client: Don't segfault when receiving error on destroyed object

If an error is received on a destroyed object, we'd get NULL passed
to display_handle_error() instead of a pointer to a valid wl_proxy.

The logging is changed to report [unknown interface] and [unknown id]
instead of the actual interface name and id.

The wl_display_get_protocol_error() documentation is updated to handle
the situation. For when the proxy was NULL, the object id 0 and
interface NULL is written.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
[Pekka: changed the error message wording]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Acked-by: Jonas Ådahl <jadahl@gmail.com>

diff --git a/src/wayland-client.c b/src/wayland-client.c
index ef12bfc..297c7a5 100644 (file)
--- a/src/wayland-client.c
+++ b/src/wayland-client.c
@@ -177,7 +177,7 @@ display_protocol_error(struct wl_display *display, uint32_t code,
                return;
 
        /* set correct errno */
-       if (wl_interface_equal(intf, &wl_display_interface)) {
+       if (intf && wl_interface_equal(intf, &wl_display_interface)) {
                switch (code) {
                case WL_DISPLAY_ERROR_INVALID_OBJECT:
                case WL_DISPLAY_ERROR_INVALID_METHOD:
@@ -790,12 +790,26 @@ display_handle_error(void *data,
                     uint32_t code, const char *message)
 {
        struct wl_proxy *proxy = object;
+       uint32_t object_id;
+       const struct wl_interface *interface;
 
-       wl_log("%s@%u: error %d: %s\n",
-              proxy->object.interface->name, proxy->object.id, code, message);
+       if (proxy) {
+               wl_log("%s@%u: error %d: %s\n",
+                      proxy->object.interface->name,
+                      proxy->object.id,
+                      code, message);
 
-       display_protocol_error(display, code, proxy->object.id,
-                              proxy->object.interface);
+               object_id = proxy->object.id;
+               interface = proxy->object.interface;
+       } else {
+               wl_log("[destroyed object]: error %d: %s\n",
+                      code, message);
+
+               object_id = 0;
+               interface = NULL;
+       }
+
+       display_protocol_error(display, code, object_id, interface);
 }
 
 static void
@@ -1756,10 +1770,12 @@ wl_display_get_error(struct wl_display *display)
 /** Retrieves the information about a protocol error:
  *
  * \param display    The Wayland display
- * \param interface  if not NULL, stores the interface where the error occurred
+ * \param interface  if not NULL, stores the interface where the error occurred,
+ *                   or NULL, if unknown.
  * \param id         if not NULL, stores the object id that generated
- *                   the error. There's no guarantee the object is
- *                   still valid; the client must know if it deleted the object.
+ *                   the error, or 0, if the object id is unknown. There's no
+ *                   guarantee the object is still valid; the client must know
+ *                   if it deleted the object.
  * \return           The error code as defined in the interface specification.
  *
  * \code