This is all stuff that the CPU does automatically for you, but which people don't realize you can do because of libraries like the CRT which were written for the lowest common denominator (eg., chips with no MMU).
-
-
Replying to @cmuratori @JustSlavic
Well, holy shit. This is quite the revelation.
1 reply 0 retweets 6 likes -
Replying to @beast_pixels @JustSlavic
Now I am wondering what people thought malloc was doing :) If you didn't know it called the OS to change the virtual memory mapping for your process, what _did_ you think it was doing?
3 replies 0 retweets 6 likes -
What about file operations on linux/mac? Are there OS provided functions that are lower level than the C runtime?
1 reply 0 retweets 0 likes -
Yes, of course. I don't do much MacOS work so I don't know what their architecture looks like, but on Linux it is the syscall table. You can see the entire thing here: https://filippo.io/linux-syscall-table/ …
1 reply 0 retweets 4 likes -
Replying to @cmuratori @wisam910 and
So like, this is what the CRT is doing. When you call "write" in libc you're not actually calling the OS, you're just calling the library, and then the library eventually does a syscall with a 1 in the RAX register to _actually_ transition to the operating system's "write".
1 reply 0 retweets 2 likes -
Replying to @cmuratori @wisam910 and
If you want, you can just make your own syscall to the OS and bypass the CRT entirely, and still call "write". That will bypass the CRT's middleman code, and ask the kernel to do the write directly.
1 reply 0 retweets 2 likes -
This would never have occurred to me in the past. I used to think CRT is the only officially supported way of talking to the kernel. I think this is the macos (darwin) system calls tablehttps://github.com/apple/darwin-xnu/blob/main/bsd/kern/syscalls.master …
3 replies 0 retweets 0 likes -
I don't know anything about Darwin so I can't comment on that. But yeah, you would assume they do something similar.
1 reply 0 retweets 0 likes -
There's this document which implies that, unlike Linux, Apple does not guarantee stability of the system calls between across OS versions https://developer.apple.com/library/archive/qa/qa1118/_index.html …
2 replies 0 retweets 1 like
IIRC Apple tends to force everyone to recompile everything on OS upgrades surprisingly often? So I would imagine that they generally don't care about this sort of thing. They seem really uninterested in back-compat in general :(
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.