projects / thirdparty / gcc.git / blame
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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 | -- -- | |
| fbf5a39b | 9 | -- Copyright (C) 1992-2003 Free Software Foundation, Inc. -- |
| cacbc350 RK |
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 2, 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. See the GNU General Public License -- | |
| 17 | -- for more details. You should have received a copy of the GNU General -- | |
| 18 | -- Public License distributed with GNAT; see file COPYING. If not, write -- | |
| 19 | -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- | |
| 20 | -- MA 02111-1307, USA. -- | |
| 21 | -- -- | |
| 22 | -- As a special exception, if other files instantiate generics from this -- | |
| 23 | -- unit, or you link this unit with other files to produce an executable, -- | |
| 24 | -- this unit does not by itself cause the resulting executable to be -- | |
| 25 | -- covered by the GNU General Public License. This exception does not -- | |
| 26 | -- however invalidate any other reasons why the executable file might be -- | |
| 27 | -- covered by the GNU Public License. -- | |
| 28 | -- -- | |
| 29 | -- GNAT was originally developed by the GNAT team at New York University. -- | |
| 71ff80dc | 30 | -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| cacbc350 RK |
31 | -- -- |
| 32 | ------------------------------------------------------------------------------ | |
| 33 | ||
| 34 | -- This is the default version used for all systems for which no special | |
| 35 | -- target-specific version of this package is provided. | |
| 36 | ||
| 37 | -- This package defines some system dependent parameters for GNAT. These | |
| 38 | -- are values that are referenced by the runtime library and are therefore | |
| 39 | -- relevant to the target machine. | |
| 40 | ||
| 41 | -- The parameters whose value is defined in the spec are not generally | |
| 42 | -- expected to be changed. If they are changed, it will be necessary to | |
| 43 | -- recompile the run-time library. | |
| 44 | ||
| 45 | -- The parameters which are defined by functions can be changed by modifying | |
| 46 | -- the body of System.Parameters in file s-parame.adb. A change to this body | |
| 47 | -- requires only rebinding and relinking of the application. | |
| 48 | ||
| 49 | -- Note: do not introduce any pragma Inline statements into this unit, since | |
| 50 | -- otherwise the relinking and rebinding capability would be deactivated. | |
| 51 | ||
| 52 | package System.Parameters is | |
| 53 | pragma Pure (Parameters); | |
| 54 | ||
| 55 | --------------------------------------- | |
| 56 | -- Task And Stack Allocation Control -- | |
| 57 | --------------------------------------- | |
| 58 | ||
| 59 | type Task_Storage_Size is new Integer; | |
| 60 | -- Type used in tasking units for task storage size | |
| 61 | ||
| 62 | type Size_Type is new Task_Storage_Size; | |
| 63 | -- Type used to provide task storage size to runtime | |
| 64 | ||
| 65 | Unspecified_Size : constant Size_Type := Size_Type'First; | |
| 66 | -- Value used to indicate that no size type is set | |
| 67 | ||
| 68 | subtype Ratio is Size_Type range -1 .. 100; | |
| 69 | Dynamic : constant Size_Type := -1; | |
| 70 | -- The secondary stack ratio is a constant between 0 and 100 which | |
| 71 | -- determines the percentage of the allocated task stack that is | |
| 72 | -- used by the secondary stack (the rest being the primary stack). | |
| 73 | -- The special value of minus one indicates that the secondary | |
| 74 | -- stack is to be allocated from the heap instead. | |
| 75 | ||
| 76 | Sec_Stack_Ratio : constant Ratio := Dynamic; | |
| 77 | -- This constant defines the handling of the secondary stack | |
| 78 | ||
| 79 | Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Ratio = Dynamic; | |
| 80 | -- Convenient Boolean for testing for dynamic secondary stack | |
| 81 | ||
| 82 | function Default_Stack_Size return Size_Type; | |
| 83 | -- Default task stack size used if none is specified | |
| 84 | ||
| 85 | function Minimum_Stack_Size return Size_Type; | |
| 86 | -- Minimum task stack size permitted | |
| 87 | ||
| 88 | function Adjust_Storage_Size (Size : Size_Type) return Size_Type; | |
| 89 | -- Given the storage size stored in the TCB, return the Storage_Size | |
| 90 | -- value required by the RM for the Storage_Size attribute. The | |
| 91 | -- required adjustment is as follows: | |
| 92 | -- | |
| 93 | -- when Size = Unspecified_Size, return Default_Stack_Size | |
| 94 | -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size | |
| 95 | -- otherwise return given Size | |
| 96 | ||
| fbf5a39b AC |
97 | Default_Env_Stack_Size : constant Size_Type := 8_192_000; |
| 98 | -- Assumed size of the environment task, if no other information | |
| 99 | -- is available. This value is used when stack checking is | |
| 100 | -- enabled and no GNAT_STACK_LIMIT environment variable is set. | |
| 101 | ||
| cacbc350 RK |
102 | Stack_Grows_Down : constant Boolean := True; |
