SigSet: Fix incorrect implementation of Eq, PartialEq and Hash

`signal::SigSet` derives `Eq`, `PartialEq` and `Hash`, but on linux, sigfillset(3)
only initializes the first 64 bits, leaving the rest uninitialized.
So two `signal::SigSets` can be different even though both have the
same set of signals.

Signed-off-by: German Maglione <gmaglione@redhat.com>

Author: germag

CHANGELOG.md

@@ -23,6 +23,9 @@ This project adheres to [Semantic Versioning](https://semver.org/).
   ([#1921](https://github.com/nix-rust/nix/pull/1921))
 
 ### Fixed
+- Fix `SigSet` incorrect implementation of `Eq`, `PartialEq` and `Hash`
+  ([#1946](https://github.com/nix-rust/nix/pull/1946))
+
 ### Removed
 
 - Removed deprecated IoVec API.

src/sys/signal.rs

@@ -12,6 +12,7 @@ use std::mem;
 use std::os::unix::io::RawFd;
 use std::ptr;
 use std::str::FromStr;
+use std::hash::{Hash, Hasher};
 
 #[cfg(not(any(target_os = "openbsd", target_os = "redox")))]
 #[cfg(any(feature = "aio", feature = "signal"))]
@@ -468,7 +469,7 @@ use std::iter::IntoIterator;
 // We are using `transparent` here to be super sure that `SigSet`
 // is represented exactly like the `sigset_t` struct from C.
 #[repr(transparent)]
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq)]
 pub struct SigSet {
     sigset: libc::sigset_t
 }
@@ -610,6 +611,27 @@ impl FromIterator<Signal> for SigSet {
     }
 }
 
+impl PartialEq for SigSet {
+    fn eq(&self, other: &Self) -> bool {
+        for signal in Signal::iterator() {
+            if self.contains(signal) != other.contains(signal) {
+                return false;
+            }
+        }
+        true
+    }
+}
+
+impl Hash for SigSet {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        for signal in Signal::iterator() {
+            if self.contains(signal) {
+                signal.hash(state);
+            }
+        }
+    }
+}
+
 /// Iterator for a [`SigSet`].
 ///
 /// Call [`SigSet::iter`] to create an iterator.
@@ -1344,4 +1366,48 @@ mod tests {
             assert!(set.contains(signal));
         }
     }
+
+    #[test]
+    fn test_eq_empty() {
+        let set0 = SigSet::empty();
+        let set1 = SigSet::empty();
+        assert_eq!(set0, set1);
+    }
+
+    #[test]
+    fn test_eq_all() {
+        let set0 = SigSet::all();
+        let set1 = SigSet::all();
+        assert_eq!(set0, set1);
+    }
+
+    #[test]
+    fn test_hash_empty() {
+        use std::collections::hash_map::DefaultHasher;
+
+        let set0 = SigSet::empty();
+        let mut h0 = DefaultHasher::new();
+        set0.hash(&mut h0);
+
+        let set1 = SigSet::empty();
+        let mut h1 = DefaultHasher::new();
+        set1.hash(&mut h1);
+
+        assert_eq!(h0.finish(), h1.finish());
+    }
+
+    #[test]
+    fn test_hash_all() {
+        use std::collections::hash_map::DefaultHasher;
+
+        let set0 = SigSet::all();
+        let mut h0 = DefaultHasher::new();
+        set0.hash(&mut h0);
+
+        let set1 = SigSet::all();
+        let mut h1 = DefaultHasher::new();
+        set1.hash(&mut h1);
+
+        assert_eq!(h0.finish(), h1.finish());
+    }
 }