How to Build libcxx and libcxxabi by clang on CentOS 7 - c++

Question

I want to use C++11 or C++14 with clang/clang++ on CentOS 7. How do I build this building environment?

Answer 1

This article teaches how to build C++11 building environment on CentOS 7: RHEL's EPEL repo provides Clang packages, but no C++ library packages. So, these parts are a bit troublesome to be built by hand. The customized C++ libraries for Clang is libc++ (libcxx) [1]. Then, libcxx also needs an ABI library, libc++abi (libcxxabi) [2]. Unfortunately, these two libraries have a circular dependency problem. For breaking the circular dependency problem, libc++ can be built without linking libc++abi. Then, with this libc++, we can build libc++abi linking libc++. Finally, with the libc++abi, we can build a new libc++ linking libc++abi.
The clang, libc++, and libc++abi environment building steps are given in the following：
Add RHEL's EPEL repo.
Open the following link and find the section "How can I use these extra packages?"
https://fedoraproject.org/wiki/EPEL
Find the epel package for your CentOS version. E.g.,:
sudo rpm -i https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
Install Subversion for getting the latest libcxx and libcxxabi.
sudo yum install svn
Install Clang and llvm-devel (with llvm-config).
sudo yum install clang llvm-devel
Install cmake.
cd /usr/local
wget https://cmake.org/files/v3.5/cmake-3.5.2-Linux-i386.sh
sudo chmod 755 cmake-3.5.2-Linux-i386.sh
sudo ./cmake-3.5.2-Linux-i386.sh
# Check cmake is in /usr/local/bin.
1st round to build libcxx without libcxxabi.
# Get libcxx.
svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx
cd libcxx
# It is not recommended to build libcxx in the source root directory.
# So, we make a tmp directory.
mkdir tmp
cd tmp
# Specifying CMAKE_BUILD_TYPE to Release shall generate performance optimized code.
# The CMAKE_INSTALL_PREFIX changes the install path from the default /usr/local to /usr.
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ..
sudo make install
cd ..
rm tmp -rf
cd ..
Build libcxxabi with libc++.
# Get libcxxabi.
svn co http://llvm.org/svn/llvm-project/libcxxabi/trunk libcxxabi
cd libcxxabi
mkdir tmp
cd tmp
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DLIBCXXABI_LIBCXX_INCLUDES=../../libcxx/include ..
sudo make install
cd ../..
2nd round to build libcxx with libcxxabi.
cd libcxx
mkdir tmp
cd tmp
# This time, we want to compile libcxx with libcxxabi, so we have to specify LIBCXX_CXX_ABI=libcxxabi and the path to libcxxabi headers, LIBCXX_LIBCXXABI_INCLUDE_PATHS.
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DLIBCXX_CXX_ABI=libcxxabi -DLIBCXX_CXX_ABI_INCLUDE_PATHS=../../libcxxabi/include ..
sudo make install
Write a C++ test program.
// t.cpp
#include <iostream>
using namespace std;
int main() {
cout << "Hello world!" << endl;
}
Test C++ compilation by clang++.
# -std specifies the C++ standard. -stdlib specifies the C++ library you want to use with clang/clang++. -lc++abi is necessary, because the new LD (linker and loader) on CentOS 7 doesn't allow indirect library linking.
clang++ -std=c++11 -stdlib=libc++ -lc++abi t.cpp
./a.out
References:
[1] http://libcxx.llvm.org/
[2] http://libcxxabi.llvm.org/