mcs/class/corlib/System.Reflection.Emit/ILGenerator.cs

   1
   2 //
   3 // System.Reflection.Emit/ILGenerator.cs
   4 //
   5 // Author:
   6 //   Paolo Molaro (lupus@ximian.com)
   7 //
   8 // (C) 2001 Ximian, Inc.  http://www.ximian.com
   9 //
  10
  11 using System;
  12 using System.Collections;
  13 using System.Diagnostics.SymbolStore;
  14 using System.Runtime.InteropServices;
  15 using Mono.CSharp.Debugger;
  16
  17 namespace System.Reflection.Emit {
  18
  19         internal struct ILExceptionBlock {
  20                 public const int CATCH = 0;
  21                 public const int FILTER = 1;
  22                 public const int FINALLY = 2;
  23                 public const int FAULT = 4;
  24
  25                 internal Type extype;
  26                 internal int type;
  27                 internal int start;
  28                 internal int len;
  29                 internal int filter_offset;
  30
  31                 internal void Debug () {
  32 #if NO
  33                         System.Console.Write ("\ttype="+type.ToString()+" start="+start.ToString()+" len="+len.ToString());
  34                         if (extype != null)
  35                                 System.Console.WriteLine (" extype="+extype.ToString());
  36                         else
  37                                 System.Console.WriteLine ("");
  38 #endif
  39                 }
  40         }
  41         internal struct ILExceptionInfo {
  42                 ILExceptionBlock[] handlers;
  43                 internal int start;
  44                 int len;
  45                 internal Label end;
  46
  47                 internal int NumHandlers () {
  48                         return handlers.Length;
  49                 }
  50
  51                 internal void AddCatch (Type extype, int offset) {
  52                         int i;
  53                         End (offset);
  54                         add_block (offset);
  55                         i = handlers.Length - 1;
  56                         handlers [i].type = ILExceptionBlock.CATCH;
  57                         handlers [i].start = offset;
  58                         handlers [i].extype = extype;
  59                 }
  60
  61                 internal void AddFinally (int offset) {
  62                         int i;
  63                         End (offset);
  64                         add_block (offset);
  65                         i = handlers.Length - 1;
  66                         handlers [i].type = ILExceptionBlock.FINALLY;
  67                         handlers [i].start = offset;
  68                         handlers [i].extype = null;
  69                 }
  70
  71                 internal void End (int offset) {
  72                         if (handlers == null)
  73                                 return;
  74                         int i = handlers.Length - 1;
  75                         if (i >= 0)
  76                                 handlers [i].len = offset - handlers [i].start;
  77                 }
  78
  79                 internal int LastClauseType () {
  80                         if (handlers != null)
  81                                 return handlers [handlers.Length-1].type;
  82                         else
  83                                 return ILExceptionBlock.CATCH;
  84                 }
  85
  86                 internal void Debug (int b) {
  87 #if NO
  88                         System.Console.WriteLine ("Handler {0} at {1}, len: {2}", b, start, len);
  89                         for (int i = 0; i < handlers.Length; ++i)
  90                                 handlers [i].Debug ();
  91 #endif
  92                 }
  93
  94                 void add_block (int offset) {
  95                         if (handlers != null) {
  96                                 int i = handlers.Length;
  97                                 ILExceptionBlock[] new_b = new ILExceptionBlock [i + 1];
  98                                 System.Array.Copy (handlers, new_b, i);
  99                                 handlers = new_b;
 100                                 handlers [i].len = offset - handlers [i].start;
 101                         } else {
 102                                 handlers = new ILExceptionBlock [1];
 103                                 len = offset - start;
 104                         }
 105                 }
 106         }
 107
 108         internal struct ILTokenInfo {
 109                 public MemberInfo member;
 110                 public int code_pos;
 111         }
 112
 113         public class ILGenerator: Object {
 114                 private struct LabelFixup {
 115                         public int size;
 116                         public int pos;                 // the location of the fixup
 117                         public int label_base;  // the base address for this fixup
 118                         public int label_idx;
 119                 };
 120                 static Type void_type = typeof (void);
 121                 private byte[] code;
 122                 private MethodBase mbuilder; /* a MethodBuilder or ConstructorBuilder */
 123                 private int code_len;
 124                 private int max_stack;
 125                 private int cur_stack;
 126                 private LocalBuilder[] locals;
 127                 private ILExceptionInfo[] ex_handlers;
 128                 private int num_token_fixups;
 129                 private ILTokenInfo[] token_fixups;
 130                 private int[] label_to_addr;
 131                 private int num_labels;
 132                 private LabelFixup[] fixups;
 133                 private int num_fixups;
 134                 private ModuleBuilder module;
 135                 private AssemblyBuilder abuilder;
 136                 private IMonoSymbolWriter sym_writer;
 137                 private Stack scopes;
 138                 private int cur_block;
 139                 private Stack open_blocks;
 140
 141                 internal ILGenerator (MethodBase mb, int size) {
 142                         if (size < 0)
 143                                 size = 128;
 144                         code_len = 0;
 145                         code = new byte [size];
 146                         mbuilder = mb;
 147                         cur_stack = max_stack = 0;
 148                         num_fixups = num_labels = 0;
 149                         label_to_addr = new int [8];
 150                         fixups = new LabelFixup [8];
 151                         token_fixups = new ILTokenInfo [8];
 152                         num_token_fixups = 0;
 153                         if (mb is MethodBuilder) {
 154                                 module = (ModuleBuilder)((MethodBuilder)mb).TypeBuilder.Module;
 155                         } else if (mb is ConstructorBuilder) {
 156                                 module = (ModuleBuilder)((ConstructorBuilder)mb).TypeBuilder.Module;
 157                         }
 158                         abuilder = (AssemblyBuilder)module.Assembly;
 159                         sym_writer = module.symbol_writer;
 160                         open_blocks = new Stack ();
 161                 }
 162
 163                 private void add_token_fixup (MemberInfo mi) {
 164                         if (num_token_fixups == token_fixups.Length) {
 165                                 ILTokenInfo[] ntf = new ILTokenInfo [num_token_fixups * 2];
 166                                 token_fixups.CopyTo (ntf, 0);
 167                                 token_fixups = ntf;
 168                         }
 169                         token_fixups [num_token_fixups].member = mi;
 170                         token_fixups [num_token_fixups++].code_pos = code_len;
 171                 }
 172
 173                 private void make_room (int nbytes) {
 174                         if (code_len + nbytes < code.Length)
 175                                 return;
 176                         byte[] new_code = new byte [(code_len + nbytes) * 2 + 128];
 177                         System.Array.Copy (code, 0, new_code, 0, code.Length);
 178                         code = new_code;
 179                 }
 180                 private void emit_int (int val) {
 181                         code [code_len++] = (byte) (val & 0xFF);
 182                         code [code_len++] = (byte) ((val >> 8) & 0xFF);
 183                         code [code_len++] = (byte) ((val >> 16) & 0xFF);
 184                         code [code_len++] = (byte) ((val >> 24) & 0xFF);
 185                 }
 186                 /* change to pass by ref to avoid copy */
 187                 private void ll_emit (OpCode opcode) {
 188                         /*
 189                          * there is already enough room allocated in code.
 190                          */
 191                         // access op1 and op2 directly since the Value property is useless
 192                         if (opcode.Size == 2)
 193                                 code [code_len++] = opcode.op1;
 194                         code [code_len++] = opcode.op2;
 195                         /*
 196                          * We should probably keep track of stack needs here.
 197                          * Or we may want to run the verifier on the code before saving it
 198                          * (this may be needed anyway when the ILGenerator is not used...).
 199                          */
 200                         switch (opcode.StackBehaviourPush) {
 201                         case StackBehaviour.Push1:
 202                         case StackBehaviour.Pushi:
 203                         case StackBehaviour.Pushi8:
 204                         case StackBehaviour.Pushr4:
 205                         case StackBehaviour.Pushr8:
 206                         case StackBehaviour.Pushref:
 207                         case StackBehaviour.Varpush: /* again we are conservative and assume it pushes 1 */
 208                                 cur_stack ++;
 209                                 break;
 210                         case StackBehaviour.Push1_push1:
 211                                 cur_stack += 2;
 212                                 break;
 213                         }
 214                         if (max_stack < cur_stack)
 215                                 max_stack = cur_stack;
 216
 217                         /*
 218                          * Note that we adjust for the pop behaviour _after_ setting max_stack.
