Comment by adastra22

Comment by adastra22 2 days ago

Everything in the UNIX compatibility layer is low-level in macOS. Not necessarily "legacy" though.

But this is no different than saying that, for example, calling out platform-specific native OS APIs from Java is "low-level." Which it is, from the perspective of compile-once, run-anywhere Java applets. macOS is a NeXT-compatible non-UNIX API, and you are supposed to use the macOS frameworks for everything. Calling down to BSD or even mach is definitely not what Apple wants you to do.

hmage 2 days ago

> macOS is a ... non-UNIX

Seems to be badly phrased and meant something else, since macOS is certified to be UNIX - https://www.opengroup.org/openbrand/register/ - contrary to Linux which is not UNIX-certified.

HN posted about this at least once - https://news.ycombinator.com/item?id=29984016

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adastra22 a day ago

UNIX is/whas a commercial product from AT&T. macOS is UNIX-certified. Not the same thing.

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raverbashing 2 days ago

Curious about this

Isn't the Mach kernel based on BSD?

How much of getaddrinfo is in the kernel, how much of it is pure "libc"?

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adastra22 2 days ago

No, mach is a microkernel, like L5. It was developed for the purpose of replacing the BSD kernel, by having a small amount of functionality in the kernel itself, and the rest of the BSD-compatibility layer implemented in user space. macOS' frameworks are then a layer on top of that.

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- messe 2 days ago
  
  IIRC most of the BSD compat was moved to kernel space for performance reasons (either just on macOS, or the version of Mach they built on top of)
  
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  egberts1 2 days ago
  
  The UNIX libcompat (a compatibility library for older UNIX functions) was integrated into Mac OS (specifically, macOS) rather than directly into Mach OS.
  Here’s the breakdown:
  • Mach OS refers to the Mach microkernel, which primarily focuses on low-level system functions such as task scheduling and memory management. It is not a full-fledged operating system, and thus, libraries like libcompat, which are higher-level UNIX compatibility libraries, would not be integrated directly into the Mach kernel itself. • Mac OS (particularly macOS, formerly OS X) is a complete operating system that includes the Mach microkernel, the BSD layer, and various other components. macOS has a strong Unix heritage, and libcompat is part of the broader Unix-like environment included in macOS to support legacy Unix APIs and applications.
  Thus, libcompat was integrated into macOS (or its predecessor, NeXTSTEP) as part of its Unix compatibility layer, rather than into the Mach kernel directly
  
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