Doubt w.r.t. to gfortran's interpretation of the Fortran2003 standard

["Alberto F. Martín Huertas" <amartin at cimne dot upc dot edu>]

Dear Fortran@gcc.gnu.org members,

I would like to know if the following Fortran2003 code snippet is 
compliant or not
with the Fortran2003 standard:

module overwrite
  type madre
   contains
     procedure :: sum => sum_madres
     generic   :: operator(+) => sum
  end type madre

  type, extends(madre) ::  hijo
contains
  procedure :: sum => sum_hijos_compliant
  generic   :: operator(+) => sum
end type hijo

contains

function sum_madres(op1,op2) result(res)
 implicit none
 class(madre), intent(in) :: op1, op2
 class(madre), pointer    :: res
 write(*,*) 'sum_madres'
end function sum_madres

function sum_hijos_compliant(op1,op2) result(res)
   implicit none
   class(hijo) , intent(in) :: op1
   class(madre), intent(in) :: op2
   class(madre), pointer    :: res
   write(*,*) 'sum_hijos'
end function

end module overwrite

program drive_ovw
  use overwrite
  implicit none

  type(madre) :: m1, m2
  class(madre), pointer :: mres
  type(hijo)  :: h1, h2
  class(madre), pointer :: hres

  mres => m1 + m2
  hres => h1 + m2
  hres => h1%sum(h2)

  !h1+h2
  !m1+h1
  !h1+m1
end program drive_ovw

When I compile it with either gfortran 4.8.1, or 4.9.1, I get the 
following compilation error:

gfortran -c -J Objects -g -O0 -fdefault-real-8 -g -fbacktrace 
-fbounds-check -std=f2003 -o Objects/overwrite.o overwrite.f90
overwrite.f90:12.29:

  generic   :: operator(+) => sum
                             1
Error: 'sum_hijos_compliant' and 'sum_madres' for GENERIC '+' at (1) are 
ambiguous

However, I can compile it with both the Intel and IBM fortran compilers, 
getting as output (as expected):

sum_madres
sum_hijos
sum_hijos

Thanks for your advice.
Best regards,
 Alberto.

--
Alberto F. Martín-Huertas
Centre Internacional de Mètodes Numèrics a l'Enginyeria (CIMNE)
Parc Mediterrani de la Tecnologia, UPC
Esteve Terradas 5, Building C3, Office 215,
08860 Castelldefels (Barcelona, Spain)
Tel.: (+34) 9341 34223
e-mail: amartin@cimne.upc.edu

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