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: only supported since gcc >= 5.1 108 * Optional: not supported by clang 109 * Optional: not supported by icc 110 * 111 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 112 */ 113#if __has_attribute(__designated_init__) 114# define __designated_init __attribute__((__designated_init__)) 115#else 116# define __designated_init 117#endif 118 119/* 120 * Optional: only supported since clang >= 14.0 121 * 122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute 123 */ 124#if __has_attribute(__error__) 125# define __compiletime_error(msg) __attribute__((__error__(msg))) 126#else 127# define __compiletime_error(msg) 128#endif 129 130/* 131 * Optional: not supported by clang 132 * 133 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 134 */ 135#if __has_attribute(__externally_visible__) 136# define __visible __attribute__((__externally_visible__)) 137#else 138# define __visible 139#endif 140 141/* 142 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 143 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 144 */ 145#define __printf(a, b) __attribute__((__format__(printf, a, b))) 146#define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 147 148/* 149 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 150 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 151 */ 152#define __gnu_inline __attribute__((__gnu_inline__)) 153 154/* 155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 156 */ 157#define __malloc __attribute__((__malloc__)) 158 159/* 160 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 161 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 162 */ 163#define __mode(x) __attribute__((__mode__(x))) 164 165/* 166 * Optional: only supported since gcc >= 7 167 * 168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86 169 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers 170 */ 171#if __has_attribute(__no_caller_saved_registers__) 172# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__)) 173#else 174# define __no_caller_saved_registers 175#endif 176 177/* 178 * Optional: not supported by clang 179 * 180 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 181 */ 182#if __has_attribute(__noclone__) 183# define __noclone __attribute__((__noclone__)) 184#else 185# define __noclone 186#endif 187 188/* 189 * Add the pseudo keyword 'fallthrough' so case statement blocks 190 * must end with any of these keywords: 191 * break; 192 * fallthrough; 193 * continue; 194 * goto <label>; 195 * return [expression]; 196 * 197 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes 198 */ 199#if __has_attribute(__fallthrough__) 200# define fallthrough __attribute__((__fallthrough__)) 201#else 202# define fallthrough do {} while (0) /* fallthrough */ 203#endif 204 205/* 206 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes 207 * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten 208 */ 209# define __flatten __attribute__((flatten)) 210 211/* 212 * Note the missing underscores. 213 * 214 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 215 * clang: mentioned 216 */ 217#define noinline __attribute__((__noinline__)) 218 219/* 220 * Optional: only supported since gcc >= 8 221 * Optional: not supported by clang 222 * Optional: not supported by icc 223 * 224 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 225 */ 226#if __has_attribute(__nonstring__) 227# define __nonstring __attribute__((__nonstring__)) 228#else 229# define __nonstring 230#endif 231 232/* 233 * Optional: only supported since GCC >= 7.1, clang >= 13.0. 234 * 235 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute 236 * clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function 237 */ 238#if __has_attribute(__no_profile_instrument_function__) 239# define __no_profile __attribute__((__no_profile_instrument_function__)) 240#else 241# define __no_profile 242#endif 243 244/* 245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 246 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 247 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 248 */ 249#define __noreturn __attribute__((__noreturn__)) 250 251/* 252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 253 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 254 */ 255#define __packed __attribute__((__packed__)) 256 257/* 258 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 259 */ 260#define __pure __attribute__((__pure__)) 261 262/* 263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 264 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 265 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 266 */ 267#define __section(section) __attribute__((__section__(section))) 268 269/* 270 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 271 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 272 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 273 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 274 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 275 */ 276#define __always_unused __attribute__((__unused__)) 277#define __maybe_unused __attribute__((__unused__)) 278 279/* 280 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 281 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 282 */ 283#define __used __attribute__((__used__)) 284 285/* 286 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute 287 * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result 288 */ 289#define __must_check __attribute__((__warn_unused_result__)) 290 291/* 292 * Optional: only supported since clang >= 14.0 293 * 294 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute 295 */ 296#if __has_attribute(__warning__) 297# define __compiletime_warning(msg) __attribute__((__warning__(msg))) 298#else 299# define __compiletime_warning(msg) 300#endif 301 302/* 303 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 304 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 305 */ 306#define __weak __attribute__((__weak__)) 307 308#endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 309