From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49725) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f9B4V-0006hk-Ha for qemu-devel@nongnu.org; Thu, 19 Apr 2018 11:02:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f9B4P-00027S-Pp for qemu-devel@nongnu.org; Thu, 19 Apr 2018 11:02:03 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51528 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f9B4P-00025g-Jw for qemu-devel@nongnu.org; Thu, 19 Apr 2018 11:01:57 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9CA85722ED for ; Thu, 19 Apr 2018 15:01:52 +0000 (UTC) From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Thu, 19 Apr 2018 17:01:41 +0200 Message-Id: <20180419150145.24795-2-marcandre.lureau@redhat.com> In-Reply-To: <20180419150145.24795-1-marcandre.lureau@redhat.com> References: <20180419150145.24795-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PATCH v6 1/5] qobject: ensure base is at offset 0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: eblake@redhat.com, berrange@redhat.com, armbru@redhat.com, pbonzini@redhat.com, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= All QObject types have the base QObject as their first field. This allows the simplification of qobject_to(). This explicitly guarantees that existing casts work correctly (even though we'd prefer to get rid of such casts in any location except the qobject.h macros) Signed-off-by: Marc-Andr=C3=A9 Lureau Reviewed-by: Eric Blake --- include/qapi/qmp/qobject.h | 5 ++--- qobject/qobject.c | 9 +++++++++ 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/include/qapi/qmp/qobject.h b/include/qapi/qmp/qobject.h index e022707578..5206ff9ee1 100644 --- a/include/qapi/qmp/qobject.h +++ b/include/qapi/qmp/qobject.h @@ -61,9 +61,8 @@ struct QObject { QEMU_BUILD_BUG_MSG(QTYPE__MAX !=3D 7, "The QTYPE_CAST_TO_* list needs to be extended"); =20 -#define qobject_to(type, obj) ({ \ - QObject *_tmp =3D qobject_check_type(obj, glue(QTYPE_CAST_TO_, type)= ); \ - _tmp ? container_of(_tmp, type, base) : (type *)NULL; }) +#define qobject_to(type, obj) \ + ((type *)qobject_check_type(obj, glue(QTYPE_CAST_TO_, type))) =20 /* Initialize an object to default values */ static inline void qobject_init(QObject *obj, QType type) diff --git a/qobject/qobject.c b/qobject/qobject.c index 23600aa1c1..87649c5be5 100644 --- a/qobject/qobject.c +++ b/qobject/qobject.c @@ -16,6 +16,15 @@ #include "qapi/qmp/qlist.h" #include "qapi/qmp/qstring.h" =20 +QEMU_BUILD_BUG_MSG( + offsetof(QNull, base) !=3D 0 || + offsetof(QNum, base) !=3D 0 || + offsetof(QString, base) !=3D 0 || + offsetof(QDict, base) !=3D 0 || + offsetof(QList, base) !=3D 0 || + offsetof(QBool, base) !=3D 0, + "base qobject must be at offset 0"); + static void (*qdestroy[QTYPE__MAX])(QObject *) =3D { [QTYPE_NONE] =3D NULL, /* No such object exists */ [QTYPE_QNULL] =3D NULL, /* qnull_ is indestructible */ --=20 2.17.0.253.g3dd125b46d