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 4.6 <= gcc < 5, we implement __has_attribute
  26  * by hand.
  27  *
  28  * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
  29  * depending on the compiler used to build it; however, these attributes have
  30  * no semantic effects for sparse, so it does not matter. Also note that,
  31  * in order to avoid sparse's warnings, even the unsupported ones must be
  32  * defined to 0.
  33  */
  34 #ifndef __has_attribute
  35 # define __has_attribute(x) __GCC4_has_attribute_##x
  36 # define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
  37 # define __GCC4_has_attribute___copy__                0
  38 # define __GCC4_has_attribute___designated_init__     0
  39 # define __GCC4_has_attribute___externally_visible__  1
  40 # define __GCC4_has_attribute___no_caller_saved_registers__ 0
  41 # define __GCC4_has_attribute___noclone__             1
  42 # define __GCC4_has_attribute___nonstring__           0
  43 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  44 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
  45 # define __GCC4_has_attribute___fallthrough__         0
  46 #endif
  47
  48 /*
  49  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  50  */
  51 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
  52
  53 /*
  54  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  55  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  56  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  57  */
  58 #define __aligned(x)                    __attribute__((__aligned__(x)))
  59 #define __aligned_largest               __attribute__((__aligned__))
  60
  61 /*
  62  * Note: users of __always_inline currently do not write "inline" themselves,
  63  * which seems to be required by gcc to apply the attribute according
  64  * to its docs (and also "warning: always_inline function might not be
  65  * inlinable [-Wattributes]" is emitted).
  66  *
  67  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  68  * clang: mentioned
  69  */
  70 #define __always_inline                 inline __attribute__((__always_inline__))
  71
  72 /*
  73  * The second argument is optional (default 0), so we use a variadic macro
  74  * to make the shorthand.
  75  *
  76  * Beware: Do not apply this to functions which may return
  77  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  78  * returning extra information in the low bits (but in that case the
  79  * compiler should see some alignment anyway, when the return value is
  80  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  81  *
  82  * Optional: only supported since gcc >= 4.9
  83  * Optional: not supported by icc
  84  *
  85  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  86  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  87  */
  88 #if __has_attribute(__assume_aligned__)
  89 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  90 #else
  91 # define __assume_aligned(a, ...)
  92 #endif
  93
  94 /*
  95  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  96  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  97  */
  98 #define __cold                          __attribute__((__cold__))
  99
 100 /*
 101  * Note the long name.
 102  *
 103  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
 104  */
 105 #define __attribute_const__             __attribute__((__const__))
 106
 107 /*
 108  * Optional: only supported since gcc >= 9
 109  * Optional: not supported by clang
 110  * Optional: not supported by icc
 111  *
 112  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
 113  */
 114 #if __has_attribute(__copy__)
 115 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
 116 #else
 117 # define __copy(symbol)
 118 #endif
 119
 120 /*
 121  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 122  * attribute warnings entirely and for good") for more information.
 123  *
 124  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 125  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 126  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 127  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 128  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 129  */
 130 #define __deprecated
 131
 132 /*
 133  * Optional: only supported since gcc >= 5.1
 134  * Optional: not supported by clang
 135  * Optional: not supported by icc
 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: not supported by clang
 147  *
 148  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 149  */
 150 #if __has_attribute(__externally_visible__)
 151 # define __visible                      __attribute__((__externally_visible__))
 152 #else
 153 # define __visible
 154 #endif
 155
 156 /*
 157  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 158  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 159  */
 160 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 161 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 162
 163 /*
 164  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 165  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 166  */
 167 #define __gnu_inline                    __attribute__((__gnu_inline__))
 168
 169 /*
 170  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 171  */
 172 #define __malloc                        __attribute__((__malloc__))
 173
 174 /*
 175  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 176  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 177  */
 178 #define __mode(x)                       __attribute__((__mode__(x)))
 179
 180 /*
 181  * Optional: only supported since gcc >= 7
 182  *
 183  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
 184  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
 185  */
 186 #if __has_attribute(__no_caller_saved_registers__)
 187 # define __no_caller_saved_registers    __attribute__((__no_caller_saved_registers__))
 188 #else
 189 # define __no_caller_saved_registers
 190 #endif
 191
 192 /*
 193  * Optional: not supported by clang
 194  *
 195  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 196  */
 197 #if __has_attribute(__noclone__)
 198 # define __noclone                      __attribute__((__noclone__))
 199 #else
 200 # define __noclone
 201 #endif
 202
 203 /*
 204  * Add the pseudo keyword 'fallthrough' so case statement blocks
 205  * must end with any of these keywords:
 206  *   break;
 207  *   fallthrough;
 208  *   goto <label>;
 209  *   return [expression];
 210  *
 211  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 212  */
 213 #if __has_attribute(__fallthrough__)
 214 # define fallthrough                    __attribute__((__fallthrough__))
 215 #else
 216 # define fallthrough                    do {} while (0)  /* fallthrough */
 217 #endif
 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  * Optional: not supported by icc
 231  *
 232  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 233  */
 234 #if __has_attribute(__nonstring__)
 235 # define __nonstring                    __attribute__((__nonstring__))
 236 #else
 237 # define __nonstring
 238 #endif
 239
 240 /*
 241  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 242  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 243  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 244  */
 245 #define __noreturn                      __attribute__((__noreturn__))
 246
 247 /*
 248  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 249  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 250  */
 251 #define __packed                        __attribute__((__packed__))
 252
 253 /*
 254  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 255  */
 256 #define __pure                          __attribute__((__pure__))
 257
 258 /*
 259  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 260  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 261  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 262  */
 263 #define __section(S)                    __attribute__((__section__(#S)))
 264
 265 /*
 266  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 267  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 268  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 269  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 270  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 271  */
 272 #define __always_unused                 __attribute__((__unused__))
 273 #define __maybe_unused                  __attribute__((__unused__))
 274
 275 /*
 276  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 277  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 278  */
 279 #define __used                          __attribute__((__used__))
 280
 281 /*
 282  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 283  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 284  */
 285 #define __weak                          __attribute__((__weak__))
 286
 287 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */