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 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 68 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 69 */ 70 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 71 72 /* 73 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-cleanup-variable-attribute 74 * clang: https://clang.llvm.org/docs/AttributeReference.html#cleanup 75 */ 76 #define __cleanup(func) __attribute__((__cleanup__(func))) 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 * 89 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 90 */ 91 #if __has_attribute(__copy__) 92 # define __copy(symbol) __attribute__((__copy__(symbol))) 93 #else 94 # define __copy(symbol) 95 #endif 96 97 /* 98 * Optional: not supported by gcc 99 * Optional: only supported since clang >= 14.0 100 * 101 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin 102 */ 103 #if __has_attribute(__diagnose_as_builtin__) 104 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin))) 105 #else 106 # define __diagnose_as(builtin...) 107 #endif 108 109 /* 110 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 111 * attribute warnings entirely and for good") for more information. 112 * 113 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 114 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 115 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 116 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 117 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 118 */ 119 #define __deprecated 120 121 /* 122 * Optional: not supported by clang 123 * 124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 125 */ 126 #if __has_attribute(__designated_init__) 127 # define __designated_init __attribute__((__designated_init__)) 128 #else 129 # define __designated_init 130 #endif 131 132 /* 133 * Optional: only supported since clang >= 14.0 134 * 135 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 136 */ 137 #if __has_attribute(__error__) 138 # define __compiletime_error(msg) __attribute__((__error__(msg))) 139 #else 140 # define __compiletime_error(msg) 141 #endif 142 143 /* 144 * Optional: not supported by clang 145 * 146 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 147 */ 148 #if __has_attribute(__externally_visible__) 149 # define __visible __attribute__((__externally_visible__)) 150 #else 151 # define __visible 152 #endif 153 154 /* 155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 156 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 157 */ 158 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 159 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 160 161 /* 162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 163 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 164 */ 165 #define __gnu_inline __attribute__((__gnu_inline__)) 166 167 /* 168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 169 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc 170 */ 171 #define __malloc __attribute__((__malloc__)) 172 173 /* 174 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 175 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 176 */ 177 #define __mode(x) __attribute__((__mode__(x))) 178 179 /* 180 * Optional: only supported since gcc >= 7 181 * 182 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 183 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 184 */ 185 #if __has_attribute(__no_caller_saved_registers__) 186 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 187 #else 188 # define __no_caller_saved_registers 189 #endif 190 191 /* 192 * Optional: not supported by clang 193 * 194 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 195 */ 196 #if __has_attribute(__noclone__) 197 # define __noclone __attribute__((__noclone__)) 198 #else 199 # define __noclone 200 #endif 201 202 /* 203 * Add the pseudo keyword 'fallthrough' so case statement blocks 204 * must end with any of these keywords: 205 * break; 206 * fallthrough; 207 * continue; 208 * goto <label>; 209 * return [expression]; 210 * 211 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 212 */ 213 #if __has_attribute(__fallthrough__) 214 # define fallthrough __attribute__((__fallthrough__)) 215 #else 216 # define fallthrough do {} while (0) /* fallthrough */ 217 #endif 218 219 /* 220 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 221 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 222 */ 223 # define __flatten __attribute__((flatten)) 224 225 /* 226 * Note the missing underscores. 227 * 228 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 229 * clang: mentioned 230 */ 231 #define noinline __attribute__((__noinline__)) 232 233 /* 234 * Note: deliberately not named '__nonnull', to avoid clashing with glibc's 235 * __nonnull() when kernel and userspace headers are combined. 236 * 237 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-nonnull 238 * clang: https://clang.llvm.org/docs/AttributeReference.html#nonnull 239 */ 240 #define __nonnull_args(x...) __attribute__((__nonnull__(x))) 241 242 /* 243 * Optional: only supported since gcc >= 8 244 * Optional: not supported by clang 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: only supported since GCC >= 11.1, clang >= 7.0. 