Use boost::empty_value

fix #1233

CHANGELOG.md

@@ -2,6 +2,7 @@ Version 183:
 
 * Fix a rare case of failed UTF8 validation
 * Verify certificates in client examples
+* Use boost::empty_value
 
 --------------------------------------------------------------------------------
 

doc/qbk/09_releases.qbk

@@ -9,6 +9,8 @@
 
 [section Release Notes]
 
+
+
 [heading Boost 1.69]
 
 [*Fixes]
@@ -17,6 +19,10 @@
 
 * ([issue 1237]) Verify certificates in client examples
 
+* ([issue 1233]) Use [@boost:/doc/html/core/empty_value.html `boost::empty_value`]
+
+
+
 [heading Boost 1.68]
 
 This version fixes a missing executor work guard in all composed operations

include/boost/beast/core/detail/empty_base_optimization.hpp

@@ -1,100 +0,0 @@
-//
-// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
-//
-// 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)
-//
-// Official repository: https://github.com/boostorg/beast
-//
-
-#ifndef BOOST_BEAST_DETAIL_EMPTY_BASE_OPTIMIZATION_HPP
-#define BOOST_BEAST_DETAIL_EMPTY_BASE_OPTIMIZATION_HPP
-
-#include <boost/type_traits/is_final.hpp>
-#include <type_traits>
-#include <utility>
-
-namespace boost {
-namespace beast {
-namespace detail {
-
-template<class T>
-struct is_empty_base_optimization_derived
-    : std::integral_constant<bool,
-        std::is_empty<T>::value &&
-        ! boost::is_final<T>::value>
-{
-};
-
-template<class T, int UniqueID = 0,
-    bool isDerived =
-        is_empty_base_optimization_derived<T>::value>
-class empty_base_optimization : private T
-{
-public:
-    empty_base_optimization() = default;
-    empty_base_optimization(empty_base_optimization&&) = default;
-    empty_base_optimization(empty_base_optimization const&) = default;
-    empty_base_optimization& operator=(empty_base_optimization&&) = default;
-    empty_base_optimization& operator=(empty_base_optimization const&) = default;
-
-    template<class Arg1, class... ArgN>
-    explicit
-    empty_base_optimization(Arg1&& arg1, ArgN&&... argn)
-        : T(std::forward<Arg1>(arg1),
-            std::forward<ArgN>(argn)...)
-    {
-    }
-
-    T& member() noexcept
-    {
-        return *this;
-    }
-
-    T const& member() const noexcept
-    {
-        return *this;
-    }
-};
-
-//------------------------------------------------------------------------------
-
-template<
-    class T,
-    int UniqueID
->
-class empty_base_optimization <T, UniqueID, false>
-{
-    T t_;
-
-public:
-    empty_base_optimization() = default;
-    empty_base_optimization(empty_base_optimization&&) = default;
-    empty_base_optimization(empty_base_optimization const&) = default;
-    empty_base_optimization& operator=(empty_base_optimization&&) = default;
-    empty_base_optimization& operator=(empty_base_optimization const&) = default;
-
-    template<class Arg1, class... ArgN>
-    explicit
-    empty_base_optimization(Arg1&& arg1, ArgN&&... argn)
-        : t_(std::forward<Arg1>(arg1),
-            std::forward<ArgN>(argn)...)
-    {
-    }
-
-    T& member() noexcept
-    {
-        return t_;
-    }
-
-    T const& member() const noexcept
-    {
-        return t_;
-    }
-};
-
-} // detail
-} // beast
-} // boost
-
-#endif

include/boost/beast/core/flat_buffer.hpp

@@ -12,8 +12,8 @@
 
 #include <boost/beast/core/detail/config.hpp>
 #include <boost/beast/core/detail/allocator.hpp>
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
 #include <boost/asio/buffer.hpp>
+#include <boost/core/empty_value.hpp>
 #include <limits>
 #include <memory>
 
@@ -44,7 +44,7 @@ namespace beast {
 template<class Allocator>
 class basic_flat_buffer
 #if ! BOOST_BEAST_DOXYGEN
-    : private detail::empty_base_optimization<
+    : private boost::empty_value<
         typename detail::allocator_traits<Allocator>::
             template rebind_alloc<char>>
 #endif
@@ -218,7 +218,7 @@ public:
     allocator_type
     get_allocator() const
     {
-        return this->member();
+        return this->get();
     }
 
