[dcrazy]

posix_spawn is emulated on Linux, but it is a native syscall on macOS (and possibly other OSes?). As discussed in the linked article, there is interest in changing Linux to adopt this model, where posix_spawn is its own fundamental primitive.

[asveikau]

Yeah, I think it is a reasonable transition path or implementation detail for some systems to implement it in userland atop fork(2), and others to natively spawn a new process without copying the old address space.