Installing clang 3.8 on Ubuntu 14.04.3

Looks like the latest version for 14.04.3 is clang 3.6 in Trusty Updates. But the developers maintain a PPA which should get you the latest version:

LLVM Debian/Ubuntu nightly packages

To install 3.8 you would first add the key:

wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key|sudo apt-key add -

and then add the repository for 3.8 by adding the following line manually to /etc/apt/sources.list (or using the gui 'Software & Updates'):

deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty-3.8 main

Screenshot here to demonstrate the technique:

Then run the following:

sudo apt-get update
sudo apt-get install clang-3.8 lldb-3.8

Test the installation as follows:

andrew@corinth:~$ clang-3.8 --version
clang version 3.8.0-svn262614-1~exp1 (branches/release_38)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
andrew@corinth:~$ 

And hopefully this will get you going...