From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 312F7EB64D8 for ; Tue, 13 Jun 2023 18:25:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239369AbjFMSZ5 (ORCPT ); Tue, 13 Jun 2023 14:25:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239585AbjFMSZz (ORCPT ); Tue, 13 Jun 2023 14:25:55 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94F4319BC for ; Tue, 13 Jun 2023 11:25:53 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-56ff697b86cso7665327b3.1 for ; Tue, 13 Jun 2023 11:25:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1686680753; x=1689272753; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=/wC7OxYLVlpkpjdnTvG5wk34KxCGp6Z9lpRvV4Sdi0k=; b=NS6raMSTq6IJwoyAF9hoVnhvJ2TgdaZvPKR8oGHBsG7p7qr+H2EibaIET9kP5OiWE+ QzjsuCR1sL/255Czh22R6L8FLF3QEv0lObiVQ6j9EN++Gl9jxwMDdS1my1AFBcY6YX/x rl5IosMS6R2fKjO9yFO7O/dalyCEwR0bRt9sZXIF1E9Ujg0vvScMVYfXMER+/tQhpV2X GPQZvpxeym/pKmCwpYzaCIUIsEYxGjS4JuMzI1/3arqfMW/WlPnJIe02sc9hWU3IdqVY Ef5s+UkxgaNkiFeCFRSr6qHW9IvdD3+7a+yPkYjAOzeZILJfsJXrtut6FR5ksiYNKenT hYZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686680753; x=1689272753; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/wC7OxYLVlpkpjdnTvG5wk34KxCGp6Z9lpRvV4Sdi0k=; b=YvvQ5/TJdwxpVdSOiDVSbC5e4kVPRdX+Nnm3SMcihHrDa/237Q9a+r4LcfWIb9PaVv fX57aCZD+iYz0QEB26VEfKTiNeGNQywtHi0C+JsIuP3FMnBWA1tvZ97+dInnkw67pNT/ aCHcB53Nm2KVqJwfgfnDSAsCnFNXJLr7s1ZwGbaYEinKopfGv6nxd56m1p/aeTLnKe4X otpO9ziyr7OADkozTqj/VWwzFKzmOs6fJ8BJxLjmtqlBPUyn6QmNIMvL5+rnMdzLLP28 2QUHTxWPuXIqv3wM/81afcp2NSmqVFTyjUX9YWgIv8Rd2qAYsdPfMRAdWzoiIg1mtzMP 59lA== X-Gm-Message-State: AC+VfDzTqSMesCD/zXHJlAsUOCij8j6t+YVu5wSNEVxaPzGqnodOsnm9 q52FaP3DcfAWba6U5Y5ixIYH7OtARwF27Q== X-Google-Smtp-Source: ACHHUZ6fQ9w93JBMabetgswF7CQkv12yPPJuJsHgnZMmbHeSJ9Zkp7NTQ8UqEZioO8yAq4lFapqfjSjSW+xeEg== X-Received: from chooglen.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:3a07]) (user=chooglen job=sendgmr) by 2002:a81:4102:0:b0:56d:791:d1a4 with SMTP id o2-20020a814102000000b0056d0791d1a4mr1237034ywa.7.1686680752898; Tue, 13 Jun 2023 11:25:52 -0700 (PDT) Date: Tue, 13 Jun 2023 11:25:51 -0700 In-Reply-To: <9fb6d7b1-00b6-93ee-efec-9dd0ab91a66d@github.com> Mime-Version: 1.0 References: <20230612230453.70864-1-chooglen@google.com> <9fb6d7b1-00b6-93ee-efec-9dd0ab91a66d@github.com> Message-ID: Subject: Re: [PATCH] setup: copy repository_format using helper From: Glen Choo To: Victoria Dye , git@vger.kernel.org Cc: Victoria Dye via GitGitGadget , Jonathan Tan , derrickstolee@github.com, gitster@pobox.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Victoria Dye writes: >> - All of them 'copy' .partial_clone. Most perform a shallow copy of the >> pointer, then set the .partial_clone = NULL so that it doesn't get >> cleared by clear_repository_format(). However, >> check_repository_format() copies the string deeply because the >> repository_format is sometimes read back (it is an "out" parameter). >> To accomodate both shallow copying and deep copying, toggle this >> behavior using the "modify_fmt_ok" parameter. > > Do you have a specific example of this happening? I see two uses of > 'check_repository_format()' in the codebase: > > 1. in 'enter_repo()' ('path.c') > 2. in 'init_db()' ('init-db.c') > > The first one calls 'check_repository_format()' with 'NULL', which causes > the function to create a temporary 'struct repository_format' that is then > discarded at the end of the function - no need to worry about the value > being cleared there. > > The second one does call 'check_repository_format()' with a 'struct > repository_format' instance, but the 'partial_clone' field field is not > accessed again after that. The only subsequent usages of the 'repo_fmt' > variable in 'init_db()' are: > > - in 'validate_hash_algorithm()', where only the 'version' and 'hash_algo' > fields are accessed. > - in 'create_default_files()', where only 'hash_algo' is accessed. > > So, shouldn't it be safe to shallow-copy-and-NULL? But