| 103 | -- This constant indicates whether the stack grows up (False) or | |
| 104 | -- down (True) in memory as functions are called. It is used for | |
| 105 | -- proper implementation of the stack overflow check. | |
| 106 | ||
| 107 | ---------------------------------------------- | |
| 108 | -- Characteristics of types in Interfaces.C -- | |
| 109 | ---------------------------------------------- | |
| 110 | ||
| 111 | long_bits : constant := Long_Integer'Size; | |
| 112 | -- Number of bits in type long and unsigned_long. The normal convention | |
| 113 | -- is that this is the same as type Long_Integer, but this is not true | |
| 114 | -- of all targets. For example, in OpenVMS long /= Long_Integer. | |
| 115 | ||
| 116 | ---------------------------------------------- | |
| 117 | -- Behavior of Pragma Finalize_Storage_Only -- | |
| 118 | ---------------------------------------------- | |
| 119 | ||
| 120 | -- Garbage_Collected is a Boolean constant whose value indicates the | |
| 121 | -- effect of the pragma Finalize_Storage_Entry on a controlled type. | |
| 122 | ||
| 123 | -- Garbage_Collected = False | |
| 124 | ||
| 125 | -- The system releases all storage on program termination only, | |
| 126 | -- but not other garbage collection occurs, so finalization calls | |
| 127 | -- are ommitted only for outer level onjects can be omitted if | |
| 128 | -- pragma Finalize_Storage_Only is used. | |
| 129 | ||
| 130 | -- Garbage_Collected = True | |
| 131 | ||
| 132 | -- The system provides full garbage collection, so it is never | |
| 133 | -- necessary to release storage for controlled objects for which | |
| 134 | -- a pragma Finalize_Storage_Only is used. | |
| 135 | ||
| 136 | Garbage_Collected : constant Boolean := False; | |
| 137 | -- The storage mode for this system (release on program exit) | |
| 138 | ||
| 07fc65c4 GB |
139 | --------------------- |
| 140 | -- Tasking Profile -- | |
| 141 | --------------------- | |
| 142 | ||
| 143 | -- In the following sections, constant parameters are defined to | |
| fbf5a39b AC |
144 | -- allow some optimizations and fine tuning within the tasking run time |
| 145 | -- based on restrictions on the tasking features. | |
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146 | |
| 147 | ---------------------- | |
| 148 | -- Locking Strategy -- | |
| 149 | ---------------------- | |
| 150 | ||
| 151 | Single_Lock : constant Boolean := False; | |
| 152 | -- Indicates whether a single lock should be used within the tasking | |
| 153 | -- run-time to protect internal structures. If True, a single lock | |
| 154 | -- will be used, meaning less locking/unlocking operations, but also | |
| 155 | -- more global contention. In general, Single_Lock should be set to | |
| 156 | -- True on single processor machines, and to False to multi-processor | |
| 157 | -- systems, but this can vary from application to application and also | |
| 158 | -- depends on the scheduling policy. | |
| 159 | ||
| 160 | ------------------- | |
| 161 | -- Task Abortion -- | |
| 162 | ------------------- | |
| 163 | ||
| 164 | No_Abort : constant Boolean := False; | |
| 165 | -- This constant indicates whether abort statements and asynchronous | |
| 166 | -- transfer of control (ATC) are disallowed. If set to True, it is | |
| 167 | -- assumed that neither construct is used, and the run time does not | |
| 168 | -- need to defer/undefer abort and check for pending actions at | |
| 169 | -- completion points. A value of True for No_Abort corresponds to: | |
| 170 | -- pragma Restrictions (No_Abort_Statements); | |
| 171 | -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); | |
| 172 | ||
| 173 | ---------------------- | |
| 174 | -- Dynamic Priority -- | |
| 175 | ---------------------- | |
| 176 | ||
| 177 | Dynamic_Priority_Support : constant Boolean := True; | |
| 178 | -- This constant indicates whether dynamic changes of task priorities | |
| 179 | -- are allowed (True means normal RM mode in which such changes are | |
| 180 | -- allowed). In particular, if this is False, then we do not need to | |
| 181 | -- poll for pending base priority changes at every abort completion | |
| 182 | -- point. A value of False for Dynamic_Priority_Support corresponds | |
| 183 | -- to pragma Restrictions (No_Dynamic_Priorities); | |
| 184 | ||
| fbf5a39b AC |
185 | --------------------- |
| 186 | -- Task Attributes -- | |
| 187 | --------------------- | |
| 188 | ||
| 189 | Default_Attribute_Count : constant := 4; | |
| 190 | -- Number of pre-allocated Address-sized task attributes stored in the | |
| 191 | -- task control block. | |
| 192 | ||
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193 | -------------------- |
| 194 | -- Runtime Traces -- | |
| 195 | -------------------- | |
| 196 | ||
| 197 | Runtime_Traces : constant Boolean := False; | |
| 198 | -- This constant indicates whether the runtime outputs traces to a | |
| 199 | -- predefined output or not (True means that traces are output). | |
| 200 | -- See System.Traces for more details. | |
| 201 | ||
| cacbc350 | 202 | end System.Parameters; |