Problem with Integer vs LongWord in Delphi and FPC

**Jimmy Valavanis** · 24-05-2007, 08:47 AM

System: Windows XP SP2, P4 3GHz
Compiler/IDE: Dephi 5.0 and FPC 2.1.4
Libraries/API: None

I've made a little testing program:

Code:

program integer_test;

{$APPTYPE CONSOLE}
var
  i: integer;
  w: longword;
  x, y: longword;
begin
  x := $FFFFFFF;  // 268435455
  y := $FFFFFFFB; // 4294967291
  i := abs(x - y);
  writeln(i);     // Delphi output: 268435460, FPC output -4 (!!!)
  w := abs(x - y);
  writeln(w);     // Delphi output: 268435460, FPC output 4026531836
  writeln;
  i := x - y;
  writeln(i);     // Delphi output: 268435460, FPC output 4 (!!!)
  w := x - y;
  writeln(w);     // Delphi output: 268435460, FPC output 4026531836
  writeln;
  readln;
end.

I compile this with Delphi and the output is:

Code:

Then I compile this with FreePascal using the following command line:

fpc integer_test.dpr -CX -XX -Xs -B -Co -al

The output is:
Code:

Code:

Notice that
i := abs(x - y);
writeln(i); -> FPC writes a negative number after abs() function

Why does this happen?

Is there an option/command line switch in FPC to get the same result as with Delphi?

Thanks