1 files changed, 20 insertions, 1 deletions
diff --git a/translate/grt/grt-stacks.ads b/translate/grt/grt-stacks.ads
index 920012c..30b9f05 100644
--- a/translate/grt/grt-stacks.ads
+++ b/translate/grt/grt-stacks.ads
@@ -16,8 +16,24 @@
 --  Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 --  02111-1307, USA.
 with System; use System;
+with Ada.Unchecked_Conversion;
 
 package Grt.Stacks is
+   --  Instance is the parameter of the process procedure.
+   --  This is in fact a fully opaque type whose content is private to the
+   --  process.
+   type Instance is limited private;
+   type Instance_Acc is access all Instance;
+   pragma Convention (C, Instance_Acc);
+
+   --  A process is identified by a procedure having a single private
+   --  parameter (its instance).
+   type Proc_Acc is access procedure (Self : Instance_Acc);
+   pragma Convention (C, Proc_Acc);
+
+   function To_Address is new Ada.Unchecked_Conversion
+     (Instance_Acc, System.Address);
+
    type Stack_Type is new Address;
    Null_Stack : constant Stack_Type := Stack_Type (Null_Address);
 
@@ -28,7 +44,8 @@ package Grt.Stacks is
 
    --  Create a new stack, which on first execution will call FUNC with
    --  an argument ARG.
-   function Stack_Create (Func : Address; Arg : Address) return Stack_Type;
+   function Stack_Create (Func : Proc_Acc; Arg : Instance_Acc)
+                         return Stack_Type;
 
    --  Resume stack TO and save the current context to the stack pointed by
    --  CUR.
@@ -50,6 +67,8 @@ package Grt.Stacks is
    procedure Error_Null_Access;
    pragma No_Return (Error_Null_Access);
 private
+   type Instance is null record;
+
    pragma Import (C, Stack_Init, "grt_stack_init");
    pragma Import (C, Stack_Create, "grt_stack_create");
    pragma Import (C, Stack_Switch, "grt_stack_switch");