mirror of
https://github.com/golang/go
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73 lines
1.2 KiB
Go
73 lines
1.2 KiB
Go
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// 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 "runtime"
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var finalized bool
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var err string
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type HeapObj [8]int64
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const filler int64 = 0x123456789abcdef0
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func (h *HeapObj) init() {
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for i := 0; i < len(*h); i++ {
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h[i] = filler
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}
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}
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func (h *HeapObj) check() {
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for i := 0; i < len(*h); i++ {
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if h[i] != filler {
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err = "filler overwritten"
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}
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}
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}
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type StackObj struct {
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h *HeapObj
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}
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func gc(shouldFinalize bool) {
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runtime.GC()
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runtime.GC()
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runtime.GC()
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if shouldFinalize != finalized {
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err = "heap object finalized at the wrong time"
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}
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}
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func main() {
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var s StackObj
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s.h = new(HeapObj)
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s.h.init()
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runtime.SetFinalizer(s.h, func(h *HeapObj) {
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finalized = true
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})
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gc(false)
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h := g(&s)
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gc(false)
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h.check()
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gc(true) // finalize here, after return value's last use. (Go1.11 never runs the finalizer.)
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if err != "" {
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panic(err)
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}
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}
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func g(p *StackObj) (v *HeapObj) {
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gc(false)
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v = p.h // last use of the stack object. the only reference to the heap object is in the return slot.
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gc(false)
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defer func() {
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gc(false)
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recover()
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gc(false)
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}()
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*(*int)(nil) = 0
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return
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}
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