[GitHub] [arrow] paleolimbot commented on a diff in pull request #12558: ARROW-15841: [R] Implement SafeCallIntoR to safely call the R API from another thread

[GitBox <gi...@apache.org>]

paleolimbot commented on code in PR #12558:
URL: https://github.com/apache/arrow/pull/12558#discussion_r843889620


##########
r/src/safe-call-into-r-impl.cpp:
##########
@@ -0,0 +1,89 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include "./arrow_types.h"
+#if defined(ARROW_R_WITH_ARROW)
+
+#include <functional>
+#include <thread>
+#include "./safe-call-into-r.h"
+
+MainRThread& GetMainRThread() {
+  static MainRThread main_r_thread;
+  return main_r_thread;
+}
+
+// [[arrow::export]]
+void InitializeMainRThread() { GetMainRThread().Initialize(); }
+
+// [[arrow::export]]
+std::string TestSafeCallIntoR(cpp11::function r_fun_that_returns_a_string,
+                              std::string opt) {
+  if (opt == "async_with_executor") {
+    std::thread* thread_ptr;
+
+    auto result =
+        RunWithCapturedR<std::string>([&thread_ptr, r_fun_that_returns_a_string]() {
+          auto fut = arrow::Future<std::string>::Make();
+          thread_ptr = new std::thread([fut, r_fun_that_returns_a_string]() mutable {
+            auto result = SafeCallIntoR<std::string>([&] {
+              return cpp11::as_cpp<std::string>(r_fun_that_returns_a_string());
+            });
+
+            fut.MarkFinished(result);
+          });
+
+          return fut;
+        });
+
+    thread_ptr->join();
+    delete thread_ptr;

Review Comment:
   I can't get this to work without a crash!



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