MySQL C++ Connector strange compile warning

MySQL C++ Connector strange compile warning

I have an application that uses the MySQL C++ Connector, version 1.1.3.
Everything works fine, but the compiler has been throwing an odd warning
that I can't seem to make go away:
sqlstring.h(38): warning C4251: 'sql::SQLString::realStr' : class
'std::basic_string<_Elem,_Traits,_Ax>' needs to have dll-interface to be
used by clients
of class 'sql::SQLString'
with
[
_Elem=char,
_Traits=std::char_traits<char>,
_Ax=std::allocator<char>
]
As I said, everything works fine, this warning is just bugging me. It
shows up in a lot of places in the Connector library. What is it and how
can I fix it?