I like the idea of adopting a fallthrough notation in our sources. I would
suggest naming it LLVM_FALLTHROUGH, though, in line with most of the rest of
llvm/Support/Compiler.h.
The 6 bugs you found seem scary, though I guess they can't be awful or we'd
have found them sooner. I'm not happy with the header changes, though -- the
asserts are both a lot hairier this way.
Jordy
On May 26, 2012, at 15:30, Alexander Kornienko wrote:
> Hello llvm-commits, clang-commits,
>
> I compiled llvm and clang with the recently added -Wimplicit-fallthrough
> diagnostic and analyzed the results. For those who are curious: there are
> about 400 'unannotated fall-through' warnings in total, about 290
> fall-through locations are annotated in comments, about 30 locations
> fall-through to an empty block (case 1: ....<no break> case 2: break;), 7
> locations have assert(false) not followed by break;
>
> From the remaining ~70 locations 6 look like real bugs. I've prepared two
> patches: for llvm and clang, which add break; for all these locations. I've
> also removed two unnecessary fall-throughs in headers to reduce total amount
> of 'unannotated fall-through' warning messages.
>
> I can't guarantee that all these 6 locations are real bugs, but they look
> very much like unintended fall-throughs.
>
> Could you, please, review this patch?
> Thanks!
>
> P.S. It would also be interesting to know what people think about converting
> fall-through annotations in comments to a checked annotation so we could use
> this diagnostic on regular basis?
> We could wrap [[clang::fallthrough]] to a macro, so the code would continue
> to work in c++98 mode, but in c++11 mode it would also allow to run this
> diagnostic (btw, is llvm compilable in c++11 mode?). Sample implementation of
> macro:
> #ifdef __clang__
> #if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
> #define FALLTHROUGH [[clang::fallthrough]]
> #endif
> #endif
>
> #ifndef FALLTHROUGH
> #define FALLTHROUGH do { } while (0)
> #endif
>
>
> --
> Best regards,
> Alexander Kornienko
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