| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S Y S T E M . P A R A M E T E R S -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1992-2005 Free Software Foundation, Inc. -- |
| -- -- |
| -- 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, 51 Franklin Street, Fifth Floor, -- |
| -- Boston, MA 02110-1301, 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. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This is the OpenVMS Alpha version |
| |
| -- This package defines some system dependent parameters for GNAT. These |
| -- are values that are referenced by the runtime library and are therefore |
| -- relevant to the target machine. |
| |
| -- The parameters whose value is defined in the spec are not generally |
| -- expected to be changed. If they are changed, it will be necessary to |
| -- recompile the run-time library. |
| |
| -- The parameters which are defined by functions can be changed by modifying |
| -- the body of System.Parameters in file s-parame.adb. A change to this body |
| -- requires only rebinding and relinking of the application. |
| |
| -- Note: do not introduce any pragma Inline statements into this unit, since |
| -- otherwise the relinking and rebinding capability would be deactivated. |
| |
| package System.Parameters is |
| pragma Pure; |
| |
| --------------------------------------- |
| -- Task And Stack Allocation Control -- |
| --------------------------------------- |
| |
| type Task_Storage_Size is new Integer; |
| -- Type used in tasking units for task storage size |
| |
| type Size_Type is new Task_Storage_Size; |
| -- Type used to provide task storage size to runtime |
| |
| Unspecified_Size : constant Size_Type := Size_Type'First; |
| -- Value used to indicate that no size type is set |
| |
| subtype Ratio is Size_Type range -1 .. 100; |
| Dynamic : constant Size_Type := -1; |
| -- The secondary stack ratio is a constant between 0 and 100 which |
| -- determines the percentage of the allocated task stack that is |
| -- used by the secondary stack (the rest being the primary stack). |
| -- The special value of minus one indicates that the secondary |
| -- stack is to be allocated from the heap instead. |
| |
| Sec_Stack_Ratio : constant Ratio := Dynamic; |
| -- This constant defines the handling of the secondary stack |
| |
| Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Ratio = Dynamic; |
| -- Convenient Boolean for testing for dynamic secondary stack |
| |
| function Default_Stack_Size return Size_Type; |
| -- Default task stack size used if none is specified |
| |
| function Minimum_Stack_Size return Size_Type; |
| -- Minimum task stack size permitted |
| |
| function Adjust_Storage_Size (Size : Size_Type) return Size_Type; |
| -- Given the storage size stored in the TCB, return the Storage_Size |
| -- value required by the RM for the Storage_Size attribute. The |
| -- required adjustment is as follows: |
| -- |
| -- when Size = Unspecified_Size, return Default_Stack_Size |
| -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size |
| -- otherwise return given Size |
| |
| Default_Env_Stack_Size : constant Size_Type := 8_192_000; |
| -- Assumed size of the environment task, if no other information |
| -- is available. This value is used when stack checking is |
| -- enabled and no GNAT_STACK_LIMIT environment variable is set. |
| |
| Stack_Grows_Down : constant Boolean := True; |
| -- This constant indicates whether the stack grows up (False) or |
| -- down (True) in memory as functions are called. It is used for |
| -- proper implementation of the stack overflow check. |
| |
| ---------------------------------------------- |
| -- Characteristics of types in Interfaces.C -- |
| ---------------------------------------------- |
| |
| long_bits : constant := 32; |
| -- Number of bits in type long and unsigned_long. The normal convention |
| -- is that this is the same as type Long_Integer, but this is not true |
| -- of all targets. For example, in OpenVMS long /= Long_Integer. |
| |
| ---------------------------------------------- |
| -- Behavior of Pragma Finalize_Storage_Only -- |
| ---------------------------------------------- |
| |
| -- Garbage_Collected is a Boolean constant whose value indicates the |
| -- effect of the pragma Finalize_Storage_Entry on a controlled type. |
| |
| -- Garbage_Collected = False |
| |
| -- The system releases all storage on program termination only, |
| -- but not other garbage collection occurs, so finalization calls |
| -- are ommitted only for outer level onjects can be omitted if |
| -- pragma Finalize_Storage_Only is used. |
| |
| -- Garbage_Collected = True |
| |
| -- The system provides full garbage collection, so it is never |
| -- necessary to release storage for controlled objects for which |
| -- a pragma Finalize_Storage_Only is used. |
| |
| Garbage_Collected : constant Boolean := False; |
| -- The storage mode for this system (release on program exit) |
| |
| --------------------- |
| -- Tasking Profile -- |
| --------------------- |
| |
| -- In the following sections, constant parameters are defined to |
| -- allow some optimizations and fine tuning within the tasking run time |
| -- based on restrictions on the tasking features. |
| |
| ---------------------- |
| -- Locking Strategy -- |
| ---------------------- |
| |
| Single_Lock : constant Boolean := True; |
| -- Indicates whether a single lock should be used within the tasking |
| -- run-time to protect internal structures. If True, a single lock |
| -- will be used, meaning less locking/unlocking operations, but also |
| -- more global contention. In general, Single_Lock should be set to |
| -- True on single processor machines, and to False to multi-processor |
| -- systems, but this can vary from application to application and also |
| -- depends on the scheduling policy. |
| |
| ------------------- |
| -- Task Abortion -- |
| ------------------- |
| |
| No_Abort : constant Boolean := False; |
| -- This constant indicates whether abort statements and asynchronous |
| -- transfer of control (ATC) are disallowed. If set to True, it is |
| -- assumed that neither construct is used, and the run time does not |
| -- need to defer/undefer abort and check for pending actions at |
| -- completion points. A value of True for No_Abort corresponds to: |
| -- pragma Restrictions (No_Abort_Statements); |
| -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); |
| |
| ---------------------- |
| -- Dynamic Priority -- |
| ---------------------- |
| |
| Dynamic_Priority_Support : constant Boolean := True; |
| -- This constant indicates whether dynamic changes of task priorities |
| -- are allowed (True means normal RM mode in which such changes are |
| -- allowed). In particular, if this is False, then we do not need to |
| -- poll for pending base priority changes at every abort completion |
| -- point. A value of False for Dynamic_Priority_Support corresponds |
| -- to pragma Restrictions (No_Dynamic_Priorities); |
| |
| --------------------- |
| -- Task Attributes -- |
| --------------------- |
| |
| Default_Attribute_Count : constant := 4; |
| -- Number of pre-allocated Address-sized task attributes stored in the |
| -- task control block. |
| |
| -------------------- |
| -- Runtime Traces -- |
| -------------------- |
| |
| Runtime_Traces : constant Boolean := False; |
| -- This constant indicates whether the runtime outputs traces to a |
| -- predefined output or not (True means that traces are output). |
| -- See System.Traces for more details. |
| |
| ------------------------------ |
| -- Exception Message Length -- |
| ------------------------------ |
| |
| Default_Exception_Msg_Max_Length : constant := 512; |
| -- This constant specifies the maximum number of characters to allow in an |
| -- exception message (see RM 11.4.1(18)). The value for VMS exceeds the |
| -- default minimum of 200 to allow for the length of chained VMS condition |
| -- handling messages. |
| |
| end System.Parameters; |
