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// run
// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Ensure that zeroing range loops have the requisite side-effects.
package main
import (
"fmt"
"os"
)
func check(n int) {
// When n == 0, i is untouched by the range loop.
// Picking an initial value of -1 for i makes the
// "want" calculation below correct in all cases.
i := -1
s := make([]byte, n)
for i = range s {
s[i] = 0
}
if want := n - 1; i != want {
fmt.Printf("index after range with side-effect = %d want %d\n", i, want)
os.Exit(1)
}
i = n + 1
// i is shadowed here, so its value should be unchanged.
for i := range s {
s[i] = 0
}
if want := n + 1; i != want {
fmt.Printf("index after range without side-effect = %d want %d\n", i, want)
os.Exit(1)
}
// Index variable whose evaluation has side-effects
var x int
f := func() int {
x++
return 0
}
var a [1]int
for a[f()] = range s {
s[a[f()]] = 0
}
if want := n * 2; x != want {
fmt.Printf("index function calls = %d want %d\n", x, want)
os.Exit(1)
}
// Range expression whose evaluation has side-effects
x = 0
b := [1][]byte{s}
for i := range b[f()] {
b[f()][i] = 0
}
if want := n + 1; x != n+1 {
fmt.Printf("range expr function calls = %d want %d\n", x, want)
os.Exit(1)
}
}
func main() {
check(0)
check(1)
check(15)
}
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