Merge #799

799: Fix nix on Dragonfly r=Susurrus a=mneumann

This commit replaces pull request https://github.com/nix-rust/nix/pull/684. It fixes building `nix` on DragonFly. All tests pass. This requires most recent libc to build: https://github.com/rust-lang/libc/pull/851.

5 files changed, 52 insertions, 33 deletions

diff --git a/src/errno.rs b/src/errno.rs
index aa152170..1f88ec78 100644
--- a/src/errno.rs
+++ b/src/errno.rs
@@ -1,4 +1,6 @@
-use libc::{self, c_int};
+#[cfg(not(target_os = "dragonfly"))]
+use libc;
+use libc::c_int;
 use std::{fmt, io, error};
 use {Error, Result};
 
@@ -12,11 +14,23 @@ cfg_if! {
             libc::__error()
         }
     } else if #[cfg(target_os = "dragonfly")] {
-        unsafe fn errno_location() -> *mut c_int {
-            // FIXME: Replace with errno-dragonfly crate as this is no longer the correct
-            //        implementation.
-            extern { fn __dfly_error() -> *mut c_int; }
-            __dfly_error()
+        // DragonFly uses a thread-local errno variable, but #[thread_local] is
+        // feature-gated and not available in stable Rust as of this writing
+        // (Rust 1.21.0). We have to use a C extension to access it
+        // (src/errno_dragonfly.c).
+        //
+        // Tracking issue for `thread_local` stabilization:
+        //
+        //     https://github.com/rust-lang/rust/issues/29594
+        //
+        // Once this becomes stable, we can remove build.rs,
+        // src/errno_dragonfly.c, and use:
+        //
+        //     extern { #[thread_local] static errno: c_int; }
+        //
+        #[link(name="errno_dragonfly", kind="static")]
+        extern {
+            pub fn errno_location() -> *mut c_int;
         }
     } else if #[cfg(any(target_os = "android",
                         target_os = "netbsd",
diff --git a/src/errno_dragonfly.c b/src/errno_dragonfly.c
new file mode 100644
index 00000000..32fb4dab
--- /dev/null
+++ b/src/errno_dragonfly.c
@@ -0,0 +1,3 @@
+#include <errno.h>
+
+int *errno_location() { return &errno; }
diff --git a/src/fcntl.rs b/src/fcntl.rs
index 86375e4a..5abf65ac 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -48,7 +48,6 @@ libc_bitflags!(
         O_DIRECTORY;
         /// Implicitly follow each `write()` with an `fdatasync()`.
         #[cfg(any(target_os = "android",
-                  target_os = "dragonfly",
                   target_os = "ios",
                   target_os = "linux",
                   target_os = "macos",
diff --git a/src/sys/socket/ffi.rs b/src/sys/socket/ffi.rs
index 265a97c9..d91b130e 100644
--- a/src/sys/socket/ffi.rs
+++ b/src/sys/socket/ffi.rs
@@ -5,32 +5,32 @@ pub use libc::{socket, listen, bind, accept, connect, setsockopt, sendto, recvfr
 
 use libc::{c_int, c_void, socklen_t, ssize_t};
 
-#[cfg(not(target_os = "macos"))]
-use libc::size_t;
-
-#[cfg(not(target_os = "linux"))]
-use libc::c_uint;
-
 use sys::uio::IoVec;
 
-#[cfg(target_os = "linux")]
-pub type type_of_cmsg_len = size_t;
-
-#[cfg(not(target_os = "linux"))]
-pub type type_of_cmsg_len = socklen_t;
-
-// OSX always aligns struct cmsghdr as if it were a 32-bit OS
-#[cfg(target_os = "macos")]
-pub type type_of_cmsg_data = c_uint;
-
-#[cfg(not(target_os = "macos"))]
-pub type type_of_cmsg_data = size_t;
-
-#[cfg(target_os = "linux")]
-pub type type_of_msg_iovlen = size_t;
-
-#[cfg(not(target_os = "linux"))]
-pub type type_of_msg_iovlen = c_uint;
+cfg_if! {
+    if #[cfg(target_os = "dragonfly")] {
+        use libc::c_uint;
+        pub type type_of_cmsg_len = socklen_t;
+        pub type type_of_cmsg_data = c_int;
+        pub type type_of_msg_iovlen = c_uint;
+    } else if #[cfg(target_os = "linux")] {
+        use libc::size_t;
+        pub type type_of_cmsg_len = size_t;
+        pub type type_of_cmsg_data = size_t;
+        pub type type_of_msg_iovlen = size_t;
+    } else if #[cfg(target_os = "macos")] {
+        use libc::c_uint;
+        pub type type_of_cmsg_len = socklen_t;
+        // OSX always aligns struct cmsghdr as if it were a 32-bit OS
+        pub type type_of_cmsg_data = c_uint;
+        pub type type_of_msg_iovlen = c_uint;
+    } else {
+        use libc::{c_uint, size_t};
+        pub type type_of_cmsg_len = socklen_t;
+        pub type type_of_cmsg_data = size_t;
+        pub type type_of_msg_iovlen = c_uint;
+    }
+}
 
 // Private because we don't expose any external functions that operate
 // directly on this type; we just use it internally at FFI boundaries.
diff --git a/src/unistd.rs b/src/unistd.rs
index f35eab9d..7a1c56c7 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -630,8 +630,11 @@ pub fn execvp(filename: &CString, args: &[CString]) -> Result<Void> {
 ///
 /// This function is similar to `execve`, except that the program to be executed
 /// is referenced as a file descriptor instead of a path.
-#[cfg(any(target_os = "android", target_os = "dragonfly", target_os = "freebsd",
-          target_os = "netbsd", target_os = "openbsd", target_os = "linux"))]
+#[cfg(any(target_os = "android",
+          target_os = "freebsd",
+          target_os = "linux",
+          target_os = "netbsd",
+          target_os = "openbsd"))]
 #[inline]
 pub fn fexecve(fd: RawFd, args: &[CString], env: &[CString]) -> Result<Void> {
     let args_p = to_exec_array(args);