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Wed, 15 Apr 2020 10:00:27 +0000 (UTC) Received: from linux.fritz.box (ovpn-114-71.ams2.redhat.com [10.36.114.71]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 574E8118DF4; Wed, 15 Apr 2020 10:00:25 +0000 (UTC) Date: Wed, 15 Apr 2020 12:00:24 +0200 From: Kevin Wolf To: Markus Armbruster Subject: Re: [PATCH for-5.1 1/8] tests-qemu-opts: Cover has_help_option(), qemu_opt_has_help_opt() Message-ID: <20200415100024.GA6916@linux.fritz.box> References: <20200409153041.17576-1-armbru@redhat.com> <20200409153041.17576-2-armbru@redhat.com> <8ea167d6-2784-1ab9-cf55-52eb7553cb4d@redhat.com> <878siyxwir.fsf@dusky.pond.sub.org> <20200414131339.GE7747@linux.fritz.box> <87v9m2p4to.fsf@dusky.pond.sub.org> <20200414142954.GH7747@linux.fritz.box> <874ktlomey.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <874ktlomey.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 14.04.2020 um 22:13 hat Markus Armbruster geschrieben: > Kevin Wolf writes: >=20 > > Am 14.04.2020 um 15:36 hat Markus Armbruster geschrieben: > >> Kevin Wolf writes: > >> > Am 14.04.2020 um 11:10 hat Markus Armbruster geschrieben: > >> >> Eric Blake writes: > >> >> > On 4/9/20 10:30 AM, Markus Armbruster wrote: > >> >> >> + { "helpme", false, false, false }, > >> >> >> + { "a,help", true, true, true }, > >> >> >> + { "a=3D0,help,b", true, true, true }, > >> >> >> + { "help,b=3D1", true, true, false }, > >> >> >> + { "a,b,,help", false /* BUG */, true, true }, > >> >> > > >> >> > So which way are you calling the bug? Without looking at the cod= e but > >> >> > going off my intuition, I parse this as option 'a' and option > >> >> > 'b,help'. The latter is not a normal option name because it conta= ins a > >> >> > ',', but is a valid option value. > >> >> > > >> >> > I agree that we have a bug, but I'm not yet sure in which directi= on > >> >> > the bug lies (should has_help_option be fixed to report true, in = which > >> >> > case the substring ",help" has precedence over ',,' escaping; or > >> >> > should qemu_opt_has_help_opt be fixed to report false, due to tre= ating > >> >> > 'b,help' after ',,' escape removal as an invalid option name). S= o the > >> >> > placement of the /* BUG */ comment matters - where you placed it,= I'm > >> >> > presuming that later in the series you change has_help_option to > >> >> > return true, even though that goes against my intuitive parse. > >> >>=20 > >> >> In addition to the canonical QemuOpts parser opts_do_parse(), we ha= ve > >> >> several more, and of course they all differ from the canonical one = for > >> >> corner cases. > >> >>=20 > >> >> I treat the canonical one as correct, and fix the others by elimina= ting > >> >> the extra parsers. > >> >>=20 > >> >> The others are: > >> >>=20 > >> >> * has_help_option() > >> >>=20 > >> >> Fixed in PATCH 5 by reusing the guts of opts_do_parse(). > >> >>=20 > >> >> * is_valid_option_list() > >> >>=20 > >> >> Fixed in PATCH 8 by not parsing. > >> >>=20 > >> >> * "id" extraction in opts_parse() > >> >>=20 > >> >> Lazy hack. Fixed in PATCH 3 by reusing the guts of opts_do_parse= (). > >> >>=20 > >> >> Back to your question: the value of has_help_option() differs from = the > >> >> value of qemu_opt_has_help_opt(). The latter uses the canonical pa= rser, > >> >> the former is one of the other parsers. I therefore judge the latt= er > >> >> right and the former wrong. > >> > > >> > Shouldn't we also consider what users would reasonably expect? > >>=20 > >> Of course we should consider reasonable user expectations. > >>=20 > >> Grumpy aside: when I do, I commonly run into objections that users > >> reasonably expect things not to change. > > > > Fair point. It's not always easy to tell whether something should be > > considered a bug in the external interface (and consequently be fixed) > > or just an idiosyncrasy that people may have get used to (and therefore > > requires deprecation before improving it). > > > > In this specific case, I'm not aware of empty option names actually > > doing anything useful anywhere, so I think it might be clearer in this > > case that it's indeed a bug. >=20 > You're right in that backward compatibility is not a convincing argument > for stuff that has no known productive uses, and is bonkers to boot. >=20 > >> > Getting it parsed as an empty option name (I assume with a default v= alue > >> > of "on"?) certainly looks like something that would surprise most us= ers > >> > and, as you can see, even some QEMU developers. > >>=20 > >> My preferred way to address QemuOpts parsing madness is replacing it > >> wholesale by keyval.c, but that's some time off, I'm afraid. > >>=20 > >> This series merely aims for more method to the same old madness. > > > > I understand. Though I think replacing with keyval will be potentially > > less problematic if QemuOpts already behaved more similar. > > > > If I were writing the code, I think I would use existing bugs and > > inconsistencies as an excuse to make QemuOpts behave more like what > > keyval can easily handle by declaring whatever is closest to keyval as > > the correct interpretation. >=20 > Fair enough. >=20 > However, >=20 > (1) is_valid_option_list()'s and opts_do_parse()'s parse of "a,b,,help" > are equidistant from keyval_parse()'s: >=20 > opts_do_parse() splits it into four parts: >=20 > "a" (desugared to a=3Don) > "b" (desugared to b=3Don) > "" (desugared to =3Don) > "help" (desugared to help=3Don) >=20 > has_help_option() splits it into two: >=20 > "a" > "b,help" >=20 > keyval_parse() fails: >=20 > Expected '=3D' after parameter 'a' >=20 > If I it implemented boolean sugar, then it would fail at the third > comma, just like ",help" fails now: >=20 > Invalid parameter '' >=20 > Fails because ",help" does not start with a valid name. >=20 > Thus, the answer to the question which of the two functions covered > by the test are wrong would be "both". opts_do_parse() can return an error. So maybe what we should do is rejecting empty option names there? > (2) This series tries hard not to write QemuOpts parsing code. It > throws away QemuOpts parsing code. Arguably, an additional error is writing QemuOpts parsing code, but maybe little enough that it's tolerable? Kevin