go/pointer/api.go - tools - Git at Google

 // 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 pointer

 import (
 	"bytes"
 	"fmt"
 	"go/token"
 	"io"

 	"golang.org/x/tools/container/intsets"
 	"golang.org/x/tools/go/callgraph"
 	"golang.org/x/tools/go/ssa"
 	"golang.org/x/tools/go/types/typeutil"
 )

 // A Config formulates a pointer analysis problem for Analyze. It is
 // only usable for a single invocation of Analyze and must not be
 // reused.
 type Config struct {
 	// Mains contains the set of 'main' packages to analyze
 	// Clients must provide the analysis with at least one
 	// package defining a main() function.
 	//
 	// Non-main packages in the ssa.Program that are not
 	// dependencies of any main package may still affect the
 	// analysis result, because they contribute runtime types and
 	// thus methods.
 	// TODO(adonovan): investigate whether this is desirable.
 	Mains []*ssa.Package

 	// Reflection determines whether to handle reflection
 	// operators soundly, which is currently rather slow since it
 	// causes constraint to be generated during solving
 	// proportional to the number of constraint variables, which
 	// has not yet been reduced by presolver optimisation.
 	Reflection bool

 	// BuildCallGraph determines whether to construct a callgraph.
 	// If enabled, the graph will be available in Result.CallGraph.
 	BuildCallGraph bool

 	// The client populates Queries[v] or IndirectQueries[v]
 	// for each ssa.Value v of interest, to request that the
 	// points-to sets pts(v) or pts(*v) be computed.  If the
 	// client needs both points-to sets, v may appear in both
 	// maps.
 	//
 	// (IndirectQueries is typically used for Values corresponding
 	// to source-level lvalues, e.g. an *ssa.Global.)
 	//
 	// The analysis populates the corresponding
 	// Result.{Indirect,}Queries map when it creates the pointer
 	// variable for v or *v.  Upon completion the client can
 	// inspect that map for the results.
 	//
 	// TODO(adonovan): this API doesn't scale well for batch tools
 	// that want to dump the entire solution.  Perhaps optionally
 	// populate a map[*ssa.DebugRef]Pointer in the Result, one
 	// entry per source expression.
 	//
 	Queries         map[ssa.Value]struct{}
 	IndirectQueries map[ssa.Value]struct{}
 	extendedQueries map[ssa.Value][]*extendedQuery

 	// If Log is non-nil, log messages are written to it.
 	// Logging is extremely verbose.
 	Log io.Writer
 }

 type track uint32

 const (
 	trackChan  track = 1 << iota // track 'chan' references
 	trackMap                     // track 'map' references
 	trackPtr                     // track regular pointers
 	trackSlice                   // track slice references

 	trackAll = ^track(0)
 )

 // AddQuery adds v to Config.Queries.
 // Precondition: CanPoint(v.Type()).
 func (c *Config) AddQuery(v ssa.Value) {
 	if !CanPoint(v.Type()) {
 		panic(fmt.Sprintf("%s is not a pointer-like value: %s", v, v.Type()))
 	}
 	if c.Queries == nil {
 		c.Queries = make(map[ssa.Value]struct{})
 	}
 	c.Queries[v] = struct{}{}
 }

 // AddQuery adds v to Config.IndirectQueries.
 // Precondition: CanPoint(v.Type().Underlying().(*types.Pointer).Elem()).
 func (c *Config) AddIndirectQuery(v ssa.Value) {
 	if c.IndirectQueries == nil {
 		c.IndirectQueries = make(map[ssa.Value]struct{})
 	}
 	if !CanPoint(mustDeref(v.Type())) {
 		panic(fmt.Sprintf("%s is not the address of a pointer-like value: %s", v, v.Type()))
 	}
 	c.IndirectQueries[v] = struct{}{}
 }

