On Fri, Oct 5, 2018 at 2:10 PM, Scott Cotton <w...@iri-labs.com> wrote: > > I have for the longest time thought of "go:nosplit" as a runtime-specific > thing which wasn't available to arbitrary package authors. > > Then, I found this from "go doc compile" > > ``` > //go:nosplit > > The //go:nosplit directive specifies that the next function declared in the > file must not include a stack overflow check. This is most commonly used by > low-level runtime sources invoked at times when it is unsafe for the calling > goroutine to be preempted. > ``` > > I am interested in knowing > 1. Can it indeed be used in arbitrary packages?
Yes. > 2. Does it indeed prevent the emission/addition of pre-emption instructions > in the function it annotates? Well, yes and no. What it does is disable the stack overflow check at function entry. At present the stack overflow check is also used as a goroutine-preemption check. So disabling the stack overflow check disables the goroutine-preemption check at function entry. And in Go 1.11 that is the only preemption check, so in Go 1.11 go:nosplit does indeed disable preemption for a function. But there are no promises that there will never be any other sort of preemption check. In fact we definitely do want to add other preemption checks that occur at points other than function entry (issues #10958, #24543). And if there is another preemption check, there are no promises that go:nosplit will disable that check. > 3. Can it be used with gccgo? Yes. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
