Open Radar

 
Summary:
The 10.12 SDK adds `stdatomic.h` to its module map, thus exposing its capabilities in line with C11 to Swift. (stdatomic.h was first available to the public in Xcode 7.)

In turn, the OSAtomic facilities were deprecated beginning in 10.12 in favor of the C11 constructs. These are unavailable in Swift, making simple value-based lock-free programming more difficult without bridging to C when targeting the new SDK as a minimum deployment target.

Steps to Reproduce:
1. Create a Swift project
2. `import Darwin.C.stdatomic` 
3. Cmd-click on `stdatomic`
4. Observe

Expected Results:
Swift imports definitions from section "7.17.7 Operations on atomic types", such as `atomic_exchange_explicit(_:_:_:)`.

Actual Results:
Swift only imports the straightforward #defines and direct C structs and functions.

Version:
Xcode Version 8.0 beta (8S128d) / OS X El Capitan Version 10.11.5 (15F34)

Notes:
This is behavior to be expected from the perspective of the Clang importer; it is likely that Swift should gyb overloads for the atomics-compatible types in the C stdlib overlay. Swift itself benefits from using LLVM's instruction set directly. IMHO, Swift should expose any capabilities of C11 that are representable in Swift. 

Configuration:
Occurs under all versions of Swift against the macOS 10.12 SDK.

Attachments: