8004727: Add compiler support for parameter reflection

Reviewed-by: jjg

langtools/src/share/classes/com/sun/tools/classfile/Attribute.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -51,6 +51,7 @@ public abstract class Attribute {
     public static final String LineNumberTable          = "LineNumberTable";
     public static final String LocalVariableTable       = "LocalVariableTable";
     public static final String LocalVariableTypeTable   = "LocalVariableTypeTable";
+    public static final String MethodParameters         = "MethodParameters";
     public static final String RuntimeVisibleAnnotations = "RuntimeVisibleAnnotations";
     public static final String RuntimeInvisibleAnnotations = "RuntimeInvisibleAnnotations";
     public static final String RuntimeVisibleParameterAnnotations = "RuntimeVisibleParameterAnnotations";
@@ -113,6 +114,7 @@ public abstract class Attribute {
             standardAttributes.put(LocalVariableTypeTable, LocalVariableTypeTable_attribute.class);
 
             if (!compat) { // old javap does not recognize recent attributes
+                standardAttributes.put(MethodParameters, MethodParameters_attribute.class);
                 standardAttributes.put(CompilationID, CompilationID_attribute.class);
                 standardAttributes.put(RuntimeInvisibleAnnotations, RuntimeInvisibleAnnotations_attribute.class);
                 standardAttributes.put(RuntimeInvisibleParameterAnnotations, RuntimeInvisibleParameterAnnotations_attribute.class);
@@ -171,6 +173,7 @@ public abstract class Attribute {
         R visitLineNumberTable(LineNumberTable_attribute attr, P p);
         R visitLocalVariableTable(LocalVariableTable_attribute attr, P p);
         R visitLocalVariableTypeTable(LocalVariableTypeTable_attribute attr, P p);
+        R visitMethodParameters(MethodParameters_attribute attr, P p);
         R visitRuntimeVisibleAnnotations(RuntimeVisibleAnnotations_attribute attr, P p);
         R visitRuntimeInvisibleAnnotations(RuntimeInvisibleAnnotations_attribute attr, P p);
         R visitRuntimeVisibleParameterAnnotations(RuntimeVisibleParameterAnnotations_attribute attr, P p);

langtools/src/share/classes/com/sun/tools/classfile/ClassWriter.java

@@ -1,6 +1,6 @@
 
 /*
- * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -479,6 +479,15 @@ public class ClassWriter {
             out.writeShort(entry.index);
         }
 
+        public Void visitMethodParameters(MethodParameters_attribute attr, ClassOutputStream out) {
+            out.writeByte(attr.method_parameter_table.length);
+            for (MethodParameters_attribute.Entry e : attr.method_parameter_table) {
+                out.writeShort(e.name_index);
+                out.writeInt(e.flags);
+            }
+            return null;
+        }
+
         public Void visitRuntimeVisibleAnnotations(RuntimeVisibleAnnotations_attribute attr, ClassOutputStream out) {
             annotationWriter.write(attr.annotations, out);
             return null;

langtools/src/share/classes/com/sun/tools/classfile/MethodParameters_attribute.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package com.sun.tools.classfile;
+
+import java.io.IOException;
+
+/**
+ * See JVMS, section 4.8.13.
+ *
+ *  <p><b>This is NOT part of any supported API.
+ *  If you write code that depends on this, you do so at your own risk.
+ *  This code and its internal interfaces are subject to change or
+ *  deletion without notice.</b>
+ */
+public class MethodParameters_attribute extends Attribute {
+
+    public final int method_parameter_table_length;
+    public final Entry[] method_parameter_table;
+
+    MethodParameters_attribute(ClassReader cr,
+                              int name_index,
+                              int length)
+        throws IOException {
+        super(name_index, length);
+
+        method_parameter_table_length = cr.readUnsignedByte();
+        method_parameter_table = new Entry[method_parameter_table_length];
+        for (int i = 0; i < method_parameter_table_length; i++)
+            method_parameter_table[i] = new Entry(cr);
+    }
+
+    public MethodParameters_attribute(ConstantPool constant_pool,
+                                      Entry[] method_parameter_table)
+        throws ConstantPoolException {
+        this(constant_pool.getUTF8Index(Attribute.MethodParameters),
+             method_parameter_table);
+    }
+
+    public MethodParameters_attribute(int name_index,
+                                      Entry[] method_parameter_table) {
+        super(name_index, 1 + method_parameter_table.length * Entry.length());
+        this.method_parameter_table_length = method_parameter_table.length;
+        this.method_parameter_table = method_parameter_table;
+    }
+
+    public <R, D> R accept(Visitor<R, D> visitor, D data) {
+        return visitor.visitMethodParameters(this, data);
+    }
+
+    public static class Entry {
+        Entry(ClassReader cr) throws IOException {
+            name_index = cr.readUnsignedShort();
+            flags = cr.readInt();
+        }
+
+        public static int length() {
+            return 6;
+        }
+
+        public final int name_index;
+        public final int flags;
+    }
+
+}

