userdata member variables are now supported

userdata now performs lookup based on tables
userdata now has reduced number of vector tables
userdata garbage collection improved
debug.hpp - new header for debugging problems with stack, mostly for internal use

sol/debug.hpp

@@ -0,0 +1,53 @@
+// The MIT License (MIT)
+
+// Copyright (c) 2013 Danny Y., Rapptz
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy of
+// this software and associated documentation files (the "Software"), to deal in
+// the Software without restriction, including without limitation the rights to
+// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+// the Software, and to permit persons to whom the Software is furnished to do so,
+// subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+#ifndef SOL_DEBUG_HPP
+#define SOL_DEBUG_HPP
+
+#include "stack.hpp"
+#include <iostream>
+
+namespace sol {
+namespace debug {
+
+inline std::string dump_types(lua_State* L) {
+    std::string visual;
+    std::size_t size = lua_gettop(L) + 1;
+    for (std::size_t i = 1; i < size; ++i) {
+        if (i != 1)
+            visual += " | ";
+        visual += type_name(L, stack::get<type>(L, i));
+    }
+    return visual;
+}
+
+inline void print_stack (lua_State* L) {
+    std::cout << dump_types(L) << std::endl;
+}
+
+inline void print_section (const std::string& message, lua_State* L) {
+    std::cout << "-- " << message << " -- [ "  << dump_types(L) << " ]" << std::endl;
+}
+
+} // debug
+} // sol
+
+#endif // SOL_DEBUG_HPP

sol/function_types.hpp

@@ -24,10 +24,14 @@
 
 #include "stack.hpp"
 #include <memory>
+#include <unordered_map>
 
 namespace sol {
 namespace detail {
-template <typename T, typename Func, typename R>
+struct ref_call_t {};
+const auto ref_call = ref_call_t{};
+
+template <typename T, typename Func, typename R, bool is_variable = std::is_member_object_pointer<Func>::value>
 struct functor {
     T* item;
     Func invocation;
@@ -43,7 +47,7 @@ struct functor {
 };
 
 template <typename T, typename Func>
-struct functor<T, Func, void> {
+struct functor<T, Func, void, false> {
     T* item;
     Func invocation;
 
@@ -56,6 +60,26 @@ struct functor<T, Func, void> {
         (member.*invocation)(std::forward<Args>(args)...);
     }
 };
+
+template <typename T, typename Func, typename R>
+struct functor<T, Func, R, true> {
+    T* item;
+    Func invocation;
+
+    template<typename... FxArgs>
+    functor(FxArgs&&... fxargs): item(nullptr), invocation(std::forward<FxArgs>(fxargs)...) {}
+
+    template<typename Arg, typename... Args>
+    void operator()(Arg&& arg, Args&&... args) {
+        T& member = *item;
+        (member.*invocation) = std::forward<Arg>(arg);
+    }
+
+    R operator()() {
+        T& member = *item;
+        return (member.*invocation);
+    }
+};
 } // detail
 
 
@@ -155,6 +179,17 @@ struct base_function {
         return r;
     }
 
+    static int ref_base_call(lua_State* L, void* inheritancedata) {
+        if (inheritancedata == nullptr) {
+            throw error("call from Lua to C++ function has null data");
+        }
+
+        base_function* pfx = static_cast<base_function*>(inheritancedata);
+        base_function& fx = *pfx;
+        int r = fx(L, detail::ref_call);
+        return r;
+    }
+
     static int base_gc(lua_State*, void* udata) {
         if (udata == nullptr) {
             throw error("call from lua to C++ gc function with null data");
@@ -176,18 +211,19 @@ struct base_function {
         return base_gc(L, *pudata);
     }
 
-    template<std::size_t i>
+    template<std::size_t I>
     struct userdata {
         static int call(lua_State* L) {
             // Zero-based template parameter, but upvalues start at 1
-            return base_call(L, stack::get<upvalue_t>(L, i + 1));
+            return base_call(L, stack::get<upvalue_t>(L, I + 1));
+        }
+
+        static int ref_call(lua_State* L) {
+            return ref_base_call(L, stack::get<upvalue_t>(L, I + 1));
         }
-    };
 
