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) -- except those that are optional.
   8  *
   9  * Any other "attributes" (i.e. those that depend on a configuration option,
  10  * on a compiler, on an architecture, on plugins, on other attributes...)
  11  * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
  12  *
  13  * This file is meant to be sorted (by actual attribute name,
  14  * not by #define identifier). Use the __attribute__((__name__)) syntax
  15  * (i.e. with underscores) to avoid future collisions with other macros.
  16  * If an attribute is optional, state the reason in the comment.
  17  */
  18
  19 /*
  20  * To check for optional attributes, we use __has_attribute, which is supported
  21  * on gcc >= 5, clang >= 2.9 and icc >= 17. In the meantime, to support
  22  * 4.6 <= gcc < 5, we implement __has_attribute by hand.
  23  *
  24  * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
  25  * depending on the compiler used to build it; however, these attributes have
  26  * no semantic effects for sparse, so it does not matter. Also note that,
  27  * in order to avoid sparse's warnings, even the unsupported ones must be
  28  * defined to 0.
  29  */
  30 #ifndef __has_attribute
  31 # define __has_attribute(x) __GCC4_has_attribute_##x
  32 # define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
  33 # define __GCC4_has_attribute___designated_init__     0
  34 # define __GCC4_has_attribute___externally_visible__  1
  35 # define __GCC4_has_attribute___noclone__             1
  36 # define __GCC4_has_attribute___optimize__            1
  37 # define __GCC4_has_attribute___nonstring__           0
  38 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  39 #endif
  40
  41 /*
  42  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  43  */
  44 #define __alias(symbol)                 __attribute__((__alias__(#symbol)))
  45
  46 /*
  47  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  48  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  49  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  50  */
  51 #define __aligned(x)                    __attribute__((__aligned__(x)))
  52 #define __aligned_largest               __attribute__((__aligned__))
  53
  54 /*
  55  * Note: users of __always_inline currently do not write "inline" themselves,
  56  * which seems to be required by gcc to apply the attribute according
  57  * to its docs (and also "warning: always_inline function might not be
  58  * inlinable [-Wattributes]" is emitted).
  59  *
  60  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  61  * clang: mentioned
  62  */
  63 #define __always_inline                 inline __attribute__((__always_inline__))
  64
  65 /*
  66  * The second argument is optional (default 0), so we use a variadic macro
  67  * to make the shorthand.
  68  *
  69  * Beware: Do not apply this to functions which may return
  70  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  71  * returning extra information in the low bits (but in that case the
  72  * compiler should see some alignment anyway, when the return value is
  73  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  74  *
  75  * Optional: only supported since gcc >= 4.9
  76  * Optional: not supported by icc
  77  *
  78  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  79  * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  80  */
  81 #if __has_attribute(__assume_aligned__)
  82 # define __assume_aligned(a, ...)       __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  83 #else
  84 # define __assume_aligned(a, ...)
  85 #endif
  86
  87 /*
  88  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  89  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  90  */
  91 #define __cold                          __attribute__((__cold__))
  92
  93 /*
  94  * Note the long name.
  95  *
  96  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
  97  */
  98 #define __attribute_const__             __attribute__((__const__))
  99
 100 /*
 101  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
 102  * attribute warnings entirely and for good") for more information.
 103  *
 104  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
 105  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
 106  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
 107  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
 108  * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
 109  */
 110 #define __deprecated
 111
 112 /*
 113  * Optional: only supported since gcc >= 5.1
 114  * Optional: not supported by clang
 115  * Optional: not supported by icc
 116  *
 117  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
 118  */
 119 #if __has_attribute(__designated_init__)
 120 # define __designated_init              __attribute__((__designated_init__))
 121 #else
 122 # define __designated_init
 123 #endif
 124
 125 /*
 126  * Optional: not supported by clang
 127  *
 128  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
 129  */
 130 #if __has_attribute(__externally_visible__)
 131 # define __visible                      __attribute__((__externally_visible__))
 132 #else
 133 # define __visible
 134 #endif
 135
 136 /*
 137  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
 138  * clang: https://clang.llvm.org/docs/AttributeReference.html#format
 139  */
 140 #define __printf(a, b)                  __attribute__((__format__(printf, a, b)))
 141 #define __scanf(a, b)                   __attribute__((__format__(scanf, a, b)))
 142
 143 /*
 144  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
 145  * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
 146  */
 147 #define __gnu_inline                    __attribute__((__gnu_inline__))
 148
 149 /*
 150  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
 151  */
 152 #define __malloc                        __attribute__((__malloc__))
 153
 154 /*
 155  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
 156  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
 157  */
 158 #define __mode(x)                       __attribute__((__mode__(x)))
 159
 160 /*
 161  * Optional: not supported by clang
 162  * Note: icc does not recognize gcc's no-tracer
 163  *
 164  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
 165  *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-optimize-function-attribute
 166  */
 167 #if __has_attribute(__noclone__)
 168 # if __has_attribute(__optimize__)
 169 #  define __noclone                     __attribute__((__noclone__, __optimize__("no-tracer")))
 170 # else
 171 #  define __noclone                     __attribute__((__noclone__))
 172 # endif
 173 #else
 174 # define __noclone
 175 #endif
 176
 177 /*
 178  * Note the missing underscores.
 179  *
 180  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
 181  * clang: mentioned
 182  */
 183 #define   noinline                      __attribute__((__noinline__))
 184
 185 /*
 186  * Optional: only supported since gcc >= 8
 187  * Optional: not supported by clang
 188  * Optional: not supported by icc
 189  *
 190  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
 191  */
 192 #if __has_attribute(__nonstring__)
 193 # define __nonstring                    __attribute__((__nonstring__))
 194 #else
 195 # define __nonstring
 196 #endif
 197
 198 /*
 199  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
 200  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
 201  * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
 202  */
 203 #define __noreturn                      __attribute__((__noreturn__))
 204
 205 /*
 206  * Optional: only supported since gcc >= 4.8
 207  * Optional: not supported by icc
 208  *
 209  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
 210  * clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
 211  */
 212 #if __has_attribute(__no_sanitize_address__)
 213 # define __no_sanitize_address          __attribute__((__no_sanitize_address__))
 214 #else
 215 # define __no_sanitize_address
 216 #endif
 217
 218 /*
 219  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
 220  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
 221  */
 222 #define __packed                        __attribute__((__packed__))
 223
 224 /*
 225  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
 226  */
 227 #define __pure                          __attribute__((__pure__))
 228
 229 /*
 230  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
 231  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
 232  * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
 233  */
 234 #define __section(S)                    __attribute__((__section__(#S)))
 235
 236 /*
 237  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
 238  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
 239  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
 240  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
 241  * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
 242  */
 243 #define __always_unused                 __attribute__((__unused__))
 244 #define __maybe_unused                  __attribute__((__unused__))
 245
 246 /*
 247  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
 248  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
 249  */
 250 #define __used                          __attribute__((__used__))
 251
 252 /*
 253  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
 254  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
 255  */
 256 #define __weak                          __attribute__((__weak__))
 257
 258 #endif /* __LINUX_COMPILER_ATTRIBUTES_H */