LC5r XZOHYUe2sUwue9QgIRFr0HBK16w3r2fwGjOcDEPTjiG2k1GHQ8RzW5X6UBxfbnq5ND3z 46AoepMARiPB4db2AWEKyvQpWrRzFaOdag3v+LwNvp+DFIMJGhjvglIU/gXIDvnuGlSB /yVw== X-Gm-Message-State: AJcUukfSeaKrDAjxeiDdL+N/nT2QlhB5T7sOk2EuSHsnUHMnAUAvyaPw +z2mXLG3qfsOQk7LF1AcYHeliHFmLP8Yts68jmgGAQ4b X-Google-Smtp-Source: ALg8bN7R8Lqy5J+fORHN97ohXazksb9JulyRoHL3U//Z2l0SX4Vgg9b/0D0ovjP0h+WZd/Xnh9x4KQcZSqx9cRq1XiU= X-Received: by 2002:a37:a44e:: with SMTP id n75mr7391724qke.26.1547075469326; Wed, 09 Jan 2019 15:11:09 -0800 (PST) MIME-Version: 1.0 References: <20190109221007.21624-1-kgybels@infogroep.be> In-Reply-To: <20190109221007.21624-1-kgybels@infogroep.be> From: Eric Sunshine Date: Wed, 9 Jan 2019 18:10:58 -0500 Message-ID: Subject: Re: [PATCH] diff: ensure correct lifetime of external_diff_cmd To: Kim Gybels Cc: Git List , Junio C Hamano , Johannes Schindelin , Karsten Blees , Johannes Sixt Content-Type: text/plain; charset="UTF-8" Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Wed, Jan 9, 2019 at 5:19 PM Kim Gybels wrote: > According to getenv(3)'s notes: > [...] > Since strings returned by getenv() are allowed to change on subsequent > calls to getenv(), make sure to duplicate when caching external_diff_cmd > from environment. > [...] > Signed-off-by: Kim Gybels > --- > diff --git a/diff.c b/diff.c > @@ -492,6 +492,9 @@ static const char *external_diff(void) > external_diff_cmd = getenv("GIT_EXTERNAL_DIFF"); > if (!external_diff_cmd) > external_diff_cmd = external_diff_cmd_cfg; > + else > + external_diff_cmd = xstrdup(external_diff_cmd); Make sense. Not shown in the context is that 'external_diff_cmd' is static, so this is not (in the traditional sense) leaking the dup'd string. I do find that the logic is obscured by doing the xstrdup() in the 'else' arm; it would be easier to grok if the condition was reversed and xstrdup() done in the 'then' arm. However, you might also consider using xstrdup_or_null(), like this: external_diff_cmd = xstrdup_or_null(getenv(...)); if (!external_diff_cmd) ...as before... > done_preparing = 1; > return external_diff_cmd; > }