* mktime.c: Fix some boundary cases and remove need for floating point.

diff --git a/lib/ChangeLog b/lib/ChangeLog
index 2660556645564b3a757bf51884c67d833d4f33a4..feb12ae5bb756d7a505ee8eaf663a8aaee348d80 100644 (file)
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,58 @@
+2003-07-07  Paul Eggert  <eggert@twinsun.com>
+
+       * mktime.c: Fix some boundary cases and remove need for floating point.
+
+       Issue a compile-time diagnostic if time_t is floating point, or if
+       two's complement arithmetic is not in effect, or if arithmetic
+       right shift does not propagate the sign.  These assumptions were
+       all in the original code but they weren't checked.
+
+       (TIME_T_MIDPOINT, verify): New macros.
+       (__isleap): Remove; it has integer overflow problems.
+       (leapyear): New function, without those problems.
+       (ydhms_tm_diff): Remove; splitting into two parts.
+       (ydhms_diff): New function, containing the arithmetic part of
+       the old ydhms_tm_diff function.  Issue a compile-time
+       diagnostic if we are not using C99 integer division.
+       Avoid casts when possible.
+       (guess_time_tm): New function, containing the checking part of
+       the old ydhms_tm_diff function.  Return the new value, rather than
+       the difference between it and the old.  Accept a new argument T
+       so that *T specifies the old value.  Check for overflow in the result.
+
+       (__mktime_internal): Use a time_t offset, not a long int offset.
+       This undoes the 2003-06-04 change, which is no longer needed now
+       that we have better overflow checking.
+       (localtime_offset): Likewise.
+       
+       (__mktime_internal): Avoid harmful overflow on hosts where time_t
+       and long are 64-bit but int is only 32-bit.
+       (ydhms_diff): Use long int to store year1 and yday1.
+       Issue a compile-time diagnostic if long int is not wide enough.
+
+       (__mktime_internal): Use long int to store adjusted year and yday.
+       Use plain C rather than preprocessor commands, if that doesn't
+       affect efficiency.
+       Check for overflow (and try to repair) after each probe
+       rather than checking only at the very end.  This avoids some bugs
+       (e.g., southern hemisphere, behind GMT, and GMT offset at minimum time
+       does not equal GMT offset at maximum time).
+       Use integer to check for overflow rather than floating point; this
+       is more portable to non-IEEE hosts, and is a tad faster.
+       When we detect that we are oscillating between two values,
+       don't check whether tm_isdst has the requested value, since
+       we already know the answer.  When tm_isdst has the wrong value,
+       use a different heuristic to find the right one, based on the
+       extreme values actually observed in practice in tz2003a,
+       rather than the (overly optimistic) "previous 3 calendar quarters".
+
+       (not_equal_tm, print_tm, check_result): Use "const T" rather than
+       "T const" to accommodate glibc style.
+       (check_result): Use less-confusing report format.  "long" -> "long int.
+       (main): Likewise.
+       Don't loop if the iteration overflows time_t.
+       Allow a negative step in the iteration.
+       
 2003-07-01  Paul Eggert  <eggert@twinsun.com>
 
        * xreadlink.c: Include <sys/types.h> unconditionally, instead of
@@ -106,6 +161,11 @@
 
 2003-06-05  Paul Eggert  <eggert@twinsun.com>
 
+       * mktime.c (__mktime_internal): When resolving a tm_isdst
+       mismatch, look in future quarters as well as past.  This fixes a
+       bug when processing fall-backwards gaps immediately after a long
+       period of daylight-saving time.
+
        * mktime.c: Assume freestanding C89 or better.
        (HAVE_LIMITS_H): Remove.  Assume it's 1.
        (__P): Remove; not used.