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[Qemu-devel] [PATCH v6 1/5] qobject: ensure base is at offset 0
From: |
Marc-André Lureau |
Subject: |
[Qemu-devel] [PATCH v6 1/5] qobject: ensure base is at offset 0 |
Date: |
Thu, 19 Apr 2018 17:01:41 +0200 |
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-André Lureau <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
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 */
--
2.17.0.253.g3dd125b46d
Re: [Qemu-devel] [PATCH v6 1/5] qobject: ensure base is at offset 0, Markus Armbruster, 2018/04/27
[Qemu-devel] [PATCH v6 2/5] qobject: use a QObjectBase_ struct, Marc-André Lureau, 2018/04/19