kc3-lang/libxkbcommon/src/utils-checked-arithmetic.h
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Hash : dc63e5f8
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Date : 2025-07-07T12:28:24
Ensure config.h is always included first While `config.h` may not be necessary in every file, it ensures consistency and makes code refactoring safer.
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src/utils-checked-arithmetic.h
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/* * SPDX-License-Identifier: ISC * * Copyright 2023 Justine Alexandra Roberts Tunney * * Permission to use, copy, modify, and/or distribute this software for * any purpose with or without fee is hereby granted, provided that the * above copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR * PERFORMANCE OF THIS SOFTWARE. */ /** * @fileoverview C23 Checked Arithmetic * * This header defines three type generic functions: * * - `bool ckd_add(res, a, b)` * - `bool ckd_sub(res, a, b)` * - `bool ckd_mul(res, a, b)` * * Which allow integer arithmetic errors to be detected. There are many * kinds of integer errors, e.g. overflow, truncation, etc. These funcs * catch them all. Here's an example of how it works: * * uint32_t c; * int32_t a = 0x7fffffff; * int32_t b = 2; * assert(!ckd_add(&c, a, b)); * assert(c == 0x80000001u); * * Experienced C / C++ users should find this example counter-intuitive * because the expression `0x7fffffff + 2` not only overflows it's also * undefined behavior. However here we see it's specified, and does not * result in an error. That's because C23 checked arithmetic is not the * arithmetic you're used to. The new standard changes the mathematics. * * C23 checked arithmetic is defined as performing the arithmetic using * infinite precision and then checking if the resulting value will fit * in the output type. Our example above did not result in an error due * to `0x80000001` being a legal value for `uint32_t`. * * This implementation will use the GNU compiler builtins, when they're * available, only if you don't use build flags like `-std=c11` because * they define `__STRICT_ANSI__` and GCC extensions aren't really ANSI. * Instead, you'll get a pretty good pure C11 and C++11 implementation. * * @see https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf * @version 1.0 (2024-12-07) */ #pragma once #include "config.h" #ifdef __has_include #define __ckd_has_include(x) __has_include(x) #else #define __ckd_has_include(x) 0 #endif #if __ckd_has_include(<stdckdint.h>) #include <stdckdint.h> #else #define __STDC_VERSION_STDCKDINT_H__ 202311L #if (!defined(__STRICT_ANSI__) && defined(__SIZEOF_INT128__)) #define __ckd_have_int128 #define __ckd_intmax __int128 #elif (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) #define __ckd_intmax long long #else #define __ckd_intmax long #endif typedef signed __ckd_intmax __ckd_intmax_t; typedef unsigned __ckd_intmax __ckd_uintmax_t; #ifdef __has_builtin #define __ckd_has_builtin(x) __has_builtin(x) #else #define __ckd_has_builtin(x) 0 #endif #if (!defined(__STRICT_ANSI__) && \ ((defined(__GNUC__) && __GNUC__ >= 5 && !defined(__ICC)) || \ (__ckd_has_builtin(__builtin_add_overflow) && \ __ckd_has_builtin(__builtin_sub_overflow) && \ __ckd_has_builtin(__builtin_mul_overflow)))) #define ckd_add(res, x, y) __builtin_add_overflow((x), (y), (res)) #define ckd_sub(res, x, y) __builtin_sub_overflow((x), (y), (res)) #define ckd_mul(res, x, y) __builtin_mul_overflow((x), (y), (res)) #elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L #define ckd_add(res, a, b) __ckd_expr(add, (res), (a), (b)) #define ckd_sub(res, a, b) __ckd_expr(sub, (res), (a), (b)) #define ckd_mul(res, a, b) __ckd_expr(mul, (res), (a), (b)) #if defined(__GNUC__) || defined(__llvm__) #define __ckd_inline \ extern __inline __attribute__((__gnu_inline__, \ __always_inline__, \ __artificial__)) #else #define __ckd_inline static inline #endif #ifdef __ckd_have_int128 #define __ckd_generic_int128(x, y) , signed __int128: x, unsigned __int128: y #else #define __ckd_generic_int128(x, y) #endif #define __ckd_sign(T) \ ((T)1 << (sizeof(T) * 8 - 1)) #define __ckd_is_signed(x) \ _Generic(x, \ signed char: 1, \ unsigned char: 0, \ signed short: 1, \ unsigned short: 0, \ signed int: 1, \ unsigned int: 0, \ signed long: 1, \ unsigned long: 0, \ signed long long: 1, \ unsigned long long: 0 \ __ckd_generic_int128(1, 0)) #define __ckd_expr(op, res, a, b) \ (_Generic(*res, \ signed char: __ckd_##op##_schar, \ unsigned char: __ckd_##op##_uchar, \ signed short: __ckd_##op##_sshort, \ unsigned short: __ckd_##op##_ushort, \ signed int: __ckd_##op##_sint, \ unsigned int: __ckd_##op##_uint, \ signed long: __ckd_##op##_slong, \ unsigned long: __ckd_##op##_ulong, \ signed long long: __ckd_##op##_slonger, \ unsigned long long: __ckd_##op##_ulonger \ __ckd_generic_int128( \ __ckd_##op##_sint128, \ __ckd_##op##_uint128))( \ res, a, b, \ __ckd_is_signed(a), \ __ckd_is_signed(b))) #define __ckd_declare_add(S, T) \ __ckd_inline char S(void *__res, \ __ckd_uintmax_t __x, \ __ckd_uintmax_t __y, \ char __a_signed, \ char __b_signed) { \ __ckd_uintmax_t __z = __x + __y; \ *(T *)__res = (T)__z; \ char __truncated = 0; \ if (sizeof(T) < sizeof(__ckd_intmax_t)) { \ __truncated = __z != (__ckd_uintmax_t)(T)__z; \ } \ switch (__ckd_is_signed((T)0) << 2 | \ __a_signed << 1 | __b_signed) { \ case 0: /* u = u + u */ \ return __truncated | (__z < __x); \ case 1: /* u = u + s */ \ __y ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | \ ((__ckd_intmax_t)((__z ^ __x) & \ (__z ^ __y)) < 0); \ case 2: /* u = s + u */ \ __x ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | \ ((__ckd_intmax_t)((__z ^ __x) & \ (__z ^ __y)) < 0); \ case 3: /* u = s + s */ \ return __truncated | \ ((__ckd_intmax_t)(((__z | __x) & __y) | \ ((__z & __x) & ~__y)) < 0); \ case 4: /* s = u + u */ \ return __truncated | (__z < __x) | ((__ckd_intmax_t)__z < 0); \ case 5: /* s = u + s */ \ __y ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | (__x + __y < __y); \ case 6: /* s = s + u */ \ __x ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | (__x + __y < __x); \ case 7: /* s = s + s */ \ return __truncated | \ ((__ckd_intmax_t)((__z ^ __x) & \ (__z ^ __y)) < 0); \ default: \ for (;;) (void)0; \ } \ } __ckd_declare_add(__ckd_add_schar, signed