QAPI patches for 2018-05-04

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Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2018-05-04' into staging

QAPI patches for 2018-05-04

# gpg: Signature made Fri 04 May 2018 08:59:16 BST
# gpg:                using RSA key 3870B400EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2018-05-04:
  qapi: deprecate CpuInfoFast.arch
  qapi: discriminate CpuInfoFast on SysEmuTarget, not CpuInfoArch
  qapi: change the type of TargetInfo.arch from string to enum SysEmuTarget
  qapi: add SysEmuTarget to "common.json"
  qapi: fill in CpuInfoFast.arch in query-cpus-fast
  qobject: Modify qobject_ref() to return obj
  qobject: Replace qobject_incref/QINCREF qobject_decref/QDECREF
  qobject: use a QObjectBase_ struct
  qobject: Ensure base is at offset 0
  qobject: Use qobject_to() instead of type cast

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

include/qapi/qmp/qbool.h

@@ -17,7 +17,7 @@
 #include "qapi/qmp/qobject.h"
 
 struct QBool {
-    QObject base;
+    struct QObjectBase_ base;
     bool value;
 };
 

include/qapi/qmp/qdict.h

@@ -25,7 +25,7 @@ typedef struct QDictEntry {
 } QDictEntry;
 
 struct QDict {
-    QObject base;
+    struct QObjectBase_ base;
     size_t size;
     QLIST_HEAD(,QDictEntry) table[QDICT_BUCKET_MAX];
 };

include/qapi/qmp/qlist.h

@@ -22,7 +22,7 @@ typedef struct QListEntry {
 } QListEntry;
 
 struct QList {
-    QObject base;
+    struct QObjectBase_ base;
     QTAILQ_HEAD(,QListEntry) head;
 };
 

include/qapi/qmp/qnull.h

@@ -16,15 +16,14 @@
 #include "qapi/qmp/qobject.h"
 
 struct QNull {
-    QObject base;
+    struct QObjectBase_ base;
 };
 
 extern QNull qnull_;
 
 static inline QNull *qnull(void)
 {
-    QINCREF(&qnull_);
-    return &qnull_;
+    return qobject_ref(&qnull_);
 }
 
 bool qnull_is_equal(const QObject *x, const QObject *y);

include/qapi/qmp/qnum.h

@@ -45,7 +45,7 @@ typedef enum {
  * convert under the hood.
  */
 struct QNum {
-    QObject base;
+    struct QObjectBase_ base;
     QNumKind kind;
     union {
         int64_t i64;

include/qapi/qmp/qobject.h

@@ -15,17 +15,17 @@
  * ------------------------------------
  *
  *  - Returning references: A function that returns an object may
- *  return it as either a weak or a strong reference.  If the reference
- *  is strong, you are responsible for calling QDECREF() on the reference
- *  when you are done.
+ *  return it as either a weak or a strong reference.  If the
+ *  reference is strong, you are responsible for calling
+ *  qobject_unref() on the reference when you are done.
  *
  *  If the reference is weak, the owner of the reference may free it at
  *  any time in the future.  Before storing the reference anywhere, you
- *  should call QINCREF() to make the reference strong.
+ *  should call qobject_ref() to make the reference strong.
  *
  *  - Transferring ownership: when you transfer ownership of a reference
  *  by calling a function, you are no longer responsible for calling
- *  QDECREF() when the reference is no longer needed.  In other words,
+ *  qobject_unref() when the reference is no longer needed.  In other words,
  *  when the function returns you must behave as if the reference to the
  *  passed object was weak.
  */
@@ -34,21 +34,21 @@
 
 #include "qapi/qapi-builtin-types.h"
 
-struct QObject {
+/* Not for use outside include/qapi/qmp/ */
+struct QObjectBase_ {
     QType type;
     size_t refcnt;
 };
 
-/* Get the 'base' part of an object */
-#define QOBJECT(obj) (&(obj)->base)
+/* this struct must have no other members than base */
+struct QObject {
+    struct QObjectBase_ base;
+};
 
-/* High-level interface for qobject_incref() */
-#define QINCREF(obj)      \
-    qobject_incref(QOBJECT(obj))
-
-/* High-level interface for qobject_decref() */
-#define QDECREF(obj)              \
-    qobject_decref(obj ? QOBJECT(obj) : NULL)
+#define QOBJECT(obj) ({                                         \
+    typeof(obj) _obj = (obj);                                   \
+    _obj ? container_of(&(_obj)->base, QObject, base) : NULL;   \
+})
 
 /* Required for qobject_to() */
 #define QTYPE_CAST_TO_QNull     QTYPE_QNULL
@@ -61,25 +61,22 @@ 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)
 {
     assert(QTYPE_NONE < type && type < QTYPE__MAX);
-    obj->refcnt = 1;
-    obj->type = type;
+    obj->base.refcnt = 1;
+    obj->base.type = type;
 }
 
-/**
- * qobject_incref(): Increment QObject's reference count
- */
-static inline void qobject_incref(QObject *obj)
+static inline void qobject_ref_impl(QObject *obj)
 {
-    if (obj)
-        obj->refcnt++;
+    if (obj) {
+        obj->base.refcnt++;
+    }
 }
 
 /**
@@ -96,25 +93,39 @@ bool qobject_is_equal(const QObject *x, const QObject *y);
  */
 void qobject_destroy(QObject *obj);
 
-/**
- * qobject_decref(): Decrement QObject's reference count, deallocate
- * when it reaches zero
- */
-static inline void qobject_decref(QObject *obj)
+static inline void qobject_unref_impl(QObject *obj)
 {
-    assert(!obj || obj->refcnt);
-    if (obj && --obj->refcnt == 0) {
+    assert(!obj || obj->base.refcnt);
+    if (obj && --obj->base.refcnt == 0) {
         qobject_destroy(obj);
     }
 }
 
+/**
+ * qobject_ref(): Increment QObject's reference count
+ *
+ * Returns: the same @obj. The type of @obj will be propagated to the
+ * return type.
+ */
+#define qobject_ref(obj) ({                     \
+    typeof(obj) _o = (obj);                     \
+    qobject_ref_impl(QOBJECT(_o));              \
+    _o;                                         \
+})
+
+/**
+ * qobject_unref(): Decrement QObject's reference count, deallocate
+ * when it reaches zero
+ */
+#define qobject_unref(obj) qobject_unref_impl(QOBJECT(obj))
+
 /**
  * qobject_type(): Return the QObject's type
  */
 static inline QType qobject_type(const QObject *obj)
 {
-    assert(QTYPE_NONE < obj->type && obj->type < QTYPE__MAX);
-    return obj->type;
+    assert(QTYPE_NONE < obj->base.type && obj->base.type < QTYPE__MAX);
+    return obj->base.type;
 }
 
 /**

include/qapi/qmp/qstring.h

@@ -16,7 +16,7 @@
 #include "qapi/qmp/qobject.h"
 
 struct QString {
-    QObject base;
+    struct QObjectBase_ base;
     char *string;
     size_t length;
     size_t capacity;