Thanks much for the info. Do you have any more pointers about how one may assess whether or ensure that a stack overflow check is not necessary in order to safely use this directive?
Scott On Fri, 5 Oct 2018 at 23:26, Ian Lance Taylor <i...@golang.org> wrote: > 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 > -- Scott Cotton http://www.iri-labs.com -- 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.
