Hi Julian,

thanks for the patch and the post-review fixes. (The revised patch was 
committed as r279628. And I have committed a few minor follow-up 
improvements.)

I still have an issues with the following.

On 12/18/19 11:51 PM, Tobias Burnus wrote:
>> +      /* Disallow duplicate bare variable references and multiple
>> +         subarrays of the same array here, but allow multiple 
>> components of
>> +         the same (e.g. derived-type) variable.  For the latter, 
>> duplicate
>> +         components are detected elsewhere.  */
> Do we have a test case for "the latter"?

Seemingly, the latter is neither tested-for nor diagnosed:

type t
   integer, allocatable :: i
end type t
type(t) :: x

!$acc enter data copyin(x%i, x, x%i) ! Bad: accepted

!$acc data pcopy(x) pcopy(x) ! OK – rejected: Symbol 'x' present on multiple clauses at (1)
!$acc end data
end

> Thirdly, I am not sure whether the following will work with your code:
> …
> !$acc data copy (x(:)%k, x(:)%j(3))
>
> This data is strided; I don't quickly see whether that's rejected. (I 
> also
> didn't check whether it is valid, but I think it is not.)

For attach/detach, the crucial bit is that the sub-references are
*allocatable* or *pointer* variables, otherwise it does not make sense to
talk about attach/detach. — For those, already the Fortran semantic
gives an error. I have attached a test case (strided-alloc-ptr.f90),
which shows that this is correctly rejected.

However, the other question is how component access w/o allocatables
or pointers is handled (i.e. they are all in the same aggregated type).
I attached a test case for this (mapping-tests.f90).

In particular:
* "copy(x, x%k)" – rejected by OpenMP and, hence, OpenACC for C/C++
    Accepted by gfortran for OpenACC  (for gfortran: missing OpenMP 4.5 feature)

* "copy(y(:)%i)" – strided access, i.e. y(1)%i + y(2)%i + …
   Is this valid OpenACC or not?
   [Currently equivalent to "copy(y)"]

* "copy(z(1)%cc(:)%i)" – also strided access, but gives an ICE

See also: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93025

Tobias