test/hotspot/jtreg/runtime/ClassUnload/ConstantPoolDependsTest.java

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/*
 * @test ConstantPoolDependsTest
 * @bug 8210094
 * @summary Create ClassLoader dependency from initiating loader to class loader through constant pool reference
 * @requires vm.opt.final.ClassUnloading
 * @modules java.base/jdk.internal.misc
 *          java.compiler
 * @library /runtime/testlibrary /test/lib
 * @build sun.hotspot.WhiteBox
 * @compile p2/c2.java MyDiffClassLoader.java
 * @run main ClassFileInstaller sun.hotspot.WhiteBox
 *                              sun.hotspot.WhiteBox$WhiteBoxPermission
 * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI ConstantPoolDependsTest
 */

import sun.hotspot.WhiteBox;


public class ConstantPoolDependsTest {
    public static WhiteBox wb = WhiteBox.getWhiteBox();
    public static final String MY_TEST = "ConstantPoolDependsTest$c1c";

    public static class c1c {
        private void test() throws Exception {
            // ConstantPool.klass_at_impl loads through constant pool and creates dependency
            p2.c2 c2_obj = new p2.c2();
            c2_obj.method2();
        }

        public c1c () throws Exception {
            test();
            ClassUnloadCommon.triggerUnloading();  // should not unload anything
            test();
            ClassUnloadCommon.triggerUnloading();  // should not unload anything
        }
    }

    static void test() throws Throwable {

        // now use the same loader to load class MyTest
        Class MyTest_class = new MyDiffClassLoader(MY_TEST).loadClass(MY_TEST);

        try {
            // Call MyTest to load p2.c2 twice and call p2.c2.method2
            MyTest_class.newInstance();
        } catch (Exception e) {
            throw new RuntimeException("Test FAILED if NoSuchMethodException is thrown");
        }
        ClassUnloadCommon.triggerUnloading();  // should not unload anything
        ClassUnloadCommon.failIf(!wb.isClassAlive(MY_TEST), "should not be unloaded");
        ClassUnloadCommon.failIf(!wb.isClassAlive("p2.c2"), "should not be unloaded");
        // Unless MyTest_class is referenced here, the compiler can unload it.
        System.out.println("Should not unload anything before here because " + MyTest_class + " is still alive.");
    }

    public static void main(String args[]) throws Throwable {
        test();
        ClassUnloadCommon.triggerUnloading();  // should unload
        System.gc();
        System.out.println("Should unload p2.c2 just now");
        ClassUnloadCommon.failIf(wb.isClassAlive(MY_TEST), "should be unloaded");
        ClassUnloadCommon.failIf(wb.isClassAlive("p2.c2"), "should be unloaded");
    }
}