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-rw-r--r--libc/time/mktime.c216
1 files changed, 145 insertions, 71 deletions
diff --git a/libc/time/mktime.c b/libc/time/mktime.c
index 683d46823..e1fbf9ea1 100644
--- a/libc/time/mktime.c
+++ b/libc/time/mktime.c
@@ -1,5 +1,5 @@
-/* Convert a `struct tm' to a time_t value.
- Copyright (C) 1993-1999, 2002-2007, 2008 Free Software Foundation, Inc.
+/* Convert a 'struct tm' to a time_t value.
+ Copyright (C) 1993-2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Paul Eggert <eggert@twinsun.com>.
@@ -21,18 +21,17 @@
mktime. */
/* #define DEBUG 1 */
-#ifdef HAVE_CONFIG_H
+#ifndef _LIBC
# include <config.h>
#endif
/* Assume that leap seconds are possible, unless told otherwise.
- If the host has a `zic' command with a `-L leapsecondfilename' option,
+ If the host has a 'zic' command with a '-L leapsecondfilename' option,
then it supports leap seconds; otherwise it probably doesn't. */
#ifndef LEAP_SECONDS_POSSIBLE
# define LEAP_SECONDS_POSSIBLE 1
#endif
-#include <sys/types.h> /* Some systems define `time_t' here. */
#include <time.h>
#include <limits.h>
@@ -43,9 +42,43 @@
# include <stdio.h>
# include <stdlib.h>
/* Make it work even if the system's libc has its own mktime routine. */
+# undef mktime
# define mktime my_mktime
#endif /* DEBUG */
+/* Some of the code in this file assumes that signed integer overflow
+ silently wraps around. This assumption can't easily be programmed
+ around, nor can it be checked for portably at compile-time or
+ easily eliminated at run-time.
+
+ Define WRAPV to 1 if the assumption is valid and if
+ #pragma GCC optimize ("wrapv")
+ does not trigger GCC bug 51793
+ <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51793>.
+ Otherwise, define it to 0; this forces the use of slower code that,
+ while not guaranteed by the C Standard, works on all production
+ platforms that we know about. */
+#ifndef WRAPV
+# if (((__GNUC__ == 4 && 4 <= __GNUC_MINOR__) || 4 < __GNUC__) \
+ && defined __GLIBC__)
+# pragma GCC optimize ("wrapv")
+# define WRAPV 1
+# else
+# define WRAPV 0
+# 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
@@ -56,9 +89,11 @@
implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift
right in the usual way when A < 0, so SHR falls back on division if
ordinary A >> B doesn't seem to be the usual signed shift. */
-#define SHR(a, b) \
- (-1 >> 1 == -1 \
- ? (a) >> (b) \
+#define SHR(a, b) \
+ ((-1 >> 1 == -1 \
+ && (long_int) -1 >> 1 == -1 \
+ && ((time_t) -1 >> 1 == -1 || ! TYPE_SIGNED (time_t))) \
+ ? (a) >> (b) \
: (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
/* The extra casts in the following macros work around compiler bugs,
@@ -69,12 +104,8 @@
#define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
/* True if negative values of the signed integer type T use two's
- complement, ones' complement, or signed magnitude representation,
- respectively. Much GNU code assumes two's complement, but some
- people like to be portable to all possible C hosts. */
+ complement, or if T is an unsigned integer type. */
#define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
-#define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)
-#define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)
/* True if the arithmetic type T is signed. */
#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
@@ -86,13 +117,11 @@
#define TYPE_MINIMUM(t) \
((t) (! TYPE_SIGNED (t) \
? (t) 0 \
- : TYPE_SIGNED_MAGNITUDE (t) \
- ? ~ (t) 0 \
- : ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1)))
+ : ~ TYPE_MAXIMUM (t)))
#define TYPE_MAXIMUM(t) \
((t) (! TYPE_SIGNED (t) \
? (t) -1 \
- : ~ (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))))
+ : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))
#ifndef TIME_T_MIN
# define TIME_T_MIN TYPE_MINIMUM (time_t)
@@ -102,14 +131,11 @@
#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));
-/* The code also assumes that signed integer overflow silently wraps
- around, but this assumption can't be stated without causing a
- diagnostic on some hosts. */
+verify (twos_complement_arithmetic,
+ (TYPE_TWOS_COMPLEMENT (int)
+ && TYPE_TWOS_COMPLEMENT (long_int)
+ && TYPE_TWOS_COMPLEMENT (time_t)));
#define EPOCH_YEAR 1970
#define TM_YEAR_BASE 1900
@@ -117,7 +143,7 @@ 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. */
@@ -141,16 +167,24 @@ const unsigned short int __mon_yday[2][13] =
#ifndef _LIBC
-/* Portable standalone applications should supply a "time_r.h" that
+/* Portable standalone applications should supply a <time.h> that
declares a POSIX-compliant localtime_r, for the benefit of older
implementations that lack localtime_r or have a nonstandard one.
See the gnulib time_r module for one way to implement this. */
-# include "time_r.h"
# undef __localtime_r
# define __localtime_r localtime_r
# define __mktime_internal mktime_internal
+# include "mktime-internal.h"
#endif
+/* Return 1 if the values A and B differ according to the rules for
+ tm_isdst: A and B differ if one is zero and the other positive. */
+static int
+isdst_differ (int a, int b)
+{
+ return (!a != !b) && (0 <= a) && (0 <= b);
+}
+
/* Return an integer value measuring (YEAR1-YDAY1 HOUR1:MIN1:SEC1) -
(YEAR0-YDAY0 HOUR0:MIN0:SEC0) in seconds, assuming that the clocks
were not adjusted between the time stamps.
@@ -163,12 +197,10 @@ 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. */
@@ -191,6 +223,53 @@ ydhms_diff (long int year1, long int yday1, int hour1, int min1, int sec1,
return seconds;
}
+/* Return the average of A and B, even if A + B would overflow. */
+static time_t
+time_t_avg (time_t a, time_t b)
+{
+ return SHR (a, 1) + SHR (b, 1) + (a & b & 1);
+}
+
+/* Return 1 if A + B does not overflow. If time_t is unsigned and if
+ B's top bit is set, assume that the sum represents A - -B, and
+ return 1 if the subtraction does not wrap around. */
+static int
+time_t_add_ok (time_t a, time_t b)
+{
+ if (! TYPE_SIGNED (time_t))
+ {
+ time_t sum = a + b;
+ return (sum < a) == (TIME_T_MIDPOINT <= b);
+ }
+ else if (WRAPV)
+ {
+ time_t sum = a + b;
+ return (sum < a) == (b < 0);
+ }
+ else
+ {
+ time_t avg = time_t_avg (a, b);
+ return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
+ }
+}
+
+/* Return 1 if A + B does not overflow. */
+static int
+time_t_int_add_ok (time_t a, int b)
+{
+ verify (int_no_wider_than_time_t, INT_MAX <= TIME_T_MAX);
+ if (WRAPV)
+ {
+ time_t sum = a + b;
+ return (sum < a) == (b < 0);
+ }
+ else
+ {
+ int a_odd = a & 1;
+ time_t avg = SHR (a, 1) + (SHR (b, 1) + (a_odd & b));
+ return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
+ }
+}
/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
assuming that *T corresponds to *TP and that no clock adjustments
@@ -199,7 +278,7 @@ ydhms_diff (long int year1, long int yday1, int hour1, int min1, int sec1,
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)
@@ -207,9 +286,8 @@ guess_time_tm (long int year, long int yday, int hour, int min, int sec,
time_t d = ydhms_diff (year, yday, hour, min, sec,
tp->tm_year, tp->tm_yday,
tp->tm_hour, tp->tm_min, tp->tm_sec);
- time_t t1 = *t + d;
- if ((t1 < *t) == (TYPE_SIGNED (time_t) ? d < 0 : TIME_T_MAX / 2 < d))
- return t1;
+ if (time_t_add_ok (*t, d))
+ return *t + d;
}
/* Overflow occurred one way or another. Return the nearest result
@@ -241,9 +319,7 @@ ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
they differ by 1. */
while (bad != ok + (bad < 0 ? -1 : 1))
{
- time_t mid = *t = (bad < 0
- ? bad + ((ok - bad) >> 1)
- : ok + ((bad - ok) >> 1));
+ time_t mid = *t = time_t_avg (ok, bad);
r = convert (t, tp);
if (r)
ok = mid;
@@ -292,9 +368,7 @@ __mktime_internal (struct tm *tp,
int mday = tp->tm_mday;
int mon = tp->tm_mon;
int year_requested = tp->tm_year;
- /* Normalize the value. */
- int isdst = ((tp->tm_isdst >> (8 * sizeof (tp->tm_isdst) - 1))
- | (tp->tm_isdst != 0));
+ int isdst = tp->tm_isdst;
/* 1 if the previous probe was DST. */
int dst2;
@@ -303,8 +377,8 @@ __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,
@@ -316,8 +390,8 @@ __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;
@@ -371,7 +445,7 @@ __mktime_internal (struct tm *tp,
int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM);
int diff = approx_biennia - approx_requested_biennia;
- int abs_diff = diff < 0 ? - diff : diff;
+ int approx_abs_diff = diff < 0 ? -1 - diff : diff;
/* IRIX 4.0.5 cc miscalculates TIME_T_MIN / 3: it erroneously
gives a positive value of 715827882. Setting a variable
@@ -382,15 +456,15 @@ __mktime_internal (struct tm *tp,
time_t overflow_threshold =
(time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM;
- if (overflow_threshold < abs_diff)
+ if (overflow_threshold < approx_abs_diff)
{
/* Overflow occurred. Try repairing it; this might work if
the time zone offset is enough to undo the overflow. */
time_t repaired_t0 = -1 - t0;
approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM);
diff = approx_biennia - approx_requested_biennia;
- abs_diff = diff < 0 ? - diff : diff;
- if (overflow_threshold < abs_diff)
+ approx_abs_diff = diff < 0 ? -1 - diff : diff;
+ if (overflow_threshold < approx_abs_diff)
return -1;
guessed_offset += repaired_t0 - t0;
t0 = repaired_t0;
@@ -424,7 +498,7 @@ __mktime_internal (struct tm *tp,
/* We have a match. Check whether tm.tm_isdst has the requested
value, if any. */
- if (isdst != tm.tm_isdst && 0 <= isdst && 0 <= tm.tm_isdst)
+ if (isdst_differ (isdst, tm.tm_isdst))
{
/* tm.tm_isdst has the wrong value. Look for a neighboring
time with the right value, and use its UTC offset.
@@ -457,22 +531,20 @@ __mktime_internal (struct tm *tp,
for (delta = stride; delta < delta_bound; delta += stride)
for (direction = -1; direction <= 1; direction += 2)
- {
- time_t ot = t + delta * direction;
- if ((ot < t) == (direction < 0))
- {
- struct tm otm;
- ranged_convert (convert, &ot, &otm);
- if (otm.tm_isdst == isdst)
- {
- /* We found the desired tm_isdst.
- Extrapolate back to the desired time. */
- t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm);
- ranged_convert (convert, &t, &tm);
- goto offset_found;
- }
- }
- }
+ if (time_t_int_add_ok (t, delta * direction))
+ {
+ time_t ot = t + delta * direction;
+ struct tm otm;
+ ranged_convert (convert, &ot, &otm);
+ if (! isdst_differ (isdst, otm.tm_isdst))
+ {
+ /* We found the desired tm_isdst.
+ Extrapolate back to the desired time. */
+ t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm);
+ ranged_convert (convert, &t, &tm);
+ goto offset_found;
+ }
+ }
}
offset_found:
@@ -483,11 +555,13 @@ __mktime_internal (struct tm *tp,
/* Adjust time to reflect the tm_sec requested, not the normalized value.
Also, repair any damage from a false match due to a leap second. */
int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec;
+ if (! time_t_int_add_ok (t, sec_requested))
+ return -1;
t1 = t + sec_requested;
+ if (! time_t_int_add_ok (t1, sec_adjustment))
+ return -1;
t2 = t1 + sec_adjustment;
- if (((t1 < t) != (sec_requested < 0))
- | ((t2 < t1) != (sec_adjustment < 0))
- | ! convert (&t2, &tm))
+ if (! convert (&t2, &tm))
return -1;
t = t2;
}
@@ -509,7 +583,7 @@ mktime (struct tm *tp)
{
#ifdef _LIBC
/* POSIX.1 8.1.1 requires that whenever mktime() is called, the
- time zone names contained in the external variable `tzname' shall
+ time zone names contained in the external variable 'tzname' shall
be set as if the tzset() function had been called. */
__tzset ();
#endif
@@ -538,7 +612,7 @@ not_equal_tm (const struct tm *a, const struct tm *b)
| (a->tm_mon ^ b->tm_mon)
| (a->tm_year ^ b->tm_year)
| (a->tm_yday ^ b->tm_yday)
- | (a->tm_isdst ^ b->tm_isdst));
+ | isdst_differ (a->tm_isdst, b->tm_isdst));
}
static void
@@ -662,6 +736,6 @@ main (int argc, char **argv)
/*
Local Variables:
-compile-command: "gcc -DDEBUG -Wall -W -O -g mktime.c -o mktime"
+compile-command: "gcc -DDEBUG -I. -Wall -W -O2 -g mktime.c -o mktime"
End:
*/
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-24 19:54:12 +0000