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[Qemu-devel] [PATCH v8 23/35] qmp: Tighten output visitor rules
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH v8 23/35] qmp: Tighten output visitor rules |
Date: |
Mon, 21 Dec 2015 10:08:28 -0700 |
Add a new qmp_output_visitor_reset(), which must be called before
reusing an exising QmpOutputVisitor on a new root object. Tighten
assertions to require that qmp_output_get_qobject() can only be
called after pairing a visit_end_* for every visit_start_* (rather
than allowing it to return a partially built object), that it must
not 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), and that it may only be called once per visit.
To keep the semantics of test_visitor_out_empty, we now have to
explicitly request a top-level visit of a NULL object, by
implementing the just-added visitor type_null() callback.
Signed-off-by: Eric Blake <address@hidden>
---
v8: rename qmp_output_reset to qmp_output_visitor_reset
v7: new patch, based on discussion about spapr_drc.c
---
include/qapi/qmp-output-visitor.h | 1 +
include/qapi/visitor-impl.h | 2 +-
qapi/qmp-output-visitor.c | 37 ++++++++++++++++++++++++-------------
tests/test-qmp-output-visitor.c | 2 ++
4 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/include/qapi/qmp-output-visitor.h
b/include/qapi/qmp-output-visitor.h
index 2266770..5093f0d 100644
--- a/include/qapi/qmp-output-visitor.h
+++ b/include/qapi/qmp-output-visitor.h
@@ -21,6 +21,7 @@ typedef struct QmpOutputVisitor QmpOutputVisitor;
QmpOutputVisitor *qmp_output_visitor_new(void);
void qmp_output_visitor_cleanup(QmpOutputVisitor *v);
+void qmp_output_visitor_reset(QmpOutputVisitor *v);
QObject *qmp_output_get_qobject(QmpOutputVisitor *v);
Visitor *qmp_output_get_visitor(QmpOutputVisitor *v);
diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index d301901..ed2934b 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -76,7 +76,7 @@ struct Visitor
void (*type_any)(Visitor *v, const char *name, QObject **obj,
Error **errp);
/* Must be provided to visit explicit null values (right now, only the
- * dealloc visitor supports this). */
+ * dealloc and qmp-output visitors support this). */
void (*type_null)(Visitor *v, const char *name, Error **errp);
/* May be NULL; most useful for input visitors. */
diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index df22999..f2c39c5 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -1,6 +1,7 @@
/*
* Core Definitions for QAPI/QMP Command Registry
*
+ * Copyright (C) 2015 Red Hat, Inc.
* Copyright IBM, Corp. 2011
*
* Authors:
@@ -88,9 +89,8 @@ static void qmp_output_add_obj(QmpOutputVisitor *qov, const
char *name,
cur = qmp_output_last(qov);
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)) {
@@ -202,18 +202,22 @@ static void qmp_output_type_any(Visitor *v, const char
*name, QObject **obj,
qmp_output_add_obj(qov, name, *obj);
}
+static void qmp_output_type_null(Visitor *v, const char *name, Error **errp)
+{
+ QmpOutputVisitor *qov = to_qov(v);
+ qmp_output_add_obj(qov, name, qnull());
+}
+
/* Finish building, and return the root object. Will not be NULL. */
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;
+ QObject *root;
+
+ assert(qov->root); /* A visit must have occurred... */
+ assert(!qmp_output_last(qov)); /* ...with each start paired with end. */
+ root = qov->root;
+ qov->root = NULL;
+ return root;
}
Visitor *qmp_output_get_visitor(QmpOutputVisitor *v)
@@ -221,7 +225,7 @@ Visitor *qmp_output_get_visitor(QmpOutputVisitor *v)
return &v->visitor;
}
-void qmp_output_visitor_cleanup(QmpOutputVisitor *v)
+void qmp_output_visitor_reset(QmpOutputVisitor *v)
{
QStackEntry *e, *tmp;
@@ -231,6 +235,12 @@ void qmp_output_visitor_cleanup(QmpOutputVisitor *v)
}
qobject_decref(v->root);
+ v->root = NULL;
+}
+
+void qmp_output_visitor_cleanup(QmpOutputVisitor *v)
+{
+ qmp_output_visitor_reset(v);
g_free(v);
}
@@ -252,6 +262,7 @@ QmpOutputVisitor *qmp_output_visitor_new(void)
v->visitor.type_str = qmp_output_type_str;
v->visitor.type_number = qmp_output_type_number;
v->visitor.type_any = qmp_output_type_any;
+ v->visitor.type_null = qmp_output_type_null;
QTAILQ_INIT(&v->stack);
diff --git a/tests/test-qmp-output-visitor.c b/tests/test-qmp-output-visitor.c
index 26dc752..74d0ac4 100644
--- a/tests/test-qmp-output-visitor.c
+++ b/tests/test-qmp-output-visitor.c
@@ -260,6 +260,7 @@ static void
test_visitor_out_struct_errors(TestOutputVisitorData *data,
visit_type_UserDefOne(data->ov, "unused", &pu, &err);
g_assert(err);
error_free(err);
+ qmp_output_visitor_reset(data->qov);
}
}
@@ -459,6 +460,7 @@ static void test_visitor_out_empty(TestOutputVisitorData
*data,
{
QObject *arg;
+ visit_type_null(data->ov, NULL, &error_abort);
arg = qmp_output_get_qobject(data->qov);
g_assert(qobject_type(arg) == QTYPE_QNULL);
/* Check that qnull reference counting is sane */
--
2.4.3
- [Qemu-devel] [PATCH v8 22/35] qapi: Add visit_type_null() visitor, (continued)
- [Qemu-devel] [PATCH v8 22/35] qapi: Add visit_type_null() visitor, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 25/35] qapi: Simplify excess input reporting in input visitors, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 19/35] qmp: Fix reference-counting of qnull on empty output visit, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 21/35] qapi: Document visitor interfaces, add assertions, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 28/35] qapi: Eliminate empty visit_type_FOO_fields, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 24/35] spapr_drc: Expose 'null' in qom-get when there is no fdt, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 31/35] qapi: Rework deallocation of partial struct, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 34/35] qapi: Change visit_type_FOO() to no longer return partial objects, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 32/35] qapi: Split visit_end_struct() into pieces, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 35/35] RFC: qapi: Adjust layout of FooList types, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 23/35] qmp: Tighten output visitor rules,
Eric Blake <=
- [Qemu-devel] [PATCH v8 33/35] qapi: Simplify semantics of visit_next_list(), Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 16/35] qapi: Swap 'name' in visit_* callbacks to match public API, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 30/35] qapi-visit: Unify struct and union visit, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 26/35] qapi: Add type.is_empty() helper, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 29/35] qapi: Canonicalize missing object to :empty, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 15/35] qom: Swap 'name' next to visitor in ObjectPropertyAccessor, Eric Blake, 2015/12/21
- [Qemu-devel] [PATCH v8 14/35] qapi: Swap visit_* arguments for consistent 'name' placement, Eric Blake, 2015/12/21