[J3] [EXTERNAL] Re: Self-assignment of allocatable component

[Damian Rouson]

Probably so.  

D

Sent from my iPhone

> On Jul 29, 2021, at 05:27, Clune, Thomas L. (GSFC-6101) <thomas.l.clune at nasa.gov> wrote:
> 
> 
> Ah,  but by the same measure, are Fortran’s pointers “less expensive” than C pointers?     Maybe allowing for a normalization factor based on the relative size of the 2 communities.
>  
> From: J3 <j3-bounces at mailman.j3-fortran.org> on behalf of j3 <j3 at mailman.j3-fortran.org>
> Reply-To: j3 <j3 at mailman.j3-fortran.org>
> Date: Wednesday, July 28, 2021 at 11:44 PM
> To: j3 <j3 at mailman.j3-fortran.org>
> Cc: Damian Rouson <damian at sourceryinstitute.org>
> Subject: [EXTERNAL] Re: [J3] Self-assignment of allocatable component
>  
> As one measure of the cost and complexity associated with a feature, someday I would love to see a count or a percentage of the of the emails on this list in response to a question roughly equal to “Is this code standard-conforming?” for code that involves a pointer.  By the suggested measure, I nominate pointers for the single most expensive feature in the history of Fortran. 
>  
> Damian
>  
> Sent from my iPhone
> 
> 
> On Jul 28, 2021, at 06:55, Vipul Parekh via J3 <j3 at mailman.j3-fortran.org> wrote:
> 
>  
> On Wed, Jul 28, 2021 at 9:01 AM Daniel C Chen via J3 <j3 at mailman.j3-fortran.org> wrote:
> Thanks Malcolm and all for the clarification.
> ..
> 
> From: "Malcolm Cohen via J3" <j3 at mailman.j3-fortran.org>
> To: "'General J3 interest list'" <j3 at mailman.j3-fortran.org>..
> 
> Hi Daniel,
>  
> Yes, you are quite right, so in that case, X=X would involve at least
> 1.      Capturing the value of X%I,
> 2.      Finalising X%I,
> 3.      Restoring the value of X%I. ..
>  
>  Hi Daniel and Malcolm,
>  
> Interesting discussion.  If I understood the clarification thus far correctly, the following program seems to me to conform - would you agree?
>  
>  module m
>    type :: t
>       character(len=10) :: objname = ""
>       integer :: dat = 0
>    contains
>       final :: finalize_t 
>    end type
>    type, extends(t) :: u
>    end type 
> contains
>    impure elemental subroutine finalize_t( this )
>       type(t), intent(inout) :: this
>       print *, "t::finalize_t invoked for ", this%objname
>    end subroutine    
> end module
> module n
>    use m 
>    type :: v
>       class(t), allocatable :: i
>    end type
> contains
>    subroutine sub()
>       type(v) :: x, y
>       allocate( t :: x%i ) ; x%i%objname = "x%i" ; x%i%dat = 42
>       allocate( u :: y%i ) ; y%i%objname = "y%i"
>       if ( allocated(y%i) ) then
>          print *, "Initially, y%i%dat = ", y%i%dat, "; expected is 0"
>       end if
>       y = x ; y%i%objname = "y%i"
>       if ( allocated(y%i) ) then
>          print *, "y%i%dat = ", y%i%dat, "; expected is 42"
>       end if
>    end subroutine 
> end module 
>    use n
>    call sub()
> end
>  
> And the program output per the standard might be as follows - note the order of the last 2 lines in the output can be ignored:
>  Initially, y%i%dat =            0 ; expected is 0
>  t::finalize_t invoked for y%i
>  y%i%dat =           42 ; expected is 42
>  t::finalize_t invoked for y%i
>  t::finalize_t invoked for x%i
>  
> However only one out of several processors I tried gave the above output.  There is variance among the rest when it comes to output from the (impure) finalizer.  Is the expected output I list above conformant, or is that the other processors are yet to conform to the standard when it comes to finalization?
>  
> Daniel, is it possible for you to check the IBM processor with this example and provide your feedback and comments?
>  
> Thanks,
> Vipul
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