dd8c04d769
adding (weak definitions to) stubs for some of the pthread functions. If the threads library is linked in, the real pthread functions will pulled in. Use the following convention for system calls wrapped by the threads library: __sys_foo - actual system call _foo - weak definition to __sys_foo foo - weak definition to __sys_foo Change all libc uses of system calls wrapped by the threads library from foo to _foo. In order to define the prototypes for _foo(), we introduce namespace.h and un-namespace.h (suggested by bde). All files that need to reference these system calls, should include namespace.h before any standard includes, then include un-namespace.h after the standard includes and before any local includes. <db.h> is an exception and shouldn't be included in between namespace.h and un-namespace.h namespace.h will define foo to _foo, and un-namespace.h will undefine foo. Try to eliminate some of the recursive calls to MT-safe functions in libc/stdio in preparation for adding a mutex to FILE. We have recursive mutexes, but would like to avoid using them if possible. Remove uneeded includes of <errno.h> from a few files. Add $FreeBSD$ to a few files in order to pass commitprep. Approved by: -arch
82 lines
2.3 KiB
C
82 lines
2.3 KiB
C
/*
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** This file is in the public domain, so clarified as of
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** June 5, 1996 by Arthur David Olson (arthur_david_olson@nih.gov).
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*
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* $FreeBSD$
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*/
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#ifndef lint
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#ifndef NOID
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static char elsieid[] = "@(#)difftime.c 7.7";
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#endif /* !defined NOID */
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#endif /* !defined lint */
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/*LINTLIBRARY*/
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#include "namespace.h"
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#include "private.h"
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#include "un-namespace.h"
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/*
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** Algorithm courtesy Paul Eggert (eggert@twinsun.com).
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*/
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#ifdef HAVE_LONG_DOUBLE
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#define long_double long double
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#endif /* defined HAVE_LONG_DOUBLE */
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#ifndef HAVE_LONG_DOUBLE
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#define long_double double
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#endif /* !defined HAVE_LONG_DOUBLE */
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double
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difftime(time1, time0)
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const time_t time1;
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const time_t time0;
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{
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time_t delta;
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time_t hibit;
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if (sizeof(time_t) < sizeof(double))
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return (double) time1 - (double) time0;
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if (sizeof(time_t) < sizeof(long_double))
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return (long_double) time1 - (long_double) time0;
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if (time1 < time0)
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return -difftime(time0, time1);
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/*
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** As much as possible, avoid loss of precision
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** by computing the difference before converting to double.
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*/
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delta = time1 - time0;
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if (delta >= 0)
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return delta;
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/*
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** Repair delta overflow.
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*/
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hibit = (~ (time_t) 0) << (TYPE_BIT(time_t) - 1);
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/*
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** The following expression rounds twice, which means
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** the result may not be the closest to the true answer.
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** For example, suppose time_t is 64-bit signed int,
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** long_double is IEEE 754 double with default rounding,
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** time1 = 9223372036854775807 and time0 = -1536.
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** Then the true difference is 9223372036854777343,
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** which rounds to 9223372036854777856
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** with a total error of 513.
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** But delta overflows to -9223372036854774273,
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** which rounds to -9223372036854774784, and correcting
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** this by subtracting 2 * (long_double) hibit
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** (i.e. by adding 2**64 = 18446744073709551616)
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** yields 9223372036854776832, which
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** rounds to 9223372036854775808
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** with a total error of 1535 instead.
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** This problem occurs only with very large differences.
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** It's too painful to fix this portably.
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** We are not alone in this problem;
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** some C compilers round twice when converting
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** large unsigned types to small floating types,
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** so if time_t is unsigned the "return delta" above
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** has the same double-rounding problem with those compilers.
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*/
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return delta - 2 * (long_double) hibit;
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}
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