Re: [TUHS] Macs and future unix derivatives

On Mon, Feb 08, 2021 at 11:37:38PM -0700, Andrew Warkentin wrote: Everything can be implemented in terms of a turing machine tape, so I'm sure that's true. Whether or not it would be *performant* and *secure* in the face of application level bugs might be a different story, though. In fact, some of the terrible semantics of the Posix interfaces exist only because there were traditional Unix vendors on the standards committee insisting on semantics that *could* be implemented using a user-mode library on top of normal file API's (I'm looking at you, fcntl locking semantics, where a close of *any* file descriptor, even a fd cloned via dup(2) or fork(2) will release the lock). So yes, Posix fcntl(2) locking *can* be implemented in terms of normal file API's.... AND IT WAS A TERRIBLE IDEA. (For more details, see [1].) [1] https://www.samba.org/samba/news/articles/low_point/tale_two_stds_os2.html I could go on about other spectactularly bad ideas enshrined in POSIX, such as telldir(2) and seekdir(2), which date all the way back to the assumption that directories should only be implemented in terms of linear linked lists with O(n) lookup performance, but I don't whine about that as feature bloat imposed by external standards, but just the cost of doing business. (Or at least, of relevance.) I'm not sure what you're referring to; if you mean the *at(2) system calls, which is why they exist in Linux (not for !@#!? Windows file streams support); they are needed to provide secure and performant user-mode file servers for things like Samba. Trying to implement a user-space file server using only the V7 Unix primitives will cause you to have some really horrible Time of Use vs Time of Check (TOUTOC) security gaps; you can narrow the TOUTOC races with some terrible performance sucking impacts, but removing them entirely is almost impossible. The reason why it's not used that much is because a lot of programmers want to be compatible with OS's that don't support those new interfaces --- and so they don't use it. And that's the final thing for folks to remember. There's an old saying, "without software, it's just a paperweight." This is just as true for an OS; if you don't have application software, who cares how clean it is? And it had better be performant, and not just a Posix-compliant layer afterthought demanded by the Product Manager as a checklist feature item. Rob Pike talked about this over two decades ago in his talk, Systems Software Research is Dead[2]. The slide talking about Standards (page #13) is especially relevant here: To be a viable computer system, one must honor a huge list of large, and often changing, standards: TCP/IP, HTTP, HTML, XML, CORBA, Unicode, POSIX, NFS, SMB, MIME, POP, IMAP, X, ... A huge amount of work, but if you don’t honor the standards you’re marginalized. [2] http://herpolhode.com/rob/utah2000.pdf That's because most people aren't going to port or rewrite application software for some random OS, whether it is a research OS or someone's new "simple, clean, reimplementation". And most users do expect to have a working web browser.... and text editor..., and their favorite games, whether it's nethack or spacewars, etc., etc., etc. If you want to call it feature bloat, so be it. But that seems to me like it's an excuse made by people who are bitter that people aren't using (or paying for, or contributing to) their pet operating system. Cheers, - Ted