boost::filesystem::path and std::string

Question

I have a String class which has a member std::string. One of the constructor is

String (std::string s)
{
    // member: std::string _mString;
    _mString = s;  // error on path assignment
}

I now have functions that take String as parameter, e.g. Load(String path);

but it turns out that boost::filesystem::path::string() is incompatible with that String constructor, yet, normally assigning is ok

boost::filesystem::path somepath("some directory")
std::string filename = somepath.extension(); // OK!

What is happening? How can I make my constructor work? Thanks.

EDIT: Issue solved by making it const ref, but still curious why the error because it seems ok to pass a copy since it can be assigned directly. Error in file xstring

void __CLR_OR_THIS_CALL _Tidy(bool _Built = false,
        size_type _Newsize = 0)
        {   // initialize buffer, deallocating any storage
        if (!_Built)
            ;
        else if (_BUF_SIZE <= _Myres)
            {   // copy any leftovers to small buffer and deallocate
            _Elem *_Ptr = _Bx._Ptr;
            if (0 < _Newsize)
                _Traits_helper::copy_s<_Traits>(_Bx._Buf, _BUF_SIZE, _Ptr, _Newsize);
            _Mybase::_Alval.deallocate(_Ptr, _Myres + 1);
            }
        _Myres = _BUF_SIZE - 1; // **** ERROR ***
        _Eos(_Newsize);
        }

Answer 1

in your constructor: String (std::string s) should be String (const std::string& s)