Motivation

In Android, new API is guarded by API level. For instance, timespec_get() was introduced with Android API level 29. API level can be determined by checking the value of __ANDROID_API__ defined in the system header <android/api-level.h>.

This value is not visible to Swift, meaning that code that is conditionally dependent on the availability of some API needs to check for it (and provide a fallback path!) in C or C++ rather than in Swift.

Proposed solution

I propose we teach the compiler, when targetting Android, to expose the API level similar to how the Swift language mode and compiler version are exposed:

var ts = timespec()
#if _apiLevel(>=29)
timespec_get(&ts, TIME_UTC)
#else
clock_gettime(CLOCK_REALTIME, &ts)
#endif
return ts

Alternatives considered

• Exposing the API level as a macro would result in it being evaluated too late and the compiler wouldn't be able to ignore the API usage.
• Exposing the API level as the de facto OS version (#available(Android 29, *)) would have a similar problem.
• "Just do it in C" is generally not the solution we want for Swift projects.

Additional information

No response