diff --git a/src/auto_mem.hh b/src/auto_mem.hh
index 8c50800e..a23d3b0e 100644
--- a/src/auto_mem.hh
+++ b/src/auto_mem.hh
@@ -53,9 +53,7 @@ public:
         : am_ptr(ptr), am_free_func(default_free) {
     };
 
-    auto_mem(auto_mem &am)
-        : am_ptr(am.release()), am_free_func(am.am_free_func)
-    {};
+    auto_mem(const auto_mem &am) = delete;
 
     template<typename F>
     explicit auto_mem(F free_func)
diff --git a/src/log_format.cc b/src/log_format.cc
index e47346be..c601f058 100644
--- a/src/log_format.cc
+++ b/src/log_format.cc
@@ -33,6 +33,8 @@
 #include <stdarg.h>
 #include <string.h>
 
+#include <memory>
+
 #include "base/string_util.hh"
 #include "fmt/format.h"
 #include "yajlpp/yajlpp.hh"
@@ -626,7 +628,7 @@ log_format::scan_result_t external_log_format::scan(logfile &lf,
     if (this->elf_type == ELF_TYPE_JSON) {
         yajlpp_parse_context &ypc = *(this->jlf_parse_context);
         logline ll(li.li_file_range.fr_offset, 0, 0, LEVEL_INFO);
-        yajl_handle handle = this->jlf_yajl_handle.in();
+        yajl_handle handle = this->jlf_yajl_handle.get();
         json_log_userdata jlu(sbr);
 
         if (!this->lf_specialized && dst.size() >= 3) {
@@ -1198,7 +1200,7 @@ void external_log_format::get_subline(const logline &ll, shared_buffer_ref &sbr,
     if (this->jlf_cached_offset != ll.get_offset() ||
         this->jlf_cached_full != full_message) {
         yajlpp_parse_context &ypc = *(this->jlf_parse_context);
-        yajl_handle handle = this->jlf_yajl_handle.in();
+        yajl_handle handle = this->jlf_yajl_handle.get();
         json_log_userdata jlu(sbr);
 
         this->jlf_share_manager.invalidate_refs();
@@ -1651,13 +1653,14 @@ void external_log_format::build(std::vector<std::string> &errors) {
                              ": structured logs cannot have regexes");
         }
         if (this->elf_type == ELF_TYPE_JSON) {
-            this->jlf_parse_context.reset(
-                new yajlpp_parse_context(this->elf_name.to_string()));
-            this->jlf_yajl_handle.reset(yajl_alloc(
-                &this->jlf_parse_context->ypc_callbacks,
-                NULL,
-                this->jlf_parse_context.get()));
-            yajl_config(this->jlf_yajl_handle.in(), yajl_dont_validate_strings,
+            this->jlf_parse_context = std::make_shared<yajlpp_parse_context>(
+                this->elf_name.to_string());
+            this->jlf_yajl_handle.reset(
+                yajl_alloc(&this->jlf_parse_context->ypc_callbacks,
+                           nullptr,
+                           this->jlf_parse_context.get()),
+                yajl_handle_deleter());
+            yajl_config(this->jlf_yajl_handle.get(), yajl_dont_validate_strings,
                         1);
         }
 
@@ -2198,11 +2201,12 @@ std::shared_ptr<log_format> external_log_format::specialized(int fmt_lock)
 
     if (this->elf_type == ELF_TYPE_JSON) {
         this->jlf_parse_context = std::make_shared<yajlpp_parse_context>(this->elf_name.to_string());
-        this->jlf_yajl_handle.reset(yajl_alloc(
-            &this->jlf_parse_context->ypc_callbacks,
-            nullptr,
-            this->jlf_parse_context.get()));
-        yajl_config(this->jlf_yajl_handle.in(), yajl_dont_validate_strings, 1);
+        this->jlf_yajl_handle.reset(
+            yajl_alloc(&this->jlf_parse_context->ypc_callbacks,
+                       nullptr,
+                       this->jlf_parse_context.get()),
+            yajl_handle_deleter());
+        yajl_config(this->jlf_yajl_handle.get(), yajl_dont_validate_strings, 1);
         this->jlf_cached_line.reserve(16 * 1024);
     }
 
diff --git a/src/log_format_ext.hh b/src/log_format_ext.hh
index f6a0af0c..86dc5b25 100644
--- a/src/log_format_ext.hh
+++ b/src/log_format_ext.hh
@@ -103,6 +103,14 @@ public:
         std::shared_ptr<pcrepp> lp_pcre;
     };
 
+    struct yajl_handle_deleter {
+        void operator()(yajl_handle handle) const {
+            if (handle != nullptr) {
+                yajl_free(handle);
+            }
+        }
+    };
+
     external_log_format(const intern_string_t name)
         : elf_file_pattern(".*"),
           elf_column_count(0),
@@ -116,7 +124,7 @@ public:
           elf_type(ELF_TYPE_TEXT),
           jlf_hide_extra(false),
           jlf_cached_offset(-1),
-          jlf_yajl_handle(yajl_free),
+          jlf_yajl_handle(nullptr, yajl_handle_deleter()),
           elf_name(name) {
         this->jlf_line_offsets.reserve(128);
     };
@@ -439,7 +447,7 @@ public:
     std::vector<char> jlf_cached_line;
     string_attrs_t jlf_line_attrs;
     std::shared_ptr<yajlpp_parse_context> jlf_parse_context;
-    auto_mem<yajl_handle_t> jlf_yajl_handle;
+    std::shared_ptr<yajl_handle_t> jlf_yajl_handle;
 private:
     const intern_string_t elf_name;
 
diff --git a/src/mapbox/variant.hpp b/src/mapbox/variant.hpp
index d7db91ae..06a46abe 100644
--- a/src/mapbox/variant.hpp
+++ b/src/mapbox/variant.hpp
@@ -75,16 +75,6 @@ public:
 
