Re: [PATCH, v2] Fortran: fix invalid rank error in ASSOCIATED when rank is remapped [PR77652]

[Mikael Morin <morin-mikael@orange.fr>]

Le 28/07/2022 à 22:19, Mikael Morin a écrit :
> I propose to prepare something tomorrow.
> 

Here you go.  I haven’t found a procedure, a template or guidelines on 
wg5-fortran.org, so I’m just asking questions as free text.
I have not put every combination of cases to limit the number of 
examples, but an answer for each example should give a good picture.
Anything to correct or change?  Anything to add?

Mikael


Hello,

we are contributors to gfortran.  We have been discussing the 
restrictions a processor is required to put on ASSOCIATED functions 
calls with regards to rank mismatch in the thread at:
> https://gcc.gnu.org/pipermail/fortran/2022-July/058012.html
The following discussions are on the same topic as well:
> https://groups.google.com/g/comp.lang.fortran/c/BQfpeDZxX3Q
> https://community.intel.com/t5/Intel-Fortran-Compiler/Intel-rejects-ASSOCIATED-pointer-target-for-non-equal-ranks/m-p/1402799/highlight/true#M162159

The position from Steve Lionel in the latter threads is that a processor 
is required to reject an ASSOCIATED function call with arguments of 
mismatching ranks as there is no bounds-remapping list.
Our understanding is that a processor shall accept it as long as it may 
accept a corresponding pointer association statement with additional 
bounds-remapping list.

Our poll of existing compilers shows the same disagreement, with two 
accepting mismatching ranks (cray 14.0, nvidia 22.5) and two rejecting 
them (NAG 7.0 & 7.1, Intel).

So we would like an official interpretation on this topic.
More specifically, for each program below, is a processor (at compile 
time) required to reject it, allowed to reject it but not required to, 
or required to accept it?

Harald Anlauf, Mikael Morin

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 1
! matrix pointer vs array target
program p
   real, dimension(100),  target  :: array
   real, dimension(:,:),  pointer :: pmatrix => null()
   print *, associated(pmatrix, array)
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 2
! array pointer vs matrix target
program p
   real, dimension(20,5), target  :: matrix
   real, dimension(:),    pointer :: parray => null()
   print *, associated(parray, matrix)
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 3
! array pointer vs rank 2 non-contiguous target
program p
   real, dimension(20,5), target  :: matrix
   real, dimension(:),    pointer :: parray => null()
   print *, associated(parray, matrix(1:20:3, 1:5:2))
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 4
! array pointer vs scalar target
program p
   real, target :: scalar
   real, dimension(:), pointer :: parray => null()
   print *, associated(parray, scalar)
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 5
! scalar pointer vs array target
program p
   real, dimension(100), target :: array
   real, pointer :: pscalar => null()
   print *, associated(pscalar, array)
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 6
! assumed rank (array) pointer vs matrix target
program p
   real, dimension(20,5), target  :: matrix
   real, dimension(:),    pointer :: parray => null()
   call sub(parray)
contains
   subroutine sub(ptr)
     real, pointer :: ptr(..)
     print *, associated(ptr, matrix)
   end subroutine sub
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 7
! assumed rank (scalar) pointer vs array target
program p
   real, dimension(100), target :: array
   real, pointer :: pscalar => null()
   call sub(pscalar)
contains
   subroutine sub(ptr)
     real, pointer :: ptr(..)
     print *, associated(ptr, array)
   end subroutine sub
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Example 8
! assumed rank (array) pointer vs scalar target
program p
   real, target :: scalar
   real, dimension(:), pointer :: parray => null()
   call sub(parray)
contains
   subroutine sub(ptr)
     real, pointer :: ptr(..)
     print *, associated(ptr, scalar)
   end subroutine sub
end

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!