 // AddExtendedQuery adds an extended, AST-based query on v to the
 // analysis. The query, which must be a single Go expression, allows
 // destructuring the value.
 //
 // The query must operate on a variable named 'x', which represents
 // the value, and result in a pointer-like object. Only a subset of
 // Go expressions are permitted in queries, namely channel receives,
 // pointer dereferences, field selectors, array/slice/map/tuple
 // indexing and grouping with parentheses. The specific indices when
 // indexing arrays, slices and maps have no significance. Indices used
 // on tuples must be numeric and within bounds.
 //
 // All field selectors must be explicit, even ones usually elided
 // due to promotion of embedded fields.
 //
 // The query 'x' is identical to using AddQuery. The query '*x' is
 // identical to using AddIndirectQuery.
 //
 // On success, AddExtendedQuery returns a Pointer to the queried
 // value. This Pointer will be initialized during analysis. Using it
 // before analysis has finished has undefined behavior.
 //
 // Example:
 // 	// given v, which represents a function call to 'fn() (int, []*T)', and
 // 	// 'type T struct { F *int }', the following query will access the field F.
 // 	c.AddExtendedQuery(v, "x[1][0].F")
 func (c *Config) AddExtendedQuery(v ssa.Value, query string) (*Pointer, error) {
 	ops, _, err := parseExtendedQuery(v.Type(), query)
 	if err != nil {
 		return nil, fmt.Errorf("invalid query %q: %s", query, err)
 	}
 	if c.extendedQueries == nil {
 		c.extendedQueries = make(map[ssa.Value][]*extendedQuery)
 	}

 	ptr := &Pointer{}
 	c.extendedQueries[v] = append(c.extendedQueries[v], &extendedQuery{ops: ops, ptr: ptr})
 	return ptr, nil
 }

 func (c *Config) prog() *ssa.Program {
 	for _, main := range c.Mains {
 		return main.Prog
 	}
 	panic("empty scope")
 }

 type Warning struct {
 	Pos     token.Pos
 	Message string
 }

 // A Result contains the results of a pointer analysis.
 //
 // See Config for how to request the various Result components.
 //
 type Result struct {
 	CallGraph       *callgraph.Graph      // discovered call graph
 	Queries         map[ssa.Value]Pointer // pts(v) for each v in Config.Queries.
 	IndirectQueries map[ssa.Value]Pointer // pts(*v) for each v in Config.IndirectQueries.
 	Warnings        []Warning             // warnings of unsoundness
 }

 // A Pointer is an equivalence class of pointer-like values.
 //
 // A Pointer doesn't have a unique type because pointers of distinct
 // types may alias the same object.
 //
 type Pointer struct {
 	a *analysis
 	n nodeid
 }

 // A PointsToSet is a set of labels (locations or allocations).
 type PointsToSet struct {
 	a   *analysis // may be nil if pts is nil
 	pts *nodeset
 }

 func (s PointsToSet) String() string {
 	var buf bytes.Buffer
 	buf.WriteByte('[')
 	if s.pts != nil {
 		var space [50]int
 		for i, l := range s.pts.AppendTo(space[:0]) {
 			if i > 0 {
 				buf.WriteString(", ")
 			}
 			buf.WriteString(s.a.labelFor(nodeid(l)).String())
 		}
 	}
 	buf.WriteByte(']')
 	return buf.String()
 }

 // PointsTo returns the set of labels that this points-to set
 // contains.
 func (s PointsToSet) Labels() []*Label {
 	var labels []*Label
 	if s.pts != nil {
 		var space [50]int
 		for _, l := range s.pts.AppendTo(space[:0]) {
 			labels = append(labels, s.a.labelFor(nodeid(l)))
 		}
 	}
 	return labels
 }

