GNU bug report logs - #30116
[PATCH] `substitute' crashes when file contains NUL characters (core-updates)

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From: ludo <at> gnu.org (Ludovic Courtès)
To: Mark H Weaver <mhw <at> netris.org>
Cc: 30116 <at> debbugs.gnu.org, Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Subject: bug#30116: [PATCH] `substitute' crashes when file contains NUL characters (core-updates)
Date: Mon, 22 Jan 2018 11:58:37 +0100

Mark H Weaver <mhw <at> netris.org> skribis:

> Maxim Cournoyer <maxim.cournoyer <at> gmail.com> writes:
>
>> ludo <at> gnu.org (Ludovic Courtès) writes:
>>
>>> Maxim Cournoyer <maxim.cournoyer <at> gmail.com> skribis:
>>>
>>>> I've encountered the following crash when trying to use substitute on a
>>>> file which contains NUL characters:
>>>
>>> Yes, that’s because Guile’s ‘regexp-exec’ simply wraps libc’s ‘regexec’,
>>> which does not handle NULs.
>>>
>>> We should consider switching to the pure-Scheme SRFI-115:
>>>
>>>   https://srfi.schemers.org/srfi-115/srfi-115.html
>>
>> This looks good, and I started looking into porting `substitute' to it,
>> but quickly noticed it doesn't seem to be implemented in Guile yet?

ISTR that the reference implementation works fine on Guile.

> Indeed.  SRFI-115 for Guile is on my TODO list, although it might be
> better to wait until after we switch to using UTF-8 encoding internally
> for strings, since that will drastically affect the implementation of
> any efficient regexp matcher on Scheme strings.

Indeed, though I suppose it doesn’t matter much for the cases where
‘substitute*’ is used?

> Anyway, 'substitute*' is to be used only on text files, and NUL bytes
> are not a valid textual character.  So, I think that this case is
> outside of what 'substitute*' is meant to do, and therefore not a bug in
> 'substitute*', although of course a more graceful error would surely be
> preferable.

Yes, that’s also a good point.

So yeah, I think it may be good “eventually” to switch to SRFI-115, but
that’s not urgent.

Thoughts?

Ludo’.

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