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Thu, 19 Sep 2019 11:53:21 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.40.205.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 74BFF5D6B0; Thu, 19 Sep 2019 11:52:54 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" References: <20190918130244.24257-1-vsementsov@virtuozzo.com> <9f41abd9-bef6-d7f1-0e52-df14a50cbe38@redhat.com> <7aa85eb5-d765-d337-7f5d-09d7a981253f@virtuozzo.com> From: Max Reitz Openpgp: preference=signencrypt Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: <9b1f5c35-b67d-dab2-c0cc-a39e88bc92c0@redhat.com> Date: Thu, 19 Sep 2019 13:52:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <7aa85eb5-d765-d337-7f5d-09d7a981253f@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.65]); Thu, 19 Sep 2019 11:53:21 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [RFC] error: auto propagated local_err 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: "fam@euphon.net" , "peter.maydell@linaro.org" , "mst@redhat.com" , "codyprime@gmail.com" , "mark.cave-ayland@ilande.co.uk" , "mdroth@linux.vnet.ibm.com" , "kraxel@redhat.com" , "qemu-block@nongnu.org" , "quintela@redhat.com" , "david@redhat.com" , "armbru@redhat.com" , "pasic@linux.ibm.com" , "borntraeger@de.ibm.com" , "marcandre.lureau@redhat.com" , "rth@twiddle.net" , "farman@linux.ibm.com" , "groug@kaod.org" , "dgilbert@redhat.com" , "alex.williamson@redhat.com" , "qemu-arm@nongnu.org" , "stefanha@redhat.com" , "jsnow@redhat.com" , "david@gibson.dropbear.id.au" , "kwolf@redhat.com" , "berrange@redhat.com" , "cohuck@redhat.com" , "qemu-s390x@nongnu.org" , "sundeep.lkml@gmail.com" , "qemu-ppc@nongnu.org" , "pbonzini@redhat.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19.09.19 12:03, Vladimir Sementsov-Ogievskiy wrote: > 19.09.2019 12:33, Max Reitz wrote: >> On 19.09.19 11:14, Vladimir Sementsov-Ogievskiy wrote: >>> 19.09.2019 11:59, Max Reitz wrote: >>>> On 18.09.19 15:02, Vladimir Sementsov-Ogievskiy wrote: >>>>> Hi all! >>>>> >>>>> Here is a proposal (three of them, actually) of auto propagation fo= r >>>>> local_err, to not call error_propagate on every exit point, when we >>>>> deal with local_err. >>>>> >>>>> It also may help make Greg's series[1] about error_append_hint smal= ler. >>>>> >>>>> See definitions and examples below. >>>>> >>>>> I'm cc-ing to this RFC everyone from series[1] CC list, as if we li= ke >>>>> it, the idea will touch same code (and may be more). >>>>> >>>>> [1]: https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg03449= .html >>>>> >>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy >>>>> --- >>>>> include/qapi/error.h | 102 +++++++++++++++++++++++++++++++++++++= ++++++ >>>>> block.c | 63 ++++++++++++-------------- >>>>> block/backup.c | 8 +++- >>>>> block/gluster.c | 7 +++ >>>>> 4 files changed, 144 insertions(+), 36 deletions(-) >>>> >>>> If the combination of =E2=80=9Cif (local_err) { error_propagate(...)= ; ... }=E2=80=9D is >>>> what=E2=80=99s cumbersome, can=E2=80=99t this be done simpler by add= ing an >>>> error_propagate() variant with a return value? >>>> >>>> i.e. >>>> >>>> bool has_error_then_propagate(Error **errp, Error *err) >>>> { >>>> if (!err) { >>>> return false; >>>> } >>>> error_propagate(errp, err); >>>> return true; >>>> } >>>> >>>> And then turn all instances of >>>> >>>> if (local_err) { >>>> error_propagate(errp, local_err); >>>> ... >>>> } >>>> >>>> into >>>> >>>> if (has_error_then_propagate(errp, local_err)) { >>>> ... >>>> } >>>> >>>> ? >>>> >>>> Max >>>> >>> >>> No, originally cumbersome is introducing local_err in a lot of new pl= aces by >>> Greg's series. MAKE_ERRP_SAFE macro makes it as simple as one macro c= all >>> instead (in each function where we need local_err). >> >> Does it need more than one local_err per function? >> >> Because if it didn=E2=80=99t, I=E2=80=99d find one =E2=80=9CError *loc= al_err;=E2=80=9D simpler than one >> macro incantation. >> >> (It has the same LoC, and it makes code readers ask the same question: >> =E2=80=9CWhy do we need it?=E2=80=9D Which has the same answer for bo= th; but one is >> immediately readable code, whereas the other is a macro.) >=20 > Not the same, you didn't count error_propagate I did, because it would part of the if () statement in my proposal. > And your example don't match Greg's case, there no "if (local_err)" in = it, Ah, right, I see. OK then. > just "error_append_hint(errp)", which don't work for error_fatal and er= ror_abort > (Yes, I agree with Kevin, that it should work only for error_fatal) True. [...] >> Now Kevin has given an actual advantage, which is that local_err >> complicates debugging. I=E2=80=99ve never had that problem myself, bu= t that >> would indeed be an advantage that may warrant some magic. Although after some more consideration I realized this probably cannot be achieved with this series, actually. Max