gcc/ada/s-secsta.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --               S Y S T E M . S E C O N D A R Y _ S T A C K                --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2004 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 with System.Storage_Elements;
  35
  36 package System.Secondary_Stack is
  37
  38    package SSE renames System.Storage_Elements;
  39
  40    Default_Secondary_Stack_Size : Natural := 10 * 1024;
  41    --  Default size of a secondary stack. May be modified by binder -D switch
  42
  43    procedure SS_Init
  44      (Stk  : in out Address;
  45       Size : Natural := Default_Secondary_Stack_Size);
  46    --  Initialize the secondary stack with a main stack of the given Size.
  47    --
  48    --  If System.Parameters.Sec_Stack_Ratio equals Dynamic, Stk is really an
  49    --  OUT parameter that will be allocated on the heap. Then all further
  50    --  allocations which do not overflow the main stack will not generate
  51    --  dynamic (de)allocation calls. If the main Stack overflows, a new
  52    --  chuck of at least the same size will be allocated and linked to the
  53    --  previous chunk.
  54    --
  55    --  Otherwise (Sec_Stack_Ratio between 0 and 100), Stk is an IN parameter
  56    --  that is already pointing to a Stack_Id. The secondary stack in this case
  57    --  is fixed, and any attempt to allocated more than the initial size will
  58    --  result in a Storage_Error being raised.
  59    --
  60    --  Note: the reason that Stk is passed is that SS_Init is called before
  61    --  the proper interface is established to obtain the address of the
  62    --  stack using System.Soft_Links.Get_Sec_Stack_Addr.
  63
  64    procedure SS_Allocate
  65      (Addr         : out Address;
  66       Storage_Size : SSE.Storage_Count);
  67    --  Allocate enough space for a 'Storage_Size' bytes object with Maximum
  68    --  alignment. The address of the allocated space is returned in Addr.
  69
  70    procedure SS_Free (Stk : in out Address);
  71    --  Release the memory allocated for the Secondary Stack. That is
  72    --  to say, all the allocated chunks. Upon return, Stk will be set
  73    --  to System.Null_Address.
  74
  75    type Mark_Id is private;
  76    --  Type used to mark the stack for mark/release processing
  77
  78    function SS_Mark return Mark_Id;
  79    --  Return the Mark corresponding to the current state of the stack
  80
  81    procedure SS_Release (M : Mark_Id);
  82    --  Restore the state of the stack corresponding to the mark M. If an
  83    --  additional chunk have been allocated, it will never be freed during a
  84
  85    function SS_Get_Max return Long_Long_Integer;
  86    --  Return maximum used space in storage units for the current secondary
  87    --  stack. For a dynamically allocated secondary stack, the returned
  88    --  result is always -1. For a statically allocated secondary stack,
  89    --  the returned value shows the largest amount of space allocated so
  90    --  far during execution of the program to the current secondary stack,
  91    --  i.e. the secondary stack for the current task.
  92
  93    generic
  94       with procedure Put_Line (S : String);
  95    procedure SS_Info;
  96    --  Debugging procedure used to print out secondary Stack allocation
  97    --  information. This procedure is generic in order to avoid a direct
  98    --  dependance on a particular IO package.
  99
 100 private
 101    SS_Pool : Integer;
 102    --  Unused entity that is just present to ease the sharing of the pool
 103    --  mechanism for specific allocation/deallocation in the compiler
 104
 105    type SS_Ptr is new SSE.Integer_Address;
 106    --  Stack pointer value for secondary stack
 107
 108    type Mark_Id is record
 109       Sstk : System.Address;
 110       Sptr : SS_Ptr;
 111    end record;
 112    --  A mark value contains the address of the secondary stack structure,
 113    --  as returned by System.Soft_Links.Get_Sec_Stack_Addr, and a stack
 114    --  pointer value corresponding to the point of the mark call.
 115
 116 end System.Secondary_Stack;