lib/intprops.h

   1 /* intprops.h -- properties of integer types
   2
   3    Copyright (C) 2001-2016 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__ || defined __IBM__TYPEOF__ \
 109      || (0x5110 <= __SUNPRO_C && !__STDC__))
 110 # define _GL_HAVE___TYPEOF__ 1
 111 #else
 112 # define _GL_HAVE___TYPEOF__ 0
 113 #endif
 114
 115 /* Return 1 if the integer type or expression T might be signed.  Return 0
 116    if it is definitely unsigned.  This macro does not evaluate its argument,
 117    and expands to an integer constant expression.  */
 118 #if _GL_HAVE___TYPEOF__
 119 # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t))
 120 #else
 121 # define _GL_SIGNED_TYPE_OR_EXPR(t) 1
 122 #endif
 123
 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)
 128
 129 /* Bound on length of the string representing an integer type or expression T.
 130    Subtract 1 for the sign bit if T is signed, and then add 1 more for
 131    a minus sign if needed.
 132
 133    Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 0 when its argument is
 134    signed, this macro may overestimate the true bound by one byte when
 135    applied to unsigned types of size 2, 4, 16, ... bytes.  */
 136 #define INT_STRLEN_BOUND(t)                                     \
 137   (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \
 138    + _GL_SIGNED_TYPE_OR_EXPR (t))
 139
 140 /* Bound on buffer size needed to represent an integer type or expression T,
 141    including the terminating null.  */
 142 #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)
 143
 144
 145 /* Range overflow checks.
 146
 147    The INT_<op>_RANGE_OVERFLOW macros return 1 if the corresponding C
 148    operators might not yield numerically correct answers due to
 149    arithmetic overflow.  They do not rely on undefined or
 150    implementation-defined behavior.  Their implementations are simple
 151    and straightforward, but they are a bit harder to use than the
 152    INT_<op>_OVERFLOW macros described below.
 153
 154    Example usage:
 155
 156      long int i = ...;
 157      long int j = ...;
 158      if (INT_MULTIPLY_RANGE_OVERFLOW (i, j, LONG_MIN, LONG_MAX))
 159        printf ("multiply would overflow");
 160      else
 161        printf ("product is %ld", i * j);
 162
 163    Restrictions on *_RANGE_OVERFLOW macros:
 164
 165    These macros do not check for all possible numerical problems or
 166    undefined or unspecified behavior: they do not check for division
 167    by zero, for bad shift counts, or for shifting negative numbers.
 168
 169    These macros may evaluate their arguments zero or multiple times,
 170    so the arguments should not have side effects.  The arithmetic
 171    arguments (including the MIN and MAX arguments) must be of the same
 172    integer type after the usual arithmetic conversions, and the type
 173    must have minimum value MIN and maximum MAX.  Unsigned types should
 174    use a zero MIN of the proper type.
 175
 176    These macros are tuned for constant MIN and MAX.  For commutative
 177    operations such as A + B, they are also tuned for constant B.  */
 178
 179 /* Return 1 if A + B would overflow in [MIN,MAX] arithmetic.
 180    See above for restrictions.  */
 181 #define INT_ADD_RANGE_OVERFLOW(a, b, min, max)          \
 182   ((b) < 0                                              \
 183    ? (a) < (min) - (b)                                  \
 184    : (max) - (b) < (a))
 185
 186 /* Return 1 if A - B would overflow in [MIN,MAX] arithmetic.
 187    See above for restrictions.  */
 188 #define INT_SUBTRACT_RANGE_OVERFLOW(a, b, min, max)     \
 189   ((b) < 0                                              \
 190    ? (max) + (b) < (a)                                  \
 191    : (a) < (min) + (b))
 192
 193 /* Return 1 if - A would overflow in [MIN,MAX] arithmetic.
 194    See above for restrictions.  */
 195 #define INT_NEGATE_RANGE_OVERFLOW(a, min, max)          \
 196   ((min) < 0                                            \
 197    ? (a) < - (max)                                      \
 198    : 0 < (a))
 199
 200 /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic.
