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Tue, 21 Jan 2020 14:22:21 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-131.ams2.redhat.com [10.36.116.131]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DA69C1001901; Tue, 21 Jan 2020 14:22:18 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 709F51138600; Tue, 21 Jan 2020 15:22:17 +0100 (CET) From: Markus Armbruster To: Paolo Bonzini Subject: Re: [RFC PATCH] qapi: Incorrect attempt to fix building with MC146818RTC=n References: <20191231184916.10235-1-philmd@redhat.com> <875zhfzc9l.fsf@dusky.pond.sub.org> <87wo9ll5on.fsf@dusky.pond.sub.org> Date: Tue, 21 Jan 2020 15:22:17 +0100 In-Reply-To: (Paolo Bonzini's message of "Tue, 21 Jan 2020 09:16:56 +0100") Message-ID: <87lfq0c2jq.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 2.84 on 10.5.11.22 X-MC-Unique: LB_AN02zMw-KR23v4dn-Kg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] 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: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Paolo Bonzini writes: > On 21/01/20 06:49, Markus Armbruster wrote: >> Paolo Bonzini writes: >>=20 >>> On 13/01/20 15:01, Markus Armbruster wrote: >>>> Philippe Mathieu-Daud=C3=A9 writes: >>>> >>>>> When configured with --without-default-devices and setting >>>>> MC146818RTC=3Dn, the build fails: >>>>> >>>>> LINK x86_64-softmmu/qemu-system-x86_64 >>>>> /usr/bin/ld: qapi/qapi-commands-misc-target.o: in function `qmp_mar= shal_rtc_reset_reinjection': >>>>> qapi/qapi-commands-misc-target.c:46: undefined reference to `qmp_rt= c_reset_reinjection' >>>>> /usr/bin/ld: qapi/qapi-commands-misc-target.c:46: undefined referen= ce to `qmp_rtc_reset_reinjection' >>>>> collect2: error: ld returned 1 exit status >>>>> make[1]: *** [Makefile:206: qemu-system-x86_64] Error 1 >>>>> make: *** [Makefile:483: x86_64-softmmu/all] Error 2 >>>>> >>>>> This patch tries to fix this, but this is incorrect because QAPI >>>>> scripts only provide TARGET definitions, so with MC146818RTC=3Dy we >>>>> get: >>>>> >>>>> hw/rtc/mc146818rtc.c:113:6: error: no previous prototype for =E2=80= =98qmp_rtc_reset_reinjection=E2=80=99 [-Werror=3Dmissing-prototypes] >>>>> 113 | void qmp_rtc_reset_reinjection(Error **errp) >>>>> | ^~~~~~~~~~~~~~~~~~~~~~~~~ >>>>> cc1: all warnings being treated as errors >>>>> make[1]: *** [rules.mak:69: hw/rtc/mc146818rtc.o] Error 1 >>>>> >>>>> Any idea? :) >>>>> >>>>> Signed-off-by: Philippe Mathieu-Daud=C3=A9 >>>>> --- >>>>> qapi/misc-target.json | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/qapi/misc-target.json b/qapi/misc-target.json >>>>> index a00fd821eb..8e49c113d1 100644 >>>>> --- a/qapi/misc-target.json >>>>> +++ b/qapi/misc-target.json >>>>> @@ -41,7 +41,7 @@ >>>>> # >>>>> ## >>>>> { 'command': 'rtc-reset-reinjection', >>>>> - 'if': 'defined(TARGET_I386)' } >>>>> + 'if': 'defined(TARGET_I386) && defined(CONFIG_MC146818RTC)' } >>>>> =20 >>>>> =20 >>>>> ## >>>> >>>> The generated qapi-commands-misc-target.h duly has >>>> >>>> #if defined(TARGET_I386) && defined(CONFIG_MC146818RTC) >>>> void qmp_rtc_reset_reinjection(Error **errp); >>>> void qmp_marshal_rtc_reset_reinjection(QDict *args, QObject **ret,= Error **errp); >>>> #endif /* defined(TARGET_I386) && defined(CONFIG_MC146818RTC) */ >>>> >>>> mc146818rtc.c includes it. But since it doesn't include >>>> config-devices.h, CONFIG_MC146818RTC remains undefined, and the >>>> prototype gets suppressed. >>>> >>>> Crude fix: make mc146818rtc.c #include "config-devices.h". >>> >>> Can we modify the code generator to leave out the #if from the header, >>> and only include it in the .c file? An extra prototype is harmless. >>=20 >> Is *everything* we generate into headers just as harmless? > > It should be, since it's just the C version of some JSON. The only > problematic thing could be different definitions of the same command for > multiple targets, and I think we want to avoid that anyway. > > To see it a different way, these are the "C bindings" to QMP, just that > the implementation is an in-process call rather than RPC. If the QAPI > code generator was also able to generate Python bindings and the like, > they would have to be the same for all QEMU binaries, wouldn't they? Ommitting the kind of #if we've been discussing is relatively harmless: #if defined(TARGET_I386) void qmp_rtc_reset_reinjection(Error **errp); void qmp_marshal_rtc_reset_reinjection(QDict *args, QObject **ret, Erro= r **errp); #endif /* defined(TARGET_I386) */ But what about this one, in qapi-types-block-core.h: typedef enum BlockdevDriver { BLOCKDEV_DRIVER_BLKDEBUG, [...] #if defined(CONFIG_REPLICATION) BLOCKDEV_DRIVER_REPLICATION, #endif /* defined(CONFIG_REPLICATION) */ [...] BLOCKDEV_DRIVER__MAX, } BlockdevDriver; If I omit it in the header, I then have to omit it in qapi-types-block-core.c's const QEnumLookup BlockdevDriver_lookup =3D { .array =3D (const char *const[]) { [BLOCKDEV_DRIVER_BLKDEBUG] =3D "blkdebug", [...] #if defined(CONFIG_REPLICATION) [BLOCKDEV_DRIVER_REPLICATION] =3D "replication", #endif /* defined(CONFIG_REPLICATION) */ [...] }, .size =3D BLOCKDEV_DRIVER__MAX }; and God knows what else. But I must not omit it in qapi-introspect.c's QLIT_QDICT(((QLitDictEntry[]) { { "meta-type", QLIT_QSTR("enum"), }, { "name", QLIT_QSTR("245"), }, { "values", QLIT_QLIST(((QLitObject[]) { QLIT_QSTR("blkdebug"), [...] #if defined(CONFIG_REPLICATION) QLIT_QSTR("replication"), #endif /* defined(CONFIG_REPLICATION) */ [...] {} })), }, {} })), because that would defeat introspection. I smell a swamp. I'd rather not complicate the generator to support not including a header I feel we *should* include. #ifdef CONFIG_FOO can occur not just in QAPI-generated code, and neglecting to include the relevant header can cause *nasty* problems not just in QAPI-generated code. Like inconsistent struct definitions in separate compilation units. Been there, debugged that, wasn't fun, do not want to go there again.