Decay bound arguments in handler wrapper parameters:

fix #1365

To reduce instantiations, the list of template parameters
to the bind and bind_front handler wrappers are decayed before
naming the class template.

CHANGELOG.md

@@ -1,3 +1,9 @@
+Version 201
+
+* Decay bound arguments in handler wrapper parameters
+
+--------------------------------------------------------------------------------
+
 Version 200
 
 * Don't include OpenSSL for core snippets

include/boost/beast/core/bind_handler.hpp

@@ -31,16 +31,19 @@ namespace beast {
     handler, whose associated allocator and associated executor will
     will be the same as those of the original handler.
 
-    Example:
+    @par Example
+
+    This function posts the invocation of the specified completion
+    handler with bound arguments:
 
     @code
-    template<class AsyncReadStream, class ReadHandler>
+    template <class AsyncReadStream, class ReadHandler>
     void
-    signal_aborted(AsyncReadStream& stream, ReadHandler&& handler)
+    signal_aborted (AsyncReadStream& stream, ReadHandler&& handler)
     {
         net::post(
             stream.get_executor(),
-            bind_handler(std::forward<ReadHandler>(handler),
+            bind_handler (std::forward <ReadHandler> (handler),
                 net::error::operation_aborted, 0));
     }
     @endcode
@@ -57,7 +60,8 @@ template<class Handler, class... Args>
 __implementation_defined__
 #else
 detail::bind_wrapper<
-    typename std::decay<Handler>::type, Args...>
+    typename std::decay<Handler>::type,
+    typename std::decay<Args>::type...>
 #endif
 bind_handler(Handler&& handler, Args&&... args)
 {
@@ -67,9 +71,11 @@ bind_handler(Handler&& handler, Args&&... args)
         Handler, void(Args...)>::value,
             "Handler requirements not met");
 #endif
-    return detail::bind_wrapper<typename std::decay<
+    return detail::bind_wrapper<
-        Handler>::type, Args...>(std::forward<
+        typename std::decay<Handler>::type,
-            Handler>(handler), std::forward<Args>(args)...);
+        typename std::decay<Args>::type...>(
+            std::forward<Handler>(handler),
+            std::forward<Args>(args)...);
 }
 
 /** Bind parameters to a completion handler, creating a new handler.
@@ -83,17 +89,20 @@ bind_handler(Handler&& handler, Args&&... args)
     handler, whose associated allocator and associated executor will
     will be the same as those of the original handler.
 
-    Example:
+    @par Example
+
+    This function posts the invocation of the specified completion
+    handler with bound arguments:
 
     @code
-    template<class AsyncReadStream, class ReadHandler>
+    template <class AsyncReadStream, class ReadHandler>
     void
-    signal_aborted(AsyncReadStream& stream, ReadHandler&& handler)
+    signal_eof (AsyncReadStream& stream, ReadHandler&& handler)
     {
         net::post(
             stream.get_executor(),
-            bind_front_handler(std::forward<ReadHandler>(handler),
+            bind_front_handler (std::forward<ReadHandler> (handler),
-                net::error::operation_aborted, 0));
+                net::error::eof, 0));
     }
     @endcode
 

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

@@ -31,8 +31,7 @@ namespace detail {
 template<class Handler, class... Args>
 class bind_wrapper
 {
-    using args_type = detail::tuple<
+    using args_type = detail::tuple<Args...>;
-        typename std::decay<Args>::type...>;
 
     Handler h_;
     args_type args_;
@@ -84,9 +83,7 @@ class bind_wrapper
                 std::forward<Vals>(vals));
     }
 
-    template<
+    template<class ArgsTuple, std::size_t... S>
-        class ArgsTuple,
-        std::size_t... S>
     static
     void
     invoke(
@@ -123,12 +120,15 @@ public:
     bind_wrapper(bind_wrapper&&) = default;
     bind_wrapper(bind_wrapper const&) = default;
 
-    template<class DeducedHandler>
+    template<
+        class DeducedHandler,
+        class... Args_>
     explicit
     bind_wrapper(
-            DeducedHandler&& handler, Args&&... args)
+        DeducedHandler&& handler,
+        Args_&&... args)
         : h_(std::forward<DeducedHandler>(handler))
-        , args_(std::forward<Args>(args)...)
+        , args_(std::forward<Args_>(args)...)
     {
     }
 

test/beast/core/bind_handler.cpp

@@ -12,6 +12,7 @@
 
 #include <boost/beast/core/detail/type_traits.hpp>
 #include <boost/beast/_experimental/unit_test/suite.hpp>
+#include <boost/beast/_experimental/test/stream.hpp>
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/bind_executor.hpp>
 #include <boost/asio/executor_work_guard.hpp>
@@ -41,6 +42,40 @@ public:
         }
     };
 
+    template <class AsyncReadStream, class ReadHandler>
+    void
+    signal_aborted (AsyncReadStream& stream, ReadHandler&& handler)
+    {
+        net::post(
+            stream.get_executor(),
+            bind_handler (std::forward <ReadHandler> (handler),
+                net::error::operation_aborted, 0));
+    }
+
+    template <class AsyncReadStream, class ReadHandler>
+    void
+    signal_eof (AsyncReadStream& stream, ReadHandler&& handler)
+    {
+        net::post(
+            stream.get_executor(),
+            bind_front_handler (std::forward<ReadHandler> (handler),
+                net::error::eof, 0));
+    }
+
+    void
+    testJavadocs()
+    {
+        BEAST_EXPECT((
+            &bind_handler_test::signal_aborted<
+                test::stream, handler<error_code, std::size_t>>));
+            
+        BEAST_EXPECT((
+            &bind_handler_test::signal_eof<
+                test::stream, handler<error_code, std::size_t>>));
+    }
+
+    //--------------------------------------------------------------------------
+
     struct copyable
     {
         template<class... Args>
@@ -469,6 +504,7 @@ public:
     void
     run() override
     {
+        testJavadocs();
         testBindHandler();
         testBindFrontHandler();
     }