Merge branch 'lukas/22/erts/fix-localtime-tz-change/OTP-18076' into maint

* lukas/22/erts/fix-localtime-tz-change/OTP-18076:
  erts: Fix localtime_r summer/winter-time change bug

1 files changed, 21 insertions, 0 deletions

diff --git a/erts/emulator/sys/unix/erl_unix_sys.h b/erts/emulator/sys/unix/erl_unix_sys.h
index 7cddd4e2b7..9287808370 100644
--- a/erts/emulator/sys/unix/erl_unix_sys.h
+++ b/erts/emulator/sys/unix/erl_unix_sys.h
@@ -318,6 +318,27 @@ int sys_stop_hrvtime(void);
 /* No use in having other resolutions than 1 Ms. */
 #define SYS_CLOCK_RESOLUTION 1
 
+ERTS_GLB_INLINE struct tm *sys_localtime_r(time_t *the_clock, struct tm *buff);
+
+#if ERTS_GLB_INLINE_INCL_FUNC_DEF
+
+ERTS_GLB_INLINE struct tm *sys_localtime_r(time_t *the_clock, struct tm *buff) {
+#ifdef HAVE_LOCALTIME_R
+    tzset(); /* POSIX.1-2004 does not require tzset to be called within
+                localtime_r, so if summer/winter-time has passed localtime_r
+                will return the time when Erlang was started. So we need to
+                call tzset() before all localtime_r calls.
+
+                localtime already calls tzset for each call, so the performance
+                penalty should be acceptable.... */
+    return localtime_r(the_clock, buff);
+#else
+    return localtime(the_clock);
+#endif
+}
+
+#endif /* ERTS_GLB_INLINE_INCL_FUNC_DEF */
+
 /* These are defined in sys.c */
 typedef void (*SIGFUNC)(int);
 extern SIGFUNC sys_signal(int, SIGFUNC);