From 47c1c6288ccd4a92fbb6f856ddf484640897c094 Mon Sep 17 00:00:00 2001
From: Dave Abrahams <dave@boostpro.com>
Date: Wed, 20 Feb 2002 05:14:41 +0000
Subject: [PATCH] Added error checking

[SVN r12862]
---
 .../python/return_internal_reference.hpp      | 20 ++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/include/boost/python/return_internal_reference.hpp b/include/boost/python/return_internal_reference.hpp
index 2f567e55..356bc9ed 100644
--- a/include/boost/python/return_internal_reference.hpp
+++ b/include/boost/python/return_internal_reference.hpp
@@ -9,14 +9,32 @@
 # include <boost/python/default_call_policies.hpp>
 # include <boost/python/reference_existing_object.hpp>
 # include <boost/python/with_custodian_and_ward.hpp>
+# include <boost/mpl/select_type.hpp>
 
 namespace boost { namespace python { 
 
+namespace detail
+{
+  template <std::size_t>
+  struct return_internal_reference_owner_arg_must_be_greater_than_zero
+# if defined(__GNUC__) && __GNUC__ >= 3 || defined(__EDG__)
+  {}
+# endif
+  ;
+}
+
 template <std::size_t owner_arg = 1, class Base = default_call_policies>
 struct return_internal_reference
     : with_custodian_and_ward_postcall<0, owner_arg, Base>
 {
-    typedef reference_existing_object result_converter;
+ private:
+    BOOST_STATIC_CONSTANT(bool, legal = owner_arg > 0);
+ public:
+    typedef typename mpl::select_type<
+        legal
+        , reference_existing_object
+        , detail::return_internal_reference_owner_arg_must_be_greater_than_zero<owner_arg>
+    >::type result_converter;
 };
 
 }} // namespace boost::python