File : s-scaval.ads
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 -- --
19 -- --
20 -- --
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
38 package 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
93 end System.Scalar_Values;