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. 39 * 40 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute 41 * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size 42 */ 43 #define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__))) 44 45 /* 46 * Note: users of __always_inline currently do not write "inline" themselves, 47 * which seems to be required by gcc to apply the attribute according 48 * to its docs (and also "warning: always_inline function might not be 49 * inlinable [-Wattributes]" is emitted). 50 * 51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 52 * clang: mentioned 53 */ 54 #define __always_inline inline __attribute__((__always_inline__)) 55 56 /* 57 * The second argument is optional (default 0), so we use a variadic macro 58 * to make the shorthand. 59 * 60 * Beware: Do not apply this to functions which may return 61 * ERR_PTRs. Also, it is probably unwise to apply it to functions 62 * returning extra information in the low bits (but in that case the 63 * compiler should see some alignment anyway, when the return value is 64 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 65 * 66 * Optional: not supported by icc 67 * 68 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 69 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 70 */ 71 #if __has_attribute(__assume_aligned__) 72 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 73 #else 74 # define __assume_aligned(a, ...) 75 #endif 76 77 /* 78 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 80 */ 81 #define __cold __attribute__((__cold__)) 82 83 /* 84 * Note the long name. 85 * 86 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 87 */ 88 #define __attribute_const__ __attribute__((__const__)) 89 90 /* 91 * Optional: only supported since gcc >= 9 92 * Optional: not supported by clang 93 * Optional: not supported by icc 94 * 95 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 96 */ 97 #if __has_attribute(__copy__) 98 # define __copy(symbol) __attribute__((__copy__(symbol))) 99 #else 100 # define __copy(symbol) 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 * Optional: not supported by icc 118 * 119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 120 */ 121 #if __has_attribute(__designated_init__) 122 # define __designated_init __attribute__((__designated_init__)) 123 #else 124 # define __designated_init 125 #endif 126 127 /* 128 * Optional: only supported since clang >= 14.0 129 * 130 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 131 */ 132 #if __has_attribute(__error__) 133 # define __compiletime_error(msg) __attribute__((__error__(msg))) 134 #else 135 # define __compiletime_error(msg) 136 #endif 137 138 /* 139 * Optional: not supported by clang 140 * 141 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 142 */ 143 #if __has_attribute(__externally_visible__) 144 # define __visible __attribute__((__externally_visible__)) 145 #else 146 # define __visible 147 #endif 148 149 /* 150 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 151 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 152 */ 153 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 154 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 155 156 /* 157 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 158 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 159 */ 160 #define __gnu_inline __attribute__((__gnu_inline__)) 161 162 /* 163 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 164 * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc 165 */ 166 #define __malloc __attribute__((__malloc__)) 167 168 /* 169 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 171 */ 172 #define __mode(x) __attribute__((__mode__(x))) 173 174 /* 175 * Optional: only supported since gcc >= 7 176 * 177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 178 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 179 */ 180 #if __has_attribute(__no_caller_saved_registers__) 181 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 182 #else 183 # define __no_caller_saved_registers 184 #endif 185 186 /* 187 * Optional: not supported by clang 188 * 189 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 190 */ 191 #if __has_attribute(__noclone__) 192 # define __noclone __attribute__((__noclone__)) 193 #else 194 # define __noclone 195 #endif 196 197 /* 198 * Add the pseudo keyword 'fallthrough' so case statement blocks 199 * must end with any of these keywords: 200 * break; 201 * fallthrough; 202 * continue; 203 * goto <label>; 204 * return [expression]; 205 * 206 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 207 */ 208 #if __has_attribute(__fallthrough__) 209 # define fallthrough __attribute__((__fallthrough__)) 210 #else 211 # define fallthrough do {} while (0) /* fallthrough */ 212 #endif 213 214 /* 215 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 216 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 217 */ 218 # define __flatten __attribute__((flatten)) 219 220 /* 221 * Note the missing underscores. 222 * 223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 224 * clang: mentioned 225 */ 226 #define noinline __attribute__((__noinline__)) 227 228 /* 229 * Optional: only supported since gcc >= 8 230 * Optional: not supported by clang 231 * Optional: not supported by icc 232 * 233 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 234 */ 235 #if __has_attribute(__nonstring__) 236 # define __nonstring __attribute__((__nonstring__)) 237 #else 238 # define __nonstring 239 #endif 240 241 /* 242 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 243 * 244 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 245 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 246 */ 247 #if __has_attribute(__no_profile_instrument_function__) 248 # define __no_profile __attribute__((__no_profile_instrument_function__)) 249 #else 250 # define __no_profile 251 #endif 252 253 /* 254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 255 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 256 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 257 */ 258 #define __noreturn __attribute__((__noreturn__)) 259 260 /* 261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 262 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 263 */ 264 #define __packed __attribute__((__packed__)) 265 266 /* 267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 268 */ 269 #define __pure __attribute__((__pure__)) 270 271 /* 272 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 274 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 275 */ 276 #define __section(section) __attribute__((__section__(section))) 277 278 /* 279 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 283 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 284 */ 285 #define __always_unused __attribute__((__unused__)) 286 #define __maybe_unused __attribute__((__unused__)) 287 288 /* 289 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 291 */ 292 #define __used __attribute__((__used__)) 293 294 /* 295 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 296 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 297 */ 298 #define __must_check __attribute__((__warn_unused_result__)) 299 300 /* 301 * Optional: only supported since clang >= 14.0 302 * 303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 304 */ 305 #if __has_attribute(__warning__) 306 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 307 #else 308 # define __compiletime_warning(msg) 309 #endif 310 311 /* 312 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 313 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 314 */ 315 #define __weak __attribute__((__weak__)) 316 317 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 318