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System exception 0x40010008: FormatMessage failed
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narayanamoorthy_k



Joined: 19 Jun 2014
Posts: 136
Location: Chennai, IN

PostPosted: Thu Feb 08, 2018 1:12 pm    Post subject: Re: Reply with quote

JohnCampbell wrote:
Generic routines provide a single call, BUT you still need to write separate routines for all possible type/rank combinations.
It is just a verbose way of doing argument checking, which /CHECK can also do.
Not a fan of long winded verbose structures in F03/08. Just more opportunities to miss-type and provide coding errors.

John


Hi John
In pursuing our earlier discussion, I have done the parts of my program, which is working perfectly. My Special thanks to you too in helping that out.

However, it has a closing error, as I mentioned in other post.

http://forums.silverfrost.com/viewtopic.php?t=3707&start=0&postdays=0&postorder=asc&highlight=

It says, DEALLOCATING the dangling FORTRAN pointers. The respective array is in allocated state, but unable to deallocate it.

I oblige your views in this regard. Please advise.

Thanks in advance
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JohnCampbell



Joined: 16 Feb 2006
Posts: 1997
Location: Sydney

PostPosted: Thu Feb 08, 2018 1:19 pm    Post subject: Reply with quote

You could try:
If ( allocated(xx) ) then
deallocate ( xx, stat=stat )
if ( stat /= 0 ) write (*,*) 'unexpected error in deallocate XX, stat=',stat
end if

or try:
deallocate ( xx, stat=stat ) ! try to deallocate and ignore error if occurs

I have no idea what a dangling pointer is. Could be you have already deallocated the target array the pointer is pointing to.

Should you be using ASSOCIATED test or NULLIFY the pointer ?
I expect you should only deallocate pointers that have been allocated.

I wouldn't write this type of code.
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narayanamoorthy_k



Joined: 19 Jun 2014
Posts: 136
Location: Chennai, IN

PostPosted: Thu Feb 08, 2018 1:34 pm    Post subject: Reply with quote

Yes I remember, you mentioned this earlier.

When I use this code, it shows the other error as stated in this thread-heading.

Perhaps, i can try the NULLIFY..

But here the BS array is a ALLOCATABLE Array, which is valid at the time of executing this "DEALLOCATE" command. I also noticed that the previous "DEALLOCATE" command was executed for the "unassigned" arrays with no error. but here the BS is in ASSIGNED state, but showing up this error.
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mecej4



Joined: 31 Oct 2006
Posts: 1024

PostPosted: Thu Feb 08, 2018 1:59 pm    Post subject: Reply with quote

If at all possible, avoid using Fortran variables with the POINTER attribute in your programs. Use allocatable types instead.

Here is a program to illustrate how a pointer may get demoted to a dangling pointer.

Code:
program dangling_pointer
   implicit none
   integer, pointer, dimension(:) :: iptr => NULL()
   allocate(iptr(3))
   iptr = (/ 123, 321, 222/)
   call sub(iptr)
   print *,iptr

contains
   subroutine sub(ipt)   
      implicit none
      integer, pointer, dimension(:) :: ipt
      ipt(2) = (ipt(1)+ipt(3))/2
      if(ipt(2) < 300)deallocate(ipt)
      return
   end subroutine sub
end program dangling_pointer
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narayanamoorthy_k



Joined: 19 Jun 2014
Posts: 136
Location: Chennai, IN

PostPosted: Fri Feb 09, 2018 5:51 am    Post subject: Reply with quote

Thank mecej4,

I also observe and agree with you. Many of our expert group here, are with the same views on Pointers.
Having arrived at a logic to resolve the challenging problem, while we face such a mistakes due to compiler, it is really painful. However, these pointer concepts are good in C++ and other object oriented programming. But there, I recall, the object references are taken at the address levels separately, but not as an alias to reference, as we do here. If that is the case, I think our FTN95 will not face such issues further. I am sure, this POINTER has to improve further still in our FTN95.
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