| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S E M _ C H 1 3 -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1992-2014, 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 -- |
| -- http://www.gnu.org/licenses 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 Table; |
| with Types; use Types; |
| with Uintp; use Uintp; |
| |
| package Sem_Ch13 is |
| 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 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. Adjusts |
| -- component positions according to either Ada 95 or Ada 2005 (AI-133). |
| |
| function Build_Invariant_Procedure_Declaration |
| (Typ : Entity_Id) return Node_Id; |
| -- If a type declaration has a specified invariant aspect, build the |
| -- declaration for the procedure at once, so that calls to it can be |
| -- generated before the body of the invariant procedure is built. This |
| -- is needed in the presence of public expression functions that return |
| -- the type in question. |
| |
| procedure Build_Invariant_Procedure (Typ : Entity_Id; N : Node_Id); |
| -- Typ is a private type with invariants (indicated by Has_Invariants being |
| -- set for Typ, indicating the presence of pragma Invariant entries on the |
| -- rep chain, note that Invariant aspects have already been converted to |
| -- pragma Invariant), then this procedure builds the spec and body for the |
| -- corresponding Invariant procedure, inserting them at appropriate points |
| -- in the package specification N. Invariant_Procedure is set for Typ. Note |
| -- that this procedure is called at the end of processing the declarations |
| -- in the visible part (i.e. the right point for visibility analysis of |
| -- the invariant expression). |
| |
| 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. |
| |
| function Minimum_Size |
| (T : Entity_Id; |
| Biased : Boolean := False) return Nat; |
| -- 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 0. |
| |
| 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 other non-elementary 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. |
| -- If the size is too small, and an error message is given, then both |
| -- Esize and RM_Size are reset to the allowed minimum value in T. |
| |
| 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. |
| |
| generic |
| 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. |
| |
| 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. |
| |
| function Same_Representation (Typ1, Typ2 : Entity_Id) return Boolean; |
| -- Given two types, where the two types are related by possible derivation, |
| -- determines if the two types have the same representation, or different |
| -- representations, requiring the special processing for representation |
| -- change. A False result is possible only for array, enumeration or |
| -- record types. |
| |
| 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 backend 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 backend. |
| |
| 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. |
| |
| procedure Validate_Independence; |
| -- This is called after the back end has been called (and thus after the |
| -- layout of components has been back annotated). It goes through the |
| -- table of saved pragma Independent[_Component] entries, checking that |
| -- independence can be achieved, and if necessary issuing error messages. |
| |
| ------------------------------------- |
| -- Table for Validate_Independence -- |
| ------------------------------------- |
| |
| -- If a legal pragma Independent or Independent_Components is given for |
| -- an entity, then an entry is made in this table, to be checked by a |
| -- call to Validate_Independence after back annotation of layout is done. |
| |
| type Independence_Check_Record is record |
| N : Node_Id; |
| -- The pragma Independent or Independent_Components |
| |
| E : Entity_Id; |
| -- The entity to which it applies |
| end record; |
| |
| package Independence_Checks is new Table.Table ( |
| Table_Component_Type => Independence_Check_Record, |
| Table_Index_Type => Int, |
| Table_Low_Bound => 1, |
| Table_Initial => 20, |
| Table_Increment => 200, |
| Table_Name => "Independence_Checks"); |
| |
| ----------------------------------- |
| -- 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. |
| |
| 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. |
| |
| ----------------------------------------------------------- |
| -- Visibility of Discriminants in Aspect Specifications -- |
| ----------------------------------------------------------- |
| |
| -- The discriminants of a type are visible when analyzing the aspect |
| -- specifications of a type declaration or protected type declaration, |
| -- but not when analyzing those of a subtype declaration. The following |
| -- routines enforce this distinction. |
| |
| procedure Install_Discriminants (E : Entity_Id); |
| -- Make visible the discriminants of type entity E |
| |
| procedure Push_Scope_And_Install_Discriminants (E : Entity_Id); |
| -- Push scope E and makes visible the discriminants of type entity E if E |
| -- has discriminants and is not a subtype. |
| |
| procedure Uninstall_Discriminants (E : Entity_Id); |
| -- Remove visibility to the discriminants of type entity E |
| |
| procedure Uninstall_Discriminants_And_Pop_Scope (E : Entity_Id); |
| -- Remove visibility to the discriminants of type entity E and pop the |
| -- scope stack if E has discriminants and is not a subtype. |
| |
| end Sem_Ch13; |