langtools/src/share/classes/com/sun/tools/javac/code/Symbol.java

@@ -1283,8 +1283,9 @@ public abstract class Symbol implements Element {
                 List<Name> paramNames = savedParameterNames;
                 savedParameterNames = null;
                 // discard the provided names if the list of names is the wrong size.
-                if (paramNames == null || paramNames.size() != type.getParameterTypes().size())
+                if (paramNames == null || paramNames.size() != type.getParameterTypes().size()) {
                     paramNames = List.nil();
+                }
                 ListBuffer<VarSymbol> buf = new ListBuffer<VarSymbol>();
                 List<Name> remaining = paramNames;
                 // assert: remaining and paramNames are both empty or both

langtools/src/share/classes/com/sun/tools/javac/jvm/ClassReader.java

@@ -217,6 +217,13 @@ public class ClassReader implements Completer {
      */
     boolean haveParameterNameIndices;
 
+    /** Set this to false every time we start reading a method
+     * and are saving parameter names.  Set it to true when we see
+     * MethodParameters, if it's set when we see a LocalVariableTable,
+     * then we ignore the parameter names from the LVT.
+     */
+    boolean sawMethodParameters;
+
     /**
      * The set of attribute names for which warnings have been generated for the current class
      */
@@ -984,7 +991,7 @@ public class ClassReader implements Completer {
             new AttributeReader(names.LocalVariableTable, V45_3, CLASS_OR_MEMBER_ATTRIBUTE) {
                 protected void read(Symbol sym, int attrLen) {
                     int newbp = bp + attrLen;
-                    if (saveParameterNames) {
+                    if (saveParameterNames && !sawMethodParameters) {
                         // Pick up parameter names from the variable table.
                         // Parameter names are not explicitly identified as such,
                         // but all parameter name entries in the LocalVariableTable
@@ -1017,6 +1024,25 @@ public class ClassReader implements Completer {
                 }
             },
 
+            new AttributeReader(names.MethodParameters, V52, MEMBER_ATTRIBUTE) {
+                protected void read(Symbol sym, int attrlen) {
+                    int newbp = bp + attrlen;
+                    if (saveParameterNames) {
+                        sawMethodParameters = true;
+                        int numEntries = nextByte();
+                        parameterNameIndices = new int[numEntries];
+                        haveParameterNameIndices = true;
+                        for (int i = 0; i < numEntries; i++) {
+                            int nameIndex = nextChar();
+                            int flags = nextInt();
+                            parameterNameIndices[i] = nameIndex;
+                        }
+                    }
+                    bp = newbp;
+                }
+            },
+
+
             new AttributeReader(names.SourceFile, V45_3, CLASS_ATTRIBUTE) {
                 protected void read(Symbol sym, int attrLen) {
                     ClassSymbol c = (ClassSymbol) sym;
@@ -1826,6 +1852,7 @@ public class ClassReader implements Completer {
         } else
             Arrays.fill(parameterNameIndices, 0);
         haveParameterNameIndices = false;
+        sawMethodParameters = false;
     }
 
     /**
@@ -1845,12 +1872,16 @@ public class ClassReader implements Completer {
         // if no names were found in the class file, there's nothing more to do
         if (!haveParameterNameIndices)
             return;
-
+        // If we get parameter names from MethodParameters, then we
-        int firstParam = ((sym.flags() & STATIC) == 0) ? 1 : 0;
+        // don't need to skip.
-        // the code in readMethod may have skipped the first parameter when
+        int firstParam = 0;
-        // setting up the MethodType. If so, we make a corresponding allowance
+        if (!sawMethodParameters) {
-        // here for the position of the first parameter.  Note that this
+            firstParam = ((sym.flags() & STATIC) == 0) ? 1 : 0;
-        // assumes the skipped parameter has a width of 1 -- i.e. it is not
+            // the code in readMethod may have skipped the first
+            // parameter when setting up the MethodType. If so, we
+            // make a corresponding allowance here for the position of
+            // the first parameter.  Note that this assumes the
+            // skipped parameter has a width of 1 -- i.e. it is not
         // a double width type (long or double.)
         if (sym.name == names.init && currentOwner.hasOuterInstance()) {
             // Sometimes anonymous classes don't have an outer
@@ -1861,17 +1892,20 @@ public class ClassReader implements Completer {
         }
 
         if (sym.type != jvmType) {
-            // reading the method attributes has caused the symbol's type to
+                // reading the method attributes has caused the
-            // be changed. (i.e. the Signature attribute.)  This may happen if
+                // symbol's type to be changed. (i.e. the Signature
-            // there are hidden (synthetic) parameters in the descriptor, but
+                // attribute.)  This may happen if there are hidden
-            // not in the Signature.  The position of these hidden parameters
+                // (synthetic) parameters in the descriptor, but not
-            // is unspecified; for now, assume they are at the beginning, and
+                // in the Signature.  The position of these hidden
-            // so skip over them. The primary case for this is two hidden
+                // parameters is unspecified; for now, assume they are
-            // parameters passed into Enum constructors.
+                // at the beginning, and so skip over them. The
+                // primary case for this is two hidden parameters
+                // passed into Enum constructors.
             int skip = Code.width(jvmType.getParameterTypes())
                     - Code.width(sym.type.getParameterTypes());
             firstParam += skip;
         }
+        }
         List<Name> paramNames = List.nil();
         int index = firstParam;
         for (Type t: sym.type.getParameterTypes()) {

langtools/src/share/classes/com/sun/tools/javac/jvm/ClassWriter.java

@@ -725,6 +725,28 @@ public class ClassWriter extends ClassFile {
         return acount;
     }
 
+    /**
+     * Write method parameter names attribute.
+     */
+    int writeMethodParametersAttr(MethodSymbol m) {
+        if (m.params != null && 0 != m.params.length()) {
+            int attrIndex = writeAttr(names.MethodParameters);
+            databuf.appendByte(m.params.length());
+            for (VarSymbol s : m.params) {
+                // TODO: expand to cover synthesized, once we figure out
+                // how to represent that.
+                final int flags = (int) s.flags() & (FINAL | SYNTHETIC);
+                // output parameter info
+                databuf.appendChar(pool.put(s.name));
+                databuf.appendInt(flags);
+            }
+            endAttr(attrIndex);
+            return 1;
+        } else
+            return 0;
+    }
+
+
     /** Write method parameter annotations;
      *  return number of attributes written.
      */
@@ -1034,6 +1056,8 @@ public class ClassWriter extends ClassFile {
             endAttr(alenIdx);
             acount++;
         }
+        if (options.isSet(PARAMETERS))
+            acount += writeMethodParametersAttr(m);
         acount += writeMemberAttrs(m);
         acount += writeParameterAttrs(m);
         endAttrs(acountIdx, acount);

langtools/src/share/classes/com/sun/tools/javac/main/Option.java

@@ -176,6 +176,8 @@ public enum Option {
 
     PROCESSORPATH("-processorpath", "opt.arg.path", "opt.processorpath", STANDARD, FILEMANAGER),
 
+    PARAMETERS("-parameters","opt.parameters", STANDARD, BASIC),
+
     D("-d", "opt.arg.directory", "opt.d", STANDARD, FILEMANAGER),
 
     S("-s", "opt.arg.directory", "opt.sourceDest", STANDARD, FILEMANAGER),

langtools/src/share/classes/com/sun/tools/javac/resources/javac.properties

@@ -55,6 +55,8 @@ javac.opt.processorpath=\
     Specify where to find annotation processors
 javac.opt.processor=\
     Names of the annotation processors to run; bypasses default discovery process
+javac.opt.parameters=\
+    Generate metadata for reflection on method parameters
 javac.opt.proc.none.only=\
     Control whether annotation processing and/or compilation is done.
 javac.opt.d=\

