------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- S Y S T E M . M E M O R Y -- -- -- -- B o d y -- -- -- -- Copyright (C) 2001-2003 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 2, 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. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This version provides ways to limit the amount of used memory for systems -- that do not have OS support for that. -- The amount of available memory available for dynamic allocation is limited -- by setting the environment variable GNAT_MEMORY_LIMIT to the number of -- kilobytes that can be used. -- -- Windows is currently using this version. with Ada.Exceptions; with System.Soft_Links; package body System.Memory is use Ada.Exceptions; use System.Soft_Links; function c_malloc (Size : size_t) return System.Address; pragma Import (C, c_malloc, "malloc"); procedure c_free (Ptr : System.Address); pragma Import (C, c_free, "free"); function c_realloc (Ptr : System.Address; Size : size_t) return System.Address; pragma Import (C, c_realloc, "realloc"); function msize (Ptr : System.Address) return size_t; pragma Import (C, msize, "_msize"); function getenv (Str : String) return System.Address; pragma Import (C, getenv); function atoi (Str : System.Address) return Integer; pragma Import (C, atoi); Available_Memory : size_t := 0; -- Amount of memory that is available for heap allocations. -- A value of 0 means that the amount is not yet initialized. Msize_Accuracy : constant := 4096; -- Defines the amount of memory to add to requested allocation sizes, -- because malloc may return a bigger block than requested. As msize -- is used when by Free, it must be used on allocation as well. To -- prevent underflow of available_memory we need to use a reserve. procedure Check_Available_Memory (Size : size_t); -- This routine must be called while holding the task lock. When the -- memory limit is not yet initialized, it will be set to the value of -- the GNAT_MEMORY_LIMIT environment variable or to unlimited if that -- does not exist. If the size is larger than the amount of available -- memory, the task lock will be freed and a storage_error exception -- will be raised. ----------- -- Alloc -- ----------- function Alloc (Size : size_t) return System.Address is Result : System.Address; Actual_Size : size_t := Size; begin if Size = size_t'Last then Raise_Exception (Storage_Error'Identity, "object too large"); end if; -- Change size from zero to non-zero. We still want a proper pointer -- for the zero case because pointers to zero length objects have to -- be distinct, but we can't just go ahead and allocate zero bytes, -- since some malloc's return zero for a zero argument. if Size = 0 then Actual_Size := 1; end if; Lock_Task.all; if Actual_Size + Msize_Accuracy >= Available_Memory then Check_Available_Memory (Size + Msize_Accuracy); end if; Result := c_malloc (Actual_Size); if Result /= System.Null_Address then Available_Memory := Available_Memory - msize (Result); end if; Unlock_Task.all; if Result = System.Null_Address then Raise_Exception (Storage_Error'Identity, "heap exhausted"); end if; return Result; end Alloc; ---------------------------- -- Check_Available_Memory -- ---------------------------- procedure Check_Available_Memory (Size : size_t) is Gnat_Memory_Limit : System.Address; begin if Available_Memory = 0 then -- The amount of available memory hasn't been initialized yet Gnat_Memory_Limit := getenv ("GNAT_MEMORY_LIMIT" & ASCII.NUL); if Gnat_Memory_Limit /= System.Null_Address then Available_Memory := size_t (atoi (Gnat_Memory_Limit)) * 1024 + Msize_Accuracy; else Available_Memory := size_t'Last; end if; end if; if Size >= Available_Memory then -- There is a memory overflow Unlock_Task.all; Raise_Exception (Storage_Error'Identity, "heap memory limit exceeded"); end if; end Check_Available_Memory; ---------- -- Free -- ---------- procedure Free (Ptr : System.Address) is begin Lock_Task.all; if Ptr /= System.Null_Address then Available_Memory := Available_Memory + msize (Ptr); end if; c_free (Ptr); Unlock_Task.all; end Free; ------------- -- Realloc -- ------------- function Realloc (Ptr : System.Address; Size : size_t) return System.Address is Result : System.Address; Actual_Size : constant size_t := Size; Old_Size : size_t; begin if Size = size_t'Last then Raise_Exception (Storage_Error'Identity, "object too large"); end if; Lock_Task.all; Old_Size := msize (Ptr); -- Conservative check - no need to try to be precise here if Size + Msize_Accuracy >= Available_Memory then Check_Available_Memory (Size + Msize_Accuracy); end if; Result := c_realloc (Ptr, Actual_Size); if Result /= System.Null_Address then Available_Memory := Available_Memory + Old_Size - msize (Result); end if; Unlock_Task.all; if Result = System.Null_Address then Raise_Exception (Storage_Error'Identity, "heap exhausted"); end if; return Result; end Realloc; end System.Memory;