| 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 ssa/interp defines an interpreter for the SSA |
| 6 | // representation of Go programs. |
| 7 | // |
| 8 | // This interpreter is provided as an adjunct for testing the SSA |
| 9 | // construction algorithm. Its purpose is to provide a minimal |
| 10 | // metacircular implementation of the dynamic semantics of each SSA |
| 11 | // instruction. It is not, and will never be, a production-quality Go |
| 12 | // interpreter. |
| 13 | // |
| 14 | // The following is a partial list of Go features that are currently |
| 15 | // unsupported or incomplete in the interpreter. |
| 16 | // |
| 17 | // * Unsafe operations, including all uses of unsafe.Pointer, are |
| 18 | // impossible to support given the "boxed" value representation we |
| 19 | // have chosen. |
| 20 | // |
| 21 | // * The reflect package is only partially implemented. |
| 22 | // |
| 23 | // * The "testing" package is no longer supported because it |
| 24 | // depends on low-level details that change too often. |
| 25 | // |
| 26 | // * "sync/atomic" operations are not atomic due to the "boxed" value |
| 27 | // representation: it is not possible to read, modify and write an |
| 28 | // interface value atomically. As a consequence, Mutexes are currently |
| 29 | // broken. |
| 30 | // |
| 31 | // * recover is only partially implemented. Also, the interpreter |
| 32 | // makes no attempt to distinguish target panics from interpreter |
| 33 | // crashes. |
| 34 | // |
| 35 | // * the sizes of the int, uint and uintptr types in the target |
| 36 | // program are assumed to be the same as those of the interpreter |
| 37 | // itself. |
| 38 | // |
| 39 | // * all values occupy space, even those of types defined by the spec |
| 40 | // to have zero size, e.g. struct{}. This can cause asymptotic |
| 41 | // performance degradation. |
| 42 | // |
| 43 | // * os.Exit is implemented using panic, causing deferred functions to |
| 44 | // run. |
| 45 | package interp // import "golang.org/x/tools/go/ssa/interp" |
| 46 | |
| 47 | import ( |
| 48 | "fmt" |
| 49 | "go/token" |
| 50 | "go/types" |
| 51 | "os" |
| 52 | "reflect" |
| 53 | "runtime" |
| 54 | "sync/atomic" |
| 55 | |
| 56 | "golang.org/x/tools/go/ssa" |
| 57 | ) |
| 58 | |
| 59 | type continuation int |
| 60 | |
| 61 | const ( |
| 62 | kNext continuation = iota |
| 63 | kReturn |
| 64 | kJump |
| 65 | ) |
| 66 | |
| 67 | // Mode is a bitmask of options affecting the interpreter. |
| 68 | type Mode uint |
| 69 | |
| 70 | const ( |
| 71 | DisableRecover Mode = 1 << iota // Disable recover() in target programs; show interpreter crash instead. |
| 72 | EnableTracing // Print a trace of all instructions as they are interpreted. |
| 73 | ) |
| 74 | |
| 75 | type methodSet map[string]*ssa.Function |
| 76 | |
| 77 | // State shared between all interpreted goroutines. |
| 78 | type interpreter struct { |
| 79 | osArgs []value // the value of os.Args |
| 80 | prog *ssa.Program // the SSA program |
| 81 | globals map[*ssa.Global]*value // addresses of global variables (immutable) |
| 82 | mode Mode // interpreter options |
| 83 | reflectPackage *ssa.Package // the fake reflect package |
| 84 | errorMethods methodSet // the method set of reflect.error, which implements the error interface. |
| 85 | rtypeMethods methodSet // the method set of rtype, which implements the reflect.Type interface. |
| 86 | runtimeErrorString types.Type // the runtime.errorString type |
| 87 | sizes types.Sizes // the effective type-sizing function |
| 88 | goroutines int32 // atomically updated |
| 89 | } |
| 90 | |
| 91 | type deferred struct { |
| 92 | fn value |
| 93 | args []value |
| 94 | instr *ssa.Defer |
| 95 | tail *deferred |
| 96 | } |
| 97 | |
| 98 | type frame struct { |
| 99 | i *interpreter |
| 100 | caller *frame |
| 101 | fn *ssa.Function |
| 102 | block, prevBlock *ssa.BasicBlock |
| 103 | env map[ssa.Value]value // dynamic values of SSA variables |
| 104 | locals []value |
| 105 | defers *deferred |
| 106 | result value |
| 107 | panicking bool |
| 108 | panic interface{} |
| 109 | } |
| 110 | |
| 111 | func (fr *frame) get(key ssa.Value) value { |
| 112 | switch key := key.(type) { |
| 113 | case nil: |
| 114 | // Hack; simplifies handling of optional attributes |
| 115 | // such as ssa.Slice.{Low,High}. |
| 116 | return nil |
| 117 | case *ssa.Function, *ssa.Builtin: |
| 118 | return key |
| 119 | case *ssa.Const: |
| 120 | return constValue(key) |
| 121 | case *ssa.Global: |
| 122 | if r, ok := fr.i.globals[key]; ok { |
| 123 | return r |
| 124 | } |
| 125 | } |
| 126 | if r, ok := fr.env[key]; ok { |
| 127 | return r |
| 128 | } |
| 129 | panic(fmt.Sprintf("get: no value for %T: %v", key, key.Name())) |
| 130 | } |
| 131 | |
| 132 | // runDefer runs a deferred call d. |
| 133 | // It always returns normally, but may set or clear fr.panic. |
| 134 | func (fr *frame) runDefer(d *deferred) { |
| 135 | if fr.i.mode&EnableTracing != 0 { |
| 136 | fmt.Fprintf(os.Stderr, "%s: invoking deferred function call\n", |
| 137 | fr.i.prog.Fset.Position(d.instr.Pos())) |
| 138 | } |
| 139 | var ok bool |
| 140 | defer func() { |
| 141 | if !ok { |
| 142 | // Deferred call created a new state of panic. |
| 143 | fr.panicking = true |
| 144 | fr.panic = recover() |
| 145 | } |
| 146 | }() |
| 147 | call(fr.i, fr, d.instr.Pos(), d.fn, d.args) |
| 148 | ok = true |
| 149 | } |
| 150 | |
| 151 | // runDefers executes fr's deferred function calls in LIFO order. |
| 152 | // |
| 153 | // On entry, fr.panicking indicates a state of panic; if |
| 154 | // true, fr.panic contains the panic value. |
| 155 | // |
| 156 | // On completion, if a deferred call started a panic, or if no |
| 157 | // deferred call recovered from a previous state of panic, then |
| 158 | // runDefers itself panics after the last deferred call has run. |
| 159 | // |
| 160 | // If there was no initial state of panic, or it was recovered from, |
| 161 | // runDefers returns normally. |
| 162 | func (fr *frame) runDefers() { |
| 163 | for d := fr.defers; d != nil; d = d.tail { |
| 164 | fr.runDefer(d) |
| 165 | } |
| 166 | fr.defers = nil |
| 167 | if fr.panicking { |
| 168 | panic(fr.panic) // new panic, or still panicking |
| 169 | } |
| 170 | } |
| 171 | |
| 172 | // lookupMethod returns the method set for type typ, which may be one |
| 173 | // of the interpreter's fake types. |
| 174 | func lookupMethod(i *interpreter, typ types.Type, meth *types.Func) *ssa.Function { |
| 175 | switch typ { |
| 176 | case rtypeType: |
