1    // Copyright 2003 Adam Megacz, see the COPYING file for licensing [GPL]
2    package org.xwt.js;
3    
4    import org.xwt.util.*;
5    import java.io.*;
6    
7    /** a JavaScript function, compiled into bytecode */
8    class CompiledFunctionImpl extends JS.Obj implements ByteCodes, Tokens {
9    
10       // Fields and Accessors ///////////////////////////////////////////////
11   
12       /** the number of formal arguments */
13       int numFormalArgs = 20;
14   
15       /** the source code file that this block was drawn from */
16        String sourceName;
17       public String getSourceName() throws JS.Exn { return sourceName; }
18       
19       /** the line numbers */
20        int[] line = new int[10];
21   
22       /** the first line of this script */
23       private int firstLine = -1;
24   
25       /** the instructions */
26        int[] op = new int[10];
27   
28       /** the arguments to the instructions */
29        Object[] arg = new Object[10];
30   
31       /** the number of instruction/argument pairs */
32        int size = 0;
33       int size() { return size; }
34   
35       /** the scope in which this function was declared; by default this function is called in a fresh subscope of the parentScope */
36       JS.Scope parentScope;
37   
38       // Constructors ////////////////////////////////////////////////////////
39   
40       private CompiledFunctionImpl cloneWithNewParentScope(JS.Scope s) throws IOException {
41           CompiledFunctionImpl ret = new JS.CompiledFunction(sourceName, firstLine, null, s);
42           // Reuse the same op, arg, line, and size variables for the new "instance" of the function
43           // NOTE: Neither *this* function nor the new function should be modified after this call
44           ret.op = this.op;
45           ret.arg = this.arg;
46           ret.line = this.line;
47           ret.size = this.size;
48           ret.numFormalArgs = this.numFormalArgs;
49           return ret;
50       }
51   
52       protected CompiledFunctionImpl(String sourceName, int firstLine, Reader sourceCode, JS.Scope parentScope) throws IOException {
53           this.sourceName = sourceName;
54           this.firstLine = firstLine;
55           this.parentScope = parentScope;
56           if (sourceCode == null) return;
57           Parser p = new Parser(sourceCode, sourceName, firstLine);
58           while(true) {
59               int s = size();
60               p.parseStatement(this, null);
61               if (s == size()) break;
62           }
63           add(-1, LITERAL, null); 
64           add(-1, RETURN);
65       }
66       
67   
68   
69       // Adding and Altering Bytecodes ///////////////////////////////////////////////////
70   
71       int get(int pos) { return op[pos]; }
72       Object getArg(int pos) { return arg[pos]; }
73       void set(int pos, int op_, Object arg_) { op[pos] = op_; arg[pos] = arg_; }
74       void set(int pos, Object arg_) { arg[pos] = arg_; }
75       int pop() { size--; arg[size] = null; return op[size]; }
76       void paste(CompiledFunctionImpl other) { for(int i=0; i<other.size; i++) add(other.line[i], other.op[i], other.arg[i]); }
77       CompiledFunctionImpl add(int line, int op_) { return add(line, op_, null); }
78       CompiledFunctionImpl add(int line, int op_, Object arg_) {
79           if (size == op.length - 1) {
80               int[] line2 = new int[op.length * 2]; System.arraycopy(this.line, 0, line2, 0, op.length); this.line = line2;
81               Object[] arg2 = new Object[op.length * 2]; System.arraycopy(arg, 0, arg2, 0, arg.length); arg = arg2;
82               int[] op2 = new int[op.length * 2]; System.arraycopy(op, 0, op2, 0, op.length); op = op2;
83           }
84           this.line[size] = line;
85           op[size] = op_;
86           arg[size] = arg_;
87           size++;
88           return this;
89       }
90       
91       public static int getLine(JS.Thread cx) {
92           if(cx.pc < 0 || cx.pc >= ((CompiledFunctionImpl)cx.currentCompiledFunction).size) return -1;
93           return ((CompiledFunctionImpl)cx.currentCompiledFunction).line[cx.pc];
94       }
95   
96   
97       // Invoking the Bytecode ///////////////////////////////////////////////////////
98   
99       /** returns false if the thread has been paused */
100      static Object eval(final JS.Thread cx) throws JS.Exn {
101          OUTER: for(;; cx.pc++) {
102          try {
103              if (cx.paused) return null;
104              cx.bind();
105              if (cx.tailCallFunction != null) {
106                  cx.stack.pop();  // discard actual return value
107                  cx.pc -= 2;
108                  cx.stack.push(new CallMarker(cx));
109                  cx.stack.push(cx.tailCallArgs);
110                  cx.currentCompiledFunction = cx.tailCallFunction;
111                  cx.tailCallFunction = null;
112                  cx.tailCallArgs = null;
