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Make printf respect the rounding mode for decimal output (bug 5044).
This commit is contained in:
Joseph Myers
parent
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commit
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12
ChangeLog
12
ChangeLog
@ -1,3 +1,15 @@
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2012-09-14 Joseph Myers <joseph@codesourcery.com>
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[BZ #5044]
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* stdio-common/printf_fp.c: Include <stdbool.h> and
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<rounding-mode.h>.
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(___printf_fp): Determine rounding using get_rounding_mode and
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round_away.
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* stdio-common/tst-printf-round.c: New file.
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* stdio-common/Makefile (tests): Add tst-printf-round.
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(link-libm): New variable.
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($(objpfx)tst-printf-round): Depend in $(link-libm).
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2012-09-13 H.J. Lu <hongjiu.lu@intel.com>
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[BZ #14576]
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@ -57,7 +57,7 @@ tests := tstscanf test_rdwr test-popen tstgetln test-fseek \
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bug19 bug19a tst-popen2 scanf13 scanf14 scanf15 bug20 bug21 bug22 \
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scanf16 scanf17 tst-setvbuf1 tst-grouping bug23 bug24 \
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bug-vfprintf-nargs tst-long-dbl-fphex tst-fphex-wide tst-sprintf3 \
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bug25
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bug25 tst-printf-round
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test-srcs = tst-unbputc tst-printf
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@ -128,3 +128,10 @@ CPPFLAGS += $(libio-mtsafe)
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$(objpfx)tst-setvbuf1.out: tst-setvbuf1.expect $(objpfx)tst-setvbuf1
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$(built-program-cmd) > $@ 2>&1
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cmp tst-setvbuf1.expect $@
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ifeq ($(build-shared),yes)
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link-libm = $(common-objpfx)math/libm.so
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else
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link-libm = $(common-objpfx)math/libm.a
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endif
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$(objpfx)tst-printf-round: $(link-libm)
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@ -39,6 +39,8 @@
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#include <unistd.h>
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#include <stdlib.h>
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#include <wchar.h>
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#include <stdbool.h>
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#include <rounding-mode.h>
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#ifdef COMPILE_WPRINTF
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# define CHAR_T wchar_t
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@ -197,9 +199,6 @@ ___printf_fp (FILE *fp,
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/* Temporary bignum value. */
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MPN_VAR(tmp);
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/* Digit which is result of last hack_digit() call. */
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wchar_t digit;
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/* The type of output format that will be used: 'e'/'E' or 'f'. */
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int type;
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@ -955,34 +954,31 @@ ___printf_fp (FILE *fp,
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}
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/* Do rounding. */
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digit = hack_digit ();
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if (digit > L'4')
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wchar_t last_digit = wcp[-1] != decimalwc ? wcp[-1] : wcp[-2];
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wchar_t next_digit = hack_digit ();
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bool more_bits;
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if (next_digit != L'0' && next_digit != L'5')
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more_bits = true;
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else if (fracsize == 1 && frac[0] == 0)
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/* Rest of the number is zero. */
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more_bits = false;
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else if (scalesize == 0)
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{
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/* Here we have to see whether all limbs are zero since no
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normalization happened. */
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size_t lcnt = fracsize;
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while (lcnt >= 1 && frac[lcnt - 1] == 0)
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--lcnt;
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more_bits = lcnt > 0;
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}
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else
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more_bits = true;
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int rounding_mode = get_rounding_mode ();
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if (round_away (is_neg, (last_digit - L'0') & 1, next_digit >= L'5',
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more_bits, rounding_mode))
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{
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wchar_t *wtp = wcp;
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if (digit == L'5'
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&& ((*(wcp - 1) != decimalwc && (*(wcp - 1) & 1) == 0)
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|| ((*(wcp - 1) == decimalwc && (*(wcp - 2) & 1) == 0))))
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{
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/* This is the critical case. */
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if (fracsize == 1 && frac[0] == 0)
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/* Rest of the number is zero -> round to even.
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(IEEE 754-1985 4.1 says this is the default rounding.) */
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goto do_expo;
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else if (scalesize == 0)
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{
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/* Here we have to see whether all limbs are zero since no
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normalization happened. */
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size_t lcnt = fracsize;
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while (lcnt >= 1 && frac[lcnt - 1] == 0)
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--lcnt;
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if (lcnt == 0)
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/* Rest of the number is zero -> round to even.
