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__ (__GNUC_MINOR__ >= 9) 31 # define __GCC4_has_attribute___copy__ 0 32 # define __GCC4_has_attribute___designated_init__ 0 33 # define __GCC4_has_attribute___error__ 1 34 # define __GCC4_has_attribute___externally_visible__ 1 35 # define __GCC4_has_attribute___no_caller_saved_registers__ 0 36 # define __GCC4_has_attribute___noclone__ 1 37 # define __GCC4_has_attribute___nonstring__ 0 38 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8) 39 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9) 40 # define __GCC4_has_attribute___fallthrough__ 0 41 # define __GCC4_has_attribute___warning__ 1 42 #endif 43 44 /* 45 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 46 */ 47 #define __alias(symbol) __attribute__((__alias__(#symbol))) 48 49 /* 50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute 51 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute 52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute 53 */ 54 #define __aligned(x) __attribute__((__aligned__(x))) 55 #define __aligned_largest __attribute__((__aligned__)) 56 57 /* 58 * Note: users of __always_inline currently do not write "inline" themselves, 59 * which seems to be required by gcc to apply the attribute according 60 * to its docs (and also "warning: always_inline function might not be 61 * inlinable [-Wattributes]" is emitted). 62 * 63 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 64 * clang: mentioned 65 */ 66 #define __always_inline inline __attribute__((__always_inline__)) 67 68 /* 69 * The second argument is optional (default 0), so we use a variadic macro 70 * to make the shorthand. 71 * 72 * Beware: Do not apply this to functions which may return 73 * ERR_PTRs. Also, it is probably unwise to apply it to functions 74 * returning extra information in the low bits (but in that case the 75 * compiler should see some alignment anyway, when the return value is 76 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 77 * 78 * Optional: only supported since gcc >= 4.9 79 * Optional: not supported by icc 80 * 81 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 82 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 83 */ 84 #if __has_attribute(__assume_aligned__) 85 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 86 #else 87 # define __assume_aligned(a, ...) 88 #endif 89 90 /* 91 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 92 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 93 */ 94 #define __cold __attribute__((__cold__)) 95 96 /* 97 * Note the long name. 98 * 99 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 100 */ 101 #define __attribute_const__ __attribute__((__const__)) 102 103 /* 104 * Optional: only supported since gcc >= 9 105 * Optional: not supported by clang 106 * Optional: not supported by icc 107 * 108 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 109 */ 110 #if __has_attribute(__copy__) 111 # define __copy(symbol) __attribute__((__copy__(symbol))) 112 #else 113 # define __copy(symbol) 114 #endif 115 116 /* 117 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 118 * attribute warnings entirely and for good") for more information. 119 * 120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 124 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 125 */ 126 #define __deprecated 127 128 /* 129 * Optional: only supported since gcc >= 5.1 130 * Optional: not supported by clang 131 * Optional: not supported by icc 132 * 133 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 134 */ 135 #if __has_attribute(__designated_init__) 136 # define __designated_init __attribute__((__designated_init__)) 137 #else 138 # define __designated_init 139 #endif 140 141 /* 142 * Optional: only supported since clang >= 14.0 143 * 144 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 145 */ 146 #if __has_attribute(__error__) 147 # define __compiletime_error(msg) __attribute__((__error__(msg))) 148 #else 149 # define __compiletime_error(msg) 150 #endif 151 152 /* 153 * Optional: not supported by clang 154 * 155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 156 */ 157 #if __has_attribute(__externally_visible__) 158 # define __visible __attribute__((__externally_visible__)) 159 #else 160 # define __visible 161 #endif 162 163 /* 164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 165 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 166 */ 167 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 168 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 169 170 /* 171 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 172 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 173 */ 174 #define __gnu_inline __attribute__((__gnu_inline__)) 175 176 /* 177 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 178 */ 179 #define __malloc __attribute__((__malloc__)) 180 181 /* 182 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 183 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 184 */ 185 #define __mode(x) __attribute__((__mode__(x))) 186 187 /* 188 * Optional: only supported since gcc >= 7 189 * 190 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 191 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 192 */ 193 #if __has_attribute(__no_caller_saved_registers__) 194 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 195 #else 196 # define __no_caller_saved_registers 197 #endif 198 199 /* 200 * Optional: not supported by clang 201 * 202 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 203 */ 204 #if __has_attribute(__noclone__) 205 # define __noclone __attribute__((__noclone__)) 206 #else 207 # define __noclone 208 #endif 209 210 /* 211 * Add the pseudo keyword 'fallthrough' so case statement blocks 212 * must end with any of these keywords: 213 * break; 214 * fallthrough; 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 * Note the missing underscores. 228 * 229 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 230 * clang: mentioned 231 */ 232 #define noinline __attribute__((__noinline__)) 233 234 /* 235 * Optional: only supported since gcc >= 8 236 * Optional: not supported by clang 237 * Optional: not supported by icc 238 * 239 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 240 */ 241 #if __has_attribute(__nonstring__) 242 # define __nonstring __attribute__((__nonstring__)) 243 #else 244 # define __nonstring 245 #endif 246 247 /* 248 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 249 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 250 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 251 */ 252 #define __noreturn __attribute__((__noreturn__)) 253 254 /* 255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 256 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 257 */ 258 #define __packed __attribute__((__packed__)) 259 260 /* 261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 262 */ 263 #define __pure __attribute__((__pure__)) 264 265 /* 266 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 267 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 268 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 269 */ 270 #define __section(section) __attribute__((__section__(section))) 271 272 /* 273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 274 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 275 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 276 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 277 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 278 */ 279 #define __always_unused __attribute__((__unused__)) 280 #define __maybe_unused __attribute__((__unused__)) 281 282 /* 283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 284 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 285 */ 286 #define __used __attribute__((__used__)) 287 288 /* 289 * Optional: only supported since clang >= 14.0 290 * 291 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 292 */ 293 #if __has_attribute(__warning__) 294 # define __compiletime_warning(msg) __attribute__((__warning__(msg))) 295 #else 296 # define __compiletime_warning(msg) 297 #endif 298 299 /* 300 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 301 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 302 */ 303 #define __weak __attribute__((__weak__)) 304 305 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 306