src/interpreter/debugger.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # Copyright 2013 Lucas Bajolet <lucas.bajolet@gmail.com>
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #     http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16
  17 # Debugging of a nit program using the NaiveInterpreter
  18 module debugger
  19
  20 intrude import naive_interpreter
  21 import nitx
  22 intrude import semantize::local_var_init
  23 intrude import semantize::scope
  24 intrude import toolcontext
  25 private import parser_util
  26
  27 redef class Model
  28         # Cleans the model to remove a module and what it defines when semantic analysis fails on injected code
  29         private fun try_remove_module(m: MModule): Bool
  30         do
  31                 var index = -1
  32                 for i in [0 .. mmodules.length[ do
  33                         if mmodules[i] == m then
  34                                 index = i
  35                                 break
  36                         end
  37                 end
  38                 if index == -1 then return false
  39                 var mmodule = mmodules[index]
  40                 mmodules.remove_at(index)
  41                 for classdef in mmodule.mclassdefs do
  42                         var mclass = classdef.mclass
  43                         for i in [0 .. mclass.mclassdefs.length[ do
  44                                 if mclass.mclassdefs[i] == classdef then
  45                                         index = i
  46                                         break
  47                                 end
  48                         end
  49                         mclass.mclassdefs.remove_at(index)
  50                         var propdefs = classdef.mpropdefs
  51                         for propdef in propdefs do
  52                                 var prop = propdef.mproperty
  53                                 for i in [0..prop.mpropdefs.length[ do
  54                                         if prop.mpropdefs[i] == propdef then
  55                                                 index = i
  56                                                 break
  57                                         end
  58                                 end
  59                                 prop.mpropdefs.remove_at(index)
  60                         end
  61                 end
  62                 return true
  63         end
  64 end
  65
  66 redef class ScopeVisitor
  67
  68         redef init(toolcontext)
  69         do
  70                 super
  71                 if toolcontext.dbg != null then
  72                         var localvars = toolcontext.dbg.frame.map
  73                         for i in localvars.keys do
  74                                 scopes.first.variables[i.to_s] = i
  75                         end
  76                 end
  77         end
  78
  79 end
  80
  81 redef class LocalVarInitVisitor
  82         redef fun mark_is_unset(node: AExpr, variable: nullable Variable)
  83         do
  84                 super
  85                 if toolcontext.dbg != null then
  86                         var varname = variable.to_s
  87                         var instmap = toolcontext.dbg.frame.map
  88                         for i in instmap.keys do
  89                                 if i.to_s == varname then
  90                                         mark_is_set(node, variable)
  91                                 end
  92                         end
  93                 end
  94         end
  95
  96 end
  97
  98 redef class ToolContext
  99         private var dbg: nullable Debugger = null
 100
 101         private var had_error: Bool = false
 102
 103         redef fun check_errors
 104         do
 105                 if dbg == null then
 106                         super
 107                 else
 108                         if messages.length > 0 then
 109                                 message_sorter.sort(messages)
 110
 111                                 for m in messages do
 112                                         if m.text.search("Warning") == null then had_error = true
 113                                         sys.stderr.write("{m.to_color_string}\n")
 114                                 end
 115                         end
 116
 117                         messages.clear
 118                 end
 119         end
 120
 121         # -d
 122         var opt_debugger_mode = new OptionBool("Launches the target program with the debugger attached to it", "-d")
 123         # -c
 124         var opt_debugger_autorun = new OptionBool("Launches the target program with the interpreter, such as when the program fails, the debugging prompt is summoned", "-c")
 125
 126         redef init
 127         do
 128                 super
 129                 self.option_context.add_option(self.opt_debugger_mode)
 130                 self.option_context.add_option(self.opt_debugger_autorun)
 131         end
 132 end
 133
 134 redef class ModelBuilder
 135         # Execute the program from the entry point (Sys::main) of the `mainmodule`
 136         # `arguments` are the command-line arguments in order
 137         # REQUIRE that:
 138         #   1. the AST is fully loaded.
 139         #   2. the model is fully built.
 140         #   3. the instructions are fully analysed.
 141         fun run_debugger(mainmodule: MModule, arguments: Array[String])
 142         do
 143                 var time0 = get_time
 144                 self.toolcontext.info("*** START INTERPRETING ***", 1)
 145
 146                 var interpreter = new Debugger(self, mainmodule, arguments)
 147
 148                 interpreter.start(mainmodule)
 149
 150                 var time1 = get_time
 151                 self.toolcontext.info("*** END INTERPRETING: {time1-time0} ***", 2)
 152         end
 153
 154         fun run_debugger_autorun(mainmodule: MModule, arguments: Array[String])
 155         do
 156                 var time0 = get_time
 157                 self.toolcontext.info("*** START INTERPRETING ***", 1)
 158
 159                 var interpreter = new Debugger(self, mainmodule, arguments)
 160                 interpreter.autocontinue = true
 161
 162                 interpreter.start(mainmodule)
 163
 164                 var time1 = get_time
 165                 self.toolcontext.info("*** END INTERPRETING: {time1-time0} ***", 2)
 166         end
 167 end
 168
 169 # Contains all the informations of a Breakpoint for the Debugger
 170 class Breakpoint
 171
 172         # Line to break on
 173         var line: Int
 174
 175         # File concerned by the breakpoint
 176         var file: String
 177
 178         redef init do
 179                 if not file.has_suffix(".nit") then file += ".nit"
 180         end
 181 end
 182
 183 # The class extending `NaiveInterpreter` by adding debugging methods
 184 class Debugger
 185         super NaiveInterpreter
 186
 187         # Keeps the frame count in memory to find when to stop
 188         # and launch the command prompt after a step out call
 189         var step_stack_count = 1
 190
 191         # Triggers a step over an instruction in a nit program
 192         var stop_after_step_over_trigger = true
 193
 194         # Triggers a step out of an instruction
 195         var stop_after_step_out_trigger= false
 196
 197         # Triggers a step in a instruction (enters a function
 198         # if the instruction is a function call)
 199         var step_in_trigger = false
 200
 201         # HashMap containing the breakpoints bound to a file
 202         var breakpoints = new HashMap[String, HashSet[Breakpoint]]
 203
 204         # Contains the current file
 205         var curr_file = ""
 206
 207         # Aliases hashmap (maps an alias to a variable name)
 208         var aliases = new HashMap[String, String]
 209
 210         # Set containing all the traced variables and their related frame
 211         private var traces = new HashSet[TraceObject]
 212
 213         # Map containing all the positions for the positions of the arguments traced
 214         # In a function call
 215         private var fun_call_arguments_positions = new HashMap[Int, TraceObject]
 216
 217         # Triggers the remapping of a trace object in the local context after a function call
 218         var aftermath = false
 219
 220         # Used to prevent the case when the body of the function called is empty
 221         # If it is not, then, the remapping won't be happening
 222         var frame_count_aftermath = 1
 223
 224         # Auto continues the execution until the end or until an error is encountered
 225         var autocontinue = false
 226
 227         #######################################################################
 228         ##                  Execution of statement function                  ##
 229         #######################################################################
 230
 231         # Main loop, every call to a debug command is done here
 232         redef fun stmt(n: nullable AExpr)
 233         do
 234                 if n == null then return
 235
 236                 var frame = self.frame
 237                 var old = frame.current_node
 238                 frame.current_node = n
 239
 240                 if sys.stdin.poll_in then process_debug_command(gets)
 241
 242                 if not self.autocontinue then
 243                         if not n isa ABlockExpr then
 244                                 steps_fun_call(n)
 245
 246                                 breakpoint_check(n)
 247
 248                                 check_funcall_and_traced_args(n)
 249
 250                                 remap(n)
 251
 252                                 check_if_vars_are_traced(n)
 253                         end
 254                 end
 255
 256                 n.stmt(self)
 257                 frame.current_node = old
 258         end
 259
 260         # Does the same as an usual send, except it will modify the call chain on the first call when injecting code at Runtime using the debugger.
