From 68ab47e4b4ecc1c4649362b8cc1e49794d1a6537 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 28 Apr 2016 15:45:32 -0600 Subject: qapi: Change visit_type_FOO() to no longer return partial objects Returning a partial object on error is an invitation for a careless caller to leak memory. We already fixed things in an earlier patch to guarantee NULL if visit_start fails ("qapi: Guarantee NULL obj on input visitor callback error"), but that does not help the case where visit_start succeeds but some other failure happens before visit_end, such that we leak a partially constructed object outside visit_type_FOO(). As no one outside the testsuite was actually relying on these semantics, it is cleaner to just document and guarantee that ALL pointer-based visit_type_FOO() functions always leave a safe value in *obj during an input visitor (either the new object on success, or NULL if an error is encountered), so callers can now unconditionally use qapi_free_FOO() to clean up regardless of whether an error occurred. The decision is done by adding visit_is_input(), then updating the generated code to check if additional cleanup is needed based on the type of visitor in use. Note that we still leave *obj unchanged after a scalar-based visit_type_FOO(); I did not feel like auditing all uses of visit_type_Enum() to see if the callers would tolerate a specific sentinel value (not to mention having to decide whether it would be better to use 0 or ENUM__MAX as that sentinel). Signed-off-by: Eric Blake Message-Id: <1461879932-9020-25-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- qapi/qapi-visit-core.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'qapi') diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c index d6bf4bd253..eada4676a2 100644 --- a/qapi/qapi-visit-core.c +++ b/qapi/qapi-visit-core.c @@ -104,6 +104,11 @@ bool visit_optional(Visitor *v, const char *name, bool *present) return *present; } +bool visit_is_input(Visitor *v) +{ + return v->type == VISITOR_INPUT; +} + void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp) { assert(obj); -- cgit v1.2.3