So the user should make sure that all of her custom boost swap overloads are declared, /before/ including any function that actually calls boost::swap... right?
David Abrahams wrote:
That is effectively impossible in practice. Someone else who is using boost::swap may #include it earlier.
MSVC has a compiler option that has the effect of #include-ing a specified header file on the first line of every source file (/FI, "Name Forced Include File"). That header file could contain the declarations of all user provided boost::swap overloads, when using MSVC 7.1... Ok, it wouldn't be particularly elegant!
We could add more unit tests, to see if it would work for those specific compilers. But only if we'd agree that there's no objection against having end-users adding their overloads to the boost namespace...
It's probably not a good idea, but as far as I'm concerned, when compilers are broken, you can do all kinds of evil things to compensate without getting sent to Heck.
Okay, I'll see if I can add such a unit test tomorrow. It would probably be based upon Joseph's "specialized_in_other" test, but having an extra boost::swap overload declared and defined /after/ the #include <boost/test/test_tools.hpp>. Hopefully that would be sufficient.
msvc-7.1 fails on both "specialized_in_global" and "specialized_in_other".
I could have sworn that's not what I saw when I responded to your message, but it appears to be the case now. Also it really surprises me because I know msvc-7.1 does do ADL.
It surprised me as well, I only encountered this ADL bug very recently, while I've been using msvc-7.1 for quite a while.
It just doesn't seem to do ADL on template arguments. :-(
I'm sorry, I'm not seeing how that is relevant to any of the failing tests. What am I missing?
Here's where msvc-7.1 fails to do ADL, in utility/swap.hpp: template<class T> void swap_impl(T& left, T& right) { using std::swap; swap(left,right); // <-- No ADL by msvc-7.1 } While msvc-7.1 would have doing ADL if T would have been a specific type, instead of a template argument. Steven Watanabe wrote:
msvc-7.1 is one of the compilers that does all look up in phase 2, I think. So...
namespace users_namespace { class X {}; void swap(X&, X&); }
#if BOOST_WORKAROUND(BOOST_MSVC, == 1310) namespace boost { using users_namespace::swap; } #endif
We have to use a #if to avoid an ODR violation for compilers that implement two-phase name lookup correctly.
So that would be an alternative workaround, to be used by end-users, right? Instead of having them provide a boost::swap overload. (I guess the #if should include GCC 3.3.1, Intel C++ 8.1, and Borland as well.) Would it be preferable to adding a boost::swap overload? Good night, Niels