issue53888_test.go

     1  // Copyright 2022 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  //go:build !race
     6  
     7  package test
     8  
     9  import (
    10  	"internal/testenv"
    11  	"testing"
    12  )
    13  
    14  func TestAppendOfMake(t *testing.T) {
    15  	testenv.SkipIfOptimizationOff(t)
    16  	for n := 32; n < 33; n++ { // avoid stack allocation of make()
    17  		b := make([]byte, n)
    18  		f := func() {
    19  			b = append(b[:0], make([]byte, n)...)
    20  		}
    21  		if n := testing.AllocsPerRun(10, f); n > 0 {
    22  			t.Errorf("got %f allocs, want 0", n)
    23  		}
    24  		type S []byte
    25  
    26  		s := make(S, n)
    27  		g := func() {
    28  			s = append(s[:0], make(S, n)...)
    29  		}
    30  		if n := testing.AllocsPerRun(10, g); n > 0 {
    31  			t.Errorf("got %f allocs, want 0", n)
    32  		}
    33  		h := func() {
    34  			s = append(s[:0], make([]byte, n)...)
    35  		}
    36  		if n := testing.AllocsPerRun(10, h); n > 0 {
    37  			t.Errorf("got %f allocs, want 0", n)
    38  		}
    39  		i := func() {
    40  			b = append(b[:0], make(S, n)...)
    41  		}
    42  		if n := testing.AllocsPerRun(10, i); n > 0 {
    43  			t.Errorf("got %f allocs, want 0", n)
    44  		}
    45  	}
    46  }
    47
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