qemu/tests/check-qnull.c
Eric Blake 3b098d5697 qapi: Add new visit_complete() function
Making each output visitor provide its own output collection
function was the only remaining reason for exposing visitor
sub-types to the rest of the code base.  Add a polymorphic
visit_complete() function which is a no-op for input visitors,
and which populates an opaque pointer for output visitors.  For
maximum type-safety, also add a parameter to the output visitor
constructors with a type-correct version of the output pointer,
and assert that the two uses match.

This approach was considered superior to either passing the
output parameter only during construction (action at a distance
during visit_free() feels awkward) or only during visit_complete()
(defeating type safety makes it easier to use incorrectly).

Most callers were function-local, and therefore a mechanical
conversion; the testsuite was a bit trickier, but the previous
cleanup patch minimized the churn here.

The visit_complete() function may be called at most once; doing
so lets us use transfer semantics rather than duplication or
ref-count semantics to get the just-built output back to the
caller, even though it means our behavior is not idempotent.

Generated code is simplified as follows for events:

|@@ -26,7 +26,7 @@ void qapi_event_send_acpi_device_ost(ACP
|     QDict *qmp;
|     Error *err = NULL;
|     QMPEventFuncEmit emit;
|-    QmpOutputVisitor *qov;
|+    QObject *obj;
|     Visitor *v;
|     q_obj_ACPI_DEVICE_OST_arg param = {
|         info
|@@ -39,8 +39,7 @@ void qapi_event_send_acpi_device_ost(ACP
|
|     qmp = qmp_event_build_dict("ACPI_DEVICE_OST");
|
|-    qov = qmp_output_visitor_new();
|-    v = qmp_output_get_visitor(qov);
|+    v = qmp_output_visitor_new(&obj);
|
|     visit_start_struct(v, "ACPI_DEVICE_OST", NULL, 0, &err);
|     if (err) {
|@@ -55,7 +54,8 @@ void qapi_event_send_acpi_device_ost(ACP
|         goto out;
|     }
|
|-    qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov));
|+    visit_complete(v, &obj);
|+    qdict_put_obj(qmp, "data", obj);
|     emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err);

and for commands:

| {
|     Error *err = NULL;
|-    QmpOutputVisitor *qov = qmp_output_visitor_new();
|     Visitor *v;
|
|-    v = qmp_output_get_visitor(qov);
|+    v = qmp_output_visitor_new(ret_out);
|     visit_type_AddfdInfo(v, "unused", &ret_in, &err);
|-    if (err) {
|-        goto out;
|+    if (!err) {
|+        visit_complete(v, ret_out);
|     }
|-    *ret_out = qmp_output_get_qobject(qov);
|-
|-out:
|     error_propagate(errp, err);

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-13-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-07-06 10:52:04 +02:00

74 lines
1.6 KiB
C

/*
* QNull unit-tests.
*
* Copyright (C) 2016 Red Hat Inc.
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qapi/qmp/qobject.h"
#include "qemu-common.h"
#include "qapi/qmp-input-visitor.h"
#include "qapi/qmp-output-visitor.h"
#include "qapi/error.h"
/*
* Public Interface test-cases
*
* (with some violations to access 'private' data)
*/
static void qnull_ref_test(void)
{
QObject *obj;
g_assert(qnull_.refcnt == 1);
obj = qnull();
g_assert(obj);
g_assert(obj == &qnull_);
g_assert(qnull_.refcnt == 2);
g_assert(qobject_type(obj) == QTYPE_QNULL);
qobject_decref(obj);
g_assert(qnull_.refcnt == 1);
}
static void qnull_visit_test(void)
{
QObject *obj;
Visitor *v;
/*
* Most tests of interactions between QObject and visitors are in
* test-qmp-*-visitor; but these tests live here because they
* depend on layering violations to check qnull_ refcnt.
*/
g_assert(qnull_.refcnt == 1);
obj = qnull();
v = qmp_input_visitor_new(obj, true);
qobject_decref(obj);
visit_type_null(v, NULL, &error_abort);
visit_free(v);
v = qmp_output_visitor_new(&obj);
visit_type_null(v, NULL, &error_abort);
visit_complete(v, &obj);
g_assert(obj == &qnull_);
qobject_decref(obj);
visit_free(v);
g_assert(qnull_.refcnt == 1);
}
int main(int argc, char **argv)
{
g_test_init(&argc, &argv, NULL);
g_test_add_func("/public/qnull_ref", qnull_ref_test);
g_test_add_func("/public/qnull_visit", qnull_visit_test);
return g_test_run();
}