diff options
Diffstat (limited to 'gl/intprops.h')
-rw-r--r-- | gl/intprops.h | 484 |
1 files changed, 402 insertions, 82 deletions
diff --git a/gl/intprops.h b/gl/intprops.h index f57f9b4d..3fe64e82 100644 --- a/gl/intprops.h +++ b/gl/intprops.h | |||
@@ -1,34 +1,33 @@ | |||
1 | /* intprops.h -- properties of integer types | 1 | /* intprops.h -- properties of integer types |
2 | 2 | ||
3 | Copyright (C) 2001-2005, 2009-2013 Free Software Foundation, Inc. | 3 | Copyright (C) 2001-2021 Free Software Foundation, Inc. |
4 | 4 | ||
5 | This program is free software: you can redistribute it and/or modify | 5 | This program is free software: you can redistribute it and/or modify it |
6 | it under the terms of the GNU General Public License as published by | 6 | under the terms of the GNU Lesser General Public License as published |
7 | the Free Software Foundation; either version 3 of the License, or | 7 | by the Free Software Foundation; either version 2.1 of the License, or |
8 | (at your option) any later version. | 8 | (at your option) any later version. |
9 | 9 | ||
10 | This program is distributed in the hope that it will be useful, | 10 | This program is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
13 | GNU General Public License for more details. | 13 | GNU Lesser General Public License for more details. |
14 | 14 | ||
15 | You should have received a copy of the GNU General Public License | 15 | You should have received a copy of the GNU Lesser General Public License |
16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ | 16 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
17 | 17 | ||
18 | /* Written by Paul Eggert. */ | ||
19 | 18 | ||
20 | #ifndef _GL_INTPROPS_H | 19 | #ifndef _GL_INTPROPS_H |
21 | #define _GL_INTPROPS_H | 20 | #define _GL_INTPROPS_H |
22 | 21 | ||
23 | #include <limits.h> | 22 | #include <limits.h> |
24 | 23 | ||
25 | /* Return an integer value, converted to the same type as the integer | 24 | /* Return a value with the common real type of E and V and the value of V. |
26 | expression E after integer type promotion. V is the unconverted value. */ | 25 | Do not evaluate E. */ |
27 | #define _GL_INT_CONVERT(e, v) (0 * (e) + (v)) | 26 | #define _GL_INT_CONVERT(e, v) ((1 ? 0 : (e)) + (v)) |
28 | 27 | ||
29 | /* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see | 28 | /* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see |
30 | <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00406.html>. */ | 29 | <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00406.html>. */ |
31 | #define _GL_INT_NEGATE_CONVERT(e, v) (0 * (e) - (v)) | 30 | #define _GL_INT_NEGATE_CONVERT(e, v) ((1 ? 0 : (e)) - (v)) |
32 | 31 | ||
33 | /* The extra casts in the following macros work around compiler bugs, | 32 | /* The extra casts in the following macros work around compiler bugs, |
34 | e.g., in Cray C 5.0.3.0. */ | 33 | e.g., in Cray C 5.0.3.0. */ |
@@ -37,67 +36,67 @@ | |||
37 | an integer. */ | 36 | an integer. */ |
38 | #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) | 37 | #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) |
39 | 38 | ||
40 | /* True if negative values of the signed integer type T use two's | 39 | /* True if the real type T is signed. */ |
41 | complement, ones' complement, or signed magnitude representation, | ||
42 | respectively. Much GNU code assumes two's complement, but some | ||
43 | people like to be portable to all possible C hosts. */ | ||
44 | #define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1) | ||
45 | #define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0) | ||
46 | #define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1) | ||
47 | |||
48 | /* True if the signed integer expression E uses two's complement. */ | ||
49 | #define _GL_INT_TWOS_COMPLEMENT(e) (~ _GL_INT_CONVERT (e, 0) == -1) | ||
50 | |||
51 | /* True if the arithmetic type T is signed. */ | ||
52 | #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) | 40 | #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) |
53 | 41 | ||
54 | /* Return 1 if the integer expression E, after integer promotion, has | 42 | /* Return 1 if the real expression E, after promotion, has a |
55 | a signed type. */ | 43 | signed or floating type. Do not evaluate E. */ |
56 | #define _GL_INT_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0) | 44 | #define EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0) |
