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-rw-r--r--stdio-common/Makefile9
-rw-r--r--stdio-common/printf_fp.c53
-rw-r--r--stdio-common/tst-printf-round.c110
3 files changed, 142 insertions, 30 deletions
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 5d7ab532f4..9811572431 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -57,7 +57,7 @@ tests := tstscanf test_rdwr test-popen tstgetln test-fseek \
bug19 bug19a tst-popen2 scanf13 scanf14 scanf15 bug20 bug21 bug22 \
scanf16 scanf17 tst-setvbuf1 tst-grouping bug23 bug24 \
bug-vfprintf-nargs tst-long-dbl-fphex tst-fphex-wide tst-sprintf3 \
- bug25
+ bug25 tst-printf-round
test-srcs = tst-unbputc tst-printf
@@ -128,3 +128,10 @@ CPPFLAGS += $(libio-mtsafe)
$(objpfx)tst-setvbuf1.out: tst-setvbuf1.expect $(objpfx)tst-setvbuf1
$(built-program-cmd) > $@ 2>&1
cmp tst-setvbuf1.expect $@
+
+ifeq ($(build-shared),yes)
+link-libm = $(common-objpfx)math/libm.so
+else
+link-libm = $(common-objpfx)math/libm.a
+endif
+$(objpfx)tst-printf-round: $(link-libm)
diff --git a/stdio-common/printf_fp.c b/stdio-common/printf_fp.c
index 5f3c904254..6e2b57c039 100644
--- a/stdio-common/printf_fp.c
+++ b/stdio-common/printf_fp.c
@@ -39,6 +39,8 @@
#include <unistd.h>
#include <stdlib.h>
#include <wchar.h>
+#include <stdbool.h>
+#include <rounding-mode.h>
#ifdef COMPILE_WPRINTF
# define CHAR_T wchar_t
@@ -197,9 +199,6 @@ ___printf_fp (FILE *fp,
/* Temporary bignum value. */
MPN_VAR(tmp);
- /* Digit which is result of last hack_digit() call. */
- wchar_t digit;
-
/* The type of output format that will be used: 'e'/'E' or 'f'. */
int type;
@@ -955,34 +954,31 @@ ___printf_fp (FILE *fp,
}
/* Do rounding. */
- digit = hack_digit ();
- if (digit > L'4')
+ wchar_t last_digit = wcp[-1] != decimalwc ? wcp[-1] : wcp[-2];
+ wchar_t next_digit = hack_digit ();
+ bool more_bits;
+ if (next_digit != L'0' && next_digit != L'5')
+ more_bits = true;
+ else if (fracsize == 1 && frac[0] == 0)
+ /* Rest of the number is zero. */
+ more_bits = false;
+ else if (scalesize == 0)
+ {
+ /* Here we have to see whether all limbs are zero since no
+ normalization happened. */
+ size_t lcnt = fracsize;
+ while (lcnt >= 1 && frac[lcnt - 1] == 0)
+ --lcnt;
+ more_bits = lcnt > 0;
+ }
+ else
+ more_bits = true;
+ int rounding_mode = get_rounding_mode ();
+ if (round_away (is_neg, (last_digit - L'0') & 1, next_digit >= L'5',
+ more_bits, rounding_mode))
{
wchar_t *wtp = wcp;
- if (digit == L'5'
- && ((*(wcp - 1) != decimalwc && (*(wcp - 1) & 1) == 0)
- || ((*(wcp - 1) == decimalwc && (*(wcp - 2) & 1) == 0))))
- {
- /* This is the critical case. */
- if (fracsize == 1 && frac[0] == 0)
- /* Rest of the number is zero -> round to even.
- (IEEE 754-1985 4.1 says this is the default rounding.) */
- goto do_expo;
- else if (scalesize == 0)
- {
- /* Here we have to see whether all limbs are zero since no
- normalization happened. */
- size_t lcnt = fracsize;
- while (lcnt >= 1 && frac[lcnt - 1] == 0)
- --lcnt;
- if (lcnt == 0)
- /* Rest of the number is zero -> round to even.
- (IEEE 754-1985 4.1 says this is the default rounding.) */
- goto do_expo;
- }
- }
-
if (fracdig_no > 0)
{
/* Process fractional digits. Terminate if not rounded or
@@ -1076,7 +1072,6 @@ ___printf_fp (FILE *fp,
}
}
- do_expo:
/* Now remove unnecessary '0' at the end of the string. */
while (fracdig_no > fracdig_min + added_zeros && *(wcp - 1) == L'0')
{
diff --git a/stdio-common/tst-printf-round.c b/stdio-common/tst-printf-round.c
new file mode 100644
index 0000000000..2bd46079ac
--- /dev/null
+++ b/stdio-common/tst-printf-round.c
@@ -0,0 +1,110 @@
+/* Test for correct rounding of printf floating-point output.
+ Copyright (C) 2012 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 <string.h>
+
+struct dec_test {
+ double d;
+ const char *fmt;
+ const char *rd, *rn, *rz, *ru;
+};
+
+static const struct dec_test dec_tests[] = {
+ { 1.5, "%.0f", "1", "2", "1", "2" },
+ { -1.5, "%.0f", "-2", "-2", "-1", "-1" },
+ { 2.5, "%.0f", "2", "2", "2", "3" },
+ { -2.5, "%.0f", "-3", "-2", "-2", "-2" },
+ { 1.4999, "%.0f", "1", "1", "1", "2" },
+ { -1.4999, "%.0f", "-2", "-1", "-1", "-1" },
+ { 1.5001, "%.0f", "1", "2", "1", "2" },
+ { -1.5001, "%.0f", "-2", "-2", "-1", "-1" },
+ { 2.4999, "%.0f", "2", "2", "2", "3" },
+ { -2.4999, "%.0f", "-3", "-2", "-2", "-2" },
+ { 2.5001, "%.0f", "2", "3", "2", "3" },
+ { -2.5001, "%.0f", "-3", "-3", "-2", "-2" },
+ { 1.0 / 3.0, "%f", "0.333333", "0.333333", "0.333333", "0.333334" },
+ { -1.0 / 3.0, "%f", "-0.333334", "-0.333333", "-0.333333", "-0.333333" },
+ { 0.2500001, "%.2e", "2.50e-01", "2.50e-01", "2.50e-01", "2.51e-01" },
+ { -0.2500001, "%.2e", "-2.51e-01", "-2.50e-01", "-2.50e-01", "-2.50e-01" },
+ { 1000001.0, "%.1e", "1.0e+06", "1.0e+06", "1.0e+06", "1.1e+06" },
+ { -1000001.0, "%.1e", "-1.1e+06", "-1.0e+06", "-1.0e+06", "-1.0e+06" },
+};
+
+static int
+test_dec_in_one_mode (double d, const char *fmt, const char *expected,
+ const char *mode_name)
+{
+ char buf[100];
+ int ret = snprintf (buf, sizeof buf, fmt, d);
+ if (ret <= 0 || ret >= (int) sizeof buf)
+ {
+ printf ("snprintf for %a returned %d\n", d, ret);
+ return 1;
+ }
+ if (strcmp (buf, expected) == 0)
+ return 0;
+ else
+ {
+ printf ("snprintf (\"%s\", %a) returned \"%s\" not \"%s\" (%s)\n",
+ fmt, d, buf, expected, mode_name);
+ return 1;
+ }
+}
+
+static int
+do_test (void)
+{
+ int save_round_mode = fegetround ();
+ int result = 0;
+
+ for (size_t i = 0; i < sizeof (dec_tests) / sizeof (dec_tests[0]); i++)
+ {
+ result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
+ dec_tests[i].rn, "default rounding mode");
+#ifdef FE_DOWNWARD
+ if (!fesetround (FE_DOWNWARD))
+ {
+ result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
+ dec_tests[i].rd, "FE_DOWNWARD");
+ fesetround (save_round_mode);
+ }
+#endif
+#ifdef FE_TOWARDZERO
+ if (!fesetround (FE_TOWARDZERO))
+ {
+ result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
+ dec_tests[i].rz, "FE_TOWARDZERO");
+ fesetround (save_round_mode);
+ }
+#endif
+#ifdef FE_UPWARD
+ if (!fesetround (FE_UPWARD))
+ {
+ result |= test_dec_in_one_mode (dec_tests[i].d, dec_tests[i].fmt,
+ dec_tests[i].ru, "FE_UPWARD");
+ fesetround (save_round_mode);
+ }
+#endif
+ }
+ return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
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