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) 1992-2011, 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 3, 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. -- 17-- -- 18-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 21-- -- 22-- You should have received a copy of the GNU General Public License and -- 23-- a copy of the GCC Runtime Library Exception along with this program; -- 24-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 25-- <http://www.gnu.org/licenses/>. -- 26-- -- 27-- GNAT was originally developed by the GNAT team at New York University. -- 28-- Extensive contributions were provided by Ada Core Technologies Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This is the Integrity OpenVMS version 33 34-- This package defines some system dependent parameters for GNAT. These 35-- are values that are referenced by the runtime library and are therefore 36-- relevant to the target machine. 37 38-- The parameters whose value is defined in the spec are not generally 39-- expected to be changed. If they are changed, it will be necessary to 40-- recompile the run-time library. 41 42-- The parameters which are defined by functions can be changed by modifying 43-- the body of System.Parameters in file s-parame.adb. A change to this body 44-- requires only rebinding and relinking of the application. 45 46-- Note: do not introduce any pragma Inline statements into this unit, since 47-- otherwise the relinking and rebinding capability would be deactivated. 48 49package System.Parameters is 50 pragma Pure; 51 52 --------------------------------------- 53 -- Task And Stack Allocation Control -- 54 --------------------------------------- 55 56 type Task_Storage_Size is new Integer; 57 -- Type used in tasking units for task storage size 58 59 type Size_Type is new Task_Storage_Size; 60 -- Type used to provide task storage size to runtime 61 62 Unspecified_Size : constant Size_Type := Size_Type'First; 63 -- Value used to indicate that no size type is set 64 65 subtype Percentage is Size_Type range -1 .. 100; 66 Dynamic : constant Size_Type := -1; 67 -- The secondary stack ratio is a constant between 0 and 100 which 68 -- determines the percentage of the allocated task stack that is 69 -- used by the secondary stack (the rest being the primary stack). 70 -- The special value of minus one indicates that the secondary 71 -- stack is to be allocated from the heap instead. 72 73 Sec_Stack_Percentage : constant Percentage := Dynamic; 74 -- This constant defines the handling of the secondary stack 75 76 Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Percentage = Dynamic; 77 -- Convenient Boolean for testing for dynamic secondary stack 78 79 function Default_Stack_Size return Size_Type; 80 -- Default task stack size used if none is specified 81 82 function Minimum_Stack_Size return Size_Type; 83 -- Minimum task stack size permitted 84 85 function Adjust_Storage_Size (Size : Size_Type) return Size_Type; 86 -- Given the storage size stored in the TCB, return the Storage_Size 87 -- value required by the RM for the Storage_Size attribute. The 88 -- required adjustment is as follows: 89 -- 90 -- when Size = Unspecified_Size, return Default_Stack_Size 91 -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size 92 -- otherwise return given Size 93 94 Default_Env_Stack_Size : constant Size_Type := 8_192_000; 95 -- Assumed size of the environment task, if no other information 96 -- is available. This value is used when stack checking is 97 -- enabled and no GNAT_STACK_LIMIT environment variable is set. 98 99 Stack_Grows_Down : constant Boolean := True; 100 -- This constant indicates whether the stack grows up (False) or 101 -- down (True) in memory as functions are called. It is used for 102 -- proper implementation of the stack overflow check. 103 104 ---------------------------------------------- 105 -- Characteristics of types in Interfaces.C -- 106 ---------------------------------------------- 107 108 long_bits : constant := 32; 109 -- Number of bits in type long and unsigned_long. The normal convention 110 -- is that this is the same as type Long_Integer, but this is not true 111 -- of all targets. For example, in OpenVMS long /= Long_Integer. 112 113 ptr_bits : constant := 32; 114 subtype C_Address is System.Address 115 range -2 ** (ptr_bits - 1) .. 2 ** (ptr_bits - 1) - 1; 116 for C_Address'Object_Size use ptr_bits; 117 -- Number of bits in Interfaces.C pointers, normally a standard address, 118 -- except on 64-bit VMS where they are 32-bit addresses, for compatibility 119 -- with legacy code. System.Aux_DEC.Short_Address can't be used because of 120 -- elaboration circularity. 121 122 C_Malloc_Linkname : constant String := "__gnat_malloc32"; 123 -- Name of runtime function used to allocate such a pointer 124 125 ---------------------------------------------- 126 -- Behavior of Pragma Finalize_Storage_Only -- 127 ---------------------------------------------- 128 129 -- Garbage_Collected is a Boolean constant whose value indicates the 130 -- effect of the pragma Finalize_Storage_Entry on a controlled type. 131 132 -- Garbage_Collected = False 133 134 -- The system releases all storage on program termination only, 135 -- but not other garbage collection occurs, so finalization calls 136 -- are omitted only for outer level objects can be omitted if 137 -- pragma Finalize_Storage_Only is used. 138 139 -- Garbage_Collected = True 140 141 -- The system provides full garbage collection, so it is never 142 -- necessary to release storage for controlled objects for which 143 -- a pragma Finalize_Storage_Only is used. 144 145 Garbage_Collected : constant Boolean := False; 146 -- The storage mode for this system (release on program exit) 147 148 --------------------- 149 -- Tasking Profile -- 150 --------------------- 151 152 -- In the following sections, constant parameters are defined to 153 -- allow some optimizations and fine tuning within the tasking run time 154 -- based on restrictions on the tasking features. 155 156 ---------------------- 157 -- Locking Strategy -- 158 ---------------------- 159 160 Single_Lock : constant Boolean := False; 161 -- Indicates whether a single lock should be used within the tasking 162 -- run-time to protect internal structures. If True, a single lock 163 -- will be used, meaning less locking/unlocking operations, but also 164 -- more global contention. In general, Single_Lock should be set to 165 -- True on single processor machines, and to False to multi-processor 166 -- systems, but this can vary from application to application and also 167 -- depends on the scheduling policy. 168 169 ------------------- 170 -- Task Abortion -- 171 ------------------- 172 173 No_Abort : constant Boolean := False; 174 -- This constant indicates whether abort statements and asynchronous 175 -- transfer of control (ATC) are disallowed. If set to True, it is 176 -- assumed that neither construct is used, and the run time does not 177 -- need to defer/undefer abort and check for pending actions at 178 -- completion points. A value of True for No_Abort corresponds to: 179 -- pragma Restrictions (No_Abort_Statements); 180 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); 181 182 --------------------- 183 -- Task Attributes -- 184 --------------------- 185 186 Default_Attribute_Count : constant := 4; 187 -- Number of pre-allocated Address-sized task attributes stored in the 188 -- task control block. 189 190 -------------------- 191 -- Runtime Traces -- 192 -------------------- 193 194 Runtime_Traces : constant Boolean := False; 195 -- This constant indicates whether the runtime outputs traces to a 196 -- predefined output or not (True means that traces are output). 197 -- See System.Traces for more details. 198 199 ----------------------- 200 -- Task Image Length -- 201 ----------------------- 202 203 Max_Task_Image_Length : constant := 256; 204 -- This constant specifies the maximum length of a task's image 205 206 ------------------------------ 207 -- Exception Message Length -- 208 ------------------------------ 209 210 Default_Exception_Msg_Max_Length : constant := 512; 211 -- This constant specifies the maximum number of characters to allow in an 212 -- exception message (see RM 11.4.1(18)). The value for VMS exceeds the 213 -- default minimum of 200 to allow for the length of chained VMS condition 214 -- handling messages. 215 216end System.Parameters; 217