You don’t even know the difference between a nil slice and an empty slice? The BAT interviewer will have to send you home to wait for the announcement.

The problem 

package main

import (
 "fmt"
 "reflect"
 "unsafe" )  func main(a) {   var s1 []int  s2 := make([]int.0)  s4 := make([]int.0)   fmt.Printf("s1 pointer:%+v, s2 pointer:%+v, s4 pointer:%+v, \n". *(*reflect.SliceHeader)(unsafe.Pointer(&s1)),*(*reflect.SliceHeader)(unsafe.Pointer(&s2)),*(*reflect.SliceHeader)(unsafe .Pointer(&s4))) fmt.Printf("%v\n", (*(*reflect.SliceHeader)(unsafe.Pointer(&s1))).Data==(*(*reflect.SliceHeader)(unsafe.Pointer(&s2))).Data)  fmt.Printf("%v\n", (*(*reflect.SliceHeader)(unsafe.Pointer(&s2))).Data==(*(*reflect.SliceHeader)(unsafe.Pointer(&s4))).Data) } Copy the code

Do nil slices point to the same address as empty slices? What does this code output?

How to answer

  • Nil slices and empty slices point to different addresses. Nil Null slice reference array pointer address is 0 (does not point to any real address)
  • The null slice reference array pointer address is present and fixed to a value
s1 pointer:{Data:0 Len:0 Cap:0}, s2 pointer:{Data:824634207952 Len:0 Cap:0}, s4 pointer:{Data:824634207952 Len:0 Cap:0}, 
false// Nil slices and empty slices point to different array addressestrue// Both empty slices point to the same array address, 824634207952Copy the code

explain

  • As mentioned in previous articles, the data structure of slicing is
type SliceHeader struct {
 Data uintptr  // Reference the array pointer address
 Len  int     // The current length of the slice
 Cap  int     // The capacity of slices
}
Copy the code

  • The big difference between nil slices and empty slices is thatThe array reference addresses pointed to are different.

  • All empty slices point to the same array reference address

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