| 1 | // Copyright 2013 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package main |
| 6 | |
| 7 | import ( |
| 8 | "fmt" |
| 9 | "go/ast" |
| 10 | "go/token" |
| 11 | "go/types" |
| 12 | "sort" |
| 13 | |
| 14 | "golang.org/x/tools/cmd/guru/serial" |
| 15 | "golang.org/x/tools/go/ast/astutil" |
| 16 | "golang.org/x/tools/go/loader" |
| 17 | "golang.org/x/tools/go/pointer" |
| 18 | "golang.org/x/tools/go/ssa" |
| 19 | "golang.org/x/tools/go/ssa/ssautil" |
| 20 | ) |
| 21 | |
| 22 | // pointsto runs the pointer analysis on the selected expression, |
| 23 | // and reports its points-to set (for a pointer-like expression) |
| 24 | // or its dynamic types (for an interface, reflect.Value, or |
| 25 | // reflect.Type expression) and their points-to sets. |
| 26 | // |
| 27 | // All printed sets are sorted to ensure determinism. |
| 28 | func pointsto(q *Query) error { |
| 29 | lconf := loader.Config{Build: q.Build} |
| 30 | |
| 31 | if err := setPTAScope(&lconf, q.Scope); err != nil { |
| 32 | return err |
| 33 | } |
| 34 | |
| 35 | // Load/parse/type-check the program. |
| 36 | lprog, err := loadWithSoftErrors(&lconf) |
| 37 | if err != nil { |
| 38 | return err |
| 39 | } |
| 40 | |
| 41 | qpos, err := parseQueryPos(lprog, q.Pos, true) // needs exact pos |
| 42 | if err != nil { |
| 43 | return err |
| 44 | } |
| 45 | |
| 46 | prog := ssautil.CreateProgram(lprog, ssa.GlobalDebug) |
| 47 | |
| 48 | ptaConfig, err := setupPTA(prog, lprog, q.PTALog, q.Reflection) |
| 49 | if err != nil { |
| 50 | return err |
| 51 | } |
| 52 | |
| 53 | path, action := findInterestingNode(qpos.info, qpos.path) |
| 54 | if action != actionExpr { |
| 55 | return fmt.Errorf("pointer analysis wants an expression; got %s", |
| 56 | astutil.NodeDescription(qpos.path[0])) |
| 57 | } |
| 58 | |
| 59 | var expr ast.Expr |
| 60 | var obj types.Object |
| 61 | switch n := path[0].(type) { |
| 62 | case *ast.ValueSpec: |
| 63 | // ambiguous ValueSpec containing multiple names |
| 64 | return fmt.Errorf("multiple value specification") |
| 65 | case *ast.Ident: |
| 66 | obj = qpos.info.ObjectOf(n) |
| 67 | expr = n |
| 68 | case ast.Expr: |
| 69 | expr = n |
| 70 | default: |
| 71 | // TODO(adonovan): is this reachable? |
| 72 | return fmt.Errorf("unexpected AST for expr: %T", n) |
| 73 | } |
| 74 | |
| 75 | // Reject non-pointerlike types (includes all constants---except nil). |
| 76 | // TODO(adonovan): reject nil too. |
| 77 | typ := qpos.info.TypeOf(expr) |
| 78 | if !pointer.CanPoint(typ) { |
| 79 | return fmt.Errorf("pointer analysis wants an expression of reference type; got %s", typ) |
| 80 | } |
| 81 | |
| 82 | // Determine the ssa.Value for the expression. |
| 83 | var value ssa.Value |
| 84 | var isAddr bool |
| 85 | if obj != nil { |
| 86 | // def/ref of func/var object |
| 87 | value, isAddr, err = ssaValueForIdent(prog, qpos.info, obj, path) |
| 88 | } else { |
| 89 | value, isAddr, err = ssaValueForExpr(prog, qpos.info, path) |
| 90 | } |
| 91 | if err != nil { |
| 92 | return err // e.g. trivially dead code |
| 93 | } |
| 94 | |
| 95 | // Defer SSA construction till after errors are reported. |
| 96 | prog.Build() |
| 97 | |
| 98 | // Run the pointer analysis. |
| 99 | ptrs, err := runPTA(ptaConfig, value, isAddr) |
| 100 | if err != nil { |
| 101 | return err // e.g. analytically unreachable |
| 102 | } |
| 103 | |
| 104 | q.Output(lprog.Fset, &pointstoResult{ |
| 105 | qpos: qpos, |
| 106 | typ: typ, |
| 107 | ptrs: ptrs, |
| 108 | }) |
| 109 | return nil |
| 110 | } |
| 111 | |
| 112 | // ssaValueForIdent returns the ssa.Value for the ast.Ident whose path |
| 113 | // to the root of the AST is path. isAddr reports whether the |
| 114 | // ssa.Value is the address denoted by the ast.Ident, not its value. |
| 115 | func ssaValueForIdent(prog *ssa.Program, qinfo *loader.PackageInfo, obj types.Object, path []ast.Node) (value ssa.Value, isAddr bool, err error) { |
| 116 | switch obj := obj.(type) { |
| 117 | case *types.Var: |
| 118 | pkg := prog.Package(qinfo.Pkg) |
| 119 | pkg.Build() |
| 120 | if v, addr := prog.VarValue(obj, pkg, path); v != nil { |
| 121 | return v, addr, nil |
| 122 | } |
| 123 | return nil, false, fmt.Errorf("can't locate SSA Value for var %s", obj.Name()) |
| 124 | |
| 125 | case *types.Func: |
| 126 | fn := prog.FuncValue(obj) |
| 127 | if fn == nil { |
| 128 | return nil, false, fmt.Errorf("%s is an interface method", obj) |
| 129 | } |
| 130 | // TODO(adonovan): there's no point running PTA on a *Func ident. |
| 131 | // Eliminate this feature. |
| 132 | return fn, false, nil |
| 133 | } |
| 134 | panic(obj) |
| 135 | } |
| 136 | |
| 137 | // ssaValueForExpr returns the ssa.Value of the non-ast.Ident |
| 138 | // expression whose path to the root of the AST is path. |
| 139 | func ssaValueForExpr(prog *ssa.Program, qinfo *loader.PackageInfo, path []ast.Node) (value ssa.Value, isAddr bool, err error) { |
| 140 | pkg := prog.Package(qinfo.Pkg) |
| 141 | pkg.SetDebugMode(true) |
| 142 | pkg.Build() |
| 143 | |
| 144 | fn := ssa.EnclosingFunction(pkg, path) |
| 145 | if fn == nil { |
| 146 | return nil, false, fmt.Errorf("no SSA function built for this location (dead code?)") |
| 147 | } |
| 148 | |
| 149 | if v, addr := fn.ValueForExpr(path[0].(ast.Expr)); v != nil { |
| 150 | return v, addr, nil |
| 151 | } |
| 152 | |
| 153 | return nil, false, fmt.Errorf("can't locate SSA Value for expression in %s", fn) |
| 154 | } |
| 155 | |
| 156 | // runPTA runs the pointer analysis of the selected SSA value or address. |
| 157 | func runPTA(conf *pointer.Config, v ssa.Value, isAddr bool) (ptrs []pointerResult, err error) { |
| 158 | T := v.Type() |
| 159 | if isAddr { |
| 160 | conf.AddIndirectQuery(v) |
| 161 | T = deref(T) |
| 162 | } else { |
| 163 | conf.AddQuery(v) |
| 164 | } |
| 165 | ptares := ptrAnalysis(conf) |
| 166 | |
| 167 | var ptr pointer.Pointer |
| 168 | if isAddr { |
| 169 | ptr = ptares.IndirectQueries[v] |
| 170 | } else { |
| 171 | ptr = ptares.Queries[v] |
| 172 | } |
| 173 | if ptr == (pointer.Pointer{}) { |
| 174 | return nil, fmt.Errorf("pointer analysis did not find expression (dead code?)") |
| 175 | } |
| 176 | pts := ptr.PointsTo() |
| 177 | |
| 178 | if pointer.CanHaveDynamicTypes(T) { |
| 179 | // Show concrete types for interface/reflect.Value expression. |
| 180 | if concs := pts.DynamicTypes(); concs.Len() > 0 { |
| 181 | concs.Iterate(func(conc types.Type, pta interface{}) { |
| 182 | labels := pta.(pointer.PointsToSet).Labels() |
| 183 | sort.Sort(byPosAndString(labels)) // to ensure determinism |
| 184 | ptrs = append(ptrs, pointerResult{conc, labels}) |
| 185 | }) |
| 186 | } |
| 187 | } else { |
| 188 | // Show labels for other expressions. |
| 189 | labels := pts.Labels() |
| 190 | sort.Sort(byPosAndString(labels)) // to ensure determinism |
| 191 | ptrs = append(ptrs, pointerResult{T, labels}) |
| 192 | } |
| 193 | sort.Sort(byTypeString(ptrs)) // to ensure determinism |
| 194 | return ptrs, nil |
| 195 | } |
| 196 | |
| 197 | type pointerResult struct { |