-    template<std::size_t N>
-    struct userdata_gc {
         static int gc(lua_State* L) {
-            for (std::size_t i = 0; i < N; ++i) {
+            for (std::size_t i = 0; i < I; ++i) {
                 upvalue_t up = stack::get<upvalue_t>(L, i + 1);
                 base_function* obj = static_cast<base_function*>(up.value);
                 std::allocator<base_function> alloc{};
@@ -202,6 +238,10 @@ struct base_function {
         throw error("failure to call specialized wrapped C++ function from Lua");
     }
 
+    virtual int operator()(lua_State*, detail::ref_call_t) {
+        throw error("failure to call reference specialized wrapped C++ function from Lua");
+    }
+
     virtual ~base_function() {}
 };
 
@@ -289,16 +329,17 @@ struct member_function : public base_function {
 };
 
 template<typename Function, typename Tp>
-struct userdata_function : public base_function {
+struct userdata_function_core : public base_function {
     typedef typename std::remove_pointer<Tp>::type T;
     typedef typename std::remove_pointer<typename std::decay<Function>::type>::type function_type;
-    typedef function_args_t<function_type> args_type;
-    typedef function_return_t<function_type> return_type;
+    typedef member_traits<Function> traits_type;
+    typedef typename traits_type::args_type args_type;
+    typedef typename traits_type::return_type return_type;
 
     detail::functor<T, function_type, return_type> fx;
 
     template<typename... FxArgs>
-    userdata_function(FxArgs&&... fxargs): fx(std::forward<FxArgs>(fxargs)...) {}
+    userdata_function_core(FxArgs&&... fxargs): fx(std::forward<FxArgs>(fxargs)...) {}
 
     template<typename Return, typename Raw = Unqualified<Return>>
     typename std::enable_if<std::is_same<T, Raw>::value, void>::type push(lua_State* L, Return&& r) {
@@ -323,7 +364,8 @@ struct userdata_function : public base_function {
 
     template<typename... Args>
     int operator()(types<void>, types<Args...> t, lua_State* L) {
-        stack::get_call(L, 2, fx, t);
+        static const std::size_t skew = static_cast<std::size_t>(std::is_member_object_pointer<function_type>::value);
+        stack::get_call(L, 2 + skew, fx, t);
         std::ptrdiff_t nargs = sizeof...(Args);
         lua_pop(L, nargs);
         return 0;
@@ -342,12 +384,128 @@ struct userdata_function : public base_function {
     int operator()(types<>, types<Args...> t, lua_State* L) {
         return (*this)(types<void>(), t, L);
     }
+};
+
+template<typename Function, typename Tp>
+struct userdata_function : public userdata_function_core<Function, Tp> {
+    typedef userdata_function_core<Function, Tp> base_t;
+    typedef typename std::remove_pointer<Tp>::type T;
+    typedef member_traits<Function> traits_type;
+    typedef typename traits_type::args_type args_type;
+    typedef typename traits_type::return_type return_type;
+
+    template<typename... FxArgs>
+    userdata_function(FxArgs&&... fxargs): base_t(std::forward<FxArgs>(fxargs)...) {}
+
+    template <typename Tx>
+    int fx_call(lua_State* L) {
+        this->fx.item = detail::get_ptr(stack::get<Tx>(L, 1));
+        if (this->fx.item == nullptr)
+            throw error("userdata for function call is null: are you using the wrong syntax? (use item:function/variable(...) syntax)");
+        return static_cast<base_t&>(*this)(tuple_types<return_type>(), args_type(), L);
+    }
 
