qapi: Make input visitors detect unvisited list tails

Fix the design flaw demonstrated in the previous commit: new method
check_list() lets input visitors report that unvisited input remains
for a list, exactly like check_struct() lets them report that
unvisited input remains for a struct or union.

Implement the method for the qobject input visitor (straightforward),
and the string input visitor (less so, due to the magic list syntax
there).  The opts visitor's list magic is even more impenetrable, and
all I can do there today is a stub with a FIXME comment.  No worse
than before.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1488544368-30622-26-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

hw/ppc/spapr_drc.c

@@ -326,7 +326,12 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name,
                     return;
                 }
             }
+            visit_check_list(v, &err);
             visit_end_list(v, NULL);
+            if (err) {
+                error_propagate(errp, err);
+                return;
+            }
             break;
         }
         default:

include/qapi/visitor-impl.h

@@ -61,6 +61,9 @@ struct Visitor
     /* Must be set */
     GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size);
 
+    /* Optional; intended for input visitors */
+    void (*check_list)(Visitor *v, Error **errp);
+
     /* Must be set */
     void (*end_list)(Visitor *v, void **list);
 

include/qapi/visitor.h

@@ -369,6 +369,19 @@ void visit_start_list(Visitor *v, const char *name, GenericList **list,
  */
 GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size);
 
+/*
+ * Prepare for completing a list visit.
+ *
+ * @errp obeys typical error usage, and reports failures such as
+ * unvisited list tail remaining in the input stream.
+ *
+ * Should be called prior to visit_end_list() if all other
+ * intermediate visit steps were successful, to allow the visitor one
+ * last chance to report errors.  May be skipped on a cleanup path,
+ * where there is no need to check for further errors.
+ */
+void visit_check_list(Visitor *v, Error **errp);
+
 /*
  * Complete a list visit started earlier.
  *

qapi/opts-visitor.c

@@ -272,6 +272,16 @@ opts_next_list(Visitor *v, GenericList *tail, size_t size)
 }
 
 
+static void
+opts_check_list(Visitor *v, Error **errp)
+{
+    /*
+     * FIXME should set error when unvisited elements remain.  Mostly
+     * harmless, as the generated visits always visit all elements.
+     */
+}
+
+
 static void
 opts_end_list(Visitor *v, void **obj)
 {
@@ -539,6 +549,7 @@ opts_visitor_new(const QemuOpts *opts)
 
     ov->visitor.start_list = &opts_start_list;
     ov->visitor.next_list  = &opts_next_list;
+    ov->visitor.check_list = &opts_check_list;
     ov->visitor.end_list   = &opts_end_list;
 
     ov->visitor.type_int64  = &opts_type_int64;

qapi/qapi-visit-core.c

@@ -90,6 +90,14 @@ GenericList *visit_next_list(Visitor *v, GenericList *tail, size_t size)
     return v->next_list(v, tail, size);
 }
 
+void visit_check_list(Visitor *v, Error **errp)
+{
+    trace_visit_check_list(v);
+    if (v->check_list) {
+        v->check_list(v, errp);
+    }
+}
+
 void visit_end_list(Visitor *v, void **obj)
 {
     trace_visit_end_list(v, obj);

qapi/qobject-input-visitor.c

@@ -51,7 +51,8 @@ static QObjectInputVisitor *to_qiv(Visitor *v)
     return container_of(v, QObjectInputVisitor, visitor);
 }
 
-static const char *full_name(QObjectInputVisitor *qiv, const char *name)
+static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
+                                 int n)
 {
     StackObject *so;
     char buf[32];
@@ -63,8 +64,10 @@ static const char *full_name(QObjectInputVisitor *qiv, const char *name)
     }
 
