如何在CentOS 7上使用clang构建libcxx和libcxxabi

Question

如何在CentOS 7上使用clang构建libcxx和libcxxabi

21

我想在CentOS 7上使用clang/clang++编译器来使用C++11或C++14。我该如何构建这个开发环境？

- Meng-Yuan Huang

如果您不想构建任何东西，可以使用C++11（不带<regex>）与Clang 3.4.2和预安装的libstdc++在CentOS 7上。启用EPEL存储库并yum install clang以获取Clang 3.4.2。 - phoenix

请参考此答案，了解如何使用SCL存储库在CentOS 7上安装最新的Clang。 - phoenix

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- Meng-Yuan Huang · Accepted Answer

本文介绍如何在CentOS 7上构建C++11构建环境：RHEL的EPEL仓库提供了Clang软件包，但没有C++库软件包。因此，这些部分需要手动构建，有点麻烦。针对Clang的定制C++库是libc++（libcxx）[1]。然后，libcxx还需要一个ABI库，libc++abi（libcxxabi）[2]。不幸的是，这两个库存在循环依赖问题。为了打破循环依赖问题，可以在不链接libc++abi的情况下构建libc++。然后，使用这个libc++，我们可以构建链接libc++的libc++abi。最后，使用libc++abi，我们可以构建链接libc++abi的新libc++。

以下是构建clang、libc++和libc++abi环境的步骤：

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

参考文献：
[1] http://libcxx.llvm.org/
[2] http://libcxxabi.llvm.org/

这段内容是关于IT技术方面的参考文献，其中包括两个链接，分别是http://libcxx.llvm.org/和http://libcxxabi.llvm.org/。请注意保留HTML标签。