I have been trying for 3 days to install clang 5.0 on an Ubuntu 16.04 machine. I have tried various guides, but nothing seems to work. When I try to simply grab the latest from SVN and build/install (as detailed here), trying to compile a simple program leads to:

> clang++ basic.cpp
/usr/include/wchar.h:39:11: fatal error: 'stdarg.h' file not found
# include <stdarg.h>

I then tried setting the -DGCC_INSTALL_PREFIX flag for cmake before building, but that leads to the even better error:

> clang++ basic.cpp
fatal error: 'iostream' file not found
#include <iostream>

The steps I've been following are (from the above guide):

> cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local/ \
-G "Unix Makefiles" path/to/llvm
> make
> make check-clang
> make install-clang

Could someone treat me like an idiot and explain step-by-step how to install clang 5.0? Or point me to a guide that even basic fools like me can follow? If you also can explain how to build and install libc++ for C++17, I would be eternally grateful.

Update: It seems I'm not installing clang correctly, since this is the the output of a verbose compilation with clang:

#include <...> search starts here:

and this is the output for g++:

#include <...> search starts here:
  • What is the output of this command: dpkg -l libstdc++-5-dev | tail -1
    – Ravexina
    Apr 15, 2017 at 18:30
  • Do you have build-essential installed?
    – Ravexina
    Apr 15, 2017 at 18:31
  • @Ravexina: ii libstdc++-5-dev:amd64 5.4.0-6ubuntu1~16.04.4 amd64 GNU Standard C++ Library v3 (development files)
    – Steve D
    Apr 15, 2017 at 23:00
  • @Ravexina: and yes, build-essential is installed.
    – Steve D
    Apr 15, 2017 at 23:01

1 Answer 1


Install clang-5 from llvm.org repositores

First, we should add the llvm.org repositories to our sources lists, the line that we should add is:

deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-5.0 main

Open nano and add the above line to this file:

sudo nano /etc/apt/sources.list.d/llvm.list

Add the repository key, it will make apt able to verify the downloaded packages.

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

After that, update your lists:

sudo apt-get update

Then install clang-5:

sudo apt-get install clang-5.0 lldb-5.0 lld-5.0

It should work.

If you want to get a list of all available packages from this newly added repository:

grep -i package: /var/lib/apt/lists/apt.llvm* | cut -f3 -d: | sort | uniq

It will give you a list like:


You can then install whatever of them you want.

It may help your compile problem

The header file that has been mentioned does not exist in your error: stdarg.h is a part of libstdc++-5-dev package.

I've got this package on my machine, so if I run:

aptitude why libstdc++-5-dev

I will get:

i   build-essential Depends g++ (>= 4:5.2)                            
i A g++             Depends g++-5 (>= 5.3.1-3~)                       
i A g++-5           Depends libstdc++-5-dev (= 5.4.0-6ubuntu1~16.04.4)

So it seems that installing the build-essential package should solve this error of yours, cause I'm not sure what you've done.

  • I have build-essential installed. But the output for my aptitude why libstdc++-5-dev is exactly the same as yours, except there is no build-essential line.
    – Steve D
    Apr 15, 2017 at 23:00
  • @SteveD I'm not sure, but maybe it's because part of your stuff are installed from repository and the other part is installed manually, maybe there are some mismatch in libraries version etc.
    – Ravexina
    Apr 16, 2017 at 7:20
  • I've updated the question body with what I think is the problem, perhaps you know how to fix it?
    – Steve D
    Apr 16, 2017 at 18:50
  • @SteveD the output are not so helpful in my eyes, maybe someones else find them more helpful. why don't you install it from repositories? I think there is a high chance your problem will go away..
    – Ravexina
    Apr 16, 2017 at 19:07
  • I need clang 5.0, which is not available in the repositories.
    – Steve D
    Apr 16, 2017 at 21:07

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