113                  cx.scope = new FunctionScope("unknown", cx.currentCompiledFunction.parentScope);
114                  cx.pc = 0;
115              }
116              if (cx.currentCompiledFunction == null) return cx.stack.pop();
117              if (cx.pc >= ((CompiledFunctionImpl)cx.currentCompiledFunction).size) return cx.stack.pop();
118              String label = null;
119              int curOP = cx.currentCompiledFunction.op[cx.pc];
120              Object curArg = cx.currentCompiledFunction.arg[cx.pc];
121              if(curOP == FINALLY_DONE) {
122                  FinallyData fd = (FinallyData) cx.stack.pop();
123                  if(fd == null) continue OUTER; // NOP
124                  curOP = fd.op;
125                  curArg = fd.arg;
126              }
127              switch(curOP) {
128              case LITERAL: cx.stack.push(curArg); break;
129              case OBJECT: cx.stack.push(new JS.Obj()); break;
130              case ARRAY: cx.stack.push(new JS.Array(JS.toNumber(curArg).intValue())); break;
131              case DECLARE: cx.scope.declare((String)(curArg==null ? cx.stack.peek() : curArg)); if(curArg != null) cx.stack.push(curArg); break;
132              case TOPSCOPE: cx.stack.push(cx.scope); break;
133              case JT: if (JS.toBoolean(cx.stack.pop())) cx.pc += JS.toNumber(curArg).intValue() - 1; break;
134              case JF: if (!JS.toBoolean(cx.stack.pop())) cx.pc += JS.toNumber(curArg).intValue() - 1; break;
135              case JMP: cx.pc += JS.toNumber(curArg).intValue() - 1; break;
136              case POP: cx.stack.pop(); break;
137              case SWAP: { Object o1 = cx.stack.pop(); Object o2 = cx.stack.pop(); cx.stack.push(o1); cx.stack.push(o2); break; }
138              case DUP: cx.stack.push(cx.stack.peek()); break;
139              case NEWSCOPE: cx.scope = new JS.Scope(cx.scope); break;
140              case OLDSCOPE: cx.scope = cx.scope.getParentScope(); break;
141              case ASSERT: if (!JS.toBoolean(cx.stack.pop())) throw je("assertion failed"); break;
142              case BITNOT: cx.stack.push(new Long(~JS.toLong(cx.stack.pop()))); break;
143              case BANG: cx.stack.push(new Boolean(!JS.toBoolean(cx.stack.pop()))); break;
144  
145              case TYPEOF: {
146                  Object o = cx.stack.pop();
147                  if (o == null) cx.stack.push(null);
148                  else if (o instanceof JS) cx.stack.push(((JS)o).typeName());
149                  else if (o instanceof String) cx.stack.push("string");
150                  else if (o instanceof Number) cx.stack.push("number");
151                  else if (o instanceof Boolean) cx.stack.push("boolean");
152                  else cx.stack.push("unknown");
153                  break;
154              }
155  
156              case NEWFUNCTION: {
157                  try {
158                      cx.stack.push(((CompiledFunctionImpl)curArg).cloneWithNewParentScope(cx.scope));
159                  } catch (IOException e) {
160                      throw new Error("this should never happen");
161                  }
162                  break;
163              }
164  
165              case PUSHKEYS: {
166                  Object o = cx.stack.peek();
167                  Object[] keys = ((JS)o).keys();
168                  JS.Array a = new JS.Array();
169                  a.setSize(keys.length);
170                  for(int j=0; j<keys.length; j++) a.setElementAt(keys[j], j);
171                  cx.stack.push(a);
172                  break;
173              }
174  
175              case LABEL: break;
176              case LOOP: {
177                  cx.stack.push(new LoopMarker(cx.pc, cx.pc > 0 && cx.currentCompiledFunction.op[cx.pc - 1] == LABEL ? (String)cx.currentCompiledFunction.arg[cx.pc - 1] : (String)null, cx.scope));
178                  cx.stack.push(Boolean.TRUE);
179                  break;
180              }
181  
182              case BREAK:
183              case CONTINUE:
184                  while(cx.stack.size() > 0) {
185                      Object o = cx.stack.pop();
186                      if (o instanceof CallMarker) ee("break or continue not within a loop");
187                      if (o instanceof TryMarker) {
188                          if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
189                          cx.stack.push(new FinallyData(curOP, curArg));
190                          cx.scope = ((TryMarker)o).scope;
191                          cx.pc = ((TryMarker)o).finallyLoc - 1;
192                          continue OUTER;
193                      }
194                      if (o instanceof LoopMarker) {
195                          if (curArg == null || curArg.equals(((LoopMarker)o).label)) {
196                              int loopInstructionLocation = ((LoopMarker)o).location;
197                              int endOfLoop = ((Integer)cx.currentCompiledFunction.arg[loopInstructionLocation]).intValue() + loopInstructionLocation;
