updates %~>% to fix #24

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: nanonext
 Type: Package
 Title: NNG (Nanomsg Next Gen) Lightweight Messaging Library
-Version: 0.10.4.9021
+Version: 0.10.4.9022
 Description: R binding for NNG (Nanomsg Next Gen), a successor to ZeroMQ. NNG is
     a socket library implementing 'Scalability Protocols', a reliable,
     high-performance standard for common communications patterns including

NEWS.md

@@ -1,4 +1,4 @@
-# nanonext 0.10.4.9021
+# nanonext 0.10.4.9022
 
 *This is a major stability release bundling the 'libnng' v1.6.0 source code.*
 

R/sync.R

@@ -284,7 +284,9 @@ unlock <- function(socket) invisible(.Call(rnng_socket_unlock, socket))
 #' @details This is an experimental operator.
 #'
 #'     The condition value of 'cv' is initially reset to zero when this operator
-#'     returns.
+#'     returns. Only one forwarder can be active on a 'cv' at any given time,
+#'     and assigning a new forwarding target cancels any currently existing
+#'     forwarding.
 #'
 #'     Changes in the condition value of 'cv' are forwarded to 'cv2', but only
 #'     on each occassion 'cv' is signalled. This means that waiting on 'cv'

src/thread.c

@@ -361,6 +361,12 @@ SEXP rnng_signal_thread_create(SEXP cv, SEXP cv2) {
   if (R_ExternalPtrTag(cv2) != nano_CvSymbol)
     Rf_error("'cv2' is not a valid Condition Variable");
 
+  SEXP existing = Rf_getAttrib(cv, nano_CvSymbol);
+  if (existing != R_NilValue) {
+    thread_duo_finalizer(existing);
+    R_ClearExternalPtr(existing);
+  }
+
   nano_thread_duo *duo = R_Calloc(1, nano_thread_duo);
   nano_cv *ncv = (nano_cv *) R_ExternalPtrAddr(cv);
   nano_cv *ncv2 = (nano_cv *) R_ExternalPtrAddr(cv2);