int *p = NULL;
int a =1000;
p = &a;
void* xx = p;
*(int*)p = 1000000;
printf("%d \n",*p);
const 修饰指针
const int a = 10;
int b = 100;
//第一种
int *p = &a;
p = &b; (V)
*p = 1000; (V)
//第二种
const int *p = &a;
p = &b; (V)
*p = 1000; (X)
//第三种
int * const p = &a;
p = &b; (X)
*p = 1000; (V)
//第四种
const int * const p = &a;
p = &b; (X)
*p = 1000; (X)