Various GPC Questions

28 Jul 1998

      I have found a couple of apparent bugs in GPC:

1. Debugger and objects.
------------------------------

There appears to be an error in debug entries generated for objects.
When viewing 
object fields under the debugger, the wrong values are shown for the
right field.

If I set a breakpoint at the end of the constructor and examine *Self, I
get

   *Self: {One = 74404, Two = 1, Three = 2}

program bad;

type
  MyObject = object
    One   : Integer;
    Two   : Integer;
    Three : Integer;
    constructor init;
  end;
var
  x : MyObject;

constructor MyObject.init;
begin
  One := 1;
  Two := 2;
  Three := 3;
end;

begin
  x.init;
end.

Direct Access Files
-----------------------

There appears to be some discrepancy between record numbering for
reading and writing.
To read record n, I specify SeekRead(n). But to write record n, I
specify SeekWrite(n).
When I execute the following program, I get:

Created File
0 : 0
1 : 1
2 : 2
3 : 3
4 : 4
5 : 5
Modified file at position 0 to 55
Modified file at position 2 to 66
Modified file at position 6 to 77
0 : 0
1 : 66
2 : 2
3 : 3
4 : 4
5 : 77

PROGRAM Bad1;

TYPE
  DAFile = File [0..5] of Integer;
VAR
  MyFile : bindable DAFile;

procedure AssignFile;
var
  b : BindingType;
begin
  unbind(MyFile);
  b := binding(MyFile);
  b.name := 'test.dat' + chr(0);
  bind(MyFile,b);
end;

procedure CreateFile;
var
  i : Integer;
begin
  AssignFile;
  Rewrite(MyFile);
  for i := 0 to 5 do
    Write(MyFile,i);
  Close(MyFile);
end;

procedure ModifyFile(index : Integer; val : Integer);
var
  pos : Integer;
begin
  AssignFile;
  SeekWrite(MyFile,Index);
  pos := Position(MyFile);
  Write(MyFile,val);
  Close(MyFile);
  Writeln('Modified file at position ',pos,' to ',val);
end;

procedure PrintFile;
var
  i,val,pos : Integer;
begin
  AssignFile;
  for i := 0 to 5 do
  begin
    SeekRead(MyFile,i);
    pos := Position(MyFile);
    Read(MyFile,val);
    WRITELN(pos,' : ',val);
  end;
  Close(MyFile);
end;

begin
  CreateFile;
  WRITELN('Created File');
  PrintFile;
  ModifyFile(0,55);
  ModifyFile(2,66);
  ModifyFile(6,77);
  PrintFile;
end.

TurboVision
---------------

I was surprised to see that the Turbo Vision source code is in C++ and I
see that
Turbo Vision is still in the TO DO list for GPC.

Whats the current situation?

I presume that GPC can't access Gnu C++ classes. Therefore someone needs
to
either write a wrapper or to convert the C++ classes into PASCAL
objects. 

Is anyone currently working on a port?

Turbo Vision is fairly important to me so I'd be interested porting it
to GPC.

Russell Thamm

Various GPC Questions

Thamm, Russell