1 /* intprops.h -- properties of integer types
3 Copyright (C) 2001-2021 Free Software Foundation, Inc.
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.
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.
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/>. */
18 /* Written by Paul Eggert. */
22 This is the gnulib "Integer Properties" header:
23 https://www.gnu.org/software/gnulib/manual/html_node/Integer-Properties.html
25 Copied into bup from gnulib as of this commit:
27 commit 257183ec1ea1517d5ae6dac2e8724a90e23e864a
28 Author: Paul Eggert <eggert@cs.ucla.edu>
29 Date: Sun Mar 14 21:28:40 2021 -0700
31 intprops: improve commentary
33 * lib/intprops.h: Improve comments about promotion etc.
37 #ifndef _GL_INTPROPS_H
38 #define _GL_INTPROPS_H
42 /* Return a value with the common real type of E and V and the value of V.
44 #define _GL_INT_CONVERT(e, v) ((1 ? 0 : (e)) + (v))
46 /* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see
47 <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00406.html>. */
48 #define _GL_INT_NEGATE_CONVERT(e, v) ((1 ? 0 : (e)) - (v))
50 /* The extra casts in the following macros work around compiler bugs,
51 e.g., in Cray C 5.0.3.0. */
53 /* True if the arithmetic type T is an integer type. bool counts as
55 #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
57 /* True if the real type T is signed. */
58 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
60 /* Return 1 if the real expression E, after promotion, has a
61 signed or floating type. Do not evaluate E. */
62 #define EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
65 /* Minimum and maximum values for integer types and expressions. */
67 /* The width in bits of the integer type or expression T.
68 Do not evaluate T. T must not be a bit-field expression.
69 Padding bits are not supported; this is checked at compile-time below. */
70 #define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT)
72 /* The maximum and minimum values for the integer type T. */
73 #define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t))
74 #define TYPE_MAXIMUM(t) \
75 ((t) (! TYPE_SIGNED (t) \
77 : ((((t) 1 << (TYPE_WIDTH (t) - 2)) - 1) * 2 + 1)))
79 /* The maximum and minimum values for the type of the expression E,
80 after integer promotion. E is not evaluated. */
81 #define _GL_INT_MINIMUM(e) \
83 ? ~ _GL_SIGNED_INT_MAXIMUM (e) \
84 : _GL_INT_CONVERT (e, 0))
85 #define _GL_INT_MAXIMUM(e) \
87 ? _GL_SIGNED_INT_MAXIMUM (e) \
88 : _GL_INT_NEGATE_CONVERT (e, 1))
89 #define _GL_SIGNED_INT_MAXIMUM(e) \
90 (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH (+ (e)) - 2)) - 1) * 2 + 1)
92 /* Work around OpenVMS incompatibility with C99. */
93 #if !defined LLONG_MAX && defined __INT64_MAX
94 # define LLONG_MAX __INT64_MAX
95 # define LLONG_MIN __INT64_MIN
98 /* This include file assumes that signed types are two's complement without
99 padding bits; the above macros have undefined behavior otherwise.
100 If this is a problem for you, please let us know how to fix it for your host.
101 This assumption is tested by the intprops-tests module. */
103 /* Does the __typeof__ keyword work? This could be done by
104 'configure', but for now it's easier to do it by hand. */
106 || (4 <= __clang_major__) \
107 || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \
108 || (0x5110 <= __SUNPRO_C && !__STDC__))
109 # define _GL_HAVE___TYPEOF__ 1
111 # define _GL_HAVE___TYPEOF__ 0
114 /* Return 1 if the integer type or expression T might be signed. Return 0
115 if it is definitely unsigned. T must not be a bit-field expression.
