- Use SWIFT_RUNTIME_EXPORT instead of SWIFT_RT_ENTRY_VISIBILITY for exposed functions
- Use `_swift_` prefixes on the names of exposed functions
- Make the global counters and per-object counters cache thread-safe by using locks
When building the stdlib for Windows x86_64, we would see the following error:
swift/stdlib/public/core/RuntimeFunctionCounters.swift:95:19: error: '(UnsafeRawPointer, Int64) -> Void' is not representable in Objective-C, so it cannot be used with '@convention(c)'
@convention(c) (_ object: UnsafeRawPointer, _ functionId: Int64) -> Void
^
This is caused by `Int64` not being mapped as on Windows x86_64, `CLong`
is mapped to `Int32` and `CLongLong` is mapped to `Int`. This causes
the `Int64` to fail to be reverse-mapped to a C type causing the FFI
construction failure.
It allows for collecting the state of runtime function counters, which are used to determine how many times a given runtime function was called.
It is possible to get the global counters, which represent the total number of invocations, or per-object counters, which represent the number of runtime functions calls for a specific object.