     QSLIST_FOREACH(so , &qiv->stack, node) {
-        if (qobject_type(so->obj) == QTYPE_QDICT) {
-            g_string_prepend(qiv->errname, name);
+        if (n) {
+            n--;
+        } else if (qobject_type(so->obj) == QTYPE_QDICT) {
+            g_string_prepend(qiv->errname, name ?: "<anonymous>");
             g_string_prepend_c(qiv->errname, '.');
         } else {
             snprintf(buf, sizeof(buf), "[%u]", so->index);
@@ -72,18 +75,24 @@ static const char *full_name(QObjectInputVisitor *qiv, const char *name)
         }
         name = so->name;
     }
+    assert(!n);
 
     if (name) {
         g_string_prepend(qiv->errname, name);
     } else if (qiv->errname->str[0] == '.') {
         g_string_erase(qiv->errname, 0, 1);
-    } else {
+    } else if (!qiv->errname->str[0]) {
         return "<anonymous>";
     }
 
     return qiv->errname->str;
 }
 
+static const char *full_name(QObjectInputVisitor *qiv, const char *name)
+{
+    return full_name_nth(qiv, name, 0);
+}
+
 static QObject *qobject_input_try_get_object(QObjectInputVisitor *qiv,
                                              const char *name,
                                              bool consume)
@@ -260,15 +269,30 @@ static GenericList *qobject_input_next_list(Visitor *v, GenericList *tail,
                                             size_t size)
 {
     QObjectInputVisitor *qiv = to_qiv(v);
-    StackObject *so = QSLIST_FIRST(&qiv->stack);
+    StackObject *tos = QSLIST_FIRST(&qiv->stack);
+
+    assert(tos && tos->obj && qobject_type(tos->obj) == QTYPE_QLIST);
 
-    if (!so->entry) {
+    if (!tos->entry) {
         return NULL;
     }
     tail->next = g_malloc0(size);
     return tail->next;
 }
 
+static void qobject_input_check_list(Visitor *v, Error **errp)
+{
+    QObjectInputVisitor *qiv = to_qiv(v);
+    StackObject *tos = QSLIST_FIRST(&qiv->stack);
+
+    assert(tos && tos->obj && qobject_type(tos->obj) == QTYPE_QLIST);
+
+    if (tos->entry) {
+        error_setg(errp, "Only %u list elements expected in %s",
+                   tos->index + 1, full_name_nth(qiv, NULL, 1));
+    }
+}
+
 
 static void qobject_input_start_alternate(Visitor *v, const char *name,
                                           GenericAlternate **obj, size_t size,
@@ -471,6 +495,7 @@ Visitor *qobject_input_visitor_new(QObject *obj)
     v->visitor.end_struct = qobject_input_pop;
     v->visitor.start_list = qobject_input_start_list;
     v->visitor.next_list = qobject_input_next_list;
+    v->visitor.check_list = qobject_input_check_list;
     v->visitor.end_list = qobject_input_pop;
     v->visitor.start_alternate = qobject_input_start_alternate;
     v->visitor.type_int64 = qobject_input_type_int64;

qapi/string-input-visitor.c

@@ -170,6 +170,35 @@ static GenericList *next_list(Visitor *v, GenericList *tail, size_t size)
     return tail->next;
 }
 
+static void check_list(Visitor *v, Error **errp)
+{
+    const StringInputVisitor *siv = to_siv(v);
+    Range *r;
+    GList *cur_range;
+
+    if (!siv->ranges || !siv->cur_range) {
+        return;
+    }
+
+    r = siv->cur_range->data;
+    if (!r) {
+        return;
+    }
+
+    if (!range_contains(r, siv->cur)) {
+        cur_range = g_list_next(siv->cur_range);
+        if (!cur_range) {
+            return;
+        }
+        r = cur_range->data;
+        if (!r) {
+            return;
+        }
+    }
+
+    error_setg(errp, "Range contains too many values");
+}
+
 static void end_list(Visitor *v, void **obj)
 {
     StringInputVisitor *siv = to_siv(v);
@@ -318,6 +347,7 @@ Visitor *string_input_visitor_new(const char *str)
     v->visitor.type_number = parse_type_number;
     v->visitor.start_list = start_list;
     v->visitor.next_list = next_list;
+    v->visitor.check_list = check_list;
     v->visitor.end_list = end_list;
     v->visitor.free = string_input_free;
 

