golang sync.Pool 指针数据覆盖问题解决

var stringPool = sync.Pool{
	New: func() any {
		return new([]string)
	},
}

func NewString() *[]string {
	v := stringPool.Get().(*[]string)
	return v
}

func PutString(s *[]string) {
	if s == nil {
		return
	}

	if cap(*s) > 2048 {
		s = nil
	} else {
		*s = (*s)[:0]
		stringPool.Put(s)
	}
}

func Test_Pool(t *testing.T) {
	dataSlice1 := demoData()
	dataSlice2 := demoData()
	dataSlice2[1] = "test4"

	fmt.Printf("dataSlice1:%v %p,dataSlice2:%v %p\n", dataSlice1, dataSlice1, dataSlice2, dataSlice2)
}

func demoData() []string {
	strsPtr := NewString()
	strs := *strsPtr
	defer func() {
		*strsPtr = strs
		PutString(strsPtr)
	}()

	strs = append(strs, "test1", "test2")
	return strs
}

func Test_Pool(t *testing.T) {
	dataSlice1 := demoData()
	dataSlice2 := demoData()
	dataSlice2[1] = "test4"

	fmt.Printf("dataSlice1:%v %p,dataSlice2:%v %p\n", dataSlice1, dataSlice1, dataSlice2, dataSlice2)
}

func demoData() []string {
	strsPtr := NewString()
	strs := *strsPtr
	defer func() {
		*strsPtr = strs
		PutString(strsPtr)
	}()

	strs = append(strs, "test1", "test2")

	// 深复制
	var items = make([]string, len(strs))
	copy(items, strs)

	return items
}

func Fprintln(w io.Writer, a ...any) (n int, err error) {
	p := newPrinter()
	p.doPrintln(a)
	n, err = w.Write(p.buf)
	p.free()
	return
}