gcc/ada/libgnat/s-parame__vxworks.ads

   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 --  This is the default VxWorks version of the package
  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
  49 package 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    --  overriden by the user with the use of binder -D switch.
  98
  99    Sec_Stack_Dynamic : constant Boolean := True;
 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    -- Locking Strategy --
 152    ----------------------
 153
 154    Single_Lock : constant Boolean := False;
 155    --  Indicates whether a single lock should be used within the tasking
 156    --  run-time to protect internal structures. If True, a single lock
 157    --  will be used, meaning less locking/unlocking operations, but also
 158    --  more global contention. In general, Single_Lock should be set to
 159    --  True on single processor machines, and to False to multi-processor
 160    --  systems, but this can vary from application to application and also
 161    --  depends on the scheduling policy.
 162
 163    -------------------
 164    -- Task Abortion --
 165    -------------------
 166
 167    No_Abort : constant Boolean := False;
 168    --  This constant indicates whether abort statements and asynchronous
 169    --  transfer of control (ATC) are disallowed. If set to True, it is
 170    --  assumed that neither construct is used, and the run time does not
 171    --  need to defer/undefer abort and check for pending actions at
 172    --  completion points. A value of True for No_Abort corresponds to:
 173    --  pragma Restrictions (No_Abort_Statements);
 174    --  pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
 175
 176    ---------------------
 177    -- Task Attributes --
 178    ---------------------
 179
 180    Max_Attribute_Count : constant := 16;
 181    --  Number of task attributes stored in the task control block
 182
 183    -----------------------
 184    -- Task Image Length --
 185    -----------------------
 186
 187    Max_Task_Image_Length : constant := 32;
 188    --  This constant specifies the maximum length of a task's image
 189
 190    ------------------------------
 191    -- Exception Message Length --
 192    ------------------------------
 193
 194    Default_Exception_Msg_Max_Length : constant := 200;
 195    --  This constant specifies the default number of characters to allow
 196    --  in an exception message (200 is minimum required by RM 11.4.1(18)).
 197
 198 end System.Parameters;