     /// Returns the size of the input sequence.

include/boost/beast/core/impl/flat_buffer.ipp

@@ -29,7 +29,7 @@ basic_flat_buffer<Allocator>::
 {
     if(begin_)
         alloc_traits::deallocate(
-            this->member(), begin_, dist(begin_, end_));
+            this->get(), begin_, dist(begin_, end_));
 }
 
 template<class Allocator>
@@ -59,7 +59,7 @@ basic_flat_buffer(std::size_t limit)
 template<class Allocator>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(Allocator const& alloc)
-    : detail::empty_base_optimization<base_alloc_type>(alloc)
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(), alloc)
     , begin_(nullptr)
     , in_(nullptr)
     , out_(nullptr)
@@ -72,7 +72,7 @@ basic_flat_buffer(Allocator const& alloc)
 template<class Allocator>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(std::size_t limit, Allocator const& alloc)
-    : detail::empty_base_optimization<base_alloc_type>(alloc)
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(), alloc)
     , begin_(nullptr)
     , in_(nullptr)
     , out_(nullptr)
@@ -85,8 +85,8 @@ basic_flat_buffer(std::size_t limit, Allocator const& alloc)
 template<class Allocator>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(basic_flat_buffer&& other)
-    : detail::empty_base_optimization<base_alloc_type>(
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(),
-        std::move(other.member()))
+        std::move(other.get()))
     , begin_(boost::exchange(other.begin_, nullptr))
     , in_(boost::exchange(other.in_, nullptr))
     , out_(boost::exchange(other.out_, nullptr))
@@ -101,9 +101,9 @@ template<class Allocator>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(basic_flat_buffer&& other,
         Allocator const& alloc)
-    : detail::empty_base_optimization<base_alloc_type>(alloc)
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(), alloc)
 {
-    if(this->member() != other.member())
+    if(this->get() != other.get())
     {
         begin_ = nullptr;
         in_ = nullptr;
@@ -133,9 +133,9 @@ basic_flat_buffer(basic_flat_buffer&& other,
 template<class Allocator>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(basic_flat_buffer const& other)
-    : detail::empty_base_optimization<base_alloc_type>(
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(),
         alloc_traits::select_on_container_copy_construction(
-            other.member()))
+            other.get()))
     , begin_(nullptr)
     , in_(nullptr)
     , out_(nullptr)
@@ -150,7 +150,7 @@ template<class Allocator>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(basic_flat_buffer const& other,
         Allocator const& alloc)
-    : detail::empty_base_optimization<base_alloc_type>(alloc)
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(), alloc)
     , begin_(nullptr)
     , in_(nullptr)
     , out_(nullptr)
@@ -181,7 +181,7 @@ template<class OtherAlloc>
 basic_flat_buffer<Allocator>::
 basic_flat_buffer(basic_flat_buffer<OtherAlloc> const& other,
         Allocator const& alloc)
-    : detail::empty_base_optimization<base_alloc_type>(alloc)
+    : boost::empty_value<base_alloc_type>(boost::empty_init_t(), alloc)
     , begin_(nullptr)
     , in_(nullptr)
     , out_(nullptr)
@@ -264,14 +264,14 @@ prepare(std::size_t n) ->
         max_,
         (std::max<std::size_t>)(2 * len, len + n));
     auto const p = alloc_traits::allocate(
-        this->member(), new_size);
+        this->get(), new_size);
     if(begin_)
     {
         BOOST_ASSERT(p);
         BOOST_ASSERT(in_);
         std::memcpy(p, in_, len);
         alloc_traits::deallocate(
-            this->member(), begin_, capacity());
+            this->get(), begin_, capacity());
     }
     begin_ = p;
     in_ = begin_;
@@ -309,7 +309,7 @@ shrink_to_fit()
         BOOST_ASSERT(begin_);
         BOOST_ASSERT(in_);
         p = alloc_traits::allocate(
-            this->member(), len);
+            this->get(), len);
         std::memcpy(p, in_, len);
     }
     else
@@ -317,7 +317,7 @@ shrink_to_fit()
         p = nullptr;
     }
     alloc_traits::deallocate(
-        this->member(), begin_, dist(begin_, end_));
+        this->get(), begin_, dist(begin_, end_));
     begin_ = p;
     in_ = begin_;
     out_ = begin_ + len;
@@ -358,7 +358,7 @@ basic_flat_buffer<Allocator>::
 move_assign(basic_flat_buffer& other, std::true_type)
 {
     reset();
-    this->member() = std::move(other.member());
+    this->get() = std::move(other.get());
     begin_ = other.begin_;
     in_ = other.in_;
     out_ = other.out_;
@@ -379,7 +379,7 @@ basic_flat_buffer<Allocator>::
 move_assign(basic_flat_buffer& other, std::false_type)
 {
     reset();
-    if(this->member() != other.member())
+    if(this->get() != other.get())
     {
         copy_from(other);
         other.reset();
@@ -398,7 +398,7 @@ copy_assign(basic_flat_buffer const& other, std::true_type)
 {
     reset();
     max_ = other.max_;
-    this->member() = other.member();
+    this->get() = other.get();
     copy_from(other);
 }
 
