[PATCH] PR libstdc++/90397 fix std::variant friend declarations

[Jonathan Wakely]

Clang diagnoses the inconsistent noexcept-specifier on the friend
declaration of __get. Add it, and also on __get_storage.

        PR libstdc++/90397
        * include/std/variant (_Variant_storage<false, Types...>::_M_storage())
        (_Variant_storage<true, Types...>::_M_reset()))
        (_Variant_storage<true, Types...>::_M_storage())): Add noexcept.
        (__get_storage): Likewise.
        (variant): Add noexcept to friend declarations for __get and
        __get_storage.

Tested powerpc64le-linux (and with clang), committed to trunk.

Backport to gcc-9-branch to follow soon.


commit ca72894f26baa3702ba0b699564bd3e356a98dba
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Fri May 10 22:17:41 2019 +0100

    PR libstdc++/90397 fix std::variant friend declarations
    
    Clang diagnoses the inconsistent noexcept-specifier on the friend
    declaration of __get. Add it, and also on __get_storage.
    
            PR libstdc++/90397
            * include/std/variant (_Variant_storage<false, 
Types...>::_M_storage())
            (_Variant_storage<true, Types...>::_M_reset()))
            (_Variant_storage<true, Types...>::_M_storage())): Add noexcept.
            (__get_storage): Likewise.
            (variant): Add noexcept to friend declarations for __get and
            __get_storage.

diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 8c7d7f37fe2..d539df125bf 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -402,7 +402,7 @@ namespace __variant
       { _M_reset(); }
 
       void*
-      _M_storage() const
+      _M_storage() const noexcept
       {
        return const_cast<void*>(static_cast<const void*>(
            std::addressof(_M_u)));
@@ -432,11 +432,11 @@ namespace __variant
        _M_index(_Np)
        { }
 
-      void _M_reset()
+      void _M_reset() noexcept
       { _M_index = variant_npos; }
 
       void*
-      _M_storage() const
+      _M_storage() const noexcept
       {
        return const_cast<void*>(static_cast<const void*>(
            std::addressof(_M_u)));
@@ -760,7 +760,7 @@ namespace __variant
 
   // Returns the raw storage for __v.
   template<typename _Variant>
-    void* __get_storage(_Variant&& __v)
+    void* __get_storage(_Variant&& __v) noexcept
     { return __v._M_storage(); }
 
   template <typename _Maybe_variant_cookie, typename _Variant>
@@ -1556,10 +1556,12 @@ namespace __variant
 #endif
 
       template<size_t _Np, typename _Vp>
-       friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v);
+       friend constexpr decltype(auto)
+       __detail::__variant::__get(_Vp&& __v) noexcept;
 
       template<typename _Vp>
-       friend void* __detail::__variant::__get_storage(_Vp&& __v);
+       friend void*
+       __detail::__variant::__get_storage(_Vp&& __v) noexcept;
 
 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \
       template<typename... _Tp> \