57 | 45 | ||
58 | 46 | ||
59 | /* Minimum and maximum values for integer types and expressions. These | 47 | /* Minimum and maximum values for integer types and expressions. */ |
60 | macros have undefined behavior if T is signed and has padding bits. | 48 | |
61 | If this is a problem for you, please let us know how to fix it for | 49 | /* The width in bits of the integer type or expression T. |
62 | your host. */ | 50 | Do not evaluate T. T must not be a bit-field expression. |
51 | Padding bits are not supported; this is checked at compile-time below. */ | ||
52 | #define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT) | ||
63 | 53 | ||
64 | /* The maximum and minimum values for the integer type T. */ | 54 | /* The maximum and minimum values for the integer type T. */ |
65 | #define TYPE_MINIMUM(t) \ | 55 | #define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t)) |
66 | ((t) (! TYPE_SIGNED (t) \ | ||
67 | ? (t) 0 \ | ||
68 | : TYPE_SIGNED_MAGNITUDE (t) \ | ||
69 | ? ~ (t) 0 \ | ||
70 | : ~ TYPE_MAXIMUM (t))) | ||
71 | #define TYPE_MAXIMUM(t) \ | 56 | #define TYPE_MAXIMUM(t) \ |
72 | ((t) (! TYPE_SIGNED (t) \ | 57 | ((t) (! TYPE_SIGNED (t) \ |
73 | ? (t) -1 \ | 58 | ? (t) -1 \ |
74 | : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1))) | 59 | : ((((t) 1 << (TYPE_WIDTH (t) - 2)) - 1) * 2 + 1))) |
75 | 60 | ||
76 | /* The maximum and minimum values for the type of the expression E, | 61 | /* The maximum and minimum values for the type of the expression E, |
77 | after integer promotion. E should not have side effects. */ | 62 | after integer promotion. E is not evaluated. */ |
78 | #define _GL_INT_MINIMUM(e) \ | 63 | #define _GL_INT_MINIMUM(e) \ |
79 | (_GL_INT_SIGNED (e) \ | 64 | (EXPR_SIGNED (e) \ |
80 | ? - _GL_INT_TWOS_COMPLEMENT (e) - _GL_SIGNED_INT_MAXIMUM (e) \ | 65 | ? ~ _GL_SIGNED_INT_MAXIMUM (e) \ |
81 | : _GL_INT_CONVERT (e, 0)) | 66 | : _GL_INT_CONVERT (e, 0)) |
82 | #define _GL_INT_MAXIMUM(e) \ | 67 | #define _GL_INT_MAXIMUM(e) \ |
83 | (_GL_INT_SIGNED (e) \ | 68 | (EXPR_SIGNED (e) \ |
84 | ? _GL_SIGNED_INT_MAXIMUM (e) \ | 69 | ? _GL_SIGNED_INT_MAXIMUM (e) \ |
85 | : _GL_INT_NEGATE_CONVERT (e, 1)) | 70 | : _GL_INT_NEGATE_CONVERT (e, 1)) |
86 | #define _GL_SIGNED_INT_MAXIMUM(e) \ | 71 | #define _GL_SIGNED_INT_MAXIMUM(e) \ |
87 | (((_GL_INT_CONVERT (e, 1) << (sizeof ((e) + 0) * CHAR_BIT - 2)) - 1) * 2 + 1) | 72 | (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH (+ (e)) - 2)) - 1) * 2 + 1) |
88 | 73 | ||
74 | /* Work around OpenVMS incompatibility with C99. */ | ||
75 | #if !defined LLONG_MAX && defined __INT64_MAX | ||
76 | # define LLONG_MAX __INT64_MAX | ||
77 | # define LLONG_MIN __INT64_MIN | ||
78 | #endif | ||
79 | |||
80 | /* This include file assumes that signed types are two's complement without | ||
81 | padding bits; the above macros have undefined behavior otherwise. | ||
82 | If this is a problem for you, please let us know how to fix it for your host. | ||
83 | This assumption is tested by the intprops-tests module. */ | ||
89 | 84 | ||
90 | /* Return 1 if the __typeof__ keyword works. This could be done by | 85 | /* Does the __typeof__ keyword work? This could be done by |
91 | 'configure', but for now it's easier to do it by hand. */ | 86 | 'configure', but for now it's easier to do it by hand. */ |
92 | #if 2 <= __GNUC__ || defined __IBM__TYPEOF__ || 0x5110 <= __SUNPRO_C | 87 | #if (2 <= __GNUC__ \ |
88 | || (4 <= __clang_major__) \ | ||
89 | || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \ | ||
90 | || (0x5110 <= __SUNPRO_C && !__STDC__)) | ||
93 | # define _GL_HAVE___TYPEOF__ 1 | 91 | # define _GL_HAVE___TYPEOF__ 1 |
94 | #else | 92 | #else |
95 | # define _GL_HAVE___TYPEOF__ 0 | 93 | # define _GL_HAVE___TYPEOF__ 0 |
96 | #endif | 94 | #endif |
97 | 95 | ||
98 | /* Return 1 if the integer type or expression T might be signed. Return 0 | 96 | /* Return 1 if the integer type or expression T might be signed. Return 0 |
99 | if it is definitely unsigned. This macro does not evaluate its argument, | 97 | if it is definitely unsigned. T must not be a bit-field expression. |
100 | and expands to an integer constant expression. */ | 98 | This macro does not evaluate its argument, and expands to an |
99 | integer constant expression. */ | ||
101 | #if _GL_HAVE___TYPEOF__ | 100 | #if _GL_HAVE___TYPEOF__ |
