From 2ca916e1064ba57dfb74281c21d047f074716fc5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Fri, 4 May 2018 09:54:24 -0400 Subject: [PATCH] qobject: Ensure base is at offset 0 All QObject types have the base QObject as their first field. This allows the simplification of qobject_to(). Backports commit 7ee9edfdb117da47c86c9764d90f0be11a648666 from qemu --- qemu/include/qapi/qmp/qobject.h | 5 ++--- qemu/qobject/qobject.c | 9 +++++++++ 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/qemu/include/qapi/qmp/qobject.h b/qemu/include/qapi/qmp/qobject.h index 9e945bab..609b0245 100644 --- a/qemu/include/qapi/qmp/qobject.h +++ b/qemu/include/qapi/qmp/qobject.h @@ -65,9 +65,8 @@ 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/qemu/qobject/qobject.c b/qemu/qobject/qobject.c index 6edaacb9..ce13affd 100644 --- a/qemu/qobject/qobject.c +++ b/qemu/qobject/qobject.c @@ -15,6 +15,15 @@ #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 *) = { NULL, /* No such object exists */ NULL, /* qnull_ is indestructible */