gcc/ada/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 -- 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
  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;