DLL export of std::exception Triggers Warning

[johnpatek]

Output from msbuild:

Build succeeded.

"J:\workspace\sigfn\build\ALL_BUILD.vcxproj" (default target) (1) ->
"J:\workspace\sigfn\build\examples\pause++.vcxproj" (default target) (5) ->
"J:\workspace\sigfn\build\src\sigfn++_a.vcxproj" (default target) (6) ->
(ClCompile target) ->
  J:\workspace\sigfn\include\sigfn.hpp(56,5): warning C4275: non dll-interface class 'std::exception' used as base for dll-interface class 'sigfn::exception' [J:\workspace\sigfn\build\src\sigfn++_a.vcxproj]
  J:\workspace\sigfn\include\sigfn.hpp(58,21): warning C4251: 'sigfn::exception::_error_message': class 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>' needs to have dll-interface to be
used by clients of class 'sigfn::exception' [J:\workspace\sigfn\build\src\sigfn++_a.vcxproj]


"J:\workspace\sigfn\build\ALL_BUILD.vcxproj" (default target) (1) ->
"J:\workspace\sigfn\build\examples\pause++.vcxproj" (default target) (5) ->
  J:\workspace\sigfn\include\sigfn.hpp(56,5): warning C4275: non dll-interface class 'std::exception' used as base for dll-interface class 'sigfn::exception' [J:\workspace\sigfn\build\examples\pause++.vcxproj
]
  J:\workspace\sigfn\include\sigfn.hpp(58,21): warning C4251: 'sigfn::exception::_error_message': class 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>' needs to have dll-interface to be
used by clients of class 'sigfn::exception' [J:\workspace\sigfn\build\examples\pause++.vcxproj]


"J:\workspace\sigfn\build\ALL_BUILD.vcxproj" (default target) (1) ->
"J:\workspace\sigfn\build\src\sigfn++.vcxproj" (default target) (8) ->
  J:\workspace\sigfn\include\sigfn.hpp(56,5): warning C4275: non dll-interface class 'std::exception' used as base for dll-interface class 'sigfn::exception' [J:\workspace\sigfn\build\src\sigfn++.vcxproj]
  J:\workspace\sigfn\include\sigfn.hpp(58,21): warning C4251: 'sigfn::exception::_error_message': class 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>' needs to have dll-interface to be
used by clients of class 'sigfn::exception' [J:\workspace\sigfn\build\src\sigfn++.vcxproj]

    6 Warning(s)
    0 Error(s)

Time Elapsed 00:00:13.25

J:\workspace\sigfn\build>