 261         # Instead of creating a pristine Frame, it will copy the actual values of the frame, and re-inject them after execution in the current context.
 262         fun rt_send(mproperty: MMethod, args: Array[Instance]): nullable Instance
 263         do
 264                 var recv = args.first
 265                 var mtype = recv.mtype
 266                 var ret = send_commons(mproperty, args, mtype)
 267                 if ret != null then return ret
 268                 var propdef = mproperty.lookup_first_definition(self.mainmodule, mtype)
 269                 return self.rt_call(propdef, args)
 270         end
 271
 272         # Same as a regular call but for a runtime injected module
 273         fun rt_call(mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
 274         do
 275                 if self.modelbuilder.toolcontext.opt_discover_call_trace.value and not self.discover_call_trace.has(mpropdef) then
 276                         self.discover_call_trace.add mpropdef
 277                         self.debug("Discovered {mpropdef}")
 278                 end
 279                 assert args.length == mpropdef.msignature.arity + 1 else debug("Invalid arity for {mpropdef}. {args.length} arguments given.")
 280
 281                 # Look for the AST node that implements the property
 282                 var mproperty = mpropdef.mproperty
 283                 if self.modelbuilder.mpropdef2npropdef.has_key(mpropdef) then
 284                         var npropdef = self.modelbuilder.mpropdef2npropdef[mpropdef]
 285                         self.parameter_check(npropdef, mpropdef, args)
 286                         if npropdef isa AMethPropdef then
 287                                 return npropdef.rt_call(self, mpropdef, args)
 288                         else
 289                                 print "Error, invalid propdef to call at runtime !"
 290                                 return null
 291                         end
 292                 else if mproperty.is_root_init then
 293                         var nclassdef = self.modelbuilder.mclassdef2nclassdef[mpropdef.mclassdef]
 294                         self.parameter_check(nclassdef, mpropdef, args)
 295                         return nclassdef.call(self, mpropdef, args)
 296                 else
 297                         fatal("Fatal Error: method {mpropdef} not found in the AST")
 298                         abort
 299                 end
 300         end
 301
 302         # Evaluates dynamically a snippet of Nit code
 303         # `nit_code` : Nit code to be executed
 304         fun eval(nit_code: String)
 305         do
 306                 var local_toolctx = modelbuilder.toolcontext
 307                 local_toolctx.dbg = self
 308                 var e = local_toolctx.parse_something(nit_code)
 309                 if e isa ABlockExpr then
 310                         nit_code = "module rt_module\n" + nit_code
 311                         e = local_toolctx.parse_something(nit_code)
 312                 end
 313                 if e isa AExpr then
 314                         nit_code = "module rt_module\nprint " + nit_code
 315                         e = local_toolctx.parse_something(nit_code)
 316                 end
 317                 if e isa AModule then
 318                         local_toolctx.had_error = false
 319                         modelbuilder.load_rt_module(self.mainmodule, e, "rt_module")
 320                         local_toolctx.run_phases([e])
 321                         if local_toolctx.had_error then
 322                                 modelbuilder.model.try_remove_module(e.mmodule.as(not null))
 323                                 local_toolctx.dbg = null
 324                                 return
 325                         end
 326                         var mmod = e.mmodule
 327                         if mmod != null then
 328                                 self.mainmodule = mmod
 329                                 var sys_type = mmod.sys_type
 330                                 if sys_type == null then
 331                                         print "Fatal error, cannot find Class Sys !\nAborting"
 332                                         abort
 333                                 end
 334                                 var mobj = new MutableInstance(sys_type)
 335                                 init_instance(mobj)
 336                                 var initprop = mmod.try_get_primitive_method("init", sys_type.mclass)
 337                                 if initprop != null then
 338                                         self.send(initprop, [mobj])
 339                                 end
 340                                 var mainprop = mmod.try_get_primitive_method("run", sys_type.mclass) or else
 341                                         mmod.try_get_primitive_method("main", sys_type.mclass)
 342                                 if mainprop != null then
 343                                         self.rt_send(mainprop, [mobj])
 344                                 end
 345                         else
 346                                 print "Error while loading_rt_module"
 347                         end
 348                 else
 349                         print "Error when parsing, e = {e.class_name}"
 350                 end
 351                 local_toolctx.dbg = null
 352         end
 353
 354         # Encpasulates the behaviour for step over/out
 355         private fun steps_fun_call(n: AExpr)
 356         do
 357                 if self.stop_after_step_over_trigger then
 358                         if self.frames.length <= self.step_stack_count then
 359                                 n.debug("Execute stmt {n.to_s}")
 360                                 while read_cmd do end
 361                         end
 362                 else if self.stop_after_step_out_trigger then
 363                         if frames.length < self.step_stack_count then
 364                                 n.debug("Execute stmt {n.to_s}")
 365                                 while read_cmd do end
 366                         end
 367                 else if step_in_trigger then
 368                         n.debug("Execute stmt {n.to_s}")
 369                         while read_cmd do end
 370                 end
 371         end
 372
 373         # Checks if a breakpoint is encountered, and launches the debugging prompt if true
 374         private fun breakpoint_check(n: AExpr)
 375         do
 376                 var currFileNameSplit = self.frame.current_node.location.file.filename.to_s.split_with("/")
 377
 378                 self.curr_file = currFileNameSplit[currFileNameSplit.length-1]
 379
 380                 var breakpoint = find_breakpoint(curr_file, n.location.line_start)
 381
 382                 if breakpoints.keys.has(curr_file) and breakpoint != null then
 383                         n.debug("Execute stmt {n.to_s}")
 384                         while read_cmd do end
 385                 end
 386         end
 387
 388         # Check if a variable of current expression is traced
 389         # Then prints and/or breaks for command prompt
 390         private fun check_if_vars_are_traced(n: AExpr)
 391         do
 392                 var identifiers_in_instruction = get_identifiers_in_current_instruction(n.location.text)
 393
 394                 for i in identifiers_in_instruction do
 395                         for j in self.traces do
 396                                 if j.is_variable_traced_in_frame(i, frame) then
 397                                         n.debug("Traced variable {i} used")
 398                                         if j.break_on_encounter then while read_cmd do end
 399                                         break
 400                                 end
 401                         end
 402                 end
 403         end
 404
 405         # Function remapping all the traced objects to match their name in the local context
 406         private fun remap(n: AExpr)
 407         do
 408                 if self.aftermath then
 409
 410                         # Trace every argument variable pre-specified
