Hopefully unbreak sendmsg and recvmsg on OSX

64-bit OSX explicitly aligns cmsg_data to 32-bit boundaries.

Author: asomers

src/sys/socket/ffi.rs

@@ -13,6 +13,13 @@ 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 = uint32_t;
+
+#[cfg(not(target_os = "macos"))]
+pub type type_of_cmsg_data = size_t;
+
 // Private because we don't expose any external functions that operate
 // directly on this type; we just use it internally at FFI boundaries.
 // Note that in some cases we store pointers in *const fields that the
@@ -37,7 +44,7 @@ pub struct cmsghdr {
     pub cmsg_len: type_of_cmsg_len,
     pub cmsg_level: c_int,
     pub cmsg_type: c_int,
-    pub cmsg_data: [size_t; 0]
+    pub cmsg_data: [type_of_cmsg_data; 0]
 }
 
 extern {

src/sys/socket/mod.rs

@@ -94,7 +94,7 @@ unsafe fn copy_bytes<'a, 'b, T: ?Sized>(src: &T, dst: &'a mut &'b mut [u8]) {
 }
 
 
-use self::ffi::{cmsghdr, msghdr, type_of_cmsg_len};
+use self::ffi::{cmsghdr, msghdr, type_of_cmsg_len, type_of_cmsg_data};
 
 /// A structure used to make room in a cmsghdr passed to recvmsg. The
 /// size and alignment match that of a cmsghdr followed by a T, but the
@@ -200,7 +200,7 @@ pub enum ControlMessage<'a> {
 pub struct UnknownCmsg<'a>(&'a cmsghdr, &'a [u8]);
 
 fn cmsg_align(len: usize) -> usize {
-    let align_bytes = mem::size_of::<size_t>() - 1;
+    let align_bytes = mem::size_of::<type_of_cmsg_data>() - 1;
     (len + align_bytes) & !align_bytes
 }