mcs/mcs/flowanalysis.cs

   1 //
   2 // flowanalyis.cs: The control flow analysis code
   3 //
   4 // Author:
   5 //   Martin Baulig (martin@ximian.com)
   6 //   Raja R Harinath (rharinath@novell.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 using System;
  12 using System.Text;
  13 using System.Collections;
  14 using System.Reflection;
  15 using System.Reflection.Emit;
  16 using System.Diagnostics;
  17
  18 namespace Mono.CSharp
  19 {
  20         // <summary>
  21         //   A new instance of this class is created every time a new block is resolved
  22         //   and if there's branching in the block's control flow.
  23         // </summary>
  24         public abstract class FlowBranching
  25         {
  26                 // <summary>
  27                 //   The type of a FlowBranching.
  28                 // </summary>
  29                 public enum BranchingType : byte {
  30                         // Normal (conditional or toplevel) block.
  31                         Block,
  32
  33                         // Conditional.
  34                         Conditional,
  35
  36                         // A loop block.
  37                         Loop,
  38
  39                         // The statement embedded inside a loop
  40                         Embedded,
  41
  42                         // part of a block headed by a jump target
  43                         Labeled,
  44
  45                         // Try/Catch block.
  46                         Exception,
  47
  48                         // Switch block.
  49                         Switch,
  50
  51                         // Switch section.
  52                         SwitchSection,
  53
  54                         // The toplevel block of a function
  55                         Toplevel
  56                 }
  57
  58                 // <summary>
  59                 //   The type of one sibling of a branching.
  60                 // </summary>
  61                 public enum SiblingType : byte {
  62                         Block,
  63                         Conditional,
  64                         SwitchSection,
  65                         Try,
  66                         Catch,
  67                         Finally
  68                 }
  69
  70                 public static FlowBranching CreateBranching (FlowBranching parent, BranchingType type, Block block, Location loc)
  71                 {
  72                         switch (type) {
  73                         case BranchingType.Exception:
  74                         case BranchingType.Labeled:
  75                         case BranchingType.Toplevel:
  76                                 throw new InvalidOperationException ();
  77
  78                         case BranchingType.Switch:
  79                                 return new FlowBranchingBreakable (parent, type, SiblingType.SwitchSection, block, loc);
  80
  81                         case BranchingType.SwitchSection:
  82                                 return new FlowBranchingBlock (parent, type, SiblingType.Block, block, loc);
  83
  84                         case BranchingType.Block:
  85                                 return new FlowBranchingBlock (parent, type, SiblingType.Block, block, loc);
  86
  87                         case BranchingType.Loop:
  88                                 return new FlowBranchingBreakable (parent, type, SiblingType.Conditional, block, loc);
  89
  90                         case BranchingType.Embedded:
  91                                 return new FlowBranchingContinuable (parent, type, SiblingType.Conditional, block, loc);
  92
  93                         default:
  94                                 return new FlowBranchingBlock (parent, type, SiblingType.Conditional, block, loc);
  95                         }
  96                 }
  97
  98                 // <summary>
  99                 //   The type of this flow branching.
 100                 // </summary>
 101                 public readonly BranchingType Type;
 102
 103                 // <summary>
 104                 //   The block this branching is contained in.  This may be null if it's not
 105                 //   a top-level block and it doesn't declare any local variables.
 106                 // </summary>
 107                 public readonly Block Block;
 108
 109                 // <summary>
 110                 //   The parent of this branching or null if this is the top-block.
 111                 // </summary>
 112                 public readonly FlowBranching Parent;
 113
 114                 // <summary>
 115                 //   Start-Location of this flow branching.
 116                 // </summary>
 117                 public readonly Location Location;
 118
 119                 static int next_id = 0;
 120                 int id;
 121
 122                 // <summary>
 123                 //   The vector contains a BitArray with information about which local variables
 124                 //   and parameters are already initialized at the current code position.
 125                 // </summary>
 126                 public class UsageVector {
 127                         // <summary>
 128                         //   The type of this branching.
 129                         // </summary>
 130                         public readonly SiblingType Type;
 131
 132                         // <summary>
 133                         //   Start location of this branching.
 134                         // </summary>
 135                         public Location Location;
 136
 137                         // <summary>
 138                         //   This is only valid for SwitchSection, Try, Catch and Finally.
 139                         // </summary>
 140                         public readonly Block Block;
 141
 142                         // <summary>
 143                         //   The number of locals in this block.
 144                         // </summary>
 145                         public readonly int CountLocals;
 146
 147                         // <summary>
 148                         //   If not null, then we inherit our state from this vector and do a
 149                         //   copy-on-write.  If null, then we're the first sibling in a top-level
 150                         //   block and inherit from the empty vector.
 151                         // </summary>
 152                         public readonly UsageVector InheritsFrom;
 153
 154                         // <summary>
 155                         //   This is used to construct a list of UsageVector's.
 156                         // </summary>
 157                         public UsageVector Next;
 158
 159                         //
 160                         // Private.
 161                         //
 162                         MyBitVector locals;
 163                         bool is_unreachable;
 164
 165                         static int next_id = 0;
 166                         int id;
 167
 168                         //
 169                         // Normally, you should not use any of these constructors.
 170                         //
 171                         public UsageVector (SiblingType type, UsageVector parent, Block block, Location loc, int num_locals)
 172                         {
 173                                 this.Type = type;
 174                                 this.Block = block;
 175                                 this.Location = loc;
 176                                 this.InheritsFrom = parent;
 177                                 this.CountLocals = num_locals;
 178
 179                                 locals = num_locals == 0
 180                                         ? MyBitVector.Empty
 181                                         : new MyBitVector (parent == null ? MyBitVector.Empty : parent.locals, num_locals);
 182
 183                                 if (parent != null)
 184                                         is_unreachable = parent.is_unreachable;
 185
 186                                 id = ++next_id;
 187
 188                         }
 189
 190                         public UsageVector (SiblingType type, UsageVector parent, Block block, Location loc)
 191                                 : this (type, parent, block, loc, parent.CountLocals)
 192                         { }
 193
 194                         private UsageVector (MyBitVector locals, bool is_unreachable, Block block, Location loc)
 195                         {
 196                                 this.Type = SiblingType.Block;
 197                                 this.Location = loc;
 198                                 this.Block = block;
 199
 200                                 this.is_unreachable = is_unreachable;
 201
 202                                 this.locals = locals;
 203
 204                                 id = ++next_id;
 205
 206                         }
 207
 208                         // <summary>
 209                         //   This does a deep copy of the usage vector.
