gcc/ada/libgnat/system.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                        GNAT RUN-TIME COMPONENTS                          --
   4 --                                                                          --
   5 --                               S Y S T E M                                --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                            (Compiler Version)                            --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2017, Free Software Foundation, Inc.         --
  11 --                                                                          --
  12 -- This specification is derived from the Ada Reference Manual for use with --
  13 -- GNAT. The copyright notice above, and the license provisions that follow --
  14 -- apply solely to the  contents of the part following the private keyword. --
  15 --                                                                          --
  16 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  17 -- terms of the  GNU General Public License as published  by the Free Soft- --
  18 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  19 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  20 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  21 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  22 --                                                                          --
  23 -- As a special exception under Section 7 of GPL version 3, you are granted --
  24 -- additional permissions described in the GCC Runtime Library Exception,   --
  25 -- version 3.1, as published by the Free Software Foundation.               --
  26 --                                                                          --
  27 -- You should have received a copy of the GNU General Public License and    --
  28 -- a copy of the GCC Runtime Library Exception along with this program;     --
  29 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  30 -- <http://www.gnu.org/licenses/>.                                          --
  31 --                                                                          --
  32 -- GNAT was originally developed  by the GNAT team at  New York University. --
  33 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  34 --                                                                          --
  35 ------------------------------------------------------------------------------
  36
  37 --  This version of System is a generic version that is used in building the
  38 --  compiler. Right now, we have a host/target problem if we try to use the
  39 --  "proper" System, and since the compiler itself does not care about most
  40 --  System parameters, this generic version works fine.
  41
  42 pragma Restrictions (No_Implicit_Dynamic_Code);
  43 --  We want to avoid trampolines in the compiler, so it can be used in systems
  44 --  which prevent execution of code on the stack, e.g. in windows environments
  45 --  with DEP (Data Execution Protection) enabled.
  46
  47 pragma Restrictions (No_Finalization);
  48 --  Use restriction No_Finalization to avoid pulling finalization (not allowed
  49 --  in GNAT) inside sem_spark.adb, when defining type Perm_Tree_Access as an
  50 --  access type on incomplete type Perm_Tree_Wrapper (which is required for
  51 --  defining a recursive type).
  52
  53 package System is
  54    pragma Pure;
  55    --  Note that we take advantage of the implementation permission to make
  56    --  this unit Pure instead of Preelaborable; see RM 13.7.1(15). In Ada
  57    --  2005, this is Pure in any case (AI-362).
  58
  59    pragma No_Elaboration_Code_All;
  60    --  Allow the use of that restriction in units that WITH this unit
  61
  62    type Name is (SYSTEM_NAME_GNAT);
  63    System_Name : constant Name := SYSTEM_NAME_GNAT;
  64
  65    --  System-Dependent Named Numbers
  66
  67    Min_Int               : constant := Long_Long_Integer'First;
  68    Max_Int               : constant := Long_Long_Integer'Last;
  69
  70    Max_Binary_Modulus    : constant := 2 ** Long_Long_Integer'Size;
  71    Max_Nonbinary_Modulus : constant := 2 ** Integer'Size - 1;
  72
  73    Max_Base_Digits       : constant := Long_Long_Float'Digits;
  74    Max_Digits            : constant := Long_Long_Float'Digits;
  75
  76    Max_Mantissa          : constant := 63;
  77    Fine_Delta            : constant := 2.0 ** (-Max_Mantissa);
  78
  79    Tick                  : constant := 0.01;
  80
  81    --  Storage-related Declarations
  82
  83    type Address is private;
  84    --  Note that we do NOT add pragma Preelaborable_Initialization in this
  85    --  version of System, since it is used for the compiler only, and typical
  86    --  earlier bootstrap compilers don't support this pragma. We don't need
  87    --  it in this context, so there is no problem in omitting it.
