From: Stefan Monnier <monnier@iro.umontreal.ca>
To: "Mattias Engdegård" <mattiase@acm.org>
Cc: michael_heerdegen@web.de, 46387@debbugs.gnu.org
Subject: bug#46387: 28.0.50; Compiled code making a variable dynamic stopped working
Date: Tue, 09 Feb 2021 10:31:24 -0500 [thread overview]
Message-ID: <jwvim71s1m4.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <B18B1DE2-0340-4A51-9B3D-8489C31C7F15@acm.org> ("Mattias Engdegård"'s message of "Tue, 9 Feb 2021 11:32:58 +0100")
> There's a lack of clarity regarding the exact semantics of local
> `defvar`. The manual says that its effect is confined to the current
> lexical scope, but what exactly does that mean?
Adding a variable to the context creates a new scope.
A `progn` should not introduce a new scope.
> As it turns out, parts of the implementation have different opinions
> about that.
Indeed, there's a fair bit a space between my above two statements.
> As you observed, the recently added optimisation on master takes
> a strict syntactic view: even a `progn` is a lexical scope,
I think that's clearly an error. Adding/removing `progn` shouldn't make
any difference in this respect.
> (Stefan, it looks like your latest Gnus patch may fall in the same trap. Or?)
The (with-suppressed-warnings (...) (defvar)) form is used at
several places. It's the preferred way to declare a variable
dynamically scoped without incurring the "not prefixed" warning and
without making the `with-suppressed-warnings` silencer cover more code
than intended.
Stefan
next prev parent reply other threads:[~2021-02-09 15:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 17:29 bug#46387: 28.0.50; Compiled code making a variable dynamic stopped working Michael Heerdegen
2021-02-09 10:32 ` Mattias Engdegård
2021-02-09 15:31 ` Stefan Monnier [this message]
2021-02-09 16:49 ` Mattias Engdegård
2021-02-09 18:48 ` Stefan Monnier
2021-02-10 3:20 ` Michael Heerdegen
2021-02-10 8:22 ` Mattias Engdegård
2021-02-10 13:49 ` Mattias Engdegård
2021-02-10 22:44 ` Michael Heerdegen
2021-02-11 8:49 ` Mattias Engdegård
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