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authorEric Blake <eblake@redhat.com>2016-04-28 15:45:32 -0600
committerMarkus Armbruster <armbru@redhat.com>2016-05-12 09:47:55 +0200
commit68ab47e4b4ecc1c4649362b8cc1e49794d1a6537 (patch)
treec3fb21b91ab1fde06d3471e02f32f694aa18837a /qapi
parentd9f62dde1303286b24ac8ce88be27e2b9b9c5f46 (diff)
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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 <eblake@redhat.com> Message-Id: <1461879932-9020-25-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'qapi')
-rw-r--r--qapi/qapi-visit-core.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index d6bf4bd..eada467 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);