From 34037d538e02a3c0616f648b972f8b1d948d52ed Mon Sep 17 00:00:00 2001
From: Damian Jarek <damian.jarek93@gmail.com>
Date: Fri, 2 Nov 2018 14:15:25 +0100
Subject: [PATCH] Simplify handler_ptr:

Replace aligned_union in handler_ptr with the built-in one to reduce
the number of template instantiations and remove the reinterpret_casts
that were required.

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>
---
 CHANGELOG.md                                  |  1 +
 include/boost/beast/core/handler_ptr.hpp      | 17 ++++-----
 include/boost/beast/core/impl/handler_ptr.ipp | 35 ++++++++++---------
 3 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3ce331d4..55c54134 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@ Version 196:
 
 * Tidy up calls to placement new
 * Remove unused type_traits
+* Simplify handler_ptr
 
 --------------------------------------------------------------------------------
 
diff --git a/include/boost/beast/core/handler_ptr.hpp b/include/boost/beast/core/handler_ptr.hpp
index d25e07df..e4117cc8 100644
--- a/include/boost/beast/core/handler_ptr.hpp
+++ b/include/boost/beast/core/handler_ptr.hpp
@@ -12,7 +12,6 @@
 
 #include <boost/beast/core/detail/allocator.hpp>
 #include <boost/beast/core/detail/config.hpp>
-#include <boost/beast/core/detail/type_traits.hpp>
 #include <boost/assert.hpp>
 #include <type_traits>
 #include <utility>
@@ -50,10 +49,11 @@ namespace beast {
 template<class T, class Handler>
 class handler_ptr
 {
-    using handler_storage_t = typename detail::aligned_union<1, Handler>::type;
-
     T* t_ = nullptr;
-    handler_storage_t h_;
+    union
+    {
+        Handler h_;
+    };
 
     void clear();
 
@@ -113,20 +113,21 @@ public:
         the owned object's constructor.
     */
     template<class DeducedHandler, class... Args>
-    explicit handler_ptr(DeducedHandler&& handler, Args&&... args);
+    explicit
+    handler_ptr(DeducedHandler&& handler, Args&&... args);
 
     /// Return a reference to the handler
     handler_type const&
     handler() const
     {
-        return *reinterpret_cast<Handler const*>(&h_);
+        return h_;
     }
 
     /// Return a reference to the handler
     handler_type&
     handler()
     {
-        return *reinterpret_cast<Handler*>(&h_);
+        return h_;
     }
 
     /// Return `true` if `*this` owns an object
@@ -167,7 +168,7 @@ public:
         return t_;
     }
 
-    /** Return ownership of the handler
+    /** Returns ownership of the handler
 
         Before this function returns, the owned object is
         destroyed, satisfying the deallocation-before-invocation
diff --git a/include/boost/beast/core/impl/handler_ptr.ipp b/include/boost/beast/core/impl/handler_ptr.ipp
index 70fbd6d8..1c64da61 100644
--- a/include/boost/beast/core/impl/handler_ptr.ipp
+++ b/include/boost/beast/core/impl/handler_ptr.ipp
@@ -41,7 +41,7 @@ handler_ptr<T, Handler>::
     if(t_)
     {
         clear();
-        handler().~Handler();
+        h_.~Handler();
     }
 }
 
@@ -52,8 +52,9 @@ handler_ptr(handler_ptr&& other)
 {
     if(other.t_)
     {
-        new(&h_) Handler(std::move(other.handler()));
-        other.handler().~Handler();
+        ::new(static_cast<void*>(std::addressof(h_)))
+            Handler(std::move(other.h_));
+        other.h_.~Handler();
         other.t_ = nullptr;
     }
 }
@@ -64,25 +65,27 @@ handler_ptr<T, Handler>::
 handler_ptr(DeducedHandler&& h, Args&&... args)
 {
     BOOST_STATIC_ASSERT(! std::is_array<T>::value);
-    typename beast::detail::allocator_traits<
+    using A = typename beast::detail::allocator_traits<
         net::associated_allocator_t<
-            Handler>>::template rebind_alloc<T> alloc{
-                net::get_associated_allocator(h)};
-    using A = decltype(alloc);
+            Handler>>::template rebind_alloc<T>;
+    A alloc{net::get_associated_allocator(h)};
+    using traits =
+        typename beast::detail::allocator_traits<A>;
     bool destroy = false;
     auto deleter = [&alloc, &destroy](T* p)
     {
         if(destroy)
-            beast::detail::allocator_traits<A>::destroy(alloc, p);
-        beast::detail::allocator_traits<A>::deallocate(alloc, p, 1);
+            traits::destroy(alloc, p);
+        traits::deallocate(alloc, p, 1);
     };
     std::unique_ptr<T, decltype(deleter)> t{
-        beast::detail::allocator_traits<A>::allocate(alloc, 1), deleter};
-    beast::detail::allocator_traits<A>::construct(alloc, t.get(),
+        traits::allocate(alloc, 1), deleter};
+    traits::construct(alloc, t.get(),
         static_cast<DeducedHandler const&>(h),
             std::forward<Args>(args)...);
     destroy = true;
-    new(&h_) Handler(std::forward<DeducedHandler>(h));
+    ::new(static_cast<void*>(std::addressof(h_)))
+        Handler(std::forward<DeducedHandler>(h));
     t_ = t.release();
 }
 
@@ -100,8 +103,8 @@ release_handler() ->
     };
     std::unique_ptr<
         Handler, decltype(deleter)> destroyer{
-            &handler(), deleter};
-    return std::move(handler());
+            std::addressof(h_), deleter};
+    return std::move(h_);
 }
 
 template<class T, class Handler>
@@ -119,8 +122,8 @@ invoke(Args&&... args)
     };
     std::unique_ptr<
         Handler, decltype(deleter)> destroyer{
-            &handler(), deleter};
-    handler()(std::forward<Args>(args)...);
+            std::addressof(h_), deleter};
+    h_(std::forward<Args>(args)...);
 }
 
 } // beast