------------------------------------------
procedure Check_Return_Construct_Accessibility (Return_Stmt : Node_Id) is
- Return_Con : Node_Id;
- Assoc : Node_Id := Empty;
- Assoc_Expr : Node_Id;
- Disc : Entity_Id;
+
+ function First_Selector (Assoc : Node_Id) return Node_Id;
+ -- Obtain the first selector or choice from a given association
+
+ --------------------
+ -- First_Selector --
+ --------------------
+
+ function First_Selector (Assoc : Node_Id) return Node_Id is
+ begin
+ if Nkind (Assoc) = N_Component_Association then
+ return First (Choices (Assoc));
+
+ elsif Nkind (Assoc) = N_Discriminant_Association then
+ return (First (Selector_Names (Assoc)));
+
+ else
+ raise Program_Error;
+ end if;
+ end First_Selector;
+
+ -- Local declarations
+
+ Assoc : Node_Id := Empty;
+ -- Assoc should perhaps be renamed and declared as a
+ -- Node_Or_Entity_Id since it encompasses not only component and
+ -- discriminant associations, but also discriminant components within
+ -- a type declaration or subtype indication ???
+
+ Assoc_Expr : Node_Id;
+ Assoc_Present : Boolean := False;
+
+ Unseen_Disc_Count : Nat := 0;
+ Seen_Discs : Elist_Id;
+ Disc : Entity_Id;
+ First_Disc : Entity_Id;
+
Obj_Decl : Node_Id;
+ Return_Con : Node_Id;
Unqual : Node_Id;
+ -- Start of processing for Check_Return_Construct_Accessibility
+
begin
-- Only perform checks on record types with access discriminants and
-- non-internally generated functions.
Unqual := Unqualify (Original_Node (Return_Con));
- -- Obtain the corresponding declaration based on the return object's
+ -- Get the corresponding declaration based on the return object's
-- identifier.
if Nkind (Unqual) = N_Identifier
(Etype (Defining_Identifier (Obj_Decl)));
end if;
+ -- Preserve the first discriminant for checking named associations
+
+ First_Disc := Disc;
+
+ -- Count the number of discriminants for processing an aggregate
+ -- which includes an others.
+
+ Disc := First_Disc;
+ while Present (Disc) loop
+ Unseen_Disc_Count := Unseen_Disc_Count + 1;
+
+ Next_Discriminant (Disc);
+ end loop;
+
+ Seen_Discs := New_Elmt_List;
+
-- Loop through each of the discriminants and check each expression
-- associated with an anonymous access discriminant.
- while Present (Assoc) and then Present (Disc) loop
- -- Unwrap the associated expression
+ -- When named associations occur in the return aggregate then
+ -- discriminants can be in any order, so we need to ensure we do
+ -- not continue to loop when all discriminants have been seen.
+
+ Disc := First_Disc;
+ while Present (Assoc)
+ and then (Present (Disc) or else Assoc_Present)
+ and then Unseen_Disc_Count > 0
+ loop
+ -- Handle named associations by searching through the names of
+ -- the relevant discriminant components.
if Nkind (Assoc)
in N_Component_Association | N_Discriminant_Association
then
- Assoc_Expr := Expression (Assoc);
+ Assoc_Expr := Expression (Assoc);
+ Assoc_Present := True;
+
+ -- We currently don't handle box initialized discriminants,
+ -- however, since default initialized anonymous access
+ -- discriminants are a corner case, this is ok for now ???
+
+ if Nkind (Assoc) = N_Component_Association
+ and then Box_Present (Assoc)
+ then
+ Assoc_Present := False;
+
+ if Nkind (First_Selector (Assoc)) = N_Others_Choice then
+ Unseen_Disc_Count := 0;
+ end if;
+
+ -- When others is present we must identify a discriminant we
+ -- haven't already seen so as to get the appropriate type for
+ -- the static accessibility check.
+
+ -- This works because all components within an others clause
+ -- must have the same type.
+
+ elsif Nkind (First_Selector (Assoc)) = N_Others_Choice then
+
+ Disc := First_Disc;
+ Outer : while Present (Disc) loop
+ declare
+ Current_Seen_Disc : Elmt_Id;
+ begin
+ -- Move through the list of identified discriminants
+
+ Current_Seen_Disc := First_Elmt (Seen_Discs);
+ while Present (Current_Seen_Disc) loop
+ -- Exit the loop when we found a match
+
+ exit when
+ Chars (Node (Current_Seen_Disc)) = Chars (Disc);
+
+ Next_Elmt (Current_Seen_Disc);
+ end loop;
+
+ -- When we have exited the above loop without finding
+ -- a match then we know that Disc has not been seen.
+
+ exit Outer when No (Current_Seen_Disc);
+ end;
+
+ Next_Discriminant (Disc);
+ end loop Outer;
+
+ -- If we got to an others clause with a non-zero
+ -- discriminant count there must be a discriminant left to
+ -- check.
+
+ pragma Assert (Present (Disc));
+
+ -- Set the unseen discriminant count to zero because we know
+ -- an others clause sets all remaining components of an
+ -- aggregate.
+
+ Unseen_Disc_Count := 0;
+
+ -- Move through each of the selectors in the named association
+ -- and obtain a discriminant for accessibility checking if one
+ -- is referenced in the list. Also track which discriminants
+ -- are referenced for the purpose of handling an others clause.
+
+ else
+ declare
+ Assoc_Choice : Node_Id;
+ Curr_Disc : Node_Id;
+ begin
+
+ Disc := Empty;
+ Curr_Disc := First_Disc;
+ while Present (Curr_Disc) loop
+ -- Check each of the choices in the associations for a
+ -- match to the name of the current discriminant.
+
+ Assoc_Choice := First_Selector (Assoc);
+ while Present (Assoc_Choice) loop
+ -- When the name matches we track that we have seen
+ -- the discriminant, but instead of exiting the
+ -- loop we continue iterating to make sure all the
+ -- discriminants within the named association get
+ -- tracked.
+
+ if Chars (Assoc_Choice) = Chars (Curr_Disc) then
+ Append_Elmt (Curr_Disc, Seen_Discs);
+
+ Disc := Curr_Disc;
+ Unseen_Disc_Count := Unseen_Disc_Count - 1;
+ end if;
+
+ Next (Assoc_Choice);
+ end loop;
+
+ Next_Discriminant (Curr_Disc);
+ end loop;
+ end;
+ end if;
+
+ -- Unwrap the associated expression if we are looking at a default
+ -- initialized type declaration. In this case Assoc is not really
+ -- an association, but a component declaration. Should Assoc be
+ -- renamed in some way to be more clear ???
+
+ -- This occurs when the return object does not initialize
+ -- discriminant and instead relies on the type declaration for
+ -- their supplied values.
elsif Nkind (Assoc) in N_Entity
and then Ekind (Assoc) = E_Discriminant
then
- Assoc_Expr := Discriminant_Default_Value (Assoc);
+ Append_Elmt (Disc, Seen_Discs);
+
+ Assoc_Expr := Discriminant_Default_Value (Assoc);
+ Unseen_Disc_Count := Unseen_Disc_Count - 1;
+
+ -- Otherwise, there is nothing to do because Assoc is an
+ -- expression within the return aggregate itself.
else
- Assoc_Expr := Assoc;
+ Append_Elmt (Disc, Seen_Discs);
+
+ Assoc_Expr := Assoc;
+ Unseen_Disc_Count := Unseen_Disc_Count - 1;
end if;
-- Check the accessibility level of the expression when the
-- discriminant is of an anonymous access type.
if Present (Assoc_Expr)
+ and then Present (Disc)
and then Ekind (Etype (Disc)) = E_Anonymous_Access_Type
then
-- Perform a static check first, if possible
Error_Msg_N
("access discriminant in return object would be a dangling"
& " reference", Return_Stmt);
- exit;
+ exit;
end if;
-- Otherwise, generate a dynamic check based on the extra
end if;
end if;
- -- Iterate over the discriminants
+ -- Iterate over the discriminants, except when we have encountered
+ -- a named association since the discriminant order becomes
+ -- irrelevant in that case.
+
+ if not Assoc_Present then
+ Next_Discriminant (Disc);
+ end if;
+
+ -- Iterate over associations
- Disc := Next_Discriminant (Disc);
if not Is_List_Member (Assoc) then
exit;
else
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