 411                         if self.frame_count_aftermath < frames.length and fun_call_arguments_positions.length > 0 then
 412
 413                                 var ids_in_fun_def = get_identifiers_in_current_instruction(get_function_arguments(frame.mpropdef.location.text))
 414
 415                                 for i in fun_call_arguments_positions.keys do
 416                                         self.fun_call_arguments_positions[i].add_frame_variable(frame, ids_in_fun_def[i])
 417                                 end
 418                         end
 419
 420                         self.aftermath = false
 421                 end
 422         end
 423
 424         # If the current instruction is a function call
 425         # We analyse its signature and the position of traced arguments if the call
 426         # For future remapping when inside the function
 427         private fun check_funcall_and_traced_args(n: AExpr) do
 428                 # If we have a function call, we need to see if any of the arguments is traced (including the caller)
 429                 # if it is, next time we face an instruction, we'll trace the local version on the traced variable in the next frame
 430                 if n isa ACallExpr then
 431                         self.aftermath = true
 432                         self.frame_count_aftermath = frames.length
 433                         fun_call_arguments_positions.clear
 434                         var fun_arguments = get_identifiers_in_current_instruction(get_function_arguments(n.location.text))
 435
 436                         for i in self.traces do
 437                                 for j in [0 .. fun_arguments.length - 1] do
 438                                         if i.is_variable_traced_in_frame(fun_arguments[j],frame) then
 439                                                 fun_call_arguments_positions[j] = i
 440                                         end
 441                                 end
 442                         end
 443                 end
 444         end
 445
 446         #######################################################################
 447         ##                   Processing commands functions                   ##
 448         #######################################################################
 449
 450         fun read_cmd: Bool
 451         do
 452                 printn "> "
 453                 return process_debug_command(gets)
 454         end
 455
 456         # Takes a user command as a parameter
 457         #
 458         # Returns a boolean value, representing whether or not to
 459         # continue reading commands from the console input
 460         fun process_debug_command(command: String): Bool
 461         do
 462                 # Step-out command
 463                 if command == "finish"
 464                 then
 465                         return step_out
 466                 # Step-in command
 467                 else if command == "s"
 468                 then
 469                         return step_in
 470                 # Step-over command
 471                 else if command == "n" then
 472                         return step_over
 473                 # Shows help
 474                 else if command == "help" then
 475                         help
 476                         return true
 477                 # Opens a new NitIndex prompt on current model
 478                 else if command == "nitx" then
 479                         new NitIndex.with_infos(modelbuilder, self.mainmodule).prompt
 480                         return true
 481                 else if command == "bt" or command == "backtrack" then
 482                         print stack_trace
 483                         return true
 484                 # Continues execution until the end
 485                 else if command == "c" then
 486                         return continue_exec
 487                 else if command == "nit" then
 488                         printn "$~> "
 489                         command = gets
 490                         var nit_buf = new FlatBuffer
 491                         while not command == ":q" do
 492                                 nit_buf.append(command)
 493                                 nit_buf.append("\n")
 494                                 printn "$~> "
 495                                 command = gets
 496                         end
 497                         step_in
 498                         eval(nit_buf.to_s)
 499                 else if command == "quit" then
 500                         exit(0)
 501                 else if command == "abort" then
 502                         print stack_trace
 503                         exit(0)
 504                 else
 505                         var parts = command.split_with(' ')
 506                         var cname = parts.first
 507                         # Shows the value of a variable in the current frame
 508                         if cname == "p" or cname == "print" then
 509                                 print_command(parts)
 510                         # Places a breakpoint on line x of file y
 511                         else if cname == "break" or cname == "b" then
 512                                 process_place_break_fun(parts)
 513                         # Removes a breakpoint on line x of file y
 514                         else if cname == "d" or cname == "delete" then
 515                                 process_remove_break_fun(parts)
 516                         # Sets an alias for a variable
 517                         else if parts.length == 2 and parts[1] == "as" then
 518                                 process_alias(parts)
 519                         # Modifies the value of a variable in the current frame
 520                         else if parts.length == 3 and parts[1] == "=" then
 521                                 process_mod_function(parts)
 522                         # Traces the modifications on a variable
 523                         else if cname == "trace" then
 524                                 process_trace_command(parts)
 525                         # Untraces the modifications on a variable
 526                         else if cname == "untrace" then
 527                                 process_untrace_command(parts)
 528                         else
 529                                 bad_command(command)
 530                         end
 531                 end
 532                 return true
 533         end
 534
 535         # Produces help for the commands of the debugger
 536         fun help do
 537                 print ""
 538                 print "Help :"
 539                 print "-----------------------------------"
 540                 print ""
 541                 print "Variables"
 542                 print " * Modification: var_name = value (Warning: var_name must be primitive)"
 543                 print " * Alias: var_name as alias"
 544                 print ""
 545                 print "Printing"
 546                 print " * Variables: p(rint) var_name (Use * to print all local variables)"
 547                 print " * Collections: p(rint) var_name '[' start_index (.. end_index) ']'"
 548                 print ""
 549                 print "Breakpoints"
 550                 print " * File/line: b(reak) file_name line_number"
 551                 print " * Remove: d(elete) id"
 552                 print ""
 553                 print "Tracepoints"
 554                 print " * Variable: trace var_name break/print"
 555                 print " * Untrace variable: untrace var_name"
 556                 print ""
 557                 print "Flow control"
 558                 print " * Next instruction (same-level): n"
 559                 print " * Next instruction: s"
 560                 print " * Finish current method: finish"
 561                 print " * Continue until next breakpoint or end: c"
 562                 print ""
 563                 print "General commands"
 564                 print " * quit: Quits the debugger"
 565                 print " * abort: Aborts the interpretation, prints the stack trace before leaving"
 566                 print " * nitx: Ask questions to the model about its entities (classes, methods, etc.)"