 // If this PointsToSet came from a Pointer of interface kind
 // or a reflect.Value, DynamicTypes returns the set of dynamic
 // types that it may contain.  (For an interface, they will
 // always be concrete types.)
 //
 // The result is a mapping whose keys are the dynamic types to which
 // it may point.  For each pointer-like key type, the corresponding
 // map value is the PointsToSet for pointers of that type.
 //
 // The result is empty unless CanHaveDynamicTypes(T).
 //
 func (s PointsToSet) DynamicTypes() *typeutil.Map {
 	var tmap typeutil.Map
 	tmap.SetHasher(s.a.hasher)
 	if s.pts != nil {
 		var space [50]int
 		for _, x := range s.pts.AppendTo(space[:0]) {
 			ifaceObjId := nodeid(x)
 			if !s.a.isTaggedObject(ifaceObjId) {
 				continue // !CanHaveDynamicTypes(tDyn)
 			}
 			tDyn, v, indirect := s.a.taggedValue(ifaceObjId)
 			if indirect {
 				panic("indirect tagged object") // implement later
 			}
 			pts, ok := tmap.At(tDyn).(PointsToSet)
 			if !ok {
 				pts = PointsToSet{s.a, new(nodeset)}
 				tmap.Set(tDyn, pts)
 			}
 			pts.pts.addAll(&s.a.nodes[v].solve.pts)
 		}
 	}
 	return &tmap
 }

 // Intersects reports whether this points-to set and the
 // argument points-to set contain common members.
 func (x PointsToSet) Intersects(y PointsToSet) bool {
 	if x.pts == nil || y.pts == nil {
 		return false
 	}
 	// This takes Θ(|x|+|y|) time.
 	var z intsets.Sparse
 	z.Intersection(&x.pts.Sparse, &y.pts.Sparse)
 	return !z.IsEmpty()
 }

 func (p Pointer) String() string {
 	return fmt.Sprintf("n%d", p.n)
 }

 // PointsTo returns the points-to set of this pointer.
 func (p Pointer) PointsTo() PointsToSet {
 	if p.n == 0 {
 		return PointsToSet{}
 	}
 	return PointsToSet{p.a, &p.a.nodes[p.n].solve.pts}
 }

 // MayAlias reports whether the receiver pointer may alias
 // the argument pointer.
 func (p Pointer) MayAlias(q Pointer) bool {
 	return p.PointsTo().Intersects(q.PointsTo())
 }

 // DynamicTypes returns p.PointsTo().DynamicTypes().
 func (p Pointer) DynamicTypes() *typeutil.Map {
 	return p.PointsTo().DynamicTypes()
 }
	// 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 pointer

	import (
	"bytes"
	"fmt"
	"go/token"
	"io"

	"golang.org/x/tools/container/intsets"
	"golang.org/x/tools/go/callgraph"
	"golang.org/x/tools/go/ssa"
	"golang.org/x/tools/go/types/typeutil"
	)

	// A Config formulates a pointer analysis problem for Analyze. It is
	// only usable for a single invocation of Analyze and must not be
	// reused.
	type Config struct {
	// Mains contains the set of 'main' packages to analyze
	// Clients must provide the analysis with at least one
	// package defining a main() function.
	//
	// Non-main packages in the ssa.Program that are not
	// dependencies of any main package may still affect the
	// analysis result, because they contribute runtime types and
	// thus methods.
	// TODO(adonovan): investigate whether this is desirable.
	Mains []*ssa.Package

	// Reflection determines whether to handle reflection
	// operators soundly, which is currently rather slow since it
	// causes constraint to be generated during solving
	// proportional to the number of constraint variables, which
	// has not yet been reduced by presolver optimisation.
	Reflection bool

	// BuildCallGraph determines whether to construct a callgraph.
	// If enabled, the graph will be available in Result.CallGraph.
	BuildCallGraph bool

	// The client populates Queries[v] or IndirectQueries[v]
	// for each ssa.Value v of interest, to request that the
	// points-to sets pts(v) or pts(*v) be computed. If the
	// client needs both points-to sets, v may appear in both
	// maps.
	//
	// (IndirectQueries is typically used for Values corresponding
	// to source-level lvalues, e.g. an *ssa.Global.)
	//
	// The analysis populates the corresponding
	// Result.{Indirect,}Queries map when it creates the pointer
	// variable for v or *v. Upon completion the client can
	// inspect that map for the results.
	//
	// TODO(adonovan): this API doesn't scale well for batch tools
	// that want to dump the entire solution. Perhaps optionally
	// populate a map[*ssa.DebugRef]Pointer in the Result, one
	// entry per source expression.
	//
	Queries map[ssa.Value]struct{}
	IndirectQueries map[ssa.Value]struct{}
	extendedQueries map[ssa.Value][]*extendedQuery

