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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . S C A L A R _ V A L U E S --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 2001-2017, Free Software Foundation, Inc. --
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package defines the constants used for initializing scalar values
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33 -- when pragma Initialize_Scalars is used. The actual values are defined
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34 -- in the binder generated file. This package contains the Ada names that
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35 -- are used by the generated code, which are linked to the actual values
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36 -- by the use of pragma Import.
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37
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38 package System.Scalar_Values is
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39
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40 -- Note: logically this package should be Pure since it can be accessed
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41 -- from pure units, but the IS_xxx variables below get set at run time,
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42 -- so they have to be library level variables. In fact we only ever
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43 -- access this from generated code, and the compiler knows that it is
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44 -- OK to access this unit from generated code.
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45
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46 type Byte1 is mod 2 ** 8;
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47 type Byte2 is mod 2 ** 16;
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48 type Byte4 is mod 2 ** 32;
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49 type Byte8 is mod 2 ** 64;
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50
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51 -- The explicit initializations here are not really required, since these
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52 -- variables are always set by System.Scalar_Values.Initialize.
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53
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54 IS_Is1 : Byte1 := 0; -- Initialize 1 byte signed
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55 IS_Is2 : Byte2 := 0; -- Initialize 2 byte signed
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56 IS_Is4 : Byte4 := 0; -- Initialize 4 byte signed
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57 IS_Is8 : Byte8 := 0; -- Initialize 8 byte signed
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58 -- For the above cases, the undefined value (set by the binder -Sin switch)
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59 -- is the largest negative number (1 followed by all zero bits).
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60
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61 IS_Iu1 : Byte1 := 0; -- Initialize 1 byte unsigned
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62 IS_Iu2 : Byte2 := 0; -- Initialize 2 byte unsigned
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63 IS_Iu4 : Byte4 := 0; -- Initialize 4 byte unsigned
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64 IS_Iu8 : Byte8 := 0; -- Initialize 8 byte unsigned
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65 -- For the above cases, the undefined value (set by the binder -Sin switch)
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66 -- is the largest unsigned number (all 1 bits).
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67
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68 IS_Iz1 : Byte1 := 0; -- Initialize 1 byte zeroes
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69 IS_Iz2 : Byte2 := 0; -- Initialize 2 byte zeroes
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70 IS_Iz4 : Byte4 := 0; -- Initialize 4 byte zeroes
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71 IS_Iz8 : Byte8 := 0; -- Initialize 8 byte zeroes
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72 -- For the above cases, the undefined value (set by the binder -Sin switch)
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73 -- is the zero (all 0 bits). This is used when zero is known to be an
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74 -- invalid value.
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75
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76 -- The float definitions are aliased, because we use overlays to set them
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77
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78 IS_Isf : aliased Short_Float := 0.0; -- Initialize short float
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79 IS_Ifl : aliased Float := 0.0; -- Initialize float
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80 IS_Ilf : aliased Long_Float := 0.0; -- Initialize long float
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81 IS_Ill : aliased Long_Long_Float := 0.0; -- Initialize long long float
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82
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83 procedure Initialize (Mode1 : Character; Mode2 : Character);
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84 -- This procedure is called from the binder when Initialize_Scalars mode
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85 -- is active. The arguments are the two characters from the -S switch,
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86 -- with letters forced upper case. So for example if -S5a is given, then
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87 -- Mode1 will be '5' and Mode2 will be 'A'. If the parameters are EV,
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88 -- then this routine reads the environment variable GNAT_INIT_SCALARS.
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89 -- The possible settings are the same as those for the -S switch (except
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90 -- for EV), i.e. IN/LO/HO/xx, xx = 2 hex digits. If no -S switch is given
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91 -- then the default of IN (invalid values) is passed on the call.
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92
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93 end System.Scalar_Values;
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