mirror of
https://sourceware.org/git/glibc.git
synced 2024-09-20 08:30:00 +00:00
646c2833ee
As reported in bug 23280, scanf functions produce incorrectly rounded result for floating-point formats in FE_UPWARD and FE_DOWNWARD modes, because they pass the input with sign removed to strtod functions, and then negate the result if there was a '-' at the start of the input. This patch fixes this by arranging for the sign to be passed to strtod rather than scanf doing the negation itself. In turn, keeping the sign around in the buffer being built up for strtod requires updating places that examine char_buffer_size (&charbuf) to allow for the sign being there as an extra character. Tested for x86_64. [BZ #23280] * stdio-common/vfscanf.c (_IO_vfscanf_internal): Pass sign of floating-point number to strtod functions rather than possibly negating result of those functions. * stdio-common/tst-scanf-round.c: New file. * stdio-common/Makefile (tests): Add tst-scanf-round. ($(objpfx)tst-scanf-round): Depend on $(libm).
52 lines
1.5 KiB
C
52 lines
1.5 KiB
C
/* Test for correct rounding of negative floating-point numbers by scanf
|
|
(bug 23280).
|
|
Copyright (C) 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/>. */
|
|
|
|
#include <fenv.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <support/check.h>
|
|
|
|
static int
|
|
do_test (void)
|
|
{
|
|
#ifdef FE_DOWNWARD
|
|
if (fesetround (FE_DOWNWARD) == 0)
|
|
{
|
|
double a = strtod ("-0.1", NULL);
|
|
double b = 0;
|
|
int r = sscanf ("-0.1", "%lf", &b);
|
|
TEST_VERIFY (r == 1);
|
|
TEST_VERIFY (a == b);
|
|
}
|
|
#endif
|
|
#ifdef FE_UPWARD
|
|
if (fesetround (FE_UPWARD) == 0)
|
|
{
|
|
double a = strtod ("-0.1", NULL);
|
|
double b = 0;
|
|
int r = sscanf ("-0.1", "%lf", &b);
|
|
TEST_VERIFY (r == 1);
|
|
TEST_VERIFY (a == b);
|
|
}
|
|
#endif
|
|
return 0;
|
|
}
|
|
|
|
#include <support/test-driver.c>
|