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 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 25 */ 26 #define __alias(symbol) __attribute__((__alias__(#symbol))) 27 28 /* 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 32 */ 33 #define __aligned(x) __attribute__((__aligned__(x))) 34 #define __aligned_largest __attribute__((__aligned__)) 35 36 /* 37 * Note: do not use this directly. Instead, use __alloc_size() since it is conditionally 38 * available and includes other attributes. 39 * 40 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute 41 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size 42 */ 43 #define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__))) 44 45 /* 46 * Note: users of __always_inline currently do not write "inline" themselves, 47 * which seems to be required by gcc to apply the attribute according 48 * to its docs (and also "warning: always_inline function might not be 49 * inlinable [-Wattributes]" is emitted). 50 * 51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 52 * clang: mentioned 53 */ 54 #define __always_inline inline __attribute__((__always_inline__)) 55 56 /* 57 * The second argument is optional (default 0), so we use a variadic macro 58 * to make the shorthand. 59 * 60 * Beware: Do not apply this to functions which may return 61 * ERR_PTRs. Also, it is probably unwise to apply it to functions 62 * returning extra information in the low bits (but in that case the 63 * compiler should see some alignment anyway, when the return value is 64 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 65 * 66 * Optional: not supported by icc 67 * 68 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 69 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 70 */ 71 #if __has_attribute(__assume_aligned__) 72 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 73 #else 74 # define __assume_aligned(a, ...) 75 #endif 76 77 /* 78 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 80 */ 81 #define __cold __attribute__((__cold__)) 82 83 /* 84 * Note the long name. 85 * 86 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 87 */ 88 #define __attribute_const__ __attribute__((__const__)) 89 90 /* 91 * Optional: only supported since gcc >= 9 92 * Optional: not supported by clang 93 * Optional: not supported by icc 94 * 95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 96 */ 97 #if __has_attribute(__copy__) 98 # define __copy(symbol) __attribute__((__copy__(symbol))) 99 #else 100 # define __copy(symbol) 101 #endif 102 103 /* 104 * Optional: not supported by gcc 105 * Optional: only supported since clang >= 14.0 106 * Optional: not supported by icc 107 * 108 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin 109 */ 110 #if __has_attribute(__diagnose_as_builtin__) 111 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin))) 112 #else 113 # define __diagnose_as(builtin...) 114 #endif 115 116 /* 117 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 118 * attribute warnings entirely and for good") for more information. 119 * 120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 124 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 125 */ 126 #define __deprecated 127 128 /* 129 * Optional: not supported by clang 130 * Optional: not supported by icc 131 * 132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 133 */ 134 #if __has_attribute(__designated_init__) 135 # define __designated_init __attribute__((__designated_init__)) 136 #else 137 # define __designated_init 138 #endif 139 140 /* 141 * Optional: only supported since clang >= 14.0 142 * 143 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 144 */ 145 #if __has_attribute(__error__) 146 # define __compiletime_error(msg) __attribute__((__error__(msg))) 147 #else 148 # define __compiletime_error(msg) 149 #endif 150 151 /* 152 * Optional: not supported by clang 153 * 154 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 155 */ 156 #if __has_attribute(__externally_visible__) 157 # define __visible __attribute__((__externally_visible__)) 158 #else 159 # define __visible 160 #endif 161 162 /* 163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 164 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 165 */ 166 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 167 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 168 169 /* 170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 171 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 172 */ 173 #define __gnu_inline __attribute__((__gnu_inline__)) 174 175 /* 176 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 177 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc 178 */ 179 #define __malloc __attribute__((__malloc__)) 180 181 /* 182 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 183 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 184 */ 185 #define __mode(x) __attribute__((__mode__(x))) 186 187 /* 188 * Optional: only supported since gcc >= 7 189 * 190 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 191 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 192 */ 193 #if __has_attribute(__no_caller_saved_registers__) 194 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 195 #else 196 # define __no_caller_saved_registers 197 #endif 198 199 /* 200 * Optional: not