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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), unless one of the compilers does not support
8 * the attribute. In that case, __has_attribute is used to check for support
9 * and the reason is stated in its comment ("Optional: ...").
10 *
11 * Any other "attributes" (i.e. those that depend on a configuration option,
12 * on a compiler, on an architecture, on plugins, on other attributes...)
13 * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
14 * The intention is to keep this file as simple as possible, as well as
15 * compiler- and version-agnostic (e.g. avoiding GCC_VERSION checks).
16 *
17 * This file is meant to be sorted (by actual attribute name,
18 * not by #define identifier). Use the __attribute__((__name__)) syntax
19 * (i.e. with underscores) to avoid future collisions with other macros.
20 * Provide links to the documentation of each supported compiler, if it exists.
21 */
22
23/*
24 * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
25 * In the meantime, to support 4.6 <= gcc < 5, we implement __has_attribute
26 * by hand.
27 *
28 * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
29 * depending on the compiler used to build it; however, these attributes have
30 * no semantic effects for sparse, so it does not matter. Also note that,
31 * in order to avoid sparse's warnings, even the unsupported ones must be
32 * defined to 0.
33 */
34#ifndef __has_attribute
35# define __has_attribute(x) __GCC4_has_attribute_##x
36# define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9)
37# define __GCC4_has_attribute___copy__ 0
38# define __GCC4_has_attribute___designated_init__ 0
39# define __GCC4_has_attribute___externally_visible__ 1
40# define __GCC4_has_attribute___no_caller_saved_registers__ 0
41# define __GCC4_has_attribute___noclone__ 1
42# define __GCC4_has_attribute___nonstring__ 0
43# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
44# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
45# define __GCC4_has_attribute___fallthrough__ 0
46#endif
47
48/*
49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
50 */
51#define __alias(symbol) __attribute__((__alias__(#symbol)))
52
53/*
54 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
55 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
56 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
57 */
58#define __aligned(x) __attribute__((__aligned__(x)))
59#define __aligned_largest __attribute__((__aligned__))
60
61/*
62 * Note: users of __always_inline currently do not write "inline" themselves,
63 * which seems to be required by gcc to apply the attribute according
64 * to its docs (and also "warning: always_inline function might not be
65 * inlinable [-Wattributes]" is emitted).
66 *
67 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
68 * clang: mentioned
69 */
70#define __always_inline inline __attribute__((__always_inline__))
71
72/*
73 * The second argument is optional (default 0), so we use a variadic macro
74 * to make the shorthand.
75 *
76 * Beware: Do not apply this to functions which may return
77 * ERR_PTRs. Also, it is probably unwise to apply it to functions
78 * returning extra information in the low bits (but in that case the
79 * compiler should see some alignment anyway, when the return value is
80 * massaged by 'flags = ptr & 3; ptr &= ~3;').
81 *
82 * Optional: only supported since gcc >= 4.9
83 * Optional: not supported by icc
84 *
85 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
86 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
87 */
88#if __has_attribute(__assume_aligned__)
89# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
90#else
91# define __assume_aligned(a, ...)
92#endif
93
94/*
95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
96 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
97 */
98#define __cold __attribute__((__cold__))
99
100/*
101 * Note the long name.
102 *
103 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
104 */
105#define __attribute_const__ __attribute__((__const__))
106
107/*
108 * Optional: only supported since gcc >= 9
109 * Optional: not supported by clang
110 * Optional: not supported by icc
111 *
112 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
113 */
114#if __has_attribute(__copy__)
115# define __copy(symbol) __attribute__((__copy__(symbol)))
116#else
117# define __copy(symbol)
118#endif
119
120/*
121 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
122 * attribute warnings entirely and for good") for more information.
123 *
124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
125 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
126 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
127 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
128 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
129 */
130#define __deprecated
131
132/*
133 * Optional: only supported since gcc >= 5.1
134 * Optional: not supported by clang
135 * Optional: not supported by icc
136 *
137 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
138 */
139#if __has_attribute(__designated_init__)
140# define __designated_init __attribute__((__designated_init__))
141#else
142# define __designated_init
143#endif
144
145/*
146 * Optional: not supported by clang
147 *
148 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
149 */
150#if __has_attribute(__externally_visible__)
151# define __visible __attribute__((__externally_visible__))
152#else
153# define __visible
154#endif
155
156/*
157 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
158 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
159 */
160#define __printf(a, b) __attribute__((__format__(printf, a, b)))
161#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
162
163/*
164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
165 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
166 */
167#define __gnu_inline __attribute__((__gnu_inline__))
168
169/*
170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
171 */
172#define __malloc __attribute__((__malloc__))
173
174/*
175 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
176 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
177 */
178#define __mode(x) __attribute__((__mode__(x)))
179
180/*
181 * Optional: only supported since gcc >= 7
182 *
183 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
184 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
185 */
186#if __has_attribute(__no_caller_saved_registers__)
187# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
188#else
189# define __no_caller_saved_registers
190#endif
191
192/*
193 * Optional: not supported by clang
194 *
195 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
196 */
197#if __has_attribute(__noclone__)
198# define __noclone __attribute__((__noclone__))
199#else
200# define __noclone
201#endif
202
203/*
204 * Add the pseudo keyword 'fallthrough' so case statement blocks
205 * must end with any of these keywords:
206 * break;
207 * fallthrough;
208 * goto <label>;
209 * return [expression];
210 *
211 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
212 */
213#if __has_attribute(__fallthrough__)
214# define fallthrough __attribute__((__fallthrough__))
215#else
216# define fallthrough do {} while (0) /* fallthrough */
217#endif
218
219/*
220 * Note the missing underscores.
221 *
222 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
223 * clang: mentioned
224 */
225#define noinline __attribute__((__noinline__))
226
227/*
228 * Optional: only supported since gcc >= 8
229 * Optional: not supported by clang
230 * Optional: not supported by icc
231 *
232 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
233 */
234#if __has_attribute(__nonstring__)
235# define __nonstring __attribute__((__nonstring__))
236#else
237# define __nonstring
238#endif
239
240/*
241 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
242 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
243 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
244 */
245#define __noreturn __attribute__((__noreturn__))
246
247/*
248 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
249 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
250 */
251#define __packed __attribute__((__packed__))
252
253/*
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
255 */
256#define __pure __attribute__((__pure__))
257
258/*
259 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
260 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
261 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
262 */
263#define __section(S) __attribute__((__section__(#S)))
264
265/*
266 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
270 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
271 */
272#define __always_unused __attribute__((__unused__))
273#define __maybe_unused __attribute__((__unused__))
274
275/*
276 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
277 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
278 */
279#define __used __attribute__((__used__))
280
281/*
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
284 */
285#define __weak __attribute__((__weak__))
286
287#endif /* __LINUX_COMPILER_ATTRIBUTES_H */