/* intprops.h -- properties of integer types
- Copyright (C) 2001-2005, 2009-2013 Free Software Foundation, Inc.
+ Copyright (C) 2001-2018 Free Software Foundation, Inc.
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
+ This program is free software: you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published
+ by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert. */
#include <limits.h>
-/* Return an integer value, converted to the same type as the integer
- expression E after integer type promotion. V is the unconverted value. */
-#define _GL_INT_CONVERT(e, v) (0 * (e) + (v))
+/* Return a value with the common real type of E and V and the value of V.
+ Do not evaluate E. */
+#define _GL_INT_CONVERT(e, v) ((1 ? 0 : (e)) + (v))
/* Act like _GL_INT_CONVERT (E, -V) but work around a bug in IRIX 6.5 cc; see
- <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00406.html>. */
-#define _GL_INT_NEGATE_CONVERT(e, v) (0 * (e) - (v))
+ <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00406.html>. */
+#define _GL_INT_NEGATE_CONVERT(e, v) ((1 ? 0 : (e)) - (v))
/* The extra casts in the following macros work around compiler bugs,
e.g., in Cray C 5.0.3.0. */
an integer. */
#define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
-/* True if negative values of the signed integer type T use two's
- complement, ones' complement, or signed magnitude representation,
- respectively. Much GNU code assumes two's complement, but some
- people like to be portable to all possible C hosts. */
-#define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
-#define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)
-#define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)
-
-/* True if the signed integer expression E uses two's complement. */
-#define _GL_INT_TWOS_COMPLEMENT(e) (~ _GL_INT_CONVERT (e, 0) == -1)
-
-/* True if the arithmetic type T is signed. */
+/* True if the real type T is signed. */
#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
-/* Return 1 if the integer expression E, after integer promotion, has
- a signed type. */
-#define _GL_INT_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
+/* Return 1 if the real expression E, after promotion, has a
+ signed or floating type. Do not evaluate E. */
+#define EXPR_SIGNED(e) (_GL_INT_NEGATE_CONVERT (e, 1) < 0)
-/* Minimum and maximum values for integer types and expressions. These
- macros have undefined behavior if T is signed and has padding bits.
- If this is a problem for you, please let us know how to fix it for
- your host. */
+/* Minimum and maximum values for integer types and expressions. */
+
+/* The width in bits of the integer type or expression T.
+ Do not evaluate T.
+ Padding bits are not supported; this is checked at compile-time below. */
+#define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT)
/* The maximum and minimum values for the integer type T. */
-#define TYPE_MINIMUM(t) \
- ((t) (! TYPE_SIGNED (t) \
- ? (t) 0 \
- : TYPE_SIGNED_MAGNITUDE (t) \
- ? ~ (t) 0 \
- : ~ TYPE_MAXIMUM (t)))
+#define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t))
#define TYPE_MAXIMUM(t) \
((t) (! TYPE_SIGNED (t) \
? (t) -1 \
- : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))
+ : ((((t) 1 << (TYPE_WIDTH (t) - 2)) - 1) * 2 + 1)))
/* The maximum and minimum values for the type of the expression E,
- after integer promotion. E should not have side effects. */
+ after integer promotion. E is not evaluated. */
#define _GL_INT_MINIMUM(e) \
- (_GL_INT_SIGNED (e) \
- ? - _GL_INT_TWOS_COMPLEMENT (e) - _GL_SIGNED_INT_MAXIMUM (e) \
+ (EXPR_SIGNED (e) \
+ ? ~ _GL_SIGNED_INT_MAXIMUM (e) \
: _GL_INT_CONVERT (e, 0))
#define _GL_INT_MAXIMUM(e) \
- (_GL_INT_SIGNED (e) \
+ (EXPR_SIGNED (e) \
? _GL_SIGNED_INT_MAXIMUM (e) \
: _GL_INT_NEGATE_CONVERT (e, 1))
#define _GL_SIGNED_INT_MAXIMUM(e) \
- (((_GL_INT_CONVERT (e, 1) << (sizeof ((e) + 0) * CHAR_BIT - 2)) - 1) * 2 + 1)
+ (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH ((e) + 0) - 2)) - 1) * 2 + 1)
+/* Work around OpenVMS incompatibility with C99. */
+#if !defined LLONG_MAX && defined __INT64_MAX
+# define LLONG_MAX __INT64_MAX
+# define LLONG_MIN __INT64_MIN
+#endif
+
+/* This include file assumes that signed types are two's complement without
+ padding bits; the above macros have undefined behavior otherwise.
