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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___designated_init__ 0
38# define __GCC4_has_attribute___externally_visible__ 1
39# define __GCC4_has_attribute___noclone__ 1
40# define __GCC4_has_attribute___optimize__ 1
41# define __GCC4_has_attribute___nonstring__ 0
42# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
43#endif
44
45/*
46 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
47 */
48#define __alias(symbol) __attribute__((__alias__(#symbol)))
49
50/*
51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
53 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
54 */
55#define __aligned(x) __attribute__((__aligned__(x)))
56#define __aligned_largest __attribute__((__aligned__))
57
58/*
59 * Note: users of __always_inline currently do not write "inline" themselves,
60 * which seems to be required by gcc to apply the attribute according
61 * to its docs (and also "warning: always_inline function might not be
62 * inlinable [-Wattributes]" is emitted).
63 *
64 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
65 * clang: mentioned
66 */
67#define __always_inline inline __attribute__((__always_inline__))
68
69/*
70 * The second argument is optional (default 0), so we use a variadic macro
71 * to make the shorthand.
72 *
73 * Beware: Do not apply this to functions which may return
74 * ERR_PTRs. Also, it is probably unwise to apply it to functions
75 * returning extra information in the low bits (but in that case the
76 * compiler should see some alignment anyway, when the return value is
77 * massaged by 'flags = ptr & 3; ptr &= ~3;').
78 *
79 * Optional: only supported since gcc >= 4.9
80 * Optional: not supported by icc
81 *
82 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
83 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
84 */
85#if __has_attribute(__assume_aligned__)
86# define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
87#else
88# define __assume_aligned(a, ...)
89#endif
90
91/*
92 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
93 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
94 */
95#define __cold __attribute__((__cold__))
96
97/*
98 * Note the long name.
99 *
100 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
101 */
102#define __attribute_const__ __attribute__((__const__))
103
104/*
105 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
106 * attribute warnings entirely and for good") for more information.
107 *
108 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
109 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
111 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
112 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
113 */
114#define __deprecated
115
116/*
117 * Optional: only supported since gcc >= 5.1
118 * Optional: not supported by clang
119 * Optional: not supported by icc
120 *
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
122 */
123#if __has_attribute(__designated_init__)
124# define __designated_init __attribute__((__designated_init__))
125#else
126# define __designated_init
127#endif
128
129/*
130 * Optional: not supported by clang
131 *
132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
133 */
134#if __has_attribute(__externally_visible__)
135# define __visible __attribute__((__externally_visible__))
136#else
137# define __visible
138#endif
139
140/*
141 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
142 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
143 */
144#define __printf(a, b) __attribute__((__format__(printf, a, b)))
145#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
146
147/*
148 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
149 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
150 */
151#define __gnu_inline __attribute__((__gnu_inline__))
152
153/*
154 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
155 */
156#define __malloc __attribute__((__malloc__))
157
158/*
159 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
160 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
161 */
162#define __mode(x) __attribute__((__mode__(x)))
163
164/*
165 * Optional: not supported by clang
166 * Note: icc does not recognize gcc's no-tracer
167 *
168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-optimize-function-attribute
170 */
171#if __has_attribute(__noclone__)
172# if __has_attribute(__optimize__)
173# define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
174# else
175# define __noclone __attribute__((__noclone__))
176# endif
177#else
178# define __noclone
179#endif
180
181/*
182 * Note the missing underscores.
183 *
184 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
185 * clang: mentioned
186 */
187#define noinline __attribute__((__noinline__))
188
189/*
190 * Optional: only supported since gcc >= 8
191 * Optional: not supported by clang
192 * Optional: not supported by icc
193 *
194 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
195 */
196#if __has_attribute(__nonstring__)
197# define __nonstring __attribute__((__nonstring__))
198#else
199# define __nonstring
200#endif
201
202/*
203 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
204 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
205 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
206 */
207#define __noreturn __attribute__((__noreturn__))
208
209/*
210 * Optional: only supported since gcc >= 4.8
211 * Optional: not supported by icc
212 *
213 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
214 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
215 */
216#if __has_attribute(__no_sanitize_address__)
217# define __no_sanitize_address __attribute__((__no_sanitize_address__))
218#else
219# define __no_sanitize_address
220#endif
221
222/*
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
224 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
225 */
226#define __packed __attribute__((__packed__))
227
228/*
229 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
230 */
231#define __pure __attribute__((__pure__))
232
233/*
234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
236 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
237 */
238#define __section(S) __attribute__((__section__(#S)))
239
240/*
241 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
242 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
243 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
244 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
245 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
246 */
247#define __always_unused __attribute__((__unused__))
248#define __maybe_unused __attribute__((__unused__))
249
250/*
251 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
253 */
254#define __used __attribute__((__used__))
255
256/*
257 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
258 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
259 */
260#define __weak __attribute__((__weak__))
261
262#endif /* __LINUX_COMPILER_ATTRIBUTES_H */