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Fri, 22 Jan 2021 16:44:08 +0100 (CET) From: Markus Armbruster To: Paolo Bonzini Subject: Re: [PATCH 05/25] keyval: simplify keyval_parse_one References: <20210118163113.780171-1-pbonzini@redhat.com> <20210118163113.780171-6-pbonzini@redhat.com> <874kj95bhd.fsf@dusky.pond.sub.org> <84476bff-27ba-4308-cd9f-cbc1dc233831@redhat.com> Date: Fri, 22 Jan 2021 16:44:08 +0100 In-Reply-To: <84476bff-27ba-4308-cd9f-cbc1dc233831@redhat.com> (Paolo Bonzini's message of "Fri, 22 Jan 2021 16:00:07 +0100") Message-ID: <87r1mdyo1j.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (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=63.128.21.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.182, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: kwolf@redhat.com, imammedo@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Paolo Bonzini writes: > On 22/01/21 14:48, Markus Armbruster wrote: >> --nbd .key= >> master: Invalid parameter '..key' >> your patch: same >> Likweise. >> If I omit the '=', your patch's message changes to >> No implicit parameter name for value 'key..' >> I consider that worse than before, because it's talking about >> something outside the user's control (lack of an implict parameter >> name) where it should instead tell the user what needs fixing in the >> input. > > I think whether it's better or worse depends on the specific erroneous > command line (think "--nbd /path/to/file.qcow2"), but I can certainly > change it. Quoting myself: Error messages based on guesses what the user has in mind can be quite confusing when we guess wrong. A strictly factual syntax error style like "I expected FOO instead of BAR here" may not be great, but has a relatively low risk of being confusing. >> Your patch also adds an "Expected parameter at end of string" error. >> Can you tell me how to trigger it? > > It is meant for "--nbd ''" but it is effectively dead code due to the > "while (*s)" in the caller. Possibilities: > > 1) leave it in as dead code I'd prefer not to. > 2) replace it with an assert Works for me. > 3) change the caller to use a do...while in such a way that it > triggers it (and be careful not to change the grammar). Only if it's not too hard, and results in better error messages. >> I believe your grammar is ambiguous. Your code seems to pick the sane >> alternative. If I'm wrong, you need to enlighten me. If I'm right, you >> need to fix your grammar. > > Will do. Can I change the EBNF to use "+" and "*" for simplicity and > clarity? I tried to stick to ISO 14977 as described in , less its foolish ',' for concatenation. I'm not at all enamored with it. All I want is something that is widely understood, and preferably not invented here. Switch to perhaps? [...]