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=-4.0 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 3DEA91F453 for ; Wed, 23 Jan 2019 05:57:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725973AbfAWF5H (ORCPT ); Wed, 23 Jan 2019 00:57:07 -0500 Received: from cloud.peff.net ([104.130.231.41]:45402 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1725950AbfAWF5H (ORCPT ); Wed, 23 Jan 2019 00:57:07 -0500 Received: (qmail 7398 invoked by uid 109); 23 Jan 2019 05:57:07 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Wed, 23 Jan 2019 05:57:07 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 15494 invoked by uid 111); 23 Jan 2019 05:57:10 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.94) with (ECDHE-RSA-AES256-GCM-SHA384 encrypted) SMTP; Wed, 23 Jan 2019 00:57:10 -0500 Authentication-Results: peff.net; auth=none Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Wed, 23 Jan 2019 00:57:05 -0500 Date: Wed, 23 Jan 2019 00:57:05 -0500 From: Jeff King To: Martin =?utf-8?B?w4VncmVu?= Cc: git@vger.kernel.org, "brian m . carlson" Subject: Re: [PATCH v3 2/2] setup: fix memory leaks with `struct repository_format` Message-ID: <20190123055704.GA19601@sigill.intra.peff.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Tue, Jan 22, 2019 at 10:45:48PM +0100, Martin Ågren wrote: > Call `clear_...()` at the start of `read_...()` instead of just zeroing > the struct, since we sometimes enter the function multiple times. This > means that it is important to initialize the struct before calling > `read_...()`, so document that. This part is a little counter-intuitive to me. Is anybody ever going to pass in anything except a struct initialized to REPOSITORY_FORMAT_INIT? If so, might it be kinder for read_...() to not assume anything about the incoming struct, and initialize it from scratch? I.e., not to use clear() but just do the initialization step? A caller which calls read_() multiple times would presumably have an intervening clear (either their own, or the one done on an error return from the read function). Other than that minor nit, I like the overall shape of this. One interesting tidbit: > +/* > + * Always use this to initialize a `struct repository_format` > + * to a well-defined, default state before calling > + * `read_repository()`. > + */ > +#define REPOSITORY_FORMAT_INIT \ > +{ \ > + .version = -1, \ > + .is_bare = -1, \ > + .hash_algo = GIT_HASH_SHA1, \ > + .unknown_extensions = STRING_LIST_INIT_DUP, \ > +} > [...] > + struct repository_format candidate = REPOSITORY_FORMAT_INIT; This uses designated initializers, which is a C99-ism, but one we've used previously and feel confident in. But... > +void clear_repository_format(struct repository_format *format) > +{ > + string_list_clear(&format->unknown_extensions, 0); > + free(format->work_tree); > + free(format->partial_clone); > + *format = (struct repository_format)REPOSITORY_FORMAT_INIT; > +} ...this uses that expression not as an initializer, but as a compound literal. That's also C99, but AFAIK it's the first usage in our code base. I don't know if it will cause problems or not. The "old" way to do it is: struct repository_format foo = REPOSITORY_FORMAT_INIT; memcpy(format, &foo, sizeof(foo)); Given how simple it is to fix if it turns out to be a problem, I'm OK including it as a weather balloon. -Peff