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[Qemu-devel] [PATCH v7 20/26] qapi: Make output visitor return qnull() i
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] [PATCH v7 20/26] qapi: Make output visitor return qnull() instead of NULL |
Date: |
Mon, 14 Sep 2015 19:57:51 +0200 |
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, failing "make check".
Commit 481b002 solved a very similar problem by introducing a special
null QObject. Using this special null QObject is clearly the right
way to resolve this FIXME, so do that, and update the test
accordingly.
However, the patch isn't quite right: it messes up the reference
counting. After about SIZE_MAX visits, the reference counter
overflows, failing the assertion in qnull_destroy_obj(). Because
that's many orders of magnitude more visits of nulls than we expect,
we take this patch despite its flaws, to get the QMP introspection
stuff in without further delay.
Naturally, we'll have to fix it for real before the release.
Signed-off-by: Markus Armbruster <address@hidden>
---
qapi/qmp-output-visitor.c | 8 ++++++--
tests/test-qmp-output-visitor.c | 3 ++-
2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index efc19d5..8dce087 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -66,9 +66,13 @@ static QObject *qmp_output_first(QmpOutputVisitor *qov)
{
QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);
- /* FIXME - find a better way to deal with NULL values */
+ /*
+ * FIXME Wrong, because qmp_output_get_qobject() will increment
+ * the refcnt *again*. We need to think through how visitors
+ * handle null.
+ */
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..a48ae72 100644
--- a/tests/test-qmp-output-visitor.c
+++ b/tests/test-qmp-output-visitor.c
@@ -485,7 +485,8 @@ 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);
+ qobject_decref(arg);
}
static void init_native_list(UserDefNativeListUnion *cvalue)
--
2.4.3
- Re: [Qemu-devel] [PATCH v7 14/26] qapi-visit: Rearrange code a bit, (continued)
- [Qemu-devel] [PATCH v7 02/26] qapi: New QAPISchema intermediate reperesentation, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 09/26] qapi: De-duplicate enum code generation, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 08/26] qapi-commands: Convert to QAPISchemaVisitor, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 12/26] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 11/26] qapi-event: Convert to QAPISchemaVisitor, fixing data with base, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 19/26] qapi: Improve built-in type documentation, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 20/26] qapi: Make output visitor return qnull() instead of NULL,
Markus Armbruster <=
- [Qemu-devel] [PATCH v7 23/26] qapi-schema: Fix up misleading specification of netdev_add, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 17/26] qapi: De-duplicate parameter list generation, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 05/26] tests/qapi-schema: Convert test harness to QAPISchemaVisitor, Markus Armbruster, 2015/09/14
- [Qemu-devel] [PATCH v7 10/26] qapi-event: Eliminate global variable event_enum_value, Markus Armbruster, 2015/09/14