 }; // class bad_variant_access
 
-template <typename R = void>
-struct MAPBOX_VARIANT_DEPRECATED static_visitor
-{
-    using result_type = R;
-
-protected:
-    static_visitor() {}
-    ~static_visitor() {}
-};
-
 #if !defined(MAPBOX_VARIANT_MINIMIZE_SIZE)
 using type_index_t = unsigned int;
 #else
@@ -170,44 +160,68 @@ template <typename T, typename... Types>
 struct value_traits
 {
     using value_type = typename std::remove_const<typename std::remove_reference<T>::type>::type;
+    using value_type_wrapper = recursive_wrapper<value_type>;
     static constexpr type_index_t direct_index = direct_type<value_type, Types...>::index;
     static constexpr bool is_direct = direct_index != invalid_value;
-    static constexpr type_index_t index = is_direct ? direct_index : convertible_type<value_type, Types...>::index;
+    static constexpr type_index_t index_direct_or_wrapper = is_direct ? direct_index : direct_type<value_type_wrapper, Types...>::index;
+    static constexpr bool is_direct_or_wrapper = index_direct_or_wrapper != invalid_value;
+    static constexpr type_index_t index = is_direct_or_wrapper ? index_direct_or_wrapper : convertible_type<value_type, Types...>::index;
     static constexpr bool is_valid = index != invalid_value;
     static constexpr type_index_t tindex = is_valid ? sizeof...(Types)-index : 0;
     using target_type = typename std::tuple_element<tindex, std::tuple<void, Types...>>::type;
 };
 
-template <typename T, typename R = void>
-struct enable_if_type
+template <typename Src, typename Dest>
+struct copy_cvref
 {
-    using type = R;
+    using type = Dest;
 };
 
-template <typename F, typename V, typename Enable = void>
-struct result_of_unary_visit
+template <typename Src, typename Dest>
+struct copy_cvref<Src const&, Dest>
 {
-    using type = typename std::result_of<F(V&)>::type;
+    using type = Dest const&;
 };
 
-template <typename F, typename V>
-struct result_of_unary_visit<F, V, typename enable_if_type<typename F::result_type>::type>
+template <typename Src, typename Dest>
+struct copy_cvref<Src&, Dest>
 {
-    using type = typename F::result_type;
+    using type = Dest&;
 };
 
-template <typename F, typename V, typename Enable = void>
-struct result_of_binary_visit
+template <typename Src, typename Dest>
+struct copy_cvref<Src&&, Dest>
 {
-    using type = typename std::result_of<F(V&, V&)>::type;
+    using type = Dest&&;
 };
 
-template <typename F, typename V>
-struct result_of_binary_visit<F, V, typename enable_if_type<typename F::result_type>::type>
+template <typename F, typename = void>
+struct deduced_result_type
+{};
+
+template <typename F, typename... Args>
+struct deduced_result_type<F(Args...), decltype((void)std::declval<F>()(std::declval<Args>()...))>
 {
-    using type = typename F::result_type;
+    using type = decltype(std::declval<F>()(std::declval<Args>()...));
 };
 
+template <typename F, typename = void>
+struct visitor_result_type : deduced_result_type<F>
+{};
+
+// specialization for explicit result_type member in visitor class
+template <typename F, typename... Args>
+struct visitor_result_type<F(Args...), decltype((void)std::declval<typename std::decay<F>::type::result_type>())>
+{
+    using type = typename std::decay<F>::type::result_type;
+};
+
+template <typename F, typename T>
+using result_of_unary_visit = typename visitor_result_type<F&&(T&&)>::type;
+
+template <typename F, typename T>
+using result_of_binary_visit = typename visitor_result_type<F&&(T&&, T&&)>::type;
+
 template <type_index_t arg1, type_index_t... others>
 struct static_max;
 
@@ -277,245 +291,174 @@ struct variant_helper<>
 template <typename T>
 struct unwrapper
 {
-    static T const& apply_const(T const& obj) { return obj; }
-    static T& apply(T& obj) { return obj; }
-};
+    using value_type = T;
 
