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