[boost] [units] objects with internal linkage in headers

13 Feb 2007

      AMDG

All the static const objects in the library cause ODR
violations for functions that use them.  You can avoid
this by only putting a reference in the unnamed namespace.

#define BOOST_UNITS_STATIC_CONSTANT(type, name)    \
    template<bool> struct name##_intance_t {       \
        static const type instance;                \
    };                                             \
    namespace {                                    \
        const type& name(name##_intance_t<true>::instance);\
    }                                              \
    template<bool b>                               \
    type name##_intance_t<b>::instance

BOOST_UNITS_STATIC_CONSTANT(energy, joule);
BOOST_UNITS_STATIC_CONSTANT(typeof(1.0*meters/second) , c) = 
299792458*meters/second;

In Christ,
Steven Watanabe