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A script to create a standalone installation of clang/LLVM/libc++. Updated for Clang/LLVM 6.0.
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Latest commit 5dd43fd Mar 22, 2019
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Makefile Updating image name for Docker build. Mar 21, 2019 Updating README. Mar 22, 2019
install-clang On macOS, we now set clang's DEFAULT_SYSROOT to the current macOS SDK. Mar 18, 2019 Start porting script to clang8. Mar 16, 2019
testit On macOS, we now set clang's DEFAULT_SYSROOT to the current macOS SDK. Mar 18, 2019


This script installs self-contained standalone 8.0 versions of clang, LLVM, libc++, compiler-rt, libc++abi, lldb, and lld, on macOS and Linux, including linking clang and LLVM against libc++ themselves as well. The script keeps all of the installation within a given target prefix (e.g., /opt/llvm), and hence separate from any already installed compilers, libraries, and include files. In particular, you can later uninstall everything easily by just deleting, e.g., /opt/llvm. Furthermore, as long as the prefix path is writable, the installation doesn't need root privileges.

If you have used older version of this script before, see News below for changes.


To see the available options, use -h:

> ./install-clang -h
Usage: install-clang [<options>] <install-prefix>

Available options:
    -A         enables assertions in LLVM libraries
    -b         build type (Release, Debug, RelWithDebInfo) [default: RelWithDebInfo]
    -c         skip cloning repositories, assume they are in place
    -h|-?      display this help
    -j <n>     build with <n> threads in parallel [default: 1]
    -m         use git/master instead of preconfigured versions
    -s <stage> begin build from <stage> [0, 1, 2]
    -u         update an existing build in <prefix> instead of installing new

Environment variables:
    CC         path to the C compiler for bootstrapping
    CXX        path to the C++ compiler for bootstrapping

For example, to build Clang on a machine with multiple cores and install it in /opt/llvm, you can use:

> ./install-clang -j 16 /opt/llvm

Once finished, just prefix your PATH with <prefix>/bin and you're ready to use the new binaries:

> clang++ --std=c++11 --stdlib=libc++ -o a.out && ./a.out
Hello, Clang!

By default, install-clang currently installs the 8.0 release branches of the relevant projects. Adding -m on the command line instructs the script to use the current git master versions instead. The script downloads all the sources from the corresponding git repositories and compiles the pieces as needed. Other OSs than macOS, and Linux are not currently supported.

The script also has an update option -u that allows for catching up with upstream repository changes without doing the complete compile/install-from-scratch cycle again. Note, however, that unless coupled with -m, this flag has no immediate effect since the git versions to use are hardcoded to the Clang/LLVM release versions.

Doing a self-contained Clang installation is a bit more messy than one would hope because the projects make assumptions about specific system-wide installation paths to use. The install-clang script captures some trial-and-error I (and others) went through to get an independent setup working. It compiles Clang up to three times, bootstrapping things with the system compiler as it goes. It also patches some of the Clang/LLVM projects to incorporate the installation prefix into configuration and search paths, and also fixes/tweaks a few other things as well.


install-clang comes with a Dockerfile to build a Docker image, based on Ubuntu, with Clang then in /opt/llvm:

# make docker-build && make docker-run
[... get a beer ...]
root@f39b941f177c:/# clang --version
clang version 8.0.0
Target: x86_64--linux-gnu
Thread model: posix
root@f39b941f177c:/# which clang

A prebuilt image is available at .


Version for Clang 8.0 (git master)

The install-clang script for Clang 8.0 comes with these changes compared to the 6.0 version:

  • Fix computed RPATH when the clang binary has been symlinked from elsehwere (#18).

  • We now honor preset environment variables CFLAGS, CXXFLAGS, and LDFLAGS to find dependencies.

  • On macOS, we now set clang's DEFAULT_SYSROOT to the current macOS SDK.

  • We apply a custom clang-format patch that adds a couple of custom formatting options.

  • Removed any customziation for FreeBSD; support had been untested in a long time.

Version for Clang 6.0 (git tag release_60)

The install-clang script for Clang 6.0 comes with these changes compared to the 3.5 version:

  • The default build type is now Release. It used to be RelWithDebInfo.

  • lldb and lld seem to built correctly on both Linux and Darwin now and both are enabled by default.

  • FreeBSD support is untested and hence disabled for now. Will be reactivated once confirmed that it's working.

  • On macOS, we no longer build for i386.

  • The Docker image is now based on Ubuntu Xenial and puts everything into /opt/clang.

Version for Clang 3.5 (git tag release_35)

The install-clang script for Clang 3.5 comes with a few changes compared to earlier version:

  • The script now supports FreeBSD as well. (Contributed by Matthias Vallentin).

  • The script now generally shared libraries for LLVM and clang, rather than static ones.

  • As libc++abi now works well on Linux as well, we use it generally and no longer support libcxxrt.

  • There are now command line options to select build mode and assertions explicitly.

  • There's no 3rd phase anymore building assertion-enabled LLVM libraries, as changing compilation options isn't useful with shared libraries.

  • In return, there's a phase 0 now if the system compiler isn't a clang; libc++abi needs clang that for its initial compilation already.

  • There's now a Dockerfile to build an image with Clang/LLVM in /opt/llvm.

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