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bug#60315: 28.2; Byte-compiler warning for free variable
From: |
Drew Adams |
Subject: |
bug#60315: 28.2; Byte-compiler warning for free variable |
Date: |
Sun, 25 Dec 2022 17:07:55 +0000 |
You might not consider this a bug, or you might consider it not worth
trying to fix. That's fine by me. I think it's worth reporting, at
least. Maybe something can be done for it, or maybe you can let me know
a good way to work around it.
Unlike `defvar', `defconst', alters the value each time it's evaluated.
E.g., if you load a file with (defconst foo bar "...") more than once
then the value of `foo' gets set each time to whatever is the current
value of `bar'. That's normal and desirable (and consistent with other
Lisps, such as CL).
How to ensure that a defconst sets the value only once, when the file
it's in is loaded? A defvar does that, but a defconst does not.
Maybe there's a better way, but I've been using this so far:
(unless (boundp 'foo) (defconst foo bar "..."))
But that results in this byte-compiler warning:
In blah-fun:
toto.el:236:34:Warning: reference to free variable
`foo'
An alternative is to use a defvar and just say in its doc string that
it's intended as a constant (don't set it etc.). Maybe that's less
confusing to users than seeing the warning? Dunno.
In GNU Emacs 28.2 (build 2, x86_64-w64-mingw32)
of 2022-09-13 built on AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Pro (v10.0.2009.19044.2364)
Configured using:
'configure --with-modules --without-dbus --with-native-compilation
--without-compress-install CFLAGS=-O2'
Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
XPM ZLIB
(NATIVE_COMP present but libgccjit not available)
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