gcc/testsuite/gnat.dg/unchecked_convert1.adb

   1 -- { dg-do run }
   2 -- { dg-options "-gnatws" }
   3
   4 with Ada.Unchecked_Conversion;
   5
   6 procedure Unchecked_Convert1 is
   7   type Byte is mod 2**8;
   8
   9   type Stream is array (Natural range <>) of Byte;
  10
  11   type Rec is record
  12     I1, I2 : Integer;
  13   end record;
  14
  15   function Do_Sum (R : Rec) return Integer is
  16   begin
  17     return R.I1 + R.I2;
  18   end;
  19
  20   function Sum (S : Stream) return Integer is
  21     subtype Chunk is Stream (1 .. Rec'Size / 8);
  22     function To_Chunk is new Ada.Unchecked_Conversion (Chunk, Rec);
  23   begin
  24     return Do_Sum (To_Chunk (S(S'First ..  S'First + Rec'Size / 8 - 1)));
  25   end;
  26
  27   A : Stream (1..9);
  28   I : Integer;
  29
  30 begin
  31   I := Sum (A(1..8));
  32 end;