.

[gnulib.git] / lib / mktime.c

diff --git a/lib/mktime.c b/lib/mktime.c
index 3803f5c..b2e6387 100644 (file)
--- a/lib/mktime.c
+++ b/lib/mktime.c
@@ -1,4 +1,4 @@
-/* mktime: convert a `struct tm' to a time_t value  zzzzzz
+/* mktime: convert a `struct tm' to a time_t value
    Copyright (C) 1993-1997, 1998 Free Software Foundation, Inc.
    Contributed by Paul Eggert (eggert@twinsun.com).
 
@@ -28,14 +28,8 @@
 # include <config.h>
 #endif
 
-/* Some systems need this in order to declare localtime_r properly.  */
-#ifndef _REENTRANT
-# define _REENTRANT 1
-#endif
-
 #ifdef _LIBC
 # define HAVE_LIMITS_H 1
-# define HAVE_LOCALTIME_R 1
 # define STDC_HEADERS 1
 #endif
 
@@ -125,16 +119,14 @@ time_t __mktime_internal __P ((struct tm *,
 
 
 #ifdef _LIBC
-# define localtime_r __localtime_r
+# define my_mktime_localtime_r __localtime_r
 #else
-# if ! HAVE_LOCALTIME_R && ! defined localtime_r
-/* Approximate localtime_r as best we can in its absence.  */
-#  define localtime_r my_mktime_localtime_r
-static struct tm *localtime_r __P ((const time_t *, struct tm *));
+/* If we're a mktime substitute in a GNU program, then prefer
+   localtime to localtime_r, since many localtime_r implementations
+   are buggy.  */
+static struct tm *my_mktime_localtime_r __P ((const time_t *, struct tm *));
 static struct tm *
-localtime_r (t, tp)
-     const time_t *t;
-     struct tm *tp;
+my_mktime_localtime_r (const time_t *t, struct tm *tp)
 {
   struct tm *l = localtime (t);
   if (! l)
@@ -142,7 +134,6 @@ localtime_r (t, tp)
   *tp = *l;
   return tp;
 }
-# endif /* ! HAVE_LOCALTIME_R && ! defined (localtime_r) */
 #endif /* ! _LIBC */
 
 
@@ -153,9 +144,8 @@ localtime_r (t, tp)
    If TP is null, return a nonzero value.
    If overflow occurs, yield the low order bits of the correct answer.  */
 static time_t
-ydhms_tm_diff (year, yday, hour, min, sec, tp)
-     int year, yday, hour, min, sec;
-     const struct tm *tp;
+ydhms_tm_diff (int year, int yday, int hour, int min, int sec,
+              const struct tm *tp)
 {
   if (!tp)
     return 1;
@@ -187,8 +177,7 @@ static time_t localtime_offset;
 
 /* Convert *TP to a time_t value.  */
 time_t
-mktime (tp)
-     struct tm *tp;
+mktime (struct tm *tp)
 {
 #ifdef _LIBC
   /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
@@ -197,17 +186,15 @@ mktime (tp)
   __tzset ();
 #endif
 
-  return __mktime_internal (tp, localtime_r, &localtime_offset);
+  return __mktime_internal (tp, my_mktime_localtime_r, &localtime_offset);
 }
 
 /* Use CONVERT to convert *T to a broken down time in *TP.
    If *T is out of range for conversion, adjust it so that
    it is the nearest in-range value and then convert that.  */
 static struct tm *
-ranged_convert (convert, t, tp)
-     struct tm *(*convert) __P ((const time_t *, struct tm *));
-     time_t *t;
-     struct tm *tp;
+ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
+               time_t *t, struct tm *tp)
 {
   struct tm *r;
 
@@ -254,19 +241,18 @@ ranged_convert (convert, t, tp)
    compared to what the result would be for UTC without leap seconds.
    If *OFFSET's guess is correct, only one CONVERT call is needed.  */
 time_t
-__mktime_internal (tp, convert, offset)
-     struct tm *tp;
-     struct tm *(*convert) __P ((const time_t *, struct tm *));
-     time_t *offset;
+__mktime_internal (struct tm *tp,
+                  struct tm *(*convert) (const time_t *, struct tm *),
+                  time_t *offset)
 {
-  time_t t, dt, t0;
+  time_t t, dt, t0, t1, t2;
   struct tm tm;
 
   /* The maximum number of probes (calls to CONVERT) should be enough
      to handle any combinations of time zone rule changes, solar time,
-     and leap seconds.  POSIX.1 prohibits leap seconds, but some hosts
-     have them anyway.  */
-  int remaining_probes = 4;
+     leap seconds, and oscillations around a spring-forward gap.
+     POSIX.1 prohibits leap seconds, but some hosts have them anyway.  */
+  int remaining_probes = 6;
 
   /* Time requested.  Copy it in case CONVERT modifies *TP; this can
      occur if TP is localtime's returned value and CONVERT is localtime.  */
@@ -312,15 +298,27 @@ __mktime_internal (tp, convert, offset)
   tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
   t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm);
 
-  for (t = t0 + *offset;
+  for (t = t1 = t2 = t0 + *offset;
        (dt = ydhms_tm_diff (year, yday, hour, min, sec,
                            ranged_convert (convert, &t, &tm)));
-       t += dt)
-    if (--remaining_probes == 0)
+       t1 = t2, t2 = t, t += dt)
+    if (t == t1 && t != t2
+       && (isdst < 0 || tm.tm_isdst < 0
+           || (isdst != 0) != (tm.tm_isdst != 0)))
+      /* We can't possibly find a match, as we are oscillating
+        between two values.  The requested time probably falls
+        within a spring-forward gap of size DT.  Follow the common
+        practice in this case, which is to return a time that is DT
+        away from the requested time, preferring a time whose
+        tm_isdst differs from the requested value.  In practice,
+        this is more useful than returning -1.  */
+      break;
+    else if (--remaining_probes == 0)
       return -1;
 
-  /* Check whether tm.tm_isdst has the requested value, if any.  */
-  if (0 <= isdst && 0 <= tm.tm_isdst)
+  /* If we have a match, check whether tm.tm_isdst has the requested
+     value, if any.  */
+  if (dt == 0 && 0 <= isdst && 0 <= tm.tm_isdst)
     {
       int dst_diff = (isdst != 0) - (tm.tm_isdst != 0);
       if (dst_diff)
@@ -531,6 +529,6 @@ main (argc, argv)
 \f
 /*
 Local Variables:
-compile-command: "gcc -DDEBUG -D__EXTENSIONS__ -DHAVE_LIMITS_H -DHAVE_LOCALTIME_R -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"
+compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"
 End:
 */