Auto merge of #95 - asajeffrey:master, r=pcwalton

Added unit test for reentrancy.

IPC channels are reentrant, in that if we call `c.send(a)` and serializing `a` calls `c.send(b)`, then the channel contents are `b` then `a`. (This comes up in the case of logging over channels, since serialization may include logging.)

This PR adds a unit test to make sure we don't break reentrancy.

Discussion with @nox on IRC.

src/test.rs

@@ -11,6 +11,8 @@ use ipc::{self, IpcReceiver, IpcReceiverSet, IpcSender, IpcSharedMemory};
 use ipc::{OpaqueIpcSender};
 use router::ROUTER;
 use libc;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::cell::RefCell;
 use std::iter;
 use std::ptr;
 use std::sync::Arc;
@@ -19,6 +21,7 @@ use std::thread;
 
 #[cfg(not(any(feature = "force-inprocess", target_os = "windows", target_os = "android")))]
 use ipc::IpcOneShotServer;
+
 #[cfg(not(any(feature = "force-inprocess", target_os = "windows", target_os = "android")))]
 use std::io::Error;
 
@@ -386,3 +389,40 @@ fn test_so_linger() {
     };
     assert_eq!(val, 42);
 }
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+struct HasWeirdSerializer (Option<String>);
+
+thread_local! { static WEIRD_CHANNEL: RefCell<Option<IpcSender<HasWeirdSerializer>>> = RefCell::new(None) }
+
+impl Serialize for HasWeirdSerializer {
+    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+        where S: Serializer
+    {
+        if self.0.is_some() {
+            WEIRD_CHANNEL.with(|chan| { chan.borrow().as_ref().unwrap().send(HasWeirdSerializer(None)).unwrap(); });
+        }
+        self.0.serialize(serializer)
+    }
+}
+
+impl Deserialize for HasWeirdSerializer {
+    fn deserialize<D>(deserializer: &mut D) -> Result<Self, D::Error>
+        where D: Deserializer
+    {
+        Ok(HasWeirdSerializer(try!(Deserialize::deserialize(deserializer))))
+    }
+}
+
+#[test]
+fn test_reentrant() {
+    let null = HasWeirdSerializer(None);
+    let hello = HasWeirdSerializer(Some(String::from("hello")));
+    let (sender, receiver) = ipc::channel().unwrap();
+    WEIRD_CHANNEL.with(|chan| { *chan.borrow_mut() = Some(sender.clone()); });
+    sender.send(hello.clone()).unwrap();
+    assert_eq!(null, receiver.recv().unwrap());
+    assert_eq!(hello, receiver.recv().unwrap());
+    sender.send(null.clone()).unwrap();
+    assert_eq!(null, receiver.recv().unwrap());
+}