| 198 | typ types.Type // type of the pointer (always concrete) |
| 199 | labels []*pointer.Label // set of labels |
| 200 | } |
| 201 | |
| 202 | type pointstoResult struct { |
| 203 | qpos *queryPos |
| 204 | typ types.Type // type of expression |
| 205 | ptrs []pointerResult // pointer info (typ is concrete => len==1) |
| 206 | } |
| 207 | |
| 208 | func (r *pointstoResult) PrintPlain(printf printfFunc) { |
| 209 | if pointer.CanHaveDynamicTypes(r.typ) { |
| 210 | // Show concrete types for interface, reflect.Type or |
| 211 | // reflect.Value expression. |
| 212 | |
| 213 | if len(r.ptrs) > 0 { |
| 214 | printf(r.qpos, "this %s may contain these dynamic types:", r.qpos.typeString(r.typ)) |
| 215 | for _, ptr := range r.ptrs { |
| 216 | var obj types.Object |
| 217 | if nt, ok := deref(ptr.typ).(*types.Named); ok { |
| 218 | obj = nt.Obj() |
| 219 | } |
| 220 | if len(ptr.labels) > 0 { |
| 221 | printf(obj, "\t%s, may point to:", r.qpos.typeString(ptr.typ)) |
| 222 | printLabels(printf, ptr.labels, "\t\t") |
| 223 | } else { |
| 224 | printf(obj, "\t%s", r.qpos.typeString(ptr.typ)) |
| 225 | } |
| 226 | } |
| 227 | } else { |
| 228 | printf(r.qpos, "this %s cannot contain any dynamic types.", r.typ) |
| 229 | } |
| 230 | } else { |
| 231 | // Show labels for other expressions. |
| 232 | if ptr := r.ptrs[0]; len(ptr.labels) > 0 { |
| 233 | printf(r.qpos, "this %s may point to these objects:", |
| 234 | r.qpos.typeString(r.typ)) |
| 235 | printLabels(printf, ptr.labels, "\t") |
| 236 | } else { |
| 237 | printf(r.qpos, "this %s may not point to anything.", |
| 238 | r.qpos.typeString(r.typ)) |
| 239 | } |
| 240 | } |
| 241 | } |
| 242 | |
| 243 | func (r *pointstoResult) JSON(fset *token.FileSet) []byte { |
| 244 | var pts []serial.PointsTo |
| 245 | for _, ptr := range r.ptrs { |
| 246 | var namePos string |
| 247 | if nt, ok := deref(ptr.typ).(*types.Named); ok { |
| 248 | namePos = fset.Position(nt.Obj().Pos()).String() |
| 249 | } |
| 250 | var labels []serial.PointsToLabel |
| 251 | for _, l := range ptr.labels { |
| 252 | labels = append(labels, serial.PointsToLabel{ |
| 253 | Pos: fset.Position(l.Pos()).String(), |
| 254 | Desc: l.String(), |
| 255 | }) |
| 256 | } |
| 257 | pts = append(pts, serial.PointsTo{ |
| 258 | Type: r.qpos.typeString(ptr.typ), |
| 259 | NamePos: namePos, |
| 260 | Labels: labels, |
| 261 | }) |
| 262 | } |
| 263 | return toJSON(pts) |
| 264 | } |
| 265 | |
| 266 | type byTypeString []pointerResult |
| 267 | |
| 268 | func (a byTypeString) Len() int { return len(a) } |
| 269 | func (a byTypeString) Less(i, j int) bool { return a[i].typ.String() < a[j].typ.String() } |
| 270 | func (a byTypeString) Swap(i, j int) { a[i], a[j] = a[j], a[i] } |
| 271 | |
| 272 | type byPosAndString []*pointer.Label |
| 273 | |
| 274 | func (a byPosAndString) Len() int { return len(a) } |
| 275 | func (a byPosAndString) Less(i, j int) bool { |
| 276 | cmp := a[i].Pos() - a[j].Pos() |
| 277 | return cmp < 0 || (cmp == 0 && a[i].String() < a[j].String()) |
| 278 | } |
| 279 | func (a byPosAndString) Swap(i, j int) { a[i], a[j] = a[j], a[i] } |
| 280 | |
| 281 | func printLabels(printf printfFunc, labels []*pointer.Label, prefix string) { |
| 282 | // TODO(adonovan): due to context-sensitivity, many of these |
| 283 | // labels may differ only by context, which isn't apparent. |
| 284 | for _, label := range labels { |
| 285 | printf(label, "%s%s", prefix, label) |
| 286 | } |
| 287 | } |
| 288 |
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