__GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 not defined on aarch64

[Alexander Monakov]

On Fri, 30 Jun 2017, Richard Earnshaw (lists) wrote:
> NO.  AN OPTION WILL NOT WORK.
> 
> An option cannot fix up existing binary objects and change the ABI that
> they expect.  You cannot force a recompile on all users so the ABI for
> this type is NOW FIXED.
> 
> Mixing objects with potentially different ABIs in play is a recipe for
> disaster.

Sorry, but just to make sure there's no misunderstanding, let me just once
remind you that this is no different from, say, -fno-exceptions: software
projects can safely enable such options on their own (for the proposed option,
if the program or library never exposes internally used atomic objects to
external code).

Alexander