Attempt to fix the CI build

.gitignore

@@ -7,3 +7,4 @@
 *.a
 /target/
 Cargo.lock
+/msrv-test/target/

.travis.yml

@@ -1,6 +1,5 @@
 language: rust
 rust:
-  - 1.32.0 # uniform paths
   - stable
   - beta
   - nightly
@@ -42,6 +41,10 @@ matrix:
         - cargo clean
         - cargo test --all --all-features
         - cargo test --all --release --all-features
+    - name: "MSRV (1.32.0) compile check"
+      rust: 1.32.0 # uniform paths
+      script:
+        - cd msrv-test && cargo build
     - stage: lint
       name: "Rust: rustfmt"
       rust: stable

README.md

@@ -34,6 +34,12 @@ draft API features, have a look at
 The current 0.9 release series requires `libzmq` 4.1 or newer. New
 release series of `zmq` may require newer `libzmq` versions.
 
+Regarding the minimum Rust version required, `zmq` is CI-tested on
+current stable, beta and nightly channels of Rust. Additionally, it is
+made sure that the code still compiles on Rust 1.32.0. However, no
+tests are run for that build, so use `zmq` on older Rust versions on
+your own risk. It is however likely that it will just work anyways.
+
 # Installation
 
 rust-zmq is available from [crates.io](https://crates.io). Users
@@ -123,7 +129,7 @@ need set `LIBZMQ_PREFIX` as described above.
 fn main() {
     let ctx = zmq::Context::new();
 
-    let mut socket = ctx.socket(zmq::REQ).unwrap();
+    let socket = ctx.socket(zmq::REQ).unwrap();
     socket.connect("tcp://127.0.0.1:1234").unwrap();
     socket.send("hello world!", 0).unwrap();
 }

examples/zguide/mtrelay/main.rs

@@ -41,8 +41,7 @@ fn main() {
     receiver
         .bind("inproc://step3")
         .expect("failed binding step 3");
-    let ctx = context.clone();
-    thread::spawn(move || step2(&ctx));
+    thread::spawn(move || step2(&context));
     //wait for signal and pass it on
     receiver.recv_msg(0).unwrap();
     println!("Test successful!");

msrv-test/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "msrv-test"
+version = "0.0.1"
+authors = ["Andreas Rottmann <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+zmq = { path = ".." }

msrv-test/src/main.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let ctx = zmq::Context::new();
+
+    let socket = ctx.socket(zmq::REQ).unwrap();
+    socket.connect("tcp://127.0.0.1:1234").unwrap();
+    socket.send("hello world!", 0).unwrap();
+}

src/lib.rs

@@ -480,10 +480,8 @@ unsafe impl Send for Socket {}
 
 impl Drop for Socket {
     fn drop(&mut self) {
-        if self.owned {
-            if unsafe { zmq_sys::zmq_close(self.sock) } == -1 {
-                panic!(errno_to_error());
-            }
+        if self.owned && unsafe { zmq_sys::zmq_close(self.sock) } == -1 {
+            panic!(errno_to_error());
         }
     }
 }
@@ -591,6 +589,13 @@ impl Socket {
     ///
     /// The Socket assumes ownership of the pointer and will close the socket
     /// when it is dropped. The returned socket will not reference any context.
+    ///
+    /// # Safety
+    ///
+    /// The socket pointer must be a socket created via the `into_raw`
+    /// method. The ownership of the socket is transferred the returned Socket,
+    /// so any other pointers to the same socket may only be used until it is
+    /// dropped.
     pub unsafe fn from_raw(sock: *mut c_void) -> Socket {
         Socket {
             sock,

src/message.rs

@@ -65,6 +65,14 @@ impl Message {
     /// function, its use is not recommended, and it will be removed in a future
     /// release. If there is a use-case that cannot be handled efficiently by
     /// the safe message constructors, please file an issue.
+    ///
+    /// # Safety
+    ///
+    /// The returned message contains uninitialized memory, and hence the
+    /// `Deref` and `DerefMut` traits must not be used until the memory has been
+    /// initialized. Since there is no proper API to do so, this function is
+    /// basically not usable safely, unless you happen to invoke C code that
+    /// takes a raw message pointer and initializes its contents.
     #[deprecated(
         since = "0.9.1",
         note = "This method has an unintuitive name, and should not be needed."

tests/compile-tests.rs

@@ -1,4 +1,4 @@
-use std::env::var;
+use std::env;
 use std::path::PathBuf;
 
 fn run_mode(mode: &'static str) {
@@ -11,9 +11,8 @@ fn run_mode(mode: &'static str) {
         profile = env!("BUILD_PROFILE")
     ));
 
-    if let Ok(name) = var::<&str>("TESTNAME") {
-        let s: String = name.to_owned();
-        config.filter = Some(s)
+    if let Ok(name) = env::var("TESTNAME") {
+        config.filter = Some(name)
     }
     config.mode = cfg_mode;
     config.src_base = PathBuf::from(format!("tests/{}", mode));