GNU bug report logs - #48321
27.2; Text copied from *grep* buffer has NUL (0x00) characters

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "R. Diez" <rdiezmail-emacs <at> yahoo.de>
To: bug-gnu-emacs <at> gnu.org
Subject: 27.2; Text copied from *grep* buffer has NUL (0x00) characters
Date: Sun, 9 May 2021 21:14:38 +0200

Emacs' default "Grep Command" is "grep --color -nH --null -e ", which
includes option "--null". This means that grep is embedding an ASCII NUL
character (a binary 0x00) after the filenames.

This is what an rgrep text search occurrence looks like in the *grep* buffer:

./some/file.txt:123:some text line

The first ':' is actually a binary null, but the *grep* buffer hides this fact.

If you copy that text line to an Emacs text file buffer, it then looks like
this:

./some/file.txt^@123:some text line

The ^@ is the representation for the binary null, but that is easy to
miss in long text lines.

A text file with an embedded NUL character causes problems
everywhere. There are errors or warnings with Meld, Pluma, Geany,
Mousepad, and probably many more.

In my opinion, copying text from a *grep* buffer that looks like ":"
should not suddenly deliver a NUL character instead. That's just
unexpected and prone to problems down the line.

Stefan Monnier suggested the following:

----8<----8<----8<----
This "what you see in NOT what you get" is indeed undesirable.  I'm not
sure it's easy to fix in a reliable way in Emacs (beside not using
`--null` as Eli points out), but I suggest you `M-x report-emacs-bug`.
Maybe grep-mode can add a `filter-buffer-substring-function` that
converts those NUL into `:`.
----8<----8<----8<----

For more information, see the discussion starting with this mailing list
message:

Text copied from *grep* buffer has NUL (0x00) characters
https://lists.gnu.org/archive/html/help-gnu-emacs/2021-05/msg00360.html

Message #8 received at 48321 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "R. Diez" <rdiezmail-emacs <at> yahoo.de>
Cc: 48321 <at> debbugs.gnu.org
Subject: Re: bug#48321: 27.2; Text copied from *grep* buffer has NUL (0x00)
 characters
Date: Tue, 11 May 2021 14:53:07 +0200

"R. Diez" <rdiezmail-emacs <at> yahoo.de> writes:

> In my opinion, copying text from a *grep* buffer that looks like ":"
> should not suddenly deliver a NUL character instead. That's just
> unexpected and prone to problems down the line.

Yup.  This is cleverly done by this bit in `grep-regexp-alist':

     nil nil
     (3 '(face nil display ":")))

That is -- the "highlight" we're applying is a `display' spec that says
that the separator should be displayed as ":".

Stefan's suggestion to transform the nul character in the filter in grep
wouldn't quite work, I think -- the filtering is done before the
matching.  So instead we need the thing that processes
`compilation-error-regexp-alist' to do the transformation after the
matches, I think?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #11 received at 48321 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "R. Diez" <rdiezmail-emacs <at> yahoo.de>
Cc: 48321 <at> debbugs.gnu.org
Subject: Re: bug#48321: 27.2; Text copied from *grep* buffer has NUL (0x00)
 characters
Date: Sat, 02 Jul 2022 17:59:26 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> Stefan's suggestion to transform the nul character in the filter in grep
> wouldn't quite work, I think -- the filtering is done before the
> matching.  So instead we need the thing that processes
> `compilation-error-regexp-alist' to do the transformation after the
> matches, I think?

I've instead used kill-transform-function in Emacs 29 to translate the
nul chars to : chars.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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