libstdc++: [_GLIBCXX_DEBUG] Fix management of __dp_sign_max_size [PR 99402]

__dp_sign precision indicates that we found out what iterator comes first or
last in the range. __dp_sign_max_size is the same plus it gives the information
of the max size of the range that is to say the max_size value such that
distance(lhs, rhs) < max_size.
Thanks to this additional information we are able to tell when a copy of n elements
to that range will fail even if we do not know exactly how large it is.

This patch makes sure that we are properly using this information.

libstdc++-v3/ChangeLog:

	PR libstdc++/99402
	* include/debug/helper_functions.h (__can_advance(_InputIterator,
	const std::pair<_Diff, _Distance_precision>&, int)): New.
	(__can_advance(const _Safe_iterator<>&,
	const std::pair<_Diff, _Distance_precision>&, int)): New.
	* include/debug/macros.h (__glibcxx_check_can_increment_dist): New,
	use latter.
	(__glibcxx_check_can_increment_range): Adapt to use latter.
	(__glibcxx_check_can_decrement_range): Likewise.
	* include/debug/safe_iterator.h
	(_Safe_iterator<>::_M_can_advance(const std::pair<_Diff, _Distance_precision>&,
	int)): New.
	(__can_advance(const _Safe_iterator<>&,
	const std::pair<_Diff, _Distance_precision>&, int)): New.
	* include/debug/safe_iterator.tcc
	(_Safe_iterator<>::_M_can_advance(const std::pair<_Diff, _Distance_precision>&,
	int)): New.
	(_Safe_iterator<>::_M_valid_range(const _Safe_iterator<>&,
	std::pair<difference_type, _Distance_precision>&, bool)): Adapt for
	__dp_sign_max_size.
	(__copy_move_a): Adapt to use __glibcxx_check_can_increment_dist.
	(__copy_move_backward_a): Likewise.
	(__equal_aux): Likewise.
	* include/debug/stl_iterator.h (__can_advance(const std::reverse_iterator<>&,
	const std::pair<_Diff, _Distance_precision>&, int)): New.
	(__can_advance(const std::move_iterator<>&,
	const std::pair<_Diff, _Distance_precision>&, int)): New.
	* testsuite/25_algorithms/copy/debug/99402.cc: New test.

6 files changed, 122 insertions, 41 deletions

diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h
index 513e5460e..c0144ce 100644
--- a/libstdc++-v3/include/debug/helper_functions.h
+++ b/libstdc++-v3/include/debug/helper_functions.h
@@ -64,7 +64,7 @@ namespace __gnu_debug
     {
     private:
       typedef
-      typename std::iterator_traits<_Iterator>::difference_type _ItDiffType;
+	typename std::iterator_traits<_Iterator>::difference_type _ItDiffType;
 
       template<typename _DiffType,
 	       typename = typename std::__is_void<_DiffType>::__type>
@@ -291,6 +291,18 @@ namespace __gnu_debug
     __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
 		  _Size);
 
+  template<typename _InputIterator, typename _Diff>
+    _GLIBCXX_CONSTEXPR
+    inline bool
+    __can_advance(_InputIterator, const std::pair<_Diff, _Distance_precision>&, int)
+    { return true; }
+
+  template<typename _Iterator, typename _Sequence, typename _Category,
+	   typename _Diff>
+    bool
+    __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
+		  const std::pair<_Diff, _Distance_precision>&, int);
+
   /** Helper function to extract base iterator of random access safe iterator
    *  in order to reduce performance impact of debug mode.  Limited to random
    *  access iterator because it is the only category for which it is possible
diff --git a/libstdc++-v3/include/debug/macros.h b/libstdc++-v3/include/debug/macros.h
index 0988437..9ac52eb 100644
--- a/libstdc++-v3/include/debug/macros.h
+++ b/libstdc++-v3/include/debug/macros.h
@@ -94,6 +94,12 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size),	\
 		      ._M_iterator(_First, #_First)			\
 		      ._M_integer(_Size, #_Size))
 
+#define __glibcxx_check_can_increment_dist(_First,_Dist,_Way)		\
+  _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Dist, _Way), \
+		      _M_message(__gnu_debug::__msg_iter_subscript_oob)	\
+		      ._M_iterator(_First, #_First)			\
+		      ._M_integer(_Way * _Dist.first, #_Dist))
+
 #define __glibcxx_check_can_increment_range(_First1,_Last1,_First2)	\
   do									\
   {									\
@@ -105,7 +111,7 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size),	\
 			._M_iterator(_Last1, #_Last1),			\
 			__FILE__,__LINE__,__PRETTY_FUNCTION__);		\
     _GLIBCXX_DEBUG_VERIFY_AT_F(						\
-			__gnu_debug::__can_advance(_First2, __dist.first),\
+			__gnu_debug::__can_advance(_First2, __dist, 1), \
 			_M_message(__gnu_debug::__msg_iter_subscript_oob)\
 			._M_iterator(_First2, #_First2)			\
 			._M_integer(__dist.first),			\
@@ -123,7 +129,7 @@ _GLIBCXX_DEBUG_VERIFY(__gnu_debug::__can_advance(_First, _Size),	\
 			._M_iterator(_Last1, #_Last1),			\
 			__FILE__,__LINE__,__PRETTY_FUNCTION__);		\
     _GLIBCXX_DEBUG_VERIFY_AT_F(						\
-			__gnu_debug::__can_advance(_First2, -__dist.first),\
+			__gnu_debug::__can_advance(_First2, __dist, -1), \
 			_M_message(__gnu_debug::__msg_iter_subscript_oob)\
 			._M_iterator(_First2, #_First2)			\
 			._M_integer(-__dist.first),			\
diff --git a/libstdc++-v3/include/debug/safe_iterator.h b/libstdc++-v3/include/debug/safe_iterator.h
index a10df19..8e138fd 100644
--- a/libstdc++-v3/include/debug/safe_iterator.h
+++ b/libstdc++-v3/include/debug/safe_iterator.h
@@ -407,6 +407,12 @@ namespace __gnu_debug
       bool
       _M_can_advance(difference_type __n, bool __strict = false) const;
 
+      // Can we advance the iterator using @p __dist in @p __way direction.
+      template<typename _Diff>
+	bool
+	_M_can_advance(const std::pair<_Diff, _Distance_precision>& __dist,
+		       int __way) const;
+
       // Is the iterator range [*this, __rhs) valid?
       bool
       _M_valid_range(const _Safe_iterator& __rhs,
@@ -958,6 +964,14 @@ namespace __gnu_debug
 		  _Size __n)
     { return __it._M_can_advance(__n); }
 
+  template<typename _Iterator, typename _Sequence, typename _Category,
+	   typename _Diff>
+    inline bool
+    __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>& __it,
+		  const std::pair<_Diff, _Distance_precision>& __dist,
+		  int __way)
+    { return __it._M_can_advance(__dist, __way); }
+
   template<typename _Iterator, typename _Sequence>
     _Iterator
     __base(const _Safe_iterator<_Iterator, _Sequence,
diff --git a/libstdc++-v3/include/debug/safe_iterator.tcc b/libstdc++-v3/include/debug/safe_iterator.tcc
index 81deb10..05c379c 100644
--- a/libstdc++-v3/include/debug/safe_iterator.tcc
+++ b/libstdc++-v3/include/debug/safe_iterator.tcc
@@ -92,25 +92,33 @@ namespace __gnu_debug
       if (__n == 0)
 	return true;
 
+      std::pair<difference_type, _Distance_precision> __dist = __n < 0
+	? _M_get_distance_from_begin()
+	: _M_get_distance_to_end();
+
       if (__n < 0)
-	{
-	  std::pair<difference_type, _Distance_precision> __dist =
-	    _M_get_distance_from_begin();
-	  return __dist.second == __dp_exact
-	    ? __dist.first >= -__n
-	    : !__strict && __dist.first > 0;
-	}
-      else
-	{
-	  std::pair<difference_type, _Distance_precision> __dist =
-	    _M_get_distance_to_end();
-	  return __dist.second == __dp_exact
-	    ? __dist.first >= __n
-	    : !__strict && __dist.first > 0;
-	}
+	__n = -__n;
+
+      return __dist.second > __dp_sign
+	? __dist.first >= __n
+	: !__strict && __dist.first > 0;
     }
 
   template<typename _Iterator, typename _Sequence, typename _Category>
+    template<typename _Diff>
+      bool
+      _Safe_iterator<_Iterator, _Sequence, _Category>::
+      _M_can_advance(const std::pair<_Diff, _Distance_precision>& __dist,
+		     int __way) const
+      {
+	return __dist.second == __dp_exact
+	  ? _M_can_advance(__way * __dist.first)
+	  : _M_can_advance(__way * (__dist.first == 0
+				    ? 0
+				    : __dist.first < 0 ? -1 : 1));
+      }
+
+  template<typename _Iterator, typename _Sequence, typename _Category>
     typename _Distance_traits<_Iterator>::__type
     _Safe_iterator<_Iterator, _Sequence, _Category>::
     _M_get_distance_to(const _Safe_iterator& __rhs) const
@@ -191,19 +199,12 @@ namespace __gnu_debug
 
       /* Determine iterators order */
       __dist = _M_get_distance_to(__rhs);
-      switch (__dist.second)
+      if (__dist.second != __dp_equality)
 	{
-	case __dp_equality:
-	  if (__dist.first == 0)
-	    return true;
-	  break;
-
-	case __dp_sign:
-	case __dp_exact:
 	  // If range is not empty first iterator must be dereferenceable.
-	  if (__dist.first > 0)
-	    return !__check_dereferenceable || _M_dereferenceable();
-	  return __dist.first == 0;
+	  return __dist.first == 0
+	    || (__dist.first > 0
+		&& (!__check_dereferenceable || _M_dereferenceable()));
 	}
 
       // Assume that this is a valid range; we can't check anything else.
@@ -225,9 +226,8 @@ namespace __gnu_debug
       __dist = std::make_pair(__rhs.base() - this->base(), __dp_exact);
 
       // If range is not empty first iterator must be dereferenceable.
-      if (__dist.first > 0)
-	return this->_M_dereferenceable();
-      return __dist.first == 0;
+      return __dist.first == 0
+	|| (__dist.first > 0 && this->_M_dereferenceable());
     }
 } // namespace __gnu_debug
 
@@ -251,7 +251,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_Ite>::__type __dist;
       __glibcxx_check_valid_range2(__first, __last, __dist);
-      __glibcxx_check_can_increment(__result, __dist.first);
+      __glibcxx_check_can_increment_dist(__result, __dist, 1);
 
       if (__dist.second > ::__gnu_debug::__dp_equality)
 	return std::__copy_move_a<_IsMove>(__first.base(), __last.base(),
@@ -268,7 +268,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_II>::__type __dist;
       __glibcxx_check_valid_range2(__first, __last, __dist);
-      __glibcxx_check_can_increment(__result, __dist.first);
+      __glibcxx_check_can_increment_dist(__result, __dist, 1);
 
       if (__dist.second > ::__gnu_debug::__dp_sign
 	  && __result._M_can_advance(__dist.first, true))
@@ -290,7 +290,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_IIte>::__type __dist;
       __glibcxx_check_valid_range2(__first, __last, __dist);
-      __glibcxx_check_can_increment(__result, __dist.first);
+      __glibcxx_check_can_increment_dist(__result, __dist, 1);
 
       if (__dist.second > ::__gnu_debug::__dp_equality)
 	{
@@ -318,7 +318,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_Ite>::__type __dist;
       __glibcxx_check_valid_range2(__first, __last, __dist);
-      __glibcxx_check_can_increment(__result, -__dist.first);
+      __glibcxx_check_can_increment_dist(__result, __dist, -1);
 
       if (__dist.second > ::__gnu_debug::__dp_equality)
 	return std::__copy_move_backward_a<_IsMove>(
@@ -335,7 +335,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_II>::__type __dist;
       __glibcxx_check_valid_range2(__first, __last, __dist);
-      __glibcxx_check_can_increment(__result, -__dist.first);
+      __glibcxx_check_can_increment_dist(__result, __dist, -1);
 
