1// run
2
3// Copyright 2015 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// Ensure that zeroing range loops have the requisite side-effects.
8
9package main
10
11import (
12	"fmt"
13	"os"
14)
15
16func check(n int) {
17	// When n == 0, i is untouched by the range loop.
18	// Picking an initial value of -1 for i makes the
19	// "want" calculation below correct in all cases.
20	i := -1
21	s := make([]byte, n)
22	for i = range s {
23		s[i] = 0
24	}
25	if want := n - 1; i != want {
26		fmt.Printf("index after range with side-effect = %d want %d\n", i, want)
27		os.Exit(1)
28	}
29
30	i = n + 1
31	// i is shadowed here, so its value should be unchanged.
32	for i := range s {
33		s[i] = 0
34	}
35	if want := n + 1; i != want {
36		fmt.Printf("index after range without side-effect = %d want %d\n", i, want)
37		os.Exit(1)
38	}
39
40	// Index variable whose evaluation has side-effects
41	var x int
42	f := func() int {
43		x++
44		return 0
45	}
46	var a [1]int
47	for a[f()] = range s {
48		s[a[f()]] = 0
49	}
50	if want := n * 2; x != want {
51		fmt.Printf("index function calls = %d want %d\n", x, want)
52		os.Exit(1)
53	}
54
55	// Range expression whose evaluation has side-effects
56	x = 0
57	b := [1][]byte{s}
58	for i := range b[f()] {
59		b[f()][i] = 0
60	}
61	if want := n + 1; x != n+1 {
62		fmt.Printf("range expr function calls = %d want %d\n", x, want)
63		os.Exit(1)
64	}
65}
66
67func main() {
68	check(0)
69	check(1)
70	check(15)
71}
72