RAII in C

It might look like overengineering because I only showed one of the _cleanup_*_ definitions. The version of the systemd code I'm looking at has nine different _cleanup_*_ variants, four of them defined via the DEFINE_TRIVIAL_CLEANUP_FUNC macro. Search for _cleanup_ at http://cgit.freedesktop.org/systemd/systemd/tree/src/shar... (and pretend the rest of that file does not exist; it lives up to the tradition of a module called "util" being used as a dumping ground for assorted bits and pieces).