include/linux/compiler_attributes.h

   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: do not use this directly. Instead, use __alloc_size() since it is conditionally
  38  * available and includes other attributes.
  39  *
  40  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
  41  * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
  42  */
  43 #define __alloc_size__(x, ...)          __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
  44
  45 /*
  46  * Note: users of __always_inline currently do not write "inline" themselves,
  47  * which seems to be required by gcc to apply the attribute according
  48  * to its docs (and also "warning: always_inline function might not be
  49  * inlinable [-Wattributes]" is emitted).
  50  *
  51  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  52  * clang: mentioned
  53  */
  54 #define __always_inline                 inline __attribute__((__always_inline__))
  55
  56 /*
  57  * The second argument is optional (default 0), so we use a variadic macro
  58  * to make the shorthand.
  59  *
  60  * Beware: Do not apply this to functions which may return
  61  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  62  * returning extra information in the low bits (but in that case the
  63  * compiler should see some alignment anyway, when the return value is
  64  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  65  *
  66  * Optional: not supported by icc
  67  *
  68  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  69  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  70  */
  71 #if __has_attribute(__assume_aligned__)
  72 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  73 #else
  74 # define __assume_aligned(a, ...)
  75 #endif
  76
  77 /*
  78  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  79  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  80  */
  81 #define __cold                          __attribute__((__cold__))
  82
  83 /*
  84  * Note the long name.
  85  *
  86  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
  87  */
  88 #define __attribute_const__             __attribute__((__const__))
  89
  90 /*
  91  * Optional: only supported since gcc >= 9
  92  * Optional: not supported by clang
  93  * Optional: not supported by icc
  94  *
  95  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
  96  */
  97 #if __has_attribute(__copy__)
  98 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
  99 #else
 100 # define __copy(symbol)
 101 #endif
 102
 103 /*
 104  * Optional: not supported by gcc
 105  * Optional: only supported since clang >= 14.0
 106  * Optional: not supported by icc
 107  *
 108  * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
 109  */
 110 #if __has_attribute(__diagnose_as_builtin__)
 111 # define __diagnose_as(builtin...)      __attribute__((__diagnose_as_builtin__(builtin)))
 112 #else
 113 # define __diagnose_as(builtin...)
 114 #endif
 115
 116 /*
 117  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 118  * attribute warnings entirely and for good") for more information.
 119  *
 120  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 121  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 122  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 123  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 124  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 125  */
 126 #define __deprecated
 127
 128 /*
 129  * Optional: not supported by clang
 130  * Optional: not supported by icc
 131  *
 132  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 133  */
 134 #if __has_attribute(__designated_init__)
 135 # define __designated_init              __attribute__((__designated_init__))
 136 #else
 137 # define __designated_init
 138 #endif
 139
 140 /*
 141  * Optional: only supported since clang >= 14.0
 142  *
 143  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
 144  */
 145 #if __has_attribute(__error__)
 146 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
 147 #else
 148 # define __compiletime_error(msg)
 149 #endif
 150
 151 /*
 152  * Optional: not supported by clang
 153  *
 154  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 155  */
 156 #if __has_attribute(__externally_visible__)
 157 # define __visible                      __attribute__((__externally_visible__))
 158 #else
 159 # define __visible
 160 #endif
 161
 162 /*
 163  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 164  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 165  */
 166 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 167 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 168
 169 /*
 170  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 171  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 172  */
 173 #define __gnu_inline                    __attribute__((__gnu_inline__))
 174
 175 /*
 176  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 177  * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
 178  */
 179 #define __malloc                        __attribute__((__malloc__))
 180
 181 /*
 182  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 183  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 184  */
 185 #define __mode(x)                       __attribute__((__mode__(x)))
 186
 187 /*
 188  * Optional: only supported since gcc >= 7
 189  *
 190  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
 191  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
 192  */
 193 #if __has_attribute(__no_caller_saved_registers__)
 194 # define __no_caller_saved_registers    __attribute__((__no_caller_saved_registers__))
 195 #else
 196 # define __no_caller_saved_registers
 197 #endif
 198
 199 /*
 200  * Optional: not supported by clang
 201  *
 202  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 203  */
 204 #if __has_attribute(__noclone__)
 205 # define __noclone                      __attribute__((__noclone__))
 206 #else
 207 # define __noclone
 208 #endif
 209
 210 /*
 211  * Add the pseudo keyword 'fallthrough' so case statement blocks
 212  * must end with any of these keywords:
 213  *   break;
 214  *   fallthrough;
 215  *   continue;
 216  *   goto <label>;
 217  *   return [expression];
 218  *
 219  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 220  */
 221 #if __has_attribute(__fallthrough__)
 222 # define fallthrough                    __attribute__((__fallthrough__))
 223 #else
 224 # define fallthrough                    do {} while (0)  /* fallthrough */
 225 #endif
 226
 227 /*
 228  * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
 229  * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
 230  */
 231 # define __flatten                      __attribute__((flatten))
 232
 233 /*
 234  * Note the missing underscores.
