Wrong filter predicate of visible locals in SA JSDB. Diff against jdk8/jdk8/hotspot. Screenshot http://dl.iteye.com/upload/picture/pic/111635/c03df4f1-8ee1-30aa-b15e-dd16ef695d2d.png

clhsdb_session

$ jps
32046 Demo
32069 Jps
$ pgrep -u sajia java
32046
$ alias | grep clhsdb
alias clhsdb='java -classpath .:$JAVA_HOME/lib/sa-jdi.jar sun.jvm.hotspot.CLHSDB'
$ clhsdb
hsdb> attach 32046
Attaching to process 32046, please wait...
hsdb> threads
32067 Low Memory Detector
32066 C2 CompilerThread1
32065 C2 CompilerThread0
32064 Signal Dispatcher
32063 Finalizer
32062 Reference Handler
32047 main
hsdb> universe
Heap Parameters:
ParallelScavengeHeap [ PSYoungGen [ eden =  [0x0000000758600000,0x0000000758883d80,0x00000007603c0000] , from =  [0x00000007618b0000,0x00000007618b0000,0x0000000762da0000] , to =  [0x00000007603c0000,0x00000007603c0000,0x00000007618b0000]  ] PSOldGen [  [0x0000000609200000,0x0000000609200000,0x000000061e140000]  ] PSPermGen [  [0x0000000604000000,0x000000060427d438,0x00000006054c0000]  ]  ] 
hsdb> jseval "jvm"
Java Hotspot Server 64 bit VM (build 20.5-b03) 
hsdb> jseval "jvm.threads"
[Thread (address=0x000000075862c7f0, name=Low Memory Detector), Thread (address=0x000000075862c6c0, name=C2 CompilerThread1), Thread (address=0x000000075862c590, name=C2 CompilerThread0), Thread (address=0x000000075862c460, name=Signal Dispatcher), Thread (address=0x0000000758601320, name=Finalizer), Thread (address=0x00000007586011e8, name=Reference Handler), Thread (address=0x0000000758600840, name=main)] 
hsdb> jseval "jvm.threads[6].frames"
[Frame (method=java.io.FileInputStream.readBytes(byte[], int, int), bci=0, line=0), Frame (method=java.io.FileInputStream.read(byte[], int, int), bci=4, line=220), Frame (method=java.io.BufferedInputStream.fill(), bci=175, line=218), Frame (method=java.io.BufferedInputStream.read(), bci=12, line=237), Frame (method=Demo.main(java.lang.String[]), bci=3, line=5)] 
hsdb> jseval "mainFrame = jvm.threads[6].frames[4]"
Frame (method=Demo.main(java.lang.String[]), bci=3, line=5) 
hsdb> jseval "for (var p in mainFrame) println(p)"
bci
thisObject
locals
thread
line
method
hsdb> jseval "mainFrame.method"
Method Demo.main(java.lang.String[]) 
hsdb> jseval "mainFrame.locals"
{} 
hsdb> 
  
hsdb> jseval "sa.threads"
sun.jvm.hotspot.runtime.Threads@3f6dadf9 
hsdb> jseval "sa.threads.first().next().next().next().next().next().next().getThreadName()"
main 
hsdb> jseval "jt = sa.threads.first().next().next().next().next().next().next()"
sun.jvm.hotspot.runtime.JavaThread@0x0000000050401800 
hsdb> jseval "jt.getLastJavaVFrameDbg()"
sun.jvm.hotspot.runtime.InterpretedVFrame@4486af30 
hsdb> jseval "jt.getLastJavaVFrameDbg().javaSender().javaSender().javaSender().javaSender().getMethod().name.asString()"
main 
hsdb> jseval "jvf = jt.getLastJavaVFrameDbg().javaSender().javaSender().javaSender().javaSender()"
sun.jvm.hotspot.runtime.InterpretedVFrame@44bb43fb 
hsdb> jseval "jvf.locals"
sun.jvm.hotspot.runtime.StackValueCollection@5de9ac4 
hsdb> jseval "jvf.locals.get(0).print(); println('')"
<0x0000000758633a00>
hsdb> inspect 0x0000000758633a00
instance of ObjArray @ 0x0000000758633a00 @ 0x0000000758633a00 (size = 24)
_mark: 1
0: "alpha" @ 0x0000000758633a30 Oop for java/lang/String @ 0x0000000758633a30
1: "beta" @ 0x0000000758633ae8 Oop for java/lang/String @ 0x0000000758633ae8
hsdb> whatis 0x0000000758633a00
Address 0x0000000758633a00: In unknown section of Java heap 
hsdb> universe
Heap Parameters:
ParallelScavengeHeap [ PSYoungGen [ eden =  [0x0000000758600000,0x0000000758883d80,0x00000007603c0000] , from =  [0x00000007618b0000,0x00000007618b0000,0x0000000762da0000] , to =  [0x00000007603c0000,0x00000007603c0000,0x00000007618b0000]  ] PSOldGen [  [0x0000000609200000,0x0000000609200000,0x000000061e140000]  ] PSPermGen [  [0x0000000604000000,0x000000060427d438,0x00000006054c0000]  ]  ] 
hsdb> quit
$ 

clhsdb_session2

$ # without patch
$ java -Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n -classpath .:$JAVA_HOME/lib/sa-jdi.jar sun.jvm.hotspot.CLHSDB
Listening for transport dt_socket at address: 8000
hsdb> verbose true
hsdb> attach 32046
Attaching to process 32046, please wait...
hsdb> jseval "mainFrame = jvm.threads[6].frames[4]"
Frame (method=Demo.main(java.lang.String[]), bci=3, line=5) 
hsdb> jseval "mainFrame.locals"
Listening for transport dt_socket at address: 8000
{} 
hsdb> quit
$ # with patch applied
$ java -Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n -classpath .:/tmp/ths/make/linux/linux_amd64_compiler2/generated/sa-jdi.jar sun.jvm.hotspot.CLHSDB
Listening for transport dt_socket at address: 8000
hsdb> verbose true
hsdb> attach 32046
Attaching to process 32046, please wait...
WARNING: Hotspot VM version 20.5-b03 does not match with SA version 20.0-b12-internal. You may see unexpected results. 
hsdb> jseval "mainFrame = jvm.threads[6].frames[4]"
Frame (method=Demo.main(java.lang.String[]), bci=3, line=5) 
hsdb> jseval "mainFrame.locals"
{args=Object 0x0000000758633a00} 
hsdb> Listening for transport dt_socket at address: 8000
inspect 0x0000000758633a00
instance of ObjArray @ 0x0000000758633a00 @ 0x0000000758633a00 (size = 24)
_mark: 1
0: "alpha" @ 0x0000000758633a30 Oop for java/lang/String @ 0x0000000758633a30
1: "beta" @ 0x0000000758633ae8 Oop for java/lang/String @ 0x0000000758633ae8
hsdb> quit
$ 

command_prompt

$ java -version
java version "1.6.0_30"
Java(TM) SE Runtime Environment (build 1.6.0_30-b12)
Java HotSpot(TM) 64-Bit Server VM (build 20.5-b03, mixed mode)
$ cat > Demo.java
import java.util.*;

public class Demo {
  public static void main(String[] args) throws Exception {
    System.in.read();
    System.out.println(Arrays.toString(args));
  }
}

$ javac -g Demo.java 
$ javap -verbose -private Demo
Compiled from "Demo.java"
public class Demo extends java.lang.Object
  SourceFile: "Demo.java"
  minor version: 0
  major version: 50
  Constant pool:
const #1 = Method       #8.#24; //  java/lang/Object."<init>":()V
const #2 = Field        #25.#26;        //  java/lang/System.in:Ljava/io/InputStream;
const #3 = Method       #27.#28;        //  java/io/InputStream.read:()I
const #4 = Field        #25.#29;        //  java/lang/System.out:Ljava/io/PrintStream;
const #5 = Method       #30.#31;        //  java/util/Arrays.toString:([Ljava/lang/Object;)Ljava/lang/String;
const #6 = Method       #32.#33;        //  java/io/PrintStream.println:(Ljava/lang/String;)V
const #7 = class        #34;    //  Demo
const #8 = class        #35;    //  java/lang/Object
const #9 = Asciz        <init>;
const #10 = Asciz       ()V;
const #11 = Asciz       Code;
const #12 = Asciz       LineNumberTable;
const #13 = Asciz       LocalVariableTable;
const #14 = Asciz       this;
const #15 = Asciz       LDemo;;
const #16 = Asciz       main;
const #17 = Asciz       ([Ljava/lang/String;)V;
const #18 = Asciz       args;
const #19 = Asciz       [Ljava/lang/String;;
const #20 = Asciz       Exceptions;
const #21 = class       #36;    //  java/lang/Exception
const #22 = Asciz       SourceFile;
const #23 = Asciz       Demo.java;
const #24 = NameAndType #9:#10;//  "<init>":()V
const #25 = class       #37;    //  java/lang/System
const #26 = NameAndType #38:#39;//  in:Ljava/io/InputStream;
const #27 = class       #40;    //  java/io/InputStream
const #28 = NameAndType #41:#42;//  read:()I
const #29 = NameAndType #43:#44;//  out:Ljava/io/PrintStream;
const #30 = class       #45;    //  java/util/Arrays
const #31 = NameAndType #46:#47;//  toString:([Ljava/lang/Object;)Ljava/lang/String;
const #32 = class       #48;    //  java/io/PrintStream
const #33 = NameAndType #49:#50;//  println:(Ljava/lang/String;)V
const #34 = Asciz       Demo;
const #35 = Asciz       java/lang/Object;
const #36 = Asciz       java/lang/Exception;
const #37 = Asciz       java/lang/System;
const #38 = Asciz       in;
const #39 = Asciz       Ljava/io/InputStream;;
const #40 = Asciz       java/io/InputStream;
const #41 = Asciz       read;
const #42 = Asciz       ()I;
const #43 = Asciz       out;
const #44 = Asciz       Ljava/io/PrintStream;;
const #45 = Asciz       java/util/Arrays;
const #46 = Asciz       toString;
const #47 = Asciz       ([Ljava/lang/Object;)Ljava/lang/String;;
const #48 = Asciz       java/io/PrintStream;
const #49 = Asciz       println;
const #50 = Asciz       (Ljava/lang/String;)V;

{
public Demo();
  Code:
   Stack=1, Locals=1, Args_size=1
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."<init>":()V
   4:   return
  LineNumberTable: 
   line 3: 0

  LocalVariableTable: 
   Start  Length  Slot  Name   Signature
   0      5      0    this       LDemo;


public static void main(java.lang.String[])   throws java.lang.Exception;
  Code:
   Stack=2, Locals=1, Args_size=1
   0:   getstatic       #2; //Field java/lang/System.in:Ljava/io/InputStream;
   3:   invokevirtual   #3; //Method java/io/InputStream.read:()I
   6:   pop
   7:   getstatic       #4; //Field java/lang/System.out:Ljava/io/PrintStream;
   10:  aload_0
   11:  invokestatic    #5; //Method java/util/Arrays.toString:([Ljava/lang/Object;)Ljava/lang/String;
   14:  invokevirtual   #6; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
   17:  return
  LineNumberTable: 
   line 5: 0
   line 6: 7
   line 7: 17

  LocalVariableTable: 
   Start  Length  Slot  Name   Signature
   0      18      0    args       [Ljava/lang/String;

  Exceptions: 
   throws java.lang.Exception
}

$ java Demo alpha beta

[alpha, beta]
$ 

getlocal.patch

diff -r bbdc75c217e7 agent/src/share/classes/sun/jvm/hotspot/utilities/soql/JSJavaFrame.java
--- a/agent/src/share/classes/sun/jvm/hotspot/utilities/soql/JSJavaFrame.java	Thu Mar 22 12:41:09 2012 -0700
+++ b/agent/src/share/classes/sun/jvm/hotspot/utilities/soql/JSJavaFrame.java	Thu Apr 19 12:19:40 2012 +0800
@@ -153,7 +153,8 @@
             List visibleVars = new ArrayList(0);
             for (int i = 0; i < localVars.length; i++) {
                 LocalVariableTableElement cur = localVars[i];
-                if (cur.getStartBCI() >= bci && cur.getLength() > 0) {
+                int startBCI = cur.getStartBCI();
+                if (startBCI <= bci && bci < startBCI + cur.getLength()) {
                     visibleVars.add(cur);
                 }
             }