Commit 51e85612 authored by Andrew Gerrand's avatar Andrew Gerrand

vet: add range variable misuse detection

R=fullung, r, remyoudompheng, minux.ma, gri, rsc
CC=golang-dev
https://golang.org/cl/6494075
parent 7e525928
......@@ -4,4 +4,4 @@
test testshort:
go build
../../../test/errchk ./vet -printfuncs='Warn:1,Warnf:1' print.go
../../../test/errchk ./vet -printfuncs='Warn:1,Warnf:1' print.go rangeloop.go
......@@ -30,6 +30,7 @@ var (
vetPrintf = flag.Bool("printf", false, "check printf-like invocations")
vetStructTags = flag.Bool("structtags", false, "check that struct field tags have canonical format")
vetUntaggedLiteral = flag.Bool("composites", false, "check that composite literals used type-tagged elements")
vetRangeLoops = flag.Bool("rangeloops", false, "check that range loop variables are used correctly")
)
// setExit sets the value for os.Exit when it is called, later. It
......@@ -60,7 +61,7 @@ func main() {
flag.Parse()
// If a check is named explicitly, turn off the 'all' flag.
if *vetMethods || *vetPrintf || *vetStructTags || *vetUntaggedLiteral {
if *vetMethods || *vetPrintf || *vetStructTags || *vetUntaggedLiteral || *vetRangeLoops {
*vetAll = false
}
......@@ -197,6 +198,8 @@ func (f *File) Visit(node ast.Node) ast.Visitor {
f.walkMethodDecl(n)
case *ast.InterfaceType:
f.walkInterfaceType(n)
case *ast.RangeStmt:
f.walkRangeStmt(n)
}
return f
}
......@@ -206,6 +209,16 @@ func (f *File) walkCall(call *ast.CallExpr, name string) {
f.checkFmtPrintfCall(call, name)
}
// walkCallExpr walks a call expression.
func (f *File) walkCallExpr(call *ast.CallExpr) {
switch x := call.Fun.(type) {
case *ast.Ident:
f.walkCall(call, x.Name)
case *ast.SelectorExpr:
f.walkCall(call, x.Sel.Name)
}
}
// walkCompositeLit walks a composite literal.
func (f *File) walkCompositeLit(c *ast.CompositeLit) {
f.checkUntaggedLiteral(c)
......@@ -242,12 +255,7 @@ func (f *File) walkInterfaceType(t *ast.InterfaceType) {
}
}
// walkCallExpr walks a call expression.
func (f *File) walkCallExpr(call *ast.CallExpr) {
switch x := call.Fun.(type) {
case *ast.Ident:
f.walkCall(call, x.Name)
case *ast.SelectorExpr:
f.walkCall(call, x.Sel.Name)
}
// walkRangeStmt walks a range statment.
func (f *File) walkRangeStmt(n *ast.RangeStmt) {
checkRangeLoop(f, n)
}
// Copyright 2012 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.
/*
This file contains the code to check range loop variables bound inside function
literals that are deferred or launched in new goroutines. We only check
instances where the defer or go statement is the last statement in the loop
body, as otherwise we would need whole program analysis.
For example:
for i, v := range s {
go func() {
println(i, v) // not what you might expect
}()
}
See: http://golang.org/doc/go_faq.html#closures_and_goroutines
*/
package main
import "go/ast"
// checkRangeLoop walks the body of the provided range statement, checking if
// its index or value variables are used unsafely inside goroutines or deferred
// function literals.
func checkRangeLoop(f *File, n *ast.RangeStmt) {
if !*vetRangeLoops && !*vetAll {
return
}
key, _ := n.Key.(*ast.Ident)
val, _ := n.Value.(*ast.Ident)
if key == nil && val == nil {
return
}
sl := n.Body.List
if len(sl) == 0 {
return
}
var last *ast.CallExpr
switch s := sl[len(sl)-1].(type) {
case *ast.GoStmt:
last = s.Call
case *ast.DeferStmt:
last = s.Call
default:
return
}
lit, ok := last.Fun.(*ast.FuncLit)
if !ok {
return
}
ast.Inspect(lit.Body, func(n ast.Node) bool {
if n, ok := n.(*ast.Ident); ok && n.Obj != nil && (n.Obj == key.Obj || n.Obj == val.Obj) {
f.Warn(n.Pos(), "range variable", n.Name, "enclosed by function")
}
return true
})
}
func BadRangeLoopsUsedInTests() {
var s []int
for i, v := range s {
go func() {
println(i) // ERROR "range variable i enclosed by function"
println(v) // ERROR "range variable v enclosed by function"
}()
}
for i, v := range s {
defer func() {
println(i) // ERROR "range variable i enclosed by function"
println(v) // ERROR "range variable v enclosed by function"
}()
}
for i := range s {
go func() {
println(i) // ERROR "range variable i enclosed by function"
}()
}
for _, v := range s {
go func() {
println(v) // ERROR "range variable v enclosed by function"
}()
}
for i, v := range s {
go func() {
println(i, v)
}()
println("unfortunately, we don't catch the error above because of this statement")
}
for i, v := range s {
go func(i, v int) {
println(i, v)
}(i, v)
}
for i, v := range s {
i, v := i, v
go func() {
println(i, v)
}()
}
}
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