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 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
26 #define __alias(symbol) __attribute__((__alias__(#symbol)))
29 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
30 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
31 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
33 #define __aligned(x) __attribute__((__aligned__(x)))
34 #define __aligned_largest __attribute__((__aligned__))
37 * Note: do not use this directly. Instead, use __alloc_size() since it is conditionally
38 * available and includes other attributes.
40 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
41 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
43 #define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
46 * Note: users of __always_inline currently do not write "inline" themselves,
47 * which seems to be required by gcc to apply the attribute according
48 * to its docs (and also "warning: always_inline function might not be
49 * inlinable [-Wattributes]" is emitted).
51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
54 #define __always_inline inline __attribute__((__always_inline__))
57 * The second argument is optional (default 0), so we use a variadic macro
58 * to make the shorthand.
60 * Beware: Do not apply this to functions which may return
61 * ERR_PTRs. Also, it is probably unwise to apply it to functions
62 * returning extra information in the low bits (but in that case the
63 * compiler should see some alignment anyway, when the return value is
64 * massaged by 'flags = ptr & 3; ptr &= ~3;').
66 * Optional: not supported by icc
68 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
69 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
71 #if __has_attribute(__assume_aligned__)
72 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
74 # define __assume_aligned(a, ...)
78 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
81 #define __cold __attribute__((__cold__))
86 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
88 #define __attribute_const__ __attribute__((__const__))
91 * Optional: only supported since gcc >= 9
92 * Optional: not supported by clang
93 * Optional: not supported by icc
95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
97 #if __has_attribute(__copy__)
98 # define __copy(symbol) __attribute__((__copy__(symbol)))
100 # define __copy(symbol)
104 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
105 * attribute warnings entirely and for good") for more information.
107 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
108 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
109 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
111 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
116 * Optional: not supported by clang
117 * Optional: not supported by icc
119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
121 #if __has_attribute(__designated_init__)
122 # define __designated_init __attribute__((__designated_init__))
124 # define __designated_init
128 * Optional: only supported since clang >= 14.0
130 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
132 #if __has_attribute(__error__)
133 # define __compiletime_error(msg) __attribute__((__error__(msg)))
135 # define __compiletime_error(msg)
139 * Optional: not supported by clang
141 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
143 #if __has_attribute(__externally_visible__)
144 # define __visible __attribute__((__externally_visible__))
150 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
151 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
153 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
154 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
157 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
158 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
160 #define __gnu_inline __attribute__((__gnu_inline__))
163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
164 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
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:
204 * return [expression];
206 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
208 #if __has_attribute(__fallthrough__)
209 # define fallthrough __attribute__((__fallthrough__))
211 # define fallthrough do {} while (0) /* fallthrough */
215 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
216 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
218 # define __flatten __attribute__((flatten))
221 * Note the missing underscores.
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
226 #define noinline __attribute__((__noinline__))
229 * Optional: only supported since gcc >= 8
230 * Optional: not supported by clang
231 * Optional: not supported by icc
233 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
235 #if __has_attribute(__nonstring__)
236 # define __nonstring __attribute__((__nonstring__))
242 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
244 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
245 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
247 #if __has_attribute(__no_profile_instrument_function__)
248 # define __no_profile __attribute__((__no_profile_instrument_function__))
250 # define __no_profile
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
255 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
256 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
258 #define __noreturn __attribute__((__noreturn__))
261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
262 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
264 #define __packed __attribute__((__packed__))
267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
269 #define __pure __attribute__((__pure__))
272 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
274 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
276 #define __section(section) __attribute__((__section__(section)))
279 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
283 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
285 #define __always_unused __attribute__((__unused__))
286 #define __maybe_unused __attribute__((__unused__))
289 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
292 #define __used __attribute__((__used__))
295 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
296 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
298 #define __must_check __attribute__((__warn_unused_result__))
301 * Optional: only supported since clang >= 14.0
303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
305 #if __has_attribute(__warning__)
306 # define __compiletime_warning(msg) __attribute__((__warning__(msg)))
308 # define __compiletime_warning(msg)
312 * Optional: only supported since clang >= 14.0
314 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
316 * disable_sanitizer_instrumentation is not always similar to
317 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
318 * insert code into functions to prevent false positives. Unlike that,
319 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
320 * functions with the attribute.
322 #if __has_attribute(disable_sanitizer_instrumentation)
323 # define __disable_sanitizer_instrumentation \
324 __attribute__((disable_sanitizer_instrumentation))
326 # define __disable_sanitizer_instrumentation
330 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
331 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
333 #define __weak __attribute__((__weak__))
335 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */