gtimezone: Add g_time_zone_get_identifier() accessor

This is a non-trivial accessor which gets the identifier string used to
create the GTimeZone — unless the string passed to g_time_zone_new() was
invalid, in which case the identifier will be `UTC`.

Implementing this required reworking how timezone information was loaded
so that the tz->name is always set at the same time as tz->t_info, so
they are in sync. Previously, the tz->name was unconditionally set to
whatever was passed to g_time_zone_new(), and then not updated if the
tz->t_info was eventually set to the default UTC information.

This includes tests for the new g_time_zone_get_identifier() API, and
for the g_date_time_get_timezone() API added in the previous commit.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=795165

docs/reference/glib/glib-sections.txt

@@ -1653,6 +1653,7 @@ GTimeType
 g_time_zone_find_interval
 g_time_zone_adjust_time
 <SUBSECTION>
+g_time_zone_get_identifier
 g_time_zone_get_abbreviation
 g_time_zone_get_offset
 g_time_zone_is_dst

glib/gtimezone.c

@@ -52,10 +52,17 @@
  * #GTimeZone is a structure that represents a time zone, at no
  * particular point in time.  It is refcounted and immutable.
  *
+ * Each time zone has an identifier (for example, ‘Europe/London’) which is
+ * platform dependent. See g_time_zone_new() for information on the identifier
+ * formats. The identifier of a time zone can be retrieved using
+ * g_time_zone_get_identifier().
+ *
  * A time zone contains a number of intervals.  Each interval has
- * an abbreviation to describe it, an offet to UTC and a flag indicating
+ * an abbreviation to describe it (for example, ‘PDT’), an offet to UTC and a
- * if the daylight savings time is in effect during that interval.  A
+ * flag indicating if the daylight savings time is in effect during that
- * time zone always has at least one interval -- interval 0.
+ * interval.  A time zone always has at least one interval — interval 0. Note
+ * that interval abbreviations are not the same as time zone identifiers
+ * (apart from ‘UTC’), and cannot be passed to g_time_zone_new().
  *
  * Every UTC time is contained within exactly one interval, but a given
  * local time may be contained within zero, one or two intervals (due to
@@ -384,7 +391,7 @@ zone_for_constant_offset (GTimeZone *gtz, const gchar *name)
   info.is_dst = FALSE;
   info.abbrev =  g_strdup (name);
 
-
+  gtz->name = g_strdup (name);
   gtz->t_info = g_array_sized_new (FALSE, TRUE, sizeof (TransitionInfo), 1);
   g_array_append_val (gtz->t_info, info);
 
@@ -394,11 +401,18 @@ zone_for_constant_offset (GTimeZone *gtz, const gchar *name)
 
 #ifdef G_OS_UNIX
 static GBytes*
-zone_info_unix (const gchar *identifier)
+zone_info_unix (const gchar  *identifier,
+                gchar       **out_identifier)
 {
   gchar *filename;
   GMappedFile *file = NULL;
   GBytes *zoneinfo = NULL;
+  gchar *resolved_identifier = NULL;
+  const gchar *tzdir;
+
+  tzdir = getenv ("TZDIR");
+  if (tzdir == NULL)
+    tzdir = "/usr/share/zoneinfo";
 
   /* identifier can be a relative or absolute path name;
      if relative, it is interpreted starting from /usr/share/zoneinfo
@@ -406,11 +420,7 @@ zone_info_unix (const gchar *identifier)
      glibc allows both syntaxes, so we should too */
   if (identifier != NULL)
     {
-      const gchar *tzdir;
+      resolved_identifier = g_strdup (identifier);
-
-      tzdir = getenv ("TZDIR");
-      if (tzdir == NULL)
-        tzdir = "/usr/share/zoneinfo";
 
       if (*identifier == ':')
         identifier ++;
@@ -421,7 +431,33 @@ zone_info_unix (const gchar *identifier)
         filename = g_build_filename (tzdir, identifier, NULL);
     }
   else
-    filename = g_strdup ("/etc/localtime");
+    {
+      gsize prefix_len = 0;
+
+      filename = g_strdup ("/etc/localtime");
+
+      /* Resolve the actual timezone pointed to by /etc/localtime. */
+      resolved_identifier = g_file_read_link (filename, NULL);
+      if (resolved_identifier == NULL)
+        {
+          /* Error */
+          if (out_identifier != NULL)
+            *out_identifier = NULL;
+          return NULL;
+        }
+
+      /* Strip the prefix and slashes if possible. */
+      if (g_str_has_prefix (resolved_identifier, tzdir))
+        {
+          prefix_len = strlen (tzdir);
+          while (*(resolved_identifier + prefix_len) == '/')
+            prefix_len++;
+        }
+
+      if (prefix_len > 0)
+        memmove (resolved_identifier, resolved_identifier + prefix_len,
+                 strlen (resolved_identifier) - prefix_len + 1  /* nul terminator */);
+    }
 
   file = g_mapped_file_new (filename, FALSE, NULL);
   if (file != NULL)
@@ -433,11 +469,18 @@ zone_info_unix (const gchar *identifier)
       g_mapped_file_unref (file);
     }
   g_free (filename);
+
+  g_assert (resolved_identifier != NULL);
+  if (out_identifier != NULL)
+    *out_identifier = g_steal_pointer (&resolved_identifier);
+
   return zoneinfo;
 }
 
 static void
-init_zone_from_iana_info (GTimeZone *gtz, GBytes *zoneinfo)
+init_zone_from_iana_info (GTimeZone *gtz,
+                          GBytes    *zoneinfo,
+                          gchar     *identifier  /* (transfer full) */)
 {
   gsize size;
   guint index;
@@ -471,6 +514,7 @@ init_zone_from_iana_info (GTimeZone *gtz, GBytes *zoneinfo)
   tz_ttinfo = tz_type_index + time_count;
   tz_abbrs = tz_ttinfo + sizeof (struct ttinfo) * type_count;
 
+  gtz->name = g_steal_pointer (&identifier);
   gtz->t_info = g_array_sized_new (FALSE, TRUE, sizeof (TransitionInfo),
                                    type_count);
   gtz->transitions = g_array_sized_new (FALSE, TRUE, sizeof (Transition),
@@ -611,7 +655,9 @@ register_tzi_to_tzi (RegTZI *reg, TIME_ZONE_INFORMATION *tzi)
 }
 
 static gint
-rules_from_windows_time_zone (const gchar *identifier, TimeZoneRule **rules)
+rules_from_windows_time_zone (const gchar   *identifier,
+                              gchar        **out_identifier,
+                              TimeZoneRule **rules)
 {
   HKEY key;
   gchar *subkey, *subkey_dynamic;
@@ -623,6 +669,10 @@ rules_from_windows_time_zone (const gchar *identifier, TimeZoneRule **rules)
   gint rules_num = 0;
   RegTZI regtzi, regtzi_prev;
 
+  g_assert (out_identifier != NULL);
+  g_assert (rules != NULL);
+
+  *out_identifier = NULL;
   *rules = NULL;
   key_name = NULL;
 
@@ -720,7 +770,6 @@ failed:
 
   g_free (subkey_dynamic);
   g_free (subkey);
-  g_free (key_name);
 
   if (*rules)
     {
@@ -730,10 +779,14 @@ failed:
       else
         (*rules)[rules_num - 1].start_year = (*rules)[rules_num - 2].start_year + 1;
 
+      *out_identifier = g_steal_pointer (&key_name);
+
       return rules_num;
     }
-  else
+
-    return 0;
+  g_free (key_name);
+
+  return 0;
 }
 
 #endif
@@ -834,7 +887,8 @@ fill_transition_info_from_rule (TransitionInfo *info,
 static void
 init_zone_from_rules (GTimeZone    *gtz,
                       TimeZoneRule *rules,
-                      gint          rules_num)
+                      gint          rules_num,
+                      gchar        *identifier  /* (transfer full) */)
 {
   guint type_count = 0, trans_count = 0, info_index = 0;
   guint ri; /* rule index */
@@ -859,6 +913,7 @@ init_zone_from_rules (GTimeZone    *gtz,
         type_count++;
     }
 
+  gtz->name = g_steal_pointer (&identifier);
   gtz->t_info = g_array_sized_new (FALSE, TRUE, sizeof (TransitionInfo), type_count);
   gtz->transitions = g_array_sized_new (FALSE, TRUE, sizeof (Transition), trans_count);
 
@@ -1217,11 +1272,18 @@ parse_identifier_boundaries (gchar **pos, TimeZoneRule *tzr)
  */
 static gint
 rules_from_identifier (const gchar   *identifier,
+                       gchar        **out_identifier,
                        TimeZoneRule **rules)
 {
   gchar *pos;
   TimeZoneRule tzr;
 
+  g_assert (out_identifier != NULL);
+  g_assert (rules != NULL);
+
+  *out_identifier = NULL;
+  *rules = NULL;
+
   if (!identifier)
     return 0;
 
@@ -1233,7 +1295,10 @@ rules_from_identifier (const gchar   *identifier,
     return 0;
 
   if (*pos == 0)
-    return create_ruleset_from_rule (rules, &tzr);
+    {
+      *out_identifier = g_strdup (identifier);
+      return create_ruleset_from_rule (rules, &tzr);
+    }
 
   /* Format 2 */
   if (!(set_tz_name (&pos, tzr.dlt_name, NAME_SIZE)))
@@ -1251,6 +1316,7 @@ rules_from_identifier (const gchar   *identifier,
 
       /* Use US rules, Windows' default is Pacific Standard Time */
       if ((rules_num = rules_from_windows_time_zone ("Pacific Standard Time",
+                                                     out_identifier,
                                                      rules)))
         {
           for (i = 0; i < rules_num - 1; i++)
@@ -1273,6 +1339,7 @@ rules_from_identifier (const gchar   *identifier,
   if (!parse_identifier_boundaries (&pos, &tzr))
     return 0;
 
+  *out_identifier = g_strdup (identifier);
   return create_ruleset_from_rule (rules, &tzr);
 }
 
@@ -1355,6 +1422,7 @@ g_time_zone_new (const gchar *identifier)
   GTimeZone *tz = NULL;
   TimeZoneRule *rules;
   gint rules_num;
+  gchar *resolved_identifier = NULL;
 
   G_LOCK (time_zones);
   if (time_zones == NULL)
@@ -1372,42 +1440,41 @@ g_time_zone_new (const gchar *identifier)
     }
 
   tz = g_slice_new0 (GTimeZone);
-  tz->name = g_strdup (identifier);
   tz->ref_count = 0;
 
   zone_for_constant_offset (tz, identifier);
 
   if (tz->t_info == NULL &&
-      (rules_num = rules_from_identifier (identifier, &rules)))
+      (rules_num = rules_from_identifier (identifier, &resolved_identifier, &rules)))
     {
-      init_zone_from_rules (tz, rules, rules_num);
+      init_zone_from_rules (tz, rules, rules_num, g_steal_pointer (&resolved_identifier));
       g_free (rules);
     }
 
   if (tz->t_info == NULL)
     {
 #ifdef G_OS_UNIX
-      GBytes *zoneinfo = zone_info_unix (identifier);
+      GBytes *zoneinfo = zone_info_unix (identifier, &resolved_identifier);
-      if (!zoneinfo)
+      if (zoneinfo != NULL)
-        zone_for_constant_offset (tz, "UTC");
-      else
         {
-          init_zone_from_iana_info (tz, zoneinfo);
+          init_zone_from_iana_info (tz, zoneinfo, g_steal_pointer (&resolved_identifier));
           g_bytes_unref (zoneinfo);
         }
 #elif defined (G_OS_WIN32)
-      if ((rules_num = rules_from_windows_time_zone (identifier, &rules)))
+      if ((rules_num = rules_from_windows_time_zone (identifier,
+                                                     &resolved_identifier,
+                                                     &rules)))
         {
-          init_zone_from_rules (tz, rules, rules_num);
+          init_zone_from_rules (tz, rules, rules_num, g_steal_pointer (&resolved_identifier));
           g_free (rules);
         }
+#endif
     }
 
+#if defined (G_OS_WIN32)
   if (tz->t_info == NULL)
     {
-      if (identifier)
+      if (identifier == NULL)
-        zone_for_constant_offset (tz, "UTC");
-      else
         {
           TIME_ZONE_INFORMATION tzi;
 
@@ -1423,13 +1490,22 @@ g_time_zone_new (const gchar *identifier)
               rules[0].start_year = MIN_TZYEAR;
               rules[1].start_year = MAX_TZYEAR;
 
-              init_zone_from_rules (tz, rules, 2);
+              init_zone_from_rules (tz, rules, 2, windows_default_tzname ());
 
               g_free (rules);
             }
         }
-#endif
     }
+#endif
+
+  g_free (resolved_identifier);
+
+  /* Always fall back to UTC. */
+  if (tz->t_info == NULL)
+    zone_for_constant_offset (tz, "UTC");
+
+  g_assert (tz->name != NULL);
+  g_assert (tz->t_info != NULL);
 
   if (tz->t_info != NULL)
     {
@@ -1835,5 +1911,29 @@ g_time_zone_is_dst (GTimeZone *tz,
   return interval_isdst (tz, (guint)interval);
 }
 
+/**
+ * g_time_zone_get_identifier:
+ * @tz: a #GTimeZone
+ *
+ * Get the identifier of this #GTimeZone, as passed to g_time_zone_new().
+ * If the identifier passed at construction time was not recognised, `UTC` will
+ * be returned. If it was %NULL, the identifier of the local timezone at
+ * construction time will be returned.
+ *
+ * The identifier will be returned in the same format as provided at
+ * construction time: if provided as a time offset, that will be returned by
+ * this function.
+ *
+ * Returns: identifier for this timezone
+ * Since: 2.58
+ */
+const gchar *
+g_time_zone_get_identifier (GTimeZone *tz)
+{
+  g_return_val_if_fail (tz != NULL, NULL);
+
+  return tz->name;
+}
+
 /* Epilogue {{{1 */
 /* vim:set foldmethod=marker: */

glib/gtimezone.h

@@ -83,6 +83,8 @@ gint32                  g_time_zone_get_offset                          (GTimeZo
 GLIB_AVAILABLE_IN_ALL
 gboolean                g_time_zone_is_dst                              (GTimeZone   *tz,
                                                                          gint         interval);
+GLIB_AVAILABLE_IN_2_58
+const gchar *           g_time_zone_get_identifier                      (GTimeZone   *tz);
 
 G_END_DECLS
 

glib/tests/gdatetime.c

@@ -1024,7 +1024,7 @@ test_GDateTime_get_second (void)
 static void
 test_GDateTime_new_full (void)
 {
-  GTimeZone *tz;
+  GTimeZone *tz, *dt_tz;
   GDateTime *dt;
 
   dt = g_date_time_new_utc (2009, 12, 11, 12, 11, 10);
@@ -1042,7 +1042,11 @@ test_GDateTime_new_full (void)
   tz = g_time_zone_new ("Pacific Standard Time");
 #endif
   dt = g_date_time_new (tz, 2010, 11, 24, 8, 4, 0);
-  g_time_zone_unref (tz);
+
+  dt_tz = g_date_time_get_timezone (dt);
+  g_assert_cmpstr (g_time_zone_get_identifier (dt_tz), ==,
+                   g_time_zone_get_identifier (tz));
+
   g_assert_cmpint (2010, ==, g_date_time_get_year (dt));
   g_assert_cmpint (11, ==, g_date_time_get_month (dt));
   g_assert_cmpint (24, ==, g_date_time_get_day_of_month (dt));
@@ -1051,12 +1055,16 @@ test_GDateTime_new_full (void)
   g_assert_cmpint (0, ==, g_date_time_get_second (dt));
 #ifdef G_OS_UNIX
   g_assert_cmpstr ("PST", ==, g_date_time_get_timezone_abbreviation (dt));
+  g_assert_cmpstr ("America/Tijuana", ==, g_time_zone_get_identifier (dt_tz));
 #elif defined G_OS_WIN32
   g_assert_cmpstr ("Pacific Standard Time", ==,
                     g_date_time_get_timezone_abbreviation (dt));
+  g_assert_cmpstr ("Pacific Standard Time", ==,
+                   g_time_zone_get_identifier (dt_tz));
 #endif
   g_assert (!g_date_time_is_daylight_savings (dt));
   g_date_time_unref (dt);
+  g_time_zone_unref (tz);
 
   /* Check month limits */
   dt = g_date_time_new_utc (2016, 1, 31, 22, 10, 42);
@@ -2084,6 +2092,7 @@ test_no_header (void)
 
   tz = g_time_zone_new ("blabla");
 
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "UTC");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 0);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2098,12 +2107,14 @@ test_posix_parse (void)
   GDateTime *gdt1, *gdt2;
 
   tz = g_time_zone_new ("PST");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "UTC");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 0);
   g_assert (!g_time_zone_is_dst (tz, 0));
   g_time_zone_unref (tz);
 
   tz = g_time_zone_new ("PST8");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "PST8");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "PST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, - 8 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2113,6 +2124,7 @@ test_posix_parse (void)
  * but passes anyway because PST8PDT is a zone name.
  */
   tz = g_time_zone_new ("PST8PDT");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "PST8PDT");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "PST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, - 8 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2123,6 +2135,7 @@ test_posix_parse (void)
 
   tz = g_time_zone_new ("PST8PDT6:32:15");
 #ifdef G_OS_WIN32
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "PST8PDT6:32:15");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "PST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, - 8 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2138,6 +2151,7 @@ test_posix_parse (void)
   g_date_time_unref (gdt1);
   g_date_time_unref (gdt2);
 #else
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "UTC");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 0);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2145,6 +2159,7 @@ test_posix_parse (void)
   g_time_zone_unref (tz);
 
   tz = g_time_zone_new ("NZST-12:00:00NZDT-13:00:00,M10.1.0,M3.3.0");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "NZST-12:00:00NZDT-13:00:00,M10.1.0,M3.3.0");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "NZST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 12 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2170,6 +2185,7 @@ test_posix_parse (void)
   g_time_zone_unref (tz);
 
   tz = g_time_zone_new ("NZST-12:00:00NZDT-13:00:00,280,77");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "NZST-12:00:00NZDT-13:00:00,280,77");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "NZST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 12 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2195,6 +2211,7 @@ test_posix_parse (void)
   g_time_zone_unref (tz);
 
   tz = g_time_zone_new ("NZST-12:00:00NZDT-13:00:00,J279,J76");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "NZST-12:00:00NZDT-13:00:00,J279,J76");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "NZST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 12 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2220,6 +2237,7 @@ test_posix_parse (void)
   g_time_zone_unref (tz);
 
   tz = g_time_zone_new ("NZST-12:00:00NZDT-13:00:00,M10.1.0/07:00,M3.3.0/07:00");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "NZST-12:00:00NZDT-13:00:00,M10.1.0/07:00,M3.3.0/07:00");
   g_assert_cmpstr (g_time_zone_get_abbreviation (tz, 0), ==, "NZST");
   g_assert_cmpint (g_time_zone_get_offset (tz, 0), ==, 12 * 3600);
   g_assert (!g_time_zone_is_dst (tz, 0));
@@ -2278,12 +2296,72 @@ test_GDateTime_floating_point (void)
   g_test_bug ("697715");
 
   tz = g_time_zone_new ("-03:00");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "-03:00");
   dt = g_date_time_new (tz, 2010, 5, 24,  8, 0, 1.000001);
   g_time_zone_unref (tz);
   g_assert_cmpint (g_date_time_get_microsecond (dt), ==, 1);
   g_date_time_unref (dt);
 }
 
+/* Check that g_time_zone_get_identifier() returns the identifier given to
+ * g_time_zone_new(), or "UTC" if loading the timezone failed. */
+static void
+test_identifier (void)
+{
+  GTimeZone *tz;
+  gchar *old_tz = g_strdup (g_getenv ("TZ"));
+
+  tz = g_time_zone_new ("UTC");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
+  g_time_zone_unref (tz);
+
+  tz = g_time_zone_new_utc ();
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
+  g_time_zone_unref (tz);
+
+  tz = g_time_zone_new ("some rubbish");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
+  g_time_zone_unref (tz);
+
+  tz = g_time_zone_new ("Z");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "Z");
+  g_time_zone_unref (tz);
+
+  tz = g_time_zone_new ("+03:15");
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "+03:15");
+  g_time_zone_unref (tz);
+
+  /* System timezone. We can’t change this, but we can at least assert that
+   * the identifier is non-NULL and doesn’t start with a slash. */
+  tz = g_time_zone_new (NULL);
+  g_assert_nonnull (g_time_zone_get_identifier (tz));
+  g_assert_cmpstr (g_time_zone_get_identifier (tz), !=, "");
+  g_assert_true (*g_time_zone_get_identifier (tz) != '/');
+  g_time_zone_unref (tz);
+
+  /* Local timezone tests. */
+  if (g_setenv ("TZ", "America/Recife", TRUE))
+    {
+      tz = g_time_zone_new_local ();
+      g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "America/Recife");
+      g_time_zone_unref (tz);
+    }
+
+  if (g_setenv ("TZ", "some rubbish", TRUE))
+    {
+      tz = g_time_zone_new_local ();
+      g_assert_cmpstr (g_time_zone_get_identifier (tz), ==, "UTC");
+      g_time_zone_unref (tz);
+    }
+
+  if (old_tz != NULL)
+    g_assert_true (g_setenv ("TZ", old_tz, TRUE));
+  else
+    g_unsetenv ("TZ");
+
+  g_free (old_tz);
+}
+
 gint
 main (gint   argc,
       gchar *argv[])
@@ -2345,6 +2423,7 @@ main (gint   argc,
   g_test_add_func ("/GTimeZone/no-header", test_no_header);
   g_test_add_func ("/GTimeZone/posix-parse", test_posix_parse);
   g_test_add_func ("/GTimeZone/floating-point", test_GDateTime_floating_point);
+  g_test_add_func ("/GTimeZone/identifier", test_identifier);
 
   return g_test_run ();
 }