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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 E M _ C H 1 3 --
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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. See the GNU General Public License --
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17 -- for more details. You should have received a copy of the GNU General --
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18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
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19 -- http://www.gnu.org/licenses for a complete copy of the license. --
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20 -- --
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21 -- GNAT was originally developed by the GNAT team at New York University. --
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22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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23 -- --
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24 ------------------------------------------------------------------------------
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25
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26 with Table;
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27 with Types; use Types;
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28 with Uintp; use Uintp;
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29
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30 package Sem_Ch13 is
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31 procedure Analyze_At_Clause (N : Node_Id);
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32 procedure Analyze_Attribute_Definition_Clause (N : Node_Id);
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33 procedure Analyze_Enumeration_Representation_Clause (N : Node_Id);
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34 procedure Analyze_Free_Statement (N : Node_Id);
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35 procedure Analyze_Freeze_Entity (N : Node_Id);
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36 procedure Analyze_Freeze_Generic_Entity (N : Node_Id);
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37 procedure Analyze_Record_Representation_Clause (N : Node_Id);
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38 procedure Analyze_Code_Statement (N : Node_Id);
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39
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40 procedure Analyze_Aspect_Specifications (N : Node_Id; E : Entity_Id);
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41 -- This procedure is called to analyze aspect specifications for node N. E
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42 -- is the corresponding entity declared by the declaration node N. Callers
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43 -- should check that Has_Aspects (N) is True before calling this routine.
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44
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131
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45 procedure Analyze_Aspects_On_Subprogram_Body_Or_Stub (N : Node_Id);
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111
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46 -- Analyze the aspect specifications of [generic] subprogram body or stub
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47 -- N. Callers should check that Has_Aspects (N) is True before calling the
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48 -- routine. This routine diagnoses misplaced aspects that should appear on
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49 -- the initial declaration of N and offers suggestions for replacements.
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50
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51 procedure Adjust_Record_For_Reverse_Bit_Order (R : Entity_Id);
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52 -- Called from Freeze where R is a record entity for which reverse bit
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53 -- order is specified and there is at least one component clause. Note:
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54 -- component positions are normally adjusted as per AI95-0133, unless
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55 -- -gnatd.p is used to restore original Ada 95 mode.
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56
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57 procedure Check_Record_Representation_Clause (N : Node_Id);
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58 -- This procedure completes the analysis of a record representation clause
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59 -- N. It is called at freeze time after adjustment of component clause bit
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60 -- positions for possible non-standard bit order. In the case of Ada 2005
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61 -- (machine scalar) mode, this adjustment can make substantial changes, so
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62 -- some checks, in particular for component overlaps cannot be done at the
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63 -- time the record representation clause is first seen, but must be delayed
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64 -- till freeze time, and in particular is called after calling the above
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65 -- procedure for adjusting record bit positions for reverse bit order.
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66
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67 procedure Initialize;
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68 -- Initialize internal tables for new compilation
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69
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70 procedure Kill_Rep_Clause (N : Node_Id);
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71 -- This procedure is called for a rep clause N when we are in -gnatI mode
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72 -- (Ignore_Rep_Clauses). It replaces the node N with a null statement. This
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73 -- is only called if Ignore_Rep_Clauses is True.
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74
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75 procedure Set_Enum_Esize (T : Entity_Id);
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76 -- This routine sets the Esize field for an enumeration type T, based
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77 -- on the current representation information available for T. Note that
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78 -- the setting of the RM_Size field is not affected. This routine also
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79 -- initializes the alignment field to zero.
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80
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81 function Minimum_Size
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82 (T : Entity_Id;
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83 Biased : Boolean := False) return Nat;
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84 -- Given an elementary type, determines the minimum number of bits required
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85 -- to represent all values of the type. This function may not be called
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86 -- with any other types. If the flag Biased is set True, then the minimum
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87 -- size calculation that biased representation is used in the case of a
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88 -- discrete type, e.g. the range 7..8 gives a minimum size of 4 with
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89 -- Biased set to False, and 1 with Biased set to True. Note that the
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90 -- biased parameter only has an effect if the type is not biased, it
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91 -- causes Minimum_Size to indicate the minimum size of an object with
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92 -- the given type, of the size the type would have if it were biased. If
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93 -- the type is already biased, then Minimum_Size returns the biased size,
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94 -- regardless of the setting of Biased. Also, fixed-point types are never
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95 -- biased in the current implementation. If the size is not known at
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96 -- compile time, this function returns 0.
