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 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
68 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
70 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
75 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
77 #define __attribute_const__ __attribute__((__const__))
80 * Optional: only supported since gcc >= 9
81 * Optional: not supported by clang
83 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
85 #if __has_attribute(__copy__)
86 # define __copy(symbol) __attribute__((__copy__(symbol)))
88 # define __copy(symbol)
92 * Optional: not supported by gcc
93 * Optional: only supported since clang >= 14.0
95 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
97 #if __has_attribute(__diagnose_as_builtin__)
98 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin)))
100 # define __diagnose_as(builtin...)
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
118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
120 #if __has_attribute(__designated_init__)
121 # define __designated_init __attribute__((__designated_init__))
123 # define __designated_init
127 * Optional: only supported since clang >= 14.0
129 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
131 #if __has_attribute(__error__)
132 # define __compiletime_error(msg) __attribute__((__error__(msg)))
134 # define __compiletime_error(msg)
138 * Optional: not supported by clang
140 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
142 #if __has_attribute(__externally_visible__)
143 # define __visible __attribute__((__externally_visible__))
149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
150 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
152 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
153 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
156 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
157 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
159 #define __gnu_inline __attribute__((__gnu_inline__))
162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
163 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
165 #define __malloc __attribute__((__malloc__))
168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
171 #define __mode(x) __attribute__((__mode__(x)))
174 * Optional: only supported since gcc >= 7
176 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
177 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
179 #if __has_attribute(__no_caller_saved_registers__)
180 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
182 # define __no_caller_saved_registers
186 * Optional: not supported by clang
188 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
190 #if __has_attribute(__noclone__)
191 # define __noclone __attribute__((__noclone__))
197 * Add the pseudo keyword 'fallthrough' so case statement blocks
198 * 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
231 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
233 #if __has_attribute(__nonstring__)
234 # define __nonstring __attribute__((__nonstring__))
240 * Optional: only supported since GCC >= 7.1, clang >= 13.0.
242 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
243 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
245 #if __has_attribute(__no_profile_instrument_function__)
246 # define __no_profile __attribute__((__no_profile_instrument_function__))
248 # define __no_profile
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
253 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
254 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
256 #define __noreturn __attribute__((__noreturn__))
259 * Optional: not supported by gcc.
261 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
263 #if __has_attribute(__overloadable__)
264 # define __overloadable __attribute__((__overloadable__))
266 # define __overloadable
270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
271 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
273 #define __packed __attribute__((__packed__))
276 * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
278 * Optional: not supported by gcc.
280 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
282 #if __has_attribute(__pass_dynamic_object_size__)
283 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type)))
285 # define __pass_dynamic_object_size(type)
287 #if __has_attribute(__pass_object_size__)
288 # define __pass_object_size(type) __attribute__((__pass_object_size__(type)))
290 # define __pass_object_size(type)
294 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
296 #define __pure __attribute__((__pure__))
299 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
300 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
301 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
303 #define __section(section) __attribute__((__section__(section)))
306 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
307 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
308 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
309 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
310 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
312 #define __always_unused __attribute__((__unused__))
313 #define __maybe_unused __attribute__((__unused__))
316 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
317 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
319 #define __used __attribute__((__used__))
322 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
323 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
325 #define __must_check __attribute__((__warn_unused_result__))
328 * Optional: only supported since clang >= 14.0
330 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
332 #if __has_attribute(__warning__)
333 # define __compiletime_warning(msg) __attribute__((__warning__(msg)))
335 # define __compiletime_warning(msg)
339 * Optional: only supported since clang >= 14.0
341 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
343 * disable_sanitizer_instrumentation is not always similar to
344 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
345 * insert code into functions to prevent false positives. Unlike that,
346 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
347 * functions with the attribute.
349 #if __has_attribute(disable_sanitizer_instrumentation)
350 # define __disable_sanitizer_instrumentation \
351 __attribute__((disable_sanitizer_instrumentation))
353 # define __disable_sanitizer_instrumentation
357 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
358 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
360 #define __weak __attribute__((__weak__))
363 * Used by functions that use '__builtin_return_address'. These function
364 * don't want to be splited or made inline, which can make
365 * the '__builtin_return_address' get unexpected address.
367 #define __fix_address noinline __noclone
369 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */