thread_local does not work for Objective-C classes with ARC

Originator:steipete
Number:rdar://39659413 Date Originated:23-Apr-2018 10:59 PM
Status:Open Resolved:
Product:Developer Tools Product Version:11.3
Classification:Other Bug Reproducible:Always
 
Summary:
thread_local does not work for Objective-C classes with ARC but works when:

- we use MRR
- we wrap it into a simple C++ class

This seems like an arbitrary restriction, as managing the C++ class is probably even more complex, lifetime-wise.

Steps to Reproduce:
Open sample. Run. Observe everything works. Uncomment

// Does not compile
//static thread_local NSNumber *testARCVariable;

Observe error: thread-local variable has non-trivial ownership: type is 'NSNumber *__strong'

Expected Results:
Objective-C objects should be storable in thread_local variables

Actual Results:
ARC blocks using thread_local with ObjC classes

Version:
11.3

Notes:
Also tested in Xcode 9.4b1 - same result.

Comments

Sample: https://github.com/PSPDFKit-labs/radar.apple.com/tree/master/39659413%20-%20thread_local%20does%20not%20work%20for%20Objective-C%20classes%20with%20ARC


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