Segmentation fault if run outside of function

Author: eacousineau

python/pybind11/BUILD.bazel

@@ -79,6 +79,12 @@ cc_binary(
     deps = [":include"],
 )
 
+cc_binary(
+    name = "test_gil_issue1723",
+    srcs = ["custom_tests/test_gil_issue1723.cc"],
+    deps = [":include"],
+)
+
 cc_binary(
     name = "test_unique_ptr_stuff",
     srcs = ["custom_tests/test_unique_ptr_stuff.cc"],

python/pybind11/custom_tests/test_gil_issue1723.cc

@@ -0,0 +1,83 @@
+// From: https://github.com/pybind/pybind11/issues/1723
+#include <iostream>
+#include <thread>
+#include <future>
+
+#include <pybind11/embed.h>
+#include <pybind11/eval.h>
+#include <pybind11/pybind11.h>
+
+namespace py = pybind11;
+
+void hello() {
+  std::cout << "hello\n";
+}
+
+struct Executor {
+
+  void execute() {
+    auto func = channel.get_future().get();
+    func();
+  }
+
+  explicit Executor(py::object callback)
+    : callback(std::move(callback)),
+      channel(),
+      worker([this]{execute();}) {
+  }
+
+  void run() {
+    pybind11::gil_scoped_release release{};
+    channel.set_value(callback);
+  }
+
+  py::object callback;
+  std::promise<py::object> channel;
+  std::thread worker;
+
+  ~Executor() {
+    worker.join();
+  }
+};
+
+void init_module(py::module m) {
+  m.def("hello", &hello, "Say hello");
+  py::class_<Executor>(m, "Executor")
+      .def(py::init<py::object>())
+      .def("run", &Executor::run);
+}
+
+int main(int, char**) {
+  py::scoped_interpreter guard{};
+
+  py::module m("test_module");
+  init_module(m);
+  py::globals()["m"] = m;
+
+  py::print("[ Eval ]");
+  py::exec(R"""(
+def bye():
+    print('bye')
+
+def main():
+    pass
+
+if True:
+    m.hello()
+    ex = m.Executor(bye)
+    ex.run()
+
+use_trace = False
+if use_trace:
+    import sys, trace
+    sys.stdout = sys.stderr
+    tracer = trace.Trace(trace=1, count=0, ignoredirs=["/usr", sys.prefix])
+    tracer.runfunc(main)
+else:
+    main()
+)""");
+
+  py::print("[ Done ]");
+
+  return 0;
+}