install-clang

This script installs self-contained standalone 9.0 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/clang), 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/clang. 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.

Usage

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: Release]
    -c         skip cloning repositories, assume they are in place
    -C         clean up after build by deleting the LLVM/clang source/build directories
    -h|-?      display this help
    -j <n>     build with <n> threads in parallel [default: 4]
    -m         use git/master instead of preconfigured versions
    -s <stage> begin build from <stage> [0, 1, 2]
    -S         build, and link against, shared libraries (this is the default on macOS)
    -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/clang, you can use:

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

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

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

By default, install-clang currently installs the 9.0 release branch of https://github.com/llvm (the "mono repository"). Adding -m on the command line instructs the script to use the current git master version instead. The script downloads the source code from GitHub 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 version.

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.

Docker

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

# 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
/opt/clang/bin/clang

A prebuilt image is available at https://hub.docker.com/r/rsmmr/clang/ .

News

Version for Clang 9 (master)

• Switch to using the LLVM "mono repo" and adapt script's build process.

• Build libunwind, and link against it.

• macOS: Allow usage of libc++'s filesystem on non-10.15 systems.

• macOS: Add -rpath <prefix>/lib to linker arguments (we already did this for Linux).

Version for Clang 8 (git branch release_80)

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 backport clang-format's new options SpaceAfterLogicalNot and SpacesInConditionalStatement from git.

• We build, and link against, static libraries by default (just as LLVM does), except on macOS. Option -S switches back to shared libraries.

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

Version for Clang 6 (git branch 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/clang.