37a4c70bd4
When the signs differ, the precision of the conversion sometimes drops below 106 bits. This strategy is identical to the hexadecimal variant. I've refactored tst-sprintf3 to enable testing a value with more than 30 significant digits in order to demonstrate this failure and its solution. Additionally, this implicitly fixes a typo in the shift quantities when subtracting from the high mantissa to compute the difference.
100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/* Copyright (C) 2012-2016 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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/* Test bug #13941. */
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#include <float.h>
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#include <math.h>
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#include <stdio.h>
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#include <string.h>
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static int
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do_test (void)
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{
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#if LDBL_MANT_DIG >= 106
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volatile union { long double l; long long x[2]; } u, v;
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char buf[64];
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#endif
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int result = 0;
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#if LDBL_MANT_DIG == 106 || LDBL_MANT_DIG == 113
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# define COMPARE_LDBL(u, v) \
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((u).l == (v).l && (u).x[0] == (v).x[0] && (u).x[1] == (v).x[1])
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#else
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# define COMPARE_LDBL(u, v) ((u).l == (v).l)
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#endif
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#define TEST_N(val, n) \
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do \
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{ \
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u.l = (val); \
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snprintf (buf, sizeof buf, "%." #n "LgL", u.l); \
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if (strcmp (buf, #val) != 0) \
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{ \
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printf ("Error on line %d: %s != %s\n", __LINE__, buf, #val); \
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result = 1; \
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} \
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if (sscanf (#val, "%Lg", &v.l) != 1 || !COMPARE_LDBL (u, v)) \
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{ \
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printf ("Error sscanf on line %d: %." #n "Lg != %." #n "Lg\n", \
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__LINE__, u.l, v.l); \
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result = 1; \
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} \
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/* printf ("%s %Lg %016Lx %016Lx\n", #val, u.l, u.x[0], u.x[1]); */ \
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} \
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while (0)
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#define TEST(val) TEST_N (val,30)
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#if LDBL_MANT_DIG >= 106
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# if LDBL_MANT_DIG == 106
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TEST (2.22507385850719347803989925739e-308L);
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TEST (2.22507385850719397210554509863e-308L);
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TEST (2.22507385850720088902458687609e-308L);
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/* Verify precision is not lost for long doubles
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of the form +1.pN,-1.pM. */
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TEST_N (3.32306998946228968225951765070082e+35L, 34);
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# endif
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TEST (2.22507385850720138309023271733e-308L);
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TEST (2.22507385850720187715587855858e-308L);
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TEST (2.2250738585074419930597574044e-308L);
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TEST (4.45014771701440227211481959342e-308L);
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TEST (4.45014771701440276618046543466e-308L);
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TEST (4.45014771701440375431175711716e-308L);
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TEST (4.45014771701440474244304879965e-308L);
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TEST (7.12023634722304600689881138745e-307L);
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TEST (1.13923781555569064960474854133e-305L);
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TEST (1.13777777777777776389998996996L);
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TEST (1.13777777777777765287768750745L);
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TEST (20988295479420645138.2044444444L);
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TEST (20988295479420643090.2044444444L);
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TEST (2.14668699894294423266045294316e-292L);
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# if LDBL_MANT_DIG == 106
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TEST (-2.35993711055432139266626434123e-292L);
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TEST (6.26323524637968345414769634658e-302L);
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TEST (1.49327164802066885331814201989e-308L);
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TEST (3.71834550652787023640837473722e-308L);
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TEST (9.51896449671134907001349268087e-306L);
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# endif
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#endif
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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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