bug#24278: 25.1; Invalid recentf file

[Eli Zaretskii <eliz@gnu.org>]

> From: Damien Cassou <damien@cassou.me>
> Date: Sun, 21 Aug 2016 08:21:47 +0200
> Cc: Nicolas Petton <nicolas@petton.fr>
> 
> frequently, the recentf file becomes invalid Lisp. For example, today, it
> looks like:
> 
>     ;;; Automatically generated by ‘recentf’ on Sat Aug 20 20:31:12 2016.
> 
>     (setq "/home/cassou/nixpkgs/lib/default.nix"recentf-list
>           '(
>             "/home/cassou/.emacs.d/default.nix"
>             "/home/cassou/.emacs.d/init.el"
>             [...]
>             ))
> 
>     (setq recentf-filter-changer-current 'nil)
> 
> Look at the string between "setq" and "recentf-list". I'm using Emacs 25
> rc1.

Very strange.  recentf-save-list, the function that saves the list,
erases the buffer it uses before it generates the contents to save,
whereas your file looks like some bogus attempt to update an existing
file by inserting stuff in its middle.  Could it be that some optional
package, or some software unrelated to Emacs, does that?  E.g., what
is this about:

> Saving file /home/cassou/.emacs.d/recentf...
> Wrote /home/cassou/.emacs.d/.undo-tree/.!home!cassou!.emacs.d!recentf.~undo-tree~
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> Wrote /home/cassou/.emacs.d/recentf

Thanks.