 567                 print " * nit: Inject dynamic code for interpretation"
 568                 print ""
 569         end
 570
 571         #######################################################################
 572         ##               Processing specific command functions               ##
 573         #######################################################################
 574
 575         # Sets the flags to step-over an instruction in the current file
 576         fun step_over: Bool
 577         do
 578                 self.step_stack_count = frames.length
 579                 self.stop_after_step_over_trigger = true
 580                 self.stop_after_step_out_trigger = false
 581                 self.step_in_trigger = false
 582                 return false
 583         end
 584
 585         #Sets the flags to step-out of a function
 586         fun step_out: Bool
 587         do
 588                 self.stop_after_step_over_trigger = false
 589                 self.stop_after_step_out_trigger = true
 590                 self.step_in_trigger = false
 591                 self.step_stack_count = frames.length
 592                 return false
 593         end
 594
 595         # Sets the flags to step-in an instruction
 596         fun step_in: Bool
 597         do
 598                 self.step_in_trigger = true
 599                 self.stop_after_step_over_trigger = false
 600                 self.stop_after_step_out_trigger = false
 601                 return false
 602         end
 603
 604         # Sets the flags to continue execution
 605         fun continue_exec: Bool
 606         do
 607                 self.stop_after_step_over_trigger = false
 608                 self.stop_after_step_out_trigger = false
 609                 self.step_in_trigger = false
 610                 return false
 611         end
 612
 613         fun bad_command(cmd: String) do
 614                 print "Unrecognized command {cmd}. Use 'help' to show help."
 615         end
 616
 617         # Prints the demanded variable in the command
 618         #
 619         # The name of the variable in in position 1 of the array 'parts_of_command'
 620         fun print_command(parts: Array[String])
 621         do
 622                 if parts.length != 2 then
 623                         bad_command(parts.join(" "))
 624                         return
 625                 end
 626                 if parts[1] == "*" then
 627                         var map_of_instances = frame.map
 628
 629                         var self_var = seek_variable("self", frame)
 630                         print "self: {self_var.to_s}"
 631
 632                         for instance in map_of_instances.keys do
 633                                 print "{instance.to_s}: {map_of_instances[instance].to_s}"
 634                         end
 635                 else if parts[1].chars.has('[') and parts[1].chars.has(']') then
 636                         process_array_command(parts)
 637                 else
 638                         var instance = seek_variable(get_real_variable_name(parts[1]), frame)
 639
 640                         if instance != null
 641                         then
 642                                 print_instance(instance)
 643                         else
 644                                 print "Cannot find variable {parts[1]}"
 645                         end
 646                 end
 647         end
 648
 649         # Process the input command to set an alias for a variable
 650         fun process_alias(parts: Array[String]) do
 651                 if parts.length != 3 then
 652                         bad_command(parts.join(" "))
 653                         return
 654                 end
 655                 add_alias(parts.first, parts.last)
 656         end
 657
 658         # Processes the input string to know where to put a breakpoint
 659         fun process_place_break_fun(parts: Array[String])
 660         do
 661                 if parts.length != 3 then
 662                         bad_command(parts.join(" "))
 663                         return
 664                 end
 665                 var bp = get_breakpoint_from_command(parts)
 666                 if bp != null then
 667                         place_breakpoint(bp)
 668                 end
 669         end
 670
 671         # Returns a breakpoint containing the informations stored in the command
 672         fun get_breakpoint_from_command(parts: Array[String]): nullable Breakpoint
 673         do
 674                 if parts[1].is_numeric then
 675                         return new Breakpoint(parts[1].to_i, curr_file)
 676                 else if parts.length >= 3 and parts[2].is_numeric then
 677                         return new Breakpoint(parts[2].to_i, parts[1])
 678                 else
 679                         return null
 680                 end
 681         end
 682
 683         # Processes the command of removing a breakpoint on specified line and file
 684         fun process_remove_break_fun(parts: Array[String])
 685         do
 686                 if parts.length != 2 then
 687                         bad_command(parts.join(" "))
 688                         return
 689                 end
 690                 if parts[1].is_numeric then
 691                         remove_breakpoint(self.curr_file, parts[1].to_i)
 692                 else if parts.length >= 3 and parts[2].is_numeric then
 693                         remove_breakpoint(parts[1], parts[2].to_i)
 694                 end
 695         end
 696
 697         # Processes an array print command
 698         fun process_array_command(parts: Array[String])
 699         do
 700                 var index_of_first_brace = parts[1].chars.index_of('[')
 701                 var variable_name = get_real_variable_name(parts[1].substring(0,index_of_first_brace))
 702                 var braces = parts[1].substring_from(index_of_first_brace)
 703
 704                 var indexes = remove_braces(braces)
 705
 706                 var index_array = new Array[Array[Int]]
 707
 708                 if indexes != null then
 709                         for index in indexes do
 710                                 var temp_indexes_array = process_index(index)
 711                                 if temp_indexes_array != null then
 712                                         index_array.push(temp_indexes_array)
 713                                         #print index_array.last
 714                                 end
 715                         end
 716                 end
 717
 718                 var instance = seek_variable(variable_name, frame)
 719
 720                 if instance != null then
 721                         print_nested_collection(instance, index_array, 0, variable_name, "")
 722                 else
 723                         print "Cannot find variable {variable_name}"
 724                 end
 725         end
 726
 727         # Processes the modification function to modify a variable dynamically
 728         #
 729         # Command of type variable = value
 730         fun process_mod_function(parts: Array[String])
 731         do
 732                 if parts.length != 3 then
 733                         bad_command(parts.join(" "))
 734                         return
 735                 end
 736                 var p0 = parts[0]
 737                 p0 = get_real_variable_name(p0)
 738                 var parts_of_variable = p0.split_with(".")
