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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--               S Y S T E M . S E C O N D A R Y _ S T A C K                --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

pragma Compiler_Unit;

with System.Storage_Elements;

package System.Secondary_Stack is

   package SSE renames System.Storage_Elements;

   Default_Secondary_Stack_Size : Natural := 10 * 1024;

   --  Default size of a secondary stack. May be modified by binder -D switch

   --  which causes the binder to generate an appropriate assignment in the

   --  binder generated file.

   procedure SS_Init

     (Stk  : in out Address;

      Size : Natural := Default_Secondary_Stack_Size);

   --  Initialize the secondary stack with a main stack of the given Size.

   --

   --  If System.Parameters.Sec_Stack_Ratio equals Dynamic, Stk is really an

   --  OUT parameter that will be allocated on the heap. Then all further

   --  allocations which do not overflow the main stack will not generate

   --  dynamic (de)allocation calls. If the main Stack overflows, a new

   --  chuck of at least the same size will be allocated and linked to the

   --  previous chunk.

   --

   --  Otherwise (Sec_Stack_Ratio between 0 and 100), Stk is an IN parameter

   --  that is already pointing to a Stack_Id. The secondary stack in this case

   --  is fixed, and any attempt to allocate more than the initial size will

   --  result in a Storage_Error being raised.

   --

   --  Note: the reason that Stk is passed is that SS_Init is called before

   --  the proper interface is established to obtain the address of the

   --  stack using System.Soft_Links.Get_Sec_Stack_Addr.

   procedure SS_Allocate

     (Addr         : out Address;

      Storage_Size : SSE.Storage_Count);

   --  Allocate enough space for a 'Storage_Size' bytes object with Maximum

   --  alignment. The address of the allocated space is returned in Addr.

   procedure SS_Free (Stk : in out Address);

   --  Release the memory allocated for the Secondary Stack. That is

   --  to say, all the allocated chunks. Upon return, Stk will be set

   --  to System.Null_Address.

   type Mark_Id is private;

   --  Type used to mark the stack for mark/release processing

   function SS_Mark return Mark_Id;

   --  Return the Mark corresponding to the current state of the stack

   procedure SS_Release (M : Mark_Id);

   --  Restore the state of the stack corresponding to the mark M. If an

   --  additional chunk have been allocated, it will never be freed during a

   --  ??? missing comment here

   function SS_Get_Max return Long_Long_Integer;

   --  Return maximum used space in storage units for the current secondary

   --  stack. For a dynamically allocated secondary stack, the returned

   --  result is always -1. For a statically allocated secondary stack,

   --  the returned value shows the largest amount of space allocated so

   --  far during execution of the program to the current secondary stack,

   --  i.e. the secondary stack for the current task.

   generic

      with procedure Put_Line (S : String);

   procedure SS_Info;

   --  Debugging procedure used to print out secondary Stack allocation

   --  information. This procedure is generic in order to avoid a direct

   --  dependance on a particular IO package.

private

   SS_Pool : Integer;

   --  Unused entity that is just present to ease the sharing of the pool

   --  mechanism for specific allocation/deallocation in the compiler

   type SS_Ptr is new SSE.Integer_Address;

   --  Stack pointer value for secondary stack

   type Mark_Id is record

      Sstk : System.Address;

      Sptr : SS_Ptr;

   end record;

   --  A mark value contains the address of the secondary stack structure,

   --  as returned by System.Soft_Links.Get_Sec_Stack_Addr, and a stack

   --  pointer value corresponding to the point of the mark call.

end System.Secondary_Stack;