[Bug string/31365] New: wcsftime produces invalid characters when the time's weekday or month is out-of-range

["bruno at clisp dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31365

            Bug ID: 31365
           Summary: wcsftime produces invalid characters when the time's
                    weekday or month is out-of-range
           Product: glibc
           Version: 2.38
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: string
          Assignee: unassigned at sourceware dot org
          Reporter: bruno at clisp dot org
  Target Milestone: ---

The wcsftime function is meant to produce, when the given time's weekday or
month is out-of-range, a result with question marks, like strftime does.

This works on little-endian platforms. But it does not work on big-endian
platforms.

How to reproduce: Compile and run this program.
================================ foo.c ==============================
#include <assert.h>
#include <errno.h>
#include <locale.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <wchar.h>

int main ()
{
  time_t t = 1509000003;
  struct tm *tm = gmtime (&t);
  wchar_t buf[100];
  size_t n;

  tm->tm_wday = -1;
  tm->tm_mon = -1;

  errno = 0;
  n = wcsftime (buf, sizeof buf / sizeof (wchar_t), L"|%a| %Y-%b-%d %H:%M:%S",
tm);
  if (n == 0)
    {
      perror ("wcsftime");
    }
  else
    {
      printf ("wcsftime output:\n");
      for (size_t i = 0; i < n; i++)
        printf ("U+0x%04x ", (unsigned int) buf[i]);
      printf ("\n");
      if (printf ("Converted to ASCII: %ls\n", buf) < 0)
        printf ("Conversion to ASCII failed.\n");
    }
}
=====================================================================

Output on ia64, ppc64le, riscv64, loongarch64:
---------------------------------------------------------------------
wcsftime output:
U+0x007c U+0x003f U+0x007c U+0x0020 U+0x0032 U+0x0030 U+0x0031 U+0x0037
U+0x002d U+0x003f U+0x002d U+0x0032 U+0x0036 U+0x0020 U+0x0030 U+0x0036
U+0x003a U+0x0034 U+0x0030 U+0x003a U+0x0030 U+0x0033 
Converted to ASCII: |?| 2017-?-26 06:40:03
---------------------------------------------------------------------

Output on mips64eb, powerpc64, sparc:
---------------------------------------------------------------------
wcsftime output:
U+0x007c U+0x3f000000 U+0x007c U+0x0020 U+0x0032 U+0x0030 U+0x0031 U+0x0037
U+0x002d U+0x3f000000 U+0x002d U+0x0032 U+0x0036 U+0x0020 U+0x0030 U+0x0036
U+0x003a U+0x0034 U+0x0030 U+0x003a U+0x0030 U+0x0033 
Conversion to ASCII failed.
---------------------------------------------------------------------

Output on hppa:
---------------------------------------------------------------------
wcsftime output:
U+0x007c U+0x3f000000 U+0x2e2e2f73 U+0x79736465 U+0x70732f75 U+0x6e69782f
U+0x73797376 U+0x2f6c696e U+0x75782f74 U+0x656c6c64 U+0x69722e63 U+0x007c
U+0x0020 U+0x0032 U+0x0030 U+0x0031 U+0x0037 U+0x002d U+0x3f000000 U+0x2e2e2f73
U+0x79736465 U+0x70732f75 U+0x6e69782f U+0x73797376 U+0x2f6c696e U+0x75782f74
U+0x656c6c64 U+0x69722e63 U+0x002d U+0x0032 U+0x0036 U+0x0020 U+0x0030 U+0x0036
U+0x003a U+0x0034 U+0x0030 U+0x003a U+0x0030 U+0x0033 
Conversion to ASCII failed.
---------------------------------------------------------------------

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