qdict: Add qdict_put_null() helper, and put it to use

Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <20170825105913.4060-2-marcandre.lureau@redhat.com>
[Update to qobject.cocci squashed in, commit message tweaked]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

include/qapi/qmp/qdict.h

@@ -53,13 +53,15 @@ void qdict_destroy_obj(QObject *obj);
 #define qdict_put(qdict, key, obj) \
         qdict_put_obj(qdict, key, QOBJECT(obj))
 
-/* Helpers for int, bool, and string */
+/* Helpers for int, bool, null, and string */
 #define qdict_put_int(qdict, key, value) \
         qdict_put(qdict, key, qnum_from_int(value))
 #define qdict_put_bool(qdict, key, value) \
         qdict_put(qdict, key, qbool_from_bool(value))
 #define qdict_put_str(qdict, key, value) \
         qdict_put(qdict, key, qstring_from_str(value))
+#define qdict_put_null(qdict, key) \
+        qdict_put(qdict, key, qnull())
 
 /* High level helpers */
 double qdict_get_double(const QDict *qdict, const char *key);

scripts/coccinelle/qobject.cocci

@@ -20,6 +20,9 @@ expression Obj, Key, E;
 |
 - qdict_put(Obj, Key, qstring_from_str(E));
 + qdict_put_str(Obj, Key, E);
+|
+- qdict_put(Obj, Key, qnull());
++ qdict_put_null(Obj, Key);
 )
 
 // Use QList macros where they make sense

target/i386/cpu.c

@@ -2454,7 +2454,7 @@ static QDict *x86_cpu_static_props(void)
 
     d = qdict_new();
     for (i = 0; props[i]; i++) {
-        qdict_put(d, props[i], qnull());
+        qdict_put_null(d, props[i]);
     }
 
     for (w = 0; w < FEATURE_WORDS; w++) {
@@ -2464,7 +2464,7 @@ static QDict *x86_cpu_static_props(void)
             if (!fi->feat_names[bit]) {
                 continue;
             }
-            qdict_put(d, fi->feat_names[bit], qnull());
+            qdict_put_null(d, fi->feat_names[bit]);
         }
     }