glibc/time/timegm.c
Paul Eggert 8e6fd2bdb2 Merge mktime, timegm from upstream Gnulib
[BZ #23603][BZ #16346]
This fixes some obscure problems with integer overflow.
Although it looks scary, it is almost all a byte-for-byte copy
from Gnulib, and the Gnulib code has been tested reasonably well.
* include/intprops.h: New file, copied from Gnulib.
* include/verify.h, time/mktime-internal.h:
New tiny files, simplified from Gnulib.
* time/mktime.c: Copy from Gnulib.  This has the following changes:
Do not include config.h if DEBUG_MKTIME is nonzero.
Include stdbool.h, intprops.h, verify.h.
Include string.h only if needed.
Include stdlib.h on MS-Windows.
Include mktime-internal.h.
(DEBUG_MKTIME): Default to 0, and simplify later uses.
(NEED_MKTIME_INTERNAL, NEED_MKTIME_WINDOWS)
(NEED_MKTIME_WORKING): Give default values to pacify -Wundef,
which glibc uses.  Default NEED_MKTIME_WORKING to DEBUG_MKTIME, to
simplify later conditionals; default the others to zero.  Use
these conditionals to express only the code needed on the current
platform.  In uses of these conditionals, explicitly spell out how
_LIBC affects things, so it’s easier to review from a glibc
viewpoint.
(WRAPV): Remove; no longer needed now that we have
systematic overflow checking.
(my_tzset, __tzset) [!_LIBC]: New function and macro, to better
compartmentalize tzset issues.  Move system-dependent tzsettish
code here from mktime.
(verify): Remove; now done by verify.h.  All uses changed.
(long_int): Use a more-conservative definition, to avoid
integer overflow.
(SHR): Remove, replacing with ...
(shr): New function, which means we needn’t worry about side
effects in args, and conversion analysis is simpler.
(TYPE_IS_INTEGER, TYPE_TWOS_COMPLEMENT, TYPE_SIGNED, TYPE_MINIMUM)
(TYPE_MAXIMUM, TIME_T_MIN, TIME_T_MAX, TIME_T_MIDPOINT)
(time_t_avg, time_t_add_ok): Remove.
(mktime_min, mktime_max): New constants.
(leapyear, isdst_differ): Use bool for booleans.
(ydhms_diff, guess_time_tm, ranged_convert, __mktime_internal):
Use long_int, not time_t, for mktime differences.
(long_int_avg): New function, replacing time_t_avg.
INT_ADD_WRAPV replaces time_t_add_ok.
(guess_time_tm): 6th arg is now long_int, not time_t const *.
All uses changed.
(convert_time): New function.
(ranged_convert): Use it.
(__mktime_internal): Last arg now points to mktime_offset_t, not
time_t.  All uses changed.  This is a no-op on glibc, where
mktime_offset_t is always time_t.  Use int, not time_t, for UTC
offset guess.  Directly check for integer overflow instead of
using a heuristic that works only 99.9...% of the time.
Access *OFFSET only once, to avoid an unlikely race if the
compiler delays a load and if this cascades into a signed integer
overflow.
(mktime): Move tzsettish code to my_tzset, and move
localtime_offset to within mktime so that it doesn’t
need a separate ifdef.
(main) [DEBUG_MKTIME]: Speed up by using localtime_r
instead of localtime.
* time/timegm.c: Copy from Gnulib.  This has the following changes:
Include mktime-internal.h.
[!_LIBC]: Include config.h and time.h.  Do not include
timegm.h or time_r.h.  Make __mktime_internal a macro,
and include mktime-internal.h to get its declaration.
(timegm): Temporary is now mktime_offset_t, not time_t.
This affects only Gnulib.
2018-09-19 17:09:08 -07:00

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1.1 KiB
C

/* Convert UTC calendar time to simple time. Like mktime but assumes UTC.
Copyright (C) 1994-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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.
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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _LIBC
# include <config.h>
#endif
#include <time.h>
#include "mktime-internal.h"
time_t
timegm (struct tm *tmp)
{
static mktime_offset_t gmtime_offset;
tmp->tm_isdst = 0;
return __mktime_internal (tmp, __gmtime_r, &gmtime_offset);
}