GNAT implemented this pragma before it was part of the standard, and a left-
over of this early implementation is the requirement that discriminants of
an unchecked_union type all must have defaults. This is not a legality rule
imposed by the Ada RM, and this patch removes it.
Tested on x86_64-pc-linux-gnu, committed on trunk
2012-11-06 Ed Schonberg <schonb...@adacore.com>
* sem_prag.adb (Analyze_Pragnma, case Unchecked_Union): remove
requirement that discriminants of an unchecked_union must have
defaults. Uncovered by discussion on LA12-042.
Index: sem_prag.adb
===================================================================
--- sem_prag.adb (revision 193217)
+++ sem_prag.adb (working copy)
@@ -14495,7 +14495,6 @@
Assoc : constant Node_Id := Arg1;
Type_Id : constant Node_Id := Get_Pragma_Arg (Assoc);
Typ : Entity_Id;
- Discr : Entity_Id;
Tdef : Node_Id;
Clist : Node_Id;
Vpart : Node_Id;
@@ -14546,21 +14545,12 @@
-- Note: in previous versions of GNAT we used to check for limited
-- types and give an error, but in fact the standard does allow
-- Unchecked_Union on limited types, so this check was removed.
+ -- Similarly, GNAT used to require that all discriminants have
+ -- default values, but this is not mandated by the RM.
-- Proceed with basic error checks completed
else
- Discr := First_Discriminant (Typ);
- while Present (Discr) loop
- if No (Discriminant_Default_Value (Discr)) then
- Error_Msg_N
- ("unchecked union discriminant must have default value",
- Discr);
- end if;
-
- Next_Discriminant (Discr);
- end loop;
-
Tdef := Type_Definition (Declaration_Node (Typ));
Clist := Component_List (Tdef);
