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vet: add range variable misuse detection
R=fullung, r, remyoudompheng, minux.ma, gri, rsc CC=golang-dev https://golang.org/cl/6494075
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// 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. | ||
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/* | ||
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 | ||
*/ | ||
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package main | ||
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import "go/ast" | ||
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// 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 | ||
}) | ||
} | ||
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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) | ||
}() | ||
} | ||
} |