如何在golang中正确打印出指针变量

type person struct{}
var tom *person = &person{}

When I use

fmt.Printf("%+v
", tom)//prints:&{}

Why the result is & plus data?It is surposed to be an address(0x0055)

When I use

fmt.Printf("%+v
", &tom)//0x0038
fmt.Printf("%p
", &tom)//0x0038

It gives me an address,it gives me 0x0038,why %v and %p has the same result?

tom is a pointer to a person. When you use &tom, you're a creating a second pointer, this a pointer to a pointer to a person.

In your first example, you're using %+v to print the default value of tom. The default value deferences the pointer and prints the struct itself.

In your second example, %+v is applying to the "double" pointer. It still deferences the pointer, getting to the initial pointer. See this example: http://play.golang.org/p/IZThhkiQXM

package main

import "fmt"

func zeroval(ival int) {
   ival = 0
}

func zeroptr(iptr *int) {
 *iptr = 0
}

func main() {
    i := 1
    fmt.Println("initial:", i)
    zeroval(i)
    fmt.Println("zeroval:", i)
    //The &i syntax gives the memory address of i, i.e. a pointer to i.
    zeroptr(&i)
    fmt.Println("zeroptr:", i)
    //Pointers can be printed too.
    fmt.Println("pointer:", &i)
}

Output:

$ go run pointers.go
initial: 1
zeroval: 1
zeroptr: 0
pointer: 0x42131100