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___noclone__             1
  41 # define __GCC4_has_attribute___nonstring__           0
  42 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  43 # define __GCC4_has_attribute___fallthrough__         0
  44 #endif
  45
  46 /*
  47  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  48  */
  49 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
  50
  51 /*
  52  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  53  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  54  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  55  */
  56 #define __aligned(x)                    __attribute__((__aligned__(x)))
  57 #define __aligned_largest               __attribute__((__aligned__))
  58
  59 /*
  60  * Note: users of __always_inline currently do not write "inline" themselves,
  61  * which seems to be required by gcc to apply the attribute according
  62  * to its docs (and also "warning: always_inline function might not be
  63  * inlinable [-Wattributes]" is emitted).
  64  *
  65  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  66  * clang: mentioned
  67  */
  68 #define __always_inline                 inline __attribute__((__always_inline__))
  69
  70 /*
  71  * The second argument is optional (default 0), so we use a variadic macro
  72  * to make the shorthand.
  73  *
  74  * Beware: Do not apply this to functions which may return
  75  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  76  * returning extra information in the low bits (but in that case the
  77  * compiler should see some alignment anyway, when the return value is
  78  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  79  *
  80  * Optional: only supported since gcc >= 4.9
  81  * Optional: not supported by icc
  82  *
  83  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  84  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  85  */
  86 #if __has_attribute(__assume_aligned__)
  87 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  88 #else
  89 # define __assume_aligned(a, ...)
  90 #endif
  91
  92 /*
  93  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  94  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  95  */
  96 #define __cold                          __attribute__((__cold__))
  97
  98 /*
  99  * Note the long name.
 100  *
 101  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
 102  */
 103 #define __attribute_const__             __attribute__((__const__))
 104
 105 /*
 106  * Optional: only supported since gcc >= 9
 107  * Optional: not supported by clang
 108  * Optional: not supported by icc
 109  *
 110  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
 111  */
 112 #if __has_attribute(__copy__)
 113 # define __copy(symbol)                 __attribute__((__copy__(symbol)))
 114 #else
 115 # define __copy(symbol)
 116 #endif
 117
 118 /*
 119  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 120  * attribute warnings entirely and for good") for more information.
 121  *
 122  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 123  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 124  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 125  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 126  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 127  */
 128 #define __deprecated
 129
 130 /*
 131  * Optional: only supported since gcc >= 5.1
 132  * Optional: not supported by clang
 133  * Optional: not supported by icc
 134  *
 135  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 136  */
 137 #if __has_attribute(__designated_init__)
 138 # define __designated_init              __attribute__((__designated_init__))
 139 #else
 140 # define __designated_init
 141 #endif
 142
 143 /*
 144  * Optional: not supported by clang
 145  *
 146  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 147  */
 148 #if __has_attribute(__externally_visible__)
 149 # define __visible                      __attribute__((__externally_visible__))
 150 #else
 151 # define __visible
 152 #endif
 153
 154 /*
 155  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 156  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 157  */
 158 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 159 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 160
 161 /*
 162  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 163  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 164  */
 165 #define __gnu_inline                    __attribute__((__gnu_inline__))
 166
 167 /*
 168  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 169  */
 170 #define __malloc                        __attribute__((__malloc__))
 171
 172 /*
 173  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 174  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 175  */
 176 #define __mode(x)                       __attribute__((__mode__(x)))
 177
 178 /*
 179  * Optional: not supported by clang
 180  *
 181  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 182  */
 183 #if __has_attribute(__noclone__)
 184 # define __noclone                      __attribute__((__noclone__))
 185 #else
 186 # define __noclone
 187 #endif
 188
 189 /*
 190  * Add the pseudo keyword 'fallthrough' so case statement blocks
 191  * must end with any of these keywords:
 192  *   break;
 193  *   fallthrough;
 194  *   goto <label>;
 195  *   return [expression];
 196  *
 197  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
 198  */
 199 #if __has_attribute(__fallthrough__)
 200 # define fallthrough                    __attribute__((__fallthrough__))
 201 #else
 202 # define fallthrough                    do {} while (0)  /* fallthrough */
 203 #endif
 204
 205 /*
 206  * Note the missing underscores.
 207  *
 208  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 209  * clang: mentioned
 210  */
 211 #define   noinline                      __attribute__((__noinline__))
 212
 213 /*
 214  * Optional: only supported since gcc >= 8
 215  * Optional: not supported by clang
 216  * Optional: not supported by icc
 217  *
 218  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 219  */
 220 #if __has_attribute(__nonstring__)
 221 # define __nonstring                    __attribute__((__nonstring__))
 222 #else
 223 # define __nonstring
 224 #endif
 225
 226 /*
 227  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 228  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 229  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 230  */
 231 #define __noreturn                      __attribute__((__noreturn__))
 232
 233 /*
 234  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 235  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 236  */
 237 #define __packed                        __attribute__((__packed__))
 238
 239 /*
 240  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 241  */
 242 #define __pure                          __attribute__((__pure__))
 243
 244 /*
 245  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 246  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 247  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 248  */
 249 #define __section(S)                    __attribute__((__section__(#S)))
 250
 251 /*
 252  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 253  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 254  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 255  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 256  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 257  */
 258 #define __always_unused                 __attribute__((__unused__))
 259 #define __maybe_unused                  __attribute__((__unused__))
 260
 261 /*
 262  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 263  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 264  */
 265 #define __used                          __attribute__((__used__))
 266
 267 /*
 268  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 269  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 270  */
 271 #define __weak                          __attribute__((__weak__))
 272
 273 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */