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Wrap

Text File | 2000-07-19 | 11KB | 244 lines

------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- S Y S T E M -- -- -- -- S p e c -- -- (Default Version) -- -- -- -- $Revision: 1.40 $ -- -- -- Copyright (C) 1992-2000 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 := Bit_Order'Val (Standard'Default_Bit_Order); -- Priority-related Declarations (RM D.1) Max_Priority : constant Positive := 30; Max_Interrupt_Priority : constant Positive := 31; 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; -------------------------------------- -- 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. 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 ---------------------------------------------- -- Boolean-Valued Floating-Point Attributes -- ---------------------------------------------- -- The constants below give the values for representation oriented -- floating-point attributes that are the same for all float types -- on the target. These are all boolean values. -- A value is only True if the target reliably supports the corresponding -- feature. Reliably here means that support is guaranteed for all -- possible settings of the relevant compiler switches (like -mieee), -- since we cannot control the user setting of those switches. -- The attributes cannot dependent on the current setting of compiler -- switches, since the values must be static and consistent throughout -- the partition. We probably should add such consistency checks in future, -- but for now we don't do this. Denorm : constant Boolean := True; -- It might be safer to set this to False ??? Machine_Rounds : constant Boolean := True; Machine_Overflows : constant Boolean := False; Signed_Zeros : constant Boolean := True; ---------------------------- -- Support of Long Shifts -- ---------------------------- -- In GNORT mode, we cannot call library routines, and in particular -- we cannot call routines for long (64-bit) shifts if such routines -- are required on the target. This comes up in the context of support -- of packed arrays. We can only represent packed arrays whose length -- is in the range 33- to 64-bits as modular types if long shifts are -- done with inline code. -- For the default version, for now we set long shifts inlined as True -- This may not be quite accurate, but until we get proper separate -- System's for each target, it is a safer choice. Long_Shifts_Inlined : constant Boolean := True; end System;