> On Mar 29, 2017, at 3:41 PM, Greg Parker <gpar...@apple.com> wrote: > >> On Mar 29, 2017, at 9:02 AM, Charles Srstka <cocoa...@charlessoft.com >> <mailto:cocoa...@charlessoft.com>> wrote: >> >>> On Mar 29, 2017, at 10:51 AM, Jens Alfke <j...@mooseyard.com >>> <mailto:j...@mooseyard.com>> wrote: >>> >>>> On Mar 29, 2017, at 6:57 AM, Daryle Walker <dary...@mac.com >>>> <mailto:dary...@mac.com> <mailto:dary...@mac.com >>>> <mailto:dary...@mac.com>>> wrote: >>>> >>>> Now the new Xcode release notes say that “• Swift now warns when an >>>> NSObject subclass attempts to override the initialize class method, >>>> because Swift can't guarantee that the Objective-C method will be called. >>>> (28954946)” >>> >>> Huh, I haven’t heard of that. And I’m confused by “the Objective-C method” >>> — what’s that? Not the +initialize method being compiled, because that’s in >>> Swift. The superclass method? >>> >>> Guess I’ll follow that Radar link and read the bug report myself. Oh, wait. >>> :( >> >> You actually can this time, since Swift’s bug reporter is actually open to >> the public. https://bugs.swift.org/browse/SR-3114 >> <https://bugs.swift.org/browse/SR-3114><https://bugs.swift.org/browse/SR-3114 >> <https://bugs.swift.org/browse/SR-3114>> >> >> Basically, with Whole Module Optimization turned on, +initialize wasn’t >> getting called. Their solution was to just get rid of +initialize. > > You don't even need WMO. Many arrangements of Swift code can bypass ObjC > +initialize. > > Invocation of +initialize is a feature of objc_msgSend(). Swift code does not > always use objc_msgSend() when calling methods: some methods are inlined, > some are called via virtual table, some are called directly. None of these > paths will provoke +initialize. > > Changing Swift's generated code to guarantee +initialize would be > prohibitively expensive. Imagine an is-initialized check in front of every > inlined call. It would be more expensive than +initialize in ObjC because > +initialize checking is free once you pay the cost of objc_msgSend(). (The > ObjC runtime checks +initialize on uncached dispatch, and never caches > anything until +initialize completes. Most dispatches are cached so they pay > nothing for +initialize support.) > > +initialize in Swift isn't safe and is too expensive to make safe, so we're > taking it away instead.
I wonder if an equivalent Swift-native feature could be added, something like a typeInit block? If the block weren’t there, nothing special would happen, and if the block were present, the compiler could basically generate the code in the example I gave, but add the static var access to the front of every initializer and static/class member. That shouldn’t impact performance too much, and wouldn’t impact at all in the case that there’s no type initializer. Charles _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
