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/* Test for strtod handling of arguments that may cause floating-point
underflow.
Copyright (C) 2012-2023 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 <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 __attribute__ ((unused)) = 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"
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