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. For GCC < 9.1, __alloc_size__ gets undefined
  39  * in compiler-gcc.h, due to misbehaviors.
  40  *
  41  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
  42  * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
  43  */
  44 #define __alloc_size__(x, ...)          __attribute__((__alloc_size__(x, ## __VA_ARGS__)))
  45
  46 /*
  47  * Note: users of __always_inline currently do not write "inline" themselves,
  48  * which seems to be required by gcc to apply the attribute according
  49  * to its docs (and also "warning: always_inline function might not be
  50  * inlinable [-Wattributes]" is emitted).
  51  *
  52  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  53  * clang: mentioned
  54  */
  55 #define __always_inline                 inline __attribute__((__always_inline__))
  56
  57 /*
  58  * The second argument is optional (default 0), so we use a variadic macro
  59  * to make the shorthand.
  60  *
  61  * Beware: Do not apply this to functions which may return
  62  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  63  * returning extra information in the low bits (but in that case the
  64  * compiler should see some alignment anyway, when the return value is
  65  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  66  *
  67  * Optional: not supported by icc
  68  *
  69  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  70  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  71  */
  72 #if __has_attribute(__assume_aligned__)
  73 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  74 #else
  75 # define __assume_aligned(a, ...)
  76 #endif
  77
  78 /*
  79  * Note the long name.
  80  *
  81  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
  82  */
  83 #define __attribute_const__             __attribute__((__const__))
  84
  85 /*
  86  * Optional: only supported since gcc >= 9
  87  * Optional: not supported by clang
  88  * Optional: not supported by icc
  89  *
  90  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
  91  */
  92 #if __has_attribute(__copy__)
  93 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
  94 #else
  95 # define __copy(symbol)
  96 #endif
  97
  98 /*
  99  * Optional: not supported by gcc
 100  * Optional: only supported since clang >= 14.0
 101  * Optional: not supported by icc
 102  *
 103  * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
 104  */
 105 #if __has_attribute(__diagnose_as_builtin__)
 106 # define __diagnose_as(builtin...)      __attribute__((__diagnose_as_builtin__(builtin)))
 107 #else
 108 # define __diagnose_as(builtin...)
 109 #endif
 110
 111 /*
 112  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 113  * attribute warnings entirely and for good") for more information.
 114  *
 115  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 116  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 117  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 118  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 119  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 120  */
 121 #define __deprecated
 122
 123 /*
 124  * Optional: not supported by clang
 125  * Optional: not supported by icc
 126  *
 127  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 128  */
 129 #if __has_attribute(__designated_init__)
 130 # define __designated_init              __attribute__((__designated_init__))
 131 #else
 132 # define __designated_init
 133 #endif
 134
 135 /*
 136  * Optional: only supported since clang >= 14.0
 137  *
 138  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
 139  */
 140 #if __has_attribute(__error__)
 141 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
 142 #else
 143 # define __compiletime_error(msg)
 144 #endif
 145
 146 /*
 147  * Optional: not supported by clang
 148  *
 149  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 150  */
 151 #if __has_attribute(__externally_visible__)
 152 # define __visible                      __attribute__((__externally_visible__))
 153 #else
 154 # define __visible
 155 #endif
 156
 157 /*
 158  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 159  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 160  */
 161 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 162 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 163
 164 /*
 165  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 166  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 167  */
 168 #define __gnu_inline                    __attribute__((__gnu_inline__))
 169
 170 /*
 171  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 172  * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
 173  */
 174 #define __malloc                        __attribute__((__malloc__))
 175
 176 /*
 177  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 178  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 179  */
 180 #define __mode(x)                       __attribute__((__mode__(x)))
 181
 182 /*
 183  * Optional: only supported since gcc >= 7
 184  *
 185  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
 186  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
 187  */
 188 #if __has_attribute(__no_caller_saved_registers__)
 189 # define __no_caller_saved_registers    __attribute__((__no_caller_saved_registers__))
 190 #else
 191 # define __no_caller_saved_registers
 192 #endif
 193
 194 /*
 195  * Optional: not supported by clang
 196  *
 197  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 198  */
 199 #if __has_attribute(__noclone__)
 200 # define __noclone                      __attribute__((__noclone__))
 201 #else
 202 # define __noclone
 203 #endif
 204
 205 /*
 206  * Add the pseudo keyword 'fallthrough' so case statement blocks
 207  * must end with any of these keywords:
 208  *   break;
 209  *   fallthrough;
 210  *   continue;
 211  *   goto <label>;
 212  *   return [expression];
 213  *
 214  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 215  */
 216 #if __has_attribute(__fallthrough__)
 217 # define fallthrough                    __attribute__((__fallthrough__))
 218 #else
 219 # define fallthrough                    do {} while (0)  /* fallthrough */
 220 #endif
 221
 222 /*
 223  * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
 224  * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
 225  */
 226 # define __flatten                      __attribute__((flatten))
 227
 228 /*
 229  * Note the missing underscores.
 230  *
 231  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 232  * clang: mentioned
 233  */
 234 #define   noinline                      __attribute__((__noinline__))
 235
 236 /*
 237  * Optional: only supported since gcc >= 8
 238  * Optional: not supported by clang
 239  * Optional: not supported by icc
 240  *
 241  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 242  */
 243 #if __has_attribute(__nonstring__)
 244 # define __nonstring                    __attribute__((__nonstring__))
 245 #else
 246 # define __nonstring
 247 #endif
 248
 249 /*
 250  * Optional: only supported since GCC >= 7.1, clang >= 13.0.
 251  *
 252  *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
 253  *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
 254  */
 255 #if __has_attribute(__no_profile_instrument_function__)
 256 # define __no_profile                  __attribute__((__no_profile_instrument_function__))
 257 #else
 258 # define __no_profile
 259 #endif
 260
 261 /*
 262  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 263  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 264  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 265  */
 266 #define __noreturn                      __attribute__((__noreturn__))
 267
 268 /*
 269  * Optional: not supported by gcc.
 270  * Optional: not supported by icc.
 271  *
 272  * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
 273  */
 274 #if __has_attribute(__overloadable__)
 275 # define __overloadable                 __attribute__((__overloadable__))
 276 #else
 277 # define __overloadable
 278 #endif
 279
 280 /*
 281  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 282  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 283  */
 284 #define __packed                        __attribute__((__packed__))
 285
 286 /*
 287  * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
 288  *
 289  * Optional: not supported by gcc.
 290  * Optional: not supported by icc.
 291  *
 292  * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
 293  */
 294 #if __has_attribute(__pass_dynamic_object_size__)
 295 # define __pass_dynamic_object_size(type)       __attribute__((__pass_dynamic_object_size__(type)))
 296 #else
 297 # define __pass_dynamic_object_size(type)
 298 #endif
 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 /*
 375  * Used by functions that use '__builtin_return_address'. These function
 376  * don't want to be splited or made inline, which can make
 377  * the '__builtin_return_address' get unexpected address.
 378  */
 379 #define __fix_address noinline __noclone
 380
 381 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */