fix: unaligned read panic on macos

Author: anonkey

changelog/2311.fixed.md

@@ -0,0 +1 @@
+Fixed `::unistd::Group::members` using read_unaligned to avoid crash on misaligned pointers

src/unistd.rs

@@ -3476,18 +3476,17 @@ impl Group {
         let mut ret = Vec::new();
 
         for i in 0.. {
-            let u = unsafe { mem.offset(i) };
-            if unsafe { (*u).is_null() } {
+            let u = unsafe { mem.offset(i).read_unaligned() };
+            if u.is_null() {
                 break;
             } else {
-                let s = unsafe {CStr::from_ptr(*u).to_string_lossy().into_owned()};
+                let s = unsafe {CStr::from_ptr(u).to_string_lossy().into_owned()};
                 ret.push(s);
             }
         }
 
         ret
     }
-
     /// # Safety
     ///
     /// If `f` writes to its `*mut *mut libc::group` parameter, then it must
@@ -3569,13 +3568,29 @@ impl Group {
     ///
     /// # Examples
     ///
+    // Disable this test on all OS except BSD as wheel group may not exist.
+    #[cfg_attr(not(any(apple_targets, bsd)), doc = " ```no_run")]
+    #[cfg_attr(any(apple_targets, bsd), doc = " ```")]
+    /// use nix::unistd::Group;
+    /// // Returns an Result<Option<Group>>, thus the double unwrap.
+    /// let group = Group::from_name("wheel").unwrap().unwrap();
+    /// assert!(group.name == "wheel");
+    /// let group_id = group.gid;
+    /// let group = Group::from_gid(group_id).unwrap().unwrap();
+    /// assert_eq!(group.gid, group_id);
+    /// assert_eq!(group.name, "wheel");
+    /// ```
     // Disable this test on all OS except Linux as root group may not exist.
     #[cfg_attr(not(target_os = "linux"), doc = " ```no_run")]
     #[cfg_attr(target_os = "linux", doc = " ```")]
     /// use nix::unistd::Group;
     /// // Returns an Result<Option<Group>>, thus the double unwrap.
-    /// let res = Group::from_name("root").unwrap().unwrap();
-    /// assert!(res.name == "root");
+    /// let group = Group::from_name("root").unwrap().unwrap();
+    /// assert!(group.name == "root");
+    /// let group_id = group.gid;
+    /// let group = Group::from_gid(group_id).unwrap().unwrap();
+    /// assert_eq!(group.gid, group_id);
+    /// assert_eq!(group.name, "root");
     /// ```
     pub fn from_name(name: &str) -> Result<Option<Self>> {
         let name = match CString::new(name) {