 219                          */
 220                         switch (opcode.StackBehaviourPop) {
 221                         case StackBehaviour.Varpop:
 222                                 break; /* we are conservative and assume it doesn't decrease the stack needs */
 223                         case StackBehaviour.Pop1:
 224                         case StackBehaviour.Popi:
 225                         case StackBehaviour.Popref:
 226                                 cur_stack --;
 227                                 break;
 228                         case StackBehaviour.Pop1_pop1:
 229                         case StackBehaviour.Popi_pop1:
 230                         case StackBehaviour.Popi_popi:
 231                         case StackBehaviour.Popi_popi8:
 232                         case StackBehaviour.Popi_popr4:
 233                         case StackBehaviour.Popi_popr8:
 234                         case StackBehaviour.Popref_pop1:
 235                         case StackBehaviour.Popref_popi:
 236                                 cur_stack -= 2;
 237                                 break;
 238                         case StackBehaviour.Popi_popi_popi:
 239                         case StackBehaviour.Popref_popi_popi:
 240                         case StackBehaviour.Popref_popi_popi8:
 241                         case StackBehaviour.Popref_popi_popr4:
 242                         case StackBehaviour.Popref_popi_popr8:
 243                         case StackBehaviour.Popref_popi_popref:
 244                                 cur_stack -= 3;
 245                                 break;
 246                         }
 247                 }
 248
 249                 private static int target_len (OpCode opcode) {
 250                         if (opcode.operandType == OperandType.InlineBrTarget)
 251                                 return 4;
 252                         return 1;
 253                 }
 254
 255                 private void InternalEndClause () {
 256                         switch (ex_handlers [cur_block].LastClauseType ()) {
 257                         case ILExceptionBlock.CATCH:
 258                                 // how could we optimize code size here?
 259                                 Emit (OpCodes.Leave, ex_handlers [cur_block].end);
 260                                 break;
 261                         case ILExceptionBlock.FAULT:
 262                         case ILExceptionBlock.FINALLY:
 263                                 Emit (OpCodes.Endfinally);
 264                                 break;
 265                         case ILExceptionBlock.FILTER:
 266                                 Emit (OpCodes.Endfilter);
 267                                 break;
 268                         }
 269                 }
 270
 271                 public virtual void BeginCatchBlock (Type exceptionType) {
 272                         if (open_blocks.Count <= 0)
 273                                 throw new NotSupportedException ("Not in an exception block");
 274                         InternalEndClause ();
 275                         ex_handlers [cur_block].AddCatch (exceptionType, code_len);
 276                         cur_stack = 1; // the exception object is on the stack by default
 277                         if (max_stack < cur_stack)
 278                                 max_stack = cur_stack;
 279                         //System.Console.WriteLine ("Begin catch Block: {0} {1}",exceptionType.ToString(), max_stack);
 280                         //throw new NotImplementedException ();
 281                 }
 282                 public virtual void BeginExceptFilterBlock () {
 283                         throw new NotImplementedException ();
 284                 }
 285                 public virtual Label BeginExceptionBlock () {
 286                         //System.Console.WriteLine ("Begin Block");
 287
 288                         if (ex_handlers != null) {
 289                                 cur_block = ex_handlers.Length;
 290                                 ILExceptionInfo[] new_ex = new ILExceptionInfo [cur_block + 1];
 291                                 System.Array.Copy (ex_handlers, new_ex, cur_block);
 292                                 ex_handlers = new_ex;
 293                         } else {
 294                                 ex_handlers = new ILExceptionInfo [1];
 295                                 cur_block = 0;
 296                         }
 297                         open_blocks.Push (cur_block);
 298                         ex_handlers [cur_block].start = code_len;
 299                         return ex_handlers [cur_block].end = DefineLabel ();
 300                 }
 301                 public virtual void BeginFaultBlock() {
 302                         if (open_blocks.Count <= 0)
 303                                 throw new NotSupportedException ("Not in an exception block");
 304                         //System.Console.WriteLine ("Begin fault Block");
 305                         //throw new NotImplementedException ();
 306                 }