     virtual int operator()(lua_State* L) override {
-        fx.item = detail::get_ptr(stack::get<Tp>(L, 1));
-        if (fx.item == nullptr)
-            throw error("userdata for function call is null: are you using wrong call syntax? (use item:function(...) synax)");
-        return (*this)(tuple_types<return_type>(), args_type(), L);
+        return fx_call<T>(L);
+    }
+
+    virtual int operator()(lua_State* L, detail::ref_call_t) override {
+        return fx_call<T*>(L);
+    }
+};
+
+template<typename Function, typename Tp>
+struct userdata_variable_function : public userdata_function_core<Function, Tp> {
+    typedef userdata_function_core<Function, Tp> base_t;
+    typedef typename std::remove_pointer<Tp>::type T;
+    typedef member_traits<Function> traits_type;
+    typedef typename traits_type::args_type args_type;
+    typedef typename traits_type::return_type return_type;
+
+    template<typename... FxArgs>
+    userdata_variable_function(FxArgs&&... fxargs): base_t(std::forward<FxArgs>(fxargs)...) {}
+
+    template <typename Tx>
+    int fx_call (lua_State* L) {
+        type t = stack::get<type>(L, 1);
+        switch(t) {
+        case type::table:
+            lua_getfield(L, 1, "sol.userdatavalue");
+            this->fx.item = detail::get_ptr(stack::get<Tx>(L, -1));
+            lua_pop(L, 1);
+            break;
+        default:
+            this->fx.item = detail::get_ptr(stack::get<Tx>(L, 1));
+            break;
+        }
+        if (this->fx.item == nullptr)
+            throw error("userdata for member variable is null");
+        int argcount = lua_gettop(L);
+        switch (argcount) {
+        case 2:
+            return static_cast<base_t&>(*this)(tuple_types<return_type>(), types<>(), L);
+        case 3:
+            return static_cast<base_t&>(*this)(tuple_types<void>(), args_type(), L);
+        default:
+            throw error("cannot get/set userdata member variable with inappropriate number of arguments");
+        }
+
+    }
+
+    virtual int operator()(lua_State* L) override {
+        return fx_call<T>(L);
+    }
+
+    virtual int operator()(lua_State* L, detail::ref_call_t) override {
+        return fx_call<T*>(L);
+    }
+};
+
+template<typename Function, typename Tp>
+struct userdata_indexing_function : public userdata_function_core<Function, Tp> {
+    typedef userdata_function_core<Function, Tp> base_t;
+    typedef typename std::remove_pointer<Tp>::type T;
+    typedef member_traits<Function> traits_type;
+    typedef typename traits_type::args_type args_type;
+    typedef typename traits_type::return_type return_type;
+
+    std::string name;
+    std::unordered_map<std::string, std::pair<std::unique_ptr<base_function>, bool>> functions;
+
+    template<typename... FxArgs>
+    userdata_indexing_function(std::string name, FxArgs&&... fxargs): base_t(std::forward<FxArgs>(fxargs)...), name(std::move(name)) {}
+
+    template <typename Tx>
+    int fx_call (lua_State* L) {
+        std::string accessor = stack::get<std::string>(L, 1 - lua_gettop(L));
+        auto function = functions.find(accessor);
+        if (function != functions.end()) {
+            if (function->second.second) {
+                stack::push<upvalue_t>(L, function->second.first.get());
+                stack::push(L, &base_function::userdata<0>::call, 1);
+                return 1;
+            }
+            else {
+                return (*function->second.first)(L);
+            }
+        }
+        if (this->fx.invocation == nullptr) {
+            std::string err = "invalid indexing \"";
+            err += accessor;
+            err += "\" on type: ";
+            err += name;
+            throw error(err);
+        }
+        this->fx.item = detail::get_ptr(stack::get<Tx>(L, 1));
+        return static_cast<base_t&>(*this)(tuple_types<return_type>(), args_type(), L);
+    }
+
+    virtual int operator()(lua_State* L) override {
+        return fx_call<T>(L);
+    }
+
+    virtual int operator()(lua_State* L, detail::ref_call_t) override {
+        return fx_call<T*>(L);
     }
 };
 

sol/stack.hpp

@@ -462,17 +462,6 @@ inline call_syntax get_call_syntax(lua_State* L, const std::string& meta) {
     return call_syntax::dot;
 }
 
-inline std::string dump_types(lua_State* L) {
-    std::string visual;
-    std::size_t size = lua_gettop(L) + 1;
-    for (std::size_t i = 1; i < size; ++i) {
-        if (i != 1)
-            visual += " | ";
-        visual += type_name(L, stack::get<type>(L, i));
-    }
-    return visual;
-}
-
 template <typename T>
 struct get_return {
     typedef decltype(get<T>(nullptr)) type;

sol/state.hpp

@@ -79,33 +79,43 @@ public:
             switch(library) {
             case lib::base:
                 luaL_requiref(L.get(), "base", luaopen_base, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::package:
                 luaL_requiref(L.get(), "package", luaopen_package, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::coroutine:
                 luaL_requiref(L.get(), "coroutine", luaopen_coroutine, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::string:
                 luaL_requiref(L.get(), "string", luaopen_string, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::table:
                 luaL_requiref(L.get(), "table", luaopen_table, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::math:
                 luaL_requiref(L.get(), "math", luaopen_math, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::bit32:
                 luaL_requiref(L.get(), "bit32", luaopen_bit32, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::io:
                 luaL_requiref(L.get(), "io", luaopen_io, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::os:
                 luaL_requiref(L.get(), "os", luaopen_os, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::debug:
                 luaL_requiref(L.get(), "debug", luaopen_debug, 1);
+                lua_pop(L.get(), 1);
                 break;
             case lib::count:
                 break;

sol/traits.hpp

@@ -46,6 +46,14 @@ struct unwrap<std::reference_wrapper<T>> {
     typedef typename std::add_lvalue_reference<T>::type type;
 };
 
