95df74e9ba
Thanks to Samuel Tardieu <sam@inf.enst.fr> for instigating this update and providing some of the changes.
243 lines
11 KiB
Ada
243 lines
11 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- S Y S T E M --
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-- --
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-- S p e c --
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-- (Default Version) --
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-- --
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-- $Revision: 1.40 $
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-- --
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-- Copyright (C) 1992-2000 Free Software Foundation, Inc. --
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-- --
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-- This specification is derived from the Ada Reference Manual for use with --
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-- GNAT. The copyright notice above, and the license provisions that follow --
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-- apply solely to the contents of the part following the private keyword. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 2, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING. If not, write --
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-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
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-- MA 02111-1307, USA. --
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-- --
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-- As a special exception, if other files instantiate generics from this --
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-- unit, or you link this unit with other files to produce an executable, --
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-- this unit does not by itself cause the resulting executable to be --
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-- covered by the GNU General Public License. This exception does not --
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-- however invalidate any other reasons why the executable file might be --
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-- covered by the GNU Public License. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
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-- --
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------------------------------------------------------------------------------
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package System is
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pragma Pure (System);
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-- Note that we take advantage of the implementation permission to
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-- make this unit Pure instead of Preelaborable, see RM 13.7(36)
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type Name is (SYSTEM_NAME_GNAT);
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System_Name : constant Name := SYSTEM_NAME_GNAT;
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-- System-Dependent Named Numbers
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Min_Int : constant := Long_Long_Integer'First;
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Max_Int : constant := Long_Long_Integer'Last;
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Max_Binary_Modulus : constant := 2 ** Long_Long_Integer'Size;
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Max_Nonbinary_Modulus : constant := Integer'Last;
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Max_Base_Digits : constant := Long_Long_Float'Digits;
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Max_Digits : constant := Long_Long_Float'Digits;
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Max_Mantissa : constant := 63;
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Fine_Delta : constant := 2.0 ** (-Max_Mantissa);
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Tick : constant := Standard'Tick;
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-- Storage-related Declarations
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type Address is private;
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Null_Address : constant Address;
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Storage_Unit : constant := Standard'Storage_Unit;
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Word_Size : constant := Standard'Word_Size;
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Memory_Size : constant := 2 ** Standard'Address_Size;
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-- Address comparison
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function "<" (Left, Right : Address) return Boolean;
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function "<=" (Left, Right : Address) return Boolean;
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function ">" (Left, Right : Address) return Boolean;
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function ">=" (Left, Right : Address) return Boolean;
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function "=" (Left, Right : Address) return Boolean;
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pragma Import (Intrinsic, "<");
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pragma Import (Intrinsic, "<=");
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pragma Import (Intrinsic, ">");
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pragma Import (Intrinsic, ">=");
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pragma Import (Intrinsic, "=");
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-- Other System-Dependent Declarations
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type Bit_Order is (High_Order_First, Low_Order_First);
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Default_Bit_Order : constant Bit_Order :=
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Bit_Order'Val (Standard'Default_Bit_Order);
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-- Priority-related Declarations (RM D.1)
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Max_Priority : constant Positive := 30;
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Max_Interrupt_Priority : constant Positive := 31;
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subtype Any_Priority is Integer
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range 0 .. Standard'Max_Interrupt_Priority;
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subtype Priority is Any_Priority
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range 0 .. Standard'Max_Priority;
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-- Functional notation is needed in the following to avoid visibility
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-- problems when this package is compiled through rtsfind in the middle
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-- of another compilation.
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subtype Interrupt_Priority is Any_Priority
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range
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Standard."+" (Standard'Max_Priority, 1) ..
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Standard'Max_Interrupt_Priority;
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Default_Priority : constant Priority :=
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Standard."/" (Standard."+" (Priority'First, Priority'Last), 2);
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private
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type Address is mod Memory_Size;
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Null_Address : constant Address := 0;
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--------------------------------------
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-- System Implementation Parameters --
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--------------------------------------
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-- These parameters provide information about the target that is used
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-- by the compiler. They are in the private part of System, where they
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-- can be accessed using Rtsfind. All values defined here must be
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-- constants, since they are accessed at compile time.
