bug#35171: 26.1; file-locked-p does not respect file-name-coding-system

bug#35171: 26.1; file-locked-p does not respect file-name-coding-system

[Olli Helenius]

The ‘file-locked-p’ function does not call ‘ENCODE_FILE’ on its argument
and thus can end up looking for a different file name than that which
was generated by ‘lock-buffer’.  Below is an Elisp expression that
demonstrates the issue.

;; Returns string "file-locked-p buggy" if the result of file-locked-p
;; is `nil' even when the buffer should be locked.
(let ((file-name-coding-system 'latin-1-unix)
      (create-lockfiles t))
  (let ((file (make-temp-file "file-locked-p-éö-" nil ".txt" "test"))
	(result nil))
    (unwind-protect
	(progn
	  (find-file-existing file)
	  (insert "modification")
          (lock-buffer)
	  (if (eq nil (file-locked-p file))
	      (setq result "file-locked-p buggy")
	    (setq result "file-locked-p ok"))
	  (save-buffer)
	  (kill-buffer)
	  result)
      (delete-file file nil))))

See also:
  http://git.savannah.gnu.org/cgit/emacs.git/tree/src/filelock.c?h=emacs-26.1#n680
  http://git.savannah.gnu.org/cgit/emacs.git/tree/src/filelock.c?h=emacs-26.1#n829

In GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.5)
 of 2019-04-05 built on localhost
Recent messages:
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Mark set [3 times]
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Making completion list...

Configured using:
 'configure
 --prefix=/nix/store/1yj0jrwh9yr2h81nl50c88lqn254ylil-emacs-26.1
 --with-modules --with-x-toolkit=gtk3 --with-xft
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Important settings:
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Major mode: Lisp Interaction

Minor modes in effect:
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/nix/store/553k4fjrf5d523zrjvm7jmw6zx23cbmf-emacs-packages-deps/share/emacs/site-lisp/elpa/seq-2.20/seq hides /nix/store/1yj0jrwh9yr2h81nl50c88lqn254ylil-emacs-26.1/share/emacs/26.1/lisp/emacs-lisp/seq
/nix/store/553k4fjrf5d523zrjvm7jmw6zx23cbmf-emacs-packages-deps/share/emacs/site-lisp/elpa/let-alist-1.0.5/let-alist hides /nix/store/1yj0jrwh9yr2h81nl50c88lqn254ylil-emacs-26.1/share/emacs/26.1/lisp/emacs-lisp/let-alist

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Memory information:
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bug#35171: 26.1; file-locked-p does not respect file-name-coding-system

[Eli Zaretskii]

> Date: Sat, 6 Apr 2019 13:17:17 +0300 (EEST)
> From: Olli Helenius <liff@iki.fi>
> 
> The ‘file-locked-p’ function does not call ‘ENCODE_FILE’ on its argument
> and thus can end up looking for a different file name than that which
> was generated by ‘lock-buffer’.  Below is an Elisp expression that
> demonstrates the issue.

Thanks, fixed on the master branch.