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by the_why_of_y 1775 days ago
FreeBSD differs quite substantially from the XNU kernel used by MacOS because XNU is based on Mach, and it was forked (Edit: from 4.3BSD) in 1988 - before Linux even existed.

The XNU kernel does not have a stable syscall ABI so perhaps it doesn't matter if the syscalls are different because the implementation of libSystem can convert as appropriate in userspace (see also: WINE).
2 comments
throw0101a 1775 days ago
> MacOS because XNU is based on Mach, and it was forked (Edit: from 4.3BSD) in 1988

As another commenter noted: XNU = Mach + FreeBSD.

What you are referring to is what NeXTSTEP was, Mach + BSD4:

* https://en.wikipedia.org/wiki/NeXTSTEP#Unix

By the time Apple got to them it was a few years later, and so they decided to updated that part of the kernel, and also brought in FreeBSD's userland.

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nix23 1775 days ago
>XNU is based on Mach

Partially, XNU is Mach AND the FreeBSD-Kernel:

https://www.youtube.com/watch?v=-7GMHB3Plc8

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rjzzleep 1775 days ago
If you look at the source of a lot of drivers on MacOS a few years ago, they were heavily based on the FreeBSD drivers.
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nix23 1775 days ago
Yes sure they do, just look the presentation.
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