Make globals() cheaper.

Author: adalisk-emikhaylov

include/pybind11/detail/non_limited_api.h

@@ -186,7 +186,7 @@ PYBIND11_NONLIMITEDAPI_FUNC(PyInterpreterState *, PyInterpreterState_Get, (), ()
 PYBIND11_NONLIMITEDAPI_FUNC(PyObject *, PyInterpreterState_GetDict, (PyInterpreterState *state), (state))
 PYBIND11_NONLIMITEDAPI_FUNC(int, pybind11_traverse, (PyObject *self, visitproc visit, void *arg), (self, visit, arg))
 PYBIND11_NONLIMITEDAPI_FUNC(int, pybind11_clear, (PyObject *self), (self))
-PYBIND11_NONLIMITEDAPI_FUNC(void, globals, (dict &out), (out))
+PYBIND11_NONLIMITEDAPI_FUNC(void, globals, (std::optional<dict> &out), (out))
 PYBIND11_NONLIMITEDAPI_FUNC(PyObject *, dict_getitemstringref, (PyObject *v, const char *key), (v, key))
 
 PYBIND11_NAMESPACE_END(non_limited_api)

include/pybind11/pybind11.h

@@ -1065,9 +1065,9 @@ using module = module_;
 /// Return a dictionary representing the global variables in the current execution frame,
 /// or ``__main__.__dict__`` if there is no frame (usually when the interpreter is embedded).
 inline dict globals() {
-    dict ret;
+    std::optional<dict> ret;
     non_limited_api::globals(ret);
-    return ret;
+    return ret.value();
 }
 
 template <typename... Args, typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>>

source/non_limited_api/non_limited_api.cpp

@@ -1876,8 +1876,10 @@ int pybind11::non_limited_api::pybind11NLA_pybind11_clear(PyObject *self)
     return 0;
 }
 
-void pybind11::non_limited_api::pybind11NLA_globals(dict &out)
+void pybind11::non_limited_api::pybind11NLA_globals(std::optional<dict> &out)
 {
+    // Here we return via `std::optional`, since default-constructing the receiving dict is apparently not free as I hoped.
+
 #if PY_VERSION_HEX >= 0x030d0000
     PyObject *p = PyEval_GetFrameGlobals();
     out = p ? reinterpret_steal<dict>(p)