bug#79300: fold-nbsp test failure

On 26/08/2025 03:24, Collin Funk wrote:
> Bruno Haible via GNU coreutils Bug Reports <[email protected]>
> writes:
> 
>> Today's CI run reports
>>    FAIL: tests/fold/fold-nbsp
>> on NetBSD 10 and Solaris 11.4.
>>
>> The log output in both cases is:
>>
>> FAIL: tests/fold/fold-nbsp
>> ==========================
>>
>> --- exp1	2025-08-24 06:57:52.605590760 +0000
>> +++ out1	2025-08-24 06:57:52.607333160 +0000
>> @@ -1,3 +1,3 @@
>>   abcdefghij
>> -klmnop qrs
>> -tuvwxyz
>> +klmnop 
>> +qrstuvwxyz
>> --- exp2	2025-08-24 06:57:52.613841250 +0000
>> +++ out2	2025-08-24 06:57:52.615577504 +0000
>> @@ -1,3 +1,3 @@
>>   abcdefghij
>> -klmnop  qr
>> -stuvwxyz
>> +klmnop
>> +qrstuvwxyz
>> FAIL tests/fold/fold-nbsp.sh (exit status: 1)
>>
>>
>> It looks like the &nbsp; character has been treated like a space.
>> If you need a correction at the Gnulib level (in the functions iswblank,
>> iswspace, c32isblank, or c32isspace), please report this to bug-gnulib.
>> Alternatively, you may declare this a "quality of implementation" issue
>> and simply disable the test on NetBSD and Solaris.
> 
> Thanks.
> 
> My initial idea was to check if U+2007 FIGURE SPACE and U+00A0 NO-BREAK
> SPACE are blank using grep. But apparently Solaris grep does not handle
> multibyte characters. Therefore, FIGURE SPACE cannot be checked. :(

Perhaps the techniques from tests/wc/wc-nbsp.sh could be used?
Maybe something like:

check_space() {
   char="$1"
   # Use -L to determine whether NBSP is printable.
   # FreeBSD 11 and OS X treat NBSP as non printable ?
   test "$(env printf "=$char=" | wc -L)" = 3 &&
     test $(env printf "=$char=" | wc -w) = 2
}

if check_space '\u2007'; then
   ...
fi


cheers,
Padraig