bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

[Li Zhai]

Package: Emacs
Version: 23.2.1

I use the command `dired-isearch-filenames-regexp' to find some files
in a directory. I use the the anchor `^' to match the files start with
something. Emacs is suspended and the CPU usage is 100%.Here is a
transcript:

1. Open a directory in dired mode.
2. Input `M-x dired-isearch-filenames-regexp RET  ^ f RET'

Emacs will suspend rather than match the file names start with `f'.

I'm using Windows XP, Emacs version 23.2.

Bye,

Li Zhai

bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

[Juri Linkov]

> I use the command `dired-isearch-filenames-regexp' to find some files
> in a directory. I use the the anchor `^' to match the files start with
> something. Emacs is suspended and the CPU usage is 100%.Here is a
> transcript:
>
> 1. Open a directory in dired mode.
> 2. Input `M-x dired-isearch-filenames-regexp RET  ^ f RET'
>
> Emacs will suspend rather than match the file names start with `f'.

Thanks for the report.  I fixed looping in lazy-highlighting.
Now the loop in `isearch-lazy-highlight-search' is exactly like
in `isearch-search' that checks for the empty match (and
`isearch-lazy-highlight-update' takes care about forwarding
point to the next character in this case).

As for implementing matching at the beginning of file names with `^',
it seems this is not possible to do.  `re-search-forward' matches only
at the beginning of a line, not in the middle of a line.

You can observe the same problem with query-replace in wdired.
For instance, type:

1. M-x wdired-change-to-wdired-mode RET
2. M-x query-replace-regexp RET ^f RET replacement RET

Do you expect that query-replace will rename file names
that start with `f'?

-- 
Juri Linkov
http://www.jurta.org/emacs/

bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

[Li Zhai]

Yes, I expect that query-replace will rename file names start with
`f'. As the search process just matched the file names, it is a simple
thought that `^' means the beginning of the file name.

If we could add some special syntax properties to the white-space
before the file name, it is possible to match the file names start
with `f'. For instance, type :

dired-isearch-filenames-regexp RET \sxf  RET

At here, the `x' means the special syntax class.

It's just my random thought. At most times, a white-space can solve my
problem, like `dired-isearch-filenames-regexp RET SPC f  RET'.

On Sun, Jun 6, 2010 at 5:54 PM, Juri Linkov <juri@jurta.org> wrote:
>> I use the command `dired-isearch-filenames-regexp' to find some files
>> in a directory. I use the the anchor `^' to match the files start with
>> something. Emacs is suspended and the CPU usage is 100%.Here is a
>> transcript:
>>
>> 1. Open a directory in dired mode.
>> 2. Input `M-x dired-isearch-filenames-regexp RET  ^ f RET'
>>
>> Emacs will suspend rather than match the file names start with `f'.
>
> Thanks for the report.  I fixed looping in lazy-highlighting.
> Now the loop in `isearch-lazy-highlight-search' is exactly like
> in `isearch-search' that checks for the empty match (and
> `isearch-lazy-highlight-update' takes care about forwarding
> point to the next character in this case).
>
> As for implementing matching at the beginning of file names with `^',
> it seems this is not possible to do.  `re-search-forward' matches only
> at the beginning of a line, not in the middle of a line.
>
> You can observe the same problem with query-replace in wdired.
> For instance, type:
>
> 1. M-x wdired-change-to-wdired-mode RET
> 2. M-x query-replace-regexp RET ^f RET replacement RET
>
> Do you expect that query-replace will rename file names
> that start with `f'?
>
> --
> Juri Linkov
> http://www.jurta.org/emacs/
>

bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

[Juri Linkov]

> Yes, I expect that query-replace will rename file names start with
> `f'. As the search process just matched the file names, it is a simple
> thought that `^' means the beginning of the file name.
>
> If we could add some special syntax properties to the white-space
> before the file name, it is possible to match the file names start
> with `f'. For instance, type :
>
> dired-isearch-filenames-regexp RET \sxf  RET
>
> At here, the `x' means the special syntax class.

`\sx' matches a character, but it would be better to match the empty string
like `^' does.

One variant is to narrow the dired buffer so the beginning of a line
will be the beginning of a file name.  Unfortunately, it's impossible
to narrow to columns, only to lines.

Another variant is to add a new predicate function in regex.c
that will specify where ^ should match, so dired will set it
to a function that returns non-nil at the beginning of a file name.

-- 
Juri Linkov
http://www.jurta.org/emacs/

bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

[Juri Linkov]

> You can observe the same problem with query-replace in wdired.
> For instance, type:
>
> 1. M-x wdired-change-to-wdired-mode RET
> 2. M-x query-replace-regexp RET ^f RET replacement RET

BTW, there is another bug in query-replace lazy-highlighting in dired.
Wdired sets `query-replace-skip-read-only' to replace only in
file names, but during replacement all read-only matches are
lazy-highlighted too.  This can be fixed with this patch:

=== modified file 'lisp/wdired.el'
--- lisp/wdired.el	2010-01-13 08:35:10 +0000
+++ lisp/wdired.el	2010-06-06 18:09:04 +0000
@@ -243,6 +243,8 @@ (defun wdired-change-to-wdired-mode ()
        (buffer-substring (point-min) (point-max)))
   (set (make-local-variable 'wdired-old-point) (point))
   (set (make-local-variable 'query-replace-skip-read-only) t)
+  (set (make-local-variable 'isearch-filter-predicate)
+       'wdired-isearch-filter-read-only)
   (use-local-map wdired-mode-map)
   (force-mode-line-update)
   (setq buffer-read-only nil)
@@ -268,6 +270,11 @@ (defun wdired-change-to-wdired-mode ()
 		 "Press \\[wdired-finish-edit] when finished \
 or \\[wdired-abort-changes] to abort changes")))
 
+(defun wdired-isearch-filter-read-only (beg end)
+  "Skip matches that have a read-only property."
+  (and (isearch-filter-visible beg end)
+       (not (text-property-not-all (min beg end) (max beg end)
+				   'read-only nil))))
 
 ;; Protect the buffer so only the filenames can be changed, and put
 ;; properties so filenames (old and new) can be easily found.

-- 
Juri Linkov
http://www.jurta.org/emacs/

bug#6362: Emacs command `dired-isearch-filenames-regexp' cause CPU usage 100%

[Juri Linkov]

> BTW, there is another bug in query-replace lazy-highlighting in dired.
> Wdired sets `query-replace-skip-read-only' to replace only in
> file names, but during replacement all read-only matches are
> lazy-highlighted too.  This can be fixed with this patch:
> [...]
> +(defun wdired-isearch-filter-read-only (beg end)
> +  "Skip matches that have a read-only property."
> +  (and (isearch-filter-visible beg end)
> +       (not (text-property-not-all (min beg end) (max beg end)
> +				   'read-only nil))))

I installed this old patch and closed this bug.