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Source file test/fixedbugs/issue5373.go

Documentation: test/fixedbugs

  // 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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