LXR linux/include/linux/build

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