116 This macro does not evaluate its argument, and expands to an
117 integer constant expression. */
118 #if _GL_HAVE___TYPEOF__
119 # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t))
121 # define _GL_SIGNED_TYPE_OR_EXPR(t) 1
124 /* Bound on length of the string representing an unsigned integer
125 value representable in B bits. log10 (2.0) < 146/485. The
126 smallest value of B where this bound is not tight is 2621. */
127 #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485)
129 /* Bound on length of the string representing an integer type or expression T.
130 T must not be a bit-field expression.
132 Subtract 1 for the sign bit if T is signed, and then add 1 more for
133 a minus sign if needed.
135 Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 1 when its argument is
136 unsigned, this macro may overestimate the true bound by one byte when
137 applied to unsigned types of size 2, 4, 16, ... bytes. */
138 #define INT_STRLEN_BOUND(t) \
139 (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \
140 + _GL_SIGNED_TYPE_OR_EXPR (t))
142 /* Bound on buffer size needed to represent an integer type or expression T,
143 including the terminating null. T must not be a bit-field expression. */
144 #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)
147 /* Range overflow checks.
149 The INT_<op>_RANGE_OVERFLOW macros return 1 if the corresponding C
150 operators might not yield numerically correct answers due to
151 arithmetic overflow. They do not rely on undefined or
152 implementation-defined behavior. Their implementations are simple
153 and straightforward, but they are harder to use and may be less
154 efficient than the INT_<op>_WRAPV, INT_<op>_OK, and
155 INT_<op>_OVERFLOW macros described below.
161 if (INT_MULTIPLY_RANGE_OVERFLOW (i, j, LONG_MIN, LONG_MAX))
162 printf ("multiply would overflow");
164 printf ("product is %ld", i * j);
166 Restrictions on *_RANGE_OVERFLOW macros:
168 These macros do not check for all possible numerical problems or
169 undefined or unspecified behavior: they do not check for division
170 by zero, for bad shift counts, or for shifting negative numbers.
172 These macros may evaluate their arguments zero or multiple times,
173 so the arguments should not have side effects. The arithmetic
174 arguments (including the MIN and MAX arguments) must be of the same
175 integer type after the usual arithmetic conversions, and the type
176 must have minimum value MIN and maximum MAX. Unsigned types should
177 use a zero MIN of the proper type.
179 Because all arguments are subject to integer promotions, these
180 macros typically do not work on types narrower than 'int'.
182 These macros are tuned for constant MIN and MAX. For commutative
183 operations such as A + B, they are also tuned for constant B. */
185 /* Return 1 if A + B would overflow in [MIN,MAX] arithmetic.
186 See above for restrictions. */
187 #define INT_ADD_RANGE_OVERFLOW(a, b, min, max) \
189 ? (a) < (min) - (b) \
192 /* Return 1 if A - B would overflow in [MIN,MAX] arithmetic.
193 See above for restrictions. */
194 #define INT_SUBTRACT_RANGE_OVERFLOW(a, b, min, max) \
196 ? (max) + (b) < (a) \
199 /* Return 1 if - A would overflow in [MIN,MAX] arithmetic.
200 See above for restrictions. */
201 #define INT_NEGATE_RANGE_OVERFLOW(a, min, max) \
206 /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic.
207 See above for restrictions. Avoid && and || as they tickle
208 bugs in Sun C 5.11 2010/08/13 and other compilers; see
209 <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00401.html>. */
210 #define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \
213 ? (a) < (max) / (b) \
216 : (min) / (b) < (a)) \
220 ? (a) < (min) / (b) \
221 : (max) / (b) < (a)))
223 /* Return 1 if A / B would overflow in [MIN,MAX] arithmetic.
224 See above for restrictions. Do not check for division by zero. */
225 #define INT_DIVIDE_RANGE_OVERFLOW(a, b, min, max) \
226 ((min) < 0 && (b) == -1 && (a) < - (max))
228 /* Return 1 if A % B would overflow in [MIN,MAX] arithmetic.
229 See above for restrictions. Do not check for division by zero.
230 Mathematically, % should never overflow, but on x86-like hosts
231 INT_MIN % -1 traps, and the C standard permits this, so treat this
232 as an overflow too. */
233 #define INT_REMAINDER_RANGE_OVERFLOW(a, b, min, max) \
234 INT_DIVIDE_RANGE_OVERFLOW (a, b, min, max)
236 /* Return 1 if A << B would overflow in [MIN,MAX] arithmetic.
237 See above for restrictions. Here, MIN and MAX are for A only, and B need
238 not be of the same type as the other arguments. The C standard says that
239 behavior is undefined for shifts unless 0 <= B < wordwidth, and that when
240 A is negative then A << B has undefined behavior and A >> B has
241 implementation-defined behavior, but do not check these other
243 #define INT_LEFT_SHIFT_RANGE_OVERFLOW(a, b, min, max) \
245 ? (a) < (min) >> (b) \
246 : (max) >> (b) < (a))
248 /* True if __builtin_add_overflow (A, B, P) and __builtin_sub_overflow
249 (A, B, P) work when P is non-null. */
250 /* __builtin_{add,sub}_overflow exists but is not reliable in GCC 5.x and 6.x,
251 see <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98269>. */
252 #if 7 <= __GNUC__ && !defined __ICC
253 # define _GL_HAS_BUILTIN_ADD_OVERFLOW 1
254 #elif defined __has_builtin
255 # define _GL_HAS_BUILTIN_ADD_OVERFLOW __has_builtin (__builtin_add_overflow)
257 # define _GL_HAS_BUILTIN_ADD_OVERFLOW 0
260 /* True if __builtin_mul_overflow (A, B, P) works when P is non-null. */
262 /* Work around Clang bug <https://bugs.llvm.org/show_bug.cgi?id=16404>. */
263 # define _GL_HAS_BUILTIN_MUL_OVERFLOW 0
265 # define _GL_HAS_BUILTIN_MUL_OVERFLOW _GL_HAS_BUILTIN_ADD_OVERFLOW
268 /* True if __builtin_add_overflow_p (A, B, C) works, and similarly for
269 __builtin_sub_overflow_p and __builtin_mul_overflow_p. */
270 #if defined __clang__ || defined __ICC
271 /* Clang 11 lacks __builtin_mul_overflow_p, and even if it did it
272 would presumably run afoul of Clang bug 16404. ICC 2021.1's
273 __builtin_add_overflow_p etc. are not treated as integral constant
274 expressions even when all arguments are. */
275 # define _GL_HAS_BUILTIN_OVERFLOW_P 0
276 #elif defined __has_builtin
277 # define _GL_HAS_BUILTIN_OVERFLOW_P __has_builtin (__builtin_mul_overflow_p)
279 # define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__)
282 /* The _GL*_OVERFLOW macros have the same restrictions as the
283 *_RANGE_OVERFLOW macros, except that they do not assume that operands
284 (e.g., A and B) have the same type as MIN and MAX. Instead, they assume
285 that the result (e.g., A + B) has that type. */
286 #if _GL_HAS_BUILTIN_OVERFLOW_P
287 # define _GL_ADD_OVERFLOW(a, b, min, max) \
288 __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0)
289 # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
290 __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0)
291 # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
292 __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0)
294 # define _GL_ADD_OVERFLOW(a, b, min, max) \
295 ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \
296 : (a) < 0 ? (b) <= (a) + (b) \
297 : (b) < 0 ? (a) <= (a) + (b) \
299 # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
300 ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \
302 : (b) < 0 ? (a) - (b) <= (a) \
304 # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
305 (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \
306 || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max))
308 #define _GL_DIVIDE_OVERFLOW(a, b, min, max) \
309 ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \
310 : (a) < 0 ? (b) <= (a) + (b) - 1 \
311 : (b) < 0 && (a) + (b) <= (a))
312 #define _GL_REMAINDER_OVERFLOW(a, b, min, max) \
313 ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \
314 : (a) < 0 ? (a) % (b) != ((max) - (b) + 1) % (b) \
315 : (b) < 0 && ! _GL_UNSIGNED_NEG_MULTIPLE (a, b, max))
317 /* Return a nonzero value if A is a mathematical multiple of B, where
318 A is unsigned, B is negative, and MAX is the maximum value of A's
319 type. A's type must be the same as (A % B)'s type. Normally (A %
320 -B == 0) suffices, but things get tricky if -B would overflow. */
321 #define _GL_UNSIGNED_NEG_MULTIPLE(a, b, max) \
322 (((b) < -_GL_SIGNED_INT_MAXIMUM (b) \
323 ? (_GL_SIGNED_INT_MAXIMUM (b) == (max) \
325 : (a) % (_GL_INT_CONVERT (a, _GL_SIGNED_INT_MAXIMUM (b)) + 1)) \
329 /* Check for integer overflow, and report low order bits of answer.
