qapi: Add parameter to visit_end_*

Rather than making the dealloc visitor track of stack of pointers
remembered during visit_start_* in order to free them during
visit_end_*, it's a lot easier to just make all callers pass the
same pointer to visit_end_*. The generated code has access to the
same pointer, while all other users are doing virtual walks and
can pass NULL. The dealloc visitor is then greatly simplified.

All three visit_end_*() functions intentionally take a void**,
even though the visit_start_*() functions differ between void**,
GenericList**, and GenericAlternate**. This is done for several
reasons: when doing a virtual walk, passing NULL doesn't care
what the type is, but when doing a generated walk, we already
have to cast the caller's specific FOO* to call visit_start,
while using void** lets us use visit_end without a cast. Also,
an upcoming patch will add a clone visitor that wants to use
the same implementation for all three visit_end callbacks,
which is made easier if all three share the same signature.

For visitors with already track per-object state (the QMP visitors
via a stack, and the string visitors which do not allow nesting),
add an assertion that the caller is indeed passing the same
pointer to paired calls.

Backports commit 1158bb2a058fcdd0c8fc3e60dc77f7a57ddbb271 from qemu

msvc/unicorn/qapi-visit.c

@@ -47,7 +47,7 @@ void visit_type_DummyForceArrays(Visitor *v, const char *name, DummyForceArrays
     }
     visit_check_struct(v, &err);
 out_obj:
-    visit_end_struct(v);
+    visit_end_struct(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_DummyForceArrays(*obj);
         *obj = NULL;
@@ -114,7 +114,7 @@ void visit_type_X86CPUFeatureWordInfo(Visitor *v, const char *name, X86CPUFeatur
     }
     visit_check_struct(v, &err);
 out_obj:
-    visit_end_struct(v);
+    visit_end_struct(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_X86CPUFeatureWordInfo(*obj);
         *obj = NULL;
@@ -144,7 +144,7 @@ void visit_type_X86CPUFeatureWordInfoList(Visitor *v, const char *name, X86CPUFe
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_X86CPUFeatureWordInfoList(*obj);
         *obj = NULL;
@@ -181,7 +181,7 @@ void visit_type_anyList(Visitor *v, const char *name, anyList **obj, Error **err
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_anyList(*obj);
         *obj = NULL;
@@ -211,7 +211,7 @@ void visit_type_boolList(Visitor *v, const char *name, boolList **obj, Error **e
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_boolList(*obj);
         *obj = NULL;
@@ -241,7 +241,7 @@ void visit_type_int16List(Visitor *v, const char *name, int16List **obj, Error *
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_int16List(*obj);
         *obj = NULL;
@@ -271,7 +271,7 @@ void visit_type_int32List(Visitor *v, const char *name, int32List **obj, Error *
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_int32List(*obj);
         *obj = NULL;
@@ -301,7 +301,7 @@ void visit_type_int64List(Visitor *v, const char *name, int64List **obj, Error *
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_int64List(*obj);
         *obj = NULL;
@@ -331,7 +331,7 @@ void visit_type_int8List(Visitor *v, const char *name, int8List **obj, Error **e
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_int8List(*obj);
         *obj = NULL;
@@ -361,7 +361,7 @@ void visit_type_intList(Visitor *v, const char *name, intList **obj, Error **err
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_intList(*obj);
         *obj = NULL;
@@ -391,7 +391,7 @@ void visit_type_numberList(Visitor *v, const char *name, numberList **obj, Error
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_numberList(*obj);
         *obj = NULL;
@@ -421,7 +421,7 @@ void visit_type_sizeList(Visitor *v, const char *name, sizeList **obj, Error **e
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_sizeList(*obj);
         *obj = NULL;
@@ -451,7 +451,7 @@ void visit_type_strList(Visitor *v, const char *name, strList **obj, Error **err
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_strList(*obj);
         *obj = NULL;
@@ -481,7 +481,7 @@ void visit_type_uint16List(Visitor *v, const char *name, uint16List **obj, Error
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_uint16List(*obj);
         *obj = NULL;
@@ -511,7 +511,7 @@ void visit_type_uint32List(Visitor *v, const char *name, uint32List **obj, Error
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_uint32List(*obj);
         *obj = NULL;
@@ -541,7 +541,7 @@ void visit_type_uint64List(Visitor *v, const char *name, uint64List **obj, Error
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_uint64List(*obj);
         *obj = NULL;
@@ -571,7 +571,7 @@ void visit_type_uint8List(Visitor *v, const char *name, uint8List **obj, Error *
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_uint8List(*obj);
         *obj = NULL;

qemu/include/qapi/visitor-impl.h

@@ -48,7 +48,7 @@ struct Visitor
     void (*check_struct)(Visitor *v, Error **errp);
 
