Re: [Emacs-diffs] master c66aaa6: Recomplexify ‘delete-trailing-whitespace’ by treating \n as whitespace again

[Sam Steingold]

Hi

This patch causes delete-trailing-whitespace to hang when some
trailing whitespace is non-modifiable.

Thanks.

> * Noam Postavsky <address@hidden> [2017-03-14 22:31:58 -0400]:
>
> branch: master
> commit c66aaa61639e72a70a4f2c4bc73645048caebe53
> Author: Noam Postavsky <address@hidden>
> Commit: Noam Postavsky <address@hidden>
>
>     Recomplexify ‘delete-trailing-whitespace’ by treating \n as whitespace 
> again
>     
>     Mostly reverts "Simplify ‘delete-trailing-whitespace’ by not treating
>     \n as whitespace" from 2016-07-04.  Setting \n to non-whitespace
>     causes the regex engine to backtrack a lot when searching for
>     "\\s-+$" (Bug#26079).
>     
>     * lisp/simple.el (delete-trailing-whitespace): Don't change newline
>     syntax, search for "\\s-$" and then skip backward over trailing
>     whitespace.
> ---
>  lisp/simple.el | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/lisp/simple.el b/lisp/simple.el
> index f110c6f..369fbf7 100644
> --- a/lisp/simple.el
> +++ b/lisp/simple.el
> @@ -633,10 +633,9 @@ buffer if the variable `delete-trailing-lines' is 
> non-nil."
>          (with-syntax-table (make-syntax-table (syntax-table))
>            ;; Don't delete formfeeds, even if they are considered whitespace.
>            (modify-syntax-entry ?\f "_")
> -          ;; Treating \n as non-whitespace makes things easier.
> -          (modify-syntax-entry ?\n "_")
> -          (while (re-search-forward "\\s-+$" end-marker t)
> -            (let ((b (match-beginning 0)) (e (match-end 0)))
> +          (while (re-search-forward "\\s-$" end-marker t)
> +            (skip-syntax-backward "-" (line-beginning-position))
> +            (let ((b (point)) (e (match-end 0)))
>                (when (region-modifiable-p b e)
>                  (delete-region b e)))))
>          (if end

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