[PATCH] libstdc++: Make debug iterator pointer sequence const [PR116369]

François Dumont frs.dumont@gmail.com
Thu May 15 05:25:15 GMT 2025


Got

On 14/05/2025 18:46, Jonathan Wakely wrote:
> On Wed, 14 May 2025 at 17:31, François Dumont <frs.dumont@gmail.com> wrote:
>> On 12/05/2025 23:03, Jonathan Wakely wrote:
>>> On 31/03/25 22:20 +0200, François Dumont wrote:
>>>> Hi
>>>>
>>>> Following this previous patch
>>>> https://gcc.gnu.org/pipermail/libstdc++/2024-August/059418.html I've
>>>> completed it for the _Safe_unordered_container_base type and
>>>> implemented the rest of the change to store the safe iterator
>>>> sequence as a pointer-to-const.
>>>>
>>>>      libstdc++: Make debug iterator pointer sequence const [PR116369]
>>>>
>>>>      In revision a35dd276cbf6236e08bcf6e56e62c2be41cf6e3c the debug
>>>> sequence
>>>>      have been made mutable to allow attach iterators to const
>>>> containers.
>>>>      This change completes this fix by also declaring debug unordered
>>>> container
>>>>      members mutable.
>>>>
>>>>      Additionally the debug iterator sequence is now a
>>>> pointer-to-const and so
>>>>      _Safe_sequence_base _M_attach and all other methods are const
>>>> qualified.
>>>>      Symbols export are maintained thanks to __asm directives.
>>>>
>>> I can't compile this, it seems to be missing changes to
>>> safe_local_iterator.tcc:
>>>
>>> In file included from
>>> /home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.h:444,
>>>                   from
>>> /home/jwakely/src/gcc/gcc/libstdc++-v3/src/c++11/debug.cc:33:
>>> /home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.tcc:
>>> In member function ‘typename
>>> __gnu_debug::_Distance_traits<_Iterator>::__type
>>> __gnu_debug::_Safe_local_iterator<_Iterator,
>>> _Sequence>::_M_get_distance_to(const
>>> __gnu_debug::_Safe_local_iterator<_Iterator, _Sequence>&) const’:
>>> /home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.tcc:47:17:
>>> error: there are no arguments to ‘_M_get_sequence’ that depend on a
>>> template parameter, so a declaration of ‘_M_get_sequence’ must be
>>> available [-Wtemplate-body]
>>>     47 | _M_get_sequence()->bucket_size(bucket()),
>>>        |                 ^~~~~~~~~~~~~~~
>>> /home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.tcc:47:17:
>>> note: (if you use ‘-fpermissive’, G++ will accept your code, but
>>> allowing the use of an undeclared name is deprecated)
>>> /home/jwakely/src/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/safe_local_iterator.tcc:59:18:
>>> error: there are no arguments to ‘_M_get_sequence’ that depend on a
>>> template parameter, so a declaration of ‘_M_get_sequence’ must be
>>> available [-Wtemplate-body]
>>>     59 | -_M_get_sequence()->bucket_size(bucket()),
>>>        |                  ^~~~~~~~~~~~~~~
>>>
>> Yes, sorry, I had already spotted this problem, but only updated the PR
>> and not re-sending patch here.
>>
>>
>>>> Also available as a PR
>>>>
>>>> https://forge.sourceware.org/gcc/gcc-TEST/pulls/47
>>>>
>>>>      /** Detach all singular iterators.
>>>>       *  @post for all iterators i attached to this sequence,
>>>>       *   i->_M_version == _M_version.
>>>>       */
>>>>      void
>>>> -    _M_detach_singular();
>>>> +    _M_detach_singular() const
>>>> + __asm("_ZN11__gnu_debug19_Safe_sequence_base18_M_detach_singularEv");
>>> Does this work on all targets?
>> No idea ! I thought the symbol name used here just had to match the
>> entries in config/abi/pre/gnu.ver.
> That linker script is not used for all targets.

Ok, got it, I only need to use this when symbol versioning is activated.

I think this new patch should do it if so.

François

-------------- next part --------------
diff --git a/libstdc++-v3/include/debug/formatter.h b/libstdc++-v3/include/debug/formatter.h
index d80e8a78dcb..8aa84adec77 100644
--- a/libstdc++-v3/include/debug/formatter.h
+++ b/libstdc++-v3/include/debug/formatter.h
@@ -96,7 +96,7 @@ namespace __gnu_debug
   template<typename _Iterator, typename _Sequence, typename _Category>
     class _Safe_iterator;
 
-  template<typename _Iterator, typename _Sequence>
+  template<typename _Iterator, typename _UContainer>
     class _Safe_local_iterator;
 
   template<typename _Sequence>
@@ -316,8 +316,8 @@ namespace __gnu_debug
 	    }
 	}
 
-      template<typename _Iterator, typename _Sequence>
-	_Parameter(_Safe_local_iterator<_Iterator, _Sequence> const& __it,
+      template<typename _Iterator, typename _UContainer>
+	_Parameter(_Safe_local_iterator<_Iterator, _UContainer> const& __it,
 		   const char* __name, _Is_iterator)
 	: _M_kind(__iterator),  _M_variant()
 	{
@@ -326,8 +326,8 @@ namespace __gnu_debug
 	  _M_variant._M_iterator._M_type = _GLIBCXX_TYPEID(_Iterator);
 	  _M_variant._M_iterator._M_constness =
 	    __it._S_constant() ? __const_iterator : __mutable_iterator;
-	  _M_variant._M_iterator._M_sequence = __it._M_get_sequence();
-	  _M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_Sequence);
+	  _M_variant._M_iterator._M_sequence = __it._M_get_ucontainer();
+	  _M_variant._M_iterator._M_seq_type = _GLIBCXX_TYPEID(_UContainer);
 
 	  if (__it._M_singular())
 	    {
diff --git a/libstdc++-v3/include/debug/safe_base.h b/libstdc++-v3/include/debug/safe_base.h
index cf3f1708ad2..7f7876e4017 100644
--- a/libstdc++-v3/include/debug/safe_base.h
+++ b/libstdc++-v3/include/debug/safe_base.h
@@ -31,6 +31,12 @@
 
 #include <ext/concurrence.h>
 
+#if _GLIBCXX_SYMVER_GNU
+# define _GLIBCXX_SYMVER_ASM(S) __asm(S)
+#else
+# define _GLIBCXX_SYMVER_ASM(S)
+#endif
+
 namespace __gnu_debug
 {
   class _Safe_sequence_base;
@@ -53,8 +59,10 @@ namespace __gnu_debug
 
   public:
     /** The sequence this iterator references; may be NULL to indicate
-	a singular iterator. */
-    _Safe_sequence_base*	_M_sequence;
+     *  a singular iterator. Stored as pointer-to-const because sequence
+     *  could be declared as const.
+     */
+    const _Safe_sequence_base*	_M_sequence;
 
     /** The version number of this iterator. The sentinel value 0 is
      *  used to indicate an invalidated iterator (i.e., one that is
@@ -92,7 +100,7 @@ namespace __gnu_debug
     : _M_sequence(0), _M_version(0), _M_prior(0), _M_next(0)
     {
       if (!std::__is_constant_evaluated())
-	this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant);
+	this->_M_attach(__seq, __constant);
     }
 
     /** Initializes the iterator to reference the same sequence that
@@ -123,11 +131,15 @@ namespace __gnu_debug
      *	unattached.
      */
     void
-    _M_attach(_Safe_sequence_base* __seq, bool __constant);
+    _M_attach(const _Safe_sequence_base* __seq, bool __constant)
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_iterator_base9"
+			  "_M_attachEPNS_19_Safe_sequence_baseEb");
 
     /** Likewise, but not thread-safe. */
     void
-    _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
+    _M_attach_single(const _Safe_sequence_base* __seq, bool __constant) throw ()
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_iterator_base16"
+			  "_M_attach_singleEPNS_19_Safe_sequence_baseEb");
 
     /** Detach the iterator for whatever sequence it is attached to,
      *	if any.
@@ -246,14 +258,18 @@ namespace __gnu_debug
 
     /** Detach all iterators, leaving them singular. */
     void
-    _M_detach_all();
+    _M_detach_all() const
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_sequence_base13"
+			  "_M_detach_allEv");
 
     /** Detach all singular iterators.
      *  @post for all iterators i attached to this sequence,
      *   i->_M_version == _M_version.
      */
     void
-    _M_detach_singular();
+    _M_detach_singular() const
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_sequence_base18"
+			  "_M_detach_singularEv");
 
     /** Revalidates all attached singular iterators.  This method may
      *  be used to validate iterators that were invalidated before
@@ -261,7 +277,9 @@ namespace __gnu_debug
      *  valid again).
      */
     void
-    _M_revalidate_singular();
+    _M_revalidate_singular() const
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_sequence_base22"
+			  "_M_revalidate_singularEv");
 
     /** Swap this sequence with the given sequence. This operation
      *  also swaps ownership of the iterators, so that when the
@@ -269,11 +287,14 @@ namespace __gnu_debug
      *  one container now reference the other container.
      */
     void
-    _M_swap(_Safe_sequence_base& __x) _GLIBCXX_USE_NOEXCEPT;
+    _M_swap(const _Safe_sequence_base& __x) const _GLIBCXX_USE_NOEXCEPT
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_sequence_base7_M_swapERS0_");
 
     /** For use in _Safe_sequence. */
     __gnu_cxx::__mutex&
-    _M_get_mutex() throw ();
+    _M_get_mutex() const throw ()
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug19_Safe_sequence_base12"
+			  "_M_get_mutexEv");
 
     /** Invalidates all iterators. */
     void
@@ -283,20 +304,21 @@ namespace __gnu_debug
   private:
     /** Attach an iterator to this sequence. */
     void
-    _M_attach(_Safe_iterator_base* __it, bool __constant);
+    _M_attach(_Safe_iterator_base* __it, bool __constant) const;
 
     /** Likewise but not thread safe. */
     void
-    _M_attach_single(_Safe_iterator_base* __it, bool __constant) throw ();
+    _M_attach_single(_Safe_iterator_base* __it, bool __constant) const throw ();
 
     /** Detach an iterator from this sequence */
     void
-    _M_detach(_Safe_iterator_base* __it);
+    _M_detach(_Safe_iterator_base* __it) const;
 
     /** Likewise but not thread safe. */
     void
-    _M_detach_single(_Safe_iterator_base* __it) throw ();
+    _M_detach_single(_Safe_iterator_base* __it) const throw ();
   };
 } // namespace __gnu_debug
 
+#undef _GLIBCXX_SYMVER_ASM
 #endif
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index 7c563381d0b..e0b1b46939c 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -224,7 +224,7 @@ namespace __gnu_debug
 			      _M_message(__msg_init_copy_singular)
 			      ._M_iterator(*this, "this")
 			      ._M_iterator(__x, "other"));
-	_Safe_sequence_base* __seq = __x._M_sequence;
+	const _Safe_sequence_base* __seq = __x._M_sequence;
 	__x._M_detach();
 	std::swap(base(), __x.base());
 	_M_attach(__seq);
@@ -445,12 +445,12 @@ namespace __gnu_debug
 
       /** Attach iterator to the given sequence. */
       void
-      _M_attach(_Safe_sequence_base* __seq)
+      _M_attach(const _Safe_sequence_base* __seq)
       { _Safe_base::_M_attach(__seq, _S_constant()); }
 
       /** Likewise, but not thread-safe. */
       void
-      _M_attach_single(_Safe_sequence_base* __seq)
+      _M_attach_single(const _Safe_sequence_base* __seq)
       { _Safe_base::_M_attach_single(__seq, _S_constant()); }
 
       /// Is the iterator dereferenceable?
@@ -500,7 +500,13 @@ namespace __gnu_debug
       typename __gnu_cxx::__conditional_type<
 	_IsConstant::__value, const _Sequence*, _Sequence*>::__type
       _M_get_sequence() const
-      { return static_cast<_Sequence*>(_M_sequence); }
+      {
+	// Looks like not const-correct, but if _IsConstant the constness
+	// is restored when returning the sequence pointer and if not
+	// _IsConstant we are allowed to remove constness.
+	return static_cast<_Sequence*>
+	  (const_cast<_Safe_sequence_base*>(_M_sequence));
+      }
 
       // Get distance to __rhs.
       typename _Distance_traits<_Iterator>::__type
diff --git a/libstdc++-v3/include/debug/safe_local_iterator.h b/libstdc++-v3/include/debug/safe_local_iterator.h
index c84f4f10093..4645d8bbe56 100644
--- a/libstdc++-v3/include/debug/safe_local_iterator.h
+++ b/libstdc++-v3/include/debug/safe_local_iterator.h
@@ -52,15 +52,14 @@ namespace __gnu_debug
   /** \brief Safe iterator wrapper.
    *
    *  The class template %_Safe_local_iterator is a wrapper around an
-   *  iterator that tracks the iterator's movement among sequences and
-   *  checks that operations performed on the "safe" iterator are
-   *  legal. In additional to the basic iterator operations (which are
-   *  validated, and then passed to the underlying iterator),
-   *  %_Safe_local_iterator has member functions for iterator invalidation,
-   *  attaching/detaching the iterator from sequences, and querying
-   *  the iterator's state.
+   *  iterator that tracks the iterator's movement among unordered containers
+   *  and checks that operations performed on the "safe" iterator are legal.
+   *  In additional to the basic iterator operations (which are validated,
+   *  and then passed to the underlying iterator), %_Safe_local_iterator has
+   *  member functions for iterator invalidation, attaching/detaching the
+   *  iterator from unordered containers, and querying the iterator's state.
    */
-  template<typename _Iterator, typename _Sequence>
+  template<typename _Iterator, typename _UContainer>
     class _Safe_local_iterator
     : private _Iterator
     , public _Safe_local_iterator_base
@@ -68,28 +67,27 @@ namespace __gnu_debug
       typedef _Iterator _Iter_base;
       typedef _Safe_local_iterator_base _Safe_base;
 
-      typedef typename _Sequence::size_type size_type;
+      typedef typename _UContainer::size_type size_type;
 
       typedef std::iterator_traits<_Iterator> _Traits;
 
-      typedef std::__are_same<
-	typename _Sequence::_Base::const_local_iterator,
-	_Iterator> _IsConstant;
+      using _IsConstant = std::__are_same<
+	typename _UContainer::_Base::const_local_iterator, _Iterator>;
 
-      typedef typename __gnu_cxx::__conditional_type<_IsConstant::__value,
-	typename _Sequence::_Base::local_iterator,
-	typename _Sequence::_Base::const_local_iterator>::__type
-      _OtherIterator;
+      using _OtherIterator = std::__conditional_t<
+	_IsConstant::__value,
+	typename _UContainer::_Base::local_iterator,
+	typename _UContainer::_Base::const_local_iterator>;
 
       typedef _Safe_local_iterator _Self;
-      typedef _Safe_local_iterator<_OtherIterator, _Sequence> _OtherSelf;
+      typedef _Safe_local_iterator<_OtherIterator, _UContainer> _OtherSelf;
 
       struct _Unchecked { };
 
       _Safe_local_iterator(const _Safe_local_iterator& __x,
 			   _Unchecked) noexcept
       : _Iter_base(__x.base())
-      { _M_attach(__x._M_sequence); }
+      { _M_attach(__x._M_safe_container()); }
 
     public:
       typedef _Iterator					iterator_type;
@@ -104,12 +102,13 @@ namespace __gnu_debug
 
       /**
        * @brief Safe iterator construction from an unsafe iterator and
-       * its sequence.
+       * its unordered container.
        *
-       * @pre @p seq is not NULL
+       * @pre @p cont is not NULL
        * @post this is not singular
        */
-      _Safe_local_iterator(_Iterator __i, const _Safe_sequence_base* __cont)
+      _Safe_local_iterator(_Iterator __i,
+			   const _Safe_unordered_container_base* __cont)
       : _Iter_base(__i), _Safe_base(__cont, _S_constant())
       { }
 
@@ -126,7 +125,7 @@ namespace __gnu_debug
 			      _M_message(__msg_init_copy_singular)
 			      ._M_iterator(*this, "this")
 			      ._M_iterator(__x, "other"));
-	_M_attach(__x._M_sequence);
+	_M_attach(__x._M_safe_container());
       }
 
       /**
@@ -141,7 +140,7 @@ namespace __gnu_debug
 			      _M_message(__msg_init_copy_singular)
 			      ._M_iterator(*this, "this")
 			      ._M_iterator(__x, "other"));
-	auto __cont = __x._M_sequence;
+	auto __cont = __x._M_safe_container();
 	__x._M_detach();
 	std::swap(base(), __x.base());
 	_M_attach(__cont);
@@ -156,7 +155,7 @@ namespace __gnu_debug
 	  const _Safe_local_iterator<_MutableIterator,
 	  typename __gnu_cxx::__enable_if<_IsConstant::__value &&
 	    std::__are_same<_MutableIterator, _OtherIterator>::__value,
-					  _Sequence>::__type>& __x) noexcept
+					  _UContainer>::__type>& __x) noexcept
 	: _Iter_base(__x.base())
 	{
 	  // _GLIBCXX_RESOLVE_LIB_DEFECTS
@@ -166,7 +165,7 @@ namespace __gnu_debug
 				_M_message(__msg_init_const_singular)
 				._M_iterator(*this, "this")
 				._M_iterator(__x, "other"));
-	  _M_attach(__x._M_sequence);
+	  _M_attach(__x._M_safe_container());
 	}
 
       /**
@@ -193,7 +192,7 @@ namespace __gnu_debug
 	  {
 	    _M_detach();
 	    base() = __x.base();
-	    _M_attach(__x._M_sequence);
+	    _M_attach(__x._M_safe_container());
 	  }
 
 	return *this;
@@ -225,7 +224,7 @@ namespace __gnu_debug
 	  {
 	    _M_detach();
 	    base() = __x.base();
-	    _M_attach(__x._M_sequence);
+	    _M_attach(__x._M_safe_container());
 	  }
 
 	__x._M_detach();
@@ -318,15 +317,15 @@ namespace __gnu_debug
        */
       operator _Iterator() const { return *this; }
 
-      /** Attach iterator to the given sequence. */
+      /** Attach iterator to the given unordered container. */
       void
-      _M_attach(_Safe_sequence_base* __seq)
-      { _Safe_base::_M_attach(__seq, _S_constant()); }
+      _M_attach(const _Safe_unordered_container_base* __cont)
+      { _Safe_base::_M_attach(__cont, _S_constant()); }
 
       /** Likewise, but not thread-safe. */
       void
-      _M_attach_single(_Safe_sequence_base* __seq)
-      { _Safe_base::_M_attach_single(__seq, _S_constant()); }
+      _M_attach_single(const _Safe_unordered_container_base* __cont)
+      { _Safe_base::_M_attach_single(__cont, _S_constant()); }
 
       /// Is the iterator dereferenceable?
       bool
@@ -353,25 +352,31 @@ namespace __gnu_debug
       typename _Distance_traits<_Iterator>::__type
       _M_get_distance_to(const _Safe_local_iterator& __rhs) const;
 
-      // The sequence this iterator references.
-      typename __gnu_cxx::__conditional_type<
-	_IsConstant::__value, const _Sequence*, _Sequence*>::__type
-      _M_get_sequence() const
-      { return static_cast<_Sequence*>(_M_sequence); }
+      // The unordered container this iterator references.
+      std::__conditional_t<
+	_IsConstant::__value, const _UContainer*, _UContainer*>
+      _M_get_ucontainer() const
+      {
+	// Looks like not const-correct, but if _IsConstant the constness
+	// is restored when returning the container pointer and if not
+	// _IsConstant we are allowed to remove constness.
+	return static_cast<_UContainer*>
+	  (const_cast<_Safe_unordered_container_base*>(_M_safe_container()));
+      }
 
-      /// Is this iterator equal to the sequence's begin(bucket) iterator?
+      /// Is this iterator equal to the container's begin(bucket) iterator?
       bool _M_is_begin() const
-      { return base() == _M_get_sequence()->_M_base().begin(bucket()); }
+      { return base() == _M_get_ucontainer()->_M_base().begin(bucket()); }
 
-      /// Is this iterator equal to the sequence's end(bucket) iterator?
+      /// Is this iterator equal to the container's end(bucket) iterator?
       bool _M_is_end() const
-      { return base() == _M_get_sequence()->_M_base().end(bucket()); }
+      { return base() == _M_get_ucontainer()->_M_base().end(bucket()); }
 
       /// Is this iterator part of the same bucket as the other one?
       template<typename _Other>
 	bool
 	_M_in_same_bucket(const _Safe_local_iterator<_Other,
-						     _Sequence>& __other) const
+						     _UContainer>& __other) const
 	{ return bucket() == __other.bucket(); }
 
       friend inline bool
@@ -404,31 +409,31 @@ namespace __gnu_debug
     };
 
   /** Safe local iterators know how to check if they form a valid range. */
-  template<typename _Iterator, typename _Sequence>
+  template<typename _Iterator, typename _UContainer>
     inline bool
-    __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>& __first,
-		  const _Safe_local_iterator<_Iterator, _Sequence>& __last,
+    __valid_range(const _Safe_local_iterator<_Iterator, _UContainer>& __first,
+		  const _Safe_local_iterator<_Iterator, _UContainer>& __last,
 		  typename _Distance_traits<_Iterator>::__type& __dist_info)
     { return __first._M_valid_range(__last, __dist_info); }
 
-  template<typename _Iterator, typename _Sequence>
+  template<typename _Iterator, typename _UContainer>
     inline bool
-    __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>& __first,
-		  const _Safe_local_iterator<_Iterator, _Sequence>& __last)
+    __valid_range(const _Safe_local_iterator<_Iterator, _UContainer>& __first,
+		  const _Safe_local_iterator<_Iterator, _UContainer>& __last)
     {
       typename _Distance_traits<_Iterator>::__type __dist_info;
       return __first._M_valid_range(__last, __dist_info);
     }
 
 #if __cplusplus < 201103L
-  template<typename _Iterator, typename _Sequence>
-    struct _Unsafe_type<_Safe_local_iterator<_Iterator, _Sequence> >
+  template<typename _Iterator, typename _UContainer>
+    struct _Unsafe_type<_Safe_local_iterator<_Iterator, _UContainer> >
     { typedef _Iterator _Type; };
 #endif
 
-  template<typename _Iterator, typename _Sequence>
+  template<typename _Iterator, typename _UContainer>
     inline _Iterator
-    __unsafe(const _Safe_local_iterator<_Iterator, _Sequence>& __it)
+    __unsafe(const _Safe_local_iterator<_Iterator, _UContainer>& __it)
     { return __it.base(); }
 
 } // namespace __gnu_debug
diff --git a/libstdc++-v3/include/debug/safe_local_iterator.tcc b/libstdc++-v3/include/debug/safe_local_iterator.tcc
index 71e532065e4..10fec3fad4a 100644
--- a/libstdc++-v3/include/debug/safe_local_iterator.tcc
+++ b/libstdc++-v3/include/debug/safe_local_iterator.tcc
@@ -44,7 +44,7 @@ namespace __gnu_debug
 	  if (__rhs._M_is_end())
 	    return
 	      {
-		_M_get_sequence()->bucket_size(bucket()),
+		_M_get_ucontainer()->bucket_size(bucket()),
 		__dp_exact
 	      };
 
@@ -56,7 +56,7 @@ namespace __gnu_debug
 	  if (__rhs._M_is_begin())
 	    return
 	      {
-		-_M_get_sequence()->bucket_size(bucket()),
+		-_M_get_ucontainer()->bucket_size(bucket()),
 		__dp_exact
 	      };
 
diff --git a/libstdc++-v3/include/debug/safe_sequence.h b/libstdc++-v3/include/debug/safe_sequence.h
index 6b35afa66c6..599f770554b 100644
--- a/libstdc++-v3/include/debug/safe_sequence.h
+++ b/libstdc++-v3/include/debug/safe_sequence.h
@@ -114,7 +114,7 @@ namespace __gnu_debug
 	  in the safe ones. */
       template<typename _Predicate>
 	void
-	_M_invalidate_if(_Predicate __pred);
+	_M_invalidate_if(_Predicate __pred) const;
 
       /** Transfers all iterators @c x that reference @c from sequence,
 	  are not singular, and for which @c __pred(x) returns @c
@@ -122,7 +122,7 @@ namespace __gnu_debug
 	  in the safe ones. */
       template<typename _Predicate>
 	void
-	_M_transfer_from_if(_Safe_sequence& __from, _Predicate __pred);
+	_M_transfer_from_if(_Safe_sequence& __from, _Predicate __pred) const;
     };
 
   /// Like _Safe_sequence but with a special _M_invalidate_all implementation
@@ -133,12 +133,12 @@ namespace __gnu_debug
     {
     protected:
       void
-      _M_invalidate_all()
+      _M_invalidate_all() const
       {
 	typedef typename _Sequence::const_iterator _Const_iterator;
 	typedef typename _Const_iterator::iterator_type _Base_const_iterator;
 	typedef __gnu_debug::_Not_equal_to<_Base_const_iterator> _Not_equal;
-	const _Sequence& __seq = *static_cast<_Sequence*>(this);
+	const _Sequence& __seq = *static_cast<const _Sequence*>(this);
 	this->_M_invalidate_if(_Not_equal(__seq._M_base().end()));
       }
     };
diff --git a/libstdc++-v3/include/debug/safe_sequence.tcc b/libstdc++-v3/include/debug/safe_sequence.tcc
index 336bf2a0b2b..62872b1d788 100644
--- a/libstdc++-v3/include/debug/safe_sequence.tcc
+++ b/libstdc++-v3/include/debug/safe_sequence.tcc
@@ -35,7 +35,7 @@ namespace __gnu_debug
     template<typename _Predicate>
       void
       _Safe_sequence<_Sequence>::
-      _M_invalidate_if(_Predicate __pred)
+      _M_invalidate_if(_Predicate __pred) const
       {
 	typedef typename _Sequence::iterator iterator;
 	typedef typename _Sequence::const_iterator const_iterator;
@@ -66,7 +66,7 @@ namespace __gnu_debug
     template<typename _Predicate>
       void
       _Safe_sequence<_Sequence>::
-      _M_transfer_from_if(_Safe_sequence& __from, _Predicate __pred)
+      _M_transfer_from_if(_Safe_sequence& __from, _Predicate __pred) const
       {
 	if (this == std::__addressof(__from))
 	  return;
@@ -104,7 +104,7 @@ namespace __gnu_debug
 	    }
 
 	  for (_Safe_iterator_base* __iter2 = __from._M_const_iterators;
-		 __iter2;)
+	       __iter2;)
 	    {
 	      _Safe_iterator_base* __victim_base = __iter2;
 	      const_iterator* __victim =
diff --git a/libstdc++-v3/include/debug/safe_unordered_base.h b/libstdc++-v3/include/debug/safe_unordered_base.h
index 1547f5b7b9d..fe32acb55f7 100644
--- a/libstdc++-v3/include/debug/safe_unordered_base.h
+++ b/libstdc++-v3/include/debug/safe_unordered_base.h
@@ -31,6 +31,12 @@
 