     /* Must be set to visit structs */
-    void (*end_struct)(Visitor *v);
+    void (*end_struct)(Visitor *v, void **obj);
 
     /* Must be set; implementations may require @list to be non-null,
      * but must document it. */
@@ -59,7 +59,7 @@ struct Visitor
     GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size);
 
     /* Must be set */
-    void (*end_list)(Visitor *v);
+    void (*end_list)(Visitor *v, void **list);
 
     /* Must be set by input and dealloc visitors to visit alternates;
      * optional for output visitors. */
@@ -68,7 +68,7 @@ struct Visitor
                             bool promote_int, Error **errp);
 
     /* Optional, needed for dealloc visitor */
-    void (*end_alternate)(Visitor *v);
+    void (*end_alternate)(Visitor *v, void **obj);
 
     /* Must be set */
     void (*type_int64)(Visitor *v, const char *name, int64_t *obj,

qemu/include/qapi/visitor.h

@@ -195,12 +195,12 @@
  *      goto outlist;
  *  }
  * outlist:
- *  visit_end_list(v);
+ *  visit_end_list(v, NULL);
  *  if (!err) {
  *      visit_check_struct(v, &err);
  *  }
  * outobj:
- *  visit_end_struct(v);
+ *  visit_end_struct(v, NULL);
  * out:
  *  error_propagate(errp, err);
  *  ...clean up v...
@@ -246,8 +246,8 @@ typedef struct GenericAlternate {
  * After visit_start_struct() succeeds, the caller may visit its
  * members one after the other, passing the member's name and address
  * within the struct.  Finally, visit_end_struct() needs to be called
- * to clean up, even if intermediate visits fail.  See the examples
+ * with the same @obj to clean up, even if intermediate visits fail.
- * above.
+ * See the examples above.
  *
  * FIXME Should this be named visit_start_object, since it is also
  * used for QAPI unions, and maps to JSON objects?
@@ -271,12 +271,14 @@ void visit_check_struct(Visitor *v, Error **errp);
 /*
  * Complete an object visit started earlier.
  *
+ * @obj must match what was passed to the paired visit_start_struct().
+ *
  * Must be called after any successful use of visit_start_struct(),
  * even if intermediate processing was skipped due to errors, to allow
  * the backend to release any resources.  Destroying the visitor early
  * behaves as if this was implicitly called.
  */
-void visit_end_struct(Visitor *v);
+void visit_end_struct(Visitor *v, void **obj);
 
 
 /*** Visiting lists ***/
@@ -303,8 +305,9 @@ void visit_end_struct(Visitor *v);
  * visit (where @obj is NULL) uses other means.  For each list
  * element, call the appropriate visit_type_FOO() with name set to
  * NULL and obj set to the address of the value member of the list
- * element.  Finally, visit_end_list() needs to be called to clean up,
+ * element.  Finally, visit_end_list() needs to be called with the
- * even if intermediate visits fail.  See the examples above.
+ * same @list to clean up, even if intermediate visits fail.  See the
+ * examples above.
  */
 void visit_start_list(Visitor *v, const char *name, GenericList **list,
                       size_t size, Error **errp);
@@ -333,12 +336,14 @@ GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size);
 /*
  * Complete a list visit started earlier.
  *
+ * @list must match what was passed to the paired visit_start_list().
+ *
  * Must be called after any successful use of visit_start_list(), even
  * if intermediate processing was skipped due to errors, to allow the
  * backend to release any resources.  Destroying the visitor early
  * behaves as if this was implicitly called.
  */
-void visit_end_list(Visitor *v);
+void visit_end_list(Visitor *v, void **list);
 
 /*
  * Start the visit of an alternate @obj.
@@ -353,8 +358,9 @@ void visit_end_list(Visitor *v);
  *
  * If @promote_int, treat integers as QTYPE_FLOAT.
  *
- * If successful, this must be paired with visit_end_alternate() to
+ * If successful, this must be paired with visit_end_alternate() with
- * clean up, even if visiting the contents of the alternate fails.
+ * the same @obj to clean up, even if visiting the contents of the
+ * alternate fails.
  */
 void visit_start_alternate(Visitor *v, const char *name,
                            GenericAlternate **obj, size_t size,
@@ -363,15 +369,14 @@ void visit_start_alternate(Visitor *v, const char *name,
 /*
  * Finish visiting an alternate type.
  *
+ * @obj must match what was passed to the paired visit_start_alternate().
+ *
  * Must be called after any successful use of visit_start_alternate(),
  * even if intermediate processing was skipped due to errors, to allow
  * the backend to release any resources.  Destroying the visitor early
  * behaves as if this was implicitly called.
- *
- * TODO: Should all the visit_end_* interfaces take obj parameter, so
- * that dealloc visitor need not track what was passed in visit_start?
  */
-void visit_end_alternate(Visitor *v);
+void visit_end_alternate(Visitor *v, void **obj);
 
 
 /*** Other helpers ***/

qemu/qapi/qapi-dealloc-visitor.c

@@ -19,54 +19,19 @@
 #include "qapi/qmp/types.h"
 #include "qapi/visitor-impl.h"
 
-typedef struct StackEntry
-{
-    void *value;
-    QTAILQ_ENTRY(StackEntry) node;
-} StackEntry;
-
 struct QapiDeallocVisitor
 {
     Visitor visitor;
-    QTAILQ_HEAD(, StackEntry) stack;
     bool is_list_head;
 };
 
-static QapiDeallocVisitor *to_qov(Visitor *v)
-{
-    return container_of(v, QapiDeallocVisitor, visitor);
-}
-
-static void qapi_dealloc_push(QapiDeallocVisitor *qov, void *value)
-{
-    StackEntry *e = g_malloc0(sizeof(*e));
-
-    e->value = value;
-
-    QTAILQ_INSERT_HEAD(&qov->stack, e, node);
-}
-
-static void *qapi_dealloc_pop(QapiDeallocVisitor *qov)
-{
-    StackEntry *e = QTAILQ_FIRST(&qov->stack);
-    QObject *value;
-    QTAILQ_REMOVE(&qov->stack, e, node);
-    value = e->value;
-    g_free(e);
-    return value;
-}
-
 static void qapi_dealloc_start_struct(Visitor *v, const char *name, void **obj,
                                       size_t unused, Error **errp)
 {
-    QapiDeallocVisitor *qov = to_qov(v);
-    qapi_dealloc_push(qov, obj);
 }
 
-static void qapi_dealloc_end_struct(Visitor *v)
+static void qapi_dealloc_end_struct(Visitor *v, void **obj)
 {
-    QapiDeallocVisitor *qov = to_qov(v);
-    void **obj = qapi_dealloc_pop(qov);
     if (obj) {
         g_free(*obj);
     }
@@ -76,14 +41,10 @@ static void qapi_dealloc_start_alternate(Visitor *v, const char *name,
                                          GenericAlternate **obj, size_t size,
                                          bool promote_int, Error **errp)
 {
-    QapiDeallocVisitor *qov = to_qov(v);
-    qapi_dealloc_push(qov, obj);
 }
 
-static void qapi_dealloc_end_alternate(Visitor *v)
+static void qapi_dealloc_end_alternate(Visitor *v, void **obj)
 {
-    QapiDeallocVisitor *qov = to_qov(v);
-    void **obj = qapi_dealloc_pop(qov);
     if (obj) {
         g_free(*obj);
     }
@@ -103,7 +64,7 @@ static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList *tail,
     return next;
 }
 
-static void qapi_dealloc_end_list(Visitor *v)
+static void qapi_dealloc_end_list(Visitor *v, void **obj)
 {
 }
 
@@ -185,7 +146,5 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
     v->visitor.type_null = qapi_dealloc_type_null;
     v->visitor.type_size = qapi_dealloc_type_size;
 
-    QTAILQ_INIT(&v->stack);
-
     return v;
 }

qemu/qapi/qapi-visit-core.c

@@ -44,9 +44,9 @@ void visit_check_struct(Visitor *v, Error **errp)
     }
 }
 
-void visit_end_struct(Visitor *v)
+void visit_end_struct(Visitor *v, void **obj)
 {
-    v->end_struct(v);
+    v->end_struct(v, obj);
 }
 
 void visit_start_list(Visitor *v, const char *name, GenericList **list,
@@ -68,9 +68,9 @@ GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size)
     return v->next_list(v, tail, size);
 }
 
