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. For GCC < 9.1, __alloc_size__ gets undefined 39 * in compiler-gcc.h, due to misbehaviors. 40 * 41 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute 42 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size 43 */ 44 #define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__))) 45 46 /* 47 * Note: users of __always_inline currently do not write "inline" themselves, 48 * which seems to be required by gcc to apply the attribute according 49 * to its docs (and also "warning: always_inline function might not be 50 * inlinable [-Wattributes]" is emitted). 51 * 52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 53 * clang: mentioned 54 */ 55 #define __always_inline inline __attribute__((__always_inline__)) 56 57 /* 58 * The second argument is optional (default 0), so we use a variadic macro 59 * to make the shorthand. 60 * 61 * Beware: Do not apply this to functions which may return 62 * ERR_PTRs. Also, it is probably unwise to apply it to functions 63 * returning extra information in the low bits (but in that case the 64 * compiler should see some alignment anyway, when the return value is 65 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 66 * 67 * Optional: not supported by icc 68 * 69 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 70 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 71 */ 72 #if __has_attribute(__assume_aligned__) 73 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 74 #else 75 # define __assume_aligned(a, ...) 76 #endif 77 78 /* 79 * Note the long name. 80 * 81 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 82 */ 83 #define __attribute_const__ __attribute__((__const__)) 84 85 /* 86 * Optional: only supported since gcc >= 9 87 * Optional: not supported by clang 88 * Optional: not supported by icc 89 * 90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 91 */ 92 #if __has_attribute(__copy__) 93 # define __copy(symbol) __attribute__((__copy__(symbol))) 94 #else 95 # define __copy(symbol) 96 #endif 97 98 /* 99 * Optional: not supported by gcc 100 * Optional: only supported since clang >= 14.0 101 * Optional: not supported by icc 102 * 103 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin 104 */ 105 #if __has_attribute(__diagnose_as_builtin__) 106 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin))) 107 #else 108 # define __diagnose_as(builtin...) 109 #endif 110 111 /* 112 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 113 * attribute warnings entirely and for good") for more information. 114 * 115 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 116 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 117 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 119 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 120 */ 121 #define __deprecated 122 123 /* 124 * Optional: not supported by clang 125 * Optional: not supported by icc 126 * 127 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 128 */ 129 #if __has_attribute(__designated_init__) 130 # define __designated_init __attribute__((__designated_init__)) 131 #else 132 # define __designated_init 133 #endif 134 135 /* 136 * Optional: only supported since clang >= 14.0 137 * 138 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 139 */ 140 #if __has_attribute(__error__) 141 # define __compiletime_error(msg) __attribute__((__error__(msg))) 142 #else 143 # define __compiletime_error(msg) 144 #endif 145 146 /* 147 * Optional: not supported by clang 148 * 149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 150 */ 151 #if __has_attribute(__externally_visible__) 152 # define __visible __attribute__((__externally_visible__)) 153 #else 154 # define __visible 155 #endif 156 157 /* 158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 159 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 160 */ 161 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 162 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 163 164 /* 165 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 166 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 167 */ 168 #define __gnu_inline __attribute__((__gnu_inline__)) 169 170 /* 171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 172 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc 173 */ 174 #define __malloc __attribute__((__malloc__)) 175 176 /* 177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 178 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 179 */ 180 #define __mode(x) __attribute__((__mode__(x))) 181 182 /* 183 * Optional: only supported since gcc >= 7 184 * 185 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 186 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 187 */ 188 #if __has_attribute(__no_caller_saved_registers__) 189 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 190 #else 191 # define __no_caller_saved_registers 192 #endif 193 194 /* 195 * Optional: not supported by clang 196 * 197 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 198 */ 199 #if __has_attribute(__noclone__) 200 # define __noclone __attribute__((__noclone__)) 201 #else 202 # define __noclone 203 #endif 204 205 /* 206 * Add the pseudo keyword 'fallthrough' so case statement blocks 207 * must end with any of these keywords: 208 * break; 209 * fallthrough; 210 * continue; 211 * goto <label>; 212 * return [expression]; 213 * 214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 215 */ 216 #if __has_attribute(__fallthrough__) 217 # define fallthrough __attribute__((__fallthrough__)) 218 #else 219 # define fallthrough do {} while (0) /* fallthrough */ 220 #endif 221 222 /* 223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 224 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 225 */ 226 # define __flatten __attribute__((flatten)) 227 228 /* 229 * Note the missing underscores. 230 * 231 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 232 * clang: mentioned 233 */ 234 #define noinline __attribute__((__noinline__)) 235 236 /* 237 * Optional: only supported since gcc >= 8 238 * Optional: not supported by clang 239 * Optional: not supported by icc 240 * 241 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 242 */ 243 #if __has_attribute(__nonstring__) 244 # define __nonstring __attribute__((__nonstring__)) 245 #else 246 # define __nonstring 247 #endif 248 249 /* 250 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 251 * 252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 253 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 254 */ 255 #if __has_attribute(__no_profile_instrument_function__) 256 # define __no_profile __attribute__((__no_profile_instrument_function__)) 257 #else 258 # define __no_profile 259 #endif 260 261 /* 262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 263 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 264 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 265 */ 266 #define __noreturn __attribute__((__noreturn__)) 267 268 /* 269 * Optional: not supported by gcc. 270 * Optional: not supported by icc. 271 * 272 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable 273 */ 274 #if __has_attribute(__overloadable__) 275 # define __overloadable __attribute__((__overloadable__)) 276 #else 277 # define __overloadable 278 #endif 279 280 /* 281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 282 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 283 */ 284 #define __packed __attribute__((__packed__)) 285 286 /* 287 * Note: the "type" argument should match any __builtin_object_size(p, type) usage. 288 * 289 * Optional: not supported by gcc. 290 * Optional: not supported by icc. 291 * 292 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size 293 */ 294 #if __has_attribute(__pass_dynamic_object_size__) 295 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type))) 296 #else 297 # define __pass_dynamic_object_size(type) 298 #endif 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 /* 375 * Used by functions that use '__builtin_return_address'. These function 376 * don't want to be splited or made inline, which can make 377 * the '__builtin_return_address' get unexpected address. 378 */ 379 #define __fix_address noinline __noclone 380 381 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 382