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 * Optional: only supported since gcc >= 8 235 * Optional: not supported by clang 236 * 237 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 238 */ 239 #if __has_attribute(__nonstring__) 240 # define __nonstring __attribute__((__nonstring__)) 241 #else 242 # define __nonstring 243 #endif 244 245 /* 246 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 247 * 248 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 249 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 250 */ 251 #if __has_attribute(__no_profile_instrument_function__) 252 # define __no_profile __attribute__((__no_profile_instrument_function__)) 253 #else 254 # define __no_profile 255 #endif 256 257 /* 258 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 259 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 260 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 261 */ 262 #define __noreturn __attribute__((__noreturn__)) 263 264 /* 265 * Optional: only supported since GCC >= 11.1, clang >= 7.0. 266 * 267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fstack_005fprotector-function-attribute 268 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safebuffers 269 */ 270 #if __has_attribute(__no_stack_protector__) 271 # define __no_stack_protector __attribute__((__no_stack_protector__)) 272 #else 273 # define __no_stack_protector 274 #endif 275 276 /* 277 * Optional: not supported by gcc. 278 * 279 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable 280 */ 281 #if __has_attribute(__overloadable__) 282 # define __overloadable __attribute__((__overloadable__)) 283 #else 284 # define __overloadable 285 #endif 286 287 /* 288 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 289 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 290 */ 291 #define __packed __attribute__((__packed__)) 292 293 /* 294 * Note: the "type" argument should match any __builtin_object_size(p, type) usage. 295 * 296 * Optional: not supported by gcc. 297 * 298 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size 299 */ 300 #if __has_attribute(__pass_dynamic_object_size__) 301 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type))) 302 #else 303 # define __pass_dynamic_object_size(type) 304 #endif 305 #if __has_attribute(__pass_object_size__) 306 # define __pass_object_size(type) __attribute__((__pass_object_size__(type))) 307 #else 308 # define __pass_object_size(type) 309 #endif 310 311 /* 312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 313 */ 314 #define __pure __attribute__((__pure__)) 315 316 /* 317 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 318 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 319 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 320 */ 321 #define __section(section) __attribute__((__section__(section))) 322 323 /* 324 * Optional: only supported since gcc >= 12 325 * 326 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-uninitialized-variable-attribute 327 * clang: https://clang.llvm.org/docs/AttributeReference.html#uninitialized 328 */ 329 #if __has_attribute(__uninitialized__) 330 # define __uninitialized __attribute__((__uninitialized__)) 331 #else 332 # define __uninitialized 333 #endif 334 335 /* 336 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 337 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 338 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 339 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 340 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 341 */ 342 #define __always_unused __attribute__((__unused__)) 343 #define __maybe_unused __attribute__((__unused__)) 344 345 /* 346 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 347 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 348 */ 349 #define __used __attribute__((__used__)) 350 351 /* 352 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 353 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 354 */ 355 #define __must_check __attribute__((__warn_unused_result__)) 356 357 /* 358 * Optional: only supported since clang >= 14.0 359 * 360 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 361 */ 362 #if __has_attribute(__warning__) 363 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 364 #else 365 # define __compiletime_warning(msg) 366 #endif 367 368 /* 369 * Optional: only supported since clang >= 14.0 370 * 371 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation 372 * 373 * disable_sanitizer_instrumentation is not always similar to 374 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers 375 * insert code into functions to prevent false positives. Unlike that, 376 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to 377 * functions with the attribute. 378 */ 379 #if __has_attribute(disable_sanitizer_instrumentation) 380 # define __disable_sanitizer_instrumentation \ 381 __attribute__((disable_sanitizer_instrumentation)) 382 #else 383 # define __disable_sanitizer_instrumentation 384 #endif 385 386 /* 387 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 388 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 389 */ 390 #define __weak __attribute__((__weak__)) 391 392 /* 393 * Used by functions that use '__builtin_return_address'. These function 394 * don't want to be splited or made inline, which can make 395 * the '__builtin_return_address' get unexpected address. 396 */ 397 #define __fix_address noinline __noclone 398 399 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 400