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

[Eric Blake <eblake@redhat.com>]

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On 09/11/2015 02:43 PM, Eric Blake wrote:

>> +++ 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);
>>  }
> 
> Missing
>  qobject_decref(arg);
> 
> Ultimately, the global qnull_ starts life with refcnt 1, and after this
> test should be back to 1.  But it is coming back as 3, so even with a
> qobject_decref, that would get it back down to 2.  So we are leaking a
> reference to qnull somewhere.
> 
> I'm still investigating, and may be able to find the patch

Squash this in, and you can have:
Reviewed-by: Eric Blake <eblake@redhat.com>

diff --git i/qapi/qmp-output-visitor.c w/qapi/qmp-output-visitor.c
index 2d6083e..b96849e 100644
--- i/qapi/qmp-output-visitor.c
+++ w/qapi/qmp-output-visitor.c
@@ -66,11 +66,7 @@ static QObject *qmp_output_first(QmpOutputVisitor *qov)
 {
     QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);

-    if (!e) {
-        return qnull();
-    }
-
-    return e->value;
+    return e ? e->value : NULL;
 }

 static QObject *qmp_output_last(QmpOutputVisitor *qov)
@@ -190,6 +186,8 @@ QObject *qmp_output_get_qobject(QmpOutputVisitor *qov)
     QObject *obj = qmp_output_first(qov);
     if (obj) {
         qobject_incref(obj);
+    } else {
+        obj = qnull();
     }
     return obj;
 }
diff --git i/tests/test-qmp-output-visitor.c
w/tests/test-qmp-output-visitor.c
index 256bffd..8bd48f4 100644
--- i/tests/test-qmp-output-visitor.c
+++ w/tests/test-qmp-output-visitor.c
@@ -486,6 +486,9 @@ static void
test_visitor_out_empty(TestOutputVisitorData *data,

     arg = qmp_output_get_qobject(data->qov);
     g_assert(qobject_type(arg) == QTYPE_QNULL);
+    /* Check that qnull reference counting is sane */
+    g_assert(arg->refcnt == 2);
+    qobject_decref(arg);
 }

 static void init_native_list(UserDefNativeListUnion *cvalue)


-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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