Current File : //usr/local/go/src/cmd/vendor/golang.org/x/tools/go/analysis/passes/copylock/copylock.go
// Copyright 2013 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.
// Package copylock defines an Analyzer that checks for locks
// erroneously passed by value.
package copylock
import (
"bytes"
"fmt"
"go/ast"
"go/token"
"go/types"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
"golang.org/x/tools/go/ast/inspector"
)
const Doc = `check for locks erroneously passed by value
Inadvertently copying a value containing a lock, such as sync.Mutex or
sync.WaitGroup, may cause both copies to malfunction. Generally such
values should be referred to through a pointer.`
var Analyzer = &analysis.Analyzer{
Name: "copylocks",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
RunDespiteErrors: true,
Run: run,
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
nodeFilter := []ast.Node{
(*ast.AssignStmt)(nil),
(*ast.CallExpr)(nil),
(*ast.CompositeLit)(nil),
(*ast.FuncDecl)(nil),
(*ast.FuncLit)(nil),
(*ast.GenDecl)(nil),
(*ast.RangeStmt)(nil),
(*ast.ReturnStmt)(nil),
}
inspect.Preorder(nodeFilter, func(node ast.Node) {
switch node := node.(type) {
case *ast.RangeStmt:
checkCopyLocksRange(pass, node)
case *ast.FuncDecl:
checkCopyLocksFunc(pass, node.Name.Name, node.Recv, node.Type)
case *ast.FuncLit:
checkCopyLocksFunc(pass, "func", nil, node.Type)
case *ast.CallExpr:
checkCopyLocksCallExpr(pass, node)
case *ast.AssignStmt:
checkCopyLocksAssign(pass, node)
case *ast.GenDecl:
checkCopyLocksGenDecl(pass, node)
case *ast.CompositeLit:
checkCopyLocksCompositeLit(pass, node)
case *ast.ReturnStmt:
checkCopyLocksReturnStmt(pass, node)
}
})
return nil, nil
}
// checkCopyLocksAssign checks whether an assignment
// copies a lock.
func checkCopyLocksAssign(pass *analysis.Pass, as *ast.AssignStmt) {
for i, x := range as.Rhs {
if path := lockPathRhs(pass, x); path != nil {
pass.ReportRangef(x, "assignment copies lock value to %v: %v", analysisutil.Format(pass.Fset, as.Lhs[i]), path)
}
}
}
// checkCopyLocksGenDecl checks whether lock is copied
// in variable declaration.
func checkCopyLocksGenDecl(pass *analysis.Pass, gd *ast.GenDecl) {
if gd.Tok != token.VAR {
return
}
for _, spec := range gd.Specs {
valueSpec := spec.(*ast.ValueSpec)
for i, x := range valueSpec.Values {
if path := lockPathRhs(pass, x); path != nil {
pass.ReportRangef(x, "variable declaration copies lock value to %v: %v", valueSpec.Names[i].Name, path)
}
}
}
}
// checkCopyLocksCompositeLit detects lock copy inside a composite literal
func checkCopyLocksCompositeLit(pass *analysis.Pass, cl *ast.CompositeLit) {
for _, x := range cl.Elts {
if node, ok := x.(*ast.KeyValueExpr); ok {
x = node.Value
}
if path := lockPathRhs(pass, x); path != nil {
pass.ReportRangef(x, "literal copies lock value from %v: %v", analysisutil.Format(pass.Fset, x), path)
}
}
}
// checkCopyLocksReturnStmt detects lock copy in return statement
func checkCopyLocksReturnStmt(pass *analysis.Pass, rs *ast.ReturnStmt) {
for _, x := range rs.Results {
if path := lockPathRhs(pass, x); path != nil {
pass.ReportRangef(x, "return copies lock value: %v", path)
}
}
}
// checkCopyLocksCallExpr detects lock copy in the arguments to a function call
func checkCopyLocksCallExpr(pass *analysis.Pass, ce *ast.CallExpr) {
var id *ast.Ident
switch fun := ce.Fun.(type) {
case *ast.Ident:
id = fun
case *ast.SelectorExpr:
id = fun.Sel
}
if fun, ok := pass.TypesInfo.Uses[id].(*types.Builtin); ok {
switch fun.Name() {
case "new", "len", "cap", "Sizeof":
return
}
}
for _, x := range ce.Args {
if path := lockPathRhs(pass, x); path != nil {
pass.ReportRangef(x, "call of %s copies lock value: %v", analysisutil.Format(pass.Fset, ce.Fun), path)
}
}
}
// checkCopyLocksFunc checks whether a function might
// inadvertently copy a lock, by checking whether
// its receiver, parameters, or return values
// are locks.
func checkCopyLocksFunc(pass *analysis.Pass, name string, recv *ast.FieldList, typ *ast.FuncType) {
if recv != nil && len(recv.List) > 0 {
expr := recv.List[0].Type
if path := lockPath(pass.Pkg, pass.TypesInfo.Types[expr].Type); path != nil {
pass.ReportRangef(expr, "%s passes lock by value: %v", name, path)
}
}
if typ.Params != nil {
for _, field := range typ.Params.List {
expr := field.Type
if path := lockPath(pass.Pkg, pass.TypesInfo.Types[expr].Type); path != nil {
pass.ReportRangef(expr, "%s passes lock by value: %v", name, path)
}
}
}
// Don't check typ.Results. If T has a Lock field it's OK to write
// return T{}
// because that is returning the zero value. Leave result checking
// to the return statement.
}
// checkCopyLocksRange checks whether a range statement
// might inadvertently copy a lock by checking whether
// any of the range variables are locks.
func checkCopyLocksRange(pass *analysis.Pass, r *ast.RangeStmt) {
checkCopyLocksRangeVar(pass, r.Tok, r.Key)
checkCopyLocksRangeVar(pass, r.Tok, r.Value)
}
func checkCopyLocksRangeVar(pass *analysis.Pass, rtok token.Token, e ast.Expr) {
if e == nil {
return
}
id, isId := e.(*ast.Ident)
if isId && id.Name == "_" {
return
}
var typ types.Type
if rtok == token.DEFINE {
if !isId {
return
}
obj := pass.TypesInfo.Defs[id]
if obj == nil {
return
}
typ = obj.Type()
} else {
typ = pass.TypesInfo.Types[e].Type
}
if typ == nil {
return
}
if path := lockPath(pass.Pkg, typ); path != nil {
pass.Reportf(e.Pos(), "range var %s copies lock: %v", analysisutil.Format(pass.Fset, e), path)
}
}
type typePath []types.Type
// String pretty-prints a typePath.
func (path typePath) String() string {
n := len(path)
var buf bytes.Buffer
for i := range path {
if i > 0 {
fmt.Fprint(&buf, " contains ")
}
// The human-readable path is in reverse order, outermost to innermost.
fmt.Fprint(&buf, path[n-i-1].String())
}
return buf.String()
}
func lockPathRhs(pass *analysis.Pass, x ast.Expr) typePath {
if _, ok := x.(*ast.CompositeLit); ok {
return nil
}
if _, ok := x.(*ast.CallExpr); ok {
// A call may return a zero value.
return nil
}
if star, ok := x.(*ast.StarExpr); ok {
if _, ok := star.X.(*ast.CallExpr); ok {
// A call may return a pointer to a zero value.
return nil
}
}
return lockPath(pass.Pkg, pass.TypesInfo.Types[x].Type)
}
// lockPath returns a typePath describing the location of a lock value
// contained in typ. If there is no contained lock, it returns nil.
func lockPath(tpkg *types.Package, typ types.Type) typePath {
if typ == nil {
return nil
}
for {
atyp, ok := typ.Underlying().(*types.Array)
if !ok {
break
}
typ = atyp.Elem()
}
// We're only interested in the case in which the underlying
// type is a struct. (Interfaces and pointers are safe to copy.)
styp, ok := typ.Underlying().(*types.Struct)
if !ok {
return nil
}
// We're looking for cases in which a pointer to this type
// is a sync.Locker, but a value is not. This differentiates
// embedded interfaces from embedded values.
if types.Implements(types.NewPointer(typ), lockerType) && !types.Implements(typ, lockerType) {
return []types.Type{typ}
}
// In go1.10, sync.noCopy did not implement Locker.
// (The Unlock method was added only in CL 121876.)
// TODO(adonovan): remove workaround when we drop go1.10.
if named, ok := typ.(*types.Named); ok &&
named.Obj().Name() == "noCopy" &&
named.Obj().Pkg().Path() == "sync" {
return []types.Type{typ}
}
nfields := styp.NumFields()
for i := 0; i < nfields; i++ {
ftyp := styp.Field(i).Type()
subpath := lockPath(tpkg, ftyp)
if subpath != nil {
return append(subpath, typ)
}
}
return nil
}
var lockerType *types.Interface
// Construct a sync.Locker interface type.
func init() {
nullary := types.NewSignature(nil, nil, nil, false) // func()
methods := []*types.Func{
types.NewFunc(token.NoPos, nil, "Lock", nullary),
types.NewFunc(token.NoPos, nil, "Unlock", nullary),
}
lockerType = types.NewInterface(methods, nil).Complete()
}
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