报错解决 ：Couldn't find any package by regex 'g++-8'

下午想在Debian 9 stretch 上安装gcc-8 g+±8
报错如下：

-> # apt install gcc-8 g++-8
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package gcc-8
E: Unable to locate package g++-8
E: Couldn't find any package by regex 'g++-8'

我在Ubuntu18.04上的官方库中找到了自带的gcc-8和g+±8，但Debian 9似乎包管理器中不带gcc-8和g+±8。

---

唯一的解决方法是进行编译安装，参考这篇博客：在CentOS/Debian/Ubuntu上编译安装最新版 GCC 8 ， cmake 3 和ninja

---

官网搜索结果显示Debian 10 buster 的包管理器中有gcc-8和g+±8：Debian – 软件包下载地址选择 – gcc-8_8.3.0-6_amd64.deb
你可以手动下载，进行安装：

wget http://ftp.cn.debian.org/debian/pool/main/i/isl/libisl19_0.20-2_amd64.deb
dpkg -i libisl19_0.20-2_amd64.deb 
...
wget http://ftp.us.debian.org/debian/pool/main/g/gcc-8/cpp-8_8.3.0-6_amd64.deb
dpkg -i cpp-8_8.3.0-6_amd64.deb
....
wget http://ftp.us.debian.org/debian/pool/main/g/gcc-8/gcc-8_8.3.0-6_amd64.deb
dpkg -i gcc-8_8.3.0-6_amd64.deb 

配依赖太麻烦了，我用Ubuntu去了。
如果你只下载一个，会报错：

-> # dpkg -i gcc-8_8.3.0-6_amd64.deb 
Selecting previously unselected package gcc-8.
(Reading database ... 173593 files and directories currently installed.)
Preparing to unpack gcc-8_8.3.0-6_amd64.deb ...
Unpacking gcc-8 (8.3.0-6) ...
dpkg: dependency problems prevent configuration of gcc-8:
 gcc-8 depends on cpp-8 (= 8.3.0-6); however:
  Package cpp-8 is not installed.
 gcc-8 depends on gcc-8-base (= 8.3.0-6); however:
  Package gcc-8-base is not installed.
 gcc-8 depends on libcc1-0 (>= 8.3.0-6); however:
  Version of libcc1-0:amd64 on system is 6.3.0-18+deb9u1.
 gcc-8 depends on binutils (>= 2.31.1); however:
  Version of binutils on system is 2.28-5.
 gcc-8 depends on libgcc-8-dev (= 8.3.0-6); however:
  Package libgcc-8-dev is not installed.
 gcc-8 depends on libisl19 (>= 0.15); however:
  Package libisl19 is not installed.
 gcc-8 depends on libmpfr6 (>= 3.1.3); however:
  Package libmpfr6 is not installed.

dpkg: error processing package gcc-8 (--install):
 dependency problems - leaving unconfigured
Processing triggers for man-db (2.7.6.1-2) ...
Errors were encountered while processing:
 gcc-8

唯一的解决方法是进行编译安装，参考这篇博客：在CentOS/Debian/Ubuntu上编译安装最新版 GCC 8 ， cmake 3 和ninja