1 | /* |
2 | * Copyright (c) 2015 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 | |
64 | /* compile-time assertion that 'x' and 'y' are equivalent types */ |
65 | #ifdef __cplusplus |
66 | #define __OS_TYPE_CHECK(x, y) do { \ |
67 | __typeof__(x) _x; \ |
68 | __typeof__(y) _y; \ |
69 | (void)(&_x == &_y, "overflow arithmetic: incompatible types"); \ |
70 | } while (0) |
71 | #else |
72 | #define __OS_TYPE_CHECK(x, y) do { \ |
73 | _Static_assert(__builtin_types_compatible_p(__typeof(x),__typeof(y)), \ |
74 | "overflow arithmetic: incompatible types"); \ |
75 | } while (0) |
76 | #endif |
77 | |
78 | #define __os_add_overflow_func(T,U,V) _Generic((T), \ |
79 | unsigned: __builtin_uadd_overflow, \ |
80 | unsigned long: __builtin_uaddl_overflow, \ |
81 | unsigned long long: __builtin_uaddll_overflow, \ |
82 | int: __builtin_sadd_overflow, \ |
83 | long: __builtin_saddl_overflow, \ |
84 | long long: __builtin_saddll_overflow \ |
85 | )(T,U,V) |
86 | |
87 | #define __os_sub_overflow_func(T,U,V) _Generic((T), \ |
88 | unsigned: __builtin_usub_overflow, \ |
89 | unsigned long: __builtin_usubl_overflow, \ |
90 | unsigned long long: __builtin_usubll_overflow, \ |
91 | int: __builtin_ssub_overflow, \ |
92 | long: __builtin_ssubl_overflow, \ |
93 | long long: __builtin_ssubll_overflow \ |
94 | )(T,U,V) |
95 | |
96 | #define __os_mul_overflow_func(T,U,V) _Generic((T), \ |
97 | unsigned: __builtin_umul_overflow, \ |
98 | unsigned long: __builtin_umull_overflow, \ |
99 | unsigned long long: __builtin_umulll_overflow, \ |
100 | int: __builtin_smul_overflow, \ |
101 | long: __builtin_smull_overflow, \ |
102 | long long: __builtin_smulll_overflow \ |
103 | )(T,U,V) |
104 | |
105 | #define os_add_overflow(a, b, res) __os_warn_unused(__extension__({ \ |
106 | __OS_TYPE_CHECK((a), (b)); \ |
107 | __OS_TYPE_CHECK((b), *(res)); \ |
108 | __os_add_overflow_func((a), (b), (res)); \ |
109 | })) |
110 | |
111 | #define os_sub_overflow(a, b, res) __os_warn_unused(__extension__({ \ |
112 | __OS_TYPE_CHECK((a), (b)); \ |
113 | __OS_TYPE_CHECK((b), *(res)); \ |
114 | __os_sub_overflow_func((a), (b), (res)); \ |
115 | })) |
116 | |
117 | #define os_mul_overflow(a, b, res) __os_warn_unused(__extension__({ \ |
118 | __OS_TYPE_CHECK((a), (b)); \ |
119 | __OS_TYPE_CHECK((b), *(res)); \ |
120 | __os_mul_overflow_func((a), (b), (res)); \ |
121 | })) |
122 | |
123 | #endif /* __has_builtin(...) */ |
124 | |
125 | /* os_add3_overflow(a, b, c) -> (a + b + c) */ |
126 | #define os_add3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \ |
127 | __typeof(*(res)) _tmp; \ |
128 | bool _s, _t; \ |
129 | _s = os_add_overflow((a), (b), &_tmp); \ |
130 | _t = os_add_overflow((c), _tmp, (res)); \ |
131 | _s | _t; \ |
132 | })) |
133 | |
134 | /* os_mul3_overflow(a, b, c) -> (a * b * c) */ |
135 | #define os_mul3_overflow(a, b, c, res) __os_warn_unused(__extension__({ \ |
136 | __typeof(*(res)) _tmp; \ |
137 | bool _s, _t; \ |
138 | _s = os_mul_overflow((a), (b), &_tmp); \ |
139 | _t = os_mul_overflow((c), _tmp, (res)); \ |
140 | _s | _t; \ |
141 | })) |
142 | |
143 | /* os_add_and_mul_overflow(a, b, x) -> (a + b)*x */ |
144 | #define os_add_and_mul_overflow(a, b, x, res) __os_warn_unused(__extension__({ \ |
145 | __typeof(*(res)) _tmp; \ |
146 | bool _s, _t; \ |
147 | _s = os_add_overflow((a), (b), &_tmp); \ |
148 | _t = os_mul_overflow((x), _tmp, (res)); \ |
149 | _s | _t; \ |
150 | })) |
151 | |
152 | /* os_mul_and_add_overflow(a, x, b) -> a*x + b */ |
153 | #define os_mul_and_add_overflow(a, x, b, res) __os_warn_unused(__extension__({ \ |
154 | __typeof(*(res)) _tmp; \ |
155 | bool _s, _t; \ |
156 | _s = os_mul_overflow((a), (x), &_tmp); \ |
157 | _t = os_add_overflow((b), _tmp, (res)); \ |
158 | _s | _t; \ |
159 | })) |
160 | |
161 | #define os_convert_overflow(a, res) os_add_overflow((a), 0, (res)) |
162 | |
163 | #endif /* _OS_OVERFLOW_H */ |
164 | |