Source file test/stackobj3.go

     1  // run
     2  
     3  // Copyright 2018 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  // This test makes sure that ambiguously live arguments work correctly.
     8  
     9  package main
    10  
    11  import (
    12  	"runtime"
    13  )
    14  
    15  type HeapObj [8]int64
    16  
    17  type StkObj struct {
    18  	h *HeapObj
    19  }
    20  
    21  var n int
    22  var c int = -1
    23  
    24  func gc() {
    25  	// encourage heap object to be collected, and have its finalizer run.
    26  	runtime.GC()
    27  	runtime.GC()
    28  	runtime.GC()
    29  	n++
    30  }
    31  
    32  var null StkObj
    33  
    34  var sink *HeapObj
    35  
    36  //go:noinline
    37  func use(p *StkObj) {
    38  }
    39  
    40  //go:noinline
    41  func f(s StkObj, b bool) {
    42  	var p *StkObj
    43  	if b {
    44  		p = &s
    45  	} else {
    46  		p = &null
    47  	}
    48  	// use is required here to prevent the conditional
    49  	// code above from being executed after the first gc() call.
    50  	use(p)
    51  	// If b==false, h should be collected here.
    52  	gc() // 0
    53  	sink = p.h
    54  	gc() // 1
    55  	sink = nil
    56  	// If b==true, h should be collected here.
    57  	gc() // 2
    58  }
    59  
    60  func fTrue() {
    61  	var s StkObj
    62  	s.h = new(HeapObj)
    63  	c = -1
    64  	n = 0
    65  	runtime.SetFinalizer(s.h, func(h *HeapObj) {
    66  		// Remember at what phase the heap object was collected.
    67  		c = n
    68  	})
    69  	f(s, true)
    70  	if c != 2 {
    71  		panic("bad liveness")
    72  	}
    73  }
    74  
    75  func fFalse() {
    76  	var s StkObj
    77  	s.h = new(HeapObj)
    78  	c = -1
    79  	n = 0
    80  	runtime.SetFinalizer(s.h, func(h *HeapObj) {
    81  		// Remember at what phase the heap object was collected.
    82  		c = n
    83  	})
    84  	f(s, false)
    85  	if c != 0 {
    86  		panic("bad liveness")
    87  	}
    88  }
    89  
    90  func main() {
    91  	fTrue()
    92  	fFalse()
    93  }
    94  

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