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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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131
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9 -- Copyright (C) 1992-2018, Free Software Foundation, Inc. --
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111
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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 -- This is the default VxWorks version of the package
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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 Size_Type is range
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57 -(2 ** (Integer'(Standard'Address_Size) - 1)) ..
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58 +(2 ** (Integer'(Standard'Address_Size) - 1)) - 1;
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59 -- Type used to provide task stack sizes to the runtime. Sized to permit
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60 -- stack sizes of up to half the total addressable memory space. This may
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61 -- seem excessively large (even for 32-bit systems), however there are many
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62 -- instances of users requiring large stack sizes (for example string
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63 -- processing).
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64
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65 Unspecified_Size : constant Size_Type := Size_Type'First;
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66 -- Value used to indicate that no size type is set
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67
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68 function Default_Stack_Size return Size_Type;
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69 -- Default task stack size used if none is specified
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70
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71 function Minimum_Stack_Size return Size_Type;
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72 -- Minimum task stack size permitted
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73
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74 function Adjust_Storage_Size (Size : Size_Type) return Size_Type;
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75 -- Given the storage size stored in the TCB, return the Storage_Size
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76 -- value required by the RM for the Storage_Size attribute. The
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77 -- required adjustment is as follows:
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78 --
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79 -- when Size = Unspecified_Size, return Default_Stack_Size
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80 -- when Size < Minimum_Stack_Size, return Minimum_Stack_Size
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81 -- otherwise return given Size
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82
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83 Default_Env_Stack_Size : constant Size_Type := 14_336;
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84 -- Assumed size of the environment task, if no other information
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85 -- is available. This value is used when stack checking is
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86 -- enabled and no GNAT_STACK_LIMIT environment variable is set.
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87 -- This value is chosen as the VxWorks default stack size is 20kB,
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88 -- and a little more than 4kB is necessary for the run time.
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89
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90 Stack_Grows_Down : constant Boolean := True;
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91 -- This constant indicates whether the stack grows up (False) or
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92 -- down (True) in memory as functions are called. It is used for
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93 -- proper implementation of the stack overflow check.
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94
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95 Runtime_Default_Sec_Stack_Size : constant Size_Type := 10 * 1024;
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96 -- The run-time chosen default size for secondary stacks that may be
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97 -- overriden by the user with the use of binder -D switch.
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98
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99 Sec_Stack_Dynamic : constant Boolean := True;
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100 -- Indicates if secondary stacks can grow and shrink at run-time. If False,
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101 -- the size of a secondary stack is fixed at the point of its creation.
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102
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103 ----------------------------------------------
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104 -- Characteristics of types in Interfaces.C --
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105 ----------------------------------------------
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106
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107 long_bits : constant := Long_Integer'Size;
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108 -- Number of bits in type long and unsigned_long. The normal convention
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109 -- is that this is the same as type Long_Integer, but this may not be true
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110 -- of all targets.
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111
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112 ptr_bits : constant := Standard'Address_Size;
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113 subtype C_Address is System.Address;
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114 -- Number of bits in Interfaces.C pointers, normally a standard address
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115
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116 C_Malloc_Linkname : constant String := "__gnat_malloc";
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117 -- Name of runtime function used to allocate such a pointer
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118
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119 ----------------------------------------------
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120 -- Behavior of Pragma Finalize_Storage_Only --
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121 ----------------------------------------------
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122
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123 -- Garbage_Collected is a Boolean constant whose value indicates the
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124 -- effect of the pragma Finalize_Storage_Entry on a controlled type.
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125
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126 -- Garbage_Collected = False
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127
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128 -- The system releases all storage on program termination only,
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129 -- but not other garbage collection occurs, so finalization calls
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130 -- are omitted only for outer level objects can be omitted if
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131 -- pragma Finalize_Storage_Only is used.
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132
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133 -- Garbage_Collected = True
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134
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135 -- The system provides full garbage collection, so it is never
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136 -- necessary to release storage for controlled objects for which
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137 -- a pragma Finalize_Storage_Only is used.
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138
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139 Garbage_Collected : constant Boolean := False;
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140 -- The storage mode for this system (release on program exit)
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141
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142 ---------------------
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143 -- Tasking Profile --
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144 ---------------------
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145
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146 -- In the following sections, constant parameters are defined to
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147 -- allow some optimizations and fine tuning within the tasking run time
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148 -- based on restrictions on the tasking features.
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149
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150 ----------------------
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151 -- Locking Strategy --
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152 ----------------------
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153
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154 Single_Lock : constant Boolean := False;
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155 -- Indicates whether a single lock should be used within the tasking
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156 -- run-time to protect internal structures. If True, a single lock
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157 -- will be used, meaning less locking/unlocking operations, but also
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158 -- more global contention. In general, Single_Lock should be set to
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159 -- True on single processor machines, and to False to multi-processor
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160 -- systems, but this can vary from application to application and also
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161 -- depends on the scheduling policy.
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162
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163 -------------------
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164 -- Task Abortion --
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165 -------------------
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166
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167 No_Abort : constant Boolean := False;
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168 -- This constant indicates whether abort statements and asynchronous
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169 -- transfer of control (ATC) are disallowed. If set to True, it is
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170 -- assumed that neither construct is used, and the run time does not
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171 -- need to defer/undefer abort and check for pending actions at
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172 -- completion points. A value of True for No_Abort corresponds to:
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173 -- pragma Restrictions (No_Abort_Statements);
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174 -- pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
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175
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176 ---------------------
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177 -- Task Attributes --
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178 ---------------------
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179
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180 Max_Attribute_Count : constant := 16;
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181 -- Number of task attributes stored in the task control block
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182
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183 -----------------------
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184 -- Task Image Length --
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185 -----------------------
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186
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187 Max_Task_Image_Length : constant := 32;
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188 -- This constant specifies the maximum length of a task's image
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189
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190 ------------------------------
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191 -- Exception Message Length --
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192 ------------------------------
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193
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194 Default_Exception_Msg_Max_Length : constant := 200;
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195 -- This constant specifies the default number of characters to allow
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196 -- in an exception message (200 is minimum required by RM 11.4.1(18)).
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197
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198 end System.Parameters;
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