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mktime: make more room for overflow

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[BZ#23789]
* time/mktime.c (long_int): Now 4⨯ int, not just 3⨯.
This is so that we can add tm_diff results to a previous guess,
which will be useful in a later patch.
This commit is contained in:
Paul Eggert 2018-11-15 22:59:33 +01:00 committed by Albert ARIBAUD (3ADEV)
parent 6c90d759f6
commit efbdddc381
2 changed files with 17 additions and 9 deletions
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6
ChangeLog
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@ -1,5 +1,11 @@
2018-11-15 Paul Eggert <eggert@cs.ucla.edu>
mktime: make more room for overflow
[BZ#23789]
* time/mktime.c (long_int): Now 4⨯ int, not just 3⨯.
This is so that we can add tm_diff results to a previous guess,
which will be useful in a later patch.
mktime: simplify offset guess
[BZ#23789]
* time/mktime.c (__mktime_internal): Omit excess precision.

20
time/mktime.c
View File

@ -120,11 +120,12 @@ my_tzset (void)
#if defined _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_INTERNAL
/* A signed type that can represent an integer number of years
multiplied by three times the number of seconds in a year. It is
multiplied by four times the number of seconds in a year. It is
needed when converting a tm_year value times the number of seconds
in a year. The factor of three comes because these products need
in a year. The factor of four comes because these products need
to be subtracted from each other, and sometimes with an offset
added to them, without worrying about overflow.
added to them, and then with another timestamp added, without
worrying about overflow.
Much of the code uses long_int to represent time_t values, to
lessen the hassle of dealing with platforms where time_t is
@ -132,12 +133,12 @@ my_tzset (void)
time_t values that mktime can generate even on platforms where
time_t is excessively wide. */
#if INT_MAX <= LONG_MAX / 3 / 366 / 24 / 60 / 60
#if INT_MAX <= LONG_MAX / 4 / 366 / 24 / 60 / 60
typedef long int long_int;
#else
typedef long long int long_int;
#endif
verify (INT_MAX <= TYPE_MAXIMUM (long_int) / 3 / 366 / 24 / 60 / 60);
verify (INT_MAX <= TYPE_MAXIMUM (long_int) / 4 / 366 / 24 / 60 / 60);
/* Shift A right by B bits portably, by dividing A by 2**B and
truncating towards minus infinity. B should be in the range 0 <= B
@ -211,9 +212,10 @@ isdst_differ (int a, int b)
were not adjusted between the timestamps.
The YEAR values uses the same numbering as TP->tm_year. Values
need not be in the usual range. However, YEAR1 must not overflow
when multiplied by three times the number of seconds in a year, and
likewise for YDAY1 and three times the number of seconds in a day. */
need not be in the usual range. However, YEAR1 - YEAR0 must not
overflow even when multiplied by three times the number of seconds
in a year, and likewise for YDAY1 - YDAY0 and three times the
number of seconds in a day. */
static long_int
ydhms_diff (long_int year1, long_int yday1, int hour1, int min1, int sec1,
@ -403,7 +405,7 @@ __mktime_internal (struct tm *tp,
if (LEAP_SECONDS_POSSIBLE)
{
/* Handle out-of-range seconds specially,
since ydhms_tm_diff assumes every minute has 60 seconds. */
since ydhms_diff assumes every minute has 60 seconds. */
if (sec < 0)
sec = 0;
if (59 < sec)