 307                 public virtual void BeginFinallyBlock() {
 308                         if (open_blocks.Count <= 0)
 309                                 throw new NotSupportedException ("Not in an exception block");
 310                         InternalEndClause ();
 311                         //System.Console.WriteLine ("Begin finally Block");
 312                         ex_handlers [cur_block].AddFinally (code_len);
 313                 }
 314                 public virtual void BeginScope () {
 315                         if (sym_writer != null) {
 316                                 if (scopes == null)
 317                                         scopes = new Stack ();
 318                                 scopes.Push (sym_writer.OpenScope (code_len));
 319                         }
 320                 }
 321                 public LocalBuilder DeclareLocal (Type localType) {
 322                         LocalBuilder res = new LocalBuilder (module, localType, this);
 323                         if (locals != null) {
 324                                 LocalBuilder[] new_l = new LocalBuilder [locals.Length + 1];
 325                                 System.Array.Copy (locals, new_l, locals.Length);
 326                                 new_l [locals.Length] = res;
 327                                 locals = new_l;
 328                         } else {
 329                                 locals = new LocalBuilder [1];
 330                                 locals [0] = res;
 331                         }
 332                         res.position = (uint)(locals.Length - 1);
 333                         return res;
 334                 }
 335                 public virtual Label DefineLabel () {
 336                         if (num_labels >= label_to_addr.Length) {
 337                                 int[] new_l = new int [label_to_addr.Length * 2];
 338                                 System.Array.Copy (label_to_addr, new_l, label_to_addr.Length);
 339                                 label_to_addr = new_l;
 340                         }
 341                         label_to_addr [num_labels] = -1;
 342                         return new Label (num_labels++);
 343                 }
 344                 public virtual void Emit (OpCode opcode) {
 345                         make_room (2);
 346                         ll_emit (opcode);
 347                 }
 348                 public virtual void Emit (OpCode opcode, Byte val) {
 349                         make_room (3);
 350                         ll_emit (opcode);
 351                         code [code_len++] = val;
 352                 }
 353                 public virtual void Emit (OpCode opcode, ConstructorInfo constructor) {
 354                         int token = abuilder.GetToken (constructor);
 355                         make_room (6);
 356                         ll_emit (opcode);
 357                         if (constructor.DeclaringType.Module == module)
 358                                 add_token_fixup (constructor);
 359                         emit_int (token);
 360                         ParameterInfo[] mparams = constructor.GetParameters();
 361                         if ((opcode.StackBehaviourPop == StackBehaviour.Varpop) && (mparams != null))
 362                                 cur_stack -= mparams.Length;
 363                 }
 364                 public virtual void Emit (OpCode opcode, double val) {
 365                         byte[] s = System.BitConverter.GetBytes (val);
 366                         make_room (10);
 367                         ll_emit (opcode);
 368                         if (BitConverter.IsLittleEndian){
 369                                 System.Array.Copy (s, 0, code, code_len, 8);
 370                                 code_len += 8;
 371                         } else {
 372                                 code [code_len++] = s [7];
 373                                 code [code_len++] = s [6];
 374                                 code [code_len++] = s [5];
 375                                 code [code_len++] = s [4];
 376                                 code [code_len++] = s [3];
 377                                 code [code_len++] = s [2];
 378                                 code [code_len++] = s [1];
 379                                 code [code_len++] = s [0];
 380                         }
 381                 }
 382                 public virtual void Emit (OpCode opcode, FieldInfo field) {
 383                         int token = abuilder.GetToken (field);
 384                         make_room (6);
 385                         ll_emit (opcode);
 386                         if (field.DeclaringType.Module == module)
 387                                 add_token_fixup (field);
 388                         emit_int (token);
 389                 }
 390                 public virtual void Emit (OpCode opcode, Int16 val) {
 391                         make_room (4);
 392                         ll_emit (opcode);
 393                         code [code_len++] = (byte) (val & 0xFF);
 394                         code [code_len++] = (byte) ((val >> 8) & 0xFF);
 395                 }
 396                 public virtual void Emit (OpCode opcode, int val) {
 397                         make_room (6);
 398                         ll_emit (opcode);
 399                         emit_int (val);
 400                 }
 401                 public virtual void Emit (OpCode opcode, long val) {
 402                         make_room (10);
 403                         ll_emit (opcode);
 404                         code [code_len++] = (byte) (val & 0xFF);
 405                         code [code_len++] = (byte) ((val >> 8) & 0xFF);
 406                         code [code_len++] = (byte) ((val >> 16) & 0xFF);
 407                         code [code_len++] = (byte) ((val >> 24) & 0xFF);
 408                         code [code_len++] = (byte) ((val >> 32) & 0xFF);
 409                         code [code_len++] = (byte) ((val >> 40) & 0xFF);
 410                         code [code_len++] = (byte) ((val >> 48) & 0xFF);
 411                         code [code_len++] = (byte) ((val >> 56) & 0xFF);
 412                 }
 413                 public virtual void Emit (OpCode opcode, Label label) {
 414                         int tlen = target_len (opcode);
 415                         make_room (6);
 416                         ll_emit (opcode);
 417                         if (num_fixups >= fixups.Length) {
 418                                 LabelFixup[] newf = new LabelFixup [fixups.Length + 16];
 419                                 System.Array.Copy (fixups, newf, fixups.Length);
 420                                 fixups = newf;
 421                         }
 422                         fixups [num_fixups].size = tlen;
 423                         fixups [num_fixups].pos = code_len;
 424                         fixups [num_fixups].label_base = code_len;
 425                         fixups [num_fixups].label_idx = label.label;
 426                         num_fixups++;
 427                         code_len += tlen;
 428
 429                 }
 430                 public virtual void Emit (OpCode opcode, Label[] labels) {
 431                         /* opcode needs to be switch. */
 432                         int count = labels.Length;
 433                         make_room (6 + count * 4);
 434                         ll_emit (opcode);
 435                         int switch_base = code_len + count*4;
 436                         emit_int (count);
 437                         if (num_fixups + count >= fixups.Length) {
 438                                 LabelFixup[] newf = new LabelFixup [fixups.Length + count + 16];
 439                                 System.Array.Copy (fixups, newf, fixups.Length);
 440                                 fixups = newf;
 441                         }
 442                         for (int i = 0; i < count; ++i) {
 443                                 fixups [num_fixups].size = 4;
 444                                 fixups [num_fixups].pos = code_len;
 445                                 fixups [num_fixups].label_base = switch_base;
 446                                 fixups [num_fixups].label_idx = labels [i].label;
 447                                 num_fixups++;
 448                                 code_len += 4;
 449                         }
 450                 }
 451                 public virtual void Emit (OpCode opcode, LocalBuilder lbuilder) {
 452                         uint pos = lbuilder.position;
 453                         bool load_addr = false;
 454                         bool is_store = false;
 455                         make_room (6);
 456
 457                         if (lbuilder.ilgen != this)
 458                                 throw new Exception ("Trying to emit a local from a different ILGenerator.");
 459
 460                         /* inline the code from ll_emit () to optimize il code size */
 461                         if (opcode.StackBehaviourPop == StackBehaviour.Pop1) {
 462                                 cur_stack --;
 463                                 is_store = true;
 464                         } else {
 465                                 cur_stack++;
 466                                 if (cur_stack > max_stack)
 467                                         max_stack = cur_stack;
 468                                 load_addr = opcode.StackBehaviourPush == StackBehaviour.Pushi;
 469                         }
 470                         if (load_addr) {
 471                                 if (pos < 256) {
 472                                         code [code_len++] = (byte)0x12;
 473                                         code [code_len++] = (byte)pos;
 474                                 } else {
 475                                         code [code_len++] = (byte)0xfe;
 476                                         code [code_len++] = (byte)0x0d;
 477                                         code [code_len++] = (byte)(pos & 0xff);
 478                                         code [code_len++] = (byte)((pos >> 8) & 0xff);
 479                                 }
 480                         } else {
 481                                 if (is_store) {
 482                                         if (pos < 4) {
 483                                                 code [code_len++] = (byte)(0x0a + pos);
 484                                         } else if (pos < 256) {
 485                                                 code [code_len++] = (byte)0x13;
 486                                                 code [code_len++] = (byte)pos;
 487                                         } else {
 488                                                 code [code_len++] = (byte)0xfe;
 489                                                 code [code_len++] = (byte)0x0e;
 490                                                 code [code_len++] = (byte)(pos & 0xff);
 491                                                 code [code_len++] = (byte)((pos >> 8) & 0xff);
 492                                         }
 493                                 } else {
 494                                         if (pos < 4) {
 495                                                 code [code_len++] = (byte)(0x06 + pos);
 496                                         } else if (pos < 256) {
 497                                                 code [code_len++] = (byte)0x11;
 498                                                 code [code_len++] = (byte)pos;
 499                                         } else {
 500                                                 code [code_len++] = (byte)0xfe;
 501                                                 code [code_len++] = (byte)0x0c;
 502                                                 code [code_len++] = (byte)(pos & 0xff);
 503                                                 code [code_len++] = (byte)((pos >> 8) & 0xff);
 504                                         }
 505                                 }
 506                         }
 507                 }
 508                 public virtual void Emit (OpCode opcode, MethodInfo method) {
 509                         if (method == null)
 510                                 throw new ArgumentNullException ("method");
 511
 512                         int token = abuilder.GetToken (method);
 513                         make_room (6);
 514                         ll_emit (opcode);
 515                         if (method.DeclaringType.Module == module)
 516                                 add_token_fixup (method);
 517                         emit_int (token);
 518                         if (method.ReturnType != void_type)
 519                                 cur_stack ++;
 520                         ParameterInfo[] mparams = method.GetParameters();
 521                         if ((opcode.StackBehaviourPop == StackBehaviour.Varpop) && (mparams != null))
 522                                 cur_stack -= mparams.Length;
 523                 }
 524                 [CLSCompliant(false)]
 525                 public void Emit (OpCode opcode, sbyte val) {
 526                         make_room (3);
 527                         ll_emit (opcode);
 528                         code [code_len++] = (byte)val;
 529                 }
 530
 531                 public virtual void Emit (OpCode opcode, SignatureHelper shelper) {
 532                         int token = abuilder.GetToken (shelper);
 533                         make_room (6);
 534                         ll_emit (opcode);
 535                         emit_int (token);
 536                 }
 537                 public virtual void Emit (OpCode opcode, float val) {
 538                         byte[] s = System.BitConverter.GetBytes (val);
 539                         make_room (6);
 540                         ll_emit (opcode);
 541                         if (BitConverter.IsLittleEndian){
 542                                 System.Array.Copy (s, 0, code, code_len, 4);
 543                                 code_len += 4;
 544                         } else {
 545                                 code [code_len++] = s [3];
 546                                 code [code_len++] = s [2];
 547                                 code [code_len++] = s [1];
 548                                 code [code_len++] = s [0];
 549                         }
 550                 }
 551                 public virtual void Emit (OpCode opcode, string val) {
 552                         int token = abuilder.GetToken (val);
 553                         make_room (6);
 554                         ll_emit (opcode);
 555                         emit_int (token);
 556                 }
 557                 public virtual void Emit (OpCode opcode, Type type) {
 558                         make_room (6);
 559                         ll_emit (opcode);
 560                         emit_int (abuilder.GetToken (type));
 561                 }
 562
 563                 public void EmitCall (OpCode opcode, MethodInfo methodinfo, Type[] optionalParamTypes) {
 564                         throw new NotImplementedException ();
 565                 }
 566
 567                 public void EmitCalli (OpCode opcode, CallingConvention unmanagedCallConv, Type returnType, Type[] paramTypes) {
