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 clang >= 14.0 128 * 129 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 130 */ 131 #if __has_attribute(__error__) 132 # define __compiletime_error(msg) __attribute__((__error__(msg))) 133 #else 134 # define __compiletime_error(msg) 135 #endif 136 137 /* 138 * Optional: not supported by clang 139 * 140 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 141 */ 142 #if __has_attribute(__externally_visible__) 143 # define __visible __attribute__((__externally_visible__)) 144 #else 145 # define __visible 146 #endif 147 148 /* 149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 150 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 151 */ 152 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 153 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 154 155 /* 156 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 157 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 158 */ 159 #define __gnu_inline __attribute__((__gnu_inline__)) 160 161 /* 162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 163 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc 164 */ 165 #define __malloc __attribute__((__malloc__)) 166 167 /* 168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 170 */ 171 #define __mode(x) __attribute__((__mode__(x))) 172 173 /* 174 * Optional: only supported since gcc >= 7 175 * 176 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 177 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 178 */ 179 #if __has_attribute(__no_caller_saved_registers__) 180 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 181 #else 182 # define __no_caller_saved_registers 183 #endif 184 185 /* 186 * Optional: not supported by clang 187 * 188 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 189 */ 190 #if __has_attribute(__noclone__) 191 # define __noclone __attribute__((__noclone__)) 192 #else 193 # define __noclone 194 #endif 195 196 /* 197 * Add the pseudo keyword 'fallthrough' so case statement blocks 198 * must end with any of these keywords: 199 * break; 200 * fallthrough; 201 * continue; 202 * goto <label>; 203 * return [expression]; 204 * 205 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 206 */ 207 #if __has_attribute(__fallthrough__) 208 # define fallthrough __attribute__((__fallthrough__)) 209 #else 210 # define fallthrough do {} while (0) /* fallthrough */ 211 #endif 212 213 /* 214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 215 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 216 */ 217 # define __flatten __attribute__((flatten)) 218 219 /* 220 * Note the missing underscores. 221 * 222 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 223 * clang: mentioned 224 */ 225 #define noinline __attribute__((__noinline__)) 226 227 /* 228 * Optional: only supported since gcc >= 8 229 * Optional: not supported by clang 230 * 231 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 232 */ 233 #if __has_attribute(__nonstring__) 234 # define __nonstring __attribute__((__nonstring__)) 235 #else 236 # define __nonstring 237 #endif 238 239 /* 240 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 241 * 242 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 243 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 244 */ 245 #if __has_attribute(__no_profile_instrument_function__) 246 # define __no_profile __attribute__((__no_profile_instrument_function__)) 247 #else 248 # define __no_profile 249 #endif 250 251 /* 252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 253 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 254 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 255 */ 256 #define __noreturn __attribute__((__noreturn__)) 257 258 /* 259 * Optional: only supported since GCC >= 11.1, clang >= 7.0. 260 * 261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fstack_005fprotector-function-attribute 262 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safebuffers 263 */ 264 #if __has_attribute(__no_stack_protector__) 265 # define __no_stack_protector __attribute__((__no_stack_protector__)) 266 #else 267 # define __no_stack_protector 268 #endif 269 270 /* 271 * Optional: not supported by gcc. 272 * 273 * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable 274 */ 275 #if __has_attribute(__overloadable__) 276 # define __overloadable __attribute__((__overloadable__)) 277 #else 278 # define __overloadable 279 #endif 280 281 /* 282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 283 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 284 */ 285 #define __packed __attribute__((__packed__)) 286 287 /* 288 * Note: the "type" argument should match any __builtin_object_size(p, type) usage. 289 * 290 * Optional: not supported by gcc. 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