Re: Order of destruct of local variables

Dan Barbus <>
Wed, 23 Jul 2008 02:36:39 CST

Don't rely on any order! This is the best choice for you to avoid
running into undefined behaviour! If you need ordered deletion than
write a little tool class for that!

     AutoCleanup autoCleanup;
     AB* ab = autoCleanup(new AB);
     AC* ac = autoCleanup(new AC);

"ac" will be destroyed before "ab"!

Actually, yes, rely on the order. It is guaranteed, and very useful.
Consider this code (used when working with boost serialization):

         SomeClass *obj = new SomeClass();

1> std::ofstream out("file.xml");
2> archive::xml_oarchive oarch(out);

         oarch << boost::serialization::make_nvp<SomeClass>("ObjData",
         return obj;

Here, you are guaranteed that the 'out' object (1) is valid past the
scope of 'oarch' (2), and still valid in oarch's destructor. Trying to
build around this, (to add extra code to get extra insurance the
destruction order is valid), complicates the code unnecessarily (using
extra accolades, dynamically allocating the memory or using smart
pointers, etc) and makes it uglier and harder to understand.


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