+ If this is a problem for you, please let us know how to fix it for your host.
+ This assumption is tested by the intprops-tests module. */
-/* Return 1 if the __typeof__ keyword works. This could be done by
+/* Does the __typeof__ keyword work? This could be done by
'configure', but for now it's easier to do it by hand. */
-#if 2 <= __GNUC__ || defined __IBM__TYPEOF__ || 0x5110 <= __SUNPRO_C
+#if (2 <= __GNUC__ \
+ || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \
+ || (0x5110 <= __SUNPRO_C && !__STDC__))
# define _GL_HAVE___TYPEOF__ 1
#else
# define _GL_HAVE___TYPEOF__ 0
signed, this macro may overestimate the true bound by one byte when
applied to unsigned types of size 2, 4, 16, ... bytes. */
#define INT_STRLEN_BOUND(t) \
- (INT_BITS_STRLEN_BOUND (sizeof (t) * CHAR_BIT \
- - _GL_SIGNED_TYPE_OR_EXPR (t)) \
+ (INT_BITS_STRLEN_BOUND (TYPE_WIDTH (t) - _GL_SIGNED_TYPE_OR_EXPR (t)) \
+ _GL_SIGNED_TYPE_OR_EXPR (t))
/* Bound on buffer size needed to represent an integer type or expression T,
/* Return 1 if A * B would overflow in [MIN,MAX] arithmetic.
See above for restrictions. Avoid && and || as they tickle
bugs in Sun C 5.11 2010/08/13 and other compilers; see
- <http://lists.gnu.org/archive/html/bug-gnulib/2011-05/msg00401.html>. */
+ <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00401.html>. */
#define INT_MULTIPLY_RANGE_OVERFLOW(a, b, min, max) \
((b) < 0 \
? ((a) < 0 \
? (a) < (min) >> (b) \
: (max) >> (b) < (a))
+/* True if __builtin_add_overflow (A, B, P) works when P is non-null. */
+#if 5 <= __GNUC__ && !defined __ICC
+# define _GL_HAS_BUILTIN_OVERFLOW 1
+#else
+# define _GL_HAS_BUILTIN_OVERFLOW 0
+#endif
+
+/* True if __builtin_add_overflow_p (A, B, C) works. */
+#define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__)
/* The _GL*_OVERFLOW macros have the same restrictions as the
*_RANGE_OVERFLOW macros, except that they do not assume that operands
(e.g., A and B) have the same type as MIN and MAX. Instead, they assume
that the result (e.g., A + B) has that type. */
-#define _GL_ADD_OVERFLOW(a, b, min, max) \
- ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \
- : (a) < 0 ? (b) <= (a) + (b) \
- : (b) < 0 ? (a) <= (a) + (b) \
- : (a) + (b) < (b))
-#define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
- ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \
- : (a) < 0 ? 1 \
- : (b) < 0 ? (a) - (b) <= (a) \
- : (a) < (b))
-#define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
- (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \
- || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max))
+#if _GL_HAS_BUILTIN_OVERFLOW_P
+# define _GL_ADD_OVERFLOW(a, b, min, max) \
+ __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0)
+# define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
+ __builtin_sub_overflow_p (a, b, (__typeof__ ((a) - (b))) 0)
+# define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
+ __builtin_mul_overflow_p (a, b, (__typeof__ ((a) * (b))) 0)
+#else
+# define _GL_ADD_OVERFLOW(a, b, min, max) \
+ ((min) < 0 ? INT_ADD_RANGE_OVERFLOW (a, b, min, max) \
+ : (a) < 0 ? (b) <= (a) + (b) \
+ : (b) < 0 ? (a) <= (a) + (b) \
+ : (a) + (b) < (b))
+# define _GL_SUBTRACT_OVERFLOW(a, b, min, max) \
+ ((min) < 0 ? INT_SUBTRACT_RANGE_OVERFLOW (a, b, min, max) \
+ : (a) < 0 ? 1 \
+ : (b) < 0 ? (a) - (b) <= (a) \
+ : (a) < (b))
+# define _GL_MULTIPLY_OVERFLOW(a, b, min, max) \
+ (((min) == 0 && (((a) < 0 && 0 < (b)) || ((b) < 0 && 0 < (a)))) \
+ || INT_MULTIPLY_RANGE_OVERFLOW (a, b, min, max))
+#endif
#define _GL_DIVIDE_OVERFLOW(a, b, min, max) \
((min) < 0 ? (b) == _GL_INT_NEGATE_CONVERT (min, 1) && (a) < - (max) \
: (a) < 0 ? (b) <= (a) + (b) - 1 \
: (a) % - (b)) \
== 0)
-
-/* Integer overflow checks.
