fix some lints caught by Clippy

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

src/c_vec.rs

@@ -200,7 +200,7 @@ impl<'a, T> IntoIterator for &'a CVec<T> {
     type Item = <&'a [T] as IntoIterator>::Item;
     type IntoIter = <&'a [T] as IntoIterator>::IntoIter;
     fn into_iter(self) -> Self::IntoIter {
-        <&[T]>::into_iter(&*self)
+        <&[T]>::into_iter(self)
     }
 }
 impl<'a, T> IntoIterator for &'a mut CVec<T> {

src/header/grp/mod.rs

@@ -449,7 +449,7 @@ pub unsafe extern "C" fn getgrent() -> *mut group {
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn endgrent() {
     unsafe {
-        *(&mut *LINE_READER.get()) = None;
+        *LINE_READER.get() = None;
     }
 }
 

src/header/netdb/dns/mod.rs

@@ -59,7 +59,7 @@ impl Dns {
     }
 
     pub fn parse(data: &[u8]) -> Result<Self, String> {
-        let name_ind = 0b1100_0000;
+        let name_ind = 0b1100_0000u8;
         let mut i = 0;
 
         macro_rules! pop_u8 {
@@ -106,7 +106,7 @@ impl Dns {
                     let name_len = pop_u8!();
                     if name_len & name_ind == name_ind {
                         i -= 1;
-                        i = (pop_n16!() - ((name_ind as u16) << 8)) as usize;
+                        i = (pop_n16!() - ((u16::from(name_ind)) << 8)) as usize;
                         continue;
                     }
                     if name_len == 0 {

src/header/netdb/lookup.rs

@@ -63,7 +63,7 @@ pub fn lookup_host(host: &str) -> Result<LookupHost, c_int> {
         let packet_data_len = packet_data.len();
 
         let packet_data_box = packet_data.into_boxed_slice();
-        let packet_data_ptr = Box::into_raw(packet_data_box) as *mut _ as *mut c_void;
+        let packet_data_ptr = Box::into_raw(packet_data_box).cast::<c_void>();
 
         let dest = sockaddr_in {
             sin_family: AF_INET as u16,
@@ -164,7 +164,7 @@ pub fn lookup_addr(addr: in_addr) -> Result<Vec<Vec<u8>>, c_int> {
         let packet_data = packet.compile();
         let packet_data_len = packet_data.len();
         let packet_data_box = packet_data.into_boxed_slice();
-        let packet_data_ptr = Box::into_raw(packet_data_box) as *mut _ as *mut c_void;
+        let packet_data_ptr = Box::into_raw(packet_data_box).cast::<c_void>();
 
         let dest = sockaddr_in {
             sin_family: AF_INET as u16,

src/header/poll/mod.rs

@@ -203,7 +203,7 @@ pub unsafe extern "C" fn ppoll(
         -1
     } else {
         let tmo = unsafe { &*tmo_p };
-        if tmo.tv_sec > (c_int::MAX / 1000) as _ {
+        if tmo.tv_sec > (c_int::MAX / 1000).into() {
             c_int::MAX
         } else {
             ((tmo.tv_sec as c_int) * 1000) + ((tmo.tv_nsec as c_int) / 1000000)

src/header/stdio/mod.rs

@@ -1275,8 +1275,7 @@ pub unsafe extern "C" fn tempnam(dir: *const c_char, pfx: *const c_char) -> *mut
         [tmpdir, dir, P_tmpdir.as_ptr().cast()]
             .iter()
             .copied()
-            .skip_while(|&d| !unsafe { is_appropriate(d) })
-            .next()
+            .find(|&d| unsafe { is_appropriate(d) })
             .unwrap_or(c"/tmp".as_ptr().cast())
     };
     let dirname_len = unsafe { string::strlen(dirname) };

src/header/stdlib/mod.rs

@@ -920,10 +920,10 @@ pub unsafe extern "C" fn posix_memalign(
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn posix_openpt(flags: c_int) -> c_int {
     #[cfg(target_os = "redox")]
-    let r = unsafe { open((b"/scheme/pty\0" as *const u8).cast(), O_CREAT) };
+    let r = unsafe { open(c"/scheme/pty".as_ptr(), O_CREAT) };
 
     #[cfg(target_os = "linux")]
-    let r = unsafe { open((b"/dev/ptmx\0" as *const u8).cast(), flags) };
+    let r = unsafe { open(c"/dev/ptmx".as_ptr(), flags) };
 
     if r < 0 && platform::ERRNO.get() == ENOSPC {
         platform::ERRNO.set(EAGAIN);

src/header/unistd/mod.rs

@@ -1261,7 +1261,7 @@ unsafe fn with_argv(
     // NULL
     unsafe { va.arg::<*const c_char>() };
 
-    f(unsafe { (&*out).assume_init_ref() }, va);
+    f(unsafe { out.assume_init_ref() }, va);
 
     // f only returns if it fails
     if argc >= 32 {

src/header/wchar/mod.rs

@@ -1040,7 +1040,7 @@ pub unsafe extern "C" fn vfwscanf(
 
     unsafe {
         let format = WStr::from_ptr(format);
-        wscanf::scanf(reader, format.into(), __valist)
+        wscanf::scanf(reader, format, __valist)
     }
 }
 

src/ld_so/dso.rs

@@ -775,7 +775,7 @@ impl DSO {
         let strtab_size = strtab_size.expect("mandatory DT_STRSZ not present");
 
         let dynstrtab = StringTable::new(
-            &*mmap,
+            mmap,
             strtab_offset as u64,
             strtab_offset as u64 + strtab_size as u64,
         );

src/platform/linux/mod.rs

@@ -164,7 +164,7 @@ impl Pal for Sys {
         unsafe {
             syscall!(EXIT, status);
         }
-        loop {}
+        unreachable!();
     }
     unsafe fn exit_thread(_stack_base: *mut (), _stack_size: usize) -> ! {
         // TODO