字符串赋值

char *p1 = "123";

const char*p2 = "1234";

p2 = p1; ///< 通过

char**p3;

const char** p4;

p4 = p3; ///< 失败？？？

char* const *p5 = p3;  ///< 通过

const char* const *p6 = p3; ///〈通过