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___designated_init__     0
  38 # define __GCC4_has_attribute___externally_visible__  1
  39 # define __GCC4_has_attribute___noclone__             1
  40 # define __GCC4_has_attribute___nonstring__           0
  41 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  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  * 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: not supported by clang
 130  *
 131  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 132  */
 133 #if __has_attribute(__externally_visible__)
 134 # define __visible                      __attribute__((__externally_visible__))
 135 #else
 136 # define __visible
 137 #endif
 138
 139 /*
 140  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 141  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 142  */
 143 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 144 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 145
 146 /*
 147  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 148  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 149  */
 150 #define __gnu_inline                    __attribute__((__gnu_inline__))
 151
 152 /*
 153  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 154  */
 155 #define __malloc                        __attribute__((__malloc__))
 156
 157 /*
 158  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 159  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 160  */
 161 #define __mode(x)                       __attribute__((__mode__(x)))
 162
 163 /*
 164  * Optional: not supported by clang
 165  *
 166  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 167  */
 168 #if __has_attribute(__noclone__)
 169 # define __noclone                      __attribute__((__noclone__))
 170 #else
 171 # define __noclone
 172 #endif
 173
 174 /*
 175  * Note the missing underscores.
 176  *
 177  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 178  * clang: mentioned
 179  */
 180 #define   noinline                      __attribute__((__noinline__))
 181
 182 /*
 183  * Optional: only supported since gcc >= 8
 184  * Optional: not supported by clang
 185  * Optional: not supported by icc
 186  *
 187  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 188  */
 189 #if __has_attribute(__nonstring__)
 190 # define __nonstring                    __attribute__((__nonstring__))
 191 #else
 192 # define __nonstring
 193 #endif
 194
 195 /*
 196  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 197  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 198  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 199  */
 200 #define __noreturn                      __attribute__((__noreturn__))
 201
 202 /*
 203  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 204  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 205  */
 206 #define __packed                        __attribute__((__packed__))
 207
 208 /*
 209  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 210  */
 211 #define __pure                          __attribute__((__pure__))
 212
 213 /*
 214  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 215  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 216  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 217  */
 218 #define __section(S)                    __attribute__((__section__(#S)))
 219
 220 /*
 221  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 222  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 223  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 224  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 225  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 226  */
 227 #define __always_unused                 __attribute__((__unused__))
 228 #define __maybe_unused                  __attribute__((__unused__))
 229
 230 /*
 231  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 232  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 233  */
 234 #define __used                          __attribute__((__used__))
 235
 236 /*
 237  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 238  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 239  */
 240 #define __weak                          __attribute__((__weak__))
 241
 242 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */