286 lines
8.6 KiB
Go
286 lines
8.6 KiB
Go
// 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 pointer
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import (
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"bytes"
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"fmt"
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"go/token"
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"io"
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"golang.org/x/tools/container/intsets"
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"golang.org/x/tools/go/callgraph"
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"golang.org/x/tools/go/ssa"
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"golang.org/x/tools/go/types/typeutil"
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)
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// A Config formulates a pointer analysis problem for Analyze. It is
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// only usable for a single invocation of Analyze and must not be
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// reused.
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type Config struct {
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// Mains contains the set of 'main' packages to analyze
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// Clients must provide the analysis with at least one
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// package defining a main() function.
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//
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// Non-main packages in the ssa.Program that are not
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// dependencies of any main package may still affect the
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// analysis result, because they contribute runtime types and
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// thus methods.
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// TODO(adonovan): investigate whether this is desirable.
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Mains []*ssa.Package
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// Reflection determines whether to handle reflection
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// operators soundly, which is currently rather slow since it
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// causes constraint to be generated during solving
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// proportional to the number of constraint variables, which
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// has not yet been reduced by presolver optimisation.
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Reflection bool
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// BuildCallGraph determines whether to construct a callgraph.
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// If enabled, the graph will be available in Result.CallGraph.
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BuildCallGraph bool
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// The client populates Queries[v] or IndirectQueries[v]
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// for each ssa.Value v of interest, to request that the
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// points-to sets pts(v) or pts(*v) be computed. If the
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// client needs both points-to sets, v may appear in both
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// maps.
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//
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// (IndirectQueries is typically used for Values corresponding
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// to source-level lvalues, e.g. an *ssa.Global.)
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//
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// The analysis populates the corresponding
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// Result.{Indirect,}Queries map when it creates the pointer
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// variable for v or *v. Upon completion the client can
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// inspect that map for the results.
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//
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// TODO(adonovan): this API doesn't scale well for batch tools
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// that want to dump the entire solution. Perhaps optionally
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// populate a map[*ssa.DebugRef]Pointer in the Result, one
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// entry per source expression.
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//
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Queries map[ssa.Value]struct{}
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IndirectQueries map[ssa.Value]struct{}
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extendedQueries map[ssa.Value][]*extendedQuery
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// If Log is non-nil, log messages are written to it.
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// Logging is extremely verbose.
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Log io.Writer
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}
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type track uint32
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const (
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trackChan track = 1 << iota // track 'chan' references
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trackMap // track 'map' references
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trackPtr // track regular pointers
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trackSlice // track slice references
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trackAll = ^track(0)
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)
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// AddQuery adds v to Config.Queries.
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// Precondition: CanPoint(v.Type()).
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func (c *Config) AddQuery(v ssa.Value) {
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if !CanPoint(v.Type()) {
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panic(fmt.Sprintf("%s is not a pointer-like value: %s", v, v.Type()))
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}
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if c.Queries == nil {
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c.Queries = make(map[ssa.Value]struct{})
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}
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c.Queries[v] = struct{}{}
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}
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// AddQuery adds v to Config.IndirectQueries.
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// Precondition: CanPoint(v.Type().Underlying().(*types.Pointer).Elem()).
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func (c *Config) AddIndirectQuery(v ssa.Value) {
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if c.IndirectQueries == nil {
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c.IndirectQueries = make(map[ssa.Value]struct{})
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}
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if !CanPoint(mustDeref(v.Type())) {
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panic(fmt.Sprintf("%s is not the address of a pointer-like value: %s", v, v.Type()))
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}
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c.IndirectQueries[v] = struct{}{}
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}
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// AddExtendedQuery adds an extended, AST-based query on v to the
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// analysis. The query, which must be a single Go expression, allows
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// destructuring the value.
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//
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// The query must operate on a variable named 'x', which represents
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// the value, and result in a pointer-like object. Only a subset of
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// Go expressions are permitted in queries, namely channel receives,
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// pointer dereferences, field selectors, array/slice/map/tuple
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// indexing and grouping with parentheses. The specific indices when
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// indexing arrays, slices and maps have no significance. Indices used
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// on tuples must be numeric and within bounds.
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//
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// All field selectors must be explicit, even ones usually elided
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// due to promotion of embedded fields.
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//
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// The query 'x' is identical to using AddQuery. The query '*x' is
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// identical to using AddIndirectQuery.
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//
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// On success, AddExtendedQuery returns a Pointer to the queried
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// value. This Pointer will be initialized during analysis. Using it
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// before analysis has finished has undefined behavior.
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//
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// Example:
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// // given v, which represents a function call to 'fn() (int, []*T)', and
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// // 'type T struct { F *int }', the following query will access the field F.
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// c.AddExtendedQuery(v, "x[1][0].F")
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func (c *Config) AddExtendedQuery(v ssa.Value, query string) (*Pointer, error) {
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ops, _, err := parseExtendedQuery(v.Type().Underlying(), query)
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if err != nil {
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return nil, fmt.Errorf("invalid query %q: %s", query, err)
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}
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if c.extendedQueries == nil {
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c.extendedQueries = make(map[ssa.Value][]*extendedQuery)
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}
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ptr := &Pointer{}
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c.extendedQueries[v] = append(c.extendedQueries[v], &extendedQuery{ops: ops, ptr: ptr})
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return ptr, nil
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}
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func (c *Config) prog() *ssa.Program {
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for _, main := range c.Mains {
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return main.Prog
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}
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panic("empty scope")
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}
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type Warning struct {
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Pos token.Pos
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Message string
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}
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// A Result contains the results of a pointer analysis.
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//
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// See Config for how to request the various Result components.
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//
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type Result struct {
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CallGraph *callgraph.Graph // discovered call graph
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Queries map[ssa.Value]Pointer // pts(v) for each v in Config.Queries.
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IndirectQueries map[ssa.Value]Pointer // pts(*v) for each v in Config.IndirectQueries.
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Warnings []Warning // warnings of unsoundness
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}
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// A Pointer is an equivalence class of pointer-like values.
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//
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// A Pointer doesn't have a unique type because pointers of distinct
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// types may alias the same object.
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//
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type Pointer struct {
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a *analysis
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n nodeid
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}
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// A PointsToSet is a set of labels (locations or allocations).
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type PointsToSet struct {
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a *analysis // may be nil if pts is nil
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pts *nodeset
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}
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func (s PointsToSet) String() string {
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var buf bytes.Buffer
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buf.WriteByte('[')
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if s.pts != nil {
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var space [50]int
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for i, l := range s.pts.AppendTo(space[:0]) {
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if i > 0 {
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buf.WriteString(", ")
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}
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buf.WriteString(s.a.labelFor(nodeid(l)).String())
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}
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}
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buf.WriteByte(']')
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return buf.String()
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}
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// PointsTo returns the set of labels that this points-to set
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// contains.
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func (s PointsToSet) Labels() []*Label {
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var labels []*Label
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if s.pts != nil {
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var space [50]int
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for _, l := range s.pts.AppendTo(space[:0]) {
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labels = append(labels, s.a.labelFor(nodeid(l)))
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}
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}
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return labels
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}
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// If this PointsToSet came from a Pointer of interface kind
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// or a reflect.Value, DynamicTypes returns the set of dynamic
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// types that it may contain. (For an interface, they will
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// always be concrete types.)
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//
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// The result is a mapping whose keys are the dynamic types to which
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// it may point. For each pointer-like key type, the corresponding
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// map value is the PointsToSet for pointers of that type.
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//
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// The result is empty unless CanHaveDynamicTypes(T).
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//
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func (s PointsToSet) DynamicTypes() *typeutil.Map {
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var tmap typeutil.Map
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tmap.SetHasher(s.a.hasher)
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if s.pts != nil {
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var space [50]int
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for _, x := range s.pts.AppendTo(space[:0]) {
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ifaceObjId := nodeid(x)
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if !s.a.isTaggedObject(ifaceObjId) {
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continue // !CanHaveDynamicTypes(tDyn)
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}
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tDyn, v, indirect := s.a.taggedValue(ifaceObjId)
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if indirect {
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panic("indirect tagged object") // implement later
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}
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pts, ok := tmap.At(tDyn).(PointsToSet)
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if !ok {
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pts = PointsToSet{s.a, new(nodeset)}
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tmap.Set(tDyn, pts)
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}
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pts.pts.addAll(&s.a.nodes[v].solve.pts)
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}
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}
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return &tmap
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}
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// Intersects reports whether this points-to set and the
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// argument points-to set contain common members.
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func (x PointsToSet) Intersects(y PointsToSet) bool {
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if x.pts == nil || y.pts == nil {
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return false
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}
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// This takes Θ(|x|+|y|) time.
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var z intsets.Sparse
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z.Intersection(&x.pts.Sparse, &y.pts.Sparse)
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return !z.IsEmpty()
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}
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func (p Pointer) String() string {
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return fmt.Sprintf("n%d", p.n)
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}
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// PointsTo returns the points-to set of this pointer.
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func (p Pointer) PointsTo() PointsToSet {
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if p.n == 0 {
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return PointsToSet{}
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}
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return PointsToSet{p.a, &p.a.nodes[p.n].solve.pts}
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}
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// MayAlias reports whether the receiver pointer may alias
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// the argument pointer.
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func (p Pointer) MayAlias(q Pointer) bool {
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return p.PointsTo().Intersects(q.PointsTo())
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}
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// DynamicTypes returns p.PointsTo().DynamicTypes().
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func (p Pointer) DynamicTypes() *typeutil.Map {
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return p.PointsTo().DynamicTypes()
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}
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