While using FreePascal in our Programming Education and Contest Hosting system (PEACH), we encountered another issue. Consider this program (students try strange things):

program LongArray;
var
  a: array [ Integer ] of Integer;
  i: Integer;
begin
  for i := 0 to 1000 do begin
    a [ i ] := i
  end { for i }
; writeln ( a [ 1000 ] )
end.

Under Delphi (v5) this gives an compile-time error (Data type too large: exceeds 2GB). Under fpc 1.0.4 it works without options (Integer is 16 bit), and crashes with option -Sd (Delphi mode, Integer is 32 bit): Segmentation fault. Also fpc 1.1 made it crash. By the way, WITHOUT option -gl (to get more extensive runtime error info), the crash is "silent", and you can only see it when you examine the exit status, which is 103 (file not open!?) or 139 when using option -Cr (range checking).

It seems to me that fpc should give a compile-time error, rather than crash.

Tom Verhoeff

It allocates only 4 bytes for the array. That will result in memory overwritting and the strange behaviour you write.

Why? Isn't Integer a range type?

Yes, but in Delphi integer = longint and this cause the size calculation of the array in the compiler to overflow. It's fixed now (the calculation is now done with int64's instead of longints).

Jonas