函数传递指针的一点小知识

    昨天晚上review以前看得书的时候，发现有一个被我因为以为自己理所当然了解而忽略的东西，发现还是又必要拿出来说一说的，特把次内容摘录如下，警告自己以后看书不能浮躁，不能想当然。

Point Parameters

A parameter can be a pointer,in which case the arguement pointer is copied.As with any nonreference type parameter,changes made to the parameter are made to the local copy.If the function assigns a new pointer value to the parameter,the calling pointer value is unchanged.

  The fact that the pointer is copied affects only assignments to the pointer.If the function takes o pointer to a nonconst type,then the function can assign through the pointer and change the value of the object to which the pointer points:

void reset(int* ip)
{
   *ip = 0;//changes the value of the object to which ip points

   ip = 0;//changes only the local value of ip,the argument is unchanged

}

如果不能理解可以这样：

p----------->address

ip = p后

p----------->address

               /\

ip-------------|共同指向address所以可以改变值，但是在函数里再赋值给ip时

ip = pp；后

p--------->address

ip-------->pp's address