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, ...)
81 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
83 #define __attribute_const__ __attribute__((__const__))
86 * Optional: only supported since gcc >= 9
87 * Optional: not supported by clang
88 * Optional: not supported by icc
90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
92 #if __has_attribute(__copy__)
93 # define __copy(symbol) __attribute__((__copy__(symbol)))
95 # define __copy(symbol)
99 * Optional: not supported by gcc
100 * Optional: only supported since clang >= 14.0
101 * Optional: not supported by icc
103 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
105 #if __has_attribute(__diagnose_as_builtin__)
106 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin)))
108 # define __diagnose_as(builtin...)
112 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
113 * attribute warnings entirely and for good") for more information.
115 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
116 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
117 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
119 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
124 * Optional: not supported by clang
125 * Optional: not supported by icc
127 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
129 #if __has_attribute(__designated_init__)
130 # define __designated_init __attribute__((__designated_init__))
132 # define __designated_init
136 * Optional: only supported since clang >= 14.0
138 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
140 #if __has_attribute(__error__)
141 # define __compiletime_error(msg) __attribute__((__error__(msg)))
143 # define __compiletime_error(msg)
147 * Optional: not supported by clang
149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
151 #if __has_attribute(__externally_visible__)
152 # define __visible __attribute__((__externally_visible__))
158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
159 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
161 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
162 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
165 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
166 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
168 #define __gnu_inline __attribute__((__gnu_inline__))
171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
172 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
174 #define __malloc __attribute__((__malloc__))
177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
178 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
180 #define __mode(x) __attribute__((__mode__(x)))
183 * Optional: only supported since gcc >= 7
185 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
186 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
188 #if __has_attribute(__no_caller_saved_registers__)
189 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
191 # define __no_caller_saved_registers
195 * Optional: not supported by clang
197 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
199 #if __has_attribute(__noclone__)
200 # define __noclone __attribute__((__noclone__))
206 * Add the pseudo keyword 'fallthrough' so case statement blocks
207 * must end with any of these keywords:
212 * return [expression];
214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
216 #if __has_attribute(__fallthrough__)
217 # define fallthrough __attribute__((__fallthrough__))
219 # define fallthrough do {} while (0) /* fallthrough */
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
224 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
226 # define __flatten __attribute__((flatten))
229 * Note the missing underscores.
231 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
234 #define noinline __attribute__((__noinline__))
237 * Optional: only supported since gcc >= 8
238 * Optional: not supported by clang
239 * Optional: not supported by icc
241 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
243 #if __has_attribute(__nonstring__)
244 # define __nonstring __attribute__((__nonstring__))
250 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
253 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
255 #if __has_attribute(__no_profile_instrument_function__)
256 # define __no_profile __attribute__((__no_profile_instrument_function__))
258 # define __no_profile
262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
263 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
264 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
266 #define __noreturn __attribute__((__noreturn__))
269 * Optional: not supported by gcc.
270 * Optional: not supported by icc.
272 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
274 #if __has_attribute(__overloadable__)
275 # define __overloadable __attribute__((__overloadable__))
277 # define __overloadable
281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
282 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
284 #define __packed __attribute__((__packed__))
287 * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
289 * Optional: not supported by gcc.
290 * Optional: not supported by icc.
292 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
294 #if __has_attribute(__pass_dynamic_object_size__)
295 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type)))
297 # define __pass_dynamic_object_size(type)
299 #if __has_attribute(__pass_object_size__)
300 # define __pass_object_size(type) __attribute__((__pass_object_size__(type)))
302 # define __pass_object_size(type)
306 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
308 #define __pure __attribute__((__pure__))
311 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
313 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
315 #define __section(section) __attribute__((__section__(section)))
318 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
319 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
320 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
321 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
322 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
324 #define __always_unused __attribute__((__unused__))
325 #define __maybe_unused __attribute__((__unused__))
328 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
329 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
331 #define __used __attribute__((__used__))
334 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
335 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
337 #define __must_check __attribute__((__warn_unused_result__))
340 * Optional: only supported since clang >= 14.0
342 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
344 #if __has_attribute(__warning__)
345 # define __compiletime_warning(msg) __attribute__((__warning__(msg)))
347 # define __compiletime_warning(msg)
351 * Optional: only supported since clang >= 14.0
353 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
355 * disable_sanitizer_instrumentation is not always similar to
356 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
357 * insert code into functions to prevent false positives. Unlike that,
358 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
359 * functions with the attribute.
361 #if __has_attribute(disable_sanitizer_instrumentation)
362 # define __disable_sanitizer_instrumentation \
363 __attribute__((disable_sanitizer_instrumentation))
365 # define __disable_sanitizer_instrumentation
369 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
370 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
372 #define __weak __attribute__((__weak__))
375 * Used by functions that use '__builtin_return_address'. These function
376 * don't want to be splited or made inline, which can make
377 * the '__builtin_return_address' get unexpected address.
379 #define __fix_address noinline __noclone
381 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */