Further changes recommended by @asomers

src/fcntl.rs

@@ -180,15 +180,10 @@ pub fn renameat<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(old_dirfd: Option<Ra
     Errno::result(res).map(drop)
 }
 
-fn wrap_readlink_result(mut v: Vec<u8>, res: ssize_t) -> Result<OsString> {
-    match Errno::result(res) {
-        Err(err) => Err(err),
-        Ok(len) => {
-            unsafe { v.set_len(len as usize) }
-            v.shrink_to_fit();
-            Ok(OsString::from_vec(v.to_vec()))
-        }
-    }
+fn wrap_readlink_result(mut v: Vec<u8>, len: ssize_t) -> Result<OsString> {
+    unsafe { v.set_len(len as usize) }
+    v.shrink_to_fit();
+    Ok(OsString::from_vec(v.to_vec()))
 }
 
 fn readlink_maybe_at<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P,
@@ -220,8 +215,7 @@ fn inner_readlink<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P)
     }
     // Uh oh, the result is too long...
     // Let's try to ask lstat how many bytes to allocate.
-    let reported_size = super::sys::stat::lstat(path)
-        .and_then(|x| Ok(x.st_size)).unwrap_or(0);
+    let reported_size = super::sys::stat::lstat(path).map_or(0, |x| x.st_size);
     let mut try_size = if reported_size > 0 {
         // Note: even if `lstat`'s apparently valid answer turns out to be
         // wrong, we will still read the full symlink no matter what.
@@ -241,14 +235,11 @@ fn inner_readlink<P: ?Sized + NixPath>(dirfd: Option<RawFd>, path: &P)
         }
         else {
             // Ugh! Still not big enough!
-            let next_size = try_size << 1;
-            if next_size < try_size {
+            match try_size.checked_shl(1) {
+                Some(next_size) => try_size = next_size,
                 // It's absurd that this would happen, but handle it sanely
                 // anyway.
-                break Err(super::Error::Sys(Errno::ENAMETOOLONG))
-            }
-            else {
-                try_size = next_size;
+                None => break Err(super::Error::Sys(Errno::ENAMETOOLONG))
             }
         }
     }