On Apr 3, 2013, at 11:28 AM, Derek Gaston <[email protected]> wrote:
> Ok - we just looked into this - Ben: It looks like you're not ever creating
> RemoteElem which is why it's not getting registered.
>
> At the bottom of remote_elem.h you have this:
>
> extern const RemoteElem* remote_elem;
>
> But that's just creating a pointer. In the .C you have this:
>
> const RemoteElem* remote_elem;
>
> But, again, that's not creating a RemoteElem.
>
> In fact, nothing is ever creating a RemoteElem... so it doesn't get
> registered with the Singleton class. In remote_elem.C you could do this:
>
> extern const RemoteElem* remote_elem = new RemoteElem;
That would be at risk of creating the RemoteElem before its underlying
reference counter is set up, which is what got us here in the first place...
in remote_elem.C, I am doing this:
namespace
{
// Class to be dispatched by Singleton::setup()
// to create the \p RemoteElem singleton.
// While this actual object has file-level static
// scope and will be initialized before main(),
// importantly the setup() method will not be invoked
// until after main().
class RemoteElemSetup : public Singleton::Setup
{
void setup ()
{
RemoteElem::create();
}
} remote_elem_setup;
}
the remote_elem_setup should get instantiated statically, and its *constructor*
adds (this) tot the list of objects to be invoked by Singleton::setup(). In
turn, that should call remote_elem_setup.setup() indirectly, and create the
singleton.
This is precisely the mechanism we described for singleton desctructors, now
turned on its head.
The only problem I can see is if the remote_elem_setup object is getting
created before the container inside libmesh_singleton.C, resulting in undefined
behavior.
-Ben
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