 210                         // </summary>
 211                         public UsageVector Clone ()
 212                         {
 213                                 UsageVector retval = new UsageVector (Type, null, Block, Location, CountLocals);
 214
 215                                 retval.locals = locals.Clone ();
 216                                 retval.is_unreachable = is_unreachable;
 217
 218                                 return retval;
 219                         }
 220
 221                         public bool IsAssigned (VariableInfo var, bool ignoreReachability)
 222                         {
 223                                 if (!ignoreReachability && !var.IsParameter && IsUnreachable)
 224                                         return true;
 225
 226                                 return var.IsAssigned (locals);
 227                         }
 228
 229                         public void SetAssigned (VariableInfo var)
 230                         {
 231                                 if (!var.IsParameter && IsUnreachable)
 232                                         return;
 233
 234                                 var.SetAssigned (locals);
 235                         }
 236
 237                         public bool IsFieldAssigned (VariableInfo var, string name)
 238                         {
 239                                 if (!var.IsParameter && IsUnreachable)
 240                                         return true;
 241
 242                                 return var.IsFieldAssigned (locals, name);
 243                         }
 244
 245                         public void SetFieldAssigned (VariableInfo var, string name)
 246                         {
 247                                 if (!var.IsParameter && IsUnreachable)
 248                                         return;
 249
 250                                 var.SetFieldAssigned (locals, name);
 251                         }
 252
 253                         public bool IsUnreachable {
 254                                 get { return is_unreachable; }
 255                         }
 256
 257                         public void ResetBarrier ()
 258                         {
 259                                 is_unreachable = false;
 260                         }
 261
 262                         public void Goto ()
 263                         {
 264                                 is_unreachable = true;
 265                         }
 266
 267                         public static UsageVector MergeSiblings (UsageVector sibling_list, Location loc)
 268                         {
 269                                 if (sibling_list.Next == null)
 270                                         return sibling_list;
 271
 272                                 MyBitVector locals = null;
 273                                 bool is_unreachable = sibling_list.is_unreachable;
 274
 275                                 if (!sibling_list.IsUnreachable)
 276                                         locals &= sibling_list.locals;
 277
 278                                 for (UsageVector child = sibling_list.Next; child != null; child = child.Next) {
 279                                         is_unreachable &= child.is_unreachable;
 280
 281                                         if (!child.IsUnreachable)
 282                                                 locals &= child.locals;
 283                                 }
 284
 285                                 return new UsageVector (locals, is_unreachable, null, loc);
 286                         }
 287
 288                         // <summary>
 289                         //   Merges a child branching.
 290                         // </summary>
 291                         public UsageVector MergeChild (UsageVector child, bool overwrite)
 292                         {
 293                                 Report.Debug (2, "    MERGING CHILD EFFECTS", this, child, Type);
 294
 295                                 bool new_isunr = child.is_unreachable;
 296
 297                                 //
 298                                 // We've now either reached the point after the branching or we will
 299                                 // never get there since we always return or always throw an exception.
 300                                 //
 301                                 // If we can reach the point after the branching, mark all locals and
 302                                 // parameters as initialized which have been initialized in all branches
 303                                 // we need to look at (see above).
 304                                 //
 305
 306                                 if ((Type == SiblingType.SwitchSection) && !new_isunr) {
 307                                         Report.Error (163, Location,
 308                                                       "Control cannot fall through from one " +
 309                                                       "case label to another");
 310                                         return child;
 311                                 }
 312
 313                                 locals |= child.locals;
 314
 315                                 if (overwrite)
 316                                         is_unreachable = new_isunr;
 317                                 else
 318                                         is_unreachable |= new_isunr;
 319
 320                                 return child;
 321                         }
 322
 323                         public void MergeOrigins (UsageVector o_vectors)
 324                         {
 325                                 Report.Debug (1, "  MERGING BREAK ORIGINS", this);
 326
 327                                 if (o_vectors == null)
 328                                         return;
 329
 330                                 if (IsUnreachable && locals != null)
 331                                         locals.SetAll (true);
 332
 333                                 for (UsageVector vector = o_vectors; vector != null; vector = vector.Next) {
 334                                         Report.Debug (1, "    MERGING BREAK ORIGIN", vector);
 335                                         if (vector.IsUnreachable)
 336                                                 continue;
 337                                         locals &= vector.locals;
 338                                         is_unreachable &= vector.is_unreachable;
 339                                 }
 340
 341                                 Report.Debug (1, "  MERGING BREAK ORIGINS DONE", this);
 342                         }
 343
 344                         //
 345                         // Debugging stuff.
 346                         //
 347
 348                         public override string ToString ()
 349                         {
 350                                 return String.Format ("Vector ({0},{1},{2}-{3})", Type, id, is_unreachable, locals);
 351                         }
 352                 }
 353
 354                 // <summary>
 355                 //   Creates a new flow branching which is contained in `parent'.
 356                 //   You should only pass non-null for the `block' argument if this block
 357                 //   introduces any new variables - in this case, we need to create a new
 358                 //   usage vector with a different size than our parent's one.
 359                 // </summary>
 360                 protected FlowBranching (FlowBranching parent, BranchingType type, SiblingType stype,
 361                                          Block block, Location loc)
 362                 {
 363                         Parent = parent;
 364                         Block = block;
 365                         Location = loc;
 366                         Type = type;
 367                         id = ++next_id;
 368
 369                         UsageVector vector;
 370                         if (Block != null) {
 371                                 UsageVector parent_vector = parent != null ? parent.CurrentUsageVector : null;
 372                                 vector = new UsageVector (stype, parent_vector, Block, loc, Block.AssignableSlots);
 373                         } else {
 374                                 vector = new UsageVector (stype, Parent.CurrentUsageVector, null, loc);
 375                         }
 376
 377                         AddSibling (vector);
 378                 }
 379
 380                 public abstract UsageVector CurrentUsageVector {
 381                         get;
 382                 }
 383
 384                 // <summary>
 385                 //   Creates a sibling of the current usage vector.
 386                 // </summary>
 387                 public virtual void CreateSibling (Block block, SiblingType type)
 388                 {
 389                         UsageVector vector = new UsageVector (
 390                                 type, Parent.CurrentUsageVector, block, Location);
 391                         AddSibling (vector);
 392
 393                         Report.Debug (1, "  CREATED SIBLING", CurrentUsageVector);
 394                 }
 395
 396                 public void CreateSibling ()
 397                 {
 398                         CreateSibling (null, SiblingType.Conditional);
 399                 }
 400
 401                 protected abstract void AddSibling (UsageVector uv);
 402
 403                 protected abstract UsageVector Merge ();
 404
 405                 // <summary>
 406                 //   Merge a child branching.
 407                 // </summary>
 408                 public UsageVector MergeChild (FlowBranching child)
 409                 {
 410                         bool overwrite = false;
 411
 412                         switch (child.Type) {
 413                         case BranchingType.Labeled:
 414                                 overwrite = true;
 415                                 break;
 416                         case BranchingType.Block:
 417                                 if (child.Block != null && child.Block != child.Block.Explicit)
 418                                         overwrite = true;
 419                                 break;
 420                         }
 421
 422                         Report.Debug (2, "  MERGING CHILD", this, child);
 423                         UsageVector result = CurrentUsageVector.MergeChild (child.Merge (), overwrite);
 424                         Report.Debug (2, "  MERGING CHILD DONE", this, result);
 425                         return result;
 426                 }
 427
 428                 public virtual bool InTryWithCatch ()
 429                 {
 430                         return Parent.InTryWithCatch ();
 431                 }
 432
 433                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 434                 public virtual bool AddBreakOrigin (UsageVector vector, Location loc)
 435                 {
 436                         return Parent.AddBreakOrigin (vector, loc);
 437                 }
 438
 439                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 440                 public virtual bool AddContinueOrigin (UsageVector vector, Location loc)
 441                 {
 442                         return Parent.AddContinueOrigin (vector, loc);
 443                 }
 444
 445                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 446                 public virtual bool AddReturnOrigin (UsageVector vector, Location loc)
 447                 {
 448                         return Parent.AddReturnOrigin (vector, loc);
 449                 }
 450
 451                 // returns true if we crossed an unwind-protected region (try/catch/finally, lock, using, ...)
 452                 public virtual bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 453                 {
 454                         return Parent.AddGotoOrigin (vector, goto_stmt);
 455                 }
 456
 457                 public virtual void StealFinallyClauses (ref ArrayList list)
 458                 {
 459                         Parent.StealFinallyClauses (ref list);
 460                 }
 461
 462                 public bool IsAssigned (VariableInfo vi)
 463                 {
 464                         return CurrentUsageVector.IsAssigned (vi, false);
 465                 }
 466
 467                 public bool IsFieldAssigned (VariableInfo vi, string field_name)
 468                 {
 469                         return CurrentUsageVector.IsAssigned (vi, false) || CurrentUsageVector.IsFieldAssigned (vi, field_name);
 470                 }
 471
 472                 public void SetAssigned (VariableInfo vi)
 473                 {
 474                         CurrentUsageVector.SetAssigned (vi);
 475                 }
 476
 477                 public void SetFieldAssigned (VariableInfo vi, string name)
 478                 {
 479                         CurrentUsageVector.SetFieldAssigned (vi, name);
 480                 }
 481
 482                 public override string ToString ()
 483                 {
 484                         StringBuilder sb = new StringBuilder ();
 485                         sb.Append (GetType ());
 486                         sb.Append (" (");
 487
 488                         sb.Append (id);
 489                         sb.Append (",");
 490                         sb.Append (Type);
 491                         if (Block != null) {
 492                                 sb.Append (" - ");
 493                                 sb.Append (Block.ID);
 494                                 sb.Append (" - ");
 495                                 sb.Append (Block.StartLocation);
 496                         }
 497                         sb.Append (" - ");
 498                         // sb.Append (Siblings.Length);
 499                         // sb.Append (" - ");
 500                         sb.Append (CurrentUsageVector);
 501                         sb.Append (")");
 502                         return sb.ToString ();
 503                 }
 504
 505                 public string Name {
 506                         get { return String.Format ("{0} ({1}:{2}:{3})", GetType (), id, Type, Location); }
 507                 }
 508         }
 509
 510         public class FlowBranchingBlock : FlowBranching
 511         {
 512                 UsageVector sibling_list = null;
 513
 514                 public FlowBranchingBlock (FlowBranching parent, BranchingType type,
 515                                            SiblingType stype, Block block, Location loc)
 516                         : base (parent, type, stype, block, loc)
 517                 { }
 518
 519                 public override UsageVector CurrentUsageVector {
 520                         get { return sibling_list; }
 521                 }
 522
 523                 protected override void AddSibling (UsageVector sibling)
 524                 {
 525                         sibling.Next = sibling_list;
 526                         sibling_list = sibling;
 527                 }
 528
 529                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 530                 {
 531                         LabeledStatement stmt = Block == null ? null : Block.LookupLabel (goto_stmt.Target);
 532                         if (stmt == null)
 533                                 return Parent.AddGotoOrigin (vector, goto_stmt);
 534
 535                         // forward jump
 536                         goto_stmt.SetResolvedTarget (stmt);
 537                         stmt.AddUsageVector (vector);
 538                         return false;
 539                 }
 540
 541                 public static void Error_UnknownLabel (Location loc, string label)
 542                 {
 543                         Report.Error(159, loc, "The label `{0}:' could not be found within the scope of the goto statement",
 544                                 label);
 545                 }
 546
 547                 protected override UsageVector Merge ()
 548                 {
 549                         Report.Debug (2, "  MERGING SIBLINGS", Name);
 550                         UsageVector vector = UsageVector.MergeSiblings (sibling_list, Location);
 551                         Report.Debug (2, "  MERGING SIBLINGS DONE", Name, vector);
 552                         return vector;
 553                 }
 554         }
 555
 556         public class FlowBranchingBreakable : FlowBranchingBlock
 557         {
 558                 UsageVector break_origins;
 559
 560                 public FlowBranchingBreakable (FlowBranching parent, BranchingType type, SiblingType stype, Block block, Location loc)
 561                         : base (parent, type, stype, block, loc)
 562                 { }
 563
 564                 public override bool AddBreakOrigin (UsageVector vector, Location loc)
 565                 {
 566                         vector = vector.Clone ();
 567                         vector.Next = break_origins;
 568                         break_origins = vector;
 569                         return false;
 570                 }
 571
 572                 protected override UsageVector Merge ()
 573                 {
 574                         UsageVector vector = base.Merge ();
 575                         vector.MergeOrigins (break_origins);
 576                         return vector;
 577                 }
 578         }
 579
 580         public class FlowBranchingContinuable : FlowBranchingBlock
 581         {
 582                 UsageVector continue_origins;
 583
 584                 public FlowBranchingContinuable (FlowBranching parent, BranchingType type, SiblingType stype, Block block, Location loc)
 585                         : base (parent, type, stype, block, loc)
 586                 { }
 587
 588                 public override bool AddContinueOrigin (UsageVector vector, Location loc)
 589                 {
 590                         vector = vector.Clone ();
 591                         vector.Next = continue_origins;
 592                         continue_origins = vector;
 593                         return false;
 594                 }
 595
 596                 protected override UsageVector Merge ()
 597                 {
 598                         UsageVector vector = base.Merge ();
 599                         vector.MergeOrigins (continue_origins);
 600                         return vector;
 601                 }
 602         }
 603
 604         public class FlowBranchingLabeled : FlowBranchingBlock
 605         {
 606                 LabeledStatement stmt;
 607                 UsageVector actual;
 608
 609                 public FlowBranchingLabeled (FlowBranching parent, LabeledStatement stmt)
 610                         : base (parent, BranchingType.Labeled, SiblingType.Conditional, null, stmt.loc)
 611                 {
 612                         this.stmt = stmt;
 613                         CurrentUsageVector.MergeOrigins (stmt.JumpOrigins);
 614                         actual = CurrentUsageVector.Clone ();
 615
 616                         // stand-in for backward jumps
 617                         CurrentUsageVector.ResetBarrier ();
 618                 }
 619
 620                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 621                 {
 622                         if (goto_stmt.Target != stmt.Name)
 623                                 return Parent.AddGotoOrigin (vector, goto_stmt);
 624
 625                         // backward jump
 626                         goto_stmt.SetResolvedTarget (stmt);
 627                         actual.MergeOrigins (vector.Clone ());
 628
 629                         return false;
 630                 }
 631
 632                 protected override UsageVector Merge ()
 633                 {
 634                         UsageVector vector = base.Merge ();
 635
 636                         if (actual.IsUnreachable)
 637                                 Report.Warning (162, 2, stmt.loc, "Unreachable code detected");
 638
 639                         actual.MergeChild (vector, false);
 640                         return actual;
 641                 }
 642         }
 643
 644         public class FlowBranchingToplevel : FlowBranchingBlock
 645         {
 646                 UsageVector return_origins;
 647
 648                 public FlowBranchingToplevel (FlowBranching parent, ToplevelBlock stmt)
 649                         : base (parent, BranchingType.Toplevel, SiblingType.Conditional, stmt, stmt.loc)
 650                 {
 651                 }
 652
 653                 // <summary>
 654                 //   Check whether all `out' parameters have been assigned.
