unix, windows: disallow NULL worker in thread pool

See #629.

src/unix/threadpool.c

@@ -153,8 +153,7 @@ void uv__work_done(uv_async_t* handle, int status) {
 static void uv__queue_work(struct uv__work* w) {
   uv_work_t* req = container_of(w, uv_work_t, work_req);
 
-  if (req->work_cb)
-    req->work_cb(req);
+  req->work_cb(req);
 }
 
 
@@ -172,6 +171,9 @@ int uv_queue_work(uv_loop_t* loop,
                   uv_work_t* req,
                   uv_work_cb work_cb,
                   uv_after_work_cb after_work_cb) {
+  if (work_cb == NULL)
+    return uv__set_artificial_error(loop, UV_EINVAL);
+
   uv__req_init(loop, req, UV_WORK);
   req->loop = loop;
   req->work_cb = work_cb;

src/win/threadpool.c

@@ -55,6 +55,9 @@ static DWORD WINAPI uv_work_thread_proc(void* parameter) {
 
 int uv_queue_work(uv_loop_t* loop, uv_work_t* req, uv_work_cb work_cb,
     uv_after_work_cb after_work_cb) {
+  if (work_cb == NULL)
+    return uv__set_artificial_error(loop, UV_EINVAL);
+
   uv_work_req_init(loop, req, work_cb, after_work_cb);
 
   if (!QueueUserWorkItem(&uv_work_thread_proc, req, WT_EXECUTELONGFUNCTION)) {

test/test-list.h

@@ -184,6 +184,7 @@ TEST_DECLARE   (fs_readdir_file)
 TEST_DECLARE   (fs_open_dir)
 TEST_DECLARE   (fs_rename_to_existing_file)
 TEST_DECLARE   (threadpool_queue_work_simple)
+TEST_DECLARE   (threadpool_queue_work_einval)
 TEST_DECLARE   (threadpool_multiple_event_loops)
 TEST_DECLARE   (thread_mutex)
 TEST_DECLARE   (thread_rwlock)
@@ -448,6 +449,7 @@ TASK_LIST_START
   TEST_ENTRY  (fs_open_dir)
   TEST_ENTRY  (fs_rename_to_existing_file)
   TEST_ENTRY  (threadpool_queue_work_simple)
+  TEST_ENTRY  (threadpool_queue_work_einval)
   TEST_ENTRY  (threadpool_multiple_event_loops)
   TEST_ENTRY  (thread_mutex)
   TEST_ENTRY  (thread_rwlock)

test/test-threadpool.c

@@ -56,3 +56,21 @@ TEST_IMPL(threadpool_queue_work_simple) {
   MAKE_VALGRIND_HAPPY();
   return 0;
 }
+
+
+TEST_IMPL(threadpool_queue_work_einval) {
+  int r;
+
+  work_req.data = &data;
+  r = uv_queue_work(uv_default_loop(), &work_req, NULL, after_work_cb);
+  ASSERT(r == -1);
+
+  uv_run(uv_default_loop());
+  ASSERT(uv_last_error(uv_default_loop()).code == UV_EINVAL);
+
+  ASSERT(work_cb_count == 0);
+  ASSERT(after_work_cb_count == 0);
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}