From 7ee9edfdb117da47c86c9764d90f0be11a648666 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Thu, 19 Apr 2018 17:01:41 +0200 Subject: [PATCH] qobject: Ensure base is at offset 0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit All QObject types have the base QObject as their first field. This allows the simplification of qobject_to(). Signed-off-by: Marc-André Lureau Reviewed-by: Eric Blake Message-Id: <20180419150145.24795-2-marcandre.lureau@redhat.com> Reviewed-by: Markus Armbruster [Commit message paragraph on type casts dropped, to avoid giving the impression type casting would be okay] Signed-off-by: Markus Armbruster --- 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 != 7, "The QTYPE_CAST_TO_* list needs to be extended"); -#define qobject_to(type, obj) ({ \ - QObject *_tmp = 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))) /* 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" +QEMU_BUILD_BUG_MSG( + offsetof(QNull, base) != 0 || + offsetof(QNum, base) != 0 || + offsetof(QString, base) != 0 || + offsetof(QDict, base) != 0 || + offsetof(QList, base) != 0 || + offsetof(QBool, base) != 0, + "base qobject must be at offset 0"); + static void (*qdestroy[QTYPE__MAX])(QObject *) = { [QTYPE_NONE] = NULL, /* No such object exists */ [QTYPE_QNULL] = NULL, /* qnull_ is indestructible */