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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 gcc < 5, we implement __has_attribute
26 * by hand.
27 */
28#ifndef __has_attribute
29# define __has_attribute(x) __GCC4_has_attribute_##x
30# define __GCC4_has_attribute___assume_aligned__ 1
31# define __GCC4_has_attribute___copy__ 0
32# define __GCC4_has_attribute___designated_init__ 0
33# define __GCC4_has_attribute___externally_visible__ 1
34# define __GCC4_has_attribute___no_caller_saved_registers__ 0
35# define __GCC4_has_attribute___noclone__ 1
36# define __GCC4_has_attribute___no_profile_instrument_function__ 0
37# define __GCC4_has_attribute___nonstring__ 0
38# define __GCC4_has_attribute___no_sanitize_address__ 1
39# define __GCC4_has_attribute___no_sanitize_undefined__ 1
40# define __GCC4_has_attribute___fallthrough__ 0
41#endif
42
43/*
44 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
45 */
46#define __alias(symbol) __attribute__((__alias__(#symbol)))
47
48/*
49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
52 */
53#define __aligned(x) __attribute__((__aligned__(x)))
54#define __aligned_largest __attribute__((__aligned__))
55
56/*
57 * Note: users of __always_inline currently do not write "inline" themselves,
58 * which seems to be required by gcc to apply the attribute according
59 * to its docs (and also "warning: always_inline function might not be
60 * inlinable [-Wattributes]" is emitted).
61 *
62 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
63 * clang: mentioned
64 */
65#define __always_inline inline __attribute__((__always_inline__))
66
67/*
68 * The second argument is optional (default 0), so we use a variadic macro
69 * to make the shorthand.
70 *
71 * Beware: Do not apply this to functions which may return
72 * ERR_PTRs. Also, it is probably unwise to apply it to functions
73 * returning extra information in the low bits (but in that case the
74 * compiler should see some alignment anyway, when the return value is
75 * massaged by 'flags = ptr & 3; ptr &= ~3;').
76 *
77 * Optional: only supported since gcc >= 4.9
78 * Optional: not supported by icc
79 *
80 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
81 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
82 */
83#if __has_attribute(__assume_aligned__)
84# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
85#else
86# define __assume_aligned(a, ...)
87#endif
88
89/*
90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
91 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
92 */
93#define __cold __attribute__((__cold__))
94
95/*
96 * Note the long name.
97 *
98 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
99 */
100#define __attribute_const__ __attribute__((__const__))
101
102/*
103 * Optional: only supported since gcc >= 9
104 * Optional: not supported by clang
105 * Optional: not supported by icc
106 *
107 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
108 */
109#if __has_attribute(__copy__)
110# define __copy(symbol) __attribute__((__copy__(symbol)))
111#else
112# define __copy(symbol)
113#endif
114
115/*
116 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
117 * attribute warnings entirely and for good") for more information.
118 *
119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
123 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
124 */
125#define __deprecated
126
127/*
128 * Optional: only supported since gcc >= 5.1
129 * Optional: not supported by clang
130 * Optional: not supported by icc
131 *
132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
133 */
134#if __has_attribute(__designated_init__)
135# define __designated_init __attribute__((__designated_init__))
136#else
137# define __designated_init
138#endif
139
140/*
141 * Optional: not supported by clang
142 *
143 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
144 */
145#if __has_attribute(__externally_visible__)
146# define __visible __attribute__((__externally_visible__))
147#else
148# define __visible
149#endif
150
151/*
152 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
153 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
154 */
155#define __printf(a, b) __attribute__((__format__(printf, a, b)))
156#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
157
158/*
159 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
160 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
161 */
162#define __gnu_inline __attribute__((__gnu_inline__))
163
164/*
165 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
166 */
167#define __malloc __attribute__((__malloc__))
168
169/*
170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
172 */
173#define __mode(x) __attribute__((__mode__(x)))
174
175/*
176 * Optional: only supported since gcc >= 7
177 *
178 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
179 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
180 */
181#if __has_attribute(__no_caller_saved_registers__)
182# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
183#else
184# define __no_caller_saved_registers
185#endif
186
187/*
188 * Optional: not supported by clang
189 *
190 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
191 */
192#if __has_attribute(__noclone__)
193# define __noclone __attribute__((__noclone__))
194#else
195# define __noclone
196#endif
197
198/*
199 * Add the pseudo keyword 'fallthrough' so case statement blocks
200 * must end with any of these keywords:
201 * break;
202 * fallthrough;
203 * continue;
204 * goto <label>;
205 * return [expression];
206 *
207 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
208 */
209#if __has_attribute(__fallthrough__)
210# define fallthrough __attribute__((__fallthrough__))
211#else
212# define fallthrough do {} while (0) /* fallthrough */
213#endif
214
215/*
216 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
217 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
218 */
219# define __flatten __attribute__((flatten))
220
221/*
222 * Note the missing underscores.
223 *
224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
225 * clang: mentioned
226 */
227#define noinline __attribute__((__noinline__))
228
229/*
230 * Optional: only supported since gcc >= 8
231 * Optional: not supported by clang
232 * Optional: not supported by icc
233 *
234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
235 */
236#if __has_attribute(__nonstring__)
237# define __nonstring __attribute__((__nonstring__))
238#else
239# define __nonstring
240#endif
241
242/*
243 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
244 *
245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
246 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
247 */
248#if __has_attribute(__no_profile_instrument_function__)
249# define __no_profile __attribute__((__no_profile_instrument_function__))
250#else
251# define __no_profile
252#endif
253
254/*
255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
256 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
257 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
258 */
259#define __noreturn __attribute__((__noreturn__))
260
261/*
262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
263 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
264 */
265#define __packed __attribute__((__packed__))
266
267/*
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
269 */
270#define __pure __attribute__((__pure__))
271
272/*
273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
274 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
275 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
276 */
277#define __section(section) __attribute__((__section__(section)))
278
279/*
280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
284 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
285 */
286#define __always_unused __attribute__((__unused__))
287#define __maybe_unused __attribute__((__unused__))
288
289/*
290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
291 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
292 */
293#define __used __attribute__((__used__))
294
295/*
296 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
297 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
298 */
299#define __must_check __attribute__((__warn_unused_result__))
300
301/*
302 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
304 */
305#define __weak __attribute__((__weak__))
306
307#endif /* __LINUX_COMPILER_ATTRIBUTES_H */