更新Ubuntu的gcc和g++版本
首先安装gcc和g++版本，依次进行如下操作：
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-4.8
sudo apt-get install g++-4.8
进入/usr/bin/把gcc/g++文件夹删除，建立链接到gcc-4.8/g++-4.8:
cd /usr/bin
sudo rm gcc
sudo ln -s gcc-4.8 gcc
sudo rm g++
sudo ln -s g++-4.8 g++
查看gcc/g++版本号
linux@ubuntu:~$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-linux-gnu/4.8/lto-wrapper
Target: i686-linux-gnu
Configured with: ../src/configure -v –with-pkgversion=’Ubuntu 4.8.1-2ubuntu1~12.04’ –with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs –enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ –prefix=/usr –program-suffix=-4.8 –enable-shared –enable-linker-build-id –libexecdir=/usr/lib –without-included-gettext –enable-threads=posix –with-gxx-include-dir=/usr/include/c++/4.8 –libdir=/usr/lib –enable-nls –with-sysroot=/ –enable-clocale=gnu –enable-libstdcxx-debug –enable-libstdcxx-time=yes –enable-gnu-unique-object –enable-plugin –with-system-zlib –disable-browser-plugin –enable-java-awt=gtk –enable-gtk-cairo –with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-i386/jre –enable-java-home –with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-i386 –with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-i386 –with-arch-directory=i386 –with-ecj-jar=/usr/share/java/eclipse-ecj.jar –enable-objc-gc –enable-targets=all –enable-multiarch –disable-werror –with-arch-32=i686 –with-multilib-list=m32,m64 –with-tune=generic –enable-checking=release –build=i686-linux-gnu –host=i686-linux-gnu –target=i686-linux-gnu
Thread model: posix
gcc version 4.8.1 (Ubuntu 4.8.1-2ubuntu1~12.04)
linux@ubuntu:~$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-linux-gnu/4.8/lto-wrapper
Target: i686-linux-gnu
Configured with: ../src/configure -v –with-pkgversion=’Ubuntu 4.8.1-2ubuntu1~12.04’ –with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs –enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ –prefix=/usr –program-suffix=-4.8 –enable-shared –enable-linker-build-id –libexecdir=/usr/lib –without-included-gettext –enable-threads=posix –with-gxx-include-dir=/usr/include/c++/4.8 –libdir=/usr/lib –enable-nls –with-sysroot=/ –enable-clocale=gnu –enable-libstdcxx-debug –enable-libstdcxx-time=yes –enable-gnu-unique-object –enable-plugin –with-system-zlib –disable-browser-plugin –enable-java-awt=gtk –enable-gtk-cairo –with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-i386/jre –enable-java-home –with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-i386 –with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-i386 –with-arch-directory=i386 –with-ecj-jar=/usr/share/java/eclipse-ecj.jar –enable-objc-gc –enable-targets=all –enable-multiarch –disable-werror –with-arch-32=i686 –with-multilib-list=m32,m64 –with-tune=generic –enable-checking=release –build=i686-linux-gnu –host=i686-linux-gnu –target=i686-linux-gnu
Thread model: posix
gcc version 4.8.1 (Ubuntu 4.8.1-2ubuntu1~12.04)