fix: clear local internals after finalizing interpreter #2101 (#3744)

* Clear local internals after finalizing interpreter

* Add descriptive comments

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: StarQTius

include/pybind11/embed.h

@@ -198,6 +198,10 @@ inline void finalize_interpreter() {
     if (builtins.contains(id) && isinstance<capsule>(builtins[id])) {
         internals_ptr_ptr = capsule(builtins[id]);
     }
+    // Local internals contains data managed by the current interpreter, so we must clear them to
+    // avoid undefined behaviors when initializing another interpreter
+    detail::get_local_internals().registered_types_cpp.clear();
+    detail::get_local_internals().registered_exception_translators.clear();
 
     Py_Finalize();
 

tests/test_embed/test_interpreter.cpp

@@ -375,3 +375,21 @@ TEST_CASE("sys.argv gets initialized properly") {
     }
     py::initialize_interpreter();
 }
+
+TEST_CASE("make_iterator can be called before then after finalizing an interpreter") {
+    // Reproduction of issue #2101 (https://github.com/pybind/pybind11/issues/2101)
+    py::finalize_interpreter();
+
+    std::vector<int> container;
+    {
+        pybind11::scoped_interpreter g;
+        auto iter = pybind11::make_iterator(container.begin(), container.end());
+    }
+
+    REQUIRE_NOTHROW([&]() {
+        pybind11::scoped_interpreter g;
+        auto iter = pybind11::make_iterator(container.begin(), container.end());
+    }());
+
+    py::initialize_interpreter();
+}