@@ -430,7 +430,7 @@ basic_flat_buffer<Allocator>::
 swap(basic_flat_buffer& other, std::true_type)
 {
     using std::swap;
-    swap(this->member(), other.member());
+    swap(this->get(), other.get());
     swap(max_, other.max_);
     swap(begin_, other.begin_);
     swap(in_, other.in_);
@@ -446,7 +446,7 @@ void
 basic_flat_buffer<Allocator>::
 swap(basic_flat_buffer& other, std::false_type)
 {
-    BOOST_ASSERT(this->member() == other.member());
+    BOOST_ASSERT(this->get() == other.get());
     using std::swap;
     swap(max_, other.max_);
     swap(begin_, other.begin_);

include/boost/beast/core/impl/multi_buffer.ipp

@@ -440,8 +440,8 @@ basic_multi_buffer(std::size_t limit)
 template<class Allocator>
 basic_multi_buffer<Allocator>::
 basic_multi_buffer(Allocator const& alloc)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(alloc)
+        base_alloc_type>(boost::empty_init_t(), alloc)
     , out_(list_.end())
 {
 }
@@ -450,8 +450,8 @@ template<class Allocator>
 basic_multi_buffer<Allocator>::
 basic_multi_buffer(std::size_t limit,
         Allocator const& alloc)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(alloc)
+        base_alloc_type>(boost::empty_init_t(), alloc)
     , max_(limit)
     , out_(list_.end())
 {
@@ -460,8 +460,8 @@ basic_multi_buffer(std::size_t limit,
 template<class Allocator>
 basic_multi_buffer<Allocator>::
 basic_multi_buffer(basic_multi_buffer&& other)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(std::move(other.member()))
+        base_alloc_type>(boost::empty_init_t(), std::move(other.get()))
     , max_(other.max_)
     , in_size_(boost::exchange(other.in_size_, 0))
     , in_pos_(boost::exchange(other.in_pos_, 0))
@@ -479,11 +479,11 @@ template<class Allocator>
 basic_multi_buffer<Allocator>::
 basic_multi_buffer(basic_multi_buffer&& other,
         Allocator const& alloc)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(alloc)
+        base_alloc_type>(boost::empty_init_t(), alloc)
     , max_(other.max_)
 {
-    if(this->member() != other.member())
+    if(this->get() != other.get())
     {
         out_ = list_.end();
         copy_from(other);
@@ -510,10 +510,10 @@ basic_multi_buffer(basic_multi_buffer&& other,
 template<class Allocator>
 basic_multi_buffer<Allocator>::
 basic_multi_buffer(basic_multi_buffer const& other)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(alloc_traits::
+        base_alloc_type>(boost::empty_init_t(), alloc_traits::
         select_on_container_copy_construction(
-            other.member()))
+            other.get()))
     , max_(other.max_)
     , out_(list_.end())
 {
@@ -524,8 +524,8 @@ template<class Allocator>
 basic_multi_buffer<Allocator>::
 basic_multi_buffer(basic_multi_buffer const& other,
         Allocator const& alloc)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(alloc)
+        base_alloc_type>(boost::empty_init_t(), alloc)
     , max_(other.max_)
     , out_(list_.end())
 {
@@ -548,8 +548,8 @@ basic_multi_buffer<Allocator>::
 basic_multi_buffer(
     basic_multi_buffer<OtherAlloc> const& other,
         allocator_type const& alloc)
-    : detail::empty_base_optimization<
+    : boost::empty_value<
-        base_alloc_type>(alloc)
+        base_alloc_type>(boost::empty_init_t(), alloc)
     , max_(other.max_)
     , out_(list_.end())
 {
@@ -689,8 +689,8 @@ prepare(size_type n) ->
             auto& e = *it++;
             reuse.erase(list_.iterator_to(e));
             auto const len = sizeof(e) + e.size();
-            alloc_traits::destroy(this->member(), &e);
+            alloc_traits::destroy(this->get(), &e);
-            alloc_traits::deallocate(this->member(),
+            alloc_traits::deallocate(this->get(),
                 reinterpret_cast<char*>(&e), len);
         }
         if(n > 0)
@@ -705,9 +705,9 @@ prepare(size_type n) ->
                         512,
                         n}));
             auto& e = *reinterpret_cast<element*>(static_cast<
-                void*>(alloc_traits::allocate(this->member(),
+                void*>(alloc_traits::allocate(this->get(),
                     sizeof(element) + size)));
-            alloc_traits::construct(this->member(), &e, size);
+            alloc_traits::construct(this->get(), &e, size);
             list_.push_back(e);
             if(out_ == list_.end())
                 out_ = list_.iterator_to(e);
@@ -795,8 +795,8 @@ consume(size_type n)
             auto& e = list_.front();
             list_.erase(list_.iterator_to(e));
             auto const len = sizeof(e) + e.size();
-            alloc_traits::destroy(this->member(), &e);
+            alloc_traits::destroy(this->get(), &e);
-            alloc_traits::deallocate(this->member(),
+            alloc_traits::deallocate(this->get(),
                 reinterpret_cast<char*>(&e), len);
         #if BOOST_BEAST_MULTI_BUFFER_DEBUG_CHECK
             debug_check();
@@ -845,8 +845,8 @@ delete_list()
     {
         auto& e = *iter++;
         auto const len = sizeof(e) + e.size();
-        alloc_traits::destroy(this->member(), &e);
+        alloc_traits::destroy(this->get(), &e);
-        alloc_traits::deallocate(this->member(),
+        alloc_traits::deallocate(this->get(),
             reinterpret_cast<char*>(&e), len);
     }
 }
@@ -886,7 +886,7 @@ void
 basic_multi_buffer<Allocator>::
 move_assign(basic_multi_buffer& other, std::false_type)
 {
-    if(this->member() != other.member())
+    if(this->get() != other.get())
     {
         copy_from(other);
         other.reset();
@@ -903,7 +903,7 @@ void
 basic_multi_buffer<Allocator>::
 move_assign(basic_multi_buffer& other, std::true_type)
 {
-    this->member() = std::move(other.member());
+    this->get() = std::move(other.get());
     auto const at_end =
         other.out_ == other.list_.end();
     list_ = std::move(other.list_);
@@ -942,7 +942,7 @@ copy_assign(
 {
     reset();
     max_ = other.max_;
-    this->member() = other.member();
+    this->get() = other.get();
     copy_from(other);
 }
 
@@ -967,7 +967,7 @@ swap(basic_multi_buffer& other, std::true_type)
         out_ == list_.end();
     auto const at_end1 =
         other.out_ == other.list_.end();
-    swap(this->member(), other.member());
+    swap(this->get(), other.get());
     swap(list_, other.list_);
     swap(out_, other.out_);
     if(at_end1)
@@ -986,7 +986,7 @@ void
 basic_multi_buffer<Allocator>::
 swap(basic_multi_buffer& other, std::false_type)
 {
-    BOOST_ASSERT(this->member() == other.member());
+    BOOST_ASSERT(this->get() == other.get());
     using std::swap;
     auto const at_end0 =
         out_ == list_.end();

include/boost/beast/core/multi_buffer.hpp

@@ -12,8 +12,8 @@
 
 #include <boost/beast/core/detail/config.hpp>
 #include <boost/beast/core/detail/allocator.hpp>
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
 #include <boost/asio/buffer.hpp>
+#include <boost/core/empty_value.hpp>
 #include <boost/intrusive/list.hpp>
 #include <iterator>
 #include <limits>
@@ -37,7 +37,7 @@ namespace beast {
 template<class Allocator>
 class basic_multi_buffer
 #if ! BOOST_BEAST_DOXYGEN
-    : private detail::empty_base_optimization<
+    : private boost::empty_value<
         typename detail::allocator_traits<Allocator>::
             template rebind_alloc<char>>
 #endif
@@ -217,7 +217,7 @@ public:
     allocator_type
     get_allocator() const
     {
-        return this->member();
+        return this->get();
     }
 
     /// Returns the size of the input sequence.

include/boost/beast/http/detail/basic_parsed_list.hpp

@@ -11,7 +11,7 @@
 #define BOOST_BEAST_HTTP_DETAIL_BASIC_PARSED_LIST_HPP
 
 #include <boost/beast/core/string.hpp>
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
+#include <boost/core/empty_value.hpp>
 #include <cstddef>
 #include <iterator>
 
@@ -42,8 +42,7 @@ public:
 #endif
 
     class const_iterator
-        : private beast::detail::
+        : private boost::empty_value<Policy>
-            empty_base_optimization<Policy>
     {
         basic_parsed_list const* list_ = nullptr;
         char const* it_ = nullptr;
@@ -120,7 +119,7 @@ public:
         void
         increment()
         {
-            if(! this->member()(
+            if(! this->get()(
                     v_, it_, list_->s_))
             {
                 it_ = nullptr;

include/boost/beast/http/fields.hpp

@@ -14,9 +14,9 @@
 #include <boost/beast/core/string_param.hpp>
 #include <boost/beast/core/string.hpp>
 #include <boost/beast/core/detail/allocator.hpp>
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
 #include <boost/beast/http/field.hpp>
 #include <boost/asio/buffer.hpp>
+#include <boost/core/empty_value.hpp>
 #include <boost/intrusive/list.hpp>
 #include <boost/intrusive/set.hpp>
 #include <boost/optional.hpp>
@@ -53,7 +53,7 @@ namespace http {
 template<class Allocator>
 class basic_fields
 #if ! BOOST_BEAST_DOXYGEN
-    : private beast::detail::empty_base_optimization<Allocator>
+    : private boost::empty_value<Allocator>
 #endif
 {
     // Fancy pointers are not supported
@@ -283,7 +283,7 @@ public:
     allocator_type
     get_allocator() const
     {
-        return this->member();
+        return this->get();
     }
 
     //--------------------------------------------------------------------------

include/boost/beast/http/impl/fields.ipp

@@ -353,15 +353,15 @@ basic_fields<Allocator>::
 template<class Allocator>
 basic_fields<Allocator>::
 basic_fields(Allocator const& alloc) noexcept
-    : beast::detail::empty_base_optimization<Allocator>(alloc)
+    : boost::empty_value<Allocator>(boost::empty_init_t(), alloc)
 {
 }
 
 template<class Allocator>
 basic_fields<Allocator>::
 basic_fields(basic_fields&& other) noexcept
-    : beast::detail::empty_base_optimization<Allocator>(
+    : boost::empty_value<Allocator>(boost::empty_init_t(),
-        std::move(other.member()))
+        std::move(other.get()))
     , set_(std::move(other.set_))
     , list_(std::move(other.list_))
     , method_(boost::exchange(other.method_, {}))
@@ -372,9 +372,9 @@ basic_fields(basic_fields&& other) noexcept
 template<class Allocator>
 basic_fields<Allocator>::
 basic_fields(basic_fields&& other, Allocator const& alloc)
-    : beast::detail::empty_base_optimization<Allocator>(alloc)
+    : boost::empty_value<Allocator>(boost::empty_init_t(), alloc)
 {
-    if(this->member() != other.member())
+    if(this->get() != other.get())
     {
         copy_all(other);
         other.clear_all();
@@ -391,8 +391,8 @@ basic_fields(basic_fields&& other, Allocator const& alloc)
 template<class Allocator>
 basic_fields<Allocator>::
 basic_fields(basic_fields const& other)
-    : beast::detail::empty_base_optimization<Allocator>(alloc_traits::
+    : boost::empty_value<Allocator>(boost::empty_init_t(), alloc_traits::
-        select_on_container_copy_construction(other.member()))
+        select_on_container_copy_construction(other.get()))
 {
     copy_all(other);
 }
@@ -401,7 +401,7 @@ template<class Allocator>
 basic_fields<Allocator>::
 basic_fields(basic_fields const& other,
         Allocator const& alloc)
-    : beast::detail::empty_base_optimization<Allocator>(alloc)
+    : boost::empty_value<Allocator>(boost::empty_init_t(), alloc)
 {
     copy_all(other);
 }
@@ -419,7 +419,7 @@ template<class OtherAlloc>
 basic_fields<Allocator>::
 basic_fields(basic_fields<OtherAlloc> const& other,
         Allocator const& alloc)
-    : beast::detail::empty_base_optimization<Allocator>(alloc)
+    : boost::empty_value<Allocator>(boost::empty_init_t(), alloc)
 {
     copy_all(other);
 }
@@ -1025,7 +1025,7 @@ set_chunked_impl(bool value)
             std::basic_string<
                 char,
                 std::char_traits<char>,
-                A> s{A{this->member()}};
+                A> s{A{this->get()}};
         #endif
             s.reserve(it->value().size() + 9);
             s.append(it->value().data(), it->value().size());
@@ -1062,7 +1062,7 @@ set_chunked_impl(bool value)
         std::basic_string<
             char,
             std::char_traits<char>,
-            A> s{A{this->member()}};
+            A> s{A{this->get()}};
     #endif
         s.reserve(it->value().size());
         detail::filter_token_list_last(s, it->value(),
@@ -1119,7 +1119,7 @@ set_keep_alive_impl(
         std::basic_string<
             char,
             std::char_traits<char>,
-            A> s{A{this->member()}};
+            A> s{A{this->get()}};
     #endif
         s.reserve(value.size());
         detail::keep_alive_impl(
@@ -1153,7 +1153,7 @@ new_element(field name,
         static_cast<off_t>(sname.size() + 2);
     std::uint16_t const len =
         static_cast<off_t>(value.size());
-    auto a = rebind_type{this->member()};
+    auto a = rebind_type{this->get()};
     auto const p = alloc_traits::allocate(a,
         (sizeof(value_type) + off + len + 2 + sizeof(align_type) - 1) /
             sizeof(align_type));
@@ -1168,7 +1168,7 @@ void
 basic_fields<Allocator>::
 delete_element(value_type& e)
 {
-    auto a = rebind_type{this->member()};
+    auto a = rebind_type{this->get()};
     auto const n =
         (sizeof(value_type) + e.off_ + e.len_ + 2 + sizeof(align_type) - 1) /
             sizeof(align_type);
@@ -1217,7 +1217,7 @@ realloc_string(string_view& dest, string_view s)
         return;
     auto a = typename beast::detail::allocator_traits<
         Allocator>::template rebind_alloc<
-            char>(this->member());
+            char>(this->get());
     char* p = nullptr;
     if(! s.empty())
     {
@@ -1246,7 +1246,7 @@ realloc_target(
         return;
     auto a = typename beast::detail::allocator_traits<
         Allocator>::template rebind_alloc<
-            char>(this->member());
+            char>(this->get());
     char* p = nullptr;
     if(! s.empty())
     {
@@ -1310,7 +1310,7 @@ move_assign(basic_fields& other, std::true_type)
     target_or_reason_ = other.target_or_reason_;
     other.method_ = {};
     other.target_or_reason_ = {};
-    this->member() = other.member();
+    this->get() = other.get();
 }
 
 template<class Allocator>
@@ -1320,7 +1320,7 @@ basic_fields<Allocator>::
 move_assign(basic_fields& other, std::false_type)
 {
     clear_all();
-    if(this->member() != other.member())
+    if(this->get() != other.get())
     {
         copy_all(other);
         other.clear_all();
@@ -1343,7 +1343,7 @@ basic_fields<Allocator>::
 copy_assign(basic_fields const& other, std::true_type)
 {
     clear_all();
-    this->member() = other.member();
+    this->get() = other.get();
     copy_all(other);
 }
 
