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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_COMPILER_ATTRIBUTES_H
3#define __LINUX_COMPILER_ATTRIBUTES_H
4
5/*
6 * The attributes in this file are unconditionally defined and they directly
7 * map to compiler attribute(s) -- except those that are optional.
8 *
9 * Any other "attributes" (i.e. those that depend on a configuration option,
10 * on a compiler, on an architecture, on plugins, on other attributes...)
11 * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
12 *
13 * This file is meant to be sorted (by actual attribute name,
14 * not by #define identifier). Use the __attribute__((__name__)) syntax
15 * (i.e. with underscores) to avoid future collisions with other macros.
16 * If an attribute is optional, state the reason in the comment.
17 */
18
19/*
20 * To check for optional attributes, we use __has_attribute, which is supported
21 * on gcc >= 5, clang >= 2.9 and icc >= 17. In the meantime, to support
22 * 4.6 <= gcc < 5, we implement __has_attribute by hand.
23 *
24 * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
25 * depending on the compiler used to build it; however, these attributes have
26 * no semantic effects for sparse, so it does not matter. Also note that,
27 * in order to avoid sparse's warnings, even the unsupported ones must be
28 * defined to 0.
29 */
30#ifndef __has_attribute
31# define __has_attribute(x) __GCC4_has_attribute_##x
32# define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9)
33# define __GCC4_has_attribute___designated_init__ 0
34# define __GCC4_has_attribute___externally_visible__ 1
35# define __GCC4_has_attribute___noclone__ 1
36# define __GCC4_has_attribute___optimize__ 1
37# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
38#endif
39
40/*
41 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
42 */
43#define __alias(symbol) __attribute__((__alias__(#symbol)))
44
45/*
46 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
47 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
48 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
49 */
50#define __aligned(x) __attribute__((__aligned__(x)))
51#define __aligned_largest __attribute__((__aligned__))
52
53/*
54 * Note: users of __always_inline currently do not write "inline" themselves,
55 * which seems to be required by gcc to apply the attribute according
56 * to its docs (and also "warning: always_inline function might not be
57 * inlinable [-Wattributes]" is emitted).
58 *
59 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
60 * clang: mentioned
61 */
62#define __always_inline inline __attribute__((__always_inline__))
63
64/*
65 * The second argument is optional (default 0), so we use a variadic macro
66 * to make the shorthand.
67 *
68 * Beware: Do not apply this to functions which may return
69 * ERR_PTRs. Also, it is probably unwise to apply it to functions
70 * returning extra information in the low bits (but in that case the
71 * compiler should see some alignment anyway, when the return value is
72 * massaged by 'flags = ptr & 3; ptr &= ~3;').
73 *
74 * Optional: only supported since gcc >= 4.9
75 * Optional: not supported by icc
76 *
77 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
78 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
79 */
80#if __has_attribute(__assume_aligned__)
81# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
82#else
83# define __assume_aligned(a, ...)
84#endif
85
86/*
87 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
88 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
89 */
90#define __cold __attribute__((__cold__))
91
92/*
93 * Note the long name.
94 *
95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
96 */
97#define __attribute_const__ __attribute__((__const__))
98
99/*
100 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
101 * attribute warnings entirely and for good") for more information.
102 *
103 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
104 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
105 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
106 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
107 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
108 */
109#define __deprecated
110
111/*
112 * Optional: only supported since gcc >= 5.1
113 * Optional: not supported by clang
114 * Optional: not supported by icc
115 *
116 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
117 */
118#if __has_attribute(__designated_init__)
119# define __designated_init __attribute__((__designated_init__))
120#else
121# define __designated_init
122#endif
123
124/*
125 * Optional: not supported by clang
126 *
127 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
128 */
129#if __has_attribute(__externally_visible__)
130# define __visible __attribute__((__externally_visible__))
131#else
132# define __visible
133#endif
134
135/*
136 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
137 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
138 */
139#define __printf(a, b) __attribute__((__format__(printf, a, b)))
140#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
141
142/*
143 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
144 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
145 */
146#define __gnu_inline __attribute__((__gnu_inline__))
147
148/*
149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
150 */
151#define __malloc __attribute__((__malloc__))
152
153/*
154 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
156 */
157#define __mode(x) __attribute__((__mode__(x)))
158
159/*
160 * Optional: not supported by clang
161 * Note: icc does not recognize gcc's no-tracer
162 *
163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-optimize-function-attribute
165 */
166#if __has_attribute(__noclone__)
167# if __has_attribute(__optimize__)
168# define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
169# else
170# define __noclone __attribute__((__noclone__))
171# endif
172#else
173# define __noclone
174#endif
175
176/*
177 * Note the missing underscores.
178 *
179 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
180 * clang: mentioned
181 */
182#define noinline __attribute__((__noinline__))
183
184/*
185 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
186 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
187 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
188 */
189#define __noreturn __attribute__((__noreturn__))
190
191/*
192 * Optional: only supported since gcc >= 4.8
193 * Optional: not supported by icc
194 *
195 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
196 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
197 */
198#if __has_attribute(__no_sanitize_address__)
199# define __no_sanitize_address __attribute__((__no_sanitize_address__))
200#else
201# define __no_sanitize_address
202#endif
203
204/*
205 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
206 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
207 */
208#define __packed __attribute__((__packed__))
209
210/*
211 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
212 */
213#define __pure __attribute__((__pure__))
214
215/*
216 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
217 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
218 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
219 */
220#define __section(S) __attribute__((__section__(#S)))
221
222/*
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
225 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
226 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
227 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
228 */
229#define __always_unused __attribute__((__unused__))
230#define __maybe_unused __attribute__((__unused__))
231
232/*
233 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
235 */
236#define __used __attribute__((__used__))
237
238/*
239 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
240 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
241 */
242#define __weak __attribute__((__weak__))
243
244#endif /* __LINUX_COMPILER_ATTRIBUTES_H */
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