qapi/trace-events

@@ -8,6 +8,7 @@ visit_end_struct(void *v, void *obj) "v=%p obj=%p"
 
 visit_start_list(void *v, const char *name, void *obj, size_t size) "v=%p name=%s obj=%p size=%zu"
 visit_next_list(void *v, void *tail, size_t size) "v=%p tail=%p size=%zu"
+visit_check_list(void *v) "v=%p"
 visit_end_list(void *v, void *obj) "v=%p obj=%p"
 
 visit_start_alternate(void *v, const char *name, void *obj, size_t size, bool promote_int) "v=%p name=%s obj=%p size=%zu promote_int=%d"

scripts/qapi-visit.py

@@ -133,6 +133,9 @@ def gen_visit_list(name, element_type):
         }
     }
 
+    if (!err) {
+        visit_check_list(v, &err);
+    }
     visit_end_list(v, (void **)obj);
     if (err && visit_is_input(v)) {
         qapi_free_%(c_name)s(*obj);

tests/test-opts-visitor.c

@@ -199,8 +199,8 @@ test_opts_range_unvisited(void)
     g_assert_cmpint(tail->value, ==, 1);
     tail = (intList *)visit_next_list(v, (GenericList *)tail, sizeof(*list));
     g_assert(tail);
+    visit_check_list(v, &error_abort); /* BUG: unvisited tail not reported */
     visit_end_list(v, (void **)&list);
-    /* BUG: unvisited tail not reported; actually not reportable by design */
 
     visit_check_struct(v, &error_abort);
     visit_end_struct(v, NULL);

tests/test-qobject-input-visitor.c

@@ -933,6 +933,7 @@ static void test_visitor_in_fail_list(TestInputVisitorData *data,
                                       const void *unused)
 {
     int64_t i64 = -1;
+    Error *err = NULL;
     Visitor *v;
 
     /* Unvisited list tail */
@@ -944,14 +945,16 @@ static void test_visitor_in_fail_list(TestInputVisitorData *data,
     g_assert_cmpint(i64, ==, 1);
     visit_type_int(v, NULL, &i64, &error_abort);
     g_assert_cmpint(i64, ==, 2);
+    visit_check_list(v, &err);
+    error_free_or_abort(&err);
     visit_end_list(v, NULL);
-    /* BUG: unvisited tail not reported; actually not reportable by design */
 }
 
 static void test_visitor_in_fail_list_nested(TestInputVisitorData *data,
                                              const void *unused)
 {
     int64_t i64 = -1;
+    Error *err = NULL;
     Visitor *v;
 
     /* Unvisited nested list tail */
@@ -964,8 +967,10 @@ static void test_visitor_in_fail_list_nested(TestInputVisitorData *data,
     visit_start_list(v, NULL, NULL, 0, &error_abort);
     visit_type_int(v, NULL, &i64, &error_abort);
     g_assert_cmpint(i64, ==, 1);
+    visit_check_list(v, &err);
+    error_free_or_abort(&err);
     visit_end_list(v, NULL);
-    /* BUG: unvisited tail not reported; actually not reportable by design */
+    visit_check_list(v, &error_abort);
     visit_end_list(v, NULL);
 }
 

tests/test-string-input-visitor.c

@@ -169,8 +169,10 @@ static void test_visitor_in_intList(TestInputVisitorData *data,
     g_assert_cmpint(tail->value, ==, 2);
     tail = (int64List *)visit_next_list(v, (GenericList *)tail, sizeof(*res));
     g_assert(tail);
+
+    visit_check_list(v, &err);
+    error_free_or_abort(&err);
     visit_end_list(v, (void **)&res);
-    /* BUG: unvisited tail not reported; actually not reportable by design */
 
     qapi_free_int64List(res);
 }