char) __ckd_declare_add(__ckd_add_uchar, unsigned char) __ckd_declare_add(__ckd_add_sshort, signed short) __ckd_declare_add(__ckd_add_ushort, unsigned short) __ckd_declare_add(__ckd_add_sint, signed int) __ckd_declare_add(__ckd_add_uint, unsigned int) __ckd_declare_add(__ckd_add_slong, signed long) __ckd_declare_add(__ckd_add_ulong, unsigned long) __ckd_declare_add(__ckd_add_slonger, signed long long) __ckd_declare_add(__ckd_add_ulonger, unsigned long long) #ifdef __ckd_have_int128 __ckd_declare_add(__ckd_add_sint128, signed __int128) __ckd_declare_add(__ckd_add_uint128, unsigned __int128) #endif #define __ckd_declare_sub(S, T) \ __ckd_inline char S(void *__res, \ __ckd_uintmax_t __x, \ __ckd_uintmax_t __y, \ char __a_signed, \ char __b_signed) { \ __ckd_uintmax_t __z = __x - __y; \ *(T *)__res = (T)__z; \ char __truncated = 0; \ if (sizeof(T) < sizeof(__ckd_intmax_t)) { \ __truncated = __z != (__ckd_uintmax_t)(T)__z; \ } \ switch (__ckd_is_signed((T)0) << 2 | \ __a_signed << 1 | __b_signed) { \ case 0: /* u = u - u */ \ return __truncated | (__x < __y); \ case 1: /* u = u - s */ \ __y ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | \ ((__ckd_intmax_t)((__x ^ __y) & \ (__z ^ __x)) < 0); \ case 2: /* u = s - u */ \ return __truncated | (__y > __x) | ((__ckd_intmax_t)__x < 0); \ case 3: /* u = s - s */ \ return __truncated | \ ((__ckd_intmax_t)(((__z & __x) & __y) | \ ((__z | __x) & ~__y)) < 0); \ case 4: /* s = u - u */ \ return __truncated | ((__x < __y) ^ ((__ckd_intmax_t)__z < 0)); \ case 5: /* s = u - s */ \ __y ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | (__x >= __y); \ case 6: /* s = s - u */ \ __x ^= __ckd_sign(__ckd_uintmax_t); \ return __truncated | (__x < __y); \ case 7: /* s = s - s */ \ return __truncated | \ ((__ckd_intmax_t)((__x ^ __y) & \ (__z ^ __x)) < 0); \ default: \ for (;;) (void)0; \ } \ } __ckd_declare_sub(__ckd_sub_schar, signed char) __ckd_declare_sub(__ckd_sub_uchar, unsigned char) __ckd_declare_sub(__ckd_sub_sshort, signed short) __ckd_declare_sub(__ckd_sub_ushort, unsigned short) __ckd_declare_sub(__ckd_sub_sint, signed int) __ckd_declare_sub(__ckd_sub_uint, unsigned int) __ckd_declare_sub(__ckd_sub_slong, signed long) __ckd_declare_sub(__ckd_sub_ulong, unsigned long) __ckd_declare_sub(__ckd_sub_slonger, signed long long) __ckd_declare_sub(__ckd_sub_ulonger, unsigned long long) #ifdef __ckd_have_int128 __ckd_declare_sub(__ckd_sub_sint128, signed __int128) __ckd_declare_sub(__ckd_sub_uint128, unsigned __int128) #endif #define __ckd_declare_mul(S, T) \ __ckd_inline char S(void *__res, \ __ckd_uintmax_t __x, \ __ckd_uintmax_t __y, \ char __a_signed, \ char __b_signed) { \ switch (__ckd_is_signed((T)0) << 2 | \ __a_signed << 1 | __b_signed) { \ case 0: { /* u = u * u */ \ __ckd_uintmax_t __z = __x * __y; \ int __o = __x && __z / __x != __y; \ *(T *)__res = (T)__z; \ return (char) \ (__o | (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 1: { /* u = u * s */ \ __ckd_uintmax_t __z = __x * __y; \ int __o = __x && __z / __x != __y; \ *(T *)__res = (T)__z; \ return (char) \ (__o | (((__ckd_intmax_t)__y < 0) & !!