+template <typename T>
+struct remove_member_pointer;
+
+template <typename R, typename T>
+struct remove_member_pointer<R T::*> {
+    typedef R type;
+};
+
 template <typename T, template <typename...> class Templ>
 struct is_specialization_of : std::false_type { };
 template <typename... T, template <typename...> class Templ>
@@ -57,6 +65,9 @@ struct are_same : std::true_type { };
 template<class T, class U, class... Args>
 struct are_same<T, U, Args...> : std::integral_constant <bool, std::is_same<T, U>::value && are_same<T, Args...>::value> { };
 
+template<typename T>
+using Type = typename T::type;
+
 template<bool B>
 using Bool = std::integral_constant<bool, B>;
 
@@ -66,6 +77,9 @@ using Not = Bool<!T::value>;
 template<typename Condition, typename Then, typename Else>
 using If = typename std::conditional<Condition::value, Then, Else>::type;
 
+template<typename Condition, typename Then, typename Else>
+using TypeIf = typename std::conditional<Condition::value, Type<Then>, Type<Else>>::type;
+
 template<typename... Args>
 struct And : Bool<true> {};
 
@@ -206,6 +220,35 @@ struct function_traits<R(*)(Args...)> {
     using arg = typename std::tuple_element<i, arg_tuple_type>::type;
 };
 
+namespace detail {
+template <typename Signature, bool b = std::is_member_object_pointer<Signature>::value>
+struct member_traits : function_traits<Signature> {
+
+};
+
+template <typename Signature>
+struct member_traits<Signature, true> {
+    typedef typename remove_member_pointer<Signature>::type Arg;
+    typedef typename remove_member_pointer<Signature>::type R;
+    typedef Signature signature_type;
+    static const bool is_member_function = false;
+    static const std::size_t arity = 1;
+    typedef std::tuple<Arg> arg_tuple_type;
+    typedef types<Arg> args_type;
+    typedef R return_type;
+    typedef R(function_type)(Arg);
+    typedef R(*function_pointer_type)(Arg);
+    typedef R(*free_function_pointer_type)(Arg);
+    template<std::size_t i>
+    using arg = typename std::tuple_element<i, arg_tuple_type>::type;
+};
+} // detail
+
+template <typename Signature>
+struct member_traits : detail::member_traits<Signature> {
+
+};
+
 struct has_begin_end_impl {
     template<typename T, typename U = Unqualified<T>,
                          typename B = decltype(std::declval<U&>().begin()),

sol/userdata.hpp

@@ -41,18 +41,16 @@ inline std::unique_ptr<T> make_unique(Args&&... args) {
 template<typename T>
 class userdata {
 private:
+    typedef std::unordered_map<std::string, std::pair<std::unique_ptr<base_function>, bool>> function_map_t;
+    const static std::array<std::string, 2> metavariablenames;
     const static std::array<std::string, 19> metafunctionnames;
-    std::string luaname;
+    function_map_t indexmetafunctions, newindexmetafunctions;
     std::vector<std::string> functionnames;
-    std::vector<std::unique_ptr<base_function>> funcs;
-    std::vector<std::unique_ptr<base_function>> ptrfuncs;
-    std::vector<std::unique_ptr<base_function>> metafuncs;
-    std::vector<std::unique_ptr<base_function>> ptrmetafuncs;
-    std::vector<luaL_Reg> functiontable;
-    std::vector<luaL_Reg> ptrfunctiontable;
+    std::vector<std::unique_ptr<base_function>> metafunctions;
     std::vector<luaL_Reg> metafunctiontable;
     std::vector<luaL_Reg> ptrmetafunctiontable;
     lua_CFunction cleanup;
+    std::string luaname;
 
     template<typename... TTypes>
     struct constructor {
@@ -84,14 +82,12 @@ private:
             T* obj = static_cast<T*>(udata);
             match_constructor(L, obj, syntax, argcount - static_cast<int>(syntax), typename identity<TTypes>::type()...);
 
