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#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 * Optional: only supported since gcc >= 9
106 * Optional: not supported by clang
107 * Optional: not supported by icc
108 *
109 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
110 */
111#if __has_attribute(__copy__)
112# define __copy(symbol) __attribute__((__copy__(symbol)))
113#else
114# define __copy(symbol)
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: only supported since gcc >= 5.1
131 * Optional: not supported by clang
132 * Optional: not supported by icc
133 *
134 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
135 */
136#if __has_attribute(__designated_init__)
137# define __designated_init __attribute__((__designated_init__))
138#else
139# define __designated_init
140#endif
141
142/*
143 * Optional: not supported by clang
144 *
145 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
146 */
147#if __has_attribute(__externally_visible__)
148# define __visible __attribute__((__externally_visible__))
149#else
150# define __visible
151#endif
152
153/*
154 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
155 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
156 */
157#define __printf(a, b) __attribute__((__format__(printf, a, b)))
158#define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
159
160/*
161 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
162 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
163 */
164#define __gnu_inline __attribute__((__gnu_inline__))
165
166/*
167 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
168 */
169#define __malloc __attribute__((__malloc__))
170
171/*
172 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
173 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
174 */
175#define __mode(x) __attribute__((__mode__(x)))
176
177/*
178 * Optional: not supported by clang
179 *
180 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
181 */
182#if __has_attribute(__noclone__)
183# define __noclone __attribute__((__noclone__))
184#else
185# define __noclone
186#endif
187
188/*
189 * Note the missing underscores.
190 *
191 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
192 * clang: mentioned
193 */
194#define noinline __attribute__((__noinline__))
195
196/*
197 * Optional: only supported since gcc >= 8
198 * Optional: not supported by clang
199 * Optional: not supported by icc
200 *
201 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
202 */
203#if __has_attribute(__nonstring__)
204# define __nonstring __attribute__((__nonstring__))
205#else
206# define __nonstring
207#endif
208
209/*
210 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
211 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
212 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
213 */
214#define __noreturn __attribute__((__noreturn__))
215
216/*
217 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
218 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
219 */
220#define __packed __attribute__((__packed__))
221
222/*
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
224 */
225#define __pure __attribute__((__pure__))
226
227/*
228 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
229 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
230 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
231 */
232#define __section(S) __attribute__((__section__(#S)))
233
234/*
235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
236 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
237 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
238 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
239 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
240 */
241#define __always_unused __attribute__((__unused__))
242#define __maybe_unused __attribute__((__unused__))
243
244/*
245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
247 */
248#define __used __attribute__((__used__))
249
250/*
251 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
253 */
254#define __weak __attribute__((__weak__))
255
256#endif /* __LINUX_COMPILER_ATTRIBUTES_H */
257