as I noted earlier > [1], if you do that it'll make the name 'check_repository_format()' a bit > misleading (since it's actually modifying its arg in place). So, if you > update to always shallow copy, 'check_repository_format()' should be renamed > to reflect its side effects. My understanding of check_repository_format() is that it serves double duty of doing a) setup of the_repository and b) populating an "out" parameter with the appropriate values. IMO a) is the side effect that could warrant the rename, and b) is the expected, "read-only" use case. >From that perspective, doing a shallow copy here isn't really introducing a weird side-effect (because the arg to an "out" parameter should be zero-ed out to begin with), but it's returning a 'wrong' value. You're right that it's safe because the NULL-ed value isn't read back right now, but it's not any good if this function gains more callers. Your point about not having side effects in check_*() is a good one though, and I'm starting to feel doubtful that we should be doing setup there either.... >> If you're comfortable with it, I would prefer for you to squash this >> into your patches so that we don't just end up changing the same few >> lines. If not, I'll Reviewed-by your patches (if I don't find any other >> concerns on a re-read) and send this as a 1-patch on top. > > Reading through the commit message & patch, I'm still not convinced this > refactor is a good idea - to me, it doesn't leave the code in a clearly > better state. If you feel strongly that it does, though, I'm happy to leave > it to others to review/decide but I would prefer that you keep it a separate > patch submission on top. Okay. Given how weird check_repository_format() and discover_git_directory() are, I think we haven't done enough investigation to properly consolidate this logic, and doing that introduces quite a lot of scope creep. It feels very unsatisfactory that we are propagating a pattern that is suspicious in some places and outright wrong in others instead of cleaning up as we go and leaving it in a better state for future authors, but this series does leave some _other_ parts in a better state (removing the global), and I think it's still a net positive. The helper function might not be a good idea yet, but I'm convinced that removing the setup from discover_git_directory() is a good idea. I think this series would be in a better state if we get rid of the wrong pattern instead of extending it. Unfortunately, I forgot to include that change in the patch I sent (ugh) but here's a patch that _just_ includes the discover_git_directory() change that I hope you can squash into your series (and you can use whatever bits of my commit message you see fit). ----- >8 --------- >8 --------- >8 --------- >8 --------- >8 ---- diff --git a/setup.c b/setup.c index 33ce58676f..b172ffd48a 100644 --- a/setup.c +++ b/setup.c @@ -1422,14 +1422,6 @@ int discover_git_directory(struct strbuf *commondir, return -1; } - the_repository->repository_format_worktree_config = - candidate.worktree_config; - - /* take ownership of candidate.partial_clone */ - the_repository->repository_format_partial_clone = - candidate.partial_clone; - candidate.partial_clone = NULL; - clear_repository_format(&candidate); return 0; } ----- >8 --------- >8 --------- >8 --------- >8 --------- >8 ---- You can see that this patch based on top of yours passes CI https://github.com/git/git/commit/9469fe3a6b0efbe89d26ef096a2eebabea59c55f https://github.com/chooglen/git/actions/runs/5258672473 > I think you may be missing changes to 'discover_git_directory()'? Like I > mentioned above, though, if you don't think 'discover_git_directory()' needs > to set up 'the_repository', then those assignments should just be removed > (not replaced with 'setup_repository_from_format()'). Ah sorry, yes they were meant to be removed. I somehow missed those as I was preparing the patch.