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qobject: Ensure base is at offset 0

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All QObject types have the base QObject as their first field. This
allows the simplification of qobject_to().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180419150145.24795-2-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message paragraph on type casts dropped, to avoid giving the
impression type casting would be okay]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
Marc-André Lureau 2018-04-19 17:01:41 +02:00 committed by Markus Armbruster
parent 46cfbf13b0
commit 7ee9edfdb1
2 changed files with 11 additions and 3 deletions
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5
include/qapi/qmp/qobject.h
View File

@ -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)

9
qobject/qobject.c
View File

@ -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 */