cmd/compile: argument escapes when it should not #18001
Comments
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For this case, it certainly doesn't escape. But what if some child function of func f() {
var t int
g(&t)
// f() can return before goroutine inside g() finishes.
}
//go:noinline
func g(a *int) {
go fn(b *int) {
// some thing here that takes enough time for f() to return first
_ = b
}(a)
}How can we determine at compile time that all the functions in call-graph rooted at |
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Passing to other (or new) goroutines makes it escape. |
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Yes, but how do you determine that at compile time? I am not sure if we can do this statically though. Consider following case: Whether the var escapes or not can not be determined until run time. type doer interface{
func do(i *int)
}
type syncDoer struct {}
func (syncDoer) do(i *int) {
// accesses i synchronously
}
type asyncDoer struct {}
func (asyncDoer) do(i *int) {
// accesses i asynchronously
go func(b *int) {
// time consuming work
_ = b
}(i)
}
func f(s doer) {
var t int
g(s, &t)
// f() can return before goroutine inside g() finishes.
}
//go:noinline
func g(s doer, a *int) {
s.do(a)
}
func haha() {
if ( ...some run-time condition... ) {
f(syncDoer{})
} else {
f(asyncDoer{})
}
} |
quentinmit
added
the
NeedsFix
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Probably too late for 1.8 unless the fix is trivial. |
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@Dhananjay92, passing object to function pointer (including interface) should also make it escape. |
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This is all due to the fact that the parameter to g doesn't have a name. This was fixed in CL 38600. On tip, everything's good: |
What version of Go are you using (
go version)?tip (0bae74e)
Compile the following code:
I think all of the three functions,
f,h,h2, should not allocate on heap. But it actually does for all three. For example,f:Escape analysis debug output shows
@dr2chase
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