-
             if (luaL_newmetatable(L, std::addressof(meta[0])) == 1) {
                 lua_pop(L, 1);
                 std::string err = "Unable to get userdata metatable for ";
                 err += meta;
                 throw error(err);
             }
-
             lua_setmetatable(L, -2);
 
             return 1;
@@ -108,59 +104,121 @@ private:
         }
     };
 
-    template <bool release = false, typename TCont>
-    static int push_upvalues (lua_State* L, TCont&& cont) {
-        int n = 0;
-        for (auto& c : cont) {
-            if (release)
-               stack::push<upvalue_t>(L, c.release());
-            else
-                stack::push<upvalue_t>(L, c.get());
-            ++n;
-        }
-        return n;
+    template<std::size_t N>
+    void build_cleanup () {
+        cleanup = &base_function::userdata<N>::gc;
     }
 
-    template <typename Meta, typename Funcs, typename FuncTable, typename MetaFuncs, typename MetaFuncTable>
-    static void push_metatable(lua_State* L, Meta&& meta, Funcs&& funcs, FuncTable&& functable, MetaFuncs&& metafuncs, MetaFuncTable&& metafunctable) {
-        luaL_newmetatable(L, std::addressof(meta[0]));
-        if (functable.size() > 1) {
-            // regular functions accessed through __index semantics
-            int up = push_upvalues(L, funcs);
-            luaL_setfuncs(L, functable.data(), up);
-        }
-        if (metafunctable.size() > 1) {
-            // meta functions
-            int up = push_upvalues(L, metafuncs);
-            luaL_setfuncs(L, metafunctable.data(), up);
-        }
-        lua_pushvalue(L, -1);
-        lua_setfield(L, -1, "__index");
-    }
-
-    template<std::size_t N, std::size_t M>
-    void build_function_tables() {}
-
-    template<std::size_t N, std::size_t M, typename... Args, typename TBase, typename Ret>
-    void build_function_tables(std::string funcname, Ret TBase::* func, Args&&... args) {
-        static_assert(std::is_base_of<TBase, T>::value, "Any registered function must be part of the class");
-        typedef typename std::decay<decltype(func)>::type function_type;
-        functionnames.push_back(std::move(funcname));
+    template<std::size_t N>
+    void build_function_tables(function_map_t*& index, function_map_t*& newindex) {
+        int extracount = 0;
+        if (!indexmetafunctions.empty()) {
+            if (index == nullptr) {
+                auto idxptr = detail::make_unique<userdata_indexing_function<void (T::*)(), T>>("__index", nullptr);
+                index = &(idxptr->functions);
+                functionnames.emplace_back("__index");
+                metafunctions.emplace_back(std::move(idxptr));
                 std::string& name = functionnames.back();
-        auto metamethod = std::find(metafunctionnames.begin(), metafunctionnames.end(), name);
-        if (metamethod != metafunctionnames.end()) {
-            metafuncs.emplace_back(detail::make_unique<userdata_function<function_type, T>>(std::move(func)));
-            ptrmetafuncs.emplace_back(detail::make_unique<userdata_function<function_type, typename std::add_pointer<T>::type>>(std::move(func)));
                 metafunctiontable.push_back( { name.c_str(), &base_function::userdata<N>::call } );
-            ptrmetafunctiontable.push_back({ name.c_str(), &base_function::userdata<N>::call });
-            build_function_tables<N + 1, M>(std::forward<Args>(args)...);
+                ptrmetafunctiontable.push_back( { name.c_str(), &base_function::userdata<N>::ref_call } );
+                ++extracount;
+            }
+            auto& idx = *index;
+            for (auto&& namedfunc : indexmetafunctions ) {
+                idx.emplace(std::move(namedfunc.first), std::move(namedfunc.second));
+            }
+        }
+        if (!newindexmetafunctions.empty()) {
+            if (newindex == nullptr) {
+                auto idxptr = detail::make_unique<userdata_indexing_function<void (T::*)(), T>>("__newindex", nullptr);
+                newindex = &(idxptr->functions);
+                functionnames.emplace_back("__newindex");
+                metafunctions.emplace_back(std::move(idxptr));
+                std::string& name = functionnames.back();
+                if (extracount > 0) {
+                    metafunctiontable.push_back( { name.c_str(), &base_function::userdata<N + 1>::call } );
+                    ptrmetafunctiontable.push_back( { name.c_str(), &base_function::userdata<N + 1>::ref_call } );
                 }
                 else {
-            funcs.emplace_back(detail::make_unique<userdata_function<function_type, T>>(std::move(func)));
