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  * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
  25  * In the meantime, to support gcc < 5, we implement __has_attribute
  26  * by hand.
  27  */
  28 #ifndef __has_attribute
  29 # define __has_attribute(x) __GCC4_has_attribute_##x
  30 # define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
  31 # define __GCC4_has_attribute___copy__                0
  32 # define __GCC4_has_attribute___designated_init__     0
  33 # define __GCC4_has_attribute___error__               1
  34 # define __GCC4_has_attribute___externally_visible__  1
  35 # define __GCC4_has_attribute___no_caller_saved_registers__ 0
  36 # define __GCC4_has_attribute___noclone__             1
  37 # define __GCC4_has_attribute___nonstring__           0
  38 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  39 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
  40 # define __GCC4_has_attribute___fallthrough__         0
  41 # define __GCC4_has_attribute___warning__             1
  42 #endif
  43
  44 /*
  45  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  46  */
  47 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
  48
  49 /*
  50  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  51  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  52  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  53  */
  54 #define __aligned(x)                    __attribute__((__aligned__(x)))
  55 #define __aligned_largest               __attribute__((__aligned__))
  56
  57 /*
  58  * Note: users of __always_inline currently do not write "inline" themselves,
  59  * which seems to be required by gcc to apply the attribute according
  60  * to its docs (and also "warning: always_inline function might not be
  61  * inlinable [-Wattributes]" is emitted).
  62  *
  63  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  64  * clang: mentioned
  65  */
  66 #define __always_inline                 inline __attribute__((__always_inline__))
  67
  68 /*
  69  * The second argument is optional (default 0), so we use a variadic macro
  70  * to make the shorthand.
  71  *
  72  * Beware: Do not apply this to functions which may return
  73  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  74  * returning extra information in the low bits (but in that case the
  75  * compiler should see some alignment anyway, when the return value is
  76  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  77  *
  78  * Optional: only supported since gcc >= 4.9
  79  * Optional: not supported by icc
  80  *
  81  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  82  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  83  */
  84 #if __has_attribute(__assume_aligned__)
  85 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  86 #else
  87 # define __assume_aligned(a, ...)
  88 #endif
  89
  90 /*
  91  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  92  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  93  */
  94 #define __cold                          __attribute__((__cold__))
  95
  96 /*
  97  * Note the long name.
  98  *
  99  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
 100  */
 101 #define __attribute_const__             __attribute__((__const__))
 102
 103 /*
 104  * Optional: only supported since gcc >= 9
 105  * Optional: not supported by clang
 106  * Optional: not supported by icc
 107  *
 108  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
 109  */
 110 #if __has_attribute(__copy__)
 111 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
 112 #else
 113 # define __copy(symbol)
 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: only supported since gcc >= 5.1
 130  * Optional: not supported by clang
 131  * Optional: not supported by icc
 132  *
 133  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 134  */
 135 #if __has_attribute(__designated_init__)
 136 # define __designated_init              __attribute__((__designated_init__))
 137 #else
 138 # define __designated_init
 139 #endif
 140
 141 /*
 142  * Optional: only supported since clang >= 14.0
 143  *
 144  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
 145  */
 146 #if __has_attribute(__error__)
 147 # define __compiletime_error(msg)       __attribute__((__error__(msg)))
 148 #else
 149 # define __compiletime_error(msg)
 150 #endif
 151
 152 /*
 153  * Optional: not supported by clang
 154  *
 155  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 156  */
 157 #if __has_attribute(__externally_visible__)
 158 # define __visible                      __attribute__((__externally_visible__))
 159 #else
 160 # define __visible
 161 #endif
 162
 163 /*
 164  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 165  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 166  */
 167 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 168 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 169
 170 /*
 171  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 172  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 173  */
 174 #define __gnu_inline                    __attribute__((__gnu_inline__))
 175
 176 /*
 177  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 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  *   goto <label>;
 216  *   return [expression];
 217  *
 218  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 219  */
 220 #if __has_attribute(__fallthrough__)
 221 # define fallthrough                    __attribute__((__fallthrough__))
 222 #else
 223 # define fallthrough                    do {} while (0)  /* fallthrough */
 224 #endif
 225
 226 /*
 227  * Note the missing underscores.
 228  *
 229  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 230  * clang: mentioned
 231  */
 232 #define   noinline                      __attribute__((__noinline__))
 233
 234 /*
 235  * Optional: only supported since gcc >= 8
 236  * Optional: not supported by clang
 237  * Optional: not supported by icc
 238  *
 239  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 240  */
 241 #if __has_attribute(__nonstring__)
 242 # define __nonstring                    __attribute__((__nonstring__))
 243 #else
 244 # define __nonstring
 245 #endif
 246
 247 /*
 248  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 249  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 250  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 251  */
 252 #define __noreturn                      __attribute__((__noreturn__))
 253
 254 /*
 255  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 256  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 257  */
 258 #define __packed                        __attribute__((__packed__))
 259
 260 /*
 261  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 262  */
 263 #define __pure                          __attribute__((__pure__))
 264
 265 /*
 266  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 267  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 268  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 269  */
 270 #define __section(section)              __attribute__((__section__(section)))
 271
 272 /*
 273  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 274  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 275  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 276  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 277  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 278  */
 279 #define __always_unused                 __attribute__((__unused__))
 280 #define __maybe_unused                  __attribute__((__unused__))
 281
 282 /*
 283  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 284  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 285  */
 286 #define __used                          __attribute__((__used__))
 287
 288 /*
 289  * Optional: only supported since clang >= 14.0
 290  *
 291  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warning-function-attribute
 292  */
 293 #if __has_attribute(__warning__)
 294 # define __compiletime_warning(msg)     __attribute__((__warning__(msg)))
 295 #else
 296 # define __compiletime_warning(msg)
 297 #endif
 298
 299 /*
 300  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 301  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 302  */
 303 #define __weak                          __attribute__((__weak__))
 304
 305 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */