[Qemu-devel] [PATCH v6 20/26] qapi: Fix output visitor to return qnull() instead of NULL

[Markus Armbruster <armbru@redhat.com>]

Before commit 1d10b44, it crashed.  Since then, it returns NULL, with
a FIXME comment.  The FIXME is valid: code that assumes QObject *
can't be null exists.  I'm not aware of a way to feed this problematic
return value to code that actually chokes on null in the current code,
but the next few commits will create one.

Commit 481b002 solved a very similar problem by introducing a special
null QObject.  Use it here, and drop the FIXME.

Update the test accordingly.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qapi/qmp-output-visitor.c       | 3 +--
 tests/test-qmp-output-visitor.c | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index efc19d5..2d6083e 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -66,9 +66,8 @@ static QObject *qmp_output_first(QmpOutputVisitor *qov)
 {
     QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);
 
-    /* FIXME - find a better way to deal with NULL values */
     if (!e) {
-        return NULL;
+        return qnull();
     }
 
     return e->value;
diff --git a/tests/test-qmp-output-visitor.c b/tests/test-qmp-output-visitor.c
index 338ada0..256bffd 100644
--- a/tests/test-qmp-output-visitor.c
+++ b/tests/test-qmp-output-visitor.c
@@ -485,7 +485,7 @@ static void test_visitor_out_empty(TestOutputVisitorData *data,
     QObject *arg;
 
     arg = qmp_output_get_qobject(data->qov);
-    g_assert(!arg);
+    g_assert(qobject_type(arg) == QTYPE_QNULL);
 }
 
 static void init_native_list(UserDefNativeListUnion *cvalue)
-- 
2.4.3