[Bug stdio/23432] incorrect printf output for integers with thousands separator and precision field larger than the number of digits (needing leading zeros)

["vincent-srcware at vinc17 dot net" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=23432

--- Comment #1 from Vincent Lefèvre <vincent-srcware at vinc17 dot net> ---
This bug is still there in glibc 2.36, but this is even worse than what I've
said, as some leading zeros are also missing, probably because glibc considers
the number of bytes of the string with the thousands separator instead of just
the number of digits. Consider the following new testcase:

#include <stdio.h>
#include <locale.h>

int main (void)
{
  volatile int m = 1234567;
  volatile long n = 1234567890;
  if (setlocale (LC_ALL, ""))
    for (int i = 0; i < 2; i++)
      {
        printf ("%.17d\n", m);
        printf ("%'.17d\n", m);
        printf ("%.17ld\n", n);
        printf ("%'.17ld\n", n);
        m = -m;
        n = -n;
      }
  return 0;
}

zira% LC_ALL=en_US.utf8 ./tst
00000000001234567
000000001,234,567
00000001234567890
00001,234,567,890
-00000000001234567
-000000001,234,567
-00000001234567890
-00001,234,567,890

zira% LC_ALL=fr_FR.utf8 ./tst
00000000001234567
00001 234 567
00000001234567890
1 234 567 890
-00000000001234567
-00001 234 567
-00000001234567890
-1 234 567 890

In the fr_FR.utf8 locale, the space is U+202F NARROW NO-BREAK SPACE, which
takes 3 bytes in UTF-8: e2 80 af. This is probably why there are even fewer
leading zeros in the output.

As this can be seen with this testcase, only the thousands separator is handled
incorrectly, not the minus sign for the negative numbers (which doesn't affect
the number of leading zeros).

Note: this might have been partially fixed recently in master (though I
couldn't see any mention related to the thousands' grouping character or the
width field in the Git log), since a change of behavior triggered a failure in
the GNU MPFR testsuite:

https://sympa.inria.fr/sympa/arc/mpfr/2023-01/msg00001.html
https://sympa.inria.fr/sympa/arc/mpfr/2023-01/msg00002.html

(the "expected" value is actually incorrect as it was based on the incorrect
behavior of glibc; so this is currently a bug in the MPFR testsuite). But note
that there is still a missing thousands' grouping character.

-- 
You are receiving this mail because:
You are on the CC list for the bug.