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Commit 35edd910 authored by Paul Gortmaker's avatar Paul Gortmaker
Browse files

bug: consolidate BUILD_BUG_ON with other bug code 



The support for BUILD_BUG in linux/kernel.h predates the
addition of linux/bug.h -- with this chunk off separate,
you can run into situations where a person gets a compile
fail even when they've included linux/bug.h, like this:

    CC      lib/string.o
  lib/string.c: In function 'strlcat':
  lib/string.c:225:2: error: implicit declaration of function 'BUILD_BUG_ON'
  make[2]: *** [lib/string.o] Error 1
  $
  $ grep linux/bug.h lib/string.c
  #include <linux/bug.h>
  $

Since the above violates the principle of least surprise, move
the BUG chunks from kernel.h to bug.h so it is all together.

Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
parent 187f1882

include/linux/bug.h

+61 −0
Original line number Diff line number Diff line
@@ -11,6 +11,67 @@ enum bug_trap_type { 


struct pt_regs;



#ifdef __CHECKER__

#define BUILD_BUG_ON_NOT_POWER_OF_2(n)

#define BUILD_BUG_ON_ZERO(e) (0)

#define BUILD_BUG_ON_NULL(e) ((void*)0)

#define BUILD_BUG_ON(condition)

#define BUILD_BUG() (0)

#else /* __CHECKER__ */



/* Force a compilation error if a constant expression is not a power of 2 */

#define BUILD_BUG_ON_NOT_POWER_OF_2(n)			\

	BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))



/* Force a compilation error if condition is true, but also produce a

   result (of value 0 and type size_t), so the expression can be used

   e.g. in a structure initializer (or where-ever else comma expressions

   aren't permitted). */

#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))

#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))



/**

 * BUILD_BUG_ON - break compile if a condition is true.

 * @condition: the condition which the compiler should know is false.

 *

 * If you have some code which relies on certain constants being equal, or

 * other compile-time-evaluated condition, you should use BUILD_BUG_ON to

 * detect if someone changes it.

 *

 * The implementation uses gcc's reluctance to create a negative array, but

 * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments

 * to inline functions).  So as a fallback we use the optimizer; if it can't

 * prove the condition is false, it will cause a link error on the undefined

 * "__build_bug_on_failed".  This error message can be harder to track down

 * though, hence the two different methods.

 */

#ifndef __OPTIMIZE__

#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))

#else

extern int __build_bug_on_failed;

#define BUILD_BUG_ON(condition)					\

	do {							\

		((void)sizeof(char[1 - 2*!!(condition)]));	\

		if (condition) __build_bug_on_failed = 1;	\

	} while(0)

#endif



/**

 * BUILD_BUG - break compile if used.

 *

 * If you have some code that you expect the compiler to eliminate at

 * build time, you should use BUILD_BUG to detect if it is

 * unexpectedly used.

 */

#define BUILD_BUG()						\

	do {							\

		extern void __build_bug_failed(void)		\

			__linktime_error("BUILD_BUG failed");	\

		__build_bug_failed();				\

	} while (0)



#endif	/* __CHECKER__ */



#ifdef CONFIG_GENERIC_BUG

#include <asm-generic/bug.h>

include/linux/kernel.h

+0 −61
Original line number Diff line number Diff line
@@ -662,67 +662,6 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { } 
	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\

	(type *)( (char *)__mptr - offsetof(type,member) );})



#ifdef __CHECKER__

#define BUILD_BUG_ON_NOT_POWER_OF_2(n)

#define BUILD_BUG_ON_ZERO(e) (0)

#define BUILD_BUG_ON_NULL(e) ((void*)0)

#define BUILD_BUG_ON(condition)

#define BUILD_BUG() (0)

#else /* __CHECKER__ */



/* Force a compilation error if a constant expression is not a power of 2 */

#define BUILD_BUG_ON_NOT_POWER_OF_2(n)			\

	BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))



/* Force a compilation error if condition is true, but also produce a

   result (of value 0 and type size_t), so the expression can be used

   e.g. in a structure initializer (or where-ever else comma expressions

   aren't permitted). */

#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))

#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))



/**

 * BUILD_BUG_ON - break compile if a condition is true.

 * @condition: the condition which the compiler should know is false.

 *

 * If you have some code which relies on certain constants being equal, or

 * other compile-time-evaluated condition, you should use BUILD_BUG_ON to

 * detect if someone changes it.

 *

 * The implementation uses gcc's reluctance to create a negative array, but

 * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments

 * to inline functions).  So as a fallback we use the optimizer; if it can't

 * prove the condition is false, it will cause a link error on the undefined

 * "__build_bug_on_failed".  This error message can be harder to track down

 * though, hence the two different methods.

 */

#ifndef __OPTIMIZE__

#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))

#else

extern int __build_bug_on_failed;

#define BUILD_BUG_ON(condition)					\

	do {							\

		((void)sizeof(char[1 - 2*!!(condition)]));	\

		if (condition) __build_bug_on_failed = 1;	\

	} while(0)

#endif



/**

 * BUILD_BUG - break compile if used.

 *

 * If you have some code that you expect the compiler to eliminate at

 * build time, you should use BUILD_BUG to detect if it is

 * unexpectedly used.

 */

#define BUILD_BUG()						\

	do {							\

		extern void __build_bug_failed(void)		\

			__linktime_error("BUILD_BUG failed");	\

		__build_bug_failed();				\

	} while (0)



#endif	/* __CHECKER__ */



/* Trap pasters of __FUNCTION__ at compile-time */

#define __FUNCTION__ (__func__)