       if (__dist.second > ::__gnu_debug::__dp_sign
 	  && __result._M_can_advance(-__dist.first, true))
@@ -358,7 +358,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_IIte>::__type __dist;
       __glibcxx_check_valid_range2(__first, __last, __dist);
-      __glibcxx_check_can_increment(__result, -__dist.first);
+      __glibcxx_check_can_increment_dist(__result, __dist, -1);
 
       if (__dist.second > ::__gnu_debug::__dp_equality)
 	{
@@ -423,7 +423,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_II1>::__type __dist;
       __glibcxx_check_valid_range2(__first1, __last1, __dist);
-      __glibcxx_check_can_increment(__first2, __dist.first);
+      __glibcxx_check_can_increment_dist(__first2, __dist, 1);
 
       if (__dist.second > ::__gnu_debug::__dp_equality)
 	return std::__equal_aux(__first1.base(), __last1.base(), __first2);
@@ -438,7 +438,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_II1>::__type __dist;
       __glibcxx_check_valid_range2(__first1, __last1, __dist);
-      __glibcxx_check_can_increment(__first2, __dist.first);
+      __glibcxx_check_can_increment_dist(__first2, __dist, 1);
 
       if (__dist.second > ::__gnu_debug::__dp_sign
 	  && __first2._M_can_advance(__dist.first, true))
@@ -457,7 +457,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       typename ::__gnu_debug::_Distance_traits<_II1>::__type __dist;
       __glibcxx_check_valid_range2(__first1, __last1, __dist);
-      __glibcxx_check_can_increment(__first2, __dist.first);
+      __glibcxx_check_can_increment_dist(__first2, __dist, 1);
 
       if (__dist.second > ::__gnu_debug::__dp_equality)
 	{
diff --git a/libstdc++-v3/include/debug/stl_iterator.h b/libstdc++-v3/include/debug/stl_iterator.h
index a9dd5b6..edeb42e 100644
--- a/libstdc++-v3/include/debug/stl_iterator.h
+++ b/libstdc++-v3/include/debug/stl_iterator.h
@@ -52,6 +52,13 @@ namespace __gnu_debug
     __can_advance(const std::reverse_iterator<_Iterator>& __it, _Size __n)
     { return __can_advance(__it.base(), -__n); }
 
+  template<typename _Iterator, typename _Diff>
+    inline bool
+    __can_advance(const std::reverse_iterator<_Iterator>& __it,
+		  const std::pair<_Diff, _Distance_precision>& __dist,
+		  int __way)
+    { return __can_advance(__it.base(), __dist, -__way); }
+
   template<typename _Iterator, typename _Sequence>
     inline std::reverse_iterator<_Iterator>
     __base(const std::reverse_iterator<_Safe_iterator<
@@ -101,6 +108,13 @@ namespace __gnu_debug
     __can_advance(const std::move_iterator<_Iterator>& __it, _Size __n)
     { return __can_advance(__it.base(), __n); }
 
+  template<typename _Iterator, typename _Diff>
+    inline bool
+    __can_advance(const std::move_iterator<_Iterator>& __it,
+		  const std::pair<_Diff, _Distance_precision>& __dist,
+		  int __way)
+    { return __can_advance(__it.base(), __dist, __way); }
+
   template<typename _Iterator>
     inline auto
     __unsafe(const std::move_iterator<_Iterator>& __it)
diff --git a/libstdc++-v3/testsuite/25_algorithms/copy/debug/99402.cc b/libstdc++-v3/testsuite/25_algorithms/copy/debug/99402.cc
new file mode 100644
index 0000000..041d222
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/copy/debug/99402.cc
@@ -0,0 +1,35 @@
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-D_GLIBCXX_DEBUG" }
+// { dg-do run }
+
+#include <algorithm>
+#include <set>
+#include <vector>
+
+// PR libstdc++/99402
+
+using namespace std;
+
+int main()
+{
+    // any container with non-random access iterators:
+    const set<int> source = { 0, 1 };
+    vector<int> dest(1);
+    copy(source.begin(), ++source.begin(), dest.begin());
+}