[gcc/devel/c++-modules] libstdc++: Define std::bad_optional_access constructor as defaulted

[Nathan Sidwell <nathan@gcc.gnu.org>]

https://gcc.gnu.org/g:d3647057913d3671312a79a77be02fc459d89fb6

commit d3647057913d3671312a79a77be02fc459d89fb6
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Jun 9 22:13:37 2020 +0100

    libstdc++: Define std::bad_optional_access constructor as defaulted
    
    The standard requires that std::bad_optional_access' default
    constructor has a non-throwing exception specification.
    
            * include/std/optional (bad_optional_access): Define default
            constructor and destructor as defaulted.
            * testsuite/20_util/optional/bad_access.cc: New test.

Diff:
---
 libstdc++-v3/include/std/optional                  |  7 +++---
 .../testsuite/20_util/optional/bad_access.cc       | 27 ++++++++++++++++++++++
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
index 37c2ba7a025..b0184a4e1c0 100644
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -84,12 +84,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   class bad_optional_access : public exception
   {
   public:
-    bad_optional_access() { }
+    bad_optional_access() = default;
+    virtual ~bad_optional_access() = default;
 
-    virtual const char* what() const noexcept override
+    const char* what() const noexcept override
     { return "bad optional access"; }
-
-    virtual ~bad_optional_access() noexcept = default;
   };
 
   void
diff --git a/libstdc++-v3/testsuite/20_util/optional/bad_access.cc b/libstdc++-v3/testsuite/20_util/optional/bad_access.cc
new file mode 100644
index 00000000000..6ebb3e2b19e
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/optional/bad_access.cc
@@ -0,0 +1,27 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <optional>
+
+using std::bad_optional_access;
+
+static_assert( std::is_nothrow_default_constructible_v<bad_optional_access> );
+static_assert( std::is_nothrow_copy_constructible_v<bad_optional_access> );
+static_assert( std::is_nothrow_copy_assignable_v<bad_optional_access> );