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) 2001-2018, 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 3,  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.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This is the default implementation of this package
33
34--  This implementation assumes that the underlying malloc/free/realloc
35--  implementation is thread safe, and thus, no additional lock is required.
36--  Note that we still need to defer abort because on most systems, an
37--  asynchronous signal (as used for implementing asynchronous abort of
38--  task) cannot safely be handled while malloc is executing.
39
40--  If you are not using Ada constructs containing the "abort" keyword, then
41--  you can remove the calls to Abort_Defer.all and Abort_Undefer.all from
42--  this unit.
43
44pragma Compiler_Unit_Warning;
45
46with System.CRTL;
47with System.Parameters;
48with System.Soft_Links;
49
50package body System.Memory is
51
52   use System.Soft_Links;
53
54   function c_malloc (Size : System.CRTL.size_t) return System.Address
55     renames System.CRTL.malloc;
56
57   procedure c_free (Ptr : System.Address)
58     renames System.CRTL.free;
59
60   function c_realloc
61     (Ptr : System.Address; Size : System.CRTL.size_t) return System.Address
62     renames System.CRTL.realloc;
63
64   -----------
65   -- Alloc --
66   -----------
67
68   function Alloc (Size : size_t) return System.Address is
69      Result : System.Address;
70   begin
71      --  A previous version moved the check for size_t'Last below, into the
72      --  "if Result = System.Null_Address...". So malloc(size_t'Last) should
73      --  return Null_Address, and then we can check for that special value.
74      --  However, that doesn't work on VxWorks, because malloc(size_t'Last)
75      --  prints an unwanted warning message before returning Null_Address.
76      --  Note that the branch is correctly predicted on modern hardware, so
77      --  there is negligible overhead.
78
79      if Size = size_t'Last then
80         raise Storage_Error with "object too large";
81      end if;
82
83      if Parameters.No_Abort then
84         Result := c_malloc (System.CRTL.size_t (Size));
85      else
86         Abort_Defer.all;
87         Result := c_malloc (System.CRTL.size_t (Size));
88         Abort_Undefer.all;
89      end if;
90
91      if Result = System.Null_Address then
92
93         --  If Size = 0, we can't allocate 0 bytes, because then two different
94         --  allocators, one of which has Size = 0, could return pointers that
95         --  compare equal, which is wrong. (Nonnull pointers compare equal if
96         --  and only if they designate the same object, and two different
97         --  allocators allocate two different objects).
98
99         --  malloc(0) is defined to allocate a non-zero-sized object (in which
100         --  case we won't get here, and all is well) or NULL, in which case we
101         --  get here. We also get here in case of error. So check for the
102         --  zero-size case, and allocate 1 byte. Otherwise, raise
103         --  Storage_Error.
104
105         --  We check for zero size here, rather than at the start, for
106         --  efficiency.
107
108         if Size = 0 then
109            return Alloc (1);
110         end if;
111
112         raise Storage_Error with "heap exhausted";
113      end if;
114
115      return Result;
116   end Alloc;
117
118   ----------
119   -- Free --
120   ----------
121
122   procedure Free (Ptr : System.Address) is
123   begin
124      if Parameters.No_Abort then
125         c_free (Ptr);
126      else
127         Abort_Defer.all;
128         c_free (Ptr);
129         Abort_Undefer.all;
130      end if;
131   end Free;
132
133   -------------
134   -- Realloc --
135   -------------
136
137   function Realloc
138     (Ptr  : System.Address;
139      Size : size_t)
140      return System.Address
141   is
142      Result      : System.Address;
143   begin
144      if Size = size_t'Last then
145         raise Storage_Error with "object too large";
146      end if;
147
148      if Parameters.No_Abort then
149         Result := c_realloc (Ptr, System.CRTL.size_t (Size));
150      else
151         Abort_Defer.all;
152         Result := c_realloc (Ptr, System.CRTL.size_t (Size));
153         Abort_Undefer.all;
154      end if;
155
156      if Result = System.Null_Address then
157         raise Storage_Error with "heap exhausted";
158      end if;
159
160      return Result;
161   end Realloc;
162
163end System.Memory;
164