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___fallthrough__ 0
44 #endif
45
46 /*
47 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
48 */
49 #define __alias(symbol) __attribute__((__alias__(#symbol)))
50
51 /*
52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
53 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
54 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
55 */
56 #define __aligned(x) __attribute__((__aligned__(x)))
57 #define __aligned_largest __attribute__((__aligned__))
58
59 /*
60 * Note: users of __always_inline currently do not write "inline" themselves,
61 * which seems to be required by gcc to apply the attribute according
62 * to its docs (and also "warning: always_inline function might not be
63 * inlinable [-Wattributes]" is emitted).
64 *
65 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
66 * clang: mentioned
67 */
68 #define __always_inline inline __attribute__((__always_inline__))
69
70 /*
71 * The second argument is optional (default 0), so we use a variadic macro
72 * to make the shorthand.
73 *
74 * Beware: Do not apply this to functions which may return
75 * ERR_PTRs. Also, it is probably unwise to apply it to functions
76 * returning extra information in the low bits (but in that case the
77 * compiler should see some alignment anyway, when the return value is
78 * massaged by 'flags = ptr & 3; ptr &= ~3;').
79 *
80 * Optional: only supported since gcc >= 4.9
81 * Optional: not supported by icc
82 *
83 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
84 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
85 */
86 #if __has_attribute(__assume_aligned__)
87 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
88 #else
89 # define __assume_aligned(a, ...)
90 #endif
91
92 /*
93 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
94 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
95 */
96 #define __cold __attribute__((__cold__))
97
98 /*
99 * Note the long name.
100 *
101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
102 */
103 #define __attribute_const__ __attribute__((__const__))
104
105 /*
106 * Optional: only supported since gcc >= 9
107 * Optional: not supported by clang
108 * Optional: not supported by icc
109 *
110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
111 */
112 #if __has_attribute(__copy__)
113 # define __copy(symbol) __attribute__((__copy__(symbol)))
114 #else
115 # define __copy(symbol)
116 #endif
117
118 /*
119 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
120 * attribute warnings entirely and for good") for more information.
121 *
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
125 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
126 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
127 */
128 #define __deprecated
129
130 /*
131 * Optional: only supported since gcc >= 5.1
132 * Optional: not supported by clang
133 * Optional: not supported by icc
134 *
135 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
136 */
137 #if __has_attribute(__designated_init__)
138 # define __designated_init __attribute__((__designated_init__))
139 #else
140 # define __designated_init
141 #endif
142
143 /*
144 * Optional: not supported by clang
145 *
146 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
147 */
148 #if __has_attribute(__externally_visible__)
149 # define __visible __attribute__((__externally_visible__))
150 #else
151 # define __visible
152 #endif
153
154 /*
155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
156 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
157 */
158 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
159 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
160
161 /*
162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
163 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
164 */
165 #define __gnu_inline __attribute__((__gnu_inline__))
166
167 /*
168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
169 */
170 #define __malloc __attribute__((__malloc__))
171
172 /*
173 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
174 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
175 */
176 #define __mode(x) __attribute__((__mode__(x)))
177
178 /*
179 * Optional: not supported by clang
180 *
181 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
182 */
183 #if __has_attribute(__noclone__)
184 # define __noclone __attribute__((__noclone__))
185 #else
186 # define __noclone
187 #endif
188
189 /*
190 * Add the pseudo keyword 'fallthrough' so case statement blocks
191 * must end with any of these keywords:
192 * break;
193 * fallthrough;
194 * goto <label>;
195 * return [expression];
196 *
197 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
198 */
199 #if __has_attribute(__fallthrough__)
200 # define fallthrough __attribute__((__fallthrough__))
201 #else
202 # define fallthrough do {} while (0) /* fallthrough */
203 #endif
204
205 /*
206 * Note the missing underscores.
207 *
208 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
209 * clang: mentioned
210 */
211 #define noinline __attribute__((__noinline__))
212
213 /*
214 * Optional: only supported since gcc >= 8
215 * Optional: not supported by clang
216 * Optional: not supported by icc
217 *
218 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
219 */
220 #if __has_attribute(__nonstring__)
221 # define __nonstring __attribute__((__nonstring__))
222 #else
223 # define __nonstring
224 #endif
225
226 /*
227 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
228 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
229 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
230 */
231 #define __noreturn __attribute__((__noreturn__))
232
233 /*
234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
235 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
236 */
237 #define __packed __attribute__((__packed__))
238
239 /*
240 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
241 */
242 #define __pure __attribute__((__pure__))
243
244 /*
245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
247 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
248 */
249 #define __section(S) __attribute__((__section__(#S)))
250
251 /*
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
253 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
256 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
257 */
258 #define __always_unused __attribute__((__unused__))
259 #define __maybe_unused __attribute__((__unused__))
260
261 /*
262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
264 */
265 #define __used __attribute__((__used__))
266
267 /*
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
270 */
271 #define __weak __attribute__((__weak__))
272
273 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */