libstdc++: Fix _Safe_local_iterator<>::_M_valid_range

Unordered container local_iterator range shall not contain any singular
iterator unless both iterators are both value-initialized.

libstdc++-v3/ChangeLog:

	* include/debug/safe_local_iterator.tcc
	(_Safe_local_iterator::_M_valid_range): Add _M_value_initialized and
	_M_singular checks.
	* testsuite/23_containers/unordered_set/debug/114316.cc: New test case.

2 files changed, 35 insertions, 1 deletions

diff --git a/libstdc++-v3/include/debug/safe_local_iterator.tcc b/libstdc++-v3/include/debug/safe_local_iterator.tcc
index 90e60e3..6d546ec 100644
--- a/libstdc++-v3/include/debug/safe_local_iterator.tcc
+++ b/libstdc++-v3/include/debug/safe_local_iterator.tcc
@@ -78,7 +78,13 @@ namespace __gnu_debug
     _M_valid_range(const _Safe_local_iterator& __rhs,
 		std::pair<difference_type, _Distance_precision>& __dist) const
     {
-      if (!_M_can_compare(__rhs))
+      if (_M_value_initialized() && __rhs._M_value_initialized())
+	{
+	  __dist = { 0, __dp_exact };
+	  return true;
+	}
+
+      if (_M_singular() || __rhs._M_singular() || !_M_can_compare(__rhs))
 	return false;
 
       if (bucket() != __rhs.bucket())
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_set/debug/114316.cc b/libstdc++-v3/testsuite/23_containers/unordered_set/debug/114316.cc
new file mode 100644
index 0000000..41b649a
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_set/debug/114316.cc
@@ -0,0 +1,28 @@
+// { dg-do run { target c++11 } }
+// { dg-require-debug-mode "" }
+
+// PR libstdc++/114316
+
+#include <unordered_set>
+#include <algorithm>
+
+#include <testsuite_hooks.h>
+
+void test01()
+{
+  std::unordered_set<int>::iterator it{};
+  VERIFY( std::find(it, it, 0) == it );
+}
+
+void test02()
+{
+  std::unordered_set<int>::local_iterator it{};
+  VERIFY( std::find(it, it, 0) == it );
+}
+
+int main()
+{
+  test01();
+  test02();
+  return 0;
+}