issue27278.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  // Issue 27278: dead auto elim deletes an auto and its
     8  // initialization, but it is live because of a nil check.
     9  
    10  package main
    11  
    12  type T struct {
    13  	_ [3]string
    14  	T2
    15  }
    16  
    17  func (t *T) M() []string {
    18  	return t.T2.M()
    19  }
    20  
    21  type T2 struct {
    22  	T3
    23  }
    24  
    25  func (t *T2) M() []string {
    26  	return t.T3.M()
    27  }
    28  
    29  type T3 struct {
    30  	a string
    31  }
    32  
    33  func (t *T3) M() []string {
    34  	return []string{}
    35  }
    36  
    37  func main() {
    38  	poison()
    39  	f()
    40  }
    41  
    42  //go:noinline
    43  func f() {
    44  	(&T{}).M()
    45  	grow(10000)
    46  }
    47  
    48  // grow stack, triggers stack copy
    49  func grow(n int) {
    50  	if n == 0 {
    51  		return
    52  	}
    53  	grow(n-1)
    54  }
    55  
    56  // put some junk on stack, which cannot be valid address
    57  //go:noinline
    58  func poison() {
    59  	x := [10]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    60  	g = x
    61  }
    62  
    63  var g [10]int
    64
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