[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PULL 20/26] qapi: Make output visitor return qnull() inste
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] [PULL 20/26] qapi: Make output visitor return qnull() instead of NULL |
Date: |
Mon, 21 Sep 2015 10:03:54 +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. We'll want to fix it for real before
the release.
Signed-off-by: Markus Armbruster <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Daniel P. Berrange <address@hidden>
Message-Id: <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
- [Qemu-devel] [PULL 03/26] qapi: QAPISchema code generation helper methods, (continued)
- [Qemu-devel] [PULL 03/26] qapi: QAPISchema code generation helper methods, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 12/26] qapi: Replace dirty is_c_ptr() by method c_null(), Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 09/26] qapi: De-duplicate enum code generation, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 11/26] qapi-event: Convert to QAPISchemaVisitor, fixing data with base, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 08/26] qapi-commands: Convert to QAPISchemaVisitor, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 10/26] qapi-event: Eliminate global variable event_enum_value, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 14/26] qapi-visit: Rearrange code a bit, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 02/26] qapi: New QAPISchema intermediate reperesentation, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 23/26] qapi-schema: Fix up misleading specification of netdev_add, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 06/26] qapi-types: Convert to QAPISchemaVisitor, fixing flat unions, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 20/26] qapi: Make output visitor return qnull() instead of NULL,
Markus Armbruster <=
- [Qemu-devel] [PULL 18/26] qapi-commands: De-duplicate output marshaling functions, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 15/26] qapi-commands: Rearrange code, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 17/26] qapi: De-duplicate parameter list generation, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 05/26] tests/qapi-schema: Convert test harness to QAPISchemaVisitor, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 19/26] qapi: Improve built-in type documentation, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 22/26] qom: Don't use 'gen': false for qom-get, qom-set, object-add, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 26/26] qapi-introspect: Hide type names, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 24/26] qapi: Pseudo-type '**' is now unused, drop it, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 13/26] qapi: Clean up after recent conversions to QAPISchemaVisitor, Markus Armbruster, 2015/09/21
- [Qemu-devel] [PULL 07/26] qapi-visit: Convert to QAPISchemaVisitor, fixing bugs, Markus Armbruster, 2015/09/21