在升级安装GCC9.3.0过程中，出现了下面的异常

configure: error: Building GCC requires GMP 4.2+, MPFR 2.4.0+ and MPC 0.8.0+.

问题分析

该问题说明要安装的GCC版本依赖确实，在编译安装异常中，给出了解决方法(注意ftp://gcc.gnu.org/pub/gcc/infrastructure/)：

configure: error: Building GCC requires GMP 4.2+, MPFR 2.4.0+ and MPC 0.8.0+.
Try the --with-gmp, --with-mpfr and/or --with-mpc options to specify
their locations. Source code for these libraries can be found at
their respective hosting sites as well as at
ftp://gcc.gnu.org/pub/gcc/infrastructure/. See also
http://gcc.gnu.org/install/prerequisites.html for additional info. If
you obtained GMP, MPFR and/or MPC from a vendor distribution package,
make sure that you have installed both the libraries and the header
files. They may be located in separate packages.

问题解决

根据问题原因，可以在错误信息提示的下载页面：ftp://gcc.gnu.org/pub/gcc/infrastructure/。下载相应的包，进行安装。

1 浏览器打开链接：http://gcc.gnu.org/pub/gcc/infrastructure/。

2、找到需要的三个包地址，下载下来(这里使用wget命令)：

wget ftp://gcc.gnu.org/pub/gcc/infrastructure/gmp-6.1.0.tar.bz2
wget ftp://gcc.gnu.org/pub/gcc/infrastructure/mpfr-3.1.4.tar.bz2
wget ftp://gcc.gnu.org/pub/gcc/infrastructure/mpc-1.0.3.tar.gz

编译安装各依赖（这些依赖的安装需要root权限，如果没有 root权限，貌似装不了，如果您可以在米有root权限下安装，请私信我）

1 安装GMP

tar -jxvf gmp-6.1.0.tar.bz2
cd gmp-6.1.0
./configure
make && make install

2 安装MPFR

tar -jxvf mpfr-3.1.4.tar.bz2
cd mpfr-3.1.4
./configure
make && make install

3 安装MPC

tar -zxvf mpc-1.0.3.tar.gz
cd mpc-1.0.3
./configure
make && make install