Sun's Java debugger, JDB, has a 'next'command that
allows you to continue execution to the next line.
This command works except for the case when the
next line is the end of a method. In this case,
doing 'next' will crash the debugger.
We're trying to build a debugger using Java debugger
APIs. During debugging, the user can choose to
step into the next instruction or step over to the
next line. We use the method RemoteThread.step() to
step into the next instruction. We use the method
RemoteThread.next()to step over to the next line.

This is similar to what JDB does. You can check out
the code for JDB by looking that the source file
'TTY.java'. RemoteThread.next() will crash the
debugger if the next instruction is at the end of
a method.

Tried this against jdb in JDK 1.0.2 and JDK 1.1beta2
and both failed.


Here is a simple test case using jdb JDK 1.1beta2:

public class Test {

    public static void main(String argv[]) {
        Test t = new Test();
        t.testBreakPoint("Hello world");
    }

   public void testBreakPoint(String abc) {
       XXX xxx = new XXX();
       String result = xxx.doIt(abc);
       System.out.println("result = " + result);
   }
}

class XXX {

    public String doIt(String abc) {
       return abc;
    }
    
}


chicosun:/home/meiphen/JAVA/2717835.jdb 7 % jdb Test
Initializing jdb...
0xee31df10:class(Test)
> stop in Test.testBreakPoint
Breakpoint set in Test.testBreakPoint
> run
run Test

Breakpoint hit: Test.testBreakPoint (Test:9)
main[1] running ...
main[1] list
5 t.testBreakPoint("Hello world");
6 }
7
8 public void testBreakPoint(String abc) {
9 => XXX xxx = new XXX();
10 String result = xxx.doIt(abc);
11 System.out.println("result = " + result);
12 }
13 }
main[1] next

Breakpoint hit: main[1] Test.testBreakPoint (Test:10)
main[1] list
6 }
7
8 public void testBreakPoint(String abc) {
9 XXX xxx = new XXX();
10 => String result = xxx.doIt(abc);
11 System.out.println("result = " + result);
12 }
13 }
14
main[1] next
main[1]
Breakpoint hit: Test.testBreakPoint (Test:11)
main[1] list
7
8 public void testBreakPoint(String abc) {
9 XXX xxx = new XXX();
10 String result = xxx.doIt(abc);
11 => System.out.println("result = " + result);
12 }
13 }
14
15 class XXX {
main[1] next
result = Hello world

Breakpoint hit: main[1] Test.testBreakPoint (Test:8)
main[1] list
4 Test t = new Test();
5 t.testBreakPoint("Hello world");
6 }
7
8 => public void testBreakPoint(String abc) {
9 XXX xxx = new XXX();
10 String result = xxx.doIt(abc);
11 System.out.println("result = " + result);
12 }
main[1] next

The communications channel closed.
Internal exception: java.io.EOFException
at java.io.DataInputStream.readUnsignedShort(DataInputStream.java)
at java.io.DataInputStream.readUTF(DataInputStream.java)
at java.io.DataInputStream.readUTF(DataInputStream.java)
at sun.tools.debug.RemoteAgent.getThreadName(RemoteAgent.java:619)
at sun.tools.debug.RemoteThread.getName(RemoteThread.java:45)
at sun.tools.ttydebug.TTY.printPrompt(TTY.java:70)
at sun.tools.ttydebug.TTY.<init>(TTY.java:1344)
at sun.tools.ttydebug.TTY.main(TTY.java:1436)