mei.chan@Corp 1997-01-16
Debugging a java application on a remote site, with jdb, giving
a host and password, seems to work a little bit. You can
connect to the running program and print its list of classes,
but setting a breakpoint crashes it. Running this program
remotely with "java -debug loop"
 
import java.lang.*;
 
public class loop {
 
  public static void main (String argv[]) {
    for(int i=0; ; i++) {
      System.out.println("i=" + i);
      try {
        Thread.sleep(2*1000);
      } catch (Exception e) {
      }
    }
  }
}
 
commands like "suspend", "resume", "threads", "locals", and
"classes" work, but this causes a crash:
 
suspend
stop at loop:9
resume
 
The messages are:
 
SIGSEGV 11* segmentation violation
    si_signo [11]: SIGSEGV 11* segmentation violation
    si_errno [0]: Error 0
    si_code [1]: SEGV_ACCERR [addr: 0xde7a8]
 
        stackbase=EE2D9000, stackpointer=EE2D76A0
 
Full thread dump:
    "main" (TID:0xee7a1860, sys_thread_t:0xee2d8de0, state:R) prio=5
*current thread*
        loop.main(loop.java:7)
        sun.tools.debug.MainThread.run(Agent.java:55)
    "main" (TID:0xee7a0f20, sys_thread_t:0xee2fade0, state:MS) prio=5
        loop.main(loop.java:9)
        sun.tools.debug.MainThread.run(Agent.java:55)
    "Breakpoint handler" (TID:0xee79f868, sys_thread_t:0xee31cde0,
state:CW) prio=9
        sun.tools.debug.BreakpointQueue.nextEvent(BreakpointQueue.java)
       
sun.tools.debug.BreakpointHandler.run(BreakpointHandler.java:187)
    "Debugger agent" (TID:0xee793dd0, sys_thread_t:0xee33ede0, state:CW)
prio=10
        java.net.SocketInputStream.read(SocketInputStream.java:92)
        java.io.BufferedInputStream.fill(BufferedInputStream.java)
        java.io.BufferedInputStream.read(BufferedInputStream.java)
        java.io.FilterInputStream.read(FilterInputStream.java)
        sun.tools.debug.Agent.run(Agent.java:343)
        java.lang.Thread.run(Thread.java)
    "Finalizer thread" (TID:0xee78f2f8, sys_thread_t:0xee3a5de0,
state:CW) prio=1
    "Async Garbage Collector" (TID:0xee78f2b0, sys_thread_t:0xee3c7de0,
state:MS) prio=1
    "Idle thread" (TID:0xee78f268, sys_thread_t:0xee3e9de0, state:R)
prio=0
    "clock handler" (TID:0xee78f180, sys_thread_t:0xee40bde0, state:CW)
prio=11
    "main" (TID:0xee78f150, sys_thread_t:0x465b0, state:MS) prio=5
        loop.main(loop.java:9)
Monitor Cache Dump:
         java.io.BufferedInputStream@EE79F980/EE828600
(key=0xee79f980): monitor owner ee33ede0: "Debugger agent"
         sun.tools.debug.BreakpointQueue@EE79F898/EE827D98
(key=0xee79f898): unowned
        Waiting to be notified:
            "Breakpoint handler"
         unknown key (key=0x465b0): unowned
         unknown key (key=0xee2fade0): unowned
         unknown key (key=0xee3c7de0): unowned
Registered Monitor Dump:
    Finalize me queue lock: unowned
        Waiting to be notified:
            "Finalizer thread"
    Thread queue lock: unowned
    Name and type hash table lock: unowned
    String intern lock: unowned
    JNI global reference lock: unowned
    BinClass lock: unowned
    Class loading lock: unowned
    Java stack lock: unowned
    Code rewrite lock: unowned
    Heap lock: unowned
    Has finalization queue lock: unowned
    Monitor IO lock: unowned
    Child death monitor: unowned
    Event monitor: unowned
    I/O monitor: unowned
    Alarm monitor: unowned
        Waiting to be notified:
            "clock handler"
    Sbrk lock: unowned
    Monitor cache expansion lock: unowned
    Monitor registry: monitor owner ee2d8de0: "main"
Thread Alarm Q:
Abort
 
In this case the machine where I was running "jdb" was
Windows 95, and the remote machine was Solaris.

The problem also reproduces if jdb runs on Solaris.