1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_COMPILER_ATTRIBUTES_H
3 #define __LINUX_COMPILER_ATTRIBUTES_H
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: ...").
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).
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.
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
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___error__ 1
34 # define __GCC4_has_attribute___externally_visible__ 1
35 # define __GCC4_has_attribute___no_caller_saved_registers__ 0
36 # define __GCC4_has_attribute___noclone__ 1
37 # define __GCC4_has_attribute___nonstring__ 0
38 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
39 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
40 # define __GCC4_has_attribute___no_sanitize_coverage__ 0
41 # define __GCC4_has_attribute___fallthrough__ 0
42 # define __GCC4_has_attribute___warning__ 1
46 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
48 #define __alias(symbol) __attribute__((__alias__(#symbol)))
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
55 #define __aligned(x) __attribute__((__aligned__(x)))
56 #define __aligned_largest __attribute__((__aligned__))
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).
64 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
67 #define __always_inline inline __attribute__((__always_inline__))
70 * The second argument is optional (default 0), so we use a variadic macro
71 * to make the shorthand.
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;').
79 * Optional: only supported since gcc >= 4.9
80 * Optional: not supported by icc
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
85 #if __has_attribute(__assume_aligned__)
86 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
88 # define __assume_aligned(a, ...)
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
95 #define __cold __attribute__((__cold__))
100 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
102 #define __attribute_const__ __attribute__((__const__))
105 * Optional: only supported since gcc >= 9
106 * Optional: not supported by clang
107 * Optional: not supported by icc
109 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
111 #if __has_attribute(__copy__)
112 # define __copy(symbol) __attribute__((__copy__(symbol)))
114 # define __copy(symbol)
118 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
119 * attribute warnings entirely and for good") for more information.
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
130 * Optional: only supported since gcc >= 5.1
131 * Optional: not supported by clang
132 * Optional: not supported by icc
134 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
136 #if __has_attribute(__designated_init__)
137 # define __designated_init __attribute__((__designated_init__))
139 # define __designated_init
143 * Optional: only supported since clang >= 14.0
145 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
147 #if __has_attribute(__error__)
148 # define __compiletime_error(msg) __attribute__((__error__(msg)))
150 # define __compiletime_error(msg)
154 * Optional: not supported by clang
156 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
158 #if __has_attribute(__externally_visible__)
159 # define __visible __attribute__((__externally_visible__))
165 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
166 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
168 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
169 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
172 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
173 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
175 #define __gnu_inline __attribute__((__gnu_inline__))
178 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
180 #define __malloc __attribute__((__malloc__))
183 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
184 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
186 #define __mode(x) __attribute__((__mode__(x)))
189 * Optional: only supported since gcc >= 7
191 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
192 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
194 #if __has_attribute(__no_caller_saved_registers__)
195 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
197 # define __no_caller_saved_registers
201 * Optional: not supported by clang
203 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
205 #if __has_attribute(__noclone__)
206 # define __noclone __attribute__((__noclone__))
212 * Add the pseudo keyword 'fallthrough' so case statement blocks
213 * must end with any of these keywords:
218 * return [expression];
220 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
222 #if __has_attribute(__fallthrough__)
223 # define fallthrough __attribute__((__fallthrough__))
225 # define fallthrough do {} while (0) /* fallthrough */
229 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
230 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
232 # define __flatten __attribute__((flatten))
235 * Note the missing underscores.
237 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
240 #define noinline __attribute__((__noinline__))
243 * Optional: only supported since gcc >= 8
244 * Optional: not supported by clang
245 * Optional: not supported by icc
247 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
249 #if __has_attribute(__nonstring__)
250 # define __nonstring __attribute__((__nonstring__))
256 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
257 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
258 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
260 #define __noreturn __attribute__((__noreturn__))
263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
264 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
266 #define __packed __attribute__((__packed__))
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
271 #define __pure __attribute__((__pure__))
274 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
275 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
276 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
278 #define __section(section) __attribute__((__section__(section)))
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
284 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
285 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
287 #define __always_unused __attribute__((__unused__))
288 #define __maybe_unused __attribute__((__unused__))
291 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
292 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
294 #define __used __attribute__((__used__))
297 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
298 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
300 #define __must_check __attribute__((__warn_unused_result__))
303 * Optional: only supported since clang >= 14.0
305 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
307 #if __has_attribute(__warning__)
308 # define __compiletime_warning(msg) __attribute__((__warning__(msg)))
310 # define __compiletime_warning(msg)
314 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
315 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
317 #define __weak __attribute__((__weak__))
319 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */