[PATCH] Add noexcept to std::shared_future copy operations (LWG DR 2799)

[Jonathan Wakely]

These functions just increment a refcount (and the base class
functions that do that are already noexcept anyway).

        * include/std/future (shared_future): Add noexcept to copy constructor
        and copy-assignment operator (LWG 2799).

Tested pwoerpc64le-linux, committed to trunk.


commit 9b66ab2fb36324e2d9cb8e99207d08d531c5cec3
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Nov 16 14:24:02 2017 +0000

    Add noexcept to std::shared_future copy operations (LWG DR 2799)
    
            * include/std/future (shared_future): Add noexcept to copy 
constructor
            and copy-assignment operator (LWG 2799).

diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future
index 73d5a60a918..d9d446bc2f6 100644
--- a/libstdc++-v3/include/std/future
+++ b/libstdc++-v3/include/std/future
@@ -896,7 +896,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr shared_future() noexcept : _Base_type() { }
 
       /// Copy constructor
-      shared_future(const shared_future& __sf) : _Base_type(__sf) { }
+      shared_future(const shared_future& __sf) noexcept : _Base_type(__sf) { }
 
       /// Construct from a future rvalue
       shared_future(future<_Res>&& __uf) noexcept
@@ -908,7 +908,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       : _Base_type(std::move(__sf))
       { }
 
-      shared_future& operator=(const shared_future& __sf)
+      shared_future& operator=(const shared_future& __sf) noexcept
       {
         shared_future(__sf)._M_swap(*this);
         return *this;