fix the compile bug for gcc
fix the compile bug for gcc

austinbyers/parameter_server,avantcredit/parameter_server,avantcredit/parameter_server,hjk41/parameter_server,hjk41/parameter_server,ashhher3/parameter_server,xindaya/parameter_server,austinbyers/parameter_server,avantcredit/parameter_server,dmlc/parameter_server,hjk41/parameter_server,austinbyers/parameter_server,dmlc/parameter_server,ashhher3/parameter_server,dmlc/parameter_server,ashhher3/parameter_server,avantcredit/parameter_server,dmlc/parameter_server,hjk41/parameter_server,ashhher3/parameter_server,xindaya/parameter_server,xindaya/parameter_server,austinbyers/parameter_server,hjk41/parameter_server,austinbyers/parameter_server,xindaya/parameter_server