[src/trunk]: src/lib/libc/time Don't try to print NULL if we can't get a time...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/7a2e76e750a4
branches:  trunk
changeset: 455611:7a2e76e750a4
user:      christos <christos%NetBSD.org@localhost>
date:      Sun Apr 07 14:51:14 2019 +0000

description:
Don't try to print NULL if we can't get a timezone name. First we try dst,
then we try the non-dst name and finally we just print ??? if that did not
work. This is not needed to handle the "TZ= date" case which was crashing
before because the default timezone was not consistently initialized, but
should handle any timezone now.

diffstat:

 lib/libc/time/strftime.c |  16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diffs (37 lines):

diff -r a02b1e9bd8e1 -r 7a2e76e750a4 lib/libc/time/strftime.c
--- a/lib/libc/time/strftime.c  Sun Apr 07 14:50:41 2019 +0000
+++ b/lib/libc/time/strftime.c  Sun Apr 07 14:51:14 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: strftime.c,v 1.44 2019/04/05 21:27:44 christos Exp $   */
+/*     $NetBSD: strftime.c,v 1.45 2019/04/07 14:51:14 christos Exp $   */
 
 /* Convert a broken-down timestamp to a string.  */
 
@@ -35,7 +35,7 @@
 static char    elsieid[] = "@(#)strftime.c     7.64";
 static char    elsieid[] = "@(#)strftime.c     8.3";
 #else
-__RCSID("$NetBSD: strftime.c,v 1.44 2019/04/05 21:27:44 christos Exp $");
+__RCSID("$NetBSD: strftime.c,v 1.45 2019/04/07 14:51:14 christos Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -544,9 +544,15 @@
 #ifdef TM_ZONE
                                pt = _add(t->TM_ZONE, pt, ptlim);
 #elif HAVE_TZNAME
-                               if (t->tm_isdst >= 0)
-                                       pt = _add(tzgetname(sp, t->tm_isdst),
-                                           pt, ptlim);
+                               if (t->tm_isdst >= 0) {
+                                       int oerrno = errno, dst = t->tm_isdst;
+                                       const char *z =
+                                           tzgetname(sp, dst);
+                                       if (z == NULL)
+                                               z = tzgetname(sp, !dst);
+                                       pt = _add(z ? z : "???", pt, ptlim);
+                                       errno = oerrno;
+                               }
 #endif
                                /*
                                ** C99 and later say that %Z must be