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Fix strtod handling of underflow (bug 14047).

This commit is contained in:
Joseph Myers 2012-10-30 13:51:27 +00:00
parent e5088dc687
commit 2a27fd6dae
21 changed files with 434 additions and 13 deletions
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21
ChangeLog
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@ -1,3 +1,24 @@
2012-10-30 Joseph Myers <joseph@codesourcery.com>
[BZ #14047]
* sysdeps/generic/tininess.h: New file.
* sysdeps/i386/tininess.h: Likewise.
* sysdeps/sh/tininess.h: Likewise.
* sysdeps/x86_64/tininess.h: Likewise.
* stdlib/tst-strtod-underflow.c: Likewise.
* stdlib/tst-tininess.c: Likewise.
* stdlib/strtod_l.c: Include <tininess.h>.
(round_and_return): Do not set errno for exact underflow cases.
Force an underflow exception when setting errno for underflow.
Determine underflow based on rounding to normal precision if
TININESS_AFTER_ROUNDING.
* stdlib/tst-strtod.c (tests): Do not expect errno to be set to
ERANGE for exact underflow cases.
* stdlib/Makefile (tests): Add tst-tininess and
tst-strtod-underflow.
($(objpfx)tst-tininess): Use $(link-libm).
($(objpfx)tst-strtod-underflow): Likewise.
2012-10-30 Andreas Jaeger <aj@suse.de>
[BZ#14767]

14
NEWS
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@ -11,13 +11,13 @@ Version 2.17
1349, 3479, 5044, 5298, 5400, 6530, 6778, 6808, 9685, 9914, 10014, 10038,
10631, 11438, 11607, 12140, 13412, 13542, 13601, 13629, 13679, 13696,
13717, 13741, 13939, 13966, 14042, 14090, 14150, 14151, 14154, 14157,
14166, 14173, 14195, 14237, 14251, 14252, 14283, 14298, 14303, 14307,
14328, 14331, 14336, 14337, 14347, 14349, 14376, 14417, 14459, 14476,
14477, 14505, 14510, 14516, 14518, 14519, 14530, 14532, 14538, 14543,
14544, 14545, 14557, 14562, 14568, 14576, 14579, 14583, 14587, 14602,
14621, 14638, 14645, 14648, 14652, 14660, 14661, 14683, 14694, 14716,
14743, 14767.
13717, 13741, 13939, 13966, 14042, 14047, 14090, 14150, 14151, 14154,
14157, 14166, 14173, 14195, 14237, 14251, 14252, 14283, 14298, 14303,
14307, 14328, 14331, 14336, 14337, 14347, 14349, 14376, 14417, 14459,
14476, 14477, 14505, 14510, 14516, 14518, 14519, 14530, 14532, 14538,
14543, 14544, 14545, 14557, 14562, 14568, 14576, 14579, 14583, 14587,
14602, 14621, 14638, 14645, 14648, 14652, 14660, 14661, 14683, 14694,
14716, 14743, 14767.
* Support for STT_GNU_IFUNC symbols added for s390 and s390x.
Optimized versions of memcpy, memset, and memcmp added for System z10 and

5
ports/ChangeLog.alpha
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@ -1,3 +1,8 @@
2012-10-30 Joseph Myers <joseph@codesourcery.com>
[BZ #14047]
* sysdeps/alpha/tininess.h: New file.
2012-10-19 Roland McGrath <roland@hack.frob.com>
* sysdeps/unix/sysv/linux/alpha/nptl/libc.abilist

5
ports/ChangeLog.am33
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@ -1,3 +1,8 @@
2012-10-30 Joseph Myers <joseph@codesourcery.com>
[BZ #14047]
* sysdeps/am33/tininess.h: New file.
2012-10-09 Roland McGrath <roland@hack.frob.com>
* sysdeps/unix/sysv/linux/am33/configure: Regenerated.

