gcc/ada/libgnat/s-parame.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) 1992-2024, 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 --  Default version used when no target-specific version is provided
  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 -Memory_Size / 2 .. Memory_Size / 2 - 1;
  57    --  Type used to provide task stack sizes to the runtime. Sized to permit
  58    --  stack sizes of up to half the total addressable memory space. This may
  59    --  seem excessively large (even for 32-bit systems), however there are many
  60    --  instances of users requiring large stack sizes (for example string
  61    --  processing).
  62
  63    Unspecified_Size : constant Size_Type := Size_Type'First;
  64    --  Value used to indicate that no size type is set
  65
  66    function Default_Stack_Size return Size_Type;
  67    --  Default task stack size used if none is specified
  68
  69    function Minimum_Stack_Size return Size_Type;
  70    --  Minimum task stack size permitted
  71
  72    function Adjust_Storage_Size (Size : Size_Type) return Size_Type;
  73    --  Given the storage size stored in the TCB, return the Storage_Size
  74    --  value required by the RM for the Storage_Size attribute. The
  75    --  required adjustment is as follows:
  76    --
  77    --    when Size = Unspecified_Size, return Default_Stack_Size
  78    --    when Size < Minimum_Stack_Size, return Minimum_Stack_Size
  79    --    otherwise return given Size
  80
  81    Default_Env_Stack_Size : constant Size_Type := 8_192_000;
  82    --  Assumed size of the environment task, if no other information is
  83    --  available. This value is used when stack checking is enabled and
  84    --  no GNAT_STACK_LIMIT environment variable is set.
  85
  86    Stack_Grows_Down  : constant Boolean := True;
  87    --  This constant indicates whether the stack grows up (False) or
  88    --  down (True) in memory as functions are called. It is used for
  89    --  proper implementation of the stack overflow check.
  90
  91    Runtime_Default_Sec_Stack_Size : constant Size_Type := 10 * 1024;
  92    --  The run-time chosen default size for secondary stacks that may be
  93    --  overridden by the user with the use of binder -D switch.
  94
  95    Sec_Stack_Dynamic : constant Boolean := True;
  96    --  Indicates if secondary stacks can grow and shrink at run-time. If False,
  97    --  the size of a secondary stack is fixed at the point of its creation.
  98
  99    ------------------------------------
 100    -- Characteristics of time_t type --
 101    ------------------------------------
 102
 103    time_t_bits : constant := Long_Integer'Size;
 104    --  Number of bits in type time_t
 105
 106    ----------------------------------------------
 107    -- Characteristics of types in Interfaces.C --
 108    ----------------------------------------------
 109
 110    long_bits : constant := Long_Integer'Size;
 111    --  Number of bits in type long and unsigned_long. The normal convention
 112    --  is that this is the same as type Long_Integer, but this may not be true
 113    --  of all targets.
 114
 115    ptr_bits  : constant := Standard'Address_Size;
 116    subtype C_Address is System.Address;
 117    --  Number of bits in Interfaces.C pointers, normally a standard address
 118
 119    C_Malloc_Linkname : constant String := "__gnat_malloc";
 120    --  Name of runtime function used to allocate such a pointer
 121
 122    ----------------------------------------------
 123    -- Behavior of Pragma Finalize_Storage_Only --
 124    ----------------------------------------------
 125
 126    --  Garbage_Collected is a Boolean constant whose value indicates the
 127    --  effect of the pragma Finalize_Storage_Entry on a controlled type.
 128
 129    --    Garbage_Collected = False
 130
 131    --      The system releases all storage on program termination only,
 132    --      but not other garbage collection occurs, so finalization calls
 133    --      are omitted only for outer level objects can be omitted if
 134    --      pragma Finalize_Storage_Only is used.
 135
 136    --    Garbage_Collected = True
 137
 138    --      The system provides full garbage collection, so it is never
 139    --      necessary to release storage for controlled objects for which
 140    --      a pragma Finalize_Storage_Only is used.
 141
 142    Garbage_Collected : constant Boolean := False;
 143    --  The storage mode for this system (release on program exit)
 144
 145    ---------------------
 146    -- Tasking Profile --
 147    ---------------------
 148
 149    --  In the following sections, constant parameters are defined to
 150    --  allow some optimizations and fine tuning within the tasking run time
 151    --  based on restrictions on the tasking features.
 152
 153    -------------------
 154    -- Task Abortion --
 155    -------------------
 156
 157    No_Abort : constant Boolean := False;
 158    --  This constant indicates whether abort statements and asynchronous
 159    --  transfer of control (ATC) are disallowed. If set to True, it is
 160    --  assumed that neither construct is used, and the run time does not
 161    --  need to defer/undefer abort and check for pending actions at
 162    --  completion points. A value of True for No_Abort corresponds to:
 163    --  pragma Restrictions (No_Abort_Statements);
 164    --  pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
 165
 166    ---------------------
 167    -- Task Attributes --
 168    ---------------------
 169
 170    Max_Attribute_Count : constant := 32;
 171    --  Number of task attributes stored in the task control block
 172
 173    -----------------------
 174    -- Task Image Length --
 175    -----------------------
 176
 177    Max_Task_Image_Length : constant := 256;
 178    --  This constant specifies the maximum length of a task's image
 179
 180    ------------------------------
 181    -- Exception Message Length --
 182    ------------------------------
 183
 184    Default_Exception_Msg_Max_Length : constant := 200;
 185    --  This constant specifies the default number of characters to allow
 186    --  in an exception message (200 is minimum required by RM 11.4.1(18)).
 187
 188 end System.Parameters;