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 * Optional: not supported by gcc
105 * Optional: only supported since clang >= 14.0
106 * Optional: not supported by icc
107 *
108 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
109 */
110#if __has_attribute(__diagnose_as_builtin__)
111# define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin)))
112#else
113# define __diagnose_as(builtin...)
114#endif
115
116/*
117 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
118 * attribute warnings entirely and for good") for more information.
119 *
120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
124 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
125 */
126#define __deprecated
127
128/*
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: only supported since clang >= 14.0
142 *
143 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
144 */
145#if __has_attribute(__error__)
146# define __compiletime_error(msg) __attribute__((__error__(msg)))
147#else
148# define __compiletime_error(msg)
149#endif
150
151/*
152 * Optional: not supported by clang
153 *
154 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
155 */
156#if __has_attribute(__externally_visible__)
157# define __visible __attribute__((__externally_visible__))
158#else
159# define __visible
160#endif
161
162/*
163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
164 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
165 */
166#define __printf(a, b) __attribute__((__format__(printf, a, b)))
167#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
168
169/*
170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
171 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
172 */
173#define __gnu_inline __attribute__((__gnu_inline__))
174
175/*
176 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
177 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
178 */
179#define __malloc __attribute__((__malloc__))
180
181/*
182 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
183 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
184 */
185#define __mode(x) __attribute__((__mode__(x)))
186
187/*
188 * Optional: only supported since gcc >= 7
189 *
190 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
191 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
192 */
193#if __has_attribute(__no_caller_saved_registers__)
194# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
195#else
196# define __no_caller_saved_registers
197#endif
198
199/*
200 * Optional: not supported by clang
201 *
202 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
203 */
204#if __has_attribute(__noclone__)
205# define __noclone __attribute__((__noclone__))
206#else
207# define __noclone
208#endif
209
210/*
211 * Add the pseudo keyword 'fallthrough' so case statement blocks
212 * must end with any of these keywords:
213 * break;
214 * fallthrough;
215 * continue;
216 * goto <label>;
217 * return [expression];
218 *
219 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
220 */
221#if __has_attribute(__fallthrough__)
222# define fallthrough __attribute__((__fallthrough__))
223#else
224# define fallthrough do {} while (0) /* fallthrough */
225#endif
226
227/*
228 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
229 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
230 */
231# define __flatten __attribute__((flatten))
232
233/*
234 * Note the missing underscores.
235 *
236 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
237 * clang: mentioned
238 */
239#define noinline __attribute__((__noinline__))
240
241/*
242 * Optional: only supported since gcc >= 8
243 * Optional: not supported by clang
244 * Optional: not supported by icc
245 *
246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
247 */
248#if __has_attribute(__nonstring__)
249# define __nonstring __attribute__((__nonstring__))
250#else
251# define __nonstring
252#endif
253
254/*
255 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
256 *
257 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
258 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
259 */
260#if __has_attribute(__no_profile_instrument_function__)
261# define __no_profile __attribute__((__no_profile_instrument_function__))
262#else
263# define __no_profile
264#endif
265
266/*
267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
268 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
269 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
270 */
271#define __noreturn __attribute__((__noreturn__))
272
273/*
274 * Optional: not supported by gcc.
275 * Optional: not supported by icc.
276 *
277 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
278 */
279#if __has_attribute(__overloadable__)
280# define __overloadable __attribute__((__overloadable__))
281#else
282# define __overloadable
283#endif
284
285/*
286 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
287 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
288 */
289#define __packed __attribute__((__packed__))
290
291/*
292 * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
293 *
294 * Optional: not supported by gcc.
295 * Optional: not supported by icc.
296 *
297 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
298 */
299#if __has_attribute(__pass_object_size__)
300# define __pass_object_size(type) __attribute__((__pass_object_size__(type)))
301#else
302# define __pass_object_size(type)
303#endif
304
305/*
306 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
307 */
308#define __pure __attribute__((__pure__))
309
310/*
311 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
313 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
314 */
315#define __section(section) __attribute__((__section__(section)))
316
317/*
318 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
319 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
320 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
321 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
322 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
323 */
324#define __always_unused __attribute__((__unused__))
325#define __maybe_unused __attribute__((__unused__))
326
327/*
328 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
329 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
330 */
331#define __used __attribute__((__used__))
332
333/*
334 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
335 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
336 */
337#define __must_check __attribute__((__warn_unused_result__))
338
339/*
340 * Optional: only supported since clang >= 14.0
341 *
342 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
343 */
344#if __has_attribute(__warning__)
345# define __compiletime_warning(msg) __attribute__((__warning__(msg)))
346#else
347# define __compiletime_warning(msg)
348#endif
349
350/*
351 * Optional: only supported since clang >= 14.0
352 *
353 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
354 *
355 * disable_sanitizer_instrumentation is not always similar to
356 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
357 * insert code into functions to prevent false positives. Unlike that,
358 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
359 * functions with the attribute.
360 */
361#if __has_attribute(disable_sanitizer_instrumentation)
362# define __disable_sanitizer_instrumentation \
363 __attribute__((disable_sanitizer_instrumentation))
364#else
365# define __disable_sanitizer_instrumentation
366#endif
367
368/*
369 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
370 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
371 */
372#define __weak __attribute__((__weak__))
373
374#endif /* __LINUX_COMPILER_ATTRIBUTES_H */
375

source code of linux/include/linux/compiler_attributes.h