Generalize alloc_cted_insert_type into allocator_constructed and remove the factory function alloc_make_insert_type()

include/boost/unordered/detail/allocator_constructed.hpp

@@ -0,0 +1,59 @@
+/* Copyright 2024 Braden Ganetsky.
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See https://www.boost.org/libs/unordered for library home page.
+ */
+
+#ifndef BOOST_UNORDERED_DETAIL_ALLOCATOR_CONSTRUCTED_HPP
+#define BOOST_UNORDERED_DETAIL_ALLOCATOR_CONSTRUCTED_HPP
+
+#include <boost/core/allocator_traits.hpp>
+#include <boost/unordered/detail/opt_storage.hpp>
+
+namespace boost {
+  namespace unordered {
+    namespace detail {
+
+      struct allocator_policy
+      {
+        template <class Allocator, class T, class... Args>
+        static void construct(Allocator& a, T* p, Args&&... args)
+        {
+          boost::allocator_construct(a, p, std::forward<Args>(args)...);
+        }
+
+        template <class Allocator, class T>
+        static void destroy(Allocator& a, T* p)
+        {
+          boost::allocator_destroy(a, p);
+        }
+      };
+
+      /* constructs a stack-based object with the given policy and allocator */
+      template <class Allocator, class T, class Policy = allocator_policy>
+      class allocator_constructed
+      {
+        opt_storage<T> storage;
+        Allocator alloc;
+
+      public:
+        template <class... Args>
+        allocator_constructed(Allocator const& alloc_, Args&&... args)
+            : alloc(alloc_)
+        {
+          Policy::construct(
+            alloc, storage.address(), std::forward<Args>(args)...);
+        }
+
+        ~allocator_constructed() { Policy::destroy(alloc, storage.address()); }
+
+        T& value() { return *storage.address(); }
+      };
+
+    } /* namespace detail */
+  }   /* namespace unordered */
+} /* namespace boost */
+
+#endif

include/boost/unordered/detail/foa/concurrent_table.hpp

@@ -1320,7 +1320,7 @@ private:
   {
     auto lck=shared_access();
 
-    auto x=alloc_make_insert_type<type_policy>(
+    alloc_cted_insert_type<type_policy,Allocator,Args...> x(
       this->al(),std::forward<Args>(args)...);
     int res=unprotected_norehash_emplace_or_visit(
       access_mode,std::forward<F>(f),type_policy::move(x.value()));

include/boost/unordered/detail/foa/core.hpp

@@ -22,6 +22,7 @@
 #include <boost/core/pointer_traits.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/predef.h>
+#include <boost/unordered/detail/allocator_constructed.hpp>
 #include <boost/unordered/detail/narrow_cast.hpp>
 #include <boost/unordered/detail/mulx.hpp>
 #include <boost/unordered/detail/static_assert.hpp>
@@ -1220,31 +1221,17 @@ class alloc_cted_insert_type
     emplace_type,typename TypePolicy::element_type
   >::type;
 
-  alignas(insert_type) unsigned char storage[sizeof(insert_type)];
-  Allocator                          al;
+  using alloc_cted = allocator_constructed<Allocator, insert_type, TypePolicy>;
+  alloc_cted val;
 
 public:
-  alloc_cted_insert_type(const Allocator& al_,Args&&... args):al{al_}
+  alloc_cted_insert_type(const Allocator& al_,Args&&... args):val{al_,std::forward<Args>(args)...}
   {
-    TypePolicy::construct(al,data(),std::forward<Args>(args)...);
   }
 
-  ~alloc_cted_insert_type()
-  {
-    TypePolicy::destroy(al,data());
-  }
-
-  insert_type* data(){return reinterpret_cast<insert_type*>(&storage);}
-  insert_type& value(){return *data();}
+  insert_type& value(){return val.value();}
 };
 
-template<typename TypePolicy,typename Allocator,typename... Args>
-alloc_cted_insert_type<TypePolicy,Allocator,Args...>
-alloc_make_insert_type(const Allocator& al,Args&&... args)
-{
-  return {al,std::forward<Args>(args)...};
-}
-
 /* table_core. The TypePolicy template parameter is used to generate
  * instantiations suitable for either maps or sets, and introduces non-standard
  * init_type and element_type:

include/boost/unordered/detail/foa/table.hpp

@@ -401,7 +401,7 @@ public:
   template<typename... Args>
   BOOST_FORCEINLINE std::pair<iterator,bool> emplace(Args&&... args)
   {
-    auto x=alloc_make_insert_type<type_policy>(
+    alloc_cted_insert_type<type_policy,Allocator,Args...> x(
       this->al(),std::forward<Args>(args)...);
     return emplace_impl(type_policy::move(x.value()));
   }