From f2c465ffa508459216f7093bf95ba001ad994206 Mon Sep 17 00:00:00 2001
From: vslashg <veloso@verylowsodium.com>
Date: Mon, 29 Feb 2016 13:33:35 -0500
Subject: [PATCH] Fix auto-pointer registration in Boost Python 1.60.

The conditional instantiation magic of maybe_register_pointer_to_python() assumes that use_value_holder and use_back_reference will be one of the boost::mpl::bool_ types, but this assumption is no longer true in Boost 1.60, where they can be standard library bool wrappers instead.

Explicitly defining these types as mpl::bool_ classes fixes https://github.com/boostorg/python/issues/56.
---
 boost/python/object/class_metadata.hpp | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/boost/python/object/class_metadata.hpp b/boost/python/object/class_metadata.hpp
index c71cf67..5009c17 100644
--- a/boost/python/object/class_metadata.hpp
+++ b/boost/python/object/class_metadata.hpp
@@ -164,7 +164,7 @@ struct class_metadata
     >::type held_type;
 
     // Determine if the object will be held by value
-    typedef is_convertible<held_type*,T*> use_value_holder;
+    typedef mpl::bool_<is_convertible<held_type*,T*>::value> use_value_holder;
     
     // Compute the "wrapped type", that is, if held_type is a smart
     // pointer, we're talking about the pointee.
@@ -175,10 +175,12 @@ struct class_metadata
     >::type wrapped;
 
     // Determine whether to use a "back-reference holder"
-    typedef mpl::or_<
-        has_back_reference<T>
-      , is_same<held_type_arg,T>
-      , is_base_and_derived<T,wrapped>
+    typedef mpl::bool_<
+        mpl::or_<
+            has_back_reference<T>
+          , is_same<held_type_arg,T>
+          , is_base_and_derived<T,wrapped>
+        >::value
     > use_back_reference;
 
     // Select the holder.