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mktime: do not assume 'long' is wide enough

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* time/mktime.c (verify): Move decl up.
(long_int): New type.
(leapyear, ydhms_diff, guess_time_tm, __mktime_internal): Use it,
to remove assumption in the code that 'long' is wide enough to
store year values.  This assumption is not true on x32 and on
some non-glibc platforms.
This commit is contained in:
Paul Eggert 2012-03-16 02:48:38 -07:00
parent 62bdf9a683
commit f04dfbc244
2 changed files with 26 additions and 12 deletions
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8
ChangeLog
View File

@ -1,5 +1,13 @@
2012-05-23 Paul Eggert <eggert@cs.ucla.edu>
mktime: do not assume 'long' is wide enough
* time/mktime.c (verify): Move decl up.
(long_int): New type.
(leapyear, ydhms_diff, guess_time_tm, __mktime_internal): Use it,
to remove assumption in the code that 'long' is wide enough to
store year values. This assumption is not true on x32 and on
some non-glibc platforms.
mktime: merge wrapv change from gnulib
* time/mktime.c (WRAPV): New macro.
(time_t_avg, time_t_add_ok, time_t_int_add_ok): New static functions.

30
time/mktime.c
View File

@ -68,6 +68,17 @@
# endif
#endif
/* Verify a requirement at compile-time (unlike assert, which is runtime). */
#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
/* A signed type that is at least one bit wider than int. */
#if INT_MAX <= LONG_MAX / 2
typedef long int long_int;
#else
typedef long long int long_int;
#endif
verify (long_int_is_wide_enough, INT_MAX == INT_MAX * (long_int) 2 / 2);
/* Shift A right by B bits portably, by dividing A by 2**B and
truncating towards minus infinity. A and B should be free of side
effects, and B should be in the range 0 <= B <= INT_BITS - 2, where
@ -124,9 +135,6 @@
#endif
#define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1)
/* Verify a requirement at compile-time (unlike assert, which is runtime). */
#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
verify (time_t_is_integer, TYPE_IS_INTEGER (time_t));
verify (twos_complement_arithmetic, TYPE_TWOS_COMPLEMENT (int));
@ -136,7 +144,7 @@ verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0);
/* Return 1 if YEAR + TM_YEAR_BASE is a leap year. */
static inline int
leapyear (long int year)
leapyear (long_int year)
{
/* Don't add YEAR to TM_YEAR_BASE, as that might overflow.
Also, work even if YEAR is negative. */
@ -182,12 +190,10 @@ const unsigned short int __mon_yday[2][13] =
detect overflow. */
static inline time_t
ydhms_diff (long int year1, long int yday1, int hour1, int min1, int sec1,
ydhms_diff (long_int year1, long_int yday1, int hour1, int min1, int sec1,
int year0, int yday0, int hour0, int min0, int sec0)
{
verify (C99_integer_division, -1 / 2 == 0);
verify (long_int_year_and_yday_are_wide_enough,
INT_MAX <= LONG_MAX / 2 || TIME_T_MAX <= UINT_MAX);
/* Compute intervening leap days correctly even if year is negative.
Take care to avoid integer overflow here. */
@ -265,7 +271,7 @@ time_t_int_add_ok (time_t a, int b)
If overflow occurs, yield the minimal or maximal value, except do not
yield a value equal to *T. */
static time_t
guess_time_tm (long int year, long int yday, int hour, int min, int sec,
guess_time_tm (long_int year, long_int yday, int hour, int min, int sec,
const time_t *t, const struct tm *tp)
{
if (tp)
@ -368,8 +374,8 @@ __mktime_internal (struct tm *tp,
int mon_remainder = mon % 12;
int negative_mon_remainder = mon_remainder < 0;
int mon_years = mon / 12 - negative_mon_remainder;
long int lyear_requested = year_requested;
long int year = lyear_requested + mon_years;
long_int lyear_requested = year_requested;
long_int year = lyear_requested + mon_years;
/* The other values need not be in range:
the remaining code handles minor overflows correctly,
@ -381,8 +387,8 @@ __mktime_internal (struct tm *tp,
int mon_yday = ((__mon_yday[leapyear (year)]
[mon_remainder + 12 * negative_mon_remainder])
- 1);
long int lmday = mday;
long int yday = mon_yday + lmday;
long_int lmday = mday;
long_int yday = mon_yday + lmday;
time_t guessed_offset = *offset;