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.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-4-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

7 files changed, 42 insertions, 67 deletions

diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
index 4cf1cf8..dcfbf92 100644
--- a/qapi/opts-visitor.c
+++ b/qapi/opts-visitor.c
@@ -180,7 +180,7 @@ opts_check_struct(Visitor *v, Error **errp)
 
 
 static void
-opts_end_struct(Visitor *v)
+opts_end_struct(Visitor *v, void **obj)
 {
     OptsVisitor *ov = to_ov(v);
 
@@ -273,7 +273,7 @@ opts_next_list(Visitor *v, GenericList *tail, size_t size)
 
 
 static void
-opts_end_list(Visitor *v)
+opts_end_list(Visitor *v, void **obj)
 {
     OptsVisitor *ov = to_ov(v);
 
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index cd68b55..9391dea 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -19,53 +19,18 @@
 #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;
 };
 
-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);
     }
@@ -75,14 +40,10 @@ 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);
     }
@@ -102,7 +63,7 @@ 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)
 {
 }
 
@@ -178,7 +139,5 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
     v->visitor.type_any = qapi_dealloc_type_anything;
     v->visitor.type_null = qapi_dealloc_type_null;
 
-    QTAILQ_INIT(&v->stack);
-
     return v;
 }
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index eada467..dba11c6 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -43,9 +43,9 @@ 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,
@@ -67,9 +67,9 @@ 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,
@@ -89,10 +89,10 @@ void visit_start_alternate(Visitor *v, const char *name,
     error_propagate(errp, err);
 }
 
-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);
     }
 }
 
diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index aea90a1..e16b4b0 100644
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -26,6 +26,7 @@
 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 */
@@ -96,7 +97,7 @@ 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];
@@ -108,6 +109,7 @@ static const QListEntry *qmp_input_push(QmpInputVisitor *qiv, QObject *obj,
     }
 
     tos->obj = obj;
+    tos->qapi = qapi;
     assert(!tos->h);
     assert(!tos->entry);
 
@@ -145,12 +147,13 @@ 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;
@@ -179,7 +182,7 @@ 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;
@@ -207,7 +210,7 @@ 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);
diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index 4d3cf78..dca8935 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -22,6 +22,7 @@
 typedef struct QStackEntry
 {
     QObject *value;
+    void *qapi; /* sanity check that caller uses same pointer */
     QTAILQ_ENTRY(QStackEntry) node;
 } QStackEntry;
 
@@ -36,7 +37,8 @@ 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)
 {
@@ -44,23 +46,26 @@ 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);
@@ -104,13 +109,13 @@ 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);
 }
 
@@ -122,7 +127,7 @@ 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,
@@ -131,10 +136,10 @@ 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);
 }
 
diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
index 0690abb..d7f3c2b 100644
--- a/qapi/string-input-visitor.c
+++ b/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,
diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c
index c6f01f9..bdc0fd0 100644
--- a/qapi/string-output-visitor.c
+++ b/qapi/string-output-visitor.c
@@ -64,6 +64,7 @@ struct StringOutputVisitor
         uint64_t u;
     } range_start, range_end;
     GList *ranges;
+    void *list; /* Only needed for sanity checking the caller */
 };
 
 static StringOutputVisitor *to_sov(Visitor *v)
@@ -274,6 +275,7 @@ start_list(Visitor *v, const char *name, GenericList **list, size_t size,
     assert(sov->list_mode == LM_NONE);
     /* We don't support visits without a list */
     assert(list);
+    sov->list = list;
     /* List handling is only needed if there are at least two elements */
     if (*list && (*list)->next) {
         sov->list_mode = LM_STARTED;
@@ -291,10 +293,11 @@ static GenericList *next_list(Visitor *v, GenericList *tail, size_t size)
     return ret;
 }
 
-static void end_list(Visitor *v)
+static void end_list(Visitor *v, void **obj)
 {
     StringOutputVisitor *sov = to_sov(v);
 
+    assert(sov->list == obj);
     assert(sov->list_mode == LM_STARTED ||
            sov->list_mode == LM_END ||
            sov->list_mode == LM_NONE ||