compiler_attributes.h 11 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281
  1. /* SPDX-License-Identifier: GPL-2.0 */
  2. #ifndef __LINUX_COMPILER_ATTRIBUTES_H
  3. #define __LINUX_COMPILER_ATTRIBUTES_H
  4. /*
  5. * The attributes in this file are unconditionally defined and they directly
  6. * map to compiler attribute(s), unless one of the compilers does not support
  7. * the attribute. In that case, __has_attribute is used to check for support
  8. * and the reason is stated in its comment ("Optional: ...").
  9. *
  10. * Any other "attributes" (i.e. those that depend on a configuration option,
  11. * on a compiler, on an architecture, on plugins, on other attributes...)
  12. * should be defined elsewhere (e.g. compiler_types.h or compiler-*.h).
  13. * The intention is to keep this file as simple as possible, as well as
  14. * compiler- and version-agnostic (e.g. avoiding GCC_VERSION checks).
  15. *
  16. * This file is meant to be sorted (by actual attribute name,
  17. * not by #define identifier). Use the __attribute__((__name__)) syntax
  18. * (i.e. with underscores) to avoid future collisions with other macros.
  19. * Provide links to the documentation of each supported compiler, if it exists.
  20. */
  21. /*
  22. * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
  23. * In the meantime, to support gcc < 5, we implement __has_attribute
  24. * by hand.
  25. */
  26. #ifndef __has_attribute
  27. # define __has_attribute(x) __GCC4_has_attribute_##x
  28. # define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9)
  29. # define __GCC4_has_attribute___copy__ 0
  30. # define __GCC4_has_attribute___designated_init__ 0
  31. # define __GCC4_has_attribute___externally_visible__ 1
  32. # define __GCC4_has_attribute___no_caller_saved_registers__ 0
  33. # define __GCC4_has_attribute___noclone__ 1
  34. # define __GCC4_has_attribute___nonstring__ 0
  35. # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  36. # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
  37. # define __GCC4_has_attribute___fallthrough__ 0
  38. #endif
  39. /*
  40. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  41. */
  42. #define __alias(symbol) __attribute__((__alias__(#symbol)))
  43. /*
  44. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  45. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  46. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  47. */
  48. #define __aligned(x) __attribute__((__aligned__(x)))
  49. #define __aligned_largest __attribute__((__aligned__))
  50. /*
  51. * Note: users of __always_inline currently do not write "inline" themselves,
  52. * which seems to be required by gcc to apply the attribute according
  53. * to its docs (and also "warning: always_inline function might not be
  54. * inlinable [-Wattributes]" is emitted).
  55. *
  56. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-always_005finline-function-attribute
  57. * clang: mentioned
  58. */
  59. #define __always_inline inline __attribute__((__always_inline__))
  60. /*
  61. * The second argument is optional (default 0), so we use a variadic macro
  62. * to make the shorthand.
  63. *
  64. * Beware: Do not apply this to functions which may return
  65. * ERR_PTRs. Also, it is probably unwise to apply it to functions
  66. * returning extra information in the low bits (but in that case the
  67. * compiler should see some alignment anyway, when the return value is
  68. * massaged by 'flags = ptr & 3; ptr &= ~3;').
  69. *
  70. * Optional: only supported since gcc >= 4.9
  71. * Optional: not supported by icc
  72. *
  73. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  74. * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  75. */
  76. #if __has_attribute(__assume_aligned__)
  77. # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  78. #else
  79. # define __assume_aligned(a, ...)
  80. #endif
  81. /*
  82. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  83. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  84. */
  85. #define __cold __attribute__((__cold__))
  86. /*
  87. * Note the long name.
  88. *
  89. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
  90. */
  91. #define __attribute_const__ __attribute__((__const__))
  92. /*
  93. * Optional: only supported since gcc >= 9
  94. * Optional: not supported by clang
  95. * Optional: not supported by icc
  96. *
  97. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
  98. */
  99. #if __has_attribute(__copy__)
  100. # define __copy(symbol) __attribute__((__copy__(symbol)))
  101. #else
  102. # define __copy(symbol)
  103. #endif
  104. /*
  105. * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
  106. * attribute warnings entirely and for good") for more information.
  107. *
  108. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
  109. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
  110. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
  111. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
  112. * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
  113. */
  114. #define __deprecated
  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. * Optional: not supported by clang
  129. *
  130. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
  131. */
  132. #if __has_attribute(__externally_visible__)
  133. # define __visible __attribute__((__externally_visible__))
  134. #else
  135. # define __visible
  136. #endif
  137. /*
  138. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
  139. * clang: https://clang.llvm.org/docs/AttributeReference.html#format
  140. */
  141. #define __printf(a, b) __attribute__((__format__(printf, a, b)))
  142. #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
  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. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-malloc-function-attribute
  150. */
  151. #define __malloc __attribute__((__malloc__))
  152. /*
  153. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
  154. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
  155. */
  156. #define __mode(x) __attribute__((__mode__(x)))
  157. /*
  158. * Optional: only supported since gcc >= 7
  159. *
  160. * gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
  161. * clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
  162. */
  163. #if __has_attribute(__no_caller_saved_registers__)
  164. # define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
  165. #else
  166. # define __no_caller_saved_registers
  167. #endif
  168. /*
  169. * Optional: not supported by clang
  170. *
  171. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
  172. */
  173. #if __has_attribute(__noclone__)
  174. # define __noclone __attribute__((__noclone__))
  175. #else
  176. # define __noclone
  177. #endif
  178. /*
  179. * Add the pseudo keyword 'fallthrough' so case statement blocks
  180. * must end with any of these keywords:
  181. * break;
  182. * fallthrough;
  183. * goto <label>;
  184. * return [expression];
  185. *
  186. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
  187. */
  188. #if __has_attribute(__fallthrough__)
  189. # define fallthrough __attribute__((__fallthrough__))
  190. #else
  191. # define fallthrough do {} while (0) /* fallthrough */
  192. #endif
  193. /*
  194. * Note the missing underscores.
  195. *
  196. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
  197. * clang: mentioned
  198. */
  199. #define noinline __attribute__((__noinline__))
  200. /*
  201. * Optional: only supported since gcc >= 8
  202. * Optional: not supported by clang
  203. * Optional: not supported by icc
  204. *
  205. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
  206. */
  207. #if __has_attribute(__nonstring__)
  208. # define __nonstring __attribute__((__nonstring__))
  209. #else
  210. # define __nonstring
  211. #endif
  212. /*
  213. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
  214. * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
  215. * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
  216. */
  217. #define __noreturn __attribute__((__noreturn__))
  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. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
  225. */
  226. #define __pure __attribute__((__pure__))
  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(section) __attribute__((__section__(section)))
  233. /*
  234. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
  235. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
  236. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
  237. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
  238. * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
  239. */
  240. #define __always_unused __attribute__((__unused__))
  241. #define __maybe_unused __attribute__((__unused__))
  242. /*
  243. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
  244. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
  245. */
  246. #define __used __attribute__((__used__))
  247. /*
  248. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
  249. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
  250. */
  251. #define __weak __attribute__((__weak__))
  252. #endif /* __LINUX_COMPILER_ATTRIBUTES_H */