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2a27fd6d JM |
1 | /* Test for strtod handling of arguments that may cause floating-point |
2 | underflow. | |
d614a753 | 3 | Copyright (C) 2012-2020 Free Software Foundation, Inc. |
2a27fd6d JM |
4 | This file is part of the GNU C Library. |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public | |
17 | License along with the GNU C Library; if not, see | |
5a82c748 | 18 | <https://www.gnu.org/licenses/>. */ |
2a27fd6d JM |
19 | |
20 | #include <errno.h> | |
21 | #include <fenv.h> | |
22 | #include <float.h> | |
23 | #include <stdbool.h> | |
24 | #include <stdio.h> | |
25 | #include <stdlib.h> | |
26 | #include <tininess.h> | |
27 | ||
28 | enum underflow_case | |
29 | { | |
30 | /* Result is exact or outside the subnormal range. */ | |
31 | UNDERFLOW_NONE, | |
32 | /* Result has magnitude at most half way between the largest | |
33 | subnormal value and the smallest positive normal value, and is | |
34 | not exact, so underflows in all rounding modes and independent | |
35 | of how tininess is detected. */ | |
36 | UNDERFLOW_ALWAYS, | |
37 | /* Result is positive, with magnitude larger than half way between | |
38 | the largest subnormal value and the least positive normal | |
39 | value, but would underflow when rounded to nearest to normal | |
40 | precision, so underflows after rounding in all modes except | |
41 | rounding upward. */ | |
42 | UNDERFLOW_EXCEPT_UPWARD, | |
43 | /* Likewise, for a negative result, underflowing after rounding | |
44 | except when rounding downward. */ | |
45 | UNDERFLOW_EXCEPT_DOWNWARD, | |
46 | /* Result is positive, with magnitude at least three quarters of | |
47 | the way from the largest subnormal value to the smallest | |
48 | positive normal value, so underflows after rounding only when | |
49 | rounding downward or toward zero. */ | |
50 | UNDERFLOW_ONLY_DOWNWARD_ZERO, | |
51 | /* Likewise, for a negative result, underflowing after rounding | |
52 | only when rounding upward or toward zero. */ | |
53 | UNDERFLOW_ONLY_UPWARD_ZERO, | |
54 | }; | |
55 | ||
56 | struct test | |
57 | { | |
58 | const char *s; | |
59 | enum underflow_case c; | |
60 | }; | |
61 | ||
62 | static const struct test tests[] = | |
63 | { | |
64 | { "0x1p-1022", UNDERFLOW_NONE }, | |
65 | { "-0x1p-1022", UNDERFLOW_NONE }, | |
66 | { "0x0p-10000000000000000000000000", UNDERFLOW_NONE }, | |
67 | { "-0x0p-10000000000000000000000000", UNDERFLOW_NONE }, | |
68 | { "0x1p-10000000000000000000000000", UNDERFLOW_ALWAYS }, | |
69 | { "-0x1p-10000000000000000000000000", UNDERFLOW_ALWAYS }, | |
70 | { "0x1.000000000000000000001p-1022", UNDERFLOW_NONE }, | |
71 | { "-0x1.000000000000000000001p-1022", UNDERFLOW_NONE }, | |
72 | { "0x1p-1075", UNDERFLOW_ALWAYS }, | |
73 | { "-0x1p-1075", UNDERFLOW_ALWAYS }, | |
74 | { "0x1p-1023", UNDERFLOW_NONE }, | |
75 | { "-0x1p-1023", UNDERFLOW_NONE }, | |
76 | { "0x1p-1074", UNDERFLOW_NONE }, | |
77 | { "-0x1p-1074", UNDERFLOW_NONE }, | |
78 | { "0x1.ffffffffffffep-1023", UNDERFLOW_NONE }, | |
79 | { "-0x1.ffffffffffffep-1023", UNDERFLOW_NONE }, | |
80 | { "0x1.fffffffffffffp-1023", UNDERFLOW_ALWAYS }, | |
81 | { "-0x1.fffffffffffffp-1023", UNDERFLOW_ALWAYS }, | |
82 | { "0x1.fffffffffffff0001p-1023", UNDERFLOW_EXCEPT_UPWARD }, | |
83 | { "-0x1.fffffffffffff0001p-1023", UNDERFLOW_EXCEPT_DOWNWARD }, | |
84 | { "0x1.fffffffffffff7fffp-1023", UNDERFLOW_EXCEPT_UPWARD }, | |
85 | { "-0x1.fffffffffffff7fffp-1023", UNDERFLOW_EXCEPT_DOWNWARD }, | |
86 | { "0x1.fffffffffffff8p-1023", UNDERFLOW_ONLY_DOWNWARD_ZERO }, | |
87 | { "-0x1.fffffffffffff8p-1023", UNDERFLOW_ONLY_UPWARD_ZERO }, | |
88 | { "0x1.fffffffffffffffffp-1023", UNDERFLOW_ONLY_DOWNWARD_ZERO }, | |
89 | { "-0x1.fffffffffffffffffp-1023", UNDERFLOW_ONLY_UPWARD_ZERO }, | |
90 | }; | |
91 | ||
92 | /* Return whether to expect underflow from a particular testcase, in a | |
93 | given rounding mode. */ | |
94 | ||
95 | static bool | |
96 | expect_underflow (enum underflow_case c, int rm) | |
97 | { | |
98 | if (c == UNDERFLOW_NONE) | |
99 | return false; | |
100 | if (c == UNDERFLOW_ALWAYS) | |
101 | return true; | |
102 | if (TININESS_AFTER_ROUNDING) | |
103 | { | |
104 | switch (rm) | |
105 | { | |
106 | #ifdef FE_DOWNWARD | |
107 | case FE_DOWNWARD: | |
108 | return (c == UNDERFLOW_EXCEPT_UPWARD | |
109 | || c == UNDERFLOW_ONLY_DOWNWARD_ZERO); | |
110 | #endif | |
111 | ||
112 | #ifdef FE_TOWARDZERO | |
113 | case FE_TOWARDZERO: | |
114 | return true; | |
115 | #endif | |
116 | ||
117 | #ifdef FE_UPWARD | |
118 | case FE_UPWARD: | |
119 | return (c == UNDERFLOW_EXCEPT_DOWNWARD | |
120 | || c == UNDERFLOW_ONLY_UPWARD_ZERO); | |
121 | #endif | |
122 | ||
123 | default: | |
124 | return (c == UNDERFLOW_EXCEPT_UPWARD | |
125 | || c == UNDERFLOW_EXCEPT_DOWNWARD); | |
126 | } | |
127 | } | |
128 | else | |
129 | return true; | |
130 | } | |
131 | ||
132 | static bool support_underflow_exception = false; | |
133 | volatile double d = DBL_MIN; | |
134 | volatile double dd; | |
135 | ||
136 | static int | |
137 | test_in_one_mode (const char *s, enum underflow_case c, int rm, | |
138 | const char *mode_name) | |
139 | { | |
140 | int result = 0; | |
141 | feclearexcept (FE_ALL_EXCEPT); | |
142 | errno = 0; | |
143 | double d = strtod (s, NULL); | |
144 | int got_errno = errno; | |
145 | #ifdef FE_UNDERFLOW | |
146 | bool got_fe_underflow = fetestexcept (FE_UNDERFLOW) != 0; | |
147 | #else | |
148 | bool got_fe_underflow = false; | |
149 | #endif | |
150 | printf ("strtod (%s) (%s) returned %a, errno = %d, %sunderflow exception\n", | |
151 | s, mode_name, d, got_errno, got_fe_underflow ? "" : "no "); | |
152 | bool this_expect_underflow = expect_underflow (c, rm); | |
153 | if (got_errno != 0 && got_errno != ERANGE) | |
154 | { | |
155 | puts ("FAIL: errno neither 0 nor ERANGE"); | |
156 | result = 1; | |
157 | } | |
158 | else if (this_expect_underflow != (errno == ERANGE)) | |
159 | { | |
160 | puts ("FAIL: underflow from errno differs from expectations"); | |
161 | result = 1; | |
162 | } | |
163 | if (support_underflow_exception && got_fe_underflow != this_expect_underflow) | |
164 | { | |
165 | puts ("FAIL: underflow from exceptions differs from expectations"); | |
166 | result = 1; | |
167 | } | |
168 | return result; | |
169 | } | |
170 | ||
171 | static int | |
172 | do_test (void) | |
173 | { | |
1ff950ad | 174 | int save_round_mode __attribute__ ((unused)) = fegetround (); |
2a27fd6d JM |
175 | int result = 0; |
176 | #ifdef FE_TONEAREST | |
177 | const int fe_tonearest = FE_TONEAREST; | |
178 | #else | |
179 | const int fe_tonearest = 0; | |
180 | # if defined FE_DOWNWARD || defined FE_TOWARDZERO || defined FE_UPWARD | |
181 | # error "FE_TONEAREST not defined, but another rounding mode is" | |
182 | # endif | |
183 | #endif | |
184 | #ifdef FE_UNDERFLOW | |
185 | feclearexcept (FE_ALL_EXCEPT); | |
186 | dd = d * d; | |
187 | if (fetestexcept (FE_UNDERFLOW)) | |
188 | support_underflow_exception = true; | |
189 | else | |
190 | puts ("underflow exception not supported at runtime, only testing errno"); | |
191 | #endif | |
192 | for (size_t i = 0; i < sizeof (tests) / sizeof (tests[0]); i++) | |
193 | { | |
194 | result |= test_in_one_mode (tests[i].s, tests[i].c, fe_tonearest, | |
195 | "default rounding mode"); | |
196 | #ifdef FE_DOWNWARD | |
197 | if (!fesetround (FE_DOWNWARD)) | |
198 | { | |
199 | result |= test_in_one_mode (tests[i].s, tests[i].c, FE_DOWNWARD, | |
200 | "FE_DOWNWARD"); | |
201 | fesetround (save_round_mode); | |
202 | } | |
203 | #endif | |
204 | #ifdef FE_TOWARDZERO | |
205 | if (!fesetround (FE_TOWARDZERO)) | |
206 | { | |
207 | result |= test_in_one_mode (tests[i].s, tests[i].c, FE_TOWARDZERO, | |
208 | "FE_TOWARDZERO"); | |
209 | fesetround (save_round_mode); | |
210 | } | |
211 | #endif | |
212 | #ifdef FE_UPWARD | |
213 | if (!fesetround (FE_UPWARD)) | |
214 | { | |
215 | result |= test_in_one_mode (tests[i].s, tests[i].c, FE_UPWARD, | |
216 | "FE_UPWARD"); | |
217 | fesetround (save_round_mode); | |
218 | } | |
219 | #endif | |
220 | } | |
221 | return result; | |
222 | } | |
223 | ||
224 | #define TEST_FUNCTION do_test () | |
225 | #include "../test-skeleton.c" |