[4.5, Patch, Fortran] PR 36704: Procedure pointer as function result

Mikael Morin mikael.morin@tele2.fr
Tue Dec 9 00:53:00 GMT 2008


Tobias Burnus wrote:
> Can you give an example? In most cases there exists both a specific and
> a generic version with the same name; e.g. "SIN(X)" exists as generic
> procedure for all kinds of REAL and COMPLEX; however, there exists also
> a specific function called "SIN" which takes the default-kind REAL as
> argument.

I was trying this:

!!!!!!!!!!!!!!!!!!!!!!!!
implicit none
procedure(real*8),   pointer :: q

q => i()
if (q(1.d0) /= sin(1.d0)) call abort ()

contains

  function i()
    intrinsic sin
    pointer :: i
    interface
      function i(x)
        real(8) :: i,x
      end function i
    end interface
    i => sin
  end function
end
!!!!!!!!!!!!!!!!!!!!!!!!!

which leads to this:

----------------------------
i ()
{
  real(kind=4) (*<T3bd>) (real(kind=8) &) (*<T3c1>) (real(kind=8) &) ppr@;

  ppr@ = (real(kind=4) (*<T3bd>) (real(kind=8) &) (*<T3c1>)
(real(kind=8) &)) _gfortran_specific__sin_r4;
  return (real(kind=4) (*<T3bd>) (real(kind=8) &)) ppr@;
}


MAIN__ ()
{
  real(kind=8) (*<T3c8>) (void) q;
  static integer(kind=4) options.0[8] = {68, 255, 0, 0, 0, 1, 0, 1};
  static real(kind=4) (*<T3bd>) (real(kind=8) &) i (void);

  _gfortran_set_options (8, (void *) &options.0);
  q = (real(kind=8) (*<T3c8>) (void)) i ();
  {
    static real(kind=8) C.1538 = 1.0e+0;

    if (q (&C.1538) !=
8.414709848078965048756572286947630345821380615234375e-1)
      {
        _gfortran_abort ();
      }
  }
}
---------------------------------


As you can see, the sin_r4 specific is called, not the sin_r8 as I expected.

But as Janus said procedure pointer interfaces are
disabled/unimplemented for now.



> 
> See in the F2003 standard:
> "13.6 Specific names for standard intrinsic functions"
> "Except for AMAX0, AMIN0, MAX1, and MIN1, the result type of the specific
>  function is the same as the result type of the corresponding generic
>  function would be if it were invoked with the same arguments as the
>  specific function."
I understand this as: The type of the result matches that of the argument
but said with a complicated and obfuscated sentence.
Too late to try to understand. I don't want to have nightmares.


> Those intrinsics marked with a bullet (*) in that list cannot be used
> as proc-pointer target (or as actual argument).
Sin is not marked with a bullet :)

Mikael



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