bug#51011: [PATCH] sort: --debug: add warnings about radix and grouping chars

[Paul Eggert]

The warnings look good, except that this one:

>    $ printf '1.0\n0.9\n' | sort -s -k1,1g --debug
>    sort: numbers use ‘.’ as a decimal point in this locale
>    0.9
>    ___
>    1.0
>    ___

seems overkill if we're in the C locale.

Also, shouldn't similar diagnostics be generated if the field separator 
is '-', or '+', or a digit in the current locale?


> +  if (numeric_field_span)
> +    {
> +      char sep_string[2] = { 0, };
> +      sep_string[0] = thousands_sep;
> +      if ((tab == TAB_DEFAULT
> +           && (isblank (to_uchar (thousands_sep))))
> +          || tab == thousands_sep)
> +        {
> +          error (0, 0,
> +                 _("field separator %s is treated as a "
> +                   "group separator in numbers"),
> +                 quote (sep_string));
> +          number_locale_warned = true;
> +        }
> +    }

This code brought it to my attention that the GNU 'sort' has had a 
longstanding bug (in code that I wrote long ago - sorry!) in that 
thousands_sep is either -1 or an unsigned char converted to int, and 
this doesn't work in some unusual cases. I installed the attached patch 
to fix that bug, and I vaguely suspect that it fixes similar bugs in GNU 
'test' and GNU 'expr'. Good thing you brought it to my attention. 
(Sorry, I'm too lazy and/or time-pressed and/or overconfident to write 
test cases....)

Anyway, with that patch installed, TAB and THOUSANDS_SEP can both be 
CHAR_MAX + 1 so the above code needs to be twiddled. Also, we can assume 
C99. So, something like following (pardon Thunderbird's line wrap):

  if (numeric_field_span
      && (tab == TAB_DEFAULT
          ? thousands_char != NON_CHAR && isblank (to_uchar (thousands_sep))
          : tab == thousands_sep))
    {
      error (0, 0,
             _("field separator %s is treated as a group separator in numbers"),
             quote (((char []) {thousands_sep, 0})));
      number_locale_warned = true;
    }

with a similar replacement to the decimal_point code.

0001-sort-fix-unlikely-bug-when-377-0.patch
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