我尝试了以下方法，但最后得到了错误。为了确保 4.8.2 没有干扰，我将其删除。
任何建议都会很棒！
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install g++-4.9
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
g++-4.9 : Depends: gcc-4.9-base (= 4.9.2-0ubuntu1~14.04) but 4.9.2-10 is to be installed
Depends: gcc-4.9 (= 4.9.2-0ubuntu1~14.04) but it is not going to be installed
Depends: libstdc++-4.9-dev (= 4.9.2-0ubuntu1~14.04) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
idf@C55t-A:/etc/apt$