5
ports/ChangeLog.hppa
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@ -1,3 +1,8 @@
2012-10-30 Joseph Myers <joseph@codesourcery.com>
[BZ #14047]
* sysdeps/hppa/tininess.h: New file.
2012-10-29 Carlos O'Donell <carlos@systemhalted.org>
* sysdeps/unix/sysv/linux/hppa/sysdep.h (ENTRY): Add cfi_startproc.

5
ports/ChangeLog.ia64
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@ -1,3 +1,8 @@
2012-10-30 Joseph Myers <joseph@codesourcery.com>
[BZ #14047]
* sysdeps/ia64/tininess.h: New file.
2012-10-25 Andreas Jaeger <aj@suse.de>
* sysdeps/unix/sysv/linux/ia64/bits/fcntl.h: Remove all

5
ports/ChangeLog.mips
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@ -1,3 +1,8 @@
2012-10-30 Joseph Myers <joseph@codesourcery.com>
[BZ #14047]
* sysdeps/mips/tininess.h: New file.
2012-10-29 Steve Ellcey <sellcey@mips.com>
* sysdeps/unix/sysv/linux/mips/mips32/Makefile: Remove.

1
ports/sysdeps/alpha/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

1
ports/sysdeps/am33/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

1
ports/sysdeps/hppa/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

1
ports/sysdeps/ia64/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

1
ports/sysdeps/mips/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

5
stdlib/Makefile
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@ -69,7 +69,8 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \
tst-makecontext tst-strtod4 tst-strtod5 tst-qsort2 \
tst-makecontext2 tst-strtod6 tst-unsetenv1 \
tst-makecontext3 bug-getcontext bug-fmtmsg1 \
tst-secure-getenv tst-strtod-overflow tst-strtod-round
tst-secure-getenv tst-strtod-overflow tst-strtod-round \
tst-tininess tst-strtod-underflow
tests-static := tst-secure-getenv
include ../Makeconfig
@ -151,3 +152,5 @@ link-libm = $(common-objpfx)math/libm.a
endif
$(objpfx)bug-getcontext: $(link-libm)
$(objpfx)tst-strtod-round: $(link-libm)
$(objpfx)tst-tininess: $(link-libm)
$(objpfx)tst-strtod-underflow: $(link-libm)

43
stdlib/strtod_l.c
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@ -62,6 +62,7 @@ extern unsigned long long int ____strtoull_l_internal (const char *, char **,
#include <string.h>
#include <stdint.h>
#include <rounding-mode.h>
#include <tininess.h>
/* The gmp headers need some configuration frobs. */
#define HAVE_ALLOCA 1
@ -209,12 +210,15 @@ static FLOAT
round_and_return (mp_limb_t *retval, intmax_t exponent, int negative,
mp_limb_t round_limb, mp_size_t round_bit, int more_bits)
{
int mode = get_rounding_mode ();
if (exponent < MIN_EXP - 1)
{
if (exponent < MIN_EXP - 1 - MANT_DIG)
return underflow_value (negative);
mp_size_t shift = MIN_EXP - 1 - exponent;
bool is_tiny = true;
more_bits |= (round_limb & ((((mp_limb_t) 1) << round_bit) - 1)) != 0;
if (shift == MANT_DIG)
@ -248,6 +252,33 @@ round_and_return (mp_limb_t *retval, intmax_t exponent, int negative,
}
else if (shift > 0)
{
if (TININESS_AFTER_ROUNDING && shift == 1)
{
/* Whether the result counts as tiny depends on whether,
after rounding to the normal precision, it still has
a subnormal exponent. */
mp_limb_t retval_normal[RETURN_LIMB_SIZE];
if (round_away (negative,
(retval[0] & 1) != 0,
(round_limb
& (((mp_limb_t) 1) << round_bit)) != 0,
(more_bits
|| ((round_limb
& ((((mp_limb_t) 1) << round_bit) - 1))
!= 0)),
mode))
{
mp_limb_t cy = __mpn_add_1 (retval_normal, retval,
RETURN_LIMB_SIZE, 1);
if (((MANT_DIG % BITS_PER_MP_LIMB) == 0 && cy) ||
((MANT_DIG % BITS_PER_MP_LIMB) != 0 &&
((retval_normal[RETURN_LIMB_SIZE - 1]
& (((mp_limb_t) 1) << (MANT_DIG % BITS_PER_MP_LIMB)))
!= 0)))
is_tiny = false;
}
}
round_limb = retval[0];
round_bit = shift - 1;
(void) __mpn_rshift (retval, retval, RETURN_LIMB_SIZE, shift);
@ -259,14 +290,20 @@ round_and_return (mp_limb_t *retval, intmax_t exponent, int negative,
# define DENORM_EXP (MIN_EXP - 2)
#endif
exponent = DENORM_EXP;
__set_errno (ERANGE);
if (is_tiny
&& ((round_limb & (((mp_limb_t) 1) << round_bit)) != 0
|| more_bits
|| (round_limb & ((((mp_limb_t) 1) << round_bit) - 1)) != 0))
{
__set_errno (ERANGE);
volatile FLOAT force_underflow_exception = MIN_VALUE * MIN_VALUE;
(void) force_underflow_exception;
}
}
if (exponent > MAX_EXP)
goto overflow;
int mode = get_rounding_mode ();
if (round_away (negative,
(retval[0] & 1) != 0,
(round_limb & (((mp_limb_t) 1) << round_bit)) != 0,

