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Comment by kevhito | Hacker News Reader

I don't understand. By your argument, and some of the replies, because "you're not guaranteed a goroutine will run at any particular time", the compiler is free to elide any suffix of a goroutine's code, even if that code has visible side effects.

I think there is something more specific to atomic going on here, where the same kinds of optimizations are already forbidden for other kinds of visible side effects like printing.

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>even if that code has visible side effects

The argument is that you told it to do that. "Just print whenever", and whenever can mean never if the world dies prematurely.

So you are telling me a valid optimization for Go is to elide the entire contents of all goroutines?

And by that argument, since main() itself is an implicitly-called goroutine (so far as I know), then the compiler can elide the entire contents of main() too, and then the rest of the contents of the program.

</reductio-ad-absurdum>

Well, sort of, yes. https://play.golang.org/p/qyfqZA5pww

  func main() {
    go fmt.Println("Hi!")
  }

This is a valid go program (eliding import etc), and it'll almost never print anything.

This is actually a classic mistake when starting with goroutines - not adding synchronization to make sure your main goroutine doesn't exit before any spawned goroutines.

Yes, but then the program would never terminate, because that's what happens at the end of main. If main returns, it's saying that the rest of the code in main has executed.

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