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) 2001-2005, 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package defines the constants used for initializing scalar values
  35 --  when pragma Initialize_Scalars is used. The actual values are defined
  36 --  in the binder generated file. This package contains the Ada names that
  37 --  are used by the generated code, which are linked to the actual values
  38 --  by the use of pragma Import.
  39
  40 package System.Scalar_Values is
  41
  42    --  Note: logically this package should be Pure since it can be accessed
  43    --  from pure units, but the IS_xxx variables below get set at run time,
  44    --  so they have to be library level variables. In fact we only ever
  45    --  access this from generated code, and the compiler knows that it is
  46    --  OK to access this unit from generated code.
  47
  48    type Byte1 is mod 2 **  8;
  49    type Byte2 is mod 2 ** 16;
  50    type Byte4 is mod 2 ** 32;
  51    type Byte8 is mod 2 ** 64;
  52
  53    --  The explicit initializations here are not really required, since these
  54    --  variables are always set by System.Scalar_Values.Initialize.
  55
  56    IS_Is1 : Byte1 := 0;  -- Initialize 1 byte signed
  57    IS_Is2 : Byte2 := 0;  -- Initialize 2 byte signed
  58    IS_Is4 : Byte4 := 0;  -- Initialize 4 byte signed
  59    IS_Is8 : Byte8 := 0;  -- Initialize 8 byte signed
  60    --  For the above cases, the undefined value (set by the binder -Sin switch)
  61    --  is the largest negative number (1 followed by all zero bits).
  62
  63    IS_Iu1 : Byte1 := 0;  -- Initialize 1 byte unsigned
  64    IS_Iu2 : Byte2 := 0;  -- Initialize 2 byte unsigned
  65    IS_Iu4 : Byte4 := 0;  -- Initialize 4 byte unsigned
  66    IS_Iu8 : Byte8 := 0;  -- Initialize 8 byte unsigned
  67    --  For the above cases, the undefined value (set by the binder -Sin switch)
  68    --  is the largest unsigned number (all 1 bits).
  69
  70    IS_Iz1 : Byte1 := 0;  -- Initialize 1 byte zeroes
  71    IS_Iz2 : Byte2 := 0;  -- Initialize 2 byte zeroes
  72    IS_Iz4 : Byte4 := 0;  -- Initialize 4 byte zeroes
  73    IS_Iz8 : Byte8 := 0;  -- Initialize 8 byte zeroes
  74    --  For the above cases, the undefined value (set by the binder -Sin switch)
  75    --  is the zero (all 0 bits). This is used when zero is known to be an
  76    --  invalid value.
  77
  78    --  The float definitions are aliased, because we use overlays to set them
  79
  80    IS_Isf : aliased Short_Float     := 0.0;  -- Initialize short float
  81    IS_Ifl : aliased Float           := 0.0;  -- Initialize float
  82    IS_Ilf : aliased Long_Float      := 0.0;  -- Initialize long float
  83    IS_Ill : aliased Long_Long_Float := 0.0;  -- Initialize long long float
  84
  85    procedure Initialize (Mode1 : Character; Mode2 : Character);
  86    --  This procedure is called from the binder when Initialize_Scalars mode
  87    --  is active. The arguments are the two characters from the -S switch,
  88    --  with letters forced upper case. So for example if -S5a is given, then
  89    --  Mode1 will be '5' and Mode2 will be 'A'. If the parameters are EV,
  90    --  then this routine reads the environment variable GNAT_INIT_SCALARS.
  91    --  The possible settings are the same as those for the -S switch (except
  92    --  for EV), i.e. IN/LO/HO/xx, xx = 2 hex digits. If no -S switch is given
  93    --  then the default of IN (invalid values) is passed on the call.
  94
  95 end System.Scalar_Values;