-void visit_end_list(Visitor *v)
+void visit_end_list(Visitor *v, void **obj)
 {
-    v->end_list(v);
+    v->end_list(v, obj);
 }
 
 void visit_start_alternate(Visitor *v, const char *name,
@@ -84,10 +84,10 @@ void visit_start_alternate(Visitor *v, const char *name,
     }
 }
 
-void visit_end_alternate(Visitor *v)
+void visit_end_alternate(Visitor *v, void **obj)
 {
     if (v->end_alternate) {
-        v->end_alternate(v);
+        v->end_alternate(v, obj);
     }
 }
 

qemu/qapi/qmp-input-visitor.c

@@ -25,6 +25,7 @@
 typedef struct StackObject
 {
     QObject *obj; /* Object being visited */
+    void *qapi; /* sanity check that caller uses same pointer */
 
     GHashTable *h;           /* If obj is dict: unvisited keys */
     const QListEntry *entry; /* If obj is list: unvisited tail */
@@ -95,7 +96,7 @@ static void qdict_add_key(const char *key, QObject *obj, void *opaque)
 }
 
 static const QListEntry *qmp_input_push(QmpInputVisitor *qiv, QObject *obj,
-                                        Error **errp)
+                                        void *qapi, Error **errp)
 {
     GHashTable *h;
     StackObject *tos = &qiv->stack[qiv->nb_stack];
@@ -107,6 +108,7 @@ static const QListEntry *qmp_input_push(QmpInputVisitor *qiv, QObject *obj,
     }
 
     tos->obj = obj;
+    tos->qapi = qapi;
     assert(!tos->h);
     assert(!tos->entry);
 
@@ -148,12 +150,13 @@ static void qmp_input_check_struct(Visitor *v, Error **errp)
     }
 }
 
-static void qmp_input_pop(Visitor *v)
+static void qmp_input_pop(Visitor *v, void **obj)
 {
     QmpInputVisitor *qiv = to_qiv(v);
     StackObject *tos = &qiv->stack[qiv->nb_stack - 1];
 
     assert(qiv->nb_stack > 0);
+    assert(tos->qapi == obj);
 
     if (qiv->strict) {
         GHashTable * const top_ht = qiv->stack[qiv->nb_stack - 1].h;
@@ -182,7 +185,7 @@ static void qmp_input_start_struct(Visitor *v, const char *name, void **obj,
         return;
     }
 
-    qmp_input_push(qiv, qobj, &err);
+    qmp_input_push(qiv, qobj, obj, &err);
     if (err) {
         error_propagate(errp, err);
         return;
@@ -209,7 +212,7 @@ static void qmp_input_start_list(Visitor *v, const char *name,
         return;
     }
 
-    entry = qmp_input_push(qiv, qobj, errp);
+    entry = qmp_input_push(qiv, qobj, list, errp);
     if (list) {
         if (entry) {
             *list = g_malloc0(size);

qemu/qapi/qmp-output-visitor.c

@@ -23,6 +23,7 @@
 typedef struct QStackEntry
 {
     QObject *value;
+    void *qapi; /* sanity check that caller uses same pointer */
     QTAILQ_ENTRY(QStackEntry) node;
 } QStackEntry;
 
@@ -37,7 +38,8 @@ struct QmpOutputVisitor
 
 #define qmp_output_add(qov, name, value) \
     qmp_output_add_obj(qov, name, QOBJECT(value))
-#define qmp_output_push(qov, value) qmp_output_push_obj(qov, QOBJECT(value))
+#define qmp_output_push(qov, value, qapi) \
+    qmp_output_push_obj(qov, QOBJECT(value), qapi)
 
 static QmpOutputVisitor *to_qov(Visitor *v)
 {
@@ -45,23 +47,26 @@ static QmpOutputVisitor *to_qov(Visitor *v)
 }
 
 /* Push @value onto the stack of current QObjects being built */
-static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value)
+static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value,
+                                void *qapi)
 {
     QStackEntry *e = g_malloc0(sizeof(*e));
 
     assert(qov->root);
     assert(value);
     e->value = value;
+    e->qapi = qapi;
     QTAILQ_INSERT_HEAD(&qov->stack, e, node);
 }
 
