X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmktime.c;h=f10e5301de184e2f1b69c836c952f4b326d59d92;hb=cd56634a4a8179fd5a4419fbb3e27211b042ab1c;hp=b63fa05606662f7cea53d02c2af3ecfbcc435a3d;hpb=d37eda272fb7b153911e44d49be4b96140894074;p=gnulib.git diff --git a/lib/mktime.c b/lib/mktime.c index b63fa0560..f10e5301d 100644 --- a/lib/mktime.c +++ b/lib/mktime.c @@ -1,87 +1,127 @@ -/* 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). +/* Convert a 'struct tm' to a time_t value. + Copyright (C) 1993-2014 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Paul Eggert . - NOTE: The canonical source of this file is maintained with the GNU C Library. - Bugs can be reported to bug-glibc@prep.ai.mit.edu. + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. - This program is free software; you can redistribute it and/or modify it - under the terms of the GNU General Public License as published by the - Free Software Foundation; either version 2, or (at your option) any - later version. - - This program is distributed in the hope that it will be useful, + The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, - USA. */ + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ /* Define this to have a standalone program to test this implementation of mktime. */ /* #define DEBUG 1 */ -#ifdef HAVE_CONFIG_H +#ifndef _LIBC # include #endif -#ifdef _LIBC -# define HAVE_LIMITS_H 1 -# define STDC_HEADERS 1 -#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 /* Some systems define `time_t' here. */ #include -#if HAVE_LIMITS_H -# include -#endif +#include + +#include /* For the real memcpy prototype. */ #if DEBUG # include -# if STDC_HEADERS -# include -# endif +# include /* Make it work even if the system's libc has its own mktime routine. */ +# undef mktime # define mktime my_mktime #endif /* DEBUG */ -#ifndef __P -# if defined (__GNUC__) || (defined (__STDC__) && __STDC__) -# define __P(args) args +/* 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 + . + 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 __P(args) () -# endif /* GCC. */ -#endif /* Not __P. */ - -#ifndef CHAR_BIT -# define CHAR_BIT 8 +# define WRAPV 0 +# endif #endif -/* The extra casts work around common compiler bugs. */ -#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) -/* The outer cast is needed to work around a bug in Cray C 5.0.3.0. - It is necessary at least when t == time_t. */ -#define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \ - ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0)) -#define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t))) - -#ifndef INT_MIN -# define INT_MIN TYPE_MINIMUM (int) -#endif -#ifndef INT_MAX -# define INT_MAX TYPE_MAXIMUM (int) +/* 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 + INT_BITS is the number of useful bits in an int. GNU code can + assume that INT_BITS is at least 32. + + ISO C99 says that A >> B is implementation-defined if A < 0. Some + 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 \ + && (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, + e.g., in Cray C 5.0.3.0. */ + +/* True if the arithmetic type T is an integer type. bool counts as + an integer. */ +#define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) + +/* True if negative values of the signed integer type T use two's + complement, or if T is an unsigned integer type. */ +#define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1) + +/* True if the arithmetic type T is signed. */ +#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) + +/* The maximum and minimum values for the integer type T. These + macros have undefined behavior if T is signed and has padding bits. + If this is a problem for you, please let us know how to fix it for + your host. */ +#define TYPE_MINIMUM(t) \ + ((t) (! TYPE_SIGNED (t) \ + ? (t) 0 \ + : ~ TYPE_MAXIMUM (t))) +#define TYPE_MAXIMUM(t) \ + ((t) (! TYPE_SIGNED (t) \ + ? (t) -1 \ + : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1))) #ifndef TIME_T_MIN # define TIME_T_MIN TYPE_MINIMUM (time_t) @@ -89,18 +129,34 @@ #ifndef TIME_T_MAX # define TIME_T_MAX TYPE_MAXIMUM (time_t) #endif +#define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1) + +verify (time_t_is_integer, TYPE_IS_INTEGER (time_t)); +verify (twos_complement_arithmetic, + (TYPE_TWOS_COMPLEMENT (int) + && TYPE_TWOS_COMPLEMENT (long_int) + && TYPE_TWOS_COMPLEMENT (time_t))); -#define TM_YEAR_BASE 1900 #define EPOCH_YEAR 1970 +#define TM_YEAR_BASE 1900 +verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0); -#ifndef __isleap -/* Nonzero if YEAR is a leap year (every 4 years, - except every 100th isn't, and every 400th is). */ -# define __isleap(year) \ - ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0)) -#endif +/* Return 1 if YEAR + TM_YEAR_BASE is a leap year. */ +static int +leapyear (long_int year) +{ + /* Don't add YEAR to TM_YEAR_BASE, as that might overflow. + Also, work even if YEAR is negative. */ + return + ((year & 3) == 0 + && (year % 100 != 0 + || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3))); +} /* How many days come before each month (0-12). */ +#ifndef _LIBC +static +#endif const unsigned short int __mon_yday[2][13] = { /* Normal years. */ @@ -109,120 +165,164 @@ const unsigned short int __mon_yday[2][13] = { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 } }; -static struct tm *ranged_convert __P ((struct tm *(*) __P ((const time_t *, - struct tm *)), - time_t *, struct tm *)); -static time_t ydhms_tm_diff __P ((int, int, int, int, int, const struct tm *)); -time_t __mktime_internal __P ((struct tm *, - struct tm *(*) (const time_t *, struct tm *), - time_t *)); +#ifndef _LIBC +/* Portable standalone applications should supply a 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. */ +# undef __localtime_r +# define __localtime_r localtime_r +# define __mktime_internal mktime_internal +# include "mktime-internal.h" +#endif -#ifdef _LIBC -# define my_mktime_localtime_r __localtime_r -#else -/* 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 * -my_mktime_localtime_r (t, tp) - const time_t *t; - struct tm *tp; +/* 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) { - struct tm *l = localtime (t); - if (! l) - return 0; - *tp = *l; - return tp; + return (!a != !b) && (0 <= a) && (0 <= b); } -#endif /* ! _LIBC */ +/* 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. + + The YEAR values uses the same numbering as TP->tm_year. Values + need not be in the usual range. However, YEAR1 must not be less + than 2 * INT_MIN or greater than 2 * INT_MAX. + + The result may overflow. It is the caller's responsibility to + detect overflow. */ -/* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP), - measured in seconds, ignoring leap seconds. - YEAR uses the same numbering as TM->tm_year. - All values are in range, except possibly YEAR. - 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_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); + + /* Compute intervening leap days correctly even if year is negative. + Take care to avoid integer overflow here. */ + int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3); + int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3); + int a100 = a4 / 25 - (a4 % 25 < 0); + int b100 = b4 / 25 - (b4 % 25 < 0); + int a400 = SHR (a100, 2); + int b400 = SHR (b100, 2); + int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400); + + /* Compute the desired time in time_t precision. Overflow might + occur here. */ + time_t tyear1 = year1; + time_t years = tyear1 - year0; + time_t days = 365 * years + yday1 - yday0 + intervening_leap_days; + time_t hours = 24 * days + hour1 - hour0; + time_t minutes = 60 * hours + min1 - min0; + time_t seconds = 60 * minutes + sec1 - sec0; + 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 (!tp) - return 1; + 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 { - /* Compute intervening leap days correctly even if year is negative. - Take care to avoid int overflow. time_t overflow is OK, since - only the low order bits of the correct time_t answer are needed. - Don't convert to time_t until after all divisions are done, since - time_t might be unsigned. */ - int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - ! (year & 3); - int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (tp->tm_year & 3); - int a100 = a4 / 25 - (a4 % 25 < 0); - int b100 = b4 / 25 - (b4 % 25 < 0); - int a400 = a100 >> 2; - int b400 = b100 >> 2; - int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400); - time_t years = year - (time_t) tp->tm_year; - time_t days = (365 * years + intervening_leap_days - + (yday - tp->tm_yday)); - return (60 * (60 * (24 * days + (hour - tp->tm_hour)) - + (min - tp->tm_min)) - + (sec - tp->tm_sec)); + 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; + } +} -static time_t localtime_offset; - -/* Convert *TP to a time_t value. */ -time_t -mktime (tp) - struct tm *tp; +/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC), + assuming that *T corresponds to *TP and that no clock adjustments + occurred between *TP and the desired time. + If TP is null, return a value not equal to *T; this avoids false matches. + 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, + const time_t *t, const 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 - be set as if the tzset() function had been called. */ - __tzset (); -#endif + if (tp) + { + 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); + if (time_t_add_ok (*t, d)) + return *t + d; + } - return __mktime_internal (tp, my_mktime_localtime_r, &localtime_offset); + /* Overflow occurred one way or another. Return the nearest result + that is actually in range, except don't report a zero difference + if the actual difference is nonzero, as that would cause a false + match; and don't oscillate between two values, as that would + confuse the spring-forward gap detector. */ + return (*t < TIME_T_MIDPOINT + ? (*t <= TIME_T_MIN + 1 ? *t + 1 : TIME_T_MIN) + : (TIME_T_MAX - 1 <= *t ? *t - 1 : TIME_T_MAX)); } /* 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; + struct tm *r = convert (t, tp); - if (! (r = (*convert) (t, tp)) && *t) + if (!r && *t) { time_t bad = *t; time_t ok = 0; - struct tm tm; /* BAD is a known unconvertible time_t, and OK is a known good one. Use binary search to narrow the range between BAD and OK until 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)); - if ((r = (*convert) (t, tp))) - { - tm = *r; - ok = mid; - } + time_t mid = *t = time_t_avg (ok, bad); + r = convert (t, tp); + if (r) + ok = mid; else bad = mid; } @@ -232,8 +332,7 @@ ranged_convert (convert, t, tp) /* The last conversion attempt failed; revert to the most recent successful attempt. */ *t = ok; - *tp = tm; - r = tp; + r = convert (t, tp); } } @@ -245,14 +344,14 @@ ranged_convert (convert, t, tp) the monotonic and mostly-unit-linear conversion function CONVERT. Use *OFFSET to keep track of a guess at the offset of the result, compared to what the result would be for UTC without leap seconds. - If *OFFSET's guess is correct, only one CONVERT call is needed. */ + If *OFFSET's guess is correct, only one CONVERT call is needed. + This function is external because it is used also by timegm.c. */ 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, t1, t2; + time_t t, gt, t0, t1, t2; struct tm tm; /* The maximum number of probes (calls to CONVERT) should be enough @@ -271,11 +370,15 @@ __mktime_internal (tp, convert, offset) int year_requested = tp->tm_year; int isdst = tp->tm_isdst; + /* 1 if the previous probe was DST. */ + int dst2; + /* Ensure that mon is in range, and set year accordingly. */ int mon_remainder = mon % 12; int negative_mon_remainder = mon_remainder < 0; int mon_years = mon / 12 - negative_mon_remainder; - int year = year_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, @@ -284,124 +387,223 @@ __mktime_internal (tp, convert, offset) /* Calculate day of year from year, month, and day of month. The result need not be in range. */ - int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)] - [mon_remainder + 12 * negative_mon_remainder]) - + mday - 1); + int mon_yday = ((__mon_yday[leapyear (year)] + [mon_remainder + 12 * negative_mon_remainder]) + - 1); + long_int lmday = mday; + long_int yday = mon_yday + lmday; + + time_t guessed_offset = *offset; int sec_requested = sec; -#if LEAP_SECONDS_POSSIBLE - /* Handle out-of-range seconds specially, - since ydhms_tm_diff assumes every minute has 60 seconds. */ - if (sec < 0) - sec = 0; - if (59 < sec) - sec = 59; -#endif - /* Invert CONVERT by probing. First assume the same offset as last time. - Then repeatedly use the error to improve the guess. */ + if (LEAP_SECONDS_POSSIBLE) + { + /* Handle out-of-range seconds specially, + since ydhms_tm_diff assumes every minute has 60 seconds. */ + if (sec < 0) + sec = 0; + if (59 < sec) + sec = 59; + } + + /* Invert CONVERT by probing. First assume the same offset as last + time. */ + + t0 = ydhms_diff (year, yday, hour, min, sec, + EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset); + + if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) + { + /* time_t isn't large enough to rule out overflows, so check + for major overflows. A gross check suffices, since if t0 + has overflowed, it is off by a multiple of TIME_T_MAX - + TIME_T_MIN + 1. So ignore any component of the difference + that is bounded by a small value. */ + + /* Approximate log base 2 of the number of time units per + biennium. A biennium is 2 years; use this unit instead of + years to avoid integer overflow. For example, 2 average + Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds, + which is 63113904 seconds, and rint (log2 (63113904)) is + 26. */ + int ALOG2_SECONDS_PER_BIENNIUM = 26; + int ALOG2_MINUTES_PER_BIENNIUM = 20; + int ALOG2_HOURS_PER_BIENNIUM = 14; + int ALOG2_DAYS_PER_BIENNIUM = 10; + int LOG2_YEARS_PER_BIENNIUM = 1; + + int approx_requested_biennia = + (SHR (year_requested, LOG2_YEARS_PER_BIENNIUM) + - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM) + + SHR (mday, ALOG2_DAYS_PER_BIENNIUM) + + SHR (hour, ALOG2_HOURS_PER_BIENNIUM) + + SHR (min, ALOG2_MINUTES_PER_BIENNIUM) + + (LEAP_SECONDS_POSSIBLE + ? 0 + : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM))); + + int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM); + int diff = approx_biennia - approx_requested_biennia; + 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 + first then doing math on it seems to work. + (ghazi@caip.rutgers.edu) */ + time_t time_t_max = TIME_T_MAX; + time_t time_t_min = TIME_T_MIN; + time_t overflow_threshold = + (time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM; + + 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; + approx_abs_diff = diff < 0 ? -1 - diff : diff; + if (overflow_threshold < approx_abs_diff) + return -1; + guessed_offset += repaired_t0 - t0; + t0 = repaired_t0; + } + } - tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE; - tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0; - t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm); + /* Repeatedly use the error to improve the guess. */ - for (t = t1 = t2 = t0 + *offset; - (dt = ydhms_tm_diff (year, yday, hour, min, sec, - ranged_convert (convert, &t, &tm))); - t1 = t2, t2 = t, t += dt) + for (t = t1 = t2 = t0, dst2 = 0; + (gt = guess_time_tm (year, yday, hour, min, sec, &t, + ranged_convert (convert, &t, &tm)), + t != gt); + t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0) if (t == t1 && t != t2 - && (isdst < 0 || tm.tm_isdst < 0 - || (isdst != 0) != (tm.tm_isdst != 0))) + && (tm.tm_isdst < 0 + || (isdst < 0 + ? dst2 <= (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 + within a spring-forward gap of size GT - T. Follow the common + practice in this case, which is to return a time that is GT - T 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; + tm_isdst differs from the requested value. (If no tm_isdst + was requested and only one of the two values has a nonzero + tm_isdst, prefer that value.) In practice, this is more + useful than returning -1. */ + goto offset_found; else if (--remaining_probes == 0) return -1; - /* If we have a match, check whether tm.tm_isdst has the requested + /* We have a match. Check whether tm.tm_isdst has the requested value, if any. */ - if (dt == 0 && 0 <= isdst && 0 <= tm.tm_isdst) + if (isdst_differ (isdst, tm.tm_isdst)) { - int dst_diff = (isdst != 0) - (tm.tm_isdst != 0); - if (dst_diff) - { - /* Move two hours in the direction indicated by the disagreement, - probe some more, and switch to a new time if found. - The largest known fallback due to daylight savings is two hours: - once, in Newfoundland, 1988-10-30 02:00 -> 00:00. */ - time_t ot = t - 2 * 60 * 60 * dst_diff; - while (--remaining_probes != 0) + /* tm.tm_isdst has the wrong value. Look for a neighboring + time with the right value, and use its UTC offset. + + Heuristic: probe the adjacent timestamps in both directions, + looking for the desired isdst. This should work for all real + time zone histories in the tz database. */ + + /* Distance between probes when looking for a DST boundary. In + tzdata2003a, the shortest period of DST is 601200 seconds + (e.g., America/Recife starting 2000-10-08 01:00), and the + shortest period of non-DST surrounded by DST is 694800 + seconds (Africa/Tunis starting 1943-04-17 01:00). Use the + minimum of these two values, so we don't miss these short + periods when probing. */ + int stride = 601200; + + /* The longest period of DST in tzdata2003a is 536454000 seconds + (e.g., America/Jujuy starting 1946-10-01 01:00). The longest + period of non-DST is much longer, but it makes no real sense + to search for more than a year of non-DST, so use the DST + max. */ + int duration_max = 536454000; + + /* Search in both directions, so the maximum distance is half + the duration; add the stride to avoid off-by-1 problems. */ + int delta_bound = duration_max / 2 + stride; + + int delta, direction; + + for (delta = stride; delta < delta_bound; delta += stride) + for (direction = -1; direction <= 1; direction += 2) + if (time_t_int_add_ok (t, delta * direction)) { + time_t ot = t + delta * direction; struct tm otm; - if (! (dt = ydhms_tm_diff (year, yday, hour, min, sec, - ranged_convert (convert, &ot, &otm)))) + ranged_convert (convert, &ot, &otm); + if (! isdst_differ (isdst, otm.tm_isdst)) { - t = ot; - tm = otm; - break; + /* 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 ((ot += dt) == t) - break; /* Avoid a redundant probe. */ } - } } - *offset = t - t0; + offset_found: + *offset = guessed_offset + t - t0; -#if LEAP_SECONDS_POSSIBLE - if (sec_requested != tm.tm_sec) + if (LEAP_SECONDS_POSSIBLE && sec_requested != tm.tm_sec) { /* 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. */ - t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60); - if (! (*convert) (&t, &tm)) + 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 (! convert (&t2, &tm)) + return -1; + t = t2; } -#endif - if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) - { - /* time_t isn't large enough to rule out overflows in ydhms_tm_diff, - so check for major overflows. A gross check suffices, - since if t has overflowed, it is off by a multiple of - TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of - the difference that is bounded by a small value. */ - - double dyear = (double) year_requested + mon_years - tm.tm_year; - double dday = 366 * dyear + mday; - double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested; + *tp = tm; + return t; +} - /* On Irix4.0.5 cc, dividing TIME_T_MIN by 3 does not produce - correct results, ie., it erroneously gives a positive value - of 715827882. Setting a variable first then doing math on it - seems to work. (ghazi@caip.rutgers.edu) */ - const time_t time_t_max = TIME_T_MAX; - const time_t time_t_min = TIME_T_MIN; +/* FIXME: This should use a signed type wide enough to hold any UTC + offset in seconds. 