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-- Note these definitions must come before the definitions of any
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-- complex types or other code that may require Rtsfind to access
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-- these entities during compilation of System itself.
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-----------------------------------
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-- Control of Exception Handling --
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-----------------------------------
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-- GNAT provides two methods of implementing exceptions:
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-- Longjmp/Setjmp (-gnatL)
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-- This approach uses longjmp/setjmp to handle exceptions. It
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-- uses less storage, and can often propagate exceptions faster,
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-- at the expense of (sometimes considerable) overhead in setting
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-- up an exception handler. This approach is available on all
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-- targets, and is the default where it is the only approach.
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-- Zero Cost (-gnatZ)
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-- This approach uses separate exception tables. These use extra
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-- storage, and exception propagation can be quite slow, but there
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-- is no overhead in setting up an exception handler (it is to this
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-- latter operation that the phrase zero-cost refers). This approach
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-- is only available on some targets, and is the default where it is
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-- available.
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Zero_Cost_Exceptions : constant Boolean := False;
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-- Set False for Longjmp/Setjmp, True for Zero Cost
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-------------------------------
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-- Control of Stack Checking --
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-------------------------------
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-- GNAT provides two methods of implementing exceptions:
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-- GCC Probing Mechanism
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-- This approach uses the standard GCC mechanism for
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-- stack checking. The method assumes that accessing
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-- storage immediately beyond the end of the stack
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-- will result in a trap that is converted to a storage
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-- error by the runtime system. This mechanism has
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-- minimal overhead, but requires complex hardware,
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-- operating system and run-time support. Probing is
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-- the default method where it is available. The stack
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-- size for the environment task depends on the operating
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-- system and cannot be set in a system-independent way.
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-- GNAT Stack-limit Checking
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-- This method relies on comparing the stack pointer
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-- with per-task stack limits. If the check fails, an
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-- exception is explicitly raised. The advantage is
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-- that the method requires no extra system dependent
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-- runtime support and can be used on systems without
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-- memory protection as well, but at the cost of more
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-- overhead for doing the check. This method is the
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-- default on systems that lack complete support for
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-- probing.
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Stack_Check_Probes : constant Boolean := True;
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-- Set True for GCC Probing, False for GNAT Stack-limit Checking
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Stack_Check_Default : constant Boolean := True;
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-- Set True for systems where stack checking is performed by default
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----------------------------------------------
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-- Boolean-Valued Floating-Point Attributes --
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----------------------------------------------
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-- The constants below give the values for representation oriented
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-- floating-point attributes that are the same for all float types
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-- on the target. These are all boolean values.
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-- A value is only True if the target reliably supports the corresponding
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-- feature. Reliably here means that support is guaranteed for all
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-- possible settings of the relevant compiler switches (like -mieee),
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-- since we cannot control the user setting of those switches.
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-- The attributes cannot dependent on the current setting of compiler
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-- switches, since the values must be static and consistent throughout
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-- the partition. We probably should add such consistency checks in future,
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-- but for now we don't do this.
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Denorm : constant Boolean := True;
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Machine_Rounds : constant Boolean := True;
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Machine_Overflows : constant Boolean := False;
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Signed_Zeros : constant Boolean := True;
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----------------------------
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-- Support of Long Shifts --
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----------------------------
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-- In GNORT mode, we cannot call library routines, and in particular
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-- we cannot call routines for long (64-bit) shifts if such routines
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-- are required on the target. This comes up in the context of support
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-- of packed arrays. We can only represent packed arrays whose length
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-- is in the range 33- to 64-bits as modular types if long shifts are
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-- done with inline code.
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-- For the default version, for now we set long shifts inlined as True
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-- This may not be quite accurate, but until we get proper separate
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-- System's for each target, it is a safer choice.
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Long_Shifts_Inlined : constant Boolean := True;
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end System;
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