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  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  68  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  69  */
  70 #define __assume_aligned(a, ...)        __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  71
  72 /*
  73  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-cleanup-variable-attribute
  74  * clang: https://clang.llvm.org/docs/AttributeReference.html#cleanup
  75  */
  76 #define __cleanup(func)                 __attribute__((__cleanup__(func)))
  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  *
  89  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
  90  */
  91 #if __has_attribute(__copy__)
  92 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
  93 #else
  94 # define __copy(symbol)
  95 #endif
  96
  97 /*
  98  * Optional: only supported since gcc >= 15
  99  * Optional: only supported since clang >= 18
 100  *
 101  *   gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
 102  * clang: https://github.com/llvm/llvm-project/pull/76348
 103  */
 104 #if __has_attribute(__counted_by__)
 105 # define __counted_by(member)           __attribute__((__counted_by__(member)))
 106 #else
 107 # define __counted_by(member)
 108 #endif
 109
 110 /*
 111  * Optional: not supported by gcc
 112  * Optional: only supported since clang >= 14.0
 113  *
 114  * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
 115  */
 116 #if __has_attribute(__diagnose_as_builtin__)
 117 # define __diagnose_as(builtin...)      __attribute__((__diagnose_as_builtin__(builtin)))
 118 #else
 119 # define __diagnose_as(builtin...)
 120 #endif
 121
 122 /*
 123  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 124  * attribute warnings entirely and for good") for more information.
 125  *
 126  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 127  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 128  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 129  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 130  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 131  */
 132 #define __deprecated
 133
 134 /*
 135  * Optional: not supported by clang
 136  *
 137  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 138  */
 139 #if __has_attribute(__designated_init__)
 140 # define __designated_init              __attribute__((__designated_init__))
 141 #else
 142 # define __designated_init
 143 #endif
 144
 145 /*
 146  * Optional: only supported since clang >= 14.0
 147  *
 148  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
 149  */
 150 #if __has_attribute(__error__)
 151 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
 152 #else
 153 # define __compiletime_error(msg)
 154 #endif
 155
 156 /*
 157  * Optional: not supported by clang
 158  *
 159  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 160  */
 161 #if __has_attribute(__externally_visible__)
 162 # define __visible                      __attribute__((__externally_visible__))
 163 #else
 164 # define __visible
 165 #endif
 166
 167 /*
 168  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 169  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 170  */
 171 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 172 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 173
 174 /*
 175  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 176  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 177  */
 178 #define __gnu_inline                    __attribute__((__gnu_inline__))
 179
 180 /*
 181  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 182  * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
 183  */
 184 #define __malloc                        __attribute__((__malloc__))
 185
 186 /*
 187  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 188  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 189  */
 190 #define __mode(x)                       __attribute__((__mode__(x)))
 191
 192 /*
 193  * Optional: only supported since gcc >= 7
 194  *
 195  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
 196  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
 197  */
 198 #if __has_attribute(__no_caller_saved_registers__)
 199 # define __no_caller_saved_registers    __attribute__((__no_caller_saved_registers__))
 200 #else
 201 # define __no_caller_saved_registers
 202 #endif
 203
 204 /*
 205  * Optional: not supported by clang
 206  *
 207  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 208  */
 209 #if __has_attribute(__noclone__)
 210 # define __noclone                      __attribute__((__noclone__))
 211 #else
 212 # define __noclone
 213 #endif
 214
 215 /*
 216  * Add the pseudo keyword 'fallthrough' so case statement blocks
 217  * must end with any of these keywords:
 218  *   break;
 219  *   fallthrough;
 220  *   continue;
 221  *   goto <label>;
 222  *   return [expression];
 223  *
 224  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 225  */
 226 #if __has_attribute(__fallthrough__)
 227 # define fallthrough                    __attribute__((__fallthrough__))
 228 #else
 229 # define fallthrough                    do {} while (0)  /* fallthrough */
 230 #endif
 231
 232 /*
 233  * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
 234  * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
 235  */
 236 # define __flatten                      __attribute__((flatten))
 237
 238 /*
 239  * Note the missing underscores.
 240  *
 241  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 242  * clang: mentioned
 243  */
 244 #define   noinline                      __attribute__((__noinline__))
 245
 246 /*
 247  * Optional: only supported since gcc >= 8
 248  * Optional: not supported by clang
 249  *
 250  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 251  */
 252 #if __has_attribute(__nonstring__)
 253 # define __nonstring                    __attribute__((__nonstring__))
 254 #else
 255 # define __nonstring
 256 #endif
 257
 258 /*
 259  * Optional: only supported since GCC >= 7.1, clang >= 13.0.
