Runtime: Less eager instantiation of type metadata in the conformance cache [5.2] #29899
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… cache The ConformanceCandidate constructor would eagerly instantiate metadata for all non-generic types in the conformance cache. This was not the intention of the code though, because it can compare nominal type descriptors -- which are emitted statically -- for those types that have them, namely everything except for foreign and Objective-C classes. Change the order of two calls so that the lazy path has a chance to run. This fixes a crash when type metadata uses weakly-linked symbols which are not available, which can come up in backward deployment scenarios. Fixes <rdar://problem/59460603>.
slavapestov
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@swift-ci Please test Linux |
tkremenek
approved these changes
Feb 18, 2020
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The ConformanceCandidate constructor would eagerly instantiate metadata for
all non-generic types in the conformance cache. This was not the intention
of the code though, because it can compare nominal type descriptors --
which are emitted statically -- for those types that have them, namely
everything except for foreign and Objective-C classes.
Change the order of two calls so that the lazy path has a chance to run.
This fixes a crash when type metadata uses weakly-linked symbols
which are not available, which can come up in backward deployment
scenarios.
Fixes rdar://problem/59460603.