+/* Check for integer overflow, and report low order bits of answer.
The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators
might not yield numerically correct answers due to arithmetic overflow.
- They work correctly on all known practical hosts, and do not rely
+ The INT_<op>_WRAPV macros also store the low-order bits of the answer.
+ These macros work correctly on all known practical hosts, and do not rely
on undefined behavior due to signed arithmetic overflow.
- Example usage:
+ Example usage, assuming A and B are long int:
- long int i = ...;
- long int j = ...;
- if (INT_MULTIPLY_OVERFLOW (i, j))
- printf ("multiply would overflow");
+ if (INT_MULTIPLY_OVERFLOW (a, b))
+ printf ("result would overflow\n");
else
- printf ("product is %ld", i * j);
+ printf ("result is %ld (no overflow)\n", a * b);
+
+ Example usage with WRAPV flavor:
+
+ long int result;
+ bool overflow = INT_MULTIPLY_WRAPV (a, b, &result);
+ printf ("result is %ld (%s)\n", result,
+ overflow ? "after overflow" : "no overflow");
+
+ Restrictions on these macros:
These macros do not check for all possible numerical problems or
undefined or unspecified behavior: they do not check for division
These macros may evaluate their arguments zero or multiple times, so the
arguments should not have side effects.
+ The WRAPV macros are not constant expressions. They support only
+ +, binary -, and *. The result type must be signed.
+
These macros are tuned for their last argument being a constant.
Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B,
_GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW)
#define INT_SUBTRACT_OVERFLOW(a, b) \
_GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW)
-#define INT_NEGATE_OVERFLOW(a) \
- INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
+#if _GL_HAS_BUILTIN_OVERFLOW_P
+# define INT_NEGATE_OVERFLOW(a) INT_SUBTRACT_OVERFLOW (0, a)
+#else
+# define INT_NEGATE_OVERFLOW(a) \
+ INT_NEGATE_RANGE_OVERFLOW (a, _GL_INT_MINIMUM (a), _GL_INT_MAXIMUM (a))
+#endif
#define INT_MULTIPLY_OVERFLOW(a, b) \
_GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW)
#define INT_DIVIDE_OVERFLOW(a, b) \
Arguments should be free of side effects. */
#define _GL_BINARY_OP_OVERFLOW(a, b, op_result_overflow) \
op_result_overflow (a, b, \
- _GL_INT_MINIMUM (0 * (b) + (a)), \
- _GL_INT_MAXIMUM (0 * (b) + (a)))
+ _GL_INT_MINIMUM (_GL_INT_CONVERT (a, b)), \
+ _GL_INT_MAXIMUM (_GL_INT_CONVERT (a, b)))
+
+/* Store the low-order bits of A + B, A - B, A * B, respectively, into *R.
+ Return 1 if the result overflows. See above for restrictions. */
+#define INT_ADD_WRAPV(a, b, r) \
+ _GL_INT_OP_WRAPV (a, b, r, +, __builtin_add_overflow, INT_ADD_OVERFLOW)
+#define INT_SUBTRACT_WRAPV(a, b, r) \
+ _GL_INT_OP_WRAPV (a, b, r, -, __builtin_sub_overflow, INT_SUBTRACT_OVERFLOW)
+#define INT_MULTIPLY_WRAPV(a, b, r) \
+ _GL_INT_OP_WRAPV (a, b, r, *, __builtin_mul_overflow, INT_MULTIPLY_OVERFLOW)
+
+/* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390. See:
+ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193
+ https://llvm.org/bugs/show_bug.cgi?id=25390
+ For now, assume all versions of GCC-like compilers generate bogus
+ warnings for _Generic. This matters only for older compilers that
+ lack __builtin_add_overflow. */
+#if __GNUC__
+# define _GL__GENERIC_BOGUS 1
+#else
+# define _GL__GENERIC_BOGUS 0
+#endif
+
+/* Store the low-order bits of A <op> B into *R, where OP specifies
+ the operation. BUILTIN is the builtin operation, and OVERFLOW the
+ overflow predicate. Return 1 if the result overflows. See above
+ for restrictions. */
+#if _GL_HAS_BUILTIN_OVERFLOW
+# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) builtin (a, b, r)
+#elif 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS
+# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
+ (_Generic \
+ (*(r), \
+ signed char: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ signed char, SCHAR_MIN, SCHAR_MAX), \
+ short int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ short int, SHRT_MIN, SHRT_MAX), \
+ int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ int, INT_MIN, INT_MAX), \
+ long int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
+ long int, LONG_MIN, LONG_MAX), \
+ long long int: \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
+ long long int, LLONG_MIN, LLONG_MAX)))
+#else
+# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
+ (sizeof *(r) == sizeof (signed char) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ signed char, SCHAR_MIN, SCHAR_MAX) \
+ : sizeof *(r) == sizeof (short int) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ short int, SHRT_MIN, SHRT_MAX) \
+ : sizeof *(r) == sizeof (int) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
+ int, INT_MIN, INT_MAX) \
+ : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
+# ifdef LLONG_MAX
+# define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
+ (sizeof *(r) == sizeof (long int) \
+ ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
+ long int, LONG_MIN, LONG_MAX) \
+ : _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long long int, \
+ long long int, LLONG_MIN, LLONG_MAX))
+# else
+# define _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow) \
+ _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
+ long int, LONG_MIN, LONG_MAX)
+# endif
+#endif
+
+/* Store the low-order bits of A <op> B into *R, where the operation
+ is given by OP. Use the unsigned type UT for calculation to avoid
+ overflow problems. *R's type is T, with extrema TMIN and TMAX.
+ T must be a signed integer type. Return 1 if the result overflows. */
+#define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \
+ (sizeof ((a) op (b)) < sizeof (t) \
+ ? _GL_INT_OP_CALC1 ((t) (a), (t) (b), r, op, overflow, ut, t, tmin, tmax) \
+ : _GL_INT_OP_CALC1 (a, b, r, op, overflow, ut, t, tmin, tmax))
+#define _GL_INT_OP_CALC1(a, b, r, op, overflow, ut, t, tmin, tmax) \
+ ((overflow (a, b) \
+ || (EXPR_SIGNED ((a) op (b)) && ((a) op (b)) < (tmin)) \
+ || (tmax) < ((a) op (b))) \
+ ? (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 1) \
+ : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a, b, op, ut, t), 0))
+
+/* Return the low-order bits of A <op> B, where the operation is given
+ by OP. Use the unsigned type UT for calculation to avoid undefined
+ behavior on signed integer overflow, and convert the result to type T.
+ UT is at least as wide as T and is no narrower than unsigned int,
+ T is two's complement, and there is no padding or trap representations.
+ Assume that converting UT to T yields the low-order bits, as is
+ done in all known two's-complement C compilers. E.g., see:
+ https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html
+
+ According to the C standard, converting UT to T yields an
+ implementation-defined result or signal for values outside T's
+ range. However, code that works around this theoretical problem
+ runs afoul of a compiler bug in Oracle Studio 12.3 x86. See:
+ https://lists.gnu.org/r/bug-gnulib/2017-04/msg00049.html
+ As the compiler bug is real, don't try to work around the
+ theoretical problem. */
+
+#define _GL_INT_OP_WRAPV_VIA_UNSIGNED(a, b, op, ut, t) \
+ ((t) ((ut) (a) op (ut) (b)))
#endif /* _GL_INTPROPS_H */
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