225
stdlib/tst-strtod-underflow.c Normal file
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@ -0,0 +1,225 @@
/* Test for strtod handling of arguments that may cause floating-point
underflow.
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 <errno.h>
#include <fenv.h>
#include <float.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <tininess.h>
enum underflow_case
{
/* Result is exact or outside the subnormal range. */
UNDERFLOW_NONE,
/* Result has magnitude at most half way between the largest
subnormal value and the smallest positive normal value, and is
not exact, so underflows in all rounding modes and independent
of how tininess is detected. */
UNDERFLOW_ALWAYS,
/* Result is positive, with magnitude larger than half way between
the largest subnormal value and the least positive normal
value, but would underflow when rounded to nearest to normal
precision, so underflows after rounding in all modes except
rounding upward. */
UNDERFLOW_EXCEPT_UPWARD,
/* Likewise, for a negative result, underflowing after rounding
except when rounding downward. */
UNDERFLOW_EXCEPT_DOWNWARD,
/* Result is positive, with magnitude at least three quarters of
the way from the largest subnormal value to the smallest
positive normal value, so underflows after rounding only when
rounding downward or toward zero. */
UNDERFLOW_ONLY_DOWNWARD_ZERO,
/* Likewise, for a negative result, underflowing after rounding
only when rounding upward or toward zero. */
UNDERFLOW_ONLY_UPWARD_ZERO,
};
struct test
{
const char *s;
enum underflow_case c;
};
static const struct test tests[] =
{
{ "0x1p-1022", UNDERFLOW_NONE },
{ "-0x1p-1022", UNDERFLOW_NONE },
{ "0x0p-10000000000000000000000000", UNDERFLOW_NONE },
{ "-0x0p-10000000000000000000000000", UNDERFLOW_NONE },
{ "0x1p-10000000000000000000000000", UNDERFLOW_ALWAYS },
{ "-0x1p-10000000000000000000000000", UNDERFLOW_ALWAYS },
{ "0x1.000000000000000000001p-1022", UNDERFLOW_NONE },
{ "-0x1.000000000000000000001p-1022", UNDERFLOW_NONE },
{ "0x1p-1075", UNDERFLOW_ALWAYS },
{ "-0x1p-1075", UNDERFLOW_ALWAYS },
{ "0x1p-1023", UNDERFLOW_NONE },
{ "-0x1p-1023", UNDERFLOW_NONE },
{ "0x1p-1074", UNDERFLOW_NONE },
{ "-0x1p-1074", UNDERFLOW_NONE },
{ "0x1.ffffffffffffep-1023", UNDERFLOW_NONE },
{ "-0x1.ffffffffffffep-1023", UNDERFLOW_NONE },
{ "0x1.fffffffffffffp-1023", UNDERFLOW_ALWAYS },
{ "-0x1.fffffffffffffp-1023", UNDERFLOW_ALWAYS },
{ "0x1.fffffffffffff0001p-1023", UNDERFLOW_EXCEPT_UPWARD },
{ "-0x1.fffffffffffff0001p-1023", UNDERFLOW_EXCEPT_DOWNWARD },
{ "0x1.fffffffffffff7fffp-1023", UNDERFLOW_EXCEPT_UPWARD },
{ "-0x1.fffffffffffff7fffp-1023", UNDERFLOW_EXCEPT_DOWNWARD },
{ "0x1.fffffffffffff8p-1023", UNDERFLOW_ONLY_DOWNWARD_ZERO },
{ "-0x1.fffffffffffff8p-1023", UNDERFLOW_ONLY_UPWARD_ZERO },
{ "0x1.fffffffffffffffffp-1023", UNDERFLOW_ONLY_DOWNWARD_ZERO },
{ "-0x1.fffffffffffffffffp-1023", UNDERFLOW_ONLY_UPWARD_ZERO },
};
/* Return whether to expect underflow from a particular testcase, in a
