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___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___nonstring__ 0
37 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
38 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
39 # define __GCC4_has_attribute___fallthrough__ 0
43 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
45 #define __alias(symbol) __attribute__((__alias__(#symbol)))
48 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
52 #define __aligned(x) __attribute__((__aligned__(x)))
53 #define __aligned_largest __attribute__((__aligned__))
56 * Note: users of __always_inline currently do not write "inline" themselves,
57 * which seems to be required by gcc to apply the attribute according
58 * to its docs (and also "warning: always_inline function might not be
59 * inlinable [-Wattributes]" is emitted).
61 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
64 #define __always_inline inline __attribute__((__always_inline__))
67 * The second argument is optional (default 0), so we use a variadic macro
68 * to make the shorthand.
70 * Beware: Do not apply this to functions which may return
71 * ERR_PTRs. Also, it is probably unwise to apply it to functions
72 * returning extra information in the low bits (but in that case the
73 * compiler should see some alignment anyway, when the return value is
74 * massaged by 'flags = ptr & 3; ptr &= ~3;').
76 * Optional: only supported since gcc >= 4.9
77 * Optional: not supported by icc
79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
80 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
82 #if __has_attribute(__assume_aligned__)
83 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
85 # define __assume_aligned(a, ...)
89 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
92 #define __cold __attribute__((__cold__))
97 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
99 #define __attribute_const__ __attribute__((__const__))
102 * Optional: only supported since gcc >= 9
103 * Optional: not supported by clang
104 * Optional: not supported by icc
106 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
108 #if __has_attribute(__copy__)
109 # define __copy(symbol) __attribute__((__copy__(symbol)))
111 # define __copy(symbol)
115 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
116 * attribute warnings entirely and for good") for more information.
118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
122 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
127 * Optional: only supported since gcc >= 5.1
128 * Optional: not supported by clang
129 * Optional: not supported by icc
131 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
133 #if __has_attribute(__designated_init__)
134 # define __designated_init __attribute__((__designated_init__))
136 # define __designated_init
140 * Optional: not supported by clang
142 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
144 #if __has_attribute(__externally_visible__)
145 # define __visible __attribute__((__externally_visible__))
151 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
152 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
154 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
155 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
159 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
161 #define __gnu_inline __attribute__((__gnu_inline__))
164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
166 #define __malloc __attribute__((__malloc__))
169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
172 #define __mode(x) __attribute__((__mode__(x)))
175 * Optional: only supported since gcc >= 7
177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
178 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
180 #if __has_attribute(__no_caller_saved_registers__)
181 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
183 # define __no_caller_saved_registers
187 * Optional: not supported by clang
189 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
191 #if __has_attribute(__noclone__)
192 # define __noclone __attribute__((__noclone__))
198 * Add the pseudo keyword 'fallthrough' so case statement blocks
199 * must end with any of these keywords:
203 * return [expression];
205 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
207 #if __has_attribute(__fallthrough__)
208 # define fallthrough __attribute__((__fallthrough__))
210 # define fallthrough do {} while (0) /* fallthrough */
214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
215 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
217 # define __flatten __attribute__((flatten))
220 * Note the missing underscores.
222 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
225 #define noinline __attribute__((__noinline__))
228 * Optional: only supported since gcc >= 8
229 * Optional: not supported by clang
230 * Optional: not supported by icc
232 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
234 #if __has_attribute(__nonstring__)
235 # define __nonstring __attribute__((__nonstring__))
241 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
242 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
243 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
245 #define __noreturn __attribute__((__noreturn__))
248 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
249 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
251 #define __packed __attribute__((__packed__))
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
256 #define __pure __attribute__((__pure__))
259 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
260 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
261 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
263 #define __section(section) __attribute__((__section__(section)))
266 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
270 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
272 #define __always_unused __attribute__((__unused__))
273 #define __maybe_unused __attribute__((__unused__))
276 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
277 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
279 #define __used __attribute__((__used__))
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
283 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
285 #define __must_check __attribute__((__warn_unused_result__))
288 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
289 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
291 #define __weak __attribute__((__weak__))
293 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */