_DarwinFoundation3 is an internal overlay that exposes low-level Darwin and POSIX C primitives to Swift, bridging system headers such as pthread, signal, mach, sched, and the sys family. It defines no Swift types of its own; instead it makes the underlying C declarations importable so Swift code can call directly into threading, signal handling, Mach, and scheduling interfaces. You do not import it explicitly. It is pulled in as part of the Darwin module on iOS, macOS, tvOS, watchOS, and visionOS.
Globals 8
SIG_DFLSIG_ERRSIG_HOLDSIG_IGNSIG_DFLSIG_IGNSIG_ERRSIG_HOLD