From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54300) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZVMn9-0008D4-AH for qemu-devel@nongnu.org; Fri, 28 Aug 2015 12:46:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZVMn6-0000K8-PS for qemu-devel@nongnu.org; Fri, 28 Aug 2015 12:46:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45127) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZVMn6-0000Jd-Ft for qemu-devel@nongnu.org; Fri, 28 Aug 2015 12:46:12 -0400 From: Markus Armbruster Date: Fri, 28 Aug 2015 18:45:54 +0200 Message-Id: <1440780366-7177-15-git-send-email-armbru@redhat.com> In-Reply-To: <1440780366-7177-1-git-send-email-armbru@redhat.com> References: <1440780366-7177-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH v2 14/26] qapi: Document that input visitor semantics are prone to leaks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: mdroth@linux.vnet.ibm.com From: Eric Blake Most functions that can return a pointer or set an Error ** value are decent enough to guarantee a NULL return when reporting an error. Not so with our generated qapi visitor functions. If the caller is not careful to clean up partially-allocated objects on error, then the caller suffers a memory leak. Properly fixing it is probably complex enough to save for a later day, so merely document it for now. Signed-off-by: Eric Blake Message-Id: <1438295587-19069-1-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- scripts/qapi-visit.py | 4 ++++ tests/test-qmp-input-visitor.c | 2 ++ 2 files changed, 6 insertions(+) diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py index 73f136f..eec5f1f 100644 --- a/scripts/qapi-visit.py +++ b/scripts/qapi-visit.py @@ -115,6 +115,10 @@ out: def generate_visit_struct_body(name): + # FIXME: if *obj is NULL on entry, and visit_start_struct() assigns to + # *obj, but then visit_type_FOO_fields() fails, we should clean up *obj + # rather than leaving it non-NULL. As currently written, the caller must + # call qapi_free_FOO() to avoid a memory leak of the partial FOO. ret = mcgen(''' Error *err = NULL; diff --git a/tests/test-qmp-input-visitor.c b/tests/test-qmp-input-visitor.c index b7a87ee..a5cfefa 100644 --- a/tests/test-qmp-input-visitor.c +++ b/tests/test-qmp-input-visitor.c @@ -636,6 +636,8 @@ static void test_visitor_in_errors(TestInputVisitorData *data, visit_type_TestStruct(v, &p, NULL, &err); g_assert(err); + /* FIXME - a failed parse should not leave a partially-allocated p + * for us to clean up; this could cause callers to leak memory. */ g_assert(p->string == NULL); error_free(err); -- 2.4.3