Joel de Guzman <joel@boost-consulting.com> writes:

Any links to the thread?

No, we've been doing this offline. I'll try to forward something to you.

...

1. The placeholders are statically initialized const POD objects in an unnamed namespace and you have likely ODR violation when used by templates in multiple translation units. 2. The placeholders are dynamically initialized references in an unnamed namespace and you risk undefined behavior when they are used without initialization due to initialization order issues 3. The placeholders are dynamically initialized objects in an unnamed namespace, and you have likely ODR violation *and* initialization order issues Seems from the doc like you have #3, which is the worst of both worlds. No?

Actually it is 4:

4. The placeholders are dynamically initialized *const* objects in namespace phoenix

That's essentially 1, in that you get a different object in each TU and are likely to end up with an ODR violation.

Well, we can easilly make them PODs, so:

5. The placeholders are statically initialized *const* POD objects in namespace phoenix

Same problem.

So, question: how does this code below constitute ODR violation?

namespace x // named { T const pod = T(); // T is a POD }

It does not. You need two translation units and a template, instantiated in each one, that uses your object "pod."

is this link relevant?: http://lists.boost.org/Archives/boost/2004/06/67159.php

Precisely.

how about: http://lists.boost.org/Archives/boost/2001/05/12609.php

I don't think so. Internal linkage doesn't save you from an ODR violation. -- Dave Abrahams Boost Consulting www.boost-consulting.com