[Bug fortran/39290] Subroutine/function ambiguity in generics

["burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39290

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |burnus at gcc dot gnu.org

--- Comment #7 from Tobias Burnus <burnus at gcc dot gnu.org> 2013-04-29 09:31:53 UTC ---
(In reply to comment #6)
>   external ff, cc
>   call q(ff)
>
> I absolutely *never* use implicit declarations, therefore I'm not sure: Is an
> "external ff" declaration supposed to get implicitly typed as real in comment
> 4?

The program is *valid*; as "ff" is referenced as function, it has to be
implicitly typed, which is "real" according to the implicit typing rules.

I concur that the standard does not very explicitly state this. But the
question (and example of comment 4) exactly matches the interpretation request
F03/0071 (cf. comment 0). J3/WG5 answered it
http://www.j3-fortran.org/doc/standing/links/016.txt - to quote from the answer
to Q2:

"2. The main program program unit is conforming, although the program
    would not be if the external procedure FF were not in fact a real
    function.  If the reference had been to QR instead of Q, it would
    be clear that FF has to be a real function, from the point of view
    of the main program scoping unit.  At the call site, the reference
    to Q is known to be a reference either to QR or QC (the interface
    block for Q is not defective), both of which require a function
    actual argument.  FF is known to be either a subroutine or a
    function, since it explicitly has the EXTERNAL attribute, and if
    it is a function it is known by implicit typing rules to be real.
    Because neither specific in the generic allows a subroutine as an
    argument, FF must therefore be a function.  Since FF is real, QR
    is called.  (The generic cannot have a specific that accepts a
    subroutine as an argument, as that would violate the requirements
    in 16.2.3.)"