-template <typename T>
-struct unwrapper<recursive_wrapper<T>>
-{
-    static auto apply_const(recursive_wrapper<T> const& obj)
-        -> typename recursive_wrapper<T>::type const&
+    template <typename V>
+    static auto apply(typename std::remove_reference<V>::type& var)
+        -> typename std::enable_if<std::is_lvalue_reference<V>::value,
+                    decltype(var.template get_unchecked<T>())>::type
     {
-        return obj.get();
+        return var.template get_unchecked<T>();
     }
-    static auto apply(recursive_wrapper<T>& obj)
-        -> typename recursive_wrapper<T>::type&
+
+    template <typename V>
+    static auto apply(typename std::remove_reference<V>::type& var)
+        -> typename std::enable_if<!std::is_lvalue_reference<V>::value,
+                    decltype(std::move(var.template get_unchecked<T>()))>::type
     {
-        return obj.get();
+        return std::move(var.template get_unchecked<T>());
     }
 };
 
 template <typename T>
-struct unwrapper<std::reference_wrapper<T>>
-{
-    static auto apply_const(std::reference_wrapper<T> const& obj)
-        -> typename std::reference_wrapper<T>::type const&
-    {
-        return obj.get();
-    }
-    static auto apply(std::reference_wrapper<T>& obj)
-        -> typename std::reference_wrapper<T>::type&
-    {
-        return obj.get();
-    }
-};
+struct unwrapper<recursive_wrapper<T>> : unwrapper<T>
+{};
 
-template <typename F, typename V, typename R, typename... Types>
+template <typename T>
+struct unwrapper<std::reference_wrapper<T>> : unwrapper<T>
+{};
+
+template <typename R, typename... Types>
 struct dispatcher;
 
-template <typename F, typename V, typename R, typename T, typename... Types>
-struct dispatcher<F, V, R, T, Types...>
+template <typename R, typename T, typename... Types>
+struct dispatcher<R, T, Types...>
 {
-    VARIANT_INLINE static R apply_const(V const& v, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v, F&& f)
     {
         if (v.template is<T>())
         {
-            return f(unwrapper<T>::apply_const(v.template get_unchecked<T>()));
+            return std::forward<F>(f)(unwrapper<T>::template apply<V>(v));
         }
         else
         {
-            return dispatcher<F, V, R, Types...>::apply_const(v, std::forward<F>(f));
-        }
-    }
-
-    VARIANT_INLINE static R apply(V& v, F&& f)
-    {
-        if (v.template is<T>())
-        {
-            return f(unwrapper<T>::apply(v.template get_unchecked<T>()));
-        }
-        else
-        {
-            return dispatcher<F, V, R, Types...>::apply(v, std::forward<F>(f));
+            return dispatcher<R, Types...>::apply(std::forward<V>(v), std::forward<F>(f));
         }
     }
 };
 
-template <typename F, typename V, typename R, typename T>
-struct dispatcher<F, V, R, T>
+template <typename R, typename T>
+struct dispatcher<R, T>
 {
-    VARIANT_INLINE static R apply_const(V const& v, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v, F&& f)
     {
-        return f(unwrapper<T>::apply_const(v.template get_unchecked<T>()));
-    }
-
-    VARIANT_INLINE static R apply(V& v, F&& f)
-    {
-        return f(unwrapper<T>::apply(v.template get_unchecked<T>()));
+        return std::forward<F>(f)(unwrapper<T>::template apply<V>(v));
     }
 };
 
-template <typename F, typename V, typename R, typename T, typename... Types>
+template <typename R, typename T, typename... Types>
 struct binary_dispatcher_rhs;
 
-template <typename F, typename V, typename R, typename T0, typename T1, typename... Types>
-struct binary_dispatcher_rhs<F, V, R, T0, T1, Types...>
+template <typename R, typename T0, typename T1, typename... Types>
+struct binary_dispatcher_rhs<R, T0, T1, Types...>
 {
-    VARIANT_INLINE static R apply_const(V const& lhs, V const& rhs, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
     {
         if (rhs.template is<T1>()) // call binary functor
         {
-            return f(unwrapper<T0>::apply_const(lhs.template get_unchecked<T0>()),
-                     unwrapper<T1>::apply_const(rhs.template get_unchecked<T1>()));
+            return std::forward<F>(f)(unwrapper<T0>::template apply<V>(lhs),
+                                      unwrapper<T1>::template apply<V>(rhs));
         }
         else
         {
-            return binary_dispatcher_rhs<F, V, R, T0, Types...>::apply_const(lhs, rhs, std::forward<F>(f));
-        }
-    }
-
-    VARIANT_INLINE static R apply(V& lhs, V& rhs, F&& f)
-    {
-        if (rhs.template is<T1>()) // call binary functor
-        {
-            return f(unwrapper<T0>::apply(lhs.template get_unchecked<T0>()),
-                     unwrapper<T1>::apply(rhs.template get_unchecked<T1>()));
-        }
-        else
-        {
-            return binary_dispatcher_rhs<F, V, R, T0, Types...>::apply(lhs, rhs, std::forward<F>(f));
+            return binary_dispatcher_rhs<R, T0, Types...>::apply(std::forward<V>(lhs),
+                                                                 std::forward<V>(rhs),
+                                                                 std::forward<F>(f));
         }
     }
 };
 
-template <typename F, typename V, typename R, typename T0, typename T1>
-struct binary_dispatcher_rhs<F, V, R, T0, T1>
+template <typename R, typename T0, typename T1>
+struct binary_dispatcher_rhs<R, T0, T1>
 {
-    VARIANT_INLINE static R apply_const(V const& lhs, V const& rhs, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
     {
-        return f(unwrapper<T0>::apply_const(lhs.template get_unchecked<T0>()),
-                 unwrapper<T1>::apply_const(rhs.template get_unchecked<T1>()));
-    }
-
-    VARIANT_INLINE static R apply(V& lhs, V& rhs, F&& f)
-    {
-        return f(unwrapper<T0>::apply(lhs.template get_unchecked<T0>()),
-                 unwrapper<T1>::apply(rhs.template get_unchecked<T1>()));
+        return std::forward<F>(f)(unwrapper<T0>::template apply<V>(lhs),
+                                  unwrapper<T1>::template apply<V>(rhs));
     }
 };
 