@@ -1364,7 +1364,7 @@ basic_fields<Allocator>::
 swap(basic_fields& other, std::true_type)
 {
     using std::swap;
-    swap(this->member(), other.member());
+    swap(this->get(), other.get());
     swap(set_, other.set_);
     swap(list_, other.list_);
     swap(method_, other.method_);
@@ -1377,7 +1377,7 @@ void
 basic_fields<Allocator>::
 swap(basic_fields& other, std::false_type)
 {
-    BOOST_ASSERT(this->member() == other.member());
+    BOOST_ASSERT(this->get() == other.get());
     using std::swap;
     swap(set_, other.set_);
     swap(list_, other.list_);

include/boost/beast/http/impl/message.ipp

@@ -197,8 +197,8 @@ template<class... BodyArgs>
 message<isRequest, Body, Fields>::
 message(header_type&& h, BodyArgs&&... body_args)
     : header_type(std::move(h))
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
-        typename Body::value_type>(
+        typename Body::value_type>(boost::empty_init_t(),
             std::forward<BodyArgs>(body_args)...)
 {
 }
@@ -208,8 +208,8 @@ template<class... BodyArgs>
 message<isRequest, Body, Fields>::
 message(header_type const& h, BodyArgs&&... body_args)
     : header_type(h)
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
-        typename Body::value_type>(
+        typename Body::value_type>(boost::empty_init_t(),
             std::forward<BodyArgs>(body_args)...)
 {
 }
@@ -228,8 +228,8 @@ message<isRequest, Body, Fields>::
 message(verb method, string_view target,
         Version version, BodyArg&& body_arg)
     : header_type(method, target, version)
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
-        typename Body::value_type>(
+        typename Body::value_type>(boost::empty_init_t(),
             std::forward<BodyArg>(body_arg))
 {
 }
@@ -243,8 +243,8 @@ message(
     FieldsArg&& fields_arg)
     : header_type(method, target, version,
         std::forward<FieldsArg>(fields_arg))
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
-        typename Body::value_type>(
+        typename Body::value_type>(boost::empty_init_t(),
             std::forward<BodyArg>(body_arg))
 {
 }
@@ -263,8 +263,8 @@ message<isRequest, Body, Fields>::
 message(status result, Version version,
     BodyArg&& body_arg)
     : header_type(result, version)
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
-        typename Body::value_type>(
+        typename Body::value_type>(boost::empty_init_t(),
             std::forward<BodyArg>(body_arg))
 {
 }
@@ -276,8 +276,8 @@ message(status result, Version version,
     BodyArg&& body_arg, FieldsArg&& fields_arg)
     : header_type(result, version,
         std::forward<FieldsArg>(fields_arg))
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
-        typename Body::value_type>(
+        typename Body::value_type>(boost::empty_init_t(),
             std::forward<BodyArg>(body_arg))
 {
 }

include/boost/beast/http/message.hpp

@@ -16,8 +16,8 @@
 #include <boost/beast/http/status.hpp>
 #include <boost/beast/http/type_traits.hpp>
 #include <boost/beast/core/string.hpp>
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
 #include <boost/beast/core/detail/integer_sequence.hpp>
+#include <boost/core/empty_value.hpp>
 #include <boost/assert.hpp>
 #include <boost/optional.hpp>
 #include <boost/throw_exception.hpp>
@@ -490,7 +490,7 @@ template<bool isRequest, class Body, class Fields = fields>
 struct message
     : header<isRequest, Fields>
 #if ! BOOST_BEAST_DOXYGEN
-    , beast::detail::empty_base_optimization<
+    , boost::empty_value<
         typename Body::value_type>
 #endif
 {
@@ -862,8 +862,8 @@ struct message
 #endif
     body()& noexcept
     {
-        return this->beast::detail::empty_base_optimization<
+        return this->boost::empty_value<
-            typename Body::value_type>::member();
+            typename Body::value_type>::get();
     }
 
     /// Returns the body
@@ -875,8 +875,8 @@ struct message
     body()&& noexcept
     {
         return std::move(
-            this->beast::detail::empty_base_optimization<
+            this->boost::empty_value<
-                typename Body::value_type>::member());
+                typename Body::value_type>::get());
     }
 