198                              cx.scope = ((LoopMarker)o).scope;
199                              if (curOP == CONTINUE) { cx.stack.push(o); cx.stack.push(Boolean.FALSE); }
200                              cx.pc = curOP == BREAK ? endOfLoop - 1 : loopInstructionLocation;
201                              continue OUTER;
202                          }
203                      }
204                  }
205                  throw new Error("CONTINUE/BREAK invoked but couldn't find a LoopMarker at " + ((CompiledFunctionImpl)cx.currentCompiledFunction).sourceName + ":" + getLine(cx));
206  
207              case TRY: {
208                  int[] jmps = (int[]) curArg;
209                  // jmps[0] is how far away the catch block is, jmps[1] is how far away the finally block is
210                  // each can be < 0 if the specified block does not exist
211                  cx.stack.push(new TryMarker(jmps[0] < 0 ? -1 : cx.pc + jmps[0], jmps[1] < 0 ? -1 : cx.pc + jmps[1], cx.scope));
212                  break;
213              }
214  
215              case RETURN: {
216                  Object retval = cx.stack.pop();
217                  while(cx.stack.size() > 0) {
218                      Object o = cx.stack.pop();
219                      if (o instanceof TryMarker) {
220                          if(((TryMarker)o).finallyLoc < 0) continue;
221                          cx.stack.push(retval); 
222                          cx.stack.push(new FinallyData(RETURN));
223                          cx.scope = ((TryMarker)o).scope;
224                          cx.pc = ((TryMarker)o).finallyLoc - 1;
225                          continue OUTER;
226                      }
227                      if (o instanceof CallMarker) {
228                          cx.scope = ((CallMarker)o).scope;
229                          cx.pc = ((CallMarker)o).pc;
230                          cx.currentCompiledFunction = (CompiledFunction)((CallMarker)o).currentCompiledFunction;
231                          cx.stack.push(retval);
232                          continue OUTER;
233                      }
234                  }
235                  throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
236              }
237  
238              case PUT: {
239                  Object val = cx.stack.pop();
240                  Object key = cx.stack.pop();
241                  Object target = cx.stack.peek();
242                  if (target == null)
243                      throw je("tried to put a value to the " + key + " property on the null value");
244                  if (!(target instanceof JS))
245                      throw je("tried to put a value to the " + key + " property on a " + target.getClass().getName());
246                  if (key == null)
247                      throw je("tried to assign \"" + (val==null?"(null)":val.toString()) + "\" to the null key");
248                  ((JS)target).put(key, val);
249                  cx.stack.push(val);
250                  break;
251              }
252  
253              case GET:
254              case GET_PRESERVE: {
255                  ObjectObject
256                  if (curOP == GET) {
257                      v = curArg == null ? cx.stack.pop() : curArg;
258                      o = cx.stack.pop();
259                  } else {
260                      v = cx.stack.pop();
261                      o = cx.stack.peek();
262                      cx.stack.push(v);
263                  }
264                  Object ret = null;
265                  if (o == null) throw je("tried to get property \"" + v + "\" from the null value");
266                  if (v == null) throw je("tried to get the null key from " + o);
267                  if (o instanceof String || o instanceof Number || o instanceof Boolean)
268                      ret = Internal.getFromPrimitive(o,v);
269                  else if (o instanceof JS) {
270                      ret = ((JS)o).get(v);
271                  } else 
272                      throw je("tried to get property " + v + " from a " + o.getClass().getName());
273                  cx.stack.push(ret);
274                  break;
275              }
276              
277              case CALLMETHOD:
278              case CALL:
279              {
280                  JS.Array arguments = new JS.Array();
281                  int numArgs = JS.toNumber(curArg).intValue();
282                  arguments.setSize(numArgs);
283                  for(int j=numArgs - 1; j >= 0; j--) arguments.setElementAt(cx.stack.pop(), j);
284                  Object o = cx.stack.pop();
285                  if(o == null) throw je("attempted to call null");
286                  Object ret;
287                  if(curOP == CALLMETHOD) {
288                      Object method = o;
289                      o = cx.stack.pop();
290                      if(o instanceof String || o instanceof Number || o instanceof Boolean) {
