So this is another issue that's going to be seen with gcc-10. I'd been hoping to get the time to fix packages correctly, but I think it's ultimately going to have to fall to the package maintainers. gcc has traditionally allowed certain type mismatches for arguments in Fortran code. GCC would issue a diagnostic under -Wargument-mismatch for these cases, but the issue was not considered fatal. Starting with gcc-10, these are now fatal errors which look something like this: Error: Rank mismatch in argument ‘array’ at (1) (rank-1 and scalar) While gcc-10 has an option to disable this diagnostic, the potential for codegen issues in this space was significant enough that I didn't think an opt-out or advertising magic flag workaround was advisable. A partial list of the affected packages (generated back in October from a partial run of my tester): R-deldir R atlas cgnslib cp2k elk elpa exciting ga getdata grib_api hdf libccp4 mpich hwchem psblas3 qrmumps qrupdate quantum-espresso scalapack scipy scorep wannier90 wsjtx xfoil xrotor One of the upstream GCC developers looked at wannier90. It turns out we're using a fairly old version (2.0.1, 2015). Newer versions (3.0 Feb 2019) already have this problem fixed. So consider this a heads-up that roughly 30-40 Fortran packages are going to start failing. Jeff