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, RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE 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 708661F5AD for ; Fri, 10 Apr 2020 15:58:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726594AbgDJP61 (ORCPT ); Fri, 10 Apr 2020 11:58:27 -0400 Received: from cloud.peff.net ([104.130.231.41]:39718 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726049AbgDJP61 (ORCPT ); Fri, 10 Apr 2020 11:58:27 -0400 Received: (qmail 4734 invoked by uid 109); 10 Apr 2020 15:58:27 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Fri, 10 Apr 2020 15:58:27 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 32376 invoked by uid 111); 10 Apr 2020 16:09:00 -0000 Received: from coredump.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.2) by peff.net (qpsmtpd/0.94) with (TLS_AES_256_GCM_SHA384 encrypted) ESMTPS; Fri, 10 Apr 2020 12:09:00 -0400 Authentication-Results: peff.net; auth=none Date: Fri, 10 Apr 2020 11:58:27 -0400 From: Jeff King To: Martin =?utf-8?B?w4VncmVu?= Cc: git@vger.kernel.org Subject: Re: [PATCH] merge: use skip_prefix to parse config key Message-ID: <20200410155827.GA71011@coredump.intra.peff.net> References: <20200410151032.23198-1-martin.agren@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200410151032.23198-1-martin.agren@gmail.com> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, Apr 10, 2020 at 05:10:32PM +0200, Martin Ågren wrote: > Instead of using `starts_with()`, the magic number 7, `strlen()` and a > fair number of additions to verify the three parts of the config key > "branch..mergeoptions", use `skip_prefix()` to jump through them > more explicitly. The conversion looks correct to me and is certainly an improvement. > We need to introduce a new variable for this (we certainly can't modify > `k` just because we see "branch."!). With `skip_prefix()` we often use > quite bland names like `p` or `str`. Let's do the same. If and when this > function needs to do more prefix-skipping, we'll have a generic variable > ready for this. I was about to comment on this in the patch, but your explanation preempted me. :) The logic here makes sense. > diff --git a/builtin/merge.c b/builtin/merge.c > index d127d2225f..bde5f14f05 100644 > --- a/builtin/merge.c > +++ b/builtin/merge.c > @@ -597,10 +597,10 @@ static void parse_branch_merge_options(char *bmo) > static int git_merge_config(const char *k, const char *v, void *cb) > { > int status; > + const char *str; > > - if (branch && starts_with(k, "branch.") && > - starts_with(k + 7, branch) && > - !strcmp(k + 7 + strlen(branch), ".mergeoptions")) { > + if (branch && skip_prefix(k, "branch.", &str) && > + skip_prefix(str, branch, &str) && !strcmp(str, ".mergeoptions")) { > free(branch_mergeoptions); > branch_mergeoptions = xstrdup(v); > return 0; In general, parsing subsections accurately involves looking from both the start and the end of the string, pulling out the section and key and leaving the rest in the middle. But I think we can get away with this left-to-right parsing because we're only interested in matching a _specific_ subsection name, and a specific key. So there are no cases it will handle incorrectly. The more general form would be: const char *subsection, *key; int subsection_len; if (!parse_config_key("branch", &subsection, &subsection_len, &key) && subsection_len == strlen(branch) && !strncmp(subsection, branch) && !strcmp(key, "mergeoptions")) ... but that's a bit more awkward (it would be less so if we had a helper function for comparing a NUL-terminated string against a ptr/len pair). -Peff