mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-09 23:00:07 +00:00
581c785bf3
I used these shell commands: ../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright (cd ../glibc && git commit -am"[this commit message]") and then ignored the output, which consisted lines saying "FOO: warning: copyright statement not found" for each of 7061 files FOO. I then removed trailing white space from math/tgmath.h, support/tst-support-open-dev-null-range.c, and sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following obscure pre-commit check failure diagnostics from Savannah. I don't know why I run into these diagnostics whereas others evidently do not. remote: *** 912-#endif remote: *** 913: remote: *** 914- remote: *** error: lines with trailing whitespace found ... remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
136 lines
4.1 KiB
C
136 lines
4.1 KiB
C
/* Copyright (C) 1991-2022 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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
|
|
#include <time.h>
|
|
|
|
#include <limits.h>
|
|
#include <float.h>
|
|
#include <stdint.h>
|
|
|
|
#define TYPE_BITS(type) (sizeof (type) * CHAR_BIT)
|
|
#define TYPE_FLOATING(type) ((type) 0.5 == 0.5)
|
|
#define TYPE_SIGNED(type) ((type) -1 < 0)
|
|
|
|
/* Return the difference between TIME1 and TIME0, where TIME0 <= TIME1.
|
|
time_t is known to be an integer type. */
|
|
|
|
static double
|
|
subtract (__time64_t time1, __time64_t time0)
|
|
{
|
|
if (! TYPE_SIGNED (__time64_t))
|
|
return time1 - time0;
|
|
else
|
|
{
|
|
/* Optimize the common special cases where time_t
|
|
can be converted to uintmax_t without losing information. */
|
|
uintmax_t dt = (uintmax_t) time1 - (uintmax_t) time0;
|
|
double delta = dt;
|
|
|
|
if (UINTMAX_MAX / 2 < INTMAX_MAX)
|
|
{
|
|
/* This is a rare host where uintmax_t has padding bits, and possibly
|
|
information was lost when converting time_t to uintmax_t.
|
|
Check for overflow by comparing dt/2 to (time1/2 - time0/2).
|
|
Overflow occurred if they differ by more than a small slop.
|
|
Thanks to Clive D.W. Feather for detailed technical advice about
|
|
hosts with padding bits.
|
|
|
|
In the following code the "h" prefix means half. By range
|
|
analysis, we have:
|
|
|
|
-0.5 <= ht1 - 0.5*time1 <= 0.5
|
|
-0.5 <= ht0 - 0.5*time0 <= 0.5
|
|
-1.0 <= dht - 0.5*(time1 - time0) <= 1.0
|
|
|
|
If overflow has not occurred, we also have:
|
|
|
|
-0.5 <= hdt - 0.5*(time1 - time0) <= 0
|
|
-1.0 <= dht - hdt <= 1.5
|
|
|
|
and since dht - hdt is an integer, we also have:
|
|
|
|
-1 <= dht - hdt <= 1
|
|
|
|
or equivalently:
|
|
|
|
0 <= dht - hdt + 1 <= 2
|
|
|
|
In the above analysis, all the operators have their exact
|
|
mathematical semantics, not C semantics. However, dht - hdt +
|
|
1 is unsigned in C, so it need not be compared to zero. */
|
|
|
|
uintmax_t hdt = dt / 2;
|
|
__time64_t ht1 = time1 / 2;
|
|
__time64_t ht0 = time0 / 2;
|
|
__time64_t dht = ht1 - ht0;
|
|
|
|
if (2 < dht - hdt + 1)
|
|
{
|
|
/* Repair delta overflow.
|
|
|
|
The following expression contains a second rounding,
|
|
so the result may not be the closest to the true answer.
|
|
This problem occurs only with very large differences.
|
|
It's too painful to fix this portably. */
|
|
|
|
delta = dt + 2.0L * (UINTMAX_MAX - UINTMAX_MAX / 2);
|
|
}
|
|
}
|
|
|
|
return delta;
|
|
}
|
|
}
|
|
|
|
/* Return the difference between TIME1 and TIME0. */
|
|
double
|
|
__difftime64 (__time64_t time1, __time64_t time0)
|
|
{
|
|
/* Convert to double and then subtract if no double-rounding error could
|
|
result. */
|
|
|
|
if (TYPE_BITS (__time64_t) <= DBL_MANT_DIG
|
|
|| (TYPE_FLOATING (__time64_t) && sizeof (__time64_t) < sizeof (long double)))
|
|
return (double) time1 - (double) time0;
|
|
|
|
/* Likewise for long double. */
|
|
|
|
if (TYPE_BITS (__time64_t) <= LDBL_MANT_DIG || TYPE_FLOATING (__time64_t))
|
|
return (long double) time1 - (long double) time0;
|
|
|
|
/* Subtract the smaller integer from the larger, convert the difference to
|
|
double, and then negate if needed. */
|
|
|
|
return time1 < time0 ? - subtract (time0, time1) : subtract (time1, time0);
|
|
}
|
|
|
|
/* Provide a 32-bit wrapper if needed. */
|
|
|
|
#if __TIMESIZE != 64
|
|
|
|
libc_hidden_def (__difftime64)
|
|
|
|
double
|
|
__difftime (time_t time1, time_t time0)
|
|
{
|
|
return __difftime64 (time1, time0);
|
|
}
|
|
|
|
#endif
|
|
|
|
strong_alias (__difftime, difftime)
|