build_bug.h 3.0 KB

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  1. #ifndef _LINUX_BUILD_BUG_H
  2. #define _LINUX_BUILD_BUG_H
  3. #include <linux/compiler.h>
  4. #ifdef __CHECKER__
  5. #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
  6. #define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
  7. #define BUILD_BUG_ON_ZERO(e) (0)
  8. #define BUILD_BUG_ON_NULL(e) ((void *)0)
  9. #define BUILD_BUG_ON_INVALID(e) (0)
  10. #define BUILD_BUG_ON_MSG(cond, msg) (0)
  11. #define BUILD_BUG_ON(condition) (0)
  12. #define BUILD_BUG() (0)
  13. #else /* __CHECKER__ */
  14. /* Force a compilation error if a constant expression is not a power of 2 */
  15. #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) \
  16. BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
  17. #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
  18. BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
  19. /*
  20. * Force a compilation error if condition is true, but also produce a
  21. * result (of value 0 and type size_t), so the expression can be used
  22. * e.g. in a structure initializer (or where-ever else comma expressions
  23. * aren't permitted).
  24. */
  25. #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
  26. #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); }))
  27. /*
  28. * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
  29. * expression but avoids the generation of any code, even if that expression
  30. * has side-effects.
  31. */
  32. #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
  33. /**
  34. * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
  35. * error message.
  36. * @condition: the condition which the compiler should know is false.
  37. *
  38. * See BUILD_BUG_ON for description.
  39. */
  40. #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
  41. /**
  42. * BUILD_BUG_ON - break compile if a condition is true.
  43. * @condition: the condition which the compiler should know is false.
  44. *
  45. * If you have some code which relies on certain constants being equal, or
  46. * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
  47. * detect if someone changes it.
  48. *
  49. * The implementation uses gcc's reluctance to create a negative array, but gcc
  50. * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
  51. * inline functions). Luckily, in 4.3 they added the "error" function
  52. * attribute just for this type of case. Thus, we use a negative sized array
  53. * (should always create an error on gcc versions older than 4.4) and then call
  54. * an undefined function with the error attribute (should always create an
  55. * error on gcc 4.3 and later). If for some reason, neither creates a
  56. * compile-time error, we'll still have a link-time error, which is harder to
  57. * track down.
  58. */
  59. #ifndef __OPTIMIZE__
  60. #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
  61. #else
  62. #define BUILD_BUG_ON(condition) \
  63. BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
  64. #endif
  65. /**
  66. * BUILD_BUG - break compile if used.
  67. *
  68. * If you have some code that you expect the compiler to eliminate at
  69. * build time, you should use BUILD_BUG to detect if it is
  70. * unexpectedly used.
  71. */
  72. #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
  73. #endif /* __CHECKER__ */
  74. #endif /* _LINUX_BUILD_BUG_H */