smeenai added a comment. In https://reviews.llvm.org/D42933#1091234, @aaron.ballman wrote:
> In https://reviews.llvm.org/D42933#1090268, @jfb wrote: > > > I was just looking at this, and I think @arphaman's patch is pretty much > > the right approach (with 2 suggested fixes below). > > > > I don't think the code we're currently warning on is broken: a user code > > has `NSInteger` with `%zd` or `NSUInteger` with `%zu`, and on all platforms > > which support those types the implementor has guaranteed that > > `(sizeof(size_t) == sizeof(NSInteger)) && (sizeof(ssize_t) == > > sizeof(NSUInteger))`. > > > Yes, but is this guaranteed to be the case or does it happen to be the case? > I'm worried about the less mainstream uses where you might find ObjC code > where this does not hold but -Wformat points out a portability concern. Also keep in mind that Obj-C might be used on non-Apple platforms, e.g. there's an active review going on for GNUstep ABI v2 right now (https://reviews.llvm.org/D46052), and WinObjC is also a thing. Those platforms might not necessarily provide the same guarantees or consistency that Apple's do. >> I agree that, if we're playing C++ pedant and look at the typedefs, then >> it's undefined behavior and the code is broken. > > This is reason alone to diagnose the code, because the optimizer is welcome > to use that UB to perform transformations the programmer did not expect. > However, I'm not certain our optimizer is currently paying attention to that > UB directly, so this may not be an immediate issue (but could be a pitfall > for the future) but I'm not certain about other optimizers for which > portability would still be a concern. I would honestly find it a bit surprising (and scary) if the optimizer actually took advantage of UB in the case where the size and alignment of the specifier and the actual type matches. Repository: rC Clang https://reviews.llvm.org/D42933 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
