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=-3.8 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 941E71F453 for ; Wed, 13 Feb 2019 18:18:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391164AbfBMSSq (ORCPT ); Wed, 13 Feb 2019 13:18:46 -0500 Received: from elephants.elehost.com ([216.66.27.132]:52631 "EHLO elephants.elehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391106AbfBMSSp (ORCPT ); Wed, 13 Feb 2019 13:18:45 -0500 X-Virus-Scanned: amavisd-new at elehost.com Received: from gnash (CPE00fc8d49d843-CM00fc8d49d840.cpe.net.cable.rogers.com [99.229.179.249]) (authenticated bits=0) by elephants.elehost.com (8.15.2/8.15.2) with ESMTPSA id x1DIIct8036773 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 13 Feb 2019 13:18:38 -0500 (EST) (envelope-from rsbecker@nexbridge.com) From: "Randall S. Becker" To: "'Junio C Hamano'" , "'Eric Sunshine'" Cc: "'Git List'" References: <20190209185930.5256-1-randall.s.becker@rogers.com> <20190209185930.5256-3-randall.s.becker@rogers.com> In-Reply-To: Subject: RE: [Patch v1 2/3] t5318: replace use of /dev/zero with generate_zero_bytes Date: Wed, 13 Feb 2019 13:18:31 -0500 Message-ID: <004701d4c3c8$8a018d20$9e04a760$@nexbridge.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQGM7GjkJQPJw2ZzFceglcz2DqNUWwGXJak9AdRbyOoBXWggQALkfM5xpjBLm0A= Content-Language: en-ca Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org > -----Original Message----- > From: Junio C Hamano On Behalf Of Junio C Hamano > Sent: February 13, 2019 12:25 > To: Eric Sunshine > Cc: randall.s.becker@rogers.com; Git List ; Randall S. > Becker > Subject: Re: [Patch v1 2/3] t5318: replace use of /dev/zero with > generate_zero_bytes > > Junio C Hamano writes: > > > Eric Sunshine writes: > > > >> On Sat, Feb 9, 2019 at 2:00 PM wrote: > >>> This change removes the dependency on /dev/zero with > >>> generate_zero_bytes appending NUL values to blocks generating wrong > signatures for test cases. > >> > >> This commit message says what the patch does but not _why_. At > >> minimum, it should explain that /dev/zero is not available on all > >> platforms, therefore, not portable, and (perhaps) cite NonStop as an > >> example. > > > > Does sombody want to do the honors? [PATCH 1/3] would become wasted > > effort until that happens. On the other hand, if this is not urgent > > (it is only urgent for those without /dev/zero, and to others it may > > be distraction/disruption this close to the final release to add > > increased risk of fat finger mistakes), obviously I can wait. > > So, before I lose the access to my primary screen (I was told that somehow I > need to reimage the workstation today X-<), here is what I have now. > > -- >8 -- > From: "Randall S. Becker" > Date: Sat, 9 Feb 2019 13:59:29 -0500 > Subject: [PATCH] t5318: replace use of /dev/zero with generate_zero_bytes > > There are platforms (e.g. NonStop) that lack /dev/zero; use the > generate_zero_bytes helper we just introduced to append stream of NULs at > the end of the file. > > The original, even though it uses "dd seek=... count=..." to make it look like it > is overwriting the middle part of an existing file, has truncated the file before > this step with another use of "dd", which may make it tricky to see why this > rewrite is a correct one. Here is how I interpret the test - might be wrong, but yanno... The first dd copies something looking like reasonable data from the test case. The second dd copies zeros from seek to the end of a fixed size block. My first attempt at a fix used truncate that extended the first to the correct size (filling with zeros). My worry there is that I'm not sure there is a guarantee of zeros, but that shouldn't matter for the test which just wants a signature mismatch. Others suggested using yes to fill in junk. My second attempt was to create the generate_zero_bytes function to replace exactly what the second dd was doing but not user /dev/zero. The fix was not to change the conditions of the test - not debating the correctness of that here - but to simply replicate the use of /dev/zero in context. So the resulting file contains [reasonable-stuff]{seek}[0]{orig_size-seek}, which is sufficient to satisfy the conditions of the test. > > Signed-off-by: Randall S. Becker > Signed-off-by: Junio C Hamano > --- > t/t5318-commit-graph.sh | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh index > 16d10ebce8..d4bd1522fe 100755 > --- a/t/t5318-commit-graph.sh > +++ b/t/t5318-commit-graph.sh > @@ -383,7 +383,7 @@ corrupt_graph_and_verify() { > cp $objdir/info/commit-graph commit-graph-backup && > printf "$data" | dd of="$objdir/info/commit-graph" bs=1 > seek="$pos" conv=notrunc && > dd of="$objdir/info/commit-graph" bs=1 seek="$zero_pos" count=0 > && > - dd if=/dev/zero of="$objdir/info/commit-graph" bs=1 > seek="$zero_pos" count=$(($orig_size - $zero_pos)) && > + generate_zero_bytes $(($orig_size - $zero_pos)) > +>>"$objdir/info/commit-graph" && > test_must_fail git commit-graph verify 2>test_err && > grep -v "^+" test_err >err && > test_i18ngrep "$grepstr" err