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qmp: Tighten output visitor rules

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Tighten assertions in the QMP output visitor, so that:

- qmp_output_get_qobject() can only be called after pairing a
visit_end_* for every visit_start_* (rather than allowing it on
a partially built object)

- qmp_output_get_qobject() cannot be called unless at least one
visit_type_* or visit_start/visit_end pair has occurred since
creation/reset (the accidental return of NULL fixed by commit
ab8bf1d7 would have been much easier to diagnose)

- ensure that we are encountering the expected object or list
type, to provide protection against mismatched push(struct)/
pop(list) or push(list)/pop(struct), similar to the qmp-input
protection added in commit bdd8e6b5.

- ensure that except for the root, 'name' is non-null inside a
dict, and NULL inside a list (this may need changing later if
we add "name.0" support for better error messages for a list,
but for now it makes sure all users are at least consistent)

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-19-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
Eric Blake 2016-04-28 15:45:26 -06:00 committed by Markus Armbruster
parent f2ff429bfa
commit 56a6f02b8c
1 changed files with 15 additions and 15 deletions
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30
qapi/qmp-output-visitor.c
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@ -82,9 +82,8 @@ static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name,
QObject *cur = e ? e->value : NULL;
if (!cur) {
/* FIXME we should require the user to reset the visitor, rather
* than throwing away the previous root */
qobject_decref(qov->root);
/* Don't allow reuse of visitor on more than one root */
assert(!qov->root);
qov->root = value;
} else {
switch (qobject_type(cur)) {
@ -93,6 +92,7 @@ static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name,
qdict_put_obj(qobject_to_qdict(cur), name, value);
break;
case QTYPE_QLIST:
assert(!name);
qlist_append_obj(qobject_to_qlist(cur), value);
break;
default:
@ -114,7 +114,8 @@ static void qmp_output_start_struct(Visitor *v, const char *name, void **obj,
static void qmp_output_end_struct(Visitor *v, Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
qmp_output_pop(qov);
QObject *value = qmp_output_pop(qov);
assert(qobject_type(value) == QTYPE_QDICT);
}
static void qmp_output_start_list(Visitor *v, const char *name, Error **errp)
@ -145,7 +146,8 @@ static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp,
static void qmp_output_end_list(Visitor *v)
{
QmpOutputVisitor *qov = to_qov(v);
qmp_output_pop(qov);
QObject *value = qmp_output_pop(qov);
assert(qobject_type(value) == QTYPE_QLIST);
}
static void qmp_output_type_int64(Visitor *v, const char *name, int64_t *obj,
@ -202,18 +204,16 @@ static void qmp_output_type_null(Visitor *v, const char *name, Error **errp)
qmp_output_add_obj(qov, name, qnull());
}
/* Finish building, and return the root object. Will not be NULL. */
/* Finish building, and return the root object.
* The root object is never null. The caller becomes the object's
* owner, and should use qobject_decref() when done with it. */
QObject *qmp_output_get_qobject(QmpOutputVisitor *qov)
{
/* FIXME: we should require that a visit occurred, and that it is
* complete (no starts without a matching end) */
QObject *obj = qov->root;
if (obj) {
qobject_incref(obj);
} else {
obj = qnull();
}
return obj;
/* A visit must have occurred, with each start paired with end. */
assert(qov->root && QTAILQ_EMPTY(&qov->stack));
qobject_incref(qov->root);
return qov->root;
}
Visitor *qmp_output_get_visitor(QmpOutputVisitor *v)