 #include <debug/safe_base.h>
 
+#if _GLIBCXX_SYMVER_GNU
+# define _GLIBCXX_SYMVER_ASM(S) __asm(S)
+#else
+# define _GLIBCXX_SYMVER_ASM(S)
+#endif
+
 namespace __gnu_debug
 {
   class _Safe_unordered_container_base;
@@ -49,6 +55,10 @@ namespace __gnu_debug
    */
   class _Safe_local_iterator_base : public _Safe_iterator_base
   {
+  public:
+    const _Safe_unordered_container_base*
+    _M_safe_container() const noexcept;
+
   protected:
     /** Initializes the iterator and makes it singular. */
     _Safe_local_iterator_base()
@@ -61,32 +71,36 @@ namespace __gnu_debug
      *  singular. Otherwise, the iterator will reference @p __seq and
      *  be nonsingular.
      */
-    _Safe_local_iterator_base(const _Safe_sequence_base* __seq, bool __constant)
-    { this->_M_attach(const_cast<_Safe_sequence_base*>(__seq), __constant); }
+    _Safe_local_iterator_base(const _Safe_unordered_container_base* __seq,
+			      bool __constant)
+    { _M_attach(__seq, __constant); }
 
     /** Initializes the iterator to reference the same container that
 	@p __x does. @p __constant is true if this is a constant
 	iterator, and false if it is mutable. */
     _Safe_local_iterator_base(const _Safe_local_iterator_base& __x,
 			      bool __constant)
-    { this->_M_attach(__x._M_sequence, __constant); }
+    { this->_M_attach(__x._M_safe_container(), __constant); }
 
     ~_Safe_local_iterator_base() { this->_M_detach(); }
 
-    _Safe_unordered_container_base*
-    _M_get_container() const noexcept;
-
     /** Attaches this iterator to the given container, detaching it
      *	from whatever container it was attached to originally. If the
      *	new container is the NULL pointer, the iterator is left
      *	unattached.
      */
     void
-    _M_attach(_Safe_sequence_base* __seq, bool __constant);
+    _M_attach(const _Safe_unordered_container_base* __seq,
+	      bool __constant)
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug25_Safe_local_iterator_base9"
+			  "_M_attachEPNS_19_Safe_sequence_baseEb");
 
     /** Likewise, but not thread-safe. */
     void
-    _M_attach_single(_Safe_sequence_base* __seq, bool __constant) throw ();
+    _M_attach_single(const _Safe_unordered_container_base* __seq,
+		     bool __constant) noexcept
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug25_Safe_local_iterator_base16"
+			  "_M_attach_singleEPNS_19_Safe_sequence_baseEb");
 
     /** Detach the iterator for whatever container it is attached to,
      *	if any.
@@ -124,10 +138,10 @@ namespace __gnu_debug
 
   public:
     /// The list of mutable local iterators that reference this container
-    _Safe_iterator_base* _M_local_iterators;
+    mutable _Safe_iterator_base* _M_local_iterators;
 
     /// The list of constant local iterators that reference this container
-    _Safe_iterator_base* _M_const_local_iterators;
+    mutable _Safe_iterator_base* _M_const_local_iterators;
 
   protected:
     // Initialize with a version number of 1 and no iterators
@@ -153,7 +167,9 @@ namespace __gnu_debug
 
     /** Detach all iterators, leaving them singular. */
     void
-    _M_detach_all();
+    _M_detach_all() const
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug30_Safe_unordered_container_base13"
+			  "_M_detach_allEv");
 
     /** Swap this container with the given container. This operation
      *  also swaps ownership of the iterators, so that when the
@@ -161,25 +177,34 @@ namespace __gnu_debug
      *  one container now reference the other container.
      */
     void
-    _M_swap(_Safe_unordered_container_base& __x) noexcept;
+    _M_swap(const _Safe_unordered_container_base& __x) const noexcept
+      _GLIBCXX_SYMVER_ASM("_ZN11__gnu_debug30_Safe_unordered_container_base7"
+			  "_M_swapERS0_");
 
   private:
     /** Attach an iterator to this container. */
     void
-    _M_attach_local(_Safe_iterator_base* __it, bool __constant);
+    _M_attach_local(_Safe_iterator_base* __it, bool __constant) const;
 
     /** Likewise but not thread safe. */
     void
-    _M_attach_local_single(_Safe_iterator_base* __it, bool __constant) throw ();
+    _M_attach_local_single(_Safe_iterator_base* __it,
+			   bool __constant) const noexcept;
 
     /** Detach an iterator from this container */
     void
-    _M_detach_local(_Safe_iterator_base* __it);
+    _M_detach_local(_Safe_iterator_base* __it) const;
 
     /** Likewise but not thread safe. */
     void
-    _M_detach_local_single(_Safe_iterator_base* __it) throw ();
+    _M_detach_local_single(_Safe_iterator_base* __it) const noexcept;
   };
+
+  inline const _Safe_unordered_container_base*
+  _Safe_local_iterator_base::
+  _M_safe_container() const noexcept
+  { return static_cast<const _Safe_unordered_container_base*>(_M_sequence); }
 } // namespace __gnu_debug
 