 655                 // </summary>
 656                 void CheckOutParameters (UsageVector vector, Location loc)
 657                 {
 658                         if (vector.IsUnreachable)
 659                                 return;
 660                         VariableInfo [] param_map = Block.Toplevel.ParameterMap;
 661                         if (param_map == null)
 662                                 return;
 663                         for (int i = 0; i < param_map.Length; i++) {
 664                                 VariableInfo var = param_map [i];
 665
 666                                 if (var == null)
 667                                         continue;
 668
 669                                 if (vector.IsAssigned (var, false))
 670                                         continue;
 671
 672                                 Report.Error (177, loc, "The out parameter `{0}' must be assigned to before control leaves the current method",
 673                                         var.Name);
 674                         }
 675                 }
 676
 677                 public override bool InTryWithCatch ()
 678                 {
 679                         return false;
 680                 }
 681
 682                 public override bool AddBreakOrigin (UsageVector vector, Location loc)
 683                 {
 684                         Report.Error (139, loc, "No enclosing loop out of which to break or continue");
 685                         return false;
 686                 }
 687
 688                 public override bool AddContinueOrigin (UsageVector vector, Location loc)
 689                 {
 690                         Report.Error (139, loc, "No enclosing loop out of which to break or continue");
 691                         return false;
 692                 }
 693
 694                 public override bool AddReturnOrigin (UsageVector vector, Location loc)
 695                 {
 696                         vector = vector.Clone ();
 697                         vector.Location = loc;
 698                         vector.Next = return_origins;
 699                         return_origins = vector;
 700                         return false;
 701                 }
 702
 703                 public override void StealFinallyClauses (ref ArrayList list)
 704                 {
 705                         // nothing to do
 706                 }
 707
 708                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 709                 {
 710                         string name = goto_stmt.Target;
 711                         LabeledStatement s = Block.LookupLabel (name);
 712                         if (s != null)
 713                                 throw new InternalErrorException ("Shouldn't get here");
 714
 715                         if (Parent == null) {
 716                                 Error_UnknownLabel (goto_stmt.loc, name);
 717                                 return false;
 718                         }
 719
 720                         int errors = Report.Errors;
 721                         Parent.AddGotoOrigin (vector, goto_stmt);
 722                         if (errors == Report.Errors)
 723                                 Report.Error (1632, goto_stmt.loc, "Control cannot leave the body of an anonymous method");
 724                         return false;
 725                 }
 726
 727                 protected override UsageVector Merge ()
 728                 {
 729                         for (UsageVector origin = return_origins; origin != null; origin = origin.Next)
 730                                 CheckOutParameters (origin, origin.Location);
 731
 732                         UsageVector vector = base.Merge ();
 733                         CheckOutParameters (vector, Block.loc);
 734                         // Note: we _do_not_ merge in the return origins
 735                         return vector;
 736                 }
 737
 738                 public bool End ()
 739                 {
 740                         return Merge ().IsUnreachable;
 741                 }
 742         }
 743
 744         public class FlowBranchingException : FlowBranching
 745         {
 746                 ExceptionStatement stmt;
 747                 UsageVector current_vector;
 748                 UsageVector catch_vectors;
 749                 UsageVector finally_vector;
 750
 751                 UsageVector break_origins;
 752                 UsageVector continue_origins;
 753                 UsageVector return_origins;
 754                 GotoOrigin goto_origins;
 755
 756                 class GotoOrigin {
 757                         public GotoOrigin Next;
 758                         public Goto GotoStmt;
 759                         public UsageVector Vector;
 760
 761                         public GotoOrigin (UsageVector vector, Goto goto_stmt, GotoOrigin next)
 762                         {
 763                                 Vector = vector;
 764                                 GotoStmt = goto_stmt;
 765                                 Next = next;
 766                         }
 767                 }
 768
 769                 bool emit_finally;
 770
 771                 public FlowBranchingException (FlowBranching parent,
 772                                                ExceptionStatement stmt)
 773                         : base (parent, BranchingType.Exception, SiblingType.Try,
 774                                 null, stmt.loc)
 775                 {
 776                         this.stmt = stmt;
 777                         this.emit_finally = true;
 778                 }
 779
 780                 protected override void AddSibling (UsageVector sibling)
 781                 {
 782                         switch (sibling.Type) {
 783                         case SiblingType.Try:
 784                         case SiblingType.Catch:
 785                                 sibling.Next = catch_vectors;
 786                                 catch_vectors = sibling;
 787                                 break;
 788                         case SiblingType.Finally:
 789                                 finally_vector = sibling;
 790                                 break;
 791                         default:
 792                                 throw new InvalidOperationException ();
 793                         }
 794                         current_vector = sibling;
 795                 }
 796
 797                 public override UsageVector CurrentUsageVector {
 798                         get { return current_vector; }
 799                 }
 800
 801                 public override bool InTryWithCatch ()
 802                 {
 803                         if (finally_vector == null) {
 804                                 Try t = stmt as Try;
 805                                 if (t != null && t.HasCatch)
 806                                         return true;
 807                         }
 808
 809                         return base.InTryWithCatch ();
 810                 }
 811
 812                 public override bool AddBreakOrigin (UsageVector vector, Location loc)
 813                 {
 814                         vector = vector.Clone ();
 815                         if (finally_vector != null) {
 816                                 vector.MergeChild (finally_vector, false);
 817                                 int errors = Report.Errors;
 818                                 Parent.AddBreakOrigin (vector, loc);
 819                                 if (errors == Report.Errors)
 820                                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 821                         } else {
 822                                 vector.Location = loc;
 823                                 vector.Next = break_origins;
 824                                 break_origins = vector;
 825                         }
 826                         return true;
 827                 }
 828
 829                 public override bool AddContinueOrigin (UsageVector vector, Location loc)
 830                 {
 831                         vector = vector.Clone ();
 832                         if (finally_vector != null) {
 833                                 vector.MergeChild (finally_vector, false);
 834                                 int errors = Report.Errors;
 835                                 Parent.AddContinueOrigin (vector, loc);
 836                                 if (errors == Report.Errors)
 837                                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 838                         } else {
 839                                 vector.Location = loc;
 840                                 vector.Next = continue_origins;
 841                                 continue_origins = vector;
 842                         }
 843                         return true;
 844                 }
 845
 846                 public override bool AddReturnOrigin (UsageVector vector, Location loc)
 847                 {
 848                         vector = vector.Clone ();
 849                         if (finally_vector != null) {
 850                                 vector.MergeChild (finally_vector, false);
 851                                 int errors = Report.Errors;
 852                                 Parent.AddReturnOrigin (vector, loc);
 853                                 if (errors == Report.Errors)
 854                                         Report.Error (157, loc, "Control cannot leave the body of a finally clause");
 855                         } else {
 856                                 vector.Location = loc;
 857                                 vector.Next = return_origins;
 858                                 return_origins = vector;
 859                         }
 860                         return true;
