253 lines
7.0 KiB
Go
253 lines
7.0 KiB
Go
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// Copyright 2013 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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package oracle
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import (
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"fmt"
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"go/ast"
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"go/token"
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"sort"
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"golang.org/x/tools/go/loader"
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"golang.org/x/tools/go/ssa"
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"golang.org/x/tools/go/ssa/ssautil"
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"golang.org/x/tools/go/types"
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"golang.org/x/tools/oracle/serial"
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)
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// peers enumerates, for a given channel send (or receive) operation,
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// the set of possible receives (or sends) that correspond to it.
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//
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// TODO(adonovan): support reflect.{Select,Recv,Send,Close}.
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// TODO(adonovan): permit the user to query based on a MakeChan (not send/recv),
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// or the implicit receive in "for v := range ch".
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func peers(q *Query) error {
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lconf := loader.Config{Build: q.Build}
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if err := setPTAScope(&lconf, q.Scope); err != nil {
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return err
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}
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// Load/parse/type-check the program.
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lprog, err := lconf.Load()
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if err != nil {
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return err
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}
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q.Fset = lprog.Fset
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qpos, err := parseQueryPos(lprog, q.Pos, false)
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if err != nil {
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return err
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}
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prog := ssautil.CreateProgram(lprog, ssa.GlobalDebug)
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ptaConfig, err := setupPTA(prog, lprog, q.PTALog, q.Reflection)
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if err != nil {
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return err
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}
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opPos := findOp(qpos)
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if opPos == token.NoPos {
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return fmt.Errorf("there is no channel operation here")
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}
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// Defer SSA construction till after errors are reported.
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prog.BuildAll()
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var queryOp chanOp // the originating send or receive operation
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var ops []chanOp // all sends/receives of opposite direction
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// Look at all channel operations in the whole ssa.Program.
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// Build a list of those of same type as the query.
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allFuncs := ssautil.AllFunctions(prog)
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for fn := range allFuncs {
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for _, b := range fn.Blocks {
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for _, instr := range b.Instrs {
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for _, op := range chanOps(instr) {
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ops = append(ops, op)
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if op.pos == opPos {
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queryOp = op // we found the query op
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}
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}
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}
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}
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}
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if queryOp.ch == nil {
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return fmt.Errorf("ssa.Instruction for send/receive not found")
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}
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// Discard operations of wrong channel element type.
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// Build set of channel ssa.Values as query to pointer analysis.
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// We compare channels by element types, not channel types, to
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// ignore both directionality and type names.
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queryType := queryOp.ch.Type()
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queryElemType := queryType.Underlying().(*types.Chan).Elem()
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ptaConfig.AddQuery(queryOp.ch)
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i := 0
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for _, op := range ops {
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if types.Identical(op.ch.Type().Underlying().(*types.Chan).Elem(), queryElemType) {
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ptaConfig.AddQuery(op.ch)
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ops[i] = op
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i++
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}
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}
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ops = ops[:i]
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// Run the pointer analysis.
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ptares := ptrAnalysis(ptaConfig)
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// Find the points-to set.
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queryChanPtr := ptares.Queries[queryOp.ch]
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// Ascertain which make(chan) labels the query's channel can alias.
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var makes []token.Pos
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for _, label := range queryChanPtr.PointsTo().Labels() {
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makes = append(makes, label.Pos())
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}
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sort.Sort(byPos(makes))
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// Ascertain which channel operations can alias the same make(chan) labels.
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var sends, receives, closes []token.Pos
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for _, op := range ops {
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if ptr, ok := ptares.Queries[op.ch]; ok && ptr.MayAlias(queryChanPtr) {
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switch op.dir {
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case types.SendOnly:
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sends = append(sends, op.pos)
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case types.RecvOnly:
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receives = append(receives, op.pos)
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case types.SendRecv:
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closes = append(closes, op.pos)
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}
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}
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}
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sort.Sort(byPos(sends))
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sort.Sort(byPos(receives))
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sort.Sort(byPos(closes))
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q.result = &peersResult{
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queryPos: opPos,
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queryType: queryType,
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makes: makes,
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sends: sends,
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receives: receives,
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closes: closes,
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}
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return nil
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}
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// findOp returns the position of the enclosing send/receive/close op.
