Subject: minor buglet
Date: Wed, 17 Nov 1999 17:44:17 PST
From: Tom Rodriguez <###@###.###>
Organization: Xerox PARC
To: Steffen Grarup <###@###.###>

Occasionally I get exceptions like this from hotspot:

8 C:/projects # java test
Exception in thread "main" java.lang.NullPointerException
        <<no stack trace available>>

which should look like this:

9 C:/projects # java -Xint test
Exception in thread "main" java.lang.NullPointerException
        at java.lang.System.arraycopy(Native Method)
        at test.t(test.java:17)
        at test.main(test.java:10)

It seems like once code is compiled you can't get accurate backtraces
from System.arraycopy, which is quite annoying. This seems to be a bug
only in the server VM. The client VM doesn't have this problem. Here's
a test program for it. Just an FYI.

tom

public class test {
    static Object[] src = new Object[10];
    static Object[] dest1 = new Object[10];
    static Object[] dest2 = null;

    static int count = 100000;

    public static void main(String[] args) {
        t(false);
        t(true);
    }

    public static void t(boolean n) {
        for (int i = 0; i < count; i++) {
            if (n && (i + 1 == count))
                System.arraycopy(src, 0, dest2, 0, src.length);
            else
                System.arraycopy(src, 0, dest1, 0, src.length);
        }
    }
}
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This issue still happens with 1.4.1-beta-b12.

The following messages are the result when we tried the above attached
program with windows2000(SP2).

M:\shares\no-trace-server>java test
Exception in thread "main" java.lang.NullPointerException
        at java.lang.System.arraycopy(Native Method)
        at test.t(test.java:16)
        at test.main(test.java:10)

M:\shares\no-trace-server>java -Xint test
Exception in thread "main" java.lang.NullPointerException
        at java.lang.System.arraycopy(Native Method)
        at test.t(test.java:16)
        at test.main(test.java:10)

M:\shares\no-trace-server>java -server test
Exception in thread "main" java.lang.NullPointerException

This is very inconvenient. Even if some error occurs, the licensee can not
do anything.
There might be the following opinion,
 "when debugging, use -client(default) first and debug all errors.
  After debugging, apply the application to he real system with -server
  option."
However, the server VM is very different from the client VM.
There is the error which happens only with server option.
Against such error, they can not do anything....

Please reconsider to add the trace feature to -sever option
and look at their comment in "COMMENT"

2002-05-22
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