build: add EnTT library

include/entt/stl/memory.hpp

@@ -0,0 +1,74 @@
+#ifndef ENTT_STL_MEMORY_HPP
+#define ENTT_STL_MEMORY_HPP
+
+/*! @cond ENTT_INTERNAL */
+#if __has_include(<entt/ext/stl/memory.hpp>)
+#    include <entt/ext/stl/memory.hpp>
+#else
+#    include <memory>
+#    include <version>
+#    include "../config/config.h"
+
+namespace entt::stl {
+
+using std::addressof;
+using std::allocate_shared;
+using std::allocator;
+using std::allocator_arg;
+using std::allocator_arg_t;
+using std::allocator_traits;
+using std::default_delete;
+using std::destroy;
+using std::enable_shared_from_this;
+using std::make_shared;
+using std::make_unique;
+using std::pointer_traits;
+using std::shared_ptr;
+using std::static_pointer_cast;
+using std::uninitialized_fill;
+using std::unique_ptr;
+using std::uses_allocator_v;
+
+} // namespace entt::stl
+
+#    ifndef ENTT_FORCE_STL
+#        if defined(__cpp_lib_to_address)
+#            define ENTT_HAS_TO_ADDRESS
+
+namespace entt::stl {
+
+using std::to_address;
+
+} // namespace entt::stl
+
+#        endif
+#    endif
+
+#    ifndef ENTT_HAS_TO_ADDRESS
+#        include <type_traits>
+
+namespace entt::stl {
+
+template<typename Type>
+constexpr Type *to_address(Type *ptr) noexcept {
+    static_assert(!std::is_function_v<Type>, "Invalid type");
+    return ptr;
+}
+
+template<typename Type>
+constexpr auto to_address(const Type &ptr) noexcept {
+    if constexpr(requires { std::pointer_traits<Type>::to_address(ptr); }) {
+        return std::pointer_traits<Type>::to_address(ptr);
+    } else {
+        return to_address(ptr.operator->());
+    }
+}
+
+} // namespace entt::stl
+#    endif
+#endif
+/*! @endcond */
+
+#undef ENTT_HAS_TO_ADDRESS
+
+#endif