102 | # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t)) | 101 | # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t)) |
103 | #else | 102 | #else |
@@ -110,19 +109,20 @@ | |||
110 | #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485) | 109 | #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485) |
111 | 110 | ||
112 | /* Bound on length of the string representing an integer type or expression T. | 111 | /* Bound on length of the string representing an integer type or expression T. |
112 | T must not be a bit-field expression. | ||
113 | |||
113 | Subtract 1 for the sign bit if T is signed, and then add 1 more for | 114 | Subtract 1 for the sign bit if T is signed, and then add 1 more for |
114 | a minus sign if needed. | 115 | a minus sign if needed. |
115 | 116 | ||
116 | Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 0 when its argument is | 117 | Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 1 when its argument is |
117 | signed, this macro may overestimate the true bound by one byte when | 118 | unsigned, this macro may overestimate the true bound by one byte when |
118 | applied to unsigned types of size 2, 4, 16, ... bytes. */ | 119 | applied to unsigned types of size 2, 4, 16, ... bytes. */ |
119 | #define INT_STRLEN_BOUND(t) \ | 120 | #define INT_STRLEN_BOUND(t) \ |
120 | (INT_BITS_STRLEN_BOUND (sizeof (t) * CHAR_BIT \ | 121 | (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \ |
121 | - _GL_SIGNED_TYPE_OR_EXPR (t)) \ | ||
122 | + _GL_SIGNED_TYPE_OR_EXPR (t)) | 122 | + _GL_SIGNED_TYPE_OR_EXPR (t)) |
123 | 123 | ||
124 | /* Bound on buffer size needed to represent an integer type or expression T, | 124 | /* Bound on buffer size needed to represent an integer type or expression T, |
125 | including the terminating null. */ | 125 | including the terminating null. T must not be a bit-field expression. */ |
126 | #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1) | 126 | #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1) |
127 | 127 | ||
128 | 128 | ||
@@ -132,7 +132,8 @@ | |||
132 | operators might not yield numerically correct answers due to | 132 | operators might not yield numerically correct answers due to |
133 | arithmetic overflow. They do not rely on undefined or | 133 | arithmetic overflow. They do not rely on undefined or |
134 | implementation-defined behavior. Their implementations are simple | 134 | implementation-defined behavior. Their implementations are simple |
135 | and straightforward, but they are a bit harder to use than the | 135 | and straightforward, but they are harder to use and may be less |
136 | efficient than the INT_<op>_WRAPV, INT_<op>_OK, and | ||
136 | INT_<op>_OVERFLOW macros described below. | 137 | INT_<op>_OVERFLOW macros described below. |
137 | 138 | ||
138 | Example usage: | 139 | Example usage: |
@@ -157,6 +158,9 @@ | |||
157 | must have minimum value MIN and maximum MAX. Unsigned types should | 158 | must have minimum value MIN and maximum MAX. Unsigned types should |
158 | use a zero MIN of the proper type. | 159 | use a zero MIN of the proper type. |
159 | 160 | ||
161 | Because all arguments are subject to integer promotions, these | ||
162 | macros typically do not work on types narrower than 'int'. | ||
163 | |||
160 | These macros are tuned for constant MIN and MAX. For commutative | 164 | These macros are tuned for constant MIN and MAX. For commutative |
161 | operations such as A + B, they are also tuned for constant B. */ | 165 | operations such as A + B, they are also tuned for constant B. */ |
162 | 166 | ||
@@ -184,7 +188,7 @@ | |||
184 | /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic. | 188 | /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic. |
185 | See above for restrictions. Avoid && and || as they tickle | 189 | See above for restrictions. Avoid && and || as they tickle |
186 | bugs in Sun C 5.11 2010/08/13 and other compilers; see | 190 | bugs in Sun C 5.11 2010/08/13 and other compilers; see |
187 | <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00401.html>. */ | 191 | <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00401.html>. */ |
188 | #define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \ | 192 | #define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \ |
189 | ((b) < 0 \ | 193 | ((b) < 0 \ |
190 | ? ((a) < 0 \ | 194 | ? ((a) < 0 \ |
@@ -223,24 +227,66 @@ | |||
223 | ? (a) < (min) >> (b) \ | 227 | ? (a) < (min) >> (b) \ |