331 The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators
332 might not yield numerically correct answers due to arithmetic overflow.
333 The INT_<op>_WRAPV macros compute the low-order bits of the sum,
334 difference, and product of two C integers, and return 1 if these
335 low-order bits are not numerically correct.
336 These macros work correctly on all known practical hosts, and do not rely
337 on undefined behavior due to signed arithmetic overflow.
339 Example usage, assuming A and B are long int:
341 if (INT_MULTIPLY_OVERFLOW (a, b))
342 printf ("result would overflow\n");
344 printf ("result is %ld (no overflow)\n", a * b);
346 Example usage with WRAPV flavor:
349 bool overflow = INT_MULTIPLY_WRAPV (a, b, &result);
350 printf ("result is %ld (%s)\n", result,
351 overflow ? "after overflow" : "no overflow");
353 Restrictions on these macros:
355 These macros do not check for all possible numerical problems or
356 undefined or unspecified behavior: they do not check for division
357 by zero, for bad shift counts, or for shifting negative numbers.
359 These macros may evaluate their arguments zero or multiple times, so the
360 arguments should not have side effects.
362 The WRAPV macros are not constant expressions. They support only
365 Because the WRAPV macros convert the result, they report overflow
366 in different circumstances than the OVERFLOW macros do. For
367 example, in the typical case with 16-bit 'short' and 32-bit 'int',
368 if A, B and R are all of type 'short' then INT_ADD_OVERFLOW (A, B)
369 returns false because the addition cannot overflow after A and B
370 are converted to 'int', whereas INT_ADD_WRAPV (A, B, &R) returns
371 true or false depending on whether the sum fits into 'short'.
373 These macros are tuned for their last input argument being a constant.
375 Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B,
376 A % B, and A << B would overflow, respectively. */
378 #define INT_ADD_OVERFLOW(a, b) \
379 _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW)
380 #define INT_SUBTRACT_OVERFLOW(a, b) \
381 _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW)
382 #if _GL_HAS_BUILTIN_OVERFLOW_P
383 # define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a)
385 # define INT_NEGATE_OVERFLOW(a) \
386 INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
388 #define INT_MULTIPLY_OVERFLOW(a, b) \
389 _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW)
390 #define INT_DIVIDE_OVERFLOW(a, b) \
391 _GL_BINARY_OP_OVERFLOW (a, b, _GL_DIVIDE_OVERFLOW)
392 #define INT_REMAINDER_OVERFLOW(a, b) \
393 _GL_BINARY_OP_OVERFLOW (a, b, _GL_REMAINDER_OVERFLOW)
394 #define INT_LEFT_SHIFT_OVERFLOW(a, b) \
395 INT_LEFT_SHIFT_RANGE_OVERFLOW (a, b, \
396 _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
398 /* Return 1 if the expression A <op> B would overflow,
399 where OP_RESULT_OVERFLOW (A, B, MIN, MAX) does the actual test,
400 assuming MIN and MAX are the minimum and maximum for the result type.
401 Arguments should be free of side effects. */
402 #define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \
403 op_result_overflow (a, b, \
404 _GL_INT_MINIMUM (_GL_INT_CONVERT (a, b)), \
405 _GL_INT_MAXIMUM (_GL_INT_CONVERT (a, b)))
407 /* Store the low-order bits of A + B, A - B, A * B, respectively, into *R.
408 Return 1 if the result overflows. See above for restrictions. */
409 #if _GL_HAS_BUILTIN_ADD_OVERFLOW
410 # define INT_ADD_WRAPV(a, b, r) __builtin_add_overflow (a, b, r)
411 # define INT_SUBTRACT_WRAPV(a, b, r) __builtin_sub_overflow (a, b, r)
413 # define INT_ADD_WRAPV(a, b, r) \
414 _GL_INT_OP_WRAPV (a, b, r, +, _GL_INT_ADD_RANGE_OVERFLOW)
415 # define INT_SUBTRACT_WRAPV(a, b, r) \
416 _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
418 #if _GL_HAS_BUILTIN_MUL_OVERFLOW
419 # if ((9 < __GNUC__ + (3 <= __GNUC_MINOR__) \
420 || (__GNUC__ == 8 && 4 <= __GNUC_MINOR__)) \
422 # define INT_MULTIPLY_WRAPV(a, b, r) __builtin_mul_overflow (a, b, r)
424 /* Work around GCC bug 91450. */
425 # define INT_MULTIPLY_WRAPV(a, b, r) \
426 ((!_GL_SIGNED_TYPE_OR_EXPR (*(r)) && EXPR_SIGNED (a) && EXPR_SIGNED (b) \
427 && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1)) \
428 ? ((void) __builtin_mul_overflow (a, b, r), 1) \
429 : __builtin_mul_overflow (a, b, r))
432 # define INT_MULTIPLY_WRAPV(a, b, r) \
433 _GL_INT_OP_WRAPV (a, b, r, *, _GL_INT_MULTIPLY_RANGE_OVERFLOW)
436 /* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390. See:
437 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193
438 https://llvm.org/bugs/show_bug.cgi?id=25390
439 For now, assume all versions of GCC-like compilers generate bogus
440 warnings for _Generic. This matters only for compilers that
441 lack relevant builtins. */
442 #if __GNUC__ || defined __clang__
443 # define _GL__GENERIC_BOGUS 1
445 # define _GL__GENERIC_BOGUS 0
448 /* Store the low-order bits of A <op> B into *R, where OP specifies
449 the operation and OVERFLOW the overflow predicate. Return 1 if the
450 result overflows. See above for restrictions. */
451 #if 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS
452 # define _GL_INT_OP_WRAPV(a, b, r, op, overflow) \
456 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
457 signed char, SCHAR_MIN, SCHAR_MAX), \
459 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
460 unsigned char, 0, UCHAR_MAX), \
462 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
463 short int, SHRT_MIN, SHRT_MAX), \
464 unsigned short int: \
465 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
466 unsigned short int, 0, USHRT_MAX), \
468 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
469 int, INT_MIN, INT_MAX), \
471 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
472 unsigned int, 0, UINT_MAX), \
474 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
475 long int, LONG_MIN, LONG_MAX), \
477 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
478 unsigned long int, 0, ULONG_MAX), \
480 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
481 long long int, LLONG_MIN, LLONG_MAX), \
482 unsigned long long int: \
483 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
484 unsigned long long int, 0, ULLONG_MAX)))
486 /* Store the low-order bits of A <op> B into *R, where OP specifies
487 the operation and OVERFLOW the overflow predicate. If *R is
488 signed, its type is ST with bounds SMIN..SMAX; otherwise its type
489 is UT with bounds U..UMAX. ST and UT are narrower than int.
