https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80534
--- Comment #9 from Freddie Chopin <freddie_chopin at op dot pl> --- Patch above (applied to 7.0.1-RC-20170425) fixes the original issue which I reported - the project builds fine and works correctly. The warnings ("dereferencing type-punned pointer will break strict-aliasing rules") are still there, but I guess this is not related after all.