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ancestors.go
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/
ancestors.go
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//+build ignore
// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2016 Datadog, Inc.
package main
import (
"fmt"
"runtime"
)
// adapted from https://github.com/golang/go/issues/22289
// run with GODEBUG=tracebackancestors=10 go run ancestors.go
func main() {
w := make(chan struct{})
go foo(w, 5)
<-w
x := make(chan struct{})
go foo(x, 3)
<-x
fmt.Print(string(stackAll()))
close(w)
}
func stackAll() []byte {
buf := make([]byte, 1024)
for {
n := runtime.Stack(buf, true)
if n < len(buf) {
return buf[:n]
}
buf = make([]byte, 2*len(buf))
}
}
const maxStackDepth = 5
func foo(w chan struct{}, timesToCallGo int) {
if timesToCallGo == 0 {
w <- struct{}{}
<-w
return
}
if timesToCallGo%2 == 0 {
d1(func() { foo(w, timesToCallGo-1) }, maxStackDepth)
} else {
d1(func() { bar(w, timesToCallGo-1) }, maxStackDepth)
}
}
func bar(w chan struct{}, timesToCallGo int) {
if timesToCallGo == 0 {
w <- struct{}{}
<-w
return
}
if timesToCallGo%2 == 0 {
d1(func() { foo(w, timesToCallGo-1) }, maxStackDepth)
} else {
d1(func() { bar(w, timesToCallGo-1) }, maxStackDepth)
}
}
func d1(fn func(), timesToRecurse int) {
if timesToRecurse == 0 {
go fn()
return
}
d1(fn, timesToRecurse-1)
}