* T L <tapir....@gmail.com> [170707 01:32]:
> Then how about this?
>
> package main
>
> import "fmt"
> import "sync/atomic"
>
> func main() {
> var x, y int32
> go func() {
> atomic.AddInt32(&x, 1)
> atomic.AddInt32(&y, 1)
> }()
>
> if atomic.LoadInt32(&y) == 1 {
> fmt.Println("x =", atomic.LoadInt32(&x)) // always 1 if it is printed?
> }
Yes, the go routine establishes a happens-before relationship such that
x is incremented before y, and the atomic Add of y and Load of y ensure
that the Load either happens before or after, but not during, the Add.
> if atomic.LoadInt32(&x) == 0 {
> fmt.Println("y =", atomic.LoadInt32(&y)) // always 0 if it is printed?
> }
No. If the Load of x returns 0, it must happen before the Add of 1 to x.
But after the test and before the Load of y, the main go routine and the
func go routine are both runnable and there is nothing to establish a
happens-before relationship between the Load of y and the Add of 1 to y.
> }
...Marvin
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