1 files changed, 113 insertions, 0 deletions
diff --git a/tests/072-precise-gc/src/Main.java b/tests/072-precise-gc/src/Main.java
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+++ b/tests/072-precise-gc/src/Main.java
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+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.lang.ref.WeakReference;
+
+public class Main {
+    public static void main(String[] args) {
+        staleStackTest();
+    }
+
+    public static void staleStackTest() {
+        WeakReference wrefs[] = new WeakReference[10];
+
+        populate(wrefs);
+
+        check(wrefs);
+    }
+
+    static void populate(WeakReference[] wrefs) {
+        /*
+         * Get a bunch of non-constant String objects into registers.  These
+         * should be the first locals declared.
+         */
+        String str0 = generateString("String", 0);
+        String str1 = generateString("String", 1);
+        String str2 = generateString("String", 2);
+        String str3 = generateString("String", 3);
+        String str4 = generateString("String", 4);
+        String str5 = generateString("String", 5);
+        String str6 = generateString("String", 6);
+        String str7 = generateString("String", 7);
+        String str8 = generateString("String", 8);
+        String str9 = generateString("String", 9);
+
+        /* stuff them into the weak references array */
+        wrefs[0] = new WeakReference(str0);
+        wrefs[1] = new WeakReference(str1);
+        wrefs[2] = new WeakReference(str2);
+        wrefs[3] = new WeakReference(str3);
+        wrefs[4] = new WeakReference(str4);
+        wrefs[5] = new WeakReference(str5);
+        wrefs[6] = new WeakReference(str6);
+        wrefs[7] = new WeakReference(str7);
+        wrefs[8] = new WeakReference(str8);
+        wrefs[9] = new WeakReference(str9);
+    }
+
+    static String generateString(String base, int num) {
+        return base + num;
+    }
+
+    static void check(WeakReference[] wrefs) {
+        /*
+         * Declare locals so that our stack overlaps the same region
+         * that populate() did.
+         */
+        String str0;
+        String str1;
+        String str2;
+        String str3;
+        String str4;
+        String str5;
+        String str6;
+        String str7;
+        String str8;
+        String str9;
+        int numValid = 0;
+
+        /*
+         * This *should* blow out all the weakly-reference objects.  If
+         * we still have stale copies of references on the stack, a
+         * conservative GC will try to hold on to those objects and the
+         * count will be nonzero.
+         *
+         * Getting a zero result here isn't conclusive, but it's a strong
+         * indicator that precise GC is having an impact.
+         */
+        System.gc();
+
+        for (int i = 0; i < wrefs.length; i++) {
+            if (wrefs[i].get() != null)
+                numValid++;
+        }
+
+        System.out.println("Valid refs: " + numValid);
+
+        /* use the locals in case the compiler gets smart */
+        str0 = generateString("String", 0);
+        str1 = generateString("String", 1);
+        str2 = generateString("String", 2);
+        str3 = generateString("String", 3);
+        str4 = generateString("String", 4);
+        str5 = generateString("String", 5);
+        str6 = generateString("String", 6);
+        str7 = generateString("String", 7);
+        str8 = generateString("String", 8);
+        str9 = generateString("String", 9);
+        System.out.println(str0+str1+str2+str3+str4+str5+str6+str7+str8+str9);
+    }
+}