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Wed, 1 Jul 2020 09:01:31 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id CA44411384A6; Wed, 1 Jul 2020 11:01:29 +0200 (CEST) From: Markus Armbruster To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 15/46] qemu-option: Tidy up opt_set() not to free arguments on failure References: <20200624164344.3778251-1-armbru@redhat.com> <20200624164344.3778251-16-armbru@redhat.com> Date: Wed, 01 Jul 2020 11:01:29 +0200 In-Reply-To: (Vladimir Sementsov-Ogievskiy's message of "Mon, 29 Jun 2020 13:37:03 +0300") Message-ID: <87ftabbod2.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=205.139.110.120; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/30 22:25:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, berrange@redhat.com, ehabkost@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Vladimir Sementsov-Ogievskiy writes: > 24.06.2020 19:43, Markus Armbruster wrote: >> opt_set() frees its argument @value on failure. Slightly unclean; >> functions ideally do nothing on failure. >> >> To tidy this up, move opt_create() from opt_set() into its callers, >> along with the cleanup. > > Hmm, let me think a bit.. > > So, prior to this patch: > > opt_set gets name/value pair and sets the option in opts object, it > seems absolutely obvious and standard behavior for Map-like object. > > The fact that for setting an option we create a QemuOpt object, and > somehow register it inside opts object is an implementation detail. You explain behavior on success. The issue is behavior on failure. > after the patch: > > opt_set gets opt object, which is already registered in opts. So, > it seems like option is "partly" set already, and opt_set only > finalize the processing. Yes, opt_set() becomes a bit of a misnomer: it doesn't add a QemuOpt to @opts, it validates a QemuOpt against its key's description, if @opts has descriptions. Hmm, opt_set() is now almost identical to qemu_opts_validate()'s loop body. Perhaps I can de-duplicate. > And, as opt_set() only finalize the "set" operation, on opt_set > failure we need additional roll-back of "set" operation first step. > > Additional fact, indirectly showing that something is unclear here > is that we pass "opts" to opt_set twice: as "opts" parameter and > inside opt: (opt->opts must be the same, assertion won't hurt if > you decide to keep the patch). Valid point. > ===== > > Semantics before the patch seems clearer to me. > > To improve the situation around "value", we can just g_strdup it > in opt_create as well as "name" argument (and use const char* > type for "value" argument as well) We don't strdup() there because opts_do_parse() extracts the value with get_opt_name(), which strdup()s it. strdup()ing it some more isn't wrong, I just dislike it. Let me try the de-duplication, and then we'll see whether you still dislike the patch.