 739
 740                 if parts_of_variable.length > 1 then
 741                         var last_part = parts_of_variable.pop
 742                         var first_part = p0.substring(0,p0.length - last_part.length - 1)
 743                         var papa = seek_variable(first_part, frame)
 744
 745                         if papa != null and papa isa MutableInstance then
 746                                 var attribute = get_attribute_in_mutable_instance(papa, last_part)
 747
 748                                 if attribute != null then
 749                                         modify_argument_of_complex_type(papa, attribute, parts[2])
 750                                 end
 751                         end
 752                 else
 753                         var target = seek_variable(parts_of_variable[0], frame)
 754                         if target != null then
 755                                 modify_in_frame(target, parts[2])
 756                         end
 757                 end
 758         end
 759
 760         # Processes the untrace variable command
 761         #
 762         # Command pattern : "untrace variable"
 763         fun process_untrace_command(parts: Array[String])
 764         do
 765                 if parts.length != 2 then
 766                         bad_command(parts.join(" "))
 767                         return
 768                 end
 769                 var variable_name = get_real_variable_name(parts[1])
 770                 if untrace_variable(variable_name) then
 771                         print "Untraced variable {parts[1]}"
 772                 else
 773                         print "{parts[1]} is not traced"
 774                 end
 775         end
 776
 777         # Processes the trace variable command
 778         #
 779         # Command pattern : "trace variable [break/print]"
 780         fun process_trace_command(parts: Array[String])
 781         do
 782                 if parts.length != 3 then
 783                         bad_command(parts.join(" "))
 784                         return
 785                 end
 786                 var variable_name = get_real_variable_name(parts[1])
 787                 var breaker:Bool
 788
 789                 if seek_variable(variable_name, frame) == null then
 790                         print "Cannot find a variable called {parts[1]}"
 791                         return
 792                 end
 793
 794                 if parts[2] == "break" then
 795                         breaker = true
 796                 else
 797                         breaker = false
 798                 end
 799
 800                 trace_variable(variable_name, breaker)
 801
 802                 print "Successfully tracing {parts[1]}"
 803         end
 804
 805         #######################################################################
 806         ##                    Trace Management functions                     ##
 807         #######################################################################
 808
 809         # Effectively untraces the variable called *variable_name*
 810         #
 811         # Returns true if the variable exists, false otherwise
 812         private fun untrace_variable(variable_name: String): Bool
 813         do
 814                 var to_remove: nullable TraceObject = null
 815                 for i in self.traces do
 816                         if i.is_variable_traced_in_frame(variable_name, frame) then
 817                                 to_remove = i
 818                         end
 819                 end
 820
 821                 if to_remove != null then
 822                         self.traces.remove(to_remove)
 823                         return true
 824                 else
 825                         return false
 826                 end
 827         end
 828
 829         # Effectively traces the variable *variable_name* either in print or break mode depending on the value of breaker (break if true, print if false)
 830         #
 831         private fun trace_variable(variable_name: String, breaker: Bool)
 832         do
 833                 for i in self.traces do
 834                         if i.is_variable_traced_in_frame(variable_name, frame) then
 835                                 print "This variable is already traced"
 836                                 return
 837                         end
 838                 end
 839
 840                 var trace_object: TraceObject
 841
 842                 if breaker then
 843                         trace_object = new TraceObject(true)
 844                 else
 845                         trace_object = new TraceObject(false)
 846                 end
 847
 848                 # We trace the current variable found for the current frame
 849                 trace_object.add_frame_variable(self.frame, variable_name)
 850
 851                 var position_of_variable_in_arguments = get_position_of_variable_in_arguments(frame, variable_name)
 852
 853                 # Start parsing the frames starting with the parent of the current one, until the highest
 854                 # When the variable traced is declared locally, the loop stops
 855                 for i in [1 .. frames.length-1] do
 856
 857                         # If the variable was reported to be an argument of the previous frame
 858                         if position_of_variable_in_arguments != -1 then
 859
 860                                 var local_name = get_identifiers_in_current_instruction(get_function_arguments(frames[i].current_node.location.text))[position_of_variable_in_arguments]
 861
 862                                 position_of_variable_in_arguments = get_position_of_variable_in_arguments(frames[i], local_name)
 863
 864                                 trace_object.add_frame_variable(frames[i], local_name)
 865                         else
 866                                 break
 867                         end
 868                 end
 869
 870                 self.traces.add(trace_object)
 871         end
 872
 873         # If the variable *variable_name* is an argument of the function being executed in the frame *frame*
 874         # The function returns its position in the arguments
 875         # Else, it returns -1
 876         private fun get_position_of_variable_in_arguments(frame: Frame, variable_name: String): Int
 877         do
 878                 var identifiers = get_identifiers_in_current_instruction(get_function_arguments(frame.mpropdef.location.text))
 879                 for i in [0 .. identifiers.length-1] do
 880                         # If the current traced variable is an argument of the current function, we trace its parent (at least)
 881                         if identifiers[i] == variable_name then return i
 882                 end
 883                 return -1
 884         end
 885
 886         # Gets all the identifiers of an instruction (uses the rules of Nit as of Mar 05 2013)
 887         #
 888         fun get_identifiers_in_current_instruction(instruction: Text): Array[String]
 889         do
 890                 var result_array = new Array[String]
 891                 var instruction_buffer = new FlatBuffer
 892
 893                 var trigger_char_escape = false
 894                 var trigger_string_escape = false
 895
 896                 for i in instruction.chars do
 897                         if trigger_char_escape then
 898                                 if i == '\'' then trigger_char_escape = false
 899                         else if trigger_string_escape then
 900                                 if i == '{' then
 901                                         trigger_string_escape = false
 902                                 else if i == '\"' then trigger_string_escape = false
 903                         else
 904                                 if i.is_alphanumeric or i == '_' then
 905                                         instruction_buffer.add(i)
 906                                 else if i == '.' then
 907                                         if instruction_buffer.is_numeric or (instruction_buffer.chars[0] >= 'A' and instruction_buffer.chars[0] <= 'Z') then
 908                                                 instruction_buffer.clear
 909                                         else
 910                                                 result_array.push(instruction_buffer.to_s)
 911                                                 instruction_buffer.add(i)
 912                                         end
 913                                 else if i == '\'' then
 914                                         trigger_char_escape = true
 915                                 else if i == '\"' then
 916                                         trigger_string_escape = true
 917                                 else if i == '}' then
 918                                         trigger_string_escape = true
 919                                 else
 920                                         if instruction_buffer.length > 0 and not instruction_buffer.is_numeric and not (instruction_buffer.chars[0] >= 'A' and instruction_buffer.chars[0] <= 'Z') then result_array.push(instruction_buffer.to_s)
 921                                         instruction_buffer.clear
 922                                 end
 923                         end
 924                 end
 925
 926                 if instruction_buffer.length > 0 and not instruction_buffer.is_numeric and not (instruction_buffer.chars[0] >= 'A' and instruction_buffer.chars[0] <= 'Z') then result_array.push(instruction_buffer.to_s)
 927
 928                 return result_array
 929         end
 930
 931         # Takes a function call or declaration and strips all but the arguments
 932         #
 933         fun get_function_arguments(function: Text): String
 934         do
 935                 var buf = new FlatBuffer
 936                 var trigger_copy = false
 937
 938                 for i in function.chars do
 939                         if i == ')' then break
 940                         if trigger_copy then buf.add(i)
 941                         if i == '(' then trigger_copy = true
 942                 end
 943
 944                 return buf.to_s
 945         end
 946
 947         #######################################################################
 948         ##                    Alias management functions                     ##
 949         #######################################################################
 950
 951         # Adds a new alias to the tables
 952         fun add_alias(var_represented: String, alias: String)
 953         do
 954                 self.aliases[alias] = var_represented
 955         end
 956
 957         # Gets the real name of a variable hidden by an alias
 958         fun get_variable_name_by_alias(alias: String): nullable String
 959         do
 960                 if self.aliases.keys.has(alias) then
 961                         return self.aliases[alias]
 962                 end
 963
 964                 return null
 965         end
 966
 967         # Gets the variable named by name, whether it is an alias or not
 968         fun get_real_variable_name(name: String): String
 969         do
 970                 var explode_string = name.split_with(".")
 971                 var final_string = new FlatBuffer
 972                 for i in explode_string do
 973                         var alias_resolved = get_variable_name_by_alias(i)
 974                         if alias_resolved != null then
 975                                 final_string.append(get_real_variable_name(alias_resolved))
 976                         else
 977                                 final_string.append(i)
 978                         end
 979                         final_string.append(".")
 980                 end
 981
 982                 return final_string.substring(0,final_string.length-1).to_s
 983         end
 984
 985         #######################################################################
 986         ##                         Print functions                           ##
 987         #######################################################################
 988
 989         # Prints an object instance and its attributes if it has some
 990         #
 991         # If it is a primitive type, its value is directly printed
 992         fun print_instance(instance: Instance)
 993         do
 994                 if instance isa MutableInstance then
 995                         print "\{"
 996                         print "\ttype : {instance},"
 997
 998                         printn("\t")
 999
1000                         print instance.attributes.join(",\n\t"," : ")
1001
1002                         print "\}"
1003                 else
1004                         print "{instance}"
1005                 end
1006         end
1007
1008         # Prints the attributes demanded in a SequenceRead
1009         # Used recursively to print nested collections
1010         fun print_nested_collection(instance: Instance, indexes: Array[Array[Int]], depth: Int, variable_name: String, depth_string: String)
1011         do
1012                 var collection: nullable SequenceRead[Object] = null
1013                 var real_collection_length: nullable Int = null
1014
1015                 if instance isa MutableInstance then
1016                         real_collection_length = get_collection_instance_real_length(instance)
1017                         collection = get_primary_collection(instance)
1018                 end
1019
1020                 if collection != null and real_collection_length != null then
1021                         for i in indexes[depth] do
1022                                 if i >= 0 and i < real_collection_length then
1023                                         if depth == indexes.length-1 then
1024                                                 print "{variable_name}{depth_string}[{i}] = {collection[i]}"
1025                                         else
1026                                                 var item_i = collection[i]
1027
1028                                                 if item_i isa MutableInstance then
1029                                                         print_nested_collection(item_i, indexes, depth+1, variable_name, depth_string+"[{i}]")
1030                                                 else
1031                                                         print "The item at {variable_name}{depth_string}[{i}] is not a collection"
1032                                                         print item_i
1033                                                 end
1034                                         end
1035                                 else
1036                                         print "Out of bounds exception : i = {i} and collection_length = {real_collection_length.to_s}"
1037
1038                                         if i < 0 then
1039                                                 continue
1040                                         else if i >= real_collection_length then
1041                                                 break
1042                                         end
1043                                 end
1044                         end
1045                 else
1046                         if collection == null then
1047                                 print "Cannot find {variable_name}{depth_string}"
1048                         else if real_collection_length != null then
1049                                 print "Cannot find attribute length in {instance}"
1050                         else
1051                                 print "Unknown error."
1052                                 abort
1053                         end
1054                 end
1055         end
1056
1057         #######################################################################
1058         ##                  Variable Exploration functions                   ##
1059         #######################################################################
1060
1061         # Seeks a variable from the current frame called 'variable_path', can introspect complex objects using function get_variable_in_mutable_instance
1062         private fun seek_variable(variable_path: String, frame: Frame): nullable Instance
1063         do
1064                 var full_variable = variable_path.split_with(".")