__x) | \ (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 2: { /* u = s * u */ \ __ckd_uintmax_t __z = __x * __y; \ int __o = __x && __z / __x != __y; \ *(T *)__res = (T)__z; \ return (char) \ (__o | (((__ckd_intmax_t)__x < 0) & !!__y) | \ (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 3: { /* u = s * s */ \ int __o = 0; \ if ((__ckd_intmax_t)(__x & __y) < 0) { \ __x = 0 - __x; \ __y = 0 - __y; \ } else if ((__ckd_intmax_t)(__x ^ __y) < 0) { \ __o = __x && __y; \ } \ __ckd_uintmax_t __z = __x * __y; \ __o |= __x && __z / __x != __y; \ *(T *)__res = (T)__z; \ return (char) \ (__o | (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 4: { /* s = u * u */ \ __ckd_uintmax_t __z = __x * __y; \ int __o = __x && __z / __x != __y; \ *(T *)__res = (T)__z; \ return (char) \ (__o | ((__ckd_intmax_t)(__z) < 0) | \ (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 5: { /* s = u * s */ \ __ckd_uintmax_t __t = 0 - __y; \ __t = (__ckd_intmax_t)(__t) < 0 ? __y : __t; \ __ckd_uintmax_t __p = __t * __x; \ int __o = __t && __p / __t != __x; \ int __n = (__ckd_intmax_t)__y < 0; \ __ckd_uintmax_t __z = __n ? 0 - __p : __p; \ *(T *)__res = (T)__z; \ __ckd_uintmax_t __m = __ckd_sign(__ckd_uintmax_t) - 1; \ return (char) \ (__o | (__p > __m + __n) | \ (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 6: { /* s = s * u */ \ __ckd_uintmax_t __t = 0 - __x; \ __t = (__ckd_intmax_t)(__t) < 0 ? __x : __t; \ __ckd_uintmax_t __p = __t * __y; \ int __o = __t && __p / __t != __y; \ int __n = (__ckd_intmax_t)__x < 0; \ __ckd_uintmax_t __z = __n ? 0 - __p : __p; \ *(T *)__res = (T)__z; \ __ckd_uintmax_t __m = __ckd_sign(__ckd_uintmax_t) - 1; \ return (char) \ (__o | (__p > __m + __n) | \ (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ case 7: { /* s = s * s */ \ __ckd_uintmax_t __z = __x * __y; \ *(T *)__res = (T)__z; \ return (char) \ (((((__ckd_intmax_t)__y < 0) && \ (__x == __ckd_sign(__ckd_uintmax_t))) || \ (__y && (((__ckd_intmax_t)__z / \ (__ckd_intmax_t)__y) != \ (__ckd_intmax_t)__x))) | \ (sizeof(T) < sizeof(__z) && \ __z != (__ckd_uintmax_t)*(T *)__res)); \ } \ default: \ for (;;) (void)0; \ } \ } __ckd_declare_mul(__ckd_mul_schar, signed char) __ckd_declare_mul(__ckd_mul_uchar, unsigned char) __ckd_declare_mul(__ckd_mul_sshort, signed short) __ckd_declare_mul(__ckd_mul_ushort, unsigned short) __ckd_declare_mul(__ckd_mul_sint, signed int) __ckd_declare_mul(__ckd_mul_uint, unsigned int) __ckd_declare_mul(__ckd_mul_slong, signed long) __ckd_declare_mul(__ckd_mul_ulong, unsigned long) __ckd_declare_mul(__ckd_mul_slonger, signed long long) __ckd_declare_mul(__ckd_mul_ulonger, unsigned long long) #ifdef __ckd_have_int128 __ckd_declare_mul(__ckd_mul_sint128, signed __int128) __ckd_declare_mul(__ckd_mul_uint128, unsigned __int128) #endif #else #ifdef _MSC_VER #pragma warning("checked integer arithmetic unsupported in this environment") #else #pragma GCC warning "checked integer arithmetic unsupported in this environment" #endif #define ckd_add(res, x, y) (*(res) = (x) + (y), 0) #define ckd_sub(res, x, y) (*(res) = (x) - (y), 0) #define ckd_mul(res, x, y) (*(res) = (x) * (y), 0) #endif /* GNU */ #endif /* stdckdint.h */