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A comment on Fuchsia is not Linux. Parent comment

Re:Fuchsia is not Linux by mediocrejoker on Wednesday April 11, 2018 @06:41PM (#16816411)
> You're not necessarily breaking existing code. Both macOS and Windows are built on non-POSIX primitives that have POSIX compatibility layers.

I was under the impression that MacOS was built from a POSIX kernel, all the way down.

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Re:Fuchsia is not Linux by derefr on Wednesday April 11, 2018 @06:50PM (#16816478)
Nope; the XNU (macOS) kernel has Mach semantics (https://developer.apple.com/library/content/documentation/Da...), not POSIX semantics.

XNU does embed BSD (and so POSIX) semantics into the kernel—some of which are their own efficient primitives, since there's no way to efficiently implement them in terms of Mach. But whatever BSD syscalls can be implemented kernel-side in terms of Mach primitives, are.

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Re:Fuchsia is not Linux by monocasa on Wednesday April 11, 2018 @08:06PM (#16816942)
It has both. Mach system calls are negative, BSD system calls are positive. The BSD side has system calls for stuff like fork() that would otherwise be pretty clearly in Mach's domain.
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