Hi,

During my investigation of vfs posix MPY 1.15, I found that there is issue in logic as following, although I have not tested it yet. Please refer to file https://github.com/micropython/micropython/blob/master/extmod/vfs_posix.c, line 271.

At first, old_path points to root buffer, member of mp_obj_vfs_posix_t .
After that, new_path also points to root buffer with new value "new_path_in". At this point, both old_path and new_path points to the same string in root buffer with the latest value "new_path_in".

So when executing rename(old_path, new_path) will be failed.

STATIC mp_obj_t vfs_posix_rename(mp_obj_t self_in, mp_obj_t old_path_in, mp_obj_t new_path_in) {
    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
    const char *old_path = vfs_posix_get_path_str(self, old_path_in);
    const char *new_path = vfs_posix_get_path_str(self, new_path_in);
    MP_THREAD_GIL_EXIT();
    int ret = rename(old_path, new_path);
    MP_THREAD_GIL_ENTER();
    if (ret != 0) {
        mp_raise_OSError(errno);
    }
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_3(vfs_posix_rename_obj, vfs_posix_rename);