Miniature guide to building Clang from source

June 22, 2016

First checkout the sources:

$ cd ~/src
$ git clone http://llvm.org/git/llvm.git
$ cd ~/src/llvm/projects
$ git clone http://llvm.org/git/compiler-rt.git
$ git clone http://llvm.org/git/libcxx.git
$ git clone http://llvm.org/git/libcxxabi.git
$ cd ~/src/llvm/tools
$ git clone http://llvm.org/git/clang.git
$ cd ~/src/llvm/tools/clang/tools
$ git clone http://llvm.org/git/clang-tools-extra.git extra

Next, do the build:

$ mkdir -p ~/src/llvm/build
$ cd ~/src/llvm/build
$ cmake -DCMAKE_INSTALL_PREFIX=/opt/clang -DCMAKE_BUILD_TYPE=RelWithDebInfo ..
$ make -j$(getconf _NPROCESSORS_ONLN)
$ sudo make install

On OS X you should also pass -DDEFAULT_SYSROOT=$(xcrun -show-sdk-path) to the cmake command. I could not find documentation for this, but it appears to default the -isysroot option. If you don’t specify this here, you will need to pass -isysroot and -Wl,-syslibroot everywhere.

Also, read the LLVM build and the git mirror documentation.