qapi: Test failure in middle of array parse

Our generated list visitors have the same problem as has been
mentioned elsewhere (see commit 2f52e20): they allocate data
even on failure. An upcoming patch will correct things to
provide saner guarantees, but first we need to expose the
behavior in the testsuite to ensure we aren't introducing any
memory usage bugs.

There are more test cases throughout the test-qmp-input-* tests
that already deal with partial allocation; a later commit will
clean up all visit_type_FOO(), without marking all of the tests
with FIXME at this time.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1446791754-23823-10-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

scripts/qapi-visit.py

@@ -138,6 +138,10 @@ def gen_visit_struct(name, base, members):
 
 
 def gen_visit_list(name, element_type):
+    # FIXME: if *obj is NULL on entry, and the first visit_next_list()
+    # assigns to *obj, while a later one fails, we should clean up *obj
+    # rather than leaving it non-NULL. As currently written, the caller must
+    # call qapi_free_FOOList() to avoid a memory leak of the partial FOOList.
     return mcgen('''
 
 void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error **errp)

tests/test-qmp-input-visitor.c

@@ -698,8 +698,10 @@ static void test_visitor_in_errors(TestInputVisitorData *data,
     TestStruct *p = NULL;
     Error *err = NULL;
     Visitor *v;
+    strList *q = NULL;
 
-    v = visitor_input_test_init(data, "{ 'integer': false, 'boolean': 'foo', 'string': -42 }");
+    v = visitor_input_test_init(data, "{ 'integer': false, 'boolean': 'foo', "
+                                "'string': -42 }");
 
     visit_type_TestStruct(v, &p, NULL, &err);
     error_free_or_abort(&err);
@@ -709,6 +711,12 @@ static void test_visitor_in_errors(TestInputVisitorData *data,
 
     g_free(p->string);
     g_free(p);
+
+    v = visitor_input_test_init(data, "[ '1', '2', false, '3' ]");
+    visit_type_strList(v, &q, NULL, &err);
+    error_free_or_abort(&err);
+    assert(q);
+    qapi_free_strList(q);
 }
 
 int main(int argc, char **argv)