From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Zach Shaftel <zshaftel@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Update 1 on Bytecode Offset tracking
Date: Sat, 18 Jul 2020 22:34:24 -0400 [thread overview]
Message-ID: <jwvlfjgiia8.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87zh7wjybj.fsf@gmail.com> (Zach Shaftel's message of "Sat, 18 Jul 2020 17:41:20 -0400")
> Sure, I'll do some more exhaustive testing. So far though, the results
> aren't great, the biggest issue being memory usage. The
> `source-map-read` can GC over 5 times more often than `read`.
Sounds fine for a prototype.
> I think it's more sensible to accept that a real implementation will
> have to be in C and this reader will just remain a prototype.
Indeed.
> Aha, I had never even considered hygienic macros in Elisp (nor had I
> recognized how trivial it is to track their source-code). That would be
> an amazing development for Emacs Lisp, but is certainly a huge
> undertaking, not something I could fit into the GSoC timeline.
No, I'm just discussing what the longer-run might look like.
> I know that it has been done in Common Lisp (by Pascal Costanza), but
> I believe that implementation serves the sole purpose of capture
> avoidance and doesn't abstract syntax. For Emacs I assume this would
> have to be done in C, but I do wonder if an Elisp implementation would
> be possible.
I haven't thought very much about it, but I can't see any reason why it
would need to be done in C, no (tho I wouldn't be surprised if it could
benefit from a bit of help from the C side, of course).
> Doing the similar thing in Elisp -- relegating source location tracking
> to code using only a specialized kind of macro, hygienic or otherwise --
> would of course be a major loss, since it would take years for that new
> paradigm to become commonplace.
Indeed, we'll need some fallback heuristic for all the existing
`defmacro`s.
Part of the issue is "tracking source location" but another important
part is to take the annotated source code and "de-annotate" it
(recursively) to pass it to the macro, since the macro expects
a raw sexp.
That's why we've been thinking about annotated representations
which are "transparent" (i.e. can be used as if they weren't annotated).
Either using "fat cons-cells" or using "fat symbols" or storing the
annotations in an eq-hash-table.
Another way to attack the problem is to rely on the Edebug spec: you can
refrain from de-annotating all the parts marked as `form` or `body` (as
long as the annotations themselves look sufficiently like normal code,
at least).
Stefan
next prev parent reply other threads:[~2020-07-19 2:34 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 23:10 Update 1 on Bytecode Offset tracking Zach Shaftel
2020-07-16 3:55 ` Stefan Monnier
2020-07-16 22:45 ` Zach Shaftel
2020-07-17 3:44 ` Eli Zaretskii
2020-07-17 16:20 ` Stefan Monnier
2020-07-17 20:19 ` Zach Shaftel
2020-07-17 22:08 ` Stefan Monnier
2020-07-18 21:41 ` Zach Shaftel
2020-07-19 2:34 ` Stefan Monnier [this message]
2020-07-21 0:28 ` Zach Shaftel
2020-07-21 2:51 ` Stefan Monnier
2020-07-16 7:25 ` Andrea Corallo via Emacs development discussions.
2020-07-17 0:24 ` Zach Shaftel
2020-07-17 13:47 ` Rocky Bernstein
2020-07-28 19:19 ` Update 2 " Zach Shaftel
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