 235  *
 236  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 237  * clang: mentioned
 238  */
 239 #define   noinline                      __attribute__((__noinline__))
 240
 241 /*
 242  * Optional: only supported since gcc >= 8
 243  * Optional: not supported by clang
 244  * Optional: not supported by icc
 245  *
 246  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 247  */
 248 #if __has_attribute(__nonstring__)
 249 # define __nonstring                    __attribute__((__nonstring__))
 250 #else
 251 # define __nonstring
 252 #endif
 253
 254 /*
 255  * Optional: only supported since GCC >= 7.1, clang >= 13.0.
 256  *
 257  *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
 258  *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
 259  */
 260 #if __has_attribute(__no_profile_instrument_function__)
 261 # define __no_profile                  __attribute__((__no_profile_instrument_function__))
 262 #else
 263 # define __no_profile
 264 #endif
 265
 266 /*
 267  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 268  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 269  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 270  */
 271 #define __noreturn                      __attribute__((__noreturn__))
 272
 273 /*
 274  * Optional: not supported by gcc.
 275  * Optional: not supported by icc.
 276  *
 277  * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
 278  */
 279 #if __has_attribute(__overloadable__)
 280 # define __overloadable                 __attribute__((__overloadable__))
 281 #else
 282 # define __overloadable
 283 #endif
 284
 285 /*
 286  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 287  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 288  */
 289 #define __packed                        __attribute__((__packed__))
 290
 291 /*
 292  * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
 293  *
 294  * Optional: not supported by gcc.
 295  * Optional: not supported by icc.
 296  *
 297  * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
 298  */
 299 #if __has_attribute(__pass_object_size__)
 300 # define __pass_object_size(type)       __attribute__((__pass_object_size__(type)))
 301 #else
 302 # define __pass_object_size(type)
 303 #endif
 304
 305 /*
 306  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 307  */
 308 #define __pure                          __attribute__((__pure__))
 309
 310 /*
 311  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 312  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 313  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 314  */
 315 #define __section(section)              __attribute__((__section__(section)))
 316
 317 /*
 318  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 319  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 320  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 321  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 322  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 323  */
 324 #define __always_unused                 __attribute__((__unused__))
 325 #define __maybe_unused                  __attribute__((__unused__))
 326
 327 /*
 328  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 329  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 330  */
 331 #define __used                          __attribute__((__used__))
 332
 333 /*
 334  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
 335  * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
 336  */
 337 #define __must_check                    __attribute__((__warn_unused_result__))
 338
 339 /*
 340  * Optional: only supported since clang >= 14.0
 341  *
 342  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
 343  */
 344 #if __has_attribute(__warning__)
 345 # define __compiletime_warning(msg)     __attribute__((__warning__(msg)))
 346 #else
 347 # define __compiletime_warning(msg)
 348 #endif
 349
 350 /*
 351  * Optional: only supported since clang >= 14.0
 352  *
 353  * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
 354  *
 355  * disable_sanitizer_instrumentation is not always similar to
 356  * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
 357  * insert code into functions to prevent false positives. Unlike that,
 358  * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
 359  * functions with the attribute.
 360  */
 361 #if __has_attribute(disable_sanitizer_instrumentation)
 362 # define __disable_sanitizer_instrumentation \
 363          __attribute__((disable_sanitizer_instrumentation))
 364 #else
 365 # define __disable_sanitizer_instrumentation
 366 #endif
 367
 368 /*
 369  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 370  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 371  */
 372 #define __weak                          __attribute__((__weak__))
 373
 374 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */