Building the Roc compiler from source

Installing LLVM, valgrind, libunwind, and libc++-dev

To build the compiler, you need these installed:

libunwind (macOS should already have this one installed)
libc++-dev
a particular version of LLVM

To run the test suite (via cargo test), you additionally need to install:

valgrind

Some systems may already have libc++-dev on them, but if not, you may need to install it. (On Ubuntu, this can be done with sudo apt-get install libc++-dev.) macOS systems should already have libunwind, but other systems will need to install it (e.g. with sudo apt-get install libunwind-dev).

To see which version of LLVM you need, take a look at Cargo.toml, in particular the branch section of the inkwell dependency. It should have something like llvmX-Y where X and Y are the major and minor revisions of LLVM you need.

For Ubuntu and Debian, you can use the Automatic installation script at apt.llvm.org:

sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)"

For macOS, you can run brew install llvm (but before you do so, check the version with brew info llvm--if it's 10.0.1, you may need to install a slightly older version. See below for details.)

There are also plenty of alternative options at http://releases.llvm.org/download.html

Troubleshooting

Create an issue if you run into problems not listed here. That will help us improve this document for everyone who reads it in the future!

LLVM installation on Linux

On some Linux systems we've seen the error "failed to run custom build command for x11". On Ubuntu, running sudo apt install pkg-config cmake libx11-dev fixed this.

If you encounter cannot find -lz run sudo apt install zlib1g-dev.

LLVM installation on macOS

It looks like LLVM 10.0.1 has some issues with libxml2 on macOS. You can install the older 10.0.0_3 by doing

$ brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/6616d50fb0b24dbe30f5e975210bdad63257f517/Formula/llvm.rb
# "pinning" ensures that homebrew doesn't update it automatically
$ brew pin llvm

If that doesn't work and you get a brew error Error: Calling Installation of llvm from a GitHub commit URL is disabled! Use 'brew extract llvm' to stable tap on GitHub instead. while trying the above solution, you can follow the steps extracting the formula into your private tap (one public version is at sladwig/tap/llvm). If installing LLVM still fails, it might help to run sudo xcode-select -r before installing again.

LLVM installation on Windows

Installing LLVM's prebuilt binaries doesn't seem to be enough for the llvm-sys crate that Roc depends on, so I had to build LLVM from source on Windows. After lots of help from @IanMacKenzie (thank you, Ian!), here's what worked for me:

I downloaded and installed Build Tools for Visual Studio 2019 (a full Visual Studio install should work tool; the Build Tools are just the CLI tools, which is all I wanted)
In the installation configuration, under "additional components" I had to check both "C++ ATL for latest v142 build tools (x86 & x64)" and also "C++/CLI support for v142 build tools"
I launched the "x64 Native Tools Command Prompt for Visual Studio 2019" application (note: not the similarly-named "x86" one!)
Make sure Python 2.7 and CMake 3.17 are installed on your system.
I followed most of the steps under LLVM's building from source instructions up to the cmake -G ... command, which didn't work for me. Instead, at that point I did the following step.
I ran cmake -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Release ../llvm to generate a NMake makefile.
Once that completed, I ran nmake to build LLVM. (This took about 2 hours on my laptop.)
Finally, I set an environment variable LLVM_SYS_100_PREFIX to point to the build directory where I ran the cmake command.

Once all that was done, cargo ran successfully for Roc!

Use LLD for the linker

Using lld for Rust's linker makes build times a lot faster, and I highly recommend it.

Create ~/.config/cargo and add this to it:

[build]
# Link with lld, per https://github.com/rust-lang/rust/issues/39915#issuecomment-538049306
# Use target-cpu=native, per https://deterministic.space/high-performance-rust.html
rustflags = ["-C", "link-arg=-fuse-ld=lld", "-C", "target-cpu=native"]

Then install lld version 9 (e.g. with $ sudo apt-get install lld-9) and add make sure there's a ld.lld executable on your PATH which is symlinked to lld-9.

That's it! Enjoy the faster builds.

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