[notalaser]

This is so, so true, that I wish there were enough beer in this world to gift you with. There's a lot of cruft in XNU, and there's even more of it in the rest of the system, but all this heap of hacks isn't just useless cruft that we'll be better off without. That heap of code also contains almost twenty years' worth of bugfixes and optimizations from more smart engineers than Apple can hope to hire and get to work together in a productive and meaningful manner. All this unpleasant cruft is what keeps the system alive and well and the users happy enough to continue using it.

More often than not, systems that get boldly rewritten from scratch end up playing catch-up for years. Frankly, I can't remember a single case when a full rewrite with an ambitious timetable wasn't a full-scale disaster. The few success stories, like (what eventually became) Firefox have taken a vastly different approach and took a lot more than users would have wanted.

A lot of idealistic (I was about to write naive) engineers think it's all a matter of throwing everything away. That's the easy part. Coming up with something better is the really hard part, and it's not achieved by just throwing the cruft away. If you innocent souls don't believe me, come on over to the Linux side, we have Gnome 3 cookies. You'll swear you're never going to touch anything that isn't xterm or macOS again.

[pcwalton]

A lot of macOS/iOS was written from scratch, though: Core Graphics (vs. Cairo and FreeType), Core Animation, Core Text (vs. pango), WindowServer (vs. X11), UIKit (vs. Cocoa), IOKit (vs. the native BSD driver framework), Cocoa Finder (vs. Carbon Finder), LLVM/clang/Swift (if you count Chris Lattner's work on it at UIUC)...

Of those, the last one is very impressive: it's a decade-long from-scratch project that has succeeded in competing with a very entrenched project (GCC) in a mature market.

Regarding GNOME 3, the delta between GNOME 2 and GNOME 3 is far less than the delta between NeXTSTEP+FreeBSD and the first version of Mac OS X.

[sedachv]

> This is so, so true, that I wish there were enough beer in this world to gift you with. There's a lot of cruft in XNU, and there's even more of it in the rest of the system, but all this heap of hacks isn't just useless cruft that we'll be better off without. That heap of code also contains almost twenty years' worth of bugfixes and optimizations from more smart engineers than Apple can hope to hire and get to work together in a productive and meaningful manner. All this unpleasant cruft is what keeps the system alive and well and the users happy enough to continue using it.

This whole premise is a false dichotomy. Apple does not have to throw away Mac OS X, and it does not have to keep piling crap on without fixing things. If you stop the excuses and rationalizations and commit to code quality you can ship an operating system with quality code and minimal bugs. The OpenBSD project has been doing this for two decades with minimal resources. There is no valid excuse other than "we are too lazy and incompetent."

[blinkingled]

Bingo! That's a beer shot :)

Oh too much code, bad code, we inherited it, throwing out away won't work etc are baloney excuses without meat. All it takes is the will to hire and commit the right resources with an objective of increasing code quality. I mean take this bug itself - Apple did fix it but only after GPZ was on their arse. No reason they couldn't have reviewed it themselves and fixed it.

[tptacek]

Hasn't the vulnerable code been here for over a decade? Why do people think this was an easy bug to spot? There are dozens of extremely qualified people looking for these things. I think there's a reason there isn't a Nemo Phrack article about this bug: it was hard to spot, and required a flash of insight about the competing lifecycles of objects in two different domains (POSIX and Mach).

[notalaser]

I was (obviously...) responding to this:

> Apple needs to take a bit of those tens of billions of dollars they have sitting around and spend it on starting from scratch with something that's not horrifically crufty.

They certainly don't have to throw everything away. Not having thrown everything away is one of the reasons why OpenBSD is a good example here. Remember all that quality code that was in place before Cranor's UVM? (Edit: actually, the fact that UVM is an improvement over it should say something, too...)

And, at the risk of sounding bitter, in my experience, very few companies have the capability to "commit to code quality", and I don't think Apple is one of them.

Edit: BTW, I really like your blog. You should write more often :-).

[sedachv]

> Remember all that quality code that was in place before Cranor's UVM?

So much before my time I was not even aware of it. For the uninitiated: https://www.usenix.org/legacy/events/usenix99/full_papers/cr...

> Edit: BTW, I really like your blog. You should write more often :-).

Thank you. :) Just this week I started thinking of getting back into it.

[tptacek]

Hold on, because, I'm pretty familiar with pre- and post- UVM OpenBSD, because Arbor Networks shipped on OpenBSD (against medical advice) and ran into a number of really bad VM bugs that Theo couldn't fix because of the UVM rewrite!

[__s]

But I am on the Linux side & wouldn't want to touch anything that is xterm or macOS again (suckless's st ftw)

Also currently running on a nice pure wayland system, no need for that X11 cruft