Andrew Zhang wrote:
On 10/10/07, Tim Ellison <[EMAIL PROTECTED]> wrote:
Gregory Shimansky wrote:
Andrew Zhang wrote:
Hi all,
I meet a problem when debugging java application with M3. It throws NPE
immediately after pressing F5/F6. Here's simple test:
public static void main(String[] args) {
int count = 100;
for(int i = 0; i < count; ++i) {
System.out.println(i); // put a breakpoint here.
}
}
It looks like a serious bug. It's reproducible here, with Eclipse 3.2.2
.
Thanks!
I tried both M3 JDK snapshot for libstdc++.so.6 and current local debug
development build of harmony, I couldn't reproduce this. Could you
please give more details which platform you are using and how you are
running this test? How does NPE stack trace look like?
Hi,
Here are some more details:
NPE stack trace:
Thread [main] (Suspended)
NullPointerException.<init>() line: 34
AbstractInterruptibleChannel.<clinit>() line: 57 [local variables
unavailable]
Platform information:
JRE: harmony-jre-580985
Eclipse: Version: 3.2.2 Build id: M20070212-1330
OS: Microsoft Windows Server 2003 R2 Standard Edition Service Pack 1
(Running on a VM)
Hello Andrew
I've just thought about one thing. Modern processors have NX bit that
protects heap from execution. Modern operating systems can enable it so
that execution of heap results in page fault.
JVMTI breakpoints use bits of heap to execute instruction under
breakpoint, and since on usual ia32 platforms it works ok (as NX bit is
disabled by default), protection is not removed currently from these
heap regions. I've just found this out trying to port JVMTI code to
x86_64 where operating systems enable NX bit by default. This is
something I'm going to fix now.
But if you have NX bit enabled as on your server, it may result in page
fault while executing an instrumented instruction. Page fault in java
code is treated as NPE by DRLVM.
So I wonder, do you have by a change enabled Execution Disable Bit (NX)?
I think windows 2003 server has such capability.
The way to debug the application: Debug As -> Debug ..., select Harmony as
the JRE and put a breakpoint at any line. The program halts at the specified
breakpoint as expected, but if you press F5 or F6, it throws the NPE. Any
idea?
It doesn't have any problem to run the application against Harmony.
Thanks!
Works for me too on Windows M3 JDK build with Eclipse 3.3.
Andrew: Could you give us the precise steps to reproduce?
Regards,
Tim
--
Gregory