224 | : (max) >> (b) < (a)) | 228 | : (max) >> (b) < (a)) |
225 | 229 | ||
230 | /* True if __builtin_add_overflow (A, B, P) and __builtin_sub_overflow | ||
231 | (A, B, P) work when P is non-null. */ | ||
232 | /* __builtin_{add,sub}_overflow exists but is not reliable in GCC 5.x and 6.x, | ||
233 | see <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98269>. */ | ||
234 | #if 7 <= __GNUC__ && !defined __ICC | ||
235 | # define _GL_HAS_BUILTIN_ADD_OVERFLOW 1 | ||
236 | #elif defined __has_builtin | ||
237 | # define _GL_HAS_BUILTIN_ADD_OVERFLOW __has_builtin (__builtin_add_overflow) | ||
238 | #else | ||
239 | # define _GL_HAS_BUILTIN_ADD_OVERFLOW 0 | ||
240 | #endif | ||
241 | |||
242 | /* True if __builtin_mul_overflow (A, B, P) works when P is non-null. */ | ||
243 | #ifdef __clang__ | ||
244 | /* Work around Clang bug <https://bugs.llvm.org/show_bug.cgi?id=16404>. */ | ||
245 | # define _GL_HAS_BUILTIN_MUL_OVERFLOW 0 | ||
246 | #else | ||
247 | # define _GL_HAS_BUILTIN_MUL_OVERFLOW _GL_HAS_BUILTIN_ADD_OVERFLOW | ||
248 | #endif | ||
249 | |||
250 | /* True if __builtin_add_overflow_p (A, B, C) works, and similarly for | ||
251 | __builtin_sub_overflow_p and __builtin_mul_overflow_p. */ | ||
252 | #if defined __clang__ || defined __ICC | ||
253 | /* Clang 11 lacks __builtin_mul_overflow_p, and even if it did it | ||
254 | would presumably run afoul of Clang bug 16404. ICC 2021.1's | ||
255 | __builtin_add_overflow_p etc. are not treated as integral constant | ||
256 | expressions even when all arguments are. */ | ||
257 | # define _GL_HAS_BUILTIN_OVERFLOW_P 0 | ||
258 | #elif defined __has_builtin | ||
259 | # define _GL_HAS_BUILTIN_OVERFLOW_P __has_builtin (__builtin_mul_overflow_p) | ||
260 | #else | ||
261 | # define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__) | ||
262 | #endif | ||
226 | 263 | ||
227 | /* The _GL*_OVERFLOW macros have the same restrictions as the | 264 | /* The _GL*_OVERFLOW macros have the same restrictions as the |
228 | *_RANGE_OVERFLOW macros, except that they do not assume that operands | 265 | *_RANGE_OVERFLOW macros, except that they do not assume that operands |
229 | (e.g., A and B) have the same type as MIN and MAX. Instead, they assume | 266 | (e.g., A and B) have the same type as MIN and MAX. Instead, they assume |
230 | that the result (e.g., A + B) has that type. */ | 267 | that the result (e.g., A + B) has that type. */ |
231 | #define _GL_ADD_OVERFLOW(a, b, min, max) \ | 268 | #if _GL_HAS_BUILTIN_OVERFLOW_P |
232 | ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \ | 269 | # define _GL_ADD_OVERFLOW(a, b, min, max) \ |
233 | : (a) < 0 ? (b) <= (a) + (b) \ | 270 | __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0) |
234 | : (b) < 0 ? (a) <= (a) + (b) \ | 271 | # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ |
235 | : (a) + (b) < (b)) | 272 | __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0) |
236 | #define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ | 273 | # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ |
237 | ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \ | 274 | __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0) |
238 | : (a) < 0 ? 1 \ | 275 | #else |
239 | : (b) < 0 ? (a) - (b) <= (a) \ | 276 | # define _GL_ADD_OVERFLOW(a, b, min, max) \ |
240 | : (a) < (b)) | 277 | ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \ |
241 | #define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ | 278 | : (a) < 0 ? (b) <= (a) + (b) \ |
242 | (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \ | 279 | : (b) < 0 ? (a) <= (a) + (b) \ |
243 | || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max)) | 280 | : (a) + (b) < (b)) |
281 | # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ | ||
282 | ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \ | ||
283 | : (a) < 0 ? 1 \ | ||
284 | : (b) < 0 ? (a) - (b) <= (a) \ | ||
285 | : (a) < (b)) | ||
286 | # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ | ||
287 | (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \ | ||
288 | || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max)) | ||
289 | #endif | ||
244 | #define _GL_DIVIDE_OVERFLOW(a, b, min, max) \ | 290 | #define _GL_DIVIDE_OVERFLOW(a, b, min, max) \ |
245 | ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \ | 291 | ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \ |
246 | : (a) < 0 ? (b) <= (a) + (b) - 1 \ | 292 | : (a) < 0 ? (b) <= (a) + (b) - 1 \ |
@@ -262,22 +308,31 @@ | |||
262 | : (a) % - (b)) \ | 308 | : (a) % - (b)) \ |
263 | == 0) | 309 | == 0) |
264 | 310 | ||
265 | 311 | /* Check for integer overflow, and report low order bits of answer. | |
266 | /* Integer overflow checks. | ||
267 | 312 | ||
268 | The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators | 313 | The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators |
269 | might not yield numerically correct answers due to arithmetic overflow. | 314 | might not yield numerically correct answers due to arithmetic overflow. |
270 | They work correctly on all known practical hosts, and do not rely | 315 | The INT_<op>_WRAPV macros compute the low-order bits of the sum, |
316 | difference, and product of two C integers, and return 1 if these | ||
317 | low-order bits are not numerically correct. | ||
318 | These macros work correctly on all known practical hosts, and do not rely | ||
271 | on undefined behavior due to signed arithmetic overflow. | 319 | on undefined behavior due to signed arithmetic overflow. |
272 | 320 | ||
273 | Example usage: | 321 | Example usage, assuming A and B are long int: |
274 | 322 | ||
275 | long int i = ...; | 323 | if (INT_MULTIPLY_OVERFLOW (a, b)) |
276 | long int j = ...; | 324 | printf ("result would overflow\n"); |
277 | if (INT_MULTIPLY_OVERFLOW (i, j)) | ||
278 | printf ("multiply would overflow"); | ||
279 | else | 325 | else |
280 | printf ("product is %ld", i * j); | 326 | printf ("result is %ld (no overflow)\n", a * b); |
327 | |||
328 | Example usage with WRAPV flavor: | ||
329 | |||
330 | long int result; | ||
331 | bool overflow = INT_MULTIPLY_WRAPV (a, b, &result); | ||
332 | printf ("result is %ld (%s)\n", result, | ||
333 | overflow ? "after overflow" : "no overflow"); | ||
334 | |||
335 | Restrictions on these macros: | ||
281 | 336 | ||
282 | These macros do not check for all possible numerical problems or | 337 | These macros do not check for all possible numerical problems or |
283 | undefined or unspecified behavior: they do not check for division | 338 | undefined or unspecified behavior: they do not check for division |
@@ -286,7 +341,18 @@ | |||
286 | These macros may evaluate their arguments zero or multiple times, so the | 341 | These macros may evaluate their arguments zero or multiple times, so the |
287 | arguments should not have side effects. | 342 | arguments should not have side effects. |
288 | 343 | ||
289 | These macros are tuned for their last argument being a constant. | 344 | The WRAPV macros are not constant expressions. They support only |
345 | +, binary -, and *. | ||
346 | |||
347 | Because the WRAPV macros convert the result, they report overflow | ||
348 | in different circumstances than the OVERFLOW macros do. For | ||
349 | example, in the typical case with 16-bit 'short' and 32-bit 'int', | ||
350 | if A, B and R are all of type 'short' then INT_ADD_OVERFLOW (A, B) | ||
351 | returns false because the addition cannot overflow after A and B | ||
352 | are converted to 'int', whereas INT_ADD_WRAPV (A, B, &R) returns | ||
353 | true or false depending on whether the sum fits into 'short'. | ||
354 | |||
355 | These macros are tuned for their last input argument being a constant. | ||
290 | 356 | ||
291 | Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B, | 357 | Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B, |
292 | A % B, and A << B would overflow, respectively. */ | 358 | A % B, and A << B would overflow, respectively. */ |
@@ -295,8 +361,12 @@ | |||
295 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW) | 361 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW) |
296 | #define INT_SUBTRACT_OVERFLOW(a, b) \ | 362 | #define INT_SUBTRACT_OVERFLOW(a, b) \ |
297 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW) | 363 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW) |
298 | #define INT_NEGATE_OVERFLOW(a) \ | 364 | #if _GL_HAS_BUILTIN_OVERFLOW_P |
299 | INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a)) | 365 | # define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a) |
366 | #else | ||
367 | # define INT_NEGATE_OVERFLOW(a) \ | ||
368 | INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a)) | ||
369 | #endif | ||
300 | #define INT_MULTIPLY_OVERFLOW(a, b) \ | 370 | #define INT_MULTIPLY_OVERFLOW(a, b) \ |
301 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW) | 371 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW) |
302 | #define INT_DIVIDE_OVERFLOW(a, b) \ | 372 | #define INT_DIVIDE_OVERFLOW(a, b) \ |
@@ -313,7 +383,257 @@ | |||
313 | Arguments should be free of side effects. */ | 383 | Arguments should be free of side effects. */ |
314 | #define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \ | 384 | #define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \ |
315 | op_result_overflow (a, b, \ | 385 | op_result_overflow (a, b, \ |
316 | _GL_INT_MINIMUM (0 * (b) + (a)), \ | 386 | _GL_INT_MINIMUM (_GL_INT_CONVERT (a, b)), \ |
317 | _GL_INT_MAXIMUM (0 * (b) + (a))) | 387 | _GL_INT_MAXIMUM (_GL_INT_CONVERT (a, b))) |
388 | |||
389 | /* Store the low-order bits of A + B, A - B, A * B, respectively, into *R. | ||
390 | Return 1 if the result overflows. See above for restrictions. */ | ||
391 | #if _GL_HAS_BUILTIN_ADD_OVERFLOW | ||
392 | # define INT_ADD_WRAPV(a, b, r) __builtin_add_overflow (a, b, r) | ||
393 | # define INT_SUBTRACT_WRAPV(a, b, r) __builtin_sub_overflow (a, b, r) | ||
394 | #else | ||
395 | # define INT_ADD_WRAPV(a, b, r) \ | ||
396 | _GL_INT_OP_WRAPV (a, b, r, +, _GL_INT_ADD_RANGE_OVERFLOW) | ||
397 | # define INT_SUBTRACT_WRAPV(a, b, r) \ | ||
398 | _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW) | ||
399 | #endif | ||
400 | #if _GL_HAS_BUILTIN_MUL_OVERFLOW | ||
401 | # if ((9 < __GNUC__ + (3 <= __GNUC_MINOR__) \ | ||
402 | || (__GNUC__ == 8 && 4 <= __GNUC_MINOR__)) \ | ||
403 | && !defined __ICC) | ||
404 | # define INT_MULTIPLY_WRAPV(a, b, r) __builtin_mul_overflow (a, b, r) | ||
405 | # else | ||
406 | /* Work around GCC bug 91450. */ | ||
407 | # define INT_MULTIPLY_WRAPV(a, b, r) \ | ||
408 | ((!_GL_SIGNED_TYPE_OR_EXPR (*(r)) && EXPR_SIGNED (a) && EXPR_SIGNED (b) \ | ||
409 | && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1)) \ | ||
410 | ? ((void) __builtin_mul_overflow (a, b, r), 1) \ | ||
411 | : __builtin_mul_overflow (a, b, r)) | ||
412 | # endif | ||
413 | #else | ||
414 | # define INT_MULTIPLY_WRAPV(a, b, r) \ | ||
415 | _GL_INT_OP_WRAPV (a, b, r, *, _GL_INT_MULTIPLY_RANGE_OVERFLOW) | ||
416 | #endif | ||
417 | |||
418 | /* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390. See: | ||
419 | https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193 | ||
420 | https://llvm.org/bugs/show_bug.cgi?id=25390 | ||
421 | For now, assume all versions of GCC-like compilers generate bogus | ||
422 | warnings for _Generic. This matters only for compilers that | ||
423 | lack relevant builtins. */ | ||
424 | #if __GNUC__ || defined __clang__ | ||
425 | # define _GL__GENERIC_BOGUS 1 | ||
426 | #else | ||
427 | # define _GL__GENERIC_BOGUS 0 | ||
428 | #endif | ||
429 | |||
430 | /* Store the low-order bits of A <op> B into *R, where OP specifies | ||
431 | the operation and OVERFLOW the overflow predicate. Return 1 if the | ||
432 | result overflows. See above for restrictions. */ | ||
433 | #if 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS | ||
434 | # define _GL_INT_OP_WRAPV(a, b, r, op, overflow) \ | ||
435 | (_Generic \ | ||
436 | (*(r), \ | ||
437 | signed char: \ | ||
438 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
439 | signed char, SCHAR_MIN, SCHAR_MAX), \ | ||
440 | unsigned char: \ | ||
441 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
442 | unsigned char, 0, UCHAR_MAX), \ | ||
443 | short int: \ | ||
444 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
445 | short int, SHRT_MIN, SHRT_MAX), \ | ||
446 | unsigned short int: \ | ||
447 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
448 | unsigned short int, 0, USHRT_MAX), \ | ||
449 | int: \ | ||
450 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
451 | int, INT_MIN, INT_MAX), \ | ||
452 | unsigned int: \ | ||
453 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
454 | unsigned int, 0, UINT_MAX), \ | ||
455 | long int: \ | ||
456 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ | ||
457 | long int, LONG_MIN, LONG_MAX), \ | ||
458 | unsigned long int: \ | ||
459 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ | ||
460 | unsigned long int, 0, ULONG_MAX), \ | ||
461 | long long int: \ | ||
462 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ | ||
463 | long long int, LLONG_MIN, LLONG_MAX), \ | ||
464 | unsigned long long int: \ | ||
465 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ | ||
466 | unsigned long long int, 0, ULLONG_MAX))) | ||
467 | #else | ||
468 | /* Store the low-order bits of A <op> B into *R, where OP specifies | ||
469 | the operation and OVERFLOW the overflow predicate. If *R is | ||
470 | signed, its type is ST with bounds SMIN..SMAX; otherwise its type | ||
471 | is UT with bounds U..UMAX. ST and UT are narrower than int. | ||
472 | Return 1 if the result overflows. See above for restrictions. */ | ||
473 | # if _GL_HAVE___TYPEOF__ | ||
474 | # define _GL_INT_OP_WRAPV_SMALLISH(a,b,r,op,overflow,st,smin,smax,ut,umax) \ | ||
475 | (TYPE_SIGNED (__typeof__ (*(r))) \ | ||
476 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, st, smin, smax) \ | ||
477 | : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, ut, 0, umax)) | ||
478 | # else | ||
479 | # define _GL_INT_OP_WRAPV_SMALLISH(a,b,r,op,overflow,st,smin,smax,ut,umax) \ | ||
480 | (overflow (a, b, smin, smax) \ | ||
481 | ? (overflow (a, b, 0, umax) \ | ||
482 | ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st), 1) \ | ||
483 | : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st)) < 0) \ | ||
484 | : (overflow (a, b, 0, umax) \ | ||
485 | ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st)) >= 0 \ | ||
486 | : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st), 0))) | ||
487 | # endif | ||
488 | |||
489 | # define _GL_INT_OP_WRAPV(a, b, r, op, overflow) \ | ||
490 | (sizeof *(r) == sizeof (signed char) \ | ||
491 | ? _GL_INT_OP_WRAPV_SMALLISH (a, b, r, op, overflow, \ | ||
492 | signed char, SCHAR_MIN, SCHAR_MAX, \ | ||
493 | unsigned char, UCHAR_MAX) \ | ||
494 | : sizeof *(r) == sizeof (short int) \ | ||
495 | ? _GL_INT_OP_WRAPV_SMALLISH (a, b, r, op, overflow, \ | ||
496 | short int, SHRT_MIN, SHRT_MAX, \ | ||
497 | unsigned short int, USHRT_MAX) \ | ||
498 | : sizeof *(r) == sizeof (int) \ | ||
499 | ? (EXPR_SIGNED (*(r)) \ | ||
500 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
501 | int, INT_MIN, INT_MAX) \ | ||
502 | : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ | ||
503 | unsigned int, 0, UINT_MAX)) \ | ||
504 | : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow)) | ||
505 | # ifdef LLONG_MAX | ||
506 | # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \ | ||
507 | (sizeof *(r) == sizeof (long int) \ | ||
508 | ? (EXPR_SIGNED (*(r)) \ | ||
509 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ | ||
510 | long int, LONG_MIN, LONG_MAX) \ | ||
511 | : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ | ||
512 | unsigned long int, 0, ULONG_MAX)) \ | ||
513 | : (EXPR_SIGNED (*(r)) \ | ||
514 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ | ||
515 | long long int, LLONG_MIN, LLONG_MAX) \ | ||
516 | : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ | ||
517 | unsigned long long int, 0, ULLONG_MAX))) | ||
518 | # else | ||
519 | # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \ | ||
520 | (EXPR_SIGNED (*(r)) \ | ||
521 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ | ||
522 | long int, LONG_MIN, LONG_MAX) \ | ||
523 | : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ | ||
524 | unsigned long int, 0, ULONG_MAX)) | ||
525 | # endif | ||
526 | #endif | ||
527 | |||
528 | /* Store the low-order bits of A <op> B into *R, where the operation | ||
529 | is given by OP. Use the unsigned type UT for calculation to avoid | ||
530 | overflow problems. *R's type is T, with extrema TMIN and TMAX. | ||
531 | T must be a signed integer type. Return 1 if the result overflows. */ | ||
532 | #define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \ | ||
533 | (overflow (a, b, tmin, tmax) \ | ||
534 | ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 1) \ | ||
535 | : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 0)) | ||
536 | |||
537 | /* Return the low-order bits of A <op> B, where the operation is given | ||
538 | by OP. Use the unsigned type UT for calculation to avoid undefined | ||
539 | behavior on signed integer overflow, and convert the result to type T. | ||
540 | UT is at least as wide as T and is no narrower than unsigned int, | ||
541 | T is two's complement, and there is no padding or trap representations. | ||
542 | Assume that converting UT to T yields the low-order bits, as is | ||
543 | done in all known two's-complement C compilers. E.g., see: | ||
544 | https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html | ||
545 | |||
546 | According to the C standard, converting UT to T yields an | ||
547 | implementation-defined result or signal for values outside T's | ||
548 | range. However, code that works around this theoretical problem | ||
549 | runs afoul of a compiler bug in Oracle Studio 12.3 x86. See: | ||
550 | https://lists.gnu.org/r/bug-gnulib/2017-04/msg00049.html | ||
551 | As the compiler bug is real, don't try to work around the | ||
552 | theoretical problem. */ | ||
553 | |||
554 | #define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t) \ | ||
555 | ((t) ((ut) (a) op (ut) (b))) | ||
556 | |||
557 | /* Return true if the numeric values A + B, A - B, A * B fall outside | ||
558 | the range TMIN..TMAX. Arguments should be integer expressions | ||
559 | without side effects. TMIN should be signed and nonpositive. | ||
560 | TMAX should be positive, and should be signed unless TMIN is zero. */ | ||
561 | #define _GL_INT_ADD_RANGE_OVERFLOW(a, b, tmin, tmax) \ | ||
562 | ((b) < 0 \ | ||
563 | ? (((tmin) \ | ||
564 | ? ((EXPR_SIGNED (_GL_INT_CONVERT (a, (tmin) - (b))) || (b) < (tmin)) \ | ||
565 | && (a) < (tmin) - (b)) \ | ||
566 | : (a) <= -1 - (b)) \ | ||
567 | || ((EXPR_SIGNED (a) ? 0 <= (a) : (tmax) < (a)) && (tmax) < (a) + (b))) \ | ||
568 | : (a) < 0 \ | ||
569 | ? (((tmin) \ | ||
570 | ? ((EXPR_SIGNED (_GL_INT_CONVERT (b, (tmin) - (a))) || (a) < (tmin)) \ | ||
571 | && (b) < (tmin) - (a)) \ | ||
572 | : (b) <= -1 - (a)) \ | ||
573 | || ((EXPR_SIGNED (_GL_INT_CONVERT (a, b)) || (tmax) < (b)) \ | ||
574 | && (tmax) < (a) + (b))) \ | ||
575 | : (tmax) < (b) || (tmax) - (b) < (a)) | ||
576 | #define _GL_INT_SUBTRACT_RANGE_OVERFLOW(a, b, tmin, tmax) \ | ||
577 | (((a) < 0) == ((b) < 0) \ | ||
578 | ? ((a) < (b) \ | ||
579 | ? !(tmin) || -1 - (tmin) < (b) - (a) - 1 \ | ||
580 | : (tmax) < (a) - (b)) \ | ||
581 | : (a) < 0 \ | ||
582 | ? ((!EXPR_SIGNED (_GL_INT_CONVERT ((a) - (tmin), b)) && (a) - (tmin) < 0) \ | ||
583 | || (a) - (tmin) < (b)) \ | ||
584 | : ((! (EXPR_SIGNED (_GL_INT_CONVERT (tmax, b)) \ | ||
585 | && EXPR_SIGNED (_GL_INT_CONVERT ((tmax) + (b), a))) \ | ||
586 | && (tmax) <= -1 - (b)) \ | ||
587 | || (tmax) + (b) < (a))) | ||
588 | #define _GL_INT_MULTIPLY_RANGE_OVERFLOW(a, b, tmin, tmax) \ | ||
589 | ((b) < 0 \ | ||
590 | ? ((a) < 0 \ | ||
591 | ? (EXPR_SIGNED (_GL_INT_CONVERT (tmax, b)) \ | ||
592 | ? (a) < (tmax) / (b) \ | ||
593 | : ((INT_NEGATE_OVERFLOW (b) \ | ||
594 | ? _GL_INT_CONVERT (b, tmax) >> (TYPE_WIDTH (+ (b)) - 1) \ | ||
595 | : (tmax) / -(b)) \ | ||
596 | <= -1 - (a))) \ | ||
597 | : INT_NEGATE_OVERFLOW (_GL_INT_CONVERT (b, tmin)) && (b) == -1 \ | ||
598 | ? (EXPR_SIGNED (a) \ | ||
599 | ? 0 < (a) + (tmin) \ | ||
600 | : 0 < (a) && -1 - (tmin) < (a) - 1) \ | ||
601 | : (tmin) / (b) < (a)) \ | ||
602 | : (b) == 0 \ | ||
603 | ? 0 \ | ||
604 | : ((a) < 0 \ | ||
605 | ? (INT_NEGATE_OVERFLOW (_GL_INT_CONVERT (a, tmin)) && (a) == -1 \ | ||
606 | ? (EXPR_SIGNED (b) ? 0 < (b) + (tmin) : -1 - (tmin) < (b) - 1) \ | ||
607 | : (tmin) / (a) < (b)) \ | ||
608 | : (tmax) / (b) < (a))) | ||
609 | |||
610 | /* The following macros compute A + B, A - B, and A * B, respectively. | ||
611 | If no overflow occurs, they set *R to the result and return 1; | ||
612 | otherwise, they return 0 and may modify *R. | ||
613 | |||
614 | Example usage: | ||
615 | |||
616 | long int result; | ||
617 | if (INT_ADD_OK (a, b, &result)) | ||
618 | printf ("result is %ld\n", result); | ||
619 | else | ||
620 | printf ("overflow\n"); | ||
621 | |||
622 | A, B, and *R should be integers; they need not be the same type, | ||
623 | and they need not be all signed or all unsigned. | ||
624 | |||
625 | These macros work correctly on all known practical hosts, and do not rely | ||
626 | on undefined behavior due to signed arithmetic overflow. | ||
627 | |||
628 | These macros are not constant expressions. | ||
629 | |||
630 | These macros may evaluate their arguments zero or multiple times, so the | ||
631 | arguments should not have side effects. | ||
632 | |||
633 | These macros are tuned for B being a constant. */ | ||
634 | |||
635 | #define INT_ADD_OK(a, b, r) ! INT_ADD_WRAPV (a, b, r) | ||
636 | #define INT_SUBTRACT_OK(a, b, r) ! INT_SUBTRACT_WRAPV (a, b, r) | ||
637 | #define INT_MULTIPLY_OK(a, b, r) ! INT_MULTIPLY_WRAPV (a, b, r) | ||
318 | 638 | ||
319 | #endif /* _GL_INTPROPS_H */ | 639 | #endif /* _GL_INTPROPS_H */ |