diff -pru include/boost/thread/win32/shared_mutex.hpp /mnt/misc/win64/mingw64-x-boost/boost_1_63_0/boost/thread/win32/shared_mutex.hpp
--- a/boost/thread/win32/shared_mutex.hpp	2017-01-19 10:36:42.848867811 -0200
+++ b/boost/thread/win32/shared_mutex.hpp	2017-01-19 12:25:48.782753800 -0200
@@ -27,18 +27,20 @@ namespace boost
     class shared_mutex
     {
     private:
-        struct state_data
+        union state_data
         {
-            unsigned shared_count:11,
-                shared_waiting:11,
-                exclusive:1,
-                upgrade:1,
-                exclusive_waiting:7,
-                exclusive_waiting_blocked:1;
-
+            struct {
+                unsigned shared_count:11,
+                    shared_waiting:11,
+                    exclusive:1,
+                    upgrade:1,
+                    exclusive_waiting:7,
+                    exclusive_waiting_blocked:1;
+            };
+            long sd_alias;
             friend bool operator==(state_data const& lhs,state_data const& rhs)
             {
-                return *reinterpret_cast<unsigned const*>(&lhs)==*reinterpret_cast<unsigned const*>(&rhs);
+                return lhs.sd_alias == rhs.sd_alias;
             }
         };