supported by clang 201 * 202 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 203 */ 204 #if __has_attribute(__noclone__) 205 # define __noclone __attribute__((__noclone__)) 206 #else 207 # define __noclone 208 #endif 209 210 /* 211 * Add the pseudo keyword 'fallthrough' so case statement blocks 212 * must end with any of these keywords: 213 * break; 214 * fallthrough; 215 * continue; 216 * goto <label>; 217 * return [expression]; 218 * 219 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 220 */ 221 #if __has_attribute(__fallthrough__) 222 # define fallthrough __attribute__((__fallthrough__)) 223 #else 224 # define fallthrough do {} while (0) /* fallthrough */ 225 #endif 226 227 /* 228 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 229 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 230 */ 231 # define __flatten __attribute__((flatten)) 232 233 /* 234 * Note the missing underscores. 235 * 236 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 237 * clang: mentioned 238 */ 239 #define noinline __attribute__((__noinline__)) 240 241 /* 242 * Optional: only supported since gcc >= 8 243 * Optional: not supported by clang 244 * Optional: not supported by icc 245 * 246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 247 */ 248 #if __has_attribute(__nonstring__) 249 # define __nonstring __attribute__((__nonstring__)) 250 #else 251 # define __nonstring 252 #endif 253 254 /* 255 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 256 * 257 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 258 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 259 */ 260 #if __has_attribute(__no_profile_instrument_function__) 261 # define __no_profile __attribute__((__no_profile_instrument_function__)) 262 #else 263 # define __no_profile 264 #endif 265 266 /* 267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 268 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 269 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 270 */ 271 #define __noreturn __attribute__((__noreturn__)) 272 273 /* 274 * Optional: not supported by gcc. 275 * Optional: not supported by icc. 276 * 277 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable 278 */ 279 #if __has_attribute(__overloadable__) 280 # define __overloadable __attribute__((__overloadable__)) 281 #else 282 # define __overloadable 283 #endif 284 285 /* 286 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 287 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 288 */ 289 #define __packed __attribute__((__packed__)) 290 291 /* 292 * Note: the "type" argument should match any __builtin_object_size(p, type) usage. 293 * 294 * Optional: not supported by gcc. 295 * Optional: not supported by icc. 296 * 297 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size 298 */ 299 #if __has_attribute(__pass_object_size__) 300 # define __pass_object_size(type) __attribute__((__pass_object_size__(type))) 301 #else 302 # define __pass_object_size(type) 303 #endif 304 305 /* 306 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 307 */ 308 #define __pure __attribute__((__pure__)) 309 310 /* 311 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 313 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 314 */ 315 #define __section(section) __attribute__((__section__(section))) 316 317 /* 318 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 319 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 320 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 321 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 322 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 323 */ 324 #define __always_unused __attribute__((__unused__)) 325 #define __maybe_unused __attribute__((__unused__)) 326 327 /* 328 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 329 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 330 */ 331 #define __used __attribute__((__used__)) 332 333 /* 334 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 335 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 336 */ 337 #define __must_check __attribute__((__warn_unused_result__)) 338 339 /* 340 * Optional: only supported since clang >= 14.0 341 * 342 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 343 */ 344 #if __has_attribute(__warning__) 345 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 346 #else 347 # define __compiletime_warning(msg) 348 #endif 349 350 /* 351 * Optional: only supported since clang >= 14.0 352 * 353 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation 354 * 355 * disable_sanitizer_instrumentation is not always similar to 356 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers 357 * insert code into functions to prevent false positives. Unlike that, 358 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to 359 * functions with the attribute. 360 */ 361 #if __has_attribute(disable_sanitizer_instrumentation) 362 # define __disable_sanitizer_instrumentation \ 363 __attribute__((disable_sanitizer_instrumentation)) 364 #else 365 # define __disable_sanitizer_instrumentation 366 #endif 367 368 /* 369 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 370 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 371 */ 372 #define __weak __attribute__((__weak__)) 373 374 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 375