Interesting debugging issue based on discussions with Jim H.

Here is the test program:

 1 public class NotDALocalVarTest
 2 {
 3 public static void main(String[] args) {
 4 int ii;
 5 Object isNotDA;
 6 Object isDA = "isDA1";
 7 Object isDANull = null;
 8 try {
 9 ii = 22;
10 isNotDA = "isNotDAv";
11 isDA = "isDAv";
12 isDANull = "isDANullv";
13 throw new RuntimeException(); // here, jdb correctly says
14 // isNotDA has value "isNotDAv"
15 } catch (RuntimeException e)
16 {
17 // here, jdb says ii has value 22 as expected,
18 // isDA has value "isDAv" as expected,
19 // isDANull has value "isDANullv" as expected,
20 // but isNotDA has value null instead of "isNotDAv"
21 System.out.println("catch");
22 }
23 System.out.println("done");
24 }
25 }


Here is a trimmed down "javap -c -l -v" dump of the program:

Classfile /C:/cygwin/home/dcubed/Projects/da-local-vars/NotDALocalVarTest.class
  Last modified Apr 22, 2011; size 924 bytes
  MD5 checksum f9c2dc654e16742a18216f1e324ac0f2
  Compiled from "NotDALocalVarTest.java"
public class NotDALocalVarTest
  SourceFile: "NotDALocalVarTest.java"
  minor version: 0
  major version: 51
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref #13.#39 // java/lang/Object."<init>":()V
   #2 = String #40 // isDA1
   #3 = String #41 // isNotDAv
   #4 = String #42 // isDAv
   #5 = String #43 // isDANullv
   #6 = Class #44 // java/lang/RuntimeException
   #7 = Methodref #6.#39 // java/lang/RuntimeException."<init>":()V
   #8 = Fieldref #45.#46 // java/lang/System.out:Ljava/io/PrintStream;
   #9 = String #47 // catch
  #10 = Methodref #48.#49 // java/io/PrintStream.println:(Ljava/lang/String;)V
  #11 = String #50 // done
<snip>
{
  public NotDALocalVarTest();
    flags: ACC_PUBLIC
    LineNumberTable:
      line 1: 0
    LocalVariableTable:
      Start Length Slot Name Signature
             0 5 0 this LNotDALocalVarTest;
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1 // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable:
        line 1: 0
      LocalVariableTable:
        Start Length Slot Name Signature
               0 5 0 this LNotDALocalVarTest;

  public static void main(java.lang.String[]);
    flags: ACC_PUBLIC, ACC_STATIC
    LineNumberTable:
      line 6: 0
      line 7: 3
      line 9: 6
      line 10: 9
      line 11: 12
      line 12: 15
      line 13: 19
      line 15: 27
      line 21: 29
      line 23: 37
      line 24: 45
    LocalVariableTable:
      Start Length Slot Name Signature
            29 8 5 e Ljava/lang/RuntimeException;
             0 46 0 args [Ljava/lang/String;
             9 37 1 ii I
            12 34 2 isNotDA Ljava/lang/Object;
             3 43 3 isDA Ljava/lang/Object;
             6 40 4 isDANull Ljava/lang/Object;
    Code:
      stack=2, locals=6, args_size=1
         0: ldc #2 // String isDA1
         2: astore_3
         3: aconst_null
         4: astore 4
         6: bipush 22
         8: istore_1
         9: ldc #3 // String isNotDAv
        11: astore_2
        12: ldc #4 // String isDAv
        14: astore_3
        15: ldc #5 // String isDANullv
        17: astore 4
        19: new #6 // class java/lang/RuntimeException
        22: dup
        23: invokespecial #7 // Method java/lang/RuntimeException."<init>":()V
        26: athrow
        27: astore 5
        29: getstatic #8 // Field java/lang/System.out:Ljava/io/PrintStream;
        32: ldc #9 // String catch
        34: invokevirtual #10 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        37: getstatic #8 // Field java/lang/System.out:Ljava/io/PrintStream;
        40: ldc #11 // String done
        42: invokevirtual #10 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
        45: return
      Exception table:
         from to target type
             6 27 27 Class java/lang/RuntimeException
      LineNumberTable:
        line 6: 0
        line 7: 3
        line 9: 6
        line 10: 9
        line 11: 12
        line 12: 15
        line 13: 19
        line 15: 27
        line 21: 29
        line 23: 37
        line 24: 45
      LocalVariableTable:
        Start Length Slot Name Signature
              29 8 5 e Ljava/lang/RuntimeException;
               0 46 0 args [Ljava/lang/String;
               9 37 1 ii I
              12 34 2 isNotDA Ljava/lang/Object;
               3 43 3 isDA Ljava/lang/Object;
               6 40 4 isDANull Ljava/lang/Object;
      StackMapTable: number_of_entries = 1
           frame_type = 255 /* full_frame */
          offset_delta = 27
          locals = [ class "[Ljava/lang/String;", top, top, class java/lang/Object, class java/lang/Object ]
          stack = [ class java/lang/RuntimeException ]

}



When local variable "isNotDA" is printed at a breakpoint on
line 21, the fastdebug VM will fail an assertion.


Here's a jdb run with Client VM fastdebug bits:

ksh do_jdb.ksh 2>&1 | tee do_jdb.client-fast.log
+ sleep 5
Initializing jdb ...
> + echo stop at NotDALocalVarTest:9
Deferring breakpoint NotDALocalVarTest:9.
It will be set after the class is loaded.
> + echo stop at NotDALocalVarTest:13
Deferring breakpoint NotDALocalVarTest:13.
It will be set after the class is loaded.
> + echo stop at NotDALocalVarTest:21
Deferring breakpoint NotDALocalVarTest:21.
It will be set after the class is loaded.
> + echo stop at NotDALocalVarTest:23
+ echo run -client-fast -showversion NotDALocalVarTest
+ sleep 3
Deferring breakpoint NotDALocalVarTest:23.
It will be set after the class is loaded.
> run -client-fast -showversion NotDALocalVarTest
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started: java version "1.7.0-ea"
Java(TM) SE Runtime Environment (build 1.7.0-ea-b139)
Java HotSpot(TM) Client VM (build 21.0-b09-fastdebug, mixed mode)

Set deferred breakpoint NotDALocalVarTest:23
Set deferred breakpoint NotDALocalVarTest:21
Set deferred breakpoint NotDALocalVarTest:13
Set deferred breakpoint NotDALocalVarTest:9

Breakpoint hit: "thread=main", NotDALocalVarTest.main(), line=9 bci=6
9 ii = 22;

main[1] + echo locals
+ echo cont
+ sleep 1
Method arguments:
args = instance of java.lang.String[0] (id=376)
Local variables:
isDA = "isDA1"
isDANull = null
main[1] >
Breakpoint hit: "thread=main", NotDALocalVarTest.main(), line=13 bci=19
13 throw new RuntimeException(); // here, jdb correctly says

main[1] + echo locals
+ echo cont
+ sleep 1
Method arguments:
args = instance of java.lang.String[0] (id=376)
Local variables:
isDA = "isDAv"
isDANull = "isDANullv"
ii = 22
isNotDA = "isNotDAv"
main[1] >
Breakpoint hit: "thread=main", NotDALocalVarTest.main(), line=21 bci=29
21 System.out.println("catch");

main[1] + echo locals
+ echo cont
+ sleep 1
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=\runtime/stackValue.hpp:64
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\jdk7_32p\jdk7\hotspot\src\share\vm\runtime/stackValue.hpp:64), pid=6892, tid=6448
# assert(type() == T_OBJECT) failed: type check
#
# JRE version: 7.0-b139
# Java VM: Java HotSpot(TM) Client VM (21.0-b09-fastdebug mixed mode windows-x86 )
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
#
# An error report file with more information is saved as:
# C:\cygwin\home\dcubed\Projects\da-local-vars\hs_err_pid6892.log
#
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp
#
Phoning home...
Using server: 10.161.186.18, port 4711
Internal exception:

The application has been disconnected
+ echo locals