211 lines
9.4 KiB
Ada
211 lines
9.4 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S Y S T E M . P A R A M E T E R S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2014, Free Software Foundation, Inc. --
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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 3, 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. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- Default version used when no target-specific version is provided
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-- This package defines some system dependent parameters for GNAT. These
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-- are values that are referenced by the runtime library and are therefore
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-- relevant to the target machine.
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-- The parameters whose value is defined in the spec are not generally
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-- expected to be changed. If they are changed, it will be necessary to
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-- recompile the run-time library.
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-- The parameters which are defined by functions can be changed by modifying
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-- the body of System.Parameters in file s-parame.adb. A change to this body
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-- requires only rebinding and relinking of the application.
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-- Note: do not introduce any pragma Inline statements into this unit, since
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-- otherwise the relinking and rebinding capability would be deactivated.
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pragma Compiler_Unit_Warning;
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package System.Parameters is
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pragma Pure;
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---------------------------------------
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-- Task And Stack Allocation Control --
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---------------------------------------
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type Task_Storage_Size is new Integer;
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-- Type used in tasking units for task storage size
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type Size_Type is new Task_Storage_Size;
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-- Type used to provide task storage size to runtime
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Unspecified_Size : constant Size_Type := Size_Type'First;
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-- Value used to indicate that no size type is set
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subtype Percentage is Size_Type range -1 .. 100;
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Dynamic : constant Size_Type := -1;
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-- The secondary stack ratio is a constant between 0 and 100 which
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-- determines the percentage of the allocated task stack that is
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-- used by the secondary stack (the rest being the primary stack).
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-- The special value of minus one indicates that the secondary
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-- stack is to be allocated from the heap instead.
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Sec_Stack_Percentage : constant Percentage := Dynamic;
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-- This constant defines the handling of the secondary stack
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Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Percentage = Dynamic;
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-- Convenient Boolean for testing for dynamic secondary stack
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function Default_Stack_Size return Size_Type;
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-- Default task stack size used if none is specified
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function Minimum_Stack_Size return Size_Type;
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-- Minimum task stack size permitted
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function Adjust_Storage_Size (Size : Size_Type) return Size_Type;
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-- Given the storage size stored in the TCB, return the Storage_Size
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-- value required by the RM for the Storage_Size attribute. The
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-- required adjustment is as follows:
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--
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-- when Size = Unspecified_Size, return Default_Stack_Size
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-- when Size < Minimum_Stack_Size, return Minimum_Stack_Size
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-- otherwise return given Size
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Default_Env_Stack_Size : constant Size_Type := 8_192_000;
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-- Assumed size of the environment task, if no other information
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-- is available. This value is used when stack checking is
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-- enabled and no GNAT_STACK_LIMIT environment variable is set.
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Stack_Grows_Down : constant Boolean := True;
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-- This constant indicates whether the stack grows up (False) or
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-- down (True) in memory as functions are called. It is used for
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-- proper implementation of the stack overflow check.
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----------------------------------------------
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-- Characteristics of types in Interfaces.C --
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----------------------------------------------
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long_bits : constant := Long_Integer'Size;
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-- Number of bits in type long and unsigned_long. The normal convention
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-- is that this is the same as type Long_Integer, but this may not be true
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-- of all targets.
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ptr_bits : constant := Standard'Address_Size;
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subtype C_Address is System.Address;
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-- Number of bits in Interfaces.C pointers, normally a standard address
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C_Malloc_Linkname : constant String := "__gnat_malloc";
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-- Name of runtime function used to allocate such a pointer
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----------------------------------------------
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-- Behavior of Pragma Finalize_Storage_Only --
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----------------------------------------------
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-- Garbage_Collected is a Boolean constant whose value indicates the
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-- effect of the pragma Finalize_Storage_Entry on a controlled type.
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-- Garbage_Collected = False
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-- The system releases all storage on program termination only,
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-- but not other garbage collection occurs, so finalization calls
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-- are omitted only for outer level objects can be omitted if
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-- pragma Finalize_Storage_Only is used.
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-- Garbage_Collected = True
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-- The system provides full garbage collection, so it is never
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-- necessary to release storage for controlled objects for which
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-- a pragma Finalize_Storage_Only is used.
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Garbage_Collected : constant Boolean := False;
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-- The storage mode for this system (release on program exit)
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---------------------
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-- Tasking Profile --
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---------------------
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-- In the following sections, constant parameters are defined to
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-- allow some optimizations and fine tuning within the tasking run time
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-- based on restrictions on the tasking features.
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----------------------
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-- Locking Strategy --
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----------------------
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Single_Lock : constant Boolean := False;
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-- Indicates whether a single lock should be used within the tasking
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-- run-time to protect internal structures. If True, a single lock
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-- will be used, meaning less locking/unlocking operations, but also
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-- more global contention. In general, Single_Lock should be set to
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-- True on single processor machines, and to False to multi-processor
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-- systems, but this can vary from application to application and also
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-- depends on the scheduling policy.
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-------------------
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-- Task Abortion --
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-------------------
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No_Abort : constant Boolean := False;
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-- This constant indicates whether abort statements and asynchronous
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-- transfer of control (ATC) are disallowed. If set to True, it is
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-- assumed that neither construct is used, and the run time does not
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-- need to defer/undefer abort and check for pending actions at
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-- completion points. A value of True for No_Abort corresponds to:
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-- pragma Restrictions (No_Abort_Statements);
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-- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
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---------------------
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-- Task Attributes --
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---------------------
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Max_Attribute_Count : constant := 32;
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-- Number of task attributes stored in the task control block
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--------------------
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-- Runtime Traces --
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--------------------
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Runtime_Traces : constant Boolean := False;
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-- This constant indicates whether the runtime outputs traces to a
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-- predefined output or not (True means that traces are output).
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-- See System.Traces for more details.
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-----------------------
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-- Task Image Length --
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-----------------------
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Max_Task_Image_Length : constant := 256;
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-- This constant specifies the maximum length of a task's image
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------------------------------
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-- Exception Message Length --
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------------------------------
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Default_Exception_Msg_Max_Length : constant := 200;
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-- This constant specifies the default number of characters to allow
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-- in an exception message (200 is minimum required by RM 11.4.1(18)).
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end System.Parameters;
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