Peter Dimov wrote:
Eric Niebler: ...
namespace { // This reference should also be statically initialized placeholder<mpl::int_<1> > const & _1 = placeholder_instance<mpl::int_<1> >::value; }
This is a problem for some precompiled header implementations.
Huh.
Some compilers have fixed theirs to allow it, some have not, some only allow(ed?) it when the variables are static.
I notice I left "static" out of the example I sent around, but yes, placeholder_instance<>::value is supposed to be a class static.
Our tests don't show the problem since they don't use precompiled headers.
Step 1: add tests that exhibit the problem with precompiled headers.
So we've relied on bug reports to iron these out, leading to the current status quo in boost/bind/placeholders.hpp.
Using inline functions:
static inline boost::arg<1> _1() { return boost::arg<1>(); }
is the most conservative option since it works everywhere, but it does have the disadvantage that one cannot overload operators for _1.
And bind is one of those libraries that we want to work even on ancient compilers.... <sigh> Maybe we can have a separate Boost.Bind v2 library, like we now have signals and signals2. -- Eric Niebler BoostPro Computing http://www.boostpro.com