275 * 276 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fstack_005fprotector-function-attribute 277 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safebuffers 278 */ 279 #if __has_attribute(__no_stack_protector__) 280 # define __no_stack_protector __attribute__((__no_stack_protector__)) 281 #else 282 # define __no_stack_protector 283 #endif 284 285 /* 286 * Optional: not supported by gcc. 287 * 288 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable 289 */ 290 #if __has_attribute(__overloadable__) 291 # define __overloadable __attribute__((__overloadable__)) 292 #else 293 # define __overloadable 294 #endif 295 296 /* 297 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 298 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 299 */ 300 #define __packed __attribute__((__packed__)) 301 302 /* 303 * Note: the "type" argument should match any __builtin_object_size(p, type) usage. 304 * 305 * Optional: not supported by gcc. 306 * 307 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size 308 */ 309 #if __has_attribute(__pass_dynamic_object_size__) 310 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type))) 311 #else 312 # define __pass_dynamic_object_size(type) 313 #endif 314 #if __has_attribute(__pass_object_size__) 315 # define __pass_object_size(type) __attribute__((__pass_object_size__(type))) 316 #else 317 # define __pass_object_size(type) 318 #endif 319 320 /* 321 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 322 */ 323 #define __pure __attribute__((__pure__)) 324 325 /* 326 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 327 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 328 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 329 */ 330 #define __section(section) __attribute__((__section__(section))) 331 332 /* 333 * Optional: only supported since gcc >= 12 334 * 335 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-uninitialized-variable-attribute 336 * clang: https://clang.llvm.org/docs/AttributeReference.html#uninitialized 337 */ 338 #if __has_attribute(__uninitialized__) 339 # define __uninitialized __attribute__((__uninitialized__)) 340 #else 341 # define __uninitialized 342 #endif 343 344 /* 345 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 346 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 347 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 348 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 349 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 350 */ 351 #define __always_unused __attribute__((__unused__)) 352 #define __maybe_unused __attribute__((__unused__)) 353 354 /* 355 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 356 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 357 */ 358 #define __used __attribute__((__used__)) 359 360 /* 361 * The __used attribute guarantees that the attributed variable will be 362 * always emitted by a compiler. It doesn't prevent the compiler from 363 * throwing 'unused' warnings when it can't detect how the variable is 364 * actually used. It's a compiler implementation details either emit 365 * the warning in that case or not. 366 * 367 * The combination of both 'used' and 'unused' attributes ensures that 368 * the variable would be emitted, and will not trigger 'unused' warnings. 369 * The attribute is applicable for functions, static and global variables. 370 */ 371 #define __always_used __used __maybe_unused 372 373 /* 374 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 375 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 376 */ 377 #define __must_check __attribute__((__warn_unused_result__)) 378 379 /* 380 * Optional: only supported since clang >= 14.0 381 * 382 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 383 */ 384 #if __has_attribute(__warning__) 385 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 386 #else 387 # define __compiletime_warning(msg) 388 #endif 389 390 /* 391 * Optional: only supported since clang >= 14.0 392 * 393 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation 394 * 395 * disable_sanitizer_instrumentation is not always similar to 396 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers 397 * insert code into functions to prevent false positives. Unlike that, 398 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to 399 * functions with the attribute. 400 */ 401 #if __has_attribute(disable_sanitizer_instrumentation) 402 # define __disable_sanitizer_instrumentation \ 403 __attribute__((disable_sanitizer_instrumentation)) 404 #else 405 # define __disable_sanitizer_instrumentation 406 #endif 407 408 /* 409 * Optional: not supported by clang 410 * 411 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-noipa 412 */ 413 #if __has_attribute(noipa) 414 # define __noipa __attribute__((noipa)) 415 #else 416 # define __noipa 417 #endif 418 419 /* 420 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 421 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 422 */ 423 #define __weak __attribute__((__weak__)) 424 425 /* 426 * Used by functions that use '__builtin_return_address'. These function 427 * don't want to be splited or made inline, which can make 428 * the '__builtin_return_address' get unexpected address. 429 */ 430 #define __fix_address noinline __noclone 431 432 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 433