| 177 | return i.rtypeMethods[meth.Id()] |
| 178 | case errorType: |
| 179 | return i.errorMethods[meth.Id()] |
| 180 | } |
| 181 | return i.prog.LookupMethod(typ, meth.Pkg(), meth.Name()) |
| 182 | } |
| 183 | |
| 184 | // visitInstr interprets a single ssa.Instruction within the activation |
| 185 | // record frame. It returns a continuation value indicating where to |
| 186 | // read the next instruction from. |
| 187 | func visitInstr(fr *frame, instr ssa.Instruction) continuation { |
| 188 | switch instr := instr.(type) { |
| 189 | case *ssa.DebugRef: |
| 190 | // no-op |
| 191 | |
| 192 | case *ssa.UnOp: |
| 193 | fr.env[instr] = unop(instr, fr.get(instr.X)) |
| 194 | |
| 195 | case *ssa.BinOp: |
| 196 | fr.env[instr] = binop(instr.Op, instr.X.Type(), fr.get(instr.X), fr.get(instr.Y)) |
| 197 | |
| 198 | case *ssa.Call: |
| 199 | fn, args := prepareCall(fr, &instr.Call) |
| 200 | fr.env[instr] = call(fr.i, fr, instr.Pos(), fn, args) |
| 201 | |
| 202 | case *ssa.ChangeInterface: |
| 203 | fr.env[instr] = fr.get(instr.X) |
| 204 | |
| 205 | case *ssa.ChangeType: |
| 206 | fr.env[instr] = fr.get(instr.X) // (can't fail) |
| 207 | |
| 208 | case *ssa.Convert: |
| 209 | fr.env[instr] = conv(instr.Type(), instr.X.Type(), fr.get(instr.X)) |
| 210 | |
| 211 | case *ssa.SliceToArrayPointer: |
| 212 | fr.env[instr] = sliceToArrayPointer(instr.Type(), instr.X.Type(), fr.get(instr.X)) |
| 213 | |
| 214 | case *ssa.MakeInterface: |
| 215 | fr.env[instr] = iface{t: instr.X.Type(), v: fr.get(instr.X)} |
| 216 | |
| 217 | case *ssa.Extract: |
| 218 | fr.env[instr] = fr.get(instr.Tuple).(tuple)[instr.Index] |
| 219 | |
| 220 | case *ssa.Slice: |
| 221 | fr.env[instr] = slice(fr.get(instr.X), fr.get(instr.Low), fr.get(instr.High), fr.get(instr.Max)) |
| 222 | |
| 223 | case *ssa.Return: |
| 224 | switch len(instr.Results) { |
| 225 | case 0: |
| 226 | case 1: |
| 227 | fr.result = fr.get(instr.Results[0]) |
| 228 | default: |
| 229 | var res []value |
| 230 | for _, r := range instr.Results { |
| 231 | res = append(res, fr.get(r)) |
| 232 | } |
| 233 | fr.result = tuple(res) |
| 234 | } |
| 235 | fr.block = nil |
| 236 | return kReturn |
| 237 | |
| 238 | case *ssa.RunDefers: |
| 239 | fr.runDefers() |
| 240 | |
| 241 | case *ssa.Panic: |
| 242 | panic(targetPanic{fr.get(instr.X)}) |
| 243 | |
| 244 | case *ssa.Send: |
| 245 | fr.get(instr.Chan).(chan value) <- fr.get(instr.X) |
| 246 | |
| 247 | case *ssa.Store: |
| 248 | store(deref(instr.Addr.Type()), fr.get(instr.Addr).(*value), fr.get(instr.Val)) |
| 249 | |
| 250 | case *ssa.If: |
| 251 | succ := 1 |
| 252 | if fr.get(instr.Cond).(bool) { |
| 253 | succ = 0 |
| 254 | } |
| 255 | fr.prevBlock, fr.block = fr.block, fr.block.Succs[succ] |
| 256 | return kJump |
| 257 | |
| 258 | case *ssa.Jump: |
| 259 | fr.prevBlock, fr.block = fr.block, fr.block.Succs[0] |
| 260 | return kJump |
| 261 | |
| 262 | case *ssa.Defer: |
| 263 | fn, args := prepareCall(fr, &instr.Call) |
| 264 | fr.defers = &deferred{ |
| 265 | fn: fn, |
| 266 | args: args, |
| 267 | instr: instr, |
| 268 | tail: fr.defers, |
| 269 | } |
| 270 | |
| 271 | case *ssa.Go: |
| 272 | fn, args := prepareCall(fr, &instr.Call) |
| 273 | atomic.AddInt32(&fr.i.goroutines, 1) |
| 274 | go func() { |
| 275 | call(fr.i, nil, instr.Pos(), fn, args) |
| 276 | atomic.AddInt32(&fr.i.goroutines, -1) |
| 277 | }() |
| 278 | |
| 279 | case *ssa.MakeChan: |
| 280 | fr.env[instr] = make(chan value, asInt64(fr.get(instr.Size))) |
| 281 | |
| 282 | case *ssa.Alloc: |
| 283 | var addr *value |
| 284 | if instr.Heap { |
| 285 | // new |
| 286 | addr = new(value) |
| 287 | fr.env[instr] = addr |
| 288 | } else { |
| 289 | // local |
| 290 | addr = fr.env[instr].(*value) |
| 291 | } |
| 292 | *addr = zero(deref(instr.Type())) |
| 293 | |
| 294 | case *ssa.MakeSlice: |
| 295 | slice := make([]value, asInt64(fr.get(instr.Cap))) |
| 296 | tElt := instr.Type().Underlying().(*types.Slice).Elem() |
| 297 | for i := range slice { |
| 298 | slice[i] = zero(tElt) |
| 299 | } |
| 300 | fr.env[instr] = slice[:asInt64(fr.get(instr.Len))] |
| 301 | |
| 302 | case *ssa.MakeMap: |
| 303 | var reserve int64 |
| 304 | if instr.Reserve != nil { |
| 305 | reserve = asInt64(fr.get(instr.Reserve)) |
| 306 | } |
| 307 | if !fitsInt(reserve, fr.i.sizes) { |
| 308 | panic(fmt.Sprintf("ssa.MakeMap.Reserve value %d does not fit in int", reserve)) |
| 309 | } |
| 310 | fr.env[instr] = makeMap(instr.Type().Underlying().(*types.Map).Key(), reserve) |
| 311 | |
| 312 | case *ssa.Range: |
| 313 | fr.env[instr] = rangeIter(fr.get(instr.X), instr.X.Type()) |
| 314 | |
| 315 | case *ssa.Next: |
| 316 | fr.env[instr] = fr.get(instr.Iter).(iter).next() |
| 317 | |
| 318 | case *ssa.FieldAddr: |
| 319 | fr.env[instr] = &(*fr.get(instr.X).(*value)).(structure)[instr.Field] |
| 320 | |
| 321 | case *ssa.Field: |
| 322 | fr.env[instr] = fr.get(instr.X).(structure)[instr.Field] |
| 323 | |
| 324 | case *ssa.IndexAddr: |
| 325 | x := fr.get(instr.X) |
| 326 | idx := fr.get(instr.Index) |
| 327 | switch x := x.(type) { |
| 328 | case []value: |
| 329 | fr.env[instr] = &x[asInt64(idx)] |
| 330 | case *value: // *array |
| 331 | fr.env[instr] = &(*x).(array)[asInt64(idx)] |
| 332 | default: |
| 333 | panic(fmt.Sprintf("unexpected x type in IndexAddr: %T", x)) |
| 334 | } |
| 335 | |
| 336 | case *ssa.Index: |
| 337 | x := fr.get(instr.X) |
| 338 | idx := fr.get(instr.Index) |
| 339 | |
| 340 | switch x := x.(type) { |
| 341 | case array: |
| 342 | fr.env[instr] = x[asInt64(idx)] |
| 343 | case string: |
| 344 | fr.env[instr] = x[asInt64(idx)] |
| 345 | default: |
| 346 | panic(fmt.Sprintf("unexpected x type in Index: %T", x)) |
| 347 | } |
| 348 | |
| 349 | case *ssa.Lookup: |
| 350 | fr.env[instr] = lookup(instr, fr.get(instr.X), fr.get(instr.Index)) |
| 351 | |
| 352 | case *ssa.MapUpdate: |
| 353 | m := fr.get(instr.Map) |
| 354 | key := fr.get(instr.Key) |
| 355 | v := fr.get(instr.Value) |
| 356 | switch m := m.(type) { |
| 357 | case map[value]value: |
| 358 | m[key] = v |
| 359 | case *hashmap: |
| 360 | m.insert(key.(hashable), v) |
| 361 | default: |
| 362 | panic(fmt.Sprintf("illegal map type: %T", m)) |
| 363 | } |
| 364 | |
| 365 | case *ssa.TypeAssert: |
| 366 | fr.env[instr] = typeAssert(fr.i, instr, fr.get(instr.X).(iface)) |
| 367 | |
| 368 | case *ssa.MakeClosure: |
| 369 | var bindings []value |
| 370 | for _, binding := range instr.Bindings { |
| 371 | bindings = append(bindings, fr.get(binding)) |
| 372 | } |
| 373 | fr.env[instr] = &closure{instr.Fn.(*ssa.Function), bindings} |
| 374 | |
| 375 | case *ssa.Phi: |
| 376 | for i, pred := range instr.Block().Preds { |
| 377 | if fr.prevBlock == pred { |
| 378 | fr.env[instr] = fr.get(instr.Edges[i]) |
| 379 | break |
| 380 | } |
| 381 | } |
| 382 | |
| 383 | case *ssa.Select: |
| 384 | var cases []reflect.SelectCase |
| 385 | if !instr.Blocking { |
| 386 | cases = append(cases, reflect.SelectCase{ |
| 387 | Dir: reflect.SelectDefault, |
| 388 | }) |
| 389 | } |
| 390 | for _, state := range instr.States { |
| 391 | var dir reflect.SelectDir |
| 392 | if state.Dir == types.RecvOnly { |
| 393 | dir = reflect.SelectRecv |
| 394 | } else { |
| 395 | dir = reflect.SelectSend |
| 396 | } |
| 397 | var send reflect.Value |
| 398 | if state.Send != nil { |
| 399 | send = reflect.ValueOf(fr.get(state.Send)) |
| 400 | } |
| 401 | cases = append(cases, reflect.SelectCase{ |
| 402 | Dir: dir, |
| 403 | Chan: reflect.ValueOf(fr.get(state.Chan)), |
| 404 | Send: send, |
| 405 | }) |
| 406 | } |
| 407 | chosen, recv, recvOk := reflect.Select(cases) |
| 408 | if !instr.Blocking { |
| 409 | chosen-- // default case should have index -1. |
| 410 | } |
| 411 | r := tuple{chosen, recvOk} |
| 412 | for i, st := range instr.States { |
| 413 | if st.Dir == types.RecvOnly { |
| 414 | var v value |
| 415 | if i == chosen && recvOk { |
| 416 | // No need to copy since send makes an unaliased copy. |
| 417 | v = recv.Interface().(value) |
| 418 | } else { |
| 419 | v = zero(st.Chan.Type().Underlying().(*types.Chan).Elem()) |
| 420 | } |
| 421 | r = append(r, v) |
| 422 | } |
| 423 | } |
| 424 | fr.env[instr] = r |
| 425 | |
| 426 | default: |
| 427 | panic(fmt.Sprintf("unexpected instruction: %T", instr)) |
| 428 | } |
| 429 | |
| 430 | // if val, ok := instr.(ssa.Value); ok { |
| 431 | // fmt.Println(toString(fr.env[val])) // debugging |
| 432 | // } |
| 433 | |
| 434 | return kNext |
| 435 | } |
| 436 | |
| 437 | // prepareCall determines the function value and argument values for a |
| 438 | // function call in a Call, Go or Defer instruction, performing |
| 439 | // interface method lookup if needed. |
| 440 | func prepareCall(fr *frame, call *ssa.CallCommon) (fn value, args []value) { |
| 441 | v := fr.get(call.Value) |
| 442 | if call.Method == nil { |
| 443 | // Function call. |
| 444 | fn = v |
| 445 | } else { |
| 446 | // Interface method invocation. |
| 447 | recv := v.(iface) |
| 448 | if recv.t == nil { |
| 449 | panic("method invoked on nil interface") |
| 450 | } |
| 451 | if f := lookupMethod(fr.i, recv.t, call.Method); f == nil { |
| 452 | // Unreachable in well-typed programs. |
| 453 | panic(fmt.Sprintf("method set for dynamic type %v does not contain %s", recv.t, call.Method)) |
| 454 | } else { |
| 455 | fn = f |
| 456 | } |
| 457 | args = append(args, recv.v) |
| 458 | } |
| 459 | for _, arg := range call.Args { |
| 460 | args = append(args, fr.get(arg)) |
| 461 | } |
| 462 | return |
| 463 | } |
| 464 | |
| 465 | // call interprets a call to a function (function, builtin or closure) |
| 466 | // fn with arguments args, returning its result. |
| 467 | // callpos is the position of the callsite. |
| 468 | func call(i *interpreter, caller *frame, callpos token.Pos, fn value, args []value) value { |
| 469 | switch fn := fn.(type) { |
| 470 | case *ssa.Function: |
| 471 | if fn == nil { |
| 472 | panic("call of nil function") // nil of func type |
| 473 | } |
| 474 | return callSSA(i, caller, callpos, fn, args, nil) |
| 475 | case *closure: |
| 476 | return callSSA(i, caller, callpos, fn.Fn, args, fn.Env) |
| 477 | case *ssa.Builtin: |
| 478 | return callBuiltin(caller, callpos, fn, args) |
| 479 | } |
| 480 | panic(fmt.Sprintf("cannot call %T", fn)) |
| 481 | } |
| 482 | |
| 483 | func loc(fset *token.FileSet, pos token.Pos) string { |
| 484 | if pos == token.NoPos { |
| 485 | return "" |
| 486 | } |
| 487 | return " at " + fset.Position(pos).String() |
| 488 | } |
| 489 | |
| 490 | // callSSA interprets a call to function fn with arguments args, |
| 491 | // and lexical environment env, returning its result. |
| 492 | // callpos is the position of the callsite. |
| 493 | func callSSA(i *interpreter, caller *frame, callpos token.Pos, fn *ssa.Function, args []value, env []value) value { |
| 494 | if i.mode&EnableTracing != 0 { |
| 495 | fset := fn.Prog.Fset |
| 496 | // TODO(adonovan): fix: loc() lies for external functions. |
| 497 | fmt.Fprintf(os.Stderr, "Entering %s%s.\n", fn, loc(fset, fn.Pos())) |
| 498 | suffix := "" |
| 499 | if caller != nil { |
| 500 | suffix = ", resuming " + caller.fn.String() + loc(fset, callpos) |
| 501 | } |
| 502 | defer fmt.Fprintf(os.Stderr, "Leaving %s%s.\n", fn, suffix) |
| 503 | } |
| 504 | fr := &frame{ |
| 505 | i: i, |
| 506 | caller: caller, // for panic/recover |
| 507 | fn: fn, |
| 508 | } |
| 509 | if fn.Parent() == nil { |
| 510 | name := fn.String() |
| 511 | if ext := externals[name]; ext != nil { |
| 512 | if i.mode&EnableTracing != 0 { |
| 513 | fmt.Fprintln(os.Stderr, "\t(external)") |
| 514 | } |
| 515 | return ext(fr, args) |
| 516 | } |
| 517 | if fn.Blocks == nil { |
| 518 | panic("no code for function: " + name) |
| 519 | } |
| 520 | } |
| 521 | |
| 522 | // generic function body? |
| 523 | if fn.TypeParams().Len() > 0 && len(fn.TypeArgs()) == 0 { |
| 524 | panic("interp requires ssa.BuilderMode to include InstantiateGenerics to execute generics") |
| 525 | } |
| 526 | |
| 527 | fr.env = make(map[ssa.Value]value) |
| 528 | fr.block = fn.Blocks[0] |
| 529 | fr.locals = make([]value, len(fn.Locals)) |
| 530 | for i, l := range fn.Locals { |
| 531 | fr.locals[i] = zero(deref(l.Type())) |
| 532 | fr.env[l] = &fr.locals[i] |
| 533 | } |
| 534 | for i, p := range fn.Params { |
| 535 | fr.env[p] = args[i] |
| 536 | } |
| 537 | for i, fv := range fn.FreeVars { |
| 538 | fr.env[fv] = env[i] |
| 539 | } |
| 540 | for fr.block != nil { |
| 541 | runFrame(fr) |
| 542 | } |
| 543 | // Destroy the locals to avoid accidental use after return. |
| 544 | for i := range fn.Locals { |
| 545 | fr.locals[i] = bad{} |
| 546 | } |
| 547 | return fr.result |
| 548 | } |
| 549 | |
| 550 | // runFrame executes SSA instructions starting at fr.block and |
| 551 | // continuing until a return, a panic, or a recovered panic. |
| 552 | // |
| 553 | // After a panic, runFrame panics. |
| 554 | // |
| 555 | // After a normal return, fr.result contains the result of the call |
| 556 | // and fr.block is nil. |
| 557 | // |
| 558 | // A recovered panic in a function without named return parameters |
| 559 | // (NRPs) becomes a normal return of the zero value of the function's |
| 560 | // result type. |
| 561 | // |
| 562 | // After a recovered panic in a function with NRPs, fr.result is |
| 563 | // undefined and fr.block contains the block at which to resume |
| 564 | // control. |
| 565 | func runFrame(fr *frame) { |
| 566 | defer func() { |
| 567 | if fr.block == nil { |
| 568 | return // normal return |
| 569 | } |
| 570 | if fr.i.mode&DisableRecover != 0 { |
| 571 | return // let interpreter crash |
| 572 | } |
| 573 | fr.panicking = true |
| 574 | fr.panic = recover() |
| 575 | if fr.i.mode&EnableTracing != 0 { |
| 576 | fmt.Fprintf(os.Stderr, "Panicking: %T %v.\n", fr.panic, fr.panic) |
| 577 | } |
| 578 | fr.runDefers() |
| 579 | fr.block = fr.fn.Recover |
| 580 | }() |
| 581 | |
| 582 | for { |
| 583 | if fr.i.mode&EnableTracing != 0 { |
| 584 | fmt.Fprintf(os.Stderr, ".%s:\n", fr.block) |
| 585 | } |
| 586 | block: |
| 587 | for _, instr := range fr.block.Instrs { |
| 588 | if fr.i.mode&EnableTracing != 0 { |
| 589 | if v, ok := instr.(ssa.Value); ok { |
| 590 | fmt.Fprintln(os.Stderr, "\t", v.Name(), "=", instr) |
| 591 | } else { |
| 592 | fmt.Fprintln(os.Stderr, "\t", instr) |
| 593 | } |
| 594 | } |
| 595 | switch visitInstr(fr, instr) { |
| 596 | case kReturn: |
| 597 | return |
| 598 | case kNext: |
| 599 | // no-op |
| 600 | case kJump: |
| 601 | break block |
| 602 | } |
| 603 | } |
| 604 | } |
| 605 | } |
| 606 | |
| 607 | // doRecover implements the recover() built-in. |
| 608 | func doRecover(caller *frame) value { |
| 609 | // recover() must be exactly one level beneath the deferred |
| 610 | // function (two levels beneath the panicking function) to |
| 611 | // have any effect. Thus we ignore both "defer recover()" and |
| 612 | // "defer f() -> g() -> recover()". |
| 613 | if caller.i.mode&DisableRecover == 0 && |
| 614 | caller != nil && !caller.panicking && |
| 615 | caller.caller != nil && caller.caller.panicking { |
| 616 | caller.caller.panicking = false |
| 617 | p := caller.caller.panic |
| 618 | caller.caller.panic = nil |
| 619 | |
| 620 | // TODO(adonovan): support runtime.Goexit. |
| 621 | switch p := p.(type) { |
| 622 | case targetPanic: |
| 623 | // The target program explicitly called panic(). |
| 624 | return p.v |
| 625 | case runtime.Error: |
| 626 | // The interpreter encountered a runtime error. |
| 627 | return iface{caller.i.runtimeErrorString, p.Error()} |
| 628 | case string: |
| 629 | // The interpreter explicitly called panic(). |
| 630 | return iface{caller.i.runtimeErrorString, p} |
| 631 | default: |
| 632 | panic(fmt.Sprintf("unexpected panic type %T in target call to recover()", p)) |
| 633 | } |
| 634 | } |
| 635 | return iface{} |
| 636 | } |
| 637 | |
| 638 | // setGlobal sets the value of a system-initialized global variable. |
| 639 | func setGlobal(i *interpreter, pkg *ssa.Package, name string, v value) { |
| 640 | if g, ok := i.globals[pkg.Var(name)]; ok { |
| 641 | *g = v |
| 642 | return |
| 643 | } |
| 644 | panic("no global variable: " + pkg.Pkg.Path() + "." + name) |
| 645 | } |
| 646 | |
| 647 | // Interpret interprets the Go program whose main package is mainpkg. |
| 648 | // mode specifies various interpreter options. filename and args are |
