[gcc r13-8460] libstdc++: Implement N3644 on _Safe_iterator<> [PR114316]

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

https://gcc.gnu.org/g:c1f57ff40738bbce9902ea25865ed6d729b10127

commit r13-8460-gc1f57ff40738bbce9902ea25865ed6d729b10127
Author: François Dumont <fdumont@gcc.gnu.org>
Date:   Thu Mar 14 22:13:57 2024 +0100

    libstdc++: Implement N3644 on _Safe_iterator<> [PR114316]
    
    Consider range of value-initialized iterators as valid and empty.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/114316
            * include/debug/safe_iterator.tcc (_Safe_iterator<>::_M_valid_range):
            First check if both iterators are value-initialized before checking if
            singular.
            * testsuite/23_containers/set/debug/114316.cc: New test case.
            * testsuite/23_containers/vector/debug/114316.cc: New test case.
    
    (cherry picked from commit 07fad7a7fc245369989e9ca746728ea78b924715)

Diff:
---
 libstdc++-v3/include/debug/safe_iterator.tcc             | 12 ++++++++++++
 libstdc++-v3/testsuite/23_containers/set/debug/114316.cc | 16 ++++++++++++++++
 .../testsuite/23_containers/vector/debug/114316.cc       | 16 ++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/libstdc++-v3/include/debug/safe_iterator.tcc b/libstdc++-v3/include/debug/safe_iterator.tcc
index 170229ad2f1..2640fc8a473 100644
--- a/libstdc++-v3/include/debug/safe_iterator.tcc
+++ b/libstdc++-v3/include/debug/safe_iterator.tcc
@@ -194,6 +194,12 @@ namespace __gnu_debug
 		   std::pair<difference_type, _Distance_precision>& __dist,
 		   bool __check_dereferenceable) const
     {
+      if (_M_value_initialized() && __rhs._M_value_initialized())
+	{
+	  __dist = std::make_pair(0, __dp_exact);
+	  return true;
+	}
+
       if (_M_singular() || __rhs._M_singular() || !_M_can_compare(__rhs))
 	return false;
 
@@ -218,6 +224,12 @@ namespace __gnu_debug
 		   std::pair<difference_type,
 			     _Distance_precision>& __dist) const
     {
+      if (this->_M_value_initialized() && __rhs._M_value_initialized())
+	{
+	  __dist = std::make_pair(0, __dp_exact);
+	  return true;
+	}
+
       if (this->_M_singular() || __rhs._M_singular()
 	  || !this->_M_can_compare(__rhs))
 	return false;
diff --git a/libstdc++-v3/testsuite/23_containers/set/debug/114316.cc b/libstdc++-v3/testsuite/23_containers/set/debug/114316.cc
new file mode 100644
index 00000000000..126ec89b5e0
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/set/debug/114316.cc
@@ -0,0 +1,16 @@
+// { dg-do run { target c++11 } }
+// { dg-require-debug-mode "" }
+
+// PR libstdc++/114316
+
+#include <set>
+#include <algorithm>
+
+#include <testsuite_hooks.h>
+
+int main()
+{
+  std::set<int>::iterator it{};
+  VERIFY( std::find(it, it, 0) == it );
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/vector/debug/114316.cc b/libstdc++-v3/testsuite/23_containers/vector/debug/114316.cc
new file mode 100644
index 00000000000..f211cf67b4c
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/debug/114316.cc
@@ -0,0 +1,16 @@
+// { dg-do run { target c++11 } }
+// { dg-require-debug-mode "" }
+
+// PR libstdc++/114316
+
+#include <vector>
+#include <algorithm>
+
+#include <testsuite_hooks.h>
+
+int main()
+{
+  std::vector<int>::iterator it{};
+  VERIFY( std::find(it, it, 0) == it );
+  return 0;
+}