'int' should be good enough for GNU code. We + can't fix this unilaterally though, as other modules invoke + __mktime_internal. */ +static time_t localtime_offset; - if (time_t_max / 3 - time_t_min / 3 < (dsec < 0 ? - dsec : dsec)) - return -1; - } +/* Convert *TP to a time_t value. */ +time_t +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 + be set as if the tzset() function had been called. */ + __tzset (); +#endif - *tp = tm; - return t; + return __mktime_internal (tp, __localtime_r, &localtime_offset); } #ifdef weak_alias weak_alias (mktime, timelocal) #endif + +#ifdef _LIBC +libc_hidden_def (mktime) +libc_hidden_weak (timelocal) +#endif #if DEBUG static int -not_equal_tm (a, b) - struct tm *a; - struct tm *b; +not_equal_tm (const struct tm *a, const struct tm *b) { return ((a->tm_sec ^ b->tm_sec) | (a->tm_min ^ b->tm_min) @@ -409,14 +611,12 @@ not_equal_tm (a, b) | (a->tm_mday ^ b->tm_mday) | (a->tm_mon ^ b->tm_mon) | (a->tm_year ^ b->tm_year) - | (a->tm_mday ^ b->tm_mday) | (a->tm_yday ^ b->tm_yday) - | (a->tm_isdst ^ b->tm_isdst)); + | isdst_differ (a->tm_isdst, b->tm_isdst)); } static void -print_tm (tp) - struct tm *tp; +print_tm (const struct tm *tp) { if (tp) printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d", @@ -428,19 +628,15 @@ print_tm (tp) } static int -check_result (tk, tmk, tl, lt) - time_t tk; - struct tm tmk; - time_t tl; - struct tm *lt; +check_result (time_t tk, struct tm tmk, time_t tl, const struct tm *lt) { if (tk != tl || !lt || not_equal_tm (&tmk, lt)) { printf ("mktime ("); - print_tm (&tmk); - printf (")\nyields ("); print_tm (lt); - printf (") == %ld, should be %ld\n", (long) tl, (long) tk); + printf (")\nyields ("); + print_tm (&tmk); + printf (") == %ld, should be %ld\n", (long int) tk, (long int) tl); return 1; } @@ -448,14 +644,12 @@ check_result (tk, tmk, tl, lt) } int -main (argc, argv) - int argc; - char **argv; +main (int argc, char **argv) { int status = 0; struct tm tm, tmk, tml; struct tm *lt; - time_t tk, tl; + time_t tk, tl, tl1; char trailer; if ((argc == 3 || argc == 4) @@ -477,7 +671,7 @@ main (argc, argv) tml = *lt; lt = &tml; } - printf ("mktime returns %ld == ", (long) tl); + printf ("mktime returns %ld == ", (long int) tl); print_tm (&tmk); printf ("\n"); status = check_result (tl, tmk, tl, lt); @@ -489,23 +683,26 @@ main (argc, argv) time_t to = atol (argv[3]); if (argc == 4) - for (tl = from; tl <= to; tl += by) + for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1) { lt = localtime (&tl); if (lt) { tmk = tml = *lt; tk = mktime (&tmk); - status |= check_result (tk, tmk, tl, tml); + status |= check_result (tk, tmk, tl, &tml); } else { - printf ("localtime (%ld) yields 0\n", (long) tl); + printf ("localtime (%ld) yields 0\n", (long int) tl); status = 1; } + tl1 = tl + by; + if ((tl1 < tl) != (by < 0)) + break; } else - for (tl = from; tl <= to; tl += by) + for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1) { /* Null benchmark. */ lt = localtime (&tl); @@ -513,13 +710,16 @@ main (argc, argv) { tmk = tml = *lt; tk = tl; - status |= check_result (tk, tmk, tl, tml); + status |= check_result (tk, tmk, tl, &tml); } else { - printf ("localtime (%ld) yields 0\n", (long) tl); + printf ("localtime (%ld) yields 0\n", (long int) tl); status = 1; } + tl1 = tl + by; + if ((tl1 < tl) != (by < 0)) + break; } } else @@ -536,6 +736,6 @@ main (argc, argv) /* Local Variables: -compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime" +compile-command: "gcc -DDEBUG -I. -Wall -W -O2 -g mktime.c -o mktime" End: */