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 | -- -- | |
| 8071b771 | 9 | -- Copyright (C) 1992-2014, Free Software Foundation, Inc. -- |
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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- -- | |
| 748086b7 | 13 | -- ware Foundation; either version 3, or (at your option) any later ver- -- |
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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 -- | |
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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/>. -- | |
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26 | -- -- |
| 27 | -- GNAT was originally developed by the GNAT team at New York University. -- | |
| 71ff80dc | 28 | -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
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29 | -- -- |
| 30 | ------------------------------------------------------------------------------ | |
| 31 | ||
| 261ce0eb | 32 | -- This is the OpenVMS Alpha version |
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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 | |
| 009186e0 | 50 | pragma Pure; |
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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 | ||
| da94696d | 65 | subtype Percentage is Size_Type range -1 .. 100; |
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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 | ||
| da94696d | 73 | Sec_Stack_Percentage : constant Percentage := Dynamic; |
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74 | -- This constant defines the handling of the secondary stack |
| 75 | ||
| da94696d | 76 | Sec_Stack_Dynamic : constant Boolean := Sec_Stack_Percentage = Dynamic; |
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77 | -- Convenient Boolean for testing for dynamic secondary stack |
| 78 | ||
| 79 | function Default_Stack_Size return Size_Type; | |
| 80 | -- Default task stack size used if none is specified | |
| 81 | ||
| 82 | function Minimum_Stack_Size return Size_Type; | |
| 83 | -- Minimum task stack size permitted | |
| 84 | ||
| 85 | function Adjust_Storage_Size (Size : Size_Type) return Size_Type; | |
| 86 | -- Given the storage size stored in the TCB, return the Storage_Size | |
| 87 | -- value required by the RM for the Storage_Size attribute. The | |
| 88 | -- required adjustment is as follows: | |
| 89 | -- | |
| 90 | -- when Size = Unspecified_Size, return Default_Stack_Size | |
| 91 | -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size | |
| 92 | -- otherwise return given Size | |
| 93 | ||
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94 | Default_Env_Stack_Size : constant Size_Type := 8_192_000; |
| 95 | -- Assumed size of the environment task, if no other information | |
| 96 | -- is available. This value is used when stack checking is | |
| 97 | -- enabled and no GNAT_STACK_LIMIT environment variable is set. | |
| 98 | ||
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99 | Stack_Grows_Down : constant Boolean := True; |
| 100 | -- This constant indicates whether the stack grows up (False) or | |
| 101 | -- down (True) in memory as functions are called. It is used for | |
| 102 | -- proper implementation of the stack overflow check. | |
| 103 | ||
| 104 | ---------------------------------------------- | |
| 105 | -- Characteristics of types in Interfaces.C -- | |
| 106 | ---------------------------------------------- | |
| 107 | ||
| 108 | long_bits : constant := 32; | |
| 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 is not true | |
| 111 | -- of all targets. For example, in OpenVMS long /= Long_Integer. | |
| 112 | ||
| d8b3ccb9 | 113 | ptr_bits : constant := 32; |
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114 | subtype C_Address is System.Address |
| 115 | range -2 ** (ptr_bits - 1) .. 2 ** (ptr_bits - 1) - 1; | |
| 116 | for C_Address'Object_Size use ptr_bits; | |
| 117 | -- Number of bits in Interfaces.C pointers, normally a standard address, | |
| d8b3ccb9 | 118 | -- except on 64-bit VMS where they are 32-bit addresses, for compatibility |
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119 | -- with legacy code. System.Aux_DEC.Short_Address can't be used because of |
| 120 | -- elaboration circularity. | |
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121 | |
| 122 | C_Malloc_Linkname : constant String := "__gnat_malloc32"; | |
| 123 | -- Name of runtime function used to allocate such a pointer | |
| 124 | ||
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125 | ---------------------------------------------- |
