free_test.go

     1  // Copyright 2025 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  package test
     6  
     7  import (
     8  	"internal/asan"
     9  	"internal/goexperiment"
    10  	"internal/msan"
    11  	"internal/race"
    12  	"testing"
    13  )
    14  
    15  func TestFreeAppendAllocations(t *testing.T) {
    16  	t.Run("slice-no-alias", func(t *testing.T) {
    17  		if !goexperiment.RuntimeFreegc {
    18  			t.Skip("skipping allocation test when runtime.freegc is disabled")
    19  		}
    20  		if race.Enabled || msan.Enabled || asan.Enabled {
    21  			// TODO(thepudds): we get 8 allocs for slice-no-alias instead of 1 with -race. This
    22  			// might be expected given some allocation optimizations are already disabled
    23  			// under race, but if not, we might need to update walk.
    24  			t.Skip("skipping allocation test under race detector and other sanitizers")
    25  		}
    26  
    27  		allocs := testing.AllocsPerRun(100, func() {
    28  			var s []int64
    29  			for i := range 100 {
    30  				s = append(s, int64(i))
    31  			}
    32  			_ = s
    33  		})
    34  		t.Logf("allocs: %v", allocs)
    35  		if allocs != 1 {
    36  			t.Errorf("allocs: %v, want 1", allocs)
    37  		}
    38  	})
    39  
    40  	t.Run("slice-aliased", func(t *testing.T) {
    41  		allocs := testing.AllocsPerRun(100, func() {
    42  			var s []int64
    43  			var alias []int64
    44  			for i := range 100 {
    45  				s = append(s, int64(i))
    46  				alias = s
    47  			}
    48  			_ = alias
    49  		})
    50  		t.Logf("allocs: %v", allocs)
    51  		if allocs < 2 {
    52  			t.Errorf("allocs: %v, want >= 2", allocs)
    53  		}
    54  	})
    55  }
    56
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