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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . M E M O R Y --
-- --
-- B o d y --
-- --
-- Copyright (C) 2001-2018, 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. --
-- --
------------------------------------------------------------------------------
-- 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;
|
