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authorEric Blake <eblake@redhat.com>2016-04-28 15:45:22 -0600
committerMarkus Armbruster <armbru@redhat.com>2016-05-12 09:47:54 +0200
commit3bc97fd5924561d92f32758c67eaffd2e4e25038 (patch)
treea544ba5f5abad205a52d6255d0560d2ee23d32ce /qapi/qapi-dealloc-visitor.c
parent7d7a337ec32c77f11ba04da412752b35e18d3c5c (diff)
qapi: Add visit_type_null() visitor
Right now, qmp-output-visitor happens to produce a QNull result if nothing is actually visited between the creation of the visitor and the request for the resulting QObject. A stronger protocol would require that a QMP output visit MUST visit something. But to still be able to produce a JSON 'null' output, we need a new visitor function that states our intentions. Yes, we could say that such a visit must go through visit_type_any(), but that feels clunky. So this patch introduces the new visit_type_null() interface and its no-op interface in the dealloc visitor, and stubs in the qmp visitors (the next patch will finish the implementation). For the visitors that will not implement the callback, document the situation. The code in qapi-visit-core unconditionally dereferences the callback pointer, so that a segfault will inform a developer if they need to implement the callback for their choice of visitor. Note that JSON has a primitive null type, with the single value null; likewise with the QNull type for QObject; but for QAPI, we just have the 'null' value without a null type. We may eventually want to add more support in QAPI for null (most likely, we'd use it via an alternate type that permits 'null' or an object); but we'll create that usage when we need it. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-15-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'qapi/qapi-dealloc-visitor.c')
-rw-r--r--qapi/qapi-dealloc-visitor.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index c19a459391..413d525ad8 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -163,6 +163,10 @@ static void qapi_dealloc_type_anything(Visitor *v, const char *name,
}
}
+static void qapi_dealloc_type_null(Visitor *v, const char *name, Error **errp)
+{
+}
+
Visitor *qapi_dealloc_get_visitor(QapiDeallocVisitor *v)
{
return &v->visitor;
@@ -193,6 +197,7 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
v->visitor.type_str = qapi_dealloc_type_str;
v->visitor.type_number = qapi_dealloc_type_number;
v->visitor.type_any = qapi_dealloc_type_anything;
+ v->visitor.type_null = qapi_dealloc_type_null;
QTAILQ_INIT(&v->stack);