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Date: Fri, 12 Oct 2007 16:02:26 +0400
From: "Alexei Fedotov" <alexei.fedotov@gmail.com>
To: dev@harmony.apache.org
Subject: Re: [vote] HARMONY-4689 - JVMTI Extension: Native Code Access
 Interface implementation
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References: <906dd82e0710120355y3455fcb1g75dbbef14e61ce94@mail.gmail.com>
	 <14ecfd680710120401t6dfa405ak5575d962c20e9883@mail.gmail.com>
	 <c30d70960710120413x740b042arc4d60ad59004856e@mail.gmail.com>
	 <14ecfd680710120437o51ee4bd8t384800af1fdbd90@mail.gmail.com>

Hello Vasily,

Now I see your attitude towards this donation. :-) When I initally
looked through interface specification, I was not very supportive and
replied with the same argument about gdb.

Unfortunately, gdb is not BSD-licensed or Apache compatible. So we
cannot link with it. It is important if we want to debug application
in a JVMTI-like way from the same process.

If you like solutions with external debuggers, you may come up with
one as well as Salikh did two years ago, and this proved to be useful.
This just does not help in two areas I've initially outlined:
defensive programming and crash handling. Having a level of internal
reflection from inside VM is very important to express assertions
about correct VM state for a debug build.

Finally I want to address your concern of a "pure viewing" nature of
NCAI. NCAI allows changes in runtime environment. For example, you can
change values of variables, or any memory location.

Thanks.


On 10/12/07, Vasily Levchenko <vasily.v.levchenko@gmail.com> wrote:
> On 10/12/07, Alexei Fedotov <alexei.fedotov@gmail.com> wrote:
> >
> > +1
> > NCAI adds very useful architectural level for VM internal debugging
> > and defensive programming. The best example is a crash handler, but
> > other utilities such us self-detection of deadlocks, is also quite
> > interesting.
>
>
> NCAI could be interface to build some kind of viewer, but no real debugger.
> 1. It couldn't be very useful  just because it's single process debugging
> model and if you set breakpoint incorrectly you could lock whole JVM.
> 2. building debugger from the very beginning you try to invent wheel once
> again, you have to develop new mechanisms that already exists in native
> debuggers.
> 3. building infrastructure for Mixed  Mode debugging using native debugger
> could be implemented in 1-2 month and it'll be really powerful and useful
> solution especially JNI developers.
>
> HP(gdb) and Sun (dbx) already introduced native debugger-centric solutions
> for debugging in mixed environments. So NCAI seams to be potential dead code
> and I won't be surprised if year or two later you'll be voting for removing
> this code.
>
> On 10/12/07, Vasily Levchenko <vasily.v.levchenko@gmail.com> wrote:
> > > Hi Mikhail,
> > > Have you got any idea how to use it? Except "Integrated Debugger for
> > > Java/JNI environment" (former MMD).
> > >
> > > On 10/12/07, Mikhail Loenko <mloenko@gmail.com> wrote:
> > > >
> > > > We now have all requisite paperwork in place for
> > > > http://issues.apache.org/jira/browse/HARMONY-4689, so let's vote to
> > > > accept:
> > > >
> > > > [ ] +1 Accept this contribution
> > > > [ ] -1 Reject because...
> > > >
> > > > As usual, 3 days unless someone complains they need more time.
> > > >
> > >
> > >
> > >
> > > --
> > > --vvl
> > >
> >
> >
> > --
> > With best regards,
> > Alexei,
> > ESSD, Intel
> >
>
>
>
> --
> --vvl
>


-- 
With best regards,
Alexei,
ESSD, Intel