 861                 }
 862
 863                 public override bool AddGotoOrigin (UsageVector vector, Goto goto_stmt)
 864                 {
 865                         LabeledStatement s = current_vector.Block == null ? null : current_vector.Block.LookupLabel (goto_stmt.Target);
 866                         if (s != null)
 867                                 throw new InternalErrorException ("Shouldn't get here");
 868
 869                         vector = vector.Clone ();
 870                         if (finally_vector != null) {
 871                                 vector.MergeChild (finally_vector, false);
 872                                 int errors = Report.Errors;
 873                                 Parent.AddGotoOrigin (vector, goto_stmt);
 874                                 if (errors == Report.Errors)
 875                                         Report.Error (157, goto_stmt.loc, "Control cannot leave the body of a finally clause");
 876                         } else {
 877                                 goto_origins = new GotoOrigin (vector, goto_stmt, goto_origins);
 878                         }
 879                         return true;
 880                 }
 881
 882                 public override void StealFinallyClauses (ref ArrayList list)
 883                 {
 884                         if (list == null)
 885                                 list = new ArrayList ();
 886                         list.Add (stmt);
 887                         emit_finally = false;
 888                         base.StealFinallyClauses (ref list);
 889                 }
 890
 891                 public bool EmitFinally {
 892                         get { return emit_finally; }
 893                 }
 894
 895                 protected override UsageVector Merge ()
 896                 {
 897                         Report.Debug (2, "  MERGING TRY/CATCH", Name);
 898                         UsageVector vector = UsageVector.MergeSiblings (catch_vectors, Location);
 899                         Report.Debug (2, "  MERGING TRY/CATCH DONE", vector);
 900
 901                         if (finally_vector != null)
 902                                 vector.MergeChild (finally_vector, false);
 903
 904                         for (UsageVector origin = break_origins; origin != null; origin = origin.Next) {
 905                                 if (finally_vector != null)
 906                                         origin.MergeChild (finally_vector, false);
 907                                 Parent.AddBreakOrigin (origin, origin.Location);
 908                         }
 909
 910                         for (UsageVector origin = continue_origins; origin != null; origin = origin.Next) {
 911                                 if (finally_vector != null)
 912                                         origin.MergeChild (finally_vector, false);
 913                                 Parent.AddContinueOrigin (origin, origin.Location);
 914                         }
 915
 916                         for (UsageVector origin = return_origins; origin != null; origin = origin.Next) {
 917                                 if (finally_vector != null)
 918                                         origin.MergeChild (finally_vector, false);
 919                                 Parent.AddReturnOrigin (origin, origin.Location);
 920                         }
 921
 922                         for (GotoOrigin origin = goto_origins; origin != null; origin = origin.Next) {
 923                                 if (finally_vector != null)
 924                                         origin.Vector.MergeChild (finally_vector, false);
 925                                 Parent.AddGotoOrigin (origin.Vector, origin.GotoStmt);
 926                         }
 927
 928                         return vector;
 929                 }
 930         }
 931
 932         // <summary>
 933         //   This is used by the flow analysis code to keep track of the type of local variables
 934         //   and variables.
 935         //
 936         //   The flow code uses a BitVector to keep track of whether a variable has been assigned
 937         //   or not.  This is easy for fundamental types (int, char etc.) or reference types since
 938         //   you can only assign the whole variable as such.
 939         //
 940         //   For structs, we also need to keep track of all its fields.  To do this, we allocate one
 941         //   bit for the struct itself (it's used if you assign/access the whole struct) followed by
 942         //   one bit for each of its fields.
 943         //
 944         //   This class computes this `layout' for each type.
 945         // </summary>
 946         public class TypeInfo
 947         {
 948                 public readonly Type Type;
 949
 950                 // <summary>
 951                 //   Total number of bits a variable of this type consumes in the flow vector.
 952                 // </summary>
 953                 public readonly int TotalLength;
 954
 955                 // <summary>
 956                 //   Number of bits the simple fields of a variable of this type consume
 957                 //   in the flow vector.
 958                 // </summary>
 959                 public readonly int Length;
 960
 961                 // <summary>
 962                 //   This is only used by sub-structs.
 963                 // </summary>
 964                 public readonly int Offset;
 965
 966                 // <summary>
 967                 //   If this is a struct.
 968                 // </summary>
 969                 public readonly bool IsStruct;
 970
 971                 // <summary>
 972                 //   If this is a struct, all fields which are structs theirselves.
 973                 // </summary>
 974                 public TypeInfo[] SubStructInfo;
 975
 976                 protected readonly StructInfo struct_info;
 977                 private static Hashtable type_hash = new Hashtable ();
 978
 979                 public static TypeInfo GetTypeInfo (Type type)
 980                 {
 981                         TypeInfo info = (TypeInfo) type_hash [type];
 982                         if (info != null)
 983                                 return info;
 984
 985                         info = new TypeInfo (type);
 986                         type_hash.Add (type, info);
 987                         return info;
 988                 }
 989
 990                 public static TypeInfo GetTypeInfo (TypeContainer tc)
 991                 {
 992                         TypeInfo info = (TypeInfo) type_hash [tc.TypeBuilder];
 993                         if (info != null)
 994                                 return info;
 995
 996                         info = new TypeInfo (tc);
 997                         type_hash.Add (tc.TypeBuilder, info);
 998                         return info;
 999                 }
1000
1001                 private TypeInfo (Type type)
1002                 {
1003                         this.Type = type;
1004
1005                         struct_info = StructInfo.GetStructInfo (type);
1006                         if (struct_info != null) {
1007                                 Length = struct_info.Length;
1008                                 TotalLength = struct_info.TotalLength;
1009                                 SubStructInfo = struct_info.StructFields;
1010                                 IsStruct = true;
1011                         } else {
1012                                 Length = 0;
1013                                 TotalLength = 1;
1014                                 IsStruct = false;
1015                         }
1016                 }
1017
1018                 private TypeInfo (TypeContainer tc)
1019                 {
1020                         this.Type = tc.TypeBuilder;
1021
1022                         struct_info = StructInfo.GetStructInfo (tc);
1023                         if (struct_info != null) {
1024                                 Length = struct_info.Length;
1025                                 TotalLength = struct_info.TotalLength;
1026                                 SubStructInfo = struct_info.StructFields;
1027                                 IsStruct = true;
1028                         } else {
1029                                 Length = 0;
1030                                 TotalLength = 1;
1031                                 IsStruct = false;
1032                         }
1033                 }
1034
1035                 protected TypeInfo (StructInfo struct_info, int offset)
1036                 {
1037                         this.struct_info = struct_info;
1038                         this.Offset = offset;
1039                         this.Length = struct_info.Length;
1040                         this.TotalLength = struct_info.TotalLength;
1041                         this.SubStructInfo = struct_info.StructFields;
1042                         this.Type = struct_info.Type;
1043                         this.IsStruct = true;
1044                 }
1045
1046                 public int GetFieldIndex (string name)
1047                 {
1048                         if (struct_info == null)
1049                                 return 0;
1050
1051                         return struct_info [name];
1052                 }
1053
1054                 public TypeInfo GetSubStruct (string name)
1055                 {
1056                         if (struct_info == null)
1057                                 return null;
1058
1059                         return struct_info.GetStructField (name);
1060                 }
1061
1062                 // <summary>
1063                 //   A struct's constructor must always assign all fields.
1064                 //   This method checks whether it actually does so.
