From a38a283fc707b404544c491e32c4adc94e4788c6 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Fri, 29 Jan 2016 06:49:00 -0700 Subject: qmp: Fix reference-counting of qnull on empty output visit Commit 6c2f9a15 ensured that we would not return NULL when the caller used an output visitor but had nothing to visit. But in doing so, it added a FIXME about a reference count leak that could abort qemu in the (unlikely) case of SIZE_MAX such visits (more plausible on 32-bit). (Although that commit suggested we might fix it in time for 2.5, we ran out of time; fortunately, it is unlikely enough to bite that it was not worth worrying about during the 2.5 release.) This fixes things by documenting the internal contracts, and explaining why the internal function can return NULL and only the public facing interface needs to worry about qnull(), thus avoiding over-referencing the qnull_ global object. It does not, however, fix the stupidity of the stack mixing up two separate pieces of information; add a FIXME to explain that issue, which will be fixed shortly in a future patch. Signed-off-by: Eric Blake Cc: qemu-stable@nongnu.org Message-Id: <1454075341-13658-25-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster (cherry picked from commit a86156401559cb4401cf9ecc704faeab6fc8bb19) Signed-off-by: Michael Roth --- tests/test-qmp-output-visitor.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'tests/test-qmp-output-visitor.c') diff --git a/tests/test-qmp-output-visitor.c b/tests/test-qmp-output-visitor.c index 0d0c859..5609bb8 100644 --- a/tests/test-qmp-output-visitor.c +++ b/tests/test-qmp-output-visitor.c @@ -461,6 +461,8 @@ 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); } -- cgit v1.1