1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S Y S T E M . P A R A M E T E R S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2003 Free Software Foundation, Inc. -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 2, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- 17-- for more details. You should have received a copy of the GNU General -- 18-- Public License distributed with GNAT; see file COPYING. If not, write -- 19-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- 20-- MA 02111-1307, USA. -- 21-- -- 22-- As a special exception, if other files instantiate generics from this -- 23-- unit, or you link this unit with other files to produce an executable, -- 24-- this unit does not by itself cause the resulting executable to be -- 25-- covered by the GNU General Public License. This exception does not -- 26-- however invalidate any other reasons why the executable file might be -- 27-- covered by the GNU Public License. -- 28-- -- 29-- GNAT was originally developed by the GNAT team at New York University. -- 30-- Extensive contributions were provided by Ada Core Technologies Inc. -- 31-- -- 32------------------------------------------------------------------------------ 33 34-- This is the default VxWorks AE 653 version of the package.` 35 36-- This package defines some system dependent parameters for GNAT. These 37-- are values that are referenced by the runtime library and are therefore 38-- relevant to the target machine. 39 40-- The parameters whose value is defined in the spec are not generally 41-- expected to be changed. If they are changed, it will be necessary to 42-- recompile the run-time library. 43 44-- The parameters which are defined by functions can be changed by modifying 45-- the body of System.Parameters in file s-parame.adb. A change to this body 46-- requires only rebinding and relinking of the application. 47 48-- Note: do not introduce any pragma Inline statements into this unit, since 49-- otherwise the relinking and rebinding capability would be deactivated. 50 51package System.Parameters is 52pragma Pure (Parameters); 53 54 --------------------------------------- 55 -- Task And Stack Allocation Control -- 56 --------------------------------------- 57 58 type Task_Storage_Size is new Integer; 59 -- Type used in tasking units for task storage size 60 61 type Size_Type is new Task_Storage_Size; 62 -- Type used to provide task storage size to runtime 63 64 Unspecified_Size : constant Size_Type := Size_Type'First; 65 -- Value used to indicate that no size type is set 66 67 subtype Ratio is Size_Type range -1 .. 100; 68 Dynamic : constant Size_Type := -1; 69 -- The secondary stack ratio is a constant between 0 and 100 which 70 -- determines the percentage of the allocated task stack that is 71 -- used by the secondary stack (the rest being the primary stack). 72 -- The special value of minus one indicates that the secondary 73 -- stack is to be allocated from the heap instead. 74 75 Sec_Stack_Ratio : constant Ratio := 50; 76 -- This constant defines the handling of the secondary stack 77 78 Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Ratio = Dynamic; 79 -- Convenient Boolean for testing for dynamic secondary stack 80 81 function Default_Stack_Size return Size_Type; 82 -- Default task stack size used if none is specified 83 84 function Minimum_Stack_Size return Size_Type; 85 -- Minimum task stack size permitted 86 87 function Adjust_Storage_Size (Size : Size_Type) return Size_Type; 88 -- Given the storage size stored in the TCB, return the Storage_Size 89 -- value required by the RM for the Storage_Size attribute. The 90 -- required adjustment is as follows: 91 -- 92 -- when Size = Unspecified_Size, return Default_Stack_Size 93 -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size 94 -- otherwise return given Size 95 96 Default_Env_Stack_Size : constant Size_Type := 14_336; 97 -- Assumed size of the environment task, if no other information 98 -- is available. This value is used when stack checking is 99 -- enabled and no GNAT_STACK_LIMIT environment variable is set. 100 -- This value is chosen as the VxWorks default stack size is 20kB, 101 -- and a little more than 4kB is necessary for the run time. 102 103 Stack_Grows_Down : constant Boolean := True; 104 -- This constant indicates whether the stack grows up (False) or 105 -- down (True) in memory as functions are called. It is used for 106 -- proper implementation of the stack overflow check. 107 108 ---------------------------------------------- 109 -- Characteristics of types in Interfaces.C -- 110 ---------------------------------------------- 111 112 long_bits : constant := Long_Integer'Size; 113 -- Number of bits in type long and unsigned_long. The normal convention 114 -- is that this is the same as type Long_Integer, but this is not true 115 -- of all targets. For example, in OpenVMS long /= Long_Integer. 116 117 ---------------------------------------------- 118 -- Behavior of Pragma Finalize_Storage_Only -- 119 ---------------------------------------------- 120 121 -- Garbage_Collected is a Boolean constant whose value indicates the 122 -- effect of the pragma Finalize_Storage_Entry on a controlled type. 123 124 -- Garbage_Collected = False 125 126 -- The system releases all storage on program termination only, 127 -- but not other garbage collection occurs, so finalization calls 128 -- are ommitted only for outer level onjects can be omitted if 129 -- pragma Finalize_Storage_Only is used. 130 131 -- Garbage_Collected = True 132 133 -- The system provides full garbage collection, so it is never 134 -- necessary to release storage for controlled objects for which 135 -- a pragma Finalize_Storage_Only is used. 136 137 Garbage_Collected : constant Boolean := False; 138 -- The storage mode for this system (release on program exit) 139 140 --------------------- 141 -- Tasking Profile -- 142 --------------------- 143 144 -- In the following sections, constant parameters are defined to 145 -- allow some optimizations and fine tuning within the tasking run time 146 -- based on restrictions on the tasking features. 147 148 ---------------------- 149 -- Locking Strategy -- 150 ---------------------- 151 152 Single_Lock : constant Boolean := False; 153 -- Indicates whether a single lock should be used within the tasking 154 -- run-time to protect internal structures. If True, a single lock 155 -- will be used, meaning less locking/unlocking operations, but also 156 -- more global contention. In general, Single_Lock should be set to 157 -- True on single processor machines, and to False to multi-processor 158 -- systems, but this can vary from application to application and also 159 -- depends on the scheduling policy. 160 161 ------------------- 162 -- Task Abortion -- 163 ------------------- 164 165 No_Abort : constant Boolean := False; 166 -- This constant indicates whether abort statements and asynchronous 167 -- transfer of control (ATC) are disallowed. If set to True, it is 168 -- assumed that neither construct is used, and the run time does not 169 -- need to defer/undefer abort and check for pending actions at 170 -- completion points. A value of True for No_Abort corresponds to: 171 -- pragma Restrictions (No_Abort_Statements); 172 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); 173 174 ---------------------- 175 -- Dynamic Priority -- 176 ---------------------- 177 178 Dynamic_Priority_Support : constant Boolean := True; 179 -- This constant indicates whether dynamic changes of task priorities 180 -- are allowed (True means normal RM mode in which such changes are 181 -- allowed). In particular, if this is False, then we do not need to 182 -- poll for pending base priority changes at every abort completion 183 -- point. A value of False for Dynamic_Priority_Support corresponds 184 -- to pragma Restrictions (No_Dynamic_Priorities); 185 186 --------------------- 187 -- Task Attributes -- 188 --------------------- 189 190 Default_Attribute_Count : constant := 4; 191 -- Number of pre-allocated Address-sized task attributes stored in the 192 -- task control block. 193 194 -------------------- 195 -- Runtime Traces -- 196 -------------------- 197 198 Runtime_Traces : constant Boolean := False; 199 -- This constant indicates whether the runtime outputs traces to a 200 -- predefined output or not (True means that traces are output). 201 -- See System.Traces for more details. 202 203end System.Parameters; 204