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 gcc < 5, we implement __has_attribute 26 * by hand. 27 */ 28 #ifndef __has_attribute 29 # define __has_attribute(x) __GCC4_has_attribute_##x 30 # define __GCC4_has_attribute___assume_aligned__ 1 31 # define __GCC4_has_attribute___copy__ 0 32 # define __GCC4_has_attribute___designated_init__ 0 33 # define __GCC4_has_attribute___error__ 1 34 # define __GCC4_has_attribute___externally_visible__ 1 35 # define __GCC4_has_attribute___no_caller_saved_registers__ 0 36 # define __GCC4_has_attribute___noclone__ 1 37 # define __GCC4_has_attribute___no_profile_instrument_function__ 0 38 # define __GCC4_has_attribute___nonstring__ 0 39 # define __GCC4_has_attribute___no_sanitize_address__ 1 40 # define __GCC4_has_attribute___no_sanitize_undefined__ 1 41 # define __GCC4_has_attribute___no_sanitize_coverage__ 0 42 # define __GCC4_has_attribute___fallthrough__ 0 43 # define __GCC4_has_attribute___warning__ 1 44 #endif 45 46 /* 47 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 48 */ 49 #define __alias(symbol) __attribute__((__alias__(#symbol))) 50 51 /* 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 55 */ 56 #define __aligned(x) __attribute__((__aligned__(x))) 57 #define __aligned_largest __attribute__((__aligned__)) 58 59 /* 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). 64 * 65 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 66 * clang: mentioned 67 */ 68 #define __always_inline inline __attribute__((__always_inline__)) 69 70 /* 71 * The second argument is optional (default 0), so we use a variadic macro 72 * to make the shorthand. 73 * 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;'). 79 * 80 * Optional: only supported since gcc >= 4.9 81 * Optional: not supported by icc 82 * 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 85 */ 86 #if __has_attribute(__assume_aligned__) 87 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 88 #else 89 # define __assume_aligned(a, ...) 90 #endif 91 92 /* 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 95 */ 96 #define __cold __attribute__((__cold__)) 97 98 /* 99 * Note the long name. 100 * 101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 102 */ 103 #define __attribute_const__ __attribute__((__const__)) 104 105 /* 106 * Optional: only supported since gcc >= 9 107 * Optional: not supported by clang 108 * Optional: not supported by icc 109 * 110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 111 */ 112 #if __has_attribute(__copy__) 113 # define __copy(symbol) __attribute__((__copy__(symbol))) 114 #else 115 # define __copy(symbol) 116 #endif 117 118 /* 119 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 120 * attribute warnings entirely and for good") for more information. 121 * 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 127 */ 128 #define __deprecated 129 130 /* 131 * Optional: only supported since gcc >= 5.1 132 * Optional: not supported by clang 133 * Optional: not supported by icc 134 * 135 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 136 */ 137 #if __has_attribute(__designated_init__) 138 # define __designated_init __attribute__((__designated_init__)) 139 #else 140 # define __designated_init 141 #endif 142 143 /* 144 * Optional: only supported since clang >= 14.0 145 * 146 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 147 */ 148 #if __has_attribute(__error__) 149 # define __compiletime_error(msg) __attribute__((__error__(msg))) 150 #else 151 # define __compiletime_error(msg) 152 #endif 153 154 /* 155 * Optional: not supported by clang 156 * 157 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 158 */ 159 #if __has_attribute(__externally_visible__) 160 # define __visible __attribute__((__externally_visible__)) 161 #else 162 # define __visible 163 #endif 164 165 /* 166 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 167 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 168 */ 169 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 170 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 171 172 /* 173 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 174 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 175 */ 176 #define __gnu_inline __attribute__((__gnu_inline__)) 177 178 /* 179 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 180 */ 181 #define __malloc __attribute__((__malloc__)) 182 183 /* 184 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 185 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 186 */ 187 #define __mode(x) __attribute__((__mode__(x))) 188 189 /* 190 * Optional: only supported since gcc >= 7 191 * 192 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 193 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 194 */ 195 #if __has_attribute(__no_caller_saved_registers__) 196 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 197 #else 198 # define __no_caller_saved_registers 199 #endif 200 201 /* 202 * Optional: not supported by clang 203 * 204 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 205 */ 206 #if __has_attribute(__noclone__) 207 # define __noclone __attribute__((__noclone__)) 208 #else 209 # define __noclone 210 #endif 211 212 /* 213 * Add the pseudo keyword 'fallthrough' so case statement blocks 214 * must end with any of these keywords: 215 * break; 216 * fallthrough; 217 * continue; 218 * goto <label>; 219 * return [expression]; 220 * 221 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 222 */ 223 #if __has_attribute(__fallthrough__) 224 # define fallthrough __attribute__((__fallthrough__)) 225 #else 226 # define fallthrough do {} while (0) /* fallthrough */ 227 #endif 228 229 /* 230 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 231 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 232 */ 233 # define __flatten __attribute__((flatten)) 234 235 /* 236 * Note the missing underscores. 237 * 238 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 239 * clang: mentioned 240 */ 241 #define noinline __attribute__((__noinline__)) 242 243 /* 244 * Optional: only supported since gcc >= 8 245 * Optional: not supported by clang 246 * Optional: not supported by icc 247 * 248 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 249 */ 250 #if __has_attribute(__nonstring__) 251 # define __nonstring __attribute__((__nonstring__)) 252 #else 253 # define __nonstring 254 #endif 255 256 /* 257 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 258 * 259 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 260 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 261 */ 262 #if __has_attribute(__no_profile_instrument_function__) 263 # define __no_profile __attribute__((__no_profile_instrument_function__)) 264 #else 265 # define __no_profile 266 #endif 267 268 /* 269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 270 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 271 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 272 */ 273 #define __noreturn __attribute__((__noreturn__)) 274 275 /* 276 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 277 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 278 */ 279 #define __packed __attribute__((__packed__)) 280 281 /* 282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 283 */ 284 #define __pure __attribute__((__pure__)) 285 286 /* 287 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 288 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 289 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 290 */ 291 #define __section(section) __attribute__((__section__(section))) 292 293 /* 294 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 295 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 296 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 297 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 298 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 299 */ 300 #define __always_unused __attribute__((__unused__)) 301 #define __maybe_unused __attribute__((__unused__)) 302 303 /* 304 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 305 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 306 */ 307 #define __used __attribute__((__used__)) 308 309 /* 310 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 311 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 312 */ 313 #define __must_check __attribute__((__warn_unused_result__)) 314 315 /* 316 * Optional: only supported since clang >= 14.0 317 * 318 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 319 */ 320 #if __has_attribute(__warning__) 321 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 322 #else 323 # define __compiletime_warning(msg) 324 #endif 325 326 /* 327 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 328 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 329 */ 330 #define __weak __attribute__((__weak__)) 331 332 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 333