380 lines
21 KiB
Ada
380 lines
21 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S E M _ C H 1 3 --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2016, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING3. If not, go to --
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-- http://www.gnu.org/licenses for a complete copy of the license. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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with Table;
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with Types; use Types;
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with Uintp; use Uintp;
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package Sem_Ch13 is
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procedure Analyze_At_Clause (N : Node_Id);
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procedure Analyze_Attribute_Definition_Clause (N : Node_Id);
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procedure Analyze_Enumeration_Representation_Clause (N : Node_Id);
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procedure Analyze_Free_Statement (N : Node_Id);
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procedure Analyze_Freeze_Entity (N : Node_Id);
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procedure Analyze_Freeze_Generic_Entity (N : Node_Id);
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procedure Analyze_Record_Representation_Clause (N : Node_Id);
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procedure Analyze_Code_Statement (N : Node_Id);
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procedure Analyze_Aspect_Specifications (N : Node_Id; E : Entity_Id);
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-- This procedure is called to analyze aspect specifications for node N. E
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-- is the corresponding entity declared by the declaration node N. Callers
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-- should check that Has_Aspects (N) is True before calling this routine.
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procedure Analyze_Aspect_Specifications_On_Body_Or_Stub (N : Node_Id);
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-- Analyze the aspect specifications of [generic] subprogram body or stub
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-- N. Callers should check that Has_Aspects (N) is True before calling the
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-- routine. This routine diagnoses misplaced aspects that should appear on
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-- the initial declaration of N and offers suggestions for replacements.
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procedure Adjust_Record_For_Reverse_Bit_Order (R : Entity_Id);
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-- Called from Freeze where R is a record entity for which reverse bit
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-- order is specified and there is at least one component clause. Adjusts
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-- component positions according to either Ada 95 or Ada 2005 (AI-133).
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procedure Check_Record_Representation_Clause (N : Node_Id);
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-- This procedure completes the analysis of a record representation clause
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-- N. It is called at freeze time after adjustment of component clause bit
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-- positions for possible non-standard bit order. In the case of Ada 2005
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-- (machine scalar) mode, this adjustment can make substantial changes, so
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-- some checks, in particular for component overlaps cannot be done at the
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-- time the record representation clause is first seen, but must be delayed
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-- till freeze time, and in particular is called after calling the above
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-- procedure for adjusting record bit positions for reverse bit order.
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procedure Initialize;
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-- Initialize internal tables for new compilation
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procedure Kill_Rep_Clause (N : Node_Id);
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-- This procedure is called for a rep clause N when we are in -gnatI mode
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-- (Ignore_Rep_Clauses). It replaces the node N with a null statement. This
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-- is only called if Ignore_Rep_Clauses is True.
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procedure Set_Enum_Esize (T : Entity_Id);
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-- This routine sets the Esize field for an enumeration type T, based
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-- on the current representation information available for T. Note that
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-- the setting of the RM_Size field is not affected. This routine also
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-- initializes the alignment field to zero.
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function Minimum_Size
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(T : Entity_Id;
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Biased : Boolean := False) return Nat;
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-- Given an elementary type, determines the minimum number of bits required
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-- to represent all values of the type. This function may not be called
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-- with any other types. If the flag Biased is set True, then the minimum
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-- size calculation that biased representation is used in the case of a
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-- discrete type, e.g. the range 7..8 gives a minimum size of 4 with
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-- Biased set to False, and 1 with Biased set to True. Note that the
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-- biased parameter only has an effect if the type is not biased, it
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-- causes Minimum_Size to indicate the minimum size of an object with
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-- the given type, of the size the type would have if it were biased. If
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-- the type is already biased, then Minimum_Size returns the biased size,
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-- regardless of the setting of Biased. Also, fixed-point types are never
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-- biased in the current implementation. If the size is not known at
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-- compile time, this function returns 0.
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procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id);
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-- Expr is an expression for an address clause. This procedure checks
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-- that the expression is constant, in the limited sense that it is safe
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-- to evaluate it at the point the object U_Ent is declared, rather than
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-- at the point of the address clause. The condition for this to be true
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-- is that the expression has no variables, no constants declared after
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-- U_Ent, and no calls to non-pure functions. If this condition is not
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-- met, then an appropriate error message is posted. This check is applied
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-- at the point an object with an address clause is frozen, as well as for
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-- address clauses for tasks and entries.
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procedure Check_Size
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(N : Node_Id;
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T : Entity_Id;
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Siz : Uint;
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Biased : out Boolean);
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-- Called when size Siz is specified for subtype T. This subprogram checks
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-- that the size is appropriate, posting errors on node N as required.
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-- This check is effective for elementary types and bit-packed arrays.
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-- For other non-elementary types, a check is only made if an explicit
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-- size has been given for the type (and the specified size must match).
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-- The parameter Biased is set False if the size specified did not require
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-- the use of biased representation, and True if biased representation
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-- was required to meet the size requirement. Note that Biased is only
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-- set if the type is not currently biased, but biasing it is the only
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-- way to meet the requirement. If the type is currently biased, then
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-- this biased size is used in the initial check, and Biased is False.
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-- If the size is too small, and an error message is given, then both
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-- Esize and RM_Size are reset to the allowed minimum value in T.
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function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean;
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-- Called at start of processing a representation clause/pragma. Used to
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-- check that the representation item is not being applied to an incomplete
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-- type or to a generic formal type or a type derived from a generic formal
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-- type. Returns False if no such error occurs. If this error does occur,
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-- appropriate error messages are posted on node N, and True is returned.
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generic
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with procedure Replace_Type_Reference (N : Node_Id);
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procedure Replace_Type_References_Generic (N : Node_Id; T : Entity_Id);
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-- This is used to scan an expression for a predicate or invariant aspect
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-- replacing occurrences of the name of the subtype to which the aspect
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-- applies with appropriate references to the parameter of the predicate
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-- function or invariant procedure. The procedure passed as a generic
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-- parameter does the actual replacement of node N, which is either a
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-- simple direct reference to T, or a selected component that represents
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-- an appropriately qualified occurrence of T.
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function Rep_Item_Too_Late
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(T : Entity_Id;
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N : Node_Id;
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FOnly : Boolean := False) return Boolean;
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-- Called at the start of processing a representation clause or a
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-- representation pragma. Used to check that a representation item for
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-- entity T does not appear too late (according to the rules in RM 13.1(9)
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-- and RM 13.1(10)). N is the associated node, which in the pragma case
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-- is the pragma or representation clause itself, used for placing error
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-- messages if the item is too late.
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--
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-- Fonly is a flag that causes only the freezing rule (para 9) to be
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-- applied, and the tests of para 10 are skipped. This is appropriate for
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-- both subtype related attributes (Alignment and Size) and for stream
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-- attributes, which, although certainly not subtype related attributes,
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-- clearly should not be subject to the para 10 restrictions (see
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-- AI95-00137). Similarly, we also skip the para 10 restrictions for
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-- the Storage_Size case where they also clearly do not apply, and for
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-- Stream_Convert which is in the same category as the stream attributes.
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--
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-- If the rep item is too late, an appropriate message is output and True
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-- is returned, which is a signal that the caller should abandon processing
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-- for the item. If the item is not too late, then False is returned, and
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-- the caller can continue processing the item.
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--
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-- If no error is detected, this call also as a side effect links the
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-- representation item onto the head of the representation item chain
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-- (referenced by the First_Rep_Item field of the entity).
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--
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-- Note: Rep_Item_Too_Late must be called with the underlying type in the
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-- case of a private or incomplete type. The protocol is to first check for
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-- Rep_Item_Too_Early using the initial entity, then take the underlying
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-- type, then call Rep_Item_Too_Late on the result.
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--
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-- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute
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-- definition clauses which have From_Aspect_Specification set. This is
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-- because such clauses are linked on to the Rep_Item chain in procedure
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-- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details.
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function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean;
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-- Given two types, where the two types are related by possible derivation,
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-- determines if the two types have the same representation, or different
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-- representations, requiring the special processing for representation
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-- change. A False result is possible only for array, enumeration or
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-- record types.
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procedure Validate_Compile_Time_Warning_Error (N : Node_Id);
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-- N is a pragma Compile_Time_Error or Compile_Warning_Error whose boolean
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-- expression is not known at compile time. This procedure makes an entry
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-- in a table. The actual checking is performed by Validate_Compile_Time_
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-- Warning_Errors, which is invoked after calling the back end.
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procedure Validate_Compile_Time_Warning_Errors;
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-- This routine is called after calling the back end to validate pragmas
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-- Compile_Time_Error and Compile_Time_Warning for size and alignment
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-- appropriateness. The reason it is called that late is to take advantage
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-- of any back-annotation of size and alignment performed by the back end.
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procedure Validate_Unchecked_Conversion
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(N : Node_Id;
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Act_Unit : Entity_Id);
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-- Validate a call to unchecked conversion. N is the node for the actual
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-- instantiation, which is used only for error messages. Act_Unit is the
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-- entity for the instantiation, from which the actual types etc. for this
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-- instantiation can be determined. This procedure makes an entry in a
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-- table and/or generates an N_Validate_Unchecked_Conversion node. The
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-- actual checking is done in Validate_Unchecked_Conversions or in the
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-- back end as required.
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procedure Validate_Unchecked_Conversions;
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-- This routine is called after calling the back end to validate unchecked
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-- conversions for size and alignment appropriateness. The reason it is
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-- called that late is to take advantage of any back-annotation of size
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-- and alignment performed by the back end.
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procedure Validate_Address_Clauses;
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-- This is called after the back end has been called (and thus after the
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-- alignments of objects have been back annotated). It goes through the
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-- table of saved address clauses checking for suspicious alignments and
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-- if necessary issuing warnings.
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procedure Validate_Independence;
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-- This is called after the back end has been called (and thus after the
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-- layout of components has been back annotated). It goes through the
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-- table of saved pragma Independent[_Component] entries, checking that
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-- independence can be achieved, and if necessary issuing error messages.
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-------------------------------------
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-- Table for Validate_Independence --
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-------------------------------------
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-- If a legal pragma Independent or Independent_Components is given for
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-- an entity, then an entry is made in this table, to be checked by a
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-- call to Validate_Independence after back annotation of layout is done.
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type Independence_Check_Record is record
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N : Node_Id;
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-- The pragma Independent or Independent_Components
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E : Entity_Id;
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-- The entity to which it applies
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end record;
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package Independence_Checks is new Table.Table (
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Table_Component_Type => Independence_Check_Record,
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Table_Index_Type => Int,
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Table_Low_Bound => 1,
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Table_Initial => 20,
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Table_Increment => 200,
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Table_Name => "Independence_Checks");
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-----------------------------------
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-- Handling of Aspect Visibility --
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-----------------------------------
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-- The visibility of aspects is tricky. First, the visibility is delayed
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-- to the freeze point. This is not too complicated, what we do is simply
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-- to leave the aspect "laying in wait" for the freeze point, and at that
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-- point materialize and analyze the corresponding attribute definition
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-- clause or pragma. There is some special processing for preconditions
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-- and postonditions, where the pragmas themselves deal with the required
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-- delay, but basically the approach is the same, delay analysis of the
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-- expression to the freeze point.
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-- Much harder is the requirement for diagnosing cases in which an early
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-- freeze causes a change in visibility. Consider:
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-- package AspectVis is
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-- R_Size : constant Integer := 32;
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--
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-- package Inner is
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-- type R is new Integer with
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-- Size => R_Size;
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-- F : R; -- freezes
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-- R_Size : constant Integer := 64;
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-- S : constant Integer := R'Size; -- 32 not 64
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-- end Inner;
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-- end AspectVis;
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-- Here the 32 not 64 shows what would be expected if this program were
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-- legal, since the evaluation of R_Size has to be done at the freeze
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-- point and gets the outer definition not the inner one.
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-- But the language rule requires this program to be diagnosed as illegal
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-- because the visibility changes between the freeze point and the end of
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-- the declarative region.