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(IEEE 754-1985 4.1 says this is the default rounding.) */
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goto do_expo;
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}
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}
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if (fracdig_no > 0)
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{
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/* Process fractional digits. Terminate if not rounded or
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@ -1076,7 +1072,6 @@ ___printf_fp (FILE *fp,
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}
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}
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do_expo:
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/* Now remove unnecessary '0' at the end of the string. */
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while (fracdig_no > fracdig_min + added_zeros && *(wcp - 1) == L'0')
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{
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110
stdio-common/tst-printf-round.c
Normal file
110
stdio-common/tst-printf-round.c
Normal file
@ -0,0 +1,110 @@
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/* Test for correct rounding of printf floating-point output.
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Copyright (C) 2012 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <fenv.h>
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#include <stdio.h>
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#include <string.h>
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struct dec_test {
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double d;
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const char *fmt;
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const char *rd, *rn, *rz, *ru;
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};
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static const struct dec_test dec_tests[] = {
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{ 1.5, "%.0f", "1", "2", "1", "2" },
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{ -1.5, "%.0f", "-2", "-2", "-1", "-1" },
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{ 2.5, "%.0f", "2", "2", "2", "3" },
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{ -2.5, "%.0f", "-3", "-2", "-2", "-2" },
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{ 1.4999, "%.0f", "1", "1", "1", "2" },
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{ -1.4999, "%.0f", "-2", "-1", "-1", "-1" },
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{ 1.5001, "%.0f", "1", "2", "1", "2" },
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{ -1.5001, "%.0f", "-2", "-2", "-1", "-1" },
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{ 2.4999, "%.0f", "2", "2", "2", "3" },
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{ -2.4999, "%.0f", "-3", "-2", "-2", "-2" },
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{ 2.5001, "%.0f", "2", "3", "2", "3" },
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{ -2.5001, "%.0f", "-3", "-3", "-2", "-2" },
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{ 1.0 / 3.0, "%f", "0.333333", "0.333333", "0.333333", "0.333334" },
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{ -1.0 / 3.0, "%f", "-0.333334", "-0.333333", "-0.333333", "-0.333333" },
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{ 0.2500001, "%.2e", "2.50e-01", "2.50e-01", "2.50e-01", "2.51e-01" },
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{ -0.2500001, "%.2e", "-2.51e-01", "-2.50e-01", "-2.50e-01", "-2.50e-01" },
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{ 1000001.0, "%.1e", "1.0e+06", "1.0e+06", "1.0e+06", "1.1e+06" },
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{ -1000001.0, "%.1e", "-1.1e+06", "-1.0e+06", "-1.0e+06", "-1.0e+06" },
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};
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static int
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test_dec_in_one_mode (double d, const char *fmt, const char *expected,
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const char *mode_name)
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{
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char buf[100];
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int ret = snprintf (buf, sizeof buf, fmt, d);
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if (ret <= 0 || ret >= (int) sizeof buf)
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{
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printf ("snprintf for %a returned %d\n", d, ret);
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return 1;
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}
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if (strcmp (buf, expected) == 0)
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return 0;
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else
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{
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printf ("snprintf (\"%s\", %a) returned \"%s\" not \"%s\" (%s)\n",
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fmt, d, buf, expected, mode_name);
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return 1;
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}
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}
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static int
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do_test (void)
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{
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int save_round_mode = fegetround ();
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int result = 0;
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for (size_t i = 0; i < sizeof (dec_tests) / sizeof (dec_tests[0]); i++)
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{
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result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
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dec_tests[i].rn, "default rounding mode");
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#ifdef FE_DOWNWARD
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if (!fesetround (FE_DOWNWARD))
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{
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result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
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dec_tests[i].rd, "FE_DOWNWARD");
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fesetround (save_round_mode);
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}
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#endif
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#ifdef FE_TOWARDZERO
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if (!fesetround (FE_TOWARDZERO))
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{
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result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
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dec_tests[i].rz, "FE_TOWARDZERO");
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fesetround (save_round_mode);
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}
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#endif
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#ifdef FE_UPWARD
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if (!fesetround (FE_UPWARD))
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{
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result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
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dec_tests[i].ru, "FE_UPWARD");
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fesetround (save_round_mode);
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}
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#endif
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}
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return result;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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