1 /* intprops.h -- properties of integer types 2 3 Copyright (C) 2001-2017 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 General Public License as published 7 by the Free Software Foundation; either version 3 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 General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <http://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 #include <verify.h> 25 26 #ifndef __has_builtin 27 # define __has_builtin(x) 0 28 #endif 29 30 /* Return a value with the common real type of E and V and the value of V. */ 31 #define _GL_INT_CONVERT(e, v) (0 * (e) + (v)) 32 33 /* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see 34 <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00406.html>. */ 35 #define _GL_INT_NEGATE_CONVERT(e, v) (0 * (e) - (v)) 36 37 /* The extra casts in the following macros work around compiler bugs, 38 e.g., in Cray C 5.0.3.0. */ 39 40 /* True if the arithmetic type T is an integer type. bool counts as 41 an integer. */ 42 #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) 43 44 /* True if the real type T is signed. */ 45 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) 46 47 /* Return 1 if the real expression E, after promotion, has a 48 signed or floating type. */ 49 #define EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0) 50 51 52 /* Minimum and maximum values for integer types and expressions. */ 53 54 /* The width in bits of the integer type or expression T. 55 Padding bits are not supported; this is checked at compile-time below. */ 56 #define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT) 57 58 /* The maximum and minimum values for the integer type T. */ 59 #define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t)) 60 #define TYPE_MAXIMUM(t) \ 61 ((t) (! TYPE_SIGNED (t) \ 62 ? (t) -1 \ 63 : ((((t) 1 << (TYPE_WIDTH (t) - 2)) - 1) * 2 + 1))) 64 65 /* The maximum and minimum values for the type of the expression E, 66 after integer promotion. E should not have side effects. */ 67 #define _GL_INT_MINIMUM(e) \ 68 (EXPR_SIGNED (e) \ 69 ? ~ _GL_SIGNED_INT_MAXIMUM (e) \ 70 : _GL_INT_CONVERT (e, 0)) 71 #define _GL_INT_MAXIMUM(e) \ 72 (EXPR_SIGNED (e) \ 73 ? _GL_SIGNED_INT_MAXIMUM (e) \ 74 : _GL_INT_NEGATE_CONVERT (e, 1)) 75 #define _GL_SIGNED_INT_MAXIMUM(e) \ 76 (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH ((e) + 0) - 2)) - 1) * 2 + 1) 77 78 /* Work around OpenVMS incompatibility with C99. */ 79 #if !defined LLONG_MAX && defined __INT64_MAX 80 # define LLONG_MAX __INT64_MAX 81 # define LLONG_MIN __INT64_MIN 82 #endif 83 84 /* This include file assumes that signed types are two's complement without 85 padding bits; the above macros have undefined behavior otherwise. 86 If this is a problem for you, please let us know how to fix it for your host. 87 As a sanity check, test the assumption for some signed types that 88 <limits.h> bounds. */ 89 verify (TYPE_MINIMUM (signed char) == SCHAR_MIN); 90 verify (TYPE_MAXIMUM (signed char) == SCHAR_MAX); 91 verify (TYPE_MINIMUM (short int) == SHRT_MIN); 92 verify (TYPE_MAXIMUM (short int) == SHRT_MAX); 93 verify (TYPE_MINIMUM (int) == INT_MIN); 94 verify (TYPE_MAXIMUM (int) == INT_MAX); 95 verify (TYPE_MINIMUM (long int) == LONG_MIN); 96 verify (TYPE_MAXIMUM (long int) == LONG_MAX); 97 #ifdef LLONG_MAX 98 verify (TYPE_MINIMUM (long long int) == LLONG_MIN); 99 verify (TYPE_MAXIMUM (long long int) == LLONG_MAX); 100 #endif 101 /* Similarly, sanity-check one ISO/IEC TS 18661-1:2014 macro if defined. */ 102 #ifdef UINT_WIDTH 103 verify (TYPE_WIDTH (unsigned int) == UINT_WIDTH); 104 #endif 105 106 /* Does the __typeof__ keyword work? This could be done by 107 'configure', but for now it's easier to do it by hand. */ 108 #if (2 <= __GNUC__ \ 109 || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \ 110 || (0x5110 <= __SUNPRO_C && !__STDC__)) 111 # define _GL_HAVE___TYPEOF__ 1 112 #else 113 # define _GL_HAVE___TYPEOF__ 0 114 #endif 115 116 /* Return 1 if the integer type or expression T might be signed. Return 0 117 if it is definitely unsigned. This macro does not evaluate its argument, 118 and expands to an integer constant expression. */ 119 #if _GL_HAVE___TYPEOF__ 120 # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t)) 121 #else 122 # define _GL_SIGNED_TYPE_OR_EXPR(t) 1 123 #endif 124 125 /* Bound on length of the string representing an unsigned integer 126 value representable in B bits. log10 (2.0) < 146/485. The 127 smallest value of B where this bound is not tight is 2621. */ 128 #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485) 129 130 /* Bound on length of the string representing an integer type or expression T. 131 Subtract 1 for the sign bit if T is signed, and then add 1 more for 132 a minus sign if needed. 133 134 Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 0 when its argument is 135 signed, this macro may overestimate the true bound by one byte when 136 applied to unsigned types of size 2, 4, 16, ... bytes. */ 137 #define INT_STRLEN_BOUND(t) \ 138 (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \ 139 + _GL_SIGNED_TYPE_OR_EXPR (t)) 140 141 /* Bound on buffer size needed to represent an integer type or expression T, 142 including the terminating null. */ 143 #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1) 144 145 146 /* Range overflow checks. 147 148 The INT_<op>_RANGE_OVERFLOW macros return 1 if the corresponding C 149 operators might not yield numerically correct answers due to 150 arithmetic overflow. They do not rely on undefined or 151 implementation-defined behavior. Their implementations are simple 152 and straightforward, but they are a bit harder to use than the 153 INT_<op>_OVERFLOW macros described below. 154 155 Example usage: 156 157 long int i = ...; 158 long int j = ...; 159 if (INT_MULTIPLY_RANGE_OVERFLOW (i, j, LONG_MIN, LONG_MAX)) 160 printf ("multiply would overflow"); 161 else 162 printf ("product is %ld", i * j); 163 164 Restrictions on *_RANGE_OVERFLOW macros: 165 166 These macros do not check for all possible numerical problems or 167 undefined or unspecified behavior: they do not check for division 168 by zero, for bad shift counts, or for shifting negative numbers. 169 170 These macros may evaluate their arguments zero or multiple times, 171 so the arguments should not have side effects. The arithmetic 172 arguments (including the MIN and MAX arguments) must be of the same 173 integer type after the usual arithmetic conversions, and the type 174 must have minimum value MIN and maximum MAX. Unsigned types should 175 use a zero MIN of the proper type. 176 177 These macros are tuned for constant MIN and MAX. For commutative 178 operations such as A + B, they are also tuned for constant B. */ 179 180 /* Return 1 if A + B would overflow in [MIN,MAX] arithmetic. 181 See above for restrictions. */ 182 #define INT_ADD_RANGE_OVERFLOW(a, b, min, max) \ 183 ((b) < 0 \ 184 ? (a) < (min) - (b) \ 185 : (max) - (b) < (a)) 186 187 /* Return 1 if A - B would overflow in [MIN,MAX] arithmetic. 188 See above for restrictions. */ 189 #define INT_SUBTRACT_RANGE_OVERFLOW(a, b, min, max) \ 190 ((b) < 0 \ 191 ? (max) + (b) < (a) \ 192 : (a) < (min) + (b)) 193 194 /* Return 1 if - A would overflow in [MIN,MAX] arithmetic. 195 See above for restrictions. */ 196 #define INT_NEGATE_RANGE_OVERFLOW(a, min, max) \ 197 ((min) < 0 \ 198 ? (a) < - (max) \ 199 : 0 < (a)) 200 201 /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic. 202 See above for restrictions. Avoid && and || as they tickle 203 bugs in Sun C 5.11 2010/08/13 and other compilers; see 204 <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00401.html>. */ 205 #define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \ 206 ((b) < 0 \ 207 ? ((a) < 0 \ 208 ? (a) < (max) / (b) \ 209 : (b) == -1 \ 210 ? 