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-- To meet this requirement, we first note that the Expression field of the
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-- N_Aspect_Specification node holds the raw unanalyzed expression, which
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-- will get used in processing the aspect. At the time of analyzing the
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-- N_Aspect_Specification node, we create a complete copy of the expression
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-- and store it in the entity field of the Identifier (an odd usage, but
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-- the identifier is not used except to identify the aspect, so its Entity
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-- field is otherwise unused, and we are short of room in the node).
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-- This copy stays unanalyzed up to the freeze point, where we analyze the
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-- resulting pragma or attribute definition clause, except that in the
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-- case of invariants and predicates, we mark occurrences of the subtype
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-- name as having the entity of the subprogram parameter, so that they
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-- will not cause trouble in the following steps.
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-- Then at the freeze point, we create another copy of this unanalyzed
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-- expression. By this time we no longer need the Expression field for
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-- other purposes, so we can store it there. Now we have two copies of
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-- the original unanalyzed expression. One of them gets preanalyzed at
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-- the freeze point to capture the visibility at the freeze point.
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-- Now when we hit the freeze all at the end of the declarative part, if
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-- we come across a frozen entity with delayed aspects, we still have one
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-- copy of the unanalyzed expression available in the node, and we again
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-- do a preanalysis using that copy and the visibility at the end of the
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-- declarative part. Now we have two preanalyzed expression (preanalysis
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-- is good enough, since we are only interested in referenced entities).
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-- One captures the visibility at the freeze point, the other captures the
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-- visibility at the end of the declarative part. We see if the entities
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-- in these two expressions are the same, by seeing if the two expressions
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-- are fully conformant, and if not, issue appropriate error messages.
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-- Quite an awkward approach, but this is an awkard requirement
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procedure Analyze_Aspects_At_Freeze_Point (E : Entity_Id);
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-- Analyze all the delayed aspects for entity E at freezing point. This
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-- includes dealing with inheriting delayed aspects from the parent type
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-- in the case where a derived type is frozen.
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procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id);
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-- Performs the processing described above at the freeze point, ASN is the
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-- N_Aspect_Specification node for the aspect.
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procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id);
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-- Performs the processing described above at the freeze all point, and
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-- issues appropriate error messages if the visibility has indeed changed.
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-- Again, ASN is the N_Aspect_Specification node for the aspect.
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procedure Inherit_Aspects_At_Freeze_Point (Typ : Entity_Id);
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-- Given an entity Typ that denotes a derived type or a subtype, this
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-- routine performs the inheritance of aspects at the freeze point.
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procedure Resolve_Aspect_Expressions (E : Entity_Id);
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-- Name resolution of an aspect expression happens at the end of the
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-- current declarative part or at the freeze point for the entity,
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-- whichever comes first. For declarations in the visible part of a
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-- package, name resolution takes place before analysis of the private
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-- part even though the freeze point of the entity may appear later.
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procedure Validate_Iterable_Aspect (Typ : Entity_Id; ASN : Node_Id);
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-- For SPARK 2014 formal containers. The expression has the form of an
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-- aggregate, and each entry must denote a function with the proper syntax
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-- for First, Next, and Has_Element. Optionally an Element primitive may
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-- also be defined.
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-----------------------------------------------------------
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-- Visibility of Discriminants in Aspect Specifications --
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-----------------------------------------------------------
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-- The discriminants of a type are visible when analyzing the aspect
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-- specifications of a type declaration or protected type declaration,
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-- but not when analyzing those of a subtype declaration. The following
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-- routines enforce this distinction.
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procedure Install_Discriminants (E : Entity_Id);
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-- Make visible the discriminants of type entity E
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procedure Push_Scope_And_Install_Discriminants (E : Entity_Id);
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-- Push scope E and makes visible the discriminants of type entity E if E
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-- has discriminants and is not a subtype.
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procedure Uninstall_Discriminants (E : Entity_Id);
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-- Remove visibility to the discriminants of type entity E
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procedure Uninstall_Discriminants_And_Pop_Scope (E : Entity_Id);
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-- Remove visibility to the discriminants of type entity E and pop the
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-- scope stack if E has discriminants and is not a subtype.
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end Sem_Ch13;
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