Merge remote-tracking branch 'remotes/kraxel/tags/usb-20170720-pull-request' into staging

usb: Fix build with newer gcc

# gpg: Signature made Thu 20 Jul 2017 09:44:55 BST
# gpg:                using RSA key 0x4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/usb-20170720-pull-request:
  usb: Fix build with newer gcc
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/usb/bus.c

@@ -407,8 +407,10 @@ void usb_register_companion(const char *masterbus, USBPort *ports[],
 void usb_port_location(USBPort *downstream, USBPort *upstream, int portnr)
 {
     if (upstream) {
-        snprintf(downstream->path, sizeof(downstream->path), "%s.%d",
-                 upstream->path, portnr);
+        int l = snprintf(downstream->path, sizeof(downstream->path), "%s.%d",
+                         upstream->path, portnr);
+        /* Max string is nn.nn.nn.nn.nn, which fits in 16 bytes */
+        assert(l < sizeof(downstream->path));
         downstream->hubcount = upstream->hubcount + 1;
     } else {
         snprintf(downstream->path, sizeof(downstream->path), "%d", portnr);