[gcc r14-9046] libstdc++: [_GLIBCXX_DEBUG] Fix std::__niter_base behavior

[Francois Dumont <fdumont@gcc.gnu.org>]

https://gcc.gnu.org/g:9739d7ebf05aefcdd85477900528d8bee69df215

commit r14-9046-g9739d7ebf05aefcdd85477900528d8bee69df215
Author: François Dumont <fdumont@gcc.gnu.org>
Date:   Wed Feb 14 06:59:12 2024 +0100

    libstdc++: [_GLIBCXX_DEBUG] Fix std::__niter_base behavior
    
    std::__niter_base is used in _GLIBCXX_DEBUG mode to remove _Safe_iterator<>
    wrapper on random access iterators. But doing so it should also preserve original
    behavior to remove __normal_iterator wrapper.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/stl_algobase.h (std::__niter_base): Redefine the overload
            definitions for __gnu_debug::_Safe_iterator.
            * include/debug/safe_iterator.tcc (std::__niter_base): Adapt declarations.

Diff:
---
 libstdc++-v3/include/bits/stl_algobase.h     | 16 +++++++++++++++-
 libstdc++-v3/include/debug/safe_iterator.tcc | 18 +++++++++++++++++-
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index e7207f672665..0f73da131729 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -317,12 +317,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _GLIBCXX_NOEXCEPT_IF(std::is_nothrow_copy_constructible<_Iterator>::value)
     { return __it; }
 
+#if __cplusplus < 201103L
   template<typename _Ite, typename _Seq>
-    _GLIBCXX20_CONSTEXPR
     _Ite
     __niter_base(const ::__gnu_debug::_Safe_iterator<_Ite, _Seq,
 		 std::random_access_iterator_tag>&);
 
+ template<typename _Ite, typename _Cont, typename _Seq>
+    _Ite
+    __niter_base(const ::__gnu_debug::_Safe_iterator<
+		 ::__gnu_cxx::__normal_iterator<_Ite, _Cont>, _Seq,
+		 std::random_access_iterator_tag>&);
+#else
+  template<typename _Ite, typename _Seq>
+    _GLIBCXX20_CONSTEXPR
+    decltype(std::__niter_base(std::declval<_Ite>()))
+    __niter_base(const ::__gnu_debug::_Safe_iterator<_Ite, _Seq,
+		 std::random_access_iterator_tag>&)
+    noexcept(std::is_nothrow_copy_constructible<_Ite>::value);
+#endif
+
   // Reverse the __niter_base transformation to get a
   // __normal_iterator back again (this assumes that __normal_iterator
   // is only used to wrap random access iterators, like pointers).
diff --git a/libstdc++-v3/include/debug/safe_iterator.tcc b/libstdc++-v3/include/debug/safe_iterator.tcc
index 6eb70cbda049..a8b24233e854 100644
--- a/libstdc++-v3/include/debug/safe_iterator.tcc
+++ b/libstdc++-v3/include/debug/safe_iterator.tcc
@@ -235,13 +235,29 @@ namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
+#if __cplusplus < 201103L
   template<typename _Ite, typename _Seq>
-    _GLIBCXX20_CONSTEXPR
     _Ite
     __niter_base(const ::__gnu_debug::_Safe_iterator<_Ite, _Seq,
 		 std::random_access_iterator_tag>& __it)
     { return __it.base(); }
 
+  template<typename _Ite, typename _Cont, typename _DbgSeq>
+    _Ite
+    __niter_base(const ::__gnu_debug::_Safe_iterator<
+		 ::__gnu_cxx::__normal_iterator<_Ite, _Cont>, _DbgSeq,
+		 std::random_access_iterator_tag>& __it)
+    { return __it.base().base(); }
+#else
+  template<typename _Ite, typename _Seq>
+    _GLIBCXX20_CONSTEXPR
+    decltype(std::__niter_base(std::declval<_Ite>()))
+    __niter_base(const ::__gnu_debug::_Safe_iterator<_Ite, _Seq,
+		 std::random_access_iterator_tag>& __it)
+    noexcept(std::is_nothrow_copy_constructible<_Ite>::value)
+    { return std::__niter_base(__it.base()); }
+#endif
+
   template<bool _IsMove,
 	   typename _Ite, typename _Seq, typename _Cat, typename _OI>
     _GLIBCXX20_CONSTEXPR