gcc/testsuite/gnat.dg/opt31.adb

   1 -- { dg-do run }
   2 -- { dg-options "-O" }
   3
   4 with Interfaces; use Interfaces;
   5 with Unchecked_Conversion;
   6
   7 procedure Opt31 is
   8
   9   type Unsigned_24 is new Unsigned_32 range 0 .. 2**24 - 1;
  10   subtype Time_T is Unsigned_24 range 0 .. 24 * 60 * 60 * 128 - 1;
  11
  12   type Messages_T is array (Positive range <>) of Unsigned_8;
  13   subtype T_3Bytes is Messages_T (1 .. 3);
  14
  15   type Rec1 is record
  16     F : Time_T;
  17   end record;
  18   for Rec1 use record
  19     F at 0 range 0 .. 23;
  20   end record;
  21   for Rec1'Size use 24;
  22
  23   type Rec2 is record
  24     I1,I2,I3,I4 : Integer;
  25     R1 : Rec1;
  26   end record;
  27
  28   function Conv is new Unchecked_Conversion (T_3Bytes, Rec1);
  29
  30   procedure Decode (M : Messages_T) is
  31     My_Rec2 : Rec2;
  32   begin
  33     My_Rec2.R1 := Conv (M (1 .. 3));
  34     if not My_Rec2.R1.F'Valid then
  35       raise Program_Error;
  36     end if;
  37   end;
  38
  39   Message : Messages_T (1 .. 4) := (16#18#, 16#0C#, 16#0C#, 16#18#);
  40
  41 begin
  42   Decode (Message);
  43 end;