	// If Log is non-nil, log messages are written to it.
	// Logging is extremely verbose.
	Log io.Writer
	}

	type track uint32

	const (
	trackChan track = 1 << iota // track 'chan' references
	trackMap // track 'map' references
	trackPtr // track regular pointers
	trackSlice // track slice references

	trackAll = ^track(0)
	)

	// AddQuery adds v to Config.Queries.
	// Precondition: CanPoint(v.Type()).
	func (c *Config) AddQuery(v ssa.Value) {
	if !CanPoint(v.Type()) {
	panic(fmt.Sprintf("%s is not a pointer-like value: %s", v, v.Type()))
	}
	if c.Queries == nil {
	c.Queries = make(map[ssa.Value]struct{})
	}
	c.Queries[v] = struct{}{}
	}

	// AddQuery adds v to Config.IndirectQueries.
	// Precondition: CanPoint(v.Type().Underlying().(*types.Pointer).Elem()).
	func (c *Config) AddIndirectQuery(v ssa.Value) {
	if c.IndirectQueries == nil {
	c.IndirectQueries = make(map[ssa.Value]struct{})
	}
	if !CanPoint(mustDeref(v.Type())) {
	panic(fmt.Sprintf("%s is not the address of a pointer-like value: %s", v, v.Type()))
	}
	c.IndirectQueries[v] = struct{}{}
	}

	// AddExtendedQuery adds an extended, AST-based query on v to the
	// analysis. The query, which must be a single Go expression, allows
	// destructuring the value.
	//
	// The query must operate on a variable named 'x', which represents
	// the value, and result in a pointer-like object. Only a subset of
	// Go expressions are permitted in queries, namely channel receives,
	// pointer dereferences, field selectors, array/slice/map/tuple
	// indexing and grouping with parentheses. The specific indices when
	// indexing arrays, slices and maps have no significance. Indices used
	// on tuples must be numeric and within bounds.
	//
	// All field selectors must be explicit, even ones usually elided
	// due to promotion of embedded fields.
	//
	// The query 'x' is identical to using AddQuery. The query '*x' is
	// identical to using AddIndirectQuery.
	//
	// On success, AddExtendedQuery returns a Pointer to the queried
	// value. This Pointer will be initialized during analysis. Using it
	// before analysis has finished has undefined behavior.
	//
	// Example:
	// // given v, which represents a function call to 'fn() (int, []*T)', and
	// // 'type T struct { F *int }', the following query will access the field F.
	// c.AddExtendedQuery(v, "x[1][0].F")
	func (c Config) AddExtendedQuery(v ssa.Value, query string) (Pointer, error) {
	ops, _, err := parseExtendedQuery(v.Type(), query)
	if err != nil {
	return nil, fmt.Errorf("invalid query %q: %s", query, err)
	}
	if c.extendedQueries == nil {
	c.extendedQueries = make(map[ssa.Value][]*extendedQuery)
	}

	ptr := &Pointer{}
	c.extendedQueries[v] = append(c.extendedQueries[v], &extendedQuery{ops: ops, ptr: ptr})
	return ptr, nil
	}

	func (c Config) prog() ssa.Program {
	for _, main := range c.Mains {
	return main.Prog
	}
	panic("empty scope")
	}

	type Warning struct {
	Pos token.Pos
	Message string
	}

	// A Result contains the results of a pointer analysis.
	//
	// See Config for how to request the various Result components.
	//
	type Result struct {
	CallGraph *callgraph.Graph // discovered call graph
	Queries map[ssa.Value]Pointer // pts(v) for each v in Config.Queries.
	IndirectQueries map[ssa.Value]Pointer // pts(*v) for each v in Config.IndirectQueries.
	Warnings []Warning // warnings of unsoundness
	}

	// A Pointer is an equivalence class of pointer-like values.
	//
	// A Pointer doesn't have a unique type because pointers of distinct
	// types may alias the same object.
	//
	type Pointer struct {
	a *analysis
	n nodeid
	}

	// A PointsToSet is a set of labels (locations or allocations).
	type PointsToSet struct {
	a *analysis // may be nil if pts is nil
	pts *nodeset
	}

	func (s PointsToSet) String() string {
	var buf bytes.Buffer
	buf.WriteByte('[')
	if s.pts != nil {
	var space [50]int
	for i, l := range s.pts.AppendTo(space[:0]) {
	if i > 0 {
	buf.WriteString(", ")
	}
	buf.WriteString(s.a.labelFor(nodeid(l)).String())
	}
	}
	buf.WriteByte(']')
	return buf.String()
	}

	// PointsTo returns the set of labels that this points-to set
	// contains.
	func (s PointsToSet) Labels() []*Label {
	var labels []*Label
	if s.pts != nil {
	var space [50]int
	for _, l := range s.pts.AppendTo(space[:0]) {
	labels = append(labels, s.a.labelFor(nodeid(l)))
	}
	}
	return labels
	}

	// If this PointsToSet came from a Pointer of interface kind
	// or a reflect.Value, DynamicTypes returns the set of dynamic
	// types that it may contain. (For an interface, they will
	// always be concrete types.)
	//
	// The result is a mapping whose keys are the dynamic types to which
	// it may point. For each pointer-like key type, the corresponding
	// map value is the PointsToSet for pointers of that type.
	//
	// The result is empty unless CanHaveDynamicTypes(T).
	//
	func (s PointsToSet) DynamicTypes() *typeutil.Map {
	var tmap typeutil.Map
	tmap.SetHasher(s.a.hasher)
	if s.pts != nil {
	var space [50]int
	for _, x := range s.pts.AppendTo(space[:0]) {
	ifaceObjId := nodeid(x)
	if !s.a.isTaggedObject(ifaceObjId) {
	continue // !CanHaveDynamicTypes(tDyn)
	}
	tDyn, v, indirect := s.a.taggedValue(ifaceObjId)
	if indirect {
	panic("indirect tagged object") // implement later
	}
	pts, ok := tmap.At(tDyn).(PointsToSet)
	if !ok {
	pts = PointsToSet{s.a, new(nodeset)}
	tmap.Set(tDyn, pts)
	}
	pts.pts.addAll(&s.a.nodes[v].solve.pts)
	}
	}
	return &tmap
	}

	// Intersects reports whether this points-to set and the
	// argument points-to set contain common members.
	func (x PointsToSet) Intersects(y PointsToSet) bool {
	if x.pts == nil \|\| y.pts == nil {
	return false
	}
	// This takes Θ(\|x\|+\|y\|) time.
	var z intsets.Sparse
	z.Intersection(&x.pts.Sparse, &y.pts.Sparse)
	return !z.IsEmpty()
	}

	func (p Pointer) String() string {
	return fmt.Sprintf("n%d", p.n)
	}

	// PointsTo returns the points-to set of this pointer.
	func (p Pointer) PointsTo() PointsToSet {
	if p.n == 0 {
	return PointsToSet{}
	}
	return PointsToSet{p.a, &p.a.nodes[p.n].solve.pts}
	}

	// MayAlias reports whether the receiver pointer may alias
	// the argument pointer.
	func (p Pointer) MayAlias(q Pointer) bool {
	return p.PointsTo().Intersects(q.PointsTo())
	}

	// DynamicTypes returns p.PointsTo().DynamicTypes().
	func (p Pointer) DynamicTypes() *typeutil.Map {
	return p.PointsTo().DynamicTypes()
	}