-template <typename F, typename V, typename R, typename T, typename... Types>
+template <typename R, typename T, typename... Types>
 struct binary_dispatcher_lhs;
 
-template <typename F, typename V, typename R, typename T0, typename T1, typename... Types>
-struct binary_dispatcher_lhs<F, V, R, T0, T1, Types...>
+template <typename R, typename T0, typename T1, typename... Types>
+struct binary_dispatcher_lhs<R, T0, T1, Types...>
 {
-    VARIANT_INLINE static R apply_const(V const& lhs, V const& rhs, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
     {
         if (lhs.template is<T1>()) // call binary functor
         {
-            return f(unwrapper<T1>::apply_const(lhs.template get_unchecked<T1>()),
-                     unwrapper<T0>::apply_const(rhs.template get_unchecked<T0>()));
+            return std::forward<F>(f)(unwrapper<T1>::template apply<V>(lhs),
+                                      unwrapper<T0>::template apply<V>(rhs));
         }
         else
         {
-            return binary_dispatcher_lhs<F, V, R, T0, Types...>::apply_const(lhs, rhs, std::forward<F>(f));
-        }
-    }
-
-    VARIANT_INLINE static R apply(V& lhs, V& rhs, F&& f)
-    {
-        if (lhs.template is<T1>()) // call binary functor
-        {
-            return f(unwrapper<T1>::apply(lhs.template get_unchecked<T1>()),
-                     unwrapper<T0>::apply(rhs.template get_unchecked<T0>()));
-        }
-        else
-        {
-            return binary_dispatcher_lhs<F, V, R, T0, Types...>::apply(lhs, rhs, std::forward<F>(f));
+            return binary_dispatcher_lhs<R, T0, Types...>::apply(std::forward<V>(lhs),
+                                                                 std::forward<V>(rhs),
+                                                                 std::forward<F>(f));
         }
     }
 };
 
-template <typename F, typename V, typename R, typename T0, typename T1>
-struct binary_dispatcher_lhs<F, V, R, T0, T1>
+template <typename R, typename T0, typename T1>
+struct binary_dispatcher_lhs<R, T0, T1>
 {
-    VARIANT_INLINE static R apply_const(V const& lhs, V const& rhs, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& lhs, V&& rhs, F&& f)
     {
-        return f(unwrapper<T1>::apply_const(lhs.template get_unchecked<T1>()),
-                 unwrapper<T0>::apply_const(rhs.template get_unchecked<T0>()));
-    }
-
-    VARIANT_INLINE static R apply(V& lhs, V& rhs, F&& f)
-    {
-        return f(unwrapper<T1>::apply(lhs.template get_unchecked<T1>()),
-                 unwrapper<T0>::apply(rhs.template get_unchecked<T0>()));
+        return std::forward<F>(f)(unwrapper<T1>::template apply<V>(lhs),
+                                  unwrapper<T0>::template apply<V>(rhs));
     }
 };
 
-template <typename F, typename V, typename R, typename... Types>
+template <typename R, typename... Types>
 struct binary_dispatcher;
 
-template <typename F, typename V, typename R, typename T, typename... Types>
-struct binary_dispatcher<F, V, R, T, Types...>
+template <typename R, typename T, typename... Types>
+struct binary_dispatcher<R, T, Types...>
 {
-    VARIANT_INLINE static R apply_const(V const& v0, V const& v1, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v0, V&& v1, F&& f)
     {
         if (v0.template is<T>())
         {
             if (v1.template is<T>())
             {
-                return f(unwrapper<T>::apply_const(v0.template get_unchecked<T>()),
-                         unwrapper<T>::apply_const(v1.template get_unchecked<T>())); // call binary functor
+                return std::forward<F>(f)(unwrapper<T>::template apply<V>(v0),
+                                          unwrapper<T>::template apply<V>(v1)); // call binary functor
             }
             else
             {
-                return binary_dispatcher_rhs<F, V, R, T, Types...>::apply_const(v0, v1, std::forward<F>(f));
+                return binary_dispatcher_rhs<R, T, Types...>::apply(std::forward<V>(v0),
+                                                                    std::forward<V>(v1),
+                                                                    std::forward<F>(f));
             }
         }
         else if (v1.template is<T>())
         {
-            return binary_dispatcher_lhs<F, V, R, T, Types...>::apply_const(v0, v1, std::forward<F>(f));
+            return binary_dispatcher_lhs<R, T, Types...>::apply(std::forward<V>(v0),
+                                                                std::forward<V>(v1),
+                                                                std::forward<F>(f));
         }
-        return binary_dispatcher<F, V, R, Types...>::apply_const(v0, v1, std::forward<F>(f));
-    }
-
-    VARIANT_INLINE static R apply(V& v0, V& v1, F&& f)
-    {
-        if (v0.template is<T>())
-        {
-            if (v1.template is<T>())
-            {
-                return f(unwrapper<T>::apply(v0.template get_unchecked<T>()),
-                         unwrapper<T>::apply(v1.template get_unchecked<T>())); // call binary functor
-            }
-            else
-            {
-                return binary_dispatcher_rhs<F, V, R, T, Types...>::apply(v0, v1, std::forward<F>(f));
-            }
-        }
-        else if (v1.template is<T>())
-        {
-            return binary_dispatcher_lhs<F, V, R, T, Types...>::apply(v0, v1, std::forward<F>(f));
-        }
-        return binary_dispatcher<F, V, R, Types...>::apply(v0, v1, std::forward<F>(f));
+        return binary_dispatcher<R, Types...>::apply(std::forward<V>(v0),
+                                                     std::forward<V>(v1),
+                                                     std::forward<F>(f));
     }
 };
 
