// run
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"fmt"
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"runtime"
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)
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type HeapObj [8]int64
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type StkObj struct {
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h *HeapObj
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}
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var n int
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var c int = -1
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func gc() {
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// encourage heap object to be collected, and have its finalizer run.
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runtime.GC()
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runtime.GC()
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runtime.GC()
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n++
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}
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func main() {
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f()
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gc() // prior to stack objects, heap object is not collected until here
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if c < 0 {
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panic("heap object never collected")
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}
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if c != 1 {
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panic(fmt.Sprintf("expected collection at phase 1, got phase %d", c))
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}
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}
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func f() {
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var s StkObj
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s.h = new(HeapObj)
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runtime.SetFinalizer(s.h, func(h *HeapObj) {
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// Remember at what phase the heap object was collected.
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c = n
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})
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g(&s)
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gc()
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}
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func g(s *StkObj) {
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gc() // heap object is still live here
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runtime.KeepAlive(s)
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gc() // heap object should be collected here
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}
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