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) 1992-2020, 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-- Version is used by VxWorks 653, VxWorks MILS, and VxWorks6 cert Ravenscar 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 Size_Type is range 57 -(2 ** (Integer'(Standard'Address_Size) - 1)) .. 58 +(2 ** (Integer'(Standard'Address_Size) - 1)) - 1; 59 -- Type used to provide task stack sizes to the runtime. Sized to permit 60 -- stack sizes of up to half the total addressable memory space. This may 61 -- seem excessively large (even for 32-bit systems), however there are many 62 -- instances of users requiring large stack sizes (for example string 63 -- processing). 64 65 Unspecified_Size : constant Size_Type := Size_Type'First; 66 -- Value used to indicate that no size type is set 67 68 function Default_Stack_Size return Size_Type; 69 -- Default task stack size used if none is specified 70 71 function Minimum_Stack_Size return Size_Type; 72 -- Minimum task stack size permitted 73 74 function Adjust_Storage_Size (Size : Size_Type) return Size_Type; 75 -- Given the storage size stored in the TCB, return the Storage_Size 76 -- value required by the RM for the Storage_Size attribute. The 77 -- required adjustment is as follows: 78 -- 79 -- when Size = Unspecified_Size, return Default_Stack_Size 80 -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size 81 -- otherwise return given Size 82 83 Default_Env_Stack_Size : constant Size_Type := 14_336; 84 -- Assumed size of the environment task, if no other information 85 -- is available. This value is used when stack checking is 86 -- enabled and no GNAT_STACK_LIMIT environment variable is set. 87 -- This value is chosen as the VxWorks default stack size is 20kB, 88 -- and a little more than 4kB is necessary for the run time. 89 90 Stack_Grows_Down : constant Boolean := True; 91 -- This constant indicates whether the stack grows up (False) or 92 -- down (True) in memory as functions are called. It is used for 93 -- proper implementation of the stack overflow check. 94 95 Runtime_Default_Sec_Stack_Size : constant Size_Type := 10 * 1024; 96 -- The run-time chosen default size for secondary stacks that may be 97 -- overridden by the user with the use of binder -D switch. 98 99 Sec_Stack_Dynamic : constant Boolean := False; 100 -- Indicates if secondary stacks can grow and shrink at run-time. If False, 101 -- the size of a secondary stack is fixed at the point of its creation. 102 103 ---------------------------------------------- 104 -- Characteristics of types in Interfaces.C -- 105 ---------------------------------------------- 106 107 long_bits : constant := Long_Integer'Size; 108 -- Number of bits in type long and unsigned_long. The normal convention 109 -- is that this is the same as type Long_Integer, but this may not be true 110 -- of all targets. 111 112 ptr_bits : constant := Standard'Address_Size; 113 subtype C_Address is System.Address; 114 -- Number of bits in Interfaces.C pointers, normally a standard address 115 116 C_Malloc_Linkname : constant String := "__gnat_malloc"; 117 -- Name of runtime function used to allocate such a pointer 118 119 ---------------------------------------------- 120 -- Behavior of Pragma Finalize_Storage_Only -- 121 ---------------------------------------------- 122 123 -- Garbage_Collected is a Boolean constant whose value indicates the 124 -- effect of the pragma Finalize_Storage_Entry on a controlled type. 125 126 -- Garbage_Collected = False 127 128 -- The system releases all storage on program termination only, 129 -- but not other garbage collection occurs, so finalization calls 130 -- are omitted only for outer level objects can be omitted if 131 -- pragma Finalize_Storage_Only is used. 132 133 -- Garbage_Collected = True 134 135 -- The system provides full garbage collection, so it is never 136 -- necessary to release storage for controlled objects for which 137 -- a pragma Finalize_Storage_Only is used. 138 139 Garbage_Collected : constant Boolean := False; 140 -- The storage mode for this system (release on program exit) 141 142 --------------------- 143 -- Tasking Profile -- 144 --------------------- 145 146 -- In the following sections, constant parameters are defined to 147 -- allow some optimizations and fine tuning within the tasking run time 148 -- based on restrictions on the tasking features. 149 150 ------------------- 151 -- Task Abortion -- 152 ------------------- 153 154 No_Abort : constant Boolean := False; 155 -- This constant indicates whether abort statements and asynchronous 156 -- transfer of control (ATC) are disallowed. If set to True, it is 157 -- assumed that neither construct is used, and the run time does not 158 -- need to defer/undefer abort and check for pending actions at 159 -- completion points. A value of True for No_Abort corresponds to: 160 -- pragma Restrictions (No_Abort_Statements); 161 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); 162 163 --------------------- 164 -- Task Attributes -- 165 --------------------- 166 167 Max_Attribute_Count : constant := 8; 168 -- Number of task attributes stored in the task control block 169 170 ----------------------- 171 -- Task Image Length -- 172 ----------------------- 173 174 Max_Task_Image_Length : constant := 32; 175 -- This constant specifies the maximum length of a task's image 176 177 ------------------------------ 178 -- Exception Message Length -- 179 ------------------------------ 180 181 Default_Exception_Msg_Max_Length : constant := 200; 182 -- This constant specifies the default number of characters to allow 183 -- in an exception message (200 is minimum required by RM 11.4.1(18)). 184 185end System.Parameters; 186