From nobody Mon Feb 9 07:23:42 2026 Delivered-To: importer@patchew.org Received-SPF: none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1580475757308369.1603346732518; Fri, 31 Jan 2020 05:02:37 -0800 (PST) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1ixVvj-0001P9-D7; Fri, 31 Jan 2020 13:01:51 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1ixVvh-0001Op-TV for xen-devel@lists.xenproject.org; Fri, 31 Jan 2020 13:01:49 +0000 Received: from relay.sw.ru (unknown [185.231.240.75]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id d48129a4-4429-11ea-8bc1-12813bfff9fa; Fri, 31 Jan 2020 13:01:44 +0000 (UTC) Received: from vovaso.qa.sw.ru ([10.94.3.0] helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1ixVvH-0000zU-VQ; Fri, 31 Jan 2020 16:01:24 +0300 X-Inumbo-ID: d48129a4-4429-11ea-8bc1-12813bfff9fa From: Vladimir Sementsov-Ogievskiy To: qemu-devel@nongnu.org Date: Fri, 31 Jan 2020 16:01:09 +0300 Message-Id: <20200131130118.1716-3-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200131130118.1716-1-vsementsov@virtuozzo.com> References: <20200131130118.1716-1-vsementsov@virtuozzo.com> MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v7 02/11] error: auto propagated local_err X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Vladimir Sementsov-Ogievskiy , Laszlo Ersek , qemu-block@nongnu.org, Paul Durrant , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , armbru@redhat.com, Max Reitz , Greg Kurz , Stefano Stabellini , Gerd Hoffmann , Stefan Hajnoczi , Anthony Perard , xen-devel@lists.xenproject.org, Eric Blake , Michael Roth , Stefan Berger Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Here is introduced ERRP_AUTO_PROPAGATE macro, to be used at start of functions with an errp OUT parameter. It has three goals: 1. Fix issue with error_fatal and error_prepend/error_append_hint: user can't see this additional information, because exit() happens in error_setg earlier than information is added. [Reported by Greg Kurz] 2. Fix issue with error_abort and error_propagate: when we wrap error_abort by local_err+error_propagate, the resulting coredump will refer to error_propagate and not to the place where error happened. (the macro itself doesn't fix the issue, but it allows us to [3.] drop the local_err+error_propagate pattern, which will definitely fix the issue) [Reported by Kevin Wolf] 3. Drop local_err+error_propagate pattern, which is used to workaround void functions with errp parameter, when caller wants to know resulting status. (Note: actually these functions could be merely updated to return int error code). To achieve these goals, later patches will add invocations of this macro at the start of functions with either use error_prepend/error_append_hint (solving 1) or which use local_err+error_propagate to check errors, switching those functions to use *errp instead (solving 2 and 3). Signed-off-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Greg Kurz Reviewed-by: Eric Blake --- CC: Eric Blake CC: Kevin Wolf CC: Max Reitz CC: Greg Kurz CC: Stefano Stabellini CC: Anthony Perard CC: Paul Durrant CC: Stefan Hajnoczi CC: "Philippe Mathieu-Daud=C3=A9" CC: Laszlo Ersek CC: Gerd Hoffmann CC: Stefan Berger CC: Markus Armbruster CC: Michael Roth CC: qemu-block@nongnu.org CC: xen-devel@lists.xenproject.org include/qapi/error.h | 83 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 82 insertions(+), 1 deletion(-) diff --git a/include/qapi/error.h b/include/qapi/error.h index d34987148d..b9452d4806 100644 --- a/include/qapi/error.h +++ b/include/qapi/error.h @@ -78,7 +78,7 @@ * Call a function treating errors as fatal: * foo(arg, &error_fatal); * - * Receive an error and pass it on to the caller: + * Receive an error and pass it on to the caller (DEPRECATED*): * Error *err =3D NULL; * foo(arg, &err); * if (err) { @@ -98,6 +98,50 @@ * foo(arg, errp); * for readability. * + * DEPRECATED* This pattern is deprecated now, the use ERRP_AUTO_PROPAGATE= macro + * instead (defined below). + * It's deprecated because of two things: + * + * 1. Issue with error_abort and error_propagate: when we wrap error_abort= by + * local_err+error_propagate, the resulting coredump will refer to + * error_propagate and not to the place where error happened. + * + * 2. A lot of extra code of the same pattern + * + * How to update old code to use ERRP_AUTO_PROPAGATE? + * + * All you need is to add ERRP_AUTO_PROPAGATE() invocation at function sta= rt, + * than you may safely dereference errp to check errors and do not need any + * additional local Error variables or calls to error_propagate(). + * + * Example: + * + * old code + * + * void fn(..., Error **errp) { + * Error *err =3D NULL; + * foo(arg, &err); + * if (err) { + * handle the error... + * error_propagate(errp, err); + * return; + * } + * ... + * } + * + * updated code + * + * void fn(..., Error **errp) { + * ERRP_AUTO_PROPAGATE(); + * foo(arg, errp); + * if (*errp) { + * handle the error... + * return; + * } + * ... + * } + * + * * Receive and accumulate multiple errors (first one wins): * Error *err =3D NULL, *local_err =3D NULL; * foo(arg, &err); @@ -348,6 +392,43 @@ void error_set_internal(Error **errp, ErrorClass err_class, const char *fmt, ...) GCC_FMT_ATTR(6, 7); =20 +typedef struct ErrorPropagator { + Error *local_err; + Error **errp; +} ErrorPropagator; + +static inline void error_propagator_cleanup(ErrorPropagator *prop) +{ + error_propagate(prop->errp, prop->local_err); +} + +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_cleanup= ); + +/* + * ERRP_AUTO_PROPAGATE + * + * This macro is created to be the first line of a function which use + * Error **errp parameter to report error. It's needed only in cases where= we + * want to use error_prepend, error_append_hint or dereference *errp. It's + * still safe (but useless) in other cases. + * + * If errp is NULL or points to error_fatal, it is rewritten to point to a + * local Error object, which will be automatically propagated to the origi= nal + * errp on function exit (see error_propagator_cleanup). + * + * After invocation of this macro it is always safe to dereference errp + * (as it's not NULL anymore) and to add information by error_prepend or + * error_append_hint (as, if it was error_fatal, we swapped it with a + * local_error to be propagated on cleanup). + * + * Note: we don't wrap the error_abort case, as we want resulting coredump + * to point to the place where the error happened, not to error_propagate. + */ +#define ERRP_AUTO_PROPAGATE() \ + g_auto(ErrorPropagator) _auto_errp_prop =3D {.errp =3D errp}; \ + errp =3D ((errp =3D=3D NULL || *errp =3D=3D error_fatal) \ + ? &_auto_errp_prop.local_err : errp) + /* * Special error destination to abort on error. * See error_setg() and error_propagate() for details. --=20 2.21.0 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel