reference_wrapper: Include <functional>.

murraycu · murraycu · commit c21aba8a028f · 2016-03-08T11:17:47.000+01:00
diff --git a/sigc++/reference_wrapper.h b/sigc++/reference_wrapper.h
@@ -19,6 +19,8 @@
 #ifndef _SIGC_REFERENCE_WRAPPER_H_
 #define _SIGC_REFERENCE_WRAPPER_H_
 
+#include <functional> // For std::reference_wrapper.
+
 namespace sigc {
 
 #ifndef SIGCXX_DISABLE_DEPRECATED
