linux c printf 相关记录

结构体成员取结构体头指针

list_entry->container_of->offsetof

344 /*
345
list_entry - get the struct for this entry
346 @ptr: the &struct list_head pointer.
347
@type: the type of the struct this is embedded in.
348 @member: the name of the list_struct within the struct.
349
/
350 #define list_entry(ptr, type, member) \
351 container_of(ptr, type, member)

684 /*
685
container_of - cast a member of a structure out to the containing structure
686 @ptr: the pointer to the member.
687
@type: the type of the container struct this is embedded in.
688 @member: the name of the member within the struct.
689

690 /
691 #define container_of(ptr, type, member) ({ \
692 const typeof( ((type
)0)->member ) __mptr = (ptr); \
693 (type
)( (char *)__mptr - offsetof(type,member) );})

Linux/include/linux/stddef.h

1 #ifndef _LINUX_STDDEF_H
2 #define _LINUX_STDDEF_H
3
4 #include
5
6 #ifdef KERNEL
7
8 #undef NULL
9 #define NULL ((void )0)
10
11 enum {
12 false = 0,
13 true = 1
14 };
15
16 #undef offsetof
17 #ifdef compiler_offsetof
18 #define offsetof(TYPE,MEMBER)
compiler_offsetof(TYPE,MEMBER)
19 #else
20 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE
)0)->MEMBER)
21 #endif
22 #endif / KERNEL /
23
24 #endif
25

__compiler_offsetof(TYPE,MEMBER)就和gcc的原子操作实现一样,也是编译器built-in