Simplify casting to QObject by not requiring the definition of the
type and assuming base QObject is at offset 0. Add a static check for
this.
Use the QEMU_GENERIC macro for keeping type safety check and error
when given an unknown type.
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
include/qapi/qmp/qobject.h | 36 ++++++++++++++++++++++++++++++++++--
qobject/qobject.c | 9 +++++++++
2 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/include/qapi/qmp/qobject.h b/include/qapi/qmp/qobject.h
index e022707578..d0aead35ec 100644
--- a/include/qapi/qmp/qobject.h
+++ b/include/qapi/qmp/qobject.h
@@ -39,8 +39,40 @@ struct QObject {
size_t refcnt;
};
-/* Get the 'base' part of an object */
-#define QOBJECT(obj) (&(obj)->base)
+/* This function gives an error if an invalid pointer type is passed
+ * to QOBJECT. For optimized builds, we can rely on dead-code
+ * elimination from the compiler, and give the errors already at link
+ * time.
+ */
+#if defined(__OPTIMIZE__) && !defined(__SANITIZE_ADDRESS__)
+const void * qobject_unknown_type(const void *);
+#else
+static inline const void *
+qobject_unknown_type(const void *unused)
+{
+ abort();
+ return NULL;
+}
+#endif
+
+/* A typecast, checking for the type of arguments */
+/* QObject is at offset 0, for all QObject-derived types */
+#define QOBJECT(x) QEMU_GENERIC(x, \
+ (QNull *, (QObject *) x), \
+ (const QNull *, (const QObject *) x), \
+ (QNum *, (QObject *) x), \
+ (const QNum *, (const QObject *) x), \
+ (QString *, (QObject *) x), \
+ (const QString *, (const QObject *) x), \
+ (QDict *, (QObject *) x), \
+ (const QDict *, (const QObject *) x), \
+ (QList *, (QObject *) x), \
+ (const QList *, (const QObject *) x), \
+ (QBool *, (QObject *) x), \
+ (const QBool *, (const QObject *) x), \
+ (QObject *, x), \
+ (const QObject *, x), \
+ qobject_unknown_type(x))
/* High-level interface for qobject_incref() */
#define QINCREF(obj) \
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 */
--
2.16.2.521.g9aa15f885a
