1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . P A R A M E T E R S --
9 -- Copyright (C) 1992-2017, Free Software Foundation, Inc. --
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. --
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. --
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/>. --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
30 ------------------------------------------------------------------------------
32 -- Version is used by VxWorks 653, VxWorks MILS, and VxWorks6 cert Ravenscar
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.
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.
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.
46 -- Note: do not introduce any pragma Inline statements into this unit, since
47 -- otherwise the relinking and rebinding capability would be deactivated.
49 package System
.Parameters
is
52 ---------------------------------------
53 -- Task And Stack Allocation Control --
54 ---------------------------------------
56 type Task_Storage_Size
is new Integer;
57 -- Type used in tasking units for task storage size
59 type Size_Type
is new Task_Storage_Size
;
60 -- Type used to provide task storage size to runtime
62 Unspecified_Size
: constant Size_Type
:= Size_Type
'First;
63 -- Value used to indicate that no size type is set
65 function Default_Stack_Size
return Size_Type
;
66 -- Default task stack size used if none is specified
68 function Minimum_Stack_Size
return Size_Type
;
69 -- Minimum task stack size permitted
71 function Adjust_Storage_Size
(Size
: Size_Type
) return Size_Type
;
72 -- Given the storage size stored in the TCB, return the Storage_Size
73 -- value required by the RM for the Storage_Size attribute. The
74 -- required adjustment is as follows:
76 -- when Size = Unspecified_Size, return Default_Stack_Size
77 -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size
78 -- otherwise return given Size
80 Default_Env_Stack_Size
: constant Size_Type
:= 14_336
;
81 -- Assumed size of the environment task, if no other information
82 -- is available. This value is used when stack checking is
83 -- enabled and no GNAT_STACK_LIMIT environment variable is set.
84 -- This value is chosen as the VxWorks default stack size is 20kB,
85 -- and a little more than 4kB is necessary for the run time.
87 Stack_Grows_Down
: constant Boolean := True;
88 -- This constant indicates whether the stack grows up (False) or
89 -- down (True) in memory as functions are called. It is used for
90 -- proper implementation of the stack overflow check.
92 Runtime_Default_Sec_Stack_Size
: constant Size_Type
:= 10 * 1024;
93 -- The run-time chosen default size for secondary stacks that may be
94 -- overriden by the user with the use of binder -D switch.
96 function Default_Sec_Stack_Size
return Size_Type
;
97 -- The default size for secondary stacks that reflects any user specified
98 -- default via the binder -D switch.
100 Sec_Stack_Dynamic
: constant Boolean := False;
101 -- Indicates if secondary stacks can grow and shrink at run-time. If False,
102 -- the size of a secondary stack is fixed at the point of its creation.
104 ----------------------------------------------
105 -- Characteristics of types in Interfaces.C --
106 ----------------------------------------------
108 long_bits
: constant := Long_Integer'Size;
109 -- Number of bits in type long and unsigned_long. The normal convention
110 -- is that this is the same as type Long_Integer, but this may not be true
113 ptr_bits
: constant := Standard
'Address_Size;
114 subtype C_Address
is System
.Address
;
115 -- Number of bits in Interfaces.C pointers, normally a standard address
117 C_Malloc_Linkname
: constant String := "__gnat_malloc";
118 -- Name of runtime function used to allocate such a pointer
120 ----------------------------------------------
121 -- Behavior of Pragma Finalize_Storage_Only --
122 ----------------------------------------------
124 -- Garbage_Collected is a Boolean constant whose value indicates the
125 -- effect of the pragma Finalize_Storage_Entry on a controlled type.
127 -- Garbage_Collected = False
129 -- The system releases all storage on program termination only,
130 -- but not other garbage collection occurs, so finalization calls
131 -- are omitted only for outer level objects can be omitted if
132 -- pragma Finalize_Storage_Only is used.
134 -- Garbage_Collected = True
136 -- The system provides full garbage collection, so it is never
137 -- necessary to release storage for controlled objects for which
138 -- a pragma Finalize_Storage_Only is used.
140 Garbage_Collected
: constant Boolean := False;
141 -- The storage mode for this system (release on program exit)
143 ---------------------
144 -- Tasking Profile --
145 ---------------------
147 -- In the following sections, constant parameters are defined to
148 -- allow some optimizations and fine tuning within the tasking run time
149 -- based on restrictions on the tasking features.
151 ----------------------
152 -- Locking Strategy --
153 ----------------------
155 Single_Lock
: constant Boolean := False;
156 -- Indicates whether a single lock should be used within the tasking
157 -- run-time to protect internal structures. If True, a single lock
158 -- will be used, meaning less locking/unlocking operations, but also
159 -- more global contention. In general, Single_Lock should be set to
160 -- True on single processor machines, and to False to multi-processor
161 -- systems, but this can vary from application to application and also
162 -- depends on the scheduling policy.
168 No_Abort
: constant Boolean := False;
169 -- This constant indicates whether abort statements and asynchronous
170 -- transfer of control (ATC) are disallowed. If set to True, it is
171 -- assumed that neither construct is used, and the run time does not
172 -- need to defer/undefer abort and check for pending actions at
173 -- completion points. A value of True for No_Abort corresponds to:
174 -- pragma Restrictions (No_Abort_Statements);
175 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
177 ---------------------
178 -- Task Attributes --
179 ---------------------
181 Max_Attribute_Count
: constant := 8;
182 -- Number of task attributes stored in the task control block
184 -----------------------
185 -- Task Image Length --
186 -----------------------
188 Max_Task_Image_Length
: constant := 32;
189 -- This constant specifies the maximum length of a task's image
191 ------------------------------
192 -- Exception Message Length --
193 ------------------------------
195 Default_Exception_Msg_Max_Length
: constant := 200;
196 -- This constant specifies the default number of characters to allow
197 -- in an exception message (200 is minimum required by RM 11.4.1(18)).
199 end System
.Parameters
;