Rollup merge of #130861 - cuviper:sun-path-offset, r=ibraheemdev

Use `mem::offset_of!` for `sockaddr_un.sun_path`
We don't need manual pointer math here anymore!
try-job: dist-i686-msvc

Author: GuillaumeGomez

library/std/src/os/unix/net/addr.rs

@@ -15,15 +15,12 @@ mod libc {
 pubtypesocklen_t = u32;
 pubstructsockaddr;
 #[derive(Clone)]
-pubstructsockaddr_un;
+pubstructsockaddr_un{
+pubsun_path:[u8;1],
+}
 }
 
-fnsun_path_offset(addr:&libc::sockaddr_un) -> usize{
-// Work with an actual instance of the type since using a null pointer is UB
-let base = (addr as*const libc::sockaddr_un).addr();
-let path = core::ptr::addr_of!(addr.sun_path).addr();
- path - base
-}
+constSUN_PATH_OFFSET:usize = mem::offset_of!(libc::sockaddr_un, sun_path);
 
 pub(super)fnsockaddr_un(path:&Path) -> io::Result<(libc::sockaddr_un, libc::socklen_t)>{
 // SAFETY: All zeros is a valid representation for `sockaddr_un`.
@@ -53,7 +50,7 @@ pub(super) fn sockaddr_un(path: &Path) -> io::Result<(libc::sockaddr_un, libc::s
  ptr::copy_nonoverlapping(bytes.as_ptr(), addr.sun_path.as_mut_ptr().cast(), bytes.len())
 };
 
-letmut len = sun_path_offset(&addr) + bytes.len();
+letmut len = SUN_PATH_OFFSET + bytes.len();
 match bytes.get(0){
 Some(&0) | None => {}
 Some(_) => len += 1,
@@ -114,13 +111,13 @@ impl SocketAddr {
 let sun_path:&[u8] =
 unsafe{ mem::transmute::<&[libc::c_char],&[u8]>(&addr.sun_path)};
  len = core::slice::memchr::memchr(0, sun_path)
-.map_or(len, |new_len| (new_len + sun_path_offset(&addr))as libc::socklen_t);
+.map_or(len, |new_len| (new_len + SUN_PATH_OFFSET)as libc::socklen_t);
 }
 
 if len == 0{
 // When there is a datagram from unnamed unix socket
 // linux returns zero bytes of address
- len = sun_path_offset(&addr)as libc::socklen_t;// i.e., zero-length address
+ len = SUN_PATH_OFFSETas libc::socklen_t;// i.e., zero-length address
 }elseif addr.sun_family != libc::AF_UNIXas libc::sa_family_t{
 returnErr(io::const_io_error!(
  io::ErrorKind::InvalidInput,
@@ -238,7 +235,7 @@ impl SocketAddr {
 }
 
 fnaddress(&self) -> AddressKind<'_>{
-let len = self.lenasusize - sun_path_offset(&self.addr);
+let len = self.lenasusize - SUN_PATH_OFFSET;
 let path = unsafe{ mem::transmute::<&[libc::c_char],&[u8]>(&self.addr.sun_path)};
 
 // macOS seems to return a len of 16 and a zeroed sun_path for unnamed addresses
@@ -287,7 +284,7 @@ impl linux_ext::addr::SocketAddrExt for SocketAddr {
  addr.sun_path.as_mut_ptr().add(1)as*mutu8,
  name.len(),
 );
-let len = (sun_path_offset(&addr) + 1 + name.len())as libc::socklen_t;
+let len = (SUN_PATH_OFFSET + 1 + name.len())as libc::socklen_t;
 SocketAddr::from_parts(addr, len)
 }
 }