jfb added a comment. In https://reviews.llvm.org/D42933#1092077, @smeenai wrote:
> In https://reviews.llvm.org/D42933#1092048, @rjmccall wrote: > > > I agree that the format-specifier checker is not intended to be a > > portability checker. > I don't disagree with the original intent, but AFAICT that's exactly the intent of the warning I'd like to get rid of. I'm making a very narrow point: there is no portability problem with the warning I'm specifically trying to silence (using `%z` with `NS[U]Integer` on Darwin). If we decide that `-Wformat` shouldn't emit portability warnings then my point is moot, so let's see if people agree to that. If not, then my point still stands. >> Any attempt to check portability problems has to account for two things: >> >> - Not all code is intended to be portable. If you're going to warn about >> portability problems, you need some way to not annoy programmers who might >> have good reason to say that they only care about their code running on >> Linux / macOS / 64-bit / 32-bit / whatever. Generally this means splitting >> the portability warning out as a separate warning group. Right, it seems like recently `-Wformat` went against this, and users aren't thrilled. >> - There are always established idioms for solving portability problems. In >> this case, a certain set of important typedefs from the C standard have been >> blessed with dedicated format modifiers like "z", but every other typedef in >> the world has to find some other solution, either by asserting that some >> existing format is good enough (as NSInteger does) or by introducing a macro >> that expands to an appropriate format (as some things in POSIX do). A >> proper format-portability warning would have to know about all of these >> conventions (in order to check that e.g. part of the format string came from >> the right macro), which just seems wildly out-of-scope for a compiler >> warning. We could provide a macro for `NS[U]Integer`, but it's been long enough and there's enough existing code with `%z`. Not sure the code churn on user is worth it, if we can instead say "`%z` works". > Apple's current recommendation for using printf with the NSInteger types is > casting to a long, per > https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html. > Are you suggesting that recommendation would change to using `%zd` instead? Indeed, I believe that came from https://github.com/llvm-mirror/clang/commit/ec08735e1b6a51c11533311b774bf6336c0a5d63 and I intend to update documentation once the compiler is updated. It's not *wrong*, it's kinda more portable in that it's what you probably want to do if it's not `NS[U]Integer`, but it's more typing and users clearly haven't been following the recommendation (because let's be honest, `%z` is fine). 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