| 649 | // the initial values of os.Args for the target program. sizes is the |
| 650 | // effective type-sizing function for this program. |
| 651 | // |
| 652 | // Interpret returns the exit code of the program: 2 for panic (like |
| 653 | // gc does), or the argument to os.Exit for normal termination. |
| 654 | // |
| 655 | // The SSA program must include the "runtime" package. |
| 656 | // |
| 657 | // Type parameterized functions must have been built with |
| 658 | // InstantiateGenerics in the ssa.BuilderMode to be interpreted. |
| 659 | func Interpret(mainpkg *ssa.Package, mode Mode, sizes types.Sizes, filename string, args []string) (exitCode int) { |
| 660 | i := &interpreter{ |
| 661 | prog: mainpkg.Prog, |
| 662 | globals: make(map[*ssa.Global]*value), |
| 663 | mode: mode, |
| 664 | sizes: sizes, |
| 665 | goroutines: 1, |
| 666 | } |
| 667 | runtimePkg := i.prog.ImportedPackage("runtime") |
| 668 | if runtimePkg == nil { |
| 669 | panic("ssa.Program doesn't include runtime package") |
| 670 | } |
| 671 | i.runtimeErrorString = runtimePkg.Type("errorString").Object().Type() |
| 672 | |
| 673 | initReflect(i) |
| 674 | |
| 675 | i.osArgs = append(i.osArgs, filename) |
| 676 | for _, arg := range args { |
| 677 | i.osArgs = append(i.osArgs, arg) |
| 678 | } |
| 679 | |
| 680 | for _, pkg := range i.prog.AllPackages() { |
| 681 | // Initialize global storage. |
| 682 | for _, m := range pkg.Members { |
| 683 | switch v := m.(type) { |
| 684 | case *ssa.Global: |
| 685 | cell := zero(deref(v.Type())) |
| 686 | i.globals[v] = &cell |
| 687 | } |
| 688 | } |
| 689 | } |
| 690 | |
| 691 | // Top-level error handler. |
| 692 | exitCode = 2 |
| 693 | defer func() { |
| 694 | if exitCode != 2 || i.mode&DisableRecover != 0 { |
| 695 | return |
| 696 | } |
| 697 | switch p := recover().(type) { |
| 698 | case exitPanic: |
| 699 | exitCode = int(p) |
| 700 | return |
| 701 | case targetPanic: |
| 702 | fmt.Fprintln(os.Stderr, "panic:", toString(p.v)) |
| 703 | case runtime.Error: |
| 704 | fmt.Fprintln(os.Stderr, "panic:", p.Error()) |
| 705 | case string: |
| 706 | fmt.Fprintln(os.Stderr, "panic:", p) |
| 707 | default: |
| 708 | fmt.Fprintf(os.Stderr, "panic: unexpected type: %T: %v\n", p, p) |
| 709 | } |
| 710 | |
| 711 | // TODO(adonovan): dump panicking interpreter goroutine? |
| 712 | // buf := make([]byte, 0x10000) |
| 713 | // runtime.Stack(buf, false) |
| 714 | // fmt.Fprintln(os.Stderr, string(buf)) |
| 715 | // (Or dump panicking target goroutine?) |
| 716 | }() |
| 717 | |
| 718 | // Run! |
| 719 | call(i, nil, token.NoPos, mainpkg.Func("init"), nil) |
| 720 | if mainFn := mainpkg.Func("main"); mainFn != nil { |
| 721 | call(i, nil, token.NoPos, mainFn, nil) |
| 722 | exitCode = 0 |
| 723 | } else { |
| 724 | fmt.Fprintln(os.Stderr, "No main function.") |
| 725 | exitCode = 1 |
| 726 | } |
| 727 | return |
| 728 | } |
| 729 | |
| 730 | // deref returns a pointer's element type; otherwise it returns typ. |
| 731 | // TODO(adonovan): Import from ssa? |
| 732 | func deref(typ types.Type) types.Type { |
| 733 | if p, ok := typ.Underlying().(*types.Pointer); ok { |
| 734 | return p.Elem() |
| 735 | } |
| 736 | return typ |
| 737 | } |
| 738 |
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