Undefined references in libstdc++ headers

[Placid Pundit]

I'm using the latest 4.1 from SVN and most things have worked up to
this point (I've built a lot of software with it).  But when linking
the Ogre3D library, I'm seeing a lot of undefined references in
libstdc++ headers:

in /usr/include/c++/4.1.0/bits/basic_string.h:230:
undefined reference to `std::basic_string<char,
std::char_traits<char>, std::allocator<char>
>::_Rep::_S_empty_rep_storage'

If I pass --enable-fully-dynamic-string when building, the next line
has a similar problem instead.  And similar problems occur throughout
the other headers.  So it looks like an installation problem.  But I
have been unable to find anything obviously wrong with it.