-            ptrfuncs.emplace_back(detail::make_unique<userdata_function<function_type, typename std::add_pointer<T>::type>>(std::move(func)));
-            functiontable.push_back({ name.c_str(), &base_function::userdata<M>::call });
-            ptrfunctiontable.push_back({ name.c_str(), &base_function::userdata<M>::call });
-            build_function_tables<N, M + 1>(std::forward<Args>(args)...);
+                    metafunctiontable.push_back( { name.c_str(), &base_function::userdata<N>::call } );
+                    ptrmetafunctiontable.push_back( { name.c_str(), &base_function::userdata<N>::ref_call } );
+                }
+                ++extracount;
+            }
+            auto& idx = *newindex;
+            for (auto&& namedfunc : newindexmetafunctions ) {
+                idx.emplace(std::move(namedfunc.first), std::move(namedfunc.second));
+            }
+        }
+        switch (extracount) {
+        case 2:
+            build_cleanup<N + 2>();
+            break;
+        case 1:
+            build_cleanup<N + 1>();
+            break;
+        case 0:
+        default:
+            build_cleanup<N + 0>();
+            break;
+        }
+    }
+
+    template<std::size_t N, typename TBase, typename Ret>
+    bool build_function(std::true_type, function_map_t*&, function_map_t*&, std::string funcname, Ret TBase::* func) {
+        static_assert(std::is_base_of<TBase, T>::value, "Any registered function must be part of the class");
+        typedef typename std::decay<decltype(func)>::type function_type;
+        indexmetafunctions.emplace(funcname, std::make_pair(detail::make_unique<userdata_variable_function<function_type, T>>(func), false));
+        newindexmetafunctions.emplace(funcname, std::make_pair(detail::make_unique<userdata_variable_function<function_type, T>>(func), false));
+        return false;
+    }
+
+    template<std::size_t N, typename TBase, typename Ret>
+    bool build_function(std::false_type, function_map_t*& index, function_map_t*& newindex, std::string funcname, Ret TBase::* func) {
+        static_assert(std::is_base_of<TBase, T>::value, "Any registered function must be part of the class");
+        typedef typename std::decay<decltype(func)>::type function_type;
+        auto metamethod = std::find(metafunctionnames.begin(), metafunctionnames.end(), funcname);
+        if (metamethod != metafunctionnames.end()) {
+            functionnames.push_back(std::move(funcname));
+            std::string& name = functionnames.back();
+            auto indexmetamethod = std::find(metavariablenames.begin(), metavariablenames.end(), name);
+            std::unique_ptr<base_function> ptr(nullptr);
+            if (indexmetamethod != metavariablenames.end()) {
+                auto idxptr = detail::make_unique<userdata_indexing_function<function_type, T>>(name, func);
+                switch( std::distance(indexmetamethod, metavariablenames.end()) ) {
+                case 0:
+                    index = &(idxptr->functions);
+                    break;
+                case 1:
+                    newindex = &(idxptr->functions);
+                    break;
+                default:
+                    break;
+                }
+                ptr = std::move(idxptr);
+            }
+            else {
+                ptr = detail::make_unique<userdata_function<function_type, T>>(func);
+            }
+            metafunctions.emplace_back(std::move(ptr));
+            metafunctiontable.push_back( { name.c_str(), &base_function::userdata<N>::call } );
+            ptrmetafunctiontable.push_back( { name.c_str(), &base_function::userdata<N>::ref_call } );
+            return true;
+        }
+        indexmetafunctions.emplace(funcname, std::make_pair(detail::make_unique<userdata_function<function_type, T>>(func), true ));
+        newindexmetafunctions.emplace(funcname, std::make_pair(detail::make_unique<userdata_function<function_type, T>>(func), true));
+        return false;
+    }
+
+    template<std::size_t N, typename TBase, typename Ret, typename... Args>
+    void build_function_tables(function_map_t*& index, function_map_t*& newindex, std::string funcname, Ret TBase::* func, Args&&... args) {
+        typedef typename std::is_member_object_pointer<decltype(func)>::type is_variable;
+        static const std::size_t V = static_cast<std::size_t>( !is_variable::value );
+        if (build_function<N>(is_variable(), index, newindex, std::move(funcname), func)) {
+            build_function_tables<N + V>(index, newindex, std::forward<Args>(args)...);
+        }
+        else {
+            build_function_tables<N>(index, newindex, std::forward<Args>(args)...);
         }
     }
 
