Use new 3.14 C APIs when available (#5854)

* Use new 3.14 C APIs when available

Use the new "unstable" C APIs for the functions added in #5494.

* style: pre-commit fixes

---------

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

Author: colesbury

include/pybind11/detail/class.h

@@ -314,8 +314,9 @@ inline void traverse_offset_bases(void *valueptr,
 
 #ifdef Py_GIL_DISABLED
 inline void enable_try_inc_ref(PyObject *obj) {
-    // TODO: Replace with PyUnstable_Object_EnableTryIncRef when available.
-    // See https://github.com/python/cpython/issues/128844
+#    if PY_VERSION_HEX >= 0x030E00A4
+    PyUnstable_EnableTryIncRef(obj);
+#    else
     if (_Py_IsImmortal(obj)) {
         return;
     }
@@ -330,6 +331,7 @@ inline void enable_try_inc_ref(PyObject *obj) {
             return;
         }
     }
+#    endif
 }
 #endif
 

include/pybind11/detail/type_caster_base.h

@@ -253,9 +253,9 @@ PYBIND11_NOINLINE handle get_type_handle(const std::type_info &tp, bool throw_if
 
 inline bool try_incref(PyObject *obj) {
     // Tries to increment the reference count of an object if it's not zero.
-    // TODO: Use PyUnstable_TryIncref when available.
-    // See https://github.com/python/cpython/issues/128844
-#ifdef Py_GIL_DISABLED
+#if defined(Py_GIL_DISABLED) && PY_VERSION_HEX >= 0x030E00A4
+    return PyUnstable_TryIncRef(obj);
+#elif defined(Py_GIL_DISABLED)
     // See
     // https://github.com/python/cpython/blob/d05140f9f77d7dfc753dd1e5ac3a5962aaa03eff/Include/internal/pycore_object.h#L761
     uint32_t local = _Py_atomic_load_uint32_relaxed(&obj->ob_ref_local);