Re: `nstrftime ()' prototype

[Ludovic Courtès]

Hi Bruno,

Bruno Haible <address@hidden> writes:

> Ludovic Courtès wrote:
>> In addition, it doesn't mention any portability problem, but AIX and
>> Solaris (at least) have a non-C99-compliant behavior (let alone GNU
>> extensions): https://savannah.gnu.org/bugs/index.php?24130 .
>
> Can you explain what the portability problem is, preferably with a testcase
> in C? It's not clear to me, from looking at the cited URLs, what you consider
> to be a problem, except that it's something related to "%z".

Yes, `%z' is not honored on all platforms: some don't support it at all
(in which case either "%z" or "" appears in the output), on some
platforms (e.g., AIX) it has different semantics, and on others it seems
to be broken (Solaris?).  Attached is a simple test program (I don't
have access to Solaris and AIX boxes myself so I can't say what the
result's like).

Another portability issue is `%Z', which is apparently not supported on
NetBSD.

Another one is this:

    /* POSIX says strftime returns 0 on buffer overrun, but old
       systems (i.e. libc 4 on GNU/Linux) might return `size' in that
       case. */
    while ((len = strftime (tbuf, size, myfmt, &t)) == 0 || len == size)

I'm sorry I don't have much more information about the "faulty" systems.
All this is gathered from $GUILE/test-suite/tests/time.test and
$GUILE/libguile/stime.c.

Anyway, I think it motivates the need for a portable `strftime'.  :-)

Thanks,
Ludo'.

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>

int
main (int argc, char *argv[])
{
  char buf[123];
  size_t size;
  time_t now;
  struct tm *local_now;

  now = time (NULL);

  setenv ("TZ", "GMT", 1);
  local_now = localtime (&now);
  size = strftime (buf, sizeof (buf), "%z", local_now);
  if (strcmp ("+0000", buf))
    {
      /* On AIX, we get "GMT".
         On Solaris, we get "+0000" (?).  */
      printf ("FAIL: GMT: got `%s'\n", buf);
      return 1;
    }

  setenv ("TZ", "EST+5", 1);
  local_now = localtime (&now);
  size = strftime (buf, sizeof (buf), "%z", local_now);
  if (strcmp ("-0500", buf))
    {
      /* On AIX, we get "EST".
         On Solaris, we get "+0000" (?).  */
      printf ("FAIL: EST: got `%s'\n", buf);
      return 2;
    }

  return 0;
}