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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- S Y S T E M . P A R A M E T E R S --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 1992-2017, Free Software Foundation, Inc. --
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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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- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- Version is used by VxWorks 653, VxWorks MILS, and VxWorks6 cert Ravenscar
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33
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34 -- This package defines some system dependent parameters for GNAT. These
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35 -- are values that are referenced by the runtime library and are therefore
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36 -- relevant to the target machine.
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37
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38 -- The parameters whose value is defined in the spec are not generally
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39 -- expected to be changed. If they are changed, it will be necessary to
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40 -- recompile the run-time library.
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41
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42 -- The parameters which are defined by functions can be changed by modifying
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43 -- the body of System.Parameters in file s-parame.adb. A change to this body
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44 -- requires only rebinding and relinking of the application.
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45
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46 -- Note: do not introduce any pragma Inline statements into this unit, since
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47 -- otherwise the relinking and rebinding capability would be deactivated.
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48
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49 package System.Parameters is
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50 pragma Pure;
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51
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52 ---------------------------------------
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53 -- Task And Stack Allocation Control --
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54 ---------------------------------------
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55
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56 type Task_Storage_Size is new Integer;
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57 -- Type used in tasking units for task storage size
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58
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59 type Size_Type is new Task_Storage_Size;
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60 -- Type used to provide task storage size to runtime
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61
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62 Unspecified_Size : constant Size_Type := Size_Type'First;
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63 -- Value used to indicate that no size type is set
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64
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65 function Default_Stack_Size return Size_Type;
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66 -- Default task stack size used if none is specified
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67
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68 function Minimum_Stack_Size return Size_Type;
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69 -- Minimum task stack size permitted
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70
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71 function Adjust_Storage_Size (Size : Size_Type) return Size_Type;
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72 -- Given the storage size stored in the TCB, return the Storage_Size
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73 -- value required by the RM for the Storage_Size attribute. The
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74 -- required adjustment is as follows:
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75 --
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76 -- when Size = Unspecified_Size, return Default_Stack_Size
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77 -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size
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78 -- otherwise return given Size
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79
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80 Default_Env_Stack_Size : constant Size_Type := 14_336;
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81 -- Assumed size of the environment task, if no other information
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82 -- is available. This value is used when stack checking is
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83 -- enabled and no GNAT_STACK_LIMIT environment variable is set.
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84 -- This value is chosen as the VxWorks default stack size is 20kB,
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85 -- and a little more than 4kB is necessary for the run time.
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86
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87 Stack_Grows_Down : constant Boolean := True;
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88 -- This constant indicates whether the stack grows up (False) or
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89 -- down (True) in memory as functions are called. It is used for
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90 -- proper implementation of the stack overflow check.
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91
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92 Runtime_Default_Sec_Stack_Size : constant Size_Type := 10 * 1024;
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93 -- The run-time chosen default size for secondary stacks that may be
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94 -- overriden by the user with the use of binder -D switch.
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95
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96 function Default_Sec_Stack_Size return Size_Type;
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97 -- The default size for secondary stacks that reflects any user specified
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98 -- default via the binder -D switch.
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99
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100 Sec_Stack_Dynamic : constant Boolean := False;
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101 -- Indicates if secondary stacks can grow and shrink at run-time. If False,
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102 -- the size of a secondary stack is fixed at the point of its creation.
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103
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104 ----------------------------------------------
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105 -- Characteristics of types in Interfaces.C --
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106 ----------------------------------------------
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107
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108 long_bits : constant := Long_Integer'Size;
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109 -- Number of bits in type long and unsigned_long. The normal convention
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110 -- is that this is the same as type Long_Integer, but this may not be true
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111 -- of all targets.
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112
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113 ptr_bits : constant := Standard'Address_Size;
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114 subtype C_Address is System.Address;
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115 -- Number of bits in Interfaces.C pointers, normally a standard address
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116
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117 C_Malloc_Linkname : constant String := "__gnat_malloc";
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118 -- Name of runtime function used to allocate such a pointer
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119
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120 ----------------------------------------------
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121 -- Behavior of Pragma Finalize_Storage_Only --
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122 ----------------------------------------------
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123
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124 -- Garbage_Collected is a Boolean constant whose value indicates the
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125 -- effect of the pragma Finalize_Storage_Entry on a controlled type.
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126
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127 -- Garbage_Collected = False
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128
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129 -- The system releases all storage on program termination only,
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130 -- but not other garbage collection occurs, so finalization calls
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131 -- are omitted only for outer level objects can be omitted if
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132 -- pragma Finalize_Storage_Only is used.
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133
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134 -- Garbage_Collected = True
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135
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136 -- The system provides full garbage collection, so it is never
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137 -- necessary to release storage for controlled objects for which
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138 -- a pragma Finalize_Storage_Only is used.
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139
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140 Garbage_Collected : constant Boolean := False;
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141 -- The storage mode for this system (release on program exit)
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142
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143 ---------------------
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144 -- Tasking Profile --
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145 ---------------------
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146
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147 -- In the following sections, constant parameters are defined to
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148 -- allow some optimizations and fine tuning within the tasking run time
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149 -- based on restrictions on the tasking features.
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150
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151 ----------------------
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152 -- Locking Strategy --
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153 ----------------------
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154
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155 Single_Lock : constant Boolean := False;
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156 -- Indicates whether a single lock should be used within the tasking
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157 -- run-time to protect internal structures. If True, a single lock
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158 -- will be used, meaning less locking/unlocking operations, but also
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159 -- more global contention. In general, Single_Lock should be set to
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160 -- True on single processor machines, and to False to multi-processor
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161 -- systems, but this can vary from application to application and also
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162 -- depends on the scheduling policy.
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163
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164 -------------------
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165 -- Task Abortion --
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166 -------------------
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167
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168 No_Abort : constant Boolean := False;
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169 -- This constant indicates whether abort statements and asynchronous
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170 -- transfer of control (ATC) are disallowed. If set to True, it is
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171 -- assumed that neither construct is used, and the run time does not
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172 -- need to defer/undefer abort and check for pending actions at
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173 -- completion points. A value of True for No_Abort corresponds to:
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174 -- pragma Restrictions (No_Abort_Statements);
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175 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
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176
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177 ---------------------
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178 -- Task Attributes --
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179 ---------------------
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180
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181 Max_Attribute_Count : constant := 8;
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182 -- Number of task attributes stored in the task control block
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183
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184 -----------------------
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185 -- Task Image Length --
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186 -----------------------
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187
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188 Max_Task_Image_Length : constant := 32;
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189 -- This constant specifies the maximum length of a task's image
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190
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191 ------------------------------
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192 -- Exception Message Length --
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193 ------------------------------
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194
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195 Default_Exception_Msg_Max_Length : constant := 200;
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196 -- This constant specifies the default number of characters to allow
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197 -- in an exception message (200 is minimum required by RM 11.4.1(18)).
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198
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199 end System.Parameters;
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