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400ecf36bb
* Makefile (GCC_DEBUG_FLAGS): Modernize for GCC 4.6.3 x86. * asctime.c (asctime_r, asctime): * date.c (main, dogmt, reset, wildinput, nondigit, oops, display) (timeout, sametm, netsettime): * difftime.c (difftime): * ialloc.c (icatalloc, icpyalloc): * localtime.c (detzcode, detzcode64, differ_by_repeat) (tzload, typesequiv, getzname, getnum, getsecs, getoffset) (getrule, transtime, tzparse, gmtload, tzsetwall, tzset) (localsub, localtime, localtime_r, gmtsub, gmtime, gmtime_r) (offtime, leaps_thru_end_of, timesub, ctime, ctime_r) (increment_overflow, long_increment_overflow) (normalize_overflow, long_normalize_overflow, tmcomp, time2sub) (time2, time1, mktime, timelocal, timegm, timeoff, gtime) (leapcorr, time2posix, posix2time): * scheck.c (scheck): * strftime.c (strftime, _fmt, _conv, _add, _yconv, _loc): * zdump.c (my_localtime, abbrok, usage, main, yeartot) (delta, abbr, dumptime): * zic.c (memcheck, eats, eat, error, warning, main) (dolink, itsdir, rcomp, associate, infile, gethms, inrule) (inzone, inzcont, inzsub, inleap, inlink, rulesub, convert) (convert64, puttzcode, puttzcode64, atcomp, is32, writezone, DO) (doabbr, updateminmax, stringoffset, stringrule, stringzone) (outzone, addtt, addtype, leapadd, yearistype, lowerit, ciequal) (itsabbr, byword, getfields, oadd, tadd, rpytime, newabbr) (mkdirs, eitol): Assume C89 or better. Mostly this consists of using function prototypes. In a few places, prototypes are required for portability to hosts where time_t does not promote to itself and where a preceding prototype does not override a definition. But while we're at it we might as well be consistent: it's safe to assume at-least-C89 these days. * ialloc.c (nonzero, imalloc, icalloc, irealloc, ifree, icfree): Remove; no longer needed now that we assume C89 or better. All callers changed to use malloc, calloc, realloc, free. * localtime.c (getzname, getqzname, leaps_thru_end_of, transtime): * zdump.c (delta, yeartot): * zic.c (eitol): Now pure. * private.h, zdump.c (ATTRIBUTE_PURE): New macro. * private.h (icalloc, imalloc, irealloc, icfree, ifree): Remove decls. * zic.c: Remove no-longer-necessary forward decls. (max_time, min_time): Now const. (setboundaries): Remove.
58 lines
1.5 KiB
C
58 lines
1.5 KiB
C
/*
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** This file is in the public domain, so clarified as of
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** 1996-06-05 by Arthur David Olson.
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*/
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/*LINTLIBRARY*/
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#include "private.h" /* for time_t, TYPE_INTEGRAL, and TYPE_SIGNED */
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double
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difftime(const time_t time1, const time_t time0)
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{
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/*
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** If (sizeof (double) > sizeof (time_t)) simply convert and subtract
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** (assuming that the larger type has more precision).
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** This is the common real-world case circa 2004.
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*/
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if (sizeof (double) > sizeof (time_t))
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return (double) time1 - (double) time0;
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if (!TYPE_INTEGRAL(time_t)) {
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/*
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** time_t is floating.
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*/
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return time1 - time0;
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}
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if (!TYPE_SIGNED(time_t)) {
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/*
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** time_t is integral and unsigned.
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** The difference of two unsigned values can't overflow
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** if the minuend is greater than or equal to the subtrahend.
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*/
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if (time1 >= time0)
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return time1 - time0;
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else return -((double) (time0 - time1));
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}
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/*
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** time_t is integral and signed.
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** Handle cases where both time1 and time0 have the same sign
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** (meaning that their difference cannot overflow).
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*/
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if ((time1 < 0) == (time0 < 0))
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return time1 - time0;
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/*
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** time1 and time0 have opposite signs.
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** Punt if unsigned long is too narrow.
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*/
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if (sizeof (unsigned long) < sizeof (time_t))
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return (double) time1 - (double) time0;
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/*
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** Stay calm...decent optimizers will eliminate the complexity below.
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*/
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if (time1 >= 0 /* && time0 < 0 */)
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return (unsigned long) time1 +
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(unsigned long) (-(time0 + 1)) + 1;
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return -(double) ((unsigned long) time0 +
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(unsigned long) (-(time1 + 1)) + 1);
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}
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