做任务给佣金的网站数字营销包括哪六种方式

1 背景

最近在研究C++20中的协程需要安装GCC版本10。用到GCC多版本切换，记录步骤。

2 安装

2.1 Ubuntu 20.04

运行如下命令安装两个版本编译器:

sudo apt install gcc-9 g++-9
sudo apt install gcc-10 g++-10

2.2 Ubuntu 18.04

默认安装最高版本gcc-7,添加Toolchain Test Builds PPA（个人软件包存档），它提供了GCC 10的最新版本

sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt install gcc-9 g++-9
sudo apt install gcc-10 g++-10

3 配置

使用update-alternatives命令配置多编译器版本:

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 90 --slave /usr/bin/g++ g++ /usr/bin/g++-9
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100 --slave /usr/bin/g++ g++ /usr/bin/g++-10

说明:

• gcc与g++版本绑定在一起了，修改gcc版本会同时修改g++版本

4 切换

使用如下命令切换编译器版本:

sudo update-alternatives --config gcc

4.1 切换到版本9

$ sudo update-alternatives --config gcc
There are 2 choices for the alternative gcc (providing /usr/bin/gcc).Selection    Path             Priority   Status
------------------------------------------------------------
* 0            /usr/bin/gcc-10   100       auto mode1            /usr/bin/gcc-10   100       manual mode2            /usr/bin/gcc-9    90        manual modePress <enter> to keep the current choice[*], or type selection number: 2

查看版本:

$ gcc --version
gcc (Ubuntu 9.4.0-1ubuntu1~20.04.3) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ g++ --version
g++ (Ubuntu 9.4.0-1ubuntu1~20.04.3) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

4.2 切换到版本10

$ sudo update-alternatives --config gcc
There are 2 choices for the alternative gcc (providing /usr/bin/gcc).Selection    Path             Priority   Status
------------------------------------------------------------
* 0            /usr/bin/gcc-10   100       auto mode1            /usr/bin/gcc-10   100       manual mode2            /usr/bin/gcc-9    90        manual modePress <enter> to keep the current choice[*], or type selection number: 1

查看版本:

$ gcc --version
gcc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ g++ --version
g++ (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.