490 Return 1 if the result overflows. See above for restrictions. */
491 # if _GL_HAVE___TYPEOF__
492 # define _GL_INT_OP_WRAPV_SMALLISH(a,b,r,op,overflow,st,smin,smax,ut,umax) \
493 (TYPE_SIGNED (__typeof__ (*(r))) \
494 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, st, smin, smax) \
495 : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, ut, 0, umax))
497 # define _GL_INT_OP_WRAPV_SMALLISH(a,b,r,op,overflow,st,smin,smax,ut,umax) \
498 (overflow (a, b, smin, smax) \
499 ? (overflow (a, b, 0, umax) \
500 ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st), 1) \
501 : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st)) < 0) \
502 : (overflow (a, b, 0, umax) \
503 ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st)) >= 0 \
504 : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st), 0)))
507 # define _GL_INT_OP_WRAPV(a, b, r, op, overflow) \
508 (sizeof *(r) == sizeof (signed char) \
509 ? _GL_INT_OP_WRAPV_SMALLISH (a, b, r, op, overflow, \
510 signed char, SCHAR_MIN, SCHAR_MAX, \
511 unsigned char, UCHAR_MAX) \
512 : sizeof *(r) == sizeof (short int) \
513 ? _GL_INT_OP_WRAPV_SMALLISH (a, b, r, op, overflow, \
514 short int, SHRT_MIN, SHRT_MAX, \
515 unsigned short int, USHRT_MAX) \
516 : sizeof *(r) == sizeof (int) \
517 ? (EXPR_SIGNED (*(r)) \
518 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
519 int, INT_MIN, INT_MAX) \
520 : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
521 unsigned int, 0, UINT_MAX)) \
522 : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
524 # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
525 (sizeof *(r) == sizeof (long int) \
526 ? (EXPR_SIGNED (*(r)) \
527 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
528 long int, LONG_MIN, LONG_MAX) \
529 : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
530 unsigned long int, 0, ULONG_MAX)) \
531 : (EXPR_SIGNED (*(r)) \
532 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
533 long long int, LLONG_MIN, LLONG_MAX) \
534 : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
535 unsigned long long int, 0, ULLONG_MAX)))
537 # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
538 (EXPR_SIGNED (*(r)) \
539 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
540 long int, LONG_MIN, LONG_MAX) \
541 : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
542 unsigned long int, 0, ULONG_MAX))
546 /* Store the low-order bits of A <op> B into *R, where the operation
547 is given by OP. Use the unsigned type UT for calculation to avoid
548 overflow problems. *R's type is T, with extrema TMIN and TMAX.
549 T must be a signed integer type. Return 1 if the result overflows. */
550 #define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \
551 (overflow (a, b, tmin, tmax) \
552 ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 1) \
553 : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 0))
555 /* Return the low-order bits of A <op> B, where the operation is given
556 by OP. Use the unsigned type UT for calculation to avoid undefined
557 behavior on signed integer overflow, and convert the result to type T.
558 UT is at least as wide as T and is no narrower than unsigned int,
559 T is two's complement, and there is no padding or trap representations.
560 Assume that converting UT to T yields the low-order bits, as is
561 done in all known two's-complement C compilers. E.g., see:
562 https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html
564 According to the C standard, converting UT to T yields an
565 implementation-defined result or signal for values outside T's
566 range. However, code that works around this theoretical problem
567 runs afoul of a compiler bug in Oracle Studio 12.3 x86. See:
568 https://lists.gnu.org/r/bug-gnulib/2017-04/msg00049.html
569 As the compiler bug is real, don't try to work around the
570 theoretical problem. */
572 #define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t) \
573 ((t) ((ut) (a) op (ut) (b)))
575 /* Return true if the numeric values A + B, A - B, A * B fall outside
576 the range TMIN..TMAX. Arguments should be integer expressions
577 without side effects. TMIN should be signed and nonpositive.