 568                         SignatureHelper helper
 569                                 = SignatureHelper.GetMethodSigHelper (module, 0, unmanagedCallConv, returnType, paramTypes);
 570                         Emit (opcode, helper);
 571                 }
 572
 573                 public void EmitCalli (OpCode opcode, CallingConventions callConv, Type returnType, Type[] paramTypes, Type[] optionalParamTypes) {
 574                         if (optionalParamTypes != null)
 575                                 throw new NotImplementedException ();
 576
 577                         SignatureHelper helper
 578                                 = SignatureHelper.GetMethodSigHelper (module, callConv, 0, returnType, paramTypes);
 579                         Emit (opcode, helper);
 580                 }
 581
 582                 public virtual void EmitWriteLine (FieldInfo field) {
 583                         throw new NotImplementedException ();
 584                 }
 585                 public virtual void EmitWriteLine (LocalBuilder lbuilder) {
 586                         throw new NotImplementedException ();
 587                 }
 588                 public virtual void EmitWriteLine (string val) {
 589                         Emit (OpCodes.Ldstr, val);
 590                         Emit (OpCodes.Call,
 591                                   typeof (Console).GetMethod ("WriteLine",
 592                                                                                           new Type[1] { typeof(string)}));
 593                 }
 594
 595                 public virtual void EndExceptionBlock () {
 596                         if (open_blocks.Count <= 0)
 597                                 throw new NotSupportedException ("Not in an exception block");
 598                         InternalEndClause ();
 599                         MarkLabel (ex_handlers [cur_block].end);
 600                         ex_handlers [cur_block].End (code_len);
 601                         ex_handlers [cur_block].Debug (cur_block);
 602                         //System.Console.WriteLine ("End Block {0} (handlers: {1})", cur_block, ex_handlers [cur_block].NumHandlers ());
 603                         open_blocks.Pop ();
 604                         if (open_blocks.Count > 0)
 605                                 cur_block = (int)open_blocks.Peek ();
 606                         //Console.WriteLine ("curblock restored to {0}", cur_block);
 607                         //throw new NotImplementedException ();
 608                 }
 609                 public virtual void EndScope () {
 610                         if (sym_writer != null) {
 611                                 sym_writer.CloseScope (code_len);
 612                                 if (scopes == null)
 613                                         throw new InvalidOperationException ();
 614                                 scopes.Pop ();
 615                         }
 616                 }
 617                 public virtual void MarkLabel (Label loc) {
 618                         if (loc.label < 0 || loc.label >= num_labels)
 619                                 throw new System.ArgumentException ("The label is not valid");
 620                         if (label_to_addr [loc.label] >= 0)
 621                                 throw new System.ArgumentException ("The label was already defined");
 622                         label_to_addr [loc.label] = code_len;
 623                 }
 624                 public virtual void MarkSequencePoint (ISymbolDocumentWriter document, int startLine,
 625                                                        int startColumn, int endLine, int endColumn) {
 626                         if (sym_writer == null)
 627                                 return;
 628
 629                         sym_writer.MarkSequencePoint (code_len, startLine, startColumn);
 630                 }
 631                 public virtual void ThrowException (Type exceptionType) {
 632                         throw new NotImplementedException ();
 633                 }
 634                 public void UsingNamespace (String usingNamespace) {
 635                         throw new NotImplementedException ();
 636                 }
 637
 638                 internal void label_fixup () {
 639                         int i;
 640                         for (i = 0; i < num_fixups; ++i) {
 641                                 int diff = label_to_addr [fixups [i].label_idx] - fixups [i].label_base;
 642                                 if (fixups [i].size == 1) {
 643                                         code [fixups [i].pos] = (byte)((sbyte) diff - 1);
 644                                 } else {
 645                                         int old_cl = code_len;
 646                                         code_len = fixups [i].pos;
 647                                         emit_int (diff - 4);
 648                                         code_len = old_cl;
 649                                 }
 650                         }
 651                 }
 652         }
 653 }