go 子切片的问题

Question

s1 := []int{1, 2, 3, 4}
s2 := s1[2:]
fmt.Printf("s1: %v, len %d, cap: %d address: %p \n", s1, len(s1), cap(s1), &s1)
fmt.Printf("s2: %v, len %d, cap: %d address: %p \n", s2, len(s2), cap(s2), &s2)
//s1: [1 2 3 4], len 4, cap: 4 address: 0xc00000c108
//s2: [3 4], len 2, cap: 2 address: 0xc00000c120

s2[0] = 99
fmt.Printf("s1: %v, len %d, cap: %d address: %p \n", s1, len(s1), cap(s1), &s1)
fmt.Printf("s2: %v, len %d, cap: %d address: %p \n", s2, len(s2), cap(s2), &s2)
//s1: [1 2 99 4], len 4, cap: 4 address: 0xc00000c108
//s2: [99 4], len 2, cap: 2 address: 0xc00000c120

s2 = append(s2, 199)
fmt.Printf("s1: %v, len %d, cap: %d address: %p \n", s1, len(s1), cap(s1), &s1)
fmt.Printf("s2: %v, len %d, cap: %d address: %p \n", s2, len(s2), cap(s2), &s2)
//s1: [1 2 99 4], len 4, cap: 4 address: 0xc00000c108
//s2: [99 4 199], len 3, cap: 4 address: 0xc00000c120

s2[1] = 1999
fmt.Printf("s1: %v, len %d, cap: %d address: %p \n", s1, len(s1), cap(s1), &s1)
fmt.Printf("s2: %v, len %d, cap: %d address: %p \n", s2, len(s2), cap(s2), &s2)
//s1: [1 2 99 4], len 4, cap: 4 address: 0xc00000c108
//s2: [99 1999 199], len 3, cap: 4 address: 0xc00000c120  <-- 这块不知道为什么, s2[1]为什么没有替换掉s1[2]

问题出在最后那次s2[1]的替换，没什么没有替换掉s1[2]中的4为1999

Answer 1

这是因为s2在完成append操作之后，不再与s1共享同一底层数组。