From 64815c61836ece60d6d01d1a1ecfc1877d5bb866 Mon Sep 17 00:00:00 2001
From: Matthew Gregan <kinetik@flim.org>
Date: Tue, 20 Jun 2017 15:30:48 +1200
Subject: Fix sendmsg on macOS when passing a zero entry cmsgs array.

---
 src/sys/socket/mod.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/sys/socket/mod.rs b/src/sys/socket/mod.rs
index 88fe02fe..c11b5367 100644
--- a/src/sys/socket/mod.rs
+++ b/src/sys/socket/mod.rs
@@ -277,12 +277,18 @@ pub fn sendmsg<'a>(fd: RawFd, iov: &[IoVec<&'a [u8]>], cmsgs: &[ControlMessage<'
         None => (0 as *const _, 0),
     };
 
+    let cmsg_ptr = if capacity > 0 {
+        cmsg_buffer.as_ptr() as *const c_void
+    } else {
+        ptr::null()
+    };
+
     let mhdr = msghdr {
         msg_name: name as *const c_void,
         msg_namelen: namelen,
         msg_iov: iov.as_ptr(),
         msg_iovlen: iov.len() as size_t,
-        msg_control: cmsg_buffer.as_ptr() as *const c_void,
+        msg_control: cmsg_ptr,
         msg_controllen: capacity as size_t,
         msg_flags: 0,
     };
-- 
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