diff options
Diffstat (limited to 'lib/gl/intprops.h')
| -rw-r--r-- | lib/gl/intprops.h | 262 |
1 files changed, 71 insertions, 191 deletions
diff --git a/lib/gl/intprops.h b/lib/gl/intprops.h index 140f6d2..f182ddc 100644 --- a/lib/gl/intprops.h +++ b/lib/gl/intprops.h @@ -1,6 +1,6 @@ /* intprops.h -- properties of integer types - Copyright (C) 2001-2019 Free Software Foundation, Inc. + Copyright (C) 2001-2022 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published @@ -15,20 +15,10 @@ You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <https://www.gnu.org/licenses/>. */ -/* Written by Paul Eggert. */ - #ifndef _GL_INTPROPS_H #define _GL_INTPROPS_H -#include <limits.h> - -/* 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 - <https://lists.gnu.org/r/bug-gnulib/2011-05/msg00406.html>. */ -#define _GL_INT_NEGATE_CONVERT(e, v) ((1 ? 0 : (e)) - (v)) +#include "intprops-internal.h" /* The extra casts in the following macros work around compiler bugs, e.g., in Cray C 5.0.3.0. */ @@ -38,19 +28,19 @@ #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) /* True if the real type T is signed. */ -#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) +#define TYPE_SIGNED(t) _GL_TYPE_SIGNED (t) /* 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) +#define EXPR_SIGNED(e) _GL_EXPR_SIGNED (e) /* Minimum and maximum values for integer types and expressions. */ /* The width in bits of the integer type or expression T. - Do not evaluate T. + Do not evaluate T. T must not be a bit-field expression. Padding bits are not supported; this is checked at compile-time below. */ -#define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT) +#define TYPE_WIDTH(t) _GL_TYPE_WIDTH (t) /* The maximum and minimum values for the integer type T. */ #define TYPE_MINIMUM(t) ((t) ~ TYPE_MAXIMUM (t)) @@ -59,78 +49,37 @@ ? (t) -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 is not evaluated. */ -#define _GL_INT_MINIMUM(e) \ - (EXPR_SIGNED (e) \ - ? ~ _GL_SIGNED_INT_MAXIMUM (e) \ - : _GL_INT_CONVERT (e, 0)) -#define _GL_INT_MAXIMUM(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) << (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. */ - -/* 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__ \ - || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \ - || (0x5110 <= __SUNPRO_C && !__STDC__)) -# define _GL_HAVE___TYPEOF__ 1 -#else -# define _GL_HAVE___TYPEOF__ 0 -#endif - -/* Return 1 if the integer type or expression T might be signed. Return 0 - if it is definitely unsigned. This macro does not evaluate its argument, - and expands to an integer constant expression. */ -#if _GL_HAVE___TYPEOF__ -# define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t)) -#else -# define _GL_SIGNED_TYPE_OR_EXPR(t) 1 -#endif - /* Bound on length of the string representing an unsigned integer value representable in B bits. log10 (2.0) < 146/485. The smallest value of B where this bound is not tight is 2621. */ #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485) /* Bound on length of the string representing an integer type or expression T. + T must not be a bit-field expression. + Subtract 1 for the sign bit if T is signed, and then add 1 more for a minus sign if needed. - Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 0 when its argument is - signed, this macro may overestimate the true bound by one byte when + Because _GL_SIGNED_TYPE_OR_EXPR sometimes returns 1 when its argument is + unsigned, 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 (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, - including the terminating null. */ + including the terminating null. T must not be a bit-field expression. */ #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1) /* Range overflow checks. The INT_<op>_RANGE_OVERFLOW macros return 1 if the corresponding C - operators might not yield numerically correct answers due to - arithmetic overflow. They do not rely on undefined or - implementation-defined behavior. Their implementations are simple - and straightforward, but they are a bit harder to use than the - INT_<op>_OVERFLOW macros described below. + operators overflow arithmetically when given the same arguments. + These macros do not rely on undefined or implementation-defined behavior. + Although their implementations are simple and straightforward, + they are harder to use and may be less efficient than the + INT_<op>_WRAPV, INT_<op>_OK, and INT_<op>_OVERFLOW macros described below. Example usage: @@ -154,6 +103,9 @@ must have minimum value MIN and maximum MAX. Unsigned types should use a zero MIN of the proper type. + Because all arguments are subject to integer promotions, these + macros typically do not work on types narrower than 'int'. + These macros are tuned for constant MIN and MAX. For commutative operations such as A + B, they are also tuned for constant B. */ @@ -174,9 +126,7 @@ /* Return 1 if - A would overflow in [MIN,MAX] arithmetic. See above for restrictions. */ #define INT_NEGATE_RANGE_OVERFLOW(a, min, max) \ - ((min) < 0 \ - ? (a) < - (max) \ - : 0 < (a)) + _GL_INT_NEGATE_RANGE_OVERFLOW (a, min, max) /* Return 1 if A * B would overflow in [MIN,MAX] arithmetic. See above for restrictions. Avoid && and || as they tickle @@ -220,16 +170,6 @@ ? (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 @@ -281,7 +221,9 @@ The INT_<op>_OVERFLOW macros return 1 if the corresponding C operators might not yield numerically correct answers due to arithmetic overflow. - The INT_<op>_WRAPV macros also store the low-order bits of the answer. + The INT_<op>_WRAPV macros compute the low-order bits of the sum, + difference, and product of two C integers, and return 1 if these + low-order bits are not numerically correct. These macros work correctly on all known practical hosts, and do not rely on undefined behavior due to signed arithmetic overflow. @@ -309,9 +251,22 @@ arguments should not have side effects. The WRAPV macros are not constant expressions. They support only - +, binary -, and *. The result type must be signed. + +, binary -, and *. + + Because the WRAPV macros convert the result, they report overflow + in different circumstances than the OVERFLOW macros do. For + example, in the typical case with 16-bit 'short' and 32-bit 'int', + if A, B and *R are all of type 'short' then INT_ADD_OVERFLOW (A, B) + returns false because the addition cannot overflow after A and B + are converted to 'int', whereas INT_ADD_WRAPV (A, B, R) returns + true or false depending on whether the sum fits into 'short'. - These macros are tuned for their last argument being a constant. + These macros are tuned for their last input argument being a constant. + + A, B, and *R should be integers; they need not be the same type, + and they need not be all signed or all unsigned. + However, none of the integer types should be bit-precise, + and *R's type should not be char, bool, or an enumeration type. Return 1 if the integer expressions A * B, A - B, -A, A * B, A / B, A % B, and A << B would overflow, respectively. */ @@ -320,12 +275,7 @@ _GL_BINARY_OP_OVERFLOW (a, b, _GL_ADD_OVERFLOW) #define INT_SUBTRACT_OVERFLOW(a, b) \ _GL_BINARY_OP_OVERFLOW (a, b, _GL_SUBTRACT_OVERFLOW) -#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_NEGATE_OVERFLOW(a) _GL_INT_NEGATE_OVERFLOW (a) #define INT_MULTIPLY_OVERFLOW(a, b) \ _GL_BINARY_OP_OVERFLOW (a, b, _GL_MULTIPLY_OVERFLOW) #define INT_DIVIDE_OVERFLOW(a, b) \ @@ -347,109 +297,39 @@ /* 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 +#define INT_ADD_WRAPV(a, b, r) _GL_INT_ADD_WRAPV (a, b, r) +#define INT_SUBTRACT_WRAPV(a, b, r) _GL_INT_SUBTRACT_WRAPV (a, b, r) +#define INT_MULTIPLY_WRAPV(a, b, r) _GL_INT_MULTIPLY_WRAPV (a, b, r) -/* 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 +/* The following macros compute A + B, A - B, and A * B, respectively. + If no overflow occurs, they set *R to the result and return 1; + otherwise, they return 0 and may modify *R. + + Example usage: + + long int result; + if (INT_ADD_OK (a, b, &result)) + printf ("result is %ld\n", result); + else + printf ("overflow\n"); + + A, B, and *R should be integers; they need not be the same type, + and they need not be all signed or all unsigned. + However, none of the integer types should be bit-precise, + and *R's type should not be char, bool, or an enumeration type. + + These macros work correctly on all known practical hosts, and do not rely + on undefined behavior due to signed arithmetic overflow. + + These macros are not constant expressions. + + These macros may evaluate their arguments zero or multiple times, so the + arguments should not have side effects. + + These macros are tuned for B being a constant. */ -/* 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))) +#define INT_ADD_OK(a, b, r) (! INT_ADD_WRAPV (a, b, r)) +#define INT_SUBTRACT_OK(a, b, r) (! INT_SUBTRACT_WRAPV (a, b, r)) +#define INT_MULTIPLY_OK(a, b, r) (! INT_MULTIPLY_WRAPV (a, b, r)) #endif /* _GL_INTPROPS_H */ |