结构体指针赋值

[victorbnu]

#include <stdio.h>
#include <windows.h>
struct regDevice {
int protocolId;
struct regDevice* next;
};

regDevice* firstMrfDataBufferDriver = NULL;

int main(int argc, char* argv[])
{
regDevice* mrfDataBufferDriver=NULL;
regDevice** prev;
mrfDataBufferDriver=(regDevice*)malloc(sizeof(regDevice));
mrfDataBufferDriver->next=NULL;
for (int i=0;i<10;i++)
{
mrfDataBufferDriver->protocolId=i;
prev = &firstMrfDataBufferDriver;
if (*prev != NULL) {
prev = &(*prev)->next;
}
*prev = mrfDataBufferDriver;
printf("%d\n",(*prev)->protocolId);
}
return 0;
}


为什么循环中，只有第一次i=0时，*prev才为NULL
其它次循环*prev就不等于NULL了呢

非常感谢

[就想叫yoko]

因为 firstMrfDataBufferDriver第一开始是NULL
后面通过*prev = mrfDataBufferDriver; 把firstMrfDataBufferDriver给修改了

[至善者善之敌]

看这三句话
regDevice* firstMrfDataBufferDriver = NULL;
regDevice** prev;

mrfDataBufferDriver->protocolId=i;
prev = &firstMrfDataBufferDriver;
if (*prev != NULL) {
prev = &(*prev)->next;
*prev = mrfDataBufferDriver;

下一个的时候，firstMrfDataBufferDriver和同一地址了，而mrfDataBufferDriver->protocolId=i;已经赋值，所以不为空

[hu7324829]

[Quote=引用 1 楼 q191201771 的回复:]
因为 firstMrfDataBufferDriver第一开始是NULL
后面通过*prev = mrfDataBufferDriver; 把firstMrfDataBufferDriver给修改了
[/Quote]
++