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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: do not use this directly. Instead, use __alloc_size() since it is conditionally
38 * available and includes other attributes.
39 *
40 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
41 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
42 */
43#define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
44
45/*
46 * Note: users of __always_inline currently do not write "inline" themselves,
47 * which seems to be required by gcc to apply the attribute according
48 * to its docs (and also "warning: always_inline function might not be
49 * inlinable [-Wattributes]" is emitted).
50 *
51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
52 * clang: mentioned
53 */
54#define __always_inline inline __attribute__((__always_inline__))
55
56/*
57 * The second argument is optional (default 0), so we use a variadic macro
58 * to make the shorthand.
59 *
60 * Beware: Do not apply this to functions which may return
61 * ERR_PTRs. Also, it is probably unwise to apply it to functions
62 * returning extra information in the low bits (but in that case the
63 * compiler should see some alignment anyway, when the return value is
64 * massaged by 'flags = ptr & 3; ptr &= ~3;').
65 *
66 * Optional: not supported by icc
67 *
68 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
69 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
70 */
71#if __has_attribute(__assume_aligned__)
72# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
73#else
74# define __assume_aligned(a, ...)
75#endif
76
77/*
78 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
80 */
81#define __cold __attribute__((__cold__))
82
83/*
84 * Note the long name.
85 *
86 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
87 */
88#define __attribute_const__ __attribute__((__const__))
89
90/*
91 * Optional: only supported since gcc >= 9
92 * Optional: not supported by clang
93 * Optional: not supported by icc
94 *
95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
96 */
97#if __has_attribute(__copy__)
98# define __copy(symbol) __attribute__((__copy__(symbol)))
99#else
100# define __copy(symbol)
101#endif
102
103/*
104 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
105 * attribute warnings entirely and for good") for more information.
106 *
107 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
108 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
109 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
111 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
112 */
113#define __deprecated
114
115/*
116 * Optional: not supported by clang
117 * Optional: not supported by icc
118 *
119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
120 */
121#if __has_attribute(__designated_init__)
122# define __designated_init __attribute__((__designated_init__))
123#else
124# define __designated_init
125#endif
126
127/*
128 * Optional: only supported since clang >= 14.0
129 *
130 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
131 */
132#if __has_attribute(__error__)
133# define __compiletime_error(msg) __attribute__((__error__(msg)))
134#else
135# define __compiletime_error(msg)
136#endif
137
138/*
139 * Optional: not supported by clang
140 *
141 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
142 */
143#if __has_attribute(__externally_visible__)
144# define __visible __attribute__((__externally_visible__))
145#else
146# define __visible
147#endif
148
149/*
150 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
151 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
152 */
153#define __printf(a, b) __attribute__((__format__(printf, a, b)))
154#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
155
156/*
157 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
158 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
159 */
160#define __gnu_inline __attribute__((__gnu_inline__))
161
162/*
163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
164 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
165 */
166#define __malloc __attribute__((__malloc__))
167
168/*
169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
171 */
172#define __mode(x) __attribute__((__mode__(x)))
173
174/*
175 * Optional: only supported since gcc >= 7
176 *
177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
178 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
179 */
180#if __has_attribute(__no_caller_saved_registers__)
181# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
182#else
183# define __no_caller_saved_registers
184#endif
185
186/*
187 * Optional: not supported by clang
188 *
189 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
190 */
191#if __has_attribute(__noclone__)
192# define __noclone __attribute__((__noclone__))
193#else
194# define __noclone
195#endif
196
197/*
198 * Add the pseudo keyword 'fallthrough' so case statement blocks
199 * must end with any of these keywords:
200 * break;
201 * fallthrough;
202 * continue;
203 * goto <label>;
204 * return [expression];
205 *
206 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
207 */
208#if __has_attribute(__fallthrough__)
209# define fallthrough __attribute__((__fallthrough__))
210#else
211# define fallthrough do {} while (0) /* fallthrough */
212#endif
213
214/*
215 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
216 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
217 */
218# define __flatten __attribute__((flatten))
219
220/*
221 * Note the missing underscores.
222 *
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
224 * clang: mentioned
225 */
226#define noinline __attribute__((__noinline__))
227
228/*
229 * Optional: only supported since gcc >= 8
230 * Optional: not supported by clang
231 * Optional: not supported by icc
232 *
233 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
234 */
235#if __has_attribute(__nonstring__)
236# define __nonstring __attribute__((__nonstring__))
237#else
238# define __nonstring
239#endif
240
241/*
242 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
243 *
244 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
245 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
246 */
247#if __has_attribute(__no_profile_instrument_function__)
248# define __no_profile __attribute__((__no_profile_instrument_function__))
249#else
250# define __no_profile
251#endif
252
253/*
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
255 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
256 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
257 */
258#define __noreturn __attribute__((__noreturn__))
259
260/*
261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
262 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
263 */
264#define __packed __attribute__((__packed__))
265
266/*
267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
268 */
269#define __pure __attribute__((__pure__))
270
271/*
272 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
274 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
275 */
276#define __section(section) __attribute__((__section__(section)))
277
278/*
279 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
283 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
284 */
285#define __always_unused __attribute__((__unused__))
286#define __maybe_unused __attribute__((__unused__))
287
288/*
289 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
291 */
292#define __used __attribute__((__used__))
293
294/*
295 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
296 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
297 */
298#define __must_check __attribute__((__warn_unused_result__))
299
300/*
301 * Optional: only supported since clang >= 14.0
302 *
303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
304 */
305#if __has_attribute(__warning__)
306# define __compiletime_warning(msg) __attribute__((__warning__(msg)))
307#else
308# define __compiletime_warning(msg)
309#endif
310
311/*
312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
313 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
314 */
315#define __weak __attribute__((__weak__))
316
317#endif /* __LINUX_COMPILER_ATTRIBUTES_H */