On 07.10.21 17:33, Jakub Jelinek wrote:
It will also be a compatibility issue if users have code compiled on a LE
system with GCC 11 and earlier with KIND=16, it will not link with GCC 12.
libgfortran ABI changed multiple times in the past already, e.g. the
so.1 -> so.2 transition in 4.2
so.2 -> so.3 transition in 4.3
so.3 -> so.4 transition in 7
so.4 -> so.5 transition in 8
and users have coped.
Yes, and it has always been a hassle for users, and we've been
criticized for it.
This is currently a change which brings users on non-POWER-systems
(the vast majority) all pain and no gain. If this cannot be
avoided, I would at least try to fit in as much of other improvements
as there are possible.
There's a PR for it somewhere, but I can think of three areas, none
of the small, and all require an ABI change:
a) Get PDTs right (Paul?)
b) Make file descriptors conform to the C interop version
c) Remove the run-time parsing of I/O arguments and
replace them with a bit field.
What I mean by the last one is that
WRITE (unit,'(A)',ADVANCE="NO")
we currently parse the "NO" at runtime, for every statement
execution. What we could be doing instead is to have
dt_parm.0.advance = __gfortran_evaluate_yesno ("NO")
where the latter function can be simplified at compile-time.
We should strive to break the ABI as few times as possible.
Best regards
Thomas
