From: "Gerd Möllmann" <gerd.moellmann@gmail.com>
To: Sebastian Miele <iota@whxvd.name>
Cc: 67321@debbugs.gnu.org
Subject: bug#67321: 29.1.90; Different parsing rules for -*- lexical-binding:t; -*- in different circumstances
Date: Tue, 21 Nov 2023 11:46:31 +0100 [thread overview]
Message-ID: <m24jhfmliw.fsf@Pro.fritz.box> (raw)
In-Reply-To: <8734wzts37.fsf@whxvd.name> (Sebastian Miele's message of "Tue, 21 Nov 2023 09:16:13 +0100")
Sebastian Miele <iota@whxvd.name> writes:
> Put the following into a file named, e.g., ‘test-script’, and ‘chmod +x’
> it.
>
> #!/bin/sh
> : ; exec emacs --script "$0" -- "$@" #; -*- lexical-binding: t; mode: emacs-lisp; -*-
>
> (defmacro lexical-binding-p ()
> '(let* ((x t)
> (f (lambda () x))
> (x nil))
> (funcall f)))
>
> (message "%s %s" lexical-binding (lexical-binding-p))
>
> When the script is run, the output is "nil nil", signifying that lexical
> binding is not enabled.
>
> Then find the file in an interactive Emacs session, and interactively
> evaluate (C-x C-e) the two expressions. The output now is "t t", i.e.,
> lexical binding is in use.
>
> https://lists.gnu.org/archive/html/emacs-devel/2023-11/msg01041.html
> contains more details, which are repeated here:
>
>> From: Jens Schmidt <jschmidt4gnu@vodafonemail.de>
>> Date: Mon, 2023-11-20 21:10 +0100
>>
>> I tried byte-compiling something similar yesterday, which also
>> indicated that the byte-compiler compiles with lexical bindings. Only
>> the scripting machinery sees dynamical bindings.
>>
>> […] It seems that the scripting machinery expects a semicolon in the
>> very first column, without that the lexical-binding line is not
>> recognized. Even a space before the semicolon breaks the recognition.
>>
>> The problem is in function `lisp_file_lexically_bound_p' from lread.c,
>> which is indeed much more strict in its recognition of the -*- ... -*-
>> stanza than the functions `set-auto-mode-1' and
>> `hack-local-variables-prop-line' from files.el. The Emacs manual
>> ((emacs) Specifying File Variables) only mentions that the stanza has
>> to be in the first line (or the second one if the first is taken by a
>> she-bang), without any restriction where the comment has to start.
>
> ((emacs) Specifying File Variables) states no restrictions on what must
> (not) precede or follow a "-*- … -*-" on the first or second line of a
> file.
>
> Expected: At least consistent behavior. Ideally, lexical binding
> should be enabled in all cases.
>
> In GNU Emacs 29.1.90 (build 1, x86_64-pc-linux-gnu, GTK+ Version
Same in master, BTW, and everything you write is correct, I think.
I guess one could recognize the ": ; exec" idiom (do nothing
successfully and then exec emacs) in command-line--load-script, but that
feels really strange and brittle.
Can I ask why that idiom is used?
next prev parent reply other threads:[~2023-11-21 10:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 8:16 bug#67321: 29.1.90; Different parsing rules for -*- lexical-binding:t; -*- in different circumstances Sebastian Miele
2023-11-21 10:06 ` Andreas Schwab
2023-11-21 11:07 ` Sebastian Miele
2023-11-21 10:46 ` Gerd Möllmann [this message]
2023-11-22 13:07 ` Sebastian Miele
2023-11-22 14:59 ` Gerd Möllmann
2023-11-22 18:10 ` Sebastian Miele
2023-11-22 19:18 ` Gerd Möllmann
2023-11-21 12:43 ` Eli Zaretskii
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