+2019-12-13 Steve Baird <baird@adacore.com>
+
+ * einfo.ads: Correct comment for Derived_Type_Link to reflect
+ that fact that this function is now used for more than just
+ generation of warnings.
+ * sem_ch3.adb (Build_Derived_Type): Do not call
+ Set_Derived_Type_Link if the derived type and the parent type
+ are in different compilation units. Such a derivation cannot be
+ a problematic "early" derivation (identifying these is what the
+ Derived_Type_Link attribute is used for) and we don't like
+ inter-unit references that go in the opposite direction of
+ semantic dependencies.
+ * sem_ch13.adb (Is_Type_Related_Rep_Item): A new function,
+ analogous to the existing function Is_Operational_Item.
+ (Rep_Item_Too_Late): Generate a hard error (with same text as
+ the warning that was previously being generated) if the
+ AI12-0109 legality rule is violated.
+
2019-12-13 Eric Botcazou <ebotcazou@adacore.com>
* doc/gnat_rm/implementation_defined_pragmas.rst: Minor tweak to
-- that do not specify a representation characteristic are operational
-- attributes.
+ function Is_Type_Related_Rep_Item (N : Node_Id) return Boolean;
+ -- Returns True for a representation clause/pragma that specifies a
+ -- type-related representation (as opposed to operational) aspect.
+
function Is_Predicate_Static
(Expr : Node_Id;
Nam : Name_Id) return Boolean;
end if;
end Is_Predicate_Static;
+ ------------------------------
+ -- Is_Type_Related_Rep_Item --
+ ------------------------------
+
+ function Is_Type_Related_Rep_Item (N : Node_Id) return Boolean is
+ begin
+ case Nkind (N) is
+ when N_Attribute_Definition_Clause =>
+ declare
+ Id : constant Attribute_Id := Get_Attribute_Id (Chars (N));
+ -- See AARM 13.1(8.f-8.x) list items that end in "clause"
+ -- ???: include any GNAT-defined attributes here?
+ begin
+ return Id = Attribute_Component_Size
+ or else Id = Attribute_Bit_Order
+ or else Id = Attribute_Storage_Pool
+ or else Id = Attribute_Stream_Size
+ or else Id = Attribute_Machine_Radix;
+ end;
+
+ when N_Pragma =>
+ case Get_Pragma_Id (N) is
+ -- See AARM 13.1(8.f-8.x) list items that start with "pragma"
+ -- ???: include any GNAT-defined pragmas here?
+ when Pragma_Pack
+ | Pragma_Import
+ | Pragma_Export
+ | Pragma_Convention
+ | Pragma_Atomic
+ | Pragma_Independent
+ | Pragma_Volatile
+ | Pragma_Atomic_Components
+ | Pragma_Independent_Components
+ | Pragma_Volatile_Components
+ | Pragma_Discard_Names
+ =>
+ return True;
+ when others =>
+ null;
+ end case;
+
+ when N_Enumeration_Representation_Clause
+ | N_Record_Representation_Clause
+ =>
+ return True;
+
+ when others =>
+ null;
+ end case;
+
+ return False;
+ end Is_Type_Related_Rep_Item;
+
---------------------
-- Kill_Rep_Clause --
---------------------
end if;
-- No error, but one more warning to consider. The RM (surprisingly)
- -- allows this pattern:
+ -- allows this pattern in some cases:
-- type S is ...
-- primitive operations for S
-- Meaning that calls on the primitive operations of S for values of
-- type R may require possibly expensive implicit conversion operations.
- -- This is not an error, but is worth a warning.
+ -- So even when this is not an error, it is still worth a warning.
if not Relaxed_RM_Semantics and then Is_Type (T) then
declare
begin
if Present (DTL)
- and then Has_Primitive_Operations (Base_Type (T))
- -- For now, do not generate this warning for the case of aspect
- -- specification using Ada 2012 syntax, since we get wrong
- -- messages we do not understand. The whole business of derived
- -- types and rep items seems a bit confused when aspects are
- -- used, since the aspects are not evaluated till freeze time.
+ -- For now, do not generate this warning for the case of
+ -- aspect specification using Ada 2012 syntax, since we get
+ -- wrong messages we do not understand. The whole business
+ -- of derived types and rep items seems a bit confused when
+ -- aspects are used, since the aspects are not evaluated
+ -- till freeze time. However, AI12-0109 confirms (in an AARM
+ -- ramification) that inheritance in this case is required
+ -- to work.
and then not From_Aspect_Specification (N)
then
- Error_Msg_Sloc := Sloc (DTL);
- Error_Msg_N
- ("representation item for& appears after derived type "
- & "declaration#??", N);
- Error_Msg_NE
- ("\may result in implicit conversions for primitive "
- & "operations of&??", N, T);
- Error_Msg_NE
- ("\to change representations when called with arguments "
- & "of type&??", N, DTL);
+ if Is_By_Reference_Type (T)
+ and then not Is_Tagged_Type (T)
+ and then Is_Type_Related_Rep_Item (N)
+ and then (Ada_Version >= Ada_2012
+ or else Has_Primitive_Operations (Base_Type (T)))
+ then
+ -- Treat as hard error (AI12-0109, binding interpretation).
+ -- Implementing a change of representation is not really
+ -- an option in the case of a by-reference type, so we
+ -- take this path for all Ada dialects if primitive
+ -- operations are present.
+ Error_Msg_Sloc := Sloc (DTL);
+ Error_Msg_N
+ ("representation item for& appears after derived type "
+ & "declaration#", N);
+
+ elsif Has_Primitive_Operations (Base_Type (T)) then
+ Error_Msg_Sloc := Sloc (DTL);
+
+ Error_Msg_N
+ ("representation item for& appears after derived type "
+ & "declaration#??", N);
+ Error_Msg_NE
+ ("\may result in implicit conversions for primitive "
+ & "operations of&??", N, T);
+ Error_Msg_NE
+ ("\to change representations when called with arguments "
+ & "of type&??", N, DTL);
+ end if;
end if;
end;
end if;
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