1 | /* intprops.h -- properties of integer types |
2 | |
3 | Copyright (C) 2001-2019 Free Software Foundation, Inc. |
4 | |
5 | This program is free software: you can redistribute it and/or modify it |
6 | under the terms of the GNU Lesser General Public License as published |
7 | by the Free Software Foundation; either version 2.1 of the License, or |
8 | (at your option) any later version. |
9 | |
10 | This program is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
13 | GNU Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public License |
16 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
17 | |
18 | /* Written by Paul Eggert. */ |
19 | |
20 | #ifndef _GL_INTPROPS_H |
21 | #define _GL_INTPROPS_H |
22 | |
23 | #include <limits.h> |
24 | |
25 | /* Return a value with the common real type of E and V and the value of V. |
26 | Do not evaluate E. */ |
27 | #define _GL_INT_CONVERT(e, v) ((1 ? 0 : (e)) + (v)) |
28 | |
29 | /* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see |
30 | <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00406.html>. */ |
31 | #define _GL_INT_NEGATE_CONVERT(e, v) ((1 ? 0 : (e)) - (v)) |
32 | |
33 | /* The extra casts in the following macros work around compiler bugs, |
34 | e.g., in Cray C 5.0.3.0. */ |
35 | |
36 | /* True if the arithmetic type T is an integer type. bool counts as |
37 | an integer. */ |
38 | #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) |
39 | |
40 | /* True if the real type T is signed. */ |
41 | #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) |
42 | |
43 | /* Return 1 if the real expression E, after promotion, has a |
44 | signed or floating type. Do not evaluate E. */ |
45 | #define EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0) |
46 | |
47 | |
48 | /* Minimum and maximum values for integer types and expressions. */ |
49 | |
50 | /* The width in bits of the integer type or expression T. |
51 | Do not evaluate T. |
52 | Padding bits are not supported; this is checked at compile-time below. */ |
53 | #define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT) |
54 | |
55 | /* The maximum and minimum values for the integer type T. */ |
56 | #define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t)) |
57 | #define TYPE_MAXIMUM(t) \ |
58 | ((t) (! TYPE_SIGNED (t) \ |
59 | ? (t) -1 \ |
60 | : ((((t) 1 << (TYPE_WIDTH (t) - 2)) - 1) * 2 + 1))) |
61 | |
62 | /* The maximum and minimum values for the type of the expression E, |
63 | after integer promotion. E is not evaluated. */ |
64 | #define _GL_INT_MINIMUM(e) \ |
65 | (EXPR_SIGNED (e) \ |
66 | ? ~ _GL_SIGNED_INT_MAXIMUM (e) \ |
67 | : _GL_INT_CONVERT (e, 0)) |
68 | #define _GL_INT_MAXIMUM(e) \ |
69 | (EXPR_SIGNED (e) \ |
70 | ? _GL_SIGNED_INT_MAXIMUM (e) \ |
71 | : _GL_INT_NEGATE_CONVERT (e, 1)) |
72 | #define _GL_SIGNED_INT_MAXIMUM(e) \ |
73 | (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH ((e) + 0) - 2)) - 1) * 2 + 1) |
74 | |
75 | /* Work around OpenVMS incompatibility with C99. */ |
76 | #if !defined LLONG_MAX && defined __INT64_MAX |
77 | # define LLONG_MAX __INT64_MAX |
78 | # define LLONG_MIN __INT64_MIN |
79 | #endif |
80 | |
81 | /* This include file assumes that signed types are two's complement without |
82 | padding bits; the above macros have undefined behavior otherwise. |
83 | If this is a problem for you, please let us know how to fix it for your host. |
84 | This assumption is tested by the intprops-tests module. */ |
85 | |
86 | /* Does the __typeof__ keyword work? This could be done by |
87 | 'configure', but for now it's easier to do it by hand. */ |
88 | #if (2 <= __GNUC__ \ |
89 | || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \ |
90 | || (0x5110 <= __SUNPRO_C && !__STDC__)) |
91 | # define _GL_HAVE___TYPEOF__ 1 |
92 | #else |
93 | # define _GL_HAVE___TYPEOF__ 0 |
94 | #endif |
95 | |
96 | /* Return 1 if the integer type or expression T might be signed. Return 0 |
97 | if it is definitely unsigned. This macro does not evaluate its argument, |
98 | and expands to an integer constant expression. */ |
99 | #if _GL_HAVE___TYPEOF__ |
100 | # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t)) |
101 | #else |
102 | # define _GL_SIGNED_TYPE_OR_EXPR(t) 1 |
103 | #endif |
104 | |
105 | /* Bound on length of the string representing an unsigned integer |
106 | value representable in B bits. log10 (2.0) < 146/485. The |
107 | smallest value of B where this bound is not tight is 2621. */ |
108 | #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485) |
109 | |
110 | /* Bound on length of the string representing an integer type or expression T. |
111 | Subtract 1 for the sign bit if T is signed, and then add 1 more for |
112 | a minus sign if needed. |
113 | |
114 | Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 0 when its argument is |
115 | signed, this macro may overestimate the true bound by one byte when |
116 | applied to unsigned types of size 2, 4, 16, ... bytes. */ |
117 | #define INT_STRLEN_BOUND(t) \ |
118 | (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \ |
119 | + _GL_SIGNED_TYPE_OR_EXPR (t)) |
120 | |
121 | /* Bound on buffer size needed to represent an integer type or expression T, |
122 | including the terminating null. */ |
123 | #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1) |
124 | |
125 | |
126 | /* Range overflow checks. |
127 | |
128 | The INT_<op>_RANGE_OVERFLOW macros return 1 if the corresponding C |
129 | operators might not yield numerically correct answers due to |
130 | arithmetic overflow. They do not rely on undefined or |
131 | implementation-defined behavior. Their implementations are simple |
132 | and straightforward, but they are a bit harder to use than the |
133 | INT_<op>_OVERFLOW macros described below. |
134 | |
135 | Example usage: |
136 | |
137 | long int i = ...; |
138 | long int j = ...; |
139 | if (INT_MULTIPLY_RANGE_OVERFLOW (i, j, LONG_MIN, LONG_MAX)) |
140 | printf ("multiply would overflow"); |
141 | else |
142 | printf ("product is %ld", i * j); |
143 | |
144 | Restrictions on *_RANGE_OVERFLOW macros: |
145 | |
146 | These macros do not check for all possible numerical problems or |
147 | undefined or unspecified behavior: they do not check for division |
148 | by zero, for bad shift counts, or for shifting negative numbers. |
149 | |
150 | These macros may evaluate their arguments zero or multiple times, |
151 | so the arguments should not have side effects. The arithmetic |
152 | arguments (including the MIN and MAX arguments) must be of the same |
153 | integer type after the usual arithmetic conversions, and the type |
154 | must have minimum value MIN and maximum MAX. Unsigned types should |
155 | use a zero MIN of the proper type. |
156 | |
157 | These macros are tuned for constant MIN and MAX. For commutative |
158 | operations such as A + B, they are also tuned for constant B. */ |
159 | |
160 | /* Return 1 if A + B would overflow in [MIN,MAX] arithmetic. |
161 | See above for restrictions. */ |
162 | #define INT_ADD_RANGE_OVERFLOW(a, b, min, max) \ |
163 | ((b) < 0 \ |
164 | ? (a) < (min) - (b) \ |
165 | : (max) - (b) < (a)) |
166 | |
167 | /* Return 1 if A - B would overflow in [MIN,MAX] arithmetic. |
168 | See above for restrictions. */ |
169 | #define INT_SUBTRACT_RANGE_OVERFLOW(a, b, min, max) \ |
170 | ((b) < 0 \ |
171 | ? (max) + (b) < (a) \ |
172 | : (a) < (min) + (b)) |
173 | |
174 | /* Return 1 if - A would overflow in [MIN,MAX] arithmetic. |
175 | See above for restrictions. */ |
176 | #define INT_NEGATE_RANGE_OVERFLOW(a, min, max) \ |
177 | ((min) < 0 \ |
178 | ? (a) < - (max) \ |
179 | : 0 < (a)) |
180 | |
181 | /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic. |
182 | See above for restrictions. Avoid && and || as they tickle |
183 | bugs in Sun C 5.11 2010/08/13 and other compilers; see |
184 | <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00401.html>. */ |
185 | #define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \ |
186 | ((b) < 0 \ |
187 | ? ((a) < 0 \ |
188 | ? (a) < (max) / (b) \ |
189 | : (b) == -1 \ |
190 | ? 0 \ |
191 | : (min) / (b) < (a)) \ |
192 | : (b) == 0 \ |
193 | ? 0 \ |
194 | : ((a) < 0 \ |
195 | ? (a) < (min) / (b) \ |
196 | : (max) / (b) < (a))) |
197 | |
198 | /* Return 1 if A / B would overflow in [MIN,MAX] arithmetic. |
199 | See above for restrictions. Do not check for division by zero. */ |
200 | #define INT_DIVIDE_RANGE_OVERFLOW(a, b, min, max) \ |
201 | ((min) < 0 && (b) == -1 && (a) < - (max)) |
202 | |
203 | /* Return 1 if A % B would overflow in [MIN,MAX] arithmetic. |
204 | See above for restrictions. Do not check for division by zero. |
205 | Mathematically, % should never overflow, but on x86-like hosts |
206 | INT_MIN % -1 traps, and the C standard permits this, so treat this |
207 | as an overflow too. */ |
208 | #define INT_REMAINDER_RANGE_OVERFLOW(a, b, min, max) \ |
209 | INT_DIVIDE_RANGE_OVERFLOW (a, b, min, max) |
210 | |
211 | /* Return 1 if A << B would overflow in [MIN,MAX] arithmetic. |
212 | See above for restrictions. Here, MIN and MAX are for A only, and B need |
213 | not be of the same type as the other arguments. The C standard says that |
214 | behavior is undefined for shifts unless 0 <= B < wordwidth, and that when |
215 | A is negative then A << B has undefined behavior and A >> B has |
216 | implementation-defined behavior, but do not check these other |
217 | restrictions. */ |
218 | #define INT_LEFT_SHIFT_RANGE_OVERFLOW(a, b, min, max) \ |
219 | ((a) < 0 \ |
220 | ? (a) < (min) >> (b) \ |
221 | : (max) >> (b) < (a)) |
222 | |
223 | /* True if __builtin_add_overflow (A, B, P) works when P is non-null. */ |
224 | #if 5 <= __GNUC__ && !defined __ICC |
225 | # define _GL_HAS_BUILTIN_OVERFLOW 1 |
226 | #else |
227 | # define _GL_HAS_BUILTIN_OVERFLOW 0 |
228 | #endif |
229 | |
230 | /* True if __builtin_add_overflow_p (A, B, C) works. */ |
231 | #define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__) |
232 | |
233 | /* The _GL*_OVERFLOW macros have the same restrictions as the |
234 | *_RANGE_OVERFLOW macros, except that they do not assume that operands |
235 | (e.g., A and B) have the same type as MIN and MAX. Instead, they assume |
236 | that the result (e.g., A + B) has that type. */ |
237 | #if _GL_HAS_BUILTIN_OVERFLOW_P |
238 | # define _GL_ADD_OVERFLOW(a, b, min, max) \ |
239 | __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0) |
240 | # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ |
241 | __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0) |
242 | # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ |
243 | __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0) |
244 | #else |
245 | # define _GL_ADD_OVERFLOW(a, b, min, max) \ |
246 | ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \ |
247 | : (a) < 0 ? (b) <= (a) + (b) \ |
248 | : (b) < 0 ? (a) <= (a) + (b) \ |
249 | : (a) + (b) < (b)) |
250 | # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ |
251 | ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \ |
252 | : (a) < 0 ? 1 \ |
253 | : (b) < 0 ? (a) - (b) <= (a) \ |
254 | : (a) < (b)) |
255 | # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ |
256 | (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \ |
257 | || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max)) |
258 | #endif |
259 | #define _GL_DIVIDE_OVERFLOW(a, b, min, max) \ |
260 | ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \ |
261 | : (a) < 0 ? (b) <= (a) + (b) - 1 \ |
262 | : (b) < 0 && (a) + (b) <= (a)) |
263 | #define _GL_REMAINDER_OVERFLOW(a, b, min, max) \ |
264 | ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \ |
265 | : (a) < 0 ? (a) % (b) != ((max) - (b) + 1) % (b) \ |
266 | : (b) < 0 && ! _GL_UNSIGNED_NEG_MULTIPLE (a, b, max)) |
267 | |
268 | /* Return a nonzero value if A is a mathematical multiple of B, where |
269 | A is unsigned, B is negative, and MAX is the maximum value of A's |
270 | type. A's type must be the same as (A % B)'s type. Normally (A % |
271 | -B == 0) suffices, but things get tricky if -B would overflow. */ |
272 | #define _GL_UNSIGNED_NEG_MULTIPLE(a, b, max) \ |
273 | (((b) < -_GL_SIGNED_INT_MAXIMUM (b) \ |
274 | ? (_GL_SIGNED_INT_MAXIMUM (b) == (max) \ |
275 | ? (a) \ |
276 | : (a) % (_GL_INT_CONVERT (a, _GL_SIGNED_INT_MAXIMUM (b)) + 1)) \ |
277 | : (a) % - (b)) \ |
278 | == 0) |
279 | |
280 | /* Check for integer overflow, and report low order bits of answer. |
281 | |
282 | The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators |
283 | might not yield numerically correct answers due to arithmetic overflow. |
