| // 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. |
| |
| // This file contains the code to check that locks are not passed by value. |
| |
| package main |
| |
| import ( |
| "bytes" |
| "fmt" |
| "go/ast" |
| |
| "code.google.com/p/go.tools/go/types" |
| ) |
| |
| // checkCopyLocks checks whether a function might |
| // inadvertently copy a lock, by checking whether |
| // its receiver, parameters, or return values |
| // are locks. |
| func (f *File) checkCopyLocks(d *ast.FuncDecl) { |
| if !vet("copylocks") { |
| return |
| } |
| |
| if d.Recv != nil && len(d.Recv.List) > 0 { |
| expr := d.Recv.List[0].Type |
| if path := lockPath(f.pkg.typesPkg, f.pkg.types[expr].Type); path != nil { |
| f.Badf(expr.Pos(), "%s passes Lock by value: %v", d.Name.Name, path) |
| } |
| } |
| |
| if d.Type.Params != nil { |
| for _, field := range d.Type.Params.List { |
| expr := field.Type |
| if path := lockPath(f.pkg.typesPkg, f.pkg.types[expr].Type); path != nil { |
| f.Badf(expr.Pos(), "%s passes Lock by value: %v", d.Name.Name, path) |
| } |
| } |
| } |
| |
| if d.Type.Results != nil { |
| for _, field := range d.Type.Results.List { |
| expr := field.Type |
| if path := lockPath(f.pkg.typesPkg, f.pkg.types[expr].Type); path != nil { |
| f.Badf(expr.Pos(), "%s returns Lock by value: %v", d.Name.Name, path) |
| } |
| } |
| } |
| } |
| |
| type typePath []types.Type |
| |
| // pathString 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() |
| } |
| |
| // 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 |
| } |
| |
| // 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 reference to this type |
| // can be locked, but a value cannot. This differentiates |
| // embedded interfaces from embedded values. |
| if plock := types.NewMethodSet(types.NewPointer(typ)).Lookup(tpkg, "Lock"); plock != nil { |
| if lock := types.NewMethodSet(typ).Lookup(tpkg, "Lock"); lock == nil { |
| 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 |
| } |