1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_COMPILER_ATTRIBUTES_H 3 #define __LINUX_COMPILER_ATTRIBUTES_H 4 5 /* 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: ..."). 10 * 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). 16 * 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. 21 */ 22 23 /* 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 26 * by hand. 27 * 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 32 * defined to 0. 33 */ 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) 42 #endif 43 44 /* 45 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 46 */ 47 #define __alias(symbol) __attribute__((__alias__(#symbol))) 48 49 /* 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 53 */ 54 #define __aligned(x) __attribute__((__aligned__(x))) 55 #define __aligned_largest __attribute__((__aligned__)) 56 57 /* 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). 62 * 63 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 64 * clang: mentioned 65 */ 66 #define __always_inline inline __attribute__((__always_inline__)) 67 68 /* 69 * The second argument is optional (default 0), so we use a variadic macro 70 * to make the shorthand. 71 * 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;'). 77 * 78 * Optional: only supported since gcc >= 4.9 79 * Optional: not supported by icc 80 * 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 83 */ 84 #if __has_attribute(__assume_aligned__) 85 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 86 #else 87 # define __assume_aligned(a, ...) 88 #endif 89 90 /* 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 93 */ 94 #define __cold __attribute__((__cold__)) 95 96 /* 97 * Note the long name. 98 * 99 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 100 */ 101 #define __attribute_const__ __attribute__((__const__)) 102 103 /* 104 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 105 * attribute warnings entirely and for good") for more information. 106 * 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 112 */ 113 #define __deprecated 114 115 /* 116 * Optional: only supported since gcc >= 5.1 117 * Optional: not supported by clang 118 * Optional: not supported by icc 119 * 120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 121 */ 122 #if __has_attribute(__designated_init__) 123 # define __designated_init __attribute__((__designated_init__)) 124 #else 125 # define __designated_init 126 #endif 127 128 /* 129 * Optional: not supported by clang 130 * 131 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 132 */ 133 #if __has_attribute(__externally_visible__) 134 # define __visible __attribute__((__externally_visible__)) 135 #else 136 # define __visible 137 #endif 138 139 /* 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 142 */ 143 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 144 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 145 146 /* 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 149 */ 150 #define __gnu_inline __attribute__((__gnu_inline__)) 151 152 /* 153 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 154 */ 155 #define __malloc __attribute__((__malloc__)) 156 157 /* 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 160 */ 161 #define __mode(x) __attribute__((__mode__(x))) 162 163 /* 164 * Optional: not supported by clang 165 * 166 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 167 */ 168 #if __has_attribute(__noclone__) 169 # define __noclone __attribute__((__noclone__)) 170 #else 171 # define __noclone 172 #endif 173 174 /* 175 * Note the missing underscores. 176 * 177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 178 * clang: mentioned 179 */ 180 #define noinline __attribute__((__noinline__)) 181 182 /* 183 * Optional: only supported since gcc >= 8 184 * Optional: not supported by clang 185 * Optional: not supported by icc 186 * 187 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 188 */ 189 #if __has_attribute(__nonstring__) 190 # define __nonstring __attribute__((__nonstring__)) 191 #else 192 # define __nonstring 193 #endif 194 195 /* 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 199 */ 200 #define __noreturn __attribute__((__noreturn__)) 201 202 /* 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 205 */ 206 #define __packed __attribute__((__packed__)) 207 208 /* 209 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 210 */ 211 #define __pure __attribute__((__pure__)) 212 213 /* 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 217 */ 218 #define __section(S) __attribute__((__section__(#S))) 219 220 /* 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 226 */ 227 #define __always_unused __attribute__((__unused__)) 228 #define __maybe_unused __attribute__((__unused__)) 229 230 /* 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 233 */ 234 #define __used __attribute__((__used__)) 235 236 /* 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 239 */ 240 #define __weak __attribute__((__weak__)) 241 242 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 243