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: AS53758 23.128.96.0/24 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, RCVD_IN_DNSWL_HI,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 1281E1F852 for ; Thu, 13 Jan 2022 20:17:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231486AbiAMURf (ORCPT ); Thu, 13 Jan 2022 15:17:35 -0500 Received: from bsmtp1.bon.at ([213.33.87.15]:3261 "EHLO bsmtp1.bon.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230001AbiAMURf (ORCPT ); Thu, 13 Jan 2022 15:17:35 -0500 Received: from [192.168.0.98] (unknown [93.83.142.38]) by bsmtp1.bon.at (Postfix) with ESMTPSA id 4JZbMG5QK4z5tl9; Thu, 13 Jan 2022 21:17:30 +0100 (CET) Message-ID: <9ce034fd-b696-60d2-c292-98285aff180a@kdbg.org> Date: Thu, 13 Jan 2022 21:17:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Subject: Re: [PATCH 2/3] reftable: remove unreachable "return" statements Content-Language: en-US To: =?UTF-8?B?w4Z2YXIgQXJuZmrDtnLDsCBCamFybWFzb24=?= Cc: git@vger.kernel.org, Junio C Hamano , Johannes Schindelin , Han-Wen Nienhuys , Taylor Blau References: <220112.865yqpxge2.gmgdl@evledraar.gmail.com> From: Johannes Sixt In-Reply-To: <220112.865yqpxge2.gmgdl@evledraar.gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Am 12.01.22 um 13:47 schrieb Ævar Arnfjörð Bjarmason: > > On Tue, Jan 11 2022, Taylor Blau wrote: > >> On Tue, Jan 11, 2022 at 05:40:22PM +0100, Ævar Arnfjörð Bjarmason wrote: >>> Remove unreachable return statements added in acb533440fc (reftable: >>> implement refname validation, 2021-10-07) and f14bd719349 (reftable: >>> write reftable files, 2021-10-07). >>> >>> This avoids the following warnings on SunCC 12.5 on >>> gcc211.fsffrance.org: >>> >>> "reftable/refname.c", line 135: warning: statement not reached >>> "reftable/refname.c", line 135: warning: statement not reached >> >> Interesting. From a cursory reading, I agree with the assessment of >> at least my compiler that these return statements are both unnecessary, >> but... >> >>> Signed-off-by: Ævar Arnfjörð Bjarmason >>> --- >>> reftable/refname.c | 1 - >>> reftable/writer.c | 1 - >>> 2 files changed, 2 deletions(-) >>> >>> diff --git a/reftable/refname.c b/reftable/refname.c >>> index 95734969324..136001bc2c7 100644 >>> --- a/reftable/refname.c >>> +++ b/reftable/refname.c >>> @@ -132,7 +132,6 @@ static int validate_refname(const char *name) >>> return REFTABLE_REFNAME_ERROR; >>> name = next + 1; >>> } >>> - return 0; >>> } >> >> In this case the loop inside of validate_refname() should always >> terminate the function within the loop body. But removing this return >> statement here relies on the compiler to determine that fact. >> >> I could well imagine on the other end of the spectrum there exists a >> compiler which _doesn't_ make this inference pass, and would complain >> about the opposite thing as you're reporting from SunCC (i.e., that this >> function which returns something other than void does not have a return >> statement outside of the loop). >> >> So in that sense, I disagree with the guidance of SunCC's warning. In >> other words: by quelching this warning under one compiler, are we >> introducing a new warning under a different/less advanced compiler? > > I'd think that any compiler who'd warn about this sort of thing at all > would be able to spot constructs like this one, which are basically: > > while (1) { > ... > if (x) > return; > ... > } > return; /* unreachable */ > > Where the elided code contains no "break", "goto" or other mechanism for > exiting the for-loop. Why not just sidestep the problematic case: diff --git a/reftable/refname.c b/reftable/refname.c index 9573496932..4f89956187 100644 --- a/reftable/refname.c +++ b/reftable/refname.c @@ -120,17 +120,17 @@ static int modification_has_ref_with_prefix(struct modification *mod, static int validate_refname(const char *name) { while (1) { char *next = strchr(name, '/'); if (!*name) { return REFTABLE_REFNAME_ERROR; } if (!next) { - return 0; + break; } if (next - name == 0 || (next - name == 1 && *name == '.') || (next - name == 2 && name[0] == '.' && name[1] == '.')) return REFTABLE_REFNAME_ERROR; name = next + 1; } return 0; } Sure, there are returns in the loop, but they are clearly error cases. The regular exit is now at the end of the function. -- Hannes