qapi: modify visitor code generation for list iteration

Modify logic such that we never assign values to the list head argument
to progress through the list on subsequent iterations, instead rely only
on having our return value passed back in as an argument on the next
call. Also update QMP I/O visitors and test cases accordingly, and add a
missing test case for QmpOutputVisitor.

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

qapi/qmp-input-visitor.c

@@ -144,8 +144,6 @@ static GenericList *qmp_input_next_list(Visitor *v, GenericList **list,
         }
         (*list)->next = entry;
     }
-    *list = entry;
-
 
     return entry;
 }
@@ -240,9 +238,11 @@ static void qmp_input_type_enum(Visitor *v, int *obj, const char *strings[],
 
     if (strings[value] == NULL) {
         error_set(errp, QERR_INVALID_PARAMETER, name ? name : "null");
+        g_free(enum_str);
         return;
     }
 
+    g_free(enum_str);
     *obj = value;
 }
 

qapi/qmp-output-visitor.c

@@ -20,6 +20,7 @@
 typedef struct QStackEntry
 {
     QObject *value;
+    bool is_list_head;
     QTAILQ_ENTRY(QStackEntry) node;
 } QStackEntry;
 
@@ -45,6 +46,9 @@ static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value)
     QStackEntry *e = g_malloc0(sizeof(*e));
 
     e->value = value;
+    if (qobject_type(e->value) == QTYPE_QLIST) {
+        e->is_list_head = true;
+    }
     QTAILQ_INSERT_HEAD(&qov->stack, e, node);
 }
 
@@ -122,12 +126,20 @@ static void qmp_output_start_list(Visitor *v, const char *name, Error **errp)
     qmp_output_push(qov, list);
 }
 
-static GenericList *qmp_output_next_list(Visitor *v, GenericList **list,
+static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp,
                                          Error **errp)
 {
-    GenericList *retval = *list;
-    *list = retval->next;
-    return retval;
+    GenericList *list = *listp;
+    QmpOutputVisitor *qov = to_qov(v);
+    QStackEntry *e = QTAILQ_FIRST(&qov->stack);
+
+    assert(e);
+    if (e->is_list_head) {
+        e->is_list_head = false;
+        return list;
+    }
+
+    return list ? list->next : NULL;
 }
 
 static void qmp_output_end_list(Visitor *v, Error **errp)

scripts/qapi-visit.py

@@ -79,11 +79,11 @@ def generate_visit_list(name, members):
 
 void visit_type_%(name)sList(Visitor *m, %(name)sList ** obj, const char *name, Error **errp)
 {
-    GenericList *i;
+    GenericList *i, **head = (GenericList **)obj;
 
     visit_start_list(m, name, errp);
 
-    for (i = visit_next_list(m, (GenericList **)obj, errp); i; i = visit_next_list(m, &i, errp)) {
+    for (*head = i = visit_next_list(m, head, errp); i; i = visit_next_list(m, &i, errp)) {
         %(name)sList *native_i = (%(name)sList *)i;
         visit_type_%(name)s(m, &native_i->value, NULL, errp);
     }

test-visitor.c

@@ -27,11 +27,11 @@ static void visit_type_TestStruct(Visitor *v, TestStruct **obj, const char *name
 
 static void visit_type_TestStructList(Visitor *m, TestStructList ** obj, const char *name, Error **errp)
 {
-    GenericList *i;
+    GenericList *i, **head = (GenericList **)obj;
 
     visit_start_list(m, name, errp);
 
-    for (i = visit_next_list(m, (GenericList **)obj, errp); i; i = visit_next_list(m, &i, errp)) {
+    for (*head = i = visit_next_list(m, head, errp); i; i = visit_next_list(m, &i, errp)) {
         TestStructList *native_i = (TestStructList *)i;
         visit_type_TestStruct(m, &native_i->value, NULL, errp);
     }
@@ -50,6 +50,8 @@ static void test_visitor_core(void)
     TestStructList *lts = NULL;
     Error *err = NULL;
     QObject *obj;
+    QList *qlist;
+    QDict *qdict;
     QString *str;
     int64_t value = 0;
 
@@ -96,7 +98,9 @@ static void test_visitor_core(void)
     g_assert(pts->y == 84);
 
     qobject_decref(obj);
+    g_free(pts);
 
+    /* test list input visitor */
     obj = qobject_from_json("[{'x': 42, 'y': 84}, {'x': 12, 'y': 24}]");
     mi = qmp_input_visitor_new(obj);
     v = qmp_input_get_visitor(mi);
@@ -110,14 +114,41 @@ static void test_visitor_core(void)
     g_assert(lts->value->x == 42);
     g_assert(lts->value->y == 84);
 
-    lts = lts->next;
-    g_assert(lts != NULL);
-    g_assert(lts->value->x == 12);
-    g_assert(lts->value->y == 24);
-
-    g_assert(lts->next == NULL);
+    g_assert(lts->next != NULL);
+    g_assert(lts->next->value->x == 12);
+    g_assert(lts->next->value->y == 24);
+    g_assert(lts->next->next == NULL);
 
     qobject_decref(obj);
+
+    /* test list output visitor */
+    mo = qmp_output_visitor_new();
+    v = qmp_output_get_visitor(mo);
+    visit_type_TestStructList(v, &lts, NULL, &err);
+    if (err) {
+        g_error("%s", error_get_pretty(err));
+    }
+    obj = qmp_output_get_qobject(mo);
+    g_print("obj: %s\n", qstring_get_str(qobject_to_json(obj)));
+
+    qlist = qobject_to_qlist(obj);
+    assert(qlist);
+    obj = qlist_pop(qlist);
+    qdict = qobject_to_qdict(obj);
+    assert(qdict);
+    assert(qdict_get_int(qdict, "x") == 42);
+    assert(qdict_get_int(qdict, "y") == 84);
+    qobject_decref(obj);
+
+    obj = qlist_pop(qlist);
+    qdict = qobject_to_qdict(obj);
+    assert(qdict);
+    assert(qdict_get_int(qdict, "x") == 12);
+    assert(qdict_get_int(qdict, "y") == 24);
+    qobject_decref(obj);
+
+    qmp_output_visitor_cleanup(mo);
+    QDECREF(qlist);
 }
 
 /* test deep nesting with refs to other user-defined types */
@@ -286,7 +317,8 @@ static void test_nested_enums(void)
     g_assert(nested_enums_cpy->has_enum2 == false);
     g_assert(nested_enums_cpy->has_enum4 == true);
 
-    qobject_decref(obj);
+    qmp_output_visitor_cleanup(mo);
+    qmp_input_visitor_cleanup(mi);
     qapi_free_NestedEnumsOne(nested_enums);
     qapi_free_NestedEnumsOne(nested_enums_cpy);
 }