-template <typename F, typename V, typename R, typename T>
-struct binary_dispatcher<F, V, R, T>
+template <typename R, typename T>
+struct binary_dispatcher<R, T>
 {
-    VARIANT_INLINE static R apply_const(V const& v0, V const& v1, F&& f)
+    template <typename V, typename F>
+    VARIANT_INLINE static R apply(V&& v0, V&& v1, F&& f)
     {
-        return f(unwrapper<T>::apply_const(v0.template get_unchecked<T>()),
-                 unwrapper<T>::apply_const(v1.template get_unchecked<T>())); // call binary functor
-    }
-
-    VARIANT_INLINE static R apply(V& v0, V& v1, F&& f)
-    {
-        return f(unwrapper<T>::apply(v0.template get_unchecked<T>()),
-                 unwrapper<T>::apply(v1.template get_unchecked<T>())); // call binary functor
+        return std::forward<F>(f)(unwrapper<T>::template apply<V>(v0),
+                                  unwrapper<T>::template apply<V>(v1)); // call binary functor
     }
 };
 
@@ -586,11 +529,19 @@ public:
     using types = std::tuple<Types...>;
 private:
     using first_type = typename std::tuple_element<0, types>::type;
+    using unwrap_first_type = typename detail::unwrapper<first_type>::value_type;
     using data_type = typename std::aligned_storage<data_size, data_align>::type;
     using helper_type = detail::variant_helper<Types...>;
 
+    template <typename V, typename T = unwrap_first_type>
+        using alternative_ref = typename detail::copy_cvref<V, T>::type;
+
     type_index_t type_index;
+#ifdef __clang_analyzer__
+    data_type data {};
+#else
     data_type data;
+#endif
 
 public:
     VARIANT_INLINE variant() noexcept(std::is_nothrow_default_constructible<first_type>::value)
@@ -644,21 +595,34 @@ private:
 
 public:
     VARIANT_INLINE variant<Types...>& operator=(variant<Types...>&& other)
+        // note we check for nothrow-constructible, not nothrow-assignable, since
+        // move_assign uses move-construction via placement new.
+        noexcept(detail::conjunction<std::is_nothrow_move_constructible<Types>...>::value)
     {
+        if (this == &other) { // playing safe in release mode, hit assertion in debug.
+            assert(false);
+            return *this;
+        }
         move_assign(std::move(other));
         return *this;
     }
 
     VARIANT_INLINE variant<Types...>& operator=(variant<Types...> const& other)
     {
-        copy_assign(other);
+        if (this != &other)
+            copy_assign(other);
         return *this;
     }
 
     // conversions
     // move-assign
-    template <typename T>
-    VARIANT_INLINE variant<Types...>& operator=(T&& rhs) noexcept
+    template <typename T, typename Traits = detail::value_traits<T, Types...>,
+              typename Enable = typename std::enable_if<Traits::is_valid && !std::is_same<variant<Types...>, typename Traits::value_type>::value>::type >
+    VARIANT_INLINE variant<Types...>& operator=(T&& rhs)
+        // not that we check is_nothrow_constructible<T>, not is_nothrow_move_assignable<T>,
+        // since we construct a temporary
+        noexcept(std::is_nothrow_constructible<typename Traits::target_type, T&&>::value
+                 && std::is_nothrow_move_assignable<variant<Types...>>::value)
     {
         variant<Types...> temp(std::forward<T>(rhs));
         move_assign(std::move(temp));
@@ -855,7 +819,7 @@ public:
 
     VARIANT_INLINE int which() const noexcept
     {
-        return static_cast<int>(sizeof...(Types)-type_index - 1);
+        return static_cast<int>(sizeof...(Types) - type_index - 1);
     }
 
     template <typename T, typename std::enable_if<
@@ -867,51 +831,44 @@ public:
 
     // visitor
     // unary
-    template <typename F, typename V, typename R = typename detail::result_of_unary_visit<F, first_type>::type>
-    auto VARIANT_INLINE static visit(V const& v, F&& f)
-        -> decltype(detail::dispatcher<F, V, R, Types...>::apply_const(v, std::forward<F>(f)))
+    template <typename F, typename V, typename T0 = alternative_ref<V>,
+              typename R = detail::result_of_unary_visit<F, T0>>
+    VARIANT_INLINE static R visit(V&& v, F&& f)
     {
-        return detail::dispatcher<F, V, R, Types...>::apply_const(v, std::forward<F>(f));
-    }
-    // non-const
-    template <typename F, typename V, typename R = typename detail::result_of_unary_visit<F, first_type>::type>
-    auto VARIANT_INLINE static visit(V& v, F&& f)
-        -> decltype(detail::dispatcher<F, V, R, Types...>::apply(v, std::forward<F>(f)))
-    {
-        return detail::dispatcher<F, V, R, Types...>::apply(v, std::forward<F>(f));
+        return detail::dispatcher<R, Types...>::apply(std::forward<V>(v), std::forward<F>(f));
     }
 
