[boost] [BGL] Visual Studio 12 finish_edge() failure, general BOOST_TTI_HAS_MEMBER_FUNCTION failure?

Subject: [boost] [BGL] Visual Studio 12 finish_edge() failure, general BOOST_TTI_HAS_MEMBER_FUNCTION failure?
From: Michael Behrns-Miller (m_at_[hidden])
Date: 2014-03-31 13:27:34

Hello boost!

In the BGL, finish_edge() is a visitor function of DFS, but it is 
optional.  It is made optional via BOOST_TTI_HAS_MEMBER_FUNCTION. Here's 
how BGL defines it:

-------------

     BOOST_TTI_HAS_MEMBER_FUNCTION(finish_edge)

     template <bool IsCallable> struct do_call_finish_edge {
       template <typename E, typename G, typename Vis>
       static void call_finish_edge(Vis& vis, const E& e, const G& g) {
         vis.finish_edge(e, g);
       }
     };

     template <> struct do_call_finish_edge<false> {
       template <typename E, typename G, typename Vis>
       static void call_finish_edge(Vis&, const E&, const G&) {}
     };

     template <typename E, typename G, typename Vis>
     void call_finish_edge(Vis& vis, const E& e, const G& g) { // Only 
call if method exists
       do_call_finish_edge<has_member_function_finish_edge<Vis, 
void>::value>::call_finish_edge(vis, e, g);
     }

-------------

In all my efforts, the Visual Studio 12 compiler fails to call 
finish_edge().  I've tried templated versions, direct versions, virtual 
versions, with and without const params, inline and not inline.  In 
every case, VS says "code will not be hit, no executable code is 
associated with this line. possible causes: preprocessor directives or 
compiler/linker optimizations".  I'm in debug mode with minimal 
optimizations, and there's no preprocessor wrapper.

It's possible there's a problem with the way I'm calling it, but it 
happens when I use a simple example from another user.  This ticket 
includes very simple sample code that should fire the finish_edge() 
function.  It does not work for me using VS 12:

https://svn.boost.org/trac/boost/ticket/9770
https://svn.boost.org/trac/boost/attachment/ticket/9770/test.cc

I have a large project depending on the BGL, which has been great 
otherwise.  I've coded a workaround by using the other non-optional 
visitor functions.  But there are edge cases (sorry, no pun intended! 
ha) that fail with my workaround.  The only possible solution is to get 
finish_edge() to fire.  I'd like to do it the intended way, rather than 
rewrite BGL code to make finish_edge() non-optional.

I'll go try this with a recent version of gcc now...

Thanks for any input at all!

Michael Behrns-Miller