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___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___nonstring__ 0 37 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8) 38 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9) 39 # define __GCC4_has_attribute___fallthrough__ 0 40 #endif 41 42 /* 43 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 44 */ 45 #define __alias(symbol) __attribute__((__alias__(#symbol))) 46 47 /* 48 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute 49 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute 50 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute 51 */ 52 #define __aligned(x) __attribute__((__aligned__(x))) 53 #define __aligned_largest __attribute__((__aligned__)) 54 55 /* 56 * Note: users of __always_inline currently do not write "inline" themselves, 57 * which seems to be required by gcc to apply the attribute according 58 * to its docs (and also "warning: always_inline function might not be 59 * inlinable [-Wattributes]" is emitted). 60 * 61 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 62 * clang: mentioned 63 */ 64 #define __always_inline inline __attribute__((__always_inline__)) 65 66 /* 67 * The second argument is optional (default 0), so we use a variadic macro 68 * to make the shorthand. 69 * 70 * Beware: Do not apply this to functions which may return 71 * ERR_PTRs. Also, it is probably unwise to apply it to functions 72 * returning extra information in the low bits (but in that case the 73 * compiler should see some alignment anyway, when the return value is 74 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 75 * 76 * Optional: only supported since gcc >= 4.9 77 * Optional: not supported by icc 78 * 79 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 80 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 81 */ 82 #if __has_attribute(__assume_aligned__) 83 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 84 #else 85 # define __assume_aligned(a, ...) 86 #endif 87 88 /* 89 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 90 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 91 */ 92 #define __cold __attribute__((__cold__)) 93 94 /* 95 * Note the long name. 96 * 97 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 98 */ 99 #define __attribute_const__ __attribute__((__const__)) 100 101 /* 102 * Optional: only supported since gcc >= 9 103 * Optional: not supported by clang 104 * Optional: not supported by icc 105 * 106 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 107 */ 108 #if __has_attribute(__copy__) 109 # define __copy(symbol) __attribute__((__copy__(symbol))) 110 #else 111 # define __copy(symbol) 112 #endif 113 114 /* 115 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 116 * attribute warnings entirely and for good") for more information. 117 * 118 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 119 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 120 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 121 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 122 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 123 */ 124 #define __deprecated 125 126 /* 127 * Optional: only supported since gcc >= 5.1 128 * Optional: not supported by clang 129 * Optional: not supported by icc 130 * 131 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 132 */ 133 #if __has_attribute(__designated_init__) 134 # define __designated_init __attribute__((__designated_init__)) 135 #else 136 # define __designated_init 137 #endif 138 139 /* 140 * Optional: not supported by clang 141 * 142 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 143 */ 144 #if __has_attribute(__externally_visible__) 145 # define __visible __attribute__((__externally_visible__)) 146 #else 147 # define __visible 148 #endif 149 150 /* 151 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 152 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 153 */ 154 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 155 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 156 157 /* 158 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 159 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 160 */ 161 #define __gnu_inline __attribute__((__gnu_inline__)) 162 163 /* 164 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 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 * goto <label>; 203 * return [expression]; 204 * 205 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 206 */ 207 #if __has_attribute(__fallthrough__) 208 # define fallthrough __attribute__((__fallthrough__)) 209 #else 210 # define fallthrough do {} while (0) /* fallthrough */ 211 #endif 212 213 /* 214 * Note the missing underscores. 215 * 216 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 217 * clang: mentioned 218 */ 219 #define noinline __attribute__((__noinline__)) 220 221 /* 222 * Optional: only supported since gcc >= 8 223 * Optional: not supported by clang 224 * Optional: not supported by icc 225 * 226 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 227 */ 228 #if __has_attribute(__nonstring__) 229 # define __nonstring __attribute__((__nonstring__)) 230 #else 231 # define __nonstring 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-weak-function-attribute 277 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 278 */ 279 #define __weak __attribute__((__weak__)) 280 281 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 282