given rounding mode. */
static bool
expect_underflow (enum underflow_case c, int rm)
{
if (c == UNDERFLOW_NONE)
return false;
if (c == UNDERFLOW_ALWAYS)
return true;
if (TININESS_AFTER_ROUNDING)
{
switch (rm)
{
#ifdef FE_DOWNWARD
case FE_DOWNWARD:
return (c == UNDERFLOW_EXCEPT_UPWARD
|| c == UNDERFLOW_ONLY_DOWNWARD_ZERO);
#endif
#ifdef FE_TOWARDZERO
case FE_TOWARDZERO:
return true;
#endif
#ifdef FE_UPWARD
case FE_UPWARD:
return (c == UNDERFLOW_EXCEPT_DOWNWARD
|| c == UNDERFLOW_ONLY_UPWARD_ZERO);
#endif
default:
return (c == UNDERFLOW_EXCEPT_UPWARD
|| c == UNDERFLOW_EXCEPT_DOWNWARD);
}
}
else
return true;
}
static bool support_underflow_exception = false;
volatile double d = DBL_MIN;
volatile double dd;
static int
test_in_one_mode (const char *s, enum underflow_case c, int rm,
const char *mode_name)
{
int result = 0;
feclearexcept (FE_ALL_EXCEPT);
errno = 0;
double d = strtod (s, NULL);
int got_errno = errno;
#ifdef FE_UNDERFLOW
bool got_fe_underflow = fetestexcept (FE_UNDERFLOW) != 0;
#else
bool got_fe_underflow = false;
#endif
printf ("strtod (%s) (%s) returned %a, errno = %d, %sunderflow exception\n",
s, mode_name, d, got_errno, got_fe_underflow ? "" : "no ");
bool this_expect_underflow = expect_underflow (c, rm);
if (got_errno != 0 && got_errno != ERANGE)
{
puts ("FAIL: errno neither 0 nor ERANGE");
result = 1;
}
else if (this_expect_underflow != (errno == ERANGE))
{
puts ("FAIL: underflow from errno differs from expectations");
result = 1;
}
if (support_underflow_exception && got_fe_underflow != this_expect_underflow)
{
puts ("FAIL: underflow from exceptions differs from expectations");
result = 1;
}
return result;
}
static int
do_test (void)
{
int save_round_mode = fegetround ();
int result = 0;
#ifdef FE_TONEAREST
const int fe_tonearest = FE_TONEAREST;
#else
const int fe_tonearest = 0;
# if defined FE_DOWNWARD || defined FE_TOWARDZERO || defined FE_UPWARD
# error "FE_TONEAREST not defined, but another rounding mode is"
# endif
#endif
#ifdef FE_UNDERFLOW
feclearexcept (FE_ALL_EXCEPT);
dd = d * d;
if (fetestexcept (FE_UNDERFLOW))
support_underflow_exception = true;
else
puts ("underflow exception not supported at runtime, only testing errno");
#endif
for (size_t i = 0; i < sizeof (tests) / sizeof (tests[0]); i++)
{
result |= test_in_one_mode (tests[i].s, tests[i].c, fe_tonearest,
"default rounding mode");
#ifdef FE_DOWNWARD
if (!fesetround (FE_DOWNWARD))
{
result |= test_in_one_mode (tests[i].s, tests[i].c, FE_DOWNWARD,
"FE_DOWNWARD");
fesetround (save_round_mode);
}
#endif
#ifdef FE_TOWARDZERO
if (!fesetround (FE_TOWARDZERO))
{
result |= test_in_one_mode (tests[i].s, tests[i].c, FE_TOWARDZERO,
"FE_TOWARDZERO");
fesetround (save_round_mode);
}
#endif
#ifdef FE_UPWARD
if (!fesetround (FE_UPWARD))
{
result |= test_in_one_mode (tests[i].s, tests[i].c, FE_UPWARD,
"FE_UPWARD");
fesetround (save_round_mode);
}
#endif
}
return result;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"

