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Re: [Patch, Fortran, OOP] PR 56261: seg fault call procedure pointer on polymorphic array


>> It is nontrivial to detect this in every case (e.g. passing a TYPE
>> actual to a CLASS formal arg), but at least we can easily detect it if
>> a polymorphic *actual* argument is involved (which means that the
>> corresponding formal arg must also be polymorphic).
>
>
> Sorry, I cannot follow here. At least at a glance, I don't see why the
> following program is invalid:
>
>   implicit none
>   type :: nc
>   end type
>   class    (nc), allocatable :: c
>   procedure(), pointer     :: f => ff
>   allocate(c)
>   call f(c)
> contains
>   subroutine ff (self)
>     TYPE(nc) :: self
>   end subroutine
> end
>
>
> I don't see a reason why an explicit interface should be required - and
> passing a CLASS to a TYPE is also fine: "The dummy argument shall be type
> compatible with the actual argument. If the actual argument is a polymorphic
> coindexed object, the dummy argument shall not be polymorphic."

I guess you're right. Somehow I was assuming that passing CLASS to
TYPE is invalid (apparently without properly thinking it through).

Of course this makes the diagnosis make harder ...


> Thus, the only place where the check can be is for:
>
>   f => ff
>
> In your example, the explicit interface of "ff" is known thus it should be
> testable at resolution time of the proc-pointer assignment.

Right. However, strictly speaking, the pointer assignment as such is
probably valid. But of course there is not much one can do with the
proc-ptr afterwards, if it's invalid to call it ...

Another problem is with external procedures, i.e. changing the
proc-ptr definition to a simple PROCEDURE statement (without POINTER).
There one does not have the assignment to check.

I'm a bit puzzled about what to do with this PR now ...

Cheers,
Janus


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