> Cc: 79380@debbugs.gnu.org
> Date: Thu, 04 Sep 2025 10:38:32 -0400
> From:  Spencer Baugh via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>
> Daniel Mendler <mail@daniel-mendler.de> writes:
> > If elisp-flymake-byte-compile-executable is nil (the default), the
> > absolute file predicate fails and as a result Flymake does not check
> > Elisp anymore:
> >
> > (file-name-absolute-p elisp-flymake-byte-compile-executable)
>
> Apologies, I accidentally posted an old version of the patch which was
> then installed.  The attached should fix it.  Please try it (and then
> feel free to push it if it works).
>
> >From 425e3f4ab95faf7c0e4a749e0c428f4c05f32cfa Mon Sep 17 00:00:00 2001
> From: Spencer Baugh <sbaugh@janestreet.com>
> Date: Thu, 4 Sep 2025 10:36:17 -0400
> Subject: [PATCH] Fix null values of elisp-flymake-byte-compile-executable
>
> * lisp/progmodes/elisp-mode.el
> (elisp-flymake-byte-compile--executable): Properly check for
> nil. (bug#79380)
> ---
>  lisp/progmodes/elisp-mode.el | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
> index e8344852829..c6951810c3e 100644
> --- a/lisp/progmodes/elisp-mode.el
> +++ b/lisp/progmodes/elisp-mode.el
> @@ -2301,13 +2301,14 @@ elisp-flymake-byte-compile--executable
>    "Return absolute file name of the Emacs executable for flymake byte-compilation."
>    (let ((filename
>           (cond
> +          ((null elisp-flymake-byte-compile-executable) nil)
>            ((file-name-absolute-p elisp-flymake-byte-compile-executable)
>             elisp-flymake-byte-compile-executable)
>            ((stringp elisp-flymake-byte-compile-executable)
>             (when-let* ((pr (project-current)))
>               (file-name-concat (project-root pr)
>                                 elisp-flymake-byte-compile-executable))))))
> -    (if (file-executable-p filename)
> +    (if (and filename (file-executable-p filename))
>          filename
>        (when elisp-flymake-byte-compile-executable
>          (message "No such `elisp-flymake-byte-compile-executable': %s"
> --
> 2.43.7

Shouldn't the tests of the value of the user option use stringp
instead of null?