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97
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98 procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id);
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99 -- Expr is an expression for an address clause. This procedure checks
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100 -- that the expression is constant, in the limited sense that it is safe
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101 -- to evaluate it at the point the object U_Ent is declared, rather than
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102 -- at the point of the address clause. The condition for this to be true
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103 -- is that the expression has no variables, no constants declared after
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104 -- U_Ent, and no calls to non-pure functions. If this condition is not
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105 -- met, then an appropriate error message is posted. This check is applied
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106 -- at the point an object with an address clause is frozen, as well as for
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107 -- address clauses for tasks and entries.
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108
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109 procedure Check_Size
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110 (N : Node_Id;
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111 T : Entity_Id;
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112 Siz : Uint;
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113 Biased : out Boolean);
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114 -- Called when size Siz is specified for subtype T. This subprogram checks
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115 -- that the size is appropriate, posting errors on node N as required.
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116 -- This check is effective for elementary types and bit-packed arrays.
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117 -- For other non-elementary types, a check is only made if an explicit
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118 -- size has been given for the type (and the specified size must match).
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119 -- The parameter Biased is set False if the size specified did not require
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120 -- the use of biased representation, and True if biased representation
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121 -- was required to meet the size requirement. Note that Biased is only
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122 -- set if the type is not currently biased, but biasing it is the only
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123 -- way to meet the requirement. If the type is currently biased, then
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124 -- this biased size is used in the initial check, and Biased is False.
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125 -- If the size is too small, and an error message is given, then both
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126 -- Esize and RM_Size are reset to the allowed minimum value in T.
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127
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128 function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean;
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129 -- Called at start of processing a representation clause/pragma. Used to
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130 -- check that the representation item is not being applied to an incomplete
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131 -- type or to a generic formal type or a type derived from a generic formal
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132 -- type. Returns False if no such error occurs. If this error does occur,
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133 -- appropriate error messages are posted on node N, and True is returned.
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134
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135 generic
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136 with procedure Replace_Type_Reference (N : Node_Id);
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137 procedure Replace_Type_References_Generic (N : Node_Id; T : Entity_Id);
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138 -- This is used to scan an expression for a predicate or invariant aspect
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139 -- replacing occurrences of the name of the subtype to which the aspect
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140 -- applies with appropriate references to the parameter of the predicate
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141 -- function or invariant procedure. The procedure passed as a generic
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142 -- parameter does the actual replacement of node N, which is either a
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143 -- simple direct reference to T, or a selected component that represents
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144 -- an appropriately qualified occurrence of T.
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145
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146 function Rep_Item_Too_Late
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147 (T : Entity_Id;
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148 N : Node_Id;
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149 FOnly : Boolean := False) return Boolean;
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150 -- Called at the start of processing a representation clause or a
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151 -- representation pragma. Used to check that a representation item for
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152 -- entity T does not appear too late (according to the rules in RM 13.1(9)
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153 -- and RM 13.1(10)). N is the associated node, which in the pragma case
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154 -- is the pragma or representation clause itself, used for placing error
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155 -- messages if the item is too late.
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156 --
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157 -- Fonly is a flag that causes only the freezing rule (para 9) to be
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158 -- applied, and the tests of para 10 are skipped. This is appropriate for
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159 -- both subtype related attributes (Alignment and Size) and for stream
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160 -- attributes, which, although certainly not subtype related attributes,
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161 -- clearly should not be subject to the para 10 restrictions (see
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162 -- AI95-00137). Similarly, we also skip the para 10 restrictions for
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163 -- the Storage_Size case where they also clearly do not apply, and for
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164 -- Stream_Convert which is in the same category as the stream attributes.
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165 --
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166 -- If the rep item is too late, an appropriate message is output and True
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167 -- is returned, which is a signal that the caller should abandon processing
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168 -- for the item. If the item is not too late, then False is returned, and
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169 -- the caller can continue processing the item.
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170 --
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171 -- If no error is detected, this call also as a side effect links the
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172 -- representation item onto the head of the representation item chain
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173 -- (referenced by the First_Rep_Item field of the entity).
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174 --
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175 -- Note: Rep_Item_Too_Late must be called with the underlying type in the
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176 -- case of a private or incomplete type. The protocol is to first check for
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177 -- Rep_Item_Too_Early using the initial entity, then take the underlying
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178 -- type, then call Rep_Item_Too_Late on the result.
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179 --
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180 -- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute
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181 -- definition clauses which have From_Aspect_Specification set. This is
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182 -- because such clauses are linked on to the Rep_Item chain in procedure
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183 -- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details.
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184
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185 function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean;
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186 -- Given two types, where the two types are related by possible derivation,
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187 -- determines if the two types have the same representation, or different
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188 -- representations, requiring the special processing for representation
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189 -- change. A False result is possible only for array, enumeration or
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190 -- record types.
