From: Michael R. Crusoe <crusoe@debian.org>
Subject: Make explicit cast to bool
--- a/src/common/func/pred.hpp
+++ b/src/common/func/pred.hpp
@@ -40,7 +40,7 @@
                 : data_(std::move(p)) { }
 
         virtual bool operator()(T x) const override {
-            return data_(x);
+            return (bool) data_(x);
         }
 
         P data_;
