[Ada] Generalizing support for interfacing with C++

[Arnaud Charlet <charlet at adacore dot com>]

Tested on i686-linux, committed on trunk

In some platforms the ABI allows the slots of the dispatch tables
to contain descriptors (instead of just address to subprograms).
This patch incorporates the required support in the compiler to
handle these platforms. The following test compiles and executes
without errors:
--
package Ada_Root is
   type Object_Type is tagged null record;
   pragma Convention(Cpp, Object_Type);
   type Class_Ptr_Type is access all Object_Type'class;
   procedure Execute(X : in out Object_Type);
   pragma Convention (Cpp, Execute);
   procedure Do_Initialize(X : in out Object_Type);
end;
package body Ada_Root is
   function Create return Class_Ptr_Type;
   pragma Export(C, Create, "create_ada_model");
   function Create return Class_Ptr_Type is
   begin
      return new Object_Type;
   end;
   procedure Execute (X : in out Object_Type) is
      Y : Object_Type'class renames Object_Type'class(X);
   begin
      Y.Do_Initialize;
   end;
   procedure Do_Initialize(X : in out Object_Type) is
   begin
      null;
   end;
end;
--
// File: cpp_root.h
#include <iomanip>
#include <iostream>
class Common_root {
public:
   virtual void execute() = 0;
   Common_root();
   int          state;
};
--
// File: cpp_main.cpp
#include <iostream>
#include <dlfcn.h>
#include "cpp_root.h"
using namespace std;
extern "C" {
  void adainit (void);
  void adafinal (void);
  Common_root* create_ada_model();
}
--
int call_dispatcher() {
   Common_root* ada_model = (*create_ada_model)();
   if(ada_model == 0) {return -1;}
   ada_model->execute();
   return 0;
}
--
int main() {
 adainit ();
 call_dispatcher();
 adafinal ();
 return 0;
}

2008-04-08  Javier Miranda  <miranda@adacore.com>
	    Robert Dewar  <dewar@adacore.com>
	    Ed Schonberg  <schonberg@adacore.com>

	* a-tags.adb (Register_Interface_Offset): New subprogram.
	(Set_Dynamic_Offset_To_Top): New subprogram (see previous comment).
	(To_Predef_Prims_Table_Ptr): Removed.
	(Acc_Size): Removed.
	(To_Acc_Size): Removed.
	(Parent_Size): Modified to the call the subprogram returning the size of
	the parent by means of the new TSD component Size_Func.

	* a-tags.ads (Offset_To_Top_Ptr): New access type declaration.
	(DT_Offset_To_Top_Offset): New constant value that is used to generate
	code referencing the Offset_To_Top component of the dispatch table's
	prologue.
	(Prim_Ptr): New declaration of access to procedure. Used to avoid the
	use of 'address to initialize dispatch table slots.
	(Size_Func): New component of the TSD. Used by the run-time to call the
	size primitive of the tagged type.

	* checks.adb (Apply_Access_Check): Avoid check when accessing the
	Offset_To_Top component of a dispatch table.
	(Null_Exclusion_Static_Checks): If the non-null access type appears in a
	deferred constant declaration. do not add a null expression, to prevent
	spurious errors when full declaration is analyzed.
	(Apply_Discriminant_Check): If both discriminant constraints share a
	node which is not static but has no side effects, do not generate a
	check for that discriminant.
	(Generate_Index_Checks): Set Name_Req to true in call to duplicate
	subexpr, since the prefix of an attribute is a name.

	* checks.ads: Fix nit in comment.

	* exp_ch3.ads, exp_ch3.adb (Freeze_Record_Type): Do not add the spec
	and body of predefined primitives in case of CPP tagged type
	derivations.
	(Freeze_Type): Deal properly with no storage pool case
	(Make_Predefined_Primitive_Specs): Generate specification of abstract
	primitive Deep_Adjust if a nonlimited interface is derived from a
	limited interface.
	(Build_Dcheck_Functions): Create discriminant-checking functions only
	for variants that have some component(s).
	(Build_Slice_Assignment): In expanded code for slice assignment, handle
	properly the case where the slice bounds extend to the last value of the
	underlying representation.
	(Get_Simple_Init_Val): New calling sequence, accomodate Invalid_Value
	(Is_Variable_Size_Record): An array component has a static size if
	index bounds are enumeration literals.

	* exp_disp.adb (Make_DT): Use the first subtype to determine whether
	an external tag has been specified for the type.
	(Building_Static_DT): Add missing support for private types.
	(Make_DT): Add declaration of Parent_Typ to ensure consistent access
	to the entity associated with the parent of Typ. This is done to
	avoid wrong access when the parent is a private type.
	(Expand_Interface_Conversion): Improve error message when the
	configurable runtime has no support for dynamic interface conversion.
	(Expand_Interface_Thunk): Add missing support to interface types in
	configurable runtime.
	(Expand_Dispatching_Call): remove obsolete code.
	(Make_DT): Replace occurrences of RE_Address by RE_Prim_Ptr, and
	ensure that all subtypes and aggregates associated with dispatch
	tables have the attribute Is_Dispatch_Table_Entity set to true.
	(Register_Primitive): Rename one variable to improve code reading.
	Replace occurrences of RE_Addres by RE_Prim_Ptr. Register copy o
	of the pointer to the 'size primitive in the TSD.

	* rtsfind.ads (RE_DT_Offset_To_Top_Offset): New entity.
	(RE_Offset_To_Top_Ptr): New entity.
	(RE_Register_Interface_Offset): New entity.
	(RE_Set_Dynamic_Offset_To_Top): New entity.
	(RE_Set_Offset_To_Top): Removed entity.
	(RE_Prim_Ptr): New entity
	(RE_Size_Func): New entity
	(RE_Size_Ptr): New entity
	(RTU_Id): Add Ada_Dispatching and Ada_Dispatching_EDF.
	(Ada_Dispatching_Child): Define this new subrange.
	(RE_Id): Add new required run-time calls (RE_Set_Deadline, RE_Clock,
	 RE_Time_Span, and RE_Time_Span_Zero).
	(RE_Unit_Table): Add new required run-time calls

	* rtsfind.adb (Get_Unit_Name): Add processing for Ada.Dispatching
	children.

	* exp_atag.ads, exp_atag.adb (Build_Offset_To_Top): New subprogram.
	(Build_Set_Static_Offset_To_Top): New subprogram. Generates code that
	 initializes the Offset_To_Top component of a dispatch table.
	(Build_Predef_Prims): Removed.
	(Build_Get_Predefined_Prim_Op_Address): Replace call to Predef_Prims by
	 its actual code.
	(Build_Set_Size_Function): New subprogram.

	* exp_ch13.adb: Do not generate storage variable for storage_size zero
	(Expand): Handle setting/restoring flag Inside_Freezing_Actions

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