Re: [PATCH] openmp, fortran: Check that event handles passed to detach clauses are not arrays [PR104131]

[Tobias Burnus <tobias@codesourcery.com>]

First, thanks for looking into the standard. I think the information is
too much spread through the standard. I keep searching for restrictions,
find them at 5 places and miss another 5. With OpenMP 5.2, it became
even worse.

On 01.03.22 09:16, Jakub Jelinek wrote:
> As there is no explicit allowing of array sections, array sections aren't
> allowed in detach, and it must be scalar integer.
> The question is if a non-coindexed coarray is a scalar integer variable or
> not.

I think the Fortran sense, yes. That only coindexed vars are disallowed
also implies this in the OpenMP spec. In terms of the implementation,
a local part of a coarray is really not much different from any other
variable, except that all coarrays have to be either in static memory
or allocatables/pointers (which are collectively allocated).

For a non-descriptor variable like:

program main
   integer, save :: a[*]
   call foo(a)
contains
   subroutine foo(x)
    integer :: x[*]
   end
end

That's also the case for the internal representation:

   static void * restrict caf_token.2;
   static integer(kind=4) * restrict a;

   void foo (integer(kind=4) * restrict x,
             void * restrict caf_token.0,
             integer(kind=8) caf_offset.1)
'x' is a pretty normal variable (admittedly, internally now a pointer)
which can be used like a noncoarray. (The pointer is there to permit
to put the var into some special, remote accessible memory.)

Tobias

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