| 126 | -- Behavior of Pragma Finalize_Storage_Only -- | |
| 127 | ---------------------------------------------- | |
| 128 | ||
| 129 | -- Garbage_Collected is a Boolean constant whose value indicates the | |
| 130 | -- effect of the pragma Finalize_Storage_Entry on a controlled type. | |
| 131 | ||
| 132 | -- Garbage_Collected = False | |
| 133 | ||
| 134 | -- The system releases all storage on program termination only, | |
| 135 | -- but not other garbage collection occurs, so finalization calls | |
| 276e95ca | 136 | -- are omitted only for outer level objects can be omitted if |
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137 | -- pragma Finalize_Storage_Only is used. |
| 138 | ||
| 139 | -- Garbage_Collected = True | |
| 140 | ||
| 141 | -- The system provides full garbage collection, so it is never | |
| 142 | -- necessary to release storage for controlled objects for which | |
| 143 | -- a pragma Finalize_Storage_Only is used. | |
| 144 | ||
| 145 | Garbage_Collected : constant Boolean := False; | |
| 146 | -- The storage mode for this system (release on program exit) | |
| 147 | ||
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148 | --------------------- |
| 149 | -- Tasking Profile -- | |
| 150 | --------------------- | |
| 151 | ||
| 152 | -- In the following sections, constant parameters are defined to | |
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153 | -- allow some optimizations and fine tuning within the tasking run time |
| 154 | -- based on restrictions on the tasking features. | |
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155 | |
| 156 | ---------------------- | |
| 157 | -- Locking Strategy -- | |
| 158 | ---------------------- | |
| 159 | ||
| 160 | Single_Lock : constant Boolean := True; | |
| 161 | -- Indicates whether a single lock should be used within the tasking | |
| 162 | -- run-time to protect internal structures. If True, a single lock | |
| 163 | -- will be used, meaning less locking/unlocking operations, but also | |
| 164 | -- more global contention. In general, Single_Lock should be set to | |
| 165 | -- True on single processor machines, and to False to multi-processor | |
| 166 | -- systems, but this can vary from application to application and also | |
| 167 | -- depends on the scheduling policy. | |
| 168 | ||
| 169 | ------------------- | |
| 170 | -- Task Abortion -- | |
| 171 | ------------------- | |
| 172 | ||
| 173 | No_Abort : constant Boolean := False; | |
| 174 | -- This constant indicates whether abort statements and asynchronous | |
| 175 | -- transfer of control (ATC) are disallowed. If set to True, it is | |
| 176 | -- assumed that neither construct is used, and the run time does not | |
| 177 | -- need to defer/undefer abort and check for pending actions at | |
| 178 | -- completion points. A value of True for No_Abort corresponds to: | |
| 179 | -- pragma Restrictions (No_Abort_Statements); | |
| 180 | -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); | |
| 181 | ||
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182 | --------------------- |
| 183 | -- Task Attributes -- | |
| 184 | --------------------- | |
| 185 | ||
| 8071b771 | 186 | Max_Attribute_Count : constant := 32; |
| 3aac5551 | 187 | -- Number of task attributes stored in the task control block |
| fbf5a39b | 188 | |
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189 | -------------------- |
| 190 | -- Runtime Traces -- | |
| 191 | -------------------- | |
| 192 | ||
| 193 | Runtime_Traces : constant Boolean := False; | |
| 194 | -- This constant indicates whether the runtime outputs traces to a | |
| 195 | -- predefined output or not (True means that traces are output). | |
| 196 | -- See System.Traces for more details. | |
| 197 | ||
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198 | ----------------------- |
| 199 | -- Task Image Length -- | |
| 200 | ----------------------- | |
| 201 | ||
| 202 | Max_Task_Image_Length : constant := 256; | |
| b11e8d6f | 203 | -- This constant specifies the maximum length of a task's image |
| dae22b53 | 204 | |
| df0db19f DR |
205 | ------------------------------ |
| 206 | -- Exception Message Length -- | |
| 207 | ------------------------------ | |
| 208 | ||
| 209 | Default_Exception_Msg_Max_Length : constant := 512; | |
| 210 | -- This constant specifies the maximum number of characters to allow in an | |
| 211 | -- exception message (see RM 11.4.1(18)). The value for VMS exceeds the | |
| 212 | -- default minimum of 200 to allow for the length of chained VMS condition | |
| 213 | -- handling messages. | |
| 214 | ||
| 84481f76 | 215 | end System.Parameters; |