qt5.9 安装mqtt模块遇到的问题:unrecognized command line option “-std=c++1z”
错误:sudoadd-apt-repositoryppa:ubuntu-toolchain-r/testsudoapt-getupdatesudoapt-getinstallg++-5sudoapt-getinstallc++-5cd/usr/binsudormgccsudormg++sudoln-s/usr/bin/gcc-5./gccsudoln-s/usr/bin/g++-5./g++解决: