After installing Ubuntu 16.04 LTS, I found that gcc 5.3 installed by default but I don't receive any updates to gcc. I opened up GCC website and I found the new release 6.1. How do I update?

Output of gcc --version:

gcc (Ubuntu 5.3.1-14ubuntu2.1) 5.3.1 20160413 Copyright (C) 2015 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.
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2 Answers

You can install GCC 6 by adding the ubuntu-toolchain-r/test PPA. To do so, run the following commands:

sudo add-apt-repository ppa:ubuntu-toolchain-r/test sudo apt update sudo apt install gcc-6

You can verify that gcc-6 is installed by running gcc-6 --version and the output should say gcc-6 (Ubuntu 6.1.1-2ubuntu12~16.04) 6.1.1 20160510.

As suggested by Mohamed Slama, if you want to further change the default GCC and G++ to the latest versions, install g++-6 with

sudo apt install g++-6

and then run

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 60 --slave /usr/bin/g++ g++ /usr/bin/g++-6
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If you want to build it from source (which I recommend as you can for example make a cross-compiler, etc.) download the source from a mirror.

Then extract it with:

tar -xvf gcc-6.1.0.tar.gz

After that change directory to there:

cd gcc-6.1.0

Then create build directory and cd to it:

mkdir build cd build

Then configure the makefile (--disable-multilib means to not build libraries for cross-compilation):

../configure --enable-languages=c,c++ --disable-multilib

If you ran into errors due to missing required libraries or other prerequisites: (Credits to this)

./contrib/download_prerequisites

And then build it:

make -j 8

This process may take some time and after done invoke this:

sudo make install

That's it!

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