 201    See above for restrictions.  Avoid && and || as they tickle
 202    bugs in Sun C 5.11 2010/08/13 and other compilers; see
 203    <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00401.html>.  */
 204 #define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max)     \
 205   ((b) < 0                                              \
 206    ? ((a) < 0                                           \
 207       ? (a) < (max) / (b)                               \
 208       : (b) == -1                                       \
 209       ? 0                                               \
 210       : (min) / (b) < (a))                              \
 211    : (b) == 0                                           \
 212    ? 0                                                  \
 213    : ((a) < 0                                           \
 214       ? (a) < (min) / (b)                               \
 215       : (max) / (b) < (a)))
 216
 217 /* Return 1 if A / B would overflow in [MIN,MAX] arithmetic.
 218    See above for restrictions.  Do not check for division by zero.  */
 219 #define INT_DIVIDE_RANGE_OVERFLOW(a, b, min, max)       \
 220   ((min) < 0 && (b) == -1 && (a) < - (max))
 221
 222 /* Return 1 if A % B would overflow in [MIN,MAX] arithmetic.
 223    See above for restrictions.  Do not check for division by zero.
 224    Mathematically, % should never overflow, but on x86-like hosts
 225    INT_MIN % -1 traps, and the C standard permits this, so treat this
 226    as an overflow too.  */
 227 #define INT_REMAINDER_RANGE_OVERFLOW(a, b, min, max)    \
 228   INT_DIVIDE_RANGE_OVERFLOW (a, b, min, max)
 229
 230 /* Return 1 if A << B would overflow in [MIN,MAX] arithmetic.
 231    See above for restrictions.  Here, MIN and MAX are for A only, and B need
 232    not be of the same type as the other arguments.  The C standard says that
 233    behavior is undefined for shifts unless 0 <= B < wordwidth, and that when
 234    A is negative then A << B has undefined behavior and A >> B has
 235    implementation-defined behavior, but do not check these other
 236    restrictions.  */
 237 #define INT_LEFT_SHIFT_RANGE_OVERFLOW(a, b, min, max)   \
 238   ((a) < 0                                              \
 239    ? (a) < (min) >> (b)                                 \
 240    : (max) >> (b) < (a))
 241
 242 /* True if __builtin_add_overflow (A, B, P) works when P is non-null.  */
 243 #define _GL_HAS_BUILTIN_OVERFLOW \
 244   (5 <= __GNUC__ || __has_builtin (__builtin_add_overflow))
 245
 246 /* True if __builtin_add_overflow_p (A, B, C) works.  */
 247 #define _GL_HAS_BUILTIN_OVERFLOW_P \
 248   (7 <= __GNUC__ || __has_builtin (__builtin_add_overflow_p))
 249
 250 /* The _GL*_OVERFLOW macros have the same restrictions as the
 251    *_RANGE_OVERFLOW macros, except that they do not assume that operands
 252    (e.g., A and B) have the same type as MIN and MAX.  Instead, they assume
 253    that the result (e.g., A + B) has that type.  */
 254 #if _GL_HAS_BUILTIN_OVERFLOW_P
 255 # define _GL_ADD_OVERFLOW(a, b, min, max)                               \
 256    __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0)
 257 # define _GL_SUBTRACT_OVERFLOW(a, b, min, max)                          \
 258    __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0)
 259 # define _GL_MULTIPLY_OVERFLOW(a, b, min, max)                          \
 260    __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0)
 261 #else
 262 # define _GL_ADD_OVERFLOW(a, b, min, max)                                \
 263    ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max)                  \
 264     : (a) < 0 ? (b) <= (a) + (b)                                         \
 265     : (b) < 0 ? (a) <= (a) + (b)                                         \
 266     : (a) + (b) < (b))
 267 # define _GL_SUBTRACT_OVERFLOW(a, b, min, max)                           \
 268    ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max)             \
 269     : (a) < 0 ? 1                                                        \
 270     : (b) < 0 ? (a) - (b) <= (a)                                         \
 271     : (a) < (b))
 272 # define _GL_MULTIPLY_OVERFLOW(a, b, min, max)                           \
 273    (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a))))       \
 274     || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max))
 275 #endif
 276 #define _GL_DIVIDE_OVERFLOW(a, b, min, max)                             \
 277   ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max)  \
 278    : (a) < 0 ? (b) <= (a) + (b) - 1                                     \
 279    : (b) < 0 && (a) + (b) <= (a))
 280 #define _GL_REMAINDER_OVERFLOW(a, b, min, max)                          \
 281   ((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max)  \
 282    : (a) < 0 ? (a) % (b) != ((max) - (b) + 1) % (b)                     \
 283    : (b) < 0 && ! _GL_UNSIGNED_NEG_MULTIPLE (a, b, max))
 284
 285 /* Return a nonzero value if A is a mathematical multiple of B, where
 286    A is unsigned, B is negative, and MAX is the maximum value of A's
 287    type.  A's type must be the same as (A % B)'s type.  Normally (A %
 288    -B == 0) suffices, but things get tricky if -B would overflow.  */
 289 #define _GL_UNSIGNED_NEG_MULTIPLE(a, b, max)                            \
 290   (((b) < -_GL_SIGNED_INT_MAXIMUM (b)                                   \
 291     ? (_GL_SIGNED_INT_MAXIMUM (b) == (max)                              \
 292        ? (a)                                                            \
 293        : (a) % (_GL_INT_CONVERT (a, _GL_SIGNED_INT_MAXIMUM (b)) + 1))   \
 294     : (a) % - (b))                                                      \
 295    == 0)
 296
 297 /* Check for integer overflow, and report low order bits of answer.
 298
 299    The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators
 300    might not yield numerically correct answers due to arithmetic overflow.
 301    The INT_<op>_WRAPV macros also store the low-order bits of the answer.
 302    These macros work correctly on all known practical hosts, and do not rely
 303    on undefined behavior due to signed arithmetic overflow.
 304
 305    Example usage, assuming A and B are long int:
 306
 307      if (INT_MULTIPLY_OVERFLOW (a, b))
 308        printf ("result would overflow\n");
 309      else
 310        printf ("result is %ld (no overflow)\n", a * b);
 311
 312    Example usage with WRAPV flavor:
 313
 314      long int result;
 315      bool overflow = INT_MULTIPLY_WRAPV (a, b, &result);
 316      printf ("result is %ld (%s)\n", result,
 317              overflow ? "after overflow" : "no overflow");
 318
 319    Restrictions on these macros:
 320
 321    These macros do not check for all possible numerical problems or
 322    undefined or unspecified behavior: they do not check for division
 323    by zero, for bad shift counts, or for shifting negative numbers.
 324
 325    These macros may evaluate their arguments zero or multiple times, so the
 326    arguments should not have side effects.
 327
 328    The WRAPV macros are not constant expressions.  They support only
 329    +, binary -, and *.  The result type must be signed.
 330
 331    These macros are tuned for their last argument being a constant.
 332
 333    Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B,
 334    A % B, and A << B would overflow, respectively.  */
 335
 336 #define INT_ADD_OVERFLOW(a, b) \
 337   _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW)
 338 #define INT_SUBTRACT_OVERFLOW(a, b) \
 339   _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW)
 340 #if _GL_HAS_BUILTIN_OVERFLOW_P
 341 # define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a)
 342 #else
 343 # define INT_NEGATE_OVERFLOW(a) \
 344    INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
 345 #endif
 346 #define INT_MULTIPLY_OVERFLOW(a, b) \
 347   _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW)
 348 #define INT_DIVIDE_OVERFLOW(a, b) \
 349   _GL_BINARY_OP_OVERFLOW (a, b, _GL_DIVIDE_OVERFLOW)
 350 #define INT_REMAINDER_OVERFLOW(a, b) \
 351   _GL_BINARY_OP_OVERFLOW (a, b, _GL_REMAINDER_OVERFLOW)
 352 #define INT_LEFT_SHIFT_OVERFLOW(a, b) \
 353   INT_LEFT_SHIFT_RANGE_OVERFLOW (a, b, \
 354                                  _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
 355
 356 /* Return 1 if the expression A <op> B would overflow,
 357    where OP_RESULT_OVERFLOW (A, B, MIN, MAX) does the actual test,
 358    assuming MIN and MAX are the minimum and maximum for the result type.
 359    Arguments should be free of side effects.  */
 360 #define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow)        \
 361   op_result_overflow (a, b,                                     \
 362                       _GL_INT_MINIMUM (0 * (b) + (a)),          \
 363                       _GL_INT_MAXIMUM (0 * (b) + (a)))
 364
 365 /* Store the low-order bits of A + B, A - B, A * B, respectively, into *R.
 366    Return 1 if the result overflows.  See above for restrictions.  */
 367 #define INT_ADD_WRAPV(a, b, r) \
 368   _GL_INT_OP_WRAPV (a, b, r, +, __builtin_add_overflow, INT_ADD_OVERFLOW)
 369 #define INT_SUBTRACT_WRAPV(a, b, r) \
 370   _GL_INT_OP_WRAPV (a, b, r, -, __builtin_sub_overflow, INT_SUBTRACT_OVERFLOW)
 371 #define INT_MULTIPLY_WRAPV(a, b, r) \
 372   _GL_INT_OP_WRAPV (a, b, r, *, __builtin_mul_overflow, INT_MULTIPLY_OVERFLOW)
 373
 374 /* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390.  See:
 375    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193
 376    https://llvm.org/bugs/show_bug.cgi?id=25390
 377    For now, assume all versions of GCC-like compilers generate bogus
 378    warnings for _Generic.  This matters only for older compilers that
 379    lack __builtin_add_overflow.  */
 380 #if __GNUC__
 381 # define _GL__GENERIC_BOGUS 1
 382 #else
 383 # define _GL__GENERIC_BOGUS 0
 384 #endif
 385
 386 /* Store the low-order bits of A <op> B into *R, where OP specifies
 387    the operation.  BUILTIN is the builtin operation, and OVERFLOW the
 388    overflow predicate.  Return 1 if the result overflows.  See above
 389    for restrictions.  */
 390 #if _GL_HAS_BUILTIN_OVERFLOW
 391 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) builtin (a, b, r)
 392 #elif 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS
 393 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
 394    (_Generic \
 395     (*(r), \
 396      signed char: \
 397        _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned char, \
 398                         signed char, SCHAR_MIN, SCHAR_MAX), \
 399      short int: \
 400        _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned short int, \
 401                         short int, SHRT_MIN, SHRT_MAX), \
 402      int: \
 403        _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
 404                         int, INT_MIN, INT_MAX), \
 405      long int: \
 406        _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
 407                         long int, LONG_MIN, LONG_MAX), \
 408      long long int: \
 409        _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
 410                         long long int, LLONG_MIN, LLONG_MAX)))
 411 #else
 412 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
 413    (sizeof *(r) == sizeof (signed char) \
 414     ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned char, \
 415                        signed char, SCHAR_MIN, SCHAR_MAX) \
 416     : sizeof *(r) == sizeof (short int) \
 417     ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned short int, \
 418                        short int, SHRT_MIN, SHRT_MAX) \
 419     : sizeof *(r) == sizeof (int) \
 420     ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
 421                        int, INT_MIN, INT_MAX) \
 422     : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
 423 # ifdef LLONG_MAX
 424 #  define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
 425     (sizeof *(r) == sizeof (long int) \
 426      ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
 427                         long int, LONG_MIN, LONG_MAX) \
 428      : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
 429                         long long int, LLONG_MIN, LLONG_MAX))
 430 # else
 431 #  define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
 432     _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
 433                      long int, LONG_MIN, LONG_MAX)
 434 # endif
 435 #endif
 436
 437 /* Store the low-order bits of A <op> B into *R, where the operation
 438    is given by OP.  Use the unsigned type UT for calculation to avoid
 439    overflow problems.  *R's type is T, with extremal values TMIN and
 440    TMAX.  T must be a signed integer type.  Return 1 if the result
 441    overflows.  */
 442 #define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \
 443   (sizeof ((a) op (b)) < sizeof (t) \
 444    ? _GL_INT_OP_CALC1 ((t) (a), (t) (b), r, op, overflow, ut, t, tmin, tmax) \
 445    : _GL_INT_OP_CALC1 (a, b, r, op, overflow, ut, t, tmin, tmax))
 446 #define _GL_INT_OP_CALC1(a, b, r, op, overflow, ut, t, tmin, tmax) \
 447   ((overflow (a, b) \
 448     || (EXPR_SIGNED ((a) op (b)) && ((a) op (b)) < (tmin)) \
 449     || (tmax) < ((a) op (b))) \
 450    ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t, tmin, tmax), 1) \
 451    : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t, tmin, tmax), 0))
 452
 453 /* Return A <op> B, where the operation is given by OP.  Use the
 454    unsigned type UT for calculation to avoid overflow problems.
 455    Convert the result to type T without overflow by subtracting TMIN
 456    from large values before converting, and adding it afterwards.
 457    Compilers can optimize all the operations except OP.  */
 458 #define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t, tmin, tmax) \
 459   (((ut) (a) op (ut) (b)) <= (tmax) \
 460    ? (t) ((ut) (a) op (ut) (b)) \
 461    : ((t) (((ut) (a) op (ut) (b)) - (tmin)) + (tmin)))
 462
 463 #endif /* _GL_INTPROPS_H */