linux_stddef.h revision 4008138e2b5248940265b160fae001d8954fae21 
1#ifndef _LINUX_STDDEF_H
2#define _LINUX_STDDEF_H
3
4#undef NULL
5#if defined(__cplusplus)
6#define NULL 0
7#else
8#define NULL ((void *)0)
9#endif
10
11#undef offsetof
12#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
13
14
15/**
16 * container_of - cast a member of a structure out to the containing structure
17 *
18 * @ptr:	the pointer to the member.
19 * @type:	the type of the container struct this is embedded in.
20 * @member:	the name of the member within the struct.
21 *
22 */
23#define container_of(ptr, type, member) ({			\
24        const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
25        (type *)( (char *)__mptr - offsetof(type,member) );})
26
27/*
28 * Check at compile time that something is of a particular type.
29 * Always evaluates to 1 so you may use it easily in comparisons.
30 */
31#define typecheck(type,x) \
32({	type __dummy; \
33	typeof(x) __dummy2; \
34	(void)(&__dummy == &__dummy2); \
35	1; \
36})
37
38
39#endif
40