Interoperabilidade entre C e Fortran 90

% cat a.c
typedef struct X X;
struct X {
 float f;
 int  d;
};

void
setf_(X *x)
{
 x->f = 1.8;
}

void setd_(X*);

void
setd2_(X *x)
{
 setd_(x);
}
% cat xmod.f90
module xmod
  type X
    real :: f
    integer :: d
  end type
end module

subroutine setd(tx)
  use xmod
  type(X) :: tx
  tx%d = 18
end subroutine
% cat b.f90
program B
  use xmod

  type(X) :: tx

  call setf(tx)
  call setd2(tx)
  print *, tx

end program
% gcc -c a.c; ifort -c xmod.f90; ifort -c b.f90; ifort -o ab a.o b.o xmod.o; ./ab
   1.800000              18