defer.hpp in passenger-6.0.8

- old
+ new

@@ -1,10 +1,10 @@
 //
 // defer.hpp
 // ~~~~~~~~~
 //
-// Copyright (c) 2003-2018 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff 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)
 //
 
@@ -17,10 +17,11 @@
 
 #include <boost/asio/detail/config.hpp>
 #include <boost/asio/async_result.hpp>
 #include <boost/asio/detail/type_traits.hpp>
 #include <boost/asio/execution_context.hpp>
+#include <boost/asio/execution/executor.hpp>
 #include <boost/asio/is_executor.hpp>
 
 #include <boost/asio/detail/push_options.hpp>
 
 namespace boost {
@@ -30,10 +31,15 @@
 /**
  * This function submits an object for execution using the object's associated
  * executor. The function object is queued for execution, and is never called
  * from the current thread prior to returning from <tt>defer()</tt>.
  *
+ * The use of @c defer(), rather than @ref post(), indicates the caller's
+ * preference that the executor defer the queueing of the function object. This
+ * may allow the executor to optimise queueing for cases when the function
+ * object represents a continuation of the current call context.
+ *
  * This function has the following effects:
  *
  * @li Constructs a function object handler of type @c Handler, initialized
  * with <tt>handler(forward<CompletionToken>(token))</tt>.
  *
@@ -48,20 +54,25 @@
  *
  * @li Performs <tt>ex.defer(std::move(handler), alloc)</tt>.
  *
  * @li Returns <tt>result.get()</tt>.
  */
-template <typename CompletionToken>
-BOOST_ASIO_INITFN_RESULT_TYPE(CompletionToken, void()) defer(
+template <BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) CompletionToken>
+BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(CompletionToken, void()) defer(
     BOOST_ASIO_MOVE_ARG(CompletionToken) token);
 
 /// Submits a completion token or function object for execution.
 /**
  * This function submits an object for execution using the specified executor.
  * The function object is queued for execution, and is never called from the
  * current thread prior to returning from <tt>defer()</tt>.
  *
+ * The use of @c defer(), rather than @ref post(), indicates the caller's
+ * preference that the executor defer the queueing of the function object. This
+ * may allow the executor to optimise queueing for cases when the function
+ * object represents a continuation of the current call context.
+ *
  * This function has the following effects:
  *
  * @li Constructs a function object handler of type @c Handler, initialized
  * with <tt>handler(forward<CompletionToken>(token))</tt>.
  *
@@ -82,21 +93,33 @@
  *
  * @li Performs <tt>Executor(ex).defer(std::move(f), alloc)</tt>.
  *
  * @li Returns <tt>result.get()</tt>.
  */
-template <typename Executor, typename CompletionToken>
-BOOST_ASIO_INITFN_RESULT_TYPE(CompletionToken, void()) defer(
-    const Executor& ex, BOOST_ASIO_MOVE_ARG(CompletionToken) token,
-    typename enable_if<is_executor<Executor>::value>::type* = 0);
+template <typename Executor,
+    BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) CompletionToken
+      BOOST_ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor)>
+BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(CompletionToken, void()) defer(
+    const Executor& ex,
+    BOOST_ASIO_MOVE_ARG(CompletionToken) token
+      BOOST_ASIO_DEFAULT_COMPLETION_TOKEN(Executor),
+    typename enable_if<
+      execution::is_executor<Executor>::value || is_executor<Executor>::value
+    >::type* = 0);
 
 /// Submits a completion token or function object for execution.
 /**
  * @returns <tt>defer(ctx.get_executor(), forward<CompletionToken>(token))</tt>.
  */
-template <typename ExecutionContext, typename CompletionToken>
-BOOST_ASIO_INITFN_RESULT_TYPE(CompletionToken, void()) defer(
-    ExecutionContext& ctx, BOOST_ASIO_MOVE_ARG(CompletionToken) token,
+template <typename ExecutionContext,
+    BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) CompletionToken
+      BOOST_ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
+        typename ExecutionContext::executor_type)>
+BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(CompletionToken, void()) defer(
+    ExecutionContext& ctx,
+    BOOST_ASIO_MOVE_ARG(CompletionToken) token
+      BOOST_ASIO_DEFAULT_COMPLETION_TOKEN(
+        typename ExecutionContext::executor_type),
     typename enable_if<is_convertible<
       ExecutionContext&, execution_context&>::value>::type* = 0);
 
 } // namespace asio
 } // namespace boost