C语言#Linux

语言#Linux"/>

C语言#Linux

代码复制于Linux内核：tools/include/linux/kernel.h
作用图：

功能：

• 1、typeof是编译器扩展的特性（推断出类型），.html#Typeof
• 2、container_of：1、先报地址强制转换为特定成员地址，变量前_为了不冲突 2、计算成员偏移字节 3、再转换为char*，为了进行字节单位的地址运算 4、最终转换为结构体类型即可。。。 5、整个宏是一个复合语句，最后一个子表达式的值就是整个表达式的值。（也是编译器扩展特性，.html）

#include <stdio.h>
#include <stdlib.h>//复制于：tools/include/linux/kernel.h#ifndef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif#ifndef container_of
/*** container_of - cast a member of a structure out to the containing structure* @ptr:	the pointer to the member.* @type:	the type of the container struct this is embedded in.* @member:	the name of the member within the struct.**/
#define container_of(ptr, type, member) ({			\const typeof(((type *)0)->member) * __mptr = (ptr);	\(type *)((char *)__mptr - offsetof(type, member)); })
#endif#ifndef max
#define max(x, y) ({				\typeof(x) _max1 = (x);			\typeof(y) _max2 = (y);			\(void) (&_max1 == &_max2);		\_max1 > _max2 ? _max1 : _max2; })
#endif#define P_INT(a) printf("The int is: [%d]\n",a)typedef struct TestBuffer {int a;double b;struct InBuffer{int aa;double bb;}c;
}TestBuffer;struct InBuffer* getInBuffer() {TestBuffer *tbp = malloc(sizeof(*tbp));if(tbp == NULL) {exit(-1);}printf("在一个函数内,所以我知道 tbp的地址: [%p].\n",tbp);return &tbp->c; 
}int main(int argc, char const *argv[])
{typeof(int) a = 10;P_INT(a);int offSetC = offsetof(TestBuffer, c);printf("成员c的地址，从结构体的地址开始算，偏移了 [%d] 个字节.\n", offSetC);struct InBuffer *inbp = getInBuffer();TestBuffer *tbp = container_of(inbp, TestBuffer, c);printf("在一个函数外，我只知道成员的地址，但是container_of可以帮我获取 结构体的地址: [%p].\n", tbp);free(tbp);return 0;
}

运行结果：

预处理后的语句，gcc -E

int main(int argc, char const *argv[])
{
// ....struct InBuffer *inbp = getInBuffer();TestBuffer *tbp = ({ const typeof(((TestBuffer *)0)->c) * __mptr = (inbp); (TestBuffer *)((char *)__mptr - ((size_t) &((TestBuffer *)0)->c)); });//....return 0;
}