4
stdlib/tst-strtod.c
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@ -60,10 +60,10 @@ static const struct ltest tests[] =
{ "0x00.0014p19", 160.0, '\0', 0 },
{ "0x1p-1023",
1.11253692925360069154511635866620203210960799023116591527666e-308,
'\0', ERANGE },
'\0', 0 },
{ "0x0.8p-1022",
1.11253692925360069154511635866620203210960799023116591527666e-308,
'\0', ERANGE },
'\0', 0 },
{ "Inf", HUGE_VAL, '\0', 0 },
{ "-Inf", -HUGE_VAL, '\0', 0 },
{ "+InFiNiTy", HUGE_VAL, '\0', 0 },

69
stdlib/tst-tininess.c Normal file
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@ -0,0 +1,69 @@
/* Test that tininess.h is correct for this architecture.
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 <float.h>
#include <stdio.h>
#include <tininess.h>
volatile float a = 0x1.fffp-126;
volatile float b = 0x1.0008p-1;
volatile float c;
volatile float m = FLT_MIN;
volatile float mm;
static int
do_test (void)
{
int result = 0;
#ifdef FE_UNDERFLOW
feclearexcept (FE_ALL_EXCEPT);
mm = m * m;
if (!fetestexcept (FE_UNDERFLOW))
{
puts ("underflow exception not supported at runtime, cannot test");
return 0;
}
feclearexcept (FE_ALL_EXCEPT);
c = a * b;
if (fetestexcept (FE_UNDERFLOW))
{
if (TININESS_AFTER_ROUNDING)
{
puts ("tininess.h says after rounding, "
"but detected before rounding");
result = 1;
}
}
else
{
if (!TININESS_AFTER_ROUNDING)
{
puts ("tininess.h says before rounding, "
"but detected after rounding");
result = 1;
}
}
#else
puts ("underflow exception not supported at compile time, cannot test");
#endif
return result;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"

33
sysdeps/generic/tininess.h Normal file
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@ -0,0 +1,33 @@
/* Specify architecture-specific rules for determining tininess of
floating-point results. Generic version.
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/>. */
#ifndef _TININESS_H
#define _TININESS_H 1
/* Under IEEE 754, an architecture may determine tininess of
floating-point results either "before rounding" or "after
rounding", but must do so in the same way for all operations
returning binary results. Define TININESS_AFTER_ROUNDING to 1 for
"after rounding" architectures, 0 for "before rounding"
architectures. The test stdlib/tst-tininess will fail if the
definition is incorrect. */
#define TININESS_AFTER_ROUNDING 0
#endif /* tininess.h */

1
sysdeps/i386/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

1
sysdeps/sh/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1

1
sysdeps/x86_64/tininess.h Normal file
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@ -0,0 +1 @@
#define TININESS_AFTER_ROUNDING 1