[PATCH] C++20 P1032 for __debug::array

[François Dumont]

I plan to commit this tomorrow.

But I really wonder if we couldn't just add some __glibcxx_checks_xxx in 
std/array ?

    * include/debug/array (array<>::fill): Add C++20 constexpr.
    (array<>::swap): Likewise.

François

diff --git a/libstdc++-v3/include/debug/array b/libstdc++-v3/include/debug/array
index 5566a087f9a..4e0fac8daac 100644
--- a/libstdc++-v3/include/debug/array
+++ b/libstdc++-v3/include/debug/array
@@ -80,11 +80,11 @@ namespace __debug
       // No explicit construct/copy/destroy for aggregate type.
 
       // DR 776.
-      void
+      _GLIBCXX20_CONSTEXPR void
       fill(const value_type& __u)
       { std::fill_n(begin(), size(), __u); }
 
-      void
+      _GLIBCXX20_CONSTEXPR void
       swap(array& __other)
       noexcept(_AT_Type::_Is_nothrow_swappable::value)
       { std::swap_ranges(begin(), end(), __other.begin()); }
@@ -282,6 +282,7 @@ namespace __debug
 #endif
 
   template<typename _Tp, std::size_t _Nm>
+    _GLIBCXX20_CONSTEXPR
     inline void
     swap(array<_Tp, _Nm>& __one, array<_Tp, _Nm>& __two)
     noexcept(noexcept(__one.swap(__two)))