Restore sigfd for corecext using the same technique as the other LIBEV_EMBED properties.

CHANGES.rst

@@ -272,9 +272,6 @@ libev
     attributes are not portable and not implemented by libuv or the
     CFFI backend. See :issue:`1076`.
 
-  - The ``sigfd`` property that was only conditionally available on
-    certain platforms and when libev was embedded, and only in the C
-    implementation, not the CFFI implementation, has been removed.
 
 1.2.2 (2017-06-05)
 ==================

src/gevent/libev/corecext.pyx

@@ -565,6 +565,16 @@ cdef public class loop [object PyGeventLoopObject, type PyGeventLoop_Type]:
         _check_loop(self)
         return libev.gevent_ev_loop_origflags(self._ptr)
 
+    @property
+    def sigfd(self):
+        _check_loop(self)
+        fd = libev.gevent_ev_loop_sigfd(self._ptr)
+        if fd >= 0:
+            return fd
+
+        # Explicitly not EV_USE_SIGNALFD
+        raise AttributeError("sigfd")
+
 
 cdef public class callback [object PyGeventCallbackObject, type PyGeventCallback_Type]:
     cdef public object callback

src/gevent/libev/libev.h

@@ -6,6 +6,11 @@
 #define gevent_ev_loop_sig_pending(loop) ((loop))->sig_pending
 #define gevent_ev_loop_backend_fd(loop) ((loop))->backend_fd
 #define gevent_ev_loop_activecnt(loop) ((loop))->activecnt
+#if EV_USE_SIGNALFD
+#define gevent_ev_loop_sigfd(loop) ((loop))->sigfd
+#else
+#define gevent_ev_loop_sigfd(loop) -1
+#endif /* !EV_USE_SIGNALFD */
 #else /* !LIBEV_EMBED */
 #include "ev.h"
 
@@ -13,6 +18,7 @@
 #define gevent_ev_loop_sig_pending(loop) -1
 #define gevent_ev_loop_backend_fd(loop) -1
 #define gevent_ev_loop_activecnt(loop) -1
+#define gevent_ev_loop_sigfd(loop) -1
 
 #define LIBEV_EMBED 0
 #define EV_USE_FLOOR -1

src/gevent/libev/libev.pxd

@@ -228,3 +228,4 @@ cdef extern from "libev.h" nogil:
     int gevent_ev_loop_sig_pending(ev_loop*);
     int gevent_ev_loop_backend_fd(ev_loop*);
     int gevent_ev_loop_activecnt(ev_loop*);
+    int gevent_ev_loop_sigfd(ev_loop*);