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___fallthrough__ 0 44 #endif 45 46 /* 47 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute 48 */ 49 #define __alias(symbol) __attribute__((__alias__(#symbol))) 50 51 /* 52 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute 53 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute 54 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute 55 */ 56 #define __aligned(x) __attribute__((__aligned__(x))) 57 #define __aligned_largest __attribute__((__aligned__)) 58 59 /* 60 * Note: users of __always_inline currently do not write "inline" themselves, 61 * which seems to be required by gcc to apply the attribute according 62 * to its docs (and also "warning: always_inline function might not be 63 * inlinable [-Wattributes]" is emitted). 64 * 65 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute 66 * clang: mentioned 67 */ 68 #define __always_inline inline __attribute__((__always_inline__)) 69 70 /* 71 * The second argument is optional (default 0), so we use a variadic macro 72 * to make the shorthand. 73 * 74 * Beware: Do not apply this to functions which may return 75 * ERR_PTRs. Also, it is probably unwise to apply it to functions 76 * returning extra information in the low bits (but in that case the 77 * compiler should see some alignment anyway, when the return value is 78 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 79 * 80 * Optional: only supported since gcc >= 4.9 81 * Optional: not supported by icc 82 * 83 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute 84 * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned 85 */ 86 #if __has_attribute(__assume_aligned__) 87 # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 88 #else 89 # define __assume_aligned(a, ...) 90 #endif 91 92 /* 93 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute 94 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute 95 */ 96 #define __cold __attribute__((__cold__)) 97 98 /* 99 * Note the long name. 100 * 101 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute 102 */ 103 #define __attribute_const__ __attribute__((__const__)) 104 105 /* 106 * Optional: only supported since gcc >= 9 107 * Optional: not supported by clang 108 * Optional: not supported by icc 109 * 110 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute 111 */ 112 #if __has_attribute(__copy__) 113 # define __copy(symbol) __attribute__((__copy__(symbol))) 114 #else 115 # define __copy(symbol) 116 #endif 117 118 /* 119 * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated' 120 * attribute warnings entirely and for good") for more information. 121 * 122 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute 123 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute 124 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute 125 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute 126 * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated 127 */ 128 #define __deprecated 129 130 /* 131 * Optional: only supported since gcc >= 5.1 132 * Optional: not supported by clang 133 * Optional: not supported by icc 134 * 135 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute 136 */ 137 #if __has_attribute(__designated_init__) 138 # define __designated_init __attribute__((__designated_init__)) 139 #else 140 # define __designated_init 141 #endif 142 143 /* 144 * Optional: not supported by clang 145 * 146 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute 147 */ 148 #if __has_attribute(__externally_visible__) 149 # define __visible __attribute__((__externally_visible__)) 150 #else 151 # define __visible 152 #endif 153 154 /* 155 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute 156 * clang: https://clang.llvm.org/docs/AttributeReference.html#format 157 */ 158 #define __printf(a, b) __attribute__((__format__(printf, a, b))) 159 #define __scanf(a, b) __attribute__((__format__(scanf, a, b))) 160 161 /* 162 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute 163 * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline 164 */ 165 #define __gnu_inline __attribute__((__gnu_inline__)) 166 167 /* 168 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute 169 */ 170 #define __malloc __attribute__((__malloc__)) 171 172 /* 173 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute 174 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute 175 */ 176 #define __mode(x) __attribute__((__mode__(x))) 177 178 /* 179 * Optional: not supported by clang 180 * 181 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute 182 */ 183 #if __has_attribute(__noclone__) 184 # define __noclone __attribute__((__noclone__)) 185 #else 186 # define __noclone 187 #endif 188 189 /* 190 * Add the pseudo keyword 'fallthrough' so case statement blocks 191 * must end with any of these keywords: 192 * break; 193 * fallthrough; 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 * Note the missing underscores. 207 * 208 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute 209 * clang: mentioned 210 */ 211 #define noinline __attribute__((__noinline__)) 212 213 /* 214 * Optional: only supported since gcc >= 8 215 * Optional: not supported by clang 216 * Optional: not supported by icc 217 * 218 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute 219 */ 220 #if __has_attribute(__nonstring__) 221 # define __nonstring __attribute__((__nonstring__)) 222 #else 223 # define __nonstring 224 #endif 225 226 /* 227 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute 228 * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn 229 * clang: https://clang.llvm.org/docs/AttributeReference.html#id1 230 */ 231 #define __noreturn __attribute__((__noreturn__)) 232 233 /* 234 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute 235 * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute 236 */ 237 #define __packed __attribute__((__packed__)) 238 239 /* 240 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute 241 */ 242 #define __pure __attribute__((__pure__)) 243 244 /* 245 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute 246 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute 247 * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate 248 */ 249 #define __section(S) __attribute__((__section__(S))) 250 251 /* 252 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute 253 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute 254 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute 255 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute 256 * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused 257 */ 258 #define __always_unused __attribute__((__unused__)) 259 #define __maybe_unused __attribute__((__unused__)) 260 261 /* 262 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute 263 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute 264 */ 265 #define __used __attribute__((__used__)) 266 267 /* 268 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute 269 * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute 270 */ 271 #define __weak __attribute__((__weak__)) 272 273 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */ 274