1------------------------------------------------------------------------------
2--                                                                          --
3--                          GNAT RUN-TIME COMPONENTS                        --
4--                                                                          --
5--                  S Y S T E M . S C A L A R _ V A L U E S                 --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 2001-2009, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package defines the constants used for initializing scalar values
33--  when pragma Initialize_Scalars is used. The actual values are defined
34--  in the binder generated file. This package contains the Ada names that
35--  are used by the generated code, which are linked to the actual values
36--  by the use of pragma Import.
37
38package System.Scalar_Values is
39
40   --  Note: logically this package should be Pure since it can be accessed
41   --  from pure units, but the IS_xxx variables below get set at run time,
42   --  so they have to be library level variables. In fact we only ever
43   --  access this from generated code, and the compiler knows that it is
44   --  OK to access this unit from generated code.
45
46   type Byte1 is mod 2 **  8;
47   type Byte2 is mod 2 ** 16;
48   type Byte4 is mod 2 ** 32;
49   type Byte8 is mod 2 ** 64;
50
51   --  The explicit initializations here are not really required, since these
52   --  variables are always set by System.Scalar_Values.Initialize.
53
54   IS_Is1 : Byte1 := 0;  -- Initialize 1 byte signed
55   IS_Is2 : Byte2 := 0;  -- Initialize 2 byte signed
56   IS_Is4 : Byte4 := 0;  -- Initialize 4 byte signed
57   IS_Is8 : Byte8 := 0;  -- Initialize 8 byte signed
58   --  For the above cases, the undefined value (set by the binder -Sin switch)
59   --  is the largest negative number (1 followed by all zero bits).
60
61   IS_Iu1 : Byte1 := 0;  -- Initialize 1 byte unsigned
62   IS_Iu2 : Byte2 := 0;  -- Initialize 2 byte unsigned
63   IS_Iu4 : Byte4 := 0;  -- Initialize 4 byte unsigned
64   IS_Iu8 : Byte8 := 0;  -- Initialize 8 byte unsigned
65   --  For the above cases, the undefined value (set by the binder -Sin switch)
66   --  is the largest unsigned number (all 1 bits).
67
68   IS_Iz1 : Byte1 := 0;  -- Initialize 1 byte zeroes
69   IS_Iz2 : Byte2 := 0;  -- Initialize 2 byte zeroes
70   IS_Iz4 : Byte4 := 0;  -- Initialize 4 byte zeroes
71   IS_Iz8 : Byte8 := 0;  -- Initialize 8 byte zeroes
72   --  For the above cases, the undefined value (set by the binder -Sin switch)
73   --  is the zero (all 0 bits). This is used when zero is known to be an
74   --  invalid value.
75
76   --  The float definitions are aliased, because we use overlays to set them
77
78   IS_Isf : aliased Short_Float     := 0.0;  -- Initialize short float
79   IS_Ifl : aliased Float           := 0.0;  -- Initialize float
80   IS_Ilf : aliased Long_Float      := 0.0;  -- Initialize long float
81   IS_Ill : aliased Long_Long_Float := 0.0;  -- Initialize long long float
82
83   procedure Initialize (Mode1 : Character; Mode2 : Character);
84   --  This procedure is called from the binder when Initialize_Scalars mode
85   --  is active. The arguments are the two characters from the -S switch,
86   --  with letters forced upper case. So for example if -S5a is given, then
87   --  Mode1 will be '5' and Mode2 will be 'A'. If the parameters are EV,
88   --  then this routine reads the environment variable GNAT_INIT_SCALARS.
89   --  The possible settings are the same as those for the -S switch (except
90   --  for EV), i.e. IN/LO/HO/xx, xx = 2 hex digits. If no -S switch is given
91   --  then the default of IN (invalid values) is passed on the call.
92
93end System.Scalar_Values;
94