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user1027802
Asked: 2019-12-24 05:01:58 +0800 CST

How to set Clang 9 as the default C++ compiler on Ubuntu 19.10?

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how do I set Clang 9 as the default C++ compiler on Ubuntu 19.10? I searched the internet, but nothing helped. Thank you for answer :)

default c++ compiler clang 19.10

2 Answers

    1. Install clang version 9 from the default Ubuntu repositories in Ubuntu 19.10 and later.

      sudo apt install clang-9

    2. /usr/bin/c++ is actually a symbolic link to:

      /etc/alternatives/c++

      which in turn is also a symbolic link to:

      /usr/bin/g++

      so on Ubuntu c++ is g++ and g++ is g++ explicitly.

      Set Clang 9 as the default C++ compiler using c++ so that build processes can still use g++ explicitly if they want to.

      sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/c++ 40
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++-9 60
sudo update-alternatives --config c++

    After running sudo update-alternatives --config c++ a menu of c++ versions will appear and you will be asked to select the default c++ version as follows: 

    Press <enter> to keep the current choice[*], or type selection number:

    Input a selection number from the menu and press Enter.

    clang-9 can also be installed in Ubuntu 18.04 if the bionic-proposed/universe repository ( deb http://XX.archive.ubuntu.com/ubuntu/ bionic-proposed universe ) is added to the Ubuntu 18.04 software sources. Replace XX in deb http://XX.archive.ubuntu.com/ubuntu/ bionic-proposed universe with your country code.

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  2. Step 1: Install prerequisites

    sudo apt-get install build-essential xz-utils curl

    Step 2: Download the necessary binaries and extract them.

    curl -SL http://releases.llvm.org/9.0.0/clang+llvm-9.0.0-x86_64-pc-linux-gnu.tar.xz | tar -xJC

    Step 3: Renaming & moving the binaries.

    mv clang+llvm-9.0.0-x86_64-pc-linux-gnu clang_9.0.0
sudo mv clang_9.0.0 /usr/local

    Step 4: Tell our system where clang-9 is

    export PATH=/usr/local/clang_9.0.0/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/clang_9.0.0/lib:$LD_LIBRARY_PATH

    Step 5: Test the installation

    clang++ -stdlib=libc++ -std=c++2a -Wall example.cpp -o example

    Note

    Clang is not a version of GCC, so it cannot be set as an alternative for /usr/bin/gcc. Never try it, you may break some packages which require GCC-specific features not available in Clang.

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