jdk/test/java/lang/StackWalker/LocalsAndOperands.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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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,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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/*
 * @test
 * @bug 8020968
 * @summary Sanity test for locals and operands
 * @run main LocalsAndOperands
 */

import java.lang.StackWalker.StackFrame;
import java.lang.reflect.*;
import java.util.List;
import java.util.stream.Collectors;

public class LocalsAndOperands {
    static Class<?> liveStackFrameClass;
    static Class<?> primitiveValueClass;
    static StackWalker extendedWalker;
    static Method getLocals;
    static Method getOperands;
    static Method getMonitors;
    static Method primitiveType;
    public static void main(String... args) throws Exception {
        liveStackFrameClass = Class.forName("java.lang.LiveStackFrame");
        primitiveValueClass = Class.forName("java.lang.LiveStackFrame$PrimitiveValue");

        getLocals = liveStackFrameClass.getDeclaredMethod("getLocals");
        getLocals.setAccessible(true);

        getOperands = liveStackFrameClass.getDeclaredMethod("getStack");
        getOperands.setAccessible(true);

        getMonitors = liveStackFrameClass.getDeclaredMethod("getMonitors");
        getMonitors.setAccessible(true);

        primitiveType = primitiveValueClass.getDeclaredMethod("type");
        primitiveType.setAccessible(true);

        Method method = liveStackFrameClass.getMethod("getStackWalker");
        method.setAccessible(true);
        extendedWalker = (StackWalker) method.invoke(null);
        new LocalsAndOperands(extendedWalker, true).test();

        // no access to local and operands.
        new LocalsAndOperands(StackWalker.getInstance(), false).test();
    }

    private final StackWalker walker;
    private final boolean extended;
    LocalsAndOperands(StackWalker walker, boolean extended) {
        this.walker = walker;
        this.extended = extended;
    }

    synchronized void test() throws Exception {
        int x = 10;
        char c = 'z';
        String hi = "himom";
        long l = 1000000L;
        double d =  3.1415926;

        List<StackWalker.StackFrame> frames = walker.walk(s -> s.collect(Collectors.toList()));
        if (extended) {
            for (StackWalker.StackFrame f : frames) {
                System.out.println("frame: " + f);
                Object[] locals = (Object[]) getLocals.invoke(f);
                for (int i = 0; i < locals.length; i++) {
                    System.out.format("  local %d: %s type %s\n", i, locals[i], type(locals[i]));

                    // check for non-null locals in LocalsAndOperands.test()
                    if (f.getClassName().equals("LocalsAndOperands") &&
                            f.getMethodName().equals("test")) {
                        if (locals[i] == null) {
                            throw new RuntimeException("kept-alive locals should not be null");
                        }
                    }
                }

                Object[] operands = (Object[]) getOperands.invoke(f);
                for (int i = 0; i < operands.length; i++) {
                    System.out.format("  operand %d: %s type %s%n", i, operands[i],
                                      type(operands[i]));
                }

                Object[] monitors = (Object[]) getMonitors.invoke(f);
                for (int i = 0; i < monitors.length; i++) {
                    System.out.format("  monitor %d: %s%n", i, monitors[i]);
                }
            }
        } else {
            for (StackFrame f : frames) {
                if (liveStackFrameClass.isInstance(f)) {
                    throw new RuntimeException("should not be LiveStackFrame");
                }
            }
        }
        // Use local variables so they stay alive
        System.out.println("Stayin' alive: "+x+" "+c+" "+hi+" "+l+" "+d);
    }

    String type(Object o) throws Exception {
        if (o == null) {
            return "null";
        } else if (primitiveValueClass.isInstance(o)) {
            char c = (char)primitiveType.invoke(o);
            return String.valueOf(c);
        } else {
            return o.getClass().getName();
        }
    }
}