[Bug locale/31542] New: printf integer formatting bug for nb_NO and nn_NO locales

["dreibh at simula dot no" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31542

            Bug ID: 31542
           Summary: printf integer formatting bug for nb_NO and nn_NO
                    locales
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: locale
          Assignee: unassigned at sourceware dot org
          Reporter: dreibh at simula dot no
  Target Milestone: ---

There is a formatting bug for integers in printf() when using locale settings
and formatting with thousands separator.

Test program printfbug.c:
#include <stdio.h>
#include <stdlib.h>
#include <locale.h>

int main(int argc, char** argv)
{
   setlocale (LC_ALL, "");

   struct lconv* loc = localeconv();
   printf("Thousands Separator: <%s>\n", loc->thousands_sep);

   for(int i = 1; i <argc; i++) {
      int    n = atoi(argv[i]);
      double f = atof(argv[i]);
      printf("double <%'10.0f>\tint <%'10d>\n", f, n);
   }
   return 0;
}

Test run:
for l in en_US de_DE nb_NO nn_NO ; do
   echo "$l:" ; LC_ALL=$l.UTF-8 ./printfbug 1 10 100 1000 10000 100000 1000000
10000000
done

Output:
en_US:
Thousands Separator: <,>
double <         1>     int <         1>
double <        10>     int <        10>
double <       100>     int <       100>
double <     1,000>     int <     1,000>
double <    10,000>     int <    10,000>
double <   100,000>     int <   100,000>
double < 1,000,000>     int < 1,000,000>
double <10,000,000>     int <10,000,000>
de_DE:
Thousands Separator: <.>
double <         1>     int <         1>
double <        10>     int <        10>
double <       100>     int <       100>
double <     1.000>     int <     1.000>
double <    10.000>     int <    10.000>
double <   100.000>     int <   100.000>
double < 1.000.000>     int < 1.000.000>
double <10.000.000>     int <10.000.000>
nb_NO:
Thousands Separator: < >
double <         1>     int <         1>
double <        10>     int <        10>
double <       100>     int <       100>
double <     1 000>     int <   1 000>
double <    10 000>     int <  10 000>
double <   100 000>     int < 100 000>
double < 1 000 000>     int <1 000 000>
double <10 000 000>     int <10 000 000>
nn_NO:
Thousands Separator: < >
double <         1>     int <         1>
double <        10>     int <        10>
double <       100>     int <       100>
double <     1 000>     int <   1 000>
double <    10 000>     int <  10 000>
double <   100 000>     int < 100 000>
double < 1 000 000>     int <1 000 000>
double <10 000 000>     int <10 000 000>

That is, en_US and de_DE are fine (they use ',' and '.' as thousands
separator). But nb_NO and nn_NO produce the wrong output when using integers
(%'10d). However, float is fine as well (%'10.0f).

For nb_NO and nn_NO, the separator is a 3-byte UTF-8 character 0xe2 0x80 0xaf,
which is UTF-8 NARROW NO-BREAK SPACE ->
https://www.fileformat.info/info/unicode/char/202f/index.htm . It seems that
for integer formatting, the number of bytes is processed, instead of counting
the actual characters. For float formatting, the number of characters is
counted correctly.

That is:
$ LC_ALL=nb_NO.UTF-8 ./printfbug 1000 | hexdump -C
00000000  54 68 6f 75 73 61 6e 64  73 20 53 65 70 61 72 61  |Thousands Separa|
00000010  74 6f 72 3a 20 3c e2 80  af 3e 0a 64 6f 75 62 6c  |tor: <...>.doubl|
00000020  65 20 3c 20 20 20 20 20  31 e2 80 af 30 30 30 3e  |e <     1...000>|
00000030  09 69 6e 74 20 3c 20 20  20 31 e2 80 af 30 30 30  |.int <   1...000|
00000040  3e 0a                                             |>.|
00000042

I can reproduce the issue under Ubuntu 22.04, Ubuntu 24.04 (development
version), and Fedora 39.

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