291                          ret = Internal.callMethodOnPrimitive(o,method,arguments);
292                          cx.stack.push(ret);
293                          break;
294                      } else if (o instanceof JS) {
295                          if (((JS)o).callMethod(method, arguments, true) == Boolean.TRUE) {
296                              ret = ((JS)o).callMethod(method,arguments,false);
297                              cx.stack.push(ret);
298                              break;
299                          } else {
300                              o = ((JS)o).get(method);
301                          }
302                      } else {
303                          throw new JS.Exn("Tried to call a method on an object that isn't a JS object: " + o);
304                      }
305                  }
306  
307                  if (o instanceof CompiledFunctionImpl) {
308                      cx.stack.push(new CallMarker(cx));
309                      cx.stack.push(arguments);
310                      cx.currentCompiledFunction = (CompiledFunction)o;
311                      cx.scope = new FunctionScope("unknown", cx.currentCompiledFunction.parentScope);
312                      cx.pc = -1;
313                      break;
314                      
315                  } else {
316                      ret = ((JS.Callable)o).call(arguments);
317                  }
318                  cx.stack.push(ret);
319                  break;
320              }
321              // fall through if exception was thrown
322              case THROW: {
323                  Object o = cx.stack.pop();
324                  if(o instanceof JS.Exn) throw (JS.Exn)o;
325                  throw new JS.Exn(o);
326              }
327  
328              case INC: case DEC: {
329                  boolean isPrefix = JS.toBoolean(curArg);
330                  Object key = cx.stack.pop();
331                  JS obj = (JS)cx.stack.pop();
332                  Number num = JS.toNumber(obj.get(key));
333                  Number val = new Double(curOP == INC ? num.doubleValue() + 1.0 : num.doubleValue() - 1.0);
334                  obj.put(key, val);
335                  cx.stack.push(isPrefix ? val : num);
336                  break;
337              }
338              
339              case ASSIGN_SUB: case ASSIGN_ADD: {
340                  Object val = cx.stack.pop();
341                  Object old = cx.stack.pop();
342                  Object key = cx.stack.pop();
343                  Object obj = cx.stack.peek();
344                  if (val instanceof CompiledFunction) {
345                      if (obj instanceof JS.Scope) {
346                          JS.Scope parent = (JS.Scope)obj;
347                          while(parent.getParentScope() != null) parent = parent.getParentScope();
348                          if (parent instanceof org.xwt.Box) {
349                              if (curOP == ASSIGN_ADD) {
350                                  ((org.xwt.Box)parent).addTrap(key, val);
351                              } else {
352                                  ((org.xwt.Box)parent).delTrap(key, val);
353                              }
354                              // skip over the "normal" implementation of +=/-=
355                              cx.pc += ((Integer)curArg).intValue() - 1;
356                              break;
357                          }
358                      }
359                  }
360                  // use the "normal" implementation
361                  cx.stack.push(key);
362                  cx.stack.push(old);
363                  cx.stack.push(val);
364                  break;
365              }
366  
367              case ADD: {
368                  int count = ((Number)curArg).intValue();
369                  if(count < 2) throw new Error("this should never happen");
370                  if(count == 2) {
371                      // common case
372                      Object right = cx.stack.pop();
373                      Object left = cx.stack.pop();
374                      if(left instanceof String || right instanceof String) cx.stack.push(JS.toString(left).concat(JS.toString(right)));
375                      else cx.stack.push(new Double(JS.toDouble(left) + JS.toDouble(right)));
376                  } else {
377                      Object[] args = new Object[count];
378                      while(--count >= 0) args[count] = cx.stack.pop();
379                      if(args[0] instanceof String) {
380                          StringBuffer sb = new StringBuffer(64);
381                          for(int i=0;i<args.length;i++) sb.append(JS.toString(args[i]));
382                          cx.stack.push(sb.toString());
383                      } else {
384                          int numStrings = 0;
385                          for(int i=0;i<args.length;i++) if(args[i] instanceof String) numStrings++;
386                          if(numStrings == 0) {