     // binary
-    // const
-    template <typename F, typename V, typename R = typename detail::result_of_binary_visit<F, first_type>::type>
-    auto VARIANT_INLINE static binary_visit(V const& v0, V const& v1, F&& f)
-        -> decltype(detail::binary_dispatcher<F, V, R, Types...>::apply_const(v0, v1, std::forward<F>(f)))
+    template <typename F, typename V, typename T0 = alternative_ref<V>,
+              typename R = detail::result_of_binary_visit<F, T0>>
+    VARIANT_INLINE static R binary_visit(V&& v0, V&& v1, F&& f)
     {
-        return detail::binary_dispatcher<F, V, R, Types...>::apply_const(v0, v1, std::forward<F>(f));
-    }
-    // non-const
-    template <typename F, typename V, typename R = typename detail::result_of_binary_visit<F, first_type>::type>
-    auto VARIANT_INLINE static binary_visit(V& v0, V& v1, F&& f)
-        -> decltype(detail::binary_dispatcher<F, V, R, Types...>::apply(v0, v1, std::forward<F>(f)))
-    {
-        return detail::binary_dispatcher<F, V, R, Types...>::apply(v0, v1, std::forward<F>(f));
+        return detail::binary_dispatcher<R, Types...>::apply(std::forward<V>(v0),
+                                                             std::forward<V>(v1),
+                                                             std::forward<F>(f));
     }
 
     // match
     // unary
     template <typename... Fs>
-    auto VARIANT_INLINE match(Fs&&... fs) const
+    auto VARIANT_INLINE match(Fs&&... fs) const&
         -> decltype(variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...)))
     {
         return variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...));
     }
     // non-const
     template <typename... Fs>
-    auto VARIANT_INLINE match(Fs&&... fs)
+    auto VARIANT_INLINE match(Fs&&... fs) &
         -> decltype(variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...)))
     {
         return variant::visit(*this, ::mapbox::util::make_visitor(std::forward<Fs>(fs)...));
     }
+    template <typename... Fs>
+    auto VARIANT_INLINE match(Fs&&... fs) &&
+        -> decltype(variant::visit(std::move(*this), ::mapbox::util::make_visitor(std::forward<Fs>(fs)...)))
+    {
+        return variant::visit(std::move(*this), ::mapbox::util::make_visitor(std::forward<Fs>(fs)...));
+    }
 
     ~variant() noexcept // no-throw destructor
     {
@@ -962,33 +919,19 @@ public:
 };
 
 // unary visitor interface
-// const
 template <typename F, typename V>
-auto VARIANT_INLINE apply_visitor(F&& f, V const& v) -> decltype(V::visit(v, std::forward<F>(f)))
+auto VARIANT_INLINE apply_visitor(F&& f, V&& v)
+    -> decltype(v.visit(std::forward<V>(v), std::forward<F>(f)))
 {
-    return V::visit(v, std::forward<F>(f));
-}
-
-// non-const
-template <typename F, typename V>
-auto VARIANT_INLINE apply_visitor(F&& f, V& v) -> decltype(V::visit(v, std::forward<F>(f)))
-{
-    return V::visit(v, std::forward<F>(f));
+    return v.visit(std::forward<V>(v), std::forward<F>(f));
 }
 
 // binary visitor interface
-// const
 template <typename F, typename V>
-auto VARIANT_INLINE apply_visitor(F&& f, V const& v0, V const& v1) -> decltype(V::binary_visit(v0, v1, std::forward<F>(f)))
+auto VARIANT_INLINE apply_visitor(F&& f, V&& v0, V&& v1)
+    -> decltype(v0.binary_visit(std::forward<V>(v0), std::forward<V>(v1), std::forward<F>(f)))
 {
-    return V::binary_visit(v0, v1, std::forward<F>(f));
-}
-
-// non-const
-template <typename F, typename V>
-auto VARIANT_INLINE apply_visitor(F&& f, V& v0, V& v1) -> decltype(V::binary_visit(v0, v1, std::forward<F>(f)))
-{
-    return V::binary_visit(v0, v1, std::forward<F>(f));
+    return v0.binary_visit(std::forward<V>(v0), std::forward<V>(v1), std::forward<F>(f));
 }
 
