package main
import "time"
import "fmt"
var index int64
func increase(){
index++
}
func read(){
fmt.Println(index)
}
func main(){
go func(N int){
for i:=0; i < N; i++{
increase()
time.Sleep(500 * time.Millisecond)
}
}(5)
time.Sleep(2 * time.Second)
read()
}
在2022年4月30日星期六 UTC+8 13:49:11<Zhaoxun Yan> 写道：
> point race means I/O on a global might clash at certain point of time.
>
> consider this example:
>
> package main
>
> import "time"
> import "fmt"
>
> var index int64
>
> func increase(){
> index++
> }
>
> func read(){
> fmt.Println(index)
> }
>
> func main(){
> go func(N){
> for i:=0; i < N; i++{
> increase()
> time.Sleep(500 * time.Millisecond)
> }
> }(5)
> time.Sleep(2 * time.Second)
> read()
> }
>
> Obviously, the increase function is writing the global variable 'index'
> while the read is reading it. It is highly unlikely that they could
> function at the same time, but not impossible. Further, if the increase
> function takes longer time to manipulate the global, such as an array which
> might enlarge itself, and reading during the changing of the global is
> dangerous.
>
> The code in my project has a little variation - the writing of the
> variable is controlled by crontask of "github.com/robfig/cron". However,
> the essence is the same. Point-time race condition is undetectable by `go
> build race`. Thanks to Rust on emphasizing the single entrance to any
> variable, I realized this possibility and have to add sync.Mutex to both
> functions.
>
> What is your opinion?
>
> Best Regards,
> Zhaoxun
>
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