langtools/src/share/classes/com/sun/tools/javac/util/Names.java

@@ -132,6 +132,7 @@ public class Names {
     public final Name LineNumberTable;
     public final Name LocalVariableTable;
     public final Name LocalVariableTypeTable;
+    public final Name MethodParameters;
     public final Name RuntimeInvisibleAnnotations;
     public final Name RuntimeInvisibleParameterAnnotations;
     public final Name RuntimeInvisibleTypeAnnotations;
@@ -265,6 +266,7 @@ public class Names {
         LineNumberTable = fromString("LineNumberTable");
         LocalVariableTable = fromString("LocalVariableTable");
         LocalVariableTypeTable = fromString("LocalVariableTypeTable");
+        MethodParameters = fromString("MethodParameters");
         RuntimeInvisibleAnnotations = fromString("RuntimeInvisibleAnnotations");
         RuntimeInvisibleParameterAnnotations = fromString("RuntimeInvisibleParameterAnnotations");
         RuntimeInvisibleTypeAnnotations = fromString("RuntimeInvisibleTypeAnnotations");

langtools/src/share/classes/com/sun/tools/javap/AttributeWriter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -46,6 +46,7 @@ import com.sun.tools.classfile.InnerClasses_attribute;
 import com.sun.tools.classfile.LineNumberTable_attribute;
 import com.sun.tools.classfile.LocalVariableTable_attribute;
 import com.sun.tools.classfile.LocalVariableTypeTable_attribute;
+import com.sun.tools.classfile.MethodParameters_attribute;
 import com.sun.tools.classfile.RuntimeInvisibleAnnotations_attribute;
 import com.sun.tools.classfile.RuntimeInvisibleParameterAnnotations_attribute;
 import com.sun.tools.classfile.RuntimeVisibleAnnotations_attribute;
@@ -386,6 +387,28 @@ public class AttributeWriter extends BasicWriter
         return null;
     }
 
+    private static final String format = "%-31s%s";
+
+    public Void visitMethodParameters(MethodParameters_attribute attr,
+                                      Void ignore) {
+
+        final String header = String.format(format, "Name", "Flags");
+        println("MethodParameters:");
+        indent(+1);
+        println(header);
+        for (MethodParameters_attribute.Entry entry :
+                 attr.method_parameter_table) {
+            String flagstr =
+                (0 != (entry.flags & ACC_FINAL) ? " final" : "") +
+                (0 != (entry.flags & ACC_SYNTHETIC) ? " synthetic" : "");
+            println(String.format(format,
+                                  constantWriter.stringValue(entry.name_index),
+                                  flagstr));
+        }
+        indent(-1);
+        return null;
+    }
+
     public Void visitRuntimeVisibleAnnotations(RuntimeVisibleAnnotations_attribute attr, Void ignore) {
         println("RuntimeVisibleAnnotations:");
         indent(+1);

