File : s-parame-xi-small.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- S Y S T E M . P A R A M E T E R S --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2014, 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 -- --
19 -- --
20 -- --
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 a generic bare board version the package, for small targets
33
34 -- This package defines some system dependent parameters for GNAT. These
35 -- are values that are referenced by the runtime library and are therefore
36 -- relevant to the target machine.
37
38 -- The parameters whose value is defined in the spec are not generally
39 -- expected to be changed. If they are changed, it will be necessary to
40 -- recompile the run-time library.
41
42 -- The parameters which are defined by functions can be changed by modifying
43 -- the body of System.Parameters in file s-parame.adb. A change to this body
44 -- requires only rebinding and relinking of the application.
45
46 -- Note: do not introduce any pragma Inline statements into this unit, since
47 -- otherwise the relinking and rebinding capability would be deactivated.
48
49 package System.Parameters is
50 pragma Pure;
51
52 ---------------------------------------
53 -- Task And Stack Allocation Control --
54 ---------------------------------------
55
56 type Task_Storage_Size is new Integer;
57 -- Type used in tasking units for task storage size
58
59 type Size_Type is new Task_Storage_Size;
60 -- Type used to provide task storage size to runtime
61
62 Unspecified_Size : constant Size_Type := Size_Type'First;
63 -- Value used to indicate that no size type is set
64
65 subtype Percentage is Size_Type range -1 .. 100;
66 Dynamic : constant Size_Type := -1;
67 -- The secondary stack ratio is a constant between 0 and 100 which
68 -- determines the percentage of the allocated task stack that is
69 -- used by the secondary stack (the rest being the primary stack).
70 -- The special value of minus one indicates that the secondary
71 -- stack is to be allocated from the heap instead.
72
73 Sec_Stack_Percentage : constant Percentage := 10;
74 -- This constant defines the handling of the secondary stack, see above
75 -- comment, so the 25 here means a 25% amount.
76
77 Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Percentage = Dynamic;
78 -- Convenient Boolean for testing for dynamic secondary stack
79
80 Default_Stack_Size : constant Size_Type := 4 * 1024;
81 -- Default task stack size used if none is specified
82
83 Minimum_Stack_Size : constant Size_Type := 512;
84 -- Minimum task stack size permitted
85
86 function Adjust_Storage_Size (Size : Size_Type) return Size_Type;
87 -- Given the storage size stored in the TCB, return the Storage_Size
88 -- value required by the RM for the Storage_Size attribute. The
89 -- required adjustment is as follows:
90 --
91 -- when Size = Unspecified_Size, return Default_Stack_Size
92 -- otherwise return given Size
93
94 Stack_Grows_Down : constant Boolean := True;
95 -- This constant indicates whether the stack grows up (False) or
96 -- down (True) in memory as functions are called. It is used for
97 -- proper implementation of the stack overflow check.
98
99 ----------------------------------------------
100 -- Characteristics of types in Interfaces.C --
101 ----------------------------------------------
102
103 long_bits : constant := Long_Integer'Size;
104 -- Number of bits in type long and unsigned_long. The normal convention
105 -- is that this is the same as type Long_Integer, but this may not be true
106 -- of all targets.
107
108 ptr_bits : constant := Standard'Address_Size;
109 subtype C_Address is System.Address;
110 -- Number of bits in Interfaces.C pointers, normally a standard address
111
112 C_Malloc_Linkname : constant String := "__gnat_malloc";
113 -- Name of runtime function used to allocate such a pointer
114
115 ----------------------------------------------
116 -- Behavior of Pragma Finalize_Storage_Only --
117 ----------------------------------------------
118
119 -- Garbage_Collected is a Boolean constant whose value indicates the
120 -- effect of the pragma Finalize_Storage_Entry on a controlled type.
121
122 -- Garbage_Collected = False
123
124 -- The system releases all storage on program termination only,
125 -- but not other garbage collection occurs, so finalization calls
126 -- are ommitted only for outer level onjects can be omitted if
127 -- pragma Finalize_Storage_Only is used.
128
129 -- Garbage_Collected = True
130
131 -- The system provides full garbage collection, so it is never
132 -- necessary to release storage for controlled objects for which
133 -- a pragma Finalize_Storage_Only is used.
134
135 Garbage_Collected : constant Boolean := False;
136 -- The storage mode for this system (release on program exit)
137
138 ---------------------
139 -- Tasking Profile --
140 ---------------------
141
142 -- In the following sections, constant parameters are defined to
143 -- allow some optimizations and fine tuning within the tasking run time
144 -- based on restrictions on the tasking features.
145
146 ----------------------
147 -- Locking Strategy --
148 ----------------------
149
150 Single_Lock : constant Boolean := True;
151 -- Indicates whether a single lock should be used within the tasking
152 -- run-time to protect internal structures. If True, a single lock
153 -- will be used, meaning less locking/unlocking operations, but also
154 -- more global contention. In general, Single_Lock should be set to
155 -- True on single processor machines, and to False to multi-processor
156 -- systems, but this can vary from application to application and also
157 -- depends on the scheduling policy.
158
159 -------------------
160 -- Task Abortion --
161 -------------------
162
163 No_Abort : constant Boolean := True;
164 -- This constant indicates whether abort statements and asynchronous
165 -- transfer of control (ATC) are disallowed. If set to True, it is
166 -- assumed that neither construct is used, and the run time does not
167 -- need to defer/undefer abort and check for pending actions at
168 -- completion points. A value of True for No_Abort corresponds to:
169 -- pragma Restrictions (No_Abort_Statements);
170 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
171
172 ---------------------
173 -- Task Attributes --
174 ---------------------
175
176 Max_Attribute_Count : constant := 0;
177 -- Number of task attributes stored in the task control block
178
179 --------------------
180 -- Runtime Traces --
181 --------------------
182
183 Runtime_Traces : constant Boolean := False;
184 -- This constant indicates whether the runtime outputs traces to a
185 -- predefined output or not (True means that traces are output).
186 -- See System.Traces for more details.
187
188 -----------------------
189 -- Task Image Length --
190 -----------------------
191
192 Max_Task_Image_Length : constant := 32;
193 -- This constant specifies the maximum length of a task's image
194
195 ------------------------------
196 -- Exception Message Length --
197 ------------------------------
198
199 Default_Exception_Msg_Max_Length : constant := 200;
200 -- This constant specifies the default number of characters to allow
201 -- in an exception message (200 is minimum required by RM 11.4.1(18)).
202
203 end System.Parameters;