284 | The INT_<op>_WRAPV macros also store the low-order bits of the answer. |
285 | These macros work correctly on all known practical hosts, and do not rely |
286 | on undefined behavior due to signed arithmetic overflow. |
287 | |
288 | Example usage, assuming A and B are long int: |
289 | |
290 | if (INT_MULTIPLY_OVERFLOW (a, b)) |
291 | printf ("result would overflow\n"); |
292 | else |
293 | printf ("result is %ld (no overflow)\n", a * b); |
294 | |
295 | Example usage with WRAPV flavor: |
296 | |
297 | long int result; |
298 | bool overflow = INT_MULTIPLY_WRAPV (a, b, &result); |
299 | printf ("result is %ld (%s)\n", result, |
300 | overflow ? "after overflow" : "no overflow"); |
301 | |
302 | Restrictions on these macros: |
303 | |
304 | These macros do not check for all possible numerical problems or |
305 | undefined or unspecified behavior: they do not check for division |
306 | by zero, for bad shift counts, or for shifting negative numbers. |
307 | |
308 | These macros may evaluate their arguments zero or multiple times, so the |
309 | arguments should not have side effects. |
310 | |
311 | The WRAPV macros are not constant expressions. They support only |
312 | +, binary -, and *. The result type must be signed. |
313 | |
314 | These macros are tuned for their last argument being a constant. |
315 | |
316 | Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B, |
317 | A % B, and A << B would overflow, respectively. */ |
318 | |
319 | #define INT_ADD_OVERFLOW(a, b) \ |
320 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW) |
321 | #define INT_SUBTRACT_OVERFLOW(a, b) \ |
322 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW) |
323 | #if _GL_HAS_BUILTIN_OVERFLOW_P |
324 | # define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a) |
325 | #else |
326 | # define INT_NEGATE_OVERFLOW(a) \ |
327 | INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a)) |
328 | #endif |
329 | #define INT_MULTIPLY_OVERFLOW(a, b) \ |
330 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW) |
331 | #define INT_DIVIDE_OVERFLOW(a, b) \ |
332 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_DIVIDE_OVERFLOW) |
333 | #define INT_REMAINDER_OVERFLOW(a, b) \ |
334 | _GL_BINARY_OP_OVERFLOW (a, b, _GL_REMAINDER_OVERFLOW) |
335 | #define INT_LEFT_SHIFT_OVERFLOW(a, b) \ |
336 | INT_LEFT_SHIFT_RANGE_OVERFLOW (a, b, \ |
337 | _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a)) |
338 | |
339 | /* Return 1 if the expression A <op> B would overflow, |
340 | where OP_RESULT_OVERFLOW (A, B, MIN, MAX) does the actual test, |
341 | assuming MIN and MAX are the minimum and maximum for the result type. |
342 | Arguments should be free of side effects. */ |
343 | #define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \ |
344 | op_result_overflow (a, b, \ |
345 | _GL_INT_MINIMUM (_GL_INT_CONVERT (a, b)), \ |
346 | _GL_INT_MAXIMUM (_GL_INT_CONVERT (a, b))) |
347 | |
348 | /* Store the low-order bits of A + B, A - B, A * B, respectively, into *R. |
349 | Return 1 if the result overflows. See above for restrictions. */ |
350 | #define INT_ADD_WRAPV(a, b, r) \ |
351 | _GL_INT_OP_WRAPV (a, b, r, +, __builtin_add_overflow, INT_ADD_OVERFLOW) |
352 | #define INT_SUBTRACT_WRAPV(a, b, r) \ |
353 | _GL_INT_OP_WRAPV (a, b, r, -, __builtin_sub_overflow, INT_SUBTRACT_OVERFLOW) |
354 | #define INT_MULTIPLY_WRAPV(a, b, r) \ |
355 | _GL_INT_OP_WRAPV (a, b, r, *, __builtin_mul_overflow, INT_MULTIPLY_OVERFLOW) |
356 | |
357 | /* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390. See: |
358 | https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193 |
359 | https://llvm.org/bugs/show_bug.cgi?id=25390 |
360 | For now, assume all versions of GCC-like compilers generate bogus |
361 | warnings for _Generic. This matters only for older compilers that |
362 | lack __builtin_add_overflow. */ |
363 | #if __GNUC__ |
364 | # define _GL__GENERIC_BOGUS 1 |
365 | #else |
366 | # define _GL__GENERIC_BOGUS 0 |
367 | #endif |
368 | |
369 | /* Store the low-order bits of A <op> B into *R, where OP specifies |
370 | the operation. BUILTIN is the builtin operation, and OVERFLOW the |
371 | overflow predicate. Return 1 if the result overflows. See above |
372 | for restrictions. */ |
373 | #if _GL_HAS_BUILTIN_OVERFLOW |
374 | # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) builtin (a, b, r) |
375 | #elif 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS |
376 | # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \ |
377 | (_Generic \ |
378 | (*(r), \ |
379 | signed char: \ |
380 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ |
381 | signed char, SCHAR_MIN, SCHAR_MAX), \ |
382 | short int: \ |
383 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ |
384 | short int, SHRT_MIN, SHRT_MAX), \ |
385 | int: \ |
386 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ |
387 | int, INT_MIN, INT_MAX), \ |
388 | long int: \ |
389 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ |
390 | long int, LONG_MIN, LONG_MAX), \ |
391 | long long int: \ |
392 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ |
393 | long long int, LLONG_MIN, LLONG_MAX))) |
394 | #else |
395 | # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \ |
396 | (sizeof *(r) == sizeof (signed char) \ |
397 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ |
398 | signed char, SCHAR_MIN, SCHAR_MAX) \ |
399 | : sizeof *(r) == sizeof (short int) \ |
400 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ |
401 | short int, SHRT_MIN, SHRT_MAX) \ |
402 | : sizeof *(r) == sizeof (int) \ |
403 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ |
404 | int, INT_MIN, INT_MAX) \ |
405 | : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow)) |
406 | # ifdef LLONG_MAX |
407 | # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \ |
408 | (sizeof *(r) == sizeof (long int) \ |
409 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ |
410 | long int, LONG_MIN, LONG_MAX) \ |
411 | : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ |
412 | long long int, LLONG_MIN, LLONG_MAX)) |
413 | # else |
414 | # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \ |
415 | _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ |
416 | long int, LONG_MIN, LONG_MAX) |
417 | # endif |
418 | #endif |
419 | |
420 | /* Store the low-order bits of A <op> B into *R, where the operation |
421 | is given by OP. Use the unsigned type UT for calculation to avoid |
422 | overflow problems. *R's type is T, with extrema TMIN and TMAX. |
423 | T must be a signed integer type. Return 1 if the result overflows. */ |
424 | #define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \ |
425 | (sizeof ((a) op (b)) < sizeof (t) \ |
426 | ? _GL_INT_OP_CALC1 ((t) (a), (t) (b), r, op, overflow, ut, t, tmin, tmax) \ |
427 | : _GL_INT_OP_CALC1 (a, b, r, op, overflow, ut, t, tmin, tmax)) |
428 | #define _GL_INT_OP_CALC1(a, b, r, op, overflow, ut, t, tmin, tmax) \ |
429 | ((overflow (a, b) \ |
430 | || (EXPR_SIGNED ((a) op (b)) && ((a) op (b)) < (tmin)) \ |
431 | || (tmax) < ((a) op (b))) \ |
432 | ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 1) \ |
433 | : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 0)) |
434 | |
435 | /* Return the low-order bits of A <op> B, where the operation is given |
436 | by OP. Use the unsigned type UT for calculation to avoid undefined |
437 | behavior on signed integer overflow, and convert the result to type T. |
438 | UT is at least as wide as T and is no narrower than unsigned int, |
439 | T is two's complement, and there is no padding or trap representations. |
440 | Assume that converting UT to T yields the low-order bits, as is |
441 | done in all known two's-complement C compilers. E.g., see: |
442 | https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html |
443 | |
444 | According to the C standard, converting UT to T yields an |
445 | implementation-defined result or signal for values outside T's |
446 | range. However, code that works around this theoretical problem |
447 | runs afoul of a compiler bug in Oracle Studio 12.3 x86. See: |
448 | https://lists.gnu.org/r/bug-gnulib/2017-04/msg00049.html |
449 | As the compiler bug is real, don't try to work around the |
450 | theoretical problem. */ |
451 | |
452 | #define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t) \ |
453 | ((t) ((ut) (a) op (ut) (b))) |
454 | |
455 | #endif /* _GL_INTPROPS_H */ |
456 | |