Check that cb is a function, not non-empty

[sam-github]

This triggers a bug on node 6.x, see https://github.com/haraka/Haraka/issues/1546 and https://github.com/strongloop/modern-syslog/pull/16, and this seems to work on older nodes as well as 6.

@bnoordhuis, does this look correct to you? I'm somewhat confused by https://github.com/nodejs/nan/issues/104.

[sam-github]

diff --git a/core.cc b/core.cc
index e4904e3..4786530 100644
--- a/core.cc
+++ b/core.cc
@@ -30,7 +30,7 @@ class Worker: public Nan::AsyncWorker {
         void HandleOKCallback() {
             Nan::HandleScope scope;

-            if(callback->GetFunction()->IsFunction())
+            if(callback)
                 callback->Call(0, NULL);
         };

@@ -80,7 +80,10 @@ NAN_METHOD(SysLog) {

     int priority = info[0]->Int32Value();
     char* message = NULL;
-    Nan::Callback *callback = new Nan::Callback(info[2].As<Function>());
+    Nan::Callback *callback = NULL;
+
+    if (info[2]->IsFunction())
+        callback = new Nan::Callback(info[2].As<Function>());

     if(node::Buffer::HasInstance(info[1])) {
         message = dupBuf(info[1]);
@@ -90,7 +93,7 @@ NAN_METHOD(SysLog) {

     if (message) {
         Nan::AsyncQueueWorker(new Worker(callback, priority, message));
-    } else if(callback->GetFunction()->IsFunction()) {
+    } else if(callback) {
         callback->Call(0, NULL);
     }

also seems to work.

[sam-github]

Thanks for the comments, Ben, and nice to hear from you, even if only at this distance. Maybe I'll see you in Europe some day, hope its going well for you out there in the wilds of northern Holland :-)

[bnoordhuis]

Thanks, Sam. You should come visit when you're in Europe, life on a farm is great!