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