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