[Ada] Ada/C++ missing call to constructor with defaults

[Arnaud Charlet <charlet at adacore dot com>]

When the type of an object is a CPP type and the object initialization
requires calling its default C++ constructor, the Ada compiler did not
generate the call to a C++ constructor which has all parameters with
defaults (and hence it covers the default C++ constructor). The
following test must now compile and execute well.

// c_class.h
class Tester {
  public:
    Tester(unsigned int a_num = 5, char* a_className = 0);
    virtual int dummy();
};

// c_class.cc
#include "c_class.h"
#include <iostream>

Tester::Tester(unsigned int a_num, char* a_className) {
  std::cout << " ctor Tester called " << a_num << ":";

  if (a_className == 0) {
     std::cout << "null";
  }

  std::cout << std::endl;
}

int Tester::dummy() {
}

--  c_class_h.ads
pragma Ada_2005;
pragma Style_Checks (Off);

with Interfaces.C; use Interfaces.C;
with Interfaces.C.Strings;

package c_class_h is

   package Class_Tester is
      type Tester is tagged limited record
         null;
      end record;
      pragma Import (CPP, Tester);

      function New_Tester
        (a_num : unsigned := 5;
         a_className : Interfaces.C.Strings.chars_ptr
                         := Interfaces.C.Strings.Null_Ptr)
         return Tester;
      pragma CPP_Constructor (New_Tester, "_ZN6TesterC1EjPc");

      function dummy (this : access Tester) return int;
      pragma Import (CPP, dummy, "_ZN6Tester5dummyEv");
   end;
   use Class_Tester;
end c_class_h;


--  main.adb
with c_class_h; use c_class_h;
procedure Main is
   use Class_Tester;

   Obj : Tester;                 --  Test
   pragma Unreferenced (Obj);
begin
   null;
end main;


project Ada2Cppc is
   for Languages use ("Ada", "C++");
   for Main use ("main.adb");

   package Naming is
     for Implementation_Suffix ("C++") use ".cc";
   end Naming;

   for Source_Dirs use (".");
   for Object_Dir use "obj";

   package Compiler is
      for Default_Switches ("ada") use ("-gnat05");
   end Compiler;

   package Builder is
      for Default_Switches ("ada") use ("-g");
   end Builder;

   package Ide is
      for Compiler_Command ("ada") use "gnatmake";
      for Compiler_Command ("c") use "gcc";
   end Ide;

end Ada2Cppc;

Command:
  mkdir obj
  gprclean -q -P ada2cppc.gpr
  gprbuild -q -P ada2cppc.gpr
  obj/main

Output:
 ctor Tester called 5:null

Tested on x86_64-pc-linux-gnu, committed on trunk

2012-10-02  Javier Miranda  <miranda@adacore.com>

	* exp_disp.adb (Set_CPP_Constructors): Handle constructor with default
	parameters that covers the default constructor.

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