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 * Note the long name. 74 * 75 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 76 */ 77 #define __attribute_const__ __attribute__((__const__)) 78 79 /* 80 * Optional: only supported since gcc >= 9 81 * Optional: not supported by clang 82 * 83 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 84 */ 85 #if __has_attribute(__copy__) 86 # define __copy(symbol) __attribute__((__copy__(symbol))) 87 #else 88 # define __copy(symbol) 89 #endif 90 91 /* 92 * Optional: not supported by gcc 93 * Optional: only supported since clang >= 14.0 94 * 95 * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin 96 */ 97 #if __has_attribute(__diagnose_as_builtin__) 98 # define __diagnose_as(builtin...) __attribute__((__diagnose_as_builtin__(builtin))) 99 #else 100 # define __diagnose_as(builtin...) 101 #endif 102 103 /* 104 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 105 * attribute warnings entirely and for good") for more information. 106 * 107 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 108 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 109 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 111 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 112 */ 113 #define __deprecated 114 115 /* 116 * Optional: not supported by clang 117 * 118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 119 */ 120 #if __has_attribute(__designated_init__) 121 # define __designated_init __attribute__((__designated_init__)) 122 #else 123 # define __designated_init 124 #endif 125 126 /* 127 * Optional: only supported since gcc >= 14 128 * Optional: only supported since clang >= 17 129 * 130 * gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896 131 * clang: https://reviews.llvm.org/D148381 132 */ 133 #if __has_attribute(__element_count__) 134 # define __counted_by(member) __attribute__((__element_count__(#member))) 135 #else 136 # define __counted_by(member) 137 #endif 138 139 /* 140 * Optional: only supported since clang >= 14.0 141 * 142 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 143 */ 144 #if __has_attribute(__error__) 145 # define __compiletime_error(msg) __attribute__((__error__(msg))) 146 #else 147 # define __compiletime_error(msg) 148 #endif 149 150 /* 151 * Optional: not supported by clang 152 * 153 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 154 */ 155 #if __has_attribute(__externally_visible__) 156 # define __visible __attribute__((__externally_visible__)) 157 #else 158 # define __visible 159 #endif 160 161 /* 162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 163 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 164 */ 165 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 166 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 167 168 /* 169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 170 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 171 */ 172 #define __gnu_inline __attribute__((__gnu_inline__)) 173 174 /* 175 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 176 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc 177 */ 178 #define __malloc __attribute__((__malloc__)) 179 180 /* 181 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 182 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 183 */ 184 #define __mode(x) __attribute__((__mode__(x))) 185 186 /* 187 * Optional: only supported since gcc >= 7 188 * 189 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 190 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 191 */ 192 #if __has_attribute(__no_caller_saved_registers__) 193 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 194 #else 195 # define __no_caller_saved_registers 196 #endif 197 198 /* 199 * Optional: not supported by clang 200 * 201 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 202 */ 203 #if __has_attribute(__noclone__) 204 # define __noclone __attribute__((__noclone__)) 205 #else 206 # define __noclone 207 #endif 208 209 /* 210 * Add the pseudo keyword 'fallthrough' so case statement blocks 211 * must end with any of these keywords: 212 * break; 213 * fallthrough; 214 * continue; 215 * goto <label>; 216 * return [expression]; 217 * 218 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 219 */ 220 #if __has_attribute(__fallthrough__) 221 # define fallthrough __attribute__((__fallthrough__)) 222 #else 223 # define fallthrough do {} while (0) /* fallthrough */ 224 #endif 225 226 /* 227 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 228 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 229 */ 230 # define __flatten __attribute__((flatten)) 231 232 /* 233 * Note the missing underscores. 234 * 235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 236 * clang: mentioned 237 */ 238 #define noinline __attribute__((__noinline__)) 239 240 /* 241 * Optional: only supported since gcc >= 8 242 * Optional: not supported by clang 243 * 244 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 245 */ 246 #if __has_attribute(__nonstring__) 247 # define __nonstring __attribute__((__nonstring__)) 248 #else 249 # define __nonstring 250 #endif 251 252 /* 253 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 254 * 255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 256 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 257 */ 258 #if __has_attribute(__no_profile_instrument_function__) 259 # define __no_profile __attribute__((__no_profile_instrument_function__)) 260 #else 261 # define __no_profile 262 #endif 263 264 /* 265 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 266 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 267 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 268 */ 269 #define __noreturn __attribute__((__noreturn__)) 270 271 /* 272 * Optional: not supported by gcc. 273 * 274 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable 275 */ 276 #if __has_attribute(__overloadable__) 277 # define __overloadable __attribute__((__overloadable__)) 278 #else 279 # define __overloadable 280 #endif 281 282 /* 283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 284 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 285 */ 286 #define __packed __attribute__((__packed__)) 287 288 /* 289 * Note: the "type" argument should match any __builtin_object_size(p, type) usage. 290 * 291 * Optional: not supported by gcc. 292 * 293 * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size 294 */ 295 #if __has_attribute(__pass_dynamic_object_size__) 296 # define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type))) 297 #else 298 # define __pass_dynamic_object_size(type) 299 #endif 300 #if __has_attribute(__pass_object_size__) 301 # define __pass_object_size(type) __attribute__((__pass_object_size__(type))) 302 #else 303 # define __pass_object_size(type) 304 #endif 305 306 /* 307 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 308 */ 309 #define __pure __attribute__((__pure__)) 310 311 /* 312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 313 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 314 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 315 */ 316 #define __section(section) __attribute__((__section__(section))) 317 318 /* 319 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 320 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 321 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 322 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 323 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 324 */ 325 #define __always_unused __attribute__((__unused__)) 326 #define __maybe_unused __attribute__((__unused__)) 327 328 /* 329 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 330 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 331 */ 332 #define __used __attribute__((__used__)) 333 334 /* 335 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 336 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 337 */ 338 #define __must_check __attribute__((__warn_unused_result__)) 339 340 /* 341 * Optional: only supported since clang >= 14.0 342 * 343 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 344 */ 345 #if __has_attribute(__warning__) 346 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 347 #else 348 # define __compiletime_warning(msg) 349 #endif 350 351 /* 352 * Optional: only supported since clang >= 14.0 353 * 354 * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation 355 * 356 * disable_sanitizer_instrumentation is not always similar to 357 * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers 358 * insert code into functions to prevent false positives. Unlike that, 359 * disable_sanitizer_instrumentation prevents all kinds of instrumentation to 360 * functions with the attribute. 361 */ 362 #if __has_attribute(disable_sanitizer_instrumentation) 363 # define __disable_sanitizer_instrumentation \ 364 __attribute__((disable_sanitizer_instrumentation)) 365 #else 366 # define __disable_sanitizer_instrumentation 367 #endif 368 369 /* 370 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 371 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 372 */ 373 #define __weak __attribute__((__weak__)) 374 375 /* 376 * Used by functions that use '__builtin_return_address'. These function 377 * don't want to be splited or made inline, which can make 378 * the '__builtin_return_address' get unexpected address. 379 */ 380 #define __fix_address noinline __noclone 381 382 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 383