 // getter interface
@@ -1020,6 +963,78 @@ ResultType const& get_unchecked(T const& var)
 {
     return var.template get_unchecked<ResultType>();
 }
+// variant_size
+template <typename T>
+struct variant_size;
+
+//variable templates is c++14
+//template <typename T>
+//constexpr std::size_t variant_size_v = variant_size<T>::value;
+
+template <typename T>
+struct variant_size<const T>
+    : variant_size<T> {};
+
+template <typename T>
+struct variant_size<volatile T>
+    : variant_size<T> {};
+
+template <typename T>
+struct variant_size<const volatile T>
+    : variant_size<T> {};
+
+template <typename... Types>
+struct variant_size<variant<Types...>>
+    : std::integral_constant<std::size_t, sizeof...(Types)> {};
+
+// variant_alternative
+template <std::size_t Index, typename T>
+struct variant_alternative;
+
+#if defined(__clang__)
+#if __has_builtin(__type_pack_element)
+#define has_type_pack_element
+#endif
+#endif
+
+#if defined(has_type_pack_element)
+template <std::size_t Index, typename ...Types>
+struct variant_alternative<Index, variant<Types...>>
+{
+    static_assert(sizeof...(Types) > Index , "Index out of range");
+    using type = __type_pack_element<Index, Types...>;
+};
+#else
+template <std::size_t Index, typename First, typename...Types>
+struct variant_alternative<Index, variant<First, Types...>>
+    : variant_alternative<Index - 1, variant<Types...>>
+{
+    static_assert(sizeof...(Types) > Index -1 , "Index out of range");
+};
+
+template <typename First, typename...Types>
+struct variant_alternative<0, variant<First, Types...>>
+{
+    using type = First;
+};
+
+#endif
+
+template <size_t Index, typename T>
+using variant_alternative_t = typename variant_alternative<Index, T>::type;
+
+template <size_t Index, typename T>
+struct variant_alternative<Index, const T>
+    : std::add_const<variant_alternative<Index, T>> {};
+
+template <size_t Index, typename T>
+struct variant_alternative<Index, volatile T>
+    : std::add_volatile<variant_alternative<Index, T>> {};
+
+template <size_t Index, typename T>
+struct variant_alternative<Index, const volatile T>
+    : std::add_cv<variant_alternative<Index, T>> {};
+
 } // namespace util
 } // namespace mapbox
 
@@ -1032,6 +1047,7 @@ struct hash< ::mapbox::util::variant<Types...>> {
         return ::mapbox::util::apply_visitor(::mapbox::util::detail::hasher{}, v);
     }
 };
+
 }
 
 #endif // MAPBOX_UTIL_VARIANT_HPP
diff --git a/src/mapbox/variant_cast.hpp b/src/mapbox/variant_cast.hpp
new file mode 100644
index 00000000..fe1ab354
--- /dev/null
+++ b/src/mapbox/variant_cast.hpp
@@ -0,0 +1,85 @@
+#ifndef VARIANT_CAST_HPP
+#define VARIANT_CAST_HPP
+
+#include <type_traits>
+
+namespace mapbox {
+namespace util {
+
+namespace detail {
+
+template <class T>
+class static_caster
+{
+public:
+    template <class V>
+    T& operator()(V& v) const
+    {
+        return static_cast<T&>(v);
+    }
+};
+
+template <class T>
+class dynamic_caster
+{
+public:
+    using result_type = T&;
+    template <class V>
+    T& operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        throw std::bad_cast();
+    }
+    template <class V>
+    T& operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return dynamic_cast<T&>(v);
+    }
+};
+
+template <class T>
+class dynamic_caster<T*>
+{
+public:
+    using result_type = T*;
+    template <class V>
+    T* operator()(V& v, typename std::enable_if<!std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return nullptr;
+    }
+    template <class V>
+    T* operator()(V& v, typename std::enable_if<std::is_polymorphic<V>::value>::type* = nullptr) const
+    {
+        return dynamic_cast<T*>(&v);
+    }
+};
+}
+
+template <class T, class V>
+typename detail::dynamic_caster<T>::result_type
+dynamic_variant_cast(V& v)
+{
+    return mapbox::util::apply_visitor(detail::dynamic_caster<T>(), v);
+}
+
+template <class T, class V>
+typename detail::dynamic_caster<const T>::result_type
+dynamic_variant_cast(const V& v)
+{
+    return mapbox::util::apply_visitor(detail::dynamic_caster<const T>(), v);
+}
+
+template <class T, class V>
+T& static_variant_cast(V& v)
+{
+    return mapbox::util::apply_visitor(detail::static_caster<T>(), v);
+}
+
+template <class T, class V>
+const T& static_variant_cast(const V& v)
+{
+    return mapbox::util::apply_visitor(detail::static_caster<const T>(), v);
+}
+}
+}
+
+#endif // VARIANT_CAST_HPP
diff --git a/src/mapbox/variant_visitor.hpp b/src/mapbox/variant_visitor.hpp
index 481eb652..54ddba0e 100644
--- a/src/mapbox/variant_visitor.hpp
+++ b/src/mapbox/variant_visitor.hpp
@@ -1,6 +1,8 @@
 #ifndef MAPBOX_UTIL_VARIANT_VISITOR_HPP
 #define MAPBOX_UTIL_VARIANT_VISITOR_HPP
 
+#include <utility>
+
 namespace mapbox {
 namespace util {
 
@@ -10,28 +12,31 @@ struct visitor;
 template <typename Fn>
 struct visitor<Fn> : Fn
 {
-    using type = Fn;
     using Fn::operator();
 
-    visitor(Fn fn) : Fn(fn) {}
+    template<typename T>
+    visitor(T&& fn) : Fn(std::forward<T>(fn)) {}    
 };
 
 template <typename Fn, typename... Fns>
 struct visitor<Fn, Fns...> : Fn, visitor<Fns...>
 {
-    using type = visitor;
     using Fn::operator();
     using visitor<Fns...>::operator();
 
