1 | /* |
2 | * Copyright (c) 2015-2018 Apple Inc. All rights reserved. |
3 | * |
4 | * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ |
5 | * |
6 | * This file contains Original Code and/or Modifications of Original Code |
7 | * as defined in and that are subject to the Apple Public Source License |
8 | * Version 2.0 (the 'License'). You may not use this file except in |
9 | * compliance with the License. The rights granted to you under the License |
10 | * may not be used to create, or enable the creation or redistribution of, |
11 | * unlawful or unlicensed copies of an Apple operating system, or to |
12 | * circumvent, violate, or enable the circumvention or violation of, any |
13 | * terms of an Apple operating system software license agreement. |
14 | * |
15 | * Please obtain a copy of the License at |
16 | * http://www.opensource.apple.com/apsl/ and read it before using this file. |
17 | * |
18 | * The Original Code and all software distributed under the License are |
19 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
20 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, |
21 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, |
22 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. |
23 | * Please see the License for the specific language governing rights and |
24 | * limitations under the License. |
25 | * |
26 | * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ |
27 | */ |
28 | |
29 | /* |
30 | * Facilities for performing type- and overflow-checked arithmetic. These |
31 | * functions return non-zero if overflow occured, zero otherwise. In either case, |
32 | * the potentially overflowing operation is fully performed, mod the size of the |
33 | * output type. See: |
34 | * http://clang.llvm.org/docs/LanguageExtensions.html#checked-arithmetic-builtins |
35 | * for full details. |
36 | * |
37 | * The compiler enforces that users of os_*_overflow() check the return value to |
38 | * determine whether overflow occured. |
39 | */ |
40 | |
41 | #ifndef _OS_OVERFLOW_H |
42 | #define _OS_OVERFLOW_H |
43 | |
44 | #include <sys/cdefs.h> |
45 | #include <stdbool.h> |
46 | #include <os/base.h> |
47 | |
48 | bool __header_always_inline OS_WARN_RESULT |
49 | __os_warn_unused(__const bool x) |
50 | { |
51 | return x; |
52 | } |
53 | |
54 | #if __has_builtin(__builtin_add_overflow) && \ |
55 | __has_builtin(__builtin_sub_overflow) && \ |
56 | __has_builtin(__builtin_mul_overflow) |
57 | |
58 | #define os_add_overflow(a, b, res) __os_warn_unused(__builtin_add_overflow((a), (b), (res))) |
59 | #define os_sub_overflow(a, b, res) __os_warn_unused(__builtin_sub_overflow((a), (b), (res))) |
60 | #define os_mul_overflow(a, b, res) __os_warn_unused(__builtin_mul_overflow((a), (b), (res))) |
61 | |
62 | #else |
63 | # error os_overflow expects type-generic builtins |
64 | #endif /* __has_builtin(...) */ |
65 | |
66 | /* os_add3_overflow(a, b, c) -> (a + b + c) */ |
67 | #define os_add3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \ |
68 | __typeof(*(res)) _tmp; \ |
69 | bool _s, _t; \ |
70 | _s = os_add_overflow((a), (b), &_tmp); \ |
71 | _t = os_add_overflow((c), _tmp, (res)); \ |
72 | _s | _t; \ |
73 | })) |
74 | |
75 | /* os_sub3_overflow(a, b, c) -> ((a - b) - c) */ |
76 | #define os_sub3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \ |
77 | __typeof(*(res)) _tmp; \ |
78 | bool _s, _t; \ |
79 | _s = os_sub_overflow((a), (b), &_tmp); \ |
80 | _t = os_sub_overflow(_tmp, (c), (res)); \ |
81 | _s | _t; \ |
82 | })) |
83 | |
84 | /* os_mul3_overflow(a, b, c) -> (a * b * c) */ |
85 | #define os_mul3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \ |
86 | __typeof(*(res)) _tmp; \ |
87 | bool _s, _t; \ |
88 | _s = os_mul_overflow((a), (b), &_tmp); \ |
89 | _t = os_mul_overflow((c), _tmp, (res)); \ |
90 | _s | _t; \ |
91 | })) |
92 | |
93 | /* os_add_and_mul_overflow(a, b, x) -> (a + b)*x */ |
94 | #define os_add_and_mul_overflow(a, b, x, res) __os_warn_unused(__extension__({ \ |
95 | __typeof(*(res)) _tmp; \ |
96 | bool _s, _t; \ |
97 | _s = os_add_overflow((a), (b), &_tmp); \ |
98 | _t = os_mul_overflow((x), _tmp, (res)); \ |
99 | _s | _t; \ |
100 | })) |
101 | |
102 | /* os_mul_and_add_overflow(a, x, b) -> a*x + b */ |
103 | #define os_mul_and_add_overflow(a, x, b, res) __os_warn_unused(__extension__({ \ |
104 | __typeof(*(res)) _tmp; \ |
105 | bool _s, _t; \ |
106 | _s = os_mul_overflow((a), (x), &_tmp); \ |
107 | _t = os_add_overflow((b), _tmp, (res)); \ |
108 | _s | _t; \ |
109 | })) |
110 | |
111 | /* os_convert_overflow(a) -> a [converted to the result type] */ |
112 | #define os_convert_overflow(a, res) os_add_overflow((a), 0, (res)) |
113 | |
114 | /* os_inc_overflow(res) -> *res += 1 */ |
115 | #define os_inc_overflow(res) __os_warn_unused(__extension__({ \ |
116 | __typeof((res)) _tmp = (res); \ |
117 | os_add_overflow(*_tmp, 1, _tmp); \ |
118 | })) |
119 | |
120 | /* os_dec_overflow(res) -> *res -= 1 */ |
121 | #define os_dec_overflow(res) __os_warn_unused(__extension__({ \ |
122 | __typeof((res)) _tmp = (res); \ |
123 | os_sub_overflow(*_tmp, 1, _tmp); \ |
124 | })) |
125 | |
126 | |
127 | #endif /* _OS_OVERFLOW_H */ |
128 | |