Adjust the calculated GMT offset on get_offset() for daylight savings time.

This only affects platforms that do not have a tm_gmtoff field in struct tm
(e.g., Solaris 2.6, HP-UX 10.20, ...).


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@61843 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 12 insertions, 2 deletions

diff --git a/time/unix/time.c b/time/unix/time.c
index a39ca75a8..35a9161f6 100644
--- a/time/unix/time.c
+++ b/time/unix/time.c
@@ -77,18 +77,28 @@ static apr_int32_t get_offset(struct tm *tm)
 #elif defined(HAVE___OFFSET)
     return tm->__tm_gmtoff;
 #else
-    /* we don't have an offset field to use, so calculate it */
+    /* We don't have an offset field to use, so calculate it.
+       mktime() is the inverse of localtime(); so, presumably,
+       passing in a struct tm made by gmtime() let's us calculate
+       the true GMT offset. However, there's a catch: if daylight
+       savings is in effect, gmtime()will set the tm_isdst field
+       and confuse mktime() into returning a time that's offset
+       by one hour. In that case, we must adjust the calculated GMT
+       offset. */
     {
         time_t t1 = time(0), t2 = 0;
         struct tm t;
+        int was_dst;
 
 #if APR_HAS_THREADS && defined(_POSIX_THREAD_SAFE_FUNCTIONS)
         gmtime_r(&t1, &t);
 #else
         t = *gmtime(&t1);
 #endif
+        was_dst = (t.tm_isdst > 0);
+        t.tm_isdst = -1;
         t2 = mktime(&t);
-        return (apr_int32_t) difftime(t1, t2);
+        return (apr_int32_t) difftime(t1, t2) + (was_dst ? 3600 : 0);
     }
 #endif
 }