Latest Rosella doesn't work with latest Winxed snapshot

Andrew Whitworth wknight8111 at gmail.com
Fri Jul 15 13:26:52 UTC 2011


I took a look at this issue myself and have some debugging details
that we can track down later:

1) I don't see the problem manifest itself in the same ways that
dukeleto does, but I do see similar problems elsewhere. It's
definitely GC-related.
2) Every place that I have seen the issue raised involves an sprintf
opcode. I don't know if this is coincidence. The segfault does not
happen during the sprintf, but sometime thereafter.
3) The backtrace from the segfault shows an endless loop of
CallContext.mark vtable calls, the CallContext is marking itself
repeatedly in a tight loop. I thought there were checks in there to
prevent an object which was being marked ("grey") from being
re-marked. I don't know why that isn't happening here
4) The segfault appears to happen when the endless loop eats up all stack space.

I can't really look at this too much until I get home tonight. I'm
going to take a quick look at some recent commits to see if I see
anything obvious. Bisecting might be hard because it's GC-related and
errors will be transient. If anybody wants to attempt, ++ from me.

--Andrew Whitworth



On Fri, Jul 15, 2011 at 2:04 AM, Jonathan "Duke" Leto <jonathan at leto.net> wrote:
> Howdy,
>
> I just attempted using the latest Rosella master branch (2179dc26f8b) with the
> very latest Parrot master, and there are some problems. It works fine on
> 2940c80 but throws a null pmc error on parrot 5718bb9, which contains two
> Winxed snapshot updates from NotFound.
>
> The null pmc error looks like this:
>
> $ winxed setup.winxed build
> Null PMC access in set_string_native()
> called from Sub 'setup_lib_constants' pc 1232 ((file unknown):367)
> (setup.winxed:339)
> called from Sub 'setup_lib_internal' pc 1032 ((file unknown):0)
> (setup.winxed:314)
> called from Sub 'setup_winxed_lib' pc 980 ((file unknown):251)
> (setup.winxed:301)
> called from Sub 'setup_stable_libraries' pc 647 ((file unknown):176)
> (setup.winxed:194)
> called from Sub 'setup_main' pc 236 ((file unknown):95) (setup.winxed:31)
> current instr.: 'main' pc 1849 ((file unknown):650) (setup.winxed:496)
> called from Sub 'main' pc 1275 (ext/winxed/driver.pir:662)
> (winxed_installed.winxed:245)
>
> I would really like for Rosella to work with Parrot 3.6.0, so if we can't
> figure this out before the release, I think we should roll back one of those
> two Winxed updates.
>
> Duke
>
> --
> Jonathan "Duke" Leto <jonathan at leto.net>
> Leto Labs LLC
> 209.691.DUKE // http://labs.leto.net
> NOTE: Personal email is only checked twice a day at 10am/2pm PST,
> please call/text for time-sensitive matters.
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