gcc 8.1.0
下载源代码包，执行contrib/download_prerequisites，如果网络不畅通，直接wget下载即可。下载之后重新执行contrib/download_prerequisites，它会校验。
可能需要的依赖
yum install gcc-c++ -y
yum install libgcc.i686 -y
yum install glibc-devel.i686 -y
不要在gcc自己的代码中configure
../gcc-8.1.0/configure –prefix=/com/test/gcc81 –enable-languages=c,c++
make
make install
glibc 2.27
把gcc加入到环境变量
echo “slibdir=/com/test/glibc227/lib64″ > configparms
这是把so放入lib64的唯一方法，参考 http://devpit.org/wiki/Gnu_Toolchain/GLIBC/Building_GLIBC#64-bit_config
# farking configparms file is a hidden/secret config file and is the only
# place slibdir can be set. If you don't set slibdir to lib64/ it'll put
# ld64.so in lib/ which'll make gcc, objdump, and friends puke.
/root/glibc-2.27/configure –prefix=/com/test/glibc227 –libdir=/com/test/glibc227/lib64
make
make install
gcc math.c -o new -lm -I /com/test/glibc227/include/ -L /com/test/glibc227/lib -Wl,-rpath=/com/test/glibc227/lib -Wl,–dynamic-linker=/com/test/glibc227/lib/ld-2.27.so
编译32位 /root/glibc-2.27/configure –prefix=/com/test/glibc227 –host=i686-linux-gnu –build=i686-linux-gnu CC=”gcc -m32″ CXX=”g++ -m32″ CFLAGS=”-O2 -march=i686″ CXXFLAGS=”-O2 -march=i686″
