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
34with System.Storage_Elements;
35
36package 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.
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
100private
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 Mark_Id is new SSE.Integer_Address;
106
107end System.Secondary_Stack;
108