| 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/loader" |
| 16 | "golang.org/x/tools/go/pointer" |
| 17 | "golang.org/x/tools/go/ssa" |
| 18 | "golang.org/x/tools/go/ssa/ssautil" |
| 19 | ) |
| 20 | |
| 21 | // The callees function reports the possible callees of the function call site |
| 22 | // identified by the specified source location. |
| 23 | func callees(q *Query) error { |
| 24 | lconf := loader.Config{Build: q.Build} |
| 25 | |
| 26 | if err := setPTAScope(&lconf, q.Scope); err != nil { |
| 27 | return err |
| 28 | } |
| 29 | |
| 30 | // Load/parse/type-check the program. |
| 31 | lprog, err := loadWithSoftErrors(&lconf) |
| 32 | if err != nil { |
| 33 | return err |
| 34 | } |
| 35 | |
| 36 | qpos, err := parseQueryPos(lprog, q.Pos, true) // needs exact pos |
| 37 | if err != nil { |
| 38 | return err |
| 39 | } |
| 40 | |
| 41 | // Determine the enclosing call for the specified position. |
| 42 | var e *ast.CallExpr |
| 43 | for _, n := range qpos.path { |
| 44 | if e, _ = n.(*ast.CallExpr); e != nil { |
| 45 | break |
| 46 | } |
| 47 | } |
| 48 | if e == nil { |
| 49 | return fmt.Errorf("there is no function call here") |
| 50 | } |
| 51 | // TODO(adonovan): issue an error if the call is "too far |
| 52 | // away" from the current selection, as this most likely is |
| 53 | // not what the user intended. |
| 54 | |
| 55 | // Reject type conversions. |
| 56 | if qpos.info.Types[e.Fun].IsType() { |
| 57 | return fmt.Errorf("this is a type conversion, not a function call") |
| 58 | } |
| 59 | |
| 60 | // Deal with obviously static calls before constructing SSA form. |
| 61 | // Some static calls may yet require SSA construction, |
| 62 | // e.g. f := func(){}; f(). |
| 63 | switch funexpr := unparen(e.Fun).(type) { |
| 64 | case *ast.Ident: |
| 65 | switch obj := qpos.info.Uses[funexpr].(type) { |
| 66 | case *types.Builtin: |
| 67 | // Reject calls to built-ins. |
| 68 | return fmt.Errorf("this is a call to the built-in '%s' operator", obj.Name()) |
| 69 | case *types.Func: |
| 70 | // This is a static function call |
| 71 | q.Output(lprog.Fset, &calleesTypesResult{ |
| 72 | site: e, |
| 73 | callee: obj, |
| 74 | }) |
| 75 | return nil |
| 76 | } |
| 77 | case *ast.SelectorExpr: |
| 78 | sel := qpos.info.Selections[funexpr] |
| 79 | if sel == nil { |
| 80 | // qualified identifier. |
| 81 | // May refer to top level function variable |
| 82 | // or to top level function. |
| 83 | callee := qpos.info.Uses[funexpr.Sel] |
| 84 | if obj, ok := callee.(*types.Func); ok { |
| 85 | q.Output(lprog.Fset, &calleesTypesResult{ |
| 86 | site: e, |
| 87 | callee: obj, |
| 88 | }) |
| 89 | return nil |
| 90 | } |
| 91 | } else if sel.Kind() == types.MethodVal { |
| 92 | // Inspect the receiver type of the selected method. |
| 93 | // If it is concrete, the call is statically dispatched. |
| 94 | // (Due to implicit field selections, it is not enough to look |
| 95 | // at sel.Recv(), the type of the actual receiver expression.) |
| 96 | method := sel.Obj().(*types.Func) |
| 97 | recvtype := method.Type().(*types.Signature).Recv().Type() |
| 98 | if !types.IsInterface(recvtype) { |
| 99 | // static method call |
| 100 | q.Output(lprog.Fset, &calleesTypesResult{ |
| 101 | site: e, |
| 102 | callee: method, |
| 103 | }) |
| 104 | return nil |
| 105 | } |
| 106 | } |
| 107 | } |
| 108 | |
| 109 | prog := ssautil.CreateProgram(lprog, ssa.GlobalDebug) |
| 110 | |
| 111 | ptaConfig, err := setupPTA(prog, lprog, q.PTALog, q.Reflection) |
| 112 | if err != nil { |
| 113 | return err |
| 114 | } |
| 115 | |
| 116 | pkg := prog.Package(qpos.info.Pkg) |
| 117 | if pkg == nil { |
| 118 | return fmt.Errorf("no SSA package") |
| 119 | } |
| 120 | |
| 121 | // Defer SSA construction till after errors are reported. |
| 122 | prog.Build() |
| 123 | |
| 124 | // Ascertain calling function and call site. |
| 125 | callerFn := ssa.EnclosingFunction(pkg, qpos.path) |
| 126 | if callerFn == nil { |
| 127 | return fmt.Errorf("no SSA function built for this location (dead code?)") |
| 128 | } |
| 129 | |
| 130 | // Find the call site. |
| 131 | site, err := findCallSite(callerFn, e) |
| 132 | if err != nil { |
| 133 | return err |
| 134 | } |
| 135 | |
| 136 | funcs, err := findCallees(ptaConfig, site) |
| 137 | if err != nil { |
| 138 | return err |
| 139 | } |
| 140 | |
| 141 | q.Output(lprog.Fset, &calleesSSAResult{ |
| 142 | site: site, |
| 143 | funcs: funcs, |
| 144 | }) |
| 145 | return nil |
| 146 | } |
| 147 | |
| 148 | func findCallSite(fn *ssa.Function, call *ast.CallExpr) (ssa.CallInstruction, error) { |
| 149 | instr, _ := fn.ValueForExpr(call) |
| 150 | callInstr, _ := instr.(ssa.CallInstruction) |
| 151 | if instr == nil { |
| 152 | return nil, fmt.Errorf("this call site is unreachable in this analysis") |
| 153 | } |
| 154 | return callInstr, nil |
| 155 | } |
| 156 | |
| 157 | func findCallees(conf *pointer.Config, site ssa.CallInstruction) ([]*ssa.Function, error) { |
| 158 | // Avoid running the pointer analysis for static calls. |
| 159 | if callee := site.Common().StaticCallee(); callee != nil { |
| 160 | switch callee.String() { |
| 161 | case "runtime.SetFinalizer", "(reflect.Value).Call": |
| 162 | // The PTA treats calls to these intrinsics as dynamic. |
| 163 | // TODO(adonovan): avoid reliance on PTA internals. |
| 164 | |
| 165 | default: |
| 166 | return []*ssa.Function{callee}, nil // singleton |
| 167 | } |
| 168 | } |
| 169 | |
| 170 | // Dynamic call: use pointer analysis. |
| 171 | conf.BuildCallGraph = true |
| 172 | cg := ptrAnalysis(conf).CallGraph |
| 173 | cg.DeleteSyntheticNodes() |
| 174 | |
| 175 | // Find all call edges from the site. |
| 176 | n := cg.Nodes[site.Parent()] |
| 177 | if n == nil { |
| 178 | return nil, fmt.Errorf("this call site is unreachable in this analysis") |
| 179 | } |
| 180 | calleesMap := make(map[*ssa.Function]bool) |
| 181 | for _, edge := range n.Out { |
| 182 | if edge.Site == site { |
| 183 | calleesMap[edge.Callee.Func] = true |
| 184 | } |
| 185 | } |
| 186 | |
| 187 | // De-duplicate and sort. |
| 188 | funcs := make([]*ssa.Function, 0, len(calleesMap)) |
| 189 | for f := range calleesMap { |
| 190 | funcs = append(funcs, f) |
| 191 | } |
| 192 | sort.Sort(byFuncPos(funcs)) |
| 193 | return funcs, nil |
| 194 | } |
| 195 | |
| 196 | type calleesSSAResult struct { |
| 197 | site ssa.CallInstruction |
| 198 | funcs []*ssa.Function |
| 199 | } |
| 200 | |
| 201 | type calleesTypesResult struct { |
| 202 | site *ast.CallExpr |
| 203 | callee *types.Func |
| 204 | } |
| 205 | |
| 206 | func (r *calleesSSAResult) PrintPlain(printf printfFunc) { |
| 207 | if len(r.funcs) == 0 { |
| 208 | // dynamic call on a provably nil func/interface |
| 209 | printf(r.site, "%s on nil value", r.site.Common().Description()) |
| 210 | } else { |
| 211 | printf(r.site, "this %s dispatches to:", r.site.Common().Description()) |
| 212 | for _, callee := range r.funcs { |
| 213 | printf(callee, "\t%s", callee) |
| 214 | } |
| 215 | } |
| 216 | } |
| 217 | |
| 218 | func (r *calleesSSAResult) JSON(fset *token.FileSet) []byte { |
| 219 | j := &serial.Callees{ |
| 220 | Pos: fset.Position(r.site.Pos()).String(), |
| 221 | Desc: r.site.Common().Description(), |
| 222 | } |
| 223 | for _, callee := range r.funcs { |
| 224 | j.Callees = append(j.Callees, &serial.Callee{ |
| 225 | Name: callee.String(), |
| 226 | Pos: fset.Position(callee.Pos()).String(), |
| 227 | }) |
| 228 | } |
| 229 | return toJSON(j) |
| 230 | } |
| 231 | |
| 232 | func (r *calleesTypesResult) PrintPlain(printf printfFunc) { |
| 233 | printf(r.site, "this static function call dispatches to:") |
| 234 | printf(r.callee, "\t%s", r.callee.FullName()) |
| 235 | } |
| 236 | |
| 237 | func (r *calleesTypesResult) JSON(fset *token.FileSet) []byte { |
| 238 | j := &serial.Callees{ |
| 239 | Pos: fset.Position(r.site.Pos()).String(), |
| 240 | Desc: "static function call", |
| 241 | } |
| 242 | j.Callees = []*serial.Callee{ |
| 243 | { |
| 244 | Name: r.callee.FullName(), |
| 245 | Pos: fset.Position(r.callee.Pos()).String(), |
| 246 | }, |
| 247 | } |
| 248 | return toJSON(j) |
| 249 | } |
| 250 | |
| 251 | // NB: byFuncPos is not deterministic across packages since it depends on load order. |
| 252 | // Use lessPos if the tests need it. |
| 253 | type byFuncPos []*ssa.Function |
| 254 | |
| 255 | func (a byFuncPos) Len() int { return len(a) } |
| 256 | func (a byFuncPos) Less(i, j int) bool { return a[i].Pos() < a[j].Pos() } |
| 257 | func (a byFuncPos) Swap(i, j int) { a[i], a[j] = a[j], a[i] } |
| 258 |
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