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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__ (__GNUC_MINOR__ >= 9)
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___nonstring__ 0
37# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
38# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
39# define __GCC4_has_attribute___fallthrough__ 0
40#endif
41
42/*
43 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
44 */
45#define __alias(symbol) __attribute__((__alias__(#symbol)))
46
47/*
48 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
51 */
52#define __aligned(x) __attribute__((__aligned__(x)))
53#define __aligned_largest __attribute__((__aligned__))
54
55/*
56 * Note: users of __always_inline currently do not write "inline" themselves,
57 * which seems to be required by gcc to apply the attribute according
58 * to its docs (and also "warning: always_inline function might not be
59 * inlinable [-Wattributes]" is emitted).
60 *
61 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
62 * clang: mentioned
63 */
64#define __always_inline inline __attribute__((__always_inline__))
65
66/*
67 * The second argument is optional (default 0), so we use a variadic macro
68 * to make the shorthand.
69 *
70 * Beware: Do not apply this to functions which may return
71 * ERR_PTRs. Also, it is probably unwise to apply it to functions
72 * returning extra information in the low bits (but in that case the
73 * compiler should see some alignment anyway, when the return value is
74 * massaged by 'flags = ptr & 3; ptr &= ~3;').
75 *
76 * Optional: only supported since gcc >= 4.9
77 * Optional: not supported by icc
78 *
79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
80 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
81 */
82#if __has_attribute(__assume_aligned__)
83# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
84#else
85# define __assume_aligned(a, ...)
86#endif
87
88/*
89 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
91 */
92#define __cold __attribute__((__cold__))
93
94/*
95 * Note the long name.
96 *
97 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
98 */
99#define __attribute_const__ __attribute__((__const__))
100
101/*
102 * Optional: only supported since gcc >= 9
103 * Optional: not supported by clang
104 * Optional: not supported by icc
105 *
106 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
107 */
108#if __has_attribute(__copy__)
109# define __copy(symbol) __attribute__((__copy__(symbol)))
110#else
111# define __copy(symbol)
112#endif
113
114/*
115 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
116 * attribute warnings entirely and for good") for more information.
117 *
118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
122 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
123 */
124#define __deprecated
125
126/*
127 * Optional: only supported since gcc >= 5.1
128 * Optional: not supported by clang
129 * Optional: not supported by icc
130 *
131 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
132 */
133#if __has_attribute(__designated_init__)
134# define __designated_init __attribute__((__designated_init__))
135#else
136# define __designated_init
137#endif
138
139/*
140 * Optional: not supported by clang
141 *
142 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
143 */
144#if __has_attribute(__externally_visible__)
145# define __visible __attribute__((__externally_visible__))
146#else
147# define __visible
148#endif
149
150/*
151 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
152 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
153 */
154#define __printf(a, b) __attribute__((__format__(printf, a, b)))
155#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
156
157/*
158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
159 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
160 */
161#define __gnu_inline __attribute__((__gnu_inline__))
162
163/*
164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
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 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
243 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
244 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
245 */
246#define __noreturn __attribute__((__noreturn__))
247
248/*
249 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
250 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
251 */
252#define __packed __attribute__((__packed__))
253
254/*
255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
256 */
257#define __pure __attribute__((__pure__))
258
259/*
260 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
262 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
263 */
264#define __section(section) __attribute__((__section__(section)))
265
266/*
267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
271 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
272 */
273#define __always_unused __attribute__((__unused__))
274#define __maybe_unused __attribute__((__unused__))
275
276/*
277 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
278 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
279 */
280#define __used __attribute__((__used__))
281
282/*
283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
284 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
285 */
286#define __must_check __attribute__((__warn_unused_result__))
287
288/*
289 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
291 */
292#define __weak __attribute__((__weak__))
293
294#endif /* __LINUX_COMPILER_ATTRIBUTES_H */