File : system.ads
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M --
-- --
-- S p e c --
-- (NT Version) --
-- --
-- $Revision: 1.8 $
-- --
-- Copyright (C) 1992-1999 Free Software Foundation, Inc. --
-- --
-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. The copyright notice above, and the license provisions that follow --
-- apply solely to the contents of the part following the private keyword. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
package System is
pragma Pure (System);
-- Note that we take advantage of the implementation permission to
-- make this unit Pure instead of Preelaborable, see RM 13.7(36)
type Name is (SYSTEM_NAME_GNAT);
System_Name : constant Name := SYSTEM_NAME_GNAT;
-- System-Dependent Named Numbers
Min_Int : constant := Long_Long_Integer'First;
Max_Int : constant := Long_Long_Integer'Last;
Max_Binary_Modulus : constant := 2 ** Long_Long_Integer'Size;
Max_Nonbinary_Modulus : constant := Integer'Last;
Max_Base_Digits : constant := Long_Long_Float'Digits;
Max_Digits : constant := Long_Long_Float'Digits;
Max_Mantissa : constant := 63;
Fine_Delta : constant := 2.0 ** (-Max_Mantissa);
Tick : constant := Standard'Tick;
-- Storage-related Declarations
type Address is private;
Null_Address : constant Address;
Storage_Unit : constant := Standard'Storage_Unit;
Word_Size : constant := Standard'Word_Size;
Memory_Size : constant := 2 ** Standard'Address_Size;
-- Address comparison
function "<" (Left, Right : Address) return Boolean;
function "<=" (Left, Right : Address) return Boolean;
function ">" (Left, Right : Address) return Boolean;
function ">=" (Left, Right : Address) return Boolean;
function "=" (Left, Right : Address) return Boolean;
pragma Import (Intrinsic, "<");
pragma Import (Intrinsic, "<=");
pragma Import (Intrinsic, ">");
pragma Import (Intrinsic, ">=");
pragma Import (Intrinsic, "=");
-- Other System-Dependent Declarations
type Bit_Order is (High_Order_First, Low_Order_First);
Default_Bit_Order : constant Bit_Order;
-- Priority-related Declarations (RM D.1)
subtype Any_Priority is Integer
range 0 .. Standard'Max_Interrupt_Priority;
subtype Priority is Any_Priority
range 0 .. Standard'Max_Priority;
-- Functional notation is needed in the following to avoid visibility
-- problems when this package is compiled through rtsfind in the middle
-- of another compilation.
subtype Interrupt_Priority is Any_Priority
range
Standard."+" (Standard'Max_Priority, 1) ..
Standard'Max_Interrupt_Priority;
Default_Priority : constant Priority :=
Standard."/" (Standard."+" (Priority'First, Priority'Last), 2);
private
type Address is mod Memory_Size;
Null_Address : constant Address := 0;
Default_Bit_Order : constant Bit_Order :=
Bit_Order'Val (Standard'Default_Bit_Order);
--------------------------------------
-- System Implementation Parameters --
--------------------------------------
-- These parameters provide information about the target that is used
-- by the compiler. They are in the private part of System, where they
-- can be accessed using Rtsfind. All values defined here must be
-- constants, since they are accessed at compile time.
-- Note these definitions must come before the definitions of any
-- complex types or other code that may require Rtsfind to access
-- these entities during compilation of System itself.
-----------------------------------
-- Control of Exception Handling --
-----------------------------------
-- GNAT provides two methods of implementing exceptions:
-- Longjmp/Setjmp (-gnatL)
-- This approach uses longjmp/setjmp to handle exceptions. It
-- uses less storage, and can often propagate exceptions faster,
-- at the expense of (sometimes considerable) overhead in setting
-- up an exception handler. This approach is available on all
-- targets, and is the default where it is the only approach.
-- Zero Cost (-gnatZ)
-- This approach uses separate exception tables. These use extra
-- storage, and exception propagation can be quite slow, but there
-- is no overhead in setting up an exception handler (it is to this
-- latter operation that the phrase zero-cost refers). This approach
-- is only available on some targets, and is the default where it is
-- available.
Zero_Cost_Exceptions : constant Boolean := False;
-- Set False for Longjmp/Setjmp, True for Zero Cost
-------------------------------
-- Control of Stack Checking --
-------------------------------
-- GNAT provides two methods of implementing exceptions:
-- GCC Probing Mechanism
-- This approach uses the standard GCC mechanism for
-- stack checking. The method assumes that accessing
-- storage immediately beyond the end of the stack
-- will result in a trap that is converted to a storage
-- error by the runtime system. This mechanism has
-- minimal overhead, but requires complex hardware,
-- operating system and run-time support. Probing is
-- the default method where it is available. The stack
-- size for the environment task depends on the operating
-- system and cannot be set in a system-independent way.
-- GNAT Stack-limit Checking
-- This method relies on comparing the stack pointer
-- with per-task stack limits. If the check fails, an
-- exception is explicitly raised. The advantage is
-- that the method requires no extra system dependent
-- runtime support and can be used on systems without
-- memory protection as well, but at the cost of more
-- overhead for doing the check. This method is the
-- default on systems that lack complete support for
-- probing. The stack size for the environment task is
Stack_Check_Probes : constant Boolean := False;
-- Set True for GCC Probing, False for GNAT Stack-limit Checking
Stack_Check_Default : constant Boolean := False;
-- Set True for systems where stack checking is performed by default
---------------------------
-- Underlying Priorities --
---------------------------
-- Important note: this section of the file must come AFTER the
-- definition of the system implementation parameters to ensure
-- that the value of these parameters is available for analysis
-- of the declarations here (using Rtsfind at compile time).
-- The underlying priorities table provides a generalized mechanism
-- for mapping from Ada priorities to system priorities. In some
-- cases a 1-1 mapping is not the convenient or optimal choice.
type Priorities_Mapping is array (Any_Priority) of Integer;
pragma Suppress_Initialization (Priorities_Mapping);
-- Suppress initialization in case gnat.adc specifies Normalize_Scalars
-- On NT, the default mapping preserves the standard 31 priorities
-- of the Ada model, but maps them using compression onto the 7
-- priority levels available in NT.
-- To replace the default values of the Underlying_Priorities mapping,
-- copy this source file into your build directory, edit the file to
-- reflect your desired behavior, and recompile with the command:
-- $ gcc -c -O3 -gnatpgn system.ads
-- then recompile the run-time parts that depend on this package:
-- $ gnatmake -a -gnatn -O3 <your application>
-- then force rebuilding your application if you need different options:
-- $ gnatmake -f <your options> <your application>
Underlying_Priorities : constant Priorities_Mapping :=
(Priority'First .. 1 => -15,
2 .. Default_Priority - 2 => -2,
Default_Priority - 1 => -1,
Default_Priority => 0,
Default_Priority + 1 .. 19 => 1,
20 .. Priority'Last => 2,
Interrupt_Priority => 15);
end System;