[vtk-developers] coding standards & switch case label accidental fallthrough

[Sean McBride]

Hi all,

I'd like to propose a coding standards change...

I have a patch here:
<https://gitlab.kitware.com/vtk/vtk/merge_requests/59>

that fixes clang -Wimplicit-fallthrough warnings, which warn when you have adjacent case labels in a switch without breaks between them.  In other words, warns when you forget a 'break', which is pretty common, and often not deliberate.

For deliberate fall-though, it provides a clang-only C++11 attribute to suppress the warning, which I wrapped into a macro VTK_FALLTHROUGH.

So I propose that, by agreed convention, all deliberate switch case fall-through must use VTK_FALLTHOUGH annotations, ex:

 switch(var)
   {
   case 1:
     bar();
     break;

   case 2:
     baz();
     VTK_FALLTHROUGH;

   case 3:
     foo();
     break;
   }

Failure to use VTK_FALLTHROUGH above will cause warnings on C++11 clang builds.  On other compilers it's less helpful, but still nicely self-documenting.

Cheers,

-- 
____________________________________________________________
Sean McBride, B. Eng                 sean at rogue-research.com
Rogue Research                        www.rogue-research.com 
Mac Software Developer              Montréal, Québec, Canada