langtools/test/tools/javac/MethodParameters.java

@@ -0,0 +1,343 @@
+/*
+ * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @summary javac should generate method parameters correctly.
+ */
+// key: opt.arg.parameters
+import com.sun.tools.classfile.*;
+import com.sun.tools.javac.file.JavacFileManager;
+import com.sun.tools.javac.main.Main;
+import com.sun.tools.javac.util.Context;
+import com.sun.tools.javac.util.Name;
+import com.sun.tools.javac.util.Names;
+import java.io.*;
+import javax.lang.model.element.*;
+import java.util.*;
+
+public class MethodParameters {
+
+    static final String Foo_name = "Foo";
+    static final String Foo_contents =
+        "public class Foo {\n" +
+        "  Foo() {}\n" +
+        "  void foo0() {}\n" +
+        "  void foo2(int j, int k) {}\n" +
+        "}";
+    static final String Bar_name = "Bar";
+    static final String Bar_contents =
+        "public class Bar {\n" +
+        "  Bar(int i) {}" +
+        "  Foo foo() { return new Foo(); }\n" +
+        "}";
+    static final String Baz_name = "Baz";
+    static final String Baz_contents =
+        "public class Baz {\n" +
+        "  int baz;" +
+        "  Baz(int i) {}" +
+        "}";
+    static final String Qux_name = "Qux";
+    static final String Qux_contents =
+        "public class Qux extends Baz {\n" +
+        "  Qux(int i) { super(i); }" +
+        "}";
+    static final File classesdir = new File("methodparameters");
+
+    public static void main(String... args) throws Exception {
+        new MethodParameters().run();
+    }
+
+    void run() throws Exception {
+        classesdir.mkdir();
+        final File Foo_java =
+            writeFile(classesdir, Foo_name + ".java", Foo_contents);
+        final File Bar_java =
+            writeFile(classesdir, Bar_name + ".java", Bar_contents);
+        final File Baz_java =
+            writeFile(classesdir, Baz_name + ".java", Baz_contents);
+        System.err.println("Test compile with -parameter");
+        compile("-parameters", "-d", classesdir.getPath(), Foo_java.getPath());
+        // First test: make sure javac doesn't choke to death on
+        // MethodParameter attributes
+        System.err.println("Test compile with classfile containing MethodParameter attributes");
+        compile("-parameters", "-d", classesdir.getPath(),
+                "-cp", classesdir.getPath(), Bar_java.getPath());
+        System.err.println("Examine class foo");
+        checkFoo();
+        checkBar();
+        System.err.println("Test debug information conflict");
+        compile("-g", "-parameters", "-d", classesdir.getPath(),
+                "-cp", classesdir.getPath(), Baz_java.getPath());
+        System.err.println("Introducing debug information conflict");
+        Baz_java.delete();
+        modifyBaz(false);
+        System.err.println("Checking language model");
+        inspectBaz();
+        System.err.println("Permuting attributes");
+        modifyBaz(true);
+        System.err.println("Checking language model");
+        inspectBaz();
+
+        if(0 != errors)
+            throw new Exception("MethodParameters test failed with " +
+                                errors + " errors");
+    }
+
+    void inspectBaz() throws Exception {
+        final File Qux_java =
+            writeFile(classesdir, Qux_name + ".java", Qux_contents);
+        final String[] args = { "-XDsave-parameter-names", "-d",
+                                classesdir.getPath(),
+                                "-cp", classesdir.getPath(),
+                                Qux_java.getPath() };
+        final StringWriter sw = new StringWriter();
+        final PrintWriter pw = new PrintWriter(sw);
+
+        // We need to be able to crack open javac and look at its data
+        // structures.  We'll rig up a compiler instance, but keep its
+        // Context, thus allowing us to get at the ClassReader.
+        Context context = new Context();
+        Main comp =  new Main("javac", pw);
+        JavacFileManager.preRegister(context);
+
+        // Compile Qux, which uses Baz.
+        comp.compile(args, context);
+        pw.close();
+        final String out = sw.toString();
+        if (out.length() > 0)
+            System.err.println(out);
+
+        // Now get the class reader, construct a name for Baz, and load it.
+        com.sun.tools.javac.jvm.ClassReader cr =
+            com.sun.tools.javac.jvm.ClassReader.instance(context);
+        Name name = Names.instance(context).fromString(Baz_name);
+
+        // Now walk down the language model and check the name of the
+        // parameter.
+        final Element baz = cr.loadClass(name);
+        for (Element e : baz.getEnclosedElements()) {
+            if (e instanceof ExecutableElement) {
+                final ExecutableElement ee = (ExecutableElement) e;
+                final List<? extends VariableElement> params =
+                    ee.getParameters();
+                if (1 != params.size())
+                    throw new Exception("Classfile Baz badly formed: wrong number of methods");
+                final VariableElement param = params.get(0);
+                if (!param.getSimpleName().contentEquals("baz")) {
+                    errors++;
+                    System.err.println("javac did not correctly resolve the metadata conflict, parameter's name reads as " + param.getSimpleName());
+                } else
+                    System.err.println("javac did correctly resolve the metadata conflict");
+            }
+        }
+    }
+
+    void modifyBaz(boolean flip) throws Exception {
+        final File Baz_class = new File(classesdir, Baz_name + ".class");
+        final ClassFile baz = ClassFile.read(Baz_class);
+        final int ind = baz.constant_pool.getUTF8Index("baz");
+        MethodParameters_attribute mpattr = null;
+        int mpind = 0;
+        Code_attribute cattr = null;
+        int cind = 0;
+
+        // Find the indexes of the MethodParameters and the Code attributes
+        if (baz.methods.length != 1)
+            throw new Exception("Classfile Baz badly formed: wrong number of methods");
+        if (!baz.methods[0].getName(baz.constant_pool).equals("<init>"))
+            throw new Exception("Classfile Baz badly formed: method has name " +
+                                baz.methods[0].getName(baz.constant_pool));
+        for (int i = 0; i < baz.methods[0].attributes.attrs.length; i++) {
+            if (baz.methods[0].attributes.attrs[i] instanceof
+                MethodParameters_attribute) {
+                mpattr = (MethodParameters_attribute)
+                    baz.methods[0].attributes.attrs[i];
+                mpind = i;
+            } else if (baz.methods[0].attributes.attrs[i] instanceof
+                       Code_attribute) {
+                cattr = (Code_attribute) baz.methods[0].attributes.attrs[i];
+                cind = i;
+            }
+        }
+        if (null == mpattr)
+            throw new Exception("Classfile Baz badly formed: no method parameters info");
+        if (null == cattr)
+            throw new Exception("Classfile Baz badly formed: no local variable table");
+
+        int flags = mpattr.method_parameter_table[0].flags;
+
+        // Alter the MethodParameters attribute, changing the name of
+        // the parameter from i to baz.  This requires Black Magic...
+        //
+        // The (well-designed) classfile library (correctly) does not
+        // allow us to mess around with the attribute data structures,
+        // or arbitrarily generate new ones.
+        //
+        // Instead, we install a new subclass of Attribute that
+        // hijacks the Visitor pattern and outputs the sequence of
+        // bytes that we want.  This only works in this particular
+        // instance, because we know we'll only every see one kind of
+        // visitor.
+        //
+        // If anyone ever changes the makeup of the Baz class, or
+        // tries to install some kind of visitor that gets run prior
+        // to serialization, this will break.
+        baz.methods[0].attributes.attrs[mpind] =
+            new Attribute(mpattr.attribute_name_index,
+                          mpattr.attribute_length) {
+                public <R, D> R accept(Visitor<R, D> visitor, D data) {
+                    if (data instanceof ByteArrayOutputStream) {
+                        ByteArrayOutputStream out =
+                            (ByteArrayOutputStream) data;
+                        out.write(1);
+                        out.write((ind >> 8) & 0xff);
+                        out.write(ind & 0xff);
+                        out.write((flags >> 24) & 0xff);
+                        out.write((flags >> 16) & 0xff);
+                        out.write((flags >> 8) & 0xff);
+                        out.write(flags & 0xff);
+                    } else
+                        throw new RuntimeException("Output stream is of type " + data.getClass() + ", which is not handled by this test.  Update the test and it should work.");
+                    return null;
+                }
+            };
+
+        // Flip the code and method attributes.  This is for checking
+        // that order doesn't matter.
+        if (flip) {
+            baz.methods[0].attributes.attrs[mpind] = cattr;
+            baz.methods[0].attributes.attrs[cind] = mpattr;
+        }
+
+        new ClassWriter().write(baz, Baz_class);
+    }
+
+    // Run a bunch of structural tests on foo to make sure it looks right.
+    void checkFoo() throws Exception {
+        final File Foo_class = new File(classesdir, Foo_name + ".class");
+        final ClassFile foo = ClassFile.read(Foo_class);
+        for (int i = 0; i < foo.methods.length; i++) {
+            System.err.println("Examine method Foo." + foo.methods[i].getName(foo.constant_pool));
+            if (foo.methods[i].getName(foo.constant_pool).equals("foo2")) {
+                for (int j = 0; j < foo.methods[i].attributes.attrs.length; j++)
+                    if (foo.methods[i].attributes.attrs[j] instanceof
+                        MethodParameters_attribute) {
+                        MethodParameters_attribute mp =
+                            (MethodParameters_attribute)
+                            foo.methods[i].attributes.attrs[j];
+                        System.err.println("Foo.foo2 should have 2 parameters: j and k");
+                        if (2 != mp.method_parameter_table_length)
+                            error("expected 2 method parameter entries in foo2, got " +
+                                  mp.method_parameter_table_length);
+                        else if (!foo.constant_pool.getUTF8Value(mp.method_parameter_table[0].name_index).equals("j"))
+                            error("expected first parameter to foo2 to be \"j\", got \"" +
+                                  foo.constant_pool.getUTF8Value(mp.method_parameter_table[0].name_index) +
+                                  "\" instead");
+                        else if  (!foo.constant_pool.getUTF8Value(mp.method_parameter_table[1].name_index).equals("k"))
+                            error("expected first parameter to foo2 to be \"k\", got \"" +
+                                  foo.constant_pool.getUTF8Value(mp.method_parameter_table[1].name_index) +
+                                  "\" instead");
+                    }
+            }
+            else if (foo.methods[i].getName(foo.constant_pool).equals("<init>")) {
+                for (int j = 0; j < foo.methods[i].attributes.attrs.length; j++) {
+                    if (foo.methods[i].attributes.attrs[j] instanceof
+                        MethodParameters_attribute)
+                        error("Zero-argument constructor shouldn't have MethodParameters");
+                }
+            }
+            else if (foo.methods[i].getName(foo.constant_pool).equals("foo0")) {
+                for (int j = 0; j < foo.methods[i].attributes.attrs.length; j++)
+                    if (foo.methods[i].attributes.attrs[j] instanceof
+                        MethodParameters_attribute)
+                        error("Zero-argument method shouldn't have MethodParameters");
+            }
+            else
+                error("Unknown method " + foo.methods[i].getName(foo.constant_pool) + " showed up in class Foo");
+        }
+    }
+
+    // Run a bunch of structural tests on Bar to make sure it looks right.
+    void checkBar() throws Exception {
+        final File Bar_class = new File(classesdir, Bar_name + ".class");
+        final ClassFile bar = ClassFile.read(Bar_class);
+        for (int i = 0; i < bar.methods.length; i++) {
+            System.err.println("Examine method Bar." + bar.methods[i].getName(bar.constant_pool));
+            if (bar.methods[i].getName(bar.constant_pool).equals("<init>")) {
+                for (int j = 0; j < bar.methods[i].attributes.attrs.length; j++)
+                    if (bar.methods[i].attributes.attrs[j] instanceof
+                        MethodParameters_attribute) {
+                        MethodParameters_attribute mp =
+                            (MethodParameters_attribute)
+                            bar.methods[i].attributes.attrs[j];
+                        System.err.println("Bar constructor should have 1 parameter: i");
+                        if (1 != mp.method_parameter_table_length)
+                            error("expected 1 method parameter entries in constructor, got " +
+                                  mp.method_parameter_table_length);
+                        else if (!bar.constant_pool.getUTF8Value(mp.method_parameter_table[0].name_index).equals("i"))
+                            error("expected first parameter to foo2 to be \"i\", got \"" +
+                                  bar.constant_pool.getUTF8Value(mp.method_parameter_table[0].name_index) +
+                                  "\" instead");
+                    }
+            }
+            else if (bar.methods[i].getName(bar.constant_pool).equals("foo")) {
+                for (int j = 0; j < bar.methods[i].attributes.attrs.length; j++) {
+                    if (bar.methods[i].attributes.attrs[j] instanceof
+                        MethodParameters_attribute)
+                        error("Zero-argument constructor shouldn't have MethodParameters");
+                }
+            }
+        }
+    }
+
+    String compile(String... args) throws Exception {
+        System.err.println("compile: " + Arrays.asList(args));
+        StringWriter sw = new StringWriter();
+        PrintWriter pw = new PrintWriter(sw);
+        int rc = com.sun.tools.javac.Main.compile(args, pw);
+        pw.close();
+        String out = sw.toString();
+        if (out.length() > 0)
+            System.err.println(out);
+        if (rc != 0)
+            error("compilation failed, rc=" + rc);
+        return out;
+    }
+
+    File writeFile(File dir, String path, String body) throws IOException {
+        File f = new File(dir, path);
+        f.getParentFile().mkdirs();
+        FileWriter out = new FileWriter(f);
+        out.write(body);
+        out.close();
+        return f;
+    }
+
+    void error(String msg) {
+        System.err.println("Error: " + msg);
+        errors++;
+    }
+
+    int errors;
+}

