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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 _ D I S P --
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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 -- This package contains routines involved in tagged types and dynamic
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27 -- dispatching.
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28
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29 with Types; use Types;
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30 package Sem_Disp is
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31
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32 procedure Check_Controlling_Formals (Typ : Entity_Id; Subp : Entity_Id);
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33 -- Check that all controlling parameters of Subp are of type Typ, that
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34 -- defaults for controlling parameters are tag-indeterminate, and that the
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35 -- nominal subtype of the parameters and result statically match the first
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36 -- subtype of the controlling type. Issues appropriate error messages if
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37 -- any of these requirements is not met.
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38
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39 procedure Check_Dispatching_Call (N : Node_Id);
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40 -- Check if the call N is a dispatching call. The subprogram is known to be
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41 -- a dispatching operation. The call is dispatching if all the controlling
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42 -- actuals are dynamically tagged. This procedure is called after overload
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43 -- resolution, so the call is known to be unambiguous.
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44
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45 procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id);
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46 -- Add Subp to the list of primitive operations of the corresponding type
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47 -- if it has a parameter of this type and is defined at a proper place for
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48 -- primitive operations (new primitives are only defined in package spec,
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49 -- overridden operation can be defined in any scope). If Old_Subp is not
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50 -- Empty we are in the overriding case. If the tagged type associated with
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51 -- Subp is a concurrent type (case that occurs when the type is declared
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52 -- in a generic because the analysis of generics disables generation of the
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53 -- corresponding record) then this routine does not add Subp to the list of
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54 -- primitive operations but leaves Subp decorated as dispatching operation
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55 -- to enable checks associated with the Object.Operation notation.
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56
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57 procedure Check_Operation_From_Incomplete_Type
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58 (Subp : Entity_Id;
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59 Typ : Entity_Id);
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60 -- If a primitive operation was defined for the incomplete view of the
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61 -- type, and the full type declaration is a derived type definition,
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62 -- the operation may override an inherited one.
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63 -- Need more description here, what are the parameters, and what does
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64 -- this call actually do???
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65
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66 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id);
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67 -- Add Old_Subp to the list of primitive operations of the corresponding
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68 -- tagged type if it is the full view of a private tagged type. The Alias
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69 -- of Old_Subp is adjusted to point to the inherited procedure of the
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70 -- full view because it is always this one which has to be called.
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71 -- What is Subp used for???
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72
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73 function Covered_Interface_Op (Prim : Entity_Id) return Entity_Id;
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74 -- Returns the interface primitive that Prim covers, when its controlling
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75 -- type has progenitors.
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76
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77 function Find_Controlling_Arg (N : Node_Id) return Node_Id;
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78 -- Returns the actual controlling argument if N is dynamically tagged, and
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79 -- Empty if it is not dynamically tagged.
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80
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81 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id;
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82 -- Check whether the subprogram Subp is dispatching, and find the tagged
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83 -- type of the controlling argument or arguments. Returns Empty if Subp
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84 -- is not a dispatching operation.
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85
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86 function Find_Primitive_Covering_Interface
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87 (Tagged_Type : Entity_Id;
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88 Iface_Prim : Entity_Id) return Entity_Id;
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89 -- Search the homonym chain for the primitive of Tagged_Type that covers
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90 -- Iface_Prim. The homonym chain traversal is required to catch primitives
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91 -- associated with the partial view of private types when processing the
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92 -- corresponding full view. If the entity is not found, then search for it
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93 -- in the list of primitives of Tagged_Type. This latter search is needed
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94 -- when the interface primitive is covered by a private subprogram. If the
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95 -- primitive has not been covered yet then return the entity that will be
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96 -- overridden when the primitive is covered (that is, return the entity
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97 -- whose alias attribute references the interface primitive). If none of
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98 -- these entities is found then return Empty.
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99
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100 type Subprogram_List is array (Nat range <>) of Entity_Id;
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101 -- Type returned by Inherited_Subprograms function
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102
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131
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103 generic
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104 with function Find_DT (Subp : Entity_Id) return Entity_Id;
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105 package Inheritance_Utilities is
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106
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107 -- This package provides generic versions of inheritance utilities
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108 -- provided here. These versions are used in GNATprove backend to adapt
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109 -- these utilities to GNATprove specific version of visibility of types.
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110
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111 function Inherited_Subprograms
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112 (S : Entity_Id;
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113 No_Interfaces : Boolean := False;
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114 Interfaces_Only : Boolean := False;
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115 One_Only : Boolean := False) return Subprogram_List;
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116
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117 function Is_Overriding_Subprogram (E : Entity_Id) return Boolean;
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118 end Inheritance_Utilities;
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119
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111
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120 function Inherited_Subprograms
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121 (S : Entity_Id;
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122 No_Interfaces : Boolean := False;
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123 Interfaces_Only : Boolean := False;
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124 One_Only : Boolean := False) return Subprogram_List;
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125 -- Given the spec of a subprogram, this function gathers any inherited
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126 -- subprograms from direct inheritance or via interfaces. The result is an
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127 -- array of Entity_Ids of the specs of inherited subprograms. Returns a
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128 -- null array if passed an Empty spec id. Note that the returned array
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129 -- only includes subprograms and generic subprograms (and excludes any
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130 -- other inherited entities, in particular enumeration literals). If
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131 -- No_Interfaces is True, only return inherited subprograms not coming
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132 -- from an interface. If Interfaces_Only is True, only return inherited
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133 -- subprograms from interfaces. Otherwise, subprograms inherited directly
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134 -- come first, starting with the closest ancestors, and are followed by
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135 -- subprograms inherited from interfaces. At most one of No_Interfaces
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136 -- and Interfaces_Only should be True.
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137 --
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138 -- If One_Only is set, the search is discontinued as soon as one entry
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139 -- is found. In this case the resulting array is either null or contains
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140 -- exactly one element.
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141
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142 function Is_Dynamically_Tagged (N : Node_Id) return Boolean;
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143 -- Used to determine whether a call is dispatching, i.e. if it is
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144 -- an expression of a class_Wide type, or a call to a function with
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145 -- controlling result where at least one operand is dynamically tagged.
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146 -- Also used to determine whether an entity has a class-wide type, or a
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147 -- function call that dispatches on the result. Used to verify that all the
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148 -- dependent expressions in a conditional expression are equally tagged.
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149
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150 function Is_Null_Interface_Primitive (E : Entity_Id) return Boolean;
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151 -- Returns True if E is a null procedure that is an interface primitive
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152
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153 function Is_Overriding_Subprogram (E : Entity_Id) return Boolean;
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154 -- Returns True if E is an overriding subprogram
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155
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156 function Is_Tag_Indeterminate (N : Node_Id) return Boolean;
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157 -- Returns true if the expression N is tag-indeterminate. An expression
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158 -- is tag-indeterminate if it is a call that dispatches on result, and all
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159 -- controlling operands are also indeterminate. Such a function call may
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160 -- inherit a tag from an enclosing call.
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161
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162 procedure Override_Dispatching_Operation
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163 (Tagged_Type : Entity_Id;
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164 Prev_Op : Entity_Id;
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165 New_Op : Entity_Id;
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166 Is_Wrapper : Boolean := False);
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167 -- Replace an implicit dispatching operation of the type Tagged_Type
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168 -- with an explicit one. Prev_Op is an inherited primitive operation which
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169 -- is overridden by the explicit declaration of New_Op. Is_Wrapper is
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170 -- True when New_Op is an internally generated wrapper of a controlling
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171 -- function. The caller checks that Tagged_Type is indeed a tagged type.
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172
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173 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id);
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174 -- If a function call is tag-indeterminate, its controlling argument is
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175 -- found in the context: either an enclosing call, or the left-hand side
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176 -- of the enclosing assignment statement. The tag must be propagated
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177 -- recursively to the tag-indeterminate actuals of the call.
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178 -- Need clear description of the parameters Control and Actual, especially
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179 -- since the comments above refer to actuals in the plural ???
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180
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181 end Sem_Disp;
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