libsystem

In fact, compilers don't even see libSystem itself when linking, they just see a.tbd file that lists all of libSystem's symbols.

The actual interface between libSystem and the kernel is private to Apple and is not guaranteed to stay argument or ABI compatible.

Compilers cannot inline syscalls on Apple platforms as that would defeat the whole point of making libSystem the stable ABI.

This is true - the compatibility boundary for OS X is at the link-against-libSystem layer.

Go backed out of their strategy on MacOS and started using libc (libsystem?), because when Apple says something is internal and may change without notice, they really mean it.

The stable interface to syscalls on Apple platforms is libSystem, which is a dynamic library.

Some libSystem libraries such as malloc and pthread were separated out in a previous release, but not open sourced; they're back now, though.

Nice, I'm glad they finally released libmalloc source after they separated it from Libsystem (or was it in Libc?

There is lots of interesting stuff in the kernel, dyld, and libSystem.

Yes, there is separate work to discern what DNS server the system is currently using: on macOS this requires a call to an undocumented function in libSystem - that both Chromium and Tailscale use!

I think most of libSystem.dylib (and its sub-dylibs) are once again open source.

(Yay free software.) wyvern:~/src/redshift/redshift-1.7/src gthomas$ otool -L redshift redshift: /System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/CoreGraphics.framework/Versions/A/CoreGraphics (compatibility version 64.0.0, current version 600.0.0) /usr/lib/libSystem.

You’re using static binary to mean “does not link to anything at all”, which on some systems results in worse portability, since the syscall interface is unstable and linking to libc/libsystem/etc is the only supported way to make syscalls.

GP clearly means “a single executable you can run on any install of the target OS without dependencies.” Whether it’s a truly honest-to-goodness static binary that don’t link to libc or libSystem or whatever is important to approximately zero people, outside of internet pedants.