Golang中的并发

Question

I have a question about concurrency in GoLang. Here is a sample code in GoLang

package main

import(
    "fmt"
    "time"
)

var m int
func add(i int){
    m++
}

func main() {
    m = 0
    for i:=0;i<100;i++{
        go add(i)
    }
    time.Sleep(time.Millisecond * 1000)
    fmt.Println(m)
}

When I execute it I always have the same result 100, even if I execute it several times.

If I do the same code in C (without mutex), sometimes I have different results.

And my question, I would like to know if GoLang implicitly manages access to a shared variable using an internal mechanism ?

Thank you.

Answer 1

No. For example, using your program,

$ go run -race dz00dz.go
==================
WARNING: DATA RACE
Read at 0x000000595200 by goroutine 7:
  main.add()
     /home/peter/gopath/src/dz00dz.go:11 +0x3d

Previous write at 0x000000595200 by goroutine 6:
  main.add()
      /home/peter/gopath/src/dz00dz.go:11 +0x59

Goroutine 7 (running) created at:
  main.main()
      /home/peter/gopath/src/dz00dz.go:17 +0x76

Goroutine 6 (finished) created at:
  main.main()
      /home/peter/gopath/src/dz00dz.go:17 +0x76
==================
100
Found 1 data race(s)
exit status 66

References:

Introducing the Go Race Detector