1065                 // </summary>
1066                 public bool IsFullyInitialized (FlowBranching branching, VariableInfo vi, Location loc)
1067                 {
1068                         if (struct_info == null)
1069                                 return true;
1070
1071                         bool ok = true;
1072                         for (int i = 0; i < struct_info.Count; i++) {
1073                                 FieldInfo field = struct_info.Fields [i];
1074
1075                                 if (!branching.IsFieldAssigned (vi, field.Name)) {
1076                                         Report.Error (171, loc,
1077                                                 "Field `{0}' must be fully assigned before control leaves the constructor",
1078                                                 TypeManager.GetFullNameSignature (field));
1079                                         ok = false;
1080                                 }
1081                         }
1082
1083                         return ok;
1084                 }
1085
1086                 public override string ToString ()
1087                 {
1088                         return String.Format ("TypeInfo ({0}:{1}:{2}:{3})",
1089                                               Type, Offset, Length, TotalLength);
1090                 }
1091
1092                 protected class StructInfo {
1093                         public readonly Type Type;
1094                         public readonly FieldInfo[] Fields;
1095                         public readonly TypeInfo[] StructFields;
1096                         public readonly int Count;
1097                         public readonly int CountPublic;
1098                         public readonly int CountNonPublic;
1099                         public readonly int Length;
1100                         public readonly int TotalLength;
1101                         public readonly bool HasStructFields;
1102
1103                         private static Hashtable field_type_hash = new Hashtable ();
1104                         private Hashtable struct_field_hash;
1105                         private Hashtable field_hash;
1106
1107                         protected bool InTransit = false;
1108
1109                         // Private constructor.  To save memory usage, we only need to create one instance
1110                         // of this class per struct type.
1111                         private StructInfo (Type type)
1112                         {
1113                                 this.Type = type;
1114
1115                                 field_type_hash.Add (type, this);
1116
1117                                 if (type is TypeBuilder) {
1118                                         TypeContainer tc = TypeManager.LookupTypeContainer (type);
1119
1120                                         ArrayList fields = null;
1121                                         if (tc != null)
1122                                                 fields = tc.Fields;
1123
1124                                         ArrayList public_fields = new ArrayList ();
1125                                         ArrayList non_public_fields = new ArrayList ();
1126
1127                                         if (fields != null) {
1128                                                 foreach (FieldBase field in fields) {
1129                                                         if ((field.ModFlags & Modifiers.STATIC) != 0)
1130                                                                 continue;
1131                                                         if ((field.ModFlags & Modifiers.PUBLIC) != 0)
1132                                                                 public_fields.Add (field.FieldBuilder);
1133                                                         else
1134                                                                 non_public_fields.Add (field.FieldBuilder);
1135                                                 }
1136                                         }
1137
1138                                         CountPublic = public_fields.Count;
1139                                         CountNonPublic = non_public_fields.Count;
1140                                         Count = CountPublic + CountNonPublic;
1141
1142                                         Fields = new FieldInfo [Count];
1143                                         public_fields.CopyTo (Fields, 0);
1144                                         non_public_fields.CopyTo (Fields, CountPublic);
1145 #if GMCS_SOURCE
1146                                 } else if (type is GenericTypeParameterBuilder) {
1147                                         CountPublic = CountNonPublic = Count = 0;
1148
1149                                         Fields = new FieldInfo [0];
1150 #endif
1151                                 } else {
1152                                         FieldInfo[] public_fields = type.GetFields (
1153                                                 BindingFlags.Instance|BindingFlags.Public);
1154                                         FieldInfo[] non_public_fields = type.GetFields (
1155                                                 BindingFlags.Instance|BindingFlags.NonPublic);
1156
1157                                         CountPublic = public_fields.Length;
1158                                         CountNonPublic = non_public_fields.Length;
1159                                         Count = CountPublic + CountNonPublic;
1160
1161                                         Fields = new FieldInfo [Count];
1162                                         public_fields.CopyTo (Fields, 0);
1163                                         non_public_fields.CopyTo (Fields, CountPublic);
1164                                 }
1165
1166                                 struct_field_hash = new Hashtable ();
1167                                 field_hash = new Hashtable ();
1168
1169                                 Length = 0;
1170                                 StructFields = new TypeInfo [Count];
1171                                 StructInfo[] sinfo = new StructInfo [Count];
1172
1173                                 InTransit = true;
1174
1175                                 for (int i = 0; i < Count; i++) {
1176                                         FieldInfo field = (FieldInfo) Fields [i];
1177
1178                                         sinfo [i] = GetStructInfo (field.FieldType);
1179                                         if (sinfo [i] == null)
1180                                                 field_hash.Add (field.Name, ++Length);
1181                                         else if (sinfo [i].InTransit) {
1182                                                 Report.Error (523, String.Format (
1183                                                                       "Struct member `{0}.{1}' of type `{2}' causes " +
1184                                                                       "a cycle in the structure layout",
1185                                                                       type, field.Name, sinfo [i].Type));
1186                                                 sinfo [i] = null;
1187                                                 return;
1188                                         }
1189                                 }
1190
1191                                 InTransit = false;
1192
1193                                 TotalLength = Length + 1;
1194                                 for (int i = 0; i < Count; i++) {
1195                                         FieldInfo field = (FieldInfo) Fields [i];
1196
1197                                         if (sinfo [i] == null)
1198                                                 continue;
1199
1200                                         field_hash.Add (field.Name, TotalLength);
1201
1202                                         HasStructFields = true;
1203                                         StructFields [i] = new TypeInfo (sinfo [i], TotalLength);
1204                                         struct_field_hash.Add (field.Name, StructFields [i]);
1205                                         TotalLength += sinfo [i].TotalLength;
1206                                 }
1207                         }
1208
1209                         public int this [string name] {
1210                                 get {
1211                                         if (field_hash.Contains (name))
1212                                                 return (int) field_hash [name];
1213                                         else
1214                                                 return 0;
1215                                 }
1216                         }
1217
1218                         public TypeInfo GetStructField (string name)
1219                         {
1220                                 return (TypeInfo) struct_field_hash [name];
1221                         }
1222
1223                         public static StructInfo GetStructInfo (Type type)
1224                         {
1225                                 if (!TypeManager.IsValueType (type) || TypeManager.IsEnumType (type) ||
1226                                     TypeManager.IsBuiltinType (type))
1227                                         return null;
1228
1229                                 StructInfo info = (StructInfo) field_type_hash [type];
1230                                 if (info != null)
1231                                         return info;
1232
1233                                 return new StructInfo (type);
1234                         }
1235
1236                         public static StructInfo GetStructInfo (TypeContainer tc)
1237                         {
1238                                 StructInfo info = (StructInfo) field_type_hash [tc.TypeBuilder];
1239                                 if (info != null)
1240                                         return info;
1241
1242                                 return new StructInfo (tc.TypeBuilder);
1243                         }
1244                 }
1245         }
1246
1247         // <summary>
1248         //   This is used by the flow analysis code to store information about a single local variable
1249         //   or parameter.  Depending on the variable's type, we need to allocate one or more elements
1250         //   in the BitVector - if it's a fundamental or reference type, we just need to know whether
1251         //   it has been assigned or not, but for structs, we need this information for each of its fields.
1252         // </summary>
1253         public class VariableInfo {
1254                 public readonly string Name;
1255                 public readonly TypeInfo TypeInfo;
1256
1257                 // <summary>
1258                 //   The bit offset of this variable in the flow vector.
1259                 // </summary>
1260                 public readonly int Offset;
1261
1262                 // <summary>
1263                 //   The number of bits this variable needs in the flow vector.
1264                 //   The first bit always specifies whether the variable as such has been assigned while
1265                 //   the remaining bits contain this information for each of a struct's fields.
1266                 // </summary>
1267                 public readonly int Length;
1268
1269                 // <summary>
1270                 //   If this is a parameter of local variable.
1271                 // </summary>
1272                 public readonly bool IsParameter;
1273
1274                 public readonly LocalInfo LocalInfo;
1275
1276                 readonly VariableInfo Parent;
1277                 VariableInfo[] sub_info;
1278
1279                 protected VariableInfo (string name, Type type, int offset)
1280                 {
1281                         this.Name = name;
1282                         this.Offset = offset;
1283                         this.TypeInfo = TypeInfo.GetTypeInfo (type);
1284
1285                         Length = TypeInfo.TotalLength;
1286
1287                         Initialize ();
1288                 }
1289
1290                 protected VariableInfo (VariableInfo parent, TypeInfo type)
1291                 {
1292                         this.Name = parent.Name;
1293                         this.TypeInfo = type;
1294                         this.Offset = parent.Offset + type.Offset;
1295                         this.Parent = parent;
1296                         this.Length = type.TotalLength;
1297
1298                         this.IsParameter = parent.IsParameter;
1299                         this.LocalInfo = parent.LocalInfo;
1300
1301                         Initialize ();
1302                 }
1303
1304                 protected void Initialize ()
1305                 {
1306                         TypeInfo[] sub_fields = TypeInfo.SubStructInfo;
1307                         if (sub_fields != null) {
1308                                 sub_info = new VariableInfo [sub_fields.Length];
1309                                 for (int i = 0; i < sub_fields.Length; i++) {
1310                                         if (sub_fields [i] != null)
1311                                                 sub_info [i] = new VariableInfo (this, sub_fields [i]);
1312                                 }
1313                         } else
1314                                 sub_info = new VariableInfo [0];
1315                 }
1316
1317                 public VariableInfo (LocalInfo local_info, int offset)
1318                         : this (local_info.Name, local_info.VariableType, offset)
1319                 {
1320                         this.LocalInfo = local_info;
1321                         this.IsParameter = false;
1322                 }
1323
1324                 public VariableInfo (Parameters ip, int i, int offset)
1325                         : this (ip.ParameterName (i), TypeManager.GetElementType (ip.ParameterType (i)), offset)
1326                 {
1327                         this.IsParameter = true;
1328                 }
1329
1330                 public bool IsAssigned (EmitContext ec)
1331                 {
1332                         return !ec.DoFlowAnalysis ||
1333                                 ec.OmitStructFlowAnalysis && TypeInfo.IsStruct ||
1334                                 ec.CurrentBranching.IsAssigned (this);
1335                 }
1336
1337                 public bool IsAssigned (EmitContext ec, Location loc)
1338                 {
1339                         if (IsAssigned (ec))
1340                                 return true;
1341
1342                         Report.Error (165, loc,
1343                                       "Use of unassigned local variable `" + Name + "'");
1344                         ec.CurrentBranching.SetAssigned (this);
1345                         return false;
1346                 }
1347
1348                 public bool IsAssigned (MyBitVector vector)
1349                 {
1350                         if (vector == null)
1351                                 return true;
1352
1353                         if (vector [Offset])
1354                                 return true;
1355
1356                         // FIXME: Fix SetFieldAssigned to set the whole range like SetAssigned below. Then, get rid of this stanza
1357                         for (VariableInfo parent = Parent; parent != null; parent = parent.Parent) {
1358                                 if (vector [parent.Offset]) {
1359                                         // 'parent' is assigned, but someone forgot to note that all its components are assigned too
1360                                         parent.SetAssigned (vector);
1361                                         return true;
1362                                 }
1363                         }
1364
1365                         // Return unless this is a struct.
1366                         if (!TypeInfo.IsStruct)
1367                                 return false;
1368
1369                         // Ok, so each field must be assigned.
1370                         for (int i = 0; i < TypeInfo.Length; i++) {
1371                                 if (!vector [Offset + i + 1])
1372                                         return false;
1373                         }
1374
1375                         // Ok, now check all fields which are structs.
1376                         for (int i = 0; i < sub_info.Length; i++) {
1377                                 VariableInfo sinfo = sub_info [i];
1378                                 if (sinfo == null)
1379                                         continue;
1380
1381                                 if (!sinfo.IsAssigned (vector))
1382                                         return false;
1383                         }
1384
1385                         vector [Offset] = true;
1386                         return true;
1387                 }
1388
1389                 public void SetAssigned (EmitContext ec)
1390                 {
1391                         if (ec.DoFlowAnalysis)
1392                                 ec.CurrentBranching.SetAssigned (this);
1393                 }
1394
1395                 public void SetAssigned (MyBitVector vector)
1396                 {
1397                         if (Length == 1)
1398                                 vector [Offset] = true;
1399                         else
1400                                 vector.SetRange (Offset, Length);
1401                 }
1402
1403                 public bool IsFieldAssigned (EmitContext ec, string name, Location loc)
1404                 {
1405                         if (!ec.DoFlowAnalysis ||
1406                                 ec.OmitStructFlowAnalysis && TypeInfo.IsStruct ||
1407                                 ec.CurrentBranching.IsFieldAssigned (this, name))
1408                                 return true;
1409
1410                         Report.Error (170, loc,
1411                                       "Use of possibly unassigned field `" + name + "'");
1412                         ec.CurrentBranching.SetFieldAssigned (this, name);
1413                         return false;
1414                 }
1415
1416                 public bool IsFieldAssigned (MyBitVector vector, string field_name)
1417                 {
1418                         int field_idx = TypeInfo.GetFieldIndex (field_name);
1419
1420                         if (field_idx == 0)
1421                                 return true;
1422
1423                         return vector [Offset + field_idx];
1424                 }
1425
1426                 public void SetFieldAssigned (EmitContext ec, string name)
1427                 {
1428                         if (ec.DoFlowAnalysis)
1429                                 ec.CurrentBranching.SetFieldAssigned (this, name);
1430                 }
1431
1432                 public void SetFieldAssigned (MyBitVector vector, string field_name)
1433                 {
1434                         int field_idx = TypeInfo.GetFieldIndex (field_name);
1435
1436                         if (field_idx == 0)
1437                                 return;
1438
1439                         vector [Offset + field_idx] = true;
1440                 }
1441
1442                 public VariableInfo GetSubStruct (string name)
1443                 {
1444                         TypeInfo type = TypeInfo.GetSubStruct (name);
1445
1446                         if (type == null)
1447                                 return null;
1448
1449                         return new VariableInfo (this, type);
1450                 }
1451
1452                 public override string ToString ()
1453                 {
1454                         return String.Format ("VariableInfo ({0}:{1}:{2}:{3}:{4})",
1455                                               Name, TypeInfo, Offset, Length, IsParameter);
1456                 }
1457         }
1458
1459         // <summary>
1460         //   This is a special bit vector which can inherit from another bit vector doing a
1461         //   copy-on-write strategy.  The inherited vector may have a smaller size than the
1462         //   current one.