-    visitor(Fn fn, Fns... fns) : Fn(fn), visitor<Fns...>(fns...) {}
+    template<typename T, typename... Ts>
+    visitor(T&& fn, Ts&&... fns)
+        : Fn(std::forward<T>(fn))
+        , visitor<Fns...>(std::forward<Ts>(fns)...) {}
 };
 
 template <typename... Fns>
-visitor<Fns...> make_visitor(Fns... fns)
+visitor<typename std::decay<Fns>::type...> make_visitor(Fns&&... fns)
 {
-    return visitor<Fns...>(fns...);
+    return visitor<typename std::decay<Fns>::type...>
+        (std::forward<Fns>(fns)...);
 }
-
+    
 } // namespace util
 } // namespace mapbox
 
diff --git a/src/views_vtab.cc b/src/views_vtab.cc
index 30de0876..aa4cd3c2 100644
--- a/src/views_vtab.cc
+++ b/src/views_vtab.cc
@@ -80,11 +80,11 @@ struct from_sqlite<text_filter::type_t> {
 };
 
 template<>
-struct from_sqlite<pair<string, pcre *>> {
-    inline pair<string, pcre *>operator()(int argc, sqlite3_value **val, int argi) {
+struct from_sqlite<pair<string, auto_mem<pcre>>> {
+    inline pair<string, auto_mem<pcre>> operator()(int argc, sqlite3_value **val, int argi) {
         const char *pattern = (const char *) sqlite3_value_text(val[argi]);
         const char *errptr;
-        pcre *code;
+        auto_mem<pcre> code;
         int eoff;
 
         if (pattern == nullptr || pattern[0] == '\0') {
@@ -101,7 +101,7 @@ struct from_sqlite<pair<string, pcre *>> {
             throw from_sqlite_conversion_error(errptr, argi);
         }
 
-        return make_pair(string(pattern), code);
+        return make_pair(string(pattern), std::move(code));
     }
 };
 
@@ -458,7 +458,7 @@ CREATE TABLE lnav_view_filters (
                    nonstd::optional<int64_t> _filter_id,
                    nonstd::optional<bool> enabled,
                    nonstd::optional<text_filter::type_t> type,
-                   pair<string, pcre *> pattern) {
+                   pair<string, auto_mem<pcre>> pattern) {
         textview_curses &tc = lnav_data.ld_views[view_index];
         text_sub_source *tss = tc.get_sub_source();
         filter_stack &fs = tss->get_filters();
@@ -470,7 +470,7 @@ CREATE TABLE lnav_view_filters (
             type.value_or(text_filter::type_t::EXCLUDE),
             pattern.first,
             *filter_index,
-            pattern.second);
+            pattern.second.release());
         fs.add_filter(pf);
         if (!enabled.value_or(true)) {
             pf->disable();
@@ -506,7 +506,7 @@ CREATE TABLE lnav_view_filters (
                    int64_t new_filter_id,
                    bool enabled,
                    text_filter::type_t type,
-                   pair<string, pcre *> pattern) {
+                   pair<string, auto_mem<pcre>> pattern) {
         auto view_index = lnav_view_t(rowid >> 32);
         int filter_index = rowid & 0xffffffffLL;
         textview_curses &tc = lnav_data.ld_views[view_index];
@@ -533,7 +533,7 @@ CREATE TABLE lnav_view_filters (
         auto pf = make_shared<pcre_filter>(type,
                                            pattern.first,
                                            tf->get_index(),
-                                           pattern.second);
+                                           pattern.second.release());
 
         if (!enabled) {
             pf->disable();
diff --git a/src/vtab_module.hh b/src/vtab_module.hh
index 8e234c60..90b0a542 100644
--- a/src/vtab_module.hh
+++ b/src/vtab_module.hh
@@ -222,7 +222,7 @@ struct ToSqliteVisitor {
     };
 
     template<typename T>
-    void operator()(T t) const {
+    void operator()(T&& t) const {
         to_sqlite(this->tsv_context, t);
     }
 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 2d4d614a..06443b77 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -30,6 +30,10 @@ add_executable(test_reltime test_reltime.cc)
 target_link_libraries(test_reltime diag PkgConfig::libpcre)
 add_test(NAME test_reltime COMMAND test_reltime)
 
+add_executable(test_auto_mem test_auto_mem.cc)
+target_link_libraries(test_auto_mem diag PkgConfig::libpcre)
+add_test(NAME test_auto_mem COMMAND test_auto_mem)
+
 add_executable(test_date_time_scanner test_date_time_scanner.cc)
 target_link_libraries(test_date_time_scanner diag PkgConfig::libpcre)
 add_test(NAME test_date_time_scanner COMMAND test_date_time_scanner)
diff --git a/test/test_auto_mem.cc b/test/test_auto_mem.cc
index deab1e65..c7b35403 100644
--- a/test/test_auto_mem.cc
+++ b/test/test_auto_mem.cc
@@ -73,7 +73,7 @@ int main(int argc, char *argv[])
     assert(md1.in() == &md1_val);
 
     {
-	auto_mem<struct my_data, my_free> md_cp(md1);
+	auto_mem<struct my_data, my_free> md_cp(std::move(md1));
 
 	assert(md1 == NULL);
 	assert(free_count == 2);