+#undef _GLIBCXX_SYMVER_ASM
 #endif
diff --git a/libstdc++-v3/src/c++11/debug.cc b/libstdc++-v3/src/c++11/debug.cc
index 3533b5e1df1..08edc770a46 100644
--- a/libstdc++-v3/src/c++11/debug.cc
+++ b/libstdc++-v3/src/c++11/debug.cc
@@ -54,7 +54,7 @@ namespace
    *  in order to limit contention without breaking current library binary
    *  compatibility. */
   __gnu_cxx::__mutex&
-  get_safe_base_mutex(void* address)
+  get_safe_base_mutex(const void* address)
   {
     // Use arbitrarily __gnu_debug::vector<int> as the container giving
     // alignment of debug containers.
@@ -70,9 +70,9 @@ namespace
 #pragma GCC diagnostic warning "-Wabi=6"
 
   void
-  swap_its(__gnu_debug::_Safe_sequence_base& __lhs,
+  swap_its(const __gnu_debug::_Safe_sequence_base& __lhs,
 	   __gnu_debug::_Safe_iterator_base*& __lhs_its,
-	   __gnu_debug::_Safe_sequence_base& __rhs,
+	   const __gnu_debug::_Safe_sequence_base& __rhs,
 	   __gnu_debug::_Safe_iterator_base*& __rhs_its)
   {
     swap(__lhs_its, __rhs_its);
@@ -84,8 +84,8 @@ namespace
   }
 
   void
-  swap_seq_single(__gnu_debug::_Safe_sequence_base& __lhs,
-		  __gnu_debug::_Safe_sequence_base& __rhs)
+  swap_seq_single(const __gnu_debug::_Safe_sequence_base& __lhs,
+		  const __gnu_debug::_Safe_sequence_base& __rhs)
   {
     swap(__lhs._M_version, __rhs._M_version);
     swap_its(__lhs, __lhs._M_iterators,
@@ -118,17 +118,17 @@ namespace
 
   void
   swap_seq(__gnu_cxx::__mutex& lhs_mutex,
-	   __gnu_debug::_Safe_sequence_base& lhs,
+	   const __gnu_debug::_Safe_sequence_base& lhs,
 	   __gnu_cxx::__mutex& rhs_mutex,
-	   __gnu_debug::_Safe_sequence_base& rhs)
+	   const __gnu_debug::_Safe_sequence_base& rhs)
   {
     lock_and_run(lhs_mutex, rhs_mutex,
 		 [&lhs, &rhs]() { swap_seq_single(lhs, rhs); });
   }
 
   void
-  swap_ucont_single(__gnu_debug::_Safe_unordered_container_base& __lhs,
-		    __gnu_debug::_Safe_unordered_container_base& __rhs)
+  swap_ucont_single(const __gnu_debug::_Safe_unordered_container_base& __lhs,
+		    const __gnu_debug::_Safe_unordered_container_base& __rhs)
   {
     swap_seq_single(__lhs, __rhs);
     swap_its(__lhs, __lhs._M_local_iterators,
@@ -139,9 +139,9 @@ namespace
 
   void
   swap_ucont(__gnu_cxx::__mutex& lhs_mutex,
-	     __gnu_debug::_Safe_unordered_container_base& lhs,
+	     const __gnu_debug::_Safe_unordered_container_base& lhs,
 	     __gnu_cxx::__mutex& rhs_mutex,
-	     __gnu_debug::_Safe_unordered_container_base& rhs)
+	     const __gnu_debug::_Safe_unordered_container_base& rhs)
   {
     lock_and_run(lhs_mutex, rhs_mutex,
 		 [&lhs, &rhs]() { swap_ucont_single(lhs, rhs); });
@@ -158,8 +158,8 @@ namespace
       }
   }
 
-  void*
-  acquire_sequence_ptr_for_lock(__gnu_debug::_Safe_sequence_base*& seq)
+  const void*
+  acquire_sequence_ptr_for_lock(__gnu_debug::_Safe_sequence_base const*& seq)
   {
 #ifdef __GTHREADS
     if (!__gnu_cxx::__is_single_threaded())
@@ -169,7 +169,7 @@ namespace
   }
 
   void
-  reset_sequence_ptr(__gnu_debug::_Safe_sequence_base*& seq)
+  reset_sequence_ptr(__gnu_debug::_Safe_sequence_base const*& seq)
   {
 #ifdef __GTHREADS
     if (!__gnu_cxx::__is_single_threaded())
@@ -327,7 +327,7 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_detach_all()
+  _M_detach_all() const
   {
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
     detach_all(_M_iterators);
@@ -339,7 +339,7 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_detach_singular()
+  _M_detach_singular() const
   {
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
     for (_Safe_iterator_base* __iter = _M_iterators; __iter;)
@@ -361,7 +361,7 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_revalidate_singular()
+  _M_revalidate_singular() const
   {
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
     for (_Safe_iterator_base* __iter = _M_iterators; __iter;
@@ -375,17 +375,17 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_swap(_Safe_sequence_base& __x) noexcept
+  _M_swap(const _Safe_sequence_base& __x) const noexcept
   { swap_seq(_M_get_mutex(), *this, __x._M_get_mutex(), __x); }
 
   __gnu_cxx::__mutex&
   _Safe_sequence_base::
-  _M_get_mutex() noexcept
+  _M_get_mutex() const noexcept
   { return get_safe_base_mutex(this); }
 
   void
   _Safe_sequence_base::
-  _M_attach(_Safe_iterator_base* __it, bool __constant)
+  _M_attach(_Safe_iterator_base* __it, bool __constant) const
   {
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
     _M_attach_single(__it, __constant);
@@ -393,7 +393,7 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_attach_single(_Safe_iterator_base* __it, bool __constant) noexcept
+  _M_attach_single(_Safe_iterator_base* __it, bool __constant) const noexcept
   {
     _Safe_iterator_base*& __its =
       __constant ? _M_const_iterators : _M_iterators;
@@ -405,7 +405,7 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_detach(_Safe_iterator_base* __it)
+  _M_detach(_Safe_iterator_base* __it) const
   {
     // Remove __it from this sequence's list
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
@@ -414,7 +414,7 @@ namespace __gnu_debug
 
   void
   _Safe_sequence_base::
-  _M_detach_single(_Safe_iterator_base* __it) noexcept
+  _M_detach_single(_Safe_iterator_base* __it) const noexcept
   {
     // Remove __it from this sequence's list
     __it->_M_unlink();
@@ -426,7 +426,7 @@ namespace __gnu_debug
 
   void
   _Safe_iterator_base::
-  _M_attach(_Safe_sequence_base* __seq, bool __constant)
+  _M_attach(const _Safe_sequence_base* __seq, bool __constant)
   {
     _M_detach();
 
