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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 4.6 <= gcc < 5, we implement __has_attribute
26 * by hand.
27 *
28 * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
29 * depending on the compiler used to build it; however, these attributes have
30 * no semantic effects for sparse, so it does not matter. Also note that,
31 * in order to avoid sparse's warnings, even the unsupported ones must be
32 * defined to 0.
33 */
34#ifndef __has_attribute
35# define __has_attribute(x) __GCC4_has_attribute_##x
36# define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9)
37# define __GCC4_has_attribute___copy__ 0
38# define __GCC4_has_attribute___designated_init__ 0
39# define __GCC4_has_attribute___externally_visible__ 1
40# define __GCC4_has_attribute___noclone__ 1
41# define __GCC4_has_attribute___nonstring__ 0
42# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
43# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
44# define __GCC4_has_attribute___fallthrough__ 0
45#endif
46
47/*
48 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
49 */
50#define __alias(symbol) __attribute__((__alias__(#symbol)))
51
52/*
53 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
54 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
55 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
56 */
57#define __aligned(x) __attribute__((__aligned__(x)))
58#define __aligned_largest __attribute__((__aligned__))
59
60/*
61 * Note: users of __always_inline currently do not write "inline" themselves,
62 * which seems to be required by gcc to apply the attribute according
63 * to its docs (and also "warning: always_inline function might not be
64 * inlinable [-Wattributes]" is emitted).
65 *
66 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
67 * clang: mentioned
68 */
69#define __always_inline inline __attribute__((__always_inline__))
70
71/*
72 * The second argument is optional (default 0), so we use a variadic macro
73 * to make the shorthand.
74 *
75 * Beware: Do not apply this to functions which may return
76 * ERR_PTRs. Also, it is probably unwise to apply it to functions
77 * returning extra information in the low bits (but in that case the
78 * compiler should see some alignment anyway, when the return value is
79 * massaged by 'flags = ptr & 3; ptr &= ~3;').
80 *
81 * Optional: only supported since gcc >= 4.9
82 * Optional: not supported by icc
83 *
84 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
85 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
86 */
87#if __has_attribute(__assume_aligned__)
88# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
89#else
90# define __assume_aligned(a, ...)
91#endif
92
93/*
94 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
96 */
97#define __cold __attribute__((__cold__))
98
99/*
100 * Note the long name.
101 *
102 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
103 */
104#define __attribute_const__ __attribute__((__const__))
105
106/*
107 * Optional: only supported since gcc >= 9
108 * Optional: not supported by clang
109 * Optional: not supported by icc
110 *
111 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
112 */
113#if __has_attribute(__copy__)
114# define __copy(symbol) __attribute__((__copy__(symbol)))
115#else
116# define __copy(symbol)
117#endif
118
119/*
120 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
121 * attribute warnings entirely and for good") for more information.
122 *
123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
125 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
126 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
127 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
128 */
129#define __deprecated
130
131/*
132 * Optional: only supported since gcc >= 5.1
133 * Optional: not supported by clang
134 * Optional: not supported by icc
135 *
136 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
137 */
138#if __has_attribute(__designated_init__)
139# define __designated_init __attribute__((__designated_init__))
140#else
141# define __designated_init
142#endif
143
144/*
145 * Optional: not supported by clang
146 *
147 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
148 */
149#if __has_attribute(__externally_visible__)
150# define __visible __attribute__((__externally_visible__))
151#else
152# define __visible
153#endif
154
155/*
156 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
157 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
158 */
159#define __printf(a, b) __attribute__((__format__(printf, a, b)))
160#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
161
162/*
163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
164 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
165 */
166#define __gnu_inline __attribute__((__gnu_inline__))
167
168/*
169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
170 */
171#define __malloc __attribute__((__malloc__))
172
173/*
174 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
175 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
176 */
177#define __mode(x) __attribute__((__mode__(x)))
178
179/*
180 * Optional: not supported by clang
181 *
182 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
183 */
184#if __has_attribute(__noclone__)
185# define __noclone __attribute__((__noclone__))
186#else
187# define __noclone
188#endif
189
190/*
191 * Add the pseudo keyword 'fallthrough' so case statement blocks
192 * must end with any of these keywords:
193 * break;
194 * fallthrough;
195 * goto <label>;
196 * return [expression];
197 *
198 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
199 */
200#if __has_attribute(__fallthrough__)
201# define fallthrough __attribute__((__fallthrough__))
202#else
203# define fallthrough do {} while (0) /* fallthrough */
204#endif
205
206/*
207 * Note the missing underscores.
208 *
209 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
210 * clang: mentioned
211 */
212#define noinline __attribute__((__noinline__))
213
214/*
215 * Optional: only supported since gcc >= 8
216 * Optional: not supported by clang
217 * Optional: not supported by icc
218 *
219 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
220 */
221#if __has_attribute(__nonstring__)
222# define __nonstring __attribute__((__nonstring__))
223#else
224# define __nonstring
225#endif
226
227/*
228 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
229 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
230 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
231 */
232#define __noreturn __attribute__((__noreturn__))
233
234/*
235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
236 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
237 */
238#define __packed __attribute__((__packed__))
239
240/*
241 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
242 */
243#define __pure __attribute__((__pure__))
244
245/*
246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
247 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
248 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
249 */
250#define __section(S) __attribute__((__section__(#S)))
251
252/*
253 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
256 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
257 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
258 */
259#define __always_unused __attribute__((__unused__))
260#define __maybe_unused __attribute__((__unused__))
261
262/*
263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
264 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
265 */
266#define __used __attribute__((__used__))
267
268/*
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
271 */
272#define __weak __attribute__((__weak__))
273
274#endif /* __LINUX_COMPILER_ATTRIBUTES_H */