mirror of
https://github.com/golang/go
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71 lines
1.7 KiB
Go
71 lines
1.7 KiB
Go
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// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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This file contains the code to check range loop variables bound inside function
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literals that are deferred or launched in new goroutines. We only check
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instances where the defer or go statement is the last statement in the loop
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body, as otherwise we would need whole program analysis.
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For example:
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for i, v := range s {
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go func() {
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println(i, v) // not what you might expect
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}()
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}
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See: http://golang.org/doc/go_faq.html#closures_and_goroutines
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*/
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package main
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import "go/ast"
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func init() {
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register("rangeloops",
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"check that range loop variables are used correctly",
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checkRangeLoop,
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rangeStmt)
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}
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// checkRangeLoop walks the body of the provided range statement, checking if
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// its index or value variables are used unsafely inside goroutines or deferred
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// function literals.
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func checkRangeLoop(f *File, node ast.Node) {
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n := node.(*ast.RangeStmt)
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key, _ := n.Key.(*ast.Ident)
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val, _ := n.Value.(*ast.Ident)
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if key == nil && val == nil {
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return
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}
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sl := n.Body.List
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if len(sl) == 0 {
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return
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}
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var last *ast.CallExpr
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switch s := sl[len(sl)-1].(type) {
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case *ast.GoStmt:
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last = s.Call
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case *ast.DeferStmt:
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last = s.Call
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default:
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return
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}
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lit, ok := last.Fun.(*ast.FuncLit)
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if !ok {
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return
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}
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ast.Inspect(lit.Body, func(n ast.Node) bool {
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id, ok := n.(*ast.Ident)
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if !ok || id.Obj == nil {
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return true
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}
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if key != nil && id.Obj == key.Obj || val != nil && id.Obj == val.Obj {
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f.Bad(id.Pos(), "range variable", id.Name, "captured by func literal")
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}
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return true
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})
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}
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