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191
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192 procedure Validate_Compile_Time_Warning_Error (N : Node_Id);
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193 -- N is a pragma Compile_Time_Error or Compile_Warning_Error whose boolean
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194 -- expression is not known at compile time. This procedure makes an entry
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195 -- in a table. The actual checking is performed by Validate_Compile_Time_
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196 -- Warning_Errors, which is invoked after calling the back end.
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197
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198 procedure Validate_Compile_Time_Warning_Errors;
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199 -- This routine is called after calling the back end to validate pragmas
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200 -- Compile_Time_Error and Compile_Time_Warning for size and alignment
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201 -- appropriateness. The reason it is called that late is to take advantage
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202 -- of any back-annotation of size and alignment performed by the back end.
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203
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204 procedure Validate_Unchecked_Conversion
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205 (N : Node_Id;
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206 Act_Unit : Entity_Id);
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207 -- Validate a call to unchecked conversion. N is the node for the actual
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208 -- instantiation, which is used only for error messages. Act_Unit is the
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209 -- entity for the instantiation, from which the actual types etc. for this
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210 -- instantiation can be determined. This procedure makes an entry in a
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211 -- table and/or generates an N_Validate_Unchecked_Conversion node. The
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212 -- actual checking is done in Validate_Unchecked_Conversions or in the
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213 -- back end as required.
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214
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215 procedure Validate_Unchecked_Conversions;
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216 -- This routine is called after calling the back end to validate unchecked
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217 -- conversions for size and alignment appropriateness. The reason it is
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218 -- called that late is to take advantage of any back-annotation of size
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219 -- and alignment performed by the back end.
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220
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221 procedure Validate_Address_Clauses;
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222 -- This is called after the back end has been called (and thus after the
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223 -- alignments of objects have been back annotated). It goes through the
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224 -- table of saved address clauses checking for suspicious alignments and
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225 -- if necessary issuing warnings.
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226
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227 procedure Validate_Independence;
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228 -- This is called after the back end has been called (and thus after the
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229 -- layout of components has been back annotated). It goes through the
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230 -- table of saved pragma Independent[_Component] entries, checking that
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231 -- independence can be achieved, and if necessary issuing error messages.
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232
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233 -------------------------------------
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234 -- Table for Validate_Independence --
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235 -------------------------------------
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236
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237 -- If a legal pragma Independent or Independent_Components is given for
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238 -- an entity, then an entry is made in this table, to be checked by a
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239 -- call to Validate_Independence after back annotation of layout is done.
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240
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241 type Independence_Check_Record is record
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242 N : Node_Id;
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243 -- The pragma Independent or Independent_Components
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244
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245 E : Entity_Id;
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246 -- The entity to which it applies
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247 end record;
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248
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249 package Independence_Checks is new Table.Table (
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250 Table_Component_Type => Independence_Check_Record,
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251 Table_Index_Type => Int,
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252 Table_Low_Bound => 1,
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253 Table_Initial => 20,
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254 Table_Increment => 200,
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255 Table_Name => "Independence_Checks");
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256
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257 -----------------------------------
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258 -- Handling of Aspect Visibility --
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259 -----------------------------------
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260
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261 -- The visibility of aspects is tricky. First, the visibility is delayed
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262 -- to the freeze point. This is not too complicated, what we do is simply
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263 -- to leave the aspect "laying in wait" for the freeze point, and at that
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264 -- point materialize and analyze the corresponding attribute definition
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265 -- clause or pragma. There is some special processing for preconditions
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266 -- and postonditions, where the pragmas themselves deal with the required
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267 -- delay, but basically the approach is the same, delay analysis of the
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268 -- expression to the freeze point.
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269
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270 -- Much harder is the requirement for diagnosing cases in which an early
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271 -- freeze causes a change in visibility. Consider:
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272
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273 -- package AspectVis is
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274 -- R_Size : constant Integer := 32;
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275 --
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276 -- package Inner is
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277 -- type R is new Integer with
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278 -- Size => R_Size;
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279 -- F : R; -- freezes
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280 -- R_Size : constant Integer := 64;
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281 -- S : constant Integer := R'Size; -- 32 not 64
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282 -- end Inner;
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283 -- end AspectVis;
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284
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285 -- Here the 32 not 64 shows what would be expected if this program were
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286 -- legal, since the evaluation of R_Size has to be done at the freeze
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287 -- point and gets the outer definition not the inner one.
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288
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289 -- But the language rule requires this program to be diagnosed as illegal
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290 -- because the visibility changes between the freeze point and the end of
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291 -- the declarative region.
