test/deferfin.go

   1 // run
   2
   3 // Copyright 2013 The Go Authors. All rights reserved.
   4 // Use of this source code is governed by a BSD-style
   5 // license that can be found in the LICENSE file.
   6
   7 // Test that defers do not prevent garbage collection.
   8
   9 package main
  10
  11 import (
  12         "runtime"
  13         "sync"
  14         "sync/atomic"
  15         "time"
  16 )
  17
  18 var sink func()
  19
  20 func main() {
  21         // Does not work with gccgo, due to partially conservative GC.
  22         // Try to enable when we have fully precise GC.
  23         if runtime.Compiler == "gccgo" {
  24                 return
  25         }
  26         N := 10
  27         count := int32(N)
  28         var wg sync.WaitGroup
  29         wg.Add(N)
  30         for i := 0; i < N; i++ {
  31                 go func() {
  32                         defer wg.Done()
  33                         v := new(string)
  34                         f := func() {
  35                                 if *v != "" {
  36                                         panic("oops")
  37                                 }
  38                         }
  39                         if *v != "" {
  40                                 // let the compiler think f escapes
  41                                 sink = f
  42                         }
  43                         runtime.SetFinalizer(v, func(p *string) {
  44                                 atomic.AddInt32(&count, -1)
  45                         })
  46                         defer f()
  47                 }()
  48         }
  49         wg.Wait()
  50         for i := 0; i < 3; i++ {
  51                 time.Sleep(10 * time.Millisecond)
  52                 runtime.GC()
  53         }
  54         if count != 0 {
  55                 println(count, "out of", N, "finalizer are not called")
  56                 panic("not all finalizers are called")
  57         }
  58 }