+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- 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;
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