compiler_attributes.h 11 KB

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  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 4.6 <= gcc < 5, we implement __has_attribute
  24. * by hand.
  25. *
  26. * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
  27. * depending on the compiler used to build it; however, these attributes have
  28. * no semantic effects for sparse, so it does not matter. Also note that,
  29. * in order to avoid sparse's warnings, even the unsupported ones must be
  30. * defined to 0.
  31. */
  32. #ifndef __has_attribute
  33. # define __has_attribute(x) __GCC4_has_attribute_##x
  34. # define __GCC4_has_attribute___assume_aligned__ (__GNUC_MINOR__ >= 9)
  35. # define __GCC4_has_attribute___copy__ 0
  36. # define __GCC4_has_attribute___designated_init__ 0
  37. # define __GCC4_has_attribute___externally_visible__ 1
  38. # define __GCC4_has_attribute___noclone__ 1
  39. # define __GCC4_has_attribute___nonstring__ 0
  40. # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
  41. # define __GCC4_has_attribute___fallthrough__ 0
  42. #endif
  43. /*
  44. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  45. */
  46. #define __alias(symbol) __attribute__((__alias__(#symbol)))
  47. /*
  48. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
  49. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-aligned-type-attribute
  50. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-aligned-variable-attribute
  51. */
  52. #define __aligned(x) __attribute__((__aligned__(x)))
  53. #define __aligned_largest __attribute__((__aligned__))
  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. * The second argument is optional (default 0), so we use a variadic macro
  66. * to make the shorthand.
  67. *
  68. * Beware: Do not apply this to functions which may return
  69. * ERR_PTRs. Also, it is probably unwise to apply it to functions
  70. * returning extra information in the low bits (but in that case the
  71. * compiler should see some alignment anyway, when the return value is
  72. * massaged by 'flags = ptr & 3; ptr &= ~3;').
  73. *
  74. * Optional: only supported since gcc >= 4.9
  75. * Optional: not supported by icc
  76. *
  77. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-assume_005faligned-function-attribute
  78. * clang: https://clang.llvm.org/docs/AttributeReference.html#assume-aligned
  79. */
  80. #if __has_attribute(__assume_aligned__)
  81. # define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  82. #else
  83. # define __assume_aligned(a, ...)
  84. #endif
  85. /*
  86. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-cold-function-attribute
  87. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-cold-label-attribute
  88. */
  89. #define __cold __attribute__((__cold__))
  90. /*
  91. * Note the long name.
  92. *
  93. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
  94. */
  95. #define __attribute_const__ __attribute__((__const__))
  96. /*
  97. * Optional: only supported since gcc >= 9
  98. * Optional: not supported by clang
  99. * Optional: not supported by icc
  100. *
  101. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
  102. */
  103. #if __has_attribute(__copy__)
  104. # define __copy(symbol) __attribute__((__copy__(symbol)))
  105. #else
  106. # define __copy(symbol)
  107. #endif
  108. /*
  109. * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
  110. * attribute warnings entirely and for good") for more information.
  111. *
  112. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-deprecated-function-attribute
  113. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
  114. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-deprecated-variable-attribute
  115. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Enumerator-Attributes.html#index-deprecated-enumerator-attribute
  116. * clang: https://clang.llvm.org/docs/AttributeReference.html#deprecated
  117. */
  118. #define __deprecated
  119. /*
  120. * Optional: only supported since gcc >= 5.1
  121. * Optional: not supported by clang
  122. * Optional: not supported by icc
  123. *
  124. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-designated_005finit-type-attribute
  125. */
  126. #if __has_attribute(__designated_init__)
  127. # define __designated_init __attribute__((__designated_init__))
  128. #else
  129. # define __designated_init
  130. #endif
  131. /*
  132. * Optional: not supported by clang
  133. *
  134. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-externally_005fvisible-function-attribute
  135. */
  136. #if __has_attribute(__externally_visible__)
  137. # define __visible __attribute__((__externally_visible__))
  138. #else
  139. # define __visible
  140. #endif
  141. /*
  142. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-format-function-attribute
  143. * clang: https://clang.llvm.org/docs/AttributeReference.html#format
  144. */
  145. #define __printf(a, b) __attribute__((__format__(printf, a, b)))
  146. #define __scanf(a, b) __attribute__((__format__(scanf, a, b)))
  147. /*
  148. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-gnu_005finline-function-attribute
  149. * clang: https://clang.llvm.org/docs/AttributeReference.html#gnu-inline
  150. */
  151. #define __gnu_inline __attribute__((__gnu_inline__))
  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. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-mode-type-attribute
  158. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-mode-variable-attribute
  159. */
  160. #define __mode(x) __attribute__((__mode__(x)))
  161. /*
  162. * Optional: not supported by clang
  163. *
  164. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noclone-function-attribute
  165. */
  166. #if __has_attribute(__noclone__)
  167. # define __noclone __attribute__((__noclone__))
  168. #else
  169. # define __noclone
  170. #endif
  171. /*
  172. * Add the pseudo keyword 'fallthrough' so case statement blocks
  173. * must end with any of these keywords:
  174. * break;
  175. * fallthrough;
  176. * goto <label>;
  177. * return [expression];
  178. *
  179. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
  180. */
  181. #if __has_attribute(__fallthrough__)
  182. # define fallthrough __attribute__((__fallthrough__))
  183. #else
  184. # define fallthrough do {} while (0) /* fallthrough */
  185. #endif
  186. /*
  187. * Note the missing underscores.
  188. *
  189. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noinline-function-attribute
  190. * clang: mentioned
  191. */
  192. #define noinline __attribute__((__noinline__))
  193. /*
  194. * Optional: only supported since gcc >= 8
  195. * Optional: not supported by clang
  196. * Optional: not supported by icc
  197. *
  198. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-nonstring-variable-attribute
  199. */
  200. #if __has_attribute(__nonstring__)
  201. # define __nonstring __attribute__((__nonstring__))
  202. #else
  203. # define __nonstring
  204. #endif
  205. /*
  206. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
  207. * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
  208. * clang: https://clang.llvm.org/docs/AttributeReference.html#id1
  209. */
  210. #define __noreturn __attribute__((__noreturn__))
  211. /*
  212. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
  213. * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
  214. */
  215. #define __packed __attribute__((__packed__))
  216. /*
  217. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
  218. */
  219. #define __pure __attribute__((__pure__))
  220. /*
  221. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-section-function-attribute
  222. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-section-variable-attribute
  223. * clang: https://clang.llvm.org/docs/AttributeReference.html#section-declspec-allocate
  224. */
  225. #define __section(S) __attribute__((__section__(#S)))
  226. /*
  227. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-unused-function-attribute
  228. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-unused-type-attribute
  229. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute
  230. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html#index-unused-label-attribute
  231. * clang: https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
  232. */
  233. #define __always_unused __attribute__((__unused__))
  234. #define __maybe_unused __attribute__((__unused__))
  235. /*
  236. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-used-function-attribute
  237. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute
  238. */
  239. #define __used __attribute__((__used__))
  240. /*
  241. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-weak-function-attribute
  242. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-weak-variable-attribute
  243. */
  244. #define __weak __attribute__((__weak__))
  245. #endif /* __LINUX_COMPILER_ATTRIBUTES_H */