FieldInSuper.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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/*
 * @test
 * @bug 8238550
 * @summary Test that verifer assignability checks involving the 'this' pointer
 *          work ok for hidden classes.
 * @compile FieldInSuperSub.jasm
 * @run main/othervm -Xverify:remote FieldInSuper
 */

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import static java.lang.invoke.MethodHandles.Lookup.ClassOption.*;
import java.nio.file.Path;
import java.nio.file.Paths;

public class FieldInSuper {

    static final Path CLASSES_DIR = Paths.get(System.getProperty("test.classes"));
    String hello = "hello";

    static byte[] readClassFile(String classFileName) throws Exception {
        File classFile = new File(CLASSES_DIR + File.separator + classFileName);
        try (FileInputStream in = new FileInputStream(classFile);
             ByteArrayOutputStream out = new ByteArrayOutputStream()) {
            int b;
            while ((b = in.read()) != -1) {
                out.write(b);
            }
            return out.toByteArray();
        }
    }

    public static void main(String[] args) throws Throwable {
        Lookup lookup = MethodHandles.lookup();
        byte[] bytes = readClassFile("FieldInSuperSub.class");

        // Define a hidden class that loads the 'this' pointer and then
        // references field 'hello' using:
        //   getfield Field FieldInSuper.hello:"Ljava/lang/String;";
        // This will cause the verifier to check that the 'this' pointer for
        // the hidden class is assignable to FieldInSuper.
        Class<?> c = lookup.defineHiddenClass(bytes, true, NESTMATE).lookupClass();
        Object fss = c.newInstance();
        c.getMethod("printMe").invoke(fss);
    }

}