Ubuntu – Installing clang 5.0 and using C++17

cclangcmakecompiling

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:
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include

and this is the output for g++:

#include <...> search starts here:
 /usr/include/c++/5
 /usr/include/x86_64-linux-gnu/c++/5
 /usr/include/c++/5/backward
 /usr/lib/gcc/x86_64-linux-gnu/5/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/5/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
...

Best Answer

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:

clang-5.0 
clang-5.0-doc 
clang-5.0-examples 
libclang-common-5.0-dev
...

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.

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