Hi all,

it turned out that 'declare target' with 'link' clause was broken in multiple ways.

The main fix is the attached patch, i.e. namely pushing the variables already to
the offload-vars list already in the FE.

When implementing it, I noticed:
* C has a similar issue when using nested functions, which is
   a GNU extension →https://gcc.gnu.org/115574

* When doing partial mapping of arrays (which is one of the reasons for 'link'),
   offsets are mishandled in Fortran (not tested in C), see FIXME in the patch)
   There: arr2(10) should print 10 but with map(arr2(10:)) it prints 19.
   (I will file a PR about this).

* It might happen that linked variables do not get linked. I have not investigated
   why, but 'arr2' gives link errors – while 'arr' works.
   See FIXME in the patch. (I will file a PR about this)

* For COMMON blocks, map(/common/) is rejected,https://gcc.gnu.org/PR115577

* When then mapping map(a,b,c) which is identical for 'common /mycom/ a,b,c',
   it fails to link the device side as the 'mycom_' symbol cannot be found on the
   device side.  (I will file a PR about this)

As COMMON as issues, an alternative would be to defer the trans-common.cc
changes to a later patch.

Comments, questions, concerns?

Tobias

PS: Tested with nvptx offloading with a page-migration supporting system with
nvptx and GCN offloading configured and no new fails observed.