 260  *
 261  *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
 262  *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
 263  */
 264 #if __has_attribute(__no_profile_instrument_function__)
 265 # define __no_profile                  __attribute__((__no_profile_instrument_function__))
 266 #else
 267 # define __no_profile
 268 #endif
 269
 270 /*
 271  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 272  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 273  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 274  */
 275 #define __noreturn                      __attribute__((__noreturn__))
 276
 277 /*
 278  * Optional: only supported since GCC >= 11.1, clang >= 7.0.
 279  *
 280  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fstack_005fprotector-function-attribute
 281  *   clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safebuffers
 282  */
 283 #if __has_attribute(__no_stack_protector__)
 284 # define __no_stack_protector           __attribute__((__no_stack_protector__))
 285 #else
 286 # define __no_stack_protector
 287 #endif
 288
 289 /*
 290  * Optional: not supported by gcc.
 291  *
 292  * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
 293  */
 294 #if __has_attribute(__overloadable__)
 295 # define __overloadable                 __attribute__((__overloadable__))
 296 #else
 297 # define __overloadable
 298 #endif
 299
 300 /*
 301  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 302  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 303  */
 304 #define __packed                        __attribute__((__packed__))
 305
 306 /*
 307  * Note: the "type" argument should match any __builtin_object_size(p, type) usage.
 308  *
 309  * Optional: not supported by gcc.
 310  *
 311  * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size
 312  */
 313 #if __has_attribute(__pass_dynamic_object_size__)
 314 # define __pass_dynamic_object_size(type)       __attribute__((__pass_dynamic_object_size__(type)))
 315 #else
 316 # define __pass_dynamic_object_size(type)
 317 #endif
 318 #if __has_attribute(__pass_object_size__)
 319 # define __pass_object_size(type)       __attribute__((__pass_object_size__(type)))
 320 #else
 321 # define __pass_object_size(type)
 322 #endif
 323
 324 /*
 325  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 326  */
 327 #define __pure                          __attribute__((__pure__))
 328
 329 /*
 330  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 331  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 332  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 333  */
 334 #define __section(section)              __attribute__((__section__(section)))
 335
 336 /*
 337  * Optional: only supported since gcc >= 12
 338  *
 339  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-uninitialized-variable-attribute
 340  * clang: https://clang.llvm.org/docs/AttributeReference.html#uninitialized
 341  */
 342 #if __has_attribute(__uninitialized__)
 343 # define __uninitialized                __attribute__((__uninitialized__))
 344 #else
 345 # define __uninitialized
 346 #endif
 347
 348 /*
 349  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 350  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 351  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 352  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 353  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 354  */
 355 #define __always_unused                 __attribute__((__unused__))
 356 #define __maybe_unused                  __attribute__((__unused__))
 357
 358 /*
 359  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 360  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 361  */
 362 #define __used                          __attribute__((__used__))
 363
 364 /*
 365  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
 366  * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
 367  */
 368 #define __must_check                    __attribute__((__warn_unused_result__))
 369
 370 /*
 371  * Optional: only supported since clang >= 14.0
 372  *
 373  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
 374  */
 375 #if __has_attribute(__warning__)
 376 # define __compiletime_warning(msg)     __attribute__((__warning__(msg)))
 377 #else
 378 # define __compiletime_warning(msg)
 379 #endif
 380
 381 /*
 382  * Optional: only supported since clang >= 14.0
 383  *
 384  * clang: https://clang.llvm.org/docs/AttributeReference.html#disable-sanitizer-instrumentation
 385  *
 386  * disable_sanitizer_instrumentation is not always similar to
 387  * no_sanitize((<sanitizer-name>)): the latter may still let specific sanitizers
 388  * insert code into functions to prevent false positives. Unlike that,
 389  * disable_sanitizer_instrumentation prevents all kinds of instrumentation to
 390  * functions with the attribute.
 391  */
 392 #if __has_attribute(disable_sanitizer_instrumentation)
 393 # define __disable_sanitizer_instrumentation \
 394          __attribute__((disable_sanitizer_instrumentation))
 395 #else
 396 # define __disable_sanitizer_instrumentation
 397 #endif
 398
 399 /*
 400  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 401  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 402  */
 403 #define __weak                          __attribute__((__weak__))
 404
 405 /*
 406  * Used by functions that use '__builtin_return_address'. These function
 407  * don't want to be splited or made inline, which can make
 408  * the '__builtin_return_address' get unexpected address.
 409  */
 410 #define __fix_address noinline __noclone
 411
 412 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */