foo.cc: In member function 'bool FTP::connect(std::__cxx11::string, int)':
foo.cc:81:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (userMap.size() >= maxUserNumber)
                 ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
foo.cc: In member function 'bool FTP::quit(std::__cxx11::string)':
foo.cc:104:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 0; i < taskFile.size(); i++)
                             ~~^~~~~~~~~~~~~~~~~
foo.cc:111:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 0; i < taskFold.size(); i++)
                             ~~^~~~~~~~~~~~~~~~~
foo.cc: In member function 'bool FTP::startdownload(std::__cxx11::string, std::__cxx11::string)':
foo.cc:211:5: warning: control reaches end of non-void function [-Wreturn-type]
     }
     ^

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