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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 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
25 */
26#define __alias(symbol) __attribute__((__alias__(#symbol)))
27
28/*
29 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
30 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
31 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
32 */
33#define __aligned(x) __attribute__((__aligned__(x)))
34#define __aligned_largest __attribute__((__aligned__))
35
36/*
37 * Note: users of __always_inline currently do not write "inline" themselves,
38 * which seems to be required by gcc to apply the attribute according
39 * to its docs (and also "warning: always_inline function might not be
40 * inlinable [-Wattributes]" is emitted).
41 *
42 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
43 * clang: mentioned
44 */
45#define __always_inline inline __attribute__((__always_inline__))
46
47/*
48 * The second argument is optional (default 0), so we use a variadic macro
49 * to make the shorthand.
50 *
51 * Beware: Do not apply this to functions which may return
52 * ERR_PTRs. Also, it is probably unwise to apply it to functions
53 * returning extra information in the low bits (but in that case the
54 * compiler should see some alignment anyway, when the return value is
55 * massaged by 'flags = ptr & 3; ptr &= ~3;').
56 *
57 * Optional: not supported by icc
58 *
59 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
60 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
61 */
62#if __has_attribute(__assume_aligned__)
63# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
64#else
65# define __assume_aligned(a, ...)
66#endif
67
68/*
69 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
70 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
71 */
72#define __cold __attribute__((__cold__))
73
74/*
75 * Note the long name.
76 *
77 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
78 */
79#define __attribute_const__ __attribute__((__const__))
80
81/*
82 * Optional: only supported since gcc >= 9
83 * Optional: not supported by clang
84 * Optional: not supported by icc
85 *
86 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
87 */
88#if __has_attribute(__copy__)
89# define __copy(symbol) __attribute__((__copy__(symbol)))
90#else
91# define __copy(symbol)
92#endif
93
94/*
95 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
96 * attribute warnings entirely and for good") for more information.
97 *
98 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
99 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
100 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
102 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
103 */
104#define __deprecated
105
106/*
107 * Optional: only supported since gcc >= 5.1
108 * Optional: not supported by clang
109 * Optional: not supported by icc
110 *
111 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
112 */
113#if __has_attribute(__designated_init__)
114# define __designated_init __attribute__((__designated_init__))
115#else
116# define __designated_init
117#endif
118
119/*
120 * Optional: only supported since clang >= 14.0
121 *
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
123 */
124#if __has_attribute(__error__)
125# define __compiletime_error(msg) __attribute__((__error__(msg)))
126#else
127# define __compiletime_error(msg)
128#endif
129
130/*
131 * Optional: not supported by clang
132 *
133 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
134 */
135#if __has_attribute(__externally_visible__)
136# define __visible __attribute__((__externally_visible__))
137#else
138# define __visible
139#endif
140
141/*
142 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
143 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
144 */
145#define __printf(a, b) __attribute__((__format__(printf, a, b)))
146#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
147
148/*
149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
150 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
151 */
152#define __gnu_inline __attribute__((__gnu_inline__))
153
154/*
155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
156 */
157#define __malloc __attribute__((__malloc__))
158
159/*
160 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
161 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
162 */
163#define __mode(x) __attribute__((__mode__(x)))
164
165/*
166 * Optional: only supported since gcc >= 7
167 *
168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
169 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
170 */
171#if __has_attribute(__no_caller_saved_registers__)
172# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
173#else
174# define __no_caller_saved_registers
175#endif
176
177/*
178 * Optional: not supported by clang
179 *
180 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
181 */
182#if __has_attribute(__noclone__)
183# define __noclone __attribute__((__noclone__))
184#else
185# define __noclone
186#endif
187
188/*
189 * Add the pseudo keyword 'fallthrough' so case statement blocks
190 * must end with any of these keywords:
191 * break;
192 * fallthrough;
193 * continue;
194 * goto <label>;
195 * return [expression];
196 *
197 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
198 */
199#if __has_attribute(__fallthrough__)
200# define fallthrough __attribute__((__fallthrough__))
201#else
202# define fallthrough do {} while (0) /* fallthrough */
203#endif
204
205/*
206 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
207 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
208 */
209# define __flatten __attribute__((flatten))
210
211/*
212 * Note the missing underscores.
213 *
214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
215 * clang: mentioned
216 */
217#define noinline __attribute__((__noinline__))
218
219/*
220 * Optional: only supported since gcc >= 8
221 * Optional: not supported by clang
222 * Optional: not supported by icc
223 *
224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
225 */
226#if __has_attribute(__nonstring__)
227# define __nonstring __attribute__((__nonstring__))
228#else
229# define __nonstring
230#endif
231
232/*
233 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
234 *
235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
236 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
237 */
238#if __has_attribute(__no_profile_instrument_function__)
239# define __no_profile __attribute__((__no_profile_instrument_function__))
240#else
241# define __no_profile
242#endif
243
244/*
245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
246 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
247 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
248 */
249#define __noreturn __attribute__((__noreturn__))
250
251/*
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
253 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
254 */
255#define __packed __attribute__((__packed__))
256
257/*
258 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
259 */
260#define __pure __attribute__((__pure__))
261
262/*
263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
264 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
265 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
266 */
267#define __section(section) __attribute__((__section__(section)))
268
269/*
270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
271 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
272 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
274 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
275 */
276#define __always_unused __attribute__((__unused__))
277#define __maybe_unused __attribute__((__unused__))
278
279/*
280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
282 */
283#define __used __attribute__((__used__))
284
285/*
286 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
287 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
288 */
289#define __must_check __attribute__((__warn_unused_result__))
290
291/*
292 * Optional: only supported since clang >= 14.0
293 *
294 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
295 */
296#if __has_attribute(__warning__)
297# define __compiletime_warning(msg) __attribute__((__warning__(msg)))
298#else
299# define __compiletime_warning(msg)
300#endif
301
302/*
303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
304 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
305 */
306#define __weak __attribute__((__weak__))
307
308#endif /* __LINUX_COMPILER_ATTRIBUTES_H */