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bug#48114: Disarchive occasionally fails tests
From: |
Ludovic Courtès |
Subject: |
bug#48114: Disarchive occasionally fails tests |
Date: |
Mon, 03 May 2021 22:03:59 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) |
Hi!
Timothy Sample <samplet@ngyro.com> skribis:
> Timothy Sample <samplet@ngyro.com> writes:
>
>> I’m still looking into this, but I wanted to quickly post this
>> reproducer for the Guile bug:
>>
>> (use-modules (ice-9 regex))
>> (define str
>> "\U101514\U103ab0\U0f6e6e\U02e278\U01d9eb\U10b996\U1089b5\uea15\U0fa074\U101e41\U02e330\u0177\u2492")
>> (match:substring (string-match "[0-8]+" str))
>>
>> This triggers the out-of-range error when run with “LC_ALL=C”.
>
> It turns out that all that’s needed is the last code point, which is
> “Number Eleven Full Stop”, or ‘⒒’.
Whaaat? “Number Eleven Full Stop”, I wonder how the Unicode folks came
up with that one. ㊷ = ㉚ + ⒓
> When Guile converts this to an ASCII C string using
> ‘u32_conv_from_encoding’, it becomes “11.”. The regex (“[0-8]+”)
> matches the “11” part with start index 0 and end index 2. The
> ‘fixup_multibyte_match’ function does nothing (it only matters when
> the locale encoding is multibyte) [1]. Guile then builds the match
> vector with the original string but keeps the ASCII offsets. In other
> words, it thinks the match substring goes from 0 to 2 in a single code
> point string:
>
> ,use (ice-9 regex)
> (string-match "11" "\u2492")
> => #("\u2492" (0 . 2))
>
> I’m not sure there’s any way to solve this nicely in Guile. It would be
> clearer if the match vector included the string as libc matched it, but
> it’s still surprising that the match happens with a different string.
Yeah, I don’t think there’s much we can do. It’s a lot of fun anyway.
Thanks for investigating!
Ludo’.