include/linux/build_bug.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_BUILD_BUG_H
   3 #define _LINUX_BUILD_BUG_H
   4
   5 #include <linux/compiler.h>
   6
   7 #ifdef __CHECKER__
   8 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
   9 #define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
  10 #define BUILD_BUG_ON_ZERO(e) (0)
  11 #define BUILD_BUG_ON_NULL(e) ((void *)0)
  12 #define BUILD_BUG_ON_INVALID(e) (0)
  13 #define BUILD_BUG_ON_MSG(cond, msg) (0)
  14 #define BUILD_BUG_ON(condition) (0)
  15 #define BUILD_BUG() (0)
  16 #else /* __CHECKER__ */
  17
  18 /* Force a compilation error if a constant expression is not a power of 2 */
  19 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n)        \
  20         BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
  21 #define BUILD_BUG_ON_NOT_POWER_OF_2(n)                  \
  22         BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
  23
  24 /*
  25  * Force a compilation error if condition is true, but also produce a
  26  * result (of value 0 and type size_t), so the expression can be used
  27  * e.g. in a structure initializer (or where-ever else comma expressions
  28  * aren't permitted).
  29  */
  30 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
  31 #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:(-!!(e)); }))
  32
  33 /*
  34  * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
  35  * expression but avoids the generation of any code, even if that expression
  36  * has side-effects.
  37  */
  38 #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
  39
  40 /**
  41  * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
  42  *                    error message.
  43  * @condition: the condition which the compiler should know is false.
  44  *
  45  * See BUILD_BUG_ON for description.
  46  */
  47 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
  48
  49 /**
  50  * BUILD_BUG_ON - break compile if a condition is true.
  51  * @condition: the condition which the compiler should know is false.
  52  *
  53  * If you have some code which relies on certain constants being equal, or
  54  * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
  55  * detect if someone changes it.
  56  *
  57  * The implementation uses gcc's reluctance to create a negative array, but gcc
  58  * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
  59  * inline functions).  Luckily, in 4.3 they added the "error" function
  60  * attribute just for this type of case.  Thus, we use a negative sized array
  61  * (should always create an error on gcc versions older than 4.4) and then call
  62  * an undefined function with the error attribute (should always create an
  63  * error on gcc 4.3 and later).  If for some reason, neither creates a
  64  * compile-time error, we'll still have a link-time error, which is harder to
  65  * track down.
  66  */
  67 #ifndef __OPTIMIZE__
  68 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
  69 #else
  70 #define BUILD_BUG_ON(condition) \
  71         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
  72 #endif
  73
  74 /**
  75  * BUILD_BUG - break compile if used.
  76  *
  77  * If you have some code that you expect the compiler to eliminate at
  78  * build time, you should use BUILD_BUG to detect if it is
  79  * unexpectedly used.
  80  */
  81 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
  82
  83 #endif  /* __CHECKER__ */
  84
  85 #endif  /* _LINUX_BUILD_BUG_H */