The following functions were replaced with their *at variants or
similar:
- lstat -> lstat -> fstatat
- stat -> stat -> fstatat
- fstat -> fstatat
- fchmod -> fchmodat
- fchown -> fchownat
- lchown -> fchownat
- mkfifo -> mkfifoat
- open -> openat
- renameat -> renameat2
- rmdir -> unlinkat
- unlink -> unlinkat
- symlink-> symlinkat
The `open_flags` logic for fstatat was redundant, as this is already
handled (and better so) in `openat2`.
Additionally, the fstatat test succeeds in os-test, and no longer
returns EINVAL. This is because `O_SYMLINK` is no longer
unconditionally passed like it was before. This is a problem because
redoxfs returns EINVAL if a node isn't a symlink but set `O_SYMLINK`.
Additionally, this adds the `SYMLOOP_MAX` constant in `limits.h` to
replace the `MAX_LEVEL` magic number used during symlink resolution.
`fstat` was kept because it is more difficult than the others to do a
drop-in replacement in terms of `fstatat` for since a naive approach
would cause mutual recursion.
Most of these changes are very simple. Among the changes made involve
taking advantage of auto-deref (`(*val).foo()` -> `val.foo()`) and
removing instances where we create a ref and immediately dereference it
(`&*val` -> `val`). There was a pretty neat case in `posix_openpt` where
some pointer verbosity was able to be reduced by using the more modern C
strings rather than the byte strings with an explicit NUL at the end.
Additionally, `exit()` now calls `unreachable!()` at the end. We
previously did `loop {}`, but clippy didn't like this. It can be up for
debate whether we want to make this `unreachable_unchecked` or similar.
There is only one change that might cause any sort of concern, and that
is the change from `.skip_while(!p).next()` -> `.find(p)`. This, like
everything else, was caught in a Clippy lint but I believe it deserves
some explanation because it isn't immediately obvious. Info about the
lint is here: https://rust-lang.github.io/rust-clippy/rust-1.89.0/index.html#skip_while_next
Speedy_Lex