slice_test.go

Documentation: cmd/compile/internal/test/testdata

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // This test makes sure that t.s = t.s[0:x] doesn't write
     6  // either the slice pointer or the capacity.
     7  // See issue #14855.
     8  
     9  package main
    10  
    11  import "testing"
    12  
    13  const N = 1000000
    14  
    15  type X struct {
    16  	s []int
    17  }
    18  
    19  func TestSlice(t *testing.T) {
    20  	done := make(chan struct{})
    21  	a := make([]int, N+10)
    22  
    23  	x := &X{a}
    24  
    25  	go func() {
    26  		for i := 0; i < N; i++ {
    27  			x.s = x.s[1:9]
    28  		}
    29  		done <- struct{}{}
    30  	}()
    31  	go func() {
    32  		for i := 0; i < N; i++ {
    33  			x.s = x.s[0:8] // should only write len
    34  		}
    35  		done <- struct{}{}
    36  	}()
    37  	<-done
    38  	<-done
    39  
    40  	if cap(x.s) != cap(a)-N {
    41  		t.Errorf("wanted cap=%d, got %d\n", cap(a)-N, cap(x.s))
    42  	}
    43  	if &x.s[0] != &a[N] {
    44  		t.Errorf("wanted ptr=%p, got %p\n", &a[N], &x.s[0])
    45  	}
    46  }
    47
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