On Oct 10, 2012, at 11:02 , Jakob Stoklund Olesen <[email protected]> wrote:
> > On Oct 10, 2012, at 10:40 AM, Sean Silva <[email protected]> wrote: > >>> - The 'kind' enums should be protected, not public. >> >> My reasoning here was that it might be convenient to allow clients to >> switch over the enum. This is also what I have documented in >> docs/HowToSetUpLLVMStyleRTTI.rst for precisely this reason. Is there a >> particular reason you would prefer it to be protected? I'm mostly >> interested for the sake of updating the documentation. > > Only that it's bad OO style to switch on the leaves of a class hierarchy. > > It's bad enough that the LLVM-style RTTI requires the hierarchy to be > enumerated in the base class, but at least the damage is centralized. > > A good compiler should be able to turn a chain of 'else if (isa<…>)' tests > into a switch, and then you can subclass without updating all clients. But for closed class hierarchies, missing a case in the if-chain can be more dangerous. Sure, you can put llvm_unreachable at the end, but if you forget? With the switch, the compiler tells you. …except that in this case, Sean has the separate First/Last entries, and in addition, there probably won't be any switches over the entire hierarchy. So here I think Jakob is right. Jordan _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