578 TMAX should be positive, and should be signed unless TMIN is zero. */
579 #define _GL_INT_ADD_RANGE_OVERFLOW(a, b, tmin, tmax) \
582 ? ((EXPR_SIGNED (_GL_INT_CONVERT (a, (tmin) - (b))) || (b) < (tmin)) \
583 && (a) < (tmin) - (b)) \
585 || ((EXPR_SIGNED (a) ? 0 <= (a) : (tmax) < (a)) && (tmax) < (a) + (b))) \
588 ? ((EXPR_SIGNED (_GL_INT_CONVERT (b, (tmin) - (a))) || (a) < (tmin)) \
589 && (b) < (tmin) - (a)) \
591 || ((EXPR_SIGNED (_GL_INT_CONVERT (a, b)) || (tmax) < (b)) \
592 && (tmax) < (a) + (b))) \
593 : (tmax) < (b) || (tmax) - (b) < (a))
594 #define _GL_INT_SUBTRACT_RANGE_OVERFLOW(a, b, tmin, tmax) \
595 (((a) < 0) == ((b) < 0) \
597 ? !(tmin) || -1 - (tmin) < (b) - (a) - 1 \
598 : (tmax) < (a) - (b)) \
600 ? ((!EXPR_SIGNED (_GL_INT_CONVERT ((a) - (tmin), b)) && (a) - (tmin) < 0) \
601 || (a) - (tmin) < (b)) \
602 : ((! (EXPR_SIGNED (_GL_INT_CONVERT (tmax, b)) \
603 && EXPR_SIGNED (_GL_INT_CONVERT ((tmax) + (b), a))) \
604 && (tmax) <= -1 - (b)) \
605 || (tmax) + (b) < (a)))
606 #define _GL_INT_MULTIPLY_RANGE_OVERFLOW(a, b, tmin, tmax) \
609 ? (EXPR_SIGNED (_GL_INT_CONVERT (tmax, b)) \
610 ? (a) < (tmax) / (b) \
611 : ((INT_NEGATE_OVERFLOW (b) \
612 ? _GL_INT_CONVERT (b, tmax) >> (TYPE_WIDTH (+ (b)) - 1) \
615 : INT_NEGATE_OVERFLOW (_GL_INT_CONVERT (b, tmin)) && (b) == -1 \
618 : 0 < (a) && -1 - (tmin) < (a) - 1) \
619 : (tmin) / (b) < (a)) \
623 ? (INT_NEGATE_OVERFLOW (_GL_INT_CONVERT (a, tmin)) && (a) == -1 \
624 ? (EXPR_SIGNED (b) ? 0 < (b) + (tmin) : -1 - (tmin) < (b) - 1) \
625 : (tmin) / (a) < (b)) \
626 : (tmax) / (b) < (a)))
628 /* The following macros compute A + B, A - B, and A * B, respectively.
629 If no overflow occurs, they set *R to the result and return 1;
630 otherwise, they return 0 and may modify *R.
635 if (INT_ADD_OK (a, b, &result))
636 printf ("result is %ld\n", result);
638 printf ("overflow\n");
640 A, B, and *R should be integers; they need not be the same type,
641 and they need not be all signed or all unsigned.
643 These macros work correctly on all known practical hosts, and do not rely
644 on undefined behavior due to signed arithmetic overflow.
646 These macros are not constant expressions.
648 These macros may evaluate their arguments zero or multiple times, so the
649 arguments should not have side effects.
651 These macros are tuned for B being a constant. */
653 #define INT_ADD_OK(a, b, r) ! INT_ADD_WRAPV (a, b, r)
654 #define INT_SUBTRACT_OK(a, b, r) ! INT_SUBTRACT_WRAPV (a, b, r)
655 #define INT_MULTIPLY_OK(a, b, r) ! INT_MULTIPLY_WRAPV (a, b, r)
657 #endif /* _GL_INTPROPS_H */