fix signed/unsigned issue pointed out by old apple gcc

diff --git a/libs/surfaces/mackie/mackie_control_protocol.cc b/libs/surfaces/mackie/mackie_control_protocol.cc
index 32be8512476eee7f4436621fd9c524d111837e7c..b55ac74c35179bef846cb3c21f5435e0d35d2f15 100644 (file)
--- a/libs/surfaces/mackie/mackie_control_protocol.cc
+++ b/libs/surfaces/mackie/mackie_control_protocol.cc
@@ -1382,7 +1382,7 @@ MackieControlProtocol::add_down_select_button (int surface, int strip)
 void
 MackieControlProtocol::remove_down_select_button (int surface, int strip)
 {
-       DownButtonList::iterator x = find (_down_select_buttons.begin(), _down_select_buttons.end(), (surface<<8)|(strip&0xf));
+       DownButtonList::iterator x = find (_down_select_buttons.begin(), _down_select_buttons.end(), (uint32_t) (surface<<8)|(strip&0xf));
        DEBUG_TRACE (DEBUG::MackieControl, string_compose ("removing surface %1 strip %2 from down select buttons\n", surface, strip));
        if (x != _down_select_buttons.end()) {
                _down_select_buttons.erase (x);