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From "Pavel Pervov" <pmcfi...@gmail.com>
Subject Re: [generic][launcher] help for drlvm specific properties
Date Wed, 20 Jun 2007 12:02:17 GMT

'java -X' usually prints out help on options, which start with -X.

What you was asking about as I understood that has syntax of
-XX:<vm_option>[=<value>]. Sun's VM has help on these options on the Web
page and no means to print it out to console.

So, I'm -1 here for printing help on -XX options.

If community still decide to print such help - there is 4-th way to do so
(which will require changing.launcher).
1) launcher recognizes several generic options and is able to determine
application class or jar name.
2) if no -vmdir or -vmdll is specified on command line - launcher tries to
load that VM, otherwise defaults to <launcher location>/default/harmonyvm
and tryies to load this one. If it fails - it prints short help message as
it does right now, when launched with some unrecognizable property name.
3) if library is loaded successfully - launcher constructs arguments array
(as it does right now) and calls to JNI_CreateJavaVM from loaded VM library.
4) if this call returns (-?, -h, -help and -X do not return from
JNI_CreateJavaVM) and if launcher finds class of jar name on the command
line - it proceeds with program startup.

What do you think on such generic startup sequence?


On 6/20/07, Vladimir Beliaev <vladimir.k.beliaev@gmail.com> wrote:
> Hello, All
> I want to add a *help *for drlvm specific system properties like '-
> Xvm.assert_dialog=false' (as asked in
> HARMONY-3409<http://issues.apache.org/jira/browse/HARMONY-3409>
> ).
> *Could you send your opinion on what way this can be done?* There are
> three
> safe ways to do this & non of them seems to be really good (please see
> technical details in
> HARMONY-3409<http://issues.apache.org/jira/browse/HARMONY-3409>).
> *way 1*: support 'java -Xhelp:prop foo' command line... Like if one runs
> 'java -X' then this help says "run '-Xhelp:prop foo' to see sytem
> properties"... In short: if one does not specify this 'foo' at the end,
> then
> a generic launcher consider command line as broken (no 'mainClass' is
> specified) & does not invoke JNI_CreateJavaVM (which print a help)...
> *way 2*: support 'java -Xhelp:prop' command line (i.e. w/o dummy 'foo')...
> To implement this the *generic* launcher is to be changed to recognize
> '-Xhelp:' as a 'help' option (like it recognizes ? -h -help -X now).
> Because
> of other VMs do not support such a '-Xhelp:' option we get
> *generic*launcher to be a bit drlvm-specific...
> *way 3*: be like other VMs and do not print a 'help for drlvm internal
> properties'. Instead, 'java -X' help output may provide a URL to
> harmony.apache.org html document explaining drlvm internal system
> properties...
> I would pick a *way 1* as it does not change *generic *launcher & we are
> free to do every thing we want with -X... I do not like *way 3* at all -
> it
> is not a big deal to create such a document, still it is one more document
> to be supported (I believe it may become out-of-date pretty in couple
> months)...
> So, what do you think?
> --
> Thanks
> Vladimir Beliaev
> Intel Middleware Products Division

Pavel Pervov,
Intel Enterprise Solutions Software Division

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