Prevent unbounded growth of the getField/setField closure caches.

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index 9983abba1410f3288f11f6f7bb3cdefdbc63ff3d..ccf55cb61711e5141177223e38e4f47fe1c17990 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -330,17 +330,22 @@ class _LocalInstanceMirror extends _LocalObjectMirror
   static var _getFieldCallCounts = new HashMap();
   static var _setFieldCallCounts = new HashMap();
   static const _closureThreshold = 20;
+  static const _cacheSizeLimit = 255;
 
   _getFieldSlow(unwrapped) {
     // Slow path factored out to give the fast path a better chance at being
     // inlined.
+    if (_getFieldCallCounts.length == 2 * _cacheSizeLimit) {

[Ivan Posva, 2014/04/25 17:07:08]

Please file a bug that we need to implement a LRU cache helper class for use in
the internal VM libraries.

[rmacnak, 2014/04/25 17:46:22]

Done.

+      // Prevent unbounded cache growth.
+      _getFieldCallCounts = new HashMap();
+    }
     var callCount = _getFieldCallCounts[unwrapped];
     if (callCount == null) {
       callCount = 0;
     }
     if (callCount == _closureThreshold) {
-      // We've seen a success getter invocation a few times: time to invest in a
-      // closure.
+      // We've seen a successful getter invocation a few times: time to invest
+      // in a closure.
       var f;
       var atPosition = unwrapped.indexOf('@');
       if (atPosition == -1) {
@@ -352,6 +357,10 @@ class _LocalInstanceMirror extends _LocalObjectMirror
         var privateKey = unwrapped.substring(atPosition);
         f = _eval('(x) => x.$withoutKey', privateKey);
       }
+      if (_getFieldClosures.length == _cacheSizeLimit) {
+        // Prevent unbounded cache growth.
+        _getFieldClosures = new HashMap();
+      }
       _getFieldClosures[unwrapped] = f;
       _getFieldCallCounts.remove(unwrapped);  // We won't look for this again.
       return reflect(f(_reflectee));
@@ -372,13 +381,16 @@ class _LocalInstanceMirror extends _LocalObjectMirror
   _setFieldSlow(unwrapped, arg) {
     // Slow path factored out to give the fast path a better chance at being
     // inlined.
+    if (_setFieldCallCounts.length == 2 * _cacheSizeLimit) {
+      _setFieldCallCounts = new HashMap();
+    }
     var callCount = _setFieldCallCounts[unwrapped];
     if (callCount == null) {
       callCount = 0;
     }
     if (callCount == _closureThreshold) {
-      // We've seen a success getter invocation a few times: time to invest in a
-      // closure.
+      // We've seen a successful setter invocation a few times: time to invest
+      // in a closure.
       var f;
       var atPosition = unwrapped.indexOf('@');
       if (atPosition == -1) {
@@ -390,6 +402,10 @@ class _LocalInstanceMirror extends _LocalObjectMirror
         var privateKey = unwrapped.substring(atPosition);
         f = _eval('(x, v) => x.$withoutKey = v', privateKey);
       }
+      if (_setFieldClosures.length == _cacheSizeLimit) {
+        // Prevent unbounded cache growth.
+        _setFieldClosures = new HashMap();
+      }
       _setFieldClosures[unwrapped] = f;
       _setFieldCallCounts.remove(unwrapped);
       return reflect(f(_reflectee, arg));