[Patch, Fortran] Calling type-bound procedures

[Daniel Kraft]

Tobias Burnus wrote:
> Hi Daniel,
> 
>> this is the cleaned-up version of my patch to allow for calling
>> type-bound procedures posted yesterday including a ChangeLog.
> 
> As a small thing: I think one should update dump-parse-tree.c; I think
> everyone tends to forget it and it is almost never used.

I thought about this but if that's ok will include this in the 
documentation-fix following up.

> I like your patch. However - thanks to NAG f95 - I just realized that we
> currently cannot implement PASS in a standard conforming matter. The
> reason is:
> 
> C453 The passed-object dummy argument shall be a scalar, nonpointer,
>      nonallocatable dummy data object with the same declared type as
>      the type being defined; all of its length type parameters
>      shall be assumed; it shall be polymorphic (5.1.1.2) if and only
>      if the type being defined is extensible.
> 
> The problem with PASS for all type-bound procedures and for procedure-
> pointer components in non-SEQUENCE, non-BIND(C) procedures is the
> following: The type needs to by polymorphic, i.e. instead of
> 
>   TYPE(mytype) :: dummy_arg
> one needs
>   CLASS(mytype):: dummy_arg
> 
> Thinking about it, it makes sense: Unless the procedure is overwritten,
> the type%inherited_proc() won't work. (I have not checked what happends
> currently.)

That's what I stumbled across and mentioned on IRC, too, after testing 
with NAG :)

> The big question is now how to handle this? For proc pointer comps with
> SEQUENCE and BIND(C) [assuming PASS is allowed for them, I have not
> checked] the current machinary can be used, but for an ordinary,
> extensible type? Shall we abort in this case with "Sorry, not
> implemented"? Too bad that Paul has not managed to recreate his CLASS
> patch :-(
> 
> Somehow type-bound procedures without PASS loose a lot of their
> usefulness. Except for this point I think the patch is OK.

 From my point of view, the best solution would be to let it as it is 
now and emit maybe a warning for type-bound procedures with PASS about 
this problem; to fix it once polymorphic entities are available will of 
course be easy, just change the check during resolution time for the 
passed-object dummy argument.  Or maybe do a GNU Fortran extension until 
then, possibly together with the warning so people know their code will 
break when this is fixed.

Alternatively, I think we could print not-implemented for each PASS and 
leave the patch otherwise as it is to allow for this change easily at a 
later point.

What's your opinion on this?

Daniel

-- 
Done:     Arc-Bar-Cav-Sam-Val-Wiz, Dwa-Elf-Gno-Hum-Orc, Law-Neu-Cha, Fem-Mal
To go:    Hea-Kni-Mon-Pri-Ran-Rog-Tou