Implement -Wimplicit-fallthrough (version 7)

[David Malcolm]

On Mon, 2016-08-29 at 09:32 -0400, Eric Gallager wrote:
> On 8/29/16, Marek Polacek <polacek@redhat.com> wrote:
> > Tobias tried my latest version and reported some ICEs.  They should
> > all be
> > fixed in this version (the only change since version 6 is the
> > cp/pt.c
> > hunk).
> > 
> > At this point I'd like to ask Jason and Joseph to review the C/C++
> > parts
> > and someone to review the ME parts so that I can finally wrap this
> > thing
> > up.  This warning found a couple of bugs in our codebase and I
> > suspect it
> > will find some in other codebases, too.
> > 
> > Does anyone have any concerns that I haven't addressed yet?
> > 
> > Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for
> > trunk?
> > 
> 
> 
> I tried v6 on my binutils-gdb fork, and it printed A LOT of
> warnings... After this patch goes in, the main question I'd have
> would
> be about the carets: it seems like it would make more sense for me
> for
> the location of the warning to be swapped with that of the fixit
> hint(s)? With the fixit pointing to the case label before the
> statement that's warned about, it makes it look like it's suggesting
> to put the fallthrough attribute or the break before the rest of the
> content of the case, which, with the break, could lead to dead code.
> I'd think it'd make more sense to point to after the body of the case
> statement instead...

Interesting.  Please can you post an example of the output that you're
referring to?

I'm working on improvements to how we print fix-its, so I'm wondering
if this is an issue with the fix-it data, or with the presentation of
it.

Thanks
Dave