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>

1 files changed, 3 insertions, 44 deletions

diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index cd68b55a1a..9391dea203 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;
 }