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 * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17. 25 * In the meantime, to support gcc < 5, we implement __has_attribute 26 * by hand. 27 */ 28 #ifndef __has_attribute 29 # define __has_attribute(x) __GCC4_has_attribute_##x 30 # define __GCC4_has_attribute___assume_aligned__ 1 31 # define __GCC4_has_attribute___copy__ 0 32 # define __GCC4_has_attribute___designated_init__ 0 33 # define __GCC4_has_attribute___externally_visible__ 1 34 # define __GCC4_has_attribute___no_caller_saved_registers__ 0 35 # define __GCC4_has_attribute___noclone__ 1 36 # define __GCC4_has_attribute___no_profile_instrument_function__ 0 37 # define __GCC4_has_attribute___nonstring__ 0 38 # define __GCC4_has_attribute___no_sanitize_address__ 1 39 # define __GCC4_has_attribute___no_sanitize_undefined__ 1 40 # define __GCC4_has_attribute___fallthrough__ 0 41 #endif 42 43 /* 44 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 45 */ 46 #define __alias(symbol) __attribute__((__alias__(#symbol))) 47 48 /* 49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute 50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute 51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute 52 */ 53 #define __aligned(x) __attribute__((__aligned__(x))) 54 #define __aligned_largest __attribute__((__aligned__)) 55 56 /* 57 * Note: users of __always_inline currently do not write "inline" themselves, 58 * which seems to be required by gcc to apply the attribute according 59 * to its docs (and also "warning: always_inline function might not be 60 * inlinable [-Wattributes]" is emitted). 61 * 62 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 63 * clang: mentioned 64 */ 65 #define __always_inline inline __attribute__((__always_inline__)) 66 67 /* 68 * The second argument is optional (default 0), so we use a variadic macro 69 * to make the shorthand. 70 * 71 * Beware: Do not apply this to functions which may return 72 * ERR_PTRs. Also, it is probably unwise to apply it to functions 73 * returning extra information in the low bits (but in that case the 74 * compiler should see some alignment anyway, when the return value is 75 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 76 * 77 * Optional: only supported since gcc >= 4.9 78 * Optional: not supported by icc 79 * 80 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 81 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 82 */ 83 #if __has_attribute(__assume_aligned__) 84 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 85 #else 86 # define __assume_aligned(a, ...) 87 #endif 88 89 /* 90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 91 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 92 */ 93 #define __cold __attribute__((__cold__)) 94 95 /* 96 * Note the long name. 97 * 98 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 99 */ 100 #define __attribute_const__ __attribute__((__const__)) 101 102 /* 103 * Optional: only supported since gcc >= 9 104 * Optional: not supported by clang 105 * Optional: not supported by icc 106 * 107 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 108 */ 109 #if __has_attribute(__copy__) 110 # define __copy(symbol) __attribute__((__copy__(symbol))) 111 #else 112 # define __copy(symbol) 113 #endif 114 115 /* 116 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 117 * attribute warnings entirely and for good") for more information. 118 * 119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 123 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 124 */ 125 #define __deprecated 126 127 /* 128 * Optional: only supported since gcc >= 5.1 129 * Optional: not supported by clang 130 * Optional: not supported by icc 131 * 132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 133 */ 134 #if __has_attribute(__designated_init__) 135 # define __designated_init __attribute__((__designated_init__)) 136 #else 137 # define __designated_init 138 #endif 139 140 /* 141 * Optional: not supported by clang 142 * 143 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 144 */ 145 #if __has_attribute(__externally_visible__) 146 # define __visible __attribute__((__externally_visible__)) 147 #else 148 # define __visible 149 #endif 150 151 /* 152 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 153 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 154 */ 155 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 156 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 157 158 /* 159 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 160 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 161 */ 162 #define __gnu_inline __attribute__((__gnu_inline__)) 163 164 /* 165 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 166 */ 167 #define __malloc __attribute__((__malloc__)) 168 169 /* 170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 172 */ 173 #define __mode(x) __attribute__((__mode__(x))) 174 175 /* 176 * Optional: only supported since gcc >= 7 177 * 178 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 179 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 180 */ 181 #if __has_attribute(__no_caller_saved_registers__) 182 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 183 #else 184 # define __no_caller_saved_registers 185 #endif 186 187 /* 188 * Optional: not supported by clang 189 * 190 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 191 */ 192 #if __has_attribute(__noclone__) 193 # define __noclone __attribute__((__noclone__)) 194 #else 195 # define __noclone 196 #endif 197 198 /* 199 * Add the pseudo keyword 'fallthrough' so case statement blocks 200 * must end with any of these keywords: 201 * break; 202 * fallthrough; 203 * continue; 204 * goto <label>; 205 * return [expression]; 206 * 207 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 208 */ 209 #if __has_attribute(__fallthrough__) 210 # define fallthrough __attribute__((__fallthrough__)) 211 #else 212 # define fallthrough do {} while (0) /* fallthrough */ 213 #endif 214 215 /* 216 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 217 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 218 */ 219 # define __flatten __attribute__((flatten)) 220 221 /* 222 * Note the missing underscores. 223 * 224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 225 * clang: mentioned 226 */ 227 #define noinline __attribute__((__noinline__)) 228 229 /* 230 * Optional: only supported since gcc >= 8 231 * Optional: not supported by clang 232 * Optional: not supported by icc 233 * 234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 235 */ 236 #if __has_attribute(__nonstring__) 237 # define __nonstring __attribute__((__nonstring__)) 238 #else 239 # define __nonstring 240 #endif 241 242 /* 243 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 244 * 245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 246 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 247 */ 248 #if __has_attribute(__no_profile_instrument_function__) 249 # define __no_profile __attribute__((__no_profile_instrument_function__)) 250 #else 251 # define __no_profile 252 #endif 253 254 /* 255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 256 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 257 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 258 */ 259 #define __noreturn __attribute__((__noreturn__)) 260 261 /* 262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 263 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 264 */ 265 #define __packed __attribute__((__packed__)) 266 267 /* 268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 269 */ 270 #define __pure __attribute__((__pure__)) 271 272 /* 273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 274 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 275 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 276 */ 277 #define __section(section) __attribute__((__section__(section))) 278 279 /* 280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 284 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 285 */ 286 #define __always_unused __attribute__((__unused__)) 287 #define __maybe_unused __attribute__((__unused__)) 288 289 /* 290 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 291 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 292 */ 293 #define __used __attribute__((__used__)) 294 295 /* 296 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 297 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 298 */ 299 #define __must_check __attribute__((__warn_unused_result__)) 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