0 \ 211 : (min) / (b) < (a)) \ 212 : (b) == 0 \ 213 ? 0 \ 214 : ((a) < 0 \ 215 ? (a) < (min) / (b) \ 216 : (max) / (b) < (a))) 217 218 /* Return 1 if A / B would overflow in [MIN,MAX] arithmetic. 219 See above for restrictions. Do not check for division by zero. */ 220 #define INT_DIVIDE_RANGE_OVERFLOW(a, b, min, max) \ 221 ((min) < 0 && (b) == -1 && (a) < - (max)) 222 223 /* Return 1 if A % B would overflow in [MIN,MAX] arithmetic. 224 See above for restrictions. Do not check for division by zero. 225 Mathematically, % should never overflow, but on x86-like hosts 226 INT_MIN % -1 traps, and the C standard permits this, so treat this 227 as an overflow too. */ 228 #define INT_REMAINDER_RANGE_OVERFLOW(a, b, min, max) \ 229 INT_DIVIDE_RANGE_OVERFLOW (a, b, min, max) 230 231 /* Return 1 if A << B would overflow in [MIN,MAX] arithmetic. 232 See above for restrictions. Here, MIN and MAX are for A only, and B need 233 not be of the same type as the other arguments. The C standard says that 234 behavior is undefined for shifts unless 0 <= B < wordwidth, and that when 235 A is negative then A << B has undefined behavior and A >> B has 236 implementation-defined behavior, but do not check these other 237 restrictions. */ 238 #define INT_LEFT_SHIFT_RANGE_OVERFLOW(a, b, min, max) \ 239 ((a) < 0 \ 240 ? (a) < (min) >> (b) \ 241 : (max) >> (b) < (a)) 242 243 /* True if __builtin_add_overflow (A, B, P) works when P is non-null. */ 244 #define _GL_HAS_BUILTIN_OVERFLOW \ 245 (5 <= __GNUC__ || __has_builtin (__builtin_add_overflow)) 246 247 /* True if __builtin_add_overflow_p (A, B, C) works. */ 248 #define _GL_HAS_BUILTIN_OVERFLOW_P \ 249 (7 <= __GNUC__ || __has_builtin (__builtin_add_overflow_p)) 250 251 /* The _GL*_OVERFLOW macros have the same restrictions as the 252 *_RANGE_OVERFLOW macros, except that they do not assume that operands 253 (e.g., A and B) have the same type as MIN and MAX. Instead, they assume 254 that the result (e.g., A + B) has that type. */ 255 #if _GL_HAS_BUILTIN_OVERFLOW_P 256 # define _GL_ADD_OVERFLOW(a, b, min, max) \ 257 __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0) 258 # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ 259 __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0) 260 # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ 261 __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0) 262 #else 263 # define _GL_ADD_OVERFLOW(a, b, min, max) \ 264 ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \ 265 : (a) < 0 ? (b) <= (a) + (b) \ 266 : (b) < 0 ? (a) <= (a) + (b) \ 267 : (a) + (b) < (b)) 268 # define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \ 269 ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \ 270 : (a) < 0 ? 1 \ 271 : (b) < 0 ? (a) - (b) <= (a) \ 272 : (a) < (b)) 273 # define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \ 274 (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \ 275 || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max)) 276 #endif 277 #define _GL_DIVIDE_OVERFLOW(a, b, min, max) \ 278 ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \ 279 : (a) < 0 ? (b) <= (a) + (b) - 1 \ 280 : (b) < 0 && (a) + (b) <= (a)) 281 #define _GL_REMAINDER_OVERFLOW(a, b, min, max) \ 282 ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \ 283 : (a) < 0 ? (a) % (b) != ((max) - (b) + 1) % (b) \ 284 : (b) < 0 && ! _GL_UNSIGNED_NEG_MULTIPLE (a, b, max)) 285 286 /* Return a nonzero value if A is a mathematical multiple of B, where 287 A is unsigned, B is negative, and MAX is the maximum value of A's 288 type. A's type must be the same as (A % B)'s type. Normally (A % 289 -B == 0) suffices, but things get tricky if -B would overflow. */ 290 #define _GL_UNSIGNED_NEG_MULTIPLE(a, b, max) \ 291 (((b) < -_GL_SIGNED_INT_MAXIMUM (b) \ 292 ? (_GL_SIGNED_INT_MAXIMUM (b) == (max) \ 293 ? (a) \ 294 : (a) % (_GL_INT_CONVERT (a, _GL_SIGNED_INT_MAXIMUM (b)) + 1)) \ 295 : (a) % - (b)) \ 296 == 0) 297 298 /* Check for integer overflow, and report low order bits of answer. 299 300 The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators 301 might not yield numerically correct answers due to arithmetic overflow. 302 The INT_<op>_WRAPV macros also store the low-order bits of the answer. 303 These macros work correctly on all known practical hosts, and do not rely 304 on undefined behavior due to signed arithmetic overflow. 305 306 Example usage, assuming A and B are long int: 307 308 if (INT_MULTIPLY_OVERFLOW (a, b)) 309 printf ("result would overflow\n"); 310 else 311 printf ("result is %ld (no overflow)\n", a * b); 312 313 Example usage with WRAPV flavor: 314 315 long int result; 316 bool overflow = INT_MULTIPLY_WRAPV (a, b, &result); 317 printf ("result is %ld (%s)\n", result, 318 overflow ? "after overflow" : "no overflow"); 319 320 Restrictions on these macros: 321 322 These macros do not check for all possible numerical problems or 323 undefined or unspecified behavior: they do not check for division 324 by zero, for bad shift counts, or for shifting negative numbers. 325 326 These macros may evaluate their arguments zero or multiple times, so the 327 arguments should not have side effects. 328 329 The WRAPV macros are not constant expressions. They support only 330 +, binary -, and *. The result type must be signed. 331 332 These macros are tuned for their last argument being a constant. 333 334 Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B, 335 A % B, and A << B would overflow, respectively. */ 336 337 #define INT_ADD_OVERFLOW(a, b) \ 338 _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW) 339 #define INT_SUBTRACT_OVERFLOW(a, b) \ 340 _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW) 341 #if _GL_HAS_BUILTIN_OVERFLOW_P 342 # define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a) 343 #else 344 # define INT_NEGATE_OVERFLOW(a) \ 345 INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a)) 346 #endif 347 #define INT_MULTIPLY_OVERFLOW(a, b) \ 348 _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW) 349 #define INT_DIVIDE_OVERFLOW(a, b) \ 350 _GL_BINARY_OP_OVERFLOW (a, b, _GL_DIVIDE_OVERFLOW) 351 #define INT_REMAINDER_OVERFLOW(a, b) \ 352 _GL_BINARY_OP_OVERFLOW (a, b, _GL_REMAINDER_OVERFLOW) 353 #define INT_LEFT_SHIFT_OVERFLOW(a, b) \ 354 INT_LEFT_SHIFT_RANGE_OVERFLOW (a, b, \ 355 _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a)) 356 357 /* Return 1 if the expression A <op> B would overflow, 358 where OP_RESULT_OVERFLOW (A, B, MIN, MAX) does the actual test, 359 assuming MIN and MAX are the minimum and maximum for the result type. 360 Arguments should be free of side effects. */ 361 #define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \ 362 op_result_overflow (a, b, \ 363 _GL_INT_MINIMUM (0 * (b) + (a)), \ 364 _GL_INT_MAXIMUM (0 * (b) + (a))) 365 366 /* Store the low-order bits of A + B, A - B, A * B, respectively, into *R. 367 Return 1 if the result overflows. See above for restrictions. */ 368 #define INT_ADD_WRAPV(a, b, r) \ 369 _GL_INT_OP_WRAPV (a, b, r, +, __builtin_add_overflow, INT_ADD_OVERFLOW) 370 #define INT_SUBTRACT_WRAPV(a, b, r) \ 371 _GL_INT_OP_WRAPV (a, b, r, -, __builtin_sub_overflow, INT_SUBTRACT_OVERFLOW) 372 #define INT_MULTIPLY_WRAPV(a, b, r) \ 373 _GL_INT_OP_WRAPV (a, b, r, *, __builtin_mul_overflow, INT_MULTIPLY_OVERFLOW) 374 375 /* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390. See: 376 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193 377 https://llvm.org/bugs/show_bug.cgi?id=25390 378 For now, assume all versions of GCC-like compilers generate bogus 379 warnings for _Generic. This matters only for older compilers that 380 lack __builtin_add_overflow. */ 381 #if __GNUC__ 382 # define _GL__GENERIC_BOGUS 1 383 #else 384 # define _GL__GENERIC_BOGUS 0 385 #endif 386 387 /* Store the low-order bits of A <op> B into *R, where OP specifies 388 the operation. BUILTIN is the builtin operation, and OVERFLOW the 389 overflow predicate. Return 1 if the result overflows. See above 390 for restrictions. */ 391 #if _GL_HAS_BUILTIN_OVERFLOW 392 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) builtin (a, b, r) 393 #elif 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS 394 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \ 395 (_Generic \ 396 (*(r), \ 397 signed char: \ 398 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned char, \ 399 signed char, SCHAR_MIN, SCHAR_MAX), \ 400 short int: \ 401 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned short int, \ 402 short int, SHRT_MIN, SHRT_MAX), \ 403 int: \ 404 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ 405 int, INT_MIN, INT_MAX), \ 406 long int: \ 407 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ 408 long int, LONG_MIN, LONG_MAX), \ 409 long long int: \ 410 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ 411 long long int, LLONG_MIN, LLONG_MAX))) 412 #else 413 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \ 414 (sizeof *(r) == sizeof (signed char) \ 415 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned char, \ 416 signed char, SCHAR_MIN, SCHAR_MAX) \ 417 : sizeof *(r) == sizeof (short int) \ 418 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned short int, \ 419 short int, SHRT_MIN, SHRT_MAX) \ 420 : sizeof *(r) == sizeof (int) \ 421 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \ 422 int, INT_MIN, INT_MAX) \ 423 : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow)) 424 # ifdef LLONG_MAX 425 # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \ 426 (sizeof *(r) == sizeof (long int) \ 427 ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ 428 long int, LONG_MIN, LONG_MAX) \ 429 : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \ 430 long long int, LLONG_MIN, LLONG_MAX)) 431 # else 432 # define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \ 433 _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \ 434 long int, LONG_MIN, LONG_MAX) 435 # endif 436 #endif 437 438 /* Store the low-order bits of A <op> B into *R, where the operation 439 is given by OP. Use the unsigned type UT for calculation to avoid 440 overflow problems. *R's type is T, with extremal values TMIN and 441 TMAX. T must be a signed integer type. Return 1 if the result 442 overflows. */ 443 #define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \ 444 (sizeof ((a) op (b)) < sizeof (t) \ 445 ? _GL_INT_OP_CALC1 ((t) (a), (t) (b), r, op, overflow, ut, t, tmin, tmax) \ 446 : _GL_INT_OP_CALC1 (a, b, r, op, overflow, ut, t, tmin, tmax)) 447 #define _GL_INT_OP_CALC1(a, b, r, op, overflow, ut, t, tmin, tmax) \ 448 ((overflow (a, b) \ 449 || (EXPR_SIGNED ((a) op (b)) && ((a) op (b)) < (tmin)) \ 450 || (tmax) < ((a) op (b))) \ 451 ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t, tmin, tmax), 1) \ 452 : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t, tmin, tmax), 0)) 453 454 /* Return A <op> B, where the operation is given by OP. Use the 455 unsigned type UT for calculation to avoid overflow problems. 456 Convert the result to type T without overflow by subtracting TMIN 457 from large values before converting, and adding it afterwards. 458 Compilers can optimize all the operations except OP. */ 459 #define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t, tmin, tmax) \ 460 (((ut) (a) op (ut) (b)) <= (tmax) \ 461 ? (t) ((ut) (a) op (ut) (b)) \ 462 : ((t) (((ut) (a) op (ut) (b)) - (tmin)) + (tmin))) 463 464 #endif /* _GL_INTPROPS_H */ 465