ada: Fix wrong finalization of aliased array of bounded vector

The problem is that Apply_Discriminant_Check introduces an unnecessary
temporary for an assignment where both sides have the same constrained
subtype but the left-hand side is an aliased component.

This comes from an approximation in the implementation introduced long
time ago to deal with aliased unconstrained objects in Ada 95, more
specifically to still generate a check when both sides have the same
unconstrained subtype in this case; it is replaced by an explicit test
that the common subtype is constrained.

gcc/ada/ChangeLog:

	* checks.adb (Apply_Discriminant_Check): Remove undocumented test
	on Is_Aliased_View applied to the left-hand side to skip the check
	in the case where the subtypes are the same, and replace it with a
	test that the subtypes are constrained.

diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb
index 6a98292d1cc163f09a786bfe2955a066b961664a..1b1ff4c5ea5b30da428a8ebc98a8903aad89b2f8 100644 (file)
--- a/gcc/ada/checks.adb
+++ b/gcc/ada/checks.adb
@@ -1539,21 +1539,18 @@ package body Checks is
          return;
       end if;
 
-      --  Suppress checks if the subtypes are the same. The check must be
-      --  preserved in an assignment to a formal, because the constraint is
-      --  given by the actual.
+      --  Suppress checks if the subtypes are the same and constrained. The
+      --  check must be preserved in an assignment to a formal, because the
+      --  constraint is given by the actual.
 
       if Nkind (Original_Node (N)) /= N_Allocator
+        and then (if Do_Access then Designated_Type (Typ) else Typ) = S_Typ
+        and then Is_Constrained (S_Typ)
         and then (No (Lhs)
                    or else not Is_Entity_Name (Lhs)
                    or else No (Param_Entity (Lhs)))
       then
-         if (Etype (N) = Typ
-              or else (Do_Access and then Designated_Type (Typ) = S_Typ))
-           and then (No (Lhs) or else not Is_Aliased_View (Lhs))
-         then
-            return;
-         end if;
+         return;
 
       --  We can also eliminate checks on allocators with a subtype mark that
       --  coincides with the context type. The context type may be a subtype