 /* Pop a value off the stack of QObjects being built, and return it. */
-static QObject *qmp_output_pop(QmpOutputVisitor *qov)
+static QObject *qmp_output_pop(QmpOutputVisitor *qov, void *qapi)
 {
     QStackEntry *e = QTAILQ_FIRST(&qov->stack);
     QObject *value;
 
     assert(e);
+    assert(e->qapi == qapi);
     QTAILQ_REMOVE(&qov->stack, e, node);
     value = e->value;
     assert(value);
@@ -105,13 +110,13 @@ static void qmp_output_start_struct(Visitor *v, const char *name, void **obj,
     QDict *dict = qdict_new();
 
     qmp_output_add(qov, name, dict);
-    qmp_output_push(qov, dict);
+    qmp_output_push(qov, dict, obj);
 }
 
-static void qmp_output_end_struct(Visitor *v)
+static void qmp_output_end_struct(Visitor *v, void **obj)
 {
     QmpOutputVisitor *qov = to_qov(v);
-    QObject *value = qmp_output_pop(qov);
+    QObject *value = qmp_output_pop(qov, obj);
     assert(qobject_type(value) == QTYPE_QDICT);
 }
 
@@ -123,7 +128,7 @@ static void qmp_output_start_list(Visitor *v, const char *name,
     QList *list = qlist_new();
 
     qmp_output_add(qov, name, list);
-    qmp_output_push(qov, list);
+    qmp_output_push(qov, list, listp);
 }
 
 static GenericList *qmp_output_next_list(Visitor *v, GenericList *tail,
@@ -132,10 +137,10 @@ static GenericList *qmp_output_next_list(Visitor *v, GenericList *tail,
     return tail->next;
 }
 
-static void qmp_output_end_list(Visitor *v)
+static void qmp_output_end_list(Visitor *v, void **obj)
 {
     QmpOutputVisitor *qov = to_qov(v);
-    QObject *value = qmp_output_pop(qov);
+    QObject *value = qmp_output_pop(qov, obj);
     assert(qobject_type(value) == QTYPE_QLIST);
 }
 

qemu/qapi/string-input-visitor.c

@@ -30,6 +30,7 @@ struct StringInputVisitor
     int64_t cur;
 
     const char *string;
+    void *list; /* Only needed for sanity checking the caller */
 };
 
 static StringInputVisitor *to_siv(Visitor *v)
@@ -120,6 +121,7 @@ start_list(Visitor *v, const char *name, GenericList **list, size_t size,
 
     /* We don't support visits without a list */
     assert(list);
+    siv->list = list;
 
     if (parse_str(siv, name, errp) < 0) {
         *list = NULL;
@@ -168,8 +170,11 @@ static GenericList *next_list(Visitor *v, GenericList *tail, size_t size)
     return tail->next;
 }
 
-static void end_list(Visitor *v)
+static void end_list(Visitor *v, void **obj)
 {
+    StringInputVisitor *siv = to_siv(v);
+
+    assert(siv->list == obj);
 }
 
 static void parse_type_int64(Visitor *v, const char *name, int64_t *obj,

qemu/scripts/qapi-event.py

@@ -101,7 +101,7 @@ def gen_event_send(name, arg_type):
     if (!err) {
         visit_check_struct(v, &err);
     }
-    visit_end_struct(v);
+    visit_end_struct(v, NULL);
     if (err) {
         goto out;
     }

qemu/scripts/qapi-visit.py

@@ -129,7 +129,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
 
     error_propagate(errp, err);
     err = NULL;
-    visit_end_list(v);
+    visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_%(c_name)s(*obj);
         *obj = NULL;
@@ -194,7 +194,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
         if (!err) {
             visit_check_struct(v, &err);
         }
-        visit_end_struct(v);
+        visit_end_struct(v, NULL);
 ''',
                          c_type=var.type.c_name(),
                          c_name=c_name(var.name))
@@ -216,7 +216,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
                    "%(name)s");
     }
 out_obj:
-    visit_end_alternate(v);
+    visit_end_alternate(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_%(c_name)s(*obj);
         *obj = NULL;
@@ -250,7 +250,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
     }
     visit_check_struct(v, &err);
 out_obj:
-    visit_end_struct(v);
+    visit_end_struct(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_%(c_name)s(*obj);
         *obj = NULL;