Re: [PATCH 09/10] fortran: Support clobbering of variable subreferences [PR88364]

[Thomas Koenig <tkoenig@netcologne.de>]

Hi Mikael,

> This adds support for clobbering of partial variable references, when
> they are passed as actual argument and the associated dummy has the
> INTENT(OUT) attribute.
> Support includes array elements, derived type component references,
> and complex real or imaginary parts.
> 
> This is done by removing the check for lack of subreferences, which is
> basically a revert of r9-4911-gbd810d637041dba49a5aca3d085504575374ac6f.
> This removal allows more expressions than just array elements,
> components and complex parts, but the other expressions are excluded by
> other conditions: substrings are excluded by the check on expression
> type (CHARACTER is excluded), KIND and LEN references are rejected by
> the compiler as not valid in a variable definition context.
> 
> The check for scalarness is also updated as it was only valid when there
> was no subreference.

First, thanks a lot for digging into this subject. I have looked through
the patch series, and it looks very good so far.

I have a concern about this part, though.  My understanding at the
time was that it is not possible to clobber an individual array
element, but that this clobbers anything off the pointer that this
is based on.

So,

   integer, dimension(3) :: a

   a(1) = 1
   a(3) = 3
   call foo(a(1))

would also invalidate the store to a(3).  Is my understanding correct?
If so, I think this we cannot revert that patch (which was introduced
because of a regression).

Best regards

	Thomas