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Thu, 28 May 2020 14:06:47 +0000 (UTC) Date: Thu, 28 May 2020 15:06:44 +0100 From: "Dr. David Alan Gilbert" To: Markus Armbruster Subject: Re: [PATCH 2/2] hmp: Simplify qom_set Message-ID: <20200528140644.GG3069@work-vm> 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> MIME-Version: 1.0 In-Reply-To: <87y2pge6nv.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.13.4 (2020-02-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/28 02:50:32 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, T_HK_NAME_DR=0.01 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 =?iso-8859-1?Q?Mathieu-Daud=E9?= , afaerber@suse.de Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Markus Armbruster (armbru@redhat.com) wrote: > "Dr. David Alan Gilbert" writes: > > > * Philippe Mathieu-Daudé (philmd@redhat.com) wrote: > >> On 5/20/20 5:11 PM, Dr. David Alan Gilbert (git) wrote: > >> > From: "Dr. David Alan Gilbert" > >> > > >> > Simplify qom_set by making it use qmp_qom_set and the JSON parser. > >> > > >> > Note that qom-set likes JSON strings quoted with ' not ", e.g.: > >> > > >> > (qemu) qom-get /machine smm > >> > "auto" > >> > (qemu) qom-set /machine smm 'auto' > >> > >> Will I get this output using "? > >> > >> (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. > > The command parses its argument as JSON. > > 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 > > { > .name = "qom-set", > .args_type = "path:s,property:s,value:s", > [...] > }, > > monitor/monitor-internal.h documents type code 's' as > > * 's' string (accept optional quote) > > The implementation boils down to: > > 1. Skip whitespace. > > 2. If looking at '"', get the string enclosed in '"', with C-like escape > sequences \n, \r, \\, \', \". > > 3. Else, get the string up to the next whitespace. > > See get_str(). > > Therefore, argument "auto" is the same as auto. Parsing auto as JSON > duly fails. > > Argument 'auto' works, but only because qobject_from_json() recognizes > single-quoted strings. This is as extension over RFC 8259. > > Using single quotes falls apart when you want to pass something > containing whitespace. Then you'd have to use > > "\"ugly and unintuitive\"" > > or, again relying on the extension > > "'ugly and unintuitive'" > > There's a better way, and Paolo pointed it out in > > 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> > > Use argument type 'S'. Documented as > > * 'S' it just appends the rest of the string (accept optional quote) > > 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? Dave > Please squash in: > > diff --git a/hmp-commands.hx b/hmp-commands.hx > index 250ddae54d..28256209b5 100644 > --- a/hmp-commands.hx > +++ b/hmp-commands.hx > @@ -1806,7 +1806,7 @@ ERST > > { > .name = "qom-set", > - .args_type = "path:s,property:s,value:s", > + .args_type = "path:s,property:s,value:S", > .params = "path property value", > .help = "set QOM property", > .cmd = hmp_qom_set, -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK