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. For GCC < 9.1, __alloc_size__ gets undefined
39 * in compiler-gcc.h, due to misbehaviors.
41 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
42 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
44 #define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
47 * Note: users of __always_inline currently do not write "inline" themselves,
48 * which seems to be required by gcc to apply the attribute according
49 * to its docs (and also "warning: always_inline function might not be
50 * inlinable [-Wattributes]" is emitted).
52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
55 #define __always_inline inline __attribute__((__always_inline__))
58 * The second argument is optional (default 0), so we use a variadic macro
59 * to make the shorthand.
61 * Beware: Do not apply this to functions which may return
62 * ERR_PTRs. Also, it is probably unwise to apply it to functions
63 * returning extra information in the low bits (but in that case the
64 * compiler should see some alignment anyway, when the return value is
65 * massaged by 'flags = ptr & 3; ptr &= ~3;').
67 * Optional: not supported by icc
69 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
70 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
72 #if __has_attribute(__assume_aligned__)
73 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
75 # define __assume_aligned(a, ...)
79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
80 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
82 #define __cold __attribute__((__cold__))
87 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
89 #define __attribute_const__ __attribute__((__const__))
92 * Optional: only supported since gcc >= 9
93 * Optional: not supported by clang
94 * Optional: not supported by icc
96 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
98 #if __has_attribute(__copy__)
99 # define __copy(symbol) __attribute__((__copy__(symbol)))
101 # define __copy(symbol)
105 * Optional: not supported by gcc
106 * Optional: only supported since clang >= 14.0
107 * Optional: not supported by icc
109 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
111 #if __has_attribute(__diagnose_as_builtin__)
112 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin)))
114 # define __diagnose_as(builtin...)
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: not supported by clang
131 * Optional: not supported by icc
133 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
135 #if __has_attribute(__designated_init__)
136 # define __designated_init __attribute__((__designated_init__))
138 # define __designated_init
142 * Optional: only supported since clang >= 14.0
144 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
146 #if __has_attribute(__error__)
147 # define __compiletime_error(msg) __attribute__((__error__(msg)))
149 # define __compiletime_error(msg)
153 * Optional: not supported by clang
155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
157 #if __has_attribute(__externally_visible__)
158 # define __visible __attribute__((__externally_visible__))
164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
165 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
167 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
168 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
172 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
174 #define __gnu_inline __attribute__((__gnu_inline__))
177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
178 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
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 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
258 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
259 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
261 #if __has_attribute(__no_profile_instrument_function__)
262 # define __no_profile __attribute__((__no_profile_instrument_function__))
264 # define __no_profile
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
269 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
270 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
272 #define __noreturn __attribute__((__noreturn__))
275 * Optional: not supported by gcc.
276 * Optional: not supported by icc.
278 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
280 #if __has_attribute(__overloadable__)
281 # define __overloadable __attribute__((__overloadable__))
283 # define __overloadable
287 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
288 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
290 #define __packed __attribute__((__packed__))
293 * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
295 * Optional: not supported by gcc.
296 * Optional: not supported by icc.
298 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
300 #if __has_attribute(__pass_dynamic_object_size__)
301 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type)))
303 # define __pass_dynamic_object_size(type)
305 #if __has_attribute(__pass_object_size__)
306 # define __pass_object_size(type) __attribute__((__pass_object_size__(type)))
308 # define __pass_object_size(type)
312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
314 #define __pure __attribute__((__pure__))
317 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
318 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
319 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
321 #define __section(section) __attribute__((__section__(section)))
324 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
325 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
326 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
327 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
328 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
330 #define __always_unused __attribute__((__unused__))
331 #define __maybe_unused __attribute__((__unused__))
334 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
335 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
337 #define __used __attribute__((__used__))
340 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
341 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
343 #define __must_check __attribute__((__warn_unused_result__))
346 * Optional: only supported since clang >= 14.0
348 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
350 #if __has_attribute(__warning__)
351 # define __compiletime_warning(msg) __attribute__((__warning__(msg)))
353 # define __compiletime_warning(msg)
357 * Optional: only supported since clang >= 14.0
359 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
361 * disable_sanitizer_instrumentation is not always similar to
362 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
363 * insert code into functions to prevent false positives. Unlike that,
364 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
365 * functions with the attribute.
367 #if __has_attribute(disable_sanitizer_instrumentation)
368 # define __disable_sanitizer_instrumentation \
369 __attribute__((disable_sanitizer_instrumentation))
371 # define __disable_sanitizer_instrumentation
375 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
376 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
378 #define __weak __attribute__((__weak__))
381 * Used by functions that use '__builtin_return_address'. These function
382 * don't want to be splited or made inline, which can make
383 * the '__builtin_return_address' get unexpected address.
385 #define __fix_address noinline __noclone
387 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */