The runtime and stubs are built for ALL targets, not specific ones. This allows
us to configure when cross-compiling to Windows again. Collapse the dual
addition of the swiftRuntime into a single build. This unifies the runtime
build for the apple and non-Apple SDKs. The difference here was the ObjC
interop sources. In order to deal with that unification add a CPP macro to
indicate whether the interop sources should be included or not.
The general rule here is that something needs to be SWIFT_CC(swift)
if it's just declared in Swift code using _silgen_name, as opposed to
importing something via a header.
Of course, SWIFT_CC(swift) expands to nothing by default for now, and
I haven't made an effort yet to add the indirect-result / context
parameter ABI attributes. This is just a best-effort first pass.
I also took the opportunity to shift a few files to just implement
their shims header and to demote a few things to be private stdlib
interfaces.
...and explicitly mark symbols we export, either for use by executables or for runtime-stdlib interaction. Until the stdlib supports resilience we have to allow programs to link to these SPI symbols.
This allows removal of the DebugDescription protocol which is invalid
because no classes actually conform to it. The problem is that we need
to send a debugDescription message to an NSObject without loading
Foundation. This is exactly what shims are for. A very simple shim
solves the problem.
