如何在CentOS 7上通过clang构建libcxx和libcxxabi

Question

我想在CentOS 7上使用带有clang/clang ++的C++ 11或C++ 14.如何构建这个构建环境？

Answer 1

本文教授如何在CentOS 7上构建C++ 11构建环境:RHEL的EPEL repo提供Clang包,但没有C++库包.因此,这些部件手工制作有点麻烦.Clang的自定义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libc ++ abi链接libc ++.最后,使用libc ++ abi,​​我们可以构建一个新的libc ++链接libc ++ abi.

clang,libc ++和libc ++ abi环境构建步骤如下:

1. 添加RHEL的EPEL回购.打开以下链接,找到"我如何使用这些额外的包？"部分. https://fedoraproject.org/wiki/EPEL
   查找适用于CentOS版本的epel软件包.例如,:

   sudo rpm -i https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
   

2. 安装Subversion以获取最新的libcxx和libcxxabi.

   sudo yum install svn
   

3. 安装Clang和llvm-devel(使用llvm-config).

   sudo yum install clang llvm-devel
   

4. 安装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.
   

5. 第一轮没有libcxxabi构建libcxx.

   # 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 ..
   

6. 使用libc ++构建libcxxabi.

   # 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 ../..
   

7. 第二轮用libcxxabi构建libcxx.

   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
   

8. 编写C++测试程序.

   // t.cpp
   #include <iostream>
   using namespace std;
   int main() {
     cout << "Hello world!" << endl;
   }
   

9. 通过clang ++测试C++编译.

   # -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/