Bring back eventfd behind a feature flag

At some point, feature flags will be switched to a conditional build system.

3 files changed, 20 insertions, 22 deletions

diff --git a/Cargo.toml b/Cargo.toml
index f1c13d57..64b7bd46 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,10 @@ exclude     = [
   "test/**/*"
 ]
 
+[features]
+
+eventfd = []
+
 [dependencies]
 libc     = "0.1.4"
 bitflags = "0.1.1"
diff --git a/src/sys/eventfd.rs b/src/sys/eventfd.rs
index 866c95a3..e8e2bd23 100644
--- a/src/sys/eventfd.rs
+++ b/src/sys/eventfd.rs
@@ -1,37 +1,31 @@
-use std::mem;
-use libc::{c_int, c_uint};
-use errno::Errno;
+use libc;
 use fcntl::Fd;
 use {Error, Result};
 
 bitflags!(
-    flags EventFdFlag: c_int {
+    flags EventFdFlag: libc::c_int {
         const EFD_CLOEXEC   = 0o2000000, // Since Linux 2.6.27
         const EFD_NONBLOCK  = 0o0004000, // Since Linux 2.6.27
         const EFD_SEMAPHORE = 0o0000001, // Since Linux 2.6.30
     }
 );
 
-pub fn eventfd(initval: usize, flags: EventFdFlag) -> Result<Fd> {
-    type F = unsafe extern "C" fn(initval: c_uint, flags: c_int) -> c_int;
+mod ffi {
+    use libc;
 
     extern {
-        // #[linkage = "extern_weak"]
-        static eventfd: *const ();
+        pub fn eventfd(initval: libc::c_uint, flags: libc::c_int) -> libc::c_int;
     }
+}
 
-    if eventfd.is_null() {
-        panic!("eventfd unsupported on this platform");
-    }
+pub fn eventfd(initval: usize, flags: EventFdFlag) -> Result<Fd> {
+    unsafe {
+        let res = ffi::eventfd(initval as libc::c_uint, flags.bits());
 
-    let res = unsafe {
-        mem::transmute::<*const (), F>(eventfd)(
-            initval as c_uint, flags.bits())
-    };
+        if res < 0 {
+            return Err(Error::last());
+        }
 
-    if res < 0 {
-        return Err(Error::Sys(Errno::last()));
+        Ok(res as Fd)
     }
-
-    Ok(res)
 }
diff --git a/src/sys/mod.rs b/src/sys/mod.rs
index fbd75d23..f25aecb4 100644
--- a/src/sys/mod.rs
+++ b/src/sys/mod.rs
@@ -5,9 +5,9 @@ pub mod epoll;
 #[cfg(any(target_os = "macos", target_os = "ios"))]
 pub mod event;
 
-// Dont' support eventfd for now
-// #[cfg(any(target_os = "linux", target_os = "android"))]
-// pub mod eventfd;
+// TODO: switch from feature flags to conditional builds
+#[cfg(feature = "eventfd")]
+pub mod eventfd;
 
 #[cfg(not(target_os = "ios"))]
 pub mod ioctl;