backwards incompatibility

[Dave Love]

It's quite a pain for supporting research systems that the gfortran
module format changes incompatibly with every (?) new version.  For
instance, you can't mix development packages built with the RHEL system
compiler with the more recent "devtoolset" compiler needed for hardware
support.  As far as I know, the proprietary compilers don't have the
same issue.  I can't find anything written about that, but I haven't
tried to understand the implementation.  Is there something written?
Otherwise, is it feasible to convert older module files to newer
formats, given that the ABI doesn't change, as I've seen in release
notes (and would hope)?  If so, where would one look in the code to see
about doing so?

Version 8 makes the situation worse by breaking run time compatibility,
not just build-time, with a different libgfortran shared library
version.  That already caused considerable disruption with Fedora
packaging after the switch to GCC 8.  With ELF, can't you use versioned
symbols to avoid a new soname, like libgcc and libgomp do?

Regardless of any annoyances, thanks for keeping a competitive free
compiler going!