1065
1066                 var full_variable_iterator = full_variable.iterator
1067
1068                 var first_instance = get_variable_in_frame(full_variable_iterator.item, frame)
1069
1070                 if first_instance == null then  return null
1071
1072                 if full_variable.length <= 1 then return first_instance
1073
1074                 full_variable_iterator.next
1075
1076                 if not (first_instance isa MutableInstance and full_variable_iterator.is_ok) then return null
1077
1078                 return get_variable_in_mutable_instance(first_instance, full_variable_iterator)
1079         end
1080
1081         # Gets a variable 'variable_name' contained in the frame 'frame'
1082         private fun get_variable_in_frame(variable_name: String, frame: Frame): nullable Instance
1083         do
1084                 if variable_name == "self" then
1085                         if frame.arguments.length >= 1 then return frame.arguments.first
1086                 end
1087
1088                 var map_of_instances = frame.map
1089
1090                 for key in map_of_instances.keys do
1091                         if key.to_s == variable_name then
1092                                 return map_of_instances[key]
1093                         end
1094                 end
1095
1096                 return null
1097         end
1098
1099         # Gets an attribute 'attribute_name' contained in variable 'variable'
1100         fun get_attribute_in_mutable_instance(variable: MutableInstance, attribute_name: String): nullable MAttribute
1101         do
1102                 var map_of_attributes = variable.attributes
1103
1104                 for key in map_of_attributes.keys do
1105                         if key.to_s.substring_from(1) == attribute_name then
1106                                 return key
1107                         end
1108                 end
1109
1110                 return null
1111         end
1112
1113         # Recursive function, returns the variable described by 'total_chain'
1114         fun get_variable_in_mutable_instance(variable: MutableInstance, iterator: Iterator[String]): nullable Instance
1115         do
1116                 var attribute = get_attribute_in_mutable_instance(variable, iterator.item)
1117
1118                 if attribute == null then return null
1119
1120                 iterator.next
1121
1122                 if iterator.is_ok then
1123                         var new_variable = variable.attributes[attribute]
1124                         if new_variable isa MutableInstance then
1125                                 return get_variable_in_mutable_instance(new_variable, iterator)
1126                         else
1127                                 return null
1128                         end
1129                 else
1130                         return variable.attributes[attribute]
1131                 end
1132         end
1133
1134         #######################################################################
1135         ##                     Array exploring functions                     ##
1136         #######################################################################
1137
1138         # Gets the length of a collection
1139         # Used by the debugger, else if we call Collection.length, it returns the capacity instead
1140         fun get_collection_instance_real_length(collection: MutableInstance): nullable Int
1141         do
1142                 var collection_length_attribute = get_attribute_in_mutable_instance(collection, "length")
1143
1144                 if collection_length_attribute != null then
1145                         var primitive_length_instance = collection.attributes[collection_length_attribute]
1146                         if primitive_length_instance isa PrimitiveInstance[Int] then
1147                                 return primitive_length_instance.val
1148                         end
1149                 end
1150
1151                 return null
1152         end
1153
1154         # Processes the indexes of a print array call
1155         # Returns an array containing all the indexes demanded
1156         fun process_index(index_string: String): nullable Array[Int]
1157         do
1158                 var from_end_index = index_string.chars.index_of('.')
1159                 var to_start_index = index_string.chars.last_index_of('.')
1160
1161                 if from_end_index != -1 and to_start_index != -1 then
1162                         var index_from_string = index_string.substring(0,from_end_index)
1163                         var index_to_string = index_string.substring_from(to_start_index+1)
1164
1165                         if index_from_string.is_numeric and index_to_string.is_numeric then
1166                                 var result_array = new Array[Int]
1167
1168                                 var index_from = index_from_string.to_i
1169                                 var index_to = index_to_string.to_i
1170
1171                                 for i in [index_from..index_to] do
1172                                         result_array.push(i)
1173                                 end
1174
1175                                 return result_array
1176                         end
1177                 else
1178                         if index_string.is_numeric
1179                         then
1180                                 var result_array = new Array[Int]
1181
1182                                 result_array.push(index_string.to_i)
1183
1184                                 return result_array
1185                         else
1186                                 return null
1187                         end
1188                 end
1189
1190                 return null
1191         end
1192
1193         # Gets a collection in a MutableInstance
1194         fun get_primary_collection(container: MutableInstance): nullable SequenceRead[Object]
1195         do
1196                 var items_of_array = get_attribute_in_mutable_instance(container, "items")
1197                 if items_of_array != null then
1198                         var array = container.attributes[items_of_array]
1199
1200                         if array isa PrimitiveInstance[Object] then
1201                                 var sequenceRead_final = array.val
1202                                 if sequenceRead_final isa SequenceRead[Object] then
1203                                         return sequenceRead_final
1204                                 end
1205                         end
1206                 end
1207
1208                 return null
1209         end
1210
1211         # Removes the braces '[' ']' in a print array command
1212         # Returns an array containing their content
1213         fun remove_braces(braces: String): nullable Array[String]
1214         do
1215                 var buffer = new FlatBuffer
1216
1217                 var result_array = new Array[String]
1218
1219                 var number_of_opening_brackets = 0
1220                 var number_of_closing_brackets = 0
1221
1222                 var last_was_opening_bracket = false
1223
1224                 for i in braces.chars do
1225                         if i == '[' then
1226                                 if last_was_opening_bracket then
1227                                         return null
1228                                 end
1229
1230                                 number_of_opening_brackets += 1
1231                                 last_was_opening_bracket = true
1232                         else if i == ']' then
1233                                 if not last_was_opening_bracket then
1234                                         return null
1235                                 end
1236
1237                                 result_array.push(buffer.to_s)
1238                                 buffer.clear
1239                                 number_of_closing_brackets += 1
1240                                 last_was_opening_bracket = false
1241                         else if i.is_numeric or i == '.' then
1242                                 buffer.append(i.to_s)
1243                         else if not i == ' ' then
1244                                 return null
1245                         end
1246                 end
1247
1248                 if number_of_opening_brackets != number_of_closing_brackets then
1249                         return null
1250                 end
1251
1252                 return result_array
1253         end
1254
1255         #######################################################################
1256         ##                   Breakpoint placing functions                    ##
1257         #######################################################################
1258
1259         # Places a breakpoint on line 'line_to_break' for file 'file_to_break'
1260         fun place_breakpoint(breakpoint: Breakpoint)
1261         do
1262                 if not self.breakpoints.keys.has(breakpoint.file) then
1263                         self.breakpoints[breakpoint.file] = new HashSet[Breakpoint]
1264                 end
1265                 if find_breakpoint(breakpoint.file, breakpoint.line) == null then
1266                         self.breakpoints[breakpoint.file].add(breakpoint)
1267                         print "Breakpoint added on line {breakpoint.line} for file {breakpoint.file}"
1268                 else
1269                         print "Breakpoint already present on line {breakpoint.line} for file {breakpoint.file}"
1270                 end
1271         end
1272
1273         #######################################################################
1274         ##                  Breakpoint removing functions                    ##
1275         #######################################################################
1276
1277         # Removes a breakpoint on line 'line_to_break' for file 'file_to_break'
1278         fun remove_breakpoint(file_to_break: String, line_to_break: Int)
1279         do
1280                 if self.breakpoints.keys.has(file_to_break) then
1281                         var bp = find_breakpoint(file_to_break, line_to_break)
1282
1283                         if bp != null then
1284                                 self.breakpoints[file_to_break].remove(bp)
1285                                 print "Breakpoint removed on line {line_to_break} for file {file_to_break}"
1286                                 return
1287                         end
1288                 end
1289
1290                 print "No breakpoint existing on line {line_to_break} for file {file_to_break}"
1291         end
1292
1293         #######################################################################
1294         ##                  Breakpoint searching functions                   ##
1295         #######################################################################
1296
1297         # Finds a breakpoint for 'file' and 'line' in the class HashMap
1298         fun find_breakpoint(file: String, line: Int): nullable Breakpoint
1299         do
1300                 if self.breakpoints.keys.has(file)
1301                 then
1302                         for i in self.breakpoints[file]
1303                         do
1304                                 if i.line == line
1305                                 then
1306                                         return i
1307                                 end
1308                         end
1309                 end
1310
1311                 return null
1312         end
1313
1314         #######################################################################
1315         ##                  Runtime modification functions                   ##
1316         #######################################################################
1317
1318         # Modifies the value of a variable contained in a frame
1319         fun modify_in_frame(variable: Instance, value: String)
1320         do
1321                 var new_variable = get_variable_of_type_with_value(variable.mtype.to_s, value)
1322                 if new_variable != null
1323                 then
1324                         var keys = frame.map.keys
1325                         for key in keys
1326                         do
1327                                 if frame.map[key] == variable
1328                                 then
1329                                         frame.map[key] = new_variable
1330                                 end
1331                         end
1332                 end
1333         end
1334
1335         # Modifies the value of a variable contained in a MutableInstance
1336         fun modify_argument_of_complex_type(papa: MutableInstance, attribute: MAttribute, value: String)
1337         do
1338                 var final_variable = papa.attributes[attribute]
1339                 var type_of_variable = final_variable.mtype.to_s
1340                 var new_variable = get_variable_of_type_with_value(type_of_variable, value)
1341                 if new_variable != null
1342                 then
1343                         papa.attributes[attribute] = new_variable
1344                 end
1345         end
1346
1347         #######################################################################
1348         ##                   Variable generator functions                    ##
1349         #######################################################################
1350
1351         # Returns a new variable of the type 'type_of_variable' with a value of 'value'
1352         fun get_variable_of_type_with_value(type_of_variable: String, value: String): nullable Instance
1353         do
1354                 if type_of_variable == "Int" then
1355                         return get_int(value)
1356                 else if type_of_variable == "Float" then
1357                         return get_float(value)
1358                 else if type_of_variable == "Bool" then
1359                         return get_bool(value)
1360                 else if type_of_variable == "Char" then
1361                         return get_char(value)
1362                 end
1363
1364                 return null
1365         end
1366
1367         # Returns a new int instance with value 'value'
1368         fun get_int(value: String): nullable Instance
1369         do
1370                 if value.is_numeric then
1371                         return int_instance(value.to_i)
1372                 else
1373                         return null
1374                 end
1375         end
1376
1377         # Returns a new float instance with value 'value'
1378         fun get_float(value:String): nullable Instance
1379         do
1380                 if value.is_numeric then
1381                         return float_instance(value.to_f)
1382                 else
1383                         return null
1384                 end
1385         end
1386
1387         # Returns a new char instance with value 'value'
1388         fun get_char(value: String): nullable Instance
1389         do
1390                 if value.length >= 1 then
1391                         return char_instance(value.chars[0])
1392                 else
1393                         return null
1394                 end
1395         end
1396
1397         # Returns a new bool instance with value 'value'
1398         fun get_bool(value: String): nullable Instance
1399         do
1400                 if value.to_lower == "true" then
1401                         return self.true_instance
1402                 else if value.to_lower == "false" then
1403                         return self.false_instance
1404                 else
1405                         print "Invalid value, a boolean must be set at \"true\" or \"false\""
1406                         return null
1407                 end
1408         end
1409
1410 end
1411
1412 redef class AMethPropdef
1413
1414         # Same as call except it will copy local variables of the parent frame to the frame defined in this call.
1415         # Not supposed to be used by anyone else than the Debugger.
1416         private fun rt_call(v: Debugger, mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
1417         do
1418                 var f = new Frame(self, self.mpropdef.as(not null), args)
1419                 var curr_instances = v.frame.map
1420                 for i in curr_instances.keys do
1421                         f.map[i] = curr_instances[i]
1422                 end
1423                 call_commons(v,mpropdef,args,f)
1424                 var currFra = v.frames.shift
1425                 for i in curr_instances.keys do
1426                         if currFra.map.keys.has(i) then
1427                                 curr_instances[i] = currFra.map[i]
1428                         end
1429                 end
1430                 if v.returnmark == f then
1431                         v.returnmark = null
1432                         var res = v.escapevalue
1433                         v.escapevalue = null
1434                         return res
1435                 end
1436                 return null
1437
1438         end
1439 end
1440
1441 # Traces the modifications of an object linked to a certain frame
1442 private class TraceObject
1443
1444         # Map of the local names bound to a frame
1445         var trace_map: HashMap[Frame, String]
1446         # Decides if breaking or printing statement when the variable is encountered
1447         var break_on_encounter: Bool
1448
1449         init(break_on_encounter: Bool)
1450         do
1451                 trace_map = new HashMap[Frame, String]
1452                 self.break_on_encounter = break_on_encounter
1453         end
1454
1455         # Adds the local alias for a variable and the frame bound to it
1456         fun add_frame_variable(frame: Frame, variable_name: String)
1457         do
1458                 self.trace_map[frame] = variable_name
1459         end
1460
1461         # Checks if the prompted variable is traced in the specified frame
1462         fun is_variable_traced_in_frame(variable_name: String, frame: Frame): Bool
1463         do
1464                 if self.trace_map.has_key(frame) then
1465                         if self.trace_map[frame] == variable_name then
1466                                 return true
1467                         end
1468                 end
1469
1470                 return false
1471         end
1472
1473 end
1474
1475 redef class ANode
1476
1477         # Breaks automatically when encountering an error
1478         # Permits the injunction of commands before crashing
1479         redef fun fatal(v: NaiveInterpreter, message: String)
1480         do
1481                 if v isa Debugger then
1482                         print "An error was encountered, the program will stop now."
1483                         self.debug(message)
1484                         while v.process_debug_command(gets) do end
1485                 end
1486
1487                 super
1488         end
1489 end