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) 1992-2016, 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 pragma Compiler_Unit_Warning;
  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    --  which causes the binder to generate an appropriate assignment in the
  43    --  binder generated file.
  44
  45    function Minimum_Secondary_Stack_Size return Natural;
  46    --  The minimum size of the secondary stack so that the internal
  47    --  requirements of the stack are met.
  48
  49    procedure SS_Init
  50      (Stk  : in out Address;
  51       Size : Natural := Default_Secondary_Stack_Size);
  52    --  Initialize the secondary stack with a main stack of the given Size.
  53    --
  54    --  If System.Parameters.Sec_Stack_Percentage equals Dynamic, Stk is really
  55    --  an OUT parameter that will be allocated on the heap. Then all further
  56    --  allocations which do not overflow the main stack will not generate
  57    --  dynamic (de)allocation calls. If the main Stack overflows, a new
  58    --  chuck of at least the same size will be allocated and linked to the
  59    --  previous chunk.
  60    --
  61    --  Otherwise (Sec_Stack_Percentage between 0 and 100), Stk is an IN
  62    --  parameter that is already pointing to a Stack_Id. The secondary stack
  63    --  in this case is fixed, and any attempt to allocate more than the initial
  64    --  size will result in a Storage_Error being raised.
  65    --
  66    --  Note: the reason that Stk is passed is that SS_Init is called before
  67    --  the proper interface is established to obtain the address of the
  68    --  stack using System.Soft_Links.Get_Sec_Stack_Addr.
  69
  70    procedure SS_Allocate
  71      (Addr         : out Address;
  72       Storage_Size : SSE.Storage_Count);
  73    --  Allocate enough space for a 'Storage_Size' bytes object with Maximum
  74    --  alignment. The address of the allocated space is returned in Addr.
  75
  76    procedure SS_Free (Stk : in out Address);
  77    --  Release the memory allocated for the Secondary Stack. That is
  78    --  to say, all the allocated chunks. Upon return, Stk will be set
  79    --  to System.Null_Address.
  80
  81    type Mark_Id is private;
  82    --  Type used to mark the stack for mark/release processing
  83
  84    function SS_Mark return Mark_Id;
  85    --  Return the Mark corresponding to the current state of the stack
  86
  87    procedure SS_Release (M : Mark_Id);
  88    --  Restore the state of the stack corresponding to the mark M. If an
  89    --  additional chunk have been allocated, it will never be freed during a
  90    --  ??? missing comment here
  91
  92    function SS_Get_Max return Long_Long_Integer;
  93    --  Return maximum used space in storage units for the current secondary
  94    --  stack. For a dynamically allocated secondary stack, the returned
  95    --  result is always -1. For a statically allocated secondary stack,
  96    --  the returned value shows the largest amount of space allocated so
  97    --  far during execution of the program to the current secondary stack,
  98    --  i.e. the secondary stack for the current task.
  99
 100    generic
 101       with procedure Put_Line (S : String);
 102    procedure SS_Info;
 103    --  Debugging procedure used to print out secondary Stack allocation
 104    --  information. This procedure is generic in order to avoid a direct
 105    --  dependance on a particular IO package.
 106
 107 private
 108    SS_Pool : Integer;
 109    --  Unused entity that is just present to ease the sharing of the pool
 110    --  mechanism for specific allocation/deallocation in the compiler
 111
 112    type SS_Ptr is new SSE.Integer_Address;
 113    --  Stack pointer value for secondary stack
 114
 115    type Mark_Id is record
 116       Sstk : System.Address;
 117       Sptr : SS_Ptr;
 118    end record;
 119    --  A mark value contains the address of the secondary stack structure,
 120    --  as returned by System.Soft_Links.Get_Sec_Stack_Addr, and a stack
 121    --  pointer value corresponding to the point of the mark call.
 122
 123 end System.Secondary_Stack;