From 7de667ed5e101d730fe54ce8a84c3d58a5d4c55c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ion=20Gazta=C3=B1aga?= <igaztanaga@gmail.com>
Date: Sun, 18 Oct 2015 21:30:10 +0200
Subject: [PATCH] Fix undefined behaviour with default casting implementations.
 Null pointers can't be dereferenced, so return a value constructed smart
 pointer in those cases.

---
 include/boost/intrusive/pointer_traits.hpp | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/include/boost/intrusive/pointer_traits.hpp b/include/boost/intrusive/pointer_traits.hpp
index 24843fd..731432b 100644
--- a/include/boost/intrusive/pointer_traits.hpp
+++ b/include/boost/intrusive/pointer_traits.hpp
@@ -223,7 +223,7 @@ struct pointer_traits
 
    template<class UPtr>
    static pointer priv_static_cast_from(boost::intrusive::detail::false_, const UPtr &uptr)
-   {  return pointer_to(*static_cast<element_type*>(to_raw_pointer(uptr)));  }
+   {  return uptr ? pointer_to(*static_cast<element_type*>(to_raw_pointer(uptr))) : pointer();  }
 
    //priv_const_cast_from
    template<class UPtr>
@@ -232,7 +232,7 @@ struct pointer_traits
 
    template<class UPtr>
    static pointer priv_const_cast_from(boost::intrusive::detail::false_, const UPtr &uptr)
-   {  return pointer_to(const_cast<element_type&>(*uptr));  }
+   {  return uptr ? pointer_to(const_cast<element_type&>(*uptr)) : pointer();  }
 
    //priv_dynamic_cast_from
    template<class UPtr>
@@ -241,15 +241,7 @@ struct pointer_traits
 
    template<class UPtr>
    static pointer priv_dynamic_cast_from(boost::intrusive::detail::false_, const UPtr &uptr)
-   {
-      element_type *p = dynamic_cast<element_type*>(&*uptr);
-     if(!p){
-        return pointer();
-     }
-     else{
-        return pointer_to(*p);
-     }
-   }
+   {  return uptr ? pointer_to(dynamic_cast<element_type&>(*uptr)) : pointer();  }
    ///@endcond
 };