1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . M E M O R Y --
9 -- Copyright (C) 2001-2002 Free Software Foundation, Inc. --
11 -- This specification is derived from the Ada Reference Manual for use with --
12 -- GNAT. The copyright notice above, and the license provisions that follow --
13 -- apply solely to the contents of the part following the private keyword. --
15 -- GNAT is free software; you can redistribute it and/or modify it under --
16 -- terms of the GNU General Public License as published by the Free Soft- --
17 -- ware Foundation; either version 2, or (at your option) any later ver- --
18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
20 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
21 -- for more details. You should have received a copy of the GNU General --
22 -- Public License distributed with GNAT; see file COPYING. If not, write --
23 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
24 -- MA 02111-1307, USA. --
26 -- As a special exception, if other files instantiate generics from this --
27 -- unit, or you link this unit with other files to produce an executable, --
28 -- this unit does not by itself cause the resulting executable to be --
29 -- covered by the GNU General Public License. This exception does not --
30 -- however invalidate any other reasons why the executable file might be --
31 -- covered by the GNU Public License. --
33 -- GNAT was originally developed by the GNAT team at New York University. --
34 -- Extensive contributions were provided by Ada Core Technologies Inc. --
36 ------------------------------------------------------------------------------
38 -- This version provides ways to limit the amount of used memory for systems
39 -- that do not have OS support for that.
41 -- The amount of available memory available for dynamic allocation is limited
42 -- by setting the environment variable GNAT_MEMORY_LIMIT to the number of
43 -- kilobytes that can be used.
45 -- Windows is currently using this version.
48 with System
.Soft_Links
;
50 package body System
.Memory
is
53 use System
.Soft_Links
;
55 function c_malloc
(Size
: size_t
) return System
.Address
;
56 pragma Import
(C
, c_malloc
, "malloc");
58 procedure c_free
(Ptr
: System
.Address
);
59 pragma Import
(C
, c_free
, "free");
62 (Ptr
: System
.Address
; Size
: size_t
) return System
.Address
;
63 pragma Import
(C
, c_realloc
, "realloc");
65 function msize
(Ptr
: System
.Address
) return size_t
;
66 pragma Import
(C
, msize
, "_msize");
68 function getenv
(Str
: String) return System
.Address
;
69 pragma Import
(C
, getenv
);
71 function atoi
(Str
: System
.Address
) return Integer;
72 pragma Import
(C
, atoi
);
74 Available_Memory
: size_t
:= 0;
75 -- Amount of memory that is available for heap allocations.
76 -- A value of 0 means that the amount is not yet initialized.
78 Msize_Accuracy
: constant := 4096;
79 -- Defines the amount of memory to add to requested allocation sizes,
80 -- because malloc may return a bigger block than requested. As msize
81 -- is used when by Free, it must be used on allocation as well. To
82 -- prevent underflow of available_memory we need to use a reserve.
84 procedure Check_Available_Memory
(Size
: size_t
);
85 -- This routine must be called while holding the task lock. When the
86 -- memory limit is not yet initialized, it will be set to the value of
87 -- the GNAT_MEMORY_LIMIT environment variable or to unlimited if that
88 -- does not exist. If the size is larger than the amount of available
89 -- memory, the task lock will be freed and a storage_error exception
96 function Alloc
(Size
: size_t
) return System
.Address
is
97 Result
: System
.Address
;
98 Actual_Size
: size_t
:= Size
;
101 if Size
= size_t
'Last then
102 Raise_Exception
(Storage_Error
'Identity, "object too large");
105 -- Change size from zero to non-zero. We still want a proper pointer
106 -- for the zero case because pointers to zero length objects have to
107 -- be distinct, but we can't just go ahead and allocate zero bytes,
108 -- since some malloc's return zero for a zero argument.
116 if Actual_Size
+ Msize_Accuracy
>= Available_Memory
then
117 Check_Available_Memory
(Size
+ Msize_Accuracy
);
120 Result
:= c_malloc
(Actual_Size
);
122 if Result
/= System
.Null_Address
then
123 Available_Memory
:= Available_Memory
- msize
(Result
);
128 if Result
= System
.Null_Address
then
129 Raise_Exception
(Storage_Error
'Identity, "heap exhausted");
135 ----------------------------
136 -- Check_Available_Memory --
137 ----------------------------
139 procedure Check_Available_Memory
(Size
: size_t
) is
140 Gnat_Memory_Limit
: System
.Address
;
143 if Available_Memory
= 0 then
145 -- The amount of available memory hasn't been initialized yet
147 Gnat_Memory_Limit
:= getenv
("GNAT_MEMORY_LIMIT" & ASCII
.NUL
);
149 if Gnat_Memory_Limit
/= System
.Null_Address
then
151 size_t
(atoi
(Gnat_Memory_Limit
)) * 1024 + Msize_Accuracy
;
153 Available_Memory
:= size_t
'Last;
157 if Size
>= Available_Memory
then
159 -- There is a memory overflow
163 (Storage_Error
'Identity, "heap memory limit exceeded");
165 end Check_Available_Memory
;
171 procedure Free
(Ptr
: System
.Address
) is
175 if Ptr
/= System
.Null_Address
then
176 Available_Memory
:= Available_Memory
+ msize
(Ptr
);
189 (Ptr
: System
.Address
;
191 return System
.Address
193 Result
: System
.Address
;
194 Actual_Size
: constant size_t
:= Size
;
198 if Size
= size_t
'Last then
199 Raise_Exception
(Storage_Error
'Identity, "object too large");
204 Old_Size
:= msize
(Ptr
);
206 -- Conservative check - no need to try to be precise here
208 if Size
+ Msize_Accuracy
>= Available_Memory
then
209 Check_Available_Memory
(Size
+ Msize_Accuracy
);
212 Result
:= c_realloc
(Ptr
, Actual_Size
);
214 if Result
/= System
.Null_Address
then
215 Available_Memory
:= Available_Memory
+ Old_Size
- msize
(Result
);
220 if Result
= System
.Null_Address
then
221 Raise_Exception
(Storage_Error
'Identity, "heap exhausted");