linux w_char 转 char

    wchar_t    returnString1[5120];
setlocale(LC_ALL, "UTF-8");
                int nLen=wcstombs(NULL, returnString1, 0);
                char* m_char=new char[nLen + 1];
                memset(m_char, 0, nLen + 1);
                int nRet=wcstombs(m_char, retstruc.returnString1, nLen + 1);
                m_char[nLen] = '\0';
    fun(m_char......................