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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. For GCC < 9.1, __alloc_size__ gets undefined
39 * in compiler-gcc.h, due to misbehaviors.
40 *
41 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
42 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
43 */
44#define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
45
46/*
47 * Note: users of __always_inline currently do not write "inline" themselves,
48 * which seems to be required by gcc to apply the attribute according
49 * to its docs (and also "warning: always_inline function might not be
50 * inlinable [-Wattributes]" is emitted).
51 *
52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
53 * clang: mentioned
54 */
55#define __always_inline inline __attribute__((__always_inline__))
56
57/*
58 * The second argument is optional (default 0), so we use a variadic macro
59 * to make the shorthand.
60 *
61 * Beware: Do not apply this to functions which may return
62 * ERR_PTRs. Also, it is probably unwise to apply it to functions
63 * returning extra information in the low bits (but in that case the
64 * compiler should see some alignment anyway, when the return value is
65 * massaged by 'flags = ptr & 3; ptr &= ~3;').
66 *
67 * Optional: not supported by icc
68 *
69 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
70 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
71 */
72#if __has_attribute(__assume_aligned__)
73# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
74#else
75# define __assume_aligned(a, ...)
76#endif
77
78/*
79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
80 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
81 */
82#define __cold __attribute__((__cold__))
83
84/*
85 * Note the long name.
86 *
87 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
88 */
89#define __attribute_const__ __attribute__((__const__))
90
91/*
92 * Optional: only supported since gcc >= 9
93 * Optional: not supported by clang
94 * Optional: not supported by icc
95 *
96 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
97 */
98#if __has_attribute(__copy__)
99# define __copy(symbol) __attribute__((__copy__(symbol)))
100#else
101# define __copy(symbol)
102#endif
103
104/*
105 * Optional: not supported by gcc
106 * Optional: only supported since clang >= 14.0
107 * Optional: not supported by icc
108 *
109 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
110 */
111#if __has_attribute(__diagnose_as_builtin__)
112# define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin)))
113#else
114# define __diagnose_as(builtin...)
115#endif
116
117/*
118 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
119 * attribute warnings entirely and for good") for more information.
120 *
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
125 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
126 */
127#define __deprecated
128
129/*
130 * Optional: not supported by clang
131 * Optional: not supported by icc
132 *
133 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
134 */
135#if __has_attribute(__designated_init__)
136# define __designated_init __attribute__((__designated_init__))
137#else
138# define __designated_init
139#endif
140
141/*
142 * Optional: only supported since clang >= 14.0
143 *
144 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
145 */
146#if __has_attribute(__error__)
147# define __compiletime_error(msg) __attribute__((__error__(msg)))
148#else
149# define __compiletime_error(msg)
150#endif
151
152/*
153 * Optional: not supported by clang
154 *
155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
156 */
157#if __has_attribute(__externally_visible__)
158# define __visible __attribute__((__externally_visible__))
159#else
160# define __visible
161#endif
162
163/*
164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
165 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
166 */
167#define __printf(a, b) __attribute__((__format__(printf, a, b)))
168#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
169
170/*
171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
172 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
173 */
174#define __gnu_inline __attribute__((__gnu_inline__))
175
176/*
177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
178 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
179 */
180#define __malloc __attribute__((__malloc__))
181
182/*
183 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
184 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
185 */
186#define __mode(x) __attribute__((__mode__(x)))
187
188/*
189 * Optional: only supported since gcc >= 7
190 *
191 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
192 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
193 */
194#if __has_attribute(__no_caller_saved_registers__)
195# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
196#else
197# define __no_caller_saved_registers
198#endif
199
200/*
201 * Optional: not supported by clang
202 *
203 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
204 */
205#if __has_attribute(__noclone__)
206# define __noclone __attribute__((__noclone__))
207#else
208# define __noclone
209#endif
210
211/*
212 * Add the pseudo keyword 'fallthrough' so case statement blocks
213 * must end with any of these keywords:
214 * break;
215 * fallthrough;
216 * continue;
217 * goto <label>;
218 * return [expression];
219 *
220 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
221 */
222#if __has_attribute(__fallthrough__)
223# define fallthrough __attribute__((__fallthrough__))
224#else
225# define fallthrough do {} while (0) /* fallthrough */
226#endif
227
228/*
229 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
230 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
231 */
232# define __flatten __attribute__((flatten))
233
234/*
235 * Note the missing underscores.
236 *
237 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
238 * clang: mentioned
239 */
240#define noinline __attribute__((__noinline__))
241
242/*
243 * Optional: only supported since gcc >= 8
244 * Optional: not supported by clang
245 * Optional: not supported by icc
246 *
247 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
248 */
249#if __has_attribute(__nonstring__)
250# define __nonstring __attribute__((__nonstring__))
251#else
252# define __nonstring
253#endif
254
255/*
256 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
257 *
258 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
259 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
260 */
261#if __has_attribute(__no_profile_instrument_function__)
262# define __no_profile __attribute__((__no_profile_instrument_function__))
263#else
264# define __no_profile
265#endif
266
267/*
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
269 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
270 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
271 */
272#define __noreturn __attribute__((__noreturn__))
273
274/*
275 * Optional: not supported by gcc.
276 * Optional: not supported by icc.
277 *
278 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
279 */
280#if __has_attribute(__overloadable__)
281# define __overloadable __attribute__((__overloadable__))
282#else
283# define __overloadable
284#endif
285
286/*
287 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
288 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
289 */
290#define __packed __attribute__((__packed__))
291
292/*
293 * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
294 *
295 * Optional: not supported by gcc.
296 * Optional: not supported by icc.
297 *
298 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
299 */
300#if __has_attribute(__pass_object_size__)
301# define __pass_object_size(type) __attribute__((__pass_object_size__(type)))
302#else
303# define __pass_object_size(type)
304#endif
305
306/*
307 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
308 */
309#define __pure __attribute__((__pure__))
310
311/*
312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
313 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
314 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
315 */
316#define __section(section) __attribute__((__section__(section)))
317
318/*
319 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
320 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
321 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
322 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
323 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
324 */
325#define __always_unused __attribute__((__unused__))
326#define __maybe_unused __attribute__((__unused__))
327
328/*
329 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
330 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
331 */
332#define __used __attribute__((__used__))
333
334/*
335 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
336 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
337 */
338#define __must_check __attribute__((__warn_unused_result__))
339
340/*
341 * Optional: only supported since clang >= 14.0
342 *
343 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
344 */
345#if __has_attribute(__warning__)
346# define __compiletime_warning(msg) __attribute__((__warning__(msg)))
347#else
348# define __compiletime_warning(msg)
349#endif
350
351/*
352 * Optional: only supported since clang >= 14.0
353 *
354 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
355 *
356 * disable_sanitizer_instrumentation is not always similar to
357 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
358 * insert code into functions to prevent false positives. Unlike that,
359 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
360 * functions with the attribute.
361 */
362#if __has_attribute(disable_sanitizer_instrumentation)
363# define __disable_sanitizer_instrumentation \
364 __attribute__((disable_sanitizer_instrumentation))
365#else
366# define __disable_sanitizer_instrumentation
367#endif
368
369/*
370 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
371 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
372 */
373#define __weak __attribute__((__weak__))
374
375/*
376 * Used by functions that use '__builtin_return_address'. These function
377 * don't want to be splited or made inline, which can make
378 * the '__builtin_return_address' get unexpected address.
379 */
380#define __fix_address noinline __noclone
381
382#endif /* __LINUX_COMPILER_ATTRIBUTES_H */