[COMMITTED] ada: Fix too small secondary stack allocation for returned aggregate

["Marc Poulhiès" <poulhies@adacore.com>]

From: Eric Botcazou <ebotcazou@adacore.com>

This restores the specific treatment of aggregates that are returned through
an extended return statement in a function returning a class-wide type, and
which was incorrectly dropped in an earlier change.

gcc/ada/

	* exp_ch3.adb (Make_Allocator_For_Return): Deal again specifically
	with an aggregate returned through an object of a class-wide type.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/exp_ch3.adb | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/exp_ch3.adb b/gcc/ada/exp_ch3.adb
index fbedc16ddd0..778eed7f16e 100644
--- a/gcc/ada/exp_ch3.adb
+++ b/gcc/ada/exp_ch3.adb
@@ -7167,9 +7167,20 @@ package body Exp_Ch3 is
                     Expression   => Alloc_Expr));
 
          else
-            Alloc :=
-              Make_Allocator (Loc,
-                Expression => New_Occurrence_Of (Typ, Loc));
+            --  If the return object is of a class-wide type, we cannot use
+            --  its type for the allocator. Instead we use the type of the
+            --  expression, which must be an aggregate of a definite type.
+
+            if Is_Class_Wide_Type (Typ) then
+               Alloc :=
+                 Make_Allocator (Loc,
+                   Expression => New_Occurrence_Of (Etype (Expr), Loc));
+
+            else
+               Alloc :=
+                 Make_Allocator (Loc,
+                   Expression => New_Occurrence_Of (Typ, Loc));
+            end if;
 
             --  If the return object requires default initialization, then it
             --  will happen later following the elaboration of the renaming.
-- 
2.40.0