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 4.6 <= gcc < 5, we implement __has_attribute
28 * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
29 * depending on the compiler used to build it; however, these attributes have
30 * no semantic effects for sparse, so it does not matter. Also note that,
31 * in order to avoid sparse's warnings, even the unsupported ones must be
34 #ifndef __has_attribute
35 # define __has_attribute(x) __GCC4_has_attribute_##x
36 # define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9)
37 # define __GCC4_has_attribute___copy__ 0
38 # define __GCC4_has_attribute___designated_init__ 0
39 # define __GCC4_has_attribute___externally_visible__ 1
40 # define __GCC4_has_attribute___noclone__ 1
41 # define __GCC4_has_attribute___nonstring__ 0
42 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
43 # define __GCC4_has_attribute___fallthrough__ 0
47 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
49 #define __alias(symbol) __attribute__((__alias__(#symbol)))
52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
53 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
54 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
56 #define __aligned(x) __attribute__((__aligned__(x)))
57 #define __aligned_largest __attribute__((__aligned__))
60 * Note: users of __always_inline currently do not write "inline" themselves,
61 * which seems to be required by gcc to apply the attribute according
62 * to its docs (and also "warning: always_inline function might not be
63 * inlinable [-Wattributes]" is emitted).
65 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
68 #define __always_inline inline __attribute__((__always_inline__))
71 * The second argument is optional (default 0), so we use a variadic macro
72 * to make the shorthand.
74 * Beware: Do not apply this to functions which may return
75 * ERR_PTRs. Also, it is probably unwise to apply it to functions
76 * returning extra information in the low bits (but in that case the
77 * compiler should see some alignment anyway, when the return value is
78 * massaged by 'flags = ptr & 3; ptr &= ~3;').
80 * Optional: only supported since gcc >= 4.9
81 * Optional: not supported by icc
83 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
84 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
86 #if __has_attribute(__assume_aligned__)
87 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
89 # define __assume_aligned(a, ...)
93 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
94 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
96 #define __cold __attribute__((__cold__))
101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
103 #define __attribute_const__ __attribute__((__const__))
106 * Optional: only supported since gcc >= 9
107 * Optional: not supported by clang
108 * Optional: not supported by icc
110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
112 #if __has_attribute(__copy__)
113 # define __copy(symbol) __attribute__((__copy__(symbol)))
115 # define __copy(symbol)
119 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
120 * attribute warnings entirely and for good") for more information.
122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
125 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
126 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
131 * Optional: only supported since gcc >= 5.1
132 * Optional: not supported by clang
133 * Optional: not supported by icc
135 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
137 #if __has_attribute(__designated_init__)
138 # define __designated_init __attribute__((__designated_init__))
140 # define __designated_init
144 * Optional: not supported by clang
146 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
148 #if __has_attribute(__externally_visible__)
149 # define __visible __attribute__((__externally_visible__))
155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
156 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
158 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
159 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
163 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
165 #define __gnu_inline __attribute__((__gnu_inline__))
168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
170 #define __malloc __attribute__((__malloc__))
173 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
174 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
176 #define __mode(x) __attribute__((__mode__(x)))
179 * Optional: not supported by clang
181 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
183 #if __has_attribute(__noclone__)
184 # define __noclone __attribute__((__noclone__))
190 * Add the pseudo keyword 'fallthrough' so case statement blocks
191 * must end with any of these keywords:
195 * return [expression];
197 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
199 #if __has_attribute(__fallthrough__)
200 # define fallthrough __attribute__((__fallthrough__))
202 # define fallthrough do {} while (0) /* fallthrough */
206 * Note the missing underscores.
208 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
211 #define noinline __attribute__((__noinline__))
214 * Optional: only supported since gcc >= 8
215 * Optional: not supported by clang
216 * Optional: not supported by icc
218 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
220 #if __has_attribute(__nonstring__)
221 # define __nonstring __attribute__((__nonstring__))
227 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
228 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
229 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
231 #define __noreturn __attribute__((__noreturn__))
234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
235 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
237 #define __packed __attribute__((__packed__))
240 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
242 #define __pure __attribute__((__pure__))
245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
247 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
249 #define __section(S) __attribute__((__section__(#S)))
252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
253 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
256 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
258 #define __always_unused __attribute__((__unused__))
259 #define __maybe_unused __attribute__((__unused__))
262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
265 #define __used __attribute__((__used__))
268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
271 #define __weak __attribute__((__weak__))
273 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */