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Fri, 29 May 2020 06:20:01 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 14E3E113864A; Fri, 29 May 2020 08:20:00 +0200 (CEST) From: Markus Armbruster To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 2/2] hmp: Simplify qom_set References: <20200520151108.160598-1-dgilbert@redhat.com> <20200520151108.160598-3-dgilbert@redhat.com> <1f627a6b-9c5f-09b3-8f75-64e95a4f5d02@redhat.com> <20200520190344.GG2820@work-vm> <87y2pge6nv.fsf@dusky.pond.sub.org> <20200528140644.GG3069@work-vm> Date: Fri, 29 May 2020 08:20:00 +0200 In-Reply-To: <20200528140644.GG3069@work-vm> (David Alan Gilbert's message of "Thu, 28 May 2020 15:06:44 +0100") Message-ID: <871rn3p8j3.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 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=207.211.31.81; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/29 01:27:49 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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: berrange@redhat.com, qemu-devel@nongnu.org, clg@kaod.org, Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , afaerber@suse.de Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" "Dr. David Alan Gilbert" writes: > * Markus Armbruster (armbru@redhat.com) wrote: >> "Dr. David Alan Gilbert" writes: >>=20 >> > * Philippe Mathieu-Daud=C3=83=C6=92=C3=82=C2=A9 (philmd@redhat.com) wr= ote: >> >> On 5/20/20 5:11 PM, Dr. David Alan Gilbert (git) wrote: >> >> > From: "Dr. David Alan Gilbert" >> >> >=20 >> >> > Simplify qom_set by making it use qmp_qom_set and the JSON parser. >> >> >=20 >> >> > Note that qom-set likes JSON strings quoted with ' not ", e.g.: >> >> >=20 >> >> > (qemu) qom-get /machine smm >> >> > "auto" >> >> > (qemu) qom-set /machine smm 'auto' >> >>=20 >> >> Will I get this output using "? >> >>=20 >> >> (qemu) qom-set /machine smm "auto" >> >> Error: Expecting a JSON value >> > >> > The error you get is: >> > >> > (qemu) qom-set /machine smm "auto" >> > Error: JSON parse error, invalid keyword 'auto' >> > >> > I think, having seen alphanumerics, it's expecting a keyword; >> > i.e. a true/false making a bool, or a null. >>=20 >> The command parses its argument as JSON. >>=20 >> Before we get there, the HMP core extracts the argument from the line of >> input. The extraction is guided by the command's .args_type, in this >> case the 's' in "value:s" in >>=20 >> { >> .name =3D "qom-set", >> .args_type =3D "path:s,property:s,value:s", >> [...] >> }, >>=20 >> monitor/monitor-internal.h documents type code 's' as >>=20 >> * 's' string (accept optional quote) >>=20 >> The implementation boils down to: >>=20 >> 1. Skip whitespace. >>=20 >> 2. If looking at '"', get the string enclosed in '"', with C-like escape >> sequences \n, \r, \\, \', \". >>=20 >> 3. Else, get the string up to the next whitespace. >>=20 >> See get_str(). >>=20 >> Therefore, argument "auto" is the same as auto. Parsing auto as JSON >> duly fails. >>=20 >> Argument 'auto' works, but only because qobject_from_json() recognizes >> single-quoted strings. This is as extension over RFC 8259. >>=20 >> Using single quotes falls apart when you want to pass something >> containing whitespace. Then you'd have to use >>=20 >> "\"ugly and unintuitive\"" >>=20 >> or, again relying on the extension >>=20 >> "'ugly and unintuitive'" >>=20 >> There's a better way, and Paolo pointed it out in >>=20 >> Subject: Re: [RFC PATCH] qom: Implement qom-get HMP command >> Date: Thu, 21 May 2020 16:24:12 +0200 >> Message-ID: <2c148331-78ae-31f7-8702-d65c37a090b0@redhat.com> >>=20 >> Use argument type 'S'. Documented as >>=20 >> * 'S' it just appends the rest of the string (accept optional = quote) >>=20 >> but the parenthesis is confusing. It really just skips whitespace, then >> extracts the remainder of the line. Can't do string with leading >> whitespace, but that's just fine for us. > > Yep, thanks - I spotted Paolo's response but thanks for the deeper > explanation. > With that would you give me a Review-by? Also fix the typo in the title "hmp: Simplify qom_set": it's qom-set. Reviewed-by: Markus Armbruster