time: in strptime(), make %z accept Z as a time zone [BZ #17886]

In ISO 8601, the timezone can be 'Z' instead of using
digits. 2014-08-17T12:33:12+0000 is often expressed as
2014-08-17T12:33:12Z.

ChangeLog

@@ -1,3 +1,9 @@
+2015-09-18  Vincent Bernat  <vincent@bernat.im>
+
+	[BZ #17886]
+	* time/strptime_l.c (__strptime_internal): Make %z accept Z as a
+	valid time zone.
+
 2015-09-17  Mike Frysinger  <vapier@gentoo.org>
 
 	* sysdeps/unix/sysv/linux/alpha/Makefile (CFLAGS-fdatasync.c): Delete.

NEWS

@@ -11,11 +11,11 @@ Version 2.23
 
   2542, 2543, 2558, 2898, 4404, 6803, 14341, 14912, 15384, 15786, 15918,
   16141, 16296, 16415, 16517, 16519, 16520, 16521, 16734, 16973, 16985,
-  17118, 17243, 17244, 17787, 17905, 18084, 18086, 18240, 18265, 18370,
-  18421, 18480, 18525, 18595, 18610, 18618, 18647, 18661, 18674, 18675,
-  18681, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796, 18820,
-  18823, 18824, 18857, 18863, 18870, 18872, 18873, 18875, 18887, 18921,
-  18951, 18952, 18961, 18966, 18967, 18970, 18977
+  17118, 17243, 17244, 17787, 17886, 17905, 18084, 18086, 18240, 18265,
+  18370, 18421, 18480, 18525, 18595, 18610, 18618, 18647, 18661, 18674,
+  18675, 18681, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796,
+  18820, 18823, 18824, 18857, 18863, 18870, 18872, 18873, 18875, 18887,
+  18921, 18951, 18952, 18961, 18966, 18967, 18970, 18977.
 
 * The obsolete header <regexp.h> has been removed.  Programs that require
   this header must be updated to use <regex.h> instead.

time/strptime_l.c

@@ -749,13 +749,19 @@ __strptime_internal (rp, fmt, tmp, statep LOCALE_PARAM)
 	    rp++;
 	  break;
 	case 'z':
-	  /* We recognize two formats: if two digits are given, these
+	  /* We recognize three formats: if two digits are given, these
 	     specify hours.  If fours digits are used, minutes are
-	     also specified.  */
+	     also specified.  'Z' is equivalent to +0000.  */
 	  {
 	    val = 0;
 	    while (ISSPACE (*rp))
 	      ++rp;
+	    if (*rp == 'Z')
+	      {
+		++rp;
+		tm->tm_gmtoff = 0;
+		break;
+	      }
 	    if (*rp != '+' && *rp != '-')
 	      return NULL;
 	    bool neg = *rp++ == '-';

time/tst-strptime2.c

@@ -31,7 +31,8 @@ static bool verbose;
      whitespace matching strptime " " format specifier, and
      timezone string matching strptime "%z" format specifier.
 
-   Note that a valid timezone string contains the following fields:
+   Note that a valid timezone string is either "Z" or contains the
+   following fields:
      Sign field consisting of a '+' or '-' sign,
      Hours field in two decimal digits, and
      optional Minutes field in two decimal digits.
@@ -155,6 +156,13 @@ do_test (void)
   expect = LONG_MAX;
   result |= compare (buf, expect, nresult);
 
+  /* Create and test input string with "Z" input (valid format).
+     Expect tm_gmtoff of 0.  */
+
+  sprintf (buf, "%s Z", dummy_string);
+  expect = 0;
+  result |= compare (buf, expect, nresult);
+
   /* Create and test input strings with sign and digits:
      0 digits (invalid format),
      1 digit (invalid format),