[gcc(refs/users/meissner/heads/ieee3)] libstdc++: Use macro for nodiscard attribute

[Michael Meissner]

https://gcc.gnu.org/g:0a1baad8eb3a6f4604a64fdbc82a5f5144fa8be4

commit 0a1baad8eb3a6f4604a64fdbc82a5f5144fa8be4
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu May 21 01:03:27 2020 +0100

    libstdc++: Use macro for nodiscard attribute
    
            * include/experimental/socket (basic_socket::is_open()
            (basic_socket_acceptor::is_open()): Use _GLIBCXX_NODISCARD macro.

Diff:
---
 libstdc++-v3/ChangeLog                   | 3 +++
 libstdc++-v3/include/experimental/socket | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 975de44434b..65039d20b9e 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,8 @@
 2020-05-21  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/experimental/socket (basic_socket::is_open()
+	(basic_socket_acceptor::is_open()): Use _GLIBCXX_NODISCARD macro.
+
 	* include/experimental/bits/net.h (__endpoint, __protocol)
 	(__acceptable_protocol, __inet_protocol): New concepts.
 	(__detail::__is_endpoint): Move trait from <experimental/socket>.
diff --git a/libstdc++-v3/include/experimental/socket b/libstdc++-v3/include/experimental/socket
index 84d23ebe37c..c74aba6919b 100644
--- a/libstdc++-v3/include/experimental/socket
+++ b/libstdc++-v3/include/experimental/socket
@@ -725,7 +725,7 @@ inline namespace v1
       native_handle_type release(error_code& __ec)
       { return __base::release(__ec); }
 
-      [[__nodiscard__]] bool
+      _GLIBCXX_NODISCARD bool
       is_open() const noexcept { return __base::is_open(); }
 
       void close() { close(__throw_on_error{"basic_socket::close"}); }
@@ -1918,7 +1918,7 @@ inline namespace v1
       native_handle_type release(error_code& __ec)
       { return __base::release(__ec); }
 
-      [[__nodiscard__]] bool
+      _GLIBCXX_NODISCARD bool
       is_open() const noexcept { return __base::is_open(); }
 
       void