  88    Null_Address : constant Address;
  89
  90    Storage_Unit : constant := Standard'Storage_Unit;
  91    Word_Size    : constant := Standard'Word_Size;
  92    Memory_Size  : constant := 2 ** Standard'Address_Size;
  93
  94    --  Address comparison
  95
  96    function "<"  (Left, Right : Address) return Boolean;
  97    function "<=" (Left, Right : Address) return Boolean;
  98    function ">"  (Left, Right : Address) return Boolean;
  99    function ">=" (Left, Right : Address) return Boolean;
 100    function "="  (Left, Right : Address) return Boolean;
 101
 102    pragma Import (Intrinsic, "<");
 103    pragma Import (Intrinsic, "<=");
 104    pragma Import (Intrinsic, ">");
 105    pragma Import (Intrinsic, ">=");
 106    pragma Import (Intrinsic, "=");
 107
 108    --  Other System-Dependent Declarations
 109
 110    type Bit_Order is (High_Order_First, Low_Order_First);
 111    Default_Bit_Order : constant Bit_Order :=
 112                          Bit_Order'Val (Standard'Default_Bit_Order);
 113    pragma Warnings (Off, Default_Bit_Order); -- kill constant condition warning
 114
 115    --  Priority-related Declarations (RM D.1)
 116
 117    Max_Priority           : constant Positive := 30;
 118    Max_Interrupt_Priority : constant Positive := 31;
 119
 120    subtype Any_Priority       is Integer      range  0 .. 31;
 121    subtype Priority           is Any_Priority range  0 .. 30;
 122    subtype Interrupt_Priority is Any_Priority range 31 .. 31;
 123
 124    Default_Priority : constant Priority := 15;
 125
 126 private
 127
 128    type Address is mod Memory_Size;
 129    Null_Address : constant Address := 0;
 130
 131    --------------------------------------
 132    -- System Implementation Parameters --
 133    --------------------------------------
 134
 135    --  These parameters provide information about the target that is used by
 136    --  the compiler. They are in the private part of System, where they can be
 137    --  accessed using the special circuitry in the Targparm unit whose source
 138    --  should be consulted for more detailed descriptions of the individual
 139    --  switch values.
 140
 141    --  This version of system.ads is used only for building the compiler.
 142    --  We really ought to use the proper target system (i.e. the one that
 143    --  corresponds to the host for the compiler), but that causes as yet
 144    --  unsolved makefile problems. For the most part the setting of these
 145    --  parameters is not too critical for the compiler version (e.g. we
 146    --  do not use floating-point anyway in the compiler).
 147
 148    AAMP                      : constant Boolean := False;
 149    Backend_Divide_Checks     : constant Boolean := False;
 150    Backend_Overflow_Checks   : constant Boolean := False;
 151    Command_Line_Args         : constant Boolean := True;
 152    Configurable_Run_Time     : constant Boolean := False;
 153    Denorm                    : constant Boolean := True;
 154    Duration_32_Bits          : constant Boolean := False;
 155    Exit_Status_Supported     : constant Boolean := True;
 156    Fractional_Fixed_Ops      : constant Boolean := False;
 157    Frontend_Layout           : constant Boolean := False;
 158    Machine_Overflows         : constant Boolean := False;
 159    Machine_Rounds            : constant Boolean := True;
 160    Preallocated_Stacks       : constant Boolean := False;
 161    Signed_Zeros              : constant Boolean := True;
 162    Stack_Check_Default       : constant Boolean := False;
 163    Stack_Check_Probes        : constant Boolean := False;
 164    Stack_Check_Limits        : constant Boolean := False;
 165    Support_Aggregates        : constant Boolean := True;
 166    Support_Composite_Assign  : constant Boolean := True;
 167    Support_Composite_Compare : constant Boolean := True;
 168    Support_Long_Shifts       : constant Boolean := True;
 169    Always_Compatible_Rep     : constant Boolean := True;
 170    Suppress_Standard_Library : constant Boolean := False;
 171    Use_Ada_Main_Program_Name : constant Boolean := False;
 172    Frontend_Exceptions       : constant Boolean := False;
 173    ZCX_By_Default            : constant Boolean := True;
 174
 175    --  Obsolete entries, to be removed eventually (bootstrap issues)
 176
 177    Front_End_ZCX_Support     : constant Boolean := False;
 178    High_Integrity_Mode       : constant Boolean := False;
 179    Long_Shifts_Inlined       : constant Boolean := True;
 180    Functions_Return_By_DSP   : constant Boolean := False;
 181    Support_64_Bit_Divides    : constant Boolean := True;
 182    GCC_ZCX_Support           : constant Boolean := True;
 183
 184 end System;