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-- --
-- --
-- S E M _ C H 1 3 --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2022, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING3. If not, go to --
-- for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
with Types; use Types;
with Sem_Disp; use Sem_Disp;
with Uintp; use Uintp;
package Sem_Ch13 is
function All_Membership_Choices_Static (Expr : Node_Id) return Boolean;
-- Given a membership test, returns True iff all choices are static.
procedure Analyze_At_Clause (N : Node_Id);
procedure Analyze_Attribute_Definition_Clause (N : Node_Id);
procedure Analyze_Enumeration_Representation_Clause (N : Node_Id);
procedure Analyze_Free_Statement (N : Node_Id);
procedure Analyze_Freeze_Entity (N : Node_Id);
procedure Analyze_Freeze_Generic_Entity (N : Node_Id);
procedure Analyze_Record_Representation_Clause (N : Node_Id);
procedure Analyze_Code_Statement (N : Node_Id);
procedure Analyze_Aspect_Specifications (N : Node_Id; E : Entity_Id);
-- This procedure is called to analyze aspect specifications for node N. E
-- is the corresponding entity declared by the declaration node N. Callers
-- should check that Has_Aspects (N) is True before calling this routine.
procedure Analyze_Aspects_On_Subprogram_Body_Or_Stub (N : Node_Id);
-- Analyze the aspect specifications of [generic] subprogram body or stub
-- N. Callers should check that Has_Aspects (N) is True before calling the
-- routine. This routine diagnoses misplaced aspects that should appear on
-- the initial declaration of N and offers suggestions for replacements.
procedure Adjust_Record_For_Reverse_Bit_Order (R : Entity_Id);
-- Called from Freeze where R is a record entity for which reverse bit
-- order is specified and there is at least one component clause. Note:
-- component positions are normally adjusted as per AI95-0133, unless
-- -gnatd.p is used to restore original Ada 95 mode.
procedure Check_Record_Representation_Clause (N : Node_Id);
-- This procedure completes the analysis of a record representation clause
-- N. It is called at freeze time after adjustment of component clause bit
-- positions for possible non-standard bit order. In the case of Ada 2005
-- (machine scalar) mode, this adjustment can make substantial changes, so
-- some checks, in particular for component overlaps cannot be done at the
-- time the record representation clause is first seen, but must be delayed
-- till freeze time, and in particular is called after calling the above
-- procedure for adjusting record bit positions for reverse bit order.
procedure Initialize;
-- Initialize internal tables for new compilation
procedure Kill_Rep_Clause (N : Node_Id);
-- This procedure is called for a rep clause N when we are in -gnatI mode
-- (Ignore_Rep_Clauses). It replaces the node N with a null statement. This
-- is only called if Ignore_Rep_Clauses is True.
procedure Set_Enum_Esize (T : Entity_Id);
-- This routine sets the Esize field for an enumeration type T, based
-- on the current representation information available for T. Note that
-- the setting of the RM_Size field is not affected. This routine also
-- initializes the alignment field to zero.
Unknown_Minimum_Size : constant Nonzero_Int := -1;
function Minimum_Size
(T : Entity_Id;
Biased : Boolean := False) return Int;
-- Given an elementary type, determines the minimum number of bits required
-- to represent all values of the type. This function may not be called
-- with any other types. If the flag Biased is set True, then the minimum
-- size calculation that biased representation is used in the case of a
-- discrete type, e.g. the range 7..8 gives a minimum size of 4 with
-- Biased set to False, and 1 with Biased set to True. Note that the
-- biased parameter only has an effect if the type is not biased, it
-- causes Minimum_Size to indicate the minimum size of an object with
-- the given type, of the size the type would have if it were biased. If
-- the type is already biased, then Minimum_Size returns the biased size,
-- regardless of the setting of Biased. Also, fixed-point types are never
-- biased in the current implementation. If the size is not known at
-- compile time, this function returns Unknown_Minimum_Size.
procedure Check_Constant_Address_Clause (Expr : Node_Id; U_Ent : Entity_Id);
-- Expr is an expression for an address clause. This procedure checks
-- that the expression is constant, in the limited sense that it is safe
-- to evaluate it at the point the object U_Ent is declared, rather than
-- at the point of the address clause. The condition for this to be true
-- is that the expression has no variables, no constants declared after
-- U_Ent, and no calls to non-pure functions. If this condition is not
-- met, then an appropriate error message is posted. This check is applied
-- at the point an object with an address clause is frozen, as well as for
-- address clauses for tasks and entries.
procedure Check_Size
(N : Node_Id;
T : Entity_Id;
Siz : Uint;
Biased : out Boolean);
-- Called when size Siz is specified for subtype T. This subprogram checks
-- that the size is appropriate, posting errors on node N as required. This
-- check is effective for elementary types and bit-packed arrays. For
-- composite types, a check is only made if an explicit size has been given
-- for the type (and the specified size must match). The parameter Biased
-- is set False if the size specified did not require the use of biased
-- representation, and True if biased representation was required to meet
-- the size requirement. Note that Biased is only set if the type is not
-- currently biased, but biasing it is the only way to meet the
-- requirement. If the type is currently biased, then this biased size is
-- used in the initial check, and Biased is False. For a Component_Size
-- clause, T is the component type.
function Has_Compatible_Representation
(Target_Typ, Operand_Typ : Entity_Id) return Boolean;
-- Given an explicit or implicit conversion from Operand_Typ to Target_Typ,
-- determine whether the types have compatible or different representation,
-- thus requiring special processing for the conversion in the latter case.
-- A False result is possible only for array, enumeration and record types.
procedure Parse_Aspect_Aggregate
(N : Node_Id;
Empty_Subp : in out Node_Id;
Add_Named_Subp : in out Node_Id;
Add_Unnamed_Subp : in out Node_Id;
New_Indexed_Subp : in out Node_Id;
Assign_Indexed_Subp : in out Node_Id);
-- Utility to unpack the subprograms in an occurrence of aspect Aggregate;
-- used to verify the structure of the aspect, and resolve and expand an
-- aggregate for a container type that carries the aspect.
function Parse_Aspect_Stable_Properties
(Aspect_Spec : Node_Id; Negated : out Boolean) return Subprogram_List;
-- Utility to unpack the subprograms in a Stable_Properties list;
-- in the case of the aspect of a type, Negated will always be False.
function Rep_Item_Too_Early (T : Entity_Id; N : Node_Id) return Boolean;
-- Called at start of processing a representation clause/pragma. Used to
-- check that the representation item is not being applied to an incomplete
-- type or to a generic formal type or a type derived from a generic formal
-- type. Returns False if no such error occurs. If this error does occur,
-- appropriate error messages are posted on node N, and True is returned.
with procedure Replace_Type_Reference (N : Node_Id);
procedure Replace_Type_References_Generic (N : Node_Id; T : Entity_Id);
-- This is used to scan an expression for a predicate or invariant aspect
-- replacing occurrences of the name of the subtype to which the aspect
-- applies with appropriate references to the parameter of the predicate
-- function or invariant procedure. The procedure passed as a generic
-- parameter does the actual replacement of node N, which is either a
-- simple direct reference to T, or a selected component that represents
-- an appropriately qualified occurrence of T.
-- This also replaces each reference to a component, entry, or protected
-- procedure with a selected component whose prefix is the parameter.
-- For example, Component_Name becomes Parameter.Component_Name, where
-- Parameter is the parameter, which is of type T.
function Rep_Item_Too_Late
(T : Entity_Id;
N : Node_Id;
FOnly : Boolean := False) return Boolean;
-- Called at the start of processing a representation clause or a
-- representation pragma. Used to check that a representation item for
-- entity T does not appear too late (according to the rules in RM 13.1(9)
-- and RM 13.1(10)). N is the associated node, which in the pragma case
-- is the pragma or representation clause itself, used for placing error
-- messages if the item is too late.
-- FOnly is a flag that causes only the freezing rule (para 9) to be
-- applied, and the tests of para 10 are skipped. This is appropriate for
-- both subtype related attributes (Alignment and Size) and for stream
-- attributes, which, although certainly not subtype related attributes,
-- clearly should not be subject to the para 10 restrictions (see
-- AI95-00137). Similarly, we also skip the para 10 restrictions for
-- the Storage_Size case where they also clearly do not apply, and for
-- Stream_Convert which is in the same category as the stream attributes.
