std: Add support for accept4 on Linux

This is necessary to atomically accept a socket and set the CLOEXEC flag at the
same time. Support only appeared in Linux 2.6.28 so we have to dynamically
determine which syscall we're supposed to call in this case.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libstd/sys/unix/weak.rs b/src/libstd/sys/unix/weak.rs
index 2cbcd62f533..e6f85c08d12 100644
--- a/src/libstd/sys/unix/weak.rs
+++ b/src/libstd/sys/unix/weak.rs
@@ -61,7 +61,11 @@ impl<F> Weak<F> {
             if self.addr.load(Ordering::SeqCst) == 1 {
                 self.addr.store(fetch(self.name), Ordering::SeqCst);
             }
-            mem::transmute::<&AtomicUsize, Option<&F>>(&self.addr)
+            if self.addr.load(Ordering::SeqCst) == 0 {
+                None
+            } else {
+                mem::transmute::<&AtomicUsize, Option<&F>>(&self.addr)
+            }
         }
     }
 }