https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85678
--- Comment #13 from Florian Weimer <fw at gcc dot gnu.org> --- (In reply to Wilco from comment #12) > Giving errors on old-style code by default sounds like a good idea. We could > add -std=legacy similar to Fortran to support building old K&R code (and > that would enable -fcommon by default). It's unfortunately not that simple. A lot of these changes (admittedly I've only tried -Werror=implicit-function-declaration by default, something that trips even experienced developers) tend to produce broken, but internally consistent builds because autoconf checks give wrong results (and everything, including the test suite, depends on those results). This was true for a significant number of core GNU components until this year, including GCC itself.
