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