Does taking address of function template specialization not force instantiation?

From:
Gerhard Menzl <clcppm-poster@this.is.invalid>
Newsgroups:
comp.lang.c++.moderated
Date:
Fri, 11 Apr 2008 11:50:18 CST
Message-ID:
<ftntlt$l93$1@news.datemas.de>
Consider:

     #include <algorithm>
     #include <vector>

     template <typename Element,
               typename Member,
               Member (Element::*memPtr)()>
     bool lessMember(Element const& left, Element const& right)
     {
         return (left.*memPtr)() < (right.*memPtr)();
     }

     class C
     {
     public:
         C(int i, long l) : m_i(i), m_l(l) {}

         int GetInt() { return m_i; }
         long GetLong() { return m_l; }

     private:
         int m_i;
         long m_l;
     };

     int main()
     {
         std::vector<C> vc;

         static int const elementCount = 3;

         for (int elem = 0; elem < elementCount; ++elem)
             vc.push_back(C(elem, elementCount - elem));

// linker error without the following line uncommented
// bool b = lessMember<C, long, &C::GetLong>(vc[0], vc[1]);

         std::sort(vc.begin(),
                   vc.end(),
                   lessMember<C, long, &C::GetLong>);
     }

Unless the function template specialization lessMember<C, long,
&C::GetLong> is called explicitly, my compiler (Visual C++ 6.0) does not
instantiate the template and causes a linker error (unresolved
external). Just taking the address of the specialization in the call to
std::sort does not seem to suffice. Is this one of the many limitations
of this outdated compiler, or does the Standard really not require an
instantiation here?

According to 14.7.1/2, a "function template specialization is implicitly
instantiated when the specialization is referenced in a context that
requires a function definition to exist". I would have assumed that
taking the address of a function (template specialization) requires its
definition.

In case instantiation is not required: is there any way to force
instantiation without an explicit specialization (in the actual code,
the function template is called from with in another function template),
and without inserting a dummy call for every specialization?

--
Gerhard Menzl

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