Freeing Memory causes SIGSEGV Error
lazarus / 39-Graphics

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itwhiz · 2011-06-04 22:55

Getting back into writing Pascal Code, and I'm trying the following
code, all it does is loads a JPG, rotates it and then displays it.

Procedure DisplayPiece(X,Y,PieceNum,Rotation: Integer);
Var

    jpg : TJPEGImage;
    bmp : TBitMap;
    bmp2 : TBitmap;
    rect : TRect;
    TileFileName  : string;
Begin
 Try
  TileFileName := GetCurrentDir + '/Tiles/' + inttostr(PieceNum) +
'.JPG';
  jpg :=TJPEGImage.Create;
  jpg.LoadFromFile(TileFileName);
  bmp :=TBitmap.Create;
  bmp.assign(jpg);
  bmp2 := Tbitmap.Create;

  bmp2 := (Rotate(bmp,rotation));



  rect := Main.Drawgrid1.CellRect((X),(Y));
  Main.Drawgrid1.Canvas.StretchDraw(rect,bmp2);
  Board_Array [X,Y] := Piece_array[PieceNum];
 Finally
 End;
  bmp.Free;
  bmp2.Free;

end;             

I've included the 2 .Free commands to manage memory usage, but when it
hits the 2nd one my program errors.

I'm using Ubuntu & Windows XP and Lazarus 0.9.26.2(on Ubuntu) &
0.9.28.2(On XP), FreePascal 2.2.4 on both.

Any ideas ?

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Blaazen · 2011-06-04 23:32

Hello,

1) You have VERY old versions of both freepascal and lazarus. Last
stable are 0.9.30 & 2.4.4
2) You did not specify the error message.
3) TileFileName := GetCurrentDir + '/Tiles/' + inttostr(PieceNum) +
'.JPG';
  - is not a cross-platform path (= will not work on Windows)
4) I cannot test all your code, Rotate is probably your own function,
but
Code: [Select]Try
  TileFileName := '/media/disk/v1/Obrázky/Zoot/toxiqueb.jpg';  //my
own bitmap
  jpg :=TJPEGImage.Create;
  jpg.LoadFromFile(TileFileName);
  bmp :=TBitmap.Create;
  bmp.assign(jpg);
  bmp2 := Tbitmap.Create;
  bmp2 := bmp;
  Image2.Picture.Assign(bmp2);  //I added this line for test purposes
only
  { (Rotate(bmp,rotation));
  rect := Main.Drawgrid1.CellRect((X),(Y));
  Main.Drawgrid1.Canvas.StretchDraw(rect,bmp2);
  Board_Array [X,Y] := Piece_array[PieceNum];    }
 Finally
 End;
  bmp.Free;
  bmp2.Free;
  jpg.Free;Causes crash on line " bmp2.Free;" because - in fact - it
tries to free "bmp" twice.
It works when I use:
Code: [Select] bmp2.Assign(bmp);
 instead of Code: [Select]bmp2 := bmp;And you should do
Code: [Select]jpg.Free;to avoid memory leak.

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itwhiz · 2011-06-04 23:53

Thanks very much for the reply, as I said I've been away from this too
long - SQL Server/Oracle developer for 10 years.

I'll upgrade my systems tomorrow to the latest version and re-write my
code.

I do agree with you that the TileFileName command should not work on
windows.
If I switch the '/' to '\' then it works on Windows but not on Ubuntu,
but this way round '/' it seems to work on both.

Thanks again for the help. I'm sure I'll have some more questions very
soon.

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Blaazen · 2011-06-05 00:07

You can use constant "DirectorySeparator", it is then done automaticly
('/' for Linux and '\' for Win)
Code: [Select]TileFileName := GetCurrentDir
+DirectorySeparator+'Tiles'+DirectorySeparator+ inttostr(PieceNum) +
'.JPG';