CustomAvailability: synthesized dynamic availability checking function should be private #85549
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…n should be private When compiling a Swift module in incremental mode, each Swift source file is compiled into an object file and we use linker to link them together. Because the predicate function for checking dynamic feature availability is eagerly synthesized per compilation unit, the linker will complain about duplicated symbols for them. Setting their visibility as private ensures that linker doesn't see them, thus addressing the linker errors. One workaround for this problem is to enable WMO. rdar://164971313
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| funcDecl->setBodySynthesizer(synthesizeAvailabilityDomainPredicateBody, | ||
| (void *)var); | ||
| funcDecl->setAccess(AccessLevel::Internal); | ||
| funcDecl->setAccess(AccessLevel::Private); |
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Why private rather than marking them as @export(implementation), which allows the linker to merge the different copies in different translation units?
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Do we worry about deserialization issues trigged by the function body of this synthesized function when marked as @export(implementation)? Previously, we have been hitting a module deserialization error (e.g.rdar://164410957).
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When compiling a Swift module in incremental mode, each Swift source file is compiled into an object file and we use linker to link them together. Because the predicate function for checking dynamic feature availability is eagerly synthesized per compilation unit, the linker will complain about duplicated symbols for them. Setting their visibility as private ensures that linker doesn't see them, thus addressing the linker errors.
One workaround for this problem is to enable WMO.
rdar://164971313