Re: Order of destruction of static members and static objects

From:
Victor Bazarov <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Fri, 27 Nov 2009 09:49:22 -0500
Message-ID:
<heoouc$ubf$1@news.datemas.de>
Juha Nieminen wrote:

  Assume we have a class like this:

class A
{
    class Container;
    static Container container;


This is a declaration. Where is the definition?

 public:
    ~A();
};

  Assume that A::~A() does something with A::container (eg. removes or
changes an element from it or whatever).

  Also assume that somewhere else there's a global instantiation of A
like this:

namespace { A anObject; }

  The question is: Is it guaranteed that 'anObject' will be destroyed
before 'A::container'?


No, it's not guaranteed. What's guaranteed, however, is that if they
are created in some order, then they are destructed in the reverse order.

  Because, obviously, if 'A::container' is destroyed first, then the
destructor of 'anObject' will be accessing a destroyed Container object.


Yep.

  If it's not guaranteed, then how can one use static members safely?


Apparently you need 'A::container' to be a singleton. See any of the
existing implementations of that pattern. Most simple ones actually
create the singleton on demand (in freestore) and never destroy it.

V
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