[fpc-devel] TBits problem

[Andrea Mauri]

Dear All,
I am not subscribed to the fpcdevel mailing list.
Anyway I am using TBits object but I found some errors using it. Before 
adding a bugreport to the bugtracker I would be sure that there is 
nothing that I am doing wrong.
Below a small procedure that highlights the wrong behaviour of TBits object.

var
   i, bsize1, bsize2: integer;
   b1, b2, b3: TBits;
   s1, s2, s3: string;
begin
   bsize1:= 16;
   bsize2:= 164;
   b1:= TBits.Create;
   b2:= TBits.Create(bsize2);
   b3:= TBits.Create;
   for i:= 0 to bsize1 - 1 do
     b1[i]:= True;

   b2.OrBits(b1);
   b3.OrBits(b1);
   for i:= b1.Size to bsize2 - 1 do
     b3[i]:= False;
   if not b2.Equals(b3) then
   begin
     s1:= bitstostring(b1);
     s2:= bitstostring(b2);
     s3:= bitstostring(b3);
   end;
   b1.Free;
   b2.Free;
   b3.Free;

where bitstostring is a simple function as below:

function bitstostring(b:TBits): string;
var
   i: integer;
   bs: string;
begin
   bs:= '';
   for i:= 0 to b.Size - 1 do
     if b[i] then
       bs:= bs + '1'
     else
       bs:= bs + '0';
   Result:= bs;
end;

What I got is that b2 has set to 1 not only the bits that are 1 in b1 
but also some other bits. b2 and b3 should be the same but they are not.

I tested it on Win32 using lazarus:
Lazarus 1.0.13 r42910M FPC 2.6.2 i386-win32-win32/win64

Could you please let me know if you can reproduce it or if I am doing 
something wrong?

Best regards,
Andrea Mauri

-- 
Dr. Andrea Mauri, PhD
Milano Chemometrics and QSAR Research Group
Department of Environmental Sciences
University of Milano-Bicocca
P.zza della Scienza, 1
20126 Milano - Italy

Tel: ++39 02 64482801
mailto:andrea.mauri at unimib.it
http://michem.disat.unimib.it/chm/