     /// Returns the body
@@ -887,8 +887,8 @@ struct message
 #endif
     body() const& noexcept
     {
-        return this->beast::detail::empty_base_optimization<
+        return this->boost::empty_value<
-            typename Body::value_type>::member();
+            typename Body::value_type>::get();
     }
 
 private:
@@ -902,8 +902,8 @@ private:
         std::piecewise_construct_t,
         std::tuple<BodyArgs...>& body_args,
         beast::detail::index_sequence<IBodyArgs...>)
-        : beast::detail::empty_base_optimization<
+        : boost::empty_value<
-            typename Body::value_type>(
+            typename Body::value_type>(boost::empty_init_t(),
                 std::forward<BodyArgs>(
                 std::get<IBodyArgs>(body_args))...)
     {
@@ -923,8 +923,8 @@ private:
         beast::detail::index_sequence<IFieldsArgs...>)
         : header_type(std::forward<FieldsArgs>(
             std::get<IFieldsArgs>(fields_args))...)
-        , beast::detail::empty_base_optimization<
+        , boost::empty_value<
-            typename Body::value_type>(
+            typename Body::value_type>(boost::empty_init_t(),
                 std::forward<BodyArgs>(
                 std::get<IBodyArgs>(body_args))...)
     {

test/beast/core/CMakeLists.txt

@@ -45,7 +45,6 @@ add_executable (tests-beast-core
     type_traits.cpp
     detail/base64.cpp
     detail/clamp.cpp
-    detail/empty_base_optimization.cpp
     detail/sha1.cpp
     detail/variant.cpp
     detail/varint.cpp

test/beast/core/Jamfile

@@ -34,7 +34,6 @@ local SOURCES =
     type_traits.cpp
     detail/base64.cpp
     detail/clamp.cpp
-    detail/empty_base_optimization.cpp
     detail/sha1.cpp
     detail/variant.cpp
     detail/varint.cpp

test/beast/core/detail/empty_base_optimization.cpp

@@ -1,98 +0,0 @@
-//
-// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
-//
-// 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)
-//
-// Official repository: https://github.com/boostorg/beast
-//
-
-// Test that header file is self-contained.
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
-
-#include <boost/beast/unit_test/suite.hpp>
-
-namespace boost {
-namespace beast {
-namespace detail {
-
-class empty_base_optimization_test
-    : public beast::unit_test::suite
-{
-public:
-    template<class T>
-    class test1
-        : private empty_base_optimization<T>
-    {
-        using Base = empty_base_optimization<T>;
-        void* m_p;
-    public:
-        explicit test1 (T const& t)
-            : Base (t)
-        {}
-
-        T&       member()       {return Base::member();}
-        T const& member() const {return Base::member();}
-    };
-
-    template<class T>
-    class test2
-    {
-        void* m_p;
-        T m_t;
-    public:
-        explicit test2 (T const& t)
-            : m_t (t)
-        {}
-
-        T&       member()       {return m_t;}
-        T const& member() const {return m_t;}
-    };
-
-    struct Empty
-    {
-        operator bool() {return true;}
-    };
-
-    static
-    bool
-    test_one()
-    {
-        test1<int> t1(1);
-        test2<int> t2(2);
-        static_assert(sizeof(t1) == sizeof(t2), "don't optimize for int");
-        if(t1.member() != 1)
-            return false;
-        if(t2.member() != 2)
-            return false;
-        return true;
-    }
-
-    static
-    bool
-    test_two()
-    {
-        test1<Empty> t1((Empty()));
-        test2<Empty> t2((Empty()));
-        static_assert(sizeof(t1) < sizeof(t2), "do optimize for Empty");
-        if(t1.member() != true)
-            return false;
-        if(t2.member() != true)
-            return false;
-        return true;
-    }
-
-    void
-    run()
-    {
-        BEAST_EXPECT(test_one());
-        BEAST_EXPECT(test_two());
-        pass();
-    }
-};
-
-BEAST_DEFINE_TESTSUITE(beast,core,empty_base_optimization);
-
-} // detail
-} // beast
-} // boost

test/beast/http/rfc7230.cpp

@@ -15,8 +15,6 @@
 #include <string>
 #include <vector>
 
-#include <boost/beast/core/detail/empty_base_optimization.hpp>
-
 namespace boost {
 namespace beast {
 namespace http {