On Mon, Mar 27, 2017 at 06:45:32PM +0200, Marek Polacek wrote: > On Mon, Mar 27, 2017 at 09:27:34AM -0700, Steve Kargl wrote: > > On Mon, Mar 27, 2017 at 05:22:12PM +0200, Markus Trippelsdorf wrote: > > > On 2017.03.27 at 06:49 -0700, Steve Kargl wrote: > > > > > > > > Go scan the gcc-patches mailing list for "fallthrough". I'll > > > > note other have concerns. Here's one example: > > > > > > > > https://gcc.gnu.org/ml/gcc-patches/2016-11/msg00300.html > > > > > > > > Without Bernd's patch to set the default to 1 you will drown > > > > in false positives once you start using gcc-7 to build a whole > > > > distro. On my Gentoo test box anything but level 1 is simply > > > > unacceptable, because you will miss important other warnings > > > > in the -Wimplicit-fallthrough noise otherwise. > > > > > > The quotation doesn't have anything to do with the current discussion, > > > which is the general usefulness of the warning. > > > It only talks about one of the (admittedly over-engineered) six > > > different levels of the warning. > > > > > > > Yes, it does. See the part about "... drown in false positives ..." > > Whoever turned this option on should have been prepared to deal > > with the fallout by investigating each and every warning (i.e., > > either fix a real bug or (un)fix valid code to prevent the false > > positive). > > Having spent hours on fixing various fallthrough cases throughout the > codebase, > deciding whether or not a particular case is an intentional fallthru, and > pursuing various maintainers if I couldn't make a call, I find your statement, > erm, incorrect . I'm sorry that apparently something has slipped through. > I would've fixed it if I'd hit it.
A grep of the ChangeLog* files in libgfortran suggests that whoever turned on this option made no effort with regards to libgfortran. % pwd /usr/home/sgk/gcc/gcc7/libgfortran % grep -i marek ChangeLog ChangeLog-2016 % grep -i polacek ChangeLog ChangeLog-2016 % grep -i fall ChangeLog ChangeLog-2016 ChangeLog-2016: (_gfortran_caf_is_present): Prevent fallthrough warnings. ChangeLog-2016: MinGW-w64. Fix bounds overflow in fallback code. The _gfortran_caf_is_present change was made by Andre Vehreschild. -- Steve 20161221 https://www.youtube.com/watch?v=IbCHE-hONow
