query on the flags required for debugging

[Dilshad Marikar]

Hi

I'd like to know the meaning of the vm parameters and system parameters needed for remote debugging.

-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5555

what is the meaning of the -Xnoagent vm param and the system param -Djava.compiler=NONE? What do they do? Can I get away with not using them?

Thanks

Dilshad

[Jeanne Boyarsky]

Dilshad,
What IDE is this for? Eclipse? NetBeans? IDEA?

[Dilshad Marikar]

i've been using eclipse and something called cqjd. But the flags in question are pretty such general to all enviromnents are they not?

Regards
Dilshad

[Jeanne Boyarsky]

Dilshad,
Some tools have different flags. I don't recall either of those being required for Eclipse though. See this article for more details.

[Dilshad Marikar]

thanks for the article Jeanne. Interesting to note that the vm parameters to enable remote debugging may vary with the vendor. Calling "java -x" from the command line appears to show the supported vm params.

[Tim Holloway]

If you want to attach jdb to a classic VM that is already running, the VM must be started with the following options:
 
Option Purpose
-Xdebug Enables debugging support in the VM
-Xrunjdwp:transport=dt_shmem,server=y,suspend=n Loads in-process debugging libraries and specifies the kind of connection to be made.
-Xnoagent Disables VM support for oldjdb
-Djava.compiler=NONE Disables the JIT compiler. This is required for debugging under the classic VM

I lifted this from http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/jdb.html which is a discussion of sun's command-line java debugger.

One of the really cool things about the Sun JVM is its support for remote debugging and resource monitoring and the fact that they provided info on how to write your clients such as the Eclipse and Intellij IDE debugging systems.

I don't know how portable that stuff is as a whole. Anything that starts with an "-X" is vendor-dependent, and "-D" items just define properties to the runtime environment which may use those properties any way it likes.