Because the type of address is unsigned int, which means unsigned plastic, (unsigned)(p) means the value of p, which means the address pointed by unsigned plastic.

For example: int a =10; The address of a is 0x 10000, and now int * p = &；; A, unsigned int addr = (unsigned)p, then the value of addr is 0x 10000.

Generally speaking, the value of the address pointed by the p pointer is converted into unsigned shaping.