@@ -174,22 +232,16 @@ public:
     template<typename... Args, typename... CArgs>
     userdata(std::string name, constructors<CArgs...>, Args&&... args): luaname(std::move(name)) {
         functionnames.reserve(sizeof...(args) + 2);
-
-        functiontable.reserve(sizeof...(args));
-        ptrfunctiontable.reserve(sizeof...(args));
         metafunctiontable.reserve(sizeof...(args));
         ptrmetafunctiontable.reserve(sizeof...(args));
 
-        funcs.reserve(sizeof...(args));
-        ptrfuncs.reserve(sizeof...(args));
-        metafuncs.reserve(sizeof...(args));
-        ptrmetafuncs.reserve(sizeof...(args));
-
-        cleanup = &base_function::userdata_gc<sizeof...(Args)>::gc;
-
-        build_function_tables<0, 0>(std::forward<Args>(args)...);
+        function_map_t* index = nullptr;
+        function_map_t* newindex = nullptr;
+        build_function_tables<0>(index, newindex, std::forward<Args>(args)...);
+        indexmetafunctions.clear();
+        newindexmetafunctions.clear();
         functionnames.push_back("new");
-        functiontable.push_back({ functionnames.back().c_str(), &constructor<CArgs...>::construct });
+        metafunctiontable.push_back({ functionnames.back().c_str(), &constructor<CArgs...>::construct });
         functionnames.push_back("__gc");
         metafunctiontable.push_back({ functionnames.back().c_str(), &destructor::destruct });
         // ptr_functions does not participate in garbage collection/new,
@@ -197,9 +249,7 @@ public:
         // to be references. This makes returns of
         // `std::vector<int>&` and `std::vector<int>*` work
 
-        functiontable.push_back({ nullptr, nullptr });
         metafunctiontable.push_back( { nullptr, nullptr } );
-        ptrfunctiontable.push_back({ nullptr, nullptr });
         ptrmetafunctiontable.push_back( { nullptr, nullptr } );
     }
 
@@ -213,27 +263,60 @@ public:
 
     void push (lua_State* L) {
         // push pointer tables first,
-        // but leave the regular T table on last so it can be linked to a type for usage with `.new(...)`
+        // but leave the regular T table on last
+        // so it can be linked to a type for usage with `.new(...)` or `:new(...)`
         push_metatable(L, userdata_traits<T*>::metatable,
-                       ptrfuncs, ptrfunctiontable,
-                       ptrmetafuncs, ptrmetafunctiontable);
+                       metafunctions, ptrmetafunctiontable);
+        lua_pop(L, 1);
+
         push_metatable(L, userdata_traits<T>::metatable,
-                       funcs, functiontable,
-                       metafuncs, metafunctiontable);
+                       metafunctions, metafunctiontable);
+        set_global_deleter(L);
+    }
+private:
+
+    template <typename Meta, typename MetaFuncs, typename MetaFuncTable>
+    static void push_metatable(lua_State* L, Meta&& metakey, MetaFuncs&& metafuncs, MetaFuncTable&& metafunctable) {
+        luaL_newmetatable(L, std::addressof(metakey[0]));
+        if (metafunctable.size() > 1) {
+            // regular functions accessed through __index semantics
+            int up = push_upvalues(L, metafuncs);
+            luaL_setfuncs(L, metafunctable.data(), up);
+        }
+
+    }
+
+    void set_global_deleter (lua_State* L) {
         // Automatic deleter table -- stays alive until lua VM dies
         // even if the user calls collectgarbage()
         lua_createtable(L, 0, 0);
         lua_createtable(L, 0, 1);
-        int up = push_upvalues<true>(L, funcs);
-        up += push_upvalues<true>(L, ptrfuncs);
-        up += push_upvalues<true>(L, metafuncs);
-        up += push_upvalues<true>(L, ptrmetafuncs);
+        int up = push_upvalues<true>(L, metafunctions);
         lua_pushcclosure(L, cleanup, up);
         lua_setfield(L, -2, "__gc");
         lua_setmetatable(L, -2);
         // gctable name by default has ♻ part of it
         lua_setglobal(L, std::addressof(userdata_traits<T>::gctable[0]));
     }
+
+    template <bool release = false, typename TCont>
+    static int push_upvalues (lua_State* L, TCont&& cont) {
+        int n = 0;
+        for (auto& c : cont) {
+            if (release)
+               stack::push<upvalue_t>(L, c.release());
+            else
+                stack::push<upvalue_t>(L, c.get());
+            ++n;
+        }
+        return n;
+    }
+};
+
+template <typename T>
+const std::array<std::string, 2> userdata<T>::metavariablenames = {
+    "__index",
+    "__newindex"
 };
 
 template <typename T>

tests.cpp

@@ -148,6 +148,18 @@ public:
     }
 };
 
+struct Vec {
+  float x, y, z;
+  Vec(float x, float y, float z) : x{x}, y{y}, z{z} {}
+  float length() {
+    return sqrtf(x*x + y*y + z*z);
+  }
+  Vec normalized() {
+    float invS = 1 / length();
+    return {x * invS, y * invS, z * invS};
+  }
+};
+
 TEST_CASE("simple/set_global", "Check if the set_global works properly.") {
     sol::state lua;
 
@@ -713,19 +725,6 @@ TEST_CASE("tables/issue-number-twenty-five", "Using pointers and references from
 }
 
 TEST_CASE("userdata/issue-number-thirty-five", "using value types created from lua-called C++ code, fixing user-defined types with constructors") {
-    struct Vec {
-        float x, y, z;
-        Vec(float x, float y, float z) : x{x}, y{y}, z{z} {}
-        float length() {
-            return sqrtf(x*x + y*y + z*z);
-        }
-
-        Vec normalized() {
-            float invS = 1 / length();
-            return {x * invS, y * invS, z * invS};
-        }
-    };
-
     struct Line {
         Vec p1, p2;
         Line() : p1{0, 0, 0}, p2{0, 0, 0} {}
@@ -753,18 +752,6 @@ TEST_CASE("userdata/issue-number-thirty-five", "using value types created from l
 }
 
 TEST_CASE("userdata/lua-stored-userdata", "ensure userdata values can be stored without keeping userdata object alive") {
-    struct Vec {
-      float x, y, z;
-      Vec(float x, float y, float z) : x{x}, y{y}, z{z} {}
-      float length() {
-        return sqrtf(x*x + y*y + z*z);
-      }
-      Vec normalized() {
-        float invS = 1 / length();
-        return {x * invS, y * invS, z * invS};
-      }
-    };
-
     sol::state lua;
     lua.open_libraries(sol::lib::base);
 
@@ -785,3 +772,31 @@ TEST_CASE("userdata/lua-stored-userdata", "ensure userdata values can be stored
     REQUIRE_NOTHROW(lua.script("v = Vec.new(1, 2, 3)\n"
                 "print(v:normalized():length())" ));
 }
+
+TEST_CASE("userdata/member-variables", "allow table-like accessors to behave as member variables for userdata") {
+    sol::state lua;
+    lua.open_libraries(sol::lib::base);
+    sol::constructors<sol::types<float, float, float>> ctor;
+    sol::userdata<Vec> udata("Vec", ctor,
+                             "x", &Vec::x,
+                             "y", &Vec::y,
+                             "z", &Vec::z,
+                             "normalized", &Vec::normalized,
+                             "length",     &Vec::length);
+    lua.set_userdata(udata);
+
+    REQUIRE_NOTHROW(lua.script("v = Vec.new(1, 2, 3)\n"
+               "v2 = Vec.new(0, 1, 0)\n"
+               "print(v:length())\n"
+               "v.x = 2\n"
+               "v2.y = 2\n"
+               "print(v.x, v.y, v.z)\n"
+               "print(v2.x, v2.y, v2.z)\n"
+               "assert(v.x == 2)\n"
+               "assert(v2.x == 0)\n"
+               "assert(v2.y == 2)\n"
+               "v.x = 3\n"
+               "local x = v.x\n"
+               "assert(x == 3)\n"
+               ));
+}