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292
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293 -- To meet this requirement, we first note that the Expression field of the
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294 -- N_Aspect_Specification node holds the raw unanalyzed expression, which
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295 -- will get used in processing the aspect. At the time of analyzing the
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296 -- N_Aspect_Specification node, we create a complete copy of the expression
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297 -- and store it in the entity field of the Identifier (an odd usage, but
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298 -- the identifier is not used except to identify the aspect, so its Entity
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299 -- field is otherwise unused, and we are short of room in the node).
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300
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301 -- This copy stays unanalyzed up to the freeze point, where we analyze the
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302 -- resulting pragma or attribute definition clause, except that in the
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303 -- case of invariants and predicates, we mark occurrences of the subtype
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304 -- name as having the entity of the subprogram parameter, so that they
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305 -- will not cause trouble in the following steps.
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306
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307 -- Then at the freeze point, we create another copy of this unanalyzed
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308 -- expression. By this time we no longer need the Expression field for
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309 -- other purposes, so we can store it there. Now we have two copies of
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310 -- the original unanalyzed expression. One of them gets preanalyzed at
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311 -- the freeze point to capture the visibility at the freeze point.
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312
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313 -- Now when we hit the freeze all at the end of the declarative part, if
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314 -- we come across a frozen entity with delayed aspects, we still have one
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315 -- copy of the unanalyzed expression available in the node, and we again
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316 -- do a preanalysis using that copy and the visibility at the end of the
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317 -- declarative part. Now we have two preanalyzed expression (preanalysis
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318 -- is good enough, since we are only interested in referenced entities).
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319 -- One captures the visibility at the freeze point, the other captures the
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320 -- visibility at the end of the declarative part. We see if the entities
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321 -- in these two expressions are the same, by seeing if the two expressions
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322 -- are fully conformant, and if not, issue appropriate error messages.
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323
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324 -- Quite an awkward approach, but this is an awkard requirement
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325
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326 procedure Analyze_Aspects_At_Freeze_Point (E : Entity_Id);
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327 -- Analyze all the delayed aspects for entity E at freezing point. This
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328 -- includes dealing with inheriting delayed aspects from the parent type
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329 -- in the case where a derived type is frozen.
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330
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331 procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id);
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332 -- Performs the processing described above at the freeze point, ASN is the
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333 -- N_Aspect_Specification node for the aspect.
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334
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335 procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id);
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336 -- Performs the processing described above at the freeze all point, and
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337 -- issues appropriate error messages if the visibility has indeed changed.
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338 -- Again, ASN is the N_Aspect_Specification node for the aspect.
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339
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340 procedure Inherit_Aspects_At_Freeze_Point (Typ : Entity_Id);
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341 -- Given an entity Typ that denotes a derived type or a subtype, this
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342 -- routine performs the inheritance of aspects at the freeze point.
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343
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344 procedure Resolve_Aspect_Expressions (E : Entity_Id);
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345 -- Name resolution of an aspect expression happens at the end of the
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346 -- current declarative part or at the freeze point for the entity,
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347 -- whichever comes first. For declarations in the visible part of a
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348 -- package, name resolution takes place before analysis of the private
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349 -- part even though the freeze point of the entity may appear later.
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350
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351 procedure Validate_Iterable_Aspect (Typ : Entity_Id; ASN : Node_Id);
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352 -- For SPARK 2014 formal containers. The expression has the form of an
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353 -- aggregate, and each entry must denote a function with the proper syntax
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354 -- for First, Next, and Has_Element. Optionally an Element primitive may
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355 -- also be defined.
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356
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357 -----------------------------------------------------------
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358 -- Visibility of Discriminants in Aspect Specifications --
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359 -----------------------------------------------------------
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360
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361 -- The discriminants of a type are visible when analyzing the aspect
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362 -- specifications of a type declaration or protected type declaration,
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363 -- but not when analyzing those of a subtype declaration. The following
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364 -- routines enforce this distinction.
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365
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366 procedure Install_Discriminants (E : Entity_Id);
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367 -- Make visible the discriminants of type entity E
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368
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369 procedure Push_Scope_And_Install_Discriminants (E : Entity_Id);
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370 -- Push scope E and makes visible the discriminants of type entity E if E
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371 -- has discriminants and is not a subtype.
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372
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373 procedure Uninstall_Discriminants (E : Entity_Id);
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374 -- Remove visibility to the discriminants of type entity E
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375
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376 procedure Uninstall_Discriminants_And_Pop_Scope (E : Entity_Id);
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377 -- Remove visibility to the discriminants of type entity E and pop the
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378 -- scope stack if E has discriminants and is not a subtype.
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379
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380 end Sem_Ch13;
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