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