387                              double d = 0.0;
388                              for(int i=0;i<args.length;i++) d += JS.toDouble(args[i]);
389                              cx.stack.push(new Double(d));
390                          } else {
391                              int i=0;
392                              StringBuffer sb = new StringBuffer(64);
393                              if(!(args[0] instanceof String || args[1] instanceof String)) {
394                                  double d=0.0;
395                                  do {
396                                      d += JS.toDouble(args[i++]);
397                                  } while(!(args[i] instanceof String));
398                                  sb.append(JS.toString(new Double(d)));
399                              }
400                              while(i < args.length) sb.append(JS.toString(args[i++]));
401                              cx.stack.push(sb.toString());
402                          }
403                      }
404                  }
405                  break;
406              }
407  
408              default: {
409                  Object right = cx.stack.pop();
410                  Object left = cx.stack.pop();
411                  switch(curOP) {
412                          
413                  case BITOR: cx.stack.push(new Long(JS.toLong(left) | JS.toLong(right))); break;
414                  case BITXOR: cx.stack.push(new Long(JS.toLong(left) ^ JS.toLong(right))); break;
415                  case BITAND: cx.stack.push(new Long(JS.toLong(left) & JS.toLong(right))); break;
416  
417                  case SUB: cx.stack.push(new Double(JS.toDouble(left) - JS.toDouble(right))); break;
418                  case MUL: cx.stack.push(new Double(JS.toDouble(left) * JS.toDouble(right))); break;
419                  case DIV: cx.stack.push(new Double(JS.toDouble(left) / JS.toDouble(right))); break;
420                  case MOD: cx.stack.push(new Double(JS.toDouble(left) % JS.toDouble(right))); break;
421                          
422                  case LSH: cx.stack.push(new Long(JS.toLong(left) << JS.toLong(right))); break;
423                  case RSH: cx.stack.push(new Long(JS.toLong(left) >> JS.toLong(right))); break;
424                  case URSH: cx.stack.push(new Long(JS.toLong(left) >>> JS.toLong(right))); break;
425                          
426                  case LT: case LE: case GT: case GE: {
427                      if (left == null) left = new Integer(0);
428                      if (right == null) right = new Integer(0);
429                      int result = 0;
430                      if (left instanceof String || right instanceof String) {
431                          result = left.toString().compareTo(right.toString());
432                      } else {
433                          result = (int)java.lang.Math.ceil(JS.toDouble(left) - JS.toDouble(right));
434                      }
435                      cx.stack.push(new Boolean((curOP == LT && result < 0) || (curOP == LE && result <= 0) ||
436                                         (curOP == GT && result > 0) || (curOP == GE && result >= 0)));
437                      break;
438                  }
439                      
440                  case EQ:
441                  case NE: {
442                      Object l = left;
443                      Object r = right;
444                      boolean ret;
445                      if (l == null) { Object tmp = r; r = l; l = tmp; }
446                      if (l == null && r == null) ret = true;
447                      else if (r == null) ret = false; // l != null, so its false
448                      else if (l instanceof Boolean) ret = new Boolean(JS.toBoolean(r)).equals(l);
449                      else if (l instanceof Number) ret = JS.toNumber(r).doubleValue() == JS.toNumber(l).doubleValue();
450                      else if (l instanceof String) ret = r != null && l.equals(r.toString());
451                      else ret = l.equals(r);
452                      cx.stack.push(new Boolean(curOP == EQ ? ret : !ret)); break;
453                  }
454  
455                  default: throw new Error("unknown opcode " + curOP);
456                  } }
457              }
458          } catch(JS.Exn e) {
459              while(cx.stack.size() > 0) {
460                  Object o = cx.stack.pop();
461                  if (o instanceof CatchMarker || o instanceof TryMarker) {
462                      boolean inCatch = o instanceof CatchMarker;
463                      if(inCatch) {
464                          o = cx.stack.pop();
465                          if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
466                      }
467                      if(!inCatch && ((TryMarker)o).catchLoc >= 0) {
468                          // run the catch block, this will implicitly run the finally block, if it exists
469                          cx.stack.push(o);
470                          cx.stack.push(catchMarker);
471                          cx.stack.push(e.getObject());
472                          cx.scope = ((TryMarker)o).scope;
473                          cx.pc = ((TryMarker)o).catchLoc - 1;
474                          continue OUTER;
475                      } else {
476                          cx.stack.push(e);
477                          cx.stack.push(new FinallyData(THROW));
478                          cx.scope = ((TryMarker)o).scope;
479                          cx.pc = ((TryMarker)o).finallyLoc - 1;
480                          continue OUTER;
481                      }
482                  }
483                  // no handler found within this func
484                  if(o instanceof CallMarker) throw e;
485              }
486              throw e;
487          } // end try/catch
488          } // end for
489      }
490  
491      // Debugging //////////////////////////////////////////////////////////////////////
492  
493      public String toString() {
494          StringBuffer sb = new StringBuffer(1024);
495          sb.append("\n" + sourceName + ": " + firstLine + "\n");
496          for (int i=0; i < size; i++) {
497              sb.append(i);
498              sb.append(": ");
499              if (op[i] < 0)
500                  sb.append(bytecodeToString[-op[i]]);
501              else
502                  sb.append(codeToString[op[i]]);
503              sb.append(" ");
504              sb.append(arg[i] == null ? "(no arg)" : arg[i]);
505              if((op[i] == JF || op[i] == JT || op[i] == JMP) && arg[i] != null && arg[i] instanceof Number) {
506                  sb.append(" jump to ").append(i+((Number) arg[i]).intValue());
507              } else  if(op[i] == TRY) {
508                  int[] jmps = (int[]) arg[i];
509                  sb.append(" catch: ").append(jmps[0] < 0 ? "No catch block" : ""+(i+jmps[0]));
510                  sb.append(" finally: ").append(jmps[1] < 0 ? "No finally block" : ""+(i+jmps[1]));
511              }
512              sb.append("\n");
513          }
514          return sb.toString();
515      } 
516  
517      // Exception Stuff ////////////////////////////////////////////////////////////////
518  
519      static class EvaluatorException extends RuntimeException { public EvaluatorException(String s) { super(s); } }
520      static EvaluatorException ee(String s) { throw new EvaluatorException(((CompiledFunctionImpl)(JS.Thread.current()).currentCompiledFunction).sourceName + ":" + JS.Thread.current().getLine() + " " + s); }
521      static JS.Exn je(String s) { throw new JS.Exn(((CompiledFunctionImpl)(JS.Thread.current()).currentCompiledFunction).sourceName + ":" + JS.Thread.current().getLine() + " " + s); }
522  
523  
524      // FunctionScope /////////////////////////////////////////////////////////////////
525  
526      static class FunctionScope extends JS.Scope {
527          String sourceName;
528          public FunctionScope(String sourceName, Scope parentScope) { super(parentScope); this.sourceName = sourceName; }
529          public String getSourceName() { return sourceName; }
530      }
531  
532  
533      // Markers //////////////////////////////////////////////////////////////////////
534  
535      public static class CallMarker {
536          int pc;
537          Scope scope;
538          CompiledFunctionImpl currentCompiledFunction;
539          public CallMarker(JS.Thread cx) { pc = cx.pc + 1; scope = cx.scope; currentCompiledFunction = cx.currentCompiledFunction; }
540      }
541      
542      public static class CatchMarker { public CatchMarker() { } }
543      private static CatchMarker catchMarker = new CatchMarker();
544      
545      public static class LoopMarker {
546          public int location;
547          public String label;
548          public JS.Scope scope;
549          public LoopMarker(int location, String label, JS.Scope scope) {
550              this.location = location;
551              this.label = label;
552              this.scope = scope;
553          }
554      }
555      public static class TryMarker {
556          public int catchLoc;
557          public int finallyLoc;
558          public JS.Scope scope;
559          public TryMarker(int catchLoc, int finallyLoc, JS.Scope scope) {
560              this.catchLoc = catchLoc;
561              this.finallyLoc = finallyLoc;
562              this.scope = scope;
563          }
564      }
565      public static class FinallyData {
566          public int op;
567          public Object arg;
568          public FinallyData(int op, Object arg) { this.op = op; this.arg = arg; }
569          public FinallyData(int op) { this(op,null); }
570      }
571  }
572  
573  /** this class exists solely to work around a GCJ bug */
574  abstract class JSCallable extends JS.Callable {
575          public abstract Object call(JS.Array args) throws JS.Exn;
576  }
577