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: users of __always_inline currently do not write "inline" themselves, 38 * which seems to be required by gcc to apply the attribute according 39 * to its docs (and also "warning: always_inline function might not be 40 * inlinable [-Wattributes]" is emitted). 41 * 42 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 43 * clang: mentioned 44 */ 45 #define __always_inline inline __attribute__((__always_inline__)) 46 47 /* 48 * The second argument is optional (default 0), so we use a variadic macro 49 * to make the shorthand. 50 * 51 * Beware: Do not apply this to functions which may return 52 * ERR_PTRs. Also, it is probably unwise to apply it to functions 53 * returning extra information in the low bits (but in that case the 54 * compiler should see some alignment anyway, when the return value is 55 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 56 * 57 * Optional: not supported by icc 58 * 59 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 60 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 61 */ 62 #if __has_attribute(__assume_aligned__) 63 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 64 #else 65 # define __assume_aligned(a, ...) 66 #endif 67 68 /* 69 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 70 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 71 */ 72 #define __cold __attribute__((__cold__)) 73 74 /* 75 * Note the long name. 76 * 77 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 78 */ 79 #define __attribute_const__ __attribute__((__const__)) 80 81 /* 82 * Optional: only supported since gcc >= 9 83 * Optional: not supported by clang 84 * Optional: not supported by icc 85 * 86 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 87 */ 88 #if __has_attribute(__copy__) 89 # define __copy(symbol) __attribute__((__copy__(symbol))) 90 #else 91 # define __copy(symbol) 92 #endif 93 94 /* 95 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 96 * attribute warnings entirely and for good") for more information. 97 * 98 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 99 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 100 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 102 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 103 */ 104 #define __deprecated 105 106 /* 107 * Optional: not supported by clang 108 * Optional: not supported by icc 109 * 110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 111 */ 112 #if __has_attribute(__designated_init__) 113 # define __designated_init __attribute__((__designated_init__)) 114 #else 115 # define __designated_init 116 #endif 117 118 /* 119 * Optional: only supported since clang >= 14.0 120 * 121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 122 */ 123 #if __has_attribute(__error__) 124 # define __compiletime_error(msg) __attribute__((__error__(msg))) 125 #else 126 # define __compiletime_error(msg) 127 #endif 128 129 /* 130 * Optional: not supported by clang 131 * 132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 133 */ 134 #if __has_attribute(__externally_visible__) 135 # define __visible __attribute__((__externally_visible__)) 136 #else 137 # define __visible 138 #endif 139 140 /* 141 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 142 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 143 */ 144 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 145 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 146 147 /* 148 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 149 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 150 */ 151 #define __gnu_inline __attribute__((__gnu_inline__)) 152 153 /* 154 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 155 */ 156 #define __malloc __attribute__((__malloc__)) 157 158 /* 159 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 160 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 161 */ 162 #define __mode(x) __attribute__((__mode__(x))) 163 164 /* 165 * Optional: only supported since gcc >= 7 166 * 167 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 168 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 169 */ 170 #if __has_attribute(__no_caller_saved_registers__) 171 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 172 #else 173 # define __no_caller_saved_registers 174 #endif 175 176 /* 177 * Optional: not supported by clang 178 * 179 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 180 */ 181 #if __has_attribute(__noclone__) 182 # define __noclone __attribute__((__noclone__)) 183 #else 184 # define __noclone 185 #endif 186 187 /* 188 * Add the pseudo keyword 'fallthrough' so case statement blocks 189 * must end with any of these keywords: 190 * break; 191 * fallthrough; 192 * continue; 193 * goto <label>; 194 * return [expression]; 195 * 196 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 197 */ 198 #if __has_attribute(__fallthrough__) 199 # define fallthrough __attribute__((__fallthrough__)) 200 #else 201 # define fallthrough do {} while (0) /* fallthrough */ 202 #endif 203 204 /* 205 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 206 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 207 */ 208 # define __flatten __attribute__((flatten)) 209 210 /* 211 * Note the missing underscores. 212 * 213 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 214 * clang: mentioned 215 */ 216 #define noinline __attribute__((__noinline__)) 217 218 /* 219 * Optional: only supported since gcc >= 8 220 * Optional: not supported by clang 221 * Optional: not supported by icc 222 * 223 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 224 */ 225 #if __has_attribute(__nonstring__) 226 # define __nonstring __attribute__((__nonstring__)) 227 #else 228 # define __nonstring 229 #endif 230 231 /* 232 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 233 * 234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 235 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 236 */ 237 #if __has_attribute(__no_profile_instrument_function__) 238 # define __no_profile __attribute__((__no_profile_instrument_function__)) 239 #else 240 # define __no_profile 241 #endif 242 243 /* 244 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 245 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 246 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 247 */ 248 #define __noreturn __attribute__((__noreturn__)) 249 250 /* 251 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 252 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 253 */ 254 #define __packed __attribute__((__packed__)) 255 256 /* 257 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 258 */ 259 #define __pure __attribute__((__pure__)) 260 261 /* 262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 264 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 265 */ 266 #define __section(section) __attribute__((__section__(section))) 267 268 /* 269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 271 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 272 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 273 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 274 */ 275 #define __always_unused __attribute__((__unused__)) 276 #define __maybe_unused __attribute__((__unused__)) 277 278 /* 279 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 281 */ 282 #define __used __attribute__((__used__)) 283 284 /* 285 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 286 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 287 */ 288 #define __must_check __attribute__((__warn_unused_result__)) 289 290 /* 291 * Optional: only supported since clang >= 14.0 292 * 293 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 294 */ 295 #if __has_attribute(__warning__) 296 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 297 #else 298 # define __compiletime_warning(msg) 299 #endif 300 301 /* 302 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 304 */ 305 #define __weak __attribute__((__weak__)) 306 307 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 308