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__ 1
31 # define __GCC4_has_attribute___copy__ 0
32 # define __GCC4_has_attribute___designated_init__ 0
33 # define __GCC4_has_attribute___externally_visible__ 1
34 # define __GCC4_has_attribute___no_caller_saved_registers__ 0
35 # define __GCC4_has_attribute___noclone__ 1
36 # define __GCC4_has_attribute___no_profile_instrument_function__ 0
37 # define __GCC4_has_attribute___nonstring__ 0
38 # define __GCC4_has_attribute___no_sanitize_address__ 1
39 # define __GCC4_has_attribute___no_sanitize_undefined__ 1
40 # define __GCC4_has_attribute___fallthrough__ 0
44 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
46 #define __alias(symbol) __attribute__((__alias__(#symbol)))
49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
53 #define __aligned(x) __attribute__((__aligned__(x)))
54 #define __aligned_largest __attribute__((__aligned__))
57 * Note: users of __always_inline currently do not write "inline" themselves,
58 * which seems to be required by gcc to apply the attribute according
59 * to its docs (and also "warning: always_inline function might not be
60 * inlinable [-Wattributes]" is emitted).
62 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
65 #define __always_inline inline __attribute__((__always_inline__))
68 * The second argument is optional (default 0), so we use a variadic macro
69 * to make the shorthand.
71 * Beware: Do not apply this to functions which may return
72 * ERR_PTRs. Also, it is probably unwise to apply it to functions
73 * returning extra information in the low bits (but in that case the
74 * compiler should see some alignment anyway, when the return value is
75 * massaged by 'flags = ptr & 3; ptr &= ~3;').
77 * Optional: only supported since gcc >= 4.9
78 * Optional: not supported by icc
80 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
81 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
83 #if __has_attribute(__assume_aligned__)
84 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
86 # define __assume_aligned(a, ...)
90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
91 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
93 #define __cold __attribute__((__cold__))
98 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
100 #define __attribute_const__ __attribute__((__const__))
103 * Optional: only supported since gcc >= 9
104 * Optional: not supported by clang
105 * Optional: not supported by icc
107 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
109 #if __has_attribute(__copy__)
110 # define __copy(symbol) __attribute__((__copy__(symbol)))
112 # define __copy(symbol)
116 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
117 * attribute warnings entirely and for good") for more information.
119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
123 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
128 * Optional: only supported since gcc >= 5.1
129 * Optional: not supported by clang
130 * Optional: not supported by icc
132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
134 #if __has_attribute(__designated_init__)
135 # define __designated_init __attribute__((__designated_init__))
137 # define __designated_init
141 * Optional: not supported by clang
143 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
145 #if __has_attribute(__externally_visible__)
146 # define __visible __attribute__((__externally_visible__))
152 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
153 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
155 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
156 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
159 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
160 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
162 #define __gnu_inline __attribute__((__gnu_inline__))
165 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
167 #define __malloc __attribute__((__malloc__))
170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
173 #define __mode(x) __attribute__((__mode__(x)))
176 * Optional: only supported since gcc >= 7
178 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
179 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
181 #if __has_attribute(__no_caller_saved_registers__)
182 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
184 # define __no_caller_saved_registers
188 * Optional: not supported by clang
190 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
192 #if __has_attribute(__noclone__)
193 # define __noclone __attribute__((__noclone__))
199 * Add the pseudo keyword 'fallthrough' so case statement blocks
200 * must end with any of these keywords:
205 * return [expression];
207 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
209 #if __has_attribute(__fallthrough__)
210 # define fallthrough __attribute__((__fallthrough__))
212 # define fallthrough do {} while (0) /* fallthrough */
216 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
217 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
219 # define __flatten __attribute__((flatten))
222 * Note the missing underscores.
224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
227 #define noinline __attribute__((__noinline__))
230 * Optional: only supported since gcc >= 8
231 * Optional: not supported by clang
232 * Optional: not supported by icc
234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
236 #if __has_attribute(__nonstring__)
237 # define __nonstring __attribute__((__nonstring__))
243 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
246 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
248 #if __has_attribute(__no_profile_instrument_function__)
249 # define __no_profile __attribute__((__no_profile_instrument_function__))
251 # define __no_profile
255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
256 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
257 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
259 #define __noreturn __attribute__((__noreturn__))
262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
263 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
265 #define __packed __attribute__((__packed__))
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
270 #define __pure __attribute__((__pure__))
273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
274 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
275 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
277 #define __section(section) __attribute__((__section__(section)))
280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
284 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
286 #define __always_unused __attribute__((__unused__))
287 #define __maybe_unused __attribute__((__unused__))
290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
291 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
293 #define __used __attribute__((__used__))
296 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
297 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
299 #define __must_check __attribute__((__warn_unused_result__))
302 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
305 #define __weak __attribute__((__weak__))
307 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */