re PR libstdc++/87135 ([C++17] unordered containers violate iterator validity requirements)

2018-09-18  François Dumont  <fdumont@gcc.gnu.org>

	PR libstdc++/87135
	* src/c++11/hashtable_c++0x.cc:
	(_Prime_rehash_policy::_M_next_bkt): Return a prime no smaller than
	requested size, but not necessarily greater.
	(_Prime_rehash_policy::_M_need_rehash): Rehash only if target size is
	strictly greater than next resize threshold.
	* testsuite/23_containers/unordered_map/modifiers/reserve.cc: Adapt test
	to validate that there is no rehash as long as number of insertion is
	lower or equal to the reserved number of elements.

From-SVN: r264413

1 files changed, 31 insertions, 8 deletions

diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/modifiers/reserve.cc b/libstdc++-v3/testsuite/23_containers/unordered_map/modifiers/reserve.cc
index e9cf7fd6f67..7f34325df87 100644
--- a/libstdc++-v3/testsuite/23_containers/unordered_map/modifiers/reserve.cc
+++ b/libstdc++-v3/testsuite/23_containers/unordered_map/modifiers/reserve.cc
@@ -18,23 +18,46 @@
 // <http://www.gnu.org/licenses/>.
 
 #include <unordered_map>
+
 #include <testsuite_hooks.h>
 
 void test01()
 {
-  const int N = 1000;
-
   typedef std::unordered_map<int, int> Map;
   Map m;
-  m.reserve(N);
 
-  std::size_t bkts = m.bucket_count();
-  for (int i = 0; i != N; ++i)
+  // Make sure max load factor is 1 so that reserved elements is directly
+  // the bucket count.
+  m.max_load_factor(1);
+
+  int i = -1;
+  for (;;)
     {
-      m.insert(std::make_pair(i, i));
-      // As long as we insert less than the reserved number of elements we
-      // shouldn't experiment any rehash.
+      m.reserve(m.bucket_count());
+
+      std::size_t bkts = m.bucket_count();
+
+      m.reserve(bkts);
       VERIFY( m.bucket_count() == bkts );
+
+      for (++i; i < bkts; ++i)
+	{
+	  m.insert(std::make_pair(i, i));
+
+	  // As long as we insert less than the reserved number of elements we
+	  // shouldn't experiment any rehash.
+	  VERIFY( m.bucket_count() == bkts );
+
+	  VERIFY( m.load_factor() <= m.max_load_factor() );
+	}
+
+      // One more element should rehash.
+      m.insert(std::make_pair(i, i));
+      VERIFY( m.bucket_count() != bkts );
+      VERIFY( m.load_factor() <= m.max_load_factor() );
+
+      if (i > 1024)
+	break;
     }
 }