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// For send and receive operations, this is the position of the <- token;
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// for close operations, it's the Lparen of the function call.
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//
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// TODO(adonovan): handle implicit receive operations from 'for...range chan' statements.
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func findOp(qpos *queryPos) token.Pos {
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for _, n := range qpos.path {
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switch n := n.(type) {
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case *ast.UnaryExpr:
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if n.Op == token.ARROW {
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return n.OpPos
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}
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case *ast.SendStmt:
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return n.Arrow
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case *ast.CallExpr:
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// close function call can only exist as a direct identifier
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if close, ok := unparen(n.Fun).(*ast.Ident); ok {
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if b, ok := qpos.info.Info.Uses[close].(*types.Builtin); ok && b.Name() == "close" {
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return n.Lparen
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}
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}
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}
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}
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return token.NoPos
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}
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// chanOp abstracts an ssa.Send, ssa.Unop(ARROW), or a SelectState.
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type chanOp struct {
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ch ssa.Value
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dir types.ChanDir // SendOnly=send, RecvOnly=recv, SendRecv=close
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pos token.Pos
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}
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// chanOps returns a slice of all the channel operations in the instruction.
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func chanOps(instr ssa.Instruction) []chanOp {
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// TODO(adonovan): handle calls to reflect.{Select,Recv,Send,Close} too.
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var ops []chanOp
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switch instr := instr.(type) {
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case *ssa.UnOp:
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if instr.Op == token.ARROW {
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ops = append(ops, chanOp{instr.X, types.RecvOnly, instr.Pos()})
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}
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case *ssa.Send:
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ops = append(ops, chanOp{instr.Chan, types.SendOnly, instr.Pos()})
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case *ssa.Select:
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for _, st := range instr.States {
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ops = append(ops, chanOp{st.Chan, st.Dir, st.Pos})
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}
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case ssa.CallInstruction:
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cc := instr.Common()
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if b, ok := cc.Value.(*ssa.Builtin); ok && b.Name() == "close" {
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ops = append(ops, chanOp{cc.Args[0], types.SendRecv, cc.Pos()})
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}
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}
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return ops
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}
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type peersResult struct {
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queryPos token.Pos // of queried channel op
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queryType types.Type // type of queried channel
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makes, sends, receives, closes []token.Pos // positions of aliased makechan/send/receive/close instrs
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}
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func (r *peersResult) display(printf printfFunc) {
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if len(r.makes) == 0 {
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printf(r.queryPos, "This channel can't point to anything.")
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return
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}
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printf(r.queryPos, "This channel of type %s may be:", r.queryType)
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for _, alloc := range r.makes {
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printf(alloc, "\tallocated here")
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}
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for _, send := range r.sends {
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printf(send, "\tsent to, here")
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}
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for _, receive := range r.receives {
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printf(receive, "\treceived from, here")
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}
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for _, clos := range r.closes {
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printf(clos, "\tclosed, here")
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}
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}
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func (r *peersResult) toSerial(res *serial.Result, fset *token.FileSet) {
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peers := &serial.Peers{
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Pos: fset.Position(r.queryPos).String(),
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Type: r.queryType.String(),
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}
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for _, alloc := range r.makes {
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peers.Allocs = append(peers.Allocs, fset.Position(alloc).String())
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}
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for _, send := range r.sends {
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peers.Sends = append(peers.Sends, fset.Position(send).String())
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}
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for _, receive := range r.receives {
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peers.Receives = append(peers.Receives, fset.Position(receive).String())
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}
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for _, clos := range r.closes {
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peers.Closes = append(peers.Closes, fset.Position(clos).String())
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}
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res.Peers = peers
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}
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// -------- utils --------
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// NB: byPos is not deterministic across packages since it depends on load order.
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// Use lessPos if the tests need it.
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type byPos []token.Pos
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func (p byPos) Len() int { return len(p) }
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func (p byPos) Less(i, j int) bool { return p[i] < p[j] }
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func (p byPos) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
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