hotspot/test/compiler/stringopts/TestStringObjectInitialization.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 */


import java.util.Arrays;

/*
 * @test
 * @bug 8159244
 * @summary Verifies that no partially initialized String object escapes from
 *          C2's String concat optimization in a highly concurrent setting.
 *          This test triggers the bug in about 1 out of 10 runs.
 * @compile -XDstringConcat=inline TestStringObjectInitialization.java
 * @run main/othervm/timeout=300 -XX:+IgnoreUnrecognizedVMOptions -XX:-UseCompressedOops -XX:-CompactStrings
 *                               -XX:-UseG1GC -XX:+UseParallelGC TestStringObjectInitialization
 */
public class TestStringObjectInitialization {

    String myString;

    public static void main(String[] args) throws Exception {
        TestStringObjectInitialization t = new TestStringObjectInitialization();
        // Create some threads that concurrently update 'myString'
        for (int i = 0; i < 100; ++i) {
            (new Thread(new Runner(t))).start();
        }
        Thread last = new Thread(new Runner(t));
        last.start();
        last.join();
    }

    private void add(String message) {
        // String escapes to other threads here
        myString += message;
    }

    public void run(String s, String[] sArray) {
        // Trigger C2's string concatenation optimization
        add(s + Arrays.toString(sArray) + " const ");
    }
}

class Runner implements Runnable {
    private TestStringObjectInitialization test;

    public Runner(TestStringObjectInitialization t) {
        test = t;
    }

    public void run(){
        String[] array = {"a", "b", "c"};
        for (int i = 0; i < 10000; ++i) {
            test.run("a", array);
        }
    }
}