gcc/ada/s-memory-mingw.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                         S Y S T E M . M E M O R Y                        --
   6 --                                                                          --
   7 --                                 B o d y                                 --
   8 --                                                                          --
   9 --          Copyright (C) 2001-2003 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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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 --  This version provides ways to limit the amount of used memory for systems
  35 --  that do not have OS support for that.
  36
  37 --  The amount of available memory available for dynamic allocation is limited
  38 --  by setting the environment variable GNAT_MEMORY_LIMIT to the number of
  39 --  kilobytes that can be used.
  40 --
  41 --  Windows is currently using this version.
  42
  43 with Ada.Exceptions;
  44 with System.Soft_Links;
  45
  46 package body System.Memory is
  47
  48    use Ada.Exceptions;
  49    use System.Soft_Links;
  50
  51    function c_malloc (Size : size_t) return System.Address;
  52    pragma Import (C, c_malloc, "malloc");
  53
  54    procedure c_free (Ptr : System.Address);
  55    pragma Import (C, c_free, "free");
  56
  57    function c_realloc
  58      (Ptr : System.Address; Size : size_t) return System.Address;
  59    pragma Import (C, c_realloc, "realloc");
  60
  61    function msize (Ptr : System.Address) return size_t;
  62    pragma Import (C, msize, "_msize");
  63
  64    function getenv (Str : String) return System.Address;
  65    pragma Import (C, getenv);
  66
  67    function atoi (Str : System.Address) return Integer;
  68    pragma Import (C, atoi);
  69
  70    Available_Memory : size_t := 0;
  71    --  Amount of memory that is available for heap allocations.
  72    --  A value of 0 means that the amount is not yet initialized.
  73
  74    Msize_Accuracy   : constant := 4096;
  75    --  Defines the amount of memory to add to requested allocation sizes,
  76    --  because malloc may return a bigger block than requested. As msize
  77    --  is used when by Free, it must be used on allocation as well. To
  78    --  prevent underflow of available_memory we need to use a reserve.
  79
  80    procedure Check_Available_Memory (Size : size_t);
  81    --  This routine must be called while holding the task lock. When the
  82    --  memory limit is not yet initialized, it will be set to the value of
  83    --  the GNAT_MEMORY_LIMIT environment variable or to unlimited if that
  84    --  does not exist. If the size is larger than the amount of available
  85    --  memory, the task lock will be freed and a storage_error exception
  86    --  will be raised.
  87
  88    -----------
  89    -- Alloc --
  90    -----------
  91
  92    function Alloc (Size : size_t) return System.Address is
  93       Result      : System.Address;
  94       Actual_Size : size_t := Size;
  95
  96    begin
  97       if Size = size_t'Last then
  98          Raise_Exception (Storage_Error'Identity, "object too large");
  99       end if;
 100
 101       --  Change size from zero to non-zero. We still want a proper pointer
 102       --  for the zero case because pointers to zero length objects have to
 103       --  be distinct, but we can't just go ahead and allocate zero bytes,
 104       --  since some malloc's return zero for a zero argument.
 105
 106       if Size = 0 then
 107          Actual_Size := 1;
 108       end if;
 109
 110       Lock_Task.all;
 111
 112       if Actual_Size + Msize_Accuracy >= Available_Memory then
 113          Check_Available_Memory (Size + Msize_Accuracy);
 114       end if;
 115
 116       Result := c_malloc (Actual_Size);
 117
 118       if Result /= System.Null_Address then
 119          Available_Memory := Available_Memory - msize (Result);
 120       end if;
 121
 122       Unlock_Task.all;
 123
 124       if Result = System.Null_Address then
 125          Raise_Exception (Storage_Error'Identity, "heap exhausted");
 126       end if;
 127
 128       return Result;
 129    end Alloc;
 130
 131    ----------------------------
 132    -- Check_Available_Memory --
 133    ----------------------------
 134
 135    procedure Check_Available_Memory (Size : size_t) is
 136       Gnat_Memory_Limit : System.Address;
 137
 138    begin
 139       if Available_Memory = 0 then
 140
 141          --  The amount of available memory hasn't been initialized yet
 142
 143          Gnat_Memory_Limit := getenv ("GNAT_MEMORY_LIMIT" & ASCII.NUL);
 144
 145          if Gnat_Memory_Limit /= System.Null_Address then
 146             Available_Memory :=
 147               size_t (atoi (Gnat_Memory_Limit)) * 1024 + Msize_Accuracy;
 148          else
 149             Available_Memory := size_t'Last;
 150          end if;
 151       end if;
 152
 153       if Size >= Available_Memory then
 154
 155          --  There is a memory overflow
 156
 157          Unlock_Task.all;
 158          Raise_Exception
 159            (Storage_Error'Identity, "heap memory limit exceeded");
 160       end if;
 161    end Check_Available_Memory;
 162
 163    ----------
 164    -- Free --
 165    ----------
 166
 167    procedure Free (Ptr : System.Address) is
 168    begin
 169       Lock_Task.all;
 170
 171       if Ptr /= System.Null_Address then
 172          Available_Memory := Available_Memory + msize (Ptr);
 173       end if;
 174
 175       c_free (Ptr);
 176
 177       Unlock_Task.all;
 178    end Free;
 179
 180    -------------
 181    -- Realloc --
 182    -------------
 183
 184    function Realloc
 185      (Ptr  : System.Address;
 186       Size : size_t)
 187       return System.Address
 188    is
 189       Result      : System.Address;
 190       Actual_Size : constant size_t := Size;
 191       Old_Size    : size_t;
 192
 193    begin
 194       if Size = size_t'Last then
 195          Raise_Exception (Storage_Error'Identity, "object too large");
 196       end if;
 197
 198       Lock_Task.all;
 199
 200       Old_Size := msize (Ptr);
 201
 202       --  Conservative check - no need to try to be precise here
 203
 204       if Size + Msize_Accuracy >= Available_Memory then
 205          Check_Available_Memory (Size + Msize_Accuracy);
 206       end if;
 207
 208       Result := c_realloc (Ptr, Actual_Size);
 209
 210       if Result /= System.Null_Address then
 211          Available_Memory := Available_Memory + Old_Size - msize (Result);
 212       end if;
 213
 214       Unlock_Task.all;
 215
 216       if Result = System.Null_Address then
 217          Raise_Exception (Storage_Error'Identity, "heap exhausted");
 218       end if;
 219
 220       return Result;
 221    end Realloc;
 222
 223 end System.Memory;