Is slice in golang thread-safe for appending

[xiaohai dai]

I know that map in golang is not thread-safe for writing.

However, I'm not sure slice/array is thread-safe for writing. I have searched the related posts and blogs in google, but find no unambiguous statement.

Thanks in advance! 

[Krzysztof Kowalczyk]

It's not and it's easy to test:

Save as t.go:

package main
import "fmt"

func main() {
 var s []int
 for i := 0; i < 100000; i++ {
 go func(n int) {
 s = append(s, n)
 }(i)
 }
 fmt.Printf("%d\n", s[0])
}

hen `go run -race t.go` and watch race detector complain.

-- kjk

[Edward Muller]

No, it is not.*

* appending can replace the underlying array, so in certain situations it can be, but that's more by accident IMO so just don't rely on that.

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[Jason Stillwell]

But it returns the new slice.

[Edward Muller]

Which may or may not have the same backing array.

https://play.golang.org/p/GsffpJc1cX

PS: I probably should have just said 'no. slices are not "thread-safe"'.  I have complicated the issue to no benefit.

[Jason Stillwell]

Oh I see, I was thinking of the more specific question "Is appending to slices thread-safe"

[xiaohai dai]

I see!

Thanks a lot!

在 2017年1月20日星期五 UTC+8上午6:40:22，Krzysztof Kowalczyk写道：

[xiaohai dai]

I see!

Thank you!

在 2017年1月20日星期五 UTC+8上午6:40:30，freeformz写道：

[xiaohai dai]

Wonderful!

The example in ttps://play.golang.org/p/GsffpJc1cX is great.

Thank you

在 2017年1月20日星期五 UTC+8上午7:04:02，freeformz写道：