DI: New way of modeling factory initializers #4225
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@swift-ci Please smoke test os x |
slavapestov
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It appears that the dispatch overlay failure is related to rdar://27226313. I'll try to fix both bugs. |
Previously, we were only able to detect factory initializers dispatched through class_method. This didn't work for factory initializers defined in protocol extensions. The end result would be that we would strong_release an uninitialized class instance, which could cause crashes. Fix DI to correctly release the old instance using dealloc_partial_ref instead. Fixes <rdar://problem/27713221>.
I apologize in advance to @jrose-apple, who is not a fan of this fix ;-) In unoptimized builds, the convenience initializers on DispatchQueue allocate and immediately deallocate an instance of OS_dispatch_queue prior to calling the C function that returns the "real" instance. This is because we don't have a way to write user-defined factory initializers yet; convenience initializers still have an 'initializing' entry point that takes an existing instance, which we have no choice but to throw away. Unfortunately, when we perform the fake allocation, we look up class metadata by calling the wrong Swift runtime function, causing a crash when we send +allocWithZone:. Fix this so that the metadata is accessed via a lookup from the Objective-C runtime, instead of making a totally fake 'foreign metadata' object -- it looks like there was code for this already, it just wasn't used in all cases. While getting metadata for a runtime-only class should be rare, this feels like a real bug fix, to me. Second, we would ultimately free the fake object by sending -release, however OS_dispatch_queue has an override of -dealloc which doesn't like to be called with a completely uninitialized instance. Here, I'm going to drop all pretense of sanity. The patch just changes IRGen to lower the dealloc_partial_ref instruction as a call to the object_dispose() Objective-C runtime function when the class in question is a runtime-only class. This frees the object without running -dealloc, which *happens* to work for OS_dispatch_queue. Fixes <rdar://problem/27226313>.
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