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  * 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: only supported since gcc >= 5.1
 117  * Optional: not supported by clang
 118  * Optional: not supported by icc
 119  *
 120  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 121  */
 122 #if __has_attribute(__designated_init__)
 123 # define __designated_init              __attribute__((__designated_init__))
 124 #else
 125 # define __designated_init
 126 #endif
 127
 128 /*
 129  * Optional: only supported since clang >= 14.0
 130  *
 131  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
 132  */
 133 #if __has_attribute(__error__)
 134 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
 135 #else
 136 # define __compiletime_error(msg)
 137 #endif
 138
 139 /*
 140  * Optional: not supported by clang
 141  *
 142  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 143  */
 144 #if __has_attribute(__externally_visible__)
 145 # define __visible                      __attribute__((__externally_visible__))
 146 #else
 147 # define __visible
 148 #endif
 149
 150 /*
 151  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 152  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 153  */
 154 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 155 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 156
 157 /*
 158  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 159  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 160  */
 161 #define __gnu_inline                    __attribute__((__gnu_inline__))
 162
 163 /*
 164  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 165  * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc
 166  */
 167 #define __malloc                        __attribute__((__malloc__))
 168
 169 /*
 170  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 171  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 172  */
 173 #define __mode(x)                       __attribute__((__mode__(x)))
 174
 175 /*
 176  * Optional: only supported since gcc >= 7
 177  *
 178  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
 179  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
 180  */
 181 #if __has_attribute(__no_caller_saved_registers__)
 182 # define __no_caller_saved_registers    __attribute__((__no_caller_saved_registers__))
 183 #else
 184 # define __no_caller_saved_registers
 185 #endif
 186
 187 /*
 188  * Optional: not supported by clang
 189  *
 190  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 191  */
 192 #if __has_attribute(__noclone__)
 193 # define __noclone                      __attribute__((__noclone__))
 194 #else
 195 # define __noclone
 196 #endif
 197
 198 /*
 199  * Add the pseudo keyword 'fallthrough' so case statement blocks
 200  * must end with any of these keywords:
 201  *   break;
 202  *   fallthrough;
 203  *   continue;
 204  *   goto <label>;
 205  *   return [expression];
 206  *
 207  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 208  */
 209 #if __has_attribute(__fallthrough__)
 210 # define fallthrough                    __attribute__((__fallthrough__))
 211 #else
 212 # define fallthrough                    do {} while (0)  /* fallthrough */
 213 #endif
 214
 215 /*
 216  * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes
 217  * clang: https://clang.llvm.org/docs/AttributeReference.html#flatten
 218  */
 219 # define __flatten                      __attribute__((flatten))
 220
 221 /*
 222  * Note the missing underscores.
 223  *
 224  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 225  * clang: mentioned
 226  */
 227 #define   noinline                      __attribute__((__noinline__))
 228
 229 /*
 230  * Optional: only supported since gcc >= 8
 231  * Optional: not supported by clang
 232  * Optional: not supported by icc
 233  *
 234  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 235  */
 236 #if __has_attribute(__nonstring__)
 237 # define __nonstring                    __attribute__((__nonstring__))
 238 #else
 239 # define __nonstring
 240 #endif
 241
 242 /*
 243  * Optional: only supported since GCC >= 7.1, clang >= 13.0.
 244  *
 245  *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
 246  *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
 247  */
 248 #if __has_attribute(__no_profile_instrument_function__)
 249 # define __no_profile                  __attribute__((__no_profile_instrument_function__))
 250 #else
 251 # define __no_profile
 252 #endif
 253
 254 /*
 255  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 256  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 257  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 258  */
 259 #define __noreturn                      __attribute__((__noreturn__))
 260
 261 /*
 262  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 263  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 264  */
 265 #define __packed                        __attribute__((__packed__))
 266
 267 /*
 268  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 269  */
 270 #define __pure                          __attribute__((__pure__))
 271
 272 /*
 273  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 274  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 275  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 276  */
 277 #define __section(section)              __attribute__((__section__(section)))
 278
 279 /*
 280  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 281  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 282  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 283  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 284  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 285  */
 286 #define __always_unused                 __attribute__((__unused__))
 287 #define __maybe_unused                  __attribute__((__unused__))
 288
 289 /*
 290  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 291  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 292  */
 293 #define __used                          __attribute__((__used__))
 294
 295 /*
 296  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
 297  * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result
 298  */
 299 #define __must_check                    __attribute__((__warn_unused_result__))
 300
 301 /*
 302  * Optional: only supported since clang >= 14.0
 303  *
 304  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
 305  */
 306 #if __has_attribute(__warning__)
 307 # define __compiletime_warning(msg)     __attribute__((__warning__(msg)))
 308 #else
 309 # define __compiletime_warning(msg)
 310 #endif
 311
 312 /*
 313  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 314  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 315  */
 316 #define __weak                          __attribute__((__weak__))
 317
 318 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */