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Date:      Thu, 30 Mar 95 11:51:00 -0800
From:      Bakul Shah <bakul@netcom.com>
To:        Richard Tobin <richard@cogsci.ed.ac.uk>
Cc:        Dave Cornejo <dave@dogwood.com>, jkh@freefall.cdrom.com (Jordan K. Hubbard), freebsd-hackers@FreeBSD.org
Subject:   Re: HotJava 
Message-ID:  <199503301951.LAA01564@netcom15.netcom.com>
In-Reply-To: Your message of "Thu, 30 Mar 95 14:21:17 %2B0100." <199503301321.OAA05112@deacon.cogsci.ed.ac.uk> 

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> The usual problems with on-the-fly code generation are

> (a) If you jump to the new code just after writing it, your pipeline may
>     get filled before the code is written.  This can be solved by
>     executing a few NOPs after generating the code.
> (b) If you have separate I/D cache, you may have to flush (part of) the
>     I cache in order to see the modified code.  This doesn't arise on
>     386/486, does it?  What about 586?

You need OS support to turn a data page into an executable
page (usually an executable page is read only & shared).
mprotect() should do the trick though.  Also, AFAIK, not
every processor allows you flush cache via user mode
instructions so you may need OS help there.

> > I must say I am not sold on Java yet.  Scheme remains my
> > favorite prototyping language.

> I'm hoping that the GNU scripting language (which will be a Scheme)
> will come along and displace perl and tk/tcl, but I'm not holding my
> breath.  At least Java exists, though Sun's experience with NeWS
> (which also encouraged downloading small programs [in postscript])
> isn't especially encouraging.

Actually, I was not thinking of any such considerations -- I
was merely expressing my opinion on the technical merits of
the language + sharing my delight in *my* use of Scheme.  I
don't have the desire to want to save/change the world and
for my own use commercial success is immaterial.

I will note that for me Java does not exist as yet (I don't
use SPARC systems) while Scheme does -- I can choose from
over 15 implementations.  Scheme would be ideal if it had a
decent interface to arbitrary C functions + an on-the-fly
code generator.




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