Add test_class_release_gil_before_calling_cpp_dtor

tests/CMakeLists.txt

@@ -119,6 +119,7 @@ set(PYBIND11_TEST_FILES
     test_callbacks
     test_chrono
     test_class
+    test_class_release_gil_before_calling_cpp_dtor
     test_class_sh_basic
     test_class_sh_disowning
     test_class_sh_disowning_mi

tests/test_class_release_gil_before_calling_cpp_dtor.cpp

@@ -0,0 +1,51 @@
+#include <pybind11/pybind11.h>
+
+#include "pybind11_tests.h"
+
+#include <string>
+#include <unordered_map>
+
+namespace pybind11_tests {
+namespace class_release_gil_before_calling_cpp_dtor {
+
+using RegistryType = std::unordered_map<std::string, int>;
+
+RegistryType &PyGILState_Check_Results() {
+    static auto *singleton = new RegistryType();
+    return *singleton;
+}
+
+template <int> // Using int as a trick to easily generate a series of types.
+struct ProbeType {
+private:
+    std::string unique_key;
+
+public:
+    explicit ProbeType(const std::string &unique_key) : unique_key{unique_key} {}
+
+    ~ProbeType() {
+        RegistryType &reg = PyGILState_Check_Results();
+        assert(reg.count(unique_key) == 0);
+        reg[unique_key] = PyGILState_Check();
+    }
+};
+
+} // namespace class_release_gil_before_calling_cpp_dtor
+} // namespace pybind11_tests
+
+TEST_SUBMODULE(class_release_gil_before_calling_cpp_dtor, m) {
+    using namespace pybind11_tests::class_release_gil_before_calling_cpp_dtor;
+
+    py::class_<ProbeType<0>>(m, "ProbeType0").def(py::init<std::string>());
+
+    py::class_<ProbeType<1>>(m, "ProbeType1", py::release_gil_before_calling_cpp_dtor())
+        .def(py::init<std::string>());
+
+    m.def("GetPyGILState_Check_Result", [](const std::string &unique_key) -> std::string {
+        RegistryType &reg = PyGILState_Check_Results();
+        if (reg.count(unique_key) == 0) {
+            return "MISSING";
+        }
+        return std::to_string(reg[unique_key]);
+    });
+}

tests/test_class_release_gil_before_calling_cpp_dtor.py

@@ -0,0 +1,19 @@
+import gc
+
+import pytest
+
+from pybind11_tests import class_release_gil_before_calling_cpp_dtor as m
+
+
+@pytest.mark.parametrize(
+    ("probe_type", "unique_key", "expected_result"),
+    [
+        (m.ProbeType0, "without_manipulating_gil", "1"),
+        (m.ProbeType1, "release_gil_before_calling_cpp_dtor", "0"),
+    ],
+)
+def test_gil_state_check_results(probe_type, unique_key, expected_result):
+    probe_type(unique_key)
+    gc.collect()
+    result = m.GetPyGILState_Check_Result(unique_key)
+    assert result == expected_result