VM: Fix memory leak during shutdown

runtime/bin/hashmap_test.cc

Index: runtime/bin/hashmap_test.cc
diff --git a/runtime/bin/hashmap_test.cc b/runtime/bin/hashmap_test.cc
index 47849e046d4bc400e5c03b160f717f483a9071c7..0a4ee31ed104d47545cc960b011d6ebfc31f404f 100644
--- a/runtime/bin/hashmap_test.cc
+++ b/runtime/bin/hashmap_test.cc
@@ -171,7 +171,7 @@ void TestSet(IntKeyHash hash, int size) {
 }
 
 
-UNIT_TEST_CASE(Set) {
+UNIT_TEST_CASE(HashMap_Basic) {
   TestSet(WordHash, 100);
   TestSet(Hash, 100);
   TestSet(CollisionHash1, 50);
@@ -180,4 +180,47 @@ UNIT_TEST_CASE(Set) {
   TestSet(CollisionHash4, 50);
 }
 
+
+UNIT_TEST_CASE(HashMap_RemoveDuringIteration) {
+  class Utils {
+   public:
+    static bool MatchFun(void* key1, void* key2) { return key1 == key2; }
+    static void* Key(intptr_t i) { return reinterpret_cast<void*>(i); }
+    static void* Value(intptr_t i) { return reinterpret_cast<void*>(i); }
+    static uint32_t HashCode(intptr_t key) { return 1; }
+  };
+
+  HashMap map(Utils::MatchFun, 8);
+
+  // Add 6 (1, 1), ..., (6, 60) entries to the map all with a hashcode of 1
+  // (i.e. have all keys have collinding hashcode).
+  //
+  // This causes the probing position in the hashmap to be 1 and open-addressing
+  // with linear probing will fill in the slots towards the right
+  // (i.e. from 1..6).
+  for (intptr_t i = 1; i <= 6 /* avoid rehash at 7 */; i++) {
+    HashMap::Entry* entry = map.Lookup(Utils::Key(i), Utils::HashCode(i), true);
+    entry->value = Utils::Value(10 * i);
+  }
+
+  // Now we iterate over all elements and delete the current element. Since all
+  // our entries have a colliding hashcode of 1, each deletion will cause all
+  // following elements to be left-rotated by 1.
+  intptr_t i = 0;
+  HashMap::Entry* current = map.Start();
+  while (current != NULL) {
+    i++;
+    EXPECT_EQ(Utils::Key(i), current->key);
+    EXPECT_EQ(Utils::Value(10 * i), current->value);
+
+    // Every 2nd element we keep to hit the left-rotation case only sometimes.
+    if (i % 2 == 0) {
+      current = map.Remove(current);
+    } else {
+      current = map.Next(current);
+    }
+  }
+  EXPECT_EQ(6, i);
+}
+
 }  // namespace dart