[PATCH v1] libstdc++: Rename _S-prefixed identifiers in .

[Luc Grosheintz]

In libstdc++ the prefix _S is used for static members only. In <mdspan>
there's several type aliases that also used the prefix _S. They now use
double underscore instead.

libstdc++-v3/ChangeLog:

        * include/std/mdspan (_ExtentsStorage::__base): New name for
        _S_base.
        (_ExtentsStorage::__storage_type): New name for _S_storage.
        (extents::__storage_type): New name for _S_storage.
        (layout_stride::mapping::__strides_type): New name for
        _S_stries_t.
        * testsuite/23_containers/mdspan/class_mandate_neg.cc: Update
        test to the new error message.

Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
 libstdc++-v3/include/std/mdspan               | 33 ++++++++++---------
 .../23_containers/mdspan/class_mandate_neg.cc |  2 +-
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 678b2619ebe..f0139a95b11 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -148,14 +148,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       class _ExtentsStorage : public _StaticExtents<_Extents>
       {
       private:
-       using _S_base = _StaticExtents<_Extents>;
+       using __base = _StaticExtents<_Extents>;
 
       public:
-       using _S_base::_S_rank;
-       using _S_base::_S_rank_dynamic;
-       using _S_base::_S_dynamic_index;
-       using _S_base::_S_dynamic_index_inv;
-       using _S_base::_S_static_extent;
+       using __base::_S_rank;
+       using __base::_S_rank_dynamic;
+       using __base::_S_dynamic_index;
+       using __base::_S_dynamic_index_inv;
+       using __base::_S_static_extent;
 
        static constexpr bool
        _S_is_dynamic(size_t __r) noexcept
@@ -242,8 +242,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        }
 
       private:
-       using _S_storage = __array_traits<_IndexType, _S_rank_dynamic>::_Type;
-       [[no_unique_address]] _S_storage _M_dyn_exts{};
+       using __storage_type = __array_traits<_IndexType,
+                                             _S_rank_dynamic>::_Type;
+       [[no_unique_address]] __storage_type _M_dyn_exts{};
       };
 
     template<typename _OIndexType, typename _SIndexType>
@@ -259,7 +260,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     template<typename _Extents>
       constexpr const array<size_t, _Extents::rank()>&
       __static_extents() noexcept
-      { return _Extents::_S_storage::_S_static_extents(); }
+      { return _Extents::__storage_type::_S_static_extents(); }
 
     // Pre-compute: \prod_{i = 0}^r _Extents[i], for r = 0,..., n (exclusive)
     template<array _Extents>
@@ -314,10 +315,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       using rank_type = size_t;
 
       static constexpr rank_type
-      rank() noexcept { return _S_storage::_S_rank; }
+      rank() noexcept { return __storage_type::_S_rank; }
 
       static constexpr rank_type
-      rank_dynamic() noexcept { return _S_storage::_S_rank_dynamic; }
+      rank_dynamic() noexcept { return __storage_type::_S_rank_dynamic; }
 
       static constexpr size_t
       static_extent(rank_type __r) noexcept
@@ -326,7 +327,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        if constexpr (rank() == 0)
          __builtin_trap();
        else
-         return _S_storage::_S_static_extent(__r);
+         return __storage_type::_S_static_extent(__r);
       }
 
       constexpr index_type
@@ -423,9 +424,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       friend span<const index_type>
       __mdspan::__dynamic_extents<extents>(const extents&, size_t, size_t);
 
-      using _S_storage = __mdspan::_ExtentsStorage<
+      using __storage_type = __mdspan::_ExtentsStorage<
        _IndexType, array<size_t, sizeof...(_Extents)>{_Extents...}>;
-      [[no_unique_address]] _S_storage _M_exts;
+      [[no_unique_address]] __storage_type _M_exts;
 
       template<typename _OIndexType, size_t... _OExtents>
        friend class extents;
@@ -1158,10 +1159,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        }
 
     private:
-      using _S_strides_t = typename __array_traits<index_type,
+      using __strides_type = typename __array_traits<index_type,
                                                   extents_type::rank()>::_Type;
       [[no_unique_address]] extents_type _M_extents;
-      [[no_unique_address]] _S_strides_t _M_strides;
+      [[no_unique_address]] __strides_type _M_strides;
     };
 
   template<typename _ElementType>
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/class_mandate_neg.cc 
b/libstdc++-v3/testsuite/23_containers/mdspan/class_mandate_neg.cc
index de19b6d85c9..787e6d801ce 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/class_mandate_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/class_mandate_neg.cc
@@ -35,7 +35,7 @@ test_element_type_mismatch()
 static_assert(test_element_type_mismatch());
 
 // { dg-prune-output "Extents must be a specialization of std::extents" }
-// { dg-prune-output "no type named '_S_storage'" }
+// { dg-prune-output "no type named '__storage_type'" }
 // { dg-prune-output "non-constant condition" }
 // { dg-prune-output "static assertion failed" }
 // { dg-prune-output "__glibcxx_assert" }
-- 
2.50.1