1463         // </summary>
1464         public class MyBitVector {
1465                 public readonly int Count;
1466                 public static readonly MyBitVector Empty = new MyBitVector ();
1467
1468                 // Invariant: vector != null => vector.Count == Count
1469                 // Invariant: vector == null || shared == null
1470                 //            i.e., at most one of 'vector' and 'shared' can be non-null.  They can both be null -- that means all-ones
1471                 // The object in 'shared' cannot be modified, while 'vector' can be freely modified
1472                 BitArray vector, shared;
1473
1474                 MyBitVector ()
1475                 {
1476                         shared = new BitArray (0, false);
1477                 }
1478
1479                 public MyBitVector (MyBitVector InheritsFrom, int Count)
1480                 {
1481                         if (InheritsFrom != null)
1482                                 shared = InheritsFrom.Shared;
1483
1484                         this.Count = Count;
1485                 }
1486
1487                 // Use this accessor to get a shareable copy of the underlying BitArray representation
1488                 BitArray Shared {
1489                         get {
1490                                 // Post-condition: vector == null
1491                                 if (shared == null) {
1492                                         shared = vector;
1493                                         vector = null;
1494                                 }
1495                                 return shared;
1496                         }
1497                 }
1498
1499                 // <summary>
1500                 //   Get/set bit `index' in the bit vector.
1501                 // </summary>
1502                 public bool this [int index] {
1503                         get {
1504                                 if (index >= Count)
1505                                         throw new ArgumentOutOfRangeException ();
1506
1507                                 if (vector != null)
1508                                         return vector [index];
1509                                 if (shared == null)
1510                                         return true;
1511                                 if (index < shared.Count)
1512                                         return shared [index];
1513                                 return false;
1514                         }
1515
1516                         set {
1517                                 // Only copy the vector if we're actually modifying it.
1518                                 if (this [index] != value) {
1519                                         if (vector == null)
1520                                                 initialize_vector ();
1521                                         vector [index] = value;
1522                                 }
1523                         }
1524                 }
1525
1526                 // <summary>
1527                 //   Performs an `or' operation on the bit vector.  The `new_vector' may have a
1528                 //   different size than the current one.
1529                 // </summary>
1530                 private MyBitVector Or (MyBitVector new_vector)
1531                 {
1532                         if (Count == 0 || new_vector.Count == 0)
1533                                 return this;
1534
1535                         BitArray o = new_vector.vector != null ? new_vector.vector : new_vector.shared;
1536
1537                         if (o == null) {
1538                                 int n = new_vector.Count;
1539                                 if (n < Count) {
1540                                         for (int i = 0; i < n; ++i)
1541                                                 this [i] = true;
1542                                 } else {
1543                                         SetAll (true);
1544                                 }
1545                                 return this;
1546                         }
1547
1548                         if (Count == o.Count) {
1549                                 if (vector == null) {
1550                                         if (shared == null)
1551                                                 return this;
1552                                         initialize_vector ();
1553                                 }
1554                                 vector.Or (o);
1555                                 return this;
1556                         }
1557
1558                         int min = o.Count;
1559                         if (Count < min)
1560                                 min = Count;
1561
1562                         for (int i = 0; i < min; i++) {
1563                                 if (o [i])
1564                                         this [i] = true;
1565                         }
1566
1567                         return this;
1568                 }
1569
1570                 // <summary>
1571                 //   Performs an `and' operation on the bit vector.  The `new_vector' may have
1572                 //   a different size than the current one.
1573                 // </summary>
1574                 private MyBitVector And (MyBitVector new_vector)
1575                 {
1576                         if (Count == 0)
1577                                 return this;
1578
1579                         BitArray o = new_vector.vector != null ? new_vector.vector : new_vector.shared;
1580
1581                         if (o == null) {
1582                                 for (int i = new_vector.Count; i < Count; ++i)
1583                                         this [i] = false;
1584                                 return this;
1585                         }
1586
1587                         if (o.Count == 0) {
1588                                 SetAll (false);
1589                                 return this;
1590                         }
1591
1592                         if (Count == o.Count) {
1593                                 if (vector == null) {
1594                                         if (shared == null) {
1595                                                 shared = new_vector.Shared;
1596                                                 return this;
1597                                         }
1598                                         initialize_vector ();
1599                                 }
1600                                 vector.And (o);
1601                                 return this;
1602                         }
1603
1604                         int min = o.Count;
1605                         if (Count < min)
1606                                 min = Count;
1607
1608                         for (int i = 0; i < min; i++) {
1609                                 if (! o [i])
1610                                         this [i] = false;
1611                         }
1612
1613                         for (int i = min; i < Count; i++)
1614                                 this [i] = false;
1615
1616                         return this;
1617                 }
1618
1619                 public static MyBitVector operator & (MyBitVector a, MyBitVector b)
1620                 {
1621                         if (a == b)
1622                                 return a;
1623                         if (a == null)
1624                                 return b.Clone ();
1625                         if (b == null)
1626                                 return a.Clone ();
1627                         if (a.Count > b.Count)
1628                                 return a.Clone ().And (b);
1629                         else
1630                                 return b.Clone ().And (a);
1631                 }
1632
1633                 public static MyBitVector operator | (MyBitVector a, MyBitVector b)
1634                 {
1635                         if (a == b)
1636                                 return a;
1637                         if (a == null)
1638                                 return new MyBitVector (null, b.Count);
1639                         if (b == null)
1640                                 return new MyBitVector (null, a.Count);
1641                         if (a.Count > b.Count)
1642                                 return a.Clone ().Or (b);
1643                         else
1644                                 return b.Clone ().Or (a);
1645                 }
1646
1647                 public MyBitVector Clone ()
1648                 {
1649                         return Count == 0 ? Empty : new MyBitVector (this, Count);
1650                 }
1651
1652                 public void SetRange (int offset, int length)
1653                 {
1654                         if (offset > Count || offset + length > Count)
1655                                 throw new ArgumentOutOfRangeException ();
1656
1657                         if (shared == null && vector == null)
1658                                 return;
1659
1660                         int i = 0;
1661                         if (shared != null) {
1662                                 if (offset + length <= shared.Count) {
1663                                         for (; i < length; ++i)
1664                                                 if (!shared [i+offset])
1665                                                     break;
1666                                         if (i == length)
1667                                                 return;
1668                                 }
1669                                 initialize_vector ();
1670                         }
1671                         for (; i < length; ++i)
1672                                 vector [i+offset] = true;
1673
1674                 }
1675
1676                 public void SetAll (bool value)
1677                 {
1678                         // Don't clobber Empty
1679                         if (Count == 0)
1680                                 return;
1681                         shared = value ? null : Empty.Shared;
1682                         vector = null;
1683                 }
1684
1685                 void initialize_vector ()
1686                 {
1687                         // Post-condition: vector != null
1688                         if (shared == null) {
1689                                 vector = new BitArray (Count, true);
1690                                 return;
1691                         }
1692
1693                         vector = new BitArray (shared);
1694                         if (Count != vector.Count)
1695                                 vector.Length = Count;
1696                         shared = null;
1697                 }
1698
1699                 StringBuilder Dump (StringBuilder sb)
1700                 {
1701                         BitArray dump = vector == null ? shared : vector;
1702                         if (dump == null)
1703                                 return sb.Append ("/");
1704                         if (dump == shared)
1705                                 sb.Append ("=");
1706                         for (int i = 0; i < dump.Count; i++)
1707                                 sb.Append (dump [i] ? "1" : "0");
1708                         return sb;
1709                 }
1710
1711                 public override string ToString ()
1712                 {
1713                         return Dump (new StringBuilder ("{")).Append ("}").ToString ();
1714                 }
1715         }
1716 }