Pascal Battleships Loadgame

Question

The following code uses a game saved in a text file in the form 0/8B1/8B1/8B1/1P6B1/1P8/7S2/7S2/1AAAAA1S2/5DDD2

(for example) and puts the correct pieces in a board. The numbers represent a series of consecutive spaces and / means a new row. The letters represent the ship in that cell of the board ( a two dimensional array).

When I run it it come sup with EXTERNAL SIGSEGV and shows me assembly code saying 00403D61 833a00 cmpl $0x0,(%edx)

Does anyone know what is wrong with it and how to fix it?

Procedure LoadGame(FileName : String; Var Board : TBoard);
Var
  Line : String;
  CurrentFile : Text;
  Row , count : Integer;
  column, counter: Integer;
Begin
  AssignFile(CurrentFile, FileName);
  Reset(CurrentFile);
  Readln(CurrentFile, Line);
  for counter := 1 to length(line) do
  begin
    if (Line[counter] in ['A'..'Z','m','h']) then
    begin
      board[row,column]:=line[counter];
      column:=column+1;
    end
    else
      if line[counter]='0' then
      begin
        for column := 0 to 9 do
        begin
          board[row,column]:='-';
        end;
      end
      else
        If line[counter]='/' then
        begin
          row :=row+1;
          column:=0;
        end
        else 
          for count := 0 to (strtoint(line[counter])-1) do
          begin
            Board[row,column+count] :='-';
            column:=column+1;
          end;
  end;
  CloseFile(CurrentFile);
End;

You should be more accurate with row and column variables which changes in chaotic ways (for the first glance) inside the main loop. — Abelisto
Stack Overflow is not intended as a substitute for debugging — David Heffernan
But there are other forums that can help with debugging, on StackExchange. I am not 100% sure, but I guess codereview.stackexchange.com might be right choice. — Rudy Velthuis

MartynA MartynA · Accepted Answer · 2016-06-04T16:24:54

You haven't initialised the variables row and column before you use them. You must do that, because since they are local variables (on the stack), they will contain random values when LoadGame is called. See changes/suggestions below. I haven't debugged your code, that's for you to do.

Procedure LoadGame(FileName : String; Var Board : TBoard);
Var
  Line : String;
  CurrentFile : Text;
  Row , count : Integer;
  column, counter: Integer;
Begin
  // Ideally, you should initialise each cell of the board with some value not used in the following so you can easily verify the effect of the loading operation

  AssignFile(CurrentFile, FileName);
  Reset(CurrentFile);
  Readln(CurrentFile, Line);

  // initialise Row and Column
  Row := 0;     // assuming the cells are zero-based
  Column := 0;  // ditto

  for counter := 1 to length(line) do
    begin
      if (Line[counter] in ['A'..'Z','m','h']) then
      begin
        board[row,column]:=line[counter];
        column:=column+1;
      end
      else
      if line[counter]='0' then
      begin
        for column := 0 to 9 do
          begin
            board[row,column]:='-';
          end;
      end
      else If line[counter]='/' then
      begin
        row :=row+1;
        column:=0;
      end

      else for count := 0 to (strtoint(line[counter])-1) do
      begin
        Board[row,column+count] :='-';
        column:=column+1;
      end;
  end;

  CloseFile(CurrentFile);
End;

Pascal Battleships Loadgame

1 Answers