@@ -443,7 +443,7 @@ namespace __gnu_debug
 
   void
   _Safe_iterator_base::
-  _M_attach_single(_Safe_sequence_base* __seq, bool __constant) noexcept
+  _M_attach_single(const _Safe_sequence_base* __seq, bool __constant) noexcept
   {
     _M_detach_single();
 
@@ -514,14 +514,9 @@ namespace __gnu_debug
   _M_get_mutex() noexcept
   { return _M_sequence->_M_get_mutex(); }
 
-  _Safe_unordered_container_base*
-  _Safe_local_iterator_base::
-  _M_get_container() const noexcept
-  { return static_cast<_Safe_unordered_container_base*>(_M_sequence); }
-
   void
   _Safe_local_iterator_base::
-  _M_attach(_Safe_sequence_base* __cont, bool __constant)
+  _M_attach(const _Safe_unordered_container_base* __cont, bool __constant)
   {
     _M_detach();
 
@@ -530,7 +525,7 @@ namespace __gnu_debug
       {
 	_M_sequence = __cont;
 	_M_version = _M_sequence->_M_version;
-	_M_get_container()->_M_attach_local(this, __constant);
+	_M_safe_container()->_M_attach_local(this, __constant);
       }
     else
       _M_version = 0;
@@ -538,7 +533,8 @@ namespace __gnu_debug
 
   void
   _Safe_local_iterator_base::
-  _M_attach_single(_Safe_sequence_base* __cont, bool __constant) noexcept
+  _M_attach_single(const _Safe_unordered_container_base* __cont,
+		   bool __constant) noexcept
   {
     _M_detach_single();
 
@@ -547,7 +543,7 @@ namespace __gnu_debug
       {
 	_M_sequence = __cont;
 	_M_version = _M_sequence->_M_version;
-	_M_get_container()->_M_attach_local_single(this, __constant);
+	_M_safe_container()->_M_attach_local_single(this, __constant);
       }
     else
       _M_version = 0;
@@ -570,14 +566,14 @@ namespace __gnu_debug
   {
     if (_M_sequence)
       {
-	_M_get_container()->_M_detach_local_single(this);
+	_M_safe_container()->_M_detach_local_single(this);
 	_M_reset();
       }
   }
 
   void
   _Safe_unordered_container_base::
-  _M_detach_all()
+  _M_detach_all() const
   {
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
     detach_all(_M_iterators);
@@ -595,12 +591,12 @@ namespace __gnu_debug
 
   void
   _Safe_unordered_container_base::
-  _M_swap(_Safe_unordered_container_base& __x) noexcept
+  _M_swap(const _Safe_unordered_container_base& __x) const noexcept
   { swap_ucont(_M_get_mutex(), *this, __x._M_get_mutex(), __x); }
 
   void
   _Safe_unordered_container_base::
-  _M_attach_local(_Safe_iterator_base* __it, bool __constant)
+  _M_attach_local(_Safe_iterator_base* __it, bool __constant) const
   {
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
     _M_attach_local_single(__it, __constant);
@@ -608,7 +604,7 @@ namespace __gnu_debug
 
   void
   _Safe_unordered_container_base::
-  _M_attach_local_single(_Safe_iterator_base* __it, bool __constant) noexcept
+  _M_attach_local_single(_Safe_iterator_base* __it, bool __constant) const noexcept
   {
     _Safe_iterator_base*& __its =
       __constant ? _M_const_local_iterators : _M_local_iterators;
@@ -620,7 +616,7 @@ namespace __gnu_debug
 
   void
   _Safe_unordered_container_base::
-  _M_detach_local(_Safe_iterator_base* __it)
+  _M_detach_local(_Safe_iterator_base* __it) const
   {
     // Remove __it from this container's list
     __gnu_cxx::__scoped_lock sentry(_M_get_mutex());
@@ -629,7 +625,7 @@ namespace __gnu_debug
 
   void
   _Safe_unordered_container_base::
-  _M_detach_local_single(_Safe_iterator_base* __it) noexcept
+  _M_detach_local_single(_Safe_iterator_base* __it) const noexcept
   {
     // Remove __it from this container's list
     __it->_M_unlink();
diff --git a/libstdc++-v3/testsuite/util/testsuite_containers.h b/libstdc++-v3/testsuite/util/testsuite_containers.h
index 37491a405dc..ab0107f79e4 100644
--- a/libstdc++-v3/testsuite/util/testsuite_containers.h
+++ b/libstdc++-v3/testsuite/util/testsuite_containers.h
@@ -210,6 +210,9 @@ namespace __gnu_test
 	clit = container.cbegin(bn);
 	assert( ++clit == container.cend(bn) );
 
+	clit = container.begin(bn);
+	assert( ++clit == container.cend(bn) );
+
 	assert( container.begin(bn) != container.cend(bn) );
       }
     };
@@ -304,6 +307,9 @@ namespace __gnu_test
 	assert( container.cbegin() != container.cend() );
 	assert( container.cbegin() != container.end() );
 	assert( container.begin() != container.cend() );
+
+	auto cit = container.begin();
+	assert( cit == container.cbegin() );
       }
   };
 


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