-- If the rep item is too late, an appropriate message is output and True
-- is returned, which is a signal that the caller should abandon processing
-- for the item. If the item is not too late, then False is returned, and
-- the caller can continue processing the item.
-- If no error is detected, this call also as a side effect links the
-- representation item onto the head of the representation item chain
-- (referenced by the First_Rep_Item field of the entity).
-- Note: Rep_Item_Too_Late must be called with the underlying type in the
-- case of a private or incomplete type. The protocol is to first check for
-- Rep_Item_Too_Early using the initial entity, then take the underlying
-- type, then call Rep_Item_Too_Late on the result.
-- Note: Calls to Rep_Item_Too_Late are ignored for the case of attribute
-- definition clauses which have From_Aspect_Specification set. This is
-- because such clauses are linked on to the Rep_Item chain in procedure
-- Sem_Ch13.Analyze_Aspect_Specifications. See that procedure for details.
procedure Validate_Unchecked_Conversion
(N : Node_Id;
Act_Unit : Entity_Id);
-- Validate a call to unchecked conversion. N is the node for the actual
-- instantiation, which is used only for error messages. Act_Unit is the
-- entity for the instantiation, from which the actual types etc. for this
-- instantiation can be determined. This procedure makes an entry in a
-- table and/or generates an N_Validate_Unchecked_Conversion node. The
-- actual checking is done in Validate_Unchecked_Conversions or in the
-- back end as required.
procedure Validate_Unchecked_Conversions;
-- This routine is called after calling the back end to validate unchecked
-- conversions for size and alignment appropriateness. The reason it is
-- called that late is to take advantage of any back-annotation of size
-- and alignment performed by the back end.
procedure Validate_Address_Clauses;
-- This is called after the back end has been called (and thus after the
-- alignments of objects have been back annotated). It goes through the
-- table of saved address clauses checking for suspicious alignments and
-- if necessary issuing warnings.
-- Handling of Aspect Visibility --
-- The visibility of aspects is tricky. First, the visibility is delayed
-- to the freeze point. This is not too complicated, what we do is simply
-- to leave the aspect "laying in wait" for the freeze point, and at that
-- point materialize and analyze the corresponding attribute definition
-- clause or pragma. There is some special processing for preconditions
-- and postonditions, where the pragmas themselves deal with the required
-- delay, but basically the approach is the same, delay analysis of the
-- expression to the freeze point.
-- Much harder is the requirement for diagnosing cases in which an early
-- freeze causes a change in visibility. Consider:
-- package AspectVis is
-- R_Size : constant Integer := 32;
-- package Inner is
-- type R is new Integer with
-- Size => R_Size;
-- F : R; -- freezes
-- R_Size : constant Integer := 64;
-- S : constant Integer := R'Size; -- 32 not 64
-- end Inner;
-- end AspectVis;
-- Here the 32 not 64 shows what would be expected if this program were
-- legal, since the evaluation of R_Size has to be done at the freeze
-- point and gets the outer definition not the inner one.
-- But the language rule requires this program to be diagnosed as illegal
-- because the visibility changes between the freeze point and the end of
-- the declarative region.
-- To meet this requirement, we first note that the Expression field of the
-- N_Aspect_Specification node holds the raw unanalyzed expression, which
-- will get used in processing the aspect. At the time of analyzing the
-- N_Aspect_Specification node, we create a complete copy of the expression
-- and store it in the entity field of the Identifier (an odd usage, but
-- the identifier is not used except to identify the aspect, so its Entity
-- field is otherwise unused, and we are short of room in the node).
-- This copy stays unanalyzed up to the freeze point, where we analyze the
-- resulting pragma or attribute definition clause, except that in the
-- case of invariants and predicates, we mark occurrences of the subtype
-- name as having the entity of the subprogram parameter, so that they
-- will not cause trouble in the following steps.
-- Then at the freeze point, we create another copy of this unanalyzed
-- expression. By this time we no longer need the Expression field for
-- other purposes, so we can store it there. Now we have two copies of
-- the original unanalyzed expression. One of them gets preanalyzed at
-- the freeze point to capture the visibility at the freeze point.
-- Now when we hit the freeze all at the end of the declarative part, if
-- we come across a frozen entity with delayed aspects, we still have one
-- copy of the unanalyzed expression available in the node, and we again
-- do a preanalysis using that copy and the visibility at the end of the
-- declarative part. Now we have two preanalyzed expression (preanalysis
-- is good enough, since we are only interested in referenced entities).
-- One captures the visibility at the freeze point, the other captures the
-- visibility at the end of the declarative part. We see if the entities
-- in these two expressions are the same, by seeing if the two expressions
-- are fully conformant, and if not, issue appropriate error messages.
-- Quite an awkward approach, but this is an awkard requirement
procedure Analyze_Aspects_At_Freeze_Point (E : Entity_Id);
-- Analyze all the delayed aspects for entity E at freezing point. This
-- includes dealing with inheriting delayed aspects from the parent type
-- in the case where a derived type is frozen.
procedure Check_Aspect_At_Freeze_Point (ASN : Node_Id);
-- Performs the processing described above at the freeze point, ASN is the
-- N_Aspect_Specification node for the aspect.
procedure Check_Aspect_At_End_Of_Declarations (ASN : Node_Id);
-- Performs the processing described above at the freeze all point, and
-- issues appropriate error messages if the visibility has indeed changed.
-- Again, ASN is the N_Aspect_Specification node for the aspect.
procedure Inherit_Aspects_At_Freeze_Point (Typ : Entity_Id);
-- Given an entity Typ that denotes a derived type or a subtype, this
-- routine performs the inheritance of aspects at the freeze point.
-- ??? Note that, for now, just a limited number of representation aspects
-- have been inherited here so far. Many of them are still inherited in
-- Sem_Ch3 and need to be dealt with. Here is a non-exhaustive list of
-- aspects that likely also need to be moved to this routine: Alignment,
-- Component_Alignment, Component_Size, Machine_Radix, Object_Size, Pack,
-- Predicates, Preelaborable_Initialization, Size and Small.
procedure Inherit_Delayed_Rep_Aspects (Typ : Entity_Id);
-- As discussed in the spec of Aspects (see Aspect_Delay declaration),
-- a derived type can inherit aspects from its parent which have been
-- specified at the time of the derivation using an aspect, as in:
-- type A is range 1 .. 10
-- with Size => Not_Defined_Yet;
-- ..
-- type B is new A;
-- ..
-- Not_Defined_Yet : constant := 64;
-- In this example, the Size of A is considered to be specified prior
-- to the derivation, and thus inherited, even though the value is not
-- known at the time of derivation. To deal with this, we use two entity
-- flags. The flag Has_Derived_Rep_Aspects is set in the parent type (A
-- here), and then the flag May_Inherit_Delayed_Rep_Aspects is set in
-- the derived type (B here). If this flag is set when the derived type
-- is frozen, then this procedure is called to ensure proper inheritance
-- of all delayed aspects from the parent type.
-- ??? Obviously we ought not to have two mechanisms to do the same thing
procedure Resolve_Aspect_Expressions (E : Entity_Id);
-- Name resolution of an aspect expression happens at the end of the
-- current declarative part or at the freeze point for the entity,
-- whichever comes first. For declarations in the visible part of a
-- package, name resolution takes place before analysis of the private
-- part even though the freeze point of the entity may appear later.
procedure Validate_Iterable_Aspect (Typ : Entity_Id; ASN : Node_Id);
-- For SPARK 2014 formal containers. The expression has the form of an
-- aggregate, and each entry must denote a function with the proper syntax
-- for First, Next, and Has_Element. Optionally an Element primitive may
-- also be defined.
procedure Validate_Literal_Aspect (Typ : Entity_Id; ASN : Node_Id);
-- Check legality of Integer_Literal, Real_Literal, and String_Literal
-- aspect specifications.
procedure Install_Discriminants (E : Entity_Id);
-- Make visible the discriminants of type entity E
procedure Uninstall_Discriminants (E : Entity_Id);
-- Remove visibility to the discriminants of type entity E
end Sem_Ch13;