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___designated_init__ 0
38 # define __GCC4_has_attribute___externally_visible__ 1
39 # define __GCC4_has_attribute___noclone__ 1
40 # define __GCC4_has_attribute___nonstring__ 0
41 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
45 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
47 #define __alias(symbol) __attribute__((__alias__(#symbol)))
50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
54 #define __aligned(x) __attribute__((__aligned__(x)))
55 #define __aligned_largest __attribute__((__aligned__))
58 * Note: users of __always_inline currently do not write "inline" themselves,
59 * which seems to be required by gcc to apply the attribute according
60 * to its docs (and also "warning: always_inline function might not be
61 * inlinable [-Wattributes]" is emitted).
63 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
66 #define __always_inline inline __attribute__((__always_inline__))
69 * The second argument is optional (default 0), so we use a variadic macro
70 * to make the shorthand.
72 * Beware: Do not apply this to functions which may return
73 * ERR_PTRs. Also, it is probably unwise to apply it to functions
74 * returning extra information in the low bits (but in that case the
75 * compiler should see some alignment anyway, when the return value is
76 * massaged by 'flags = ptr & 3; ptr &= ~3;').
78 * Optional: only supported since gcc >= 4.9
79 * Optional: not supported by icc
81 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
82 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
84 #if __has_attribute(__assume_aligned__)
85 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
87 # define __assume_aligned(a, ...)
91 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
92 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
94 #define __cold __attribute__((__cold__))
99 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
101 #define __attribute_const__ __attribute__((__const__))
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: only supported since gcc >= 5.1
117 * Optional: not supported by clang
118 * Optional: not supported by icc
120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
122 #if __has_attribute(__designated_init__)
123 # define __designated_init __attribute__((__designated_init__))
125 # define __designated_init
129 * Optional: not supported by clang
131 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
133 #if __has_attribute(__externally_visible__)
134 # define __visible __attribute__((__externally_visible__))
140 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
141 * clang: https://clang.llvm.org/docs/AttributeReference.html#format
143 #define __printf(a, b) __attribute__((__format__(printf, a, b)))
144 #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
147 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
148 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
150 #define __gnu_inline __attribute__((__gnu_inline__))
153 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
155 #define __malloc __attribute__((__malloc__))
158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
159 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
161 #define __mode(x) __attribute__((__mode__(x)))
164 * Optional: not supported by clang
166 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
168 #if __has_attribute(__noclone__)
169 # define __noclone __attribute__((__noclone__))
175 * Note the missing underscores.
177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
180 #define noinline __attribute__((__noinline__))
183 * Optional: only supported since gcc >= 8
184 * Optional: not supported by clang
185 * Optional: not supported by icc
187 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
189 #if __has_attribute(__nonstring__)
190 # define __nonstring __attribute__((__nonstring__))
196 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
197 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
198 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
200 #define __noreturn __attribute__((__noreturn__))
203 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
204 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
206 #define __packed __attribute__((__packed__))
209 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
211 #define __pure __attribute__((__pure__))
214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
215 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
216 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
218 #define __section(S) __attribute__((__section__(#S)))
221 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
222 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
225 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
227 #define __always_unused __attribute__((__unused__))
228 #define __maybe_unused __attribute__((__unused__))
231 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
232 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
234 #define __used __attribute__((__used__))
237 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
238 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
240 #define __weak __attribute__((__weak__))
242 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */