fix all and update CHANGELOG.md

Author: hicqu

CHANGELOG.md

@@ -30,6 +30,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#491](https://github.com/nix-rust/nix/pull/491))
 
 ### Changed
+- `epoll_ctl` now could accept None as argument `event`
+  when op is `EpollOp::EpollCtlDel`.
+  ([#480](https://github.com/nix-rust/nix/pull/480))
 - Removed the `bad` keyword from the `ioctl!` macro
   ([#478](https://github.com/nix-rust/nix/pull/478))
 - Changed `TimeVal` into an opaque Newtype

src/sys/epoll.rs

@@ -3,6 +3,7 @@ use libc::{self, c_int};
 use std::os::unix::io::RawFd;
 use std::ptr;
 use std::mem;
+use ::Error;
 
 bitflags!(
     #[repr(C)]
@@ -25,7 +26,7 @@ bitflags!(
     }
 );
 
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Eq, PartialEq)]
 #[repr(C)]
 pub enum EpollOp {
     EpollCtlAdd = 1,
@@ -91,8 +92,13 @@ pub fn epoll_create1(flags: EpollCreateFlags) -> Result<RawFd> {
 pub fn epoll_ctl<'a, T>(epfd: RawFd, op: EpollOp, fd: RawFd, event: T) -> Result<()>
     where T: Into<&'a mut EpollEvent>
 {
-    let res = unsafe { libc::epoll_ctl(epfd, op as c_int, fd, &mut event.into().event) };
-    Errno::result(res).map(drop)
+    let event: &mut EpollEvent = event.into();
+    if event as *const EpollEvent == ptr::null() && op != EpollOp::EpollCtlDel {
+        Err(Error::Sys(Errno::EINVAL))
+    } else {
+        let res = unsafe { libc::epoll_ctl(epfd, op as c_int, fd, &mut event.event) };
+        Errno::result(res).map(drop)
+    }
 }
 
 #[inline]

test/sys/test_epoll.rs

@@ -9,6 +9,10 @@ pub fn test_epoll_errno() {
     let result = epoll_ctl(efd, EpollOp::EpollCtlDel, 1, None);
     assert!(result.is_err());
     assert_eq!(result.unwrap_err(), Error::Sys(Errno::ENOENT));
+
+    let result = epoll_ctl(efd, EpollOp::EpollCtlAdd, 1, None);
+    assert!(result.is_err());
+    assert_eq!(result.unwrap_err(), Error::Sys(Errno::EINVAL));
 }
 
 #[test]