langtools/test/tools/javap/MethodParameters.java

@@ -0,0 +1,165 @@
+/*
+ * Copyright (c) 2010, 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @summary javac should generate method parameters correctly.
+ */
+
+import java.io.*;
+import java.util.*;
+
+public class MethodParameters {
+
+    static final String Foo_name = "Foo";
+    static final String Foo_contents =
+        ("public class Foo {\n" +
+         "  Foo() {}\n" +
+         "  Foo(int i) {}\n" +
+         "  void foo0() {}\n" +
+         "  void foo2(int j, int k) {}\n" +
+         "}").replaceAll(" +", " ");
+    static final String Init0_expected =
+        ("  Foo();\n" +
+         "    flags: \n" +
+         "    Code:\n" +
+         "      stack=1, locals=1, args_size=1\n" +
+         "         0: aload_0       \n" +
+         "         1: invokespecial #1                  // Method java/lang/Object.\"<init>\":()V\n" +
+         "         4: return        \n" +
+         "      LineNumberTable:\n" +
+         "        line 2: 0").replaceAll(" +", " ");
+    static final String Init1_expected =
+        ("  Foo(int);\n" +
+         "    flags: \n" +
+         "    Code:\n" +
+         "      stack=1, locals=2, args_size=2\n" +
+         "         0: aload_0       \n" +
+         "         1: invokespecial #1                  // Method java/lang/Object.\"<init>\":()V\n" +
+         "         4: return        \n" +
+         "      LineNumberTable:\n" +
+         "        line 3: 0\n" +
+         "    MethodParameters:\n" +
+         "      Name                                Flags\n" +
+         "      i").replaceAll(" +", " ");
+    static final String foo0_expected =
+        ("  void foo0();\n" +
+         "    flags: \n" +
+         "    Code:\n" +
+         "      stack=0, locals=1, args_size=1\n" +
+         "         0: return        \n" +
+         "      LineNumberTable:\n" +
+         "        line 4: 0").replaceAll(" +", " ");
+    static final String foo2_expected =
+        ("  void foo2(int, int);\n" +
+         "    flags: \n" +
+         "    Code:\n" +
+         "      stack=0, locals=3, args_size=3\n" +
+         "         0: return        \n" +
+         "      LineNumberTable:\n" +
+         "        line 5: 0\n" +
+         "    MethodParameters:\n" +
+         "      Name                                Flags\n" +
+         "      j                              \n" +
+         "      k").replaceAll(" +", " ");
+
+    static final File classesdir = new File("methodparameters");
+    static final String separator = System.getProperty("line.separator");
+
+    public static void main(String... args) throws Exception {
+        new MethodParameters().run();
+    }
+
+    void run() throws Exception {
+        classesdir.mkdir();
+        final File Foo_java =
+            writeFile(classesdir, Foo_name + ".java", Foo_contents);
+        compile("-parameters", "-d", classesdir.getPath(), Foo_java.getPath());
+        System.out.println("Run javap");
+        String output =
+            javap("-c", "-verbose", "-classpath",
+                  classesdir.getPath(), Foo_name);
+        String normalized =
+            output.replaceAll(separator, "\n").replaceAll(" +", " ");
+
+        if (!normalized.contains(Init0_expected))
+            error("Bad output for zero-parameter constructor.  Expected\n" +
+                  Init0_expected + "\n" + "but got\n" + normalized);
+        if (!normalized.contains(Init1_expected))
+           error("Bad output for one-parameter constructor.  Expected\n" +
+                 Init1_expected + "\n" + "but got\n" + normalized);
+        if (!normalized.contains(foo0_expected))
+           error("Bad output for zero-parameter method.  Expected\n" +
+                 foo0_expected + "\n" + "but got\n" + normalized);
+        if (!normalized.contains(foo2_expected))
+           error("Bad output for two-parameter method  Expected\n" +
+                 foo2_expected + "\n" + "but got\n" + normalized);
+
+        if (0 != errors)
+            throw new Exception("MethodParameters test failed with " +
+                                errors + " errors");
+    }
+
+    String javap(String... args) {
+        StringWriter sw = new StringWriter();
+        PrintWriter out = new PrintWriter(sw);
+        //sun.tools.javap.Main.entry(args);
+        int rc = com.sun.tools.javap.Main.run(args, out);
+        if (rc != 0)
+            throw new Error("javap failed. rc=" + rc);
+        out.close();
+        System.out.println(sw);
+        return sw.toString();
+    }
+
+    String compile(String... args) throws Exception {
+        System.err.println("compile: " + Arrays.asList(args));
+        StringWriter sw = new StringWriter();
+        PrintWriter pw = new PrintWriter(sw);
+        int rc = com.sun.tools.javac.Main.compile(args, pw);
+        pw.close();
+        String out = sw.toString();
+        if (out.length() > 0)
+            System.err.println(out);
+        if (rc != 0)
+            error("compilation failed, rc=" + rc);
+        return out;
+    }
+
+    File writeFile(File dir, String path, String body) throws IOException {
+        File f = new File(dir, path);
+        f.getParentFile().mkdirs();
+        FileWriter out = new FileWriter(f);
+        out.write(body);
+        out.close();
+        return f;
+    }
+
+    void error(String msg) {
+        System.err.println("Error: " + msg);
+        errors++;
+    }
+
+    int errors;
+
+}