on Thu Jun 14 2007, Eric Niebler <eric-AT-boost-consulting.com> wrote:
David Abrahams wrote:
on Thu Jun 14 2007, Eric Niebler <eric-AT-boost-consulting.com> wrote:
I also seem to recall that there was still some question as to whether the use of the reference violated the ODR, if the reference is not optimized away. I don't think we ever got an answer to that question.
I don't think there ever was any question about that. At least, I never had a question about it. References don't have any identity distinct from the object they reference.
Funny you should say that, since you were the one who sent the "Are references subject to ODR?" question to the std reflector:
David Abrahams <dave@boost-consulting.com> 4/1/06 reply-to c++std-core@accu.org to undisclosed-recipients <> date Apr 1, 2006 9:02 AM subject Are references subject to ODR? To: C++ core language mailing list Message c++std-core-11390
Is the following program legal?
// a.cpp int x; int& y = x;
// b.cpp extern int x; int& y = x;
My impression is that it is not legal because references are not explicitly given an exemption in 3.2/5
If I am right, should it be so? It's hard to imagine how this could be a problem.
The result of ensuing discussion was that a reference is a pointer, and so they *do* have identity.
That's a different question than I thought you were referring to. I would put the reference itself in an unnamed namespace, and I'm pretty sure that handles it. As long as the reference refers to something not in an unnamed namespace: template<typename T> struct static_const { static T const value; }; template<typename T> T const static_const<T>::value = {}; struct placeholder {}; namespace // <<============== HERE { placeholder const &_1 = static_const<placeholder>::value; } template<class T> void foo(T const &) { // use _1 here. OK, _1 refers to the same object // in all translation units. It doesn't matter that the // reference is has a different identity; the object is // the same: static_const<placeholder>::value } -- Dave Abrahams Boost Consulting http://www.boost-consulting.com The Astoria Seminar ==> http://www.astoriaseminar.com