ABCL 1.8.0

Mark Evenson evenson at
Fri Oct 30 21:14:06 UTC 2020

> On Oct 30, 2020, at 16:22, Vibhu Mohindra <vibhu.mohindra at> wrote:
> On 30/10/2020 15:40, Blake McBride wrote:
>> I'd like to add that I care far, far less about "efficiently [implement
>> atomic memory compare and swap operations" than I do about bug fixes and
>> ANSI CL conformance.  And it still seems like a lot of work is remaining
>> in those areas.
>> Thanks!
>> Blake
> How about the following solution? Apologies if it's obviously unworkable.
> This is the issue:
> which says it requires CAS on a few ABCL functions (svref etc.).
> The valuable feature of CAS is that it doesn't require a context switch,
> unlike Java's "synchronized". So let's weaken the requirement above
> (very slightly, if at all) to "anything roughly as lightweight as CAS".
> Presumably abcl-2 will use some new JDK11 CAS feature to implement svref
> etc.
> But it could use a "fallback-CAS" implementation when it finds itself on
> an old JRE.
> Say one built upon this (JDK5 feature) as a primitive:
> As long as fallback-CAS spins and doesn't switch context, it'll meet the
> weakened requirement above.
> No?
> Then ABCL-2 will work fast on JDK11 and still almost as fast as that
> even on older versions of Java.
> I should probably read up on what specific JDK11 CAS feature abcl-2
> relies upon, that doesn't exist in JDK8. I haven't kept up.
> Vibhu

I think I can keep all the current source running on ABCL2, moving new
functionality to some subclass of CONS that implements the CAS semantics I need
in my pursuit of running the [QVM][] on ABCL.   Therefore we should be able to fold
existing bugs into fixing abcl-1.8.0 while proceeding to develop abcl2.  This
strategy would be somewhat akin to the current mechanism of building support
for Alessio’s ScriptEngine code when the underlying JDK supports it.

None-the-less, it would be advisable for people “stuck” on openjdk8 to start to
evaluate what it would take to run on openjdk11.

Hopefully, we can somehow please everyone.


"A screaming comes across the sky.  It has happened before but there is nothing 
to compare to it now."

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