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: only supported since gcc >= 4.9 58 * Optional: not supported by icc 59 * 60 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 61 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 62 */ 63 #if __has_attribute(__assume_aligned__) 64 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 65 #else 66 # define __assume_aligned(a, ...) 67 #endif 68 69 /* 70 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 71 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 72 */ 73 #define __cold __attribute__((__cold__)) 74 75 /* 76 * Note the long name. 77 * 78 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 79 */ 80 #define __attribute_const__ __attribute__((__const__)) 81 82 /* 83 * Optional: only supported since gcc >= 9 84 * Optional: not supported by clang 85 * Optional: not supported by icc 86 * 87 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 88 */ 89 #if __has_attribute(__copy__) 90 # define __copy(symbol) __attribute__((__copy__(symbol))) 91 #else 92 # define __copy(symbol) 93 #endif 94 95 /* 96 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 97 * attribute warnings entirely and for good") for more information. 98 * 99 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 100 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 102 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 103 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 104 */ 105 #define __deprecated 106 107 /* 108 * Optional: only supported since gcc >= 5.1 109 * Optional: not supported by clang 110 * Optional: not supported by icc 111 * 112 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 113 */ 114 #if __has_attribute(__designated_init__) 115 # define __designated_init __attribute__((__designated_init__)) 116 #else 117 # define __designated_init 118 #endif 119 120 /* 121 * Optional: not supported by clang 122 * 123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 124 */ 125 #if __has_attribute(__externally_visible__) 126 # define __visible __attribute__((__externally_visible__)) 127 #else 128 # define __visible 129 #endif 130 131 /* 132 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 133 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 134 */ 135 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 136 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 137 138 /* 139 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 140 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 141 */ 142 #define __gnu_inline __attribute__((__gnu_inline__)) 143 144 /* 145 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 146 */ 147 #define __malloc __attribute__((__malloc__)) 148 149 /* 150 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 151 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 152 */ 153 #define __mode(x) __attribute__((__mode__(x))) 154 155 /* 156 * Optional: only supported since gcc >= 7 157 * 158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 159 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 160 */ 161 #if __has_attribute(__no_caller_saved_registers__) 162 # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 163 #else 164 # define __no_caller_saved_registers 165 #endif 166 167 /* 168 * Optional: not supported by clang 169 * 170 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 171 */ 172 #if __has_attribute(__noclone__) 173 # define __noclone __attribute__((__noclone__)) 174 #else 175 # define __noclone 176 #endif 177 178 /* 179 * Add the pseudo keyword 'fallthrough' so case statement blocks 180 * must end with any of these keywords: 181 * break; 182 * fallthrough; 183 * continue; 184 * goto <label>; 185 * return [expression]; 186 * 187 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 188 */ 189 #if __has_attribute(__fallthrough__) 190 # define fallthrough __attribute__((__fallthrough__)) 191 #else 192 # define fallthrough do {} while (0) /* fallthrough */ 193 #endif 194 195 /* 196 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 197 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 198 */ 199 # define __flatten __attribute__((flatten)) 200 201 /* 202 * Note the missing underscores. 203 * 204 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 205 * clang: mentioned 206 */ 207 #define noinline __attribute__((__noinline__)) 208 209 /* 210 * Optional: only supported since gcc >= 8 211 * Optional: not supported by clang 212 * Optional: not supported by icc 213 * 214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 215 */ 216 #if __has_attribute(__nonstring__) 217 # define __nonstring __attribute__((__nonstring__)) 218 #else 219 # define __nonstring 220 #endif 221 222 /* 223 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 224 * 225 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 226 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 227 */ 228 #if __has_attribute(__no_profile_instrument_function__) 229 # define __no_profile __attribute__((__no_profile_instrument_function__)) 230 #else 231 # define __no_profile 232 #endif 233 234 /* 235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 236 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 237 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 238 */ 239 #define __noreturn __attribute__((__noreturn__)) 240 241 /* 242 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 243 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 244 */ 245 #define __packed __attribute__((__packed__)) 246 247 /* 248 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 249 */ 250 #define __pure __attribute__((__pure__)) 251 252 /* 253 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 255 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 256 */ 257 #define __section(section) __attribute__((__section__(section))) 258 259 /* 260 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 261 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 264 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 265 */ 266 #define __always_unused __attribute__((__unused__)) 267 #define __maybe_unused __attribute__((__unused__)) 268 269 /* 270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 271 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 272 */ 273 #define __used __attribute__((__used__)) 274 275 /* 276 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 277 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 278 */ 279 #define __must_check __attribute__((__warn_unused_result__)) 280 281 /* 282 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 283 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 284 */ 285 #define __weak __attribute__((__weak__)) 286 287 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 288