1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M _ D I S P -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2015, Free Software Foundation, Inc. -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- 17-- for more details. You should have received a copy of the GNU General -- 18-- Public License distributed with GNAT; see file COPYING3. If not, go to -- 19-- http://www.gnu.org/licenses for a complete copy of the license. -- 20-- -- 21-- GNAT was originally developed by the GNAT team at New York University. -- 22-- Extensive contributions were provided by Ada Core Technologies Inc. -- 23-- -- 24------------------------------------------------------------------------------ 25 26-- This package contains routines involved in tagged types and dynamic 27-- dispatching. 28 29with Types; use Types; 30package Sem_Disp is 31 32 procedure Check_Controlling_Formals (Typ : Entity_Id; Subp : Entity_Id); 33 -- Check that all controlling parameters of Subp are of type Typ, that 34 -- defaults for controlling parameters are tag-indeterminate, and that the 35 -- nominal subtype of the parameters and result statically match the first 36 -- subtype of the controlling type. Issues appropriate error messages if 37 -- any of these requirements is not met. 38 39 procedure Check_Dispatching_Call (N : Node_Id); 40 -- Check if the call N is a dispatching call. The subprogram is known to be 41 -- a dispatching operation. The call is dispatching if all the controlling 42 -- actuals are dynamically tagged. This procedure is called after overload 43 -- resolution, so the call is known to be unambiguous. 44 45 procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id); 46 -- Add Subp to the list of primitive operations of the corresponding type 47 -- if it has a parameter of this type and is defined at a proper place for 48 -- primitive operations (new primitives are only defined in package spec, 49 -- overridden operation can be defined in any scope). If Old_Subp is not 50 -- Empty we are in the overriding case. If the tagged type associated with 51 -- Subp is a concurrent type (case that occurs when the type is declared 52 -- in a generic because the analysis of generics disables generation of the 53 -- corresponding record) then this routine does not add Subp to the list of 54 -- primitive operations but leaves Subp decorated as dispatching operation 55 -- to enable checks associated with the Object.Operation notation. 56 57 procedure Check_Operation_From_Incomplete_Type 58 (Subp : Entity_Id; 59 Typ : Entity_Id); 60 -- If a primitive operation was defined for the incomplete view of the 61 -- type, and the full type declaration is a derived type definition, 62 -- the operation may override an inherited one. 63 -- Need more description here, what are the parameters, and what does 64 -- this call actually do??? 65 66 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id); 67 -- Add Old_Subp to the list of primitive operations of the corresponding 68 -- tagged type if it is the full view of a private tagged type. The Alias 69 -- of Old_Subp is adjusted to point to the inherited procedure of the 70 -- full view because it is always this one which has to be called. 71 -- What is Subp used for??? 72 73 function Covers_Some_Interface (Prim : Entity_Id) return Boolean; 74 -- Returns true if Prim covers some interface primitive of its associated 75 -- tagged type. The tagged type of Prim must be frozen when this function 76 -- is invoked. 77 78 function Find_Controlling_Arg (N : Node_Id) return Node_Id; 79 -- Returns the actual controlling argument if N is dynamically tagged, and 80 -- Empty if it is not dynamically tagged. 81 82 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id; 83 -- Check whether the subprogram Subp is dispatching, and find the tagged 84 -- type of the controlling argument or arguments. Returns Empty if Subp 85 -- is not a dispatching operation. 86 87 function Find_Primitive_Covering_Interface 88 (Tagged_Type : Entity_Id; 89 Iface_Prim : Entity_Id) return Entity_Id; 90 -- Search the homonym chain for the primitive of Tagged_Type that covers 91 -- Iface_Prim. The homonym chain traversal is required to catch primitives 92 -- associated with the partial view of private types when processing the 93 -- corresponding full view. If the entity is not found, then search for it 94 -- in the list of primitives of Tagged_Type. This latter search is needed 95 -- when the interface primitive is covered by a private subprogram. If the 96 -- primitive has not been covered yet then return the entity that will be 97 -- overridden when the primitive is covered (that is, return the entity 98 -- whose alias attribute references the interface primitive). If none of 99 -- these entities is found then return Empty. 100 101 type Subprogram_List is array (Nat range <>) of Entity_Id; 102 -- Type returned by Inherited_Subprograms function 103 104 function Inherited_Subprograms 105 (S : Entity_Id; 106 No_Interfaces : Boolean := False; 107 Interfaces_Only : Boolean := False; 108 One_Only : Boolean := False) return Subprogram_List; 109 -- Given the spec of a subprogram, this function gathers any inherited 110 -- subprograms from direct inheritance or via interfaces. The result is an 111 -- array of Entity_Ids of the specs of inherited subprograms. Returns a 112 -- null array if passed an Empty spec id. Note that the returned array 113 -- only includes subprograms and generic subprograms (and excludes any 114 -- other inherited entities, in particular enumeration literals). If 115 -- No_Interfaces is True, only return inherited subprograms not coming 116 -- from an interface. If Interfaces_Only is True, only return inherited 117 -- subprograms from interfaces. Otherwise, subprograms inherited directly 118 -- come first, starting with the closest ancestors, and are followed by 119 -- subprograms inherited from interfaces. At most one of No_Interfaces 120 -- and Interfaces_Only should be True. 121 -- 122 -- If One_Only is set, the search is discontinued as soon as one entry 123 -- is found. In this case the resulting array is either null or contains 124 -- exactly one element. 125 126 function Is_Dynamically_Tagged (N : Node_Id) return Boolean; 127 -- Used to determine whether a call is dispatching, i.e. if it is 128 -- an expression of a class_Wide type, or a call to a function with 129 -- controlling result where at least one operand is dynamically tagged. 130 -- Also used to determine whether an entity has a class-wide type, or a 131 -- function call that dispatches on the result. Used to verify that all the 132 -- dependent expressions in a conditional expression are equally tagged. 133 134 function Is_Null_Interface_Primitive (E : Entity_Id) return Boolean; 135 -- Returns True if E is a null procedure that is an interface primitive 136 137 function Is_Overriding_Subprogram (E : Entity_Id) return Boolean; 138 -- Returns True if E is an overriding subprogram 139 140 function Is_Tag_Indeterminate (N : Node_Id) return Boolean; 141 -- Returns true if the expression N is tag-indeterminate. An expression 142 -- is tag-indeterminate if it is a call that dispatches on result, and all 143 -- controlling operands are also indeterminate. Such a function call may 144 -- inherit a tag from an enclosing call. 145 146 procedure Override_Dispatching_Operation 147 (Tagged_Type : Entity_Id; 148 Prev_Op : Entity_Id; 149 New_Op : Entity_Id; 150 Is_Wrapper : Boolean := False); 151 -- Replace an implicit dispatching operation of the type Tagged_Type 152 -- with an explicit one. Prev_Op is an inherited primitive operation which 153 -- is overridden by the explicit declaration of New_Op. Is_Wrapper is 154 -- True when New_Op is an internally generated wrapper of a controlling 155 -- function. The caller checks that Tagged_Type is indeed a tagged type. 156 157 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id); 158 -- If a function call is tag-indeterminate, its controlling argument is 159 -- found in the context: either an enclosing call, or the left-hand side 160 -- of the enclosing assignment statement. The tag must be propagated 161 -- recursively to the tag-indeterminate actuals of the call. 162 -- Need clear description of the parameters Control and Actual, especially 163 -- since the comments above refer to actuals in the plural ??? 164 165end Sem_Disp; 166