Re: To branch or not to branch

[Jean Abou Samra]

Le 21/09/2022 à 08:29, Jonas Hahnfeld via Discussions on LilyPond 
development a écrit :
> Hi all,
>
> according to the plan laid out in
> https://lists.gnu.org/archive/html/lilypond-devel/2022-08/msg00032.html
> we are supposed to branch stable/2.24 this week "unless some really big
> problems are reported". In the last discussion on this topic in
> https://lists.gnu.org/archive/html/lilypond-devel/2022-09/msg00070.html
> the rare crashes on Windows were identified as a blocker. These seem to
> be fixed now, at least for reasonable user scores (we can still trigger
> it when running the garbage collection in every translator slot); see
> https://gitlab.com/lilypond/lilypond/-/issues/6361 for full details.
>
> There is also https://gitlab.com/lilypond/lilypond/-/issues/6430 which
> is a problem for OLL on Windows. I can't personally comment if it's
> "critical enough" to block the branching / release.
>
> Please comment, also with other issues and thoughts. It's a bit
> frustrating if there are no clear replies and I'm left to guess...



My thoughts:

I don't think the call/cc issue should block branching,
especially now that it's worked around in OLL. The classical
use for call/cc is escape continuations, emulating "return"
statements from imperative languages. Guile 2 has call/ec
(and its variant let/ec) that support this case (also
more efficiently). I didn't see them crash, and they're
implemented completely differently, so I don't see a reason
for them to be broken. I expect that almost all uses of
call/cc can be replaced with let/ec. The one in OLL actually
couldn't, but this is a pretty rare programming style.

I'm undecided on whether call/cc should eventually block
the stable release if we don't have a fix for it. I'm
a fan of call/cc (I mean, introducing it in the Curry-Howard
correspondence changes the logic from intuitionistic to
classical :-), but I doubt many people use it or even know
what it is.

On the other hand, there is actually one use in LilyPond
(in articulate.ly), and I didn't investigate what other tools
Guile implements in terms of call/cc...

So, to be continued, but I'm less worried about this one
than the GC one.

Now to GC. I'm a bit worried by the report from "Ya Gloops"
that some 200-pages scores still crash
(https://lists.gnu.org/archive/html/lilypond-user/2022-09/msg00238.html).
Yes, they're artificial, but they don't call the GC
explicitly, and some people do write scores with the same size...

So I'd be cautious about releasing 2.24 without a full fix
for this one. That said, Ivan Maidanski is making some
comments on the BDWGC issue. A fix in 3 months is not
hopeless, is it?

And if we do get a fix, waiting before branching won't have
helped stability, so overall I think it's OK to branch now,
although I don't have deep insights on the BDWGC issue.